US20060266318A1

US20060266318A1 - Valve timing control apparatus and internal combustion engine

Info

Publication number: US20060266318A1
Application number: US11/389,153
Authority: US
Inventors: Seiji Suga; Hidekazu Yoshida; Tomoya Tsukada
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2005-05-24
Filing date: 2006-03-27
Publication date: 2006-11-30
Also published as: JP2006328986A; JP4553795B2

Abstract

Valve timing control apparatus includes a driving rotary member driven by an engine; a driven rotary member arranged to rotate relative to the driving rotary member and adapted to rotate a camshaft of the engine; and a hydraulic control section to rotate the driven rotary member relative to the driving rotary member hydraulically. A lock mechanism is arranged to be brought, in accordance with a hydraulic pressure supplied from the hydraulic control section, from a lock state to prevent relative rotation of the driven rotary member relative to the driving rotary member, to an unlock state to allow the relative rotation, through an standby state to prepare for the unlock state without allowing the relative rotation of the driven rotary member relative to the driving rotary member.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an internal combustion engine equipped with a valve timing control apparatus and/or a valve timing control apparatus for controlling a valve timing of an internal combustion engine such as opening and closing timings of intake or exhaust valve.
A published Japanese Patent Specification Publication No. 2000-002104 shows a valve timing control apparatus (VTC) of a vane type including a rotary unit of a timing sprocket member and a vane member, and a lock mechanism including a lock pin to limit relative rotation between the timing sprocket member and vane member.

SUMMARY OF THE INVENTION

When the engine remains in a stop state for a long time, most of the oil is drained from the advance and retard pressure chambers in the valve timing control apparatus of this document. Therefore, when the hydraulic fluid is supplied to the advance or retard pressure chamber at the time of a next engine start, air is compressed in the pressure chamber. As a result, the air pressure in the pressure chamber becomes higher and acts on the lock pin, so that the lock mechanism may be unlocked improperly, and hence the vane member may fluctuate in the forward and reverse directions and cause undesired noises. Therefore, it is an object of the present invention to provide valve timing control apparatus to solve problems in earlier technology.
According to one aspect of the present invention, a valve timing control apparatus for an internal combustion engine, comprises: a driving rotary member adapted to be driven by the engine; a driven rotary member arranged to rotate relative to the driving rotary member and adapted to rotate a camshaft of the engine; a hydraulic control section to rotate the driven rotary member relative to the driving rotary member hydraulically; and a lock mechanism arranged to be brought, in accordance with a hydraulic pressure supplied from the hydraulic section, from a lock state to prevent relative rotation of the driven rotary member relative to the driving rotary member, to an unlock state to allow the relative rotation of the driven rotary member relative to the driving rotary member, through an standby state to prepare for the unlock state without allowing the relative rotation of the driven rotary member relative to the driving rotary member.
According to another aspect of the invention, an internal combustion engine comprises: a crankshaft; a camshaft; a valve timing control rotary mechanism including a driving rotary member driven by the crankshaft of the engine, and a driven rotary member) which is arranged to be driven by the driving rotary member and to drive the camshaft, and which is arranged to rotate relative to the driving rotary member to alter a rotational position of the driven rotary member relative to the driving rotary member; a hydraulic section to rotate the driven rotary member relative to the driving rotary member in an advance direction by an advance fluid pressure in an advance pressure chamber and in a retard direction by a retard fluid pressure in a retard pressure chamber; a control section to control the hydraulic section to supply a fluid pressure selectively to the advance pressure chamber or the retard pressure chamber in accordance with an engine operating condition, and to perform an engine starting operation by first supplying the fluid pressure to a first chamber which is one of the advance and retard pressure chambers, and then supplying the fluid pressure a second chamber which is the other of the advance and retard pressure chambers; and a lock mechanism arranged to prevent relative rotation of the driven rotary member relative to the driving rotary member when the lock mechanism is in a lock state, and to allow the relative rotation of the driven rotary member when in an unlock state, the lock mechanism being set in the lock state at a time of an engine start and then brought to the unlock state in accordance with the fluid pressure in the second chamber after the engine start. The lock mechanism is further arranged to be set, before the unlock state is reached, to a standby state preparing for the unlock state while preventing the relative rotation of the driven rotary member relative to the driving rotary member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view taken across a line F1-F1 in FIG. 2, for showing an internal combustion engine provided with a valve timing control system according to a first embodiment of the present invention.
FIG. 2 is a sectional view taken across a line F2-F2 in FIG. 1, for showing the valve timing control system of FIG. 1.
FIG. 3A is a sectional view taken across the line F2-F2 in FIG. 1, for showing the valve timing control system of FIG. 1 at the time of a start of the engine. FIG. 3B is an enlarged view of a part of FIG. 3A.
FIG. 4A is a sectional view taken across the line F2-F2 in FIG. 1, for showing the valve timing control system of FIG. 1 at the time of an idling operation of the engine. FIG. 4B is an enlarged view of a part of FIG. 4A.
FIG. 5A is a sectional view taken across the line F2-F2 in FIG. 1, for showing the valve timing control system of FIG. 1 at the time of an operation in a low speed, low load region of the engine. FIG. 5B is an enlarged view of a part of FIG. 5A.
FIG. 6A is a sectional view taken across the line F2-F2 in FIG. 1, for showing the valve timing control system of FIG. 1 at the time of an operation in a medium speed, medium load region of the engine. FIG. 6B is an enlarged view of a part of FIG. 6A.
FIG. 7 is a partial cutaway view showing a valve timing control apparatus according to a second embodiment of the present invention.
FIG. 8 is a partial cutaway view for illustrating operation of the valve timing control apparatus of FIG. 7 with a vane member at a most retarded position.
FIG. 9 is a partial cutaway view for illustrating operation of the valve timing control apparatus of FIG. 7 with the vane member at an intermediate rotational position.
FIG. 10 is a partial cutaway view for illustrating operation of the valve timing control apparatus of FIG. 7 with the vane member at a most advanced position.
FIG. 11 is a partial cutaway view showing a valve timing control apparatus according to a third embodiment of the present invention.
FIG. 12 is a partial cutaway view for illustrating operation of the valve timing control apparatus of FIG. 11 with a vane member at the most retarded position.
FIG. 13 is a partial cutaway view for illustrating operation of the valve timing control apparatus of FIG. 11 with the vane member at the intermediate rotational position.
FIG. 14 is a partial cutaway view for illustrating operation of the valve timing control apparatus of FIG. 11 with the vane member at the most advanced position.
FIG. 15 is a sectional view taken across a line F15-F15 shown in FIG. 16, showing a valve timing control apparatus according to a fourth embodiment of the present invention.
FIG. 16 is a sectional view taken across a line F16-F16 shown in FIG. 15.
FIG. 17 is a sectional view taken across a line F17-F17 shown in FIG. 18, showing a valve timing control apparatus according to a fifth embodiment of the present invention.
FIG. 18 is a sectional view taken across a line F18-F18 shown in FIG. 17.
FIG. 19 is an enlarged view of a main portion of FIG. 17.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an internal combustion engine equipped with a valve timing control apparatus or system according to a first embodiment of the present invention. FIG. 2 shows the valve timing control apparatus in section taken across a line F2-F2 in FIG. 1 whereas FIG. 1 is a sectional view taken across a line F1-F1 shown in FIG. 2. In this embodiment, the present invention is applied to an intake valve's side. However, it is possible to apply the invention to an exhaust valve's side.
A timing sprocket member 1 is driven through a timing chain 61 by a crankshaft62 of the internal combustion engine. Timing sprocket member 1 serves as a driving rotary member adapted to be driven by the engine. A camshaft 2 is rotatable relative to sprocket member 1. A vane member 3 serves as a driven rotary member. Vane member 3 is fixed at an end of camshaft 2 so that they rotate as a unit, and which is encased rotatably in sprocket member 1. A hydraulic circuit or hydraulic section 4 is a component of a hydraulic control section to rotate vane member 3 in a forward rotational direction and a reverse rotational direction in sprocket member 1 by the action of oil pressure.
Timing sprocket member 1 includes a sprocket housing 5, a front cover 6 and a rear cover 7 which are joined together by fastening devices which, in this example, are three small-diameter bolts 8. Housing 5 is a hollow cylindrical member extending axially from a front open end to a rear open end. Housing 5 includes a toothed portion 5 a formed integrally on the periphery of housing 5, and arranged to engage in links of timing chain 61. Vane member 3 is enclosed rotatably in housing 5. Front cover 6 is in the form of a circular disk, and arranged to close the front open end of housing 5. Rear cover 7 is in the form of an approximately circular disk and arranged to close the rear open end of housing 5. Front cover 6, housing 5 and rear cover 7 are joined together to form a housing encasing the vane member 3, by the before-mentioned bolts 8 extending in the axial direction of camshaft 2.
Housing 5 is approximately in the form of a hollow cylinder open at both ends. Housing 5 includes a plurality of partitions 10 projecting radially inwards from an inside circumferential wall surface of cylindrical housing 5. Projecting partitions 10 serve as shoes. In this example, the number of partitions 10 is three, and these three partitions 10 are arranged at angular intervals of approximately 120°, circumferentially in the inside circumference of housing 5. Each partition 10 extends axially from the front open end to the rear open end of housing 5, and has an approximately trapezoidal cross section as viewed in FIG. 2. In this example, housing 5 includes a front end surface which is substantially flat and which is joined with front cover 6, and a rear end surface which is substantially flat and which is joined with rear cover 7. Each partition 10 of this example includes a front end surface which is flat, and flush and continuous with the flat front end surface of housing 5, and a rear end surface which is flat, and flush and continuous with the flat rear end surface of housing 5. A bolt hole 11 is formed approximately at the center of each partition 10. Each bolt hole 11 passes axially through one of partitions 10, and receives one of the axially extending bolts 8. Each partition 10 includes an inner end surface which is sloping in conformity with the outer shape of a later-mentioned vane rotor (14) of vane member 3. A retaining groove 11 extends axially in the form of cutout in the inner end surface of each partition at a higher position. A U-shaped seal member 12 is fit in each retaining groove 11, and urged radially inwards by a leaf spring (not shown) fit in the retaining groove 11.
Front cover 6 includes a center bolt hole 6 a having a relatively large inside diameter; and three bolt holes 6 b each receiving one of the axially extending bolts 8. These three bolt holes 6 b are arranged around the center bolt hole 6 a.
Rear cover 7 includes a center bearing hole 7 a supporting rotatably a front end portion 2 a of camshaft 2; and three threaded holes 7 b into which three bolts 8 are screwed, respectively.
Camshaft 2 is rotatably supported through a cam bearing 13 on an upper portion of a cylinder head S of the engine. Camshaft 2 includes one or more cams formed integrally on the outer circumference of camshaft 2 at predetermined positions. Each cam is arranged to open an intake valve of the engine through a valve lifter.
Vane member 3 of this example is a jointless single member made of sintered alloy. Vane member 3 includes a central vane rotor 14 and a plurality of vanes 15 projecting radially outwards. In this example, the number of vanes 15 is three, and these three vanes 15 are arranged at angular intervals of approximately 1200 circumferentially around vane rotor 14. Vane rotor 14 is annular and includes a center bolt hole 14 a at the center. Vane member 3 is fixed to a front end 2 a of camshaft 2 by a cam bolt 16 extending axially through the center bolt hole 14 a.
The three vanes 15 are approximately rectangular, and these vanes 15 are unequal in circumferential width L measured in the circumferential direction around a common center axis of a rotary mechanism composed of vane member 3 and timing sprocket 1. A first one of the three vanes 15 is a smaller vane having a smallest circumferential width L1, a second one is a medium vane having an intermediate circumferential width L2 greater than L1, and a third one is a larger vane having a largest circumferential width L3 greater than L2. These vanes are formed so that a weight balance is attained as a whole of the vane member 3. The three vanes 15 of vane member 3 and the three partitions 10 of timing sprocket member 1 are arranged alternately in the circumferential direction around the center axis, as shown in FIG. 2. Namely, each vane 15 is located circumferentially between adjacent two of the partitions 10. Each vane 15 includes a retaining groove receiving a U-shaped seal member 16 in sliding contact with the inside cylindrical surface of housing 5, and a leaf spring (not shown) for urging the seal member 16 radially outward and thereby pressing the seal member 16 to the inside cylindrical surface of housing 5.
Each vane 15 includes a first side surface facing in the rotational direction of vane member 3 and a second side surface facing in a rotational direction opposite to the rotational direction. In the case of the smaller vane having the smallest width L1, the retaining groove is formed at a middle of an outer end of the vane. In the medium vane 15 having the intermediate width L2, the retaining groove is formed in the outer end of the vane at a position closer to the first side surface of the vane. In the greater vane 15 having the greater width L3, the retaining groove is formed in the outer end of the vane at a position closer to the second side surface of the vane.
An advance fluid pressure chamber 17 and a retard fluid pressure chamber 18 are formed on both sides of each vane 15. Advance pressure chamber 17 is defined between the second side surface of each vane 15 and the adjacent partition 10 to which the second side surface of the vane faces. Retard pressure chamber 18 is defined between the first side surface of each vane 15 and the adjacent partition 10 to which the first side surface of the vane faces.
Hydraulic circuit 4 includes a first fluid pressure passage or advance fluid pressure passage 19 leading to the advance chambers 17 to supply and drain an advance fluid pressure of an operating oil to and from advance chambers 17; a second fluid pressure passage or retard fluid pressure passage 20 leading to the retard chambers 18 to supply and drain a retard fluid pressure of the operating oil to and from retard chambers 18, and a directional control valve or selector valve 23 connecting the advance pressure passage 17 and retard pressure passage 18 selectively with a supply passage 21 and a drain passage 22. In this example, control valve 23 is a solenoid valve. A fluid pump 25 is connected with supply passage 21, and arranged to draw the hydraulic operating fluid or oil from an oil pan 24 of the engine, and to force the fluid into supply passage 21. Directional control valve 23 of this example is a one-way type pump. Drain passage 22 is connected to oil pan 24, and arranged to drain the fluid to oil pan 24. At least one of directional control valve 23 and pump 25 can serve as an actuating device for forcing one of first and second movable (lock) members backwards, as mentioned later.
Advance fluid pressure passage 19 includes a first passage section 19 a, a second passage section 19 b serving as a pressure chamber, and three branch passages (not shown) connecting second passage section 19 b, respectively, with the three advance chambers 17. Passage section 19 a extends in cylinder head S, and further extends axially in camshaft 2, to second passage section 19 b. Second passage section 19 b is formed by vane member 3, at a position between vane rotor 14 and the front end of camshaft 2. The three branch passages are formed in vane member 3 and extend radially in vane member 3.
Retard fluid pressure passage 20 includes a first passage section 20 a extending in cylinder head S and axially in camshaft 2, and a second passage section 20 b formed in vane rotor 14. Second passage section 20 b is approximately L-shaped, and connected with each retard pressure chamber 18.
Directional control valve 45 of this example is a solenoid valve having four ports and two positions. A valve element inside the control valve 45 is arranged to alter the connection between the passages 19 and 20 and the supply and drain passages 21 and 22.
A controller 26 produces a control signal, and controls the solenoid control valve 45 by sending the control signal to the valve 45. A sensor section 63 collects input information on operating conditions of the engine and a vehicle in which this timing control apparatus is installed. Input information is supplied to controller 26. The sensor section 63 of this example includes a crank angle sensor 64 for sensing a speed of the engine, an air flowmeter 65 for sensing an intake air quantity of the engine, a cam angle sensor 66 and an input device 67, such as an ignition switch or a vehicle main switch, to sense a start of the engine. Controller 26 determines a current operating state from the signals from crank angle sensor 64 and air flowmeter 65, and further determines a relative rotational position between sprocket member 1 and camshaft 2. Controller 26 serves as a main component of a control section in the hydraulic control section which includes the hydraulic section 4 and the control section.
Vane member 3, advance and retard chambers 17 and 18 and hydraulic circuit 4 form a varying mechanism varying the relative rotational position between the driving rotary member such as sprocket member 1 and the driven rotary member such as vane member 3. Sprocket member 1 and vane member 3 form a valve timing control rotary mechanism. A control section for controlling the relative displacement between the driving rotary member such as sprocket member 1 and the driven rotary member such as vane member 3 may include at least one of the hydraulic circuit 4 and controller 26. The control section may further include the sensor section 63. Control valve 23 or hydraulic circuit 4 including control valve 23 serves as a hydraulic control section.
A lock mechanism or restraint mechanism is a mechanism to prevent and allow the relative rotation between the driving rotary member that is sprocket member 1 in this example and the driven rotary member that is vane member 3 in this example. The lock mechanism is provided between the sprocket member 1 and vane member 3. In this example, the lock mechanism is formed between housing 5 and a portion of vane rotor 14 adjacent to the smaller vane 15 having the circumferential width L1. The lock mechanism includes a first lock or restraint unit or mechanism 27 provided in vane rotor 14 of vane member 3 and a second lock or restraint unit or mechanism 28 provided in housing 5 of sprocket member 3.
First lock or restraint unit or mechanism 27 (which is a driven-side lock unit in this example), as shown in FIGS. 1˜3, includes a first (or driven-side) movable lock member 30. First lock member 30 is slidably received in a first slide hole 29 formed in vane member 3. In this example, first slide hole 29 is formed in a boss portion 14 b formed in vane rotor 14. Boss portion 14 b is located on an advance chamber's side of the smaller vane 15 having the smallest width L1. As shown in FIG. 2, boss portion 14 b is located circumferentially between the smaller vane 15 and the adjacent partition 10 defining and bounding the advance chamber 17 for the smaller vane 15. First slide hole 29 extends radially in vane member 3, and first lock member 30 is movable radially in the radially extending first slide hole 29. First lock member 30 is a cup-shaped member in the form of a hollow cylinder having one end closed. First lock member 30 includes a circumferential wall extending in a radial outward direction of vane member 3 from an open inner end to an outer end, and a forward end portion 30 a closing the outer end of the circumferential wall.
First lock unit 27 on the driven side further includes a first (or driven-side) spring 31. First spring 31 is disposed between vane member 3 and first lock member 30 and arranged to bias or urge first lock member 30 forwards toward the sprocket member 1 in a radial outward direction which may not be an exact direction of a radius emanating from the center axis of vane member 3. In this example, first spring 31 is a coil spring disposed between the inside surface of the forward end portion 30 a of first lock member 30 and the bottom of first slide hole 29 formed in boss portion 14 b of vane member 3. An outer portion of first spring 31 is inserted into the inside of first lock member 30 and enclosed by the circumferential wall of first lock member 30.
First slide hole 29 of this example extends radially from the bottom to an outer end opening into the advance fluid pressure chamber 17 for the vane 15 of the smallest width L1. The depth of first slide hole 29 is longer than the length of first lock member 30.
The forward end portion 30 a of first lock member 30 is exposed to the advance fluid pressure in the advance chamber 17, so that the advance fluid pressure is applied to the forward end portion 30 a so as to force the first lock member 30 backwards toward the bottom of first slide hole 29, in a radial inward direction away from the sprocket member 1. The forward end portion 30 a of first lock member 30 of this example has an outside convex surface which is spherical or shaped like a circular arc in section. First lock member 30 further includes an outward flange 30 b formed at the inner or backward end of the circumferential wall of first lock member 30. A hollow cylindrical stopper 35 is fixed in the first slide hole by press fitting, and arranged to limit a radial outward movement of first lock member 30 by abutting against the outward flange 30 b of first lock member 30, as shown in FIG. 3A. Therefore, stopper 35 and outward flange 30 b determines a forward limit position beyond which first movable member 30 can not be moved and projected by first spring 31.
First (or driven-side) spring 31 is set at such a spring force that first spring 31 can push the first lock member 30 forwards when the hydraulic pressure in the advance fluid pressure chamber 17 is low without the supply of the advance fluid pressure, and that first spring 31 is compressed by the advance fluid pressure in the advance fluid pressure chamber 17, to allow the first lock member 30 to be moved backwards deeper in the first slide hole 29 toward the bottom of first slide hole 29 when the hydraulic pressure in the advance fluid pressure chamber 17 becomes high by receiving the supply of the advance fluid pressure.
Second lock or restraint unit or mechanism 28 (which is a driving-side lock unit in this example), as shown in FIGS. 1˜3, includes a second (or driving-side) movable lock member 33 (which can serve as a movable abutting member). Second lock member 33 is slidably received in a second slide hole 32 formed in sprocket member 1. In this example, second slide hole 32 is formed in a boss portion 5 b formed integrally at the side of the partition 15 defining the advance chamber 17 of the vane 15 having the smallest width L1. Boss portion 5 b is located circumferentially between the smaller vane 15 and the adjacent partition 10 defining and bounding the advance chamber 17 for the smaller vane 15. Second slide hole 32 extends radially in sprocket member 1, and second lock member 33 is movable radially in the radially extending slide hole 32. Second lock member 33 is shaped approximately like a cup, and includes a circumferential wall extending in a radial inward direction of sprocket member 1, from an outer end to an inner end, and a forward end portion formed so as to close the inner end of the circumferential wall.
Second lock unit 37 on the driving side further includes a second (or driving-side) spring 34. Second spring 34 is disposed between sprocket member 1 and second lock member 33, and arranged to bias or urge second lock member 33 forwards toward the vane member 3 in a radial inward direction which may not be an exact direction of a radius converging to the center axis of vane member 3. In this example, second spring 34 is a coil spring disposed between the inside surface of the forward end portion of second lock member 33 and the bottom of second slide hole 32 formed in boss portion 5 b of sprocket member 1. An inner portion of second spring 34 is inserted into the inside of second lock member 33 and enclosed by the circumferential wall of second lock member 33.
Second slide hole 32 of this example extends radially inward from an outer open hole end to an inner open hole end. A spring retainer 40 is fit and fixed in second slide hole 32. Second spring 34 is disposed between this spring retainer 40 and the forward end portion of second lock member 33. In this example, spring retainer 40 is composed of two discs each formed with a hole at the center. Second slide hole 32 includes an outer large-diameter section extending from the outer hole end, toward the inner hole end of second slide hole 32; an inner small-diameter section extending from the inner hole end toward the outer hole end of second slide hole 32; and an annular step shoulder surface 32 a formed between the large-diameter section and the small-diameter section. Annular step shoulder surface 32 a faces approximately in the radial outward direction toward the outer hole end. In this example, the spring retainer 40 is fixed in the large-diameter section of second slid hole 32 at an intermediate position between the outer hole end and the step shoulder surface 32 a.
Second lock member 33 includes an outer large-diameter section slidably fit in the outer large-diameter portion of second slide hole 32; an inner small-diameter section slidably fit in the inner small-diameter section of second slide hole 32; and an annular step shoulder surface 33 a formed between the large-diameter section and the small-diameter section of second lock member 33. The inner small-diameter section of second lock member 33 is greater in diameter than the forward end portion 30 a of first lock member 30. Inner small-diameter section includes a forward end portion as mentioned more in detail later. Annular shoulder surface 33 a faces approximately in the radial inward direction. Annular step shoulder surface 33 a serves as a pressure receiving surface of an outward flange.
An annular pressure chamber 33 b is formed around the second lock member 33 between the annular shoulder surface 33 a of second lock member 33 and annular shoulder surface 32 a of second slide hole 32. The annular shoulder surface 33 a of second lock member 33 is arranged to receive the pressure in the annular pressure chamber 33 b. Sprocket member 1 is formed with a communication passage 36 for introducing one of the advance fluid pressure and the retard fluid pressure to the annular pressure chamber 33 b to apply the hydraulic pressure to second lock member 33 to move the second lock member 33 backwards. In this example, communication passage 36 extends from a first passage end opening in the retard fluid pressure chamber 18, through the vane 15, to a second passage end 36 a opening into the annular pressure chamber 33, as shown in FIG. 2. Therefore, second lock member 33 is arranged to move backwards toward the spring retainer 40 serving as the bottom of second slide hole 32, in the radial outward direction by the application of the retard fluid pressure introduced from the retard fluid pressure chamber 18 into the annular pressure chamber 33 b. The annular step shoulder surface 32 a faces approximately in the radial outward direction, and functions to limit radial inward movement of second lock member 33 by abutting on the annular step shoulder surface 33 a of second lock member 33, and thereby to determine a forward limit position (or a most projected position) of second lock member 33. Spring retainer 40 confronts the back end of second lock member 33, and functions to limit radial outward movement of second lock member 33 by abutting on the back end of second lock member 33, and thereby to determine a backward limit position (or a most retracted position) of second lock member 33.
Second (or driving-side) spring 34 is set at such a spring force that second spring 34 can push the second lock member 33 forwards when the hydraulic pressure in the retard fluid pressure chamber 18 is low without supply of the retard fluid pressure, and that second spring 34 is compressed by the retard fluid pressure supplied to the annular pressure chamber 33 b from the retard fluid pressure chamber 18, to allow the second lock member 33 to be moved backwards deeper in the second slide hole 32 toward the bottom of second slide hole 32 when the hydraulic pressure in the annular pressure chamber 33 b becomes high by receiving the supply of the retard fluid pressure. The spring force of second spring 34 is set greater than the spring force of first spring 31.
The forward end portion of second lock member 33 includes a disk-shaped wall 37 shaped like a circular disk, and a (lock) recess 38 depressed backwards to the bottom formed by the disk-shaped wall 37. On the other hand, the forward end portion of first lock member 30 is in the form of a (lock) projection which can engage in the recess 38 of second lock member 33. Forward end portion of second lock member 33 includes the above-mentioned disk-shaped wall 37 forming the bottom of recess 38, and separating the inside cavity of the circumferential wall of second lock member 33 and the inside of recess 38. The inside diameter of recess 38 (which is a circular recess in this example) is set greater than the outside diameter of the forward end portion (projection) 30 a of first lock member 30. Therefore, the forward end portion 30 a of first lock member 30 is loosely fit in recess 38 of second lock member 33 in a lock state in which the forward end portion 30 a of first lock member 30 is received in recess 38 of second lock member 33 as shown in FIG. 2 and FIGS. 3A and 3B.
Forward end portion 30 a of first lock member 30 includes an outside circumferential side surface which abuts against an inside circumferential side surface of recess 38 of forward end portion of second lock member 33, and thereby prevents rotation of vane member 3 relative to sprocket member 1 when the first and second lock members 30 and 33 are in the lock state. The outside circumferential side surface of forward portion 30 a of first lock member 30 extends along the axis of first lock member 30, and the inside circumferential side surface of recess 39 of second lock member 33 extends along the axis of second lock member 33. In this example, the outside circumferential side surface of forward portion 30 a of first lock member 30 is a cylindrical surface, and the inside circumferential side surface of recess 38 of second lock member 33 is also a cylindrical surface.
The forward end portion of second lock member 33 is further formed with a guide surface 39 serving as guide means or retracting means for guiding first and second lock members 30 and 33 into the lock state in which the projection (30 a) of first lock member 30 is fit loosely in the recess 38 of second lock member 33. In this example, the guide surface 39 is in the form of an annular tapered surface or conical surface.
In the state in which no hydraulic pressures are supplied to the advance and retard fluid pressure chambers 17 and 18 for example at the time of engine stoppage, the vane member 3 is set at a predetermined (lockable) rotational position (which is the most retarded position in this example) as shown in FIGS. 1, 2, 3A and 3B. In this state, the vane 15 having the greatest circumferential width L3 abuts against the adjacent partition 10 of sprocket member 1 in the retard rotational direction. In this state, the vane 15 of the medium width L2 is spaced by a minute clearance C from the adjacent partition 10 in the retard rotational direction. The vane 15 having the medium width L2 does not abut on the adjacent partition 10. Similarly, the vane 15 of the smallest width L1 is spaced by a minute clearance C from the adjacent partition 10 without abutting on the partition 10. When vane member 3 is located at this predetermined (lockable or most retarded) position relative to sprocket member 1, the forward end portion 30 a of first lock member 30 can enter the recess 38 of second lock member 33, and the first and second lock members 30 and 33 can shift into the lock state.
The relative positions of first and second lock members 30 and 33 relative to each other are set in the following manner. When second lock member 33 is located at the backward limit (most retracted) position and first lock member 30 is located at the forward limit (most projected) position, a part of the forward end portion 30 a of first lock member 30 is engaged in the lock recess 38 of second lock member 33, and first and second lock member are said to be in a standby or unlock ready state.
The minute clearance C of each of these vanes 15 (of the medium and smallest widths) is determined in accordance with the average torque, sliding friction and the size of the vane 15. These minute clearances C are effective for preventing adhesion of the vanes to partitions 10 and thereby improving the response speed of vane rotation. It is possible set a clearance for each of all the three vanes 15 so that, in the predetermined lockable rotational position, each of all the vanes is set apart from the corresponding partition 10.
The thus-constructed valve timing control apparatus is operated as follows: At the time of start of the engine, controller 26 produces the control signal, and solenoid directional control valve 23 is set to the position to connect the supply passage 21 with second (retard) fluid passage 20 and connect the drain passage 22 with first (advance) fluid passage 19. Therefore, the fluid pressure produced by pump 25 is supplied through second passage 20 to retard chambers 18 whereas the advance chambers 17 are held in the low pressure state with no supply of hydraulic pressure as in the engine stop state.
Therefore, first lock member 30 projects forwards in the radial outward direction by the force of first spring 31, as shown in FIGS. 3A and 3B, until the forward limit position is reached by abutment of flange 30 b against the inner end of stopper 35. On the other hand, second lock member 33 projects forwards in the radial inward direction by the force of second spring 34 until the forward limit position is reached by abutment of flange 33 a against shoulder surface 32 a since the hydraulic pressure inside the retard chambers 18 is not increased sufficiently. Therefore, the forward end portion 30 a of first lock member 30 is engaged in the recess 38 of second lock member 33. In this state, the outside circumferential surface of forward end portion 30 a of first lock member 30 abuts against the inner side surface of lock recess 38 of second lock member 33, and thereby prevents the relative rotation between vane member 3 and sprocket member 1.
Therefore, as shown in FIG. 2 and FIG. 3A, the wide vane having the greatest width L3 abuts against the adjacent partition 10 on the advance chamber's side, and the first and second lock members 30 and 33 are put in the lock state to prevent the relative rotation between vane member 3 and sprocket member 1.
In this state, the relative rotational angle of camshaft 2 relative to timing sprocket member 1 is held on the retard side, and the opening and closing timings of the intake valve are controlled to the retard side. By so doing, this valve timing control system can improve the combustion efficiency by utilizing inertial intake air, and improve the engine cranking performance. Moreover, the lock mechanism of first and second lock members 30 and 33 in the lock state can prevent vibrations or flapping of vane member 3 due to alternating torque of camshaft 2 between the positive and negative sides in the engine starting operation.
In an idling operation after an engine start, for example, the solenoid directional control valve 23 is held in the existing state and the hydraulic pressure in retard fluid pressure chambers 18 becomes higher. When the hydraulic pressure in retard chambers 18 becomes higher than the level of the alternating torque, the flange portion 33 a of second lock member 33 is acted upon by the fluid pressure introduced into the pressure chamber 33 b through communication passage 36; and the second lock member 33 compresses second spring 34 and moves backwards against the spring force of second spring 34.
However, in this state, the first lock member 30 is still held at the forward limit position or most projected position by the force of first spring 31. Therefore, the forward end portion 30 a of first lock member 30 at the forward limit position is still located in the lock recess 38 of second lock member 33 at the backward limit position or most retracted position, as shown in FIGS. 4A and 4B. In this state (called standby state or unlock ready state) shown in FIGS. 4A and 4B, the first and second lock members 30 and 33 still remain engaged with each other and prevent the rotation of vane member 3 relative to sprocket member 1. In this example, the length of the abutment of forward end portion 30 a of first lock member 30 against the lock recess 38 is approximately equal to or lower than 0.2 mm. Thus, in this standby state, the vane member 3 is not allowed to rotate freely but locked or restrained. Vane member 3 is held stably at the position shown in FIGS. 4A and 4B since the hydraulic pressure in the retard pressure chambers 18 is increased.
When the vehicle starts moving, and the engine operating point enters a predetermined low speed, low load region, the controller 26 sends the control signal and switches the directional control valve 23 to the state connecting the supply passage 21 with first (advance) passage 19, and the drain passage 22 with second (retard) passage 20. Therefore, the fluid is returned from retard chambers 18 through second passage 20 and drain passage 22 to oil pan 24, and the hydraulic pressure in retard chambers 18 becomes low. On the other hand, the hydraulic pressure in advance chambers 17 becomes high by the supply of the fluid pressure.
Therefore, second lock member 33 tries to move forwards by the force of second spring 34 to the forward limit position with a decrease of the hydraulic pressure in the retard pressure chambers 18. However, the wall 37 of second lock member 33 receives the hydraulic pressure of the advance chambers 17, and this hydraulic pressure overcomes the spring force of second spring 34, so that second lock member 33 is held at the backward limit position or most retracted position, as shown in FIGS. 5A and 5B. On the other hand, first lock member 30 moves backwards toward the bottom of first slide hole 29 against the force of first spring 31 by receiving the hydraulic pressure in advance chambers 17. In this case, the forward end portion 30 a of first lock member 30 in the standby state of FIGS. 4A and 4B can disengage from lock recess 38 of second lock member 33 rapidly, and the lock mechanism is unlocked or released immediately. Therefore, vane member 3 rotates in the clockwise direction from the rotational position shown in FIGS. 4A and 4B, to the rotational position shown in FIGS. 5A and 5B, intermediate between the most retarded position and the most advanced position.
When the engine operating point shifts into a medium speed, medium load region, and the supply pressure to advance chambers 17 becomes high, the vane member 3 is further rotated in the advance direction (that is, the, clockwise direction as viewed in FIGS. 6A and 6B) until the greater vane 15 abuts against the adjacent partition 15 on the retard chamber's side as shown in FIG. 6A and the most advanced position shown in FIGS. 6A and 6B is reached by vane member 3. Therefore, camshaft 2 is rotated relative to timing sprocket member 1 in the advance direction, and the opening and closing timings of the intake valve are controlled to the advance side. Therefore, the valve timing control system can decrease the pumping loss of the engine and thereby improve the engine output.
When the engine operating point further shifts into a high speed region, the controller 26 switches the solenoid valve 23 to the state connecting the supply passage 21 with second passage 20, and the drain passage 22 with first passage 19 as in the idling operation. By so doing, controller 26 decreases the hydraulic pressure in advance chambers 17 and increases the hydraulic pressure in retard chambers 18. Therefore, vane member 3 is returned in the counterclockwise direction to the most retarded position shown in FIG. 4A, and the camshaft 2 is rotated in the retard direction relative to timing sprocket member 1, so that the opening and closing timings of the intake valve are controlled to the retard side. Thus, the valve timing control system can improve the intake charging efficiency and improve the engine output.
In this case, first lock member 30 is projected forwards toward the forward limit position by the force of first spring 31. However, second lock member 33 is retracted backwards to the backward limit position in second slide hole 32 by the force of the retard fluid pressure in retard chambers 18 introduced into the annular pressure chamber 33 b through communication passage 36. When vane member 3 is rotated to the retard side with the first lock member in the forward limit position and the second lock member in the backward limit position, the projecting end portion 30 a of first lock member 30 in the projected state abuts against the tapered guide surface 39 and moves backward by being pushed by guide surface 39. In this way, the forward end portion 30 a of first lock member 30 slides on the tapered guide surface 39 of second lock member 33 and finally fits into the lock recess 38 of second lock member 33.
In the stop state of the engine, the vane member 3 is restored to the most retarded position shown in FIGS. 2 and 3A by the idling operation before the stoppage of the engine. That is, the vane member 3 returns to the most retarded position while fluctuating by the effect of alternating torque. On the other hand, with a decrease in the hydraulic pressure in retard chambers 18, the second lock member 33 is projected forward to the forward limit position, and the forward end portion 30 a of first lock member 30 engages in the recess 38 of second lock member 33 by being guided by guide surface 39.
If the engine is stopped by an engine stall without experiencing the idling operation, the vane member 3 is rotated by the effect of the alternating torque to the most retarded position, and the first lock member 30 engages into the lock recess 38 of second lock member 33 automatically under the guidance of guide surface 39.
At the same time with the engine stall, the oil pump 25 is stopped, and stops the supply of hydraulic pressure to the advance and retard chambers. Therefore, the first and second lock members 30 and 33 are both projected forwards by first and second springs 31 and 34, respectively. When the vane member 3 is rotated from the position shown in FIG. 6A toward the position shown in FIG. 4A by the action of the alternating torque, the first lock member 10 remaining in the projected position collides against the second lock member 33 in the projected position. In this case, the forward end portion 30 a of first lock member 30 abuts against the annular tapered guide surface 39, and moves backwards gradually by being pushed by the guide surface 39 against the force of first spring 31 until the forward end portion 30 a of first lock member 30 enters the lock recess 38 of second lock member 33.
Therefore, at the time of a restart of the engine, the vane member 3 is locked against rotation relative to sprocket member 1, and the engine can be started smoothly as in the normal engine starting operation.
By controlling the supply and drainage of the hydraulic pressure to and from the advance and retard chambers 17 and 18 in accordance with the engine operating conditions, this valve timing control system can hold the vane member 3 at a desired intermediate rotational position as shown in FIG. 5A.
Thus, in addition to the valve timing control mechanism (1, 3 etc.) capable of controlling the valve timing by controlling the hydraulic pressures in advance and retard chambers 17 and 18; the valve timing control system according to this embodiment has the lock mechanism including the first and second movable lock members 30 and 33 which are arranged to lock the vane member adequately without being erroneously released. Even if an air pressure acts in a starting operation of the engine after long term stoppage, and pushes the second lock member backwards, the engagement between the first and second lock members is not canceled as shown in FIGS. 4A and 4B. Thus, the first and second lock members may be brought to the standby state, but the vane member is not released by the air pressure. The air pressure can only serve as a standby pressure or an unlock preparing pressure. The air pressure cannot serve as a control start pressure to unlock the lock mechanism.
Thereafter, the lock mechanism is unlocked when the solenoid valve 23 is switched, and the hydraulic fluid pressure (control start pressure) is supplied to advance chambers 17. In this case, the first and second lock members are already in the standby state in which the contact or abutting area between the first and second lock members is reduced significantly as compared to the lock state. Consequently, the engagement between the first and second lock members can be canceled smoothly and quickly, by the supply of the hydraulic pressure to advance chambers 17.
Therefore, this lock mechanism can ensure a reliable and quick unlocking operation, and prevent flapping noises of the vane member 3 by preventing the first and second lock members from being unlocked erroneously by an air pressure. This lock mechanism can prevent an undesired hanging state in which the forward end portion of first lock member 30 is not disengaged from the lock recess 38 completely, but caught by lock recess 38 of second lock member 33.
FIGS. 7˜10 show a valve timing control apparatus according to a second embodiment of the present invention. In the second embodiment, second lock member 33 is arranged to move backwards against the spring force of second spring 34 by the effect of a centrifugal force, instead of the hydraulic pressure in retard chambers 18. The spring force of second spring 34 is set smaller than a centrifugal force of a predetermined magnitude produced in housing 5 during rotation. In this example, second spring 34 is so set that second spring 34 starts compression by the centrifugal force of housing 5 when the engine rotational speed becomes equal to or higher than an idle speed of about 900 rpm.
An air release passage 41 is formed in the circumferential wall of housing 5 of sprocket member 1. Air release passage 41 connects the annular pressure chamber 33 b with the outside, and thereby opens the inside of the annular pressure chamber 33 a to the atmosphere to allow free movement of second lock member 33 in second slide hole 32. Therefore, second lock member 33 can compress the second spring 34 and move smoothly backwards by receiving a centrifugal force of a predetermined magnitude or more during engine operation. In this embodiment, the communication passage 36 connecting the retard chamber 18 with the second slide hole 32 is eliminated.
When the centrifugal force of housing 5 is still weak after a start of the engine, the second lock member 33 is held projected forwards by second spring 34, and engaged with first lock member 30.
Thereafter, when the engine speed enters an idling operation of about 900 rpm, the centrifugal force of housing 5 increases, and forces the second lock member 33 backwards into second slide hole 32 by compressing the second spring 34 gradually as shown in FIG. 8. On the other hand, first lock member 30 is held at the forward limit position or most projected position by the force of first spring 31. Therefore, the forward end portion 30 a of first lock member 30 is still in the lock recess of 38 of second lock member 33, and the side surface of forward end portion 30 a of first lock member 30 abuts against the inner side surface of lock recess 38 of second lock member 33 with a reduced contact or abutting area. In this state (that is, the standby state), the first and second lock members 30 and 33 still engage with each other in the smaller contact area, and thereby prevents the vane member 3 from rotating relative to sprocket member 1. Moreover, the supply of hydraulic pressure to retard pressure chambers 18 is still continued, and hence the vane member 3 is held at the most retarded position shown in FIG. 8.
When the engine speed increases from the low speed low load region above 900 rpm to the medium speed medium load region, the directional control valve 23 is switched by controller 26 to the state to supply the hydraulic pressure to the advance chambers 17 instead of the retard chambers 18, so the hydraulic pressure in retard chamber 18 decreases and the hydraulic pressure in advance chambers 17 increases. Therefore, second lock member 33 is held at the backward limit position by the hydraulic pressure acting on the wall 37, and the first lock member 30 moves backwards into first slide hole 29 by the hydraulic pressure of the advance chambers 17 acting on the forward end portion 30 a.
Thus, first lock member 30 can disengage quickly from the standby state shown in FIG. 8, and allow the relative rotation of vane member 3. Therefore, vane member 3 rotates in the clockwise direction as viewed in FIG. 8 or the advance direction, from the most retarded position of FIG. 8, to an intermediate position shown in FIG. 9 or to the most advanced position shown in FIG. 10. Thus, camshaft 2 is rotated in the advance direction with respect to timing sprocket member 1, and the same effects as in the first embodiment can be obtained.
In this state, second lock member 33 receives the centrifugal force, and the hydraulic pressure in advance pressure chambers 17 at the forward end portion including wall 37. Therefore, second lock member 33 is retracted to the backward limit position as shown in FIGS. 9 and 10.
Thus, in the second embodiment, by utilizing the centrifugal force to move second lock member 33 backwards, the lock mechanism is simplified to the advantage of cost reduction.
FIGS. 11˜14 show a valve timing control apparatus or system according to a third embodiment of the present invention. In the third embodiment, the first and second movable lock members 30 and 33 are in the form of a pin. In this embodiment, the first and second lock members or lock pins 30 and 33 are identical in size and shape. Each of first and second lock pins 30 and 33 includes a flange or slide portion 30 c or 33 c formed integrally at the back end of the pin.
Slide holes 29 and 32 are formed so that the axes of slide holes 29 and 32 overlap each other in the circumferential direction of vane member 3. Each slide hole 29 or 32 includes a front small diameter section, a rear large diameter section, and a step shoulder surface 29 a or 32 a formed between the small and large diameter sections. The flange 30 c or 33 c of each lock pin 30 or 33 is slidably received in the rear large diameter section of the corresponding slide hole 29 or 32. The step shoulder surface 29 a or 32 a of each slide hole 29 or 32 faces backwards toward the bottom of the slide hole, and limits the forward movement of the corresponding lock member 30 or 33 by abutting against the flange 30 c or 33 c of the lock pin, thereby to determine the most projected position of the lock member.
First lock member 30 is moved backwards by the hydraulic pressure in advance chambers 17. When first lock member 30 is at the backward limit position or most retracted position, the forward end of first lock member 30 (which is substantially flat in this example) is flush with the outer surface in which first slide hole 29 is opened. This outer surface is substantially flat in this example. On the other hand, second lock member 33 is retracted backwards by the hydraulic pressure in the retard pressure chamber 18 introduced to the pressure chamber 33 b, and the hydraulic pressure in the advance chamber 17 acting on the forward end portion of second lock member 33, to the backward limit position or most retracted position determined by the abutment of second slide portion 33 c against spring retainer 40. In this backward limit position or most retracted position, the forward end portion of second lock member 33 projects slightly from the open end of second slide hole 32 as shown in FIGS. 13 and 14.
At the most retarded position as shown in FIG. 12, the forward portions of first and second lock pins 30 and 33 abut against each other, and thereby the first and second lock pins 30 and 33 prevent rotation of vane member 3 in the clockwise (advance) direction as viewed in FIG. 12. On the other hand, the vane 15 having the greatest circumferential width L3 abuts on the adjacent partition 10. Therefore, the vane member 3 is held at the most retarded position.
First and second springs 31 and 34 are set small relatively in diameter. A back end portion of first spring 31 is received in a spring retaining hole formed in the bottom of first slide hole 29. A back end portion of second spring 34 is received in a spring retaining hole formed in a spring retainer 40 defining the bottom of second slide hole 32. In the other respects, the third embodiment is substantially identical in construction to the first embodiment.
In an engine starting operation, the first lock pin 30 abuts against second lock pin 33 as shown in FIG. 11 and thereby prevents rotation of vane member 3. In an idling operation, the hydraulic pressure supplied from retard chambers 18 to the pressure chamber 33 b pushes second lock pin 33 to the backward limit position. However, the forward end portion of second lock pin 33 is still projected slightly. Therefore, the forward end portion of second lock pin 33 abuts against the first lock pin 30 with a smaller contact (or abutting) area (the standby state).
When the engine speed is further increased, and the engine operating point enters the low speed low load region, the solenoid valve 23 is switched to the state supplying the hydraulic pressure to advance chambers 17, and the pressure in advance chambers 17 become high. Therefore, as shown in FIG. 13, first lock pin 30 is retracted backwards in first slide hole 29 by the hydraulic pressure acting on the forward end of first lock pin 30, and thereby disengaged from second lock pin 33 held slightly projected at the backward limit position; and the vane member 3 is rotated in the advance (clockwise) direction by the hydraulic pressure in advance chambers 17. In a medium speed high load region, for example, the hydraulic pressure in advance chambers 17 is further increased, and the vane member 3 is held at the most advanced position at which the vane 15 having the greatest circumferential width L3 abuts on the adjacent partition 10 as shown in FIG. 14.
In the high speed high load region, the operating oil is drained from advance chambers 17 and the vane member 3 is rotated in the retard (counterclockwise) direction. However, immediately after this switching operation, the hydraulic pressure is supplied to retard chambers 18 and the hydraulic pressure in advance chambers 17 is not abruptly decreased. Therefore, first lock pin 30 is not projected so much, and second lock pin 33 is slightly retracted, so that the vane member 3 can rotate to the most retarded position without interference between first and second lock pins 30 and 33.
In the third embodiment, the first and second lock members 30 and 33 are identical to each other, so that the manufacturing cost can be reduced. The valve timing control apparatus according to the third embodiment can improve the fuel consumption and other engine performance as in the preceding embodiments.
FIGS. 15 and 16 show a valve timing control apparatus or system according to a fourth embodiment of the present invention. In the fourth embodiment, first and second lock members 30 and 33 are arranged in the axial direction instead of the radial direction.
An axial first slide hole 29 is formed in the vane 15 having a larger circumferential width. First slide hole 29 extends in the axial direction along the center axis of vane member 3. First slide hole 29 is a stepped hole having a larger section and a smaller section having a cross sectional size smaller than the cross sectional size of the larger section. An axial second slide hole 32 is formed in a thick wall portion of rear plate 7 of timing sprocket member 1 at a position confronting the first slide hole when vane member 3 is at a predetermined (most retarded) rotational position. Second slide hole 32 extends in the axial direction along the common center axis of vane member 3 and timing sprocket member 1. A back end of second slide hole 32 is closed by a spring retainer 40. Spring retainer 40 of this example is composed of two thin circular disks. Spring retainer 40 is fixed to rear plate 7 so as to form the bottom of second slide hole 32. An air release hole is formed approximately at the center of each disk of spring retainer 40 to ensure smooth movement of second lock member 33 in second slide hole 32.
First lock member 30 is a cup-shaped member including a cylindrical wall extending from a backward end to a forward end toward rear cover 7, and a forward end portion 30 a closing the forward end of the cylindrical wall. Second lock member 33 is a cup-shaped member including a cylindrical wall extending from a backward end to a forward end toward front cover 6, and a forward end portion closing the forward end of the cylindrical wall. First lock member 30 is slidably received in first slide hole 29 so that first lock member 30 can move forwards and backwards in the axial direction. Second lock member 33 is slidably received in second slide hole 32 so that second lock member 33 can move forwards and backwards in the axial direction.
The forward end portion 30 a of first lock member 30 is formed with a (lock) projection which is a cylindrical projection projected axially, in this example. First lock member 30 further includes an outward flange formed integrally at the backward end and arranged to abut on a step 29 c formed in first slide hole 29 to limit the forward movement of first lock member 30. In this example, first lock member 30 is arranged to receive the advance fluid pressure to move backwards.
The forward end portion of second lock member 33 is formed with a (lock) recess 38 in which the projection formed in forward end portion 30 a of first lock member 30 can be fit loosely. Recess 38 of FIG. 15 is axially depressed. The outside surface of cylindrical wall of second lock member 33 is stepped, and there is formed an annular step shoulder surface 33 b receiving the hydraulic pressure in an annular pressure chamber 32 a formed around second lock member 33. The pressure receiving area of the annular step shoulder surface 33 b is set at an appropriate value.
A groove 42 is formed in the front side surface of vane member 3 confronting front cover 6, as shown in FIG. 15. This groove 42 connects the inside of first slide hole 29 with the outside, and thereby ensures smooth movement of first lock member 30 in first slide hole 29 by releasing a back pressure of first lock member 30.
A communication passage 36 extends from one of retard chambers 18 to the annular pressure chamber 32 a to supply the hydraulic pressure from the retard chamber 18 to pressure chamber 32 a. The hydraulic pressure in the advance chambers 17 is introduced into the interspace between the forward end portion of second lock member 33 and the forward end portion 30 a of first lock member 30. In the other respects, the fourth embodiment is substantially identical to the first embodiment.
Therefore, the fourth embodiment can provide the same effects as the first embodiment. In an engine starting operation, the hydraulic pressure in annular pressure chamber 33 b is not increased yet, and the second lock member 33 is held engaged with first lock member 30. In an idling operation, the hydraulic pressure supplied in pressure chamber 33 b is increased, and second lock member 33 is retracted backwards to the backward limit position. In this state (that is, the standby state), the first and second lock members 30 and 33 engage with each other with a reduced contact (or abutting) area to prevent the relative rotation of vane member 3 relative to sprocket member 1.
When, for example, the engine speed is increased into the low speed low load region, the solenoid valve 23 is switched to the state supplying the hydraulic pressure to advance chambers 17, and the first lock member 30 is retracted by the hydraulic pressure in advance chambers 17 to the backward limit position against the force of first spring 31. Therefore, first lock member 30 disengages from second lock member 33, and vane member 3 is rotated in the advance (clockwise) direction by the hydraulic pressure in advance chambers 17. When the engine operating point is further shifted from the low speed low load region to the medium speed high load region, the hydraulic pressure in advance chambers 17 is further increased, and the vane member 3 is rotated to the most advance position.
Thus, the timing control system of the fourth embodiment can improve the engine performance sufficiently in accordance with the engine operating conditions. Furthermore, even if, in the engine starting operation, air is compressed and the air pressure in pressure chamber 32 a acts on second lock member 33 and moves second lock member 33 to the backward limit position, the first and second lock members 30 and 33 remain engaged with each other in the standby state, and prevent undesired noises due to flapping movement of vane member 3.
In the fourth embodiment, first and second lock members 30 and 33 are arranged axially along the axis of camshaft 2. Therefore, the lock mechanism receives no influence of the centrifugal force of housing 5, and the first and second lock members 30 and 33 can be moved only by the hydraulic pressures and the spring forces. Thus, the fifth embodiment can improve the control response to control the relative rotation between timing sprocket member 1 and camshaft 2.
FIGS. 17˜19 show a valve timing control apparatus or system according to a fifth embodiment of the present invention. In the fifth embodiment, first and second lock members 30 and 33 are arranged in the axial direction as in the fourth embodiment, and the second lock mechanism is simplified or eliminated unlike the fourth embodiment.
A fixed lock member or engaging member 44 is forcibly fit and fixed in a mounting hole 43 formed in a rear cover 7 at a position corresponding to the position of the second slide hole 32 of the fourth embodiment. Fixed lock member 44 is U-shaped in cross section as shown in FIG. 17. A fixed lock recess 38 is formed in fixed lock member 44. Fixed lock member 44 can serve as an abutting portion to abut against a movable lock member.
A movable lock member 30 is approximately identical in construction to the first lock member 30 of the fourth embodiment. The forward end portion 30 a of movable lock member 30 is tapered so that the outer circumferential surface is conical, and the cross sectional size become smaller toward the forward end. Movable lock member 30 is biased forwards toward the fixed lock recess 38 by a spring 31.
A pressure chamber 45 is formed between a step shoulder surface of a flange 30 b formed at the back end of movable lock member 30 and a step shoulder surface 29 c formed in a slide hole 29. The hydraulic pressure in one of the retard chambers 18 is introduced into this pressure chamber 45 by a first fluid (oil) passage 46 formed in the larger vane 15, as shown in FIG. 18.
The hydraulic pressure in one of the advance chambers 17 is introduced by a second fluid (oil) passage 47 formed in the larger vane 15, as shown in FIG. 18, into the interspace between the forward end portion of movable lock member 30 and the fixed lock recess 38.
The pressure chamber 45 is designed in the following manner. The pressure receiving area of the portion receiving the hydraulic pressure of the retard pressure chamber 18 is smaller than the pressure receiving are of the forward end portion of lock member 30 receiving the hydraulic pressure of the advance chamber 17; and the pressure force is slightly greater than the spring force of spring 31.
Therefore, in the thus-constructed system according to the fifth embodiment, the hydraulic pressure introduced from the retard chamber 18 into pressure chamber 45 is not increased so much in an engine starting operation, and therefore the movable lock member 30 is held engaged in lock recess 38 by spring 31. In an idling operation after the engine starting operation, the pressure in pressure chamber 45 becomes higher, and the movable lock member 30 moves backward. However, since the pressure receiving area in the pressure chamber 45 is set smaller as mentioned before, the movable lock member 30 does not reach the backward limit position, but the movable lock member 30 is retained at an intermediate position by the relationship between the hydraulic pressure in pressure chamber 45 and the spring force of spring 31. In this state (that is, the standby state) in which the movable lock member 30 is half or partly retracted, a part of the forward end portion 30 a of lock member 30 is still engaged in lock recess 38, so that lock member 30 is engaged in the fixed lock recess 38.
When the engine speed is increased into the low speed low load region, the solenoid valve 23 is switched to the state supplying the hydraulic pressure to advance chambers 17, and the movable lock member 30 is retracted, by the hydraulic pressure supplied from one of the advance chambers 17 to the interspace between forward end portion 30 a and lock recess 38, up to the backward limit position against the force of spring 31. Therefore, movable lock member 30 quickly disengages from lock recess 38, and vane member 3 is rotated in the advance (clockwise) direction by the hydraulic pressure in advance chambers 17. When the engine operating point is further shifted from the low speed low load region to the medium speed high load region, the hydraulic pressure in advance chambers 17 is further increased, and the vane member 3 is rotated to the most advanced position.
Thus, the timing control system of the fifth embodiment can improve the engine performance sufficiently in accordance with the engine operating conditions. Furthermore, even if, in the engine starting operation, air is compressed in retard chambers 18 and the air pressure acts in pressure chamber 45 and moves the lock member 30 backwards, the lock member 30 remains engaged with the lock recess 38 in the standby state, and prevents undesired noises due to flapping movement of vane member 3.
The present invention is not limited to the illustrated embodiments. Various variations and modifications are possible. For example, instead of the timing sprocket member 1, the driving rotary member may be a timing pulley driven through a timing belt of rubber. This arrangement is advantageous for reduction of vibrations and noises.
Moreover, the driving rotary member may be a gear member driven by a gear mechanism transmitting motion by a combination of two or more gears. In this case, the driving force can be transmitted securely. Furthermore, as the gear mechanism, it is possible to employ scissors gear to reduce backlash noises.
The valve timing control actuator may be a helical type VTC actuator, instead of the vane type VTC actuator. In the helical type, the relative rotational phase is shifted with axial movement of a tubular toothed member.
The valve timing control actuator may be electric or electromagnetic, instead of the hydraulic actuator. In this case, the relative rotational phase between the driving and driven members is altered by an electric device such as an electric motor or an electromagnetic brake.
It is sufficient to provide only one pair of the advance fluid pressure chamber and retard fluid pressure chamber. The number of pairs of the advance and retard chambers may be one, or may be two, three or four or more. When the number of pairs is increased especially in the case of the vane type VTC actuator, the pressure receiving areas are increased, and the response characteristic of the VTC actuator is improved.
It is not always necessary to dispose the first and second lock members in one of the advance and retard fluid pressure chambers. The first and second lock members may be placed at a position separate from the advance and retard chambers.
The first and second lock members may be placed at various portions of the driving and driven rotary members which are arranged to rotate relative to each other. The first and second lock members need not be placed between a member, such as a sprocket, driven directly by a crankshaft, and a member, such as a vane member, driving directly a camshaft. At least one of the first and second lock members may be mounted in a member (such as the above-mentioned tubular toothed member of the helical VTC actuator) interposed between the member directly driven by the crankshaft and the member directly driving the camshaft.
The first and second lock members may be shaped in various forms. Either or both of the first and second movable members may be in the form of a cylindrical pin, a polygonal pin polygonal in cross section, a ring-shaped member, or a plate-shaped member, or in the form of a lever.
Instead of the engagement between the (lock) recess 38 and the (lock) projection like tenon and mortise, it is possible to employ various forms for abutting portions of first and second lock members. When the relative rotation of the rotary mechanism of driving rotary member and driven rotary member is limited within a predetermined range, it is possible to arrange the first and second movable members to prevent the relative rotation between the driving and driven members only in one direction by abutment between the first and second movable members in the circumferential direction, and to prevent the relative rotation in the opposite direction by the rotary mechanism of the driving and driven members.
Instead of a coil spring, it is possible to employ, as at least one of the first and second bias members, a leaf spring or a disk spring. The directions of forward and backward movement of the first and second lock members are not limited to the radial direction and the axial direction. It is possible to employ various directions as the directions of the first and second movable members.
Instead of the tapered or conical surface around the recess 38, it is possible to employ various forms of the retracting portion for guiding the first and second lock member into engagement or into the lock state. For example, a tapered surface may be formed around the projection of one lock member to be engaged in the recess of the other lock member. Moreover, it is possible to form a tapered surface only in a part of the circumference of the recess 38. In this case, the lock member formed with the recess is arranged so that the rotation about its own axis is limited or prevented. Furthermore, it is possible to employ, as the retracting portion or retracting means, a mechanism using one or more links, or a cam mechanism or other shaped portion or device for moving at least one of the first and second lock members backwards by using a relative rotation between the driving and driven rotary members, or translating a relative rotation between the driving and driven rotary members into a linear motion of at least one of the first and second lock members.
This application is based on a prior Japanese Patent Application No. 2005-150320 filed on May 24, 2005. The entire contents of this Japanese Patent Application No. 2005-150320 are hereby incorporated by reference.
Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims.

Claims

1. A valve timing control apparatus for an internal combustion engine, comprising:

a driving rotary member adapted to be driven by the engine;

a driven rotary member arranged to rotate relative to the driving rotary member and adapted to rotate a camshaft of the engine;

a hydraulic control section to rotate the driven rotary member relative to the driving rotary member hydraulically; and

a lock mechanism arranged to be brought, in accordance with a hydraulic pressure supplied from the hydraulic control section, from a lock state to prevent relative rotation of the driven rotary member relative to the driving rotary member, to an unlock state to allow the relative rotation of the driven rotary member relative to the driving rotary member, through an standby state to prepare for the unlock state without allowing the relative rotation of the driven rotary member relative to the driving rotary member.

2. The valve timing control apparatus as claimed in claim 1,

wherein the driven rotary member is arranged to rotate relative to the driving rotary member in an advance direction when a fluid pressure is supplied to an advance pressure chamber, and in a retard direction when a fluid pressure is supplied to a retard pressure chamber;

wherein the hydraulic control section is configured to first supply the fluid pressure to a first chamber which is one of the advance and retard pressure chambers in an engine starting operation, and then to supply the fluid pressure to a second chamber which is the other of the advance and retard chambers; and

wherein the lock mechanism is arranged to shift from the lock state to the unlock state when the fluid pressure in the second chamber increases.

3. The valve timing control apparatus as claimed in claim 2, wherein the lock mechanism is held in the lock state in the engine starting operation, and shifted to the standby state before the lock mechanism is shifted to the unlock state with an increase of the fluid pressure in the second chamber.

4. The valve timing control apparatus as claimed in claim 2, wherein the lock mechanism is held in the lock state in the engine starting operation, and shifted to the standby state when an engine speed increases.

5. The valve timing control apparatus as claimed in claim 2, wherein the lock mechanism is allowed to shift from the lock state to the standby state by an increase in an air pressure in one of the advance and retard chambers, but prevented from being shifted to the unlock state by the air pressure.

6. The valve timing control apparatus as claimed in claim 2, wherein the lock mechanism is shifted from the lock state to the standby state in accordance with the fluid pressure in the first chamber.

7. The valve timing control apparatus as claimed in claim 2, wherein the lock mechanism includes a movable lock member arranged to move forwards when the fluid pressure in the second chamber is low, and to move backwards when the fluid pressure in the second chamber is increased; and an abutting portion arranged to abut against the movable lock member when the movable lock member is moved forwards and thereby to prevent the relative rotation of the driven rotary member relative to the driving rotary member; and an abutment area in which the movable lock member abuts on the abutting portion to prevent the relative rotation between the driving and driven rotary members is reduced when the lock mechanism is brought from the lock state to the standby state, but the abutting area remains greater than zero in the standby state.

8. The valve timing control apparatus as claimed in claim 7, wherein the lock mechanism further includes a bias member to bias the movable lock member forwards toward the abutting portion.

9. The valve timing control apparatus as claimed in claim 7, wherein a length of the abutment of the movable lock member against the abutting portion, as measured along an imaginary line along which the movable lock member moves forwards and backwards is reduced when the lock mechanism is brought from the lock state to the standby state.

10. The valve timing control apparatus as claimed in claim 9, wherein the movable lock member abuts against the abutting portion so that the abutting portion limits movement of the movable lock member in a direction substantially perpendicular to the imaginary line along which the movable lock member moves forwards and backwards.

11. The valve timing control apparatus as claimed in claim 9, wherein the length of the abutment of the movable lock member against the abutting portion is equal to or smaller than 1 mm when the lock mechanism is in the standby state.

12. The valve timing control apparatus as claimed in claim 9, wherein the length of the abutment of the movable lock member against the abutting portion is equal to or smaller than 0.2 mm when the lock mechanism is in the standby state.

13. The valve timing control apparatus as claimed in claim 7, wherein the abutting portion is stationary relative to a first rotary member which is one of the driving and driven rotary members, and the movable lock member is mounted in a second rotary member which is the other of the driving and driven rotary members.

14. The valve timing control apparatus as claimed in claim 7, wherein the abutting portion is a portion of a movable abutting member mounted movably in a first rotary member which is one of the driving and driven rotary members, and the movable lock member is mounted movably in a second rotary member which is the other of the driving and driven rotary members.

15. The valve timing control apparatus as claimed in claim 14, wherein the movable abutting member is arranged to move forwards toward the movable lock member and backwards away from the movable lock member; the lock mechanism is in the lock state when the movable lock member is projected forwards and the movable abutting member is projected forwards; the lock mechanism is in the unlock state when the movable lock member is retracted backwards and the movable abutting member is retracted backwards; and the lock mechanism is in the standby state when the movable lock member is projected forwards and the movable abutting member is retracted backwards.

16. The valve timing control apparatus as claimed in claim 15, wherein the lock mechanism further includes a second bias member to bias the movable abutting member forwards toward the movable lock member.

17. The valve timing control apparatus as claimed in claim 15, wherein the movable lock member is held in the standby state even if the movable abutting member is moved backwards to a backward limit position to which a backward movement of the movable abutting member is limited.

18. The valve timing control apparatus as claimed in claim 15, wherein the movable abutting member is moved backwards away from the movable lock member in accordance with the fluid pressure in the first chamber to which the fluid pressure is first supplied in the engine starting operation.

19. The valve timing control apparatus as claimed in claim 18, wherein the movable abutting member includes a step shoulder surface arranged to receive the fluid pressure in the first chamber and thereby to be retracted backwards away from the movable lock member in accordance with the fluid pressure in the first chamber.

20. The valve timing control apparatus as claimed in claim 7, wherein the abutting portion includes a lock recess arranged to receive a forward end portion of the movable lock member.

21. The valve timing control apparatus as claimed in claim 2, wherein the driven rotary member includes a vane projecting radially outwards and separating the advance fluid pressure chamber and the retard fluid pressure chamber; and the driving rotary member enclosing the driven rotary member and defining the advance and retard fluid pressure chambers between the driving rotary member and the driven rotary member.

22. The valve timing control apparatus as claimed in claim 7, wherein the movable lock member is arranged to move radially around an axis of the driven rotary member.

23. The valve timing control apparatus as claimed in claim 7, wherein the movable lock member is arranged to move axially along an axis of the driven rotary member.

24. The valve timing control apparatus as claimed in claim 7, wherein the lock mechanism includes a retracting section to guide the movable lock member and the abutting portion into the lock state by retracting at least one of the movable lock member and the abutting portion.

25. The valve timing control apparatus as claimed in claim 24, wherein the retracting section includes a tapered surface formed in one of the movable lock member and the abutting portion.

26. The valve timing control apparatus as claimed in claim 2, wherein the hydraulic control section includes a control valve to control the fluid pressures in the advance and retard pressure chambers; and a controller to control the control valve to first supply the fluid pressure to the first chamber which is one of the advance and retard pressure chambers at the time of a start of the engine, and then to supply the fluid pressure to the second chamber which is the other of the advance and retard chambers.

27. An internal combustion engine comprising:

a crankshaft;

a camshaft;

a valve timing control rotary mechanism including,

a driving rotary member driven by the crankshaft of the engine, and

a driven rotary member) which is arranged to be driven by the driving rotary member and to drive the camshaft, and which is arranged to rotate relative to the driving rotary member to alter a rotational position of the driven rotary member relative to the driving rotary member;

a hydraulic section to rotate the driven rotary member relative to the driving rotary member in an advance direction by an advance fluid pressure in an advance pressure chamber and in a retard direction by a retard fluid pressure in a retard pressure chamber;

a control section to control the hydraulic section to supply a fluid pressure selectively to the advance pressure chamber or the retard pressure chamber in accordance with an engine operating condition, and to perform an engine starting operation by first supplying the fluid pressure to a first chamber which is one of the advance and retard pressure chambers, and then supplying the fluid pressure a second chamber which is the other of the advance and retard pressure chambers; and

a lock mechanism arranged to prevent relative rotation of the driven rotary member relative to the driving rotary member when the lock mechanism is in a lock state, and to allow the relative rotation of the driven rotary member when in an unlock state, the lock mechanism being set in the lock state at a time of an engine start and then brought to the unlock state in accordance with the fluid pressure in the second chamber after the engine start,

the lock mechanism being further arranged to be set, before the unlock state is reached, to a standby state preparing for the unlock state while preventing the relative rotation of the driven rotary member relative to the driving rotary member.