WO1998003778A1

WO1998003778A1 - Valve drive system and cylinder head for an internal combustion engine

Info

Publication number: WO1998003778A1
Application number: PCT/DE1997/001514
Authority: WO
Inventors: Dieter Reitz
Original assignee: Dieter Reitz
Priority date: 1996-07-20
Filing date: 1997-07-18
Publication date: 1998-01-29
Also published as: DE19780736D2; EP0914546A1; EP0914546B1; DE59703557D1; DE19640520A1

Abstract

The invention concerns a valve drive system for an internal combustion engine, the valve drive system being provided between its at least one lifting valve (12) and its camshaft (34) in order to control the variable lift sequence. The valve drive system comprises a pressure-transmission arrangement which presses against the lifting valve (12), and a contact member (35) which abuts a cam (16) on the camshaft (34) and, as it changes position owing to the rotation of the cam (16), brings about an oscillating movement of the pressure-transmission arrangement. The pressure-transmission arrangement has a contact surface (80) via which pressure is transmitted. The contact surface (80), which can pivot about the bearing axis (14), comprises a first surface region (80.1) which has a circular-cylindrical curvature having the bearing axis (14) as the longitudinal axis of the cylinder, and a second surface region (80.2) which adjoins the first surface region (80.1) and has a non-circular-cylindrical curvature.

Description

DESCRIPTION

Valve train and cylinder head of an internal combustion engine

TECHNICAL AREA

The invention relates to a valve train and a cylinder head of an internal combustion engine equipped with such a valve train. The valve train is present between its at least one stroke valve and its camshaft for controlling the variable stroke course.

STATE OF THE ART

Such a generic valve drive is known from EP-Al 0 638 706, with which a valve stroke profile can be variably adjusted with regard to stroke size and stroke duration. The valve train has a rocker arm, which is suspended from a pin in a pendulous manner. The bolt is mounted in an elongated hole of the rocker arm and can press against the outside of the rocker arm by means of an outside

Eccentric take different positions. As a result, the position of the rocker arm's pendulum axis differs depending on the position of the bolt within the elongated hole. The rocker arm carries a roller that presses against a camshaft. By means of its contact surface which is curved on its underside, the rocker arm presses on a further rocker arm, referred to as a rocker arm, which in turn has a pressing effect on the lift valve. The contact surface area of the rocker arm that acts on the rocker arm and thus indirectly on the lift valve comprises a different outer surface area of the rocker arm, depending on the position of the bolt within the elongated hole and thus in dependence on the respective self-aligning bearing. When adjusting the Self-aligning bearings can variably design both the maximum lifting height and the opening time of the lifting valve, to the extent that when the maximum lifting size is increased, the opening time also increases. The phase position of the maximum stroke remains approximately constant.

The elongated hole pin bearing of the rocker arm has a disadvantageous effect. A play of the bolt in the slot cannot be avoided for reasons of assembly. This game increases when the internal combustion engine is operating due to material wear in the area of line contact between the elongated hole and the bolt. In connection with the tolerances of the curved contact surface on the underside of the rocker arm, this can lead to a lifting movement of the valve even when the cam with its cam base circle takes effect. In conjunction with the hydraulic valve lash adjuster installed in the rocker arm, an undesired stroke movement in the upper resting point of the stroke valve may only be a few hundredths of a millimeter, since otherwise the hydraulic element may be inflated. The latter would have the consequence that the lift valve, for example the inlet valve, can no longer be closed completely.

From DE-Al 43 42 806 a valve train is known in which two rocker arms are positioned between the camshaft and the lift valve. The rocker arms which engage in the space between the camshaft and the valve train from opposite directions are adjustable around the camshaft. In this valve train, the valve stroke curve changes in such a way that the stroke time is always changed at the same time as the maximum stroke height, namely in the same way, that is, the stroke height and stroke duration are simultaneously increased or decreased. The valve train known from DE-Al 43 22 480 requires two camshafts to adjust the valve lift of a valve. Depending on the mutual alignment of the relevant cams of the two camshafts, the swivel path of a swivel lever pressing against the valve can be designed to be variable in order to adjust the valve lift and the opening time of the valve at the same time.

From DE-Al 29 51 361 a valve train is known, with which the valve lift course of a lift valve can only be adjusted in size. The valve train has two swivel levers which engage in the space between the camshaft and the valve from opposite directions. The swivel levers are arranged one above the other. While one swivel lever is rotatably mounted, the other swivel lever is designed with its axis of rotation so as to be longitudinally displaceable. This longitudinally displaceable training requires a great deal of design effort. The cylinder is also pierced laterally by the necessary construction elements. Apart from this, the space required in addition to the cylinder head is hardly available in today's engine compartments. Finally, the practically existing point contact between the longitudinally displaceable swivel lever and the valve stem is unsuitable for large-scale use.

In the valve train known from DE-C2 33 32 699, a flat tappet which scans the cam of the camshaft is pivoted about the camshaft axis by means of its guide. As a result, the control times are changed, the valve lift changes only insignificantly. PRESENTATION OF THE INVENTION

On the basis of this prior art, the object of the invention is to provide a valve train which enables the valve lift course and the valve opening duration to be adjusted in a structurally satisfactory manner and with which the most compact possible cylinder head can be designed.

This invention is given for a valve train by the features of claim 1 and for a corresponding cylinder head by the features of claim 20.

Starting from the prior art known from EP-AI 0 638 706 mentioned at the outset, the valve train according to the invention is distinguished by the use of a contact surface of its pressure transmission device which has a first surface area and an adjoining second different surface area which is arranged in this way and are designed such that a lifting movement of the lifting valve can be set only by means of the second, not by means of the first, surface area.

The first surface area can have a circular-cylindrical curvature, with the bearing axis as the cylinder longitudinal axis, and the second surface area can have a non-circular-cylindrical curvature that deviates therefrom. As long as the pressure transmission device acts on the lift valve with its first surface area, that is to say with its circular-cylindrical contact surface, a pivoting movement of the pressure transmission device caused by scanning the rotating camshaft cam and thus the contact surface around this bearing axis does not cause any stroke movement the lift valve, such as in particular an intake valve; namely, the contact surface rolls on a non-moving contact surface of the lift valve. Only when the pressure transmission device is deflected to a greater extent, that is to say pivoted, and with the adjoining contact surface region, which is no longer curved in the shape of a circular cylinder, lies against the contact surface of the lift valve can a lift movement of the valve be generated. Depending on the orientation of the contact surface to the contact surface of the globe valve, that is, depending on the "zero position" of the contact surface and thus the pressure transmission device, the opening of a valve can be delayed. In addition, the valve can also be closed earlier.

According to an essential further development of this embodiment of the invention, the curved contact surface is followed by a third surface area, which likewise has a circular cylindrical curvature, and also with the bearing axis as the longitudinal axis of the cylinder, about which the pressure transmission device or its contact surface pivots. This third surface area preferably has a radius that is larger than the radius of the above-mentioned first surface area

The contact surface of the pressure transmission device, which presses against the lifting valve, can also be slowly displaceable along an axis of movement. The first surface area can then have a flat surface running parallel to the movement axis and the second surface area can have a different surface, at least not running parallel to the movement axis. As long as this contact surface with its first surface area, that is, with its plane, to the axis of movement acts parallel contact surface on the lift valve, causes a caused by scanning the rotating camshaft cam in the axis of motion oscillating movement of the pressure transmission device and thus the contact surface in turn no stroke movement of the lift valve, such as in particular an intake valve; namely, the contact surface slides on a non-moving contact surface of the globe valve. A stroke movement of the valve can only be generated when the pressure transmission device experiences a larger stroke in the axis of movement and thereby with the adjoining second surface area, which is no longer arranged parallel to the axis of movement and does not need to be even, on the contact surface of the stroke valve . Here too, the phase position of the maximum stroke can be adjusted forwards or backwards depending on the arrangement of the adjusting shaft and the direction of rotation of the camshaft. These adjustment options do not require an additional phase adjuster on the camshaft.

After an essential further development of this embodiment of the invention, the second surface area is followed by a third surface area, which in turn is flat and parallel to the movement axis. This third surface area can be closer to the inlet valve than the first surface area named above.

As soon as the contact surface with its third surface area acts on the lift valve, the correspondingly wide-open lift valve can be left in this lift position; the contact surface rolls or slides on its contact surface with the lift valve without causing an additional positive or negative lift movement of the valve. The valve can therefore remain in its preferably maximum open position over a certain period of time. Due to the fact that a phase adjustment to enable a changed opening or closing time of the lift valve in the valve drive according to the invention is not necessary, the camshaft can be driven at an unchanged constant speed. This makes it possible to provide a single camshaft for controlling both the intake and exhaust valves of an engine of an internal combustion engine. For this purpose, space is freed up above the cylinder head of this engine, in which the valve train with its pressure transmission devices can be placed. The space required above a cylinder head is practically not larger when the valve train according to the invention is arranged, so that a very slim cylinder head can be constructed.

The cylinder head of an internal combustion engine designed in accordance with the invention is characterized in that a first valve train is present between the single camshaft and the at least one exhaust valve, and that a second valve train, the aforementioned inventive valve train, is present between this single camshaft and the at least one intake valve. In addition, a valve train according to the invention can also be used for the outlet valve. This second valve train has the above-mentioned pressure transmission device, which carries out an oscillating movement with its contact surface.

The position of the reversal points of the oscillating contact surface can be brought about both by changing the position of a body scanning the contour of a camshaft cam and by an adjusting device additionally acting on the pressure transmission device. As a result, depending on the reversal effects caused by the adjusting device, points of the contact surface, whose different surface areas are optionally available for the pressure transmission caused by turning the cam.

In such a cylinder head, the camshaft and adjusting shaft can be present at approximately the same height above the valves with their essential components. It is also possible to arrange the adjustment shaft between the valves below the camshaft.

Further features and advantages of the invention can be found in the features further specified in the claims and in the exemplary embodiments below.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the drawing. Show it:

Fig. 1 shows a cross section through a cylinder head

Internal combustion engine with a first embodiment of a valve train according to the invention,

Fig. 2 shows a cross section through a cylinder head

Internal combustion engine with a second embodiment of a valve train for the simultaneous actuation of the existing intake and exhaust valves,

3 shows a schematic representation of the contour of a contact surface which presses on an inlet valve, of a pressure transmission device present in the valve train, Fig. 4 shows a cross section through a cylinder head

Internal combustion engine with a third embodiment of a valve train according to the invention, in a first position of the adjusting shaft,

5 shows a section through the cylinder head according to FIG. 4, with a second position of the adjusting shaft,

Fig. 6 is a diagram with several valve lift profiles.

WAYS OF CARRYING OUT THE INVENTION

A section of a cylinder head 10 with an intake valve 12 is shown in FIG. 1 of an internal combustion engine. Above the cylinder head 10 and thus also above the intake valve 12, there is an overhead camshaft 34, from which its axis 14 and one of several cams, an intake cam 16 serving to actuate the intake valve 12, can be seen.

On the cam 16, a roller 35 is rotatably attached, which is needle-supported in the present case. The axis of rotation 36 of the roller 35 is parallel to the axis 14 of the camshaft 34 and parallel to a further shaft 30. This shaft 30 can be moved back and forth on a circumferential circle 31 with the radius R2 around the center point M (axis 14). For this purpose, the shaft 30 is fastened on a swivel element 32. This swivel element 32 can also be adjusted in a corresponding circular arc about the axis 14 with a constant radius.

The pivoting element 32 is adjusted relative to the respective rotational alignment of the camshaft 34 by means of a gearwheel 54 fastened on an adjusting shaft 56, which is connected to a toothing 52 present on the swivel element 32 is in meshing engagement. The gear 54 is fixed on the adjusting shaft 56 in a rotationally fixed manner. By turning the adjusting shaft 56 and thus the gear 54, this becomes

Swivel element 32 is adjusted relative to camshaft 34 in one or the other direction of rotation.

On the shaft 30, which is fastened to the swivel element 32, a swivel lever 74 is rotatably mounted, which carries the roller 35 at its upper end in FIG. 1, which abuts the inlet cam 16.

At the lower end in FIG. 1, one end of a push rod 76 presses against the pivot lever 74. The other end of this push rod 76 presses against a pivot element 78 encompassing the camshaft 34 in an annular manner. The pivot element 78 is fastened to the camshaft 34 in a relatively rotatable manner. When the camshaft 34 rotates and the inlet cam 16 rotates accordingly, the pivot lever 74 is pivoted about the shaft 30 by the roller 35, depending on whether the cam 16 with its cam base circle 16.1 or its cam elevation 16.2 is in the region of the roller 35. Accordingly, the push rod 76 presses more or less against the swivel rod 78. Rotating the inlet cam 16, for example counterclockwise, will therefore push the push rod 76 to the right, as shown in FIG. 1, and thus also the swivel element 78, likewise counterclockwise, about the axis 14 (center point M) swivel.

The inlet valve 12 is trimmed underside of the pivot ^¬ elements 78 has a specially shaped contact surface 80th This contact surface 80 presses on a roller 82 which is rotatably held on a further rocker arm 84. This lower rocker arm 84 abuts a contact surface 22 of the inlet valve 12 from above. This rocker arm 84 is pivotally mounted on a hydraulic bolt 23. Depending on how far the roller 82 is pressed from above, the valve plate 40 of the valve 12 is moved more or less far from the valve seat 42 and the inlet channel 44 is thereby opened to different lengths and lengths.

The contact surface 80 of the swivel element 78 has a first surface area 80.1, which has a circular-cylindrical curvature with the camshaft axis 14 as the longitudinal axis of the cylinder. The radius of this cylindrical curvature has the constant dimension R1 (see also FIG. 3). This surface area 80.1 is followed by a further surface area 80.2 on the contact surface 80, which has an alternating distance from the axis 14. This second surface area 80.2 is followed by a third surface area 80.3, which again has a circular-cylindrical curvature, with the camshaft axis 14 as the cylinder longitudinal axis. The radius of this third surface area 80.3 has the constant dimension R3. R3 is larger than Rl of the first surface area 80.1.

If the contact surface 80 rolls on the roller 82 in the area of the first surface area 80.1 and the third surface area 80.3, during the rolling movement within these two partial areas 80.1 and 80.3, no relative adjustment of the valve plate 40 with respect to its valve seat 42 and thus no change in the stroke position of the Inlet valve 12. Only within the central surface area 80.2 does rotation of the pivot element 78 and thus pivoting of the contact surface 80 change the stroke position of the inlet valve 12. This effect can be used in different ways. In the closed position of the inlet valve 12 shown in FIG. 1, the roller 82 is not in the area

80.1 of the contact surface 80. However, the roller 35 abutting the inlet cam 16 is still in the region of the

Cam base circle 16.1. When the camshaft 34 is rotated counterclockwise and thus also when the inlet cam 16 is rotated counterclockwise, the roller 35 will roll for a while in the area of the cam base circle 16 1 of the E cam cam 16. Only when the roller 35 comes into the area of the cam elevation 16.2 from the inlet cam 16 is the pivot lever 74 pivoted counterclockwise about the shaft 30, and thus also the pivot element 78 with the contact surface 80 is pivoted counterclockwise gcrs n via the push rod 76. Then the different, increasingly larger distances from the axis 14 having the second surface area 80.2 come into contact with the roller 82 of the lower rocker arm 84 one after the other. As a result, the inlet valve 12 is opened ever further in succession. The opening of the inlet valve 12 begins with a delay only at the point in time when the inlet cam 16 with its cam elevation

16.2 has reached the area of the roller 35.

If the pivoting element 78 is pivoted so far counterclockwise that the third surface area 80.3 comes into contact with the roller 82, the then respectively open position of the inlet valve 12 is not changed; pivoting the swivel element 78 to the swivel area in which the third surface area 30.3 is in contact with the roller 82 does not cause a change in the stroke position of the inlet valve 12 because of the -> - cylindrical curvature of this third surface area 12. The opened inlet valve 12 therefore becomes its open position maintained as long as the third surface area 80.3 in Is in contact with the roller 82. In this way, a maximally opened inlet valve 12 can be kept open uniformly over a predetermined period of time. It is only when the pivoting element 78 is pivoted back in a clockwise direction that a

Rolling of the roller 35 from the cam elevation 16.2 in the direction of the cam base circle 16.1 is the cause, the inlet valve 12 can move back into its closed position in FIG. 1.

The swivel element 32, which is not shown in more detail, can be held on a component comprising the camshaft 34, for example. The adjusting shaft 56, which enables the pivoting element 32 to pivot relative to the alignment of the camshaft 34, can be rotated in the usual way.

Instead of the roller 35, the pivot lever 74 can also bear against the camshaft 34 with a correspondingly shaped sliding surface. In addition, the contact surface 80 can also rest against a bucket tappet provided, for example, for hydraulic play compensation of an inlet valve.

2 shows a cylinder head 10.2, each with an intake valve 12.2 and an exhaust valve 13.2. A rocker arm 84 lies on the inlet valve 12.2, as has already been described above in connection with FIG. 1 for the inlet valve 12 there. The roller 82 present on the rocker arm 84 bears from below on the contact surface 80, which in turn has three surface areas 80.1, 80.2 and 80.3. These three surface areas are arranged from left to right in FIG. 2, while they are arranged from right to left in FIG. 1. The contact surface 80 is part of a swivel element 78.2 which surrounds an adjusting shaft 56.2 in a ring shape, rotatable relative to the same. A pressure spring 92 presses against an extension 90 of this swivel element 78.2 from below, which is supported with its lower end on the cylinder head 10.2. The

Compression spring 92 thus wants to rotate the swivel element 78.2 counterclockwise around the adjusting shaft 56.2.

On the adjusting shaft 56.2 there is a swivel lever 94 which projects in a threatening manner and which in the present example protrudes obliquely into the area between the two valves 12.2 and 13.2. At the free end of this pivot lever 94, a rocking lever 96 is rotatably held. At the free end 98 of the rocker arm 96, the roller 35, which abuts the inlet cam 16, is rotatably supported on the one hand, and the one end of a push rod 76.2 is supported on the one hand. The other end of this push rod 76.2 presses against the swivel element 78.2. The push rod 76.2 thus presses clockwise against the swivel element 78.2. When the roller 35 rolls along the circumference of the inlet cam 16, when the inlet cam 16 is rotated clockwise, the roller 35 becomes, when it comes into contact with the cam elevation 16.2, the push rod 76.2 to the right and thus the pivoting element 78.2 in a clockwise direction about the axis 100 the adjustment shaft 56.2 rotated. Thus, with correspondingly further adjustment of the push rod 76.2 to the right, the surface areas 80.1, 80.2 and possibly 80.3 come into contact with the roller 82, as has already been described above in connection with FIG. 1. In this way, the inlet valve 12.2 can be adjusted as well as the inlet valve 12 described in connection with FIG. 1. In addition, an exhaust cam 116 is also present on the only camshaft whose camshaft axis 14 is drawn. This exhaust cam 116 abuts on a rocker arm 184 via a roller 182 which in turn presses against the exhaust valve 13.2. This control of the exhaust valve 13 2 by means of the exhaust cam 116 is known

It is important in the present case, however, that the intake and exhaust valves 12.2, 13.2 arranged in the cylinder head 10.2 are controlled by a single camshaft, while the exhaust valve 13.2 is controlled in a manner known per se by the camshaft (camshaft axis 14) positioned above this exhaust valve 13.2 is used, the same camshaft is also used to control the opposite inlet valve 12.2. The valve train required for this is arranged in the area above the two valves 12.2, 13 2 and next to this camshaft. The cylinder head

10.2 can thereby build very slim upwards. This is also possible, in particular, in that a phase adjustment of the inlet valve 12.2 is not necessary to change the opening or opening end, since this can be brought about by the adjusting shaft 56.2, which is positioned instead of a second camshaft Such a cylinder head can therefore be built extremely compact. Nevertheless, the intake valves can be actuated variably in terms of stroke amplitude and opening duration via mechanical transmission elements. Also related to the surface area

80.3 of the contact surface 80 a constant opening position of the inlet valve is possible. The components of the valve train are short and compact, so that a natural vibration behavior of the parts can practically not occur. The contact surface 80 is shown enlarged again in FIG. 3. In a first surface area 80.1 there is a circular cylindrical surface with a constant radius R1. The surface area 80.1 is followed by a second surface area 80.2, the distance from the center M of which increases. The third surface area 80.3 is in turn followed by a circular cylindrical surface with a constant radius R3. In the area of the transition arch, which is present between the two cylindrical surface areas 80.1 and 80.3, there is a different distance from the center point M. As long as the circular cylindrical surface areas 80.1 and 80.3 roll on the roller 82 (FIGS. 1, 2), there is no relative adjustment of the lift valve 12 or 12.2. An adjustment of the inlet valve 12 or 12.2 takes place only in the contact area of the transition bend, the middle surface area 80.2, as is described in more detail above in connection with FIGS. 1 and 2.

There is the possibility of valve shutdown by the roller 82 only running in the area 80.1 of the contact surface 80 per work cycle.

The pivoting of the swivel elements 32, 94 not only serves to change the stroke maximum and opening duration, but also changes the phase position of the respective stroke maximum relative to the camshaft / crankshaft, so that particularly favorable motorized components are used, with a suitable design of the components and corresponding direction of rotation of the camshaft may be operating points for fuel consumption and exhaust emissions Darge ^¬ provides no additional twisting of the intake camshaft. A cylinder head 210 of an internal combustion engine is shown in FIG. 4 with an intake valve 212 and an exhaust valve 213. Above the cylinder head 210 and thus also above the valves there is an overhead camshaft 215, of which a cam 216 serving to control the intake valve 212 can be seen and which rotates about its axis 217 during engine operation.

The cam 216 is scanned by a roller 221. The roller 221 is rotatably mounted on a pin 222 by means of needles and transmits the cam stroke to the rocker arm 220. The rocker arm 220 oscillates about the axis 223 of a pin 224. With its contact surface 225, the rocker arm 220 is pressed against the rounded end face 231 of the plunger 230 and sets it in an oscillating motion according to the cam stroke. The plunger 230 has the shape of a cylinder and is mounted so that it can move longitudinally in a bore in the frame 265. The tappet mass is reduced by a cutout 232. The plunger 230 has a recess at its end opposite the end face 231, as a result of which the contact surface 238 is formed, against which a further needle-bearing roller 241 bears. This contact area is divided into three surface areas. The first surface area 235 is flat and runs parallel to the ram longitudinal axis 233, which also represents the axis of movement. The second surface area 236 has an arbitrary contour, which, however, is not at the same time plane and runs parallel to the plunger axis 233 and opens in the direction of the plunger axis 233 into the first surface area 235 and the third surface area 237. The third surface area 237 in turn runs flat and parallel to Tappet axis 233, being closer to the inlet valve than the first surface area 235. Depending on the stroke position of the ice cream 230, the roller 241 alternately presses against the surface areas 235, 236 and 237. The roller 241 transmits the valve actuation force to the rocker arm 240 via a pin 242, which, in a known manner, is supported on a hydraulic pin 248 and at its other end presses on the valve stem end of the inlet valve 212 via a contour 245.

If the roller 241 runs on the surface areas 235 or 237, the tappet 230 does not experience any restoring force through the valve spring 214 of the inlet valve 212. Therefore, the return spring 250 is required, which acts on the tappet 230 via a riveted spring plate 251 and this, the rocking lever 220 with its roller 221 and the cams 216 constantly in printing contact. The return spring 250 is supported in the cylinder head 2 L0 by a screwed-in cover 218.

The adjusting shaft 260 is rotatably mounted in the frame 265 and the bearing cover 266 parallel to the camshaft 215. A cranked lever 262 is non-rotatably connected at its broad end to the adjusting shaft 260 by a pin - this lever end does not lie in the plane of the drawing and is partially shown in the opening. The lever 262 rotatably supports the pin 224 at its narrow end. The pin axis 223 is the axis of rotation of the pivot lever 220 and can simultaneously be pivoted about its axis 261 by rotating the adjusting shaft 260.

By rotating the adjusting shaft 260 counterclockwise from the position shown in FIG. 4, the position shown in FIG. 5 can be reached in extreme cases. The phase position of the maximum stroke on the swivel lever 220 changes. Assuming constant rotation of the camshaft 215 counterclockwise, the stroke maximum occurs earlier in the position of the adjusting shaft according to FIG. 5 than in the position shown in FIG. 4. In the present case, the contact surface 225 of the rocker arm 220 is designed so that during the adjustment of the adjusting shaft 260, the plunger 230 moves more and more towards the camshaft 215 in its respective rest position between the stroke events with simultaneous early adjustment of the maximum stroke. This effect and the changed lever ratio on the rocker arm 220 cause the plunger 230 in the arrangement according to FIG. 5 to perform a shortened stroke at an early stroke maximum, and the roller 241 only on the surface area because of the rest position of the plunger 230 toward the camshaft 215 235 rolls back and forth so that there is no lifting movement at the inlet valve 212.

In the arrangement according to FIG. 4, the roller 241 reaches the surface area 236 after a very slight stroke movement of the tappet 230, so that a stroke movement of the inlet valve 212 takes place, and finally the surface area 237, the valve remaining at the maximum stroke height.

At the intermediate positions of the adjusting shaft 260, the roller 241 alternately passes through the surface regions 235 and 236 in such a way that different portions of the stroke movement of the tappet 230 on the non-valve-opening surface region 235 or on the valve-opening surface region 236 are eliminated. Therefore, twisting the adjusting shaft 260 along with the change in the valve opening and closing times causes a continuous change in the stroke amplitude and the opening duration of the intake valve 212. 6 shows an example of a family of valve lift curves as can be generated by means of the valve drive shown in FIGS. 4 and 5 with the camshaft rotating to the left. In this case, the valve opens at an almost constant phase position, while the stroke amplitude increases continuously with the opening time. When the surface area 237 is reached by the roller 241, the stroke amplitude remains constant, while the opening duration continues to increase. This corresponds to an extension of the stroke curve, as can be seen on the curve with a stroke amplitude of 10 millimeters.

The outlet valve 213 is actuated via a rocker arm 270 known per se. It is rotatably mounted on a shaft 275 and transmits its movement via a hydraulic valve lash adjuster 274 to the exhaust valve 213. The cam is scanned by a needle-bearing roller 271 and a bearing pin 272. With a left-rotating camshaft 215 and corresponding valve timing, the roller 271 can also den otherwise scan the cam 216 of the camshaft 215 assigned to the intake valve. In other cases, it is possible to provide an additional exhaust cam on the camshaft 215 to the side of the intake cam 216 and to arrange the roller 271 laterally offset on the rocker arm 270.

If the arrangement of the adjusting shaft 260 aimed below the cam shaft 215, so it is possible the adjustment ^¬ shaft 260 and to execute the shaft 275 integral with a common axis.

Claims

EXPECTATIONS

01) valve train of an internal combustion engine which is present between its at least one lift valve (12, 212) and its camshaft (34, 215) for controlling the variable stroke profile,

with a pressure transmission device that is adjustable transversely to the camshaft axis and presses against the lift valve (12, 212),

- With a contact body (35, 221) which bears against a cam (16, 216) of the camshaft (34, 215) and which, when the position is changed by rotating the cam (16, 216), causes an oscillating movement of the pressure transmission device ,

- The pressure transmission device has a contact surface (80, 238) via which the pressure transmission takes place, so that the contact surface (80, 238) has at least one

- a first surface area (80.1, 235), which is arranged and designed in such a way that no stroke movement of the lift valve occurs during the oscillating movement of the pressure transmission device, - a second surface area (80.2, 236), which is attached to the first surface area ( 80.1, 235) and which is arranged and designed such that a lifting movement of the lifting valve occurs during the oscillating movement of the pressure transmission device. 02) valve train according to claim 1, characterized in that

the contact surface (80) can be pivoted about a bearing axis (14, 100) aligned parallel to the camshaft axis (14),

- The first surface area (80.1) has a circular, cylindrical curvature, with the bearing axis (14, 100) as the longitudinal axis of the cylinder,

- The second surface area (80.2) has a non-circular cylindrical curvature.

03) Valve train according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that

- The contact surface (80) has a third surface area (80.3), which is also a circular cylindrical

Has curvature, also with the bearing axis (14, 100) as the longitudinal axis of the cylinder, wherein

- The radius (R3) of this third surface area (80.3) is larger than the radius (Rl) of the first surface area (80.1).

04) valve drive according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that

- The pressure transmission device contains - a swivel element (78) having the contact surface (80),

- Pressure transmission members (74, 76; 76.2, 96, 94), on the one hand, the pressure transmission between the body (35) resting on the cam (16) and the swivel element (78) can be produced, and on the other hand, the pivoting of the swivel element (78) about the bearing axis (14, 100) can be produced. 05) valve train according to claim 4, characterized in that

the bearing axis is the camshaft axis (14), so that the pivoting element (78) can be pivoted about the camshaft (34),

- A pivoting lever (74) which can be pivoted about another shaft (30), with one end region pressing against the pivoting element (78) having the contact surface (80), and at the other end region of the body (35) bearing against the cam (16) is attached

- The shaft (30) is adjustable concentrically to the camshaft (34), namely along the circumference of a circle (31) with the radius (R2), the center of which is the axis of rotation (14) of the camshaft (34).

06) valve train according to claim 5, d a d u r c h g e k e n n z e i c h n e t that

- A push rod (76) between the pivot lever (74) and the pivot element (78) is present.

07) Valve drive according to claim 5 or 6, d a d u r c h g e k e n n z e i c h n e t that

- An adjusting device for the pivot lever 74 is available, with which its orientation to the camshaft axis can be changed.

08) Valve train according to claim 7, d a d u r c h g e k e n n z e i c h n e t that

an arbitrarily rotatable adjusting shaft (56) with parallel alignment is provided next to and at a distance from the camshaft (34),

- There is a transmission connection between the adjusting shaft (56) and the pivot lever (74). 09) valve train according to one of the preceding claims, characterized in that

- The bearing axis (100) is the axis of rotation of an arbitrarily rotatable adjusting shaft (56.2) aligned parallel and at a distance from the camshaft axis (14),

- The swivel element (78.2) having the contact surface (80) surrounds the adjusting shaft (56.2) in a ring and is pivotably mounted to the adjusting shaft (56.2),

- The body (35) resting on the cam (16) is supported on the one hand on the adjusting shaft (56.2), on the other hand presses against the swivel element (78.2).

10) valve train according to claim 9, d a d u r c h g e k e n e z e i c h n e t that - on the adjusting shaft (56.2) a first pivot lever (94) is attached, on which a rocker arm (96) is pivotally held,

- The body (35) resting on the cam (16) is mounted on the rocker arm (96), - The rocker arm (96) is held in a pushing manner by means of a push rod [76.2) on the swivel element (78.2).

11) Valve train according to claim 9, d a d u r c h g e k e n n z e i c h n e t that

- The swivel element (78.2) has a cantilever arm (90) which is supported on an elastically deformable pressure member (92).

12) Valve train according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that

- The contact surface (80) presses directly against the valve (12) or indirectly by means of transmission elements known per se, such as, for example, by means of a roller drag lever (84) on the valve (12). 13) valve train according to claim 1, characterized in that

- The contact surface (238) is longitudinally displaceable along a movement axis (233), - The first surface area (235) is flat and runs parallel to the movement axis (233),

- The second surface area (236) does not run parallel to the movement axis (233).

14) Valve train according to claim 13, d a d u r c h g e k e n n z e i c h n e t that

- The second surface area (236) is not flat.

15) Valve train according to claim 13 or 14, d a d u r c h g e k e n n z e i c h n e t that

- The contact surface (238) has a third surface area (237) which adjoins the second surface area (236) in the direction of the movement axis (233) and which in turn is flat and at the same time runs parallel to the movement axis (233), wherein

- This third surface area (237) is closer to the lift valve (212) than the first surface area

(235).

16) Valve train according to one of the preceding claims 13 to 15, d a d u r c h g e k e n n z e i c h n e t that

- Contains the pressure transmission device

a plunger (230) having the contact surface (238), the longitudinal axis of which is the movement axis (233), - Pressure transmission members (220, 262), on the one hand, the pressure transmission between the body (221) resting on the cam (216) and the plunger (230) can be established, and on the other hand, the displacement of the rest position of the plunger taken between two stroke events (230) can be produced along the movement axis (233).

17) Valve train according to one of the preceding claims 13 to 16, d a d u r c h g e k e n n z e i c h n e t that

- there is an adjustment shaft (260) which can be rotated about its axis (261) in parallel and at a distance from the camshaft (215), - a first lever (262) is attached to the adjustment shaft (260), on which a rocker arm (220) is attached is held pivotable,

- The body (221) lying against the cam (216) is mounted in the rocker arm (220), - The rocker arm (220) presses against the plunger (230).

18) Valve train according to one of the preceding claims 13 to 17, d a d u r c h g e k e n n z e i c h n e t that

- The plunger (230) has a plate (251) which is supported on an elastically deformable pressure member (250).

19) Valve train according to one of the preceding claims 13 to 18, d a d u r c h g e k e n n z e i c h n e t that

- The contact surface (238) presses directly or indirectly against the valve (212) by means of transmission elements known per se, for example by means of a roller rocker arm (240). 20) Cylinder head of an internal combustion engine

- With at least one inlet (12.2, 212) and one outlet valve (13.2, 213),

- with a camshaft to control the stroke of the valves (12.2, 13.2, 212, 213),

with a valve train between this camshaft and the respective valve,

• according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that - between this one camshaft and the at least one exhaust valve (13.2, 213) a first valve train and

- Between this one camshaft and the at least one inlet valve (12.2, 212) there is a second valve train, - This second valve train has the pressure transmission device which has different surface areas (80.1, 80.2, 80.3, 235, 236, 237) of the contact surface (80 , 238) presses against the inlet valve (12.2, 212), - the respective position of the surface areas both due to the change in position of a body (35, 221) sensing the contour of a cam (16, 216) of the camshaft, and also due to a pressure transmission device additionally acting adjusting device (adjusting shaft 56, 56.2, 260) can be produced, so that

- Depending on the displacement of the resting point between two stroke events of the contact surface (80, 238) on the pressure transmission device caused by the adjusting device, the different surface areas (80.1, 80.2, 80.3, 235, 236, 237) of those caused by the rotation of the cam Pressure transmission is available. 21) Cylinder head according to claim 20, characterized in that

- The respective position of the surface areas (80.1, 80.2, 80.3) by pivoting the contact surface (80) about which a bearing axis (14, 100) can be effected.

22) Cylinder head according to claim 20, d a d u r c h g e k e n n z e i c h n e t that

- The respective position of the surface areas (235, 236, 237) can be effected by longitudinally displacing the contact surface (238) along an axis of movement (233).

23) Cylinder head according to one of claims 20 to 22, characterized in that the second valve train according to the invention is also present between the one camshaft (34, 215) and the at least one exhaust valve (13.2, 213), so that the stroke profile of the Exhaust valve (13.2, 213) can be controlled in the same way as that of the inlet valve (12.2, 212).

24) Cylinder head according to one of claims 20 to 23, d a d u r c h g e k e n n z e i c h n e t that

- There are at least two stroke valves (12, 13, 212, 213) aligned at an acute angle to one another, - The camshaft (34, 215) and the adjusting shaft (56, 260) are present above the valves (12, 13, 212, 213) are.

25) Cylinder head according to one of claims 20 to 24, characterized in that - the camshaft and the adjusting shaft are present at approximately the same height above the valves. 26) Cylinder head according to one of claims 20 to 24, characterized in that

- there are at least two stroke valves (12, 13, 212, 213) aligned at an acute angle, - above the valves (12, 13, 212, 213) the camshaft (34, 215) and below between the valves (12, 13, 212, 213) the adjusting shaft (56, 260) is available.

27) Cylinder head according to one of claims 20 to 26, d a d u r c h g e k e n n z e i c h n e t that

- The pressure transmission device is essentially between the camshaft (34, 215), the adjusting shaft (56, 260) and the inlet valve (12, 212).