WO1992008880A1

WO1992008880A1 - Internal combustion engines

Info

Publication number: WO1992008880A1
Application number: PCT/GB1991/002039
Authority: WO
Inventors: Leonard James Smith
Original assignee: Leonard James Smith
Priority date: 1990-11-17
Filing date: 1991-11-18
Publication date: 1992-05-29
Also published as: GB2270114A; GB9025056D0; GB2270114B; GB9310125D0

Abstract

The inlet and exhaust valves (28, 30) of an internal combustion engine are each mounted in a recess (50, 40) in one side of the corresponding port (18, 20) and slide between a valve closed position in which the valve head (32) extends across the port, and a valve open position in which the valve head is withdrawn into the recess and leaves the port unobstructed. Each valve head is tapered between a flat face (36) on its combustion chamber (11) side, which makes gas sealing contact with a ramp (44) in the recess around the port when in the valve closed position, and a convex face (38) on its opposite side, which abuts projections (54) under the cylinder head (16). Shoulders (48) in the recess co-operate with flanges (46) on the sides of the valve head to guide the valve head. The valve head is on a valve stem (34) perpendicular to the port axis and operated by a solenoid (72) or by a fluid actuator (70) using engine lubricating oil. The valve timing is controlled by solenoids (72, 150) responsive to an electronic control unit (160) which monitors engine speed sensors (108, 116), an accelerator demand sensor (92), a temperature sensor (96) and an oil pressure sensor (98).

Description

INTERNAL COMBUSTION ENGINES

This invention relates to internal combustion engines, and is particularly concerned with the valves that are provided, especially in four stroke engines, for opening and closing the combustion chamber to allow unburnt fuel and air into the chamber and burnt exhaust gases out of the chamber.

Nearly all internal combustion engines of this type that are commercially produced utilise poppet valves for this purpose. These are opened by lifting the valve head off its seat into the combustion chamber by forces transmitted from a camshaft, and closed by means of a return spring. One of the many factors that affect the efficiency of an engine is the timing of the opening of the respective inlet and exhaust valves. The valve timing is normally fixed in relation to the camshaft, which in turn is synchronised to the engine speed.

A variable connection between engine speed and valve timing can be introduced by using electrical control signals to replace invariable mechanical linkages between the rotation of the crankshaft and the operation of the valves. It is an object of this invention to provide an improved valve suitable for this purpose. According to the present invention, in an internal combustion engine with one or more valves for controlling the passage of gases through corresponding ports into and out of a combustion chamber, at least one of the said valves comprises a valve head mounted in a recess in one side of the corresponding port and movable between a valve closed position in which the valve head extends from the recess across the port and closes the port, and a valve open position in which the valve head is withdrawn from the port into the recess and leaves the port unobstructed.

Preferably the recess surrounds the port, and in the valve open position the valve head is located on one side of the recess, while in the valve closed position the valve head extends across the port and has edges that lie within the recess all around the port. It is particularly preferred that the valve head should make gas sealing contact with the port on the combustion chamber side of the head, when in the valve closed position.

The valve head may be tapered and positively located by its taper when in the valve closed position. The taper may be formed between a flat face of the valve head on its combustion chamber side and a convex face on its opposite side. The floor of the recess may be provided with a ramp on the combustion chamber side against which the flat face of the valve head can make gas sealing contact.

Guide means may be provided within the recess to co-operate with side edges of the valve head to guide the valve head during its movement across the port. In a preferred embodiment, the guide means comprise shoulders within the recess supporting flanges on the side edges of the valve head.

The valve head may be mounted on a valve stem lying perpendicular to the port axis, and the stem may be slideably located in a valve guide, in which it may be slid axially by valve actuation means operating on the valve stem. The actuation means may comprise a fluid actuator, and the fluid may be engine lubricating oil, provided under a pressure by an oil pump.

⁵ The fluid actuator may comprise a chamber and a movable sealing member therein operatively connected to the valve, means fpr providing fluid under pressure to either side of the said sealing member, and means for receiving fluid displaced from either side of the said sealing member by the pressure of fluid provided to the ¹⁰ other side thereof.

The timing of the valve opening and/or the valve closing may be controlled, at least in part, by an electromagnetic actuator. It may also be controlled, at least in part, by signals derived from

¹⁵ means responsive to the engine speed and to operator-controlled acceleration selection means. The means responsive to the engine speed will normally include synchronisation means, whereby the timing of the valve can be properly related to the engine operating cycle. The acceleration selection means may be a conventionally

20 operated accelerator pedal or the like, the state of which, under operator control, indicates the demand being made of the engine by the operator at any instant. The timing of the valve may also be controlled, at least in part, by signals from the said means which is additionally responsive to at least one of engine operating

--- temperature and engine lubricating oil pressure.

In a conventional engine, the combustion chamber is located beneath a cylinder head at one end of a cylinder barrel, the cylinder head contains the gas ports, and a gas seal is maintained between a face

^**-^*--' on the cylinder head mating with a complementary face on the cylinder barrel, around the combustion chamber. In accordance with the invention, the said recess may be formed in the said face of the cylinder barrel, around the corresponding port. Further, the valve may be mounted in a valve guide which is held between the 35 cylinder head and the cylinder barrel. These features are of particular value in simplifying the manufacture and assembly of the engine.

5 In a further aspect the invention provides a valve for use in such an internal combustion engine, comprising a valve head mounted on a valve stem, the thickness of the head being tapered away from the valve stem, and the taper being formed between a flat face on one side of the head set at a shallow angle to the valve stem and a 10 convex face on the opposite side of the head. The valve head may be provided with flanged side edges parallel to the longitudinal axis of the valve stem.

One embodiment of the invention is illustrated, by way of example, 15 in the accompanying drawings, in which :

Figure 1 is a vertical cross section through the cylinder head and upper part of the cylinder barrel of an internal combustion engine in accordance with the invention; 0

Figure 2 is an isometric partial internal view showing the exhaust valve open in its recess;

Figure 3 is a similar view to Figure 1 showing the exhaust valve ²⁵ closed;

Figure 4 is a schematic elevation of one end of the engine;

Figure 5 is a longitudinal cross section through the oil -^*-⁰ distributor schematically shown in Figure 4;

Figure 6 is a transverse cross section through the oil distributor, taken on the line X-X of Figure 5;

³⁵ Figure 7 is an elevation of the other end of the oil distributor to that shown in Figure 4; and Figure 8 is a diagrammatic representation of the valve timing control system for the engine.

The engine shown in the drawings is a four cylinder, four stroke internal combustion engine, which is of generally conventional design except for the cylinder head, including the valves and the valve actuating mechanisms, and the upper ends of the cylinders in the cylinder block; these features are shown in Figures 1 to 3, which shows one cylinder only. The other three cylinders are similar.

As shown in Figures 1 to 3, a combustion chamber 11 is formed in the top end of a cylinder barrel 12 in the space bounded by the crown of a piston 14 below and the underside of a cylinder head 16 above. The cylinder head has an inlet port 18 for unburnt fuel/air mixtures and an exhaust port 20 for the burnt combustion gases. A spark plug 22 is mounted centrally in the cylinder head. The cylinder head forms a gas tight seal against the top of the cylinder barrel, except of course through the gas ports, over complementary mating faces which are for the most part flat, along plane 24. The cylinder head is held down by bolts 26. An inlet valve 28 and an exhaust valve 30 are provided to open and close the corresponding ports. Although these valves have different actuators, to be described below, the essential valve structures are the same and will be described in detail in respect of the exhaust valve, which is also shown in Figures 2 and 3.

The exhaust valve 30 comprises an essentially rectangular valve head 32 mounted on a valve stem 34 which lies in the general plane of the valve head, perpendicular to the port axis. The lower face 36 of the valve head is flat and lies at a shallow angle to the longitudinal axis of the valve stem, while the upper face 38 of the head is slightly convex. The effect is to taper the valve head from the thickest part, where it meets the valve stem, to the nose of the valve head remote from the valve stem. The valve head 32 lies in a recess 40 to one side of the exhaust port. The valve stem extends out of the rear of the recess between the cylinder head and the top of the cylinder barrel. It is supported here by a valve guide 42, through which it passes, and in which it is axially slideable.

The recess 40 surrounds the exhaust port 20, and includes a ramp 44, at an angle corresponding to the angle of the lower face 36 of the valve head, in the region immediately surrounding the port.

The side edges of the valve head have flanges 46, parallel to the valve stem, which are supported by shoulders 48 on the sides of the recess which guide the valve head and lift it off the floor of the recess when the valve is withdrawn from the port in the valve open position (Figure 2).

A similar recess 50 is provided in respect of the inlet port 18 and valve 28.

The lower face of the cylinder head 16 includes two projections 54 which correspond in outline to the recesses 40, 50, and which enter the recesses when the cylinder head is mounted on the cylinder barrel. The assembly of the head onto the barrel in this way positively locates exhaust valve guide 42 and inlet valve guide 52 and traps the valves in the recesses. The valve guides can then be screwed to the cylinder head and the cylinder barrel to complete the assembly.

The head of the exhaust valve is now supported, by flanges 46 on shoulders 48, with a very small clearance between the concave top face 38 and the lower face of the projection 54 from the cylinder head into the recess 40. When the valve is moved forward into the closed position, across the port (Figure 3), the valve head is positively located by its taper when the lower flat face 36 meets ramp 44 and upper convex face 38 abuts projection 54, so that a gas seal is made with the port where the valve head contacts the ramp. The taper between the flat and convex faces allows for thermal expansion of the cylinder head, cylinder and valve, enabling a gas seal to be achieved whatever the temperatures of the different components. Since the valve heads are always outside the combustion chamber, there is no risk of the crown of the piston contacting a valve. When the valves are open, there is no impediment to the free flow of gases through the respective ports. Further, by withdrawing the exhaust valve head from the gas stream, it will not be subjected to as much heating as a comparable poppet valve. This permits the use of less coolant and smaller capacity water pumps. Additionally, because there is no valve or valve guide in the port when the valve is open, the overall dimensions of the port can be made smaller for the same gas flow. The engine castings can accordingly be made smaller and lighter. The valves can also be made much lighter than poppet valves of equivalent port area, which can be a very significant advantage at high engine speeds. Since the valves operate across the cylinder, the overall height of the engine can be kept to a minimum.

A further advantage is that the ports are sealed by the valves at the junction between the cylinder barrel and cylinder head, so no cylinder head gasket is required. It should be noted in this connection that the drawings do not show water cooling passages, which have been omitted for the sake of clarity. However, simple '0' ring seals of rubber or the like are sufficient to safeguard the water passages between the cylinder head and cylinder barrel or block.

In the drawings, the exhaust valve 30 is shown operated by oil. The guide 42, as shown in Figure 1, forms one wall of a chamber 60 divided into two parts by a flexible diaphragm seal 62. The end of the valve stem 34 is fixed to the diaphragm. Oil pipes 64, 66 lead into the chamber on either side of the diaphragm. If oil is pumped into the chamber through pipe 64, the diaphragm moves to the right (as shown) and oil is displaced through pipe 66. The valve is thereby opened. If oil under pressure is pumped into the chamber through pipe 66, the valve is correspondingly closed, with displaced oil leaving the chamber through pipe 64. The valve guide is thus an integral part of a fluid actuator 70.

5 The inlet valve 28, in contrast, is actuated by a solenoid 72. A coil spring 74 normally holds the valve in the open position, but when energised by an electric current, solenoid winding 78 produces a magnetic field which draws solenoid cap 80 towards the valve guide 52. The outer end of the inlet valve stem 80 is mounted in 10 the solenoid cap, and the valve is accordingly closed across the inlet port while the solenoid is energised.

Figure 4 shows an end view of the engine. Cylinder head 16 is fitted with an exhaust manifold 82 and an inlet manifold 84. The

15 inlet manifold is provided with a fuel injector 86 for each cylinder, with an associated electrical control lead 88, and a butterfly throttle valve 90, with a position sensor 92 to indicate throttle opening. The throttle is, of course, controlled by the operator (the driver in the case of a motor vehicle) according to

L.0 the acceleration (including deceleration and constant speed) selected at any time.

The cylinder head is also provided with an ignition lead 94 for the spark plug and a temperature sensor 96 for coolant water.

25

Figure 4 also shows the locations on the cylinder block of the solenoid actuators 72 for the inlet valve, an engine oil pressure sensor 98, the fluid actuators 70 for the exhaust valves and oil pipes 64, 66 connecting them to an oil distributor 100 which is driven at half engine speed by a toothed belt 102 from a crankshaft pulley. A timing disc 104 on the crankshaft pulley carries markers 106 which are read by an appropriate sensor 108. A drive pulley 110 for the oil distributor carries a synchronisation disc 112 with a further marker 114 which is detected by a sensor 116. ό The oil distributor 100 is more clearly seen in Figures 5, 6 and 7. Its principal components are a static outer casing 120, an inner rotor 130, and an adjustable end cover 140, which can be rotated over a limited arc of about 25° by an incremental solenoid 150 connected to a radial arm 152 mounted on the end cover.

The casing has a total of nine oil ports. There are four ports 122 spaced at 90° intervals around the casing for supplying oil to pipes 66 on the valve closing sides of the four exhaust valve fluid actuators, and four corresponding ports 124 nearer the end cover of the casing for supplying oil under pressure to pipes 64 on the valve opening sides of the exhaust valve fluid actuators. The ninth port is an oil outlet port 126 in the casing at a location between the two sets of four ports 122, 124, and circumferentially offset from these by about 45°.

The end cover 140 is integral with a short cylindrical sleeve 142 which extends between the rotor 130 and the casing 120 in the region of the valve opening pressure ports 124, and the sleeve includes four passages 144 corresponding to these ports. However, passages 144 are somewhat elongated in a circumferential direction. The rotor is provided with an axial bore 132 which communicates through the end cover with a pressurised oil supply pipe 134. This delivers engine lubricating oil under pressure from a suitable pump (not shown). Two radial bores 136, 138 connect the axial bore with the respective ports 122, 124 in the casing for opening and closing the exhaust valves, according to the rotational position of the rotor. The two radial bores are mutually offset in rotation, by about 135°, so as to provide an appropriate overlap between valve opening and valve closing, as the rotor is turned by drive belt 102 on pulley 110. In response to movements of the solenoid 150, the end cover 140 is rotated to turn the sleeve 142, and in this way the timing of the valve opening is varied with respect to engine rotation and valve closing. When oil under pressure is delivered to the exhaust valve actuator 70 by one or other of the ports 122, 124, a corresponding amount of displaced oil is returned to the adjacent port in the casing. This is at that moment connected not to the corresponding radial bore in the rotor, which would be filled with oil under pressure, but with a relief port formed by a broad groove 154 on the outer surface of the rotor, which leads to a continuous circumferential channel 156 which is in permanent communication with the oil outlet port 126 in the casing, from which the returned oil passes to a sump.

It should be noted that while, in the illustrated embodiment of the invention, the inlet valves are controlled entirely by solenoids and the exhaust valves are driven by fluid actuators but with timing controlled, in part, by a solenoid, various other combinations are possible. All valves could be fluid actuated, or all valves could be electromagnetically operated, for example. Valves could be actuated by fluids other than oil, and the timing of fluid actuated engine valves could be governed entirely by electromagnetically operated control valves.

Figure 8 illustrates the electronic control system, which is centred on solid state control unit 160. On switching on the ignition, an auxiliary electric oil pump (not shown) begins to build up engine oil pressure; and the control unit is switched on and begins to monitor sensors 108 (timing disc) and 116

(synchronisation disc) which indicate whether the engine is running and the position in the four stroke cycle of each cylinder; sensor 92 (operator demand); sensor 96 (coolant temperature); and sensor 98 (oil pressure).

On operating the starter motor (not shown) to turn the crankshaft, the control unit reads the crankshaft revolution rate from sensors 108 and 116. As soon as the engine speed reaches a minimum of, for example, 250 r.p.m., the unit begins to control the appropriate inlet valve solenoids 72, the fuel injectors 80 through control⁰ leads 88, the exhaust valve timing solenoid 150 through control leads 162, and the ignition timing through control lead 164 to the ignition distributor (not shown). The auxiliary oil pump is switched off as soon as the engine speed is sufficient to give full pressure from the main crankshaft-driven oil pump. The inlet and 5 exhaust valve timings continue to be adjusted as the engine runs according to engine speed and operator-selected acceleration demand, and according to parameters programmed into the control unit in respect of ignition settings, fuel requirements and valve operating system. 10

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Claims

1. An internal combustion engine with one or more valves for controlling the passage of gases through corresponding ports into and out of a combustion chamber, wherein at least one of said valves comprises a valve head mounted in a recess in one side of the corresponding port and movable between a valve closed position in which the valve head extends from the recess across the port and closes the port, and a valve open position in which the valve head is withdrawn from the port into the recess and leaves the port unobstructed.

2. An internal combustion engine according to claim 1 wherein the recess surrounds the port, and in the valve open position the valve head is located on one side of the recess, and in the valve closed position the valve head extends across the port and has edges that lie within the recess all around the port.

3. An internal combustion engine according to claim 2 wherein the valve head makes gas sealing contact with the port on the combustion chamber side of the head, when in the valve closed position.

4. An internal combustion engine according to claim 2 or claim 3 wherein the valve head is tapered and is positively located by its taper when in the valve closed position.

5. An internal combustion engine according to claim 4 wherein the taper is formed between a flat face of the valve head on its combustion chamber side and a convex face on its opposite side.

6. An internal combustion engine according to any one of claims 2 to 5 wherein guide means within the recess co-operate with side edges of the valve head to guide the valve head during movement thereof across the port.

7. An internal combustion engine according to any one of the preceding claims wherein the valve head is mounted on a valve stem lying perpendicular to the port axis.

8. An internal combustion engine according to claim 7 wherein the valve stem stem is slideably located in a valve guide and is slideable axially in the guide by valve actuation means operating on the valve stem.

9. An internal combustion engine according to any one of the preceding claims wherein the valve is provided with actuation means comprising a fluid actuator.

10. An internal combustion engine according to claim 9 wherein the fluid is engine lubricating oil.

11. An internal combustion engine according to claim 9 or claim 10 wherein the fluid actuator comprises a chamber and a movable sealing member therein operatively connected to the valve, means for providing fluid under pressure to either side of the said sealing member, and means for receiving fluid displaced from either side of the said sealing member by the pressure of fluid provided to the other side thereof.

12. An internal combustion engine according to any one of the preceding claims, in which the combustion chamber is located beneath a cylinder head at one end of a cylinder barrel, the cylinder head contains the gas ports, and a gas seal is maintained between a face on the cylinder head mating with a complementary face on the cylinder barrel, around the combustion chamber; wherein the said recess is formed in the said face of the cylinder barrel, around the corresponding port.

13. An internal combustion engine according to claim 12 wherein the valve is mounted in a valve guide which is held between the cylinder head and the cylinder barrel.

14. An internal combustion engine according to any one of the preceding claims wherein the timing of the valve opening and/or valve closing is controlled, at least in part, by an electro¬ magnetic actuator.

15. An internal combustion engine according to any one of the preceding claims wherein the timing of the valve opening and/or valve closing is controlled, at least in part, by signals derived from means responsive to the engine speed and to operator- controlled acceleration selection means.

16. An internal combustion engine according to claim 15 wherein the timing of the valve is controlled, at least in part, by signals from the said means which is additionally responsive to at least one of engine operating temperature and engine lubricating oil pressure.

17. A valve for use in an internal combustion engine according to any one of the preceding claims, comprising a valve head mounted on a valve stem, the thickness of the head being tapered away from the valve stem, and the taper being formed between a flat face on one side of the head set at a shallow angle to the valve stem and a convex face on the opposite side of the head.

18. A valve according to claim 17 wherein the valve head has flanged side edges parallel to the longitudinal axis of the valve stem.