GB2228534A - Hydraulic i.c. engine valve actuation - Google Patents

Abstract

The inlet and exhaust valves are both opened and closed by hydraulic actuation. Distributors 12 and 13 each comprise a sleeve (16, Figs. 1 and 2) concentrically mounted over a shaft (14) rotated at half engine speed, and pathways (50 to 54) for fluid for actuating the valves include ports (27, 26) in the shaft and ports (31, 41) in the sleeve, which ports communicate during part only of the relative rotation. A bore (20) in the shaft is provided with a port (27, 26) at each end and contains a freely sliding piston (28), and inlet ports (31, 34) and outlet ports (41, 44) in the sleeve communicate with the shaft ports as the shaft rotates relative to the sleeve, such that an inlet port (31) in the sleeve communicates with a port (27) at one end of the bore at the same time as an outlet port (41) in the sleeve communicates with a port (26) at the other end of the bore. Fluid is expelled from the bore by the piston shuttling to and fro as the shaft rotates within the sleeve, opening the end ports to successive inlets and outlets in the sleeve. The sleeve is angularly adjustable to vary valve timing and valves 107, 108 control fluid flow to the distributors 12 and 13 to determine valve lift. Control may be effected by a computer. <IMAGE>

Description

INTERNAL COMBUSTION ENGINES This invention relates to internal combustion engines. More specifically, the invention is concerned with the control of inlet and exhaust valves to the combustion chambers of such engines, with especial reference to actuating such valves hydraulically and timing the opening and closing of the valves during the engine cycle.

Taking as an example a conventional four cylinder in-line four stroke petrol engine, with one inlet and one exhaust valve in the combustion chamber of each cylinder, the cylinders fire at equal intervals in the order 1-3-4-2 during two rotations of the crankshaft, which corresponds to one engine cycle. In each cylinder, both valves are closed during the power stroke; the exhaust valve opens for the exhaust stroke; the inlet valve opens for the induction stroke, before the exhaust valve has fully closed; and both valves are closed for the compression stroke prior to ignition of the petrol vapour/air mixture.

The performance of the engine is affected by the timing of valve opening and valve closing, and by the extent to which the valves are opened. If the valves are mechanically actuated, from a camshaft, these variables are governed by the fixed cam profiles, which will normally be different for the inlet valves than for the exhaust valves.

Hydraulic tappets are sometimes used between the cam and valve, to avoid the problems of wear and noise that arise with mechanical tappets. In these cases hydraulic pressure generated by the camshaft is used to open the valves, which are later returned to their seats by conventional valve springs.

The present invention is concerned with valves that are actuated fully hydraulically. An object of the invention is to provide means for delivering hydraulic fluid to the valves at the correct moments to initiate opening or closing. In embodiments of the invention means are also provided for varying the valve timings and for controlling the degree to which the valves open, to enhance the performance of the engine.

Preferably, the invention makes use of an engine management system, typically an engine management computer1 to control the engine valve operation and increase engine flexibility, necessitating fewer gear changes; improve engine torque throughout the engine speed range; and increase engine economy, with special reference to engine idle and low load conditions.

In accordance with the invention there is provided an internal combustion engine having a combustion chamber provided with at least one inlet or exhaust valve and means for providing hydraulic fluid under pressure to open and to close the said at least one valve.

According to the invention there is also provided a hydraulic fluid distributor for a hydraulically actuated inlet or exhaust valve of a combustion chamber of an internal combustion engine, comprising: a sleeve member concentrically mounted over a shaft member, whereby the said members are relatively rotatable; means for rotating one of said members in proportion to engine speed; and a pathway for hydraulic fluid for actuating the valve including a port in the shaft member and a port in the sleeve member, which ports are adapted to communicate for the passage of hydraulic fluid during part only of the relative rotation of the said members.

According to the invention there is also provided an internal combustion engine comprising: a combustion chamber provided with at least one hydraulically actuated inlet or exhaust valve; a hydraulic fluid distributor, comprising a shaft member and a sleeve member concentrically and rotatably mounted thereover, one of said members being rotatable in proportion to engine speed, and including a pathway for hydraulic fluid for actuating the valve including a port in the shaft member and a port in the sleeve member, which ports are adapted to communicate for the passage of hydraulic fluid during part only of the relative rotation of the said members; and means for providing hydraulic fluid under pressure through said pathway to actuate said valve.

It is anticipated that at least one inlet valve and at least one exhaust valve, normally all such valves, in each combustion chamber1 will be supplied with actuating fluid in the foregoing manner.

A distributor may be provided with a plurality of said pathways for hydraulic fluid1 each such pathway being for fluid for a valve or valves in a single combustion chamber. One distributor may deliver fluid to either inlet or exhaust valves, or to both.

Separate distributors may be provided for opening the valves and for closing the valves.

Preferably, while one of said members is rotatable in proportion to engine speed, the other of said members is independently rotatable to vary the timing in the engine cycle at which the said ports communicate for the passage of hydraulic fluid.

It is generally convenient to rotate the shaft member in proportion to engine speed, and to advance or retard the valve timing by rotating the sleeve member. In such cases, the shaft member will be referred to herein as a rotor. The sleeve member may be accommodated within a static housing, to which the necessary hydraulic conduits can be connected.

Hydraulic fluid flow control means may be provided, whereby the quantity of hydraulic fluid distributed to the valve may be regulated or controlled.

In accordance with the invention hydraulic fluid flow control means may comprise a variable throttle valve. This may be controlled by cam means, which may in turn be responsive to an engine management system. In an preferred embodiment, fluid flow control means for hydraulic fluid for closing engine valves may be adapted to close in anticipation of stopping the engine, whereby open engine valves remain open. The said valves may remain open until the engine has restarted and working hydraulic pressure has been re-established.

The valves to be actuated in the combustion chambers may be of generally conventional design, having a valve head, fitting a port in the combustion chamber, mounted on a stem which is slidable along a valve guide. The valve stem may be connected to a hydraulic piston, so that movement of the piston by hydraulic fluid from a distributor serves to actuate the valve, either opening it or closing it.

According to the invention, an actuator for an engine valve may comprise double acting piston means operably connected to the valve, inlets for hydraulic fluid for actuating the piston to open and to close the valve, each inlet including non-return valve means, and an outlet for displaced fluid on each side of the piston, each outlet being adapted to open in response to fluid pressure on the opposite side of the piston.

One embodiment of the invention is illustrated, by way of example only, in the accompanying drawings, in which: Figure 1 is a sectional elevation of a distributor in accordance with the invention; Figure 2 is a sectional plan view, taken on the line ll-ll of Figure 1, showing the distributor with its central shaft or rotor advanced through 90" (in the direction of arrow R); Figure 3 is a general diagram of the hydraulic system; Figure 4 is an end elevation of a hydraulic fluid flow control valve; Figure 5 is a sectional view taken on the line V-V of Figure 4; Figures 6, 7 and 8 show diagrammatically the operation of an engine valve actuator; and Figure 9 is a sectional elevation showing a piston of the actuator of Figure 8 connected to an engine valve stem.

The operation of the hydraulic valve actuation system to be described is under the control of an engine management system, utilising suitably programmed computer means.

In Figures 1 and 2, a distributor 12 comprises a rotor 14 and a cylindrical sleeve 16 over the rotor, concentrically mounted in a static housing 18. As viewed in these drawings, the left hand half of the distributor is the mirror image of the right hand half. The two halves are fed by one hydraulic fluid supply conduit, and each half functions as a distributor of hydraulic fluid independently of, but simultaneously with, the other.

As will be seen, the left hand half of the distributor supplies hydraulic fluid for four combustion chamber inlet valves, and the right hand half supplies hydraulic fluid for four exhaust valves. In a more complex system, the halves could be separated into two independently functioning distributors.

For simplicity, the following description refers principally to the left hand or inlet valve half of the distributor, but it will be understood that the right hand or exhaust valve half is similar in essential respects.

Rotor 14 is provided with left hand axial bore 20 separated from right hand bore 21 by wall 24 at the mid-length of the rotor. Bore 20 is provided with port 26 at the outer end and port 27 at the inner end, and contains freely sliding piston 28 provided with projecting stops 29 at either end, dimensioned to prevent the piston occluding either of the ports at the ends of the bores. Bore 21 is similarly provided with two ports and a piston, giving the rotor four ports in all.

Rotor 14 is connected to the engine by suitable gearing, a chain drive or any alternative, so that it always rotates at exactly half engine speed.

Sleeve 16 is provided with sixteen ports altogether (eight inlet ports and eight outlet ports) adapted to communicate with the four rotor ports, as the rotor turns within the sleeve. On the left hand side, ie the side relating to the left hand bore 20, are two diametrically opposite outer outlet ports 41, 44 (Figure 1) and, at 90" about the circumference of the sleeve, two diametrically opposite outer inlet ports 32, 33 (Figure 2); and, axially spaced from the outer ports, two diametrically opposite inner inlet ports 34, 31 (Figure 1) and circumferentially between them two diametrically opposite inner outlet ports 43, 42 (Figure 2). The right hand side of sleeve 16 has eight corresponding ports, relating to bore 21.

Static housing 18 is provided with a single inlet 50 at its mid-length which follows a labyrinthine passage to communicate with all eight inlet ports of the sleeve (the left hand sleeve inlet ports being designated 31, 32, 33, 34). The housing is also provided with eight outlet ports (the left hand housing outlet ports being designated 51, 52, 53, 54) adapted to communicate with all eight outlet ports of the sleeve (the left hand sleeve outlet ports being designated 41, 42, 43, 44).

The sleeve can be rotated to a limited extent (eg up to about 200) with respect to the housing while retaining port communication with the inlet and outlet ports of the housing. This is achieved by circumferentiaily elongating the inlet and outlet port openings in the housing.

In the illustrated embodiment of the invention, the left hand half (bore 20) of distributor 12 supplies hydraulic fluid for opening the inlet valves to the combustion chambers of cylinders 1, 3, 4 and 2, in that order, of an in-line four cylinder four stroke internal combustion engine. The right hand half, bore 21, provides fluid for opening the exhaust valves of these cylinders. A second distributor 13 (Figure 3), identical in construction to distributor 12, acts to provide fluid for closing these valves.

The operation of the distributors can be followed by considering just the left hand half of distributor 12, opening the inlet valves.

Fluid is provided under pressure at inlet 50, and rotor 14 is turned at half engine speed by means of a suitable drive taken from the engine. As can be seen in Figure 1, fluid initially passes through inlet port 31 in the sleeve which is aligned with port 27 in the rotor. Piston 28 is driven to the left and expels an equal amount of fluid through rotor port 26, which is aligned with sleeve outlet port 41 and housing outlet port 51. This is taken by line 61 to open the inlet valve of cylinder 1.

When the rotor has turned through 900 in the direction of arrow R, the position shown in Figure 2 is reached. Fluid from inlet 50 now passes through inlet port 33 in the sleeve which is aligned with port 26 in the rotor. Piston 26 is driven back to the right and expels an equal amount of fluid through rotor port 27, which is aligned with sleeve outlet port 43 and housing outlet port 53. This is taken by line 63 to open the inlet valve of cylinder 3.

At further 900 intervals, piston 28 shuttles left and right again, as, in turn, fluid is admitted to the rotor through sleeve inlet ports 34 and 32.

As the piston moves, it expels hydraulic fluid to open the inlet valves of cylinders 4 and 2 in turn1 through sleeve outlet ports 44 and 42, housing outlet ports 54 and 52, and lines 64 and 62.

In this manner the inlet valves of cylinders 1, 3, 4 and 2 are opened in sequence at 900 intervals referenced to the rotor, corresponding to 1800 intervals referenced to engine rotation. At the same times the exhaust valves of cylinders 3, 4, 2 and 1 are opened by fluid expelled from the right hand bore 21 of distributor 12, delivered to the valves by lines 73, 74, 72 and 71 respectively. Each cylinder thus has its inlet valve opened 1800 after its exhaust valve, ie exactly one quarter of the way through the four stroke cycle, although this timing can be changed by changing the alignments of the ports between the left hand (engine inlet) and right hand (engine exhaust) sides of distributor 12.

Distributor 13 operates to close the valves in the same sequence at an appropriate intervai after they have opened. As shown in Figure 3, lines 81, 82, 83 and 84 deliver fluid to close the inlet valves in cylinders 1, 2, 3 and 4 respectively, while lines 91, 92, 93 and 94 deliver the fluid for closing the exhaust valves in the same respective cylinders.

It can now be seen that by rotating sleeve 16 in the direction of the arrow S (Figure 1), the timing of the valve opening can be advanced; and by rotating sleeve 16 in the opposite direction (arrow S', Figure 2), the valve timing can be retarded. The timing of valve closing can be adjusted by rotating the corresponding sleeve in distributor 13. The two sleeves can be rotated by providing them outside the distributors with sector gears driven by a movable rack. If the rack is common to the two sleeves, both valve opening and valve closing are advanced or retarded together.

Referring now particularly to Figure 3, the overall distribution of hydraulic fluid is shown. Pump 101 takes fluid from reservoir 102 via non-return valve 103, and recirculating the fluid at 104 as necessary. The fluid is delivered under pump pressure through conduit 112 and thence by way of flow control valve 107 to housing inlet 50 in the opening distributor 12; and fluid is delivered under pump pressure through conduit 113 and thence by way of flow control valve 108 to the closing distributor 13.

From these distributors, fluid is delivered under pressure, through nonreturn valves, via conduits 61 and 81 to the inlet valve actuator 131 of engine cylinder 1; via conduits 71 and 91 to the exhaust valve actuator 132 of cylinder 1; via conduits 62 and 82 to the inlet valve actuator 133 of cylinder 2; via conduits 72 and 92 to the exhaust valve actuator 134 of cylinder 2; via conduits 63 and 83 to the inlet valve actuator 135 of cylinder 3; via conduits 73 and 93 to the exhaust valve actuator 136 of cylinder 3; via conduits 64 and 84 to the inlet valve actuator 137 of cylinder 4; and via conduits 74 and 94 to the exhaust valve actuator 138 of cylinder 4.

Fluid is returned from these valve actuators by return lines, which are omitted from the drawings for the sake of clarity and simplicity.

Figures 4 and 5 show one of the similar hydraulic fluid flow control valves 107 and 108, located in lines 112 and 113 respectively.

A cylinder 121 has an opposite pair of ports 122, 123 adjacent one end, and houses a piston 124 which is biassed away from the ported end of the cylinder by spring 125. The further end of the piston bears against cam 127 mounted on shaft 128 in housing 126. The cam can be rotated by means of lever 129 to advance the piston into the cylinder and partially close the ports, thereby regulating the quantity of hydraulic fluid passing through line 112 to the distributor 12.

Movement of lever 129 is under the control of the engine management computer. When the engine is running normally, the closing distributor control valve 108 remains in the full flow condition, as shown in Figure 5.

However, when the ignition is switched off to stop the engine, cam 127 is turned to fully close the valve, which prevents hydraulic fluid from closing any open engine valves. When the engine is to be restarted, the valves will be held open, so offering little compression resistance to the starter motor. As the engine can then be spun faster by the starter, hydraulic pressure is built up more quickly. When working pressure has been reached the cam is turned to open the valve 108 fully and allow the valves to be closed in the normal way.

The opening distributor control valve 107 is however varied in normal running by the engine management computer. The full flow condition is only reached at times of peak demand on engine power.

The operation of the eight hydraulic actuators 131-138 for the engine inlet and exhaust valves is illustrated in Figures 6, 7 and 8, taking as an example the actuator 131 for the inlet valve of cylinder 1. All the other actuators are similar.

Actuator 131 comprises a body 141 containing a piston 143, which is secured to the valve stem, as will later be described with reference to Figure 9. Conduit 61 from distributor 12 leads into the body for supplying hydraulic fluid to open the engine inlet valve, and conduit 81 from distributor 13 leads into the body to supply fluid to close the valve.

Figure 6 shows the piston in the valve open position, at an instant when hydraulic fluid has just begun to be delivered in conduit 81 to close the engine inlet valve. The pressure has moved spool 145 against biassing spring 146, opening exit port 148, and thereby allowing residual pressure above piston 143 to drop. This enables spool 151 to be moved by its biassing spring 152 to close conduit 61 and exit port 154. As spool 145 continues to rise (Figure 7), hydraulic fluid from conduit 81 can flow to piston 143, raising it until the engine inlet valve that it carries is closed.

At this point there can be no further movement of piston 143, so the hydraulic pressure rises, further moving spool 145 against spring 146, and opening pressure relief port 156 (Figure 8).

To open the engine inlet valve, this sequence is generally reversed, with hydraulic fluid being delivered by conduit 61, except that there is no pressure relief port corresponding to port 156. This is not required on valve opening, because the correct volume of hydraulic fluid to open the valve exactly to the extent required by the engine management system is supplied by flow control valve 107 to distributor 12, while the flow control valve 108 is normally kept in the full flow position to ensure complete valve closure.

Figure 9 shows piston 143 in more detail. Engine inlet valve stem 161 passes up into the piston where it is held by conventional split valve collets 163. The collets are tapered and are held firmly in their tapered seat in the piston by screw cap 165.

While the invention has been described with reference to specific elements and combinations, it is envisaged that the invention may reside in all matters disclosed, and that alternative elements and combinations are within the scope of the invention. Furthermore, the foregoing description is not intended to suggest that any element mentioned is indispensable to the invention. What is identified as the invention should not be construed as limiting the extent of the disclosure of this specification.

Claims (23)

1. An internal combustion engine comprising: a combustion chamber provided with at least one hydraulically actuated inlet or exhaust valve; a hydraulic fluid distributor, comprising a shaft member and a sleeve member concentrically and rotatably mounted thereover, one of said members being rotatable in proportion to engine speed1 and including a pathway for hydraulic fluid for actuating the valve including a port in the shaft member and a port in the sleeve member, which ports are adapted to communicate for the passage of hydraulic fluid during part only of the relative rotation of the said members; and means for providing hydraulic fluid under pressure through said pathway to actuate said valve.

2. An internal combustion engine according to claim 1 comprising a plurality of said combustion chambers each provided with at least one hydraulically actuated inlet valve and at least one hydraulically actuated exhaust valve, and each said valve in each combustion chamber is supplied with actuating fluid from a said hydraulic fluid distributor.

3. An internal combustion engine according to claim 1 or claim 2 wherein a said hydraulic fluid distributor is provided with a plurality of said pathways for hydraulic fluid, each such pathway supplying fluid for a valve or valves in a single combustion chamber.

4. An internal combustion engine according to any one of the preceding claims comprising a first distributor for hydraulic fluid for opening the valve or valves and a second distributor for hydraulic fluid for closing the valve or valves.

5. An internal combustion engine according to any one of the preceding claims wherein, while one of said members is rotatable in proportion to engine speed, the other of said members is independently rotatable to vary the timing in the engine cycle at which the said ports communicate for the passage of hydraulic fluid.

6. An internal combustion engine according to claim 5 wherein the shaft member is rotated in proportion to engine speed and the sleeve member is rotated to advance or retard the valve timing.

7. An internal combustion engine according to any one of the preceding claims wherein the shaft member is rotated at half engine speed by means of a drive taken from the engine.

8. An internal combustion engine according to any one of the preceding claims wherein the sleeve member is accommodated within a static housing to which hydraulic conduits to the valve or valves are connected.

9. An internal combustion engine having a combustion chamber provided with at least one inlet or exhaust valve and means for providing hydraulic fluid under pressure to open and to close the said at least one valve.

10. An internal combustion engine according to any one of the preceding claims comprising hydraulic fluid flow control means, whereby the quantity of hydraulic fluid distributed to the said valve or valves may be regulated or control led.

11. An internal combustion engine according to claim 10 wherein the hydraulic fluid flow control means comprise a variable throttle valve.

12. An internal combustion engine according to claim 12 wherein the variable throttle valve is controlled by means responsive to an engine management system including programmed computer means.

13. An internal combustion engine according to any one of claims 10 to 12 wherein flow control means for hydraulic fluid for closing an engine valve is adapted to close in anticipation of stopping the engine, whereby open engine valves remain open.

14. An internal combustion engine according to claim 13 wherein the said valve is adapted to remain open until the engine has restarted and working hydraulic pressure is re-established.

15. An internal combustion engine according to any one of the preceding claims wherein each said valve to be actuated in the combustion chambers is connected to a hydraulic piston, so that movement of the piston by hydraulic fluid from a distributor serves to actuate the valve, either opening it or closing it.

16. An internal combustion engine according to claim 15 including an actuator for an engine valve which comprises double acting piston means operably connected to the valve, inlets for hydraulic fluid for actuating the piston to open and to close the valve, each inlet including non-return valve means, and an outlet for displaced fluid on each side of the piston, each outlet being adapted to open in response to fluid pressure on the opposite side of the piston.

17. A hydraulic fluid distributor for a hydraulically actuated inlet or exhaust valve of a combustion chamber of an internal combustion engine, comprising: a sleeve member concentrically mounted over a shaft member1 whereby the said members are relatively rotatable; means for rotating one of said members in proportion to engine speed; and a pathway for hydraulic fluid for actuating the valve including a port in the shaft member and a port in the sleeve member, which ports are adapted to communicate for the passage of hydraulic fluid during part only of the relative rotation of the said members.

18. A hydraulic fluid distributor according to claim 17 provided with a plurality of said pathways for hydraulic fluid, each such pathway being for fluid for a valve or valves in a single combustion chamber.

19. A hydraulic fluid distributor according to claim 18 wherein each said pathway includes corresponding inlet and outlet ports in the sleeve member for each engine valve to be actuated by fluid from the distributor.

20. A hydraulic fluid distributor according to any one of claims 17 to 19 comprising a bore in the shaft member1 the bore being provided with a port at each end and containing a freely sliding piston, and inlet ports and outlet ports in the sleeve member which are adapted to communicate with the shaft ports as the shaft rotates relative to the sleeve, such that an inlet port in the sleeve member is in communication with a port at one end of the bore at the same time as an outlet port in the sleeve member is in communication with a port at the other end of the bore, and an inlet port in the sleeve member is in communication with a port at the other end of the bore at the same time as an outlet port in the sleeve member is in communication with a port in the one end of the bore.

21. A hydraulic fluid distributor according to claim 20 wherein stops are provided to prevent the piston occluding the ports at the ends of the bore.

22. An internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.

23. A hydraulic fluid distributor substantially as herein described with reference to and as illustrated in the accompanying drawings.