GB2124701A - Actuating system for engine valves - Google Patents

Abstract

Pistons 13, 14 connected to the engine valve 10 are supplied with liquid under pressure by a high pressure pump 15 and a rotary valve 17. The valve defines a first flow path 25, 28, 29 to direct fluid at high pressure to act on the pistons to open the engine valve and a second flow path 30, 31, 32, 33 allows liquid to escape from a cylinder 12 containing the pistons to allow the valve to close. The second flow path includes an electrically controlled valve 34 which is opened to cause closure of the engine valve. <IMAGE>

Description

SPECIFICATION Actuating system for valves This invention relates to an actuating system for a valve of a reciprocating piston internal combustion engine.

The conventional way of operating the valves of a reciprocating piston internal combustion engine is by means of cams driven by the engine. It is possible with such an arrangement to alter the valve open period but such arrangements are expensive and are usually confined to engines built for research purposes. Systems are known in which the valves are operated electromagnetically but the power required to operate such systems is considerable and again the application of such systems is confined to engines used for research purposes. Electrohydraulic systems are also known but again these are complex.

The object of the present invention is to provide an actuating system of the kind specified in a simple and convenient form.

According to the invention an actuating system for a valve of a reciprocating piston internal combustion engine comprises fluid pressure operable piston means connected to the stem of the valve, the valve being resiliently loaded to the closed position, a high pressure pump for delivering fluid under pressure in timed relationship with the desired timing of the valve, rotary valve means driven in synchronism with the engine, said rotary valve means defining a first flow path which connects a cylinder containing said piston means to the outlet of the high pressure pump when it is required to open the valve, a second flow path connected with said cylinder, and an electrically controlled valve through which said second flow path can be connected to a drain.

In the accompanying drawings: Figures 1 and 2 are diagrammatic views of one example of the system.

Referring to Figure 1 of the drawings an engine valve in this particular example an inlet valve, is indicated at 10 and it is biased in the usual manner, to the closed position by means of a spring.

Connected to the stem of the valve means is piston means generally indicated at 11 and which comprises a cylinder 12 in which is located an annular piston 13 having a limited stroke. Housed within the annular piston is a further piston 14 which defines a shoulder for engagement by the piston 13, the piston 14 engaging the valve stem. When fluid under pressure is supplied to the cylinder 12 the whole of the area of the two pistons is exposed to this pressure and a high force is created acting in the direction to lift the valve from its seating. The force exerted on the valve member decreases when the piston 13 reaches the end of its stroke, however, further movement of the valve can occur under the action of the piston 14.

The actuating mechanism includes a high pressure pump which is generally indicated at 15 and a low pressure pump which is generally indicated at 16. Conveniently the high pressure pump and the low pressure pump are of a construction closely resembling the similarly designed pumps of a rotary distributor fuel injection pump. The rotary parts of the pumps 15 and 16 are coupled by means of a rotary member 17 housed within a surrounding body and the rotary member is driven in the direction indicated by the arrow A, by the associated four stroke engine at half engine crankshaft spped.

The low pressure pump 16 is of the sliding vane type and it has an inlet 18 connected to a source of hydraulic fluid 19 and an outlet 20. The outlet pressure of the low pressure pump is controlled by means of a by-pass valve 21 which can connect the outlet 20 to the inlet 18 when the pressure at the outlet exceeds a predetermined value.

The high pressure pump comprises a pair of pumping plungers 22 which are housed within a transverse bore formed in the rotary member 17. At their outer ends the plungers are engaged by cam followers including rollers engageable with the internal peripheral surface of a cam ring 23. The system as described is for operating four inlet valves and hence the cam is provided with two pairs of equi-angularly spaced and diametrically opposed cam lobes indicated at 24. The leading faces at least of the cam lobes are shaped so that the movement of the valve corresponds closely to that which would be obtained using the conventional form of cam.

The bore intermediate the plungers is connected by way of a central passage 25 formed in the rotary member, with a circumferential groove 26 formed on the periphery of the member and which is in constant communication with a supply passage 27 which is connected by way of a non-return valve 28A, to the outlet 20 of the low pressure pump. In addition, the central passage 25 communicates with a first flow path to each cylinder 12. The flow path comprises, in the example, four supply ports 28 which are equi-angularly spaced about the periphery of the rotating member 17. The flow path also includes a part circumferential groove 29 formed on the rotary member and which is connected to the central passage 25. As shown in the diagram the groove 29 subtends an angle of slightly more than 900.

The rotary member 17 defines a second flow path and this includes in the particular example, four equi-angularly spaced ports 30 opening onto the periphery of the rotary member and a groove 31 formed in the rotary member, the groove 31 subtending an angle of slightly more than 909 The groove is connected to a circumferential groove 32 on the rotary member and this is in permanent communication with a port 33 formed in the surrounding housing. The ports 30 communicate with the cylinder 12 respectively. The port 33 communicates with an electromagnetically operable valve generally indicated at 34 and when the valve 34 is opened, fluid flowing through the passage 33 from a cylinder 12, flows to the outlet 20 of the low pressure pump. When the pressure at the outlet exceeds the setting of the valve 21 the fluid flows to drain.

The valve 34 is arranged to be opened to permit flow of fluid through the second flow path, in order to achieve closing of the engine valve and the flow of electric current in the actuator of the valve is controlled by an electronic control system generally indicated at 35. The control system receives signals from transducers 36,37 which sense the passage of appropriate marks on a component which rotates with the rotary member 17. The transducer 37 provides pulses corresponding to the top dead centre positions of the pistons of the associated engine whilst the transducer 36 provides a series of pulses which are utilised in the control system to provide an engine speed signal in addition to engine crankshaft position signals.

In operation, when the cam followers move down the trailing faces of the cam lobes 24, fluid flows by way of the non-return valve 28A, the port 27 and the groove 26 to the bore containing the plungers 22 and since the fluid is at the outlet pressure of the low pressure pump 16, the plungers are forced outward lytheirmaximum extent. During continued rotation of the rotary member the plungers 22 start to move inwardly thereby displacing fluid from the bore containing the plungers along the central passage 25. The valve 28A closes under the action of its spring and fluid is supplied to the groove 29 which is in communication with one of the ports 28. The cylinder 12 to which that port is connected, thereto receives fluid under pressure and as described, the piston means will move to open the associated engine valve.It is arranged that the displacement of the plungers is greater than the amount of fluid required to open the valve and the surpius fluid can be stored in an accumulator, returned to the outlet of the low pressure pump through a high pressure relief valve or as shown in Figure 1, returned to an accumulator 38 which can also act as a relief valve.

Where a relief valve or its equivalent is provided, the valve must have an opening pressure greater than the pressure required to open the engine valve.

As the rotary member 17 continues to rotate, the groove 29 will move out of register with the port 28 to which fluid has been supplied and if the valve 34 is closed, the engine valve will then be hydraulically locked in the open position. The port 30 which is associated with the cylinder which has just received liquid will open to the groove 31 immediately after the groove 29 has moved out of register with the associated port 28. When the groove 31 does register with a port 30 no flow of liquid can take place from the cylinder until the valve 34 is opened and this is under the control of the control system 35.

It is therefore possible to vary the time the inlet valve is open by controlling the operation of the valve 34. It will be appreciated that the valve 34 must be opened before the communication of the groove 31 with a port 30 is broken, in order to allow sufficient time for displacement of the fluid in the cylinder 12 under the action of the valve spring. The valve will require a finite real time to close and therefore the period considered in terms of degrees of engine crankshaft rotation during which valve closure occurs, will depend upon the engine speed. At low engine speeds the closure of the valve will take place in a comparatively small number of engine degrees but the period will extend as the engine speed increases.

The relative disposition of the grooves 29 and 31 means that the engine valve will always be opened when fluid is supplied by the high pressure pump, even if for example, the valve 34 sticks in the open position. In this situation the valve would close as soon as the groove 31 is brought into register with the appropriate port 30.

If in the example described in Figure 1, the valve 34 remains in the closed position, the engine valves will remain in the open position. This problem can be overcome by providing, as shown in Figure 2, an additional series of grooves 41 which communicate with the circumferential groove 32 and which can register with a port 39 connected, for example, to the outlet of the low pressure pump. In this manner even if the valve 34 does not open fluid can flow from the cylinders 12 by way of the grooves 41 and the port 39, thereby to allow the engine valve to close. It will be appreciated that the grooves 41 subtend a smaller angle than the groove 31.

It is possible to form the groove 31 as a continuous groove which in effect, connects the cylinders 12 to each other. In order to avoid interaction between the valves one way valves (not shown), would be provided between each cylinder and its respective port 30, these valves being disposed to allow fluid flow from the respective cylinder.

The control system 35 can be arranged to close the valve 34 prior to the closing engine valve contacting its seat. This action will avoid the engine valve hammering its seat. Closing the valve 34 in this manner will result in the creation of a high fluid pressure in the various passages connected to the cylinder and in passage 33. This pressure is relieved by means of a high pressure relief valve 40. The valve 34 will be quickly reopened to avoid engine valve oscillation. It is possible by controlling the current supplied to the valve 34, to shape the closing characteristic of the engine valve.

Claims (10)

1. An actuating system for a valve of a reciprocating piston engine comprising fluid pressure operable piston means connected to the stem of the valve, the valve being resiliently loaded to the closed postion, a high pressure pump for delivering fluid under pressure in timed relationship with the desired timing of the valve, rotary valve means driven in synchronism with the engine, said rotary valve means defining a first flow path which connects a cylinder containing said piston means to the outlet of the high pressure pump when it is required to open the valve a second flow path connected with said cylinder, and an electrically controlled valve through which said second flow path can be connected to a drain.

2. An actuating system according to Claim 1 in which said high pressure pump comprises a reciprocable plunger pump having a rotary part driven in synchronism with the associated engine.

3. An actuating system according to Claim 2 including a control system for said electrically controlled valve and means for providing signals to the control system indicative of the position of the rotary parts of the engine.

4. An actuating system according to Claim 3 in which said electrically controlled valve is arranged to close before the engine valve contacts its seat, the system including a high pressure relief valve to limit the pressure developed upstream of the electrically controlled valve.

5. An actuating system according to any one of the preceding claims in which said high pressure pump is arranged to deliver more fluid than is required to effect opening of the engine valve, the system including an accumulator to store the surplus liquid.

6. An actuating system according to any one of the preceding claims in which said rotary valve means includes means for connecting said cylinder with a drain to assure closure of the engine valve in the event of failure of said electrically controlled valve.

7. An actuating system according to any one of the preceding claims in which said piston means comprises a first piston and a second piston, said first piston having a limited stroke, the two pistons acting together to effect the initial opening of the engine valve.

8. An actuating system according to Claim 7 in which said first piston is of annular form and the second piston is slidable within the first piston, said second piston defining an abutment engageable by the first piston.

9. An actuating system for a valve of a reciprocating piston engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

10. An actuating system for a valve of a reciprocating piston engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 as modified by Figure 2 of the accompanying drawings.