GB1294217A - Improvements relating to internal combustion engines - Google Patents

Abstract

1294217 Valve gear regulating ROBERT BOSCH GmbH 28 Aug 1970 [30 Aug 1969 16 Dec 1969 12 Feb 1970 14 Feb 1970 25 Feb 1970 5 March 1970] 41454/70 Heading F1B [Also in Division F2] An inlet or exhaust valve control system comprises a working piston acting directly or indirectly on a valve stem for intermittently actuating the engine valve and a solenoid valve for intermittently controlling the supply of fluid under pressure from a substantially continuously available source for operating the working piston. Fluid e.g. liquid fuel is fed from a pump 14, Fig.1 to a bore 20 controlled by a ball 22 acted on by a spring-loaded armature 28. When winding 33 is energized the armature 28 is retracted thereby allowing fluid pressure to move ball 22 onto an opposed seat to close return line 25, 26 and to permit fluid flow via bore 23 to act on piston 9 which moves to open valve 2. An enlarged collar on the piston 9 co-operates with recesses to form a hydraulic damper. The flange and the wall of the recess may be conical to obtain progressive damping. When the winding 33 is de-energized the spring 27 moves armature 28 and ball 22 to close bore 20 so that fluid in chamber 11 can flow via chamber 21, bores 24,25 and line 26 to the reservoir 13. In another embodiment the energization of the winding causes a valve 40, Fig.2 to be displaced against spring 42 by fluid fed through passage 41 thereby connecting a groove 43 to a groove 45 and isolating the latter from bores 49. Pressure fluid flows via passage 37 and grooves 38,43,45 to the end face of a working piston 48 to open valve 2. Both em - bodiments may be arranged so that a rocker lever transmits the force from the working piston to the valve stem. In another embodiment the movement of a working piston 9a, Fig.4 is hydraulically retarded towards the end of each stroke by the entry of a flange 34a into respective recesses 35a,35<SP>1</SP>a and a valve spool 37a controls a return passage and an inlet passage which by-pass the solenoid valve 8a. Piston 9a is moved when the solenoid valve 8a opens passage 20a to chamber 11a and after a specific travel opens passage 40a to admit an unthrottled flow of fluid from passage 19a and groove 38a into chamber 11a to increase the speed of the piston 9a. When the solenoid valve 8a is de-energized fluid displaced by the piston 9a and fluid delivered from passage 40a flow into passage 25a where pressure is retained by a restriction 43. The latter pressure acts, via passage 45a, on spool 37a which is displaced against spring 46a until it abuts a step 47a. The inlet passage 19a is thereby isolated from passage 40a and the return passage 26a is connected to the passage 40a so that an unthrottled fluid flow can take place from chamber 11a to the suction side of the pump through bore 40a groove 39a and passages 26a,26<SP>1</SP>a. When piston 9a assumes its original Fig.4 position the fluid pressure in passage 25a falls thereby permitting spring 46a to return spool 37a to the Fig.4 position. In a modification of this embodiment the return travel of the piston (9a) Fig.6 (not shown) is effected hydraulically. In an embodiment otherwise similar to Fig.1 the movement of a working piston (9b) Fig.8 (not shown) is damped hydraulically by movement of a flange (34b) into a recess (35b) into which lubricant is admitted, the lubricant which is forced from the recesses flowing into the spring chamber. In another embodiment the output of a feed pump (14c) Fig.10 (not shown) is controlled by an electronic control (38c) in dependence on the positions of the accelerator pedal (40c) or brake pedal so that the valve lift may be varied. The valve timing may be controlled independently of the valve lift. In a further embodiment the pump output is varied in dependence on the position of an accelerator pedal (39d) Fig.12 (not shown) or engine speed or ambient pressure or engine temperature. In part load operation of the embodiment the relative positions (crank angle) of the closing of the exhaust valve and opening of the exhaust valve are varied in dependence on the accelerator position and the slope or drop of the valve opening curves are varied in accordance with engine speed. To obtain engine braking the opening or closing of the exhaust valve is varied in dependence on the position of the brake pedal and engine speed. In another embodiment the opening movement of the valve is limited hydraulically when a further solenoid (45a) Fig.14 (not shown) is energized. In all embodiments the feed pump may be a radial piston pump, an axial piston pump or a gear pump.