GB912138A - Vehicle engine braking and fuel control system - Google Patents

Abstract

912,138. Regulating; valve gear. CUMMINS, C. L. Nov. 19, 1959, No. 39347/59. Class 7(6) [Also in Group XXXI] A vehicle driving and braking system comprises a multicylinder crank-shaft engine having fuel supply and air inlet means and cam actuated exhaust means and is provided with control means, which, when operating, causes pressure fluid to actuate means, operating in synchronization with the crankshaft, to open the exhaust means when the corresponding piston is at or near the top of the compression stroke without alteration of the normal operation or timing of the exhaust means. Fig. 1. A self-adjusting hydraulic system for each cylinder or each pair of cylinders is provided to exhaust each cylinder 21 at the top of the compression stroke by an inter-connection which opens an exhaust valve 30 when a fuel injector plunger 170 is seated whilst permitting independent opening of the exhaust valve 30 by a rocker 32. A hydraulic master cylinder, the spring-loaded piston 270 of which is located over a cam-shaft actuated pushrod 171a movement of which causes a spring-loaded slave piston 37 to open the exhaust valve 30. A gear pump 45 draws oil from a crankcase sump 41 through a filter 43 and maintains a regulated pressure through an appropriate solenoid operated valve 276, of several solenoid valves corresponding to the cylinders, and a check valve 280 to a control valve 288. To effect engine braking, the number of cylinders or cylinder pairs required is manually selected by setting a switch 317. At a predetermined minimum engine speed a centrifugal governor 312 closes a switch 304 and thereafter driver operation of the brake pedal 73 closes a switch 307 to energize the solenoid valve or valves 276 which admits pressure oil into the conduits 277. The spring- loaded piston 282 is moved to permit pressure oil to pass through conduit 281 into conduits 283, 274 and 273 to effect hydraulic interconnection of the master and slave pistons 270, 37. When the control valve chamber 290 is not under pressure the spring 287 returns the piston 282 to allow oil present in conduits 273, 274 and 283 to drain to the sump. Fig. 1 B. A speed-responsive hydraulic or pneumatic system which applies varying degrees of braking effort is brought into operation by depressing the brake pedal 73. Oil or air passes through a valve 403, to a valve 405, having ports 408, 410, which are interconnected when a speedresponsive governor 306 retracts a shaft 314, to permit a spring 406 to move the valve piston against a stop 407. Depression of pedal 73 moves the lever 92 away from the contact roller 414 to allow actuation of the valve body 380 by the spring 402. In a modification (Fig. 1A not shown) a non-speed-responsive mechanical control is effected by hand operation of a knob, mounted on the vehicle instrument panel, which is connected by a flexible cable to a sliding piston selector valve replacing the valves 276. Fig. 2. In a detailed embodiment of the hydraulic system of Fig. 1, engine oil under pressure enters a chamber 290 to force a spring-loaded valve body 327 into the position shown where the oil flows through a check valve 332 and conduit 273 to force a master piston 270 downwards into the operating position. When oil pressure in the line 291 is cut off, the valve body 327 is forced downwards to align a groove 337 with the port 330 to allow oil from the system to drain back to the sump through a hole 340. The piston 270 is connected to a rocker arm screw 301 by a link pin 341 which is retained by a ring 344. When the system is inoperative the piston 270 and link pin 341 are retracted into the housing 326 by a spring 272a. A hollow slave piston 37a is spring-loaded inwardly by an encased spring 40 which is held by a retainer plate 348, extensions of which protrude through slots in piston 37a to engage a retaining ring 351 and a slot 352. The slave piston 37a is slotted to straddle a rocker arm 32 to operate dual exhaust valves 30 through a crosshead 300. In another embodiment (Fig. 6 not shown) the master piston is actuated directly by the cam-shaft, the system operation being otherwise as for Fig. 1. Figs. 8 and 9. In a modified form of Fig. 1, to effect fuel cut-off during engine braking, hold-down of the fuel injector plunger 170 is accomplished by a parallel hydraulic circuit which acts on a hold-down piston 372 through an addition control valve, incorporated in valve 282, and a check valve 365. The hold-down piston 372 is retracted by a spring 374 or 374a. Fig. 11. In a further embodiment, a hydraulic mechanism opens the exhaust valve 30 of a four-stroke diesel engine by means of a plunger 56 actuated from an auxiliary cam-shaft 33. The piston 37 is energized by fluid drawn from the sump through a filter 43 by a pump 45, pressure being maintained in the conduit 54 by check valves 52, 53. The plunger 56 has pinion teeth 60 in engagement with a rack 61 actuated by a plunger 62. A spring 63 normally retains the plunger 62 against a stop screw 65, in which position grooves 66, 67, are aligned respectively with conduits 50, 51, so that as plunger 56 rises, fluid in chamber 55 escapes through grooves 66, 67 without any fluid movement in conduit 54. In the position shown with the grooves 66, 67 not in alignment with conduits 50, 51, movement of plunger 56 results in movement of plunger 37 to open the exhaust valve 30. Fuel shut-off is effected by the closing of a switch 74 attached to the foot throttle 26, the switch 74 and a manual switch 80 being in the earth lead of a solenoid 82 which, when energized moves a piston 83 to close off the fuel line 84. The circuit is completed through normal generator cut-out switch. The fuel cut-off valve may form part of a fuel injector. The system is made operative by the depression of brake pedal 73 to close switches 90, 91. Switch 91 is in circuit with solenoid 82 and switch 90 with a manual switch 97, is in the earth circuit of a solenoid 101, energization of which moves a valve piston 104 to connect conduit 50 with a conduit 111 so that oil pressure in chamber 69 moves the plunger 62 with its rack 61 into the position shown. In Fig. 13 (not shown) the embodiment of Fig. 11, is modified to apply to a carburettor mounted with its throttle valve connected by a linkage to a pedal 26 there being an inlet manifold extra-air entry having a valve operated by the solenoid 82 so as to admit all the air required for compression braking. Fig. 14. In another modified form of Fig. 11, the valve operating plunger 37 is supplied by a high pressure pump 131, through an engine driven distributer 132, the high pressure fluid entering through conduit 143 and bores 144, 145, 146 to actuate the plunger 37. Return feed of oil is through port 147, ring duct 148 and conduit 152. During braking energization of the solenoid valve 156 feeds the normal engine oil pressure to the back face of the distributer to effect sealing thereof whilst simultaneous energization of a solenoid valve 163 feeds the high pressure circuit. Fig. 16. In a further modification fuel is cut off when a foot throttle 26 is released to energize solenoid 190 which lifts valve 191 to connect pressure fluid to a twin ram cylinder 194, Fig. 19. Rams 195, one for each of a pair of cylinders are forced outwardly against springs 196, so that in each case a cam face 197 engages a slotted sleeve 198, secured to the injector plunger 170 which is held seated after being moved by the pushrod 171a. Whilst the plunger 170 is held down the rocker 171 has a full range of movement. In order to actuate valve 30 by movement of the rocker 171 a pin 173, Fig. 17, is slidably mounted in a bore 174 of the rocker arm 171. Movement of the pin 173 into a locking position in a slot in rocker 32 is effected hydraulically by a ram 180 which moves under control of a solenoid-actuated valve 183. A spring 203, Fig. 21, is provided to hold the rocker arm 171 at the farthest point of its oscillation. Fig. 22. Hydraulic hold-down of the injector plunger 170 is effected by the provision of a piston 211 in a cylinder bore 210. Fluid is introduced above the piston 211 through conduit 193 by the solenoid-actuated valve 190, 191. In the released position of pedal 26 release of a pin 93 initiates compression braking and also closing of contacts 74, 75 controls, through the solenoid valve, hydraulic hold-down of the injector plunger. In a modification, Fig. 23 (not shown), a separate exhaust valve may be actuated by the ram 37 of Fig. 11. Fig. 24. During compression braking, pressure fluid is released into conduit 246 to cause rams 247 and 248 to move. Ram 247 moves a rod 250 to the right to push the lever 251 clockwise against a spring 252 to open the intake air valve 240. Ram 248 moves rod 253 against a stop on a fuel pump rack 243 to prevent the spring 244 moving the rack to the left to feed fuel to the engine. Fig. 25. When the plunger 56, Fig. 11, rises fluid is forced through conduit 54 into a recess 264 to move rod part 262 upwards to open the exhaust valve. When plunger 56 falls the rod parts 261, 262 seat upon each other and the pushrod resumes normal exhaust valve operation. Specification 746,090 is referred to.