758,835. Clutch control. BORG-WARNER CORPORATION. Oct. 7, 1953 [Oct. 22, 1952], No. 27534/53. Class 80(2) [Also in Group XXIX] A main friction clutch 11 or other engaging device on a motor vehicle is engaged by liquid pressure acting on a piston servomotor 31 and supplied by an enginedriven pump 22 to a chamber 27 at a pressure regulated by a valve 42, relieving to pump-suction 49 past a seat 45, under the variable downward load of enginemanifold depression acting on an upwardly spring-loaded diaphragm 52, to vary clutch-engaging pressure with engine torque, and the action of the said depression on the diaphragm can be modified to cause complete clutch disengagement by a selectively operable device such as the vehicle gear-shift lever 20 and/or the engine accelerator pedal 16. A metering orifice 47 in the valve 42. or in a by - pass duct, is controlled by a tapered needle 46. or a disc, on a temperature-responsive disc or bellows 50, fixed at its lower end, to compensate for viscosity-temperature change, thus maintaining pump delivery pressure 27 proportional to the square of the engine speed for automatic decluch at engine idle and re-engagement with speed increase irrespective of acceleraor pedal position. Provision is made for automatic de-clutch by accelerator-release in certain lower speed ratios with a cold engine fast idling at speeds above that required for speed-responsive decluch; for automatic declutch coincidental with gear-shift, which may act on the valve 42 through a solenoid; and in one form (Fig. 5 not shown) for automatic declutch by braking the vehicle to a stop in high speed ratio. Manual lock in and out of the clutch is provided, and the pump 22 supplies an engine lubricating main 26 directly and the clutch servo-feed 27 through a spring-loaded valve 29 which only opens after a predetermined pressure has been built up in the lubricating main. In Fig. 1, the first of three embodiments, the selective control of regulatorvalve suction is through a control valve 72 which, on release of the usual accelerator 16, in first-speed or reverse, moves rightwards to cut off a vent 74 and substitute a suction connection 75 so that the diaphragm 52, assisted by a second diaphragm 61, opens the regulator valve 42 fully for clutch release. In second and third gear this action is prevented by cams 84 on the shift-lever 20 which obstruct valve movement either directly or through a cable, and cause acceleratorrelease merely to deflect a blade-spring 80 on an accelerator-operated lever 18. The gear-shift lever 20 operates the shift member 21 through a spring-centralized lost-motion connection 96, which permits the blade-spring 80 to move control valve 72 rightwards to clutch-release position as soon as the shift-lever is moved from either second or high speed position during a shift. The accelerator-operated lever 18 is connected with the engine throttle 15 through a lost-motion connection 94 which allows control' valve actuation to be unaffected by fast-idle setting of the throttle. The accelerator linkage includes a lever 89, which at release position, is near dead centre, to give gradual action on the clutch at that point. A non-return valve 112 in the suction line 59 controls a restricted by-pass 114, so that application of suction, which causes clutch release, is always rapid, whilst re-engagement, with the throttle open and the non-return valve 112 consequently closed, due to reduced enginesuction, is slow. since the suction on the lower diaphragm 61 can now only reduce through the restrictor 114. The clutch can be permanently locked in by pulling out a dashboard button 115 which overcomes a disengaging spring 35. Fig. 3 not shown, eliminates the lower diaphragm 61 and controls depression on the single operative diaphragm by two venting ball valves in parallel, one permitted to open by accelerator depression, the other opened by movement of the shift lever into high gear only, both valves being connected to the diaphragm chamber through a spring-loaded vacuumlimit valve, the loading spring of which is such that the valve only opens, for clutch release, when both the gear-shift and accelerator valves are closed. Declutch by accelerator release therefrom occurs only in ratios other than high. and may be prevented at all times by a manual override opening the gear-shift valve. Further, the reduced vacuum maintained by the vacuum-limit valve after accelerator depression still causes clutch engaging pressure to be torque-responsive. A floor-mounted push button mechanically opens the regulator valve for manual clutch release, e.g. to prevent creep during fast idle. Fig. 4 provides solenoid operation for the regulator valve 208, together with a single suction-loaded diaphragm 215 for torque-responsive clutch pressure. A solenoid 212 is energized to open the valve for clutch release at the servomotor 210, by initial movement of a spring-centralised lost-motion gear-shift lever 256 from a gear position, and is de-energized for clutch re-engagement after gear shift either by release of the lever or by the lever opening an additional switch 266 in reaching its new gear position. With a cold engine, release of the accelerator 238 compresses a spring 236 to maintain closed a vent-valve 234 communicating with the diaphragm-chamber 217 through a spring- loaded vacuum-limit valve 228, thus allowing full suction to act on the diaphragm 215 for clutch-release under fast idle conditions. With the engine warm, the usual temerature - responsive combined automatic choke and fast idle 243 opens this vent valve 234 permanently, so that accelerator release is now ineffective to produce clutch release. Speed-responsive clutch release however still occurs by reduction of regulated pump-pressure at normal idle speeds. A restrictor 225 in the engine manifold connection of the diaphragm chamber causes clutch engagement to be gradual, and the vacuum-limit valve 228 still maintains a reduced vacuum on the diaphragm after the ventvalve 234 has opened, so that clutch-engaging pressure at 205 is still subject to torque-responsive regulation by the valve 208. Fig. 5 not shown, also has solenoid control by a shift lever switch, but has the following differences from the preceding embodiment. The accelerator valve is separate from an additional valve controlled by the choke or other thermostat for providing clutch release by accelerator release during fast idle. The needle valve control (46, Fig. 1) of pump pressure is replaced by a separate by-pass disc valve controlled by a thermostat disc and by a solenoid which is energized by establishment of third-speed to close down the by-pass fully or partly, thereby increasing clutch pressure. The energizing circuit is broken by depresion of the service brake pedal to provide for clutch release if the vehicle is braked to a stop in third speed. The diaphragm-loading spring of the regulator valve is in this case adjustable.