748,379. Clutch control. BORG-WARNER CORPORATION. Oct. 7, 1953 [Oct. 22, 1952] No. 27533/53 Class 80(2) A main friction disc clutch 11 on a motorvehicle is engaged by fluid-pressure supplied by a pump 37 or 38 to a piston 32 through a throttle-control valve 81 opened by depression of the usual accelerator pedal 127, and overridden when, at a predetermined speed, a governor valve 79, driven by the clutch output shaft 13, operates a governor-control valve 83 for opening a by-pass which cuts out the accelerator - release declutch action. The said governor valve 79 also provides speed-responsive pressure 151, which, acting in opposition to acceleratorresponsive ("TV") pressure 139, provided by a throttle-pressure valve 82, controls a compensating valve 84 which variably loads a main regulating valve 80 to supply throttle- and speed-responsive clutchengaging pressure. A solenoid valve 85, controlled by a switch 206 on the usual' gear shift lever 207, provides clutch release coincidental with gear shift, and a cushion valve 87 retards final clutch engagement by inserting a restrictor 224 in the line after permitting rapid initial engagement to the cushion point. Gear pumps 37, 38 driven respectively by the input and output shafts 12, 13 of the clutch, supply lines 109, 138 from a sump 78, the output pump 38 providing clutch engagement for a push start. All the valves except the governor valve 79 are housed in a common chest 88. Clutch construction. The input shaft 12 drives through a spring coupling 23 a housing 19, in which are splined clutch discs 28, interleaved with discs splined on a hub 21 splined on the output shaft 13, the housing 19 also forming a cylinder for the piston 32 which clamps the discs through a lever-acting disc spring 33 and presser plate 27 when fluid pressure is supplied through passages 34, 35, 213. The clutch drives through a countershaft-type three-speeds and reverse gear with balked synchromesh on second and high. 1. Operation. Initial. With accelerator released, engine idling and vehicle stationary. The delivery line 109 of the input pump 37 supplies pressure through the regulator valve 80 to a line 112, now blanked by valves 79, 81, 82 and 83. Pressure in the line 112 passes through a line 177, ports 170, 171 in the compensating valve 84 and line 113 to act rightwards on a land 93 of the main regulator valve 80, where, assisted by rightward pump-pressure loading on a land 90, and opposed by a spring 102, it causes a land 91 to meter to exhaust 106, thus regulating pressure in the line 112 to a desired maximum. The clutch cylinder 19 is exhausted through line 213, a non-return valve 223 in the cushion-valve 87, line 199, solenoid valve 85, line 191, governor-control valve 83, line 137, throttle-control valve 81 and bleed 129. 2. Accelerator depression - substitutes the regulator-fed main 112 for the bleed 129 so that engaging pressure is now supplied to the clutch cylinder 19 through a path which is the same as the previous exhaust path up to the cushion valve 87, the non-return valve 223 of which now closes so that pressure is supplied through a groove 220 in the piston 214, until the cushion point is reached when build up of engaging pressure depresses the piston 214 cutting out this path and leaving only the restricted path 224, so that further increase in engaging pressure is retarted. The same accelerator depression also, through a spring 124, loads the throttlepressure valve 82 against a blade-spring 126, which valve meters throttle-variable, "TV," pressure to a line 139 to act leftwards on a land 161 of the compensating valve 84, causing metering at the ports 170, 171 which forward pressure to an endport 175 to act leftwards on the compensating valve 84 and, as before, through the line 113, acts rightwards on the main regulator valve 80. Metering action of the compensating valve ports 170, 171 causes compensated pressure in the line 113 to be reduced in proportion as the accelerator is depressed and the final regulated pressure metered to the line 112 by the main regulator valve is thus increased with increasing accelerator depression. 3. Clutch engaged; below predetermined speed. Increase in speed of the clutch output shaft 13 causes the radially disposed differentially-landed centrifugal valvemember of the governor valve 79 to meter a speed-responsive pressure to a line 151 acting rightwards on the compensating valve 84 in opposition to leftward TV pressure, so that compensating pressure 113 is now increased with speed as well as reduced with accelerator depression. This pressure 113 acting rightwards on the main regulator valve 80 causes clutch-engaging line-pressure 112 to be reduced with speed and increased with accelerator depression. 4. Clutch engaged; above predetermined speed. At all times the governor pressure 151 acts leftwards on the governor-control valve 83 and when this pressure reaches a predetermined value, corresponding to that produced at a road speed of 12 m.p.h. in high gear, the valve 83 is shifted to the left, connecting the pressure-main 112, 138, 177 directly to the clutch feed and cutting out the line 137 leading to the throttlecontrol valve 81, so that accelerator-release cannot now cause clutch-release. 5. Gear shift. Operation of the switch 206 prior to gear shift moves the solenoid valve 85 to the right, exhausting the line 199 at 198 for rapid declutch through the non-return valve 223, re-engagement on release of the solenoid valve 85 being as above described.