GB789285A - Improvements relating to power transmission mechanisms - Google Patents

Abstract

789,285. Clutches. GENERAL MOTORS CORPORATION. June 27,1956, No. 19881/56. Addition to 690,592. Class 80 (2). In a multiplate friction clutch 16, 18 with engagement. and disengagement effected by supplying pressure oil alternatively to cylinder chambers 26, 28 on opposite sides of a piston 30 secured to the driving shaft 12 and with means whereby, above a predetermined speed, engagement pressure is automatically increased, as in the parent Specification, the pressure oil for disengagement is supplied to chamber 28 direct from pump 42 through pipes 84, 82, tube 46 and passages 36 and is thus higher than that supplied to chamber 26 for engagement, which is through pipe 68, pressure-reducing valve 76, pipe 62, tube 44 and passages 32, both supplies being under the control of a double piston valve 64. During the initial engagement and disengagement stages, cooling oil is supplied direct from pump 42 through pipes 66, 92, tube 48 and passages 38, 49, under the control of a spring- loaded piston valve 94, between the clutch plates and to the chamber 28. The valves 64, 94 are operated by a double-acting hydraulic servomotor 101, the piston 102 of which has a plate 130 co-operating with a flange 142 on valve 94 and with spaced flanges 132, 136 on valve 64, which latter is normally held in either engaged or disengaged position by a spring detent 138. The servo is controlled by rotary valves 105, 119, operated either directly by levers 104, 118 or indirectly by remotely -controlled solenoids, which serve to apply pump pressure to one or other side of piston 102 and to exhaust the other side. A piston valve 172, rigid with valve 64, controls supply from pump 42 to a spring-loaded accumulator 176. To engage the clutch, valves 64, 94 and piston 102 being initially in their left-hand positions, valves 105, 119 are turned into the positions E, V as shown, in which pressure oil is supplied to left-hand side of servo 101 and right-hand side is vented, while valve 105 also commences to charge accumulator 176 and a cylinder 152, containing a piston 146 cooperating with valve 94, through bleed passage 156, pipe 153, valve 172 and pipe 162. Plate 130 thus moves valves 64, 94, 172 fully to the right, causing oil at reduced pressure to be supplied to chamber 26 and connecting chamber 28 to exhaust, and also causing cooling oil to be supplied to the clutch plates and to chamber 28, maintaining the latter substantially full, so that the centrifugal effects of oil in the two chambers 26, 28 balance. Valve 105 continues to charge cylinder 152, but accumulator 176 is now charged directly from pump 42 through pipe 178 and valve 172. When clutch engagement is complete, valve 105 is turned to position V<SP>1</SP>, thereby venting left-hand side of servo 101 and, via bleed 156, the cylinder 152. Valve 94 therefore moves to its left-hand position, cutting off the supply of cooling oil and carrying with it plate 130, this movement being damped by the bleed 156. During this movement, valves 64, 172 do not move, due to the space between flanges 132, 136. An orifice 49A in the end wall of chamber 28 partially empties the latter and, at full speed, a speed-responsive valve 52 opens to complete the emptying, and the centrifugal pressure in chamber 26 now augments the engagement pressure. To effect disengagement, valve 119 is turned to position D and the righthand side of servo 101 is thus charged and plate 130 moves valves 64, 172 to their left-hand position. Thus, chamber 26 is vented and chamber 28 is charged, and the charged accumulator 176 is now cut off from pipe 178 and discharges into cylinder 152, forcing valve 94 to the right to supply cooling oil to the clutch. The oil in cylinder 152 and accumulator is slowly exhausted via bleed 156 and valve 105, so that valve 94 eventually moves back to the left and cuts off the supply of cooling oil.