GB796948A - Improved variable-speed power transmission mechanism and hydraulic control system therefor - Google Patents

Abstract

796,948. Controlling change-speed gearing., GENERAL MOTORS CORPORATION. Dec. 5, 1956 [Dec. 5, 1955], No. 37158/56. Class 80 (2). A pressure regulator valve, for an hydraulic control system for a vehicle variablespeed transmission, is biased towards a regulator chamber, having a one-way valve connection with the inlet and a restricted passage to the outlet to delay the closing of the valve exhaust to inlet on a fall in inlet pressure. Gearing.-An enginedriven input shaft 1 is connected to the impeller 2 of a torque converter having a turbine 3 connected to a transmission input shaft 4, and reactors 6, 7 in one-way clutch connection with a fixed member 8. The shaft 4 carries two sun-gears 9, 10 of two epicyclic trains 9, 15, 16 and 10, 18, 19, which by engagement of brakes 14 to planet carrier 13 or 21 to annulus 19 provides reverse or forward drive to a hollow output shaft 11. The shaft 11 may be connected to a transmission output shaft 12 through a direct drive clutch 24, a high-speed train 27, 26, 28 or a low-speed train 33, 32, 36 through respective engagement of the clutch 24, brake 29 or brake 37 and thus providing an overdrive, direct and underdrive ratios in both directions of rotation. Control system.-Input and output shaftdriven pumps 42, 43 draw fluid from a sump 41 and discharge it to a main supply passage 49 directly and through a one-way valve 52 respectively. The main supply 49 is connected to a pressure regulator valve 44 directly through a by-pass passage 54 and through a main passage 57 and a filter 56. A relief valve 59 normally prevents flow from the passage 54 to an inlet port 61 to which the passage 57 is connected but under conditions where the flow through the filter 56-is restricted the valve 59 opens to admit fluid directly to the inlet 61. The regulator valve 44 has a slidable plunger 62 having a cross-passage 63 to connect the inlet 61 through an.axial passage 64 and spring-biased check-valve 67 to a pressure regulator chamber 65 to the right of the plunger which is urged to the right by a spring 66. As pressure in the inlet 61 increases the plunger 62 moves to the left against the spring 66 to uncover a port and allow fluid to be passed to the feed passage 68 of the torque converter. Movement of the plunger also allows the inlet from the passage 54 to be connected to a relief exhaust port 69 through apertures 71 in the plunger. Fluid under pressure in the chamber 65 prevents a rapid movement of the plunger 62 to the right since the only escape for the fluid trapped in the chamber is by a vent 72 in a land of the plunger. The passage 57 is connected by passages 76, 77 to two ports of a forward/reverse selector valve 46 of the kind described in Specification 792,398, controlling the admission of fluid to the reverse servo 86 of the brake 14 and the forward servo 92 of the brake 21. The inlet 61 of the regulator valve 44 is also connected by a passage 70 to a cut-off valve 98 disposed between the valve 44 and a manual ratio selector valve 47 controlling the fluid supply to the clutch 24 and brakes 29 and 37. The cut-off valve 98 is normally held in the open position by a spring 122 having a preselected variable loading by an adjustable abutment 125. A reduced portion 121 of the valve slides in a chamber to which vehicle brake fluid pressure is.admitted through a passage 124, closable by a shut-off valve 129. On application of the vehicle brakes, fluid under pressure in the passage 124 moves the valve 98 to deprive the manual selector valve 47 of fluid pressure and consequently to disconnect the drive. The loading of the spring 122 may be adjusted so that any desired degree of application of the brakes may be made before the valve 98 moves.