Patent GB-909908-A (GB)
Title: Control system for a vehicle change-speed transmission
IPC: B62D11/08
Filed: 1961-05-17
Abstract: 909,908. Hydraulic brakes. GENERAL MOTORS CORPORATION. May 17, 1961 [June 6, 1960], No. 17954/61. Class 103 (1). [Also in Groups XXIV and XXXI] Control mechanism for an amphibious vehicle having an engine-driven cross-shaft, an output shaft on each side and a separate planetary change-speed gear between the cross-shaft and each output shaft, comprises a steering valve movable from a straight steering position to control the gearing so as to produce a different speed ratio on the two sides, and a two-position control valve operative in its first position to select the ratios of the gearing in such a way that either in the straight steering position the two change-speed gears give high ratios and, on turning a curve, a high ratio on one side and an intermediate ratio on the other, the control valve in its second position selecting intermediate ratios on both sides when the steering valve is set for straight drive and, when turning, an intermediate ratio on one side with disengagement of the gear on the other side simultaneously with the application of a brake to the output shaft of the latter gear. Gearing.-A shaft 14, Fig. 1b which may be driven from the vehicle engine through a change-speed gear (not shown), transmits drive through bevel gears to a cross-shaft 18 formed at its two ends with ring gears 22. Planet pinions 24 carried by left and right-hand side output shafts 44, 34 mesh the ring gears 22 and also mesh sun gears 26 which can be stationed for reduced ratio drive by admission of oil under pressure through pipes 141, 152 to servomotors containing ring-shaped pistons 32 thereby caused to engage multi-disc brakes 29. Alternatively, by admitting oil under pressure through pipes 142, 151 to servomotors containing ring-shaped pistons 37 multi-disc clutches 33 can be engaged to lock-up the two gears. When the ratio establishing clutches and brakes 29, 33 are disengaged, oil under pressure can be admitted through pipes 138, 153 to act upon pistons 44 coacting through balls 47 and cam slopes with brake-pressure plates 43 contacting multi-disc brakes 42 engaged to station the two output shafts 34. When oil under pressure is first admitted to engage the brokes 42, the rotation imparted to the brake-pressure plates 43 causes the balls 47 to ride-up their cam slopes, so that selfenergizing action aids engagement thereof. Direct manual engagement of the brakes 42 may be effected by rods or cables secured to ears 48 on the brake-pressure plates 43. Control.-When a control valve 54, Fig. 1a is in neutral, an engine-driven pump 52 is vented to an exhaust pipe 57 including a pressuremaintaining valve 76, Fig. lb, and through pipes 136, 148, 162 for lubrication of the clutches and brakes in the gearing. When the control valve 54 is moved to the L1 Land Drive position, the pump 52 is connected to a main pipe 56 leading to a pressure-regulator valve 61. At first, regulated pressure is supplied only therethrough to a drive pipe 71, but as the pressure increases, the pressure-regulator valve 61 opens to supply oil to a steering pipe 72. So long as a steering valve control 80 is in its straight-drive position, drive pressure 71 is connected through steering valves 81, 82 to pipes 83, 91, and thence passes back through the control valve 54 to the pipes 142, 151 for engagement of both the direct drive clutches 33. The brakes are then vented. By turning the steering control 80, e.g. rightwards, a valve 101 in the steering valve 81 is similarly slidden rightwards, shutting-off the drive pipe 71 from the pipe 83 and venting the latter to an exhaust 87 to disengage the right clutch 33. The steering pipe 72 is then progressively connected by the valve 101 to a pipe 84, and finally the valve 101 engages a pressure-control valve 103 which enforces full pressure in the pipe 84. The control valve 54 now connects the pipe 84 to the pipe 141 for engagement of the right sun-gear brake 29, thus providing a step-down ratio to the right-hand drive shaft 34. Similarly, a step-down ratio may be provided to the left-hand drive shaft 34 by turning the steering valve control 80 leftwards. On moving the control valve 54 to its W1 Water Drive position, with the steering drive control 80 in its straight steer position, the drive pipe 71 as before is connected to the pipes 83, 91. The pipe 83 is now connected through the control valve 54 to engage the right-hand sun gear brake 29 and the pipe 91 is connected through the valve 54 to the pipe 152 to engage the left-hand sun gear brake 29. The clutch servos are vented, and both gears give a reduced drive. On turning the steering valve control 80 rightwards, the valve 101 shuts off feed from the drive pipe 71 to the pipe 83 and vents the latter to exhaust 87, disengaging the right-hand reduced ratio brake 29. The valve 101 then progressively supplies pressure regulated by the valve 103 to the pipe 84, now connected through the control valve 54 to the pipe 138 for engagement of the right-hand output shaft brake 42 to station the right-hand output shaft 34. Similarly, on turning the steering control leftwards, the left-hand output shaft brake 42 is engaged. Lubricating lines leading to the clutches and brakes are fed according to the setting of the steering and control valves 81, 82, 54.