GB1211482A - Hydraulic control for change speed gear transmission - Google Patents

Abstract

1,211,482. Change speed control. DR.-ING. H.C.F. PORSCHE K.G. 16 Aug., 1968 [16 Aug., 1967], No. 39289/68. Heading F2D. In a vehicle change-speed planetary gear, e.g. giving three forward gears and reverse, which are selectively engaged by hydraulic servo-actuated brakes B1 B2 and clutches K1, K2 controlled by an automatic shift valve 27 in accordance with vehicle speed, (sensed by a governor unit 43, Fig. 3), the shifts are timed by a multiple fluid interlock between the apply and release pressure chambers of the breakes and apply chambers of the clutches wherein a release chamber D1 of a first brake B1 is in permanent communication with an apply chamber D6 of a clutch K2; and the apply chamber D2 of the same brake B1 is in permanent communication with the release chamber D3 of the second brake B2 and is connectable through the selector valve 26 with the apply chamber D5 of the other clutch K1. Spring-loaded accumulators 21, 22 connected in the chambers D 1 , D 3 assist in smoothing the shifts. Again, Fig. 7, (not shown), in a two forward gear and reverse change-speed gear, the accumulator 24 is omitted, and chamber D2 is connected to the apply chamber D5 of clutch K1. The governor unit 43 may be subjected to accelerator pedal 65 modulation through linkage 64 which includes a barometrically operated control expansible chamber 66 to provide a connection for the elevation at which the vehicle is driven. An over-riding manual control 84 prevents automatic upshifts in forward gears, and positions the gear in parking P, reverse R, and neutral O. The control 84 may be used to provide complete manual control. Gear arrangement.-The engine drives the gear input shaft 8 through a torque converter 5-7. The gear 2 comprises two planetary trains having a common sun 10 and an output shaft 15 drivingly connected to the planet carrier 13 of the first train and the ring gear 14 of the second train. For first gear, a clutch K1, connects the ring gear 11 to the input shaft 8, and the brake B2 is applied to hold the planet carrier 18. For second, using the first train alone, the clutch K1 remains engaged, and the sun 10 is held by applying a brake B1. For direct drive third, clutches K1, K2 are both engaged to lock-up the first train. For reverse, using the second train alone, the clutch K2 is engaged, and brake B2 applied. In park, all clutches and brakes are released. Fluid pressure circuit.-A pump 34 only supplies oil through a line 37 and restricted orifices 38 to shift valve 27 and through a pressure regulating valve 35 and line 33 to the differential piston of brake screw 20, and through line 41 to apply chamber D5 of clutch K1 and line 39 to valve 27. Governor unit 43, Fig. 3, comprises rotating masses 44 linked to end abutments 55, 56 axially movable along but rotatable with a sleeve 46 driven by the output shaft 15 through a gear-wheel 47 coupled to the sleeve by a known torque coupling 48 which slips under excessive strain to prevent damage to the governor. The abutment 56 is axially located on sleeve 46 by a cam 62 on a lever 63 forming part of the accelerator pedal linkage 64. The other abutment 55 is connected to the spool of the shift valve 27 and positions that in response to vehicle speed. Spring biased rollers 75 engage in grooves 74 in a sleeve 73 connected to the valve spool to form an indexing device 45. The manual lever 84 operates on the spool to prevent automatic upshifts by means of a rod 81 carrying a cap 82 spring-biased away therefrom. A worm wheel 67 driven by the sleeve 46 may drive the speedometer. In the two forward speed embodiment of Fig. 7 (not shown), the two forward speeds correspond to the second and third forward speed gears of the first embodiment, the planetary gearing being identical.