Patent GB-530421-A (GB)
Title: Improved change-speed gearing for motor vehicles
IPC: F16H61/02
Filed: 1939-06-23
Abstract: 530,421. Variable-speed gearing. GENERAL MOTORS CORPORATION. June 23. 1939, No. 18332. Convention date, July 1, 1938. [Class 80 (ii)] [Also in Group XXXIV] Change-speed gearing for motor vehicles comprises a number of epicyclic gears 18, 162, 176, Fig. 1, the last of which is a reversing-gear, and the first serves for automatically establishing the drive between the engine and the gearing under the control of a speed governor. The engine shaft 3 carries an annulus gear 4 with internal teeth meshing with planet gears 6 mounted on a carrier 7, the sun gear 21 being carried by a sleeve 9 mounted on the output shaft 10. The carrier 7 also accommodates clutch plates 16 alternating with plates 20 carried by a drum 18 connected to the sleeve 9, the plates being pressed into contact, against the action of springs 22, by fluid pressure applied to pistons 32 from a passage 34 and pipe 101. A brake band 30 encircling the drum 18 is operated by fluid-pressure means shown in Fig. 2 and at 60, Fig. 8. The second gear element 162 comprises similar clutch plates 155, 160 actuated by fluid pressure applied to pistons 166 through a pipe 33<1>, the drum 162 being surrounded by a brake band 170. also actuated by fluid-pressure means shown in Fig. 7 and at 190, Fig. 8. The shaft 10 carries pinions 151, 152 gearing respectively with planet gears ,158, 154 mounted on carriers 159, 156. The gears 158 mesh with an annulus gear 161 on the drum 162, and the gears 154 mesh with an annulus gear 157 formed on the carrier 159. The carrier 156 drives the tail shaft 300, on which is supported a sun gear 171 forming an extension of the drum 162 and engaging planet pinions 173 of the reverse unit mounted on a carrier 172 fixed to the shaft 300. An annulus gear 175 is formed on the drum 176 encircled by a brake band 180 operated by fluid-pressure means 210, Fig. 8. Four forward speeds are obtainable as follows-(1) with brakes 30 and 170 both applied ; (2) with clutch 16, 20, engaged and brake 170 applied ; (3) with brake 30 applied and clutch 155, 160 engaged; (4) with both clutches in action. For reversing, the brakes 30 and 180 are applied. For the automatic transmission of the drive from the engine to the gearing, in accordance with engine speed, there is provided a valve device 90, Fig. 8, actuated by the centrifugal force on a weight W attached to the valve, so as to vary the oil pressure supplied to a pipe 104 by a pump P driven by the engine, this oil pressure acting on a piston valve operating within a cylinder 119. When the engine is idling, with the vehicle stationary, the piston valve is in its uppermost position so as to allow oil to flow from the pump by pipe 105 to pipe 102. which moves piston 67, Fig. 2, to the left against the pressure of springs 78, so as to release the brake 30. As the speed of the engine is increased, the pump pressure is sufficient to move the piston valve downwards against spring action, thereby connecting pipe 102 to exhaust, allowing the springs 78 to anchor the end 39 of the brake 30. Further increase of speed moves the piston valve further, so as to admit the oil to pipe 103, thereby applying the brake 30 through piston 77. The various speeds and reverse are obtained by means of balanced selector valves V<1>, V<2>, V<3>, V<4> arranged as indicated in Fig. 8, and controlled means of a slotted cam plate actuated by a lever on the steering-wheel. For the reverse, the valves V<1> and V<4> are in the upper position shown, but the valves V<2> and V' are moved down to connect the pump line 115 to pipes 195 and 215, thus releasing brake 170 by moving the piston 188, Fig. 7, to the right and applying brake 180 by moving piston 213, Fig. 8, to the left. For low forward speed, the valve V' only is moved down, the valves V', V<2>, and V' exhausting pipes 101, 195, and 215 from the brake cylinder, so that the brakes 30 and 170 are applied, and the brake 180 released. For second speed, valves V' and V<4> are moved down, so that oil pressure is again supplied to pipe 101, releasing brake 30 and engaging clutch 16, 20 by acting on the pistons 32, while brake 170 remains applied. For third speed, valves V<2> and V<4> are moved down, brake 30 being thereby applied, brake 170 released. and clutch 155, 160 engaged by means of the pistons 166. For top speed, valves V', V<3>, and V<4> are moved down, releasing the brakes and engaging both clutches. In order to obtain a clutch-engaging pressure in proportion to the movement of the accelerator pedal, the latter is connected to a lever 232<1> which raises a compensation valve C more or less, thereby varying the pressure admitted from the pump line 115 to a pipe 100 which supplies the pressure to auxiliary pistons 65, Fig. 2, and 194, Fig. 7, thereby modifying the action of the brakes 30 and 170. Means may be provided for applying the brake 180 mechanically when emergency braking of the vehicle is required. The valves V<1> ... V<4>, instead of being actuated manually, may be controlled automatically in accordance with speed, as described in Specifications 463,643, 484,301, and 503,276.