Patent GB-885901-A (GB)
Title: Control system for a torque transmission
IPC: F16H47/08
Filed: 1960-01-15
Abstract: 885,901. Variable-speed gears. GENERAL MOTORS CORPORATION. Jan. 15, 1960 [Jan. 23, 1957], No. 1527/60. Class 80 (2). [Also in Group XXXIV] In a variable-speed gear having a pair of friction brakes 26, 36 alternatively engageable for introducing forward and reverse, separate sources of pressure fluid are provided for actuating the brakes and for cooling them, and the cooling fluid to one brake is augmented by control fluid during engagement of that brake. A pump 103 supplies control fluid from a sump 101 through a line 106 to a selector valve 136 from which lines 144, 143 lead to servo cylinders 242, 271 of the brakes 26, 36. A pump 110 supplies coolant from a sump 108 through a line 112 to the selector valve, whence, in the neutral position shown, liquid is supplied through lines 156, 157 and passages 252, 253 and 278, 279 to the brake plates. When the selector valve 136 is moved to the forward drive position, liquid from line 106 is supplied through line 144 to actuate the brake 26, and is also supplied through a line 148 to the coolant line 156 to increase the supply of cooling liquid to the brake 26. At the same time a land b of the selector valve closes a port 147 leading to the line 157, and a reduced flow of coolant is supplied to the reverse brake 36 through a restriction 152 between the lines 156, 157. A restricted passage 264 between the servo cylinder 242 and the coolant line 156 further increases the supply of coolant to brake 26. The pressure in the servo line 144 is controlled by a regulating valve 191, the pressure in line 144 acts on differential areas of lands c, b of the spool 193 of the regulating valve, moving it to the left against the pressure of a spring 199 and thus opening a path to the cooling line 156 of the forward brake 26. Pressure in line 144 downstream of the regulating valve is led through a one-way restriction 218 to a space behind a plunger 198 to move it to the right thus increasing the spring pressure on the regulating valve spool. The pressure in line 144 is thus gradually increased. In shifting from forward to neutral or reverse the engine speed is temporarily reduced, this is accomplished by a knock-down valve 171 having a piston 172 centred by springs and subject to the pressures in the servo lines 143, 144 through passages 184, 187 and 183, 186. Control fluid from line 106 is supplied through a restriction 178 and an annular channel 181 to a cylinder 82 to move the piston 81 to the right to enable an engine-driven governor to operate the fuel control of the engine in accordance with the setting of a manual control lever 93. In the forward position of the selector valve 136 the valve piston 172 is moved to its left-hand position by the pressure in line 144, and a path is opened from the right-hand end of the chamber of valve 171 through a channel 179 and an annular channel 181 to the cylinder 82. In shifting the selector valve 136 from the forward to the neutral or reverse position, the servo line 144 is opened to exhaust. The cylinder 82 therefore rapidly exhausts through the channels 181, 179, the right-hand end of the valve chamber and line 144. In the neutral position of the selector valve the valve piston 172 is centred by its springs and the pressure in cylinder 82 rises as liquid passes through the restriction 178 so that the governor can again function normally. In the reverse position of the selector valve the valve piston 172 is biased to the right and the cylinder 82 is again pressurized. The arrangement for the reverse brake 36 is the same as that for the forward brake. Variable-speed gearing.-A gear selector valve 116 is provided for selectively supplying liquid from the line 106 to high and intermediate ratio brakes 46, 56 and to a low-ratio (direct drive) clutch 57. The brakes and clutch are part of a variable-speed gear comprising a turbo converter having a pump P, two one-way mounted reactors S and a turbine T driving a sun 21 of a first epicyclic train. The first train has a ring gear 24 fast with a sun 32 of a second train and is stationable by the forward brake 26, and planets 23 on a carrier 28 also carrying planets 31, 41 of the second and a third train. The ring gear 34 of the second train is stationable by the reverse brake 36, the third train has a sun gear fast on an output shaft 43 and a ring gear 44 stationable by the high-ratio brake 46 and fast with a planet carrier of a fourth train having a ring gear 52 stationable by the intermediate brake 56 and clutchable to the output shaft by the low-ration clutch 57.