Patent GB-864778-A (GB)
Title: Variable-speed power transmissions
IPC: F16H47/08
Filed: 1958-01-10
Abstract: 864,778. Change-speed control; variable-speed gear. BORG-WARNER CORPORATION. Jan. 10, 1958 [Jan. 11, 1957], No. 1045/58. Class 80 (2). In a change-speed gear having low and high speeds under the control of a selector valve operated by manual shift means, the connection between the shift means and the valve allows movement of the shift means from high to low without movement of the valve. Function summary.-A compound planet gear, driven always wholly through a torque converter 30 of the over-run reactor type provides two reduced ratios, direct-drive, neutral and reverse by two band-brakes 33, 34 and two disc clutches 31, 32, all under fluid-pressure control. A manual valve 116 provides low, drive, neutral and reverse (L.N.D.R.) in that order. L gives low and intermediate speeds and D intermediate and direct drive under the control of an automatic shift-valve 117 actuated by fluid-pressure from input and output shaft pumps 160, 161, respectively, the pressure from the pump 160 being regulated in accordance with inlet manifold, 213, suction. Movement of the manual shift lever 149 to an undesirable position is prevented from action on the valve 116 by a lost-motion connection 142 and an output shaft speed-responsive piston 139. Accelerator kick-downshift is provided by a ball-valve 195 which vents the chamber 172 at the end of the valve assembly 117. Servopressure is increased with speed and decreased with throttle opening by a pressure control valve 118 partially under the control of a vacuumresponsive motor 119. Gear arrangement.-Intermeshed planets 60, 61 mesh suns 55, 56 selectively clutchable by clutches 32, 31, respectively, to a convertordriven input-shaft 27, the planets 60 also meshing a ring-gear 35 fast on the final output shaft 26. Low speed is by driving the smaller sun 55 through the front clutch 31 and holding the planet carrier by the rear brake 34. Intermediate is with the clutch 31 engaged together with the front brake 33 for the larger sun 56. Direct drive is by driving both suns through the two clutches 31, 32. Reverse is by engagement of the rear clutch 32 and the rear brake 34. Fluid supply.-The input driven pump 160 supplies fluid to the torque converter 30 by a duct 241 through a pressure-reducing valve 120 which balances pump outlet pressure on the right-hand end of piston 235 and the force of spring 238 against the fluid-pressure on the enlarged piston 237. A pressure-reducing valve 121 is provided in the outlet 243 from the converter to maintain a predetermined pressure in the conduit 251 for gear lubrication. A pressure control valve 118 between the inlet 206 of the pump 160 and the outlet 207 to the manual valve 116 maintains the pressure in accordance with manifold suction and outlet pressure from driven shaft pump 161. The piston 198 of the valve 118 is loaded rightwards by delivery pressure in orifice 204 and by the pressure applied to the front brake 31 through pipe 83 through a restrictor 203, and the piston is loaded leftwards by a lever 224 actuated by a push-rod 218. The push-rod 218 is loaded to the left by a spring 228 acting on a fixed collar 227, by a pair of springs 222, 223 within a piston 219 having a piston-rod abutting the push-rod 218, and by a spring 214a acting against a diaphragm 209 having a stud 212 abutting the rod 217; the diaphragm being in a vacuum motor 119 connected to the engine inlet manifold 213. Increasing speed of the driven shaft 26 increases the pressure from pump 161 which pressure acts on piston 219 against springs 222, 223 to reduce the loading on the valve 198 and reduce engaging pressure of the fluid with vehicle speed. Decrease in torque measured by manifold depression moves the diaphragm 209 against spring 214a to unload the rods 217 and 218 and reduce fluid pressure with decreasing torque. A check valve 254 is arranged between the deliveries 232 of pump 161 and 159 of pump 160 which valve when opened limits the delivery pressure of pump 161 to that controlled by the pressure control valve 118. This check-valve provides higher delivery pressures in conduit 232 with higher outputs from the engine. Operation:-Neutral (N).-With the manual selector valve 116 in N position, the land 126 blocks the inlet 159 and prevents fluid actuating the two clutches and the two brakes. Drive (D).-When the valve 116 is moved to the D position, intermediate speed drive is initiated and subsequent change to high speed (direct drive) is obtained by automatic operation of the valve 117. In the D position fluid is supplied from inlet 159 to port 134 and front clutch 31 through pipe 83. At this time the valve 117 is held to the left by a spring 182 to abut a piston 167 against a stop 185, and fluid passes through a passage 135a, port 178 and port 179 to engage the front brake 33 through pipe 182. This causes engagement of intermediate drive. As the vehicle moves forwards the pump 161 delivers pressure fluid to the space 137 and through a restrictor 187 and port 180 to the space 172 ; pressure is also supplied to the piston 219. As vehicle speed increases the loading of the piston 219 by the two springs is increasingly counteracted by the pump 161 pressure resulting in a drop in the controlled outlet pressure from pump 160 which is holding the brake and clutch engaged. Since the engaging pressure is maintained in proportion to the torque smooth changes of ratio are obtained, the pressure changes being effective up to the speed at which the torque converter 30 commences to act as a fluid coupling. Increasing pressure in the space 172 moves the piston 167 and valve 117 to the right, against the spring 182 and the pressure in port 181, to connect the passage 135a with the port 177, pipe 86 and rear clutch 32, and at the same time close port 179 to pressure to disengage the front brake 33. As rear brake 34 remains engaged due to the position of the valve 116, direct drive is engaged. Kickdownshift.-Movement of the accelerator pedal 155 to open throttle kickdownshift position moves a cam-plate 153 to engage the end of a push-rod 152 to unseat a ball valve 195 and vent the space 172 through 188, chamber 193 and duct 196 to the sump, this reduction of pressure on the piston 167 allows the pressure on the right of valve 117 and spring 182 to move the valve 117 to the left and so engage intermediate gear. Low (L).-When the manual valve 116 is moved to the L position land 127 blocks port 135 and cuts off fluid to the right of valve 117; at the same time land 126 allows fluid from 159 to pass to the rear brake 34 through port 132 and pipe 158. Also pressure from 159 engages the front clutch 31 through port 134, thus engaging the low-speed train. With the manual selector valve 116 in L position automatic shift to intermediate is. allowed by a lost-motion pin- and-slot connection 142 between the valve and its operating-lever 149, the pin being normally held against the end of the slot by a spring 145. As vehicle speed increases in L ratio the pressure from pump 161 increases and restrictor orifice 187 allows pressure build-up to move a piston 139 against a spring 141 to move the manual valve 116 to D position and initiate intermediate drive. Automatic change to direct drive under wide throttle conditions with the valve 116 in L position is prevented by a cam surface 151 on lever 149 moving the rod 152 to unseat the ball 195 and vent the chamber 172, thus preventing movement of the piston 167 for further upshift. As vehicle speed drops the pressure on the piston 139 drops and the springs 141 and 145 return the piston and valve 116 to L position. Reverse (R).-With the manual valve 116 in the R position the inlet 159 is connected to port 132 to engage the rear brake 34, and pressure is also fed through duct 184 to the righthand end of the valve 117 which moves to the left to pass fluid through port 131, check-valve 157, port 176, bore 171 and port 177 to the rear clutch 32 to engage the reverse train. Pressure in the chamber 200 of the pressure control valve 118 is vented through port 136 to provide increased servo pressure for the reverse brake and clutch engagement. In a second embodiment, Fig. 3 (not shown), the method of operation is substantially the same but the construction of the various valves has been simplified. A bimetallic strip holds a conical valve in a sharp edge orifice to provide compensation for viscosity increases to maintain the pressures on the pistons 139, 167 constant regardless of temperature.