Patent GB-726079-A (GB)
Title: Improved variable speed power transmission mechanism for motor vehicles
IPC: B60W30/18
Filed: 1953-02-11
Abstract: 726,079. Change-speed gear. GENERAL MOTORS CORPORATION. Feb. 11, 1953 [Feb. 20, 1952], No. 3796153. Class 80 (2). A three-speed and reverse gear for a vehicle, between aligned input and output shafts 1, 70, provides mechanical  direct-drive through an input-connected central shaft 20 and rear disc-clutch 55, and two reduced ratios through an input fluid-coupling 10, cone clutch 22 and countershaft pair 31, 36, with return pair 42, 41 for low, and 37, 44 with cone clutch 52 for second speed. The wheels 31 and 44 are journaled on, and 41 splined on, an outer hollow shaft 40 permanently connected to the final output shaft 70 through the outer member 55 of the direct-drive disc clutch, the inner member of which latter is fast on the input-connected inner shaft 20. The splined wheel 41 is mechanically moved, through a shift-rail 170, to mesh wheel 42 or an idler 47 for low or reverse respectively. All three friction clutches are engaged by oil pressure, the countershaft driving clutch 22 being also disengaged by oil-pressure. The inner shaft 20 is connected to the input 1 through a spring coupling 16. Function summary. A low speed, neutral and reverse manual control 180, Fig. 8, mechanically operates the shiftrail 170, Fig. 2, of the splined wheel 41, Fig. 1, and is associated with a yielding spring coupling 186, Figs. 2, 9, which permits an initial movement whilst the shift-rail is locked at 166, Fig. 2, such movement releasing the countershaftdrive cone clutch 22 and the shift-rail lock 166 during the shift. A threeposition manual control 174, Fig. 8, of a valve 127, Fig. 2, interlocked with the first; neutral, reverse control 180, provides two operative positions one, 2nd, for enforced second speed, the other DR (Drive), giving automatic shift between second and high speeds by an auto-shift valve 123, subject to opposing oil pressures varying respectively with vehicle speed, as determined by an output-driven pump Q, and engine throttle-valve position acting at 176 on a valve 128 providing regulated "TV" (throttle-variable) pressure 214; and accelerator kickdown 3-2 shift acting at 129 and effective only below a predetermined vehicle speed. A timing valve 124 provides transitional shifts between second and high speeds. A lock 236 is engaged with the low-reverse shiftrail 170 by output-pump pressure to prevent shift to low or reverse during movement of the vehicle. For a towed engine-start the output-pump Q supplies pressure to engage the direct drive clutch 55. Pressure augmentation is provided for enforced second-speed operation. Clutches. The direct-drive clutch 55 comprises a disc-pack compressed by oil-pressure applied to an annular piston 108 and released by a spring 65. The second-speed clutch comprises a hollow cone 53 splined to the driving second-speed wheel 44 and clamped to the outer output cone 54 by applying oil-pressure at 145 to an inner coned piston 52. The countershaft-drive clutch comprises a hollow cone 29 splined on the countershaft-drive wheel 31, and clamped to an inner input cone 27 by pressurizing a chamber 103 to act leftwards on an outer cone 22 sliding axially on pins 26 on the inner. A sinuous spring 112 assists engaging pressure. Release is by exhausting the chamber 103 and pressurizing an opposing chamber 103a. Fluid-supply system. Input and output driven pumps P Q supply the system, their respective delivery lines 131, 155 being connected by a check-valve 135, the loading-spring of which opposes the output pump Q, so that the pressuremain 131 is normally supplied by the input pump P, whilst the output pump Q provides only speedgoverned pressure for the auto-shift valve and pressure for a towed engine start. The fluidcoupling 10 and a lubricating line 152 are supplied from a main pressure regulating valve 122 through a cooler 148, provided with a by-pass 150. Fluid-system components. The following valves are provided and function as described later. A combined clutch-control valve and shiftrail lock 120, which temporarily unlocks the lowreverse shift rail 170 at 166 and disengages the countershaft=drive clutch 22 during a shift of that rail, under control of a low-reverse shift-prepare valve 126 itself operated by initial movement of the manual rockshaft 180. A tow-start valve 121 effective during towing the vehicle to shut-off the input 'pump P and act as a pressure regulator for the output-pump. A main pressure regulator 122 effective at all times except during towed start. An automatic 2-3; 3-2 shift-valve 123 subject to the opposing speed and TV pressures. A timing- valve 124 providing transition in the automatic shift. A manual valve 127 operated directly by the interlocked control 174, Fig. 8, for DR or second speed. A TV regulator valve, 128, supplying throttle-valve regulated pressure from the supply main 131 to a TV-regulated line 214, in accordance with pressure applied to its loading spring 213 by an arm 176 linked to the engine throttle control. The latter arm 176 also actuates a kickdown shift valve 129 at full-throttle position. Mechanical shift system. Freely mounted on the manually-rocked 1st, N, R shaft 180, Figs. 2 and 9, is an arm 182, the forked end 194 of which receives a pin 193, projecting from the shift-rail 170 of the 1st-rev. wheel 41 so as always to actuate the rail when rocked. Between the rail-actuating arm 182 and an arm 181 fast on the rockshaft 180 is a slotted cam-plate 183 which can swing freely within the limits of its slot 185 about an eccentric axis on the arm 182 defined by a pin 184 on the plate engaging a hole in the arm. Pins 189, 190 on the rockshaft arm 181 engage opposite sides of the cam-plate 183 at points 191, 192 on radially opposite sides of its swing-axis 184, so that no matter in which 'direction the rockshaft 180 is turned, its initial movement always rocks camplate 183 about the pin 184 in one and the same direction i.e. clockwise in Fig. 2, such movement being permitted by compression of the spring 186 against the rail-actuating arm 182 which latter is initially held stationary by the locked shiftrail 170. This initial cam-plate swing pushes the low-reverse shift-prepare valve 126 leftwards, Fig. 2,. to cause simultaneous release of the countershaftdrive clutch 22 and the shift-rail 170, as described later, whereupon the rail-actuating arm 182 is moved through the cam-plate 183 and the spring 186 finally restores the cam-plate to the valve-release position shown. Interlock. The interlock between the arm 181, Fig. 8, of the 1st-reverse shift rail and that, 174, of the 2nd-DR control of the valve 127, Fig. 2, both of which are manually actuated by means not described, comprises two outwardly spring-loaded balls 208, 209 in an internally-shouldered driftsleeve 205. Movement of either arm 174 or 181 from neutral, depresses the corresponding ball against the adjacent shoulder 211, thus preventing movement of the other arm 181 or 174, out of neutral. In the extreme operative position of either shaft, shoulders 210 underlie the adjacent ends of the drift sleeve 205 positively preventing movement of one shaft out of neutral whilst the other is in an operative position. The balls 208 209 also act as locating detents. Operation neutral. Initially in neutral with the engine running, the input pump P pressurizes the supply-main 131 which feeds past the main regulator 122 to the underface of the shift-lock valve 120, keeping the shift-rail 170 locked at 166; through the low-reverse shift-prepare valve 126, line 197, shift-lock valve 120, and line 199 to the engaging chamber 103 of the countershaft-drive clutch 122 which thus remains engaged in neutral; to the upper face of the towed-start valve 121 maintaining it down, as shown; and past the main regulator 122 to the fluid coupling and lubrication lines 146. Line pressure 131 also passes to the manual valve 127 which, in Fig. 2, is shown in the drive position DR. For neutral the valve 127 is moved by the manual arm 174, Fig. 8, one step rightwards of Fig. 2 to N position, in which it exhausts a line 230 which otherwise feeds the second speed or direct drive clutches 52, 55 through the automatic shift valve 123 in operative positions. In neutral therefore the clutches 52, 55 are inoperative and drive through the fluid coupling and front clutch 22 passes only as far as the countershaft. Starting in first or reverse. With the manual valve 127 in neutral (one step right of Fig. 2), the manual rock-arm 181, Fig. 8, can be moved from N to 1st or reverse. Initial movement operates the shift-prepare valve 126, as above described, changing over the pressure and exhaust connections of lines 197, 201, so that the engaging chamber 103 of the countershaft-drive clutch 22 is exhausted through line 199, shift-lock valve 120, line 197 and valve 126, whilst its disengaging chamber 103a is pressurized through line 203 shift-lock valve 120, line 201 and valve 126. The countershaft-drive clutch 22 thus disengages, and at the same time pressure in the line 201, acting with the spring 202, pushes down the shift-lock valve 126, to release the shift-rail at 166 this movement also exhausting the clutch engaging line 199 at 198a to maintain clutch disengagement until completion of the shift. If the vehicle is not moving the rear shift-rail lock 236 will be free, as shown, so that continued movement of the manual rock-arm 181 takes the shift-rail 170 to its operative 1st or R position, whereupon the spring 186 re-asserts itself, releasing the shift-prepare valve 126 for re-engagement of the countershaft-drive clutch 22 and shift-rail lock 166. Drive then ensues through the now-meshed sliding wheel 41 direct to the output shaft 70. Enforced second speed. With the manual lstrev. rock-arm 181 in neutral, the shift-arm 174, Fig. 8, of the manual valve 127, Fig. 2, is moved to 2nd position (two steps right of Fig. 2) where it directs full line-pressure 131 through port 139 to the re