Patent GB-841069-A (GB)
Title: Improvements relating to variable speed power transmission mechanism
IPC: F16H47/08
Filed: 1958-01-01
Abstract: 841,069. Variable-speed gear; friction clutches; change-speed control. FORD MOTOR CO. Ltd. (Ford Motor Co.). Jan. 1, 1958, No. 41/58. Class 80 (2). [Also in Groups XXIX and XXXIV] A power transmission mechanism comprises an hydrokinetic torque converter and a pair of planetary gear units, the torque converter including first and second turbines, each gear unit including a sun-gear, a ring gear and a planet carrier, the primary turbine being connected to the ring gear of the first of the planetary gear units and the second turbine being connected to both the carrier of the first gear unit and the ring gear of the second gear unit, brake means acting on the sun-gears absorbing the reaction torque in the gearing and the carrier of the second gear unit being connected to an output shaft. Function summary.-A motor car transmission comprises an hydrokinetic torque converter having twin turbines 42, 72 connected to two elements of a first planetary gear 54, increasing speed of rotation causing the two turbines to rotate together so that the planetary gear is effectively locked in itself, the third element of the first planetary gear being connected in series with a second planetary gear 80 which can be locked up for direct drive by an hydraulically controlled friction clutch 162. Control of the gearing is effected automatically in response to output speed by an hydraulic circuit under the control of a manually operated ratio range selector M. The power loading applied to the ratio establishing clutches and brakes of the planetary gearing is dependent at low speeds on output shaft speed and the setting of the car throttle, and at higher speeds is dependent upon output speed in a manner similar to that of engine torque. Engine braking of the car can be effected by operation of the manual ratio range selector which, when the throttle has been released, can be set to a " hill braking " position. Between 40 m.p.h. and 20 m.p.h. the gearing is then held in the intermediate range. As the speed of the car decreases to below 20 m.p.h., with the ratio range selector in the " hill braking " position, the gearing is automatically conditioned for reverse drive, so that increased engine braking is effected. If the car speed falls below 8 m.p.h., the gearing is automatically returned to the intermediate forward speed position. Kick-down of the car throttle also establishes the intermediate ratio range. Over kick-down to an extreme position causes tiltable reactor blades 82 to be turned to increase the torque obtained from the hydrokinetic converter. Gearing.-The hydrokinetic torque converter comprises an impeller 36 rotating with an engine shaft 10, the first turbine 42 fast with the ring gear 52 of the first planetary gear 54, the second turbine 72 fast with the planet carrier 106 of the first planetary gear, a non-adjustable reactor 58 mounted on a one-way detent 66 and the second reactor having its blades 82 adjustable by engine throttle setting to change the converter characteristics. Also fast with the second turbine 72 and the planet carrier 106 is the ring gear 158 of the second planetary gear 80. The carrier 154 of the second planetary gear 80 is fast with an output shaft 174. On starting the car from rest, a brake 186 is applied to hold a race 122 stationary and, through a one-way clutch 120 and a torque transmitting tube 116, hold the sun-gear 112 of the first planetary gear 54 stationary. The brake 186 simultaneously acts through a second one-way clutch 172 and a sleeve shaft 150 to hold the sun-gear 152 of the second planetary gear stationary. As the engine speed increases, the first turbine 42 begins to rotate and drives through its sleeve shaft 48 to the ring gear 52 of the first planetary gear 54, which transmits a reduced ratio drive through its planet carrier 106 to the ring gear 158 of the second planetary gear 80 which, similarly, transmits a further reduced ratio drive through its planet carrier 154 to the output shaft 174. The reactions of both planet gears are taken by the one-way clutches 120, 172 and the brake 186. With further increasing speed, the torque applied to the second turbine 72 gradually increases and approaches that applied to the first turbine 42, so that the second turbine begins to rotate with a speed approaching that of the first turbine. Accordingly the planet carrier 106 of the first planetary gear 54 begins to rotate at a speed similar to that of the ring gear 52, and the first planetary gear 54 is effectively transmitting a direct drive. Forward rotation of the sun-gear 112 is permitted by overrunning of the one-way clutch 120 connected thereto by the torque transmitting sleeve 116. To obtain direct drive, the multidisc clutch 162 is engaged to lock up the second planetary gear 80. To obtain reverse, a brake 184 is applied to hold stationary the planet carrier 106 of the first planetary gear 54 and, with it, the second turbine 72. The brake 186 and the clutch 162 are released and a multidisc clutch 142 is engaged. Rotation of the first turbine 42 turns the sun-gear 112 of the first planetary gear backwards and acts through the one-way clutch 120 and the engaged clutch 142 to rotate the sun-gear 152 of the second planetary gear 80 backwards, the reaction on the ring gear 158 of this planetary gear being also taken by the brake 184 so that its planet carrier 154 and the output shaft 174 rotate backwardly. A parking ratchet 182 is provided on the output shaft 174. Friction clutches.-The forward direct drive clutch comprises interleaved multidises 162 engaged against the bias of a spring 170 when fluid under pressure is caused to act upon a piston 168 contained within the clutch housing. The reverse drive clutch comprises interleaved multidises 142 engaged when a piston 136 is moved leftwards by fluid under pressure to cause a disengaging spring ring 140 to act upon a pressure plate 138. Change-speed control.-Control of the gearing is effected by an hydraulic circuit fed from input and output driven pumps, the output driven pump acting upon a governor valve 246 which is operative to connect the output driven pump to the control circuit when the input pump is not operative, so that the car engine can be pushed started. Line pressure is supplied from the input pump to a pipe 200, 202 leading to the manually operated ratio range selector valve M. Line pressure is also supplied through the pipe 200 to the governor valve 246 which is subjected to static pressure of the output driven pump through a Venturi throat 242, 244 and to dynamic pressure of the output pump through a pipe 236, the governor valve also being subjected to the pressure of the input driven pump through a pipe 238. The governor valve is effected to co-ordinate the various pressures to govern the line pressure from the input driven pump and supply it to a pipe 250 in accordance with output speed. Governor pressure is supplied from the pipe 250 through a pipe 252 to a compensating valve 228 which, at low pressures, modulates the pressure in accordance with governor pressure and the setting of the car throttle, and at higher speeds modulates it in accordance with output speed in a manner corresponding to engine torque. Throttle position modulation is imposed upon the compensating valve by a valve 212 supplying line pressure through pipes 216, 218, 220 to a pipe 222, 224. Line pressure supplied through the compensating valve 228 to a pipe 232 acts upon a main regulating valve 262 to adjust the line pressure in the pipe 200 &c. and hence adjust the power loading on the various clutch and brake elements in dependence of the torque requirements of the transmission. Governor pressure in the pipe 252 also acts upon a ratio shift valve 268. When the car moves off, line pressure passes from the pipe 202 through the ratio range selector valve M set in the " Drive " position to a passage 204 leading through a hill brake valve 290 positioned as shown to a pipe 206 and the servomechanism applying the low-speed brake 186. With increasing car speed, the first planetary gear 54 effectively locks up, as already described, and governor pressure in the pipe 252, modulated by the throttle setting, gradually increases until it is able to actuate the ratio shift valve 268. Line pressure supplied through the.ratio range selector valve to a pipe 208 is then supplied through a pipe 210 to the direct drive clutch 162, so that the second planetary gear 80 is locked up. The low-speed brake 186 remains engaged while the gear gives its direct drive. Cushioned engagement of the direct drive clutch 162 is obtained by line pressure in the pipe 210 acting upon an accumulator valve 270. Line pressure acts upon the ratio shift valve 268 when in its lower, direct drive position, in such a way as to prevent its upward movement to produce a downshift until a lower road speed has been reached than required for an upshift. A down shift in the transmission may be effected by opening the motor-car throttle sufficiently wide to increase engine torque to such a degree that the primary turbine 42 rotates more quickly than the secondary turbine 72. The first planet gear 54 then gives a reduced ratio, while the second planetary gear 80 remains locked up. A down shift in the second planetary gear may be obtained by opening the car throttle sufficiently wide to increase the pressure in the pipe 224 and move the ratio shift valve 268 upwards to its lowspeed position. A further down shift may be obtained by opening the throttle to its extreme position when the valve element 214 blocks an exhaust passage adjacent a pipe 272 leading through a pipe 274 to a stator valve 254. Simultaneously line pressure in the pipe 220 is caused to pass through the throttle valve to the pipes 272, 274 and the stator valve 254 so that, at speeds below 40 m.p.h., the stator valve is moved downwardly by line pressure against converter pressure. Line pr