Patent GB-1028889-A (GB)
Title: Automatic change speed transmission
IPC: F16H59/18
Filed: 1964-11-02
Abstract: 1,028,889. Change-speed control. FORD MOTOR CO. Ltd. Nov. 2, 1964 [Dec. 31, 1963], No. 44528/64. Heading F2D. The control circuit of Specification 912,399 (Group XXIV) is modified by the replacement of the inhibitor valve and the transition valve. The modified valves provide a 2-3 upshift with concomitant brake disengagement, clutch engagement at zero trottle settings, and a timedelay of the brake disengagement up to a throttle setting determined by the calibration of the new transition valve; above this throttle setting, the modified valves do not alter the functioning of the circuit. The inhibitor valve is replaced by an inhibitor valve 227, controlled as before by output governor pressure 238, and by opposed pressure in a pipe 236 and a branch 242. The transition valve is replaced by a 1-2 transition and 2-3 backout valve 202, biased to vent the front servo pipe 206 to an exhaust port 345 by pressure in a pipe 263 and control pressure 236 applied through a branch 244 to a differential area land 246, these two pressures acting against the bias of a spring 247 and TV pressure from a pipe 339 connected through the inhibitor valve, when in its downward position, to a pipe 341 leading to the base of the valve 202. Once a 1.2 upshift has taken place, a 2-1 downshift cannot occur while the inhibitor valve is held downwards by governor pressure 238, thus preventing pressure passing through a pipe 220 to the 1-2 shift valve 212. Before a 1-2 upshift, the pipe 220 is under pressure and connects through the inhibitor valve with the branch 242, holding the inhibitor valve upwards, as shown. When the inhibitor valve moves downwards, the pipe 236 is vented to exhaust at 343, and the pipe 341 connects with TV pressure 339. TV pressure then acts upon the land 246 of the 1-2 transition valve to aid the spring 247, and the exhaust port 345 is closed, main pressure 200 instead being fed to the pipe 206 energizing the front servo. Before a 1-2 upshift, control pressure 236 acting on the valve land 246 holds the 1-2 transition valve downwards. When with increasing speed the 1-2 shift point is reached, control pressure 236 is exhausted through the 1-2 shift valve, so the spool of the transition valve 202 moves upwards, connecting main pressure 200 to the pipe 206 extending to the brake apply chamber of the front servo. Second ratio is thus established. With further increasing speed, the 2-3 shift point is reached, and the 2-3 shift valve moves, to cause pressure to engage the rear clutch through a pipe 274 and also to supply the same pressure to the disengage side of the front servo through pipes 362, 348. Direct drive is then obtained. If a 2-3 upshift occurs under zero or minimum torque conditions, TV pressure is supplied to the pipe 341, since the spool of the inhibitor valve is in its downward position. This occurs immediately after movement of the 1-2 shift valve to the upshift position. TV pressure is then passed to the lower end of the 1-2 transition valve 202. On initial movement of the 2-3 shift valve in the upshift direction, pressure in the pipe 274 acts through the pipe 263 on the upper end of the 1-2 transition valve 202, and ultimately overcomes the spring 247. The valve 202 then moves downwardly, venting the pipe 206 to the exhaust port 345, and releases the brake apply chamber of the front servo. The valve 202 and the spring 247 can be calibrated so that the brake apply servo is vented at the moment the rear clutch servo becomes effective. If the 2-3 upshift occurs at a part &o. open throttle setting, the pressure in the pipe 341 is greater. Accordingly, the 1-2 transition valve 202 moves only when the pressure in the pipe 274 has correspondingly increased. A time-delay is thus imposed on the release of the intermediate speed brake, to provide some overlap between release of the brake and engagement of the clutch. At small throttle settings, the shift point of the 1-2 transition valve 202 is determined solely by the calibration of the spring 247. Increasing TV pressure augments the bias of the spring 247 until the end point of the valve spool 202 is the same as the end point of the servo. Beyond this, the valve system functions in the usual way to provide an upshift dependent upon torque demand &c., and the transition point is not determined by the calibration of the valve 202.