Patent GB-1261471-A (GB)
Title: Shift control systems for automatic transmissions
Inventor: TOYODA EIJI
IPC: F16H47/08
Filed: 1970-01-05
Abstract: 1,261,471. Change-speed gear. TOYOTA JIDOSHA KOGYO K.K. 5 Jan., 1970 [25 March, 1969], No. 390/70. Heading F2D. Fluid - pressure engaged ratio - selecting clutches and brakes, in a two or three speed and reverse automatic transmission on a motorvehicle, are controlled in response to electric signals representing output speed and enginethrottle setting, and provision is made for two different conditions of vehicle operation; one set of shift lines catering for operation on level roads, the other for mountainous terrain. Change between one condition and the other is automatic in response to a gradient-detecting device, which functions by measuring the acceleration of the vehicle at pre-set limits of throttle opening and output speed. Function summary.-Although a two-speed gear may be used, the only embodiment described is a three-speed gear, with a manual ranging valve 120 having settings PRND2L; L providing a fixed, two-way low; 2 a similar second; and D automatic shift between oneway low, second and third ratios, under control of 1-2 and 2-3 shift-valves operated by electric signals responsive to output speed and throttle setting. The acceleration control, above referred to, functions between second and third ratios only. Servo pressure augmentation is provided in reverse, and also, to a lesser degree in low, or also low and second. Gear arrangement.-The three-speed and reverse gear comprises triple planet steps 11, Fig. 2, meshing an output sun 19 and input suns 9, 10 (the latter through a planetary idler) driven through an input torque-converter 2 and selector clutches 6, 7 respectively. The front clutch 6 is engaged to drive the rear sun 9 in all forward ratios; first being by holding the planet carrier by a one-way detent 23 in D setting or by a rear band-brake 21 for two-way manual low; second by applying a front band-brake 22 to the front sun 10; and third by both clutches 6, 7 for lock-up. Reverse uses the rear clutch 7 and rear brake 21. Fluid pressure supply and regulation.-A single input-driven pump 101, Fig. 4, supplies the system main 121 and a pressure regulating valve 105 loaded by a spring 106 and fluid pressure in three chambers as follows. Load chamber 108 receives delivery pressure 121 for constant output pressure; load chamber 107 is fed from a manual valve line 128 in R setting for reverse pressure augmentation; and negative load chamber 109 is fed from a line 134b pressurized by upshift of the 1-2 shift valve 130 (described below), or alternatively of the 2-3 shift valve 135, to reduce system pressure on entering second or alternatively third ratio in D or 2 setting of the manual valve. Three pressure levels are thus established, the highest being for reverse, the lowest for ratios two and three, or alternatively three only. Shift valves.-Automatic 1-2 and 2-3 shift valves 130, 135 are each downshifted to the left, against opposing springs by energizing solenoids 132, 137 respectively. Starting in D setting with the front clutch 6 pressurized through the manual valve line 124, the remaining servos are exhausted at the shift-valves, their solenoids being energized. At a given signal, representing output speed and engine throttlesetting, the solenoid 132 is de-energized and the 1-2 valve 130 upshifts to the right, pressurizing the front brake apply chamber 22a for second ratio. A further signal de-energizes the solenoid 137 to upshift the 2-3 valve 135, pressurizing a line 139 leading to the rear clutch 7 and release chamber 22b of the front brake, for third ratio. This line 139 is isolated by a ball check-valve 141 from a line 128 used to engage the rear clutch in reverse. Electrical control.-In the electric circuit, Fig. 12, the 1-2 and 2-3 shift-valve solenoids are shown at 132, 137 respectively, and are energized for downshift and de-energized for upshift. The two control parameters are a throttle position detector 200 and an output speed detector 320. Throttle position is detected by a potentiometer (Fig. 17, not shown) having a slide operated through a cam by the engine accelerator pedal to supply a signal line 210. Speed is detected by a polarized pick-up adjacent a notched wheel (Fig. 18, not shown) rotating with the output shaft, the pick-up output being processed in an amplifier, (Fig. 19, not shown), amplitude limiter for wave-shaping, and a converter producing a D.C. voltage output 212 responsive to output speed.  A primary circuit 202, 220 controls level road shifts, and a secondary circuit 221 changes the shift speeds for gradient operation in response to a further parameter, acceleration, obtained by differentiating output speed with respect to time.  The primary level road, shift control comprises similar 1-2 and 2-3 shift circuits 202, 220 respectively. Each comprises a selective switching circuit 327, the output signal 217, representing speed, of which is taken either directly from the RPM line 212 or from a RPM modulator 326 under control of a feedback line 219, the voltage of which, when cancelled by an upshift signal, switches the selection circuit to the RPM modulator 326 so that return downshift is at a lower speed for hysteresis. The speed signal 217 and throttle-setting signal 213 feed a shift-point circuit 328, (Fig. 20, not shown), which receives the signals through preset potentiometers feeding a differential amplifier which emits an output voltage signal 218 for downshift when the throttle component exceeds the speed component, the signal being otherwise cancelled, for upshift. The secondary, or gradient, shift circuit 221 is effective between second and thid ratios only, and co-operates with the above-described normal 2-3 circuit 220 through an OR circuit 225. It comprises a gradient circuit 223 in which an AND circuit 349 emits a downshift signal when three signals, as follows, are received simultaneously from a throttle-setting circuit 341, signalling throttle-setting exceeding 1.8/4; a RPM circuit 342 signalling output speed below 1600 RPM; and an acceleration circuit 343, 346 signalling that acceleration is below 0À05 g for more than one second. The AND signal 233 operates a bi-stable memory circuit 224, (Fig. 24, not shown), comprising a multivibrator, to deliver a signal 234 to the OR circuit 225 which energizes the solenoid 137 for 3-2 downshift. The return upshift is effected by the circuit 222 which switches the bi-stable memory circuit 224, to erase the downshift signal, by a signal 228 received from an AND circuit 340 when throttle setting exceeds 0.5/4 and output speed exceeds 1800 RPM. The signal 234 from the bi-stable memory circuit to the OR circuit 225 is effective to erase the signal 235, for upshift, only if a downshift signal has not been transmitted to the OR circuit 225 by the primary shift circuit 220.  The acceleration circuit 343 (Fig. 22, not shown) is fed from the output RPM circuit and comprises a low-pass filter and a differentiator which obtains the acceleration term dN/dt, which feeds an acceleration setting circuit 346 (Fig. 23, not shown) including a potentiometer, reference voltage (Zener diode), amplifier and delay, so that a signal 232 is emitted when the acceleration is less than 0À05 g for a period of not less than one second. The setting of the potentiometer or the reference voltage may be varied in accordance with output speed or throttle setting to provide a variable acceleration shift-value covering a range of gradients.