Patent GB-1281445-A (GB)
Title: Automatic shift control systems for automatic transmissions
Inventor: ITO SHIN
IPC: F16H47/06
Filed: 1970-03-06
Abstract: 1281445 Change-speed gear TOYOTA JIDOSHA KOGYO KK 6 March 1970 [1 April 1969] 10872/70 Heading F2D [Also in Division H3T] An automatic electronic control, for the solenoids 132, 137 of shift-valves controlling the supply of fluid pressure to friction clutches and brakes in a torque-converter driven automatic transmission on a motor-vehicle, responds to output speed and engine torque as manifested by throttle setting or engine inletmanifold depression, and the driver has an additional control for changing the shift-points to cater for different conditions of operation, e.g. in mountainous terrain as opposed to level road. The change is a single switched change from one shift-line to another, only the 2-3, 3-2 line being treated in the described embodiment. Further changes may be dialled by action on variable resistors in the control circuits. Function summary.-Two, three or four ratio gears, with one reverse, may be used, but the only embodiment described is a three speed and reverse gear, subject to control by a manual selector valve 120 having settings PRND2L; D giving automatic shifts between all three ratios, 2 between the first two and L a fixed twoway low. In the absence of electrical power with the shift - valve solenoids de-energized, D setting gives third, 2 second, and L first ratio respectively. The speed-line change referred to above, acts by cancelling the effect of throttle control below a fixed output speed. Servo pressure augmentation is provided in first ratio, and, to a higher degree, in reverse, no other pressure control being provided. Gear arrangement.-The gear, Fig. 2, not shown, comprises triple-step planets (11) meshing three suns, one (19) fast on the output shaft (18), the other two (9, 10) driven selectively from the input shaft 1, through the torque-converter and two selector clutches 6, 7. A planetary idler (15) is intermeshed between the front input sun (10) and its planet step. A one-way brake (23) takes reaction of the planet-carrier in automatic low and is bridged by a band-brake 21a for manual low and reverse. A band-brake 22a, 22b holds the front sun (10) for second ratio, using the same clutch 6 as in first: both clutches 6, 7 together provide direct-drive third; and the clutch 7 and brake 21a reverse. Fluid circuit. Pressure supply and regulation.-A single input-driven pump 101, Fig. 5, supplies a system main 121, the torque-converter, cooler 104 and lubrication line 103, under control of a pressure-regulating valve 105, loaded by a spring 106 and by fluid pressure in two chambers 107, 109 as follows. In first ratio both chambers are exhausted and a constant mean pressure is established by the spring 106. On entering second ratio a line 134b pressurizes the lower chamber 109, negatively loading the regulator to reduce system pressure below the mean in both second and third ratios, whilst in reverse a line 128 pressurizes the upper chamber 107, for positive load, to increase regulated pressure above the mean. Automatic shift valves.-1-2 and 2-3 shiftvalves 130, 135 are biased to their rightward setting for upshift by springs 131a, 136a, and are downshifted left by energizing their respective solenoids 132, 137. Initially, in D setting of the manual valve 120, both shiftvalve solenoids are energized to the downshift portion shown. The clutch 6 alone is pressurized, as in all forward ratios, through the manual valve 120 and the vehicle starts in one-way low. Increase in speed signals a shift to second by de-energizing the solenoid 132, and the 1-2 valve 130 upshifts to pressurize the apply chamber 22a of the second-speed brake introducing second ratio. Further speed increase de-energizes the 2-3 valve solenoid 137 to pressurize the direct clutch 7 and release chamber 22b of the second speed brake, thus introducing third ratio. A check-valve 141 isolates a line 128 having a similar clutch function in reverse. Electrical circuit; speed voltage.-Output speed is sensed by a polarized pickup, Figs. 13A, 13B, not shown, adjacent a notched wheel rotating with the output shaft, the resulting signal 311, Fig. 12, being processed to a speed-responsive D.C. voltage En, 312, in an amplifier, amplitude limiter and a frequency discriminating and rectifying circuit 310, producing a digital to analogue change. TV voltage.-A voltage signal E(N), 321, representing engine throttle setting, is obtained by a six-stage resistor tapping, Fig. 16, not shown, operated stepwise by the engine throttle and fed by a constant voltage to provide a stepped TV voltage 321. The 1-2, 2-1 shift circuit 358, which is not subject to the shift point variation control, comprises a discriminating circuit 330, Fig. 17, including a comparator, which may be composed of a differntial amplifier and a Zener diode or Schmitt circuit, and compares fixed reference voltages 335c, 335e with voltages 335a, 335b representing selected proportions of the speedresponsive voltage 312, 333, and throttleresponsive voltage 321, 332 respectively, as determined by adjustable potentiometers 337, 339. When a predetermined proportion exists between the speed and throttle voltages, a signal issues at 331, which, with or without amplification, energizes the solenoid 132 for a 2-1 downshift. Above the predetermined proportion the signal 331 is absent and the solenoid is de-energized for 1-2 upshift. Upshift-downshift, hysteresis is provided by a feed-back circuit 340 including a transistor 341, which is switched off by signal absence on upshift, to insert a resistor 343 into the speed potentiometer 337, thus reducing the corresponding downshift speed. The resistor 343 is short-circuited on downshift by the reappearance of a shift-signal 331 which switches on the transistor 341. The 2-3, 3-2 control circuit 363 is provided with the shift-line modifying control referred to above. It comprises two circuits, one 361, being the same as the 1-2, 2-1 shift-circuit 358 described above. The other circuit 362 provides for shift-line change and can be switched in manually at 352. Its discriminating and feed-back circuits 330<SP>11</SP>, 34011 are the same as those 330, 340 of the 1-2 and 2-3 circuits 358, 361, with the exception that now the throttle-responsive voltage 321, 333 is replaced by a fixed reference voltage 360 so that suppression of the output signal 331<SP>11</SP> for upshift from this circuit occurs only at speeds where the speed-responsive voltage 312, 333<SP>11</SP> exceeds the fixed reference voltage 33211. The outputs 331<SP>1</SP>, 33111 from the two circuits 361, 362, feed the 2-3 shift-valve solenoid 137  through an OR circuit 354, so that the presence or absence of a signal at either one circuit alone produces downshift or upshift respectively, signals occurring together having no effect. The resultant shift-curve is shown in Fig. 19, where the solid lines are the upshifts and the chain-lines the downshifts. The 1-2, 2-1 shift lines are V (output speed) = f 1 # and f' 1 # respectively where # is the throttle opening, and f indicates function. Similar, but displaced lines f 2 # and f<SP>1</SP> 2 # are the 2-3 and 3-2 shift lines with the change-switch 352 open, using the circuit 361 alone. Closing the switch 352 introduces the circuit, 362, providing the lines V=D and V=D<SP>1</SP> (the reference voltage). Irrespective of throttle opening, upshift can now occur only when the speed-voltage V exceeds the reference voltage D (vertical line). Above this line the shift-line continues with V=f 2 # as before, so that throttle controlled shifts are again possible. The position of the shift line V=D can also be displaced by a driver-control of the reference voltage 360. More than two sets of shift lines may be provided by selectively modifying the throttle or speed voltages, or by controlling the sliders of the various potentiometers. In this latter case shift lines may be displaced but their form is not changed.