Patent GB-1285826-A (GB)
Title: Automatic transmission systems having means for reducing shock during gear shifting
Inventor: SUMIYOSHI M
IPC: F16H61/06
Filed: 1970-07-09
Abstract: 1285826 Change-speed control TOYOTA JIDOSHA KOGYO KK and NIPPONDENSO KK 9 July 1970 [18 July 1969] 33411/70 Heading F2D Liquid servo pressure for actuating ratioselecting friction engaging means in a torqueconverter-driven automatic transmission on a motor-vehicle, under shift-control of a manual ranging valve and an electrically operated automatic shift valve, is subject to pressurecontrol by a main regulator valve, Fig. 11, of which the loading is subject to electrical control by a shift signal to reduce the servo pressure for a predetermined time interval immediately before or after initiation of a shift. During downshift the reduction occurs only below a predetermined engine speed. The steady pressure level is also reduced above a predetermined turbine speed to reduce power consumption. Function summary.-Although more than two ratios may be controlled, the described embodiment is for two ratios only. Shifts are in response to electrically detected output speed and torque-converter slip, or engine throttle setting, an upshift signal 512 being derived from an AND circuit 510 when a variety of conditions, as specified below, are simultaneously satisfied, and downshift signal 522 from an OR circuit 530 when one only of several conditions is satisfied. The conditions take account of the differing slip values on drive and coast, and also of absolute speed of input and output of the gear. Gear arrangement.-The torque-converterdriven two-speed and reverse gear, Fig. 1 (not shown), comprises a stepped planet bevel train with a forward clutch (20) and direct-reverse clutch (30) selectively driving two small sidewheels, output issuing from a single large side wheel. The single upshift from reduced to direct drive is by releasing a low brake (40) from the planet-carrier and engaging the direct-reverse clutch (30), with the forward clutch (20). The low brake (40) is used with the direct-reverse clutch (30) for reverse. An additional forward ratio may be provided by an additional brake (60) on the direct-reverse clutch (30). Fluid circuit, Fig. 2 (not shown), comprises a manual PRNDL ranging valve (261) which, in P and R, blocks main pressure (221) from a main regulator valve (252). D and L settings both have the same fluid effect in supplying the for. ward clutch (20) and a shift-valve (270) automatically upshifted by a solenoid 280, energization of which is prevented in L setting, the shiftvalve (270) supplying alternatively the lowreverse brake (40) or direct-reverse clutch (30). Two-way check valves (291, 295) isolate the lines of the direct-reverse clutch (30) and low-reverse brake (40) when their pressurization is not required. Electrical circuit.-Fig. 4 shows the shift circuit for controlling energization of the shiftvalve solenoid 280. The servo pressure control circuit which forms an adjunct to Fig. 4, is shown in Fig. 13 and described separately later. Speed response.-Polarized pick-ups, adjacent notched discs rotating with the respective members, generate a speed responsive frequency, 310, 321, 331, which is fed through an amplifier, amplitude limiter and frequency-D.C. voltage converter in circuits 310, 320, 330 (detailed in Fig. 6, not shown), to appear as D.C. voltage signals 312, 322, 332, representing respectively the speeds N 1 , N 2 , N 3  of the torque-converter impeller and turbine, and the final output shaft of the gear. Slip response.-Voltage signals 412, 422, 432, 442, representing predetermined limits of torqueconverter slip are derived by feeding potentiometer selected proportions of the impeller and turbine speed voltages N 1 , N 2 , to a differential amplifier in circuits 410 ... 440 detailed in Fig. 7 (not shown). The circuit is designed to produce shift signals according to shift lines, Figs. 3a, 3b (not shown), which require a shift when the converter slip ratio N 1  : N 2  lies between specified limits (one for drive the other for coast), which differ for up and down shift; and also when engine and input speeds N 1 , N 3  are outside specified limits. These limits are shown in Fig. 4 and the circuits 340 &c. are adjusted to provide them. Action is as follows. Upshift is required when engine speed N 1  exceeds 1200 RPM; and slip-ratio N 1  : N 2  exceeds 0À90 but is less than 1À05 (coast). When these three conditions are all satisfied at the same time an AND circuit 510 is triggered to send an upshift signal 512 operating a bi-stable memory circuit 540 (a bi-stable multi-vibrator and amplifier) to provide a voltage output 542 energizing the shift-vlave solenoid 280 for upshift. The AND circuit also requires two additional signals before it can be so triggered. The first of these, 572, is derived from a NOT circuit 570, in which the signal 572 is suppressed until a predetermined time after a preceding shift signal, as determined by a signal from a timing hold circuit 560, (Fig. G, not shown), which differentiates the signal from the solenoid-valve line 542 to actuate a mono-stable vibrator providing the signal 562. The second signal 592 is derived from a circuit 590 indicating that low gear is established, by absence of voltage in the solenoid line 542, this gear-position circuit 590 being fed from the solenoid line 542 through a NOT circuit 610 which erases the signal 612 fed to the gear position circuit 590 when voltage is present in the solenoid line 542, which would indicate an upshifted condition of the solenoid shift valve. Downshift is required when any one of the following states occurs alone. Slip ratio below 0À60 or above 1À10, or output speed below 600 R.P.M., The signal 532 then delivered by an OR circuit 530 feeds an AND circuit 520, which, if already in receipt of a high gear signal 542 and a signal 572 from the time-hold circuit 560, emits a signal 522 to change the bi-stable memory circuit 540 to its other stable position, de-energizing the valve-solenoid 280 for downshift. Shift pressures control.-Servo pressure 221, for the ratio-establishing clutches and brakes, is normally maintained constant by a loading spring 703 on the main regulator valve 252, Fig. 11. Immediately before, or after, initiation of a shift, a solenoid 810 of a valve 800 is energized to supply main pressure 221 through a line 804 to act below the regulator valve 252 and reduce regulated pressure for a predetermined time, after which the pressure 804 is bled to exhaust 805 restoring full regulated-pressure. During continuous operation at high speed, the reduction is maintained. A signal 632 for energizing the pressurereducing solenoid 810 is derived from the shift circuit shown in Fig. 4, with the additions shown in Fig. 13. The upshift signal 512, Figs. 4 and 13, feeds, through a time-hold circuit 640 and line 642, an OR circuit 630, which, if the signal 642 is present alone, energizes the pressure-reducing solenoid 810 for an interval determined by the time-hold circuit 640. The downshifts signal 522 is fed to an AND circuit 620, together with a signal 372 indicating that engine speed is less than a predetermined level (1000R.P.M.), the output signal 622 energizing the pressure-reducing solenoid 810 through a time hold circuit 650 and the OR circuit 630 as before. Thus the time interval for pressure reduction during shift may have different up and down shift values, and reduction is suppressed on downshift above an engine speed of 1000 R.P.M. During continuous running, if the converter turbine speed exceeds a value (3000 R.P.M.) set by a circuit 380, a signal 382 is fed continuously to the OR circuit 630, energizing the solenoid 810 continuously to reduce the level of steady servo pressure, thus reducing power consumption by the engine-driven supply pump. Time-delay circuits 661, 663 may be provided to cause the transient pressure reduction during shift to precede or follow shift initiation.