Patent GB-1284547-A (GB)
Title: Control for automatic transmission
IPC: F16H47/08
Filed: 1969-08-21
Abstract: 1284547 Change-speed control NIPPON DENSO KK and TOYOTA JIDOSHA KOGYO KK 21 Aug 1969 [18 Oct 1968] 41842/69 Heading F2D An electronic circuit controlling energization of a solenoid 280 of an automatic shift-valve controlling fluid-pressure-engaged clutches and brakes in a torque-converter-driven planetary transmission on a vehicle, includes an AND circuit 510 which produces an upshift solenoidenergizing signal when every one of the following six signals is present, the numerical values stated being arbitrary to the particular installation. 342, Engine speed N 1  > 1200 R.P.M.; 362 torque-converter turbine speed N 2  > 1200 R.P.M.; 412 converter slip-ratio N 2 /N 1  > 0À85; 442 slip ratio < 1À10; 592 low gear setting indicator operative; 572 a predetermined time interval after preceding shift. For downshift an OR circuit 530 and AND circuit 520 produce a downshift solenoid de-energizing signal when at least one of signals 352, N 1  < 600; 422 slipratio < 0À60; 432 slip-ratio > 1À20; 372, N 3  < 600, is present together with an upshifted setting signal 580 and the time-delay signal 572. Gear arrangement.-Two embodiments are described, one giving two-speeds and reverse, the other three-speeds and reverse. In the twospeed embodiment a torque-converter-driven stepped bevel planet train, the carrier is held by a band brake 40 for a single forward reduced ratio, driving a rear side-wheel 51 through a clutch 20, or for a single reduced reverse, driving a front side-wheel 57 through a clutch 30, the clutches being engaged together and the brake released for direct-drive. In the three-speed embodiment an additional brake 60 is provided for the front side wheel 57. Fluid system.-A system main 221 receives pressure from a single input-driven pump 17, with pressure-regulator 252 (not described). In Park and Neutral settings of a manual selector valve 262 the pressure main 221 is blocked, whilst in Drive setting the main feeds a line 222 which directs pressure to the front clutch 20, effective for both forward ratios, and to a 1-2 automatic shift-valve 272, which is moved from its spring-loaded right position, shown, supplying line 224 of the reduced-drive brake 40, to a left position by energizing a solenoid 281, to exhaust the brake 40, and supply the rear clutch 30 for direct drive. Low setting of the manual valve 262 provides the same fluid circuit as in D, but the solenoid 281 is not energized. Reverse setting exhausts the line 222 and pressurizes a line 227 for engaging the rear clutch 30 and brake 40. The fluid circuit for the three-speed embodiment, Fig. 23 (not shown), has an additional solenoid valve for 2-3 shift, fed through the 1-2 valve and supplying pressure to the rear clutch and release side of the intermediate brake. Speed sensing is by 32-toothed wheels 72, 82, 92, on the converter impeller 12, turbine shaft 14, and final output shaft 56, with electromagnetic pick-ups 71, 81, 91, which generate a speed-proportional electrical frequency. An alternative hydraulic differential speed slip sensor (Fig. 24A, not shown), comprises pumps driven at appropriate ratios by the converter pump and turbine, and delivering to opposite sides of a diaphragm, Fig. 24B (not shown), carrying contacts which complete an electric circuit when a predetermined slip ratio is exceeded. An alternative mechanical sensor, Figs. 25A, 25B (not shown), comprises a three-element planet gear, with sun and ring driven at appropriate ratios by the converter pump and turbine, the planet-carrier being frictionally connected to a nut, which, at a predetermined slip-ratio, is screwed along a threaded shaft secured to the sun, to close an electric contact. Hydraulic sensing of speed by pressureresponsive switch, or mechanical sensing by centrifugal switch may also be used instead of electric sensing. Shift condition requirement.-Three parameters, as follows, determine the shift point. Input speed N 1 , output speed N 3  and slip-ratio N 2 /N 1  (output to input speed) in the torque converter. Figs. 6A to 6C (not shown) are curves showing preferred shift points in a particular case as follows.  (1) Upshift.-When N 1  and N 3  both exceed 1200 R.P.M. and the converter slip-ratio is greater than 0À85 on forward drive and less than 1À10 on overrun. (2) Downshift.-When at least one of N 1  or N 3  is less than 600 R.P.M., or N 2 /N 1  is below 0À60 on drive or greater than 1À20 on overrun. In the first two cases the speed N 2  is obtained by computation from N 3  using the prevailing gear ratio. Electronic circuit, using electric speed and slip sensing. The electrical outputs 311, 321, 331 of the three speed sensors 71, 81, 91, representing N 1 , N 2  and N 3 , are fed to a logic circuit, Fig. 7, which processes the information and controls energization of the single solenoid 280 of the shift valve. The signals 311 &c. from the speed sensors are first converted to a D.C. voltage in circuits 310 &c., which each comprise an amplifier; amplitude limiter; and a frequency demodulating rectifier (Figs. 9 and 10, not shown). N 1 , N 2  and N 3  voltage outputs 312, 322, 332 are fed to differentiating circuits 340 ... 370 with the following outputs. Circuits 340, 360 produce output signals 342, 362 only when engine speed N 1 , and vehicle speed computed to N 2 , exceed 1200 R.P.M., to prevent upshift below either speed. Circuits 350, 360 produce output signals 352, 362 only when N 1  and computed N 2  are below 600 R.P.M., to prevent downshift above either speed. Circuits 410 ... 440 all produce signals 412 &c. representing limits of slip-ratio N 2 /N 1 . Circuits 410, 440 produce signals only above and below 0À85 and 1À10 slip ratio respectively for the upshift limits; 420, 430 signals below 0À60 and above 1À20 for downshift limits. These circuits 410 ... 440, Fig. 11 (not shown), each comprise tapped potentiometers feeding adjusted proportions of the N 1 , N 2  signals to a differentiating and amplifier circuit which, e.g. for circuit 410, detects the value N 2  - 0À85N 1  and emits a signal 412 only when that value is positive, i.e. when (N 2 /N 1  > 0À85. Additional information signals taking part in the control of the following logic circuit are provided by high and low gear setting indicators 580, 590, which change over the signal supply to erase a succeding signal of like kind; and a time-delay signal 572 which prevents the emission of a new signal to the shift solenoid 280 until after the elapse of a predetermined time interval, which is sufficient to ensure completion of the preceding shift. The high and low gear setting indicators 580, 590 feed a phase-reversing NOT circuit 610 which erases the solenoid-conduct signal on upshift and provides a signal on downshift. The time-delay circuit, Fig. 13 (not shown), comprises a differential circuit, rectifier, monostable multivibrator and a NOT phase-reversing circuit 570 which, when the shift solenoid 280 is rendered conducting for upshift or non-conducting for downshift, erases the output signal 572 for a predetermined time. The logic circuit for processing the above information comprises, for upshift, an AND circuit which emits a signal 512 for operating a bi-stable memory circuit 540 to energize the solenoid 280 for upshift, when it receives all the following six signals-312, 412, 442, 362, 592, 572, which respectively imply that engine speed exceeds 1200 R.P.M.; converter slip-ratio lies between 0À85 and 1À10; computed turbine speed exceeds 1200 R.P.M.; the shift solenoid 280 is at that time de-energized in low gear setting; and the prescribed time interval has elapsed after the preceding shift. Absence of any one of these six signals erases the shift signal. Downshift control differs from upshift, being monitored by an AND circuit 520 which requires, in addition to the time-delay and shiftsetting signals 572, 542, one additional signal 532 provided by an OR circuit fed with four signals 352, 422, 432 and 372, at least one of which can produce the output signal 532. Thus, after the prescribed time interval following the preceding shift, and providing the shift solenoid 280 is already energized in high gear setting, it can be de-energized for downshift by any one at least of the following. Engine speed below 600 R.P.M.; converter slip ratio less than 0À60 or greater than 1À20; computed turbine speed less than 600 R.P.M.. The electronic control of the two shift-valve solenoids of the three-speed embodiment is in Figs. 27-40 (not shown), and it differs from the single solenoid two-speed control in the following respects. There are additionally one bi-stable memory curcuit for the additional solenoid; two additional AND circuits such as 510, Fig. 17, one additional OR circuit such as 520, and a three-position gear indicator itself including an AND circuit; two additional speed and four additional slip computing circuits such as 340 ... 370. The latter provide for the speed and slip ranges of the additional ratio which are specified in shift curves as for the two-speed form (Figs. 26A, 26B, not shown). Detail modifications.-Where upshift-downshift hysteresis is not required, the OR circuit 530 and bi-stable memory circuit 540 may be omitted. Hysteresis may be retained without the OR circuit 530 by using fixed shift points instead of range limits as shown.