Patent GB-1316657-A (GB)
Title: Electrical automatic shift control systems with hilly country detecting unit
IPC: F16H61/02
Filed: 1970-09-24
Abstract: 1316657 Change speed control TOYOTA JIDOSHA KOGYO KK and NIPPONDENSO KK 24 Sept 1970 [27 Sept 1969 20 Oct 1969 14 Nov 1969 12 Feb 1970] 45588/70 Heading F2D An automatic control for solenoid shift-valves 1270, 1290, producing hydraulic engagement of ratio-selecting clutches and brakes 20, 30 and 40, 60 in a torque-converter-driven planetary change-speed gear on a motor-vehicle, comprises an electronic circuit, Fig. 4, including inter alia bi-stable memory circuits 1540, 1640 which are driven to one stable portion by circuits detecting either upgrades or downgrades, and into the other stable position by a hilly country release circuit. Signals issued by the following parameters all take part in the control. Vehicle, engine and torque-converter turbine speeds, torque-converter slip-ratio, engine setting, service brake pressure and signal lamp, throttle vehicle inclination and acceleration, ratio setting and time delay. The control is applied to a three-speed gear, and, in general, when the hilly country detector signals a predetermined state of gradient, a 2-3 upshift is prevented until the release circuit signals that the hilly state is passed. Gear arrangement.-The gear, Fig. 1, not shown, provides two reduced ratios, directdrive and one reverse, and comprises two input clutches 20, 30, Fig. 2, driving opposite small bevel side-wheels of a stepped bevel planet gear, the front clutch 20 effective for all forward ratios, the rear, 30, for direct-drive and reverse only. Low and second ratio band brakes 40, 60 hold the planet carrier and one small side wheel respectively, the drive issuing from a larger side-wheel meshing the large planet step. Fluid system.-A single input-driven pump 17, Fig. 2, supplies a manual PRNDL valve 1260, which in its reverse setting, R, shown feeds directly the rear clutch 30 and brake 40. In D and L settings the manual valve feeds directly the front clutch 20 and a 1-2 solenoid shift-valve 1270, which, in its rightward downshift position shown, feeds only the rear brake 40 for first ratio, and in its leftward upshift position to which it is moved by energizing the solenoid 1280, it changes from the rear 40 to the front brake 60 for second ratio, and at the same time feeds a 2-3 shift valve 1290, which, when upshifted left by energizing the solenoid 1300, engages the rear clutch 30 and supplies release pressure to the front brake 30 for direct-drive third ratio. Electric speed detection.-The speeds of input N1, torque-converter turbine N2 and output N3 are detected by polarized magnetic pick-ups adjacent notched discs rotating with the respective members, to provide speed responsive variable frequency signals 311, 321, 331, Fig. 4, which are converted to speedresponsive D.C. voltage signals 312, 322, 332 in circuits 310 &c. each comprising a wave shaper, amplitude limiter and A.C.-D.C. converter. Shift requirements.-Shifts are required at specified limits of input and output speeds N1, N3, and torque-converter slip-ratio N2 : N1, the latter being below unity for drive and above unity on overrun, these limits being shown in the boxes 1340 &c. of Fig. 4. Thus the first circuit 1340 issues a voltage signal 1342 when engine speed N1 falls below 600 R.P.M. The slip circuits 1410 &c. (detailed in Fig. 27, not shown) feed potentiometer-selected proportions of N1 N2 signals 312, 322 to a differential amplifier, which emits a voltage signal 1412, &c. when the N2 : N1 (slip) ratio exceeds or falls below the approriate limit stated on the boxes 1410 &c. of Fig. 4. Revolution setting circuits 1340 &c. (detailed in Fig. 26, not shown) compare potentiometer-selected proportions of N1 N3 voltage signals 312, 332 with a reference voltage and issue amplified voltage signals 1342, &c., when the speeds exceed or fall below the stated limits. The N2 speeds 1350-1380 are derived from the product of N3 and the appropriate gear ratio of the transmission. Also included in the control circuit are first, second and third gear position circuits 1822, &c. which, under control of a shift position logic circuit 1810, energized by the shift-valve solenoids 1280, 1300, issue voltage signals 1822, &c. When the appropriate ratio is established; and a synchronized timing hold circuit 1710 which issues a voltage signal 1712 for a predetermined time after a shift to prevent any further shift signal from becoming effective. The circuit also includes the hilly country detecting unit 1930, extering additional control on the shift points, and detailed separately below.  Shift sequence (1) level running.-Ignoring, for the time being, the effect of the hilly country circuit 1930, shift sequence is as follows. In first ratio neither solenoid 1280, 1300 is energized. The 1-2, 2-1 shift curves (Fig. 3A, not shown) show that 1-2 upshift is required when vehicle speed exceeds 15 K.P.H. (N2 > 1402 R.P.M.), and torque-converter slip ratio exceeds 0À85 and is less than 1À25, which condition produces three signals 1412, 1372 and 1452, which are applied to an AND circuit 1510 along with a signal 1822 indicating that first ratio is established, and a signal 1722 from a NOT (phase inverter) circuit 1720, indicating no signal 1712 from the time hold circuit 1710 (i.e. the preceding shift to first is not less than a predetermined time earlier). With all these five signals present at the same time the AND circuit 1510 issues a signal 1512 driving the bi-stable memory 1540 to the other of its stable positions, producing a signal 1542 to energize the valve solenoid 1280 for 1-2 upshift. Downshift requires a variety of conditions applied singly. Thus 2-1 downshift is required when engine speed N1 is below 600 R.P.M.; or turbine speed N2 below 552 R.P.M.; or slip ratio below 0À75 or above 1À35, providing signals 1342, 1352, 1472 or 1432, either one of which, when applied alone to an OR circuit 1530 emits a signal 1532 to an AND circuit 1520, which, together with a second gear position signal 1832 and a signal 1722 from the time hold and NOT circuits 1710, 1720, emits a signal 1522 driving the bi-stable memory 1540 back to the first of its stable positions, deenergizing the solenoid 1280 for 2-1 downshift. 2-3 and 3-2 shift conditions are indicated in Fig. 3B, not shown. Action is similar to the 1-2, 2-1 shift, using the 2-3 valve solenoid 1300 and a second circuit including a bi-stable memory 1640, two AND circuits 1610, 1620, and an OR circuit 1630, the same as those described above for second ratio, but signalled by differently valued slip-ratio and speed-setting circuits as indicated on the boxes in Fig. 4. Hilly country detector.-The signal 1642 for energizing the top gear solenoid 1300 is received through an additional AND circuit 1910, which is effective for upshift only when it also receives a signal 1922 from a NOT circuit 1920, rendered effective by absence of signal 1932 from a hilly country detector 1930. Thus the signal 1932 prevents 2-3 upshift. Three different detectors are described with reference to Fig. 5, and Figs. 13 and 15, not shown. The hilly country detector 1930 of Fig. 5, has a downgrade circuit 3100 and an upgrade circuit, a signal 3142 or 3202 from either of which drives a bi-stable memory 3600 to issue a signal 1932 inhibiting 2-3 upshift, as above described, this signal being erased, to restore normal shift action, by a signal 3302 from a release circuit 3300. The downgrade circuit 3100 issues its signal 3142 when there are present together at an AND circuit four signals comprising a signal 3112 generated at 3110 by the usual service brake lamp; a signal 1842 indicating that third ratio is established; a signal 1442 indicating a converter slip-ratio exceeding 1À15, and a signal 3132 indicating that vehicle acceleration exceeds 0À016 g., determined at 3120, for a period not less than 0À5 second, determined by a timehold 3130. The acceleration detector 3120 is detailed in Fig. 9, not shown, and comprises a circuit which differentiates the D.C. output speed signal 332. The time gate circuit 3130 (detailed in Fig. 10, not shown) comprises two transistors triggered through a constant voltage diode and capacitor. The upgrade circuit 3200, Fig. 5, may detect an upgrade by using the same slip signal 1482 (less than 0À65) as that which produces the 3-2 downshift on an incline, together with a signal that, after downshift to second, the slip ratio does not exceed 1À0 for three seconds (for engine braking), and a signal from a circuit detecting that acceleration is less than 0À5 g. An alternative circuit is detailed below. The hilly country release circuit 3300, Fig. 5, generates a signal 3302 which changes the bistable memory 3600 to premit 2-3 upshift when the hilly condition is no longer present. The signal 3302 is generated when slip-ratio remains above 0À9 and below 1À0 for several seconds at an accelerator pedal displacement of less than half stroke. Fig. 11, not shown, is an alternative release circuit, and comprises an AND circuit fed with five signals as follows. A signal 1422, Fig. 4, indicating slip-ratio exceeding 0À90; 1462 indicating slip ratio below 1À05; 1832, indicating second gear; 1352 turbine speed N2 below 1660 R.P.M.; and a signal from a vehicle acceleration detector fed with the output speed signal 332 and detecting acceleration. With all these signals present the AND circuit feeds a second AND circuit together with a time-hold circuit indicating that the condition has persisted for at least three seconds, whereupon the release signal 3302 is issued. The hilly country detector of Fig. 13, not shown, is generally similar to that of Fig. 5, except that it has a different, upgrade detector circuit 3200, providing three output signals (3202a, 3202b, 3202c). The first (3202a) is one which provides normal 3-2 downshift on the incline, i.e. slip below 0À65 in third gear. The second (3202b), is derived from an AND circuit fed with a signal when slip exceeds 1À05, a second