GB1463498A - Motor vehicle automatic gearboxes - Google Patents

Abstract

1463498 Change speed control AUTOMOTIVE PRODUCTS Ltd 1 May 1974 [8 May 1973 25 Jan 1974] 21908/73 and 03496/74 Heading F2D Fluid pressure, engaging ratio-establishing friction clutches A, B and brakes C, D, F in a planetary change-speed gear on a motor vehicle, is controlled through shift valves 11 . . . 15 actuated automatically by signals representing output speed and torque demand, with manual override, and is, by a modulator valve 34 directly actuated by the shift signals, reduced rapidly during shift, followed by immediate commencement of, and slow increase to, recovery, to allow a slip period. Control may be pneumatic, hydraulic or, as shown, electronic. Gear arrangement.-The torque-converterdriven gear is of the double bevel stepped planet type, with one input clutch A effective for all forward ratios, another B for direct drive and reverse; a one-way low brake G, with parallel two-way brake F for manual low and reverse; and second and third ratio brakes D, C. Fluid system.-A single pump 21, Fig. 9, supplies fluid pressure in common to five solenoid valves 11 . . . 15 energizing the respective clutches and brakes A . . . D at a pressure regulated by a main regulator valve 23 (see also Fig. 11), subject to loading through the solenoid modulator valve 34 and having an outlet 25 supplying a low pressure regulator valve 24, spilling to exhaust and to the torque converter 26 in which pressure is maintained by a spring-loaded ball relief valve 28. Transient pressure control.-The main regulator valve 23, Fig. 11, with inlet 22 and low pressure outlet 25, is loaded leftwards for pressure increase by a spring 46 and by fluid pressure acting on a piston 47 and supplied at 49 by the solenoid modulator valve 34. To provide immediate pressure reduction on exhausting 49 and subsequent immediate commencement of recovery, followed by gradual increase on re-pressurizing 49, either the modulator valve 34 or the regulator 23 may have a one-way valve 51 with restrictor 52 and an accumulator 53. Two forms of solenoid modulator valve 34 are described, Fig. 12, and Fig. 13, not shown, in which the regulator valve loading passage 49, Fig. 11, is exhausted during shift by energizing and de-energizing respectively the solenoid. In Fig. 12, the one-way restrictor 51 of Fig. 11 is incorporated in the solenoid modulator instead of in the regulator 23. Fluid pressure is supplied to a restricted inlet 59, and, in the normal running position, urges upwards a valve plunger 55 to close an exhaust seat 60, pressure passing to the outlet 63, and thence to the regulator load passage 49, through passages 58, 61. Energizing a solenoid winding 54 during gear shift depresses the valve plunger 55, immediately exhausting the delivery passage 63 through passages 61, 64 and exhaust 60, to reduce regulator valve loading and hence line pressure. The loading pressure is slowly restored through the restrictor 59 after shift by de-energizing the solenoid winding 54. Alternatively, a large capacity solenoid valve may be incorporated in the main pressure line to provide direct relief. Electronic control.-The block diagram, Fig. 7, not shown, comprises a manual selector lever (1), operating a logic control (3), which receives a D.C. signal from a potentiometer (4) operated by the engine throttle, and a vehicle speed responsive frequency signal from a generator driven by a wheel in the drive train; and individual amplifier stages (6 . . . 10) energizing solenoids (11 . . . 15) of the respective shift valves and also connected to the input of a differentiator (74) which triggers a squarewave generator (75), the amplified signal from which energizes the solenoid modulator valve 34 for reducing line pressure during shift. The differentiator, detailed in Fig. 14, not shown, comprises a summing junction (77) connected by capacitors to each of the amplifier stages (6 . . . 10) and, through a resistor (R1) to negative line, thereby providing a positive pulse to a transistor (T1) forming the squarewave generator, the output of which is amplified by three transistor stages (T2, T3, T4), producing a D.C. signal at terminals (78, 79) energizing the solenoid of the modulator valve 34, or by reversing the action of the first amplifier transistor, producing a de-energizing signal therefor.