Patent GB-1401512-A (GB)
Title: Control circuit for an automatic gearbox
IPC: F16H59/70
Filed: 1972-06-27
Abstract: 1401512 Change-speed control AUTOMOBILES PEUGOET and REGIE NATIONALE DES USINES RENAULT 27 June 1972 [21 July 1971] 30012/72 Heading F2D In a planetary automatic transmission on a motor vehicle, wherein ratio-selecting clutches E1, E2, and brakes F1, F2, are applied by hydraulic pressure, the level of which is controlled by a main pressure regulating valve VRP, the latter is loaded by pressure acting on a reduced step, e.g. 7 of the valve spool in a chamber, e.g. 9, of the valve, communicating with a chamber, e.g. 67 of a modulator valve MF2 associated with a particular ratio, and having a spool 61 shifted between two positions by actuating pressure, 126, supplied to a brake F2 of that ratio, either to exhaust or maintain closed and under pressure the regulator valve chamber 9. Thus, on upshift involving engagement of the brake F2, the regulator chamber 9 is exhausted and the level of line pressure reduced. The control described provides three ratios and one reverse, the line pressure level being decreased stepwise at both 1-2 and 2-3 upshifts by exhausting successively two regulator loading chambers 9, 8, each having a regulator spool step 7, 6, and exhausted by respective valve spools 61, 51 of modulator units MF2, ME2, actuated respectively by the pressurization of brake F2 and clutch E2 on successive 1-2 and 2-3 upshifts to produce the stepwise reduction of line pressure. The pressure regulator valve VRP is also subject constantly to loading pressure by a spring 4 and by throttle pressure 107 from a throttle valve VPi, loaded by engine intake depression, such throttle pressure 107 also communicating permanently, through restrictors, with the first and second modulatorcontrolled chambers 9, 8 of the regulator valve VRP. Pressure supply.-A single engine-driven pump P supplies a torque converter C, main regulator VRP, throttle valve VPi, a manual selector valve Vs and lubrication lines 131, 132. Shift valves.-A manual valve Vs selects, in addition to PRN and automatic A, invariable II and I ratios. In all forward ratios the manual valve directly pressurizes the clutch E1. A single three-position automatic shift valve VPa selects first ratio (clutch E1 only) when two solenoid exhaust valves e1, e2 are both deenergized to allow line pressure 101, 112 to build up in two end-chambers 32, 33, thus maintaining an extreme left position of the valve spool 31, as shown. An intermediate position, pressurizing the second ratio brake F2, is established by energizing the solenoid valve e1 to exhaust the lower end-chamber 32; and an extreme right position pressurizing the third ratio clutch E2 and releasing the brake F2 is established by energizing also the solenoid valve e2 to exhaust the end-chambers 32, 33, the rightward movement of the valve spool 31 being produced by line pressure 101, 111 acting on a differential land of the spool. The shift-valve solenoids e1, e2 are energized by an electronic control circuit, not described, operating in response to output speed and engine throttle setting. Shift quality control.-The rate of engagement of the second ratio brake F2 and third ratio clutch E2 is controlled by the modulator units MF2, ME2 respectively. Each includes a spring and throttle-pressure loaded accumulator 62, 52 and a combined or separate (Fig. 4, not shown) valve section 61, 51 controlling regulator-valve loading by controlling exhaust of the loading chambers 8, 9 as described above. When, by pressurizing lines 116, 119, 130, the shift valve VPa signals a 1-2 upshift, the second-ratio brake F2 is pressurized through lines 119, 126 and the accumulator 62 of the modulator unit MF2 is stroked rightwards, taking along the valve spool 61 which then exhausts the line 105 of the load chamber 9 of the main regulator valve VRP, producing the first step down in regulated pressure. For the 2-3 upshift the shift valve VPa additionally pressurizes lines 117, 121, feeding the third-ratio clutch E2, the accumulator 52, and also through a line 125 shifting right an interlock valve VR1 which exhausts the line 119, thus releasing the second-ratio brake F2. The same third ratio line pressure 117 also acts in a chamber 68 to maintain the rightward position of a separate end spool 65 of the modulator unit MF2, thus ensuring that the regulator valve load line 105 is maintained exhausted. The second regulator-valve load line 104, communicating with the main regulator load chamber 8, is also exhausted, through the valve 51 of the modulator unit ME2, so that with both chambers 8, 9 exhausted, the regulator valve VRP produces a second step-down in pressure for third ratio. During a 3-2 downshift, the piston valves 51, 61 of both modulator units initially move left, cutting off the exhaust lines 104, 105 from both regulator chambers 8, 9, and thus temporarily raising line pressure to its maximum value for rapid filling of the second-ratio-brake F2.