Patent GB-1217268-A (GB)
Title: Hydraulic control system for automatic transmission
IPC: F16H61/00
Filed: 1968-12-13
Abstract: 1,217,268. Change-speed control. NISSAN JIDOSHA K.K. 13 Dec., 1968 [19 Dec., 1967], No. 59432/68. Heading F2D. In an automatic transmission on a motorvehicle, of the kind wherein ratio-selecting clutches 4, 5 and brakes 6, 7 are actuated by liquid pressure controlled by a manual ranging valve 104 and 1-2, 2-3 shift valves 105, 106, actuated by opposing liquid pressures responsive to output speed and engine torque (throttle pressure manifested by inlet manifold depression or throttle setting), and the servo pressure applied continuously to the selector clutches and brakes is controlled by a main pressure regulator 102, the loading of the regulator is controlled by four additional valves viz, a line pressure booster 103 (at the left of the regulator), a cut-down valve 114; a boost change-over valve 110; and a coast boost valve 115, which combine to produce the following effects. Line pressure increases with throttle pressure and has a one-step decrease with speed; is decreased at low speed low throttle pressure, for soft starting engagement; has a one-step increase at a low speed, followed by graduated increase to a maximum in accordance with throttle pressure; is increased when entering manual second ratio at high speed, low throttle pressure for instant engine braking; and is augmented in reverse, and, although increasing with throttle pressure as above, is independent of speed. Gear arrangement.-The gear, Fig. 1, not shown, is the usual torque-converter-driven Simpson two-train planet set, providing two reduced ratios, direct-drive and one reverse. Input clutches 4, 5 selectively drive the common suns (19, 20) or first ring-gear (22), 5 being engaged for all forward ratios, 4 for direct-drive and reverse only. Reaction of the rear carrier (27) in first ratio is taken by a one-way brake (10) in automatic drive, and by a two way disc-brake 7 in manual low. Output is taken from the connected first carrier (24) and rear ring-gear (25). Control pressures.-Governor pressure 220 is provided by an output-mounted two-stage governor 112, 113; TV (throttle-variable) pressure 207 by a valve 107 regulated by a diaphragm 502, loaded by engine inlet-manifold depression, or by engine throttle setting; modulated TV pressure 208 by a TV modulator valve 108 which reduces TV pressure before supply to the shift-valves 105, 106: kickdown pressure 209 by a solenoid kickdown valve 109. Manual valve.-A manual ranging-valve 104 has settings Park, Reverse, Neutral, Drive, 2 and 1. Drive gives automatic shift between all three ratios. 2 setting gives invariable second ratio through a second ratio lock-up valve 116. 1 setting gives invariable first ratio after an automatic downshift from second if vehicle speed was above that for 2-1 downshift at the time of manual selection of first. Servo pressure regulation.-The main regulator valve 102 regulates line pressure 200 from a single input-driven pump 101, spilling first to the torque converter 3, then to exhaust. Rightward loading, for pressure increase, is by a spring 311 and TV pressure 207 applied to the line booster 103. Opposing loading, for pressure reduction, as controlled by the three valves 110, 114, 115, as follows. Primary control is exerted by the cut-down valve 114, which controls communication between a line 222 leading to the smaller right end face of the regulator 102, and either TV pressure 207 or a line 221 controlled by the coasting booster valve 115 and boost change-over valve 110. At high speeds, governor pressure 220, acting leftwards on the cutdown valve 114, prevails over a spring and TV pressure 207 acting rightwards on differential lands, to shift the cut-down valve 114 left, thus applying TV pressure 207 to the right face of the regulator 102, where it opposes the same TV pressure 207 acting rightwards on the larger left hand face of the regulator. This causes a stepped reduction in line pressure 200, followed by graduated increase with TV pressure. At lower speeds or higher TV pressure, the cutdown valve 114 remains rightwards, as shown and pressure in the regulator opposing line 222 is supplied through a line 221. At low TV pressure 207, the coast-booster valve 115 connects this line 221 directly to line pressure 200, for a stepped reduction to minimum line pressure. At high TV pressure 207 the valve 115 moves left to exhaust the line 221 so that the regulator 102 regulates to a maximum line pressure 200 under TV control at 103. Thus the combined effect of the valves 114, 115 is to provide low line pressure at low speed, low TV, to reduce shock at starting selector shift; at higher speed and higher TV, for normal drive, a stepwise decrease in line pressure with speed, followed by TV-responsive increase; at low speed, high TV, a stepwise increase in line pressure, followed by TV-responsive increase to a maximum, for high torque capacity at low speed. The change over valve 110 is operative only in manual setting 2, and manual setting 1 only during second speed operation preceding subsequent automatic 2-1 downshift in that setting. The valve 110 is in parallel with the coast-boost valve 115 controlling the regulatorvalve load line 221. In Drive setting, and in first speed of 1 setting, the change-over valve 110 in maintained rightwards by line pressure 203, or 215 respectively, acting on differential lands, to block the line 221, and exhaust a line 223 at 206, and is thus without effect. Selection of manual second 2, exhausts the line 203, whereupon the change-over valve 110 moves left (shown), connecting the line 221 through the line 223 to the left side of the regulator 102. At low TV pressure 207, the line 221 is also connected through the coastboost valve 115 to line pressure 200, so that line pressure in line 223 acts on differential lands of the regulator 102 in a pressure-increasing rightward direction, increasing line pressure to a maximum. This gives full pressure for enginebraking on a closed throttle manual downshift to 2 setting. On a similar manual downshift to 1 setting, if the speed is such that governor pressure first maintains second ratio by the 1-2 shift valve 105, conditions are as for manual shift to 2-setting, but after automatic downshift to first ratio, first-speed apply-pressure 215 shifts the change-over valve 110 right to cancel the line pressure increase, as in D setting. Reverse is similar to 1 setting, except that the line 206 now receives line pressure which passes through the change-over valve 110 and line 223 to load the regulator 102 to maximum pressure, which is independent of speed since the governor feed line 201 is exhausted in R setting. In Fig. 7, not shown, the coast-boost valve 115 has a graduated regulating action instead of a step. Three dimensional charts (Figs. 4-6, not shown) are included, showing the variation of line pressure with TV and governor pressure under the above described conditions.