GB1437942A - Liquid pressure control systems for variable speed transmission mechanisms - Google Patents

Abstract

1437942 Change-speed control AUTOMOTIVE PRODUCTS Ltd 25 May 1973 [25 May 1972] 24784/72 Heading F2D In a four speed and reverse automatic transmission (not described) on a motor vehicle, liquid - pressure - engaged ratio - establishing clutches 14, 19 and brakes 21, 64, 65, are controlled by a single automatic shift valve 15, the spool 39 of which is moved stepwise between four axial positions by liquid pressure supplied selectively through two flow paths to ports 71, 79, through an auxiliary valve or valves, e.g. 74, 75, to act on separate end pistons 49, 51 shifting the valve spool as described below. Figs. 6 to 9, not shown, use a single auxiliary valve (211) moved into three positions by speed-responsive pressure supplied by an output-driven pump and opposed by a spring, loaded by the engine accelerator and a manual mechanical override. Figs. 1A, 1B, shown, use two auxiliary valves 74, 75, opened by energizing solenoids through an electronic circuit (not described) responding to output speed and load. Pressure supply and regulation.-A single input-driven pump 10 feeds a main pressure regulator valve 11 which spills to a chamber 107 under the influence of delivery pressure 104 opposed by a spring 109, by pressure from the reverse port 35 of a manual selector valve 23, and by line pressure supplied at 111 by a solenoid valve 76 energized when engine throttle opening exceeds a predetermined value. The spill chamber 107 feeds a spring-loaded secondary regulator valve 101 feeding a torqueconverter 103 and lubrication line 122, and, through a manually or thermostatically controlled valve 127, an oil cooler 126. Manual selector valve 23 has four settings, drive, neutral (shown), reverse and park lock. Operation. Drive. First ratio.-Moving the manual selector 23 one step left supplies pressure from a port 29 to a line 30 which directly feeds the clutch 14, which is a forward clutch, engaged in all forward ratios. Line pressure 30 also passes to inlet ports 57, 58 of the automatic shift valve 15, but is initially blanked there, so that the forward clutch engages alone and provides first ratio for starting. 1-2 Upshift.-Under the appropriate speedload condition the electronic circuit energizes the solenoid valve 74 which feeds line pressure 30 at 77 to the left face of the piston 49 and at 78 to the right face of the opposite piston 51 of the automatic shift valve 15. Both pistons 49, 51 move inwards to shoulders 47, 48, the piston 51 taking along the valve spool 39 one step left in opposition to a spring 56 between the spool and the left piston 49. Line pressure 30 now passes through ports 57, 59 of the shift valve to engage the brake 64 for second ratio. 2-3 Upshift.-The appropriate signal energizes the solenoid valve 75, whilst maintaining 74 energized. Line pressure through 75 and a port 79 is applied to a space between the right piston 51 and the right face of the valve spool 39, shifting the latter a second step left, until stopped by a central stem 54 on the left piston 49, whereupon the second brake 64 is exhausted at 66 and the third brake 65 pressurized at 58, 61. 3-4 Upshift.-The solenoid valve 74 is de-energized leaving 75 energized alone, whereupon the left piston 49 and valve spool 39 are moved together a third step left, exhausting the two brakes 64, 65 and pressurizing the clutch 19, which is used with 14 for fourth ratio. Reverse.-Movement of the manual valve 12 one step right from neutral (shown) to reverse, supplies line pressure 29 past a ball valve 81, through ports 97, 98 of a shift smoothing valve 68 (described below) and the automatic shift valve 15, to the direct-reverse clutch 19 and, closing the valve ball 82 on to a seat 83, to the reverse brake 21 through a restrictor 84, which ensures prior engagement of the clutch 19. On release of reverse brake pressure, the brake 21 exhausts rapidly by lifting the ball valve off its seat, thus by-passing the restrictor 84. Transient pressure control.-During a shift, the automatic shift-valve exhaust ports 71, 66, 67 communicate with exhaust through the shift smoothing valve 68 which is loaded to the left position, shown, by a spring 87 and torqueconverter pressure 124 to permit unrestricted exhaust of an off-going clutch or brake, and rightwards, to restrict the exhaust, by line pressure 30 applied to the left face through a solenoid valve 73 energized during gear shift. In Figs. 5, 5A and 6 to 9, not shown, the two pistons (167, 168) for stepping the automatic shift valve are both at the same end of the spool (137) one on a smaller third piston (169) the other abutting the latter. In Figs. 5, 5A, not shown, the smoothing valve 68 of Fig. 1 is omitted, and pressure for the reverse brake (193) is reduced in relation to that for the directreverse clutch (162) by a reducing valve (189). In Figs. 6 to 9, not shown, the two flow paths for stepping the automatic shift valve are provided by a single four position auxiliary valve (211) the spool of which is moved axially in three steps by speed-responsive pressure from an output driven pump acting directly on one end face in opposition to a spring (224) loaded by the engine throttle control, acting on the opposite end face. A manually operable rod can be moved to act directly on the latter face for forced downshift.