Patent GB-1282791-A (GB)
Title: Variable-ratio power transmission mechanisms
Inventor: SCHAEFER ROBERT HERMAN
IPC: F16H61/02
Filed: 1970-07-30
Abstract: 1282791 Change-speed control GENERAL MOTORS CORP 30 July 1970 [25 Aug 1969] 36911/70 Heading F2D In an automatic transmission on a motorvehicle, wherein a ratio-shift control means such as a shift-valve 136 is actuated in the upshift direction by an output speed responsive governor signal, such as the fluid pressure 34 provided by a pitot head 33, in opposition to a variable downshift bias signal including a component such as fluid pressure 62 responsive to engine torque demand, as manifested by intake depression, fuel or throttle setting, the downshift speeds at any given torque demand being lower than the corresponding upshift speeds, the difference between those speeds, i.e. the hysteresis, decreases as the torque demand increases towards its maximum. Such decrease provides a more sensitive shift control by torque demand in the higher ranges of torque demand. Function summary.-Although applicable to move ratios, the two embodiments disclosed are for control of two ratios only, by engaging a direct-drive clutch 23 and a reduced drive brake 27 of a simple planetary gear set 9. A manual selector valve 44 has three settings N; D giving the two automatic ratios, and D1 enforcing low below a safe engine speed, which is higher than that at which a similar detent downshift can be made by full-throttle energization of a solenoid valve 132. Fluid pressure supply and regulation.-A single input-driven pump 38 supplies the main 42 of a system which includes three pressure regulators. A first regulator maintains a constant main pressure 42 of 100-150 p.s.i.; a second regulator 55 regulates the low-ratio D-1 line 53 to a lower value (33 p.s.i.); and the solenoid detent valve 132, when effective, also regulates detent pressure 133 to a value (30 p.s.i.) slower than D-1 pressure 53. Governor pressure 34 is provided only by the pitot head 33 in the output rotated can 32. Modulator (TV) pressure takes two forms in the two embodiments. In Fig. 1 engine intake depression 78 acts on a spring-loaded diaphragm 72 to load a regulator valve 56, which meters modulated (TV) pressure 62, which is also used to load a slidable plug 106 of an inverse modulator valve 86, which meters inverse modulator pressure 114 from drive line pressure 52. The plug 106 acts on the metering spool 88 through a small sliding pin 104, itself subject to rightward delivery pressure 112, 114, which extends the initial straight horizontal part of the inverse modulator pressure curve (Fig. 3, not shown) on the low throttle region, this curve terminating in another horizontal line when the metering spool 88 is stopped by a pin 95 before zero depression is attained in the modulator valve 56 at full throttle. Because of this, both the minimum and the maximum values of inverse modulator pressure 114 are definite constants unaffected by barometric, tolerances and other variations in the corresponding values of intake depression. Shift valve 136 has two butting spools 138, 152 urged leftward for upshift by governor pressure 34. In the downshift position shown, wherein drive line pressure 52 is directed to the reduced drive brake 27, rightward downshift load is by an adjustable spring 168, and by modulator pressure 62 and inverse modulator pressure 114 acting respectively on differential lands c, b of the spool 152. On upshift to the left, modulator pressure 62 remains effective on the land c, but inverse modulator loading 114 now acts between equal lands a, b of the spool 152 so that its effect is cancelled. The reduced drive brake 27 is exhausted and drive line pressure 52 is supplied at 148 to the direct-drive clutch 21 and also acts leftward on the differential land b of the spool 138 (larger than land a). Thus pressure providing the primary hysteresis opposing the return downshift, which occurs when governor pressure 34 and primary hysteresis 148 are overcome by the spring 168 and modulator pressure 62. Summation of the downshift bias forces results in the shift curves of Fig. 10. Upshift curve 342 is always above that of downshift 341, but has a lesser slope so that hysteresis diminishes in the direction of full throttle (FT), and both curves have straight horizontal ends at fixed values before closed or full throttle are reached. The shift valve load-spring 168 is adjusted by removing a pin 170 and turning a sleeve 166 to expose end notches of different depths to receive the pin 170 (Fig. 2a, not shown). Detent and manual downshift lines 133, 53, one connected to a shuttle valve 134 which opens the higher pressure to a chamber 155 of the shift valve 136 to enforce downshift below a safe engine speed. Fig. 2, not shown, has similar action, but with the following differences. The separate modulator and inverse modulator valves 56, 86 are replaced by a single inverted modulator valve (210), which comprises a spring-loaded regulator valve loaded negatively by a lost-motion mechanical connection to the engine throttle or fuel feed, the lost motion providing the initial flat curve as for Fig. 1. In the shift valve (290) the inverse modulator pressure acts leftwards (upshift) on a large end land (c) of the valve spool (296) in the downshift position; and additionally in the same upshift direction on a second differential land (b) in the upshift position. The solenoid regulator (detent) valve 132 of Fig. 1 is described in Fig. 2, not shown, and comprises a regulator valve (362) with constant spring load, but normally locked exhausted by line pressure applied to a chamber above the valve through a restrictor. Energizing a solenoid at full throttle exhausts this chamber and permits the valve to regulate a constant detent pressure in the detent line (374).