DE2040953

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 t