VARIABLE-RATIO POWER TRANSMISSION MECHANISM

1,271,341. Change-speed control. GENERAL MOTORS CORP. 30 July, 1970 [25 Aug., 1969], No. 36912/70. Heading F2D. A substantially zero-movement hydraulic link 123, between an engine torque-demand control 34 and a modulator valve 44, which regulates pressure 144 inversely proportional to torque demand (inverse TV pressure), to act with output pitot governor pressure 74 on a shift-valve 160 controlling reduced, 67, and direct, 63, ratios in a two or more ratio transmission on a motor-vehicle, comprises rollseal diaphragms in sending and receiving units 36, 42, the send-diaphragm being loaded by the torque-demand control 34 through a spring 238, whilst the receive-diaphragm acts directly on the valve-spool 102 of the modulator valve 44, through a pin-strut 118, in opposition to a pressure-increasing load spring 106. The spacing of the modulator valve-spool lands a, b is only very slightly less than, or equal to, that between the main pressure port 94, 95 and exhaust port 152, so that the spool 102 regulates inverse modulator pressure 144 with virtually no significant movement, and since the hydraulic link 123 is pressurized through the spring 238 by the torque-demand lever 34, the link transmits a variable pressure also with no significant fluid movement, thus eliminating wear. The torque-demand lever 34 is mechanically linked to the engine throttle, fuel injection rack, engine-governor-actuated fuel feed or the speed control of a fuel-feed engine governor. A torsion spring 272 loads the torque-demand lever 34 to idle (OT) setting where an integral lever arm 264 acts upwards through an adjustable nut on a valve stem 228, which lifts a valve element 234 off a seat 256 on a diaphragm mounting member 242, permitting low-viscosity hydraulic fluid to flow from a reservoir 206, through a central passage 255 to a diaphragm chamber 208 communicating with the flexible connecting hose 123. Throttle opening movement, (towards FT) first closes the valve at seat 256, and then applies pressure to the liquid in the chamber 208 through the spring 238. This pressure is proportional to throttle opening movement and causes the regulator valve 44, which receives it at the unit 42, to regulate pressure 144 inversely proportional to such movement. The shift valve 160 comprises a valve spool 162 with two equal lands b, c and a smaller end land a, and a control spool 166 with three differential lands a, b and c. Rightward bias is always by the spring 170 alone. In the rightward downsh