GB1154590A - Hydrostatic Transmission. - Google Patents

Abstract

1,154,590. Hydrostatic transmission. CHRYSLER CORP. 12 Oct., 1966 [21 Oct., 1965; 13 Dec., 1965], No. 45582/66. Headings F2C and F2D. In a hydrostatic transmission for a motor vehicle wherein a pump cylinder body 20 is fast with an input shaft 30 and has pistons 32 engaging a fixed inclination swash-plate 24 fast with a motor cylinder body 22 which is fast with an output shaft 40 and has pistons 56 engaging a variable swash-plate 26, a valve 262 is provided to block the high pressure line 174, 179 between the pump and motor when the motor swash-plate is vertical and thus reduce hammering noises, vibrations and leakage in direct drive. The motor swash-plate 26 pivots about cylindrical surfaces 96, 98 and its inclination is automatically varied by a servomotor 118 supplied with pressure liquid from a control (not shown) responsive to transmission pressure, accelerator pedal position and engine speed. When the swash-plate 26 is vertical it closes a valve 266 whereupon pressure builds up in a duct 364 and chamber 318 (Fig. 1Q) and moves a piston 302 right against the bias of springs 312, 314. The piston 302 acts through a rod 330 to move right a spool 274 of the valve 262 whereupon a surrounding sleeve is urged by a spring to follow the movement of the spool 274 to close a part 158 between the pump and motor high pressure lines 174, 179. A valve plate 146 which interconnects the pump and motor high pressure lines and connects the motor low pressure line to a chamber 178, is rotated through 180 degrees for reverse ratio by selectively supplying pressure liquid to servomotors 251, 252 the pistons 257, 258 of which act through a rack 264 and pinion 248 to rotate the valve plate. High pressure liquid passes through ducts 372, 380, 382 to a modulator valve 462 (Fig. 1P) in a stationary end plate 220 and modulated pressure passes through ducts 483, 442, 436 to the control for the servo 118. The modulated pressure moves a shuttle valve 478 (Fig. 1P) left whereupon make-up liquid is supplied to the chamber 178 through ducts 472, 476, 394, 396, 398. During overrun the higher pressure which is in the low pressure ducts acts through a duct 480 to move the shuttle valve 478 right whereupon the higher pressure is supplied to the control whilst make up fluid is supplied through ducts 472, 484 to the normally high pressure ducts. A by-pass valve (402), (Figs. 1 and 1T, not shown) in the duct 382 is normally held closed by pressure liquid supplied to a piston (404) but in neutral the pressure supply is cut whereupon the valve opens to short circuit the high and low pressure lines.