Patent GB-1136565-A (GB)
Title: Improvements in or relating to power transmission apparatus
Inventor: POMPE WILHELMUS ANTONIUS MARIA
IPC: F16H61/662
Filed: 1965-12-16
Abstract: 1,136,565. Variable speed control. BUREAU VOOR WERKTUIGBOUW IR W. A. M. POMPE N.V. 16 Dec., 1965, No. 25561/65. Heading F2D. A continuously variable hydrostatic transmission or friction gear 3 for a motor vehicle is controlled by input or output torque responsive means 6 acting in opposition to means 18 responsive to accelerator pedal position and/or input or output speed. As shown an engine 1 drives through a centrifugal clutch 2, friction gear 3, torque detector 6 and reverse gear 8<SP>1</SP>. The torque detector 6 produces a force proportional to torque which acts through a link 8 on the ratio control lever 4 of the gear 3 to reduce its output speed during normal drive. A servo piston 21 applies an opposing force responsive to accelerator pedal position and engine speed to the lever 4 through links 15, 16. One end of the lever 15 acts on a device 10 which applies friction loading to the gear such that in the absence of force from the piston 21 the loading is minimal. Pressure liquid is supplied to the servo 18 from a pump 426 at a pressure determined by a throttle valve 419 and relief valve 420. Depression of an accelerator pedal 417 closes the valve 420 and acts through a rod 428 to move the spool of the valve 419 down to open the throttle valve whereupon low pressure is supplied to the servo 18 and the vehicle accelerates in low gear. As the engine speed increases a governor 416 moves the spool of valve 419 up to increase the throttling action and the pressure in the servo 18 to upshift the gear. Upshift beyond direct-drive is normally prevented by a stop 27 on the rod 17 of the piston 21 engaging a spring 27a. To provide engine braking when descending a hill the upper limit of the gear is restricted by a servo 25 supplied from the pump 426 through a manual control valve 423. The piston 26 of the servo 25 projects a stop 23 into the path of the piston-rod 17 and limits its upshift movement. More than one limiting servo 25 may be provided. The engine throttle valve 418 is actuated by a cam 427 fast with the rod 428. With a gear 3 providing a zero output speed and reverse ratios the clutch 2 and reverse gear 8<SP>1</SP> are omitted and reversing valves 28, 29 under the control of a lever 30 selectively supply pressure liquid from the pump 426 to the right and left sides of the piston 21 for forward and reverse ratios respectively. Friction gears.-In Fig. 2 (not shown) an engine (113) drives the input roller (101) of the gear through a centrifugal clutch (112). A friction ring (103) engages the roller (101) and is carried by a cone (102) freely rotatable in a housing (105) pivoted at (104) to an axially slidable element (106). The cone (102) is connected through gears (108a, 108b), a torque responsive screw and nut (109, 110) and a reverse gear (125) to an output shaft (126). A spring pressed wedge (107a) biases the ring (103) and roller (101) into light frictional contact. A servo piston (114a) acts through a lever (115) to increase the frictional contact pressure between the ring (103) and roller (101) and also moves the ring (103) left against the bias of the screw and nut (109, 110) to upshift the gear. A ratio limiting servo (121) is also provided. In Fig. 3 (not shown) an input disc (201) frictionally engages a disc (203) geared at (207, 208) to an output shaft (209) rotatably mounted in one end of a rod 210 pivoted at 211 to a frame. The disc (203) is rotatably carried by a bracket (206) pivoted on a rod (212) between axially slidable sleeves (213, 214). Spring pressed cams (227) urge the discs (201, 203) into light frictional engagement. A servo (228) acts through levers (224, 218, 219) on the bracket (206) to increase the friction contact between the discs and to move the bracket axially in either direction from a central zero output position for forward and reverse drive. The action of the servo is opposed by the torque responsive action between the gears (207, 208). A ratio limiting servo 230 is provided. Hydrostatic transmission.-In Fig. 4 (not shown) a variable displacement pump (301) is in closed circuit with parallel fixed or variable displacement motors (302) connected to the vehicle wheels and the fluid lines (306, 307) are connected to cylinders (304, 305) the pistons of which act on the pump displacement lever (308) and bias the latter towards its zero output position in opposition to a control servo (303). Modified control circuit.-In Fig. 6 (not shown) the opposite ends of a ratio shifting servo 501 are supplied with pressure liquid by pumps (503a, 503b). Relief valves (507, 508) between the pumps and servo are respectively closed by depressing pedals (505, 504) to permit pressure build up at the right or left end of the servo for forward or reverse drive. The pressure build up is controlled by a throttle valve (519), the spool (515) of which is moved axially by an engine or vehicle speed responsive governor (516). The relief valves (507, 508) may be operated by electric, pneumatic or hydraulic means responsive to temperature, speed, pressure or acceleration.