Patent GB-1021873-A (GB)
Title: Improvements in or relating to hydrostatic transmission
IPC: F16H61/433
Filed: 1962-09-07
Abstract: 1,021,873. Hydrostatic transmissions; valves. Y. KUZE. Sept. 7, 1962 [Sept. 16, 1961], No. 34312/62. Headings F2C, F2D and F2V. [Also in Division F1] A hydrostatic . transmission comprises a swash-plate pump and motor unit, the inclination of the pump swash-plate 4 being variable by hydraulic means to vary the transmission ratio, and the motor swash-plate being adjusted by hydraulic means for forward or reverse drive or a valve controlling supply and exhaust of liquid to the motor being actuated for determining forward and reverse. As shown in Fig. 1, a pump cylinder barrel 26 is fast with an input shaft 25, and the pump swash-plate 4 is pivotally mounted in a stationary housing 2 by means of diametrically arranged pins 1. The motor cylinder barrel 126 is carried by an output shaft 125 and the motor swash-plate 104 carries diametrically arranged pins 101 rotatably mounted in the stationary housing. A valve plate 21 for the pump is mounted on an eccentric projection 20 of a sleeve 17 mounted in the casing 2. Ports 23 concentrically disposed about the projection 20 register with the pump cylinders on the intake strokes of their pistons 24, and the cylinders on the discharge strokes of the pistons register with a crescent-shaped space 28 formed between the periphery of the plate 21 and an annular member 27 carried by the pump cylinder barrel. Liquid from the space 28 is discharged through passages 32 in the member 27 to an annular space 31 and thence through passages 33, 30, 130, 133 provided in a member 16 fast with the housing 2, to the motor. The valve plate 121 for the motor is similar to the pump valve plate and is carried by an eccentric projection 120 of the sleeve 17, liquid discharged by the pump being supplied to the space 128 between the periphery of the valve plate 121 and an annular member 127 fast with the motor cylinder barrel. Liquid is discharged from the motor cylinders through ports 123 in the valve plate to the hollow interior of the sleeve 17 and from thence is supplied through the ports 23 in the valve plate 21 to the intake side of the pump. Make-up liquid is supplied by a pump p from a reservoir T to a port 15 in the housing 2 and thence through a passage in the member 16 and ports 19 to the interior of the sleeve 17. Liquid from the pressure side of the transmission is supplied through a port 34 to a valve housing 35 containing valves 36, 46, respectively, controlling the supply of liquid to a differential piston 6 controlling the pump swash-plate and to a piston 106 controlling the motor swashplate. The valve 36 is biased by a spring 37 to the right-hand position shown in which both sides of the piston 6 are open to the pressure side of the transmission, so that the piston 6 tends to move to the right under hydraulic pressure against the bias of a spring 13. In operation under light loads the spring 13 biases the swashplate 4 to its position of maximum inclination to give maximum pump output and a high transmission ratio, and as the load increases and consequently the pressure in the pressure side of the transmission increases, the piston 6 is moved to the right against the bias of the spring 13 and adjusts the swash-plate 4 to give a lower transmission ratio. The transmission can be put in neutral by displacing valve 36 to the left by a pedal 38 to open the right-hand side of the piston 6 to exhaust so that the pressure on the left-hand side of the piston moves the swashplate 4 to a vertical position limited by an abutment 44 formed in the casing 2. In the righthand position of valve 46 shown liquid from the high-pressure side of the transmission is supplied to the left-hand side of a piston 106 controlling the motor swash-plate 104 so that it is maintained in position for forward drive, and on moving valve 46 to the left, liquid is supplied to the right-hand side of the piston 106 to move the swash-plate into the dotted line position to give reverse. The maximum pressures in the high and low pressure sides of the transmission are limited by valves V1, V2. The liquid from the high-pressure side of the transmission serves to lubricate and form a bearing between the member 27 which rotates with the pump cylinder barrel and the stationary member 16 and between the member 127 and the member 16. In a modification (Fig. 2, not shown) the differential piston 6 is replaced by two pistons of different size acting at diametrically opposite points of the pump swash-plate. The motor swash-plate is similarly controlled by two differently sized pistons. In the modification of Fig. 15 the motor swash-plate is fixed, and forward and reverse is controlled by actuating the motor valve 121 which is mounted on the eccentric projection 120 of the sleeve 17 which is formed in two parts; the part having the projection 20 for the pump valve plate 21 is fixed, but the portion having the projection 120 is rotatably mounted in the member 16 and can be rotated through 180 degrees by supplying liquid to a cylinder 66<SP>1</SP> and exhausting a cylinder 66 and vice versa under the control of valve A6. The pistons act through a series of balls acting on a vane provided on this part of the sleeve 17.