Patent GB-973397-A (GB)
Title: Improvements in variable speed hydromechanical power transmission
IPC: F16H39/14
Filed: 1963-08-01
Abstract: 973,397. Hydraulic transmission. INTERNATIONAL HARVESTER CO. Aug. 1, 1963 [Aug. 7, 1962], No. 30539/63. Heading F2C. [Also in Division F1] In a continuously variable hydrostatic transmission, for a tractor, comprising a swashplate pump and a swashplate motor in closed circuit, a cylinder block 30 fast with the output (input) shaft 27 has an inner ring of pump pistons 34 engaging an adjustable pump swashplate 53 rotating with the input (output) shaft 23 and an oppositely extending outer ring of motor pistons 40 engaging a non-rotatable adjustable motor swashplate 46 and is abutted on its ends by annular ported face valve members 20, 106 respectively fixed and rotating with the input (output) shaft. The valve member 20 has kidney ported ducts 104, 105 respectively connecting the motor cylinders with inner and outer concentric fluid passages 43, 44 in the cylinder block and is circumferentially adjustable in the fixed casing for correct phase relation with the motor swashplate 46. The valve member 106 has kidney ported ducts 111, 112 respectively connecting the pump cylinders with the outer and inner passages 44, 43. The pump and motor cylinder ports are arcuate and of a length equal to the distance between the corresponding kidney ports in the valve members to avoid hydraulic lock or fluid leakage. The pump swashplate is trunnioned by journal bearings 54 in a backing plate 57 which is circumferentially adjustable, through normally covered holes 58<SP>1</SP>, on the input shaft 23 for correct phase relationship with the valve member 106. The tilt adjusting means for the pump swashplate comprises an annular channel 62 helically guided in the casing by four radial lugs 64 and engaging follower rollers on an ear portion of the swashplate. The channel 62 is helically moved to tilt the swashplate through a linkage connected to a fifth radial lug of the channel. The motor swashplate 46 is trunnioned by journal bearings 47 in a casing 17 and has an extending shaft 52 by which it is tilt adjusted. The pump and motor swashplates are independently controlled as by double-acting, lockable hydraulic servomotors. The controls for each swashplate should be allowed to float in neutral so that the respective plates may coact to find their true neutral positions. Replenishment of fluid leaking from the circuit is through one-way valves 140, 142 and ducts 137, 138 in the valve member 20 communicating with the ducts 104, 105. Each of the pump and motor pistons has an axial duct 36 allowing fluid pressure into a cuplike chamber formed in the face of its usual thrust shoe to assume a portion of the piston thrust. The thrust loads on the swashplates 46, 53 are taken by the cylinder block 30 respectively through the journal bearings 47, the casing 17 and the valve member 20, and the journal bearings 54, the shaft 23 and the valve member 106. The space 135 between the valve member 106 and the blanked-off hollow output shaft 27 is pressurized through a valve having small and large pistons 116, 117. The small piston is acted on by pressure in a duct 130 communicating with the ducts 111, 112 in the valve member 106 through a diametral bore 131 and a circumferential groove 129 in the input shaft, and ducts 124, 127 in the member 106. One-way ball-type valves 125, 128 act to maintain the duct 130 at high pressure. The pressure on the piston 116 urges the piston 117 rightwardly to pressurize the space 135. To replenish liquid lost through leakage rightward movement of the piston 116 uncovers a port 136 to pass pressure fluid into the space 135, the pressure acting on the large piston 117 to throttle the port 136. In operation, with the swashplates 53, 46 respectively in the perpendicular and extreme clockwise positions, the output shaft is stationary. By tilting the thrust plate 53 clockwise a reduced foward drive is obtained. With the swashplate 53 in the extreme clockwise position the swashplate 46 is tilted anticlockwise to increase output speed until its perpendicular position is reached for hydraulic lock 1/1 ratio drive. By continuing anticlockwise tilting of the switchplate 46 a forward overdrive is obtained. For reverse, again starting from the perpendicular and extreme clockwise positions of the swashplates 53, 46 respectively, the swashplate 53 is tilted anticlockwise for reduced reverse to a 1/1 reverse ratio. Reverse overdrive is obtained by tilting the swashplate 46 towards the perpendicular position.