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US 5,486,142 AGranted
Hydrostatic transmission including a simplified ratio controller
AssigneeMartin Marietta Corporation
InventorLawrence R. Folsom
Life of this patent
Estimating the term…
Abstract
A continuously variable hydrostatic transmission includes an input shaft connected to drive a hydraulic pump unit, a grounded hydraulic motor unit, and an output shaft. A wedge-shaped swashplate is pivotally mounted to the output shaft in driving connection to receive output torque resulting from the exchange of pressurized hydraulic fluid between the pump and motor units through specially configured ports in the swashplate. A hydraulically actuated ratio controller shifts the axial positions of spherical bearings mounting a pump cylinder block in the hydraulic pump unit and a motor cylinder block in the hydraulic motor unit to adjust the swashplate angle relative to the output shaft axis and thereby change transmission ratio.
Claims20
A continuously variable hydrostatic transmission comprising, in combination:
- a housing;
- an input shaft journaled in the housing to receive torque from a prime mover;
- a pump unit including a first carrier driven by the input shaft and mounting an annular array of pump pistons, and a first cylinder block providing an annular array of pump cylinders for respectively receiving the pump pistons;
- a motor unit including a second carrier fixed to the housing and mounting an annular array of motor pistons, and a second cylinder block providing an annular array of motor cylinders for respectively receiving the motor pistons;
- an output shaft journaled in the housing and adapted for driving connection to a load;
- an annular swashplate surrounding the output shaft and having an input face and an output face arranged at an acute angle relative to each other, the input face confronting the first cylinder block and the output face confronting the second cylinder block, the swashplate further including slots accommodating pumped fluid flow between the pump cylinders and the motor cylinders through openings in the first and second cylinder blocks;
- a connector pivotally coupling the swashplate to the output shaft in torque-coupled relation;
- and
- a ratio controller selectively exerting coordinated axial forces on the first and second cylinder blocks to adjustably set an angle of the swashplate relative to an axis of the output shaft according to a desired speed ratio between the input and output shafts.
6 more elements
A continuously variable hydrostatic transmission comprising, in combination:
- a housing;
- an input shaft journaled in the housing to receive torque from a prime mover;
- a pump unit including a first carrier, driven by the input shaft and mounting an annular array of pump pistons, and a first cylinder black providing an annular array of pump cylinders for respectively receiving the pump pistons;
- a motor unit including a second carrier, fixed to the housing and mounting an annular array of motor pistons, and a second cylinder block providing an annular array of motor cylinders for respectively receiving the motor pistons;
- an output shaft journaled in the housing and adapted for driving connection to a load;
- an annular swashplate surrounding the output shaft and having an input face and an output face arranged at an acute angle relative to each other, the input face confronting the first cylinder block and the output face confronting the second cylinder block, the swashplate further including slots accommodating pumped fluid flow between the pump cylinders and the motor cylinders through openings in the first and second cylinder blocks;
- a connector pivotally coupling the swashplate to the output shaft in torque-coupled relation;
- a ratio controller for adjustably setting an angle of the swashplate relative to an axis of the output shaft according to a desired speed ratio between the input and output shafts;
- and
- an annular manifold block and an annular portplate positioned in juxtaposed relation between radial flange portions of the second carrier and the output shaft, the manifold block fixed to the housing, and the portplate fixed to the output shaft and including first and second ports, the manifold block including:
- axial through-holes in respective fluid communication with the motor cylinders through holes in posts mounting the pump pistons and the first and second portplate slots;
- a first annular cavity in fluid communication with the first portplate slot and those of the motor cylinders in a low pressure side of the motor unit;
- and
- a second annular cavity in fluid communication with the second portplate slot and those of the motor cylinders in a high pressure side of the motor unit,
- at least one of the first and second cavities connected in a hydraulic fluid circuit with the ratio controller.
12 more elements
A continuously variable hydrostatic transmission comprising, in combination:
- a housing;
- an input shaft journaled in the housing to receive torque from a prime mover;
- a pump unit including a first carrier, driven by the input shaft and mounting an annular array of pump pistons, and a first cylinder black providing an annular array of pump cylinders for respectively receiving the pump pistons;
- a motor unit including a second carrier, fixed to the housing and mounting an annular array of motor pistons, and a second cylinder block providing an annular array of motor cylinders for respectively receiving the motor pistons;
- an output shaft journaled in the housing and adapted for driving connection to a load;
- an annular swashplate surrounding the output shaft and having an input face and an output face arranged at an acute angle relative to each other, the input face confronting the first cylinder block and the output face confronting the second cylinder block, the swashplate further including slots accommodating pumped fluid flow between the pump cylinders and the motor cylinders through openings in the first and second cylinder blocks;
- a connector pivotally coupling the swashplate to the output shaft in torque-coupled relation, the connector including a hub fixed on the output shaft and an arm extending radially from the hub and having a free end pivotally connected to the swashplate at a pivot axis oriented transversely to the output shaft, the pivot axis being radially offset from the output shaft axis by a distance substantially equal to a circle radius conforming to positions of the annular arrays of pump and motor cylinders;
- and
- a ratio controller for pivoting the swashplate about the pivot axis to adjustably set an angle of the swashplate relative to an axis of the output shaft according to a desired speed ratio between the input and output shafts.
6 more elements
Dependencies are inferred from the claim text.