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US 5,493,862 AGranted
Continuously variable hydrostatic transmission
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 is pivotally linked to the swashplate to selectively adjust the swashplate angle relative to the output shaft axis and thereby change transmission ratio.
Claims20
A continuously variable hydrostatic transmission comprising:
- a housing;
- an input shaft journaled in the housing for receiving input torque from a prime mover;
- an output shaft journaled in the housing for imparting output torque to a load and having an axis;
- a pump unit coupled to the input shaft;
- a motor unit grounded to the housing;
- a swashplate including an input face confronting the pump unit, an output face confronting the motor unit and oriented at an acute angle relative to the input face, and a plurality of circumferentially spaced ports extending between the input and output faces;
- a coupling drivingly connected to the output shaft and pivotally connected to the swashplate to accommodate both torque transfer between the swashplate and the output shaft and angular orientational adjustment of the swashplate relative to the output shaft axis;
- a controller coupled to selectively angularly adjust the swashplate angular orientation to a desired transmission drive ratio between the input and output shafts;
- and
- an axially extending passage in one of the input and output shafts for introducing hydraulic fluid to the pump unit, when driven by the input shaft, the pump unit pumps hydraulic fluid to the motor unit through the swashplate ports, causing torque to be exerted on the swashplate to drive the output shaft.
7 more elements
A continuously variable hydrostatic transmission comprising:
- a housing;
- an input shaft journaled in the housing for receiving input torque from a prime mover;
- an output shaft journaled in the housing for imparting output torque to a load and having an axis;
- a hydraulic pump unit coupled to the input shaft;
- a wedge-shaped swashplate including ports accommodating hydraulic fluid transfer between the hydraulic pump unit and the hydraulic motor unit;
- a coupling drivingly connected to the output shaft and pivotally connected to the swashplate to accommodate torque transfer between the swashplate and the output shaft and angular movement of the swashplate about a first transverse pivot axis in orthogonal, intersecting relation with the output shaft axis;
- and
- a transmission ratio controller including 1) an actuating member mounted for sliding axial motion on the output shaft, 2) a control sleeve closely surrounding the output shaft and having a first axial end connected to the actuating member and a second axial end, 3) a radially extending tang having an inner end connected to the second axial end of the sleeve, and 4) a pin interconnecting the swashplate and the tang at a second transverse pivot axis parallel to and radially spaced from the first traverse pivot axis, such that axial motion of the actuating member is converted to transmission ratio-changing pivotal motion of the swashplate about the first transverse pivot axis.
5 more elements
A hydraulic machine comprising:
- a housing;
- an input shaft journaled in the housing;
- a hydraulic pump unit driven by the input shaft, the pump unit including a cylinder and a piston for pressurizing hydraulic fluid in the cylinder;
- and
- a hydrostatic thrust bearing including:
- a first bearing member mounted by the housing and having a first bearing surface,
- a second bearing member mounted by a moving part of the pump unit and having a second bearing surface in sliding contact with the first bearing surface at an interface,
- at least one cavity formed in one of the first and second bearing surfaces at the interface, and
- an opening into the cavity in fluid flow communication with the cylinder through which hydraulic fluid flows to fill the cavity and through which the hydraulic fluid in the cavity is pressurized from the pressurized hydraulic fluid in the cylinder to generate thrust forces proportional to a surface area of the cavity in opposition to thrust loadings generated by the machine.
6 more elements
A hydraulic machine comprising:
- a housing;
- an input shaft journaled in the housing for receiving input torque from a prime mover;
- an output shaft journaled in the housing for imparting torque to a load;
- a hydraulic pump unit coupled to the input shaft;
- a hydraulic motor unit grounded to the housing;
- a wedge-shaped swashplate drivingly coupled to the output shaft and including ports extending between an input face confronting the pump unit and an output face confronting the motor unit;
- a controller linked to the swashplate for adjusting the angular orientation of the swashplate relative to an axis of the output shaft;
- a valve having an energy storing position and an energy recovery position;
- and
- a hydraulic fluid accumulator in hydraulic fluid flow communication with the pump and motor units through the valve for storing hydraulic energy during propulsion of the pump unit by the prime mover while the valve is in the energy storing position and for recovering hydraulic energy back to the pump and motor units while the valve is in the energy recovery position to drive one of the input shaft, the output shaft, and both the input and output shafts, depending upon swashplate angular orientation.
7 more elements
Dependencies are inferred from the claim text.