Martin Marietta Corporation

General Dynamics Land Systems, Inc.

Other

General Dynamics Defense Systems, Inc.

Berkshire Powertech, Inc.

Robert Francis Larkin

Lawrence R Folsom

William R Kerr

Donald Mark Purcell

An infinitely variable hydromechanical crossdrive steering transmission having a multiple of forward and reverse ratio ranges and a separately selectable low ratio range in both forward and reverse. The forward and reverse ratio ranges are enabled to shift between ratio ranges in a synchronous manner in both speed and torque, thus smoothly propelling the vehicle from rest through the multiple transmission ranges to maximum speed in a stepless manner.

Steering transmission for tracked vehicles

To control transmission ratio of a continuously variable hydrostatic transmission including an input shaft, an output shaft, a hydraulic pump unit driven by the input shaft, a grounded hydraulic motor unit, and a wedge-shaped swashplate drivingly, pivotally connected to the output shaft and positioned to accommodate pumped hydraulic fluid exchanges between the pump and motor units. A ratio controller is provided having a pair of hydraulically actuated, differentially sized pistons coupled by a linkage mechanism to pivot the swashplate in opposite transmission ratio-changing directions. The smaller piston is incorporated internally of the output shaft, while the larger piston, of an annular shape, coaxially surrounds the output shaft. The linkage mechanism has geometry effective to translate axial forces exerted by the pistons into amplified ratio-changing moments exerted on the swashplate. The ratio controller also includes a control valve selectively positioned to change the hydraulic fluid pressure acting on the larger piston, such as to set a transmission ratio and also to determine the ratio-changing direction of swashplate pivotal motion.

Continuously variable hydrostatic transmission ratio controller capable

In a multi-range, continuously variable transmission, input engine power is split between a belt-type, continuously variable transmission unit and a system of interconnected planetary gears. This gear system then combines the split power received from the engine and the transmission unit output to produce a transmission output for propelling a vehicle in multiple forward ranges and one reverse range, each range of continuously variable speed produced by stroking the transmission unit. Synchronous shifting between ranges is achieved by selectively clutching or braking elements of the planetary gear sets at appropriate stroke settings of the transmission unit, such that the vehicle may be smoothly accelerated from rest to maximum speed.

Multi-range, belt-type, continuously variable transmission

A multi-range, synchronous shifting, hydromechanical transmission according to the present invention is suitable for application in an automotive drivetrain including a high speed engine. The transmission receives split power inputs from the engine; one input being geared down to a suitable lower speed for driving a continuously variable hydrostatic transmission unit, while the other input drives a counter shaft from which mechanical outputs are take at different speed ratios. A planetary gear set, driven by the hydrostatic transmission unit output, is shiftable to provide either a narrow continuously variable speed hydrostatic output, range suitable for transmission operation in low output ranges or a wide continuously variable speed hydrostatic output range suitable for transmission operation in high output ranges. A gear system includes a plurality of gears selectively conditioned by plural clutches and brakes to combine the hydrostatic outputs from the planetary gear set and the mechanical outputs from the counter shaft, such as to produce vehicle propulsion transmission outputs in any one of four continuously variable speed forward ranges and one continuously variable speed reverse range.

Multi-range, hydromechanical transmission for application in high

A hydromechanical transmission receives split power inputs from a vehicle engine, one split input driving a hydrostatic power unit and the other split input driving a mechanical power input. The infinitely variable hydrostatic power output is combined in the mechanical power unit with multiple ratios of its split input power to achieve multiple ratios of hydromechanical output power for smoothly propelling a vehicle from rest through multiple transmission ranges to maximum speed, with synchronous shifting between ranges. The hydromechanical transmission is particularly applicable to off-road vehicles, such as agricultural tractors.

Multi-range with infinitely variable ratio in each range,

A hydromechanical transmission receives split power inputs from a vehicle engine, one split input driving a hydrostatic power unit and the other split input driving a mechanical power input. The infinitely variable hydrostatic power output is combined in the mechanical power unit with multiple ratios of its split input power to achieve multiple ratios of hydromechanical output power for smoothly propelling a vehicle from rest through multiple transmission ranges to maximum speed, with synchronous shifting between ranges.

Multi-range, hydromechanical transmission for motor vehicles

A continuously variable hydrostatic transmission includes axially aligned input and output shafts journaled by a transmission housing and respectively coupled to a prime mover and a load. The input shaft drives a hydraulic pump unit, while a hydraulic motor unit is grounded to the transmission housing. A wedge-shaped swashplate is pivotally connected to the output shaft in operative position to accommodate pressurized hydraulic fluid exchanges between the pump and motor units. A controller is coupled to adjust the angular orientation of the swashplate relative to the output shaft axis and thus set the transmission ratio. A hydraulic circuit, connected into the hydraulic motor unit, is selectively operable to vent high and low fluid pressure sides of the swashplate to atmosphere, thus imposing a neutral transmission ratio condition regardless of the transmission ratio set by the controller.

Continuously variable hydrostatic transmission with neutral-setting

A double-acting hydraulic cylinder is controlled by a pair of three-way solenoid valves respectively fluid connected to the two ends of the cylinder and energized in parallel with a continuous stream of pulse width modulated (PWM) pulses to create a mean effective fluid pressure balance at the cylinder ends that hold a desired position of a connected load and mean effective fluid pressure imbalances in the cylinder ends that produce variable rate load movement in either of two directions to a desired new position, all determined by the pulse duty cycle.

Positioning apparatus and method utilizing PWM control of a

A controller for changing the ratio of a continuously variable hydrostatic transmission, as determined by the angular position of a swashplate, including an actuator having a cylinder slidingly receiving a piston to define a pair of chambers. A pair of solenoid valves, each configured to connect a respective chamber selectively to sump pump pressure or atmospheric pressure, are energized with a stream of pulses to create differential fluid pressures in the chambers, thereby producing movement of the piston; the piston movement being linked to the swashplate to produce a corresponding adjustment of the swashplate angular position. The rate of change of the swashplate angular position is controlled by pulse width modulating the pulse stream.

Continuously variable hydrostatic transmission including a pulse width

A hydrostatic transmission includes wedge-shaped swashplate operatively positioned between a hydraulic pump unit driven by an input shaft and a grounded hydraulic motor unit to accommodate pumped exchanges of hydraulic fluid between the units. The swashplate, drivingly coupled to an output shaft, is angularly adjustable about a pivot axis oriented in intersecting, orthogonal relation to the output shaft axis to infinitely variable transmission ratios. Pilot bearings, mounted by the swashplate, support cylinder blocks of the hydraulic pump and motor units for nutating motions centered on the swashplate pivot axis to minimize the resultant moment on the swashplate. Piston rods in the hydraulic pump and motor units are oriented in outwardly flared, acute angles to the output shaft axis to expand the range of permissible angular adjustment of the swashplate by a ratio controller.

Continuously variable hydrostatic transmission having swashplate-mounted

To control the transmission ratio of a continuously variable hydrostatic transmission including an input shaft, an output shaft, an pump unit driven by the input shaft, a grounded motor unit, and an a wedge-shaped swashplate drivingly and pivotally connected to the output shaft in hydraulic fluid-communicating position between the pump and motor units, a ratio controller is provided having a hydraulically actuated piston incorporated internally of the output shaft. A pilot valve, also incorporated internally of the output shaft, operates to create differential fluid pressures at opposite end faces of the piston, forcing axial motion of the piston and ratio-changing pivotal movement of the swashplate linked to the piston.

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Pittsfield, MA, United States of America

Robert Francis Larkin