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A hybrid hydraulic drive system for a vehicle comprises a prime mover, a transmission connecting the prime mover to drive wheels, a fluid energy storage accumulator, and a reversible hydraulic machine in fluid communication with the energy storage accumulator and drivingly coupled to the prime mover

A hybrid hydraulic drive system for a vehicle comprises a prime mover, a transmission connecting the prime mover to drive wheels, a fluid energy storage accumulator, and a reversible hydraulic machine in fluid communication with the energy storage accumulator and drivingly coupled to the prime mover upstream of the transmission. The hybrid hydraulic drive system is arranged such that in a retarding mode the reversible hydraulic machine retards the drive wheels of the vehicle by pumping fluid into the accumulator. In a driving mode the reversible hydraulic machine supplies a supplementary power to the drive wheels of the vehicle using the pressurized fluid from the accumulator to assist propulsion of the vehicle. In a neutral mode the reversible hydraulic machine is disconnected from the prime mover to render the reversible hydraulic machine substantially inoperative to exert any significant driving or retarding influence on the drive wheels.

대표청구항 ▼

What is claimed is: 1. A hybrid hydraulic drive system for a motor vehicle, said system operable in three modes of operation including a driving mode, a retarding mode and a neutral mode, said system comprising: a prime mover and a transmission connecting said prime mover to drive wheels; at least

What is claimed is: 1. A hybrid hydraulic drive system for a motor vehicle, said system operable in three modes of operation including a driving mode, a retarding mode and a neutral mode, said system comprising: a prime mover and a transmission connecting said prime mover to drive wheels; at least one fluid energy storage accumulator operable to store and release a pressurized fluid: a reversible hydraulic machine operatively coupled to an output shaft of said prime mover upstream of the transmission, said reversible hydraulic machine being in fluid communication with said at least one energy storage accumulator; and said hybrid hydraulic drive system being arranged such that in said retarding mode said reversible hydraulic machine retards the drive wheels of the vehicle by pumping fluid into said at least one energy storage accumulator, in said driving mode said reversible hydraulic machine supplies a supplementary power to the drive wheels of the vehicle using said pressurized fluid from said at least one energy storage accumulator to assist propulsion of said vehicle, and in said neutral mode said reversible hydraulic machine is disconnected from said prime mover to render said reversible hydraulic machine substantially inoperative to exert any significant driving or retarding influence on said drive wheels; said hybrid hydraulic drive system thereby in use being adapted to supply said supplementary regenerative power and retardation to said drive wheels substantially independently of said prime mover. 2. The hybrid hydraulic drive system as defined in claim 1, further comprising a coupling device for coupling said reversible hydraulic machine to said prime mover. 3. The hybrid hydraulic drive system as defined in claim 2, wherein said coupling device includes a clutch assembly provided for selectively coupling said reversible hydraulic machine to said prime mover. 4. The hybrid hydraulic drive system as defined in claim 3, wherein in said neutral mode said clutch assembly of said coupling device disconnects said reversible hydraulic machine from said prime mover. 5. The hybrid hydraulic drive system as defined in claim 3, wherein said clutch assembly is a friction clutch assembly. 6. The hybrid hydraulic drive system as defined in claim 1, further comprising a hydraulic fluid reservoir provided for storing an appropriate amount of hydraulic fluid, said hydraulic fluid reservoir is in fluid communication with an inlet of said reversible hydraulic machine. 7. The hybrid hydraulic drive system as defined in claim 1, wherein said at least one fluid energy storage accumulator is a hydro-pneumatic accumulator. 8. The hybrid hydraulic drive system as defined in claim 1, wherein said at least one fluid energy storage accumulator includes a plurality of fluid energy storage accumulators. 9. The hybrid hydraulic drive system as defined in claim 1, wherein said reversible hydraulic machine is operatively coupled to said output shaft of said prime mover at a rear end thereof. 10. The hybrid hydraulic drive system as defined in claim 1, wherein said reversible hydraulic machine is operatively coupled to said output shaft of said prime mover at a front end thereof. 11. The hybrid hydraulic drive system as defined in claim 1, further comprising a torque converter disposed between said prime mover and said transmission, said torque converter includes a turbine drivingly connected .to said output shaft of said prime mover, wherein said reversible hydraulic machine is operatively coupled to said turbine of said torque converter. 12. The hybrid hydraulic drive system as defined in claim 6, further comprising a particulate filter for filtering said hydraulic fluid. 13. The hybrid hydraulic drive system as defined in claim 6, further comprising a heat exchanger for cooling said hydraulic fluid. 14. The hybrid hydraulic drive system as defined in claim 13, further including a cooling fan associated with said heat exchanger for forced cooling of said hydraulic fluid flowing through said heat exchanger. 15. The hybrid hydraulic drive system as defined in claim 14, wherein said cooling fan is driven by a hydraulic motor. 16. The hybrid hydraulic drive system as defined in claim 14, wherein said cooling fan is driven by an electric motor. 17. The hybrid hydraulic drive system as defined in claim 1, wherein said reversible hydraulic machine is a reversible hydraulic pump/motor unit capable to function both as a hydraulic pump and a hydraulic motor. 18. The pressurized hydraulic fluid system as defined in claim 17, wherein said hydraulic pump/motor unit includes a variable-displacement axial piston hydraulic motor/pump.