Hydraulic power steering system
AssigneeVolvo Truck Corporation
InventorGabriel Trönnberg
Life of this patent
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Abstract
A hydraulic power steering system comprising: a first hydraulic pump driven by a rotation of the driving wheels of a vehicle such that a first hydraulic pressure is generated; a second hydraulic pump arranged such that a second hydraulic pressure is generated; a clutch arrangement switchable between an engaged state in which the clutch arrangement is arranged to transmit power from the engine to drive the second hydraulic pump, and a disengaged state in which the clutch arrangement is arranged to disengage power transmission from the engine to the second hydraulic pump; and a hydraulic power steering arrangement to be connected to a steering system of the vehicle to amplify steering input exerted by a driver by applying a hydraulic pressure provided by the first and/or second hydraulic pressure.
Claims13
A hydraulic power steering system for a vehicle having an engine for propelling the vehicle and a transmission output shaft for carrying power generated by the engine to drive driving wheels of the vehicle, the system comprising:
- a first hydraulic pump arranged to be mechanically driven by the transmission output shaft such that the first hydraulic pump is driven by a rotation of the driving wheels when the vehicle is in motion such that a first hydraulic pressure is generated;
- a second hydraulic pump arranged to be mechanically driven by power provided by the engine such that a second hydraulic pressure is generated;
- a clutch arrangement for mechanically connecting the second hydraulic pump with the engine, the clutch arrangement being switchable between an engaged state in which the clutch arrangement is arranged to transmit power from the engine to drive the second hydraulic pump, and a disengaged state in which the clutch arrangement is arranged to disengage power transmission from the engine to the second hydraulic pump, wherein the clutch arrangement is in the disengaged state, and wherein the hydraulic pressure is solely caused by the first hydraulic pressure generated by the first hydraulic pump when the vehicle is in motion while the engine is turned off;
- and
- a hydraulic power steering arrangement in fluid connection with the first and the second hydraulic pumps;
- wherein the hydraulic power steering arrangement is arranged to be connected to a steering system of the vehicle to amplify steering input exerted by a driver of the vehicle to a steering wheel of the steering system by applying a hydraulic pressure provided by the first and/or second hydraulic pressure to the hydraulic power steering arrangement.
A method for operating a hydraulic power steering system of a vehicle, the vehicle having an engine for propelling the vehicle and a transmission output shaft for carrying power generated by the engine to drive driving wheels of the vehicle, the method comprising;
- generating a first hydraulic pressure by driving, when the vehicle is in motion, a first hydraulic pump, the first hydraulic pump being arranged to be mechanically driven by the transmission output shaft such that the first hydraulic pump is driven by a rotation of the driving wheels;
- generating a second hydraulic pressure by driving a second hydraulic pump, the second hydraulic pump being mechanically driven by power provided by the engine;
- and
- amplifying steering input exerted to a steering wheel of the vehicle by a driver of the vehicle, by applying a hydraulic pressure caused by the first and/or second hydraulic pressure to a hydraulic power steering arrangement, the hydraulic power steering arrangement being in fluid connection with the first and the second hydraulic pumps;
- wherein the hydraulic power steering system further comprises a clutch arrangement for mechanically connecting the second hydraulic pump with the engine, wherein the clutch arrangement is switchable between an engaged state in which the clutch arrangement is arranged to transmit power from the engine to drive the second hydraulic pump, and a disengaged state in which the clutch arrangement is arranged to disengage power transmission from the engine to the second hydraulic pump;
- wherein the method further comprises:
- switching the clutch arrangement between the engaged state and the disengaged state;
- and switching, when the vehicle is in motion, and the engine is turned off, the clutch arrangement to the disengaged state such that the hydraulic pressure is solely caused by the first hydraulic pressure generated by the first hydraulic pump.
Dependencies are inferred from the claim text.