Dual-Pump Hydraulic Steering for Engine-Off Assist
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Solution Overview
Problem
Existing hydraulic power steering systems face challenges in providing fail-safe and energy-efficient steering assistance, especially when the engine is turned off, leading to potential safety risks and increased energy consumption.
Innovation Solution
A hydraulic power steering system with a clutch arrangement that switches between two hydraulic pumps, one driven by the transmission output shaft and the other by the engine, allowing for efficient power steering assistance in various scenarios, including when the engine is off, using a bi-stable clutch and engine control system for optimal energy management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two hydraulic pumps are used continuously to ensure steering assistance when the engine is off, then steering reliability is improved, but energy consumption increases
Solution Approach 1:
The system dynamically switches between two hydraulic pump configurations based on operating conditions: (1) Engine-driven pump when engine is running, and (2) Transmission-driven pump when engine is off. This dynamic reconfiguration ensures continuous steering assistance while minimizing energy consumption by using the available power source in each state.
Solution Approach 2:
The system uses the transmission output shaft's rotational energy (which would otherwise be wasted during coasting or downhill driving) to drive the hydraulic pump and provide steering assistance. This self-service approach converts available kinetic energy into useful hydraulic power without requiring additional fuel consumption.
2Use of energy by moving object
If the engine is turned off to improve fuel efficiency, then energy efficiency is improved, but steering assistance reliability deteriorates
Solution Approach 1:
The transmission output shaft serves as an intermediary power source that transfers rotational energy from the driving wheels to the hydraulic pump when the engine is off. This intermediary mechanism enables steering assistance without requiring the main engine to be running, thus maintaining fuel efficiency while ensuring reliability.
3Device complexity
If a single hydraulic pump driven by the engine is used, then device complexity is reduced, but steering assistance reliability when engine is off deteriorates
Solution Approach 1:
The hydraulic pump is designed with multi-functionality to be driven by two different power sources: the engine (via clutch arrangement) and the transmission output shaft. This universal design allows the same pump to provide steering assistance in both engine-on and engine-off conditions, maintaining reliability without requiring two separate pump systems.
Data Source
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AI summary
A hydraulic power steering system comprising: as first hydraulic pump (112) driven by a rotation of the driving wheels (110) of a vehicle such that a first hydraulic pressure (114) is generated; a second hydraulic pump (116) arranged such that a second hydraulic pressure (118) is generated; a clutch arrangement (120) switchable between an engaged state (122) in which the clutch arrangement (120) is arranged to transmit power from the engine (104) to drive the second hydraulic pump (116), and a disengaged state (124) in which the clutch arrangement (120) is arranged to disengage power transmission from the engine (104) to the second hydraulic pump (116); and a hydraulic power steering arrangement (126) to be connected to a steering system (129) of the vehicle (102) to amplify steering input exerted by a driver by applying a hydraulic pressure provided by the first and/or second hydraulic pressure (114, 118).