Power Steering Dual Pump Fluid Switching
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Solution Overview
Problem
Conventional power steering apparatuses cannot effectively utilize both the main and subsidiary pumps concurrently, limiting the effective use of the subsidiary pump and resulting in inefficiencies and increased drive loss when one pump malfunctions.
Innovation Solution
A power steering apparatus with a control valve and return passage changeover valve system that allows selective use of either pump, enabling concurrent fluid supply and reducing pump capacity and drive loss by isolating the malfunctioning pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the subsidiary pump is used only as a backup when the main pump malfunctions, then the system reliability is improved, but the effective use of the subsidiary pump is insufficient and drive loss increases
Solution Approach 1:
The patent implements dynamic switching between the main pump and subsidiary pump based on real-time operating conditions. The switching valve dynamically redirects fluid flow to enable the subsidiary pump to contribute during normal operation, transforming the static backup configuration into a dynamic load-sharing system that reduces energy loss while maintaining reliability.
Solution Approach 2:
The subsidiary pump is designed to serve dual functions: it acts as a backup when the main pump malfunctions and simultaneously operates as a load-sharing pump during normal conditions. This multi-functionality is achieved through the switching valve that can direct fluid flow from either pump to the power cylinder, maximizing the utilization of both pumps and reducing overall drive loss.
2Loss of energy
If both pumps are used concurrently, then the drive loss is reduced and pumps can be downsized, but the device complexity increases due to additional valves and passages
Solution Approach 1:
The patent segments the fluid passage system into distinct pathways with a switching valve that can direct flow from either the main pump or subsidiary pump to the power cylinder. This segmentation allows independent control of each pump's contribution while maintaining a relatively simple overall structure, enabling concurrent operation without excessive complexity.
Solution Approach 2:
The switching valve serves as an intermediary component that manages the complex fluid distribution between two pumps and the power cylinder. By introducing this single mediating device, the system achieves concurrent pump operation and flexible flow management without requiring multiple complex valves or passages, thus minimizing the increase in device complexity.
3Ease of manufacture
If the subsidiary pump is downsized to reduce cost, then the manufacturing cost is reduced, but the pump capacity is insufficient when operating alone
Solution Approach 1:
The patent merges the output capacities of both the main pump and subsidiary pump to meet the total steering assist requirement. The switching valve enables fluid from both pumps to be combined and directed to the power cylinder simultaneously, allowing each pump to be downsized while their combined capacity maintains sufficient power output, thus reducing manufacturing cost without sacrificing performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous steering assist by switching to the operational pump, reducing drive loss and allowing for downsized pumps, while ensuring effective fluid management and reduced costs.
Implementation Method 1
a first check valve disposed between the first pump and the return passage changeover valve, the first check valve being operated to allow only a flow of the working fluid flowing from a side of the first pump toward a side of the return passage changeover valve
Implementation Method 2
a second check valve disposed between the second pump and the return passage changeover valve, the second check valve being operated to allow only a flow of the working fluid flowing from the side of the second pump toward a side of the return passage changeover valve
Implementation Method 3
the return passage changeover valve including a valve element accommodating bore and a valve element disposed within the valve element accommodating bore so as to be moveable along an axial direction of the valve element accommodating bore
Implementation Method 4
a first pump that is rotationally driven to supply the working fluid to the power cylinder by a first drive source
Implementation Method 5
a second pump that is rotationally driven to supply the working fluid to the power cylinder by a second drive source provided separately from the first drive source
Implementation Method 6
a power cylinder with a pair of pressure chambers which applies a steering force to the steerable road wheel on the basis of a differential pressure between a pressure of a working fluid in one of the pair of pressure chambers and a pressure of the working fluid in the other thereof
Data Source
AI summary
A power steering apparatus including a power cylinder, first and second pumps, a control valve serving for selectively supplying a working fluid supplied from the first or second pump to one of a pair of pressure chambers of the power cylinder in accordance with a steering operation, first and second reservoir tanks, and a return passage changeover valve disposed between the control valve and the first and second pumps, the return passage changeover valve serving for communicating the first and second pumps with the control valve regardless of an axial position of a valve element and communicating one of the first and second reservoir tanks with the control valve in accordance with the axial position of the valve element to thereby carry out changeover between circulating fluid passages for circulating the working fluid to the first reservoir tank and the second reservoir tank.