Load-Reaction Switching Valve for Steering Circuit Override
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Solution Overview
Problem
In off-highway vehicles, existing steering systems face challenges in seamlessly integrating manual and automated steering circuits, particularly in ensuring smooth operation and load-reaction feedback when the electro-hydraulic steering circuit is active, which can lead to unwanted actuation of the hydrostatic steering circuit.
Innovation Solution
The introduction of a load-reaction switching valve assembly that enables or disables the load-reaction feature by selectively communicating fluid between the hydrostatic and electro-hydraulic steering circuits, allowing the hydrostatic circuit to override the electro-hydraulic circuit for manual steering corrections and providing feedback through the load-reaction feature when needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the electro-hydraulic steering circuit is active, then automated steering control is achieved, but manual steering corrections cannot override the automated circuit
Solution Approach 1:
The switching valve assembly dynamically changes its internal configuration based on the position of the first proportional valve. When the first proportional valve is in neutral position, the switching valve enables load-reaction feedback by connecting the hydrostatic circuit to the electro-hydraulic circuit. When the first proportional valve is actuated, the switching valve automatically disconnects the hydrostatic circuit, allowing pure electro-hydraulic control. This dynamic switching resolves the contradiction by automatically adapting the system behavior to the current steering state.
2Ease of operation
If the hydrostatic steering circuit is connected for manual control, then operator feedback is provided, but unwanted actuation occurs when the electro-hydraulic circuit is active
Solution Approach 1:
The load-reaction switching valve assembly acts as an intermediary device that selectively mediates between the hydrostatic steering circuit and the electro-hydraulic steering circuit. It monitors the state of the first proportional valve and automatically switches the connection state of the hydrostatic circuit accordingly. This intermediary function prevents unwanted actuation by isolating the hydrostatic circuit when the electro-hydraulic circuit is actively controlling the actuator, while still enabling load-reaction feedback when appropriate.
3Adaptability or versatility
If parallel steering circuits are used for both manual and automated control, then flexibility is improved, but integration complexity increases
Solution Approach 1:
The switching valve assembly merges the control functions of the hydrostatic and electro-hydraulic circuits into a unified system. Instead of having two completely independent parallel circuits that require complex coordination, the switching valve physically integrates them by automatically connecting or disconnecting the hydrostatic circuit based on the first proportional valve's position. This merging approach maintains the flexibility of having both manual and automated control capabilities while reducing integration complexity through automatic switching logic.
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
This solution ensures smooth operation by allowing the hydrostatic steering circuit to override the electro-hydraulic circuit for manual steering corrections and provides load-reaction feedback, enhancing the vehicle's steering precision and operator control.
Implementation Method 1
The load-reaction switching valve assembly includes a spool valve member (180) disposed within a bore (106) of the housing (100) and selectively movable between a first position and a second position. The spool valve member (180) includes a spool body (182) and a valve stem (184) extending axially from the spool body (182).
Implementation Method 2
The spool valve member (180) is selectively movable between a first position and a second position. In the first position, the spool valve member (180) allows the first control port (48) of the fluid controller (40) to be in fluid communication with the first port (26) of the actuator (24).
Data Source
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AI summary
A steering system for a vehicle includes a fluid pump, an actuator in selective fluid communication with the fluid pump, a hydrostatic steering system and an electro-hydraulic steering system. The hydrostatic steering system includes a fluid controller having a first proportional valve in fluid communication with the fluid pump and a fluid meter in fluid communication with the first proportional valve and the actuator. The electro-hydraulic steering system includes a second proportional valve in selective fluid communication with the fluid pump and the actuator. The second proportional valve is disposed in parallel to the first proportional valve. The electro-hydraulic steering circuit further includes a load-reaction switching valve assembly disposed in series with the first proportional valve of the hydrostatic steering system. The load-reaction switching valve allows fluid communication between the actuator and the fluid controller when the first proportional valve is in a neutral position.