Hydraulic Valve Bleeding via Spool Positioning
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Solution Overview
Problem
Selective control valves in vehicle hydraulic systems face damage from thermal expansion of trapped oil, and existing solutions like physical relief valves are costly and introduce leakage and hysteresis issues.
Innovation Solution
A vehicle hydraulic system that automatically bleeds selective control valves by using a valve control unit to generate bleed commands based on vehicle speed and hydraulic reservoir temperature, moving the main spool to specific positions to release trapped pressure without the need for physical relief valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a physical relief valve is provided to protect valves from thermal expansion damage, then valve protection is improved, but cost increases and leakage rate increases
Solution Approach 1:
The patent extracts the harmful trapped oil from the system by providing an escape passage that allows oil to be bled from the outlet port back to the inlet port, eliminating the need for a physical relief valve while preventing thermal expansion damage
Solution Approach 2:
The escape passage acts as an intermediary pathway that mediates between the trapped oil and the hydraulic reservoir, providing a controlled release mechanism that avoids the leakage and cost issues of traditional relief valves
2Reliability
If a physical relief valve is provided to protect valves from thermal expansion damage, then valve protection is improved, but device complexity and cost increase
Solution Approach 1:
The escape passage is merged with the existing valve body structure, integrating the protection function into the directional control valve itself rather than adding a separate physical relief valve component
Solution Approach 2:
The escape passage serves multiple functions: it protects against thermal expansion damage, provides a bleeding mechanism for trapped oil, and maintains system pressure control, eliminating the need for dedicated relief valve components
3Reliability
If a physical relief valve is provided to protect valves from thermal expansion damage, then valve protection is improved, but hysteresis is introduced resulting in undesirable operating points
Solution Approach 1:
The patent replaces the mechanical relief valve system with an electronic control system that uses a sensor to detect pressure and a controller to actuate the spool, eliminating mechanical hysteresis and providing precise control of the bleeding process
Solution Approach 2:
The system incorporates feedback through pressure sensors that monitor the hydraulic pressure and provide signals to the controller, which adjusts the spool position to maintain precise pressure control without the hysteresis characteristic of mechanical relief valves
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
Prevents valve damage from thermal expansion by automatically releasing pressure, reducing leakage, and eliminating hysteresis, while being cost-effective and reliable, as the system only bleeds pressure when necessary, ensuring efficient operation without physical relief valves.
Implementation Method 1
thermal expansion of the oil can create pressures that can damage the valves
Data Source
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AI summary
A system (10) for bleeding a valve in a vehicle hydraulic system including a hydraulic directional control valve (12), in particular a selective control valve, a main spool (18) for controlling communication between a pump (32), a hydraulic reservoir (28) and first and second work ports (48, 50). The main spool (18) is movable from a neutral position to an extend position and to a retract position. The main spool (18) is also movable to respective first and second bleed positions wherein the respective work port (48, 50) is communicated with the hydraulic reservoir (28) before the other work port (50, 48) is communicated with the pump (32).