Hydraulic Pump Displacement Valve With Mechanical Feedback Failsafe
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Solution Overview
Problem
Conventional electrical displacement control (EDC) mechanisms for hydraulic pumps face issues such as slow off-stroke rates, high initial current requirements, and limited valve opening during on-stroke response due to the 'fail to max' condition, which are problematic in systems with limited electrical power and require significant solenoid travel for precise displacement control.
Innovation Solution
A hydraulic pump with a mechanical feedback control mechanism using a movable displacement control member and a displacement control valve assembly that includes a control valve member and a biasing member to provide precise positioning of the control actuator, allowing for fast response and reduced current requirements, while preventing overshooting to the 'fail to max' condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrical displacement control (EDC) is used with fail to max condition, then the pump defaults to maximum displacement when power is removed, but this requires slowing down the off-stroke rate electronically and uses significant solenoid travel, resulting in slow response and high current requirements
Solution Approach 1:
The patent replaces the electrical displacement control system with a mechanical feedback control system. The control valve member is mechanically coupled to the control piston, and the biasing member provides mechanical force to position the control valve. This mechanical system eliminates the need for electronic rate slowing and reduces solenoid current requirements while maintaining reliable failsafe operation at maximum displacement.
Solution Approach 2:
The patent implements mechanical feedback control where the control valve member responds to pressure differential across it, which is generated by the control piston movement. The biasing member provides continuous mechanical feedback force to the control valve, creating a self-regulating system that maintains precise displacement control without electronic intervention and enables fast response rates.
2Reliability
If conventional EDC valve timing is configured to minimize overshooting to fail to max, then a significant percentage of solenoid plunger travel is used between metering position and fail to max, but this limits the valve opening during on-stroking and prevents fast on-stroke response
Solution Approach 1:
The patent replaces the electrical solenoid control system with a mechanical feedback control system using a control valve member and biasing member. The control valve member is mechanically coupled to the control piston and responds to pressure differential across it. This mechanical system provides precise control with adequate valve opening during on-stroking, enabling fast response rates without the overshooting problems of conventional EDC systems.
3Reliability
If conventional EDC requires high initial current to exit fail to max condition on startup, then the system can overcome the biasing force, but this is problematic during engine starting where electrical power is limited
Solution Approach 1:
The patent replaces the electrical displacement control system with a mechanical feedback control system. The biasing member provides mechanical force to position the control valve member, eliminating the need for high initial current during startup. The mechanical system requires minimal electrical power to operate, making it suitable for engine starting conditions where electrical power is limited.
4Adaptability or versatility
If conventional EDC is used, then electrical power can control displacement, but this increases device complexity and energy consumption compared to mechanical control systems
Solution Approach 1:
The patent replaces the complex electrical displacement control system with a simpler mechanical feedback control system. The control valve member, biasing member, and their mechanical coupling to the control piston create a self-regulating system that eliminates electronic control circuitry, reducing device complexity and energy consumption while maintaining adaptability through mechanical design.
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
The mechanical feedback control mechanism enables fast response times during both off-stroke and on-stroke transitions, reduces the risk of overshooting to the failsafe state, and lowers the solenoid current requirements, enhancing the efficiency and reliability of hydraulic pump operation.
Implementation Method 1
displacement control valve assembly configured to provide mechanical feedback control of positioning of the control actuator
Implementation Method 2
control valve member that is movable within a fluid flow path of the control valve assembly to control a flow of fluid to or from the control actuator
Implementation Method 3
mechanical feedback control mechanism using a movable displacement control member and a displacement control valve assembly that includes a control valve member and a biasing member to provide precise positioning of the control actuator
Data Source
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AI summary
A variable displacement hydraulic pump including a control actuator configured to interact with a movable displacement control member to control the displacement of the pump; and a displacement control valve assembly configured to provide mechanical feedback control of positioning of the control actuator and thereby the displacement control member. The displacement control valve assembly includes a control valve member that is movable within a fluid flow path of the control valve assembly to control a flow of fluid to or from the control actuator. The control valve assembly includes a first valve part, a second valve part, and a biasing member configured to selectively position respective one or more portions of the first and second valve parts relative to each other to open or close a vent flow passage in response to an operating state of the pump. When in a normal operating state of the pump, the biasing member is configured to position the first and second valve parts relative to each other such that the vent flow passage is closed, and the control valve member moves in the fluid flow path to control the flow of fluid to or from the control actuator. When in a failsafe state of the pump, the biasing member is configured to position the first and second valve parts relative to each other such that the vent flow passage is opened, thereby enabling fluid from the control actuator to escape via the vent flow passage.