Variable Displacement Vane Pump Fail-Safe Pilot Valve
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Solution Overview
Problem
Existing variable displacement vane pumps face limitations in fail-safe functionality, particularly when the PWM valve fails, leading to poor regulation characteristics and potential damage due to high pressure and temperature issues, and require additional costly components for specific fail-safe pressure settings.
Innovation Solution
Incorporating a pressure controlled pilot valve that moves between active and inactive positions based on output pressure, overriding the PWM valve to control pump pressure and prevent excessive pressure, thereby ensuring safe operation and reducing the risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PWM valve is used to control pump pressure, then pressure regulation is improved, but the system lacks fail-safe functionality and may suffer from high pressure and temperature issues when the valve fails
Solution Approach 1:
A pilot valve is introduced as an intermediary component that mediates between the PWM valve and the control chamber. The pilot valve receives a pilot pressure signal and modulates the control pressure accordingly, providing fail-safe functionality while maintaining the simplicity of PWM control. When the PWM valve fails, the pilot valve can independently regulate pressure through its mechanical response to pilot pressure changes.
Solution Approach 2:
The system replaces purely electrical/PWM control with a hybrid mechanism that incorporates mechanical pressure sensing and response. The pilot valve uses mechanical elements (spring, valve needle) to sense pilot pressure and automatically adjust control pressure, providing passive fail-safe protection without requiring additional electronic control systems.
2Reliability
If additional components are added to provide fail-safe pressure settings, then safety is improved, but system cost and complexity increase
Solution Approach 1:
The pilot valve serves multiple functions: it provides fail-safe pressure regulation, enables passive pressure control, and works cooperatively with the PWM valve during normal operation. This multi-functionality eliminates the need for separate fail-safe components, reducing overall system complexity while maintaining safety.
Solution Approach 2:
The fail-safe functionality is merged into the existing PWM control architecture through the pilot valve mechanism. Rather than adding independent fail-safe components, the pilot valve is integrated into the control chamber system, sharing the same fluid pathways and working in conjunction with existing pump components.
3Productivity
If the control chamber pressure is not properly regulated, then pump performance is improved, but excessive pressure and temperature damage may occur
Solution Approach 1:
The system implements feedback control where the pilot pressure (derived from outlet pressure) is fed back to the pilot valve, which then adjusts the control chamber pressure. This closed-loop feedback mechanism automatically regulates pressure, preventing excessive pressure and temperature conditions while maintaining optimal pump performance.
Solution Approach 2:
The pilot valve performs preliminary pressure regulation by modulating the control pressure before it reaches the control chamber. This preliminary action prevents excessive pressure buildup from occurring in the first place, protecting the system from pressure and temperature damage while maintaining productivity.
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 pressure controlled pilot valve effectively manages pump pressure in fail-safe conditions, preventing excessive pressure and maintaining stable operation, even in the event of PWM valve failure, while reducing costs and improving regulation range and temperature stability.
Implementation Method 1
a resilient structure biasing the control slide towards the first slide position
Implementation Method 2
controls pressure in the control chamber via fluid communication from the outlet, through the fifth channel and through the second channel to the control chamber
Implementation Method 3
allowing the electrical valve to pressurize the control chamber by delivering fluid in through the first channel and vent the control chamber via the third and fourth channels
Implementation Method 4
a rotor with at least one vane mounted in the housing and configured for rotation within and relative to the control slide, the at least one vane configured for engagement with an inside surface of the control slide during rotation thereof
Data Source
AI summary
A variable displacement vane pump has a pressure controlled valve moveable between first and at least second valve positions based on an output pressure of the pressurized lubricant delivered through the outlet. The pressure controlled valve provides an integrated fail safe function to the pump when an electrical valve fails. The pressure controlled valve is inactive in the first position for an output pressure below a threshold level, allowing an electrical valve (pulse width modulation (PWM) valve) to selectively control pressure in the control chamber under normal operation of the pump. In fail safe regulation mode, the electrical valve function is disabled and the pressure controlled valve is active in its second position, controlling pressure in the control chamber. Channels and vents in the pump can be opened and closed based on selective movement of the valve when the outlet pressure is at or above a threshold level.