Variable Displacement Pump Over-speed Control via Bypass Flow
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Solution Overview
Problem
Existing hydraulic power systems in machines face challenges in effectively controlling over-speed conditions, particularly when traveling down hills, as they tend to increase engine and motor speeds beyond desired limits, leading to potential damage and inefficient fuel consumption.
Innovation Solution
A hydraulic power control system that includes a variable displacement pump and motor connected in a closed loop, with a controller that adjusts pump displacement based on engine speed signals to prevent over-speed conditions by redirecting fluid flow through bypass passages, minimizing waste flow and maximizing retarding capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the machine travels down a hill under over-speed conditions, then the engine and pump speeds increase beyond desired limits, but this causes potential damage and inefficient fuel consumption
Solution Approach 1:
The controller continuously monitors engine speed and system parameters, and automatically adjusts pump displacement in real-time based on feedback signals. When over-speed conditions are detected, the controller reduces pump displacement to increase retarding effect and slow the engine speed, preventing damage while maintaining system reliability.
Solution Approach 2:
The system dynamically changes the displacement parameter of the variable displacement pump based on operating conditions. During over-speed conditions, the pump displacement is reduced to increase the retarding effect, thereby controlling engine speed and preventing it from exceeding desired limits, while avoiding damage and improving fuel efficiency.
2Reliability
If known control systems are used to protect engine and pump from over-speed, then some protection is provided, but the retarding effect is insufficient and effectiveness depends on sensor accuracy and response time
Solution Approach 1:
The hydraulic system provides its own retarding capability through the variable displacement pump and motor combination. During over-speed conditions, the pump displacement is adjusted to create a retarding effect that slows the machine, eliminating the need for external braking systems and providing self-contained over-speed protection with sufficient retarding capability.
Solution Approach 2:
The variable displacement pump serves multiple functions: it provides hydraulic power during normal operation and simultaneously provides retarding capability during over-speed conditions. This multi-functionality allows the same component to protect the system from over-speed while also providing effective slowing capability, without requiring separate protection systems.
3Reliability
If pump displacement is reduced to increase retarding effect, then over-speed protection is improved, but fuel consumption efficiency must be optimized
Solution Approach 1:
The pump displacement is dynamically adjusted based on real-time operating conditions rather than being fixed. During over-speed conditions, the displacement is temporarily reduced to provide retarding effect and protect the system. During normal operation, the displacement is optimized for fuel efficiency. This dynamic adjustment allows the system to maintain both over-speed protection and fuel consumption efficiency.
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 system effectively reduces engine and motor speeds during over-speed conditions, preventing damage and optimizing fuel efficiency by minimizing waste flow and enhancing retarding capabilities, thus ensuring predictable machine operation.
Implementation Method 1
A variable displacement pump is fluidly connected to a first passageway and a second passage way... redirecting fluid flow through bypass passages
Implementation Method 2
A hydraulic motor is fluidly connected to the first and second passageways in a closed hydraulic loop with the variable displacement pump. The hydraulic motor operates by a flow of hydraulic fluid originating from the variable displacement pump
Implementation Method 3
an engine operating at an engine speed... An engine or another prime mover operating a hydraulic pump
Data Source
AI summary
A hydraulic power control system includes an engine driving a variable displacement pump. The variable displacement pump is fluidly connected to a first passageway and a second passageway, and has a selectively variable displacement that is adjustable in response to a pump displacement command signal. A hydraulic motor fluidly connected to the first and second passageways operates by a flow of hydraulic fluid originating from the pump. A controller receives an engine speed signal and adjusts pump displacement based on the engine speed signal to reduce the rotation speed of the pump when an overrun condition is present.