Closed-loop Hydraulic Regeneration via Load-holding Valves
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Solution Overview
Problem
Closed-loop hydraulic systems for heavy equipment, such as excavators and dozers, have historically been less efficient in regeneration compared to open-loop systems due to pressure limitations from charge relief valves, leading to increased complexity and cost.
Innovation Solution
A hydraulic system with a variable displacement pump, load-holding valves, and a regeneration valve, controlled by a controller to manage fluid flow between passages, allowing selective connection and blocking to optimize regeneration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed-loop hydraulic system uses charge relief valves to limit pressure, then system safety is improved, but regeneration efficiency deteriorates due to pressure limitations
Solution Approach 1:
The system divides the hydraulic circuit into separate head-end and rod-end passages with independent load-holding valves, allowing regeneration to occur without being constrained by charge relief valve pressure limits. This segmentation enables the rod-end chamber to pressurize independently during regeneration, improving efficiency while maintaining overall system safety through the load-holding valves.
Solution Approach 2:
Load-holding valves are introduced as intermediary components between the pump and the actuator chambers. These valves act as mediators that can maintain high pressure during regeneration without requiring the entire system to operate at elevated pressure levels, thus resolving the contradiction between safety and regeneration efficiency.
2Productivity
If a closed-loop system implements regeneration by directly connecting rod-end and head-end chambers, then regeneration capability is improved, but system complexity increases due to additional valves and control requirements
Solution Approach 1:
The load-holding valves are integrated into the existing closed-loop circuit architecture, merging the regeneration function with the load-holding function. This combination allows the system to achieve regeneration capability without adding separate complex valve assemblies, thereby improving regeneration capability while minimizing the increase in system complexity.
Solution Approach 2:
The load-holding valves serve multiple functions: they maintain pressure during normal operation, enable regeneration by blocking fluid return to the pump, and provide safety protection. This multi-functionality improves regeneration capability while avoiding the need for dedicated regeneration valves that would increase system complexity.
3Power
If the pump operates at higher pressures in an open-loop system, then power output is improved, but energy loss increases due to pressure drops across relief valves
Solution Approach 1:
The system converts what would normally be wasted energy (fluid returning to the pump during regeneration) into useful work by directing it to the head-end chamber. The load-holding valves prevent the harmful pressure drop across relief valves by maintaining pressure differential, thus improving power output while reducing energy loss through the regeneration process.
Solution Approach 2:
The system dynamically changes the pressure parameters in different parts of the circuit. During regeneration, the rod-end chamber operates at high pressure while the head-end chamber receives fluid at lower pressure, optimizing both power output and energy efficiency by avoiding unnecessary high-pressure operation across the entire system.
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 enhances regeneration efficiency, reduces energy loss, and simplifies control, resulting in improved performance and cost-effectiveness by redirecting fluid flow to maximize speed and minimize energy waste.
Implementation Method 1
the pressure of the fluid acts on hydraulic surfaces of the chambers to affect movement of the actuator
Implementation Method 2
a first load-holding valve disposed within the first passage and movable between a flow-blocking position and a flow-passing position
Implementation Method 3
the regeneration valve may be configured to selectively fluidly connect the first passage with the second passage
Data Source
AI summary
A hydraulic system is disclosed that has first and second passages connecting a pump to an actuator in closed-loop manner, and first and second load-holding valves within the first and second passages. The hydraulic system may also have a regeneration valve connected to the first and second passages between the actuator and the first and second load-holding valves to selectively connect the first and second passages. The hydraulic system may further have a controller configured to cause a control valve to simultaneous move the first and second load-holding valves toward flow-blocking positions when pump displacement is about zero. The controller may also be configured to selectively cause the regeneration valve to connect the first and second passages when pump displacement is non-zero, and to cause only one of the first and second load-holding valves to move to its flow-blocking position when the regeneration valve connects the first and second passages.