Hydraulic Pump and Bypass Valve Control for Precision Operation
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Solution Overview
Problem
Conventional hydraulic drive systems for working machines, such as hydraulic excavators, face challenges in achieving both good operability during normal operations and reducing energy loss during precision operations, especially due to variations in load pressures, leading to inefficiencies in both normal and precision work modes.
Innovation Solution
The system employs a controller with a pump delivery rate control unit and a center bypass valve control unit to adjust the displacement of the variable displacement hydraulic pump and the center bypass valve based on the operation mode and load pressure, ensuring optimal flow volumes and pressures for normal and precision operations, thereby maintaining good operability and reducing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the system is set to assure good controllability in normal work, then operability in normal operation is improved, but energy loss increases during precision operation
Solution Approach 1:
The system dynamically adjusts the opening degree of the center bypass valve based on operation mode (normal vs. precision) and load pressure conditions. During normal operation, the valve is fully open for high operability. During precision operation, the valve opening is dynamically controlled based on load pressure to reduce extra flow volume and energy loss while maintaining required performance.
Solution Approach 2:
The system changes the opening degree parameter of the center bypass valve according to different operation modes and load pressure levels. In normal operation mode, the valve is fully open (100% opening). In precision operation mode, the valve opening is adjusted based on load pressure: fully closed for high load pressure, and partially open for low load pressure, thereby optimizing energy efficiency.
2Loss of energy
If the extra flowvolume to reservoir is reduced in precision operation, then energy loss is reduced, but operability in normal work deteriorates
Solution Approach 1:
The center bypass valve opening degree is dynamically adjusted based on the selected operation mode. In normal operation mode, the valve is fully open to maximize operability. In precision operation mode, the valve opening is dynamically controlled based on load pressure conditions to reduce energy loss while maintaining precision operation performance.
Solution Approach 2:
The system changes the valve opening parameter from fully open (100%) in normal mode to dynamically controlled openings (0% or partial) in precision mode based on load pressure, thereby reducing extra flow volume and energy loss without compromising normal operation performance.
3Adaptability or versatility
If the center bypass valve is controlled by load pressure only, then precision operation under different loads can be optimized, but system complexity increases
Solution Approach 1:
The system uses load pressure feedback to control the center bypass valve opening degree during precision operation. The controller receives load pressure signals and automatically adjusts the valve opening accordingly: fully closed for high load pressure and partially open for low load pressure, enabling optimized precision operation under different load conditions without requiring complex manual control.
Data Source
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AI summary
To provide a hydraulic drive system for a working machine, which can realize the assurance of good operability in normal operation and precision operation and a reduction in energy loss in the precision operation. A controller (31) is provided with a pump delivery rate control unit (40) and a center bypass valve control unit (50). The pump delivery rate control unit (40) performs control processing to output, to a control terminal of a solenoid-operated proportional reducing valve (21), a control signal to make a displacement of a variable displacement hydraulic pump (10) smaller than a displacement corresponding to normal operation when a working element control device is in a manipulation mode considered to correspond to precision operation. The center bypass valve control unit (50) performs control processing to output, to a control terminal of a proportional solenoid valve (23), a control signal to make a center bypass valve (22) have a relatively large opening amount despite the center bypass valve (22) is in a switched state between a fully open position and a fully closed position when the working element control device is in a manipulation mode considered to correspond to the precision operation and a load pressure on a working element actuator is in a low state.