Hydraulic Drive System for Construction Machine with Adaptive Pressure Control
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Solution Overview
Problem
Conventional hydraulic drive systems for construction machines, such as hydraulic excavators, experience energy loss during traveling operations due to the differential pressure across flow control valves being maintained at the same level as other actuators, which results in inefficient energy use.
Innovation Solution
A hydraulic drive system with a travel detection device and a setting changing device that adjusts the target differential pressure for load sensing control, reducing energy loss by lowering the differential pressure across traveling flow control valves during traveling operations, while maintaining necessary actuator speed and flow rate distribution for other actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the differential pressure across flow control valves is maintained at the same level for all actuators, then the flow rate distribution to actuators can be controlled according to opening area ratios during combined operation, but energy loss increases during traveling operations
Solution Approach 1:
The patent applies local quality by providing different differential pressure control characteristics for traveling flow control valves versus other flow control valves. Specifically, the traveling flow control valve is equipped with a traveling pressure compensating valve that maintains a smaller, fixed differential pressure, while other flow control valves use pressure compensating valves that maintain differential pressure based on load sensing. This localized differentiation reduces energy loss during traveling operations while preserving flow rate distribution control for other actuators.
Solution Approach 2:
The patent implements dynamics by making the differential pressure control system adaptive to different operating modes. The traveling pressure compensating valve dynamically maintains a fixed differential pressure specifically during traveling operations, while the load sensing system dynamically adjusts differential pressure based on actual load conditions during work operations. This dynamic adaptation allows the system to optimize energy efficiency during traveling while maintaining operational flexibility during work.
2Speed
If the maximum opening area of traveling flow control valve is reduced to lower the maximum flow rate, then the differential pressure loss across the valve increases, but the necessary actuator speed can be maintained
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the differential pressure parameter during traveling operations. Instead of relying on reduced opening area to limit flow rate (which increases pressure loss), the traveling pressure compensating valve actively maintains a fixed, smaller differential pressure across the traveling flow control valve. This parameter change allows the valve to pass the necessary flow rate for actuator speed while minimizing energy loss through reduced pressure differential.
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
This configuration enhances energy efficiency by reducing energy loss during traveling operations while ensuring necessary actuator speed and flow rate distribution for other actuators, improving overall energy efficiency.
Implementation Method 1
the delivery pressure of the main pump is higher than a maximum load pressure of the plurality of actuators by a target differential pressure
Implementation Method 2
differential pressures across the corresponding flow control valves are kept at the differential pressure PLS
Implementation Method 3
a hydraulic fluid can be fed to the plurality of actuators at a ratio depending on opening areas of the flow control valves
Data Source
AI summary
A hydraulic drive system for a construction machine has a travel detection device which detects whether or not the operation mode is a traveling operation and a setting changing device. The setting changing device sets the target differential pressure of load sensing control at an absolute pressure Pa when the operation mode is not a traveling operation, and sets the target differential pressure of the load sensing control at an absolute pressure Pa′ rather than the absolute pressure Pa. In this way, in the actuator operation other than traveling, a necessary actuator speed can be obtained and supplied with the necessary maximum flow rate. In addition, during the combined operation, a flow rate in accordance with the opening area ratios of flow control valves can be distributed to actuators different in load pressure from one another; and energy efficiency is enhanced due to less energy loss during traveling operation.