Hydraulic Driving System Pressure Control for Construction Machines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In hydraulic driving systems for construction machines, the load-sensing control system fails to maintain adequate pressure for track motors during obstacles or slope climbing, leading to insufficient output torque due to limitations in the signal pressure variable relief valve, which restricts the delivery pressure of the hydraulic pump.
Innovation Solution
A hydraulic driving system with a main relief valve and a signal pressure relief valve configuration that adjusts set pressures dynamically, ensuring the differential pressure between the hydraulic pump's delivery pressure and the highest load pressure remains within target ranges, even when specific actuators reach their stroke ends, thereby maintaining active operation of other actuators and increasing the load pressure of active actuators to the desired set pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the signal pressure variable relief valve restricts the delivery pressure of the hydraulic pump to maintain differential pressure control, then the load-sensing control can maintain stable operation during combined actuator operations, but the delivery pressure cannot increase sufficiently during track operations over obstacles or slopes, resulting in insufficient output torque
Solution Approach 1:
The relief valve function is segmented into two independent valves: the signal pressure variable relief valve (16) that maintains differential pressure control stability by limiting highest load pressure, and the main relief valve (14) that provides the pressure boost during track operations. This segmentation allows each valve to specialize in one function without compromising the other, resolving the contradiction between control stability and power output.
Solution Approach 2:
The signal pressure variable relief valve acts as an intermediary between the highest load pressure line and the load-sensing control system. It mediates the pressure signal to ensure stable differential pressure control while allowing the main relief valve to independently provide pressure boost when needed for track operations, thus resolving the conflict between stability and power.
2Power
If the set pressure of the main relief valve is increased to provide sufficient pressure during track operations, then the output torque of track motor improves, but the differential pressure between delivery pressure and highest load pressure becomes excessive, causing instability in load-sensing control
Solution Approach 1:
The pressure control function is divided into two independent pressure control paths: one through the signal pressure variable relief valve that maintains stable differential pressure for load-sensing control, and another through the main relief valve that provides high pressure for track operations. This segmentation allows both high power output and stable control to coexist without interference.
3Reliability
If the signal pressure variable relief valve limits the highest load pressure to maintain differential pressure, then load-sensing control stability is maintained, but the load pressure cannot reach the required set pressure during track operations over obstacles
Solution Approach 1:
The pressure limitation function is segmented between two valves: the signal pressure variable relief valve (16) that limits highest load pressure to maintain differential pressure control stability, and the main relief valve (14) that overrides this limitation during track operations to provide the necessary high load pressure for overcoming obstacles and slopes.
Solution Approach 2:
The main relief valve's set pressure is made dynamic, increasing from a first value to a second value when track operation is detected. This dynamic adjustment allows the system to adapt pressure levels based on operational mode, providing both stable differential pressure control during normal operation and sufficient load pressure during track operations.
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 ensures that other actuators remain active during combined operations and that the load pressure of specific actuators increases reliably to the increased set pressure of the main relief valve, enhancing maneuverability and output torque, particularly during track operations.
Implementation Method 1
a main relief valve that limits a maximum pressure of the delivery pressure of the hydraulic pump; and a signal pressure relief valve connected to the highest load pressure line via a restrictor and configured to limit the maximum pressure of the highest load pressure introduced to a downstream side of the restrictor, to a pressure lower than a set pressure of the main relief valve
Implementation Method 2
the differential pressure between the delivery pressure of the hydraulic pump and the highest load pressure of a plurality of actuators is maintained at a target differential pressure
Data Source
AI summary
In a hydraulic driving system for construction machines, when track motors 3f and 3g are operated and the delivery pressure of a main pump 2 increases to a second value PS2 of the set pressure of a main relief valve 14, the set pressure of a signal pressure relief valve 16 increases from a third value PA1 to a fourth value PA2, which is smaller than the second value PS2 of the set pressure of the main relief valve 14, the difference between the second value PS2 and the fourth value PA2 being smaller than the target LS differential pressure. With such a structure, even if one of actuators reaches the stroke end and the delivery pressure of the hydraulic pump rises to the set pressure of the main relief valve, the other actuators do not stop, and further when the main relief valve is configured to increase the set pressure during operation of a specific actuator, the load pressure of the specific actuator does not increase to the increased set pressure of the main relief valve.