Hydraulic Valve Pressure Sequencing for Stable Mode Transition
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Solution Overview
Problem
The existing hydraulic systems for working machines face difficulties in smoothly transitioning from a warm-up mode to a normal mode, leading to unstable pressure control in the entire hydraulic circuit, which can result in incorrect pressure management.
Innovation Solution
A hydraulic system with a controller that sets the output-port pressure of one activation valve to a preloading pressure and the other to a lower pressure, then gradually increases the normal pressure, while managing the hydraulic fluid delivery and prime mover speed to stabilize the pressure transition, utilizing bypass fluid passages and check valves to facilitate smooth mode switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both activation valves are simultaneously switched during mode transition, then the warm-up mode transitions to normal mode, but the pressure control of the entire hydraulic circuit becomes unstable
Solution Approach 1:
The controller performs preliminary action by switching one activation valve before the other during mode transition. Specifically, when transitioning from warm-up to normal mode, the controller first switches the first activation valve to connect its output port to the tank port, then subsequently switches the second activation valve. This sequential switching prevents simultaneous valve transitions that would cause pressure instability, while still achieving complete mode transition.
Solution Approach 2:
The mode transition process is segmented into sequential steps rather than occurring simultaneously. The controller divides the transition into distinct phases: first switching one activation valve, then switching the other activation valve after a predetermined time interval. This segmentation of the transition process eliminates the harmful effect of simultaneous switching on pressure stability.
2Reliability
If one activation valve is switched before the other during mode transition, then pressure stability is maintained, but the transition time increases
Solution Approach 1:
The controller implements periodic action by switching activation valves at predetermined time intervals. After switching the first activation valve, the controller waits for a predetermined time period before switching the second activation valve. This periodic timing approach balances pressure stability requirements with efficient transition timing, preventing both simultaneous switching (which causes instability) and unnecessarily delayed switching (which increases transition time).
Data Source
AI summary
In a hydraulic system for a working machine, a controller is configured or programmed to increase an output-port pressure of one activation valve for one hydraulic device and an output-port pressure of another activation valve for another hydraulic device to a normal pressure higher than a preloading pressure from a state where the output-port pressure of the one activation valve is equal to the preloading pressure and the output-port pressure of the other activation valve is lower than the preloading pressure, by causing the output-port pressure of the one activation valve to be lower than the preloading pressure and increasing the output-port pressure of the other activation valve to the normal pressure.