Hydraulic Bypass Valve Control to Prevent Excavator Surge Pressure
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Solution Overview
Problem
Hydraulic systems in work machines experience surge pressures due to delays in the operation of center bypass cutoff valves, leading to reduced work efficiency and operator fatigue.
Innovation Solution
A hydraulic excavator with a controller that adjusts the opening of the bypass cutoff valve based on operation pressure, using a solenoid proportional valve to prevent surge pressures by maintaining optimal fluid flow and pressure during actuator operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a center bypass cutoff valve is provided downstream of the control valve to make the discharged pressure from the hydraulic pump higher than the load pressure, then the hydraulic system can maintain pressure during operation, but a surge pressure is generated due to delay in opening of the center bypass cutoff valve when returning the control valve
Solution Approach 1:
The control device opens the center bypass cutoff valve in advance before the control valve returns to its neutral position. This preliminary action ensures that the bypass passage is already open when the control valve closes, preventing pressure surge by allowing hydraulic fluid to flow through the bypass passage continuously without sudden pressure changes.
2Productivity
If the center bypass cutoff valve is opened in advance to prevent surge pressure, then work efficiency is improved, but the timing control becomes more complex
Solution Approach 1:
The control device uses feedback from the control valve's position or operation state to determine the optimal timing for opening the center bypass cutoff valve. By monitoring the control valve's return motion, the control device can automatically adjust the bypass valve timing, simplifying the control logic while maintaining effective surge pressure prevention.
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
Prevents surge pressures during actuator stoppage, enhancing work implement positioning and reducing operator fatigue, thereby improving work efficiency and fuel economy.
Implementation Method 1
a solenoid proportional valve for generating a pilot pressure for controlling the bypass cutoff valve
Implementation Method 2
a hydraulic pump, a hydraulic actuator driven by a hydraulic fluid delivered from the hydraulic pump
Data Source
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AI summary
A work machine includes a flow control valve that controls a flow rate of a hydraulic fluid supplied to a hydraulic actuator, a center bypass line that introduces the hydraulic fluid from a pump through a center bypass passage section of the flow control valve into the tank, a bypass cutoff valve that controls an opening of the center bypass line, a solenoid proportional valve that generates a pilot pressure for controlling the bypass cutoff valve, a pilot valve that generates a pilot pressure for controlling the flow control valve on the basis of an amount of operation of an operation device, and a controller that controls the solenoid proportional valve on the basis of the amount of operation. The controller controls the solenoid proportional valve to reduce an opening area of the bypass cutoff valve according to an increase in the amount of operation in a case the amount of operation is less than a predetermined amount of operation, and controls the solenoid proportional valve to make the opening area of the bypass cutoff valve larger than the minimum opening area in a case the amount of operation is a maximum amount of operation.