Hydraulic Bleed-Off Valve Control for Excavator Auto Accuracy
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Solution Overview
Problem
The existing bleed-off function in hydraulic excavators can cause a shortage of flow rate supplied to actuators during automatic control, leading to decreased accuracy of control due to delayed target flow rates and unstable flow supply.
Innovation Solution
A work machine with a bleed-off valve that adjusts the flow rate returned to the tank, and a controller that adjusts the bleed-off valve's opening amount based on the automatic control function selector switch, ensuring the bleed-off function is suppressed during automatic control to maintain accurate actuator control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bleed-off function is activated to reduce vibration and shock during manual operation, then operability is improved, but flow rate supplied to actuators becomes insufficient during automatic control
Solution Approach 1:
The bleed-off valve opening amount is dynamically adjusted based on the operation mode (manual or automatic control). During manual operation, the valve opens to discharge excess fluid and reduce vibration. During automatic control, the valve closes to prevent flow rate shortage. This dynamic adaptation resolves the contradiction by changing system behavior according to operational context.
Solution Approach 2:
The opening amount of the bleed-off valve is changed as a control parameter depending on the operation mode. By varying this parameter (from fully open during manual operation to closed during automatic control), the system achieves both smooth manual operation and sufficient flow rate for automatic control accuracy.
2Ease of operation
If the bleed-off function discharges part of the operating fluid to reduce vibration, then operability is improved, but accuracy of control of the actuator position and speed decreases
Solution Approach 1:
The system dynamically switches the bleed-off valve state based on control mode. During automatic control, the valve closes to ensure all pump output reaches the actuator, maintaining positioning and speed accuracy. During manual operation, the valve opens to dampen vibrations, improving operability without compromising automatic control precision.
Solution Approach 2:
The bleed-off function is selectively applied only during manual operation mode, while being suppressed during automatic control mode. This localized application of the bleed-off effect ensures that accuracy requirements during automatic control are met while still providing vibration reduction benefits during manual operation.
3Ease of operation
If the bleed-off valve opens to reduce vibration during manual operation, then operability is improved, but flow rate supply becomes unstable when load on actuator varies
Solution Approach 1:
The bleed-off valve opening amount is dynamically adjusted based on operation mode. During manual operation, the valve opens to provide stable flow rate supply that compensates for load variations. During automatic control, the valve closes to maintain precise flow rate control. This dynamic adjustment ensures stability in both operational contexts.
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 excellent operability during manual operation by reducing vibration and shock, while maintaining accurate control of the machine body or work device during automatic control by preventing flow rate shortages and delays.
Implementation Method 1
a bleed-off valve that is disposed on a hydraulic fluid line connecting the delivery line to the hydraulic fluid tank and adjusts a flow rate of the hydraulic fluid returned from the delivery line to the hydraulic fluid tank
Implementation Method 2
a plurality of solenoid proportional valves that reduce pressure of hydraulic fluid supplied from the pilot pump and that generate operation pressures of the plurality of flow rate controllers
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Provided is a work machine which can achieve both of excellent operability when an operator manually operates a machine body or a work device and an accuracy of control of the machine body or the work device when a controller performs automatic control. The controller is configured to, in a case where the automatic control function selector switch gives an instruction to disable the automatic control function, adjust an opening amount of a bleed-off valve to a maximum opening amount or an opening amount corresponding to input amounts of control levers, and in a case where the automatic control function selector switch gives the instruction to enable the automatic control function, adjust the opening amount of the bleed-off valve, in at least part of an operation region of the control levers, so as to be smaller than the opening amount with the instruction to disable the automatic control function being given.