Excavator Pilot Line Bypass for Area Limit Response Control
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Solution Overview
Problem
In hydraulic excavators, the area limiting control mechanism using a solenoid proportional valve leads to pressure loss and leakage, reducing the work implement's response, and existing temperature detection systems fail to warn operators of low hydraulic fluid temperatures in stagnant lines, causing reduced response and potential area breaches.
Innovation Solution
A work machine with a changeover valve system that enables or disables area limiting control by bypassing the solenoid proportional valve, using fluid temperature detection to determine the operational state and maintain hydraulic fluid temperature, ensuring responsive operation while preventing area breaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If area limiting control is performed using a solenoid proportional valve, then the work implement can be controlled not to enter a predetermined area, but pressure loss and leakage flow occur in the solenoid proportional valve which reduces response of the work implement
Solution Approach 1:
The system dynamically switches between two operational modes: area limiting control mode (using solenoid proportional valve) and ordinary operation mode (direct pilot pressure guidance). The changeover valve enables the system to adapt its control architecture based on work requirements, allowing high-precision area limiting control when needed while maintaining fast response for time-critical operations.
Solution Approach 2:
The solenoid proportional valve adjusts the pilot pressure parameters (reducing or boosting) to achieve area limiting control. By changing the pressure parameters through the valve, the system can control the work implement's movement boundaries while managing the trade-off between control precision and response speed.
2Speed
If the changeover valve bypasses the solenoid proportional valve to improve response, then work requiring high response can be performed, but the temperature of hydraulic fluid in the line portion decreases which further reduces response
Solution Approach 1:
The fluid temperature detection device continuously monitors the temperature of hydraulic fluid in the line portion and provides feedback to the controller. When the temperature drops below a predetermined threshold, the controller activates the heating device to warm the fluid, ensuring that response performance is maintained even when the changeover valve is in bypass mode.
Solution Approach 2:
The heating device pre-heats the hydraulic fluid in the line portion before cold weather operations or during periods when bypass mode is expected to be used. This preliminary heating action prevents the fluid temperature from dropping to levels that would degrade response performance.
3Temperature
If the fluid temperature is low, then the viscosity of hydraulic fluid increases which reduces response of the work implement
Solution Approach 1:
The heating device changes the temperature parameter of the hydraulic fluid by applying thermal energy. This parameter change reduces the fluid's viscosity, thereby improving the response characteristics of the work implement during cold weather 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
The system allows for effective area limiting control while maintaining the hydraulic fluid temperature, enhancing the work implement's response and preventing unintended area entry by dynamically managing the solenoid proportional valve's operation based on detected fluid temperatures.
Implementation Method 1
a first fluid temperature detection device that detects as a first fluid temperature a temperature of hydraulic fluid flowing through, out of the pilot lines, lines between the changeover valves and the solenoid proportional valves
Implementation Method 2
a plurality of solenoid proportional valves disposed in a plurality of pilot lines through which the pilot pressures are guided to the directional control valves, the solenoid proportional valves being operable between a fully open position at which the pilot pressures are not reduced and a fully closed position at which the pilot pressures are interrupted
Implementation Method 3
a plurality of changeover valves disposed in the pilot lines, the changeover valves being capable of being brought into a communication position at which communication is provided through the pilot lines or a bypass position at which the solenoid proportional valves are bypassed
Data Source
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AI summary
A work machine is provided. The work machine includes a changeover valve capable of disabling area limiting control by bypassing an area limiting control solenoid proportional valve disposed in a pilot line through which pilot pressure generated by a hydraulic pilot type operation device is guided to a directional control valve and the work machine can perform the area limiting control while ensuring response of a work implement. When a first fluid temperature T1 is higher than a first predetermined temperature Ta and a control changeover switch 66 specifies disabling of the area limiting control, a controller 25 brings a plurality of changeover valves 51 to 55 into a bypass position. When the first fluid temperature T1 is equal to or lower than the first predetermined temperature Ta, the controller 25 brings the changeover valves into a communication position and places the solenoid proportional valves in a fully open position.