Wheel Loader Travel Valve Control to Prevent Creeping
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Solution Overview
Problem
The existing wheel loader technology allows the working device to move forward or backward even when the accelerator is not operated, leading to unintended movement known as the 'creeping phenomenon'.
Innovation Solution
A wheel loader with a traveling device and a controller that maintains the switching valve in a neutral position until the prime mover reaches a predetermined rotation speed, includes a display to indicate the selected mode, and shifts the valve to neutral if the rotation speed drops below a second predetermined speed or after a specific time, preventing unintended movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the forward/backward-traveling switching valve is connected to the servo-cylinder and switched between forward-traveling position and backward-traveling position, then the traveling direction of the wheel loader can be switched, but the working device may move forward or backward even when the accelerator is not operated (creeping phenomenon)
Solution Approach 1:
The controller is configured to hold the switching valve at the neutral position after the switching operation member is operated to select the traveling mode until the rotation speed of the prime mover becomes not less than a first predetermined rotation speed. This preliminary action prevents the creeping phenomenon by ensuring the valve only shifts to traveling position when the engine is running at sufficient speed.
Solution Approach 2:
The controller monitors the rotation speed of the prime mover and uses this feedback to control the switching valve position. When the rotation speed drops below a second predetermined rotation speed or after a predetermined time period, the controller shifts the valve back to neutral position, providing continuous feedback-based control to prevent unintended movement.
2Productivity
If the switching valve is shifted to traveling position when the switching operation member is operated, then the wheel loader can travel in selected direction, but the wheel loader may move when the accelerator is not operated
Solution Approach 1:
The system changes the operational parameters by introducing rotation speed thresholds (first predetermined rotation speed for engagement, second predetermined rotation speed for disengagement) and time-based parameters (predetermined time period). These parameter changes ensure the switching valve only operates when appropriate engine speed and time conditions are met, preventing creeping while maintaining traveling responsiveness.
3Speed
If the controller shifts the switching valve when the set rotation speed is not less than the first predetermined rotation speed, then the wheel loader travels in the selected direction, but the valve may need to shift back when rotation speed drops
Solution Approach 1:
The control system dynamically adjusts the switching valve position based on real-time rotation speed conditions and time elapsed. The controller monitors whether the rotation speed remains above the second predetermined rotation speed and whether the predetermined time period has elapsed, dynamically shifting the valve between neutral and traveling positions as conditions change, providing adaptive control that manages complexity through dynamic response.
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 the wheel loader from moving forward or backward when the accelerator is not operated, ensuring controlled operation and reducing unintended movement.
Implementation Method 1
a charge pump to supply pilot fluid to the first servo-cylinder
Implementation Method 2
a hydraulic pump, including a swashplate, to supply hydraulic fluid to the traveling motor
Implementation Method 3
the swashplate of the hydraulic pump is tiltable between a forward traveling side to make the hydraulic pump deliver hydraulic fluid to drive the traveling motor in the forward traveling direction and a backward traveling side to make the hydraulic pump deliver hydraulic fluid to drive the traveling motor in the backward traveling direction
Data Source
Figure 1
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Figure 3
AI summary
To prevent a working machine (1) from moving forward or backward under a state where the accelerator is not being operated. The working machine (1) includes a traveling device, a traveling motor (51) to output power to the traveling device, a hydraulic pump (50), including a swashplate, to supply hydraulic fluid to the traveling motor (51), a prime mover to drive the hydraulic pump (50), a first servo-cylinder (61) to set an angle of the swashplate of the hydraulic pump (50), a charge pump (PI) to supply pilot fluid to the first servo-cylinder (61), a switching valve shiftable between a traveling position to supply the pilot fluid from the charge pump (PI) to the first servo-cylinder (61) and a neutral position to stop the pilot fluid supply to the first servo-cylinder (61), a switching operation member operable to select either a traveling mode or a neutral mode, and a controller (90) to shift the switching valve between the traveling position and the neutral position. The controller (90) is configured or programed to hold the switching valve at the neutral position after the switching operation member is operated to select the traveling mode until a rotation speed of the prime mover becomes not less than a first predetermined rotation speed.