Wheel Loader Hydraulic Control for Lifting Speed
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Solution Overview
Problem
In wheel loaders, simultaneous steering and lifting operations are hindered by a circuit configuration that prioritizes steering, leading to insufficient hydraulic oil flow for lifting at low engine speeds, resulting in decreased work efficiency and potential cost and size increases from additional hydraulic pumps.
Innovation Solution
A working vehicle with an electric steering operation device, solenoid control valves, rotational speed, and operation state sensors, controlled by a controller that limits steering operation speed when the engine is at low idle and lifting is performed, ensuring adequate hydraulic oil flow to the lifting actuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a priority valve is used to allow hydraulic oil to flow to the steering cylinder preferentially over the working device cylinder, then steering operation reliability is improved, but lifting operation speed deteriorates when the engine is driven at low rotational speed
Solution Approach 1:
The patent applies dynamics by making the steering operation speed variable based on engine rotational speed. The controller limits the steering operation speed when the engine is driven at low rotational speed (below threshold Nth) to ensure adequate hydraulic oil flow for lifting operations, while allowing normal steering speed when the engine operates above the threshold. This dynamic adjustment resolves the contradiction by adapting steering priority to actual hydraulic system capabilities.
Solution Approach 2:
The patent changes the parameter of steering operation speed based on engine rotational speed conditions. By monitoring engine speed and dynamically adjusting the maximum allowable steering speed, the system ensures that hydraulic oil flow is sufficient for both steering and lifting operations. This parameter change approach allows the system to maintain reliability while preventing productivity loss during low-speed engine operation.
2Productivity
If a hydraulic pump for steering and a hydraulic pump for loading are respectively provided, then lifting operation speed is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies universality by making a single hydraulic pump serve both steering and working device functions. The pump is designed with sufficient capacity to handle both operations, and the control system intelligently manages hydraulic oil distribution based on operational needs. This eliminates the need for separate hydraulic pumps while maintaining adequate performance for both steering and lifting operations.
Solution Approach 2:
The patent introduces a controller as an intermediary that manages the single hydraulic pump's output to serve multiple functions. The controller monitors engine rotational speed and operational state, then dynamically adjusts steering operation speed to ensure adequate hydraulic flow for lifting operations. This intermediary control mechanism allows one pump to effectively perform the roles that would otherwise require two separate pumps.
3Productivity
If the steering operation speed is limited when the engine is driven in a low idle state, then lifting operation speed is improved, but steering responsiveness deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by proactively limiting steering operation speed before hydraulic oil flow becomes insufficient. The controller monitors engine rotational speed and preemptively restricts steering speed when the engine operates below threshold Nth, preventing the situation where steering and lifting operations would compete for insufficient hydraulic flow. This preliminary action ensures lifting operations can proceed at required speeds while maintaining acceptable steering responsiveness.
Solution Approach 2:
The patent implements feedback by continuously monitoring engine rotational speed and operational state, then dynamically adjusting steering operation speed accordingly. The controller receives feedback from the engine speed sensor and working device operation state, and automatically limits steering speed only when necessary (low engine speed combined with active lifting operation). This feedback mechanism maintains steering responsiveness under normal conditions while ensuring adequate hydraulic flow for lifting when needed.
Data Source
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AI summary
Provided is a working vehicle capable of increasing lifting operation speed of a working device without increasing cost, even when provided with a circuit configuration that prioritizes a steering operation over a working device operation. A wheel loader 1 comprises a priority valve 451 configured to allow hydraulic oil discharged from a hydraulic pump 41 to flow into a steering drive circuit 43 preferentially over a working device drive circuit 44, and further comprises: an electric steering lever 30; a pair of solenoid control valves 34A, 34B configured to control a steering directional control valve 33; and a controller 5. The controller 5 is configured to control the pair of solenoid control valves 34A, 34B so as to limit operation speed of a steering 3 when determining that an engine 40 is in a low idle state and a lift arm 21 is performing a lifting operation.