Wheel Loader Tractive Force Control for Hydraulic Stall Recovery
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Solution Overview
Problem
Operators of conventional wheel loaders face difficulties in selecting the optimal level of maximum tractive force, leading to frequent adjustments during excavation work to prevent stalling or slipping, which reduces operability and efficiency.
Innovation Solution
A wheel loader system with a tractive force control mechanism that automatically reduces maximum tractive force when specific conditions are met, such as during excavation and when the working implement is in a raising hydraulic stall condition, using sensors to detect work phase, drive circuit pressure, and engine rotation speed to adjust the tractive force control level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the operator selects a lower level of maximum tractive force to prevent slipping or stalling, then the occurrence of slip or stall phenomena is suppressed, but the productivity of the wheel loader is reduced
Solution Approach 1:
The patent implements dynamic adjustment of tractive force control levels based on real-time detection of work conditions (excavation, travel, etc.). The control level is not fixed but changes dynamically according to the detected work phase, allowing the system to optimize between preventing slip/stall and maintaining productivity for each specific condition.
Solution Approach 2:
The system uses feedback from work condition detection (excavation detection, travel detection) to automatically adjust the tractive force control level. This closed-loop control eliminates the need for manual operator adjustment and ensures the appropriate control level is applied for each work phase, resolving the contradiction between reliability and productivity.
2Adaptability or versatility
If the operator continually reselects the level of maximum tractive force during excavation work in response to changing work conditions, then the adaptability to different work conditions is improved, but the ease of operation is reduced
Solution Approach 1:
The system performs self-adjustment of tractive force control levels by automatically detecting work conditions and selecting appropriate control levels without operator intervention. The excavation detection device and control unit work together to autonomously manage the tractive force control, eliminating the burden of manual adjustment while maintaining adaptability.
Solution Approach 2:
The system continuously monitors work conditions through detection devices and uses this feedback to automatically adjust control parameters. This real-time feedback mechanism ensures the system adapts to changing conditions without requiring operator attention or manual reselection, improving ease of operation while maintaining adaptability.
3Reliability
If the operator reduces maximum tractive force manually during excavation, then the raising hydraulic stall condition can be prevented, but the productivity is reduced and operability is worsened
Solution Approach 1:
The system detects the raising hydraulic stall condition in advance through monitoring work conditions and hydraulic system parameters. By detecting the condition before it fully develops, the control unit can proactively adjust tractive force control levels to prevent the stall condition, avoiding the need for reactive manual intervention and maintaining productivity.
Solution Approach 2:
The system uses feedback from hydraulic pressure sensors and work condition detection to identify the precursor signs of raising hydraulic stall. This feedback enables automatic adjustment of tractive force control levels to prevent the stall condition, resolving the contradiction between reliability and productivity by eliminating manual intervention.
4Reliability
If the operator performs multiple operations to adjust tractive force control levels during excavation, then the working implement can recover from raising hydraulic stall condition, but the time required for adjustment increases
Solution Approach 1:
The system automatically manages the recovery process from raising hydraulic stall condition by detecting the stall state and autonomously adjusting tractive force control levels. This eliminates the need for multiple manual operations by the operator, reducing the time loss while ensuring reliable recovery from the stall condition.
Solution Approach 2:
The control unit is programmed with predefined adjustment strategies for recovering from raising hydraulic stall conditions. When a stall condition is detected, the system immediately implements the appropriate control level adjustment without requiring operator decision-making or multiple sequential operations, significantly reducing the time required for recovery.
Data Source
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AI summary
A tractive force control part of a wheel loader reduces the maximum tractive force when determination conditions are satisfied during tractive force control. The determination conditions include that the work phase is excavation, that the working implement is in the raising hydraulic stall condition and that drive circuit pressure is greater than or equal to a predetermined pressure threshold.