Work Vehicle Automatic Downshift Control via Acceleration and Brake Pressure
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Solution Overview
Problem
The existing automatic downshift determination method in work vehicles, based on hydraulic pressure of the boom cylinder, boom height, and vehicle speed, often results in delays due to false determinations, requiring a small speed threshold to prevent errors, which further delays the execution of the downshift.
Innovation Solution
A work vehicle equipped with an engine, hydraulic pump, travel device, transmission, accelerator operating member, vehicle speed detector, and a control unit that determines the automatic downshift by considering the operating amount of the accelerator, vehicle acceleration, vehicle speed, and hydraulic pressure of the brake device, allowing for more accurate and quicker determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the predetermined speed threshold is set to a small value to prevent false determination, then the accuracy of state determination is improved, but the execution delay of automatic downshift increases
Solution Approach 1:
The patent introduces a new evaluation dimension by incorporating vehicle acceleration into the downshift determination criteria. Instead of relying solely on vehicle speed (one dimension), the system now evaluates both speed and acceleration (two dimensions). This dimensional expansion allows the use of higher speed thresholds without causing false determinations, as the acceleration parameter provides additional discriminative power to distinguish between legitimate downshift conditions and normal operation.
Solution Approach 2:
The patent changes the parameters used for downshift determination from only vehicle speed to a combination of vehicle speed and vehicle acceleration. By introducing acceleration as an additional parameter, the system can set less stringent speed thresholds (higher values) while maintaining determination accuracy, thereby reducing execution delay without sacrificing precision.
2Reliability
If the predetermined speed threshold is set to a small value to avoid false determination when plunging into dirt mound, then the reliability of determination is improved, but the productivity due to delayed downshift execution deteriorates
Solution Approach 1:
By adding vehicle acceleration as a second evaluation dimension, the system achieves more reliable determination with less stringent speed thresholds. The acceleration parameter helps distinguish between temporary speed drops during work operations and conditions requiring downshift, improving reliability while enabling faster response time.
Solution Approach 2:
The system performs preliminary evaluation using both speed and acceleration data before triggering downshift. This preliminary multi-parameter assessment ensures reliable determination while allowing the use of higher speed thresholds that enable earlier detection and faster execution of the downshift action, thereby improving productivity.
3Measurement precision
If multiple determination conditions (accelerator operating amount, vehicle acceleration, vehicle speed, brake hydraulic pressure) are used, then the measurement precision of vehicle state is improved, but the device complexity increases
Solution Approach 1:
The control unit leverages existing multi-functional sensors and actuators already present in the vehicle. The accelerator operating member detector, vehicle speed detector, brake hydraulic pressure detector, and acceleration calculator all serve multiple functions within the overall vehicle control system. By utilizing these existing components for downshift determination, the patent achieves high measurement precision without significantly increasing device complexity.
Solution Approach 2:
The system uses data already being collected and processed by the vehicle's existing control systems. The vehicle speed detector provides speed data for both cruise control and downshift determination; the accelerator operating member detector serves engine control and transmission control; the brake hydraulic pressure detector serves braking control and downshift determination. This self-service approach allows comprehensive multi-parameter monitoring without adding dedicated hardware for each function.
Data Source
AI summary
A control unit in a work vehicle executes an automatic downshift for shifting a transmission from a current speed range to a speed range that is lower than the current speed range when at least a first condition, a second condition, a third condition, and a fourth condition are satisfied. The first condition is that an operating amount of an accelerator operating member of the work vehicle is equal to or greater than a predetermined accelerator threshold. The second condition is that a vehicle speed of the work vehicle is less than a predetermined speed threshold. The third condition is that a vehicle acceleration of the work vehicle is equal to or less than a predetermined acceleration threshold. The fourth condition is that that the hydraulic pressure of a hydraulic fluid supplied to a brake device of the work vehicle is less than a predetermined brake threshold.