Gearshift Controller Torque Converter Speed Ratio Excavation
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Solution Overview
Problem
Industrial vehicles like wheel loaders experience inadequate driving force during excavation work due to automatic upshifts when the torque converter speed ratio is large, leading to insufficient power when trying to dart at earth and sand at lower speeds.
Innovation Solution
A gearshift controller that includes a speed ratio detection unit and a gearshift control unit, which allows manual downshift to the first speed for a predetermined time period upon operator instruction, preventing undesirable upshifts based on torque converter speed ratios, ensuring sufficient driving force is maintained during excavation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If automatic gearshift control is performed based on torque converter speed ratio, then fuel efficiency is improved, but driving force becomes insufficient during excavation work requiring low-speed operation
Solution Approach 1:
The gearshift control system dynamically adjusts its behavior based on operational context. During excavation work, when the operation lever is operated, the system transitions from automatic speed-ratio-based control to manual override mode, allowing the driver to maintain first speed for extended periods despite torque converter conditions that would normally trigger upshifts. This dynamic adaptation resolves the contradiction by enabling fuel-efficient automatic control during normal operation while permitting manual intervention when maximum driving force is required.
Solution Approach 2:
The system changes the control parameter threshold by introducing a time-based condition. When the operation lever is operated, the gearshift control unit maintains first speed regardless of the torque converter speed ratio for a predetermined time period. This parameter change allows the system to override the normal speed-ratio-based control logic, preventing upshifts that would reduce driving force during critical excavation moments while maintaining fuel efficiency during normal operation.
2Loss of energy
If upshift is performed when torque converter speed ratio is large, then transmission efficiency is improved, but driving force becomes insufficient before reaching the work position
Solution Approach 1:
The system applies preliminary anti-action by preemptively preventing upshifts when excavation work is anticipated. When the operation lever is operated, the gearshift control unit locks the transmission in first speed for a predetermined time period, counteracting the automatic upshift command that would otherwise be generated by the torque converter speed ratio. This preliminary prevention ensures driving force is maintained before the vehicle reaches the work position, while transmission efficiency is preserved during normal non-excitation operation.
3Power
If manual downshift to first speed is allowed during excavation, then driving force is sufficient, but automatic gearshift control based on speed ratio becomes ineffective
Solution Approach 1:
The system dynamically switches between automatic and manual control modes based on the operation lever state. When the operation lever is not operated, automatic gearshift control based on torque converter speed ratio is fully active. When the operation lever is operated, the system transitions to manual override mode where first speed is maintained for a predetermined time period. This dynamic switching resolves the contradiction by allowing manual downshift during excavation while preserving automatic control for normal operation.
Data Source
AI summary
A gearshift controller for an industrial vehicle, includes: a speed ratio detection unit that detects a speed ratio of speeds of an input axis and of an output axis of a torque converter; a gearshift control unit that shifts up a speed stage when the detected speed ratio is equal to or more than a first predetermined value and shifts down the speed stage when the detected speed ratio is equal to or less than a second predetermined value, which is smaller than the first predetermined value; and an operation member with which a downshift to the first speed is instructed by operation thereof by an operator. When the downshift is instructed by the operationmember, the gearshift control unit controls the speed stage to be kept at the first speed for a predetermined time period regardless of the speed ratio detected by the speed ratio detection unit.