Motor Control Device for Working Vehicle Speed Ratio Adaptation
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Solution Overview
Problem
Existing motor control devices for wheel loaders restrict engine rotational speed, leading to insufficient travel driving force and reduced mobility and workability.
Innovation Solution
A motor control device that adjusts engine maximum rotational speed based on the torque converter speed ratio, restricting it more in the acceleration region to provide sufficient driving force while maintaining engine speed restriction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If engine rotational speed is restricted, then fuel economy is improved, but travel driving force becomes insufficient and mobility is reduced
Solution Approach 1:
The patent applies dynamics by making the engine maximum rotational speed variable rather than fixed. The control device dynamically adjusts the engine speed limit based on the torque converter speed ratio - allowing higher speeds when the ratio indicates acceleration needs, and enforcing stricter limits when the ratio indicates cruising conditions. This dynamic adjustment resolves the contradiction by adapting the restriction level to actual driving conditions.
Solution Approach 2:
The patent changes the parameter of engine maximum rotational speed based on the torque converter speed ratio. By using the speed ratio as a reference, the system adjusts the engine speed parameter to achieve optimal balance between fuel economy and driving force. When the torque converter speed ratio indicates acceleration region, the engine speed limit is raised to provide sufficient driving force; when in non-acceleration region, the limit is lowered to improve fuel economy.
2Loss of energy
If engine rotational speed is restricted, then fuel economy is improved, but mobility and workability are reduced
Solution Approach 1:
The system dynamically adjusts engine speed restrictions based on real-time torque converter speed ratio measurements. This allows the system to maintain high mobility and workability when needed (by allowing higher engine speeds during acceleration) while achieving fuel economy benefits during steady-state operation, thus resolving the contradiction between fuel economy and productivity.
Solution Approach 2:
The engine maximum rotational speed parameter is changed according to the torque converter speed ratio. This parameter adjustment strategy enables the system to maintain productivity by allowing higher speeds when the torque converter indicates acceleration requirements, while improving fuel economy when the ratio indicates cruising conditions, thus balancing both objectives.
3Device complexity
If engine rotational speed is restricted uniformly, then engine speed control is simplified, but acceleration performance is reduced
Solution Approach 1:
The patent changes the engine maximum rotational speed parameter based on the torque converter speed ratio. By using the speed ratio as a reference parameter, the system implements a relatively simple control logic that adjusts engine speed limits to maintain acceleration performance while still providing fuel economy benefits, avoiding the need for complex multi-parameter control systems.
Data Source
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AI summary
A motor control device for a working vehicle includes: a rotational speed control device that controls a rotational speed of a motor in accordance with an operation amount of an accelerator pedal; a travel drive device that transmits rotation of the motor to wheels through a torque converter and a transmission; a speed ratio detection device that detects a speed ratio of an input shaft and an output shaft of the torque converter; and a speed restriction device that restricts a maximum rotational speed of the motor in accordance with a speed ratio detected by the speed ratio detection device. In the motor control device for a working vehicle, the speed restriction device restricts the maximum rotational speed when a detected speed ratio is in an acceleration region of the rotational speed of the motor to less than the maximum rotational speed when a detected speed ratio is in a non-acceleration region.