Working Vehicle Lockup Clutch Torque Control
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Solution Overview
Problem
In work vehicles, the sudden increase in vehicle speed when the lockup clutch switches from a non-connected to a connected state leads to unintended acceleration and reduced fuel economy, prompting operators to disable lockup clutch-switching control to maintain ease of operation.
Innovation Solution
Implementing a controller that manages engine torque curves differently based on the lockup clutch state, using a first engine torque curve during torque conversion travel and a second, reduced engine torque curve during lockup travel to inhibit sudden speed increases and improve fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lockup clutch is switched from non-connected state to connected state, then fuel economy is improved, but vehicle speed increases sharply causing unintended acceleration
Solution Approach 1:
The controller performs preliminary action by switching the lockup clutch to non-connected state before the vehicle reaches the switch speed, then delays the switching to connected state until after the vehicle has passed the switch speed. This anticipatory control prevents the sharp speed increase by ensuring the clutch engagement occurs when the vehicle is already moving at a higher speed, making the transition imperceptible to the operator.
Solution Approach 2:
The invention introduces dynamic control by making the lockup clutch switching decision dependent on real-time vehicle speed relative to the switch speed. Instead of a fixed switching point, the controller continuously monitors vehicle speed and adjusts the clutch state based on whether the current speed is below or above the switch speed, creating a dynamic response that adapts to changing operating conditions and prevents unintended acceleration.
2Use of energy by moving object
If lockup clutch-switching control is enabled, then fuel economy improves, but operator ease of operation decreases due to perceived unintended acceleration
Solution Approach 1:
By switching the lockup clutch to non-connected state before the vehicle reaches the switch speed, the controller prepares the system in advance. This preliminary action ensures that when the vehicle approaches the critical speed range, the clutch is already in the appropriate state to prevent perceptible speed changes, thereby maintaining operator comfort while preserving fuel economy benefits.
Solution Approach 2:
The controller continuously monitors vehicle speed and uses this feedback to determine the appropriate lockup clutch state. By comparing real-time vehicle speed with the switch speed threshold, the controller dynamically adjusts clutch engagement to eliminate perceptible speed changes, ensuring smooth operation that maintains operator ease of use while achieving fuel economy improvements.
Data Source
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AI summary
An objective of the present invention is to inhibit an increase in vehicle speed immediately after a lockup clutch has been switched from a non-connected state to a connected state, and to improve fuel economy. In a work vehicle, a controller controls an engine on the basis of an engine torque curve for defining a relationship between the engine speed, the engine output torque, and the operation amount of the accelerator operation member. The controller controls the engine on the basis of a first engine torque curve during torque conversion travel. The controller controls the engine on the basis of a second engine torque curve during lockup travel. The engine output torque of the second engine torque curve is less than the engine output torque of the first engine torque curve in at least a portion of the range of the engine speed when at least the operation amount of the accelerator operation member is a predetermined operation amount that is less than maximum.