Lock-up Clutch Control for Second-Time Kick-Down Acceleration
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Solution Overview
Problem
Drivers experience a sense of incongruity due to insufficient acceleration during second-time kick-down requests in vehicles with automatic transmissions, as the down-shift amount is limited to avoid high engine noise and immediate up-shift, leading to inadequate torque amplification.
Innovation Solution
A vehicle control apparatus with a kick-down controller and a lock-up controller that adjusts the disengagement condition for the lock-up clutch based on accelerator operation and down-shift amount conditions, easing the disengagement condition for second-time kick-down requests and performing pressure reduction control in the preceding stages of both normal and second-time kick-down requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the down-shift amount is increased to provide sufficient acceleration feeling during second-time kick-down request, then the acceleration performance is improved, but the engine noise increases and immediate up-shift occurs
Solution Approach 1:
The patent changes the disengagement condition parameters for the lock-up clutch based on the kick-down request type. For second-time kick-down requests, the disengagement condition is eased (lower threshold values), allowing the lock-up clutch to disengage more readily. This enables sufficient acceleration feeling through torque converter slip without requiring excessive down-shift amount that would cause high engine noise and immediate up-shift.
2Power
If the lock-up clutch is disengaged during kick-down control, then the torque amplification effect is achieved, but the fuel efficiency decreases
Solution Approach 1:
The patent dynamically adjusts the lock-up clutch control strategy based on the kick-down request type. For normal kick-down requests, the lock-up clutch is disengaged to provide torque amplification. For second-time kick-down requests, the disengagement condition is eased, allowing the lock-up clutch to remain engaged longer, thereby reducing torque converter slip and improving fuel efficiency while still providing sufficient acceleration feeling.
3Speed
If the disengagement condition for lock-up clutch is eased for second-time kick-down request, then the acceleration feeling is improved, but the clutch wear increases
Solution Approach 1:
The patent selectively eases the disengagement condition parameters (threshold values) only for second-time kick-down requests, not for all kick-down operations. This targeted parameter change provides improved acceleration feeling when needed while limiting the frequency and duration of lock-up clutch disengagement, thereby reducing overall clutch wear and extending clutch life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances acceleration response and improves the driver's feeling of kick-down control by more likely disengaging the lock-up clutch during second-time requests, thereby better reflecting the driver's intention and reducing the sense of incongruity, while maintaining fuel efficiency and clutch life.
Implementation Method 1
lock-up disengagement (engagement of the lock-up clutch is disengaged) along with the down-shift is performed, thereby producing a torque amplification effect by the torque converter
Implementation Method 2
automatic transmission having a torque converter provided with a lock-up clutch
Data Source
AI summary
A vehicle control apparatus for a vehicle including an automatic transmission having a torque converter provided with a lock-up clutch, and including a kick-down controller that performs kick-down control to change a transmission ratio to a low side and to increase a number of engine revolutions based on a kick-down request in accordance with an accelerator operation and a lock-up controller that performs lock-up disengagement control based on the kick-down request to set the lock-up clutch to a disengaged state according to meeting of a disengagement condition. When the kick-down request not during the kick-down control is called a normal kick-down request and the kick-down request during the kick-down control is called a second-time kick-down request, the lock-up controller performs lock-up disengagement control according to the second-time kick-down request based on the disengagement condition which is more eased than the disengagement condition used for the normal kick-down request.