Automatic Transmission Upshift Control Under Lockup Clutch Slip
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Solution Overview
Problem
Existing automatic transmission systems struggle to perform upshifts under high engine rotation speeds, especially when a large acceleration request is made by the driver, due to differences in engine and input shaft rotation speeds caused by the lockup clutch's engagement or slipping state.
Innovation Solution
The automatic transmission system includes a torque converter with a lockup clutch and a variator that adjusts the speed ratio between the input and output shafts, where upshift is initiated when the input shaft reaches a specific rotation speed, with the initiation speed adjusted based on the lockup clutch's engagement state and output torque, allowing for higher engine rotation speeds during acceleration requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If upshift is performed based on input shaft rotation speed with a fixed margin when lockup clutch is disengaged or slipping, then excessive increase in engine rotation speed is suppressed, but upshift cannot be performed under high engine rotation speed when acceleration request is large
Solution Approach 1:
The patent applies dynamics by making the rotation speed margin a variable parameter rather than a fixed value. The control device dynamically adjusts the margin based on detected engine output torque: when torque is large (indicating high acceleration request), the margin is reduced to allow upshift at higher engine speeds; when torque is small, the margin is increased to suppress excessive speed increases. This dynamic adjustment resolves the contradiction between achieving high-speed upshift and maintaining control accuracy.
Solution Approach 2:
The patent changes the parameter of rotation speed margin based on engine output torque conditions. By linking the margin parameter to torque detection, the system adapts the upshift control strategy to current operating conditions, allowing the same upshift mechanism to serve both purposes: suppressing excessive speed increases during normal operation and enabling high-speed upshift during acceleration requests.
2Productivity
If upshift is performed at lower rotation speed to account for lockup clutch slip, then engine rotation speed excessive increase is prevented, but responsiveness to driver acceleration request is reduced
Solution Approach 1:
The system changes the control parameter (rotation speed margin) based on torque conditions that reflect driver acceleration requests. When the driver requests strong acceleration (indicated by large engine torque), the system reduces the margin parameter, allowing upshift to occur at higher engine speeds and improving responsiveness. This parameter adaptation allows the system to respond appropriately to varying driver intentions.
Solution Approach 2:
The control device uses feedback from engine output torque detection to adjust upshift timing. By continuously monitoring torque and using this information to modify the rotation speed margin, the system creates a closed-loop control that responds to actual operating conditions, including driver acceleration requests, thereby improving productivity without excessive energy loss.
Data Source
AI summary
[PROBLEMS] When an acceleration request from a driver is large, upshift is performed under a high engine rotation speed.[SOLUTIONS] Provided is an automatic transmission, including: a torque converter that is disposed downstream of a drive source in a power transmission path and is provided with a lockup clutch; and a transmission mechanism that is disposed downstream of the torque converter and changes a speed ratio between an input shaft and an output shaft, in which in a state where the lockup clutch is engaged, when a rotation speed of the input shaft reaches a first rotation speed, the automatic transmission starts upshift, and in a state where the lockup clutch is disengaged or slips, when the rotation speed of the input shaft reaches a second rotation speed obtained by subtracting a first predetermined rotation speed from the first rotation speed, the automatic transmission starts upshift, and the first predetermined rotation speed decreases as an output torque of the drive source increases.