Automatic Transmission Clutch Control for Unintended Downshifts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Unintended downshifts in automatic transmissions due to failures like a faulty rotation speed sensor can cause vehicle deceleration, leading to driver discomfort as the existing control systems fail to detect and mitigate such shifts effectively.
Innovation Solution
The automatic transmission system reduces the torque transmission capacity of the clutch when a high change rate of the driving source's rotation speed is detected, thereby relaxing the braking force and minimizing deceleration, using a transmission controller that adjusts hydraulic pressure to the clutch to prevent unintended downshifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the automatic transmission system uses conventional fail detection methods based on solenoid valve states or calculated speed ratios, then it can detect certain types of failures, but it cannot detect failures of rotation speed sensors that cause abnormal speed ratio calculations
Solution Approach 1:
The patent introduces an intermediary detection mechanism that monitors the change rate of driving source rotation speed as a mediator between the rotation speed sensor and the control system. This intermediary parameter (change rate) serves as a reliable indicator of abnormal downshifts caused by sensor failures, enabling detection without adding complex sensor arrays or redundant detection systems
Solution Approach 2:
The system implements feedback by continuously monitoring the change rate of driving source rotation speed and comparing it against predetermined thresholds. When the change rate exceeds the threshold, the system immediately responds by reducing clutch torque transmission capacity, creating a closed-loop feedback mechanism that detects and corrects abnormal downshifts in real-time
2Productivity
If the clutch maintains full torque transmission capacity during normal operation, then power transmission efficiency is maximized, but during unintended downshifts it causes excessive vehicle deceleration and driver discomfort
Solution Approach 1:
The patent applies dynamics by making the clutch torque transmission capacity adjustable rather than fixed. The control system dynamically modifies the clutch's torque transmission capacity based on real-time detection of driving source rotation speed change rates, allowing the system to optimize between power transmission efficiency and driver comfort by reducing torque capacity only when abnormal downshifts are detected
Solution Approach 2:
The system changes the operational parameter of the clutch (torque transmission capacity) in response to detected abnormal conditions. By modifying this parameter from full capacity to reduced capacity during unintended downshifts, the system eliminates excessive deceleration and driver discomfort while maintaining full capacity during normal operation for optimal power transmission
Data Source
AI summary
[PROBLEMS] To reduce a sense of discomfort given to a driver due to vehicle deceleration caused by a downshift that is not intended by the driver, which is caused by a failure of a rotation speed sensor or the like.[SOLUTIONS] An automatic transmission includes: a transmission mechanism configured to shift rotation of a driving source and transmit the rotation to a driving wheel; and a clutch configured to control transmission of a torque from the driving source to the driving wheel, wherein when a change rate of a rotation speed of the driving source is equal to or higher than a predetermined change rate, a torque transmission capacity of the clutch is reduced.