Selection Solenoid Valve Diagnosis for Rapid CVT Range Changes
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Solution Overview
Problem
Existing automatic transmission systems misjudge the selection solenoid valve as abnormal when a selecting operation across no-drive ranges is performed in a short time, due to incomplete drainage of clutch pressure, leading to false hydraulic pressure abnormalities.
Innovation Solution
Implementing a selection solenoid valve abnormality diagnosing unit that assesses the engagement time and operation speed conditions, specifically allowing abnormality diagnosis only when the no-drive range selection time exceeds a predetermined setting time and the turbine rotation speed meets certain threshold values, preventing misjudgment of maximum hydraulic pressure abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If abnormality diagnosis is performed based on engagement time alone, then abnormality detection capability is improved, but false positive rate increases due to rapid selecting operations
Solution Approach 1:
The system performs preliminary verification by checking whether the selector lever has remained in the no-drive range for a predetermined time period before allowing abnormality diagnosis to proceed. This preliminary action prevents rapid selecting operations from triggering false abnormality diagnoses, as the diagnosis is only permitted when the no-drive range selection time exceeds the predetermined threshold.
Solution Approach 2:
The system dynamically adjusts the diagnostic process based on the selecting operation speed. When rapid selecting operations are detected (selection time shorter than predetermined time), the abnormality diagnosis function is restricted. This dynamic adjustment allows the system to adapt to different operating conditions and avoid false positives while maintaining detection capability under normal conditions.
2Speed
If the selection solenoid valve controls engagement/disengagement in synchronization with selector lever operations, then responsiveness is improved, but misjudgment occurs during rapid range changes
Solution Approach 1:
Before performing abnormality diagnosis, the system checks whether the selector lever has remained in the no-drive range for a predetermined time. This preliminary verification ensures that the clutch pressure has been completely drained before diagnosis begins, preventing misjudgment during rapid range changes while maintaining the responsive control of the selection solenoid valve.
Solution Approach 2:
The system introduces an intermediate verification step (checking no-drive range selection time) between the selector lever operation and the abnormality diagnosis. This intermediary check acts as a buffer that prevents direct causation between rapid selecting operations and false abnormality judgments, allowing the solenoid valve to remain responsive while avoiding misjudgment.
Data Source
AI summary
Selection solenoid valve (75) controls engagement/disengagement of travel clutch (31, 32) in synchronization with a selecting operation of selector lever (90) that selects a range position of belt-type continuously variable transmission (CVT). Selection solenoid valve abnormality diagnosing unit (8a) is configured to, when performing a selecting operation from no-drive range to drive range, if a time required for travel clutch (31, 32) to be judged to be engaged from a start of selection of the drive range is less than a predetermined time, judge selection solenoid valve (75) to be a maximum hydraulic pressure side abnormality. When performing the selecting operation of drive range→no-drive range→drive range, if a selecting operation speed condition indicating that a no-drive range selection time is shorter than a setting time (Tth) is satisfied, execution of abnormality diagnosis of selection solenoid valve (75) is not permitted. With this configuration, misjudgment is prevented.