Vehicle Clutch State Detection Using Rotation Speed Difference
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Solution Overview
Problem
In vehicles with an engine, a first motor generator, a second motor generator, and a differential device, determining whether a power transmission shut-off state is established is challenging due to potential vibration and noise from torque transmission, and existing solutions require additional sensors, increasing component count and manufacturing costs.
Innovation Solution
A vehicle system that includes an electronic control unit to manage the first and second motor generators and a clutch, controlling the rotation speed difference between the input and output shafts to determine the power transmission shut-off state without a clutch sensor, suppressing engine cranking when the state is not established, and controlling the second motor generator to generate torque lower than rolling resistance to prevent vehicle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is added to detect clutch state, then determination accuracy of power transmission shut-off state is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The system uses existing sensors (rotation speed sensors for input shaft and output shaft) to determine clutch state and power transmission shut-off state. The control unit calculates rotation speed difference between input and output shafts, and based on this calculation and predetermined thresholds, determines whether the clutch is engaged or disengaged. This self-service approach eliminates the need for additional clutch state sensors while maintaining determination accuracy.
Solution Approach 2:
The existing rotation speed sensors, originally designed for other control functions, are utilized multi-functionally to also detect clutch state. By calculating the rotation speed difference between input and output shafts, the system extracts clutch state information from data already being collected for other purposes, avoiding additional hardware requirements.
2Use of energy by moving object
If engine cranking is performed when power transmission shut-off state is not established, then battery charging is achieved, but vibration and noise occur due to torque transmission to drive wheels
Solution Approach 1:
The control unit continuously monitors the rotation speed difference between input shaft and output shaft to determine clutch state in real-time. Based on this feedback, it decides whether to permit engine cranking. When the clutch is determined to be engaged (power transmission shut-off state not established), the control unit suppresses engine cranking to prevent harmful torque transmission to drive wheels, while still allowing cranking when the clutch is disengaged.
Solution Approach 2:
The system performs preliminary determination of clutch state by calculating rotation speed difference before allowing engine cranking to occur. This preliminary check prevents the harmful effect of torque transmission by suppressing cranking commands when the clutch is engaged, thereby avoiding vibration and noise before they can occur.
3Power
If torque of second motor generator is increased to provide reaction force, then engine starting capability is improved, but torque transmission to drive wheels causes vibration and noise
Solution Approach 1:
The control unit monitors clutch state through rotation speed difference feedback and uses this information to control the second motor generator. When the clutch is determined to be engaged, the control unit suppresses second motor generator operation that would generate torque, even if engine starting is requested. This feedback-based control ensures engine starting capability is maintained when appropriate while preventing harmful torque transmission when clutch is engaged.
Data Source
AI summary
A vehicle includes an engine, a first motor generator, a second motor generator, a transmission, a differential device, and an electronic control unit. The transmission includes an input shaft, an output shaft, and a clutch. The electronic control unit is configured to detect a rotation speed difference between the input shaft and the output shaft when the clutch is controlled so as to be brought into a power transmission shut-off state. The electronic control unit is configured to, when the rotation speed difference detected by the electronic control unit is smaller than a target rotation speed difference between the input shaft and the output shaft that occurs in a case where the power transmission shut-off state of the clutch is established, suppress cranking of the engine by the first motor generator.