Standstill Clutch Torque Checking Using Electric Motor Slip
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Solution Overview
Problem
In electric or hybrid motor vehicles, multi-plate clutches experience deviations in torque transmission due to factors like friction coefficient changes caused by water or contaminants, leading to potential safety issues and reduced driving comfort, as existing methods fail to accurately assess positioning accuracy without additional component expenditure.
Innovation Solution
A method involving holding a shaft stationary and using an electric machine to set and compare a defined setpoint torque, either by accelerating to the first slip or maintaining a constant speed, to assess clutch positioning accuracy, allowing for identification of deviations and implementation of correction measures, including detection of water penetration in wet-running clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch positioning accuracy is not checked, then the device complexity remains low, but the reliability deteriorates due to unmonitored torque transmission deviations
Solution Approach 1:
The clutch system performs self-diagnosis by using its own actuator to generate test torques and comparing expected versus actual torque transmission. The control unit leverages existing sensors and actuators to monitor clutch performance without requiring external testing equipment, enabling the system to self-verify its operational accuracy.
Solution Approach 2:
The method involves dynamically changing operational parameters by varying the actuator position and measuring the corresponding torque transmission at different operating points. By systematically varying these parameters and comparing measured values against expected values, the system detects deviations in clutch positioning accuracy without additional hardware.
2Measurement precision
If additional sensors or measurement devices are added to check clutch accuracy, then the measurement precision improves, but the device complexity and cost increase
Solution Approach 1:
The system uses existing components (actuator, sensors already present in the clutch assembly) to perform measurements. The control unit processes data from these existing sensors to determine clutch positioning accuracy, eliminating the need for additional dedicated measurement devices while maintaining high measurement precision.
Solution Approach 2:
Existing sensors and actuators in the clutch system are made multi-functional by using them both for normal operation and for diagnostic measurements. The actuator serves both to engage/disengage the clutch and to perform positioning accuracy tests, while existing sensors monitor both operational parameters and diagnostic data.
3Reliability
If the clutch is checked frequently, then the reliability improves through early error detection, but the productivity decreases due to repeated testing interruptions
Solution Approach 1:
The clutch positioning accuracy check is performed periodically at predetermined intervals or under specific operating conditions rather than continuously. This periodic monitoring approach ensures reliable detection of positioning deviations while minimizing interruptions to normal vehicle operation and maintaining productivity.
Solution Approach 2:
The system performs preliminary checks during normal operation to detect potential issues before they lead to failures. By monitoring clutch positioning accuracy proactively during regular use, the system can identify and address problems early without requiring separate dedicated testing sessions that would interrupt productivity.
Data Source
AI summary
Methods are provided for checking the actuating accuracy of a clutch arranged in a force flow between a fixable shaft and an electric machine of an electric or hybrid motor vehicle when at a standstill. One method includes: fixing the shaft, setting a defined setpoint torque on the clutch to be checked, continuously ramping up the electric machine up until the first slipping of the clutch, comparing the achieved torque of the electric machine with the setpoint torque preset on the clutch. Another method includes: fixing the shaft, ramping up the electric machine to a defined rotational speed, setting a defined setpoint torque on the clutch to be checked, comparing the torque of the electric machine needed to maintain a constant rotational speed with the setpoint torque set on the clutch.