Dog Clutch Backlash Compensation for Smooth EV Transmission Shifting
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Solution Overview
Problem
Existing control methods for engaging dog clutches in electrified transmissions suffer from increased noise, vibration, and wear due to grinding during shifting, and face challenges in accurately determining engagement positions due to axial clearance and misalignment.
Innovation Solution
A method that involves locking the transmission shaft, positioning the actuator at a prescribed position, commanding the electric machine to rotate, and updating the engagement threshold position based on the actuator's position, allowing for automatic compensation for degradation and backlash in the clutch system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If dog clutches are used in electrified transmissions, then dynamic performance is improved, but grinding during engagement increases noise, vibration, and wear
Solution Approach 1:
The system performs preliminary calibration to determine the actual engagement position of the dog clutch teeth before normal operation. This advance knowledge allows the control system to compensate for manufacturing variations and axial clearance, ensuring smooth engagement without grinding that causes noise, vibration, and wear.
Solution Approach 2:
The system uses feedback from the calibration process to continuously adjust the actuator positioning. By monitoring the actual engagement position and comparing it with the target position, the control system can make real-time corrections to eliminate grinding during shifting, thereby reducing noise, vibration, and wear on the clutch components.
2Reliability
If axial clearance is provided to permit relative motion, then wear is prevented, but engagement position accuracy decreases due to normal distribution variations
Solution Approach 1:
The system performs self-calibration by automatically determining the actual engagement position of the dog clutch teeth during a calibration routine. This self-service approach eliminates the need for external specialized equipment and allows the system to compensate for its own manufacturing variations and axial clearance, maintaining both wear prevention and engagement accuracy.
Solution Approach 2:
The system changes the operational parameters by adjusting the actuator position based on the calibrated engagement position. By modifying the positioning parameters dynamically rather than relying on fixed manufacturer specifications, the system can account for axial clearance variations and maintain precise engagement while still permitting the relative motion needed to prevent wear.
3Manufacturing precision
If individual calibration is performed to reduce grinding, then engagement accuracy improves, but manufacturing time increases
Solution Approach 1:
The system performs self-calibration using its own control unit and actuator without requiring external specialized calibration equipment. This self-service capability allows individual calibration to be performed quickly and efficiently during the manufacturing process, improving engagement accuracy while minimizing the time loss compared to traditional calibration methods.
Solution Approach 2:
The system replaces complex mechanical calibration equipment with a software-based calibration routine executed by the control unit. By substituting mechanical calibration tools with an electronic control process, the system achieves precise engagement calibration without the time-consuming setup and operation of specialized mechanical equipment.
4Measurement precision
If special equipment is used to calibrate controller and actuator, then positioning accuracy improves, but device complexity increases
Solution Approach 1:
The control unit and actuator perform self-calibration using internally available sensors and actuators without requiring external specialized calibration equipment. This self-service approach maintains high positioning accuracy while dramatically reducing device complexity by eliminating the need for separate calibration tools and equipment.
Solution Approach 2:
The control unit is designed to serve multiple functions: it controls normal transmission operation, performs calibration routines, and processes engagement position data. By making the control unit universal and multi-functional, the system eliminates the need for separate dedicated calibration equipment, thereby maintaining positioning accuracy while reducing overall device complexity.
Data Source
AI summary
A method for controlling an engagement of a dog clutch in an electrified drivetrain, comprising: locking a shaft of a transmission; positioning an actuator of the transmission at a prescribed position; commanding an electric machine to rotate at a speed; and updating the engagement threshold position when the electric machine stalls based on the prescribed position of actuator.