Dual-Drive Actuator With Coupling Device For Fail-Safe Parking
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Solution Overview
Problem
Existing electronic transmission range selectors in vehicles lack a reliable fail-safe mechanism to securely place the vehicle in park mode in case of actuator power source failures or electrical conductor malfunctions.
Innovation Solution
A dual-drive system transmission system with a primary drive system for normal operation and a secondary fail-safe drive system powered independently, using a coupling device with a drive ring and carrier to ensure the vehicle transmission is returned to the park range in case of abnormal operation or power failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single actuator is used for transmission range selection, then the device complexity is reduced, but the reliability fails to ensure secure parking in case of power source or electrical conductor failures
Solution Approach 1:
The transmission range selection system is segmented into two independent actuators: a primary actuator for normal operation and a secondary actuator for fail-safe operation. This segmentation allows the system to maintain reliability by having redundant components while managing complexity through clear functional separation and independent operation of each actuator subsystem.
2Reliability
If a dual-drive system with independent power sources is implemented, then the reliability is improved for fail-safe operation, but the device complexity and space requirement increase
Solution Approach 1:
The secondary actuator and its independent power source are pre-configured and ready for immediate operation in case of primary system failure. This preliminary preparation ensures that fail-safe operation can be executed without delay or additional complexity during emergency situations, as all components are already in place and configured.
Solution Approach 2:
A coupling device with a drive ring and carrier is introduced as an intermediary mechanism to coordinate the operation of both actuators. The coupling device manages the complexity by providing a unified interface for controlling the output shaft, allowing either actuator to independently drive the transmission range selector through the same mechanical pathway.
3Ease of operation
If the drive ring provides lost motion relative to the carrier during normal operation, then the ease of operation is improved for the primary actuator, but the mechanism complexity increases for the coupling device
Solution Approach 1:
The coupling device incorporates dynamic characteristics by allowing the drive ring to rotate independently of the carrier during normal primary actuator operation, providing lost motion capability. This dynamic design enables the system to easily accommodate primary actuator movement while the secondary actuator remains disengaged, and seamlessly transitions to engaged operation when fail-safe mode is activated.
Data Source
AI summary
An electronic transmission range select actuator (ETRSA) includes two independent drive systems that are each able to actuate a common shaft, for example an output shaft of the ETRSA, via a coupling device disposed between and connecting the gear trains of each system. The first drive system of the two independent drive systems is used during normal vehicle operation to change the transmission gear range to a desired gear range. The second drive system is used in case of abnormal operation of the first drive system to return the vehicle transmission to the park transmission range.