Roller Park Gear Locking for Fail-Safe Shift-by-Wire Parking
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Solution Overview
Problem
Existing shift by wire systems for automatic transmissions are bulky, complex, and expensive due to the need for external electromechanical actuators and sensors to ensure defaulting to park in power loss situations and maintaining out-of-park configurations despite single element failures.
Innovation Solution
A shift by wire parking system utilizing a roller-parking gear mechanism actuated by an electromechanical actuator and held in place by a latching solenoid and spring, which includes a circumferential body that locks the park gear in position, reducing the need for external components and simplifying the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external electromechanical actuators with motors, sensors, and controllers are mounted outside the transmission housing to ensure default-to-park functionality and maintain out-of-park configuration during failures, then reliability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent combines the parking mechanism and default-to-park functionality into a single integrated assembly housed within the transmission housing. The spring-loaded circumferential bodies automatically engage with the park gear teeth when the electromechanical actuator fails or power is lost, eliminating the need for separate external safety systems while maintaining reliability.
Solution Approach 2:
The spring-loaded circumferential bodies provide automatic fail-safe engagement without requiring external sensors or controllers. When power is lost or the actuator fails, the springs automatically drive the circumferential bodies into engagement with the park gear teeth, achieving default-to-park functionality through self-actuating mechanical means.
2Reliability
If external electromechanical actuators with motors and sensors are used to maintain out-of-park configuration during single element failures, then reliability is improved, but the system becomes bulky and expensive
Solution Approach 1:
The patent integrates the fail-safe mechanism directly into the parking assembly within the transmission housing, combining the actuator, springs, and locking components into a compact unified system. This eliminates the need for bulky external actuators and sensors while maintaining the ability to maintain out-of-park configuration during failures.
Solution Approach 2:
The spring-loaded circumferential bodies automatically maintain engagement with the park gear teeth during failures without requiring external sensors or control systems. The mechanical self-latching mechanism provides fail-safe operation while occupying minimal space within the transmission housing.
3Reliability
If external electromechanical actuators with multiple components are mounted outside the transmission housing to provide all required features, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent consolidates multiple functions (parking, default-to-park, and fail-safe operation) into a single integrated assembly that can be manufactured as one unit. This eliminates the need for separate external components, reducing part counts, assembly steps, and manufacturing costs while maintaining all required reliability features.
Solution Approach 2:
The spring-loaded circumferential bodies provide automatic fail-safe functionality without requiring expensive external sensors, controllers, or backup actuators. This mechanical self-service approach significantly reduces component costs while ensuring reliable default-to-park operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a compact, cost-effective, and reliable shift by wire parking system that defaults to park in power loss situations and maintains out-of-park configurations without the need for external actuators, enhancing vehicle safety and reducing system complexity.
Implementation Method 1
a spring directly coupled to the engagement pin and movable between the locked pin position and the unlocked pin position
Implementation Method 2
a solenoid actuator configured to move the engagement pin between the locked pin position and the unlocked pin position
Data Source
AI summary
A shift by wire parking system includes a park gear including a gear body and a plurality of teeth. The teeth are circumferentially spaced from one another. The park gear defines a plurality of void spaces between each pair of the plurality of teeth. The shift by wire parking system includes a circumferential body sized to fit inside each of the plurality of void spaces to lock a position of the park gear. The circumferential body is movable towards and away from the park gear between an engaged position and a disengaged position. In the disengaged position, the circumferential body is disposed outside each of the plurality of void spaces, thereby allowing the park gear to rotate. In the engaged position, the circumferential body is disposed inside one of the void spaces to lock the position of the park gear.