Vehicle Transmission Default-to-Park Mechanism
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Solution Overview
Problem
Shift-by-wire vehicle transmissions often experience delays in achieving commanded transmission states, and there is a need for a mechanism to default to park mode during predetermined events without extended delays.
Innovation Solution
A mechanism featuring a rotatable plate, latching mechanism, and biasing member that overrides operator selections to shift the transmission to park mode, utilizing a coaxial configuration where the plate and output member interfere with each other to ensure rapid return to park position upon release from the latching mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shift-by-wire transmission system is used to enable flexible gear selection, then the transmission can be controlled electronically with multiple modes, but delays occur in achieving commanded transmission states and defaulting to park mode
Solution Approach 1:
The biasing member (spring) is pre-loaded to store energy that automatically acts to rotate the output member to the park position when the latching mechanism releases. This preliminary storage of mechanical energy enables immediate action without delay when the default-to-park function is activated, resolving the time delay issue while maintaining electronic control flexibility.
2Speed
If a mechanical default-to-park mechanism is added to override electronic control, then rapid return to park is achieved, but the device complexity and packaging space increase
Solution Approach 1:
The default-to-park mechanism is integrated into the existing shift-by-wire transmission structure. The rotatable plate is coupled to the output member, and the latching mechanism interfaces with the electronic control system. This merging of mechanical override components with the electronic control architecture achieves rapid park return while minimizing additional complexity and packaging space requirements.
Solution Approach 2:
The rotatable plate serves multiple functions: it transmits rotational motion from the output member to the mode selector, provides a mounting surface for the latching mechanism, and works with the biasing member to enable rapid park return. This multi-functionality reduces the number of separate components needed, addressing the device complexity concern.
3Area of stationary object
If the plate and output member are configured to interfere with each other in a coaxial arrangement, then minimal packaging space is used, but the mechanical interference complexity increases
Solution Approach 1:
The coaxial arrangement positions the rotatable plate and output member along the same rotational axis, utilizing the axial dimension rather than requiring lateral space. This dimensional arrangement allows the mechanical interference elements to engage radially while keeping the overall packaging footprint minimal, effectively resolving the space versus complexity trade-off.
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
Enables the transmission to default to park mode during predetermined events while achieving commanded states quickly, using minimal packaging space and few components, thus addressing the delay issue in shift-by-wire systems.
Implementation Method 1
The biasing member biases the plate to rotate in the second direction of rotation to return the output member to the park position when the plate is released by the latching mechanism.
Data Source
AI summary
A default-to-park mechanism for a transmission includes an output member, a rotatable plate, a latching mechanism, and a biasing member. The output member is rotatable to park, reverse, neutral, and drive positions. The rotatable plate is coaxial with the output member. The plate and the output member interfere with one another such that the plate is moved in a first direction of rotation by the output member and the output member is moved in a second direction of rotation by the plate. The plate is releasably held by the latching mechanism to prevent rotation in the second direction of rotation when the output member is in the reverse, neutral, and drive positions. The biasing member biases the plate to rotate in the second direction of rotation to return the output member to the park position when the plate is released by the latching mechanism.