Pawl Return Spring With Inactive Coils For Transmission Assembly
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Solution Overview
Problem
Existing park brake assemblies for automatic transmissions face challenges in proper assembly and alignment of the park pawl due to the design of return springs with active coils, which can complicate installation and require complex machined surfaces within the transmission housing.
Innovation Solution
A pawl return spring with both active and inactive coil regions is introduced, where the active coil region biases the park pawl out of engagement and the inactive coil region aids in alignment and installation by providing a positioning feature without additional grounding, allowing for easier assembly and reduced tool complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a return spring with only active coils is used to bias the park pawl, then the park pawl can be biased out of engagement, but proper alignment and positioning of the park pawl during assembly becomes difficult
Solution Approach 1:
The return spring is segmented into two distinct functional regions: an active coil region that provides biasing force and an inactive coil region that provides alignment and positioning. This segmentation allows each region to independently perform its specific function, resolving the contradiction between biasing capability and assembly alignment.
Solution Approach 2:
Different portions of the return spring are given different properties: the active coil region has torsional flexibility for biasing, while the inactive coil region has structural rigidity for alignment. This local differentiation of properties enables the single component to simultaneously address both biasing and alignment requirements.
2Manufacturing precision
If additional grounding surfaces are added to the transmission housing for proper spring alignment, then alignment precision improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The return spring is designed to be self-aligning through its inactive coil region, which inherently provides positioning features during assembly. This eliminates the need for additional grounding surfaces or alignment features in the transmission housing, allowing the spring to self-position without external assistance.
Solution Approach 2:
The inactive coil region serves multiple functions: it provides structural support, enables alignment during assembly, and maintains positioning without requiring additional components or housing modifications. This multi-functionality reduces overall device complexity while achieving precise alignment.
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 dual coil design simplifies the return spring's design, improves installation by reducing the need for machined surfaces, and maintains proper alignment and preload of the park pawl, enhancing the overall efficiency and ease of assembly within the transmission housing.
Implementation Method 1
The active coils of the grounded return spring bias the park pawl away from the park gear during operation of the vehicle while it is not in 'park.'
Implementation Method 2
A pawl return spring is provided with a positioning and alignment feature to aid in proper assembly of the park pawl during assembly of automotive transmissions.
Data Source
AI summary
A pawl return spring includes a surface contacting portion adapted to contact a transmission housing. The surface contacting portion includes a first connection region and a second connection region opposite the first connection region. The pawl return spring includes an active coil region connected to the first connection region and disposed about a central longitudinal axis to provide torsional effort to the system. The pawl return spring also includes an inactive coil region connected to the second connection region and disposed about the central longitudinal axis that does not provide torsional effort to the system.