Transmission Shift Crank Arm Metal Casting and Polymeric Member
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Solution Overview
Problem
The existing manufacturing processes for transmission shift mechanism crank arms are costly and prone to inconsistencies due to the staking of ball components, which can lead to positional inaccuracies and failure, especially when using injection molded plastic that lacks the strength for durable sliding engagement with camming slots.
Innovation Solution
A polymeric member is moveably coupled with a unitary metal casting, allowing rotational disposition and axial capture, facilitating a more efficient and cost-effective assembly process by eliminating the need for complex machining and staking operations, and enabling the use of injection molded parts that can withstand rolling engagement with camming slots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a staking process is used to fix the ball component on the arm portion, then manufacturing cost is reduced, but positional precision and reliability deteriorate due to over/under staking and ball separation
Solution Approach 1:
The ball component and arm portion are combined into a single unitary metal casting, eliminating the need for separate ball component attachment processes. This merging resolves the contradiction by removing the staking process entirely, thereby eliminating positional precision issues while maintaining cost-effectiveness through integrated manufacturing.
Solution Approach 2:
The invention uses a composite structure where a polymeric member is integrated with a metal casting. The metal casting provides the structural strength and precision positioning, while the polymeric member provides self-lubricating properties. This composite approach resolves the contradiction by combining materials that individually address different requirements.
2Ease of manufacture
If injection molded plastic is used for the ball component, then manufacturing cost is reduced, but strength and durability worsen due to differential cooling reducing strength near the exterior surface
Solution Approach 1:
The invention replaces the injection molded plastic ball with a unitary metal casting that provides the necessary strength. The metal material eliminates the differential cooling issue inherent in injection molding, while maintaining cost-effectiveness through efficient casting processes. The self-lubricating properties are achieved through the metal-polymer interface rather than relying on plastic material properties.
Solution Approach 2:
The invention changes the material parameter from injection molded plastic to metal casting, fundamentally altering the manufacturing process and material properties. This parameter change resolves the strength issue by using material (metal) that does not suffer from differential cooling weaknesses, while maintaining manufacturing efficiency through casting processes.
3Device complexity
If the ball component is non-rotatably fixed on the arm portion, then manufacturing complexity is reduced, but wear and reliability worsen due to sliding engagement with the camming slot
Solution Approach 1:
The invention transitions from a static, non-rotating ball component to a dynamic system where the polymeric member can rotate on the metal casting. This rotational movement changes the engagement mode from sliding to rolling, significantly reducing wear and improving durability while maintaining simple assembly through the unitary casting structure.
Solution Approach 2:
The invention changes the motion parameter of the ball component from fixed/non-rotating to rotatable. This parameter change transforms the engagement mechanism from sliding contact to rolling contact, resolving the contradiction by reducing wear and improving reliability while the unitary casting maintains assembly simplicity.
4Manufacturing precision
If machining is used to form the ball component from extruded plastic, then dimensional precision is improved, but manufacturing cost increases
Solution Approach 1:
The invention merges the ball component formation with the arm portion manufacturing into a single unitary metal casting process. This eliminates the need for separate extrusion and machining operations, resolving the contradiction by achieving dimensional precision through the casting process itself while significantly reducing manufacturing cost through process integration.
Solution Approach 2:
The invention changes the manufacturing process parameter from machining extruded plastic to metal casting. This parameter change resolves the contradiction by using a casting process that inherently provides the necessary dimensional precision without requiring costly subsequent machining operations.
Data Source
AI summary
An assembly includes a polymeric member and a unitary metal casting. The metal casting is engaged with and relatively moveably capturing the polymeric member on the metal casting. The polymeric member includes an opening extending through the polymeric member. The opening defines a rotational axis of the polymeric member and includes a central cylindrical portion and first and second end portions having diameters greater than the central cylindrical portion. The first and second end portions are disposed proximate opposite ends of the opening, and the metal casting substantially fills the central cylindrical portion and the first and second end portions of the opening, thereby rotatably disposing and axially capturing the polymeric member on the metal casting. The assembly can be adapted for use as a crank arm in a transmission shift mechanism.