Ball Joint Torque Control via Induction Heating
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Solution Overview
Problem
The existing ball joint manufacturing methods face challenges in accurately managing the tightening torque of the housing acting on the ball section due to resin shrinkage during injection molding, making it difficult to maintain clearance accuracy and torque management.
Innovation Solution
A method involving induction heating of the ball section to a temperature above the glass transition point of the resin but below the melting point, followed by cooling, is repeated while rotating the ball stud, to create a consistent gap between the ball section and the housing, allowing for precise torque adjustment without using a ball seat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If injection molding is performed with resin material to form the housing, then the housing is formed to cover the ball section, but the resin shrinkage makes it difficult to ensure clearance accuracy between the ball section and the ball seat
Solution Approach 1:
The invention removes the ball seat component from the housing structure. Instead of having a ball seat installed in the housing with a clearance between the ball section and ball seat, the housing directly accommodates the ball section with its inner spherical surface. This extraction of the ball seat eliminates the clearance accuracy issues that arose from resin shrinkage during injection molding, as there is no separate ball seat to maintain precise clearance relationships with the ball section.
Solution Approach 2:
The housing is designed to perform multiple functions: it provides structural support, contains the ball section for rotation, and directly defines the clearance through its inner spherical surface without requiring a separate ball seat component. This multi-functionality integrates the clearance management function directly into the housing structure, eliminating the need for precise clearance control between separate components.
2Reliability
If a ball seat is provided between the inner wall of the housing and the ball section, then torque related to sliding is managed, but the tightening allowance for the ball section becomes difficult to control due to resin shrinkage
Solution Approach 1:
The ball seat is completely removed from the design. The housing's inner spherical surface directly contacts and supports the ball section, eliminating the need for a separate ball seat component. This extraction simplifies the torque management mechanism while improving control over the tightening allowance, as the housing structure itself directly defines the clearance and contact characteristics.
3Ease of manufacture
If the ball section is tightened due to resin shrinkage after injection molding, then the housing is formed, but it is difficult to ensure the clearance accuracy between the ball section and the ball seat
Solution Approach 1:
By removing the ball seat component entirely, the invention eliminates the clearance accuracy problems caused by resin shrinkage during injection molding. The housing directly accommodates the ball section with its inner spherical surface, so there is no separate ball seat whose clearance relationship with the ball section needs to be controlled during the molding process.
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
This approach enables accurate tightening torque management of the housing on the ball section, ensuring consistent performance and reliability in the ball joint and stabilizer link manufacturing processes.
Implementation Method 1
an induction heating step of subjecting the ball section to induction heating until a temperature of the ball section reaches a predetermined target temperature within a range which exceeds a glass transition point of a resin material constituting the housing
Implementation Method 2
a cooling step of cooling the ball section which has been subjected to the induction heating until the temperature of the ball section reaches at least a temperature of the glass transition point or less of the resin material
Data Source
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AI summary
The ball joint manufacturing method for manufacturing a ball joint including a ball stud which includes a substantially spherical metal ball section, and a resin housing rotatably accommodating the ball section of the ball stud, includes: a step of forming the housing to cover an outer periphery of the ball section; an induction heating step of subjecting the ball section to induction heating in a state in which the ball section is accommodated in an accommodation section of the housing until the temperature of the ball section reaches a predetermined target temperature; and a cooling step of cooling the ball section which has been subjected to the induction heating, wherein a torque adjustment step including the induction heating step and the cooling step is repeatedly performed.