Ball Joint Holder Segmentation for Torque Stability
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Solution Overview
Problem
The existing ball joints with thermoplastic resin holders experience torque fluctuations due to temperature changes, affecting the adhesion between the ball portion, elastic sliding contact member, and holder, leading to unstable rocking of the ball stud.
Innovation Solution
A ball joint design featuring a holder made of synthetic resin with a first and second member having concave spherical ball sliding contact surfaces, joined by welding, and annular fixation reference surfaces to maintain constant spacing, preventing molten resin from protruding and ensuring smooth rocking of the ball stud.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the holder is made of thermoplastic resin with high adhesion to the ball portion, then the ball portion is securely held, but the torque value fluctuates with temperature changes
Solution Approach 1:
The holder is divided into a first member and a second member that are joined by welding. The first member includes the ball sliding contact surface, while the second member includes the opening portion. This segmentation allows the ball portion to be held securely by the first member while the second member provides structural support, reducing temperature-induced torque fluctuations.
Solution Approach 2:
The ball portion is extracted from direct contact with the thermoplastic resin holder and instead contacts the first member's ball sliding contact surface. This separation removes the ball portion from the temperature-sensitive resin, stabilizing the torque value while maintaining secure holding through the first member's concave spherical surface.
2Ease of manufacture
If the holder is formed by injection molding around the ball portion, then the ball portion is securely accommodated, but molten resin may protrude and affect the sliding contact surfaces
Solution Approach 1:
The first member and second member are prepared separately with their respective ball sliding contact surfaces formed before joining. The first member is designed with a concave spherical surface that precisely accommodates the ball portion, ensuring high manufacturing precision for the sliding contact surface before the welding process occurs.
Solution Approach 2:
By dividing the holder into two members that are joined by welding, the design prevents molten resin from protruding onto the ball sliding contact surfaces during injection molding. The first member's sliding contact surface is formed independently, ensuring its quality is not compromised by the molding process.
3Device complexity
If the holder is made as a single integrated piece, then the structure is simple, but temperature changes cause torque fluctuations
Solution Approach 1:
The holder is segmented into a first member and a second member joined by welding. The first member contains the ball sliding contact surface that directly supports the ball portion, while the second member provides structural support with the opening portion. This segmentation isolates the ball portion from temperature-sensitive resin, stabilizing torque despite the increased structural complexity.
Solution Approach 2:
The ball portion is extracted from direct contact with the thermoplastic resin by introducing a first member with a ball sliding contact surface. This separation removes the ball portion from the temperature fluctuation environment, stabilizing torque while maintaining a relatively simple overall holder structure through the two-member design.
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 design stabilizes the torque required to rock the ball stud, reducing resistance and ensuring consistent performance by maintaining a constant spacing between the sliding contact surfaces and preventing resin protrusion during welding.
Implementation Method 1
the first member and the second member respectively include joining surfaces fixed to each other by welding
Implementation Method 2
a first ball sliding contact surface having a concave spherical shape approximate to a spherical surface of the ball portion
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided is a ball joint that is less affected by fluctuations in environmental temperature, and is capable of stabilizing a torque value required to rock a ball stud in a holder. The ball joint includes: a ball stud (1) including: a shaft member (11); and a ball portion (10) formed at one end of the shaft member (11); and a holder (2) made of a synthetic resin and configured to accommodate the ball portion in a pivotable manner. The holder (2) includes: an opening portion (30) from which the shaft member protrudes; a first member (20) including a first ball sliding contact surface (24) having a concave spherical shape approximate to a spherical surface of the ball portion; and a second member (3) including: a second ball sliding contact surface (31) having a concave spherical shape approximate to the spherical surface of the ball portion; and the opening portion (30) formed in a center of the second ball sliding contact surface. Further, the first member (20) and the second member (3) respectively include joining surfaces (25, 32) fixed to each other by welding, and respectively include fixation reference surfaces (28, 34) that are brought into abutment against each other.