Shoulderless Tolerance Ring Radial Stiffness
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Solution Overview
Problem
Current tolerance rings in steering systems, such as rack and pinion steering systems, require improvements in terms of stiffness and manufacturing costs due to the need for precise tolerances and durability, especially in applications where torque transmission and relative motion prevention are critical.
Innovation Solution
A tolerance ring design featuring a cylindrical body with a gap and shoulderless wave structures that protrude radially, providing an interference fit between a bearing and a housing, which enhances radial compressive stiffness and maintains the bearing stationary while allowing a sliding shaft to move axially, thereby maintaining engagement between the rack gear and pinion gear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional tolerance rings with shoulders are used, then radial compressive stiffness is maintained, but manufacturing complexity and cost increase
Solution Approach 1:
The patent removes the shoulder feature from the wave structures, extracting only the essential radial protrusion function. This simplifies manufacturing by eliminating the complex shoulder formation process while maintaining the radial compressive stiffness through the wave structures alone.
Solution Approach 2:
The patent modifies the geometric parameters of the wave structures by eliminating shoulders and adjusting the radial protrusion dimensions. This parameter change simplifies the structure while maintaining or improving radial compressive stiffness through optimized wave geometry.
2Manufacturing precision
If very close tolerances are required for press fits, then torque transmission accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The tolerance ring uses resilient material properties and wave structure geometry to compensate for dimensional variations. This parameter-based approach allows broader manufacturing tolerances while maintaining torque transmission accuracy through elastic deformation and radial force distribution.
Solution Approach 2:
The patent employs resilient material with specific elastic properties that allow the tolerance ring to accommodate dimensional variations. This material selection enables relaxed manufacturing tolerances while maintaining functional precision through elastic compensation.
3Reliability
If interference fit is provided between bearing and housing, then relative motion prevention is improved, but assembly complexity increases
Solution Approach 1:
The tolerance ring uses dynamic resilient material properties to provide the interference fit effect. The wave structures deform elastically during assembly and maintain continuous radial pressure, providing reliable relative motion prevention through dynamic adaptation rather than rigid interference.
Solution Approach 2:
The patent utilizes the elastic modulus and resilience parameters of the material to achieve the interference fit function. By selecting appropriate material parameters and wave structure geometry, the system achieves reliable bearing-housing fixation without complex assembly procedures.
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 proposed tolerance ring design achieves improved stiffness and reduced manufacturing costs by providing a reliable interference fit and biasing force, ensuring precise alignment and durability in steering assemblies, as demonstrated by comparison test data showing lower stiffness with shoulderless wave structures compared to traditional designs.
Implementation Method 1
A tolerance ring generally comprises a strip of resilient material, for example a metal such as spring steel, the ends of which are brought together to form a ring. When the ring is located in the annular space between, for example, a bearing and a bore in a housing in which the bearing is located, the protrusions are compressed. Each protrusion acts as a spring and exerts a radial force against the bearing and the surface of the bore, providing an interference fit between the bearing and the housing.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A tolerance ring can include a generally cylindrical body that can include a sidewall that defines a top and a bottom. The sidewall can include an upper unformed band and a lower unformed band opposite the upper unformed band. A plurality of shoulderless wave structures can protrude radially from the sidewall between the upper unformed band and the lower unformed band. Each shoulderless wave structure can be connected only to the upper unformed band and the lower unformed band. The sidewall of the tolerance ring can also include a plurality of unformed sections and a gap that extends along the entire axial length of the body. Each unformed section can be located between a pair of adjacent shoulderless wave structures. Moreover, the gap can establish a split in the body.