Pulley Structure With Spring Restraint for Accurate Press-Fit Alignment
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Solution Overview
Problem
The existing pulley structure with a torsion coil spring experiences unstable posture and deformation due to eccentric or inclined axis, leading to poor production quality and reduced productivity during press-fitting, resulting in potential wear and shortened lifespan.
Innovation Solution
Incorporating a constraining surface on the other rotation body that aligns with the torsion coil spring's end region to stabilize its axis before press-fitting, ensuring proper contact and minimizing displacement, thereby preventing distortion and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the torsion coil spring is pressed against the contact surface using a press machine, then the torsion coil spring can be fixed in position, but the pressing load concentrates on a portion where the torsion coil spring is in contact with the inclined surface, causing the other end region to be distorted
Solution Approach 1:
The inclined surface is designed to preliminarily guide and align the torsion coil spring's other end region before the press-fitting operation begins. This preliminary action ensures the spring is properly positioned and oriented, preventing distortion during the subsequent pressing operation by distributing the initial contact load across a larger area of the inclined surface.
Solution Approach 2:
The inclined surface acts as an intermediary element between the press machine and the torsion coil spring. It mediates the pressing operation by providing a gradual transition surface that guides the spring into its final position, preventing direct concentrated loading on the spring's other end region and thereby avoiding distortion.
2Ease of manufacture
If the axis of the torsion coil spring is inclined with respect to the axis of the other rotation body, then the torsion coil spring can be installed, but the other end region may be stuck on the inclined surface and distorted by the pressing load
Solution Approach 1:
The inclined surface introduces a deliberate asymmetric geometric feature on the other rotation body. This asymmetric design creates a natural guiding mechanism that accommodates and corrects minor misalignments during installation, allowing the spring to be easily installed while simultaneously ensuring proper alignment through the inclined geometry that directs the spring into the correct position.
3Duration of action of stationary object
If the other end region of the torsion coil spring is separated from the other rotation body during relative rotation, then fatigue resistance can be improved, but the fixing force for the other rotation body may be smaller than for the one rotation body
Solution Approach 1:
The design implements local quality differentiation by allowing the other end region to separate from the other rotation body during operation, while maintaining fixed contact at the one end region with the one rotation body. This localized separation strategy preserves fatigue resistance at the critical other end region while ensuring sufficient fixing force is maintained at the one end region, achieving both objectives through spatially differentiated contact characteristics.
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 solution stabilizes the torsion coil spring's posture, enhances production quality, and increases productivity by reducing the need for manual adjustments and minimizing wear, thus extending the pulley structure's lifespan.
Implementation Method 1
a torsion coil spring which is provided between the outer rotation body and the inner rotation body... When the torsion coil spring is twisted in a diameter increasing direction due to a relative rotation between the outer rotation body and the inner rotation body
Implementation Method 2
an outer circumferential surface of the one end region of the torsion coil spring is pressed against a pressure contact surface by a self-elastic restoring force of the torsion coil spring in the diameter increasing direction
Data Source
Figure 1
Figure 2~3
Figure 4~5B
AI summary
In this pulley structure (1), a spring (4) is press fit to a cylindrical body (3a) of an inner rotating body (3). An outer peripheral surface of the cylindrical body (3a) comprises a first contact surface (11), an opposing surface (12), and an incline surface (13). The first contact surface (11) is contacted with an inner peripheral surface (4by) of an other end-side region (4b) of the spring (4) the diameter of which has been expanded by pressing. The opposing surface (12) is located more to one end side of an axial direction than the first contact surface (11), and is spaced apart from and opposes the inner peripheral surface of the spring (4). The opposing surface (12) includes a restraint surface (12a) connected to the first contact surface (11), with the incline surface (13) therebetween, at an end section of the opposing surface on the other side of the axial direction. The diameter (D2) of the restraint surface (12a) is somewhat smaller than a standard dimension of the inner diameter (D4) of the spring (4) before pressing. When, prior to pressing, the spring (4) is set to the inner rotating body (3) such that the cylindrical body (3a) is inserted into the spring (4), the spring (4) is then restrained at the restraint surface (12a), and any offset relative to the axis of another rotating body is curbed.