Belt Tensioner Press-Fit Stop Geometry Against Axial Loosening
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Solution Overview
Problem
Press-fit-interlocking connections in belt tensioners for internal combustion engines face challenges in maintaining security against loosening under axial loads, as existing solutions rely on friction and caulking or roller burnishing for interlocking, which can fail under overload.
Innovation Solution
The implementation of an edge support with stop parts having equal and different radii of curvature in two main planes, causing excessive material stress and preventing mutual displacement through Hertzian contact, enhancing the interlocking connection's security by allowing the components to 'dig in' and block axial movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a press-fit connection with friction-locking is used to join the outer part and inner part, then the connection can be assembled without additional fastening elements, but the connection may fail under overload conditions
Solution Approach 1:
The connection is segmented into two independent functional elements: a press-fit connection for normal operation and a separate axial interlocking connection (stop parts) for overload protection. This segmentation allows each element to perform its specific function optimally without compromising the other.
Solution Approach 2:
The axial stop parts are pre-configured with specific radii of curvature during manufacturing to ensure that under axial load, they generate excessive material stresses that cause the supporting edge to penetrate the contact partner's surface, creating a preliminary mechanical interlock that prevents detachment.
2Reliability
If caulking or roller burnishing is used to create an interlocking connection, then axial detachment is prevented, but additional process steps are required
Solution Approach 1:
The stop parts are designed to automatically create the interlocking effect through their geometric configuration (radii of curvature) during the pressing operation itself. The excessive material stresses generated during assembly cause the supporting edge to penetrate the contact partner's surface, creating the interlocking connection without requiring separate caulking or roller burnishing process steps.
Solution Approach 2:
The invention merges the press-fit connection and the interlocking connection into a single integrated joining operation. The axial stop parts with specific radii of curvature enable both the friction-locking press fit and the mechanical interlock to be achieved in one assembly step, eliminating the need for separate caulking or roller burnishing processes.
3Stability of the object's composition
If the stop parts have equal radii of curvature in both main planes, then the contact is symmetric, but the material stresses are insufficient to prevent loosening
Solution Approach 1:
The stop parts are designed with asymmetric radii of curvature: equal radii in the first main plane of curvature (perpendicular to the cylinder axis) for symmetric contact, and different radii in the second main plane (containing the cylinder axis) to generate excessive material stresses. This asymmetric configuration ensures that under axial load, the supporting edge penetrates the contact partner's surface, creating a secure mechanical interlock that prevents loosening.
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 solution reinforces the interlocking connection's security against loosening by inducing local material deformation, eliminating the need for additional process steps like caulking and ensuring a single joining step, thereby enhancing the reliability of the press-fit-interlocking connection.
Implementation Method 1
The edge support, which forms the axial interlocking connection either as an end section of the press-fit or as a Hertzian contact with line contact, causes local material stresses by contact with the stop parts which, when the stop is subjected to axial load, are so excessive that the supporting edge penetrates the surface of the contact partner
Implementation Method 2
the supporting edge penetrates the surface of the contact partner, which is accordingly elastically and, if necessary, also plastically deformed
Implementation Method 3
the supporting edge penetrates the surface of the contact partner, which is accordingly elastically and, if necessary, also plastically deformed
Data Source
AI summary
A press-fit-interlocking connection of an inner part to an outer part which is fastened to the inner part includes a cylindrical press joint (3) between the outer part and the inner part. The interlocking connection is formed by an axial stop having contacting stop parts (18, 19) on the inner part and on the outer part. The connection has an edge support in contact with the stop parts which contact one another, in a first main plane of curvature (E1) to which the cylinder axis of the press joint is perpendicular, with equal radii of curvature (ra1, ra2), and in a second main plane of curvature (E2) in which the cylinder axis of the press joint lies, with different radii of curvature (ra2, ri2).