Low-Expansion Joining Fixture for Precise Shaft Assembly
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Solution Overview
Problem
Joining components on a shaft, such as camshaft components, is challenging due to the reliance on precise axial dimensioning, which is affected by temperature fluctuations and material differences between steel and sinter materials, leading to high costs and dimensional inaccuracies.
Innovation Solution
A joining device with a heat expansion coefficient lower than steel is used, specifically made from materials like silicon nitride ceramic or iron nickel alloy, to minimize temperature-induced dimensional variances and ensure precise axial positioning through thermal shrink fits or press-fitting methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a joining device made of steel is used, then the device has sufficient strength and durability, but the axial dimension precision deteriorates due to high heat expansion coefficient (12 μm/m°C) causing dimensional variances under temperature fluctuations
Solution Approach 1:
The patent changes the material parameter (heat expansion coefficient) of the joining device from typical steel values (12 μm/m°C) to a specialized material with α ≤ 10.0 μm/m°C, thereby reducing thermal expansion effects and improving axial dimension precision under temperature fluctuations
Solution Approach 2:
The patent employs composite or specialized materials (such as sintered materials or metal matrix composites) that combine low heat expansion properties with sufficient mechanical strength, allowing the joining device to maintain both structural integrity and dimensional stability
2Ease of manufacture
If sinter materials are used for components like sensor wheels, then cost is reduced, but axial dimension precision deteriorates due to difficulty in achieving precise dimensional control
Solution Approach 1:
The patent uses a joining device made from material with uniform and controlled properties (α ≤ 10.0 μm/m°C) that compensates for variations in the components being joined, thereby achieving consistent axial dimension precision regardless of whether the components are made from steel or sinter materials
Solution Approach 2:
By controlling the heat expansion parameter of the joining device material, the patent creates a stable reference frame that maintains precise axial dimensions even when joining components with varying thermal properties, thus enabling cost-effective sinter material usage without sacrificing precision
3Productivity
If thermal shrink fit method is used for joining multiple components, then productivity is improved, but manufacturing precision deteriorates due to different heat input causing dimensional variances
Solution Approach 1:
The patent changes the thermal parameter (heat expansion coefficient) of the joining device to be lower than that of the components, which stabilizes the device's dimensions during thermal shrink fit operations and prevents dimensional variances caused by differential thermal expansion, thereby maintaining precision during high-speed multi-component joining
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 significantly reduces dimensional variances and coaxiality issues, leading to improved axial precision, reduced rejects, and cost savings by minimizing the need for additional precision processes.
Implementation Method 1
a highly precise axial dimension is desirable, which however does not only depend on a positioning accuracy of the joining axis but in major parts also on temperature fluctuations of the components to be joined and of the joining device itself
Implementation Method 2
When for example multiple components are simultaneously joined on the shaft using the joining device according to the invention, for example by means of a thermal shrink fit
Implementation Method 3
ensure precise axial positioning through thermal shrink fits or press-fitting methods
Data Source
AI summary
A joining device for joining components on a shaft, e.g., for joining camshaft components on a camshaft tube, is disclosed. The joining device includes a joining device body composed of a material with a heat expansion coefficient that is lower than 10.0 μm/m° C. The heat expansion coefficient of the joining device is smaller than that of the components and/or the shaft.