Spline Nut Shaft Structure With Thrust Bearing for Radial Downsizing
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Solution Overview
Problem
Existing shaft devices with radial bearings are limited in size reduction due to the larger outer diameter required for radial support, which hinders the miniaturization of spline nut and spline shaft systems, particularly in surface mounters for electronic component mounting.
Innovation Solution
The implementation of a thrust-type bearing with a biasing member, such as a coil spring, that supports the spline nut axially, allowing for a smaller outer diameter and enabling the overall device to be downsized radially by integrating the bearing within a housing portion and utilizing a ball spline mechanism for rotational support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a radial bearing is used to support the spline nut, then the spline nut can rotate smoothly, but the outer diameter of the bearing increases the radial size of the shaft device
Solution Approach 1:
The patent changes the bearing type parameter from radial bearing to thrust bearing, which fundamentally alters the load direction and enables radial size reduction. The thrust bearing supports axial loads through rolling elements arranged in a circular pattern, allowing the spline nut to rotate smoothly while maintaining a compact radial footprint.
Solution Approach 2:
The patent transitions from radial support (radial bearing) to axial support (thrust bearing), effectively moving the support function to a different dimension. This dimensional change allows the bearing to accommodate the same rotational function with a significantly reduced outer diameter, as the load is now carried in the axial direction rather than radially.
2Area of stationary object
If the bearing outer diameter is reduced to downsize the shaft device, then the radial size decreases, but the bearing structure becomes more complex
Solution Approach 1:
The thrust bearing is nested within the housing portion, with the rolling elements contained between the shaft-side track plate and housing-side track plate. This nested arrangement allows the bearing components to be compactly organized within the available space, reducing radial size while maintaining structural integrity through the integrated track plate design.
Solution Approach 2:
The housing-side track plate is merged with the bottom wall of the housing portion, eliminating the need for a separate track plate component. This merging reduces the overall number of parts and simplifies the bearing structure, achieving radial size reduction without excessive complexity.
3Productivity
If multiple shaft devices are arranged in a mounting head, then more spline shafts can be accommodated, but the radial space requirement increases
Solution Approach 1:
The use of thrust bearings changes the spatial parameters of each shaft device, reducing the radial dimension. This parameter change enables higher spline shaft density in the mounting head, as multiple compact shaft devices can be arranged in limited radial space without excessive area consumption.
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 configuration reduces the radial size of the shaft device, enabling more compact surface mounters with increased spline shaft density and reduced component count, while maintaining smooth rotational support and axial movement capabilities.
Implementation Method 1
a biasing member configured to bias the bearing in an axial direction of the spline shaft
Implementation Method 2
a bearing of thrust type rotatably supporting the spline nut relative to the nut support
Data Source
AI summary
A shaft device includes a nut support including a shaft hole, a spline shaft extending through the shaft hole of the nut support, a spline nut having a tubular shape, a bearing of thrust type rotatably supporting the spline nut relative to the nut support, and a biasing member configured to bias the bearing in an axial direction of the spline shaft. The spline nut is disposed coaxially with a portion of the spline shaft protruding upward from the shaft hole and connected to the spline shaft through a spline mechanism.