Linear Motion Guide Crowning Structure for Excessive Moment Loads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Motion guide apparatuses malfunction prematurely and rattle when subjected to excessive moments due to insufficient stiffness or mounting precision, causing balls to collide with the end of the movable member and leading to uneven load distribution.
Innovation Solution
A motion guide apparatus with a crowning and chamfer design where the total length of the crowning and chamfer is greater than four times the diameter of the rolling element, and the chamfer is formed at the end of the crowning to prevent collisions, along with inclined surfaces that distribute load effectively, ensuring the balls can receive load without excessive pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of the crowning is increased to prevent ball collision with the movable member end, then the reliability is improved, but the load capacity and stiffness are reduced
Solution Approach 1:
The crowning is divided into multiple inclined surfaces (first inclined surface, second inclined surface, third inclined surface) with different slopes. This segmentation allows each surface to serve a specific function: the gentler first and second surfaces guide balls smoothly without excessive load, while the steeper third surface provides adequate length to prevent collisions, thus resolving the contradiction between reliability and load capacity.
Solution Approach 2:
Different portions of the crowning have different inclination angles tailored to their specific functions. The first inclined surface has a smaller angle for smooth ball entry, the second has a moderate angle for transition, and the third has a larger angle to extend the effective length. This local differentiation optimizes both the protective function (reliability) and the load-bearing function.
2Reliability
If the depth of the crowning is increased to prevent ball collision, then the reliability is improved, but the load capacity is reduced
Solution Approach 1:
The invention changes the parameter of inclination angle along the crowning length. By using multiple inclined surfaces with progressively different angles, the effective length of the crowning is extended without increasing the maximum depth excessively. This parameter variation allows the balls to be guided over a longer distance with controlled load, preventing collisions while maintaining load capacity.
3Reliability
If the crowning length is increased to accommodate ball movement, then the reliability is improved, but the stiffness of the motion guide apparatus is reduced
Solution Approach 1:
The crowning is segmented into multiple inclined surfaces with different angles. The first and second inclined surfaces with smaller angles accommodate ball movement smoothly, while the third inclined surface with a larger angle provides the necessary length extension. This segmentation allows the crowning to be sufficiently long for reliability without requiring uniform length throughout, thus preserving stiffness in the overall structure.
Solution Approach 2:
Different sections of the crowning have different inclination characteristics optimized for their local function. The gentler slopes in the first and second inclined surfaces handle the ball guidance function, while the steeper third inclined surface provides length extension. This local quality differentiation allows the crowning to achieve the required length for reliability without uniformly reducing the stiffness of the entire motion guide apparatus.
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 design prevents premature malfunction and rattling by allowing balls to enter the path without colliding with the end of the movable member, increasing the number of balls that can receive load and enhancing the load capacity, thus extending the apparatus' life.
Implementation Method 1
a movable member configured to be assembled to the track member via a plurality of rolling elements in such a manner as to be movable relative to the track member
Implementation Method 2
the distance of approach between the movable member and the track member due to the elastic deformation of a contact portion of the rolling element, and the elastic deformation amount of the rolling element rolling surface of the track member, the loaded rolling element rolling surface of the movable member, and the rolling element
Data Source
AI summary
A motion guide apparatus which can prevent the motion guide apparatus from rattling when being used in an environment Where an excessive moment works thereon. A crowning is formed at an end of a loaded rolling element rolling surface of a movable member, and a chamfer is formed at an end of the crowning. Let a total length of the crowning and the chamfer in a length direction of the loaded rolling element rolling surface be L. Let the diameter of a ball be Da. L/Da>4 is set. A maximum depth D of the chamfer is set to equal to or greater than the elastic deformation amount of a rolling element rolling surface of a track member, the loaded rolling element rolling surface of the movable member, and the rolling element under a radial load equal to or greater than 60% of the basic dynamic load rating.