Linear Motion Guide Unit Roller Skew Correction
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Solution Overview
Problem
Conventional linear motion guide units face issues with rollers rolling in inclined postures, leading to skew and increased sliding friction, which requires high precision components and is costly to prevent.
Innovation Solution
The design incorporates a retainer plate with slits forming elastically deformable cantilevered retainer portions and protrusions with inclined surfaces, which correct the posture of rollers to be orthogonal to the guide surface, reducing friction and heat generation by ensuring proper alignment as they enter load areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional retainer plates are used to retain rollers, then the rollers can be retained on the raceway surface, but the rollers become inclined and generate skew causing increased sliding friction and heat
Solution Approach 1:
The retainer plate's guide surface is changed from a conventional flat surface to an inclined surface that matches the crowning curvature of the raceway. This parameter change in the guide surface geometry allows the rollers to be retained while preventing inclination and skew, thereby eliminating the harmful sliding friction and heat generation without compromising roller retention reliability
2Reliability
If high precision components are used to reduce the gap between rollers and guide surface, then skew can be prevented, but the manufacturing cost increases significantly
Solution Approach 1:
Instead of requiring high precision manufacturing to reduce gaps, the invention changes the geometric parameter of the guide surface to be inclined and curved, matching the crowning of the raceway. This design allows the use of standard manufacturing tolerances while still preventing roller skew, thereby significantly reducing manufacturing costs while maintaining reliability
3Productivity
If a small gap is maintained between roller end surfaces and guide surface for smooth circulation, then rollers can circulate freely, but the rollers become inclined and skew occurs
Solution Approach 1:
The guide surface is designed with an inclined geometry that follows the crowning curvature of the raceway. This parameter change allows the guide surface to maintain optimal contact with the roller end surfaces throughout the circulation path, preventing inclination and skew while still allowing smooth roller circulation with appropriate clearance
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 allows rollers to roll smoothly and reduces the need for high precision components, thereby lowering costs and preventing fluctuations in sliding friction and heat generation.
Implementation Method 1
a retainer member of a retainer plate has a slit at each of opposite end portions thereof so as to form a pair of elastically deformable cantilevered retainer portions each having a protrusion
Data Source
AI summary
A linear motion guide unit restrains fluctuations in sliding friction and generation of heat by correcting the postures of rollers having been inclined in a no-load area such that their axes become orthogonal to a guide surface of a carriage to thereby introduce the rollers in proper postures into a load area. A retainer plate of the guide unit has a guide surface for guiding end surfaces of the rollers and has protrusions protruding from the guide surface at its opposite end portions facing crownings of the carriage. The rollers rolling from a turnaround passage to a load-carrying race are pressed by the protrusions toward the guide surface of the carriage so as to be arrayed in such a posture that the axes of the rollers become orthogonal to the guide surface on the inlet side of the crowning of the carriage, whereby the occurrence of roller skew is prevented.