Ball Screw Nut Circulation Part Fixing Without Precision Through Holes
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Solution Overview
Problem
Conventional ball screw devices face issues with positional accuracy of through holes and insufficient fixing force of the circulation part, leading to potential deformation and clogging of the circulation passage, which affects the smooth circulation of balls and the longevity of the circulation part.
Innovation Solution
A ball screw device design featuring a housing concave groove on the nut with engaging recess portions and fixing portions that include engaging convex portions, allowing the circulation part to be securely attached without relying on precise positioning of through holes, enhancing the fixing force and reducing the risk of deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the circulation part is positioned by inserting leg portions into through holes of the nut, then the circulation part can be fixed to the nut, but high positional accuracy is required for the through holes which increases manufacturing complexity and cost
Solution Approach 1:
A positioning protrusion is introduced as an intermediary element that mediates between the circulation part and the nut. The positioning protrusion fits into a positioning groove on the outer circumferential surface of the nut, providing accurate positioning without requiring high-precision through holes. This intermediary structure transfers the positioning function from the through holes to the protrusion-groove interface, resolving the contradiction between positioning accuracy and manufacturing ease.
2Strength
If only leg portions are inserted into through holes for fixing, then the structure is simple, but the fixing force is insufficient which may cause the circulation part to lift up
Solution Approach 1:
The fixing structure merges multiple functions into a unified system. The leg portions inserted into through holes provide primary fixing, while additional fixing protrusions engage with corresponding grooves on the nut's outer circumferential surface. This combination of fixing mechanisms works synergistically to provide sufficient holding force against ball pressure, preventing the circulation part from lifting up while maintaining structural simplicity.
Solution Approach 2:
The fixing structure is segmented into multiple independent fixing elements: leg portions for radial fixing and fixing protrusions for axial and circumferential fixing. This segmentation allows each element to perform its specific fixing function optimally, distributing the load and providing comprehensive fixation without requiring a single complex fixing mechanism.
3Manufacturing precision
If through holes are formed with high positional accuracy, then the circulation part can be properly positioned, but the manufacturing cost increases
Solution Approach 1:
The positioning protrusion and groove interface serves as an intermediary positioning mechanism that replaces the need for high-precision through holes. This intermediary structure provides the necessary positioning accuracy through its geometric fit, while being significantly easier and cheaper to manufacture using standard machining operations, thus resolving the cost-precision trade-off.
Data Source
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AI summary
[Problem] A structure of a ball screw device is achieved capable of relaxing positional accuracy for forming a through hole and enhancing a fixing force of a circulation part to a nut. [Solution] A housing concave groove 10 is provided on the outer circumferential surface of a nut 3, which linearly extends in the axial direction so as to open to end surfaces on both outer sides in the axial direction of the nut 3. A circulation part 5 is arranged inside the housing concave groove 10. By engaging an engaging convex portion 23 of a fixing portion 17 provided in the end portion on each of both outer sides in the axial direction of the circulation part 5 with an engaging recess portion provided in the end portion of each of both outer sides in the axial direction of the housing concave groove 10, the circulation part 5 is prevented from displacing toward the outer side in the radial direction and displacing in the circumferential direction with respect to the nut 3.