Ball Screw Nut Anti-Rotation With Integrated Key Retention
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Solution Overview
Problem
Conventional ball screw devices require additional parts like retaining rings and screws to prevent key slipping, increasing manufacturing costs and complicating shape accuracy, especially when the key is integrally formed on the housing.
Innovation Solution
The ball screw device incorporates anti-rotation members with retaining concave portions on the nut or fitting cylinder and guide concave grooves in the housing, allowing for effective prevention of nut rotation with a reduced number of parts, thereby minimizing manufacturing costs and ensuring shape accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retaining members such as retaining rings and screw members are attached to the opening of the insertion hole to prevent the key from slipping out, then the key can be retained, but the number of parts increases and manufacturing cost increases
Solution Approach 1:
The retaining function is merged into the anti-rotation member itself. The anti-rotation member has a tapered outer-circumferential surface that engages with a tapered groove in the insertion hole, combining anti-rotation and retention functions into a single component, eliminating the need for separate retaining members.
Solution Approach 2:
The retention function is extracted from separate retaining members and integrated into the anti-rotation member's structure. The anti-rotation member's tapered surface design provides both anti-rotation and axial retention capabilities.
2Manufacturing precision
If the key is integrally formed on the inner-circumferential surface of the housing to ensure shape accuracy, then shape accuracy is improved, but manufacturing cost increases due to reduced yield
Solution Approach 1:
The key is segmented from the housing and formed as a separate component. This allows the key to be manufactured independently with standard machining processes, ensuring shape accuracy without the cost penalty of integral formation. The key can be precisely machined and then assembled into the housing.
Solution Approach 2:
Instead of forming the key integrally with the housing (which increases cost), the patent inverts the approach by making the key a separate, precision-machined component that is assembled into the housing. This separate key can be manufactured with high precision using standard processes, maintaining shape accuracy while improving manufacturing efficiency.
3Reliability
If additional retaining members are added to prevent key slipping, then key retention is ensured, but manufacturing cost increases
Solution Approach 1:
The retention function is merged into the anti-rotation member's tapered surface design. The anti-rotation member's outer-circumferential surface is tapered to engage with a corresponding tapered groove in the insertion hole, providing both anti-rotation and axial retention in a single component, eliminating the need for additional retaining members and reducing manufacturing cost.
Solution Approach 2:
The anti-rotation member is designed to perform multiple functions: preventing rotation of the nut and simultaneously retaining the key against axial slipping. This multi-functional design eliminates the need for separate retaining members, reducing part count and manufacturing cost while ensuring reliable key retention.
Data Source
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AI summary
A ball screw device capable of achieving anti-rotation of a nut, which is a linear motion element, with a small number of parts and reducing the manufacturing cost is provided. Of the anti-rotation member 7 that prevent the nut 3 from rotating relative to the housing 6, the radially inner portion is arranged inside the retaining concave portion 19 with radially inner portion held between the closed surface 20 of the retaining concave portion 19 provided on the outercircumferential surface of the nut 3 and the end surfaces 5x on the one side in the axial direction of the piston 5 externally fitted and fixed to the nut 3, and the radially outer portion is arranged inside the guide concave groove 24 provided on the inner-circumferential surface of the cylinder hole 8 of the housing 6.