Ball Screw Circulation Member Structure for Smooth Ball Return
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Solution Overview
Problem
Existing ball screw devices in electric power steering systems face issues with smooth circulation of balls due to interference from circulation members, leading to hindered ball circulation and assembly challenges.
Innovation Solution
A ball screw device design featuring a circulation member with a facing surface having both pressing and non-pressing areas, where the non-pressing area is located on the inner circumferential side of the ball screw nut, preventing displacement and allowing for easy assembly by preventing resistance during insertion, and featuring protruding portions that stabilize the circulation member's posture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the circulation member is attached to the attachment hole with a press-fitted structure, then the circulation member's position is stabilized, but assembly resistance increases and assemblability deteriorates
Solution Approach 1:
The invention applies press-fitted structure only at specific locations (pressing portions) rather than the entire circumference of the circulation member. The pressing portions are strategically positioned to provide positional stability while leaving other areas with clearance for easier assembly, thus resolving the contradiction between stability and assemblability.
Solution Approach 2:
The contact interface between the circulation member and attachment hole is segmented into two distinct zones: pressing portions that provide stabilization and non-pressing portions that facilitate assembly. This segmentation allows each zone to fulfill its specific function without interfering with the other.
2Reliability
If the circulation member is attached with a press-fitted structure, then displacement is prevented, but assembly difficulty increases
Solution Approach 1:
The press-fitted structure is applied locally only at the pressing portions rather than uniformly around the entire circumference. This localized approach provides sufficient displacement prevention for reliable operation while maintaining clearance in other areas to reduce assembly difficulty.
3Reliability
If the circulation member has a press-fitted structure, then circulation smoothness is maintained, but assembly resistance increases
Solution Approach 1:
The press-fitted structure is implemented only at specific pressing portions rather than the entire circumference. This localized press-fitting maintains the circulation smoothness by stabilizing the circulation member's position while reducing overall assembly resistance by leaving other areas with clearance.
Data Source
AI summary
A ball screw device includes a screw shaft having a first screw groove formed on an outer circumference thereof, a ball screw nut having a second screw groove formed on an inner circumference thereof, and a plurality of balls disposed in a spiral ball raceway wherein the first screw groove and the second screw groove face each other. A circulation member is attached to an attachment hole radially penetrating the ball screw nut and a circulation path is formed, the circulation path allowing endless circulation of each of the balls rolling in the ball raceway by short-circuiting between two points of the ball raceway.