Ball Screw Mechanism Compact Nut Design
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Solution Overview
Problem
Conventional ball screw mechanisms require a larger nut member due to the external ball return passage, complicating fabrication and assembly, and reducing productivity.
Innovation Solution
A ball screw mechanism with a cylindrical nut member and external circulation passages on either end, utilizing first and second return members to guide and circulate balls between the nut member and the ball screw shaft, allowing for a smaller radial size and simplified assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ball return passage is disposed on the outer circumferential side of the nut member, then the balls can be circulated, but the nut member becomes larger in radial size
Solution Approach 1:
The invention relocates the ball return passage from the radial direction (outer circumferential side) to the axial direction (through the end members). This dimensional change allows balls to circulate without increasing the radial size of the nut member, thereby resolving the contradiction between reliable ball circulation and compact radial dimensions.
2Reliability
If the ball return passage is formed in the nut member, then balls can be returned axially, but the manufacturing process becomes troublesome and complex
Solution Approach 1:
The invention divides the ball circulation system into separate components: the nut member and the end members. The ball return passage is formed in the end members rather than the nut member itself. This segmentation simplifies the manufacturing of the nut member while maintaining the ball return function through the attached end members.
Solution Approach 2:
The invention extracts the ball return passage function from the nut member and places it in the end members. This extraction allows the nut member to be manufactured independently with a simpler structure, while the end members provide the ball circulation path, thereby simplifying the overall manufacturing process.
3Reliability
If end members are installed inside both ends of the nut member, then ball circulation is enabled, but the assembly becomes complicated and productivity is lowered
Solution Approach 1:
The invention merges the end members with the ball return passage function into a single integrated component. This combination eliminates the need for separate ball return mechanisms, simplifying the assembly process and improving productivity while maintaining reliable ball circulation.
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 enables a smaller radial size for the nut member and improves productivity by simplifying the manufacturing process and reducing costs, while maintaining effective ball circulation and linear motion conversion.
Implementation Method 1
a screw shaft (12) having a first ball screw groove (22) engraved on an outer circumferential surface thereof, a cylindrical shaped nut member (14) having a second ball screw groove (26) on an inner circumferential surface thereof
Implementation Method 2
balls (16) disposed via the helical grooves between the screw shaft and the nut member
Data Source
AI summary
A ball screw mechanism is equipped with a ball screw shaft formed from a metallic material, a displacement nut inserted over an outer circumferential side of the ball screw shaft, steel balls installed between a first screw groove formed on the ball screw shaft and a second screw groove formed in the displacement nut, and a pair of first and second return members, through which the steel balls are circulated between one end side and another end side of the displacement nut. The first and second return members include main body parts mounted respectively onto one end and another end of the displacement nut, and cylindrical parts that project outwardly with respect to the main body parts. A return passage, through which the steel balls are circulated, is formed inside of the main body parts and the cylindrical parts.