Ball Screw Radial Gap Tuning to Prevent Groove Peeling
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Solution Overview
Problem
Ball screw devices experience shortened life due to peeling on surfaces when a load with a radial component is applied, as existing designs with small radial gaps lead to tilting and interference between balls and screw grooves.
Innovation Solution
Increasing the radial gap and intentionally allowing a tilt error in the axially moving body, represented by a ratio of radial movement to axial span, to prevent interference and peeling, while maintaining the deflection within acceptable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the radial gap is made small to prevent ball interference, then the rigidity is improved, but peeling occurs on the surfaces of screw grooves and balls when radial load is applied, shortening device life
Solution Approach 1:
The invention changes the radial gap parameter from a small value (conventional design) to a larger value within a specific range (0.01 to 0.05 times the ball diameter). This parameter change allows the screw shaft to tilt slightly under radial load, preventing ball interference and peeling while maintaining acceptable rigidity through controlled tilt rather than rigid constraint.
2Duration of action of moving object
If the radial gap is increased to prevent peeling, then the device life is improved, but the rigidity decreases and the screw shaft becomes less stable
Solution Approach 1:
The invention optimizes the radial gap parameter to a specific range (0.01 to 0.05 times the ball diameter) that balances two competing requirements: large enough to allow tilt and prevent peeling, but small enough to maintain rigidity. This controlled parameter change resolves the contradiction by finding the optimal middle ground.
3Stability of the object's composition
If a sliding bearing is added to support the screw shaft to prevent tilting, then the stability is improved, but the device complexity increases significantly
Solution Approach 1:
The invention extracts the tilt-prevention function from a separate sliding bearing component and integrates it into the ball screw device itself through controlled radial gap design. This allows the screw shaft to have controlled tilt capability without requiring additional support components, thereby maintaining stability while avoiding increased device complexity.
Solution Approach 2:
The ball screw device itself provides the tilt accommodation function through its internal radial gap design, rather than requiring external support components. The radial gap allows the screw shaft to self-adjust its angle under load, making the system self-sufficient and avoiding additional complexity.
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 approach extends the life of the ball screw device by allowing tilt when a radial load is applied, preventing early peeling and maintaining operational integrity.
Implementation Method 1
a large number of balls 123 arranged between the screw groove of the screw shaft 122 and the screw groove of the nut 121. The rotational driving force of the motor 102 is decelerated via gears 116 and 117 and transmitted to the nut 121. Then, the rotational motion of the nut 121 is converted into the axial movement of the screw shaft 122 via the balls 123.
Data Source
AI summary
A ball screw device 4 includes a screw shaft 9 having a screw groove 9a formed in an outer peripheral surface, a nut 8 having a screw groove 8a formed in an inner peripheral surface, and a large number of balls 10 arranged between the screw groove 9a of the screw shaft 9 and the screw groove 8a of the nut 8. A ratio Δr/L1 of a radial gap Δr, which is a maximum amount of radial movement of the nut 8 with respect to the screw shaft 9, to an axial span L1 between the large number of balls 10 is made larger than 1/2000.