Non-Circulating Ball Screw Mechanism for Low Vibration Motion
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Solution Overview
Problem
Conventional circulating ball screws face issues such as sphere jamming, vibration, noise, heat increase, and power transmission loss due to sphere contact, and struggle with reducing backlash and pitch error, especially under high loads and high-speed rotation.
Innovation Solution
A ball screw mechanism with a spiral groove screw shaft and a power transmission mechanism using ball bearings and spheres, where the spheres are arranged in contact with a concave spherical contact surface of the inner ring of the ball bearings, allowing smooth movement without sphere return circulation, reducing contact between spheres, and incorporating a hollow structure for compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If spheres are circulated in a conventional ball screw, then the ball screw can sustain continuous operation, but spheres get caught or cause biting behaviors during drive reversal
Solution Approach 1:
The invention extracts and eliminates the sphere circulation system from the ball screw mechanism. By removing the return pipe and circulation path, the patent avoids all problems associated with sphere return, including catching, biting behaviors, and clogging during drive reversal, while maintaining continuous operation capability through a different mechanical design
Solution Approach 2:
Instead of circulating spheres through a return pipe as in conventional designs, the invention inverts the approach by allowing spheres to remain stationary in the nut after completing their function. The spheres are not returned to the inlet but remain in place, fundamentally changing the operational paradigm from circulation to static positioning
2Productivity
If high-speed rotation is performed in a circulating ball screw, then productivity increases, but fluctuations in sphere loads increase causing clogging in return pipe
Solution Approach 1:
The invention removes the return pipe circulation system entirely, eliminating the clogging problem that occurs at high speeds. By extracting the circulation mechanism, the patent allows high-speed rotation to proceed without the harmful fluctuations and clogging that plague conventional circulating ball screws
3Measurement precision
If gaps between spheres and track grooves are removed to reduce backlash, then positioning precision improves, but spheres beat each other causing vibration, noise, and heat
Solution Approach 1:
The invention extracts and removes the sphere-to-sphere contact scenario by eliminating the circulation system. Spheres are positioned statically in the nut without needing to return through each other, thereby eliminating beating, vibration, noise, and heat generation while maintaining zero backlash through precise positioning
Solution Approach 2:
The invention introduces a groove structure at the bottom of the spiral groove as an intermediary element. This groove receives and accommodates spheres, preventing them from contacting each other while maintaining close contact with the track groove for zero backlash, thus mediating between precision requirements and vibration prevention
4Measurement precision
If preload is applied to reduce backlash or increase rigidity, then positioning precision improves, but spheres are strongly pressed against each other causing power transmission loss
Solution Approach 1:
The invention extracts and eliminates the sphere-to-sphere contact scenario that causes power transmission loss. By removing the circulation system and allowing spheres to remain stationary, the patent enables preload application without the harmful effect of spheres being pressed against each other, thereby maintaining both rigidity and power transmission efficiency
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 solution prevents sphere jamming and contact-related issues, improving power transmission efficiency, reducing vibration and noise, and allowing for a compact, lightweight, and cost-effective design with reduced backlash and pitch error.
Implementation Method 1
a screw shaft 2 that includes a spiral groove 2a
Implementation Method 2
a plurality of ball bearings 5 and a plurality of spheres 4 respectively corresponding to the ball bearings 5
Data Source
AI summary
There is provided a ball screw mechanism for which a return of a sphere, such as a conventional circulating ball screw, need not to be considered, and that can prevent vibration and noise and avoid an increase in heat by ensuring smooth movement of a sphere without causing ball jam or the like of a sphere on a screw shaft. The present invention includes a screw shaft 2 that has a spiral groove 2a and extends linearly, a housing 30 that surrounds a periphery of the screw shaft 2, and a plurality of spheres 4 and ball bearings 5 that transmits thrust of the screw shaft 2 to the housing 30. Each ball bearing 5 includes an outer ring 7 attached and fixed to the housing 30 at regular intervals along the spiral groove 2a of the screw shaft 2, and an inner ring 6 provided with a concave spherical contact surface 5a in contact with the sphere 4 on a side surface facing the screw shaft 2. Each inner ring 6 is rotatably disposed about rotation axes N1 to N4 orthogonal to a rotation axis O of the screw shaft 2. The spheres 4 are arranged, each in contact with the contact surface 5a of each of the ball bearings 5, at regular intervals adjacent to each other in the spiral groove 2a of the screw shaft 2.