Four-Bearing Preload Layout for Uniform Rigidity and Low Torque Variation
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Solution Overview
Problem
Existing bearing devices face challenges in achieving uniform pre-load distribution and high radial rigidity, leading to torque variation and reduced positioning accuracy, particularly when increasing the number of bearings.
Innovation Solution
A bearing device configuration with a tubular outer member, a shaft member, and four bearings arranged axially, where a spring applies a constant pre-load between the second and third bearings, allowing their inner rings to move axially, and equivalent pre-load is applied to the first and fourth bearings, ensuring uniform pre-load distribution and increased radial rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the number of bearings is increased to improve rigidity and positioning accuracy, then radial rigidity is improved, but uniform pre-load distribution becomes difficult to achieve
Solution Approach 1:
The bearing device is divided into multiple independent bearing units (first, second, third, and fourth bearings) that are arranged axially. Each bearing can be pre-loaded independently through the spring mechanism, allowing uniform pre-load distribution across all bearings while maintaining high radial rigidity through the combined effect of multiple bearings.
Solution Approach 2:
A spring mechanism is introduced to dynamically apply pre-load to the bearings. The spring can be designed with specific elasticity coefficients to ensure that each bearing receives the appropriate pre-load force, maintaining uniform distribution even when the number of bearings is increased.
2Stability of the object's composition
If a gap is provided between inner rings of bearings and the shaft to suppress torque variation, then torque variation is reduced, but radial rigidity is insufficiently increased
Solution Approach 1:
Different regions of the bearing device have different characteristics: the inner rings of the second and third bearings are separated from the shaft to reduce torque variation, while the outer rings of all bearings are fixed to the outer member to maintain radial rigidity. This local differentiation resolves the contradiction between torque stability and radial strength.
3Force
If inner rings of bearings are fixed to the shaft to apply pre-load, then pre-load is applied to bearings, but pre-load is not uniform at upper and lower bearings
Solution Approach 1:
A spring mechanism is introduced as an intermediary element between the bearings and the shaft. The spring applies pre-load to the inner rings of the second and third bearings in a controlled manner, ensuring uniform pre-load distribution. The spring acts as a mediator that distributes force evenly across multiple bearings rather than allowing direct fixed connection.
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 configuration effectively suppresses torque variation and enhances positioning accuracy by maintaining uniform pre-load across all bearings, improving radial rigidity and reducing micro-vibration and noise.
Implementation Method 1
a spring applying a constant pre-load is provided between inner rings of the second bearing and the third bearing
Data Source
AI summary
There is provided a bearing device including: a tubular sleeve; a shaft held inside the sleeve; and a first bearing, a second bearing, a third bearing, and a fourth bearing, rotatably holding the shaft with respect to the sleeve and arranged in this order in an axial direction. An outer circumferential surface of an outer ring of each of the first to fourth bearings is fixed to an inner circumferential surface of the sleeve, a gap is provided between inner circumferential surfaces of inner rings of the second and third bearings and the shaft, and a spring applying a constant pre-load is provided between the inner rings of the second and third bearings.