Balance Wheel Shaft Guide Bearing for Low-Friction Precision Centering
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Solution Overview
Problem
Existing watch mechanisms face issues with imprecise positioning and excessive friction of the balance wheel's rotating shaft, leading to reduced chronometric accuracy and rapid wear due to gravity and orientation-dependent friction, which conventional materials and geometries fail to adequately address.
Innovation Solution
A device for guiding the balance wheel's rotating shaft using materials with a Young's modulus less than or equal to 100 GPa, such as ceramics or polymers, and a geometry with slight clearance and point or line contact to minimize friction and maintain centering, incorporating a solid body with a guide opening to counteract gravity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a circular guide opening with larger diameter than the pivot is used, then the pivot can move freely with less friction, but the positioning precision deteriorates and angular play increases
Solution Approach 1:
The guide opening transitions from a uniform circular shape to an optimized geometry with varying cross-sectional characteristics. The opening has a smaller dimension in the radial direction (perpendicular to rotation axis) to reduce angular play, while maintaining adequate clearance in the axial direction to allow free pivot movement. This localized differentiation of dimensional constraints resolves the contradiction between movement freedom and positioning precision.
Solution Approach 2:
The guide opening employs asymmetric dimensional constraints with different clearance requirements in different directions. The radial dimension (a) is made smaller than the axial dimension (b), creating an elliptical or rectangular cross-section rather than a circular one. This asymmetric geometry provides tight radial guidance for precision while allowing axial movement freedom, directly addressing the technical contradiction.
2Measurement precision
If the guide opening diameter is reduced to improve positioning precision, then angular play decreases, but friction increases and pivot wear accelerates
Solution Approach 1:
The guide opening geometry is optimized with different dimensional clearances in different directions: tight radial clearance (dimension a) for precision positioning, and larger axial clearance (dimension b) to minimize friction and wear. This localized quality differentiation allows the system to achieve precision without the penalty of excessive friction that would result from uniformly reducing the opening diameter.
Solution Approach 2:
The guide opening employs curved or rounded corners in its cross-sectional geometry, transitioning from sharp angular shapes to smooth rounded forms. This curvature optimization reduces stress concentration at the pivot contact points and minimizes friction during rotation, thereby reducing energy loss and wear while maintaining precise positioning through the overall constrained geometry.
3Ease of manufacture
If conventional metallic materials are used for the guide bearing, then the structure is simple and easy to manufacture, but the friction forces are too high and wear is rapid
Solution Approach 1:
The guide bearing material undergoes a parameter change from conventional metallic materials to ceramic materials. This material substitution fundamentally changes the friction and wear characteristics, providing lower friction coefficients and reduced wear rates. The ceramic material maintains structural simplicity and manufacturability while dramatically improving the energy loss and durability parameters.
4Measurement precision
If the guide opening has tight clearance to reduce angular play, then positioning precision improves, but the pivot cannot accommodate movement due to gravity in different orientations
Solution Approach 1:
The guide opening employs differentiated dimensional clearances to address different functional requirements: tight radial clearance (dimension a) to minimize angular play and improve positioning precision, and adequate axial clearance (dimension b) to allow the pivot to accommodate gravitational effects in various orientations. This localized quality differentiation resolves the contradiction between precision and adaptability.
Solution Approach 2:
The solution moves the accommodation of gravitational effects to a different dimension (axial direction) while maintaining tight constraints in the radial direction. By allowing movement freedom in the axial dimension while constraining the radial dimension, the system achieves both precision in the rotation plane and adaptability to gravitational forces acting in various orientations.
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 reduces frictional losses and maintains precise chronometric accuracy by minimizing angular play and ensuring consistent operation regardless of the watch's orientation, while allowing for lubrication to further reduce friction.
Implementation Method 1
A device for guiding a rotating shaft (6) of a balance spring, characterized in that at least one end of the rotating shaft (6), in particular at one end of the shaft or at a pivot (6') fixed to the shaft, passes through a guide opening (2) of a solid body (15) and that at least one guide bearing (2) supports the rotating shaft (6) at one end with contact parts made of a material having a Young's modulus less than or equal to 100 GPa
Implementation Method 2
The friction is thus independent of the watch's position. In a horizontal position, the additional friction of the cylindrical part of the pivot against the olive-shaped jewel is therefore similar to that experienced in a vertical position
Data Source
Figure 1~2
Figure 3a~3c
Figure 4~6
AI summary
The device (1) is designed to guide a rotating shaft (6) of a balance spring. The device comprises at least the rotating shaft and a bearing (2) for guiding one end of the rotating shaft of the balance spring, the bearing comprising at least a blade (3) and a contact surface (5) for retaining the end of the rotating shaft of the balance spring. At least one end portion of the shaft and at least the blade and the contact surface of the bearing are made of a material having a Young's modulus less than or equal to 100 GPa and/or to reduce the coefficient of friction of the contacting parts. The device further comprises at least one means for reducing the effect of gravity depending on the orientation of the device or the timepiece incorporating it.The means for reducing the effect of gravity includes at least one solid body (15) with a guiding aperture, such as a holed stone (15), the aperture of which is arranged along the axis of the rotating shaft (6) in a centered position. An end rod of the rotating shaft or a pivot fixed to the shaft passes through the aperture of the solid body to guide the rotating shaft without excessive angular play due to the effect of gravity.