Instrumental Unit Rotary Shaft Stabilization
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Solution Overview
Problem
Existing rotary shaft support structures in meter apparatuses face challenges with settling over time, leading to increased small swing and instability, which affects the smoothness and stability of indicator movement, and are not suitable for miniaturization due to the required large installation space.
Innovation Solution
An instrumental unit featuring a step motor, a gear with a recess for a controlling spring, and a case design that includes a spring pressing member and stopper member to stabilize the rotary shaft, utilizing a leaf spring with a U-shaped cross-section and orthogonal axis symmetry to maintain a stable load spring force and prevent excessive displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin spring is used to reduce small swing during rotary shaft rotation, then the small swing is reduced, but settling occurs over time which decreases the pressing force and increases small swing again
Solution Approach 1:
The patent changes the material parameter from resin to metal (leaf spring), and changes the geometric parameter by forming a curved shape with specific radius of curvature. This combination provides both immediate small swing reduction and long-term stability without settling, as the metal material maintains consistent elastic properties over time.
2Reliability
If a leaf spring is installed downwardly below the gear to provide controlling force, then the rotary shaft can rotate smoothly, but relatively large installation space is required in the thickness direction of the case
Solution Approach 1:
The patent repositions the leaf spring from the vertical dimension (below the gear) to the radial dimension (between the gear and case in the thickness direction). The leaf spring is formed to curve along the radial direction, allowing it to provide controlling force while fitting within the limited radial space, thus reducing case thickness.
Solution Approach 2:
Instead of installing the leaf spring in the conventional downward position below the gear, the patent inverts the installation position to place it above the gear, between the gear and the case. This inverted positioning allows the leaf spring to function effectively while minimizing the required case thickness.
3Ease of manufacture
If the rotary shaft is made greatly displaceable in shaft direction to accommodate the leaf spring, then the leaf spring can be installed, but the position becomes unstable and indicator movement lacks smoothness
Solution Approach 1:
The patent changes the displacement parameter by forming the leaf spring with a specific radius of curvature that provides optimal elastic restoring force. This curved geometry, combined with metal material properties, ensures the rotary shaft maintains stable positioning while still allowing sufficient displacement for leaf spring installation and operation.
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 provides a stable and smooth turning movement of the rotary shaft and indicator, enhances light guiding performance by maintaining the rotary shaft's position close to the light source, and supports miniaturization efforts by reducing the case thickness.
Implementation Method 1
the controlling spring is bent in a curved state and a reaction force from the controlling spring at that time is used as a load, and thus, a controlling force on the rotary shaft is generated
Data Source
AI summary
An instrumental unit includes: a step motor; a gear including: a gear body rotated by torque of the step motor, the gear body including a first surface formed with a recess and a second surface opposite to the first surface; and a rotary shaft projecting from the first and second surfaces; a controlling spring accommodated in the recess, a center of the controlling spring through which the rotary shaft projects, the controlling spring having lengths in long and short axis directions orthogonal to each other and having a line-symmetric shape with respect to each of the long and short axis directions; and a case accommodating the step motor, the gear body and the controlling spring, an inner surface of the case including: a first portion supporting the second surface; and a second portion pressing the controlling spring in the recess of the first surface.