MEMS Micromotor Pinion Interface for Clock Wheel Torque Transmission
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Solution Overview
Problem
Existing mechanical interfacing solutions for micromotors and toothed wheels in timepieces face challenges in achieving reliable meshing and torque transmission due to radial play and alignment issues, leading to potential mechanical stress and handling difficulties during assembly.
Innovation Solution
A mechanical arrangement where a pinion coaxial with the rotor is connected via pins to a housing, allowing radial and circumferential operating clearances, and the rotor is guided by a shared shaft with the pinion, enabling independent movement and efficient torque transmission while minimizing exposure and improving handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a micro-actuator is adjusted in relation to the wheel for each assembled part to achieve reliable meshing, then the meshing reliability is improved, but the assembly complexity and handling difficulty increase due to the need for precise adjustment
Solution Approach 1:
A pin system is introduced as an intermediary element between the rotor and pinion. The pin is received in a housing with controlled clearances, mediating the connection and allowing independent radial play while ensuring reliable torque transmission and meshing without complex adjustment procedures
Solution Approach 2:
The invention specifies controlled radial operating clearance and circumferential operating clearance parameters in the pin housing design. By optimizing these clearance parameters, the system achieves reliable meshing while accommodating manufacturing tolerances and enabling easier assembly without requiring precise adjustment for each part
2Manufacturing precision
If a spring system is integrated on the MEMS to take up positioning play, then the positioning accuracy is improved, but the mechanism protrudes from the chip side making handling more difficult and exposing it to dust
Solution Approach 1:
The pin housing is nested within the rotor structure, with the pin received in an associated housing that is integral to or mounted on the rotor. This nested arrangement contains the positioning mechanism within the chip footprint, preventing protrusion and reducing dust exposure while maintaining positioning accuracy through controlled clearances
3Power
If the micromotor and gear train are made independent in radial play, then the torque transmission efficiency is improved, but the structural complexity increases
Solution Approach 1:
The system is segmented into independent rotational components: the rotor with its housing and the pinion with its own mounting. Each component can accommodate radial play independently through the pin housing clearance design, allowing pure torque transmission without coupling the radial movements. The segmentation is achieved through the pin connection mechanism that decouples the radial degrees of freedom
Solution Approach 2:
The pin in housing arrangement serves as an intermediary that couples the rotor and pinion for torque transmission while decoupling their radial movements. The housing provides controlled clearances that allow independent radial play, and the pin transmits only the tangential torque forces, filtering out radial displacement variations
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 solution ensures reliable meshing and efficient torque transmission between the micromotor and gear train, reducing mechanical stress and facilitating assembly by maintaining the micromotor and gear train's independence in radial play, while allowing for pure torque transfer.
Implementation Method 1
In silicon micro-actuators, one way of converting electrostatic energy into work is to have 'comb' structures, formed of respectively mobile and fixed fingers and placed at two different potentials
Implementation Method 2
The linear movement on silicon being of the order of a few tens of microns, the toothed wheel driven by the pawls must have teeth of equivalent dimensions
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The arrangement has a pinion (62) coaxial to and arranged above a rotor (42), and connected in rotation to the rotor by a pin (66) received in openings i.e. slots (68), where the rotor is driven by an actuator of a micro electro-mechanical system micromotor. The pinion is meshed with a toothed wheel (28), and the pin is integrated to the pinion. The pinion is supported on a bearing (60) when an axial effort oriented downwards is applied on the pinion. The rotor is guided in rotation by a shaft (64) mounted in the plate.