Electromechanical Clock Wheel Position Detection via Elastic Torque
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Solution Overview
Problem
Existing electromechanical watch movements face challenges in detecting the angular position of a wheel without complex and costly sensors, and previous solutions using magnets or modified tooth profiles are inefficient and prone to manufacturing issues.
Innovation Solution
A compact device using an elastic element, such as a wire spring, secured to the wheel to create a localized resistive torque by meshing with a mobile component's toothing, allowing precise detection of the angular position through analysis of motor pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical devices, capacitive sensors, inductive sensors, or Hall sensors are used to detect the angular position of the wheel, then the detection precision is improved, but the device complexity, cost, and size increase
Solution Approach 1:
The wheel serves its dual function of transmitting mechanical motion and providing angular position information. The existing wheel structure with its teeth and hollows is utilized to generate detection signals through mechanical interaction with the pinion, eliminating the need for separate detection sensors and reducing overall device complexity
Solution Approach 2:
An elastic element is introduced as an intermediary between the wheel and pinion to generate the detection mechanism. This elastic element deforms under the pinion's teeth, creating localized resistive torque that serves as a mechanical signal for angular position detection without requiring complex electronic sensors
2Measurement precision
If magnets are used to generate additional resistive torque for position detection, then the detection capability is improved, but the magnetic force creates axial components that increase bearing friction
Solution Approach 1:
The magnetic detection system is replaced with a purely mechanical detection mechanism using an elastic element. The elastic element deforms mechanically under the pinion teeth to generate resistive torque, eliminating magnetic forces and their associated axial components that would increase bearing friction
Solution Approach 2:
The magnetic elements are completely removed from the system. Instead, a simple elastic element is used to generate the necessary mechanical interaction for position detection, extracting the problematic magnetic force component while retaining the detection functionality
3Measurement precision
If the magnet is arranged on the periphery of the wheel, then the angular position detection is enabled, but it requires additional space that is not always easy to clear in the movement
Solution Approach 1:
The detection mechanism is nested within the existing gear train structure. The elastic element is positioned in the hollows of the wheel, utilizing the existing spatial arrangement of the wheel and pinion teeth, thereby detecting angular position without requiring additional peripheral space
4Measurement precision
If a ferromagnetic element and magnet are arranged close to each other on the wheel, then angular position detection is achieved, but the magnetic force acts over a relatively large angular distance requiring analysis of multiple motor steps
Solution Approach 1:
The elastic element is positioned to interact with only one specific tooth of the pinion at a time, creating a highly localized resistive torque effect. This localization allows for precise identification of the reference axis position within a single motor step, eliminating the need to analyze multiple steps
5Measurement precision
If the profile of the teeth is locally modified to create a hard point, then position detection is enabled, but it complicates the manufacturing of the wheel and may block rotation due to backlash
Solution Approach 1:
Instead of modifying the entire wheel structure or tooth profiles, the invention segments the detection function by adding a separate, simple elastic element. This element can be independently manufactured and positioned in the hollows of the wheel, simplifying the overall manufacturing process while enabling position detection
Solution Approach 2:
The invention changes the physical state of the detection mechanism from rigid (modified tooth profiles) to elastic. The elastic element can deform to accommodate manufacturing tolerances and backlash, ensuring reliable operation without requiring extremely precise manufacturing
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
Enables accurate and cost-effective detection of the wheel's reference axis with reduced complexity and size, avoiding the need for external sensors and minimizing manufacturing complications.
Implementation Method 1
an elastic element secured to the wheel and arranged so as to extend, in projection in a general plane of this wheel in which its teeth are located, in a given hollow between two adjacent teeth of this set
Data Source
Figure 1
Figure 2A~3
Figure 4~5C
AI summary
The electromechanical watch movement comprises a stepper motor, a wheel (22) driven in rotation by this motor, a pinion (24) meshing with this wheel, and a device for detecting the angular position of the wheel. This detection device determines the passage of a reference half-axis (42) of this wheel through a reference angle (αREF) defined by this wheel and the pinion, and includes for this purpose an electronic circuit capable of detecting an additional localized resistive torque during the stepper drive of the wheel. The localized resistive torque is generated by an elastic element (28) fixed to the wheel, a portion of which is superimposed at least on a given groove in the teeth (23) of this wheel. The pinion (24) has teeth (25) that are located at least partially at the level of the elastic element, such that these teeth press against this elastic element when they enter said given groove.