Magnetic Escapement Torque Compensation

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Solution Overview

Problem

Timepiece movements with rotating elements and annular magnetized structures experience parasitic friction and magnetic disturbance torques due to ferromagnetic parts, disrupting the operation of magnetic systems, particularly in magnetic escapements, without easy solutions to modify materials or design.

Innovation Solution

A timepiece movement mechanism with a first set of magnetic elements interacting with an annular magnetized structure, supplemented by a second set of magnetic compensation elements arranged to generate a phase-shifted magnetic disturbance torque, reducing the overall magnetic disturbance torque exerted on the rotating element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If ferromagnetic parts are located at the periphery of the rotating element, then the magnetic interaction with the annular magnetized structure generates functional magnetic forces, but parasitic friction force and magnetic disturbance torque are generated on the rotating element

Engineering Contradiction:

Improvemagnetic interaction forceVSAvoidmagnetic disturbance torque

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The patent introduces compensation magnetic elements that generate a harmful magnetic disturbance torque opposite in phase to the original disturbance torque. By strategically positioning these compensation elements, the harmful effect is converted into a beneficial cancellation effect, reducing the net magnetic disturbance torque on the rotating element to a minimum value.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The compensation magnetic elements act as magnetic counterweights that generate opposing magnetic disturbance torques. Similar to mechanical counterweights balancing gravitational forces, these magnetic elements balance the magnetic disturbance torques by positioning them at specific angular offsets that create equal and opposite rotational effects.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Reliability

If magnetic compensation elements are added to reduce magnetic disturbance torque, then the magnetic system operation is improved, but the device complexity increases

Engineering Contradiction:

Improvemagnetic system operationVSAvoidnumber of magnetic elements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent optimizes the configuration parameters of compensation magnetic elements including their magnetic moment magnitudes, angular positions, and orientations. By carefully selecting these parameters, the compensation elements achieve effective torque cancellation with minimal addition to system complexity, rather than requiring large numbers of elements.

Inventive Principle:

Principle #35Parameter changes

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 arrangement significantly reduces the maximum absolute torque value, minimizing interference with the rotating element's operation, with embodiments achieving a maximum resultant torque less than 15% of the initial disturbance torque.

Implementation Method 1

the ferromagnetic part exerts a radial attraction on the annular magnetized structure

Methodology Applied

Scientific EffectMagnetic attraction: Magnetism

Implementation Method 2

the rotating element is also subjected to a magnetic disturbance torque that varies as a function of the angular position of the rotating element

Methodology Applied

Scientific EffectMagnetic torque: Magnetism

Data Source

PatentUS11822294B2Timepiece movement comprising a rotating element provided with a magnetized structure having a periodic configuration

Publication Date: 2023.11.21 MONTRES BREGUET SA

AI summary

A timepiece movement includes a magnetic escapement formed of a magnetic escape wheel with an annular magnetized structure and a pallet fork whose shaft is formed by a ferromagnetic material. The pallet shaft exerts on the escape wheel a magnetic disturbance torque due to the fact that the annular magnetized structure exhibits an angular variation of at least one defining physical parameter thereof, such that the magnetic attraction varies as a function of the angular position of the escape wheel and has a tangential component. A magnetic compensation pin is incorporated in the timepiece movement, this magnetic compensation pin being arranged such that the second magnetic disturbance torque that it exerts on the escape wheel exhibits an angular phase shift relative to the first magnetic disturbance torque generated by the pallet shaft, so as to compensate largely for this first magnetic disturbance torque.