Linear Actuator Yoke Design for Magnetic Leakage Control
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Solution Overview
Problem
Existing electric toothbrushes with linear actuators face issues of high manufacturing cost, weight due to magnetic leakage, and insufficient inertial force, leading to compromised handleability and brushing efficiency.
Innovation Solution
A linear actuator design featuring a yoke made of magnetic material that secures the permanent magnet and coil, reducing magnetic leakage and increasing inertial force without adding weight or complexity, by forming a magnetic circuit and using the yoke as a magnetic shield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the coil and permanent magnets are placed inside a shield case composed of magnetic material to prevent magnetic leakage, then magnetic leakage is reduced, but manufacturing cost increases and weight increases
Solution Approach 1:
The yoke is integrated with the casing to form a unified structure that serves both as structural support and as a magnetic shield. This merging eliminates the need for a separate shield case, reducing manufacturing cost and assembly complexity while maintaining magnetic leakage prevention
Solution Approach 2:
The yoke performs multiple functions simultaneously: it provides structural support for the coil and permanent magnets, guides magnetic flux within the actuator, and acts as a magnetic shield to contain magnetic fields. This multi-functionality reduces the need for additional components
2Object-affected harmful factors
If the coil and permanent magnets are placed inside a shield case composed of magnetic material to prevent magnetic leakage, then magnetic leakage is reduced, but weight increases due to increased handleability deterioration
Solution Approach 1:
The yoke is integrated with the casing to form a unified structure that serves both as structural support and as a magnetic shield. This merging eliminates the need for a separate shield case, reducing manufacturing cost and assembly complexity while maintaining magnetic leakage prevention
Solution Approach 2:
The yoke performs multiple functions simultaneously: it provides structural support for the coil and permanent magnets, guides magnetic flux within the actuator, and acts as a magnetic shield to contain magnetic fields. This multi-functionality reduces the need for additional components
3Weight of moving object
If a lightweight shaft is reciprocated to reduce weight, then weight is reduced, but sufficient inertial force cannot be ensured and brushing force is insufficient
Solution Approach 1:
The yoke acts as an intermediary component that couples the lightweight reciprocating shaft with the stationary casing. By providing a rigid magnetic circuit path through the yoke, it enables the transmission of electromagnetic force to the shaft while the shaft itself remains lightweight, achieving both low weight and sufficient driving force
4Reliability
If at least two magnets are provided to improve performance, then performance is improved, but structure becomes complicated and assemblability deteriorates
Solution Approach 1:
The magnetic circuit is segmented into distinct functional zones within the yoke structure, with the permanent magnet positioned to create specific magnetic flux patterns. This segmentation allows for optimized magnetic field distribution while maintaining a relatively simple overall structure
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 enhances magnetic efficiency, reduces magnetic leakage, and increases the brushing force of the electric toothbrush without increasing the number of parts or weight, improving handleability and cleaning efficiency.
Implementation Method 1
a coil which linearly reciprocates the output member by having a variable magnetic field act on the permanent magnet
Implementation Method 2
a yoke which is composed of a magnetic material, has a midway portion tightly secured to the other magnetic pole of the permanent magnet, extends to the exterior of the coil along the exterior of the permanent magnet with a space from the permanent magnet
Data Source
AI summary
Provided is a linear actuator which is simple in structure, inexpensive to manufacture, in addition, has small magnetic leakage, and can provide a large inertial force without increasing the number of parts and weight. The linear actuator is provided with an output shaft 12 which is supported on a supporting case 11 so as to linearly reciprocate freely, an elastic member 13 which biases the output shaft 12 toward a middle position of the linear reciprocation thereof, a permanent magnet 14 which is fixed to the output shaft 12, a coil 15 which linearly reciprocates the output shaft 12 by having a variable magnetic field act on the permanent magnet 14 and is fixed to the supporting case 11 such that the coil 15 faces one of magnetic poles of the permanent magnet 14, a yoke 16, which is composed of a magnetic material, has a midway portion tightly secured to the other magnetic pole of the permanent magnet 14, extends to the exterior of the coil 15 along the exterior of the permanent magnet 14 with a space from the permanent magnet 14, and has an end portion disposed close to the exterior of the coil 15, and power supply means for forming a variable magnetic field on the coil 15.