Voice Coil Actuator for Miniaturized Electric Toothbrush
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Solution Overview
Problem
Conventional electric toothbrushes face challenges in miniaturization due to the need for a drive source, motion direction converting mechanisms, and resonance vibrating mechanisms, which also lead to noise and inefficiency issues.
Innovation Solution
An actuator configuration featuring a permanent magnet, coil, and a linear elastic member, where an alternating current of resonance frequency is supplied to the coil to achieve back-and-forth rotating motion without a drive transmitting mechanism, utilizing a magnetic circuit with a U-shaped outer yoke and a voice coil for efficient vibration transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a regular motor or linear drive actuator is used as a drive source, then the toothbrush can be driven, but the device size increases due to the need for additional motion direction converting mechanisms or torque generating mechanisms
Solution Approach 1:
The patent combines the drive source and motion direction converting mechanism into a single integrated actuator unit. The voice coil motor directly generates oscillating torque around the output shaft axis, eliminating the need for separate motion direction converting mechanisms. This merging of functions reduces the overall volume of the handle part while maintaining the toothbrush drive function.
Solution Approach 2:
The actuator serves multiple functions simultaneously: it acts as both the drive source (generating oscillating torque) and the motion direction converting mechanism (producing back-and-forth rotating motion directly). This multi-functionality reduces the number of separate components needed, thereby reducing the volume of the handle part.
2Ease of operation
If a motion direction converting mechanism is provided apart from the actuator, then the desired motion can be achieved, but noise is produced and power loss occurs
Solution Approach 1:
The patent extracts the motion direction converting function from separate mechanical components and integrates it directly into the actuator's operation. The voice coil motor's electromagnetic field directly generates oscillating torque, eliminating the need for intermediate mechanical conversion mechanisms that would produce noise and power loss.
Solution Approach 2:
The patent replaces traditional mechanical motion direction converting mechanisms with an electromagnetic system. The voice coil motor uses electromagnetic fields to directly generate oscillating torque, substituting mechanical linkages, gears, or cam mechanisms with an electromagnetic field-based solution that reduces noise and power loss.
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 miniaturization of electric toothbrushes by eliminating the need for additional drive mechanisms, reducing noise, and improving efficiency through low power consumption and effective vibration transmission.
Implementation Method 1
a coil that is placed in the air gap and surrounds the permanent magnet... an alternating current supplying section that supplies an alternating current of approximately a same frequency as a resonance frequency of the movable body to the coil
Implementation Method 2
a linear elastic member that has its one end fixed to the fixed body and the other end fixed to the movable body, and that supports the movable body on the fixed body to be able to rotate about an axis along the output shaft
Implementation Method 3
a permanent magnet that is placed to oppose the opposing inner wall planes over an air gap and that has different magnetic pole planes that oppose the inner wall planes respectively
Data Source
AI summary
Disclosed is an actuator that realizes reciprocal rotational motion of an electric toothbrush, for example, without utilizing a drive transmission mechanism that is separate from the drive source. In the actuator, a fixed body (120) has a coil (128) that is disposed around a magnet (160) and faces the magnetic planes with different polarities within the magnet (160) at individual prescribed distances, and an outer yoke (150) that covers the outer periphery of the coil (128). The fixed body (120) rotatably supports a movable body (110), which holds the magnet (160), via a coil spring that is an elastic member (130) made from a wire. An alternating current supplying part (140) supplies an alternating current having roughly the same resonance frequency as that of the fixed body (120) to the coil (128) to cause the movable body (110) to vibrate in a reciprocal rotational motion. The coil spring that is the elastic member (130) uniformly disperses stress generated by the vibration.