Hall Sensor Force Detection in Resonant Motor Hygiene Device
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Solution Overview
Problem
Existing personal hygiene devices with resonant motors face challenges in accurately measuring external treatment forces due to the combined motion of the permanent magnet and the need for Hall sensors to adapt sensitivity ranges, which is complicated by limited space, manufacturing tolerances, and interference from gravity and vibrations.
Innovation Solution
A personal hygiene device design featuring a motor carrier pivot-mounted against a spring element, with a Hall sensor and sensor permanent magnet positioned to detect relative motion, optimizing the magnetic field strength and sensitivity range to accurately measure treatment forces within specific thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall sensor is used to monitor the combined motion of the permanent magnet unit, then the external treatment force can be measured, but the sensitivity range of the Hall sensor must be adapted to accommodate the full range of combined motions, which complicates the device
Solution Approach 1:
The patent extracts the measurement of pivoting motion from the combined motion monitoring. By specifically measuring only the pivoting motion component caused by external treatment force, the Hall sensor's sensitivity range requirements are reduced, simplifying the device while maintaining measurement precision for force detection
Solution Approach 2:
The patent segments the motion components by separating the oscillating motion of the resonant motor from the pivoting motion caused by external force. The Hall sensor is positioned and configured to detect only the pivoting component, which simplifies the sensitivity range requirements compared to monitoring the full combined motion
2Measurement precision
If the Hall sensor is positioned to monitor combined motion, then force measurement is possible, but limited space and manufacturing tolerances make sensitivity range adaptation difficult
Solution Approach 1:
The patent extracts the pivoting motion measurement from the combined motion, positioning the Hall sensor to detect only the pivoting component. This reduces the impact of manufacturing tolerances on sensor positioning because the sensor only needs to accurately capture the pivoting motion arc, not the full combined motion envelope
Solution Approach 2:
Instead of positioning the Hall sensor to monitor the permanent magnet's position directly, the patent inverts the approach by having the sensor monitor the pivoting motion of the motor carrier relative to the handle. This indirect measurement approach reduces sensitivity to manufacturing tolerances in sensor placement
3Adaptability or versatility
If the Hall sensor monitors the full range of combined motions, then complete motion information is obtained, but the sensitivity range must be increased, which may reduce measurement precision for small forces
Solution Approach 1:
The patent extracts the pivoting motion component from the combined motion, allowing the Hall sensor to operate in a reduced sensitivity range optimized for detecting small forces. The sensor only needs to capture the pivoting arc caused by external force, not the full oscillation amplitude, thereby maintaining high precision for small force detection
Solution Approach 2:
The patent dynamically separates the motion components by using the known oscillation characteristics of the resonant motor to isolate the pivoting motion caused by external force. This dynamic separation allows the Hall sensor to maintain optimal sensitivity for force detection while the system adapts to different operating conditions
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 design simplifies the measurement of external treatment forces, provides optimal sensitivity range adaptation, and effectively communicates force feedback to the user, ensuring proper force application without exceeding maximum limits.
Implementation Method 1
a Hall sensor mounted in fixed relationship to the handle or to the motor carrier, and a sensor permanent magnet, in particular of cylindrical shape, mounted in fixed relationship to the other one of the handle or motor carrier so that a pivoting motion of the motor carrier leads to a relative movement between the sensor permanent magnet and the Hall sensor
Implementation Method 2
the motor comprising a motor permanent magnet and a coil element for providing an alternating electromagnetic field interacting with the motor permanent magnet so that an oscillating motion of the drive shaft is excited in operation
Implementation Method 3
The resonant motor comprises a coil unit for providing an alternating electromagnet field and a permanent magnet unit for interacting with the alternating electromagnetic field. Such a spring-mass system has a resonant behavior, i.e. depending on the motor design, which means the mass and the spring constant, the amplitude of the armature portion becomes maximal when the frequency of the periodic external force is at the natural or resonance frequency of the spring-mass system
Implementation Method 4
a motor carrier that is pivot mounted against at least one spring element arranged between the handle and the motor carrier
Data Source
AI summary
A personal hygiene device has a handle, a treatment head, and a motor carrier disposed in the handle. The motor is pivot-mounted against at least one spring element arranged between the handle and the motor carrier. The motor has a stator portion fixedly mounted at the motor carrier and an armature portion spring mounted at the motor carrier to allow a motion relative to the motor carrier. The armature portion is coupled with a drive shaft connected with the treatment head for transferring motion thereto, wherein an external treatment force acting on the brush head leads to pivoting of the motor carrier relative to the handle. The motor has a motor permanent magnet and a coil for providing an alternating electromagnetic field interacting therewith to excite an oscillating motion of the drive shaft. A Hall sensor is fixedly mounted to the handle or to the motor carrier; and a sensor permanent magnet is fixedly mounted to the other one of the handle and motor carrier, so that a pivoting motion of the motor carrier leads to a relative movement between the sensor permanent magnet and the Hall sensor.