Magnet-Hall Sensor Switch for Power Tool Direction Reversal
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Solution Overview
Problem
Existing cordless power tools require complex actuators to reverse motor polarity for changing the direction of rotation, which can be cumbersome and less efficient in precision applications.
Innovation Solution
A power tool design utilizing a single magnet and a hall sensor to change the drive direction and lock the forward/reverse switch actuator into position, where the magnet contacts different ferromagnetic members based on its position and cooperates with a hall sensor to reverse motor polarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single magnet and hall sensor system is used to reverse motor polarity, then device complexity is reduced, but reliability of actuator positioning may be compromised
Solution Approach 1:
The patent replaces complex mechanical actuators with a magnetic field-based system. A single magnet positioned in different locations within the motor housing creates magnetic fields that are detected by hall sensors, which then trigger polarity reversal. This substitutes mechanical actuation mechanisms with a magnetic sensing and control system, reducing mechanical complexity while maintaining functional reliability through precise magnetic field detection.
Solution Approach 2:
The patent introduces hall sensors as intermediary elements between the magnet positions and the motor control system. The hall sensors detect the magnetic field strength and polarity at specific locations, converting magnetic field information into electrical signals that control the polarity reversal. This intermediary sensing mechanism ensures reliable actuator positioning detection without requiring direct mechanical contact or complex mechanical linkages.
2Manufacturing precision
If a single magnet is used to change drive direction, then manufacturing precision requirements are reduced, but measurement precision of actuator position may be affected
Solution Approach 1:
The patent implements a feedback system using hall sensors to detect the magnet's position based on magnetic field strength. The control system continuously monitors the hall sensor outputs and uses this feedback information to determine when the magnet reaches specific positions, thereby controlling the polarity reversal timing. This feedback mechanism compensates for variations in manufacturing tolerances and ensures precise actuator position detection without requiring extremely tight manufacturing precision.
Solution Approach 2:
The patent utilizes changes in magnetic field parameters (strength and direction) as the magnet moves to different positions. By monitoring these parameter changes through hall sensors, the system can precisely determine actuator position. The magnetic field parameters naturally vary with position, providing a built-in measurement mechanism that reduces dependency on mechanical precision while maintaining detection accuracy.
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
This design simplifies the actuation process, allowing a single magnet to efficiently change the drive direction and lock the actuator, enhancing precision and ease of use in cordless power tools.
Implementation Method 1
a magnet positioned within a tool housing and configured to contact a first ferromagnetic member when the actuator is in the first position and contact a second ferromagnetic member when the actuator is in the second position
Implementation Method 2
a hall sensor positioned within the tool housing and configured to reverse the polarity across the armature of the motor in response to movement of the magnet between the first and second positions
Data Source
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AI summary
A power tool includes a housing, an electric motor mounted in the housing, and a switching device for reversing rotation direction of the motor. The switching device includes an actuator slidably secured to the housing and movable between first and second positions. The actuator includes a magnet. A first ferromagnetic member is attached to a first housing section so as to be within range of attraction force of the magnet when the actuator is in the first position and a second ferromagnetic member is attached to a second housing section so as to be within range of attraction force of the magnet when the actuator is in the second position. A hall sensor is attached to the housing so as to be proximate the magnet as the actuator is moved between first and second positions. Proximity of the magnet and hall sensor reverses the direction of rotation of the motor.