Electric Hand Tool Electromagnetic Brake Control
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Solution Overview
Problem
Conventional electric hand tools, such as grinding machines, face issues with grinding quality degradation and increased motor burden due to constant contact between a damping body and the grinding disc, leading to wear and pollution, and existing solutions require position detection or complex damping mechanisms.
Innovation Solution
An electric hand tool employing an electromagnetic brake system with a brake loop that causes a short circuit between coils and the driving module, utilizing residual rotational energy to generate a magnetic field that interferes with the rotor's magnetic field, effectively stopping the rotor without a damping body, and incorporating an eccentric block for centrifugal force to manage residual rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a damping body is used to decelerate the grinding disc, then the rotational speed can be reduced after motor shutdown, but the grinding quality is degraded and wear occurs between the damping body and contact plane
Solution Approach 1:
The patent replaces the mechanical damping body system with an electromagnetic braking system. The electromagnetic brake uses magnetic fields to generate braking force on the rotor, eliminating the need for mechanical contact between a damping body and the grinding disc. This substitution resolves the contradiction by providing speed control without mechanical wear that degrades grinding quality.
Solution Approach 2:
The patent removes the damping body from the system entirely and replaces it with an electromagnetic braking mechanism. By extracting the problematic mechanical contact component and substituting it with a non-contact electromagnetic field-based braking system, the invention eliminates wear between the damping body and contact plane while maintaining the ability to control rotational speed.
2Speed
If a damping body is used to decelerate the grinding disc, then rotational speed can be controlled, but wear is caused by abrasion between the damping body and contact plane requiring regular replacement
Solution Approach 1:
The electromagnetic braking system replaces the mechanical damping body, eliminating abrasion and wear between contacting surfaces. The electromagnetic brake uses magnetic fields to apply braking force without physical contact, thereby improving reliability by removing components that require regular replacement due to wear.
Solution Approach 2:
The electromagnetic braking system is integrated into the motor control circuitry, utilizing the existing coils and magnetic fields. The brake loop causes coils to form short circuits that generate braking force automatically when the motor shuts down, eliminating the need for separate mechanical braking components and reducing maintenance requirements.
3Speed
If a damping body is used to decelerate the grinding disc, then rotational speed can be reduced, but powder is produced due to abrasion causing pollution
Solution Approach 1:
By replacing the mechanical damping body with an electromagnetic braking system, the invention eliminates the abrasion that generates harmful powder. The electromagnetic brake applies braking force through magnetic fields without mechanical contact, thereby preventing the generation of pollution-causing abrasion particles.
4Speed
If a damping body is used to decelerate the grinding disc, then rotational speed can be controlled, but the electric motor burden is increased
Solution Approach 1:
The electromagnetic braking function is achieved by causing the motor coils to form short circuits through the brake loop. This utilizes the motor's own electromagnetic fields and current to generate braking force, eliminating the need for separate braking motors or mechanical systems that would increase the overall power burden on the electric motor system.
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 solution simplifies the tool structure by eliminating the need for a damping body, improving grinding quality, reducing wear, and preventing pollution, while efficiently stopping the rotor using electromagnetic braking.
Implementation Method 1
a sensing current is generated by the rotor continually rotating through the residual rotational energy, a first magnetic field is produced by a plurality of permanent magnets provided on the electric motor, and an interfering impulsive force is generated by interfering the first magnetic field with a second magnetic field
Implementation Method 2
a sensing current is generated by the rotor continually rotating through the residual rotational energy
Implementation Method 3
an interfering impulsive force is generated by interfering the first magnetic field with a second magnetic field, to stop the rotor from rotating
Implementation Method 4
the tool axis comprises an eccentric block to generate a centrifugal force
Data Source
Figure 1
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AI summary
An electric hand tool (1) is provided. The electric hand tool (1) receives a shutdown signal (121) issued by a shutdown element (12) under control during an operation process of the electric hand tool (1), so as to request a driving module (11) to stop providing a driving signal (111) to a plurality of coils (134) provided at the electric motor (13), and to conduct a brake loop (15) connected to the coils (134) and the driving module (11). Thus, a short circuit is formed between the coils (134) and the driving module (11) to cause the electric motor (13) to temporarily enter a power generating state to generate a sensing current. The coils (134) receive the sensing current to establish a first magnetic field. The first magnetic field interferes with a second magnetic field produced by a plurality of permanent magnets (133) to form an interfering repulsive force that stops the rotor (131) from rotating, thereby achieving an object of braking promptly.