Brushless DC Motor Detent Torque Plate Magnetic Short Circuit
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Solution Overview
Problem
Existing brushless DC motors face performance loss and noise issues due to mechanical contact from restraining springs used for detent position control, which also lead to inconsistent inhibition and reduced maximum inhibition capability.
Innovation Solution
A brushless DC motor design incorporating a cogging torque plate with T-shaped pole shoes that create a magnetic short circuit between adjacent rotor poles, eliminating the need for locking springs and allowing for higher inhibition with minimal performance reduction, by arranging the cogging torque plate outside the stator's magnetic field during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If restraining springs are used to hold the motor in detent position when de-energized, then the motor can be prevented from rotating, but the springs brake the motor during operation causing performance loss
Solution Approach 1:
The patent replaces the mechanical restraining spring system with a magnetic field-based detent mechanism. The detent torque plate with pole shoes interacts magnetically with the rotor cup's permanent magnets to provide detent positioning, eliminating the need for mechanical contact during operation and thus avoiding performance loss while maintaining reliable detent control.
Solution Approach 2:
The patent extracts the detent function from the mechanical spring system and implements it separately through the detent torque plate. This allows the spring to be completely removed or greatly reduced, eliminating its harmful braking effect during operation while preserving the detent positioning capability through magnetic interaction alone.
2Reliability
If restraining springs are used to provide inhibition torque, then the motor can be held in position, but mechanical contact generates unwanted noise during operation
Solution Approach 1:
The patent substitutes the mechanical spring-based position holding system with a magnetic field-based detent mechanism. The detent torque plate creates magnetic attraction forces that hold the rotor in desired positions without any mechanical contact, thereby eliminating the noise generated by spring-gear interaction while maintaining reliable position holding.
3Reliability
If restraining springs are used to maximize inhibition capability, then higher detent torque can be achieved, but it becomes extremely difficult to produce consistent inhibition within defined tolerance limits
Solution Approach 1:
The patent changes the fundamental parameter of detent generation from mechanical spring force to magnetic field interaction. The magnetic detent torque can be precisely controlled by adjusting the magnetic field strength, pole shoe geometry, and air gap, allowing consistent inhibition within narrow tolerance ranges without the manufacturing variability inherent in mechanical spring systems.
Solution Approach 2:
The patent replaces the mechanical spring system with a magnetic field-based detent mechanism that offers superior controllability and consistency. The magnetic interaction provides smooth, adjustable detent torque that can be precisely tuned through field strength and geometric parameters, eliminating the difficulty of achieving consistent inhibition with mechanical springs.
4Reliability
If a brake disk made of ferromagnetic material is placed within the stator coil's magnetic field area to achieve currentless detent, then the rotor can be held in defined position when switched off, but the brake disk influences the magnetic field interaction during operation reducing motor performance
Solution Approach 1:
The patent positions the detent torque plate in a different spatial dimension - axially displaced from the stator coil's magnetic field area. The detent plate is located at the axial ends of the stator, where it interacts with the rotor cup's permanent magnets without interfering with the radial magnetic field between the stator coils and rotor, thus achieving detent positioning without performance loss.
Solution Approach 2:
The patent creates different local magnetic environments: the stator coil region maintains its rotating magnetic field for motor operation, while the axial end regions where the detent torque plate is located provide a static magnetic field for detent positioning. This local differentiation allows both functions to operate independently without mutual interference.
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 enables the generation of significant detent torque within a narrow tolerance range without affecting the motor's electrical behavior, reducing power losses and noise, and providing consistent inhibition performance.
Implementation Method 1
the pole shoes of the detent torque plate are arranged such that they form a magnetic short circuit in the locking position between two adjacent poles of the rotating rotor cup
Implementation Method 2
a detent torque plate connected to the stator with a plurality of pole shoes for generating a the rotating rotor cup is provided in a locking position bringing cogging torque
Implementation Method 3
There are two magnetic fields in an electric motor with permanent magnets. One is generated by the permanent magnet and is also present when there is no current.
Implementation Method 4
A second is generated by current-carrying coils. The interaction of the two magnetic fields causes the motor to rotate and generate torque.
Data Source
Figure 1
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Figure 3
AI summary
The invention relates to a brushless direct-current motor (1), comprising a stator (2), a rotor cup (30) that revolves around the stator (2) and has a plurality of permanent-magnet poles (N, S), and a detent torque plate (4) that is connected to the stator (2) and has several pole shoes (41) for generating a detent torque that brings the revolving rotor cup (30) into a detent position. The pole shoes (41) are each arranged in the detent position between two adjacent poles (N, S) of the revolving rotor cup (30) to form a magnetic short circuit. The detent torque plate (4) is arranged substantially outside of the magnetic rotating field produced by the stator (2) during operation, whereby the production of the detent torque is decoupled from the electrical behavior of the brushless direct-current motor (1) and the power of the brushless direct-current motor (1) is not substantially influenced by the presence of the detent torque plate (4).