Axially Extended Permanent Magnet for Integrated Angle Detection
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Solution Overview
Problem
Existing synchronous motors face challenges in achieving compact, inexpensive, and reliable angle detection within the motor without interfering with the magnetic fields used for torque generation, while maintaining low moment of inertia and minimizing mechanical changes.
Innovation Solution
The motor incorporates an axially extended permanent magnet area that serves as a strong magnetic field transmitter for a sensor device, allowing for compact, integrated angle detection inside the motor, using sensors like Wiegand sensors that can operate at low speeds and provide high resolution with minimal interference from stator windings, and integrates the evaluation unit for angular position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an incremental encoder is attached to the rotor shaft for angle detection, then angle detection capability is provided, but the moment of inertia increases and the device becomes more complex
Solution Approach 1:
The patent merges the angle detection function with the existing permanent magnet area by axially extending the permanent magnets. This integration eliminates the need for separate encoders or angle sensors, thereby maintaining low moment of inertia while providing accurate angle detection through magnetic field sensing.
Solution Approach 2:
The permanent magnet area serves dual functions: generating torque for motor operation and providing a magnetic field for angle detection. By extending the permanent magnets axially beyond the stator winding area, the same magnetic components perform both propulsion and sensing functions, reducing overall system complexity and inertia.
2Object-affected harmful factors
If a sensor is positioned in the axial area separated from the stator winding, then interference from stator windings is reduced, but the magnetic field strength available for sensing decreases
Solution Approach 1:
The patent utilizes the axial dimension to resolve the contradiction between interference reduction and field strength. By extending the permanent magnets axially beyond the stator winding area, the sensor can be positioned in a region where it experiences strong magnetic fields from the extended magnets while being spatially separated from the interfering stator windings in the radial direction.
3Strength
If the permanent magnet area is axially extended beyond the stator winding area, then a strong magnetic field is provided for the sensor, but the manufacturing complexity increases
Solution Approach 1:
The permanent magnet area is segmented into two distinct axial regions: a first axial area that overlaps with the stator winding area for torque generation, and a second axial area that extends beyond the stator winding area for angle detection. This segmentation allows each region to be optimized for its specific function while simplifying the manufacturing process by clearly defining the boundaries and purposes of each magnetic zone.
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 enables reliable, high-resolution angle detection with low susceptibility to failure, maintaining a low moment of inertia and reducing the need for additional angle sensors, by utilizing the same magnetic field for torque generation and angle detection, with minimal mechanical changes and robust energy supply even at slow speeds.
Implementation Method 1
synchronous motors have a permanent magnet area provided on the rotor which is provided in cooperation with the stator field for torque generation
Implementation Method 2
Precisely these permanent magnet parts that are designed in this way and are located in the permanent magnet area are now designed to be axially extended. In this way, this extension is a transmitter with a very strong magnetic field for the sensor
Implementation Method 3
The sensor device is arranged at the axial end of the extension and is used for detecting the angular position of the rotor
Implementation Method 4
Because the folding of the impulse wire sensors, especially Wiegand sensors, occurs abruptly and leads to strong signal currents even at the slowest rotational speeds with almost standstill
Data Source
Figure 1
AI summary
Electric motor and use of a permanent magnet area which is provided on the rotor of an electric motor, with the permanent magnet area interacting with the field produced by the stator of the electric motor in order to produce torque, with the permanent magnet area extending further axially along at least one axial end area than that area at which the laminated core of the stator extends and/or over which the stator winding of the stator extends, with a sensor device being arranged at the axial end.