Motor Magnetic Sensor Positioning for Flux Interference Reduction
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Solution Overview
Problem
In existing motors, the Hall element is easily influenced by magnetic flux from the coil, making it difficult to detect the rotational position of the rotor with high accuracy.
Innovation Solution
The motor design includes a magnet with a projection portion that extends towards the bearing, positioning the magnetic sensor between the rotor core and the bearing, allowing it to detect magnetic flux in the radial direction without interference from the coil, and is housed in a holder with conductive plate-like members for terminal connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Hall element is disposed just above the coil, then the structure is simple, but the Hall element is easily influenced by magnetic flux from the coil, making it difficult to detect rotational position with high accuracy
Solution Approach 1:
The magnetic sensor is positioned in the axial direction between the rotor core and bearing, rather than radially above the coil. This dimensional repositioning allows the sensor to detect magnetic flux from the magnet's projection portion while being separated from the coil's magnetic flux path, thereby reducing interference and improving detection accuracy
Solution Approach 2:
The magnet's projection portion acts as an intermediary structure that guides and concentrates magnetic flux toward the magnetic sensor. This projection portion enables the sensor to detect rotational position accurately by providing a dedicated magnetic flux path that is separate from the coil's magnetic field
2Measurement precision
If the magnetic sensor is positioned between the rotor core and bearing, then detection accuracy is improved, but the device complexity increases due to additional holder and terminal structures
Solution Approach 1:
The holder integrates multiple functions: it supports the magnetic sensor, provides electrical insulation between the sensor terminal and rotor, and serves as a mounting structure. By combining these functions into a single component, the overall device complexity is reduced despite the sensor's repositioning
Solution Approach 2:
The holder structure serves multiple purposes simultaneously: mechanical support for the sensor, electrical insulation barrier, and structural element of the motor assembly. This multi-functionality reduces the need for separate components, offsetting the complexity introduced by the sensor's new position
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 configuration enables accurate detection of the rotational position of the rotor with reduced influence from the coil's magnetic flux, allowing for a more reliable and compact motor design.
Implementation Method 1
the magnetic sensor detects a magnetic flux in a radial direction of the magnet
Data Source
AI summary
A motor includes a rotational shaft, a bearing supporting the rotational shaft, a magnet including plural magnetic poles in a circumferential direction, a rotor core disposed inside the magnet, and a magnetic sensor. The magnet includes a projection portion projecting toward a side of the bearing with respect to the rotor core in a direction of the rotational shaft. The magnetic sensor is positioned between the rotor core and the bearing in the direction of the rotational shaft and is positioned inside an inner peripheral surface of the projection portion.