Rotational Angle Detection in Electric Rotating Machines
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Solution Overview
Problem
Existing electric rotating machines face challenges in accurately detecting the rotational angle of an output shaft due to size and weight reduction, leading to noise suppression and decreased rotation accuracy, particularly in integrated systems where the ring magnet and hall element positioning is critical.
Innovation Solution
The electric rotating machine optimizes the arrangement of a sensor magnet and rotation sensor by magnetizing the sensor magnet in a circumferential direction and placing the rotation sensor between the magnetic body and sensor magnet, ensuring an appropriate amplitude ratio between radial and circumferential magnetic flux density components to reduce angle detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the ring magnet and hall element are arranged in close vicinity to reduce size, then the size and weight of the apparatus are reduced, but the rotational angle detection accuracy deteriorates due to increased sensitivity to positional accuracy requirements
Solution Approach 1:
The patent applies local quality by optimizing the specific positioning of the hall element within the magnetic field distribution. Instead of requiring high positional accuracy for multiple hall elements, the invention identifies a specific location where the magnetic flux density components satisfy a predetermined relationship (amplitude ratio between radial and circumferential components), thereby achieving accurate rotational angle detection at that particular location without stringent requirements for overall positioning precision.
Solution Approach 2:
The patent utilizes parameter changes by varying the spatial position of the hall element to find an optimal location. The invention changes the position parameter of the hall element until the magnetic flux density components satisfy the predetermined relationship, thereby transforming the detection accuracy problem into a parameter optimization problem that can be solved by adjusting position rather than requiring high manufacturing precision.
2Reliability
If multiple hall elements are used to detect magnetic flux density at plural positions, then the rotational angle detection coverage is improved, but the device complexity and manufacturing difficulty increase due to the need to manage positional accuracy of multiple elements
Solution Approach 1:
The patent applies the taking out principle by extracting the essential detection function to a single hall element positioned at the optimal location. Instead of requiring multiple hall elements to cover different positions, the invention identifies and utilizes the specific region where the magnetic flux density components satisfy the predetermined relationship, thereby achieving reliable detection with a single sensor and eliminating the complexity of managing multiple elements and their positional 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 configuration enhances the rotational angle detection accuracy by minimizing errors in the magnetic flux density components, improving the overall detection precision and noise tolerance while maintaining a compact design.
Implementation Method 1
N-pole and S-pole are magnetized in a circumferential direction around the output shaft in the sensor magnet
Implementation Method 2
a sensor magnet fixed to the output shaft and generating a magnetic field for detecting a rotational angle of the output shaft
Data Source
AI summary
In an electric rotating machine including an output shaft, a magnetic body fixed inside a case surrounding the output shaft, a sensor magnet fixed to the output shaft and generating a magnetic field for detecting a rotational angle of the output shaft and a rotation sensor fixed inside the case, arranged between the magnetic body and the sensor magnet in an axial direction of the output shaft and outputting a signal in accordance with the intensity of the magnetic field for detecting the rotational angle, N-pole and S-pole are magnetized in a circumferential direction around the output shaft in the sensor magnet and the rotation sensor is arranged in an area in which amplitudes of a radial-direction component Br around the output shaft and a circumferential-direction component Bθ in a magnetic flux density B of the magnetic field are equivalent.