Brushless Motor Position Detection with Offset Hall ICs
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Solution Overview
Problem
Existing brushless motors with double precision position detection face challenges in achieving high reliability due to detection angle errors between main and sub-Hall ICs, which affect the accuracy of rotor position detection.
Innovation Solution
A brushless motor position detection device with a stator and rotor configuration that includes a magnetic pole position detecting magnet and both main and sub-Hall ICs, where the sub-Hall ICs are offset to maintain the difference in magnetic flux density within a prescribed limit, ensuring minimal detection angle error and achieving quadruple precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of Hall ICs is increased from three to six (adding sub-Hall ICs) to achieve quadruple precision position detection, then the rotation position detection resolution is improved, but the detection angle error increases due to mounting position inaccuracies
Solution Approach 1:
The patent adjusts the magnetic pole positions of the detecting magnet to optimize the magnetic flux density distribution. By changing the magnetic pole position parameter, the system achieves a state where the difference in maximum magnetic flux density between first and second Hall element mounting positions is within a prescribed limit, thereby minimizing detection angle errors while maintaining quadruple precision resolution.
Solution Approach 2:
The patent uses a magnetic pole position detecting magnet with poles that correspond to the rotor poles to create a replicated magnetic field pattern. This copying approach allows the Hall elements to detect position information with high precision by comparing the magnetic flux densities from the replicated field, reducing the impact of mounting position variations.
2Measurement precision
If the magnetic pole position detecting magnet is designed with 2n poles for an n-pole rotor to achieve double precision, then the detection resolution is improved, but further doubling to 4n poles for quadruple precision increases the complexity of maintaining consistent magnetic flux density across multiple Hall IC mounting positions
Solution Approach 1:
The patent optimizes the magnetic pole position parameter of the detecting magnet to achieve a configuration where the magnetic flux density distribution satisfies the requirement for quadruple precision detection. By adjusting this parameter, the system maintains consistent magnetic flux density characteristics across multiple Hall IC mounting positions without requiring complex structural modifications.
3Measurement precision
If the offset between main Hall ICs and sub-Hall ICs is adjusted to achieve quadruple precision, then the position detection resolution is improved, but the mounting position accuracy requirement becomes more stringent
Solution Approach 1:
The patent changes the magnetic pole position parameter of the detecting magnet to compensate for mounting position variations. By optimizing this parameter, the system achieves quadruple precision detection while relaxing the stringent mounting position accuracy requirements, as the magnetic field configuration naturally compensates for minor positioning errors.
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
The solution effectively minimizes detection angle errors between main and sub-Hall ICs, enhancing the reliability and accuracy of rotor position detection to quadruple precision levels, enabling precise operation in applications like throttle valves and VG turbo systems.
Implementation Method 1
a set of first Hall elements mounted on a plane facing the magnetic pole position detecting magnet for detecting the position of the rotor
Data Source
AI summary
A brushless motor position detection device has a set of first Hall elements (main Hall ICs 18 for detecting magnetic pole positions) and a set of second Hall elements (sub-Hall ICs 19 for detecting magnetic pole positions) mounted on a plane facing a magnetic pole position detecting magnet 16 for detecting the position of a rotor 12. They are subjected to offset adjustment and are mounted in such a manner that the difference between the maximum value of the magnetic flux density at the mounting positions of the first Hall elements and the maximum value of the magnetic flux density at the mounting positions of the second Hall elements is held within a prescribed limit (mounted in such a manner as to have the offset of a prescribed machine angle in the circumferential direction) to bring the detection accuracy of the plurality of sets of the Hall elements into agreement.