Absolute Encoder Device With Dual Magnetic Patterns
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Solution Overview
Problem
Existing absolute encoder devices face challenges in achieving high resolution and accuracy while being cost-effective and easy to assemble, due to limitations in magnetic sensor configurations and the need for additional components to manage magnetic fields and interference.
Innovation Solution
An absolute encoder device with a permanent magnet featuring a first magnetic pattern of two poles and a second magnetic pattern of multiple poles, where both sensors and a signal processing circuit are integrated on a single substrate, reducing the need for additional support members and simplifying assembly, and the magnetic patterns are positioned to minimize leakage fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bipolar permanent magnet is used with a magnetic sensor, then the device is less expensive and has better environmental resistance, but the resolution and accuracy are limited due to restricted resistance change ratio
Solution Approach 1:
The permanent magnet is segmented into multiple magnetic poles (first magnetic pattern with two poles, second magnetic pattern with multiple poles) instead of using a simple bipolar magnet. This segmentation allows different magnetic patterns to be detected by different sensors, enabling high resolution and accuracy while maintaining cost-effectiveness through the use of magnetic sensors rather than optical components.
Solution Approach 2:
The patent introduces a multi-dimensional magnetic field structure by creating multiple magnetic patterns (first pattern with two poles, second pattern with multiple poles) on the permanent magnet. This dimensional complexity in the magnetic field configuration enables higher measurement precision while still using cost-effective magnetic sensors, resolving the contradiction between low cost and high precision.
2Measurement precision
If two types of magnetic patterns are combined on the permanent magnet to achieve higher resolution and accuracy, then measurement precision improves, but device complexity increases due to additional substrates and magnetic shield plates
Solution Approach 1:
Multiple magnetic patterns (first magnetic pattern and second magnetic pattern) are merged onto a single permanent magnet instead of using separate magnets or substrates. This consolidation reduces the number of components and simplifies the overall device structure while maintaining the ability to achieve high resolution and accuracy through the combined magnetic patterns.
Solution Approach 2:
The single permanent magnet serves multiple functions by incorporating both the first magnetic pattern (for absolute angle detection) and the second magnetic pattern (for relative angle detection with higher resolution). This multi-functional design eliminates the need for separate substrates and shield components, reducing device complexity while achieving high measurement precision.
3Volume of moving object
If magnetic patterns are positioned closer together to reduce device size, then compactness improves, but magnetic field interference increases affecting detection accuracy
Solution Approach 1:
Different regions of the permanent magnet are given different magnetic pattern characteristics (first magnetic pattern with two poles, second magnetic pattern with multiple poles). This local differentiation allows each magnetic pattern to be optimized for its specific detection function while minimizing interference between them, enabling compact design without sacrificing accuracy.
Solution Approach 2:
The patent uses the permanent magnet itself as an intermediary structure that houses both magnetic patterns. By integrating the patterns within the same magnet body rather than placing them as separate components, the design achieves compactness while the magnet's structure helps manage and minimize magnetic field interference between the different patterns.
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 high-resolution and high-accuracy angle detection without complex calculations, reduces assembly complexity and costs, and minimizes the impact of external magnetic fields, facilitating the production of a compact and efficient encoder device.
Implementation Method 1
a sensor using a spin-valve giant magnetoresistive element (SV-GMR) as a magnetoresistive element
Implementation Method 2
A pinned layer magnetization direction is fixed, and a free layer magnetization direction changes in accordance with an external magnetic field direction
Implementation Method 3
a magnetic field of the first magnetic pattern and a magnetic field of the second magnetic pattern
Data Source
Figure 1~2
Figure 3(a)~4
Figure 5(a)~5(b)
AI summary
It is an object to provide a compact absolute encoder device, which is readily assembled and realizes high resolution. The present invention provides an absolute encoder device (1), including: a permanent magnet (4) including a first magnetic pattern 14 (bipolar) and a second magnetic pattern (16) (multipolar); a first magnetic sensor (5) for detecting a magnetic field of the first magnetic pattern (14); a second magnetic sensor (6) for detecting a magnetic field of the second magnetic pattern (16); and a signal processing circuit (7) for calculating an absolute rotation angle of a rotation shaft (2) based on output signals of the first and second magnetic sensors (5 and 6). The first and second magnetic sensors (5 and 6) and the signal processing circuit (7) are fixed to a single substrate (8). The first magnetic pattern (14) is formed on a plane extending in a direction crossing an axial direction inside the permanent magnet (4), and the second magnetic pattern (16) is formed on an outer peripheral surface of the permanent magnet (4).