Position Detecting Device Using AMR and GMR Elements
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Solution Overview
Problem
Current position detecting devices using magnetic absolute-type encoders face challenges in achieving stable recording and high resolution due to limitations in distinguishing polarized directions and maintaining uniform magnetization intensity, leading to reduced signal quality and detection errors, especially in industrial machines requiring high precision.
Innovation Solution
A position detecting device with a recording medium having a first track for non-repetitive binary information and a second track specifying the reading section, where the first track includes an effective section for recording and an invalid section at the border, allowing for stable recording without 'absence of record' and maintaining a superior spacing characteristic, enabling detection of continuous signals within 50% or more of one bit length with a virtually constant magnetic field intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AMR elements are used to read magnetic scale patterns, then the device can detect absolute position, but it cannot distinguish polarized directions leading to reduced measurement precision
Solution Approach 1:
The patent combines AMR elements with a bias magnetic field generation mechanism to create a hybrid detection system. The bias field shifts the operating point of the AMR elements to a region where they can distinguish polarity changes, merging the absolute position detection capability of AMR elements with the polarity discrimination ability provided by the bias field mechanism.
Solution Approach 2:
The bias magnetic field acts as an intermediary that modifies the magnetic field distribution around the AMR elements. This intermediary field enables the AMR elements to detect polarity information by shifting their operating characteristics, allowing them to distinguish between different magnetic polarizations that would otherwise be indistinguishable.
2Measurement precision
If GMR elements are used instead of AMR elements, then the output signal improves and spacing characteristic enhances, but the device complexity increases
Solution Approach 1:
The patent changes the physical parameters of the magnetic detection elements by transitioning from AMR to GMR technology. This parameter change utilizes the Giant Magneto-Resistive effect instead of the Anisotropic Magneto-Resistive effect, achieving higher output signals and better spacing characteristics through the inherent properties of multi-layer magnetic film structures.
3Ease of manufacture
If continuous recording of binary information is performed without invalid sections, then the recording process simplifies, but the magnetic field intensity becomes non-uniform leading to detection errors
Solution Approach 1:
The patent segments the continuous recording track into distinct sections by introducing invalid sections at specific locations. These invalid sections create controlled interruptions in the magnetic field pattern, allowing the system to maintain uniform magnetic field intensity characteristics while still enabling continuous recording operation. The segmentation prevents magnetic field saturation and ensures consistent detection 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
The solution enables stable recording and improved signal detection within a broader range, enhancing the spacing characteristic and maintaining consistent magnetic field intensity, thus overcoming the limitations of existing technologies in achieving high-resolution and precise position detection.
Implementation Method 1
the absolute-value-forming code is read from the magnetic scale in which the pattern codes of the absolute-value-forming code using the M-code pattern are recorded, by using magneto-resistive effect elements (MR elements)
Implementation Method 2
AMR elements using the Anisotropic Magneto-Resistive (AMR) effect of a ferromagnetic metal (for example, Ni—Fe film having a small saturated magnetic field, Ni—Co film having a great MR rate of change)
Implementation Method 3
GMR elements having a greater rate of change in resistance in comparison with the AMR elements, and consequently make it possible to provide a better spacing characteristic and a higher output in comparison with the AMR elements. Moreover, in the magnetic film that exerts the GMR effect, since the resistance change is exerted isotropically regardless of a relative angle between the magnetic field and the electric current
Data Source
AI summary
A position detecting device that includes a recording medium provided with a first recording track in which a non-repetitive signal composed of binary information is recorded and a second recording track in which a signal for specifying a reading section within a section of information of 1 unit for the non-repetitive signal and information reading means that includes a first detection head and a second detection head and for reading each 1 unit information of the non-repetitive signal from the first recording track by using the first detection head in the reading section within a section of information of 1 unit for the non-repetitive signal specified based upon the signal recorded in the second recording track by the second detection head.