Magnetic Sensor Dual Detection Circuit Positioning

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Solution Overview

Problem

Existing magnetic sensor systems face challenges in determining abnormal events due to significant differences in the positions of detection circuits, leading to inconsistent output values when the magnetic flux directions change with the relative positional relationship between the scale and magnetic sensor, especially in applications with varying pitch lengths.

Innovation Solution

A magnetic sensor system with first and second detection circuits positioned 1.25% or less apart from each other, utilizing spin-valve magnetoresistive elements to maintain opposite output characteristics, allowing for accurate abnormal event detection through computation of detection signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the first and second detection circuits are disposed at significantly different positions to reduce their footprint, then the device complexity is reduced, but the measurement precision deteriorates because the magnetic flux directions become inconsistent

Engineering Contradiction:

Improvefootprint of detection circuitsVSAvoidconsistency of output values

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent changes the positional parameter between detection circuits from a large separation to a very small separation (1.25% of pitch or less). This parameter change ensures that both detection circuits experience essentially the same magnetic flux direction while still allowing the system to detect abnormal events through differential measurement of their output values.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the detection circuits are disposed far apart to accommodate different pitch lengths, then the adaptability improves, but the reliability deteriorates because abnormal event detection becomes inaccurate

Engineering Contradiction:

Improveaccommodation of varying pitch lengthsVSAvoidabnormal event detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the positional parameter to be a small fraction (1.25%) of the pitch length, which automatically adapts to different pitch lengths while maintaining detection accuracy. This proportional relationship ensures that the detection circuits remain close enough to experience consistent magnetic flux directions regardless of the specific pitch length.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a universal detection circuit configuration that works across different pitch lengths and scale types (rotating or linear). By positioning circuits at 1.25% of pitch or less, the system achieves multi-functionality in detecting both normal positional changes and abnormal events across various application scenarios.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If the detection circuits are positioned close together to maintain consistent magnetic flux directions, then the measurement precision improves, but the device complexity increases due to tighter integration requirements

Engineering Contradiction:

Improveconsistency of output valuesVSAvoidintegration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent specifies a quantitative parameter (1.25% of pitch or less) that balances measurement precision with integration feasibility. This precise parameter definition provides clear design guidance while achieving the goal of consistent magnetic flux exposure without excessive integration complexity.

Inventive Principle:

Principle #35Parameter changes

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

Enables reliable determination of abnormal events in magnetic sensors by ensuring consistent output values even with changes in the relative positional relationship and pitch length, improving the system's ability to detect anomalies accurately.

Implementation Method 1

Each of the first and second detection circuits includes a magnetoresistive element. The magnetoresistive element includes: a magnetization pinned layer having a magnetization in a pinned direction; a free layer having a magnetization that varies depending on an applied magnetic field

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS9297635B2Magnetic sensor system including two detection circuits

Publication Date: 2016.03.29 TDK CORP

AI summary

A magnetic sensor system includes a scale and a magnetic sensor arranged in a relative positional relationship variable in a first direction, and a computing unit. The magnetic sensor includes a first detection circuit disposed at a first position and a second detection circuit disposed at a second position. Each of the first and second detection circuits includes a spin-valve magnetoresistive element. The difference between the first position and the second position in the first direction is smaller than or equal to 1.25% of a one-pitch amount of change in the relative positional relationship between the scale and the magnetic sensor. The computing unit generates an abnormal-event determination signal indicative of the presence of an abnormal event in the magnetic sensor by computation using detection signals from the first and second detection circuits.