Curved Magnet Facing Surface for Position Detection Linearity
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Solution Overview
Problem
Conventional position detection devices face challenges in maintaining linearity of detection values at high temperatures due to demagnetization effects, which affect the accuracy of position calculation based on magnetic flux density components.
Innovation Solution
The position detection device incorporates magnets with facing surfaces that are curved and positioned farther away from the movement trajectory at both ends than the center, ensuring that the demagnetizing factors for magnetic flux density components in perpendicular and parallel directions are reduced, maintaining linearity of detection outputs across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional rectangular parallelepiped magnets are used with standard detection methods, then the device structure is simple and easy to manufacture, but the detection linearity deteriorates at high temperatures due to demagnetization effects
Solution Approach 1:
The magnet uses a curved facing surface (arc-shaped swelling end edge) instead of a flat rectangular surface. This curvature is specifically designed to generate a magnetic flux density distribution that follows a sine curve pattern, which maintains detection linearity even when temperature-induced demagnetization occurs. The curved geometry compensates for the non-linear effects of thermal demagnetization.
Solution Approach 2:
The invention changes the geometric parameters of the magnet's facing surface from a standard rectangular shape to a curved shape with specific radius of curvature. This parameter modification alters the magnetic field distribution pattern, creating a sine-curve-like distribution that is inherently more resistant to temperature-induced non-linearity in position detection.
2Temperature
If the magnet is heated to high temperature, then the magnetic flux density decreases due to demagnetization, but the rate of decrease becomes non-uniform across different directions, causing detection non-linearity
Solution Approach 1:
The curved facing surface of the magnet is specifically designed to counteract the non-uniform demagnetization effects that occur at high temperatures. The arc-shaped geometry ensures that the magnetic flux density distribution maintains a sine curve pattern even when the overall magnetic strength decreases due to thermal effects, thereby preserving detection linearity across a wide temperature range.
Solution Approach 2:
The magnet's facing surface has non-uniform curvature and magnetic properties distributed across its area. The curved geometry creates different local magnetic field characteristics that collectively produce a sine curve distribution, allowing the system to maintain linearity despite uniform thermal demagnetization affecting the entire magnet.
3Ease of manufacture
If standard flat-faced magnets are used, then the manufacturing process is simple, but the magnetic flux density distribution does not follow a sine curve, requiring complex correction circuits
Solution Approach 1:
By incorporating a curved facing surface into the magnet design, the invention generates a natural sine curve magnetic flux density distribution. This eliminates the need for complex correction circuits that would otherwise be required to linearize the detection output, simplifying the overall device while maintaining manufacturing feasibility through standard curved surface machining or molding techniques.
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 design effectively reduces the difference in demagnetizing factors between magnetic flux density components, ensuring accurate and linear position detection even at high temperatures by matching the attenuation rates of magnetic flux density components, thus maintaining the linearity of detection outputs.
Implementation Method 1
a magnetic sensor that detects a component of magnetic flux emerging from the magnet that is parallel to the movement trajectory
Implementation Method 2
a magnetic sensor that detects a component of the magnetic flux that is perpendicular to the movement trajectory
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3(A)~3(B)
AI summary
[Object] To provide a position detection device that includes a magnetic sensor and that can suppress variation in linearity of measured values due to a temperature change. [Solution] A movement unit 10 is provided with a first magnet 11 and a second magnet 12. A detection unit 20 includes a first magnetic sensor having an axis of sensitivity Sx and a second magnetic sensor having an axis of sensitivity Sz. The movement unit 10 and the detection unit 20 are movable relatively to each other along a movement trajectory Tx. The magnets 11 and 12 have facing surfaces 11a and 12a, each of which is a projecting curved surface having a shape such that both ends thereof are positioned farther away from the movement trajectory Tx than a center portion thereof. This shape can suppress the linearity error for measured values when the magnets are demagnetized in a high-temperature environment.