Rotational Input Device with Ridge Magnetic Substance for Angle Error Reduction
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Solution Overview
Problem
Rotational input devices using magnetic substances and sensors often experience angle errors due to misalignment of the sensor element relative to the magnetic substance, leading to increased distortion in magnetic field lines and subsequent errors in rotation angle detection.
Innovation Solution
The rotational input device incorporates a magnetic substance with two ridges protruding parallel to each other, aligned with the magnetization direction, which cancels out distortions in the magnetic field lines between them, ensuring the field lines extend in the magnetization direction, thus minimizing angle errors even with sensor misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sensor element is misaligned relative to a magnetic substance, then manufacturing and installation become easier, but angle detection precision deteriorates due to barrel-shaped distortion in magnetic field lines
Solution Approach 1:
The magnetic substance is designed with different local geometries: a flat bottom surface for general magnetic field generation and two protruding ridges for distortion compensation. This local differentiation allows the ridges to specifically address the barrel-shaped distortion problem in the region between them, while the rest of the magnetic substance maintains its magnetic field generation function. The sensor element can be installed on the flat bottom surface without requiring precise alignment, yet the ridges ensure accurate angle detection.
Solution Approach 2:
The magnetic substance features an asymmetric structure with two protruding ridges that break the rotational symmetry of the otherwise circular or rectangular magnetic substance. This asymmetric ridge configuration creates a specific magnetic field pattern that compensates for misalignment effects. The ridges are positioned at specific locations to generate counteracting magnetic field components that eliminate the barrel-shaped distortion, allowing the sensor to accurately detect angles even when not perfectly centered.
2Measurement precision
If the sensor element is positioned closer to the magnetic substance, then detection sensitivity improves, but misalignment errors increase due to stronger barrel-shaped distortion
Solution Approach 1:
The bottom surface of the magnetic substance is designed with differentiated local regions: a flat area for sensor placement and two protruding ridges for distortion control. This local quality differentiation allows the sensor to be positioned close to the magnetic substance for high sensitivity while the ridges specifically address the distortion problem in the near-field region, enabling close positioning without proportionally increased misalignment 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
This configuration significantly reduces angle errors by maintaining straight magnetic field lines in the region between the ridges, allowing for precise detection of rotation angles even when the sensor element is misaligned, as demonstrated by reduced angle errors compared to traditional designs.
Implementation Method 1
a vector distribution of magnetic field lines H0 appears around the magnetic substance 810... the magnetic field lines H0 from the north magnetic pole to the south magnetic pole are directed straight in central part... of the magnetic substance 810
Implementation Method 2
The sensor element 820 includes a sensor element body 820a and a detection mechanism 821 disposed at substantially the center of the sensor element body 820a. The detection mechanism 821 can detect a rotation angle of the magnetic substance 810
Data Source
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AI summary
A rotational input device (100) includes an insulating substrate (30), a sensor element (20) disposed on the insulating substrate, and a magnetic substance (10) spaced close to the sensor element. The sensor element includes a detection mechanism (21) configured to detect orientations of magnetic field lines (H1) around the sensor element and has a sensor element parallel surface (20c) facing the magnetic substance. The magnetic substance has a bottom surface (10a) that is located adjacent to the sensor element so as to face the sensor element parallel surface, and includes two ridges (11) that protrude from the bottom surface toward the sensor element and extend parallel to each other. The two ridges each have a ridge parallel surface located adjacent to the sensor element such that the ridge parallel surface is substantially parallel to the sensor element parallel surface. The ridge parallel surface has a substantially rectangular shape in plan view. The magnetic substance is magnetized in a magnetization direction (Ml) identical to a longitudinal direction of the ridges.