Stacked Flat Coil Position Sensor for Accuracy and Cost
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Solution Overview
Problem
Existing non-contact type throttle position sensors face issues with detection accuracy, temperature drift, and practicality due to limitations in inductance and manufacturing costs, particularly with sheet-shaped flat coils.
Innovation Solution
A non-contact type position sensor is developed by stacking multiple layers of flat coils in series to increase overall inductance and impedance, allowing for accurate position detection despite a small-size/thin coil structure, while reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sheet-shaped flat coils are used to reduce manufacturing cost and size, then manufacturing cost and device size are reduced, but sufficient inductance cannot be obtained
Solution Approach 1:
The patent transitions from a single-layer flat coil to a multi-layer stacked coil structure. By adding the vertical dimension (stacking multiple layers), the total inductance increases while maintaining the flat coil manufacturing advantages. Each layer contributes to the overall inductance, solving the limitation of insufficient inductance in single-layer flat coils without sacrificing manufacturing ease or increasing device footprint area.
2Volume of moving object
If the coil diameter is reduced to make the sensor smaller, then device size is reduced, but the output signal level decreases
Solution Approach 1:
The patent compensates for the reduced output signal level caused by smaller coil diameter by stacking multiple layers of flat coils. The vertical stacking increases the effective number of turns and overall inductance, thereby restoring and enhancing the output signal level despite the reduced horizontal footprint. This allows the sensor to maintain small size while achieving sufficient output signal strength.
Solution Approach 2:
The patent combines multiple flat coils in series to form a stacked coil structure. By merging the inductance contributions of multiple layers, the overall inductance and output signal level are enhanced. This combining approach allows the sensor to achieve high output signal levels without requiring large individual coil dimensions.
3Reliability
If conventional non-contact type sensors are used, then contact wear is eliminated, but detection accuracy and temperature drift compensation are problematic
Solution Approach 1:
The patent employs push-pull type coil poles with differential connection, which changes the electrical configuration to inherently compensate for temperature drift. By using two coil poles connected in a differential manner, temperature-induced changes affect both coils equally and are rejected in the differential output, thereby maintaining detection accuracy across temperature variations while preserving the non-contact reliability advantage.
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 enhances position detection accuracy and output signal levels, effectively addressing the limitations of existing sensors by increasing inductance and impedance, and provides robustness against temperature drift and assembly errors.
Implementation Method 1
a flat coil for detecting the position of a metallic workpiece relative to a first direction. Therein, the coil generates an output signal that is dependent on its impedance.
Implementation Method 2
the impedance variation of the coil pole, which depends on relative positional relationship between the coil section and the magnetism-responsive member
Implementation Method 3
a coil positioned on a thin substrate sandwiched to a layer a high magnetic permeability material acting as an amplifier for the inductance measured at the terminals of the coil
Implementation Method 4
When a magnet passes in front a sheet of high magnetic permeability material, the magnetic field thereof is locally saturated, and the magnetic permeability collapses on the saturated surface.
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 3A~4
AI summary
A plurality of layers of flat coils (L41 - L46) are stacked and connected in series with each other to form a single coil pole (L4), and the coil pole is energized by an A.C. signal. Magnetism responsive member, provided to be opposed to the coil pole in a non-contact manner, is displaced relative to the coil pole, so that correspondency, to the coil section, of the magnetism-responsive member varies in response to variation in the relative position and thus impedance variation occurs in the coil pole. Position detection signal is provided on the basis of an output signal, responsive to the impedance variation, taken out from the coil pole.