Flexible Sensor Unit for Compact Rotary Encoder
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Solution Overview
Problem
Conventional rotary encoders require significant space due to the protrusion of sensor housings, especially in small electric motors, leading to larger motor housings and limited compactness.
Innovation Solution
A flexible sensor unit comprising an integrated sensor circuit on a flexible printed circuit board is used, allowing the sensor unit to be bent and nested against the measuring scale, maintaining a uniform distance and reducing overall diameter, with optional rigid support for stability and precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional sensor housing is used on the outer circumference of the scale, then the sensor can perform its scanning function, but the rotary encoder occupies excessive space and increases the overall motor housing dimensions
Solution Approach 1:
The patent employs a flexible printed circuit board (PCB) as the sensor carrier instead of a rigid housing. This flexible PCB can be bent to conform to the outer circumference of the scale, eliminating the need for a protruding sensor housing. The flexible nature allows the sensor to maintain close proximity to the scale surface while following its curvature, significantly reducing the radial space required and thus compacting the overall rotary encoder dimensions.
Solution Approach 2:
The patent transitions from a planar sensor arrangement to a three-dimensional curved configuration. By bending the flexible PCB to match the cylindrical surface of the scale, the sensor is positioned in a spatial arrangement that optimizes the distance to the scale while minimizing the protrusion in the radial direction. This dimensional adaptation allows the sensor to effectively scan the scale without requiring additional housing space.
2Volume of moving object
If the sensor is positioned close to the scale to reduce size, then compactness is improved, but maintaining uniform distance and preventing contact becomes difficult
Solution Approach 1:
The flexible PCB inherently conforms to the curved surface of the scale, allowing the sensor mounted on it to maintain a substantially uniform distance from the scale across different angular positions. This flexibility enables the sensor array to adapt to the cylindrical geometry, ensuring consistent measurement conditions while staying close to the scale for compact design. The PCB acts as a compliant mounting substrate that naturally follows the scale's contour.
Solution Approach 2:
The flexible PCB provides a dynamic adaptation capability, allowing the sensor assembly to flex and conform to the scale's surface profile. This dynamic characteristic enables the sensor to maintain optimal positioning relative to the rotating scale, ensuring reliable operation while accommodating manufacturing tolerances and preventing contact during rotation.
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 achieves a compact rotary encoder with increased usable graduations and reduced field distortions, suitable for small electric motors, while maintaining precise scanning capabilities.
Implementation Method 1
The sensor positioned on the outer circumference of the magnet wheel can be a Hall element or a magnetoresistive sensor. Both alternatives enable contactless reading of the periodically recurring magnetization of the pole wheel.
Implementation Method 2
If the material measure is a magnet wheel with a radial field effect, field distortions are also compensated for by the inventive design of the sensor unit, since the sensor circuit is aligned perpendicularly to the radial field effect over its entire length.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to an encoder (2) for a rotary encoder (1), in particular for an electric motor, for scanning a rotationally symmetrical dimension (3). According to the invention, the encoder comprises at least one integrated sensor circuit (4), wherein the integrated sensor circuit is flexible and mounted on a similarly flexible printed circuit board (5), and wherein the integrated sensor circuit and the printed circuit board form a flexible sensor unit (6), and the sensor unit is bent out of a plane. The invention also provides a rotary encoder with an encoder according to the invention and an electric motor with such a rotary encoder.