Linear Encoder Spacer Positioning for Compact Scale Design
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Solution Overview
Problem
Conventional linear encoders have an undesirably large size due to the need for longer transverse lengths of the scale and head to maintain a spacer that prevents contact with graduations, which can damage them and reduce measurement accuracy.
Innovation Solution
The spacer is positioned on the head to overlap with the graduations, allowing the scale to serve as a plate member, reducing the transverse lengths of both the scale and head without compromising measurement accuracy, and using electromagnetic induction for reading graduations to maintain accuracy even with increased distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spacer is positioned to prevent contact with graduations, then the graduations are protected from damage, but the transverse length of the scale and head increases
Solution Approach 1:
The patent combines the spacer function with the scale structure by making the spacer an integral part of the scale assembly. The spacer is positioned at the end of the scale in the longitudinal direction, merging the protective spacer function with the scale's structural elements rather than being a separate component, thus reducing the overall transverse length while maintaining graduation protection.
Solution Approach 2:
The patent repositions the spacer from a lateral position (perpendicular to the reading direction) to a longitudinal position (at the end of the scale in the measurement direction). This dimensional change allows the spacer to protect graduations from lateral contact while eliminating the need for extended transverse length, as the protection is achieved through longitudinal positioning instead.
2Measurement precision
If the distance between graduations and reading part is reduced, then measurement accuracy improves, but the head and scale structure becomes more complex
Solution Approach 1:
The patent extracts the spacer function from the head assembly and integrates it into the scale structure. By making the spacer a separate element attached to the scale rather than part of the head, the head's structure is simplified while the spacer continues to maintain the optimal distance for measurement accuracy, reducing overall structural complexity.
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 reduces the overall size of the linear encoder while maintaining high detection accuracy, avoiding the need for additional components and ensuring the spacer does not contact the graduations, thus preserving measurement precision.
Implementation Method 1
an electromagnetic induction method, a capacitance method, a photoelectric method, and the like are applicable. Whatever method is used, a distance between the graduations formed on the scale and the reading part situated on the head is desirably small, because reducing the above distance improves the accuracy of detecting an amount of a relative movement
Implementation Method 2
when an electric current is applied to the excitation coil 121A, an electromotive current is generated in the scale coil 111A forming the graduations 111, and subsequently in the detection coil 121B. Then, when the head 120 moves with respect to the scale 110, electromagnetic couplings among the coils 111A, 121A, and 121B change depending on an amount of a movement of the head 120
Data Source
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AI summary
A linear encoder includes a plate-type scale and a head which moves along the longitudinal direction of the scale. The scale has graduations formed on a surface of the scale and arranged along the longitudinal direction of the scale. The head includes a reading part which detects an amount of a relative movement of the head with respect to the scale by reading graduations formed on the scale. The head includes four bearings each having a rotation axis extending along the transverse direction of the scale. Each of the bearings is situated on the head so as to abut against a surface of the scale, to function as a spacer to maintain a distance between the scale and the head. The scale acts as a plate member interposed between the reading part and the graduations.