Rotary Encoder Scale Truncated Cone Light Blocking Portion
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Solution Overview
Problem
Radial direction optical path type rotary encoders face challenges in maintaining accuracy and resolution due to burr generation and die deterioration during injection-molding, leading to performance variations among products.
Innovation Solution
A cylindrical or truncated conical scale with a light blocking portion formed outside the light transmittable region, allowing for tolerance in burr formation and die deterioration, ensuring consistent light passage and improved resolution without strict positional accuracy requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a drum type scale is entirely formed of resin by injection-molding with slits formed by arranging thin column-shaped light blocking portions, then the scale can be manufactured as a single integrated component, but burrs are generated in the light blocking portion causing variation in light transmission and performance instability
Solution Approach 1:
The patent applies preliminary action by forming the light blocking portion with a specific geometric configuration (truncated cone shape with larger base at light source side) before manufacturing. This pre-designed shape anticipates burr formation and die deterioration, ensuring that even if burrs occur or the die dulls, the light blocking portion maintains its functional integrity and light transmission characteristics remain stable.
2Measurement precision
If the light blocking portion is formed with precise dimensions to block light accurately, then resolution is improved, but the die deteriorates quickly due to repeated injection-molding causing rounding and dulling
Solution Approach 1:
The patent applies beforehand cushioning by designing the light blocking portion with a truncated cone shape that has a larger base area at the light source side. This geometric configuration creates a buffer zone that compensates for die deterioration over time. As the die dulls and burrs form, the tapered design ensures the light blocking portion maintains sufficient light blocking capability, thereby extending the die's service life while preserving resolution.
3Manufacturing precision
If the side surface of the light blocking portion is formed inside the light transmittable region, then strict positional accuracy is required, but this increases assembly complexity and reduces tolerance to manufacturing variations
Solution Approach 1:
The patent applies asymmetry by configuring the light blocking portion with a truncated cone shape where the base area is larger at the light source side and tapers toward the light detector side. This asymmetric design creates a natural tolerance margin: the larger base provides a broader acceptable positioning range, reducing assembly complexity while maintaining manufacturing precision. The asymmetric geometry ensures that even with positional variations, the light blocking function remains effective.
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 effectively suppresses performance variations and maintains high resolution by allowing burrs to exist outside the light transmittable region, tolerating die deterioration, and enabling wider irradiation angles, thus simplifying assembly and maintaining accuracy.
Implementation Method 1
a light transmitting portion through which light passes and a light blocking portion by which light with a predetermined width in a circumferential direction is blocked
Data Source
AI summary
In a radial optical path type rotary encoder, in order to be able to reduce deterioration of resolution and variation among products due to burrs during molding and/or rounding of a die, a scale for a rotary encoder is provided with a scale body which is formed substantially in a cylindrical shape, the scale body having a side surface portion in which a light transmitting portion through which light passes and a light blocking portion by which light with a predetermined width in a circumferential direction is blocked are formed alternately in the circumferential direction, wherein the side surface on a light-incident side of the light blocking portion is formed outside a light transmittable region having an outer edge defined by a light beam tangent to the side surface of the light blocking portion amidst the light passing through the light transmitting portion, in a lateral cross-section view.