Absolute Position Measuring Apparatus via Nested Rotary Encoders
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Solution Overview
Problem
Conventional absolute position measuring apparatuses for spindles are limited in downsizing and manufacturing cost due to the need for wide key grooves and increased manufacturing complexity, especially when trying to measure small-sized objects.
Innovation Solution
The apparatus employs a spindle with a first and second rotary encoder, where the first encoder has a first gear and the second encoder has a second gear, with a relay gear transmitting rotation to differentiate their speeds, eliminating the need for linear and spiral key grooves, allowing for a more compact design and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional key grooves (linear and spiral) are used to transmit rotation to rotary encoders, then the apparatus can measure absolute position, but the key grooves require wide spacing and increase manufacturing complexity and cost
Solution Approach 1:
The patent extracts the rotation transmission function from the complex key groove system and relocates it to a separate gear mechanism. The gear engages with a simple linear key groove, separating the rotational movement function from the position measurement function, thereby simplifying manufacturing while maintaining measurement precision.
Solution Approach 2:
The patent introduces a gear as an intermediary element between the linear key groove and the rotary encoder. This gear mediates the transmission of rotational movement, allowing the encoder to receive rotation without requiring complex spiral key grooves, thus reducing manufacturing complexity while preserving measurement capability.
2Measurement precision
If two rotary encoders are directly mounted on the spindle to detect phase signals, then absolute position can be calculated, but the apparatus size increases
Solution Approach 1:
The patent implements a nested configuration where one rotary encoder is positioned inside the other, with both encoders sharing a common central axis. The first rotary encoder is disposed inside the second rotary encoder, allowing both phase signal detection functions to be integrated in a compact arrangement, thereby reducing apparatus size while maintaining measurement precision.
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 enables the downsizing of the apparatus, reduces manufacturing costs, and simplifies assembly by eliminating the need for complex key grooves, while maintaining accurate absolute position calculations based on differentiated phase signals.
Implementation Method 1
the first rotary encoder includes: a first rotor; a first holder that rotatably holds the first rotor about the axis of the spindle and is rotated by the rotation of the spindle, the first holder being provided with a first gear on an outer circumference thereof; a first stator that is supported by the main body and provided facing the first rotor by a predetermined gap; the second rotary encoder includes: a second rotor; a second holder that rotatably holds the second rotor about the axis of the spindle and is provided with a second gear on an outer circumference thereof; a second stator that is supported by the main body and provided facing the second rotor by the predetermined gap; a relay gear that transmits a rotation of the first gear to the second gear; and the number of cogs for the first gear, the relay gear and the second gear is set to differentiate rotation speeds of the first gear and the second gear
Data Source
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AI summary
An absolute position measuring apparatus includes a first rotary encoder that detects a rotation of a spindle (3) as a phase signal which varies in a first cycle and a second rotary encoder that detects the rotation of the spindle (3) as another phase signal which varies in a second cycle. A rotation of a first rotor (42) of the first rotary encoder is transmitted to a second rotor (51) via a relay gear (53) that is meshed with a first gear (48) provided on an outer circumference of a first rotary cylinder (43) and a second gear (55) provided on an outer circumference of a second rotary cylinder (52). Thus, an absolute position of the spindle is calculated on the basis of two phase signals that are different in cycle. Further, it is not necessary to provide a conventionally-known spiral key groove so that the apparatus can be easily downsized. Manufacturing costs can be also reduced.