JP2004109074A - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder capable of minimizing a measurement error due to the eccentricity of a pulse plate with a low-cost structure. <P>SOLUTION: This optical encoder is composed by forming a slit pattern 5 of the pulse plate 1 by forming an angle toward the traveling direction of the pulse plate 1. The angle is preferably set at 45° toward the traveling direction of the pulse plate. The optical encoder may be so composed that the slit pattern 5 with the angle set, and a radial slit pattern 6 are formed, and the respective measurement values thereof may be compared with each other. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a speed fluctuation measuring device of a rotating body in OA equipment such as a copying machine, and more particularly, to a speed fluctuation measuring device applicable to a speed fluctuation measuring device of a rotating body in an automobile, an industrial machine or the like.
[0002]
[Prior art]
2. Description of the Related Art An optical rotary encoder has been used as a speed variation device of a rotating body conventionally used. The optical encoder obtains data by a pulse plate provided with a pattern consisting of a slit-shaped light transmitting portion and a light shielding portion at a constant period, and optical means and light receiving means arranged opposite to each other with the pulse plate interposed therebetween. If the pulse plate is mounted eccentrically with respect to the rotation axis of the encoder, information that should not exist on the rotation axis due to rotation fluctuation is observed as speed fluctuation.
FIG. 6 is a schematic plan view of a conventional general optical encoder, in which a slit pattern 6 is formed radially from the center of the pulse plate 1. In FIG. 6A, the center of the pulse plate 1 and the center of the rotating shaft 4 are concentric, and the gap A and the gap B are equal. However, if the pulse plate 1 is mounted eccentrically with respect to the rotating shaft 4 as shown in FIG. 6B, the reading position of the optical unit 2 and the light receiving unit 3 is outside the slit pattern 6 on the plus side of the eccentricity. Therefore, the interval B ′ between the slit patterns 6 is increased, and the rotation of the pulse plate 1 is apparently slow. On the other hand, on the negative side of the eccentricity, the reading position passes through the inside of the slit pattern 6, so that the interval A 'between the slit patterns 6 becomes narrow, and the rotation of the pulse plate 1 becomes apparently faster.
To solve this problem, a method has been considered in which a plurality of optical means are provided, and the read data is corrected by an arithmetic unit to eliminate the influence of the eccentricity of the mounting of the pulse plate (for example, see Patent Documents 1 and 2). However, this method increases the cost due to an increase in the number of components.
[0003]
[Patent Document 1]
JP-A-5-18783 [Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-346677
[Problems to be solved by the invention]
In view of the above problems, it is an object of the present invention to provide an optical encoder that has a low-cost configuration and minimizes an error due to the influence of eccentricity.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention according to claim 1 has a pulse plate provided with a pattern including a slit-shaped light transmitting portion and a light shielding portion at a constant period, and is opposed to the pulse plate with the pulse plate interposed therebetween. An optical encoder having an optical unit and a light receiving unit, wherein the slit pattern is formed at an angle toward the traveling direction of the pulse plate.
According to a second aspect of the present invention, there is provided the optical encoder according to the first aspect, wherein the angle of the slit pattern is 45 °.
According to a third aspect of the present invention, in the optical encoder according to the first or second aspect, the pulse plate has a slit pattern having an angle in a traveling direction of the pulse plate, and a radial pattern from a center of the pulse plate. And a means for comparing the transit times of the respective slit patterns.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side sectional view showing the configuration of the optical encoder. The pulse plate 1 is provided with a pattern formed of a slit-shaped light transmitting portion and a light shielding portion at a constant period, and is attached to the rotating shaft 4. The optical means 2 is disposed opposite to the light receiving means 3 with the pulse plate 1 interposed therebetween, and reads data.
2 and 3 are schematic plan views showing the optical encoder of the present invention. As shown in FIG. 2, the slit pattern 5 is provided at an angle toward the traveling direction of the pulse plate 1. Since the slit pattern 5 has the same number of divisions as the conventional radial slit pattern, there is no change in the performance of the encoder. When there is no eccentricity as shown in FIG. 2A, the gap A is equal to the gap B. However, when eccentricity occurs at the time of mounting as shown in FIG. B 'becomes wider. Therefore, like the conventional slit pattern, the rotation of the pulse plate 1 appears to be slow on the positive side of the eccentricity, and the rotation of the pulse plate apparently increases on the negative side of the eccentricity.
[0007]
However, since the slit pattern 5 has an angle, errors due to eccentricity can be suppressed. The distance D from the time when the slit A passes through the reading position to the time when the slit B passes through the reading position shown in FIG. 3B is shorter than the radial slit pattern. At this time, the apparent angular velocity ω tends to be slow, that is, the apparent passing time from the slit A to the slit B tends to be long. Can be.
On the other hand, the time from when the slit B passes through the reading position to when the slit A passes through the reading position is longer than in the conventional radial slit pattern. At this time, the apparent angular velocity ω tends to increase, that is, the apparent passage time from the slit B to the slit A tends to be short. Can be.
[0008]
It is preferable that the angle provided in the slit pattern 5 be 45 ° C. in the direction of travel of the pulse plate 1.
FIG. 4 is a diagram for explaining the angle of the slit pattern 5. As shown in FIG. 4, by setting the angle of the slit pattern 5 to 45 °, the mounting eccentric amount ΔY and the correction amount ΔX caused by the variation of the slit passage time can be made substantially equal, so that the rotational speed of the shaft and The mounting eccentric amount can be measured from the fluctuation time.
[0009]
FIG. 5 shows an example of the pulse plate 1 in which a radial slit pattern 6 is formed in addition to the 45 ° C. slit pattern 5. By providing a configuration as shown in FIG. 5 and providing a means for comparing the transit times of the respective slit patterns 5 and 6, the amount of eccentricity can be measured more reliably. By measuring the time difference between the reading position A of the slit pattern 5 and the reading position B of the slit pattern 6, the amount of eccentricity in each of the slit patterns 5 and 6 can be measured in real time. It is possible.
In FIG. 5, the radial slit pattern 6 is arranged outside the pulse plate 1 and the angled slit pattern 5 is arranged inside. However, the present invention is not limited to this, and the reverse configuration may be used. Absent.
[0010]
【The invention's effect】
As described above, according to the present invention, with a low-cost configuration, it is possible to minimize the measurement error due to the influence of the eccentricity of mounting the pulse plate, and easily measure the amount of eccentricity of the mounting of the pulse plate in real time. Can be provided.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a configuration of an optical encoder.
FIGS. 2A and 2B are schematic plan views showing an optical encoder according to the present invention, wherein FIG. 2A shows a state in which a pulse plate and a rotation axis are concentric, and FIG. 2B shows an eccentric state.
3A and 3B are schematic plan views showing an optical encoder according to the present invention, wherein FIG. 3A shows a state in which the rotation axis is concentric with the pulse plate, and FIG. 3B shows an eccentric state.
FIG. 4 is a diagram for explaining an angle of a slit pattern.
FIGS. 5A and 5B are schematic plan views showing the optical encoder of the present invention, wherein FIG. 5A shows a state in which the rotation axis is concentric with the pulse plate, and FIG. 5B shows an eccentric state.
6A and 6B are schematic plan views of a conventional optical encoder, in which FIG. 6A shows a state in which a pulse plate and a rotation axis are concentric, and FIG. 6B shows an eccentric state.
[Explanation of symbols]
Reference Signs List 1 pulse plate 2 optical means 3 light receiving means 4 rotating shaft 5 slit pattern (with an angle)
6 slit pattern (radial)

Claims (3)

In a pulse plate provided with a slit pattern consisting of a light transmitting portion and a light shielding portion at a constant period, and an optical encoder having optical means and light receiving means disposed opposite to each other with the pulse plate interposed therebetween,
An optical encoder, wherein the slit pattern is formed at an angle toward the traveling direction of the pulse plate. The optical encoder according to claim 1,
The angle of the said slit pattern is 45 degrees, The optical encoder characterized by the above-mentioned. The optical encoder according to claim 1 or 2,
The pulse plate has a slit pattern that forms an angle in the direction of travel of the pulse plate and a slit pattern that is formed radially from the center of the pulse plate, and compares the passage times of the respective slit patterns. An optical encoder comprising means.

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