JP2009058243A - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder capable of precisely detecting an absolute angle of a rotation axis. <P>SOLUTION: This encoder includes an eccentricity circular slit 25 being eccentric with respect to a rotation axis which is composed of a plurality of rotation slits and an incremental slit 35 being radial to the rotation axis. Absolute value of the rotation angle is obtained using the eccentricity circular slit 25, and by performing its interpolation division using the signals at the incremental slit, the absolute position at high resolution is detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical encoder used as a positioning sensor for a rotary drive device such as a motor.

Conventionally, as an optical encoder for detecting the absolute angle of a rotating shaft, there is one provided with an annular slit formed eccentrically with respect to the rotating shaft (for example, see Patent Document 1).
6 is a plan view of a conventional optical encoder, and FIG. 7 is a side sectional view. In the figure, 11 is a rotating shaft, 13 is a rotating disk, 15 is an annular slit, 16 is a light projecting element A, 17 is a light receiving element A, 18 is a light projecting element B, and 19 is a light receiving element B. The light receiving element A and the light receiving element B are one-dimensional image sensors such as a PSD (position sensing detector).
The light emitted from the light projecting element A enters the light receiving element A after passing through the opening of the annular slit. Similarly, the light irradiated from the light projecting element B also enters a part of the light receiving element B after passing through the opening of the annular slit.
When the rotating shaft rotates, the annular slit is formed eccentrically with respect to the rotating shaft, so the distance from the center of the rotating shaft to the annular slit irradiated with light from the light projecting element A changes according to the rotation angle. To do. Therefore, after the light irradiated from the light projecting element A passes through the opening of the annular slit, the part that enters the light receiving element A changes.

Similarly, when the rotating shaft rotates, the distance from the center of the rotating shaft to the annular slit irradiated with light from the light projecting element B also changes according to the rotation angle, and the light irradiated from the light projecting element B is annular. After passing through the opening of the slit, the part incident on the light receiving element B also changes.
The light receiving element A and the light receiving element B generate a signal according to the position where the light is incident, but the light receiving element A and the light receiving element B are mechanically disposed at a position 90 ° away from the rotating disk. Therefore, a sinusoidal signal whose output signal phase is also shifted by 90 ° is obtained. By calculating using these two-phase signals, the rotation angle θ of the rotating shaft can be uniquely determined from 0 ° to 360 °.

Further, Patent Documents 2 and 3 disclose that a plurality of concentric annular slits around the rotation axis center and a radius at a certain distance from the rotation axis center for the purpose of correcting a rotation angle detection error due to the eccentricity of the rotating disk. Incremental slits along the direction are provided. Further, fixed slits are arranged to face both the slits. Each of these fixed slits is composed of an A-phase fixed slit for extracting an A-phase signal and a B-phase fixed slit for extracting a B-phase signal shifted by 90 ° from the A-phase signal. Light from the light emitting element is detected by the light receiving element through the slit and the fixed slit.
When there is no eccentricity of the rotating disk with respect to the rotating shaft, the signal obtained through the annular slit is constant and does not change, but when there is eccentricity, a signal corresponding to the eccentricity can be obtained and the angle obtained through the incremental slit A highly accurate encoder is realized by correcting the signal with an eccentricity signal.


JP-A-4-343008 Japanese Patent Laid-Open No. 4-086521 JP 2001-264119 A

However, in the rotation angle detection device of Patent Document 1, it is necessary to arrange a light receiving element made of PSD at a position shifted by 90 ° along the rotation direction in order to detect the absolute value of the rotation angle, which increases the size of the device. . Further, since the conventional optical encoder detects light passing through one annular slit by the light receiving element, the amount of received light is small and the S / N is low. Further, if the opening slit width of the annular slit is increased in order to increase the amount of light, the area of the light receiving portion increases, stray current flows through the light receiving element, and S / N cannot be improved. Therefore, there is a problem that the resolution is low.
Further, only one cycle of a sine wave can be obtained from the light receiving element A and the light receiving element B by rotating the rotating disk by 360 ° mechanical angle. In order to detect the angle based on this signal, there has been a problem that the resolution is low.

In the conventional methods of Patent Documents 2 and 3, the fixed slit portions for A-phase and B-phase signals can be made in the same fixed slit and can be made compact, but for the purpose of correcting the rotational axis eccentricity error. It is an annular slit centered on the center of the rotation axis, and there is no description about detection of the absolute value of the rotation angle. Moreover, since it is not the purpose of detecting the absolute value of the rotation angle, the slit pitch of the annular slit is not described.
An object of the present invention is to solve the above-mentioned problems and to provide an optical encoder capable of detecting a rotation axis absolute angle with high accuracy and small size.

In order to solve the above problems, the present invention is configured as follows.
According to a first aspect of the present invention, there is provided an optical encoder that includes a rotating disk attached to a rotating shaft and a light projecting / receiving element provided on a fixed member, and detects the rotation angle of the rotating shaft. A plurality of annular slits that are eccentric with respect to the rotation center of the rotation shaft are formed, a first fixed slit is disposed opposite the annular slit, and irradiation is performed from a first light projecting element provided on the fixed member. And a first light receiving element that detects light transmitted through or reflected by the annular slit and further transmitted through the first fixed slit.

According to a second aspect of the present invention, the optical encoder according to the first aspect comprises the first fixed slit and a light receiving element configured in a plurality of slit patterns of the first light receiving element. .
According to a third aspect of the present invention, the slit pitch of the annular slit of the optical encoder according to the first aspect of the present invention is set to be equal to or less than an eccentric amount with respect to the rotation center of the annular slit.
According to a fourth aspect of the present invention, the first fixed slit of the optical encoder according to the first aspect is composed of a plurality of groups of slits whose phases are shifted to detect a sine wave signal having a plurality of phases. The light receiving element is composed of a plurality of light receiving elements equal to the number of the slit groups of the first fixed slit.

According to a fifth aspect of the present invention, there is provided an optical encoder that includes a rotating disk attached to a rotating shaft and a light projecting / receiving element provided on a fixed member, and detects the rotation angle of the rotating shaft. A plurality of annular slits that are eccentric with respect to the rotation center of the rotation shaft are formed, a first fixed slit is disposed opposite the annular slit, and irradiation is performed from a first light projecting element provided on the fixed member. A first light receiving element that detects light transmitted through or reflected by the annular slit and transmitted through the first fixed slit, and is a radial incremental slit on the rotating disk with respect to the rotation center of the rotating shaft. An incremental fixing slit is disposed opposite to the incremental slit, irradiated from a light projecting element, and the incremental Incremental light-receiving element that detects light transmitted through or reflected from the optical path and further through the incremental fixed slit, an angle signal obtained by processing a signal from the first light-receiving element, and the incremental light-receiving element An arithmetic circuit for calculating an absolute angle from an angle signal is provided.
According to a sixth aspect of the present invention, the optical encoder according to the fifth aspect further comprises an arithmetic unit that calculates a high-resolution absolute angle by adding a signal obtained by further interpolating the signal obtained from the incremental light-receiving element. It is what.
The invention according to claim 7 is characterized in that the incremental fixing slit and the incremental light receiving element of the optical encoder according to claim 5 are configured by a light receiving element configured in a plurality of slit patterns.

According to an eighth aspect of the present invention, the incremental fixed slit of the optical encoder according to the fifth aspect is composed of a plurality of phase-shifted slit groups for detecting a plurality of sine wave signals, and the incremental light receiving element. Is composed of a plurality of slits equal to the number of the slit groups of the incremental fixed slits.
According to a ninth aspect of the present invention, in the optical encoder according to the fifth aspect, the first light projecting element and the incremental light projecting element are constituted by a common light projecting element.

According to the first aspect of the present invention, the light that has passed through or reflected through the plurality of annular slits is received by the light receiving element through the fixed slit, so that the size can be reduced, the amount of received light is increased, and the signal S / N is increased. Become.


According to invention of Claim 2 and 7, a fixed slit can be abbreviate | omitted by comprising a light receiving element in several slit pattern shape, and a structure can be simplified.
According to the third aspect of the present invention, the absolute value of the rotation angle can be uniquely determined by the A-phase and B-phase signals by setting the slit pitch to be equal to or less than the eccentric amount, and signal processing using a counter or the like becomes unnecessary. Signal processing can be simplified.
According to the fourth and eighth aspects of the invention, since a plurality of phase signals such as the A phase and the B phase can be configured on the same fixed slit, the size can be reduced.
According to the fifth aspect of the present invention, a high-resolution absolute angle signal is obtained by adding the signal obtained from the incremental slit to the lower order of the absolute value signal obtained by processing the signal from the first light receiving element. It is done.
According to the sixth aspect of the present invention, a high-resolution absolute angle signal can be obtained by adding a signal obtained by further interpolating the signal obtained from the incremental slit.
According to the ninth aspect of the present invention, the first light projecting element and the incremental light projecting element can be constituted by one light projecting element, and the size can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view of an encoder according to the present invention, FIG. 2 is a side sectional view, and FIG. 3 is a plan view of a first fixed slit. In the figure, 11 is a rotating shaft, 13 is a rotating disk, 25 is an annular slit composed of a plurality of slits, 16 and 22 are a first light projecting element, a first light receiving element, 21 provided on a fixing member (not shown), respectively. Is a first fixed slit. The annular slit 25 is a concentric pattern with the same pitch and different diameter in the radial direction, and the center of the concentric circle is eccentric unlike the center of the rotation axis. The first light receiving element 22 is a light amount detecting element such as a photodiode or a phototransistor. As shown in FIG. 3, the first fixed slit 21 is a parallel pattern having the same pitch as the slit pitch of the annular slit 25. The fixed slit includes an A-phase fixed slit A for extracting an A-phase signal and a B-phase fixed slit B for extracting a B-phase signal that is 90 ° out of phase with respect to the A-phase signal. In this case, the number of slit groups is two, and the first light receiving element 22 is also composed of two light receiving elements. Further, not only two phases of A phase and B phase, but also A- and B-added fixed slits for four-phase signal output, which are 180 ° out of phase with respect to A phase and B phase, may be used. In this case, the number of slit groups is four, and the first light receiving element 22 is composed of four light receiving elements. The fixed slit can be omitted by making the shape of the light receiving element a slit pattern equal to the slit pitch of the first fixed slit.

  When the rotating shaft rotates, the annular slit 25 is formed eccentrically with respect to the rotating shaft, so the distance from the center of the rotating shaft to the annular slit 25 irradiated with the light from the light projecting element 16 is the rotation angle. Will change accordingly. As a result, the patterns of the annular slit 25 and the fixed slit 21 are shifted, the amount of light incident on the light receiving element 22 changes, and the above-described sinusoidal A and B phase signals corresponding to the rotation angle are detected by the light receiving element. The Based on these two output signals, the rotation angle θ of the rotating shaft can be uniquely determined from 0 ° to 360 ° by calculating in the subsequent circuit. In particular, if the slit pitch of the annular slit 25 and the fixed slit 21 is set larger than the amount of eccentricity, and the rotation angle of the rotating disk is 360 ° so that the signal obtained by the eccentricity is within one cycle of the sine wave signal. The rotation angle θ can be uniquely determined without complicating signal processing such as a counter. For example, if the amount of eccentricity of the annular slit with respect to the rotation axis is 40 μm, the slit pitch between the annular slit and the fixed slit may be 50 μm.

  The encoder of the present embodiment can detect a plurality of phase signals such as a two-phase or four-phase signal for detecting the absolute value of the rotation angle with a configuration having a plurality of annular slits 25 and fixed slits 21, and a small configuration. Since the light that has passed through the plurality of annular slits 25 and the fixed slit 21 is received by the light receiving element 22, the amount of received light increases, the S / N of the signal increases, and the angular resolution increases.

FIG. 4 is a plan view of the optical encoder of the second embodiment, and FIG. 5 is a side sectional view. The same components as those of the encoder of the first embodiment are denoted by the same reference numerals and description thereof is omitted. Different points will be described. In the figure, 35 is a radial incremental slit with respect to the center of rotation, 36 is an incremental light projecting element, 32 is an incremental light receiving element, and 31 is an incremental fixed slit. In order to detect the absolute value of the rotation angle and the rotation direction, the incremental fixed slit 31 is composed of a slit made of a parallel pattern having the same pitch as the incremental slit pitch 35, like the first fixed slit shown in FIG. In order to detect a sine wave signal of a phase, it consists of a plurality of slit groups whose phases are shifted. Similarly to the first light receiving element 22, the incremental light receiving element 32 is also composed of light receiving elements equal to the number of slit groups of the incremental fixed slit 31.
Although the incremental light projecting element 36 is provided separately from the first light projecting element 16, a single light projecting element may be used for reducing the size.

When the rotation shaft rotates, each incremental light receiving element 32 outputs a sine wave signal corresponding to the rotation angle. An absolute angle signal is obtained by arithmetically processing the absolute position of the angle obtained from the same component as in the first embodiment and the incremental signal by an arithmetic circuit (not shown).
Further, the obtained sinusoidal incremental signal is interpolated by an arithmetic unit (not shown) and added to obtain a high-resolution absolute angle signal of the rotating shaft.
The absolute position signal of the angle obtained from the same component as in the first embodiment only needs to have a resolution within one cycle of the sine wave of the incremental signal, and the resolution of the encoder as a whole is the interpolation resolution of the incremental signal. Because of this, a very high resolution can be obtained.

The present invention can detect an absolute position at an angle with higher resolution than a conventional encoder even when used in a reflective encoder.

It is a top view which shows the structure of the optical encoder which shows 1st Example of this invention. It is a sectional side view which shows the structure of the optical encoder which shows 1st Example of this invention. It is a top view which shows the 1st fixed slit of the optical encoder of this invention. It is a top view which shows the structure of the optical encoder which shows 2nd Example of this invention. It is a sectional side view which shows the structure of the optical encoder which shows 2nd Example of this invention. It is a top view which shows the structure of the conventional optical encoder. It is a sectional side view which shows the structure of the conventional optical encoder.

Explanation of symbols

11 Rotating shaft 13 Rotating disk 15 Annular slit 16 First light projecting element A
17 Light receiving element A
18 Light Emitting Element B
19 Light receiving element B
21 First fixed slit 22 First light receiving element 25 Annular slit 31 composed of a plurality of slits 31 Incremental fixed slit 32 Incremental light receiving element 35 Incremental slit 36 Incremental light projecting element

Claims (9)

In an optical encoder comprising a rotary disk 13 attached to the rotary shaft 11 and a light projecting / receiving element provided on a fixed member, and detecting the rotation angle of the rotary shaft,
Forming a plurality of annular slits 25 eccentric on the rotation center of the rotating shaft on the rotating disk 13,
A first fixed slit 21 is arranged opposite to the annular slit 25,
A first light receiving element 22 is provided for detecting light emitted from the first light projecting element 16 provided on the fixed member, transmitted or reflected through the annular slit 25, and further transmitted through the first fixed slit 21. An optical encoder characterized by that.
The optical encoder according to claim 1, wherein the first fixed slit (21) and the first light receiving element (22) are configured by a light receiving element configured in a plurality of slit patterns.
The optical encoder according to claim 1, wherein a slit pitch of the annular slit is equal to or less than an eccentric amount with respect to a rotation center of the annular slit.
The first fixed slit 21 is composed of a plurality of slit groups whose phases are shifted to detect a sine wave signal having a plurality of phases, and the first light receiving element 22 is the number of slit groups of the first fixed slit. The optical encoder according to claim 1, wherein the optical encoder is composed of a plurality equal to each other.
In an optical encoder comprising a rotary disk 13 attached to the rotary shaft 11 and a light projecting / receiving element provided on a fixed member, and detecting the rotation angle of the rotary shaft,
Forming a plurality of annular slits 25 eccentric on the rotation center of the rotating shaft on the rotating disk 13,
A first fixed slit 21 is arranged opposite to the annular slit 25,
A first light receiving element 22 is provided for detecting light emitted from the first light projecting element 16 provided on the fixed member, transmitted or reflected through the annular slit 25, and further transmitted through the first fixed slit 21. ,
A radial incremental slit 35 is formed on the rotary disk 13 with respect to the rotation center of the rotary shaft 11,
An incremental fixing slit 31 is disposed opposite the incremental slit 35,
An incremental light receiving element 32 that detects light that has been irradiated from the incremental light projecting element 36, transmitted or reflected through the incremental slit 35, and further transmitted through the incremental fixed slit 31;
An optical encoder comprising an arithmetic circuit for calculating an absolute angle from an angle signal obtained by processing a signal from the first light receiving element and an angle signal obtained from the incremental light receiving element.
6. The optical encoder according to claim 5, further comprising an arithmetic unit for further interpolating and dividing a signal obtained from the incremental light receiving element and adding a high resolution angle signal.
The optical encoder according to claim 5, wherein the incremental fixing slit (31) and the incremental light receiving element (32) are constituted by light receiving elements configured in a plurality of slit patterns.



The incremental fixed slits 31 are each composed of a plurality of slit groups whose phases are shifted to detect a plurality of sine wave signals, and the incremental light receiving elements 32 are equal to the number of slit groups of the incremental fixed slits. 6. The optical encoder according to claim 5, wherein the optical encoder is composed of a plurality.
  6. The optical encoder according to claim 5, wherein the first light projecting element and the incremental light projecting element are configured by a common light projecting element.

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