JPH11173873A - Absolute type rotary encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absolute type rotary encoder capable of miniaturizing the entire device in spite of being of a low price. SOLUTION: This absolute type rotary endoder comprises nine pattern plates P0, P1, P2, P3, P4, P5, P6, P7, P8 in which patterns comprising a translucent part transmitting lights and a light shielding part shielding lights are formed in a mutually different form; an axial body 2 rotating integrally each pattern plate P by supporting the pattern plate P at a position apart from each other by a specified distance, and nine photoelectric sensors S0, S1, S2, S3, S4, S5, S6, S7, S8, respectively having a light emitting part 12 and a light receiving part 13 arranged on both sides of each pattern plate P. The above pattern is formed in the plurality of pattern plates P so that a signal output from the plurality of photoelectric sensors S outputs a gray code. In each pattern plate P, after a photosensitive material is applied on a resin-made thin plate having translucency, a record of images and a developing process are performed, thereby the above patterns are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute type rotary encoder.

[0002]

2. Description of the Related Art Absolute type rotary encoders have the function of measuring the absolute position of the rotation angle as compared with incremental type rotary encoders which count up pulse signals as the pattern plate rotates.

[0003] As such an absolute type rotary encoder, one described in, for example, Japanese Patent Publication No. 4-5322 is known. That is, the absolute type rotary encoder described in this publication is
A pattern comprising a light-transmitting portion that transmits light and a light-shielding portion that blocks light is formed on a plurality of tracks that are concentric with each other in a pattern plate having a disc-like shape. The absolute angle position of the pattern plate is measured by measuring with the same number of photoelectric sensors as the number of tracks arranged in the radial direction.

[0004]

In such a conventional absolute type rotary encoder, when an angle is detected in a small unit, the entire apparatus becomes larger with an increase in the size of the pattern plate, and the apparatus becomes expensive. Disadvantage.

That is, in the above-described conventional absolute type rotary encoder, for example, 360 °
In order to detect the absolute position of the angle at every 1 ° in the range of, it is necessary to recognize at least 360 kinds of signals. Therefore, at least 9 tracks are formed in the radial direction of the pattern plate, and 9 tracks are formed. Need to be arranged in the radial direction of the pattern plate.

For this reason, it is necessary to employ a very small photoelectric sensor. However, such a small photoelectric sensor is generally expensive, so that the entire apparatus is extremely expensive. Become.

[0007] Even if such an expensive small photoelectric sensor is used, a predetermined interval is required between the photoelectric sensors, so that the size of the pattern plate must be larger than a certain size. As a result, the size of the entire apparatus increases accordingly.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide an absolute-type rotary encoder that can be reduced in size while being inexpensive.

[0009]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of pattern plates each having a pattern formed of a light-transmitting portion that transmits light and a light-shielding portion that blocks light; By supporting the plurality of pattern plates at positions separated from each other by a predetermined distance, a shaft body for integrally rotating the plurality of pattern plates, and a light emitting unit disposed on both sides of the plurality of pattern plates and a light receiving unit And a number of photoelectric sensors corresponding to the plurality of pattern boards each having a portion.

According to a second aspect of the present invention, in the first aspect of the present invention, the patterns on the plurality of pattern plates are arranged such that signals output from the plurality of photoelectric sensors output gray codes. Has formed.

According to a third aspect of the present invention, in each of the first and second aspects of the invention, each of the pattern plates is formed by applying a photosensitive material to a light-transmitting resin thin plate. After that, the pattern is formed by subjecting the thin plate to image recording and development processing.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an absolute type rotary encoder according to the present invention, and FIG. 2 is a perspective view of a main part thereof.

As shown in these figures, this absolute type rotary encoder has nine pattern plates P0, each having a pattern formed of a light transmitting portion for transmitting light and a light shielding portion for blocking light in different forms. P1, P2, P
3, P4, P5, P6, P7, P8 (hereinafter collectively referred to as "pattern plate P"), and by supporting the pattern plates P at positions separated from each other by a predetermined distance, each pattern plate P Nine photoelectric sensors S0 and S, each having a shaft body 2 for integrally rotating the light source and light emitting units 12 and light receiving units 13 disposed on both sides of each pattern plate P, respectively.
1, S2, S3, S4, S5, S6, S7, S8 (when collectively referred to as “photoelectric sensor S”).

FIG. 4 to FIG.
0, P1, P2, P3, P4, P5, P6, P7, P8
FIG.

As shown in these figures, each pattern plate P
A substantially D-shaped hole 5 for penetrating the shaft body 2 is formed in the center of a pattern 3 comprising a light-transmitting portion and a light-shielding portion, and a start mark 4 indicating a reference position. Is formed from a disc-shaped resin-made thin plate having a light-transmitting property.

In these figures, particularly, the pattern 3 and the start mark 4 are represented by enclosing a light transmitting portion that transmits light with a line. That is, the entire surface of the pattern plate P is a region having a light shielding property,
There, the light transmitting portion of the pattern 3 and the start mark 4 are formed as light transmitting regions.

The pattern 3 and the start mark 4 on the pattern plate P are formed by using a photolithography technique. That is, when manufacturing the pattern plate P, a photosensitive film in which a photosensitive material is applied to the surface of a thin resin plate having a light-transmitting property is used, and a desired pattern is reduced on the photosensitive film. After projecting and exposing, the exposed photosensitive film is subjected to a developing process to obtain a pattern 3.
And a start mark 4 are formed. Thereafter, the pattern plate P is manufactured by punching the photosensitive film into a predetermined shape.

As described above, by manufacturing the pattern plate P by photolithography using a resin thin plate, the pattern plate P can be manufactured with higher precision and at lower cost.

The shape of the pattern 3 to be formed on each pattern plate P will be described later.

Referring again to FIGS. 1 and 2, the shaft body 2 is supported at both ends by bearings 15 supported by a pair of L-shaped brackets 14 so that the shaft body 2 extends around a horizontal axis. Is configured to be rotatable. The shaft body 2 has a substantially D-shaped cross-sectional shape similar to the hole 5 formed in each of the pattern boards P.

Each pattern board P is supported by the shaft body 2 by passing the shaft body 2 through the hole 5 of each pattern board P. At this time, since the shaft body 2 has a substantially D-shaped cross-sectional shape similar to the hole 5 formed in each pattern plate P,
The pattern plate P is positioned with respect to the shaft 2. Spacers 16 are provided between the pattern boards P. For this reason, each pattern board P is fixed at a position separated from each other by the width of the spacer 16.

Each of the photoelectric sensors S includes a sensor support plate 1
7 are arranged at a predetermined pitch. The sensor support plate 17 has a pair of L-shaped brackets 1 at both ends.
4 is supported. The L-shaped bracket 14 is connected to a casing or the like (not shown).

As shown in FIG. 3, each photoelectric sensor S and each pattern plate P are connected to the film surface side of each pattern plate P,
That is, the photosensitive material applied at the time of photolithography is arranged so that the side where the non-light-transmitting light-shielding portion 6 remains is located close to the light receiving portion 13 side of the photoelectric sensor S. With this arrangement, each pattern 3 can be detected with higher accuracy.

Next, the shape of the pattern 3 to be formed on each pattern plate P will be described.

FIG. 13 is an explanatory diagram showing the output state of each photoelectric sensor S for each angle. Note that, in the absolute type rotary encoder according to this embodiment, 3
In the range of 60 °, the absolute value of the angle can be detected every 1 °.

In this absolute type rotary encoder, when the position on the extension of the start mark 4 is arranged at an angular position facing the light projecting portion 12 and the light receiving portion 13 of the photoelectric sensor S, each pattern plate P It is recognized that the angular position is located at the position of 0 °. In FIG. 13, a state in which the light transmitting portion of each pattern plate P faces the light projecting portion 12 and the light receiving portion 13 of the photoelectric sensor S and the light receiving portion 13 receives light from the light projecting portion 12 is shown as “ "1" indicates that the light blocking portion of each pattern board P faces the light projecting portion 12 and the light receiving portion 13 of the photoelectric sensor S and the light receiving portion 13 does not receive light from the light projecting portion 12 as "0". It is expressed by Further, in this absolute type rotary encoder, the output of the photoelectric sensor S0 represents the first bit signal, and the output of the photoelectric sensor S8 represents the ninth bit signal.

That is, as shown in FIG.
Is represented by the code “001101010”.
This is because the light projecting part 12 and the light receiving part 13 of the photoelectric sensor S8 face the light shielding part of the pattern 3 on the pattern plate P8, and the light projecting part 12 and the light receiving part 13 of the photoelectric sensor S7 are located on the pattern plate P7. The light projecting part 12 and the light receiving part 13 of the photoelectric sensor S6 face the light shielding part of the pattern 3, and the light transmitting part 12 and the light receiving part of the photoelectric sensor S5 face the light transmitting part of the pattern 3 on the pattern board P6. 13 is the pattern plate P5
And the photoelectric sensor S
4, the light projecting part 12 and the light receiving part 13 of the photoelectric sensor S3 face the light shielding part of the pattern 3 on the pattern plate P4, and the light projecting part 12 and the light receiving part 13 of the photoelectric sensor S3 are the light transmitting part of the pattern 3 on the pattern plate P3. And the light projecting unit 1 of the photoelectric sensor S2
2 and the light receiving portion 13 are the patterns 3 on the pattern plate P2.
, The light projecting portion 12 and the light receiving portion 13 of the photoelectric sensor S1 face the light transmitting portion of the pattern 3 on the pattern board P1, and the light projecting portion 12 and the light receiving portion 1 of the photoelectric sensor S0.
3 indicates that it faces the light-shielding portion of the pattern 3 on the pattern plate P0.

As shown in FIG. 13, in this absolute type rotary encoder, an angle for each 1 ° is represented by a 9-bit code within a range of 360 °. That is, as shown in FIG.
01101010 ”,“ 1 ° ”is a code“ 001101011 ”, and“ 2 ° ”
“°” is represented by a code “001101001”. 51 which can be represented by these 9-bit codes
An angle for each 1 ° in a range of 360 ° is expressed using 360 types of the two types of information.

At this time, as shown in FIG. 13, the pattern is formed on each pattern plate P such that the signal output from each photoelectric sensor S outputs a gray code. Here, the gray code is a case where the number changes from a certain number to the next number (in this embodiment, the angle is 1).
This is a code having a characteristic that only one digit of all digits changes (only one bit changes).

In the absolute type rotary encoder, when a binary code that progresses between 0 and 1 is used as the output code, the output code changes from one number to the next number (when the angle changes by 1 °). To
In some cases, two or more of all digits change. In this case, since it is difficult to change each of them at exactly the same time, a reading error may occur due to a shift in reading timing.

On the other hand, when the output code of the absolute type rotary encoder is a gray code, there is an effect that the occurrence of the above-described reading error can be prevented.

Particularly, in this embodiment, FIG.
As shown in FIG. 7, even when the detection angle changes from 359 ° to 0 °, only one of all digits changes (only one bit changes), that is, a gray code, A gray code that is configured cyclically from 0 ° to 360 ° is used. For this reason, in the entire angle range from 0 ° to 360 °, it is possible to prevent the occurrence of a reading error and accurately detect the angle.

In the absolute type rotary encoder having the above configuration, the absolute position of the rotation angle of the shaft body 2 can be measured by the output code composed of the signal output from each photoelectric sensor S. .

At this time, since the absolute angular position is detected by rotating the nine pattern plates P supported by the shaft 2 and integrally, the size of each pattern plate P can be reduced. In addition, it is possible to reduce the size of the absolute rotary encoder as a whole. In addition, a general commercial product can be used as the photoelectric sensor S, and the device can be manufactured at low cost.

Further, since the size of each pattern plate P can be reduced, even when a resin thin film obtained by forming a pattern 3 by photolithography of a photosensitive film is used as each pattern plate P, The detection accuracy of the absolute type rotary encoder does not deteriorate due to the bending of the pattern plate P or the like.

However, the present invention is not limited to such an embodiment. As the pattern plate P, it is also possible to use a pattern plate in which a pattern formed of a light transmitting portion and a light shielding portion is formed by etching a metal plate to form an opening.

In the above-described embodiment, 9
By using the pattern boards P, the absolute value of the angle can be detected every 1 ° in the range of 360 °. However, a configuration may be used in which the absolute value of the angle is detected using eight or less pattern boards P. However, when, for example, eight pattern plates P are used, only 256 types of information can be obtained at the maximum, so that 360
In other words, the absolute value of the angle cannot be detected every 1 ° in the range of °.

[0038]

According to the first aspect of the present invention, a plurality of pattern plates each having a pattern formed of a light transmitting portion for transmitting light and a light shielding portion for blocking light in different forms, and a plurality of patterns are provided. By supporting the plates at positions separated from each other by a predetermined distance, a shaft body for integrally rotating the plurality of pattern plates, and a light projecting unit and a light receiving unit disposed on both sides of the plurality of pattern plates are respectively provided. Since the number of photoelectric sensors corresponding to the plurality of pattern plates is provided, each pattern plate can be reduced in size, and accordingly, the entire device can be reduced in size. In addition, since a general photoelectric sensor can be used, the device can be made inexpensive.

According to the second aspect of the present invention, since the signals output from the plurality of photoelectric sensors form the patterns on the plurality of pattern plates so as to output the gray code, the read timing is shifted. , It is possible to prevent the occurrence of a reading error.

According to the third aspect of the present invention, each pattern plate is formed by applying a photosensitive material to a light-transmitting resin thin plate and then performing image recording and development processing on the thin plate. Since the pattern is formed by the method, the pattern plate can be manufactured with higher accuracy and at lower cost.

[Brief description of the drawings]

FIG. 1 is a front view of an absolute type rotary encoder according to the present invention.

FIG. 2 is a perspective view of a main part of an absolute type rotary encoder according to the present invention.

FIG. 3 is an enlarged explanatory diagram showing an arrangement relationship between a photoelectric sensor S and a pattern plate P;

FIG. 4 is a plan view showing a pattern plate P0.

FIG. 5 is a plan view showing a pattern plate P1.

FIG. 6 is a plan view showing a pattern plate P2.

FIG. 7 is a plan view showing a pattern plate P3.

FIG. 8 is a plan view showing a pattern plate P4.

FIG. 9 is a plan view showing a pattern plate P5.

FIG. 10 is a plan view showing a pattern plate P6.

FIG. 11 is a plan view showing a pattern plate P7.

FIG. 12 is a plan view showing a pattern plate P8.

FIG. 13 is an explanatory diagram showing an output state of each photoelectric sensor S for each angle.

[Explanation of symbols]

 2 shaft 3 pattern 4 start mark 5 hole 12 light projecting part 13 light shielding part 15 bearing 16 spacer P pattern plate S photoelectric sensor

Claims (3)

[Claims] 1. A plurality of pattern plates each having a pattern formed of a light-transmitting portion that transmits light and a light-shielding portion that blocks light in different forms, and the plurality of pattern plates being separated from each other by a predetermined distance. By supporting, the plurality of pattern boards correspond to the plurality of pattern boards each having a shaft body that integrally rotates the plurality of pattern boards, and a light emitting unit and a light receiving unit disposed on both sides of the plurality of pattern boards. An absolute type rotary encoder comprising: a plurality of photoelectric sensors; 2. The absolute type rotary encoder according to claim 1, wherein the patterns on the plurality of pattern plates are formed such that signals output from the plurality of photoelectric sensors output gray codes. Rotary encoder. 3. The absolute type rotary encoder according to claim 1, wherein each of said pattern plates is formed by applying a photosensitive material to a light-transmitting resin thin plate, and then applying said photosensitive plate to said thin plate. An absolute type rotary encoder in which the pattern is formed by performing image recording and development processing on the image.