WO2016092638A1

WO2016092638A1 - Encoder and encoder-equipped motor

Info

Publication number: WO2016092638A1
Application number: PCT/JP2014/082597
Authority: WO
Inventors: 康吉田; 松谷　泰裕; 宏樹近藤; 幾磨室北; 正信原田; 次郎村岡
Original assignee: 株式会社安川電機
Priority date: 2014-12-09
Filing date: 2014-12-09
Publication date: 2016-06-16
Also published as: JPWO2016092638A1; JP6010876B1; CN106104214A; CN106104214B

Abstract

[Problem] To provide an encoder capable of improving detection accuracy, and an encoder-equipped motor. [Solution] This encoder comprises: patterns SA1, SA2 along a measurement direction C; a light source 131 that emits light to the patterns SA1, SA2; and light reception arrays PA1, PA2 each arranged along the measurement direction C and receiving light emitted from the light source 131 and reflected by the respective patterns SA1, SA2. A plurality of light reception elements provided in each light reception array PA1, PA2 each have the same maximum outer dimension TPA2 in the measurement direction C and the same maximum outer dimension WPA2 in a width direction R perpendicular to the measurement direction, and the light reception elements provided at different distances from the light source 131 have different shapes such that the light reception amount of each light reception element becomes the same.

Description

Encoder and motor with encoder

The disclosed embodiment relates to an encoder and a motor with an encoder.

In Patent Document 1, an optical signal from an absolute pattern that can uniquely represent the absolute position of a rotating disk by a combination of positions of reflection slits within a predetermined angle is received by a plurality of light receiving elements of an absolute light receiving element group. An encoder that detects independently is described.

Japanese Patent No. 4945674

In order to improve detection accuracy in the above encoder, further optimization of the device configuration is required.

The present invention has been made in view of such problems, and an object thereof is to provide an encoder and a motor with an encoder that can improve detection accuracy.

In order to solve the above problems, according to one aspect of the present invention, an absolute pattern along a measurement direction, a light source configured to emit light to the absolute pattern, and a light source arranged along the measurement direction are arranged. A plurality of light receiving elements configured to receive light emitted from the light source and transmitted or reflected by the absolute pattern, wherein the plurality of light receiving elements are each of a maximum outer dimension in the measurement direction. And an encoder in which the maximum external dimensions in the width direction perpendicular to the measurement direction are equal to each other, and the light receiving elements having different distances from the light source have different shapes so that the received light amounts are equal to each other. The

Further, according to another aspect of the present invention, a motor with an encoder having a motor and the encoder is provided.

According to another aspect of the present invention, an absolute pattern along the measurement direction, a light source configured to emit light to the absolute pattern, and arranged along the measurement direction and emitted from the light source There is provided an encoder comprising a plurality of light receiving elements configured to receive light transmitted or reflected through the absolute pattern and means for equalizing the received light amounts of the light receiving elements.

According to the present invention, detection accuracy can be improved.

It is explanatory drawing for demonstrating the servo system which concerns on one Embodiment. It is explanatory drawing for demonstrating the encoder which concerns on the same embodiment. It is explanatory drawing for demonstrating the disk which concerns on the same embodiment. It is explanatory drawing for demonstrating the pattern which concerns on the same embodiment. It is explanatory drawing for demonstrating the optical module and light receiving array which concern on the embodiment. FIG. 6 is an explanatory diagram for explaining a light receiving operation along a section AA in FIGS. 4 and 5. It is explanatory drawing for demonstrating the light intensity distribution of the reflected light on the board | substrate of the optical module which concerns on the embodiment. It is explanatory drawing explaining the shape and dimension setting of the light receiving element which concern on the embodiment. It is explanatory drawing for demonstrating the change characteristic of the analog detection signal in the case of the rectangular-shaped light receiving element which does not have a pointed part. It is explanatory drawing for demonstrating the change characteristic of the analog detection signal in the case of the light receiving element which has a pointed part. It is explanatory drawing for demonstrating the difference of the change characteristic of each received light quantity of the light receiving element which does not have a pointed part, and the light receiving element which has a pointed part. It is explanatory drawing for demonstrating the shape of the several light receiving element with which the light receiving array which concerns on the same embodiment is provided. It is explanatory drawing for demonstrating the shape of the several light receiving element with which the light receiving array which concerns on the modification which made the light receiving area the same with three light receiving elements is provided. It is explanatory drawing for demonstrating the shape of the several light receiving element with which the light receiving array which concerns on the modification which made the light receiving area the same with seven light receiving elements is provided. It is explanatory drawing for demonstrating the shape of the some light receiving element with which the light receiving array which concerns on the modification which made the light receiving area the same in all nine light receiving elements is provided. It is explanatory drawing for demonstrating the shape of the some light receiving element with which the light receiving array which concerns on the modification which comprised the light receiving element only by the tip part is provided. It is explanatory drawing for demonstrating the shape of the some light receiving element with which the light receiving array which concerns on the modification which varied the light-receiving area by all nine light receiving elements. It is explanatory drawing for demonstrating the shape of the some light receiving element with which the light receiving element which the light receiving element equips only the edge part on the opposite side to the light source side with which the light receiving array which concerns on the modification is provided.

Hereinafter, an embodiment will be described with reference to the drawings.

In addition, the encoder according to the embodiment described below can be applied to various types of encoders such as a rotary type (rotary type) and a linear type (linear type). Hereinafter, a rotary encoder will be described as an example so that the encoder can be easily understood. When applied to other types of encoders, it is possible to make an appropriate change such as changing the object to be measured from a rotary disk to a linear linear scale.

<1. Servo system>
First, the configuration of a servo system including an encoder according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, the servo system S includes a servo motor SM and a control device CT. The servo motor SM includes an encoder 100 and a motor M.

The motor M is an example of a power generation source that does not include the encoder 100. The motor M is a rotary motor in which a rotor (not shown) rotates with respect to a stator (not shown), and a rotational force is generated by rotating a shaft SH fixed to the rotor around an axis AX. Output.

Although the motor M alone may be referred to as a servo motor, in this embodiment, a configuration including the encoder 100 is referred to as a servo motor SM. That is, the servo motor SM corresponds to an example of a motor with an encoder. In the following, for convenience of explanation, a case where the motor with an encoder is a servo motor controlled so as to follow a target value such as a position and a speed will be described. However, the present invention is not necessarily limited to the servo motor. The motor with an encoder includes a motor used other than the servo system as long as the encoder is attached, for example, when the output of the encoder is used only for display.

The motor M is not particularly limited as long as the encoder 100 can detect position data and the like, for example. The motor M is not limited to an electric motor that uses electricity as a power source. For example, a motor using another power source such as a hydraulic motor, an air motor, or a steam motor. It may be. However, for convenience of explanation, a case where the motor M is an electric motor will be described below.

Encoder 100 is connected to the side opposite to the rotational force output side of shaft SH of motor M. However, it is not necessarily limited to the opposite side, and the encoder 100 may be coupled to the rotational force output side of the shaft SH. The encoder 100 detects the position of the motor M (also referred to as a rotation angle) by detecting the position of the shaft SH (rotor), and outputs position data representing the position. The encoder 100 is not limited to being directly connected to the motor M, and may be connected via other mechanisms such as a brake device, a speed reducer, and a rotation direction changer.

The encoder 100 detects at least one of the speed of the motor M (also referred to as rotational speed or angular velocity) and the acceleration of the motor M (also referred to as rotational acceleration or angular acceleration) in addition to or instead of the position of the motor M. May be. In this case, the speed and acceleration of the motor M can be detected by, for example, processing such as first or second order differentiation of the position with time or counting a detection signal (for example, an incremental signal described later) for a predetermined time. . For convenience of explanation, the following description will be made assuming that the physical quantity detected by the encoder 100 is a position.

The control device CT acquires the position data output from the encoder 100, and controls the rotation of the motor M based on the position data. Therefore, in this embodiment in which an electric motor is used as the motor M, the control device CT controls the rotation of the motor M by controlling the current or voltage applied to the motor M based on the position data. Furthermore, the control device CT obtains a host control signal from a host control device (not shown), and a rotational force capable of realizing the position and the like represented by the host control signal is output from the shaft SH of the motor M. Thus, it is possible to control the motor M. When the motor M uses another power source such as a hydraulic type, an air type, or a steam type, the control device CT controls the rotation of the motor M by controlling the supply of these power sources. Is possible.

<2. Encoder>
Next, the encoder 100 according to the present embodiment will be described. As shown in FIG. 2, the encoder 100 includes a disk 110, an optical module 130, and a position data generation unit 140. The encoder 100 is a so-called reflective encoder in which the light source 131 and the light receiving arrays PA1, PA2, etc. provided in the optical module 130 are arranged on the same side with respect to the patterns SA1, SA2, etc. of the disk 110. However, the encoder 100 is not limited to the reflective encoder, and may be a so-called transmissive encoder in which the light source 131 and the light receiving arrays PA1, PA2 and the like are arranged on the opposite side with the disk 110 interposed therebetween. However, for convenience of explanation, a case where the encoder 100 is a reflective encoder will be described below.

Here, for convenience of explanation of the structure of the encoder 100, the vertical direction is determined as follows and used as appropriate. In FIG. 2, the direction in which the disk 110 faces the optical module 130, that is, the Z-axis positive direction is “up” and the Z-axis negative direction is “down”. However, the direction varies depending on the installation mode of the encoder 100 and the like, and does not limit the positional relationship between the components of the encoder 100.

(2-1. Disc)
As shown in FIG. 3, the disk 110 is formed in a disk shape, and is arranged such that the disk center O substantially coincides with the axis AX. The disk 110 is connected to the shaft SH of the motor M and rotates by the rotation of the shaft SH. In the present embodiment, a disk-shaped disk 110 is described as an example of an object to be measured for measuring the rotation of the motor M, but other members such as an end face of the shaft SH are to be measured. It can also be used as a target. In the example shown in FIG. 2, the disk 110 is directly connected to the shaft SH, but may be connected via a connecting member such as a hub.

As shown in FIG. 3, the disk 110 has a plurality of patterns SA1, SA2, and SI. The disk 110 rotates with the drive of the motor M, but the optical module 130 is fixedly disposed while facing a part of the disk 110. Therefore, the patterns SA1, SA2, SI and the optical module 130 are relative to each other in the measurement direction (the direction of arrow C shown in FIG. 3; hereinafter referred to as “measurement direction C” as appropriate) as the motor M is driven. Moving.

Here, the “measurement direction” is a measurement direction when each pattern formed on the disk 110 by the optical module 130 is optically measured. In the rotary encoder in which the object to be measured is the disk 110 as in this embodiment, the measurement direction coincides with the circumferential direction of the disk 110. For example, the object to be measured is a linear scale, and the mover is a stator. In a linear encoder that moves with respect to, the measurement direction is a direction along a linear scale.

(2-2. Optical detection mechanism)
The optical detection mechanism includes patterns SA1, SA2, SI, an optical module 130, and the like.

(2-2-1. Pattern)
Each pattern is formed on the upper surface of the disk 110 as a track arranged in a ring shape with the disk center O as the center. Each pattern has a plurality of reflective slits (hatched portions in FIG. 4) arranged along the measurement direction C over the entire circumference of the track. Each reflection slit reflects light emitted from the light source 131.

The disk 110 is formed of a material that reflects light, such as metal. Then, a material having a low reflectance (for example, chromium oxide) is disposed on the surface of the disk 110 where light is not reflected by coating or the like, so that a reflective slit is formed in the portion that is not disposed. In addition, a reflective slit may be formed by making the part which does not reflect light into a rough surface by sputtering etc., and reducing a reflectance.

Note that the material and manufacturing method of the disk 110 are not particularly limited. For example, the disk 110 can be formed of a material that transmits light, such as glass or transparent resin. In this case, a reflective slit can be formed by disposing a material (for example, aluminum) that reflects light on the surface of the disk 110 by vapor deposition or the like.

When the encoder 100 is configured as the above-described transmissive encoder, each pattern formed on the disk 110 has a plurality of transmissive slits arranged along the measurement direction C over the entire circumference of the track. Each transmission slit transmits light emitted from the light source 121.

Three patterns are provided in the width direction (in the direction of arrow R shown in FIG. 3; hereinafter referred to as “width direction R” as appropriate) on the upper surface of the disk 110. The “width direction” is a radial direction of the disk 110, that is, a direction substantially perpendicular to the measurement direction C, and the length of each pattern along the width direction R corresponds to the width of each pattern. The three patterns are arranged concentrically in the order of SA1, SI, SA2 from the inner side to the outer side in the width direction R. In order to explain each pattern in more detail, FIG. 4 shows a partially enlarged view of the vicinity of the area facing the optical module 130 of the disk 110.

(2-2-1-1. Absolute pattern)
As shown in FIG. 4, the plurality of reflective slits included in the patterns SA <b> 1 and SA <b> 2 are arranged on the entire circumference of the disk 110 so as to have an absolute pattern along the measurement direction C. These patterns SA1 and SA2 correspond to examples of absolute patterns.

It should be noted that the “absolute pattern” is a pattern in which the position and ratio of the reflection slit within an angle at which a light receiving array of the optical module 130 described later faces is uniquely determined within one rotation of the disk 110. That is, for example, in the case of the example of the absolute pattern shown in FIG. 4, when the motor M is at an angular position, a combination of bit patterns by detection or non-detection of each of the plurality of light receiving elements of the opposed light receiving array is as follows: The absolute position of the angular position is uniquely expressed. The “absolute position” refers to an angular position with respect to the origin within one rotation of the disk 110. The origin is set at an appropriate angular position within one rotation of the disk 110, and an absolute pattern is formed with this origin as a reference.

Note that, according to this pattern example, it is possible to generate a pattern in which the absolute position of the motor M is represented in a one-dimensional manner by the number of light receiving elements in the light receiving array. However, the absolute pattern is not limited to this example. For example, it may be a multidimensional pattern represented by bits of the number of light receiving elements. In addition to a predetermined bit pattern, a pattern in which a physical quantity such as the amount of light received by a light receiving element or a phase changes so as to uniquely represent an absolute position, a pattern in which a code sequence of an absolute pattern is modulated, etc. There may be other various patterns.

In the present embodiment, the same absolute pattern is offset in the measurement direction C by a length of, for example, 1/2 of 1 bit, and formed as two patterns SA1 and SA2. This offset amount corresponds to, for example, half the pitch P of the reflection slits of the pattern SI. If the pattern SA1, SA2 is not offset as described above, there is the following possibility. That is, when the absolute position is represented by a one-dimensional absolute pattern as in the present embodiment, the bit pattern transition point is caused by the fact that each light receiving element of the light receiving arrays PA1 and PA2 is positioned in the vicinity of the end of the reflecting slit. In the region, the absolute position detection accuracy may be lowered. In the present embodiment, since the patterns SA1 and SA2 are offset, for example, when the absolute position of the pattern SA1 corresponds to the change of the bit pattern, the absolute position is calculated using the detection signal from the pattern SA2, By performing the reverse, the absolute position detection accuracy can be improved. In such a configuration, the amount of light received by the two light receiving arrays PA1 and PA2 needs to be uniform, but in the present embodiment, the two light receiving arrays PA1 and PA2 are arranged at substantially the same distance from the light source 131. Therefore, the above configuration can be realized.

Instead of offsetting the absolute patterns of the patterns SA1 and SA2, for example, the light receiving arrays PA1 and PA2 corresponding to the patterns SA1 and SA2 may be offset without offsetting the absolute patterns.

Also, two absolute patterns are not necessarily formed, and only one may be used. However, hereinafter, for convenience of explanation, a case where two patterns SA1 and SA2 are formed will be described.

(2-2-1-2. Incremental pattern)
On the other hand, the plurality of reflective slits included in the pattern SI are arranged on the entire circumference of the disk 110 so as to have an incremental pattern along the measurement direction C.

The “incremental pattern” is a pattern that is regularly repeated at a predetermined pitch as shown in FIG. Here, “pitch” refers to the arrangement interval of the reflective slits in the pattern SI having an incremental pattern. As shown in FIG. 4, the pitch of the pattern SI is P. The incremental pattern is different from an absolute pattern that represents an absolute position with each of the presence / absence of detection by a plurality of light receiving elements as a bit, and the position of the motor M within each pitch or within one pitch depending on the sum of the detection signals by at least one light receiving element. Represents. Therefore, although the incremental pattern does not represent the absolute position of the motor M, it can represent the position with very high accuracy compared to the absolute pattern.

In the present embodiment, the minimum length in the measurement direction C of the reflection slits of the patterns SA1 and SA2 matches the pitch P of the reflection slits of the pattern SI. As a result, the resolution of the absolute signal based on the patterns SA1 and SA2 matches the number of reflection slits of the pattern SI. However, the minimum length is not limited to this example, and it is desirable that the number of reflection slits of the pattern SI is set to be equal to or larger than the resolution of the absolute signal.

(2-2-2. Optical module)
As shown in FIGS. 2 and 5, the optical module 130 is formed as a single substrate BA parallel to the disk 110. As a result, the encoder 100 can be thinned and the optical module 130 can be easily manufactured. Therefore, as the disk 110 rotates, the optical module 130 moves relative to the patterns SA1, SA2, and SI in the measurement direction C. The optical module 130 is not necessarily configured as a single substrate BA, and each configuration may be configured as a plurality of substrates. In this case, it is only necessary that these substrates are arranged together. Further, the optical module 130 does not have to be a substrate.

As shown in FIGS. 2 and 5, the optical module 130 has a light source 131 and a plurality of light receiving arrays PA1, PA2, PI1, PI2 on a surface of the substrate BA facing the disk 110.

(2-2-2-1. Light source)
As shown in FIG. 3, the light source 131 is disposed at a position facing the pattern SI. The light source 131 emits light to the opposed portions of the three patterns SA1, SA2, and SI that pass through the opposed positions of the optical module 130.

The light source 131 is not particularly limited as long as it is a light source capable of irradiating light to the irradiation region. For example, an LED (Light Emitting Diode) can be used. As shown in FIG. 6, the light source 131 is configured as a point light source in which no optical lens or the like is disposed, and emits diffused light from the light emitting unit. Note that the term “point light source” does not need to be a strict point. For light sources that can be considered to emit diffused light from a substantially point-like position in terms of design or operating principle, light from a finite emission surface is used. May be emitted. The “diffused light” is not limited to light emitted from a point light source in all directions, and includes light emitted while diffusing in a finite fixed direction. In other words, the diffused light here includes light that is more diffusive than parallel light. By using the point light source in this way, the light source 131 can irradiate light almost evenly to the three patterns SA1, SA2, and SI that pass through the opposed positions. Further, since the light is not condensed and diffused by the optical element, an error due to the optical element is not easily generated, and the straightness of the light to the pattern can be improved.

(2-2-2-2. Magnification ratio of projected image)
The plurality of light receiving arrays are arranged around the light source 131 and have a plurality of light receiving elements (dot hatched portions in FIG. 5) that respectively receive the light reflected by the reflection slits of the associated pattern. The plurality of light receiving elements are arranged along the measurement direction C as shown in FIG.

As shown in FIG. 6, the light emitted from the light source 131 is diffused light. Therefore, the pattern image projected on the optical module 130 is enlarged by a predetermined enlargement factor ε corresponding to the optical path length. That is, as shown in FIGS. 4 to 6, the lengths of the patterns SA1, SA2, and SI in the width direction R are WSA1, WSA2, and WSI, and the reflected light is projected onto the optical module 130 in the width direction. Assuming that the length of R is WPA1, WPA2, and WPI, WPA1, WPA2, and WPI are ε times as long as WSA1, WSA2, and WSI. In this embodiment, as shown in FIGS. 5 and 6, the length in the width direction R of the light receiving element of each light receiving array is set substantially equal to the shape of each slit projected onto the optical module 130. An example is shown. However, the length of the light receiving element in the width direction R is not necessarily limited to this example.

Similarly, the measurement direction C in the optical module 130 also has a shape in which the measurement direction C in the disk 110 is projected onto the optical module 130, that is, a shape affected by the magnification factor ε. In order to facilitate understanding, the measurement direction C at the position of the light source 131 will be described as an example as shown in FIG. The measurement direction C in the disk 110 is circular with the axis AX as the center. On the other hand, the center in the measurement direction C projected on the optical module 130 is a position separated from the optical center Op, which is the in-plane position of the disk 110 on which the light source 131 is disposed, by a distance εL. The distance εL is a distance obtained by enlarging the distance L between the axis AX and the optical center Op at an enlargement factor ε. In FIG. 2, this position is conceptually shown as the measurement center Os. Therefore, the measurement direction C in the optical module 130 is centered on the measurement center Os that is separated from the optical center Op by a distance εL in the direction of the axis AX on the line where the optical center Op and the axis AX ride, and the distance εL is the radius. On the line to be.

4 to 6, the corresponding relationship in the measurement direction C in each of the disk 110 and the optical module 130 is represented by arc-shaped lines Lcd and Lcp. 4 represents a line along the measurement direction C on the disk 110, while the line Lcp illustrated in FIG. 5 and the like represents a line along the measurement direction C on the substrate BA (the line Lcd is an optical module). Line projected onto 130).

As shown in FIG. 6, when the gap length between the optical module 130 and the disk 110 is G and the protrusion amount of the light source 131 from the substrate BA is Δd, the enlargement ratio ε is expressed by the following (formula 1). It is.
ε = (2G−Δd) / (G−Δd) (Formula 1)

(2-2-2-3. Light receiving array for absolute and incremental use)
As each light receiving element, for example, a photodiode can be used. Each light receiving element is formed in a shape having a predetermined light receiving area, and outputs an analog detection signal having a magnitude corresponding to the total light amount received in the entire light receiving area (hereinafter referred to as “light receiving amount”). However, the light receiving element is not limited to a photodiode, and is not particularly limited as long as it can receive light emitted from the light source 131 and convert it into an electric signal.

The light receiving array in the present embodiment is arranged corresponding to the three patterns SA1, SA2, and SI. The light receiving array PA1 is configured to receive the light reflected by the pattern SA1, and the light receiving array PA2 is configured to receive the light reflected by the pattern SA2. The light receiving arrays PI1 and PI2 are configured to receive light reflected by the pattern SI. The light receiving array PI1 and the light receiving array PI2 are divided on the way, but correspond to the same track. As described above, the number of light receiving arrays corresponding to one pattern is not limited to one, and may be plural.

The light source 131 and the light receiving arrays PA1 and PA2 are arranged in the positional relationship shown in FIG. That is, two sets of light receiving arrays PA1 and PA2 corresponding to the absolute pattern are arranged in parallel at positions offset from each other in the width direction R with the light source 131 interposed therebetween. In this example, the light receiving array PA1 is disposed on the inner peripheral side and the light receiving array PA2 is disposed on the outer peripheral side, and the distances between the light receiving arrays PA1 and PA2 and the light source 131 are substantially equal. Each of the light receiving arrays PA1 and PA2 has an axisymmetric shape with respect to a line Lo passing through the light source 131 (optical center Op) and parallel to the Y axis. A plurality (for example, 9 in this embodiment) of light receiving elements included in the light receiving arrays PA1 and PA2 are arranged at a constant pitch along the measurement direction C (line Lcp). The shapes of the plurality of light receiving elements will be described later.

In the present embodiment, a one-dimensional pattern is illustrated as an absolute pattern. Therefore, the light receiving arrays PA1 and PA2 corresponding to the pattern are arranged along the measurement direction C (line Lcp) so as to receive the light reflected by the reflecting slits of the corresponding patterns SA1 and SA2. A plurality of (for example, 9 in this embodiment) light receiving elements are provided. In the plurality of light receiving elements, as described above, each light reception or non-light reception is treated as a bit and represents an absolute position of 9 bits. The light reception signals received by each of the plurality of light receiving elements are handled independently of each other in the position data generation unit 140 (see FIG. 2), and the absolute position encrypted (encoded) into a serial bit pattern is It decodes from the combination of these received light signals. The light receiving signals of the light receiving arrays PA1 and PA2 are referred to as “absolute signals”. When an absolute pattern different from the present embodiment is used, the light receiving arrays PA1 and PA2 have a configuration corresponding to the pattern. The number of light receiving elements included in the light receiving arrays PA1 and PA2 may be other than nine, and the number of bits of the absolute signal is not limited to nine.

The light source 131 and the light receiving arrays PI1, PI2 are arranged in the positional relationship shown in FIG. That is, the light receiving arrays PI1 and PI2 corresponding to the incremental pattern are arranged in the measurement direction C with the light source 131 interposed therebetween. Specifically, the light receiving arrays PI1 and PI2 are arranged so as to be line symmetric with respect to the line Lo as a symmetry axis. The light source 131 is arranged between the light receiving arrays PI1 and PI2 arranged as one track in the measurement direction C.

The light receiving arrays PI1 and PI2 have a plurality of light receiving elements arranged along the measurement direction C (line Lcp) so as to receive the light reflected by the reflecting slits of the associated pattern SI. Each of these light receiving elements has the same shape (substantially rectangular in this example).

In the present embodiment, a total of four sets of light receiving elements (indicated by “SET” in FIG. 5) are included in one pitch of the incremental pattern of pattern SI (one pitch in the projected image, ie, ε × P). A plurality of sets of four light receiving elements are arranged along the measurement direction C. In the incremental pattern, reflection slits are repeatedly formed for each pitch. Therefore, when the disk 110 rotates, each light receiving element generates a periodic signal of one cycle (referred to as 360 ° in electrical angle) at one pitch. To do. Since four light receiving elements are arranged in one set corresponding to one pitch, adjacent light receiving elements in one set receive an incremental phase signal which is a periodic signal having a phase difference of 90 ° from each other. Will be output. Each incremental phase signal is divided into A + phase signal, B + phase signal (phase difference with respect to A + phase signal is 90 °), A− phase signal (phase difference with respect to A + phase signal is 180 °), B− phase signal (with respect to B + phase signal). The phase difference is called 180 °.

Since the incremental pattern represents a position in one pitch, the signal of each phase in one set and the signal of each phase in another set corresponding to it have values that change similarly. Accordingly, signals of the same phase are added over a plurality of sets. Accordingly, four signals whose phases are shifted by 90 ° are detected from the many light receiving elements of the light receiving array PI shown in FIG. Accordingly, four signals whose phases are shifted by 90 ° are generated from the light receiving arrays PI1 and PI2, respectively. These four signals are referred to as “incremental signals”.

In this embodiment, one set corresponding to one pitch of the incremental pattern includes four light receiving elements, and the light receiving array PI1 and the light receiving array PI2 each have a set having the same configuration as an example. However, the number of light receiving elements in one set is not particularly limited, for example, two light receiving elements are included in one set. Further, the total number of light receiving elements of the light receiving arrays PIL and PIR is not limited to the example shown in FIG. The light receiving arrays PI1 and PI2 may be configured to acquire light receiving signals having different phases.

Further, the light receiving array corresponding to the incremental pattern is not limited to a mode in which two light receiving arrays such as the light receiving arrays PI1 and PI2 are arranged with the light source 131 interposed therebetween. For example, the light source 131 may be arranged as one light receiving array along the measurement direction C on the outer peripheral side or the inner peripheral side. Further, incremental patterns having different resolutions may be formed on a plurality of tracks of the disk 110, and a plurality of light receiving arrays corresponding to the respective tracks may be provided.

Heretofore, the outline of the light receiving array has been described. Next, before describing the shape and the like of each light receiving element included in the light receiving arrays PA1 and PA2, the position data generating unit 140 which is the remaining configuration will be described.

(2-3. Position data generator)
The position data generation unit 140, from the optical module 130, at the timing of measuring the absolute position of the motor M, two absolute signals each having a bit pattern representing the first absolute position, and four signals whose phases are shifted by 90 °. Incremental signal including. Then, the position data generation unit 140 calculates the second absolute position of the motor M represented by these signals based on the acquired signals, and outputs position data representing the calculated second absolute position to the control device CT.

Note that the position data generation method by the position data generation unit 140 can use various methods, and is not particularly limited. Here, a case where the absolute position is calculated from the incremental signal and the absolute signal to generate position data will be described as an example.

The position data generation unit 140 binarizes each of the absolute signals from the light receiving arrays PA1 and PA2, and converts them into bit data representing an absolute position. Then, the first absolute position is specified based on the correspondence between the predetermined bit data and the absolute position. That is, the “first absolute position” here is an absolute position having a low resolution before the incremental signal is superimposed. On the other hand, among the incremental signals of the four phases from the light receiving arrays PI1 and PI2, the incremental signals having a phase difference of 180 ° are subtracted from each other. Thus, by subtracting a signal having a phase difference of 180 °, it is possible to cancel a manufacturing error or a measurement error of the reflection slit within one pitch. The signals resulting from the subtraction as described above are referred to herein as “first incremental signal” and “second incremental signal”. The first incremental signal and the second incremental signal have a phase difference of 90 ° in electrical angle with each other (simply referred to as “A phase signal”, “B phase signal”, etc.). Therefore, the position data generation unit 140 identifies the position within one pitch from these two signals. The method for specifying the position within one pitch is not particularly limited. For example, when the incremental signal, which is a periodic signal, is a sine wave signal, the electrical angle φ is calculated by performing an arctan operation on the division result of the two A-phase and B-phase sine wave signals as an example of the above-described specific method. There is a way to do it. Alternatively, there is a method of converting two sine wave signals into an electrical angle φ using a tracking circuit. Alternatively, there is a method of specifying the electrical angle φ associated with the values of the A-phase and B-phase signals in a table created in advance. At this time, the position data generation unit 140 preferably performs analog-digital conversion of the two sine wave signals of the A phase and the B phase for each detection signal.

The position data generation unit 140 superimposes the position within one pitch specified based on the incremental signal on the first absolute position specified based on the absolute signal. Accordingly, it is possible to calculate the second absolute position with higher resolution than the first absolute position based on the absolute signal. The position data generation unit 140 multiplies the second absolute position calculated in this way to further improve the resolution, and then outputs it to the control device CT as position data representing a highly accurate absolute position.

(2-4. Shape of each light receiving element of absolute light receiving array)
Next, the shape of each light receiving element included in the light receiving arrays PA1 and PA2 will be described.

If all of the diffused light emitted from the light source 131 is reflected on the disk 110 and applied to the substrate BA of the optical module 130, the intensity distribution of the reflected light becomes farther from the optical center Op as shown in FIG. It becomes a concentric distribution that decays. Note that the dotted circle in FIG. 7 represents the isointensity line of the reflected light, and the light intensity is higher on the inner peripheral side and the light intensity is lower on the outer peripheral side. The distribution of the light intensity of the reflected light is concentric as described above, while the light is attenuated according to the optical path length, while the optical axis is in the irradiation space of diffuse light from the light source 131 (in the reflection space). This is because the structure is such that the light is received by a flat substrate BA perpendicular to the substrate. Actually, the reflected light is applied to the areas corresponding to the patterns SA1, SA2, and SI of the disk 110 on the substrate BA.

As described above, in each of the absolute light receiving arrays PA1 and PA2, a plurality of light receiving elements are arranged along the arc-shaped line Lcp with the measurement center Os as the center of curvature, while the optical center Op is measured. It is arranged at a position greatly separated from the center Os. For this reason, the light intensity in each light receiving element of the light receiving arrays PA1, PA2 changes according to the distance from the light source 131 in the measurement direction C. The light receiving array PA2 will be described in detail. Since the light receiving array PA2 has a line-symmetric shape with respect to the line Lo as described above, the light intensity at each light receiving element is highest at the light receiving element P5 on the line Lo. In this order, they are line-symmetrically lower in the order closer to the line Lo, that is, in the order of the light receiving elements P4 and P6, the light receiving elements P3 and P7, the light receiving elements P2 and P8, and the light receiving elements P1 and P9. The same applies to the light receiving array PA1. Further, since the light receiving array PA1 and the light receiving array PA2 are arranged side by side with the light source 131 therebetween, the light intensity in each light receiving element of the light receiving arrays PA1 and PA2 is highest at the end Eo on the light source side. , And lowest at the end En on the opposite side of the light source 131.

Here, in the present embodiment, each light receiving element constituted by, for example, a photodiode outputs an analog value detection signal according to the amount of light received in the entire light receiving area as described above. The received light amount is obtained by integrating the light intensity at each light receiving point in the light receiving area. For this reason, if the light intensity distribution is different among the light receiving elements, even if the light receiving areas are the same, the amount of received light is different, and the change characteristics of the analog detection signal between the light receiving elements. Will be different. In this case, since the change timing of the binarized signal is shifted between the light receiving elements, the absolute position may be erroneously detected. In addition, it is conceivable to adjust the threshold value for conversion to a binarized signal corresponding to the change characteristics of each light receiving element so that the change timing of the binarized signal does not shift between the light receiving elements. The configuration and signal processing are complicated, which can cause an increase in cost.

On the other hand, it is also conceivable to take a method of changing the light receiving area by adjusting the outer dimensions in the measurement direction C or the width direction R between the light receiving elements, and making the received light quantity uniform. However, when the external dimensions in the measurement direction C of each light receiving element are changed, the interval between adjacent light receiving elements becomes non-uniform, so that light leakage from each other occurs due to the influence of irregular reflection between the light receiving elements. As a result, the amount of crosstalk to be generated becomes non-uniform, and as a result, the amount of received light may become non-uniform. Further, when the external dimensions of each light receiving element in the width direction R are changed, the light receiving element having a shorter length in the width direction is more susceptible to the positional deviation in the width direction of the reflected light due to the eccentricity of the disk 110, False detection may occur.

Therefore, in the present embodiment, in each of the light receiving array PA1 and the light receiving array PA2, the maximum outer dimension in the measurement direction C and the maximum outer dimension in the width direction R of each light receiving element are set to be equal to each other, and the respective received light amounts are mutually equal. The light receiving elements having different distances from the light source 131 are formed in different shapes so as to be equal. Here, the description that the outer diameter and the amount of received light are “equal” does not mean a strict meaning, but means that tolerances and errors in manufacturing are allowed and are substantially equal. Further, the “light reception amount” here is the maximum light reception amount when each light receiving element receives reflected light over the entire light receiving area.

In this embodiment, as an example of a shape that realizes such a condition, in the light receiving arrays PA1 and PA2, some or all of the plurality of light receiving elements are each formed into a shape having a tapered pointed portion. Although the position of the tip is not particularly limited, in the present embodiment, a case where the light receiving element includes the tip at the end in the width direction R will be described. Here, the light receiving array PA2 out of the light receiving arrays PA1 and PA2 will be described as a specific example. The light receiving array PA1 has the same shape as that of the light receiving array PA2 except that the light receiving array PA1 is symmetrical in the width direction R, and the description thereof is omitted.

(2-4-1. Details of shape of light receiving element having pointed portion)
In FIG. 8, the shape of the light receiving element P6, which is one of the nine light receiving elements included in the light receiving array PA2, is enlarged and shown as an example. With reference to FIG. 8, the shape and dimension setting of each part of the light receiving element having a pointed portion will be described in detail.

The shape of the light receiving element P6 is roughly a shape in which corners of a basic quadrilateral shape are trimmed. This basic quadrangular shape has a length in the measurement direction C as TPA2 (in this example, a length ε times the minimum length P (basic bit length) in the measurement direction C of the reflective slit of the pattern SA2), and the width direction. It is a rectangular shape in which the length of R is WPA2. In any of the light receiving elements P1 to P9 included in the light receiving array PA2, the basic rectangular shape, that is, the maximum external dimension TPA2 in the measurement direction C and the maximum external dimension WPA2 in the width direction R are set to be equal in common. . Note that the above-described basic quadrangular shape does not need to be strictly parallel between two opposing sides, and each corner does not need to be strictly right-angled, and may be substantially rectangular.

Further, here, “trimming” means chamfering at a predetermined inclination angle with respect to one corner of the square shape. Then, at least one of the both end portions En and Eo in the width direction R of the light receiving element P6 is trimmed at the same inclination angle with respect to two corner portions respectively positioned on the end portions En and Eo. A substantially isosceles triangular point Ps is formed on the portions En and Eo. In the case of the light receiving element P6 shown in FIG. 8, the apex portion Ps is formed at each of the both end portions En and Eo in the width direction R. Even in this case, the maximum outer dimension in the width direction R (that is, each end portion at both ends) The distance between the vertices of Ps) is maintained at the length WPA2. Thereby, the light receiving element P6 is formed in a hexagonal shape symmetrical with respect to the measurement direction C with a line Loc passing through the measurement center Os and the apex of each tip portion Ps as an axis of symmetry. The light receiving elements (light receiving elements P2, P3, P5, P7, and P8) in which only one of the two end portions En and Eo is formed have a pentagonal shape that is symmetric with respect to the measurement direction C with the line Loc as an axis of symmetry. Formed.

In addition, the shape of the pointed portion Ps may be a tapered shape, and may be, for example, a trapezoidal shape or a rounded arc shape other than the triangular shape. Further, the pointed portion Ps may be formed by a method other than the trimming of a basic rectangular corner.

Further, when the width direction dimension of the tip portion Ps formed at the end portion Eo on the light source side is Wo and the width direction dimension of the tip portion Ps formed at the end portion En on the opposite side of the light source 131 is Wn, If the total Wo + Wn of the widthwise dimensions of both the tip portions Ps is equal between the elements, it can be said that the light receiving area is also equal. In other words, if the ratio of Wo + Wn to the maximum external dimension WPA2 in the width direction R of the light receiving element is equal, the light receiving area of the entire light receiving element is also equal.

In the following, a light receiving element having a pointed portion Ps at at least one of the end Eo on the light source side and the end En on the opposite side, in other words, a light receiving element in which Wo + Wn is a value greater than 0 (in this example, the light receiving element) P2 to P8) are also referred to as “first light receiving elements”. In addition, a square-shaped light receiving element that does not have the pointed part Ps at both ends Eo and En, in other words, a light receiving element in which Wo + Wn is substantially 0 (Wo = Wn = 0) (in this example, the light receiving elements P1, P9) is also referred to as “second light receiving element”.

As described with reference to FIG. 7, the light intensity of each light receiving element is highest at the end Eo on the light source side and lowest at the end En on the opposite side to the light source 131. For this reason, even if Wo + Wn is the same between the light receiving elements, that is, the light receiving area is the same, increasing the ratio of the width direction dimension Wo of the tip portion Ps on the end Eo side close to the light source 131 causes the received light amount to be relative. Can be made small. Conversely, the amount of received light can be relatively increased by increasing the proportion of the width direction dimension Wn of the tip portion Ps on the end portion En side far from the light source 131.

Further, as described with reference to FIG. 7, the light intensity in the plurality of light receiving elements P1 to P9 of the light receiving array PA2 is higher as the light receiving element is closer to the line Lo, that is, closer to the light source 131 on the substrate BA. The farther away, that is, the light receiving element farther from the light source 131 on the substrate BA becomes lower. For this reason, in this embodiment, the two light receiving elements P1 and P9 located farthest from the light source 131 are the second light receiving elements having the largest light receiving area, and the other light receiving elements P2 to P8 are the first light receiving elements. The shape of the light receiving element is adjusted so that the received light amount is the same with reference to the received light amount at the light receiving elements P1 and P9.

From the above, the shapes of the plurality of light receiving elements P1 to P9 of the light receiving array PA2 can be the modes shown in FIGS. 5 and 7, for example. That is, the two light receiving elements P1 and P9 located at both ends are rectangular second light receiving elements which are not trimmed at all. Further, the two light receiving elements P2 and P8 positioned in the immediate vicinity thereof are first light receiving elements having substantially the same shape and having a pointed portion Ps having a relatively low width direction dimension Wn on the end portion En side. Further, the two light receiving elements P3 and P7 positioned in the immediate vicinity thereof are first light receiving elements having substantially the same shape and having a pointed portion Ps having a relatively high width direction dimension Wn on the end portion En side. Further, the two light receiving elements P4 and P6 positioned in the immediate vicinity of each other are first light receiving elements having substantially the same shape, each having a tip portion Ps on both sides of the end portion Eo and the end portion En. Further, the light receiving element P5 closest to the light source 131 inside thereof is a first light receiving element having a pointed portion Ps having a relatively high width direction dimension Wo on the end Eo side.

In this example, among the nine light receiving elements P1 to P9 in the light receiving array PA2, the five light receiving elements P3 to P7 close to the light source 131 have the same Wo + Wn, that is, the light receiving areas are equal. The light receiving elements P3 to P5 and the light receiving elements P5 to P7 constituting the light receiving elements P3 to P7 correspond to an example of a plurality of light receiving elements having different distances from the light source 131 and equal areas. Between the light receiving elements P3 to P7 having the same area, the ratio of the width direction dimension Wo of the pointed portion Ps formed at the end Eo on the light source 131 side with respect to Wo + Wn (hereinafter referred to as “Wo ratio” as appropriate). In the measurement direction C, the light receiving element closer to the light source 131 is set to be larger. Specifically, the Wo ratio (100% in this example) of the light receiving element P5 is larger than the Wo ratio of the light receiving elements P4 and P6, and the Wo ratio of the light receiving elements P4 and P6 is the above of the light receiving elements P3 and P7. It is larger than the Wo ratio (0% in this example).

Further, in this example, among the light receiving elements P1 to P9, for the first light receiving elements having different areas, that is, the light receiving elements P2 and P3 and the light receiving elements P7 and P8, Wo + Wn is light received close to the light source 131 in the measurement direction C. The device is larger. Specifically, Wo + Wn of the light receiving element P3 is larger than Wo + Wn of the light receiving element P2, and similarly Wo + Wn of the light receiving element P7 is larger than Wo + Wn of the light receiving element P8. The light receiving elements P2, P3 and the light receiving elements P7, P8 correspond to an example of a plurality of first light receiving elements having different distances from the light source and different areas.

Note that the shape of the plurality of light receiving elements P1 to P9 of the light receiving array PA2 is not limited to the above. For example, the light receiving elements P1 and P9 at both ends of the light receiving array PA2 may be the first light receiving elements provided with the pointed portion Ps. Further, the number of light receiving elements having the same area in the light receiving elements P1 to P9 may be other than 5, or the areas of all the light receiving elements may be different from each other. In addition, the relationship of the Wo ratio in the first light receiving elements having the same area and the relationship of Wo + Wn in the first light receiving elements having the different areas may be other than the above. However, in this embodiment, the case where it is the above-mentioned shape is demonstrated for convenience of explanation.

As described above, with respect to each of the light receiving array PA1 and the light receiving array PA2, it is possible to make the received light amounts equal to each other while making the maximum outer dimension in the measurement direction C and the maximum outer dimension in the width direction R of each light receiving element equal to each other. . In addition, the shape of each light receiving element of the light receiving arrays PA1 and PA2 described above corresponds to an example of a unit that equalizes the amount of light received by each light receiving element.

In addition, since the first light receiving element has the pointed portion Ps, an advantageous effect can be obtained even when the detection signal is converted into a binarized signal. Hereinafter, the effect will be described in detail.

(2-4-2.2 Effect of the tip when converting a binary signal)
First, as a comparative example, a change characteristic of an analog detection signal in the case of a rectangular light receiving element PD ′ not having a pointed portion Ps will be described with reference to FIG. In FIG. 9, with respect to the rectangular light receiving element PD ′, the irradiation surface Rs of the reflected light from the reflection slits of the patterns SA1 and SA2 proceeds in the order of the positions X1 to X11 along the measurement direction C over time. To do. The irradiation surface Rs is larger than the light receiving element PD ′ in the width direction R, and has a rectangular shape having the same size as the light receiving element PD ′ in the measurement direction C. Here, it is assumed that the light intensity distribution in the irradiation surface Rs is uniform. Corresponding to each of these positions X1 to X11, the amount of light received by the light receiving element PD ′ changes with the change characteristics as shown by the thick line VX.

In this case, the amount of received light monotonically increases from the timing of the position X2 where the irradiation surface Rs begins to overlap with the light receiving element PD ′ to the timing of the position X6 where the irradiation surface Rs completely overlaps with the light receiving element PD ′. To do. Further, from the timing of the position X6 at which the received light amount becomes the maximum to the timing of the position X10 at which the irradiation surface Rs and the light receiving element PD 'do not overlap, the received light amount decreases monotonically in a linear function.

On the other hand, the change characteristic of the analog detection signal in the case of the light receiving element PD having the tip portion Ps is shown in FIG. In FIG. 10, in order to facilitate understanding, a case where the light receiving element PD is formed only by the tip portion Ps is illustrated. Similarly to the above, the irradiation surface Rs is larger than the light receiving element PD in the width direction R, has a rectangular shape having the same size as the light receiving element PD in the measurement direction C, and the light intensity distribution in the irradiation surface Rs is uniform. And In FIG. 10, when the irradiation surface Rs advances with respect to the light receiving element PD in the order of positions Y1 to Y11 with time, the received light amount in the light receiving element PD is indicated by a thick line VY corresponding to each position Y1 to Y11. It changes with time with such change characteristics.

In this case, the amount of received light is a quadratic function (a cubic function or higher) from the timing of the position Y2 where the irradiation surface Rs begins to overlap the light receiving element PD to the timing of the position Y6 where the irradiation surface Rs completely overlaps the light receiving element PD. (It may be a multi-order function). During this time, the timing of the position Y4 where the irradiation surface Rs overlaps half of the light receiving element PD becomes an inflection point, and the time change rate (curve slope) of the amount of received light becomes the largest at this point. In addition, the received light amount decreases in a quadratic function from the timing of the position Y6 where the received light amount becomes maximum to the timing of the position Y10 where the irradiation surface Rs and the light receiving element PD do not overlap. During this time, the timing of the position Y8 where the irradiation surface Rs overlaps half of the light receiving element PD becomes the inflection point, and the time change rate (curve slope) of the amount of received light becomes the largest at this point.

Here, as shown in FIG. 11, the change characteristics of the received light amount in the case of the light receiving element PD ′ and in the case of the light receiving element PD are compared. In FIG. 11, for easy comparison, the respective light receiving areas are equal, the irradiation light having the same light intensity is irradiated with a uniform distribution, and the maximum received light amounts in the respective change characteristics are equal. And

In FIG. 11, in any of the light receiving elements PD ′ and PD, the timing at which the overlapping area with the irradiation surface Rs becomes half of the light receiving area, that is, the timing of the positions X4, X8, Y4, Y8 in FIGS. Thus, the received light quantity becomes half of the maximum received light quantity, and the characteristic lines VX and VY intersect. The threshold value for converting the analog detection signal from the light receiving element into a binarized signal is preferably set to a value that is half the maximum received light amount. However, the threshold value is relative to the change characteristic of the amount of received light due to, for example, fluctuation of the light intensity of the irradiation light due to aging degradation of the light source 131 or manufacturing individual difference, or fluctuation of light receiving sensitivity due to aging deterioration of the light receiving element or manufacturing individual difference. May vary. The fluctuation of the threshold fluctuates within a fluctuation range ΔT centered on the reference value that is half of the above-described maximum received light quantity. However, in the case of the light receiving element PD ′, the change characteristic increases and decreases in a linear function. Therefore, the change timing of the binarized signal fluctuates within the corresponding fluctuation width Δtx.

On the other hand, in the case of the light receiving element PD, as described above, it becomes an inflection point of the characteristic curve at the timing of the reference value that is half of the maximum received light amount, and the curve is largely inclined around the characteristic curve. For this reason, the change in the change timing of the binarized signal with respect to the change width ΔT of the threshold can be suppressed to a change width Δty that is sufficiently narrower than the change width Δtx in the case of the light receiving element PD ′. As described above, since the first light receiving element in the present embodiment is formed in a shape having the tip portion Ps, an effect of suppressing the influence due to the fluctuation of the threshold when the analog detection signal is converted into the binarized signal. There is.

<3. Examples of effects according to this embodiment>
In the embodiment described above, the encoder 100 includes the light receiving arrays PA1 and PA2 that are arranged along the measurement direction C and receive the light emitted from the light source 131 and reflected by the patterns SA1 and SA2. A plurality of light receiving elements (light receiving elements P1 to P9 in the example shown in FIG. 5 and the like) included in the light receiving arrays PA1 and PA2 have the same maximum outer dimension in the measurement direction C and the maximum outer dimension in the width direction R. In addition, the light receiving elements having different distances from the light source 131 have different shapes so that the received light amounts are equal to each other. As a result, in each of the light receiving arrays PA1 and PA2, the amount of light received by each light receiving element is uniform, so that detection accuracy of 1 bit and 1 bit can be made uniform to prevent erroneous detection of absolute positions, and detection accuracy can be improved. Further, it is not necessary to adjust the signal output of each light receiving element, and the threshold for converting the analog detection signal from each light receiving element into a binarized signal can be shared by each light receiving element. The circuit configuration can be simplified.

Further, since the maximum external dimensions in the measurement direction C of the respective light receiving elements of the light receiving arrays PA1 and PA2 are equal to each other, the intervals in the measurement direction C of the respective light receiving elements can be made uniform. Thereby, since the crosstalk amount between each light receiving element adjacent in the measurement direction C can be made uniform, the uniformity of the amount of light received by each light receiving element can be further enhanced. In addition, processing for removing noise due to crosstalk from the signals of the respective light receiving elements is facilitated.

Further, as described above, for example, when the length of the light receiving element in the width direction R is shortened as the light source 131 is approached, the light receiving element having a shorter length in the width direction R has a smaller width in the width direction R of the light due to the eccentricity of the disk 110. The influence of misalignment is increased, and detection errors are likely to occur. In the present embodiment, since the maximum outer dimensions in the width direction R of the respective light receiving elements of the light receiving arrays PA1 and PA2 are equal to each other, the influence of the eccentricity can be reduced, and even when the disk 110 has an eccentricity, it is absolutely necessary. It is possible to make it difficult for position detection errors to occur.

In the present embodiment, the plurality of light receiving elements included in the light receiving arrays PA1 and PA2 have a plurality of light receiving elements having different distances from the light source 131 and equal areas (in the example shown in FIG. 5 and the like, the light receiving elements P3 to P7). The following effects are obtained. That is, since the junction capacitance (capacitance) is equal in the light receiving elements having the same area, the response speed can be made uniform among the light receiving elements. As a result, the absolute position detection accuracy when the motor M rotates at high speed can be improved.

In the present embodiment, the plurality of light receiving elements included in the light receiving arrays PA1 and PA2 are first light receiving elements each having a tapered pointed portion Ps at the end in the width direction R (in the example shown in FIG. In the case of including P2 to P8), the following effects are obtained. That is, in the case of the second light receiving element not provided with the tip portion Ps (square shape), since the edge in the measurement direction C is parallel to the width direction R, the output change of the analog detection signal when the irradiation region Rs by the pattern passes is primary. It is a functional monotonous increase and monotonic decrease (see FIG. 9 above). On the other hand, the first light receiving element having the tip portion Ps at the end portion in the width direction R has a shape in which the edge in the measurement direction C is inclined with respect to the width direction R. The change in output of the analog detection signal increases and decreases in a quadratic function, and the degree of change in the output of the analog detection signal in the vicinity of the threshold value can be increased (the slope is abrupt) (see FIG. 10 above). As a result, the phase shift of the binarized signal with respect to the fluctuation of the threshold value is reduced, so that even if the threshold value fluctuates, an absolute position detection error can be made difficult to occur (see FIG. 11).

In the present embodiment, among the plurality of light receiving elements of the light receiving arrays PA1 and PA2, the plurality of first light receiving elements having the same area (light receiving elements P3 to P7 in the example shown in FIG. 5 and the like) The first light-receiving elements whose width direction dimensions Wo + Wn are equal to each other, and the ratio of the width direction dimension Wo of the tip portion Ps formed at the end Eo on the light source 131 side to the total Wo + Wn is closer to the light source 131 in the measurement direction C. If it is large, the following effects are obtained. That is, since the light attenuates according to the optical path length, the irradiation intensity of the light emitted from the light source 131 and reflected by the patterns SA1 and SA2 has a concentric distribution that attenuates with increasing distance from the light source 131 with the light source 131 at the center. . In such a light intensity distribution, the first light receiving element closer to the light source 131 has a relatively large light intensity for the first light receiving element far from the light source 131 by increasing the proportion of the tip portion Ps on the light source 131 side. While securing the light receiving area of the region, it is possible to gradually reduce the light receiving area of the region where the light intensity of the first light receiving element closer to the light source 131 is relatively large. Therefore, it is possible to achieve a uniform amount of received light while making the area of each light receiving element uniform.

In the present embodiment, a plurality of light receiving elements included in the light receiving arrays PA1 and PA2 are arranged in the measurement direction C with the first light receiving elements sandwiched therebetween, and two second light receiving elements that do not have the pointed portion Ps (see FIG. In the example shown in 5 etc., when the light receiving elements P1, P9) are included, the following effects are obtained. That is, the second light receiving element that does not include the pointed portion Ps has a larger area than the first light receiving element that includes the pointed portion Ps. For this reason, the light receiving elements at both ends of the light receiving arrays PA1 and PA2 that are located farthest from the light source 131 are used as the second light receiving elements, and the first light receiving elements are arranged therebetween, so that a plurality of light receiving arrays PA1 and PA2 are provided. The light receiving amount of each light receiving element can be made uniform while ensuring the maximum amount of light received by the entire light receiving element.

In the present embodiment, the second light receiving elements (light receiving elements P1 and P9 in the example shown in FIG. 5 and the like) have a square shape, and the first light receiving elements (light receiving elements P2 to P8 in the example shown in FIG. 5 and the like) The following effects can be obtained when the rectangular corner is trimmed. That is, for each first light receiving element, the trimming area, position, and the like may be adjusted based on the square shape of the second light receiving element, so that the design of the shape of the first light receiving element can be facilitated.

In the present embodiment, the plurality of light receiving elements included in the light receiving arrays PA1 and PA2 are a plurality of first light receiving elements having different distances from the light source 131 and different areas (in the example illustrated in FIG. 5 and the like, the light receiving elements P2 and P2). In a plurality of first light receiving elements including P3 and light receiving elements P7 and P8), the total Wo + Wn of the widthwise dimensions of the tip portion Ps is set to be larger in the measurement direction C as the first light receiving element is closer to the light source 131. The following effects are obtained. That is, in the light intensity distribution, by increasing the widthwise dimension of the tip portion Ps as the first light receiving element closer to the light source 131, the light receiving area can be gradually reduced as the first light receiving element closer to the light source 131 is. Therefore, it is possible to make the amount of light received by each light receiving element uniform.

In the present embodiment, when two sets of light receiving elements constituting each of the light receiving arrays PA1 and PA2 are arranged in parallel at positions offset from each other in the width direction R so as to sandwich the light source 131, The effect like this is obtained. That is, when the reliability of the detection signal is reduced due to one of the plurality of light receiving elements (for example, the light receiving array PA2) corresponding to the transition of the absolute pattern, the signal from the other plurality of light receiving elements (for example, the light receiving array PA1) The detection signal can be used and vice versa. Thereby, the reliability of the detection signal of the light receiving element can be improved, and the absolute position detection accuracy can be improved.

In the present embodiment, the encoder 100 is a point light source in which the light source 131 emits diffused light to the patterns SA1 and SA2, and the patterns SA1 and SA2 are patterns that reflect the light emitted from the light source 131, and the light receiving array. When the plurality of light receiving elements PA1 and PA2 are configured as reflective encoders that receive the light reflected by the patterns SA1 and SA2, the following effects are obtained. That is, in the reflection type encoder, by using a point light source that emits diffused light, the light amount distribution of the reflected light from the patterns SA1 and SA2 tends to become a trapezoidal shape that further spreads from the irradiation area corresponding to the patterns SA1 and SA2. Crosstalk is likely to occur between light receiving elements adjacent in the measurement direction C. Therefore, this configuration capable of making the crosstalk amount uniform is more effective when applied to a reflective encoder. In addition, by configuring as a reflective encoder, the plurality of light receiving elements P1 to P9 of the light receiving arrays PA1 and PA2 can be disposed close to the light source 131, so that the encoder 100 can be reduced in size.

<4. Modified example>
The embodiment has been described in detail with reference to the accompanying drawings. However, it goes without saying that the scope of the technical idea is not limited to the embodiment described here. It is obvious that a person having ordinary knowledge in the technical field to which the embodiments belong can make various changes, modifications, combinations, and the like within the scope of the technical idea described in the claims. It is. Accordingly, the technology after these changes, corrections, combinations, and the like are naturally within the scope of the technical idea. Hereinafter, such modifications will be described in order. In the following description, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

The shape of each light receiving element of the light receiving arrays PA1 and PA2 is not limited to the above embodiment, and various other forms are conceivable. Hereinafter, variations in the shapes of these light receiving elements will be described with reference to FIGS. 12 to 18, only the shape of each light receiving element of the light receiving array PA2 is shown, and the other configurations are not shown. In practice, the light receiving elements are arranged along the arc-shaped line Lcp (arranged along the measurement direction C). However, in FIGS. 12 to 18, it is easy to understand the shape relationship between the light receiving elements. Therefore, it is schematically shown in a linear arrangement.

(4-1. Shape of light receiving element of embodiment: When there are five light receiving elements of the same area)
For comparison, FIG. 12 shows the shape of each light receiving element of the light receiving array PA2 in the above embodiment. In this example, the two light receiving elements P1 and P9 positioned at both ends of the light receiving array PA2 are second light receiving elements that do not have the pointed portion Ps, and the first light receiving elements P2 to P8 that have the pointed portion Ps are disposed therebetween. ing. In addition, the first light receiving elements P3 to P7 have the same light receiving area, and in these first light receiving elements P3 to P7, the above-mentioned Wo ratio is set larger as the light receiving elements closer to the light source 131 in the measurement direction C. Further, for the first light receiving elements P2 and P3 and the first light receiving elements P7 and P8 having different areas, the light receiving element closer to the light source 131 in the measurement direction C has a larger Wo + Wn at the tip portion Ps.

The light receiving elements having different maximum distances from the light source 131 so that the maximum outer dimensions in the measurement direction C and the maximum outer dimensions in the width direction R of the light receiving elements are equal to each other and the received light amounts are equal to each other. The same applies to each modified example described below.

(4-2. When there are three light receiving elements of the same area)
It is good also as a shape as shown in FIG. In this example, the light receiving elements P2 to P4 and P6 to P8 are first light receiving elements having a pointed portion Ps on the end portion En side. The light receiving element P5 closest to the light source 131 is a first light receiving element having a pointed portion Ps on the end Eo side.

The three first light receiving elements P4 to P6 have the same light receiving area, and in these first light receiving elements P4 to P6, the light receiving element closer to the light source 131 in the measurement direction C is set larger. For the first light receiving elements P2 to P4 and the first light receiving elements P6 to P8 having different areas, the light receiving elements closer to the light source 131 in the measurement direction C have a larger Wo + Wn at the tip portion Ps. Also in this modification, the same effect as the above embodiment can be obtained.

(4-3. Seven light receiving elements with the same area)
Moreover, it is good also as a shape as shown in FIG. In this example, the light receiving elements P2 and P8 are first light receiving elements having a pointed portion Ps on the end En side. The light receiving elements P3, P4, P6, and P7 are first light receiving elements each having a pointed portion Ps on both sides of the end portions Eo and En. The light receiving element P5 closest to the light source 131 is a first light receiving element having a pointed portion Ps on the end Eo side.

The light receiving areas of the seven first light receiving elements P2 to P8 are equal, and in these first light receiving elements P2 to P8, the Wo ratio is set to be larger as the light receiving element is closer to the light source 131 in the measurement direction C. In the present modification, the first light receiving elements having different areas are not arranged. Also in this modification, the same effect as the above embodiment can be obtained.

(4-4. When all light receiving elements have the same area)
Moreover, it is good also as a shape as shown in FIG. In this example, all the light receiving elements P1 to P9 are the first light receiving elements having the pointed portion Ps, and the second light receiving elements not having the pointed portion Ps are not arranged. Further, the two light receiving elements P1 and P9 located at both ends are first light receiving elements having a pointed end portion Ps on the end portion En side. The light receiving elements P2 to P4 and P6 to P8 are first light receiving elements each having a pointed portion Ps on both sides of the end portions Eo and En. The light receiving element P5 closest to the light source 131 is a first light receiving element having a pointed portion Ps on the end Eo side.

The light receiving areas of all the first light receiving elements P1 to P9 are the same, and in these first light receiving elements P1 to P9, the Wo ratio is set to be larger as the light receiving elements are closer to the light source 131 in the measurement direction C. In this modification as well, the first light receiving elements having different areas are not arranged. Also in this modification, the same effect as the above embodiment can be obtained.

(4-5. When the light receiving element is composed of only the tip)
Moreover, it is good also as a shape as shown in FIG. In this example, all the light receiving elements P1 to P9 are configured by only the pointed portion Ps. That is, the two light receiving elements P1 and P9 located at both ends are the first light receiving elements that are formed only by the tip portion Ps facing the end portion En side (that is, formed by Wn = WPA2). Further, the light receiving elements P2 to P8 are first light receiving elements formed only at the pointed ends Ps directed to both sides of the ends Eo and En (that is, formed by Wo + Wn = WPA2).

(4-6. When the areas of all light receiving elements are different)
Moreover, it is good also as a shape as shown in FIG. In this example, the two light receiving elements P1 and P9 located at both ends are second light receiving elements that do not have the pointed portion Ps. The light receiving elements P2 to P8 are first light receiving elements having a pointed portion Ps on the end Eo side. All the light receiving elements P1 to P9 have different light receiving areas. In the first light receiving elements P2 to P8 having different light receiving areas, Wo + Wn of the pointed portion Ps is larger as the light receiving element is closer to the light source 131 in the measurement direction C. Also in this modification, the same effect as the above embodiment can be obtained.

(4-7. When the tip is formed only on the side opposite to the light source)
Moreover, it is good also as a shape as shown in FIG. In this example, the first light receiving elements P2 to P8, excluding the second light receiving elements P1 and P9 at both ends, have a pointed end portion Ps only on the end portion En side opposite to the light source 131. As in the modification example (4-6), all the light receiving elements P1 to P9 have different light receiving areas. In the first light receiving elements P2 to P8 having different light receiving areas, Wo + Wn of the pointed portion Ps is larger as the light receiving element is closer to the light source 131 in the measurement direction C. Also in this modification, the same effect as the above embodiment can be obtained.

In addition, in the above description, when there are descriptions such as “vertical”, “parallel”, and “plane”, the description is not strict. That is, the terms “vertical”, “parallel”, and “plane” are acceptable in design and manufacturing tolerances and errors, and mean “substantially vertical”, “substantially parallel”, and “substantially plane”. .

In addition, in the above description, when there is a description such as “same”, “equal”, “different”, etc., in terms of external dimensions and shape, the description is not strict. That is, the terms “identical”, “equal”, and “different” mean that “tolerance and error in manufacturing are allowed in design and that they are“ substantially identical ”,“ substantially equal ”, and“ substantially different ”. .

S servo system SM servo motor CT controller M motor SH shaft 100 encoder 110 disk 130 optical module 131 light source 140 position data generator SA1, SA2, SI pattern PA1, PA2 light receiving array PI1, PI2 light receiving array P1, P2, P3, P4 , P5, P6, P7, P8, P9 Light receiving element C Measuring direction R Width direction AX Rotating axis O Disk center Op Optical center Lcd, Lcp, Lo, Loc Line BA substrate

Claims

An absolute pattern along the measurement direction,
A light source configured to emit light to the absolute pattern;
A plurality of light receiving elements arranged along the measurement direction and configured to receive light emitted from the light source and transmitted or reflected by the absolute pattern;
The plurality of light receiving elements are:
The light receiving elements having different maximum distances from the light source such that the maximum outer dimensions in each of the measurement directions and the maximum outer dimensions in the width direction perpendicular to the measurement directions are equal to each other and the received light amounts are equal to each other. Have different shapes,
Encoder.
The plurality of light receiving elements are:
Including a plurality of light receiving elements having different distances from the light source and equal areas.
The encoder according to claim 1.
The plurality of light receiving elements are:
Including a first light receiving element provided with a tapered pointed end at the end in the width direction;
The encoder according to claim 1 or 2.
The plurality of first light receiving elements having the same area are
The sum of the width direction dimensions of the tip portion is equal to each other, and the ratio of the width direction size of the tip portion formed at the end portion on the light source side to the sum is close to the light source in the measurement direction. The larger the light receiving element,
The encoder according to claim 3.
The plurality of light receiving elements are:
Including two second light receiving elements that are arranged with the first light receiving element in between in the measurement direction and do not include the pointed portion,
The encoder according to claim 3 or 4.
The second light receiving element is
A square shape,
The first light receiving element includes:
The square corner is a trimmed shape.
The encoder according to claim 5.
The plurality of light receiving elements are:
A plurality of the first light receiving elements having different distances from the light source and different areas from each other;
The plurality of first light receiving elements having different areas are:
The sum of the widthwise dimensions of the tip is larger in the first light receiving element closer to the light source in the measurement direction,
The encoder according to any one of claims 2 to 6.
The plurality of light receiving elements are:
Two sets are arranged in parallel at positions offset from each other in the width direction so as to sandwich the light source,
The encoder according to any one of claims 1 to 7.
The light source is
A point light source configured to emit diffused light to the absolute pattern;
The absolute pattern is
A pattern configured to reflect light emitted from the light source;
The plurality of light receiving elements are:
Configured to receive light reflected by the absolute pattern;
The encoder according to any one of claims 1 to 8.
A motor,
The encoder according to any one of claims 1 to 9,
A motor with an encoder.