JP5434760B2 - Encoder - Google Patents

Description

  The present invention relates to an encoder.

  For example, in a rotary encoder that detects a rotation angle, a light emitting element and an image sensor are arranged to face each other so as to sandwich a disc-shaped scale (symbol plate), and light emitted from the light emitting element by the image sensor There is one that detects light through a pattern and detects a rotation angle of a scale based on a photoelectric conversion signal obtained by an image sensor that has received the light (see, for example, Patent Document 1).

JP-T-2006-524335

Such a rotary encoder may be attached to a scale with respect to a rotating shaft of a motor by an operator, for example. At this time, there is a possibility that the central axis of the pattern of the scale attached to the rotating shaft and the rotating central axis of the rotating shaft are displaced. As described above, when the scale attached in an eccentric state with respect to the rotation axis is rotated, the position of light incident through the scale pattern fluctuates on the image sensor.
That is, depending on how the scale is attached, the position of the image sensor and the position of the scale are relatively deviated, so that the area where light from the scale is incident on the image sensor varies according to the rotation. For this reason, the photoelectric conversion element that outputs a photoelectric conversion signal based on light incident through the scale changes according to the rotation of the rotation axis, and a sufficient output level as a pattern signal for detecting a pattern on the scale. It becomes difficult to obtain the pattern signal. Therefore, there is a problem that the reliability of the obtained pattern signal may be lowered.

  An object of the present invention is to provide an encoder capable of improving the reliability of a pattern signal obtained for detecting a pattern on a scale according to the relative deviation between the position of an image sensor and the position of the scale. It is in.

  An encoder according to one aspect of the present invention is a scale that is connected to a support portion having a first movement axis and has a reference pattern provided with reference to the second movement axis and a position information pattern provided with reference to the reference pattern. A plurality of first photoelectric conversion elements that receive the first light through the reference pattern and output a first photoelectric conversion signal based on the first light; and a first through the position information pattern A photoelectric conversion unit having a plurality of second photoelectric conversion elements that receive two light and output a second photoelectric conversion signal based on the second light, and the scale based on the second photoelectric conversion signal And a control unit that selects the second photoelectric conversion element corresponding to the position information of the scale based on the first photoelectric conversion signal.

  According to the present invention, the reliability of a pattern signal obtained for detecting a pattern on a scale can be improved.

It is a block diagram which shows the structure of the rotation mechanism using the rotary encoder of the 1st Embodiment of this invention. It is a perspective view which shows the external appearance structure of the rotation mechanism using the rotary encoder of the 1st Embodiment of this invention. It is explanatory drawing of the structure of the scale in the rotary encoder of the 1st Embodiment of this invention. It is explanatory drawing of the pattern currently formed in each track | truck of the scale in the rotary encoder of the 1st Embodiment of this invention. It is explanatory drawing of the fluctuation | variation of the position of the pattern on the image sensor in this embodiment. It is explanatory drawing of the fluctuation | variation of the position of the pattern on the image sensor in this embodiment. It is a functional block diagram based on operation | movement of the control part in the rotary encoder of the 1st Embodiment of this invention. It is a flowchart used for description of the initialization process in the rotary encoder of the 1st Embodiment of this invention. It is explanatory drawing of an example of the correction amount for every rotation angle memorize | stored in the memory in the rotary encoder of the 1st Embodiment of this invention. It is explanatory drawing of the structure of the scale in the encoder of the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a rotation mechanism using a rotary encoder according to a first embodiment of the encoder of the present invention. FIG. 2 is a perspective view showing the external configuration. Here, the rotary encoder 1 that rotates the scale will be described below as the encoder. However, the present invention is not limited to this, and a linear encoder that linearly moves the scale may be used.

As shown in FIG. 1, the rotation motor (motor) 11 is provided in the main body of the housing 10 and is attached to the approximate center of the upper end surface 10 a of the housing 10. A rotating shaft 12 of the rotary motor 11 protrudes from the upper end surface 10a of the housing 10 main body. A disc-shaped scale 21 is attached to the rotary shaft 12 of the rotary motor 11. The rotation shaft 12 rotates around a rotation center axis (first movement axis) C1.
Further, the light emitting element 22 and the image sensor 23 are provided to face each other with the scale 21 interposed therebetween.
As shown in FIG. 2, a cylindrical member 20 that covers the upper end surface 10 a is attached to the upper end surface 10 a of the main body 10 by a fixing member 16.

As shown in FIG. 3, the scale 21 includes an incremental track 31, an absolute track 32, and a reference track 33 that are formed concentrically with a central axis C <b> 2.
The incremental track 31 and the absolute track 32 have an incremental pattern IP and an absolute pattern AP as patterns (position information patterns) for acquiring information (hereinafter referred to as position information) indicating the rotation angle of the rotary motor 11, respectively. Prepare. The position information includes information indicating the rotation angle of the rotary shaft 12 rotated by the rotary motor 11 and the rotation angle of the scale 21 rotating with the rotation of the rotary shaft 12.
The reference track 33 includes a reference pattern RP for detecting a relative displacement between the scale 21 and the image sensor 23 caused by the eccentricity of the scale 21.

  The rotary encoder 1 according to the present embodiment is a transmissive type device, and the incremental pattern IP, the absolute pattern AP, and the reference pattern RP are arranged to face the light emitting element 22, and It is arranged at a position where the incident light is emitted onto the photoelectric conversion surface of the image sensor 23. The rotary encoder 1 according to the present embodiment is not limited to a transmission type, and may be a reflection type device. In this case, the incremental pattern IP, the absolute pattern AP, and the reference pattern RP can be rotated (moved) to a position where light incident from the light emitting element 22 is reflected toward the photoelectric conversion surface (light receiving surface) of the image sensor 23. Is provided.

FIG. 4 shows a pattern formed on each track of the scale 21. As shown in FIG. 4, an incremental pattern IP is formed on the incremental track 31. In this incremental pattern IP, for example, slits with a minimum identification width IT indicating a logical state are formed at equal intervals.
An absolute pattern AP is formed on the absolute track 32. This absolute pattern AP has a minimum identification width AT wider than the minimum identification width IT of the incremental pattern IP. For example, a slit of a 6-bit M-sequence pattern (in the figure, each of the transmission portions formed with the minimum identification width AT). White portions and black portions of non-transmissive portions) are formed at equal intervals.
The incremental pattern IP and the absolute pattern AP are provided based on the reference pattern RP, and the absolute pattern AP is provided at a constant interval M1 on the side closer to the central axis C2 than the reference pattern RP. Yes. Further, the incremental pattern IP is provided at a constant interval M2 on the side farther from the central axis C2 than the reference pattern RP.

A reference pattern RP is formed on the reference track 33. The reference pattern RP is an annular total transmission pattern based on the central axis (second movement axis) C2 of the scale 21.
The track width RW of the reference pattern RP is different from the track width IW of the incremental pattern IP and the track width AW of the absolute pattern AP. In the present embodiment, the track width RW of the reference pattern RP is narrower than the track width IW of the incremental pattern IP and the track width AW of the absolute pattern AP, and the track width IW and the track width AW are the same.
Thus, by narrowing the track width RW of the reference pattern RP, the position on the image sensor 23 corresponding to the reference pattern RP can be detected with higher accuracy. In addition, the initialization process that detects the relative displacement between the scale 21 and the image sensor 23 using the reference pattern RP is compared with the position detection process that detects position information using the incremental pattern IP and the absolute pattern AP. Therefore, the track width of the reference pattern RP can be made narrower than the track widths of the incremental pattern IP and the absolute pattern AP.

  Each pattern may be formed as a reflection pattern instead of a slit. Further, in the case of a reflection pattern, the reference pattern RP may be a total reflection annular pattern.

Returning to FIG. 1, the control system of the rotary encoder 1 will be described. The rotary encoder includes a light emitting element 22, an image sensor 23, a control unit 24, a sensor drive unit 25, a light source control unit 27, and a light source drive. A unit 28, an amplifier 35, an A / D conversion unit 36, and a memory 37 are provided. The rotary motor 11 includes a rotary shaft 12, a movement instruction input unit 13, a motor control unit 14, and a motor drive unit 15.
Note that the control unit 24 of the rotary encoder 1 according to the present embodiment obtains a position corresponding to the reference pattern RP in the image sensor 23 by executing an initialization process when the power is turned on, for example. Then, after the initialization process is completed, the control unit 24 proceeds to the position information detection process, and corresponds to the absolute pattern AP and the incremental pattern IP based on the position corresponding to the reference pattern RP obtained in the initialization process. The position on the image sensor 23 is selected.

The movement instruction input unit 13 receives a movement instruction signal for rotating the rotary shaft 12 and outputs the movement instruction signal to the motor control unit 14. The motor control unit 14 generates a motor drive signal for rotating the rotating shaft 12 by the instructed movement amount based on the movement instruction signal, and outputs the motor drive signal to the motor drive unit 15. The motor drive unit 15 drives the rotary motor 11 and rotates the rotary shaft 12 based on the input motor drive signal.
The motor control unit 14 generates a motor drive signal to be given to the motor drive unit 15 based on the position information output from the control unit 24 in addition to the movement instruction signal output from the movement instruction input unit 13, and the scale. The rotation of 21 can also be controlled.

  The light emitting element 22 is a light source that emits light incident on the image sensor 23 in order to detect a track pattern formed on the scale 21, and includes, for example, an LED (Light Emitting Diode). A light emission control signal output from the light source control unit 27 is input to the light source element 22 to the light source driving unit 28. When the light source driving unit 28 is driven, the light emitting element 22 emits light and is irradiated with light. .

The image sensor (photoelectric conversion unit) 23 includes a photoelectric conversion surface that receives light incident from the light emitting element 22 via the scale 21, photoelectrically converts the received light, and outputs a photoelectric conversion signal to the amplification unit 35.
In the image sensor 23, a plurality of photoelectric conversion elements forming pixels are arranged two-dimensionally in the row direction and the column direction. As the image sensor 23, a general-purpose CCD (Charge Coupled Device) image sensor or a CMOS (Complementary MOS) image sensor can be used.

  The photoelectric conversion signal output from the image sensor 23 is amplified by the amplification unit 35, digitized by the A / D conversion unit 36, and then input to the control unit 24.

  The image sensor 23 obtains a photoelectric conversion signal from the photoelectric conversion element to which the drive signal is input based on the drive signal from the sensor drive unit 25, and sends it to the control unit 24 via the amplifier 35 and the A / D conversion unit 36. Output. The sensor drive unit 25 is controlled by the control unit 24 and outputs a drive signal to the photoelectric conversion element designated by the control unit 24. That is, in the image sensor 23, the pixel reading position is controlled by the control unit 24.

  Although details will be described later, for example, when all pixel readout is set in the initialization process, the control unit 24 controls the sensor driving unit 25 so as to obtain output signals from all the photoelectric conversion elements of the image sensor 23. Can be driven. Thereby, the control unit 24 obtains the photoelectric conversion signals output from all the photoelectric conversion elements of the image sensor 23, and determines the photoelectric conversion element on which the light is incident through the reference pattern RP based on these photoelectric conversion signals. To do. The photoelectric conversion element on which light having passed through the reference pattern RP is incident is a photoelectric conversion element corresponding to the reference track 33 (hereinafter referred to as a reference photoelectric conversion element R_pix), and the control unit 24 determines the rotation angle of the scale 21 (that is, the reference photoelectric conversion element R_pix). The reference photoelectric conversion element R_pix corresponding to the scale position information indicating the position of the scale 21 is determined, and the photoelectric conversion signal output from the reference photoelectric conversion element R_pix is obtained as a reference pattern signal indicating the reference pattern RP.

On the other hand, when detecting the rotation angle (position information) of the rotating shaft 12 of the rotary motor 11 in the position information detection process, the control unit 24 determines the reference photoelectric conversion element R_pix corresponding to the reference track 33 detected in the initialization process. As a reference, a photoelectric conversion element corresponding to the incremental pattern IP (hereinafter referred to as incremental pattern photoelectric conversion element I_pix) and a photoelectric conversion element corresponding to the absolute pattern AP (hereinafter referred to as absolute pattern photoelectric conversion element A_pix) are selected.
Therefore, the image sensor 23 is controlled by the sensor driving unit 25 so as to output the photoelectric conversion signals obtained at least in the incremental pattern photoelectric conversion element I_pix and the absolute pattern photoelectric conversion element A_pix to the control unit 24 in the position information detection process. The As described above, when the rotary encoder 1 in the present embodiment detects position information (rotation position) of the rotary motor 11 (position information detection processing), the pixel portion necessary for detecting the position information (at least an incremental pattern photoelectric sensor). By reading out the conversion element I_pix and the absolute pattern photoelectric conversion element A_pix), it is possible to suppress heat generation and improve accuracy.

In addition, the control unit 24 detects the incremental pattern IP pattern signal (hereinafter referred to as the incremental pattern signal IS) based on the light obtained through the incremental track 31 based on the photoelectric conversion signal obtained from the image sensor 23 in the position information detection process. And an absolute pattern AP pattern signal (hereinafter referred to as an absolute pattern signal AS) based on the light obtained through the absolute track 32. The control unit 24 detects the rotation angle of the rotary shaft 12 of the scale 21 and the rotary motor 11 based on the incremental pattern signal IS and the absolute pattern signal AS.
For example, this pattern signal is a signal (for example, “1010110...”) Indicating a logical state included in each pattern as shown in FIG. Based on the pattern signal, the control unit 24 can obtain position information indicating the current position of the scale (incremental pattern IP and absolute pattern AP).

As described above, the control unit 24 detects the photoelectric conversion signal of the reference photoelectric conversion element R_pix corresponding to the reference pattern RP based on the photoelectric conversion signal output from the image sensor 23 in the initialization process. Here, the control unit 24 uses, as a reference photoelectric conversion element R_pix, a photoelectric conversion element that outputs a photoelectric conversion signal whose output level is equal to or higher than a predetermined threshold among the photoelectric conversion signals output from the image sensor 23. decide. As the output level of the photoelectric conversion signal determined by the control unit 24, light intensity, light amount, and the like can be used.
Then, the control unit 24 causes the memory 37 to store a reference reading position indicating the reference photoelectric conversion element R_pix corresponding to the rotation angle of the rotating shaft 12.

Further, the control unit 24 determines the incremental pattern photoelectric conversion element I_pix and the absolute pattern photoelectric conversion element with respect to the reference photoelectric conversion element R_pix based on the positional relationship between the incremental track 31, the absolute track 32, and the reference track 33 formed on the scale 21. Determine A_pix. For example, the control unit 24 reads the reference photoelectric conversion element R_pix (reference reading position) stored in the memory 37, and uses this as a reference to determine the incremental pattern photoelectric conversion element that is determined according to the rotation angle of the rotary shaft 12. The position information reading position indicating the I_pix and the absolute pattern photoelectric conversion element A_pix is determined.
Then, the control unit 24 sets the incremental pattern photoelectric conversion element I_pix and the absolute pattern photoelectric conversion element A_pix corresponding to the reference photoelectric conversion element R_pix to the reference reading position indicating the reference photoelectric conversion element R_pix determined by the initialization process. Information in which the position information reading position shown is associated is stored in the memory 37.

In the first embodiment of the present invention, when the position information is acquired, the image sensor 23 selects a pixel used for detection of the incremental pattern IP of the incremental track 31 and the absolute pattern AP of the absolute track 32 to select a pattern signal. Control is performed to read out (photoelectric conversion signal).
Thereby, for example, even when the center axis C2 of the scale 21 is eccentric with respect to the rotation center axis C1 of the rotation shaft 12, the position corresponding to the incremental pattern IP or the absolute pattern AP in the image sensor 23. Since the information reading position can be selected at the time of initialization, the control unit 24 can obtain a pattern signal having a sufficient output level.

Here, the reference reading position and the position information reading position will be described.
FIG. 5 and FIG. 6 are diagrams for explaining changes in the position information reading position corresponding to the absolute pattern AP and the incremental pattern IP on the image sensor 23. Note that an area where light through the absolute pattern AP is incident on the image sensor 23 is referred to as an absolute pattern irradiation area AR, and an area where light is incident through the incremental pattern IP on the image sensor 23 is referred to as an incremental pattern irradiation area IR. .

  FIG. 5A is a diagram showing an absolute pattern irradiation area AR_a and an incremental pattern irradiation area IR_a formed on the image sensor 23 when the rotary shaft 12 (scale 21) is at point A. FIG. FIG. 5B is a diagram showing an absolute pattern irradiation area AR_b and an incremental pattern irradiation area IR_b when the rotation axis 12 is at a point B different from the point A, and FIG. It is a figure which shows absolute pattern irradiation area | region AR_c and incremental pattern irradiation area | region IR_c when 12 exists in C point different from A point and B point. The points A to C are position information indicating different positions on the scale 21 and can be represented by the rotation angle (rotation angle) of the scale 21.

  For example, when the rotation center axis C1 of the rotation shaft 12 and the center axis C2 of the scale 21 coincide with each other and no eccentricity occurs, the relative displacement between the attached scale 21 and the image sensor 23 occurs. It has not occurred. Therefore, as shown in FIG. 5A, the absolute pattern irradiation area AR_a and the incremental pattern irradiation area IR_a are obtained even when the rotary shaft 12 rotates and the scale 21 moves to the B point or the C point. It is formed at a fixed position. This fixed position is considered that the amount of change in the absolute pattern irradiation area AR and the incremental pattern irradiation area IR hardly moves on the image sensor 23 even if the scale 21 rotates following the rotation shaft 12. It is a position that is a slight difference in the range.

However, when the scale 21 is eccentric, as shown in FIGS. 5 (b) and 5 (c), the absolute pattern irradiation area AR and the incremental pattern irradiation area IR are positioned at points A indicated by dotted lines. It will be out of position.
That is, as shown in FIG. 5B, the absolute pattern irradiation area AR_b and the incremental pattern IR_b at the point B are moved from the respective positions at the point A (positions indicated by dotted lines in the drawing) to the left side of the drawing. Further, as shown in FIG. 5C, the absolute pattern irradiation area AR_c and the incremental pattern IR_c are moved to the right side of the page from the respective positions of the point A (positions indicated by dotted lines in the drawing).

That is, the position information reading position in the image sensor 23 is determined based on, for example, the absolute pattern irradiation area AR_a or the incremental pattern irradiation area IR_a at the point A shown in FIG. 5A and is not changed according to the rotation of the rotary shaft 12. The absolute pattern signal AS and the incremental pattern signal IS at the points B and C cannot be detected.
Therefore, in the rotary encoder according to the first embodiment, when the incremental pattern signal IS or the absolute pattern signal AS is detected, the incremental pattern is determined according to the position information reading position based on the reference reading position corresponding to the reference pattern RP. The signal IS and the absolute pattern signal AS are detected.

  Referring to FIG. 6, in the initialization process, the reference photoelectric conversion element R_pix according to the rotation of the rotating shaft 12 is determined. For example, as the reference photoelectric conversion element R_pix, the reference photoelectric conversion element R_pix_a in which the rotation axis 12 is detected at the point A, the reference photoelectric conversion element R_pix_b in which the rotation axis 12 is detected at the point B, and the rotation axis 12 detected at the point C. Assume that the determined reference photoelectric conversion elements R_pix_c are respectively determined. 6A to 6C show reference photoelectric conversion elements R_pix_a to R_pix_c determined for points A to C, respectively.

As shown in FIG. 6A, when the reference photoelectric conversion element R_pix_a is determined as the reference reading position at the point A, the absolute pattern is closer to the central axis C2 of the scale 21 by an interval M1 from the reference photoelectric conversion element R_pix_a. The irradiation area AR_a is determined, and the incremental pattern irradiation area IR_a is determined at a distance M2 away from the center axis C2 of the scale 21 from the reference photoelectric conversion element R_pix_a.
Similarly, as shown in FIG. 6B, when the reference photoelectric conversion element R_pix_b is determined as the reference reading position at the point B, the distance from the reference photoelectric conversion element R_pix_b is close to the central axis C2 of the scale 21 by the interval M1. The absolute pattern irradiation area AR_b is determined in the direction, and the incremental pattern irradiation area IR_b is determined in the direction far from the center axis C2 of the scale 21 by the interval M2 from the reference photoelectric conversion element R_pix_b.
As shown in FIG. 6C, when the reference photoelectric conversion element R_pix_c is determined as the reference reading position at the point C, the reference photoelectric conversion element R_pix_c is closer to the central axis C2 of the scale 21 by the interval M1. The absolute pattern irradiation area AR_c is determined, and the incremental pattern irradiation area IR_c is determined at a distance M2 away from the center axis C2 of the scale 21 from the reference photoelectric conversion element R_pix_c.

  As described above, in the rotary encoder 1 according to the present embodiment, in the initialization process, the reference reading position corresponding to the reference pattern RP is detected for each rotation angle of the rotary shaft 12, and the detected reference reading position corresponds to the rotation angle. In addition, it is stored in the memory 37. Then, the position information reading position corresponding to the absolute pattern AP and the incremental pattern IP respectively determined based on the reference reading position is selected and stored in the memory 37 in association with the rotation angle. As a result, even if the center axis C2 of the scale 21 is eccentric with respect to the rotation center axis C1, the incremental pattern signal IS and the absolute pattern signal IS are detected according to the position information reading position on the photoelectric conversion surface of the image sensor 23. The photoelectric conversion element that reads the pattern signal AS can be changed according to the change in the position information reading position.

  Therefore, the output levels of the incremental pattern signal IS and the absolute pattern signal AS are sufficiently secured, and the photoelectric conversion elements that output the incremental pattern signal IS and the absolute pattern signal AS are included in a plurality of photoelectric conversion elements including the image sensor 23. You can choose from. Therefore, the rotary encoder 1 in the present embodiment only needs to perform power and control on the selected photoelectric conversion element, and can contribute to cost reduction. In addition, since the control unit 24 may use the photoelectric conversion signal from the photoelectric conversion element corresponding to the position information reading position in order to generate the incremental pattern signal IS and the absolute pattern signal AS, the other obtained from the image sensor 23 Based on a plurality of photoelectric conversion signals, a control load such as determining a photoelectric conversion signal from a photoelectric conversion element corresponding to a position information reading position each time is reduced.

Here, the process in the control part 24 is demonstrated in detail.
FIG. 7 is a functional block diagram based on the operation of the control unit 24 in the first embodiment of the present invention. In the initialization process, the rotating shaft 12 of the rotary motor 11 is rotated once, and light passing through the rotating scale 21 enters the image sensor 23. Then, the image sensor 23 outputs a photoelectric conversion signal based on the incident light to the reference pattern detection position acquisition unit 51 via the amplification unit 35 and the A / D converter 36.
Based on the photoelectric conversion signal input from the image sensor 23, the reference pattern detection position acquisition unit 51 corresponds, for example, to a pixel (photoelectric conversion element) that outputs a photoelectric conversion signal whose output level is equal to or higher than a threshold value, to the reference pattern RP. The reference reading position is determined. Then, the reference pattern detection position acquisition unit 51 stores a reference reading position in the memory 37 according to the position (for example, the rotation angle) of the scale 21 from which the photoelectric conversion signal is output. Note that the rotation angle of the scale 21 associated with the reference reading position is obtained by detecting the absolute position of the scale 21 by the absolute position detecting unit 52 as described later.

  In the initialization process, the image sensor 23 is set to the all-pixel readout state. Thus, even when the eccentric amount of the scale 21 is large and the movement amounts of the absolute pattern irradiation area AR and the incremental pattern irradiation area IR in the image sensor 23 are large, the scale 21 is based on the light via the reference pattern RP of the reference track 33. A photoelectric conversion signal can be obtained.

In the initialization process, the absolute position detection unit 52 obtains an absolute pattern signal AS corresponding to the absolute pattern AP based on the photoelectric conversion signal output from the image sensor 23, and determines the absolute position of the scale 21. The absolute position detection unit 52 obtains the rotation angle of the scale 21 based on the absolute position, and stores it in the memory 37 in association with the reference reading position obtained by the reference pattern detection position acquisition unit 51. The absolute position detection unit 52 outputs absolute position information indicating the absolute position of the scale 21 to the position calculation unit 59.
In the position information detection process, the position information reading position of the image sensor 23 is controlled by the control unit 25, and the photoelectric conversion signal output from the absolute photoelectric conversion element A_pix corresponding to the position information reading position is the absolute position detection unit 52. Is input. Therefore, the absolute position detection unit 52 detects the absolute position of the scale 21 based on this photoelectric conversion signal.

The incremental position detection unit 53 performs photoelectric conversion output from the incremental photoelectric conversion element I_pix corresponding to the position information reading position when the position information reading position of the image sensor 23 is controlled by the control unit 25 in the position information detection process. A signal is input. For example, the incremental position detection unit 53 detects the rotation direction (clockwise or counterclockwise) of the scale 21 using the A-phase signal and the B-phase signal output from the incremental photoelectric conversion element I_pix, and calculates the position. To the unit 59.
The incremental position detection unit 53 detects a relative angle (for example, a moving amount from the current position) of the rotating shaft 12 from a predetermined rotation angle based on the count value counted by the counter 54, and indicates the relative angle. The relative position information is output to the position calculation unit 59.
The counter 54 counts the number of times that the logical state of the incremental pattern IP has changed based on the A-phase signal and the B-phase signal obtained by the incremental position detection unit 53, and calculates the position via the incremental detection unit 53. To the unit 59.

The absolute pattern reading position determining unit 55 uses the reference reading position (reference photoelectric conversion element R_pix) stored in the memory 37 as a reference, and the reading position (absolute pattern photoelectric conversion element A_pix) corresponding to the absolute pattern AP on the image sensor 23. ) Is determined, and the sensor driving unit 25 is controlled to drive the absolute pattern photoelectric conversion element A_pix.
Further, the incremental pattern reading position determination unit 56 uses the reference reading position (reference photoelectric conversion element R_pix) stored in the memory 37 as a reference, and the reading position (incremental pattern photoelectric conversion) corresponding to the incremental pattern IP on the image sensor 23. The element I_pix) is determined, and the sensor driving unit 25 is controlled to drive the incremental pattern photoelectric conversion element I_pix.

  Note that the absolute pattern reading position determination unit 55 and the incremental pattern reading position determination unit 56 determine whether the reference reading position and the position information reading position each time the rotation angle changes based on the reference reading position stored in the memory 37. The position information reading position (the absolute pattern photoelectric conversion element A_pix and the incremental pattern photoelectric conversion element I_pix) may be determined using the intervals M1 and M2 that are information indicating the relative positional relationship. In addition, the absolute pattern reading position determining unit 55 and the incremental pattern reading position determining unit 56 determine the position information reading position in advance and store it in the memory 37 in association with the rotation angle. Each time is changed, the corresponding position information reading position may be read with reference to the memory 37 to control the sensor driving unit 25.

  The sensor driving unit 25 controls to output the photoelectric conversion signal obtained by the absolute pattern photoelectric conversion element A_pix to the absolute position detection unit 52 based on the position information reading position determined by the absolute pattern reading position determination unit 55. To do. Further, the sensor driving unit 25 controls to output a photoelectric conversion signal obtained by the incremental pattern photoelectric conversion element I_pix to the incremental position detection unit 53 according to the position information reading position determined by the incremental pattern reading position determination unit 56. To do.

  The position calculator 59 receives the absolute position information detected by the absolute position detector 52 and the relative position information detected by the incremental position detector 53. The position calculation unit 59 combines the absolute position information from the absolute position detection unit 52 and the relative position information from the incremental position detection unit 53 to obtain the rotation angle of the rotary shaft 12.

  FIG. 8 is a flowchart for explaining the process in the initialization process. As shown in FIG. 8, the control unit 24 gives a command to the sensor driving unit 25, and sets the image sensor 23 to the all-pixel reading state (step S1). Then, the control unit 24 gives a command to the motor control unit 14 and causes the rotary motor 11 to rotate the scale 21 once (step S2). And the control part 24 detects the reference | standard reading position which is a position on the image sensor 23 corresponding to the reference | standard pattern RP in each rotation angle from the photoelectric conversion output signal of the image sensor 23 (step S3). Then, the control unit 24 stores the detected reference reading position in the memory 37 in association with each rotation angle (step S4).

  FIG. 9 is an example of the position of the image sensor 23 of the reference pattern RP for each rotation angle stored in the memory 37. In the information stored in the memory 37 shown in FIG. 9, when the rotation angle of the rotation shaft 12 is changed by 5 degrees as the position information of the rotation shaft 12, the reference reading position (for example, the reference reading position) obtained by the initialization process is changed. The photoelectric conversion element R_pix) includes information corresponding to the position information reading position (for example, the absolute pattern photoelectric conversion element A_pix and the incremental pattern photoelectric conversion element I_pix) corresponding to the reference reading position.

  As described above, in the first embodiment according to the present invention, the scale 21 is provided with the reference track 33, the rotation angle when the scale 21 is rotated is detected by the initialization process, and the reference pattern RP is included. A corresponding reference reading position on the image sensor 23 is obtained, and information in which the reference reading position is associated with this rotation angle is stored in the memory 37. Then, using this reference reading position as a reference, the position information reading position on the image sensor 23 corresponding to the absolute pattern AP or the incremental pattern IP is selected. As a result, the rotary encoder 1 according to the present embodiment accurately detects the pattern signal corresponding to the absolute pattern AP or the incremental pattern IP and detects the position of the scale 21 even if the rotating shaft 12 is eccentric. be able to.

  In the first embodiment described above, the reference track 33 is disposed between the incremental track 31 and the absolute track 32. However, the reference track 33 may be disposed at any position.

  In the above description, the light from the light emitting element 22 is transmitted through the pattern (absolute pattern AP, incremental pattern IP, reference pattern RP) on the scale 21 and received by the image sensor 23. However, the present invention is not limited to this, and a configuration in which the light is reflected by a pattern on the scale 21 may be used.

  In the above example, the light emitting element 22 is provided on the lower side and the image sensor 23 is provided on the upper side. However, the image sensor 23 may be provided on the lower side and the light emitting element 22 may be provided on the upper side.

  Moreover, although the above-mentioned description is the structure of the rotary encoder 1 which detects the rotation angle of a rotating shaft, this invention can be similarly used also for the linear encoder which detects the position on a straight line. In the case of a linear encoder, the present invention can solve the problem caused by the relative misalignment between the image sensor and the pattern generated by yawing.

<Second Embodiment>
FIG. 10 shows a scale 121 in the encoder of the second embodiment of the present invention. As shown in FIG. 10, the scale 121 in the encoder according to the second embodiment of the present invention is provided with an incremental track 131, an absolute track 132, and a reference track 133. The incremental track 131 and the absolute track 132 are the same as those in the first embodiment.

  In the second embodiment, a bar code 141 is provided on the reference track 133 as shown in FIG. The bar code 141 records information necessary for initialization, such as a serial number for classifying a device, a device type, a circle diameter, and an encoder type. In the second embodiment of the present invention, the information of the barcode 141 is acquired at the time of initialization, and various operation settings can be performed. Other configurations are the same as those in the first embodiment described above, and thus description thereof is omitted.

<Third Embodiment>
An example of a method for attaching the rotary encoder 1 according to this embodiment will be described.
Referring to FIGS. 1 and 2, a rotary motor 11 is accommodated in the housing 10 body. As described above, the rotating shaft 12 of the rotary motor 11 protrudes from the upper end surface 10a of the housing 10.
Before assembling the rotary encoder 1, the main body 10 and the cylindrical member 20 are separate members, and the scale 21 is not attached to the rotary shaft 12. An image sensor 23 is attached to the inside of the cylindrical member 20, and includes a connection unit for connecting the image sensor 23, the sensor driving unit 25, and the amplifier 35.

First, with respect to the rotary shaft 12 protruding from the housing 10, the convex portion of the rotary shaft 12 is fitted into the concave portion of the joint portion 21 a of the scale 21, and the scale 21 is placed (set) on the rotary shaft 12. . Here, the joint portion 21a of the scale 21 and the convex portion of the rotating shaft 12 are meshed so as to be held together while securing a certain degree of freedom so that the scale 21 placed on the rotating shaft 12 does not wobble. It is preferable that
When the scale 21 is set with the joint portion 21a aligned with the rotating shaft 12, the light emitting portion 22 of the light emitting element 22 and the incremental pattern IP, absolute pattern AP, and reference pattern RP of the scale 21 face each other.

Next, the cylindrical member 22 is placed on the upper end surface 10a of the casing 10 and fixed so that light transmitted through the incremental pattern IP, the absolute pattern AP, and the reference pattern RP of the scale 21 is incident on the photoelectric conversion surface of the image sensor 23. The cylindrical member 22 and the housing 10 are fixed by the member 16.
Note that the positioning of the image sensor 23 with respect to the scale 21 and the light emitting element 22 is performed as follows as shown in FIG. This is performed together with a predetermined fixing member 16 on the end face 10a. For example, when the fixing member 16 is a screw, screw holes for fixing the fixing members 16a, 16b, and 16c in the cylindrical member 16 are determined in advance. Also in the case 10, screw holes for fixing the fixing members 16a, 16b, and 16c are determined in advance. When the housing 10 and the cylindrical member 20 are fixed by aligning the screw holes for fixing the fixing members 16a, 16b, and 16c, as shown in FIG. The image sensor 23 is attached to the inside of the cylindrical member 20 at a position where the light transmitted through .about.33 enters the photoelectric conversion surface of the image sensor 23.

  The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Case 11 Rotating motor 12 Rotating shaft 21 Scale 22 Light emitting element 23 Image sensor 24 Control part 25 Sensor drive part 37 Memory

Claims (8)

A scale having a reference pattern connected to the support having the first movement axis and provided with reference to the second movement axis, and a position information pattern provided with reference to the reference pattern;
A plurality of first photoelectric conversion elements that receive the first light through the reference pattern and output a first photoelectric conversion signal based on the first light, and a second through the position information pattern A photoelectric conversion unit having a plurality of second photoelectric conversion elements that receive light and output a second photoelectric conversion signal based on the second light;
A controller that detects position information of the scale based on the second photoelectric conversion signal, and that selects the second photoelectric conversion element corresponding to the position information of the scale based on the first photoelectric conversion signal;
An encoder comprising: The controller is
The second photoelectric conversion element corresponding to position information of the scale is selected based on the first photoelectric conversion element that outputs the first photoelectric conversion signal that is equal to or greater than a predetermined threshold. The encoder according to item 1. The controller is
The scale is moved by operating the support unit, the second photoelectric conversion element corresponding to the position information of the scale is selected, and the selected second photoelectric conversion element is used as the position information of the scale. The encoder according to claim 1, wherein information associated with the encoder is stored in a storage unit. The controller is
The movement amount of the scale is detected based on the second photoelectric conversion signal corresponding to the position information of the scale with reference to the information stored in the storage unit. Encoder.   The encoder according to any one of claims 1 to 4, wherein the reference pattern of the scale has a track width different from a track width of the position information pattern. The reference pattern of the scale is
The encoder according to any one of claims 1 to 5, wherein the encoder is formed with a second track width that is narrower than the position information pattern formed with the first track width.   The encoder according to any one of claims 1 to 6, wherein at least a part of the reference pattern includes barcode information.   The encoder according to claim 1, wherein the reference pattern is a pattern for detecting a relative displacement between the scale and the photoelectric conversion unit.

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