JP4885670B2 - Absolute type linear encoder - Google Patents

Description

  The present invention relates to an absolute linear encoder for detecting an absolute position. In particular, the present invention relates to an absolute linear encoder that has a long measuring range and is easy to handle.

  In order to enable measurement of a long measuring range by using a linear scale, it is necessary to manufacture a long scale. However, in the case of a photoelectric scale, for example, the length of an exposure apparatus for forming a scale on the scale is limited, so that it is difficult to manufacture a single long scale.

  Therefore, in the incremental scale in which the scale pattern for detecting the relative displacement has repetitive continuity, as described in Patent Documents 1 to 5, a plurality of incremental scales are arranged in a line in the detection direction, and the scale connecting portion However, it has been proposed that a continuous sine wave (A and B phase analog signals) can be output in spite of a discontinuous scale.

  Further, an absolute scale capable of detecting an absolute position with respect to the incremental scale has been put into practical use. This absolute scale does not require an initial operation for acquiring the origin position or reference position when the power is turned on, unlike the incremental scale, and is particularly advantageous for a multi-head in which a large number of detection heads are mounted on one scale. It is. In addition, an absolute scale can be used instead of a separate motor-side hall sensor for determining the magnetic pole position, which is advantageous for use in feedback control of a linear motor.

JP 2004-233346 A JP-A-10-18791 JP-A-6-137899 JP-A-6-194186 JP 2000-55647 A

  However, in the case of an absolute scale for detecting an absolute position, for example, producing a single absolute scale that is longer than 3 m is, for example, at each position on a scale in which a plurality of constant pitch continuous patterns are combined in parallel. Therefore, the scale pattern has no repeated continuity and is not easy. Further, even if a long scale can be manufactured, there is a problem that transportation and mounting work are not easy if it is a single one.

  The present invention has been made to solve the above-mentioned conventional problems, and provides a long absolute linear encoder that can realize a long measuring range, is easy to transport and mount, and is inexpensive and easy to use. The task is to do.

The present invention relates to an absolute type linear encoder for detecting an absolute position, a plurality of absolute scales arranged in a line in the detection direction and having an absolute scale for detecting the absolute position, and a scale on the absolute scale. Absolute position data for each scale that generates absolute position data for each detector, and a plurality of detectors that are connected and fixed at intervals that allow simultaneous detection of the graduations of two adjacent absolute scales at the scale connection section for detection A generator, and an arithmetic unit that outputs the absolute position of the entire length of all connected absolute scales based on the absolute position data for each detector and the offset value between the detectors, and the plurality of absolute scales , this with the absolute scale consisting of a different absolute position data By is obtained by solving the above problems.

  It is possible to further include a determination unit for performing a hysteresis process at the time of switching, for switching the plurality of detectors.

  The absolute position to be output can be determined using the absolute position data from the plurality of detectors.

The present invention also provides an absolute linear encoder for detecting an absolute position, a plurality of absolute scales arranged in a line in the detection direction and having an absolute scale for detecting the absolute position, and the absolute scale on the absolute scale. In order to detect the scale, the scale connection section has multiple detectors that are connected and fixed at intervals that can simultaneously detect the scales of two adjacent absolute scales, and an absolute value for each scale that generates absolute position data for each detector. A position data generation unit; and an arithmetic unit that outputs an absolute position in the entire length of all connected absolute scales based on absolute position data for each detector and an offset value between the detectors, and absolute scale has the same absolute scale, be placed upside down to each other By, Ru der that solves the above problems.

  According to the present invention, by dividing the scale into a plurality of the length measurement range of the final absolute encoder, the length of each scale is reduced (for example, 3 m for a side length range of 6 m). Since it can be configured with two scales), long production facilities are not required, scale production is easy, and production costs can be reduced. In addition, transportation costs and storage costs are also advantageous.

  Further, in the case of a single product, not only transportation and storage but also handling in the mounting work is not easy, but if it is a divided scale, it can be mounted for every short scale and mounting is easy.

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

  The first embodiment of the present invention, in which two absolute scales are connected, is arranged in a row in the detection direction (left-right direction in the figure) as shown in FIG. 1 (perspective view of main part) and FIG. 2 (block diagram of signal processing circuit). Two absolute scales (hereinafter also simply referred to as scales) 10A and 10B having different absolute scales (hereinafter also simply referred to as scales) 12A and 12B for detecting an absolute position, and the absolute scale 10A. 10B, the scale connecting part 14 for detecting the scales 12A, 12B on the connecting plate (the user's bracket is also acceptable) with an arbitrary center interval D that can simultaneously detect the scales 12A, 12B of the two adjacent scales 10A, 10B. ) Detection head having detectors 22A and 22B fixed by 24 and electrically connected by a connecting cable 26 As shown in FIG. 2, the absolute position data generators 32A and 32B that generate absolute position data for each detector 22A and 22B, and the output values of the absolute position data generators 32A and 32B of the detectors 22A and 22B, as shown in FIG. The memory 34 for storing the position setting value for switching between and the offset value of the absolute position data between the different scales 10A, 10B (absolute position data between the detectors 22A, 22B), the absolute position data generating units 32A, 32B Of the absolute position data generators 32A and 32B according to the output of the output and the position set value stored in the memory 34, and the offset value stored in the memory 34 as necessary by the output of the determiner 36 And a signal processing circuit 30 having a computing unit 38 that adds and outputs the signals.

  In FIG. 1, 16 is a scale fixing screw for fixing the scales 10 </ b> A and 10 </ b> B to one of the objects to be measured, and 28 is a cable for electrically connecting the detection head 20 and the signal processing circuit 30.

  The scales 10A and 10B have absolute scales 12A and 12B for detecting unique absolute positions in all measurement lengths of all absolute scales arranged in a line in the detection direction. Accordingly, there is no absolute position data indicating the same absolute position on the absolute scales 12A and 12B.

  The operation will be described below.

  First, when the scales 10A and 10B are fixed to the measurement object with the scale fixing screw 16, the strict continuity of the scale cycle, which is necessary when detecting the conventional incremental scale with one detector, is not necessary. Therefore, it is not necessary to perform alignment precisely, and the position is fixed firmly so that the relative position does not change, and the difference in position detection data between the detectors 22A and 22B, that is, the distance is stored in the memory 34 as an offset value.

  Then, as shown in FIG. 3, for example, the detector 22A normally detects the scale 12A of the scale 10A to be used as a reference. In the range to the left of the output switching point, the output YA of the detector 22A is used as it is. The output value Y of absolute position data output as a system is assumed.

  On the other hand, when it is determined that the detector 22A is on the right side of the output switching point from the absolute position data generation unit 32A of the detector 22A to the absolute value data generation unit 32B of the other detector 22B, A value Y = YB + b obtained by adding an offset value (negative value) b between the two detectors to the output value YB of the detector 22B of FIG.

  In this way, even if the scales are discontinuous at the connecting portions of the plurality of scales, the absolute detection positions of the two detectors 22A and 22B can be determined, and continuous position detection can be performed.

  When switching the absolute position data of the detectors 22A and 22B, it is possible to provide hysteresis in the processing in the determiner 68, change the position of the output switching point in the counting direction, and avoid frequent switching.

  In the present embodiment, the absolute position data to be output can be determined using the absolute position data from the two detectors 22A and 22B, so that determination and switching by the determiner 36 are easy. On the other hand, in the incremental scale, it is impossible to detect on which incremental scale the detectors 22A and 22B are located immediately after the power is turned on. Therefore, a separate sensor for detecting on which incremental scale the detector is located is required. In addition, it is necessary to separately provide a pattern detected by this sensor in the incremental scale. This complicates the configuration of the detection unit and scale scale.

  In addition, when the scale is attached, it is not necessary to align the scale. If one of the two detectors 22A and 22B can be detected, even if there is a missing portion between the scale marks 12A and 12B at the scale connecting portion 14. Continuous output is possible.

  Further, the offset value b between the scales can be obtained in a state where the two detectors 22A and 22B are opposed to each other with the scale connecting portion 14 interposed therebetween after the scale is attached.

  Further, the difference D (or the center distance D between the two detectors) between the absolute position data of the detectors 22A and 22B can be obtained in a state where each detector faces the same scale.

  If the distance between the scales changes with time, the change amount can be detected and a re-correction alarm can be output, or the offset value can be automatically corrected. For example, periodically check and correct the offset value, or set the check position where the two detectors 22A and 22B detect YA and YB in advance, and use it as a trigger to automatically check and correct the offset value You can also

  The two detectors 22A and 22B may be built in the same housing.

  FIG. 4 shows the main configuration and operation of the second embodiment having n scales. In the figure showing an example of n = 3, 10C is a third scale, 14A is a connecting portion 1 between the scales 10A and 10B, and 14B is a connecting portion 2 between the scales 10B and 10C.

  In the present embodiment, scale A, scale B, and scale C each have a unique position detection value (that is, the same position detection value does not exist, and each is a combination of scales that output a unique position detection value). It has a scale.

  Further, the absolute value Y of the entire scale to which the scales A, B, and C are connected is defined as the absolute value of the center position of the detector A.

  At the switching point in the connecting portion 1 and the connecting portion 2, the absolute position data for the scale A and the scale B or the scale B and the scale C is simultaneously detected by the detector A and the detector B.

Each offset value b ₁ , b ₂ , b ₃ , b ₄ can be determined by actual measurement using a master scale. At this time, the inter-detector distance D is included in the offset values b ₁ , b ₂ , b ₃ , and b ₄ .

  In the first and second embodiments, since each scale needs to be able to uniquely determine an absolute position value, a unique absolute scale over the entire length is required.

Next, a reference embodiment that can use an absolute scale having the same scale, is advantageous in terms of cost, and has no limit on the maximum measurement length will be described in detail.

In the first reference embodiment, as shown in FIG. 5 (essential perspective view) and FIG. 6 (block diagram of signal processing circuit), the same absolute scales arranged in a line in the detection direction are used as main scales 42A and 42B. The absolute scales 40A and 40B, the steel tape 46 as an identification code disposed on the side surface of one scale (right scale 40B in the figure), and the main scales 42A and 42B on the absolute scales 40A and 40B are detected. Therefore, in the scale connecting portion 44, two main position detectors 52A, 52B fixed at a center interval D capable of simultaneously detecting main scales 42A, 42B of two adjacent absolute scales 40A, 40B, and the steel tape 46. A detection head having a magnetic sensor 54 as a code identification sensor for detecting the presence or absence of 46. 50, as shown in FIG. 6, an absolute position data generator 62A, 62B provided for each of the main position detectors 52A, 52B, a scale identification determiner for identifying the scale based on the output of the magnetic sensor 54 64, a position setting value for switching the output value of each absolute position data generating unit 62A, 62B, a memory 66 for storing an offset value of the absolute position data between different scales, and an absolute position data from the output of the scale discriminator 64 A determination unit 68 that determines which of the outputs of the generation units 62A and 62B is used, and a signal having an arithmetic unit 70 that adds and outputs an offset value stored in the memory 66 according to the output of the determination unit 68. And a processing circuit 60.

  The scales 40A and 40B have main scales 42A and 42B for absolute position detection that are unique within one scale.

The operation of this reference embodiment is the same as that of the second reference embodiment shown in FIG.

In this reference embodiment of the scale two, since the steel tape 46 is arranged on the side of the right scale 40B as a 1-bit identification code, the identification code sensor also one magnetic sensor 54 for detecting this Good. A magnetic metal tape other than steel tape may be attached, or a step may be provided on the scale base of the magnetic material. Further, it may be provided not only on one side surface of the scale but also on the other side surface so that two or more n bits are provided.

Further, as in the second reference embodiment in which three scales 40A, 40B, and 40C shown in FIG. 7 (perspective view of the main part) and FIG. You may provide the code which identifies a scale in the surface arrange | positioned in the direction.

In this reference embodiment, as shown in FIG. 8, on the protective film 43 on the main scale 42 of the electromagnetic induction type made of a copper foil pattern, and prints the light-dark pattern 48 of n bits for optical detection, detects this Detection is performed by photoelectric sensors 72A and 72B such as photo reflectors as code identification sensors mounted on the head 50. In FIG. 8, 40 is a scale base made of, for example, stainless steel, and 41 is an insulating plate.

The signal processing circuit of Embodiment shown in Fig. The same components as those in FIG.

In the second reference embodiment, the main scales are opposed to n scales 40A, 40B, 40C having absolute scales (main scales) 42A, 42B, 42C for main positions (n = 3 in the figure). Detected by the two detectors 52A and 52B, the two scale identification sensors 72A and 72B determine which detector absolute position data should be output according to the position on the scale, and set a predetermined offset value. Add and output. In this case, when the scale is attached, the alignment between the scales may not be exact, and the absolute position data difference between the scales is stored as an offset value.

  Then, as shown in FIG. 10, the absolute value of the output is obtained by adding the offset value to the detection position of the other scales (for example, 40B and 40C) with respect to the scale (for example, 40A) to be the reference among the n scales. Determine the data.

In this reference embodiment, scale A, scale B, and scale C are scales having the same absolute position detection value. Further, the absolute value Y of the entire scale to which the scales A, B, and C are connected is defined as the absolute value of the center position of the detector A.

  At the switching point in the connecting portion 1 and the connecting portion 2, the absolute position data for the scale A and the scale B or the scale B and the scale C is simultaneously detected by the detector A and the detector B.

Each offset value b ₅ , b ₆ , b ₇ , b ₈ can be determined by actual measurement using a master scale. At that time, the inter-detector distance D is included in the offset values b ₅ , b ₆ , b ₇ , and b ₈ .

  In order to identify which scale the detectors A and B are on when the power is turned on, a separate scale identification sensor is required. This sensor can be configured, for example, so that an identification pattern is provided on each scale, and a sensor for detecting the pattern is provided in one or both of the detectors A and B.

That is, in this preferred embodiment, during power-up, the sensor 72A, to determine the boundary region 72B signal level, employing detectors, select the required offset value, calculates the absolute position value. After the power is turned on, the detector switching point and the corresponding offset value are determined from the absolute value.

According to the reference mode, a plurality of scales in a limited absolute range are used by the scale identification code, and a long absolute position can be detected. Further, since the absolute position value to be output can be determined using the absolute value by the two detectors and the sufficient scale identification code with coarse accuracy, the switching is easy.

  Furthermore, since the absolute position scale and the scale identification pattern are not on the same plane, the scale can be easily arranged. On the other hand, if they are on the same plane, the scale width increases and the detector becomes complicated.

Next, a third embodiment of the present invention is shown in FIG.

  In the present embodiment, the same absolute scale 40 is disposed in the reverse direction by rotating one side (40A on the left side in the figure) forward and the other (40B on the right side in the figure) 180 °. Is. Correspondingly, the left detector 52A is positively arranged and the right detector 52B is rotationally arranged.

  In the present embodiment, the ABS detection signal is output only when both the scale and the detector are in the normal arrangement, or when both the scale and the detector are in the rotation arrangement, and the error signal is output in the other combinations. That is, when the head 50 is on the left scale 40A, the detector 52A outputs an ABS detection signal, and the detector 52B outputs an error. Conversely, when the head 50 is on the right scale 40B, the detector 52B outputs an ABS detection signal, and the detector 52A outputs an error.

Therefore, the ABS position Y in the entire measurement range is
When the detector 52B → error output by the detector _{52A → Y A, Y = Y} A,
When the detector 52B → _{Y B} at the detector _{52A → Y A, Y = Y} A,
When the detector 52B → _{Y B} at the detector 52A → error output, and _{Y =} Y B + b.
According to the present embodiment, there is an advantage that (1) a sensor for detecting the position of the head 50 is not required, and (2) it can be easily configured if there are two identical ABS scales and two identical detectors.

  Instead of using the above error output method, both detector A and detector B output a detection signal instead of an error at the position to switch between detection signals of detector A and detector B. It can also be set to a predetermined position within the range. Furthermore, a hysteresis can be provided at this switching position.

  In the embodiment, the absolute scale is an electromagnetic induction type. However, the configuration of the main absolute scale is not limited to this, and may be a photoelectric type or a capacitance type, for example.

The perspective view which shows the principal part structure of 1st Embodiment of this invention. Similarly, a block diagram showing a signal processing circuit Figure showing operation The figure which shows the principal part structure and operation | movement of 2nd Embodiment of this invention. The perspective view which shows the principal part structure of a 1st reference form Similarly, a block diagram showing a signal processing circuit The perspective view which shows the principal part structure of a 2nd reference form Same cross-sectional view Similarly, a block diagram showing a signal processing circuit Diagram showing the operation of the reference form The front view which shows the structure of 3rd Embodiment of this invention.

Explanation of symbols

10A, 10B, 40A, 40B ... Absolute scale 12A, 12B, 42A, 42B ... Absolute scale 14, 14A, 14B, 44 ... Scale connection part 20, 50 ... Detection head 22A, 22B, 52A, 52B ... Detector 24 ... Connection Plates 30, 60 ... Signal processing circuits 32A, 32B, 62A, 62B ... Absolute position data generators 34, 66 ... Memory 36, 68 ... Determinator 38, 70 ... Calculator 54 ... Magnetic sensor (code identification sensor)
64 ... Scale identification determination device 72A, 72B ... Photoelectric sensor (code identification sensor)

Claims (4)

In absolute type linear encoder for detecting absolute position,
A plurality of absolute scales arranged in a row in the detection direction and having an absolute scale for detecting an absolute position;
A plurality of detectors connected and fixed at intervals capable of simultaneously detecting the scales of two adjacent absolute scales at the scale connecting portion for detecting the scale on the absolute scale;
An absolute position data generator for each scale that generates absolute position data for each detector;
An arithmetic unit that outputs the absolute position in the entire length of all connected absolute scales based on the absolute position data for each detector and the offset value between the detectors;
Equipped with a,
The absolute type linear encoder, wherein the plurality of absolute scales have absolute scales composed of absolute position data different from each other .   2. The absolute linear encoder according to claim 1, further comprising a determination unit that performs a hysteresis process at the time of switching to switch the plurality of detectors. 2. The absolute linear encoder according to claim 1 , wherein an absolute position to be output is determined using absolute position data obtained by the plurality of detectors. In absolute type linear encoder for detecting absolute position,
A plurality of absolute scales arranged in a row in the detection direction and having an absolute scale for detecting an absolute position;
A plurality of detectors connected and fixed at intervals capable of simultaneously detecting the scales of two adjacent absolute scales at the scale connecting portion for detecting the scale on the absolute scale;
An absolute position data generator for each scale that generates absolute position data for each detector;
An arithmetic unit that outputs the absolute position in the entire length of all connected absolute scales based on the absolute position data for each detector and the offset value between the detectors;
With
Wherein the plurality of absolute scales have the same absolute scale, characteristics and be a luer Busoryuto linear encoders that are disposed vertically opposite to each other.

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