JP4393696B2 - Measuring system - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a length measurement system, and more particularly to a length measurement system suitable for application in preventing a decrease in measurement accuracy due to a length measurement roller.
[0002]
[Prior art]
While feeding a belt-like workpiece made of metal, paper, plastic sheet, etc., when a predetermined process such as printing is performed on the workpiece, it is necessary to accurately control the feed length, and thus travel Measuring the feed length of a workpiece is performed. Thus, the measuring device for measuring the feed length of the workpiece is roughly divided into a contact type called a length measuring roller for contacting the workpiece traveling on the roller and measuring the length from the rotation of the roller, and a workpiece. There are two types of non-contact types called Doppler laser displacement meters that optically measure their length without contact.
[0003]
The contact type is less expensive than the non-contact type, and the latter has the advantage that there is less variation in measurement depending on the target material, while the latter has a variation in measurement, especially for metals that have a difference in reflectance. There is. In addition, in the case of a non-contact type measuring instrument, it is difficult to continuously operate for a long period of time, so that a contact type is frequently used.
[0004]
In FIG. 8A, the length measuring roller used as such a contact-type measuring device is brought into contact with a workpiece (not shown) with the length measuring roller 10 as shown in an outline of the entire length as viewed from the side. The contact roller 12 to be rotated is rotatably supported on the frame 14, and an encoder 18 is connected to the rotation shaft of the contact roller 12 via a coupling 16. Further, on the outer peripheral surface of the contact roller 12, a rubber-like substance made of urethane, rubber, or the like is used to prevent slippage with the workpiece, as shown in FIG. A uniformly bonded lining layer 12A is formed.
[0005]
[Problems to be solved by the invention]
However, the lining layer 12A attached to the contact roller in order to prevent slippage between the length measurement work and the workpiece to be measured is worn over time, and the contact roller 12 Since the diameter is reduced and the circumference is shortened, there has been a problem that the length measurement accuracy is inevitably lowered with time.
[0006]
The present invention has been made to solve the above-described conventional problems, and corrects a measurement error caused by a decrease in the circumference of a contact roller brought into contact with a traveling workpiece due to wear, thereby achieving stable length measurement accuracy. It is an object to provide a length measuring system that can be maintained.
[0007]
[Means for Solving the Problems]
The present invention sets in advance a contact roller that is rotated in contact with a continuously traveling workpiece, an encoder that outputs a pulse signal in synchronization with the rotation of the contact roller, and the number of pulse signals output from the encoder. In the length measuring system for calculating the workpiece feed length by multiplying the measured length measuring resolution, a circumference measuring means for measuring the circumference of the contact roller and the measured circumference for one rotation of the contact roller A calculation means for calculating a length measurement resolution by dividing by the number of pulse signals output from the encoder during the period, a comparison means for comparing the measured current circumference with the previous circumference measured, And a means for updating the set length measurement resolution with the new length measurement resolution calculated based on the current circumference when the difference between the current and previous circumferences is greater than or equal to a predetermined error. The above problem It is that persists.
[0008]
That is, in the present invention, for example, when the circumference of the contact roller is periodically measured and the change in circumference over time is monitored, the circumference is worn and shortened beyond a predetermined error. In this case, the length measurement resolution is recalculated based on the circumference, and the set value is updated and corrected, so that highly accurate length measurement is always possible regardless of the wear of the contact roller. This makes it possible to maintain stable measurement accuracy.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 is a schematic perspective view including a block diagram showing an outline of the entire length measuring system according to the first embodiment of the present invention.
[0011]
The length measuring system of the present embodiment includes a contact roller 12 that is rotated in contact with a belt-like workpiece W such as paper that continuously travels, and an encoder 18 that outputs a pulse signal in synchronization with the rotation of the contact roller 12. 8 having a length measuring roller 10 (not shown in FIG. 1) having the above-described configuration, and a pulse counter board 20 for counting the pulse signals output from the encoder 18, and the counter board 20 for counting. An arithmetic device (personal computer) 22 for calculating the workpiece feed length by multiplying the number of pulse signals (hereinafter also referred to as the pulse number) by a preset length measurement resolution is provided.
[0012]
In this embodiment, as a circumference measuring means for measuring the circumference of the contact roller 12, an image taken by the camera 24 under illumination by a camera (imaging means) 24 described later and a light source 26 is used. The image processing board 28 for converting to image data of a predetermined format, and the calculation for performing the calculation for measuring the circumference of the contact roller 12 by performing image processing to be described later on the image data inputted from the board 28 And a device 22. That is, the image processing means for calculating the diameter of the contact roller 12 includes the image processing board 28 and the arithmetic device 22. In the figure, reference numeral 29 denotes a backup roller.
[0013]
Further, a measuring means for dividing the measured circumference by the number of pulse signals output during one rotation of the contact roller 12 to calculate the length measurement resolution, and measuring the present circumference. Comparison means to compare with the previous circumference, and when the difference between the current circumference and the previous circumference is more than a predetermined error, set by the new measurement resolution calculated based on this circumference The means for updating the length measurement resolution that has been performed is configured by software in the arithmetic unit 22.
[0014]
As described above, in this embodiment, the circumference measuring means includes the camera 24 installed in the vicinity of the axial end of the contact roller 12, the image processing board 28 connected to the camera 24, and the board 28. And the arithmetic device 22 that processes image data input from the camera 24, the camera 24 images the entire axial end of the contact roller 12 with the axial center as the origin on the image, and the arithmetic device 22 performs image processing. Image data input from the board 28 is processed to calculate the diameter of the contact roller 12 by image processing.
[0015]
This image processing will be described in detail. In the present embodiment, the entire end in the axial direction (length direction) of the contact roller 12 is periodically imaged by the camera 24, and the roller diameter at that time is determined from the captured image. calculate. FIG. 2 shows an image thereof. In order to take an image, as shown in FIG. 2A, the image is placed at a predetermined position of the end (end surface) of the roller 12 in order to prevent eccentricity of the contact roller 12. The mark M is attached, and the same position is always input by the camera 24 so that image processing can be performed for the position. Further, as shown in FIG. 5B, the image is taken so that the axial center of the contact roller 12 coincides with the center of the image indicated by + (the origin of coordinates on the image). By providing the initial point (center coordinate of the roller) on the image as an initial value in advance, the diameter D of the roller can be easily obtained by image processing. When the diameter D is obtained, the length measurement resolution: λ [mm / Pulse] is given by the following equation: λ = (π × D) / (number of encoder pulses for one rotation) (1)
Is required.
[0016]
Next, the operation of this embodiment will be described with reference to the flowchart of FIG.
[0017]
As the work W starts running, the tracking of the change in the circumference of the contact roller 12 is started (step 1), and the end of the contact roller 12 is periodically imaged (image input) by the camera 24 (step 2). An image is input to the arithmetic unit 22 via the image processing board 28 and image processing is performed (step 3), and the roller diameter D at the time of imaging is calculated, and the length measurement resolution is calculated by the equation (1) ( Step 4) compares the resolution with the previous resolution set so far (step 5), and determines whether or not the current resolution is so low that the error becomes a problem compared to the previous resolution ( Step 6) If it has decreased, it is updated to the current resolution (Step 7), then returns to Step 1 to start monitoring again and repeats the process.
[0018]
According to this embodiment described in detail above, it is possible to automatically correct a length measurement error due to wear of the contact roller which inevitably occurs, and to prevent a decrease in length measurement accuracy. Moreover, stable measurement accuracy can be maintained by periodically measuring the roller diameter and automatically updating the length measurement resolution.
[0019]
FIG. 4 is a schematic perspective view corresponding to FIG. 1 showing an outline of the entire length measuring system according to the second embodiment of the present invention.
[0020]
The length measuring system according to the present embodiment is a displacement sensor 30 as an analog signal input from the sensor 30 as a circumference measuring means constituted by the camera 24, the image processing board 28 and the arithmetic unit 22 in the first embodiment. 1 is substantially the same as that shown in FIG. 1 except that an A / D conversion board 32 for converting a digital signal into a digital signal and an arithmetic unit 22 for processing a digital signal input from the board 32 are provided. is there.
[0021]
In the present embodiment, the displacement sensor 30 is arranged at a predetermined distance L from the axis center on a line orthogonal to the axis center of the contact roller 12 as schematically shown in FIG. It has been fixed. Then, the arithmetic unit 22 calculates the radius of the contact roller 12 by processing the detection value by the displacement sensor 30 input as a digital signal via the A / D conversion board 32 as follows. The length is to be measured.
[0022]
The circumferential length, that is, the roller diameter D is calculated using the relationship between the distance d to the roll surface output from the displacement sensor 30 and the radius D / 2 as follows: d = LD−2−D = 2 (L− d) ... (2)
Is calculated by That is, depending on the displacement sensor 30, the radius of the contact roller 12 is measured.
[0023]
As shown in FIG. 5B, the value of the output distance d changes periodically for each rotation (between the Z phases of the encoder output) due to the eccentricity of the contact roller 12, and therefore, for one rotation. Use the average value. However, the roller diameter may be obtained by the above equation (2) from the radius of a constant position, for example, the radius measured at the rising timing of the Z phase, that is, the distance d.
[0024]
Since the output value of the displacement sensor 30 is easily affected by noise or the like, the moving average D ′ in the vicinity is expressed by the following equation: D ′ = ΣD / (number of sensor samplings) (3)
The circumference resolution λ [mm / Pulse] is calculated by the following equation: λ = (π × D ′) / (number of encoder pulses for one rotation) (4)
Calculated by
[0025]
In this embodiment, as shown in the flowchart of FIG. 6, instead of steps 2 to 4 in the first embodiment shown in FIG. 3 in steps 12 and 13, measurement by the displacement sensor 30 described above, By calculating the roller diameter and the length measurement resolution by the arithmetic unit 22, similarly stable length measurement accuracy can be maintained.
[0026]
【Example】
FIG. 7 is a schematic perspective view showing a main part of a marking device to which the length measuring system of the second embodiment is applied. In this apparatus, when marking the workpiece W conveyed in the flow direction indicated by the arrow by the RM (removable) drive roller 34 by the ink jet 36, the workpiece is fed by the length measuring roller 10 having the contact roller 12 for positioning. The length is measured. Incidentally, a printing paper can be given as the work W, and a register mark can be given as the mark.
[0027]
As described above, when the length measuring roller 10 is used for a long period of time, the contact roller 12 is worn down and the diameter becomes small. For this reason, the length measurement resolution is also reduced, and marking at an accurate position cannot be performed.
[0028]
Thus, the diameter of the contact roller 12 is measured using the measurement method according to the second embodiment, and the length measurement resolution is sequentially updated in accordance with the change in the diameter of the roller, so that accurate workpiece feeding is always performed. The amount can be measured. Thereby, it can prevent reliably that the position shift of marking arises. Although the description is omitted, the same applies to the case where the length measurement system of the first embodiment is applied.
[0029]
Now, assume that the specifications of the length measuring roller 10 to be used are encoder: 5,000 [Pulse / rotation], the diameter of the contact roller: 80 [mm], and the length measurement resolution is 50 [μm / Pulse]. As a result of continuing the length measurement by the length measuring roller 10, if the contact roller 12 is evenly worn and its diameter becomes 78 [mm], the length measuring resolution is 49 [μm / Pulse]. The error caused by one rotation is 6.283 [μm].
[0030]
And if the tolerance of length measurement resolution is less than 1 [μm / Pulse], the length measurement resolution is automatically updated because (previous length measurement resolution)> (current length measurement resolution). Is done. As described above, irrespective of the inevitably occurring roller wear (reduction), stable length measurement accuracy can be provided, which can greatly contribute to productivity improvement.
[0031]
Although the present invention has been specifically described above, the present invention is not limited to that shown in the above embodiment, and various modifications can be made without departing from the scope of the invention.
[0032]
For example, in the above-described embodiment, the marking device is taken as a specific example, but the target to which the length measurement system of the present invention can be applied is not limited to this.
[0033]
In the embodiment, the case where the circumference of the contact roller 12 is obtained by measuring the diameter or the radius is shown. However, the present invention is not limited to this, and it is needless to say that the circumference may be directly measured.
[0034]
In the above embodiment, the comparison between the current circumference and the previous circumference is performed for the length measurement resolution calculated from the circumference. However, the present invention is not limited to this, and the circumferences themselves may be compared. Needless to say, the diameter or radius before calculating the circumference may be compared.
[0035]
【The invention's effect】
As described above, according to the present invention, it is possible to correct the measurement error caused by the circumferential length of the contact roller brought into contact with the traveling workpiece being shortened due to wear, and maintain stable length measurement accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an outline of a length measurement system according to a first embodiment of the present invention. FIG. 2 is a diagram showing a principle of circumference measurement in the first embodiment. FIG. 4 is a schematic perspective view showing an outline of a length measurement system according to the second embodiment of the present invention. FIG. 5 is a diagram showing the principle of circumference measurement in the second embodiment. FIG. 7 is a schematic perspective view showing the outline of a marking device to which the length measuring system of the second embodiment is applied. FIG. 8 is a front view and an outline view showing the outline of the length measuring roller. Explanation of]
DESCRIPTION OF SYMBOLS 10 ... Measuring roller 12 ... Contact roller 12A ... Lining layer 14 ... Frame 16 ... Coupling 18 ... Encoder 20 ... Pulse counter board 22 ... Arithmetic device 24 ... Camera 26 ... Light source 28 ... Image processing board 30 ... Displacement sensor 32 ... A / D conversion board 34 ... RM drive roller 36 ... inkjet

Claims (3)

A contact roller that is rotated in contact with a continuously traveling work, an encoder that outputs a pulse signal in synchronization with the rotation of the contact roller, and a number of pulse signals output from the encoder. In a measuring system that calculates the workpiece feed length by multiplying the long resolution,
A circumference measuring means for measuring the circumference of the contact roller;
Calculation means for calculating a length measurement resolution by dividing the measured circumference by the number of pulse signals output from the encoder during one rotation of the contact roller;
Comparison means for comparing the measured circumference this time with the previous circumference measured,
And a means for updating the set length measurement resolution with the new length measurement resolution calculated based on the current circumference when the difference between the current and previous circumferences is greater than or equal to a predetermined error. A length measurement system characterized by this. The circumference measuring means captures the axial end of the contact roller with the axial center as the origin on the image, and image processing for processing the obtained image and calculating the diameter of the contact roller The length measuring system according to claim 1, wherein the length measuring system is a means. The circumference measuring means processes a displacement sensor disposed at a predetermined distance from the axis center on a line orthogonal to the axis center of the contact roller, and a detection value from the displacement sensor to the roller surface. 2. The length measuring system according to claim 1, wherein the length measuring system is means for calculating a radius of the contact roller.

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