JP2007278786A - Displacement detection apparatus for paper being transferred and control method for paper transfer apparatus equipped with displacement detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement detection apparatus which, even when a slip occurs in paper being transferred, can detect its amount of slip and detect the paper length and skew accurately. <P>SOLUTION: The displacement detection apparatus comprises a light emitting section 44 for irradiating the surface of the paper being transferred with laser light originating from a laser light source 45 and a light receiving section 47 having an image sensor 48 which receives laser light reflected off the surface of the paper within a fixed area B on which the laser light is irradiated, reads an interference fringe pattern imaged, and converts it into an electric signal. A controller 50 to which the electric signal of the interference fringe pattern is input is connected to the light receiving section 47. The image sensor 48 reads the interference fringe pattern within the fixed area B of the paper P being periodically transferred. The controller 50 compares the positions of common parts T1, T2 of a plurality of interference fringe patterns read by the image sensor 48 periodically to calculate the amount of displacement of the paper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a displacement detection device for conveyance paper such as printing paper or plate-making paper, and a control method for a paper conveyance device provided with the displacement detection device.

  A paper transport device that sequentially transports a large number of papers is used in various machines such as stencil printers that transport printing paper and plate-making paper, photo printing machines, photocopiers, or automatic readers that transport mail and forms. These paper transport devices are usually provided with a paper detection device for detecting the presence or absence of paper to be transported and the movement state of paper such as a jam.

  FIG. 14 shows an example of a conventional paper conveyance device and paper detection device. In FIG. 14, the conveyance means includes a pair of upper and lower conveyance rollers 101 and 102, and a lower drive-side conveyance roller 102. Are coupled to the motor 104 via the power transmission mechanism 103. Conventionally, a transmissive optical sensor 105 that detects light shielding is used as the paper detection device. The optical sensor 105 includes a light emitting unit 111 and a light receiving unit 112 arranged with a sheet conveyance path interposed therebetween, and the light receiving unit 112 is connected to the controller 120. On the other hand, the motor 104 is provided with an encoder 123 that detects the rotation speed and rotation amount (rotation angle) of the motor 104 and is connected to the controller 120. Although the light from the light emitting unit 111 is blocked by the paper P, the presence of the paper P can be detected. In addition to detecting the presence of the paper P, the following paper state or requirement is detected. It has become.

(1) Paper Length The light from the light emitting unit 111 is blocked by the paper P being conveyed, thereby detecting the front end of the paper P in the conveyance direction F. Thereafter, the light from the light emitting unit 111 is detected by the light receiving unit 112. By receiving light again, the rear end of the paper P is detected, and the rotation amount (rotation angle) of the motor 104 is detected by the encoder 123 from the time when the front edge of the paper P is detected to the time when the rear edge is detected. Is calculated (see Patent Document 1, etc.).

(2) Skew In order to detect the situation in which the paper P is transported obliquely with respect to the transport direction F, a predetermined interval is provided in the direction orthogonal to the transport direction F of the paper P as shown in FIG. A plurality of transmissive photosensors 200-1, 2, 3 are arranged, and the skew of the paper P is detected based on the difference in detection timing of each photosensor 200-1, 2, 3 (Patent Document 2).
JP 2001-232922 A JP 2000-168221 A

  As shown in FIGS. 14 and 15, the detection method using an optical sensor using light blocking and transmission has the following problems.

(1) It is difficult to detect the slip amount.
Paper dust or the like may adhere to the outer peripheral surface of the transport roller 102 or the roller may be worn, so that the paper may slip on the outer peripheral surface of the roller. Tends to be smaller than the expected paper feed amount. With respect to such a slip phenomenon, the transmission type optical sensor can detect the slip phenomenon itself as long as the length of the conveyance paper is uniform, but it can detect the slip amount accurately. It is difficult.

(2) Inaccuracy in detection of paper length Since it is difficult to accurately detect the slip amount with a transmission type optical sensor as described above, slipping occurs when papers of different lengths are mixed. When the phenomenon occurs, an error occurs in the accumulated length, and the paper length cannot be accurately detected.

(3) The skew detection speed is slow As shown in FIG. 15, in the method of detecting skew by the difference in detection timing of the plurality of optical sensors 200-1, 2, and 3, when the paper P is skewed, The time from the detection timing of the optical sensor 200-1 that detects the front edge of the paper the fastest to the detection timing of the optical sensor 200-3 that detects the latest or the intermediate optical sensor 200-2 is required, and the detection speed becomes slow.

(Object of invention)
SUMMARY OF THE INVENTION An object of the present invention is a displacement detection device that can easily detect a slip amount and a two-dimensional displacement amount of a sheet, and ensures slip amount, sheet position, transport speed, displacement amount and skew even during a slip. Disclosed is a displacement detection device and a method for controlling a sheet conveying device including the displacement detection device.

  In order to solve the above-mentioned problem, a displacement detection device for a conveyance sheet according to claim 1, a light emitting unit for irradiating a laser beam from a laser light source to a surface of a sheet being conveyed at a predetermined position on a sheet conveyance path, and the laser The laser beam reflected from the paper surface within a certain detection area irradiated with light is received, the interference fringe pattern of the laser light due to the irregularities on the paper surface is read, the interference fringe pattern due to the irregularities on the paper surface is read, and the electrical signal A light receiving unit having an image sensor for converting the image sensor to the light receiving unit, and a control device to which an electric signal of the interference fringe pattern is input is connected to the light receiving unit. The control device is configured to read an interference fringe pattern in a detection region, and the control device is configured to share a plurality of interference fringe patterns periodically read by the image sensor. Comparing the position of the part, and is configured to calculate the displacement of the paper.

According to the above configuration, the displacement amount (movement amount) of the sheet can be accurately detected from any conveyance position with respect to the sheet being conveyed, and in particular, the displacement amount in the two-dimensional direction can be accurately detected. Moreover, because it uses laser light to detect the interference fringe pattern, it has high sensor sensitivity and can reliably detect even when there is no contrast difference on the paper surface that cannot be detected with LED light. Regardless of the material, the amount of displacement can be reliably detected.
In addition, since the laser beam has strong coherency, it is possible to reliably detect even a minute unevenness change.

  According to a second aspect of the present invention, in the conveyance paper displacement detection device according to the first aspect, the control device is configured such that the displacement amount in the paper conveyance direction of the interference fringe pattern read at a predetermined cycle is set in advance. When the amount of displacement is smaller than the correct conveyance amount, the paper is recognized to be in a slip state.

  According to the above configuration, the slip of the sheet can be recognized from any transport position with respect to the sheet being transported, and the slip amount can be accurately calculated.

  According to a third aspect of the present invention, in the conveyance sheet displacement detecting device according to the second aspect, the control device is configured to issue a warning when the detected slip amount is larger than a predetermined amount.

  According to the above configuration, it is possible to quickly recognize a slip state that hinders paper conveyance.

  According to a fourth aspect of the present invention, in the conveyance sheet displacement detection device according to the first or second aspect, the control device calculates a displacement amount of the interference fringe pattern in a conveyance direction and a displacement amount in a direction orthogonal to the conveyance direction. When the amount of displacement in the direction orthogonal to the transport direction is equal to or greater than a predetermined value, the transport paper is recognized to be skewed.

  According to the above configuration, it is possible to easily recognize the skew of the sheet and the skew angle thereof with a single sensor in substantially real time.

  According to a fifth aspect of the invention, in the conveyance paper displacement detection device according to the first or second aspect, the control device detects the front and rear edges in the paper conveyance direction, and the interference fringes read at a predetermined cycle. It is configured to detect the amount of displacement of the pattern in the paper conveyance direction and calculate the paper length.

  According to the above configuration, the paper length can be accurately measured.

  According to a sixth aspect of the present invention, there is provided a control method for a sheet conveying apparatus including the displacement detecting apparatus according to the first aspect, a conveying unit that conveys the sheet, and a drive motor that drives the conveying unit. When the sheet does not exist in the detection area of the displacement detection device, as the first feedback control, the rotation speed of the drive motor is maintained at a constant value, and when the sheet exists in the detection area, the second As the feedback control, the rotation of the drive motor is performed so that the movement speed of the conveyance surface of the conveyance means becomes a value substantially corresponding to the movement speed of the paper calculated from the displacement amount in the paper conveyance direction detected by the displacement detection device. Control the speed.

  According to the above configuration, the rotation speed of the drive motor is changed by the second feedback control so as to substantially correspond to the conveyance speed of the sheet only when the sheet is detected, so that the rotation of the motor is meaningless when the sheet is not detected. It is not necessary to change it, and the control of the rotational speed of the motor by the control device is not complicated, and the service life of the drive motor is increased. Further, since the control (change) always starts from the constant motor rotation speed when the sheet non-detection state changes to the sheet detection state, the motor rotation control can be started promptly.

  According to a seventh aspect of the present invention, in the control method for the paper conveying device according to the sixth aspect, the control device shifts from a state in which no paper is present in a detection area of the displacement detection device to a state in which paper is present. Then, for a predetermined time, the moving speed of the conveying surface of the conveying means is compared with the paper moving speed detected by the displacement detection device, and the difference between the moving speed of the conveying surface of the conveying means and the paper moving speed is When the value is larger than the predetermined value, the first feedback control is continued, and when the value is less than the predetermined value, the second feedback control is switched.

  According to the above configuration, it is possible to avoid a situation in which the rotational speed of the drive motor changes drastically at the time of switching from the first feedback control when the paper is not detected to the second feedback control when the paper is detected. The above control can be switched smoothly.

  According to an eighth aspect of the present invention, in the method for controlling a paper conveyance device according to the sixth or seventh aspect, the displacement detection device is configured to read the interference fringe pattern on the conveyance surface of the conveyance unit. The displacement detecting device detects the amount of displacement of the conveying surface of the conveying means by using the displacement detecting device, and the detected displacement amount is detected on the conveying surface of the conveying means. In comparison with a predetermined displacement amount, when a detection error occurs between the detected displacement amount and the predetermined displacement amount, the detected displacement amount is corrected to the same value as the predetermined displacement amount.

  According to the above configuration, the measurement accuracy of the displacement detection device itself can be easily and accurately corrected when the displacement detection device is installed. That is, in the displacement detection device that receives the laser beam reflected from the paper surface and reads the interference fringe pattern, if the distance (height) or the arrangement angle from the paper surface to the light receiving unit is different, the paper quality and the paper surface pattern In combination with the difference, etc., the amount of reflection of the laser beam changes, an error occurs in the measured value, and the reading accuracy changes, but by correcting the accuracy of the displacement detector itself, the arrangement position and angle of the light receiving unit can be changed. Regardless, accurate displacement amount detection can be performed.

  According to a ninth aspect of the present invention, in the method for controlling a paper conveying apparatus according to any one of the sixth to eighth aspects, the conveying means is a conveying roller.

  According to a tenth aspect of the present invention, in the method for controlling a paper conveying apparatus according to any one of the sixth to eighth aspects, the conveying means is a conveying belt wound around a plurality of rollers.

  According to an eleventh aspect of the present invention, in the control method for the paper conveying device according to the ninth aspect, a mark indicating a reference position of one rotation of the conveying roller is attached, and the conveying roller is rotated once and the displacement detecting device is used. The amount of displacement in the circumferential direction of the mark is detected, and the detected amount of displacement is compared with the true total length of the transport roller obtained by calculation, and between the detected displacement amount and the true total length. When a detection error has occurred, the detected displacement is corrected to the same value as the true total circumference.

  According to the above configuration, in the paper transport device using the transport roller as the transport means, it is possible to easily and accurately correct the measurement accuracy when the displacement detection device is installed.

  A twelfth aspect of the present invention is the method for controlling a paper conveying apparatus according to the tenth aspect, wherein the conveying belt is provided with a mark indicating a reference position of one cycle of the conveying belt, and the conveying belt is made to make one turn. A displacement detection device detects a displacement amount of the mark, compares the detected displacement amount with a true full length of the transport belt obtained by calculation, and a detection error is detected between the detected displacement amount and the true full length. When this occurs, the detected displacement is corrected to the same value as the true full length.

  According to the above configuration, in the paper conveying apparatus using the conveying belt as the conveying means, the measurement accuracy can be corrected easily and accurately when the displacement detecting device is installed.

  According to a thirteenth aspect of the present invention, in the control method for the paper conveying device according to the sixth or seventh aspect, the interference fringe pattern of the paper is read by the reading device, and is stored in the storage unit of the control device as the original interference fringe pattern. The interference fringe pattern of the sheet inside is read by the displacement detection device, and the read interference fringe pattern is compared with the original interference fringe pattern, and it is recognized that the both interference fringe patterns are out of a predetermined range of identity. By doing so, a paper abnormality is detected.

  According to the above-described configuration, it is possible to quickly detect an abnormality of a sheet, for example, mixing of a defective printing sheet, a blank sheet, another type of sheet, and the like, and it is also possible to detect a double feed of sheets.

  According to a fourteenth aspect of the present invention, in the method for controlling a paper conveying device according to the sixth or seventh aspect, the interference fringe pattern read from an arbitrary paper by reading the interference fringe patterns of the sequentially conveyed paper by the displacement detecting device. Is compared with the interference fringe pattern of the paper read before the paper, and the abnormality of the paper is detected by recognizing that both the interference fringe patterns are out of a predetermined range of identity.

  According to the above configuration, since it is not necessary to use a reading device such as a scanner, the structure can be simplified and the cost can be reduced.

[First embodiment of the present invention]
FIG. 1 to FIG. 11 show a first embodiment of a paper transport device provided with a transport paper displacement detection device according to the present invention, and will be described below with reference to the drawings.

(Outline of paper transport device)
FIG. 1 is a schematic diagram of a main part of a sheet conveying apparatus including a displacement detection device. For convenience of explanation, the upstream side (conveying start end side) of the conveying direction F of the sheet P is “rear side”, and the sheet conveying direction F Hereinafter, the downstream side (conveyance end side) is referred to as “front side”, and the paper width direction (horizontal direction orthogonal to the paper conveyance direction F) is referred to as “left-right direction”.

  As a conveying means, a pair of conveying rollers 1 and 2 are vertically arranged opposite to each other, and the driving conveying roller 2 arranged on the lower side outputs the output of the driving motor 5 via the belt transmission mechanism 7. When the drive motor 5 rotates in conjunction with the shaft 6 and the drive motor 5 rotates, the drive roller 2 on the upper side is also driven in the direction of arrow R2 at the same time. That is, the sheet P is sandwiched between the upper and lower transport rollers 1 and 2 and is rotated in the R1 and R2 directions so that the sheet P is transported in the transport direction F.

  The drive motor 5 is connected to a control device (controller) 50, and is configured such that driving, stopping, and rotation speed are controlled by a control signal output from the control device 50.

  The displacement detection device 41 is arranged on the conveyance direction F side with respect to the conveyance rollers 1 and 2 and is located above the conveyance path of the paper P. The displacement detection device 41 is electrically connected to the control device 50 and detects various types of detected paper. A value signal is input to the control device 50.

  The drive motor 5 is provided with an encoder 11 that detects the amount of rotation (rotation angle) of the output shaft 6. The encoder 11 includes, for example, a rotating plate 21 that rotates integrally with the output shaft 6, and the rotating plate 21. The rotating disk 21 is formed with a plurality of slits 23 at equal intervals in the circumferential direction, and these slits are detected by the detecting unit 22. Is to be detected. The detection unit 22 is electrically connected to a control device (controller) 50, and inputs the detected rotation amount (rotation angle) of the drive motor 5 to the control device 50.

(Details of displacement detector)
FIG. 3 is a simplified perspective view of the displacement detection device 41. The displacement detection device 41 includes a light emitting unit 44 incorporating a laser light source (laser oscillation unit) 45 and a light receiving unit 47 incorporating an image sensor 48. The image sensor 48 is electrically connected to the control device 50. If necessary, a lens 46 is disposed in front of the laser light source 45 in the light emitting unit 44, and a lens 49 is also disposed below the image sensor 48 in the light receiving unit 47.

  The light emitting unit 44 is installed at a predetermined distance (for example, 7 mm to 10 mm) and a predetermined angle from the paper P in the transport path, and irradiates the laser light from the laser light source 45 onto the paper P through the lens 46. It is like that. The irradiation area S and the first displacement detection device 41 shown on the paper P are exaggerated with dimensions larger than the actual size in order to facilitate understanding thereof.

  The light receiving unit 47 is arranged at a predetermined distance (for example, 5 mm to 10 mm) from the paper P in the transport path. In particular, the image sensor 48 is arranged to be substantially parallel to the paper. The laser beam reflected from the surface of P is received by the image sensor 48 through the lens 49, so that, for example, an interference fringe pattern (speckle pattern) of the laser beam as shown in the upper part of FIG. 4 is formed on the image sensor. Then, the formed interference fringe pattern is read, converted into an electric signal, and input to the control device 50. The reading area B of the paper P by the image sensor 48 is shown in a substantially square shape in the irradiation area S. The reason why the interference fringes are generated will be explained in detail. When the laser light hits the paper surface (rough surface), the slight unevenness on the paper surface can cause a slight difference in the distance from the paper surface, which reflects from the paper. This is because a phase difference occurs in the diffused light. The interference fringe pattern is determined by the state of the paper surface. If the paper is stationary, the interference fringe pattern is also stationary. If the paper is moved, the interference fringe pattern is also moved at the same speed as the paper. The irregularities on the surface of the paper that cause the interference fringe pattern are formed not only by the roughness of the surface, but also by a variety of paper fiber patterns or unevenness.

  The image sensor 48 is a matrix in which a large number of image sensor pixels that detect interference fringes (light / dark) patterns of laser light are arranged in a matrix. For example, 30 × 30 = 900 pixels (1 pixel = 1/800 inch) The interference fringe pattern in the reading area B can be read (photographed).

  Further, the image sensor 48 is set to periodically read the interference fringe pattern in the reading area B on the paper P being conveyed, and the detection cycle is set to 130 μsec, for example. Note that this detection cycle can be changed as appropriate according to the type of paper, and can be changed, for example, to a maximum of about 81 μsec. Also, 1 pixel = 1/800, which is a reference for resolution, can be appropriately changed.

  By such a displacement detection device 41, the displacement amount (movement amount), movement speed, slip, slip amount, skew, skew angle, and sheet length of the sheet P moving in the conveyance path are detected. Of course, the presence or absence of the paper P can also be detected.

(Control content)
In order to control the drive and stop of the drive motor 5 and the rotational speed, the control device incorporates a program for performing the following steps, for example.

(1) In FIGS. 2 and 3, when the paper P does not exist in the detection area B of the displacement detection device 41, the rotation speed of the drive motor 5 is maintained at a constant value as the first feedback control, and the detection area When the sheet P exists in B, as the second feedback control, the movement speed (circumferential speed) of the outer peripheral transport surface of the transport roller 2 is the amount of displacement in the transport direction F of the paper P detected by the displacement detection device 41. The rotational speed of the drive motor 5 is controlled so that the value substantially corresponds to the moving speed of the paper P calculated from the above.

(2) In addition to the above control, the movement of the outer peripheral conveying surface of the conveying roller 2 for a predetermined time after the transition from the state in which the sheet P does not exist in the detection area B of the displacement detection device 41 to the state in which the sheet P exists. The speed is compared with the sheet movement speed in the conveyance direction F detected by the displacement detection device 41. When the difference between the movement speed of the outer peripheral conveyance surface of the conveyance roller 2 and the sheet movement speed is larger than a predetermined value, The first feedback control is continued, and when it is below a predetermined value, the second feedback control is switched.

(3) Read the interference fringe pattern of the sequentially conveyed paper by the displacement detection device, compare the interference fringe pattern read from any paper P with the interference fringe pattern of the paper P read before the paper, By recognizing that both the interference fringe patterns are out of a predetermined range of identity, the abnormality of the paper P is detected.

[Detection of moving amount and moving speed in transport direction]
FIG. 3 shows a method for detecting the movement amount and movement speed of the paper P in the transport direction F, and the upper and lower stages show states before and after one reading cycle by the image sensor 48. For example, if the position of the paper P shown in the upper row is the nth reading position by the displacement detection device 41, the position of the paper P shown in the lower row indicates the (n + 1) th reading position one cycle after the position shown in the upper row. ing.

  In FIG. 3, the interference fringe patterns of the reading area B of the sheet P at the position shown in the upper stage and the reading area B of the sheet P at the position shown in the lower stage are read by the image sensor 48, and each interference fringe pattern is converted into an electric signal. Conversion is performed and input to the control device 50, the displacement of the common part of both interference fringe patterns is calculated, and the movement amount and movement speed of the paper P are detected.

  FIG. 4 schematically shows an example of an interference fringe pattern formed on the image sensor 48 in an easy-to-understand manner. The upper part of FIG. 4 corresponds to the state of the upper part of FIG. 4 shows the interference fringe pattern of the reading region B at the position. The lower part of FIG. 4 corresponds to the lower part of FIG. 3 and shows the interference fringe pattern of the reading area B at the (n + 1) th reading position after one cycle. The common part of the interference fringe pattern is temporarily indicated by a triangle T (1,2). As shown in the lower part, the position of the common portion (shaded triangle) T1 at the n-th reading and the position of the common portion T2 (black triangle) at the (n + 1) -th reading are the same reading area. The amount of movement A1 (= A) in the conveyance direction F of the paper P in a predetermined cycle can be obtained from the difference D1 in the conveyance direction of T1 and T2 by comparing on the two-dimensional coordinates in B. Further, the moving speed of the paper P can be obtained from the moving amount A1 (D1) and a predetermined period (time).

  If the displacement amount D1 (movement amount A1) thus determined is the same as the displacement amount (movement amount) corresponding to the preset movement speed, the movement amount and movement speed of the paper P in the transport direction F are: It can be recognized that the normal value set in advance is maintained.

(Slip detection)
5 and 6 show a case where the paper P is completely stopped due to slip, and FIGS. 7 and 8 show a case where the paper P is moving in a slip state. 7 shows the same relationship as the relationship between the upper and lower steps in FIG. 3, and the upper and lower steps in FIGS. 6 and 8 show the same relationship as the relationship between the upper and lower steps in FIG. .

  In FIG. 5, when the paper P is completely stopped due to the slip, the paper P does not move forward and stops from the n-th reading at the upper stage to the n + 1-th reading at the lower stage. ing.

  Therefore, as shown in FIG. 6, the common portions T1 and T2 are not displaced between the common portion T1 at the time of the upper nth reading and the common portion T2 at the time of the lower (n + 1) th reading. The displacement amounts of the common portions T1 and T2 are zero. When such a displacement amount 0 is detected, it is recognized that the sheet P is completely stopped due to slipping, and for example, the printing press is stopped, and maintenance of the conveying means is performed.

  On the other hand, in FIG. 7, when the paper P is moving in a slipping state, the paper P is temporarily normal from the n-th reading at the upper stage to the n + 1-th reading at the lower stage. It moves with a movement amount A2 smaller than the movement amount A1.

  Accordingly, as shown in FIG. 8, a displacement amount D2 between the common portion T1 at the time of the n-th reading in the upper stage and the common portion T2 at the time of the (n + 1) -th reading is obtained, and this is calculated as a normal displacement set in advance. By comparing with the amount D1, the slip amount in a predetermined cycle can be obtained. In this case, for example, the rotational speed of the drive motor 5 in FIG. 1 is increased according to the obtained slip amount.

(Detection of paper length)
FIG. 9 shows a paper length detection method. The upper part shows a state at the start of length detection, and the lower part shows a state at the end of length detection. At the time of starting the upper length detection, the front end of the paper P is detected by the image sensor 48, and thereafter, as indicated by the phantom line in the lower stage, the reading area B (B ′) is read for each cycle. By determining the amount of displacement of the common portion, the amount of movement of the paper P for each period is detected. Then, when the trailing edge of the paper P is detected, the length L1 in the transport direction F of the paper P is obtained by integrating the displacement amount of the common part detected for each cycle.

  In this length detection method, even if the paper P slips, the amount of displacement of the common portion for each period changes according to the slip amount. Therefore, even if slip occurs, the paper length L1 is accurately obtained. be able to.

(Detect paper skew)
10 and 11 show a method for detecting the skew of a sheet. The upper and lower stages of FIG. 10 show the same relationship as the upper and lower stages of FIG. 3, and the upper and lower stages of FIG. 4 shows the same relationship between the upper and lower stages of FIG.

  That is, in FIG. 10, the left and right applied pressures or frictional forces of the rollers or the like are changed during one cycle or several cycles from the nth reading position in the upper stage to the (n + 1) th reading position shown in the lower stage. The paper P may be skewed due to a difference or the like.

  In the lower part of FIG. 11, when the paper P is skewed, the common portion T1 is displaced to T2 as the paper P is skewed. Specifically, the common portion T1 is displaced by a displacement amount D2 in the paper conveyance direction F, and is also displaced by a displacement amount E2 in a direction perpendicular to the conveyance direction F. The displacement direction and the displacement amount of the paper P are detected from the displacement amount D2 in the transport direction F and the displacement amount E2 in the direction perpendicular to the transport direction F. That is, the skew state of the paper P itself can be detected, and the skew angle θ and the displacement amount in the skew direction can also be detected.

  If skew of the paper P is detected as described above, for example, the printing machine is stopped.

[Detection of presence of paper and control of rotation speed of drive motor]
The rotational speed of the drive motor 5 is controlled based on the contents of the control according to various conditions of paper conveyance. Hereinafter, the control method will be summarized based on the relationship with the displacement detection device 41.

(1) According to the above control content (1), when the sheet P does not exist in the detection area B of the displacement detection device 41 in FIG. 2, the rotation speed of the drive motor 5 is kept constant by the first feedback control. Keep in value. That is, when the sheet is not detected, the drive motor 5 is rotated at a preset constant rotation speed, and thereby the transport roller 2 is rotated so as to have a preset movement speed.

  On the other hand, when the paper P is fed into the detection area B and the presence of the paper P is detected by the displacement detection device 41, the moving speed (circumferential speed) of the outer peripheral transport surface of the transport roller 2 is determined by the second feedback control. The rotational speed of the drive motor 5 is controlled so as to have a value substantially corresponding to the moving speed of the paper P calculated from the displacement amount in the transport direction F of the paper P detected by the displacement detector 41. That is, the transport roller 2 is rotated so that the moving speed is substantially the same as the actual moving speed of the paper P.

  As a result, the rotational speed of the motor 5 is not changed insignificantly when no paper is detected, the rotational speed control of the drive motor 5 by the control device 41 is not complicated, and the service life of the drive motor 5 is extended. Further, when the paper non-detection state changes to the paper detection state, the control (change) always starts from the constant rotation speed of the motor 5, so that the rotation control of the drive motor 5 can be started promptly.

(2) In addition to the above control, according to the control content (2) described above, after the transition from the state in which the paper P is not present in the detection area B of the displacement detection device 41 to the state in which the paper P is present, The moving speed of the outer peripheral conveying surface of the conveying roller 2 is compared with the paper moving speed detected by the displacement detection device, and the difference between the moving speed of the conveying outer peripheral surface of the conveying roller 2 and the paper moving speed is a predetermined value. When it is larger, the first feedback control is continued, and when it is less than a predetermined value, the second feedback control is switched.

  As a result, it is possible to avoid a situation in which the rotational speed of the drive motor 5 changes suddenly and greatly when switching from the first feedback control at the time of paper non-detection to the second feedback control at the time of paper detection. The above control can be switched.

(3) Further, according to the control content (3) described above, the interference fringe pattern of the sequentially conveyed paper is read by the displacement detection device, and the interference fringe pattern read from an arbitrary paper is read before the paper. Compared with the interference fringe pattern of the paper, the abnormality of the paper is detected by recognizing that both the interference fringe patterns are out of a predetermined range of identity.

[Second embodiment of the present invention]
FIG. 12 shows a second embodiment of the sheet conveying apparatus provided with the displacement detecting device 41 according to the present invention. The structure different from that of the first embodiment shown in FIG. 1 is divided into left and right so as to have a space portion in the central portion in the axial direction, and a displacement detection device 41 is arranged in the central space portion so as to be positioned almost directly above the drive-side transport roller 2. Yes. In addition, a linear mark T extending in the axial direction, for example, is attached to the outer peripheral conveyance surface of the drive side conveyance roller 2 in order to directly detect one rotation of the drive side conveyance roller 2 by the displacement detection device 41. Other structures are the same as those of the first embodiment shown in FIG. 1, and the same components are denoted by the same reference numerals and description thereof is omitted.

  If the displacement detection device 41 is arranged directly above the driving-side conveyance roller 2 as in the configuration of FIG. 12, the detection accuracy of the conveyance state of the paper P by the displacement detection device 41 is improved. That is, the transported paper P is in a stable state where the flutter is the smallest and the flatness is maintained at the portion sandwiched between the upper and lower transport rollers 1 and 2 (nip portion), and this portion is detected. Since the interference fringe pattern on the paper surface is detected as the area, for example, the interference fringe on the paper surface is more accurate than in the case where the displacement detection device 41 is arranged on the conveyance direction F side of the conveyance roller 2 as shown in FIG. A pattern can be detected and detection accuracy is improved.

  The displacement detection device 41 differs in the sharpness of the reflected laser light depending on the height from the paper surface, which may cause an error in detection accuracy. By using the attached mark T, it is possible to easily adjust the detection accuracy when the displacement detector 41 itself is installed.

  That is, first, the radius (or diameter) of the driving-side transport roller 2 is measured in advance by a measuring device such as a caliper, a micrometer, or an electronic image measuring device, and is calculated from the measured radius (or diameter). The true total length C1 of the outer peripheral conveyance surface of the driving side conveyance roller 2 is obtained.

  Next, after the displacement detection device 41 is installed at a predetermined position as shown in FIG. 12, the drive-side transport roller 2 is idled without transporting the sheet, and the mark T passing periodically through the upper end of the transport roller 2 is displaced. Detected by the detection device 41, thereby detecting the movement amount C <b> 2 of the outer peripheral conveyance surface in one rotation of the conveyance roller 2. Then, the detected movement amount C2 is compared with the true total circumference length C1, and if there is a difference, the movement amount C2 is corrected so as to coincide with the true total circumference length C1.

[Third embodiment of the present invention]
FIG. 13 shows a third embodiment of a sheet conveying apparatus provided with a displacement detecting device 41 according to the present invention. The structure different from the first embodiment shown in FIG. A belt conveyance device 60 having a mechanism 61 is provided, and a displacement detection device 41 is disposed directly above the belt conveyance mechanism 60. Other structures are the same as those of the first embodiment shown in FIG. 1, and the same components are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 13, a belt conveying device 60 is composed of a pair of front and rear rotating rollers 62, 63, a conveying belt 64 wound around both rollers 62, 63, and the like. It is linked to the output shaft of the motor 5 through a transmission mechanism.

  The suction mechanism 61 includes a suction box 65 having a number of suction holes at the upper end, and a suction fan 66 connected to the suction box 65 via a duct or the like. A number of suction holes are also formed in the transport belt 64, and the paper P on the transport belt 64 is sucked by the suction box 65 so that the paper P is attracted to the transport belt 64 and transported in the transport direction F. ing.

  Although not shown, a linear mark T similar to the mark T shown in FIG. 12 is used on the outer peripheral conveyance surface of the conveyance belt 64 in order to directly detect the movement amount of the circumference of the conveyance belt 64 by the displacement detection device 41. Is attached. In the case of the conveyor belt 64, the entire circumference of the conveyor belt 64 is measured in advance, the conveyor belt 64 is rotated without conveying the paper P, and the mark T that periodically passes through the detection range is displaced. By detecting by the detection device 41, the movement amount of the outer peripheral conveyance surface in one circumference of the conveyance belt 64 is detected. Then, the detected movement amount is compared with the true total circumference of the conveyor belt 64, and when there is a difference, the detected movement amount is corrected so as to coincide with the true total circumference.

[Other embodiments]
(1) In the first embodiment, as a method of detecting a paper abnormality, the interference fringe pattern of the sequentially conveyed paper P is read by the displacement detection device 41 and read from an arbitrary paper P. By comparing the pattern with the interference fringe pattern of the paper P read before the paper P, abnormalities of the paper such as white paper and printing failure are detected. However, a reading device such as a scanner can be used. In this case, the interference fringe pattern on the paper P is read by a reading device such as a scanner and stored as an original interference fringe pattern in the storage unit of the control device. Then, in the paper transporting operation, the interference fringe pattern of the paper P being transported is read by the displacement detection device 41, and the read interference fringe pattern is compared with the original interference fringe pattern. By detecting that it is out of the range of the identity of the paper, the abnormality of the paper is detected.

  The displacement detection device according to the present invention and the control method of the paper conveyance device provided with the displacement detection device include a stencil printing machine, a photo printing machine, a copying machine, or a postal item or a form for conveying a stencil sheet or printing paper. It can be used for various machines such as an automatic reader.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified perspective view showing a first embodiment of a sheet conveying apparatus provided with a displacement detection device according to the present invention. FIG. 2 is a schematic side view of the sheet conveying device in FIG. 1. FIG. 6 is an explanatory diagram illustrating a method for detecting a moving amount and a moving speed of a sheet. It is a figure which shows the change of the interference fringe pattern by the image sensor corresponding to FIG. It is explanatory drawing which shows the detection method when a paper stops by a slip. It is a figure which shows the change of the interference fringe pattern by the image sensor corresponding to FIG. It is explanatory drawing which shows the detection method when the paper is moving in the slip state. It is a figure which shows the change of the interference fringe pattern by the image sensor corresponding to FIG. FIG. 10 is an explanatory diagram illustrating a method for detecting a length in a conveyance direction of a sheet. FIG. 6 is an explanatory diagram illustrating a method for detecting skew of a sheet. It is a figure which shows the change of the interference fringe pattern by the image sensor corresponding to FIG. It is a simplified perspective view which shows 2nd Embodiment of the paper conveying apparatus provided with the displacement detection apparatus by this invention. It is a simplified perspective view which shows 3rd Embodiment of the paper conveying apparatus provided with the displacement detection apparatus by this invention. It is the schematic of the conventional light-shielding type optical sensor. It is explanatory drawing which shows the skew detection method using the conventional light-shielding type optical sensor.

Explanation of symbols

1, 2 Transport rollers (transport means)
DESCRIPTION OF SYMBOLS 4 Displacement detection apparatus 5 Drive motor 11 Encoder 41 Displacement detection apparatus 44 Light emission part 45 Laser light source (Laser laser oscillation part)
46 Lens 47 Light-receiving part 48 Image sensor 49 Lens 50 Control device 60 Belt conveying device (conveying means)

Claims (14)

A light emitting unit that emits laser light from a laser light source to the surface of the paper being transported at a predetermined position on the paper transport path, and a laser beam that is reflected from the paper surface within a certain detection area irradiated with the laser light are received. And a light receiving unit having an image sensor that reads an interference fringe pattern of the laser light due to the unevenness of the paper surface and converts it into an electrical signal,
Connected to the light receiving unit is a control device to which an electrical signal of the interference fringe pattern is input,
The image sensor is configured to read an interference fringe pattern in the detection area of the paper being conveyed periodically;
The control device is configured to compare a position of a common portion of a plurality of interference fringe patterns periodically read by the image sensor and calculate a displacement amount of the paper. Detection device. The conveyance sheet displacement detection device according to claim 1,
The control device recognizes that the sheet is in a slip state when the displacement amount of the interference fringe pattern read in a predetermined cycle is smaller than a preset displacement amount during normal conveyance. It is comprised in the displacement detection apparatus characterized by the above-mentioned. In the conveyance sheet displacement detection device according to claim 2,
3. The conveyance sheet displacement detection device according to claim 2, wherein the control device is configured to issue a warning when the detected slip amount is larger than a predetermined amount. In the displacement detection apparatus of the conveyance paper of Claim 1 or 2,
The control device calculates a displacement amount in the conveyance direction of the interference fringe pattern and a displacement amount in a direction orthogonal to the conveyance direction, and the conveyance sheet is skewed when the displacement amount in the direction orthogonal to the conveyance direction is equal to or greater than a predetermined value. A displacement detection device for a conveyance sheet, wherein the displacement detection device is configured to recognize that the conveyance sheet is being used. In the displacement detection apparatus of the conveyance paper of Claim 1 or 2,
The control device is configured to detect a front end and a rear end in a paper transport direction, detect a displacement amount in the paper transport direction of the interference fringe pattern read at a predetermined period, and calculate a paper length. A displacement detection device for transporting paper, characterized by comprising: In the control method of the paper conveyance apparatus provided with the displacement detection apparatus of Claim 1, the conveyance means which conveys a paper, and the drive motor which drives this conveyance means,
When the sheet is not present in the detection area of the displacement detector by the control device, the rotation speed of the drive motor is maintained at a constant value as the first feedback control, and the sheet is present in the detection area. Sometimes, as the second feedback control, the moving speed of the conveying surface of the conveying means is a value substantially corresponding to the moving speed of the paper calculated from the displacement amount in the paper conveying direction detected by the displacement detecting device. A method for controlling a sheet conveying device, wherein the rotational speed of a drive motor is controlled. In the control method of the paper conveyance device according to claim 6,
After the transition from the state where no paper is present in the detection area of the displacement detection device to the state where the paper is present, the control device detects the movement speed of the conveyance surface of the conveyance means and the displacement detection device for a predetermined time. The first feedback control is continued when the difference between the movement speed of the conveyance surface of the conveyance means and the sheet movement speed is greater than a predetermined value, and when the difference is less than the predetermined value. And a control method for the sheet conveying device, wherein the control is switched to the second feedback control. In the control method of the paper conveying apparatus according to claim 6 or 7,
The displacement detection device is disposed on the transport unit so that an interference fringe pattern on the transport surface of the transport unit can be read.
The conveyance means is idled by a predetermined displacement amount, the displacement detection device detects the displacement amount of the conveyance surface of the conveyance means, and compares the detected displacement amount with the predetermined displacement amount of the conveyance surface of the conveyance means, Control of a sheet conveying apparatus, wherein when a detection error occurs between the detected displacement amount and the predetermined displacement amount, the detected displacement amount is corrected to the same value as the predetermined displacement amount. Method. In the control method of the paper conveyance device according to any one of claims 6 to 8,
A method for controlling a sheet conveying apparatus, wherein the conveying means is a conveying roller. In the control method of the paper conveyance device according to any one of claims 6 to 8,
The method of controlling a sheet conveying apparatus, wherein the conveying means is a conveying belt wound around a plurality of rollers. In the control method of the paper conveyance device according to claim 9,
With a mark indicating a reference position of one rotation of the transport roller,
Detecting the amount of displacement in the circumferential direction of the mark by the displacement detection device by rotating the transport roller once;
The detected displacement is compared with the true full circumference of the transport roller obtained by calculation, and when a detection error occurs between the detected displacement and the true full circumference, the detected displacement Is corrected to the same value as the true perimeter, a method for controlling a sheet conveying apparatus. In the control method of the paper conveying device according to claim 10,
A mark indicating a reference position of one cycle of the conveyor belt is attached to the conveyor belt,
Rotate the conveyor belt to detect the displacement amount of the mark by the displacement detection device,
The detected displacement amount is compared with the true total length of the transport belt obtained by calculation. When a detection error occurs between the detected displacement amount and the true total length, the detected displacement amount is A method for controlling a sheet conveying device, wherein the sheet is corrected to the same value as the total length. In the control method of the paper conveying apparatus according to claim 6 or 7,
Read the interference fringe pattern of the paper by the reading device, store it in the storage unit of the control device as the original interference fringe pattern,
While reading the interference fringe pattern of the paper being conveyed by the displacement detection device, compare the read interference fringe pattern and the original interference fringe pattern,
A control method for a paper transport device that detects a paper abnormality by recognizing that both interference fringe patterns are out of a predetermined range of identity. In the control method of the paper conveying apparatus according to claim 6 or 7,
Read the interference fringe pattern of the sequentially conveyed paper by the displacement detector,
Compare the interference fringe pattern read from any paper with the interference fringe pattern of the paper read before the paper,
A control method for a sheet conveying apparatus, wherein the abnormality of the sheet is detected by recognizing that both the interference fringe patterns are out of a predetermined range of identity.

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