JP2005067822A - Document conveying device and image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document conveying device for suppressing variation in document conveying speed, and an image reading device having the document conveying device. <P>SOLUTION: The document conveying device comprises first and second driving rollers 20 and 21 for conveying the document, a first pulley 33 and a second pulley 34, and a motor 27 for transmitting a rotation force to the first and second driving rollers 20 and 21 via a timing belt 36 to drive it. The first pulleys 33 and 34 are designed so that integral multiple of the value obtained by converting the length of one rotation thereof to the peripheral length of the first and second driving rollers 20 and 21 is substantially the same as the clearance between a first reading unit 28 and a second reading unit 29 located on the downstream side in the conveying direction of the document 11 than the first reading unit 28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an original conveying apparatus that conveys an original and an original reading type image reading apparatus that moves and reads an original.

FIG. 9 shows a conventional document moving type image reading apparatus.
When the leading edge of the document 11 inserted from the document table 8 is detected by the first paper detector 9, the image reading device recognizes that the document has been inserted, and the first roller 1 and the second roller 2. The roller 2 is rotated. The document 11 is guided to the reading unit 3 by the rotation of the first roller, and an image is read. The document 11 whose image has been read is discharged out of the apparatus by the second roller 2. The timing to start reading the document 11 is determined according to the detection result of the second paper detector 10.

  An illumination device 5 is provided inside the reading unit 3 and irradiates the image surface of the document 11 with a predetermined amount of light. Reflected light corresponding to the image pattern reflected on the image plane is focused on the light receiving element 7 through the selfoc lens 6 at an equal magnification. The analog output level of the light receiving element 7 corresponding to the image of the document 11 is converted from an analog value to a digital value by the A / D conversion circuit 51, and the converted digital value is stored in the memory 52 as image data.

  There are several types of reading units 3 applied to such an image reading apparatus. The first type shown in FIG. 10 is a method of reading the image surface of the document 11 by the reading unit 3 a having a length that can cover the maximum width of the document 11. The second type shown in FIG. 11 is a system in which a plurality of reading units 3b having a length less than the width of the document 11 are arranged in the width direction of the document 11 and the images read by these are synthesized. The third type shown in FIG. 12 is a method of reading with a plurality of reading units as in the second type, but is a method of using a reduction type reading unit 3c that reads an optical image reduced by the reduction lens 15. is there.

  As described above, the document movement type image reading apparatus is roughly provided with the above three types of reading units.

  The merit of using the first type reading unit is that a high-quality image can be obtained with a simple configuration. However, the reading unit used in this method needs to cover the entire width direction of the original document. For example, when reading an A0 width document, a reading unit having a length equal to or greater than the A0 width is required. The price of the reading unit increases dramatically as the length becomes longer due to the influence of the yield. Therefore, the reading unit having a length of A0 width or more is very effective. As a result, the cost of the image reading apparatus itself increases.

  The image reading apparatus using the second type reading unit is a method devised to compensate for the shortcomings of the first type reading unit. By using a plurality of reading units having a short length, the component cost is reduced. (That is, the cost of the reading unit) can be reduced. However, in such a configuration, since it is necessary to synthesize images read by a plurality of reading units, processing of image data becomes complicated.

  As a specific method of reading an image, first, a part of the document in the width direction is read by a reading unit arranged on the upstream side in the document conveying direction, and then an unread image is read by a reading unit located on the downstream side. Read the area.

At this time, the image data read by the upstream reading unit is temporarily stored in a predetermined place (storage device) for synthesis with the image read by the downstream reading unit, and then delayed by the downstream reading unit. It is synthesized with the read image data.
The joints of the reading unit's divisions ensure the position accuracy of the reading unit so that the images are properly connected during image composition, and adjust the parts that cannot be suppressed by the parts accuracy to secure the position. doing.

  However, as a drawback of such a divided reading type, a certain degree of image accuracy can be ensured by ensuring or adjusting the accuracy, but there is a limit to improvement in accuracy due to the following causes, and as a result, as shown in FIG. As described above, an image shift is caused in the joint portion.

  If the document feeding speed is always constant, there is no image shift at the joint, but actually, the document transport speed fluctuates periodically as shown in FIG. The cause of this was a flutter of the outer periphery with respect to the axis of the transport roller or a flare of the axis of the pulley driving the roller.

  The merit of the image reading apparatus using the third type reading unit is that the cost of the reading unit itself can be reduced in the same manner as the image reading apparatus using the second type reading unit, and a reduction optical system is provided. Therefore, the effect of cost reduction can be obtained more significantly by applying a reading unit that is shorter than that of the second type. However, since the reduction optical system is used, an optical path length longer than that of the image reading apparatus using the second type reading unit is required, and the size of the image reading apparatus is increased. Further, due to the same cause as that of the image reading apparatus using the second type reading unit, an image shift occurs in the joint portion of the image.

There is an “image reading apparatus” disclosed in Patent Document 1 as a conventional technique for improving image quality by suppressing image deviation caused by fluctuations in the document conveyance speed.
The invention described in Patent Document 1 improves the image quality of a read image by correcting an image shift in the sub-scanning direction caused by a change in the conveyance speed of an original based on correction data stored in advance in a memory. It is.

However, the invention described in Patent Document 1 does not reduce fluctuations in the document conveyance speed, but corrects an image based on correction data. Further, the image shift cannot be corrected unless correction data that differs depending on a combination of conditions such as the document conveyance speed and the material is stored in the memory in advance. In other words, the invention described in the cited document 1 must always execute image processing (correction processing) unrelated to the original image reading, and correction data is stored in the memory in advance. In such a situation, image quality degradation cannot be reduced.
JP-A-10-145552

  As described above, in a document moving type image reading apparatus that divides an image, reads it from a document, and synthesizes it, in order to reduce image misalignment occurring at a joint portion of the image in any situation, It was necessary to suppress fluctuations in the conveyance speed.

  SUMMARY An advantage of some aspects of the invention is that it provides a document conveying device that suppresses fluctuations in the document conveying speed and an image reading apparatus including the document conveying device.

  In order to achieve the above object, the present invention includes, as a first aspect, a conveyance roller that conveys a document and a rotating body having a specific number of engagement teeth, and the engagement teeth provide rotational force to the conveyance roller. And a driving unit that transmits and drives, and the rotating body has a positive multiple of a value obtained by converting the length of one rotation into the circumferential length of the conveying roller. Provided is a document conveying device characterized in that it is designed to be substantially the same as the interval between one reference position and a second reference position located downstream of the first reference position in the document conveying direction. It is. With such a configuration, it is possible to reduce fluctuations in the document conveyance speed.

  In the first aspect of the present invention, when the interval between the first reference position and the second reference position is “l”, the rotation period “S” of the rotating body is converted into the circumferential length of the conveying roller. It is preferable that the diameter of the conveying roller and the number of engaging teeth are set so that the integral multiple of the value is approximately “l”. In addition to this, it is more preferable to set the diameter of the conveying roller and the number of engaging teeth so that the rotation period “S” of the rotating body is minimized. In this way, fluctuations in the document conveyance speed can be reduced more efficiently.

  In order to achieve the above object, according to a second aspect of the present invention, there is provided a document movement type image reading apparatus that reads an image on a document while moving the document. A first driving means including a first roller to be passed through and a first rotating body having a specific number of teeth; the first driving means for driving the first roller by transmitting torque to the first roller; A first reading unit that reads a partial image from the document conveyed by the first roller and generates first image data; and the first reading unit of the reading unit in the document conveying direction. A second reading unit that is arranged on the downstream side and reads an image of an area that has not been read from the original by the first reading unit to generate second image data; and first image data delayed by a predetermined time; Second picture Means for combining the data with each other to generate a composite image, a second roller for conveying the document on which the image has been read by the first and second reading means, and discharging it from the reading section, and a specific number of teeth And a second driving means for driving the second roller by transmitting a rotational force to the second roller, and the first rotating body has a length corresponding to the first rotation. The positive multiple of the value converted into the roller circumference is designed to be substantially the same as the interval between the first and second reading means, and the second rotating body has a length corresponding to one rotation. It is an object of the present invention to provide an image reading apparatus characterized in that a positive multiple of the value converted into the circumference of the second roller is designed to be substantially the same as the interval between the first and second reading means. In this way, it is possible to reduce periodic fluctuations in the document conveyance speed and to reduce the occurrence of image shift at image joints.

  In the second aspect of the present invention, when the interval between the first and second reading means is “l”, the rotation period “S1” of the first rotating body is equal to the circumferential length of the first roller. An integer multiple of the converted value is approximately “l”, and an integer multiple of the rotation period “S2” of the second rotating body converted to the circumference of the second roller is approximately “l”. The diameters of the first and second rollers and the number of teeth of the first and second rotating bodies are preferably set. In the above configuration, the diameters of the first and second rollers and the first and second rollers are such that the rotation period “S1” of the first rotating body and the rotation period “S2” of the second rotating body are minimized. More preferably, the number of engaging teeth of the rotating body is set. In this way, it is possible to more efficiently reduce periodic fluctuations in the document conveyance speed and reduce the occurrence of image shifts at image joints.

  According to the present invention, it is possible to provide an original conveying apparatus that suppresses fluctuations in the original conveying speed and an image reading apparatus including the original conveying apparatus.

(Example)
FIG. 1 shows a configuration of an image reading apparatus in which the present invention is preferably implemented. The image reading apparatus includes a first driving roller 20, a second driving roller 21, a first driven roller 22, a second driven roller 23, a motor 27, a first reading unit 28, and a second reading unit 29. , A pressure plate (white reference plate) 30, a second paper detector 31, a first paper detector 32, a first pulley 33, a second pulley 34, a motor pulley 35, and a timing belt 36.

  The first drive roller 20 is a roller that conveys the document 11 inserted from the document insertion port 8 to the reading unit. The second drive roller 21 guides and conveys the document 11 that has been read in the direction opposite to the insertion slot. The first driven roller 22 is a roller for sandwiching the document 11 with the first drive roller 20. The second driven roller 23 is a roller for sandwiching the document 11 with the second drive roller 21. The motor 27 is a drive source for the first drive roller 20 and the second drive roller 21. The first reading unit 28 includes an illumination device (not shown), a light receiving element, a unity magnification imaging element, and the like, and reads an image of a partial area of the document 11 to generate image data. The second reading unit 29 is arranged on the downstream side of the first reading unit 28 in the transport direction of the document 11 and reads an image from an area that has not been read by the first reading unit 28. The pressure plate 30 is a member for bringing the document 11 into close contact with the contact glass and serves as a reference for density when reading an image. The second paper detector 31 is a sensor for detecting that the document 11 has been conveyed to the reading position. The first paper detector 32 is a sensor for detecting that the document 11 is inserted between the first drive roller 20 and the first driven roller 22. The first pulley 33 is a pulley for transmitting the driving force from the timing belt 36 to the first driving roller 20. The second pulley 34 is a pulley for transmitting the driving force from the timing belt 36 to the second driving roller 21. The motor pulley 35 is a pulley for transmitting the driving force generated by the motor 27 to the timing belt 36. The timing belt 36 is a belt for transmitting the driving force generated by the motor 27 to the first pulley 33 and the second pulley 34.

  In the above configuration, the timing belt 36 is a toothed belt, and each pulley engaged with the timing belt 36 is a pulley for a toothed belt.

  The image data read by the first reading unit 28 is output as an analog signal from the first light receiving element, and as shown in FIG. 2, a digital value (for example, 256 gradation digital) is output by the A / D conversion circuit 41. Value). The image data converted into the digital value is temporarily stored in a memory (not shown) provided in the delay circuit 43 for a predetermined time.

  Thereafter, similarly to the image data read by the first light receiving unit 28, the image data read by the second reading unit 29 is also converted into a digital value by the A / D conversion circuit 42. The image data read by the first reading unit 28 is read from the memory in accordance with the output of the image data from the second reading unit 29 (after a lapse of T time from reading by the first reading unit 28), and is synthesized. The circuit 44 combines the image data read by the second reading unit 29 into image data for one line, and then sends it to the subsequent processing step.

  By the way, in said structure, it is ideal that the 1st and 2nd rollers 20 and 21 and the 1st and 2nd pulleys 33 and 34 do not have the outer periphery or pitch circle flared with respect to the axial center. In actuality, however, a slight amount of deflection occurs due to the accuracy of part processing.

  For this reason, as described above, periodic unevenness as shown in FIG. 3 occurs in the document feed speed, and as a result, a step occurs at the reading seam.

  However, in the present invention, the interval between the reading positions associated with the reading delay between the first reading unit 28 and the second reading unit 29 is set to “l”, the first and second driving rollers 20, 21 and the first driving unit 20. When the period of one rotation of the second pulleys 33 and 34 is “S”, an integral multiple of the value obtained by converting “S” into the circumference of the document conveying roller is “l” or close to it. In this way, the outer diameter of each roller or pulley and the fraction of the gear are set. This prevents the occurrence of image shift at the reading seam.

Specifically, as shown in FIG.
The interval between the reading positions of the first reading unit 28 and the second reading unit 29 due to the reading delay is “l”.
The outer diameter of the document conveying rollers (the first driving roller 20 and the second driving roller 21) is L (in the case where there are a plurality, L ₁ , L ₂ ,..., L _n ).
The number of teeth of the roller pulley (the first pulley and the second pulley 34) that drives the document conveying roller is Z ₂
・ The number of teeth of the motor pulley (motor pulley 35 (motor shaft direct connection)) that drives the roller pulley is Z ₁
Assuming that
For original conveying roller (in other words, a value obtained by converting the period of one rotation in the circumferential length of the document transport rollers) the amount of movement of the document accompanying the period S ₂ of one rotation of the document conveying roller is L × [pi. It is designed so that the value of L × π is the same as the above “l” or a positive multiple of L × π is “l”.

For the pulley that drives the document conveying roller, the period of one rotation of the pulley is the same as the period S _{2 of} one rotation of the document conveying roller, and the value obtained by converting the period of one rotation into the circumference of the document conveying roller is L × π. Therefore, the design is such that the value of L × π is the same as the above “l”, or the positive multiple of L × π is the same as “l”.

For the pulley that drives the motor, the period S ₁ of one rotation of the motor pulley is S ₂ × (Z ₁ / Z ₂ ), and the value obtained by converting the period of one rotation of the motor pulley into the circumference of the document reading roller is (L × π) × (Z ₁ / Z ₂ ). Therefore, it is designed so that this value is the same as the above “l” or a positive multiple of (L × π) × (Z ₁ / Z ₂ ) is “l”.

  Document conveying speed when each member is designed to satisfy the above conditions (when an integral multiple of a value obtained by converting the period of one rotation into the circumference of the document conveying roller is “l” for each member) The relationship with time is shown in FIGS. 5 (a) and 5 (b) and FIGS. 6 (a) and 6 (b). The distance that the document 11 is transported per unit time is expressed as a waveform of a hatched portion in the drawing while passing through the first reading unit 28 and then passing through the second reading unit 29. Is done. Here, the amount of deviation caused by the difference between the target value of the document conveying speed and the actual speed is expressed as the area of the shaded portion, but the amount of deviation caused when the actual conveying speed is larger than the target value. The absolute value is the same between the (positive deviation amount) and the deviation amount (negative deviation amount) generated when the actual conveyance speed falls below the target value. Therefore, the total deviation amount of the delay time t ′ is zero because the positive deviation amount and the negative deviation amount are offset.

  For each of the above members, FIG. 7 shows the relationship between the document conveying speed and time when the period of one rotation is an integer multiple of the value converted to the circumference of the document conveying roller. . In this case, since the absolute value does not match between the positive deviation amount and the negative deviation amount, they are not completely canceled out, and the larger one of the positive and negative deviation amounts remains. However, even in this case, since the total shift amount is only the difference between the positive and negative shift amounts, the image shift at the joint is reduced.

  Therefore, ideally, an integer multiple of a value obtained by converting the period of one rotation of each of the above members to the circumference of the document conveying roller is preferably “l”, but the image misalignment is within a practical range. As described above, it is also possible to set so that an integral multiple of a value obtained by converting the period of one rotation of each of the above members into the circumference of the document conveying roller becomes a value close to “l”.

  In the above description, the interval between the reading positions due to the reading delay of the first reading unit 28 and the second reading unit 29 is fixed to “l”, and the diameter of the document conveying roller and The number of teeth of the pulley that drives the roller is set, but conversely, the outer diameter of each member may be set so as to satisfy the same relationship from the roller diameter and the number of teeth of the pulley.

  In the above description, the configuration using a pulley as the driving means has been described as an example. However, the driving means may be a driving means other than a pulley such as a gear / sprocket.

  Further, in the above description, for simplification of description, the description has been given by taking as an example a configuration provided with two drive pulleys (first and second drive pulleys 33 and 34), but as shown in FIG. The same applies to the case where three or more pulleys are interlocked.

  In addition, when there are a plurality of combinations of settings that satisfy the above conditions, it is preferable to apply a setting that shortens the rotation period of the pulley. This is because the fluctuation period of the document conveying speed is shortened as one pulley period is shortened, and when the fluctuation period of the document conveying speed is shortened, the rotation period of each member is converted to the circumference of the document conveying roller. This is because even when the difference between the positive multiple and “l” is the same, the image shift at the joint is reduced.

  When the cycle of the image conveyance speed is rough (the fluctuation cycle is long), the influence of image displacement appears greatly at the joint. Therefore, the value obtained by converting the cycle of one rotation of the rotating member into the circumference of the document conveyance roller is It is preferably close to “l”.

  In addition, the said Example is an example of the suitable implementation of this invention, and this invention is not limited to this.

1 is a diagram illustrating a configuration of an image reading apparatus according to a preferred embodiment of the present invention. It is a figure which shows the flow of the image data read from the original. FIG. 6 is a diagram illustrating a state in which the document conveyance speed fluctuates periodically. It is a figure which shows arrangement | positioning of the pulley applied to an image reading apparatus. FIG. 6 is a diagram illustrating a relationship between a document conveyance speed and time when a positive variation amount and a negative variation amount of a document conveyance speed are offset. FIG. 6 is a diagram illustrating a relationship between document transport speed and time when a variation amount of a positive document transport speed and a variation amount of a negative document transport speed are offset. FIG. 10 is a diagram illustrating a relationship between document conveyance speed and time when a positive variation amount and a negative variation amount of the document conveyance speed are not completely offset. It is a figure which shows the structural example in the case of driving a drive roller with four pulleys. It is a figure which shows the structure of the conventional image reading apparatus. FIG. 2 is a diagram illustrating an optical system of an image reading apparatus that reads a document with a single reading unit and generates image data. FIG. 2 is a diagram illustrating an optical system of an image reading apparatus of a type in which an original is divided and read by a plurality of reading units to generate image data and synthesize each image data. It is a figure which shows the optical system of the image reading apparatus of a system provided with a reduction optical system. FIG. 6 is a diagram illustrating a state in which an image shift has occurred at a joint between images in an image reading apparatus that reads a document with a plurality of reading units.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st roller 2 2nd roller 3, 3a, 3b, 3c Reading unit (light receiving element)
DESCRIPTION OF SYMBOLS 4 Contact glass 5 Illuminating device 6 1 time magnification imaging element 7 Light receiving element 8 Original table 9 1st paper detector 10 2nd paper detector 20 1st drive roller 21 2nd drive roller 22 1st driven roller 23 Second driven roller 27 Motor 28 First reading unit 29 Second reading unit 30 Pressure plate (white reference plate)
31 Second paper detector 32 First paper detector 33 First pulley 34 Second pulley 35 Motor pulley 36 Timing belt

Claims (6)

A transport roller for transporting the document;
Including a rotating body having a specific number of engaging teeth, and driving means for transmitting the driving force to the conveying roller by the engaging teeth,
The rotating body has a first reference position through which a document transported by the transport roller passes a first multiple of a value obtained by converting the length of one rotation into the peripheral length of the transport roller, and the first An original conveying apparatus, wherein the original conveying apparatus is designed to be substantially the same as a distance from a second reference position located downstream of the reference position in the original conveying direction. When the interval between the first reference position and the second reference position is “l”,
The diameter of the conveying roller and the number of engaging teeth are set so that an integral multiple of a value obtained by converting the rotation period “S” of the rotating body to the circumference of the conveying roller is approximately “l”. The document feeder according to claim 1.   3. The document conveying apparatus according to claim 2, wherein the diameter of the conveying roller and the number of engaging teeth are set so that the rotation period “S” of the rotating body is minimized. An original moving type image reading apparatus that reads an image on an original while moving the original,
A first roller that conveys the document and passes the reading unit;
First driving means including a first rotating body having a specific number of teeth, and transmitting the rotational force to the first roller by the teeth;
A first reading unit disposed in the reading unit and configured to read a partial image from a document conveyed by the first roller and generate first image data;
A second image data is obtained by reading an image of an area that is disposed downstream of the first reading unit of the reading unit in the transport direction of the document and not read by the first reading unit from the document. A second reading means for generating;
Means for combining the first image data and the second image data delayed by a predetermined time to generate a composite image;
A second roller that conveys a document on which an image has been read by the first and second reading means and discharges the original from the reading unit;
Including a second rotating body having a specific number of teeth, and a second driving means for driving the second roller by transmitting a rotational force;
In the first rotating body, a positive multiple of a value obtained by converting the length of one rotation into the circumferential length of the first roller is substantially the same as the interval between the first and second reading means. Designed to
The second rotating body is designed so that a positive multiple of a value obtained by converting the length of one rotation into the circumference of the second roller is substantially the same as the interval between the first and second reading means. An image reading apparatus. When the interval between the first and second reading means is “l”,
The rotation period “S1” of the first rotating body is approximately “l”, which is an integral multiple of the value converted to the circumference of the first roller, and the rotation period “S2” of the second rotating body. , The diameter of the first and second rollers and the number of teeth of the first and second rotating bodies are such that an integral multiple of the value converted into the circumference of the second roller is approximately “l”. The image reading apparatus according to claim 4, wherein the image reading apparatus is set.   The diameters of the first and second rollers and the first and second rotations so that the rotation period “S1” of the first rotating body and the rotation period “S2” of the second rotating body are minimized. 6. The image reading apparatus according to claim 5, wherein the number of engagement teeth of the body is set.

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