JP4208470B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus such as a copying machine, a scanner, and a facsimile machine, and more particularly to an image reading apparatus including a sheet conveying apparatus that automatically conveys a sheet-like document to an image reading unit, and an image including the image reading apparatus. The present invention relates to a forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image reading apparatus provided in a digital copying machine, a printer, a facsimile, or the like, an automatic document feeder (hereinafter referred to as ADF “Auto Document Feeder”) is used to automatically feed a sheet-like document to the image reading apparatus. There are some that can be opened and closed freely.
[0003]
As one of reading methods by an image reading apparatus provided with an ADF, an image reading means is fixed at a predetermined reading position of a platen glass provided in the image reading apparatus, and the original is moved at a constant speed on the reading position. Therefore, a method of reading an image (hereinafter referred to as “streaming reading”) is known. The flow reading, as a reading method of processing a sheet-like document having a large amount of high speed, a technique used in many products.
[0004]
In order to perform high-speed and stable image reading in flow reading, it is necessary to prevent the original from floating from the platen glass at the reading position in order to prevent image blur due to blurring or flapping of the original. As a method for this, there is used a method of providing a platen roller that is rotationally driven at a predetermined interval with respect to the platen glass at the flow reading position. Compared with the method that suppresses the lifting of the document by a fixing member such as a guide plate, the scanning reading using the platen roller can reduce the conveyance load while limiting the lifting amount to a smaller size, and can be performed at a higher speed. High-quality image reading is possible.
[0005]
FIG. 9 shows an example of a conventional image reading apparatus. The image reading apparatus shown in FIG. 9 uses an original platen glass 100 for a method of reading a document placed and fixed (hereinafter referred to as “book reading”), a flow reading glass 101 for a flow reading method, and both reading methods. A reading sensor 102 such as a contact image sensor which is a shared image reading means is provided.
[0006]
In the flow-reading method, the platen roller 104 is disposed at a predetermined interval with respect to the upper surface of the flow-reading glass 101, and is driven to rotate at a predetermined speed. This realizes stable document transportation while limiting the amount of floating of the document from the upper surface of the flow-reading glass 101 during the flow-reading.
[0007]
[Problems to be solved by the invention]
In the flow reading using the platen roller 104, when the reading position, that is, the stop position of the reading sensor 102 varies with respect to the platen roller, there is a problem that the luminance level of the read image varies. The cause of this phenomenon will be described with reference to the schematic diagram of the conventional image reading apparatus shown in FIG.
[0008]
FIG. 10 shows the path of light emitted from the illuminating means 105 for the book reading method shown in (a) and the flow reading method shown in (b). Here, for the sake of explanation, the path of light emitted from the illumination means on one side and transmitted through the document is schematically shown by a two-dot chain line. Further, the case where the reading position in the flow reading method is shifted from the position immediately below the center of the platen roller 104 to the upstream side in the document conveying direction is shown.
[0009]
In the case of the book reading method shown in FIG. 10 (a), the light transmitted through the document 106 is reflected in the direction of the reading sensor 102 by the white pressure plate 107 pressing the document 106 against the document table glass 100, and irradiates the back side of the document. . On the other hand, in the case of the flow reading method shown in FIG. 10B, the light transmitted through the document 106 is reflected by the white platen roller 104, but a part thereof is separated from the reading sensor 102 due to the curvature of the platen roller 104. It will be reflected in the direction.
[0010]
For this reason, the amount of light that irradiates the original 106 from the back surface is reduced, and the brightness when the reflected light from the original is read by the image sensor 109 via the lens 108 is reduced. As the reading position moves away from just below the center of the platen roller 104, the amount of light reflected in the direction of the reading sensor 102 also decreases, so that even when the same document is read, the luminance of the image further decreases. Further, the higher the light transmittance of the original 106, the greater the influence of this phenomenon. Therefore, the lower the thickness of the original 106 sheet, the more remarkable the decrease in luminance.
[0011]
In order to perform image reading without being affected by the decrease in luminance, it is necessary to accurately position the reading sensor 102 directly under the rotation center of the platen roller 104 that can obtain luminance substantially equal to that of book reading.
[0012]
However, it is difficult to accurately position the reading sensor 102 with respect to the platen roller 104 due to the accuracy of the stop position of the reading sensor 102 and the backlash of the hinge portion of the ADF 103 that is attached to be freely opened and closed.
[0013]
Also, dust tends to adhere to the surface of the flow reading glass 101 immediately below the center of the platen roller 104 or downstream in the document transport direction. There is a problem of end. For this reason, it is desirable that the reading position is set slightly upstream from directly below the center of the platen roller 104.
[0014]
Further, in order to prevent the generation of streak images due to dust on the flow reading glass 101, the image is read at the position of the flow reading while rotating the platen roller 104 in a state where the document is not conveyed, and the flow reading glass 101 is read. A method has been proposed in which the dust on the surface of the platen roller 104 is distinguished from the dust on the platen roller 104 and the reading position is moved when dust on the flow reading glass 101 is detected. When such a streak image prevention operation is performed, the reading position of the flow reading inevitably moves.
[0015]
As described above, it is difficult to always position the scanning reading position at the same position with respect to the platen roller 104 because of the influence of component accuracy and the operation to prevent the generation of streak images. As a result, the above-described luminance variation occurs.
[0016]
The present invention solves the above-described conventional problems, and an object of the present invention is to provide an image reading apparatus that enables stable image reading with little change in luminance of an image even when the reading position varies, and image formation having the image reading apparatus. A device is provided.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a typical configuration according to the present invention includes a document conveying unit that conveys a sheet-like document, a transparent member that supports the document at an image reading position, and a position facing the transparent member. A reading unit that irradiates the original on the transparent member with light from an illuminating unit and reads an image of the original at the image reading position; and a position opposite to the illuminating unit and the reading unit opposite to the transparent member. And a rotating body that conveys the original by rotating, and reads the image while conveying the original, and based on reading the image of the reading means while rotating the rotating body without conveying the original In the image reading apparatus capable of moving the image reading position when dust on the transparent member is detected ,
When the original is read by the reading unit while the original is being conveyed, the light irradiated from the illumination unit is transmitted through the original, and the transmitted light is reflected from the back surface of the original. A reflecting member that is a white sheet, and the reflecting member is attached to a guide member that forms an upstream sheet conveyance path with respect to a direction in which the rotating body conveys the document rather than immediately below the rotation center of the rotating body; The image reading position is between the position just below the rotation center of the rotating body and the tip of the reflecting member on the rotating body side, and when the original is not being conveyed by the rotating body, the surface of the rotating body is The position is set to be read by the reading means.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
[First Embodiment]
An image reading apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 is a detailed cross-sectional explanatory view of the flow reading portion of the image reading apparatus, FIG. 2 is an overall cross-sectional explanatory view of the image reading apparatus, and FIG. 3 is a schematic explanatory view showing a luminance fluctuation preventing effect by the reflecting member, 4 and 5 are graphs showing the relationship between the scanning reading position and the brightness of the original white background.
[0020]
{Overall configuration of image reading apparatus}
As shown in FIG. 2, the image reading apparatus A according to the present embodiment has an ADF 2 that is an automatic document feeder provided on the upper part of the image reading unit 1.
[0021]
The image reading unit 1 can read an original by either a book reading method or a flow reading method. In other words, an original table glass 3 for book reading is provided on the upper surface of the image reading unit 1, and one side of the original table glass 3 is used as a transparent member for supporting a document for flow reading. Glass 4 is provided.
[0022]
A reading means 5 for reading an image written on the original is provided below the glass. The reading means 5 is arranged at the imaging position of the illumination means 6 such as a xenon tube that irradiates light on the original on the glass, the Selfoc lens 7 that forms an image of reflected light from the original, and the Selfoc lens 7. A contact image sensor 8 is housed integrally in a casing 9. The casing 9 is abutted against the platen glass 3 or the flow reading glass 4 via a highly slidable abutting member (not shown), and the reading means 5 is arranged at a predetermined distance from the manuscript surface. ing.
[0023]
On the other hand, the ADF 2 is attached to the upper part of the image reading unit 1 by a hinge or the like so as to be freely opened and closed, and supplies a document to the image reading unit 1, and the sheet-like document loaded on the document placing unit 10 is 1 feeding roller 11 a and the conveying roller 11 B to 11 f as original conveying means for conveying one by sheet, a platen roller 12 serving as a rotary member to prevent the document from floating from the glass 4 skimming during the flow reading, after the image reading A document discharge unit 13 for discharging the document is provided.
[0024]
In the case of the book reading method, the original placed on the original table glass 3 is fixed by the white pressure plate 14 attached to the ADF 2, and the reading means 5 is driven at a predetermined speed in the sub-scanning direction (left-right direction in FIG. 2). While reading the document. In the book reading method, the ADF 2 functions as a pressure plate for fixing the document on the platen glass 3.
[0025]
In the case of the flow-reading method, the document stacked on the document placement unit 10 of the ADF 2 is fed by the feed roller 11a and is transported below the platen roller 12 at a predetermined speed by the transport rollers 11b, 11c, and 11d. Is done. The reading means 5 is limited in the floating amount from the upper surface of the flow reading glass 4 by the platen roller 12 rotating at a predetermined rotational speed, and the reading means 5 stopped at the predetermined reading position is the upper surface of the platen roller 12 and the flow reading glass 4. An image is read by irradiating light from the illumination unit 6 to the original conveyed between the two. The document that has passed through the platen roller 12 is guided to the transport rollers 11e and 11f by the jump table 15, and is discharged to the document discharge unit 13.
[0026]
{Luminance fluctuation prevention configuration during panning}
Next, a configuration for preventing luminance fluctuation at the time of flow reading will be described. As shown in FIG. 1, the ADF 2 of the present embodiment is provided with a white flexible sheet member 16 serving as a reflecting member on the upstream side of the platen roller 12 in the document conveying direction. The white sheet member 16 is attached and disposed so as to be substantially parallel to the flow-reading glass 4 with respect to a guide member that guides the document to the platen roller 12. The distance C2 between the white sheet member 16 and the flow reading glass 4 is larger than the distance C1 between the flow reading glass 4 and the surface of the platen roller 12, and the distance between the flow reading glass 4 and the rotation center of the platen roller 12 is. They are arranged so as to be smaller than (C1 + R) (C1 <C2 <C1 + R).
[0027]
Further, the tip position 17 where the sheet member 16 is closest to the platen roller 12 is viewed from the reading position by the reading means 5 when viewed from the rotating body direction (reading direction), that is, upward from the lower direction perpendicular to the flow reading glass 4. When the platen roller 12 and the white sheet member 16 located at the position of the platen roller 12 are viewed, the white sheet member 16 is substantially the same as the platen roller 12 in the entire image reading range of the reading means 5 in the main scanning direction (longitudinal direction of the platen roller 12). It is arranged to hide the part. Further, the reading position in the flow reading method is set to a position where the surface of the platen roller 12 is read when the document is not conveyed.
[0028]
The effect of preventing the decrease in luminance by the white sheet member 16 of the present embodiment will be described with reference to the schematic diagram shown in FIG. FIG. 3 schematically shows a path of light that is irradiated with light from the illumination means 6 on one side (left side in the present embodiment), and that light passes through the document. Further, the reading position in the flow reading method is set to a position shifted from the position just below the rotation center of the platen roller 12 to the upstream side in the document conveying direction.
[0029]
The light transmitted through the document 18 is reflected in the direction of the reading means 5 by the white sheet member 16, and more light irradiates the document 18 from the back surface than in the conventional example shown in FIG. I understand that. As a result, a decrease in luminance when the reading position is away from directly below the center of the platen roller 12 is reduced.
[0030]
FIG. 4 and FIG. 5 show the measurement results of the relationship between the reading position when the original is scanned and the luminance of the original white background (0 to 255 level). 4 shows the measurement results in the case of the present embodiment with the white sheet member 16 attached, and FIG. 5 shows the measurement results in the case where the white sheet member 16 is not attached.
[0031]
When the white sheet member 16 is not provided, as shown in FIG. 5, the brightness of the white background portion of the document greatly decreases as the reading position moves away from just below the rotation center of the platen roller 12. On the other hand, when the white sheet member 16 is provided as in this embodiment, as shown in FIG. 4, the decrease in luminance is small, and even when the reading position varies, the change in luminance is substantially reduced. It turns out that it can be suppressed to a problem-free level.
[0032]
The distance C2 between the white sheet member 16 and the flow reading glass 4 is larger than the distance C1 between the flow reading glass 4 and the surface of the platen roller 12, and the distance between the flow reading glass 4 and the rotation center of the platen roller 12 ( Since the white sheet member 16 is arranged so as to be smaller than (C1 + R), the white sheet member 16 does not come into contact with the document 18 regulated by the platen roller 12, and the conveyance of the document 18 is hindered or the document surface is rubbed. Therefore, the light from the illumination means 6 is reflected.
[0033]
In the present embodiment, the white sheet member 16 is arranged so as to hide a part of the platen roller 12 in substantially the entire reading area when viewed from the reading position by the reading means 5 (in the direction of the platen roller 12). Therefore, the light irradiated from the reading position by the illuminating means 6 and transmitted through the document is surely reflected by the white sheet member 16 or the platen roller 12, and the luminance is not lowered.
[0034]
Further, since the white sheet member 16 is mounted in parallel with the flow reading glass 4, the light transmitted through the original is reflected in the same manner as when reflected by the white pressure plate 14 in the case of book reading. No substantial change in luminance occurs.
[0035]
In addition, the reading position at the time of flow reading is set between the position just below the rotation center of the platen roller 12 and the leading end 17 of the white sheet member 16, that is, a position where the surface of the platen roller 12 is read when the document is not being conveyed. Therefore, it is possible to detect the dust on the flow-reading glass 4 and the dust on the platen roller 12, and to perform a detection operation, and to perform high-quality image reading that prevents the generation of streaks. Further, by setting the reading position upstream of the rotation center of the platen roller 12 in the document conveying direction, it is difficult for dust to adhere to the platen roller 12.
[0036]
[Second Embodiment]
Next, a second embodiment of the image reading apparatus according to the present invention will be described with reference to FIGS. 6 is a detailed cross-sectional explanatory view of the flow reading portion, and FIG. 7 is a schematic explanatory view showing a luminance fluctuation preventing effect.
[0037]
The difference between the present embodiment and the first embodiment described above is that in the first embodiment, the white sheet member 16 is flowed and attached in parallel to the reading glass 4, but the white sheet member 16 of the present embodiment is The distance from the flow-reading glass 4 is arranged so as to increase as the distance from the platen roller 12 is approached. Other configurations are the same as those of the first embodiment described above.
[0038]
That is, as shown in FIG. 6, the distance between the white sheet member 16 and the flow-reading glass 4 is such that the distance C4 at the downstream end is larger than the distance C3 at the upstream end in the document transport direction. Is attached diagonally. The minimum distance C3 between the white sheet member 16 and the flow reading glass 4 is larger than the distance C1 between the flow reading glass 4 and the surface of the platen roller 12, and the maximum distance between the white sheet member 16 and the flow reading glass 4 is maximum. The distance C4 is arranged to be smaller than the distance (C1 + R) between the flow reading glass 4 and the center of the platen roller 12.
[0039]
The effect of preventing the luminance reduction by the white sheet member 16 of the present embodiment will be described with reference to the schematic diagram shown in FIG. FIG. 7 schematically shows the path of light emitted from the illumination means 6 on one side and transmitted through the document.
[0040]
The light transmitted through the document 18 is reflected by the white sheet member 16 toward the reading means 5. Since the white sheet member of the present embodiment is disposed with an inclination with respect to the flow reading glass 4, it has the effect of condensing the light transmitted through the document 18 in the direction of the reading means 5, as shown in FIG. In addition, it can be seen that more light irradiates the document 18 from the back side than the flow reading unit of the first embodiment. As a result, a decrease in luminance when the reading position moves away from just below the rotation center of the platen roller 12 is further reduced, and stable image reading with little change in luminance is performed even when the reading position varies.
[0041]
In addition, when the white sheet member 16 is inclined, if the concave shape is formed with respect to the illumination unit 6, the light from the illumination unit 6 is more effectively condensed on the reading unit 5. .
[0042]
[Third Embodiment]
In the above embodiment, the image reading apparatus has been described. However, as shown in FIG. 8, the present invention is also applied to an image forming apparatus C such as a copying machine in which an image reading apparatus A and an image recording apparatus B are integrated. can do.
[0043]
FIG. 8 is an overall schematic explanatory diagram of the image forming apparatus, and the image reading apparatus A has the same configuration as that described in the first embodiment. The image recording apparatus B records an image based on the image data read by the image reading apparatus A or image data read and transmitted from another image reading apparatus.
[0044]
That is, when an image recording signal is input, any one of the feeding media 20a, 20b, 20c, 20d, and 20e selected from the recording media set in the sheet storage portions 19a, 19b, 19c, and 19d and the tray 19e and the conveyance The roller 31 is driven and conveyed to the image forming means to form an image.
[0045]
The image forming means is selected according to the image information on the photosensitive drum 21, the charger 22 for uniformly charging the surface of the photosensitive drum 21, and the surface of the photosensitive drum 21 charged by the charger 22. Exposure means 23 for performing exposure, and a developing device for developing the electrostatic latent image formed on the photosensitive drum 21 by exposure by the exposure means 23 and forming a toner image to be transferred onto the conveyed recording medium 24, a transfer charger 25 for transferring the toner image developed on the surface of the photosensitive drum 21 to a recording medium, and a separation charger for separating the recording medium having the toner image transferred from the photosensitive drum 21 26 and a cleaner 27 for removing the toner remaining on the photosensitive drum 21 after the toner image is transferred, and an image is formed on a recording medium by electrophotography.
[0046]
Then, the recording medium on which the image is formed is conveyed to the fixing device 29 by the conveying unit 28, and after the toner image is heated and fixed, it is discharged to the discharge tray 30.
[0047]
As described above, by forming the image forming apparatus C by integrating the image reading apparatus A and the image recording apparatus B, it is possible to effectively prevent luminance fluctuations when the document is read and read as in the above-described embodiment. Thus, stable image reading can be performed, and based on this, high-quality image formation can be performed at high speed.
[0048]
[Other Embodiments]
In the above-described embodiment, an example in which a contact image sensor is used as an image reading unit has been described. However, a reflection mirror and a CCD are used. A type of direct exposure to the body surface may also be used.
[0049]
Further, in the above-described embodiment, in order to avoid the influence of dust on the flow reading glass 4, the reading position is set on the upstream side in the document conveying direction with respect to the rotation center of the platen roller 12, and the white sheet member is set on the upstream side. 16 was established. However, the flow reading position may be set on both sides of the platen roller 12 directly below the rotation center, and the white sheet member 16 may be provided on the upstream side and the downstream side in the document conveyance direction.
[0050]
Furthermore, in the above-described embodiment, the white sheet member that easily reflects light is used as the reflecting member. However, the reflecting member is not limited to this, and any member that can effectively reflect the light from the illumination unit 6 can be used. Good.
[0051]
【The invention's effect】
As described above, the present invention provides a reflecting member composed of a flexible white sheet for reflecting light emitted from the illumination unit from the back side of the document when the document is read by the reading unit while conveying the document. Because of the provision, the light transmitted through the document is reflected in the direction of the image reading means, and the document is irradiated from the back side. Therefore, even when the image reading position of the flow reading varies, stable image reading with little change in the luminance of the image can be performed. The image reading position is set between the position just below the rotation center of the rotator and the tip of the reflecting member on the rotator side, and a position where the surface of the rotator is read by the reading means when the document is not being conveyed by the rotator. Therefore, when the document is not conveyed, the surface of the rotator can be read to perform dust detection processing, and the image reading position can be set while avoiding directly under the center of the rotator where adhesive dust is likely to adhere.
[Brief description of the drawings]
FIG. 1 is a detailed sectional view of a flow reading unit of an image reading apparatus according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of the image reading apparatus according to the first embodiment of the present invention.
FIG. 3 is a schematic diagram showing a luminance fluctuation preventing effect of the image reading apparatus according to the first embodiment of the present invention.
FIG. 4 is a graph showing a relationship between a scanning reading position and a white background luminance of the original in the image reading apparatus according to the first embodiment of the present invention.
FIG. 5 is a graph showing a relationship between a reading position for flow reading and a luminance of a white background portion of a document when a white sheet member is not provided.
FIG. 6 is a detailed cross-sectional view of a flow reading unit of the image reading apparatus according to the second embodiment of the present invention.
FIG. 7 is a schematic diagram illustrating a luminance fluctuation preventing effect of the image reading apparatus according to the second embodiment of the present invention.
FIG. 8 is a cross-sectional view of an image forming apparatus according to a third embodiment of the present invention.
FIG. 9 is a cross-sectional view of an image reading apparatus according to a conventional technique.
FIG. 10 is a schematic diagram showing luminance fluctuation factors of an image reading apparatus according to a conventional technique.
[Explanation of symbols]
A ... Image reading device B ... Image recording device C ... Image forming device 1 ... Image reading unit 2 ... ADF
3 ... Original plate glass 4 ... Flow-reading glass 5 ... Reading means 6 ... Illuminating means 7 ... Selfoc lens 8 ... Image sensor 9 ... Casing
10 ... Original place
11 a ... feed roller
11 b ~11f ... transport roller
12… Platen roller
13 ... Document output section
14 ... White pressure plate
15 ... Jump stand
16 White sheet material
17… Tip position
18… manuscript
21… Photoconductor drum
22… Charger
23… Exposure means
24… Developer
25… Transfer charger
26… Separate charger
27… cleaner
28 ... Conveying section
29… Fixer
30… discharge tray
31… Conveying roller

Claims (4)

A document conveying unit configured to convey a sheet-shaped document, a transparent member that supports the document at an image reading position, and a position facing the transparent member, and the document on the transparent member is irradiated with light from an illuminating unit, A reading unit that reads an image of the document at the image reading position; a rotating body that is provided at a position opposite to the illuminating unit and the reading unit so as to face the transparent member, and that conveys the document by rotating; The image reading position is detected when dust on the transparent member is detected based on reading of an image of the reading means while rotating the rotating body without conveying the document while conveying the document. In a movable image reading device,
When the original is read by the reading unit while the original is being conveyed, the light irradiated from the illumination unit is transmitted through the original, and the transmitted light is reflected from the back surface of the original. It has a reflective member that is a white sheet,
The reflecting member is attached to a guide member that forms an upstream sheet conveyance path with respect to a direction in which the rotating body conveys the document than directly below the rotation center of the rotating body,
The image reading position is between the position immediately below the rotation center of the rotating body and the tip of the reflecting member on the rotating body side, and when the original is not conveyed by the rotating body, the surface of the rotating body is the reading means. An image reading apparatus, wherein the image reading apparatus is set at a position to be read by.   The image reading apparatus according to claim 1, wherein the reflecting member is disposed in parallel with the transparent member.   The image reading apparatus according to claim 1, wherein the reflection member is disposed such that a distance from the transparent member increases as the distance from the transparent member decreases. An image forming apparatus that includes a document conveying unit that conveys a sheet-like document, and records information read by an image reading device that reads the document while conveying the document on a recording medium.
The image reading device according to any one of claims 1 to 3,
Image forming means for recording information read by the image reading device on the recording medium;
An image forming apparatus comprising:

Images