JP2005159482A - Image scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image scanner capable of obtaining a good quality image through a simple arrangement. <P>SOLUTION: The document reader comprises a means (carrying pair roller) 21, 23 for carrying a document toward a document reading section 9, a section (contact type image sensor) 4 for reading the document at the document reading section 9, and a white reference plate 7 becoming a white reference at the time of reading the document and retaining the document on the document reading section 9 wherein the white reference plate 7 is provided with a means 25 for regulating the retaining force of the document. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to an image reading apparatus.

  In general, an image reading apparatus receives reflected light by applying light to a white reference plate disposed at a position opposite to a reading unit in a reading unit of a document, and shading data serving as a reference for white density and density unevenness at the time of reading the document. The white reference is determined based on such data, and shading correction is performed. Further, the white reference plate is pressed against the original surface by the pressing force of the spring, thereby preventing the original from floating from the reading surface.

  However, when the original is transported while pressing the original against the reading surface with the white reference plate, the white reference plate is scratched due to friction between the original and the white reference plate, or the toner on the back side of the original adheres to the white reference plate. There has been a problem that the reference plate is contaminated, and the image quality is deteriorated because appropriate shading data cannot be obtained.

  In order to solve this problem, in the prior art described in Patent Document 1, the surface of the white reference plate is covered with a transparent member, and the white reference plate is pressed against the document surface by the pressing force of the spring.

  On the other hand, in the prior art described in Patent Document 2, a white reference plate elevator is provided in the document reading unit, and when acquiring shading data, the white reference plate is lowered and brought into close contact with the contact glass. The white reference plate is retracted upward.

Japanese Patent Laid-Open No. 9-270884 JP 2002-359931 A

  However, in the prior art described in Patent Document 1 described above, the white reference plate has a constant pressing force against the original surface. Therefore, when a special original such as a thick original or a folded original is conveyed, The bent portion or the mountain folded portion hits the white reference plate, and the white reference plate is pushed upward. In this case, there is a problem that the distance between the white reference plate and the reading surface of the document is not constant, and appropriate shading data cannot be obtained, resulting in deterioration of image quality.

  Further, the prior art described in Patent Document 2 has a problem that the white reference plate elevator requires a separate drive device such as an electromagnetic clutch, and the configuration becomes complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that has a simple configuration and can obtain a high quality image.

  In order to solve the above-mentioned problem, the invention described in claim 1 includes a conveying unit that conveys an original toward the original reading unit, a reading unit that reads the original in the original reading unit, and a white at the time of reading the original. And a white reference plate that serves as a reference and presses the document on the document reading unit, and the white reference plate is provided with adjusting means for adjusting a pressing force on the document.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the white reference plate is obtained by applying white coating to an extruded mold member made of aluminum alloy.

  According to a third aspect of the present invention, in the invention according to the first or second aspect, the image reading apparatus includes an operation member that switches a pressing force of the white reference plate against the document, and the pressing force is determined by operating the operating member. Can be switched to a plurality of stages.

  The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the pressing force of the white reference plate against the document is 28 N or less.

  According to the first aspect of the present invention, since the white reference plate is provided with the adjusting means for adjusting the pressing force on the original, the pressing force of the white reference plate on the original can be adjusted according to the type of original used. Therefore, in the case of special originals such as thick originals and folded originals other than normal originals, the white reference plate is pushed against the mountain folds of the original by increasing the pressing force of the white reference plate against the original. It can be prevented from moving upward. Therefore, a good image quality can be obtained by keeping the distance between the white reference plate and the original reading surface constant and performing optimum reading. Here, the normal document means a document other than a special document such as a thick document or a folded document.

  According to the invention described in claim 2, the same effect as that of the invention described in claim 1 can be obtained, and the white reference plate is made of an extruded material made of an aluminum alloy, so that high rigidity is ensured. It is possible to prevent the deflection due to the white reference plate being pushed by the document. Therefore, the original can be surely pressed and the optimum original can be read.

  According to the invention described in claim 3, the same effect as that of the invention described in claim 1 or 2 can be obtained and the pressing force of the white reference plate can be switched by the operation member. Simple.

  According to the fourth aspect of the present invention, the same effect as that of any one of the first to third aspects can be obtained, and the pressing force of the white reference plate against the original should be 28 N or less. Thus, appropriate image reading can be performed not only for a normal document but also for a special paper such as a folded document.

The maximum pressing force of the white reference plate against the original was set to 28 N. As a result of the experiment, the folded portion of the original folded from a thick paper (1 mm: basis weight 135 g / m ² ) of A1Y width (841 mm) which is the maximum paper width. This is because the force required to hold the crest formed by opening the flat is flat (0.3 mm or less) is 20N, and the white weight 8N of the white reference plate is added to this force.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an image reading unit of the image forming apparatus illustrated in FIG. 3, and is a cross-sectional view illustrating a normal document being conveyed. FIG. 2 is a diagram illustrating an image reading unit of the image forming apparatus illustrated in FIG. FIG. 3 is a cross-sectional view of the image forming apparatus according to the present embodiment.

  As shown in FIG. 3, the image forming apparatus 1 according to the present embodiment includes an image forming unit 10 in the main body of the image forming apparatus, and the image forming unit 10 has a drum-shaped image carrier (photosensitive member). 11, a charging device 12, a developing device 13, a cleaning device 15 and the like are provided around it.

  A fixing device 17 is provided at a position downstream of the image forming unit 10. The fixing device 17 is provided with a fixing roller incorporating a heater and a pressure roller that presses the fixing roller from below.

  A roll-shaped paper feed unit 21 is provided below the image forming unit 10 and is conveyed to the upper image forming unit 10 at a predetermined timing. A paper tray 6 is provided at the lower part of the apparatus main body, and a document on which image formation has been performed in the image forming unit 10 passes through a pair of discharge rollers and is discharged outside the machine, and descends on the rear side of the machine. Are accommodated in the paper tray 6.

  An image reading unit (image reading device) 19 for reading a document is provided on the upper part of the image forming unit 10. The image reading unit 19 includes a contact image sensor unit (reading unit) 4 provided in the document reading unit 9 of the document and a white reference when reading the document at a position opposite to the document conveyance path of the contact image sensor unit 4. And a white reference plate 7 for pressing the document. Further, an adjusting means 25 for adjusting the pressing force of the white reference plate 7 against the document is provided above the white reference plate 7. Further, conveyance roller pairs (conveying means) 21 and 23 for conveying the document toward the front side or the rear side of the machine are provided at the front and rear positions of the contact image sensor unit 4 on the document conveyance path.

  The contact image sensor unit 4 has a contact glass 5 attached to the upper surface thereof, and irradiates light on a document conveyed to a reading position on the contact glass 5 and photoelectrically converts the reflected light to convert the document. An image on the surface (original surface) on the side of the contact glass 5 is read.

  The white reference plate 7 is white coated on an extruded mold member made of an aluminum alloy, and the white reference plate 7 is held by a holding portion 27 having a substantially rectangular parallelepiped shape. Further, a long hole 29 is formed at both ends of the holding portion 27, and the shaft 31 suspended from the document transport cover 33 is locked in the long hole 29, and the holding portion 27 is disposed at a predetermined position. Has been. In this manner, the holding portion 27 is locked at a predetermined position, so that a certain gap is formed in the document conveyance path between the white reference plate 7 and the contact glass 5.

  Further, a compression spring 35 is provided on the upper portion of the holding portion 27, and the receiving member 34 fixed to the upper end of the compression spring 35 receives a force to urge the compression spring 35 so that the white reference plate 7 is moved upward. It is designed to be pressed down strongly.

  The adjusting unit 25 includes left and right levers (operation members) 37 positioned above the document transport cover 33 and a bracket 39 that applies a force to the receiving member 34 in response to the operation of the levers. The bracket 39 is attached to the same fixing plate 41.

  The lever 37 includes a rotation shaft 43 rotatably attached to the fixed plate 41, a knob portion 45 that operates the lever 37, and a movable portion 47 that moves in the front-rear direction by the operation of the knob portion 45. I have. A bracket 39 provided below the fixed plate 41 is wound around a rotary shaft 49 that is rotatably attached to the fixed plate 41 and a rotary shaft 49 that biases the bracket 39 upward. And a pressing plate 53 that moves downward against the urging force of the spring 51 and contacts the receiving member 34. In addition, the bracket 39 is provided with an inclined portion 55 that is inclined obliquely upward toward the front of the machine, and a recessed portion 57 that is formed at an upper position of the inclined portion 55. By moving the knob portion 45 from the position shown in FIG. 1 to the front side of the machine, the movable portion 47 rises along the inclined portion 55 and the bracket 39 is pushed downward. Then, when the movable portion 47 is engaged with the recessed portion 57, the pressing plate 53 presses the compression spring 35, and a constant pressing force acts on the white reference plate 7. In the present embodiment, the pressing force of the white reference plate 7 against the document is 28N. On the other hand, by moving the knob portion 45 from the state of FIG. 2 to the rear side of the machine, the movable portion 47 comes off from the recessed portion 57 and returns to the state of FIG.

In the present embodiment, the pressing force of the white reference plate 7 against the document is 28N. However, the pressing force is not limited to this, and the compression spring 35 is changed to be within a range of 0 to 28N (preferably 3 to 28N). It can be changed freely. The pressing force of the white reference plate 7 is set to 28 N when a thick original (1 mm: basis weight 135 g / m ² ) having an A1Y width (841 mm) is folded in half and then the original is placed on the contact glass 5. This is because the force required to hold the mountain folded portion formed by opening the document flat (less than 0.3 mm) is about 20 N, and the weight 8 N of the white reference plate 7 is added to this force. The pressing force required for thick paper having an A1Y width (841 mm) is about 20 N. However, the required pressing force differs depending on the original size, and for example, about 14 N for a thick paper original having an A2Y width (594 mm). Similarly, it is about 10 N for a thick paper document with an A3Y width (420 mm), and about 7 N for a thick paper document with an A4Y width (297 mm).

  Further, when special paper such as a thick original or a folded original is not used, it is not necessary to apply a load to the white reference plate 7 that holds the original.

  Next, the operation of the image reading unit according to this embodiment will be described. In the image reading unit 19, the document inserted from the front side of the machine is conveyed to the document reading unit 9 by the conveyance roller pair 21. In the document reading unit 9, the document conveyed to the reading position on the contact glass 5 is irradiated with light from the contact image sensor unit 4, and the reflected light is photoelectrically converted, whereby the surface on the contact glass 5 side of the document ( The image on the original surface is read. Then, based on the document data read by the image reading unit 19, an image is formed in the image forming unit 10, passes through a pair of discharge rollers and is discharged to the outside of the machine, descends on the rear side of the machine, and moves into the paper tray 6. It is stored in.

  Next, the switching operation of the pressing force of the white reference plate for the document will be described. When reading a normal document (a document that is not a thick paper or a folded document), as shown in FIG. The white reference plate 7 is not subjected to a load. In this case, when a normal document passes through the document reading unit 9, the white reference plate 7 is hardly pushed upward, so that the document can be optimally read, and a high quality image can be obtained.

  On the other hand, when reading thick paper or a folded document, the position of the knob portion 45 of the lever 37 is changed from the rear side of the machine as shown in FIG. 1, and the position of the knob portion 45 of the lever 37 is changed to the machine position as shown in FIG. Set to the front side. At this time, the compression spring 35 in the holding portion 27 of the white reference plate 7 is pressed by the pressing plate 53, and a constant load (28N) is applied to the white reference plate 7. In this way, when a certain pressing force is applied to the white reference plate 7, for example, when the document to be conveyed is a folded document, the white reference plate 7 is pushed upward at a folded portion of the document that can be opened. Can be prevented, and appropriate image reading can be performed.

  Further, since the white reference plate 7 is made of an extruded material made of an aluminum alloy, high rigidity can be ensured, and deflection can be prevented from being caused by the white reference plate 7 being pushed by a document. Therefore, the original can be surely pressed and the optimum original can be read.

  Since the switching of the pressing force of the white reference plate 7 can be performed by lever operation, the configuration is simple and the switching of the pressing force is easy.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. In the above-described embodiment, the contact type image sensor unit 4 is used as the reading unit. However, the present invention is not limited to this. For example, a reduction optical system may be used.

FIG. 4 is a diagram illustrating an image reading device of the image forming apparatus illustrated in FIG. 3, and is a cross-sectional view illustrating a normal document during conveyance. FIG. 2 is a diagram illustrating an image reading unit of the image forming apparatus illustrated in FIG. 1, and a cross-sectional view illustrating a state during conveyance of a special document such as a folded document. 1 is a cross-sectional view of an image forming apparatus according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Reading means (contact image sensor part)
7 White reference plate 9 Document reading unit 21, 23 Conveying means (conveying roller pair)
25 Adjustment means 37 Operation member (lever)

Claims (4)

  A conveying unit that conveys the document toward the document reading unit, a reading unit that reads the document in the document reading unit, and a white reference plate that serves as a white reference when reading the document and presses the document on the document reading unit, An image reading apparatus, wherein the white reference plate is provided with adjusting means for adjusting a pressing force on the original.   2. The image reading apparatus according to claim 1, wherein the white reference plate is white coated on an extruded die made of an aluminum alloy.   The image reading apparatus according to claim 1, wherein the image reading apparatus includes an operation member that switches a pressing force of the white reference plate with respect to the document, and the pressing force can be switched in a plurality of stages by operating the operation member. Reader. The image reading apparatus according to claim 1, wherein the pressing force of the white reference plate against the document is 28 N or less.

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