JP5219497B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a recording paper inspection apparatus for inspecting the surface of a recording paper on which an image is formed by an image forming apparatus.

  2. Description of the Related Art Conventionally, various apparatuses have been proposed for forming an image on recording paper by an image forming apparatus such as a printer or a copying machine, and determining the quality of image formation on the image-formed recording paper.

  For example, there has been proposed an image forming apparatus including an image reading unit disposed opposite to an image forming surface of a recording sheet downstream from the image forming unit of the image forming apparatus in the traveling direction of the recording sheet (for example, Patent Documents). 1). The quality of image formation is determined by comparing the inspection image data acquired by the image reading unit with the document image data. Further, based on the determination of whether image formation is good or not, the paper is sorted into a paper discharge tray and a disposal tray.

Also proposed is a configuration in which both sides of a recording sheet are inspected by reading the first side by the image reading unit after forming the first side image and reading the second side by the image reading unit after forming the second side image. (For example, refer to Patent Document 2).
JP 2005-205796 A JP 2005-208004 A

  However, what is proposed in Patent Documents 1 and 2 is intended to inspect the image formed image, and inspects the stain on the back surface of the image forming surface caused by an abnormality in the image forming apparatus. It was not considered to do. Therefore, when there is no problem on the image forming surface, there is a problem that even if the back surface is dirty, it is determined as a non-defective product. Further, what is proposed in Patent Document 2 is inspected on both sides, but if the back side becomes dirty during image formation on the second side, it is determined as a non-defective product.

  According to the present invention, there is provided an image forming unit that forms an image on a recording sheet based on input image data, a first surface of the recording sheet on which an image is formed by the image forming unit, and outputs first image data. A first reading unit; a second reading unit that reads a second surface of the recording paper on which an image is formed by the image forming unit; and outputs second image data; and the first surface is inspected based on the first image data. And an inspection means for inspecting the second surface based on the second image data. The inspection means, when the image forming means forms an image on the first surface of the recording paper, A test in which the image formed on the first surface is inspected based on the reference image data indicating the image formed on the first surface and the first image data, and the image is formed based on the second image data. Check for dirt on the second side of the paper When the image forming unit forms an image on the first surface and the second surface of the recording paper, the image forming unit is configured to perform the above operation based on the reference image data indicating the image formed on the first surface and the first image data. The image formed on the first surface is inspected, and the image formed on the second surface is inspected based on the reference image data indicating the image formed on the second surface and the second image data. It is characterized by that.

  According to the present invention, when an image is formed on one side, stains on the formed image and the back side can be inspected. When images are formed on both sides, the images formed on both sides can be inspected. In this way, it can be inspected that there are no defects on both sides of the recording paper that is the product.

  FIG. 1 is a cross-sectional view of a tandem type intermediate transfer type color image forming apparatus according to an embodiment of the present invention. The image forming apparatus according to the present embodiment includes a printer 100 and an inspection apparatus 200. The printer 100 is an electrophotographic laser beam printer using a contact charging method and a two-component contact development method.

  In the printer 100, four image forming stations Pa, Pb, Pc, and Pd are juxtaposed in series in the image feeding direction. Each of the image forming stations Pa, Pb, Pc, and Pd includes a photosensitive drum, a charging device, an exposure device, a developing device, a cleaning device, and a primary transfer device, which are image carriers.

  The developing devices at the image forming stations Pa, Pb, Pc, and Pd sequentially develop the latent images on the photosensitive drum with yellow, magenta, cyan, and black toners. The primary transfer device of each image forming station Pa, Pb, Pc, Pd transfers the toner image on the photosensitive drum onto the intermediate transfer belt 11. The recording paper P stored in the recording paper cassette 15 is transported to a secondary transfer unit comprising secondary transfer rollers 12 and 13. The toner image carried on the intermediate transfer belt 11 is secondarily transferred onto the recording paper P by the secondary transfer roller 13. The toner image on the recording paper P is fixed by the fixing device 9 by heating and pressing. The recording paper that has passed through the fixing device 9 is conveyed to the inspection device 200. These image forming operations are controlled by the control unit 17. A cleaning blade 14 for cleaning the secondary transfer residual toner and the like adhering to the surface of the intermediate transfer belt 11 is provided in contact with the downstream side of the intermediate transfer belt 11 from the secondary transfer position.

  The image-formed recording paper P discharged from the printer 100 is conveyed into the inspection apparatus 200. A recording paper conveyance path 27 in the inspection apparatus 200 is provided with a CIS (contact image sensor) unit 21 facing the image forming surface of the recording paper P and a CIS unit 22 facing the back surface. The CIS units 21 and 22 are reading units that read the front and back surfaces of the recording paper at the timing when the recording paper on which the image is formed passes the reading position. The control unit 26 determines the quality of the recording paper front and back surfaces based on the reading result. When the control unit 26 determines that the front and back surfaces of the recording paper are good, the recording paper transport path A is selected, and the recording paper P is discharged to the paper discharge tray 23. When a defect is confirmed on the front and back surfaces of the recording paper, the recording paper transport path B is selected and the recording paper P is transported to the escape tray 24. Switching of the recording paper conveyance path is performed by a deflection plate 25 provided at a branch point of the conveyance path. The deflection plate 25 is controlled by the control unit 26.

  Next, the CIS units 21 and 22 will be described. Since the CIS units 21 and 22 have the same configuration, the CIS unit 22 facing the back side of the recording paper will be described as a representative.

  FIG. 2 is a cross-sectional view of the CIS unit 22 as viewed from the front of the entire apparatus. The CIS unit 22 includes a CIS 221, a light source 222, and a lens array 223. As the light source 222, an LED, a xenon tube, or the like is used. In this embodiment, it is assumed that the recording paper is read to some extent at high speed, and a xenon tube two-light system that is considered to be able to earn the most light amount at present is adopted. The lens array 223 guides reflected light from the recording paper to the CIS 221.

  The recording paper detection sensor 228 detects the recording paper P. The reference white sheet 226 is used as a reference when adjusting the amount of light emitted from the light source 222 to the recording paper. The CIS 221 detects the amount of light reflected from the reference white sheet 226 and adjusts the light amount of the light source 222 when the recording paper is not inspected. The cover glass 225 covers the reference white sheet 226 so as not to be stained when the recording paper passes through the conveyance path. The reference white plate support member 227 is made of a high-density uniform member for attaching the white reference sheet 226. Further, the contamination detection of the recording paper passage portion of the CIS unit 22 is also performed at the same time. The dustproof sheet 224 is a transparent sheet for the CIS 221 and prevents dust from adhering to the surface of the lens array 223.

  FIG. 3 is a plan view of the CIS unit 22 when the CIS unit 22 is viewed from the recording paper surface. The light source 222 illuminates the recording paper P in the width direction (main scanning direction) of the recording paper P to be inspected, and the lens array 223 guides the reflected light from the recording paper P to the CIS 221. In this way, image detection in the entire area perpendicular to the traveling direction of the recording paper P can be performed.

  Next, recording paper reading by the CIS units 21 and 22 will be described. The CIS unit 21 reads the surface (image forming surface) of the recording paper P facing the CIS unit 21, and the CIS unit 22 reads the surface of the recording paper P facing the CIS unit 22 (back surface of the image forming surface). , Respectively, obtain inspection image data. Image reading by the CIS 221 in the CIS units 21 and 22 is performed based on an output from a recording paper detection sensor 228 provided immediately before the image reading position. The control unit 26 controls the start and end of reading based on the output from the recording paper detection sensor 228. In response to the leading edge of the recording paper reaching the image reading position, the CIS 221 performs image reading until the trailing edge of the recording paper passes the image reading position. The CIS 221 combines a plurality of line-shaped images obtained at this time, and outputs them to the control unit 26 as inspection image data. Then, the control unit 26 performs an inspection based on the inspection image data acquired by the CIS unit.

  The CIS units 21 and 22 may be provided anywhere as long as they are downstream of the fixing unit 9 in the recording paper traveling direction. However, it is desirable that the CIS units 21 and 22 be close to the fixing unit 9 in order to shorten the entire processing time. In addition, a device other than the CIS may be used for reading the image on the recording paper.

  FIG. 4 is a block diagram of the control unit 26. The control unit 26 includes a CPU 261, a RAM 262 used as a working memory, and a ROM 263 in which programs executed by the CPU 261 and various data are stored. The control unit 26 has an image signal I / F 264 for inputting image data read by the CIS units 21 and 22. The control unit 26 also has an I / O 265 for inputting a signal from the recording paper detection sensor 228 and outputting a signal to the deflection plate driving unit 251 that drives the deflection plate 25.

  Next, the inspection of the image forming surface and the back surface of the recording paper of this embodiment will be described. First, an image is formed on one side of the recording paper P by the printer 100. Thereafter, image data on the image forming surface of the recording paper P conveyed from the printer 100 to the inspection apparatus 200 is acquired by the CIS unit 21, and image data on the non-image forming surface is acquired by the CIS unit 22.

  Subsequently, the control unit 26 inspects the recording paper in response to an instruction from the control unit 17. The control unit 17 outputs various instructions to the printer 100 and controls the entire printer. When executing image formation, the control unit 17 instructs the recording paper to form an image based on the document image data input from the computer via the network or input using the scanner function of the printer. .

  The control unit 26 compares the inspection image data output from the CIS unit 21 with the original image data transmitted from the control unit 17 to determine whether the image formation result is acceptable. As a result of comparison and collation, when the difference amount between the two image data is small, it is determined as normal, and when the difference amount is large, it is determined as defective.

  In response to an instruction from the control unit 17, the control unit 26 performs a stain inspection on the non-image forming surface (the back surface of the image forming surface). Normally, in the case of single-sided image formation, the image data read by the CIS unit 22 must be in a blank sheet state. Therefore, the inspection on the non-image forming surface is performed by comparing the blank image data with the inspection image data acquired by the CIS unit 22 to determine whether there is image data such as dirt. Can do.

  First, the inspection image data of the non-image forming surface is acquired by the CIS unit 22. Next, the control unit 26 binarizes the inspection image data input from the CIS unit 22 with a predetermined threshold value. Subsequently, the presence / absence of a black portion having a predetermined area or more is detected in the inspection image data after binarization. Then, if there is an image (for example, a black portion) having a predetermined area or more, it is determined that there is dirt.

  Here, the threshold value at the time of binarization is set lower than the binarization threshold value at the time of inspection of the image forming surface so that it is converted into black data even if it is a low density (high luminance) stain. It is desirable to do. In addition, it is desirable to set a permissible width for comparison and collation when inspecting a non-image forming surface to be narrower than that when inspecting an image forming surface. By setting such a threshold value, even a low density and small area stain can be detected with high accuracy as a stain on the recording paper.

  When the control unit 26 determines that the non-image forming surface is dirty, the deflection plate driving unit 251 is controlled so that the recording paper P is conveyed to the escape tray 24 at the position of the deflection plate 25. At the same time, the inspection result is output to the control unit 17.

  The following are possible causes of the smudge on the non-image forming surface of the single-sided recording paper. The secondary transfer roller 13, the fixing roller 92, and the recording paper P are transported to the transport path of the recording paper P in the intermediate transfer type printer 100 including the intermediate transfer belt 11 so as to face the back surface of the recording paper P. There are a plurality of conveying rollers for the purpose.

  Here, when fog toner or scattered toner adheres to the intermediate transfer belt 11 and there is no recording paper on the secondary transfer roller 13, these adhere directly to the secondary transfer roller 13 and become dirty. There is. Further, when a paper jam occurs during the conveyance of the recording paper P to the secondary transfer roller 13, the toner image to be transferred to the recording paper P is directly transferred to the secondary transfer roller 13. Further, when the cleaning of the intermediate transfer belt 11 with the cleaning blade 14 is insufficient, the toner that has passed through the cleaning blade 14 not only contaminates the image forming surface of the recording paper P but also the secondary transfer roller 13. There is.

  Further, when the toner on the recording paper P is fixed by the fixing device 9, the toner that has adhered to the fixing roller 91 may adhere to the fixing roller 92 without being sufficiently cleaned. Further, when forming a double-sided image, the fixing roller 92 comes into contact with the fixed toner surface on the first side, but at that time, the toner may adhere to the fixing roller 92. As described above, when the toner adheres to the member that contacts the back surface of the recording paper, the toner adheres to the back surface of the recording paper that is transported thereafter, and the back surface of the recording paper becomes dirty.

  Among these causes of backside contamination, in the case of a paper jam in the recording paper conveyance path, the toner adhering to the secondary transfer roller 13 decreases as it is transferred to the subsequent recording paper. However, when the intermediate transfer belt 11 is poorly cleaned or the developer charging ability is reduced due to a large amount of image forming operation and fogging of the white background or toner scattering occurs, the secondary transfer roller 13 is constantly charged with toner. Will stick. In such a case, there is a high possibility that the backside stains are continuously generated. In such a case, the non-defective rate of the recording paper by the inspection in the inspection apparatus 200 is reduced, and the toner may be carried to an undesired place of the image forming apparatus.

  FIG. 5 is a flowchart executed by the control unit 26 relating to the image forming surface inspection during the single-sided image formation in the present embodiment. When the image-formed recording paper is conveyed to the inspection apparatus 200, the control unit 26 causes the CIS unit 21 to read image data on the image forming surface of the recording paper (S1). Next, the control unit 26 determines (determines) whether the difference between the read image data and the document image data is larger than a threshold (S2). If it is larger than the threshold value, the control unit 26 determines whether the image inspection is good or bad (NG), and increments the NG page counter C by 1 (S3).

  Next, the control unit 26 determines whether or not the value of the NG page counter C is 5 or more (S4). When it is determined that C is 5 or more, the control unit 26 instructs the control unit 17 to stop the image forming job of the printer 100 (S5). In addition, the control unit 26 instructs the control unit 17 to display on the operation unit of the image forming apparatus 100 to stop the operation by the image inspection (S6). In step S2, if it is equal to or less than the threshold value, the control unit 26 determines whether the image inspection is good or not, and clears the NG page counter C to zero (S7). In this way, when it is determined that a predetermined number of sheets are consecutively NG in the image inspection of the image forming surface of the recording paper, the operation of the printer is stopped and the user is instructed to confirm the cause of the image defect.

  Next, when it is determined that the image inspection is OK, or when the NG page counter C is less than 5, the control unit 26 backs up the value of the NG page counter (S8), and detects the pass / fail result of the image inspection. Save in the buffer (S9). The detection history buffer stores pass / fail results of the past 50 image inspections. When an image inspection of a new recording sheet is performed, the previous 50 sheets of data are erased. Then, it is determined whether the ratio determined as NG in the past 50 image inspection results is 30% or more (S10). When it is determined that it is 30% or more, the control unit 26 proceeds to step 5 and performs the above-described control. When it is determined in step S10 that the image forming job is smaller than 30%, the control unit 26 confirms whether the image forming job by the printer 100 is completed (S11). If the image forming job continues, the control unit 26 returns to step S1. In this way, even when 30% or more of the past 50 sheet inspection histories are determined to be NG in the recording sheet image inspection, the operation of the printer is stopped and the cause is confirmed by the user.

  FIG. 6 is a flowchart executed by the control unit 26 relating to the inspection of the non-image forming surface in the present embodiment. When the image-formed recording paper is conveyed to the inspection apparatus 200, the control unit 26 causes the CIS unit 22 to read image data on the back side of the recording paper (S21). Next, the control unit 26 determines whether or not the image data read by the CIS unit 22 is larger than a stain detection threshold (S22). If it is larger than the threshold value, the control unit 26 determines that the stain quality is NG and increments the dirty page counter D by 1 (S23).

  Next, the control unit 26 determines whether or not the value of the dirty page counter D is 5 or more (S24). If it is determined that D is 5 or more, the control unit 26 instructs the control unit 17 to stop the image forming job of the printer 100 (S25). In addition, the control unit 26 instructs the control unit 17 to display on the operation unit or the like that the operation is stopped due to the dirt inspection (S26). In step S22, when it is smaller than the stain detection threshold value, the control unit 26 determines whether the stain is good or not, and clears the dirty page counter D to zero (S27). In this way, when it is determined that the predetermined number of sheets are NG in the stain inspection on the non-image forming surface, the operation of the printer is stopped and the operation unit is caused to display the cause of the stain to the user. Prompt for confirmation.

  Next, when it is determined to be OK in the back dirt inspection, or when the dirty page counter D is less than 5, the control unit 26 backs up the value of the dirty page counter (S28), and detects the result of the dirt inspection. Save in the history buffer (S29). The detection history buffer stores pass / fail results of the past 50 sheets of dirt inspection. When a new recording sheet is inspected for dirt, the previous 50 sheets of data are erased. Then, it is determined whether or not the ratio at which the stain is judged as NG in the past 50 stain inspection results is 20% or more (S30). When it is determined that it is 20% or more, the control unit 26 proceeds to step S25 and performs the above-described control. When it is determined in step S30 that the image forming job is smaller than 20%, the control unit 26 confirms whether the image forming job by the printer is completed (S31). If the image forming job continues, the control unit 26 returns to step S21. In this way, even when 20% or more is judged NG in the inspection history of the past 50 sheets in the recording paper contamination inspection, the operation of the printer is stopped and the cause of contamination on the non-image forming surface is determined by the user. Instructed to confirm.

  The above control is executed every time the recording paper on which an image is formed is conveyed from the printer 100 to the inspection device 200 and arrives at the detection position of the CIS units 21 and 22. As a result, high-precision image inspection and stain inspection can be performed on the image forming surface and non-image forming surface of single-sided recording paper, and high-quality recording paper can be output. Also, it is possible to determine whether the problem causing the image defect or smudge is accidental or steady, stop the image forming operation of the printer, and instruct the resolution of the cause of the image defect or smudge. Recording paper can be reduced, and loss of image formation efficiency can be reduced.

  In the present embodiment, the image forming apparatus configured by the printer 100 and the inspection apparatus 200 is shown as an example, but the present invention is not limited to this. For example, the same effect can be obtained even when a recording paper inspection device for inspecting the image forming surface and the non-image forming surface of the recording paper is provided in the printer 100 downstream of the fixing device 9 in the recording paper conveyance direction. .

(Embodiment 2)
Next, Embodiment 2 will be described. In the first embodiment, the image inspection on the image forming surface of the single-sided recording paper and the stain inspection on the non-image forming surface are performed. On the other hand, in the second embodiment, image formation image inspection is performed on the second and second sides of the double-sided recording sheet conveyed from the printer. Since the configuration of the printer and the inspection device is the same as that of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  The operation of double-sided image formation by the printer 100 of this embodiment will be described with reference to FIG. Since the image formation on the first side of the double-sided recording paper is the same as in the first embodiment, description thereof is omitted. The recording paper P that has passed through the fixing device 9 is sent to the recording paper conveyance path C, conveyed to the double-side reversing path 16, and then the conveyance direction is switched, so that the front and back surfaces of the recording paper P are reversed. Then, the recording paper P is conveyed again to the secondary transfer rollers 12 and 13, and the toner image formed on the second surface is secondarily transferred to the back surface of the recording paper P and fixed by the fixing device 9. The recording paper P with images formed on both sides is sent to the recording paper transport path D and transported to the inspection apparatus 200.

  The inspection apparatus 200 includes a CIS unit 21 that faces the second side of both sides of the double-sided recording paper and a CIS unit 22 that faces the first side of both sides. Since the detailed configuration of the CIS units 21 and 22 is the same as that of the first embodiment, the description thereof is omitted. When the recording paper P on which both sides of the image are formed is transported to the image reading position of the CIS units 21 and 22, the inspection image data on the second side on both sides is transferred by the CIS unit 21, and the inspection image data on the first side on both sides is supplied by the CIS unit 22. To get. Subsequently, the control unit 26 inspects the recording paper in accordance with an instruction from the control unit 17.

  When the recording paper is inspected, the control unit 26 compares the inspection image data output from the CIS units 21 and 22 with the previously stored document image data to determine whether the image formation result is good or bad. . The document image data is input from the image forming control unit. As a result of comparison and collation, when the difference amount between the two image data is small, it is determined as normal, and when the difference amount is large, it is determined as defective. Then, the obtained inspection result is output to the control unit 17. When the control unit 26 determines that the image formation result of the double-sided recording paper is a non-defective product, the recording paper transport path A is selected, and the recording paper P is discharged to the paper discharge tray 23.

  If it is determined that at least one of the image formation results on the first and second sides of the double-sided surface is defective, the recording paper conveyance path B is selected, the recording paper P is conveyed to the escape tray 24, and the inspection result is It is output to the control unit 26. Then, another recording sheet P is fed again to form a double-sided image.

  Also in this embodiment, the control unit 26 performs the control shown in the flowchart of FIG. 5 for the image inspection on the first and second sides of both sides.

  As described above, high-quality double-sided recording paper can be obtained by inspecting the recording paper on the second side of both sides when the double-sided image is formed by the CIS unit 21 and inspecting the recording paper on the first side of both sides by the CIS unit 22. Can do.

  In addition, since the inspection of double-sided recording paper after image formation on both sides of the recording paper is inspected by one image reading by two CIS units, the adhesion of dirt on the transparent dustproof sheet 224 and cover glass 225 of the CIS unit is reduced. can do. Further, the inspection condition by the inspection apparatus 200 and the printer stop condition may be changed between the inspection of the recording paper and the contamination inspection.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure of a CIS unit. It is a top view of a CIS unit. 3 is a block diagram of a control unit 26. FIG. It is a flowchart regarding an image forming surface inspection. It is a flowchart regarding a non-image forming surface inspection.

Explanation of symbols

13 Secondary transfer roller 17 Control unit 21, 22 CIS unit 23 Paper discharge tray 24 Escape tray 25 Deflection plate 26 Control unit 92 Fixing roller 100 Printer 200 Inspection device

Claims (3)

Image forming means for forming an image on recording paper based on the input image data;
A first reading unit that reads a first surface of a recording sheet on which an image is formed by the image forming unit and outputs first image data;
A second reading means for reading a second surface of the recording paper on which an image is formed by the image forming means and outputting second image data;
Inspection means for inspecting the first surface based on the first image data and inspecting the second surface based on the second image data;
The inspection means includes
When the image forming unit forms an image on the first surface of the recording paper, the image forming unit is formed on the first surface based on the reference image data indicating the image formed on the first surface and the first image data. And inspecting the second surface of the recording paper on which the image is formed based on the second image data,
When the image forming unit forms an image on the first surface and the second surface of the recording paper, the first image data is based on the reference image data indicating the image formed on the first surface and the first image data. Inspecting the image formed on the surface, and inspecting the image formed on the second surface based on the reference image data indicating the image formed on the second surface and the second image data. An image forming apparatus.   The image forming apparatus according to claim 1, wherein if the predetermined number of consecutive failures are determined by the inspection unit, image formation is stopped and the user is notified.   3. The image forming apparatus according to claim 1, wherein image formation is stopped when a rejection rate of the inspection result by the inspection unit is higher than a predetermined rate.

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