Image formation device and conveyance control method

Abstract

To provide an image formation device and a conveyance control method that can prevent occurrence of periodic image abnormality.SOLUTION: An image formation device which forms an image on each of a plurality of recording media being continuously conveyed, includes: a detection unit for detecting periodic image abnormalities on recording media based on scanned information for the recording media with images formed thereon, and a conveyance control unit for controlling conveyance of each of the recording media according to the result of detection by the detection unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a transport control method. [Background technology]

[0002] Conventionally, in image forming apparatuses, there are known techniques for suppressing the occurrence of image abnormalities such as density unevenness when such abnormalities occur. For example, Patent Document 1 discloses a configuration for suppressing the occurrence of density unevenness by correcting the image density through image processing in response to density unevenness that occurs due to periodic changes in the distance between the photosensitive drum and the developing device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-63298 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, image abnormalities include those that occur periodically due to rotational fluctuations of the drive source, etc. Since the range of fluctuations of such periodic image abnormalities is difficult to accurately predict, it is difficult to correct the image density, which in turn causes the problem of worsening density fluctuations.

[0005] An object of the present invention is to provide an image forming apparatus and a transport control method that can prevent periodic image abnormalities from occurring. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention comprises: An image forming apparatus that forms an image on each of a plurality of recording media that are continuously conveyed, a detection unit that detects periodic image abnormalities on a recording medium based on read information of the recording medium on which an image is formed; a conveyance control unit that controls conveyance of each recording medium based on the detection result of the detection unit; Equipped with.

[0007] The transport control method according to the present invention comprises: 1. A method for controlling conveyance of an image forming apparatus that forms an image on each of a plurality of recording media that are continuously conveyed, comprising: Detecting periodic image abnormalities on the recording medium based on read information of the recording medium on which an image is formed; Controlling the conveyance of each recording medium based on the detection results; It has. [Effects of the Invention]

[0008] According to the present invention, it is possible to avoid the occurrence of periodic image abnormalities. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an image forming system including an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing the configuration of a control unit. [Figure 3] FIG. 10 is a diagram illustrating an example of the occurrence of periodic image abnormalities. [Figure 4] 10A and 10B are diagrams for explaining an example of control for positioning an image abnormality between recording media; [Figure 5] 10A and 10B are diagrams for explaining an example of control for positioning an image abnormality between recording media; [Figure 6] 10 is a flowchart illustrating an example of a transport control operation in the transport control unit. [Figure 7] 10A and 10B are diagrams for explaining an example of control for positioning an image abnormality at a predetermined image position. [Figure 8] 10 is a flowchart illustrating an example of a transport control operation in the transport control unit. [Figure 9] FIG. 10 is a diagram showing an example in which the occurrence cycle of periodic image abnormalities is within a predetermined length. [Figure 10] 10 is a flowchart illustrating an example of a transport control operation in the transport control unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Fig. 1 is a block diagram showing an image forming system 1 including an image forming apparatus according to an embodiment of the present invention.

[0011] 1, the image forming system 1 is a system that can read an image formed on a recording medium (described later) and change the transport settings of the recording medium in accordance with the read information of the read recording medium to form an image. The image forming system 1 has a paper feeder 10, an image forming device 20, and a reader 30.

[0012] The paper feed device 10 has, for example, multiple paper feed units inside, and feeds recording media one by one to the image forming device 20. The paper feed units store recording media identified based on basis weight, size, etc.

[0013] The image forming apparatus 20 is, for example, an intermediate transfer type color image forming apparatus that uses electrophotographic process technology. Specifically, the image forming apparatus 20 primarily transfers toner images of each color (Yellow, M, C, and K) formed on a photosensitive drum onto an intermediate transfer belt, and then superimposes the four color toner images on the intermediate transfer belt, and then secondarily transfers the images onto paper S sent from a paper feed tray unit, thereby forming an image. Note that the image forming apparatus 20 may be an image forming apparatus other than an intermediate transfer type.

[0014] The image forming apparatus 20 includes an image forming section 21, a fixing section 22, a conveying section 23, a control section 24, and the like.

[0015] The control unit 24 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The CPU reads out a program corresponding to the processing content from the ROM, loads it into the RAM, and centrally controls the operations of each block of the image forming apparatus 20 in cooperation with the loaded program.

[0016] The image forming unit 21 forms an image (toner image) on the recording medium fed from the paper feed device 10. The image forming unit 21 has image forming units for forming images using color toners of Y, M, C, and K components, an intermediate transfer unit, and the like.

[0017] The fixing unit 22 fixes the toner image onto the recording medium by applying heat and pressure to the recording medium, onto which the toner image has been transferred, in a fixing nip.

[0018] The conveying unit 23 includes a conveying path, a paper discharge unit, etc. The conveying path includes a plurality of conveying roller pairs such as a registration roller pair, and a normal conveying path that passes the recording medium through the image forming unit 21 and the fixing unit 22 and discharges it outside the image forming apparatus 20.

[0019] The recording media housed in the paper feeder 10 are fed one by one from the top and transported to the image forming device 20. The recording media transported to the image forming device 20 are transported to the image forming unit 21 by a transport path unit. In the image forming unit 21, the toner images on the intermediate transfer belt are secondarily transferred all at once onto one side of the recording media, and a fixing process is carried out in the fixing unit 22. The recording media on which the image has been formed are discharged outside the machine by a paper discharge unit equipped with paper discharge rollers, and transported to the reading device 30.

[0020] The reading device 30 is a device for reading a recording medium on which an image has been formed, and has a reading unit 31. The reading device 30 is provided with a transport path 30A connected to the paper discharge port of the image forming device 20. The reading unit 31 is, for example, a scanner, and is arranged so as to be able to read information on the recording medium transported on the transport path 30A. The information on the recording medium is information on the image formed on the recording medium, etc.

[0021] The reading device 30 feeds back the read information of the recording medium read by the reading unit 31 to the image forming device 20 via a communication unit (not shown). As a result, the control unit 24 of the image forming device 20 controls the transport between each of the multiple recording media that are continuously transported, in accordance with the read information of the recording media.

[0022] Next, a detailed description will be given of the control of conveyance by the control unit 24. Fig. 2 is a block diagram showing the configuration of the control unit 24.

[0023] 2, the control unit 24 includes a detection unit 241 and a transport control unit 242. Note that in FIG. 2, configurations showing control of image forming operations and the like are omitted.

[0024] The detection unit 241 detects periodic image abnormalities on the recording medium based on read information of the recording medium on which an image is formed. Specifically, the detection unit 241 performs image analysis based on the read information of the recording medium. For example, the detection unit 241 calculates the difference in each luminance value between image information based on the read information and information of a normal image, and extracts the difference value for each position in the transport direction of the recording medium.

[0025] Periodic image abnormalities are image abnormalities that occur periodically, for example, when a recording medium passes through the image forming unit 21 during image formation. For example, vibrations caused when a recording medium passes the transfer position of the intermediate transfer belt are transmitted to the contact area between the intermediate transfer belt and the photosensitive drum, causing temporary fluctuations in pressure at the contact area. This temporary pressure fluctuation causes color fluctuations (uneven density) in part of the image, resulting in periodic image abnormalities.

[0026] A normal image is an image in which no periodic image abnormalities occur, and may be information read by the reading unit 31, or may be information on image data such as a RIP image. Note that the detection unit 241 may detect an image abnormality, for example, on an image based on a solid image, or on an image based on image data of a print job. In this embodiment, image abnormality is detected on an image based on a solid image.

[0027] When the detection unit 241 confirms that a location where the difference value for each position in the conveyance direction of the recording medium is greater than a threshold value (which can be set arbitrarily) occurs periodically, it detects the location as a periodic image abnormality.

[0028] For example, suppose that when image formation is performed by continuously conveying multiple recording media set at a fixed conveying interval, it is confirmed from the read information that density unevenness occurs at regular intervals on each recording medium. In this case, the detection unit 241 detects the occurrence of periodic image abnormalities. Also, if the image forming unit 21 is provided with a sensor capable of monitoring the rotation speed of the photosensitive drum or the like, and the detection result of the sensor confirms that the rotation speed fluctuates periodically, the detection unit 241 detects the occurrence of periodic image abnormalities.

[0029] Figure 3 shows an example in which consecutively conveyed recording media P1, P2, and P3 are lined up in the conveyance direction, and density unevenness occurs in approximately the same location on each recording medium. In the example shown in Figure 3, a predetermined solid image is formed on each recording medium P1, P2, and P3, and two vertical lines of density unevenness occur on each recording medium. Also, below recording medium P1, the extracted results of the difference values ​​are shown, with the vertical axis representing the difference values ​​of each brightness value between the image information based on the read information and the information of the normal image, and the horizontal axis representing the position in the conveyance direction of recording medium P1.

[0030] The transport control unit 242 controls the transport of each recording medium based on the detection result of the detection unit 241. Specifically, the transport control unit 242 controls the transport of each recording medium so that the images formed on each recording medium are not affected by the periodic image abnormality based on the detection result of the detection unit 241. More specifically, the transport control unit 242 controls the transport of the recording media so that the position of the periodic image abnormality is located between the recording media.

[0031] In this way, for example, the conveyance of each recording medium S1, S2 is controlled so that the position of the image abnormality in the conveyance direction is located between the recording medium S1 and the recording medium S2, as shown in Fig. 4. The upper part of Fig. 4 shows an example of recording media P1, P2 in Fig. 3.

[0032] As a result, the periodic image abnormality is located between the recording medium S1 and the recording medium S2, and therefore the periodic image abnormality is not formed on the recording medium, thereby making it possible to avoid the occurrence of the periodic image abnormality.

[0033] Further, the conveyance control may be performed by adjusting the conveyance timing at the image transfer position in the image forming unit 21.

[0034] Specifically, the conveyance control may be performed by adjusting at least one of the timing of feeding the recording medium in the paper feed device 10 and the timing of registering the recording medium in the conveyance section 23 .

[0035] For example, if the position of the periodic image abnormality is near the leading edge of the recording medium, the conveyance control unit 242 delays at least one of the paper feed timing and registration timing of the first recording medium in the print job from the normal timing (for example, the initial setting timing, etc.). Also, if the position of the periodic image abnormality is near the trailing edge of the recording medium, the conveyance control unit 242 advances at least one of the paper feed timing and registration timing of the first recording medium in the print job from the normal timing. Also, for recording media other than the first in the print job, the conveyance control unit 242 may appropriately adjust at least one of the paper feed timing and registration timing in accordance with the conveyance control.

[0036] The paper feed timing may be used for coarse adjustment to adjust the transport interval to a relatively large value. The registration timing may be used for fine adjustment to adjust the transport interval to a relatively small value. The transport control unit 242 may control transport using both the paper feed timing and the registration timing, or may control transport using either the paper feed timing or the registration timing.

[0037] By doing so, it is possible to easily avoid the formation of periodic image abnormalities on the recording medium.

[0038] In addition, the transport control unit 242 controls the image formation position on each recording medium in accordance with the transport control. That is, the transport control unit 242 controls the image formation position on each recording medium so that it is a position different from the position of the periodic image abnormality.

[0039] In this way, the image that needs to be formed on the recording medium and the periodic image abnormality do not overlap, and the image can be formed on the recording medium in accordance with the transport control.

[0040] Furthermore, when controlling the conveyance, the conveyance control unit 242 may adjust the distance between successively conveyed recording media. For example, if the width for avoiding periodic image abnormalities is wider than the originally set distance between recording media, the range of periodic image abnormalities may overlap with each recording media unless the distance between recording media is adjusted.

[0041] 5 shows an example in which the range of the image abnormality is wider than the distance D1 between the recording media P1 and P2. In this case, even if the transport timing of the recording media S1 and S2 is shifted while maintaining the distance D1, there is a possibility that the range of the image abnormality will overlap with the recording media.

[0042] Therefore, the transport control unit 242 controls the transport by adjusting the distance between the successively transported recording media S1 and S2. The distance between the successively transported recording media is the distance in the transport direction between the first recording medium and the second recording medium transported after the first recording medium.

[0043] For example, the transport control unit 242 controls the transport so that the distance D2 between the recording medium S1 and the recording medium S2 is greater than the distance D1.

[0044] By doing so, it becomes easier to avoid the occurrence of periodic image abnormalities.

[0045] The detection unit 241 may detect an image abnormality before a print job, or at an appropriate timing during a print job.

[0046] An example of the operation of the conveyance interval control in the conveyance control unit 242 configured as above will be described. Fig. 6 is a flowchart showing an example of the operation of the conveyance interval control in the conveyance control unit 242. The flowchart shown in Fig. 6 is executed as appropriate when a job for detecting image abnormalities is input to the image forming apparatus 20.

[0047] 6, the transport control unit 242 acquires read information of the recording medium (step S101). After step S101, the transport control unit 242 determines whether or not a periodic image abnormality has been detected based on the acquired read information (step S102).

[0048] If the determination result shows that no periodic image abnormality has been detected (step S102, NO), this control ends.

[0049] On the other hand, if a periodic image abnormality is detected (step S102, YES), the transport control unit 242 controls the transport so that the image abnormality is located between the recording media (step S103). Specifically, the transport control unit 242 sets the transport timing so that the position of the periodic image abnormality is located between the recording media, and sets the image formation position on each recording medium according to that setting.

[0050] After step S103, this control ends. After this control, a print job is started, and the transport of the recording medium in the print job is controlled by the transport set in this control. Note that if it is determined in step S102 that no periodic image abnormality has been detected, the print job is started with the same settings as the job in the flowchart shown in FIG. 5.

[0051] According to the present embodiment configured as described above, the transport control unit 242 controls the transport of each recording medium so that the images formed on each recording medium are not affected by the periodic image abnormality based on the detection result of the detection unit 241. Specifically, the transport control unit 242 controls the transport so that the position of the periodic image abnormality is located between the recording media.

[0052] This makes it possible to avoid the occurrence of periodic image abnormalities.

[0053] Furthermore, by adjusting the distance between the first and second recording media in the transport direction, it is possible to more easily avoid the occurrence of periodic image abnormalities.

[0054] In the above embodiment, the transport control is performed by adjusting the distance between the first and second recording media in the transport direction, but the present invention is not limited to this. For example, the transport control may be performed by adjusting the transport speed of the recording media without adjusting the distance between the first and second recording media.

[0055] In the above embodiment, the transport is controlled so that the position of the periodic image abnormality is located at a position between the recording media, but the present invention is not limited to this. For example, the transport control unit 242 may control the transport so that the position of the image abnormality is located at a position corresponding to a predetermined image included in the image formed on the recording media.

[0056] The predetermined image is an image that is not easily affected by density unevenness, such as a text image.

[0057] The conveyance control unit 242 controls conveyance by, for example, adjusting the timing at which image formation starts on each recording medium so that the position of the image abnormality corresponds to a predetermined image.

[0058] By doing this, the position of the image abnormality formed on the recording medium will be a position corresponding to the predetermined image. For example, Figure 7 shows an example in which transport is controlled so that the predetermined image W is within the range of the image abnormality. This prevents the image formed on the recording medium from being affected by the periodic image abnormality, making it easier to prevent an image affected by the periodic image abnormality from being formed on the recording medium.

[0059] Furthermore, the predetermined image is not limited to a character image, and may be, for example, an image other than the specific color. The specific color is a color corresponding to a developing unit in which the rotation speed of a photosensitive drum or the like periodically fluctuates. For example, let us say that the color K among Y, M, C, and K corresponds to the specific color. In this case, the predetermined image may be an image composed of at least one of the colors Y, M, and C.

[0060] Images containing a specific color are prone to periodic image abnormalities due to fluctuations in rotation speed, so by positioning the periodic image abnormalities at positions corresponding to images other than the specific color, it is possible to more easily avoid periodic image abnormalities caused by the specific color.

[0061] An example of the operation of transport control will be described with reference to the example shown in Fig. 7. Fig. 8 is a flowchart showing an example of the operation of transport control in the transport control unit 242. Note that steps S101, S102, and S103 in Fig. 8 are the same as steps S101, S102, and S103 in Fig. 6.

[0062] 8, after determining YES in step S102, the conveyance control unit 242 determines whether the image of the print job includes a predetermined image (step S104). If the determination result shows that the image of the print job does not include a predetermined image (step S104, NO), the process proceeds to step S103.

[0063] On the other hand, if the image of the print job includes a predetermined image (step S104, YES), the transport control unit 242 controls the transport so that the position of the image abnormality is the position of the predetermined image (step S105). Note that even if the image of the print job includes a predetermined image, if the range of the image abnormality is wider than the range of the predetermined image, the transport control unit 242 determines NO in step S104. After step S105, this control ends.

[0064] Furthermore, the conveyance control unit 242 may control conveyance so that the position of the image abnormality is located at a position corresponding to a non-image area included in the image formed on the recording medium.

[0065] By doing this, an image is not formed at the position of the image abnormality, so it is possible to easily avoid an image affected by periodic image abnormality from being formed on the recording medium.

[0066] In the above embodiment, periodic image abnormalities in the recording medium are detected based on the read information of the recording medium, but the present invention is not limited to this. For example, the detection unit 241 may detect periodic image abnormalities in the recording medium based on information about the characteristics of the recording medium in addition to the read information of the recording medium.

[0067] The characteristics of the recording medium include, for example, the rigidity and thickness of the recording medium.

[0068] For example, the higher the rigidity of the recording medium, the greater the fluctuation in density unevenness (image abnormality). Therefore, the detection unit 241 may change the detection criteria for periodic image abnormalities according to the characteristics of the recording medium by decreasing the threshold value for comparing the difference between image information based on read information and information on a normal image as the rigidity of the recording medium increases.

[0069] In the above embodiment, when a periodic image abnormality is detected, the transport is controlled so that the image abnormality is located between recording media or at a position corresponding to a predetermined image. However, even if the transport of the recording media is controlled, it may not be possible to avoid the effects of the image abnormality, depending on, for example, the occurrence period of the image abnormality.

[0070] For example, as shown in FIG. 9, if the occurrence cycle of image abnormalities is approximately one-fourth the length of the recording medium in the conveying direction, the influence of image abnormalities cannot be avoided even if conveyance control is performed.

[0071] Therefore, the conveyance control unit 242 suspends conveyance control and image formation if the occurrence cycle of the image abnormality is within a predetermined length. The predetermined length is a length that cannot completely avoid the effects of periodic image abnormalities, for example, a length within the length of the recording medium in the conveyance direction.

[0072] This can prevent printing that includes periodic image abnormalities, and can also serve as a trigger for urging maintenance and part replacement of the image forming apparatus 20 to prevent future occurrence of periodic image abnormalities.

[0073] An example of the operation of transport control will be described with reference to the example shown in Fig. 9. Fig. 10 is a flowchart showing an example of the operation of transport control in the transport control unit 242. Note that steps S101, S102, and S103 in Fig. 10 are the same as steps S101, S102, and S103 in Fig. 6.

[0074] 10, after determining YES in step S102, the transport control unit 242 determines whether the occurrence cycle of the image abnormality is within a range in which the image abnormality can be avoided (step S106). If the determination result shows that the occurrence cycle of the image abnormality is within a range in which the image abnormality can be avoided (step S106, YES), the process proceeds to step S103.

[0075] On the other hand, if the occurrence cycle of the image abnormality is not within a range where the image abnormality can be avoided (step S106, NO), the conveyance control unit 242 stops image formation of the print job (step S107). After step S107, this control ends. If this control ends via step S107, the print job is stopped.

[0076] Furthermore, in the above embodiment, the reading unit is provided outside the image forming apparatus, but the present invention is not limited to this, and the reading unit may be provided inside the image forming apparatus.

[0077] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from the gist or main features thereof. [Explanation of symbols]

[0078] 1. Image forming system 10 Paper feeder 20 Image forming device 21 Image forming unit 22 Fixing section 23 Conveyor 24 Control Unit 30 Reading device 30A Transport Route 31 Reading unit 241 Detection unit 242 Transport control unit

Claims

1. An image forming apparatus that forms an image on each of a plurality of recording media that are continuously conveyed, a detection unit that detects periodic image abnormalities on a recording medium based on read information of the recording medium on which an image is formed; a conveyance control unit that controls conveyance of each recording medium based on the detection result of the detection unit; An image forming apparatus comprising:

2. the conveyance control unit controls the conveyance so that the position of the image abnormality in the conveyance direction of the recording medium is located at a position between the recording media. The image forming apparatus according to claim 1 .

3. the transport control unit controls the transport by adjusting a distance in a transport direction between a first recording medium and a second recording medium that is transported next to the first recording medium. The image forming apparatus according to claim 2 .

4. the conveyance control unit controls the conveyance so that a position of the image abnormality in a conveyance direction of the recording medium corresponds to a position of a predetermined image included in an image formed on the recording medium. The image forming apparatus according to claim 1 .

5. the conveyance control unit controls the conveyance by adjusting the timing at which image formation starts on each recording medium. The image forming apparatus according to claim 4 .

6. The predetermined image is a character image. The image forming apparatus according to claim 4 .

7. the conveyance control unit controls the conveyance by adjusting a conveyance timing at a position where an image is transferred in an image forming unit. The image forming apparatus according to claim 1 .

8. the conveyance control unit stops image formation when the occurrence cycle of the image abnormality is within a predetermined length. The image forming apparatus according to claim 1 .

9. the conveyance control unit controls an image formation position on each recording medium in accordance with the control of the conveyance. The image forming apparatus according to claim 1 .

10. the conveyance control unit controls the conveyance by adjusting at least one of a feeding timing of the recording medium and a registration timing of the recording medium. The image forming apparatus according to claim 7 .

11. 1. A method for controlling conveyance of an image forming apparatus that forms an image on each of a plurality of recording media that are continuously conveyed, comprising: Detecting periodic image abnormalities on the recording medium based on read information of the recording medium on which an image is formed; Controlling the conveyance of each recording medium based on the detection results; having Transport control method.

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