JP5871131B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 discloses a latent image forming device that forms a latent image on the surface of the image carrier based on an image carrier, an image recorded on a medium, and the latent image on the surface of the image carrier is made a visible image. A developing device for developing, a high image density determining means for determining whether or not an image density of the image to be formed is higher than a predetermined determination density, and a high image density by the high image density determining means. When it is determined that there is a density difference reducing image, the latent image forming device reduces the density difference between the image forming area and the outside of the image forming area outside the image forming area where the image is formed. An image forming apparatus comprising: a density difference reducing image creation instructing unit for forming a color difference.

JP 2010-008549 A

  An object of the present invention is to provide an image forming apparatus capable of improving the image quality when there is a difference in image density between continuously formed images while suppressing a decrease in productivity.

  According to a first aspect of the present invention, there is provided a conveying unit that sequentially conveys a plurality of recording media, an image forming unit that sequentially forms an image on a plurality of recording media sequentially conveyed by the conveying unit, the conveying unit, and the image And a control unit that controls the forming unit, the control unit configured to control the adjacent image forming units when the image density difference between the two adjacent images formed by the image forming unit is the first image density difference. Formation of both adjacent images when the difference in image density between the two adjacent images is greater than the first image density difference than the first time interval during which the image is formed. This is an image forming apparatus that controls the second time interval to be increased.

  According to a second aspect of the present invention, the conveying unit conveys the recording medium so that the image forming unit forms an image on the first surface of the recording medium, and the image is formed on the first surface of the recording medium. The recording medium is reversed and conveyed so that an image is formed on the second surface of the recording medium by the image forming unit at a predetermined time after formation, and the control means A difference between an image density of an image formed on one surface and an image density of an adjacent image formed by the image forming unit and the image formed on the first surface of the recording medium; Based on the difference between the image density of the image formed on the second surface and the image density of the image formed on the second surface of the recording medium and the image formed by the image forming unit adjacent to each other. The time when the image forming unit forms an image on the first surface of the recording medium is controlled. The image forming apparatus according to claim 1, in which.

  According to a third aspect of the present invention, the control means controls to form both adjacent images at the first time interval when the difference in image density is equal to or less than a first threshold, and the image density When the difference between the first and second images exceeds the first threshold, the time interval for forming both adjacent images is controlled to be the second time interval, and the second difference between the image densities is larger than the first threshold. 3. The image forming apparatus according to claim 1, wherein when the threshold value of the second time interval is exceeded, control is performed so that a time interval in which both adjacent images are formed becomes a third time interval that is larger than the second time interval. is there.

  According to the first aspect of the present invention, the image quality in the case where there is a difference in image density between successively formed images while suppressing a decrease in productivity as compared with the case where the present configuration is not provided. An image forming apparatus that can be improved can be provided.

  According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, an image forming apparatus in which images are formed on both sides of a recording medium is produced as compared with the case where the present configuration is not provided. Image quality can be improved when there is a difference in image density between successively formed images.

  According to the third aspect of the present invention, in addition to the effect of the first aspect of the present invention according to the first or second aspect, a reduction in productivity can be further suppressed as compared with the case where the present configuration is not provided.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a side view of an image forming unit used in an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows the hardware constitutions of the control part which concerns on embodiment of this invention. FIG. 6 is a schematic diagram illustrating an example of an image formation timing when images are sequentially formed on one side of a plurality of sheets of paper P. (A) represents the image density of the image formed on each of the five sheets, and (b) to (d) are timings for forming the image having the image density shown in (a) on each of the sheets. (B) is a timing in the comparative example, and (c) and (d) are examples of timing based on control by the control unit 13. FIG. 6 is a schematic diagram illustrating a first example of an image forming timing when images are sequentially formed on both surfaces of a plurality of sheets of paper P. (A) represents the image density of the image on the first surface and the image density of the image on the second surface formed on each of the five sheets, and (b) to (d) are denoted by (a). (B) is a timing in the comparative example, and (c) and (d) are examples of timing based on control by the control unit 13. is there. FIG. 10 is a schematic diagram illustrating a second example of an image formation timing when images are sequentially formed on both surfaces of a plurality of sheets of paper P. FIG. 10 is a schematic diagram illustrating a third example of an image formation timing when images are sequentially formed on both surfaces of a plurality of sheets P. FIG. 10 is a schematic diagram illustrating a fourth example of an image formation timing when images are sequentially formed on both surfaces of a plurality of sheets P. FIG. 10 is a schematic diagram illustrating a fifth example of an image formation timing when images are sequentially formed on both surfaces of a plurality of sheets of paper P. 7 is a flowchart illustrating an example of control of an image formation timing by the control unit 13 when images are sequentially formed on both surfaces of a plurality of sheets P.

  An example of an image forming apparatus according to an embodiment of the present invention will be described.

  As shown in FIG. 1, an image forming apparatus 10 according to the present embodiment forms a color image or a black and white image, and includes a first processing unit 10A and a first processing unit 10A arranged on the left side when viewed from the front. And a second processing unit 10B that is detachably disposed on the right side. The housings of the first processing unit 10A and the second processing unit 10B are composed of a plurality of frame materials.

  A control unit 13 that includes an image signal processing unit that performs image processing on image data sent from a computer, and that controls the drive of each unit of the image forming apparatus 10, inside the second processing unit 10 </ b> B and above the vertical direction. Is provided. A power supply unit 230 is provided below the control unit 13. The power supply unit 230 supplies power to each part of the image forming apparatus 10 by changing an alternating current taken from outside into a direct current.

  On the other hand, an image forming unit 32 is provided inside the first processing unit 10A. Above the image forming section 32, the first special color (V), second special color (W), yellow (Y), magenta (M), cyan (C), and black (K) toner (development) Toner cartridges 14V, 14W, 14Y, 14M, 14C, and 14K for storing the agent are provided in the horizontal direction so as to be replaceable. The first special color and the second special color are selected from special colors (including transparency) other than yellow, magenta, cyan, and black. Further, in the following description, when distinguishing V, W, Y, M, C, and K, an explanation is given by adding an alphabetic character of V, W, Y, M, C, or K after the number. When V, W, Y, M, C, and K are not distinguished, V, W, Y, M, C, and K are omitted.

  Under the toner cartridges 14, six image forming units 16 corresponding to the toners of the respective colors are provided side by side in correspondence with the toner cartridges 14. An exposure unit 40 is provided for each forming unit 16. The exposure unit 40 receives the image data subjected to image processing from the control unit 13 described above, modulates a semiconductor laser (not shown) according to the color material gradation data, and emits the exposure light L from these semiconductor lasers. It is comprised so that it may radiate | emit. Specifically, an electrostatic latent image is formed on the photoconductor 18 by irradiating the surface of the photoconductor 18 (see FIG. 2) described later with exposure light L corresponding to each color.

  As shown in FIG. 2, the image forming unit 16 includes a photoreceptor 18 that is driven to rotate in the direction of arrow A (clockwise in FIG. 2). A corona discharge method (non-contact charging method) scorotron charger 20 that charges the photosensitive member 18 and an exposure light L emitted by the exposure unit 40 are formed on the photosensitive member 18 around the photosensitive member 18. A developing device 22 that develops the electrostatic latent image with each color developer (toner), a cleaning blade 24 that cleans the surface of the photoreceptor 18 after the transfer, and a light that irradiates the surface of the photoreceptor 18 after the transfer. An erase lamp 26 is provided for performing static elimination. The scorotron charger 20, the developing device 22, the cleaning blade 24, and the erase lamp 26 are arranged in this order from the upstream side to the downstream side in the rotation direction of the photoconductor 18 so as to face the surface of the photoconductor 18. Yes.

  Further, the developing device 22 is disposed on the side of the image forming unit 16 (right side in the drawing in this embodiment), and a developer containing member 22A filled with a developer G containing toner and a developer containing member 22A. And a developing roll 22 </ b> B that moves the filled toner to the surface of the photoreceptor 18. The developer accommodating member 22A is connected to the toner cartridge 14 (see FIG. 1) through a toner supply path (not shown), and the toner is supplied from the toner cartridge 14.

  As shown in FIG. 1, an endless intermediate transfer belt 34 that contacts each photoconductor 18 is provided below each image forming unit 16. Inside the intermediate transfer belt 34, six primary transfer rolls 36 are arranged as six primary transfer members that multiplex-transfer the toner images formed on the respective photoreceptors 18 to the intermediate transfer belt 34. The intermediate transfer belt 34 includes a drive roll 38 driven by a motor (not shown), a tension applying roll 41 that adjusts the tension of the intermediate transfer belt 34, a support roll 42 that is disposed opposite to a secondary transfer roll 62 described later, It is wound around a plurality of support rolls 44 and is circulated and moved in the direction of arrow B (counterclockwise direction) in FIG.

  Specifically, each primary transfer roll 36 is disposed opposite to the photoreceptor 18 of each image forming unit 16 with the intermediate transfer belt 34 interposed therebetween. The primary transfer roll 36 is applied with a transfer bias voltage having a polarity opposite to the toner polarity by a power supply unit (not shown). With this configuration, the toner image formed on the photoreceptor 18 is transferred to the intermediate transfer belt 34. A cleaning blade 46 whose tip is in contact with the intermediate transfer belt 34 is provided on the opposite side of the drive roll 38 and the intermediate transfer belt 34. The cleaning blade 46 is disposed on the intermediate transfer belt 34 that circulates and moves. Residual toner and paper dust are removed.

  On the other hand, under the first processing unit 10A, two large paper cassettes 48 that store paper P as an example of a recording medium are provided side by side in the horizontal direction, and a large amount of paper P is stored. It is possible. Since the two paper feed cassettes 48 have the same configuration, only one paper feed cassette 48 will be described, and description of the other paper feed cassette 48 will be omitted.

  The transport system 51 transports the paper P fed from the paper feed cassette 48 to the transfer position T to form an image on the first surface of the paper P, and reverses the paper P by the reversing unit 200 described later. Thus, an image is formed on the second surface of the paper P.

  The paper feed cassette 48 can be pulled out from the first processing unit 10A. When the paper feed cassette 48 is pulled out from the first processing unit 10A, a bottom plate 50 provided in the paper feed cassette 48 on which the paper P is placed is provided. The lowering is performed by the operation of a driving unit (not shown). When the bottom plate 50 is lowered, the user can replenish the paper P. When the paper feed cassette 48 is attached to the first processing unit 10A, the bottom plate 50 is raised by the operation of the drive unit. Above the one end side of the paper feed cassette 48, a delivery roll 52 for delivering the paper P from the paper feed cassette 48 to the transport path 60 is provided, and the uppermost paper P placed on the rising bottom plate 50 is delivered. The roll 52 comes into contact. Further, a separation roll 56 that prevents double feeding of the paper P is provided on the downstream side in the recording medium conveyance direction of the sending roll 52 (hereinafter simply referred to as “downstream side”). A plurality of transport rolls 54 are provided for transporting the sheet downstream in the transport direction.

  The conveyance path 60 provided on the upper side of the paper feed cassette 48 folds the paper P delivered from the paper feed cassette 48 to the opposite side (left side in the drawing) at the first turn-back portion 60A, and further reverses at the second turn-back portion 60B. It is folded back to the side (right side in the drawing) and extends toward the transfer position T sandwiched between the secondary transfer roll 62 and the support roll 42.

  An aligner (not shown) for correcting the inclination of the conveyed paper P is provided at a portion sandwiched between the second folding portion 60B and the transfer position T, and a portion sandwiched between the aligner and the transfer position T. Is provided with an alignment roll 64 for adjusting the timing (timing) of moving the toner image on the intermediate transfer belt 34 and the timing (timing) of conveying the paper P.

  The secondary transfer roll 62 is applied with a transfer bias voltage having a polarity opposite to the toner polarity by a power supply unit (not shown). With this configuration, the toner images of each color that have been multiplex-transferred onto the intermediate transfer belt 34 are secondarily transferred onto the paper P that has been transported along the transport path 60 by the secondary transfer roll 62. Further, a preliminary path 66 extending from the side surface of the first processing unit 10A is provided so as to join the second folding unit 60B of the transport path 60, and an external path disposed adjacent to the first processing unit 10A is provided. A sheet P sent from a large-capacity stacking unit (not shown) can enter the transport path 60 through the spare path 66.

  On the other hand, on the downstream side of the transfer position T, a plurality of transport members 70 are provided for transporting the paper P on which the toner image has been transferred toward the second processing unit 10B. The conveying member 70 includes a plurality of belt members wound around a driving roll and a driven roll (not shown), and the paper P is directed downstream by rotating the driving roll to rotate the belt member. It is designed to be transported.

  The downstream side of the conveying member 70 extends from the first processing unit 10A to the second processing unit 10B, and the paper P sent out by the conveying member 70 is received by the conveying device 80 provided in the second processing unit 10B. Further, it is conveyed downstream. Further, a fixing unit 82 as an example of a fixing unit that fixes the toner image transferred onto the surface of the paper P to the paper P with heat and pressure is provided on the downstream side of the conveying device 80.

  The fixing unit 82 includes a fixing belt 84 and a pressure roll 88 disposed in pressure contact with the fixing belt 84. A contact portion N where the fixing belt 84 and the pressure roll 88 come into contact is formed. At the contact portion N, the paper P is pressurized and heated to fix the toner image.

  On the downstream side of the fixing unit 82 on the conveyance path 60 of the sheet P, a conveyance unit 108 is provided as an example of a conveyance unit that conveys the sheet P sent from the fixing unit 82 to the downstream side. A cooling unit 110 as an example of a cooling unit for cooling the paper P heated by the fixing unit 82 is provided on the downstream side of the transport unit 108 on the transport path 60.

  On the downstream side of the cooling unit 110 on the transport path 60, a decurling unit 140 is provided as an example of a correction unit that corrects the warp of the paper P.

  A discharge roll 198 is provided on the transport path 60 downstream of the decurling unit 140 to discharge the paper P on which an image has been formed to a discharge unit 196 attached to the side surface of the second processing unit 10B. Here, when forming images on both sides of the paper P, the paper P is conveyed to the reversing unit 200 provided downstream of the decurling unit 140.

  The reversing unit 200 is provided with a reversing path 202. The reversing path 202 includes a branch path 202A that branches from the transport path 60, a paper transport path 202B that transports the paper P transported along the branch path 202A toward the first processing unit 10A, and a paper transport path 202B. A reversing path 202C is provided that folds the paper P conveyed in the reverse direction in the reverse direction to switch back and reverse the paper. With this configuration, the paper P that has been switched back in the reverse path 202C is transported toward the first processing unit 10A, and further enters the transport path 60 provided above the paper feed cassette 48 to the transfer position T. It will be sent again.

  With the above configuration, when images are sequentially formed on both sides of a plurality of sheets P, after the images are formed on the first side of a certain sheet P, the sheet P is reversed by the reversing unit 200 and the first sheet P is reversed. Until an image is formed on the two sides, an image is formed on the first side or the second side of another paper P different from the paper P. However, during this time, the number of other sheets P on which images are formed on the first side or the second side depends on the control by the control unit 13 and may be zero. During this time, the maximum number of other sheets P on which an image is formed on the first surface or the second surface is determined by, for example, the configuration of the transport path 60.

  When images are formed on both sides of the paper P, an image is formed on the first surface at the transfer position T with respect to the paper P fed from the paper feed cassette 48, and then reversed by the reversing unit 200 and transferred again. The time until the image is formed on the second surface after returning to the position T (hereinafter referred to as “circulation time”) is determined in advance. The lap time is determined by, for example, the configuration of the transport path 60. Thus, the image formation on the second surface is performed at a predetermined time after the image formation on the first surface is performed.

  FIG. 3 is a block diagram illustrating a hardware configuration of the control unit 13.

  The control unit 13 has a configuration in which a CPU 204, a memory 206, and an input / output unit 208 are connected by a bus. The input / output unit 208 is connected to the driving units of the image forming unit 32 and the conveyance system 51 described above.

  That is, the control unit 13 includes a component as a computer, and the CPU 204 controls the image forming unit 32 and the conveyance system 51 by executing a program stored in the memory 206. However, part or all of the control by the control unit 13 may be realized by hardware.

  When images are sequentially formed on a plurality of papers P, the control unit 13 controls the transport system 51 so that the papers P are sequentially transported on the transport path 60 and the papers sequentially transported to the transfer position T. The image forming unit 32 is controlled so as to sequentially form the respective images with respect to P.

  Here, the influence on the image quality due to the difference in image density when the images are sequentially formed on the plurality of sheets P and the control of the control unit 13 will be described. The image density refers to the ratio of the area where toner is applied to the area of the paper P.

  FIG. 4 is a schematic diagram illustrating an example of image formation timing (timing) when images are sequentially formed on one side of a plurality of sheets P by the image forming apparatus 10. Here, the paper No. 1 to paper No. 1 An example in which images are sequentially formed on one side of five sheets indicated as 5 is shown as an example.

  4A, five sheets of paper No. 1-No. 5 represents the image density of an image formed on each of the five. Here, the image density of the image formed on the paper is classified into two groups, and one of the groups is a group having an image density higher than a predetermined image density Q1 (hereinafter referred to as a high image density group). In the example, the other group is a group having an image density lower than a predetermined image density Q2 (hereinafter referred to as a low image density group). 5 sheets No. 1-No. The image density of the image formed on each of the images 5 is classified into groups by the control unit 13. The predetermined image densities Q1 and Q2 may be Q1 = Q2 or Q1> Q2.

  In FIG. 4, a sheet filled with black represents a sheet on which an image belonging to a high image density group is formed, and a hatched sheet represents an image belonging to a low image density group. Represents the paper to be formed.

  4B to 4D, images having the image density shown in FIG. 1-No. 5, (b) is a timing in the comparative example, and (c) and (d) are examples of timing based on the control by the control unit 13. Specifically, the horizontal axis is time t, and the presence / absence of image formation is indicated for each time. When an image is formed, it is indicated on which paper the image is formed. Yes. In the example shown in FIG. 4, as a unit of time t, a distance corresponding to the width in the transport direction of the paper P is a time corresponding to the transport of the transport system 51 (hereinafter referred to as a transport time of the paper P). Yes.

  In the example shown in FIG. 4B, five sheets of paper No. 1 on which images are sequentially formed are displayed. 1-No. For image 5, images are formed on adjacent sheets at regular time intervals. In this case, the paper No. No. 2 after image formation on image No. 2 3 and paper No. 3 4 after image formation on image No. 4. In image formation to 5, desired image quality may not be obtained due to the difference in image density of the formed image. Possible reasons include, for example, that temperature adjustment by the fixing unit 82 cannot keep up with changes in image density, and that toner supply can't keep up with changes in image density, and that color changes.

  On the other hand, the control unit 13 in the present embodiment adjusts the time interval at which the image is formed according to the difference in image density between the images adjacent to each other when the image forming unit 32 forms the image. The forming unit 32 and the transport system 51 are controlled. More specifically, when the difference between the image densities of the two adjacent images formed by the image forming unit 32 is the first image density difference, the first time interval at which the two adjacent images are formed. However, when the difference in image density between the two adjacent images is a second image density difference larger than the first image density difference, the second time interval in which the two adjacent images are formed is increased. Control. The time interval at which the image is formed is not uniformly set, but is adjusted according to the difference in image density, and the reduction in productivity is suppressed.

  The control unit 13 according to the present embodiment performs the image formation of the low image density group immediately after the image formation of the high image density group and the image formation of the high image density group immediately after the image formation of the low image density group. In the case where the image forming process is performed, control is performed to delay the formation timing of the subsequent image among the formed images by a predetermined time and adjust the image formation time interval between the two images. However, only when the image formation of the low image density group is performed immediately after the image formation of the high image density group, or when the image formation of the high image density group is performed immediately after the image formation of the low image density group. Alternatively, it may be controlled to adjust the time interval of image formation between both images.

  The predetermined time to be delayed by the control unit 13 is, for example, a time required for preparation for forming a subsequent image, and may be determined according to an image density difference. An example of preparation for the subsequent image formation corresponds to temperature adjustment of the fixing unit 82 or toner supply operation, but is not limited to this, and includes a state of waiting without performing any special operation.

  4C illustrates an example in which the control unit 13 controls the time interval between the image formation of the high image density group and the image formation of the low image density group as the conveyance time of the sheet P for one sheet. (D) shows an example in which the control unit 13 controls the time interval between the image formation of the high image density group and the image formation of the low image density group as the conveyance time of the paper P for two sheets. Show.

  Next, a case where images are sequentially formed on both surfaces of a plurality of sheets P by the image forming apparatus 10 will be described.

  FIGS. 5 to 9 are schematic diagrams illustrating an example of an image formation timing when images are sequentially formed on both surfaces of a plurality of sheets P by the image forming apparatus 10. In the example shown in FIGS. 1 to paper No. 1 An example in which images are sequentially formed on both surfaces of five sheets indicated as 5 is shown as an example.

  In FIG. 5 to FIG. 9, in FIG. 1-No. 5 shows the image density of the image on the first surface and the image density of the image on the second surface formed on each of 5. Similarly to FIG. 4, the paper shown in black and black represents a paper on which an image belonging to the high image density group is formed, and the paper shown hatched in the low image density group. It represents a sheet on which an image to which it belongs is formed.

  As shown in FIG. 5 to FIG. 9, in the image forming apparatus 10 according to the present embodiment, when images are formed on both sides of the paper P, the above-described rotation time after the image is formed on the first surface of the paper P. After a lapse of time, an image is formed on the second surface of the paper P.

  Further, as shown in FIGS. 5 to 9, in the image forming apparatus 10 according to the present embodiment, when images are formed on both sides of the paper P, the paper P is left to leave room for image formation on the second side to be interrupted. The image formation on the first surface is controlled not to be performed continuously in time. For example, when n is a natural number and image formation is performed on the first surface of the sheet P at the time t = n, the subsequent image formation on the first surface of another sheet P is equivalent to one unit of time. Control is performed after time t = n + 2 with an interval of.

  5 to 9, as in FIG. 4, in (b) to (d), an image having the image density shown in (a) is displayed on the sheet No. 1-No. 5, (b) is a timing in the comparative example, and (c) and (d) are examples of timing based on the control by the control unit 13.

  In the example shown in FIG. 5 to FIG. 9B, the image is formed on the first surface of each of the five sheets at intervals of one unit of time. At this time, the formation of the image classified into the high image density group and the formation of the image classified into the low image density group are performed adjacent to each other, and as described above, a desired image quality may not be obtained. is there.

  On the other hand, in the control unit 13 in the present embodiment, as shown in FIGS. 5C to 9D, the time interval between the image formation of the high image density group and the image formation of the low image density group. Is controlled so as to be free for a predetermined time. In FIG. 5C to FIG. 9C, the control unit 13 controls the time interval between the image formation of the high image density group and the image formation of the low image density group as the conveyance time of one sheet of paper P. (D) shows an example in which the control unit 13 controls the time interval between the image formation of the high image density group and the image formation of the low image density group as the conveyance time of the paper P for two sheets. An example of the case is shown.

  Although FIGS. 4 to 9 show examples in which images are sequentially formed on five sheets, the number of sheets is not limited to five.

Next, the control of the image formation timing by the control unit 13 will be described in detail using a flowchart.
FIG. 10 is a flowchart illustrating an example of control of the image forming timing by the control unit 13 when images are sequentially formed on both sides of a plurality of sheets P.

  In step 100 (S100), it is determined whether or not there is a preceding sheet P being conveyed by the conveyance system 51. If the preceding paper P exists, the process proceeds to step 102. If the preceding paper P does not exist, the process proceeds to step S122.

  In step 102 (S102), the image density of the image formed on the first surface of the paper P to be fed next to the transport path 60 is acquired.

  In step 104 (S104), when the next sheet P to be fed to the transport path 60 is currently fed, the formation of the image on the first surface of the sheet P and the timing of image formation are the adjacent images. Obtain the image density. The images adjacent to the image formation timing include an image scheduled to be formed immediately before the image formation timing on the first surface of the paper P and an image scheduled to be formed immediately thereafter.

  Here, step 104 will be further described with reference to FIG. At this time, the sheet No. 1-No. 3 exists as the preceding paper P, and paper No. Assume that 4 is a sheet P to be fed next. In this case, the control unit 13 determines the paper number. Assuming that paper No. 4 is fed at the present time, the paper No. 1 to paper No. 1 In the image forming time of No. 3, the paper No. 4 is applied. In FIG. 5B, the sheet No. Although the image forming timing of No. 5 is shown in the figure, at present, the paper No. The image formation timing of 5 is unknown.

  As shown in (b) of FIG. Assuming that paper No. 4 is fed at present, the paper No. The image forming timing of the first side of No. 3 is adjacent to the image formation on the first side of the first sheet. This is adjacent to the image formation on the first second surface.

  Therefore, in this example, in step 104, the paper No. 3 and the image density of the image formed on the first surface of the sheet No. The image density of the image formed on the first second surface is acquired.

  Next, in step 106 (S106), it is determined whether or not the group to which the image density acquired in step 102 belongs and any of the groups to which the image density acquired in step 104 belongs. In step S108, the process proceeds to step 108, and if it belongs to the same group, the process proceeds to step 110.

  In the example in FIG. 5B, the paper No. acquired in step 102 is displayed. 4 belongs to the low image density group, while the sheet No. 4 obtained in step 104 is the image density of the first surface. 3 image density on the first surface and paper No. The image density of the first second surface belongs to the high image density group, and the process proceeds to step 108.

  In step 108 (S108), it is determined whether or not the image formation timings of both images determined to belong to groups having different image densities in step 106 are equal to or greater than a predetermined time interval. If it is equal to or longer than the predetermined time interval, the process proceeds to step 110. On the other hand, if the time interval is less than the predetermined time interval, the process proceeds to step 118, and the current feeding of the paper P is postponed.

  In the example in FIG. 5B, if the predetermined time interval is the transport time of one sheet of paper P, the paper No. The first surface image formation time No. 4 is a paper No. 4 performed immediately before. 3 from the image formation of the first surface of the third side. However, the paper No. The first surface image formation time No. 4 is a paper No. 4 performed immediately thereafter. It is not separated from the image formation on the first second surface by a predetermined time interval. Therefore, in this case, the process proceeds to step 118 and the current paper No. The paper feed of 4 is postponed.

  On the other hand, in step 110 (S110), the image density of the image formed on the second surface of the paper P fed next to the transport path 60 is acquired.

  In step 112 (S112), when the next sheet P to be fed to the transport path 60 is fed at the present time, the formation of the image on the second surface of the sheet P and the timing of image formation are the adjacent images. Obtain the image density.

  Similar to the description in step 104, the paper No. will be described with reference to FIG. As the image density of the image on which the image formation on the second surface of 4 and the time are adjacent, the paper No. 4 is used. The image density of the image formed on the second surface 3 is acquired. In FIG. 5B, the sheet No. Although the image forming timing of No. 5 is shown in the figure, at present, the paper No. The image formation timing of 5 is unknown.

  Next, in step 114 (S114), it is determined whether or not the group to which the image density acquired in step 110 belongs and any of the groups to which the image density acquired in step 112 belongs. Therefore, the process proceeds to step 116, and if it belongs to the same group, the process proceeds to step 122.

  Similar to the description in step 106, the paper No. acquired in step 110 will be described with reference to FIG. 4 belongs to the low image density group, while the sheet No. The image density of the second surface No. 3 belongs to the high image density group, and the process proceeds to Step 116.

  In step 116 (S116), it is determined whether or not the image formation timings of both images determined to belong to different groups in step 114 are equal to or greater than a predetermined time interval. If it is equal to or longer than the predetermined time interval, the routine proceeds to step 122. On the other hand, if the time interval is less than the predetermined time interval, the process proceeds to step 118, and the current feeding of the paper P is postponed.

  In the example in FIG. 5B, if the predetermined time interval is the transport time of one sheet of paper P, the paper No. The image forming timing of the second side of No. 4 is paper No. 4 performed immediately before that. 3 from the image formation on the second side of the third side.

  In step 118 (S118), it is confirmed whether a print job still remains. If all the pages have been fed, the answer is No in step 118 and the process ends. On the other hand, if it is determined in step 108 or step 116 that the image forming interval is not equal to or longer than the predetermined time, the result in step 118 is Yes, and the process proceeds to step 120.

  In step 120 (S120), the process waits until the next paper feeding time. Specifically, as the next paper feeding time, image formation on the first side of the paper P is not performed continuously in time, and the image forming time of the preceding paper P and the paper P to be fed are not changed. Wait until the image formation timing does not overlap.

  On the other hand, in step 122 (S122), the transport system 51 is controlled to send the paper P to the transport path 60, and an image is formed on the first surface and the second surface of the paper P transported to the transfer position T. The image forming unit 32 is controlled accordingly.

  In the flowchart, the case where images are formed on both sides of the paper P is taken as an example. However, when an image is formed on one side, the operation relating to the second side of the paper P in the flowchart is not necessary.

  In the above description, the image density of the image is classified into two groups, a high image density group and a low image density group, but may be classified into three or more groups. Further, the interval between the image forming timings may be controlled simply according to the difference in image density without being classified into groups.

  In addition, a predetermined time may be changed as an interval between image formation timings according to the difference in image density. For example, when the difference in image density is equal to or smaller than the first threshold value, both adjacent images are formed at the first time interval (for example, the minimum time interval that can be set) assuming that there is no image density difference. And when a difference in image density exceeds a first threshold value, a second time interval (for example, one sheet) in which the time interval in which both adjacent images are formed is larger than the first time interval. The time interval at which both adjacent images are formed when the difference in image density exceeds a second threshold value that is greater than the first threshold value is controlled to be the second time interval. Control may be performed so that the third time interval is longer (for example, the transport time of the paper P for two sheets). In this way, it is expected that the time interval for delaying image formation will not be a predetermined time uniformly, but only the time necessary to obtain a desired image quality. The decrease is further suppressed.

  In the above description, an example is described in which the time interval for image formation is delayed by a conveyance time of m (m is a natural number) sheets. However, the control unit 13 is delayed by a paper conveyance time in millimeters. You may control to delay by the time interval which the user set.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 13 Control part 32 Image forming part 51 Conveyance system 60 Conveyance path 200 Inversion unit

Claims (3)

Conveying means for sequentially conveying a plurality of recording media;
An image forming unit that sequentially forms images on a plurality of recording media sequentially conveyed by the conveying unit;
Control means for controlling the conveying means and the image forming unit,
The control means is configured such that when the difference in image density between the images adjacent to each other formed by the image forming unit is the first image density difference, the two adjacent images are formed. However, the second time interval at which the two adjacent images are formed is increased when the difference between the image densities of the two adjacent images is a second image density difference larger than the first image density difference. An image forming apparatus to be controlled. The conveying means conveys the recording medium so as to form an image on the first surface of the recording medium by the image forming unit, and is predetermined after the image is formed on the first surface of the recording medium. The recording medium is reversed and conveyed so that an image is formed on the second surface of the recording medium by the image forming unit when
The control means includes: an image density of an image formed on the first surface of the recording medium; and an image density of an image formed by the image forming unit adjacent to the image formed on the first surface of the recording medium. And the image density of the image formed on the second surface of the recording medium and the image formed by the image forming unit adjacent to the image formed on the second surface of the recording medium. The image forming apparatus according to claim 1, wherein a timing at which an image is formed by the image forming unit on the first surface of the recording medium is controlled based on a difference from the density. The control means controls to form both adjacent images at the first time interval when the difference in image density is equal to or less than a first threshold, and the difference in image density exceeds the first threshold. If the difference in image density exceeds a second threshold value that is greater than the first threshold value, the time interval in which both adjacent images are formed is controlled to be the second time interval. 3. The image forming apparatus according to claim 1, wherein the time interval for forming the matching images is controlled to be a third time interval that is larger than the second time interval.

Images