JP5103226B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a technique for preventing the influence of dew condensation inside an image forming apparatus such as a copying machine, a printer, a facsimile, and the like, and in particular, image defects due to dew condensation during printing in a special environment, particularly in a low temperature / high humidity environment. It prevents without adding a water absorbing member.

  An image forming apparatus has a heat generating member such as a motor and a fixing device in a housing, and it is inevitable that condensation occurs due to a temperature difference between the inside and outside of the housing. In particular, the fixing device applies a heating / pressurizing action to a recording medium to be passed. Since such a recording medium contains moisture, the contained moisture evaporates by heating, thereby causing a predetermined low temperature / high humidity. Under the environment, dew condensation occurs in the vicinity of the fixing device, and water droplets on the recording medium conveyance path cause troubles in conveyance of the recording medium such as jam and skew. Also, the image quality deteriorates due to the occurrence of a false image such as black streaks due to the water droplets transferred to the recording medium.

  There have been proposals for the problem of condensation in the recording medium conveyance path. For example, in Patent Document 1, by starting the image forming apparatus after selecting the condensation removal mode, the development of the electrostatic latent image and the transfer of the image to the recording medium sent from the paper feeding device are not performed. It has been proposed to remove the condensation on the surface of the photosensitive drum with the recording medium by performing only the rotation and the conveying operation of the recording medium.

  Patent Document 2 discloses an image forming apparatus that takes out a recording medium one by one from a recording medium supply unit on which a plurality of recording media are stacked, conveys the recording medium, and forms an image. Condensation sensor that detects dew condensation that occurs in the transport path and a control unit that controls the transport of the recording medium according to the output result from the dew condensation sensor. It has been proposed that at least one recording medium including the uppermost layer among the recording media stacked on the recording medium supply unit is transported along the transport path when the occurrence of the above is detected.

  Further, in Patent Document 3, a first paper transport path and a second paper transport path are provided downstream of the fixing device, and the duplex printing mode and the second paper transport path passing through the second paper transport path are set. In the paper transport device that switches to the single-sided printing mode that does not pass through, the paper transporting roll (inverter roll 9) included in the second paper transporting path is idled in the single-sided printing mode, so that the paper transporting roll (inverter roll It has been proposed that a gas layer is formed around 9) and the water vapor rising from the fixing device is shut out to prevent the occurrence of condensation.

  In recent years, the number of media that transport recording media in the direction opposite to the gravitational direction is increasing, and it is more advantageous for condensation than the horizontal transport type. It is impossible to prevent this, and it is necessary to study airflow design, guide design, materials, etc.

JP-A-8-234649 JP 2006-206236 A JP 2005-274835 A

  In the proposals of Patent Document 1 and Patent Document 2 that remove condensation when condensation occurs, the condensation formed on the conveyance path / photosensitive member is removed by adhering and adsorbing to the recording medium by passing a blank recording medium. Therefore, waste occurs in the recording medium. The present invention eliminates the need to add a special water-absorbing member to a recording medium defect or image deterioration due to condensation even when performing double-sided printing immediately after single-sided mass printing in a low-temperature and high-humidity environment, and does not waste the recording medium. It is an object of the present invention to prevent double-sided productivity and minimize double-sided productivity, to achieve stable image formation and improve user convenience.

The above object is achieved according to the present invention, the toner image is transferred, in the image forming apparatus for fixing an image forming apparatus capable of performing double-sided image formation by reversing the recording medium, the image formed on the first surface A first double-sided printing mode in which transfer and fixing are performed on the second surface opposite to the first surface of the recording medium after passing through a double-sided conveyance path, and double-sided conveyance after forming an image on the first surface. A second surface that passes through the fixing device without performing transfer to the second surface opposite to the first surface of the recording medium passing through the path, and then performs transfer and fixing to the second surface. This is solved by providing a print mode.

Transferring the toner image, in the image forming apparatus for fixing an image forming apparatus capable of performing double-sided image formation by interleaf control for flight circulate a plurality of recording medium by reversing the recording medium, the interleaf a first double-sided printing mode for performing double-sided image formation by the control, is passed through a fixing device without performing transcription prior to the second surface of the image formation of the recording medium of the first sheet Kyushijun, thereafter The above problem can also be solved by providing a second double-sided printing mode in which an image is formed on the second side and the interleaf control is performed. Transferring the toner image, in the image forming apparatus for fixing an image forming apparatus capable of performing double-sided image forming two recording medium by reversing the recording medium at BBAA control to machine circulation, BBAA control A first double-sided printing mode in which double-sided image formation is performed, and a second double-sided printing mode in which one side of the first recording medium in the paper feeding order is passed through the fixing device without being transferred , and thereafter BBAA control is performed . The above problem can also be solved by providing the above.

  It is preferable that the fixing device is configured to have a branch point of the single-sided printing path and the reversing path above the fixing device. A sensor for temperature or humidity is provided, and the both modes are based on the result of comparing the value detected by the sensor with a predetermined value, or when the single-sided paper count before the duplex printing command exceeds a predetermined value. It is preferable to perform switching selection. The selection of switching between the two modes can be performed manually or automatically. In the second double-sided printing mode, the linear speed of the rollers provided in the reversing path is made slower than the other recording medium-conveying rollers, or the recording medium conveying speed of the fixing device in the second double-sided printing mode It is effective to make the temperature setting or transfer bias setting of the fixing device different from that in the first duplex printing mode.

  According to the present invention, in the second double-sided printing mode, water droplets existing in the double-sided printing conveyance path can be evaporated by the fixing device, and the image deterioration due to water droplet adhesion at the time of image formation is not increased, and the user's This can be prevented without deteriorating usability.

  In FIG. 1, the basic configuration and operation of the printer according to the present invention will be described, and then the configuration and operation unique to the present invention will be described. This printer has a configuration in which a paper feed cassette 2 that stores paper 29 as a recording medium is disposed below the image forming apparatus main body 1 serving as a base, and an image forming unit 3 is disposed above the paper cassette. Yes. The image forming unit 3 includes an image forming unit 8 including four image forming units 8Y, 8C, 8M, and 8BK as a plurality of image forming units including an image carrier, and a plurality of rollers 4, 5, and 6. An intermediate transfer unit 7 having a flexible endless belt wound around these rollers, an optical writing unit 15 for performing optical writing on each image carrier, and a sheet 29 And a fixing device 22 for fixing the toner image. The image forming units 8Y, 8C, 8M, 8BK and the intermediate transfer unit 7 are detachable from the apparatus main body 1. A conveyance path R for conveying the paper 29 is formed between the paper feeding unit 2 and the fixing device 22. The roller 6 is disposed facing the conveyance path R. In this embodiment, the intermediate transfer unit 7, the image forming unit 8, the optical writing unit 15, and the fixing device 22 constitute constituent elements inside the apparatus, and are arranged at a substantially center in the apparatus main body 1.

  The space between the rollers 4 and 5 of the intermediate transfer belt 7a corresponds to the lower side belt running side of this belt. In the intermediate transfer belt 7 a, a secondary transfer roller 20 serving as a secondary transfer device is disposed at a portion facing the roller 6 so as to face the conveyance path R, and a belt for cleaning the belt surface at a portion facing the roller 4. A cleaning device 21 is provided.

  The image forming unit 8 is disposed below the intermediate transfer belt 7a by being disposed so as to face the lower running side of the belt. Each image forming unit includes a photosensitive drum 10 as an image carrier that is in contact with the intermediate transfer belt 7a. Around each photosensitive drum 10, a charging device 11, a developing device 12, and a cleaning device 13 are arranged. A transfer roller 14 that performs primary transfer is provided inside the intermediate transfer belt at a position where each photosensitive drum 10 is in contact with the intermediate transfer belt 7a.

  In this embodiment, the image forming units 8Y, 8C, 8M, and 8BK are basically configured in the same structure, and in FIG. 1, only the configuration of the image forming unit 8BK is denoted by a reference symbol. The difference in each image forming unit is only the color of toner as a developer stored in each developing device 12. The developing devices 12 of the image forming units 8Y, 8C, 8M, and 8BK store yellow, cyan, magenta, and black toners, respectively. When the toner decreases, each developing device 12 is supplied with replenishing toner from toner replenishing bottles T1, T3, T3, and T4 disposed on the upper portion of the apparatus main body 1, respectively.

  The optical writing unit 15 irradiates the surface of each photoconductive drum with the light modulated laser beam L to form a latent image for each color on the photoconductive surface. It is arranged below.

  The toner supply bottles T1, T2, T3, T4, the intermediate transfer unit 7, the image forming unit 8, and the optical writing unit 15 are disposed in the apparatus main body 1 so as to be inclined in the same direction. The installation area is smaller than the case where it is horizontally arranged in 1.

  When the image forming operation is started, the photosensitive drums 10 of the respective image forming units 8 are rotated in the clockwise direction by a driving device (not shown), and the surface of each photosensitive drum is uniformly set to a predetermined polarity by the charging device 11. Is charged. The surface of each charged photosensitive drum is irradiated with laser light L from the optical writing unit 15 to form an electrostatic latent image on each surface. At this time, image information to be exposed on each photosensitive drum is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed in this way is visualized as a toner image by the toner of each developing device 12 when passing between each photoconductor and the developing device 12.

  Of the plurality of rollers 4, 5 and 6 around which the intermediate transfer belt 7a is wound, one roller is driven to rotate counterclockwise by a driving device (not shown), whereby the intermediate transfer belt 7a is counterclockwise indicated by an arrow. Driven in the direction, the other rollers are driven to rotate. A yellow toner image formed by the image forming unit 8Y including the developing device 12 having yellow toner is transferred by the transfer roller 14 to the intermediate transfer belt 7a that travels in this manner. To the transferred yellow toner image, a cyan toner image formed by the image forming units 8C, 8M, and 8BK, a magenta toner image, and a black toner image are sequentially superimposed and transferred by the transfer roller 14, and thus the intermediate transfer belt 7a. Carries a full-color toner image on its surface.

  Residual toner adhering to the surface of each photoconductive drum after the toner image is transferred is removed from the surface of the photoconductive drum by each cleaning device 13, and then the surface is subjected to a static eliminating action by a neutralizing device (not shown). The potential is initialized to prepare for the next image formation.

  The sheet 29 fed from the sheet feeding unit 2 is sent to the transport path R, and the sheet feeding timing is measured by the registration roller pair 24 disposed on the sheet feeding side with respect to the secondary transfer roller 20. And the secondary transfer roller 20. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt is applied to the secondary transfer roller 20, whereby the toner image on the surface of the intermediate transfer belt 7 a is collectively applied to the paper 29. And transferred. The paper 29 to which the toner image has been transferred is conveyed to the fixing device 22, and when passing through the fixing device 22, heat and pressure are applied to melt and fix the toner image. The printed matter 29A on which the toner image has been fixed is located at the end of the transport path R and is transported to a discharge portion (discharge / switchback roller 23) constituted by the upper portion of the apparatus main body 1. It is discharged to the configured loading section 36. After the toner image is transferred to the paper 29, the toner remaining on the intermediate transfer belt 7a is removed from the cleaning device 21.

  The printer configured as described above is provided with four image forming units 8Y, 8M, 8C and 8BK facing the intermediate transfer belt 7a, and sequentially transfers the toner images of the respective colors onto the intermediate transfer belt 7a. The image forming time can be greatly shortened as compared with a type in which a single image means has a four-color developing device, and a toner image is superimposed and transferred onto an intermediate transfer belt and then transferred onto a sheet. In addition, since the stacking portion 36 is formed on the upper portion of the apparatus main body 1, the stacking section 36 does not jump out from the apparatus main body 1, and the installation area and the occupied area are reduced.

  The above description is an image forming operation when a full-color image is formed on the paper 29. A single-color image is formed using any one of the image forming units of the image forming unit 8, or two colors or A three-color image can also be formed. When monochrome printing is performed using the printer of this aspect, an electrostatic latent image is formed only on the photosensitive drum of the image forming unit 8BK, developed by the unit, transferred to the paper 29, and the fixing device. Fixing at 22 is sufficient.

  FIG. 2 is an enlarged view of the fixing device 22 and the paper reversing path. As described above, the fixing device or unit fixes the toner on the sheet at a high temperature and high pressure. Therefore, as shown in FIG. 2, a branch point 52 between the single-sided conveyance path 50 and the double-sided conveyance path 51 on the downstream side of the fixing apparatus is a fixing device. In the case where the temperature is above 22, when the apparatus is started from a state where the temperature inside the apparatus is low, condensation occurs due to water vapor generated by the moisture of the paper and the moisture of the toner. Since the single-sided conveyance path 50 is a sheet conveyance path for both normal printing and double-sided printing, the amount of water droplet adhesion is small for two reasons: the temperature is raised by a high-temperature sheet, and the sheet carries moisture away from the apparatus. However, the more continuous single-sided paper is passed through the double-sided conveyance path 51, the more easily water droplets adhere to the conveyance path. Especially during the first double-sided printing after single-sided large-scale printing, water droplets 60 on the surface of the transport path accumulated so far adhere to the paper surface (the back side during double-sided printing), and transfer defects will occur at the transfer section during the next image formation. It may cause image defects.

  First, a normal double-sided printing operation in the configuration shown in FIG. 2 will be described. Focusing on a single sheet, the sheet conveyed from the sheet feeding device 2 (FIG. 1) is skew-corrected by a pair of registration rollers 24, transferred by a secondary transfer unit 54 for transferring a toner image, and then fixed. After fixing at the nip 56, the sheet passes through the single-sided conveyance path 50 and is conveyed to the switchback path 57. After that, the sheet is conveyed to the double-sided conveyance path 51 by the reverse operation of the discharge / switchback roller 23, and the double-sided conveyance roller 58. Is transferred again to the registration roller pair 24 before the toner image transfer, and the toner image transfer on the second surface (in this case, the second surface indicates the back surface of the first sheet on which image formation has been completed) is transferred. After that, the paper passes through the fixing nip 56 and is discharged from the paper discharge port 59 to the outside of the apparatus. With regard to such a double-sided printing operation, if a large amount of printing is performed under a low temperature start condition and the inside of the machine is not yet warmed, the water droplet 60 in the double-sided conveyance path 51 is picked up at the tip of the second surface during the double-sided printing operation. There is a risk that a two-sided transfer defective image occurs.

  Accordingly, paper conveyance for preventing defective transfer images under such conditions will be exemplarily described by focusing on one sheet (first sheet in the sheet feeding order to which water droplets adhere). In order to remove the water droplets on the second surface of the first sheet in the paper feeding order, the second surface of the paper that passes through the double-sided conveyance path 51 and reaches the secondary transfer unit 54 is left blank without any image formation. Then, after passing through the fixing nip, the sheet is again conveyed to the switchback path 57 and switched back to enter the duplex conveying path 51. Then, since the surface on which image formation has already been performed (first surface) comes to the image forming side, image formation is not performed again, and image formation is performed after the paper is reversed using the switchback path 57. As a result, water droplets can be evaporated at the fixing nip 56, the cost is not increased, the paper is not wasted, and the optimum image can be formed even under the above conditions without deteriorating the user-friendliness.

  Next, in FIG. 3, the first double-sided interleaf control (normal double-sided printing mode) and the second interleaf control (double-sided printing including empty paper for moisture removal) in non-stacked interleaf double-sided printing. Mode: two examples). FIG. 3A shows conventional interleaf double-sided control (first mode). The definition of the phrase in FIG. 3 will be described first. A phrase such as “one-sided back” in the square represents the image order, and the square itself represents the image formation order. Words such as “paper feed 1” below the square represent the order of feeding from the paper feeder. Words such as “paper discharge 1” above the square represent the order of paper discharge.

As seen in FIG. 3 (a), which is a surface table one surface to generate defective transfer. 3 (b) and 3 (c) include a place for forming a blank sheet and changing the direction of this portion (second mode). This difference depends on when the two operations described above are performed. As can be seen from the fact that they are the same from the seventh square, normal interleaf control is performed thereafter.

  The necessity of changing to the above mode may be determined, for example, by information on the temperature / humidity sensor in the machine, the number of job counters, etc., and may be selected by the user, or may be determined automatically by control. In addition, in order to ensure that moisture adheres to the paper, in the second mode, if the double-sided conveyance roller 58 (FIG. 2) is slowed down and the paper is slackened and rubbed against the guide plate, water droplets are reliably removed. it can.

  In addition, when transporting paper without carrying out a transfer operation, the moisture content of the paper is changed to other values in order to change the temperature of the fixing device and the passing speed to promote evaporation and to optimize the image. If the transfer bias is changed in accordance with the paper that is lower than the paper in the paper feeding order, a more optimal image can be formed.

  The above example is an interleaf double-sided control that outputs three or more sheets, and empty sheets are inserted twice in consideration of out of order. On the other hand, FIG. 3D is an example of two-sheet output (BBAA output). In this case, empty paper can be used only once by bringing empty paper (blank paper) to the top. You may continue the double-sided printing after the 3rd sheet after this. Accordingly, the empty paper can be completed only once and double-sided printing of the third or more sheets is also possible.

  A flow combining these is shown in FIG. First, switching between the first mode and the second mode is performed by detecting temperature / humidity with a temperature or humidity sensor and comparing it with a predetermined value. Also, the mode switching selection is made when the single-sided sheet count before the double-sided printing command is compared with a predetermined value and exceeds the predetermined value. The mode selection may be determined by a user operation, or a control means for automatically determining may be provided. These can be used independently.

1 is a schematic configuration diagram of an image forming apparatus. FIG. 3 is a diagram illustrating a fixing device and a sheet reversing path. It is a conceptual diagram for explaining the interleaf control of duplex printing, a is the conventional interleaf duplex control, b and c are the interleaf control according to the present invention, and d is the BBAA control according to the present invention. is there. It is a flow in the interleaf control according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 22 Fixing device 23 Discharge / switch back roller 24 Registration roller pair 50 Single-sided conveyance path 51 Double-sided conveyance path 52 Branch point 54 Secondary transfer part 56 Fixing nip 57 Switchback path 58 Double-sided conveyance roller 59 Paper discharge port 60 Water droplet

Claims (12)

In an image forming apparatus capable of performing double-sided image formation by reversing the recording medium as an image forming apparatus for transferring and fixing a toner image,
A first double-sided printing mode for performing the first surface of the recording medium reaches the transfer position via the conveying path transfer to the second surface which is opposite the fixing after image formation on the first surface, the first surface After the image is formed, the sheet is passed through the fixing device without transferring to the second surface opposite to the first surface of the recording medium, which passes through the double-sided conveyance path, and then transferred and fixed to the second surface. And a second double-sided printing mode. In an image forming apparatus capable of performing double-sided image formation by interleaf control in which a recording medium is reversed and a plurality of recording media are circulated in the apparatus, as an image forming apparatus that transfers and fixes a toner image.
A first double-sided printing mode for performing double-sided image formation by the interleaf control is passed through the fixing device without performing transcription prior to the second surface of the image formation of the first recording medium Kyushijun, An image forming apparatus comprising: a second double-sided printing mode for forming an image on the second side and performing interleaf control thereafter. In an image forming apparatus capable of performing double-sided image formation by BBAA control in which a recording medium is reversed and two recording media are circulated in the apparatus as an image forming apparatus for transferring and fixing a toner image.
A first double-sided printing mode in which double-sided image formation is performed by BBAA control, and a second double-sided mode in which one side of the first recording medium in the paper feeding order is passed through the fixing device without being transferred , and thereafter BBAA control is performed . An image forming apparatus comprising: a printing mode .   The image forming apparatus according to claim 1, wherein a branch point of a single-sided printing path and a reversing path is above the fixing device. A sensor relating to temperature or humidity is provided, and switching between the first double-sided printing mode and the second double-sided printing mode is selected based on a result of comparison of a detection value by the sensor with a predetermined value. 5. The image forming apparatus according to claim 4. 5. The switching selection between the first double-sided printing mode and the second double-sided printing mode is performed when the single-sided sheet passing count before the double-sided printing command exceeds a predetermined value set in advance. The image forming apparatus according to claim 1. The image forming apparatus according to claim 1, wherein switching between the first duplex printing mode and the second duplex printing mode can be manually performed. . The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to be able to automatically switch between the first duplex printing mode and the second duplex printing mode .   5. The linear speed of the roller provided in the reversing path is made slower than the other recording medium conveying rollers in the second duplex printing mode. Image forming apparatus.   5. The image according to claim 1, wherein the recording medium conveyance speed of the fixing device in the second double-sided printing mode is different from the speed in the first double-sided printing mode. Forming equipment.   5. The image forming apparatus according to claim 1, wherein the temperature setting of the fixing device in the second double-sided printing mode is different from the setting in the first double-sided printing mode. 6. .   The image forming apparatus according to claim 1, wherein the transfer bias setting in the second double-sided printing mode is different from the setting in the first double-sided printing mode.

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