JP2014178418A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of, when a printing mode is switched to a color printing mode or a monochrome printing mode, switching a drive method of drive means of an intermediate transfer belt in accordance with the printing mode and excellently suppressing generation of color shifting, an image disturbance, or the like.SOLUTION: A printer 100 which forms an image on a sheet P using toner is configured to comprise: photoreceptor drums 1Y, 1M, 1C, 1K; image forming units 60Y, 60M, 60C, 60K including an intermediate transfer belt 8 which rotates endlessly, a transfer drive motor 101 and the like; a light exposure device 7; sheet feeding means such as a sheet feeding cassette 26; and control means which controls each section. The control means performs image formation, switching a drive control method for the transfer drive motor 101 which rotationally drives the intermediate transfer belt 8 to a FB control method or a FG control method in accordance with switching to a monochrome printing mode or a color printing mode.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile machine, or a plotter apparatus.

  2. Description of the Related Art Conventionally, image forming apparatuses that form color images using a plurality of color toners have been widely implemented as analog or digital color copiers, printers, facsimile machines, and the like. Recently, it has been widely implemented as a multifunction printer (MFP) or the like. Such an image forming apparatus includes an intermediate transfer member, and forms a toner image of a different color by attaching a developer such as toner to a latent image on the surface of a plurality of image carriers, and forms a toner image of each color. Transfer is performed by being superimposed on an endless belt (intermediate transfer belt) conveyed on the intermediate transfer member (intermediate transfer). Thereafter, in synchronization with the conveyance timing of the sheet conveyed to the end of the intermediate transfer body, the toner image on the intermediate transfer belt is transferred onto the sheet (secondary transfer), and fixed by a fixing unit, whereby a color image is obtained. Or a monochrome image is formed.

  Here, the transfer of the toner image of the image carrier to the intermediate transfer belt is performed by pressing the intermediate transfer belt against the image carrier with an intermediate transfer roller arranged corresponding to each image carrier. . When printing a color image, the primary transfer roller for all colors is brought into contact with the intermediate transfer roller during intermediate transfer, so that the image carrier of each color and the intermediate transfer belt are brought into contact with each other on the intermediate transfer roller. Color images are transferred sequentially to enable color printing. On the other hand, when printing a monochrome image, the primary transfer roller corresponding to a color other than black is moved away from the intermediate transfer roller, and the black only intermediate transfer roller and the image carrier are brought into contact with the intermediate transfer belt. By doing so, monochrome printing is possible.

  The conveyance drive of the intermediate transfer belt is driven and controlled by a drive motor. As a drive control system for this drive motor, a system (FB control) that feeds back the fluctuation of the transfer speed of the intermediate transfer belt to the drive motor by a signal from an encoder provided coaxially with a support roller that stretches the intermediate transfer belt. And a method (FG control) for controlling the rotational fluctuation component of the drive motor itself is already known.

  However, when color printing is performed, the toner images of the respective colors may be misaligned during the intermediate transfer of the toner image to the intermediate transfer belt, which may cause color misregistration in the image. As the cause, the speed of the intermediate transfer belt varies due to the eccentricity of the driving roller that drives the intermediate transfer belt and the temperature change. Further, when thick paper is used as the paper, the transport speed of the thick paper may change as compared with the case where plain paper is used. For this reason, the paper conveyance timing and the toner image transfer timing from the intermediate transfer belt are shifted, and the image transfer may not be performed well, and streaky image disturbance may occur in the image.

  Techniques for suppressing such color shifts and image disturbances and improving image quality are disclosed (for example, see Patent Documents 1 to 7). For example, Patent Document 1 discloses a configuration in which a driving roller is disposed in the vicinity of a portion where the largest load fluctuation occurs in order to prevent a significant speed fluctuation of the intermediate transfer belt in any printing method. . With this configuration, for example, an object is to obtain high image quality even when the contact condition of the primary transfer roller to the intermediate transfer belt is different in monochrome printing or color printing.

  However, the transfer driving control of the intermediate transfer belt described in Patent Document 1 does not support switching between the FB control and the FG control according to detailed conditions such as the type, thickness, and printing mode of the paper. On the other hand, for example, Patent Document 6 discloses a method for determining in advance whether a monochrome mode or thick paper before starting a print job and determining a control method corresponding to this determination. In this case, when the monochrome mode or the thick paper is determined, the FG control method is switched. In other cases, for example, in color printing, the FB control method is switched.

  As described above, in Patent Document 6 and the like, it is determined which control method is to be used for each print job. However, when printing a document composed of a plurality of sheets in which color originals and monochrome originals are mixed, monochrome printing and color printing are mixed in one print job. For this reason, in the determination before the start of the print job, even if such a mixture exists, printing is performed with one of the control methods. In addition, as for paper, plain paper and cardboard may be mixed and conveyed. From the above, even when monochrome printing and color printing coexist, switch between a control method that supports monochrome printing and a control method that supports color printing within a single print job. Development of a technique that can print well without causing it is desired.

  The present invention has been made in view of the above circumstances, and when the print mode is switched to monochrome printing or color printing, the intermediate transfer belt driving means is adapted to a more suitable control method corresponding to the print mode. An image forming apparatus capable of switching between the control methods and suppressing the occurrence of color misregistration and image distortion even when monochrome printing and color printing are mixed and the print mode is changed during printing. The purpose is to provide.

  In order to achieve the above object, an image forming apparatus according to the present application includes a plurality of image carriers, and an image forming unit that forms toner images by attaching toner to latent images formed on the surfaces of the plurality of image carriers. The toner image on the surface of the image carrier is transferred onto the surface of the belt member that moves endlessly or the recording material held on the surface of the belt member by sequentially superimposing the toner images on the plurality of image carriers. A transfer unit that forms a multicolor image or a single color image, a drive unit that drives and moves the belt member, and a belt member conveyance speed driven by the drive unit are detected, and the drive unit is controlled based on the detection result. Then, the first control method for controlling the conveying speed of the belt member and the signal generated from the driving means are detected, and the driving means is driven so as to hold a predetermined driving force based on the detection result. Control belt means Driving control means for controlling the driving of the driving means by switching to any one of the second control methods for controlling the conveyance speed of the image forming apparatus, the drive control means for each image during the formation of a plurality of images, It is determined whether the image is a multicolor image or a single color image, and the control method of the driving means is set to either the first control method or the second control method in accordance with the determination result. It is characterized by switching.

  According to the present invention, when switching the printing mode to monochrome printing or color printing, it is possible to switch the control method of the driving means of the intermediate transfer belt to a more suitable control method corresponding to the printing mode, Even when monochrome printing and color printing are mixed and the print mode is changed during printing, an image forming apparatus capable of suppressing occurrence of color misregistration, image disturbance, and the like can be obtained.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment. It is an enlarged view which shows the detail of the image formation unit of FIG. FIG. 6 is an explanatory diagram for describing a drive configuration of an intermediate transfer unit that rotationally drives an intermediate transfer belt. 6 is a flowchart illustrating a flow of control method switching processing during execution of a print job. 7 shows a table associating print modes and paper types with print speeds and control methods. FIG. 7 is an explanatory diagram for explaining an operation at the time of switching a print mode in an intermediate transfer unit during execution of a print job, and is a diagram illustrating a configuration of a primary transfer roller. It is the schematic which shows the positional relationship of the filler of the contact / separation drive gear with respect to a photosensor, and the primary transfer roller for three colors.

  Hereinafter, an image forming apparatus according to Embodiment 1 of the present application will be described with reference to FIGS. FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to the first embodiment. FIG. 2 is an enlarged view showing details of the image forming unit of the image forming apparatus of FIG. The first embodiment is an example in which the image forming apparatus is applied to a tandem full-color printer (hereinafter simply referred to as “printer”). The image forming apparatus referred to in the present application is not limited to a printer, but includes a copying machine, a facsimile machine, a printing machine, and an apparatus that combines these functions. The printer of this embodiment forms an image using toners of four colors of yellow, cyan, magenta, and black, and is provided with members corresponding to the respective colors. Hereinafter, in the description and drawings of the present specification, at the end of the reference numeral, Y is added to the yellow member, M is added to the magenta member, C is added to the cyan member, and K is added to the black member. Display or explain. Further, in the following description, the upper or upper portion of the page of FIG. 1 is the upper or upper portion of the printer 100, and the lower or lower portion of the plane of FIG. 1 is the lower or lower portion of the printer.

[Printer configuration and operation]
As shown in FIG. 1, the printer 100 according to the first embodiment includes photoconductor drums 1Y, 1M, 1C, and 1K, image forming units 60Y, 60M, 60C, and 60K, an exposure device 7, and a paper feed cassette 26. And control means (not shown) for controlling the entire operation of the printer 100 including the operations of these units. This control means is a drive for controlling the drive of a transfer drive motor 101 described later by appropriately switching between a first control means described later and a second control means when the print mode is switched to the color print mode or the monochrome print mode. It also has a function as a control means.

  The control means includes a CPU (Central Processing Unit) that executes various calculations and drive control of each part, a ROM (Read Only Memory) that stores in advance fixed data such as a computer program, a work area that stores various data in a rewritable manner, etc. RAM (Random Access Memory) functioning as an HDD, a hard disk drive (HDD) for storing and storing various data, and the like.

  Photosensitive drums 1Y, 1M, 1C, and 1K as image carriers are image forming means for forming images of yellow (Y), magenta (M), cyan (C), and black (K), which will be described later. Function as. As shown in FIG. 1, four photosensitive drums 1Y, 1M, 1C, and 1K are arranged in parallel at equal intervals in the printer 100. During printing, a transfer drive motor 101 and a drive that will be described later are driven. The roller 14 is rotationally driven in a certain direction. These photosensitive drums 1Y, 1M, 1C, and 1K have a layer structure in which an organic semiconductor layer that is a photoconductive material is provided on the surface of an aluminum cylinder of about 30 mm to 120 mm.

  Further, image forming members such as developing devices 2Y, 2M, 2C, and 2K and cleaning devices 3Y, 3M, 3C, and 3K are sequentially arranged around the photosensitive drums 1Y, 1M, 1C, and 1K. Yes. These devices constitute image forming units 60Y, 60M, 60C, and 60K that can be detached from the main body of the printer 100 for each color.

  Next, a detailed configuration of the image forming units 60Y, 60M, 60C, and 60K will be described with reference to FIG. The developing devices 2Y, 2M, 2C, and 2K form electrostatic latent images on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K, and form toner images by attaching toners of various colors to the electrostatic latent images. The developing devices 2Y, 2M, 2C, and 2K include developing rollers 21Y, 21M, 21C, and 21K, developing blades 22Y, 22M, 22C, and 22K, conveying screws 23Y, 23M, 23C, and 23K, and charging rollers 24Y, 24M, and 24C. , 24K and the like.

  The cleaning devices 3Y, 3M, 3C, and 3K are devices that collect toner remaining on the surface of the photosensitive drums 1Y, 1M, 1C, and 1K after the toner image is transferred. The cleaning devices 3Y, 3M, 3C, 3K are configured to include cleaning brushes 31Y, 31M, 31C, 31K, cleaning blades 32Y, 32M, 32C, 32K, toner recovery screws 33Y, 33M, 33C, 33K, and the like. ing.

  As shown in FIG. 1, an exposure device 7 is provided below the photosensitive drums 1Y, 1M, 1C, and 1K. The exposure device 7 scans the surface of the photosensitive drums 1Y, 1M, 1C, and 1K charged by the charging rollers 24Y, 24M, 24C, and 24K as charging means with laser light corresponding to the image data of each color. An electrostatic latent image is formed.

  The exposure device 7 is a laser scanning type exposure device having a laser light source, a polygon mirror, and the like, and emits light beams modulated in accordance with image data to be formed from four semiconductor laser light sources (not shown). To emit. This light beam scans the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K via an aperture lens (not shown), a polygon mirror 71, a scanning lens 72, and a mirror 73, and an electrostatic latent image is formed on the surface. Form.

  Below the exposure device 7, paper feeding means including a paper feeding cassette 26, a paper feeding roller 27, and the like is installed. The paper feed cassette 26 stores a plurality of sheets P as sheet-like recording materials, and a paper feed roller 27 is brought into contact with the uppermost paper P. The paper feed roller 27 is rotated by driving means (not shown), and feeds the uppermost paper P of the paper feed cassette 26 toward the paper feed path indicated by the one-dot chain line in FIG.

  A registration roller pair 28 is installed on the downstream side of the paper feed path. The registration roller pair 28 rotates to pinch and hold the paper P, but temporarily stops rotating when the paper P is pinched. Then, at an appropriate timing, the paper P is sent out to a secondary transfer roller pair described later.

  As shown in FIG. 1, the developing devices 2Y, 2M, 2C, and 2K are each provided with two screws 23Y, 23M, 23C, and 23K for stirring and conveying the toner and the carrier. In addition, toner cartridges 32Y, 32M, 32C, and 32K that store toner of each color are installed on the cartridge support portion 51 above the developing devices 2Y, 2M, 2C, and 2K. Toner is supplied into the developing devices 2Y, 2M, 2C, and 2K from toner supply means (not shown) connected to the toner cartridges 32Y, 32M, 32C, and 32K. The toner is agitated together with the carrier by the conveying screws 23Y, 23M, 23C, and 23K shown in FIG. 2, and is conveyed in the developing blades 22Y, 22M, 22C, and 22K directions.

  The toner and the carrier thus conveyed are supplied to the surfaces of the developing roller rollers 21Y, 21M, 21C, and 21K in a state where the thickness of the toner layer to be placed is regulated by the developing blades 22Y, 22M, 22C, and 22K. To form a toner layer. Then, the latent image is visualized by transferring the toner from the toner layer on the surface of the developing rollers 21Y, 21M, 21C, and 21K to the photosensitive drums 1Y, 1M, 1C, and 1K. In this way, the latent images formed on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K by the beam light are developed by the developing devices 2Y, 2M, 2C, and 2K that handle toner of a predetermined color, and are visualized. (Toner image) (development).

  Further, as shown in FIG. 2, an endless intermediate transfer belt 8 that moves endlessly on the upper part of the four photosensitive drums 1Y, 1M, 1C, and 1K, and the intermediate transfer belt 8 moves while being stretched. An intermediate transfer unit 15 is disposed. The intermediate transfer unit 15 includes primary transfer rollers 9Y, 9M, 9C, and 9K as transfer means disposed opposite to the photosensitive drums 1Y, 1M, 1C, and 1K, a driven roller 11, and secondary transfer as transfer means. A plurality of rollers such as a roller 12, a cleaning backup roller 13, and a driving roller 14 are provided. The intermediate transfer belt 8 is stretched by a driving roller 14, a driven roller 11 as a support roller, a secondary transfer roller 12, and a cleaning backup roller 13. In the intermediate transfer unit 15, the intermediate transfer belt 8 is moved in the direction of the arrow by driving the drive roller 14 from a transfer drive motor 101 as a drive unit. By this movement, the toner images carried by the photosensitive drums 1Y, 1M, 1C, and 1K are electrostatically transferred onto the surface of the intermediate transfer belt 8 (primary transfer).

  Note that toner and deposits remaining on the surface of the photosensitive drums 1Y, 1M, 1C, and 1K without being transferred to the intermediate transfer belt 8 are cleaned by the cleaning devices 3Y, 3M, 3C, and 3K shown in FIGS. The blades 32Y, 32M, 32C, and 32K are removed. The toner and the like removed from the cleaning blades 32Y, 32M, 32C, and 32K are conveyed to a waste toner storage unit (not shown) by the toner collection screws 33Y, 33M, 33C, and 33K. Lubricants are applied to the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K from which the toner has been removed by the cleaning brushes 31Y, 31M, 31C, and 31K.

  In the primary transfer, assuming that the left side of FIG. 1 is upstream, the toner images are sequentially superimposed and transferred onto the surface of the intermediate transfer belt 8 by the photosensitive drums 1Y, 1M, 1C, and 1K. After this primary transfer, the toner image transferred to the surface of the intermediate transfer belt 8 enters a secondary transfer roller pair including a secondary transfer roller 12 and a secondary transfer bias roller 19 facing the toner image on the downstream side. (Secondary transfer). Further, the toner remaining on the intermediate transfer belt 8 without being transferred to the paper P is removed by the belt cleaning device 10 and the cleaning backup roller 13.

  The latent image (toner image) transferred onto the paper P as described above is easily peeled off from the paper P as it is. Therefore, the paper P is further conveyed to the fixing device 20 having a fixing roller pair (nip portion) composed of a fixing roller 20a having a heater H in the tube and a pressure roller 20b opposed to the fixing roller 20a. In the fixing device 20, the toner of the latent image melted by the heat of the heater H of the fixing roller 20a is fixed on the paper P by applying pressure at the nip portion composed of the fixing roller 20a and the pressure roller 20b. . Finally, the paper P is discharged to the outside via the paper discharge roller pair 29, whereby a series of printing processes is completed. The paper P discharged to the outside is stacked on the stack 50a.

[Configuration of intermediate transfer unit]
Next, the configuration of the intermediate transfer unit 15 that moves the intermediate transfer belt 8 and the details of the drive control system will be described with reference to FIG. FIG. 3 is a schematic diagram showing the intermediate transfer unit 15 related to driving of the photosensitive drums 1Y, 1M, 1C, and 1K and the intermediate transfer belt 8 among the drive configurations of the image forming units 60Y, 60M, 60C, and 60K. is there. 3 shows a state where the photosensitive drums 1Y, 1M, 1C, and 1K and the intermediate transfer unit 15 of FIG. 1 are viewed from the opposite side (back side), that is, a state viewed from the drive unit side. For convenience of drawing, etc., FIG. 3 is drawn on a scale different from the scale between the members in FIG.

  As shown in FIG. 3, the intermediate transfer unit 15 includes a transfer drive motor 101, photosensitive drum drive gears 102Y, 102M, 102C, and 102K, transfer idler gears 103, 104, An intermediate transfer member drive gear 105, a second drive motor 106, a drive relay gear 107, and the like are provided. Further, as described above, the transfer drive motor 101 and other drive means are controlled by the control means as the drive control means.

  In this embodiment, the photosensitive drums 1Y, 1M, 1C, and 1K and the intermediate transfer belt 8 are divided into a monochrome printing mode for forming a monochrome image (monochromatic image) and a color printing mode for forming a color image (multicolor image). It is comprised so that a contact state may be changed. In the color printing mode, the photosensitive drums 1Y, 1M, 1C, and 1K for the respective colors are brought into contact with the intermediate transfer belt 8 while being rotated. On the other hand, in the monochrome printing mode, only the black photosensitive drum 1K is rotated and brought into contact with the intermediate transfer belt 8, so that the primary transfer rollers 9Y, 9M, and 9C for three colors other than black are moved to the photosensitive drum. Move in a direction away from 1Y, 1M, 1C. At the same time, the rotation of these photosensitive drums 1Y, 1M, 1C is stopped. For such switching, driving means for the black photosensitive drum 1K and driving means for the other color photosensitive drums 1Y, 1M, and 1C are provided separately. Hereinafter, each driving means will be described.

  The transfer drive motor 101 mainly has a function of directly driving the intermediate transfer body drive gear 105. As shown in FIG. 3, the transfer drive motor 101 is also configured to have a function as a drive means of a photosensitive drum drive gear 102Y for rotating the photosensitive drum 1Y for black.

  In the case of the configuration shown in FIG. 3, the gear cut on the shaft of the transfer driving motor 101 meshes with the photosensitive drum driving gear 102K, and finally the driving force is transmitted to the photosensitive drum 1K. The driving force transmitted to the photosensitive drum driving gear 102K is also transmitted to the transfer idler gears 103 and 104 and further to the intermediate transfer member driving gear 105. The intermediate transfer member driving gear 105 and the secondary transfer roller 12 are jointly connected mainly coaxially.

  On the other hand, as a driving means for the other three-color photosensitive drums 1Y, 1M, and 1C, there is a configuration in which a driving motor is installed for each color. However, in the first embodiment, as in the configuration shown in FIG. 3, the driving unit is configured to drive the photosensitive drums 1Y, 1M, and 1C for three colors by one second driving motor 106. Specifically, a gear cut on the shaft of the second drive motor 106 meshes with and drives the photosensitive drum driving gear 102C and the photosensitive drum driving gear 102M. Further, the driving relay gear 107 that meshes with the driving of the photosensitive drum driving gear 102M drives the photosensitive drum driving gear 102Y that meshes with the driving relay gear 107. Finally, the driving force of each of the photosensitive drum driving gears 102Y, 102M, and 102C is transmitted to the photosensitive drums 1Y, 1M, and 1C, and rotates them in the direction indicated by the arrow.

  As described above, the rotation of the black photosensitive drum 1K and the three-color photosensitive drums 1Y, 1M, and 1C is independently performed. These photosensitive drums 1Y, 1M, and 1C transfer the latent images of the respective colors separately.

  Here, the conveyance speed of the intermediate transfer belt 8 is uneven due to the undulation of the intermediate transfer belt 8, the distortion of the surfaces of the primary transfer rollers 9Y, 9M, 9C, and 9K, and the rotation unevenness of the transfer drive motor 101 and the second drive motor 106. May occur. Due to the unevenness of the conveyance speed, a position where the toner images of the respective colors are transferred may be shifted, resulting in image color shift or image disturbance.

  There are mainly two ways to reduce the color misregistration: a feedback control system (FB control system) as a first control system and an FG control system (motor constant speed control system) as a second control system. The control method is taken. In the FB control method, the rotation variation of the drive roller 14 is detected as rotation information by an encoder sensor attached on the same axis as the drive roller 14. A correction value of the motor rotational speed calculated from the fluctuation is returned to the transfer drive motor 101, and the rotational speed of the transfer drive motor 101 is feedback-controlled. In the FG control method, the FG signal emitted from the motor is directly read and the motor is driven at a constant rotational speed so that the frequency of the FG signal is maintained at a target constant frequency. Reduces rotation unevenness.

  In order to suppress color misregistration and image disturbance more effectively and to obtain good image quality, these control methods use the advantages of each method rather than using only one of them, such as print mode. It is preferable to select a more suitable control method corresponding to various conditions. For example, the FB control is preferable in that it can correct the fluctuation due to the distortion of the surfaces of the primary transfer rollers 9Y, 9M, 9C, and 9K and the secondary transfer roller 12, but depending on the correction, there may be a sudden speed fluctuation. As a result, the image becomes partially dense at the timing of the correction, and it may appear as a band (shock jitter). Therefore, it is desirable to determine the control method depending on whether priority is given to color misregistration correction or shock jitter correction depending on the printing speed and printing mode. In consideration of these points, in the present application, drive control of the intermediate transfer unit 15 is performed as follows.

[Drive control of intermediate transfer unit]
Hereinafter, drive control of the intermediate transfer belt 8 during printing by the intermediate transfer unit 15 in the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart illustrating a flow of control method switching processing during execution of a print job. FIG. 4 shows a table in which print modes and paper types are associated with print speeds and control methods.

  First, when printing is performed by the printer 100, for example, depending on the monochrome printing mode for performing monochrome printing or the color printing mode for performing color printing, and further, depending on the type of paper (transfer paper) P to be printed, the image quality, and the like. The printing speed and control method will be selected. Therefore, as shown in FIG. 5, for each of monochrome printing or color printing, the printing speed for each sheet and the control method of the transfer drive motor 101 for each printing speed are set in advance and stored in the memory or the like of the control means. deep. The control method can be set or changed on an operation panel (not shown) before printing for each of the above conditions.

  Hereinafter, the flow of the switching process between the FB control method and the FG control method will be described with reference to the flowchart of FIG. First, in step S1, it is determined whether or not the color printing mode is set. If YES is determined in step S1, that is, if the color printing mode is set, the printing speed is determined in step S2. Here, first, it is determined whether it is plain paper, thick paper 1, thick paper 2, or thick paper 3 according to the type and thickness of the paper P. This determination is performed as follows. First, the paper feed cassette 26 and thickness are selected on the operation panel, and when the judgment result of a paper thickness detection sensor (not shown) in the selected paper feed cassette 26 is met, the conveyance speed and fixing of the paper P are fixed. The pressing force of the roller 20a is determined. Based on this determination, the type and thickness of the paper P are determined. Based on this determination, the printing speed corresponding to the type and thickness of the paper is determined with reference to the color column shown in the table of FIG.

  It should be noted that any method may be used to determine whether the mode is the monochrome printing mode or the color printing mode in accordance with the configuration of the printer 100 or the like. In this embodiment, as will be described in detail later, when the printer 100 switches between the monochrome printing mode and the color printing mode, the primary transfer rollers 9Y, 9M, 9C, and 9K shown in FIG. 108 is moved in the contact direction or the separation direction with respect to the intermediate transfer belt 8. The control unit detects the switching of the signal from the photosensor that monitors the movement state, and determines the type of the print mode based on the detection result.

  Next, in step S3, a contact operation of the primary transfer rollers 9Y, 9M, and 9C for color to the photosensitive drums 1Y, 1M, and 1C is executed for printing in the color printing mode. Specifically, the primary transfer rollers 9Y, 9M, and 9C are moved in a direction approaching the photosensitive drums 1Y, 1M, and 1C for color printing, and the primary transfer rollers 9Y, 9M, and 9C and the photosensitive drums 1Y, 1M, and 1C are moved. 1C is brought into contact with the intermediate transfer belt 8.

  In the next step S4, a control method is determined. To do so, first, based on this determination result, the type of paper P is set as the printing condition. When the printing conditions are set as described above, the control method information of the transfer driving motor 101 shown in the table of FIG. 5 stored in the memory is referred to for the combination of the conditions (color printing mode and the type of the paper P). Then, a control method (FG control method or FB control method) corresponding to the condition is selected.

  On the other hand, if NO is determined in step S1, that is, if the monochrome printing mode is selected, the printing speed is determined in step S5. Also in this case, the type and thickness of the paper P are determined, and based on this determination, the monochrome speed shown in the table of FIG. 5 is referred to and the printing speed corresponding to the type and thickness of the paper is determined.

  Next, in step S6, the control method corresponding to the printing condition (monochrome print mode and type of paper P) is selected from the type of paper P with reference to the table shown in FIG. Note that color misregistration does not occur in the monochrome printing mode, so the printing speed may be selected according to the type of paper P or the like. Therefore, in this embodiment, in the case of monochrome printing, as shown in Table 5 of FIG. 5, the FG control method is set for all control methods.

  Next, in step S7, the control method selected in step S4 or step S6 is switched to drive the transfer drive motor 101 so as to achieve the selected printing speed, and the image forming units 60Y, 60M, 60C, 60K and intermediate Printing is performed by the transfer unit 15.

  When printing for one image (one sheet of paper P) is completed, it is determined in step S8 whether printing is completed, that is, whether one print job is completed. If the determination in step S8 is YES, that is, if the print job is completed, the process ends. On the other hand, if the determination in step S8 is NO, that is, if the print job is in progress, the process returns to step S1 and the processing from the determination of the print mode to printing is performed for the next image (steps S1 to S1). Step S7) is repeated.

  As described above, in the first embodiment, the processing of Step S1 to Step S7 is repeated from the start to the end of one print job, and the print mode is determined for each image to be printed. Therefore, even when the monochrome print mode and the color print mode are mixed in one print job, a suitable control method corresponding to the print mode can be selected. In the present embodiment, not only the print mode but also the finer conditions such as the type and thickness of the paper P are dealt with to switch to a more suitable control method and print speed. Therefore, it is possible to perform printing without being affected not only by the print mode but also by the paper type, etc., to further improve the effect of preventing color misregistration and printing disturbance, and to maintain excellent image quality. it can. The printing conditions other than the printing mode are not limited to the type and thickness of the paper P. For example, more detailed condition classification is performed in response to environmental changes such as temperature and humidity and other conditions. Thus, more suitable control method switching and printing speed adjustment may be performed.

  Next, the operation at the time of switching the print mode in the intermediate transfer unit 15 after determining the print mode and selecting the control method in steps S1 to S4 during execution of the print job will be described with reference to FIGS. Will be described with reference to FIG. FIG. 6 is a schematic diagram showing a configuration of primary transfer rollers (9K to 9Y in FIG. 1) mainly corresponding to color colors other than black. 6 is a view of the intermediate transfer unit 15 as seen from the same direction as FIG. That is, it is the figure seen from the opposite side to FIG. FIG. 7 is a schematic diagram showing the positional relationship between the filler 112 of the contact / separation drive gear 111 with respect to the photosensor (not shown) and the primary transfer rollers 9Y, 9M, and 9C for three colors.

  As shown in FIG. 6, the intermediate transfer unit 15 includes the primary transfer body contact / separation drive motor 108, levers 110Y, 110M, 110C, and 4 which press the four primary transfer rollers 9Y, 9M, 9C, and 9K toward the intermediate transfer belt 8, respectively. 110K, and link mechanisms 109Y, 109M, and 109C that connect to the three color levers 110Y, 110M, and 110C, a link mechanism 109K that connects to the black lever 110K, and the like. The intermediate transfer unit 15 further includes a contact / separation drive gear 111 having a cam (not shown), a filler 112, and the like. Details of these will be described later.

  In the intermediate transfer unit 15, the primary transfer rollers 9Y, 9M, 9C, and 9K used for printing are pushed down toward the opposing photosensitive drums 1Y, 1M, 1C, and 1K in accordance with the monochrome printing mode or the color printing mode. . With this pressing operation, the photosensitive drums 1Y, 1M, 1C, and 1K of the color to be transferred are pressed against the intermediate transfer belt 8. In this embodiment, as shown in FIG. 6, the contact / separation (contact and separation) of the primary transfer roller 9K for black and the contact / separation of the primary transfer rollers 9Y, 9M, 9C for the other three colors It is configured to be performed independently.

  First, the black primary transfer roller 9K will be described. The intermediate transfer unit 15 shown in FIG. 6 is mounted on the main body of the printer 100, and the shaft of the primary transfer roller 9K for black (K) and the lever 110K connected through the link mechanism 109K are locked. As a result, the primary transfer roller 9K for black is always in contact with the photosensitive drum 1K via the intermediate transfer belt 8.

  On the other hand, the vertical movement of the primary transfer rollers 9Y, 9M, and 9C for the other three colors is controlled by the following configuration. First, when one primary transfer body contact / separation drive motor 108 is driven, the drive is transmitted to the contact / separation drive gear 111 cut off the shaft of the primary transfer body contact / separation drive motor 108. The driven contact / separation drive gear 111 drives a cam provided coaxially with the contact / separation drive gear 111. The driven cam operates the levers 110Y, 110M, and 110C that are applied to the three primary transfer rollers 9Y, 9M, and 9C, and the three colors are used for the three colors via the three link mechanisms 109Y, 109M, and 109C. The primary transfer rollers 9Y, 9M, and 9C are configured to move up and down. The moving means in the contact direction or separation direction of the primary transfer rollers 9Y, 9M, 9C, and 9K with respect to the intermediate transfer belt 8 is not limited to the above-described configuration. Other configurations may be employed as long as the movement in the separation direction is possible.

  Further, the contact / separation drive gear 111 is provided with a filler shape (hereinafter referred to as “filler 112”). A photo sensor (not shown) is attached at an arbitrary position in the passage region of the filler 112 accompanying the rotation of the contact / separation drive gear 111 in the direction indicated by the arrow in FIG. The entry / exit timing of the filler 112 within the detection range of the photosensor and the relationship between the vertical positions of the primary transfer rollers 9Y, 9M, and 9C for the three colors are associated with each other.

  That is, the sequence is such that the primary transfer body contact / separation drive motor 108 stops a certain time after the photosensor signal is switched due to the entry and exit of the filler 112. By adopting such a sequence, the contact state and the separation state of the primary transfer rollers 9Y, 9M, and 9C for the three colors with respect to the photosensitive drums 1Y, 1M, and 19C are determined.

  FIG. 7 shows the relationship between the position of the filler 112 of the contact / separation drive gear 111 with respect to the photosensor and the positions of the primary transfer rollers 9Y, 9M, and 9C. As shown in FIG. 7, the filler 112 leaves the detection range of the photosensor, and the signal of the photosensor switches from Low to High. After 50 msec from this switching, the primary transfer body contact / separation drive motor 108 stops, and the primary transfer rollers 9Y, 9M, and 9C for three colors are separated from each other. This switches to the monochrome printing mode.

  Conversely, when the primary transfer rollers 9Y, 9M, and 9C are brought into contact with each other, the primary transfer body contact / separation drive motor 108 is operated to drive the contact / separation drive gear 111, and the filler provided in the contact / separation drive gear 111 is driven. 112 again falls within the detection range of the photo sensor, and the signal of the photo sensor switches from High to Low. After 50 msec from this switching, the primary transfer body contact / separation drive motor 108 stops. At the same time, the primary transfer rollers 9Y, 9M, and 9C for three colors are in contact with the surfaces of the photosensitive drums 1Y, 1M, and 1C, and the intermediate transfer belt 8 is applied to all the photosensitive drums 1Y, 1M, 1C, and 1K. It will abut. As a result, the color printing mode is switched.

  Note that the time from when the sensor signal is switched to when the primary transfer body contact / separation drive motor 108 stops depends on the transition time to each of the contact and separation states of the primary transfer rollers 9Y, 9M, and 9C. Here, when switching between the monochrome print mode and the color print mode occurs during the execution of one print job, the contact and separation operations of the primary transfer rollers 9Y, 9M, and 9C for three colors are executed. Along with this, signal switching of the photosensor as shown in FIG. 7 occurs. Therefore, the control unit of the printer 100 determines the print mode based on the state of the photosensor signal and switches the control method of the transfer drive motor 101.

  As described above, in the first embodiment, when the printing mode is switched between the monochrome printing mode and the color printing mode, the control of the transfer driving motor 101 that drives the intermediate transfer belt 8 corresponding to the printing mode. The method is switched. By driving and printing the transfer drive motor 101 in accordance with this control method, in the color printing mode, color misregistration can be satisfactorily suppressed, and a color image with excellent image quality can be obtained. Further, even in the monochrome printing mode, it is possible to obtain an excellent monochrome image by suppressing image disturbance on the stripe.

  Also, conventionally, before starting a print job, the print mode and paper type are determined in advance, and when the monochrome print mode or cardboard print mode is determined, or when an abnormality is found in the encoder sensor, the transfer motor is turned on. Switching to the FG control method. For this reason, when monochrome printing and color printing coexist in the middle of execution of one print job, it has not been possible to cope with printing modes other than the preset printing mode.

  On the other hand, in the present application, during the print job, the print mode is determined, and switching between the monochrome print mode and the color print mode is performed (in the first embodiment, the determination is based on the contact / separation of the primary transfer roller). Yes. Corresponding to this switching, the control mode of the transfer drive motor is also switched. Therefore, even when monochrome printing and color printing are mixed in a single print job, switching to the corresponding print mode and drive method enables printing to improve color misalignment and image distortion. Can be suppressed.

  The image forming apparatus according to Embodiment 1 of the present application has been described above. However, this embodiment is an example, and the present application is not limited thereto. During the formation of a plurality of images, for each image, it is determined whether the image is a multicolor image (color print mode) or a single color image (monochrome print mode). It is only necessary that the control method of the transfer belt driving means can be switched to a more suitable control method. Thus, even when the print mode is changed during image formation, it is possible to suppress the occurrence of color misregistration, image disturbance, and the like, thereby solving the problems of the present application.

1Y, 1M, 1C, 1K Photosensitive drum (image carrier)
2Y, 2M, 2C, 2K developing device (image forming means)
8 Intermediate transfer belt (transfer belt member)
9Y, 9M, 9C, 9K Primary transfer roller (transfer means)
11 Follower roller (support roller)
12 Secondary transfer roller (support roller, transfer means)
13 Cleaning backup roller (support roller)
14 Drive roller (drive means)
15 Intermediate transfer unit (transfer means)
60Y, 60M, 60C, 60K Image forming unit (image forming means)
101 Transfer drive motor (drive means)
108 Primary transfer body contact / separation drive motor (transfer roller drive motor)

JP 2006-133816 A JP 2011-043723 A JP 2009-294641 A JP 2011-059150 A JP 2011-248003 A JP 2012-063518 A JP 2013-003485 A

Claims (4)

A plurality of image carriers;
Image forming means for forming toner images by attaching toner to latent images formed on the surfaces of the plurality of image carriers;
The toner images on the surface of the image carrier are sequentially superposed on the surface of the belt member that moves endlessly or on a recording material held on the surface of the belt member. Transfer means for transferring and forming a multicolor image or a single color image;
Driving means for driving and moving the belt member;
A first control method for detecting a conveying speed of the belt member by driving the driving means, and controlling the conveying speed of the belt member by controlling the driving means based on the detection result; and the driving A second signal that detects a signal generated from the means and controls the driving means to control the conveying speed of the belt member so that the driving means holds a predetermined driving force based on the detection result; Switching to any of the control methods, and driving control means for controlling the driving of the driving means,
The drive control means determines whether the image is a multicolor image or a single color image for each of the images during the formation of a plurality of images, and in response to the determination result, the drive means An image forming apparatus, wherein the control method is switched to either the first control method or the second control method.   The drive control unit further selects the control method of the drive unit according to an image forming condition including the type or thickness of the recording material, either the first control method or the second control method. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to. The image forming means includes a plurality of transfer rollers respectively disposed corresponding to the plurality of image carriers, and a transfer roller that moves the transfer roller in a direction in which the transfer roller is in contact with the belt member and in a direction in which the transfer roller is separated from the belt member. A drive motor,
The control means is configured to determine whether the image is a multicolor image or a single color image, and the transfer roller when the transfer roller moves in a contact direction or a separation direction with respect to the belt member. 2. The drive motor signal switching is detected, the type of the image is determined based on the detection result, and the control method of the driving unit is switched according to the type of the image. Or the image forming apparatus according to 2; The belt member is stretched by a plurality of support rollers including a driving roller driven by the driving means,
The drive control means detects rotation information of one support roller selected from the plurality of support rollers, and feedback-controls the drive means of the belt member based on the detection result. The image forming apparatus according to any one of 1 to 3.