Image forming apparatus, image forming method, and program

Abstract

To provide an image forming apparatus that prevents the occurrence of a waiting time caused by forcible consumption of toner and prevents influence on image quality.SOLUTION: An image forming apparatus comprises an image carrier, developing means, an intermediate transfer body, first transfer means that performs primary transfer, second transfer means that performs secondary transfer, and a control unit. An operation of performing image formation so that a transfer rate of the primary transfer and a transfer rate of the secondary transfer become maximum or substantially maximum is defined as a normal operation. When an amount of toner consumption per unit travel distance of a developing member is equal to or less than a threshold, the control unit increases an amount of toner to be supplied from the developing means to the image carrier to an amount including an amount of toner to form a toner image and larger than that in the normal operation, controls the first transfer means and the second transfer means to transfer the toner image to a recording medium, and increases at least one of an amount of first transfer residual toner and an amount of second transfer residual toner compared with that in the normal operation.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] In an electrophotographic image forming apparatus, toner is supplied from a developing unit to an image carrier to form a toner image, and the toner image is then transferred to an intermediate transfer member or a recording medium. After the toner image is transferred to the recording medium, it is fixed by a fixing unit to form an image.

[0003] In such an image forming apparatus, when image formation at a low print ratio is repeated, the toner balance in the developing unit decreases, and the toner remains in the developing unit for a long period of time. In this case, the toner is repeatedly rubbed by the regulating blade of the developing unit, and the charging characteristics of the toner deteriorate. As a result, deterioration of image quality occurs, such as unevenness and fluctuations in image density.

[0004] To solve this problem, conventional techniques have proposed forcibly consuming toner in certain cases. Against this background, Patent Document 1 proposes a technique for effectively utilizing toner, instead of forcibly consuming toner or discarding it after forcibly consuming toner.

[0005] In Patent Document 1, if the print rate of a specific color continues to be below a certain threshold, the print rate of the color with a print rate below the certain threshold is increased compared to the setting for the current output when outputting a color image. Also, in Patent Document 1, if the print rate of a specific color continues to be below a certain threshold, a certain amount of the color with a print rate below the certain threshold is overlaid on the black image when outputting a monochrome image. For this reason, in Patent Document 1, consumable toner is added to the toner image formed on the recording medium. Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the consumable toner is overlaid on the toner image on the recording medium, which has the problem of affecting the image quality of the formed image. For example, this can cause changes in the density and color of the image, as well as affecting fixing offset. Therefore, there is a need for a technology that does not affect image quality when forcibly consuming toner with the aim of preventing deterioration of image quality due to toner degradation.

[0007] At the same time, there is a need to solve the problems with the conventional technology. In the conventional technology, a pattern for forcibly consuming toner is printed after image formation, and the forcible consumption of toner causes waiting time. When waiting time occurs due to the forcible consumption of toner, it can reduce user convenience and productivity. In Patent Document 1, there is no waiting time due to the forcible consumption of toner, but as mentioned above, image quality can be affected.

[0008] Therefore, the present invention aims to provide an image forming device that, when forcibly consuming toner for the purpose of preventing deterioration of image quality due to toner deterioration, does not cause waiting time due to the forcible consumption of toner and does not affect image quality. [Means for solving the problem]

[0009] In order to solve the above problems, the image forming apparatus of the present invention comprises: an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer means for secondarily transferring the toner image from the intermediate transfer body to a recording medium; a control unit, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the amount of toner supplied from the developing unit to the image carrier to include an amount of toner for forming the toner image and to be greater than that in the normal operation, controls the first transfer unit and the second transfer unit to transfer the toner image to the recording medium, and increases at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner to be greater than that in the normal operation. It is characterized by: [Effects of the Invention]

[0010] According to the present invention, when toner is forcibly consumed for the purpose of preventing deterioration of image quality due to toner deterioration, an image forming device can be provided that does not cause waiting time due to the forcible consumption of toner and does not affect image quality. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an overall schematic view for explaining an example of an image forming apparatus of the present invention. [Figure 2] FIG. 2 is a schematic diagram of the main part of FIG. 1. [Figure 3] FIG. 10 is a schematic diagram for explaining an example of a normal operation. [Figure 4] 4A to 4C are schematic diagrams (1) to (3) for explaining toner images on the members in FIG. 3. [Figure 5] 4A and 4B are diagrams for explaining selected values ​​of the transfer current in FIG. 3 and the transfer rate at that time. [Figure 6] FIG. 10 is a schematic diagram illustrating an example of a toner refresh operation. [Figure 7] 7A to 7C are schematic diagrams (1) to (3) for explaining toner images on the respective members in FIG. 6. [Figure 8] 7A and 7B are diagrams for explaining selected values ​​of the transfer current in FIG. 6 and the transfer rate at that time. [Figure 9]FIG. 10 is a diagram for explaining an example of a case where it is determined whether to perform a normal operation or a toner refresh. [Figure 10] 10 is a flow chart showing an example of image formation. [Figure 11] FIG. 1 is an example of a functional block diagram. [Figure 12] FIG. 2 is a diagram illustrating an example of a hardware configuration. [Figure 13] FIG. 10 is a schematic diagram for explaining another example of the toner refresh operation. [Figure 14] 14A to 14C are schematic diagrams (1) to (3) for explaining toner images on the respective members in FIG. 13. [Figure 15] 14A and 14B are diagrams for explaining selected values ​​of the transfer current in FIG. 13 and the transfer rate at that time. [Figure 16] FIG. 10 is a schematic diagram for explaining another example of the toner refresh operation. [Figure 17] 17A to 17C are schematic diagrams (1) to (3) for explaining toner images on each member in FIG. 16. [Figure 18] 17A and 17B are diagrams for explaining selected values ​​of the transfer current in FIG. 16 and the transfer rate at that time. [Figure 19] FIG. 10 is a schematic diagram for explaining another example of the toner refresh operation. [Figure 20] 20A and 20B are schematic diagrams for explaining toner images on each member in FIG. 19. [Figure 21] 20 is a diagram for explaining selected values ​​of the transfer current in FIG. 19 and the transfer rate at that time. FIG. [Figure 22] FIG. 10 is a schematic diagram for explaining the operation of the toner refresh according to Comparative Example 1. [Figure 23] 23A to 23C are schematic diagrams (1) to (3) for explaining the toner images on the members in FIG. 22. DETAILED DESCRIPTION OF THE INVENTION

[0012] The image forming apparatus, image forming method, and program according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what a person skilled in the art can conceive. Any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0013] (First embodiment) The image forming apparatus of this embodiment comprises an image carrier, a developing means having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image, an intermediate transfer body, a first transfer means for performing a primary transfer of the toner image from the image carrier to the intermediate transfer body, a second transfer means for performing a secondary transfer of the toner image from the intermediate transfer body to a recording medium, and a control unit.When the normal operation is an operation of forming an image so that the transfer rate of the primary transfer is maximized or approximately maximized and so that the transfer rate of the secondary transfer is maximized or approximately maximized, the control unit, when the toner consumption per unit traveling distance of the developing member is equal to or less than a threshold value, adjusts the amount of toner supplied from the developing means to the image carrier to include the amount of toner required to form the toner image and to be greater than that in the normal operation, and controls the first transfer means and the second transfer means to transfer the toner image to the recording medium, and adjusts the amount of at least one of the first transfer residual toner and the second transfer residual toner to be greater than that in the normal operation.

[0014] The image forming method of the present embodiment is an image forming method performed by an image forming apparatus including an image carrier, a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image, an intermediate transfer body, a first transfer unit that performs primary transfer of the toner image from the image carrier to the intermediate transfer body, and a second transfer unit that performs secondary transfer of the toner image from the intermediate transfer body to a recording medium, and includes a control step, and When the operation of forming the toner image is set to normal operation, the control process is characterized in that, when the toner consumption per unit travel distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes the amount of toner required to form the toner image and is greater than that in the normal operation, the first transfer means and the second transfer means are controlled to transfer the toner image to the recording medium, and at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner is greater than that in the normal operation.

[0015] The program of this embodiment is a program that causes an image forming apparatus to execute a control process, the image forming apparatus having an image carrier, a developing means having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image, an intermediate transfer body, a first transfer means that performs a primary transfer of the toner image from the image carrier to the intermediate transfer body, and a second transfer means that performs a secondary transfer of the toner image from the intermediate transfer body to a recording medium. When an image forming operation is performed so that the transfer rate of the primary transfer is maximized or approximately maximized and so that the transfer rate of the secondary transfer is maximized or approximately maximized, the control process is characterized in that, when the toner consumption per unit traveling distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes the amount of toner required to form the toner image and is greater than that in the normal operation, and controls the first transfer means and the second transfer means to transfer the toner image to the recording medium, and increases at least one of the amount of first transfer residual toner and the amount of second transfer residual toner greater than that in the normal operation.

[0016] In some prior art techniques, an increased amount of toner is transferred onto a recording medium due to forced toner consumption, but this affects the quality of the image on the recording medium. In an embodiment of the present invention, the increased amount of toner due to forced toner consumption (also called toner refresh) is not transferred to a recording medium, or the amount transferred is small, so the increased amount of toner is intentionally left on the image carrier or intermediate transfer body. In image formation involving forced toner consumption according to the present invention, the amount of transfer residual toner remaining on the image carrier or intermediate transfer body is greater than in normal operation. The increased transfer residual toner is removed and collected by a cleaning device, as in normal operation.

[0017] According to an embodiment of the present invention, when toner is forcibly consumed in order to prevent deterioration of image quality due to toner degradation, no waiting time is required due to the forcible consumption of toner, and image quality is not affected.

[0018] In an embodiment of the present invention, there is no need to forcibly consume toner during non-image formation periods, such as at the end of image formation, and there is no need to output a separate pattern for the purpose of forcibly consuming toner. In an embodiment of the present invention, toner can be forcibly consumed at the same time as image formation on a recording medium, thereby preventing downtime caused by forcibly consuming toner. Furthermore, since the additional toner due to forcible consumption is not transferred to the recording medium, or only a small amount is transferred, the additional toner can be prevented from affecting the image. Even if the additional toner becomes residual toner, it is removed and collected by a cleaning device, thereby preventing the additional toner from affecting other areas. Furthermore, since the additional toner is removed in the same manner as in normal operation, there is no need to add a process for removing the additional toner.

[0019] Furthermore, in the embodiment of the present invention, a determination is made as to whether to forcibly consume toner, and depending on the result of the determination, it is possible to easily and instantly switch between normal image formation (normal operation) and image formation involving forcible toner consumption, which prevents additional time required for forcible toner consumption and improves the effectiveness of preventing downtime.

[0020] <Example of overall configuration of image forming apparatus> Fig. 1 is a schematic diagram for explaining the overall configuration and operation of an image forming apparatus according to an embodiment of the present invention, and Fig. 2 is a schematic diagram for explaining the main parts of Fig. 1.

[0021] 1 is a tandem color multifunction printer, and includes, for example, a document transport unit 3, a document reader 4, a paper output tray 5, a paper feed unit 7, registration rollers 9, a photosensitive drum 11, a developing device 13, and a primary transfer bias roller 14.

[0022] The document transport unit 3 transports the document to the document reading unit 4. The document reading unit 4 reads image information from the document. The output tray 5 holds the output image. The paper feed unit 7 stores recording media P such as transfer paper. The registration rollers 9 may also be called timing rollers, and adjust the transport timing of the recording media P.

[0023] Photoconductor drums 11Y, 11M, 11C, and 11BK are examples of image carriers, on which toner images of each color (yellow, magenta, cyan, and black) are formed. When the photoconductor drums 11Y, 11M, 11C, and 11BK are not to be distinguished from one another, they may be referred to as photoconductor drum 11. There may be only one photoconductor drum, and the present invention may also be applied to a monochrome image forming apparatus.

[0024] Developing device 13 is an example of a developing means, and supplies toner to photoconductor drum 11 to form a toner image. Developing device 13 develops the electrostatic latent image formed on photoconductor drum 11 with toner. As a result of development, a toner image (which may also be referred to as a visible image) is formed on photoconductor drum 11. The developer used for development may be a one-component system or a two-component system.

[0025] The primary transfer bias roller 14 is an example of a first transfer member that the first transfer means has, and performs primary transfer of the toner image from the photosensitive drum 11 to the intermediate transfer belt 17. The primary transfer bias roller 14 is provided opposite the photosensitive drum 11. The primary transfer bias roller 14 may also be called a primary transfer roller or the like.

[0026] The image forming apparatus 1 also includes an intermediate transfer belt 17, a secondary transfer bias roller 18, a fixing device 20, a toner container 28, an intermediate transfer belt cleaning device 30, and a waste toner collection container 80.

[0027] The intermediate transfer belt 17 is an example of an intermediate transfer body, and multiple color toner images are transferred onto the intermediate transfer belt 17. The intermediate transfer belt 17 is conveyed by, for example, a conveying roller 19 and an opposing roller 18A.

[0028] The secondary transfer bias roller 18 is an example of a second transfer member that the second transfer means has, and performs a second transfer of the toner image from the intermediate transfer belt 17 to the recording medium P. The secondary transfer bias roller 18 is provided opposite an opposing roller 18A that is provided on the inner periphery of the intermediate transfer belt 17. The secondary transfer bias roller 18 may also be referred to as a secondary transfer roller or the like. The toner image transferred onto the recording medium P by the secondary transfer bias roller 18 may also be referred to as an unfixed image or the like.

[0029] The fixing device 20 fixes the unfixed image on the recording medium P. The toner container 28 contains toner of each color (yellow, cyan, magenta, black) to be supplied to the developing device 13.

[0030] The intermediate transfer belt cleaning device 30 is an example of a second cleaning unit, and cleans the second transfer residual toner remaining on the intermediate transfer belt 17 after the secondary transfer. The intermediate transfer belt cleaning device 30 has, for example, an intermediate transfer belt cleaning blade 31. The intermediate transfer belt cleaning blade 31 removes the toner adhering to the surface of the intermediate transfer belt 17.

[0031] The transfer residual toner remaining on the intermediate transfer belt 17 after the secondary transfer is also referred to as second transfer residual toner. As will be described later, the transfer residual toner remaining on the photosensitive drum 11 after the primary transfer is also referred to as first transfer residual toner.

[0032] The waste toner collection container 80 collects the waste toner removed by the intermediate transfer belt cleaning device 30 and the like.

[0033] 2 illustrates the photosensitive drum 11 and the periphery of the photosensitive drum 11. The illustrated example is common to each color (yellow, cyan, magenta, black), so the reference symbols Y, M, C, and BK are omitted. The figure illustrates the photosensitive drum 11, charging unit 12, developing device 13, primary transfer bias roller 14, photosensitive cleaning device 15, intermediate transfer belt 17, etc. Regarding FIG. 2, the following will explain the parts not explained above.

[0034] The photoconductor cleaning device 15 cleans the first transfer residual toner remaining on the photoconductor drum 11 after the primary transfer. The transfer residual toner remaining on the photoconductor drum 11 after the primary transfer is also referred to as the first transfer residual toner. The photoconductor cleaning device 15 has, for example, a photoconductor cleaning blade 15a. The photoconductor cleaning blade 15a removes the toner adhering to the surface of the photoconductor drum 11.

[0035] The photoconductor cleaning device 15 and the intermediate transfer belt cleaning device 30 may have any configuration. By providing these cleaning devices, the transfer residual toner can be effectively removed. A cleaning unit that cleans the first transfer residual toner remaining on the photoconductor drum 10 after the primary transfer may be referred to as a first cleaning unit, etc. A cleaning unit that cleans the second transfer residual toner remaining on the intermediate transfer belt 17 after the secondary transfer may be referred to as a second cleaning unit, etc. The photoconductor cleaning device 15 is an example of a first cleaning unit, and the intermediate transfer belt cleaning device 30 is an example of a second cleaning unit.

[0036] The charging unit 12 is an example of a charging means and charges the photosensitive drum 11. Charging may be of a contact type or a non-contact type. The charging unit 12 is, for example, a charging roller. Charging by the charging unit 12 may also be referred to as a charging process.

[0037] Developing device 13 is an example of a developing means, and supplies toner to photosensitive drum 11 to form a toner image on photosensitive drum 11. Developing device 13 has, for example, developing roller 13a and stirring rollers 13b and 13c. Developing roller 13a supplies toner to photosensitive drum 11. Development by developing device 13 may also be referred to as a developing process.

[0038] The following describes an example of the operation during normal color image formation in the image forming apparatus 1. Note that for the image forming process performed on the photosensitive drums 11Y, 11M, 11C, and 11BK, reference will also be made to FIG. 2 as necessary.

[0039] First, the document is transported from the document table by the transport rollers of the document transport unit 3 and placed on the contact glass of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document placed on the contact glass.

[0040] More specifically, the document reading unit 4 scans the image of the document on the contact glass while irradiating it with light emitted from an illumination lamp. The light reflected from the document is then focused on a color sensor via a group of mirrors and a lens. The color image information of the document is read by the color sensor in units of RGB (red, green, and blue) color separation light, and then converted into electrical image signals. Furthermore, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, and other processing based on the RGB color separation image signals, thereby obtaining color image information of yellow, magenta, cyan, and black.

[0041] The image information for each color (yellow, magenta, cyan, and black) is then sent to a writing unit, which then emits laser light L (see FIG. 2) based on the image information for each color toward the surface of the corresponding photosensitive drum 11.

[0042] Each of the four photosensitive drums 11 rotates clockwise in FIGS. 1 and 2. The surface of each photosensitive drum 11 is uniformly charged where it faces the charging unit 12. This creates a charging potential on the surface of each photosensitive drum 11. The charged surface of each photosensitive drum 11 then reaches the irradiation position of the corresponding laser beam. In the writing unit, four light sources emit laser beams corresponding to image signals, one for each color. Each laser beam passes through a separate optical path for each color component: yellow, magenta, cyan, and black. This process may also be referred to as the exposure process.

[0043] The laser light corresponding to the yellow component is irradiated onto the surface of the first photoconductor drum 11Y from the left side of the paper in Fig. 1. At this time, the laser light of the yellow component is scanned in the direction of the rotation axis of the photoconductor drum 11Y (main scanning direction) by a polygon mirror rotating at high speed. In this way, an electrostatic latent image (which may also be referred to as a latent image) corresponding to the yellow component is formed on the surface of the photoconductor drum 11Y after it has been charged by the charging unit 12.

[0044] Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the photosensitive drum 11M, which is the second from the left on the paper, and an electrostatic latent image corresponding to the magenta component is formed. The laser light corresponding to the cyan component is irradiated onto the surface of the photosensitive drum 11C, which is the third from the left on the paper, and an electrostatic latent image corresponding to the cyan component is formed. The laser light corresponding to the black component is irradiated onto the surface of the photosensitive drum 11BK, which is the fourth from the left on the paper, and an electrostatic latent image corresponding to the black component is formed.

[0045] Thereafter, the surface of each photosensitive drum 11 on which the electrostatic latent image of each color has been formed reaches a position facing the developing device 13. Then, toner of each color is supplied from each developing device 13 onto each photosensitive drum 11, and the electrostatic latent image on each photosensitive drum 11 is developed.

[0046] Thereafter, the surface of each photosensitive drum 11 after the development process reaches a portion facing the intermediate transfer belt 17, which serves as an image carrier. Here, a primary transfer bias roller 14 is installed at each facing portion so as to abut against the inner circumferential surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, the toner images of each color formed on each photosensitive drum 11 are sequentially superimposed and primarily transferred onto the intermediate transfer belt 17. This process may also be referred to as a primary transfer process.

[0047] After the primary transfer process, the surface of each photosensitive drum 11 reaches a position facing the photosensitive drum cleaning device 15. Then, the photosensitive drum cleaning device 15 removes and collects untransferred toner remaining on each photosensitive drum 11. This process may be referred to as a primary cleaning process.

[0048] The untransferred toner removed and collected by the photosensitive drum cleaning device 15 is transported as waste toner via a transport path to be collected in a waste toner collection container 80. The untransferred toner remaining on the photosensitive drum 11 may also be referred to as untransferred toner.

[0049] Thereafter, the surface of each photosensitive drum 11 is neutralized by a neutralization unit as necessary, and a series of image forming processes on each photosensitive drum 11 is completed.

[0050] Meanwhile, the intermediate transfer belt 17, onto which the toner of each color on each photosensitive drum 11 is superimposed and primarily transferred, travels counterclockwise in FIG. 1 and reaches a position facing the secondary transfer bias roller 18. Then, at the position facing the secondary transfer bias roller 18, the color toner images carried on the intermediate transfer belt 17 are secondarily transferred onto the recording medium P. This process may also be referred to as a secondary transfer process.

[0051] Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning device 30. Then, untransferred toner adhering to the intermediate transfer belt 17 is removed and collected by the intermediate transfer belt cleaning device 30, completing the series of image formation processes on the intermediate transfer belt 17. The series of image formation processes on the intermediate transfer belt 17 may also be referred to as a transfer process or the like.

[0052] The untransferred toner removed and collected by the intermediate transfer belt cleaning device 30 is transported as waste toner to a waste toner collection container 80 via a transport path and collected there.

[0053] Here, the recording medium P transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 is transported from the paper feed unit 7 via the registration rollers 9 and the like. The space between the intermediate transfer belt 17 and the secondary transfer bias roller 18 may also be referred to as a secondary transfer nip or the like.

[0054] More specifically, the recording medium P is fed by a paper feed roller 8 from a paper feed unit 7 that stores the recording medium P, passes through a conveyance guide, and is then guided to a registration roller 9. The recording medium P that has reached the registration roller 9 is conveyed in time toward the secondary transfer nip.

[0055] The recording medium P onto which the full-color image has been transferred is then guided to the fixing device 20. In the fixing device 20, the color image is fixed onto the recording medium P at the fixing nip between a fixing roller and a pressure roller. This process may also be referred to as a fixing process. After the fixing process, the recording medium P is discharged as an output image outside the apparatus main body by a paper discharge roller, and is stacked on a paper discharge tray 5. In this way, a series of image forming processes is completed.

[0056] <Normal operation (normal image formation)> Next, before describing the forced toner consumption in this embodiment, normal operation will be described. Normal operation may also be referred to as normal image formation, normal printing, normal operation, etc. This embodiment is capable of performing normal image formation and image formation with toner refresh. Normal operation is an operation in which image formation is performed so that the transfer rate of the primary transfer is maximized or nearly maximized, and so that the transfer rate of the secondary transfer is maximized or nearly maximized. The transfer rate is described later in FIG. 5. Normal operation also refers to an image formation operation performed in a state in which the amount of toner consumed per unit travel distance of the developing member is greater than a threshold, as described later.

[0057] 3 is a schematic diagram for explaining normal operation. The matters explained in FIGS. 1 and 2 above are applicable to normal operation. Here, matters related to the transfer of toner images in normal operation will be mainly explained.

[0058] First, toner is supplied from the developing roller 13a to form a toner image 211 on the photosensitive drum 11. The toner image 211 is primarily transferred to the intermediate transfer belt 17 at the transfer nip between the photosensitive drum 11 and the primary transfer bias roller 14. A toner image 212 is a toner image transferred to the intermediate transfer belt 17.

[0059] The transfer residual toner 213 is toner that has not been transferred in the primary transfer and remains on the photosensitive drum 11, and corresponds to the first transfer residual toner. The transfer residual toner 213 on the photosensitive drum 11 is removed and collected by the photosensitive cleaning blade 15a of the photosensitive cleaning device 15.

[0060] The toner image 212 on the intermediate transfer belt 17 is secondarily transferred to the recording medium P at the transfer nip between the opposing roller 18A and the secondary transfer bias roller 18. The toner image 214 is the toner image transferred to the recording medium P.

[0061] The transfer residual toner 215 is toner that has not been secondarily transferred and remains on the intermediate transfer belt 17, and corresponds to second transfer residual toner. The transfer residual toner 215 on the intermediate transfer belt 17 is removed and collected by the intermediate transfer belt cleaning blade 31 of the intermediate transfer belt cleaning device 30.

[0062] In this way, the toner image is transferred onto the recording medium P. As described above, the toner image on the recording medium P is conveyed to the fixing device 20 and fixed by the fixing device 20.

[0063] Fig. 4 is a schematic diagram for explaining what kind of toner is carried on each member in Fig. 3. (1) to (3) in Fig. 4 are schematic diagrams of toner images on the photosensitive drum 11, the intermediate transfer belt 17, and the recording medium P in Fig. 3, and (1) to (3) are also shown in Fig. 3.

[0064] (1) is a diagram of the photosensitive drum 11 as seen from above, and as seen toward the center of the photosensitive drum 11. (1) also shows the state when the toner image 211 moves from the position where the photosensitive drum 11 and the developing roller 13a face each other to the position where the photosensitive drum 11 and the primary transfer bias roller 14 face each other. (2) is a diagram of the intermediate transfer belt 17 as seen from above, and also as seen from the inside of the intermediate transfer belt 17. (2) also shows the state when the toner image 212 moves from the time the toner image is transferred onto the intermediate transfer belt 17 to the position where the intermediate transfer belt 17 and the secondary transfer bias roller 18 face each other. (3) is a diagram of the recording medium P as seen from above, and also as seen from the side onto which the toner image 214 has been transferred. (3) also shows the state after the toner image 214 has been transferred onto the recording medium P.

[0065] In normal operation, toner for image formation is supplied to the photosensitive drum 11, and the toner for image formation is transferred onto the intermediate transfer belt 17 and the recording medium P. This is shown in FIGS.

[0066] FIG. 5 shows an example of the relationship between the transfer current flowing through the transfer member and the transfer rate during primary and secondary transfer. (A) is an example of primary transfer, and (B) is an example of secondary transfer. In the figure, the horizontal axis represents the transfer current, and the vertical axis represents the transfer rate. The primary transfer current is, for example, the current flowing through the primary transfer bias roller 14, and the secondary transfer current is, for example, the current flowing through the secondary transfer bias roller 18.

[0067] The transfer current can be adjusted by adjusting the voltage applied to the transfer member, for example, by controlling the transfer power supply. The transfer power supply is an example of a transfer voltage application unit that applies a voltage to the transfer member. The transfer power supply is controlled by, for example, a control unit.

[0068] The transfer rate indicates how much toner has been transferred, and can be confirmed, for example, by comparing the mass of the toner before transfer with the mass of the transferred toner. The primary transfer rate (A) is the rate of toner transferred from the photosensitive drum 11 to the intermediate transfer belt 17. The secondary transfer rate (B) is the rate of toner transferred from the intermediate transfer belt 17 to the recording medium P.

[0069] As shown in Figures 5A and 5B, the transfer rate changes as the transfer current changes. The relationship between the transfer current and the transfer rate may be referred to as a transfer rate curve or a transfer rate curve. As shown in Figures 5A and 5B, the transfer rate typically reaches its maximum when the transfer current reaches a certain value. In normal operation, the transfer current is selected to maximize the transfer rate (or to approach its maximum). The selected transfer current is indicated by a vertical dashed line in the figure. In normal operation, the transfer current is selected to maximize the transfer rate for both the primary and secondary transfers. This maximizes the transfer of the toner image for image formation from the photosensitive drum 11 to the intermediate transfer belt 17, and maximizes the transfer of the toner image for image formation from the intermediate transfer belt 17 to the recording medium P. As shown in the figures, normal operation is an operation in which image formation is performed so that the transfer rate for the primary transfer is maximized or nearly maximized, and so that the transfer rate for the secondary transfer is maximized or nearly maximized. The term "nearly maximized" above can be selected as appropriate. For example, if the maximum value is 100%, then 90% or more is considered to be nearly maximized.

[0070] Even when the transfer current is selected so as to maximize the transfer rate, residual toner may remain on the photosensitive drum 11 or intermediate transfer belt 17. In Figure 3, the residual toner is indicated by reference numerals 212 and 215. However, such residual toner does not necessarily have to remain.

[0071] When performing such normal image formation, repeated low-print-ratio image formation reduces the toner balance in the developing device, causing the toner to remain there for a long period of time. As a result, the toner is repeatedly rubbed by the regulating blade, etc., causing deterioration in the charging characteristics of the toner, resulting in degradation of image quality such as unevenness and fluctuations in image density.

[0072] To address this issue, it is possible to forcibly consume the toner in the developing device when repeating image formation with a low print rate. For example, it is possible to forcibly consume the toner in the developing device after image formation is completed. However, this requires time to consume the toner, resulting in waiting times and reduced user convenience and productivity. In response to this issue, for example, Patent Document 1 proposes consuming toner simultaneously with image formation rather than after image formation is completed. In Patent Document 1, to forcibly consume the toner in the developing device, the toner to be consumed is layered on top of the toner used for image formation on the recording medium. However, this approach can affect image quality. For example, it can cause changes in image density and color, as well as affect fixing offset.

[0073] <Forced toner consumption (toner refresh)> The present inventors have conducted extensive research into the above-mentioned problems and have arrived at the present invention. Hereinafter, forced consumption of toner (toner refresh) in one embodiment of the present invention will be described. In this embodiment, when image formation with a low print rate is repeated, toner is forcibly consumed at the same time as image formation. Since toner does not need to be consumed during non-image formation periods, such as after image formation has finished, it is possible to prevent the time required for toner consumption. This makes it possible to suppress a decrease in user convenience and productivity. The time required for toner consumption is also referred to as the occurrence of downtime.

[0074] In this embodiment, when toner is consumed, the transfer rate is adjusted so that the toner to be consumed remains on the image carrier or intermediate transfer body as transfer residual toner. This reduces the impact of the toner to be consumed on the image formed on the recording medium, and prevents deterioration of image quality. The forced consumption of toner is also called toner refresh, forced toner consumption, toner consumption, etc.

[0075] FIG. 6 is a schematic diagram for explaining this embodiment, and is similar to FIG. 3. The matters explained in FIGS. 1 and 2 and the matters explained in the normal operation can be applied to this embodiment. The operation shown in FIG. 6 is an operation performed when the toner consumption amount per unit travel distance is equal to or less than a threshold, and is a toner refresh operation. Threshold determination will be described later.

[0076] In this embodiment, toner for consumption is supplied from the developing means to the image carrier during image formation in addition to toner for image formation. That is, when performing image formation involving toner refresh, the control unit in this embodiment increases the amount of toner supplied from the developing device 13 to the photosensitive drum 11 compared to normal operation. Therefore, toner for image formation and additional toner are supplied to the photosensitive drum 11. As shown in FIG. 6, the photosensitive drum 11 carries a toner image 211, which is toner for image formation, and additional toner 231, which is toner for consumption.

[0077] For the sake of explanation, the toner image 211, which is toner for image formation, and the additional toner 231, which is toner for consumption, are shown stacked in the figure, but this stacked configuration is not necessary. It is not necessary to be able to strictly distinguish between the toner image 211 and the additional toner 231 on the photosensitive drum 11.

[0078] In this embodiment, a toner image 212 is also transferred onto the intermediate transfer belt 17. As in normal operation, the toner image 212 that has been primarily transferred onto the intermediate transfer belt 17 is secondarily transferred onto the recording medium P at the transfer nip between the opposing roller 18A and the secondary transfer bias roller 18. As shown in the figure, the increased toner 231 is not transferred onto the recording medium P, so the effect of the toner consumed on the image can be suppressed.

[0079] In this embodiment, the value of the primary transfer current is adjusted to reduce the primary transfer rate compared to normal image formation. This reduces the transfer rate during primary transfer from the photosensitive drum 11 to the intermediate transfer belt 17, and the increased toner 231 is not transferred to the intermediate transfer belt 17 but remains on the photosensitive drum 11 as transfer residual toner. For this reason, in the illustrated example, the amount of primary transfer residual toner is greater than in normal operation.

[0080] In other words, in this embodiment, the amount of toner supplied from the developing device 13 to the photosensitive drum 11 is greater than in normal operation, and the first transfer means is controlled so that the amount of first transfer residual toner remaining on the photosensitive drum 11 is greater than in normal operation.

[0081] The transfer residual toner 213 and the increased toner 231 on the photosensitive drum 11 are removed and collected by the photosensitive drum cleaning blade 15a of the photosensitive drum cleaning device 15. Therefore, there is no adverse effect even if more toner (increased toner) than in normal operation is supplied to the photosensitive drum 11.

[0082] In this embodiment, the control unit controls the first transfer means to increase the amount of first transfer residual toner compared to normal operation. The first transfer means includes, for example, a first transfer member (e.g., primary transfer bias roller 14) facing photosensitive drum 11 and a primary transfer power supply that applies voltage to the first transfer member. The control unit controls, for example, the primary transfer power supply, and controls the voltage applied from the primary transfer power supply to the primary transfer bias roller. This allows the primary transfer current to be adjusted, and the primary transfer rate to be adjusted.

[0083] Fig. 7 is a schematic diagram for explaining what kind of toner is carried on each member in Fig. 6. Fig. 7 is a diagram similar to Fig. 4 showing normal operation, and (1) to (3) in Fig. 7 correspond to (1) to (3) in Fig. 6, similar to (1) to (3) in Fig. 3 and Fig. 4.

[0084] In Figure 7, (1) shows the additional toner 231. That is, the toner for image formation and the additional toner 231 are supplied from the developing means to the photosensitive drum 11. In addition, (2) and (3) do not show the additional toner 231. This indicates that the additional toner 231 has not been transferred to the intermediate transfer belt 17 and the recording medium P, as shown in Figure 6.

[0085] However, the present invention also includes a case where a small amount of the increment toner 231 is transferred to the intermediate transfer belt 17 and the recording medium P. This embodiment is configured so that the amount of transfer residual toner (first transfer residual toner) remaining on the photosensitive drum 11 is greater than in normal operation. Therefore, even when the increment toner 231 is transferred to the intermediate transfer belt 17 and the recording medium P, the case where the amount of the first transfer residual toner is greater than in normal operation corresponds to this embodiment.

[0086] Fig. 8 is a diagram for explaining the selection of the transfer current in this embodiment. The relationship between the transfer current and the transfer rate (transfer rate curve) shown in Fig. 8 is the same as that shown in Fig. 5, and the transfer rate reaches its maximum when the transfer current has a certain value.

[0087] As shown in FIG. 8A, in this embodiment, the value of the primary transfer current is lowered compared to normal operation. In the figure, the selected primary transfer current is indicated by a vertical dashed line. By selecting a primary transfer current value lower than normal operation, the primary transfer rate becomes lower than normal operation. As a result, the increased toner 231 is not transferred from the photosensitive drum 11 to the intermediate transfer belt 17, and remains on the photosensitive drum 11 as primary transfer residual toner.

[0088] 8A, the value of the primary transfer current to be selected can be appropriately selected. The value of the primary transfer current should be selected within a range that allows the amount of toner required for image formation on the recording medium P to be transferred onto the intermediate transfer belt 17. The transfer current can be adjusted by controlling the transfer power supply, for example, in the same way as in normal operation. The transfer current is adjusted by the output value from the transfer power supply connected to each transfer bias roller, for example.

[0089] As shown in Figure 8(B), in this embodiment, the value of the secondary transfer current is set to the same as in normal operation. This maximizes (or approaches) the secondary transfer rate, and the toner required for image formation is transferred to the recording medium P. Therefore, even if the primary transfer rate is reduced as in (A), it is possible to prevent any adverse effect on the image formed on the recording medium P.

[0090] This embodiment will be explained again. The toner refresh (forced toner consumption) operation of this embodiment is performed when image formation with a low print rate is repeated. In this embodiment, the control unit increases the amount of toner supplied from the developing roller 13a to the photosensitive drum 11 compared to normal operation. The control unit reduces the primary transfer rate when performing the primary transfer of toner from the photosensitive drum 11 to the intermediate transfer belt 17 compared to normal operation. During the primary transfer, the control unit transfers onto the intermediate transfer belt 17 the amount of toner required for image formation onto the recording medium P. The control unit sets the secondary transfer rate, at which toner is transferred from the intermediate transfer belt 17 to the recording medium P, to the same rate as normal operation, and transfers onto the recording medium P the amount of toner required for image formation.

[0091] In this embodiment, there is no need to forcibly consume toner during non-image formation times, such as at the end of image formation, and there is also no need to output a separate pattern for the purpose of forcibly consuming toner. In this embodiment, toner refresh can be performed at the same time as image formation on the recording medium P, thereby preventing downtime caused by forcibly consuming toner. Furthermore, the increased amount of toner used for toner refresh is not transferred to the recording medium P, or only a small amount is transferred, so the increased amount of toner can be prevented from affecting the image. Furthermore, even if the increased amount of toner becomes residual toner, it is removed and collected by the cleaning device, so the increased amount of toner can be prevented from affecting other areas. Another advantage is that the increased amount of toner is removed in the same way as in normal operation, so there is no need to add a process to remove the increased amount of toner.

[0092] As described above, in this embodiment, when the toner consumption per unit travel distance of the developing member is below a threshold value, the control unit controls the first transfer means to make the primary transfer rate lower than in normal operation and make the amount of first transfer residual toner greater than in normal operation. As described in the supplementary explanation below, past findings have shown that allowing transfer residual toner to be input into the cleaning device maintains improved cleaning performance. In this embodiment, more transfer residual toner is input into the photosensitive member cleaning device than in normal operation, which stabilizes the behavior of the tip of the photosensitive member cleaning blade compared to normal operation. Therefore, in this embodiment, the cleaning performance of the photosensitive member cleaning device can be improved, making it easier to maintain image quality.

[0093] The supply of toner from the developing means when toner refresh is performed in this embodiment will be described again. In this embodiment, when the toner consumption per unit travel distance of the developing member is below a threshold value, the amount of toner supplied from the developing means to the image carrier includes both a first toner amount, which is the amount of toner required to form a desired image on the recording medium, and a second toner amount required to forcibly consume the toner. In this way, when performing toner refresh, by supplying toner from the developing means in an amount that includes both the first toner amount and the second toner amount, it is possible to reliably form the desired image on the recording medium even when performing toner refresh.

[0094] The image forming apparatus of this embodiment includes a first cleaning unit that cleans first transfer residual toner remaining on the image carrier after the primary transfer, and a second cleaning unit that cleans second transfer residual toner remaining on the intermediate transfer member after the secondary transfer. Furthermore, in this embodiment, when the toner consumption per unit travel distance of the developing member is equal to or less than a threshold, the control unit controls the first transfer unit and the second transfer unit to transfer the first toner amount to the recording medium and input the second toner amount as transfer residual toner to at least one of the first cleaning unit and the second cleaning unit. In this way, when performing toner refresh, the first amount of toner for forming an image is transferred to the recording medium, and the second amount of toner for forced consumption is cleaned as transfer residual toner. This allows the desired image to be reliably formed on the recording medium even when toner refresh is performed, and the consumed toner is cleaned without affecting the image on the recording medium.

[0095] The method for increasing the amount of toner supplied from the developing roller 13a to the photosensitive drum 11 can be selected as appropriate. For example, the voltage applied to the developing roller 13a can be adjusted. To adjust the voltage applied to the developing roller 13a, for example, a development power supply that applies voltage to the developing roller can be controlled. Alternatively, the voltage applied to the developing roller 13a can be adjusted to achieve a target amount of toner increase based on the correlation between the development potential calculated during device design and the amount of toner adhered to the photosensitive drum 11. The development potential corresponds to the difference between the surface potential of the photosensitive drum and the voltage applied to the developing roller.

[0096] The amount of toner to be supplied from the developing roller 13a to the photosensitive drum 11 can be appropriately selected. For example, the amount of toner to be increased in forced toner consumption (toner refresh) is set to an amount that satisfies both transferability and the amount required for refreshment for each model. Furthermore, the amount of toner to be increased may be determined taking into consideration not only the amount of toner stored in the developing means, but also the amount of toner to be forcedly consumed from the amount of toner stored in the developing means.

[0097] Furthermore, the areas where toner is increased during toner refresh can be selected as appropriate. For example, the areas where toner is increased are primarily the user's output image area. The user's output image area is the area to which toner is to be attached in the image that the user has instructed to be printed. When toner is increased in the output image area, when the increased amount of toner is transferred to the recording medium, the impact on the image can be reduced compared to the non-output image area. The output image area may also be referred to as the print area, and the non-output image area may also be referred to as the non-print area.

[0098] Next, an example of determination of normal operation and toner refresh in this embodiment will be described. 9 is a diagram for explaining an example of the determination in this example. The upper diagram is a diagram for explaining an example of the timing for determining whether to perform image formation by normal operation or image formation accompanied by toner refresh on the photosensitive drum 11.

[0099] In the diagram above, along the travel of the photosensitive drum 11, for example, at points (1) to (4), the toner consumption amount A per unit travel distance is acquired or updated, and / or a determination is made as to whether to perform normal operation or image formation with toner refresh. T1 to T3 are schematic examples of areas where imaging (image formation) is performed. In this example, T1 to T3 correspond to pages 1 to 3, respectively, with page 3 being the final page.

[0100] For the sake of explanation, the recording medium P is shown on the photosensitive drum 11, but the explanation in the above figure is not limited to the direct transfer method in which a toner image is transferred from the photosensitive drum 11 to the recording medium P. The explanation in the above figure also applies to the secondary transfer method in which a toner image is transferred to the recording medium P via the intermediate transfer belt 17. The illustrated paper area corresponds to the recording medium P when the toner image is transferred via the intermediate transfer belt 17.

[0101] The lower diagram plots the toner consumption A per unit travel distance for (1) to (4) in the upper diagram. Hereinafter, the toner consumption A per unit travel distance of the developing member may be referred to as the average toner consumption A, the toner consumption A per unit travel distance, or simply as A. In the lower diagram, the vertical axis represents the toner consumption A per unit travel distance, and the horizontal axis represents the travel distance of the developing member (e.g., the developing roller). The travel distance shown horizontally corresponds to the upper and lower diagrams. The lower diagram also shows the threshold B for performing toner refresh. If A is smaller than B, operation is performed under the image creation conditions for toner refresh.

[0102] In (1) of the diagram above, before forming the image of the first page, the toner consumption amount A per unit travel distance (average toner consumption amount A) is obtained. The obtained A is compared with threshold value B to determine whether to perform toner refresh. The diagram below plots the toner consumption amount A per unit travel distance in (1) of the diagram above. This plot is represented by a. As shown in the diagram below, in the execution determination before forming the image of the first page, because average toner consumption amount A is greater than threshold value B, in other words, because average toner consumption amount a is greater than threshold value B, toner refresh is not performed. For this reason, at T1, image formation is performed under the imaging conditions for normal operation.

[0103] In (2) of the diagram above, toner consumption A per unit travel distance is updated before forming the image of the second page. The updated A is compared with threshold value B to determine whether to perform toner refresh. The diagram below plots toner consumption A per unit travel distance in (2) of the diagram above. This plot is represented by b. As shown in the diagram below, in the execution determination before forming the image of the second page, average toner consumption A is smaller than threshold value B, that is, average toner consumption b is smaller than threshold value B, so toner refresh is performed. In other words, image formation is performed under the imaging conditions for toner refresh. For this reason, image formation is performed at T2 under the imaging conditions for toner refresh.

[0104] In (3) in the diagram above, the toner consumption amount A per unit travel distance is updated before forming the image of the third page. The updated A is compared with threshold value B to determine whether to perform toner refresh. The diagram below plots the toner consumption amount A per unit travel distance in (3) in the diagram above. This plot is represented by c. As shown in the diagram below, in the execution determination before forming the image of the third page, the average toner consumption amount A is greater than threshold value B, that is, the average toner consumption amount c is greater than threshold value B, so toner refresh is not performed. For this reason, image formation is performed at T3 under the imaging conditions for normal operation.

[0105] In (4) of the diagram above, the toner consumption amount A per unit travel distance is updated after the image formation of the third page (final page) in preparation for the next image formation. The diagram below plots the toner consumption amount A per unit travel distance in (4) of the diagram above. This plot is represented by d. When the next image formation is performed, the value of d is obtained as the average toner consumption amount A, and a threshold determination is made, as in (1) of the diagram above.

[0106] Next, an example of the flow of image formation will be described. FIG. 10 shows the flow of this example, in which it is determined whether to form an image under the image forming conditions for toner refresh or under the image forming conditions for normal operation.

[0107] In S1, a print job is received. In S2, the average toner consumption amount A per unit travel is acquired from, for example, a storage unit (for example, a system memory 902 in FIG. 12, which will be described later). In S3, it is determined whether the acquired average toner consumption amount A per unit travel is smaller than the toner refresh threshold value B. If the answer to S3 is YES, S4 is carried out to set the image forming conditions for toner refresh. If the answer to S3 is NO, S5 is carried out to set the image forming conditions for normal operation. In S6, printing (image formation) starts under the set image creation conditions. In S7, printing of one page is completed under the set image forming conditions.

[0108] Although not particularly limited, S2 and S3 correspond to, for example, (1) in the example shown in Fig. 9. In addition, if S3 is NO and an image is formed under the imaging conditions of normal operation, this corresponds to, for example, T1 in the example shown in Fig. 9. In addition, in S2, the average toner consumption amount A per unit travel is acquired, which is the average toner consumption amount A updated after the previous image formation was completed. When performing the first image formation, for example, the average toner consumption amount A may be set to an initial value, and the image forming conditions for normal operation may be set when the first threshold determination is made. In addition, in S4 in the drawing, for the sake of explanation, the amount of toner adhesion is increased, and the transfer rate is also reduced below that of normal operation.

[0109] In S8, the average toner consumption amount A per unit travel is updated. Here, "updating" may also be referred to as "calculating." As will be described later, the average toner consumption amount A is calculated, for example, from the print count information input into the print count memory for each color and the travel distance of the development unit. Also, if a toner refresh is performed, the average toner consumption amount A is calculated by adding the amount of toner consumed in the toner refresh.

[0110] In S9, it is determined whether printing is complete. This determination is made by determining, for example, whether the number of pages specified in the print job have been printed. If printing is complete, the flow ends, but if printing is not complete, processing continues from S3. In this example, the determination in S3 is made for each page.

[0111] Although not particularly limited, an example of when the second determination in S3 is YES and toner refresh is performed corresponds to T2 in the example shown in FIG. 9. Also, when T3 in the example shown in FIG. 9 is performed, for example, since it is the printing of the final page, the determination in S9 in FIG. 10 is YES (printing completed). At this time, since the average toner consumption amount A has been updated in S8, the average toner consumption amount A is set to reflect the printing of T3. Therefore, the next time S2 is performed, the average toner consumption amount A reflecting the printing of T3 is acquired.

[0112] The method for calculating the toner consumption amount A per unit running distance of the developing member (average toner consumption amount A) is not particularly limited, and for example, a conventional method may be used. An example of the method for calculating the average toner consumption amount A will be described below.

[0113] The average toner consumption A is calculated using the print count information input into the print count memory for each color and the travel distance of the developing member for each color. The calculation method is to calculate it using the following formula 1 within the target output section.

[0114] Toner consumption per unit distance A = Accumulated value of print counter × Target toner adhesion amount / Development travel distance (Equation 1)

[0115] The unit of the accumulated value of the print counter is, for example, the number of dots. The unit of the target toner adhesion amount is, for example, g / cm 2 The target toner adhesion amount is a design value for the amount of toner on the recording medium. The unit of the developing travel distance is, for example, mm. The developing travel distance is, for example, the rotation distance of the developing roller. The developing travel distance may also be called the image forming travel distance.

[0116] The developing travel distance is set to the travel distance of the most recent fixed section. For example, if 50 pages of A4 size are printed, the rotation distance of the developing roller when 50 pages are printed is set. The developing roller travel distance may also be referred to as the developing unit travel distance.

[0117] The numerator in Equation 1 may be referred to as the cumulative toner amount, etc. By dividing the cumulative toner amount by the traveled distance, the average amount of toner consumed in a certain section can be found, and the average toner consumption amount A per unit distance can be calculated. The amount of toner consumed is affected by the characteristics of the toner, developer, and development unit. Since the amount of toner consumed is not constant and is constantly fluctuating depending on the output image, it is necessary to find the average amount of toner consumed in a certain section, as described above.

[0118] In this embodiment, the toner consumption amount A per unit travel distance of the developing member is calculated based on the travel distance of the developing member, as shown in the above formula 1. Although toner deterioration may be calculated based on the area of ​​the output image, it is preferable to calculate based on the travel distance of the developing member, as in this embodiment, because this allows toner deterioration to be predicted accurately. The degree of toner deterioration in the developing device is more closely correlated with the drive of the developing roller, so it is preferable to calculate the toner consumption amount A per unit travel distance using the development travel distance, as in formula 1.

[0119] A threshold value is determined for the toner consumption amount A per unit travel distance calculated as described above. If it falls below a certain threshold value B, it is determined that toner refresh is necessary, and the image creation conditions are changed. In other words, the image creation conditions for normal operation are changed to those for toner refresh. Note that threshold value B can be set appropriately and is not particularly limited, but can be set taking into consideration, for example, the toner capacity in the developing means, the type of toner, the configuration of the developing means (regulating blade, agitation, etc.), etc.

[0120] The image-making condition items can be selected as appropriate. Examples of the image-making condition items to be changed include the development potential value for increasing the amount of toner adhesion, the writing exposure energy value, and the transfer current value. When changing from the image-making conditions for normal operation to the image-making conditions for toner refresh, for example, changes are made such as increasing the development potential value, increasing the exposure energy value, or decreasing the transfer current value (see FIG. 8(A) etc.). The image-making conditions can be changed by changing each item individually, or multiple image-making conditions for toner refresh can be prepared as, for example, print modes and a print mode can be selected.

[0121] After changing from the imaging conditions for normal operation to the imaging conditions for toner refresh, image formation is performed under the changed imaging conditions. As explained in the example flow of Figure 10, after printing one page is completed, the toner consumption amount A per unit travel distance is updated. When image formation is performed under the imaging conditions for toner refresh, the toner consumption amount A per unit travel distance is updated using the increased amount of toner. The toner consumption amount A per unit travel distance updated in this way is used for the next threshold determination. When a certain threshold is exceeded, the imaging conditions for toner refresh are changed (returned) to the imaging conditions for normal operation and image formation is performed.

[0122] FIG. 11 is a diagram for explaining an example of a functional block diagram of this embodiment. 11(A) shows a control unit 400, a charging power supply 401, a developing power supply 402, a photoconductor cleaning power supply 403, an intermediate transfer belt cleaning power supply 404, a primary transfer power supply 405, and a secondary transfer power supply 406. The control unit 400 controls each component in the image forming apparatus based on print information. The components shown in the figure are examples, and may be changed as appropriate.

[0123] An example of control will be described. The control unit 400 controls the charging power supply 401 to adjust the voltage applied to the charging unit 12. The control unit 400 controls the development power supply 402 to adjust the voltage applied to the development member (e.g., the development roller 13a). The control unit 400 controls the photoconductor cleaning power supply 403 to control the ON / OFF of the photoconductor cleaning device 15. The control unit 400 controls the intermediate transfer belt cleaning power supply 404 to control the ON / OFF of the intermediate transfer belt cleaning device 30.

[0124] However, the photoconductor cleaning power supply 403 and the intermediate transfer belt cleaning power supply 404 are not essential. Furthermore, the cleaning device being ON may refer to, for example, the operation of a component for recovery (such as a screw). Furthermore, although not shown, the control unit 400 may also control a writing unit that exposes the photoconductor drum 11.

[0125] The control unit 400 controls the primary transfer power supply 405 to adjust the voltage applied to the primary transfer bias roller 14. The control unit 400 controls the secondary transfer power supply 406 to adjust the voltage applied to the secondary transfer bias roller 18. By adjusting the voltage in this manner, it is possible to adjust the transfer current flowing through the transfer bias roller. Furthermore, by adjusting the transfer current in this manner, it is possible to adjust the transfer rate. Furthermore, the primary transfer power supply 405 and the secondary transfer power supply 406 may be combined into one transfer power supply.

[0126] 11(B) shows the control unit 400 and print count memories 410K, 410C, 410M, and 410Y for K, C, M, and Y, respectively. When describing the print count memories 410K, 410C, 410M, and 410Y without distinction, they will be referred to as print count memory 410.

[0127] The print count memory 410 is used to calculate the amount of toner consumed per unit travel distance. The print count memory 410 can store the amount of toner consumed, for example, information counting the number of printed dots.

[0128] The control unit 400 calculates the amount of toner consumed per unit travel distance using the information stored in the print count memory 410, performs threshold determination, and determines whether to perform toner refresh. The control unit 400 also calculates and sets image creation conditions according to the amount of toner consumed required when performing toner refresh. These image creation conditions include, for example, the potential of the photosensitive member, the voltages applied to the charging unit and developing member, the amount of light for writing, the current setting value for primary transfer, and the current setting value for secondary transfer.

[0129] Next, an example of the hardware configuration of the image forming apparatus of this embodiment will be described, in which the image forming apparatus is an MFP (Multifunction Peripheral / Product / Printer).

[0130] 12 is a diagram showing the hardware configuration of the MFP of this example. The MFP 9 includes a controller 910, a short-range communication circuit 920, an engine control unit 930, an operation panel 940, and a network I / F 950.

[0131] Of these, the controller 910 has a CPU 901, which is the main part of the computer, a system memory (MEM-P) 902, a north bridge (NB) 903, a south bridge (SB) 904, an ASIC (Application Specific Integrated Circuit) 906, a local memory (MEM-C) 907, which is a storage unit, an HDD controller 908, and an HD 909, which is also a storage unit, and is configured such that the NB 903 and the ASIC 906 are connected by an AGP (Accelerated Graphics Port) bus 921.

[0132] Of these, the CPU 901 is a control unit (control unit 400 in FIG. 11) that performs overall control of the MFP 9. The NB 903 is a bridge that connects the CPU 901 with the MEM-P 902, SB 904, and AGP bus 921, and includes a memory controller that controls reading and writing to the MEM-P 902, a PCI (Peripheral Component Interconnect) master, and an AGP target.

[0133] The MEM-P 902 comprises a ROM 902a, which is memory for storing programs and data that realize the functions of the controller 910, and a RAM 902b, which is used for expanding the programs and data and as a drawing memory during memory printing. The programs stored in the RAM 902b may be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM, CD-R, or DVD.

[0134] The SB 904 is a bridge for connecting the NB 903 with PCI devices and peripheral devices. The ASIC 906 is an integrated circuit (IC) for image processing applications that has hardware elements for image processing and functions as a bridge connecting the AGP bus 921, PCI bus 922, HDD 908, and MEM-C 907. The ASIC 906 includes a PCI target and AGP master, an arbiter (ARB) that forms the core of the ASIC 906, a memory controller that controls the MEM-C 907, multiple direct memory access controllers (DMACs) that perform image data rotation using hardware logic, and a PCI unit that transfers data between the scanner unit 931 and printer unit 932 via the PCI bus 922. A USB (Universal Serial Bus) interface or an IEEE 1394 (Institute of Electrical and Electronics Engineers) interface may also be connected to the ASIC 906.

[0135] The MEM-C907 is a local memory used as an image buffer for copying and a code buffer. The HD909 is a storage for storing image data, font data used during printing, and forms. The HD909 controls the reading and writing of data from and to the HD909 under the control of the CPU901. The AGP bus 921 is a bus interface for a graphics accelerator card proposed to speed up graphics processing, and direct high-throughput access to the MEM-P902 enables the graphics accelerator card to operate at high speed.

[0136] Further, the short-distance communication circuit 920 includes a short-distance communication circuit 920a. The short-distance communication circuit 920 is a communication circuit such as NFC or Bluetooth.

[0137] Furthermore, the engine control unit 930 is made up of a scanner unit 931 and a printer unit 932. The operation panel 940 is equipped with a panel display unit 940a, such as a touch panel, that displays current setting values ​​and selection screens and receives inputs from the operator, and an operation panel 940b that includes a numeric keypad that receives setting values ​​for image formation conditions such as density setting conditions and a start key that receives a copy start command. The controller 910 controls the entire MFP 9, and controls, for example, drawing, communication, and inputs from the operation panel 940. The scanner unit 931 or the printer unit 932 includes an image processing unit that performs error diffusion, gamma conversion, and the like.

[0138] The MFP 9 can sequentially switch among the document box function, copy function, printer function, and facsimile function using the application switching key on the operation panel 940. When the document box function is selected, the MFP 9 enters document box mode, when the copy function is selected, the MFP 9 enters copy mode, when the printer function is selected, the MFP 9 enters printer mode, and when the facsimile mode is selected, the MFP 9 enters facsimile mode.

[0139] The network I / F 950 is an interface for performing data communication using the communication network 100. The short-range communication circuit 920 and the network I / F 950 are electrically connected to the ASIC 906 via a PCI bus 922.

[0140] <Considerations for each color regarding forced toner consumption> The purpose of toner refresh is to consume deteriorated toner in a developer that has been used for a long period of time with low image quality (low toner consumption). Therefore, in the case of an image forming apparatus that uses multiple types of toner, it is preferable to perform forced toner consumption (toner refresh) for each toner. Since the degree of deterioration differs for each color, it is preferable to determine not only whether toner refresh is necessary but also the amount of toner refresh required for each color. Here, we will provide a supplementary explanation in addition to the above explanation regarding the case where multiple types of toner are used.

[0141] The image forming apparatus shown as an example in Figures 1 and 2 has developing devices 13 that perform development using toner of each color (yellow, magenta, cyan, and black). Each developing device 13 has its own developing roller 13a. A determination as to whether toner refresh is an image forming condition is made for each color. For example, the above formula 1 etc. is calculated for each color, and the toner consumption amount A per unit travel distance is calculated for each color. As in the example of Figure 11(B), a print count memory can be prepared for each color (K, C, M, and Y), so formula 1 etc. can be calculated for each color. For example, the development travel distance is determined by the travel distance of the developing roller 13a of each developing device 13.

[0142] In this way, it is possible to determine whether or not to set the image forming condition for toner refresh for each color. Also, threshold value B may be common to all colors, or may be different for each color.

[0143] Furthermore, since the amount of toner consumption is not constant and constantly fluctuates depending on the output image, it is necessary to calculate the average amount of toner consumption over a certain period. Therefore, the cumulative amount of toner consumption is divided by the travel distance of the developing member or the cumulative area of ​​the output paper to calculate the amount of toner consumption per unit travel distance. This average amount of toner consumption is calculated for each color and used for judgment.

[0144] Next, an example in which the conditions for determining toner refresh are met will be described. When determining whether toner refresh is necessary for each color, there may be some toners among the toners of each color that are determined to need to be refreshed and some toners that are determined not to need to be refreshed. In this case, toner refresh may be performed only on the toners that are determined to need to be refreshed, or on all the toners.

[0145] Whether to refresh only the toner that has been targeted for toner refresh or to refresh all the toner can be determined, for example, as follows: For example, different control is performed depending on whether the transfer rate adjustment is for the primary transfer or the secondary transfer.

[0146] When the transfer rate is adjusted in the primary transfer, each color can be transferred independently to the intermediate transfer belt, so toner refresh can be performed only on the toner that is the target of toner refresh. In this case, toner that does not require toner refresh is not refreshed, so a deterioration in toner yield (unnecessarily accelerating toner consumption) can be prevented. The toner consumption amount A per unit travel distance is updated only for the developing means that has performed toner refresh.

[0147] When the transfer rate is adjusted during secondary transfer, the transfer rate fluctuates uniformly for all toners, so toner refresh is preferably performed on all toners to suppress color variations in the image. Therefore, in the case of secondary transfer, the increase amount is uniform for all toners. In this case, toner refresh is performed even on toners that do not require toner refresh, which may result in a deterioration in toner yield, but on the other hand, it suppresses color variations in the image and prevents control from becoming complicated.

[0148] One embodiment taking the above description into consideration will now be described. In one embodiment, an image forming apparatus includes a plurality of developing means, and a control unit determines for each developing means whether the toner consumption per unit travel distance of the developing member is below a threshold value. For developing means where the toner consumption is below the threshold value, the amount of toner supplied from the developing means to the image carrier is set to an amount that includes the amount of toner required to form the toner image and is greater than that in normal operation. For developing means where the toner consumption is not below the threshold value, the amount of toner supplied from the developing means to the image carrier is set to the same amount as in normal operation. The control unit performs control different from that in normal operation on the first transfer means corresponding to the developing means where the toner consumption is below the threshold value, and makes the amount of first transfer residual toner of the target toner greater than that in normal operation. By doing this, when the image forming apparatus has a plurality of toners and a plurality of developing means, toner refresh can be performed only on the toners and developing means that are the target of toner refresh, thereby preventing a deterioration in toner yield.

[0149] In the case of direct transfer, since transfer is performed only once, if there is toner determined to require toner refresh, it is preferable to perform toner refresh on all toners in order to suppress color fluctuations in the image, even if there is toner that does not require toner refresh.

[0150] (Second embodiment) Next, another embodiment of the present invention will be described, and a description of matters common to the above embodiment will be omitted.

[0151] In this embodiment, as in the first embodiment, a threshold value is determined for the amount of toner consumed per unit travel distance, and a toner refresh operation (forced consumption of toner) is performed according to the determination result. In the toner refresh operation in this embodiment, the primary transfer rate is set to the same as in normal operation, and the value of the secondary transfer current is adjusted to reduce the secondary transfer rate below that in normal operation.

[0152] In this way, the increased amount of toner in the toner refresh remains on the intermediate transfer belt 17 after the secondary transfer and is transported to the intermediate transfer belt cleaning device 30. In this embodiment as well, the increased amount of toner is not transferred to the recording medium P, so even if toner is forcibly consumed by the toner refresh, it is possible to suppress the effect on the image on the recording medium P. Alternatively, even if the increased amount of toner is transferred to the recording medium P, it is possible to reduce the effect on the image.

[0153] FIG. 13 is a schematic diagram for explaining this embodiment, and is similar to FIGS. 3 and 6. The matters explained in FIGS. 1, 2, and 6 above and the matters explained in the normal operation above can be applied to this embodiment. The operation shown in FIG. 13 is an operation performed when the toner consumption amount per unit travel distance is equal to or less than a threshold, and is the toner refresh operation of this embodiment. The threshold can be determined in the same manner as in the above embodiments.

[0154] In the toner refresh operation of this embodiment, as in the first embodiment, in addition to the toner for image formation, increased toner 231 for forced toner consumption is supplied from the developing roller 13a to the photosensitive drum 11. In this embodiment, since the primary transfer rate is the same as in normal operation (see FIG. 15(A) described later), the increased toner 231 is transferred to the intermediate transfer belt 17 by the primary transfer bias roller 14, as shown in FIG.

[0155] On the other hand, after the primary transfer, transfer residual toner 213 remains on the photosensitive drum 11, as in normal operation. However, as explained above, the transfer residual toner 213 does not necessarily have to be generated. In addition, it does not matter whether the transfer residual toner 213 is due to the toner image 211 for image formation or the increment toner 231. The same applies to other embodiments.

[0156] The toner image 212 for image formation on the intermediate transfer belt 17 and the increment toner 231 are transported to the secondary transfer position. The secondary transfer position can also be said to be the position where the intermediate transfer belt 17 and the secondary transfer bias roller 18 face each other. In this embodiment, the secondary transfer rate is lowered than in normal operation (see FIG. 15(B) described later). For this reason, as shown in FIG. 13, the increment toner 231 is not transferred (or is barely transferred) to the recording medium P, and remains on the intermediate transfer belt 17 as secondary transfer residual toner. Because only the toner image 214 necessary for image formation is transferred to the recording medium P, image quality is ensured and the increment toner 231 is prevented from affecting the image on the recording medium P.

[0157] The remaining toner remaining on the intermediate transfer belt 17 after the secondary transfer is the toner indicated by the reference numeral 215 and the increased toner 231, and these are collected by the intermediate transfer belt cleaning blade 31 of the intermediate transfer belt cleaning device 30. Therefore, even if the secondary transfer rate is reduced and the increased toner 231 is not transferred to the recording medium P, no other effects are caused.

[0158] The control unit in this embodiment controls the second transfer means to increase the amount of second transfer residual toner compared to normal operation. The second transfer means includes, for example, a second transfer member (e.g., secondary transfer bias roller 18) facing intermediate transfer belt 17 and a secondary transfer power supply that applies voltage to the second transfer member. The control unit controls, for example, the secondary transfer power supply, and controls the voltage applied from the secondary transfer power supply to the secondary transfer bias roller. This allows the secondary transfer current to be adjusted, and the secondary transfer rate to be adjusted.

[0159] Figure 14 is a schematic diagram for explaining what kind of toner is carried on each member in Figure 13. Figure 14 is a diagram similar to Figure 4 showing normal operation, and (1) to (3) in Figure 14 correspond to (1) to (3) in Figure 13, similar to (1) to (3) in Figures 3 and 4.

[0160] In Figure 14, the increased toner 231 is shown in (1). That is, as in the first embodiment, the toner for image formation and the increased toner 231 are supplied from the developing means to the photosensitive drum 11. The increased toner 231 is also shown in (2). This indicates that the increased toner 231 has been transferred to the intermediate transfer belt 17, as shown in Figure 13. The increased toner 231 is not shown in (3). This indicates that the increased toner 231 has not been transferred to the recording medium P, as shown in Figure 13.

[0161] Figure 15 is a diagram for explaining the selection of transfer current in this embodiment. The relationship between transfer current and transfer rate (transfer rate curve) shown in Figure 15 is the same as that shown in Figure 5, and the transfer rate reaches its maximum at a certain value of transfer current. The vertical dashed line in the figure indicates the selected transfer current.

[0162] 15A, in this embodiment, the value of the primary transfer current is set to the same as in normal operation, which maximizes (or nearly maximizes) the primary transfer rate, and the toner required for image formation and the additional toner 231 are transferred onto the intermediate transfer belt 17.

[0163] As shown in FIG. 15(B), in this embodiment, the value of the secondary transfer current is lowered compared to normal operation. By selecting a secondary transfer current value lower than normal operation, the secondary transfer rate becomes lower than normal operation. As a result, the increased toner 231 is not transferred from the intermediate transfer belt 17 to the recording medium P, and remains on the intermediate transfer belt 17 as secondary transfer residual toner. Therefore, even if the primary transfer rate is set to the same as normal operation as in (A), it is possible to prevent any effect on the image formed on the recording medium P.

[0164] In this embodiment, there is no need to forcibly consume toner during non-image formation times, such as at the end of image formation, and there is no need to output a separate pattern for the purpose of forcibly consuming toner. In this embodiment, toner refresh can be performed at the same time as image formation on the recording medium P, thereby preventing downtime caused by forcibly consuming toner. Furthermore, the increased amount of toner used for toner refresh is not transferred to the recording medium P, or only a small amount is transferred, so the increased amount of toner can be prevented from affecting the image. Furthermore, even if the increased amount of toner becomes residual toner, it is removed and collected by the cleaning device, so the increased amount of toner can be prevented from affecting other areas. Furthermore, because the increased amount of toner is removed in the same way as in normal operation, there is no need to add a process to remove the increased amount of toner.

[0165] As described above, in this embodiment, when the toner consumption per unit travel distance of the developing member is below a threshold value, the control unit controls the second transfer means to make the secondary transfer rate lower than in normal operation and make the amount of second transfer residual toner greater than in normal operation. As described in the supplementary explanation below, past findings have shown that allowing waste toner to be input into the cleaning device maintains improved cleaning performance. In this embodiment, more residual toner is input into the intermediate transfer belt cleaning device than in normal operation, which stabilizes the behavior of the tip of the intermediate transfer belt cleaning blade compared to normal operation. Therefore, in this embodiment, the cleaning performance of the intermediate transfer belt cleaning device can be improved, making it easier to maintain image quality.

[0166] (Third embodiment) Next, another embodiment of the present invention will be described, and a description of matters common to the above embodiment will be omitted.

[0167] In this embodiment, as in the above embodiment, a threshold value is determined for the amount of toner consumed per unit travel distance, and a toner refresh operation (forced toner consumption) is performed according to the determination result. In the toner refresh operation in this embodiment, the values ​​of the primary transfer current and the secondary transfer current are adjusted to reduce both the primary transfer rate and the secondary transfer rate below those in normal operation.

[0168] As shown in FIG. 18 (described later), in this embodiment, when the primary transfer rate and the secondary transfer rate are reduced, the reduction amount is smaller than in the first and second embodiments. In this embodiment, the increased amount of toner in toner refresh remains on the photosensitive drum 11 after the primary transfer, and remains on the intermediate transfer belt 17 after the secondary transfer. This remaining increased amount of toner is transported to the photosensitive drum cleaning device 15 and the intermediate transfer belt cleaning device 30. In this embodiment, the increased amount of toner is not transferred to the recording medium P, so that even if toner is forcibly consumed by toner refresh, it is possible to suppress the impact on the image on the recording medium P. Or, even if the increased amount of toner is transferred to the recording medium P, it is possible to reduce the impact on the image.

[0169] FIG. 16 is a schematic diagram for explaining this embodiment, and is similar to FIG. 3 and the like. The matters explained in FIGS. 1, 2, and 6 above and the matters explained in the normal operation above can be applied to this embodiment. The operation shown in FIG. 16 is an operation performed when the toner consumption amount per unit travel distance is equal to or less than a threshold, and is the toner refresh operation of this embodiment. The threshold can be determined in the same manner as in the above embodiment.

[0170] In the toner refresh operation of this embodiment, in addition to the toner for image formation, the developing roller 13a supplies the photosensitive drum 11 with the additional toner 231 for forced toner consumption, as in the above embodiment.

[0171] In this embodiment, the primary transfer rate is set lower than in normal operation (see FIG. 18A described later), and therefore, as shown in FIG. 16, the increased toner 231 remains on the photosensitive drum 11 as transfer residual toner. The increased toner 231 remaining on the photosensitive drum 11 is indicated by reference numeral 232. The primary transfer rate in this embodiment is set lower than in normal operation and higher than in the first embodiment. Therefore, of the increased toner 231 supplied to the photosensitive drum 11, a portion remains on the photosensitive drum 11, and a portion is transferred to the intermediate transfer belt 17 by the primary transfer bias roller 14. The increased toner 231 transferred to the intermediate transfer belt 17 is indicated by reference numeral 233.

[0172] As in the above embodiment, the transfer residual toner on the photosensitive drum 11 is removed by the photosensitive drum cleaning blade 15a. The transfer residual toner on the photosensitive drum 11 corresponds to the toner image 213 and the increment toner 232.

[0173] The toner image 212 for image formation on the intermediate transfer belt 17 and the additional toner 233 are transported to the secondary transfer position. In this embodiment, the secondary transfer rate is lowered compared to normal operation (see FIG. 18(B) described later). For this reason, as shown in FIG. 16, the additional toner 233 is not transferred to the recording medium P, but remains on the intermediate transfer belt 17 as secondary transfer residual toner. Since only the toner image 214 necessary for image formation is transferred to the recording medium P, image quality is ensured and the additional toner due to forced consumption can be prevented from affecting the image on the recording medium P.

[0174] The secondary transfer rate in this embodiment is set lower than that in normal operation, but higher than that in the second embodiment. This takes into consideration that the increased amount of toner 233 transferred to the intermediate transfer belt 17 is less than the increased amount of toner 231 transferred to the intermediate transfer belt 17 in the second embodiment. In this embodiment, it is possible to transfer the toner image 212 necessary for image formation onto the recording medium P, while preventing the increased amount of toner from being transferred onto the recording medium P.

[0175] This point will be explained again. In the primary transfer in this embodiment, the selection of the primary transfer rate divides the increment toner 231 supplied to the photosensitive drum 11 into a toner that remains on the photosensitive drum 11 (increment toner 232) and a toner that is transferred to the intermediate transfer belt 17 (increment toner 233). In the secondary transfer in this embodiment, the selection of the secondary transfer rate transfers the toner image 212 necessary for image formation onto the recording medium P, while the increment toner 233 remains on the intermediate transfer belt 17. For this reason, in this embodiment, the increment toner supplied to the photosensitive drum 11 remains on the photosensitive drum 11 and the intermediate transfer belt 17 and is not transferred to the recording medium P, and therefore does not affect the image on the recording medium P.

[0176] Figure 17 is a schematic diagram for explaining what kind of toner is carried on each member in Figure 16. Figure 17 is a diagram similar to Figure 4 showing normal operation, and (1) to (3) in Figure 17 correspond to (1) to (3) in Figure 16, similar to (1) to (3) in Figures 3 and 4.

[0177] In Figure 17, (1) shows the additional toner 231. That is, as in the first embodiment, the toner for image formation and the additional toner 231 are supplied from the developing means to the photosensitive drum 11. Also, (2) shows the additional toner 233. This indicates that, as shown in Figure 16, the additional toner 233, which is a part of the additional toner 231, has been transferred to the intermediate transfer belt 17. In (3), the additional toner 233 is not shown. This indicates that, as shown in Figure 16, the additional toner 233 has not been transferred to the recording medium P.

[0178] Figure 18 is a diagram for explaining the selection of transfer current in this embodiment. The relationship between transfer current and transfer rate (transfer rate curve) shown in Figure 18 is the same as that shown in Figure 5, and the transfer rate reaches its maximum at a certain value of transfer current. The vertical dashed line in the figure indicates the selected transfer current.

[0179] As shown in FIG. 18A, in this embodiment, the value of the primary transfer current is lower than in normal operation. By selecting a primary transfer current value lower than in normal operation, the primary transfer rate becomes lower than in normal operation. Furthermore, in this embodiment, the value of the primary transfer current is selected so that the primary transfer rate is higher than in the first embodiment. The white circles in the figure represent values ​​selected in the example shown in FIG. 8A of the first embodiment. Therefore, the primary transfer rate in this embodiment is lower than in normal operation and higher than in the first embodiment. Therefore, the increased toner 231 is divided into that which is transferred to the intermediate transfer belt 17 and that which remains on the photosensitive drum 11.

[0180] As shown in FIG. 18B, in this embodiment, the value of the secondary transfer current is set lower than in normal operation. By selecting a secondary transfer current value lower than in normal operation, the secondary transfer rate is lower than in normal operation. Furthermore, in this embodiment, the value of the secondary transfer current is selected so that the secondary transfer rate is higher than in the second embodiment. The white circles in the figure represent values ​​selected in the example shown in FIG. 15B of the second embodiment. Therefore, the secondary transfer rate in this embodiment is lower than in normal operation and higher than in the second embodiment. Therefore, even if the amount of increased toner 233 on the intermediate transfer belt 17 is less than the amount of increased toner 231, it is possible to transfer the amount of toner image required for image formation to the recording medium P, and the increased toner 233 can remain on the intermediate transfer belt 17.

[0181] In this embodiment, there is no need to forcibly consume toner during non-image formation times, such as at the end of image formation, and there is no need to output a separate pattern for the purpose of forcibly consuming toner. In this embodiment, toner refresh can be performed at the same time as image formation on the recording medium P, thereby preventing downtime caused by forcibly consuming toner. Furthermore, the increased amount of toner used for toner refresh is not transferred to the recording medium P, or only a small amount is transferred, so the increased amount of toner can be prevented from affecting the image. Furthermore, even if the increased amount of toner becomes residual toner, it is removed and collected by the cleaning device, so the increased amount of toner can be prevented from affecting other areas. Furthermore, because the increased amount of toner is removed in the same way as in normal operation, there is no need to add a process to remove the increased amount of toner.

[0182] As described above, in this embodiment, when the toner consumption per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means and the second transfer means to make the primary transfer rate lower than in normal operation, and the secondary transfer rate lower than in normal operation, and to make the amount of first transfer residual toner and the amount of second transfer residual toner higher than in normal operation. As described in the supplementary explanation below, past findings have shown that allowing transfer residual toner to be input into the cleaning device maintains improved cleaning performance. In this embodiment, more transfer residual toner is input into the photoconductor cleaning device and the intermediate transfer belt cleaning device than in normal operation, which stabilizes the behavior of the tips of the photoconductor cleaning blade and the intermediate transfer belt cleaning blade than in normal operation. Therefore, in this embodiment, the cleaning performance of the photoconductor cleaning device and the intermediate transfer belt cleaning device can be improved, making it easier to maintain image quality.

[0183] (Fourth embodiment) Next, another embodiment of the present invention will be described, and a description of matters common to the above embodiment will be omitted.

[0184] The above embodiment is an example of a secondary transfer method using an intermediate transfer member. The present invention is not limited to this, and also includes a direct transfer method in which an image is transferred directly from an image carrier to a recording medium. This embodiment is a direct transfer method. The direct transfer method may also be called a primary transfer method. In this embodiment, as in the above embodiment, a threshold value is determined for the amount of toner consumed per unit travel distance, and a toner refresh operation (forced toner consumption) is performed depending on the determination result.

[0185] FIG. 19 is a schematic diagram for explaining this embodiment, and is similar to FIG. 3 and the like. The matters explained in FIGS. 1, 2, and 6 above and the matters explained in the normal operation above can be applied to this embodiment. The operation shown in FIG. 19 is an operation performed when the toner consumption amount per unit travel distance is equal to or less than a threshold, and is the toner refresh operation of this embodiment. The threshold can be determined in the same manner as in the above embodiment.

[0186] Toner for image formation and additional toner for forced consumption are supplied from developing roller 13a to photosensitive drum 11. In the figure, a toner image 211 for image formation and additional toner 231 are shown on photosensitive drum 11. The toner image 211 for image formation and additional toner 231 on photosensitive drum 11 are transported to the primary transfer position where photosensitive drum 11 and primary transfer bias roller 14 face each other. Although this is referred to as primary transfer, in the case of a direct transfer method, primary transfer may simply be referred to as transfer.

[0187] In this embodiment, the primary transfer rate is set lower than in normal operation (see FIG. 21, which will be described later). Therefore, as shown in FIG. 19, the increased toner 231 is not transferred to the recording medium P, but remains on the photosensitive drum 11 as transfer residual toner. Because only the toner image 214 necessary for image formation is transferred onto the recording medium P, image quality is ensured and the increased toner 231 can be prevented from affecting the image on the recording medium P.

[0188] The remaining toner remaining on the photosensitive drum 11 after transfer is the toner 213 and the increased toner 231, which are removed and collected by the photosensitive cleaning blade 15a of the photosensitive cleaning device 15. Therefore, even if the primary transfer rate is reduced and the increased toner 231 is not transferred to the recording medium P, no other effects are caused.

[0189] Figure 20 is a schematic diagram for explaining what kind of toner is carried on each member in Figure 19. Figure 20 is a diagram similar to Figure 4 showing normal operation, and (1) and (2) in Figure 20 correspond to (1) and (2) in Figure 19.

[0190] In Figure 20, (1) shows the increased toner 231. That is, as in the first embodiment, the toner for image formation and the increased toner 231 are supplied from the developing means to the photosensitive drum 11. In (2), the increased toner 231 is not shown. This indicates that the increased toner 231 has not been transferred to the recording medium P, as shown in Figure 19.

[0191] FIG. 21 is a diagram for explaining the selection of transfer current in this embodiment. The relationship between transfer current and transfer rate (transfer rate curve) shown in FIG. 21 is the same as that in FIG. 5, and the transfer rate is maximized at a certain value of transfer current. The vertical dashed line in the figure indicates the selected transfer current. In the case of the direct transfer method, since transfer occurs only once, there is no need to refer to it as primary transfer, and it would be sufficient to simply refer to it as transfer, but in FIG. 21 it is referred to as primary transfer. Primary transfer can be read as transfer as appropriate.

[0192] As shown in FIG. 21, in this embodiment, the value of the primary transfer current is lowered compared to normal operation. By selecting a primary transfer current value lower than that of normal operation, the primary transfer rate becomes lower than that of normal operation. As a result, the increased toner 231 is not transferred from the photosensitive drum 11 to the recording medium P, and remains on the photosensitive drum 11 as transfer residual toner. This prevents the increased toner 231 from affecting the image formed on the recording medium P.

[0193] In this embodiment, there is no need to forcibly consume toner during non-image formation times, such as at the end of image formation, and there is no need to output a separate pattern for the purpose of forcibly consuming toner. In this embodiment, toner refresh can be performed at the same time as image formation on the recording medium P, thereby preventing downtime caused by forcibly consuming toner. Furthermore, the increased amount of toner used for toner refresh is not transferred to the recording medium P, or only a small amount is transferred, so the increased amount of toner can be prevented from affecting the image. Furthermore, even if the increased amount of toner becomes residual toner, it is removed and collected by the cleaning device, so the increased amount of toner can be prevented from affecting other areas. Furthermore, because the increased amount of toner is removed in the same way as in normal operation, there is no need to add a process to remove the increased amount of toner.

[0194] Normal operation of the direct transfer method can be considered as forming an image under image forming conditions in which the increased amount of toner 231 is not supplied in Figure 19. This can be considered in the same way as the comparison between Figure 3, which shows normal operation of the secondary transfer method, and Figure 6, which shows an example of forced toner consumption in the secondary transfer method. Furthermore, the primary transfer current in normal operation of the direct transfer method can be selected as shown in Figure 5(A).

[0195] The present embodiment will be described again. The image forming apparatus of the present embodiment includes an image carrier, a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image, a transfer unit for transferring the toner image from the image carrier to a recording medium, and a control unit, wherein when an operation of forming an image so as to maximize or substantially maximize a transfer rate of the transfer is defined as a normal operation, the control unit controls the amount of toner supplied from the developing unit to the image carrier to include the amount of toner required to form the toner image and to be greater than that in the normal operation when the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, and controls the transfer unit to transfer the toner image to the recording medium and to leave a greater amount of residual toner than that in the normal operation.

[0196] In addition, in one example of this embodiment, when the toner consumption per unit traveling distance of the developing member is below a threshold value, the control unit controls the transfer means to make the transfer rate lower than in the normal operation and make the amount of residual toner after transfer greater than in the normal operation. As described in the supplementary explanation below, past findings have shown that allowing transfer residual toner to be input into the cleaning device maintains improved cleaning performance. In this embodiment, more transfer residual toner is input into the photosensitive member cleaning device than in normal operation, which stabilizes the behavior of the tip of the photosensitive member cleaning blade compared to normal operation. Therefore, in this embodiment, the cleaning performance of the photosensitive member cleaning device can be improved, making it easier to maintain image quality.

[0197] The image forming method of this embodiment is an image forming method performed by an image forming apparatus that includes an image carrier, a developing means having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image, and a transfer means that transfers the toner image from the image carrier to a recording medium, and includes a control step, wherein when normal operation is an operation of forming an image so that the transfer rate of the transfer is maximized or nearly maximized, the control step, when the toner consumption per unit traveling distance of the developing member is below a threshold value, increases the amount of toner supplied from the developing means to the image carrier, including the amount of toner required to form the toner image, and increases it compared to the normal operation, and controls the transfer means to transfer the toner image to the recording medium and increase the amount of residual toner after transfer compared to the normal operation.

[0198] The program of this embodiment is a program that causes an image forming apparatus to execute a control process, the image forming apparatus having an image carrier, a developing means having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image, and a transfer means that transfers the toner image from the image carrier to a recording medium. When the normal operation is an operation of forming an image so that the transfer rate of the transfer is maximized or nearly maximized, the control process is characterized in that, when the toner consumption per unit traveling distance of the developing member is below a threshold value, the amount of toner supplied from the developing means to the image carrier is increased to include the amount of toner required to form the toner image and to be greater than in the normal operation, and the transfer means is controlled to transfer the toner image to the recording medium and to increase the amount of residual toner remaining after transfer to be greater than in the normal operation.

[0199] (Comparative Example 1) Next, Comparative Example 1, which is not included in the present invention, will be described. Comparative Example 1 is an example in which an increased amount of toner for forced consumption of toner is superimposed on a toner image on a recording medium. In Comparative Example 1, the toner including the increased amount of toner is transferred from the photosensitive drum 11 to the intermediate transfer belt 17, and the transfer rate is set so that the toner including the increased amount of toner is transferred from the intermediate transfer belt 17 to the recording medium P. In Comparative Example 1, toner can be forcedly consumed without causing downtime, but the amount of toner on the recording medium becomes greater than the amount of toner required for image formation, which affects image quality.

[0200] FIG. 22 is a schematic diagram for explaining Comparative Example 1, and is similar to FIG. 3 and the like. Explanation of matters common to the above-described embodiments will be omitted. In the toner refresh operation of Comparative Example 1, as in the first embodiment, in addition to the toner for image formation, an additional toner 231 for forced toner consumption is supplied from the developing roller 13a to the photosensitive drum 11. In this embodiment, the primary transfer rate is the same as in normal operation, so as shown in the figure, the additional toner 231 is transferred to the intermediate transfer belt 17 by the primary transfer bias roller 14.

[0201] The toner image 212 for image formation and the incremental toner 231 on the intermediate transfer belt 17 are transported to the secondary transfer position. In Comparative Example 1, the secondary transfer rate is set to the same as in normal operation, so as shown in the figure, the incremental toner 231 is transferred to the recording medium P by the secondary transfer bias roller 18. As a result, the toner image 214 for image formation and the incremental toner 231 are transferred onto the recording medium, resulting in an amount of toner that exceeds the amount necessary for image formation, which affects image quality.

[0202] Figure 23 is a schematic diagram for explaining what kind of toner is carried on each member in Figure 22. Figure 23 is a diagram similar to Figure 4 showing normal operation, and (1) to (3) in Figure 23 correspond to (1) to (3) in Figure 22.

[0203] In Figure 23, all of (1) to (3) show the increased toner 231. (1) shows that the toner for image formation and the increased toner 231 are supplied from the developing means to the photosensitive drum 11. (2) shows that the increased toner 231 has been transferred to the intermediate transfer belt 17. (3) shows that the increased toner 231 has been transferred to the recording medium P.

[0204] The primary transfer current and secondary transfer current in Comparative Example 1 are selected to be the same as those in FIG. 5 for normal operation, and therefore are not shown here.

[0205] (supplementary explanation) In the present invention, the first to third embodiments are selected as appropriate depending on the device configuration, purpose, and the like. It has been known from past findings that if residual toner is input to the cleaning device, the cleaning performance is maintained at an improved level. Therefore, when the margin of the cleaning device is low, the cleaning performance is likely to be improved.

[0206] When considering the selection of an embodiment from this perspective, there is no particular limitation, but for example, if the margin of error of the photosensitive drum cleaning device is low, the first embodiment may be selected. In this case, the cleaning performance of the photosensitive drum cleaning device is likely to be improved and the improved cleaning performance is likely to be maintained. Therefore, even if the increased amount of toner remains as transfer residual toner, it can be effectively removed and collected. Alternatively, for example, if the margin of error of the intermediate transfer belt cleaning device is low, the second embodiment can be selected. In this case, the cleaning performance of the intermediate transfer belt cleaning device is likely to be improved, and the improved cleaning performance can be easily maintained. Therefore, even if the increased amount of toner remains as residual toner after transfer, it can be effectively removed and collected.

[0207] As mentioned above, in the present invention, both the secondary transfer method and the direct transfer method (primary transfer method) can be used. The value of the transfer current can be adjusted appropriately depending on the purpose, and in both the secondary transfer method and the direct transfer method, it is calculated from the transfer rate curve (correlation between transfer current and transfer rate) obtained at the time of design, and set so as to cancel out the increased amount of toner supplied by the developing means.

[0208] An example will be shown below. For example, an example will be explained in which the toner supplied from the developing means is increased by 20% as the additional toner for forced consumption. The designed toner adhesion amount for image formation on the recording medium is 0.4 mg / cm. 2 When the increment of toner is added, the total amount of toner adhered to the recording medium is 0.48 mg / cm 2 This is the design value 0.4 + 0.08 (20% increase) = 0.48 mg / cm 2 In this case, the transfer current is selected so that the transfer rate is reduced from 100% to 80%. The residual toner is 0.08 mg / cm, which is the increment of the toner. 2 increases.

[0209] The amount of increased toner for forced consumption is not limited and can be selected as appropriate. As exemplified above, the amount of increased toner can be determined, for example, taking into consideration the toner capacity contained in the developing unit. In addition, for example, the amount of increased toner may be determined, for example, taking into consideration a target value or a guideline for the number of times toner refresh is performed (for example, the number of pages printed). If it is desired to perform toner refresh less frequently, the amount of increased toner can be increased, and if a higher number of toner refreshes is acceptable, the amount of increased toner can be decreased.

[0210] For example, aspects of the present invention are as follows. <1> an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer means for secondarily transferring the toner image from the intermediate transfer body to a recording medium; a control unit, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the amount of toner supplied from the developing unit to the image carrier to include an amount of toner for forming the toner image and to be greater than that in the normal operation, controls the first transfer unit and the second transfer unit to transfer the toner image to the recording medium, and increases at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner to be greater than that in the normal operation. An image forming apparatus characterized by: <2> When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means to make the primary transfer rate lower than that in the normal operation and to make the amount of the first transfer residual toner larger than that in the normal operation. Characterized by <1> 2. The image forming apparatus according to claim 1 . <3> When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the second transfer means to make the secondary transfer rate lower than that in the normal operation and to make the amount of the second transfer residual toner larger than that in the normal operation. Characterized by <1> 2. The image forming apparatus according to claim 1 . <4> When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means and the second transfer means to make the primary transfer rate lower than that in the normal operation, and to make the secondary transfer rate lower than that in the normal operation, and to make the amount of the first transfer residual toner and the amount of the second transfer residual toner larger than those in the normal operation. Characterized by <1> 2. The image forming apparatus according to claim 1 . <5> When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes both a first toner amount, which is a toner amount necessary to form a desired image on the recording medium, and a second toner amount necessary to forcibly consume the toner. Characterized by <1> from <4> 10. The image forming apparatus according to claim 9, wherein <6> a first cleaning means for cleaning first transfer residual toner remaining on the image carrier after the primary transfer; a second cleaning means for cleaning second transfer residual toner remaining on the intermediate transfer body after the secondary transfer; When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means and the second transfer means to transfer the first amount of toner onto the recording medium, and inputs the second amount of toner as transfer residual toner into at least one of the first cleaning means and the second cleaning means. Characterized by <5> 2. The image forming apparatus according to claim 1 . <7> an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; a transfer means for transferring a toner image from the image carrier to a recording medium; a control unit, When an operation of forming an image so that the transfer rate of the transfer is maximized or substantially maximized is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the amount of toner supplied from the developing means to the image carrier to include an amount of toner for forming the toner image and to be greater than that in the normal operation, and controls the transfer means to transfer the toner image to the recording medium and to increase the amount of the transfer residual toner to be greater than that in the normal operation. An image forming apparatus characterized by: <8> When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the transfer means to make the transfer rate lower than that in the normal operation and to make the amount of the transfer residual toner larger than that in the normal operation. Characterized by <7> 2. The image forming apparatus according to claim 1 . <9> When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold, the amount of toner supplied from the developing means to the image carrier includes both a first toner amount, which is a toner amount necessary to form a desired image on the recording medium, and a second toner amount necessary to forcibly consume the toner. Characterized by <7> or <8> 2. The image forming apparatus according to claim 1 . <10> a cleaning means for cleaning the image carrier after the transfer toner has been removed; When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the transfer means to transfer the first amount of toner onto the recording medium and input the second amount of toner to the cleaning means as transfer residual toner. Characterized by <9> 2. The image forming apparatus according to claim 1 . <11> an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer unit that performs a second transfer of the toner image from the intermediate transfer body to a recording medium, a control step, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, In the control step, when the toner consumption amount per unit travel distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes the amount of toner for forming the toner image and is greater than that in the normal operation, the first transfer means and the second transfer means are controlled to transfer the toner image to the recording medium, and at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner is made greater than that in the normal operation. An image forming method comprising: <12> an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer unit that performs second transfer of a toner image from the intermediate transfer body to a recording medium, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control process controls the amount of toner supplied from the developing means to the image carrier to include the amount of toner required to form the toner image and to be greater than that in the normal operation, controls the first transfer means and the second transfer means to transfer the toner image to the recording medium, and increases at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner to be greater than that in the normal operation. A program characterized by: <13> an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; a transfer unit that transfers a toner image from the image carrier to a recording medium, a control step, When an operation of forming an image so that the transfer rate of the transfer is maximized or substantially maximized is defined as a normal operation, The control step, when the toner consumption amount per unit travel distance of the developing member is equal to or less than a threshold value, causes the amount of toner supplied from the developing means to the image carrier to include the amount of toner for forming the toner image and to be greater than that in the normal operation, and controls the transfer means to transfer the toner image to the recording medium and to increase the amount of the transfer residual toner to be greater than that in the normal operation. An image forming method comprising: <14> an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; a transfer unit that transfers a toner image from the image carrier to a recording medium, When an operation of forming an image so that the transfer rate of the transfer is maximized or substantially maximized is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control process increases the amount of toner supplied from the developing means to the image carrier, including the amount of toner required to form the toner image, and also increases the amount of toner remaining after transfer, by controlling the transfer means to transfer the toner image onto the recording medium and increase the amount of toner remaining after transfer, compared to the amount of toner remaining after transfer. A program characterized by: [Explanation of symbols]

[0211] 1. Image forming device 3 Document transport section 4 Document reader 5 Output tray 7 Paper feed section 9 Registration roller 11 Photosensitive drum 13 Developing device 14 Primary transfer bias roller 15 Photoconductor cleaning device 17 Intermediate transfer belt 18 Secondary transfer bias roller 20 Fixing device 28 Toner container 30 Intermediate transfer belt cleaning device 80 Waste toner collection container [Prior art documents] [Patent documents]

[0212] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-083647

Claims

1. an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer means for secondarily transferring the toner image from the intermediate transfer body to a recording medium; a control unit, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the amount of toner supplied from the developing unit to the image carrier to include the amount of toner required to form the toner image and to be greater than that in the normal operation, controls the first transfer unit and the second transfer unit to transfer the toner image to the recording medium, and increases at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner to be greater than that in the normal operation. An image forming apparatus characterized by:

2. When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means to make the primary transfer rate lower than that in the normal operation and make the amount of the first transfer residual toner larger than that in the normal operation.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the second transfer means to make the secondary transfer rate lower than that in the normal operation and make the amount of the second transfer residual toner larger than that in the normal operation.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. When the toner consumption amount per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means and the second transfer means to make the primary transfer rate lower than that in the normal operation, and to make the secondary transfer rate lower than that in the normal operation, and to make the amount of the first transfer residual toner and the amount of the second transfer residual toner larger than that in the normal operation.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes both a first toner amount, which is a toner amount necessary to form a desired image on the recording medium, and a second toner amount necessary to forcibly consume the toner.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. a first cleaning unit that cleans the first transfer residual toner remaining on the image carrier after the primary transfer; a second cleaning means for cleaning second transfer residual toner remaining on the intermediate transfer body after the secondary transfer; When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the first transfer means and the second transfer means to transfer the first amount of toner onto the recording medium, and inputs the second amount of toner as transfer residual toner to at least one of the first cleaning means and the second cleaning means.

6. The image forming apparatus according to claim 5,

7. an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; a transfer means for transferring a toner image from the image carrier to a recording medium; a control unit, When an operation of forming an image so that the transfer rate of the transfer is maximized or substantially maximized is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the amount of toner supplied from the developing means to the image carrier to include an amount of toner for forming the toner image and to be greater than that in the normal operation, and controls the transfer means to transfer the toner image to the recording medium and to increase the amount of the transfer residual toner to be greater than that in the normal operation. An image forming apparatus characterized by:

8. When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the transfer means to make the transfer rate lower than that in the normal operation and to make the amount of the transfer residual toner larger than that in the normal operation.

8. The image forming apparatus according to claim 7,

9. When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes both a first toner amount, which is a toner amount necessary to form a desired image on the recording medium, and a second toner amount necessary to forcibly consume the toner.

8. The image forming apparatus according to claim 7,

10. a cleaning means for cleaning the image carrier after the transfer toner has been removed; When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control unit controls the transfer means to transfer the first amount of toner onto the recording medium and input the second amount of toner to the cleaning means as transfer residual toner.

10. The image forming apparatus according to claim 9,

11. an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer unit that secondarily transfers a toner image from the intermediate transfer body to a recording medium, a control step, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, In the control step, when the toner consumption amount per unit travel distance of the developing member is equal to or less than a threshold value, the amount of toner supplied from the developing means to the image carrier includes the amount of toner for forming the toner image and is greater than that in the normal operation, the first transfer means and the second transfer means are controlled to transfer the toner image onto the recording medium, and at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner is made greater than that in the normal operation. An image forming method comprising:

12. an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; an intermediate transfer member; a first transfer means for primarily transferring a toner image from the image carrier to the intermediate transfer body; a second transfer unit that performs a second transfer of a toner image from the intermediate transfer body to a recording medium, When an operation of forming an image so that the transfer rate of the primary transfer is maximum or approximately maximum and so that the transfer rate of the secondary transfer is maximum or approximately maximum is defined as a normal operation, The control process includes controlling the amount of toner supplied from the developing means to the image carrier to include the amount of toner required to form the toner image and to be greater than that in the normal operation when the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, controlling the first transfer means and the second transfer means to transfer the toner image onto the recording medium, and controlling at least one of the amount of the first transfer residual toner and the amount of the second transfer residual toner to be greater than that in the normal operation. A program characterized by:

13. an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; a transfer unit that transfers a toner image from the image carrier to a recording medium, a control step, When an operation of forming an image so that the transfer rate of the transfer is maximized or substantially maximized is defined as a normal operation, The control step, when the toner consumption amount per unit travel distance of the developing member is equal to or less than a threshold value, causes the amount of toner supplied from the developing means to the image carrier to include the amount of toner for forming the toner image and to be greater than that in the normal operation, and controls the transfer means to transfer the toner image to the recording medium and to increase the amount of the transfer residual toner to be greater than that in the normal operation. An image forming method comprising:

14. an image carrier; a developing unit having a developing member facing the image carrier and supplying toner to the image carrier to form a toner image; a transfer unit that transfers a toner image from the image carrier to a recording medium, When an operation of forming an image so that the transfer rate of the transfer is maximized or substantially maximized is defined as a normal operation, When the amount of toner consumed per unit travel distance of the developing member is equal to or less than a threshold value, the control process increases the amount of toner supplied from the developing means to the image carrier, including the amount of toner required to form the toner image, and also increases the amount of toner remaining after transfer, by controlling the transfer means to transfer the toner image onto the recording medium and increase the amount of toner remaining after transfer, compared to the amount of toner remaining after transfer. A program characterized by:

Images