Image-forming device

Abstract

To suppress consumption of developer that a user does not intend.SOLUTION: An image-forming device comprises: a first image-forming section for forming an image by using a developer with a first color; a second image-forming section for forming an image by using a developer with a second color; a transfer section for transferring an image formed by the first image-forming section and an image formed by the second image-forming section to a recording medium and printing them; and a developer disposal operation execution section for executing developer disposal operation for disposing developer. The developer disposal operation execution section executes the developer disposal operation only for the developer with the first color but does not execute the developer disposal operation for the developer with the second color when performing printing using the developer with the first color without using the developer with the second color to a predetermined recording medium.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] An electrophotographic image forming apparatus includes an exposure device, a development unit having a photosensitive drum and a developer, a transfer device having a transfer belt, and a fixing device. In this image forming apparatus, the exposure device forms an electrostatic latent image on the photosensitive drum, the development unit develops the electrostatic latent image on the photosensitive drum with toner using the developer to form a toner image, the transfer device transfers the toner image on the photosensitive drum to the recording medium while conveying the recording medium sandwiched between the photosensitive drum and the transfer belt, and the fixing device fixes the toner image transferred to the recording medium.

[0003] In such electrophotographic image forming devices, repeated printing using toner generates degraded toner in the developing unit. Because this degraded toner is a cause of deterioration in image quality, conventional image forming devices discard the degraded toner in the developing unit by ejecting it onto the photosensitive drum and collecting it in a waste toner collection container within the image forming unit (see, for example, Patent Document 1).

[0004] In such an image forming apparatus, toner disposal is performed when, for example, a print pattern with a low print rate and low toner consumption continues.

[0005] On the other hand, in an image forming apparatus using an electrophotographic method, when color printing is performed, an image is formed using four color development units, for example, black, yellow, magenta, and cyan, and when monochrome printing is performed, an image is formed using a black development unit.

[0006] Some image forming devices are equipped with a separation mechanism that separates the development unit from the transfer device (specifically, separates the photosensitive drum from the transfer belt). When performing monochrome printing on standard recording media such as copy paper, this image forming device places the black development unit in contact with the transfer device (i.e., moves the development unit to a transfer position where the transfer device can transfer), while separating the yellow, cyan, and magenta development units from the transfer device (i.e., moves the development units to separation positions where the transfer device cannot transfer). In this case, the recording medium is conveyed sandwiched between one photosensitive drum and the transfer belt.

[0007] On the other hand, when performing monochrome printing on recording media that require stable transport, such as envelopes or cardboard, the image forming device may also abut yellow, cyan, and magenta development units against the transfer device, and monochrome printing may be performed while the recording medium is sandwiched and transported between up to four photosensitive drums and a transfer belt. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-45481 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in conventional image forming devices, when monochrome printing continues on recording media such as envelopes or cardboard, the yellow, cyan, and magenta development units operate without consuming much toner, so the device determines that printing has continued with a low print rate and low toner consumption for yellow, cyan, and magenta toner, and discards the toner.

[0010] For this reason, in the conventional image forming apparatus, even when only monochrome printing is performed, yellow, cyan, and magenta toners are discarded and consumed, which can lead to a situation where the yellow, cyan, and magenta toners must be replaced. In other words, in the conventional image forming apparatus, there is a problem in that developers may be consumed unintentionally by the user.

[0011] The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus that can suppress consumption of developer unintentionally by the user. [Means for solving the problem]

[0012] In order to solve this problem, the image forming apparatus of the present invention comprises a first image forming unit that forms an image using a developer of a first color, a second image forming unit that forms an image using a developer of a second color, a transfer unit that transfers and prints the image formed by the first image forming unit and the image formed by the second image forming unit onto a recording medium, and a developer disposal operation execution unit that executes a developer disposal operation to discard the developer, wherein when printing is performed on a specified recording medium using the developer of the first color without using the developer of the second color, the developer disposal operation execution unit executes the developer disposal operation only for the developer of the first color and does not execute the developer disposal operation for the developer of the second color.

[0013] In addition, the image forming apparatus of the present invention includes a first image forming unit that forms an image using a developer of a first color, a second image forming unit that forms an image using a developer of a second color, a transfer unit that transfers and prints the image formed by the first image forming unit and the image formed by the second image forming unit onto a recording medium, a developer disposal operation execution unit that executes a developer disposal operation to discard the developer, and a separation mechanism that moves each of the first image forming unit and the second image forming unit to a contact position in contact with the transfer unit or a separation position separated from the transfer unit, and when printing is performed using the developer of the first color without using the developer of the second color while the first image forming unit and the second image forming unit are in the contact position, the developer disposal operation execution unit executes the developer disposal operation only for the developer of the first color and does not execute the developer disposal operation for the developer of the second color.

[0014] This allows the present invention to avoid a situation where, for example, when printing using only a first color developer, the user unintentionally discards and consumes a second color developer. [Effects of the Invention]

[0015] According to the present invention, it is possible to realize an image forming apparatus that can suppress consumption of developer unintentionally by the user. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a side cross-sectional view showing the configuration of a printing mechanism of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control system of the image forming apparatus according to the first embodiment. [Figure 3] 4 is a flowchart showing a printing process procedure according to the first embodiment. [Figure 4] 10 is a flowchart showing a printing process procedure according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0018] 1. First Embodiment [1-1. Configuration of the printing mechanism of the image forming device] FIG. 1 shows the configuration of the printing mechanism of image forming apparatus 1 of the first embodiment. This image forming apparatus 1 is an electrophotographic color printer that prints monochrome images and color images on a sheet-like recording medium P. This image forming apparatus 1 has a roughly box-shaped apparatus housing 2. Here, the right side of the apparatus housing 2 in the drawing is the front side of the image forming apparatus 1, the left side of the drawing is the rear side of the image forming apparatus 1, the front side of the drawing is the left side of the image forming apparatus 1, the back side of the drawing is the right side of the image forming apparatus 1, the top side of the drawing is the upper side of the image forming apparatus 1, and the bottom side of the drawing is the lower side of the image forming apparatus 1.

[0019] A stacker 3 onto which recording media P printed by the image forming apparatus 1 are ejected is provided on the top surface of the device housing 2. A tray 4 for storing recording media P is also disposed at the bottom inside the device housing 2. A transport path R for transporting the recording media P is also formed inside the device housing 2, connecting the tray 4 and the stacker 3. A hopping roller 5, a registration roller 6, four developing units 7 (7K, 7Y, 7M, 7C), a transfer unit 8, a fixing unit 9, and a discharge roller 10 are also provided inside the device housing 2 along this transport path R.

[0020] The hopping roller 5 is a member that picks up the recording medium P stored in the tray 4 and sends it out onto the conveying path R. The registration roller 6 is a member that transports the recording medium P sent out onto the conveying path R without skewing it. The four developing units 7 (7K, 7Y, 7M, 7C) correspond to each of the multiple color developers (for example, four color toners: black (K), yellow (Y), magenta (M), and cyan (C)) used in the image forming apparatus 1, and are arranged along the conveying path R in the order of developing units 7K, 7Y, 7M, and 7C from the upstream side in the medium conveying direction.

[0021] The developing units 7 (7K, 7Y, 7M, 7C) are units that form images using toner, and the developing units 7K, 7Y, 7M, 7C form images using black (K), yellow (Y), magenta (M), and cyan (C) toner, respectively.

[0022] Here, the configuration of each developing unit 7 (7K, 7Y, 7M, 7C) will be described. Each developing unit 7 (7K, 7Y, 7M, 7C) has the same configuration except for the toner color, and each has a photosensitive drum 20, a charging roller 21, an LED head 22, a developing device 23, a cleaning device 24, and a charge removing section 25. It should be noted that the LED head 22 may be provided as a separate unit from the developing unit 7.

[0023] As an example, the photosensitive drum 20 used was an aluminum tube having a thickness of 0.75 mm and an outer diameter of 30 mm, on which a charge generating layer having a thickness of 0.5 μm and a charge transport layer having a thickness of 20 μm were provided. The charging roller 21 is a member for uniformly charging the surface of the photosensitive drum 20, and is made of a conductor shaft made of, for example, SUS material, covered with a conductive elastic material such as epichlorohydrin, and is arranged so as to be in contact with the photosensitive drum 20.

[0024] The LED head 22 is an exposure device for selectively exposing the uniformly charged surface of the photosensitive drum 20 to light to form an electrostatic latent image pattern. The LED head 22 has LED elements and a lens array, and is positioned at a position where the light emitted from the LED elements forms an image on the surface of the photosensitive drum 20.

[0025] The developing unit 23 is a device for developing the electrostatic latent image formed on the photosensitive drum 20 with toner to form a toner image. The developing unit 23 is configured to receive toner from a toner cartridge (not shown), and includes a developing roller 30, a supply roller 31, and a regulating blade 32.

[0026] The developing roller 30 is a component for developing an electrostatic latent image formed on the surface of the photosensitive drum 20 by adhering toner to the image. It is positioned in contact with the surface of the photosensitive drum 20 and is configured, for example, by disposing an elastic layer in a roll shape on a conductive shaft (core metal) made of SUS material, with a surface layer covering the elastic layer. The elastic layer of the developing roller 30 is made of, for example, urethane rubber or silicone rubber, and the surface layer is made of, for example, a material treated with a urethane solution or coated with acrylic resin or acrylic-fluorine copolymer resin. Those with a surface layer made of acrylic resin or acrylic-fluorine copolymer resin contain carbon black to impart conductivity.

[0027] Supply roller 31 is a member for supplying toner to developing roller 30, is arranged so as to contact developing roller 30, and is formed of, for example, a conductive shaft made of SUS material and an elastic layer. The elastic layer of supply roller 31 is, for example, a conductive silicone rubber foam layer or a conductive urethane rubber foam layer, to which acetylene black, carbon black, or the like is added to make it semi-conductive.

[0028] The regulating blade 32 is a member for forming a uniform thin layer of toner on the developing roller 30, and is positioned so that its tip is pressed against the developing roller 30. This regulating blade 32 is made of, for example, SUS with a plate thickness of 0.08 mm, and is bent at the portion that comes into contact with the developing roller 30, with a radius of curvature of 0.2 mm at the bent portion and a linear pressure of 30 gf / cm on the developing roller 30. The radius of curvature and linear pressure of the regulating blade 32 can be adjusted according to the amount of toner on the developing roller 30 and the charge amount of the toner.

[0029] The cleaning device 24 is a device for scraping off and discarding residual toner remaining on the photosensitive drum 20 due to untransferred toner and waste toner moved from the developing device 23 onto the photosensitive drum 20, and has a cleaning blade 33 made of, for example, rubber. This cleaning blade 33 is positioned so that its tip contacts the surface of the photosensitive drum 20. The cleaning device 24 stores the residual toner and waste toner scraped off by the cleaning blade 33. The waste toner will be described in detail later.

[0030] The charge removal unit 25 is a device in which a plurality of LED chips are arranged on a substrate, and is disposed opposite the photosensitive drum 20. The charge removal unit 25 exposes the surface of the photosensitive drum 20 to light to reset the surface potential of the photosensitive drum 20. Each of the developing units 7 (7K, 7Y, 7M, 7C) is configured as described above.

[0031] The transfer unit 8 has four transfer rollers 26 (26K, 26Y, 26M, 26C) and a transfer belt 27. Each transfer roller 26 (26K, 26Y, 26M, 26C) is a member for transferring a toner image formed on the photosensitive drum 20 of each development unit 7 (7K, 7Y, 7M, 7C) to the recording medium P or the transfer belt 27, and is disposed opposite the photosensitive drum 20 of each development unit 7 (7K, 7Y, 7M, 7C) with the transfer belt 27 sandwiched therebetween. Each transfer roller 26 (26K, 26Y, 26M, 26C) is made of, for example, a conductive elastic foam.

[0032] The transfer belt 27 is a member for transporting the recording medium P, is formed in a ring shape, and is stretched between a drive roller 28 provided at the rear side of the transfer unit 8 and an idle roller 29 provided at the front side. The upper straight portion of the transfer belt 27 is disposed so as to pass between the photosensitive drum 20 of each developing unit 7 (7K, 7Y, 7M, 7C) and each transfer roller 26 (26K, 26Y, 26M, 26C), and runs in accordance with the rotation of the drive roller 28. A belt cleaning device 34 is provided so as to come into contact with the lower straight portion of the transfer belt 27 and clean toner off the transfer belt 27.

[0033] The fixing unit 9 is a device for fixing the toner image transferred onto the recording medium P by applying heat and pressure, and includes a heat roller 35 and a pressure roller 36. The heat roller 35 is, for example, an iron tube having an outer diameter of 28 mm, with an elastic layer of silicone rubber disposed on the tube, and a PFA tube serving as a toner release layer covering the elastic layer. The heat roller 35 is equipped with a halogen lamp (not shown) inside the tube as a heat source. On the other hand, the pressure roller 36 does not have an elastic layer, but is instead an iron tube with a PFA tube. The discharge roller 10 is a member that discharges the recording medium P into the stacker 3 outside the device housing 2.

[0034] During printing, the image forming apparatus 1 sends out the recording medium P from the tray 4 onto the conveying path R using the hopping roller 5, and conveys it to the transfer belt 27 using the registration roller 6. Next, while conveying the recording medium P using the transfer belt 27, the image forming apparatus 1 transfers the toner image formed on the photosensitive drum 20 of the developing unit 7 onto the recording medium P using the transfer roller 26. Thereafter, the image forming apparatus 1 fixes the toner image onto the recording medium P using the fixing device 9, and discharges the recording medium P into the stacker 3 using the discharge roller 10.

[0035] 1, inside the device housing 2, a separation mechanism 55 (see FIG. 2) for separating each of the developing units 7 (7K, 7Y, 7M, 7C) from the transfer unit 8 is provided.

[0036] Specifically, the separation mechanism 55 moves each of the developing units 7 (7K, 7Y, 7M, 7C) in a direction (e.g., upward) away from the transfer unit 8, thereby separating the photosensitive drum 20 of each of the developing units 7 (7K, 7Y, 7M, 7C) from the transfer belt 27. The position of each of the developing units 7 (7K, 7Y, 7M, 7C) when separated from the transfer unit 8 is called the separation position. At the separation position, the photosensitive drum 20 is separated from the transfer belt 27, so that the toner image cannot be transferred to the recording medium P.

[0037] The separation mechanism 55 also moves each of the developing units 7 (7K, 7Y, 7M, 7C) in the separation position in a direction (e.g., downward) that brings them closer to the transfer unit 8, thereby bringing the photosensitive drum 20 of each of the developing units 7 (7K, 7Y, 7M, 7C) into contact with the transfer belt 27. The position of each of the developing units 7 (7K, 7Y, 7M, 7C) when in contact with the transfer unit 8 is called the contact position. At the contact position, the photosensitive drum 20 is in contact with the transfer belt 27, so that the toner image can be transferred onto the recording medium P.

[0038] The separation mechanism 55 is also capable of moving the developing units 7K, 7Y, 7M, and 7C individually to the separation position and the contact position, for example.

[0039] In the image forming apparatus 1, plain paper such as copy paper, envelopes, cardboard, etc. can be used as the recording medium P. When performing monochrome printing on the recording medium P, which is plain paper, the image forming apparatus 1 abuts the black developing unit 7K against the transfer unit 8 (i.e., moves it to the abutting position), while separating the yellow, cyan, and magenta developing units 7Y, 7M, and 7C from the transfer unit 8 (i.e., moves it to the separating position), thereby performing monochrome printing. In this case, the recording medium P is conveyed while being sandwiched between one photosensitive drum 20 and the transfer belt 27.

[0040] On the other hand, when monochrome printing is performed on a recording medium P that requires stable transport, such as an envelope or thick paper, the image forming apparatus 1 is configured so that all of the developing units 7K, 7Y, 7M, and 7C are brought into contact with the transfer unit 8, and monochrome printing is performed while the recording medium P is sandwiched and transported between a maximum of four photosensitive drums 20 and the transfer belt 27. Note that the image forming apparatus 1 uses a paper weight of, for example, 150 [g / m 2 ] or thicker is treated as thick paper that needs to be transported stably. The printing mechanism of the image forming apparatus 1 is configured as described above.

[0041] [1-2. Functional configuration of image forming device] 2 shows the configuration of the control system of image forming apparatus 1. The control system of image forming apparatus 1 includes a control unit 40, a receiving unit 41, a toner disposal operation control unit 42, a toner disposal count holding unit 43, a toner disposal count calculation unit 44, a drum count measurement unit 45, a dot count measurement unit 46, a toner disposal threshold holding unit 47, a drive control unit 48, a fixing control unit 49, an exposure control unit 50, a voltage control unit 51, a separation mechanism control unit 52, a drum motor 53, a belt motor 54, a fuser 9, an LED head 22, a charging roller 21, a developing roller 30, a supply roller 31, a regulating blade 32, a transfer roller 26, a charge removal unit 25, and a separation mechanism 55.

[0042] Of these, the toner disposal operation control unit 42, the toner disposal count holding unit 43, the toner disposal count calculation unit 44, the drum count measurement unit 45, the dot count measurement unit 46, and the toner disposal threshold holding unit 47 are included in the control unit 40, for example.

[0043] When a print job including print information such as image data and printing conditions and a print instruction for the print job are sent from a host device such as a PC (personal computer) (not shown), the image forming apparatus 1 receives these at the receiving unit 41 and sends them to the control unit 40. When the control unit 40 receives the print instruction, the toner disposal operation control unit 42 determines whether to execute toner disposal.

[0044] Here, we will explain toner disposal. In the image forming apparatus 1, there are cases where the amount of toner consumed by the entire apparatus becomes excessively low, or where only a specific color is used, resulting in excessively low toner consumption in the developing units 7 of unused colors.

[0045] When the amount of toner consumed decreases, the toner continues to be stirred up in the developing unit 7, and the toner adhering to the developing roller 30 continues to be rubbed by the supply roller 31, the regulating blade 32, and the photosensitive drum 20. In this case, the toner on the developing roller 30 tends to be frictionally charged and have a high potential, and if the toner potential becomes too high, it can cause stains on the image.

[0046] Furthermore, toner is damaged by continued rubbing, and the external additives contained therein are peeled off from the toner surface, which prevents the toner from being properly charged, resulting in image smearing, fogging, blurring, and deterioration of graininess.

[0047] In this way, if the amount of toner consumed becomes excessively low, toner with an excessively high potential or with external additives peeled off (called degraded toner) will be generated in the developing unit 7, degrading image quality. Therefore, in order to prevent such degradation of image quality, the image forming apparatus 1 is designed to forcibly consume toner with an excessively low amount of toner consumed by discarding it (i.e., by performing toner disposal).

[0048] The specific operation of toner disposal will be described later, but briefly, an electrostatic latent image of a disposal pattern for discarding toner is formed on the photosensitive drum 20 and developed with toner to form a toner image of the disposal pattern. This toner image is then scraped off the photosensitive drum 20 by the cleaning device 24 and discarded without being transferred. In this embodiment, the image forming apparatus 1 performs this toner disposal operation as part of the preparatory operation performed before the printing operation.

[0049] Returning now to the explanation of the control system configuration, the toner disposal operation control unit 42 determines whether to discard toner based on the printing conditions (color printing or monochrome printing, paper settings, etc.) included in the print job sent from the host device and the toner disposal count stored in the toner disposal count storage unit 43. The toner disposal count, which will be described in detail later, is information indicating the amount of toner to be discarded.

[0050] When the toner disposal operation control unit 42 determines that toner disposal should be performed, the control unit 40 sends a toner disposal operation instruction and the printing information contained in the print job received from the higher-level device to the drive control unit 48, the fixing control unit 49, the exposure control unit 50, the voltage control unit 51, and the separation mechanism control unit 52, and issues printing operation instructions to these units.

[0051] On the other hand, if the toner disposal operation control unit 42 determines not to perform toner disposal, the control unit 40 sends the printing information contained in the print job received from the higher-level device to the drive control unit 48, the fixing control unit 49, the exposure control unit 50, the voltage control unit 51, and the separation mechanism control unit 52, and issues instructions for the printing operation to these units.

[0052] The drive control unit 48 rotates the drum motor 53 and belt motor 54 in accordance with instructions from the control unit 40, thereby rotating the photosensitive drum 20 and drive roller 28 in the directions of the arrows in FIG. 1. The voltage control unit 51 controls the voltages applied to the charging roller 21, developing roller 30, supply roller 31, regulating blade 32, static eliminator 25, and transfer roller 26 in accordance with instructions from the control unit 40. The exposure control unit 50 causes the LED head 22 to emit light in accordance with instructions from the control unit 40. The fixing control unit 49 controls the temperature of the fixing unit 9 in accordance with instructions from the control unit 40.

[0053] The spacing mechanism control unit 52 operates the spacing mechanism 55 in accordance with instructions from the control unit 40, thereby moving each developing unit 7 to the spacing position or the abutment position. For example, when the control unit 40 determines from the printing conditions included in the print job received from the host device that the current printing is monochrome printing on recording medium P, which is plain paper, it instructs the spacing mechanism control unit 52 to move the developing units 7Y, 7M, and 7C to the spacing position. In response to this, the spacing mechanism control unit 52 moves the developing units 7Y, 7M, and 7C to the spacing position.

[0054] Furthermore, when the control unit 40 determines from the printing conditions included in the print job that the current printing is monochrome printing on a recording medium P that requires stable transport, such as an envelope or cardboard, it instructs the separation mechanism control unit 52 to move all of the development units 7K, 7Y, 7M, and 7C to their contact positions. In response to this, the separation mechanism control unit 52 moves the development units 7K, 7Y, 7M, and 7C to their contact positions.

[0055] The drum count measurement unit 45 and the dot count measurement unit 46 measure the drum count and the dot count during the toner disposal operation and the printing operation. The drum count is a count according to the number of rotations of the photosensitive drum 20. For example, the number of rotations of the photosensitive drum 20 during the printing operation to print three A4 sheets of paper is measured as three counts.

[0056] The dot count is a count corresponding to the number of light-emitting dots of the LED head 22. Specifically, the dot count is a value obtained by dividing the number of light-emitting dots by 8192, and for example, an image density (print rate) of 5% on one sheet of A4 paper is 792 counts. In this way, in this embodiment, the actual number of light-emitting dots is divided by 8192 (2 to the 13th power), thereby reducing the dot count value.

[0057] In addition, image density (printing rate) is the ratio of the image area of ​​an actually printed image to the image area when a solid image is printed on the recording medium P, and is synonymous with the ratio of the number of dots actually printed within the printing area of ​​the recording medium P to the number of dots when a solid image is printed over the entire printing area of ​​the recording medium P.

[0058] The toner waste count calculation unit 44 calculates the toner waste count based on the drum count and dot count measured by the drum count measurement unit 45 and dot count measurement unit 46, and the toner waste threshold held by the toner waste threshold holding unit 47, and sends the calculated toner waste count holding unit 43 to be held therein. The method of calculating the toner waste count will be described in detail later. The control system of the image forming apparatus 1 is configured as described above.

[0059] As a computer, the image forming apparatus 1 is equipped with, for example, a CPU, memory, a storage unit, and various interfaces, and by the CPU executing a program read from the storage unit, the image forming apparatus 1 functions as a control unit 40, a receiving unit 41, a toner disposal operation control unit 42, a toner disposal count holding unit 43, a toner disposal count calculation unit 44, a drum count measurement unit 45, a dot count measurement unit 46, a toner disposal threshold holding unit 47, a drive control unit 48, a fixing control unit 49, an exposure control unit 50, a voltage control unit 51, and a separation mechanism control unit 52.

[0060] [1-3. Printing Operation of Image Forming Device] Next, a description will be given of the printing operation of the image forming apparatus 1. Note that this printing operation is an operation that is executed by the control unit 40 controlling each unit in accordance with a printing instruction from a host device.

[0061] The image forming device 1 applies a charging voltage to the charging roller 21 using the voltage control unit 51 to uniformly charge the surface of the photosensitive drum 20, and then causes the LED head 22 to emit light using the exposure control unit 50 to form an electrostatic latent image on the surface of the photosensitive drum 20.

[0062] The image forming apparatus 1 applies a development voltage to the developing roller 30, on whose surface a thin toner layer has been formed, by the voltage control unit 51, to develop the electrostatic latent image on the photosensitive drum 20. Here, the supply voltage and regulating voltage are applied to the supply roller 31 and the regulating blade 32 by the voltage control unit 51 in order to form a uniform thin toner layer on the developing roller 30 and to set the charge amount of the toner in the thin toner layer to a predetermined value.

[0063] Next, the image forming apparatus 1 applies a transfer voltage to the transfer roller 26 using the voltage control unit 51 to transfer the toner image on the photosensitive drum 20 onto the recording medium P, and then fixes the toner image on the recording medium P to the recording medium P using the fixing unit 9. The recording medium P with the fixed toner image is discharged to the stacker 3 by the discharge roller 10. This completes the printing operation of the image forming apparatus 1. Any toner remaining on the photosensitive drum 20 that was not transferred is removed by the cleaning device 24. The surface potential of the photosensitive drum 20 is also reset by exposure by the discharge unit 25.

[0064] When the image forming apparatus 1 is operated in a normal temperature and humidity environment using negatively charged toner, the applied voltage settings are, for example, −1050 V for the charging voltage, −200 V for the developing voltage, −300 V for the supply voltage, and −300 V for the regulating blade voltage. The surface of the photosensitive drum 20 is charged when a charging voltage equal to or greater than a predetermined value is applied to the charging roller 21, and the surface potential changes in proportion to the applied charging voltage. In this embodiment, when a charging voltage of −1050 V is applied, the surface potential of the photosensitive drum 20 becomes −500 V. The latent image potential of the electrostatic latent image formed by the light emitted from the LED head 22 becomes −50 V, and the toner from the developing roller 30 is reversely developed onto the electrostatic latent image. When positively charged toner is used, the sign of the voltage is reversed.

[0065] [1-4. Toner Disposal Operation of Image Forming Device] Next, the toner disposal operation of the image forming apparatus 1 will be described. The image forming apparatus 1 of this embodiment is basically configured to discard toner with an excessively low toner consumption amount and forcibly consume it. On the other hand, as described above, when monochrome printing is performed on a recording medium P that requires stable transport, such as an envelope or cardboard, the image forming apparatus 1 brings not only the black developing unit 7K but also the yellow, magenta, and cyan developing units 7Y, 7M, and 7C into contact with the transfer unit 8 to supplement the transport force of the recording medium P, and monochrome printing is performed while the recording medium P is transported sandwiched between up to four photosensitive drums 20 and the transfer belt 27.

[0066] In this way, when monochrome printing is performed on a recording medium P such as an envelope or cardboard by bringing the developing units 7Y, 7M, and 7C into contact with the transfer unit 8, the developing units 7Y, 7M, and 7C in the image forming apparatus 1 operate with almost no toner consumption, so the yellow, cyan, and magenta toner behaves in the same way as when color printing is performed with excessively little toner consumption. In this case, if yellow, cyan, and magenta toner are discarded, the yellow, cyan, and magenta toners may be forcibly consumed and need to be replaced, even though only monochrome printing is performed.

[0067] Therefore, in the image forming device 1 of this embodiment, in order to prevent yellow, magenta, and cyan toner (i.e., toner of a color not intended by the user) from being consumed even when only monochrome printing is being performed, the developing units 7Y, 7M, and 7C are also abutted against the transfer unit 8, and when monochrome printing is performed on a recording medium P such as an envelope or cardboard, yellow, magenta, and cyan toner are not discarded.

[0068] In this case, the image forming apparatus 1 postpones the disposal of yellow, magenta, and cyan toner until the next color printing. For this reason, in the image forming apparatus 1, when monochrome printing is performed on a recording medium P such as an envelope or cardboard with the developing units 7Y, 7M, and 7C also abutted against the transfer unit 8, the image forming apparatus 1 does not discard yellow, magenta, and cyan toner, but calculates and stores the toner disposal count required for toner disposal during the next color printing.

[0069] In the following explanation, monochrome printing performed on a recording medium P such as copy paper by separating the development units 7Y, 7M, and 7C from the transfer unit 8 will be referred to as normal media monochrome printing, and monochrome printing performed on a recording medium P such as an envelope or cardboard by abutting the development units 7Y, 7M, and 7C against the transfer unit 8 will be referred to as special media monochrome printing.

[0070] Taking the above points into consideration, the toner disposal operation will be described in detail below. As described above, in the image forming apparatus 1, the toner disposal operation is performed as part of the preparatory operation carried out before the printing operation. The timing for performing the toner disposal operation is not limited to the preparatory operation, but may also be when the power is turned on, when the cover of the apparatus housing 2 is opened or closed, during various correction operations, after the printing operation is completed, or at multiple timings.

[0071] This toner disposal operation is performed by a toner disposal operation control unit 42 included in the control unit 40, which controls each unit. The toner disposal operation control unit 42 performs the following operations: selectively exposing the surface of the photosensitive drum 20, which has been uniformly charged by the charging roller 21, with the LED head 22 to form an electrostatic latent image of a disposal pattern on the surface of the photosensitive drum 20; and developing the electrostatic latent image with toner using the developing roller 30 to form a toner image of the disposal pattern on the surface of the photosensitive drum 20. During this toner disposal operation, the toner disposal operation control unit 42 controls the voltage applied to the transfer roller 26 using the voltage control unit 51 so that the toner image formed on the surface of the photosensitive drum 20 is not transferred to the transfer belt 27. Through this toner disposal operation, the toner image of the disposal pattern formed on the photosensitive drum 20 is removed by the cleaning device 24 as waste toner and stored in the cleaning device 24.

[0072] The toner disposal operation control unit 42 executes this toner disposal operation for each of black, yellow, magenta, and cyan toners.

[0073] The amount of toner discarded by the toner discard operation is, for example, one toner discard count, which in this embodiment is equivalent to 5% of the image density (print rate) on one A4 sheet of paper. In other words, the toner discard count is information indicating the amount of waste toner, which is the amount of toner to be discarded, and calculating the toner discard count is synonymous with calculating the amount of waste toner. The toner discard operation is as described above.

[0074] [1-5. Toner waste count calculation method] Next, we will explain how to calculate the toner waste count. If the drum count per printing operation (i.e., per print job) is Drx, the dot count per printing operation is Dtx, the toner waste count conversion coefficient is Y, and the toner waste threshold is A, the toner waste count Kx is calculated using the following formula (1).

[0075] Kx = Kx + (A × Drx - Dtx) / Y (1)

[0076] This toner waste count Kx is calculated for each toner color by the toner waste count calculation unit 44. Specifically, the x in Kx indicates the toner color, and the black toner waste count is calculated as Kbk, the yellow toner waste count as Kye, the magenta toner waste count as Kma, and the cyan toner waste count as Kcy.

[0077] In this embodiment, the toner waste conversion coefficient Y is set to 792, and the toner waste threshold A is set to the dot count for a pixel density of 1.5% on one sheet of A4 paper. Therefore, in equation (1), if the dot count Dtx per printing operation (i.e., the amount of toner consumed per printing operation) is less than A×Drx (i.e., the threshold for the amount of toner consumed per printing operation), the (A×Drx-Dtx) part becomes a positive value, and the amount of toner consumption is deemed excessively low, so the value of the toner waste count Kx (amount of wasted toner) increases.

[0078] On the other hand, if the dot count Dtx per printing operation is greater than A x Drx, then (A x Drx - Dtx) becomes a negative value, and the amount of toner consumed is deemed to be above a certain amount, so the value of the waste toner count Kx (amount of waste toner) decreases. In other words, even if the waste toner count Kx has accumulated, if the amount of toner used in printing is large, the waste toner count Kx will decrease, and the amount of waste toner will become smaller.

[0079] The toner waste count calculation unit 44 rounds down the numerical value of the toner waste count Kx for each color calculated by equation (1) to an integer, for example, and stores the result in the toner waste count storage unit 43. If the toner waste count calculation unit 44 calculates the toner waste count Kx for each color calculated by equation (1) as a negative number, it replaces it with, for example, 0 and stores the result.

[0080] [1-6. Printing process procedure] Next, a specific processing procedure (referred to as a printing processing procedure) when the image forming apparatus 1 executes a printing operation will be described with reference to the flowchart shown in Fig. 3. Note that the printing processing procedure is a processing procedure that is mainly executed by the control unit 40.

[0081] In step SP101, when the control unit 40 receives a print instruction from the host device via the receiving unit 41 and starts printing, the control unit 40 proceeds to step SP102.

[0082] In step SP102, the control unit 40 determines whether the current printing is monochrome printing (normal medium monochrome printing or special medium monochrome printing) based on the printing conditions included in the print job received along with the print instruction. If it is determined to be monochrome printing, the control unit 40 obtains a positive result in step SP102 and proceeds to step SP103, but if it is determined not to be monochrome printing (i.e., color printing), the control unit 40 obtains a negative result in step SP102 and proceeds to step SP109.

[0083] In step SP103, control unit 40 determines whether the accumulated black toner waste count Kbk is equal to or greater than 1. If it is determined that the accumulated black toner waste count Kbk is equal to or greater than 1, control unit 40 obtains a positive result in step SP103 and proceeds to step SP104, whereas if it is determined that the accumulated black toner waste count Kbk is not equal to or greater than 1, control unit 40 obtains a negative result in step SP103 and proceeds to step SP106.

[0084] In step SP104, the control unit 40 executes the black toner disposal operation by the toner disposal operation control unit 42, and then proceeds to step SP105. In this embodiment, even if two or more black toner disposal counts Kbk have accumulated, the toner disposal operation is executed for one count of the toner disposal count Kbk.

[0085] In step SP105, control unit 40 causes toner waste count calculation unit 44 to subtract black toner waste count Kbk, and then proceeds to step SP106. Specifically, since toner waste count calculation unit 44 performed the black toner waste operation one count in step SP104, it subtracts 1 from toner waste count Kbk (-1).

[0086] In step SP106, the control unit 40 executes a printing operation (monochrome printing) based on the print job received together with the print instruction, and then proceeds to step SP107.

[0087] On the other hand, in step SP109, to which control unit 40 proceeds because the current printing is color printing, control unit 40 determines whether the accumulated toner waste count Kx for each of black, yellow, cyan, and magenta is 1 or greater. If it determines that the accumulated toner waste count Kx for at least one of black, yellow, cyan, and magenta is 1 or greater, control unit 40 obtains a positive result in step SP109 and proceeds to step SP110. If it determines that the accumulated toner waste count Kx for all of black, yellow, cyan, and magenta is not 1 or greater, control unit 40 obtains a negative result in step SP109 and proceeds to step SP112.

[0088] In step SP110, the control unit 40 executes the toner disposal operation only for the toner of the color for which the toner disposal count Kx is 1 or more by the toner disposal operation control unit 42, and then proceeds to step SP111. Note that in this case, the toner disposal operation is executed for one count of the toner disposal count Kx.

[0089] Although it is possible to perform the toner disposal operation for two or more counts, this will increase the printing time and shorten the life of the moving parts, etc. For this reason, in this embodiment, the toner disposal operation is performed for one count.

[0090] In step SP111, the control unit 40 causes the toner disposal count calculation unit 44 to subtract 1 (-1) from the toner disposal count Kx of the color for which the toner disposal operation was performed in step SP110, and then proceeds to step SP112.

[0091] In step SP112, the control section 40 executes a printing operation (color printing) based on the print job received together with the print instruction, and then proceeds to step SP107.

[0092] In step SP107, the control unit 40 acquires the drum count Drx and dot count Dtx for each executed printing operation. If the current printing operation is monochrome printing on a normal medium, the control unit 40 acquires the drum count Drx and dot count Dtx for black of the four color toners. On the other hand, if the current printing operation is monochrome printing on a special medium or color printing, the control unit 40 acquires the drum count Drx and dot count Dtx for each of the colors black, yellow, cyan, and magenta. Note that in the case of monochrome printing on a special medium, yellow, cyan, and magenta are not used, so their dot counts Dtx are set to 0.

[0093] In the next step SP108, the control unit 40 uses the drum count Drx and dot count Dtx acquired in step SP107 to calculate the toner waste count Kx using the toner waste count calculation unit 44, and stores the result in the toner waste count storage unit 43. The printing process procedure is as described above.

[0094] [1-7. Summary and Effects] As described above, in the first embodiment, the image forming apparatus 1 includes a development unit 7K, which is an example of a first image forming unit that forms an image using black toner, which is an example of a first color developer; development units 7Y, 7M, and 7C, which are an example of a second image forming unit that forms an image using yellow, magenta, and cyan toner, which are examples of a second color developer; a transfer unit 8, which is an example of a transfer unit that transfers a toner image, which is an example of an image formed by the development units 7K, 7Y, 7M, and 7C, to a recording medium P; and a toner disposal operation control unit 42 and a toner disposal count calculation unit 44, which are examples of a developer disposal operation execution unit that executes a toner disposal operation, which is an example of a developer disposal operation that discards black, yellow, magenta, and cyan toner.

[0095] When performing special medium monochrome printing using black toner but not yellow, magenta, or cyan toner on a recording medium P such as an envelope or thick paper, which is an example of a specified recording medium (i.e., an envelope-shaped recording medium P or a recording medium P having a specified thickness or more), the toner disposal operation control unit 42 performs a toner disposal operation only for black toner, and does not perform a toner disposal operation for the yellow, magenta, or cyan toner that is not used for the special medium monochrome printing.

[0096] From another perspective, in the first embodiment, the image forming apparatus 1 is provided with a developing unit 7K, which is an example of a first image forming unit that forms an image using black toner, which is an example of a developer of one color; developing units 7Y, 7M, and 7C, which are an example of a second image forming unit that forms an image using yellow, magenta, and cyan toner, which are examples of a developer of a second color; a transfer unit 8, which is an example of a transfer unit that transfers a toner image, which is an example of an image formed by the developing units 7K, 7Y, 7M, and 7C, to a recording medium P; a toner disposal operation control unit 42 and a toner disposal count calculation unit 44, which are examples of a developer disposal operation execution unit that executes a toner disposal operation, which is an example of a developer disposal operation that discards black, yellow, magenta, and cyan toner; and a separation mechanism 55 that moves each of the developing units 7K, 7Y, 7M, and 7C to a contact position in contact with the transfer unit 8 or a separation position separated from the transfer unit 8.

[0097] When monochrome printing is performed on the recording medium P using black toner but not yellow, magenta, or cyan toners while the developing units 7K, 7Y, 7M, and 7C are in their respective contact positions, the toner disposal operation control unit 42 executes the toner disposal operation only for black toner, but does not execute the toner disposal operation for the yellow, magenta, or cyan toners not used in the monochrome printing. In the present embodiment, the toner disposal operation is executed only for black toner when monochrome printing is performed to form a toner image on the recording medium P using only black toner. However, this is not a limitation. The toner disposal operation may be executed only for black toner when printing is performed that can be considered to be essentially composed of only black toner images. For example, when printing is performed such that the toner image of colors other than black is less than 1% in the printable area of ​​the recording medium P to form a mark or the like, the toner disposal operation may be executed only for black toner. This configuration also results in a toner image formed using only black toner. In the present embodiment, the toner disposal operation is executed only for black toner. However, this is not a limitation. The toner disposal operation may be executed in a manner that can be considered to be essentially discarding only black toner. For example, when performing monochrome printing to form a toner image on recording medium P using only black toner, a toner disposal operation may be performed to discard toner other than black (e.g., yellow, magenta, cyan, etc.) so that the amount of discarded toner is less than 10% of the amount of discarded black toner. In this mode, the toner disposal operation is performed only for black toner.

[0098] As a result, in the image forming apparatus 1 of the first embodiment, when monochrome printing is performed using only black toner, it is possible to avoid a situation in which the user unintentionally discards and consumes yellow, magenta, and cyan toner. Thus, the image forming apparatus 1 of the first embodiment can suppress the consumption of toner unintentionally by the user.

[0099] Furthermore, in the image forming device 1, when printing monochrome on special media, the toner waste count calculation unit 44 calculates the toner waste count, which indicates the amount of waste toner, which is an example of the amount of waste developer, for yellow, magenta, and cyan toner, and then, at the next color printing (specifically, during the preparation operation before the color printing operation), the toner waste operation is performed based on the calculated toner waste count. This makes it possible to suppress degradation of image quality due to degraded toner for yellow, magenta, and cyan as well.

[0100] Furthermore, in the image forming apparatus 1, the toner disposal operation performed before the printing operation is counted as one toner disposal count, and if the amount of toner used in the printing operation is large, the accumulated toner is counted as one toner disposal count. By reducing the remaining toner discard count, there is also the advantage that toner is not discarded unnecessarily.

[0101] 2. Second Embodiment Next, a second embodiment will be described. This second embodiment differs from the first embodiment in that the amounts of yellow, magenta, and cyan waste toner are increased during the first color printing after special medium monochrome printing is performed compared to normal color printing. Therefore, this point will be mainly described below.

[0102] Specifically, the image forming device 1 of the second embodiment is configured to perform a toner disposal operation for up to four toner disposal counts for yellow, magenta, and cyan during the first color printing after performing monochrome printing on special media.

[0103] Here, the amount of toner discarded in the toner discarding operation for four toner discard counts (that is, the amount of discarded toner) is equivalent to one rotation of the developing roller 30, which is four times the normal amount.

[0104] [2-1. Printing process procedure] Next, a printing process procedure executed by the image forming apparatus 1 of the second embodiment will be described with reference to the flowchart shown in Fig. 4. Note that the processes of steps SP201 to SP208 are similar to the processes of steps SP101 to SP108 (see Fig. 3) described in the first embodiment, and therefore description thereof will be omitted.

[0105] If a negative result is obtained in step SP202 because the current printing is color printing, the control unit 40 proceeds to step SP209, where it determines whether the printing immediately before the current color printing was special medium monochrome printing. If it is determined that the immediately before printing was not special medium monochrome printing, the control unit 40 obtains a negative result in step SP209 and proceeds to step SP210, but if it is determined that the immediately before printing was special medium monochrome printing, the control unit 40 obtains a positive result in step SP209 and proceeds to step SP214.

[0106] The processing of steps SP210 to SP213 is similar to the processing of steps SP109 to SP112 (see FIG. 3) described in the first embodiment, and therefore a description thereof will be omitted.

[0107] In step SP214, which is the procedure to follow if the immediately preceding printing was special medium monochrome printing, the control unit 40 determines whether the accumulated toner waste count Kx for each of yellow, magenta, and cyan is 2 or greater. If it is determined that the accumulated toner waste count Kx for all of yellow, magenta, and cyan is not 2 or greater, the control unit 40 obtains a negative result in step SP214 and proceeds to step SP210, where it determines whether the accumulated toner waste count Kx for each of black, yellow, magenta, and cyan is 1 or greater.

[0108] On the other hand, if it is determined that the accumulated toner waste count Kx for at least one of yellow, magenta, and cyan is 2 or more, the control unit 40 obtains a positive result in step SP214 and proceeds to step SP215.

[0109] In step SP215, the control unit 40 executes the toner disposal operation only for toner of a color for which the toner disposal count Kx accumulated by the toner disposal operation control unit 42 is equal to or greater than 1. At this time, the toner disposal operation control unit 42 executes the toner disposal operation for a maximum of 1 count of the toner disposal count Kbk for black toner, and executes the toner disposal operation for a maximum of 4 counts of the toner disposal count for each of yellow, magenta, and cyan toner.

[0110] Specifically, for example, if the yellow toner waste count Kx (Kye) is 5, the toner waste operation control unit 42 executes the toner waste operation for yellow for four counts of the toner waste count Kx (Kye). Furthermore, for example, if the magenta toner waste count Kx (Kma) is 2, the toner waste operation control unit 42 executes the toner waste operation for magenta for two counts of the toner waste count Kx (Kma). Furthermore, for example, if the cyan toner waste count Kx (Kcy) is 1, the toner waste operation control unit 42 executes the toner waste operation for cyan for one count of the toner waste count Kx (Kcy).

[0111] In this embodiment, a toner disposal operation for two or more counts is realized by performing the toner disposal operation using an extended disposal pattern, which is an extension of the basic disposal pattern used in a toner disposal operation for one count in the sub-scanning direction (the direction of rotation of the photosensitive drum 20). For example, a toner disposal operation for four counts uses an extended disposal pattern, which is four basic disposal patterns connected in the sub-scanning direction. Therefore, the amount of toner disposed of in this case is four times that of a toner disposal operation for one count.

[0112] In the next step SP216, the control unit 40 causes the toner waste count calculation unit 44 to subtract the toner waste count Kx of the color for which the toner waste operation was performed in step SP215 by the amount of the toner waste count Kx that was performed, and then proceeds to step SP213. The printing process procedure is as described above.

[0113] [2-2. Summary and Effects] As explained above, in the second embodiment, the toner disposal operation control unit 42 of the image forming device 1 is configured to discard a larger amount of toner in the yellow, magenta, and cyan toner disposal operation that is executed when color printing is performed for the first time after special medium monochrome printing has been performed than in the toner disposal operation that is executed in other cases (i.e., normal toner disposal operation). That is, in the image forming device 1, when color printing is performed for the first time after special medium monochrome printing has been performed, the toner disposal operation is executed for a maximum of four counts (a maximum of four times the normal amount of discarded toner) based on the toner disposal counts that indicate the amounts of yellow, magenta, and cyan discarded toner calculated up to that point.

[0114] As a result, in the image forming apparatus 1 of the second embodiment, even if, for example, monochrome printing on special media continues and the amount of deteriorated yellow, magenta, and cyan toner increases in the developing units 7Y, 7M, and 7C, the deteriorated yellow, magenta, and cyan toner can be sufficiently discarded by performing a toner discard operation for up to four counts. Thus, with the image forming apparatus 1 of the second embodiment, it is possible to further suppress degradation of image quality due to deteriorated yellow, magenta, and cyan toner.

[0115] Furthermore, in the image forming apparatus 1 of the second embodiment, the amount of toner discarded in four counts of toner discarding operation (i.e., the amount of discarded toner) is set to an amount equivalent to one rotation of the developing roller 30. In this way, if the amount of discarded toner is set to one rotation of the developing roller 30, it is possible to sufficiently discard the deteriorated toner generated around the developing roller 30.

[0116] In other words, in the image forming device 1 of the second embodiment, the amount of waste toner is set to a maximum amount equivalent to one rotation of the developing roller 30, thereby reducing toner consumption while suppressing degradation of image quality due to degraded toner.

[0117] 3. Other Embodiments [3-1. Another embodiment 1] In the first and second embodiments described above, when monochrome printing (special medium monochrome printing) is performed on a recording medium P such as an envelope or thick paper by abutting the developing units 7K, 7Y, 7M, and 7C against the transfer unit 8, the present invention is applied so that the toner disposal operation is not performed for the yellow, magenta, and cyan toners that are not used for special medium monochrome printing. In other words, the toner disposal operation is not performed for the toners that are used in the developing units 7 in the abutment position but are not used for printing.

[0118] Therefore, the present invention can be applied not only to special media monochrome printing, but also to various printing operations in which the development unit 7, which uses toner of a color not used in printing, is also brought into contact with the transfer unit 8, so that the toner disposal operation is not performed for toner of a color not used in printing.

[0119] For example, when printing on a recording medium P such as an envelope or cardboard using only two colors, yellow and magenta, the toner disposal operation may not be performed for black and cyan toner. Also, in an image forming apparatus equipped with a developing unit (not shown) that uses special color toner such as white or clear, when printing on a recording medium P such as an envelope or cardboard using the special color, the toner disposal operation may not be performed for toner other than the special color.

[0120] On the other hand, in the image forming apparatus 1, depending on the temperature and humidity of the surrounding environment, the recording medium P may become slippery or may not adhere well to the transfer belt 27, resulting in unstable transport. For this reason, in the image forming apparatus 1, when monochrome printing is performed in a surrounding environment where transport is unstable, it is desirable to stabilize transport by bringing the developing units 7K, 7Y, 7M, and 7C into contact with the transfer unit 8, even if the recording medium P is plain paper rather than an envelope or cardboard. Even when monochrome printing is performed in such a surrounding environment where transport is unstable, the present invention may be applied so that the toner disposal operation is not performed for toner of colors not used in printing.

[0121] In this case, a temperature sensor and a humidity sensor may be provided in the image forming apparatus 1, and the control unit 40 may determine whether the surrounding environment is such that the transport of the recording medium P becomes unstable based on the detection results of these temperature and humidity sensors.

[0122] [3-2. Other embodiment 2] In the first embodiment described above, the toner disposal operation performed during the preparatory operation before a printing operation is equivalent to one toner disposal count. However, the toner disposal operation may be performed up to multiple toner disposal counts. In other words, the maximum amount of toner to be disposed of by the toner disposal operation may be changed as appropriate. Also, the maximum amount of toner to be disposed of by the toner disposal operation may be changed depending on the timing of the toner disposal operation. For example, when the toner disposal operation is performed when the power is turned on or after a printing operation is completed, the maximum amount of toner to be disposed of may be increased compared to when the toner disposal operation is performed during preparatory operation, such as up to three toner disposal counts.

[0123] Furthermore, in the second embodiment described above, the yellow, magenta, and cyan toner disposal operations performed when printing in color after monochrome printing on special media are limited to a maximum of four toner disposal counts. However, the toner disposal operations may be limited to a maximum of five toner disposal counts or three toner disposal counts. In other words, the maximum amount of waste toner for the yellow, magenta, and cyan toner disposal operations performed when printing in color after monochrome printing on special media may also be changed as appropriate.

[0124] Furthermore, in the first and second embodiments described above, the amount of waste toner for one toner waste count is set to 5% of the image density (print rate) on one A4 sheet of paper, but this is just an example, and the amount of waste toner for one toner waste count may be changed as appropriate.

[0125] [3-3. Other embodiment 3] Furthermore, in the second embodiment described above, the toner disposal operation for one count is realized by using an extended disposal pattern in which multiple basic disposal patterns used in the toner disposal operation for one count are connected in the sub-scanning direction (the direction of rotation of the photosensitive drum 20).

[0126] Without being limited to this, for example, by using a waste pattern different from that used when performing a toner waste operation for one count, or by changing the development voltage from that used when performing a toner waste operation for one count, the amount of toner used per unit area in the waste pattern can be increased, thereby realizing a toner waste operation for multiple counts without using an extended waste pattern.

[0127] [3-4. Other embodiment 4] Furthermore, in the above-described embodiment, the present invention is applied to image forming apparatus 1, which is an electrophotographic color printer, but the present invention is not limited to this and can be applied to various image forming apparatuses, such as copying machines, facsimile machines, MFPs (Multi Function Peripherals), etc. Also, for example, the present invention can be applied to an image forming apparatus that does not have a separation mechanism 55.

[0128] [3-5. Other embodiment 5] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments, and the scope of application of the present invention also extends to embodiments in which the above-described embodiments and part or all of the other embodiments are combined as desired. [Industrial Applicability]

[0129] The present invention can be widely used in printers that have a function for discarding degraded toner, for example. [Explanation of symbols]

[0130] 1...image forming apparatus, 2...apparatus housing, 7...developing unit, 8...transfer unit, 20...photosensitive drum, 21...charging roller, 22...LED head, 23...developing device, 24...cleaning device, 25...discharge unit, 26...transfer roller, 27...transfer belt, 30...developing roller, 31...supply roller, 32...regulating blade, 33...cleaning blade, 40...control unit, 41...receiving unit, 42...toner waste operation control unit, 43...toner waste count holding unit, 44...toner waste count calculation unit, 45...drum count measurement unit, 46...dot count measurement unit, 47...toner waste count holding unit, 48...drive control unit, 49...fixing control unit, 50...exposure control unit, 51...voltage control unit, 52...separation mechanism control unit, 55...separation mechanism, Kx...toner waste count, P...recording medium

Claims

1. a first image forming unit that forms an image using a developer of a first color; a second image forming unit that forms an image using a developer of a second color; a transfer unit that transfers and prints the image formed by the first image forming unit and the image formed by the second image forming unit onto a recording medium; a developer disposal operation execution unit that executes a developer disposal operation for discarding the developer; Equipped with The developer disposal operation execution unit When printing is performed on a predetermined recording medium using the first color developer without using the second color developer, the developer disposal operation is performed only for the first color developer, and the developer disposal operation is not performed for the second color developer. An image forming apparatus characterized by:

2. The predetermined recording medium is an envelope-shaped recording medium.

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

3. The predetermined recording medium is a recording medium having a predetermined thickness or more.

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

4. The developer disposal operation execution unit When printing is performed on a predetermined recording medium using the first color developer without using the second color developer, the developer disposal operation is not performed for the second color developer, and a waste developer amount that is the amount of developer to be discarded is calculated.

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

5. The developer disposal operation execution unit Calculating the amount of waste developer for the second color developer based on the amount of developer for the second color used for printing 5. The image forming apparatus according to claim 4.

6. The developer disposal operation execution unit After printing is performed on a predetermined recording medium using the developer of the first color, when printing is performed using the developer of the second color, the developer of the second color is discarded by the developer discarding operation based on the amount of discarded developer calculated for the developer of the second color.

6. The image forming apparatus according to claim 4, wherein the image forming apparatus is a recording medium.

7. The developer disposal operation execution unit In the developer disposal operation for the second color developer, which is executed when printing is performed for the first time using the second color developer after printing has been performed using the first color developer on a predetermined recording medium, the amount of developer to be disposed of is greater than the amount of developer to be disposed of in the developer disposal operation for the second color developer, which is executed in other cases.

7. The image forming apparatus according to claim 6, wherein the image forming apparatus is a recording medium.

8. a separation mechanism configured to move each of the first image forming unit and the second image forming unit to a contact position where the first image forming unit and the second image forming unit are in contact with the transfer unit or to a separation position where the first image forming unit and the second image forming unit are separated from the transfer unit; The developer disposal operation execution unit When printing is performed on a predetermined recording medium using the first color developer but not the second color developer with the first image forming unit and the second image forming unit in the abutting position, the developer disposal operation is performed only for the first color developer and not for the second color developer.

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

9. a first image forming unit that forms an image using a developer of a first color; a second image forming unit that forms an image using a developer of a second color; a transfer unit that transfers and prints the image formed by the first image forming unit and the image formed by the second image forming unit onto a recording medium; a developer disposal operation execution unit that executes a developer disposal operation to discard the developer; a separation mechanism that moves each of the first image forming unit and the second image forming unit to a contact position where the first image forming unit and the second image forming unit are in contact with the transfer unit or to a separation position where the first image forming unit and the second image forming unit are separated from the transfer unit; Equipped with The developer disposal operation execution unit When printing is performed using the developer of the first color but not the developer of the second color with the first image forming unit and the second image forming unit in the abutting position, the developer disposal operation is performed only for the developer of the first color, and the developer disposal operation is not performed for the developer of the second color. An image forming apparatus characterized by:

Images