Image forming apparatus

Abstract

To prevent image defects such as stripes and fogging caused by foreign matter separated from a sheet material while suppressing an increase in cost due to an increase in the number of components and an increase in size of an image forming apparatus.SOLUTION: An amount of the toner of the first color transferred onto the conveyance belt when the toner of the first color is transferred from the first developing device onto the conveyance belt without being transferred onto the sheet material is larger than an amount of the toner of the second color transferred onto the conveyance belt when the toner of the second color is transferred from the second developing device onto the conveyance belt without being transferred onto the sheet material.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic system. [Background technology]

[0002] An electrophotographic image forming apparatus has the following configuration.

[0003] The image forming apparatus forms color images using a plurality of photosensitive drum units and a plurality of developing devices. The plurality of developing devices each have a developing container containing toner, which is a developer of a different color, and a developing roller, which is a developer carrier.

[0004] The electrostatic latent image formed on the photosensitive drum is developed on the photosensitive drum in a developing section where a developing roller is brought into contact with the photosensitive drum. The sheet material is electrostatically attracted to a conveyor belt and conveyed. The toner image developed on the photosensitive drum is transferred to the conveyed sheet material by the potential difference between the photosensitive drum and a transfer roller facing the photosensitive drum.

[0005] When the sheet material comes into contact with the photosensitive drum, foreign matter (mainly paper fibers, fillers, dust, etc.) that is released from the sheet material may be transferred to the photosensitive drum and adversely affect the image formation process.

[0006] To prevent this, a foreign matter recovery device equipped with a foreign matter separation roller that attracts and recovers foreign matter from the cleaning roller is disclosed in Patent Document 1. In Patent Document 1, the foreign matter recovery device is installed on the photosensitive drum on the most upstream side in the direction of movement of the sheet material to recover the foreign matter. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2010-165000 Summary of the Invention [Problem to be solved by the invention]

[0008] However, foreign particles that slip through the nip between the cleaning roller and photosensitive drum may reach the development section and be collected in the developer container. Small amounts of foreign particles may have little impact if collected in the developer container. However, in recent years, as part of efforts to improve usability, there has been a trend toward longer lifespans for consumables, such as photosensitive drum units and developing devices, in order to reduce the frequency of consumable replacement by users. As a result, if foreign particles accumulate in the developer container, they may cause image defects such as unintended streaks. Furthermore, as the ratio of the amount of foreign particles to the amount of toner in the developer container increases, the toner's charging performance may decrease, potentially causing image defects known as fogging.

[0009] The amount of foreign matter that is released from the sheet material at the transfer portion tends to be greater the more upstream the developing device is in the direction of sheet material movement, and the more upstream the developing device is, the greater the accumulation of foreign matter tends to be. Therefore, the frequency of image defects tends to be higher the more upstream the station is.

[0010] For this reason, Patent Document 1 discloses a configuration in which a foreign matter collection device is installed only in the most upstream photosensitive drum unit, but since no foreign matter collection device is provided in stations other than the most upstream, it is ineffective in stations other than the most upstream. On the other hand, installing foreign matter collection devices in stations other than the most upstream increases the number of parts, leading to increased costs and potentially increasing the size of the image forming apparatus. Furthermore, it is ineffective against foreign matter that has slipped through the nip with the photosensitive drum without being collected by the cleaning roller.

[0011] The present invention aims to solve the above-mentioned problems, suppressing increases in cost due to an increase in the number of parts and an increase in the size of the image forming apparatus, while preventing image defects such as streaks and fogging caused by foreign matter loosened from the sheet material. [Means for solving the problem]

[0012] Therefore, the image forming apparatus according to the present invention includes a first developing device including a first photosensitive drum on which an electrostatic latent image is formed to form an image of a first color, a first toner accommodating section that accommodates toner corresponding to the first color, and a first developing roller that supplies toner from the first toner accommodating section to the first photosensitive drum; a second developing device including a second photosensitive drum on which an electrostatic latent image is formed to form an image of a second color, a second toner accommodating section that accommodates toner corresponding to the second color, and a second developing roller that supplies toner from the second toner accommodating section to the second photosensitive drum; an endless conveying belt that is configured to be able to contact the first photosensitive drum and the second photosensitive drum, and that rotates and moves while attracting and conveying a sheet material; and a conveying roller that conveys the electrostatic latent image of the first color on the first photosensitive drum. The image forming apparatus is provided with a first transfer roller configured to transfer toner onto the sheet material or the conveying belt, and a second transfer roller configured to transfer second color toner on the second photosensitive drum onto the sheet material or the conveying belt, wherein the first photosensitive drum is located upstream of the second photosensitive drum in the conveying direction of the sheet material, and the amount of first color toner transferred onto the conveying belt when the first color toner is transferred onto the conveying belt without the first color toner being transferred from the first developing device to the sheet material is greater than the amount of second color toner transferred onto the conveying belt when the second color toner is transferred onto the conveying belt without the second color toner being transferred from the second developing device to the sheet material. [Effects of the Invention]

[0013] As described above, according to the present invention, it is possible to prevent image defects such as streaks and fogging caused by foreign matter loosened from the sheet material while suppressing increases in cost due to an increase in the number of parts and an increase in the size of the image forming apparatus. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an overall schematic view showing an image forming apparatus according to first to third embodiments. [Figure 2]FIG. 2 is a schematic cross-sectional view of a photosensitive drum unit and a developing device according to the first to third embodiments. [Figure 3] FIG. 2 is a schematic view illustrating a photosensitive drum unit and a part of a developing cartridge and a conveyor belt unit. [Figure 4] FIG. 2 is a schematic diagram illustrating developer discharge, showing a photosensitive drum unit, a developer cartridge, and a part of a conveyor belt unit. [Figure 5] 10A and 10B are schematic diagrams illustrating an example of a toner pattern ejected onto a conveyor belt. [Figure 6] FIG. 10 is a schematic diagram illustrating developer discharge in a third embodiment in which discharged toner is re-collected in a developer container. [Figure 7] FIG. 10 is a schematic view showing an image forming apparatus equipped with a drum unit equipped with a recovery member according to a fourth embodiment. [Figure 8] FIG. 10 is a schematic diagram of a system according to a fifth embodiment. [Figure 9] 13 is a flowchart showing details of processing specific to the fifth embodiment. [Figure 10] FIG. 2 is a schematic diagram showing a two-piece cartridge including a process cartridge and a toner cartridge. [Figure 11] 13 is a flowchart showing processing specific to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings. However, the functions, materials, shapes, relative positions, etc. of the components described in these embodiments are not intended to limit the scope of the present invention unless otherwise specified. Furthermore, the functions, materials, shapes, etc. of components that have already been described in the following description are the same as those described in the initial description unless otherwise specified.

[0016] First Embodiment An image forming apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

[0017] First, the configuration of the image forming apparatus will be described.

[0018] Fig. 1 is a cross-sectional view of an image forming apparatus 1 according to this embodiment. The image forming apparatus 1 shown in Fig. 1 is a color laser printer that uses an electrophotographic image forming process, and forms a color image on a sheet material (e.g., printing paper) using a developer (e.g., toner) supplied from developing cartridges 8 (8Y, 8M, 8C, 8K) that are developing devices.

[0019] In this embodiment, an example is shown in which a color image is formed using four photosensitive drums 4 (4Y, 4M, 4C, 4K) that are image carriers and four developing cartridges 8 (8Y, 8M, 8C, 8K). The four developing cartridges 8 contain toner of different colors (e.g., yellow, cyan, magenta, and black). The number of developing cartridges 8 and photosensitive drum units 30 may be one to three, or may be five or more, depending on the number of colors used.

[0020] In this embodiment, the configuration and operation of each of the four developing cartridges 8 (8Y, 8M, 8C, 8K) are substantially the same except for the colors of the images they form. Therefore, unless a distinction is particularly required, the suffixes Y, M, C, and K at the end of the reference numerals will be omitted and a general description will be given.

[0021] The image forming device 1 is composed of an image forming device main body 2 (hereinafter referred to as the "device main body 2"), a cartridge tray 3 that is detachable from the device main body 2, a developing cartridge 8 that is detachable from the cartridge tray 3, a photosensitive drum unit 30, and a controller (not shown).

[0022] The apparatus main body 2 includes an exposure device 10, a conveyor belt unit 11, a paper feed unit 18, a fixing device 21, a discharge unit 22, and a front door 40.

[0023] In the image forming apparatus 1, the exposure device 10 is provided above the developer cartridges 8 and cartridge tray 3, and outputs laser light (not shown) corresponding to image information. The laser light scans and exposes the surfaces of the photosensitive drums 4 (4Y, 4M, 4C, 4K). The developer cartridges 8, which serve as developing devices, are provided to develop developer on the scanned and exposed surfaces of the photosensitive drums 4. The development process by which a toner image is formed on the surface of the photosensitive drum 4 will be described later.

[0024] The conveyor belt unit 11 is provided below the developing cartridges 8 and the cartridge tray 3 in the image forming apparatus 1. The conveyor belt unit 11 has an endless conveyor belt 12 that circulates and rotates while facing and contacting all of the photosensitive drums 4.

[0025] The conveyor belt 12 is made of a single-layer film material using a resin film or a multi-layer film material having a rubber layer provided on a resin base layer. The conveyor belt 12 is stretched by a drive roller 13 and a driven roller 14. The conveyor belt 12 contacts a sheet material S such as printing paper on its upper outer peripheral surface and moves in a circular motion to bring the sheet material S into contact with the photosensitive drum 4. In this way, the sheet material S is conveyed toward the photosensitive drum 4.

[0026] Transfer rollers 16 are arranged in parallel to the conveyor belt 12, abutting against the inside of the conveyor belt 12 and facing the photosensitive drums 4. A predetermined bias is applied to the transfer rollers 16 during transfer, and an electric field is generated in the sheet material S via the conveyor belt 12. This electric field causes the toner on the photosensitive drums 4 to be transferred to the sheet material S in contact with the photosensitive drums 4.

[0027] The paper feed unit 18 is provided below the conveyor belt unit 11. The paper feed unit 18 has a paper feed tray 19 that stores a stack of sheet materials S, and a paper feed roller 20.

[0028] The fixing device 21 and the discharge unit 22 are provided above the apparatus main body 2. The fixing device 21 fixes the toner image transferred onto the sheet material S by applying heat and pressure, and the discharge unit 22 discharges the sheet material S that has passed through the fixing device 21 onto a discharge tray 23.

[0029] The cartridge tray 3 has a detachable drum unit 30 provided with photosensitive drums 4 corresponding to the four developer cartridges 8. FIG. 2 shows the drum unit 30 and the developer cartridges 8 in detail.

[0030] As shown in FIG. 2, the drum unit 30 includes a charging device 5, a charge removal light source 31, and a cleaning roller 32.

[0031] The developing cartridge 8 has a developing container 28 (toner storage section) that stores toner T, and a developing roller 6 that is a rotatable developer carrier that carries developer on its surface. The developing cartridge 8 also has a supply roller 26 that supplies toner to the developing roller 6, and a regulating blade 60 that contacts the surface of the developing roller 6 to regulate the layer thickness of the toner carried on the surface of the developing roller 6.

[0032] (Image formation process) Next, the image forming process will be described with reference to FIGS.

[0033] During the image formation process, the photosensitive drums 4 are rotated in the direction of arrow D at a predetermined speed. The conveyor belts 12 of the conveyor belt unit 11 are also rotated in the direction of arrow C at a speed corresponding to the speed of the photosensitive drums 4. First, the surfaces of the photosensitive drums 4 are uniformly charged to a predetermined polarity and a predetermined potential by the charging device 5. Then, the exposure device 10 outputs laser light corresponding to the image signals for each color, and scans and exposes the surfaces of the photosensitive drums 4. As a result, electrostatic latent images corresponding to the image signals for each color are formed on the surfaces of the photosensitive drums 4.

[0034] The toner T in the developing container 28 is circulated in the developing container by an agitating sheet 51 fixed to an agitating shaft 50, and is conveyed to the supply roller 26. The supply roller 26 supplies the toner T to the developing roller 6.

[0035] The developing roller 6 has a configuration in which a roller shaft made of metal or the like is coated with a rubber layer. The rubber layer is made of, for example, elastic rubber or a sponge material. The supply roller 26 has a configuration in which a roller shaft made of metal or the like is coated with a sponge layer.

[0036] The developing roller 6 is driven to rotate at a predetermined speed in the direction of arrow E. The toner T supplied to the developing roller 6 enters between the developing roller 6 and the layer regulating blade 60 and is carried on the developing roller 6 as a thin layer of a constant thickness. At this time, the toner T is charged to a predetermined polarity by friction between the layer regulating blade 60, the supply roller 26, and the developing roller 6. Hereinafter, in this embodiment, the toner will be described as being positively charged.

[0037] The layer control blade 60 is made of a metal plate such as stainless steel with a resin member bonded to it. Depending on the shape and material of the resin member, the pressure applied to the invading toner T and the amount of frictional charge can be controlled. Silicone rubber or urethane rubber is used as the resin member.

[0038] The toner T carried on the developing roller 6 and charged to a predetermined charge amount is supplied to the electrostatic latent image formed on the photosensitive drum 4. As a result, the developer adheres to the electrostatic latent image, developing it (making it visible), and a toner image is formed on the surface of the photosensitive drum 4.

[0039] A positive voltage is applied to the developing roller 6 from a development power supply (not shown). The potential of the electrostatic latent image formed on the surface of the photosensitive drum 4 is positive, and the absolute value of the voltage is greater than that of the applied voltage to the developing roller 6 in the non-printing area where toner T is not developed, and is smaller than that of the applied voltage to the developing roller 6 in the printing area where toner T is developed. By setting it in this way, the positively charged toner T moves from the developing roller 6 to the electrostatic latent image formed on the photosensitive drum 4.

[0040] Furthermore, when the sheet material S is fed one by one at a predetermined control timing, the leading edge of the toner image on the surface of the first photosensitive drum 4Y moves to the transfer section, which is the opposing point to the conveyor belt 12. Then, the timing at which the sheet material S is conveyed to the transfer section is synchronized with the rotation of the photosensitive drum 4Y. The sheet material S is conveyed to the conveyor belt 12 at a predetermined control timing so that the print start position at the transfer section coincides between the sheet material S and the photosensitive drum 4Y.

[0041] The toner images on the photosensitive drums 4 are sequentially transferred onto the sheet material S, which is being conveyed in contact with the conveyor belt 12, by an electric field formed between each photosensitive drum 4 and the transfer roller 16. At this time, a negative voltage is applied to the transfer roller 16 from a transfer power source (not shown). This makes it possible to electrically attract the positive toner to the sheet material S.

[0042] The sheet material S onto which the four-color toner images have been transferred is separated from the transfer belt 12 and conveyed to the fixing device 21. The toner images on the sheet material S are thermally fixed in the fixing device 21. Thereafter, the sheet material S is discharged onto a discharge tray 23 by a discharge unit 22.

[0043] After the toner T is transferred onto the sheet material S, the surface of the photosensitive drum 4 is neutralized by the neutralization light source 31 until the surface potential is close to 0 V. By neutralizing the surface potential of the photosensitive drum 4, the cleaning performance of the cleaning roller 32 is improved against transfer residual toner remaining on the photosensitive drum 4 and foreign matter transferred from the transfer recipient to the photosensitive drum 4 (the detailed function of the cleaning roller 32 will be described later). Furthermore, by stabilizing the surface potential of the photosensitive drum 4, the surface of the photosensitive drum 4 can be uniformly charged by the charging device 5.

[0044] Next, referring to FIG. 3, a method for dealing with residual toner after transfer will be described.

[0045] 3 is a schematic diagram showing the configuration of the developing cartridge 8 and a part of the conveyor belt unit 11, with a focus on the drum unit 30. FIG. 3(a) shows the state during image formation, and FIG. 3(b) shows the state during the temporary collected toner discharging operation in which toner is discharged from the cleaning roller 32.

[0046] 3(a), the potential of the surface of the photosensitive drum 4 that has passed through the transfer portion is reduced to nearly 0 V by a discharging process using a discharging light source 31. During image formation, a negative voltage is applied to the cleaning roller 32, and the positively charged residual toner T moves along the electric field from the photosensitive drum 4 to the cleaning roller 32 and is collected.

[0047] FIG. 3(b) shows a discharge operation in which residual toner accumulated on the cleaning roller 32 is discharged at a predetermined timing. The discharge operation is performed separately from the image forming operation. First, a positive voltage is applied to the cleaning roller 32 with respect to the photosensitive drum 4, whose potential has been lowered to 0 V by the discharging light source 31. This electric field causes the positive residual toner T to be transferred to the photosensitive drum 4. The developing roller 6 can be separated from the photosensitive drum 4, and is separated from the photosensitive drum 4 before the residual toner T discharged onto the surface of the photosensitive drum 4 passes through the developing unit. The residual toner T that has passed through the developing unit is transferred to the conveyor belt 12 at the transfer unit and collected by the cleaning device 15 of the conveyor belt unit 11 shown in FIG. 1.

[0048] Next, the behavior of foreign matter A, such as paper powder, fillers, and dust, transferred from the sheet material S to the photosensitive drum 4 will be described with reference to Figure 3(a), which shows the operation during image formation. The amount of foreign matter A generated is particularly large in the drum unit 30Y, which is the most upstream of the multiple drum units 30 in the direction of movement of the sheet material S, and since some of the foreign matter A is removed upstream, the amount of foreign matter A generated is smaller in the more downstream drum units.

[0049] A negative high voltage of, for example, about -1000V is applied to the transfer roller 16Y, and the positive toner image on the photosensitive drum 4Y is transferred onto the sheet material S. At this time, some of the foreign matter A present on the surface of or inside the sheet material S becomes negatively charged due to negative discharge or charge injection, and the negatively charged foreign matter A is transferred onto the photosensitive drum 4Y along the electric field. Because a negative voltage is applied to the cleaning roller 32, negatively charged foreign matter A is difficult to collect by the cleaning roller 32. Foreign matter A that cannot be collected and passes through the temporary collection section passes through the charging section and exposure section before reaching the development section.

[0050] When foreign matter A passes through the charging section, it is subjected to a positive corona discharge from the corona charger 5, and some foreign matter becomes positively charged. After passing through the exposure section, an electrostatic image is formed on the surface of the photosensitive drum 4, and positively charged foreign matter A that adheres to the non-image area on the surface of the photosensitive drum 4 is collected by the developing roller 6 in the developing section. On the other hand, negatively charged foreign matter A that adheres to the image area on the surface of the photosensitive drum 4 is subjected to an electrostatic force that transfers it to the developing roller 6, but due to the influence of the toner that transfers from the developing roller 6 onto the photosensitive drum 4, it is not collected by the developing roller 6 and remains on the photosensitive drum 4.

[0051] Some of the foreign matter A collected by the developing roller 6 remains carried by the developing roller 6 and continues to rotate, while others are peeled off at the contact point with the supply roller 26 and mix with the toner T in the developing container 28. The foreign matter A collected in the developing container 28 often remains around the developing roller 6 and supply roller 32 in the developing container 28.

[0052] Materials commonly found in paper sheets include talc and paper fibers, which tend to be negatively charged, and calcium carbonate, which tends to be positively charged. Fibers and other materials that accumulate in the developer container 28 can cause image defects, such as unintended streaks, on images. Calcium carbonate also mixes with and rubs against the toner, removing positive charges from the toner and reducing its charge. This can lead to toner adhering to non-image areas on the paper, resulting in an image defect known as fogging.

[0053] (Exhalation motion) The so-called expulsion mode, in which foreign matter transferred from the sheet material S and carried on the developing roller via the photosensitive drum 4 or remaining in the developing container 28 is expelled together with the toner, which is the developer, will be described in detail using Figures 4 and 5.

[0054] FIG. 4 is a schematic diagram showing the developing cartridge 8, the drum unit 30 at its center, and a part of the conveyor belt unit 11 when foreign matter A is being expelled together with toner.

[0055] FIG. 5 is a schematic diagram showing an example of a toner pattern discharged onto the conveyor belt 12. As shown in FIG.

[0056] When the discharge mode is executed, the photosensitive drum 4, the developing roller 6, and the supply roller 26 start to rotate. Then, the exposure device 10 starts to expose the surface of the photosensitive drum 4, and the surface of the photosensitive drum 4 is continuously exposed across the entire width of the printing range. A positive voltage is applied to the developing roller 6 in FIG. 4 from a development power supply (not shown). The potential of the electrostatic latent image formed on the surface of the photosensitive drum 4 is positive, and its absolute value is smaller than that of the voltage applied to the developing roller 6. Here, the electrostatic latent image is formed so as to develop a solid image with a high printing rate across the entire longitudinal area of ​​the photosensitive drum 4.

[0057] When the electrostatic latent image passes through the developing section, positively charged toner T moves from the developing roller 6 to the exposed area on the photosensitive drum 4. Here, positively charged foreign matter A remaining in the developing unit 28 moves to the photosensitive drum 4 together with the toner T. On the other hand, negatively charged foreign matter A cannot move to the photosensitive drum 4 by the electric field. However, by using the electrostatic latent image to form a toner pattern with a high printing rate, a large amount of toner T moves to the photosensitive drum 4, and it becomes possible to move negatively charged foreign matter A along with the toner T to the photosensitive drum 4. This makes it possible to expel foreign matter A from the developing container 28 onto the photosensitive drum 4 regardless of polarity.

[0058] A voltage of negative polarity relative to the surface potential of the photosensitive drum 4Y is applied to the transfer roller 16Y, which attracts and transfers the positively charged toner image on the photosensitive drum 4Y onto the conveyor belt 12. In the transfer section, as in the developing section, foreign matter A can be transferred onto the conveyor belt 12 together with a large amount of toner T.

[0059] The spit patterns of each color on the conveyor belt 12 will be described using Figure 5. The conveyor belt 12 rotates and conveys in the direction of the arrow, starting from transfer position 17Y, the first station located at the most upstream side of the conveyor belt for yellow, followed downstream by transfer position 17M, the second station for magenta, transfer position 17C, the third station for cyan, and transfer position 17K, the fourth station located at the most downstream side of the conveyor belt for black. The spit patterns of each color are 27Y, 27M, 27C, and 27K from upstream to downstream. The length of each spit pattern in the longitudinal direction perpendicular to the conveyance direction of the conveyor belt 12 spans the entire width of the printable area. The lengths in the conveyance direction are also related by the magnitude relationship shown in Equation 1. This allows the area of ​​the spit patterns to increase as the conveyance direction of the conveyor belt 12 increases. 25Y≧25M≧25C≧25K (Formula 1)

[0060] In other words, the amount of toner spit out is set to increase further upstream in the transport direction of the transport belt 12. This is because the amount of foreign matter A collected tends to be greater further upstream in the transport direction of the transport belt 12 and less further downstream. By spitting out more toner further upstream, the upstream stations actively spit out foreign matter A, while downstream stations, where there is not as much foreign matter A as upstream and there is no need to spit out toner, reduce the amount of toner spit out and suppress toner consumption, thereby making it possible to efficiently spit out foreign matter A collected in the developing device.

[0061] The thrown-out toner transferred onto the conveyor belt 12 is collected by a cleaning device 15 of the conveyor belt unit 11.

[0062] Next, the results of verifying the effect of the ejection method specific to this embodiment using an image forming apparatus will be described.

[0063] The paper is Canon Redlabel 80g / m 2 Letter size paper was used and single-sided continuous printing was performed. The printing pattern had an equal printing rate for each color and a low printing rate of 2% or less.

[0064] The paper feed environment is a room temperature of 23°C and a humidity of 50%. The toner discharged pattern conforms to the pattern shown in Figure 5. The length in the transport direction is equivalent to four rotations of the developing roller for color Y at the first station, three rotations of the developing roller for color M at the second station, two rotations of the developing roller for color C at the third station, and one rotation of the developing roller for color K at the fourth station, with the amount of toner discharged decreasing from the upstream station to the downstream station.

[0065] The degree of fogging was evaluated objectively by visual inspection and rated on a three-level scale: A, B, or C. Rank A means that the fogging is good and not noticeable in practical use, rank B means that it is noticeable when looking carefully at the image but is still within the practical range, and rank C means that the fogging is so bad that it is not suitable for practical use.

[0066] Under the above conditions, a total of 5,000 sheets were passed through, both without the ejection and with the ejection mode of this embodiment applied every 50 sheets of continuous paper passing. The level of fogging was then evaluated. The results are shown in Table 1 below.

[0067] [Table 1]

[0068] As shown in Table 1, fogging occurred at a level unsuitable for practical use at the first and second stations where spit-out was not performed, whereas when spit-out was performed, it improved to a satisfactory level that was practically unnoticeable. Fog also improved at all other stations, confirming the effectiveness of spit-out. Furthermore, the amount of toner used for spit-out was significantly reduced, particularly at the downstream stations: compared to four revolutions of the developing roller 6 at the first station, three revolutions at the second station, two revolutions at the third station, and one revolution at the fourth station.

[0069] In the verification experiment, the length of the discharge pattern in the transport direction is explained as an integer multiple of the developing roller 6, but it is not limited to this as long as the magnitude relationship of Equation 1 is met.

[0070] Furthermore, toner consumption may be reduced by not discharging toner at downstream stations where the fogging level is good to begin with. For example, only the fourth station, which is ranked A, may not discharge toner. Alternatively, if rank B is acceptable, the third and fourth stations may not discharge toner, and the first and second stations may perform sweeping.

[0071] Furthermore, although a solid image is exemplified as the ejection pattern, a halftone image with a high printing rate may also be used.

[0072] As described above, according to the present invention, in addition to normal printing, there is a discharge mode in which toner is discharged from the developing roller, and by varying the amount of toner discharged between stations while increasing the amount of toner discharged from the upstream station, it is possible to prevent image degradation and reduce the toner consumption required for the discharge mode.

[0073] Compared to the case where a foreign matter collection device is provided only in the most upstream station, it is possible to prevent image degradation without installing a foreign matter collection device in stations other than the most upstream station, while appropriately reducing the number of parts and preventing unnecessary increases in costs.

[0074] In this way, the present invention solves the above-mentioned problems, suppresses increases in costs due to an increase in the number of parts, and increases in the size of the image forming apparatus, while preventing image defects such as streaks and fogging caused by foreign matter loosened from the sheet material.

[0075] Of the stations, the one on the upstream side is referred to as the first station, and the one on the downstream side is referred to as the second station. In this embodiment, the amount of toner transferred onto the conveyor belt, i.e., the toner discharge amount, is greater at the first station than at the second station. In other words, the toner discharge amount of the toner color (first color) at the first station is greater than the toner discharge amount of the toner color (second color) at the second station.

[0076] Here, the components constituting the first station may be referred to as a first photosensitive drum, a first toner storage unit, a first developing roller, and a first transfer roller, respectively. Similarly, the components constituting the second station may be referred to as a second photosensitive drum, a second toner storage unit, a second developing roller, and a second transfer roller, respectively. The developer cartridge of the first station may be referred to as a first cartridge, and the developer cartridge of the second station may be referred to as a second cartridge. The mode in which toner is discharged onto the first photosensitive drum and transferred to the belt at the first station may be referred to as a first discharge mode, and the mode in which toner is discharged onto the second photosensitive drum and transferred to the belt at the second station may be referred to as a second discharge mode.

[0077] Second Embodiment In the first embodiment, differences were provided so that the discharge patterns of the developing devices were different. In the present embodiment, the discharge patterns of the developing devices are not changed, but the frequency of discharge performed by each developing device is changed.

[0078] The length of the discharge pattern in the longitudinal direction perpendicular to the conveyor belt 12 is the entire width of the printable area, and the length in the conveying direction is four revolutions of the developing roller. In other words, the discharge pattern is the same as that of the first station in the first embodiment.

[0079] On the other hand, the sweeping frequency was set differently for each station as shown in the following Table 2. The number of sheets is the predetermined number of sheets for which the discharging operation is performed at each station.

[0080] [Table 2]

[0081] As shown in Table 2, the upstream station has a smaller number of sheets to enter the toner discharge mode, increasing the frequency of toner discharge and increasing the amount of toner discharged by the upstream station. This means that the amount of toner discharged by the downstream station can be reduced, and similar to the first embodiment, it is possible to prevent image degradation and reduce the toner consumption required for the toner discharge mode.

[0082] Here, the first station is the yellow station located most upstream, the second station is the magenta station located downstream of the first station, the third station is the cyan station located downstream of the second station, and the fourth station is the black station located downstream of the third station.

[0083] As shown in Table 2, it is desirable that the predetermined number of sheets for the downstream stations be an integer multiple of that for the first station. This is to synchronize the timing of the discharge of the first station with the timing of the discharge of the second station and subsequent downstream stations. The discharge operation requires the operation of cleaning the toner on the conveyor belt 12, which can cause downtime. Here, setting the predetermined number of sheets for the downstream stations to an integer multiple of that for the first station has the effect of preventing the frequency of the discharge mode being executed more frequently than necessary.

[0084] Furthermore, as an effect unique to this embodiment, unlike the first embodiment in which the ejection operation is performed at all stations, ejection may be limited to specific stations that have reached a predetermined number of sheets, and in such cases, the time required for image formation of the ejection pattern can be shortened.

[0085] <Third embodiment> In the description of the first embodiment, it was explained that the toner T expelled onto the photosensitive drum 4 is transferred to the conveying belt 12 and collected by the cleaning device 15 of the conveying belt unit 11, but on the other hand, a certain effect can be obtained even if the toner T is not transferred to the conveying belt 12 but is re-collected in the developing unit.

[0086] The operation of discharging toner as developer from the developing unit and then recovering the discharged toner again by the developing roller 6 will be described in detail with reference to Figure 6. Figure 6 is a schematic diagram for explaining how the discharged toner is recovered again in the developing container 28.

[0087] Foreign matter A adhering to the surface of the developing roller 6 is expelled onto the photosensitive drum 4 together with the toner, as in the first embodiment. A high voltage of positive polarity equal to or greater than 0 V is applied to the transfer roller 16Y. The positive toner on the photosensitive drum 4 passes through the transfer section while still carried by the photosensitive drum 4. A positive voltage of 0 V or higher is applied to the cleaning roller 32, so the toner passes through the temporary collection section where the cleaning roller 32 is provided while still carried by the photosensitive drum 4. A negative voltage is applied to the developing roller 6 from a power supply device (not shown), and the expelled toner carried on the photosensitive drum 4 is collected by the developing roller 6 as shown in FIG. 6. The toner collected on the developing roller 6 is scraped off from the surface of the developing roller 6 by a supply roller 26 that rotates in the counter direction to the developing roller 6.

[0088] In this way, the discharged toner is collected again in the developing device, and the toner is reused, thereby enabling effective use of the toner.

[0089] Furthermore, there is no need for a recovery process from the conveyor belt 12 to the cleaning device 15, and the downtime can be reduced by simplifying the discharge operation.

[0090] This series of operations allows the foreign matter adhering to the developing roller 6 to be temporarily removed from the developing roller 6. This makes it possible to suppress image defects such as streaks caused by the foreign matter on the developing roller 6.

[0091] The foreign matter scraped off from the developing roller 6 remains around the developing roller 6 and the supply roller 26. If the developing device is designed for a long life, it is advisable to periodically perform the toner ejection operation described in the first embodiment. Then, as in the first embodiment, the ejected toner can be collected by the conveyor belt 12 and the foreign matter can be removed from the developing container 28.

[0092] <Fourth embodiment> In this embodiment, the drum unit 30Y1 located on the most upstream side in the moving direction of the conveyor belt 12 has a unique configuration, and this embodiment will be described in detail with reference to FIG.

[0093] 7(a) is a schematic cross-sectional view of the image forming apparatus of this embodiment, showing the drum unit 30Y1, which is a configuration unique to this embodiment and is located on the most upstream side in the direction of movement of the conveyor belt 12, the developing cartridge 8Y, the drum units 30M, 30C, and 30K other than the most upstream side, and the developing cartridges 8M, 8C, and 8K.

[0094] 7(b) is a drum unit equipped with a foreign matter collection mechanism including a foreign matter separation roller 33, a foreign matter separation scraper member 34, and a foreign matter collection container 35. FIG. 7(b) is a diagram illustrating the foreign matter collection operation by the drum unit 30Y1.

[0095] As mentioned above, the amount of foreign matter A generated is large at the station furthest upstream in the direction of movement of the sheet material S. This is because most of the foreign matter A is removed upstream, and the amount of foreign matter A generated decreases further downstream. For this reason, the foreign matter collection mechanism, which includes the foreign matter separation roller 33, foreign matter collection roller scraper 34, and foreign matter collection container 35 used to separate and collect foreign matter A, is installed only on the furthest upstream drum unit 30Y1, and is not installed on the other drum units 30M, 30C, and 30K. By providing these components only on stations where they are most needed, costs can be reduced, while stations where they are less needed can have foreign matter removed by a discharge operation.

[0096] A negative voltage is applied to the cleaning roller 32, which temporarily collects positive toner. The surface of the cleaning roller 32 is coated with sponge rubber or the like to improve collection of toner T and foreign matter A. Therefore, some negatively charged foreign matter mechanically adheres to the cleaning roller 32. A power supply (not shown) applies a positive voltage to the foreign matter separating roller 33 relative to the cleaning roller 32, causing negatively charged foreign matter A to be collected by the foreign matter separating roller 33. The foreign matter collected by the foreign matter collecting roller 33 is scraped off by a foreign matter separating roller scraper 34 and collected in a foreign matter collecting container 35. The collected foreign matter A does not return to the photosensitive drum 4 and does not affect the developing unit, which is a downstream process. By collecting foreign matter using the foreign matter collecting mechanism in this way, the amount of foreign matter collected by the most upstream developing cartridge 8 decreases.

[0097] Since the toner T temporarily collected by the cleaning roller 32 has a positive polarity, it is held by the cleaning roller 32 without moving to the foreign matter separation roller 33. As in the first embodiment, the cleaning roller 32 can be cleaned by performing a process of expelling the temporarily collected toner from the cleaning roller 32.

[0098] Here, the effect of the ejection method specific to this embodiment was verified using an image forming apparatus under the conditions of the first embodiment. An image forming apparatus having a foreign matter collection mechanism at the most upstream station was used, and the printing conditions and the conditions for visual evaluation of fogging were the same as those of the first embodiment.

[0099] While the longitudinal length of the spit pattern is the same as in the first embodiment, the length of the spit pattern in the transport direction is set to two revolutions of the developing roller for the yellow color at the first station. In other words, it is set shorter than three revolutions of the developing roller for the magenta color at the second station, thereby reducing the amount of yellow toner consumed in the spit operation at the first station. In addition, the length is set to two revolutions of the developing roller for the cyan color at the third station, and one revolution of the developing roller for the black color at the fourth station. The results of verifying the effects are shown in Table 3 below.

[0100] [Table 3]

[0101] When no discharge is performed (no discharge), the first station has a better cover level than the downstream second station, as shown in Table 3. This is due to the effect of the foreign material collection mechanism in the first station.

[0102] When spit-out was present, the spit-out pattern of the first station was set to the same as that of the third station, and even though toner consumption due to spit-out in the first station was reduced, a sufficient fogging improvement effect was obtained.

[0103] As described above, according to the present invention, when a specific station is provided with a configuration such as a foreign matter collection mechanism for reducing foreign matter collected in the developer cartridge, the amount of toner discharged may be adjusted to be less than that of downstream stations. That is, the amount of toner discharged may be set to be less than that of downstream stations by setting an appropriate amount of discharge depending on whether or not each station has a foreign matter collection mechanism or the like that corresponds to the foreign matter.

[0104] As described above, the configuration of this embodiment makes it possible to further reduce the amount of toner consumed in the ejection process.

[0105] Fifth Embodiment FIG. 8 is a schematic diagram of a system according to this embodiment.

[0106] The system according to this embodiment is composed of a host computer 100, which is an information processing device, a controller 121, and a print engine 122. The print engine includes a device main body 2, a cartridge tray 3, a developing cartridge 8, and a photosensitive drum unit 30.

[0107] Images and documents created by the host computer 100 are input as image data to the controller 121. It can also be said that the controller 121 acquires the image data. The controller 121 receives image data to be printed from the host computer 100, converts the image data into print data for printing by the print engine 122, and outputs the print data to the print engine 122. The print engine 122 executes printing based on the print data output from the controller 121.

[0108] Next, a description will be given of the controller 121. The controller 121 includes a host I / F unit 101, a CPU 102, a RAM 103, a ROM 104, an image processing unit 105, and an engine I / F unit .

[0109] The host I / F unit 101 functions as an interface for receiving image data transferred from the host computer 100. The CPU 102 controls the entire controller 121 using programs and data stored in the RAM 103 and the ROM 104, and also executes the processes performed by the controller 121, which will be described later.

[0110] The RAM 103 has a storage capacity necessary for temporarily storing information when the CPU 102 and the image processing unit 105 execute various processes. The ROM 104 stores in advance a control program for controlling the entire controller 121 by the CPU 102, various programs and data for executing various processes performed by the controller 121, setting data for the controller 121, and the like.

[0111] Image processing unit 105 is a unit that performs image processing for outputting an image by print engine 122 on image data input via host I / F unit 101, and is provided separately from CPU 102. Engine I / F unit 106 transfers the print data that has been image-processed by image processing unit 105 to print engine 122. Internal bus 107 is a bus that connects each unit.

[0112] Specifically, the controller 121 receives image data from the host computer 100, and performs rasterization based on the image data in the image processing unit 105 to generate image data in units of pixels. The rasterized image data has YMCK color components, and each pixel has an 8-bit (256 gradations) value for each color component.

[0113] Next, the processing specific to this embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the details of the processing specific to this embodiment. This processing is performed each time a sheet of material is printed. For each sheet of material, a decision is made as to whether or not to perform the discharge mode specific to this embodiment, and a discharge pattern is also determined.

[0114] (Step 1: Pixel counting) First, a so-called pixel count process is performed, in which the number of pixels is calculated and accumulated from the YMCK image data processed by the controller 121. The number of pixels refers to the number of pixels in the image data, but in the print engine 122, it is the number of dots for forming a toner image on the photosensitive drum 4. Since the number of dots depends on the resolution of the print engine 122 when printing, in this embodiment, the explanation will be given assuming a resolution of, for example, 600 dpi.

[0115] When expressing each color with gradation in printing, it is desirable to make corrections to the gradation. For example, if it is 8 bits (256 gradations), it is possible to modulate 8 bits (256 gradations) with the exposure pulse width from the exposure device 10. For example, in this case, the nth gradation is, for example, n / 255 (Formula 2) When the exposure device 10 is fully lit with one pixel, the gradation n is 255, so 255 / 255=1...(Formula 3) This becomes:

[0116] The controller 121 executes pixel counting, which counts the number of pixels (pixel count) of one sheet material, in the CPU 102, and adds it to the integrated value PC_1st of the pixel count, which is a variable in the area of ​​the RAM 103, and overwrites it.

[0117] The above process is performed for each station, and the pixel count integrated value is overwritten as integrated value PC_1st at the first station, integrated value PC2_st at the second station, integrated value PC_3st at the third station, and integrated value PC_4st at the fourth station.

[0118] (Step 2: Counting the number of pages) In the page number count process, the controller 121 accumulates the number of pages of exposed latent images. Specifically, after the exposure device 10 exposes the photosensitive drum 4, the CPU 102 executes page number counting and adds 1 to the page count number N in the RAM 103 area for each sheet of material, overwriting the count.

[0119] (Step 3: Judgment based on number of sheets passed) In this step, CPU 102 determines whether or not the page count N accumulated in step 2 exceeds a predetermined number. If it exceeds the predetermined number, the process proceeds to step 4, and if it does not exceed the predetermined number, the process ends. In this invention, the predetermined number is described as 100.

[0120] (Step 4: Reset page count) In this step, the CPU 102 resets the page count number N in the RAM 103 area to zero.

[0121] (Step 5: Compare pixel counts to a predetermined value) In this step, the CPU 102 compares the pixel count cumulative value PC_1st stored in the RAM 103 with a predetermined pixel count value PCU_1st stored in the ROM 104. The pixel count cumulative value PC_1st may be referred to as a first pixel count value, and the predetermined pixel count value PCU_1st may be referred to as a first predetermined value. In this embodiment, the pixel count cumulative value PCU_1st for the first station is set to 64,000,000 pixels. If the pixel count cumulative value PC_1st is 64,000,000 pixels or greater, the process proceeds to step 7; if the pixel count cumulative value PC_1st is less than 64,000,000 pixels, the process proceeds to step 6.

[0122] (Step 6: Discharge mode) In this step, the process in which the controller 121 determines the discharge pattern and the discharge mode in which the discharge pattern is discharged will be described.

[0123] First, the process of determining the discharge pattern will be described. The CPU 102 calculates the difference ΔPC_1st between the integrated value PC_1st of the pixel count stored in the RAM 103 area and the predetermined value PCU_1st of the pixel count recorded in the ROM 104 area. ΔPC_1st=PCU_1st-PC_1st...(Formula 4)

[0124] In step 5, the pixel count integrated value PC_1st and the predetermined pixel count value PCU_1st have been compared, and ΔPC_1st is positive. Here, the CPU 102 forms an image pattern for consuming toner equivalent to the number of pixels ΔPC_1st that is less than the predetermined pixel count value.

[0125] Next, the output operation will be described. The method for determining the image pattern to be output is unique to this embodiment, but the output operation itself for outputting that pattern is executed in accordance with the procedure of the first embodiment. The image pattern formed in this embodiment is sent by the CPU 102 to the image processing unit 105, and after processing by the image processing unit 105, is sent to the print engine 122 as printable bitmap data.

[0126] (Step 7: Reset pixel count) In this step, the CPU 102 resets the pixel count number PC_1st in the RAM 103 area to 0, and then the entire process ends.

[0127] The above-described process has been exemplified for the first station, but similar processes are performed for the other stations. A unique feature of this embodiment is that the predetermined pixel count value for at least one station is different from that of the other stations. Furthermore, the predetermined pixel count value for an upstream station is set to be larger than that for a downstream station. The predetermined pixel count value for each station may be set, for example, as shown in Table 4 below.

[0128] [Table 4]

[0129] The predetermined pixel count value of the first station, 64,000,000 pixels, is approximately equal to the total number of pixels required to print 100 sheets of A4-sized paper with a 2% print rate of a given yellow pattern. Similarly, the second station prints magenta at 1.5%, the third station prints cyan at 1%, and the fourth station prints black at 0.5% print rate.

[0130] That is, if there is a station where the average print rate for each color is lower than the above print rate when a predetermined number of sheets have been printed, a discharging process specific to this embodiment is executed.

[0131] In order to confirm the effect of this embodiment, paper was passed through the image forming apparatus.

[0132] The sheet material is Canon Redlabel with a basis weight of 80 g / m. 2 After 100 sheets of letter-sized paper were continuously passed through one side, the pattern discharged onto the conveyor belt 12 was checked. The print pattern was set so that the print rate of each color was 1%.

[0133] At the third and fourth stations, where the toner consumption during printing exceeded the predetermined pixel count value, no spit pattern was drawn on the conveyor belt 12. On the other hand, the yellow toner at the first station drew a spit pattern for 6.7 revolutions of the developing roller in the conveyance direction, and the magenta toner at the second station drew a spit pattern for 3.3 revolutions of the developing roller.

[0134] This is because the predetermined pixel count value is set to be larger the more upstream, as shown in Table 3. The pixel count at the first and second stations is below the predetermined value, and the pixel count at the third and fourth stations is above the predetermined value. Note that developing toner during normal printing also has the effect of expelling foreign matter mixed in the developer cartridge 8. As described above, one of the effects unique to this embodiment is that it is possible to further optimize the toner consumed in the expelling mode by not executing the expelling mode when there is a lot of printing, or by executing the expelling mode after subtracting the toner consumed during printing.

[0135] Sixth Embodiment This embodiment will be described with reference to Figure 10. Figure 10 shows a two-body configuration consisting of a process cartridge 62 in which the drum cartridge 30 and the developing device are integrated, and a toner cartridge 63 (toner container) filled with toner.

[0136] When the toner cartridge 63 is installed in the image forming apparatus and coupled with the process cartridge 62, the toner supply shutter 65 opens, allowing toner to be supplied from the toner cartridge 63 to the process cartridge 62. A toner transport screw 66 is provided in the toner storage section of the toner cartridge 63, and this transport screw 66 transports toner to a supply port, and the toner transported to the vicinity of the supply port drops from the supply port, thereby realizing toner supply to the process cartridge 62. The amount of toner supplied can be controlled by controlling the number of rotations of the transport screw 66.

[0137] On the other hand, the process cartridge 62 has a receiving port (not shown) for receiving replenished toner from the toner cartridge 63 provided directly below the toner replenishment shutter 65 .

[0138] Furthermore, as a stabilizing means for maintaining a predetermined amount of toner contained in the process cartridge 62, a toner amount detecting means for detecting the surface of the toner contained in the process cartridge 62 is provided. There are several types of toner amount detecting means, but in this embodiment, an optical detecting means is used. The process cartridge 62 is provided with a light incident window 64 through which light from an optical element (not shown) provided in the main body of the image forming apparatus is incident, and a light receiving window 63 that receives light incident from the light incident window 64 and passes the light to a light receiving element in the main body of the apparatus.

[0139] When the toner contained in the process cartridge 62 is consumed by printing, the toner amount detection means detects the decrease in toner. Also, when the toner contained in the process cartridge 62 decreases, a motor (not shown) that controls the rotation of the toner transport screw 66 of the toner cartridge 63 rotates, and toner is replenished while the amount of toner replenished is controlled by the number of rotations.

[0140] In other words, by replenishing toner into the process cartridge 62 whose remaining toner amount has decreased due to printing, the amount of toner in the container of the process cartridge 62 is properly restored. In other words, this operation keeps the amount of toner contained in the process cartridge 62 constant at a predetermined amount.

[0141] The processing specific to this embodiment will be described with reference to FIGS.

[0142] FIG. 11 is a flowchart showing the processing specific to this embodiment, in which the number of revolutions of the motor that drives the conveying screw 66 is used for control instead of the pixel count number used in the fourth embodiment.

[0143] As in the fourth embodiment, this process is performed each time a sheet of paper is passed through, and a decision is made for each sheet as to whether to perform the discharge mode and to determine the discharge pattern. Therefore, there are many processes in common with the fourth embodiment, and a description of the common processes will be omitted.

[0144] (Step 1: Counting the number of motor rotations) First, the print engine 122 sends a toner replenishment request to the controller 121 based on the detection result of a toner amount detection means that detects the amount of toner by detecting the surface of the toner contained in the process cartridge 62. Upon receiving the toner replenishment request, the controller 121 sends a command to the print engine 122 to rotate the conveying screw 66 (first screw) of the toner cartridge 63 (first toner container). This process is carried out until the replenishment request from the print engine 122 is completed. The CPU 102 in the controller 121 accumulates the number of rotations of the conveying screw 66 of the toner cartridge 63, and records and temporarily stores this accumulated value in the RAM 103. That is, the controller 121 acquires motor rotation information, performs counting of the number of motor rotations, and stores and records the accumulated value in the memory area MC_1st of the RAM 103.

[0145] Steps 2 to 4 are the same as those in the fourth embodiment, and therefore their explanation will be omitted.

[0146] (Step 5: Compare the motor rotation speed with the specified value) In this step, CPU 102 compares the integrated value MC_1st (first number of rotations) of the number of motor rotations stored in the RAM 103 area with a predetermined value MCU_1st (first predetermined value) of the number of motor rotations pre-recorded in the ROM 104 area. If the integrated value MC_1st of the number of motor rotations is equal to or greater than MCU_1st, the process proceeds to step 7, where the integrated value MC_1st of the number of motor rotations is reset. If the integrated value MCU_1st is less than MCU_1st, the process proceeds to step 6.

[0147] (Step 6: Discharge mode) In this step, a so-called discharging mode will be described in which the controller 121 performs a process of determining a discharging pattern and the print engine 122 performs a discharging operation of discharging the discharging pattern.

[0148] First, the process of determining the discharge pattern will be described. The CPU 102 calculates the difference ΔMC_1st between the integrated value MC_1st of the motor rotation number in the RAM 103 area and the predetermined value MCU_1st of the motor rotation number recorded in the ROM 104 area. ΔMC_1st=MCU_1st-MC_1st...(Formula 5)

[0149] Here, CPU 102 calculates the difference ΔMC_1st, which is the difference in the number of motor rotations that is less than a predetermined value. CPU 102 then rotates the motor the number of times equal to the difference to form an image pattern that consumes an amount of toner that corresponds to the amount of toner that would be required to replenish toner. This image pattern is determined as the image pattern for the discharge mode, and is converted into bitmap data by image processing unit 105 and sent to print engine 122. A configuration may be adopted in which multiple image patterns are stored in ROM in advance, and a pattern is selected by referencing a table according to the number of motor rotations.

[0150] Image forming devices that require toner replenishment tend to require process cartridge replacement less frequently than image forming devices that require toner cartridges. In other words, the process cartridges are often designed to have a longer lifespan. When calculating the amount of toner consumed in the toner discharge mode, pixel counting may result in an error compared to the actual amount of toner consumed.

[0151] In an image forming apparatus that requires toner replenishment, the amount of toner to be discharged can be estimated more accurately by using the rotation speed of the supply motor, which has a high correlation with the amount of replenished toner, instead of pixel counting as in this embodiment. This makes it possible to optimize the amount of toner consumed in the discharge mode even in an image forming apparatus that has a dual cartridge configuration of a process cartridge and a toner cartridge. [Explanation of symbols]

[0152] 1. Image forming device 2. Device body 3 Cartridge tray 4 Photosensitive drum 6 Developing roller 8 Developer cartridge 10 Exposure equipment 11 Conveyor belt unit 15 Cleaning device 16 Transfer roller 121 Controller 122 Printing Engine 26 Supply roller 30 Drum unit 31 Static elimination light source 32 Cleaning roller 62 Process cartridge 63 Toner cartridge 66 Toner transport screw 100 host computer 102 CPU 103 RAM 104 ROM 105 Image processing section

Claims

1. a first photosensitive drum on which an electrostatic latent image is formed to form an image of a first color; a first toner container that contains a toner corresponding to the first color; a first developing roller that supplies the toner from the first toner container to the first photosensitive drum; a first developing device having a second photosensitive drum on which an electrostatic latent image is formed to form an image of a second color; a second toner container configured to contain a toner corresponding to the second color; a second developing roller that supplies the toner from the second toner container to the second photosensitive drum; a second developing device having an endless conveyor belt configured to be able to contact the first photosensitive drum and the second photosensitive drum, and to rotate and move while adsorbing the sheet material to convey the sheet material; a first transfer roller configured to transfer the toner of the first color on the first photosensitive drum to the sheet material or the conveyor belt; a second transfer roller configured to transfer the second color toner on the second photosensitive drum to the sheet material or the conveyor belt; Equipped with the first photosensitive drum is disposed upstream of the second photosensitive drum in a conveying direction of the sheet material during transfer; the amount of the first color toner transferred onto the conveyor belt when the first color toner is transferred onto the conveyor belt is greater than the amount of the second color toner transferred onto the conveyor belt when the second color toner is transferred onto the conveyor belt; An image forming apparatus characterized by:

2. a first discharging mode is a discharging mode when a first color toner is transferred onto the conveyor belt without a first color toner being transferred from the first developing device to the sheet material, and a second discharging mode is a discharging mode when a second color toner is transferred onto the conveyor belt without a second color toner being transferred from the second developing device to the sheet material, the frequency at which the first discharging mode is executed is higher than the frequency at which the second discharging mode is executed; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. a scraping member that contacts the first photosensitive drum and scrapes off foreign matter; a collection container for collecting the foreign matter scraped by the scraping member; The first developing device further has a recovery section having 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. An image forming apparatus that forms a color image based on image data acquired from an information processing apparatus, a controller that acquires the image data, separates the image data into toner color components, calculates the number of pixels for each color component, integrates the number of pixels for each color component, calculates a pixel count value integrated for each color component, and compares the pixel count value with a predetermined value; a memory means for storing a predetermined value to be compared with the pixel count value; when a first pixel count value, which is a pixel count value for the toner of the first color, exceeds a first predetermined value, which is a predetermined value for the toner of the first color, a discharge mode is executed in which the toner of the first color is transferred onto the conveyor belt without being transferred from the first developing device to the sheet material; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. a first toner container that contains toner to be transported to the first toner container; a first screw that transports and supplies toner from the first toner container to the first toner storage portion; a controller that acquires rotation information of the first screw, accumulates a first rotation number that is the number of rotations of the first screw, and compares the first rotation number with a predetermined value; a memory means for storing a predetermined value to be compared with the first number of rotations, When the first number of rotations exceeds the predetermined value, a discharge mode is executed in which the toner of the first color is transferred onto the conveyor belt without being transferred from the first developing device to the sheet material.

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

6. when the toner of the first color is transferred onto the conveyor belt without being transferred from the first developing device to the sheet material, the transferred toner is collected by the first developing roller; 2. The image forming apparatus according to claim 1, wherein:

7. a first photosensitive drum on which an electrostatic latent image is formed to form an image of a first color; a first toner container that contains a toner corresponding to the first color; a first developing roller that supplies the toner from the first toner container to the first photosensitive drum; a first developing device having a second photosensitive drum on which an electrostatic latent image is formed to form an image of a second color; a second toner container configured to contain a toner corresponding to the second color; a second developing roller that supplies the toner from the second toner container to the second photosensitive drum; a second developing device having an endless conveyor belt configured to be able to contact the first photosensitive drum and the second photosensitive drum, and to rotate and move while adsorbing the sheet material to convey the sheet material; a first transfer roller configured to transfer the toner of the first color on the first photosensitive drum to the sheet material or the conveyor belt; a second transfer roller configured to transfer the second color toner on the second photosensitive drum to the sheet material or the conveyor belt; Equipped with the first photosensitive drum is provided upstream of the second photosensitive drum in the conveying direction of the sheet material, an area occupied on the conveying belt by the toner of the first color transferred onto the conveying belt when the toner of the first color is transferred onto the sheet material from the first developing device without the toner of the first color being transferred onto the sheet material is larger than an area occupied on the conveying belt by the toner of the second color transferred onto the conveying belt when the toner of the second color is transferred onto the conveying belt without the toner of the second color being transferred onto the sheet material from the second developing device; An image forming apparatus characterized by:

Images