JP6645447B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus.

  For example, Patent Literature 1 discloses a tandem-type image forming apparatus 1 of an electrophotographic type including a plurality of image forming units 10Y, 10M, 10C, and 10K each including a photoconductor 11 and an intermediate transfer belt 30. Is disclosed.

JP-A-2006-212209

  By the way, it is known that the chargeability (one of the performances of the photoreceptor), which will be described later, occurs in the support (an example of the photoreceptor) during the manufacturing process. In addition, the life of the carrier also varies due to the variation in the charging ability. As a result, for example, in the case of the tandem-type image forming apparatus 1 disclosed in Patent Document 1, the replacement time of the plurality of image forming units 10Y, 10M, 10C, and 10K is determined by the photoconductor 11 that constitutes each image forming unit. Of the toner due to the charging ability of the toner.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus in which a plurality of carriers have a combination of at least two or more levels of charging ability and which can reduce a difference in replacement time (life) of the plurality of carriers.

  A first image forming apparatus of the present invention includes a carrier that rotates around an axis and carries a latent image, a charging device that charges the carrier, and exposes the carrier charged by the charging device to form a latent image. An exposure device that forms, a developing device that develops the latent image as a toner image of each color using toner of each color, and a removing unit that removes remaining toner remaining on the carrier without being transferred by contacting the carrier. A plurality of toner image forming devices, a transfer device for transferring a toner image of each color developed on the carrier by each of the plurality of toner image forming devices to a medium, the plurality of toner image forming devices, And a control device for controlling the transfer device, wherein a value obtained by dividing the surface potential by a current flowing through the carrier in order to bring the carrier to a predetermined surface potential is defined as a charging ability. The carrier is At least two or more levels of charging ability are provided, and the control device is configured such that, after the toner image forming operation, the toner image forming apparatus having the lower charging ability has more toner from the developing device than the carrier. And a toner supply operation of rotating the carrier around the axis for a predetermined period of time.

  In the second image forming apparatus of the present invention, the control device may further include: supplying a larger amount of toner from the developing device to the carrier as the rotation time of the carrier in the toner image forming operation is longer; I do.

  In a third image forming apparatus according to the present invention, the plurality of toner image forming apparatuses further include a storage unit storing the charging ability of each of the carriers measured before shipment of a product, and The device determines the amount of toner to be supplied from the developing device to the carrier during the toner supply operation, based on the charging ability stored in each of the storage units.

  The fourth image forming apparatus of the present invention is further configured such that the control device is capable of measuring the charging ability of each of the carriers using the plurality of toner image forming devices. An amount of toner to be supplied from the developing device to the carrier during the toner supply operation is determined based on the charging ability.

  In the fifth image forming apparatus of the present invention, when a time longer than a time determined at the time of the toner image forming operation is required, the toner image forming operation is interrupted, the toner supply operation is performed, and the toner image forming operation is performed again. Resume operation.

  In a sixth image forming apparatus according to the present invention, the charging device further includes a charging member that discharges while contacting the carrier and charges the carrier.

  In the seventh image forming apparatus of the present invention, the carrier is a single-layer type organic photoreceptor.

  According to the image forming apparatus of the present invention, in an image forming apparatus in which a plurality of carriers have a combination of at least two or more levels of charging ability, a difference in replacement time (life) of the plurality of carriers can be reduced.

FIG. 2 is a schematic view of the image forming apparatus according to the embodiment as viewed from the front side. FIG. 2 is a schematic view of a photoreceptor constituting the image forming apparatus of the present embodiment and peripheral portions thereof as viewed from the front side. FIG. 2 is a block diagram illustrating a relationship between a control device included in the image forming apparatus according to the embodiment and each component included in the image forming apparatus. FIG. 4 is a flowchart showing a control flow of a toner image forming operation and a control flow of a toner supply operation by the control device of the embodiment. 5 is a graph that defines a relationship between a charging ability used for determining a toner supply amount and a toner supply coefficient in a control flow of the toner supply operation according to the embodiment. FIG. 4 is a schematic diagram illustrating a toner image supplied to a photoconductor in a toner supply operation according to the exemplary embodiment. 9 is a graph showing a relationship between the number of printed sheets of a plurality of photoconductors and the amount of wear of the photoconductor in a comparative embodiment. 5 is a graph illustrating a relationship between a toner supply coefficient and a wear amount of a photoconductor in the case of the present embodiment. 5 is a graph showing the relationship between the number of printed sheets of a plurality of photoconductors and the amount of wear of the photoconductor in the case of the present embodiment. 4 is a table showing conditions of an example. 9 is a table showing conditions of Comparative Example 1. 9 is a table showing conditions of Comparative Example 2. 9 is a table summarizing experimental results of Examples and Comparative Examples 1 and 2. FIG. 11 is a flowchart showing a control flow of a toner image forming operation and a control flow of a toner supply operation in a first modified example. FIG. 13 is a flowchart illustrating a control flow of a toner image forming operation and a control flow of a toner supply operation in a second modified example. FIG. 13 is a schematic diagram illustrating a toner image supplied to a photoconductor in a toner supply operation according to a third modified example. 15 is a graph that defines a relationship between a charging ability used for determining a toner supply amount and a toner supply coefficient in a control flow of a toner supply operation according to a fourth modified example.

<Overview>
Hereinafter, the configuration, image forming operation (see FIG. 4), toner supply operation (see FIG. 4), effects, examples, and modifications of the image forming apparatus 10 (see FIG. 1) of the present embodiment will be described with reference to the drawings. The description will be made in the order of these descriptions.

  In the following description, the directions indicated by arrows Fr and Rr in the drawing are indicated by front and rear sides in the apparatus depth direction, and the directions indicated by arrows R and L are indicated by right and left sides in the apparatus width direction, and arrows U and Lo, respectively. The directions shown are the upper side and the lower side in the apparatus height direction, respectively. In this specification, a state in which the image forming apparatus 10 is viewed from the near side in the apparatus depth direction will be described as the front of the image forming apparatus 10.

<Configuration of Image Forming Apparatus>
As shown in FIG. 1, the image forming apparatus 10 includes a paper feed cassette 20, a toner image forming unit 30, a transfer device 40, a transport device 50, a fixing device 60, a control device CU, a power supply PS, , And is an electrophotographic apparatus. Further, the image forming apparatus 10 of the present embodiment is a tandem-type electrophotographic apparatus that forms a color image using the single-color units 31Y, 31M, 31C, and 31K described below.

  The paper feed cassette 20 has a function of storing the medium S.

  The toner image forming unit 30 has a function of performing each step of charging, exposing, and developing to form a toner image held on a belt TB described later. The toner image forming unit 30 includes single color units 31Y, 31M, 31C, and 31K that form toner images of respective colors (Y (yellow), M (magenta), C (cyan), and K (black)). . As shown in FIG. 1, each of the single-color units 31Y, 31M, 31C, and 31K includes a photoconductor PC (an example of a carrier), a charging device 32, an exposure device 34, a developing device 36, and a static eliminator. 37, a cleaning blade 38 (an example of a removing unit), and a storage unit MR (see FIG. 2). Here, each of the single color units 31Y, 31M, 31C, and 31K is an example of a toner forming apparatus. Further, the toner image forming unit 30 is an example of a plurality of toner image forming apparatuses. Each single-color unit 31 is a replacement part that can be attached to and detached from the main body of the image forming apparatus 10.

  The photoconductor PC has a drum shape and, while carrying a latent image formed by the exposure device 34, is driven by a driving source (not shown) and rotates clockwise as viewed from the front side (rotates around an axis). ) The photoconductor PC of the present embodiment is, for example, a single-layer organic photoconductor. That is, the photoconductor PC of the present embodiment is a so-called positive charging type photoconductor.

  The charging device 32 has a function of charging the photoconductor PC while a voltage is applied from the power supply PS. As shown in FIGS. 1 and 2, the charging device 32 of the present embodiment is driven by the photoconductor PC while contacting the photoconductor PC, and discharges the photoconductor PC to charge the photoconductor PC. It is configured to include a charging roller 32A (an example of a charging member).

  The developing device 36 has a function of developing the latent image formed on the photoconductor PC by the exposure device 34 as a toner image using the toner of each color. The developing device 36 has a developing roller 36A that faces the photoconductor PC and rotates around an axis (see FIGS. 1 and 2), and develops a toner image using toner attached to the outer periphery thereof. I have. Further, the developing device 36 is configured to apply a voltage in which an AC voltage is superimposed on a DC voltage from the power supply PS to the developing roller 36A so that the toner T on the outer periphery of the developing roller 36A flies to the photoconductor PC and moves. It has become.

  The static eliminator 37 has a function of irradiating the photoconductor PC with light after passing through the transfer position (the position at which the photoconductor PC comes into contact with the belt TB) to neutralize the photoconductor PC.

  The cleaning blade 38 has a function of removing residual toner remaining on the photoconductor PC without being transferred to the belt TB (toner remaining on the photoconductor PC without being transferred to the belt TB) from the photoconductor PC. The cleaning blade 38 is formed of a long plate-shaped rubber, and removes toner from the photoconductor PC while the edge at one end in the short direction thereof is in contact with the photoconductor PC. (Not shown).

The storage unit MR stores the charging ability α measured before shipment of the photoconductor PC of each single-color unit 31 (for example, at the time of assembling each single-color unit 31 after manufacturing the photoconductor PC). Here, the charging ability α means a value obtained by dividing the surface potential V0 by a current Idc flowing through the photoconductor PC in order to bring the photoconductor PC to a predetermined surface potential V0. That is, the charging ability α is represented by the following equation 1.

(Equation 1) α = V0 / Idc

The charging ability α is, for example, a value determined by a current Idc necessary for charging a plurality of photoconductors PC to the same surface potential V0 as shown in Expression 1. As the magnitude of the current Idc increases, the charging ability α decreases. The smaller the charging ability α, the more current is required for charging to the surface potential V0, and the lower the charging ability α. In addition, the lower the charging ability α, the larger the current Idc that flows to make the surface potential V0 the surface potential. Specifically, in the case of the present embodiment, the current flowing from the charging roller 32A to the photoconductor PC due to discharge increases. Therefore, as the photoconductor PC has a lower charging ability α, the mechanical strength of the surface layer due to the discharge is reduced and the photoconductor PC is more likely to be worn. From the above, it can be said that the photoconductor PC having the lower charging ability α is more likely to be worn during the toner image forming operation. In the case of the present embodiment, the photoconductors PC constituting each single color unit 31 are a combination having at least two or more levels of charging ability α. In other words, the plurality of (four) photoconductors PC constituting the toner image forming unit 30 of the present embodiment are configured by a combination of photoconductors PC that are easily worn during the toner image forming operation.

  The charging roller 32A, the developing device 36, the static eliminator 37, and the cleaning blade 38, which constitute the toner image forming unit 30, are arranged clockwise around the photoconductor PC in the stated order when viewed from the front side. (See FIG. 2). The exposure device 34 forms a latent image between the charging roller 32A of the photoconductor PC and the developing device 36. In FIG. 1, reference numerals of the single color units 31M, 31C, 31K other than the single color unit 31Y are omitted.

  The transfer device 40 has an endless belt TB, and primary-transfers the toner images of each color formed by the toner image forming unit 30 onto the belt TB that rotates in the direction of arrow X in FIG. It has a function of secondarily transferring the held toner images of each color to the medium S.

  The transport device 50 has a function of transporting the medium S stored in the sheet cassette 20 along a transport path (two-dot line P in FIG. 1). Note that the arrow Y in FIG. 1 indicates the transport direction of the medium S.

  The fixing device 60 has a function of fixing the toner images of each color secondary-transferred onto the medium S by the transfer device 40 to the medium S.

  The control unit CU has a function of controlling each unit constituting the image forming apparatus 10 (see FIG. 3 described later). The function of the control unit CU will be described in the description of an image forming operation and a toner supply operation described later.

<Image forming operation>
Next, an image forming operation by the image forming apparatus 10 of the present embodiment will be described with reference to FIGS.

  The control device CU that has received the image data from the external device (not shown) activates each unit of the image forming apparatus 10 (see FIG. 3).

  When the toner image forming unit 30 is operated, in each of the single color units 31Y, 31M, 31C, and 31K, each photoconductor PC is rotated around an axis by a drive source (not shown) (see step S10 in FIG. 4). The charging device 32 charges each photoconductor PC, each exposure device 34 exposes each photoconductor PC, and each developing device 36 develops the latent image on each photoconductor PC as a toner image of each color. As a result, a toner image of each color is formed on each photoconductor PC (see step S20 in FIG. 4).

  Next, when the transfer device 40 and the transport device 50 are operated, the toner images of each color formed by the toner image forming unit 30 are primarily transferred to the belt TB (see step S20 in FIG. 4). The medium S contained in the sheet cassette 20 is transported by the transport device 50 at the timing when the toner images of the respective colors primarily transferred onto the belt TB are secondarily transferred onto the belt TB and held on the belt TB. The toner images of the respective colors are secondarily transferred to the medium S (see step S20 in FIG. 4). The medium S on which the toner images of the respective colors are secondarily transferred is transported by the transport device 50 toward the fixing device 60.

  Next, when the fixing device 60 is operated and the medium S on which the toner images of each color are secondarily transferred is conveyed to the fixing device 60, the toner images of each color are fixed on the medium S ((color) image on the medium S). Is formed).

  Then, the medium S on which the toner image is fixed (the medium S on which the image is formed) is discharged out of the image forming apparatus 10 by the transport device 50, and the image forming operation ends.

<Toner supply operation>
Next, the toner supply operation of the present embodiment will be described with reference to FIGS. The toner supply operation of the present embodiment is performed, for example, after the toner image forming operation.

  Here, the technical meaning of performing the toner supply operation will be described. As described above, in the case of the image forming apparatus 10 of the present embodiment, the plurality of photoconductors PC have different charging abilities α. Therefore, when a plurality of photoconductors PC are used under the same condition, the life of each photoconductor PC differs due to the charging ability α of each photoconductor PC (see FIG. 7 described later). Further, in the image forming apparatus 10 of the present embodiment, after the toner image forming operation, toner is supplied from each developing device 36 to each photoconductor PC, and the supplied toner is used as a lubricant in the cleaning blade 38 to make each photoconductor PC Is rotated around an axis for a predetermined period, so that each photoconductor PC is scraped by each cleaning blade 38. In this case, the photoconductor PC stays at the contact portion between each cleaning blade 38 and each photoconductor PC, and the more the toner that functions as a lubricant (the larger the toner supply coefficient k to be described later), the more easily the photoconductor PC is scraped (see FIG. 8). . The toner supply operation of this embodiment adjusts the amount of toner to be supplied to each photoconductor PC based on the charging ability α of the plurality of photoconductors PC, and adjusts the amount of toner supplied to each photoconductor PC (each single-color unit 31). It is intended to make the life (replacement time) of the single color unit 31 uniform (to reduce the difference in the replacement time of each single color unit 31). As a result, when replacing each single color unit 31 of the image forming apparatus 10, there is an advantage that, for example, a service person can replace a plurality of single color units 31 at a time.

  Hereinafter, the toner supply operation of the present embodiment will be specifically described. As shown in FIG. 4, after the toner image forming operation (the operation composed of steps S10, S20 and S30), the control device CU determines the moving distance L of each photoconductor PC during the toner image forming operation. It is calculated (see step S40 in FIG. 5). Here, the moving distance means a distance that an arbitrary position on the outer periphery of the photoconductor PC has moved as the photoconductor PC rotates around the axis during the toner image forming operation. That is, the longer the drive time (rotation time) of the photoconductor PC, the longer the movement distance L.

  Next, the control unit CU calculates a toner supply amount to be supplied to each single-color unit 31 (each photoconductor PC) using the movement distance L calculated in step S40 and a toner supply coefficient k described later (FIG. 4). Step S50).

Here, the toner supply amount in the present embodiment is a product of a maximum image forming width and a toner band width x to be described later (see Expression 2), like a rectangular solid image having a predetermined density shown in FIG. ).

(Equation 2) x = k × L

Further, as shown in FIG. 5, the toner supply coefficient k is determined using a linear function having a smaller relationship as the charging ability α becomes higher (see Equation 3). The control unit CU calculates the toner supply coefficient k using Expression 3 based on the charging ability α of each photoconductor PC stored in the storage unit MR.

(Equation 3) k = α × a + b (a <0, b> 0)

  As a result, when step S50 is performed by the control device CU, the amount of toner supplied from each developing device 36 to each photoconductor PC is calculated. Specifically, the toner band width x of the photoconductor PC having the higher charging ability α is set to be smaller than the toner band width x of the photoconductor PC having the lower charging ability α than the photoconductor PC.

  Next, the control unit CU performs a polishing operation based on the toner supply amount of each photoconductor PC calculated in step S50 (see step S60 in FIG. 4). Specifically, the control device CU causes each developing device 36 to rotate a toner band corresponding to the toner supply amount calculated in step S50 for each photoconductor PC while rotating each photoconductor PC around an axis by a driving source. The photosensitive member PC is formed (toner is supplied). Then, the control unit CU rotates each photoconductor PC around the axis for a predetermined period. As a result, each photoconductor PC is scraped by each cleaning blade 38 in a state where the toner supply amount based on the respective charging ability α is supplied.

  Then, when the predetermined period in step S60 has elapsed, the control device CU stops the drive source of each photoconductor PC and ends the toner supply operation.

<Effect>
Next, effects of the present embodiment will be described with reference to the drawings.

  For example, as in Comparative Example 2 described below, when the same amount of toner is supplied (assuming the same toner supply coefficient k) to perform the polishing operation regardless of the charging ability α of each photoconductor PC during the toner supply operation ( 12), each photoconductor PC has a different service life and has a different life (see the result of Comparative Example 2 in FIG. 13), and each monochrome unit 31 is replaced at a different replacement time (see FIG. 7).

  On the other hand, in the case of the present embodiment, during the toner supply operation, the supply amount of the toner supplied to each photoconductor PC is determined based on the charging ability α of each photoconductor PC (FIGS. 5 and 6). reference). Specifically, the lower the charging ability α of the photoconductor PC, the smaller the toner supply amount. Therefore, the lower the charging ability α of the photoconductor PC, the more difficult it is to remove the photoconductor PC.

  Therefore, in the image forming apparatus 10 of the present embodiment, when the plurality of photoconductors PC have at least two or more combinations of the charging abilities α, the difference in the replacement time (lifetime) of the plurality of photoconductors PC can be reduced ( 9 and 13). In this case, by adjusting the toner supply amount, it is possible to reduce the difference in the replacement time (life) of the plurality of photoconductors PC while reducing the amount of toner consumption during the toner supply operation. The use of the charging roller 32A as in the present embodiment is considered to be effective because, for example, the film thickness of the photoconductor PC is larger than that of a case where the charging device is a scorotron type. Further, as in the present embodiment, when the photoconductor PC is a single-layer type organic photoconductor, the photoconductor PC is considered to be effective because the film reduction speed of the photoconductor PC is larger than that in the case of a stacked organic photoconductor. .

  Further, in the case of the present embodiment, the longer the drive time (rotation time) of the photoconductor PC at the time of forming the toner image, the more toner is supplied from each development device 36 to each photoconductor PC, and the toner supply operation is performed. Therefore, in the case of the present embodiment, the photoconductor PC can be more appropriately shaved than when the toner amount is constant regardless of the drive time of the photoconductor PC at the time of forming a toner image.

  In the case of the present embodiment, the charging ability α of each photoconductor PC is measured before the product is shipped and stored in the storage unit MR. Therefore, in the case of the present embodiment, it is not necessary to measure the charging ability α of each photoconductor PC during the toner supply operation. That is, in the case of the present embodiment, the toner supply operation can be performed without the time for measuring the charging ability α of each photoconductor.

<Study by Example and Comparative Example>
Next, an experiment using an example of the present embodiment and a comparative example will be described.

[Conditions of Examples and Comparative Examples]
FIG. 11 shows the charging ability α of the photoconductor PC (photoconductors 1 to 4) used in the embodiment and the toner supply coefficient k. 12 and 13 show the charging ability α of the photoconductor PCs (photoconductors 1 to 4) used in the comparative examples (comparative examples 1 and 2) which are different from the conditions of the present embodiment, and the toner supply coefficient. k.

[Experiment Details]
The photoconductors 1 to 4 of the embodiment and comparative examples (Comparative Examples 1 and 2) were attached to an FS-C5030 (A4 color printer manufactured by Kyocera Document Solutions Co., Ltd.), and ten sheets were printed during one toner image forming operation. Was performed for 200,000 sheets, and the abrasion amount of each photoconductor of the example and the comparative example was measured.

  Here, the charging roller used had a diameter of 12 mm and was made of rubber mainly composed of epichlorohydrin rubber. Further, a cleaning blade made of a rubber containing urethane rubber as a main component was used. Further, each photoreceptor was charged with 5 parts by mass of a charge generating agent (metal-free phthalocyanine), 50 parts by mass of a hole transporting agent, 35 parts by mass of an electron transporting agent, and 100 parts by mass of a binder resin (viscosity average molecular weight 67000) with tetrahydrofuran. A photoreceptor coating solution prepared by mixing and dispersing with 800 parts by mass in a ball mill for 50 hours is applied on a conductive substrate (aluminum tube) by dip coating, and then dried with hot air at 100 ° C. for 40 minutes. A photosensitive layer having a thickness of 36 μm (diameter 30 mm) was used.

〔result〕
In Comparative Example 1, the photoreceptor 3 having a low charging ability α had a large amount of wear, and reached its end of life early. Further, in Comparative Example 2, although the abrasion amount was small with the photoreceptor 4 having the high charging ability α, the toner supply amount became excessive and the toner consumption was accelerated. On the other hand, in the example, the abrasion amounts of the respective photoconductors were equal (the difference was small) as compared with the comparative examples 1 and 2, and both the life and the reduction of the toner consumption could be realized.

  As described above, the present invention has been described with the above embodiment as an example, but the technical scope of the present invention is not limited to the above embodiment. For example, the technical scope of the present invention includes the following embodiments.

  For example, in the present embodiment, an example of the photoconductor PC has been described as a single-layer organic photoconductor. However, the photoconductor PC may be a stacked organic photoconductor.

  Further, in the present embodiment, the charging ability α of each photoconductor PC is measured and stored in the storage unit MR before the product is shipped, and in the toner supply operation, based on the charging ability α stored in the storage unit MR. It was explained that it was performed. However, for example, as in the first modification of FIG. 14, after the toner image forming operation (after step S30) and before step S40, the charging capability α is measured using each single-color unit 31 (step S35). The toner supply amount may be determined based on the charging ability α. In this case, it is effective in that the toner supply amount can be adjusted more in accordance with the use situation.

  In the present embodiment, the toner supply operation has been described as being performed after the toner image forming operation. However, when the number of printed sheets in one toner image forming operation is large, for example, when the operation takes a time longer than a predetermined time, as shown in the second modification of FIG. , The toner supply operation may be interrupted once, and the remaining toner image forming operation may be resumed. In this case, it can be said that the toner supply operation can be performed at an appropriate timing even when the number of printed sheets in one toner image forming operation is large.

  In the present embodiment, in the toner supply operation, the toner supply amount is a rectangular solid image whose one side is a toner band width x derived from a toner supply coefficient k which is a function of the charging ability α of each photoconductor PC. (See FIG. 6). However, the toner supply amount may be derived based on each charging ability α. For example, as in the third modification example of FIG. 16, a solid image having basically the same area may be used, and the density of the solid image may be changed according to the difference in the amount of supplied toner.

  Further, it has been described that the toner supply coefficient k of the present embodiment is determined using the linear function of Equation 3 described above (see FIG. 5). However, the toner supply coefficient k need not be a linear function of Equation 3 as long as the function decreases as the charging ability α increases. For example, a relational expression in which k is proportional to 1 / α (k is inversely proportional to α) may be used as in the fourth modification example of FIG.

10 Image Forming Apparatus 30 Toner Image Forming Unit (Example of Plural Toner Image Forming Apparatus)
31 Single Color Unit (Example of Toner Image Forming Apparatus)
32 Charging device 32A Charging member 36 Developing device 38 Cleaning blade 40 Transfer device CU Control device PC Photoconductor (an example of a carrier)
MR storage unit S Medium α Charging ability

Claims (5)

A carrier that rotates around an axis and carries a latent image, a charging device that charges the carrier, an exposure device that exposes the carrier charged by the charging device to form a latent image, and toner of each color. A developing device that develops the latent image as a toner image of each color, and a plurality of toner image forming apparatuses each including a removing unit that removes residual toner remaining on the carrier without being transferred in contact with the carrier,
A transfer device for transferring a toner image of each color developed on the carrier in each of the plurality of toner image forming devices to a medium,
A control device for controlling the plurality of toner image forming devices and the transfer device;
With
In the case where a value obtained by dividing the surface potential by a current flowing through the carrier in order to bring the carrier to a predetermined surface potential is defined as charging ability, the plurality of carriers have at least two or more levels of charging ability. And the combination
After the toner image forming operation, the control device causes the developing device to supply more toner from the developing device to the carrier as the toner image forming device having the carrier having the lower charging ability, and the carrier is set for a predetermined period of time. There rows toner supply operation of rotating around,
The plurality of toner image forming apparatuses have a storage unit that stores the charging ability measured before shipment of a product in each of the carriers,
The control device determines an amount of toner to be supplied from the developing device to the carrier during the toner supply operation, based on the charging ability stored in each of the storage units.
Image forming device. The control device performs the toner supply operation by supplying more toner from the developing device to the carrier as the rotation time of the carrier in the toner image forming operation is longer,
The image forming apparatus according to claim 1. If the control device requires a time equal to or longer than a time determined during the toner image forming operation, the control device interrupts the toner image forming operation, performs the toner supply operation, and restarts the toner image forming operation again.
The image forming apparatus according to any one of claims 1 or 2. The charging device is configured to include a charging member that discharges while contacting the carrier and charges the carrier.
The image forming apparatus according to any one of claims 1-3. The carrier is a single-layer organic photoconductor,
The image forming apparatus according to any one of claims 1-4.

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