JP2007233377A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and its control method that reduce a retransfer phenomenon of toner without scattering and without a decrease in dot reproducibility by charging the order of image formation according to the use state of a developing unit. <P>SOLUTION: The image forming apparatus includes an image carrier 1 for forming an image, a transfer means of forming images of respective colors on the image carrier one after another by using a plurality of developing units 4 having developers of the different colors and transferring the images of the respective colors formed on the image carrier to a transfer body 11 or recording medium, and a control means of switching the order of formation of the images on the image carrier using the plurality of developing units according to use amounts of the plurality of developing units. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an image forming apparatus capable of changing the order of image formation and a control method thereof.

  In a color image forming apparatus that forms a color image on a transfer material by superimposing a plurality of color toner images, an electrostatic latent image is formed on an image carrier, and this is successively developed with toner and transferred each time. There is a method of transferring onto a material and superimposing a plurality of color toner images. There is also a method in which a plurality of toner images are superposed on an intermediate transfer member and these are collectively transferred onto a transfer material. However, both methods cause a phenomenon in which the toner transferred onto the transfer material or the intermediate transfer member is transferred to the photosensitive member (hereinafter referred to as “retransfer phenomenon”).

  This retransfer phenomenon is caused by a toner having a small amount of charged charge among transferred toners, a toner charged to a reverse charge due to a discharge phenomenon at a position where a toner image is transferred (also referred to as a transfer nip) or a transfer current. Is generated by transfer to the photosensitive member by electrostatic force or van der Waals force.

  Examples of the influence on the image due to the retransfer phenomenon include a decrease in image density and a decrease in image density uniformity.

  The influence on the image due to the retransfer phenomenon increases with an increase in the amount of use of the developing device (or developing cartridge) (number of prints, driving time of the developer carrying member, etc.). The reason for this is that as the usage amount of the developing device (or developing cartridge) increases, embedding of the external additive into the toner base, liberation of the external additive from the toner base, etc. occur, which contributes to improvement in toner fluidity. This is because the amount of the external additive on the toner surface decreases. As a result, as the toner fluidity decreases, the toner chargeability decreases, and the retransfer phenomenon is likely to occur.

  The following examples exist as a method for reducing the influence on the image due to the retransfer phenomenon.

  For example, density data of all pixels for one page of the document is integrated for each reproduction color (for each color of yellow, magenta, cyan, and black) from the document image data, and images are formed in ascending order from a color with a small integrated value. (For example, refer to Patent Document 1). The above system can reduce the influence on the image due to the retransfer phenomenon. The reason will be explained. For example, the toner first transferred from the photosensitive member onto the transfer member or to the recording medium has an opportunity to retransfer three times. On the other hand, the toner finally transferred from the photosensitive member onto the transfer member or to the recording medium has no chance of retransfer phenomenon. In other words, the opportunity for occurrence of the retransfer phenomenon increases as the order of image formation increases. Therefore, if the image formation is performed in the order from the smallest amount of toner transferred onto the transfer body or the recording medium, it is possible to reduce the influence on the image due to the retransfer phenomenon.

In addition, by removing the charge on the surface of the photoconductor before the photoconductor enters the transfer nip, the potential difference between the photoconductor surface and the intermediate transfer belt or transfer material is reduced, and the transfer current and discharge amount in the transfer nip are reduced. There is a known method for reducing the retransfer phenomenon by reducing the amount of reversely charged toner. For example, see Patent Document 2.
JP 2000-330354 A JP-A-5-165383

  However, the prior art has the following problems. In the invention of Patent Document 1, images are formed in ascending order from a color having a small integrated value of density data of all pixels. However, if the amount of the developing device (or developing cartridge) that forms an image first is large, the image may be affected by the retransfer phenomenon. The above-mentioned influence on the image due to the retransfer phenomenon is remarkable when an image in which image data is locally concentrated is printed.

  In the invention of Patent Document 2, the re-transfer phenomenon can be greatly reduced by exposure of the photosensitive member before transfer, but there are effects on other images such as scattering due to exposure before transfer and reduction of dot reproducibility.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus and a control method therefor that can reduce a toner retransfer phenomenon without causing scattering and a decrease in dot reproducibility. .

  In order to achieve the above object, the present invention has the following configuration.

  (1) An image carrier for forming an image and a plurality of developing devices having developers of different colors are used to sequentially form images of each color on the image carrier, and each color formed on the image carrier The order of forming the image on the image carrier using the plurality of developing units is switched based on the usage of each of the plurality of developing units and the transfer means for transferring the image on the transfer body or the recording medium An image forming apparatus comprising: a control unit;

  (2) An image carrier for forming an image and a plurality of developing units having developers of different colors are used to sequentially form images of each color on the image carrier, and each color formed on the image carrier. The plurality of developments based on transfer means for transferring the image on the transfer body or the recording medium, the remaining amount of the developer in the plurality of developing units, and the usage amount of the plurality of developing units, respectively. An image forming apparatus comprising: a control unit that switches a sequence of forming an image on the image carrier using a container.

  (3) Using a plurality of developing devices having different color developers, images of the respective colors are formed on the image carrier in a first order, and the images of the respective colors formed on the image carrier are transferred onto a transfer member or a recording medium. A first image forming mode to be transferred to the image forming unit and images of the respective colors are formed on the image carrier in an order different from the first order, and the images of the respective colors formed on the image carrier are transferred to a transfer member or a recording medium. A second image forming mode, and a method for detecting a usage amount of each of the plurality of developing devices, and according to a detected usage amount of each of the plurality of developing devices. And a control step of switching from the first image mode to the second image forming mode.

  By providing the above configuration, the present invention can provide an image forming apparatus and a control method therefor that can reduce the toner re-transfer phenomenon without causing scattering and a decrease in dot reproducibility.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  A first embodiment of an image forming apparatus according to the present invention will be described. First, the overall configuration of the image forming apparatus will be described with reference to FIG. The image forming apparatus shown in FIG. 1 is a color printer that uses an electrophotographic system and adopts an intermediate transfer system.

  The image forming apparatus shown in FIG. 1 has a photoreceptor 1 as an image carrier and is driven to rotate in the direction indicated by the arrow. The surface of the photoreceptor 1 is negatively charged by the charging roller 2 and is uniformly charged to −600V. The exposure optical system 3 irradiates the surface of the photoreceptor 1 with scanning light whose emission is controlled based on image data, and removes negative charges to form a latent image. The potential of the latent image portion is approximately −100V. This latent image is developed in the order determined by the amount of use of the developing cartridge by each color developing device (hereinafter referred to as “developing cartridge”) 4y, 4m, 4c, 4k. Each of the developing cartridges 4y, 4m, 4c, and 4k contains toner that is a developer of each of yellow, magenta, cyan, and black, and is attached to the rotary 5. The developing cartridges 4y, 4m, 4c, and 4k are opposed to the photosensitive member 1 when the rotary 5 revolves every 90 degrees, develop the latent image on the photosensitive member 1 with toner of each color, and sequentially develop the images of each color. Form. The toner comprises a toner base containing a binder resin, a colorant, a charge control agent, and the like, and an external additive that is externally added to the base. The toner is a non-magnetic one component. FIG. 1 shows a state in which the yellow developing cartridge 4y is arranged at the developing position.

  Next, the developing cartridge will be described with reference to FIG. The developing cartridge is a developing cartridge in which a developing roller 6 that carries toner, a toner supply roller 7, a developing blade 8, and the like are integrated into a unit. The developing cartridge (each developing device) is configured to be detachable from the image forming apparatus main body. The developing cartridge includes a storage unit 17 capable of storing various information.

  Data is written to and read from the storage unit 17 by a signal processing unit provided in the main body of the image forming apparatus. The storage unit 17 stores usage amount information such as the number of prints from the initial use of the developing cartridge and the accumulated time of the developing roller driving time.

  A constant amount of negatively charged toner is supplied onto the developing roller 6 facing the photoreceptor 1, and a developing bias is applied to the developing roller 6 by a power source (not shown). The developing bias sets a potential difference between the charging potential and the latent image (exposed portion) potential to an appropriate value, so that a stable print image can be obtained regardless of the environment and the usage status of the developing cartridge.

Thereafter, the toner image developed on the photosensitive member 1 is sequentially primary transferred onto the intermediate transfer belt 11 as an intermediate transfer member at a primary transfer nip portion which is a primary transfer position. The intermediate transfer belt 11 is stretched by a roller 16, a driving roller 13, and a tension roller 14 that are disposed opposite to a secondary transfer roller 12 as a secondary transfer unit, and is at a substantially constant speed with the photoreceptor 1 in the direction indicated by the arrow. Rotate. The secondary transfer roller 12 is disposed so as to be in contact with and separated from the intermediate transfer belt 11. The secondary transfer roller 12 is normally separated from the intermediate transfer belt 11, but is in contact with the intermediate transfer belt 11 when performing a secondary transfer process described later. As the intermediate transfer belt 11, a resin film belt such as PVDF, polyamide, polyimide, PET, nylon, or polycarbonate having a thickness of about 50 μm to 300 μm and a volume resistivity of about 10 ⁻¹² Ωcm to 10 ⁻⁷ Ωcm can be used. Further, a rubber belt or the like in which a high resistance resin layer having a good releasability with a thickness of several tens of μm is provided on a low resistance rubber base layer having a thickness of about 0.5 to 2 mm can be used. The resistance value of the intermediate transfer belt 11 can be adjusted with carbon, ZnO, SnO ₂ , TiO ₂ or other conductive fillers. A primary transfer bias of positive polarity is applied to the primary transfer roller 10 by a power source. The primary transfer bias value is subjected to constant voltage control. The voltage value applied at the time of image formation takes into consideration the resistance fluctuations of the primary transfer roller 10 and the intermediate transfer belt 11 due to factors of the environment and usage conditions, and the primary transfer voltage value at which a desired primary transfer current value is obtained before the transfer operation. It is decided by detecting.

  The primary transfer residual toner remaining on the surface of the photoreceptor 1 after the primary transfer process is removed by the cleaning blade 9 having an elastic blade and is stored in the waste toner container 15.

  When the primary transfer process is completed and the formation of a full-color or single-color image on the intermediate transfer belt 11 is completed, the secondary transfer roller 12 that has been separated from the intermediate transfer belt 11 is brought into contact with the intermediate transfer belt 11. Then, a transfer material as a recording medium is conveyed from the paper feed cassette to a secondary transfer nip portion that is a secondary transfer position. A positive polarity bias (+1 kv) is applied to the secondary transfer roller 12 from the secondary transfer bias power source, and the toner image on the intermediate transfer belt 11 is secondarily transferred collectively onto the transfer material. The transfer material carrying the four color toner images on the surface through the secondary transfer process is conveyed to a fixing device, where the toner image on the surface is fixed and image formation is completed.

  Next, the mechanism of the retransfer phenomenon will be described.

  FIG. 3 is an enlarged explanatory view of the primary transfer nip portion, and the retransfer phenomenon will be described using this. Assume that image formation is basically performed in the order of yellow, magenta, cyan, and black. The yellow toner image transferred to the intermediate transfer belt may cause a retransfer phenomenon in the primary transfer process (magenta, cyan, black) for the second and subsequent colors. In FIG. 3, for example, a case where the primary transfer process of the magenta toner image 23 is performed will be described. During the primary transfer process of the magenta toner image 23, a part of the yellow toner 22 on the intermediate transfer belt is transferred to the photoreceptor 1. This transferred toner 24 is called retransfer toner. This re-transfer phenomenon is considered to transfer positive polarity (positive polarity) and weak negative polarity (weak negative polarity) toner to the photoreceptor 1 by electrostatic force, van der Waals force, or the like.

The retransfer toner 24 is
(1) Toner having a small charge amount among yellow toners 22 on the intermediate transfer belt (2) Toner having a charge amount decreased due to discharge or transfer current at the transfer nip position or charged to the opposite charge It is considered.

  FIG. 4 shows the transfer current dependency of the amount of retransfer toner in an initial use state, a development cartridge printed with 3,500 sheets (5% printing), and a development cartridge printed with 7,000 sheets (5% printing).

  Here, the measurement method and definition of the retransfer toner amount will be described. During the primary transfer process for the second color (magenta), the main body power supply of the image forming apparatus is turned off to stop the driving of the photosensitive member 1. On the photoreceptor 1 that has been stopped, there exists retransfer toner in which a part of the yellow toner on the intermediate transfer belt has been transferred to the photoreceptor 1. The retransfer toner is transferred onto an adhesive tape and adhered to white recording paper. The difference in reflection density obtained by subtracting the reflection density (Macbeth density) of the reference tape to which no toner is attached from the reflection density (Macbeth density) of the tape was defined as the retransfer toner amount.

  Regardless of the color of the toner contained in the developing cartridge, when the primary transfer current of all colors is increased (that is, when the primary transfer bias is increased), the amount of retransfer toner increases. This is presumably because the discharge amount and the primary transfer current in the transfer nip increased by increasing the primary transfer voltage as described above.

  Further, it was obtained that the retransfer toner amount increases as the number of printed sheets increases. This is because the amount of external additive on the toner surface that contributes to the improvement in toner fluidity is increased by the friction of the toner when the usage amount of the developing cartridge (the number of printed sheets, the driving time of the developer carrier, etc.) increases. This is because it decreases.

  As a target value of the retransfer toner amount for each color, the total retransfer toner amount is preferably 0.2 or less. The total retransfer toner amount is a total value of three retransfer toner amounts (Macbeth density) generated in the primary transfer process for the second and subsequent colors in the case of the first color, and the third color in the case of the second color. This is the total value of the retransfer toner amount (Macbeth density) for two times generated in the subsequent primary transfer process.

  The primary transfer current during actual image formation is 8.7 μA. When the primary transfer current is 8.7 μA, when 7000 sheets are printed, the amount of retransfer toner in one transfer process is 0.11, and when it is retransferred three times, it is about 0.33. This is far more than 0.2. Therefore, in this embodiment, the total retransfer toner amount is reduced by selecting a developing cartridge with a small number of prints as the first color having three retransfer opportunities.

  Next, a method for determining the order of image formation (mode determination method) will be described. In the toner contained in the developing cartridge (inside the developing device), the decrease in the amount of external additive on the toner surface that contributes to the improvement in toner fluidity is caused by the cumulative number of prints when the printing rate of all colors is almost the same. It is thought that it depends. For this reason, in this embodiment, the order of image formation is performed in ascending order of the total number of printed sheets from the initial use of the developing cartridge.

  Hereinafter, the printing operation of this embodiment will be described with reference to FIGS.

  FIG. 5 is a block diagram illustrating a control system according to the first embodiment. FIG. 6 is a flowchart of image formation according to the first embodiment.

  The image forming apparatus detects a print signal (step 1).

  The main body of the image forming apparatus has a reading means for reading the number of prints stored in the storage means of the developing cartridge. The CPU 18 of the image forming apparatus transfers the information on the number of prints of the developing cartridge stored in the storage means of the developing cartridge from the reading / writing means 19 of the main body of the image forming apparatus to the calculating means 20 (Step 2).

  The calculating means 20 determines the order in which image forming operations are performed from the number of prints called from the storage means of each developing cartridge (step 3).

  The CPU 18 controls the drive unit 21 of the rotary 5 to form an image in the order determined by the calculation unit 20. The photosensitive member 1 is rotationally driven, and an image forming operation is started in the order determined in Step 3 (Step 4).

  After the job is completed, the number of prints of each developing cartridge detected by the print number detecting means 25 is written in the storage means 17 of the developing cartridge, and the number of prints is updated (step 5).

  For example, consider a case where the usage amount of each developing cartridge is yellow (7000 prints), magenta (3500 prints), cyan (new), and black (7000 prints). FIG. 7 shows the retransfer toner amount when a single color 100% image (also referred to as solid black) is output without changing the order of image formation, and FIG. 8 shows the changed case. As can be seen from the drawing, the image formation order of yellow (Y), magenta (M), cyan (Cy), and black (Bk) is changed to cyan (Cy), magenta (M), yellow (Y), Change to black (Bk) order. By changing the color order for image formation in this way, the total color retransfer toner amount can be made 0.2 or less of the target value.

  In this embodiment, the order of image formation is determined based on the number of prints. However, when it is desired to eliminate factors such as the size of the print size, the order of image formation is determined based on the accumulated developing roller driving time from the initial use. You may do it.

  In this embodiment, an intermediate transfer type image forming apparatus is used. However, the image forming apparatus is not limited to the intermediate transfer type image forming apparatus, and a direct transfer type in which direct transfer is performed on a recording sheet conveyed on a conveyance belt. I do not care.

  Although the retransfer toner amount is evaluated by the reflection density of the adhesive tape, the retransfer toner amount may actually be determined by the weight of the retransfer toner on the photoreceptor 1.

  In this embodiment, the image forming operation is performed in ascending order of the number of accumulated prints as the usage amount of the developing cartridge. However, the order of image formation by a specific developing cartridge may be fixed and the order of other developing cartridges may be changed in consideration of fixing properties, toner mixing into the developing cartridge, and the like. In this embodiment, the retransfer toner amount depends on the number of prints. However, when the retransfer toner amount is different for each color, the order of image formation may be considered in consideration of the color difference.

  In this embodiment, the primary transfer current value is set to 8.7 μA for all colors regardless of the usage state of the developing cartridge. However, the primary transfer current value can be set to a large value within a range where the retransfer phenomenon does not increase in consideration of the case where the transferability is greatly reduced when the usage amount of the developing cartridge is increased.

  Further, the order of image formation may be switched and the image formation conditions may be changed together. For example, the primary transfer current values set after changing the order to cyan (Cy), magenta (M), yellow (Y), and black (Bk) are yellow (Y), magenta (M), cyan (Cy), black ( Bk) may be set to a value different from the primary transfer current value in the case of the image formation order.

  A second embodiment of the image forming apparatus according to the present invention will be described. In the first embodiment, the number of printed sheets is used as the usage amount of each developing cartridge in order to determine the order of image formation of the developing cartridge. When the printing rate of all the developing cartridges is substantially constant, a correlation is obtained between the decrease in the amount of the external additive on the toner surface that contributes to the improvement in toner fluidity and the number of printed sheets. However, the decrease in the amount of the external additive on the toner surface that contributes to the improvement in toner fluidity is promoted as the toner amount in the developing cartridge decreases. This is because when the amount of toner in the developing cartridge is small, the chance that the same toner is rubbed against the developing blade, the toner supply roller, and the photosensitive member increases as compared to when the amount of toner is large. As a result, when the amount of toner in the developing cartridge is small, a reduction in the amount of external additive on the toner surface that contributes to improvement in toner fluidity is promoted.

  For example, two cases in which 3000 images with different printing rates are printed are taken as an example.

  (1) When 3000 images with a printing rate of 5% are printed.

  (2) When printing 600 images with a printing rate of 50% and printing images with a printing rate of 1% from the 601st sheet to the 3000th sheet.

  Comparing (1) and (2), the total number of printed sheets is the same for 3000 sheets, but the amount of toner in the developing cartridge at the end of printing 3000 sheets is greatly different. In the case of (2), the amount of toner in the developing cartridge is very small at the time when 600 sheets are printed, and the subsequent printing operation reduces the amount of external additive on the toner surface that contributes to improvement in toner fluidity. It is promoted more than in the case of (1).

  In this embodiment, in order to cope with such a situation, an index value A is introduced as an index value that can be correlated with a decrease in the amount of the external additive on the toner surface that contributes to an improvement in toner fluidity. The image forming order of the developing cartridge is determined by the calculated index value A.

  Next, a method for calculating the index value A will be described. The decrease in the amount of the external additive on the toner surface that contributes to the improvement in toner fluidity is promoted as the toner amount in the developing cartridge is decreased, and is reduced as the toner amount in the developing cartridge is increased.

  The index value A relating to the decrease in the amount of the external additive indicates the amount of decrease in the external additive present on the toner surface that contributes to the improvement in toner fluidity. Specifically, the values indicate the amount of the external additive embedded in the toner base and the amount of the external additive released from the toner base.

According to the study of the present inventors, the decrease in the amount of external additive on the toner surface that contributes to the improvement in toner fluidity is
Driving time of developing roller 6 × constant T (Formula 1)
Therefore, the integrated value from the initial use of Equation 1 is defined as the index value A.

  Here, the constant T in Equation 1 is a constant determined so as to obtain a correlation between the index value A and the amount of the external additive on the toner surface that contributes to improvement in toner fluidity.

  The constant T depends on the amount of toner in the developing cartridge, and if the amount of toner is small, a decrease in the amount of external additive on the toner surface that contributes to improvement in toner fluidity is promoted, so that the constant T is set to a large value. .

  In this embodiment, the usable toner amount (toner amount accommodated in the unused state) when the developing cartridge is unused is 300 g. A table of the toner amount in the developing cartridge and the constant T is shown in FIG. Further, the toner remaining amount detecting means in the developing cartridge performs capacitance type sequential remaining amount detection. This method is a known method for detecting the amount of toner in the developing cartridge by detecting the capacitance between a plurality of electrodes arranged in the developing cartridge, and detailed description thereof is omitted. To do.

  As a remaining toner (developer remaining amount) detection method, an optical detection method using a light transmission time using a light emitting element and a light receiving element, a torque detection method, and the number of pixels of image data are counted. A pixel count method or the like may be used.

  Hereinafter, the printing operation of this embodiment will be described with reference to FIGS.

  FIG. 10 is a block diagram illustrating a control system according to the second embodiment. FIG. 11 is a flowchart of image formation according to the second embodiment.

  The image forming apparatus detects a print signal (step 6).

  The CPU 18 of the image forming apparatus updates the index value A (updated after completion of image formation (step 10)) stored in the storage means 17 of the developing cartridge from the read / write means 19 of the main body of the image forming apparatus. (Step 7).

  The calculating means 20 determines the order in which the image forming operation is performed from the index value A that is read from the storage means 17 of each developing cartridge (step 8).

  The CPU controls the drive unit 21 of the rotary 5 to form an image in the order determined by the calculation unit 20. Detection of the driving time of the developing roller 6 is started by the driving time detecting means 26 of the developing roller 6. The photosensitive member 1 is rotationally driven, and the image forming operation is started in the order determined in Step 3. The remaining amount of toner is detected during image formation (step 9).

  After completion of the job, the value of Expression 1 (developing roller 6 driving time × constant T) is calculated from the detection results of the driving time detection means 26 of the developing roller 6 and the remaining toner amount detecting means. A value obtained by adding the value of Expression 1 to the index value A called in Step 7 is written as the index value A in the storage means 17 of the developing cartridge and updated (Step 10).

  FIG. 12 shows the retransfer toner amount when image formation is performed by determining the order of image formation based on the index value A when the usage state (printing rate and number of prints) of the developing cartridges for each color is different. Show.

  FIG. 13 shows the retransfer toner amount when image formation is performed in the order of decreasing the total number of printed sheets in the usage state of the developing cartridge.

  Comparing FIG. 12 and FIG. 13, according to the present embodiment, the retransfer toner is different from the case where the order is determined by the total number of prints by changing the order of image formation according to the index value A of the developing cartridge. It was confirmed that the amount could be reduced.

  According to this embodiment, it is possible to perform image formation in consideration of variations in the amount of decrease in the external additive due to the difference in the print printing rate between the developing cartridges.

  In this embodiment, the difference due to the environment of the image forming apparatus is not taken into consideration, but the constant T may be changed depending on the environment (temperature and humidity conditions) in which the image forming apparatus is placed as well as the remaining amount of toner. I do not care.

  In this embodiment, as in the first embodiment, the primary transfer current value is set to 8.7 μA for all colors regardless of the usage state of the developing cartridge. However, the primary transfer current value can be set to a large value within a range where the retransfer phenomenon does not increase in consideration of the case where the transferability is greatly reduced when the usage amount of the developing cartridge is increased.

  Similarly to the first embodiment, the image forming order may be switched and the image forming conditions may be changed. For example, the primary transfer current values set after changing the order to cyan (Cy), magenta (M), yellow (Y), and black (Bk) are yellow (Y), magenta (M), cyan (Cy), black ( Bk) may be set to a value different from the primary transfer current value in the case of the image formation order.

  In the image forming apparatus of the present embodiment, a four-cycle color printer in which four developing cartridges are mounted on the rotary 5 is used. However, the present invention is not limited to this. For example, as an example of another four-cycle image forming apparatus, there is an image forming apparatus using an intermediate transfer member in which four developing cartridges are mounted on the outer periphery of a photosensitive member. In this image forming apparatus, it is possible to select a developing cartridge that forms an image only by changing the high voltage applied to the input terminal of each developing cartridge while the developing cartridge is fixed.

  The image forming apparatus according to the present invention is not limited to a four-cycle color image forming apparatus, and an intermediate transfer belt is used as long as the contact and separation between the photosensitive member and the intermediate transfer belt can be switched. A tandem image forming apparatus may be used.

1 is an overall configuration explanatory diagram illustrating an image forming apparatus according to a first exemplary embodiment. FIG. 3 is a schematic cross-sectional view illustrating a developing cartridge of Example 1. It is a schematic diagram of the generation mechanism of retransfer. FIG. 6 is a diagram illustrating the transfer current dependency of the retransfer toner amount according to the first exemplary embodiment. 2 is a block diagram illustrating a control system in Embodiment 1. FIG. 3 is a flowchart of a printing operation according to the first exemplary embodiment. 6 is a diagram illustrating a retransfer toner amount when the color order of image formation is not changed in Embodiment 1. FIG. FIG. 6 is a diagram illustrating a retransfer toner amount when the color order of image formation is changed in the first exemplary embodiment. 6 is a diagram illustrating a correlation between a toner amount and a constant T in Example 2. FIG. 6 is a block diagram illustrating a control system in Embodiment 2. FIG. 10 is a flowchart of a printing operation according to the second embodiment. FIG. 10 is a diagram illustrating the retransfer toner amount of each developing cartridge in Example 2. FIG. 10 is a diagram illustrating a retransfer toner amount when image formation is performed in order of the number of prints in the second embodiment.

Explanation of symbols

1 Photoconductor (corresponding to image carrier)
2 Charging roller 3 Exposure optics 4 Developing cartridge (corresponding to developing unit)
5 Rotary 6 Developing roller 7 Toner supply roller 8 Developing blade 9 Cleaning blade 10 Primary transfer roller 11 Intermediate transfer belt (corresponding to transfer body)
12 Secondary transfer roller 13 Driving roller 14 Tension roller 15 Waste toner container 16 Roller 17 disposed opposite to the secondary transfer roller Storage means 18 CPU
19 Reading / Writing Unit 20 Arithmetic Unit 21 Rotary Driving Unit 22 Intermediate Transfer Belt Yellow Toner 23 Magenta Toner 24 Retransfer Toner 25 Printed Number Detection Unit 26 Developing Roller Driving Time Detection Unit

Claims (11)

An image carrier for forming an image;
Transfer means for sequentially forming images of the respective colors on the image carrier using a plurality of developing devices having different color developers, and transferring the images of the respective colors formed on the image carrier to a transfer member or a recording medium; ,
Control means for switching the order in which images are formed on the image carrier using the plurality of developing devices based on the usage amounts of the plurality of developing devices;
An image forming apparatus comprising: Having a detecting means for detecting the usage amount of each of the plurality of developing devices;
The control means switches the order of forming an image on the image carrier using the plurality of developing devices based on the usage amounts of the plurality of developing devices detected by the detecting means. The image forming apparatus according to claim 1. Detecting means for detecting the amount of use of each of the plurality of developing devices;
Each of the plurality of developing devices has storage means for storing information,
The image forming apparatus according to claim 1, wherein the control unit stores usage amounts of the plurality of developing units detected by the detection unit in respective storage units of the plurality of developing units. The developing device has a developer carrier for conveying the developer to the image carrier,
2. The image forming apparatus according to claim 1, wherein the means for detecting the usage amount of each developing device is a means for detecting the number of printed sheets or a means for detecting the driving time of the developer carrier.   The plurality of developing devices are developers that contain yellow, magenta, cyan, and black developers, and the control unit determines the order of image formation by the developing devices that contain yellow, magenta, and cyan developers. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched. An image carrier for forming an image;
Transfer means for sequentially forming images of the respective colors on the image carrier using a plurality of developing devices having different color developers, and transferring the images of the respective colors formed on the image carrier to a transfer member or a recording medium; ,
The order of forming an image on the image carrier using the plurality of developing devices is switched based on the remaining amount of developer in each of the plurality of developing devices and the usage amount of each of the plurality of developing devices. Control means;
An image forming apparatus comprising: A usage amount detecting means for detecting a usage amount of each of the plurality of developing devices;
A remaining amount detecting means for detecting the remaining amount of developer in each of the plurality of developing devices,
The control means includes a remaining amount of developer in each of the plurality of developing devices detected by the usage amount detecting means, and a usage amount of each of the plurality of developers detected by the remaining amount detection means. The image forming apparatus according to claim 6, wherein the order of forming images on the image carrier is switched using the plurality of developing units. The developer has a developer carrier;
The usage amount detecting means is means for detecting a driving time of a developer carrier of the developing device;
8. The control unit according to claim 7, wherein the control unit switches the order of forming an image on the image carrier based on the driving time and the remaining amount of developer detected by the remaining amount detecting unit. Image forming apparatus.   The plurality of developing devices are developers that contain yellow, magenta, cyan, and black developers, and the control unit determines the order of image formation by the developing devices that contain yellow, magenta, and cyan developers. The image forming apparatus according to claim 6, wherein the image forming apparatus is switched. A plurality of developing devices having different color developers are used to form images of each color on the image carrier in a first order, and the images of each color formed on the image carrier are transferred to a transfer body or a recording medium. A first image forming mode and a second image in which an image of each color is formed on the image carrier in an order different from the first order, and an image of each color formed on the image carrier is transferred to a transfer body or a recording medium. An image forming mode, and an image forming apparatus control method comprising:
Detecting each usage amount of the plurality of developing devices;
A control step of switching from the first image mode to the second image forming mode in accordance with the detected amount of use of each of the plurality of developing devices;
A control method for an image forming apparatus, comprising: And a step of detecting a remaining amount of developer in the plurality of developing devices,
In the control step, the first image mode is changed to the second image forming mode in accordance with the detected usage amounts of the plurality of developing devices and the detected remaining amounts of developer in the plurality of developing devices. The method of controlling an image forming apparatus according to claim 10, wherein the method is a switching step.

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