JP2021196523A - Image forming apparatus and image forming method - Google Patents

Abstract

To provide an image forming apparatus that can supply a necessary amount of toner to a contact part of a cleaning blade and an image carrier surface and thereby can maintain cleaning performance.SOLUTION: An image forming apparatus comprises: an image carrier 21 that has an image carrier surface 21a for carrying a toner image formed with an electrified toner; a transfer device 24 that applies an electric charge having a polarity opposite to that of the electrified toner through a sheet-like medium S to transfer the toner image on the image carrier surface to the sheet-like medium; a cleaning device 26 that scrapes off and removes, with a cleaning blade 26a, a residual toner not transferred to the medium and remaining on the image carrier surface; and a discharge device 40 that discharges the electric charge having a polarity opposite to the electrified toner to the image carrier surface immediately before the toner image is transferred to the medium.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus and an image forming method.

The image forming apparatus for forming the toner image is provided with a cleaning mechanism for removing the toner remaining on the image-carrying surface such as the photoconductor and the intermediate transfer belt. This cleaning mechanism is generally configured to scrape off residual toner on the image-supporting surface by friction, mainly using a rubber cleaning blade. In such a cleaning mechanism, if foreign matter such as paper dust is caught in the edge portion of the cleaning blade, the cleaning blade is damaged, causing cleaning failure. As a technique for preventing this, a technique for preventing damage to the cleaning blade by supplying toner to the cleaning blade while leaving a certain amount or more of toner on the image-supporting surface is disclosed. As such a technique, the following Patent Document 1 states, "When a toner image is formed, a captured toner image that is difficult to see is formed in a non-image forming region where the toner image is not formed, and the captured toner image is held by the image carrier. It is provided with a means for executing an operation of bringing the toner remaining on the image carrier without being transferred from the captured toner image to a portion in contact with the cleaning member (cleaning blade). "

Japanese Unexamined Patent Publication No. 2018-156023

However, a general image forming apparatus is designed so that the transfer rate in the transfer unit is about 90%. Therefore, only a very small amount of toner of about 10% can be left on the image-supporting surface, and it is difficult to supply the required amount of toner to the contact portion between the cleaning blade and the image-supporting surface. rice field.

Therefore, the present invention provides an image forming apparatus and an image forming method capable of supplying a required amount of toner to the contact portion between the cleaning blade and the image-supporting surface, thereby maintaining cleaning performance. The purpose is.

In the present invention for achieving such an object, an image carrier having an image-supporting surface for supporting a toner image by a charged toner and a charge of opposite polarity to the charged toner via a sheet-like medium. By applying It is an image forming apparatus including a cleaning device for removing and a discharging device for discharging a charge having the opposite polarity to the charged toner with respect to the image-supporting surface immediately before transferring the toner image to the medium.

According to the present invention, an image forming apparatus and an image forming method capable of supplying a required amount of toner to the contact portion between the cleaning blade and the image-supporting surface and thereby preventing cleaning defects can be provided. Can be provided.

It is a schematic diagram which shows the structure of the image forming apparatus of an embodiment. It is a block diagram explaining the structure of the control apparatus which the image forming apparatus which concerns on embodiment has. It is a flowchart which shows the image formation method which concerns on embodiment. It is a figure which shows the transfer rate of toner for each factor, and the reverse transfer rate. It is a figure explaining the exposure for image formation carried out in the image formation method of an embodiment. It is a figure explaining the microexposure carried out in the image formation method of an embodiment. It is a figure for demonstrating the development state of toner by an exposure intensity. It is a figure explaining the transfer of toner to a recording medium by the state of adhesion of toner to an image-carrying surface. It is a figure for demonstrating the development state of toner in a fine exposure. It is a figure (the 1) explaining the setting of a fine exposure area. It is a figure (the 2) explaining the setting of a fine exposure area. It is a figure explaining the effect of giving a reverse charge to the toner which is carried out in the image formation method of an embodiment. It is a figure which shows the chart created in the modification 1 of embodiment. It is a flowchart explaining the modification 2 of embodiment.

Hereinafter, embodiments of an image forming apparatus to which the present invention is applied and an image forming method will be described in detail with reference to the drawings.

≪Image forming device≫
FIG. 1 is a schematic view showing the configuration of the image forming apparatus 1 of the embodiment. The image forming apparatus 1 shown in FIG. 1 is of an electrophotographic type that forms a toner image on a sheet-shaped recording medium S, and includes an image forming unit 10, a transfer unit 20, and a fixing apparatus 30. Further, the image forming apparatus 1 further includes a discharge device 40 and a control device 60. Hereinafter, detailed configurations of each part and the device of the image forming apparatus 1 will be described.

<Image forming unit 10>
The image forming unit 10 has four image forming units 10y, 10m, 10c, and 10k for forming toner images of, for example, yellow (Y), magenta (M), cyan (C), and black (K). .. Each of the image forming units 10y, 10m, 10c, and 10k includes a photoconductor 11, a cleaning device 12, a charging device 13, an exposure device 14, and a developing device 15 arranged around the photoconductor 11. These are as follows.

[Photoreceptor 11]
The photoconductor 11 is one of the image carriers on which a toner image is formed, and has a drum shape rotated by a drive motor, and the drum-shaped side peripheral surface 11a is used as an image carrier surface. The photoconductors 11 of the image forming units 10y, 10m, 10c, and 10k are arranged in a direction perpendicular to the axial direction while keeping the axial direction parallel to each other.

[Cleaning device 12]
The cleaning device 12 removes residual toner on the side peripheral surface 11a of the photoconductor 11. Such a cleaning device 12 includes a cleaning blade (not shown here). The cleaning blade is arranged in a state of being in contact with the side peripheral surface 11a over the entire axial direction of the side peripheral surface 11a, and removes toner by scraping the toner from the side peripheral surface 11a.

[Charging device 13]
The charging device 13 uniformly charges the side peripheral surface 11a of the photoconductor 11 from which the residual toner has been removed by the cleaning device 12. As an example, the charging device 13 negatively charges the side peripheral surface 11a of the photoconductor 11.

[Exposure device 14]
The exposure apparatus 14 exposes the side peripheral surface 11a negatively charged by the charging apparatus 13 to form an electrostatic latent image by irradiation with a laser beam. In particular, the exposure apparatus 14 carries out normal exposure for forming a toner image on the recording medium S and fine exposure for leaving toner on the intermediate transfer belt 21 of the transfer unit 20 described below. The fine exposure is an exposure having a lower exposure intensity than the normal exposure. The exposure and fine exposure performed by such an exposure device 14 are performed based on the instructions from the control device 60 described below.

[Developer 15]
The developing device 15 is formed on the side peripheral surface 11a of the photoconductor 11 by supplying a negatively charged toner to the side peripheral surface 11a of the photoconductor 11 on which the electrostatic latent image is formed by the exposure device 14. Toner of each color is attached to the electrostatic latent image. As a result, a toner image to which the yellow toner is attached is formed on the side peripheral surface 11a of the photoconductor 11 in the image forming unit 10y. A toner image to which magenta toner is attached is formed on the surface of the photoconductor 11 in the image forming unit 10 m. A toner image to which cyan toner is attached is formed on the photoconductor 11 of the image forming unit 10c. Further, a toner image to which black toner is attached is formed on the photoconductor 11 of the image forming unit 10k.

<Transfer unit 20>
The transfer unit 20 is arranged in parallel with the image forming unit 10. The transfer unit 20 includes an intermediate transfer belt 21, a plurality of rollers 22, a plurality of primary transfer rollers 23, a secondary transfer roller 24, a static elimination roller 25, and a cleaning device 26. These are as follows.

[Intermediate transfer belt 21]
The intermediate transfer belt 21 is one of the image carriers for supporting the toner image by the charged toner. The intermediate transfer belt 21 is configured as a rotating endless belt, is arranged in a state of being hung on a plurality of rollers 22, and its outer peripheral surface is an image-supporting surface 21a. Such an intermediate transfer belt 21 rotates in a direction opposite to the rotation direction of each of the photoconductors 11 of the image forming units 10y, 10m, 10c, and 10k. Further, the intermediate transfer belt 21 is arranged between the cleaning device 12 and the developing device 15 in a state where the image-supporting surface 21a is sequentially in contact with the side peripheral surfaces 11a of all the photoconductors 11.

[Roller 22]
The roller 22 is inscribed in the intermediate transfer belt 21, and the image-supporting surface 21a of the intermediate transfer belt 21 is arranged on the inner peripheral side of the intermediate transfer belt 21 so as to be in contact with the side peripheral surfaces 11a of all the photoconductors 11. It is set up. One of these rollers 22 is configured as a drive roller for rotating the intermediate transfer belt 21.

[Primary transfer roller 23]
The primary transfer roller 23 is located on the inner peripheral side of the intermediate transfer belt 21 at a position facing the photoconductor 11 of each image forming unit 10y, 10m, 10c, 10k, and is placed between the intermediate transfer belt 11 and the photoconductor 11. It is arranged in a state of sandwiching 21. These primary transfer rollers 23 are transfer devices to which a voltage having the opposite polarity to that of the toner is applied to transfer the toner adhering to the image-supporting surface 21a of the photoconductor 11 to the image-supporting surface 21a of the intermediate transfer belt 21. be.

[Secondary transfer roller 24]
The secondary transfer roller 24 is a transfer device that transfers the toner image to the recording medium S. The secondary transfer roller 24 is arranged at a position facing one of the plurality of rollers 22 on the image-carrying surface 21a side of the intermediate transfer belt 21, and is placed between the intermediate transfer belt 21 and the recording medium. Hold S. The secondary transfer roller 24 applies a charge having a polarity opposite to that of the toner to the image-supporting surface 21a side of the intermediate transfer belt 21 via the recording medium S. As a result, the nip portion where the secondary transfer roller 24 and the roller 22 come into contact with each other conveys the toner image formed on the image-supporting surface 21a of the intermediate transfer belt 21 from the medium supply device (not shown here). This is the transfer position to be transferred to the recording medium S.

[Static elimination roller 25]
The static elimination roller 25 is arranged on the downstream side of the secondary transfer roller 24 in the rotation direction of the intermediate transfer belt 21 and on the upstream side of the primary transfer roller 23 so as to face the image supporting surface 21a, and the charge of the intermediate transfer belt 21 is charged. To remove.

[Cleaning device 26]
The cleaning device 26 is arranged on the downstream side of the static elimination roller 25 in the rotation direction of the intermediate transfer belt 21 and on the upstream side of the primary transfer roller 23 so as to face the image supporting surface 21a. The cleaning device 26 is for removing the toner remaining on the image-supporting surface 21a of the intermediate transfer belt 21. Such a cleaning device 26 includes a cleaning blade 26a that is in contact with the image-carrying surface 21a. The cleaning blade 26a is arranged in a state of being in contact with the image-supporting surface 21a over the entire width direction of the intermediate transfer belt 21, and removes toner from the image-supporting surface 21a that moves relative to the cleaning blade 26a. Remove.

<Fixing device 30>
The fixing device 30 is arranged on the downstream side of the secondary transfer roller 24 in the transfer unit 20 with respect to the transport direction x of the recording medium S. The fixing device 30 nips and conveys the recording medium S supplied from the secondary transfer roller 24 in a heated state, and fixes the toner image transferred to the recording medium S to the recording medium S.

<Discharge device 40>
The discharge device 40 is arranged on the downstream side of the primary transfer roller 23 in the rotation direction of the intermediate transfer belt 21 and on the upstream side of the secondary transfer roller 24. The discharge device 40 is a corona discharge device that discharges a charge having a polarity opposite to that of the toner with respect to the image-supporting surface 21a immediately before the secondary transfer roller 24. The discharge of the discharge device 40 imparts a charge of opposite polarity to the toner on the image-supporting surface 21a. In such a discharge device 40, the discharge potential is controlled by an instruction from the control device 60 described below.

<Control device 60>
The control device 60 controls the driving of each of the above-mentioned parts based on the image data. In particular, this control device 60 performs control for leaving a required amount of residual toner on the image-supporting surface 21a of the intermediate transfer belt 21 after passing through the secondary transfer roller 24. Here, the required amount of residual toner is an amount that can prevent foreign matter such as paper dust caught between the image-supporting surface 21a and the cleaning blade 26a of the cleaning device 26 from reaching the edge of the cleaning blade 26a. This is an amount that can prevent the occurrence of cleaning defects. This required amount is an amount obtained experimentally, and will be described below as the required residual toner amount [Q].

Such a control device 60 is configured by a computer. A computer is hardware used as a so-called computer. The computer may include a CPU (Central Processing Unit), a RAM (Random Access Memory), a non-volatile storage unit such as a ROM (Read Only Memory) or an HDD (hard disk drive), and a network interface. ..

The control device 60 configured by such a computer stores an image forming program for forming a toner image on the recording medium S in a non-volatile storage unit. In particular, this control device 60 holds an image forming program for leaving a required amount of residual toner on the image-supporting surface 21a after toner transfer when performing image forming. Further, the control device 60 controls the drive of the exposure device 14 and the discharge device 40 of the image forming units 10y, 10m, 10c, and 10k by executing the processing based on the stored image forming program.

FIG. 2 is a block diagram illustrating a configuration of a control device 60 included in the image forming device 1 according to the embodiment. As shown in this figure, the control device 60 is connected to each image forming unit 10y, 10m, 10c, 10k, a transfer unit 20, a fixing device 30, and a discharging device 40, and controls each of these parts. Such a control device 60 includes a data acquisition unit 61, a residual toner amount calculation unit 62, a residual toner shortage amount calculation unit 63, a fine exposure area setting unit 64, and an exposure as each functional unit that executes a control program. It includes a data creation unit 65, a discharge voltage setting unit 66, and an image formation control unit 67. The procedure of the program executed by each of these functional units will be described in detail in the following image forming method.

≪Image formation method≫
Next, the image forming method implemented in the image forming apparatus 1 as described above will be described. FIG. 3 is a flowchart showing an example of an image forming method according to an embodiment, and shows a procedure for forming a toner image carried out by an image forming program included in the control device 60 of the image forming apparatus 1. The procedure shown in this flowchart is started when the execution of the image forming job is input to the image forming apparatus 1 from the input unit or the external apparatus (not shown here). Hereinafter, the image forming method of the embodiment will be described with reference to FIGS. 1 and 2 and other necessary drawings according to the flowchart of FIG.

<Step S101>
In step S101, the data acquisition unit 61 acquires data necessary for image formation. The data acquired by the data acquisition unit 61 is job data and factor data relating to factors that affect the amount of residual toner on the image-supporting surface 21a.

Of these, the job data is data related to the recording medium S such as the type and color of the recording medium S, and image data of an image formed on the recording medium S. These job data are input from an input unit (not shown here) or received from an external device in the execution of an image forming job, and are stored in a storage unit of the control device 60 or a predetermined storage unit. Data.

Further, the factor data includes (a) environmental humidity, (b) toner residence time, and (c) transfer current in the upstream portion when the job of image formation is executed. Of these, (a) environmental humidity is the humidity of the environment in which the image forming apparatus 1 is arranged. (B) The toner residence time is the toner residence time in the developing apparatus 15 of the image forming units 10y, 10m, 10c, and 10k. Further, the transfer current in the upstream portion (c) is the transfer current in the image forming units 10y, 10m, 10c, and 10k, which are the upstream portions of the secondary transfer roller 24. It is assumed that these factor data are input from the input unit (not shown here) or acquired from each detector (not shown here).

<Step S102>
In step S102, the residual toner amount calculation unit 62 calculates the residual toner amount [Q1] based on the data acquired by the data acquisition unit 61. Here, the residual toner amount [Q1] is the image-carrying surface of the intermediate transfer belt 21 after passing through the secondary transfer roller 24 without being transferred to the recording medium S when the image formation job is performed under the reference conditions. The amount of residual toner remaining in 21a. Further, the image formation under the reference condition is defined as the image formation by normal exposure based only on the image data.

The residual toner amount calculation unit 62 calculates the residual toner amount [Q1] by the following formula (1) based on the data acquired by the data acquisition unit 61.

In the above formula (1), the toner adhesion amount [g / cm2] is the toner adhesion amount per unit area in the image forming portion of the image-supporting surface 21a. The medium area [cm2] is the area of the recording medium S and is obtained from the input information of the job. The print rate [%] is the area of the area where the image is formed in the recording medium S, and is a value for each page calculated from the image data. The transfer rate [%] is the transfer rate of the toner from the image-supporting surface 21a of the intermediate transfer belt 21 to the recording medium S. Here, the transcription rate represented by the above formula (1) is affected as follows by the value of the above-mentioned factor data.

FIG. 4 is a diagram showing the toner transfer rate and the reverse transfer rate for each factor. As shown in this figure, the transfer rate of toner decreases with (a) an increase in environmental humidity and (b) an increase in toner residence time in a developing apparatus. This is because the transfer rate of the toner is largely due to the amount of charge of the toner. That is, the toner is negatively charged by stirring in the developing device 15, but when the environmental humidity is high or the toner residence time in the developing device 15 is prolonged and the toner deteriorates, the toner in the developing device 15 is charged. Is less likely to be charged, so that the transfer rate decreases.

Further, the reverse transfer rate of the toner (c) increases with an increase in the transfer current in the upstream portion. This is because, in the primary transfer rollers 23 of the image forming units 10y, 10m, 10c, and 10k, the toner may be charged in the opposite polarity by applying a voltage having a polarity opposite to that of the toner. In this case, reverse transfer occurs in which the toner is transferred in the direction opposite to the original transfer direction on the downstream side of the transfer. Therefore, since the amount of residual toner [Q1] changes depending on the magnitude of the transfer current, these conditions are complexly calculated for each transfer unit to obtain the reverse transfer rate.

The residual toner amount calculation unit 62 holds data on the toner transfer rate / reverse transfer rate for these factors. Then, with reference to the retained data, the toner transfer rate is calculated based on the factor data acquired in step S101, and the calculated transfer rate is applied to the above formula (1) to calculate the residual toner amount [Q1].

<Step S103>
In step S103, the residual toner shortage amount calculation unit 63 has a residual toner shortage amount based on the residual toner amount [Q1] calculated by the residual toner amount calculation unit 62 and the required residual toner amount [Q] set in advance. Calculate [Q2].

Here, the required residual toner amount [Q] means that, as described above, foreign matter such as paper dust caught between the image-supporting surface 21a and the cleaning blade 26a of the cleaning device 26 is the edge of the cleaning blade 26a. Is an amount that can prevent you from reaching. Such a required residual toner amount [Q] is a value obtained experimentally in advance, and is, for example, a value for each type of recording medium S. It is assumed that the required residual toner amount [Q] is input from an input unit (not shown) and held in the residual toner shortage amount calculation unit 63. The residual toner deficiency amount [Q2] is the residual toner amount deficient in image formation under the above-mentioned reference conditions.

The residual toner shortage calculation unit 63 selects the required residual toner amount [Q] corresponding to the type of the recording medium S that forms an image in the job, based on the input information of the job. Then, the difference between the selected required residual toner amount [Q] and the residual toner amount [Q1] calculated in step S102 is calculated as the residual toner shortage amount [Q2].

<Step S104>
In step S104, the fine exposure area setting unit 64 performs fine exposure based on the image data acquired by the data acquisition unit 61 and the residual toner shortage amount [Q2] calculated by the residual toner shortage amount calculation unit 63. Set the area to be used.

Here, the fine exposure is an exposure in which the exposure intensity of the exposure apparatus 14 is set to be weaker than that of the normal exposure for image formation, and the exposure intensity is adjusted so that the toner is not transferred to the recording medium S as much as possible. It is a weakened exposure. Such a fine exposure is an exposure for supporting the toner on the image-supporting surface 21a with a thickness and an interval such that the toner is not transferred to the recording medium S.

Hereinafter, prior to explaining the setting of the fine exposure region, the details of the fine exposure will be described first in comparison with the normal exposure for image formation.

-About fine exposure-
FIG. 5 is a diagram illustrating exposure for image formation carried out in the image forming method of the embodiment. As shown in this figure, in the exposure by the image forming apparatus, a screen process for expressing the gradation by controlling the exposure intensity and the exposure area is generally used. At this time, in the exposure in normal image formation, the gradation is formed by repeating the procedure of first increasing the exposure intensity in one pixel and then expanding the exposure pixel area within an arbitrary area. .. On the other hand, the fine exposure is carried out as follows.

FIG. 6 is a diagram illustrating the fine exposure performed in the image forming method of the embodiment. As shown in this figure, in the case of fine exposure, gradation is formed by repeating the procedure of first expanding the exposed pixel area and then increasing the exposure intensity of each pixel within an arbitrary area. ..

FIG. 7 is a diagram for explaining the development state of the toner depending on the exposure intensity, and shows each potential during development. As shown in this figure, in the electrophotographic image forming apparatus 1, the charging apparatus 13 charges the photoconductor 11 to a negative photoconductor potential [V1]. Further, the developing apparatus 15 charges the toner to a negative developing potential [Vt] which is lower in absolute value than that of the photoconductor 11. As a result, an electric field is formed so that the toner does not adhere to the side peripheral surface 11a of the photoconductor 11. Therefore, the toner is not transferred to the recording medium S, and an image is not formed.

In such a configuration, the exposure apparatus 14 performs exposure by irradiating the side peripheral surface 11a of the photoconductor 11 with a laser beam, and lowers the potential of the exposed portion to the post-exposure potentials [V2] and [V2']. At this time, if the exposure intensity by the exposure apparatus 14 is sufficiently strong (A), the post-exposure potential [V2] becomes lower than the development potential [Vt], and an electrostatic latent image is formed in the exposed portion. As a result, the toner of the developed amount corresponding to the difference between the post-exposure potential [V2] and the developing potential [Vt] adheres to the electrostatic latent image of the side peripheral surface 11a and is transferred to the corresponding region of the recording medium S. The image is formed.

On the other hand, when the exposure intensity by the exposure apparatus 14 is weak (B), the post-exposure potential [V2] is not lower than the development potential [Vt], and the toner does not adhere to the exposed portion. Therefore, no image is formed in the corresponding region of the recording medium S.

Therefore, as described above with reference to FIG. 5, in the normal exposure for image formation, the post-exposure potential [V2] of the photoconductor is first gradually increased in the gradation expression. It is common to give priority to lowering the value, and then to expose the adjacent part to increase the area, and then to form the gradation.

On the other hand, in the fine exposure described with reference to FIG. 6, the exposure intensity is kept weak so that the toner is not transferred to the recording medium S as much as possible so that the post-exposure potential [V2] of the photoconductor does not drop too much. It is an exposure.

Here, in the toner transfer portion from the image-supporting surface 21a of the intermediate transfer belt 21 to the recording medium S, the secondary transfer roller 24 applies a reverse charge to the toner via the recording medium S, whereby the intermediate transfer belt The toner image is transferred from the image-supporting surface 21a of 21 to the recording medium S. At this time, the amount of toner transferred to the recording medium S varies depending on the state of adhesion of the toner to the image-supporting surface 21a of the intermediate transfer belt 21.

FIG. 8 is a diagram illustrating the transfer of the toner 2 to the recording medium S due to the adhesion state of the toner 2 to the image-supporting surface 21a, in which the toner 2 is densely packed on the image-supporting surface 21a of the intermediate transfer belt 21. The case (A) and the low case (B) are shown. As shown in these figures, when the dense state of the toner 2 is high (A), the transfer amount of the toner 2 to the recording medium S is larger than when it is low (B). This is because when the density of the toner 2 is high (A), the influence of the reverse charge applied from the secondary transfer roller 24 greatly acts on the toner 2. Further, it is also caused by the fact that the toner 2 is locally concentrated and the attractive force between the toners 2 acts greatly. Therefore, even if the toner 2 adheres to the image-supporting surface 21a of the intermediate transfer belt 21, if the dense body of the toner 2 is sufficiently low and discrete, the intermediate transfer belt is not transferred to the recording medium S. It can be seen that the toner 2 is left on the image-carrying surface 21a of the 21. For this reason, in the above-mentioned fine exposure, it is important to carry out the fine exposure so that the toner is developed discretely.

FIG. 9 is a diagram for explaining the development state of the toner in the fine exposure, and explains the reason why the toner is developed discretely in the fine exposure. As described above, when the exposure intensity by the exposure apparatus 14 is weak (A), the post-exposure potential [V2] does not fall significantly below the development potential [Vt]. However, the control of the exposure intensity is complicated, and the exposure intensity is generally used in several steps in order to cope with the increase in the image formation speed. Therefore, in the first-stage exposure intensity, if the post-exposure potential [V2] does not fall below the development potential [Vt], the exposure is performed at the second-stage exposure intensity. However, since the resolution of the exposure intensity is low, the post-exposure potential [V2] may be significantly lower than the development potential [Vt] in the second stage exposure intensity. In this case, there is a possibility that a large amount of toner will be developed even though a small amount of toner is desired to be developed.

Therefore, when the toner is not developed in the first step in the fine exposure, the adjacent pixels and the pixels slightly separated are exposed with the exposure intensity of the second step (B). By doing so, the post-exposure potential [V2], which does not fall below the development potential [Vt] in units of one pixel, falls below the development potential [Vt] by the sum of the two pixels. In this case, the post-exposure potential [V2] drops in total even when the pixels are exposed at a distance, because the exposure area per laser is generally wider than the area of one pixel in the high-resolution exposure apparatus 14. Because it is designed.

As described above, in performing fine exposure, it is necessary to control the exposure intensity and the exposure position so that a very small amount of toner can be developed. For this reason, the fine exposure is performed discretely on each pixel at intervals so that the toner is not as dense as possible on the peripheral surfaces 11a and 21a, as described above, in which the exposure with a weak exposure intensity is performed. ..

In the above description, in the implementation of fine exposure, the exposure area is gradually increased by the exposure intensity of the first stage, and the exposure intensity of the second stage is obtained after the entire area is exposed in an arbitrary area. And said. However, the exposure intensity and whether or not the toner is developed are various factors such as the difference (fog margin) between the development potential [Vt] and the photoconductor potential [V1], the sensitivity of the photoconductor, and the charge amount of the toner. Is determined by. Therefore, as long as the condition that a very small amount of toner is developed can be satisfied, a method such as using the exposure intensity of the second step may be taken first. These conditions may be obtained experimentally in advance, and a plurality of conditions may be used properly according to the state of the actual machine.

-About setting the fine exposure area-
In this step S104, the fine exposure area setting unit 64 sets the area for performing the fine exposure as described above on the recording medium S. At this time, the fine exposure area setting unit 64 sets the fine exposure area based on the image data acquired in step S101 and the residual toner shortage amount [Q2] calculated in step S103.

FIG. 10 is a diagram (No. 1) for explaining the setting of the fine exposure region. As shown in this figure, the fine exposure area setting unit 64 finely exposes the area [Ar1] in which the toner can be transferred, excluding the image forming area [Ar2] based on the image data acquired in step S101. Set the area. As a result, the influence of the fine exposure on the image forming region [Ar2] is suppressed. The fine exposure region setting unit 64 sets a fine exposure region on the recording medium S in a non-image formation region in which the image formation region [Ar2] is removed, a region outside the recording medium S, or a region between the recording media S. Set. At this time, it is important that the fine exposure area setting unit 64 sets the fine exposure area in a region separated from the image forming region [Ar2] by a predetermined interval [D]. This interval [D] is as follows.

FIG. 11 is a diagram (No. 2) for explaining the setting of the fine exposure region. This figure shows the potential of the side peripheral surface 11a of the photoconductor 11 when the normal exposure and the fine exposure are carried out close to each other (A) and when the normal exposure and the fine exposure are carried out separately (B). ing.

As shown in this figure, when normal exposure and fine exposure are carried out in close proximity to each other (A), the post-exposure potential [V2] of the photoconductor is added up at an intermediate position between these exposures. As a result, the toner is excessively developed outside the range of normal exposure for image formation, and the effect of fine exposure is exerted on the range of image formation. On the other hand, when the normal exposure and the fine exposure are performed separately (B), the post-exposure potentials [V2] due to these exposures do not affect each other. Therefore, the range in which the fine exposure is performed is set at a position separated by an interval that the post-exposure potential [V2] does not affect the normal exposure for forming an image. This interval in the exposure corresponds to the interval [D] set for the image forming region [Ar2] described with reference to FIG.

When the fine exposure area setting unit 64 sets the fine exposure area in the area separated from the image formation area [Ar2] by a predetermined interval [D] as described above, the fine exposure area setting unit 64 does not affect the image first. The fine exposure areas are set outside the recording medium S and then on the recording medium S in the order of priority. In this case, the fine exposure areas are set in the above-mentioned priority order so that the area is such that the residual toner shortage amount [Q2] is satisfied.

In particular, when the fine exposure region is set on the recording medium S, it is desirable to set so as to suppress the transfer of the toner in the fine exposure region onto the recording medium S as much as possible. Therefore, on the recording medium S, the transfer of the toner on the recording medium S in the fine exposure region is prevented by setting the fine exposure region by dividing it into each fine region.

Further, it is desirable that the amount of residual toner supplied to the cleaning device 26 is uniform over the entire axial direction of the cleaning blade 26a in the cleaning device 26. In that case, the axial direction may be divided into several areas, and a fine exposure area may be set for each area. In this case, in the previous step S102, the residual toner amount calculation unit 62 calculates the residual toner amount [Q1] for each divided region. Further, in step S103, the residual toner shortage calculation unit 63 calculates the residual toner shortage amount [Q2] for each divided region. Then, in this step S104, the fine exposure area setting unit 64 sets the fine exposure area for each divided area. At this time, the fine exposure area setting unit 64 sets a fine exposure area having an area sufficient to supply the residual toner shortage amount [Q2].

The above description is simply described as the time of secondary transfer from the intermediate transfer belt 21 to the recording medium S, but in reality, the same applies to the time of primary transfer from the photoconductor 11 of each color to the intermediate transfer belt 21. It is preferable to calculate the above, calculate the amount of residual toner on the photoconductor 11 in the same manner, and calculate them in a complex manner to determine the fine exposure area of each color.

Further, it is preferable that the fine exposure region setting unit 64 allocates the fine exposure region setting to each photoconductor 11 in consideration of the color of the toner. That is, even if the exposure intensity and the discreteness of the fine exposure are set so that the toner is not transferred to the recording medium S in the fine exposure, the transfer of the toner to the recording medium S due to the fine exposure is set to zero. That is difficult. Therefore, the fine exposure region setting unit 64 allocates more fine exposure region settings to the photoconductor 11 for forming a toner image having a color that is inconspicuous with respect to the recording medium S. For example, if the recording medium S is white, more settings for the fine exposure region are allocated to the photoconductor 11 of the yellow (Y) image forming unit 10y.

<Step S105>
In step S105, the exposure data creation unit 65 sets each image forming unit 10y, 10m, 10c, based on the image data acquired by the data acquisition unit 61 and the fine exposure area set by the fine exposure area setting unit 64. The exposure data for the exposure scanning performed in the exposure apparatus 14 of 10k is created.

<Step S106>
In step S106, the discharge voltage setting unit 66 sets the discharge voltage by the discharge device 40. Here, transfer of the toner to the recording medium S will be described when a charge having the opposite polarity is applied to the toner immediately before the secondary transfer roller 24 by the discharge of the discharge devices 40 to.

FIG. 12 is a diagram illustrating the effect of applying a reverse charge to the toner, which is carried out in the image forming method of the embodiment. This figure shows the state of the toner 2 between the intermediate transfer belt 21 and the recording medium S before and after passing through the secondary transfer roller 24, and shows a normal exposure region (A) for image formation and a slight exposure. Area (B) of.

As shown in this figure, when a reverse charge (+ charge) is applied to the toner 2 by applying a discharge voltage from the discharge device 40, the toner 2 is discrete in the fine exposure region (B), so that it is intermediate. Most of the toner 2 on the transfer belt 21 is charged with the opposite polarity (+). Therefore, the toner 2 is not transferred to the secondary transfer roller 24 side charged with the reverse polarity (+), and most of the toner 2 remains on the intermediate transfer belt 21 even after passing through the secondary transfer roller 24. ..

On the other hand, in the normal exposure region (A), since the toner 2 is intensive, only the toner 2 located on the surface layer of the toner 2 on the intermediate transfer belt 21 is charged with the opposite polarity (+). do. Therefore, when passing through the secondary transfer roller 24 charged with the reverse polarity (+), the negative electrode toner 2 having no reverse polarity is transferred to the recording medium S. At this time, the reverse polarity (+) toner 2 located on the surface layer of the toner 2 on the intermediate transfer belt 21 is also transferred to the recording medium S together with the negative electrode toner 2.

Therefore, in this step S106, the discharge voltage setting unit 66 suppresses the transfer of the toner 2 in the fine exposure region (B) onto the recording medium S, while suppressing the transfer of the toner 2 in the normal exposure region (A) onto the recording medium S. The discharge voltage in the discharge device 40 is set so as not to interfere with the transfer to. That is, the discharge voltage setting unit 66 maintains the same transfer rate of the toner constituting the toner image formed by the normal exposure to the recording medium depending on whether the discharge from the discharge device 40 is performed or not. So, the discharge voltage in the discharge device 40 is set.

Here, the ease of charging the toner 2 is affected by various factors such as environmental humidity. Therefore, the discharge voltage setting unit 66 sets the discharge voltage by the discharge device 40 based on the data experimentally obtained for each of various factors. Further, it is desirable that the amount of reverse charge applied by the discharge device 40 is set to maximize the transfer residual toner within a range that does not usually affect the image, but the residual toner is not increased more than necessary. It also needs to be properly controlled. Therefore, the discharge voltage setting unit 66 determines the required residual toner amount [Q] based on experimental data from the area of the fine exposure region set in step S104 and the residual toner amount calculated in step S102. The discharge voltage of the discharge device 40 is set to, and the amount of charge having the opposite polarity to the toner is adjusted.

Further, depending on the image formation state of the image unit, even if the discharge voltage of the discharge device 40 is the same, the influence on the transfer rate of the toner on the recording medium S may be different. Specifically, the smaller the area where the image forming portions are continuous, such as thin lines and independent dots, the more remarkable the decrease in toner transfer rate due to the addition of reverse charge. This is the same phenomenon as the relationship between normal exposure and fine exposure. Therefore, the discharge voltage setting unit 66 sets the amount of reverse charge applied (discharge voltage) smaller as the minimum value of the continuous area of the image forming unit is smaller in each page or in a predetermined range divided in the axial direction. do. As a result, the influence of the reverse charge applied by the discharge device 40 on the image forming portion is suppressed to a small value.

<Step S107>
In step S107, the image formation control unit 67 controls each exposure device 14 based on the exposure data created by the exposure data creation unit 65, and is set by the discharge voltage setting unit 66 calculated by the discharge voltage setting unit 66. Based on this, the discharge voltage of the discharge device 40 is controlled, and the image forming process is executed.

As a result, the exposure apparatus 14 performs normal exposure for image formation and fine exposure to the region set in step S104. Further, the discharge device 40 discharges at the discharge voltage set in step S106.

<Step S108>
In step S108, the image formation control unit 67 determines whether or not the image formation for all the pages set in the job is completed. The image formation control unit 67 ends the process when it is determined that the process is completed (YES), returns to step S102 when it is determined that the process is not completed (NO), and processes the next page after step S102. Is repeated.

In the procedure of the image forming method described using the flowchart of FIG. 3, it was decided to create the exposure data for each page, set the discharge voltage, and execute the image forming process. However, the procedure of the image forming method may be a procedure of creating exposure data and setting a discharge voltage in any image forming unit, or a procedure of performing through all pages. Further, the procedure of the image forming method may be a procedure of performing an image forming process after creating exposure data and setting a discharge voltage in an arbitrary range for a plurality of pages or all pages. It is desirable that this procedure be carried out so as to maximize productivity in consideration of the load of calculation processing and the balance with other controls.

<< Effect of the embodiment >>
According to the embodiment described above, the transfer of the toner 2 can be suppressed by applying a reverse charge to the toner 2 by the discharge device 40 immediately before the transfer portion of the toner S with respect to the recording medium S. In particular, in addition to the normal exposure for image formation, by combining with the fine exposure with reduced exposure intensity, the transfer of toner in the finely exposed portion is suppressed while suppressing the influence on the normal image formation, and the image supporting surface 21a is covered. The amount of residual toner can be increased. As a result, the residual toner can be supplied in a necessary and sufficient amount between the image-supporting surface 21a and the cleaning blade 26a, and even in a situation where paper dust or the like reaches the cleaning portion, the cleaning blade 26a is not damaged and cleaning is performed. It becomes possible to maintain the performance.

<< Modification 1 >>
Next, a modification 1 of the above-described embodiment will be described. As shown in FIG. 1, the image forming apparatus 1 of the modification 1 has a configuration in which a toner adhesion amount detecting apparatus 50 is provided so as to face the image supporting surface 21a of the intermediate transfer belt 21. As a result, the processing by the residual toner amount calculation unit 62 shown in FIG. 2 is different. Other configurations are the same as those of the above-described embodiment. Therefore, in the following, the configuration of the toner adhesion amount detection device 50 and the processing by the residual toner amount calculation unit 62 will be described.

<Toner adhesion amount detection device 50>
The toner adhesion amount detecting device 50 is arranged on the downstream side of the secondary transfer roller 24 in the rotation direction of the intermediate transfer belt 21 and on the upstream side of the static elimination roller 25. The toner adhesion amount detecting device 50 detects the amount of toner remaining on the image-supporting surface 21a of the intermediate transfer belt 21 that has passed through the secondary transfer roller 24. Such a toner adhesion amount detecting device 50 is a device that optically detects the toner adhesion amount to the image-supporting surface 21a, that is, the residual toner amount.

<Residual toner amount calculation unit 62>
The residual toner amount calculation unit 62 holds the residual toner amount experimentally detected by the toner adhesion amount detecting device 50 in advance for each type of the recording medium S, and the residual toner amount in the job is based on the held residual toner amount. Is calculated.

Here, the residual toner amount held by the residual toner amount calculation unit 62 is a value obtained experimentally in advance. In this case, a chart for detecting the residual toner amount is formed on each recording medium S in advance, and in that case, the residual toner amount on the image-supporting surface 21a of the intermediate transfer belt 21 is detected by the toner adhesion amount detecting device 50. I will do it.

FIG. 13 is a diagram showing a chart created in the first modification of the embodiment, and shows a chart for detecting the amount of residual toner. As shown in this figure, the chart formed on each recording medium S is formed so that each image of each gradation by each color toner corresponds to the detection range of the toner adhesion amount detecting device 50. It also forms a microexposure area for performing microexposure. The toner adhesion amount detecting device 50 detects the residual toner amount in the region on the image-supporting surface 21a corresponding to each image and the fine exposure region in this chart. The residual toner amount calculation unit 62 holds the residual toner amount detected by the toner adhesion amount detecting device 50 in association with the type of the recording medium S.

As the image forming method carried out in such a configuration, step S102 described with reference to FIG. 3 may be carried out as follows, and the other steps are the same as those in the embodiment.

<Step S102>
In step S102, the residual toner amount calculation unit 62 corresponds to the recording medium S used in the job from the data of the residual toner amount held based on the information about the recording medium S acquired by the data acquisition unit 61. Extract the amount of residual toner to be used. The amount of residual toner extracted here is the standard amount of residual toner. Next, the residual toner amount calculation unit 62 calculates the residual toner amount in this job based on the image data acquired by the data acquisition unit 61 and the extracted reference residual toner amount.

<Effect of Modification 1>
According to such a modification 1, the amount of residual toner at the time of image formation can be accurately calculated for each of a wide variety of recording media S having different materials, thicknesses, water contents, unevenness, and the like. Therefore, the residual toner shortage amount can be calculated more accurately, and the fine exposure region can be set based on the result. Therefore, it is possible to more reliably maintain the cleaning performance without damaging the cleaning blade 26a.

The formation of the chart described above and the detection of the residual toner amount by the toner adhesion amount detecting device 50 are performed for each recording medium to be used in cooperation with the service and the user, for example, when the image forming apparatus 1 is installed. I will leave it. Further, it may be performed again when a new recording medium S to be used appears.

Further, the formation of the chart described above and the detection of the residual toner amount by the toner adhesion amount detecting device 50 may be performed, for example, based on the driving torque of the intermediate transfer belt 21 during image formation. That is, it is a value that varies depending on the amount of residual toner on the image-supporting surface 21a of the intermediate transfer belt 21, and when the amount of residual toner is small, the friction between the image-supporting surface 21a and the cleaning blade 26a increases and the drive torque increases.

Therefore, the image formation control unit 67 shown in FIG. 2 holds in advance the minimum value of the drive torque when the residual toner amount on the image-supporting surface 21a is the required residual toner amount [Q] as a threshold value. Further, the image formation control unit 67 acquires the measured value of the drive torque of the intermediate transfer belt 21 from the drive unit of the intermediate transfer belt 21, and forms a chart when it is determined that the acquired drive torque exceeds the threshold value. Then, the amount of residual toner is detected by the toner adhesion amount detecting device 50. Then, the residual toner amount calculation unit 62 calculates the residual toner amount in the job being executed based on the detected residual toner amount (step S102).

Further, when the image formation control unit 67 determines that the acquired drive torque exceeds the threshold value, the image formation control unit 67 notifies the external device of the shortage of the residual toner amount and prompts the user to form a chart. May be good. When the chart is formed, the toner adhesion amount detecting device 50 detects the residual toner amount with respect to the image-supporting surface 21a. Then, the residual toner amount calculation unit 62 calculates the residual toner amount in the job based on the detected residual toner amount. This corresponds to step S102 shown in FIG. 3, and further steps S103 and subsequent steps are performed.

Further, when forming the chart described with reference to FIG. 13, a reverse charge may be applied to the toner for forming the chart by a predetermined discharge voltage from the discharge device 40 shown in FIG. .. In this case, in step S106 described with reference to FIG. 3, the discharge when the job is executed is further based on the residual toner amount detected by the toner adhesion amount detecting device 50 and the discharge voltage when the chart is formed. The voltage may be set.

Further, the toner adhesion amount detecting device 50 may be arranged so as to face the recording medium S that has passed through the secondary transfer roller 24 (see FIG. 1). In this case, the toner adhesion amount detecting device 50 measures the amount of toner transferred onto the recording medium S. Further, in this case, the residual toner amount calculation unit 62 detects the toner amount of the chart formed on the recording medium S. Then, the residual toner amount calculation unit 62 estimates the toner transfer rate from the toner amount in the chart, and further calculates the residual toner amount [Q1] based on the above equation (1).

<< Modification 2 >>
Next, a modification 2 of the embodiment will be described above. In the above-described embodiment, as shown in the flowchart of FIG. 3, after setting the discharge voltage in step S106, the image forming process is performed according to the setting in step S107. However, the discharge voltage may be adjusted at any time based on the drive torque of the intermediate transfer belt 21 measured in the execution of the image forming process. In this case, step S107 is omitted, and the following flows are carried out in parallel.

FIG. 14 is a flowchart illustrating a modification 2 of the embodiment, and is a procedure carried out by the discharge voltage setting unit 66 shown in FIG. The procedure shown in this flowchart is started in synchronization with the start of the image forming process of the job, and is repeated at a predetermined speed. Hereinafter, the modified example 2 will be described with reference to FIGS. 1, 2, and 14.
<Step S201>
First, in step S201, the discharge voltage setting unit 66 acquires the value of the drive torque of the intermediate transfer belt 21 from the drive unit of the intermediate transfer belt 21.

<Step S202>
In step S202, the discharge voltage setting unit 66 determines whether the acquired drive torque value is within the preset allowable range, exceeds the allowable range, or is below the allowable range. Here, the drive torque of the intermediate transfer belt 21 is a value that varies depending on the amount of residual toner on the image-supporting surface 21a of the intermediate transfer belt 21, and when the amount of residual toner is small, the friction between the image-supporting surface 21a and the cleaning blade 26a. Increases and the drive torque increases. Therefore, the discharge voltage setting unit 66 holds in advance the allowable range of the drive torque when the residual toner amount on the image-supporting surface 21a is the required residual toner amount [Q]. The discharge voltage setting unit 66 proceeds to step S203 when it is determined that the acquired drive torque exceeds the allowable range (OV), and when it is determined that it is below the allowable range (UND), the next step. Proceed to S204. If it is determined that the permissible range is within the allowable range (YES), the process is terminated.

<Step S203>
In step S203, the discharge voltage setting unit 66 increases the discharge voltage by the discharge device 40 by a preset increase range, and ends the process.

<Step S204>
In step S204, the discharge voltage setting unit 66 reduces the discharge voltage by the discharge device 40 by a preset increase range, and ends the process.

<Effect of variant 2>
According to such a modification 2, since the discharge voltage is adjusted at any time based on the drive torque of the intermediate transfer belt 21, a necessary and sufficient amount remains between the image-supporting surface 21a and the cleaning blade 26a at any time. Toner can be supplied.

In the second modification, the discharge voltage of the discharge device 40 is increased or decreased by the drive torque of the intermediate transfer belt 21, but the discharge voltage of the discharge device 40 may be increased or decreased by the charge amount of the toner. In this case, for example, a charge amount detecting device for detecting the charge amount of the toner is provided at a position facing the image supporting surface 21a of the developing device 15 or the intermediate transfer belt 21. Then, the discharge voltage setting unit 66 sets the discharge voltage of the discharge device 40 based on the charge amount of the toner measured by the charge amount detection device.

Therefore, the discharge voltage setting unit 66 holds in advance an allowable range of the toner charge amount when the residual toner amount on the image-supporting surface 21a is the required residual toner amount [Q]. When the discharge voltage setting unit 66 determines that the charge amount of the toner measured by the charge amount detection device exceeds the allowable range, the discharge voltage setting unit 66 increases the discharge voltage by the discharge device 40 by a preset increase range. .. On the other hand, when the discharge voltage setting unit 66 determines that the charge amount of the toner measured by the charge amount detection device is less than the allowable range, the discharge voltage setting unit 66 increases the discharge voltage by the discharge device 40 by a preset increase range. Decrease.

≪Others≫
In any of the embodiments and modifications 1 and 2 described above, if the residual toner cannot be supplied in a necessary and sufficient amount between the image-supporting surface 21a and the cleaning blade 26a, it is usually between the recording media S. The shortage of residual toner may be supplemented by forming a considerable amount of toner band by exposure. Further, in the above embodiments and Modifications 1 and 2, both the fine exposure and the reverse charge applied to the toner immediately before transfer to the recording medium S have been described, but the present invention does not carry out the fine exposure. Even if only the reverse charge is applied, the effect of increasing the amount of residual toner can be obtained without affecting the image formation. Further, the reverse charge may be applied in combination with other means such as increasing the amount of fog toner instead of the fine exposure and forming an image by normal exposure to a blank sheet portion.

Further, the present invention can be applied even when the side peripheral surface 11a of the photoconductor 11 is used as an image-carrying surface and the intermediate transfer belt 21 is used as a sheet-like medium. This makes it possible to maintain the cleaning performance without damaging the cleaning raid of the cleaning device 12 provided on the side peripheral surface 11a of the photoconductor 11. In this case, the discharge device 40 may be arranged downstream of each primary transfer roller 23 and upstream of each cleaning device 12 in the rotation direction of each photoconductor 11.

1 ... Image forming device 2 ... Toner 11 ... Photoconductor 14 ... Exposure device 15 ... Developing device 21 ... Intermediate transfer belt (image carrier)
21a ... Image-supporting surface 24 ... Secondary transfer roller (transfer device)
26 ... Cleaning device 26a ... Cleaning blade 40 ... Discharge device 50 ... Toner adhesion amount detection device 62 ... Residual toner amount calculation unit 64 ... Fine exposure area setting unit 66 ... Discharge voltage setting unit S ... Recording medium

Claims (16)

An image carrier having an image-carrying surface for supporting a toner image made of charged toner, and an image carrier.
A transfer device that transfers a toner image on the image-supporting surface to the sheet-shaped medium by applying a charge having the opposite polarity to the charged toner via the sheet-shaped medium.
A cleaning device that removes residual toner that remains on the image-supporting surface without being transferred to the medium by scraping it with a cleaning blade.
An image forming apparatus comprising a discharge device for discharging a charge having the opposite polarity to the charged toner with respect to the image-carrying surface immediately before transferring the toner image to the medium. A photoconductor charged with the same polarity as the toner,
An exposure apparatus that performs exposure to form an electrostatic latent image on the surface of the photoconductor, and an exposure apparatus.
A developing device for supplying the charged toner to the surface of the photoconductor on which the electrostatic latent image is formed is provided.
The exposure device performs normal exposure for forming the toner image on the surface of the photoconductor by adhesion of the toner to the electrostatic latent image, and fine exposure having a lower exposure intensity than the normal exposure. Item 1. The image forming apparatus according to Item 1. The image forming apparatus according to claim 2, wherein the discharging device discharges the toner image formed by the normal exposure at a voltage at which the transfer rate to the medium is maintained. A fine exposure area setting unit for setting a region for performing the fine exposure based on the amount of the residual toner on the image-carrying surface is provided.
The image forming apparatus according to claim 2 or 3, wherein the exposure apparatus performs the fine exposure according to the setting in the fine exposure region setting unit. The fine exposure region setting unit sets the fine exposure region in a region where the potential change on the surface of the photoconductor due to the fine exposure is not affected by the potential change on the surface of the photoconductor due to the normal exposure. The image forming apparatus according to claim 4. The image forming apparatus according to any one of claims 1 to 5, further comprising a residual toner amount calculation unit for calculating the amount of residual toner based on image data relating to a toner image formed on the medium. The image forming apparatus according to claim 6, wherein the residual toner amount calculation unit calculates the amount of the residual toner together with the image data based on environmental data, the degree of deterioration of the toner, and the formation conditions of the toner image. A toner adhesion amount detection device that detects the toner adhesion amount on the image-carrying surface after the toner is transferred to the medium, and a toner adhesion amount detection device.
The image forming apparatus according to any one of claims 1 to 5, further comprising a residual toner calculation unit that calculates the amount of residual toner based on the toner adhesion amount detected by the toner adhesion amount detection device. A toner adhesion amount detection device that detects the toner adhesion amount in the toner image transferred to the medium, and a toner adhesion amount detection device.
The image forming apparatus according to any one of claims 1 to 5, further comprising a residual toner calculation unit that calculates the amount of residual toner based on the toner adhesion amount detected by the toner adhesion amount detection device. The image forming apparatus according to any one of claims 4 to 9, further comprising a discharge voltage setting unit that sets the discharge voltage of the discharge device based on the amount of residual toner. A charge amount detecting device for detecting the charge amount of the toner is provided.
The image forming apparatus according to any one of claims 1 to 9, further comprising a discharge voltage setting unit that sets the discharge voltage of the discharge device based on the charge amount of the toner detected by the charge amount detection device. Any of claims 1 to 9 including a discharge voltage setting unit that increases or decreases the discharge voltage of the discharge device according to the area of a portion where the toner image is continuous based on image data relating to the toner image formed on the medium. The image forming apparatus according to item 1. Any of claims 1 to 9 including a discharge voltage installation unit that sets the discharge voltage of the discharge device so that the drive torque of the image carrier that moves relative to the cleaning blade is within a predetermined range. The image forming apparatus according to item 1. The image carrier is a photoconductor that is charged to have the same polarity as the polarity of the toner.
The image forming apparatus according to any one of claims 1 to 13, wherein the sheet-shaped medium is an intermediate transfer belt. The image carrier is an intermediate transfer belt.
The image forming apparatus according to any one of claims 1 to 13, wherein the sheet-shaped medium is a recording medium. A toner image made of charged toner is supported on the image-supporting surface of the image-supporting body, and the toner image is supported on the image-supporting surface.
By applying a charge of opposite polarity to the charged toner via the sheet-shaped medium by the transfer device, the toner image on the image-supporting surface is transferred to the sheet-shaped medium.
The residual toner that remained on the image-supporting surface without being transferred to the medium was scraped off by a cleaning blade of a cleaning device to remove it.
An image forming method in which an image-bearing surface immediately before transferring a toner image is discharged with a charge having the opposite polarity to the charged toner by a discharge device.

Images