JP4956240B2 - Image forming apparatus, method for controlling image forming apparatus, program, and recording medium - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile, and a control method for the image forming apparatus.

  In recent years, for example, a tandem type full-color copying machine has been used as an image forming apparatus. Such a tandem type color copying machine has an advantage that the printing speed is faster than the one-drum system because four image forming units of magenta, yellow, cyan, and black are separately provided.

  FIG. 6 is a partial configuration diagram of such a tandem full-color copying machine. In FIG. 6, a black image forming unit 301, a yellow image forming unit 302, a cyan image forming unit 303, and a magenta image forming unit 304 are provided. Each image forming unit includes photosensitive drums 301a, 302a, 303a, and 304a, and developing rollers 301b, 302b, 303b, and 304b that supply toner of each color to the photosensitive drums 301a, 302a, 303a, and 304a. Further, primary transfer rollers 311, 312, 313, and 314 are arranged to face the respective photosensitive drums.

  An intermediate transfer belt 315 is provided between the photosensitive drum and the primary transfer roller. A secondary transfer roller 316 is provided in the vicinity of the downstream side of the black image forming unit 301 with respect to the rotation direction of the intermediate transfer belt 315 so as to press the intermediate transfer belt 315. A driving roller 317 is provided inside the intermediate transfer belt 315 so as to face the secondary transfer roller 316, and the driving roller 317 rotates the intermediate transfer belt 315.

  Further, a fur brush roller 318 for removing toner remaining on the surface of the intermediate transfer belt 315 is provided in the vicinity of the upstream side of the magenta image forming unit 304, and a fur brush is provided inside the intermediate transfer belt 315. A driven roller 319 is provided opposite to the roller 318. Further, a tension roller 320 for applying tension to the intermediate transfer belt 315 is provided inside the intermediate transfer belt 315, upstream of the driven roller 319 and downstream of the driving roller 317.

  In such an image forming apparatus, when the printing rate of the document is low, the amount of toner supplied from the developing rollers 301b, 302b, 303b, and 304b to the photosensitive drums 301a, 302a, 303a, and 304a is reduced. Will continue to remain on the developing roller. If the toner particles continue to remain on the developing roller, the toner particles are excessively charged and do not move to the photosensitive drum, and image density reduction and fogging may occur.

  Therefore, when the image is not formed, a larger alternating bias than that at the time of image formation is applied, and the remaining toner is forcibly moved from the developing roller onto the photosensitive drum, thereby toning the toner on the developing roller. The operation | movement which replaces was performed (for example, refer patent document 1).

  The toner moved onto the photosensitive drum is discharged onto the intermediate transfer belt 315. Here, the discharged toner is positively charged, and is conveyed on the intermediate transfer belt 315 and applied with a brush so as to have a negative polarity by the brush contact and electrostatic force. Removed.

The secondary transfer roller 316 is applied with a voltage so as to have a negative polarity in order to transfer the positively charged toner to the paper when passing the paper, but when the discharged toner passes. The applied voltage is switched so that the surface has a positive polarity so that the toner does not adhere to the secondary transfer roller 316.
JP 2000-310909 A

  However, the black toner and the yellow, cyan, and magenta color toners generally have different toner resistance due to the difference in carbon content (other additives, etc.), and the resistance value of the black toner is higher than that of the color toner. Lower.

  Therefore, the charge amount on the photosensitive drum is also different. For example, the charge amount of black toner is about 10 (μC / g), and the charge amount of color toner is about 15 (μC / g). .

  Accordingly, the charge amount of black toner discharged on the intermediate transfer belt 315 is different from that of color toner.

  In this way, when the charge amount varies depending on the toner, the electrostatic force when passing through the fur brush roller 318 having a negative polarity on the surface is different, which may cause a cleaning failure.

  An object of the present invention is to provide an image forming apparatus and a control method for the image forming apparatus that can suppress a cleaning failure at the time of toner replacement in consideration of the problems of the conventional image forming apparatus.

In order to achieve the above object, the first present invention provides:
A plurality of image carriers on which toner images are formed; and
A plurality of developer carriers for carrying the toner to supply toner to each of the image carriers;
A plurality of primary transfer portions arranged facing each of the image carriers,
An intermediate transfer member disposed between the plurality of image carriers and the plurality of primary transfer units to superimpose the toner images on the surfaces of the plurality of image carriers;
A secondary transfer portion for transferring the superimposed toner image from the intermediate transfer member onto a recording medium;
A removing unit provided to remove toner on the intermediate transfer member, and applied with a voltage so as to have a polarity opposite to the charge of the toner;
When the toner on the developer carrying member is replaced without supplying the recording medium to the secondary transfer unit, the intermediate transfer that is rotating from each developer carrying member via the respective image carrying member. A charge adjustment unit that adjusts the charge of the toner discharged to each region that sequentially passes through the removal unit without overlapping on the body;
Control that is controlled by the charge adjustment unit so as to reduce the difference in toner charge in each region for each of the regions that sequentially pass through the charge adjustment unit based on the type of toner or the position of the image carrier. And an image forming apparatus.
The second aspect of the present invention is
The controller is
In the image forming apparatus according to the first aspect of the invention, the charge adjusting unit controls the toner charge in each region to be substantially uniform between the regions.

The third aspect of the present invention
The controller is
By applying a charge having the same polarity as the polarity of the toner to the toner in the region for each region by the charge adjusting unit , the charge of the toner in each region is substantially uniform between the regions. 1 is an image forming apparatus according to a first aspect of the present invention that performs control.

The fourth aspect of the present invention is
The charge adjusting unit is the secondary transfer unit,
The secondary transfer portion is
A secondary transfer member disposed in contact with the intermediate transfer member;
A secondary transfer member application unit that applies a voltage to the secondary transfer member;
The controller is
When the recording medium passes, a voltage is applied to the secondary transfer member so as to have a polarity opposite to the charge of the toner,
When the toner on the developer carrying member is replaced, when the region passes, the secondary transfer member application unit applies a voltage to the secondary transfer member so as to have the same polarity as the charge of the toner. 3 is an image forming apparatus according to a third aspect of the present invention.

The fifth aspect of the present invention is
To neutralize the recording medium that has passed through the secondary transfer unit, a neutralization member provided on the downstream side of the secondary transfer unit and in the vicinity of the intermediate transfer unit, and the toner on the neutralization member A neutralization unit having a neutralization member application unit that applies a voltage of the same polarity as the electrode of
The charge adjusting unit is the charge eliminating unit,
The controller is
When the recording medium passes, a voltage is applied to the neutralizing member so as to have the same polarity as the charge of the toner, and the recording medium is neutralized,
Wherein when replacing the toner on the developer carrying member, even when the region passes so as to apply the electric load voltage of the same polarity of the toner to the charge removing member, for controlling the charge removing member applying unit, 3 is an image forming apparatus according to a third aspect of the present invention;

The sixth aspect of the present invention
The removing unit is
A fur brush roller in contact with the intermediate transfer member;
In the image forming apparatus according to the first aspect of the present invention, the fur brush roller includes a removal voltage applying unit that applies a voltage having a polarity opposite to the charge of the toner.

The seventh aspect of the present invention
The different types of toner are four color toners of black, yellow, cyan and magenta,
The intermediate transfer member is an intermediate transfer belt,
The plurality of image carriers and the plurality of primary transfer portions correspond to the four color toners, and are arranged in the order of black, yellow, cyan, and magenta from the side closer to the secondary transfer portion along the intermediate transfer belt. Has been
The controller is
A charge of the same value is applied to the area on the intermediate transfer belt where the yellow toner is discharged, the area where the cyan toner is discharged, and the area where the magenta toner is discharged,
The image forming apparatus according to the third aspect of the present invention, wherein the charge adjusting unit is controlled so that a charge having a value larger than the charge is applied to an area where the black toner is discharged on the intermediate transfer belt. Device.

Further, the eighth aspect of the present invention is
A plurality of image carriers on which toner images are formed; and
A plurality of developer carriers for carrying toner to supply the toner to each of the image carriers;
A plurality of primary transfer portions arranged facing each of the image carriers,
An intermediate transfer member disposed between the plurality of image carriers and the plurality of primary transfer units to superimpose the toner images on the surfaces of the plurality of image carriers;
A secondary transfer portion for transferring the superimposed toner image from the intermediate transfer member onto a recording medium;
A control method for an image forming apparatus, comprising: a removing unit that is provided to remove toner on the intermediate transfer body and to which a voltage is applied so as to have a polarity opposite to the charge of the toner
When the toner on the developer carrying member is replaced without supplying the recording medium to the secondary transfer unit, the intermediate transfer that is rotating from each developer carrying member via the respective image carrying member. The charge of the toner discharged to each area that sequentially passes through the removal unit without overlapping on the body is changed according to the type of toner or the position of the image carrier, and the toner in each area. Is a control method of an image forming apparatus provided with a charge adjustment step of adjusting so as to reduce the difference in charge between the two.

The ninth invention relates to
A program for causing a computer of an image forming apparatus to execute a control method for an image forming apparatus according to an eighth aspect of the present invention.

The tenth aspect of the present invention is
A recording medium on which the program of the ninth aspect of the present invention is recorded, and is a recording medium that can be used by a computer.

  According to the present invention, it is possible to provide an image forming apparatus and a control method for the image forming apparatus that can suppress a cleaning failure at the time of toner replacement.

  Hereinafter, a copying machine as an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a front sectional view of a copying machine according to an embodiment of the present invention. As shown in FIG. 1, the copying machine 1 according to the first embodiment includes two sheet feeding cassettes 2 for storing sheets on which images are formed at the bottom. In addition, the copying machine 1 includes a document reading unit 3 that reads an image of a document by using an exposure lamp, a lens, a mirror, and the like.

  The copying machine 1 according to the present embodiment is a color copying machine using a tandem method, and includes a black image forming unit 4, a yellow image forming unit 5, a cyan image forming unit 6, and a magenta arranged in order in the horizontal direction. An image forming unit 7 is provided. An intermediate transfer belt 8 for superimposing images formed by these image forming units is disposed.

  Further, a secondary transfer unit 9 that transfers the toner image superimposed on the intermediate transfer belt 8 to a sheet and a fixing unit 10 that fixes the transferred toner image to the sheet are provided. Further, a discharge tray 13 for discharging the sheet on which the toner image is fixed is provided below the document reading unit 3.

  Next, the image forming unit will be described. Since the basic configurations of the four image forming units 4, 5, 6, and 7 are the same, the magenta image forming unit 7 will be described as an example. As shown in FIG. 1, the magenta image forming unit 7 includes a photosensitive drum 70, a charger 71, a developing device 72, a cleaning unit 73, and the like. In addition, a laser scanner unit (hereinafter referred to as an electrostatic latent image) that forms an electrostatic latent image by optically scanning the surface of each photosensitive drum charged by each charger in each of the four image forming units 4, 5, 6, 7. (Referred to as LSU) 12 is provided below the image forming unit. Further, a primary transfer roller 17 is disposed so as to face the photosensitive drum 70 with the intermediate transfer belt 8 interposed therebetween. The developing device 72 is provided with a developing roller 75 disposed in contact with the photosensitive drum 70 in order to supply toner to the surface of the photosensitive drum 70.

  Between the photosensitive drum 70 and the primary transfer roller 17, between the photosensitive drum 60 and the primary transfer roller 16, between the photosensitive drum 50 and the primary transfer roller 15, and between the photosensitive drum 40 and the primary transfer roller 14. The intermediate transfer belt 8 is wound around the primary transfer rollers 14, 15, 16 and 17 so as to pass therethrough.

  The secondary transfer unit 9 is disposed in the vicinity of the downstream side of the black image forming unit 4 with respect to the rotation direction of the intermediate transfer belt 8 so as to press the intermediate transfer belt 8 (described later). 2). A driving roller 21 is provided inside the intermediate transfer belt 8 so as to face the secondary transfer roller 92.

  Further, a neutralization unit 24 for removing the charge of the paper is provided in the vicinity of the downstream of the secondary transfer roller 92 with reference to the paper conveyance direction in order to prevent sticking to the paper conveyance path. ing. A belt cleaning unit 11 for removing residual toner on the surface of the intermediate transfer belt 8 is disposed in the vicinity of the upstream side of the magenta image forming unit 7. A driven roller 22 is provided inside the intermediate transfer belt 8 so as to face the belt cleaning unit 11. Further, a tension roller 23 for applying tension to the intermediate transfer belt 8 is disposed between the driving roller 21 and the driven roller 22.

  FIG. 2 is an enlarged configuration diagram in the vicinity of the intermediate transfer belt 8.

  As shown in FIG. 2, the charge removal unit 24 includes a charge removal member 241 and a voltage application unit 242 for applying a voltage to the charge removal member 241. In addition, the secondary transfer unit 9 includes a voltage application unit 91 for applying a voltage to the secondary transfer roller 92. Further, the drive roller 21 is grounded.

  Next, the configuration of the belt cleaning unit 11 will be described.

  The belt cleaning unit 11 includes a fur brush roller 111 disposed to face the driven roller 22 across the intermediate transfer belt 8, a collection roller 112 disposed to press the fur brush roller 111, and a collection roller And a rubber blade 113 for removing the toner on 112. One of the bearings of the collection roller 112 is conductive, and a voltage application unit 114 that supplies a voltage to the collection roller 112 through this bearing is provided. On the other hand, the bearing of the fur brush roller 111 is non-conductive, and the voltage applied to the recovery roller 112 can act as a cleaning voltage without loss. Note that the driven roller 22 disposed to face the collection roller 112 is grounded. A control unit 25 is provided to control the voltage application units 91, 114, and 242.

  Although not shown in FIG. 2, the photosensitive drums 40, 50, 60, and 70 are grounded, and the primary transfer rollers 14, 15, 16, and 17 are each provided with a voltage application unit. Yes. Each component of the voltage application unit and the image forming unit is controlled by the control unit 25.

  An example of the plurality of image carriers of the present invention corresponds to the photosensitive drums 40, 50, 60, and 70 of the present embodiment, and an example of the plurality of developer carriers of the present invention is the present embodiment. Corresponds to the developing rollers 45, 55, 65 and 75. An example of a plurality of primary transfer units of the present invention corresponds to the primary transfer rollers 14, 15, 16, 17 of the present embodiment and a voltage application unit that applies a voltage to each primary transfer roller. An example of the transfer member corresponds to the intermediate transfer belt 8 of the present embodiment. An example of the secondary transfer unit of the present invention corresponds to the secondary transfer unit 9 of the present embodiment, and an example of the removal unit of the present invention corresponds to the belt cleaning unit 11 of the present embodiment. An example of the charge adjustment unit of the present invention corresponds to the secondary transfer unit 9, and an example of the control unit of the present invention corresponds to the control unit 25 of the present embodiment.

  An example of the secondary transfer member of the present invention corresponds to the secondary transfer roller 92 of the present embodiment, and an example of the secondary transfer member application unit of the present invention is applied to the voltage application unit 91 of the present embodiment. Equivalent to. An example of the removal voltage application unit of the present invention corresponds to the voltage application unit 114 of the present embodiment.

  An operation at the time of image formation of the copying machine of the present embodiment having the above configuration will be described. FIG. 3 is a diagram showing the state of charging of each component during image formation, and is a diagram of the vicinity of the intermediate transfer belt 8 similar to FIG.

  Based on the image data read by the document reading unit 3, the surfaces of the photosensitive drums 40, 50, 60, 70 of the magenta image forming unit 7, the cyan image forming unit 6, the yellow image forming unit 5, and the black image forming unit 4. A toner image is formed on (see FIG. 1). At this time, the toner on the photosensitive drum is positively charged, and the toner images are intermediately transferred in the order of magenta, cyan, yellow, and black by the primary transfer rollers 14, 15, 16, and 17 to which a negative voltage is applied. Overlaid on the belt 8.

  At the same time, the paper is fed from the paper feed cassette 2 and the toner image superimposed on the intermediate transfer belt 8 is transferred onto the paper P by the secondary transfer roller 92 (see FIG. 3). Here, since the toner image is positively charged, a voltage is applied to the secondary transfer roller 92 by the voltage applying unit 91 so that the surface thereof is negatively charged.

  In addition, a voltage is applied by the voltage application unit 242 so that a positive charge is generated in the charge removal member 241 when the paper is passed. For this reason, neutralization is performed on the back surface (the surface on which the toner image is not formed) that passes through the secondary transfer roller 92 and is negatively charged, and the paper P is transported smoothly.

  Then, the sheet on which the toner image is fixed by the fixing unit 10 is discharged to the discharge tray 13 (see FIG. 1). Incidentally, the toner S (see FIG. 3) remaining on the intermediate transfer belt 8 during the transfer onto the sheet is removed by the negatively charged fur brush roller 111 via the recovery roller 112.

  Next, the operation at the time of toner replacement of the copying machine of the present embodiment will be described, and an example of the control method of the image forming apparatus of the present invention will be described. FIG. 4 is a diagram showing the charged state of each component when the toner is replaced, and is a diagram of the vicinity of the intermediate transfer belt 8 similar to FIG.

  A threshold value of the average printing rate for a predetermined number of sheets is set in advance, and a value lower than this threshold value is determined as a low printing state. For example, this value can be set to 3%. The average printing rate is the ratio of the area occupied by the toner to the area of the paper (for example, a value obtained by converting the paper size to A4 size).

  When the control unit 25 determines that the average printing rate is equal to or less than the threshold value, after completing one job, the developing rollers 45, 55, 65, and 75 and the photosensitive drum are used rather than during normal image formation. By increasing the effective value of the alternating electric field between 40, 50, 60, and 70, the residual toner on the developing rollers 45, 55, 65, and 75 is forcibly moved to the photosensitive drum. Note that the image forming operation may be forcibly terminated without waiting for the end of one job. In short, it is sufficient that the sheet is not supplied to the secondary transfer roller 92.

  The toner of each color that has moved to the photosensitive drums 40, 50, 60, 70 is discharged onto the intermediate transfer belt 8. FIG. 5 shows the state of the toner discharged on the intermediate transfer belt 8. As shown in FIG. 5, a region 34 where black toner is discharged, a region 35 where yellow toner is discharged, a region 36 where cyan toner is discharged, and a magenta toner are discharged on the intermediate transfer belt 8. A region 37 is formed. FIG. 4 shows regions 34, 35, 36, and 37 in which the intermediate transfer belt 8 is moving.

  Here, as described in the background art, in order to prevent the toner discharged on the intermediate transfer belt 8 from adhering to the secondary transfer roller 92, the secondary surface is charged so that the surface is positively charged when the toner is replaced. A voltage is applied to the transfer roller 92. When the areas 34, 35, 36, and 37 where the toner is discharged pass through the secondary transfer roller 92, the secondary transfer roller 92 is positively charged, and thus the toner charge in each area increases.

  On the other hand, in the present embodiment, the black toner and the yellow, cyan, and magenta color toners have different resistance values depending on the carbon content (other external additives and the like). That is, since the black toner has a higher carbon content than the color toner, the resistance value is smaller than that of the color toner. Thus, when the resistance value is low, the charge amount is difficult to increase, so the black toner has a smaller charge amount than the color toner.

  Therefore, in the present embodiment, the voltage applied to the secondary transfer roller 92 when the area 34 where the black toner is discharged passes through the voltage applied when the other areas 35, 36, and 37 pass. The control is performed so that the charge amount of the toner in the regions 34, 35, 36, and 37 is substantially uniform. That is, the amount of increase in the charge amount of the toner in the region 34 is made larger than the amount of increase in the charge amount of the toner in the regions 35, 36, and 37, so that the charge amount of the color toner in the regions 35, 36, and 37 is increased. Then, the control is performed so as to match the charge amount of the black toner in the region 34. This control corresponds to an example of the charge adjustment step of the present invention. Since the charge removal member 241 is not energized, the charge of the toner passing through the intermediate transfer belt 8 is not affected by the charge removal member 241.

  Subsequently, the toner on the areas 34, 35, 36, and 37 that have passed through the secondary transfer roller 92 is removed by the fur brush roller 111. The fur brush roller 111 increases the number of times of contact with the toner due to physical disturbance by the hair tip, and collects the toner from the intermediate transfer belt 8 by electrostatic adhesion between the hair tip and the toner. The uniform reference value described above is a value determined by conditions such as the cleaning bias applied to the fur brush roller 111, the toner particle diameter, and the surrounding structure. Note that the uniform width corresponding to the above-described substantially uniform value is a uniform reference value (hereinafter referred to as a reference value) in the configuration of the present embodiment in which the charge amount of the black toner is matched with the charge amount on the color toner side. This corresponds to a width of ± 10%.

  Here, in the present embodiment, in each of the regions 34, 35, 36, and 37, the toner charge amount is adjusted to the negative polarity by adjusting the secondary transfer roller 92. The fur brush roller 111 can be effectively removed.

  Hereinafter, examples of the present embodiment will be described.

Example 1
As the fur brush roller 111, the material is nylon, the outer diameter is 17 mm, the bristle length is 4.5 mm, the fineness is 6D (denier), the yarn resistance is 11.5 (logΩ) (manufactured by Toei Sangyo Co., Ltd., model number UUN ( 6 nylon, carbon type, uniform dispersion type)) and a brush density of 120 KF / inch ² were used.

  The secondary transfer roller 92 is made of foamed synthetic rubber of epichlorohydrin and nitrile, having a hardness of 35 ± 5 ° (Asker-C) and a resistance of 7 (logΩ). The resistance value of the secondary transfer roller 92 is a value obtained by measuring a current by applying a voltage to the shaft in a state where a load is applied to the roller by a metal plate.

  As the intermediate transfer belt 8, for example, a base layer with PVDF (polyvinylidene fluoride), an intermediate layer with CR rubber, and a surface with fluorine coating was used. The nip width between the intermediate transfer belt 8 and the fur brush roller 111 is set to 1 mm.

  Under such conditions, the amount of toner discharged on the intermediate transfer belt is measured after passing through the primary transfer roller 14 of the black toner and before reaching the secondary transfer roller 92. 3 corresponds to +19.5 (μC / μg), and the other color toners (corresponding to regions 35, 36, and 37 in FIG. 3) are all +31.3 (μC / g). . The charge amount of each toner was measured using a toner charge amount measuring device manufactured by Trek. The particle size of each toner was about 7.5 μm.

  Further, the fur brush roller 111 is controlled at a constant current of −20 μA. Under the conditions of this embodiment, the reference value can be set to 34 (μC / g), which is slightly larger than the charge amount of the color toner.

  When the black toner region 34 passes through the secondary transfer roller 92 so as to match the reference value, a voltage of 800 V is applied to the secondary transfer roller 92 and the surface thereof is positively charged. When the other color toner regions 35, 36, and 37 pass, a voltage of 500 V is applied to the secondary transfer roller.

  The black toner charge amount after passing through the secondary transfer roller 92 is +33.8 (μC / g), and the color toner charge amount is +34.2 (μC / g). Within ± 10%.

  In this state, when passing through the fur brush roller 111, the toner could be removed in any region.

(Comparative Example 1)
On the other hand, in any of the regions 34, 35, 36, and 37, the voltage applied to the secondary transfer roller 92 is set to a constant value of 500 V, and the rest is the same as that in the above embodiment, and the fur brush roller 111 performs intermediate processing. An experiment was conducted to remove the toner on the transfer belt 8.

  The black toner charge amount after passing through the black primary transfer roller 14 and before passing through the secondary transfer roller 92 is +19.5 (μC / g), and the charge amounts of the other color toners are 31. .3 (μC / g). Since the charge removal member 241 is not energized, the charge of the toner passing through the intermediate transfer belt 8 is not affected by the charge removal member 241.

  The charge amount of the black toner after passing through the secondary transfer roller 92 to which a voltage of 500 V is applied is +23.8 (μC / g), and the charge amounts of the other color toners are 35.3. (ΜC / g), which is not within ± 10% of the reference value.

  In this state, when passing through the fur brush roller 111, black toner remained on the intermediate transfer belt 8. This is presumably because the black toner has a smaller positive charge amount than other color toners, and the electrostatic force generated between the black toner and the fur brush roller 111 is reduced.

  As described above, the charge amount of the toner in each region is increased by the secondary transfer roller 92 so that the toner charge amount is within the range that can be effectively removed by the fur brush roller 111 under the conditions of this embodiment. It can be seen that the toner can be effectively removed from the intermediate transfer belt 8.

(Embodiment 2)
The copier according to the second embodiment of the present invention will be described below.

  The basic configuration of the copying machine of the second embodiment is the same as that of the first embodiment, but the control method at the time of toner replacement is different. Therefore, the description will focus on the differences from the first embodiment.

  In the copying machine of the second embodiment, similarly to the first embodiment, excessively charged toner is discharged onto the intermediate transfer belt 8 in the low printing state (see FIG. 3).

  When each of the regions 34, 35, 36, and 37 passes through the secondary transfer roller 92, unlike the first embodiment, the voltage applied to the secondary transfer roller 92 is not changed for each region and is constant. A voltage is applied to the secondary transfer roller 92.

  Conventionally, the charge eliminating member 241 is applied with a voltage so as to be positively charged only when the paper is passed, and no voltage is applied when the toner is replaced. By applying a voltage to 241, control is performed so that the charge amount of the toner in the region is made uniform. This control corresponds to an example of the charge adjustment step of the present invention.

  That is, when the region 34 where the black toner is discharged passes and when the other regions 35, 36, and 37 pass, the voltage applied to the charge removal member 241 is changed to pass the charge removal member 241. The toner charge amount in each subsequent region can be made uniform as in the first embodiment.

  An example of the charge adjustment unit of the present invention corresponds to the charge removal unit 24 of the second embodiment, and an example of the charge removal member application unit of the present invention corresponds to the voltage application unit 242 of the second embodiment.

  Hereinafter, Example 2 of the second embodiment will be described.

(Example 2)
The fur brush roller 111, the secondary transfer roller 92, and the intermediate transfer belt 8 are the same as those in the first embodiment, and thus the description thereof is omitted. Note that a voltage of 500 V is applied to the secondary transfer roller 92 so as to be charged to +. The particle size of each toner was about 7.5 μm. Further, the fur brush roller 111 is controlled at a constant current of −20 μA. Under the conditions of this embodiment, the reference value can be set to 34 (μC / g), which is slightly larger than the charge amount of the color toner.

  When the charge amount of the toner discharged onto the intermediate transfer belt is measured after passing through the primary transfer roller 14 of the black toner and before reaching the secondary transfer roller 92, the black toner (corresponding to the region 34 in FIG. 3) is The color toner was +18.2 (μC / μg), and the other color toners (corresponding to the regions 35, 36, and 37 in FIG. 3) were all +32.7 (μC / g).

  When the black toner region 34 passes through the charge removal member 241 so as to match the reference value, the charge removal member 241 is positively charged with a current of +16 μA. Further, when the other color toner regions 35, 36, and 37 pass, a current of +10 μA flows through the charge removal member 241.

  The charge amount of the black toner after passing through the secondary transfer roller 92 and the charge removal member 241 is +34.1 (μC / g), and the charge amount of the color toner is +33.9 (μC / g). It is within the range of ± 10% of the reference value.

  In this state, when passing through the fur brush roller 111, the toner could be removed in any region.

  From Example 2 and the above comparative example, the charge amount of the black toner is increased more than the charge amount of the color toner by the charge eliminating member 241 so that the charge amount of the toner between the regions is substantially uniform. It can be seen that the toner can be effectively removed from the transfer belt 8.

  In the above-described embodiment, since the black toner has a different charge amount from the other toners, control is performed by separately dividing the increase in charge amount (charge up) for black and color. If the charge amount of the magenta toner is also different, control may be performed by changing the charge-up amount for each type of different toner.

  In the above-described embodiment, it is preferable that the control is performed so that the charge of the toner between the regions is substantially uniform, but the toner after the control is more after the control than before the control. The toner can be removed more efficiently than before by reducing at least the difference in charge.

  In the above description, the control is performed so as to match the charge amount on the color toner side, but the control may be performed so as to match the charge amount on the black toner side.

  In the copying machine of the above-described embodiment, the charge amount of the toner discharged from the magenta image forming unit 7 passes through the cyan image forming unit 6, the yellow image forming unit 5, and the black image forming unit 4. Since the color toner has almost the same charge amount for all three colors, the charge amount may increase or decrease while passing through each image forming unit depending on the material of the intermediate transfer belt 8 or the like. is there. In such a case, the charge-up amount is adjusted based on the distance of each image forming unit from the secondary transfer roller 92 or the charge removal member 241.

  In the above-described embodiment, the existing secondary transfer roller 92 and the charge eliminating member 241 are used as an example of the charge adjusting unit of the present invention in order to charge up the toner. May be provided. As this configuration, for example, a conductive roller that is arranged on the downstream side of the driving roller 21 and on the upstream side of the driven roller 21 to which a voltage can be applied can be cited.

  As an example of the recording medium of the present invention, paper is used in the above embodiment, but an OHP sheet or the like may be used.

  The program of the present invention is a program for causing a computer to execute the operation of the charge adjustment step of the above-described control method of the image forming apparatus of the present invention, and is a program that operates in cooperation with the computer.

  The recording medium of the present invention is a recording medium that records a program for causing a computer to execute all or part of the charge adjustment process of the control method of the image forming apparatus of the present invention described above, and can be read by the computer. The read program is a recording medium for executing the operation in cooperation with the computer.

  The “process operation” of the present invention means the operation of all or part of the process.

  Further, one use form of the program of the present invention may be an aspect in which the program is recorded on a recording medium such as a ROM readable by a computer and operates in cooperation with the computer.

  Also, one use form of the program of the present invention is an aspect in which the program is transmitted through a transmission medium such as the Internet, a transmission medium such as light, radio wave, and sound wave, read by a computer, and operates in cooperation with the computer. Also good.

  The computer of the present invention described above is not limited to pure hardware such as a CPU, but may include firmware, an OS, and peripheral devices.

  As described above, the configuration of the present invention may be realized by software or hardware.

  INDUSTRIAL APPLICABILITY The image forming apparatus and the image forming apparatus control method according to the present invention have an effect capable of suppressing poor cleaning at the time of toner replacement, and are useful as a copying machine, a printer, a facsimile, and the like.

1 is a front configuration diagram of a copying machine according to a first embodiment of the present invention. 1 is a configuration diagram near an intermediate transfer belt of a copying machine according to a first embodiment of the present invention. 1 is a configuration diagram for explaining an operation at the time of paper passing in a copying machine according to a first embodiment of the present invention. FIG. 2 is a plan view showing an intermediate transfer belt of the copying machine according to Embodiment 1 of the present invention and toner discharged on the intermediate transfer belt when the toner is replaced. 1 is a configuration diagram for explaining an operation at the time of toner replacement in the copier according to the first embodiment of the present invention. Configuration diagram of the vicinity of an intermediate transfer belt of a conventional image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copier 2 Paper feed cassette 3 Image reading part 4 Black image forming part 5 Yellow image forming part 6 Cyan image forming part 7 Magenta image forming part 8 Intermediate transfer belt 9 Secondary transfer part 10 Fixing part 11 Belt cleaning part 12 LSU
13 Discharge tray 14, 15, 16, 17 Primary transfer roller 21, 22 Roller 23 Tension roller 24 Static elimination unit 25 Control unit

Claims (10)

A plurality of image carriers on which toner images are formed; and
A plurality of developer carriers for carrying the toner to supply toner to each of the image carriers;
A plurality of primary transfer portions arranged facing each of the image carriers,
An intermediate transfer member disposed between the plurality of image carriers and the plurality of primary transfer units to superimpose the toner images on the surfaces of the plurality of image carriers;
A secondary transfer portion for transferring the superimposed toner image from the intermediate transfer member onto a recording medium;
A removing unit provided to remove toner on the intermediate transfer member, and applied with a voltage so as to have a polarity opposite to the charge of the toner;
When the toner on the developer carrying member is replaced without supplying the recording medium to the secondary transfer unit, the intermediate transfer that is rotating from each developer carrying member via the respective image carrying member. A charge adjustment unit that adjusts the charge of the toner discharged to each region that sequentially passes through the removal unit without overlapping on the body;
Control that is controlled by the charge adjustment unit so as to reduce the difference in toner charge in each region for each of the regions that sequentially pass through the charge adjustment unit based on the type of toner or the position of the image carrier. And an image forming apparatus. The controller is
The image forming apparatus according to claim 1, wherein the charge adjusting unit controls the toner charge in each region to be substantially uniform between the regions. The controller is
By applying a charge having the same polarity as the polarity of the toner to the toner in the region for each region by the charge adjusting unit, the charge of the toner in each region is substantially uniform between the regions. The image forming apparatus according to claim 1, wherein control is performed. The charge adjusting unit is the secondary transfer unit,
The secondary transfer portion is
A secondary transfer member disposed in contact with the intermediate transfer member;
A secondary transfer member application unit that applies a voltage to the secondary transfer member;
The controller is
When the recording medium passes, a voltage is applied to the secondary transfer member so as to have a polarity opposite to the charge of the toner,
When the toner on the developer carrying member is replaced, when the region passes, the secondary transfer member application unit applies a voltage to the secondary transfer member so as to have the same polarity as the charge of the toner. The image forming apparatus according to claim 3, wherein To neutralize the recording medium that has passed through the secondary transfer unit, a neutralization member provided on the downstream side of the secondary transfer unit and in the vicinity of the intermediate transfer unit, and the toner on the neutralization member A neutralization unit having a neutralization member application unit that applies a voltage of the same polarity as the electrode of
The charge adjusting unit is the charge eliminating unit,
The controller is
When the recording medium passes, a voltage is applied to the neutralizing member so as to have the same polarity as the charge of the toner, and the recording medium is neutralized,
The charge removal member application unit is controlled so that a voltage having the same polarity as the charge of the toner is applied to the charge removal member even when the region passes when the toner on the developer carrying member is replaced. Item 4. The image forming apparatus according to Item 3. The removing unit is
A fur brush roller in contact with the intermediate transfer member;
The image forming apparatus according to claim 1, further comprising a removal voltage applying unit configured to apply a voltage having a polarity opposite to the charge of the toner to the fur brush roller. The different types of toner are four color toners of black, yellow, cyan and magenta,
The intermediate transfer member is an intermediate transfer belt,
The plurality of image carriers and the plurality of primary transfer portions correspond to the four color toners, and are arranged in the order of black, yellow, cyan, and magenta from the side closer to the secondary transfer portion along the intermediate transfer belt. Has been
The controller is
A charge of the same value is applied to the area on the intermediate transfer belt where the yellow toner is discharged, the area where the cyan toner is discharged, and the area where the magenta toner is discharged,
4. The image forming apparatus according to claim 3, wherein the charge adjusting unit is controlled so that a charge having a value larger than the charge is applied to a region where the black toner is discharged on the intermediate transfer belt. . A plurality of image carriers on which toner images are formed; and
A plurality of developer carriers for carrying toner to supply the toner to each of the image carriers;
A plurality of primary transfer portions arranged facing each of the image carriers,
An intermediate transfer member disposed between the plurality of image carriers and the plurality of primary transfer units to superimpose the toner images on the surfaces of the plurality of image carriers;
A secondary transfer portion for transferring the superimposed toner image from the intermediate transfer member onto a recording medium;
A control method for an image forming apparatus, comprising: a removing unit that is provided to remove toner on the intermediate transfer body and to which a voltage is applied so as to have a polarity opposite to the charge of the toner,
When the toner on the developer carrying member is replaced without supplying the recording medium to the secondary transfer unit, the intermediate transfer that is rotating from each developer carrying member via the respective image carrying member. The charge of the toner discharged to each area that sequentially passes through the removal unit without overlapping on the body is changed according to the type of toner or the position of the image carrier, and the toner in each area. A method for controlling an image forming apparatus, comprising a charge adjustment step of adjusting so as to reduce a difference in charge between the two . A program for causing a computer of the image forming apparatus to execute the control method of the image forming apparatus according to claim 8. A recording medium on which the program according to claim 9 is recorded, the recording medium being usable by a computer.

Images