JPH11212381A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of effectively removing residual toner on an intermediate transfer body, being conventionally difficult to be removed. SOLUTION: This device is provided with image carriers 2BK, 2Y, 2C and 2M on a surface of which the toner image is respectively formed, the toner image forming units 5, 6, 7 and 8 forming the toner image, based on the image information on the respective image carrier, an intermediate transfer body 3 receiving transfer of the toner image formed by the respective toner image forming unit, a corona discharging unit 9 transferring the toner image on the intermediate transfer body 3, heat transferring rolls 11 and 4 transferring the toner image on a recording medium P by closely adhering the recording medium P to the intermediate transfer body 3 on which the toner image is transferred, holding the toner image there between, heating while pressurizing the toner image held by the transfer body 3 and the medium P in a closely adhered state a cleaner 16 cleaning the toner on the intermediate transfer body 3, and cleaning controlling means 1 controlling the respective toner image forming unit so that the cleaning toner image is formed on a specified cleaning object area on the intermediate transfer body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used for an electrophotographic copying machine, a printer, and the like.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus of this kind, an intermediate transfer type image forming apparatus disclosed in Japanese Patent Publication No. 49-209 and Japanese Patent Application Laid-Open No. 62-206567 has been known. FIG. 4 shows a typical configuration example. FIG. 4 is a schematic configuration diagram of a conventional intermediate transfer type image forming apparatus.

The image forming apparatus shown in FIG. 4 has a photosensitive layer on the surface, on which an electrostatic latent image is formed, and an image carrier 100 rotating in the direction of arrow A, and a periphery of the image carrier 100. Black (B) formed on the image carrier 100
k), yellow (Y), magenta (M), and cyan (C) electrostatic latent images corresponding to the respective colors are developed with respective color toners, and the toner images T of the respective colors are formed on the image carrier 100.
Developing devices 103, 104, 105, and 106, which receive the primary transfer of the toner image from the image carrier 100 at the primary transfer position T1, a belt-shaped intermediate transfer member 101 circulating in the direction of arrow B, and the primary transfer position T1 A corona discharger 1 that is arranged to face the image carrier 100 and primarily transfers the toner image T on the image carrier 100 to the intermediate transfer body 101
07, located at the secondary transfer position T2,
A bias roll 108 for transferring the upper toner image onto the recording medium 102 at a time is provided.

In this image forming apparatus, the first color Bk toner image is formed on the image carrier 100 during the first rotation of the image carrier 100, and the Bk toner image is primarily transferred onto the intermediate transfer member 101. Next, the Y toner image of the second color is formed on the image carrier 100 during the second rotation of the image carrier 100, and the Y toner image is superimposed on the Bk toner image on the intermediate transfer member 101. As the primary transfer, as well as the third
The M and C toner images of the fourth color are primarily transferred so as to be superimposed on the Bk and Y toner images, and a combined toner image in which the four color toner images are combined is formed on the intermediate transfer body 101.

As described above, the intermediate transfer member 1 is obtained by the multiple transfer.
After the four-color composite toner image is formed on the recording medium 01, the composite toner image is secondarily transferred collectively to the recording medium 102, whereby a desired color image is formed on the recording medium 102. Prior to the development of the intermediate transfer type color image forming apparatus as described above, the color image forming apparatus employed a method in which toner images of respective colors formed on an image carrier were directly multiple-transferred to a recording medium. Therefore, due to many factors such as the thickness and surface characteristics of the recording medium, the transport characteristics of the recording medium with respect to the image carrier, and the occurrence of image disturbance and color shift during multiple transfer, the color formed on the recording medium The image quality was affected.

However, as shown in FIG.
01, the intermediate transfer member 10
Since the composite toner image formed by the multiple transfer once onto the print medium 1 is collectively transferred to the recording medium 102, it is possible to eliminate the instability factor caused by the recording medium as described above.
It is possible to effectively prevent the image from being disturbed and the color from being shifted during the multiple transfer.

However, this type of image forming apparatus has the following problems. That is, in the image forming apparatus of this system, both the primary transfer of the toner image T from the image carrier 100 to the intermediate transfer member 101 and the secondary transfer of the toner image T from the intermediate transfer member 101 to the recording medium 102 are both electrostatic. This is performed by a transfer method. Therefore, a corona discharger 107 is provided at the primary transfer position T1, and a voltage having a polarity opposite to the polarity of the toner is applied to the corona discharger 107 to perform primary transfer. A bias roll 108 is provided at the secondary transfer position T2, and a voltage having a polarity opposite to the polarity of the toner is applied to the bias roll 108 to perform secondary transfer.

[0008] From the image carrier 100 to the intermediate transfer body 101
When the line toner image is transferred multiple times during the primary transfer to the printer, the line toner image of the next color, which is transferred over the already transferred line toner image, may be scattered violently. This is generally considered to be due to the following causes. (1) The transfer electric field also acts on a region in the transfer prenip portion where the image carrier and the intermediate transfer member are not in close contact.

(2) After passing through the transfer nip, when the image carrier and the intermediate transfer member are separated from each other, a discharge is generated between the two. Conventionally, various measures have been taken to improve the problem of toner image scattering, but a sufficient improvement effect has not been obtained. According to the study of the present inventors, it has been found that the scattering of the toner image appears remarkably when a semiconductor material is used as the intermediate transfer member. One of the causes is that when the intermediate transfer body is a low-resistance body, the transfer charge spreads through the intermediate transfer body to the transfer prenip portion, and as a result,
As described in the above item (1), it can be considered that the transfer electric field acts even in the transfer prenip region where the image carrier and the intermediate transfer member are not in close contact. However, in addition to this cause, the following causes are considered. That is,
In the primary transfer, after the toner layer having a predetermined charge is electrostatically transferred to the intermediate transfer member, the charge supplied from the corona discharger, which is the driving force of the transfer, gradually decreases from the intermediate transfer member. It is considered that the toner holding ability of the intermediate transfer member is reduced, and as a result, toner scattering occurs due to the repulsive action of the charges of the toners. Therefore, in order to prevent toner scattering at the time of the primary transfer, it is understood that charge decay of the intermediate transfer member should be prevented.

However, when an intermediate transfer member having no charge decay is used, during the secondary transfer from the intermediate transfer member to a recording medium, a high-density toner image multiplex-transferred onto the intermediate transfer member is collectively transferred. Since a high transfer electric field is required in order to perform the above operation, in an intermediate transfer body having no charge decay, discharge occurs between the intermediate transfer body and the recording medium, and image quality defects are likely to occur. In order to prevent the image quality defect due to the discharge at the time of the secondary transfer, as disclosed in Japanese Patent Publication No. 3-63758, it is required to perform the secondary transfer from the intermediate transfer body to the recording medium. A method of preventing discharge between the intermediate transfer body and the recording medium during the secondary transfer by melting the toner image on the intermediate transfer body by the heating and pressure means and transferring the toner image collectively to the recording medium. Is considered to be effective.

[0011]

However, the image forming apparatus of the type in which the toner image is melted and transferred by means of heating and pressure during the secondary transfer as described above has the following problems. . Generally, in order to clean toner and other deposits remaining on the intermediate transfer member, a cleaning method in which a cleaning member having a strong toner adhesion is brought into contact with the intermediate transfer member and toner and other deposits are adhered thereto is used. Widely used. As this cleaning method, for example, Japanese Patent Publication No. 4-45829 discloses that a metal is used for a surface material of a cleaning member, and a silicon rubber is used for a transfer layer of an intermediate transfer member. A cleaning method utilizing a difference in adhesion to a hot-melt toner is disclosed.
No. 307 discloses a cleaning method in which a resin compatible with toner is applied as an adhesive layer on the surface of a cleaning member.

However, the former Japanese Patent Publication No. 4-4582
According to the method disclosed in Japanese Patent Application Laid-Open No. 9-205, as is apparent from the graph shown in FIG.
A low-density toner image with a low toner coverage on the intermediate transfer member cannot be cleaned. FIG. 5 is a graph showing the relationship between the toner coverage on the intermediate transfer member and the cleaning efficiency.

[0013] This graph shows the toner coverage on the surface of the intermediate transfer member when a cleaning roller covered with silicone rubber having a hardness of 60 degrees heated to a surface temperature of 100 degrees is used. This is a graph showing a relationship with cleaning efficiency indicating how much toner is removed. As shown in FIG. 5, the cleaning efficiency sharply decreases when the toner coverage decreases to about 40% or less. The reason for this is that, in a high-density image with a high toner coverage, when the toner is melted, the cohesion between the adjacent toners causes the adhesive force between the cleaning member surface and the toner to cover the entire image, so that all the toner can be cleaned. However, when the toner coverage is low, such as in fog or halftone images, the toner particle density is low, and even if the toner is melted, the cohesive force between adjacent toner particles is weak. It is presumed that the adhesion of the toner becomes non-uniform, and that the cleaning member is originally weak in toner adhesion, so that cleaning failure is likely to occur.

On the other hand, in the latter method disclosed in Japanese Patent Publication No. 9307/1992, the adhesion is gradually reduced due to the deposition of the deposits on the surface of the adhesive layer, and the cleaning property is reduced by the unevenness of the deposits. In order to prevent these, it is necessary to remove the deposits by some means.However, it is difficult to remove only the deposits because the adhesive layer and the deposits are integrated. There is a problem that the layer itself is easily damaged.

The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus capable of effectively removing residual toner having a low toner coverage on an intermediate transfer member, which is difficult to remove. I do.

[0016]

An image forming apparatus according to the present invention for achieving the above object has an image carrier having a toner image formed on a surface thereof, and forms a toner image based on image information on the image carrier. An intermediate transfer member for receiving the transfer of the toner image on the image carrier formed by the toner image forming device while circulating, and transferring the toner image on the image carrier onto the intermediate transfer member. A predetermined recording medium is brought into close contact with the primary transfer means for transferring the toner image on the intermediate transfer body after the toner image is transferred by the primary transfer means so as to sandwich the toner image on the intermediate transfer body. Heat transfer means for transferring the toner image onto the recording medium by heating and pressing the toner image sandwiched between the transfer body and the recording medium while keeping the toner image in close contact, and cleaning means for cleaning the toner on the intermediate transfer body Cleaning control means for controlling the toner image forming means so that a cleaning toner image covering the cleaning target area is formed in a predetermined cleaning target area on the intermediate transfer member. .

[0017]

Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing an embodiment of the image forming apparatus of the present invention. FIG. 1 shows a schematic configuration when an image forming apparatus of the present invention is applied to an electrophotographic color copying machine.

In this image forming apparatus, toner images corresponding to each color of black (Bk), yellow (Y), magenta (M) and cyan (C) are formed on the surface. Carriers 2Bk, 2Y, 2M, 2C,
A toner image forming unit 5 for forming a toner image based on the image information corresponding to each color on each of these image carriers;
6, 7, 8 to receive the primary transfer of the toner image on each image carrier formed by each of these toner image forming units;
The intermediate transfer member 3 on the belt circulating in the direction of arrow B and the toner image on each image carrier are transferred to the respective primary transfer positions T1.
, Four corona dischargers 9 for primary transfer onto the intermediate transfer member 3, and the intermediate transfer member 3 after the respective color toner images are primarily transferred by the corona dischargers 9 at the secondary transfer position T <b> 2.
A predetermined recording medium P is brought into close contact with the toner image therebetween, and the intermediate transfer member 3 and the toner image sandwiched between the recording media P are heated and pressed while keeping the toner image in contact with the intermediate transfer member 3 to thereby form an intermediate transfer member. 3, a pair of rolls for secondarily transferring the toner image on the recording medium P, that is, a heat transfer roll 1
1 and a pressure roll 4, a cleaner 16 for cleaning the toner on the intermediate transfer body 3 and a pressure roll 4, and a cleaning toner image covering the cleaning target area is formed on a predetermined cleaning target area on the intermediate transfer body 3. A cleaning control device 1 for controlling the toner image forming units 5, 6, 7, and 8 is provided. The formation of the cleaning target area and the cleaning toner image will be described later.

Here, the toner image forming units 5, 6, 7, and 8 in the present embodiment correspond to the toner image forming means according to the present invention, and include an image signal processing device in a normal electrophotographic process, It includes a charger, an exposure device, a developing device, and an image carrier cleaner. Further, the corona discharger 9 in the present embodiment corresponds to a primary transfer unit according to the present invention, and the heat transfer roll 11 and the pressure roll 4 in the present embodiment correspond to a heat transfer unit according to the present invention. Things.

The image forming apparatus of this embodiment is provided with a heating plate 28 for heating the toner image on the intermediate transfer body 3 on the upstream side of the heating transfer means of the intermediate transfer body 3. In the embodiment, the cleaner 16 provided downstream of the heating plate 28 of the intermediate transfer body 3 and the pressure roll 4 provided further downstream of the cleaner 16 include:
This corresponds to the cleaning means according to the present invention.

The cleaner 16 includes a cleaning roll 21 that rotates in contact with the surface of the intermediate transfer member 3 and a cleaning blade 22 that removes toner attached to the cleaning roll 21. In addition, the pressure roller 4 has a function as a cleaning roller to the pressure roller 4 serving as a heat transfer unit that rotates in contact with the surface of the intermediate transfer member 3, and the cleaning roller removes toner attached to the pressure roller 4. The blade 29 is provided. Therefore, the pressure roll 4 in the present embodiment functions as both the heat transfer unit and the cleaning unit according to the present invention.

Further, the cleaning control device according to the present embodiment.
1 corresponds to the cleaning control means according to the present invention.
You. The intermediate transfer member 3 is made of a polyimide resin having excellent heat resistance.
On the surface of oil, aramid resin, etc.
Layered with fluorine resin, silicon rubber, fluorine rubber, etc.
Or fluororesin, silicone rubber,
Materials with good heat resistance and toner release properties such as rubber
It is. The electric resistance value of the intermediate transfer body 3 is the electric charge after the primary transfer.
Prevents attenuation and charge diffusion to the transfer pre-nip area
Volume resistivity of 10 to prevent¹³Ω · cm or less
Top, front and back resistivity 10¹²Ω / □ -10 ^FifteenAdjust to Ω / □
It is arranged. This is because the volume resistivity is 10¹³Ω · cm or less
When it is above, the time constant of charge decay becomes 10 seconds or more,
So that the charge is sufficiently retained even after one rotation of the transfer body
Because it becomes. Note that the back surface resistivity is 10¹⁶Ω / □ or more
The discharge occurs when the image carrier and the intermediate transfer member are separated.
As the scattering of toner image occurs and it becomes active,
The resistivity is 10^FifteenΩ / □ or less is desirable.

Here, the electrical resistivity of the intermediate transfer member 3 is measured by a high resistivity meter (Hiresta IP, manufactured by Mitsubishi Yuka).
A HR100 probe (inner electrode diameter: 50 mm, ring electrode inner diameter: 53 mm, manufactured by Mitsubishi Yuka) was connected to the probe, and a measurement was made one minute after a voltage of 500 V was applied between the electrodes. Further, the same probe may be used to calculate and obtain from a constant voltage power supply and a minute ammeter measured under the same conditions as above.

The heat transfer roll 11 has a hardness of 50 degrees to 9 degrees.
It is covered with a surface material of 0 degrees, and has a built-in heat source such as a ceramic heater or a halogen lamp, and is heated from 100 degrees to 150 degrees by this heat source. As the pressure roll 4 forming a pair with the heat transfer roll 11 at the secondary transfer position T2, a rubber roll having a hardness of 50 to 90 degrees made of silicone rubber, fluorine rubber, or the like is used. Further, a material whose surface is coated with a fluororesin may be used. Further, similarly to the heating transfer roll 11, a heat source may be incorporated, and a voltage may be applied between the heating transfer roll 11 and the pressure roll 4.

On the opposite side of the pressure roll 4 from the side facing the heat transfer roll 11, a metal cleaning blade 29 for scraping off toner dirt attached to the surface of the pressure roll 4 is attached to the pressure roll 4. Deployed in abutment. Next, the operation of the image forming apparatus thus configured will be described. The toner image forming units 5, 6, 7, and 8 form image carriers 2 Bk, 2 Y, and 2 by a normal electrophotographic process.
An electrostatic latent image corresponding to each color of Bk, Y, M, C according to image information is formed on M, 2C, and the electrostatic latent image is developed with toner of each color to form an image carrier 2Bk. , 2Y, 2
A toner image corresponding to each of the above colors is formed on M and 2C.
These toner images are used as image carriers 2Bk, 2Y, 2M, and 2C.
Are transported to the respective primary transfer positions T1 with the rotation in the direction of arrow A. Each image carrier is arranged at a respective primary transfer position T1 so as to abut a belt-shaped intermediate transfer member 3 which is stretched over a plurality of rolls and circulates in the direction of arrow B.

The toner images of each color formed on the image carriers 2Bk, 2Y, 2M, and 2C are transferred to the respective primary transfer positions T.
In 1, primary transfer is sequentially performed so as to be superimposed on the surface of the intermediate transfer body 3. A corona discharger 9 having a transfer baffle 10 for preventing the transfer prenip portion from being charged is disposed on the back surface side of the intermediate transfer body 3 at each primary transfer position T1. The toner image on each image carrier is electrostatically attracted to the intermediate transfer member 3 by applying a voltage having a polarity opposite to the charge polarity of the toner.

The primary transfer means is not limited to a corona discharger, but may use a conductive roll or a conductive brush to which a voltage is applied as long as it utilizes electrostatic force. The reason why the electrostatic force is used for the primary transfer is that when the primary transfer using the adhesive force of the toner due to heat or pressure is adopted, the image carrier is easily damaged. In this way, the toner image primarily transferred to the intermediate transfer member 3 is conveyed to the heating plate 28 as the intermediate transfer member 3 circulates in the direction of arrow B, and is heated from 150 degrees to 200 degrees. The heating plate 28 heats and fuses the intermediate transfer member 3 from the back side.

Next, the toner image is conveyed to a secondary transfer position T2 where the heat transfer roll 11 and the pressure roll 4 are pressed against each other. On the other hand, at the timing when the toner image reaches the secondary transfer position T2, the recording medium P unloaded from the tray 13 by the feed roller 12 is moved to the secondary transfer position T2.
2 and is sandwiched between the pressure roll 4 and the intermediate transfer member 3.

Thus, the intermediate transfer member 3 and the recording medium P
Is pressed and heated by the pressing force between the heat transfer roll 11 and the pressure roll 4 while the intermediate transfer body 3 and the recording medium P are in close contact with each other. In this way, the toner image that is pressurized, heated and melted at the secondary transfer position T2 is secondarily transferred to the recording medium P. In this embodiment, since the toner image is melted and transferred by the heating and pressing means as described above, even if an intermediate transfer body having no charge decay is used, the toner image is transferred between the intermediate transfer body 3 and the recording medium P. There is no occurrence of a discharge to cause an image quality defect.

The intermediate transfer body 3 heated by the heating transfer roll 11 and the pressure roll 4 to a high temperature is
Is cooled by cooling rollers 17 and 18 which rotate in contact with the roller. The cooling rollers 17 and 18 are made of a metal material having good heat conductivity such as aluminum, and the temperature of the cooling rollers 17 and 18 is kept close to the inside temperature by circulating the air inside the cooling rollers 17 and 18.

The recording medium P having received the transfer of the toner image from the intermediate transfer member 3 at the secondary transfer position T2 is
7, the intermediate transfer member 3
, And is sent to a fixing device (not shown) by the conveyor belt 15 to perform a fixing process of the toner image. The fixing process in the image forming apparatus may be configured to also serve as the heat transfer unit at the secondary transfer position T2. However, in order to obtain sufficient color fixing properties, the fixing is performed by the independent fixing device as described above. It is better to let.

The peeling claw 14 and the cleaner 16 are
These members are configured so as to be able to freely contact and separate from the intermediate transfer member 3, and these members are used except when the secondary transfer is performed.
Has been drawn into the standby position away from the In the image forming apparatus of the present embodiment, as described above,
A pressure roll 4 and a cleaner 16 are provided. The cleaning control device 1 controls the toner image forming unit so that a cleaning toner image covering the cleaning target region is formed in a predetermined cleaning target region on the intermediate transfer body 3. Then, the cleaning toner image formed on the intermediate transfer member 3 is cleaned.

In considering the problem of cleaning the residual toner on the intermediate transfer member, it is necessary to pay attention to the relationship between the toner coverage on the intermediate transfer member and the cleaning efficiency. As shown in FIG. 5 referred to in the description of the prior art, a low-density image having a toner coverage of 40% or less, such as a fog or a halftone image, cannot be cleaned. The reason for this is that, as already discussed, in a high-density image with a high toner coverage, when the toner is melted, the cohesion between the adjacent toners causes the adhesive force between the cleaning member surface and the toner to cover the entire image. The toner can be cleaned, but if the toner coverage is low, such as in fog or halftone images, the toner particle density is low, and even if the toner melts, the cohesion between adjacent toner particles is weak. It is presumed that the adhesion of the toner to the cleaning member becomes non-uniform, and that the cleaning member is originally weak in toner adhesion, so that cleaning failure is likely to occur.

As described above, in the image forming apparatus of the present invention, the cleaning control means controls the toner image forming means to cover the area to be cleaned on the intermediate transfer member with a toner coverage of 40% or more. It is preferable to control the cleaning toner image to be formed at a high rate. With this configuration, a low-density residual toner image having a low toner coverage, such as a fog or a halftone image, can be effectively cleaned.

In the present embodiment, the fog toner formed on the non-sheet passing portion on the intermediate transfer body 3 after the completion of the secondary transfer,
Alternatively, toner generated due to paper jam or the like can be effectively removed as a cleaning target. Secondary transfer position T
2, the paper passing portion on the intermediate transfer body 3 where the toner image is transferred from the intermediate transfer body 3 to the recording medium P has a transfer efficiency of 100.
%, The toner does not remain on the intermediate transfer member 3 and thus cleaning is not required. However, the fogging toner formed in the non-sheet passing portion and the toner generated due to paper jam remain on the intermediate transfer member 3. In the image forming apparatus of the present embodiment, the toner remaining on the intermediate transfer body 3 after the completion of the secondary transfer is heated and melted at the portion of the heating plate 28, and then can be removed by the adhesive force of the cleaner 16. In this case, the cleaning toner images formed on at least two or more image carriers are superimposed to increase the toner coverage to 40% or more, and then the toner is effectively removed by cleaning with the cleaner 16. Can be.

That is, in the image forming apparatus of the present invention, the residual toner on the intermediate transfer member is fogged toner adhered to a non-sheet passing area on the intermediate transfer member other than the area where the recording medium overlaps the surface of the intermediate transfer member. In some cases, the cleaning control means preferably controls the toner image forming means to form a cleaning toner image covering the cleaning target area with the non-sheet passing area as a cleaning target area. Further, when the residual toner on the intermediate transfer member is based on an untransferred image generated due to a paper jam or the like, the cleaning control unit causes the toner image forming unit to provide a desired cleaning target on the intermediate transfer member. It is also preferable that the control is performed such that an area is set and a cleaning toner image covering the area to be cleaned is formed.

Before changing the size of the recording medium, at least two of the image carriers from the image carrier 2Bk to the image carrier 2C are applied to the fog toner in the non-sheet passing portion on the intermediate transfer member. The toner image developed on one or more image carriers is transferred to a region including a non-sheet passing portion on the intermediate transfer member, and the toner coverage is increased to 40% or more. Can be removed. The timing to improve the toner coverage by superimposing images is as long as it is before changing the size of the recording medium,
It may be after the copying operation is completed or before the copying operation is started.

Further, in the image forming apparatus of the present invention, the cleaning control means selectively supplies the toner image forming means to a cleaning target area having a toner coverage of less than 40% among the cleaning target areas on the intermediate transfer member. It is also preferable that the control is performed so that the cleaning toner image is formed. Further, in the image forming apparatus of the present invention, when the size of the recording medium is changed, the cleaning control unit superimposes the pre-change recording medium on the intermediate transfer body with the toner image forming unit. It is also one of the preferable modes that the area other than the area is set as a cleaning target area and the cleaning target area is controlled to form a cleaning toner image.

Generally, in this type of image forming apparatus, a patch toner image of a plurality of gradations for controlling a tone curve of an image is formed on an image carrier every fixed number of prints or when the power is turned on. Is detected by a sensor, and the image forming conditions are optimized based on the detection result. This involves forming a patch toner image on an image carrier using a patch signal of a reference density, detecting the development density of the patch toner image on the image carrier, and developing conditions such as toner density and development bias, or the exposure amount. The tone curve of an image is optimally controlled by adjusting an exposure condition such as an image processing condition such as an image area ratio. Since this patch toner image is transferred to the intermediate transfer member 3, it is necessary to clean the intermediate transfer member 3.

Therefore, in the image forming apparatus of the present invention,
When the residual toner on the intermediate transfer member is based on the patch toner image for image density detection formed on the image carrier, the cleaning control unit sends the patch toner image to the toner image forming unit. It is preferable that control is performed so that the formed area is set as a cleaning target area and a cleaning toner image covering the cleaning target area is formed.

In the image forming apparatus of the present embodiment, two types of patch toner images for controlling the tone curve are formed on the toner image forming units 5, 6, 7, and 8 with the toner coverage of 20% and 60%, respectively. Is done. The densities of the two types of patch toner images formed on each of these image carriers are detected by density detection sensors provided on each of the image carriers, and a tone curve is predicted based on the detection results. Image processing conditions are adjusted. The formation position of the patch toner image formed on each image carrier is determined so that when the patch toner image is transferred to the intermediate transfer member, at least two colors or more are superimposed and the toner coverage is 40% or more. Because of the adjustment, the patch toner image is effectively cleaned by the cleaner 16. That is, for example,
For each color, patch toner images having a toner coverage of 20% and 60% are formed side by side in the axial direction of each image carrier, and when these patch toner images are transferred to the intermediate transfer member, the patch toner images of each color are formed. It is formed so as to be arranged in a direction perpendicular to the moving direction of the intermediate transfer member. A patch toner image with a Bk toner coverage of 60%, a patch toner image with a Y toner coverage of 20%, a patch toner image with a Bk toner coverage of 20%, and a patch toner image with a Y toner coverage of 60%; A patch toner image having an M toner coverage of 60%, a patch toner image having a C toner coverage of 20%, and a patch toner image having an M toner coverage of 20% and a patch toner image having a C toner coverage of 60% are respectively superposed. Thus, the patch toner image forming position in the axial direction of the image carrier is adjusted.

Further, in the image forming apparatus of the present invention, the image carrier, the toner image forming means, and the primary transfer means are provided corresponding to each of the plurality of colors, and each toner image forming means is provided on each image carrier. The primary transfer means acts so that the toner images of the respective color toners formed on the intermediate transfer body are sequentially superimposed on each other. The image forming apparatus further includes an image density detecting unit including a sensor for detecting the density of the patch toner image, and a control unit for cleaning, wherein each patch toner image formed on each image carrier is The toner image forming means may be controlled so that a cleaning toner image having a toner coverage of 40% or more is formed so as to be superimposed on the cleaning target area on the intermediate transfer member.

In the above description, the configuration of the image forming apparatus having a plurality of image carriers has been described. However, the present invention is not limited to this example. For example, the image forming apparatus includes one image carrier and a plurality of developing units.
The present invention can also be applied to an image forming apparatus that forms a color image by repeating the operation of primary transfer of one color toner image to the intermediate transfer body every cycle for a plurality of cycles.

That is, the toner image forming means forms a patch toner image of each color for detecting the image density on the image carrier, and includes a sensor for detecting the density of the patch toner image. A cleaning control unit configured to superimpose a plurality of color patch toner images formed on the image carrier on a cleaning target area on the intermediate transfer body to form a cleaning toner image having a toner coverage of 40% or more. It is also one of the preferable embodiments to control the toner image forming unit so that the toner image is formed.

Next, a cleaner used in the image forming apparatus of this embodiment will be described. FIG. 2 is a diagram illustrating a configuration example of a cleaner used in the image forming apparatus illustrated in FIG. The cleaner 16 corresponds to the cleaner 16 that is a cleaning unit of the intermediate transfer body 3 in the image forming apparatus shown in FIG. 1, and includes a metal material such as aluminum, stainless steel, and nickel, and a rubber such as silicone rubber and fluorine rubber. A cleaning roller 21 made of a material or a resin surface material such as polyimide, nylon or fluorine, a cleaning blade 22 for removing toner adhered to the cleaning roll 21, a heat source 2 such as a ceramic heater or a halogen lamp built in the cleaning roll 21;
3, and the retract mechanism 20.

As described above, by incorporating the heat source in the cleaning roll 21, even for an image having a large heat capacity such as a solid image, the toner melted by contact with the roll dissipates heat and solidifies to reduce the adhesive force. It can be prevented from lowering. The cleaner 16 is retracted by the retract mechanism 20 to a standby position where the cleaning roll 21 does not contact the intermediate transfer body 3 during a normal image forming cycle, and the cleaning roll 21 contacts the intermediate transfer body 3 during a cleaning cycle. The intermediate transfer member 3 is moved to an operating position where the toner is removed. The toner adhering to the cleaning roll 21 is scraped off by a metal cleaning blade 22 that contacts the cleaning roll 21.

The pressure roll 4, which is another cleaning means in this embodiment, has substantially the same configuration as the cleaner 16, and the toner adhered to the pressure roll 4 is transferred to the pressure roll 4. It is scraped off by the abutting metal cleaning blade 29. FIG. 3 is a diagram illustrating another configuration example of the cleaner used in the image forming apparatus of the present embodiment.

The cleaner 16 ′ includes a cleaning roll 21, a heat source 23 and a heat source similar to the cleaner 16 shown in FIG.
In addition to having the retract mechanism 20, the heat source 2 such as a day toning roll 24, a ceramic heater or a halogen lamp built in the day toning roll 24.
5, and a cleaning blade 26. The cleaner 16 ′ is extended to an operation position where the cleaning roll 21 contacts the intermediate transfer body 3 during a cleaning cycle. Then, the residual toner on the intermediate transfer body 3 is once adhered to the cleaning roll 21, and the toner adhered to the cleaning roll 21 is removed from the cleaning roll 21.
Is attached to a day-toning roll 24 having a built-in heat source 25 which rotates in contact with the roller. Day Toning Roll 24
The toner adhering to the roller is scraped off by a metal cleaning blade 26 which comes into contact with the day toning roll 24. In this way, the cleaner is
The first cleaning roller 21 is made of a relatively soft material such as a rubber roll to secure a sufficient nip with the intermediate transfer member 3 and the second By forming the eye daytoning roll 24 from a relatively hard material such as a metal roll, the toner can be easily scraped off by a metal cleaning blade.

With this configuration, in the image forming apparatus of the present embodiment, even a material having low toner adhesion can be used as a surface material of the cleaning member. By using the pressure roller 4 for secondary transfer requiring performance as a cleaning means for the intermediate transfer member, a dedicated cleaner can be eliminated.

[0050]

As described above, according to the image forming apparatus of the present invention, the toner is formed such that the cleaning toner image covering the cleaning target area is formed in the predetermined cleaning target area on the intermediate transfer member. Equipped with cleaning control means for controlling the image forming means, effectively removing residual toner having a low toner coverage on the intermediate transfer body, such as fog and halftone images, which is difficult to remove. And an image forming apparatus capable of performing the operation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a cleaner used in the image forming apparatus illustrated in FIG. 1;

FIG. 3 is a diagram illustrating another configuration example of the cleaner used in the image forming apparatus of the present embodiment.

FIG. 4 is a schematic configuration diagram of a conventional intermediate transfer type image forming apparatus.

FIG. 5 is a graph showing the relationship between the toner coverage on the intermediate transfer member and the cleaning efficiency.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cleaning control apparatus 2Bk, 2Y, 2M, 2C Image carrier 3 Intermediate transfer body 4 Pressure roll 5, 6, 7, 8 Toner image forming unit 10 Transfer baffle 11 Heat transfer roll 12 Feed roller 13 Tray 14 Peeling claw 15 Conveying belt 16, 16 'Cleaner 17, 18 Cooling roller 20 Retract mechanism 21 Cleaning roll 22, 26, 29 Cleaning blade 23, 25 Heat source 24 Daytoning roll 28 Heating plate 100 Image carrier 101 Intermediate transfer body 102 Recording medium 103, 104 , 105, 106 Developing device 107 Corona discharger 108 Bias roll

Claims (7)

[Claims] An image carrier on which a toner image is formed,
Toner image forming means for forming a toner image based on image information on the image carrier, and an intermediate transfer member which receives the transfer of the toner image on the image carrier formed by the toner image forming means while circulating. A primary transfer unit for transferring the toner image on the image carrier onto the intermediate transfer body; and a toner image on the intermediate transfer body on the intermediate transfer body after the toner image is transferred by the primary transfer unit. A predetermined recording medium is brought into close contact with the intermediate transfer member, and the toner image sandwiched between the intermediate transfer body and the recording medium is heated and pressed while keeping the adhesion state, whereby the toner image is transferred onto the recording medium. Heating transfer means, cleaning means for cleaning toner on the intermediate transfer body, and the toner image so that a cleaning toner image covering the cleaning target area is formed in a predetermined cleaning target area on the intermediate transfer body. An image forming apparatus comprising the cleaning control means for controlling the forming means. 2. The image forming apparatus according to claim 1, further comprising a heating unit configured to heat a toner image on the intermediate transfer body, upstream of the heating transfer unit, on the intermediate transfer body, and the cleaning unit includes a heating unit. A cleaning roll provided on the intermediate transfer body downstream of the heating unit and rotating in contact with the surface of the intermediate transfer body; and a toner removing member for removing toner attached to the cleaning roll. The image forming apparatus according to claim 1, wherein 3. The heating transfer means comprises a pair of rolls, and a roll of the pair of rolls in contact with the intermediate transfer member is a heating roll provided with a heating means, and the pair of rolls is provided. Wherein the roll on the side in contact with the recording medium comprises a pressure roll for applying a pressing force to the heating roll, and the pressure roll also serves as the cleaning means. The image forming apparatus according to claim 1. 4. The cleaning control means controls the toner image forming means so that the toner coverage of the cleaning target area after the cleaning toner image is formed on the cleaning target area on the intermediate transfer member is 40%. 2. The image forming apparatus according to claim 1, wherein the cleaning toner image having the above toner coverage is formed. 5. The cleaning control device according to claim 1, wherein the toner image forming unit selectively supplies a cleaning toner image to a cleaning target region having a toner coverage of less than 40% among the cleaning target regions on the intermediate transfer member. 5. The image forming apparatus according to claim 4, wherein the image forming is performed. 6. The cleaning control unit according to claim 1, wherein when the size of the recording medium is changed, an area other than an area on the intermediate transfer body on which the recording medium before the change has been superimposed on the toner image forming unit. 2. The image forming apparatus according to claim 1, wherein a cleaning toner image is formed in the cleaning target area by setting the area as a cleaning target area. 7. The toner image forming means for forming a patch toner image of each color for detecting image density on the image carrier, and further comprising a sensor for detecting the density of the patch toner image. An image density detection unit, wherein the cleaning control unit superimposes a plurality of color patch toner images formed on the image carrier on a cleaning target area on the intermediate transfer body, and the toner coverage is 40% or more. 2. An image forming apparatus according to claim 1, wherein said toner image forming means is controlled so that said cleaning toner image is formed.