JP2023072953A - Image forming apparatus - Google Patents

Abstract

To protect an intermediate transfer belt and suppress reduction in transfer image quality when small-sized recording materials are continuously conveyed.SOLUTION: An image forming apparatus transfers a toner image formed on an image carrier according to an image signal to an intermediate transfer body, and transfers the toner image transferred to the intermediate transfer body to a recording material to form an image, and the image forming apparatus has: cleaning means that removes an attachment attached to the intermediate transfer body; and toner supply control means that supplies toner to the cleaning means. In supplying toner to the cleaning means, when performing recording processing on a predetermined number or more of recording materials with a smaller width than a maximum conveyable size, the toner supply control means controls to reduce an amount of toner inside a conveyance area of the recording material compared with that outside the conveyance area.SELECTED DRAWING: Figure 7

Description

The present invention relates to an image forming apparatus that forms an image by transferring a toner image from an intermediate transfer member to a recording material.

An image forming apparatus forms an unfixed toner image on a sheet-like recording material by an image forming device, and then fixes the toner image as a fixed image by a fixing device.

Various methods have been proposed for the fixing means, but a fixing device of a thermo-pressure fixing method that heats and presses a toner image to fix it is generally used. The fixing device includes a heating rotary body (fixing roller, fixing film, etc.) heated by a heating means, and a pressure rotary body (pressure roller, pressure belt, etc.) which forms a fixing nip portion by being in pressure contact therewith. have. By rotating both rotating bodies and introducing a recording material carrying an unfixed toner image into the fixing nip portion and conveying the recording material, the toner image is transferred to the surface of the recording material by the heat and nip pressure of the heating rotating body. Settle.

In such a fixing device, when a small-size recording material having a width smaller than the maximum size recording material having the maximum width that can be conveyed to the apparatus is continuously conveyed and fixing is performed, the non-contact of the heating rotator occurs. The surface temperature rises excessively in the conveying area (non-contact area with the recording material). Here, the non-conveyance region is a region of the heating rotator in the longitudinal direction of the heating rotator that does not come into contact with the recording material when the small-size recording material is conveyed. This is because when the small-sized recording material is continuously conveyed, heat is partially accumulated in the non-conveying area of the fixing nip portion where the recording material does not pass, as much as the recording material does not absorb heat. This phenomenon is called edge temperature rise or non-conveying area temperature rise of the fixing device, and if this edge temperature rise becomes too high, it leads to the occurrence of hot offset and thermal deterioration of device components.

As one of countermeasures against the temperature rise in the non-transport area, there is known a mechanism that disposes a cooling fan for cooling the non-transport area. Japanese Patent Application Laid-Open No. 2002-200003 discloses a configuration in which cooling fans blow air to the left and right sides of a fixing roller in the longitudinal direction.

Japanese Patent Application Laid-Open No. 2015-158600

However, if the cooling fan mechanism described in Japanese Patent Application Laid-Open No. 2002-200003 continues to blow air even while the recording material is passing through the fixing roller, the water in the recording material may evaporate, and the evaporated water may reach the cleaning blade. .

The evaporated moisture reaches the cleaning blade by moving with air blowing from a cooling fan mechanism or airflow generated by rotation of the intermediate transfer belt, or by adhering to the intermediate transfer belt itself. At this time, at the contact portion (cleaning nip) between the intermediate transfer belt and the cleaning blade, the area where the small-sized recording material is conveyed is lubricated by paper dust and residual toner after transfer, but moisture accumulates in the non-conveying area, causing the cleaning nip. Frictional resistance increases.

When the recording material non-conveying area of the intermediate transfer belt continues to receive frictional resistance, the intermediate transfer belt plastically deforms, and when conveying a recording material larger than the small size, the area affected by plastic deformation. However, there is a problem that the transferred image quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to protect an intermediate transfer member and suppress deterioration of transferred image quality when a small-sized recording material is continuously conveyed.

A typical configuration according to the present invention for achieving the above object is to transfer a toner image formed on an image carrier to an intermediate transfer member according to an image signal, and transfer the toner image transferred to the intermediate transfer member to a recording material. In an image forming apparatus for forming an image by transferring a toner image onto the intermediate transfer member, a toner image is continuously formed on a recording material having a width smaller than the maximum size of the recording material, and a cleaning means for cleaning the deposits adhering to the intermediate transfer member. During the continuous image forming job, on the surface of the intermediate transfer member, the first image area corresponding to the first recording material and the second image area corresponding to the second recording material subsequent to the first recording material a control unit capable of executing a mode in which toner is formed in a non-image area and the toner is supplied to the cleaning unit, and when the mode is executed, the control unit conveys the recording material more than outside the conveying area. It is characterized by controlling to reduce the amount of toner in the area.

According to the image forming apparatus of the present invention, it is possible to protect the intermediate transfer body and suppress deterioration of image quality even when small-sized recording materials are continuously conveyed.

1 is a schematic diagram showing the configuration of an image forming apparatus; FIG. Perspective view of cooling device Explanatory drawing of the toner band width formed on the intermediate transfer belt Explanatory drawing of the toner band width formed on the intermediate transfer belt Block diagram for controlling the toner swath image Flowchart of toner band formation control Relational diagram of the toner band image (density) formed on the intermediate transfer belt and the intermediate transfer unit Relational diagram of the toner band image (length in the conveying direction) formed on the intermediate transfer belt and the intermediate transfer unit Relational diagram of the toner band image (supply frequency) formed on the intermediate transfer belt and the intermediate transfer unit Block diagram for controlling a toner band image according to an image signal according to the second embodiment. FIG. 10 is a relational diagram of a toner band image formed on an intermediate transfer belt and width direction image information according to the second embodiment;

An image forming apparatus according to embodiments of the present invention will be specifically described below with reference to the drawings.

[First embodiment]
<Overall Configuration of Image Forming Apparatus>
FIG. 1 is a schematic cross-sectional view of an image forming apparatus 200 of the present embodiment (a cross section substantially perpendicular to the rotation axis direction of a photosensitive drum 1, which will be described later). The image forming apparatus 200 of this embodiment is a laser beam printer that employs an intermediate transfer method and a tandem method, and is capable of forming a full-color image using an electrophotographic method. The image forming apparatus 200 can form and output an image on the recording material S based on image information read from a document or image information input from an external device. The recording material S includes a recording sheet such as plain paper and special paper such as coated paper, special-shaped materials such as envelopes and index paper, plastic film for overhead projectors, cloth, and the like.

Image forming apparatus 200 has, as a plurality of image forming units, four image forming units Pa, Pb, Pc, and Pd that form yellow, magenta, cyan, and black toner images, respectively. For elements having the same or corresponding functions or configurations in the image forming units Pa, Pb, Pc, and Pd for each color, A, b, c, and d may be omitted for general description. In this embodiment, the image forming section P includes photosensitive drums 1 (1a, 1b, 1c, 1d), charging rollers 2 (2a, 2b, 2c, 2d), exposure devices 3 (3a, 3b, 3c, 3d), which will be described later. ), developing devices 4 (4a, 4b, 4c, 4d), primary transfer rollers 5 (5a, 5b, 5c, 5d), and drum cleaning devices 6 (6a, 6b, 6c, 6d). .

A photosensitive drum 1, which is a rotatable drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) serving as an image carrier for carrying a toner image, is rotationally driven in the direction of an arrow R1 (clockwise direction) in the figure. be. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential by the charging roller 2 and then scanned and exposed by the exposure device 3 according to image information to form an electrostatic latent image on the photosensitive drum 1 . . The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as developer by the developing device 4 to form a toner image.

An intermediate transfer unit 20 is arranged to face the four photosensitive drums 1 . The intermediate transfer unit 20 has an intermediate transfer belt 7 configured as an endless belt as a rotatable intermediate transfer body, and a plurality of tension rollers (support rollers) around which the intermediate transfer belt 7 is stretched. . In this embodiment, the intermediate transfer unit 20 has a secondary transfer inner roller 8, a steering roller 17, a separation roller 19, and an upstream guide roller 18 as a plurality of tension rollers.

The intermediate transfer belt 7 is wound around a plurality of tension rollers 8, 17, 18, and 19, and faces the photosensitive drums 1 of the image forming portions P on the outer peripheral surface thereof. Further, on the inner peripheral surface side of the intermediate transfer belt 7, primary transfer rollers 5, which are roller-type primary transfer members as primary transfer means, are arranged corresponding to the respective photosensitive drums 1. As shown in FIG. The primary transfer roller 5 presses the inner peripheral surface of the intermediate transfer belt 7 toward the photosensitive drum 1 to form a primary transfer portion (primary transfer nip) T1 where the photosensitive drum 1 and the intermediate transfer belt 7 are in contact.

The intermediate transfer belt 7 rotates in the direction of arrow R3 (counterclockwise direction) by a drive motor (not shown) to rotate the inner secondary transfer roller 8 functioning as a driving roller. direction (counterclockwise direction). The secondary transfer inner roller 8 is opposed to a secondary transfer outer roller 9 to be described later with the intermediate transfer belt 7 interposed therebetween, and together with the secondary transfer outer roller 9, a secondary transfer portion T2 to be described later is formed.

The toner image formed on the photosensitive drum 1 is primarily transferred onto the rotating intermediate transfer belt 7 by the action of the primary transfer roller 5 at the primary transfer portion T1. For example, when a full-color image is formed, yellow, magenta, cyan, and black toner images formed on the photosensitive drums 1 are sequentially primary-transferred onto the intermediate transfer belt 7 so as to be superimposed.

The toner image formed on the intermediate transfer belt 7 is nipped and conveyed between the intermediate transfer belt 7 and the secondary transfer outer roller 9 by the action of the secondary transfer outer roller 9 at the secondary transfer portion T2. Secondarily transferred onto the recording material S. The recording material S is housed in a feeding cassette 90 as a recording material housing portion. The recording materials S accommodated in the feeding cassette 90 are fed one by one by a feeding roller 91 or the like as feeding means, and conveyed toward a registration roller pair 92 . The registration roller pair 92 corrects the skew of the recording material S and feeds the recording material S to the secondary transfer portion T2 in accordance with the progress of the image forming operation of each image forming portion P. FIG. The recording material S onto which the toner image has been transferred at the secondary transfer portion T2 is heated and pressurized when passing through the roller nip portion of the fixing device 13 constituted by the roller pair of the heating roller 14 and the pressure roller 15. The toner image is fixed on the recording material S, and the recording material S with the image formed on the back side is discharged to the discharge tray 93 .

On the other hand, adherents such as toner remaining on the photosensitive drum 1 after the primary transfer (primary transfer residual toner) are removed and collected from the photosensitive drum 1 by a drum cleaning device 6 as a photosensitive member cleaning means. Adhered matter such as toner remaining on the intermediate transfer belt 7 after the secondary transfer (secondary transfer residual toner) is removed from the intermediate transfer belt 7 by a belt cleaning device 11 as intermediate transfer body cleaning means. be recovered.

The belt cleaning device 11 is arranged at a position facing the steering roller 17 with the intermediate transfer belt 7 interposed therebetween. At the contact portion (cleaning nip 113) between the intermediate transfer belt 7 and the cleaning blade 111 (cleaning nip 113), the cleaning blade 111 scrapes off adherents such as secondary transfer residual toner from the surface of the intermediate transfer belt 7, thereby cleaning the intermediate transfer belt 7. to clean.

An operation display unit 40 serving as a user interface is provided on the upper surface of the apparatus body 201 . The operation display unit 40 has a display unit such as a liquid crystal panel capable of displaying current setting information, etc., and an operation unit such as various buttons through which an operator such as a user or service staff can input information.

<Cooling device>
Next, a cooling device (blowing device) that cools the fixing device 13 by blowing air will be described.

FIG. 2 is a perspective view of the cooling device 500 viewed from the rear side. The cooling device 500 is arranged adjacent to the fixing device 13, and fixes the recording material Ssmall, which is smaller in width Wsmall than the recording material Smax with the maximum width Wmax, among the recording materials S usable in the image forming apparatus 200. It is used when performing processing (image heating processing). This is to selectively cool the non-contact area by blowing air in order to prevent an excessive temperature rise in the area of the heating roller 14 that does not contact the recording material S (hereinafter referred to as the non-conveying area). .

The cooling device 500 has cooling fans 501a and 501b, air ducts 502a and 502b, and openings 503a and 503b. When the temperature of the surface of the heating roller 14 detected by a thermistor (not shown) rises to a predetermined temperature (200° C. in this example), the cooling fans 501a and 501b receive a command (signal to start operation) from the control unit 50. Start driving. Cooling air from cooling fans 501a and 501b passes through air ducts 502a and 502b, respectively, through openings 503a and 503b, and flows through a portion of the heating roller 14 in the longitudinal direction (width direction), in this example, both ends. Sprays into nearby areas.

Here, the cooling fans 501a and 501b can be arbitrarily changed in rotation speed by the control unit 50 according to the thermistor.

<Mechanism of fine dust generation>
In the fixing device 13, it is known that fine dust (UFP) is generated due to the release agent contained in the toner when the recording material S is fixed. Here, the mechanism of UFP generation will be described.

The fixing device 13 fixes the toner image by bringing the recording material S into contact with a pair of high-temperature rollers (heating roller 14 and pressure roller 15). When the fixing process is performed using such a configuration, part of the toner may be transferred (adhered) to the heating roller 14 during the fixing process. This phenomenon is called an offset phenomenon, and countermeasures are essential because the offset phenomenon causes image defects.

Therefore, the toner used in the image forming apparatus 200 generally includes wax as a release agent. When this toner is heated, the wax inside melts and oozes out. Therefore, when the toner image is fixed, the surface of the heating roller 14 is covered with the melted wax. become. The heating roller 14, the surface of which is covered with wax, has the effect of making it difficult for toner to adhere due to the release action of the wax.

In the present embodiment, in addition to pure wax, compounds containing the molecular structure of wax are also called wax. For example, a compound obtained by reacting a resin molecule of a toner with a wax molecular structure such as a hydrocarbon chain is also called a wax. In addition to wax, a substance having a release action such as silicone oil may be used as the release agent.

A part of the wax evaporates (evaporates) when it melts. It is considered that this is because the size of the molecular component contained in the wax varies. In other words, wax contains a low-molecular-weight component with a short chain and a low boiling point and a high-molecular-weight component with a long-chain and a high boiling point. When the vaporized (gasified) wax component is cooled in air, fine particles of several nanometers to several hundreds of nanometers are generated (most of the fine particles generated are presumed to have particle diameters of several nanometers to several tens of nanometers. ). That is, this fine particle is the aforementioned UFP.

Since the UFP is generated by the mechanism described above, the UFP is most generated from the fixing nip portion N where heat is applied to the wax. In addition, since the temperature of the heating roller 14 reaches its maximum temperature on the upstream side of the fixing nip portion N due to the rotation of the heating roller 14 and the arrangement of the heater 39, the generation of UFP is also maximum on the upstream side of the fixing nip portion N. It can be inferred that Furthermore, since the UFP is also generated from the toner image transferred to the recording material S, it can be seen that the UFP is generated from the entire image area of the fixing nip portion N. FIG.

<Fatigue Deformation of Intermediate Transfer Belt>
As described above, during the image forming operation, secondary transfer residual toner and the like adhere to the surface of the intermediate transfer belt 7 in the width direction (direction perpendicular to the rotation direction of the intermediate transfer belt) up to the maximum image width WT. A belt cleaning device 11 is provided for scraping. As shown in FIG. 3, the width W11 of the cleaning blade 111 is also configured to satisfy the relationship W11>WT in order to scrape off the secondary transfer residual toner. As described above, the cooling device 500 blows cooling air to the heating roller 14 of the fixing device 13 , and the cooling air also reaches the recording material S while the recording material S is passing through the fixing nip portion N. When the environment in which the image forming apparatus 200 is installed is humid, the recording material S absorbs moisture, and the moisture in the recording material S is evaporated by the heating of the fixing device 13, and the evaporated moisture is fixed by the cooling air. Stay in the anterior space. Furthermore, as the intermediate transfer belt 7 is conveyed in the R2 direction, an air current is generated from the pre-fixing space toward the belt cleaning device 11 , and the evaporated moisture may flow toward the belt cleaning device 11 .

As described above, the belt cleaning device 11 scrapes off deposits on the intermediate transfer belt 7 with the cleaning blade 111 . The scraped adhering matter adheres to the cleaning nip 113 , and when the adhering matter is additionally scraped off, it falls in such a manner that a part of the adhering matter is replaced and stored in the cleaning container 112 . In other words, deposits basically continue to stay in the cleaning nip 113 . When the moisture-laden air reaches the belt cleaning device 11, it mixes with the deposits on the cleaning nip 113 to form a viscous mixture. This mixture acts as resistance while the intermediate transfer belt 7 is conveyed. Since the intermediate transfer belt is mainly composed of a synthetic resin having a thickness of 100 μm or less, fatigue deformation occurs in the intermediate transfer belt 7 when resistance is continuously applied by the cleaning blade 111 and the mixture. If the intermediate transfer belt 7 uniformly stretches due to fatigue deformation over the entire belt width W7 region or the maximum image width WT region, there is no effect on the transfer image quality on the recording material S. image quality is affected. This principle will be explained below.

When the recording material S is conveyed, as described above, paper dust adheres to the surface of the intermediate transfer belt 7 together with secondary transfer residual toner at the secondary transfer portion T2. It is generally known that paper dust is mainly composed of chips generated during cutting, delaminated paper fibers, clay, talc, titanium dioxide, barium sulfate, calcium carbonate and other fillers. The secondary transfer residual toner and paper dust are finally scraped off by the cleaning blade 111 of the belt cleaning device 11 . As described above, if secondary transfer residual toner and paper dust continue to be supplied, the deposits at the cleaning nip 113 will be replaced and the cleaning nip will be lubricated. For example, when a recording material Ssmall having a narrow width Wsmall is continuously conveyed, the area of Wsmall shown in FIG. However, since secondary transfer residual toner and paper dust are not supplied to the area outside Wsmall, the deposits on the cleaning nip 113 are not replaced. That is, in the area outside Wsmall, the mixture with moisture continues to stay, and the frictional resistance increases, causing fatigue deformation in the intermediate transfer belt 7, and the area where the intermediate transfer belt 7 stretches (Wsmall An area up to the end of the cleaning blade 111 on the outer side) and an area where no elongation occurs (an area indicated by Wsmall) are generated. The stretch of the intermediate transfer belt 7 occurs along with irregular unevenness in the outer peripheral direction, and the primary transfer efficiency decreases (the image becomes lighter) in concave portions than in the normal state, and the primary transfer efficiency increases in the convex portions. (the image becomes darker).

If these conditions occur, the image quality will not be affected by continuing to convey the recording material Ssmall with the narrow width Wsmall. When the sheet Smax is conveyed, the deterioration of the transferred image quality becomes apparent outside Wsmall (the non-conveying area of the recording material Ssmall).

<Toner band image to prevent blade curling and its effect>
In the cleaning nip 113, if the secondary transfer residual toner and paper dust are not supplied, the deposits are gradually depleted. In such a case, the frictional force between the intermediate transfer belt 7 and the cleaning blade 111 at the cleaning nip 113 suddenly increases, and the cleaning blade 111 may turn over, making cleaning impossible. Therefore, the toner band image B shown in FIG. 4 is periodically directed toward the cleaning nip 113 according to the command of the toner band image control unit 53 so as not to deplete the adhering matter in the cleaning nip 113 and to replace the adhering matter. are supplying.

The width of the toner band image B is the maximum exposure width W3 of the exposure device 3, and the density CB of the toner band, the conveying direction length LB, and the supply frequency BN vary depending on the surrounding environment. In order to prevent the toner band image from being transferred onto the recording material S at the secondary transfer portion, the toner belt image is inserted between or behind the continuously passing recording materials, passes through the secondary transfer portion, and reaches the cleaning nip 113 . At this time, the toner image is transferred to the recording material S at the secondary transfer portion so that the toner band image is not attracted to the secondary transfer outer roller 9 and is not transferred to the back surface of the recording material S that is conveyed next. A bias having a sign opposite to that for transfer is added.

<Toner Band Image to Prevent Fatigue Deformation of Intermediate Transfer Belt and Its Effect>
When the recording material Ssmall in the narrow conveying area Wsmall is continuously conveyed in a high-humidity environment, in the area outside Wsmall (non-conveying area of the recording material Ssmall), the amount of toner band sufficient to prevent the cleaning blade from being turned over. Even if image B is fed, if the deposit changes to a wet mixture between regular feeding intervals, it will lead to fatigue deformation of the intermediate transfer belt 7 . Therefore, in a humid environment, it is necessary to frequently supply the toner band image B to the cleaning nip 113 and replace the adhering matter before the adhering matter changes to a moist mixture. However, if the frequency of supplying the toner band image B or the amount of toner in the toner band image B is increased, the amount of toner consumed per print increases, resulting in an increase in the toner yield. Therefore, it is required to reduce this increase in toner yield.

The fatigue deformation of the intermediate transfer belt 7 is caused by the difference in frequency of replacement of the deposits accumulated in the cleaning nip 113 between the conveying area and the non-conveying area of the recording material S. FIG. In the conveying area, paper dust is supplied to the cleaning blade 111 together with the secondary transfer residual toner at the secondary transfer portion T2 and replaces the adhered matter. can be made relatively small. This makes it possible to reduce the increase in yield in a humid environment.

<Toner supply control>
Therefore, in the present embodiment, toner is efficiently supplied to the cleaning nip by changing the amount of supplied toner between inside and outside the recording material conveying area. Note that the toner supply control to the cleaning nip is performed by a first image area corresponding to a predetermined recording material (first recording material) on the surface of the intermediate transfer belt 7 and a recording material following the first recording material (first image area). The toner is supplied to the non-image area between the second image area corresponding to the second recording material and the toner to the cleaning nip.

FIG. 5 is a block diagram showing a control configuration for that purpose. In this embodiment, when toner is supplied to the cleaning nip, the width direction of the recording material conveyed by the recording material information acquisition unit 51 (the direction orthogonal to the conveying direction of the recording material) is controlled by a command from the controller 49. ) and information on the number of conveyed sheets of the same width are acquired, and the environmental information acquisition unit 52 acquires temperature and humidity information of the operating environment. Next, based on the information, the toner band image control section 53 determines a toner band image in which the amount of toner in the width direction is changed, and the image forming section 54 forms the toner band image.

The recording material information acquisition unit 51 determines the size of the recording material to be conveyed by the size detection unit, acquires the length of the recording material in the width direction, and acquires the number of conveyed sheets by counting the recording materials that are sequentially conveyed. do. It should be noted that the size and the number of sheets to be printed may be obtained by the operator input from the input unit. Further, the temperature and humidity within the apparatus are obtained as environment information by means of temperature and humidity detection means provided in the apparatus.

As shown in the flow chart of FIG. 6, the toner supply control procedure is such that when a print job is received (S1), it is determined whether or not the conveyed recording material is a narrow recording material (S2). Here, the narrow recording material is a recording material having a width (Wsmall) smaller than the maximum transportable width of the recording material. Further, it is determined whether or not the number of sheets N conveyed to the narrow recording material has been continuously conveyed and recorded more than a set threshold number of sheets Na (S3), and the threshold humidity set by the apparatus internal humidity H as the recording environment. It is determined whether or not Ha is greater than or equal to Ha (S4).

As a result, when a predetermined number of sheets or more of recording are continuously performed on a narrow recording material in an environment where the humidity is equal to or higher than the threshold value, the toner supply control of the present embodiment is executed to form a toner band image (S5). , supplies toner to the cleaning nip (S6). On the other hand, when the conditions of steps S2 to S4 are not satisfied, the recording JOB is started without executing the toner supply control of this embodiment (S7).

Here, the toner supply control for supplying toner to the cleaning nip according to the present embodiment, which is executed in steps S5 and S6, is controlled so that the amount of toner inside the conveying area of the recording material S is smaller than that outside the conveying area. It is. If a toner band image portion with a small amount of toner is set over a non-conveying area of the recording material, fatigue deformation of the intermediate transfer belt 7 will occur locally in that portion. Therefore, in the present embodiment, as shown in FIG. 7, the small toner portion WBinner is always narrow in consideration of part tolerances and backlash of parts involved in image formation, running performance of the intermediate transfer belt, feeding performance of the recording material, and the like. It is set so as to be inside the conveying area Wsmall of the recording material (WBinner⊂Wsmall). At this time, the gaps in the small toner portion WBinner are determined by taking into account the tolerances and backlash of the parts involved in image formation, the running performance of the intermediate transfer belt, the transportability of the recording material, etc., and the gaps Wgap It is the inside area in the held state. That is, the toner band is formed so that the small toner portion WBinner=Wsmall−2×Wgap. Here, the large toner portion WBouter is a portion inside the exposure width W3 and outside the small toner portion WBinner.

In this embodiment, as shown in FIG. 7, a difference in toner amount is generated depending on the density as a configuration for producing a difference in toner amount between the inside and outside of the conveying area of the recording material. That is, the toner is set so that CBinner<CBouter, where CBinner is the toner concentration of the small toner portion WBinner within the recording material conveying area, and CBouter is the toner concentration of the large toner portion WBouter outside the recording material conveying area. Forms a band image.

In the above example, the amount of toner is changed by changing the density of the toner forming the toner band inside and outside the conveying area of the recording material. The toner amount may be changed by changing the length (the length of the intermediate transfer belt in the conveying direction). Specifically, as shown in FIG. 8, when the belt length in the conveying direction of the small toner portion WBinner is LBinner, and the belt length in the conveying direction of the large toner portion WBouter is LBouter, LBinner<LBouter. to supply toner to the cleaning nip.

Further, the toner amount may be varied depending on the frequency of supplying toner images at the same position in the width direction of the intermediate transfer belt. As shown in FIG. 9, where NBinner is the supply frequency in the small toner portion WBinner and NBouter is the supply frequency in the large toner portion WBouter, a toner band is formed so that NBinner<NBouter, and toner is supplied to the cleaning nip. . In FIG. 9, in the first toner band formation (first toner band) B1, a toner band common to the small toner portion WBinner and the large toner portion WBouter is formed, and in the next toner band (second toner band) B2, the large toner portion By forming a toner band only on the WBouter, a difference is provided in the amount of toner supplied to the cleaning nip. By increasing the number of toner bands formed in the large toner portion WBouter than the toner band formed in the small toner portion WBinner, a difference is provided in the amount of toner to be supplied.

Also, by combining the toner supply methods shown in FIGS. 7 to 9, a difference in toner amount may be provided between the inside and outside of the conveying area of the recording material.

[Second embodiment]
Next, toner supply control to the cleaning nip according to the second embodiment will be described.

When a narrow recording material such as an OHP sheet that does not generate paper dust is continuously conveyed, fatigue deformation of the intermediate transfer belt 7 occurs even within the narrow conveying area Wsmall. The reason for this is that, first, because paper dust does not replace the adhering matter, the adhering matter on the cleaning nip 113 tends to change into a wet mixture even in the narrow conveying area Wsmall. As described above, when the intermediate transfer belt 7 is uniformly elongated due to fatigue deformation over the entire belt width W7 or the maximum image width WT, the transfer image quality on the recording material S is not affected.

However, of the image to be formed, residual transfer toner that has not been transferred to the recording material S at the secondary transfer portion T2 is supplied to the cleaning nip 113, and as a result, deposits are formed on the portion where the image exists to some extent in the width direction. replacement occurs. Therefore, a difference in frictional resistance occurs between the portion where the exchange is possible and the portion where the exchange is not possible, resulting in fatigue deformation within the transport area Wsmall. In order to avoid this, if the frequency of supplying the toner band image B or the amount of toner of the toner band image B are increased, the amount of toner consumed per print increases and the toner yield increases.

Therefore, in the present embodiment, information about an image to be formed is acquired, and the amount of toner in the width direction of the toner band image B is changed from the amount of toner in the width direction, thereby reducing the increase in the toner yield.

As shown in FIG. 10, the control configuration of the present embodiment is such that, in response to a command from the controller 49, information on the width direction of the recording material conveyed by the recording material information acquisition unit 51 and information on the number of conveyed recording materials of the same width is obtained as an image. An information acquisition unit 55 acquires information about an image to be formed, and an environment information acquisition unit 52 acquires temperature and humidity information of the operating environment. Next, based on the information, the toner band image control section 53 determines a toner band image in which the amount of toner in the width direction is changed, and the image forming section 54 forms the toner band image. This point is the same as the embodiment described above. In addition, taking into consideration the part tolerance and backlash of the parts related to image formation, the running performance of the intermediate transfer belt, the conveying performance of the recording material, etc., the toner-poor portion WBinner is positioned with a gap Wgap at both ends from the image portion Wimage. The inner area (WBinner=Wimage-2×Wgap) is also the same as in the above embodiment.

In the present embodiment, image information is obtained by the image information obtaining unit 55 when forming a toner band in the conveying area of the recording material to be the low toner portion WBinner. The amount of toner in the toner band is changed depending on the area where the amount of toner is small.

The image information acquisition unit 55 acquires the toner density in the width direction of the image to be formed with respect to the distance in the width direction. In this embodiment, the integrated value of the video count in each divided area of the image forming area is obtained. A region divided by a length of 5 mm in the recording material conveying direction and 10 mm in the width direction perpendicular to the sheet conveying direction is defined as a unit divided area, and the presence or absence of an image in the divided pattern on the A4R sheet is shown. The video count is a value obtained by converting the input image data from RGB data, which are luminance values, into YMCK data, which are density values, and integrating the density value data (0 to 255 levels) of each pixel for each color component. . The video count value is calculated by the controller 49 of the main body. The maximum video count value for one divided area is 200% (100% for monochrome), and the ratio to that is calculated as the image ratio (0 to 200%). The calculated values are summed up in the recording material conveying direction to obtain toner density information in the width direction.

When the toner density information in the width direction is obtained, the density of the toner band image B is determined by comparing with a certain threshold value. For example, in FIG. 11, when there is image information (video count value) larger than a threshold in the width direction (Wimage1 to Wimage4), the area contains toner, and is classified as low toner areas WBinner1 to WBinner4. Also, WBinner is set to WBinner=Wimage-2×Wgap so that the low toner portion WBinner is always inside the image portion Wimage. The small toner portion WBinner, which should correspond to Wimage4 in FIG. 11, is not set because WBinner=Wimage-2×Wgap cannot be satisfied.

Also, in changing the toner amount by the width method of the toner band image by acquiring image information, the difference in the toner amount between the small toner portion WBinner and the large toner portion WBouter is the density CB shown in FIGS. It is created based on the band length LB, the supply frequency BN of the toner image at the same position in the width direction, and the like.

By changing the amount of toner forming the toner band according to the image information in the conveying area of the recording material as described above, the amount of toner supplied to the cleaning nip can be further reduced.

P: image forming unit S: recording material T2: secondary transfer unit 7: intermediate transfer belt 11: belt cleaning device 13: fixing device 49: controller 50: control unit 51: recording material information acquisition unit 52: environment information acquisition unit 53 Toner band image control unit 54 Image forming unit 111 Cleaning blade 113 Cleaning nip 200 Image forming apparatus 201 Apparatus body Wsmall Narrow conveying area WBinner Small toner area WBouter Large toner area Wimage Image area

Claims (8)

An image forming apparatus for forming an image by transferring a toner image formed on an image bearing member to an intermediate transfer member according to an image signal, and transferring the toner image transferred on the intermediate transfer member to a recording material to form an image,
a cleaning means for cleaning deposits adhering to the intermediate transfer body;
During a continuous image forming job for continuously forming toner images on a recording material having a width smaller than the maximum size of the recording material, a first image area corresponding to the first recording material and a first image area on the surface of the intermediate transfer member a control unit capable of executing a mode in which toner is formed in a non-image area between a first recording material and a second image area corresponding to a second recording material and the toner is supplied to the cleaning means;
has
The image forming apparatus according to claim 1, wherein, when executing the mode, the control section performs control so that the amount of toner inside a conveying area of the recording material is smaller than that outside the conveying area of the recording material. signal counting means for counting image signals for each divided area in a direction perpendicular to the rotation direction of the image carrier;
When supplying toner to the conveying area, the control unit performs control so that an area in which the image signal value is greater than a threshold is smaller than an area in which the image signal value is equal to or less than the threshold in the area in the conveying direction of the recording material. The image forming apparatus according to claim 1, characterized by: 3. The image forming apparatus according to claim 1, wherein, when supplying toner to said cleaning means, said control section makes the toner concentration inside the conveying area smaller than that outside the conveying area. 3. The image forming apparatus according to claim 1, wherein when supplying the toner to the cleaning means, the control section makes the toner supply width in the transport direction smaller within the transport area than outside the transport area. Device. The control unit forms a toner band in the width direction of the recording material when supplying toner to the cleaning unit, and the toner band is formed in a first toner band having a maximum forming width and in an area outside the conveying area. 3. The image forming apparatus according to claim 1, wherein said second toner band is formed by said second toner band. Having a humidity detection means for detecting the humidity in the device,
2. The toner supply control by said control unit so as to reduce the amount of toner inside the conveying area of the recording material than outside the conveying area of the recording material is executed when humidity inside the apparatus is equal to or higher than a predetermined humidity. The image forming apparatus according to any one of claims 1 to 5. having environment detection means for detecting device humidity,
When the humidity detected by the environment detection means is equal to or higher than a predetermined humidity and the controller supplies toner to the cleaning means, and when recording a predetermined number of sheets or more on a recording material having a width smaller than the maximum conveyable size. 7. The image forming apparatus according to any one of claims 1 to 6, wherein control is performed so that the amount of toner inside the conveying area of the recording material is smaller than that outside the conveying area of the recording material. fixing means for heating the recording material to fix the toner image transferred onto the recording material;
an air blowing unit for blowing air to the fixing unit;
has
8. The image forming apparatus according to claim 1, wherein the intermediate transfer member is an endless belt member.

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