JP2003066672A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus by which the occurrence of a defective image due to the soiling of a transfer material is prevented by preventing the developer of a detection pattern from sticking to an attracting means. SOLUTION: In the image forming apparatus having several process stations 2a-2d including photoreceptive drums 21 at which an image is formed, a feeding belt 1 moved by coming into contact with several photoreceptive drums 21 and to feed the transfer material P, transfer blades 3a-3d to transfer a toner image on the photoreceptive drums 21 to the transfer material P, an attracting roller 5 to electrostatically attract the transfer material P to the feeding belt 1 and optical resist sensors 131 and 132 to detect a specified detection patterns formed on the feeding belt 1, the abutting surface of the attracting means to a transfer material feeding means is formed of a surface layer material incorporating at least a fluorinated resin and an electrical conductivity imparting member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a laser beam printer or a copying machine.

[0002]

2. Description of the Related Art Conventionally, various systems such as an electrophotographic system, a thermal transfer system and an inkjet system have been adopted as an image forming apparatus. Among these, the image forming apparatus using the electrophotographic method is superior in terms of high speed, high image quality, and quietness.

FIG. 5 shows an example of a conventional electrophotographic image forming apparatus.

The image forming apparatus 200 has a photosensitive drum 221 which is a drum-shaped image bearing member rotatable in the arrow direction, and the surface of the photosensitive drum 221 is a primary charger 2 which is a charging means.
After being uniformly charged by 22, an exposing unit 223 such as an LED or a laser exposes the electrostatic latent image to form an electrostatic latent image. After that, the developing device 224 electrostatically attaches a developer (toner) to the electrostatic latent image to form a toner image on the photosensitive drum 221. Next, the toner image is electrostatically transferred by the transfer member 103, which is a transfer unit, onto the transfer material P that has been transferred to a transfer position facing the photosensitive drum 221 by a transfer unit (not shown).

After that, the unfixed toner image transferred onto the transfer material P is fixed by being heated and pressed by the fixing device 227 to form a permanent image. On the other hand, the transfer residual toner remaining on the photosensitive drum 221 after the transfer is removed by a cleaning blade 225 which is a cleaning unit, and is collected in a waste toner container 226. The photosensitive drum 221 whose surface is thus cleaned is repeatedly used for image formation.

Further, in recent years, color image forming apparatuses using an electrophotographic system have become widespread. There are various types of electrophotographic color image forming apparatuses. For example,
In addition to the well-known multiple transfer system and intermediate transfer system, a multiple development system in which a color image is superposed on the surface of the photoconductor and then collectively transferred to form an image, or an image forming means of different colors ( There is an in-line method in which a toner image is formed in each of the process stations, and each toner image is transferred onto a transfer material conveyed by a conveyance belt so as to be superimposed to form a color image.

The color image forming apparatus of the in-line system has many advantages such as high speed and a small number of toner image transfers, which is advantageous in image quality.

FIG. 6 shows a conventional color image forming apparatus using an in-line system.

As shown in FIG. 6, an electrostatic attraction conveyor belt 101 (hereinafter simply referred to as a "conveyor belt") serving as a conveyor.
Are stretched around a driving roller 107, a suction opposing roller 106, and tension rollers 108 and 109, and are rotationally driven in the arrow X direction.

Along the horizontal transfer material carrying surface of the conveyor belt 101, first, second, third and fourth process stations 102a, 102b and 102c which are image forming means for black, magenta, cyan and yellow, respectively. , 102d are arranged side by side, and the transfer belt 101 rotates in the direction of the arrow X, whereby the transfer material P is sequentially transferred to each of the process stations 102a to 102d.

The internal structure of each of the process stations 102a to 102d is as described with reference to FIG. 5, and the colors of the developers included in the developing devices 224 are different from each other.

The photosensitive drums 221a to 221d in the process stations 102a to 102d are in contact with the transfer blades 103a, 103b, 103c and 103d, which are transfer means, via the conveyor belt 101, and the transfer blades 103a to 103d are Transfer bias is applied from the transfer bias power sources 104a, 104b, 104c, 104d.

Conventionally, in an electrophotographic image forming apparatus, for example, an organic semiconductor electrophotographic photosensitive member (OPC photosensitive member) having a negative polarity is used as a photosensitive drum to develop an exposed portion whose negative charge is attenuated by exposure. In this case, a developer containing a negative polarity toner is used. Therefore, at the time of transfer, the transfer bias power sources 104a-1
A positive transfer bias is applied from 04d.

When the transfer material P is sent out from the feeding cassette 115 into the image forming apparatus by the feeding roller 114, first, for example, a roller shape for synchronizing the image forming operation and the conveyance of the transfer material P is formed. Synchronous rotating body, that is,
After being sandwiched by the registration roller 110 and the registration facing roller 113, the transfer material P is guided to a suction unit N where the transfer belt P is suctioned.

In the suction part N, a suction roller 105 as a suction means faces the suction facing roller 106 via the transport belt 101, and sandwiches the transport belt 101 and the transfer material P. A voltage is applied to the attraction roller 105 from an attraction bias power source 112, which is a high voltage power source, so that the transfer material P is charged. The transfer material P to which the electric charge is applied is electrostatically adsorbed to the conveyor belt 101 by polarizing the conveyor belt 101.

FIG. 7 shows an example of a conventional suction roller. As the suction roller 105, a conductive rubber 105a or a roller in which a conductive sponge 105a is formed on a core metal 105b is used.

In this way, the transfer material P adsorbed on the conveyor belt 101 sequentially passes through the process stations 102a to 102d, and the toner images of the respective colors on the photosensitive drums 221a to 221d are transferred one after another. Thereafter, the transfer material P is conveyed to the fixing device 227, where the color image of the unfixed toner is heated and pressed to become a permanent image.

The conveyor belt 101 has a thickness of 50 to 200 μm,
Resin films such as PVdF (vinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), polyimide, PET (polyethylene terephthalate), and polycarbonate with a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ωcm, and a thickness of 0 A rubber base layer having a thickness of about 5 to 2 mm, such as EPDM, is covered with urethane rubber in which a fluororesin such as PTFE is dispersed.

In the color image forming apparatus, regarding the color balance of each process unit, a density patch image of each color, that is, a detection pattern is formed on the conveyor belt 101,
This is read by the density detection sensor 133 and is fed back to the process forming conditions such as the high pressure condition and the laser power to match the maximum density and halftone gradation characteristics of each color, that is, the image density control is performed.

Image density control is performed by controlling the maximum density of each color (hereinafter,
“Dmax”) is kept constant and halftone gradation characteristics are kept linear with respect to the image signal.

The control of Dmax has a great meaning to keep the color balance of each color constant, and at the same time prevent scattering of overlaid characters due to excessive toner loading and fixing failure.

On the other hand, the halftone gradation control prevents the output density from being shifted with respect to the input image signal due to the non-linear input / output characteristic (γ characteristic) peculiar to electrophotography, so that a natural image cannot be formed. Therefore, it is common to perform image processing that cancels the γ characteristic and keeps the input / output characteristic linear.

Generally, the density detecting sensor irradiates a density patch with a light source, detects the reflected light source intensity with a light receiving sensor, handles the image density as light intensity information, and electrically processes it.

In the in-line type image forming apparatus, new restrictions are imposed for forming a good image as in the conventional apparatus. That is, since the color images are formed by different process stations, the color balance is likely to be lost, and the registration for each color is difficult to match, which is an essential drawback.

In the color registration control, similarly to the density control, a patch for detecting a resist, that is, a detection pattern is formed on the conveyor belt 101, and this is read by the optical registration sensors 131 and 132, and the patch is set at an image writing position or the like. A means for performing correction by feeding back is used.

The resist sensors 131 and 132 read the resist patch formed by the line image by the focused light receiving sensor, and use the temporal intensity change of the signal of the light receiving sensor when the resist patch passes as positional deviation information. It is electrically processed.

Both optical sensors for density detection and resist detection are classified into two types, a specular reflection type and a diffuse reflection type, depending on the reflected light to be detected.

The diffuse reflection type detects scattered light emitted from the light source to the patch in all directions, the reflected light is weak, and the reflectance changes depending on the spectral sensitivity of the toner.

On the other hand, in the regular reflection type, as shown in FIG. 7, an optical axis Ll of light emitted from a light emitting element 201 such as an LED to a patch and an optical axis L2 of reflected light incident on a light receiving element 202.
Is to detect so-called specularly reflected light in which the angle α with the target surface is equal.

When the specular reflection light is detected, the toner amount is detected by the reduction of the light amount due to the specular reflection light from the belt 101, which is the target surface, being hidden by the toner, regardless of the spectral sensitivity of the toner. Moreover, it has a feature that the absolute value of the light intensity is high.

When resist detection is performed, it is necessary to reduce the spot diameter of the irradiation light or the received light to improve the spatial resolution, and therefore, the amount of received light is adjusted from the viewpoint of ensuring the dynamic range of the sensor. It is desirable to use a specular reflection type that can be secured.

When a black belt is used, the diffuse reflection type sensor cannot detect black toner. This is because the diffused reflection type sensor does not return the reflected light regardless of the presence or absence of black toner on the belt.

From the above, the regular reflection type is generally used also in the resist detection and the density detection.
From the technical background as described above, a method has also been proposed in which both the density detection and the resist detection are performed using the same optical sensor.

The toner image formed on the conveyor belt 1 for density detection and resist detection is collected and cleaned by the conveyor belt cleaning means. In addition to this, as the conveyor belt cleaning means, there is blade cleaning or the like. As shown in FIG. 6, the blade cleaning is a cleaning method in which the blade 117 is brought into contact with the conveyor belt 101 to scrape off the toner on the conveyor belt 101.

As a cleaning method different from the blade cleaning, a separate cleaning means is not provided,
Cleaning in which a cleaning bias having the same polarity as that of the transfer is applied to the transfer members 103a to 103d to collect the toner on the conveyor belt 101 into the waste toner container (see FIG. 5) via the photosensitive drums 221a to 221d. There is also a method. This method will be called a photoreceptor recovery method.

[0036]

Since the conveyor belt 101 does not normally carry a toner image directly on its surface,
It is rarely contaminated by the toner image. However, when a system is used in which a resist patch or a density patch is directly formed on the conveyor belt 101 and is detected, it is necessary to attach toner as a resist patch or a density patch on the conveyor belt 101.

When the photoconductor recovery method is used to clean the toner, the toner image for density detection and resist detection transferred on the conveyor belt 101 is cleaned because no separate cleaning means such as a blade is provided. It reaches the adsorption portion N without being damaged.

The toner transferred to the conveyor belt for density detection and resist detection passes through the adsorption portion N while existing on the conveyance belt 101, so that the toner adheres to the adsorption roller 105 forming the adsorption portion N. To do. If a transfer material such as paper passes through the adsorption portion N after the toner adheres, the toner may be transferred to the transfer material and cause stains.

When a separate cleaning means 117 such as blade cleaning is provided, even if toner is attached to the conveyor belt 101 for density detection and resist detection, the conveyor belt 101 rotates and passes through the separate cleaning means 117. Cleaning is performed as needed. For this reason,
The suction process is usually performed in a state where the toner is not attached to the suction roller 105 of the suction unit N.

However, the cleaning means 117 is separately provided.
Even if the cleaning belt is installed, if the cleaning performance deteriorates due to long-term use, a large amount of toner may
If it exists on 101, cleaning failure such as toner slipping may occur. In such a state, as in the photoconductor recovery method, the toner transferred to the conveyor belt 101 for density detection and resist detection is transferred to the conveyor belt 101.
It passes through the suction unit N while existing above, and at that time, toner adheres to the suction roller 105. When the transfer material such as paper passes through the adsorption portion N after the toner is attached, the toner is transferred to the transfer material, which causes stains.

Therefore, it is an object of the present invention to provide an image forming apparatus capable of preventing the developer of the detection pattern from adhering to the adsorption means and preventing the occurrence of image defects due to stains on the transfer material.

[0042]

In order to solve the above-mentioned problems, a typical structure of an image forming apparatus according to the present invention has a plurality of image forming means including an image carrier on which an image is formed, and a plurality of the above-mentioned image forming means. Conveying means that moves in contact with the image carrier and conveys the transfer material, transfer means that transfers the toner image on the image carrier to the transfer material, and electrostatically attracts the transfer material to the conveying means. In an image forming apparatus having an adsorbing unit for adhering to the transfer unit and a detecting unit for detecting a predetermined detection pattern formed on the conveying unit, the adsorbing unit has at least a contact surface of the transfer material conveying unit with a fluororesin and a conductive material. It is characterized by being formed of a surface layer material including a property imparting member.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment A first embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is an explanatory diagram of a transfer area, FIG. 3 is an explanatory diagram of a detection pattern,
FIG. 4 is an explanatory diagram of the suction roller.

(Whole Apparatus) As shown in FIG. 1, the image forming apparatus of the present embodiment is an in-line type color image forming apparatus, and an electrostatic adsorption conveyance belt 1 (hereinafter, referred to as a conveyance means).
The first, second, third, and fourth process stations 2a, 2b, which are image forming units for black, magenta, cyan, and yellow, are arranged along a horizontal transfer material carrying surface of a "conveyor belt"). 2c and 2d are juxtaposed.

The conveyor belt 1 is stretched around a driving roller 7, a suction opposing roller 6, tension rollers 8 and 9, and is indicated by an arrow X.
Driven to rotate.

Each of the process stations 2a to 2d is a so-called process cartridge and is detachably attached to the main body of the apparatus. As shown in FIG. 2, the photosensitive drum 21 which is an image carrier, and the primary which is a charging unit. Charging roller
22, a developing device 24, and a cleaning unit including a cleaning blade 25 and a waste toner container 26 are integrated together. Each process station 2a-
The internal configurations of 2d are different only in the color of the developer included in the developing device 24.

By rotating the conveying belt 1 in the direction of arrow X in the drawing, the transfer material P is sequentially conveyed from the feeding cassette 15 to the process stations 2a to 2d by the feeding roller 14.

When the transfer material P is fed from the feeding cassette 15 into the image forming apparatus by the feeding roller 14, first,
A synchronous rotating member in the form of a roller, that is, a suction unit that is sandwiched between the registration roller 10 and the registration facing roller 13 and that suctions the transfer material P and the conveyor belt 1 in synchronization with the image forming operation. Guided by N.

In the suction section N, a suction roller 5 as a suction means is arranged to face the suction facing roller 6 via the conveyor belt 1 and to sandwich the conveyor belt 1 and the transfer material P. A voltage is applied to the attraction roller 5 from an attraction bias power source 12, which is a high voltage power source. In this embodiment, the attraction bias is set to 1 kV. By applying the attraction bias, the transfer material P is charged, and the charged transfer material P is electrostatically attracted to the transport belt 1 by polarizing the transport belt 1.

In each of the process stations 2a to 2d, a toner image of each color is formed on the transfer material P by using the electrophotographic method. As an example of the toner, polyester or styrene-acrylic resin is used as a binder, optimal color materials (pigments, dyes, etc.) are arranged for each color, a charge control material is added, and a diameter of 4 μm is obtained by a pulverization method or a polymerization method. ~
It is general to use a fine powder of about 10 μm. The image forming process at this time is similar to that of the conventional electrophotographic image forming apparatus described with reference to FIG. That is, in FIG. 2, a photosensitive drum 21 (a negative polarity OPC drum in this embodiment) is rotatably supported, and its surface is uniformly charged to about −600 V by a primary charger 22 and then exposed. An electrostatic latent image is formed by exposing by means of means 23 according to image information. After that, the developing device 24 reversely develops black, magenta, cyan, and yellow toner (regular charging polarity is negative) for each process station 2a to 2d to electrostatically attach and visualize the toner, and the photosensitive drum 21a. Toner images of the respective colors are formed on 21d.

(Developing Device) As shown in FIG.
Toners are stored inside, and these toners are supplied to the developing roller 31 disposed in contact with the photosensitive drum 21 by a stirring member (not shown) or the like. As the developing roller 31, for example, a metal cored bar covered with a conductive elastic rubber and a dielectric layer coated thereon is used. In the present embodiment, the dielectric layer has a film thickness of 30 μm in which silicon balls are dispersed.
The urethane resin of is used. With such a dielectric layer structure, the releasability is improved.

The toner regulating blade 32 is brought into contact with the upstream side of the contact portion M with the photosensitive drum 21 on the developing roller 31 in the counter direction to coat the developing roller 31 with a thin layer of toner. The toner regulating blade 32 also has a role of charging the toner with a negative electric charge when the toner passes. As the toner regulating blade 32, for example, a metal leaf spring having elasticity such as phosphor bronze or SUS, or urethane rubber or silicon rubber supported by a metal leaf spring, or a rubber surface coated with nylon is used. To be

Further, as a means for supplying toner to the developing roller 31, a toner supplying roller 33 is arranged in contact with the developing roller 31 on the upstream side of the contact position with the toner regulating blade 32. The toner supply roller 33 can be made of, for example, a material such as polyurethane foam having an appropriate unevenness on the surface.

When a developing bias is applied to the core metal portion of the developing roller 31, the surface potential of the developing roller 31 becomes substantially the same as the value of the developing bias. The developing bias is the photosensitive drum 21.
It is an appropriate value for the charging potential and the latent image potential. Then, by the action of the electric field formed between the photosensitive drum 21 and the developing roller 31, only the toner on the developing roller 31 corresponding to the latent image portion on the photosensitive drum 21 is transferred onto the photosensitive drum 21, The developing process is completed.

The toner image developed on the photosensitive drum 21 is
It is rotationally moved to the transfer portion and transferred to the transfer material P. That is, the photosensitive drums 21a to 21d in each process station
Is in contact with transfer blades 3a, 3b, 3c and 3d, which are transfer means, via the conveyor belt 1, and transfer bias power supplies 4a, 4b, 4c, and
A predetermined transfer voltage is applied from 4d. For example, as the transfer voltage, the transfer bias power supplies 4a to 4d are +1.5 kV.
(A voltage having a polarity opposite to the regular charging polarity of the toner) is applied.

In this way, the transfer material P adsorbed to the conveyor belt 1 sequentially passes through the process stations 2a to 2d, and the toner images of the respective colors on the photosensitive drums 21a to 21d are transferred one after another. After that, the transfer material P is conveyed to the fixing device 16,
Here, the color image of the unfixed toner is heated and pressed to become a permanent image.

The transfer residual toner remaining on the photosensitive drums 21a to 21d after the transfer is removed by the cleaning blades 25a to 25d as the collecting means and collected in the waste toner containers 26a to 26d as the collecting means. The photosensitive drum whose surface is thus cleaned is repeatedly used for image formation.

The conveyor belt 1 has a thickness of 100 μm or more.
About 200 μm, volume resistivity 1.0 ⁸Ωcm ~ 10¹³Ωc
PVDF, ETFE, polycarbonate with resistance adjusted to about m
Absorbs resin films such as bonates, PET, and polyimide
Good adhesiveness and transferability, as well as moderate self-damping property
Depending on the system, it is possible to prevent charge-up without providing static elimination means.
It is suitable for application of this embodiment.

Further, as the transfer blades 3a to 3d,
As an example, a PET film having a thickness of 100 μm, a free length to a support of about 3 mm, and a volume resistivity of 10 ⁵ Ωcm is 45 °.
The contact belt was used so as to be in the forward direction with respect to the traveling direction of the conveyor belt 1 at the angle of. As the transfer blade, a film made of a material other than those described above can be used as the transfer means as long as it has a volume resistivity of 10 ² Ωcm to 10 ⁹ Ωcm. Of course, in addition to this, a sponge type or solid type rubber roller having a similar resistance range may be used.

Here, the volume resistivity of the conveyor belt is J
Using a measuring probe compliant with IS method 6911, ADVAN
The resistance value obtained by applying 100 V with a high resistance meter R8340 manufactured by TEST Co., Ltd. is a value normalized by the thickness of the conveyor belt.

The suction roller facing roller 6 according to this embodiment is a metal roller. As the drive roller 7, a metal roller provided with a rubber layer on the core metal to prevent slippage in a thickness range of approximately 0.5 mm to 3 mm was used. An insulating type having a resistance value of 10 ¹⁵ Ωcm or more was used as an example of the rubber layer, but a low resistance type may be used. Metal rollers were used for the tension rollers 8 and 9. With respect to the cores of the tension rollers 8 and 9 and the driving roller 7, the conveyor belt 1 is a self-damping system, and there are no members (electrodes) facing each other with the conveyor belt 1 in between. Either can be used.

(Registration Detecting and Density Detecting System) There are individual differences between the image forming apparatuses in the timing of matching the toner images of the respective colors on the transfer material due to variations in the peripheral length of the conveyor belt and the mounting positions of the process stations. If the timings do not match, the toner images of the respective colors are formed on the transfer material with a shift (registration misregistration), which causes variations in tint. Therefore, it is necessary to detect the resist regularly or in real time to correct this timing. First, the resist detection will be described.

In order to perform this resist detection, this image forming apparatus has first to fourth process stations for forming a predetermined resist detection pattern on the conveyor belt 1 prior to the transfer of the toner image onto the transfer material. A means for controlling 2a to 2d, that is, a detection pattern forming means is provided. The resist detection pattern is formed by transferring a plurality of lines parallel to the main scanning direction, which are formed on the photoconductors 21a to 21d in the process stations 2a to 2d of each color, to the conveyor belt 1.

Further, the image forming apparatus is provided with optical registration sensors 131 and 132 as detecting means facing the conveyor belt 1 at the most downstream side in the conveying direction of the transfer material P by the conveyor belt 1. , The center position of the line of the resist detection pattern is detected. The image registration position is controlled by adjusting the image writing timing as necessary based on the detection results of the optical registration sensors 131 and 132.

Further, the image density varies depending on the temperature and humidity conditions in which the image forming apparatus is used and the degree of use of the process station. In order to correct this fluctuation, the image density is controlled. Here, the image density control will be described.

Similarly to the registration detection, this image forming apparatus also controls the process stations 2a to 2d for forming a predetermined density detection pattern on the conveyor belt 1 prior to the image forming process in the density control. ,
That is, a detection pattern forming means is provided. Similarly to the registration detection, an optical density sensor 133 as a detection unit for performing density detection is provided facing the conveyor belt 1 at the most downstream side in the conveyance direction of the transfer material by the conveyor belt 1, and detects the density. The density is detected by irradiating the pattern with predetermined light and detecting the reflection component thereof. Based on the detection result, the image density is controlled by adjusting the developing bias, the charging potential and the like.

Optical resist sensors 131 and 132 for performing resist detection and density detection, and optical density sensor 13
The positional relationship of 3 in the longitudinal direction is shown in FIG.

Optical registration sensors 131 and 132 for detecting registration are provided at substantially both ends of the conveyor belt 1 in the width direction. In addition, an optical density sensor 13 that detects density
3 is provided at a substantially central portion of the conveyor belt 1 in the width direction.

The optical registration sensors 131, 132 and the optical density sensor 133 shown in FIG. 7 are used. Here, the operation of the optical sensors 131 to 133 will be briefly described.

As shown in FIG. 7, the optical sensors 131 to 1
33 includes a light emitting element 201 such as an LED and a light receiving element 202 such as a photodiode. The irradiation light from the light emitting element 201 enters the conveyor belt at an angle of α = 45 ° and is reflected at the detection position 203. The light receiving element 202 is provided at a position for detecting the specular reflection component of the irradiation light.

Although the optical sensors 131 to 133 of the type that detect specular reflection light are used in the description of the present embodiment, the type of sensors that detect diffused light and the light that has passed through the conveyor belt and the toner image formed thereon are used. It is also possible to use a sensor of the type that detects the.

The optical sensors 131 to 133 are provided at the most downstream side in the transporting direction of the transfer material by the transport belt 1 so as to face the transport belt.

Next, the structure of the suction roller 5 in this embodiment will be described.

First, the suction roller 5 is brought into contact with the conveyor belt 1 from both ends of the shaft (not shown) by improperly applying a spring force, so that a total pressure of about 1 kg is applied. For the purpose, the suction roller 5 is required to have conductivity so as to give a sufficient charge on the transfer material. Specifically, the actual resistance value is 10
^It is desirable to set it to about ⁵ to 10 ⁷ Ω.

On the other hand, releasability is required to prevent the toner of a predetermined detection pattern formed on the conveyor belt 1 from adhering and accumulating on the suction roller 5.

Therefore, in this embodiment, as shown in FIG. 4A, a base layer 52 made of a conductive elastic member is provided on the metal shaft 51, and a conductive material is further provided on the outer periphery of the base layer 52. Is used to provide conductivity, and a conductive film layer 53 to which an insoluble fluororesin is added is provided.

As the conductive elastic material used for the base layer, a non-foamed or foamed conductive rubber composition containing a conductive material can be used. Specific components include butadiene, isoprene, chloroprene, styrene butadiene, ethylene propylene, polynorbornene, styrene-butadiene-styrene (SBS), polyurethane,
Examples thereof include rubber such as silicone.

As the conductive material to be added to these rubber compositions, carbon black, graphite, metals, various metal oxides (tin oxide, titanium oxide, etc.), ionic substances, charge transfer complexes and the like can be used. In this case, the volume resistivity of the base layer is preferably adjusted to about 10 ¹ to 10 ⁹ Ωcm.

Next, the conductive film layer 53 will be described. This conductive film layer 53 is, for example, nylon, polyester, urethane-modified acrylic resin, phenol resin, acrylic resin,
Epoxy resin, urethane resin, urea resin and the like are mixed with carbon black, graphite, metal oxides such as tin oxide and titanium oxide, conductive materials such as ionic substances and charge transfer complexes. In this case, the volume resistivity of the conductive film layer 53 is
It is preferable to adjust the thickness to about 10 ⁴ to 10 ¹⁰ Ωcm and the thickness to about 5 to 500 μm.

In the present embodiment, the insoluble fluorocarbon resin is arranged near the surface of the contact portion with the member to be charged, that is, in the conductive film layer 53 in FIG. 4A. In this case, the insoluble fluororesin may be disposed only on the surface portion of the conductive film layer 53 or may be disposed on the entire conductive film layer 53, in short, the insoluble fluororesin on the surface where the member to be charged contacts the charging member. Should exist. In this case, a part of the insoluble fluororesin may be exposed on the surface or may not be exposed.

Specific examples of the insoluble fluororesin include:
Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylpinyl ether Copolymer (EPE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE),
Examples thereof include polyphenylidene fluoride (PVDF) and polyvinyl fluoride (PVF).

Here, the insoluble fluororesin is preferably dispersed in the conductive film layer 53 as a powder.

The particle size of the insoluble fluororesin particles is 30.
μm or less, preferably 10 μm or less, more preferably 6
A value of μm or less is suitable. If a powder having an excessively large particle size is used, the irregularities on the surface of the adsorbing member become severe and there is a risk of toner accumulating in the concave parts.

The amount of the insoluble fluororesin added is appropriately 3 parts by weight or more, preferably 5 parts by weight or more, and more preferably 10 parts by weight or more with respect to 100 parts by weight of the base polymer.

In this embodiment, the suction roller 5 has a thickness of approximately 3 on a cored bar made of stainless steel and having a diameter of about 6 mm.
mm, surface length about 222 mm, carbon-added solid butadiene rubber / liquid polyisoprene rubber (weight ratio 30 /
70), an elastic layer consisting of 70) is formed, a carbon coating layer having a thickness of about 120 μm is added by a dipping method, and a T coating layer having a thickness of about 10 μm is formed by a dipping method.
A coating layer was formed by adding 70 parts by weight of io _{2 and} 20 parts by weight of fluorine particles [LDIE (Daikin Industries, particle size 0.2 μm)] to 100 parts by weight of resin (alcohol-soluble nylon, Teikoku Chemical Industry).

As a result, the actual resistance value of the suction roller (diameter
The total pressure of the suction roller is about 1 kg against the 30 mm metal roller.
Resistance measurement by pressurizing with + 200V voltage application
Value) is approximately 5 × 10 _Five Adjusted to Ω.

In a normal printing process, in order to adsorb the transfer material P onto the conveyor belt 1 prior to the transfer process, a voltage of about +200 V to +3 KV is applied to the adsorbing roller 5 to produce about 5 μA to 50 μA. The adsorption current can be passed through the transfer material P, and good adsorption performance can be obtained.

Next, a description will be given of a toner cleaning method in which the detection toner is not deposited on the suction roller 5 and is cleaned from the conveyor belt 1 when the resist or the density detection is performed using the suction roller.

As described above, the optical registration sensors 131, 132 and the optical density sensor formed on the conveyor belt 1 are used.
The detected toner image detected by 133 is conveyed by the conveyance belt 1 on the side opposite to the transfer material conveyance section, and reaches the facing surface of the suction roller 5. At this time, since the suction roller 5 does not have a special releasing mechanism, it remains in contact with the conveyor belt 1. Therefore, the bias power supply 12
As a result, a toner adhesion preventing bias of approximately −300 V having a dynamic polarity with respect to the toner is applied to the attraction roller 5.

As a result, due to the conductivity imparted to the conductive film layer 53 of the suction roller 5, the toner having a negative charge can be repelled and the toner can be electrically attached to the surface of the suction roller 5. Further, since the fluororesin attached to the conductive film layer 53 of the suction roller 5 has a releasability for the toner, the adhesive force of the toner image on the surface of the suction roller 5 overcomes the repulsive electrolysis and the toner is attracted. It is possible to prevent the adhesion to the surface of the roller 5. Further, by setting the value of the toner adhesion preventing bias applied to the suction roller 5 to be equal to or less than the discharge threshold value in the vicinity of the contact portion between the suction roller 5 and the transport belt 1, the toner charge on the transport belt 1 is changed by the discharge. , The polarity is reversed and the toner is attracted by the toner 5
Can be prevented from adhering to the surface. Therefore, the toner does not accumulate on the surface of the suction roller 5.

As described above, the resist detecting toner and the density detecting toner which have passed through the suction portion N without adhering to the suction roller 5 are subjected to the photoconductor recovery cleaning method.
Reverse transfer is performed from the transport belt 5 to the photoconductors 21a to 21d, and the process stations, that is, the process cartridges 2a to 21d.
It is cleaned by being collected in the 2d waste toner container 26.

The photoconductor recovery cleaning method will be specifically described below.

As shown in FIG. 1, in the first process station 2a, the switch 5a in the transfer bias power source 4a is switched to apply a cleaning bias having a reverse polarity to that at the time of transfer to the transfer blade 3a so that the toner having a normal polarity is supplied. The process cartridge 2a
The waste toner container 26 is collected. Further, by passing through the first process station 2a, the polarity opposite to the normal polarity, no polarity, or the main polarity, but the amount of charge is small, so that the toner is not attracted to the photosensitive drum 21a. Of the toner of the opposite polarity.

Next, at the second process station 2b, a cleaning bias having the same polarity as that at the time of transfer is applied to the transfer blade 3b, and the opposite polarity toner not adsorbed on the photosensitive drum 21a at the first process station 2a is applied to the process cartridge 2b. Is collected by the waste toner container 26 by adsorbing it to the photosensitive drum 21b of
Alternatively, the toner on the conveyor belt 1 which has the opposite polarity but is not attracted to the photosensitive drum 21b because the charge amount is small is charged to the normal polarity.

Further, in the third process station 2c, the switch 5c in the transfer bias power source 4c is switched to apply a cleaning bias having a reverse polarity to that at the time of transfer to the transfer blade 3c, so that toner having a normal polarity is applied to the photosensitive drum 21.
It is not adsorbed to the photosensitive drum 21c because it has a polarity opposite to the regular polarity, is non-polar, or has a regular charge but has a small amount of charge. The toner on the transport belt 1 is charged to the opposite polarity. Since most of the toner is collected in the first to third process stations 2a to 2c, the amount of toner remaining on the conveyor belt 1 is small and the toner is easily charged to the opposite polarity.

Furthermore, in the fourth process station 2d, a cleaning bias of the same polarity is applied to the transfer blade 3d at the same time as the transfer, and the third process station 2c
Then, the toner of the opposite polarity not adsorbed on the photosensitive drum 21 is adsorbed on the photosensitive drum 21d of the fourth process station 2d and collected in the waste toner container 26 in the process cartridge 2d.

In this embodiment, the toner charging polarity is negative and the cleaning bias of the same polarity as during transfer is +.
1kV, cleaning bias with reverse polarity to 1 at transfer is 1
It was performed at kV.

With the above configuration, the resist and density detection can be performed by one.
The operation was performed every 100 sheets, and the toner was not accumulated on the suction roller 5 during the print durability of 150,000 sheets in total, and the image stain on the transfer material did not occur. Further, there was no occurrence of image stains due to poor cleaning of the conveyor belt 1, and in combination with the stabilization of print image quality by density control, it was possible to always maintain good print images.

As described above, by providing the surface layer portion containing the fluororesin and the conductive insoluble member on the surface layer of the suction roller 5, it is possible to prevent the toner accumulation on the suction roller 5.

Further, by appropriately applying the cleaning bias to the suction roller 5, the prevention of the toner accumulation on the suction roller 5 can be achieved even better.

As a result, the suction roller 5 is moved to the conveyor belt 1.
No special mechanism is required to separate from. Also,
Since no special member for cleaning the conveyor belt 1 is required, the cost of the device can be reduced significantly.

[Second Embodiment] Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 4 is an explanatory diagram of the suction roller. The same parts as those of the first embodiment will be designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, instead of the suction roller 5 having a two-layer structure composed of the base layer 52 and the conductive film layer 53 as shown in FIG. 4 (a) in the first embodiment, FIG. The suction roller 50 is used in the one-layer structure as shown.

In this case, the insoluble fluororesin is used as the conductive film layer.
Instead of 53, it is arranged on the elastic base layer 54. Even if the insoluble fluororesin is arranged only on the surface of the elastic base layer 54,
Alternatively, it may be disposed on the entire elastic base layer 54, and the member to be charged may be exposed or exposed on the surface in contact with the charging member.

The suction roller is not limited to one layer and two layers, and may have three or more layers. Also,
The base layer 52 or the conductive film layer 53 of the first embodiment may be further divided into a plurality of layers to form a multi-layer.

With the above-described structure, it is possible to prevent toner from accumulating on the suction roller 50, as in the first embodiment.

Further, by appropriately applying the cleaning bias to the suction roller 50, the prevention of the toner accumulation on the suction roller 50 can be achieved even better.

As a result, the suction roller 50 is moved to the conveyor belt 1.
No special mechanism is required to separate from. Also,
Since no special member for cleaning the conveyor belt 1 is required, the cost of the device can be reduced significantly.

Third Embodiment Next, a third embodiment of the image forming apparatus according to the present invention will be described. The same parts as those of the first embodiment will be designated by the same reference numerals and the description thereof will be omitted.

In the first embodiment, the bias voltage applied to the suction roller 5 for preventing toner accumulation is approximately -3.
The case where the voltage is set to 00V has been described.

On the other hand, in use, the toner may be unexpectedly charged. As an example, when the printer stops in the middle of recording due to a jam or the like, or when durable printing is performed at 32.5 ° C. and 85% RH in an extremely high temperature and high humidity state, the toner image on the conveyor belt is (Not only the detection pattern, but when the toner is accidentally transferred directly onto the conveyor belt at the time of jam, etc.)
It may be almost zero or may be inverted. In such a case, as a bias voltage value for cleaning the suction roller 5 or for preventing toner accumulation, for example, a cleaning bias of −300 V having the same polarity as the toner and a toner having a size different from that at the time of the suction process are used. Two types of + 300V cleaning with opposite polarity
A bias voltage (bipolar) may be used.

As an example, at the time of return rotation after the detection of the resist or the density or the occurrence of a jam, a bias voltage of −300 V is first applied to the suction roller 5 to rotate the conveyor belt 1 substantially once, and then the suction roller 5 is rotated. Even if toner is once deposited on the suction roller 5, the suction roller 5 can be completely cleaned. At this time, the same cleaning bias as in the first embodiment may be applied to the transfer first to fourth process stations.

By applying the cleaning bias as described above, as in the first embodiment, by providing the surface layer portion containing the fluororesin and the conductive insoluble member on the surface layer of the adsorption roller 5, the adsorption roller 5 can be provided. Toner accumulation can be prevented.

Further, by appropriately applying the cleaning bias to the suction roller 5, the prevention of toner accumulation on the suction roller 5 can be achieved more satisfactorily.

As a result, the suction roller 5 is moved to the conveyor belt 1.
No special mechanism is required to separate from. Also,
Since no special member for cleaning the conveyor belt 1 is required, the cost of the device can be reduced significantly.

[0116]

As described above, according to the present invention,
Even if a toner image, which is a detection pattern for detecting resist and density, is directly formed on the conveyor belt, by providing a surface layer portion containing a fluororesin and a conductive insoluble member on the surface layer of the suction roller, It was possible to prevent toner accumulation.

Further, by appropriately applying the cleaning bias to the suction roller, the above-mentioned object can be achieved more satisfactorily.

As a result, a special mechanism for separating the suction roller from the conveyor belt becomes unnecessary. Further, since a special member for cleaning the conveyor belt is not required, it is possible to significantly reduce the cost of the device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is an explanatory diagram of a transfer periphery.

FIG. 3 is an explanatory diagram of a detection pattern.

FIG. 4 is an explanatory diagram of a suction roller.

FIG. 5 is an explanatory diagram of a conventional transfer periphery.

FIG. 6 is a configuration diagram of a conventional image forming apparatus.

FIG. 7 is an illustration of toner pattern detection means.

[Explanation of symbols]

Ll, L2 ... Optical axis M ... Contact part N ... Adsorption part P ... Transfer material 1 ... Conveyor belt 2a to 2d ... Process station 3a to 3d ... Transfer blade 4a to 4d ... Transfer bias power source 5 ... Suction roller 6 ... Adsorption facing roller 7 ... Drive roller 8, 9 ... Tension roller 10 ... Registration roller 12… Bias power supply 13… Registration facing roller 14… Feeding roller 15… Feed cassette 21 ... Photosensitive drum 22… Primary charger 24 ... Developer 25… Cleaning blade 50… Suction roller 51… Metal shaft 52… Base layer 53 ... Conductive layer 54 ... Elastic base layer 131… Optical resist sensor 132… Optical resist sensor 133… Optical density sensor

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Claims (5)

[Claims] 1. A plurality of image forming means including an image bearing body on which an image is formed, a transport means for moving in contact with the plurality of image bearing bodies and transporting a transfer material, and on the image bearing body. A transfer means for transferring the toner image onto the transfer material; an adsorption means for electrostatically adsorbing the transfer material on the conveying means; and a detecting means for detecting a predetermined detection pattern formed on the conveying means. In the image forming apparatus having the image forming apparatus, the adsorbing means has a surface contacting the transfer material conveying means with a surface layer material including at least a fluororesin and a conductivity imparting member. 2. A cleaning unit for cleaning a toner image on the transfer material conveying unit is not provided at least downstream of the detecting unit on the path facing the suction unit. 1. The image forming apparatus according to 1. 3. The method according to claim 1, wherein in the step of forming the predetermined detection pattern on the transfer material transporting means, a bias voltage having a dynamic polarity and toner is applied to the suction means at a predetermined timing. The image forming apparatus according to item 1. 4. A toner having a value different from the attraction bias and a bias voltage having a dynamic polarity or a reverse polarity are applied to the attraction means at a predetermined timing, other than the attraction step of attracting the transfer material to the conveying means. The image forming apparatus according to claim 1, wherein: 5. A cleaning bias for electrostatically recovering the detection pattern on the conveying means after the detection by the detecting means to the image carrier of the plurality of image forming means is applied to the transfer means. The image forming apparatus according to claim 1, wherein the image is applied.