JP4860845B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a laser beam printer or a copying machine.
[0002]
[Prior art]
Conventionally, various systems such as an electrophotographic system, a thermal transfer system, and an ink jet system have been adopted as an image forming apparatus. Among these, an image forming apparatus using an electrophotographic method is superior in terms of high speed, high image quality, and quietness.
[0003]
FIG. 5 shows an example of a conventional electrophotographic image forming apparatus.
[0004]
The image forming apparatus 200 includes a photosensitive drum 221 that is a drum-shaped image carrier that can rotate in the direction of an arrow. After the surface of the photosensitive drum 221 is uniformly charged by a primary charger 222 that is a charging unit. Then, an electrostatic latent image is formed by exposing according to image information by an exposure means 223 such as an LED or a laser. Thereafter, a developer (toner) is electrostatically attached to the electrostatic latent image by the developing device 224 to form a toner image on the photosensitive drum 221. Next, the toner image is electrostatically transferred by the transfer member 103 as 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).
[0005]
Thereafter, the unfixed toner image transferred onto the transfer material P is fixed by being heated and pressed by the fixing device 227, thereby forming 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 as a cleaning unit and collected in a waste toner container 226. The photosensitive drum 221 whose surface is thus cleaned is repeatedly used for image formation.
[0006]
In recent years, color image forming apparatuses using an electrophotographic system have also 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 superimposed on the surface of the photoconductor and then transferred at once to form an image, or image formation of different colors There is an in-line method in which each toner image is formed by means (process station), and each toner image is transferred onto a transfer material conveyed by a conveyor belt to form a color image.
[0007]
An in-line color image forming apparatus is capable of speeding up and has many advantages such as being advantageous in image quality because the number of times of toner image transfer is small.
[0008]
FIG. 6 shows a conventional color image forming apparatus using the in-line method.
[0009]
As shown in FIG. 6, an electrostatic adsorption conveyance belt 101 (hereinafter simply referred to as “conveyance belt”) serving as conveyance means is stretched around a drive roller 107, adsorption opposing roller 106, tension rollers 108 and 109, and an arrow X It is rotationally driven in the direction.
[0010]
Along the horizontal transfer material carrying surface of the conveyor belt 101, first, second, third, and fourth process stations 102a, 102b, 102c, and 102d, which are image forming units for black, magenta, cyan, and yellow, are provided. The transfer material P is juxtaposed, and the transfer material P is sequentially transferred to the process stations 102a to 102d by the rotation of the transfer belt 101 in the arrow X direction.
[0011]
The internal configuration of each of the process stations 102a to 102d is as described with reference to FIG. 5, and only the color of the developer that the developing device 224 has is different.
[0012]
The photosensitive drums 221a to 221d in the process stations 102a to 102d are in contact with transfer blades 103a, 103b, 103c, and 103d, which are transfer means, via a conveyor belt 101. The transfer blades 103a to 103d are connected to a transfer bias power source. A transfer bias is applied from 104a, 104b, 104c, and 104d.
[0013]
Conventionally, in an electrophotographic image forming apparatus, for example, when a negative organic semiconductor electrophotographic photosensitive member (OPC photosensitive member) is used as a photosensitive drum to develop an exposed portion where negative charges are attenuated by exposure. A developer containing negative polarity toner is used. Accordingly, during transfer, a positive transfer bias is applied to the transfer blades 103a to 103d from the transfer bias power supplies 104a to 104d.
[0014]
When the transfer material P is fed from the feed cassette 115 into the image forming apparatus by the feed roller 114, first, for example, synchronization in the form of a roller is performed for synchronizing the image forming operation and the transfer of the transfer material P. After being once sandwiched between the rotating body, that is, the registration roller 110 and the registration counter roller 113, it is guided to the suction portion N where the transfer material P and the transport belt 101 are sucked.
[0015]
The suction unit N is configured such that a suction roller 105 as a suction unit faces the suction facing roller 106 via the transport belt 101 and sandwiches the transport belt 101 and the transfer material P. A charge is applied to the transfer material P when a voltage is applied to the suction roller 105 from the suction bias power source 112 which is a high-voltage power source. The transfer material P to which the charge is applied is electrostatically attracted to the transport belt 101 by polarizing the transport belt 101.
[0016]
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.
[0017]
In this way, the transfer material P adsorbed on the conveyance belt 101 sequentially passes through the process stations 102a to 102d, and the respective color toner images on the photosensitive drums 221a to 221d are successively transferred. Thereafter, the transfer material P is conveyed to the fixing device 227, where the color image of the unfixed toner is heated and pressurized to become a permanent image.
[0018]
The conveyor belt 101 has a thickness of 50 to 200 μm and a volume resistivity of 10 ⁹ ~Ten ¹⁶ Resin films such as PVdF (vinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), polyimide, PET (polyethylene terephthalate), polycarbonate, and EPDM having a thickness of about 0.5 to 2 mm, etc. The base layer of the rubber is covered with a urethane rubber in which a fluorine resin such as PTFE is dispersed.
[0019]
In the color image forming apparatus, with respect to the color balance for each process unit, a density patch image of each color, that is, a detection pattern is formed on the conveyor belt 101, and this is read by the density detection sensor 133. Thus, a means for matching the maximum density and halftone gradation characteristics of each color by feeding back, that is, image density control is performed.
[0020]
The purpose of image density control is to keep the maximum density of each color (hereinafter referred to as “Dmax”) constant, and to keep the halftone gradation characteristics linear with respect to the image signal.
[0021]
The control of Dmax has a great meaning of preventing the scattering of characters and the fixing failure due to the excessive application of toner as well as keeping the color balance of each color constant.
[0022]
On the other hand, halftone gradation control is performed in order to prevent a natural image from being formed due to a shift in output density with respect to an input image signal due to nonlinear input / output characteristics (γ characteristics) unique to electrophotography. In general, image processing that cancels the characteristics and keeps the input / output characteristics linear is performed.
[0023]
In general, a density detection sensor irradiates a density patch with a light source, detects a reflected light source intensity with a light receiving sensor, handles image density as light intensity information, and performs electrical processing.
[0024]
In an in-line image forming apparatus, a new restriction for forming a good image occurs as in the conventional apparatus. In other words, since each color image is formed at a different process station, the color balance tends to be lost, or registration for each color is difficult to achieve.
[0025]
In color registration control, as in the case of density control, a resist detection patch, that is, a detection pattern is formed on the conveyance belt 101, which is read by the optical registration sensors 131 and 132, and fed back to the image writing position or the like. A means for performing correction is used.
[0026]
The registration sensors 131 and 132 read the registration patch formed by the line image with the focused light reception sensor, and electrically detect the temporal intensity change of the light reception sensor signal when the registration patch passes as the positional deviation information. Processing is in progress.
[0027]
Both density detection and resist detection optical sensors are classified into two types, a regular reflection type and a diffuse reflection type, depending on the reflected light to be detected.
[0028]
The irregular reflection type detects scattered light omnidirectionally applied to a patch from a light source, the reflected light is weak, and the reflectance changes depending on the spectral sensitivity of the toner.
[0029]
On the other hand, in the regular reflection type, as shown in FIG. 7, the angle α between the optical axis L1 of the light irradiating the patch from the light emitting element 201 such as an LED and the optical axis L2 of the reflected light incident on the light receiving element 202 is the target surface α. Are detected so-called specularly reflected light.
[0030]
When detecting specularly reflected light, the amount of toner is detected by reducing the amount of light caused by the specularly reflected light from the belt 101 being the target surface being hidden by the toner, regardless of the spectral sensitivity of the toner, It has the characteristic that the absolute value of light intensity is high.
[0031]
When performing resist detection, it is necessary to reduce the spot diameter of the irradiated light or received light to improve the spatial resolution, so that the amount of received light can be secured from the viewpoint of securing the dynamic range of the sensor. It is desirable to use a reflective type.
[0032]
Further, when a belt having a black color is used, black toner cannot be detected by the irregular reflection type sensor. This is because the reflected light is not returned by the irregular reflection type sensor regardless of the presence or absence of the black toner on the belt.
[0033]
From the above, it is common to use a regular reflection type also in resist detection and density detection. From the technical background as described above, a method of performing both density detection and resist detection using the same optical sensor has also been proposed.
[0034]
The toner image formed on the conveyor belt 1 for density detection and registration detection is collected and cleaned by the conveyor belt cleaning means. Other examples of the conveying belt cleaning means include blade cleaning. The blade cleaning is a cleaning method in which the blade 117 is brought into contact with the transport belt 101 and the toner on the transport belt 101 is scraped off as shown in FIG.
[0035]
Further, as a cleaning method different from the blade cleaning, no cleaning means is provided separately, and a cleaning bias having the same polarity as the reverse polarity is applied to the transfer members 103a to 103d so that the toner on the conveyor belt 101 is exposed. There is also a cleaning method of collecting in a waste toner container (see FIG. 5) via the drums 221a to 221d. This method will be referred to as a photoreceptor recovery method.
[0036]
[Problems to be solved by the invention]
Since the conveyor belt 101 does not normally carry a toner image directly on the surface, it is less likely to be contaminated by the toner image. However, when using a system that directly forms a registration patch or density patch on the conveyance belt 101 and detects this, it is necessary to attach toner as a registration patch or density patch on the conveyance belt 101.
[0037]
When the photoconductor recovery method is used to clean the toner, since no separate cleaning means such as a blade is provided, the toner image for density detection and registration detection transferred onto the conveyor belt 101 is cleaned. It will reach the suction part N without.
[0038]
The toner transferred to the conveyance belt for density detection and registration detection passes through the adsorption unit N in a state where the toner is present on the conveyance belt 101, so that the toner adheres to the adsorption roller 105 forming the adsorption unit N. If the transfer material such as paper passes through the suction portion N after the toner adheres, the toner may move to the transfer material and cause dirt.
[0039]
When a separate cleaning means 117 such as blade cleaning is provided, even when toner is attached on the transport belt 101 for density detection and registration detection, the transport belt 101 rotates and passes through the separate cleaning means 117. Cleaning is performed as needed. Therefore, the suction process is performed in a state where the toner is not normally attached to the suction roller 105 of the suction portion N.
[0040]
However, even when a separate cleaning means 117 is provided, if the cleaning performance deteriorates due to long-term use or the like, if a large amount of toner exists on the transport belt 101, a cleaning failure such as toner slipping may occur. . In such a state, as in the photoconductor recovery method, the toner transferred to the conveyance belt 101 for density detection and registration detection passes through the adsorption portion N in a state where the toner is present on the conveyance belt 101, and is adsorbed at that time. The toner adheres to the roller 105. When the transfer material such as paper passes through the suction portion N after the toner adheres, the toner moves to the transfer material and causes dirt.
[0041]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing the developer having a detection pattern from adhering to an adsorbing unit and preventing the occurrence of an image defect due to transfer material contamination.
[0042]
[Means for Solving the Problems]
In order to solve the above problems, a typical configuration of an image forming apparatus according to the present invention is as follows. A plurality of image forming means including an image carrier that carries a toner image; a conveying means that is rotatable and capable of carrying a transfer material together with the plurality of image carriers; and a plurality of the image carriers. A plurality of transfer means for transferring a toner image onto the transfer material from the image carrier by applying a transfer bias; and a transfer material disposed upstream of the plurality of image forming means in the rotation direction of the conveying means. In the image forming apparatus, comprising: a suction unit that electrostatically attracts the transport unit; and a detection unit that detects a predetermined detection pattern formed by the image forming unit on the transport unit. , Formed of a surface layer material including at least a fluororesin and a conductivity imparting member, and the detection pattern on the transport unit after detection by the detection unit contacts the adsorption unit , Said a bias below the discharge threshold in abutment of the transfer bias and the polarity opposite said suction roller a bias of said conveying means to said suction means when It is characterized by that.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
[First embodiment]
A first embodiment of an 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 around a transfer, FIG. 3 is an explanatory diagram of a detection pattern, and FIG. 4 is an explanatory diagram of a suction roller.
[0044]
(Whole device)
As shown in FIG. 1, the image forming apparatus of the present embodiment is an in-line type color image forming apparatus, and a horizontal transfer material of an electrostatic adsorption transport belt 1 (hereinafter simply referred to as “transport belt”) as a transport unit. The first, second, third, and fourth process stations 2a, 2b, 2c, and 2d, which are image forming units for black, magenta, cyan, yellow, and each color, are juxtaposed along the carrying surface.
[0045]
The conveyor belt 1 is stretched around a driving roller 7, a suction counter roller 6, tension rollers 8 and 9, and is driven to rotate in the direction of arrow X.
[0046]
Each of the process stations 2a to 2d can be attached to and detached from the apparatus main body as a so-called process cartridge. As shown in FIG. 2, a photosensitive drum 21 as an image carrier and a primary charging roller 22 as a charging means. The developing device 24 and the cleaning means including the cleaning blade 25 and the waste toner container 26 are integrated together. The internal configurations of the process stations 2a to 2d differ only in the color of the developer that the developing device 24 has.
[0047]
The conveyor belt 1 rotates in the direction of arrow X in the drawing, and sequentially conveys the transfer material P from the feeding cassette 15 to the process stations 2a to 2d by the feeding roller 14.
[0048]
When the transfer material P is fed from the feeding cassette 15 into the image forming apparatus by the feeding roller 14, first, the transfer material P is sandwiched between synchronous rollers that are in the form of rollers, that is, the registration roller 10 and the registration facing roller 13. In synchronism with the image forming operation, the transfer material P and the transport belt 1 are guided to the suction portion N where the suction is performed.
[0049]
The suction unit N is configured such that the suction roller 5 as a suction unit faces the suction counter roller 6 through the transport belt 1 and sandwiches the transport belt 1 and the transfer material P. A voltage is applied to the suction roller 5 from a suction bias power source 12 which is a high voltage power source. In this embodiment, the adsorption bias is 1 kV. By applying the suction bias, a charge is applied to the transfer material P, and the transfer material P to which the charge is applied is electrostatically attracted to the transport belt 1 by polarizing the transport belt 1.
[0050]
In each of the process stations 2a to 2d, a toner image of each color is formed on the transfer material P using an electrophotographic method. As an example, the toner is made of polyester or styrene-acrylic resin as a binder, and an optimal color material (pigment, dye, etc.) is arranged for each color, and a charge control material is added and the diameter is 4 μm by pulverization or polymerization. It is common to use a fine powder of about 10 μm. The image forming process at this time is the same as that of the conventional electrophotographic image forming apparatus described with reference to FIG. That is, in FIG. 2, a photosensitive drum 21 (negative 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 according to the image information by means 23. Thereafter, the developing device 24 makes the black, magenta, cyan, and yellow toners (normal charging polarity is minus) reversal developed for each process station 2a to 2d so as to be electrostatically attached and visualized, and the photosensitive drum 21a. A toner image of each color is formed on ˜21d.
[0051]
(Developer)
As shown in FIG. 2, toner is stored in the developing device 24, and the toner is supplied to a developing roller 31 disposed in contact with the photosensitive drum 21 by a stirring member (not shown). Is done. As the developing roller 31, for example, a metal core covered with a conductive elastic rubber and coated with a dielectric layer is used. In this embodiment, a urethane resin having a film thickness of 30 μm in which silicon balls are dispersed is used as the dielectric layer. With such a dielectric layer configuration, the releasability is improved.
[0052]
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 to coat the toner on the developing roller 31 with a thin layer. The toner regulating blade 32 also has a role of charging the toner with a negative 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, urethane rubber supported by the metal leaf spring, silicon rubber, or a rubber coated nylon coating is used. It is done.
[0053]
Further, as a means for supplying toner to the developing roller 31, a toner supply roller 33 is disposed 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 moderate unevenness on the surface.
[0054]
When a developing bias is applied to the cored bar portion of the developing roller 31, the surface potential of the developing roller 31 becomes almost the same value as the developing bias value. The developing bias is an appropriate value between the charging potential of the photosensitive drum 21 and the latent image potential. Thus, 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 by the action of the electric field formed between the photosensitive drum 21 and the developing roller 31. The development process is completed.
[0055]
The toner image developed on the photosensitive drum 21 rotates and moves to the transfer portion and is transferred to the transfer material P. That is, the photosensitive drums 21a to 21d in each process station are in contact with transfer blades 3a, 3b, 3c, and 3d as transfer means via the conveyance belt 1, and the transfer blades 3a to 3d are supplied with a transfer bias power source. A predetermined transfer voltage is applied from 4a, 4b, 4c, and 4d. For example, +1.5 kV (voltage having a polarity opposite to the normal charging polarity of the toner) is applied to the transfer bias power sources 4a to 4d as the transfer voltage.
[0056]
In this way, the transfer material P adsorbed on the transport belt 1 sequentially passes through the process stations 2a to 2d, and the color toner images on the photosensitive drums 21a to 21d are successively transferred. Thereafter, the transfer material P is conveyed to the fixing device 16 where the color image of the unfixed toner is heated and pressed to become a permanent image.
[0057]
Further, the transfer residual toner remaining on the photosensitive drums 21a to 21d after the transfer is removed by cleaning blades 25a to 25d as a collecting means and collected in waste toner containers 26a to 26d as a collecting means. The photosensitive drum whose surface is thus cleaned is repeatedly used for image formation.
[0058]
The transport belt 1 has a thickness of about 100 μm to 200 μm and a volume resistivity of 1.0. ⁸ Ωcm ~ 10 ¹³ Resin film such as PVDF, ETFE, polycarbonate, PET, polyimide, etc., whose resistance is adjusted to about Ωcm, has good adsorbability and transferability. It is suitable for application of the present embodiment because it can be prevented.
[0059]
For example, the transfer blades 3a to 3d have a thickness of 100 μm, a free length to the support of about 3 mm, and a volume resistivity of 10 ^Five An Ωcm PET film was used in contact with the traveling direction of the conveyor belt 1 at an angle of 45 ° so as to be in the forward direction. The transfer blade has a volume resistivity of 10 ² Ωcm ~ 10 ⁹ Any film of a material other than those described above can be used as the transfer means as long as it is in the range of Ωcm. Of course, in addition to this, a sponge type or solid type rubber roller having a similar resistance range may be used.
[0060]
Here, the volume resistivity of the transport belt is normalized with the thickness of the transport belt by using a measurement probe conforming to JIS method 6911 and applying 100 V with a high resistance meter R8340 manufactured by ADVANTEST. It is the value.
[0061]
The suction roller facing roller 6 according to the present embodiment is a metal roller. Further, the drive roller 7 used was a metal roller provided with a rubber layer having a thickness in the range of about 0.5 mm to 3 mm on the metal core to prevent slipping. The resistance value of this rubber layer is 10 ¹⁵ Although an insulation type of Ωcm or more is used as an example, it may be of low resistance. For the tension rollers 8 and 9, metal rollers were used. Regarding the cores of the tension rollers 8 and 9 and the drive roller 7, the conveying belt 1 is a self-attenuating system, and there are no members (electrodes) that face the conveying belt 1 between them. Either can be used.
[0062]
(Registration detection, concentration detection system)
Due to variations in the circumferential length of the conveyor belt and the mounting position of the process station, the timing for matching the toner images of the respective colors on the transfer material varies among the image forming apparatuses. If this timing does not match, the toner images of the respective colors are formed on the transfer material in a shifted manner (registration misalignment), resulting in variations in color. Therefore, it is necessary to detect the resist periodically or in real time to correct this timing. First, registration detection will be described.
[0063]
In order to perform the resist detection, the image forming apparatus includes first to fourth process stations 2a to 2d for forming a predetermined resist detection pattern on the conveying belt 1 prior to transfer of the toner image onto the transfer material. Means for controlling the detection, that is, detection pattern forming means is provided. This resist detection pattern is formed by transferring a plurality of lines parallel to the main scanning direction formed on the photoconductors 21a to 21d in the color process stations 2a to 2d to the transport belt 1.
[0064]
Further, the image forming apparatus is provided with optical registration sensors 131 and 132 as detection means facing the conveyance belt 1 on the most downstream side in the conveyance direction of the transfer material P by the conveyance belt 1. The center position of the pattern line is detected. Based on the detection results of the optical registration sensors 131 and 132, the image registration position is controlled by adjusting the image writing timing as necessary.
[0065]
Also, 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 variation, the image density is controlled. Here, this image density control will be described.
[0066]
Similar to the resist detection, the image forming apparatus also controls the process stations 2a to 2d for forming a predetermined density detection pattern on the conveying belt 1 prior to the image forming process. Pattern forming means is provided. An optical density sensor 133 as a detecting means for detecting density is also provided opposite to the conveying belt 1 on the most downstream side along the conveying direction of the transfer material by the conveying belt 1 in the same manner as the resist detection. The density is detected by irradiating the pattern with predetermined light and detecting the reflected component. Based on the detection result, the image density is controlled by adjusting the developing bias and the charging potential.
[0067]
FIG. 3 shows the positional relationship in the longitudinal direction of the optical resist sensors 131 and 132 that perform resist detection and density detection, and the optical density sensor 133.
[0068]
Optical registration sensors 131 and 132 that perform registration detection are provided at substantially both ends of the conveyance belt 1 in the width direction. Further, the optical density sensor 133 that performs density detection is provided at a substantially central portion in the width direction of the conveyor belt 1.
[0069]
The optical resist sensors 131 and 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.
[0070]
As shown in FIG. 7, the optical sensors 131 to 133 include a light emitting element 201 such as an LED and a light receiving element 202 such as a photodiode. Light emitted from the light emitting element 201 is incident on the conveyance 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 regular reflection component of the irradiation light.
[0071]
In the description of this embodiment, optical sensors 131 to 133 that detect specularly reflected light are used. However, the type that detects diffused light and the light that has passed through the conveyor belt and the toner image formed thereon are detected. A type of sensor can also be used.
[0072]
The optical sensors 131 to 133 are configured so as to be opposed to the conveyance belt on the most downstream side in the conveyance direction of the transfer material by the conveyance belt 1.
[0073]
Next, the configuration of the suction roller 5 in this embodiment will be described.
[0074]
First, the abutment roller 5 is brought into contact with the conveyor belt 1 from both ends (not shown) of the shaft by improperly applying the spring load with a pressurizing force of about 1 kg. For the purpose, the suction roller 5 needs to have conductivity for providing a sufficient charge on the transfer material.
Specifically, the actual resistance value is 10 ^Five ~Ten ⁷ It is desirable to be about Ω.
[0075]
On the other hand, it is necessary to have releasability for preventing the toner of a predetermined detection pattern formed on the conveyor belt 1 from adhering and accumulating on the suction roller 5.
[0076]
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 blended on the outer periphery of the base layer 52. A layer provided with a conductive layer 53 to which conductivity is given and an insoluble fluororesin is added is used.
[0077]
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 rubbers such as butadiene, isoprene, chloroprene, styrene butadiene, ethylene propylene, polynorbornene, styrene-butadiene-styrene (SBS), polyurethane, and silicone.
[0078]
In addition, as a conductive material to be blended with these rubber compositions, carbon black, graphite, metal, 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 10 ¹ ~Ten ⁹ It is preferable to adjust to about Ωcm.
[0079]
Next, the conductive film layer 53 will be described. This conductive layer 53 is made of, for example, nylon, polyester, urethane-modified acrylic resin, phenol resin, acrylic resin, epoxy resin, urethane resin, urea resin, etc., metal oxide such as carbon black, graphite, tin oxide, titanium oxide, It is a mixture of conductive materials such as ionic substances and charge transfer complexes. In this case, the volume resistivity of the conductive film layer 53 is 10 ^Four ~Ten ^Ten The thickness is preferably adjusted to about 5 to 500 μm to about Ωcm.
[0080]
In this embodiment, the insoluble fluororesin is disposed in the vicinity of the surface of the contact portion with the member to be charged, that is, in the conductive film layer 53 in FIG. In this case, the insoluble fluororesin may be disposed only on the surface of the conductive film layer 53 or on the entire conductive film layer 53. In short, the insoluble fluororesin is disposed on the surface where the member to be charged contacts the charging member. As long as it exists. In this case, the insoluble fluororesin may be partially exposed on the surface or in a non-exposed state.
[0081]
Specific examples of the insoluble fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoro. Ethylene-hexafluoropropylene-perfluoroalkylpinyl ether copolymer (EPE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE) ), Polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and the like.
[0082]
Here, it is desirable that the insoluble fluororesin is dispersed in the conductive film layer 53 as a powder.
[0083]
The insoluble fluororesin particles have a particle size of 30 μm or less, preferably 10 μm or less, more preferably 6 μm or less. If a powder having a too large particle size is used, the surface of the adsorbing member becomes rugged and there is a risk of toner collecting in the recess, so the above particle size range is preferable.
[0084]
The amount of the insoluble fluororesin added is 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.
[0085]
In this embodiment, the suction roller 5 is a solid butadiene rubber / liquid polyisoprene rubber (weight ratio 30) in which carbon having a thickness of about 3 mm and a surface length of about 222 mm is added to a stainless steel core bar having a diameter of about 6 mm. / 70), a urethane coating layer to which carbon having a thickness of about 120 μm is added by a dipping method, and a TiO film having a thickness of about 10 μm by a dipping method. ₂ A coating layer was formed by adding 70 parts by weight 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).
[0086]
As a result, the actual resistance value of the suction roller (measured resistance value when the suction roller is pressed with a total pressure of approximately 1 kg and a voltage of +200 V is applied to a metal roller having a diameter of 30 mm) is approximately 5 × 10. _Five Adjusted to Ω.
[0087]
In a normal printing process, in order to adsorb the transfer material P onto the transport belt 1 prior to the transfer process, an adsorption current of about 5 μA to 50 μA is applied by applying a voltage of about +200 V to +3 KV to the adsorption roller 5. Can be made to flow through the transfer material P, and good adsorption performance can be obtained.
[0088]
Next, a description will be given of a toner cleaning method in which the toner for detection is not deposited on the suction roller 5 and is cleaned from the transport belt 1 when the resist or density detection is performed using the suction roller.
[0089]
As described above, the detected toner image formed on the transport belt 1 and detected by the optical registration sensors 131 and 132 and the optical density sensor 133 is disposed on the transport belt 1 on the side opposite to the transfer material transport section. And reaches the opposite surface of the suction roller 5. At this time, since the suction roller 5 does not have a special release mechanism, it remains in contact with the conveyor belt 1. Therefore, the bias power source 12 causes the toner same A polar toner adhesion preventing bias of approximately −300 V is applied.
[0090]
As a result, the toner imparted to the conductive film layer 53 of the suction roller 5 repels negatively charged toner, and the toner can adhere electrically to the surface of the suction roller 5. In addition, the fluororesin attached to the conductive film layer 53 of the suction roller 5 gives the toner releasability, so that the adhesion force of the toner image to the surface of the suction roller 5 is superior to the above repulsion electrolysis, and the toner is absorbed. It is possible to prevent the roller 5 from adhering to the surface. Further, by setting the value of the toner adhesion prevention 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 discharge. The polarity can be reversed to prevent the toner from adhering to the surface of the suction roller 5. For this reason, toner does not accumulate on the surface of the suction roller 5.
[0091]
As described above, the resist detection toner and the density detection toner that have passed through the suction portion N without adhering to the suction roller 5 are reversely transferred from the transport belt 5 to the photoreceptors 21a to 21d by the photoreceptor recovery cleaning method. Then, it is cleaned by being collected in the waste toner container 26 of the process station, that is, the process cartridges 2a to 2d.
[0092]
Hereinafter, the photoconductor recovery cleaning method will be described in detail.
[0093]
As shown in FIG. 1, in the first process station 2a, a switch 5a in the transfer bias power source 4a is switched, a cleaning bias having a polarity opposite to that at the time of transfer is applied to the transfer blade 3a, and normal polarity toner is applied to the photosensitive drum. It is adsorbed by 21a and collected in the waste toner container 26 of the process cartridge 2a. Further, by passing through the first process station 2a, the polarity opposite to the normal polarity, non-polarity, or main polarity on the conveyor belt 1 that is not attracted to the photosensitive drum 21a due to a small amount of charge. The toner is charged to the opposite polarity.
[0094]
Next, in 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 toner of the opposite polarity that has not been attracted to the photosensitive drum 21a in the first process station 2a is removed from the photosensitive drum of the process cartridge 2b. The toner on the conveyor belt 1 is attracted to the waste toner container 26 and collected in the waste toner container 26, and the toner on the conveyor belt 1 that has not been attracted to the photosensitive drum 21b due to a small amount of charge, which is normal polarity, nonpolarity, or opposite polarity. To charge.
[0095]
Further, in the third process station 2c, the switch 5c in the transfer bias power source 4c is switched, a cleaning bias having a polarity opposite to that at the time of transfer is applied to the transfer blade 3c, and normal polarity toner is attracted to the photosensitive drum 21c. The toner is collected in the waste toner container 26 in the cartridge 2c, and has a polarity opposite to the normal polarity, non-polarity, or a normal polarity on the conveying belt 1 that is not attracted to the photosensitive drum 21c because of a small charge amount. Charge the toner to the opposite polarity. Since most of the toner is collected at the first to third process stations 2a to 2c, the amount of toner remaining on the transport belt 1 is small, and the toner tends to be charged to the opposite polarity.
[0096]
Further, in the fourth process station 2d, a cleaning bias having the same polarity is applied to the transfer blade 3d at the same time as the transfer, and the toner of the opposite polarity that has not been attracted to the photosensitive drum 21 in the third process station 2c is supplied to the fourth process station 2d. It is adsorbed on the photosensitive drum 21d and collected in a waste toner container 26 in the process cartridge 2d.
[0097]
In this embodiment, the charging polarity of the toner is negative, the cleaning bias having the same polarity as that at the time of transfer is +1 kV, and the cleaning bias having the polarity opposite to that at the time of transfer is 12 kV.
[0098]
With the above configuration, registration and density detection are performed every 100 sheets, and toner accumulation on the suction roller 5 does not occur through a print durability of a total of 150,000 sheets, and image stains on the transfer material may occur. There wasn't. In addition, there was no occurrence of image smear due to poor cleaning of the conveyor belt 1, and a good print image could always be maintained in combination with stabilization of print image quality by density control.
[0099]
As described above, by providing the surface layer portion including the fluororesin and the conductive insoluble member on the surface layer of the suction roller 5, toner accumulation on the suction roller 5 can be prevented.
[0100]
Further, by appropriately applying a cleaning bias to the suction roller 5, prevention of toner accumulation on the suction roller 5 can be achieved even better.
[0101]
This eliminates the need for a special mechanism for separating the suction roller 5 from the transport belt 1. Further, since a special member for cleaning the transport belt 1 is not required, the cost of the apparatus can be greatly reduced.
[0102]
[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. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.
[0103]
In this embodiment, instead of the suction roller 5 having a two-layer structure including the base layer 52 and the conductive film layer 53 as shown in FIG. 4A in the first embodiment, as shown in FIG. A one-layer structure using a suction roller 50 is used.
[0104]
In this case, the insoluble fluororesin is disposed on the elastic base layer 54 instead of the conductive film layer 53. The insoluble fluororesin may be disposed only on the surface portion of the elastic base layer 54, or may be disposed on the entire elastic base layer 54. Even if the member to be charged is exposed on the surface in contact with the charging member, it is exposed. It may be in a state.
[0105]
Note that the suction roller is not limited to one layer or two layers, and may have a structure of three or more layers. Further, 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 multilayer.
[0106]
With the configuration described above, toner accumulation on the suction roller 50 can be prevented as in the first embodiment.
[0107]
Further, by appropriately applying a cleaning bias to the suction roller 50, prevention of toner accumulation on the suction roller 50 can be achieved even better.
[0108]
This eliminates the need for a special mechanism for separating the suction roller 50 from the transport belt 1. Further, since a special member for cleaning the transport belt 1 is not required, the cost of the apparatus can be greatly reduced.
[0109]
[Third embodiment]
Next, a third embodiment of the image forming apparatus according to the present invention will be described. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.
[0110]
In the first embodiment, the case where the bias voltage for preventing toner accumulation applied to the suction roller 5 is set to approximately −300 V has been described.
[0111]
On the other hand, in use, the toner may be unexpectedly charged. As an example, when the printer stops during recording due to a jam or the like, or when a durable print is performed at 32.5 ° C. and 85% RH in an extremely high temperature and high humidity state, the toner image placed on the transport belt The charge (not only in the detection pattern but also in the case where the toner is mistakenly transferred directly onto the conveyance belt at the time of jam) may become almost zero or may be reversed. In such a case, as a bias voltage value for cleaning the suction roller 5 or preventing toner accumulation, for example, a −300V cleaning bias having the same polarity as the toner, and a toner having a different size from that in the suction step. Two types (both polarities) of bias voltages for cleaning of +300 V having opposite polarities may be used.
[0112]
As an example, at the time of return rotation after detection of resist or density or after occurrence of a jam, first, a bias voltage of −300 V is applied to the suction roller 5 to rotate the conveyor belt 1 approximately once, and then once onto the suction roller 5. Even when toner accumulates, the suction roller 5 can be completely cleaned. At this time, a cleaning bias similar to that in the first embodiment may be applied to the transfer first to fourth process stations.
[0113]
By applying the cleaning bias as described above, similarly to the first embodiment, by providing a surface layer portion including a fluororesin and a conductive insoluble member on the surface layer of the suction roller 5, toner accumulation on the suction roller 5 is achieved. Can be prevented.
[0114]
Further, by appropriately applying a cleaning bias to the suction roller 5, prevention of toner accumulation on the suction roller 5 can be achieved even better.
[0115]
This eliminates the need for a special mechanism for separating the suction roller 5 from the transport belt 1. Further, since a special member for cleaning the transport belt 1 is not required, the cost of the apparatus can be greatly reduced.
[0116]
【Effect of the invention】
As described above, according to the present invention, the fluororesin and the conductive insoluble member are formed on the surface of the suction roller even when the toner image, which is a detection pattern for detecting the resist and density, is directly formed on the conveyance belt. By providing the surface layer portion including the toner, toner accumulation on the suction roller could be prevented.
[0117]
Furthermore, the above object can be achieved more satisfactorily by appropriately applying a cleaning bias to the suction roller.
[0118]
This eliminates the need for a special mechanism for separating the suction roller from the transport belt. Further, since a special member for cleaning the transport belt is not necessary, the cost of the apparatus can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image forming apparatus according to a first embodiment.
FIG. 2 is an explanatory diagram around a transfer.
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 the periphery of a conventional transfer.
FIG. 6 is a configuration diagram of a conventional image forming apparatus.
FIG. 7 is an explanatory diagram of a toner pattern detection unit.
[Explanation of symbols]
L1, L2 ... Optical axis
M ... Abutting 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 opposed roller
7 ... Driving roller
8, 9 ... tension roller
10… Registration roller
12… Bias power supply
13… Registration roller
14… feed 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

Claims (4)

A plurality of image forming means including an image carrier that carries a toner image; a conveying means that is rotatable and capable of carrying a transfer material together with the plurality of image carriers; and a plurality of the image carriers. A plurality of transfer means for transferring a toner image onto the transfer material from the image carrier by applying a transfer bias ; and a transfer material disposed upstream of the plurality of image forming means in the rotation direction of the conveying means. In an image forming apparatus comprising: a suction unit that electrostatically attracts to a transport unit; and a detection unit that detects a predetermined detection pattern formed by the image forming unit on the transport unit.
The surface layer of the adsorption means is formed of a surface layer material including at least a fluororesin and a conductivity imparting member ,
When the detection pattern on the transport unit after detection by the detection unit comes into contact with the suction unit, the suction roller and the transport unit come into contact with a bias having a polarity opposite to the transfer bias. An image forming apparatus that applies a bias that is equal to or lower than a discharge threshold value in a portion .  The cleaning means for cleaning the toner image on the transfer material conveying means does not exist at least on the path to face the suction means downstream of the detecting means in the rotation direction of the conveying means. The image forming apparatus according to 1. Detection pattern on the transfer means after detection by the prior Symbol detection unit, after contact with the adsorption means, said image bearing from the said conveying means by applying the transfer bias having a reverse polarity cleaning bias to said transfer means The image forming apparatus according to claim 1 , wherein the image forming apparatus is electrostatically moved to the body. The image forming apparatus according to claim 1, wherein the suction unit is a suction roller.

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