JP2010145902A - Transfer cleaning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer cleaning device which is capable of obtaining efficient and satisfactory cleaning performance upon both normal printing and jamming or the like, and an image forming apparatus. <P>SOLUTION: The transfer cleaning device includes a scorotron 70 for charging toner transferred to an intermediate transfer belt 31 and a cleaning brush roller 80, which is brought into contact with the intermediate transfer belt 31 and cleans off the toner charged by the scorotron 70. As operation mode, the transfer cleaning device has a first operation mode, wherein the scorotron 70 positively charges the toner and a negative voltage is applied to the cleaning brush roller 80, and a second operation mode, wherein the scorotron 70 is stopped and a positive voltage is applied to the cleaning brush roller 80. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention includes a developing device that performs development by a toner jumping phenomenon using a non-magnetic one-component toner, and in the image forming apparatus of a type that transfers a developed image by the developing device to an intermediate transfer medium. The present invention relates to a transfer cleaning device having a configuration for cleaning toner from a transfer medium. The present invention also relates to an image forming apparatus provided with such a transfer cleaning device.

In an image forming apparatus, a plurality of color toner images formed on a plurality of photoconductor surfaces are primarily transferred to a transfer medium such as an intermediate transfer belt, and the toner image transferred to the transfer medium is transferred to a recording medium such as paper. A device that performs image transfer by secondary transfer is known.

In the image forming apparatus having such a configuration, for example, various cleanings are performed in order to clean and remove residual toner in the secondary transfer remaining on the transfer medium after the secondary transfer from the transfer medium and prepare for the next transfer. Various devices have been proposed.

For example, in Patent Document 1 (Japanese Patent Laid-Open No. 7-64444), a DC voltage having a polarity opposite to the charge of the toner is applied and slid on the toner image carrier to collect residual toner on the toner image carrier. A conductive brush roll, and a collection roll that collects toner by applying a DC voltage that has the same polarity as the voltage applied to the conductive brush roll and is higher than the voltage value, and is brought into contact with the conductive brush roll In a bias cleaning device having a cleaner unit comprising:
Disclosed is a bias cleaning device comprising toner charge amount reducing means for reducing the charge amount of toner on the toner image carrier, upstream of the cleaner unit in the rotation direction of the toner image carrier. Has been.
JP 7-64444 A

In the cleaning device described in Patent Document 1, a corotron is used as a toner charge amount reducing means. However, the transfer residual toner is charged both positively and negatively, and is charged before the brush cleaning by the corotron as in the prior art. Even if the amount is reduced, efficient brush cleaning can be performed on toner charged to one polarity, but effective brush cleaning can be performed on toner charged to the other polarity. In general, however, the conventional technique has a problem that the toner cannot be efficiently removed by brush cleaning, and a good cleaning property cannot be obtained.

Therefore, in order to solve such problems, using corona generating means such as corotron,
The applicant has proposed a method in which the transfer residual toner charged in both positive and negative is aligned with one polarity and cleaned by a brush to which a bias is applied. However, even in such a system, it is difficult to uniformize the polarity of a multilayer and relatively large amount of toner due to the occurrence of a jam to one of the polarities by means of corona generation means, which is efficient when a jam occurs. There was a problem that proper cleaning could not be performed.

The present invention is to solve the above-mentioned problems, and a transfer cleaning device according to the present invention includes a corona charging unit that charges the toner transferred to a transfer medium, and a corona charging unit that contacts the transfer medium and contacts the transfer medium. And a cleaning brush roller that cleans the toner charged in the first operation mode in which the corona charging unit performs positive charging and a negative voltage is applied to the cleaning brush roller. And a second operation mode in which the corona charging unit is stopped and a positive voltage is applied to the cleaning brush roller.

An image forming apparatus according to the present invention includes a corona charging unit that charges the toner transferred to a transfer medium, and a cleaning brush that contacts the transfer medium and cleans the toner charged by the corona charging unit. A first operation mode in which a negative voltage is applied to the cleaning brush roller and the corona charging unit is stopped. And a second operation mode in which a positive voltage is applied to the cleaning brush roller.

In addition, an image forming apparatus according to the present invention includes a conveyance unit that conveys a recording medium, a detection unit that is provided in the conveyance unit and detects a passage state of the recording medium, and the detection unit passes the recording medium. When it is detected that there is no abnormality in the state, the operation is performed in the first operation mode.

In addition, the image forming apparatus according to the present invention includes a transfer roller that is in contact with the transfer medium and through which the recording medium is inserted into a nip between the transfer medium, and the detection unit includes the transfer medium. When an abnormality is detected while the recording medium is inserted between the nips, the recording medium operates in the first operation mode after operating in the second operation mode.

The image forming apparatus according to the present invention further includes a patch sensor that detects the toner transferred to the transfer medium. When the toner is detected by the patch sensor, a second sensor is formed.
Operates in an operating manner.

In the image forming apparatus according to the present invention, the toner has an average particle diameter of 5 μm or less and a circularity of 0.95 or more.

Further, in the image forming apparatus according to the present invention, the surface roughness of the collection roller is equal to or less than the average particle diameter of the toner.

In the image forming apparatus according to the present invention, the outer periphery of the cleaning brush roller rotates in a direction opposite to the moving direction of the transfer medium at a position where the cleaning brush roller is in contact with the transfer medium.

In the transfer cleaning device and the image forming apparatus according to the present invention, the corona charging unit performs positive charging and a negative voltage is applied to the cleaning brush roller, and the corona charging unit stops. And a second operation mode in which a positive voltage is applied to the cleaning brush roller, so that efficient and good cleaning properties can be obtained at both the timing of normal printing and the occurrence of a jam. It becomes.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an example of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing a developing device common to the developing devices used in the image forming apparatus according to the embodiment of the present invention.

As shown in FIG. 1, the image forming apparatus 1 of this example is formed as a tandem type image forming apparatus, and has a housing body 2, and an image forming unit 3 is provided in the housing body 2.
An intermediate transfer unit (hereinafter also referred to as a primary transfer unit) 4, a paper feed unit 5, a secondary transfer unit 6, a fixing unit 7, and a recording medium conveying means 8 are provided. Consumables in the image forming unit 3 and the paper feeding unit 5 are configured to be detachable from the housing main body 2, and these can be removed and repaired or exchanged including the primary transfer unit 4.

The image forming unit 3 will be described with respect to an example using a plurality of different colors (in this example, a plurality of four different colors. For example, one of the four colors may be one, two, or three. The image forming station may be provided with five or more colors (hereinafter, described as four colors). These image forming stations are a yellow image forming station 9Y, a magenta image forming station 9M, a cyan image forming station 9C, and a black image forming station 9K. The yellow image forming station 9Y forms a yellow (Y) image. The magenta image forming station 9M forms a magenta (M) image. Further, the cyan image forming station 9C forms a cyan (C) image. Furthermore,
The black image forming station 9K forms a black (K) image. In this case, in this example, the arrangement order of the image forming stations 9Y, 9M, 9C, and 9K for the respective colors Y, M, C, and K is linearly arranged in this order in the right direction in FIG. The arrangement order of the image forming stations 9Y, 9M, 9C, and 9K for each color is not limited to this, and can be arbitrarily set.

In addition, these image forming stations 9Y, 9M, 9C, and 9K are provided with photoconductors 10Y, 10M, 10C, and 10K that are photoconductors, respectively. Also, these photoreceptors 10
In the vicinity of Y, 10M, 10C, and 10K, charging devices 11Y, 11M, and 11C, respectively.
, 11K are arranged. These charging devices 11Y, 11M, 11C, and 11K charge the photoreceptors 10Y, 10M, 10C, and 10K, respectively. Further, each photoconductor 10Y, 10
Exposure devices 12Y, 12M, 12C, and 12K are disposed in the vicinity of the periphery of M, 10C, and 10K on the downstream side of the charging device in their rotational directions, respectively. These exposure apparatuses 12Y
, 12M, 12C, and 12K write latent images on the photoconductors 10Y, 10M, 10C, and 10K, respectively. Further, developing devices 13Y, 13M, 13C, and 13K are disposed in the vicinity of the periphery of each of the photoconductors 10Y, 10M, 10C, and 10K on the downstream side of the exposure device in the rotation direction thereof. These developing devices 13Y, 13M, 13C, and 13K develop latent images on the photoreceptors 10Y, 10M, 10C, and 10K, respectively. Further, each photoconductor 10Y, 10
In the vicinity of the periphery of M, 10C, and 10K, neutralization devices 14Y, 14M, 14C, and 14K are disposed on the downstream side of the developing device in their rotational directions, respectively. These static eliminators 14Y
, 14M, 14C, and 14K respectively neutralize the photoreceptors 10Y, 10M, 10C, and 10K. Further, cleaners 15Y, 15M, 15C, and 15K are disposed in the vicinity of the periphery of the photoconductors 10Y, 10M, 10C, and 10K on the downstream side of the static eliminator in the rotation direction thereof. These cleaners 15Y, 15M, 15C, and 15K clean the photoreceptors 10Y, 10M, 10C, and 10K, respectively.

Each color image forming station 9Y, 9M, 9C, 9K, each charging device, each charging device, each exposure device, each developing device, each neutralizing device, and each cleaner, each color Y, M, C, K
Regardless of the configuration.

Each of the charging devices 11Y, 11M, 11C, and 11K includes a charging roller including a conductive rubber roller connected to a high voltage generation source. These charging rollers uniformly charge the surfaces of the corresponding photoreceptors 10Y, 10M, 10C, and 10K.

Each exposure device 12Y, 12M, 12C, and 12K has an LED lamp connected to the photoreceptors 10Y, 10Y,
LED line heads arranged in rows in the axial direction of M, 10C, and 10K are used. L
The ED line head has a shorter optical path length and is more compact than the laser scanning optical system. Therefore, the LED line head can be disposed close to the photoreceptors 10Y, 10M, 10C, and 10K, and the apparatus main body can be downsized.

The intermediate transfer belt 31 is an endless belt, is stretched around a driving roller 29 and a tension roller 30 and the like, and the photoreceptors 10Y and 10M are formed by the primary transfer portions 4Y, 4M, 4C, and 4K.
It is rotationally driven by the driving roller 29 while contacting with 10C and 10K. As such an intermediate transfer belt 31, a polycarbonate single layer belt imparted with conductivity by carbon black, a polyimide single layer belt imparted with conductivity by carbon black, or a polycarbonate imparted conductivity by carbon black. Similarly, a multilayer belt provided with a rubber layer and a fluorine coating layer using a polyimide imparted with conductivity as a base material is used. The resistance of the intermediate transfer belt 31 with such a material and configuration is approximately 10 ⁹ to 10 ¹³ Ω (
(Measured by applying 100 V for 10 seconds using a Hiresta as a measuring instrument).

The primary transfer portions 4Y, 4M, 4C, and 4K are arranged such that the primary transfer rollers 51Y, 51M, 51C, and 51K are opposed to each other with the photoreceptors 10Y, 10M, 10C, and 10K and the intermediate transfer belt 31 interposed therebetween. The developed toner development images of the respective colors on the photoreceptors 10Y, 10M, 10C, and 10K are sequentially superimposed and transferred onto the intermediate transfer belt 31 with the contact position with 10C and 10K as the transfer position, and a full-color toner development image is obtained. Form.

In the secondary transfer unit 6, the secondary transfer roller 38 is disposed to face the driving roller 29 with the intermediate transfer belt 31 interposed therebetween. At the transfer position where the secondary transfer roller 38 is disposed, the full-color toner image formed on the intermediate transfer belt 31 is transferred to the recording medium conveying means 8.
The image is transferred to a recording medium such as paper, film, or cloth that is conveyed by the printer.

In the image forming apparatus 1, a recording medium such as a sheet set in the sheet feeding unit 5 is sent out to the recording medium transport unit 8 by a pickup roller 36 one by one at a predetermined timing. In the recording medium conveying means 8, the recording medium is conveyed to the secondary transfer position by the conveying roller pair 37 and the like, and the single color toner developed image and the full color toner developed image formed on the transfer belt 31 are transferred to the recording medium. The secondary-transferred recording medium is further conveyed to the fixing unit 7. The fixing unit 7 includes a heating roller 39 and a pressure roller 40 that is biased to the heating roller 39 with a predetermined pressure. A recording medium is inserted between the nips, and the recording medium is placed on the recording medium. The transferred single-color toner image or full-color toner image is fused and fixed to a sheet material such as paper.

A plurality of paper detection sensors 75 are provided in the recording medium conveying means 8 so that passage information of the recording medium can be obtained. Such a paper detection sensor 75 is configured to transmit a detection result to a control unit (not shown) or the like, and the detection result of the paper detection sensor 75 is referred to by the control unit, so that the recording medium is passed. Is detected. The control unit controls the operation of the transfer cleaning device 60 according to the detection result of the passing state.

Further, the tension roller 30 stretches the intermediate transfer belt 31 together with the drive roller 29 and the like, and the tension roller 30 is stretched around the tension roller 30 of the intermediate transfer belt 31.
A transfer cleaning device 60 for cleaning the intermediate transfer belt 31 is in contact with and disposed.

A patch sensor 78 for detecting the density of the toner image on the intermediate transfer belt 31 is provided in the vicinity of the intermediate transfer belt 31. The image forming apparatus has a predetermined timing,
A control operation for controlling the density of the image is executed.
Is used. That is, when the control operation is executed, a patch image (test pattern) as a toner image is developed, and the patch image is transferred to the intermediate transfer belt 31. Then, the density of the patch image transferred to the intermediate transfer belt 31 is detected by the patch sensor 78, the detection result is transmitted to a control unit (not shown), and this control unit is based on the detected density of the patch image. , Adjust the image density. Further, the control unit that has received information from the patch sensor 78 controls the operation of the transfer cleaning device 60 accordingly.

Next, the configuration of the developing device used in the image forming apparatus according to the embodiment of the present invention will be described. As shown in FIG. 2, the developing devices 13Y, 13M, 13C, and 13K include developing device housings 16Y, 16M, 16C, and 16K, respectively. Each developer housing 1
6Y, 16M, 16C, and 16K are provided with toner storage portions 17Y, 17M, 17C, and 17K that store the toners TY, TM, TC, and TK, respectively. In addition, the toner storage units 17Y, 17M, 17C, and 17K have toners TY, TM, TC, and T, respectively.
Toner agitating members 18Y, 18M, 18C and 18K for agitating K are provided. Furthermore,
The developing device housings 16Y, 16M, 16C, and 16K are provided with toner supply rollers 19Y, 19M, 19C, and 19K, respectively. Further, each developer housing 16Y
, 16M, 16C, and 16K include developing rollers 20Y, 20M, 20C, and 20 respectively.
K is provided. Furthermore, each developer housing 16Y, 16M, 16C, 16K
Regulating blades 21Y, 21M, 21C, and 21K are provided, respectively.

The developing rollers 20Y, 20M, 20C and 20K are subjected to blasting or rolling on the surface of a cylindrical metal (aluminum, iron) pipe, Ni plating (layer thickness 0.1 to 5 μm), and surface roughness. In which Rz = 3 to 10 μm is used. Also, the regulating blades 21Y, 21
For M, 21C, and 21K, conductive urethane rubber containing carbon or the like in urethane rubber and imparting conductivity is used. In this embodiment, the toners TY and TM used are used.
, TC, and TK are polymerized toners having an average particle diameter of 5 μm or less and a circularity of 0.95 or more.

The toner supply rollers 19Y, 19M, 19C, and 19K supply the toners TY, TM, TC, and TK from the toner storage units 17Y, 17M, 17C, and 17K to the developing rollers 20Y, 20M, 20C, and 20K, respectively. To do. Also, each developing roller 20Y, 20
M, 20C, and 20K convey the supplied toners TY, TM, TC, and TK to the photoreceptors 10Y, 10M, 10C, and 10K, respectively. At this time, each regulating blade 21Y, 21
M, 21C, and 21K regulate the toner layer thicknesses of the toners TY, TM, TC, and TK on the developing rollers 20Y, 20M, 20C, and 20K, respectively. Each developing roller 20Y, 20
The electrostatic latent images of the respective colors of the photoreceptors 10Y, 10M, 10C, and 10K are developed by the toners TY, TM, TC, and TK conveyed by M, 20C, and 20K, respectively.

In a state where the developing devices 13Y, 13M, 13C, and 13K are set in the image forming station, the developing rollers 20Y, 20M, 20C, and 20K are the photoreceptors 10Y, 10M, 10C,
Development is performed while being driven to rotate in a direction opposite to the rotation direction of the photosensitive members 10Y, 10M, 10C, and 10K (see arrows in the drawing) with a slight gap (for example, 100 to 300 μm) from 10K. It has a function of developing latent images formed on the photoreceptors 10Y, 10M, 10C, and 10K with toner supplied to the peripheral surfaces of the rollers 20Y, 20M, 20C, and 20K. Such a developing action is performed by applying a developing bias in which an AC voltage is superimposed on a DC voltage from a developing bias power source (not shown) to the developing rollers 20Y, 20M, 20C, and 20K, and between the developing roller and the photoconductor. This is done by applying an oscillating voltage and supplying toner from the developing roller to the electrostatic latent image portion formed on the photoreceptor.

The toner supply rollers 19Y, 19M, 19C, and 19K have a surface formed of a urethane sponge, and the peripheral surfaces of the toner supply rollers 19Y, 19M, 19C, and 19K are in contact with the developing rollers 20Y, 20M, 20C, and 20K. It rotates in the direction opposite to the developing roller (counterclockwise in FIG. 1). A voltage equivalent to the developing bias voltage applied to the developing roller 107 is also applied to the supply roller 105.

The developing rollers 20Y, 20M, 20C, and 20K include regulating blades 21Y, 21M, and 2
The toner adhering to the peripheral surface of the developing roller 1C, 21K is always pressed against the peripheral surface of the developing roller uniformly by the action of the leaf spring members 22Y, 22M, 22C, 22K. The excess amount is scraped off so that a certain amount of toner is carried on the peripheral surface of the developing roller. The regulating blades 21Y, 21M, 21C, and 21K also have a function of appropriately charging the toner 113.

The toners TY, TM, TC, and TK used in the image forming apparatus 1 according to the present embodiment are all non-magnetic one-component toners and have negative charging characteristics.
That is, in the present embodiment, the toner conveyed on the developing rollers 20Y, 20M, 20C, and 20K is negatively charged by passing through the nips of the regulating blades 21Y, 21M, 21C, and 21K. In this embodiment, the toner having such a negative charge characteristic is described as an example. However, the present invention can also be realized by using a toner having a positive charge characteristic. In that case, a polarity opposite to that described in the specification may be used for polarity such as bias application.

As shown in FIG. 2, the developing rollers 20Y, 20M, 20C, and 20K and the toner supply rollers 19Y, 19M, 19C, and 19K have the same rotation direction α.
The rotation direction α is counterclockwise opposite to the rotation direction of the photoconductors 10Y, 10M, 10C, and 10K.

Each developing roller 20Y, 20M, 20C, 20K and each photoconductor 10Y, 10M, 10C,
A predetermined development gap is set between 10K and 10K. Accordingly, each of the developing devices 13Y, 13M, 13C, and 13K performs jumping development using a non-magnetic one-component toner. In that case, when developing, each developing roller 20Y, 20M, 2
A developing bias in which an AC voltage is superimposed on a DC voltage is applied to 0C and 20K, respectively.
In these jumping developments, each toner reciprocates between each developing roller and each photoconductor five times or more.

In each of the developing devices 13Y, 13M, 13C, and 13K of the image forming apparatus 1 of this example, a predetermined uneven pattern that is larger than the toner particle size is formed on the outer peripheral surface of each of the developing rollers 20Y, 20M, 20C, and 20K. A toner layer is formed on the developing rollers 20Y, 20M, 20C, and 20K.

Next, the configuration of the transfer cleaning device used in the image forming apparatus according to the embodiment of the present invention will be described. FIG. 3 is a cross-sectional view schematically showing a transfer cleaning device used in the image forming apparatus according to the embodiment of the present invention. In FIG. 3, 60 is a transfer cleaning device, 61 is a cleaning device housing, 70 is a scorotron, 71 is a wire, 72
Is a house, 75 is a grid, 80 is a cleaning brush roller, 81 is a roller section, 8
Reference numeral 2 denotes a brush portion, 85 denotes a collection roller, 86 denotes a collection roller cleaning blade holding member, and 87 denotes a collection roller cleaning blade.

In recent years, an image forming apparatus has attempted to realize a higher-definition image by using a toner having a smaller average particle diameter than conventional ones. By the way, the cleaning of the secondary transfer residue of the toner having a small average particle diameter, that is, the toner having a high circularity and a small particle diameter, cannot completely scrape off the toner on the intermediate transfer belt only by cleaning with a blade. . Further, since the secondary transfer residual toner has both positive and negative charging characteristics, it is difficult to completely remove the toner even by cleaning only with a brush roller to which a bias is applied.

Therefore, in the transfer cleaning device 60 according to the present embodiment, the scorotron 70 disposed on the upstream side of the cleaning brush roller 80 is operated to make the charged state of the toner positive, and then the cleaning brush roller 80 performs brush cleaning. By adopting such a configuration, the cleaning property of the intermediate transfer belt 31 is improved.

Here, in order to suppress the generation of ozone accompanying the operation of the scorotron 70, it is preferable to operate the scorotron 70 so as to generate a positive charge. Therefore, in the present embodiment, positive charging is performed by the scorotron 70. At the same time, a negative voltage is applied to the cleaning brush roller 80 to perform cleaning during normal printing.

In the transfer cleaning device 60 according to the present embodiment, the intermediate transfer belt 31 has a primary transfer portion 4Y.
A cleaner that mainly removes toner from the surface of the intermediate transfer belt 31 upstream of receiving the transfer of the toner image at 4M, 4C, and 4K. What the transfer cleaning device 60 cleans remains on the intermediate transfer belt 31 without being transferred to the recording medium by the secondary transfer unit 6.
There is remaining toner for normal printing and toner for all images (all toner for one image) remaining on the intermediate transfer belt 31 without being transferred to the recording medium due to occurrence of paper jam or the like.

Here, the toner remaining on the intermediate transfer belt 31 due to the occurrence of a jam or the like is a multi-layered and relatively large amount of toner, so even if the scorotron 70 is operated, the charged state of the toner is uniformly made positive. Therefore, the transfer cleaning device 60 according to the present embodiment has a cleaning operation mode for occurrence of jam, which is different from the cleaning operation mode in normal printing.

In the present embodiment, the operation mode of the transfer cleaning device 60 during normal printing is referred to as a first operation mode, and the other operation modes are referred to as second operation modes.

The transfer cleaning device 60 generally has two configurations: a charging member that charges toner on the surface of the intermediate transfer belt 31, and a cleaner member that removes toner from the intermediate transfer belt 31. The former configuration is centered on the scorotron 70, and the latter configuration is centered on the cleaning brush roller 80. In this embodiment, the case where the scorotron 70 is used as the charging member will be described. However, in the present invention, not only the scorotron but also other corona generating means such as corotron can be used as the charging member.

The scorotron 70 is a general one that generates a predetermined charge by being accommodated in a house 72 and allowing a predetermined current to flow through the wire 71 and adjusting the potential of the grid 73. In such a scorotron 70, generation of ozone can be suppressed when operated so as to generate a positive charge. Therefore, in this embodiment, the scorotron 70 is operated so that the toner on the intermediate transfer belt 31 is positively charged. .

The cleaning brush roller 80 has a structure in which a brush portion 82 made of a conductive brush such as acrylic carbon, nylon carbon, polyester-carbon, or polypropylene-carbon is provided around a roller portion 81 that is a metal core. The cleaning brush roller 80 having such a structure rotates the outer periphery at a constant speed in the opposite direction to the movement of the intermediate transfer belt 31 at the contact position with the intermediate transfer belt 31 in order to make it easy to peel off the toner from the intermediate transfer belt 31 ( Constant speed, counter rotation). The depth of biting of the brush portion 82 of the cleaning brush roller 80 into the intermediate transfer belt 31 is determined by the intermediate transfer belt 3.
1 to a degree that does not cause mechanical damage. In addition, the resistance of the brush part 82 as described above is 10 ⁴ to 10 ⁸ Ω (calculated from the current value when 300 V is applied between the shaft and the flat plate in the metal flat plate).
It is.

The collection roller 85 is a conductive roller composed of a metal roller such as iron, aluminum, or stainless steel having a surface roughness of 5 μm or less that is equal to or less than the average particle diameter of the toner. The collection roller 85 is configured to attract toner by providing a potential difference with the cleaning brush roller 80. Further, when the surface roughness is 5 μm or less, which is equal to or less than the average particle diameter of the toner, the recovery roller cleaning blade 87 makes it easy to scrape off the toner. The collection roller 85 is rotated in the direction of the width with respect to the cleaning brush roller 80, and the rotation speed of the collection roller 85 is the same as that of the cleaning brush roller 80.

The collection roller cleaning blade holding member 86 is a metal member that holds the collection roller cleaning blade 87 extending in the axial direction of the rollers. Urethane rubber is used for the collection roller cleaning blade 87.

FIG. 4 is a view for explaining the contact angle of the collection roller cleaning blade 87 with respect to the collection roller 85. In FIG. 4, aa ′ is a tangential plane at the line where the collection roller cleaning blade 87 contacts the collection roller 85, bb ′ is a plane obtained by extending the contact surface of the collection roller cleaning blade 87, and θ ₂ is a contact angle of the collection roller cleaning blade 87 with respect to the collection roller 85. The contact condition when the collection roller cleaning blade 87 contacts the collection roller 85 is a biting depth of 0.5 mm, and the cleaning angle θ ₂ is 20 ° to 30 ° with a counter.

As the contact angle as described above, the deeper the bite and the larger the contact angle, the greater the pressure at the nip, and the recovery roller cleaning blade 87.
Will be warped. On the other hand, if the bite is made shallower and the contact angle is made smaller, the collection roller cleaning blade 87 will be turned up. Considering this, the angle θ ₂ is preferably 20 ° to 30 ° as described above.

Next, the current and voltage applied to each roller and corona charging means in the transfer cleaning device 60 will be described. FIG. 5 is a diagram illustrating the toner cleaning principle of the transfer cleaning device used in the image forming apparatus according to the embodiment of the present invention.

The scorotron wire current application unit 91 applies current I1 to the wire 71 of the scorotron 70 during normal printing (in the first operation mode), and current I1 during jam occurrence (in the second operation mode). It is a current source to allow 'to flow. In the second operation mode, since the scorotron 70 is stopped, I1 ′ = 0 [A].

Further, the scorotron grid voltage application unit 92 applies the voltage V2 to the grid 73 of the scorotron 70 during normal printing (in the first operation mode), or when a jam occurs (
This is a voltage source for applying the voltage V2 ′ in the second operation mode). In the second operation mode, since the scorotron 70 is stopped, V2 ′ = 0 [V].

The cleaning brush roller voltage application unit 95 includes a cleaning brush roller 8.
This is a voltage source for applying a bias voltage V3 during normal printing (in the first operation mode) to 0 and applying a bias voltage V3 ′ when a jam occurs (in the second operation mode). Here, the bias voltage V3 applied by the cleaning brush roller voltage application unit 95 is the Scorotron 70.
V3 is a bias voltage applied to collect the positively charged toner at V3.
Is a negative voltage. On the other hand, when a jam occurs (during the second operation mode), the bias voltage is applied to collect the negatively charged toner that passes through the stopped scorotron 70, so V3. 'Is a positive voltage.

In addition, the collection roller voltage application unit 96 performs normal printing on the collection roller 85 (first
This is a voltage source that applies the bias voltage V4 in the operation mode) and the bias voltage V4 ′ in the event of a jam (in the second operation mode). Here, since the bias voltage V4 applied by the recovery roller voltage application unit 96 is a bias voltage applied for suction from the cleaning brush roller 80 to the recovery roller 85, V4 is a negative voltage having a higher potential than V3. It is. On the other hand, when the jam occurs (during the second operation mode), the scorotron 7
This is a bias voltage that is applied to suck the negatively charged toner that has passed through the negatively charged toner as it is from the cleaning brush roller 80 to the collection roller 85, so that V4 ′ has a higher potential than V3 ′. It is a positive voltage.

Here, a predetermined potential difference is set between the cleaning brush roller 80 and the collection roller 85 by providing a relationship of V4 <V3 <0, 0 <V3 ′ <V4 ′. As a result, the positively charged toner during normal printing (during the first operation mode) moves from the cleaning brush roller 80 to the collection roller 85 side, and is scraped off by the collection roller cleaning blade 87. In the second operation mode, the negatively charged toner moves from the cleaning brush roller 80 toward the collecting roller 85 and is scraped off by the collecting roller cleaning blade 87.

FIG. 6 is a diagram illustrating an operation example of the current application unit and the voltage application unit during normal printing (in the first operation mode) and when a jam occurs (in the second operation mode). In particular, as shown in FIGS. 6A and 6B, a scorotron wire current application unit 91 and a scorotron grid voltage application unit 92 are provided.
Operates the scorotron 70 to generate a positive charge in the first operation mode,
The scorotron 70 is stopped during the operation mode. 6C and 6D, the cleaning brush roller voltage application unit 95 and the recovery roller voltage application unit 96 are provided.
Applies a bias voltage having a different polarity to the cleaning brush roller 80 and the recovery roller 85 in accordance with the operation of the scorotron 70 (during the first operation mode) and the stop (during the second operation mode).

Next, the intermediate transfer belt 31 in the transfer cleaning device 60 configured as described above.
The mechanism of cleaning the toner will be described with reference to FIG. Figure 5 shows normal printing (
The toner cleaning from the intermediate transfer belt 31 in the first operation mode) is schematically shown.

The neutral toner supplied from the toner supply roller 19 to the developing roller 20 is negatively charged by the regulating blade 21, moves to the photoreceptor 10 as a developed image, and is further transferred to the intermediate transfer belt 31. On the intermediate transfer belt 31 that has passed through the secondary transfer unit 6, there is residual toner that remains without being transferred to the recording medium. Most of such toners are negatively charged toners, but there are toners that are positively charged toners of opposite polarity. That is, the remaining toner on the intermediate transfer belt 31 to be cleaned by the transfer cleaning device 60 is a toner in which both positive charging and negative charging are mixed.

Therefore, in the present embodiment, the scorotron 70 causes the positive charge to be applied to the intermediate transfer belt 31 so that the toner is aligned with a positive polarity. Thus, the toner on the intermediate transfer belt 31 positively charged by the scorotron 70 is attracted to the cleaning brush roller 80, and the toner on the cleaning brush roller 80 is moved to the collection roller 85, and is collected by the collection roller cleaning blade 87. Scrap it off.

In the transfer cleaning device 60 configured as described above, the transfer residual toner charged in both positive and negative directions is charged to one polarity by the scorotron 70 and then collected by the cleaning brush roller 80 to which the bias of the other polarity is applied. As a result, good cleaning properties can be obtained.

By the way, in the first operation mode during normal printing as shown in FIG. 5, the residual toner remaining without being transferred to the recording medium is cleaned by the secondary transfer unit 6, but in such an operation mode, a paper jam or the like is performed. As a result of this, there is a problem that it is impossible to clean the toner for all the images that have not been transferred to the recording medium (all the toner for one image). Such problems will be described in more detail. FIG. 7 is a diagram for explaining a problem in collecting toner when a paper jam occurs in the first operation state.

The toner remaining on the intermediate transfer belt 31 without being transferred to the recording medium when a paper jam occurs is a negatively charged toner having multiple layers as shown in the figure. Even if the multi-layer negatively charged toner is to be positively charged by operating the scorotron 70, only the upper layer can be positively charged as shown in the figure, and a negative bias voltage is applied. In the collecting roller cleaning blade 87, the positive charge of the upper layer portion is merely cleaned.
That is, negatively charged toner that remains without being cleaned remains on the intermediate transfer belt 31 that has passed through the collection roller cleaning blade 87.

In order to cope with such a problem, the transfer cleaning device 60 according to the present embodiment provides a second operation mode when a jam occurs. A second operation mode of the transfer cleaning device 60 will be described. FIG. 8 is a diagram schematically illustrating toner cleaning from the intermediate transfer belt 31 when a jam occurs (during the second operation mode).

As shown in the figure, the scorotron 70 is used when a jam occurs (during the second operation mode).
And the negatively charged toner is allowed to pass through. The cleaning brush roller voltage application unit 95 and the collection roller voltage application unit 96 apply a positive bias voltage to the cleaning brush roller 80 and the collection roller 85 so as to attract negatively charged toner. By such a second operation mode, as shown in the figure, the multilayer negatively charged toner generated by paper jam or the like is efficiently collected.

As described above, in the present embodiment, the first operation mode in which the scorotron 70 performs positive charging and a negative voltage is applied to the cleaning brush roller 80, and the scorotron 7
The second operation mode in which 0 is stopped and a positive voltage is applied to the cleaning brush roller 80, so that efficient and good cleaning performance can be obtained at both timings of normal printing and jam occurrence. Can be obtained.

Cleaning based on the second operation mode of the transfer cleaning device 60 is performed by the intermediate transfer belt 3.
This is also effective when cleaning a patch image (test pattern) formed on the surface 1. This is because such a patch image (test pattern) is detected by the patch sensor 78 without being transferred by the secondary transfer unit 6, and is similar to the multilayer negatively charged toner at the time of paper jam. Because it can be treated as. Therefore, in the transfer cleaning device 60 according to the present embodiment, when the patch sensor 78 is activated and operated for density detection or the like, the cleaning according to the second operation mode is set.

The paper jam described above has been described assuming that the recording medium has not reached the secondary transfer unit 6. That is, the cleaning operation of the transfer cleaning device 60 when a paper jam is detected at a stage where the recording medium is not inserted into the nip between the intermediate transfer belt 31 and the secondary transfer roller 38 has been described. It was a thing.

On the other hand, a paper jam may occur and be detected when the recording medium is inserted into the nip between the intermediate transfer belt 31 and the secondary transfer roller 38. In such a paper jam, secondary transfer residual toner and untransferred multilayer negatively charged toner remain on the intermediate transfer belt 31. FIG. 9 shows such a jam, and is a diagram schematically showing a paper jam that occurs while the recording medium passes through the nip of the secondary transfer unit 6.

The secondary transfer residual toner is a toner charged to both positive and negative, and the positively charged toner cannot be removed only by the operation according to the second operation mode. FIG. 10 is a diagram schematically showing how the recording medium is cleaned in the second operation mode when paper jam occurs while the recording medium passes through the nip of the secondary transfer unit 6. As shown in FIG. 10, positively charged toner remains on the intermediate transfer belt 31 that has passed the cleaning brush roller 80.

Therefore, in the present embodiment, when a paper jam occurs while the recording medium passes through the nip of the secondary transfer unit 6, the transfer cleaning device 60 is operated in the second operation mode at least while the intermediate transfer belt 31 rotates once. Thereafter, the intermediate transfer belt 31 is rotated while the transfer cleaning device 60 is operated in the first operation mode, thereby cleaning both the multilayer negatively charged toner and the untransferred toner.

Next, a preferred cleaning operation mode by the transfer cleaning device 60 in each case will be summarized. FIG. 11 is a diagram showing a flowchart of operation mode determination processing in the transfer cleaning device according to the embodiment of the present invention. Such a flowchart is executed by a control unit (not shown) that controls the transfer cleaning device 60.

In FIG. 11, when the process of determining the operation mode of the transfer cleaning device 60 is started in step S100, the process proceeds to step S101 to acquire operation information of the patch sensor 78, and the patch sensor 78 operates in step S102. It is determined whether or not. Step S
When the determination in 102 is YES, the process proceeds to step S108, and when the determination is NO, the process proceeds to step S103.

In step S103, detection information from a plurality of paper detection sensors 75 arranged in the recording medium conveyance path is acquired. In step S104, it is determined whether or not a paper jam has been detected. If the determination is NO, the process proceeds to step S107, and the transfer cleaning device 60 is determined to operate in the first operation mode.

When the determination in step S104 is YES, the process proceeds to step S105, and it is determined whether or not a recording medium exists in the secondary transfer nip. When the result of this determination is NO, the process proceeds to step S108, and it is determined to operate the transfer cleaning device 60 in the second operation mode. When the determination in step S105 is YES, the process proceeds to step S106, and it is determined to operate in the second operation mode while the intermediate transfer belt 31 rotates once, and then to operate in the first operation mode. In step S109, the operation mode determination process of the transfer cleaning device 60 ends.

As described above, according to the present invention, by appropriately using the first operation mode and the second operation mode, the normal transfer in the image forming apparatus, the test by the patch, the jam during the secondary transfer, the secondary transfer It is possible to obtain an efficient and good cleaning property at each timing such as when a previous jam occurs.

Next, examples and comparative examples of the present invention will be described. FIG. 12 is a diagram illustrating a configuration of an image forming apparatus used for acquiring data of an example and a comparative example. In FIG. 10, the same reference numerals as those in the previous embodiment denote the same components as those in the previous embodiment.

In both the example and the comparative example, a jumping development method using a non-magnetic one-component toner is used as the developing method. In both the example and the comparative example, the toner has an average particle diameter of 5 μm or less and a circularity of 0.95 or more. The polymerized toner was used.

In both the example and the comparative example, the operating conditions of the scorotron wire current application unit 91 and the scorotron grid voltage application unit 92 when operating the scorotron 70 are shown in FIG.
It was the same as that shown in (B).

  Table 1 summarizes the setting conditions that differ between Example 1 and Comparative Examples 1 to 3.

With the settings as described above, the following two items (1) and (2) were evaluated in two stages of ○.
(1) Visually evaluate the cleaning stain on the printing paper after 10K continuous printing with 5% duty printing.
(2) After continuous printing of 10K sheets, cleaning is performed when a 100% duty image is left without being secondarily transferred on the intermediate transfer belt 31, and the stain on the intermediate transfer belt 31 is evaluated.

When the contamination of the intermediate transfer belt 31 is evaluated in (2), the tape transfer OD value on the belt remaining after cleaning of the intermediate transfer belt 31 (the OD value is measured by attaching a tape on which nothing is transferred to J paper). Evaluation was carried out based on the difference (B−A) between (A) and J (paper), and the remaining cleaning (tape transferred to J paper). Macbeth was used as the OD value measuring device.

  Table 2 shows the two-stage evaluation results for item (1) and item (2).

The first embodiment is a cleaning brush roller 80 in which the transfer residual toner is positively charged and a negative voltage is applied in normal printing. Further, the non-secondary transfer toner of the 100% duty image is sent to the cleaning brush roller 80 while being negatively charged and cleaned by applying a positive voltage.

In Comparative Example 1, residual toner in normal printing can be cleaned, but 100% d
The non-secondary transfer toner of the uty image cannot be charged by the scorotron 70 and is sent to the cleaning brush roller 80 while partially containing the negative polarity toner. Therefore, the cleaning brush roller 80 to which a negative voltage is applied is used for cleaning. I can't finish it.

In Comparative Example 2, since the untransferred toner is not aligned with the positive polarity by the scorotron 70, the negative polarity toner cannot be cleaned by the cleaning brush roller 80.

In Comparative Example 3, since the untransferred toner is not aligned with the negative polarity by the scorotron 70,
The positive polarity toner cannot be cleaned by the cleaning brush roller 80.

Let us verify the above results theoretically. FIG. 13 is a diagram showing the charge amount-number distribution of the cleaning target toner in item (1), and FIG. 14 is a diagram showing the charge amount-number distribution of the cleaning target toner in item (2).

As shown in FIG. 13, in Example 1 and Comparative Example 1, the toner in the positive area indicated by the dotted line (with secondary transfer and with corona charge) is removed, and therefore, the cleaning property is good. . On the other hand, in Comparative Example 2 and Comparative Example 3, since each hatched area indicated by a solid line (with secondary transfer and without corona charging) is only removed, the cleaning property is inferior. Become.

On the other hand, as shown in FIG. 14, in Example 1 and Comparative Example 3, the toner in the negative area shown by the solid line (no secondary transfer, no corona charging) is removed, and therefore the cleaning property is good. Become. In contrast, in Comparative Example 1 and Comparative Example 2, a dotted line (no secondary transfer,
Each hatched area shown in (with corona charge) is simply removed,
This means that the cleaning property is inferior.

As described above, in the transfer cleaning device and the image forming apparatus according to the present invention, the corona charging unit performs positive charging and a negative voltage is applied to the cleaning brush roller, and the corona charging unit includes And a second operation mode in which a positive voltage is applied to the cleaning brush roller, so that efficient and good cleaning properties can be obtained at both timings of normal printing and jam occurrence. Is possible.

1 is a cross-sectional view schematically illustrating an example of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing a developing device common to each developing device used in an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing a transfer cleaning device used in an image forming apparatus according to an embodiment of the present invention. It is a figure explaining the contact angle of a collection roller cleaning blade. FIG. 3 is a diagram illustrating a toner cleaning principle of a transfer cleaning device used in an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the operation example of the current application part and voltage application part at the time of normal printing (at the time of a 1st operation mode), jam generation, etc. (at the time of a 2nd operation mode). FIG. 6 is a diagram illustrating a problem when collecting toner when a paper jam occurs in the first operation state. FIG. 10 is a diagram schematically illustrating toner cleaning from the intermediate transfer belt 31 when a jam occurs (second operation mode). FIG. 4 is a diagram schematically illustrating a paper jam that occurs when a recording medium passes through a nip of a secondary transfer unit. FIG. 6 is a diagram schematically illustrating a state in which a paper jam generated while a recording medium passes through a nip of a secondary transfer unit 6 is cleaned in a second operation mode. It is a figure which shows the flowchart of the operation | movement mode determination process in the transfer cleaning apparatus which concerns on embodiment of this invention. FIG. 2 is a diagram illustrating a configuration of an image forming apparatus used for acquiring data of an example and a comparative example. It is a figure which shows the charge amount-number distribution of the cleaning object toner in item (1). It is a figure which shows charge amount-number distribution of the cleaning object toner in item (2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Housing main body, 3 ... Image forming unit, 4 ...
Intermediate transfer unit (primary transfer unit), 4Y, 4M, 4C, 4K ... primary transfer unit, 5
...... Feeding unit, 6 ... secondary transfer unit, 7 ... fixing unit, 8 ... recording medium conveying means, 9, 9Y, 9M, 9C, 9K ... image forming station, 10, 10Y
10M, 10C, 10K ... photosensitive member, 11, 11Y, 11M, 11C, 11K ...
Charging device, 12, 12Y, 12M, 12C, 12K... Exposure device, 13, 13Y, 13
M, 13C, 13K ... developing device, 14, 14Y, 14M, 14C, 14K ... neutralizing device, 15, 15Y, 15M, 15C, 15K ... cleaner, 16Y, 16M, 16
C, 16K: Developer housing, 17Y, 17M, 17C, 17K ... Toner reservoir, 18Y, 18M, 18C, 18K ... Toner stirring member, 19, 19Y, 19M, 1
9C, 19K ... Toner supply roller, 20, 20Y, 20M, 20C, 20K ...
Developing roller, 21, 21Y, 21M, 21C, 21K ... regulating blade, 22Y, 2
2M, 22C, 22K ... leaf spring member, TY, TM, TC, TK ... toner, 29
..Drive roller, 30 ... tension roller, 31 ... intermediate transfer belt, 38
..Secondary transfer roller, 36 ... Pickup roller, 37 ... Transport roller pair,
39 ... heating roller, 40 ... pressure roller, 41 ... discharge tray, 42 ...
Paper discharge roller pair, 60 ... transfer cleaning device, 61 ... cleaning device housing, 70 ... scorotron, 71 ... wire, 72 ... house, 73 ... grid, 75 ... paper Detection sensor, 78 ... Patch sensor, 80 ... Cleaning brush roller, 81 ... Roller part, 82 ... Brush part, 85 ... Recovery roller,
86: Recovery roller cleaning blade holding member, 87 ... Recovery roller cleaning blade, 91 ... Scorotron wire current application unit, 92 ... Scorotron grid voltage application unit, 95 ... Cleaning brush roller voltage Application unit, 96... Recovery roller voltage application unit

Claims (8)

A corona charging unit for charging the toner transferred to the transfer medium;
A cleaning brush roller that contacts the transfer medium and cleans the toner charged by the corona charging unit,
As an operation mode,
A first operation mode in which the corona charging unit performs positive charging and a negative voltage is applied to the cleaning brush roller;
And a second operation mode in which a positive voltage is applied to the cleaning brush roller while the corona charging unit is stopped. A corona charging unit for charging the toner transferred to the transfer medium;
A cleaning brush roller that contacts the transfer medium and cleans the toner charged by the corona charging unit,
As an operation mode,
A first operation mode in which the corona charging unit performs positive charging and a negative voltage is applied to the cleaning brush roller;
An image forming apparatus comprising: a second operation mode in which the corona charging unit is stopped and a positive voltage is applied to the cleaning brush roller. A transport unit for transporting the recording medium;
A detection unit that is provided in the transport unit and detects a passing state of the recording medium;
The image forming apparatus according to claim 2, wherein the image forming apparatus operates in the first operation mode when the detection unit detects that there is no abnormality in a passing state of the recording medium. A transfer roller that is in contact with the transfer medium and through which the recording medium is inserted into a nip with the transfer medium;
The operation of the first operation mode after the operation of the second operation mode is performed when the detection unit detects an abnormality in a state where the recording medium is inserted between the nips. Image forming apparatus. A patch sensor for detecting the toner transferred to the transfer medium,
The image forming apparatus according to claim 3, wherein when the toner is detected by the patch sensor, the image forming apparatus operates in a second operation mode. The image forming apparatus according to claim 2, wherein the toner has an average particle diameter of 5 μm or less and a circularity of 0.95 or more. The image forming apparatus according to claim 2, wherein a surface roughness of the collection roller is equal to or less than an average particle diameter of the toner. The image forming apparatus according to claim 2, wherein an outer periphery of the cleaning brush roller rotates at a position in contact with the transfer medium in a direction opposite to a moving direction of the transfer medium.

Images