JP2007310312A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having an intermediate transfer body cleaning device that has a simple structure, is compact, and capable of achieving a reduction in the cost of the apparatus and the formation of an image of high image quality. <P>SOLUTION: In an intermediate transfer body cleaning device 50, the polarity of the contact charge potential of a first cleaning fur brush roller 52a caused by the first cleaning fur brush roller 52a and a first cleaning blade 70a is different from the polarity of the contact charge potential of a second cleaning fur brush roller 52b caused by the first cleaning fur brush roller 52b and a second cleaning blade 70b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system or an electrostatic recording system. The present invention particularly relates to a color image forming apparatus including an intermediate transfer member cleaning device for cleaning an intermediate transfer member that forms a multicolor image by transferring and transferring images formed on an image carrier.

  In recent years, for example, in an image forming apparatus that forms an image by an electrophotographic method, an intermediate transfer that transfers a multicolor image from an intermediate transfer member to a recording material in response to the need for a high-quality image on a wide variety of paper as a recording material. A type of image forming apparatus is widely used.

  In other words, in the color image forming apparatus having such a configuration, toner images formed on the image carrier, such as yellow, magenta, cyan, and black, are transferred onto the intermediate transfer member and formed on the intermediate transfer member. The superimposed image thus transferred is collectively transferred onto a recording material.

  In such an intermediate transfer type image forming apparatus, in order to form a toner image on the intermediate transfer member, a cleaning device for cleaning the residual toner remaining on the intermediate transfer member after transfer to the recording material is required. .

  Generally, a blade method and a fur brush method are employed for cleaning residual toner, and the blade method presses an elastic blade such as a rubber blade against an intermediate transfer member to mechanically scrape off the toner. .

  In the fur brush method, a cylindrical substrate with a bristle brush attached to the surface is brought into contact with the transfer residual toner on the intermediate transfer member, and at the same time, a bias voltage having a polarity opposite to that of the toner is applied to the brush to make mechanical and electrical contact. The toner is electrostatically (electrostatically) cleaned.

  In the intermediate transfer type image forming apparatus, the cleaning device must be retracted from the intermediate transfer body while multi-color toner images are superimposed on the intermediate transfer body. Therefore, if the mechanical load is large when the cleaning device is in contact with or separated from the intermediate transfer member, the position of the toner image of each color is shifted.

  For this reason, it can be said that the fur brush method with a smaller contact load is suitable as a cleaning device for the intermediate transfer member than the blade method.

  As the fur brush method, there is a method as described in Patent Document 1. An example of a cleaning apparatus employing such a fur brush system is shown in FIG.

  The cleaning device 50 </ b> A has a cleaner case 51, and an upper portion thereof is covered with an upper cover 61. The cleaner case 51 includes a first cleaning unit 50a for cleaning mainly positively charged toner and a second cleaning unit 50b for cleaning mainly negatively charged toner.

  The first cleaning unit 50a includes a first fur brush 52a as a first cleaning roller, a metal first bias roller 53a in contact with the first fur brush 52a, and a surface of the first bias roller 53a. And a first cleaning blade 54a that scrapes off the toner on the top. The first fur brush 52a, the first bias roller 53a, and the first cleaning blade 54a are integrally held by the first cleaning support 55a and rotate around the fulcrum 56 with respect to the cleaner case 51. It is supported movably.

  The second cleaning unit 50b includes a second fur brush 52b as a second cleaning roller, a metal second bias roller 53b in contact with the second fur brush 52b, and the surface of the second bias roller 53b. And a second cleaning blade 54b that scrapes off the toner on the top. The second fur brush 52b, the second bias roller 53b, and the second cleaning blade 54b are integrally held by the second cleaning support 55b and rotate around the fulcrum 57 with respect to the cleaner case 51. It is supported movably.

  The first cleaning blade 54a and the second cleaning blade 54b are made of urethane having a thickness of 2 to 3 mm.

  A spiral conveying screw 60 for conveying the toner scraped off from both the first cleaning blade 54a and the second cleaning blade 54b to a toner collecting unit (not shown) is disposed.

  Further, a squeeze sheet 58 for preventing the toner scraped off from the surface of the intermediate transfer member 10 from spilling is disposed.

  The squeeze sheet 58 is made of a film-like sheet, is located at the lower end opening of the cleaner case 51, and is supported by the cleaner case 51 so as to be rotatable around a fulcrum 59.

  Here, the brush used for the 1st fur brush 52a and the 2nd fur brush 52b is comprised from the conductive acrylic fiber.

Patent Document 3 describes a cleaning device using frictional charging. This cleaning device is made of a material in which the brush fibers of the brush roller in contact with the charging roller are frictionally charged to a polarity opposite to the charging polarity of the toner on the charging roller by contact with the surface of the charging roller.
JP 2001-255749 A JP 2003-228264 A

  A conventional fur brush type cleaning device described in Patent Document 1 and the like includes a fur brush as a plurality of cleaning rollers, a plurality of bias rollers in contact with each fur brush roller, a bias applying unit such as a bias generator, Furthermore, a scraping member for scraping off the toner on each bias roller is required.

  However, in recent years, there has been a demand for a lower-cost and higher-quality apparatus, and therefore there has been a demand for cost reduction by simplifying the cleaning apparatus.

  For this reason, the bias roller and the bias generator described in Patent Document 1 have a problem of increasing the size of the cleaning device and increasing the cost.

  Also, the cleaning device using frictional charging described in Patent Document 2 has difficulty in collecting the reversal toner due to toner scattering. Therefore, when such a cleaning device is used as a cleaning device for an intermediate transfer member, it becomes difficult to collect toner charged in a direction opposite to the charging direction of the toner with respect to the surface potential of the intermediate transfer member. The challenge remains to get.

  An object of the present invention is to provide an intermediate transfer member cleaning device that has a simple structure, can achieve downsizing, can reduce the cost of the device, and can realize high-quality image formation. An image forming apparatus is provided.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to an image carrier on which an electrostatic image is formed, developing means for developing the electrostatic image on the image carrier into a developer image, and a developer on the image carrier. A primary transfer means for transferring the image to the intermediate transfer member, a secondary transfer means for transferring the developer image transferred to the intermediate transfer member to the recording material, and a cleaning for cleaning the transfer residual developer on the intermediate transfer member. An image forming apparatus comprising:
The cleaning device includes a first cleaning unit, and a second cleaning unit provided downstream of the first cleaning unit in the moving direction of the intermediate transfer member,
The first cleaning unit includes a first cleaning fur brush roller that rotates in contact with the intermediate transfer member, and a first cleaning blade that contacts and charges the first cleaning fur brush roller. And comprising
The second cleaning unit includes a second cleaning fur brush roller that rotates in contact with the intermediate transfer member, and a second cleaning blade that contacts and charges the second cleaning fur brush roller in contact with the second cleaning fur brush roller. And comprising
The contact charging potential of the first cleaning fur brush roller generated by the contact between the first cleaning fur brush roller and the first cleaning blade, and the contact between the second cleaning fur brush roller and the second cleaning blade. The contact charging potential of the second cleaning fur brush roller has a different polarity from each other.
An image forming apparatus characterized by the above.

  According to the present invention, the structure is simple, miniaturization can be achieved, and the cost of the apparatus can be reduced. Moreover, in the present invention, high-quality image formation can be realized.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. In this embodiment, the image forming apparatus is an electrophotographic color image forming apparatus of an intermediate transfer system provided with a rotary developing device.

  In this embodiment, the color image forming apparatus 100 has a digital color image reader unit 100R in the upper part and a digital color image printer unit 100P in the lower part. The document image is read by the reader unit 100R. The printer unit 100P includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) as an image carrier, and an image such as a charging unit, a developing unit, a transfer unit, and an intermediate transfer unit around the printer unit 100P. Forming means are arranged.

  The document image read by the reader unit 100R is converted into an optical signal for each color by a laser output unit (not shown). The laser beam converted into the optical signal is reflected by the polygon mirror 3a and exposed to the surface of the photosensitive drum 1 through the lens 3b and the folding mirror 3c.

  Around the photosensitive drum 1, a primary charger 2 as a charging unit is disposed, and the photosensitive drum 1 is uniformly charged. The uniformly charged photosensitive drum 1 is exposed to the laser light from the reader unit 100R as described above. As a result, an electrostatic image is formed on the photosensitive drum 1.

  On the other hand, a rotary developing device 4 as a developing means is provided facing the photosensitive drum 1. The rotary developing device 4 includes a developing rotary 4A. In this embodiment, the developing rotary 4A is mounted with developing units (4a, 4b, 4c, 4d) containing yellow, magenta, cyan, and black toners. Has been. The development rotary 4 </ b> A rotates and moves a predetermined developer to a development position facing the photosensitive drum 1. The developing unit moved to the developing position develops the electrostatic image formed on the photosensitive drum 1 to form a developer image, that is, a toner image. In each case, the toner image is primary-transferred on an intermediate transfer member, on an intermediate transfer belt 10 that is an endless belt in this embodiment, by a primary transfer roller 5 serving as a primary transfer unit in a primary transfer portion T1. Transcribed. The photosensitive drum 1 is subjected to the next image formation after the transfer residual toner is removed by the photosensitive drum cleaning device 6.

  The image forming operation is repeated as many times as necessary while the developing device is switched by the developing rotary 4A. As a result, a color image in which the toner images are superimposed on the intermediate transfer belt 10 is formed.

  The transfer sheet S as a recording material is fed out from the cassettes 20a, 20b, 20c or the multi-manual feed 20d, conveyed by the conveying rollers 21, 22, 23, and subjected to skew correction and timing by the registration rollers 24. Then, it is conveyed toward the secondary transfer portion T2.

  Thereafter, the color image on the intermediate transfer belt 10 is secondarily transferred onto the transfer sheet S at a secondary transfer portion T2 including a secondary transfer roller 15 as a secondary transfer unit.

  The transfer paper S that has passed through the secondary transfer portion T2 is heat-fixed by the fixing portion 30 and is then discharged or double-sided image forming process.

  Further, the intermediate transfer belt 10 on which the toner image has been transferred to the transfer paper S is cleaned by the intermediate transfer body cleaning device 50 in order to remove the transfer residual toner.

  Next, the cleaning device 50 for the intermediate transfer belt 10 will be described with reference to FIG. The cleaning device 50 is downstream of the secondary transfer portion T2 provided with the secondary transfer roller 15 in the moving direction of the intermediate transfer belt 10, and more than the primary transfer portion T1 provided with the primary transfer roller 5. Arranged upstream.

  In the present embodiment, the cleaning device 50 has a housing 51, and the upper portion thereof is covered with an upper cover 61. In the present embodiment, in the present embodiment, as will be described later, for example, a first cleaning unit 50a for cleaning mainly negatively charged toner, and mainly for cleaning positively charged toner. Second cleaning section 50b.

  In the present embodiment, the second cleaning unit 50 b is located downstream of the first cleaning unit 50 a with respect to the moving direction of the intermediate transfer belt 10.

  The first cleaning unit 50a includes a first fur brush (that is, a first cleaning fur brush roller) 52a as a first cleaning roller, and a first cleaning blade 70a that contacts the first cleaning fur brush roller 52a. Have The first cleaning fur brush roller 52a and the first cleaning blade 70a are integrally held by the first cleaning support 55a, and are supported so as to be rotatable about the fulcrum 56 with respect to the housing 51.

  The second cleaning unit 50b includes a second fur brush (that is, a second cleaning fur brush roller) 52b as a second cleaning roller, and a second cleaning blade 70b in contact with the second cleaning fur brush roller 52b. Have The second cleaning fur brush roller 52b and the second cleaning blade 70b are integrally held by the second cleaning support body 55b and supported so as to be rotatable about the fulcrum 57 with respect to the housing 51.

  That is, according to this embodiment, the second cleaning fur brush roller 52b is provided on the downstream side of the first cleaning fur brush roller 52a with respect to the moving direction of the intermediate transfer belt 10.

  Further, the first cleaning fur brush roller 52a and the second cleaning fur brush roller 52b are arranged opposite to each other around the support roller 12 of the intermediate transfer belt 10, and each contact with the intermediate transfer belt 10 during the cleaning operation. Yes. On the other hand, when the cleaning supports 55a and 55b rotate around the fulcrums 56 and 57, the first cleaning fur brush roller 52a and the second cleaning fur brush roller 52b move in the directions of arrows A and B, respectively. The intermediate transfer belt 10 can be retracted to a non-contact position.

  Further, in the housing 51, there is provided a spiral conveying screw 60 for conveying the toner scraped off from the first cleaning blade 70a and the second cleaning blade 70b to a toner collecting unit (not shown).

  Further, a squeeze sheet 58 made of a film-like sheet is attached to the lower end opening of the housing 51. The squeeze sheet 58 is supported so as to be rotatable about a fulcrum 59 with respect to the housing 51.

  FIG. 3 shows a charged column. This shows the order of those that easily emit electrons or those that easily receive electrons.

  In other words, when contact and friction are made between different kinds of substances, those that are easily charged positive (+) as shown in FIG. 3 are placed higher, and those that are easily charged negative (−) are placed lower. It is.

  When any A and B materials are rubbed together from the charged column, if the A material is closer to the + side than the B material (A> B), it indicates that A is charged on the + side and B is charged on the-side. ing. In the case of contact and friction between those in the positions close to each other on the charge train, the charge amount is relatively small, and the charge amount increases as the distance increases.

  Here, in the cleaning device 50 of the present embodiment, regarding the cleaning brush, that is, the first cleaning fur brush roller 52a and the second cleaning fur brush roller 52b are selected from brushes having different charge row orders. Yes.

  That is, in the present embodiment, the first cleaning fur brush roller 52a is made of acrylic fiber, and the second cleaning fur brush roller 52b is made of nylon fiber. The first cleaning blade 70a and the second cleaning blade 70b are made of a polyester resin having a thickness of 0.2 mm.

Further, as the intermediate transfer belt 10, an appropriate amount of carbon black is contained as an antistatic agent in a resin such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate, acrylic, vinyl chloride, or various rubbers. Accordingly, the intermediate transfer belt 10 is prepared so that the volume resistivity is 1 × 10 ⁸ to 1 × 10 ¹³ [Ω · cm]. The thickness is 0.07 to 0.5 [mm].

  Whichever material is used for the intermediate transfer belt 10, acrylic is used as the first cleaning fur brush roller 52a, nylon is used as the second cleaning fur brush roller 52b, and the first and second If polyester is used as the cleaning blades 70a and 70b, the first cleaning fur brush roller 52a and the second cleaning fur brush roller 52b are charged with different polarities according to the order of the charged rows, and achieve cleaning of the intermediate transfer belt 10. be able to.

  That is, in the present embodiment, the first cleaning fur brush roller 52a is positively charged (+), and the second cleaning fur brush roller 52b is negatively charged (−).

  The support roller 12 of the intermediate transfer belt 10 is connected to GND through a path (not shown). That is, the intermediate transfer belt 10 itself is substantially discharged to 0 V by grounding the support roller 12. On the other hand, the first and second cleaning fur brush rollers 52a and 52b are floats, and are rubbed by the first and second cleaning blades 70a and 70b and frictionally charged to the respective polarities as described above.

  Here, the surface potential of the intermediate transfer belt 10 will be described.

  In the image forming apparatus using the intermediate transfer belt, as shown in FIG. 4, for example, the image forming apparatus passes through a primary transfer portion T <b> 1 sandwiched between a primary transfer roller 5 to which a positive bias having a polarity opposite to that of toner is applied and the photosensitive drum 1. The potential of the intermediate transfer belt 10 is first increased and attenuated up to the first support roller 11.

  This is because, as shown in FIG. 5A, the negative charge and the positive charge held by the intermediate transfer belt 10 immediately after passing through the primary transfer portion T1 are not equal amounts but an excess positive charge (hereinafter referred to as “excess charge”). The intermediate transfer belt 10 is apparently positively charged.

  The surplus charges are conveyed by the intermediate transfer belt 10 and moved away from the primary transfer roller 5, whereby the potential of the intermediate transfer belt 10 rises.

  As shown in FIG. 5B, this is the same reason that the potential of the charged body rises as the charged body is separated from the ground electrode.

  That is, as the separation distance increases, the capacitance of the capacitor, the air layer, decreases, and the potential difference from the reference potential (potential of the charged object) increases.

  This is the reason why the potential of the intermediate transfer belt 10 first rises.

  However, after the potential rises, the potential of the intermediate transfer belt 10 is attenuated this time up to the support roller 11 as shown in FIG.

  This is because the above-described surplus charge held by the intermediate transfer belt 10 decreases while being conveyed.

  For example, as shown in FIG. 6A, when the transport is stopped when surplus charges have been transported, the potential of the intermediate transfer belt 10 at that portion attenuates with time as shown in FIG. 6B.

  The fact that the potential of the intermediate transfer belt 10 is attenuated even though the distance from the surface of the primary transfer roller 5 does not change means that the above-mentioned surplus charge held by the intermediate transfer belt 10 decreases with time.

  Therefore, this is the main reason why the potential of the intermediate transfer belt 10 is attenuated between the rise of the potential and the support roller 11.

  In the intermediate transfer belt 10, the toner image on the intermediate transfer belt 10 is transferred to the recording material S by the secondary transfer portion T2, but the intermediate transfer belt 10 is maintained in a state where the potential is attenuated, and the cleaning device 50 is Move to the position where it was placed.

  As described above, according to the present exemplary embodiment, the toner image on the intermediate transfer belt 10 is negatively (−) charged as the charging polarity, but is negatively (−) charged during the development process and the transfer process. Transfer residual toner and positive (+) charged reversal toner are generated.

  In this embodiment, the first cleaning fur brush roller 52a charged positive (+) and the second cleaning fur brush roller 52b charged negative (−) are negative (−) on the intermediate transfer belt 10. ) Or positive (+) charged transfer residual toner can be collected. However, for this reason, the electric charges of the first and second cleaning fur brush rollers 52a and 52b decay with time. Therefore, in order to keep the first and second cleaning fur brush rollers 52a and 52b in a charged state of a predetermined value, the first and second cleaning fur brush rollers 52a and 52b are maintained to rotate, thereby maintaining the first and second cleaning fur brush rollers 52a and 52b. It is necessary to maintain frictional charging with the cleaning blades 70a and 70b.

  The toner collection capabilities of the first and second cleaning fur brush rollers 52 a and 52 b depend on the peripheral speeds of the first and second cleaning fur brush rollers 52 a and 52 b and the intermediate transfer belt 10. In this embodiment, the first and second cleaning fur brush rollers 52a and 52b are rotated in the counter direction at 150 mm / s and the intermediate transfer belt 10 is rotated in the counter direction at 300 mm / s, thereby obtaining a good cleaning effect.

  FIG. 7 shows the first and second cleaning fur brush rollers 52a and 52b, the intermediate transfer belt 10, and the toner (transfer residual toner and transfer toner) on the intermediate transfer belt 10 when the cleaning device 50 of this embodiment is operated. The charging state with the reversal toner) is shown.

  As shown in FIG. 7, the first cleaning fur brush roller 52a is charged to about +1.5 KV, and the transfer residual toner charged to −0 to −2 KV can be collected. Further, the second cleaning fur brush roller 52b provided on the downstream side of the first fur brush 52a with respect to the moving direction of the intermediate transfer belt 10 is charged to about −2 KV, and the reverse is charged to about +0 to +1.5 KV. The toner can be collected.

  The above charged voltage indicates the initial charged voltage (a state where time decay such as half-life does not occur) in accordance with JIS L 1094 method (friction charged voltage measurement method), and is measured at a temperature / humidity state of 20 ° C. and 40% RH. ing.

  In the description of the above embodiment, the first and second cleaning blades 70a and 70b are made of polyester resin, the first cleaning fur brush roller 52a is made of nylon fiber, and the second cleaning fur brush roller 52b is made of It demonstrated as what produces with an acrylic fiber. However, it is not limited to this. For example, the first and second cleaning blades 70a and 70b are made of polyester resin, the first cleaning fur brush roller 52a is made of acrylic fiber, and the second cleaning fur brush roller 52b is made of nylon fiber. Is also possible. Furthermore, it can be formed of other materials.

  What is important in the present embodiment is that the first and second cleaning blades 70a and 70b are made of the same order of materials in the charge train, and the first cleaning fur brush roller 52a and the second cleaning fur brush roller 52b are The first and second cleaning blades 70a and 70b are made of a material having a different rank in the charging row, and the first cleaning fur brush roller 52a and the second cleaning fur brush roller 52b are ranked in the charging row. Are made of different materials.

  According to the present invention, the contact charging potential of the first cleaning fur brush roller 52a generated by the contact between the first cleaning fur brush roller 52a and the first cleaning blade 70a, the second cleaning fur brush roller 52b, and the second cleaning blade 70b. The contact charging potential of the second cleaning fur brush roller 52b generated by the contact with is different in polarity.

  With such a configuration, according to the present invention, the structure is simple, the size can be reduced, and the cost of the apparatus can be reduced. Moreover, in the present invention, high-quality image formation can be realized.

Example 2
The cleaning device 50 having a characteristic configuration of the present invention is not limited to an intermediate transfer type color image forming apparatus provided with a rotary developing device facing one image carrier as described in the first embodiment, but also various kinds of devices. The present invention can be applied to an image forming apparatus having a configuration.

  FIG. 8 shows a schematic configuration of a tandem color image forming apparatus which is another embodiment of the image forming apparatus according to the present invention.

  In this embodiment, the image forming apparatus 100 is provided with an intermediate transfer belt 10 as an endless (belt-shaped) intermediate transfer body that travels in the direction of arrow X in the apparatus main body 100A. The intermediate transfer belt 10 is wound around support rollers 11, 12, and 13. Four image forming portions P (Pa, Pb, Pc, Pd) are arranged in series along the horizontal portion of the intermediate transfer belt 10. These image forming portions P (Pa, Pb, Pc, Pd) have substantially the same configuration, and are respectively yellow (Y), magenta (M), cyan (C), and black (K) colors. The difference is that a toner image is formed.

  First, the image forming portion Pa will be described. The image forming portion Pa includes a drum-shaped electrophotographic photosensitive member, that is, a photosensitive drum 1a, which is a rotatable image carrier. Around the photosensitive drum 1a, a primary charger 2a as a primary charging means, an exposure device 3a as an exposure means, a developing device 4a as a developing means, a primary transfer roller 5a as a primary transfer means, and a cleaning as a cleaning means. Process equipment such as the apparatus 6a is arranged.

  The other image forming units Pb, Pc, and Pd have the same configuration as the image forming unit Pa. That is, the image forming portions Pb, Pc, and Pd are respectively photosensitive drums 1b, 1c, and 1d, primary chargers 2b, 2c, and 2d, exposure devices 3b, 3c, and 3d, developing devices 4b, 4c, and 4d, and a transfer roller 5b. 5c, 5d, and cleaning devices 6b, 6c, 6d.

  These image forming portions Pa, Pb, Pc, and Pd differ in that each forms a toner image of each color of yellow, magenta, cyan, and black. Also, yellow toner (yellow developer), magenta toner (magenta developer), cyan toner (cyan developer) are respectively provided in the developing devices 4a, 4b, 4c, and 4d disposed in the image forming portions Pa, Pb, Pc, and Pd. ) And black toner (black developer).

  Next, an image forming operation of the image forming apparatus having the above configuration will be described.

  The photosensitive drum 1a is uniformly charged by the primary charger 2a, and an image signal based on the yellow component color of the original is projected from the exposure device 3a onto the photosensitive drum 1a via a polygon mirror or the like to form an electrostatic image. . Next, yellow toner is supplied from the developing device 4a, and the electrostatic image is developed as a yellow toner image.

  The yellow toner image arrives at the primary transfer portion T1a where the photosensitive drum 1a and the intermediate transfer belt 10 come into contact with the rotation of the photosensitive drum 1a. In the present embodiment, a primary transfer roller 5a is disposed in the primary transfer portion T1a as a primary transfer unit, and a primary transfer bias is applied thereto. Accordingly, the yellow toner image on the photosensitive drum 1 a is primarily transferred to the intermediate transfer belt 10.

  The intermediate transfer belt 10 carrying the yellow toner image is conveyed to the next image forming unit Pb. By this time, the magenta toner image formed on the photosensitive drum 1b by the same method as described above in the image forming unit Pb is transferred onto the yellow toner image in the primary transfer unit T1b where the transfer roller 5b is disposed. The Similarly, as the elastic intermediate transfer belt 10 advances to the image forming portions Pc and Pd along the arrow direction, a cyan toner image and a black toner image are respectively transferred to the primary transfer portions T1c and T1d where the transfer rollers 5c and 5d are arranged. Is superimposed and transferred onto the toner image.

  By this time, the recording material S sent out from the paper feed cassette 20 by the paper feed roller 21 and the other transport rollers 22 to 25 reaches the secondary transfer portion T2. In the secondary transfer portion T2, a secondary transfer roller 15 as a secondary transfer unit is disposed so as to face the backup roller 13 and sandwich the intermediate transfer belt 10. A transfer bias is applied to the secondary transfer roller 15, whereby the above-described four color toner images are transferred (secondary transfer) onto the recording material S.

  The recording material S to which the toner image is transferred is conveyed to the fixing unit 30. The fixing unit 30 fixes the toner image on the recording material S by heat and pressure.

  Transfer residual toner on the photosensitive drum 1 (1a, 1b, 1c, 1d) that could not be transferred by the primary transfer portion T1 (T1a, T1b, T1c, T1d) is respectively cleaned by the cleaning devices 6 (6a, 6b, 6c, 6d).

  Further, the transfer residual toner on the intermediate transfer belt 10 that could not be transferred by the secondary transfer portion T2 is cleaned by an intermediate transfer body cleaning device 50 as an intermediate transfer body cleaning means, and is used for the next image formation. .

  Since the intermediate transfer member cleaning device 50 in the present embodiment is the same as the cleaning device 50 described in the first embodiment, the description thereof is omitted.

  Next, the configuration of each unit will be described.

  The photosensitive drum 1 (1a, 1b, 1c, 1d) as an image carrier is configured by applying an organic photoconductor layer (OPC) to the outer peripheral surface of an aluminum cylinder having a diameter of 80 mm. Both ends of the photosensitive drum 1 are rotatably supported by flanges. The photosensitive drum 1 is rotationally driven in the counterclockwise direction in the drawing by transmitting a driving force from a driving motor (not shown) to one end.

  The primary charger 2 (2a, 2b, 2c, 2d) is a conductive roller formed in a roller shape. The roller 2 is brought into contact with the surface of the photosensitive drum 1 and a charging bias voltage is applied by a power source (not shown) to uniformly charge the surface of the photosensitive drum 1 to a negative polarity.

  In the present embodiment, the exposure device 3 (3a, 3b, 3c, 3d) is composed of an LED array having a polygon mirror (not shown) attached to the tip thereof, and lighting control is performed according to an image signal by a drive circuit (not shown).

  Each of the developing devices 4 (4a, 4b, 4c, 4d) includes a toner storage unit 7 (7a, 7b, 7c, 7d) that stores yellow, magenta, cyan, and black toners having negative charging characteristics, and a photosensitive member. It is adjacent to the surface of the body drum 1 and is driven to rotate by a drive unit (not shown). And it has the developing roller 8 (8a, 8b, 8c, 8d) which develops by applying a developing bias voltage with the developing bias power supply which is not shown in figure. In this embodiment, as described above, the toner storage unit 7 stores toners of yellow, magenta, cyan, and black in order from the upstream side in the conveyance direction of the recording material S.

  In this embodiment, the intermediate transfer belt 10 has a peripheral length (L) of 2400 mm and a speed V of 300 mm per second.

  The transfer roller 5 (5a, 5b, 5c, 5d), which is disposed inside the intermediate transfer belt 10 so as to face the photosensitive drums 1a, 1b, 1c, 1d and is in contact with the intermediate transfer belt 10, has a transfer bias. A power source (power source) 51 (51a, 51b, 51c, 51d) is connected. A positive voltage is applied to the transfer roller 5. By this electric field, the negative color toner images on the photosensitive drum 1 are sequentially transferred to the intermediate transfer belt 10 in contact with the photosensitive drum 1 to form a color image.

  The intermediate transfer belt 10 has the same configuration as that described in the first embodiment.

  Also in the present embodiment, it is possible to achieve the same effect as that of the first embodiment.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. It is a schematic block diagram which shows one Example of a cleaning apparatus. FIG. 6 is a charge train diagram of a cleaning brush. FIG. 6 is a diagram for explaining a relationship between an intermediate transfer belt potential and a belt position. It is a figure explaining the relationship between to-be-charged body potential and separation distance. FIG. 6 is a diagram illustrating a relationship between an intermediate transfer belt potential and a belt stop time. It is a figure explaining the charge state at the time of the cleaning by the cleaning apparatus according to this invention. It is a schematic block diagram which shows the other Example of the image forming apparatus which concerns on this invention. It is sectional drawing which shows the structure of the conventional cleaning apparatus.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Primary charger (primary charging means)
3 Exposure equipment (exposure means)
4 (4a, 4b, 4c, 4d) Developing device (developing means)
5 Primary transfer roller (primary transfer means)
6 Image carrier cleaning device 10 Intermediate transfer belt (intermediate transfer member)
15 Secondary transfer roller (secondary transfer means)
50 intermediate transfer member cleaning device 50a first cleaning unit 50b second cleaning unit 52a first cleaning fur brush roller 52b second cleaning fur brush roller 70a first cleaning blade 70b second cleaning blade

Claims (6)

An image carrier on which an electrostatic image is formed, developing means for developing the electrostatic image on the image carrier to form a developer image, and transferring the developer image on the image carrier to an intermediate transfer member Image forming comprising: a primary transfer unit; a secondary transfer unit that transfers the developer image transferred to the intermediate transfer member to a recording material; and a cleaning device that cleans the residual transfer developer on the intermediate transfer member. In the device
The cleaning device includes a first cleaning unit, and a second cleaning unit provided downstream of the first cleaning unit in the moving direction of the intermediate transfer member,
The first cleaning unit includes a first cleaning fur brush roller that rotates in contact with the intermediate transfer member, and a first cleaning blade that contacts and charges the first cleaning fur brush roller in contact with the first cleaning fur brush roller. And comprising
The second cleaning unit includes a second cleaning fur brush roller that rotates in contact with the intermediate transfer member, and a second cleaning blade that contacts and charges the second cleaning fur brush roller. And comprising
The contact charging potential of the first cleaning fur brush roller generated by the contact between the first cleaning fur brush roller and the first cleaning blade, and the contact between the second cleaning fur brush roller and the second cleaning blade. The contact charging potential of the second cleaning fur brush roller has a different polarity from each other.
An image forming apparatus.   The first and second cleaning blades are made of materials of the same order in a charging row, and the first cleaning fur brush roller and the second cleaning fur brush roller are charged with the first and second cleaning blades. The first cleaning fur brush roller and the second cleaning fur brush roller are made of materials having different orders in the row, and the first cleaning fur brush roller and the second cleaning fur brush roller are made of different orders of material in the charging row. Item 2. The image forming apparatus according to Item 1.   The first and second cleaning blades are made of a polyester resin, and the first cleaning fur brush roller and the second cleaning fur brush roller are made of one of the cleaning fur brush rollers with acrylic fiber, and the other The image forming apparatus according to claim 2, wherein the cleaning fur brush roller is made of nylon fiber.   The image forming apparatus according to claim 1, wherein the intermediate transfer member is an endless belt-shaped intermediate transfer belt. 5. The intermediate transfer belt according to claim 1, wherein the intermediate transfer belt has a volume resistivity of 1 × 10 ⁸ to 1 × 10 ¹³ [Ω · cm] and a thickness of 0.07 to 0.5 [mm]. The image forming apparatus according to any one of the items.   The cleaning device is disposed downstream of the secondary transfer unit and upstream of the primary transfer unit in the moving direction of the intermediate transfer member. The image forming apparatus according to any one of the above items.

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