JP5251636B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a FAX, or a multifunction machine that forms an image by, for example, an electrophotographic system or an electrostatic recording system.

  In general, the image forming apparatus includes a cleaning device that cleans residual toner from the image carrier. In this cleaning device, a brush to which a voltage is applied is brought into contact with the image carrier, and toner is electrically attracted to the brush.

  Here, when the brush is driven to rotate before the voltage is applied to the brush at the start of rotation of the image carrier, the toner remaining in the brush is not electrically restrained, so that the brush fiber May be ejected onto the image carrier due to the mechanical mechanical action that moves, causing image smearing.

  Therefore, conventionally, control is performed so that a voltage is applied to the brush before the brush and the image carrier rotate (see Japanese Patent Application Laid-Open No. 2006-58422: Patent Document 1).

JP 2006-58422 A

  However, in the conventional image forming apparatus, since the voltage is applied to the brush when the image carrier is stopped before the rotation starts, the contact portion of the image carrier with the brush is affected by the voltage application. Compared to the time of rotation, the battery is greatly charged.

  When there is a seal member (for example, a filming removal member or a dust prevention seal) that contacts the image carrier downstream of the brush, the charged contact portion of the image carrier removes the toner accumulated in the seal member. There is a problem that the image is attracted electrically and the image is stained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing image contamination due to toner contamination.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A rotatable image carrier on which a toner image is formed;
A conductive cleaning member that contacts the surface of the image carrier and cleans toner remaining on the surface of the image carrier;
A voltage applying unit that applies a voltage having a polarity opposite to that of the toner to the cleaning member;
A seal member that is disposed downstream of the cleaning member in the rotational direction of the image carrier and that contacts the image carrier;
A control unit for controlling the voltage application unit,
The surface of the image carrier includes a first region where a toner image is formed and a second region where a toner image is not formed,
The control unit applies a voltage to the cleaning member so that at least a part of the potential of the second region is higher than the potential of the first region in a state where the image carrier is rotating. Applying, applying a potential to the surface of the image carrier, and electrically attracting the toner accumulated in the seal member to the at least part of the second region to clean the seal member. Yes.

  According to the image forming apparatus of the present invention, the control unit is configured such that the potential of the at least part of the second region is higher than the potential of the first region when the image carrier is rotating. A voltage is applied to the cleaning member so as to be higher, a potential is applied to the surface of the image carrier, and the toner accumulated in the seal member is electrically attracted to the at least part of the second region. Since the sealing member is cleaned, even if a potential that attracts the toner electrically is generated in the first region of the image carrier, the toner does not accumulate in the sealing member, and the first No contamination by toner occurs in the area 1. Therefore, image contamination due to toner contamination can be prevented.

  In the image forming apparatus according to an embodiment, the control unit applies to the cleaning member when the image carrier is in contact with at least a part of the second region. The voltage to be applied is made larger than the voltage applied to the cleaning member when it is in contact with the first region, and the potential of the at least part of the second region is set to be higher than that of the first region. Set higher than the potential.

  According to the image forming apparatus of this embodiment, the control unit applies the cleaning member when the image carrier is in contact with the at least part of the second region. The voltage to be applied is made larger than the voltage applied to the cleaning member when it is in contact with the first region, and the potential of the at least part of the second region is set to be higher than that of the first region. Since the potential is higher than the potential, a potential sufficient to electrically attract the toner can be reliably generated in the at least part of the second region, and image contamination due to toner contamination can be reliably prevented.

  In the image forming apparatus according to the embodiment, the control unit may be configured such that the potential of the at least part of the second region in a state where the image carrier is rotating is equal to that before the image carrier starts rotating. A voltage is applied to the cleaning member so as to be higher than the potential of the first region in the stopped state, and a potential is applied to the surface of the image carrier.

  According to the image forming apparatus of this embodiment, the control unit is configured so that the potential of the at least part of the second region in a state where the image carrier is rotating is equal to that before the image carrier starts rotating. Since the voltage is applied to the cleaning member so as to be higher than the potential of the first region in the stopped state, and the potential is applied to the surface of the image carrier, the at least part of the second region. In addition, it is possible to more reliably generate a potential sufficient to electrically attract the toner, and it is possible to more reliably prevent image contamination due to toner contamination.

  In the image forming apparatus according to the embodiment, the control unit applies the cleaning member when the image carrier is in contact with the at least part of the second region in a rotating state. The voltage is made larger than the voltage applied to the cleaning member when the image carrier is in contact with the first region when the image carrier is stopped before the rotation starts. The potential of the at least part of the second region in the state in which the image carrier is in operation is set higher than the potential of the first region in the state in which the image carrier is stopped before the rotation is started.

  According to the image forming apparatus of this embodiment, the control unit applies the cleaning member when contacting the at least part of the second region in a state where the image carrier is rotating. The voltage is made larger than the voltage applied to the cleaning member when the image carrier is in contact with the first region when the image carrier is stopped before the rotation starts. The potential of the at least part of the second region in the state of being in the state is higher than the potential of the first region in the state of being stopped before the rotation of the image carrier. A potential enough to electrically attract toner can be more reliably generated in at least a part of the area 2, and image contamination due to toner contamination can be more reliably prevented.

  In the image forming apparatus of one embodiment, when the maximum potential of the first region is V1 and the at least part of the potential of the second region is V2, (V2−V1) ≧ 50 volts is satisfied. Fulfill.

  According to the image forming apparatus of this embodiment, since (V2−V1) ≧ 50 volts is satisfied, a potential enough to electrically attract toner can be more reliably generated in the at least part of the second region. .

  In the image forming apparatus according to the embodiment, the control unit performs the cleaning operation of the seal member every time one print job is completed.

  Here, the print job refers to a print operation for a set of images handled by the user. For example, an operation of copying a bundle of documents is a single print job.

  According to the image forming apparatus of this embodiment, the control unit performs the cleaning operation of the seal member every time one print job is completed, so that the seal member can be efficiently cleaned.

  In the image forming apparatus according to an embodiment, the seal member is a foam having elasticity that slidably contacts the image carrier and scrapes off deposits on the image carrier.

  In the image forming apparatus of one embodiment, the seal member is a film that is attached to an opening of a casing surrounding the cleaning member and prevents leakage of toner in the casing to the outside.

  In the image forming apparatus according to an embodiment, the seal member is a blade having elasticity that slidably contacts the image carrier and scrapes off deposits on the image carrier.

  According to the image forming apparatus of the present invention, the control unit is configured such that the potential of the at least part of the second region is higher than the potential of the first region when the image carrier is rotating. A voltage is applied to the cleaning member so as to be higher, a potential is applied to the surface of the image carrier, and the toner accumulated in the seal member is electrically attracted to the at least part of the second region. Since the sealing member is cleaned, image contamination due to toner contamination can be prevented.

1 is a simplified configuration diagram showing an embodiment of an image forming apparatus of the present invention. It is a simplified block diagram of a cleaning device. 6 is a graph showing the potential of the surface of the intermediate transfer belt immediately upstream of the seal member as time elapses. It is explanatory drawing explaining cleaning of a sealing member. It is a simplified block diagram of another cleaning apparatus. It is a simplified block diagram of another cleaning apparatus.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a simplified configuration diagram showing an embodiment of an image forming apparatus according to the present invention. This image forming apparatus is a tandem type digital color printer. This image forming apparatus has a rotatable annular (as an image carrier) intermediate transfer belt 7 at a substantially central portion inside thereof.

  The intermediate transfer belt 7 is made of a semiconductive material and is supported on the outer peripheral portions of the cleaning facing roller 6 and the transfer facing roller 18. At least one of the cleaning counter roller 6 and the transfer counter roller 18 is provided with a drive unit (not shown). The drive unit rotates the at least one roller to rotate the intermediate transfer belt 7. It rotates in the direction of arrow A.

  In the lower horizontal portion of the intermediate transfer belt 7, four image forming units 20Y, 20M, 20C, and 20K respectively corresponding to yellow (Y), magenta (M), cyan (C), and black (K) toners. Is provided. The four image forming units 20Y, 20M, 20C, and 20K are arranged along the intermediate transfer belt 7.

  Each of the image forming units 20Y, 20M, 20C, and 20K has a drum-shaped photoconductor 22 on which a toner image is formed. Each photoconductor 22 is disposed to face the outer peripheral surface of the intermediate transfer belt 7.

  Around the photosensitive member 22, a charger 24, a print head unit 26, a developing device 28, a primary transfer roller 30 (as a primary transfer member), and a cleaner 32 are sequentially arranged along the rotation direction. Is provided.

  The charger 24 uniformly charges the surface of the photoreceptor 22. The print head unit 26 forms an electrostatic latent image on the uniformly charged surface of the photoconductor 22 by exposing according to each color image data.

  The developing device 28 develops the electrostatic latent image formed on the surface of the photoreceptor 22 with each color toner to form a toner image.

  The primary transfer roller 30 is disposed facing the inner peripheral surface of the intermediate transfer belt 7 so as to sandwich the intermediate transfer belt 7 together with the photosensitive member 22. The primary transfer roller 30 transfers the toner image on the photoconductor 22 to the intermediate transfer belt 7.

  The cleaner 32 collects and cleans the toner remaining on the surface of the photoreceptor 22 after the primary transfer.

  The print head unit 26 includes a large number of LEDs arranged in a main scanning direction parallel to the axial direction of the photosensitive member 22.

  A secondary transfer roller 34 (as a secondary transfer member) is pressed against the outside of the portion of the intermediate transfer belt 7 supported by the transfer counter roller 18. That is, the secondary transfer roller 34 is disposed to face the outer peripheral surface of the intermediate transfer belt 7.

  A contact area between the secondary transfer roller 34 and the intermediate transfer belt 7 forms a transfer area 36. The secondary transfer roller 34 conveys the sheet S (as a recording material) with the intermediate transfer belt 7 while pinching it, and transfers the toner image on the intermediate transfer belt 7 to the sheet S.

  The secondary transfer roller 34 can be retracted to a position where it is not in contact with the intermediate transfer belt 7 by a retracting mechanism (not shown).

  A cleaning device 1 is provided at a portion of the intermediate transfer belt 7 supported by the cleaning counter roller 6. The cleaning device 1 is disposed to face the outer peripheral surface of the intermediate transfer belt 7.

  The cleaning device 1 includes a casing 11 and a cleaning member 12 disposed in the casing 11.

  The cleaning member 12 has conductivity. The cleaning member 12 contacts the surface of the intermediate transfer belt 7 and cleans the toner remaining on the surface of the intermediate transfer belt 7 after passing through the secondary transfer roller 34. The cleaning member 12 is applied with a voltage to electrically attract the toner.

  The toner cleaned by the cleaning member 12 is collected in the casing 11 surrounding the cleaning member 12.

  A controller 80 for controlling the driving unit and the cleaning device 1 is provided. That is, the control unit 80 controls the rotation of the intermediate transfer belt 7 and the voltage applied to the cleaning member 12.

  A paper feed cassette 42 is detachably disposed at the lower part of the image forming apparatus. The sheets S stacked and accommodated in the sheet feeding cassette 42 are sent out one by one from the uppermost one to the conveying path 46 by the rotation of the sheet feeding roller 44.

  The conveyance path 46 extends from the paper feed cassette 42 to the paper discharge tray 43 through the nip portion of the timing roller pair 48, the secondary transfer region 36, and the fixing unit 50. The timing roller pair 48 feeds the paper S sent from the paper feed cassette 42 to the transfer area 36 in synchronization with the image on the intermediate transfer belt 7.

  A timing sensor 52 is disposed in the vicinity of the timing roller pair 48. The timing sensor 52 detects that the leading edge of the sheet S sent out from the sheet feeding cassette 42 to the conveyance path 46 is nipped by the timing roller pair 48.

  When the leading edge of the sheet S is detected by the timing sensor 52, the timing roller pair 48 temporarily stops its rotation, and then the sheet S is fed in synchronization with the toner image on the intermediate transfer belt 7. Paper is fed to the next transfer area 36.

  A paper thickness sensor 54 is disposed to face one roller 48a of the timing roller pair 48. The paper thickness sensor 54 detects the amount of movement of the roller 48a when the leading edge of the paper is nipped by the timing roller pair 48, and determines whether the paper is plain paper, thick paper or OHP sheet. Is determined.

  The fixing unit 50 includes a fixing belt 60 supported by a pair of rollers 56 and 58 and driven to rotate in the direction of arrow B, and a fixing roller which is pressed against the roller 56 via the fixing belt 60 and driven to rotate in the direction of the arrow. 62. A nip portion between the fixing belt 60 and the fixing roller 62 through which the sheet onto which the toner image is secondarily transferred passes is a fixing region 64. The fixing belt 60 is heated by a heater (not shown).

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

  When an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the image forming apparatus, the image signal processing unit converts the image signal into yellow, cyan, magenta, and black. A digital image signal is generated, and this signal is transmitted to the LED drive circuit for the print head.

  This drive circuit performs exposure by causing the print head units 26 of the image forming units 20Y, 20M, 20C, and 20K to emit light based on the input digital signals. This exposure is performed with a time difference in the order of yellow, cyan, magenta, and black. As a result, an electrostatic latent image for each color is formed on the surface of each photoconductor 22.

  The electrostatic latent image formed on each photoconductor 22 is developed by each developing device 28 and becomes a toner image of each color. Then, the toner images of the respective colors are primarily transferred in a superimposed manner on the intermediate transfer belt 7 moving in the direction of arrow A by the action of each primary transfer roller 30 to which a positive primary transfer voltage is applied. That is, a toner image is formed on the surface of the intermediate transfer belt 7.

  In this way, the toner images of the respective colors superimposed on the intermediate transfer belt 7 reach the transfer area 36 as the intermediate transfer belt 7 moves. Then, the superimposed toner images of the respective colors are sent out from the paper feed cassette 42 to the conveyance path 46 by the action of the secondary transfer roller 34 to which a secondary transfer voltage having the same polarity as the primary transfer voltage is applied. By the driving of the timing roller pair 48, secondary transfer is collectively performed on the sheet S passing through the transfer region 36. The toner remaining on the intermediate transfer belt 7 after the secondary transfer is collected by the cleaning device 1.

  The sheet S on which the toner image is secondarily transferred passes through the conveyance path 46 and is sent to the fixing unit 50 where the toner image passes through the fixing region 64 to be fixed on the sheet S by heating. Then, the paper S is discharged to the paper discharge tray 43.

  The color image forming operation is performed as described above. In the case of a monochrome image, only the image forming unit 20K is operated on the intermediate transfer belt 7 based on the input monochrome image data. A black toner image is formed. Thereafter, similarly, the black toner image is secondarily transferred to the paper S in the transfer region 36, heated and fixed by the fixing unit 50, and the paper S is discharged to the paper discharge tray 43.

  As shown in FIG. 2, the cleaning device 1 is a so-called single brush device, and can be used when the toner on the intermediate transfer belt 7 has a substantially single polarity.

  The cleaning device 1 includes the casing 11, the cleaning member 12, and a voltage application unit 5 a that applies a voltage to the cleaning member 12.

  The casing 11 has an opening, and a part of the intermediate transfer belt 7 enters the opening.

  The cleaning member 12 comes into contact with the intermediate transfer belt 7 and counter-rotates to scrape off the toner, the cleaning roller 2a that contacts and rotates the toner in the cleaning brush 2a, and a recovery roller 3a on the recovery roller 3a. And a scraper 4a that mechanically scrapes off the toner.

  The cleaning brush 2a includes a metal core that is a solid or hollow bar made of a conductive material such as metal, and conductive brush fibers that are implanted on the outer periphery of the metal core. The brush fibers may be woven into a conductive base fabric and wound around and bonded to the core metal, or may be directly planted on the core metal with a conductive adhesive.

This brush fiber is made of a material in which carbon is dispersed in a resin such as nylon, polyester, acrylic, or rayon to impart conductivity. The fineness is 1D to 10D, the density is 50 kF / inch ^{2 to} 300 kF / inch ² , and the yarn resistance is 10 ⁵ Ω to 10 ¹³ Ω. Further, the amount of biting into the intermediate transfer belt 7 is set to about 0.5 mm to 2.0 mm.

  The collection roller 3a is made of a conductive material such as metal or conductive resin, and is made of a solid or hollow bar. In order to reduce the frictional resistance, the surface may be subjected to a treatment such as polishing, plating or coating. Further, the amount of biting into the cleaning brush 2a is set to about 0.5 mm to 2.0 mm.

  The scraper 4a is a metal blade or a rubber blade, and its tip is in contact with the surface of the collection roller 3a. The thickness, pressure contact angle, pressure contact force, and the like of the scraper 4a are set according to the toner type, the toner external additive, and the material of the collection roller. In the case of a metal blade, a method of manufacturing by chemical treatment such as etching may be used in order to enhance the ridge line system of the tip that contacts the collection roller 3a. Further, in order to prevent tip wear and improve hardness, the tip of the metal blade may be subjected to treatment such as plating, baking, or coating.

  A seal member 10 is provided downstream of the cleaning member 12 in the rotational direction of the intermediate transfer belt 7. The seal member 10 prevents deposits (such as toner) from being discharged downstream in the rotational direction of the intermediate transfer belt 7.

  The seal member 10 is a foam having elasticity, and slidably contacts the intermediate transfer belt 7 to scrape off deposits (such as toner) on the intermediate transfer belt 7. This deposit is taken into the foam cell of the sealing member 10 itself.

The material of the sealing member 10 is polyurethane foam, urethane foam, rubber sponge material, or the like. The thickness is ³ mm to 7 mm, the density is 45 to 100 kg / m ³ , the hardness is 4 to 15 kPa (25% compression hardness), and the number of cells is 40 to 120 cells / 25 mm, The contact width with the intermediate transfer belt 7 is 8 mm to 20 mm, and the amount of biting into the intermediate transfer belt 7 is about 0.5 mm to 2 mm.

  The voltage application unit 5a applies a voltage having a polarity opposite to that of the toner to the collection roller 3a. In this embodiment, the polarity of the toner is negative and the polarity of the collection roller 3a is positive. The voltage application unit 5 a is controlled by the control unit 80.

  When a voltage is applied to the recovery roller 3a from the voltage application unit 5a, a potential difference is generated between the intermediate transfer belt 7 and the cleaning brush 2a due to this voltage, and the negatively charged toner 8a is charged. However, an electric field is formed so as to move from the intermediate transfer belt 7 to the cleaning brush 2a.

  Further, since it is applied from the collection roller 3a, a potential difference is generated between the cleaning brush 2a and the collection roller 3a, and the toner 8a in the cleaning brush 2a moves to the collection roller 3a. An electric field is also formed.

  By this electric field, the toner 8 a on the intermediate transfer belt 7 can be collected in the casing 11.

  Next, control of voltage application to the cleaning member 12 and rotation of the intermediate transfer belt 7 by the control unit 80 will be described.

  As shown in FIG. 3, first, the cleaning member 12 is energized to apply a voltage during a period T1 during which the intermediate transfer belt 7 is stopped before rotation. By this application, a potential is applied to the surface of the intermediate transfer belt 7.

  In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the potential of the surface of the intermediate transfer belt 7 immediately before the seal member 10. In FIG. 3, the energization period T4 refers to a period during which the cleaning member 12 is energized.

  When the intermediate transfer belt 7 is stopped, the surface potential of the intermediate transfer belt 7 is V1. Thereafter, when the intermediate transfer belt 7 is rotated, the potential of the intermediate transfer belt 7 becomes V0 (<V1).

  Before and after the rotation of the intermediate transfer belt 7, a constant voltage is applied to the cleaning member 12, but charging is greater when the intermediate transfer belt 7 is stopped than when the intermediate transfer belt 7 is rotated. Therefore, the potential V1 when the belt is stopped becomes larger than the potential V0 when the belt rotates.

  Before the belt rotates, a voltage is applied to the cleaning member 12 to prevent the toner from scattering from the casing 11 during the belt rotation.

  Here, as shown in FIG. 1, the surface of the intermediate transfer belt 7 includes a first region Z1 where a toner image is formed and a second region Z2 where a toner image is not formed. The first region Z1 and the second region Z2 are separated in the circumferential direction of the intermediate transfer belt 7.

  Then, after applying a potential to the first region (toner image forming region) Z1, the voltage applied to the cleaning member 12 is increased during the belt rotation period T2, and the second region (toner image non-forming) Region) The potential of at least part of Z2 is V2 (> V1).

  Thereafter, the voltage applied to the cleaning member 12 is returned to the original state, the belt potential is set to V0, and then the intermediate transfer belt 7 is stopped. The belt potential is V1 immediately after the belt is stopped and just before the belt is rotated. Thereafter, energization of the cleaning member 12 is stopped in a stop period T3 after the belt rotation.

  That is, as shown in FIG. 4, the control unit 80 causes the at least part of the potential in the second region Z2 to be in the first region Z1 when the intermediate transfer belt 7 is rotating. A voltage is applied to the cleaning member 12 so as to be higher than the potential, and a potential is applied to the surface of the intermediate transfer belt 7.

  Then, the toner 8a accumulated in the seal member 10 is electrically attracted to the at least part of the second region Z2, and the seal member 10 is cleaned.

  Specifically, the control unit 80 applies the cleaning member 12 when it is in contact with the at least part of the second region Z2 in a state where the intermediate transfer belt 7 is rotating. The voltage is set larger than the voltage applied to the cleaning member 12 when it is in contact with the first region Z1, and the potential of the at least part of the second region Z2 is set to the first region Z2. The potential is made higher than the potential of the region Z1.

  Further, the control unit 80 is in a state in which the potential of the at least part of the second area Z2 in a state where the intermediate transfer belt 7 is rotating is stopped before the intermediate transfer belt 7 starts rotating. A voltage is applied to the cleaning member 12 so as to be higher than the potential of the first region Z1 in FIG.

  Specifically, the control unit 80 applies a voltage to the cleaning member 12 when the intermediate transfer belt 7 is in contact with at least a part of the second region Z2 in a rotating state. Is made larger than the voltage applied to the cleaning member 12 when the intermediate transfer belt 7 is in contact with the first region Z1 in a stopped state before the rotation starts. The potential of the at least part of the second region Z2 in a state where the roller 7 is rotating is higher than the potential of the first region Z1 in a state where the intermediate transfer belt 7 is stopped before the rotation starts. Make it high.

  The relationship between the maximum potential V1 of the first region Z1 and the at least part of the potential V2 of the second region Z2 satisfies 1000 volts ≧ (V2−V1) ≧ 50 volts.

  The control unit 80 performs the cleaning operation of the seal member 10 every time one print job is completed. Here, the print job refers to a print operation for a set of images handled by the user. For example, an operation of copying a bundle of documents is a single print job.

  More specifically, the print job includes image data to be printed and setting data at the time of printing (for example, the number of copies, double-sided printing, etc.). The print job is stored in the memory of the image forming apparatus.

  According to the image forming apparatus having the above configuration, the control unit 80 is configured such that the potential of the at least part of the second region Z2 is the first region Z1 when the intermediate transfer belt 7 is rotating. A voltage is applied to the cleaning member 12 so as to be higher than the potential of the intermediate transfer belt 7, and a potential is applied to the surface of the intermediate transfer belt 7 so that the toner accumulated in the seal member 10 is at least in the second region Z2. Since the seal member 10 is cleaned by being electrically attracted to a part, even if a potential to attract the toner is generated in the first region Z1 of the intermediate transfer belt 7, the seal member is generated. No toner is accumulated in the toner 10, and the first area Z1 is not contaminated with toner. Therefore, image contamination due to toner contamination can be prevented.

  Further, the control unit 80 determines the voltage applied to the cleaning member 12 when the intermediate transfer belt 7 is rotating and in contact with the at least part of the second region Z2. The potential of the at least part of the second region Z2 is set higher than the voltage applied to the cleaning member 12 when it is in contact with the first region Z1, and the potential of the first region Z1 is increased. Therefore, a potential sufficient to electrically attract toner can be reliably generated in the at least part of the second region Z2, and image contamination due to toner contamination can be reliably prevented.

  Further, the control unit 80 is in a state in which the potential of the at least part of the second area Z2 in a state where the intermediate transfer belt 7 is rotating is stopped before the intermediate transfer belt 7 starts rotating. Since the voltage is applied to the cleaning member 12 so as to be higher than the potential of the first region Z1 in FIG. 5 and the potential is applied to the surface of the intermediate transfer belt 7, the at least part of the second region Z2 is applied to the at least part of the second region Z2. In addition, it is possible to more reliably generate a potential enough to electrically attract the toner, and it is possible to more reliably prevent image contamination due to toner contamination.

  Further, the control unit 80 determines the voltage applied to the cleaning member 12 when the intermediate transfer belt 7 is in contact with the at least part of the second region Z2 in the rotating state. The voltage applied to the cleaning member 12 when the transfer belt 7 is in contact with the first region Z1 in a stopped state before the rotation starts is set to be larger than the voltage applied to the cleaning member 12. The potential of the at least part of the second region Z2 in the state where the intermediate transfer belt 7 is stopped is made higher than the potential of the first region Z1 in the state where the intermediate transfer belt 7 is stopped before the rotation is started. The at least part of the second region Z2 can generate a potential that can attract the toner electrically, thereby preventing the image from being contaminated with toner more reliably. That.

  Further, since (V2−V1) ≧ 50 volts is satisfied, a potential enough to electrically attract the toner can be more reliably generated in the at least part of the second region Z2. Further, since 1000 volts ≧ (V2−V1) is satisfied, there is no problem with the withstand voltage. On the other hand, if the voltage is less than 50 volts, the potential becomes weak. On the other hand, when it exceeds 1000 V, there is a problem that the voltage increases and breaks.

  Moreover, since the said control part 80 performs the cleaning operation | movement of the said sealing member 10 for every completion | finish of one printing job, the said sealing member 10 can be cleaned efficiently.

  In addition, as the cleaning member 12, only the cleaning brush 2a may be used, and a voltage may be directly applied to the cleaning brush 2a. At this time, the toner collected by the brush may be mechanically knocked off using a flicker bar or the like. Alternatively, toner is accumulated in the brush without using flicker, and after a predetermined time, a voltage having a polarity opposite to the cleaning voltage is applied to the brush, and the toner is returned to the intermediate transfer belt to refresh the brush. It may be.

(Second Embodiment)
FIG. 5 shows a second embodiment of the image forming apparatus of the present invention. The difference from the first embodiment will be described. In the second embodiment, the configuration of the cleaning device is different. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 5, the cleaning device 1 </ b> A is a so-called double brush device, in the casing 11, on the upstream side of the cleaning member 12 of the first embodiment (FIG. 2), and another cleaning brush 2 b and Another collection roller 3b is provided. The other collection roller 3b is applied with a negative polarity by another voltage application unit 5b.

  Then, a minus bias is applied to the other cleaning brush 2b from the other collection roller 3b. Due to this bias, the plus toner 8b out of the plus and minus toners 8a and 8b mixed on the intermediate transfer belt 7 is attracted to the other cleaning brush 2b and moved to the other collection roller 3b, and another scraper 4b. Is scraped off.

  The negative toner 8a remaining on the intermediate transfer belt 7 is cleaned by the cleaning member 12 as described in the first embodiment.

  The voltage applied to the cleaning member 12 is controlled by the control unit 80 as described in the first embodiment, and has the same effect as in the first embodiment.

  As in the first embodiment, the collection rollers 3a and 3b may be omitted and only the cleaning brushes 2a and 2b may be used. Further, the cleaning member 12 (plus bias) may be arranged upstream of the other cleaning brush 2b and the other collection roller 3b (minus bias).

(Third embodiment)
FIG. 6 shows a third embodiment of the image forming apparatus of the present invention. The difference from the first embodiment will be described. In the third embodiment, the configuration of the cleaning device is different. In the third embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 6, the cleaning device 1B is provided with a charging brush 9 in the casing 11 on the upstream side of the cleaning member 12 of the first embodiment (FIG. 2). The charging brush 9 is applied with a negative polarity by another voltage application unit 5b.

  A negative bias is applied to the charging brush 9 from the other voltage application unit 5b. Due to this bias, the plus toner 8b among the plus and minus toners 8a and 8b on the intermediate transfer belt 7 is negatively charged, and the toner on the intermediate transfer belt 7 is aligned with the minus charged toner 8a.

  The negative toner 8a remaining on the intermediate transfer belt 7 is cleaned by the cleaning member 12 as described in the first embodiment.

  The voltage applied to the cleaning member 12 is controlled by the control unit 80 as described in the first embodiment, and has the same effect as in the first embodiment.

The charging brush 9 includes conductive brush fibers on one side of a thin plate of a conductive material such as metal. The brush fibers may be woven into a conductive base fabric and adhered to the sheet metal, or may be directly planted on the sheet metal with a conductive adhesive. The brush fiber is made of a material in which carbon is dispersed in a resin such as nylon, polyester, acrylic, or rayon to impart conductivity. The fineness is 1D to 10D, the density is 50 kF / inch ^{2 to} 300 kF / inch ² , and the yarn resistance is 10 ⁵ Ω to 10 ¹³ Ω. Further, the amount of biting into the intermediate transfer belt 7 is set to about 0.5 mm to 2.0 mm.

  Here, the charging brush has been described as the charging member. However, the charging member is not necessarily a brush. For example, a charging device including a thin conductive sheet-like member, a wire using corona discharge, or a sawtooth electrode. As long as it is a charging member that imparts a charge to the toner, these may be used.

  As in the first embodiment, the collection roller 3a may be omitted and only the cleaning brush 2a may be used.

  In addition, this invention is not limited to the above-mentioned embodiment. For example, the sealing member may be a film that is attached to the opening of the casing 11 and prevents leakage of toner in the casing 11 to the outside. Further, the sealing member may be a blade having elasticity that slidably contacts the intermediate transfer belt 7 and scrapes off deposits (such as toner) on the intermediate transfer belt 7.

  In addition, the cleaning member 12 may be energized to apply a voltage simultaneously with the start of the rotation of the intermediate transfer belt 7. Even if they are applied simultaneously, the potential of the intermediate transfer belt 7 becomes higher than the time of stable driving due to the rise of the driving portion of the intermediate transfer belt 7.

  In addition to the intermediate transfer belt 7, a photosensitive member may be used as the image carrier. Further, the interval for performing the cleaning operation of the seal member may be performed for each page of the paper, or may be performed for a certain period of time, or may be performed when the power is turned on. It may be performed when other control occurs. Alternatively, a sensor may be added downstream of the seal member, and dirt may be read by this sensor, and the cleaning operation of the seal member may be performed when the value exceeds a specified value.

1, 1A, 1B Cleaning device 2a Cleaning brush 2b Other cleaning brush 3a Collection roller 3b Other collection roller 4a Scraper 4b Other scraper 5a Voltage application unit (plus bias application unit)
5b Other voltage application part (minus bias application part)
6 Cleaning counter roller 7 Intermediate transfer belt (image carrier)
8a (negatively charged) toner 8b (positively charged) toner 9 charging brush 10 sealing member 11 casing 12 cleaning member 80 control unit Z1 first area (toner image forming area)
Z2 second area (toner image non-formation area)

Claims (9)

A rotatable image carrier on which a toner image is formed;
A conductive cleaning member that contacts the surface of the image carrier and cleans toner remaining on the surface of the image carrier;
A voltage applying unit that applies a voltage having a polarity opposite to that of the toner to the cleaning member;
A seal member that is disposed downstream of the cleaning member in the rotational direction of the image carrier and that contacts the image carrier;
A control unit for controlling the voltage application unit,
The surface of the image carrier includes a first region where a toner image is formed and a second region where a toner image is not formed,
The control unit applies a voltage to the cleaning member so that at least a part of the potential of the second region is higher than the potential of the first region in a state where the image carrier is rotating. Applying, applying a potential to the surface of the image carrier, and electrically attracting the toner accumulated in the seal member to the at least part of the second region to clean the seal member. Image forming apparatus. The image forming apparatus according to claim 1.
The control unit contacts the first region with a voltage to be applied to the cleaning member when the image carrier is in contact with the at least part of the second region. The potential of the at least part of the second region is set to be higher than the potential of the first region by making it larger than the voltage applied to the cleaning member during the operation. Image forming apparatus. The image forming apparatus according to claim 1, wherein
The control unit is configured such that the potential of the at least part of the second region in a state where the image carrier is rotating is the first region in a state where the image carrier is stopped before the rotation is started. An image forming apparatus, wherein a voltage is applied to the cleaning member so as to be higher than the potential of the image bearing member, and the potential is applied to the surface of the image carrier. The image forming apparatus according to claim 3.
The control unit applies a voltage to be applied to the cleaning member when the image carrier is in contact with the at least part of the second region in a state where the image carrier is rotating before the image carrier starts to rotate. The voltage applied to the cleaning member when it is in contact with the first area in a stopped state is larger than the voltage applied to the cleaning member in the second area when the image carrier is rotating. The image forming apparatus according to claim 1, wherein at least a part of the potential is set higher than the potential of the first region in a state where the image carrier is stopped before the rotation is started. The image forming apparatus according to any one of claims 1 to 4,
An image forming apparatus, wherein (V2−V1) ≧ 50 volts is satisfied when the maximum potential of the first region is V1 and the potential of at least a part of the second region is V2. The image forming apparatus according to any one of claims 1 to 5,
The image forming apparatus, wherein the controller performs a cleaning operation of the seal member every time one print job is completed. The image forming apparatus according to any one of claims 1 to 6,
The image forming apparatus according to claim 1, wherein the seal member is a foam having elasticity that slidably contacts the image carrier and scrapes off deposits on the image carrier. The image forming apparatus according to any one of claims 1 to 6 ,
The image forming apparatus according to claim 1, wherein the seal member is a film that is attached to an opening portion of a casing surrounding the cleaning member and prevents leakage of toner in the casing to the outside. The image forming apparatus according to any one of claims 1 to 6 ,
The image forming apparatus according to claim 1, wherein the seal member is a blade having elasticity that slidably contacts the image carrier and scrapes off deposits on the image carrier.

Images