JP5358110B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent residual toner on an image carrier peeled by an auxiliary cleaning member from being held in the auxiliary cleaning member. <P>SOLUTION: In a printer 10 including a transfer belt 125 on which a toner image is carried, and a belt cleaning device 30 which is arranged to be opposed to the surface of the transfer belt 125 and removes the residual toner remaining on the surface thereof by cleaning, the belt cleaning device 30 includes a main cleaning member 40 to which bias having a reverse polarity to the residual toner is applied, thereby electrically removing the residual toner from an image carrying surface, and the auxiliary cleaning member 50 which is provided on the just upstream side of the main cleaning member 40 and equipped with brush bristles 532 made to abut on the image carrying surface orthogonal to the moving direction of the transfer belt 125 along the entire width direction thereof in advance. The brush bristles 532 are formed of material having the same charging polarity as that of the transfer belt 125. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus including a cleaning device that is disposed to face an image bearing surface of an image bearing member such as a transfer belt and cleans residual toner remaining on the image bearing surface.

  2. Description of the Related Art Conventionally, an image forming apparatus provided with a cleaning device that removes residual toner remaining on a transfer belt as an image carrier and cleans it as described in Patent Document 1 is known. A cleaning device applied to the image forming apparatus includes a main cleaning member that cleans the entire image carrying area of a rotating transfer belt (conveying belt 80 in Patent Document 1), and immediately upstream of the main cleaning member. And an auxiliary cleaning member provided on the head. The auxiliary cleaning member is for locally cleaning an area corresponding to a mark image created in a part in the width direction of the image carrying area so as to determine an image forming condition on the transfer belt. A member that does not require power, such as a blade, a cylindrical brush, or an elastic roll (paragraph [0013] of Patent Document 1) is used.

According to such a cleaning apparatus, in addition to the main cleaning member, the auxiliary cleaning member that cleans the portion corresponding to the mark image is provided, so that the portion where the cleaning load is locally increased is effectively cleaned. A better cleaning process for the transfer belt can be realized.
JP 2000-131969 A

  However, in the cleaning device described in Patent Document 1, the auxiliary cleaning member provided on the upstream side of the main cleaning member is subjected to cleaning processing only in an area corresponding to the mark image on the transfer belt, and other areas. Since the toner is not subjected to a cleaning process, it is insufficient for reliably removing residual toner on the transfer belt.

  In addition, when the charging polarity of the transfer belt and the charging polarity of the brush of the auxiliary cleaning member that is in sliding contact with the transfer belt are reversed, an electric field attracting each other is formed between them, The adhered residual toner is induced by this electric field according to the charging state and is easily adsorbed to the brush, which causes a problem that the brush holds the residual toner. That is, if the brush embracs the toner, it cannot be removed, so that the amount of entrapping is accumulated, resulting in a disadvantage that the auxiliary cleaning member cannot perform its function.

  The present invention has been made in order to eliminate the conventional inconvenience, and is capable of always uniformly cleaning the entire surface of the image bearing surface of the image bearing member, and then performing a cleaning process using a main cleaning member. An object of the present invention is to provide an image forming apparatus configured to prevent the residual toner on the image carrier scraped off by the auxiliary cleaning member before being held by the auxiliary cleaning member.

According to the first aspect of the present invention, an image carrier that moves in a predetermined direction and has an image carrier surface on which a toner image is carried, a casing, the casing, the casing, and the image carrier surface are arranged opposite to each other. A main cleaning member that electrically removes residual toner remaining on the image bearing surface, a power supply device that applies a bias having a polarity opposite to that of the residual toner to the main cleaning member, and the main cleaning member in the moving direction of the image bearing surface. An auxiliary cleaning member that is provided immediately upstream of the cleaning member and is in contact with the image carrying surface, and the auxiliary cleaning member is rotatable about the shaft portion and a shaft portion fitted into the casing. An image carrying surface disposed on the frame and having the same charging polarity as the charging polarity of the image carrier, and the weight of the auxiliary cleaning member Possess the bristles are in contact, the said frame of said auxiliary cleaning member is rotated in the shank around in a state in which the bristles are spaced from the image bearing member surface, the main cleaning member And being exposed to the outside of the casing .

  According to such a configuration, the auxiliary cleaning member provided immediately upstream of the main cleaning member is first brought into contact with the entire width direction of the image carrying surface perpendicular to the moving direction of the image carrier. Prior to the full-scale cleaning process by the cleaning member, the image carrier can be pre-cleaned over the entire width by the auxiliary cleaning member. Compared to the conventional partial pre-cleaning process, The entire surface is uniformly cleaned.

The auxiliary cleaning member has the same charging polarity as that of the image carrier, so that an electric field is formed between the auxiliary cleaning member and the image carrier to repel each other. Residual toner adhering to the carrier is mechanically scraped off by the auxiliary cleaning member. This residual toner scraped off is generated by an electric field that electrostatically repels the auxiliary cleaning member and the image carrier. There is no transfer from the image carrier to the auxiliary cleaning member, and therefore, there is no inconvenience that the scraped residual toner is held in the auxiliary cleaning member. In addition, the auxiliary cleaning member can effectively sweep off the residual toner adhering to the image carrying surface by the brush bristles that are the constituent elements, and the residual toner around the brush composed of a plurality of brush bristles. A uniform electric field suitable for removal from the image bearing surface is created.

Further , according to this configuration, in a state where the frame of the auxiliary cleaning member is rotated around the shaft portion and the brush bristles are separated from the image carrier surface, the main cleaning member is attached to the casing. Exposed to the outside.

The invention described in claim 2 is characterized in that, in the invention described in claim 1, the electric resistance value of each of the bristle is set to 1 × 10 ¹⁰ Ω or less.

According to this configuration, the electrical resistance value of each bristle is set to 1 × 10 ¹⁰ Ω or less, which is lower than that of a normal insulator, so that it is easy to energize. Therefore, it is possible to suppress the residual toner from being electrostatically attracted by the bristles as compared with the case of a normal insulator.

  According to the image forming apparatus of the present invention, first, the auxiliary cleaning member provided immediately upstream of the main cleaning member is brought into contact with the entire width direction of the image carrying surface perpendicular to the moving direction of the image carrier. Therefore, a pre-cleaning process can be performed by this contact over the entire width of the image carrier, and the image carrier surface of the image carrier is generally uniform compared to the conventional partial pre-cleaning process. Can be cleaned.

  The brush bristles have the same charging polarity as that of the image carrier, and an electric field is formed between the bristles and the image carrier to repel each other. As a result, there is no inconvenience that the brush bristles carry the residual toner that is left, so the residual toner held by the bristles deteriorates the cleaning function of the auxiliary cleaning member, and the environment around the bristles is contaminated with the residual toner. It is possible to effectively prevent the occurrence of inconvenience such as a situation.

  First, an outline of the internal structure of a printer according to an embodiment of the image forming apparatus of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram of a front sectional view for explaining an embodiment of the internal structure of the printer. As shown in FIG. 1, a printer (image forming apparatus) 10 according to this embodiment includes an image forming unit that forms an image in an apparatus body 11 having a box shape based on image information transmitted from an external device such as a computer. 12, a fixing unit 13 that fixes the image formed by the image forming unit 12 and transferred to the paper P, and a paper storage unit 14 that stores the transfer paper P are internally provided. A basic configuration is formed by providing a paper discharge unit 15 for discharging the paper P after the fixing process at the upper part of the apparatus main body 11.

  At an appropriate position on the upper surface of the apparatus main body 11, an operation panel (not shown) for inputting the output conditions of the paper P and the like is provided. This operation panel is provided with a power key, a start button (not shown), various keys for inputting output conditions, and the like.

  The image forming unit 12 forms a toner image on the paper P fed from the paper storage unit 14, and in the present embodiment, the image forming unit 12 is directed from the upstream side (the right side of the paper surface in FIG. 1) to the downstream side. Sequentially arranged magenta unit 12M using magenta toner (developer), cyan unit 12C using cyan toner, yellow unit 12Y using yellow toner, and black toner And a black unit 12K using the above.

  Each of the units 12M, 12C, 12Y, and 12K is provided with a photosensitive drum 121 and a developing device 122, respectively. The photosensitive drum 121 is for forming an electrostatic latent image and a toner image (visible image) along the electrostatic latent image on the peripheral surface. Each photosensitive drum 121 receives supply of toner from the corresponding developing device 122 while rotating counterclockwise in FIG. Each developing device 122 is replenished with toner from an unillustrated toner cartridge disposed on the front side of the apparatus main body 11 (the front side of the paper surface of FIG. 1).

  As the developer, a so-called two-component developer composed of a toner and a carrier can be used. The toner is a fine powder having a particle diameter of 6 to 12 μm in which additives such as a colorant, a charge control agent and wax are dispersed in a binder resin. On the other hand, the carrier is magnetic particles having a particle size of 60 to 200 μm such as magnetite (Fe 3 O 4), and is used to charge the toner. The toner is a consumable that is appropriately replenished from the toner cartridge (not shown) to the developing device 122, whereas a predetermined amount of the carrier is loaded in the developing device 122 in advance, and is used without being consumed. It is common to be done.

  A charging device 123 is provided immediately below each photoconductor drum 121, and an exposure device 124 is provided further below each charging device 123. Each photosensitive drum 121 is uniformly charged at its peripheral surface by the charging device 123, and laser light corresponding to each color based on image data input from a computer or the like is charged from the exposure device 124 to the photosensitive member after charging. By irradiating the circumferential surface of the drum 121, an electrostatic latent image is formed on the circumferential surface of each photosensitive drum 121. By supplying toner from the developing device 122 to such an electrostatic latent image, a toner image is formed on the peripheral surface of the photosensitive drum 121.

  A transfer belt (image carrier) 125 is disposed above each photosensitive drum 121. The transfer belt 125 is stretched between the driving roller 125a on the left side and the driven roller 125b on the right side in FIG. 1, and the lower side surface (portion moving in the left direction in FIG. 1) is the photosensitive drum 121. Abut. The transfer belt 125 has an image bearing surface on the outer peripheral surface thereof, and is pressed against the peripheral surface of the photosensitive drum 121 by a transfer roller 126 provided corresponding to the photosensitive drum 121. Rotating between the driving roller 125 a and the driven roller 125 b while synchronizing with 121.

  In the present embodiment, a tension roller 125c is provided between the driving roller 125a and the driven roller 125b and at a position close to the driven roller 125b. The tension roller 125c applies tension to the transfer belt 125, and is biased upward by a biasing force of a biasing member (not shown). Accordingly, the portion facing upward of the transfer belt 125 (the belt moving to the right in FIG. 1) is pushed upward by the tension roller 125c, whereby the transfer belt 125 is moved to the portion of the tension roller 125c. The shape of the mountain is the summit.

  As the transfer belt 125 circulates, the toner image of the magenta toner is transferred onto the surface of the transfer belt 125 by the photosensitive drum 121 of the magenta unit 12M, and then the photosensitive member of the cyan unit 12C is located at the same position on the transfer belt 125. The transfer of the cyan toner image by the drum 121 is performed in the overcoating state, and then the transfer of the yellow toner image by the photosensitive drum 121 of the yellow unit 12Y is performed in the overcoating state at the same position on the transfer belt 125. Then, the transfer of the black toner image by the photosensitive drum 121 of the last black unit 12K is performed in an overcoated state, whereby a color toner image is formed on the surface of the transfer belt 125. The color toner image formed on the surface of the transfer belt 125 is transferred to the paper P conveyed from the paper storage unit 14.

  Further, a drum cleaning device 127 that removes and cleans residual toner on the peripheral surface of the photosensitive drum 121 is provided at the left position in FIG. 1 of each photosensitive drum 121. The peripheral surface of the photosensitive drum 121 cleaned by the drum cleaning device 127 is directed to the charging device 123 for a new charging process.

  Waste toner removed from the peripheral surface of the photosensitive drum 121 by the drum cleaning device 127 is collected in a toner collection bottle (not shown) through a predetermined path.

  At the left position of the image forming unit 12 in FIG. 1, a paper conveyance path 111 extending in the vertical direction is formed. The paper transport path 111 is provided with a transport roller pair 112 at an appropriate position, and the paper P from the paper storage unit 14 is directed toward the transfer belt 125 that is wound around the drive roller 125 a by the drive of the transport roller pair 112. Be transported. In the sheet conveyance path 111, a second transfer roller 113 that is in contact with the surface of the transfer belt 125 is provided at a position facing the driving roller 125a. Then, the sheet P being conveyed through the sheet conveyance path 111 is pressed and held between the transfer belt 125 and the second transfer roller 113, whereby the toner image on the transfer belt 125 is transferred to the sheet P.

  The fixing unit 13 performs a fixing process on the toner image on the paper transferred by the image forming unit 12. The fixing unit 13 includes a heating roller 131 having an energization heating element as a heating source therein, a fixing roller 132 disposed opposite to the heating roller 131 on the left side in FIG. 1, the fixing roller 132 and the heating roller. A fixing belt 133 stretched between the rollers 131 and a pressure roller 134 disposed to face the fixing roller 132 with the fixing belt 133 interposed therebetween.

  The sheet P supplied to the fixing unit 13 in a state where the toner image on the transfer belt 125 is transferred by passing through the nip portion between the transfer belt 125 and the second transfer roller 113 is supplied to the pressure roller 134. Then, the fixing process is performed by obtaining heat from the fixing belt 133 while passing between the toner and the high-temperature fixing belt 133.

  The color-printed paper P that has been subjected to the fixing process passes through a paper discharge conveyance path 114 extending from the upper part of the fixing unit 13 to a paper discharge tray 151 of a paper discharge unit 15 provided at the top of the apparatus main body 11. It will be discharged towards.

  The sheet storage unit 14 includes a manual feed tray 141 that can be freely opened and closed on the right side wall of the apparatus main body 11 in FIG. 1, and a sheet tray 142 that is removably mounted in the apparatus main body 11 below the exposure device 124. And. A sheet bundle in which a plurality of sheets P are stacked is stored in the sheet tray 142.

  The manual feed tray 141 is for manually feeding the paper P one by one toward the image forming unit 12 by manual feed operation, and is usually stored on the right wall surface of the apparatus main body 11, but manually fed. Only when this is done, as shown in FIG. 1, it is pulled out from the wall surface and used for manual paper feeding.

  The paper tray 142 includes a box body whose upper surface is open on the entire surface, and can store a sheet bundle P1 formed by stacking a plurality of sheets P. The uppermost sheet P of the sheet bundle P1 stored in the sheet tray 142 is fed from the sheet bundle P1 toward the sheet conveyance path 111 by driving the pickup roller 143 from the upper surface of the downstream end (left end in FIG. 1). Then, the sheet P fed out one by one from the sheet tray 142 passes through the sheet conveyance path 111 by driving the conveyance roller pair 112, and the nip portion between the second transfer roller 113 and the transfer belt 125 in the image forming unit 12. Will be sent to.

  In this embodiment, secondary transfer (a color image on the lower surface of the transfer belt 125 is transferred to the paper P at the nip portion between the transfer belt 125 and the second transfer roller 113 at the position of the drive roller 125a). A belt cleaning device 30 is provided at a position corresponding to the driven roller 125b (see FIG. 1) for removing and cleaning the residual toner remaining on the lower surface of the transfer belt 125 after being performed. ing.

  In this embodiment, the driving roller 125a, the driven roller 125b, and the tension roller 125c, the transfer belt 125 wound around these rollers, the transfer rollers 126, and the belt cleaning device 30 are provided. An intermediate transfer unit 20 mounted and unitized is employed.

  Hereinafter, the intermediate transfer unit 20 will be described with reference to FIGS. 2 and 3. 2 and 3 are perspective views showing an embodiment of the intermediate transfer unit 20. FIG. 2 shows a state where the belt cleaning device 30 is removed from the unit frame 21, and FIG. 3 shows a state where the belt cleaning device 30 is a unit. A state of being mounted on the frame 21 is shown. In FIG. 2, the XX direction is referred to as the left-right direction and the Y-Y direction is referred to as the front-rear direction. In particular, the -X direction is referred to as the left, the + X direction is referred to as the right, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear.

  The intermediate transfer unit 20 is formed by mounting a transfer belt 125 and a belt cleaning device 30 on a unit frame 21 via a driving roller 125a, a driven roller 125b, and a tension roller 125c.

  The unit frame 21 includes a front frame 211 that is long in the left-right direction, a rear frame 212 having substantially the same shape that is opposed to the front frame 211 at the rear, and left upper edges of the front and rear frames 211 and 212. And an erection frame 213 provided therebetween. The length of the front frame 211 and the rear frame 212 is set so that the image forming unit 12 can be traversed in the left-right direction within the apparatus main body 11, and the length of the installation frame 213 is transferred in the front-rear direction. It is set slightly longer than the belt width of the belt 125.

  A driving roller shaft 22 is installed between the front and rear frames 211 and 212 at a position immediately below the installation frame 213 so as to be rotatable about the axis. The drive roller 125a is fitted on the drive roller shaft 22 so as to be concentric and integrally rotatable. A driven shaft 23 is installed at the right end positions of the front and rear frames 211 and 212. The driven roller 125b is concentrically fitted around the driven shaft 23 so as to be rotatable.

  Further, a tension roller shaft 24 provided between the front and rear frames 211 and 212 is provided slightly to the left of the driven shaft 23. The tension roller 125c is fitted around the tension roller shaft 24 so as to be concentric and rotatable. The transfer belt 125 is wound around the driving roller 125a, the driven roller 125b, and the tension roller 125c.

  A drive gear 221 is attached to the rear end of the drive roller shaft 22 so as to be concentric and integrally rotatable. Then, a driving force of a driving motor (not shown) is transmitted to the driving roller shaft 22 through the driving gear 221. Due to the driving rotation of the driving roller 125a, the transfer belt 125 is viewed clockwise from the front (−Y direction). Orbit around.

  The belt cleaning device 30 is mounted between the right end portions of the front and rear frames 211 and 212 in the intermediate transfer unit 20. Hereinafter, the belt cleaning device 30 will be described in detail with reference to FIGS. FIG. 4 is an exploded perspective view of the belt cleaning device 30, and FIGS. 5 and 6 are assembled perspective views thereof. 5 shows a state in which the auxiliary cleaning member 50 is set in the closed posture, and FIG. 6 shows a state in which the auxiliary cleaning member 50 is set in the open posture. FIG. 7 is a sectional view taken along line VII-VII in FIG. 4 to 7 are the same as those shown in FIG. 2 (X is the left-right direction (-X: leftward, + X: rightward), Y is the front-rear direction (-Y: forward, + Y: backward)).

  First, as shown in FIG. 4, the belt cleaning device 30 includes a main cleaning member 40 that electrically removes residual toner on the surface of the transfer belt 125 in a casing 31 attached to the unit frame 21, and the main cleaning member. 40, an auxiliary cleaning member 50 positioned on the upstream side in the circumferential direction of the transfer belt 125 is attached.

  The casing 31 includes a front plate 32, a rear plate 33 disposed opposite to the front plate 32 at the rear, a bottom plate 34 installed between lower edges of the front and rear plates 32, 33, and front and rear plates 32, 33. A right side plate 35 and a top plate 36 are provided between the right edges of the left and right sides, and the left side is open. The casing 31 is screwed in a state where the inner surface side of the front plate 32 is brought into contact with the outer surface side of the right end of the front frame 211 and the outer surface side of the rear plate 33 is brought into contact with the inner surface side of the right end of the rear frame 212. As a result, the unit frame 21 is fixed.

  The main cleaning member 40 includes a fur brush 41 whose peripheral surface is in contact with the surface of the transfer belt 125, a recovery roller 42 whose peripheral surface is in contact with the peripheral surface of the fur brush 41, and the recovery roller 42. And a blade 43 for scraping off the residual toner collected on the peripheral surface.

  The fur brush 41 includes a brush shaft 411 and a fur brush body 412 that is externally fitted to the brush shaft 411 so as to be integrally rotatable. The fur brush main body 412 is formed by uniformly planting brush hairs on the peripheral surface of a synthetic resin cylinder into which the brush shaft 411 is inserted. The fur brush 41 has a casing 31 as a result of a brush shaft 411 passing through the front and rear plates 32 and 33 being inserted into the fur brush main body 412 in a state where it is disposed at a fixed position in the lower left part between the front and rear plates 32 and 33. It is attached to.

In the present embodiment, the fur brush body 412 has an outer diameter dimension set to 17 mm. The fur bristles 412 are made of polyamide having a fineness of 6 denier. Each bristle is in contact with the surface of the transfer belt 125 with the length dimension set to 4.5 mm and the nip dimension set to 1 mm. The brush density is set to 120 KF / inch ² . Further, the electrical resistance value of the fur brush body 412 is set to 1 × 10 ^11.5 Ω. A bias current of −20 μA is applied to such a bristle from the power supply device 60 (FIG. 7). The residual toner on the transfer belt 125 that is positively charged by the electric adhesion force due to the application of the minus bias is transferred from the transfer belt 125 to the fur brush main body 412.

  The collection roller 42 includes a collection roller shaft 421 and a collection roller main body 422 made of an elastomer such as rubber or soft synthetic resin that is concentrically and externally fitted to the collection roller shaft 421. The collection roller 42 is mounted on the casing 31 with the collection roller shaft 421 inserted between the front and rear plates 32 and 33 at a position obliquely above and to the right of the fur brush 41. The installation position of the collection roller 42 is set so that the circumferential surface of the collection roller 42 interferes with the fur brush body 412 of the fur brush 41 in a state where the collection roller 42 is mounted on the casing 31.

  A brush shaft side gear 413 is concentrically and externally fitted to the brush shaft 411 so that the brush shaft 411 is mounted on the casing 31 in a state where the brush shaft 411 is mounted on the casing 31. In the state where the collection roller shaft 421 is mounted on the casing 31, the collection roller shaft side gear 423 is concentrically fitted on the front end portion thereof so as to be integrally rotatable. These gears 412 and 422 are set to have a diameter so as to mesh with each other.

  In this embodiment, the driving force of a drive motor (not shown) is transmitted to the brush shaft side gear 413, and the fur brush 41 rotates integrally around the brush shaft 411 due to the rotation of the brush shaft side gear 413. Further, the collection roller 42 rotates around the collection roller shaft 421 in the direction opposite to the fur brush 41 by the rotation of the collection roller shaft side gear 423 engaged with the brush shaft side gear 413.

  The blade 43 is for scraping off the residual toner transferred from the bristles of the fur brush 41 to the peripheral surface of the collection roller 42. The blade 43 is fixed by screws to an inclined plate 361 extending in a downwardly inclined manner from the left edge of the top plate 36 of the casing 31 toward the left, and as shown in FIG. In addition, the lower edge is in contact with the circumferential surface of the collection roller body 422. Therefore, when the collection roller 42 rotates counterclockwise around the collection roller shaft 421, the residual toner adhering to the peripheral surface of the collection roller main body 422 is scraped off by the blade 43 and collected in the casing 31. The toner is collected in the toner storage space 310.

  The auxiliary cleaning member 50 cleans the surface of the transfer belt 125 prior to the main cleaning member 40. Residual toner adhering to the surface of the transfer belt 125 is lifted off from the transfer belt 125 by the wiping process, so that the main cleaning member 40 can more effectively remove the residual toner from the transfer belt 125. Can be done.

The auxiliary cleaning member 50 includes a ladder frame 51 (frame) that is rotatably mounted on the upper surface of the casing 31, a brush support fitting 52 (frame) that is fixed to the ladder frame 51, and a brush support. And a bar brush 53 attached to the metal fitting 52.

The ladder-shaped frame 51 includes a columnar frame 511 (shaft portion) extending in the front-rear direction, a square-shaped frame 512 extending in the front-rear direction so as to face the columnar frame 511 on the left side, A plurality of installation plates 513 extending between the columnar frame 511 and the square-shaped frame 512 and extending in the left-right direction are provided at a predetermined pitch. The length dimension (left-right dimension) of the erection plate 513 is set slightly shorter than the left-right dimension of the front and rear plates 32, 33. In the present embodiment, a total of 10 such construction plates 513 are employed, but an appropriate number can be used depending on the situation.

  The columnar frame 511 is set to have substantially the same length as the outer dimension between the front and rear plates 32 and 33 of the casing 31, whereas the square frame 512 has a length dimension of the front and rear plates 32 and 32. It is set slightly shorter than the inner dimension between 33. As a result, in a state where the columnar frame 511 and the square frame frame 512 are connected to each other via the plurality of installation plates 513, both ends of the columnar frame 511 are directed outward from the installation plates 513 at the ends. It is in a protruding state.

  On the other hand, in the front plate 32 and the rear plate 33, fitting grooves for fitting both end portions of the columnar frame 511 formed by being recessed downward from the upper edge surface of the right end thereof. 321 and 331 are provided. The ladder-like frame 51 can rotate integrally around the columnar frame 511 by fitting both end portions of the columnar frame 511 into the corresponding fitting grooves 321 and 331, respectively.

  The brush support bracket 52 includes a support plate 521 elongated in the front-rear direction, an edge weir 522 formed by bending upward from the right edge of the support plate 521 over the entire length, and the edge weir. A pair of front and rear brackets 523 projecting from a target position in the front-rear direction of 522, and an extension plate 524 extending rightward from the edge dam 522 between the pair of brackets 523 are provided.

  Each bracket 523 is fixed at a position corresponding to the fourth construction plate 513 from the end. The bracket 523 is formed in a bowl shape that is bent at a right angle in a front view as viewed from the −Y direction, and a protruding piece 523a that protrudes outward from the edge dam 522, and the protruding piece 523a. It consists of a bent piece 523b that is bent rightward from the leading edge. Each bent piece 523b has a through hole 523c.

  On the other hand, the ladder-like frame 51 is provided with a columnar body 513a that protrudes upward from the left end position of each construction plate 513 that is fourth from the front end and fourth from the rear end. A screw hole 513b corresponding to the through hole 523c of the bracket 523 is screwed on the upper surface of the pair of cylindrical bodies 513a. Therefore, in a state where the bent piece 523b of each bracket 523 is placed on the corresponding cylindrical body 513a, a predetermined screw is inserted into the through hole 523c and screwed into the screw hole 513b to be fastened. As shown in FIG. 5, the metal fitting 52 is attached to the ladder frame 51.

  The brush support fitting 52 has a predetermined position between the driven roller 125b and the tension roller 125c in a state where the auxiliary cleaning member 50 is mounted on the casing 31 and the left end portion of the brush support fitting 52 is on the transfer belt 125. The dimension is set so as to be opposed to the position.

  In this state, the extension plate 524 of the brush support fitting 52 is brought into contact with the upper edge surfaces of the two erection plates 513 at the center, whereby the brush support fitting 52 is front-faced with the upper end of the protruding piece 523a as a fulcrum. It is prevented from rotating clockwise as viewed.

  The bar brush 53 is formed by planting a large number of brush hairs 532 on the lower surface side of a synthetic resin base sheet 531. The base sheet 531 has a length in the front-rear direction that is set to be the same as that of the support plate 521, and a width in the left-right direction is set to be approximately half that of the support plate 521. In the present embodiment, the bar brush 53 is attached to the left half side of the lower surface of the support plate 521 via a double-sided tape 54 as an insulating material having an adhesive layer formed on the front and back surfaces.

In the present embodiment, the bar brush 53 has a left-right width dimension in plan view of 15 mm and a longitudinal dimension of 310 mm. The brush bristles 532 are made of a material having an electrostatically negative charging polarity, such as polyvinyl chloride resin (polyamide-based meaning), acrylic resin, or polyester resin. In the present embodiment, the brush bristles 532 are made of polyester having a latitude of 6 denier. The length of the brush bristles 532 is set to 4.5 mm, and the brush density is set to 120 KF / inch ² . Further, the electrical resistance value of the brush bristles 532 is 1 × 10 ¹⁰ Ω or less. The brush bristles 532 made of polyester have a resistance value of 1 × 10 ⁶ Ω. In the present embodiment, the auxiliary cleaning member 50 has a total weight of 280 g.

  The reason why the bristle 532 having a negative charging polarity is employed as the bristle 532 is as follows. That is, the transfer roller 125 with which the bristle 532 is slidably contacted is usually coated with polytetrafluoroethylene (hereinafter referred to as PTFE), which is a smooth and tough synthetic resin material, on the surface side. Are electrostatically negatively charged, so that the bristles 532 have the same charging polarity, thereby forming an electric field repelling each other between the bristles 532 and the transfer belt 125, Residual toner adhering to the transfer belt 125 is hardly electrostatically attracted to the brush bristles 532 by the action of the electric fields repelling each other.

  Incidentally, the residual toner is positively charged in this embodiment, but is not only at a very low potential, but also in a very unstable state. As a result, the surface of the transfer belt 125 is negatively charged. The charging characteristics of the toner and the negative charging characteristics of the bristles 532 are in conflict, and it is not certain which residual toner is drawn to depending on the electrostatic condition of the residual toner at that time.

  This means that when the normal transfer process is executed, whether the brush bristles 532 embed residual toner or not has a large difference regardless of whether the brush bristles 532 have a positive or negative charge polarity. However, when the residual toner once held in the bristles 532 is released, the charging polarity of the bristles 532 is set to be the same as the charging characteristics of the surface of the transfer belt 125. It has been experimentally confirmed that the release efficiency is remarkably improved. This will be described in detail in the “Examples” section below.

  Then, in a state where the brush bristles 532 and the transfer belt 125 have the same charging polarity, the surface of the transfer belt 125 is wiped with the brush bristles 532, and the residual toner scraped off from the surface of the transfer belt 125 is thereby removed. In the state of being lifted from the surface of the transfer roller 125, the belt reaches the downstream belt cleaning device 30 according to the rotation of the transfer belt 125. The residual toner reaching the belt cleaning device 30 is removed by the fur brush 41 rotating here.

The reason why the resistance value of the bristles 532 is set to 1 × 10 ¹⁰ Ω or less, which is a low value as an insulator, is to suppress the generation of static electricity of the bristles 532 by increasing the conductivity. . In order to reduce the resistance value of the brush bristles 532, in the present embodiment, carbon black is uniformly contained in the bristles 532, or carbon black is not formed on the outer peripheral surface of normal brush bristles that do not contain carbon black. A laminate of synthetic resin materials having a high content is employed.

  In addition to using a material having a negative charging polarity as the material of the bristle 532, in this embodiment, a positive bias of +300 V is applied to the bristle 532 from the power supply device 60 at +3 μA. ing. As a result, the residual toner whose charge amount is approximately +3 μC / g until it passes through the auxiliary cleaning member 50 is increased in positive charge amount to +20 μC / g after passing through the auxiliary cleaning member 50. Since the main cleaning member 40 is reached, it is effectively adsorbed by the fur brush body 412 to which a negative bias is applied in the main cleaning member 40, thereby being reliably removed from the surface of the transfer belt 125.

  As shown in FIG. 5, the auxiliary cleaning member 50 thus configured has a cylindrical frame 511 fitted into the fitting grooves 321 and 331 of the front and rear plates 32 and 33 of the casing 31, as shown in FIG. 31 is attached. Then, as shown in FIG. 5, the brush bristles 532 of the bar brush 53 are placed on the transfer belt 125 immediately on the left side of the driven roller 125b with the auxiliary cleaning member 50 mounted on the casing 31 and set in the closed posture as shown in FIG. Abut.

  Therefore, when the auxiliary cleaning member 50 is rotated clockwise around the columnar frame 511 in a state where the auxiliary cleaning member 50 is set to the closed posture, the auxiliary cleaning member 50 is, as shown in FIG. The posture is changed to the open posture, whereby the fur brush 41, the collection roller 42 and the like inside the casing 31 are exposed to the outside. In this state, a predetermined maintenance operation is performed as necessary.

  When the auxiliary cleaning member 50 is set to the closed posture, the auxiliary cleaning member 50 is on the surface of the casing 31 facing the fitting grooves 321 and 331 of the front and rear plates 32 and 33 and the transfer belt 125. It will be in the state supported by. In this state, the force with which the bar brush 53 presses the surface of the transfer belt 125 depends on the weight of the auxiliary cleaning member 50. This pressing force is a function of the center of gravity position of the auxiliary cleaning member 50 in the left-right direction.

Specifically, the total weight of the auxiliary cleaning member 50 is W, the effective length of the auxiliary cleaning member 50 in the left-right direction (the distance between the central portion of the bar brush 53 in the left-right direction and the groove centers of the fitting grooves 321 and 331) ) L, the distance between the center of gravity of the auxiliary cleaning member 50 in the left-right direction and the center of the bar brush 53 in the left-right direction, L1, the center of gravity of the auxiliary cleaning member 50 in the left-right direction and the grooves of the fitting grooves 321 and 331 When the distance from the heart position is L2,
The pressing force W1 at which the bristles 532 of the bar brush 53 press the transfer belt 125 is:
W1 = (L2 / L) × W (1)
It becomes.

On the other hand, the pressing force W2 at which the ladder frame 51 presses the groove bottoms of the fitting grooves 321 and 331 is:
W2 = (L1 / L) × W (2)
It becomes.

  Therefore, for example, when the position of the center of gravity of the auxiliary cleaning member 50 in the left-right direction is exactly in the middle (that is, when L2 = L / 2), the pressing force W1 at which the brush bristles 532 press the transfer belt 125 is (1 ), “W / 2”. In the present embodiment, since the weight of the auxiliary cleaning member 50 is 280 g, the brush bristles 532 press the surface of the transfer belt 125 with 140 g that is half of the weight. In the case where the auxiliary cleaning member 50 is supported by the front and rear plates 32 and 33 so as to be rotatable around the columnar frame 511 as in the present embodiment, the 140 g corresponds to the auxiliary belt according to the present invention with respect to the transfer belt 125. This means that the cleaning member 50 has its own weight.

  Since the auxiliary cleaning member 50 presses the surface of the transfer belt 125 with its own weight, the portion of the transfer belt 125 where the bristles 532 are in contact is displaced up and down (tension roller 125c). Is biased upward by a biasing force of a biasing member (not shown), the tension roller 125c moves up and down at the start of the rotation of the transfer belt 125, and the transfer belt 125 is displaced up and down by this. ) Since the auxiliary cleaning member 50 swings by rotating forward and backward around the cylindrical frame 511 so as to follow this displacement, the pressing force of the bristles 532 against the transfer belt 125 does not change.

  Accordingly, since the surface of the transfer belt 125 is always pressed by the brush bristles 532 with the same pressing force, the pressing force of the brush bristles 532 changes due to the displacement of the transfer belt 125 and varies in the wiping process. The occurrence of inconvenience such as this is effectively prevented.

  In the present embodiment, the bar brush 53 is supported by the brush support bracket 52 via the insulating double-sided tape 54, so that it is disconnected from the electrical system of the printer 10 and is in an electrically floating state. ing. That is, the bar brush 53 is not applied with a voltage to the bar brush 53, and the bar brush 53 is not grounded. This is done for the following reason.

  That is, the toner image formed on the surface of the transfer belt 125 is normally charged to +20 to +30 μc / g. If the amount of charge is this value, the main cleaning member 40 imparts a charge having a reverse polarity. As a result, the toner on the transfer belt 125 is easily peeled off from the transfer belt 125 electrically. When the toner image on the transfer belt 125 faces the second transfer roller 113, the second transfer roller 113. As a result, the charge amount of the residual toner that passes through the second transfer roller 113 and remains on the transfer belt 125 is substantially equal to the reverse polarity. It becomes about +5 μc / g.

  Then, when a negative voltage having a reverse polarity is applied to the residual toner having a low charge amount of about +5 c / g by the auxiliary cleaning member 50 or is grounded, the residual toner is extremely low corresponding to the excess. It becomes a charged state or a negative charged state. Accordingly, in this state, the residual toner that has reached the fur brush 41 due to the rotation of the transfer belt 125 is applied to the fur brush 41 even though a negative bias having a polarity opposite to that of the residual toner is applied (or a negative bias). The residual toner cannot be effectively removed by suction.

  Incidentally, it has been experimentally confirmed that when the charged state of the bar brush 53 is grounded, the charge amount of the residual toner, which was +5 μc / g, is reduced to +0.5 μc / g.

  In order to eliminate this inconvenience, in this embodiment, the bar brush 53 is in an electrically floating state. Therefore, the residual toner on the transfer belt 125 that has reached the bar brush 53 around the transfer belt 125 is lifted from the surface of the transfer belt 125 by the brush bristles 532 of the bar brush 53, but has a reverse polarity bias. Is not applied or grounded. Therefore, the residual toner that has passed through the bar brush 53 is merely peeled off from the transfer belt 125 mechanically, and there is no change in electrical characteristics. Is removed by electrical suction by the fur brush 41 to which is applied.

  The residual toner attached to the brush bristles of the fur brush 41 rotating around the brush shaft 411 is transferred to the peripheral surface of the collecting roller 42 rotating while the peripheral surface abuts against the brush bristles of the fur brush 41. . Residual toner adhering to the peripheral surface of the collection roller 42 is scraped off by the blade 43 in accordance with the rotation of the collection roller 42 and collected in the collection toner storage space 310.

  As described above in detail, the printer 10 according to this embodiment is opposed to the transfer belt 125 on which the toner image formed according to the image information is carried while moving in a predetermined direction, and the surface of the transfer belt 125. And a belt cleaning device 30 which is disposed and cleans and removes residual toner remaining on the surface.

  The belt cleaning device 30 is provided on the upstream side of the main cleaning member 40 and the main cleaning member 40 that electrically removes the residual toner from the image bearing surface by applying a bias having a polarity opposite to that of the residual toner. And an auxiliary cleaning member 50 having brush bristles 532 that are in contact with the entire width direction of the image bearing surface orthogonal to the moving direction of the transfer belt 125 in advance. It is formed of a material having the same charging polarity as the charging polarity.

  According to this configuration, the brush bristles 532 of the auxiliary cleaning member 50 provided immediately upstream of the main cleaning member 40 first contact over the entire width direction of the image carrying surface orthogonal to the moving direction of the transfer belt 125. Therefore, prior to the full-scale cleaning process by the main cleaning member 40, the transfer belt 125 can be pre-cleaned over the entire width by the brush bristles 532 of the auxiliary cleaning member 50, and the conventional partial pre-cleaning can be performed. Compared with the processing, the image carrying surface of the transfer belt 125 is cleaned uniformly throughout.

  The brush bristles 532 have the same charging polarity as that of the transfer belt 125, so that an electric field is formed between the bristles 532 and the transfer belt 125 to repel each other. The residual toner adhering to the belt 125 is mechanically scraped off by the brush bristles 532. The scraped residual toner is generated by an electric field that causes the brush bristles 532 and the transfer belt 125 to repel each other electrostatically. The transfer from the transfer belt 125 to the brush bristles 532 is suppressed, so that there is no inconvenience that the scraped residual toner is held in the bristles 532.

Moreover, since the electrical resistance value of each bristle 532 is set to 1 × 10 ¹⁰ Ω or less, which is lower than the resistance value of a normal insulator (usually 1 × 10 ¹² Ω), the electrostatic charge amount is Thus, it is possible to keep the bristles 532 from attracting the residual toner electrostatically lower than usual.

  When using the bristle having a negative charging polarity according to the present invention, how much less the amount of toner can be held in compared with using the bristle having a positive charging polarity. In order to confirm, the following effect confirmation test was conducted.

  First, as a bristle (Example) having a negative charging polarity according to the present invention, a polyester synthetic resin was used. On the other hand, the thing made from a polyamide-type synthetic resin was employ | adopted as a bristle (comparative example) provided with the positive charging polarity which is a comparison object.

  Then, in order to force toner into the brush bristles of the embodiment, first, a negative bias is applied to the brush bristles 532 of the auxiliary cleaning member 50, and transfer processing is performed on approximately 10,000 sheets in this state. gave. By the transfer process, approximately 3.2 g of toner was held in the brush hair of the example.

  Subsequently, with the negative bias applied to the brush bristles 532 stopped, the transfer belt 125 was idled for 60 seconds (an operation in which no image forming process was performed). As a result, the toner once held in the brush hair is released when the negative bias disappears. After 60 seconds had elapsed, the idle operation of the transfer belt 125 was stopped, and the amount of toner remaining on the bristles was weighed to be 0.8 g. This indicates that 75% of the entrapped 3.2 g of toner has been released.

  Next, the same treatment as that of the brush bristles of the example was applied to the bristles of the comparative example, and the amount of toner remaining on the bristles after the 60-second run of the transfer belt 125 was weighed. Met. This indicates that in the comparative example, only 38% of the toner held by the brush bristles is released.

The toner is composed of a polyester-based synthetic resin having a negative charge polarity in the core, which is a main component of the toner, to which various fine powdery additives having a positive charge polarity are attached. Yes. This initially toner, but positively charged in total, the then is either charged to any positive and negative depending on the circumstances.

  Therefore, by applying a negative bias to the brush bristles 532, the toner that is totally positively charged is once adsorbed and held by the brush bristles 532. However, there are cases where various fine additives are removed from the core of the toner due to vibrations or the like after being embraced. As a result, the polarity of the core having a negative charging polarity becomes dominant as the total toner charging polarity.

  If the application of the negative bias to the bristle 532 is stopped in this state, if the bristle 532 has a negative charging polarity, the negatively charged core of the toner is discharged from the bristle 532, As a result, the toner once held in the brush bristles 532 is released.

  On the other hand, when the bristle 532 has a positive charging polarity, the negatively charged core of the toner is further embraced, so that a negative bias is applied to the bristle 532. It is considered that the amount of toner released when the operation is stopped is reduced.

  Table 1 summarizes the preconditions and test results of this test.

  As can be seen from Table 1, in the embodiment using the brush hair having a negative charging polarity, even if the brush hair once encloses a large amount of toner by applying a negative bias to the brush hair. Since it was easily released from the bristle by stopping the negative bias application, it was confirmed that the reproduction of the bristle was extremely easy.

  On the other hand, in the case of the comparative example using a brush hair having a positive charging polarity, once the brush hair embracs the toner, the embraced toner is then easily released. It was confirmed that it was difficult.

  If a material having a negative charging polarity is used as the bristle 532 of the auxiliary cleaning member 50, even if the bristle 532 embracs a large amount of toner, the embracing is performed during maintenance work to be performed as appropriate. It is shown that it is possible to easily release the contained toner, and from the standpoint of maintenance work, it is confirmed that it is preferable to use the brush hair 532 of the auxiliary cleaning member 50 having a negative charging polarity. I was able to.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the printer 10 is described as an example of the image forming apparatus to which the intermediate transfer unit 20 is applied. However, the image forming apparatus is not limited to this, and may be a copying machine or a facsimile machine. May be.

  (2) In the above-described embodiment, a conveying unit such as a spiral feeder is provided in the collected toner storage space 310 of the casing 31, and the collected toner collected in the collected toner storage space 310 by driving the conveying unit is used as a predetermined waste toner. You may make it carry in to a hopper for the purpose.

  (3) In the above embodiment, the auxiliary cleaning member 50 is pressed against the transfer belt 125 by its own weight, but instead of this, the image carrying surface of the transfer belt 125 is urged by the urging force of a predetermined urging member. May be pressed. In this way, the transfer belt 125 is configured to circulate in the vertical direction, for example, so that the weight of the auxiliary cleaning member 50 is used to press the auxiliary cleaning member 50 against the transfer belt 125. Even in such a case, the auxiliary cleaning member 50 can be pressed against the transfer belt 125 by the urging force of the urging member, and the versatility of the layout of the auxiliary cleaning member 50 is improved. be able to.

  (4) In the above embodiment, the transfer belt 125 is made of PTFE having an electrostatic negative charging polarity, so that the bristle 532 has the same charging polarity. Therefore, when the transfer belt 125 has a positive charging polarity, such as a polyamide, for example, the brush bristles 532 have the same charging polarity. A material such as polyamide or rayon is used.

  (5) In the above embodiment, the brush bristles 532 of the auxiliary cleaning member 50 are brought into contact with the surface of the transfer belt 125, but instead of the brush bristles 532, residual toner on the transfer belt 125 is removed. Various members (such as a blade) that can be scraped off may be used.

It is explanatory drawing of front sectional view for demonstrating one Embodiment of the internal structure of a printer. FIG. 5 is a perspective view showing an embodiment of an intermediate transfer unit, and shows a state where a belt cleaning device is detached from a unit frame. FIG. 3 is a perspective view showing a state where a belt cleaning device is mounted on a unit frame in the intermediate transfer unit shown in FIG. 2. It is a disassembled perspective view which shows one Embodiment of a belt cleaning apparatus. FIG. 5 is a perspective view showing a state where the bar brush is set in a closed posture in the belt cleaning device shown in FIG. 4. FIG. 5 is a perspective view showing a state in which the bar brush is set to an open posture in the belt cleaning device shown in FIG. 4. It is the VII-VII sectional view taken on the line of FIG.

10 Printer (image forming device)
11 Apparatus Main Body 111 Paper Conveying Path 112 Conveying Roller Pair 113 Transfer Roller 114 Paper Discharge Conveying Path 12 Image Forming Unit 12C Cyan Unit 12K Black Unit 12M Magenta Unit 12Y Yellow Unit 121 Photosensitive Drum 122 Developing Device 123 Charging Device 124 Exposure device 125 Transfer belt (image carrier)
125a driving roller 125b driven roller 125c tension roller 126 transfer roller 127 drum cleaning device 13 fixing unit 131 heating roller 132 fixing roller 133 fixing belt 134 pressure roller 14 paper storage unit 141 manual tray 142 paper tray 143 pickup roller 15 paper discharge unit 151 Output tray 20 Intermediate transfer unit 21 Unit frame 211 Front frame 212 Rear frame 213 Installation frame 22 Drive roller shaft 221 Drive gear 23 Drive shaft 24 Tension roller shaft 30 Belt cleaning device 31 Casing 310 Collected toner storage space 32 Front plate 321 Fit Groove 33 Rear plate 331 Insertion groove 34 Bottom plate 35 Right plate 36 Top plate 361 Inclined plate 40 Main cleaning member 41 Fur brush 411 Shear shaft 412 Fur brush body 413 Brush shaft side gear 42 Collection roller 421 Collection roller shaft 422 Collection roller body 423 Collection roller shaft side gear 43 Blade 50 Auxiliary cleaning member 51 Ladder-shaped frame 511 Columnar frame 512 Square material frame 513 Construction plate 513a Cylindrical body 513b Screw hole 52 Brush support bracket 521 Support plate 522 Edge weir 523 Bracket 523a Projection piece 523b Piece 523c Through hole 524 Extension plate 53 Bar brush 531 Base sheet 532 Brush hair 54 Double-sided tape (insulating material) 60 Power supply device P Paper P1 Paper bundle

Claims (2)

An image carrier that moves in a predetermined direction and has an image bearing surface on which a toner image is carried;
A casing,
A main cleaning member disposed in the casing and disposed opposite the image bearing surface to electrically remove residual toner remaining on the image bearing surface;
A power supply device that applies a bias having a polarity opposite to that of the residual toner to the main cleaning member;
An auxiliary cleaning member that is provided immediately upstream of the main cleaning member in the moving direction of the image carrying surface and is in contact with the image carrying surface;
The auxiliary cleaning member is
A shaft portion fitted into the casing;
A frame that is rotatable around the shaft portion;
Brush bristles disposed on the frame, having the same charging polarity as the charging polarity of the image carrier, and being brought into contact with the image carrying surface by the weight of the auxiliary cleaning member;
Have,
The main cleaning member is exposed to the outside of the casing in a state where the frame of the auxiliary cleaning member is rotated around the shaft portion and the brush bristles are separated from the surface of the image carrier. An image forming apparatus. 2. The image forming apparatus according to claim 1, wherein an electrical resistance value of each of the brush hairs is set to 1 × 10 ¹⁰ Ω or less.

Images