JP2015187673A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that removes a residual toner from the surface of an image carrier and extends the life of a cleaning device.SOLUTION: An image forming apparatus of the present invention includes an intermediate transfer belt 23, a cleaning device 11 that includes a bar brush 41 and a bias brush 42, a moving device 47 that moves the bar brush 41 between a first position P1 for separating the bar brush 41 from the intermediate transfer belt 23 and a second position P2 for bringing the bar brush 41 into contact with the intermediate transfer belt 23. The moving device 47 includes an urging member 60, a contact member 61 that has the other end in contact with a rotation shaft part 21b, and a connection member 62 that connects the contact member 61 with the bar brush 41. When the reaction force of the bias brush 42 is larger than the urging force of the urging member 60, the contact member 61 is pressed by the rotation shaft part 21b to hold the bar brush 41 at the first position P1, and when the reaction force is reduced to be the urging force or less, the contact member 61 rotates to move the bar brush 41 to the second position P2.

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In order to form a color image, an electrophotographic image forming apparatus employing an intermediate transfer method is widely known. An intermediate transfer type image forming apparatus includes a plurality of photosensitive members that carry toner images of a plurality of colors, an intermediate transfer belt as an image carrier that contacts the plurality of photosensitive members, and a toner image on the photosensitive member as an intermediate transfer belt. A primary transfer portion that transfers to the surface, a secondary transfer portion that collectively transfers a color toner image on the intermediate transfer belt to a sheet, and a toner that has not been completely transferred to the sheet (hereinafter referred to as “residual toner”). ) From the surface of the intermediate transfer belt.

  In a cleaning device for an intermediate transfer type image forming apparatus, a bias cleaning method is widely adopted. The bias cleaning method is a method in which residual toner is removed from the surface of the intermediate transfer belt by a cleaning member to which a bias having a polarity opposite to the charging polarity of the residual toner is applied. Note that the intermediate transfer belt includes a plurality of layers including an elastic layer in order to extend the life and improve the quality of an output image.

  By the way, the intermediate transfer type image forming apparatus has excellent productivity because it batch-transfers color toner images onto a sheet, but the toner image of each color is superimposed on the surface of the intermediate transfer belt. There was a tendency for the amount of residual toner to increase. In addition, when a color image is formed by superimposing toner, the amount of charge of the superimposed toner increases, so that the voltage required for transfer also increases. Further, due to the deterioration of the developer, the residual toner may have a polarity opposite to that at the time of development or may be nearly nonpolar. When these factors overlap, the cleaning device using only the cleaning member described above may not be able to effectively remove residual toner from the surface of the intermediate transfer belt.

  Therefore, a cleaning device for effectively removing residual toner from the intermediate transfer belt has been proposed. For example, Patent Document 1 discloses a cleaning device including a cleaning member that contacts an intermediate transfer belt, and an auxiliary cleaning member that contacts the intermediate transfer belt on the upstream side of the cleaning member. The auxiliary cleaning member frictionally charges the residual toner to a predetermined polarity (polarity during development). For this reason, the cleaning member can easily remove residual toner from the surface of the intermediate transfer belt by a bias cleaning method.

JP 2012-053175 A

  In recent years, low-quality paper such as recycled paper is sometimes used from the viewpoint of cost reduction and resource reuse. Further, in a region where paper is manufactured by a manufacturing facility with insufficient performance, it may be necessary to use low-quality paper.

  Such low-quality paper may contain a large amount of talc or calcium carbonate as a surface treatment agent or filler. When the image forming operation is repeated on such a sheet, paper dust containing talc and calcium carbonate adheres to the surface of the image carrier. In particular, the low-quality paper as described above is used before the whitening of the image carrier (mainly a phenomenon in which whitening occurs due to accumulation of external additives on the surface of the image carrier) reaches a certain level. A large amount of paper powder containing talc and calcium carbonate adheres to the surface of the image carrier. When the paper dust on the image carrier is frictionally charged by the auxiliary cleaning member, the cleaning dust or the auxiliary cleaning member is clogged with paper dust. For this reason, the function of the auxiliary cleaning member that frictionally charges the residual toner is deteriorated.

  Further, since the cleaning member contracts as it continues to be used, the function of the cleaning member that mechanically scrapes the residual toner also deteriorates. The deterioration of the function of the cleaning member hindered good image formation over a long period of time. In addition, the surface layer of the image carrier may be scraped by the hardened paper powder clogged in the auxiliary cleaning member. In this case, there is a problem that the friction coefficient of the shaved portion is increased and the secondary transfer performance of the image carrier is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image forming apparatus for effectively removing residual toner from the surface of an image carrier and extending the life of a cleaning apparatus. And

  In order to achieve the above object, an image forming apparatus of the present invention comprises an image carrier that rotates to carry a toner image, an auxiliary cleaning member that charges residual toner adhering to the surface of the image carrier, and the residual A cleaning device including a cleaning member to which a bias having a polarity opposite to that of the toner is applied, and the auxiliary cleaning member being spaced apart from the surface of the image carrier or contacting the surface of the image carrier with a first pressure. A moving device that moves between the first position and a second position that is brought into contact with the surface of the image carrier with a second pressure that is greater than the first pressure, and the auxiliary cleaning member is the cleaning member The cleaning member is disposed upstream of the rotation direction of the image carrier, and the center of the cleaning member is positioned below the rotation center of the rotation shaft portion of the image carrier. The moving device includes a biasing member that biases the cleaning member into contact with the surface of the image carrier, one end portion rotatably connected to the cleaning member, and the other end portion rotated. A contact member that contacts the shaft, and a connecting member that connects between the contact member and the auxiliary cleaning member, and the cleaning member and the image based on an elastic force of the cleaning member. When the reaction force acting with the carrier is larger than the urging force of the urging member, the abutting member is pressed against the rotating shaft portion by the reaction force so as not to rotate, and via the connecting member. When the auxiliary cleaning member is held at the first position and the reaction force becomes equal to or less than the urging force of the urging member as the whitening of the surface of the image carrier progresses, the contact member Rotate towards Through Rutotomoni the connecting member and moving the auxiliary cleaning member in the second position from the first position.

  According to this configuration, the cleaning member receives a reaction force from the image carrier due to the urging force received from the urging member and its own elastic force. For example, in the case of a new cleaning member that does not wear, the elastic force of the cleaning member is strong, so this reaction force is greater than the biasing force of the biasing member. In this state, the contact member is held in a state where it is not rotated by being pressed by the rotating shaft portion. At the same time, the auxiliary cleaning member connected to the contact member via the connecting member is held in the first position. That is, in the initial state where the performance of the cleaning member can be ensured, the residual toner is removed from the surface of the image carrier mainly by the function of the cleaning member without actively exerting the function of the auxiliary cleaning member. Further, by holding the auxiliary cleaning member at the first position, the paper dust attached to the surface of the image carrier is not charged by the auxiliary cleaning member (or the charge amount is suppressed). Thereby, clogging of paper dust with respect to the cleaning member and the auxiliary cleaning member can be prevented. That is, the lifetime of the cleaning device can be extended.

  On the other hand, when wear (deterioration) of the cleaning member progresses as the whitening of the surface of the image carrier progresses, the elastic force of the cleaning member becomes weak and the reaction force becomes less than the urging force of the urging member. In this state, since the pressing force of the contact member against the rotation shaft portion decreases, the contact member rotates downward due to its own weight or the weight of the connecting member. In conjunction with the rotation of the contact member, the auxiliary cleaning member connected to the contact member via the connecting member moves from the first position to the second position. That is, the function of the auxiliary cleaning member is automatically exhibited based on the performance degradation of the cleaning member. Accordingly, the auxiliary cleaning unit frictionally charges the residual toner on the surface of the image carrier to a predetermined polarity (polarity during development), and the cleaning member can effectively remove the charged residual toner. As described above, good image formation can be performed over a long period of time. Note that if the whitening of the surface of the image carrier has reached a certain level, paper dust does not easily adhere to the surface of the image carrier. For this reason, the amount of the paper dust that is frictionally charged by the auxiliary cleaning member is small, and it is difficult to cause a problem that the cleaning powder or the auxiliary cleaning member is clogged with paper dust.

  In this case, it is preferable that the moving device further includes a second urging member that urges the auxiliary cleaning member toward the image carrier.

  According to this configuration, the auxiliary cleaning member is urged with a stable pressing force against the surface of the image carrier by the second urging member. Thereby, the auxiliary cleaning member can appropriately charge the residual toner adhering to the surface of the image carrier.

  In this case, the moving device further includes a third urging member that is provided between the rotating shaft portion and the cleaning member and urges the cleaning member toward the image carrier. preferable.

  According to this configuration, the cleaning member is urged with a stable pressing force against the surface of the image carrier by the third urging member. As a result, the cleaning member can appropriately remove the residual toner adhering to the surface of the image carrier.

  In this case, the image forming apparatus further includes a plurality of photoreceptors that carry toner images of different colors, and the image carrier is wound around a plurality of rollers and carries a toner image transferred from the plurality of photoreceptors. The auxiliary cleaning member has charging brush hairs implanted on the lower surface of the base portion, and the cleaning member has removal brush hairs implanted on the outer peripheral surface of the cylindrical body rotating around the axis. It is preferable.

  According to this configuration, the intermediate transfer belt as the image carrier sequentially carries a plurality of toner images having different colors in a superimposed manner. For this reason, the amount of residual toner increases. However, the auxiliary cleaning member moves in the contact / separation direction with respect to the surface of the image carrier in accordance with the wear of the cleaning member. Therefore, each of the cleaning member and the auxiliary cleaning member can continue to exhibit the function of removing the residual toner. Thereby, the lifetime of the cleaning device can be extended.

  According to the present invention, residual toner can be effectively removed from the surface of the image carrier. In addition, the lifetime of the cleaning device can be extended.

1 is a cross-sectional view schematically showing an internal structure of a color printer according to a first embodiment of the present invention. 1 is a block diagram illustrating an electrical configuration of a color printer according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing the color printer cleaning device according to the first embodiment of the present invention, in which the bar brush is in a first position. FIG. 3 is a cross-sectional view schematically showing the color printer cleaning device according to the first embodiment of the present invention, in which the bar brush is in a second position. It is a table | surface which shows the relationship between the performance of the cleaning apparatus of the color printer which concerns on 1st Embodiment of this invention, and the presence or absence of a bar brush. It is sectional drawing which shows typically a part of cleaning apparatus of the color printer which concerns on the modification of 1st Embodiment of this invention. It is sectional drawing which shows typically the cleaning apparatus of the color printer which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows typically the cleaning apparatus of the color printer which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
With reference to FIGS. 1 and 2, the overall configuration of a color printer 1 as an image forming apparatus will be described. FIG. 1 is a cross-sectional view schematically showing the internal structure of the color printer 1. FIG. 2 is a block diagram showing an electrical configuration of the color printer 1. In the description of the present embodiment, for the sake of convenience, the front side of the sheet of FIG. 1 is defined as the front side (front side) of the color printer 1.

  As shown in FIG. 1, the color printer 1 includes a substantially box-shaped apparatus main body 2, a paper feed cassette 3 provided at the lower part of the apparatus main body 2, a paper discharge tray 4 provided at the upper part of the apparatus main body 2, It has.

  The color printer 1 includes an intermediate transfer unit 10, a cleaning device 11, a paper feeding unit 12, an image forming unit 13, a fixing device 14, and a control device 15 in the apparatus main body 2.

  The intermediate transfer unit 10 is provided at a substantially central portion inside the apparatus main body 2. The cleaning device 11 is disposed on the left side of the intermediate transfer unit 10. The paper feed unit 12 is provided near the right side of the paper feed cassette 3 in order to supply the paper S in the paper feed cassette 3 to the transport path 16. The image forming unit 13 is provided below the intermediate transfer unit 10. The fixing device 14 is provided on the downstream side of the conveyance path 16. The control device 15 is provided for comprehensively controlling each component of the color printer 1.

  The intermediate transfer unit 10 includes a driving roller 20 provided on one end side (right end side) in the longitudinal direction, a driven roller 21 provided on the other end side (left end side) in the longitudinal direction, a lower left side of the driving roller 20, and a driven roller 21. A pair of tension rollers 22 provided on the lower right side and an intermediate transfer belt 23 as an image carrier that is wound around the rollers 20, 21, and 22 are provided.

  The drive roller 20 is connected to the belt motor 20a via a gear train (not shown) (see FIG. 2). The driven roller 21 is urged leftward by a coil spring 21a (see FIG. 3). The intermediate transfer belt 23 is given a predetermined tension by a driven roller 21 and a pair of tension rollers 22. The intermediate transfer belt 23 rotates counterclockwise in FIG. 1 by driving the belt motor 20a.

  The intermediate transfer belt 23 includes, for example, an elastic layer provided on the outer peripheral surface of the base material layer, and a release layer provided so as to cover the elastic layer. The base material layer is made of, for example, polyvinylidene fluoride or polyimide resin. The elastic layer is made of, for example, hydrin rubber, chloroprene rubber, polyurethane rubber, or the like. The release layer is made of, for example, acrylic, silicon, fluorine resin, or the like.

  The cleaning device 11 removes residual toner adhering to the surface of the intermediate transfer belt 23. The details of the cleaning device 11 will be described later.

  The image forming unit 13 is configured to form an image using four color (yellow, magenta, cyan, black) supply developers stored in four toner containers 24. The image forming unit 13 includes four drum units 25 and four exposure units 26. The developer stored in the toner container 24 is a so-called two-component developer containing toner and a carrier.

  The four drum units 25 are juxtaposed in the left-right direction below the intermediate transfer belt 23. Since the four drum units 25 have the same configuration, only one drum unit 25 is illustrated in the following description.

  The drum unit 25 includes a photosensitive drum 30 rotatably supported, a charging device 31 arranged around the photosensitive drum 30 in the order of the transfer process, a developing device 32, a primary transfer roller 33, and a drum cleaning device 34. , Including.

  A photosensitive drum 30 as a photosensitive member is disposed so as to face the primary transfer roller 33 from below with the intermediate transfer belt 23 interposed therebetween. The photosensitive drum 30 is in contact with the surface of the intermediate transfer belt 23. The photosensitive drum 30 is connected to a drum motor 30a through a gear train (not shown) (see FIG. 2). A secondary transfer roller 35 is disposed on the right side of the drive roller 20 so as to face the intermediate transfer belt 23. The secondary transfer roller 35 forms a secondary transfer nip portion 35 a with the intermediate transfer belt 23.

  As shown in FIG. 2, the control device 15 includes a CPU 15a (Central Processing Unit), a memory 15b, a bus 15c, and an interface 15d.

  The CPU 15a executes arithmetic processing according to each program and the like. The memory 15b includes a ROM (Read Only Memory), a RAM (Random Access Memory), a flash memory, and the like. The memory 15b stores programs used for arithmetic processing by the CPU 15a, rated values of various biases, and the like. The memory 15b temporarily stores calculation results of the CPU 15a. The bus 15c connects the CPU 15a, the memory 15b, and the interface 15d. Various control objects such as a belt motor 20a and a drum motor 30a are electrically connected to the interface 15d. In addition, although illustration is abbreviate | omitted, drive devices, such as a motor, a power supply, etc. are connected to the interface 15d in addition, and it is suitably controlled by CPU15a.

  Here, the operation of the color printer 1 will be described. When the color printer 1 is powered on, the control device 15 executes initialization of various parameters. When image data is input from a personal computer or the like connected to the color printer 1 and an instruction to start printing is given, the control device 15 executes an image forming process as follows.

  Each exposure unit 26 performs exposure corresponding to image data (see the broken line arrow in FIG. 1) on the surface of each photosensitive drum 30 charged to a predetermined potential by each charging device 31 to form an electrostatic latent image. . Each developing device 32 develops the electrostatic latent image into a toner image with the toner supplied from the toner container 24. That is, the four photosensitive drums 30 carry toner images having different colors (for example, four color toner images). Each primary transfer roller 33 primarily transfers a toner image from the photosensitive drum 30 to the intermediate transfer belt 23 by applying a primary transfer bias. The intermediate transfer belt 23 rotates and sequentially supports toner images of respective colors that are primarily transferred from the four photosensitive drums 30. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 23.

  On the other hand, the paper S supplied from the paper feed cassette 3 is transported through the transport path 16 and passes through the secondary transfer nip portion 35a. The secondary transfer roller 35 transfers the full-color toner image onto the paper S by the applied secondary transfer bias. The fixing device 14 fixes the toner image on the paper S. The paper S after the fixing process is discharged to the paper discharge tray 4. The drum cleaning device 34 removes the toner remaining on the surface of the photosensitive drum 30 after the transfer.

  Next, the cleaning device 11 will be described with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view schematically showing the cleaning device 11 and shows a state where the bar brush 41 is in the first position P1. FIG. 4 is a cross-sectional view schematically showing the cleaning device 11 and shows a state where the bar brush 41 is in the second position P2.

  As shown in FIG. 3, the cleaning device 11 includes a casing 40, a bar brush 41, a bias brush 42, a collection roller 43, a blade 44, a regulation sheet 45, a collection screw 46, and a moving device 47. It is configured to include.

  The casing 40 is formed in a substantially box shape that opens the right side surface. The upper part of the casing 40 is covered with a lid (not shown) that can be opened and closed. For example, the operator can perform maintenance and the like inside the casing 40 by opening the lid.

  The bar brush 41 as an auxiliary cleaning member is disposed upstream of the bias brush 42 in the rotation direction of the intermediate transfer belt 23. The bar brush 41 is disposed above the driven roller 21 with the intermediate transfer belt 23 interposed therebetween.

  The bar brush 41 includes a base portion 50 that extends in the front-rear direction, and a plurality of charging brush hairs 51 that are implanted on the lower surface of the base portion 50.

  The base part 50 is made of, for example, a synthetic resin material. The charging brush bristles 51 are made of, for example, a polyester or acrylic insulating thread. The charging brush bristles 51 are preferably located on the opposite side of the charging polarity of the toner in a charging series. For example, when the toner is a positively charged toner, it is preferable that the charging brush bristles 51 are positioned on the minus side of the toner in a charging series. As a result, the bar brush 41 charges the residual toner adhering to the surface of the intermediate transfer belt 23. The charging brush bristles 51 are not limited to insulating yarns. The charging brush bristles 51 may be made of, for example, a conductive yarn containing carbon. In this case, the thickness of the conductive yarn is preferably 2 denier or more.

  The bias brush 42 as a cleaning member is disposed to face the lower left side of the driven roller 21 with the intermediate transfer belt 23 interposed therebetween. The bias brush 42 is disposed such that its center C1 is positioned below the rotation center C2 of the driven roller 21 that supports the intermediate transfer belt 23 (see the two-dot chain line in FIG. 3).

  The bias brush 42 includes a cylindrical body 53 that is provided around the brush shaft 52 and a plurality of removal brush hairs 54 that are provided on the outer peripheral surface of the cylindrical body 53.

  The brush shaft 52 extends in the front-rear direction and is rotatably supported on both front and rear walls of the casing 40. The cylinder 53 is press-fitted and fixed to the outer peripheral surface of the brush shaft 52. The removal brush bristles 54 are made of, for example, a polyester, nylon, or acrylic conductive yarn. The tip of the removal brush bristles 54 is in contact with the surface of the intermediate transfer belt 23. The rigidity of the removal brush bristles 54 is preferably set lower (smaller) than the rigidity of the charging brush bristles 51 of the bar brush 41.

  The bias brush 42 is electrically connected to the power supply device 42a (see FIG. 2). The power supply device 42a is electrically connected to the interface 15d (see FIG. 2). A bias having a polarity opposite to that of the residual toner is applied to the bias brush 42 from a power supply device 42 a controlled by the control device 15.

  The collection roller 43 is disposed on the upper left side of the bias brush 42. The center C3 of the collection roller 43 is disposed at substantially the same position as the rotation center C2 of the driven roller 21. The collection roller 43 extends in the front-rear direction and is rotatably supported on both front and rear walls of the casing 40. The surface layer portion of the collection roller 43 is made of, for example, rubber or soft synthetic resin. The outer peripheral surface of the collection roller 43 is in contact with the removal brush bristles 54 of the bias brush 42.

  The blade 44 is formed in a plate shape by synthetic resin, for example. The blade 44 is disposed on the upper left side of the collection roller 43. The proximal end portion of the blade 44 is attached to the casing 40 via a fixture 44a. The tip of the blade 44 is in contact with the outer peripheral surface of the collection roller 43.

  The regulation sheet 45 is formed in a film shape with, for example, a synthetic resin. The restriction sheet 45 is disposed on the lower left side of the collection roller 43. The base end portion of the restriction sheet 45 is attached to the sheet attachment portion 40 a of the casing 40. The front end of the regulation sheet 45 is in contact with the outer peripheral surface of the collection roller 43. The restriction sheet 45 divides the inside of the casing 40 and constitutes a screw accommodating chamber 40b on the left side.

  The collection screw 46 has a helical screw blade on the outer peripheral surface of the rotating shaft extending in the front-rear direction. The recovery screw 46 is housed in the screw housing chamber 40 b and is rotatably supported on both front and rear walls of the casing 40. The bias brush 42, the collection roller 43, and the collection screw 46 are connected to the drive motor 11a via a gear train (not shown) (see FIG. 2). The drive motor 11a is electrically connected to the interface 15d (see FIG. 2).

  The moving device 47 has a first position P1 (see FIG. 3) for separating the bar brush 41 from the surface of the intermediate transfer belt 23 and a second position P2 (see FIG. 4) for contacting the surface of the intermediate transfer belt 23 with a predetermined pressure. ) And is provided to move between. The moving device 47 includes an urging member 60, a contact member 61, and a connecting member 62. The moving device 47 is provided on the front side in the casing 40, for example.

  The biasing member 60 is configured by a so-called coil spring. The left end portion of the urging member 60 is connected to the seat attachment portion 40 a of the casing 40. The right end of the urging member 60 is connected to a frame (not shown) that supports the bias brush 42. The urging member 60 urges the bias brush 42 to contact the surface of the intermediate transfer belt 23 with the sheet attachment portion 40a as a receiving portion. The right end portion of the urging member 60 may be connected to the left end portion of the contact member 61.

  The contact member 61 is formed in a plate shape from a synthetic resin material having excellent slidability. The contact member 61 is formed in a substantially hook shape in which a right end portion is bent downward in a front view. The contact member 61 has a left end portion (one end portion) rotatably connected to the bias brush 42 and a right end portion (the other end portion) connected to the rotation shaft portion 21 b of the driven roller 21 serving as the rotation shaft portion of the intermediate transfer belt 23. It is in contact. Specifically, the contact member 61 rotates in the vertical direction about a rotation shaft portion 61 a that is coaxial with the brush shaft 52 of the bias brush 42. The contact member 61 has a contact surface 61 b that contacts the outer peripheral surface of the rotation shaft portion 21 b of the driven roller 21. The contact surface 61b is formed in a substantially arc shape when viewed from the front.

  The connecting member 62 connects the contact member 61 and the bar brush 41. The connecting member 62 has an arm part 63 and a brush support part 64.

  The arm part 63 is formed in a substantially rod shape extending in the vertical direction with metal or the like. The lower end portion of the arm portion 63 is rotatably connected to the right hook portion of the contact member 61. The arm part 63 extends from the lower end part to the upper left.

  The brush support portion 64 is formed in a substantially bar shape that extends in the left-right direction with metal or the like. The right end portion of the brush support portion 64 is supported so as to be rotatable with respect to the casing 40 using the swing shaft portion 65 as a fulcrum. The intermediate portion of the brush support portion 64 supports the upper surface of the base portion 50 of the bar brush 41. The left end portion of the brush support portion 64 is rotatably connected to the upper end portion of the arm portion 63. That is, the contact member 61, the arm part 63, and the brush support part 64 constitute a link mechanism. As a result, the bar brush 41 swings in the vertical direction together with the connecting member 62 (brush support portion 64). The angle formed by the arm part 63 and the brush support part 64 is an acute angle.

  Next, the operation (residual toner removing process) of the cleaning device 11 will be described. In the following description, it is assumed that the residual toner attached to the surface of the intermediate transfer belt 23 is mainly positively charged. The power supply device 42a is controlled by the control device 15 to apply a negative polarity (opposite polarity to the residual toner) bias to the bias brush 42.

  As shown in FIG. 3, the removal brush bristles 54 of the bias brush 42 are in contact with the surface of the intermediate transfer belt 23. Therefore, the bias brush 42 receives the reaction force B from the intermediate transfer belt 23 by the urging force A received from the urging member 60 and its own elastic force. That is, the reaction force B acts between the bias brush 42 and the intermediate transfer belt 23 based on the elastic force of the bias brush 42 (removal brush bristles 54). When the reaction force B is larger than the urging force A of the urging member 60, the contact member 61 is pressed by the reaction force B against the rotation shaft portion 21 b of the driven roller 21 so as not to rotate and via the connecting member 62. The bar brush 41 is held at the first position P1.

  For example, in the case of a new bias brush 42 with no wear, since the elastic force of the bias brush 42 is strong (large), the reaction force B is larger than the biasing force A of the biasing member 60. In this state (A <B), the contact surface 61b of the contact member 61 is held in a state in which it does not rotate by being pressed by the peripheral surface of the rotation shaft portion 21b of the driven roller 21. At the same time, the bar brush 41 connected to the contact member 61 via the connecting member 62 is held at the first position P1. That is, the bar brush 41 is spaced upward from the surface of the intermediate transfer belt 23.

  When the image forming process is executed in this state, the removal brush bristles 54 of the bias brush 42 slide relatively on the surface of the rotating intermediate transfer belt 23. The removal brush bristles 54 of the bias brush 42 adsorb residual toner by an electrostatic adsorbing force acting between the residual toner adhering to the surface of the intermediate transfer belt 23. As a result, the residual toner is removed from the surface of the intermediate transfer belt 23.

  The collection roller 43 receives the residual toner that has moved to the removal brush bristles 54 of the bias brush 42. The blade 44 scrapes off the residual toner that has moved to the collection roller 43. The collection screw 46 conveys the scraped residual toner toward a collection box (not shown). Residual toner is accumulated in the collection box.

  By the way, the surface of the intermediate transfer belt 23 is whitened (a phenomenon in which the surface gradually becomes white due to deposits) by repeating the image forming process. Further, since the removal brush bristles 54 of the bias brush 42 are in sliding contact with the surface of the intermediate transfer belt 23, they are worn by repeated residual toner removal processing. When the wear (deterioration) of the bias brush 42 proceeds with the progress of whitening of the surface of the intermediate transfer belt 23, the elastic force of the bias brush 42 becomes weak. Then, the reaction force B becomes equal to or less than the urging force A of the urging member 60 (A ≧ B). In addition, the outer diameter of the bias brush 42 is slightly smaller than when it is new.

  As shown in FIG. 4, when the reaction force B becomes equal to or less than the urging force A of the urging member 60, the abutting member 61 rotates downward and moves the bar brush 41 to the first via the connecting member 62. Move from the position P1 to the second position P2. That is, when the pressing force of the contact surface 61b of the contact member 61 against the rotation shaft portion 21b of the driven roller 21 decreases, the contact member 61 uses the rotation shaft portion 61a as a fulcrum according to its own weight or the weight of the connecting member 62. As below (clockwise in FIG. 4). In conjunction with the rotation of the contact member 61, the bar brush 41 connected to the contact member 61 via the connecting member 62 moves from the first position P1 to the second position P2. That is, the connecting member 62 (brush support portion 64) rotates counterclockwise in FIG. 4 with the swing shaft portion 65 as a fulcrum. As a result, the bar brush 41 (charging brush bristles 51) contacts the surface of the intermediate transfer belt 23 from above.

  When the image forming process is executed in this state, the charging brush bristles 51 of the bar brush 41 slide relatively on the surface of the rotating intermediate transfer belt 23. The charging brush bristles 51 of the bar brush 41 come into contact with, for example, a residual toner charged to a negative polarity or a residual toner whose polarity is almost zero, and charge the residual toner to a positive polarity.

  Thereafter, as already described, the bias brush 42 (removal brush bristles 54) adsorbs the positively charged residual toner. That is, residual toner is removed from the surface of the intermediate transfer belt 23. The residual toner is accumulated in the collection box by the action of the collection roller 43, the blade 44 and the collection screw 46.

  Next, the relationship between the performance of the cleaning device 11 of the color printer 1 according to the first embodiment and the presence or absence of the bar brush 41 will be described with reference to FIG.

  Here, terms and the like shown in FIG. 5 will be described. “When there is a bar brush” refers to a case where the residual toner removal process is executed using the bar brush 41 and the bias brush 42. “When there is no bar brush” refers to the case where the residual toner removal process is executed using only the bias brush 42. The “cleaning current” refers to a current supplied from the power supply device 42a to the bias brush 42. “Slight whitening”, “Now whitening”, and “High whitening” indicate the degree of whitening of the surface of the intermediate transfer belt 23. “O” means that the performance of the cleaning device 11 is sufficiently exhibited, and a part of the image transferred to the paper S does not remain on the next paper S. “X” means that the performance of the cleaning device 11 is not sufficiently exhibited and a part of the image transferred to the paper S remains on the next paper S.

  Referring to the start of use of the intermediate transfer belt 23 (when whitening has not occurred), the cleaning device 11 exhibits sufficient performance regardless of the presence or absence of the bar brush 41. On the other hand, when the surface of the intermediate transfer belt 23 is whitened, the cleaning device 11 performs better in the “when the bar brush is present” than in the “when there is no bar brush”. Therefore, it was confirmed that a good residual toner removal process can be performed by using the bias brush 42 and the bar brush 41 after whitening occurs.

  According to the color printer 1 according to the first embodiment described above, in the initial state where the performance of the bias brush 42 can be ensured (for example, when it is new), the function of the bar brush 41 is not exerted actively, and the bias is mainly performed. Residual toner is removed from the surface of the intermediate transfer belt 23 by the function of the brush 42. Further, by holding the bar brush 41 at the first position P1, paper dust attached to the surface of the intermediate transfer belt 23 is not charged by the bar brush 41. Thereby, clogging of paper dust with respect to the bias brush 42 and the bar brush 41 can be prevented. That is, the lifetime of the cleaning device 11 can be extended.

  On the other hand, the function of the bar brush 41 is automatically exhibited based on the performance degradation of the bias brush 42. As a result, the bar brush 41 frictionally charges the residual toner on the surface of the intermediate transfer belt 23 to a predetermined polarity (polarity during development), and the bias brush 42 can effectively remove the charged residual toner. As described above, good image formation can be performed over a long period of time. Note that if the whitening of the surface of the intermediate transfer belt 23 reaches a certain level, paper dust does not easily adhere to the surface of the intermediate transfer belt 23. For this reason, the amount of paper powder frictionally charged by the bar brush 41 is small, and it is difficult for the bias brush 42 (removal brush hair 54) and the bar brush 41 (charged brush hair 51) to be clogged with paper powder.

  In addition, paper dust is unlikely to clog the brush bristles 51, 54, so paper dust is unlikely to collect on the outer peripheral surface of the collection roller 43. For this reason, clogging of paper dust between the collection roller 43 and the regulation sheet 45 can be prevented. Therefore, it is possible to prevent the leading end portion of the regulation sheet 45 from floating from the outer peripheral surface of the collection roller 43. Thereby, it is possible to suppress a problem that the residual toner returns from the screw storage chamber 40b to the space on the bias brush 42 side.

  Further, according to the color printer 1 according to the first embodiment, the intermediate transfer belt 23 sequentially carries a plurality of toner images having different colors. For this reason, the amount of residual toner increases. However, the bar brush 41 moves in the contact / separation direction with respect to the surface of the intermediate transfer belt 23 according to wear of the bias brush 42. For this reason, each of the bias brush 42 and the bar brush 41 can continue to exhibit the residual toner removing function. Thereby, lifetime improvement of the cleaning apparatus 11 can be achieved.

  Note that talc contained in paper powder has a property of being easily charged negatively, and calcium carbonate contained in paper powder has a property of being easily charged positively. For this reason, when the bar brush 41 is brought into contact with the surface of the intermediate transfer belt 23 before the whitening of the intermediate transfer belt 23 proceeds, talc or calcium carbonate adheres to the charging brush hairs 51 regardless of the charging polarity of the bar brush 41. . On the other hand, the bar brush 41 described above is separated from the surface of the intermediate transfer belt 23 in a state before the whitening progresses, so that the paper dust is effectively prevented from adhering to the charging brush bristles 51.

(Modification of the first embodiment)
In the color printer 1 (cleaning device 11) according to the first embodiment described above, the bar brush 41 at the first position P1 is separated from the surface of the intermediate transfer belt 23, but the present invention is not limited to this.

  As shown in FIG. 6, the moving device 47 includes a first position P1 where the bar brush 41 is brought into contact with the surface of the intermediate transfer belt 23 with a first pressure, and a second position larger than the first pressure on the surface of the intermediate transfer belt 23. You may move between the 2nd position P2 made to contact with pressure. According to this configuration, by holding the bar brush 41 at the first position P1, the amount of charge of the paper dust attached to the surface of the intermediate transfer belt 23 is suppressed. Thereby, the same operation and effect as the color printer 1 according to the first embodiment can be obtained.

(Second Embodiment)
Next, a color printer 1 according to the second embodiment will be described with reference to FIG. FIG. 7 is a cross-sectional view schematically showing the cleaning device 11. In addition, about the structure similar to the color printer 1 which concerns on above-mentioned 1st Embodiment (a modification is included), the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The moving device 47 of the cleaning device 11 provided in the color printer 1 according to the second embodiment further includes a second urging member 70 that urges the bar brush 41 toward the intermediate transfer belt 23.

  The second urging member 70 is configured by a so-called coil spring. The second urging member 70 has an upper end connected to the top surface 40 c of the casing 40 and a lower end connected to the left end of the brush support portion 64 of the connecting member 62. The second urging member 70 urges the bar brush 41 downward via the brush support portion 64 as a receiving portion of the top surface 40 c of the casing 40. The urging force of the second urging member 70 is set to be smaller (weaker) than the pressing force of the contact member 61 urged by the urging member 60 to the rotating shaft portion 21b.

  According to the color printer 1 according to the second embodiment described above, the bar brush 41 is urged with a stable pressing force against the surface of the intermediate transfer belt 23 by the second urging member 70. Thereby, the bar brush 41 can appropriately charge the residual toner adhering to the surface of the intermediate transfer belt 23. Moreover, according to this structure, the effect | action and effect similar to the color printer 1 which concerns on 1st Embodiment can be acquired. Note that the second urging member 70 can be suitably used when the bar brush 41 described in the modification of the first embodiment is brought into contact with the intermediate transfer belt 23 with the first pressure.

(Third embodiment)
Next, a color printer 1 according to the third embodiment will be described with reference to FIG. FIG. 8 is a cross-sectional view schematically showing the cleaning device 11. In addition, about the structure similar to the color printer 1 which concerns on above-mentioned 1st Embodiment (a modification is included), the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The moving device 47 of the cleaning device 11 provided in the color printer 1 according to the third embodiment is installed between the rotating shaft portion 21 b of the driven roller 21 and the bias brush 42, with the bias brush 42 facing the intermediate transfer belt 23. A third urging member 80 for urging is further provided.

  The third urging member 80 is configured by a so-called coil spring. The third urging member 80 has a left end connected to the brush shaft 52 of the bias brush 42 and a right end connected to the axial center of the rotating shaft 21 b of the driven roller 21. The left end portion of the third urging member 80 may be connected to the brush shaft 52 via the contact member 61.

  The total value (A + N) of the urging force A of the urging member 60 and the urging force N of the third urging member 80 (more precisely, the horizontal component of the urging force) is the bias brush 42 in the initial state (when new). Is set to be smaller (weaker) than the reaction force B. In this state (A + N <B), the contact member 61 is held in a non-rotatable manner on the peripheral surface of the rotating shaft portion 21b, and the bar brush 41 (the connecting member 62) is held at the first position P1 (FIG. 8). See solid and dashed lines). On the other hand, the contact member 61 rotates downward in a state where the wear of the bias brush 42 has progressed (A + N ≦ B). That is, the bar brush 41 (the connecting member 62) moves from the first position P1 to the second position P2 (see the two-dot chain line in FIG. 8).

  According to the color printer 1 according to the third embodiment described above, the bias brush 42 is urged with a stable pressing force against the surface of the intermediate transfer belt 23 by the third urging member 80. Thereby, the bias brush 42 can appropriately remove the residual toner adhering to the surface of the intermediate transfer belt 23. Moreover, according to this structure, the effect | action and effect similar to the color printer 1 which concerns on 1st Embodiment can be acquired. Note that the configuration (features) described in the modification of the first embodiment and the second embodiment may be applied to the color printer 1 (cleaning device 11) according to the third embodiment.

  Although the moving device 47 of the cleaning device 11 provided in the color printer 1 according to the first to third embodiments is provided on the front side, the present invention is not limited to this. For example, the moving device 47 may be provided on the back side, or may be provided on both the front and rear sides.

  The color printer 1 according to the first to third embodiments uses the intermediate transfer belt 23 as an image carrier, but the present invention is not limited to this. For example, instead of the intermediate transfer belt 23, a photosensitive drum may be used as the image carrier.

  In the description of each embodiment, the case where the present invention is applied to the color printer 1 is shown as an example. However, the present invention is not limited thereto, and the present invention is applied to, for example, a monochrome printer, a copying machine, a facsimile machine, or a multifunction machine. May be.

  The above description of each embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, and may have various technically preferable limitations. The technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. Furthermore, the components in each embodiment of the present invention described above can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of each embodiment of the present invention described above does not limit the contents of the invention described in the claims.

1 Color printer (image forming device)
11 Cleaning device 21b Rotating shaft 23 Intermediate transfer belt (image carrier)
30 Photosensitive drum (photosensitive member)
41 Bar brush (auxiliary cleaning member)
42 Bias brush (cleaning member)
47 Moving Device 50 Base 51 Charging Brush Bristles 52 Brush Shaft 53 Cylinder 54 Removal Brush Bristles 60 Biasing Member 61 Abutting Member 62 Connecting Member 70 Second Biasing Member 80 Third Biasing Member P1 First Position P2 Second position

Claims (4)

An image carrier that rotates and carries a toner image;
A cleaning device comprising: an auxiliary cleaning member for charging residual toner adhering to the surface of the image carrier; and a cleaning member to which a bias having a polarity opposite to that of the residual toner is applied.
A first position where the auxiliary cleaning member is separated from the surface of the image carrier or is brought into contact with the surface of the image carrier with a first pressure, and a second pressure greater than the first pressure on the surface of the image carrier. A second position to be brought into contact with, and a moving device to be moved between,
The auxiliary cleaning member is disposed upstream of the cleaning member in the rotation direction of the image carrier,
The cleaning member is disposed such that the center thereof is located below the rotation center of the rotation shaft portion of the image carrier,
The mobile device is
An urging member that urges the cleaning member to contact the surface of the image carrier;
An abutting member that rotatably connects one end to the cleaning member and contacts the other end to the rotating shaft;
A connecting member that connects between the contact member and the auxiliary cleaning member,
When the reaction force acting between the cleaning member and the image carrier based on the elastic force of the cleaning member is larger than the urging force of the urging member, the contact member cannot be rotated by the reaction force. The auxiliary cleaning member is held in the first position via the connecting member while being pressed by the rotating shaft portion,
When the reaction force becomes equal to or less than the urging force of the urging member as the whitening of the surface of the image carrier progresses, the abutting member rotates downward and the An image forming apparatus, wherein the auxiliary cleaning member is moved from the first position to the second position.   The image forming apparatus according to claim 1, wherein the moving device further includes a second urging member that urges the auxiliary cleaning member toward the image carrier.   The moving device further includes a third urging member that is provided between the rotating shaft portion and the cleaning member and urges the cleaning member toward the image carrier. The image forming apparatus according to claim 1. A plurality of photoconductors carrying toner images of different colors;
The image carrier is an intermediate transfer belt that carries a toner image that is wound around a plurality of rollers and transferred from the plurality of photosensitive members,
The auxiliary cleaning member has charged brush bristles implanted on the lower surface of the base portion,
4. The image forming apparatus according to claim 1, wherein the cleaning member has removal brush bristles planted on an outer peripheral surface of a cylindrical body rotating around an axis. 5.

Images