JP2009217004A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus capable of cleaning an image density detecting means without scratching the transmission part of the image density detecting means. <P>SOLUTION: A printer 10 includes: an intermediate transfer belt 16; an image density detection sensor 44 for detecting the density of an image in the image formation area W1 on the intermediate transfer belt 16; a brush 50 disposed in the non-image formation area on the intermediate transfer belt 16; a contact member 46 for triboelectrically charging the brush 50; a cleaning member 48 for cleaning the brush 50. When the intermediate transfer belt 16 moves, the leading end part of the brush 50 comes into contact with the contact member 46, then the brush is triboelectrically charged. When the charged brush 50 passes through the image density detection sensor 44, the brush attracts fine powder with an electrostatic attraction force in a non-contact state. The fine powder attracted to the brush 50 is scraped by the cleaning member 48. Accordingly, the image density detection sensor 44 is cleaned, without having the transmission plate 54 thereof scratch. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  As a full-color image forming apparatus employing an electrophotographic system, an image holding body that holds a toner image in which an electrostatic latent image is visualized with toner, and an intermediate transfer body on which the toner image formed on the image holding body is transferred And a density control means for controlling the density of the toner image primarily transferred to the intermediate transfer member are known.

  The density control means includes a density sensor that detects the density of a toner image formed in a predetermined pattern at a predetermined location on the intermediate transfer member. The density sensor is composed of a light emitting unit and a light receiving unit. Light emitted from the light emitting unit is reflected by the toner image having the predetermined pattern, and a predetermined voltage is generated when the reflected light enters the light receiving unit. . Then, the density of the toner image on the intermediate transfer member is corrected based on the voltage value of the density sensor.

  In the density sensor, the detection surface through which the emitted light and the reflected light are transmitted is located close to the intermediate transfer member, and the scattered toner easily adheres to the detection surface. For this reason, what provided the cleaning means which removes the stain | pollution | contamination of the detection surface of a density sensor is proposed (for example, refer patent document 1, 2).

In Patent Document 1, cleaning is performed by rubbing the detection surface of an optical sensor with a cleaning brush attached to the surface of a photoconductor as a rotating body. Moreover, in patent document 2, the brush is attached to the belt surface rotationally driven, and the detection surface of a sensor is made to contact a brush and is cleaned.
JP 09-146367 A JP2007-79321A

  In the cleaning means described in Patent Literature 1 and Patent Literature 2, the detection surface is damaged because it contacts the detection surface of the sensor for cleaning.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of cleaning without damaging a transmission part of an image density detecting means.

  An image forming apparatus according to a first aspect of the present invention includes a developer holding member that is rotatably provided and has an image area on which an image formed with a developer is held, and a light emitting unit that emits light toward the image area. And a light receiving portion that receives the reflected light reflected by the image region, and a transmission portion that covers the light emitting portion and the light receiving portion and transmits the emitted light and the reflected light, and is disposed to face the image region. An image density detecting means for detecting an image density based on the amount of reflected light received by the light receiving section; and a position that does not face the image area, and is frictionally charged by the rotation of the developer holding member, and the transmitting section. An adsorbing member that adsorbs dust adhering to the non-contact, a contact member that is brought into contact with the adsorbing member by rotation of the developer holding member and frictionally charges the adsorbing member, and dust adsorbed by the adsorbing means. Sucking It is characterized in that it has a cleaning means for removing from the means.

  The image forming apparatus according to claim 2 of the present invention is characterized in that the suction member is fixed to the outside of the image area of the developer holding member.

  An image forming apparatus according to a third aspect of the present invention is characterized in that the contact member is a housing of the image density detecting means.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus including a guide member that tilts the suction member and brings the suction member closer to the transmission portion.

  In an image forming apparatus according to a fifth aspect of the present invention, the suction member is fixed to the outside of the image area around the transmissive portion, and the contact member is fixed to the developer holding member. It is a feature.

  The image forming apparatus according to claim 6 of the present invention is characterized in that the charging polarity of the adsorption member is opposite to the charging polarity of the developer.

  The image forming apparatus according to claim 7 of the present invention is characterized in that the cleaning means is arranged upstream of the image density detecting means in the rotation direction of the developer holding member.

  According to the first aspect of the present invention, cleaning can be performed without damaging the transmissive portion as compared with the case where dust is removed by contact with the transmissive portion of the image density detecting means.

  According to the second aspect of the present invention, the adsorbing member can pass near the transmission part as compared with the case where the present configuration is not provided.

  The invention of claim 3 can reduce the number of parts as compared with the case where this configuration is not provided.

  According to the invention of claim 4, the adsorption member can be brought closer to the transmission part as compared with the case where this configuration is not provided.

  According to the invention of claim 5, the distance from the transmission part can be made constant as compared with the case where this configuration is not provided.

  According to the sixth aspect of the present invention, a large amount of the developer attached to the transmission part can be removed as compared with the case where this configuration is not provided.

  According to the seventh aspect of the present invention, the fine powder adsorbed on the adsorbing member can be prevented from adhering to the transmission part.

  A first embodiment of an image forming apparatus of the present invention will be described with reference to the drawings.

  FIG. 1 shows a printer 10 as an image forming apparatus. The printer 10 includes development units 12Y, 12M, 12C, and 12K for yellow, magenta, cyan, and black, and photoconductors 14Y, 14M, 14C, and 14K that are arranged in parallel facing the intermediate transfer belt 16. This is a so-called tandem-type full-color printer that superimposes four color toner images while the intermediate transfer belt 16 makes one round.

  The printer 10 is provided with a paper feed tray 18 at the bottom. Recording paper P is stored in the paper feed tray 18, and a paper feed roll 20 is in contact with the leading end of the recording paper P in the transport direction. The recording paper P is fed from the paper feed tray 18 to the downstream side in the transport direction one by one by a paper feed roll 20 and a paper handling means (not shown). Two sets of transport rolls 22 are arranged on the downstream side in the transport direction of the paper feed roll 20, and the recording paper P is transported to the upper transfer unit 24 by the transport force of the transport roll 22.

  The transfer unit 24 includes a belt conveyance roll 26A around which the intermediate transfer belt 16 is wound, and a transfer roll 28 that is in pressure contact with the belt conveyance roll 26A. The intermediate transfer belt 16 is sandwiched between the opposed portions of the belt conveyance roll 26A and the transfer roll 28, and the toner image is transferred from the intermediate transfer belt 16 when the recording paper P passes through the opposed portions.

  A fixing unit 30 is disposed above the transfer unit 24 and downstream in the transport direction. The fixing unit 30 includes a fixing roll 32 that includes a heat source and a pressure roll 34 that is in pressure contact with the fixing roll 32. Here, the toner image on the recording paper P is fixed on the recording paper P as the toner melts and solidifies when it passes through the facing portion between the fixing roll 32 and the pressure roll 34. The recording sheet P on which the fixing is completed is discharged by a discharge roll 36 disposed on the downstream side of the fixing unit 30 in the transport direction.

  Next, the image forming unit 40 that transfers and superimposes toner images from the photoconductors 14Y, 14M, 14C, and 14K to the intermediate transfer belt 16 will be described. Note that when distinguishing each color of yellow, magenta, cyan, and black, Y, M, C, and K are added after the code. However, if there is no need to distinguish each color, Y, M, C, and K are omitted.

  As shown in FIGS. 1, 2A, and 2B, in the image forming unit 40, the intermediate transfer belt 16 includes a belt conveyance roll 26A and a belt conveyance roll 26B disposed below the belt conveyance roll 26A. Are wound around a belt conveyance roll 26C disposed diagonally to the right of the belt conveyance roll 26B and on the opposite side of the conveyance path of the recording paper P.

  The surface of the intermediate transfer belt 16 between the belt conveyance roll 26B and the belt conveyance roll 26C facing diagonally to the left is a transfer surface 16A to which the toner image is transferred from the photoreceptors 14Y, 14M, 14C, and 14K. . As described above, the developing units 12Y, 12M, 12C, and 12K and the photoconductors 14Y, 14M, 14C, and 14K are arranged in parallel on the transfer surface 16A, and the photoconductors 14Y, 14M, 14C, and 14K are arranged. It is in contact with the transfer surface 16A.

  Further, transfer rollers 38Y, 38M, 38C, and 38K for primary transfer of the toner image to the intermediate transfer belt 16 are provided at positions facing the photoconductors 14Y, 14M, 14C, and 14K with the intermediate transfer belt 16 interposed therebetween. ing. A transfer voltage having a polarity opposite to that of the toner is applied to the transfer rolls 38Y, 38M, 38C, and 38K.

  A charging roll 42 for charging the surface of the photoconductor 14 and a developing roll 13 provided in the developing unit 12 are in contact with the outer peripheral surface of the photoconductor 14 in order in the rotation direction. Further, between the charging roll 42 and the developing roll 13, an LED array head 17 that performs line exposure on the outer peripheral surface of the photoreceptor 14 is disposed.

  Here, image formation of the printer 10 will be described.

  First, image data output from an image reading device (not shown) or a personal computer is subjected to predetermined image processing by an image processing device (not shown). The image processing apparatus performs predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing on the input reflectance data. Is given. The image data subjected to the image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the LED array head 17 for each color.

  Each LED array head 17 irradiates each photoconductor 14Y, 14M, 14C, 14K with a light beam according to the color material gradation data. The surfaces of the photoreceptors 14Y, 14M, 14C, and 14K are previously charged with a predetermined potential by the charging roll 42, and the electrostatic latent image is formed by exposing the surface by the light beam and lowering the potential. The formed electrostatic latent images are developed as toner images of respective colors Y, M, C, and K by the developing units 12Y, 12M, 12C, and 12K.

  Subsequently, the toner images formed on the photoreceptors 14Y, 14M, 14C, and 14K are primarily transferred onto the intermediate transfer belt 16 by the transfer rolls 38Y, 38M, 38C, and 38K. The primary transfer is performed by sequentially superimposing the toner images on the surface of the intermediate transfer belt 16. The intermediate transfer belt 16 onto which the toner image has been transferred is conveyed to the transfer unit 24.

  On the other hand, in accordance with the timing at which the toner image is conveyed to the transfer unit 24, a recording paper P having a predetermined size is sent from the paper feed tray 18 to the transfer unit 24. The recording paper P is temporarily stopped before reaching the transfer unit 24, and a registration roll (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 16 holding the toner image. The position and the position of the toner image are aligned.

  In the transfer unit 24, the recording paper P conveyed at the same time is sandwiched between the intermediate transfer belt 16 and the transfer roll 28. At this time, a voltage (secondary transfer bias) having a polarity opposite to the toner charging polarity (minus polarity) is applied to the transfer roll 28, and the unfixed toner image held on the intermediate transfer belt 16 is transferred onto the recording paper P. Electrostatic transfer (secondary transfer) is performed collectively.

  Subsequently, the recording paper P on which the toner image has been electrostatically transferred is conveyed to the fixing unit 30 while being peeled off from the intermediate transfer belt 16 by the transfer roll 28. The unfixed toner image on the recording paper P conveyed to the fixing unit 30 is heated and pressed by the fixing roll 32 and the pressure roll 34 and fixed on the recording paper P. The recording paper P after fixing is discharged out of the printer 10.

  After the transfer to the recording paper P is completed, the residual toner remaining on the intermediate transfer belt 16 is removed from the intermediate transfer belt 16 by a cleaning means such as a brush (not shown). In this way, image formation by the printer 10 is performed.

  Next, the adsorption member, the image density detection unit, the contact member, and the cleaning unit will be described.

  As shown in FIGS. 2A and 2B, the intermediate transfer belt 16 has an image forming area W1 in which a toner image is formed and a toner image on both outer sides of the image forming area W1 in the width direction of the surface. Is formed with a non-image forming area W2 in which is not formed, and is rotated in the direction of arrow A. A brush 50 as an adsorption member is attached to a part of one side of the two non-image forming regions W2.

  The brush 50 has a configuration in which a plurality of fiber bodies are collected and extend from the surface of the intermediate transfer belt 16 in a substantially vertical direction. The fibrous body constituting the brush 50 is made of a material having a charging polarity opposite to the charging polarity of each color toner described above. In this embodiment, as an example, each color toner is made of polyester or the like and has a negative charge polarity, and therefore, the fibrous body of the brush 50 is made of a material having a positive charge polarity.

  Examples of materials that are easily charged on the plus side include glass, nylon, and wool. Here, nylon is used. Note that when a material having a positive charge polarity is used for each color toner, the brush 50 is a material that is easily charged on the negative side. For example, polytetrafluoroethylene, silicone, polyacrylonitrile, vinyl chloride, polyethylene, Polypropylene or the like can be used.

  On the other hand, an image density detection sensor 44 that detects the image density of the toner image primarily transferred to the intermediate transfer belt 16 and a tip of the brush 50 are located downstream of the photoreceptor 14K in the moving direction of the intermediate transfer belt 16. A pedestal 52 (see FIG. 5) is constituted by a contact member 46 that contacts and rubs and a cleaning member 48 that collects the fine powder adhering to the brush 50 and cleans the brush 50, such as a bracket provided inside the printer 10. 3 (b)).

  The image density detection sensor 44, the contact member 46, and the cleaning member 48 face the transfer surface 16A, and are arranged in this order from the downstream side in the moving direction of the intermediate transfer belt 16 to the upstream side. The fine powder collected by the brush 50 includes not only toner but also paper dust of the recording paper P and dust inside the printer 10.

  Here, FIG. 3A shows a state in which the intermediate transfer belt 16 is viewed from the transfer surface 16A side. The image density detection sensor 44, the contact member 46, and the cleaning member 48 are opposed to the intermediate transfer belt 16. It is shown with an imaginary line so that the position can be understood.

  As shown in FIGS. 3A and 3B, the image density detection sensor 44 includes a light emitting unit 56 that emits light and emits light inside a housing 44A that constitutes the main body, and a transfer surface 16A. A light receiving unit 58 that receives the reflected light reflected by the toner image and converts it into an electrical signal. Further, a transmission plate 54 capable of transmitting emitted light and reflected light is provided above the light emitting unit 56 and the light receiving unit 58. The transmission plate 54 is fixed to the housing 44A so as to cover the light emitting unit 56 and the light receiving unit 58, and protrudes from the upper surface of the housing 44A. This prevents fine powder such as toner from entering the light emitting unit 56 and the light receiving unit 58.

  The light emitting unit 56 and the light receiving unit 58 are disposed at positions facing the image forming region W1. Further, the region on the upper surface of the housing 44A opposite to the transmission plate 54 is disposed at a position facing the non-image forming region W2. Here, when the brush 50 moves to the image density detection sensor 44 along with the movement of the intermediate transfer belt 16, the height of the housing 44A is set in advance so that the tip of the brush 50 does not contact the housing 44A. Is set.

  A power supply line and a signal line (not shown) are connected to the image density detection sensor 44, and an electric signal output from the light receiving unit 58 is sent to a control unit (not shown) of the printer 10 via the signal line. It is done. The control unit determines the density of the toner image based on this electrical signal. When the toner density (toner amount) is larger or smaller than a predetermined set value, the control unit changes the potential difference between the photoconductor 14 and the developing roll 13 or between the photoconductor 14 and the transfer roll 38. The toner transfer amount on the transfer surface 16A is adjusted by changing the primary transfer bias, which is the potential difference between the two.

  For example, the contact member 46 is formed by forming a negatively charged polyethylene in a rectangular parallelepiped shape, and is fixed to a portion of the pedestal 52 facing the non-image forming region W2 of the intermediate transfer belt 16, and the upper surface 46A is a transfer member. It is disposed substantially parallel to the surface 16A. The contact member 46 has a predetermined height from the pedestal 52 to the upper surface 46A so that the upper surface 46A can contact the tip of the brush 50. It is preferable that the frictional charge trains of the contact member 46 and the brush 50 are separated from each other.

  The cleaning member 48 is fixed to a portion of the pedestal 52 that faces the non-image forming area W <b> 2 of the intermediate transfer belt 16. Further, the cleaning member 48 is made of resin and has a hollow box shape, and an inclined portion 60 in which an upper surface portion facing the transfer surface 16A is inclined downward from the downstream side in the moving direction of the intermediate transfer belt 16 to the upstream side is formed. ing. A plurality of through holes 62 are formed in the inclined portion 60, and fine powder such as toner can be accommodated in the cleaning member 48 through the through holes 62.

  Among the side walls of the cleaning member 48, a pair of side walls 49 </ b> A and 49 </ b> B in a direction orthogonal to the inclination direction of the inclined portion 60 and a side wall 49 </ b> C on the high position side in the inclination direction of the inclined portion 60 extend upward. The slanted portion 60 is enclosed in a U shape to suppress the scattering of fine powder. The inclined portion 60 comes into contact with the brush 50 from the low position side to the high position side.

  Next, the operation of the first embodiment of the present invention will be described. For convenience of explanation, the time when the brush 50 comes into contact with the contact member 46 will be described as the start time. It is assumed that finely charged fine powder T containing toner has already adhered to the transmission plate 54 of the image density detection sensor 44 by image formation a plurality of times.

  As shown in FIG. 4A, when the intermediate transfer belt 16 rotates and moves in the direction of arrow A, the tip of the brush 50 comes into contact with the upper surface 46A of the contact member 46 and is rubbed and frictionally charged. . When the tip of the brush 50 is separated from the contact member 46 by the movement of the intermediate transfer belt 16, each fiber body of the brush 50 is in a positively charged state.

  Subsequently, as shown in FIG. 4B, due to the movement of the intermediate transfer belt 16, the tip of the brush 50 passes through the area facing the non-image forming area W <b> 2 of the image density detection sensor 44 in a non-contact state. . At this time, the negatively charged fine powder T adhering to the transmission plate 54 moves to the fibrous body of the brush 50 by electrostatic force and is adsorbed and collected. Further, negatively charged toner scattered in the printer 10 is also collected by the fiber body of the brush 50 by electrostatic force. As a result, the fine powder T on the upper surface of the transmission plate 54 of the image density detection sensor 44 is removed, and the light emitted from the light emitting portion 56 (see FIG. 3B) and the reflected light from the toner image in the image forming region W1. It becomes difficult to be blocked.

  Subsequently, as shown in FIG. 4C, when the intermediate transfer belt 16 rotates once, the tip portion of the brush 50 rubs the inclined portion 60 of the cleaning member 48. At this time, the fine powder T adsorbed on the fibrous body of the brush 50 is mechanically scraped off at the edge of the through hole 62 and falls into the cleaning member 48. Thereby, the fiber body of the brush 50 is cleaned.

  Since the above-described three processes of the charging process, the adsorption process, and the cleaning process are repeated while the intermediate transfer belt 16 is rotating, the fine powder T adheres to the transmission plate 54 that is the detection surface of the image density detection sensor 44. Is suppressed.

  Since the cleaning member 48 is disposed close to the upstream side of the image density detection sensor 44 in the moving direction of the intermediate transfer belt 16, a section from the cleaning member 48 to the image density detection sensor 44 via the contact member 46. The distance is getting shorter. Accordingly, the brush 50 can approach the image density detection sensor 44 in a state where the fine powder T is hardly adsorbed, and a reduction in the ability to collect the fine powder T from the image density detection sensor 44 is suppressed.

  Next, a second embodiment of the image forming apparatus of the present invention will be described with reference to the drawings. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  5A and 5B show a peripheral portion of the intermediate transfer belt 16 of the printer 70 as the image forming apparatus. The printer 70 has a configuration in which an image density detection sensor 72 is provided in place of the image density detection sensor 44 and the contact member 46 of the printer 10 described above.

  The image density detection sensor 72 is provided with a light emitting unit 56, a light receiving unit 58, and a transmission plate 54 at a position facing the image forming region W 1 of the intermediate transfer belt 16. Further, the image density detection sensor 72 has a contact portion that protrudes slightly above the upper surface of the transmission plate 54 at a corner near the cleaning member 48 at a position facing the non-image forming region W2 of the intermediate transfer belt 16. 74 is provided. The contact portion 74 has a substantially rectangular shape in plan view, and has a height at which the tip of the brush 50 can contact.

  Next, the operation of the second embodiment of the present invention will be described.

  As shown in FIG. 6A, when the intermediate transfer belt 16 (not shown) rotates and moves in the direction of arrow A, the tip of the brush 50 comes into contact with the upper surface of the contact portion 74 of the image density detection sensor 72. Rubbed and frictionally charged. When the front end portion of the brush 50 is separated from the contact portion 74 due to the movement of the intermediate transfer belt 16, each fiber body of the brush 50 is in a positively charged state.

  Subsequently, as shown in FIG. 6B, the movement of the intermediate transfer belt 16 causes the tip of the brush 50 to pass through the region facing the non-image forming region W <b> 2 of the image density detection sensor 72 in a non-contact state. . At this time, the negatively charged fine powder T adhering to the transmission plate 54 moves to the fibrous body of the brush 50 by electrostatic force and is adsorbed and collected. Further, negatively charged toner scattered in the printer 70 is also collected by the fiber body of the brush 50 by electrostatic force. As a result, the fine powder T on the upper surface of the transmission plate 54 of the image density detection sensor 72 is removed, and the light emitted from the light emitting portion 56 (see FIG. 5B) and the reflected light from the toner image in the image forming region W1. It becomes difficult to be blocked.

  When the intermediate transfer belt 16 rotates once, the tip of the brush 50 rubs against the inclined portion 60 of the cleaning member 48 (see FIG. 5B). At this time, the fine powder T adsorbed on the fibrous body of the brush 50 is mechanically scraped off at the edge of the through hole 62 and falls into the cleaning member 48. Thereby, the fiber body of the brush 50 is cleaned.

  Since the above-described three processes of the charging process, the adsorption process, and the cleaning process are repeated while the intermediate transfer belt 16 is rotating, the fine powder T adheres to the transmission plate 54 that is the detection surface of the image density detection sensor 72. Is suppressed.

  Next, a third embodiment of the image forming apparatus of the present invention will be described with reference to the drawings. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  7A and 7B show the peripheral portion of the intermediate transfer belt 16 of the printer 80 as the image forming apparatus. The printer 80 has a configuration in which an image density detection sensor 82 and a guide member 88 are provided instead of the image density detection sensor 44 and the contact member 46 of the printer 10 described above.

  The image density detection sensor 82 includes a rectangular parallelepiped casing 83. A concave portion 84 is formed in a portion of the upper surface of the housing 83 facing the image forming region W1 of the intermediate transfer belt 16. The recess 84 is opened from the approximate center of the upper surface of the housing 83 in the moving direction of the intermediate transfer belt 16 toward the downstream side, and is substantially U-shaped in plan view. A transmission plate 54 is fitted on the bottom surface of the recess 84, and a light emitting unit 56 and a light receiving unit 58 are provided below the transmission plate 54. The bottom surface of the recess 84 and the top surface of the transmission plate 54 are arranged on the same plane.

  Further, the image density detection sensor 82 is provided with a contact surface 86 made of polyethylene on the upstream side from the approximate center of the upper surface of the housing 83 in the moving direction of the intermediate transfer belt 16. The contact surface 86 is at a height that allows contact with the tip of the brush 50, is easily charged negatively, and is negatively charged by frictional charging with the tip of the brush 50. At this time, the brush 50 is positively charged. A ground wire (not shown) is attached to a part of the surface of the housing 83 to prevent excessive charges from accumulating in a portion other than the contact surface 86 of the housing 83.

  The guide member 88 is disposed between the transfer surface 16A in the non-image forming area W2 and the upper surface of the image density detection sensor 82. The guide member 88 has a shape in which a rectangular plate made of resin is bent into a mountain shape at two locations, and the inclined portion 88A is formed from the upstream side to the downstream side in the moving direction of the intermediate transfer belt 16. A plane portion 88B and an inclined portion 88C are formed.

  The inclined portion 88A is inclined in a direction from the non-image forming area W2 to the image forming area W1 in plan view. The planar portion 88B is disposed substantially parallel along the recess 84 in plan view. The inclined portion 88C is inclined in a direction from the image forming area W1 to the non-image forming area W2 in plan view.

  Next, the operation of the third embodiment of the present invention will be described.

  As shown in FIG. 8A, when the intermediate transfer belt 16 (not shown) rotates and moves in the direction of arrow A, the tip of the brush 50 comes into contact with the inclined portion 88A of the guide member 88, and the inclined portion. Guided in a direction approaching the transmission plate 54 along 88A. The tip of the brush 50 moves along the flat portion 88 </ b> B, contacts the contact surface 86, and is positively charged when separated from the contact surface 86. The contact surface 86 is negatively charged.

  Subsequently, as shown in FIGS. 8B and 8C, part of the tip of the brush 50 passes through the transmission plate 54 in a non-contact state by the movement of the intermediate transfer belt 16. At this time, the negatively charged fine powder T adhering to the transmission plate 54 moves to the fibrous body of the brush 50 by electrostatic force and is adsorbed and collected. Further, negatively charged toner scattered in the printer 70 is also collected by the fiber body of the brush 50 by electrostatic force.

  Thereby, the fine powder T on the upper surface of the transmission plate 54 of the image density detection sensor 82 is removed, and the light emitted from the light emitting portion 56 (see FIG. 7B) and the reflected light from the toner image in the image forming region W1 are blocked. It becomes difficult to be done. Further, since the negatively charged contact surface 86 is charged with the same polarity as that of the fine powder T, it becomes difficult for the fine powder T to newly adhere thereto. In addition, in FIG.8 (c), illustration of the light emission part 56 and the light-receiving part 58 is abbreviate | omitted.

  The brush 50 to which the fine powder T has been adsorbed moves along the inclined portion 88C after passing the flat portion 88B by the movement of the intermediate transfer belt 16, and is disposed at the original position. When the intermediate transfer belt 16 rotates once, the tip of the brush 50 rubs against the inclined portion 60 of the cleaning member 48 (see FIG. 7B). At this time, the fine powder T adsorbed on the fibrous body of the brush 50 is mechanically scraped off at the edge of the through hole 62 and falls into the cleaning member 48. Thereby, the fiber body of the brush 50 is cleaned.

  Since the above-described three processes of the charging process, the adsorption process, and the cleaning process are repeated while the intermediate transfer belt 16 is rotating, the fine powder T adheres to the transmission plate 54 that is the detection surface of the image density detection sensor 82. Is suppressed. In addition, since the brush 50 is disposed in proximity to the transmission plate 54 in a non-contact manner, the fine powder T is easily adsorbed. Further, when paper dust, dust, or the like approaches the charged brush 50, a reverse charge is induced by dielectric polarization, and is attracted to the brush 50 and collected.

  Next, a fourth embodiment of the image forming apparatus of the present invention will be described with reference to the drawings. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  9A and 9B show a peripheral portion of the intermediate transfer belt 16 of the printer 90 as the image forming apparatus. The printer 90 is different from the above-described printer 10 in the arrangement of the image density detection sensor, the brush, the contact member, and the cleaning member, and the image density detection sensor 92, the brush 50, the contact member 94, and the cleaning member 96 are provided. It has been.

  The image density detection sensor 92 of the printer 90 is provided with a transmission plate 54, a light emitting unit 56, and a light receiving unit 58 at a position facing the image forming region W 1 of the intermediate transfer belt 16. The image density detection sensor 92 has a brush 50 attached to the surface of the intermediate transfer belt 16 that faces the non-image forming area W2.

  As an example, the contact member 94 is formed of polyethylene that is easily negatively charged in a rectangular parallelepiped shape, and is fixed to the non-image forming region W <b> 2 on the outer peripheral surface of the intermediate transfer belt 16. Further, the contact member 94 has a predetermined height from the transfer surface 16A to the lower surface 94A so that the lower surface 94A can come into contact with the tip of the brush 50. It is preferable that the frictional charging trains of the contact member 94 and the brush 50 are separated from each other.

  The cleaning member 96 is fixed in the non-image forming region W2 on the outer peripheral surface of the intermediate transfer belt 16 and on the downstream side of the contact member 94 in the moving direction of the intermediate transfer belt 16. Further, the cleaning member 96 is made of resin and has a hollow box shape, and an inclined portion 98 in which a lower surface portion facing the tip portion of the brush 50 is inclined downward from the downstream side in the moving direction of the intermediate transfer belt 16 to the upstream side. Is formed. A plurality of through holes 99 are formed in the inclined portion 98, and fine powder such as toner can be accommodated in the cleaning member 96 through the through holes 99.

  Next, the operation of the fourth exemplary embodiment of the present invention will be described. For convenience of explanation, the time when the brush 50 comes into contact with the contact member 94 will be described as the start time. It is assumed that finely charged fine powder T containing toner has already adhered to the transmission plate 54 of the image density detection sensor 92 by image formation a plurality of times.

  As shown in FIGS. 10A and 10B, when the intermediate transfer belt 16 rotates and moves in the direction of arrow A, the tip of the brush 50 comes into contact with the lower surface 94A of the contact member 94 and rubs. And frictionally charged. When the contact member 94 moves away from the tip of the brush 50 due to the movement of the intermediate transfer belt 16, each fiber body of the brush 50 is in a positively charged state.

  Here, as shown in FIG. 10C, the negatively charged fine powder T adhering on the transmission plate 54 moves to the fibrous body of the brush 50 by electrostatic force, and is adsorbed and collected. Further, negatively charged toner scattered in the printer 10 is also collected by the fiber body of the brush 50 by electrostatic force. Thereby, the fine powder T on the upper surface of the transmission plate 54 of the image density detection sensor 92 is removed, and the light emitted from the light emitting portion 56 (see FIG. 9) and the reflected light from the toner image in the image forming region W1 are not easily blocked. .

  Subsequently, when the intermediate transfer belt 16 makes one rotation, the tip of the brush 50 rubs against the inclined portion 98 of the cleaning member 96. At this time, the fine powder T adsorbed on the fibrous body of the brush 50 is mechanically scraped off at the edge of the through hole 99 and stored in the cleaning member 96. Thereby, the fiber body of the brush 50 is cleaned.

  Since the above-described three processes of the charging process, the adsorption process, and the cleaning process are repeated while the intermediate transfer belt 16 is rotating, the fine powder T adheres to the transmission plate 54 that is the detection surface of the image density detection sensor 92. Is suppressed.

  In addition, this invention is not limited to said embodiment.

  Not only the image density detection of the intermediate transfer belt 16 but also the image density detection of the photoreceptor 14 may be performed.

  The image density detection sensor 44 is not limited to one in which the light emitting unit 56 and the light receiving unit 58 are in one casing. For example, even if the light emitting unit 56 and the light receiving unit 58 are attached to separate casings, the fine powder T can be electrostatically adsorbed by the passage of the brush 50 as long as they are arranged in parallel or close to each other.

  In the printer 80 of the third embodiment, a contact member may be separately provided instead of the contact surface 86 to frictionally charge the brush 50. Further, the guide member 88 may have a curved shape as well as a bent shape. Furthermore, the upper portion of the guide member 88 may be curved. Further, the guide member 88 may be formed integrally with the image density detection sensor 82.

  The cleaning member 48 may have a cylindrical shape (roll shape) in addition to the box shape. When using a cylindrical thing, you may support it rotatably. Further, the cleaning member 48 may be made of a conductive material and grounded so that the electrostatic adhesion force of the fine powder T to the brush 50 may be weakened. Then, the toner adhering to the brush 50 may be adsorbed to the cleaning member 48. Further, the position of the cleaning member 48 may be disposed downstream of the transfer unit 24 in the moving direction of the intermediate transfer belt 16.

  The fibrous body of the brush 50 may contain or apply a charging agent.

1 is an overall view of an image forming apparatus according to a first embodiment of the present invention. 1 is a partially enlarged view of an image forming apparatus according to a first embodiment of the present invention. 2A is a plan view of an intermediate transfer belt of the image forming apparatus according to the first embodiment of the present invention. FIG. (B) It is a perspective view which shows the image density detection means of the image forming apparatus which concerns on 1st Embodiment of this invention, a contact member, and the cleaning means. FIG. 3 is a schematic diagram illustrating each process of charging, suction, and cleaning by the suction member, the contact member, and the cleaning unit of the image forming apparatus according to the first embodiment of the present invention. (A) It is a top view of the intermediate transfer belt of the image forming apparatus which concerns on 2nd Embodiment of this invention. (B) It is a perspective view which shows the image density detection means of the image forming apparatus which concerns on 2nd Embodiment of this invention, a contact member, and the cleaning means. FIG. 10 is a schematic diagram illustrating each process of charging and adsorption by an adsorption member and a contact member of an image forming apparatus according to a second embodiment of the present invention. (A) It is a top view of the intermediate transfer belt of the image forming apparatus which concerns on 3rd Embodiment of this invention. (B) It is a perspective view which shows the image density detection means of the image forming apparatus which concerns on 3rd Embodiment of this invention, a contact member, a cleaning means, and a guide member. It is a schematic diagram which shows each process of the charging by the adsorption | suction member of the image forming apparatus which concerns on 3rd Embodiment of this invention, and a contact member, and adsorption | suction. (A) It is a top view of the intermediate transfer belt of the image forming apparatus which concerns on 4th Embodiment of this invention. (B) It is a perspective view which shows the image density detection means of the image forming apparatus which concerns on 4th Embodiment of this invention, a contact member, and the cleaning means. It is a schematic diagram showing each process of charging and adsorption by an adsorption member and a contact member of an image forming apparatus according to a fourth embodiment of the present invention.

Explanation of symbols

10 Printer (image forming device)
16 Intermediate transfer belt (Developer holding member)
44 Image density detection sensor (image density detection means)
46 Contact member (Contact member)
48 Cleaning member (cleaning means)
50 Brush (Suction member)
54 Transmission plate (Transmission part)
56 Light Emitting Unit (Light Emitting Unit)
58 Light receiver (light receiver)
70 Printer (image forming device)
72 Image density detection sensor (image density detection means)
74 Contact part (contact member)
80 Printer (image forming device)
82 Image density detection sensor (image density detection means)
86 Contact surface (contact member)
88 Guide member (Guide member)
90 Printer (image forming device)
92 Image density detection sensor (image density detection means)
T Fine powder (dust)
W1 Image formation area (image area)
W2 Non-image forming area (outside of image area)

Claims (7)

A developer holding member that is rotatably provided and has an image area in which an image formed with the developer is held;
A light emitting unit that emits light toward the image region; a light receiving unit that receives reflected light reflected by the image region; and a transmission unit that covers the light emitting unit and the light receiving unit and transmits the emitted light and reflected light. An image density detecting means that is disposed opposite to the image area and detects the density of the image based on the amount of reflected light received by the light receiving unit;
An adsorbing member that is provided at a position not facing the image area, and adsorbs dust that is frictionally charged by the rotation of the developer holding member and adhered to the transmitting portion in a non-contact manner;
A contact member that contacts the suction member by rotation of the developer holding member and frictionally charges the suction member;
Cleaning means for removing dust adsorbed by the adsorption means from the adsorption means;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the suction member is fixed outside the image area of the developer holding member.   The image forming apparatus according to claim 2, wherein the contact member is a casing of the image density detection unit.   The image forming apparatus according to claim 2, further comprising a guide member that tilts the suction member to approach the transmitting portion. The suction member is fixed to the outside of the image area around the transmission portion;
The image forming apparatus according to claim 1, wherein the contact member is fixed to the developer holding member.   The image forming apparatus according to claim 1, wherein a charging polarity of the adsorption member is opposite to a charging polarity of the developer.   7. The image formation according to claim 1, wherein the cleaning unit is disposed upstream of the image density detection unit in a rotation direction of the developer holding member. apparatus.

Images