JP2013148669A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably capture magnetic metal powder falling down on a support member arranged below a developing device employing a rotary change system.SOLUTION: An image forming apparatus 10 includes: a developing device 70 employing a rotary change system that develops a latent image on a latent image holding body 62 with a developer held by magnetic force to form a developer image; and a foam sheet 96 that is provided on a support member 90 arranged below the developing device 70, and has a cell diameter of 11 to 23/25 mm for capturing magnetic metal powder falling down on the support member 90.

Description

  The present invention relates to an image forming apparatus.

  An image in which a foreign material capturing member made of a magnet sheet or an adhesive sheet is provided on a separating member arranged below the rotation switching type developing device, and foreign materials such as magnetic metal falling on the separating member are captured. A forming apparatus is conventionally known (see, for example, Patent Document 1).

JP 2000-298384 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reliably capturing magnetic metal powder falling on a supporting member disposed below a rotation switching type developing device.

  In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention forms a developer image by developing a latent image on a latent image holding member with a developer held by a magnetic force. A rotation switching type developing device, and a foam sheet having a cell diameter of 11 to 23 pieces / 25 mm, which is provided on a support member disposed below the developing device and captures the falling magnetic metal powder; It is characterized by having.

  The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the support member is an isolation member that separates at least the fixing device and the developing device. Yes.

  According to the first aspect of the present invention, the magnetic metal drops on the support member as compared with the configuration in which the foam sheet having a cell diameter of 11 to 23 pieces / 25 mm is not provided on the support member. The powder can be reliably captured.

  According to invention of Claim 2, compared with the structure which provides a foam sheet in a supporting member different from a separating member, a reduction in a number of parts can be aimed at and manufacturing cost can be reduced.

Overall configuration diagram of an image forming apparatus according to the present embodiment Configuration of an image forming unit according to the present embodiment Perspective view showing foam sheet provided on catch pan

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In FIG. 1, an arrow V is an upward direction (vertical direction) of the image forming apparatus 10, and an arrow H is a right direction (horizontal direction) of the image forming apparatus 10. The front side in the direction perpendicular to the paper surface shown in FIG. In this embodiment, the recording paper P is employed as an example of the recording medium, and the upstream side in the transport direction of the recording paper P may be simply referred to as “upstream side”, and the downstream side in the transport direction may be simply referred to as “downstream side”.

  As shown in FIG. 1, the image forming apparatus 10 includes a sheet storage unit 12 that stores recording paper P from the lower side to the upper side in the vertical direction, and a sheet storage unit that is provided above the sheet storage unit 12. The image forming unit 14 for forming an image on the recording paper P supplied from 12, the document reading unit 16 for reading the document G provided on the upper side of the image forming unit 14, and the image forming unit 14 for image formation And a control unit 20 that controls the operation of each unit of the apparatus 10.

  The paper storage unit 12 is provided with a first storage unit 22, a second storage unit 24, and a third storage unit 26 that store recording papers P of different sizes. Each of the first storage unit 22, the second storage unit 24, and the third storage unit 26 is provided with a delivery roll 32 that sends the stored recording paper P to the transport path 28 in the image forming apparatus 10. A pair of transport rolls 34 and 36 that transport the recording paper P one by one are provided in the transport path 28 on the downstream side of each delivery roll 32.

  Further, a pair of transports are performed so that the recording paper P sent from a reverse transport path 29 (to be described later) joins the transport path 28 and is transported downstream of the transport roll 36 of the third storage unit 26. A roll 50 is provided. An alignment roll 38 that temporarily stops the recording paper P and feeds it to a secondary transfer position to be described later at a predetermined timing is provided downstream of the transport roll 50.

  In addition, in the front view of the image forming apparatus 10, the upstream conveyance path 28 including the conveyance roll 50 is formed in a straight line in the vertical direction. The downstream conveyance path 28 including the alignment roll 38 is formed in a substantially straight line from the left side of the image forming unit 14 to the right side, that is, the paper discharge unit 15 provided on the right side surface of the apparatus main body 10A. Further, a reverse conveyance path 29 is provided below the conveyance path 28 on the downstream side including the alignment rolls 38, and the recording paper P is reversed and conveyed.

  The reversal conveyance path 29 has a first guide member 31 that guides the recording paper P from the conveyance path 28 to the reversal conveyance path 29 and a straight line in the vertical direction from the lower right side of the image forming unit 14 to the lower right side of the paper storage unit 12. A reversing unit 33 provided in the reversing unit 33, a second guiding member 35 for guiding the recording paper P conveyed to the reversing unit 33 from the reversing unit 33 to a conveying unit 37 described later, and a recording sheet guided by the second guiding member 35. And a transport unit 37 that transports P.

  The downstream side of the transport unit 37 is joined to a transport path 28 between the transport roll 36 and the transport roll 50 of the third storage unit 26. The reversing unit 33 is provided with a pair of transport rolls 42 at a predetermined interval, and the transport unit 37 is provided with a pair of transport rolls 44 at a predetermined interval. It is provided at multiple locations.

  The first guide member 31 has a substantially triangular prism shape when viewed from the front, and the leading end portion is moved to either the transport path 28 or the reverse transport path 29 by a driving unit (not shown), so that the recording paper P is transported through the transport path. 28 or the reverse conveyance path 29 is guided. Similarly, the second guide member 35 has a substantially triangular prism shape when viewed from the front, and the recording paper P is moved by moving the leading end to either the reversing unit 33 or the conveying unit 37 by a driving unit (not shown). The reversing unit 30 or the conveyance unit 37 is guided.

  Further, a foldable manual sheet feeding unit 46 is provided on the left side surface of the apparatus main body 10A. The recording paper P supplied from the manual paper feed unit 46 is transported by the transport roll 48 and is joined to the transport path 28 downstream of the transport roll 50 and upstream of the alignment roll 38. It has become.

  The document reading unit 16 includes a document transport device 52 that automatically transports the document G one by one, a platen glass 54 that is disposed below the document transport device 52 and on which one document G is placed, and the document transport device 52. And a document reading device 56 that reads the document G conveyed by the document G or the document G placed on the platen glass 54.

  The document conveying device 52 has an automatic conveyance path 55 in which a plurality of pairs of conveyance rolls 53 are arranged. A part of the automatic conveyance path 55 is arranged so that the recording paper P passes over the platen glass 54. Yes. Further, the document reading device 56 reads the document G conveyed by the document conveying device 52 in a state of being stationary at the left end portion of the platen glass 54, or reads the document G placed on the platen glass 54 while moving in the right direction. It is supposed to read.

  The image forming unit 14 includes a cylindrical photosensitive member 62 as an example of a latent image holding member disposed in an approximate center of the apparatus main body 10A with the direction from the front side to the back side of the apparatus main body 10A being the axial direction. Have. The photosensitive member 62 is rotated in a direction indicated by an arrow + R (clockwise direction in the drawing) by a driving unit (not shown) and holds an electrostatic latent image formed by light irradiation. A corotron charging member 64 that charges the outer peripheral surface of the photoconductor 62 is provided above the photoconductor 62 and at a position facing the outer peripheral surface (surface) of the photoconductor 62.

  An exposure device 66 is provided at a position downstream of the charging member 64 in the rotation direction of the photoconductor 62 and facing the outer peripheral surface of the photoconductor 62. The exposure device 66 is configured by a ROS (Raster Optical Scanner) system that scans laser light with a polygon mirror, and is based on an image signal corresponding to each toner color on the outer peripheral surface of the photosensitive member 62 charged by the charging member 64. Then, light is irradiated (exposed) to form an electrostatic latent image.

  The exposure device 66 is not limited to the ROS method, and may be configured by, for example, an LED (Light Emitting Diode) method. Further, the electrostatic latent image formed on the outer peripheral surface of the photoconductor 62 is developed with toner of each predetermined color on the downstream side in the rotation direction of the photoconductor 62 from the portion irradiated with light by the exposure device 66. A rotation switching type developing device 70 is provided as an example of the developing means to be visualized. The developing device 70 will be described later.

  An intermediate transfer unit in which a toner image (developer image) formed on the outer peripheral surface of the photoconductor 62 is primarily transferred downstream of the developing device 70 in the rotation direction of the photoconductor 62 and below the photoconductor 62. 60 (see FIG. 2) is provided. The intermediate transfer unit 60 has an endless intermediate transfer belt (intermediate transfer member) 68 as an example of a transfer image holding member that moves in the direction of an arrow −R (counterclockwise direction in the drawing).

  The intermediate transfer belt 68 is in contact with a drive roll 61 that is rotationally driven by the control unit 20, a tension applying roll 63 for applying tension to the intermediate transfer belt 68, and an inner peripheral surface (back surface) of the intermediate transfer belt 68. Then, the belt is wound around a plurality of transport rolls 65 that are driven to rotate, and an auxiliary roll 69 that rotates in contact with the inner peripheral surface of the intermediate transfer belt 68 at a secondary transfer position described later.

  Further, on the opposite side of the photoconductor 62 across the intermediate transfer belt 68, a primary transfer roll for primary transfer of the toner image formed on the outer peripheral surface of the photoconductor 62 to the outer peripheral surface (surface) of the intermediate transfer belt 68. 67 is provided.

  The primary transfer roll 67 is in contact with the inner peripheral surface of the intermediate transfer belt 68 at a position away from the position where the photoreceptor 62 and the intermediate transfer belt 68 are in contact with the downstream side in the moving direction of the intermediate transfer belt 68. The primary transfer roll 67 is energized from a power source (not shown) so as to primarily transfer the toner image on the photoreceptor 62 to the outer peripheral surface of the intermediate transfer belt 68 with a potential difference from the grounded photoreceptor 62. It has become.

  Further, on the opposite side of the auxiliary roll 69 across the intermediate transfer belt 68, the secondary transfer as an example of a transfer unit that secondarily transfers the toner image primarily transferred onto the outer peripheral surface of the intermediate transfer belt 68 onto the recording paper P. A roll 71 is provided. Between the secondary transfer roll 71 and the auxiliary roll 69 is a secondary transfer position for transferring the toner image to the recording paper P. The secondary transfer roll 71 is moved by an intermediate transfer belt 68 by a retract mechanism (not shown). It is comprised so that contact / separation (contact, separation) is possible with respect to the outer peripheral surface.

  That is, the secondary transfer roll 71 is separated from the outer peripheral surface of the intermediate transfer belt 68 until the toner images of the respective colors are primarily transferred to the outer peripheral surface of the intermediate transfer belt 68. When the toner images of the respective colors are primarily transferred, the toner images on the outer peripheral surface of the intermediate transfer belt 68 are brought into contact with the outer peripheral surface and are energized from a power source (not shown) to cause a potential difference from the grounded auxiliary roll 69. Secondary transfer is performed on the recording paper P.

  Further, on the opposite side of the drive roll 61 across the intermediate transfer belt 68, a cleaning device 100 as an example of a developer recovery device that recovers residual toner remaining on the outer peripheral surface of the intermediate transfer belt 68 after the secondary transfer. Is provided. As shown in FIG. 2, the cleaning device 100 includes a housing 102 in which a rectangular opening 104 that is disposed to face the intermediate transfer belt 68 is formed.

  The cleaning device 100 is provided on the upper side of the opening 104, and comes into contact with the intermediate transfer belt 68 to collect residual toner, and a position opposite to the cleaning blade 106 (lower side). A seal member 108 is provided in the opening 104 and contacts the intermediate transfer belt 68 to seal a gap between the housing 102 and the intermediate transfer belt 68.

  Further, the cleaning device 100 collects dust including residual toner and a suction unit (not shown) for sucking residual toner and the like on the intermediate transfer belt 68 into the housing 102. The filter 110 includes a retract mechanism (not shown) that moves the cleaning blade 106 and the seal member 108 between a position where they are in contact with the outer peripheral surface of the intermediate transfer belt 68 and a position where they are separated from the outer peripheral surface. .

  The cleaning blade 106 is a rubber plate having a rectangular shape in plan view, and is attached to the support plate 112 so that the longitudinal direction thereof is along the longitudinal direction of the opening 104. That is, the cleaning blade 106 is provided along the downstream edge of the opening 104 in the conveyance direction (arrow -R direction) of the intermediate transfer belt 68.

  The sealing member 108 is a rectangular transparent film material in plan view, and the movable member 114 is in contact with the intermediate transfer belt 68 along the upstream edge of the opening 104 in the conveyance direction of the intermediate transfer belt 68. Is attached. The leading end portion of the seal member 108 is disposed facing the downstream side in the moving direction of the intermediate transfer belt 68.

  The filter 110 is an aggregate of fibers and is formed in a long rectangular shape along the longitudinal direction of the housing 102. Further, at the lower part of the casing 102, the blades are formed in a spiral shape on the outer peripheral surface of the rotation shaft with the longitudinal direction of the casing 102 as the axial direction, and are driven into rotation so that the inside of the casing 102 is rotated. A transport auger 116 is provided for transporting the collected residual toner to one axial end thereof.

  Further, a mark (not shown) attached to the outer peripheral surface of the intermediate transfer belt 68 is detected at a position facing the tension applying roller 63 around the intermediate transfer belt 68, thereby detecting the outer peripheral surface of the intermediate transfer belt 68. A position detection sensor 83 is provided that detects a predetermined reference position and outputs a position detection signal that serves as a reference for the start timing of the image forming process.

  Further, on the downstream side in the rotation direction of the photoconductor 62 with respect to the primary transfer roll 67, the residual toner remaining on the outer peripheral surface of the photoconductor 62 is removed without being primarily transferred to the outer peripheral surface of the intermediate transfer belt 68. A cleaning device 73 is provided.

  As shown in FIG. 2, the cleaning device 73 collects residual toner and the like by a cleaning blade 86 and a brush roll 88 that are in contact with the outer peripheral surface of the photoconductor 62, and conveys the residual toner by a conveyance auger 89. Yes. Further, on the upstream side in the rotation direction of the photoconductor 62 with respect to the cleaning device 73 (downstream side with respect to the primary transfer roll 67), a static elimination device 75 is provided that applies charge to the outer peripheral surface of the photoconductor 62 and performs static elimination. Yes.

  The static eliminator 75 applies an electric charge to the outer peripheral surface of the photoconductor 62 before removing the residual toner and the like by the cleaning device 73, and thereby removes static electricity, thereby adhering the outer peripheral surface of the photoconductor 62 due to static electricity such as residual toner. And the recovery rate of the residual toner or the like is increased. Further, on the downstream side in the rotation direction of the photoconductor 62 with respect to the cleaning device 73 and on the upstream side with respect to the charging member 64, in order to remove the residual potential on the outer peripheral surface of the photoconductor 62, A static eliminator 85 is provided.

  As shown in FIG. 1, the secondary transfer position of the toner image by the secondary transfer roll 71 is set in the middle of the transport path 28, and the transport direction of the recording paper P in the transport path 28 (indicated by the arrow A). ), A fixing device 80 for fixing the toner image on the recording paper P onto which the toner image has been transferred by the secondary transfer roll 71 is provided downstream of the secondary transfer roll 71.

  The fixing device 80 includes a heat source that generates heat when energized, a heating roll 82 disposed on the toner image surface side (upper side) of the recording paper P, and a lower side of the heating roll 82. And a pressure roll 84 that pressurizes the outer peripheral surface of 82. A transport roll 40 that transports the recording paper P toward the paper discharge unit 15 or the reversing unit 33 is provided downstream of the fixing device 80 in the transport direction of the recording paper P in the transport path 28.

  Further, toner cartridges 78Y, 78M for accommodating yellow (Y), magenta (M), cyan (C), and black (K) toners are provided below the document reading device 56 and above the developing device 70, respectively. 78C and 78K are provided to be exchangeable side by side in the horizontal direction. The first special color (E) and the second special color (F) are blank. Accordingly, in the present embodiment, as an example, a case will be described in which image formation is performed with four colors Y, M, C, and K, and the first special color E and the second special color F are unused.

  Next, the developing device 70 and the separating member 90 provided below the developing device 70 will be described.

  As shown in FIG. 2, the developing device 70 has developing devices 72Y, 72M, 72C, and 72K corresponding to the toner colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. doing. The first special color (E) developer 72E and the second special color (F) developer 72F are equipped with dummy developers.

  The developing units 72Y to 72K are arranged side by side in the circumferential direction (counterclockwise direction in this order), and are rotated by 60 ° at a central angle by a motor (not shown) as a rotational drive source. The developing devices 72Y, 72M, 72C, and 72K that perform the development processing are switched so as to face the outer peripheral surface of the photosensitive member 62.

  Since the developing devices 72Y, 72M, 72C, and 72K have the same configuration, the developing device 72Y will be described here, and the description of the other developing devices 72M, 72C, and 72K will be omitted.

  The developing device 72Y includes a case member 76 serving as a main body. Toner and carrier supplied into the case member 76 from a toner cartridge 78Y (see FIG. 1) via a toner supply path (not shown). A developer (not shown) is filled.

  Further, the case member 76 is formed with a rectangular opening 76 </ b> A that faces the outer peripheral surface of the photoconductor 62, and the developing roller 74 whose outer peripheral surface faces the outer peripheral surface of the photoconductor 62 is formed in the opening 76 </ b> A. Is provided. Further, a plate-shaped regulating member 79 for regulating the layer thickness of the developer is provided along the longitudinal direction of the opening 76A at a portion near the opening 76A in the case member 76.

  The developing roller 74 includes a cylindrical developing sleeve 74A that is rotatably provided, and a magnetic member 74B that includes a plurality of magnetic poles fixed inside the developing sleeve 74A. The developing sleeve 74A rotates. Thus, a magnetic brush for the developer (carrier) is formed, and the layer thickness is regulated by the regulating member 79, whereby a developer layer held by a magnetic force is formed on the outer peripheral surface of the developing sleeve 74A. ing. The developer layer on the outer peripheral surface of the developing sleeve 74A is conveyed to a position facing the photoconductor 62, and a toner corresponding to a latent image (electrostatic latent image) formed on the outer peripheral surface of the photoconductor 62 is attached. Development.

  Further, in the case member 76, two conveying augers 77 formed in a spiral shape are arranged in parallel so as to be rotatable, and the two conveying augers 77 are rotated to be filled in the case member 76. The developer is circulated and conveyed in the axial direction of the developing roll 74 (longitudinal direction of the developing device 72Y).

  The four developing rolls 74 provided in each of the developing units 72Y, 72M, 72C, and 72K are arranged in the circumferential direction so that the distance from the adjacent developing roll 74 is 60 ° at the central angle. By switching the developing device 72, the next developing roll 74 faces the outer peripheral surface of the photoconductor 62.

  In addition, as shown in FIGS. 1 to 3, unnecessary developer (including cloud) falling from the developing device 72 is above the fixing device 80 and below the developing device 70. In order to prevent the sheet from falling to the surface (in order to catch the developer), a metal separating member (hereinafter referred to as “catch pan”) 90 as an example of a supporting member that is separated from at least the fixing device 80 is disposed. .

  The catch pan 90 is located immediately below the developing device 70 along the outer shape (outer peripheral surface) of the developing device 70 and from the right end of the curved surface portion 92 to the right side surface of the apparatus main body 10A. And a flat surface portion 94 arranged so as to extend substantially, and is formed to have a width equal to or greater than the length along the rotation axis direction of the developing device 70.

  A polyester polyurethane foam sheet (hereinafter referred to as “foam sheet”) 96 as an example of a foam sheet is attached to the upper surface 90A of the catch pan 90 by an adhesive means such as a double-sided tape (not shown). It is attached. The foam sheet 96 is Everlite SF HR-13 or HR-20 manufactured by Bridgestone, and the cell diameter is 11 to 16 pieces / 25 mm for HR-13, and 17 to 23 for HR-20. It is ½ / 25mm.

  Thereby, in addition to unnecessary developer (including cloud) falling from the developing device 72, magnetic metal powder having a size of about 100 μm to 300 μm falling from above in the apparatus main body 10A is captured. It is like that. Examples of the magnetic metal powder having a size of about 100 μm to 300 μm include cutting powder (so-called burrs) at the screw fastening portion and sputtering at the frame welding portion.

  Further, the gap between the upper surface 90A of the catch pan 90 and the outermost peripheral surface of the developing device 70 is, for example, 4 mm. Therefore, the thickness of the foam sheet 96 is 2 mm to 3 mm. That is, it is desirable that the gap between the upper surface 96A of the foam sheet 96 and the outermost peripheral surface of the developing device 70 be at least about 1 mm.

  The catch pan 90 captures unnecessary developer (including cloud) falling from the developing device 72 and magnetic metal powder falling from above in the apparatus main body 10A. It also functions as a heat insulating member that prevents heat generated from the fixing device 80 from being transmitted to the developing device 70.

  Next, the operation of the image forming apparatus 10 configured as described above will be described. First, an image forming process in the image forming apparatus 10 will be described.

  As shown in FIG. 1, when the image forming apparatus 10 operates, image data of each color of yellow (Y), magenta (M), cyan (C), and black (K) is supplied from an image processing apparatus (not shown) or from the outside. Are sequentially output to the exposure device 66. At this time, as an example, the developing device 70 is rotated and held so that the developing device 72 </ b> Y (see FIG. 2) faces the outer peripheral surface of the photoconductor 62.

  Further, the cleaning blade 106 and the seal member 108 of the cleaning device 100 operate the retract mechanism until the toner images of the respective colors are transferred onto the intermediate transfer belt 68 in a multiple (primary) manner and are secondarily transferred onto the recording paper P. Is separated from the outer peripheral surface of the intermediate transfer belt 68.

  Subsequently, the light emitted from the exposure device 66 according to the image data exposes the outer peripheral surface of the photosensitive member 62 charged by the charging member 64, and the outer peripheral surface of the photosensitive member 62 corresponds to yellow image data. An electrostatic latent image is formed. Further, the electrostatic latent image formed on the outer peripheral surface of the photoconductor 62 is developed as a yellow toner image by the developing device 72Y. The yellow toner image on the outer peripheral surface of the photoconductor 62 is transferred to the intermediate transfer belt 68 by the primary transfer roll 67.

  Subsequently, when the developing device 70 is rotated by 60 ° in the arrow + R direction and the developing device 72M faces the outer peripheral surface of the photoconductor 62, charging, exposure, and development processes are performed, and magenta on the outer peripheral surface of the photoconductor 62 is performed. The toner image is transferred onto the yellow toner image on the intermediate transfer belt 68 by the primary transfer roll 67. Similarly, cyan (C) and black (K) toner images are sequentially transferred onto the intermediate transfer belt 68 in a multiple transfer manner.

  On the other hand, the recording paper P sent out from the paper storage unit 12 and transported through the transport path 28 is subjected to secondary transfer in synchronization with the multiple transfer of each toner image onto the intermediate transfer belt 68 by the positioning roll 38. Transported to position. The toner image that has been multiplex-transferred onto the intermediate transfer belt 68 is secondarily transferred by the secondary transfer roll 71 onto the recording paper P that has been conveyed to the secondary transfer position.

  Further, after the secondary transfer, the cleaning blade 106 and the seal member 108 of the cleaning device 100 come into contact with the outer peripheral surface of the intermediate transfer belt 68 by the operation of the retract mechanism unit. The residual toner remaining on the outer peripheral surface of the intermediate transfer belt 68 is peeled off by the cleaning blade 106 and collected in the housing 102.

  At this time, the seal member 108 is also in contact with the outer peripheral surface of the intermediate transfer belt 68 to seal the gap between the housing 102 and the intermediate transfer belt 68. This prevents residual toner collected in the housing 102 from leaking to the outside of the housing 102.

  Subsequently, the recording paper P to which the toner image has been transferred is conveyed toward the fixing device 80 in the direction of arrow A (right direction in the drawing). In the fixing device 80, the toner image is fixed on the recording paper P by being heated and pressed by the heating roll 82 and the pressure roll 84. Further, the recording paper P on which the toner image is fixed is discharged to the paper discharge unit 15 as an example.

  When images are formed on both sides of the recording paper P, after fixing the image on the surface by the fixing device 80, the recording paper P is sent to the reversing unit 33 along the arrow -V direction and along the arrow + V direction. By feeding it out, the leading edge and the trailing edge of the recording paper P are switched. Then, the recording paper P is conveyed in the direction of arrow B (the left direction in the figure) by the reverse conveying path 29 and further fed into the conveying path 28 to perform image formation and fixing on the back surface of the recording paper P.

  Note that after the secondary transfer to the back surface of the recording paper P, the cleaning blade 106 and the seal member 108 of the cleaning device 100 are brought into contact with the outer peripheral surface of the intermediate transfer belt 68 by the operation of the retract mechanism, as described above. The residual toner remaining on the outer peripheral surface of the intermediate transfer belt 68 is peeled off by the cleaning blade 106 and collected in the housing 102.

  Next, the operation of the foam sheet 96 will be described.

  If magnetic metal powder such as chips from the screw fastening portion and spatter from the frame welding portion remain in the apparatus main body 10A, some of them may be caused by vibration or impact during transportation or operation of the image forming apparatus 10. It may fall near the developing device 70.

  When such a magnetic metal powder is sandwiched between the developing roll 74 and the photoconductor 62, the surface of the photoconductor 62 is scratched and an image defect (color point) is generated. In particular, in the rotation switching type developing device 70, when the developing device 72 rotates (revolves), the surrounding magnetic metal powder may be adsorbed by a magnetic force.

  As a countermeasure, it has been proposed to provide a magnet sheet on the catch pan 90 disposed below the developing device 70. However, in this case, since it is necessary to make the magnetic force of the magnetic sheet weaker than the magnetic force of the developing device 72, problems such as weak holding power of the magnetic metal powder have occurred. In addition, since the surface of the magnet sheet is smooth, there is a possibility that the magnetic metal powder that has fallen repels on the magnet sheet and cannot be captured.

  As a countermeasure, it has also been proposed to provide an adhesive sheet on the catch pan 90 disposed below the developing device 70. However, in this case, the adhesive sheet is contaminated with a cloud or the like generated around the developing device 72, thereby causing a problem that the adhesive effect of the adhesive sheet gradually fades. Further, when the adhesive effect of the adhesive sheet is weakened, the magnetic metal powder that has fallen may repel on the adhesive sheet and cannot be captured.

  Therefore, in the present embodiment, the foam sheet 96 is attached to the entire upper surface 90A of the catch pan 90 disposed below the developing device 70. That is, the foam sheet 96 is Everlite SF HR-13 or HR-20 manufactured by Bridgestone, and the cell diameter is 11 to 16 pieces / 25 mm for HR-13, and 17 pieces for HR-20. It is ~ 23 / 25mm. That is, the cell diameter of the foam sheet 96 is relatively coarse.

  Therefore, the magnetic metal powder dropped on the upper surface 96A of the foam sheet 96 is reliably captured in the cell and is not attracted even by the magnetic force of the developing device 72. Further, since the foam sheet 96 has a sponge shape capable of absorbing an impact, there is no possibility that the magnetic metal powder falling on the upper surface 96A will be repelled and cannot be captured. Further, even if the upper surface 96A of the foam sheet 96 is contaminated by a cloud or the like generated around the developing device 72, the capturing effect does not deteriorate.

  Thus, when the foam sheet 96, that is, Everlite SF HR-13 or HR-20 manufactured by Bridgestone, is provided on the upper surface 90A of the catch pan 90, the magnetic metal powder is stably captured. Therefore, the adhesion of the magnetic metal powder to the developing device 70 (developing device 72) and the photosensitive member 62 is suppressed or prevented. Moreover, the foam sheet 96 is less expensive than the magnet sheet, and has an advantage that it is easy to handle when it is attached to the catch pan 90.

  The image forming apparatus 10 according to the present embodiment has been described with reference to the drawings. However, the image forming apparatus 10 according to the present embodiment is not limited to the illustrated one and does not depart from the gist of the present invention. The design can be changed as appropriate within the range. For example, the developing device 70 may be a four-color developing device in which the first special color (E) and the second special color are not provided from the beginning.

  Further, the support member to which the foam sheet 96 is attached is not limited to the catch pan (isolation member) 90. However, the configuration in which the foam sheet 96 is provided (attached) to the existing catch pan 90 reduces the number of parts compared to the configuration in which the foam sheet 96 is provided (attached) to a support member different from the catch pan 90. There is an advantage that the manufacturing cost can be reduced.

10 image forming apparatus 62 photoconductor (an example of a latent image holder)
70 Developing device 90 Catch pan (an example of an isolation member / support member)
96 Foam sheet (an example of a foam sheet)

Claims (2)

A rotation switching type developing device that develops a latent image on the latent image holding member with a developer held by a magnetic force to form a developer image;
A foam sheet having a cell diameter of 11 to 23 pieces / 25 mm, which is provided on a support member disposed below the developing device and captures the falling magnetic metal powder;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the support member is an isolation member that isolates at least the fixing device and the developing device.