JP6010058B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that supplies a developer to an image carrier and an image forming apparatus including the developing device.

  In general, in an electrophotographic image forming apparatus, an electrostatic latent image formed on the surface of an image carrier is developed with toner carried on a developer carrier in a developing device, thereby forming an image. ing.

  In recent years, with the increase in color and speed of image forming apparatuses, the configuration of the developing apparatus has become complicated and the rotation of the toner stirring member in the developing apparatus has been accelerated. For this reason, the inside of the developing device becomes a positive pressure atmosphere higher than the atmospheric pressure, and scattering of toner in the developing device becomes a problem. In particular, inside the developing device, scattered toner may accumulate on the wall surface around the blade that regulates the amount of toner carried on the developer carrier. When the accumulated toner aggregates and falls, an image defect appears in the image as a black spot.

  In order to prevent the accumulation of scattered toner, Patent Document 1 proposes an image forming apparatus in which a film is provided above the blade and the film is moved up and down to prevent the scattered toner from adhering to the wall surface. Yes. Patent Document 2 proposes an image forming apparatus in which a toner receiving member is provided above a blade and the toner receiving member is vibrated to recirculate the toner dropped on the toner receiving member. Further, Patent Document 3 proposes an image forming apparatus configured to form an air flow path so as to cross the inside of the developing device and to discharge scattered toner along this path.

JP 2011-197285 A JP 2012-208469 A JP 2011-197290 A

  The image forming apparatuses proposed in Patent Documents 1 and 2 are configured to collect the scattered toner and return it to the developing apparatus to contribute again to development. However, the scattered toner contains a lot of toner whose charging is not stable. Such an unstablely charged toner may be scattered again even if it is returned to the developing device. In addition, the image forming apparatus proposed in Patent Document 2 is configured such that the discharged toner is collected by a filter, which may cause problems such as filter clogging.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus provided with a developing device capable of reliably collecting scattered toner.

  In order to achieve the above object, the developing device of the present invention comprises a toner carrier for supplying toner to an image carrier on which an electrostatic latent image is formed, and a toner carrier carrying a developer comprising toner and carrier. A toner supply member that supplies toner to the toner carrier in a region facing the toner carrier, a blade that regulates the amount of developer carried on the toner supplier, the toner carrier, the toner supplier, and the blade A developing device comprising a casing in which the housing is housed, a through hole formed so as to penetrate the inside and the outside of the casing in a space between the facing region and the blade, and the outside of the casing A duct having one end communicating with the through-hole and an exhaust device provided at the other end of the duct, and the exhaust device creates a negative pressure inside the duct. Therefore and forming an air flow towards the exhaust system through the through-hole and the duct from the space between said facing region blade.

  By adopting such a configuration, the scattered toner existing in the space between the opposed region of the toner carrier and the toner supply body and the blade can be reliably collected through the through hole and the duct.

  In the developing device of the present invention, the through hole may be formed in the casing above the blade.

  By adopting such a configuration, the scattered toner can be collected through the through-holes and ducts before accumulating around the blade and the blade, thus preventing toner accumulation around the blade and the blade. be able to.

  In the developing device of the present invention, the flow path of the airflow includes a filter that is disposed upstream of the exhaust device and cannot pass the developer, and a developer recovery unit that is disposed below the filter. It may be characterized by being provided.

  By adopting such a configuration, the scattered toner is captured by the filter, and the captured scattered toner falls freely and is collected by the developer collecting unit. Since the developer collecting unit is formed in the developing device, the collected scattered toner can be collected together with the developing device when the developing device is replaced.

  In the developing device of the present invention, the exhaust device may be a fan.

  By adopting such a configuration, the cost of the exhaust device can be reduced.

  In the developing device of the present invention, the exhaust device may be a suction pump.

  By adopting such a configuration, the installation space for the exhaust device can be reduced.

  An image forming apparatus according to the present invention includes any one of the developing devices described above.

  According to the present invention, it is possible to provide an image forming apparatus including a developing device that can reliably collect scattered toner.

1 is a front view schematically showing an internal structure of a color printer according to an embodiment of the present invention. 1 is a perspective view of a developing device according to an embodiment of the present invention. 1 is a front cross-sectional view of a developing device according to an embodiment of the present invention. FIG. 2 is an enlarged front sectional view showing a part of a developing device according to an embodiment of the present invention.

  Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

  First, the overall configuration of the color printer 1 (image forming apparatus) will be described with reference to FIG. FIG. 1 is a front view schematically showing the overall configuration of a color printer. The front side in FIG. 1 is the front side (front side) of the color printer, and the left and right directions will be described with reference to the direction when the color printer is viewed from the front.

  The color printer 1 includes a box-shaped printer main body 2, a paper feed cassette 3 that stores paper (recording medium) is provided in the lower part of the printer main body 2, and a paper discharge tray is provided in the upper part of the printer main body 2. 4 is provided.

  An intermediate transfer belt 5 is disposed between a plurality of rollers in the central portion inside the printer main body 2. Below the intermediate transfer belt 5, four image forming units 8 are provided for each toner color (for example, four colors of magenta, cyan, yellow, and black). Each image forming unit 8 is rotatably provided with a photosensitive drum (image carrier) 9, and around the photosensitive drum 9, a charger 10, a developing device 11, a primary transfer unit 12, and the like. The cleaning device 13 and the static eliminator 14 are arranged in the order of the primary transfer process. Below each image forming unit 8, an exposure device 20 composed of a laser scanning unit (LSU) is arranged. Above the intermediate transfer belt 5, toner containers 16 corresponding to the image forming units 8 are accommodated side by side in the left-right direction for each toner color.

  On the right side inside the printer main body 2, a paper conveyance path 17 extending in the vertical direction from the paper feed cassette 3 toward the paper discharge tray 4 is provided. A paper feeding unit 18 is provided at the upstream end of the conveyance path 17, and a secondary transfer unit 19 is provided at one end (right end in the drawing) of the intermediate transfer belt 5 at a middle portion of the conveyance path 17, and downstream of the conveyance path 17. A fixing device 20 is provided at the section, and a paper discharge port 21 is provided at the downstream end of the transport path 17.

  Next, an image forming operation of the color printer 1 having such a configuration will be described. When the color printer 1 is turned on, various parameters are initialized, and initial settings such as temperature setting of the fixing device 24 are executed. When image data is input from a computer or the like connected to the color printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 9 is charged by the charger 10, an electrostatic latent image is formed on the surface of the photosensitive drum 9 by laser light (see arrow P) from the exposure device 7. Next, the electrostatic latent image is developed into a toner image of a corresponding color by the developing device 11 with the toner supplied from the toner container 16. This toner image is primarily transferred to the surface of the intermediate transfer 5 in the primary transfer portion 12. Each image forming unit 8 sequentially repeats the above operation, whereby a full-color toner image is formed on the intermediate transfer belt 5. Note that the toner and charge remaining on the photosensitive drum 9 are removed by the cleaning device 13 and the static eliminator 14.

  On the other hand, the paper taken out from the paper feed cassette 3 by the paper feed unit 18 is conveyed to the secondary transfer unit 19 in synchronism with the image forming operation described above, and in the secondary transfer unit 19 on the intermediate transfer belt 6. A full color toner image is secondarily transferred to the paper. The sheet on which the toner image is secondarily transferred is conveyed to the downstream side of the conveyance path 17 and enters the fixing device 20, where the toner image is fixed on the sheet. The sheet on which the toner image is fixed is discharged from the discharge outlet 21 onto the discharge tray 4.

  Next, the developing device 11 will be described with reference to FIGS. 2 is a perspective view of the developing device, FIG. 3 is a cross-sectional view of the developing device, and FIG. 4 is an enlarged cross-sectional view of a part of the casing of the developing device. The developing device 11 includes a casing 30 in which a two-component developer containing toner and a carrier (hereinafter referred to as a developer) is accommodated.

  As shown in FIGS. 2 and 3, the casing 30 has a substantially triangular shape in front and a box shape extending in the longitudinal direction of the photosensitive drum 9, and includes an upper wall portion 30 a and a bottom wall portion 30 b. A hollow portion surrounded by the left wall portion 30c, the right wall portion 30d, and the front and rear wall portions (both not shown) is formed. An opening 31 is formed in the upper part of the right wall portion 30d.

  As shown well in FIG. 4, below the opening 31, an inclined surface 32 facing the upper left direction is formed on the inner surface of the right wall portion 30 d. Under the inclined surface 32, a through hole 33 that penetrates the right wall portion 30 d and communicates the inside and the outside of the casing 30 is formed by an upper plane portion 34 and a lower plane portion 35 that face each other in the vertical direction. Yes. The upper surface of the lower flat portion 35 is inclined in the upper left direction. Below the lower flat surface portion 35 is formed a U-shaped upper concave portion 36 whose front shape is reversed left and right. Further, below the upper concave portion 36, an L-shaped hook-shaped portion 37 whose front shape is reversed left and right is provided on the outer surface of the right wall portion 30 d, and the outer surface of the right wall portion 30 d and the hook-shaped portion 37 are A lower concave portion (developer recovery portion) 38 having an open upper surface is formed between them.

  Further, between the outer surface of the upper flat portion 34 and the upper end portion of the outer surface of the bowl-shaped portion 37, a cover plate 39 having a U-shaped front shape, which is a member different from the casing 30, is fixed. The cover plate 39 forms a duct 40 that communicates from the through hole 33 to a space surrounded by the lower flat surface portion 35, the upper concave portion 36, and the lower concave portion 38.

A filter 41 is disposed on the opening surface of the upper recess 36 inside the duct 40. The filter 41 is formed of a material that prevents the passage of toner (for example, a nonwoven fabric filter having a basis weight of 400 g / m ² , a mesh member).

  The space between the upper recess 36 and the filter 41 communicates with an opening (not shown) formed in the front wall portion of the casing 30. A fan (exhaust device) (see FIG. 2) is installed outside the opening. The fan 42 operates so as to create a negative pressure in the space between the upper recess 36 and the filter 41.

  Further, a toner scattering prevention plate 44 is provided on the right wall portion 30d so as to extend from the upper end portion of the outer surface to the opening portion 31. The toner scattering prevention plate 44 includes a thin flat plate plate 45 and an L-shaped plate 46 that is attached to the inner surface of the flat plate plate 45 and has an L-shape that is upside down. The toner scattering prevention plate 44 reduces the area of the opening 31 as much as possible to prevent the scattering of the scattered toner from the opening 31.

  A sheet member 47 is attached to the inclined surface 32 of the right wall portion 30d. The sheet member 47 is made of a material having good surface smoothness (for example, a fluororesin or the like), and the lower end extends to above the inner end of the lower flat surface portion 35.

  Referring again to FIG. 3, a partition wall 49 extending in the longitudinal direction of the photosensitive drum 9 is erected at the lower portion of the casing 30, and the partition wall 49 causes the left stirring chamber 50, the right transfer chamber 51, It is divided into.

  Inside the casing 30 are a stirring screw 53 that stirs the developer in the stirring chamber 50, a transport screw 54 that stirs the developer in the transport chamber 51, and a magnetic roller that carries the developer above the transport screw 54. (Toner supply body) 55, development roller (toner carrier) 56 that carries toner opposite to the magnetic roller 55 on the upper right side of the magnetic roller 55, and development carried and disposed in the vicinity of the magnetic roller 55 A blade 57 for regulating the amount of the agent is accommodated.

  The agitation screw 53 and the conveying screw 54 have rotation shaft portions 53a and 54a, and screw blades 53b and 54b formed in a spiral shape along the axial direction on the outer peripheral surfaces of the rotation shaft portions 53a and 54a, respectively. Both ends of the stirring screw 53 are rotatably supported by the casing 30 in the stirring chamber 50. Both ends of the transport screw 54 are pivotally supported in the transport chamber 51 so that the casing 30 can rotate.

  The magnetic roller 55 includes a circular sleeve 55a and a magnetic pole roller 55b inserted into the sleeve 55a. The sleeve 55a is formed of a nonmagnetic metal material, and a shallow groove extending in the longitudinal direction of the photosensitive drum 9 is formed on the entire outer circumferential surface. A DC voltage and an AC voltage are applied to the sleeve 55a as a developing bias. The magnetic pole roller 55b is a cylindrical magnet, and is magnetized to a predetermined pole along the circumferential direction.

  The magnetic roller 55 is located above the conveying screw 54 and to the left of the through hole 33 of the right wall 30d of the casing 30. The sleeve 55a can be rotated counterclockwise in FIG. 3, and the magnetic pole roller 55b has a predetermined pole. Each is supported by the casing 30 so as to be located at the position.

  The developing roller 56 includes a tubular sleeve 56a and a shaft member 56b inserted into the sleeve 56a. The sleeve 56a is made of a nonmagnetic metal material. A DC voltage or an AC voltage is applied to the sleeve 56a as a developing bias. A magnetic pole member 56c is formed on the shaft member 56b so as to protrude radially from a part of the outer peripheral surface. The magnetic pole member 56c has a polarity different from that of the opposite magnetic pole roller 55b.

  The developing roller 56 is located at the upper right of the magnetic roller 55 and faces the inclined surface 32 of the right wall portion 30d, the sleeve 56a is rotatable in the counterclockwise direction of FIG. 3, and the shaft member 56b is a magnetic pole roller 55b of the magnetic roller 55. The magnetic pole members 56c are respectively supported by the casing 30 so as to face the predetermined poles. The developing roller 56 is opposed to the magnetic roller 55 with a predetermined interval. A region facing each other is defined as a facing region R. Further, the developing roller 56 is exposed at the right surface portion from the opening 31 of the casing 30 and faces the photosensitive drum 9.

  The blade 57 is an elongated member that is elongated in the longitudinal direction of the photosensitive drum 9. The blade 57 is disposed on the upper surface of the lower flat surface portion 35 below the through-hole 33 of the right wall portion 30d with the tip surface facing the magnetic roller 55, and is supported by the pin 59 via the protection plate 58. Yes. The tip surface of the blade 57 is opposed to the surface of the magnetic roller 55 on the upstream side in the rotation direction of the magnetic roller 55 from the facing region R between the magnetic roller 55 and the developing roller 56. A slight gap is formed between the front end surface of the blade 57 and the surface of the magnetic roller 55, and the amount (height) of the developer carried on the magnetic roller 55 is adjusted when passing through the blade 57. The height of the gap is regulated.

  In the developing device 11 having the above configuration, the toner supplied from the toner container 16 is mixed with the carrier by the stirring screw 53 and the transport screw 54 in the stirring chamber 50 and the transport chamber 51, respectively. The developer composed of toner and carrier is conveyed in the axial direction of each of the screws 53 and 54 while being agitated by the agitating screw 53 and the conveying screw 54, and developer passages (illustrated) formed at both ends of the partition wall 49. Not) is circulated through the stirring chamber 50 and the transfer chamber 51. By circulating while being stirred, the toner is charged by friction with the carrier.

  The developer containing the charged toner is conveyed to the magnetic roller 55 by the conveying screw 54 and forms a magnetic brush on the surface of the magnetic roller 55. The magnetic brush 55 is regulated to a predetermined thickness when passing through the blade 57 with the rotation of the sleeve 55 a of the magnetic roller 55, and is then conveyed to a region R facing the magnetic roller 55 and the developing roller 56. Then, a toner thin layer is formed on the developing roller 56 by the difference between the voltage applied to the sleeve 55a of the magnetic roller 55 and the voltage applied to the sleeve 56a of the developing roller 56 and the magnetic field. That is, the magnetic roller 55 supplies only the toner from the carried developer to the developing roller 56.

  The toner thin layer formed on the developing roller 56 is conveyed to the opening 31 by the rotation of the sleeve 56 a of the developing roller 56 and faces the photosensitive drum 9. Since alternating current and direct current voltages are applied to the sleeve 56a of the developing roller 56, the toner flies due to the potential difference between the photosensitive drum 9 and the developing roller 56, and the electrostatic latent image on the photosensitive drum 9 is developed with the toner. Is done.

  The toner remaining without being developed is conveyed to a facing region R between the developing roller 56 and the magnetic roller 55 and collected by a magnetic brush formed on the surface of the magnetic roller 55. The magnetic brush is peeled off from the magnetic roller 55 at the same pole portion where the magnetic pole member 56 c and the magnetic pole roller 55 b face each other, and then falls into the transfer chamber 51.

  When the fan 42 is operated simultaneously with the start of the developing operation, the inside of the duct 40 becomes negative pressure, and an air flow F from the inside of the casing 30 toward the fan 42 is generated in the duct 40. Specifically, from the space S between the opposed region R of the magnetic roller 55 and the developing roller 56 and the blade 57, the space passes through the through hole 33 and the space inside the cover plate 39, passes through the filter 41, and passes through the upper recess 36. An airflow F (see FIG. 2) is generated that flows inward and flows forward in the upper recess 36 toward the fan 42. Due to the generation of the air flow F, the space S between the facing region R of the magnetic roller 55 and the developing roller 56 and the blade 57 becomes negative pressure.

  In the space S between the blade R and the opposed region R between the magnetic roller 55 and the developing roller 56, the toner that has not flown to the photosensitive drum 9 because the charge amount is not stable or the magnetic brush of the magnetic roller 55. The detached toner is scattered. These scattered toners ride on the air current and pass through the duct 40 to reach the filter 41. When passing through the filter 41, the toner is captured by the filter 41, and only air is exhausted to the outside through the space in the upper recess 36. The toner captured by the filter 41 is dropped and stored in the lower concave portion 38 by its own weight.

  Even when the scattered toner falls on the filter plate 47, it is collected by riding in an air current before being deposited on the filter plate 47.

  As described above, according to the developing device 11 according to the embodiment of the present invention, the scattered toner existing in the space S between the facing region R and the blade 57 is quickly removed via the through hole 33 and the duct 40. It can be recovered. Furthermore, since the through-hole 33 is formed above the blade 57, the scattered toner can be collected before accumulating in the blade 57 and its surroundings. Therefore, it is possible to prevent image defects caused by scattered toner such as black spots. Further, since the space S between the facing region R and the blade becomes negative pressure, it is difficult for the toner to scatter outside from the opening 31 of the casing 30, so that the toner scatter to the outside of the developing device 11 can also be prevented. The toner contamination inside the printer main body 2 can be suppressed.

  In addition, the deteriorated toner that cannot contribute to the development work is accommodated in the lower recess 38 provided in the casing 30 without being returned to the inside of the casing 30, so that the deteriorated toner can be removed from the developer. Further, since the stored toner is collected together with the developing device 11 when the developing device 11 is replaced, there is no need to separately collect the stored toner.

  Furthermore, since the fan 42 is used to make the inside of the duct 40 have a negative pressure, the cost required for collecting the scattered toner can be reduced. A suction pump can be used instead of the fan 42. In this case, the installation space can be reduced.

  Furthermore, in the embodiment of the present invention, the case where the configuration of the present invention is applied to the color printer 1 has been described. However, in other different embodiments, the image forming apparatus other than the printer 1 such as a copying machine, a facsimile machine, and a multifunction machine is used. The configuration of the present invention may be applied.

  Furthermore, since the above description of the embodiments of the present invention describes preferred embodiments of the developing device and the image forming apparatus according to the present invention, various technically preferable limitations may be imposed. However, the technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the above-described components in the embodiment of the present invention can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of the 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)
9 Photosensitive drum (image carrier)
11 Developing Device 30 Casing 33 Through Hole 38 Lower Recess (Developer Recovery Unit)
40 Duct 41 Filter 42 Fan (exhaust device)
55 Magnetic roller (toner supply)
56 Developing roller (toner carrier)
57 blade

Claims (6)

A toner carrier for supplying toner to an image carrier on which an electrostatic latent image is formed, and a developer comprising toner and carrier are carried, and toner is supplied to the toner carrier in a region facing the toner carrier. A developing device comprising: a toner supply body; a blade that regulates the amount of developer carried on the toner supply body; and a casing that accommodates the toner carrier, the toner supply body, and the blade. ,
A through hole formed so as to penetrate the inside and the outside of the casing in a space between the facing region and the blade, a duct having one end communicating with the through hole in the outside of the casing, An exhaust device provided at the other end, and by making the inside of the duct negative pressure by the exhaust device, the space between the opposed region and the blade passes through the through hole and the duct. A developing device that forms an air flow toward the exhaust device.   The developing device according to claim 1, wherein the through hole is formed in the casing above the blade.   The air flow path is provided with a filter that is disposed upstream of the exhaust device so that the developer cannot pass therethrough, and a developer recovery unit that is disposed below the filter. The developing device according to claim 1 or 2.   The developing device according to claim 1, wherein the exhaust device is a fan.   The developing device according to claim 1, wherein the exhaust device is a suction pump.   An image forming apparatus comprising the developing device according to claim 1.

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