JP4854356B2 - Developing device and image forming apparatus having the same - Google Patents

Description

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

  An image forming apparatus such as a copying machine or a printer that employs an electrophotographic system includes a photosensitive drum (image carrier) and a developing device that visualizes an electrostatic latent image by supplying a developer to the photosensitive drum. I have. In general, the developing device includes a casing in which the developer is accommodated, a developing roller disposed in the casing so as to oppose the photosensitive drum, and a stirring and conveying screw (stirring and conveying member) that stirs and conveys the developer in the casing. It has. The stirring and conveying screw usually has a shaft portion and a spiral (blade portion) formed in a spiral shape in the axial direction on the outer peripheral portion of the shaft portion.

  In such a developing device, for example, when toner as a one-component developer is accommodated, as the toner is stirred and conveyed by the agitating and conveying screw, the wax on the toner surface and the surface treatment agent are gradually peeled off and flow. It may lose its properties and adhere to and accumulate on the spiral of the stirring and conveying screw. In such a state, the stirring function and the transporting function of the stirring and transporting screw are hindered.

  Therefore, as a conventional developing device, a device in which the shape of the spiral is improved to make it difficult for toner to adhere is known. (For example, refer to Patent Document 1). The spiral shown in Patent Document 1 is devised so that the agitation function and the transport function are compatible.

  A technique for scraping off toner adhering to a layer thickness regulating blade that regulates the layer thickness of toner on the developing roller is also known (for example, Patent Document 2).

On the other hand, the electrophotographic image forming apparatus further includes a cleaning device around the photosensitive drum for removing toner remaining on the surface of the photosensitive drum. The cleaning device usually has a cleaning blade that comes into contact with the surface of the photosensitive drum and a stirring and conveying screw that stirs and conveys the toner scraped off by the cleaning blade in one direction. In the cleaning device, toner may adhere to the agitating / conveying screw as in the developing device, so that a polyethylene terephthalate film is attached so as to extend radially from the shaft portion of the agitating / conveying screw in order to scrape the toner. Are known.
JP2000-250299A JP 2001-249538 A

  In the method of improving the shape of the spiral as in the developing device of Patent Document 1, the shape of the spiral is complicated, and even if the shape is improved, toner adhesion cannot be sufficiently prevented.

  In addition, the technology that employs a resinous film like the above cleaning device can scrape off the toner adhering to the spiral, but the function of conveying the toner is hindered, so this technology was adopted in the developing device. In such a case, the function that the developing device should have cannot be sufficiently secured.

  An object of the present invention is to prevent a static electricity from being accumulated by such a configuration in a developing device equipped with a stirring and conveying member while suppressing a developer from adhering to the stirring and conveying member to deteriorate a stirring function and a conveying function. There is to do.

The developing device of the present invention includes a casing, a first stirring and conveying member, a conductive member, and a developer removing unit. The casing can accommodate the developer. The first stirring and conveying member includes a first shaft portion that is rotatably disposed in the casing, and a spiral first blade portion that is formed on the outer peripheral portion of the first shaft portion. The conductive member is attached to the casing. The developer removing unit includes a first scraping member that can contact the first blade portion and that contacts the conductive member, and a holding member that is attached to the casing and holds the first scraping member.

  In this developing device, the developer adhering to the first blade portion of the first stirring / conveying member causes the first scraping member held by the holding portion to move to the first blade portion as the first stirring / conveying member rotates. Since it is scraped off by contact, it is possible to prevent the developer from adhering to and accumulating on the first stirring and conveying member.

  Along with such a scraping operation, the first scraping member may be charged with static electricity due to friction with the developer or the like, but since it is grounded to the conductive member, it has the same potential as the potential on the casing side. Thus, static electricity can be prevented from being accumulated. Therefore, it can be avoided that the accumulated static electricity is discharged and induces noise to adversely affect the developing operation.

The developing device of the present invention further includes a developer carrier and a developing bias input unit in the developing device. The developer carrier is rotatably disposed in the casing and supplies the developer to the image carrier of the image forming apparatus. The developing bias input unit is attached to the casing, receives a predetermined developing bias applied to the developer carrying member, and is electrically connected to the conductive member.

  As a method for releasing static electricity accumulated in the scraping member, for example, it is conceivable to ground the member on the image forming apparatus side. However, since the scraping member is in the casing, there is a possibility that the developing bias leaks in such a method. is there. However, in this developing device, the scraping member is grounded to the conductive member and the developing bias input portion, so that the same potential as the developing bias can be maintained, and thereby, the developing bias leaks and noise is generated. Can be suppressed. Further, since the scraping member has the same potential as the developing bias, it is possible to prevent the developer from adhering to the scraping member itself.

Oite the developing equipment of the present invention, the first scraping member is preferably disposed side by side a plurality in the axial direction in accordance with the helical pitch of the first blade portion. Moreover, it is preferable that the electroconductive member is extended in the axial direction along the 1st stirring conveyance member.

  Since each scraping member can be created individually, it can be easily created in a shape suitable for avoiding the accumulation of static electricity.

A developing device of the present invention, in the developing device, and a second shaft portion which is rotatably disposed in the first agitation transport member parallel to the casing, the second blade portion formed on an outer circumferential portion of the second shaft portion It is preferable to further include a second stirring and conveying member having the following. The developer removing unit preferably further includes a second scraping member that can contact the second blade portion and contact the conductive member, and the holding member further holds the second scraping member. .

  In this developing device, in particular, in the circulation stirring type device, the developer adhering to the two stirring and conveying members is scraped off by the first scraping member and the second scraping member, respectively.

Oite the developing equipment of the present invention, scraping member is preferably formed of a metal wire having elasticity.

  In this developing device, the use of such a scraping member makes it easy for static electricity to accumulate, but since it is grounded to the conductive member, it can be avoided that static electricity accumulates and discharge occurs. it can.

The image forming apparatus of the present invention includes an image carrier, a developing device, and a transfer device. Developing devices are equipment that to supply developer to the image carrier. The transfer device is a device that transfers the developer supplied to the image carrier to a recording medium.

  According to the present invention, the developer adhering to the first blade portion of the first agitating / conveying member causes the first scraping member held by the holding portion to be the first blade portion as the first agitating / conveying member rotates. Therefore, the developer can be prevented from adhering to and accumulating on the first stirring and conveying member. Along with such a scraping operation, the first scraping member may be charged with static electricity due to friction with the developer or the like, but since it is grounded to the conductive member, it has the same potential as the potential on the casing side. Thus, static electricity can be prevented from being accumulated. Therefore, it can be avoided that the accumulated static electricity is discharged and induces noise to adversely affect the developing operation.

<Configuration of image forming apparatus>
FIG. 1 shows a multifunction machine 1 as an image forming apparatus in which an embodiment of the present invention is adopted.

  The multifunction machine 1 is an image forming apparatus having functions as a copying machine, a printer, a facsimile machine, and a scanner, and includes an operation panel (not shown), an image reading unit 5, a control unit (not shown), a feeding unit. A paper unit 9, an image forming unit 11, a fixing unit 13, and a paper discharge unit 15 are provided.

  The operation panel has a start key for instructing copying and reading of a document, a setting key for setting various printing conditions, and the like. The operation panel has a touch panel type liquid crystal display on which various operation screens are displayed.

  The image reading unit 5 is for reading image information of a document on the document table 2 on the upper surface of the multifunction machine main body 1a, and has an optical system, a CCD, etc. (not shown).

  The control unit includes a microcomputer including a CPU, a RAM, a ROM, and the like, and performs control of input / output units such as the image reading unit 5 and the image forming unit 11, image processing for image information, and the like. Various program data for these operations are stored in the ROM, read out to the RAM by the CPU, and executed.

  The paper feed unit 9 has a plurality of paper feed cassettes 10 arranged at the bottom of the multifunction machine main body 1a, and a manual feed tray 12 provided on the side of the multifunction machine main body 1a. A sheet feeding roller 8 for conveying the recording medium) to the image forming unit 11 one by one and a driving motor (not shown) for driving the sheet feeding roller 8 are provided.

  The image forming unit 11 forms a toner image on a sheet conveyed from the sheet feeding unit 9 by an electrophotographic process, and is a photosensitive drum 21 (rotated in a predetermined rotation direction (arrow X direction)). An image carrier), and a main charging device 23, an exposure device 25, a developing device 27, a transfer device 29, a cleaning device 31, and a charge eliminating device 33, which are arranged around the photosensitive drum 21 in order from the upstream side in the rotation direction. ing.

  The photosensitive drum 21 is a rotating body having a photosensitive layer on its surface, and rotates at a predetermined rotation speed in response to an image formation command.

  The main charging device 23 has a charging wire to which a high voltage is applied. By applying a predetermined potential to the surface of the photosensitive drum 21 by corona discharge by the charging wire, the photosensitive drum 21 is uniformly charged. .

  The exposure device 25 includes a laser light source, a polygon mirror, and the like, and the surface potential of the photosensitive drum 21 is selectively attenuated by irradiating the charged photosensitive drum 21 with laser light based on image information. An electrostatic latent image is formed.

  The developing device 27 is a device for supplying toner to the photosensitive drum 21 to visualize the electrostatic latent image on the surface of the photosensitive drum 21. Details will be described later.

  The transfer device 29 is a device for transferring the toner image formed on the surface of the photosensitive drum 21 to the paper side by a transfer bias.

  The cleaning device 31 includes a casing 32, a cleaning blade 30 that contacts the surface of the photosensitive drum 21, and agitation for conveying the toner scraped off in the casing 32 to one side in the axial direction (the back side in FIG. 1). It has a conveying screw (not shown) and scrapes off and collects the toner remaining on the surface of the photosensitive drum 21.

  The neutralization device 33 is for removing the residual potential on the surface of the photosensitive drum 21.

  The fixing unit 13 is disposed on the downstream side of the image forming unit 11 in the sheet conveyance direction, and includes a heating roller 16 and a pressure roller 18 incorporating a heater, and the sheet onto which the toner image has been transferred is applied to both the rollers 16 and 18. The toner image is melted and fixed by being nipped.

  The paper discharge unit 15 is for discharging the paper that has passed through the fixing unit 13 to the paper discharge tray 14 on the side of the multifunction machine main body 1a, and includes a roller and a drive motor that drives the roller. .

  The multifunction machine 1 further includes an automatic document feeder 17 and a toner replenishing device (not shown) as other input / output units. The automatic document feeder 17 is mounted on the upper surface of the multifunction machine main body 1a so as to be openable and closable, and can continuously feed a plurality of documents one by one to the document table 2. The toner replenishing device is for replenishing toner from a toner cartridge (not shown) disposed above the developing device 27, and the remaining amount of toner is detected by a remaining amount detection sensor (not shown) of the developing device 27. When it is detected that the amount has decreased, the replenishment operation is performed.

<Developing device>
Next, the developing device 27 will be described in detail with reference to FIGS.

  In FIG. 3, the upper surface portion of the rear end portion of the developing device 27 is omitted for convenience of explanation.

  The developing device 27 performs development using toner as a one-component developer, and includes a casing 41, a developing roller 43, a layer thickness regulating blade 45, and first and second stirring and conveying screws 47 and 49. (First and second stirring and conveying members), a developer removing unit 51, and a developing bias applying means 53.

  The casing 41 is a housing made of resin, and contains toner inside. The front end portion of the casing 41 is opened, and the upper surface portion of the rear end portion is communicated with a toner cartridge (not shown). Further, the casing 41 has a partition wall 41a formed between the first and second stirring and conveying screws 47 and 49 so as to extend in a vertical direction and extend over a region excluding both end portions in the axial direction.

  The developing roller 43 is rotatably attached to the opening portion of the front end portion of the casing 41 and is disposed adjacent to the photosensitive drum 21. The developing roller 43 supplies toner in the casing 41 to the photosensitive drum 21, and is fixedly disposed on the inner peripheral side of the developing sleeve 43a and a developing sleeve 43a that is rotationally driven in the direction of arrow C, and is a predetermined one. And a magnet roller 43b having a plurality of magnetic poles formed at circumferential positions.

  The layer thickness regulating blade 45 is a member for regulating the thickness of the toner layer supplied to the developing sleeve 43a, and is disposed with a predetermined gap between the tip portion and the developing sleeve 43a.

  The second agitating and conveying screw 49 conveys the toner in the casing 41 to one side in the axial direction (the direction from the back side to the near side in FIG. 2) while agitating the toner. At the same time, the toner in the casing 41 is circulated and conveyed. The second agitating and conveying screw 49 is arranged in parallel with the first agitating and conveying screw 47 via the partition wall 41a, and is arranged in the casing 41 so as to be rotatable in the arrow B direction. The second agitating and conveying screw 49 includes a shaft 71 (second shaft portion), a spiral spiral 73 (second blade portion) formed on the outer peripheral portion of the shaft 71, and an outer peripheral portion of one axial end portion of the shaft 71. It has the plate-shaped part 75 formed in this. The plate-like portion 75 at the front end in the transport direction is for transporting toner to the first stirring and transporting screw 47 side on one side in the axial direction, and extends from the shaft 71 to the outer peripheral side.

  The first agitating and conveying screw 47 conveys the toner in the casing 41 to the other side in the axial direction (the direction from the front side to the back side in FIG. 2) while agitating the toner. It is arranged to be freely rotatable. The first stirring and conveying screw 47 includes a shaft 61 (first shaft portion), a spiral 63 (first blade portion) formed in a spiral shape on the outer peripheral surface of the shaft 61, and an outer peripheral portion of the tip end portion of the shaft 61 in the transport direction. It has the plate-shaped part 65 formed in this. The plate-like portion 65 is for conveying toner to the second stirring and conveying screw 49 side on the other side in the axial direction, and extends from the shaft 61 to the outer peripheral side.

  The developer removing unit 51 is provided in a portion of the upper surface portion of the casing 41 that is positioned above the partition wall 41a and slightly on the front end side, and as shown in FIGS. It has a spring member 83 (first scraping member) and a plurality of second spring members 85 (second scraping members).

  The plurality of first and second spring members 83 and 85 are formed of a metal wire having a spring property (for example, SUS304). Here, the first and second spring members 83 and 85 have three shapes corresponding to the axial region. including.

  As a first shape, a spring member 85 a that protrudes toward the second agitating and conveying screw 49 is held at one axial end of the holding portion 81. Further, at the other axial end of the holding portion 81, two spring members 83a projecting from the first stirring and conveying screw 47 are held at the same axial position. Each of the spring members 83a and 85a has a rectangular tip.

  As a second shape, a plurality of spring members 85b projecting toward the second agitating / conveying screw 49 side and a plurality of springs projecting toward the first agitating / conveying screw 47 side are provided in the region excluding both axial ends of the holding portion 81. A member (not shown) is held. These spring members 85b are each formed with a rectangular tip and folded so that the toner adhering to the spirals 63 and 73 can be scraped off.

  As the third shape, three spring members 85c projecting toward the second agitating and conveying screw 49 are held at the other end in the axial direction of the holding portion 81 and at the one end next to the spring member 85a. . Further, at one end in the axial direction of the holding portion 81, three spring members 83c that project toward the first stirring and conveying screw 49 are disposed. Each of the spring members 83c and 85c has a V-shaped tip so that the toner adhering mainly to the spirals 63 and 73 can be scraped off.

  3 to 6, for convenience of explanation, the spring members 83 and 85 are not shown in all the axial regions of the holding portion 81, but all of the omitted regions have the second shape. It is assumed that the spring member 85b is held. Each of the spring members 83 and 85 has a pair of starting end portions attached to the holding portion 81, and each starting end portion is below the developing stay 103 (described later) of the developing bias applying means 53 from below. It is in contact.

  The holding portion 81 is a member for holding the plurality of first and second spring members 83, 85, and extends in the axial direction and is connected to each other in the front-rear direction. 95.

  The first plate 93 is disposed on the first stirring and conveying screw 47 side, and is fixed to the rear end portion of the developing stay 103 with, for example, an adhesive. A portion on the rear end side of the first plate 93 is formed with a plurality of attachment portions 93a to which spring members 83c and the like can be attached at predetermined intervals in the axial direction according to the helical pitch of the first agitating and conveying screw 47. It has a shape. Each attachment portion 93a is formed with an insertion hole 93b through which a starting end portion such as a spring member 83c is inserted. The first plate 93 has a notch 93c formed at an axial position corresponding to the position of each mounting portion 93a. The notch 93c is a starting end of a spring member 83c and the like passing through the insertion hole 93b. Guide the part upward. Further, the first plate 93 has an engaging protrusion 93 d for snapping to the second plate 95.

  The second plate 95 has an engagement hole 95 a for snapping to the first plate 93 by the engagement protrusion 93 d of the first plate 93. The second plate 95 is formed with an insertion hole 95b through which a starting end portion such as a spring member 85b is inserted, and a front end side such as the spring member 85b is connected to the front end side surface of the second plate 95. A guide hole 95c for guiding to the front end side is formed. Further, the second plate 95 has locking portions 95b that are locked to the locking holes 103a of the developing stay 103 of the developing bias applying means 53 at the upper end of the second plate 95 at three axial end portions and a central portion. Is formed.

  The development bias applying means 53 has a development bias input terminal 101 and a development stay 103. The developing bias input terminal 101 is for applying a predetermined developing bias to the developing roller 43, and is connected to a developing bias power source (not shown). The development stay 103 is a metal plate-like member extending in the axial direction, the end on the front end side is bent at a right angle so as to face downward, and the end on the rear end side is also bent at a right angle so as to face downward, The first plate 93 and the second plate 95 are disposed on the rear end side. The developing stay 103 is attached to the upper surface portion of the front end side of the casing 41 by screws. The development stay 103 is a metal (for example, SECC) member that is electrically connected to the development bias input terminal 101. When the development bias is applied to the development bias input terminal 101, the development stay 103 becomes equipotential thereto. Further, the developing stay 103 is configured such that static electricity is not accumulated in the spring members 83 and 85 by contacting the leading end portions of the spring members 83 and 85.

<Operation of Image Forming Apparatus>
Next, the operation of the multifunction device 1 will be described.

  When the multifunction device 1 is turned on, various parameters are initialized in the control unit, and the heater of the fixing unit 13 is heated, and the initial operation is performed. When the initial operation is completed, a predetermined print standby screen is displayed on the operation panel.

  In this state, for example, when a document is placed on the document table 2 and the start key is pressed, the image information of the document is read and the sheet is fed from the sheet feeding cassette 10. At this time, in the image forming unit 11, the photosensitive drum 21 is rotationally driven, charged, and then exposed based on the read image information to form an electrostatic latent image. Then, toner is supplied from the developing device 27. Thus, a toner image is formed. Then, at a predetermined timing, the sheet is conveyed to the image forming unit 11 and the toner image is transferred from the photosensitive drum 21. The sheet on which the toner image is transferred is further conveyed downstream, and the toner image is melted and fixed by passing through the fixing unit 13, and is discharged onto the discharge tray 14 by the discharge unit 15.

  During this series of image forming operations, in the developing device 27, the two agitating and conveying screws 47 and 49 convey the toner in opposite directions while agitating the toner, so that the toner is circulated and conveyed in the casing 41. At the same time, a part of the toner is supplied from the first stirring and conveying screw 47 to the developing roller 43 side. If such an operation is repeated, when the wax or the surface treatment agent on the toner surface is peeled off and the fluidity is gradually lowered, the toner may adhere to and accumulate on the spirals 63 and 73 of the agitating and conveying screws 47 and 49. However, in the developing device 27, since the spring members 83 and 85 are brought into contact with the spirals 63 and 73 and the toner is scraped off, the adhesion and accumulation of the toner is suppressed, whereby the stirring of the stirring and conveying screws 47 and 49 is suppressed. It can be avoided that both the functions of the transfer and the conveyance are hindered.

  Each of the spring members 83 and 85 is a separate member and may be individually created according to the position where it is attached because it may be attached individually when the toner removal unit is assembled. Therefore, it becomes easy to create different shapes, and for example, compared to a case where the spring members 83a, 85b, and 83c are connected by a single wire, it is sufficient to use a mold having a simple shape, thereby reducing costs. it can.

  Further, since the spring members can be individually created, for example, the spring members can be used for developing devices of other image forming apparatuses other than the multi-function machine 1 and can be shared across multiple models. Therefore, it is possible to reduce the cost.

<Other embodiments>
(A) The shape, type, and location of the scraping member are not limited to those described in the above embodiment, and can be determined as appropriate according to the helical pitch and the shape of the stirring and conveying member.

  (B) The developing stay is not limited to a metal, but may be formed of another material such as a conductive resin as long as it is made of a conductive material and is electrically connected to the developing bias applying means.

  (C) The developing device is not limited to the circulating stirring type, and may be one having only one stirring and conveying member. In this case, only the first scraping member is held by the holding portion.

  (D) The developer accommodated in the developing device is not limited to a one-component developer, and may be a two-component developer, and may be magnetic or non-magnetic.

  (E) The image forming apparatus is not limited to a multifunction machine, and may be a copying machine, a printer, or a facsimile machine.

  (F) The configuration of the holding portion is not limited to that described in the above embodiment, and for example, the first plate may be configured as a metal member integrated with the developing stay.

1 is a longitudinal sectional view showing a multifunction machine in which an embodiment of the present invention is adopted. FIG. 2 is a longitudinal sectional view of a developing device of the multifunction machine. FIG. 3 is a perspective view showing the developing device with a part broken away. FIG. 3 is a perspective view illustrating a toner removal unit of the developing device with a part thereof omitted. FIG. 5 is an enlarged view of a main part of the toner removing unit in FIG. 4. FIG. 5 is a rear perspective view showing the toner removing unit of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multifunctional device 27 Developing device 29 Transfer device 21 Photosensitive drum (image carrier)
41 Casing 47 1st stirring conveyance screw (1st stirring conveyance member)
49 2nd stirring conveyance screw (2nd stirring conveyance member)
61, 71 shafts (first shaft portion, second shaft portion)
63, 73 spiral (first blade part, second blade part)
65,75 Plate-like part 51 Toner removal unit (developer removal unit)
81 Holding portion 83 First spring member (first scraping member)
85 Second spring member (second scraping member)
103 Development stay (conductive member)

Claims (4)

A resin casing capable of accommodating the developer;
A developer carrier that is rotatably disposed in the casing and supplies developer to the image carrier of the image forming apparatus;
A first agitation transport member having a first shaft portion rotatably disposed in the casing, and a spiral first blade portion formed on an outer peripheral portion of the first shaft portion;
A metal conductive member mounted on the casing;
A first scraping member is formed from a metal wire having a contact with and elastically in contact possible and and the conductive member to the first blade part, a and the first scraping member is mounted on said casing A developer removing unit having a holding member for holding;
A developing bias input unit that is attached to the casing and receives a predetermined developing bias applied to the developer carrier, and is electrically connected to the conductive member;
A developing device comprising: A plurality of the first scraping members are arranged in the axial direction according to the helical pitch of the first blade portion,
The conductive member extends along the axial direction of the first stirring and conveying member.
The developing device according to claim 1 . A second agitating and conveying member having a second shaft portion disposed in parallel with the first agitating and conveying member and rotatably in the casing, and a second blade portion formed on an outer peripheral portion of the second shaft portion. Further comprising
The developer removing unit is contactable to said second blade section and further comprises a second scraping member abuts on the conductive member,
The holding member further holds the second scraping member;
The developing device according to claim 1 or 2 . The image carrier;
A developing device according to any one of the three developer claims 1 to be supplied to the image bearing member,
A transfer device for transferring the developer supplied to the image carrier to a recording medium;
An image forming apparatus.

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