JP5476870B2 - Developing device, process cartridge, image forming apparatus, developer replacement method - Google Patents

Description

  The present invention relates to a developing device that is provided in an image forming apparatus such as a copying machine, a facsimile machine, or a printer and supplies a so-called two-component developer to an image carrier, a process cartridge provided with such a developing device, and such an image forming apparatus provided with these. The present invention relates to a developer replacing method for replacing a two-component developer in a developing device using such a developing device, a process cartridge, and an image forming apparatus.

  Conventionally, a developing device using a so-called two-component developer (hereinafter referred to as a developer) containing a toner and a magnetic carrier has been widely used in image forming apparatuses such as copiers, facsimiles, and printers (for example, [Patent Reference 1] to [Patent Document 3]). In such a developing device, the toner is charged by the friction of the developer inside, the developer charged with the toner is carried on the developer carrying member such as a developing roller, and the toner charged by the electrostatic force by the electric field is photoreceptord. The latent image on the image carrier is developed by moving toward the image carrier.

  Since the developer in such a developing device consumes toner by developing the latent image on the image carrier, the toner concentration in the developer is supplemented with the toner consumed by replenishing new toner. Is maintained within a predetermined range. On the other hand, in such a developing device, the carrier is repeatedly consumed with almost no consumption, so that the coat layer of the surface layer is worn out due to the friction of the developer or the addition of toner resin or toner to the coat layer. Deteriorated due to adhesion of the agent. When the carrier is deteriorated, the ability to charge the toner is lowered, causing a problem that the toner is scattered and the background of the formed image is stained.

  As a measure for preventing such a problem from occurring, a service person visits the user periodically to exchange carriers, but this increases the maintenance cost. On the other hand, various techniques for replacing the developer on the developing device side have been proposed (see, for example, [Patent Document 1] to [Patent Document 3]), and according to this technique, the maintenance cost for a serviceman is reduced. Can be done.

  As such a technique, a technique (for example, [Patent Documents] including means for supplying a new developer into the developing device and an opening for overflowing excess developer generated when the new developer is supplied by this means. 1)), and a mechanism for forcibly discharging the developer from the discharge port before or after the new developer is supplied by this means (for example, [Patent Document 2]). (See Patent Document 3).

  However, in the former technique, the developer can be excessively discharged depending on the position of the opening. That is, in general, such a developing device is provided with a member for stirring the developer for the purpose of rubbing the developer to charge the toner, and the like. Since the agent may jump, depending on the position of the opening, the developer that has jumped out is discharged from the opening in addition to the overflow. When discharge due to such jumping of the developer occurs, the amount of developer in the developing device may fall below the required amount, and when such a state occurs, the developing ability of the developing device decreases and formation occurs. There is a problem that the density of the generated image may be insufficient or the density of the image may be uneven.

  On the other hand, in the latter technique, such a mechanism has a shutter of a discharge port (for example, refer to [Patent Document 2]). Depending on the structure of the mechanism, unintended discharge of the developer from the discharge port is prevented or suppressed. It becomes possible. However, in this technique, when the fluidity of the developer is lowered due to deterioration of the developer or environmental fluctuation, the control accuracy of the developer discharge amount by such a mechanism may be lowered. When the developer discharge amount increases, there may be a problem that the image density becomes insufficient as described above. When the developer discharge amount decreases, the developer fills the developing device and the outside of the developing device. May cause problems such as overflowing. Further, the latter technique has a problem that the development apparatus can be increased in size or the cost can be increased due to the provision of such a mechanism.

  The present invention is a developing device that is provided in an image forming apparatus such as a copying machine, a facsimile, or a printer and supplies a so-called two-component developer to an image carrier, and discharges an appropriate amount of the two-component developer by overflow with a simple configuration. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, a process cartridge including such a developing device, such an image forming apparatus including these, such a developing device, a process cartridge, and a developer replacing method for replacing a two-component developer in the developing device using the image forming apparatus. .

In order to achieve the above object, a first aspect of the present invention provides a developer carrying member for carrying a two-component developer containing a toner and a carrier, and supplying the carried two-component developer to an image carrier. the two-component developer in the first developer conveying member to supply the developer carrier conveys from one end portion side in a first direction toward the other end side, the first developer conveying located below the member, the two-component developer is conveyed from the one end side in a second direction toward the other end side, one end side of the first developer conveying member from the other end A second developer conveying member that pushes up and delivers the two-component developer, a first region where the first developer conveying member conveys the two-component developer, and a second developer conveying member. It has a second region for transporting the two-component developer, and a first region and a second region therein An image case, a partition member for partitioning the first region and the second region, and the other end side of the first developer conveying member in the first region, the second in the second region and one end side of the developer conveying member communicates, and partition member having a communicating portion for transferring the received 2 component developer is dropped from the first region to the second region, of the developing case, the The two-component developer is formed at a position corresponding to the upstream end portion of the partition member in the same direction among the positions downstream of the communication portion in the direction 2 and from the second region to the outside of the developing case. possess a developer outlet for extravasation of the developer the two-component developer carried on the carrier is collected in the region other than the first region, the second developer conveying member, the A rotating shaft extending in the direction of 2, and the rotating shaft provided integrally with the rotating shaft; And a developer transport unit for transporting the two-component developer in the second direction by rotating in the second direction, and the developer transport unit is arranged at a position including the developer discharge port in the second direction. in a developing device for chromatic distribution portion.

According to a second aspect of the present invention, in the developing device according to the first aspect, a third region for collecting the two-component developer released from the developer carrying member and the second region collected in the third region are collected. And a third developer conveying member for conveying the component developer in the third region .

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, the two-component developer that has jumped up when being conveyed by the second developer conveying member is discharged from the developer discharge port. In order to prevent this, a developer splash-up preventing member provided opposite to the second developer transport member is provided.

  According to a fourth aspect of the present invention, in the developing apparatus according to any one of the first to third aspects, the first developer conveying member that discharges the two-component developer overflowing from the developer discharge port; It has a developer discharge member provided between the second developer transport member.

According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the two-component developer recovered in the third region is received from the third region to the second region. It has the opening part for passing, It is characterized by the above-mentioned.

A sixth aspect of the present invention is the developing apparatus according to any one of the first to fifth aspects, further comprising a developer supply port for supplying the new two-component developer to the second region. To do.

  According to a seventh aspect of the present invention, there is provided a process cartridge comprising the developing device according to any one of the first to sixth aspects and an image carrier for developing a latent image by the developing device.

  An eighth aspect of the invention is an image forming apparatus having the developing device according to any one of the first to sixth aspects or the process cartridge according to the seventh aspect.

  According to a ninth aspect of the present invention, the developing device according to any one of the first to sixth aspects, the process cartridge according to the seventh aspect, or the image forming apparatus according to the eighth aspect is used, and When the two-component developer or a new carrier is supplied into the developing device, the two-component developer in the developing device is replaced by overflowing the excess two-component developer from the developer discharge port. There is a developer exchange method.

The present invention comprises a developer carrying member for carrying a two-component developer containing a toner and a carrier and supplying the carried two-component developer to an image carrier, and the one-component side of the two-component developer. A first developer conveying member that is conveyed in a first direction toward the other end side and that is supplied to the developer carrier, and is located below the first developer conveying member, and the two-component development agent is conveyed from the one end side in a second direction toward the other end, passes from the other end side is pushed up the two-component developer on the one end side of the first developer conveying member A second developer conveying member; a first region where the first developer conveying member conveys the two-component developer; and a second developer conveying member conveying the two-component developer. a region, a developing casing having a first region and a second region therein, the first region and the second region A partition member that separates the other end portion side of the first developer transport member in the first region and the one end portion side of the second developer transport member in the second region, A partition member having a communication part for dropping the two-component developer and transferring it from the first area to the second area, and a position of the developing case downstream of the communication part in the second direction is formed at a position corresponding to the upstream end of the partition member in the same direction, the two-component developer possess a developer outlet for the overflow from the second region to the outside of the developing case, The two-component developer carried on the developer carrying member is collected in a region other than the first region, and the second developer transport member includes a rotation shaft extending in the second direction, and the rotation shaft. And the two-component developer by rotating together with the same rotating shaft. And a developer conveying portion for conveying the second direction, since the developing device for perforated non arrangement portion of the developer conveying portion to a position which includes the developer discharge opening in a second direction, By specifying the arrangement position of the developer discharge port and having the non- arranged portion, the second portion is not supplied to the developer carrier but is supplied from the communicating portion with a simple configuration but is conveyed by the first developer conveying member. Appropriate amount of two-component developer including two-component developer that has fallen into the area can be retained at the developer discharge port and discharged due to overflow, preventing the increase in size and cost of the device with a simple configuration. In addition, it is possible to provide a developing device capable of contributing to good image formation over time by keeping the amount of the developer appropriate and suppressing the carrier while changing the carrier.

  In order to prevent the two-component developer that has jumped up when being transported by the second developer transport member from being discharged from the developer discharge port, the second developer transport member is provided to face the second developer transport member. If the developer splash prevention member is provided, the arrangement position of the developer discharge port is specified and the developer splash prevention member is provided, so that an appropriate amount of the two-component developer can be discharged with a simple configuration. It is possible to stay at the arrangement position of the printer and discharge it by overflowing instead of jumping up, while keeping the amount of developer properly and preventing or suppressing the increase in size and cost of the device with a simple configuration and the carrier. It is possible to provide a developing device that can be exchanged and contribute to good image formation over time.

  If it has a developer discharge member provided between the first developer transport member and the second developer transport member that discharges the two-component developer overflowing from the developer discharge port, By specifying the arrangement position of the developer discharge port, it is possible to retain an appropriate amount of two-component developer at the arrangement position of the developer discharge port with a simple configuration and discharge it by overflow. Contribute to good image formation over time by keeping the amount of developer appropriate and replacing the carrier while preventing or suppressing the increase in size and cost of the device with the arrangement position of the discharge member specified It is possible to provide a developing device capable of the above.

  The present invention resides in a process cartridge including such a developing device and an image carrier on which a latent image is developed by the developing device. Therefore, by specifying the arrangement position of the developer discharge port, an appropriate amount can be obtained with a simple configuration. The two-component developer can be retained at the position of the developer discharge port and discharged by overflow, and the amount of developer can be reduced while preventing or suppressing an increase in size and cost of the apparatus with a simple configuration. It is possible to provide a process cartridge that can be handled as a replacement part that can be appropriately maintained and can be replaced as a carrier and contribute to good image formation over time and can be easily maintained.

  Since the present invention is in such a developing device or an image forming apparatus having such a process cartridge, by specifying the arrangement position of the developer discharge port in the developing device, an appropriate amount of two-component developer can be obtained with a simple configuration. It is possible to stay at the position of the developer discharge port and discharge it by overflowing, while maintaining or maintaining the amount of developer properly while preventing or suppressing the increase in size and cost of the device with a simple configuration. It is possible to provide an image forming apparatus that can be exchanged and perform good image formation over time.

  The present invention uses such a developing device, such a process cartridge, or such an image forming apparatus, and when the new two-component developer or new carrier is supplied into the developing device, the excess two-component development. Since there is a developer replacement method for replacing the two-component developer in the developing device by overflowing the developer from the developer discharge port, a simple configuration can be obtained by specifying the position of the developer discharge port Therefore, an appropriate amount of the two-component developer can be retained at the position where the developer discharge port is disposed and discharged by overflowing. It is possible to provide a developer exchange method capable of maintaining an appropriate amount and exchanging the carrier and contributing to good image formation over time.

1 is a schematic front view of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic front view showing a configuration around one image carrier among a plurality of image carriers provided in the image forming apparatus shown in FIG. 1. FIG. 3 is a schematic right side sectional view of the developing device shown in FIG. 2. FIG. 3 is a schematic plan sectional view of the developing device shown in FIG. 2. FIG. 3 is a schematic front view of a developing device having a configuration different from that of the developing device shown in FIG. 2. FIG. 3 is a perspective view showing an arrangement mode of a developer carrier, a first developer conveying member, a second developer conveying and a collecting conveying member provided in the developing device shown in FIG. 2.

  FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a multifunction peripheral of a copying machine, a printer, and a facsimile machine, and can perform full color image formation. When used as a printer, the image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside. This is the same when the image forming apparatus 100 is used as a facsimile.

  The image forming apparatus 100 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, cardboard, cardboard, and envelopes. It is. The image forming apparatus 100 is also a double-sided image forming apparatus capable of forming images on both sides of a sheet as a recording medium.

  The image forming apparatus 100 includes a main body 101 that occupies a center position in the vertical direction, a reading device 21 that is positioned above the main body 101 and that reads a document, and a document that is loaded and loaded with a document toward the reading device 21. An automatic document feeder 22 called ADF, and a sheet feeding table on which sheets conveyed below the photosensitive drums 20Y, 20M, 20C, 20BK and the intermediate transfer belt 11 are positioned below the main body 101. As a sheet feeding device 23.

  The image forming apparatus 100 includes a plurality of photosensitive drums 20Y, 20M, 20C, and 20BK that can form images as images corresponding to colors separated into yellow, magenta, cyan, and black, respectively. 1 is a tandem type image forming apparatus that employs a tandem structure in which the two are arranged side by side. The photosensitive drums 20Y, 20M, 20C, and 20BK have the same diameter, and an intermediate transfer as an intermediate transfer body that is an endless belt that is an almost endless belt disposed in the inside of the main body 101 of the image forming apparatus 100. They are arranged at equal intervals on the outer peripheral surface side of the belt 11, that is, on the image forming surface side.

  The intermediate transfer belt 11 is movable in the arrow A1 direction, which is the clockwise direction in the figure, while facing the respective photosensitive drums 20Y, 20M, 20C, and 20BK. The visible image, that is, the toner image formed on each of the photosensitive drums 20Y, 20M, 20C, and 20BK is superimposed and transferred to the intermediate transfer belt 11 that moves in the direction of the arrow A1, and is then collectively transferred to the sheet. It has become. As described above, the image forming apparatus 100 employs an intermediate transfer method, in other words, an indirect transfer method.

  In the superimposing transfer to the intermediate transfer belt 11, the toner images formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are superimposed on the same position on the intermediate transfer belt 11 in the process in which the intermediate transfer belt 11 moves in the A1 direction. A primary transfer device serving as a first transfer unit serving as a transfer charger disposed at a position facing each of the photosensitive drums 20Y, 20M, 20C, and 20BK with the intermediate transfer belt 11 interposed therebetween. By applying a voltage from a certain primary transfer roller 12Y, 12M, 12C, or 12BK, the timing is shifted from the upstream side toward the downstream side in the A1 direction, and the position immediately below each photosensitive drum 20Y, 20M, 20C, or 20BK, that is, the transfer position. Is done.

  The photosensitive drums 20Y, 20M, 20C, and 20BK are arranged in this order from the upstream side in the A1 direction. The photosensitive drums 20Y, 20M, 20C, and 20BK are provided in image stations 60Y, 60M, 60C, and 60BK, respectively, for forming yellow, magenta, cyan, and black images.

  The image forming apparatus 100 is arranged opposite to the image forming unit 60 as an image forming unit constituted by four image stations 60Y, 60M, 60C, and 60BK, and below the respective photosensitive drums 20Y, 20M, 20C, and 20BK. A transfer belt unit 10 as an intermediate transfer unit provided with the intermediate transfer belt 11, and disposed so as to be opposed to the intermediate transfer belt 11 and in contact with the intermediate transfer belt 11. A secondary transfer roller 17 that is a secondary transfer device as a second transfer unit that rotates in the same direction as the intermediate transfer belt 11 and transfers a toner image on the intermediate transfer belt 11 to a sheet, and a secondary transfer roller 17 A conveyance device 76 that conveys a sheet on which the toner image on the intermediate transfer belt 11 has been transferred, and a toner image that is disposed to face the intermediate transfer belt 11. And an intermediate transfer belt cleaning device 14 for cleaning the upper intermediate transfer belt 11 after being transferred to the sheet.

  The image forming apparatus 100 also includes an optical scanning device 8 that is an exposure unit that is a writing unit as an optical writing device that is a writing unit disposed facing the image stations 60Y, 60M, 60C, and 60BK. The sheet conveyed from the feeding device 23 is transferred between the intermediate transfer belt 11 and the secondary transfer roller 17 at a predetermined timing in accordance with the toner image formation timing by the image stations 60Y, 60M, 60C, and 60BK. And a sensor (not shown) for detecting that the leading edge of the sheet has reached the registration roller pair 13.

  The image forming apparatus 100 also includes a fixing device 6 as a belt-fixing type fixing unit for fixing a toner image on the sheet when the sheet conveyed by the conveying device 76 enters, and a fixed sheet outside the main body 101. The sheet discharge unit 79 includes a sheet discharge path for discharging the sheet and a reversing path for conveying the sheet toward the registration roller pair 13 again. The sheet discharge unit 79 conveys the sheet to any one of the paths, and the sheet discharge unit 79 forms an image on one surface. And a duplex unit 96 that is a sheet reversing device as a sheet refeeding unit that switches the sheet back and reverses the sheet when the sheet is conveyed to the reversing path and conveys the sheet again toward the registration roller pair 13. ing.

  The image forming apparatus 100 also includes a paper discharge tray 75 that is disposed outside the main body 101 and stacks sheets on which images have been formed, a manual sheet feeding device 33 that is disposed on the right side surface of the main body 101 in FIG. As described above, a discharged developer storage tank 61 as a discharged developer storage section for storing the developer discharged from the developing devices 50Y, 50M, 50C, and 50BK provided in the image stations 60Y, 60M, 60C, and 60BK, and image formation An operation panel (not shown) that operates the apparatus 100 and a control unit (not shown) that controls the operation of the entire image forming apparatus 100 are provided.

  In addition to the intermediate transfer belt 11, the transfer belt unit 10 includes primary transfer rollers 12Y, 12M, 12C, and 12BK, a driving roller 72, a transfer inlet roller 73, and a tension roller 74 around which the intermediate transfer belt 11 is wound. And driving means (not shown).

  The transfer belt unit 10 is swung counterclockwise around the drive roller 72 in FIG. 1 by the driving means, so that the photosensitive drum 20BK is kept in contact with the intermediate transfer belt 11 and the photosensitive drum 20BK is maintained. 20Y, 20M, and 20C can be separated from the intermediate transfer belt 11.

  The state shown in FIG. 1 is a case where full-color image formation is performed, and the photosensitive drums 20Y, 20M, and 20C are separated from the intermediate transfer belt 11 when black single-color image formation is performed. The operation of the driving means is performed by the control means.

  Since the image forming apparatus 100 includes the intermediate transfer belt cleaning device 14, in principle, black residual toner is also transferred from the intermediate transfer belt 11 to the photosensitive drums 20 </ b> Y and 20 </ b> M even when a black monochrome image is formed. Therefore, the photosensitive drums 20Y, 20M, and 20C need not be separated from the intermediate transfer belt 11, but the intermediate transfer belt is cleaned for some reason. In consideration of the case where the residual toner cannot be completely removed even with the apparatus 14, the photosensitive drums 20Y, 20M, and 20C are separated from the intermediate transfer belt 11 when a black monochrome image is formed. This is because the black toner is easily noticeable and has a great influence on the image when it adheres to the photosensitive drums 20Y, 20M, and 20C.

  For the same reason, the photosensitive drum 20BK for forming a black image is disposed downstream of the other photosensitive drums 20Y, 20M, and 20C in the A1 direction. When full-color image formation is performed, the black toner is passed through the intermediate transfer belt 11 so that the intermediate transfer belt 11 and the photosensitive drums 20Y, 20M, 20C, and 20BK are kept in contact with each other. In order to prevent or suppress adhesion to 20M and 20C, it is most preferable that the photosensitive drum 20BK is disposed at the most downstream position in the A1 direction and the transfer to the intermediate transfer belt 11 is performed last. is there.

The conveying device 76 includes an endless conveying belt 5 that conveys a sheet, and a driving roller 15 and a driven roller 16 around which the conveying belt 5 is wound.
The secondary transfer roller 17 faces the transfer entrance roller 73 and is in pressure contact with the intermediate transfer belt 11 with the transfer entrance roller 73. The secondary transfer roller 17 may be configured to employ a non-contact charger, or may be configured as a transfer conveyance unit that is used as a member common to the driven roller 16 of the conveyance device 76 and conveys the sheet toward the fixing device 6. It may be what you do.

  The optical scanning device 8 scans and exposes the surfaces to be scanned formed by the surfaces of the photosensitive drums 20Y, 20M, 20C, and 20BK, and forms a laser beam based on an image signal for forming an electrostatic latent image. The laser beam is scanned by a polygon mirror (not shown) that emits a laser beam (not shown), a polygon mirror (not shown) that scans the laser beam emitted by the light source, and a polygon motor (not shown) that rotates the polygon mirror. The laser beam is imaged on the photosensitive drums 20Y, 20M, 20C, and 20B, and a large number of optical elements (not shown) for scanning are provided.

  The fixing device 6 includes a heating roller 62 having a heat source therein, a fixing belt 64 wound around the heating roller 62, a fixing roller 65 wound around the fixing belt 64 together with the heating roller 62, and the fixing roller 65. And a pressure roller 63 that presses the fixing belt 64. By passing a sheet carrying a toner image through a fixing portion that is a pressure contact portion between the fixing belt 64 and the pressure roller 63, heat and pressure can be obtained. By this action, the carried toner image is fixed on the surface of the sheet.

  The paper discharge unit 79 conveys the fixed sheet conveyed from the fixing device 6 toward the duplex unit 96, the paper discharge roller 98 that discharges the sheet to the outside of the main body 101, and the fixed sheet. There is provided a switching claw 94 for switching between discharging to the outside of the main body 101 through the paper discharge path with the conveying roller 97 or guiding it into the reverse path with the paper discharge roller 98 to enter the duplex unit 96.

  The duplex unit 96 includes a tray 92 on which a sheet having an image formed on one surface, which has been conveyed from the sheet discharge unit 79, is temporarily stacked, a reverse roller 93 that switches back the sheet on the tray 92, and a reverse roller 93. A sheet feed roller 95 for feeding the switched back sheet toward the registration roller 13 is provided.

The sheet feeding device 23 includes a paper bank 26 having a plurality of sheet feeding cassettes 25 on which a large number of sheets are stacked, and a sheet feeding roller that contacts the upper surface of the topmost sheet among the sheets stacked on the sheet feeding cassette 25. A feeding roller 24, a separation roller 27 that separates the sheet fed by the feeding roller 24 one by one, and a sheet fed by the paper feeding roller 24 and the separation roller 27 toward the registration roller pair 13. And a sheet feeding path 29 through which a sheet conveyed by the conveyance roller 28 passes.
The sheet feeding path 29 is provided so as to be continuous from the sheet feeding device 23 into the main body 101, and a conveyance roller 28 is also disposed in the sheet feeding path 29 in the main body 101.

  In the sheet feeding device 23, the feeding roller 24 is rotationally driven in the counterclockwise direction in the drawing, and the separation roller 27 acts to guide the uppermost sheet into the sheet feeding path 29 and rotate the conveying roller 28. Thus, the sheet is fed toward the registration roller pair 13 and the conveyed sheet is abutted against the registration roller pair 13 and stopped.

  The manual sheet feeding device 33 includes a manual feed tray 34 on which sheets are stacked, a feed roller 35 as a feed roller that contacts the upper surface of the uppermost sheet among the sheets stacked on the manual feed tray 34, and a feed roller 35. , A separation roller 36 that separates the sheets fed out one by one, and a paper sensor that detects that the sheet is placed on the manual feed tray 34.

  In the manual sheet feeding device 33, the feeding roller 35 is driven to rotate in the clockwise direction in the drawing, and the separation roller 36 acts to guide the uppermost sheet into the sheet feeding path 29 on the main body 101 side and the registration roller. The sheet fed toward the pair 13 is stopped by abutting against the registration roller pair 13.

  The reading device 21 includes a contact glass 21a on which a document is placed, a light source (not shown) that irradiates light on the document placed on the contact glass 21a, and a first light source (not shown) that reflects light reflected from the light source. A first traveling body 21b that includes a reflector and travels in the left-right direction in FIG. 1; a second traveling body 21c that includes a second reflector (not shown) that reflects light reflected by the reflector of the first traveling body 21b; An image forming lens 21d for forming an image of light from the second traveling body 21c, a reading sensor 21e for receiving the light passing through the image forming lens 21d and reading the contents of the document are provided.

  The automatic document feeder 22 has a document table 22a on which a document is placed. The automatic document feeder 22 is rotatable with respect to the reading device 21, and exposes the contact glass 21a when rotated upward. Yes. When copying using the image forming apparatus 100, the document is set on the document table 22a of the automatic document feeder 22, or the automatic document feeder 22 is turned upward to manually move the document onto the contact glass 21a. After the document is placed on the automatic document feeder 22, the automatic document feeder 22 is closed and the document is pressed against the contact glass 21a.

  The discharged developer storage tank 61 is detachable from the main body 101. Easily dispose of the developer discharged from the developing devices 50Y, 50M, 50C and 50BK outside the discharged developer storage tank 61 or replace the discharged developer storage tank 61 with a new one. It is to make it.

The operation panel has a start button for starting copying, a numeric keypad for inputting the number of copies, a mode selection key for selecting an image forming mode such as whether to perform full color image formation or black single color image formation, etc. It has.
The control means includes a CPU, a memory as a storage means, and the like.

  Regarding the image stations 60Y, 60C, 60M, and 60BK, the configuration will be described as a representative of the configuration of the image station 60Y including the photosensitive drum 20Y. Since the configuration of other image stations is substantially the same, in the following description, for the sake of convenience, reference numerals corresponding to the reference numerals assigned to the configuration of the image station including the photosensitive drum 20Y are used for other image stations. A detailed description will be omitted as appropriate for the station configuration, and those with Y, C, M, and K at the end of the reference numerals are used to form yellow, cyan, magenta, and black images, respectively. It is assumed that this is the configuration.

  As shown in FIG. 2, the image station 60Y including the photosensitive drum 20Y has a primary transfer roller 12Y and a cleaning member around the photosensitive drum 20Y along the rotation direction B1 that is counterclockwise in the drawing. A cleaning device 40Y as a means, a static eliminator as a static eliminator (not shown), a charging device 30Y as a charging unit as a charging means, and a developing device 50Y as a developing unit as a developing means.

  The photosensitive drum 20Y, the cleaning device 40Y, the charging device 30Y, the charge eliminating device, and the developing device 50Y are integrated to form a process cartridge 95Y. The process cartridge 95Y can be pulled out of the main body 101 along a guide rail (not shown) fixed to the main body 101, can be pushed into the main body 101, and is detachably installed on the main body 101. .

  When the process cartridge 95Y is pushed into the main body 101, it is loaded and positioned at a predetermined position suitable for image formation. Making a process cartridge in this way is very preferable because it can be handled as a replacement part, so that the maintainability is remarkably improved. In the state where the process cartridge 95Y is pushed into the main body 101 and positioned, the width direction of the photosensitive drum 20Y, in other words, the axial direction is horizontal.

  The process cartridge 95Y is configured by integrating at least the photosensitive drum 20Y and the developing device 50Y among the photosensitive drum 20Y, the cleaning device 40Y, the charging device 30Y, the charge eliminating device, and the developing device 50Y. The unit is detachably installed on the main body 101.

  The charging device 30Y includes a charging roller 31Y that rotates in contact with the surface of the photosensitive drum 20Y, and a cleaning roller 32Y that rotates in contact with the charging roller 31Y. The charging roller 31Y is connected to a voltage applying means (not shown) for applying a bias of an alternating current component to a direct current, and in the charging region facing the photosensitive drum 20Y, the surface of the photosensitive drum 20Y is neutralized at the same time as the charging roller 31Y. The polarity is charged.

The cleaning roller 32Y is driven to rotate by the charging roller 31Y to clean the charging roller 31Y.
As described above, in this embodiment, a charging system using a contact roller is used. However, the charging system may use a proximity roller or a non-contact type such as a scorotron system. It may be.

  The primary transfer roller 12Y has a shaft 37Y that is rotatably supported by the main body 101 and serves as a rotation center of the primary transfer roller 12Y. A predetermined voltage suitable for primary transfer is applied to the primary transfer roller 12Y by a bias application unit and a bias control unit having a power source (not shown).

  As shown in FIG. 2, the optical scanning device 8 shown in FIG. 1 irradiates a region between the charged region and the developing region on the photosensitive drum 20Y with a laser beam L that is light-modulated according to image information. The surface of the photosensitive drum 20Y after being charged by the charging roller 31Y is exposed to form an electrostatic latent image that is visualized as a yellow toner image by the developing device 50Y.

  The cleaning device 40Y has a cleaning case 43Y having an opening at a portion facing the photoconductor drum 20Y, and scrapes off unnecessary materials such as residual toner, carrier, and paper dust on the photoconductor drum 20Y in contact with the photoconductor drum 20Y. The brush roller 45Y as a rotating brush to be cleaned and the rotating direction B1 of the photosensitive drum 20Y contact the photosensitive drum 20Y at a position downstream of the brush roller 45Y and scrape off unnecessary matter on the photosensitive drum 20Y. And a cleaning blade 41Y as a blade for cleaning.

  The cleaning device 40Y is also rotatably supported by the cleaning case 43Y, scraped off by the brush roller 45Y and the cleaning blade 41Y, and removed unnecessary materials such as waste toner generated by the removal to the discharged developer storage tank 61. It has a discharge screw 42Y that constitutes a part of a waste toner path (not shown) for transporting the toner toward it.

  The developing device 50Y is disposed in close proximity to the photoconductive drum 20Y so as to face the photoconductive drum 20Y from the developing case 55Y having an opening at a portion facing the photoconductive drum 20Y. A developing roller 51Y as a developer carrying member that carries a two-component developer (hereinafter referred to as a developer) including the above and a doctor as a regulating member that regulates the developer on the developing roller 51Y to a certain height. And a developing blade 52Y.

  The developing device 50Y also has three developer conveying means as shown in FIG. That is, it is arranged opposite to the developing roller 51Y, and a developer supply unit serving as a developer supplying unit that is a developer conveying unit that agitates and conveys the developer from the back side to the near side and supplies the developer to the developing roller 51Y. A first conveying screw 53Y, which is a single developer conveying member, and a developer that is located below the first conveying screw 53Y and conveys the developer from the near side to the far side of the sheet while stirring, and the conveyed developer is the first conveying screw. A second conveying screw 54Y as a second developer conveying member as an agitating and conveying member as a developer agitating and conveying means that is a developer conveying means conveyed by 53Y, and a first conveying screw 53Y and a position below the first conveying screw 53Y. 2 between the developing roller 51Y and the photosensitive drum 20Y in a state of being held on the developing roller 51Y and positioned at the horizontal position of the conveying screw 54Y, that is, the developing roller The developer that has passed through the developing area, which is the area where 51Y and the photosensitive drum 20Y face each other, is collected from the developing roller 51Y, conveyed while being stirred from the back side to the front side of the sheet, and conveyed, and conveyed by the second conveying screw 54Y. And a third conveying screw 18Y as a third developer conveying member as a collecting and conveying member as developer collecting means which is a developer conveying means.

  The developing device 50Y also includes a first storage chamber 58Y serving as a first region, which is a developer container in which the first transport screw 53Y is accommodated and the first transport screw 53Y transports the developer, and a second transport screw 54. A second storage chamber 59Y serving as a second region, which is a developer container in which the second transport screw 54Y is accommodated and the developer, and a third transport screw 18Y are accommodated, and the third transport screw 18Y transports the developer. And a third storage chamber 19Y as a third region which is a developer container.

  The developing device 50Y is also provided between the first transport screw 53Y and the second transport screw 54Y and between the first transport screw 53Y and the third transport screw 18Y, and the first storage chamber 58Y and the second storage chamber 59Y. And a partition wall 57Y as a first partition member for partitioning the first storage chamber 58Y and the third storage chamber 19Y, and a second transport screw 54Y and a third transport screw 18Y. It has a partition wall 99Y as a second partition member that partitions the two storage chambers 59Y and the third storage chamber 19Y.

  The developing device 50Y also includes a developer container 80Y as a developer container that is a new developer container that contains a so-called premix new developer containing yellow toner and a carrier, and a developer container 80Y. And a developer supply port 87Y provided in the developing case 55Y that communicates with the second storage chamber 59Y, and a toner concentration detection means that is provided at the bottom of the second storage chamber 59Y and measures the toner concentration in the developer. And a toner concentration detection sensor 56Y as a toner concentration detection device which is a T sensor as a toner concentration measurement sensor.

  The developing device 50Y is also transported from the second storage chamber 59Y to the outside of the developing device 50Y, in other words, by the developer discharge port 66Y for allowing excess developer to overflow to the outside of the developing case 55Y and the second transport screw 54Y. In order to prevent the developer that has sometimes sprung up from being discharged from the developer discharge port 66Y, a dome shape as a developer jump preventing member provided so as to form an arc shape facing the second conveying screw 54Y. Is provided between the dome 67Y, the first transport screw 53Y, and the second transport screw 54Y. The developer overflowing from the developer discharge port 66Y is placed outside the developing device 50Y, in other words, outside the developing case 55Y. It has a discharge screw 68Y as a developer discharge member for discharging.

  The developing device 50Y also includes a bias applying unit (not shown) that applies a developing bias of a DC component, a developing driving unit (not shown) that drives the developing roller 51Y, and a first conveying screw 53Y that rotates in the opposite direction to the developing roller 51Y. The second transport screw 54Y is rotationally driven in the opposite direction to the first transport screw 53Y, the third transport screw is rotationally driven in the opposite direction to the first transport screw 54Y, and the discharge screw 68Y is rotated in the first transport screw. 54Y has a conveyance driving means (not shown) that is driven to rotate in the opposite direction, a developer supply means (not shown) that supplies the developer from the developer container 80Y to the second storage chamber 59Y through the developer supply port 87Y, and the like. ing.

  The developing roller 51Y is disposed in parallel or horizontally with the photoconductive drum 20Y, and its width direction, in other words, the axial direction coincides with the width direction of the photoconductive drum 20Y, in other words, the axial direction. Thereby, the distance between the developing roller 51Y and the photosensitive drum 20Y becomes constant in the applied direction, and the developer is satisfactorily developed by uniformly supplying the carried developer to the photosensitive drum 20Y in the axial direction. The developing roller 51Y includes a magnet roller 81Y as a magnetic field generating unit, and a nonmagnetic developing sleeve 82Y that includes the magnet roller 81Y and is driven in the C1 direction, which is the clockwise direction in the drawing, by the developing driving unit.

  Although not shown, the magnet roller 81Y includes a plastic roller fixed to the developing case 55Y, and a magnet block that is a plurality of magnets that are embedded in the plastic roller 84Y and form a plurality of magnetic poles indicated by N or S in FIG. have.

  The developing sleeve 82Y is composed of an aluminum tube having a diameter of 25 mm, and V grooves along the axial direction are arranged in parallel on the surface. The developing sleeve 82Y is rotatably supported by the developing case 55Y and the magnet roller 81Y. A developing bias of an appropriate size is applied between the developing sleeve 82Y and the photosensitive drum 20Y by a bias applying unit. The gap between the developing sleeve 82Y and the photosensitive drum 20Y in the developing region, that is, the developing gap is set to be 0.3 ± 0.05 mm. The surface of the developing sleeve 82Y may be subjected to sandblasting instead of forming the V groove.

  The developing blade 52Y is formed of a SUS material. A gap between the developing sleeve 82Y and the developing blade 52Y, that is, a doctor gap is set to be 0.3 ± 0.04 mm, and the developer on the developing sleeve 82Y is thinned.

  The toner concentration in the developer is controlled to be within a predetermined range of about 4 to 11% by weight based on the detection by the toner concentration detection sensor 56Y, and the mixing ratio of the toner to the carrier is controlled by the following control by the control unit. Is always kept at an appropriate value, and contributes to obtaining a high-quality image. When the toner density is reduced as the toner is consumed by the development, and the toner density detection sensor 56Y detects that the toner density falls below the lower limit of the predetermined range, the developer container 80Y removes the developer. The developer is supplied to the second storage chamber 59Y by the supply means. Therefore, the new developer in the developer container 80Y has a toner concentration that exceeds the lower limit value, preferably the predetermined range.

  The toner concentration detection sensor 56Y measures the toner concentration based on the magnetic permeability of the developer, and its output is taken out as a voltage Vout and input to the control means, and the toner concentration is discriminated based on the magnitude of the voltage Vout. The The toner concentration is in units of% by weight.

  In a developer containing toner and a magnetic carrier, if the toner concentration is low, the carrier ratio increases and the magnetic permeability is increased.If the toner concentration is high, the carrier ratio is decreased and the magnetic permeability is decreased. The decrease in toner density TC and the increase in voltage Vout are in a substantially direct relationship.

  Therefore, when the control means recognizes a decrease in toner density based on the output voltage Vout from the toner density detection sensor 56Y, the control means drives the developer supply means until the output voltage Vout recovers to a predetermined level. The developer is supplied from the developer container 80Y to the second storage chamber 59Y.

  The first transport screw 53Y, the second transport screw 54Y, the third transport screw 18Y, and the discharge screw 68Y are arranged to extend in the width direction of the developing roller 51Y, in other words, in the longitudinal direction of the developing roller 51Y. The first transport screw 53Y, the second transport screw 54Y, the third transport screw 18Y, and the discharge screw 68Y are all shaft portions 53aY, 54aY, 18aY, and 68aY that are rotation shafts that form the center of rotation, and shaft portions 53aY, 54aY, 18aY, 68aY integral resin shaft 53aY, 54aY, 18aY, 68aY and rotating with the shaft portion 53aY, resin screw 53bY which is a spiral blade portion as a developer conveying portion for conveying the developer 54bY, 18bY, and 68bY. The direction in which the blades are formed is such that the first transport screw 53Y and the second transport screw 54Y are in the same direction, and the third transport screw 18Y and the discharge screw 68Y are in the opposite directions.

  Each of the first transport screw 53Y, the second transport screw 54Y, and the third transport screw 18Y has a diameter of 22 mm, a screw pitch of 25 mm, and a rotation speed of about 700 rpm. The first transport screw 53Y, the second transport screw 54Y, and the third transport screw 18Y may be metal screws, and the blades may be swash plate-shaped.

  The first transport screw 53Y, the third transport screw 18Y, and the discharge screw 68Y are shown in FIG. 2 from one end side thereof located on the back side in FIG. 2 by setting the rotation direction and the formation direction of the screws 53bY, 18bY, and 68bY. The developer is transported in the first direction toward the other end located on the near side. The second conveying screw 54Y is directed from the one end side located on the near side in the figure to the other end side located on the back side in the figure by setting the rotation direction and the forming direction of the screw 54bY. The developer is conveyed in a second direction opposite to the first direction.

  As shown in FIG. 3, the partition wall 57Y is located between the first transfer screw 53Y and the second transfer screw 54Y, on the other end side of the first transfer screw 53Y in the first storage chamber 58Y, that is, on the left side in FIG. In addition, the one end side of the second conveying screw 54Y in the second storage chamber 59Y, that is, the left side in the figure is connected, and the communication for transferring the developer from the first storage chamber 58Y to the second storage chamber 59 in a falling manner. It has the opening part 85Y which is the 1st opening which is the 1st communication part as a part. This figure shows a state in which the developing device 50Y is viewed from the photosensitive drum 20Y side.

  The partition wall 57Y is also positioned between the first transfer screw 53Y and the second transfer screw 54Y, at one end side of the first transfer screw 53Y in the first storage chamber 58Y, that is, on the right side in the drawing, and in the second storage chamber 59Y. As the second communicating portion for communicating the other end side of the second conveying screw 54Y, that is, the right side in the drawing, and transferring the developer from the second accommodating chamber 59Y to the second accommodating chamber 58 in a pushed-up manner. It has the opening part 86Y which is a 2nd hole.

  The developer is transferred from the other end side of the first conveying screw 53Y to the one end side of the second conveying screw 54Y positioned below the first conveying screw 53Y by the opening 85Y, and the other end portion of the second conveying screw 54Y by the opening 86Y. The developer is transferred from the first side to the one end side of the first conveying screw 53Y positioned above the first conveying screw 53Y, thereby forming a circulation path through which the developer is circulated and conveyed in the first accommodating chamber 58Y and the second accommodating chamber 59Y. Is done.

  The openings 85Y and 86Y are both disposed in a region corresponding to the image forming region R in the axial direction of the photosensitive drum 20Y. Thereby, the developing device 50Y is downsized.

  The developer discharge port 66Y is located downstream of the opening 85Y in the developer transport direction by the second transport screw 54Y. The developer supply port 87Y is located downstream of the developer discharge port 66Y in the developer transport direction by the second transport screw 54Y. The position of the developer replenishing port 87Y shown in the figure is merely a position where the developer is replenished in the transport direction of the developer by the second transport screw 54Y, and is indicated by an alternate long and short dash line by reference numeral 87Y. The developer is not actually replenished in the square positions shown. The same applies to the discharge screw 68Y shown in the figure, and the position of the discharge screw 68Y shown in the figure is the position where the discharge screw 68Y is arranged in the developer conveyance direction by the second conveyance screw 54Y. However, the discharge screw 68Y is not actually disposed at the position indicated by the reference numeral 68Y.

  In the first storage chamber 58Y, the first transport screw 53Y is rotationally driven by the transport drive means, thereby developing the developer roller 51Y while transporting the developer in the first storage chamber 58Y from the right side to the left side in the drawing. To supply. The developer transported to the vicinity of the end in the first storage chamber 58Y by the first transport screw 53Y falls into the second storage chamber 59Y through the opening 85Y, and is transferred by the second transport screw 54Y. Is done.

  In the second storage chamber 59Y, the second transport screw 54Y is rotationally driven by the transport driving means, thereby transporting the developer in the second storage chamber 59Y from the left side to the right side in the drawing. At this time, when the developer is supplied from the developer container 80Y, the supplied new developer is conveyed while being stirred and mixed in the existing developer. The developer transported to the vicinity of the end of the second storage chamber 59Y by the second transport screw 54Y is lifted upward from the bottom through the opening 86Y, and returns into the first storage chamber 58Y.

  The toner thus supplied is agitated and mixed while being agitated and conveyed with the developer by the first conveying screw 53Y and the second conveying screw 54Y, frictionally charged, and supplied from the first storage chamber 58Y to the developing roller 51Y. And supported.

  The developing roller 51Y has a developing region between the developing roller 51Y and the photosensitive drum 20Y by the rotation of the developer roller 52Y controlled by the developing blade 52Y and the development bias by the bias applying means with the layer thickness regulated. In addition, the developer whose amount is appropriately adjusted by the developing blade 52Y is carried, and the yellow toner in the developer is electrostatically transferred to the electrostatic latent image formed on the surface of the photosensitive drum 20Y. The image is visualized as a yellow toner image.

  Thus, since the developer conveyed by the first conveying screw 53Y in the first accommodating chamber 58Y is carried on the developing roller 51Y in the course of conveyance, the amount of developer in the first accommodating chamber 58Y is the first amount. It gradually decreases toward the downstream side in the developer conveyance direction by the conveyance screw 53Y.

  As shown in FIG. 4, the partition wall 99Y is provided between the second transfer screw 54Y and the third transfer screw 18Y, at one end side of the second transfer screw 54Y in the second storage chamber 59Y, that is, on the right side in FIG. A third communication for communicating the other end side of the discharge screw 68Y in the third storage chamber 19Y, that is, the right side in the drawing, and transferring the developer from the third storage chamber 19Y to the second storage chamber 59Y in an overflowing manner. It has the opening part 91Y which is the 3rd opening as a part. This figure shows the developing device 50Y as viewed from above.

  The developer transported by the third transport screw 18Y and collected from the developing roller 51Y is transported by the second transport screw 54Y from the downstream end portion in the transport direction of the developer by the third transport screw 18Y. The second storage chamber 59Y enters from the third storage chamber 19Y through the opening 91Y at the upstream end in the direction.

  The opening 91Y is in an area corresponding to the arrangement area S of the developing roller 51Y in the axial direction of the developing roller 51Y and outside the area corresponding to the image forming area R in the axial direction of the photosensitive drum 20Y, that is, a non-image. It is disposed in a region corresponding to the formation region. Accordingly, in the third storage chamber 19Y, in the image forming region R, in the vicinity of the downstream end portion in the developer transport direction by the third transport screw 18Y, or in the region corresponding to the downstream side of the image forming region R in the same direction, If the developer is excessively filled, the developer is transferred from the third storage chamber 19Y to the second storage chamber 59Y by the bypass formed by the opening 91Y, so that the toner concentration recovered from the developing roller 51Y is increased. The lowered developer is not excessively filled in the area, and the developer is prevented or suppressed from being directly pumped up to the developing roller 51Y, and development in which density unevenness is prevented or suppressed is performed. .

In order to perform this function more satisfactorily, the opening 91Y may be disposed in a corresponding region outside the region S where the developing roller 51Y is disposed. In this case, the length of the developing roller 51Y can be set to the minimum length in a range including the image forming region R.
In either case, the opening 91Y can be disposed in an area corresponding to the image forming area R. In this case, the developing device 50Y is downsized while ensuring the minimum function.

  Similarly to the second transport screw 54Y, the third transport screw 18Y extends from the first transport screw 53Y in the left direction in FIG. 3 and the right direction in FIG. The opening 91Y is located upstream of the developer discharge port 66Y and the developer supply port 87Y in the developer transport direction by the second transport screw 54Y. Corresponding to the third conveying screw 19Y and the second conveying screw 54Y extending from the first conveying screw 53Y, the third accommodating chamber 19Y and the second accommodating chamber 59Y extend from the first accommodating chamber 58Y. The part and the opening 91Y form a so-called detour path of the developer, and this function is mainly exhibited by this detour path. Note that the position of the developer discharge port 66Y shown in FIG. 4 is merely a position at which the developer is discharged in the developer transport direction by the second transport screw 54Y, and is indicated by a dashed line by reference numeral 66Y. The developer is not actually discharged at the square positions shown.

  The developer supply port 87Y is located in an area corresponding to the image forming area R, and contributes to the downsizing of the developing device 50Y. The new developer supply position occupies a position upstream of the second conveyance chamber 54Y in the developer conveyance direction by the second conveyance screw 54Y, and the new developer agitation conveyance distance and time are ensured. Dispersion in the agent is performed well.

  In the third storage chamber 19Y, the third transport screw 18Y is driven to rotate by the transport drive means, and the developer in the third storage chamber 19Y released from the developing roller 51Y is removed from the left side in FIG. Transport to the right. Since the developer transported by the third transport screw 18Y in the third storage chamber 19Y is released and collected from the developing roller 51Y, the amount of developer in the third storage chamber 19Y is not shown. Then, it gradually increases toward the downstream side in the developer conveying direction by the third conveying screw 18Y. The developer transported to the vicinity of the end in the third storage chamber 19Y by the third transport screw 18Y enters the second storage chamber 59Y through the opening 91Y and is transferred by the second transport screw 54Y.

Transport of the developer entering from the first storage chamber 58Y, the third storage chamber 19Y, the developer discharged from the developer discharge port 66Y, and the developer replenished from the developer container in the second storage chamber 59Y. Details of the flow and the like will be described later.
In this embodiment, the DC component developing bias is applied by the bias applying means. However, the developing bias may be an AC component, or an AC component superimposed on the DC component.

  As described above, in the developing device 50Y, the developer stirred and transported by the first transport screw 53Y, the second transport screw 54Y, and the third transport screw 18Y is pumped up from the first storage chamber 53Y by the magnetic force of the magnet roller 81Y. Then, the toner is carried on the developing sleeve 82Y and conveyed to a developing region facing the photosensitive drum 20Y, and toner is supplied to the latent image on the photosensitive drum 20Y for development. The developer that has consumed the developed toner is collected from the surface thereof into the third storage chamber 19Y as the developing sleeve 82Y rotates, and is transported to the second storage chamber 59Y by the third transport screw 18Y. The developer that has been transported in the first storage chamber 58Y but not carried on the developing sleeve 82Y is transported to the storage chamber 59Y by the first transport screw 53Y, and the second transport screw 54Y makes a new developer in a timely manner. The cycle of being conveyed to the first storage chamber 58Y while being stirred and pumped up again on the surface of the developing sleeve 82Y is repeated. The magnet block is arranged to repeat such a cycle.

  In the developing device 50Y, in such a cycle, the carrier is discharged from the developer discharge port 66Y, so that the coat layer on the surface of the carrier is worn by the friction of the developer, or the toner resin or the toner additive adheres to the coat layer. The carrier is prevented or suppressed from being deteriorated by maintaining the ability to charge the toner by the carrier, and the toner scattering and the background stain of the formed image are prevented or suppressed.

  The carrier discharge from the developer discharge port 66Y in this cycle will be described in detail as follows. As described above, when the toner density is reduced by development, a new developer having a toner density higher than the appropriate toner density for development is supplied so that the toner density falls within an appropriate range. Therefore, when a new developer is replenished, the total amount of developer in the developing device 50Y increases. By utilizing this, excess developer is overflowed from the developer discharge port 66Y, thereby discharging the carrier, gradually replacing the developer, and replacing the carrier, thereby preventing deterioration of the carrier over time. Or suppress.

  However, since the developer can be excessively discharged from the developer discharge port 66Y depending on the position of the developer discharge port 66Y, in this embodiment, the position of the developer discharge port 66Y is particularly set to the second transport screw. Of the positions downstream of the opening 85Y in the developer transport direction by 54Y, the position corresponding to the upstream end of the partition wall 57Y in the transport direction. The reason why the position of the developer discharge port 66Y is set to this position will be described below.

  Incidentally, FIG. 3 shows that the developer discharge port 66Y is disposed at a position corresponding to the upstream end of the first transport screw 53Y in the developer transport direction by the first transport screw 53Y. Thus, at this position, since the developer is pushed up from the opening 86Y, a large amount of developer is always present, so that the developer is excessively discharged from the developer discharge port 66Y.

  As shown in FIG. 3, when the developer discharge port 66Y is disposed at a position corresponding to the end of the second transport screw 54Y on the downstream side in the developer transport direction by the second transport screw 54Y. At this position, a large amount of developer always exists to push up the developer from the opening 86Y, and therefore the developer is excessively discharged from the developer discharge port 66Y.

  However, when the arrangement position of the developer discharge port 66Y is set to a position corresponding to the end portion of the first conveyance screw 53Y on the downstream side in the developer conveyance direction by the first conveyance screw 53Y, it is shown in FIG. As described above, since the developer falls from the opening 85Y at this position, only a small amount of the developer exists, so that the developer is sprung up by the rotation of the first conveying screw 53Y and the developer discharge port 66Y. The developer will be excessively discharged.

  On the other hand, when the arrangement position of the developer discharge port 66Y is set to a position corresponding to the end of the second conveyance screw 54Y on the upstream side in the conveyance direction of the developer by the second conveyance screw 54Y, at this position, for the following reason Thus, it is possible to prevent or suppress the developer from being excessively discharged from the developer discharge port 66Y.

  The reason for this is that at this position, the developer is allowed to stay at a suitable level only when the new developer is replenished and the total amount of the developer in the developing device 50Y increases, and the developer is discharged from the developer discharge port 66Y. This is because an appropriate amount can be discharged. In order to retain the developer at such a position that the developer overflows from the developer discharge port 66Y, the developing device 50Y includes a developer discharge port 66Y in the developer transport direction by the second transport screw 54Y. And the non-arrangement part 69Y of the screw 54bY is provided at a position upstream of this position. In this non-arranged portion 69, since the developer transport action by the screw 54bY does not occur, the developer that has entered from the third storage chamber 19Y, including the developer that has dropped from the first storage chamber 58Y, is not included. Only when the new developer is replenished and the total amount of developer in the developing device 50Y increases, only the excess developer is discharged from the developer discharge port 66Y.

  Further, at this position, even when the total amount of the developer in the developing device 50Y is an appropriate amount and the amount of the developer at the position is reduced, the developer due to the developer jumping up by the second transport screw 54Y. This is because excessive discharge can be easily prevented or suppressed. Since such a jump does not occur in the non-arranged portion 69, providing the non-arranged portion 69 at this position prevents or suppresses the developer from jumping up at such a position. The resulting excessive discharge of the developer can be easily prevented or possible. Even in the case where such jumping occurs, it is possible to prevent the developer itself from jumping up by providing the dome 67Y, and even if the jumping occurs, the developer that has been jumped up is left in the developer discharge port. It is suppressed or prevented from jumping into 66Y and being discharged. The arrangement position, size, shape, and the like of the dome 67Y are set such that the developer does not jump up, or the developer jumped up jumps into the developer discharge port 66Y and is discharged or suppressed. Easy to set. For example, in this embodiment, the arrangement position of the dome 67Y is a position including the arrangement position of the developer discharge port 66Y in the developer conveyance direction by the second conveyance screw 54Y.

  For this reason, in the developing device 50Y, in particular, the developer discharge port 66Y is disposed at a position downstream of the opening 85Y in the developer transport direction by the second transport screw 54Y. The position occupies a position corresponding to the upstream end of the partition wall 57Y in the direction, and the developer is discharged from the second storage chamber 59Y to the outside through the developer discharge port 66Y.

  As a result, the carrier is exchanged while maintaining a proper amount of developer in the developing device 50Y with a simple configuration and high accuracy without providing a mechanism for forcibly discharging the developer from the developer discharge port 66Y. Further, when such a mechanism is provided, it is necessary to provide a shutter for opening and closing the developer discharge port 66Y. However, in this embodiment, since it is not necessary to provide such a mechanism, it is not necessary to provide such a shutter, and the structure is inexpensive with a simple configuration. It becomes a device. However, in this embodiment, the discharge screw 68Y is used, and the arrangement position, size, shape, etc. of the discharge screw 68Y are set so as to keep the developer discharge port 66Y closed except during rotation. ing. The discharge screw 68Y has a surplus overflowing from the developer discharge port 66Y after the developer replenishing means is driven and new developer is supplied from the developer container 80Y to the second storage chamber 59Y by the control of the control means. The developer is rotated by the conveyance driving means for a time sufficient to discharge the developer.

  In the present embodiment, the developer discharged from the developing devices 50Y, 50M, 50C, and 50BK using the developer discharge member such as the discharge screw 68Y is discharged by being collectively stored in the discharged developer storage tank 61. However, the developer discharge member and the discharged developer storage tank 61 are not provided, and the developer is discharged from the developer discharge port to each of the developing devices 50Y, 50M, 50C, and 50BK. A discharged developer storage section such as a waste bottle for storing the developer may be detachably provided. Such a configuration is particularly effective for an image forming apparatus having one developing device such as a monochromatic image forming apparatus.

  In the developing device 50Y of this embodiment, in addition to such a configuration, the rotation direction of the second conveying screw 54Y is set so that the developer is moved away from the developing roller 51Y and the third conveying screw 18Y toward the developer discharge port 66Y. Yes. As a result, developer stagnation in the non-arranged portion 69Y is likely to occur on the developer discharge port 66Y side, and the developer can be quickly discharged from the developer discharge port 66Y.

  Regarding the rotation direction, the rotation direction of the first conveying screw 53Y is set to a direction in which the developer is brought closer to the developing roller 51Y side. As a result, the developer in the first storage chamber 58Y increases so as to be biased toward the developing roller 51Y, and the developer is efficiently supplied to the developing roller 51Y. The stay of the developer in the non-arranged portion 69Y is likely to occur on the developer discharge port 66Y side, and the developer can be quickly discharged from the developer discharge port 66Y.

  Regarding the rotation direction, the rotation direction of the third transport screw 18Y is set to the direction in which the developer is moved away from the developing roller 51Y toward the partition wall 99Y. As a result, the developer in the third storage chamber 19Y increases so as to be biased toward the partition wall 99Y, the developer carried on the developing roller 51Y is efficiently collected, and the collected developer is opened. It quickly overflows from the third storage chamber 19Y toward the second storage chamber 59Y through the portion 91Y.

  Further, with respect to the rotation direction, the rotation direction of the discharge screw 68Y is set so as to keep the developer away from the developer discharge port 66Y. As a result, the developer once discharged from the developer discharge port 66Y is unlikely to return from the developer discharge port 66Y into the second storage chamber 59Y, and the excess developer is quickly discharged from the second storage chamber 59Y. Is called.

  Further, since the discharge screw 68Y is disposed between the first conveyance screw 53Y and the second conveyance screw 54Y, the developing device 50Y can be downsized, and the discharge screw 68Y is placed at this position. As the developer is disposed, the developer discharge port 66Y occupies a position directly above or close to the second transport screw 54Y. Therefore, the developer splashed up by the second transport screw 54Y is discharged from the developer. It is difficult to enter the exit 66Y.

  Further, the upstream end of the second transport screw 54 in the transport direction of the developer by the second transport screw 54Y so that the developer entering from the third storage chamber 19Y is efficiently retained at the position of the developer discharge port 66Y. A screw 54bY may be provided in the part. Further, if retention is caused at the position of the developer discharge port 66Y, the screw 54bY is disposed so as to overlap the position at which the developer discharge port 66Y is disposed in the developer transport direction by the second transport screw 54Y. You may do it.

  In the developing device 50Y having such a configuration, when a new developer is supplied into the second storage chamber 59Y, the non-arrangement portion 69Y in the transport direction of the developer by the second transport screw 54Y in the second storage chamber 59Y. The developer that has fallen from the first storage chamber 58Y and the developer that has entered from the third storage chamber 19Y are retained, and the retained developer is gradually provided with the screw 54bY. The sheet is pushed to the position and is conveyed downstream in the conveying direction by the rotation of the second conveying screw 54Y that is rotationally driven by the conveying driving means. At this time, a part of the staying developer corresponding to the excess developer is discharged from the developer discharge port 66Y, the amount of the developer in the developing device 50Y is maintained appropriately, and the carrier is exchanged. The developer discharged from the developer discharge port 66 </ b> Y is transported by a discharge screw 68 </ b> Y that is rotationally driven by a transport driving unit, and is stored in a discharged developer storage tank 61.

  When the excess developer is discharged from the developer discharge port 66Y and the amount of developer in the developing device 50Y becomes appropriate, the developer at the position where the developer discharge port 66Y is disposed in the developer transport direction by the second transport screw 54Y. Although the amount decreases, it is prevented or suppressed that the developer is excessively discharged from the developer discharge port 66Y due to the presence of the non-arrangement portion 69Y and the dome 67Y.

  The amount of developer delivered from the opening 86Y to the first storage chamber 58Y includes the amount of developer entering the second storage chamber 59Y from the opening 91Y and the amount of developer entering the second storage chamber 59Y from the opening 85Y. Is approximately equal to the sum of This “abbreviation” is caused by the consumption and supply of toner.

  The developer replenished from the developer container 80Y is dropped from the first developer chamber 53Y and the existing developer in which the replenished developer has entered the third chamber 19Y and the toner amount has decreased. In the process of being stirred and mixed in the existing developer and transported while being diffused, transported in the second storage chamber 59Y, and in the process of transporting through the first storage chamber 58Y and the third storage chamber 19Y, the toner concentration Is made uniform.

  In the image forming apparatus 100 having such a configuration, when copying, the operation panel is started with the document set on the automatic document feeder 22 or the document placed on the contact glass 21a as described above. Press the button. When the image forming apparatus 100 is used as a printer, an image forming start operation is performed after image data to be formed is selected and input by an external input device such as a PC connected to the image forming apparatus 100.

  When copying is performed and the original is set on the automatic document feeder 22, the read original is read by the reading device 21 after the set original is fed onto the contact glass 21a. Is placed on the contact glass 21a, the document is read by the reading device 21 when the start button is pressed, and image data is generated.

  When reading a document, the first traveling body 21b and the second traveling body 21c travel, the light from the light source is emitted toward the document, and the reflected light from the document surface is reflected by the first reflector to the second traveling body. Reflected in the direction of 21c, the direction is changed by 180 degrees by the second reflector, enters the reading sensor 21e through the imaging lens 21d, and the contents of the original are read by the reading sensor 21e.

  Based on the generated image data or the input image data, the image stations 60Y, 60M, 60C, and 60BK having the above-described configuration operate.

  In the image station 60Y, the surface of the photosensitive drum 20Y is uniformly charged by the charging roller 31Y as it rotates in the B1 direction, and corresponds to the yellow color by exposure scanning of the laser light L from the optical scanning device 8. An electrostatic latent image is formed, and this electrostatic latent image is developed satisfactorily and uniformly with yellow toner by the developing device 50Y. The yellow toner image obtained by development is developed in the A1 direction by the primary transfer roller 12Y. Unnecessary materials including toner that has been primarily transferred to the moving intermediate transfer belt 11 and remained after the transfer are removed by the cleaning device 40Y, and are used for the next static elimination and charging by the static elimination device and the charging roller 31Y.

  Similarly, the toner images of the respective colors are formed on the other photoconductive drums 20C, 20M, and 20BK, and the formed toner images of the respective colors are transferred intermediately by the primary transfer rollers 12C, 12M, and 12BK. Primary transfer is sequentially performed at the same position on the belt 11 to form a full-color composite color image. The toner image superimposed on the intermediate transfer belt 11 is moved to the secondary transfer nip which is a position facing the secondary transfer roller 17 as the intermediate transfer belt 11 rotates in the A1 direction, and is secondarily transferred to the sheet. The

  A sheet conveyed between the intermediate transfer belt 11 and the secondary transfer roller 17 is fed from the corresponding sheet feeding cassette 25 by the selection of one feeding roller 24 of the sheet feeding device 23, and is fed. Is fed from the manual feed tray 34 by the rotation of the feed roller 35 of the manual paper feed device 33, or fed from the duplex unit 96 by the paper feed roller 95. The timing at which the front end portion of the toner image on the intermediate transfer belt 11 faces the secondary transfer roller 17 by the registration roller pair 13 based on the detection signal from the sensor. It was sent out by.

  When the toner images of all colors are transferred and carried on the sheet, the sheet is transported to the transport device 76 and enters the fixing device 6, and is heated when passing through the fixing portion between the fixing belt 64 and the pressure roller 63. By the action of pressure and pressure, the carried toner image is fixed and a color image is formed on the sheet. The fixed sheet that has passed through the fixing device 6 is stacked on the discharge tray 75 via the discharge roller 98 or enters the duplex unit 96 via the conveyance roller 97 according to the position of the switching claw 94. In preparation for double-sided image formation. On the other hand, the intermediate transfer belt 11 that has finished the secondary transfer is cleaned by removing residual toner and the like remaining on the intermediate transfer belt cleaning device 14 to prepare for the next image formation.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

For example, as shown in FIG. 6 , the present invention does not include a recovery conveyance member such as the third conveyance screw 18Y, and a two-component developer is provided between the first developer conveyance member and the second developer conveyance member. The present invention can be applied to a developing device that is stirred and conveyed and supplied to a developer carrier. As shown in FIG. 5 , the first developer conveying member and the second developer conveying member are not arranged side by side in the vertical direction as in the above-described embodiment, but instead of the second developer conveying member. The one end part side should just be located below the other end part side of the 1st developer conveyance member. When the first developer conveying member and the second developer conveying member are arranged in parallel in the vertical direction, they may be arranged in the vertical direction as shown in FIG. Although it is possible to reduce the size of the developing device in the left-right direction in the figure, as shown in FIG. 2, the developing devices may be arranged side by side so as to partially overlap in the vertical direction. It becomes possible.

When the collection conveyance member is omitted as shown in FIG. 6 , the second developer conveyance member functions as a collection conveyance member together with the developer agitating member. In combination with the occurrence of the toner on the side opposite to the developer carrier, the developer is efficiently recovered from the developer carrier. Further, by adopting such a rotation direction, even if the developer is splashed up by the rotation of the second developer conveying member, it is suppressed or prevented that the developer that has been splashed up is returned to the developer carrier side. . In order to suppress or prevent the developer splashed up by the rotation of the second developer conveying member from returning to the developer carrier, a developer splash-up preventing member such as the dome 67Y is provided. Although preferable, as shown in the figure, the member is not an essential component.

  In the configuration shown in FIG. 2, the developer discharging member such as the discharging screw 68Y is disposed between the first developer conveying member and the second developer conveying member. For example, as described above, there are advantages that the developer bounced up by the second developer conveying member does not easily enter the developer discharge port and that the developing device can be downsized. As shown in FIG. 5, the developer discharge member may not be disposed between the first developer transport member and the second developer transport member.

  Regarding the replenishment of the developer, it may be performed separately from the replenishment of the new toner and the replenishment of the new carrier so that excess developer overflows when the new carrier is replenished. Replenishment and new developer replenishment may be performed separately, so that excess developer overflow may occur when new developer is replenished, or new developer replenishment and new carrier replenishment may occur. The replenishment may be performed separately so that excess developer overflows at least when a new carrier is replenished.

The developing device to which the present invention is applied includes only one developer carrier in either the configuration shown in FIG . 2 or the configuration shown in FIG. 6 , but the developer carrier is an image carrier. A plurality may be arranged in parallel in the moving direction. In the configuration shown in FIG. 6 , the developer container 80Y is not shown.

  The present invention is not a so-called tandem type image forming apparatus, but a so-called one-drum type image forming apparatus that sequentially forms toner images of each color on a single photosensitive drum and sequentially superimposes the color toner images to obtain a color image. It can be similarly applied to.

  Any type of image forming apparatus may employ a direct transfer method in which a toner image of each color is directly transferred to a sheet or the like without using an intermediate transfer member. That is, the transfer target may be a sheet. In this case, the toner images on the plurality of image carriers are directly transferred to the sheet.

The intermediate transfer member is not limited to a belt shape but may be a drum shape.
The image forming apparatus may not be a copier, a printer, and a facsimile machine, but may be a single unit thereof, or may be a multi-function machine of another combination such as a copier and printer. .
The image forming apparatus may be capable of forming only a monocolor image.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

20Y, 20M, 20C, 20BK Image carrier 50Y Developing device 51Y Developer carrier 53Y First developer transport member, transport supply member 54Y Second developer transport member 54aY Rotating shaft 54bY Developer transport unit 57Y Partition member 58Y First area 59Y Second area 66Y Developer discharge port 67Y Developer splash-up prevention member 68Y Developer discharge member 69Y Non-placement part 85Y Communication part 95Y Process cartridge 100 Image forming apparatus

JP 2005-292511 A Japanese Patent No. 3264765 JP-A-10-90991

Claims (9)

A developer carrying member for carrying a two-component developer containing a toner and a carrier and supplying the carried two-component developer to an image carrier;
A first developer conveying member that conveys the two-component developer in a first direction from one end to the other end and supplies the developer to the developer carrying member;
First developer positioned below the conveying member, the two-component developer is conveyed from the one end side in a second direction toward the other end, from the other end side first developer A second developer conveying member that pushes up and delivers the two- component developer to one end of the conveying member;
A first region in which a first developer conveying member conveys the two-component developer;
A second region in which a second developer conveying member conveys the two-component developer;
A developing case having a first region and a second region therein;
A partition member that partitions the first region and the second region, the other end of the first developer transport member in the first region, and the second developer transport member in the second region A partition member having a communication portion for communicating with one end portion of the first component and dropping the two-component developer from the first region to the second region;
The developing case is formed at a position corresponding to the upstream end of the partition member in the same direction out of the positions downstream of the communicating portion in the second direction, and from the second region to the outside of the developing case. the two-component developer possess a developer outlet for extravasation in,
The two-component developer carried on the developer carrier is collected in a region other than the first region;
The second developer conveying member conveys the two-component developer in the second direction by being provided integrally with the rotating shaft extending in the second direction and rotating together with the rotating shaft. and a developer conveying unit for, developing device for perforated non arrangement portion of the developer conveying portion to a position which includes the developer discharge opening in a second direction. The developing device according to claim 1,
A third region for collecting the two-component developer released from the developer carrier;
And a third developer conveying member configured to convey the two-component developer collected in the third area in the third area . The developing device according to claim 1 or 2,
In order to prevent the two-component developer that has jumped up when being transported by the second developer transport member from being discharged from the developer discharge port, the second developer transport member is provided to face the second developer transport member. A developing device comprising a developer splash-up preventing member. The developing device according to any one of claims 1 to 3,
A developer discharge member provided between the first developer transport member and the second developer transport member for discharging the two-component developer overflowing from the developer discharge port is provided. Development device. In the developing device according to any one of claims 1 to 4,
A developing device comprising an opening for delivering the two-component developer collected in the third region from the third region to the second region . The developing device according to any one of claims 1 to 5,
A developing device comprising a developer supply port for supplying the new two-component developer to the second region .   A process cartridge comprising the developing device according to claim 1 and an image carrier on which a latent image is developed by the developing device.   An image forming apparatus comprising the developing device according to claim 1 or the process cartridge according to claim 7.   A new two-component developer or a new carrier using the developing device according to any one of claims 1 to 6, the process cartridge according to claim 7, or the image forming device according to claim 8. A developer replacement method for replacing the two-component developer in the developing device by causing an excess of the two-component developer to overflow from the developer discharge port when the developer is supplied into the developing device.

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