JP5954003B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to the structure of a developing device used in an image forming apparatus.

  2. Description of the Related Art In image forming apparatuses such as copying machines, printers, and facsimiles, a two-component developing method using a two-component developer in which toner and a carrier are mixed is known. In the developing device used in such an image forming apparatus of the two-component developing system, when the air flow to the inside becomes large in the balance between the air flow from the inside of the developing device to the outside and the air flow from the outside to the inside, The developer is ejected to the outside together with the pressure from the gap at the end of the developing roller or the like, causing problems such as fouling. Therefore, a method is known in which a pressure inside the developing device is released by attaching a filter that does not allow the developer to pass through the developing device.

  Further, in “Patent Document 1”, in order to provide an image forming apparatus that forms a stable image, a third screw not adjacent to the developing roller is provided in order to improve the uniformity of the developing performance, and adjacent to the developing roller. By providing a partition wall between the first and second screws and transferring the developer through a communication path provided outside the development area, the developer used in the development operation is always a toner. A developing device that is subjected to development again after density adjustment is disclosed is disclosed.

  Further, in “Patent Document 2”, in order to suppress uneven development density in the developer conveyance direction of the supply conveyance screw, the outer peripheral lower end of the upstream end of the developer conveyance direction in the screw blade of the inclined conveyance screw is defined in the screw blade of the reception conveyance screw. A developing device is disclosed that is positioned at a height level lower than the lower end of the outer periphery at the downstream end in the developer transport direction.

  However, in the above-described technique, the balance between the discharge air flow when the developer is transported from the developing doctor unit to the developing roller and the suction air flow when the developer is collected from the developing roller into the developing device in the two-component development method. The pressure inside the developing device has been determined. For this reason, the pressure inside the developing device is substantially constant, and the filter for releasing the pressure can be mounted in a place where the developing device can be easily attached. A one-way circulation system in which the screw is partitioned by a partition was adopted, and a device was devised to always maintain a constant toner concentration. Accordingly, there is a problem that the pressure fluctuates inside the developing device other than the developing doctor unit and the developer collecting unit from the developing roller.

  In addition, due to the recent increase in speed and functionality of machines, the amount of developer required inside the developing device increases according to the printing speed and the area of the printing area, and the conveying screw's conveying ability and stirring ability are improved. Is required. As the printing area increases, the required development area increases, and as a result, the amount of developer supply required increases, and the amount of developer used per unit time also increases. There is a problem that the amount of the toner increases and the pressure inside the developing device increases.

  The present invention solves the above-mentioned problems, and a developing device which can dispose a filter so as to release the pressure of a portion where the pressure rises locally inside the developing device and can be easily replaced is mounted. An object is to provide an image forming apparatus.

  The invention according to claim 1 is a one-way circulation type developing device that includes a plurality of conveying screws for conveying the developer, and circulates the developer in one direction in the apparatus, from the first conveying screw to the second. And a plurality of openings provided in the communication portion and communicating with the outside of the apparatus, and one of the openings is for supplying a developer or a developer. It is used for discharging, and a filter for releasing the air inside the apparatus to the outside except when the developer is charged or when the developer is discharged is attached to the opening.

  According to the present invention, the filter for discharging the pressure (air) inside the apparatus is provided in the opening for supplying the developer or discharging the developer so as to prevent the internal pressure in the developing apparatus from increasing. It is possible to prevent an increase in pressure in the apparatus and suppress scattering of the developer to the outside of the apparatus, and it is possible to continuously perform good image formation by continuously performing a good developing operation.

1 is a schematic view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic view of a developing device to which an embodiment of the present invention can be applied. 1 is a schematic view of a developing device to which an embodiment of the present invention can be applied. 1 is a schematic view of a developing device to which an embodiment of the present invention can be applied. 1 is a schematic view of a developing device used in an embodiment of the present invention. 1 is a schematic view of a developing device used in an embodiment of the present invention. 1 is a schematic view of an image forming apparatus including a developing device used in an embodiment of the present invention. It is the schematic at the time of filter mounting | wearing of the image development apparatus used for one Embodiment of this invention.

  FIG. 1 shows an image forming apparatus to which an embodiment of the present invention can be applied. In the drawing, a printer 50 as an image forming apparatus includes an image forming unit 51y that is an image forming unit that forms a yellow image, an image forming unit 51m that is an image forming unit that forms a magenta image, and a cyan image. An image forming unit 51c that is an image forming unit that forms an image, an image forming unit 51k that is an image forming unit that forms a black image, an intermediate transfer member 52 on which four color images are temporarily transferred, and the like. It has almost the center.

  The image forming units 51 for each color are configured in the same manner for all four colors except for the color of the toner used, and the yellow image forming unit 51y will be described below as a representative. In FIG. 1, reference numeral 54 denotes a photosensitive drum as an image carrier, reference numeral 55 denotes a charging unit that charges the photosensitive drum 54, and reference numeral 56 develops an electrostatic latent image formed on the photosensitive drum 54. Reference numeral 59 denotes a developing device, which indicates a cleaning unit for collecting untransferred toner on the photosensitive drum 54, and the image forming unit 51y includes these members.

  Reference numeral 53 denotes an exposure unit that irradiates the photosensitive drum 54 with exposure light L based on the image information, and reference numeral 58 denotes a toner image formed on the photosensitive drum 54 that is transferred to a recording paper P that is a transfer material 1. A secondary transfer unit 60 is a secondary transfer unit that collectively transfers the full-color toner image on the intermediate transfer member 52 onto the recording paper P. Reference numerals 61, 62, and 63 are paper feeding units that store the recording paper P. Reference numeral 64 denotes a fixing unit that fixes an unfixed toner image transferred onto the recording paper P, reference numeral 90 denotes a waste toner bottle that stores waste toner collected by the cleaning unit 59 and the secondary transfer unit 60, and reference numeral 1 denotes a toner. Each bottle is shown.

  Next, the operation of the printer 50 during image formation will be described. First, image information is converted into an electrical signal by the image forming unit 51y and then transmitted to the exposure unit 53. Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 53 toward the photosensitive drum 54.

  The photosensitive drum 54 rotates counterclockwise in FIG. 1, and the surface thereof is uniformly charged at a position facing the charging unit 55. The surface of the photosensitive drum 54 charged by the charging unit 55 reaches the irradiation position of the exposure light L, and an electrostatic latent image corresponding to the image information is formed at this position.

  The electrostatic latent image formed on the surface of the photosensitive drum 54 then reaches a portion facing the developing device 56, and the electrostatic latent image is visualized by the developing device 56. Hereinafter, this developing operation will be described. The toner in the developing device 56 is mixed with a carrier by a stirring roller together with toner supplied from a toner hopper (not shown). The frictionally charged toner is supplied onto the developing roller together with the carrier. Thereafter, the toner carried on the developing roller passes through a doctor blade and is thinned, and then reaches a portion facing the photoconductive drum 54. The electrostatic latent image formed on the photoconductive drum 54 at this facing position is reached. Adhere to the image. The toner supplied from the toner hopper is appropriately supplied as the toner in the developing device 56 is consumed, and the toner consumption in the developing device 56 is indirectly detected by a toner density sensor including an optical sensor (not shown) facing the photosensitive drum 54. Detected.

  The surface of the photosensitive drum 54 developed by the developing device 56 reaches a portion facing the primary transfer portion 58, and the toner image on the photosensitive drum 54 is primarily transferred to the intermediate transfer member 52 at this position. . At this time, a small amount of untransferred toner that is not transferred to the intermediate transfer member 52 exists on the photosensitive drum 54. The surface of the photosensitive drum 54 having untransferred toner that has passed through the primary transfer portion 58 reaches a portion facing the cleaning portion 59, and the untransferred toner is collected in the cleaning portion 59 by a cleaning blade that contacts the photosensitive drum 54. Is done. The collected toner is conveyed as a waste toner toward a waste toner bottle 90 through a waste toner conveyance path (not shown). The surface of the photosensitive drum 54 that has passed through the cleaning unit 59 reaches a neutralization unit (not shown), where the surface of the photosensitive drum 54 is neutralized, and a series of image forming processes is completed.

  As described above, the toner image formed by the yellow image forming unit 51y is transferred to the intermediate transfer member 52, and similarly, a magenta image forming unit 51m The toner images of the respective colors are also transferred to the intermediate transfer member 52 from the image forming unit 51c and the black image forming unit 51k. The color toner image primarily transferred onto the intermediate transfer member 52 is sent to the secondary transfer unit 60 as the intermediate transfer member 52 travels.

  On the other hand, the recording paper P fed to the secondary transfer unit 60 operates as follows. First, one of the paper feed units 61, 62, and 63 of the printer 50 is selected automatically or manually. In the present embodiment, it is assumed that the paper feeding unit 61 is selected. By driving the paper feed roller, one sheet of recording paper P stored in the paper feed unit 61 is fed toward the transport path K, and the recording paper P passing through the transport path K reaches the registration roller pair. To do. Then, when the registration roller pair rotates at a predetermined timing, the recording paper P is fed toward the secondary transfer unit 60 at a timing aligned with the toner image on the intermediate transfer member 52.

  The recording paper P after the transfer process onto which the toner image has been transferred in the secondary transfer unit 60 passes through the secondary transfer unit 60 and then is sent to the fixing unit 64 via a conveyance path. In the fixing unit 64, the unfixed toner on the recording paper P is fixed on the recording paper P by heat and pressure, and the recording paper P after the fixing process is discharged from the printer 50 as an output image. With the above operation, a series of image forming processes is completed.

  FIG. 2 is a schematic cross-sectional view of a conventionally known one-way circulation developing device having a plurality of conveying screws that can be used in the printer 50 in place of the developing device 56 described above. FIG. FIG. 4 is an explanatory view showing the developer conveyance direction in the developing device. In FIG. 4, the arrow indicates the developer transport direction.

  In FIG. 2, the developing device 4 includes a developing roller 8 having a magnet inside, a first screw 9, a second screw 10, a third screw 11, and a blade 12, each of which is a conveying screw. The rotation shafts 13 of the conveying screws 9, 10, 11 are parallel to the image carrier 2, and are positioned at a position between the upper first screw 9 and the lower second screw 10 arranged vertically. Three screws 11 are disposed. Each of the transport screws 9, 10, and 11 is rotationally driven by a driving unit (not shown) to stir and transport the developer in the developing device 4.

  The first screw 9 supplies developer to the developing roller 8 while being agitated and conveyed, and the developing roller 8 that rotates in the clockwise direction holds the supplied developer by magnetic force to form a magnetic brush. The blade 12 regulates the height of the formed magnetic brush and returns the developer scraped off by the regulation to the first screw 9. The developer agitated and transported to the downstream position on the left side in FIG. 4 of the first screw 9 without being supplied to the developing roller 8 moves due to the stay and falls from the collection opening N3 to the periphery of the second screw 10. .

  Further, the developer whose toner density has been reduced by the development is recovered from the developing roller 8 by the agitating and conveying of the second screw 10 and conveyed to the downstream position on the left side of the second screw 10 in FIG. The developer conveyed to the downstream position of the second screw 10 moves to the third screw 11 that conveys the developer obliquely upward through the second communication path N2 due to a certain amount of stay. The moved developer is conveyed together with the toner replenished from the toner replenishing port N4 to the downstream position on the right side in FIG. The developer agitating and conveying by the third screw 11 is provided so as not to be confused with the developer agitated and conveyed by another conveying screw in the width of the image area where the image carrier 2 forms an electrostatic latent image. It is performed in a state where it is blocked by the partition wall 15. In the above-described configuration, there is a problem in that the internal pressure locally increases in the communication passages N1 and N2 serving as the developer delivery portions between the conveying screws due to the retention of the developer.

  The configuration of the present invention that solves the above-described problems will be described below. 5 to 7 each show a developing device adopting an embodiment of the present invention, FIG. 5 is a schematic view showing a developer transport direction in the developing device 20, and FIG. 6 is a perspective view of the developing device 20. FIG. 7 is a schematic view showing a state mounted on the image forming apparatus 21. In this developing device 20, the same reference numerals are given to the same members as those of the developing device 4 described above, and the description thereof is omitted.

  As shown in FIG. 5, the developing device 20 has openings P1 and P2 in the communication path N1, and each opening P1 and P2 is provided with a shutter (not shown) that can be opened and closed. A shutter (not shown) is opened when a developer bottle or a developer cartridge is attached to the developing device 20, and a developer can be charged and discharged. Here, the opening P1 functions as a developer inlet and the opening P2 functions as a developer outlet.

  As shown in FIG. 6, in the developing device 20, a developer inlet P1 is provided above the communicating portion N1 on the front side of the device, and a developer outlet P2 is provided below. As shown in FIG. 7, the developer bottle Q is attached to the communication portion N1 provided on the front side of the image forming apparatus 21 so that the developer can be easily charged and discharged with respect to the developing device 20. ing. Here, the developer bottle Q attached below is used for discharging the developer, and the developer bottle Q attached above is used for supplying the developer. The filter which is a characteristic part of the present invention is attached to a mounting portion of the developer bottle Q provided at the developer inlet P1. In FIG. 7, the developing device 20 is provided integrally with an image carrier, a cleaning device, and the like, and constitutes a process cartridge 22 that is detachable from the main body of the image forming device 21.

  FIG. 8 shows a state where the filter unit R is mounted on the developer bottle Q mounting portion of the developer inlet P1 of the developing device 20. As described above, since the internal pressure of the developer delivery communication portion N1 from the third screw 11 to the first screw 9 locally increases due to the retention of the developer, the internal pressure can be increased by attaching the filter unit R to this portion. (Air) can be discharged to the outside of the developing device 20. As a result, the developing device 20 has a relatively negative pressure, so that the scattering of the developer to the outside of the developing device 20 can be suppressed.

  Further, the filter unit R is a member that, due to its characteristics, has its eyes closed with the developer over time as the internal pressure is discharged, and the pressure discharge effect is gradually reduced and needs to be replaced periodically. In the present invention, the mounting portion of the filter unit R has the same configuration as the developer replacement mechanism (the mounting portion of the developer bottle Q), and therefore it is easy to attach and detach the filter unit R. Furthermore, since it is disposed in a portion that can be easily attached and detached from the outside of the apparatus, work at the time of periodic replacement is easy and workability is improved. In the above configuration, the filter unit R is provided at the developer inlet P1. However, the filter unit R may be provided at the developer outlet P2.

As described above, according to the present invention, the filter for discharging the pressure (air) inside the apparatus is disposed in the opening for supplying the developer or discharging the developer in order to prevent the internal pressure in the developing apparatus from increasing. As a result, the pressure inside the developing device can be prevented from rising and the scattering of the developer to the outside of the device can be suppressed, and good image formation can be continuously performed by continuously performing a good developing operation. it can.
Further, according to the present invention, the filter mounting portion has the same configuration as the developer replacement mechanism, so that the mounting and dismounting operation is easy and the mounting and dismounting from the outside of the apparatus is also easy. Workability can be improved.

  In each of the above embodiments, a printer is shown as the image forming apparatus. However, the image forming apparatus to which the present invention can be applied is not limited to this, and the present invention can also be applied to an image forming apparatus such as a copying machine, a plotter, a facsimile machine, and a multifunction machine. The invention is applicable.

9 Transport screw (first screw)
10 Conveying screw (second screw)
11 Conveying screw (third screw)
20 Developing Device 21 Image Forming Device 22 Process Cartridge N1 Communication Ports P1, P2 Opening R Filter (Filter Unit)
Q Developer bottle

JP 2001-249545 A JP 2007-316495 A

Claims (8)

A developing device of a one-way circulation system comprising a plurality of conveying screws for conveying the developer and circulating the developer in one direction in the apparatus,
A communicating portion that transfers the developer from the first conveying screw to the second conveying screw; and a plurality of openings that are provided in the communicating portion and communicate with the outside of the apparatus, and one of the openings. Is for developer input or developer discharge, and the opening is provided with a filter for releasing the air inside the apparatus to the outside except when the developer is charged or the developer is discharged. . The developing device according to claim 1,
A developing device, wherein each opening is provided with an openable / closable shutter. The developing device according to claim 1 or 2,
2. A developing device according to claim 1, wherein the filter cannot pass toner particles. The developing device according to any one of claims 1 to 3,
A developing device, wherein a developer bottle is detachably attached to each of the openings. A process cartridge that is detachable from the main body of the image forming apparatus,
5. A process cartridge comprising the developing device according to claim 1 and an image carrier that carries an electrostatic latent image integrally. An image forming apparatus that includes an image forming unit including an image carrier that carries an electrostatic latent image, and that forms an image on a recording sheet,
An image forming apparatus comprising the developing device according to claim 1 as the image forming unit. An image forming apparatus having image forming means for forming an image on a recording paper,
An image forming apparatus comprising the process cartridge according to claim 5 as the image forming means. The image forming apparatus according to claim 6 or 7,
An image forming apparatus, wherein the filter can be replaced without removing the developing device from the apparatus main body.

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