JP2013020117A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two component developing device, including one agitation member with no conveyance function in the shaft direction, at a low price, and certainly suppressing unevenness of the toner density.SOLUTION: A developing device comprises: a housing; a developing sleeve provided in a prescribed position of the housing; one agitation member positioned in parallel with the developing sleeve, and agitating a developer within the housing and supplying it to the developing sleeve; and a toner conveyance tube positioned in parallel with the agitation member and feeding toner to an area of the agitation member. The toner conveyance tube rotatable in a circumferential direction can be stopped at an arbitrary rotation angle position. On a circumferential surface of the conveyance tube, formed are a plurality of toner discharge holes. The plurality of toner discharge holes make it possible to feed the toner to the area of the agitation member from each of a plurality of areas divided in the shaft direction of the conveyance tube. Opening patterns of the discharge holes are formed different in the circumferential direction so that the opening state by the discharge holes in the conveyance tube shaft direction is made changeable. The toner is fed at a desired position in the shaft direction of the conveyance tube by stopping the conveyance tube at a prescribed position.

Description

  The present invention relates to a developing device mounted on an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having both functions, and in particular, two-component development mainly composed of a carrier and toner. The present invention relates to a developing device that includes a developer and includes a developer stirring unit that does not have a conveying function in the axial direction (longitudinal direction).

FIG. 7 shows a schematic sectional configuration of a general two-component developing device.
The developing unit has an agitation unit for storing and agitating the developer, and screws 13a and 13b are arranged.

  A magnet 9 is fixed inside a developing sleeve 12 which is attached to the developing unit and faces the photosensitive drum as an image carrier, and the developer in the developing unit is in a direction perpendicular to the paper surface using screws 13a and 13b. The developer is transported with stirring (for example, the developer is transported from the paper surface to the back side by the screw 13a, and the developer is transported to the front side of the paper surface by the screw 13b at a back side not shown). 12 is carried. As the developing sleeve 12 rotates, the developer is uniformly layered on the developing sleeve by the blade 15. After the toner is developed into an electrostatic latent image at a portion facing the photosensitive drum (not shown), the developer is again collected by the developing device.

  The toner concentration of the developer (ratio of the toner amount to the total developer amount) is detected by a toner concentration sensor (not shown), and the toner is replenished from another location (not shown) into the developing device according to the measured toner concentration. .

  The toner supplied to the developer is uniformly stirred into the developer while being conveyed by the screws 13a and 13b of the stirring unit. The developer is circulated by the two screws 13a and 13b, and has a role of stirring the toner. With such a configuration, the toner density of the developer can be controlled uniformly and constantly, and a high-quality image can be maintained for a long period of time.

However, in the above conventional example, since two screws are used, there is a drawback that the developing device becomes large and the cost increases.
When only one stirring means is used for two-component development as in the case of one-component development, an image with unevenness in the longitudinal direction is formed due to insufficient stirring in the longitudinal direction. This is due to the characteristic of two-component development that the toner density that does not occur in one-component development becomes non-uniform.

  One stirring member that is usually used is a stirring bar in which elliptical plates are arranged obliquely and parallel to each other. Such a stirrer has a large ability to stir the developer, but has little ability to transport in the longitudinal direction and is inferior to the stirring ability in the longitudinal direction.

  For this reason, two screws are often used for two-component development. In particular, an apparatus that requires high image quality such as a color copying machine requires two screws, and the developing device becomes large. . In order to solve such problems, there is a proposal of Patent Document 1. According to this, a plurality of sponge supply rollers are provided in the upper part of the agitating unit, and a gear box is installed on each roller so that the plurality of supply rollers can be driven independently. In such a configuration, the apparatus becomes large (larger) and more expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a toner replenishment mechanism that can reliably suppress the occurrence of uneven toner density at low cost in a two-component developing device that has a single stirring member and does not have an axial conveyance function. It is to realize a developing device.

  An object of the present invention is to provide a developing device for visualizing an electrostatic latent image on a latent image carrier using a two-component developer, a housing, a developing sleeve to be disposed at a predetermined position of the housing, and a developing sleeve. A stirring member that is positioned in parallel and stirs the developer in the housing and supplies it to the developing sleeve, and a toner transport pipe that is positioned in parallel to the stirring member and replenishes toner in the region of the stirring member. In the developing device, the toner transport tube is rotatable in the circumferential direction and can be stopped at an arbitrary rotational angle position, and a plurality of toner discharge holes are formed on the peripheral surface of the toner transport tube. A plurality of toner discharge holes can replenish toner from a plurality of regions divided in the axial direction of the toner conveyance tube to the region of the agitating member, respectively, and the toner conveyance tube axial direction opening state by the discharge holes Form a different aperture patterns in the circumferential direction can be changed, by stopping the toner conveying pipe at a predetermined position, by supplying the toner in the axial direction of the desired position of the toner conveying pipe, is solved.

  According to the present invention, in a two-component developing device that has a single stirring member and does not have a transport function in the axial direction, the toner transport pipe positioned parallel to the stirring member and thus parallel to the developing sleeve rotates in the circumferential direction. It is possible to stop at an arbitrary rotational angle position, and a plurality of toner discharge holes are formed on the peripheral surface of the toner transport tube, and these toner discharge holes are divided in the axial direction of the toner transport tube. The toner can be replenished from the plurality of areas to the area of the agitating member, and different opening patterns are formed in the circumferential direction so that the opening state of the toner conveying tube axial direction by the discharge holes can be changed. By stopping the tube at a predetermined position, it is possible to replenish toner at a desired position in the axial direction of the toner conveying tube. It is possible to reduce the degree deviation.

1 is an overall configuration diagram of a color copying machine. 1 is a schematic cross-sectional configuration diagram of a developing device according to an embodiment of the present invention. FIG. 6 is a development view of a conveyance pipe for showing an opening pattern of the toner conveyance pipe. FIG. 6 is a longitudinal sectional view of a toner conveying tube. It is a schematic perspective view of a toner transfer mechanism. It is a schematic sectional block diagram of the developing device which concerns on another embodiment. It is a schematic cross-sectional block diagram of the developing device for two-component development which has the conveyance function in the axial direction which concerns on a prior art.

First, the configuration of the entire color copying machine as an image forming apparatus will be described with reference to FIG. 1 in the operation during normal color image formation.
The document D is transported from the document table in the direction of the arrow in the drawing by the transport roller of the document transport unit 51 and placed on the contact glass 53 of the document reading unit (scanner) 55. Then, the document reading unit 55 optically reads the image information of the document D placed on the contact glass 53. Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. Then, from the writing unit 2, laser light (exposure light) based on the image information of each color is incident on the polygon mirror 3 and reflected, and then passes through the lenses 4 and 5, thereby yellow, magenta, cyan, Each black color component passes through a separate optical path and is emitted toward the photosensitive drum 21 which is an image carrier of the corresponding process cartridge 20Y, 20M, 20C, 20BK.

  On the other hand, each of the four photosensitive drums 21 rotates in the clockwise direction in FIG. 1, and the surface thereof is uniformly charged at a position facing the charging unit 22 (charging process). Thus, a charged potential is formed on the photosensitive drum 21. Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of each laser beam.

  Laser light of each color component is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 21 by the polygon mirror 3 that rotates at high speed on the surface of the photosensitive drum that has reached the irradiation position, and corresponds to each color component. An electrostatic latent image is formed on each photosensitive drum 21 (exposure process).

  Thereafter, the surface of the photosensitive drum 21 on which the electrostatic latent images of the respective colors are formed reaches positions facing the developing units (developing devices) 23Y, 23M, 23C, and 23BK, respectively. Then, each color toner is supplied from the developing units 23Y, 23M, 23C, and 23BK onto the photosensitive drum 21, and the latent image on the photosensitive drum 21 is developed (developing step).

  Then, the surface of the photosensitive drum 21 after the development process reaches a position facing the intermediate transfer belt 27. Here, the transfer bias roller 24 is installed at each facing position so as to contact the inner peripheral surface of the intermediate transfer belt 27. Then, at the position of the transfer bias roller 24, the images of the respective colors formed on the photosensitive drum 21 are sequentially superimposed and transferred onto the intermediate transfer belt 27 (first transfer step).

  The surface of the photosensitive drum 21 after the first transfer process reaches a position facing the cleaning unit 25. The untransferred toner remaining on the photosensitive drum 21 is collected by the cleaning unit 25 (cleaning process). Thereafter, the surface of the photosensitive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes on the photosensitive drum 21 is completed.

  On the other hand, the surface of the intermediate transfer belt 27 on which the images of the respective colors on the photosensitive drum 21 are transferred in an overlapping manner travels in the direction of the arrow in the drawing and reaches the position of the second transfer bias roller 28. Then, at the position of the second transfer bias roller 28, the full-color image on the intermediate transfer belt 27 is secondarily transferred onto the recording medium P conveyed from the paper feeding unit 61 via the conveyance guide 63, the registration roller 64, and the like. (Second transfer step). Thereafter, the surface of the intermediate transfer belt 27 reaches the position of the intermediate transfer belt cleaning unit 29. Then, the untransferred toner on the intermediate transfer belt 27 is collected by the intermediate transfer belt cleaning unit 29, and a series of transfer processes on the intermediate transfer belt 27 is completed.

  Thereafter, the recording medium P on which the full-color image is transferred is guided to the fixing unit 66 by the conveyance belt 30. In the fixing unit 66, the color image is fixed on the recording medium P at the nip between the heating roller 67 and the pressure roller 68. The recording medium P after the fixing process is discharged as an output image by the paper discharge roller 69 to the outside of the apparatus main body, and a series of image forming processes is completed.

  The configuration of the developing device according to one embodiment of the present invention will be described with reference to FIG. In the developing device (developing unit) 23, a developing sleeve 12 is provided at a position facing the photosensitive drum in the housing, and rotates in the direction of the arrow. The developing sleeve 12 includes a magnet 10 in a predetermined position. A stirring member 13 with a stirring blade is disposed obliquely below the developing sleeve 12 in FIG. 2 and rotates in the same direction as the developing sleeve 12. A toner conveying tube 14 that is rotatable and can be stopped at an arbitrary rotational position is installed above the agitating portion where the agitating member 13 is disposed, and a range toward the agitating portion is opened. The toner conveying tube 14 is provided with a plurality of openings (toner discharge holes), and toner is supplied to the agitating unit of the developing device through the openings. FIG. 3 shows a state where the surface of the toner conveyance tube is developed. The opening of the transport pipe 14 is divided into three in the axial direction (longitudinal direction) (center, front, back). Moreover, it is divided by 45 degrees in the circumferential direction, and the pattern of the opening is different at each angular position. That is, all the replenishment patterns are covered independently or in combination at the center, near side, and back position, and the arbitrary patterns can be selected. For example, the rotation of the toner conveying tube 14 is controlled so that the 45 ° pattern is positioned at the three portions and the 270 ° pattern is positioned at the communicating portion 16 with the agitating portion. In the developing device according to the present invention, the agitating member 13 is composed of a single paddle-like member that does not have a conveying function in the axial direction, so that the developer is conveyed in the axial direction like a conventional two screw. Do not circulate. In such a developing device having no axial conveyance function, the replenishment position is divided in the axial direction to perform toner replenishment control at low cost. In this example, although it is divided into three in the axial direction, the number of divisions is arbitrary, and it has been verified that even two divisions are sufficiently effective.

  A seal 18 made of resin such as PET is disposed between the toner conveyance tube 14 and the communication portion 16, and is in contact with the toner conveyance tube 14 or with a minute gap. As will be described later, since the toner is transported to the developing device by air, at this time, the toner serves to seal the flow of toner from the opening other than the downward opening of the transport pipe 14 into the developing device through the clearance of the developing device. ing.

  The developer containing the toner replenished to the stirring unit by such a characteristic replenishment method is attracted to the developing sleeve 12 from the stirring unit by the magnetic action of the magnet 10 included in the developing sleeve 12, and is regulated by the regulating blade 15. A thin layer is formed on the developing sleeve. Thereafter, the developer contacts the photosensitive drum 21 facing the developing sleeve 12, and the toner is developed on the electrostatic latent image on the drum. The developed developer is again collected by the developing device and returned to the stirring section.

  Here, detection of toner density will be described. Conventionally, the toner concentration in the developer is generally detected by a magnetic permeability sensor or the like installed in the developing device, and the consumed toner is generally replenished based on the detection result. However, in this example, such a sensor is not provided, and the toner consumption amount is estimated based on the image information recognized by the document reading unit (scanner) 55 and the toner supply amount is determined. Further, by obtaining toner consumption amount information divided in the axial direction, the required toner amount is calculated in detail at each position in the axial direction. For example, if an image biased toward the back side continues to be output, the toner concentration of the developer in the back side region decreases, but the toner concentration in the center or front side region does not decrease. In such a case, it is necessary to supply toner only to the back side. At this time, the pattern of the opening of the toner conveying tube 14 corresponds to the pattern of 225 ° in FIG. 3, and the rotation of the conveying tube is controlled so that the pattern faces the communication portion 16, and the rear side region The toner density is surely adjusted so that the toner is replenished only in the axial direction and density unevenness in the axial direction of the developing sleeve and the stirring member does not occur. As described above, the toner can be replenished to an arbitrary position among the three positions in the axial direction. FIG. 4 shows a cross section of the toner transport tube 14. This figure shows a state where three openings appear, that is, a state of communication with the stirring unit in the 45 ° pattern of FIG. The toner conveyance tube 14 is connected to a toner transfer tube 33 of a toner transfer mechanism, which will be described later, via a bearing and is rotated by a gear 17. The gear is driven and transmitted by a motor (not shown). A stepping motor or the like whose rotation angle can be controlled is used as the motor.

  Next, the configuration and operation of the toner transfer mechanism will be described in detail with reference to FIG. The toner transfer mechanism is connected to the developing device 23 (the toner transfer tube 14), and is composed of a toner transfer tube 33 made of a material excellent in flexibility and toner resistance, and an air pump attached to one end of the toner transfer tube 33. 32, a toner storage unit 34, a toner delivery unit 35 connected to the toner storage unit 34 and containing a screw, a screw driving motor 36, and the like. In this toner transfer mechanism, when the toner in the toner storage unit 34 falls by its own weight onto the toner delivery unit 35, the toner is sent to the junction with the toner transfer tube 33 by the screw in the toner delivery unit 35 driven by the motor 36. Since the air pump 32 generates a pressure in the toner transfer tube 33, the toner is transferred to the developing device 23 by this. By using the flexible transfer tube 33 and air transporting the toner, the degree of freedom in the layout of the toner transport path is increased, so that the toner container 34 can be installed at a location away from the developing device 23 and the image forming apparatus can be installed. Can be downsized.

  When the toner is conveyed by air, the necessary toner amount calculated from the image information of the original read by the image reading unit is determined as the drive time of the screw, and the toner is discharged. The toner is dispersed and transported in the air, enters the toner transport pipe 14 in the developing device, and is replenished to the developer in the developing stirring section through the opening 16. As described above, since the toner is dispersed in the air, the toner is easily stirred. By replenishing toner by this air conveyance method, the replenished toner can be made uniform in the storage developer in a shorter time. As in this example, in the method in which the developer collected from the developing sleeve is pumped up immediately from the stirring unit to the developing sleeve, the toner must be quickly stirred with the developer to impart charge to the toner. Air conveyance is suitable for such a system.

  Finally, the configuration of the developing device according to the improved embodiment will be described. As described above, the developer on the developing sleeve returns to the stirring unit after being developed, but if the developer in the stirring unit is large in volume, it may be pumped up again without leaving the developing sleeve. . In particular, when the toner concentration is high or the developer deteriorates due to long-term operation and the fluidity is lowered, the bulk tends to increase. Therefore, a partition plate 19 is provided between the developing sleeve 12 and the stirring member 13 as shown in FIG. The partition plate 19 can force the developer to flow toward the stirring unit.

  By performing toner replenishment control with such a configuration, in a developing device using only one stirring member, a stable and uniform high-quality image can be obtained, and a small-sized developing device can be realized at low cost.

DESCRIPTION OF SYMBOLS 10 Magnet 12 Developing sleeve 13 Stirring member 14 Toner conveyance pipe 15 Regulating blade 16 Communication portion 18 Seal 23 Developing device

Japanese Patent Laid-Open No. 08-123174

Claims (5)

A developing device for visualizing an electrostatic latent image on a latent image carrier using a two-component developer, a housing, a developing sleeve to be disposed at a predetermined position of the housing, and a developing sleeve that is positioned in parallel with the developing sleeve. In a developing device, comprising: a stirring member that stirs developer in a housing and supplies the developer sleeve to a developing sleeve; and a toner transport pipe that is positioned parallel to the stirring member and replenishes toner in the region of the stirring member. ,
The toner transport tube is rotatable in the circumferential direction and can be stopped at an arbitrary rotation angle position. A plurality of toner discharge holes are formed on a peripheral surface of the toner transport tube, and the plurality of toner discharge holes are formed. The toner can be replenished from the plurality of regions divided in the axial direction of the toner conveying tube to the respective regions of the agitating member. In the circumferential direction so that the opening state of the toner conveying tube in the axial direction by the discharge holes can be changed. A developing device having different opening patterns and supplying toner at a desired position in an axial direction of the toner transport tube by stopping the toner transport tube at a predetermined position.   The developing device according to claim 1, wherein a partition plate for developer flow is provided between the developing sleeve and the stirring member.   An image forming apparatus comprising the developing device according to claim 1.   A toner container arranged at a different position from the developing device and a toner transfer mechanism using air are used. The toner is transferred from the toner container to the toner transport pipe and supplied to the stirring member region from the toner discharge hole. The image forming apparatus according to claim 3.   5. The toner replenishment amount and a toner replenishment position of a toner transport tube by a toner discharge hole are determined based on a toner consumption amount calculated from image information data to be formed. Image forming apparatus.

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