JP4857981B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that develops an electrostatic latent image on an image holding member disposed adjacently with toner in a developer composed of toner and a carrier, and an image forming apparatus including the developing device.

  Conventionally, an electrostatic latent image is formed on an image holding member such as a photosensitive member, and the electrostatic latent image is developed with toner to obtain a toner image. There is known an image forming apparatus that forms an image on a sheet by transferring and fixing the image on the sheet.

  In such an image forming apparatus, a developer containing toner and a carrier is accommodated in a developer agitating chamber, and the agitated developer is agitated while being moved by a rotating member or the like. Some toners that are charged and electrostatically attached to a carrier are used to develop an electrostatic latent image formed on the surface of the image carrier. In such an image forming apparatus, for example, the toner concentration of the developer existing in a predetermined region in the developer agitating chamber (the ratio of the toner when the developer amount is 100 is expressed in%) is expressed as a developer agitation. The toner is detected by a toner concentration sensor over the wall of the chamber, and toner replenishment in an amount corresponding to the detected density value is performed to the developer stirring chamber.

  However, in the corners of the developer stirring chamber and the inner surface of the wall, the stirring force by the rotating member is weak, and the toner agglomerates and adheres to the inner surface of the wall or the like in the predetermined area where the toner concentration sensor is detecting the concentration. As a result, image quality defects such as a decrease in image density may occur even though the detected toner density is equal to or higher than a reference value.

Therefore, toner in the developer is unevenly distributed by storing a developer having a particle diameter of about several tens of μm and a developer composed of toner and a carrier together with a sphere having a diameter of about several millimeters and moving and stirring the developer. It is conceivable to use a proposal (refer to Patent Document 1) that suppresses toner charging unevenness and stabilizes image quality as a measure for preventing erroneous detection of toner concentration caused by uneven distribution of toner in the developer. It has been.
JP-A-6-337590

  However, it is expected that mixing of the spheres with the developer in the developer agitating chamber will eliminate the uneven distribution of toner in the developer, but the developer is accommodated by the amount accommodated in the developer accommodating chamber. The amount of developer in the room is inevitably reduced, and as a result, the developer deteriorates due to an increase in the number of collisions with the sphere, and the charging performance of the toner decreases. For this reason, image quality defects may occur due to the occurrence of fog or the like due to toner charging defects.

  In view of the above circumstances, an object of the present invention is to provide a developing device that contributes to suppression of occurrence of image quality defects.

In order to achieve the above object, the developing device of the present invention comprises:
A developer that contains a developer containing a toner and a carrier and develops the electrostatic latent image on the image carrier with the developer,
A stirring chamber having a replenishing port for replenishing toner, containing the developer and stirring the developer inside;
A stirring member that is provided in the stirring chamber and stirs while moving the developer contained in the stirring chamber in the stirring chamber;
A stirring auxiliary member that is unevenly distributed in a predetermined region in the stirring chamber irrespective of the movement of the developer and moves in the predetermined region as the developer is stirred by the stirring member to assist the stirring of the developer. It is characterized by that.

  According to the present invention, since stirring in the predetermined region is assisted by the stirring auxiliary member unevenly distributed in the predetermined region in the stirring chamber, at least the stirring property in the predetermined region is high. Further, since the stirring auxiliary member is unevenly distributed in the stirring chamber, a sufficient stirring property can be obtained even with a small amount, and deterioration of the developer can be avoided. Improvement in the stirring property of the developer and avoidance of deterioration can contribute to suppression of occurrence of poor image quality.

  Here, the developing device of the present invention preferably includes a toner concentration detection unit that detects the toner concentration of the developer present in the predetermined region in the stirring chamber, and the typical toner concentration detection unit includes the stirring unit. The toner concentration of the developer existing in the predetermined area in the room is indirectly detected by detecting the magnetic permeability of the developer through the wall of the stirring chamber.

  By providing a toner concentration detection unit that detects the toner concentration of the developer present in the predetermined area in the stirring chamber, it is possible to grasp the toner concentration of the substance in the stirring chamber, thereby further suppressing the occurrence of image quality defects. Can contribute.

  Further, the stirring assisting member may be a member in which a plurality of chunks are connected in series.

  Here, the stirring member has a rotation shaft and a plate portion standing on the rotation shaft, and the developer is stirred by rotating about the rotation shaft. It is also a preferable aspect that the member is a member in which a plurality of lumps are connected in series and one end is fixed to the plate portion of the stirring member.

  When the agitation auxiliary member has a plurality of lump portions connected in series and one end fixed to the plate portion of the agitation member, the developer is agitated more effectively by the addition of rotational movement. Can do.

In order to achieve the above object, an image forming apparatus of the present invention comprises:
An electrostatic latent image is formed on the image holding member, and the electrostatic latent image is developed with a developer to obtain a developed image. The developed image is transferred and fixed on the paper, thereby fixing the toner image on the paper. In an image forming apparatus for forming an image
A developer for developing the electrostatic latent image on the image carrier with toner;
This developer is
A developer that contains a developer containing toner and a carrier and develops the electrostatic latent image on the image carrier with the developer,
A stirring chamber having a replenishing port for replenishing toner, containing the developer and stirring the developer inside;
A stirring member that is provided in the stirring chamber and stirs while moving the developer contained in the stirring chamber in the stirring chamber;
A stirring auxiliary member that is unevenly distributed in a predetermined region in the stirring chamber irrespective of the movement of the developer and moves in the predetermined region as the developer is stirred by the stirring member to assist the stirring of the developer. It is characterized by that.

  According to the present invention, it is possible to contribute to the suppression of the occurrence of image quality defects.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a printer that is an embodiment of an image forming apparatus of the present invention, including an embodiment of a developing device of the present invention.

  The printer 1 shown in FIG. 1 is generated by the exposure device 12 based on image data transmitted from the outside on the surface of the photosensitive member 10 rotated in the direction of arrow A, to which a predetermined charge is applied by the charger 11. The electrostatic latent image formed by irradiating the exposure light is developed with the toner in the developer composed of toner and magnetic carrier housed in the developing device 13, and the toner image obtained by this development is converted into paper. A monochrome image dedicated machine that forms an image on a recording sheet by transferring it by a transfer roll 14 onto a recording sheet pulled out from the tray 16 by a sheet conveying device 16a and conveyed in the direction of arrow B, and fixing it by a fixing device 15. is there. The developing device of the present invention may be applied not only to a monochrome image dedicated machine but also to a color image machine.

  FIG. 2 is a perspective view from the upper surface of the developing device shown in FIG.

  The developing device 13 shown in FIG. 2 includes two augers 131 that agitate the developer composed of toner and magnetic carrier while conveying the developer in the direction of the arrow, and rotatably support these augers 131. The developer agitating chamber 132 provided with a partition plate 1321 for partitioning the auger 131, the developing roll 133 holding the developer agitated in the developer agitating chamber 132, and the developer agitating chamber 132 are replenished with toner. And a magnetic permeability sensor 134 for indirectly detecting the toner concentration of the developer by detecting the magnetic permeability of the developer.

  Further, FIG. 2 shows a state in which a stirring auxiliary member 135, which will be described in detail later, is swingably attached to one of the two augers 131 that stir the developer in the developer storage chamber. Yes.

  FIG. 3 is a view showing a case where the AA cross section and the BB cross section of the developing unit shown in FIG. 2 are viewed from the left side in FIG.

A developing roll 133 shown in FIG. 3 is provided in the vicinity of the photosensitive member 10 and is rotated in the direction of arrow C, and is fixed to the inside of the developing sleeve 1331 independently of the developing sleeve 1331. , And a magnet roll 1332 in which a plurality of magnetic poles (not shown) are arranged in the circumferential direction of the developing sleeve 1331.

  The magnetic roller 1332 attracts the magnetic carrier, to which the charged toner is electrostatically attached due to friction with the carrier by stirring, by the magnetic force, so that the developing sleeve 1331 holds the magnetic carrier to which the toner is attached on the surface. Further, the developing sleeve 1331 rotates to convey the held magnetic carrier to the developing region 130 that is an electric field region formed between the developing sleeve 1331 and the photosensitive member 10. The toner electrostatically attached to the magnetic carrier conveyed to the developing area 130 adheres to the electrostatic latent image side formed on the surface of the photoconductor, so that a toner image is formed on the surface of the photoconductor. It is formed.

  An auger 131 shown in FIG. 3 has a rotating shaft 1311 and a plate portion 1312 erected on the rotating shaft 1311. The auger 131 is agitated while moving the developer by rotating around the rotating shaft 1311.

  The magnetic permeability sensor 134 shown in FIG. 3A detects the magnetic permeability of the developer present in the detection area in the developer stirring chamber 132 where the sensor surface 1341 is directed through the wall. The toner density inside is indirectly detected.

  FIG. 3B shows a toner replenishment port 132 a provided for replenishing toner in the developer agitating chamber. This developer 13 is indirectly detected by a transmittance sensor 134. The toner is supplied from a toner cartridge (not shown) according to the toner density.

  3A includes a nylon thread 1352 and a brass ball 1351 through which the nylon thread 1352 is inserted. FIG. 3A illustrates the stirring assist member 135. The member 135 is shown with one end of a nylon thread 1352 attached to a part of the plate portion 1312 of the auger 131. The stirring assisting member 135 moves in the developer stirring chamber as the auger 131 rotates. Among them, the developer present on the side of the magnetic permeability sensor with respect to the partition plate 1321 and in the range where the sensor surface 1341 is directed through the wall of the developer stirring chamber 132 is mainly stirred. Therefore, according to the developing device 13 of this embodiment, toner aggregation in the detection region can be suppressed without significantly eroding the developer amount in the developer stirring chamber 132 having a constant capacity, and the brass ball 1351 can be suppressed. Degradation due to numerous collisions between the toner and the developer is also avoided, which can contribute to the suppression of image quality defects in the printer 1 of the present embodiment.

  Next, experiments conducted on the examples of the present invention and comparative examples for the present invention will be described.

  The embodiment is a DocuCenterColor 450 modified to a monochrome image dedicated machine having the same configuration as the configuration of the printer 1 described above, and 229.5 g of developer is accommodated in the developer accommodating chamber. A 0.5 mm diameter through-hole is made in 0.5 g of a brass ball (product name: 2 types of brass) made by Sato Steel Co., Ltd., 0.5 g, and a nylon thread of 0.405 mm diameter made by Toray Fishing Co., Ltd. The other end of the agitation assisting member that is inserted through the strong big game No. 6) and connects one end is attached to the plate portion of the auger.

  In Comparative Example 1, the auxiliary stirring member 135 is removed from the example.

  In Comparative Example 2, instead of the stirring assisting member of Example, 100 g of brass balls (product name: 2 types of brass) manufactured by Sato Steel Co., Ltd. and having a diameter of 3 mm were accommodated in the developer accommodating chamber. For these Examples, Comparative Example 1 and Comparative Example 2, the accuracy of toner density detection, the occurrence of a decrease in image density, the occurrence of a decrease in toner chargeability, and the fogging when printing with an image density of 20% was performed at 100 KPV The occurrence of this was evaluated. In addition, about the generation | occurrence | production of fogging, presence or absence is confirmed by visual observation, and (circle) means that it is favorable and x means a defect about comprehensive evaluation. In Examples, Comparative Example 1 and Comparative Example 2, as a toner replenishing method for the developer stirring chamber, a method called trickleless, in which only the toner is replenished without replenishing the carrier that is normally replenished with the toner, is used. It was adopted.

  As shown in Table 1, in the example in which 0.5 g of the stirring auxiliary member is attached to the plate portion of the auger with respect to 229.5 g of the developer, and in Comparative Example 1 in which this stirring auxiliary member is omitted, the toner Although both charging property and fogging are good, in Comparative Example 1, since the stirring assist member is omitted, erroneous detection of the toner concentration occurs, and the toner concentration as an entity in the developer containing chamber is reduced. Since the image density decreased to 3%, the image density decreased to 0.4 and an image defect occurred. In Comparative Example 2, the amount of brass spheres relative to the developer contained in the developer agitating chamber is significantly larger than that in the embodiment, and these are not connected and can be freely moved in the developer containing chamber. The toner density detection accuracy and the image density are as good as in the examples, but the amount of brass spheres is extremely large, so that the deterioration of the developer is intensified and the chargeability of the toner reaches 20 μc / g. A drop occurred and fogging occurred. From the above results, the comprehensive evaluation is good only for the examples, and both Comparative Example 1 and Comparative Example 2 are poor. From the above experimental results, it was confirmed that the developing device of this embodiment contributes to the suppression of the occurrence of image quality defects.

  Here, in the embodiment described with reference to FIG. 1 to FIG. 3, an example in which the brass ball 1351 is used as the stirring auxiliary member 135 has been described, but the shape of the lump according to the present invention is not limited to a sphere, An indefinite shape, a rectangular parallelepiped, a cube, an ellipsoid, etc. may be sufficient. However, it is more preferable to have a shape that does not damage the inner wall of the developer stirring chamber. When the inner wall is damaged, the toner adheres to the scratch, and when the adhered toner is peeled off due to some bounce, trimmer clogging occurs, and there is a concern that streaky image omission occurs on the halftone image. Because. Moreover, as a stirring auxiliary member said to this invention, except the brass ball | bowl 1352 mentioned in embodiment, the product made from resin, the mixture of a metal and resin, a covering, etc. are mentioned. However, a non-magnetic material or a magnetic material having substantially no residual magnetization is preferable. If there is residual magnetization, the two-component developer is adsorbed by magnetic force, the fluidity is deteriorated, the supply of the developer to the developing roll is reduced, the developer layer on the developing roll becomes non-uniform, and the image density This is because there is a concern that unevenness occurs. Further, as the stirring assisting member referred to in the present invention, other chemical fibers, natural fibers, metal fibers, or a combination of them may be used instead of the nylon yarn mentioned in the embodiment.

  In the embodiment described with reference to FIGS. 1 to 3, an example in which the toner concentration in the developer stirring chamber is indirectly detected by the magnetic permeability has been described. However, the developer concentration in the developer stirring chamber is not limited. The present invention is not limited to this as long as the toner concentration is detected, and an optical sensor having a sensor surface that enters the stirring chamber may be used in order to optically detect the toner concentration in the developer stirring chamber. In the above description, the example in which the stirring assisting member 135 is attached to the plate portion 1312 of the auger 131 has been described, but the stirring assisting member according to the present invention is not limited to the movement of the developer in the developer stirring chamber. The rotating shaft 1311 of the auger 131 or the developer stirring chamber may be used as long as it is unevenly distributed in a predetermined region in the stirring chamber and moves in the predetermined region as the developer is stirred by the stirring member to assist the stirring of the developer. It may be attached to a part of the inner wall. Furthermore, as the agitation auxiliary member referred to in the present invention, in addition to the one in which a nylon thread is inserted into a through hole opened in a brass ball and one end is connected, a lump is connected in a state where a certain interval is secured. Alternatively, the rings may be connected in a chain.

1 is a schematic configuration diagram of a printer that is an embodiment of an image forming apparatus of the present invention, including an embodiment of a developing device of the present invention. FIG. FIG. 2 is a perspective view from the upper surface of the developing device shown in FIG. 1. FIG. 3 is a diagram illustrating a case where an AA cross section of the developing device illustrated in FIG. 2 is viewed from a toner supply port side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 13 Developing device 13a Toner replenishment port 131 Stirring auger 132 Developer stirring chamber 1321 Partition plate 133 Developing roll 1331 Developing sleeve 1332 Magnet roll 134 Magnetic permeability sensor 135 Stirring auxiliary member 1351 Brass ball 1352 Nylon thread

Claims (2)

A developer that contains a developer containing a toner and a carrier and develops the electrostatic latent image on the image carrier with the developer,
A stirring chamber having a replenishing port for replenishing toner, containing the developer and stirring the developer therein;
A rotating shaft and a plate portion erected on the rotating shaft, provided in the stirring chamber , and rotated around the rotating shaft so that the developer accommodated in the stirring chamber is discharged in the stirring chamber. A stirring member that stirs while moving;
And thread attached to the plate portion of the agitation member consists of brass balls attached to the yarn, and a stirring assisting member for assisting a stirring motion the developer with the agitation of the developer by the stirring member A developing device comprising: An electrostatic latent image is formed on an image holding member, the latent electrostatic image is developed with a developer to obtain a developed image, and the developed image is transferred and fixed on a sheet to thereby fix the toner image on the sheet. In an image forming apparatus for forming an image
A developer for developing the electrostatic latent image on the image carrier with toner;
The developer is
A developer that contains a developer containing a toner and a carrier and develops the electrostatic latent image on the image carrier with the developer,
A stirring chamber having a replenishing port for replenishing toner, containing the developer and stirring the developer therein;
A rotating shaft and a plate portion erected on the rotating shaft, provided in the stirring chamber , and rotated around the rotating shaft so that the developer accommodated in the stirring chamber is discharged in the stirring chamber. A stirring member that stirs while moving;
And thread attached to the plate portion of the agitation member consists of brass balls attached to the yarn, and a stirring assisting member for assisting a stirring motion the developer with the agitation of the developer by the stirring member An image forming apparatus comprising the image forming apparatus.

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