JP2005077491A - Development device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device which obtains stable image density, even if image formation based on a specific image partly including an extreme density difference is repeated. <P>SOLUTION: The development device includes a developing roll which holds thereon a developer composed of toner and magnetic carrier, and a housing which accommodates the development roll. The development device is provided with a partition member which divides the interior of the housing into a developer storage part which is formed adjacent to the development roll and stores the developer, and a toner storage part which is formed with the developer storage part located between the development roll and the toner storage part itself and mainly stores the toner; a toner feeding member which is disposed in the toner storage part and feeds the toner in the toner storage part into the developer storage part through a predetermined opening; and a toner axial direction moving member which is disposed in the toner storage part and moves the toner in the toner storage member, in the direction of the rotary shaft of the development roll. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is arranged in the vicinity of an image carrier on which an electrostatic latent image is formed and rotates while carrying a developer composed of toner and a magnetic carrier, and rotates the developer to a development area close to the image carrier. The present invention relates to a developing device that develops an electrostatic latent image formed on the image carrier by being conveyed.

  2. Description of the Related Art Conventionally, a developing device used in an image forming apparatus such as an electrophotographic printer or a copying machine includes, for example, a development composed of toner and a magnetic carrier on a developing roll disposed in the vicinity of an image carrier such as a photosensitive roll. In some cases, the electrostatic latent image on the photoreceptor roll is developed by transporting the developer to a development area formed in a facing portion between the photoreceptor roll and the development roll while holding the developer.

  In the developer used in the developing device, the toner and the magnetic carrier are mixed at a predetermined ratio, whereby the toner in the developer is charged to a predetermined charge amount, and the electrostatic charge on the photoreceptor roll is charged. Toner development is performed according to the latent image.

  However, the developing device has a problem in that the structure of the developing device becomes complicated because a density control device for maintaining the toner concentration in the developer at a predetermined density is required.

  In view of this, recently, a developer accommodating portion that accommodates the developer in the vicinity of the developing roll, and a toner accommodating portion that is formed at a position sandwiching the developer accommodating portion between the developing roll and mainly accommodates toner. And a developing device that adjusts the charge amount of the toner in the developer accommodating portion by appropriately feeding toner into the developer accommodating portion (see, for example, Patent Document 1). This eliminates the need for a complicated mechanism for adjusting the toner density.

  FIG. 1 is a schematic configuration diagram of an example of a type of developing device that appropriately supplies toner to a developer container and adjusts the toner charge amount.

  FIG. 1 shows a housing 10 of the developing device 1. The developing roll with the side facing the developing area 20 formed between the housing 10 and the photoreceptor roll 30 exposed to the outside is shown. 11 is disposed.

  In the housing 10 shown in FIG. 1, the interior of the housing is located at a position where the developer accommodating portion 21 that accommodates the developer carried on the developing roll and the developer accommodating portion 21 is sandwiched between the developing roll. A partition plate 13 that divides the toner into a toner container 22 that mainly stores toner, a developer stirring member 12 that is disposed in the developer container and stirs the developer, and the toner in the toner container that is disposed in the toner container. An agitator 15 for supplying the developer container and a layer thickness control member 14 for controlling the layer thickness of the developer disposed through a gap so as to face the developing roll are provided.

  The partition plate 13 has an upper end close to both the developing roll 11 and the layer thickness regulating member 14 and a first opening 40 and a second opening 50 between the developing roll 11 and the layer thickness regulating member 14. In addition, the third opening 60 is formed between the lower end of the housing inner wall 10a and the housing inner wall 10a, and the amount of developer passing through the first opening 40 according to the toner concentration in the developer. The excess developer that passes through the first opening 40 and is blocked by the layer thickness regulating member 14 passes through the second opening 50 and is guided to the third opening 60.

  Further, FIG. 1 shows a state where a photoconductor roll 30 that forms a developing region 20 between the developing roll 11 and a magnet 11 a is disposed inside the developing roll 11.

  Hereinafter, how the toner charge amount in the developer accommodating portion is adjusted by appropriately feeding the toner into the developer accommodating portion 21 will be described.

  The first opening 40 is set in advance to be larger than the gap between the layer thickness control member 14 and the developing roll. There is a developer that can pass through the gap between the layer thickness control member 14 and the developing roll trying to pass through the first opening 40 and a developer that is blocked by the layer thickness control member 14 and cannot pass through, but the toner concentration in the developer is If it is high, the magnetic attraction force by the developing roll magnetic pole in the vicinity of the second opening 50 is greater than the pressure at which the developer that is blocked and cannot pass through the second opening 50 overflows, and the developer There is no overflow from the second opening 50. When the toner concentration of the developer accommodated in the developer accommodating portion 21 decreases every time image formation is performed, the concentration of the magnetic carrier in the developer increases conversely. As a result, the force for carrying and transporting the developer on the developing roll 11 in which the magnet 11a is disposed is also increased. As a result, the developer pressure blocked by the layer thickness regulating member 14 becomes stronger than the magnetic attraction force for holding the developer near the second opening 50 than when the toner concentration in the developer is high. The developer flows out onto the partition plate 13 through the second opening 50. That is, when the toner concentration in the developer is low, the developer flows out through the opening 50, so that an empty space is created in the developer accommodating portion, and the toner on the toner accommodating portion side is removed through the third opening 60. The developer can be taken into the developer container side. When the toner concentration is high, the carrier concentration is low and the developer magnetization is low, so that a large conveying force cannot be obtained. As a result, the developer pressure blocked by the layer thickness regulating member 14 is near the opening 50. Since the magnetic attraction force is smaller than the developer, the developer does not flow out through the opening 50.

In accordance with a change in the amount of the developer regulated by the partition plate 13, the toner is sent to the empty space formed in the developer accommodating portion while the agitator 15 disposed in the toner accommodating region rotates. The toner is supplied to the third opening 50.
Japanese Patent Application Laid-Open No. 07-333912

  However, in an image forming apparatus using the above-described developing device, when image formation based on a predetermined image in which the density difference is extremely different depending on the part is repeated, a portion having a high density despite having a sufficient amount of remaining toner in the toner containing portion. The phenomenon that the density | concentration of a liquid falls gradually was seen.

  FIG. 2 is a graph showing a change in image density of a patch image formed every time a predetermined number of images having extremely different density differences depending on the portion are printed.

  2 includes three parts: a part having an image density of 100% (represented by A in FIG. 2) and two parts having an image density of 0% (represented by B and C in FIG. 2). Each time 20 predetermined images are printed, the actual image density change of the patch image formed so as to have the same image density is shown in each of the portions A, B, and C. From here, the density 100 The image density of the patch image of the part A where% image formation is performed is more than 160 prints compared to the image density of the patch images of the parts B and C where image formation of 0% density is performed. You can see how it gradually decreases from the beginning.

  In view of the above circumstances, an object of the present invention is to provide a developing device capable of obtaining a stable image density even when a predetermined image having extremely different density differences depending on a portion is repeatedly formed.

In order to achieve the above object, the developing device of the present invention comprises:
By rotating while carrying a developer composed of toner and a magnetic carrier, which is arranged in the vicinity of the image carrier on which the electrostatic latent image is formed, this developer is conveyed to a development area close to the image carrier. A developing device comprising: a developing roll for developing an electrostatic latent image formed on the image carrier; and a housing for housing the developing roll in a state where the developing area side of the developing roll is exposed to the outside. ,
A layer thickness regulating member arranged on the upstream side of the developing area in the rotation direction of the developing roll with respect to the developing area and regulating the layer thickness of the developer carried on the developing roll;
A developer accommodating portion that is disposed in the housing roll upstream of the layer thickness regulating member in the developing roll rotation direction and is formed at a position adjacent to the developing roll inside the housing, and contains the developer. A partition member that is formed at a position sandwiching the developer accommodating portion between the developing roll and a toner accommodating portion that mainly accommodates toner, the upper end of both the developing roll and the layer thickness regulating member A first opening is formed between the developing roller and the layer thickness regulating member in proximity to the developing roll, and a lower end is disposed between the housing inner wall and the lower end close to the housing inner wall. A third opening for supplying toner from the toner container to the developer container is formed, and when the toner density is low, the developer passing through the first opening and blocked by the layer thickness regulating member is removed. And the partition member leading to the third aperture is passed through the serial second opening,
A toner delivery member that is disposed in the toner containing portion and sends the toner in the toner containing portion to the developer containing portion from the third opening;
And a toner axial direction moving member arranged in the toner accommodating portion and configured to move the toner of the toner accommodating member in the rotation axis direction of the developing roll.

  The developing device of the present invention includes a toner axial direction moving member that moves the toner in the toner containing member in the direction of the rotation axis of the developing roll. As a result, according to the developing device of the present invention, image formation based on a predetermined image in which the density difference is extremely different depending on the portion is repeatedly performed, and the toner consumption amount is extremely large in the direction of the rotation axis of the developing roll in the toner accommodating portion. Even if the area is generated, the uneven distribution of the toner in the toner container in the rotation axis direction of the developing roll is suppressed by the toner axis direction moving member, so that a stable image density can be obtained.

  Here, it is preferable that the toner delivery member and the toner axial movement member that drive both the toner delivery member and the toner axial movement member have a common drive source.

  In this case, the structure can be simplified as compared with the case where the drive source is provided separately.

  The toner delivery member may also serve as the toner axial movement member.

  According to the developing device of the present invention, it is possible to obtain a stable image density even when image formation based on a predetermined image whose density difference is extremely different depending on a portion is repeated.

  Hereinafter, embodiments of the developing device of the present invention will be described.

  FIG. 3 is a diagram showing a first embodiment of the developing device of the present invention. 3 that are the same as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.

  The developing device 100 shown in FIG. 3 is a component of a color printer that is an electrophotographic image forming apparatus, and includes a developer containing portion in which a developer composed of toner and a magnetic carrier is contained in the vicinity of the developing roll, and And a toner container for supplying toner to the developer container at a position where the developer container is sandwiched between the developer roll, and by appropriately feeding the toner into the developer container, This type of developing device adjusts the charge amount of the toner. 3 that are the same as those shown in FIG. 1 are assigned the same reference numerals as those shown in FIG. Further, the illustration of the developer accommodating portion and the toner accommodating portion in FIG. 3 is omitted in order to avoid complexity, but these ranges are the same as the ranges shown in FIG.

  FIG. 3 shows the housing 10 of the developing device 100, and the developing roll 11 exposes the side of the housing 10 facing the developing area 20 formed between the developing roll 11 and the photoreceptor roll 30 to the outside. It is also shown that it is arranged in a state of being covered. A magnet 11 a is disposed inside the developing roll 11.

  Further, the housing 10 is mainly arranged at a position where the inside of the housing is sandwiched between the developer containing portion 21 for containing the developer carried on the developing roll and the developing roll. A partition plate 13 that divides the toner into a toner containing portion 22 that contains toner, a developer stirring member 12 that is provided in the developer containing portion and stirs the developer, and the toner in the toner containing portion that is provided in the toner containing portion is used as the developer. An agitator 15 for supplying to the storage unit and a layer thickness control member 14 for controlling the layer thickness of the developer carried on the developing roll are provided.

  The partition plate 13 has an upper end close to both the developing roll 11 and the layer thickness regulating member 14 and a second opening 50 between the first roll 40 and the layer thickness regulating member 14 between the developing roll 11. Further, the third opening 60 is formed between the lower end of the housing inner wall 10a and the housing inner wall 10a.

  The partition plate 13 guides the excess developer passing through the first opening 40 and blocked by the layer thickness regulating member 14 through the second opening 50 to the third opening 60 when the toner concentration is low. It is.

  Further, FIG. 3 shows a state in which the photoconductor roll 30 that forms the developing region 20 between the developing roll 11 and the magnet 11 a are disposed inside the developing roll 11.

  The toner container mainly stores toner, and as described above, the developer guided from the second opening 50 to the third opening 60 by the partition plate 13 and the magnetic carrier in the developer container. A small amount of magnetic carrier to compensate for natural loss is also accommodated.

  The agitator 15 includes toner delivery members 151b and 152b, toner axis direction moving members 151a and 152a for moving the toner in the toner accommodating portion in the direction of the rotation axis of the developing roll, a base 15c, and a rotation shaft 15d. By rotating, the toner is supplied to the third opening 60, and the toner is moved in the axial direction of the rotation shaft 15d.

  4 is an external perspective view of the agitator shown in FIG.

  The agitator 15 shown in FIG. 4 has a function of rotating in the direction of arrow B to supply toner to the third opening 60 and moving the toner in the toner storage portion in the axial direction of the rotation shaft 15d.

  FIG. 5 is a top view and a side view of the agitator shown in FIG.

  FIG. 5A shows a view when the agitator 15 is viewed from the upper side in FIG. 4, and FIG. 5B shows a view when the agitator 15 is viewed from the right side in FIG. The hatched toner axial movement members 151a and 152a only indicate that they are attached to the base 15c in an inclined state. There is no meaning.

  5A shows a motor 153 for rotating the agitator 15 in the direction of arrow B, a pinion gear 153a attached to the shaft of the motor, and a driven gear attached to the rotation shaft and meshed with the pinion gear 153a. 153b is also shown.

  Hereinafter, how the developing device 100 according to the present embodiment obtains a stable image density in image formation that is repeated for a predetermined image in which the density difference is extremely different from part to part will be described.

  In the developing device 100, image formation based on a predetermined image in which the density difference is extremely different depending on the part is repeated, and a developer used for developing a part having an extremely high image density is accommodated. When the toner concentration in a part of the region decreases and the concentration of the magnetic carrier in the developer in that region increases, the force for supporting the developer on the developing roll 11 in that part also increases. In this case, a larger amount of developer passes through the partition plate 13 and is transported to the layer thickness regulating member than in the case where the toner concentration in the developer is high. As a result, a space is created, and a larger amount of toner on the toner container side can be taken into the partial area in the developer container through the third opening 50 than in other areas in the developer container. As a result, the toner concentration in the developer should be optimized as a whole of the developer accommodating portion. However, if this state continues for a long time, the toner concentration gradually increases to the partial area in the developer accommodating portion. A low developer is supplied, and this is a cause of a decrease in image density even though the remaining amount of toner is sufficient. This is an area in the toner container that supplies toner to the partial area in the developer container, but the toner amount is sufficient as a whole, but the toner is supplied to the partial area in the toner container. This is because the amount of toner was locally reduced.

  Therefore, in the developing device 100, the toner in the toner storage portion is moved in the axial direction by the above-described toner axial direction moving members 151a and 152a. As a result, even if the image formation based on a predetermined image whose density difference is extremely different depending on the portion is repeated and the toner supply to the partial area in the developer accommodating portion is repeatedly performed, a part of the toner accommodating portion in the toner accommodating portion is repeated. A local decrease in the toner amount in the area where the toner is supplied to the area is suppressed. Therefore, according to the developing device 100, a stable image density can be obtained even if a predetermined image having extremely different density differences depending on the portion is repeatedly formed.

  Next, a second embodiment of the developing device of the present invention will be described.

  FIG. 6 is a diagram showing a second embodiment of the developing device of the present invention.

  The difference between the developing device 200 shown in FIG. 6 and the developing device 100 according to the first embodiment shown in FIG. 3 is only the agitator disposed in the toner accommodating portion, and only the agitator 150 will be described below. The common parts are not shown.

  The agitator 150 of the developing device 200 is different from the agitator 15 of the developing device 100 of the first embodiment in that the toner feeding members 151b and 152b, the toner axial direction moving members 151a and 152a, the base 15c, and the rotating shaft 15d are included. It consists of dual-purpose members 151 and 152, a base 15c, and a rotating shaft 15d that have both the function of feeding toner to the third opening 60 by rotating and the function of moving the toner in the toner storage portion in the direction of the rotating shaft.

  7 is a top view and a side view of the agitator shown in FIG.

  7A shows the case where the agitator 150 is viewed from the upper side in FIG. 6, and FIG. 7B shows the case where the agitator 150 is viewed from the right side in FIG. In addition, what is shown with diagonal lines in the dual-purpose members 151 and 152 only indicates that they are attached to the base 15c in a wavy shape as shown in FIG. 7B. There is no special meaning to this diagonal line. 7 also shows a motor 153 for rotating the agitator 150 in the direction of arrow B, a pinion gear 153a attached to the shaft of the motor, and a driven gear 153b attached to the rotation shaft and meshing with the pinion gear 153a. Has been.

  In the developing device 200 according to the present embodiment, the toner in the toner container is supplied to the opening 60 and moved in the direction of the rotation shaft 15d even when image formation based on a predetermined image whose density difference is extremely different depending on the portion is repeated. A stable image density can be obtained by the function of the dual-purpose members 151 and 152.

  FIG. 8 is a graph showing changes in image density of a patch image formed every time a predetermined number of identical images are printed in the embodiment of the present invention.

  In FIG. 8, in each of the developing device 100 according to the first embodiment and the developing device 200 according to the second embodiment, a portion having a density of 100% (represented by A in FIG. 2) and 2 having an image density of 0%. Each time 20 images of three parts (represented by B and C in FIG. 2) are printed, the patch images formed by the parts A, B, and C so as to have the same image density are printed. Only the portion A is compared, and for comparison with these, an image density change (see FIG. 2) of the portion A in the conventional developing device 1 is also shown. As can be seen from FIG. 8, according to the developing device 100 according to the first embodiment and the developing device 200 according to the second embodiment, image formation based on a predetermined image in which the density difference is extremely different depending on the portion is repeated. Also, a stable image density can be obtained.

  In the above-described embodiment, as a shape of the toner axial direction moving member for moving the toner in the toner accommodating portion in the direction in which the rotation axis of the toner delivery member extends, a plate-like thing is attached to the base obliquely. However, the present invention is not limited to this as long as it has a shape capable of moving the toner in the toner container in the direction in which the rotation axis of the toner delivery member extends. In addition, in the above-described embodiment, the case where the toner delivery member and the toner axial movement member have a motor as a common drive source has been described as an example, but the present invention is not limited thereto. As long as both the toner delivery member and the toner axial movement member are provided, the motor may be provided separately, and the drive source is connected to the motor. Not intended to be.

FIG. 3 is a schematic configuration diagram of an example of a developing device that adjusts a toner charge amount by appropriately supplying toner to a developer storage unit. 6 is a graph showing a change in image density of a patch image formed every time a predetermined number of images having extremely different density differences depending on a portion are printed. 1 is a diagram illustrating a first embodiment of a developing device of the present invention. FIG. 4 is an external perspective view of the agitator shown in FIG. 3. FIG. 5 is a top view and a side view of the agitator shown in FIG. 4. It is a figure which shows 2nd Embodiment of the image development apparatus of this invention. FIG. 7 is a top view and a side view of the agitator shown in FIG. 6. 6 is a graph showing a change in image density of a patch image formed every time a predetermined number of identical images are printed in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100,200 Developing device 10 Housing 11 Developing roll 12 Developer stirring member 13 Partition plate 14 Layer thickness control member 15 Agitator 151a, 152a Toner axial direction moving member 151b, 152b Toner sending member 153 Motor 153a Pinion gear 153b Driven gear 15c Base 15d Rotating shaft 20 Development area 21 Developer container 22 Toner container 30 Photosensitive roll 40 First opening 50 Second opening 60 Third opening

Claims (3)

By rotating while carrying a developer composed of toner and a magnetic carrier, which is arranged in the vicinity of an image carrier on which an electrostatic latent image is formed, and transporting the developer to a development area near the image carrier. A developing device comprising: a developing roll that develops an electrostatic latent image formed on the image bearing member; and a housing that accommodates the developing roll in a state where the developing area side of the developing roll is exposed to the outside. ,
A layer thickness regulating member that regulates the layer thickness of the developer that is arranged on the upstream side of the developing roll in the rotation direction of the developing roll and supported by the developing roll, with respect to the developing area;
A developer containing portion disposed inside the housing at a position upstream of the developing roll rotation direction with respect to the layer thickness regulating member, the developer containing portion being formed in a position adjacent to the developing roll inside the housing; A partition member that is formed at a position sandwiching the developer accommodating portion between the developing roll and a toner accommodating portion that mainly accommodates toner, the upper end of both the developing roll and the layer thickness regulating member A first opening and a second thickness opening between the developing roll and the layer thickness regulating member, and a lower end between the housing inner wall and the housing inner wall. A third opening for supplying toner from the toner container to the developer container is formed. When the toner concentration is low, the developer passing through the first opening and blocked by the layer thickness regulating member is removed. The second A partition member for guiding the third opening by pass through the mouth,
A toner delivery member that is disposed in the toner accommodation unit and delivers the toner in the toner accommodation unit from the third opening to the developer accommodation unit;
A developing device comprising: a toner axial direction moving member disposed in the toner containing portion and configured to move the toner of the toner containing member in the rotational axis direction of the developing roll. 2. The development according to claim 1, further comprising a common drive source for driving both the toner delivery member and the toner axial movement member, the toner delivery member and the toner axial movement member. apparatus. The developing device according to claim 1, wherein the toner feeding member also serves as the toner axial direction moving member.

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