JPH0830064A - Developing device - Google Patents

Abstract

PURPOSE:To inexpensively provide a developing device capable of accurately keeping a gap between a developing roll and an image carrier without making the device larger in a multicolor image forming device. CONSTITUTION:This developing device 300 is constituted of plural developer storing chambers 301, 302, 303 and 304 divided by partitions, and it is provided with developing rolls at the opening parts of the developer storing chambers. The developing roll has positioning rolls abutting on the image carrier on both sides in an axial direction and is supported movably to the image carrier side. The developing roll and the positioning roll are energized to the image carrier side by the energizing means. Thus, the developing device is made compact and flat, the gap between the respective plural developing rolls and the image carrier is kept constant without being affected by the deflection of the developing roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus for forming a multicolor image on an image bearing member such as a photoconductor by using an electrophotographic method. The present invention relates to a developing device that visualizes toner by adhering toner, and particularly to a developing device that can accurately maintain a gap between a developing roll and an image carrier.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a latent image due to a difference in charging potential is formed on an image carrier, toner is attached to the latent image to visualize the latent image, and then the toner image is formed on a sheet or the like. Images are obtained by transferring and fixing. As an image forming apparatus that forms a multicolor image, an image forming apparatus that sequentially forms toner images of a plurality of colors on an image carrier and then transfers the toner images onto a sheet in a single transfer step is also known. ing. FIG. 7 is a schematic configuration diagram showing an example of an image forming apparatus that forms such a multicolor image.

In this image forming apparatus, an image carrying member 101 on which an electrostatic latent image is formed by irradiating a laser beam 109 from an image exposing device 110 after being uniformly charged, and the image carrying member 101. 4 arranged around and containing yellow, magenta, cyan, and black toners, respectively
Developing devices 501, 502, 503, 504 on the table and the developing device 501 in the rotation direction of the image carrier 101.
And a pre-transfer charger for charging the toner on the image carrier 101 to an appropriate amount on the downstream side of the developing device 504. 104, a transfer charger 105 that transfers the toner image on the surface of the image carrier 101 to the paper supplied by the paper guide 111, and a peeling charger 106 that separates the transferred paper from the image carrier 101. A transport belt 112 for transporting the sheet, a cleaning device 107 for cleaning the toner remaining on the image carrier 101 downstream of the peeling charger 106, and a static erasing exposure device 108 for neutralizing the image carrier 101. And have. Each developing device is provided with toner supply units 505, 506, 507, 508 for supplying the consumed toner.

In such an image forming apparatus, the image carrier 1
01 is charged by the charger 102, and a laser beam 109a from the laser beam generator 109 forms a latent image corresponding to a yellow image at a predetermined position on the image carrier 101.
At this time, the laser light irradiates the image portion, and the yellow toner having the same polarity charge as the surface potential polarity of the charged image carrier 101 is transferred from the developing device 501 to the image carrier 101 in the bias electric field. The latent image is visualized by transferring to the laser irradiation part of. Next, as a second cycle, the image carrier 101 is recharged by the charger 102, irradiated with laser light in the previous (yellow) step, and the portion of the image carrier 101 whose potential has dropped is near the original potential again. To recover. After that, image light corresponding to magenta is again irradiated to a predetermined position of the image carrier 101 by the laser light from the laser light generator 109 to form a latent image. The developing device 502 contains magenta toner having the same electric charge as the surface potential polarity of the charged image carrier 101, and the latent image is visualized by transferring the toner to the laser light irradiation part. Thereafter, similarly, the third cyan image development cycle and the fourth black image development cycle are repeated, and four colors of yellow, magenta, cyan, and black are superimposed on the image carrier 101 according to the irradiation image. A toner image is formed. The toner image and the image carrier 101 are irradiated by the pre-transfer charger 104 and charged to a state suitable for transfer, and then transferred by the transfer charger 105 onto the transfer sheet that has entered along the paper guide 112.
The toner image in which the four colors of yellow, magenta, cyan, and black are superposed on the image carrier 101 is transferred in one step.

In such an image forming process, a developing device is a device for visualizing the toner by adhering toner to the latent image on the image carrier as described above, and various developing devices have been proposed. As the most general type of such a developing device, as shown in FIG. 5, a developing roll 510 is provided at a position close to and opposite to an image carrier, and a thin layer of developer is formed on the developing roll 510. In some cases, the latent image is visualized by transporting the toner to the image carrier 101 and transferring the toner to the image carrier 101 within an electric field formed at the position where the latent image is formed. This developing device stores a developer consisting of toner and carrier in a housing 580, and a developer supply member 530a and a stirring member 530b arranged so as to be partially or wholly embedded in the developer. Developing roll 10
1 and a developer layer thickness regulating member 520. The developing roll 510 includes a developing sleeve 510a and a permanent magnet 510b having a plurality of poles. In addition, the developing sleeve 510
A bias voltage in which a direct current is superimposed on an alternating current is applied to a. In such a developing device 500, the gap a between the developing roll and the image bearing member has a great influence on the image density and image quality, and therefore it is necessary to accurately maintain the gap a. Therefore, FIG.
As shown in FIG. 3, a positioning roll 584 having a diameter slightly larger than the radius of the developing roll is held on both sides in the axial direction of the developing roll while keeping the developing roll 510 and the axial center thereof aligned with each other.
By pressing this positioning roll against the image carrier, the gap between the developing roll and the image carrier is maintained. Therefore, as shown in FIG. 5, the housing 580 of the developing device has a structure in which a guide member 582 is supported so as to be able to move forward and backward with respect to the image carrier, and a spring 583 biases the housing 580 toward the image carrier. ing.

[0006]

However, in the developing device as described above, since the entire developing device is moved,
It requires a complicated mechanism and is costly. Further, when a plurality of developing devices are required, such as a color image forming apparatus, a large space is required, which causes a problem that the image forming apparatus becomes large. The present invention has been made in view of the problems as described above, and an object thereof is to maintain the gap between the developing roll and the image carrier with good accuracy at a low cost without increasing the size of the image forming apparatus. To provide a developing device.

[0007]

In order to solve the above problems, the invention according to claim 1 is such that a plurality of developer accommodating chambers which are partitioned by partition walls in the housing and each accommodate a developer of a different color. And a plurality of developing rolls rotatably supported at the opening of each of the developer accommodating chambers, all of the plurality of developing rolls closely facing a single image carrier. In the apparatus, with respect to each of the developing rolls, a positioning roll that is supported on both sides in the axial direction of the developing roll so that its axis coincides with the developing roll, and is in contact with the image carrier, and is fixedly supported. A plurality of bearing portions that are attached to the housing and that support the developing rolls so that the developing rolls can be moved in a direction of advancing and retracting with respect to the image carrier. An urging means for urging the developing roll and the positioning roll toward the image carrier, and a position close to or in contact with the developing roll at a position where the tangent line of the developing roll is substantially parallel to the moving direction of the developing roll. And a layer thickness regulating member. For example, when the layer thickness regulating member is a trimming member provided close to and opposite to the developing roll, as shown in FIG. 8, the developing roll is supported so as to move in the direction of reference numeral b shown in the drawing, A trimming member d is provided so as to face a position c where the tangent line a of the developing roll is substantially parallel to the moving direction b of the developing roll.

According to a second aspect of the present invention, in the developing device according to the first aspect, the bearing portion is movable in a direction normal to the surface of the image carrier on which the respective developing rolls face each other. To support. According to a third aspect of the invention, in the developing device according to the first aspect,
The bearing portion supports each of the developing rolls so as to be movable in the same direction. That is, the moving directions of the developing rollers are set to be parallel to each other.

In the first aspect of the invention, the positioning roll abuts the image carrier, and the difference between the radii of the positioning roll and the developing roll causes a gap between the image carrier and the developing roll. The gap is set to be larger than the radius of. Therefore, it is desirable to have a large radius of about 0.3 to 0.9 mm in order to obtain a good image. Further, the means for urging the developing roll and the positioning roll toward the image carrier is not particularly limited as long as it produces a pressure to bring the positioning roll into contact with the image carrier, and for example, a spring or the like can be used. it can. The layer thickness regulating member may be a plate-shaped trimmer having a tip protruding so as to come close to the image carrier, or a plate or the like that is rubbed against the image carrier.

[0010]

In the developing device according to the first aspect of the invention, the developing devices for a plurality of colors do not exist independently, but
The integrated developing device is divided into each developer accommodating portion by a partition, each developing roll is provided in each opening portion, and the developing roll of each color is brought into contact with the image carrier on both sides in the axial direction. A positioning roll, a bearing portion that supports the developing roll so that the developing roll can move in a direction in which the developing roll advances and retracts with respect to the image carrier, and a biasing unit that biases the developing roll and the positioning roll toward the image carrier. ing.
For this reason, a large-scale mechanism required for moving each developing device in the conventional image forming apparatus and maintaining the developing roll at a predetermined distance from the image carrier is not required, and a low-cost and compact image forming apparatus can be manufactured. . Even if the image carrier shakes, the developing roll moves by the bearing portion and is pressed toward the image carrier by the urging means, so that the positioning roll always contacts the image carrier and is The distance between the image carriers is kept constant. Therefore, a uniform image can be obtained. Further, the layer thickness regulating member is close to or in contact with the developing roll at a position where the tangent line of the developing roll is parallel to the moving direction of the developing roll, so that the layer thickness regulating member and the developing roll when the developing roll moves. It is possible to minimize the gap between the gap and the contact pressure, and thus to form a uniform developer layer on the developing roll even if the developing roll moves a little, and obtain a uniform and good image. You can

In the developing device according to the second aspect of the present invention, the bearing portion supports the developing roller so as to be movable in the direction normal to the surface of the opposing image carrier, whereby the image carrier swings. However, there is no change in the position of the surface of the image bearing member with respect to the rotation direction, and the developing roll can be reliably advanced and retracted and development can be performed without being affected by the shake crossing. In the developing device according to the third aspect of the present invention, since the developing roll is supported so as to be movable in the advancing and retreating direction with respect to the image carrier, and the plurality of developing rolls are movable in the same direction. The developer containing portion can be thinned, and the developing device can be downsized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of a color image forming apparatus in which the developing device of the present invention is used. This image forming apparatus has a cylindrical image carrier 1 and a developing device 300 surrounded by a plurality of developer accommodating chambers for accommodating yellow, magenta, cyan and black toners by partition walls. , A charger 2 for uniformly charging the surface of the image carrier 1 on the upstream side of the developing device 300 in the rotation direction of the image carrier 1, and on the image carrier 1 on the downstream side of the developing device. A pre-transfer charger 4 that charges the toner to an appropriate amount, and a transfer charger 5 that transfers the toner image on the surface of the image carrier 1 to the paper supplied by the paper guide 11.
A peeling charger 6 that peels the transferred sheet from the image carrier 1, a conveyor belt 12 that conveys the peeled sheet, and remains on the image carrier 1 downstream of the peeling charger 6. It has a cleaning device 7 for cleaning the toner to be discharged, and a discharge exposure device 8 for discharging the image carrier 1.

The cylindrical image carrier 1 rotates at a speed of 160 mm / sec in the direction of the arrow shown in the drawing, and the charger 2
Laser light 9 from an image exposure device 10 charged to 650 V and having a semiconductor laser and a polygon rotating mirror 9 built-in
At a, a latent image corresponding to a yellow image is formed at a predetermined position on the image carrier 1. At this time, the laser light irradiates the image portion, and the yellow toner having the same charge as the charge polarity of the image carrier 1 emits the laser light of the image carrier 1 from the developing roller 310 in the developer accommodating chamber 301. The latent image is visualized by transferring to the irradiation part. Next, in the second cycle, the image carrier 1 is recharged by the charger 2 and is irradiated with the laser beam in the previous (yellow) step. Recover to near.
After that, the laser light from the image exposure device 10 irradiates image light corresponding to a magenta image again to a predetermined position of the image carrier 1 to form a latent image. A magenta toner having the same polarity as the surface potential polarity of the charged image carrier 1 is accommodated in the developer accommodating chamber 302, and the latent image is visualized by transferring the toner to the laser light irradiation portion. It Thereafter, similarly, the third cyan image development cycle, 4
By repeating the developing cycle of the black image for the second time, yellow, magenta, cyan, and
A toner image in which the four colors of black are superimposed is formed. The toner image and the image carrier 1 are irradiated by the pre-transfer charger 4 and are charged in a state suitable for transfer, and then transferred onto the transfer sheet 4 along the paper guide 12 by the transfer charger 5. The toner image on which the colors are superimposed is transferred in one step.

In the above image forming apparatus, the potential difference between the developing bias voltage applied to the developing device for forming the bias electric field and the latent image potential of the exposed portion of the image carrier is called the developing potential difference. The potential difference is set so that a toner image can be stably formed on the image carrier without being affected by characteristic changes and variations of the image carrier and the developer, and environmental changes in temperature and humidity.

As shown in FIG. 2, the developing device 300 includes four developer accommodating chambers 301 inside a housing 381.
Partitions 302, 303, 304 separate the toner supply units 305, 306, 30 in the developer storage chambers.
From 7, 308, yellow, magenta, cyan, and black toners are replenished and supplied, respectively. Developing rolls are respectively provided at the portions of the developer accommodating chamber facing the image carrier, and these developing rolls are mounted in the long holes 386 on the side surface of the housing as shown in FIG. Movable bearing portion 385
Supported by. The long axis of the long hole 386 and the guide 382 are set in a direction to advance and retreat to the image carrier,
The developing roll is biased toward the image carrier by a spring 383 which is a biasing means.

Positioning rolls 38 are provided coaxially with the developing rolls on both sides of the developing rolls supported by bearings.
4 is attached and the positioning roll is brought into contact with the image carrier, so that the difference in radius between the positioning roll and the developing roll is kept constant as a gap between the developing roll and the image carrier during development. Even if the image carrier swings, the positioning roll pressed by the spring against the image carrier is kept in contact with the image carrier, so that the developing roll may move along the guide due to the shake. it can. In this embodiment, if the gap between the developing roll and the image bearing member is narrower than 0.3 mm, it is difficult to obtain a stable image having a uniform density due to scattering of the developer. Even if an oscillating electric field is applied to the sheet, its effect is lowered and a sufficient development density cannot be obtained, or an edge effect appears, and a clear image may not be obtained. Therefore, the distance between the developing roll and the image carrier is preferably about 0.3 to 0.9 mm.

The developing roll 310 is a developing sleeve 310a.
And a magnet roll 310b having a plurality of poles. Both ends of the magnet roll 310b are fixed, while the developing sleeve 310a is moved in the same direction as the opposing image carrier by a driving device (not shown). Is driven to rotate. The developing sleeve 310a is applied with a developing bias voltage in which a DC voltage of -500 V and an alternating current having a peak-to-peak voltage of 1.5 Kv and a frequency of 6 KHz are superimposed.

In such a developing device, the developer is agitated by the agitating members 330a and 330b, circulates in the developer accommodating chamber 301, and is supplied to the developing roll 310.
As the toner is consumed by the development, new toner is supplied from the toner supply unit 305, and the toner concentration of the developer is kept constant in the developer accommodating chamber. The developer supplied to the developing roll 310 is moved by the rotation of the developing sleeve 310a, and is adjusted to a required layer thickness of the developer in the developing area by the layer thickness regulating member 320. At this time, the layer thickness regulating member is provided so that the tangent line of the developing roll is close to the developing roll at a position parallel to the moving direction of the developing roll, and the layer is formed when the developing roll 310 moves by the bearing portion. It is possible to minimize fluctuations in the gap between the thickness regulating member and the developing roll.

In this embodiment, the diameter of the image carrier is 12
When set to 0 mm, each developer storage chamber 301, 302, 30
When the distance between the layer thickness regulating member and the developing roller in Nos. 3 and 304 was adjusted to 0.5 mm, the shake crossing of the image carrier was 0.
It was confirmed that there was no change in the distance between the layer thickness regulating member and the developing roll with respect to 1 mm, and that a developer layer having a constant layer thickness could be formed on the developing roll. Further, in this embodiment, in order to properly control the triboelectric charge of the developer and effectively control the developer by the oscillating electric field, the toner is composed of a toner having an average particle size of 10 μm and a carrier having an average particle size of 40 μm. A component developer was used, but in order to obtain a high quality image, an average particle size of 20
It is preferable to combine a toner having a particle size of not more than mm with a carrier having an average particle size of 10 to 60 μm.

According to this embodiment, a plurality of developing devices are not installed independently, but a plurality of developer accommodating chambers partitioned by partition walls in an integrated housing and each developer accommodating chamber. With the developing rolls arranged, the gap between each developing roll and the image carrier can be kept constant.
Therefore, the number of parts of the entire developing device can be reduced, the device can be downsized and flattened, and an excellent image can be obtained. Also, the gap between the layer thickness regulating member and the image carrier is
Since the developer layer having a constant thickness can be formed on the developing sleeve without being affected by the shake of the image carrier, the obtained image density is stable.

Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is the same as the above-described embodiment except that each layer thickness regulating member 420 is located close to the developing roll at a position where the tangent of the developing roll is parallel to the moving direction of the developing roll below the developing roll 410. It has the same configuration as the above. Also in the present embodiment, the layer thickness of the developer on the developing sleeve can be kept constant without being affected by the shake crossing of the image bearing member, and an image having a stable density can be obtained. In the above-described embodiment, the non-contact development is performed using the two-component developer, but the present invention is not limited to this, and the present invention can be widely applied to other types of developing devices.

[0022]

As described above, the developing device according to the invention described in claim 1 is partitioned into a plurality of developer accommodating chambers by the partition walls, and the developing rolls are provided at the openings of each developer accommodating chamber. Each of the developing rolls has a positioning roll that contacts the image bearing member on both sides thereof, and a bearing portion that allows the developing roll to move to the image bearing member side and a developing roll and a positioning roll on the image bearing member side. Since the developing device has a biasing means, the developing device can be made compact and flat, and the gap between the developing roll and the image carrier can be kept constant without being affected by shake. Further, even if the developing roll moves due to the shake of the image carrier, the fluctuation of the gap between the layer thickness regulating member and the developing roll can be minimized. Therefore, the developer layer on the surface of the developing roll can be kept uniform, and an image having a stable developing density can be obtained.

In the developing device according to the second aspect of the present invention, even if the image bearing member or the developing roll is shaken, the developing roll moves in the direction normal to the surface of the image bearing member, so that there is no inconvenience such as deviation of the developing position. The developing roll advances and retreats appropriately, and the gap between the developing roll and the image carrier is always kept constant. In the developing device according to the third aspect of the invention, since the plurality of developing rolls can move in the same direction, each developer accommodating portion can be made thin, and the developing device can be miniaturized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus to which a developing device according to an exemplary embodiment of the present invention is applied.

FIG. 2 is a schematic configuration diagram showing a developing device of the above embodiment.

3A and 3B are a schematic perspective view and a partial cross-sectional view showing a configuration of a main part of the developing device.

FIG. 4 is a schematic configuration diagram illustrating a developing device that is another embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a developing device used in a conventional image forming apparatus.

FIG. 6 is a diagram illustrating a positioning roll used in a conventional developing device.

FIG. 7 is a schematic configuration diagram showing an example of a conventional image forming apparatus.

FIG. 8 is a schematic diagram illustrating the configuration of the present invention.

[Explanation of symbols]

 1,101 image carrier 300,500 developing device 301,302,303,304 developer accommodating chamber 305,306,307,308 toner supply unit 310,410,510 developing roll 320,420,520 layer thickness regulating member 330, 430 Stirring member 382, 582 Guide 383, 583 Spring (biasing means) 384, 584 Positioning roll 385 Bearing part 386 Long hole 405, 406, 407, 408 Toner supply part 501, 502, 503, 504 Developing device

Claims (3)

[Claims] 1. A plurality of developer accommodating chambers, which are partitioned by partition walls in a housing, and each accommodate a developer of a different color, and a plurality of rotatably supported parts in which each of the developer accommodating chambers opens. A developing roll, wherein all of the plurality of developing rolls face a single image carrier in close proximity to each other, and for each of the developing rolls, the developing roll is provided on both sides in the axial direction of the developing roll. A positioning roll supported so that its axis coincides with that of the roll and abutting against the image carrier, and a fixing roll mounted on the housing that is fixed and supported, in the direction of advancing and retracting with respect to the image carrier, of each developing roll. A plurality of bearing portions that support these developing rolls so that they can move, and a biasing means that biases the developing rolls and the positioning roll toward the image carrier. And a layer thickness regulating member that is brought into proximity with or in contact with the developing roll at a position where the tangent line of the developing roll is substantially parallel to the moving direction of the developing roll. 2. The developing device according to claim 1, wherein the bearing portion supports each of the developing rolls so as to be movable in a direction normal to a surface of an image bearing member facing the developing roller. Developing device. 3. The developing device according to claim 1, wherein the bearing portion supports the respective developing rolls so as to be movable in the same direction.