JPH04254879A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a high concentration picture image stable for a long time by making constitution in which the carrying speed of a (J) developer becomes slower in a portion other than an end part of a carrying means. CONSTITUTION:A pitch of a first carrying means 16 is made narrow in the course of carrying, and a carrying speed is made slow in a portion from the developing vessel center to a diveloper carrying downstream side other than an end part of the developing vessel. That is for example, a screw 16, a first carrying means, and a screw 17, a second carrying means, can be balanced by making the pitch 15mm and 20mm respectively, consequently an upstream side pitch P1 and a downstream side pitch P2 are made 17mm and 15mm respectively in the screw 16 for providing a residence part. Consequently a pitch is changed from the pitch P1 to the pitch P2 to slow carrying a developer halfway, obtaining constitution having high carrying efficiency and preventing compression rise in the developer at an end part.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an image forming apparatus that forms a latent image on an image carrier and visualizes the latent image using a developing device. The present invention relates to an image forming apparatus using a two-component developer made of a carrier that imparts electric charge.

0002

[Background Art] In recent years, there has been a demand for smaller size and lower cost in image forming apparatuses using electrophotography or electrostatic recording, for example, and this has tended to increase the size of the apparatus and increase manufacturing costs. Progress is being made to make certain developing devices smaller, lighter, and lower in cost.

[0003] In developing devices that are designed to be smaller, lighter, and lower in cost, especially those that use a two-component developer containing toner and carrier, the toner in the developing device is consumed as the device is used. In this case, it is necessary to replenish the developing device with toner commensurate with consumption. However, if you simply replenish toner, the mixing time between the replenished toner and the existing carrier in the developing device is short, so sufficient triboelectricity may not be applied to the replenished toner, resulting in background fog and reverse fog appearing on the image. Ta.

[0004] Such problems are particularly noticeable in full-color copying machines, etc., which require a large amount of toner consumption and replenishment. Therefore, as a means to solve this problem, a developing device has been proposed in which the supplied toner is sufficiently mixed and stirred with the existing developer using two screw-type stirring and conveying means arranged in parallel before being subjected to development. ing. The developing device has a developing container divided into a developing chamber and a stirring chamber, and in the stirring chamber, the replenished toner is mixed and stirred by a conveying means. The mixed and agitated toner is transported to the developing chamber from one of the openings at both ends of the developing container, and development is performed in the developing chamber using the transported toner. This developing device is provided with a developer concentration detection means for detecting that the toner concentration has decreased due to toner consumption, and the developer whose toner concentration has decreased due to development is transferred from the other opening to the stirring chamber. transport. Further, new toner is replenished in response to a signal from the developer concentration detection means, and the replenished toner and the developer are mixed and stirred again in the stirring chamber and circulated, thereby achieving the above-mentioned effect. This is to solve the problem of insufficiency in the provision of tribodies.

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned developing device, the developing container is divided into a developing chamber and a stirring chamber, and in the developing chamber, the developer is stirred along the developing width direction of the developer carrier.・Transporting. For this reason, when attempting to continuously obtain high-density images, a gradient in developer concentration occurs in the development width direction of the developer carrier, resulting in uneven image density. In order to solve this problem, it is possible to increase the conveyance speed, but according to this method, the gradient of the developer concentration is almost eliminated, but the developer at the end of the developer container, especially on the downstream side of the developer conveyance, There have been problems in that the compression of the image carrier is increased, and the seal member at the end is damaged, and the developer overflows from the end and is fused between the developer carrier and the image carrier. As a result, the image becomes significantly distorted, making it extremely difficult to obtain a stable image over a long period of time.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of solving the above-mentioned problems and producing stable high-density images over a long period of time.

[0007]

[Means for Solving the Problems] According to the present invention, the above object includes an image carrier on which an electrostatic latent image is formed, and a developing device that develops the latent image on the image carrier. In the image forming apparatus, the developing device includes a developer carrier that supports and transports developer to a developing area, and a developer carrier that is adjacent to the developer carrier and extends in the development width direction of the developer carrier. a spiral-shaped first conveyance means disposed along the developer carrier for conveying the developer in one direction along the development width direction of the developer carrier; A spiral-shaped second conveyance means is provided for conveying the developer in a direction opposite to the first conveyance means, and at least one of the conveyance means is configured such that the conveyance speed of the developer at a portion other than the end portion of the conveyance means is slow. This is achieved by forming the

[0008]

[Operation] According to the present invention, in an image forming apparatus including an image carrier on which an electrostatic latent image is formed and a developing device that develops the latent image on the image carrier, the developing device a developer carrier that carries and transports the developer to the developer carrier; A spiral-shaped first conveying means for conveying in one direction along the development width direction of the holder, and a spiral-shaped second conveying means for conveying in the opposite direction to the first conveying means, By adopting a configuration in which the developer transport speed is slow at parts other than the edges, a uniform image can be obtained even if the developer transport speed is increased to activate the circulation of the developer in the developer container. A stable image can be obtained over a long period of time without problems such as the developer being strongly compressed at the edges, damaging the seals at the edges, or causing fusion at the edges of the image.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment and a second embodiment of the present invention will be explained based on the drawings.

First Embodiment First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The image forming apparatus of this embodiment visualizes a latent image formed on an image carrier 1 such as a photoreceptor or dielectric by electrophotography or electrostatic recording using a developing device. The developed visible image is transferred to a transfer material such as paper and made into a permanent image by a fixing means.

Since the transfer means, fixing means, etc. in such an image forming apparatus are well known, only the image carrier 1 and the developing device 2 are shown in FIG. Material feeding means, fixing means, other image forming means, etc. are omitted.

In FIG. 1, a developing device 2 disposed facing an image carrier 1 includes a developing container 3, a developing sleeve 4 as a developer carrier, and a blade 5 as a developer layer regulating member. .

The inside of the developing container 3 is divided into a developing chamber (first chamber) 7 and a stirring chamber (second chamber) 8 by a partition wall 6 extending perpendicularly to the plane of the paper in FIG. The upper part of the partition wall 6 is open, so that excess developer in the developing chamber 7 is collected and circulated in the screw section on the stirring chamber side. In this embodiment, a two-component developer 11 containing toner and carrier is stored in the developing chamber 7 and the stirring chamber 8, and the toner for replenishment is supplied from the conveyance upstream side of the stirring chamber screw according to the signal of the developer concentration detection means. will be replenished accordingly.

Note that openings (not shown) are formed in the partition wall 6 at the front and rear ends in FIG. 1 to allow the developing chamber 7 and the stirring chamber 8 to communicate with each other.

The developing chamber 7 of the developing container 3 is connected to the latent image carrier 1.
The developing sleeve 4 is rotatably provided so as to be partially exposed in the opening 13, and is open at a position corresponding to the developing area facing the opening 13. The developing sleeve 4 is made of a non-magnetic material, rotates in the direction of the arrow in FIG. 1 during a developing operation, and has a magnet 14 fixed therein as a magnetic field generating means.

In this embodiment, the magnet 14 is the developing magnet S1.
and magnetic poles N1, S2, N2, N3 that transport the developer 11.
and has. Further, the blade 5 is made of a non-magnetic material such as aluminum, and is disposed on the upstream side of the developing sleeve 4 in the rotational direction. The amount of the developer 11 conveyed to the developing area on the developing sleeve 4, specifically, the thickness of the developer 11 on the developing sleeve 4 is regulated. Therefore, in this embodiment, the tip of the blade 5 and the developing sleeve 4 are
Both the non-magnetic toner and the magnetic particles pass between the surfaces of the magnetic toner and the magnetic particles and are sent to the development zone.

According to the present invention, in the above-mentioned configuration, a screw-type first conveying means 16 is further arranged in the developing chamber 7 adjacent to the developing sleeve 4 and along the developing width direction of the developing sleeve 4. Ru. As shown in FIG. 2, the screw type first conveying means 16 is a screw having a spiral blade member 16b around a rotating shaft 16a, and rotates in the direction of the arrow to move the developing chamber to the bottom of the developing chamber 7. 7 is conveyed in one direction along the development width direction of the development sleeve 4. Further, within the stirring chamber 8, a screw type second conveying means 17 having the same structure as the screw type first conveying means 16 is arranged approximately parallel to the first conveying means 16 and rotates in the direction of the arrow. The developer in the stirring chamber 8 is transported in the opposite direction to the first transport means 16.

As described above, the developer 11 is circulated between the developing chamber 7 and the stirring chamber 8 by the rotation of the first conveying means 16 and the second conveying means 17.

The developer 11 in the developing chamber 7 is supported on the developing sleeve 4 by the action of the built-in magnet 14, and the layer thickness is regulated by the blade 5, and the developer 11 is conveyed to the developing area. The developer that has undergone the development action in the development area is transported to the development chamber 7 by the development sleeve 4, and is scraped off from the top of the development sleeve 4 by the repulsion magnetic poles N3 and N2 to the first transport means 16 and collected. Ru. Furthermore, the developer stirred and conveyed as the first conveying means 16 rotates is drawn up by the pole N2 on one side of the repulsion magnetic pole and conveyed to the regulating section. The regulating section consists of a blade 5 and a carrier returner 21, in which the developer moves as shown by the thick arrow and is drawn up and transported from the regulating section to the developing section, and the developer is pushed back by the carrier returner. , into parts that fall into the stirring chamber 8. The developer that has fallen into the stirring chamber is mixed with the developer that has just been mixed with the supplied toner in the stirring chamber, and is conveyed to the developing chamber again. What is important here is to improve the efficiency of stirring and conveyance within the developing device without increasing the compression of the developer at the end of the screw in order to obtain a uniform and stable image. Therefore, in the present invention, as shown in FIG. 2, the pitch of the first conveyance means is narrowed in the middle of conveyance, so that the conveyance speed becomes slower in the downstream part of the developer conveyance from the center of the developer container, except at the end of the developer container. did. This improves agitation and conveyance inside the developer container, and at the same time does not increase compression of the developer at the end of the developer container, prevents damage to the seal at the end of the screw, and prevents toner lumps from forming in the developer. It was possible to prevent the occurrence of white spots in the image and significant deterioration of image quality due to fusion at the edges.

In this example, the screw shaft diameter is 8 mm.
, the spiral outer diameter was 20 mm. The screws 16 and 17 have pitches of 15 mm and 20 m, respectively.
In this example, in order to create a retention area, P1 is set to 17 m in the screw 16.
m and P2 were set to 15 mm. This allows P1 to P
Since the pitch changes to 2 and the conveyance of the developer slows down from the middle, it is possible to establish a configuration in which the conveyance efficiency can be made high and the compression of the developer at the end portions does not increase. Furthermore, as mentioned above, the developer that remains in the developing chamber falls into the stirring chamber, so even when solid images are continuously obtained, the developer concentration can be efficiently maintained at a constant level. became.

<Second Embodiment> Next, a second embodiment of the present invention will be explained using FIG. 3. Note that the same reference numerals are given to the same parts as in the first embodiment, and the explanation thereof will be omitted.

FIG. 3 shows a second embodiment of the apparatus. In this case, the fins 16c are used for the purpose of improving the stirring efficiency, but the staggered arrangement allows the conveyance speed to be increased more than in the non-staggered portions, so the same effect as in the first embodiment can be obtained.

<Third Embodiment> Next, a third embodiment of the present invention will be described using FIG. 4. Note that the same reference numerals are given to the same parts as in the first embodiment, and the explanation thereof will be omitted.

FIG. 4 shows a third embodiment of the apparatus. In this case, the fins are separated into 16c and 16c', and the conveyance speed can be increased if the fin is narrower, so L1
By setting <L2, the same effect as in the first embodiment can be obtained. Furthermore, although not shown in the drawings, the pitch of the screw may be configured to be continuously narrowed from the middle.

[0026]

[Effects of the Invention] As explained above, according to the present invention,
By configuring the developer to be transported at a slower speed at portions other than the ends of the transport means, uniform images can always be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a conveyance means of the device shown in FIG. 1;

FIG. 3 is a schematic plan view of a device according to a second embodiment of the present invention.

FIG. 4 is a schematic plan view of a device according to a third embodiment of the present invention.

[Explanation of symbols]

1 Image carrier 2 Developing device 4 Developer carrier (developing sleeve) 16 First conveyance means 17 Second conveyance means

Claims (1)

[Claims] 1. An image forming apparatus comprising an image carrier on which an electrostatic latent image is formed, and a developing device that develops the latent image on the image carrier, wherein the developing device is configured to and a developer carrier disposed adjacent to the developer carrier and along the development width direction of the developer carrier, which carries and conveys the developer. a spiral-shaped first conveying means that conveys the developer in one direction along the development width direction of the body; and a first conveying means arranged substantially parallel to the first conveying means and conveying the developer in a direction opposite to the first conveying means. An image forming apparatus characterized in that a spiral second conveyance means is provided, and at least one of the conveyance means is formed such that the developer conveyance speed at a portion other than an end of the conveyance means is slow.