JP2003057929A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem on an image defect such as the irregularity of an image and the irregularity of a screw pitch or to eliminate toner scattering being trouble arising from irregular electrification caused by irregular stirring in a developing device avoiding the insufficient stirring of developer in a developer storing container and attracting the developer which is not carried because it comes off from the outside diameter of a screw to the screw, so that the irregular stirring is eliminated. SOLUTION: This developing device is equipped with a developer storing container 65 in which two-component developer having magnetic particles and toner is stored, a toner replenishing device replenishing the developer storing container with the toner, developer stirring and carrying means 66 and 67 stirring and carrying the developer in the developer storing container, and a developer carrier 68 carrying the developer and supplying the toner to an external image carrier. In the device, a permanent magnet 80 is used as at least a part of the developer stirring and carrying means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a developing device using a two-component developer composed of carrier and toner,
In particular, the developer agitating / conveying means disposed in the developing device used in the conventional electrophotographic image forming apparatus agitates and reliably agitates the developer that has remained without being conveyed,
The present invention relates to a developing device that can carry and eliminate uneven charging.

[0002]

2. Description of the Related Art Recently, as a market demand for electrophotographic image forming apparatuses, color image forming apparatuses such as color copying machines and color printers have been increasing. The color image forming apparatus is provided with a developing device for a plurality of colors around one photoconductor, and toner of each color is supplied from each developing device to the electrostatic latent image on the photoconductor to form a composite toner image. Then, a so-called one-drum type is known in which a color image is recorded by transferring and fixing the synthetic toner image on a transfer paper. As a developer to be used in this one-drum type color image forming apparatus, four developing devices are mounted around one shaft at a predetermined circumferential pitch because of the installation space, and all the developing devices are centered around the shaft. A revolver type in which any one of the developing devices is stopped at the developing position facing the photoconductor to selectively develop the electrostatic latent image on the photoconductor by configuring the developing devices to rotate integrally. Developing device is used. In addition, a plurality of photoconductors are arranged adjacent to each other, and a developing device containing one color toner is provided for each photoconductor, and a monochromatic toner image is formed on each photoconductor by the toner supplied from each developing device. Then, a so-called tandem type is also known in which a monochrome toner image on each photoconductor is sequentially transferred to an intermediate transfer body to form a synthetic toner image, and then the synthetic toner image is collectively transferred and fixed on a transfer paper. ing. Comparing the 1-drum type and the tandem type color image forming system, the former has one photosensitive member, so that it can be relatively downsized and the cost can be reduced. The image forming operation is repeated a plurality of times (usually four times) to form a full-color image, which makes it difficult to increase the image forming speed, and the latter is conversely large and costly. However, there is an advantage that it is easy to increase the image forming speed.

Recently, even a full-color image forming apparatus is desired to have an image forming speed comparable to that of a monochrome image forming apparatus. Therefore, a tandem type color image forming apparatus having an advantage of being able to form an image at high speed is formed. The system is getting attention. However, unlike the revolver type developing device used in the one-drum type image forming device, the developing device used in the tandem type image forming device does not rotate (revolve) about an axis. For this reason, the developer located at a position close to the inner wall of the developer accommodating container is likely to stay without being completely stirred and conveyed by the stirring / conveying screw in the container. That is, the developing device is provided with a plurality of stirring / conveying screws extending in parallel in the developer accommodating container, and by rotating these stirring / conveying screws, the carrier and toner are agitated to charge the toner and agitate. The developed developer is conveyed in a predetermined direction. But,
If the tip of the stirring / conveying means such as the stirring / conveying screw is close to the inner wall of the container, it may cause firefly which is an image defect due to the stirring / conveying or the noise may increase. The tip portion of the stirring / conveying means is dimensioned so as to be at a position sufficiently separated from the inner wall of the container. When each developing device arranged around the shaft revolves like a revolver type developing device, the developer in each developing device tends to flow, so that the agitation / conveying means may not reach the corners. Even if the developer does not stay, it stirs well.
Can be transported. However, since each developing device equipped in the tandem-type image forming apparatus does not revolve, the developer located outside the outer diameter side edge of the screw in the developer accommodating container must be stirred and transported. And the toner stays in a state where it is not sufficiently charged. Furthermore, since the capacity of the developer accommodating container is fixed, the amount of developer to be contained is also fixed. Since the storage amount of the developer is greatly related to the life of the developer, that is, the maintenance interval, it is desirable to use the developer in such a manner that the developer is not conveyed or stirred as much as possible and the developer is not wasted. As the market demands in the future, color machines tend to shift to the tandem type in order to further increase the speed, so such waste of unused developer is eliminated and all of the replenishment in the container is eliminated. It is indispensable to efficiently use the above developer.

By the way, Japanese Unexamined Patent Application Publication No. 2001-92251 (Canon) discloses a technique in which a magnet is disposed in the vicinity of a toner replenishing port to provide a developer constraining region to increase agitability. However, in such a structure in which only the magnets are partially arranged, all the developer that tends to stay on the outer diameter side of the stirring / conveying means is sucked and stirred.
It is difficult to carry. In addition, Japanese Patent Laid-Open No. 2001-0
In Japanese Patent No. 92253, a height control member is provided above the developer accommodating container of the toner replenishment side screw to increase agitability.
That technology is disclosed. However, it is difficult to prevent the developer on the outer diameter side from accumulating over the entire length of the developer stirring / conveying means. Further, there is a drawback that the structure becomes complicated due to an increase in the number of parts of the developing device. Further, in Utility Model Registration No. 3070414, a downstream end portion of the spiral stirring rod is provided with a plate-shaped paddle fin adjacent to the inner wall of the developer container and extending radially outward. A technique for preventing the developer from staying is disclosed. Further, Japanese Patent Laid-Open No. 11-202626 discloses a technique in which a paddle is provided on the downstream side of the stirring screw in the developer conveying direction to enhance the dispersibility of the developer by the outward pressure from the paddle.
However, even if a paddle fin is provided to increase the stirring pressure, it is not possible to completely prevent uneven stirring, and especially to prevent the developer located in the outer diameter direction from staying over the entire length of the stirring means. It is difficult. Stirring unevenness caused by the generation of stagnant toner on the outer diameter side of the screw causes image unevenness due to charging unevenness and toner scattering, and screw pitch unevenness causes a problem of image defects.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the developer in the developer accommodating container is insufficiently stirred, and the developer that is not conveyed outside the screw outer diameter is conveyed by the magnetic force to the screw side. It is an object of the present invention to eliminate the unevenness of stirring by attracting the toner to eliminate the problem of image defects such as image unevenness and screw pitch unevenness, or the toner scattering which is a problem caused by uneven charging due to uneven stirring. That is, in the present invention, in order to use all the developer without wasting the stagnant developer which is outside the screw outer diameter in the developer accommodating container and uses all the developer without waste, Provided is a developing device in which all of the developer can be utilized for image formation without waste by applying magnetic force (magnetic force lower than the magnetic force of the developer carrier) to at least a part.

[0006]

In order to solve the above-mentioned problems, the invention of claim 1 provides a developer accommodating container for accommodating a two-component developer having magnetic particles and toner, and the developer accommodating container. A toner replenishing device for replenishing toner, a developer stirring / conveying means for conveying the developer in the developer container while stirring, and a developer for supporting the developer and supplying the toner to an external image carrier. In a developing device including a carrier, at least a part of the developer agitating / conveying means is a permanent magnet. According to a second aspect of the invention, the developer agitating / conveying means is a screw including a rotating shaft and a spiral blade protruding on the outer periphery of the rotating shaft. According to the invention of claim 3, the developer is agitated.
The conveying means agitates the toner replenished from the toner replenishing device and the developer in the developer accommodating container, and a toner replenishment side stirring screw for conveying, and / or agitates the developer in the developer accommodating container, It is characterized in that it is a developer carrying member side stirring screw to be conveyed. According to a fourth aspect of the present invention, when the developer stirring / conveying means is the screw, at least a part of the spiral blade projecting on the outer periphery of the rotary shaft is a permanent magnet. . The invention of claim 5 is characterized in that only the tip of the spiral blade is made of a permanent magnet. The invention of claim 6 is characterized in that at least a part of the rotating shaft is a permanent magnet. The invention of claim 7 is characterized in that the permanent magnet provided in at least a part of the developer stirring / conveying means is made of a plastic magnet. The invention of claim 8 is characterized in that the permanent magnet provided in at least a part of the developer stirring / conveying means is formed by sintering a magnetic material.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is an internal configuration diagram of a color image forming apparatus to which a developing device according to an embodiment of the present invention is applied, and specifically, a tandem type indirect transfer type electrophotographic copying apparatus. In the figure, reference numeral 100 is a copying apparatus main body, 200 is a paper feeding table on which the copying apparatus main body 100 is mounted, 300 is a scanner (reading optical system) mounted on the copying apparatus main body 100, and 400 is an automatic document feeder (ADF) which is further mounted thereon. ). Copying device body 1
At the center position of 00, an endless belt-shaped intermediate transfer member 10 extending in the lateral direction is provided. In the illustrated example, the intermediate transfer member is wound around the three support rollers 14, 15 and 16 so that the intermediate transfer member can be rotated and conveyed clockwise in the drawing. In this illustrated example, an intermediate transfer member cleaning device 17 that removes residual toner remaining on the intermediate transfer member 10 after image transfer is provided to the left of the second support roller 15 among the three support rollers. In addition, among the three support rollers, on the intermediate transfer body 10 stretched between the first support roller 14 and the second support roller 15, black, yellow, magenta, and cyan are provided along the transport direction. The four image forming units 18 are arranged side by side to form the tandem image forming unit 20. An exposure device 21 is further provided immediately above the tandem image forming unit 20 as shown in FIG. On the other hand, the secondary transfer device 2 is provided on the side opposite to the tandem image forming section 20 with the intermediate transfer body 10 interposed therebetween.
2 is provided. In the illustrated example, the secondary transfer device 22 includes a secondary transfer belt 24, which is an endless belt, between two rollers 23.
And is arranged by being pressed against the third supporting roller 16 via the intermediate transfer body 10, and the image on the intermediate transfer body 10 is transferred to a sheet. Next to the secondary transfer device 22,
A fixing device 25 for fixing the transferred image on the sheet is provided.
The fixing device 25 is configured by pressing the pressure roller 27 against the fixing belt 26 which is an endless belt. The above-described secondary transfer device 22 also has a sheet conveying function of conveying the sheet after the image transfer to the fixing device 25. In the illustrated example, such a secondary transfer device 22 and a fixing device 25
A sheet reversing device 28 for reversing the sheet in order to record images on both sides of the sheet is provided in parallel with the tandem image forming unit 20 described above.

Now, when making a copy using this color electrophotographic apparatus, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened and the contact glass 3 of the scanner 300 is opened.
The original is set on the sheet 2, and the automatic document feeder 400 is closed and pressed by it. When a start switch (not shown) is pressed, when an original is set on the automatic document feeder 400, the original is conveyed and moved onto the contact glass 32, and then when the original is set on the other contact glass 32. Immediately, the scanner 300 is driven to drive the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source, and the light reflected from the document surface is further reflected and directed toward the second traveling body 34, reflected by the mirror of the second traveling body 34, and passed through the imaging lens 35. It is put in the reading sensor 36 to read the contents of the document. When a start switch (not shown) is pressed, one of the support rollers 14, 15, 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate.
0 is conveyed by rotation. At the same time, the photoconductor 40 is rotated by each of the image forming means 18 so that each photoconductor 40 is rotated.
A monochrome image of black, yellow, magenta, and cyan is formed. Then, as the intermediate transfer body 10 is conveyed, the single color images are sequentially transferred to form a composite color image on the intermediate transfer body 10. On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, a sheet is fed from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages, and the separation roller 45 is provided. Then, the sheets are separated one by one into the sheet feeding path 46, conveyed by the conveying rollers 47, guided to the sheet feeding path 48 in the copying machine main body 100, and abutted against the registration rollers 49 to be stopped. And
The registration roller 49 is rotated in synchronism with the composite color image on the intermediate transfer body 10 so that the intermediate transfer bodies 10 and
The sheet is fed between the secondary transfer device 22 and the secondary transfer device 22, and the secondary transfer device 22 transfers the sheet to record a color image on the sheet. The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, and after fixing the transferred image by applying heat and pressure in the fixing device 25, the sheet is switched by the switching claw 55 and discharged by the discharge roller 56. And is stacked on the sheet discharge tray 57. Alternatively, the sheet is turned over by the switching claw 55.
8 and then reverses and guides it to the transfer position again, records an image on the back side, and then discharges the paper to the discharge tray 5 with the discharge roller 56.
Discharge onto 7. On the other hand, the intermediate transfer body 10 after the image transfer
The intermediate transfer member cleaning device 17 removes the residual toner remaining on the intermediate transfer member 10 after the image transfer, and prepares for another image formation by the tandem image forming unit 20.

In the tandem image forming section 20 described above, the individual image forming means 18 are described in detail, for example, as shown in FIG.
A charging device 60, a developing device 61, a primary transfer device 62, a photoconductor cleaning device 63, a charge eliminating device 64 and the like are provided. The developing device 61 includes a toner replenishment side stirring screw 6 as a developer stirring / conveying means in a developer accommodating container 65.
6, a developer carrying member side stirring screw 67, and a developer carrying member (developing roller) 68. A toner supply port (not shown) is provided on the outer wall of the container adjacent to the toner supply side stirring screw 66 to supply toner from a toner supply device (not shown). The toner replenishment side stirring screw 66 stirs and conveys the toner replenished from the toner replenishing device and the developer (two-component developer having magnetic particles and toner) in the developer container 65. In addition, the developer carrying member side stirring screw 6
7 stirs and conveys the developer in the developer accommodating container 65. The developer stirring / conveying means is not limited to the illustrated screws 66 and 67, and various stirring / conveying means can be envisioned.

FIG. 3A is an exploded perspective view of the developing device 61,
(B) is a configuration diagram of a main part. In the developer container 65, a toner replenishment side stirring screw 66 and a developer carrying member side stirring screw 67 are arranged in parallel. Each of the screws 66 and 67 includes a rotating shaft 70 and a spiral blade 71 that is integrally projected and integrally formed on the outer periphery of the rotating shaft 70. A characteristic configuration of the present invention is that the developer stirring / conveying means 6 conveys the developer in the developer accommodating container 65 while stirring.
6.67, and a developer carrier 68 that carries a developer and supplies toner to an external image carrier
1 is that at least a part of the developer stirring / conveying means 66, 67 is a permanent magnet. As described above, in the tandem image forming apparatus, unlike the one-drum type image forming apparatus, the developing device itself does not rotate due to the revolution (as shown in FIG. 2, the developing device is fixed). The developer is stirred and conveyed only by the screws 66 and 67 as the developer stirring and conveying means. Developer-bearing member side or toner replenishment side screws 66, 67
By imparting magnetism to at least a part of the toner (providing a permanent magnet), the developer that should be left in the developer container when the permanent magnet is not present is attracted to the screw, thereby eliminating waste of the developer. It is possible to use. Permanent magnet is a developer (carrier with toner attached)
Not only is sucked, but also by the rotation of the screw, for example, the magnetic force from the tip 71a of the screw forms a brush of developer, which should be called a carrier curtain, in the outer diameter direction of the screw. Move to the downstream side in the transport direction. Screw 6
The shafts 70 and the spiral blades 71 forming the parts 6 and 67 may be entirely made of permanent magnets, but the developer in a portion farther than the outer diameter portion of the screw or the developer in a closer portion is attracted. It is possible to arbitrarily select the site where the permanent magnet is provided, depending on the difference in purpose such as whether or not. In addition, as the permanent magnets provided at appropriate positions of the screws 66 and 67,
For example, a plastic magnet can be used. The shaft 70 and the spiral blade 71 are wholly or partially formed using a plastic magnet. Alternatively, the permanent magnet uses a magnetic material (permanent magnet material) with screws 66, 67.
A part (or all) of the above may be molded by sintering. By setting the magnetic force of the permanent magnet to be smaller than the magnetic force of the permanent magnet forming the developer carrying member 68, it is possible to prevent interference with the magnet on the developer carrying member 68 side. The site where the permanent magnet having such a configuration is provided is, for example, the whole or part of the outer circumference of the rotary shaft 70, and / or the whole or part of the spiral blade 71. For example, if the permanent magnet 80 is fixed to a portion along the tip edge 71a of the spiral blade 71, the screw 6
The developer located farther than the outer diameters of 6, 67 can be sucked.

[0011]

As described above, according to the present invention as set forth in claims 1 to 9, the developer in the developer accommodating container is not sufficiently stirred, and the developer which is not conveyed outside the screw outer diameter is attracted to the screw. Therefore, it is possible to eliminate uneven stirring, and to eliminate toner scattering, which is a problem of image defects such as uneven image and uneven screw pitch, or a problem caused by uneven charging due to uneven stirring. Moreover, since it can be realized by modifying only a part or all of the existing stirring / conveying means by using a permanent magnet, it is possible to improve at a low cost. By using a permanent magnet having a magnetic force weaker than that of the magnet forming the developer carrying member, the developer carrying force of the developer carrying member is not reduced. Further, since the carrier curtain can be formed on the outer diameter side of the screw and can be moved in the carrying direction together with the toner attached to the carrier curtain, the accumulated developer can be eliminated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an example of an image forming apparatus to which a developing device of the present invention is applied.

FIG. 2 is a diagram showing a configuration of a developing device according to an embodiment of the present invention.

FIG. 3A is an exploded perspective view of the developing device, and FIG.

[Explanation of symbols]

10 intermediate transfer body, 18 image forming means 18, 20 tandem image forming section, 61 developing device, 65 developer container, 66 toner replenishment side stirring screw, 67 developer carrier side stirring screw, 68 developer carrier (developing roller ), 70 rotating shaft, 71 spiral blade, 80 permanent magnet.

Claims (8)

[Claims] 1. A developer container for containing a two-component developer containing magnetic particles and toner, a toner replenishing device for replenishing the developer container with toner, and a developer in the developer container. In a developing device comprising: a developer stirring / conveying means for conveying the toner while stirring; and a developer carrying body for carrying the developer and supplying the toner to an external image carrying body, the developer stirring / conveying means A developing device, wherein at least a part of the developing device is a permanent magnet. 2. The developing device according to claim 1, wherein the developer agitating / conveying means is a screw including a rotating shaft and a spiral blade projecting from the outer periphery of the rotating shaft. 3. The developer stirring / conveying means stirs and replenishes the toner replenished from the toner replenishing device and the developer in the developer accommodating container with a toner replenishing side stirring screw, and / or a developing device. Stir the developer in the agent container,
The developing device according to claim 1 or 2, wherein the developing device is a developer carrying member side stirring screw. 4. When the developer agitating / conveying means is the screw, at least a part of the spiral blade protruding on the outer periphery of the rotary shaft is a permanent magnet. 2. The developing device according to 2 or 3. 5. The developing device according to claim 4, wherein only the tip portion of the spiral blade is a permanent magnet. 6. The developing device according to claim 4, wherein at least a part of the rotating shaft is a permanent magnet. 7. The developing device according to claim 1, wherein the permanent magnet provided in at least a part of the developer agitating / conveying means is a plastic magnet. 8. The developing device according to claim 1, wherein the permanent magnet provided in at least a part of the developer agitating / conveying means is formed by sintering a magnetic material.