JP2009092874A - Developing device, process cartridge, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of reducing nonuniform image density by quickening a conveying speed, and capable of restraining the scattering of a developer from a toner replenishment port. <P>SOLUTION: A developer recovery means 8 is arranged in the under side of a developing roller 11, and a developer stirring conveying means 9 is arranged horizontally along the developer recovery means 8. A developer supply means 10 is arranged in the upper side of the developer stirring conveying means 9. The developer is transferred, from the developer recovery means 8 to the developer stirring conveying means 9 via the second opening 17, and a portion that is opposed to the toner-replenishing port 16 is closed by a partitioning plate 18. The spiral pitch of the portion opposed to the toner replenishing port 16 of the developer stirring conveying means 9 is set smaller than the other so as not to make the developer splash from the toner-replenishing port 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device that visualizes a latent image on a latent image carrier, a developing device that supplies toner into a developer container that contains the developer, a process cartridge integrally including the developing device, The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter having at least one of the developing device or a process cartridge, and a multifunction machine provided with at least one of them.

Patent Document 1 describes a developing device provided with a collection conveyance path for collecting a collected developer separately from a developer supply conveyance path and a stirring conveyance path.
In this developing apparatus, a supply conveyance path that supplies the developer carrying body while conveying the developer at substantially the same height as the developer carrying body, and a supply conveyance path that collects the recovered developer below the developer carrying body. And a collection conveyance path for conveying in the same direction. Furthermore, the excess developer that has reached the downstream end in the developer transport direction of the supply transport path and reaches the downstream end in the developer transport direction of the recovery transport path at substantially the same height as the recovery transport path and below the supply transport path An agitation conveyance path for agitating the recovered developer thus prepared is provided.
The supply conveyance path, the recovery conveyance path, and the stirring conveyance path are provided in parallel to the developer carrier, and each conveyance path is partitioned by a partition member. An opening for passing the agitated developer to the supply conveyance path is provided in a partition member between the supply conveyance path and the downstream end of the agitation conveyance path. Also, the partition member with the agitation conveyance path at the downstream end of the supply conveyance path has an opening for passing excess developer to the agitation conveyance path, and the partition member with the agitation conveyance path at the downstream end of the recovery conveyance path An opening for passing the collected developer to the stirring conveyance path is provided. When the developer is transferred between the transport paths, the transport direction of the developer is changed substantially at a right angle.

In this type of developing device, the toner is replenished through a toner replenishing port provided on the upstream side of the agitation transport path, and is agitated by mixing with the excess developer and the recovered developer.
In recent years, there has been a demand for stability in image quality that does not cause density unevenness. In this case, it is possible to reduce image density unevenness by increasing the number of rotations of the developer conveying means or the conveying speed.

Japanese Patent Laid-Open No. 11-167260

However, increasing the number of revolutions of the developer conveying means may lead to a decrease in the life of the bearing, and may cause the developer to jump up from the toner replenishing port, resulting in toner scattering in the machine and toner dropping on the image. There was a problem.
The joining part of the excess developer and the collected developer in the agitation transport path is necessarily close to the toner replenishing port, and the problem is that the developer splashing from the toner replenishing port is promoted by the influence of the flow-in operation. there were.

  The main object of the present invention is to provide a developing device that can reduce image density unevenness by increasing the conveyance speed and can suppress the developer jumping up from the toner supply port.

  To achieve the above object, according to the first aspect of the present invention, there is provided a developer carrying body for developing a latent image formed on a latent image carrying body by transporting a developer containing toner and a magnetic carrier; A developer container for containing a developer to be supplied to the developer carrier, a developer supply means for supplying the developer to the developer carrier, and a thickness suitable for developing the developer on the developer carrier. The developer regulating member set on the developer and the developer on the regulated developer carrying member, after the developer necessary for the latent image carrying member has been applied, separated from the developer carrying member and released from the developer carrying member. A developer collecting means for collecting the developer, and a section serving as a detour path is separately provided between the section of the developer supplying means and the section of the developer collecting means. Screw-like developer agitating and conveying means for conveying A first opening communicating the developer conveying direction downstream of the agitating and conveying means with the developer conveying means upstream of the developer conveying direction; the developer agitating and conveying means upstream of the developer conveying direction; and the developer recovery A second opening communicating with the developer conveying direction downstream of the developer, and a toner replenishing port provided above the developer agitating / conveying means upstream of the developer agitating / conveying means and above the developer agitating / conveying means The spiral pitch of the developer agitating / conveying means at a portion facing the toner supply port is smaller than the others.

According to a second aspect of the present invention, in the developing device according to the first aspect, the spiral outer diameter of the portion where the spiral pitch of the developer agitating / conveying means is small is smaller than the others.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the toner replenishing port does not overlap the second opening.

According to a fourth aspect of the present invention, a process cartridge includes the developing device according to any one of the first to third aspects, and is detachably attached to the main body of the image forming apparatus.
According to a fifth aspect of the present invention, an image forming apparatus includes the developing device according to any one of the first to third aspects.
According to a sixth aspect of the invention, an image forming apparatus includes the process cartridge according to the fourth aspect.

According to the present invention, it is possible to suppress the developer from jumping up from the toner replenishing port by reducing the radial force in the developer transporting force of the developer agitating / conveying means at the portion facing the toner replenishing port. .
In addition, since the developer from the developer collecting means is not directly delivered to the toner supply port, the draft surface of the developer can be lowered, and the developer can be prevented from jumping up from the toner supply port.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
First, an outline of the configuration of a color copier of a tandem type intermediate transfer system as an image forming apparatus according to the present embodiment will be described based on FIG.
The color copying machine 100 includes an apparatus main body 101, a scanner 102 provided on the upper surface of the apparatus main body 101, and an automatic document feeder (ADF) 103 provided on the scanner 102.
A paper feed unit 104 including a plurality of paper feed cassettes 104a, 104b, 104c, and 104d is provided at the lower portion of the apparatus main body 101.
An endless intermediate transfer belt 105 as an intermediate transfer member is disposed at a substantially central portion of the apparatus main body 101. The intermediate transfer belt 105 is supported by being wound around a plurality of support rollers 106, 107, 108, and the like, and is rotationally driven in a clockwise direction in the drawing by a drive source (not shown).
In the vicinity of the support roller 108, an intermediate transfer member cleaning device 109 for removing residual toner remaining on the intermediate transfer belt 105 after the secondary transfer is provided.
On the intermediate transfer belt 105 stretched between the support roller 106 and the support roller 107, four colors of yellow (Y), magenta (M), cyan (C), and black (K) are arranged along the conveyance direction. Process cartridges 22Y, 22M, 22C, and 22K as image forming means are arranged side by side to constitute a tandem image forming unit 20. However, these four color orders are examples and are not intended to be limited to this.
The process cartridge 22 is configured to be detachable from the image forming apparatus main body.

An exposure device 8 is disposed above the tandem image forming unit 20. A secondary transfer roller 110 as a transfer device is disposed on the opposite side of the intermediate transfer belt 105 from the support roller 108. The image on the intermediate transfer belt 105 is transferred to a sheet (paper) fed from the paper feeding unit 104 by the secondary transfer roller 110.
On the left side of the secondary transfer roller 110, a fixing device 111 for fixing the transferred image on the sheet is provided. The fixing device 111 has a configuration in which a pressure roller 111b is pressed against an endless belt-like fixing belt 111a.
Below the fixing device 111, a sheet reversing device 112 that reverses the sheet when recording images on both sides of the sheet is provided substantially parallel to the tandem image forming unit 20 described above.

Image formation in the image forming apparatus is performed by a known process.
That is, first, the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged by the charging rollers 3Y, 3M, 3C, and 3K, and then, from the exposure device 8 according to reading information of the scanner 102, lasers, LEDs, and the like. The electrostatic latent image is formed on the photosensitive drums 1Y, 1M, 1C, and 1K by irradiating the writing light. Thereafter, the toner is attached by developing devices 5Y, 5M, 5C, and 5K that contain a two-component developer composed of a magnetic carrier and toner, and each of the photosensitive drums 1Y, 1M, Monochromatic images of yellow, magenta, cyan, and black are formed on 1C and 1K, respectively.

Along with the conveyance of the intermediate transfer belt 105, these single color images are sequentially transferred by applying a transfer bias by the respective transfer rollers 6 Y, 6 M, 6 C, and 62 K as primary transfer means, and a superimposed image is formed on the intermediate transfer belt 105. To do.
The toner remaining on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the image is transferred is cleaned by the cleaning devices 4Y, 4M, 4C, and 4K. Thereafter, the surface potentials of the photoconductive drums 1Y, 1M, 1C, and 1K are initialized by a static eliminator (not shown) to prepare for image formation again.

On the other hand, the selected one of the sheet feeding cassettes of the sheet feeding unit 104 or the sheet fed from the manual feed tray 113 is temporarily stopped by the registration roller pair 114, and the skew is corrected.
The registration roller pair 114 is rotationally driven in synchronization with the composite color image on the intermediate transfer belt 105, and the sheet is fed between the intermediate transfer belt 105 and the secondary transfer roller 110. A color image is transferred to
The sheet after the image transfer is sent to the fixing device 111 where heat and pressure are applied to fix the transferred image, and the sheet is stacked on the paper discharge tray 116 by the paper discharge roller pair 115.
Alternatively, the conveyance path is switched by a switching claw (not shown), put into the sheet reversing device 112, reversed there and guided again to the transfer position, and after the image is recorded also on the back surface, the paper discharge roller pair 115 discharges it. The paper is discharged onto the paper tray 116.
After the image transfer, the intermediate transfer belt 105 has the residual toner removed by the intermediate transfer member cleaning device 109, and prepares for another image formation by the tandem image forming unit 20.

Next, the developing device 5 in the present embodiment will be described in detail. As shown in FIG. 2, the developing device 5 includes a developer collecting unit 8 disposed below the developing roller 11 in the developing container 7, and a developer stirring and conveying unit disposed horizontally beside the developer collecting unit 8. 9. There are three developer conveying means called developer supply means 10 disposed above the developer stirring and conveying means 9, and these conveying means all have a screw-like conveying shape. The developer recovery means 8, the developer agitation transport means 9, and the developer supply means 10 are a supply path P1 as a section of the developer supply means partitioned by a partition wall 13, a recovery path P2 as a section of the developer recovery means, The developer is accommodated in a conveyance path P3 as a section of the developer stirring and conveying means serving as a detour path between these sections.
The developer thinned by a developing doctor 12 as a developer regulating member made of stainless steel is transferred to a photosensitive drum 1 as a latent image carrier and developed on a developing roller 11 as a developer carrier.
The surface of the developing roller 11 is V-groove or sandblasted and is made of an aluminum base tube with a diameter of 25 mm, and the gap between the developing doctor 12 and the photosensitive drum 1 is about 0.3 mm.

The developed developer is collected by the developer collecting means 8 (arrow B in FIG. 2) and conveyed to the front side in the thickness direction in FIG. 2 (downstream of the collecting path). In the non-image area portion, the developer is transported (arrow C in FIG. 2) at a location where the developer agitating / conveying means 9 has no partition member (second opening 17; see FIG. 5), and the developer agitating and transporting in the vicinity thereof. Toner is supplied from the upper side of the means 9 through the toner supply port 16 (see FIG. 7).
The developer collected after development and the toner supplied in the required amount are conveyed while being dispersed by the developer agitating / conveying means 9 on the back side in the thickness direction of the paper surface (downstream of the conveying path). Near the most downstream position of the developer agitating and conveying means 9, a first opening 14 (see FIG. 3) that communicates the downstream of the conveyance path P3 and the upstream of the supply path P1 is provided. Then, the developer is transferred to the developer supply means 10 (arrow D in FIG. 2).
Developer is sequentially supplied from the developer supply means 10 to the photosensitive drum 1 from the upstream side (arrow A in FIGS. 2 and 3). An opening 15 communicating with the upstream of the transport path P3 is provided near the most downstream of the supply path P1, from which the developer is transferred to the developer stirring and transporting means 6 (arrow E in FIG. 3).

Each developer conveying means is made of a resin screw or a metal screw, and each screw diameter is set to 22 mm, the screw pitch is set to 25 mm, and the rotation speed is set to about 700 rpm.
FIG. 3 illustrates the configuration of FIG. 2 viewed from the longitudinal and lateral directions. Both the part where the developer is lifted from the developer stirring and conveying means 9 to the developer supplying means 10 (opening 14) and the part where the developer is dropped from the developer supplying means 10 to the developer stirring and conveying means 9 (opening 15) are formed. It is provided in the region α. In FIG. 3, symbol H indicates a developing area where the developing roller 11 supplies toner to the photosensitive drum 1.

FIG. 4 shows the entire flow of the developer. The downstream end of the developer supply means 10 is actually located on the back side of the upstream end of the developer stirring and conveying means 9 and the downstream end of the developer collecting means 8 (see FIGS. 5 and 7). In this figure, it is drawn out for easy understanding.
In such a configuration, there is a possibility that the developer is excessively filled downstream of the developer collecting means 8, and in this case, the low density developer is re-pumped to the developing roller 11, resulting in uneven image density. The problem that occurs.
Further, downstream of the developer supply means 10, at the time of low TC, the bulk of the developer is reduced, resulting in insufficient supply of the developer to the developing roller 11, resulting in image density unevenness.

In order to solve such a problem, in this embodiment, as shown in FIG. 5, a partition plate 18 is provided at a developer delivery portion between the upstream of the developer agitating / conveying means 9 and the downstream of the developer collecting means 8. The second opening 17 and the toner replenishing port 16 are not overlapped with each other. In FIG. 5, the partition between the developer agitating / conveying means 9 and the developer collecting means 8 is omitted.
As a result, it is possible to prevent the developer from being excessively filled downstream of the developer recovery means 8 and the developer from jumping up through the toner supply port 16 due to the fluid pressure. That is, since the developer is not directly transferred from the developer collecting means 8 to the toner supply port 16, it is possible to suppress the developer from jumping up.
In this embodiment, the spiral outer diameter of the blade 9a of the developer agitating / conveying means 9 at the portion facing the toner supply port 16 is set smaller than the blade 9b at the other portion, and the spiral pitch is set small. Has been.
As a result, even if the developer conveyance speed is increased as a whole, the portion facing the toner supply port 16 has a small conveyance speed and conveyance amount, so that the developer can be prevented from jumping up through the toner supply port 16.

  Further, as shown in FIG. 6, the developer recovery means 8 and the developer agitation transport means 9 are arranged substantially horizontally, so that the efficiency of the developer delivery from the developer recovery means 8 to the developer agitation transport means 9 is improved. Is not lowered, that is, the developer is delivered to the developer agitating / conveying means 9 without loss, so that overflow of the agent downstream of the developer collecting means 8 can be prevented.

  In the above-described embodiment, the configuration in which the process cartridge 22 integrally provided with the developing device 5 is mounted on the image forming apparatus is illustrated, but the developing device 5 may be directly included in the image forming apparatus.

1 is an overall schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a schematic sectional drawing in the direction orthogonal to the axial direction of a developing device. It is a schematic sectional drawing along the axial direction of a developing device. FIG. 3 is a perspective view of a developing device showing an axial flow of developer. FIG. 6 is a perspective view of a main part centering on a transfer portion between a developer collecting unit and a developer stirring and conveying unit of the developing device. It is a cross-sectional schematic diagram in the direction orthogonal to the axial direction for explaining the arrangement relationship of the respective conveying means of the developing device. 1 is an overall perspective view of a developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum as a latent image carrier 7 Developer container 8 Developer collection means 9 Developer stirring conveyance means 10 Developer supply means 11 Developer roller as developer carrier 12 Developer doctor as developer regulating member 14 First Opening 16 toner supply port 17 second opening 22 process cartridge

Claims (6)

A developer carrying member for developing a latent image formed on the latent image carrying member by conveying a developer containing toner and a magnetic carrier;
A developer container containing a developer to be supplied to the developer carrier;
Developer supply means for supplying a developer to the developer carrier;
A developer regulating member for setting the developer on the developer carrier to a thickness suitable for development;
A developer collecting means for collecting the developer separated from the developer carrying body after the developer on the regulated developer carrying body has provided the necessary developer to the latent image carrying body; and With
A section serving as a detour path is separately provided between the section of the developer supply means and the section of the developer collection means, and a screw-like developer agitation transport means for transporting the developer is provided in the separate section. Installed,
A first opening communicating the developer agitating and conveying means downstream of the developer conveying direction and the developer supplying means upstream of the developer conveying direction;
A second opening for communicating the developer agitating and conveying means upstream of the developer conveying direction and the developer collecting means downstream of the developer conveying direction;
A developing device provided with a toner replenishing port provided in the developer conveying direction upstream of the developer agitating and conveying means and above the developer agitating and conveying means and for replenishing toner;
The developing device according to claim 1, wherein a spiral pitch of the developer agitating / conveying means at a portion facing the toner replenishing port is smaller than the others. The developing device according to claim 1,
2. A developing device according to claim 1, wherein a spiral outer diameter of the portion where the spiral pitch of the developer agitating / conveying means is small is smaller than the others. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein the toner replenishing port does not overlap with the second opening.   A process cartridge that integrally includes the developing device according to claim 1 and is detachable from a main body of the image forming apparatus.   An image forming apparatus comprising the developing device according to claim 1.   An image forming apparatus comprising the process cartridge according to claim 4.

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