JP2003330340A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of rise in an amount of the electrification of developer and prevent image fog, and soil on the interior of the apparatus which is caused by developer scatter, in the case where transfer residual toner recovered by a cleaner is recycled and circulated in a developing device and reused for image formation. <P>SOLUTION: The image forming apparatus develops an electrostatic latent image formed on an image carrier 1 by the use of a developer layer carried on the developer carrier 41 of the development device 4, transfers the developed image to a recording medium by a transfer device 5A, then removes transfer residual developer on the image carrier 1 by a cleaner 6, and returns the developer removed by the cleaner 6 to the main body 40 of the development device, thereby repeatedly using the developer for image formation. In the image forming apparatus, developer electrifying device 10 is disposed between the transfer device 5A and the cleaner 6, thereby electrifying the transfer residual developer to the electrification polarity of the developer electrifying device 10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner image formed on the surface of an electrostatic latent image carrier by a developing device, the toner image being transferred to a transfer material by a transfer device, and the image carrier having passed through a transfer position. The present invention relates to an image forming apparatus in which a transfer residual toner image adhering to the surface of a body is removed by a cleaning device, and the removed transfer residual toner is returned to a developing device by a toner recycling device for reuse.

[0002]

2. Description of the Related Art In recent years, the need for high-quality, high-speed image forming apparatuses based on digital technology has increased with the progress of advanced information technology. Further, the amount of hard copies printed on paper tends to increase more and more, and social demand for an image printing apparatus capable of printing with energy saving and resource saving is increasing. In order to meet these demands, the following technologies have been developed and introduced, and further problems have been created.

A developer having a smaller particle diameter is used for higher image quality, and printing is performed at high speed. The problem that occurs here is that as the toner surface area increases with the reduction in particle size, the developer charge amount rises insufficiently due to frictional charging with the carrier, and if printing is performed at higher speeds, replenishment is replenished. Since the developer is used for image formation in a short time, the proportion of the developer whose charge amount of the developer does not rise sufficiently tends to increase.

To save energy and resources, the developer used once for image formation is recycled and repeatedly used for image formation. The problem that occurs here is that the recycled developer causes fluidity deterioration and electrical property deterioration once it is used for image formation, and the developer charge amount does not rise sufficiently due to frictional charging property deterioration. Easy to increase.

As a result of the occurrence of the above problems, problems such as "fog" in which the developer adheres in the non-printed area of the electrostatic latent image carrier or "dirt due to developer scattering" from the developing device occur.

[0006]

SUMMARY OF THE INVENTION The present invention solves each of the problems described above, and even when a developer is recycled and used, by compensating for deterioration in the buildup of the charge amount of the developer, image fogging and developer scattering occur. It is an object of the present invention to provide an image forming apparatus that prevents stains due to stains and realizes high image quality, high productivity, energy saving, and resource saving.

[0007]

The above-mentioned problems can be solved by the following image forming apparatus of the present invention.

(1) The electrostatic latent image formed on the electrostatic latent image bearing member is developed and visualized by using the developer layer carried on the developer bearing member of the developing device, and the visualized image is formed. After transferring to a recording medium by a transfer device, the transfer residual developer on the electrostatic latent image carrier is removed by a cleaning device, the developer removed by the cleaning device is returned to the developing device main body, and repeated image formation is performed. In the image forming apparatus to be implemented, a developer charging addition device is installed between the transfer device and the cleaning device, and the charge having the charging polarity of the developer charging addition device is added to the transfer residual developer. A characteristic image forming apparatus.

(2) The electrostatic latent image formed on the electrostatic latent image carrier is developed and visualized by using the developer layer carried on the developer carrier of the developing device, and the visualized image is displayed. After transferring to a recording medium by a transfer device, the transfer residual developer on the electrostatic latent image carrier is removed by a cleaning device, the developer removed by the cleaning device is returned to the developing device main body, and repeated image formation is performed. In the image forming apparatus to be carried out, after being cleaned by the cleaning device, a developer transport path returned to the developing device main body,
An image forming apparatus comprising: a developer charging addition device, wherein the charge having the charging polarity of the developer charging addition device is added to the transfer residual developer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an image forming apparatus equipped with the toner recycling apparatus of the present invention will be described with reference to the drawings.

[Embodiment of Image Forming Apparatus] FIG. 1 is an overall configuration diagram of the image forming apparatus A.

In the image forming apparatus A, a charging device 2 is provided around a rotating electrostatic latent image carrier (hereinafter referred to as an image carrier) 1.
Image exposure device (image writing unit) 3, developing device 4, transfer device 5
It has an image forming unit in which A, the static eliminator 5B, and the cleaning device 6 are arranged. The image forming unit uniformly charges the surface of the image carrier 1 by the charging device 2 and then performs exposure scanning based on the image data read from the original by the laser beam of the image exposure device 3 to form a latent image. Then, the latent image is reversely developed by the developing device 4 to form a toner image on the surface of the image carrier 1.

On the other hand, the sheet feeding cassettes 7A and 7B arranged in the middle stage of the image forming apparatus A, the large-capacity sheet feeding trays 7C and 7D arranged in the lower stage, and the manual sheet feeding tray 7E arranged sideways are supplied. Recorded recording paper (hereinafter referred to as paper) S
Is sent to the transfer position via the registration roller 7F.

At the transfer position, the toner image is transferred onto the paper S by the transfer device 5A. After that, the electric charge on the back surface of the sheet S is erased by the static eliminator 5B and the image carrier 1
The sheet is separated from the sheet, is heated and fixed by the fixing device 8, is conveyed by the reverse conveying section 9C, and is discharged by the sheet discharge roller 9A.

When images are formed on both sides of the paper S,
The sheet S heat-fixed by the fixing device 8 is branched from the normal sheet discharge path by the conveyance path switching plate 9B, switched back and turned upside down in the reversing conveyance section 9C, and then passes through the image forming section again. Form an image on the back of S,
After passing through the fixing device 8, the paper is ejected outside the device by the paper ejection roller 9A.

On the other hand, the surface of the image carrier 1 after image processing is
The cleaning device 6 removes the developer remaining on the surface to prepare for the next image formation.

FIG. 2 is a sectional view showing an embodiment of the image forming portion arranged around the image carrier 1.

[Developing Device] In FIG. 2, the developing device 4
Is a developing device main body 40 that contains a two-component developer composed of toner and a carrier, and a developer bearing member that is rotatably supported by the developing device main body 40 and rotates in a counterclockwise direction (hereinafter referred to as a developing roller). 41, a paddle-shaped developer supply member (hereinafter, referred to as a paddle wheel) 42 that is driven to rotate to supply the developer to the developing roller 41, and a screw shape that drives and rotates to stir the developer and convey the developer to the paddle wheel 42 A developer stirring / conveying member (hereinafter referred to as a stirring screw) 43, 44, a developer layer thickness regulating member (hereinafter referred to as a regulating blade) 45 for regulating the developer layer thickness on the developing roller 41 to a predetermined amount, A toner replenishing device 47 for replenishing new toner into a developer stirring chamber 46 having a stirring screw 44 is constituted. The developer contained in the developing device main body 40 is agitated by the agitating screws 43 and 44, so that the toner and the carrier are triboelectrically charged with opposite polarities. This developer is carried and conveyed on the developing roller 41 to which a bias voltage having the same polarity as the charging polarity of the toner is applied. The developer whose layer thickness is regulated by the regulation blade 45 is carried to the developing area between the developing roller 41 and the image carrier 1. In this developing area, the toner in the developer is electrostatically transferred to the electrostatic latent image formed on the surface of the image carrier 1, and the electrostatic latent image is visualized as a toner image.

When the toner concentration detection sensor 48 detects a decrease in the toner concentration of the developer contained in the developing device main body 40, the toner replenishing device 47 operates to develop the toner contained in the toner container. It is replenished in the apparatus body 40.

[Cleaning device] Cleaning device 6
Is a cleaning blade 61 and a toner guide roller 6
2. The toner conveying screw 63.

The transfer residual toner adhering to the surface of the image bearing member 1 is removed from the surface of the image bearing member 1 by the cleaning blade 61 of the cleaning device 6, guided by the toner guide roller 62, and the toner conveying screw 63. The collected toner is further conveyed to the developing device 4 by the toner recycling device.

[Toner Recycling Device] Transfer residual toner collected by the toner carrying screw 63 is carried obliquely upward by a collected toner carrying screw 65 rotating in a collected toner guide tube 64 connected to the toner carrying screw 63, and developed. It is sent to the recycled toner supply port 40A of the apparatus main body 40.

[Developer charging addition device] First configuration condition (see FIG. 2) Between the transfer device 5A and the cleaning device 6 arranged near the outer peripheral surface of the image carrier 1, that is, from the transfer device 5A. The developer charging addition device 10 of the present invention is installed downstream of the image carrier 1 in the rotation direction and upstream of the cleaning device 6.

The developer charging addition device 10 shown in FIG. 2 is a corotron discharger. FIG. 3 is a cross-sectional view showing various embodiments of another developer charging addition device 10. FIG. 3A is a conductive roller that contacts the image carrier 1 to be charged, and FIG.
Is a conductive fur brush that contacts the image carrier 1 to be charged,
FIG. 3C shows a magnetic brush charging device formed on a magnetic sleeve carrying a low resistance magnetic carrier.

As a developer charging addition device 10, a corotron discharge device, a conductive roller, a conductive fur brush, and a magnetic brush charging device were used to examine image fogging and in-machine contamination. In addition, in FIGS. 3A to 3C, a necessary high-voltage DC power supply, or a rotary drive system is installed if necessary.

Second Configuration Condition FIG. 4 is a sectional view showing another embodiment of the image forming portion arranged around the image carrier 1. Since the configuration other than the developer charging / applying device 20 is the same as that in FIG. 2, only the points different from FIG. 2 will be described.

The developer charging addition device 20 of the present invention is installed in the toner recycling path, that is, in the toner conveying path between the cleaning device 6 and the developing device.

The developer charging adding device 20 shown in FIG. 4 is a conductive roller that contacts the toner guide roller 62 and is charged.

FIG. 5 is a cross-sectional view showing various embodiments of another developer charging adding device 20. FIG. 5A shows a conductive fur brush which is charged by contacting the toner guide roller 62, and FIG. 5B shows a magnetic brush charging device formed on a magnetic sleeve carrying a low resistance magnetic carrier.

As the developer charging addition device 20, a conductive roller, a conductive fur brush, and a magnetic brush charging device were used, and image fogging and stain inside the machine were examined. Note that FIG.
In (a) and (b), the necessary high-voltage direct current power supply or, if necessary, the rotary drive system was installed.

Example developer: polymerized toner (styrene-acrylic, particle size 6.5)
μm) Ferrite carrier (silicone resin coat, particle size 6
0 μm) Image forming apparatus: Experimental machine Konica 7065 modified machine (monochrome, digital copier / printer, 600 dpi (where dpi indicates the number of dots per 2.54 cm),
Laser beam diameter main scanning 55 μm / sub scanning 80 μm),
With toner recycling mechanism, experimental environment: temperature 20 ° C, humidity 50% RH Paper type: plain paper Konica Copy J Paper (registered trademark), A3 size paper, evaluation method (1) Image fog: Characters with 6% printing rate Chart A3 size image is printed, and "image fog" is evaluated in the white area on the image carrier 1. The image with the worst image fog in the white paper is visually extracted, and one sheet is printed with an image densitometer. The fog density of the part where the image fog was the worst was measured.

If the reflection absolute density is less than 0.006, a good image with little image fog "○" 0.006 to 0.007 is an image with a little image fog "Δ" If it is more than 0.007, an image with a lot of image fog “×” (2) In-machine stain image was visually confirmed every 25,000 sheets, and the visual confirmation was intermittently continued up to 250,000 sheets in the maintenance cycle for judgment.

[First Embodiment of Developer Charging Addition Device] Transfer device 5A disposed near the outer peripheral surface of image carrier 1.
The developer charging addition device 10 of the present invention is installed between the cleaning device 6 and the cleaning device 6 (see FIGS. 2 and 3).

Experimental conditions Experimental machine: A modified Situos 7065 (registered trademark) machine (see FIGS. 1 and 2) was used.

Developer charging addition device 10: A negative charging DC corona discharge, which is the normal charging polarity of the toner, is carried out during copying to give a charge to the transfer residual toner on the image carrier 1 before the cleaning device 6. .

In order to change the amount of electric charge to be applied, the value of the current (constant current drive) passed through the discharge wire was made variable. The charge of the charged toner was measured by the blow-off method. After the charge is applied, the image carrier 1 to which the toner is attached is taken out. The mass of the entire image carrier 1 was measured. Image carrier 1
Is grounded via a charge meter (coulomb meter).

The toner was removed from the surface of the photoconductor by blowing nitrogen gas onto the transfer residual toner after the charge was applied, and then the total mass of the image carrier 1 was measured again, and the mass M of the blown toner was measured. The counter charge Q when the toner was blown off was measured with a charge meter. Finally, Q / M was calculated to determine the transfer residual toner charge amount after the charge was applied.

Experimental condition Linear velocity ratio (V) between the developing roller 41 and the image carrier 1 at the time of image formation
_S / V _P) = 1.5, the toner concentration from 4.5 to 5.2%, recycled developer back during the rotation of the image bearing member 1 to the developing unit 4 in a row, the experimental environment, a normal temperature, normal humidity (20 ° C, 50% R
H), 5 character chart with 6% printing rate for each image output condition
00 copies were made and the image fogging was confirmed. Furthermore, 2
The stain inside the machine was visually confirmed after every copy of 5,000 sheets. Finally, the maintenance cycle was intermittently continued up to 250,000 copies, and the stains inside the machine were visually confirmed and judged.

Experimental Results of Embodiment 1 Table 1 shows the results of actual measurement of toner charge amount, image fog, and in-machine stain by setting a corotron discharge current between the transfer device 5A and the cleaning device 6.

[0040]

[Table 1]

(1) By increasing the corotron current of the developer charging device 10, it is possible to increase the charge amount of the transfer residual toner (toner to be recycled toner) (at an absolute value of 45 μC / g or more). If you can prevent problems).

(2) By increasing the corotron current (absolute value: 150 μA or more), it was possible to prevent the occurrence of defects such as image fog and stain inside the machine. In Table 1,
◯ indicates a good condition without image fogging and stains inside the machine, Δ indicates a slight failure, and x indicates a failure.

[Second Embodiment of Developer Charging Addition Device] An embodiment in which the type of the developer charging addition device 10 installed between the transfer device 5A and the cleaning device 6 is changed (shown in FIG. 2). First configuration condition).

Experimental conditions Experimental machine: A modified Situos 7065 (registered trademark) machine (see FIGS. 1 and 2) was used.

Developer charge adding device 10: Between the transfer device 5A and the cleaning device 6, the developer charge adding device 10
In addition to the corotron discharger, any of a conductive roller, a conductive fur brush, and a magnetic brush was installed (see FIG. 3).

A negative DC high voltage bias, which is the normal charging polarity of the toner, was applied during copying to charge the transfer residual toner on the image carrier 1 before the cleaning device 6.

A bias of -300 to -800 V is applied to the conductive roller, the conductive fur brush, and the magnetic brush.
When image reproduction is the linear velocity ratio of the developing roller 41 and the image bearing member _{1 (V S / V P)} = 1.5, the toner concentration from 4.5 to 5.2%,
The recycled developer is continuously returned to the developing device 4 while the image carrier 1 is rotating. The experimental environment is room temperature and normal humidity (20 ° C., 50 ° C.).
% RH), 500 character copy charts with 6% printing rate were copied for each developer charging device 10 and the image fog was confirmed.

Contamination inside the machine was visually confirmed every 25,000 sheets, and finally, the maintenance cycle was intermittently continued up to 250,000 sheets and visually confirmed and judged.

Experimental Results of Embodiment 2 Table 2 shows the results of examining the occurrence of image fog and in-machine stain depending on the presence or absence of various developer charging addition devices 10.

[0050]

[Table 2]

When the type of the developer charging addition device 10 installed between the transfer device 5A and the cleaning device 6 is changed, the corona discharge developer charging addition device 10 is replaced by a contact charging roller, a contact charging fur brush, a belt. Even if replaced with an electromagnetic brush, it was possible to prevent problems such as image fogging and stains inside the machine.

[Third Embodiment of the Developer Charging Addition Device] In the toner recycling path, that is, between the recycling toner conveying paths from the cleaning device 6 to the developing device 4,
The developer charging addition device 20 of the present invention is installed (see FIG. 4).

Experimental conditions Experimental machine: A modified Situos 7065 (registered trademark) machine (see FIGS. 1 and 4) was used.

A conductive roller was installed as a developer charging addition device 20 in the recycled toner conveying path between the cleaning device 6 and the developing device 4 (see FIG. 4).

A negative DC high voltage bias, which is the normal charging polarity of the toner, is applied to the conductive roller, the opposing toner guide roller 62 is grounded, and the recycled toner after cleaning is passed through the gap to give an electric charge to the toner to change the charge amount. Improve.

A conductive fur brush may be arranged instead of the conductive roller, and the conductive fur brush may be installed in contact with the toner guide roller 62.

A negative DC high voltage bias, which is the normal charging polarity of the toner, is applied to the conductive fur brush, the opposing toner guide roller 62 is grounded, and the recycled toner after cleaning is passed between them to give an electric charge to the toner and to change the charge amount. Improve.

A magnetic sleeve may be provided instead of the conductive fur brush, a magnetic carrier may be supported on the outer periphery of the magnetic sleeve to form a magnetic brush, and the magnetic brush may be brought into contact with the toner guide roller 62.

A bias voltage of -300 to -800 V is applied to the conductive roller, the conductive fur brush, and the magnetic brush, and at the time of image formation, the linear velocity ratio (V _S between the developing roller 41 and the image carrier 1). / V _P) = 1.5, the toner concentration from 4.5 to 5.2%
Set to.

The recycled toner is continuously returned to the developing device 4 while the image carrier 1 is rotating. The experimental environment is normal temperature and normal humidity (20 ° C., 50% RH).

Image fog was confirmed after copying 500 character charts each having a 6% printing rate for each developer charging device.

The stain inside the machine was visually confirmed every 25,000 sheets, and finally the maintenance cycle was intermittently continued up to 250,000 sheets, and the stain inside the machine was visually confirmed and judged.

Experimental results of the third embodiment A comparative examination of image fogging and in-machine stain when the developer charging addition device 20 is installed in the recycled toner conveying path between the cleaning device 6 and the developing device 4 is shown. Three
Shown in.

[0064]

[Table 3]

Even if the developer charging device 20 is installed in the recycled toner conveying path and replaced with a conductive roller, a conductive fur brush, or a magnetic brush, it is possible to prevent the occurrence of defects such as image fog or stain inside the machine. .

[0066]

As is apparent from the above description, the image forming apparatus of the present invention has the following effects.

(1) The transfer residual toner collected by the cleaning device is recycled and returned to the developing device,
When it is reused for image formation, by supplementing the rising deterioration of the charge amount of the developer by the developer charging addition device,
An image forming apparatus that prevents image fogging and in-machine contamination due to scattering of a developer, and achieves high image quality, high production, energy saving, and resource saving is realized.

(2) In particular, it is effective in preventing image fogging and stains inside the machine which are likely to occur when a large amount of toner is consumed and a large amount of toner is consumed by using an image forming apparatus capable of high speed printing. is there.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus.

FIG. 2 is a cross-sectional view showing an embodiment of an image forming unit arranged around an image carrier.

FIG. 3 is a cross-sectional view showing various embodiments of another developer charging device.

FIG. 4 is a cross-sectional view showing another embodiment of the image forming unit arranged around the image carrier.

FIG. 5 is a cross-sectional view showing various embodiments of another developer charging device.

[Explanation of symbols]

4 Developing device 5A transfer device 6 cleaning device 10,20 Developer charging device 40 Developing device main body 41 developer carrier (developing roller) 47 Toner supply device 61 cleaning blade 62 toner guide roller 63 Toner transport screw 64 Collected toner guide tube 65 Recovery toner transport screw A image forming apparatus

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H035 AA01 AA06 AA14 AA15 AB02                       AC01                 2H077 AA37 AB02 AB13 AC03 AC16                       AD06 AD13 AD31 AD35 AE02                       AE06 BA08 EA01 GA01                 2H134 GA01 GB02 HD01 JA02 JA11                       JA14 KB02 KB11 KC10 KH01                       KH09 KH17 KJ05

Claims (9)

[Claims] 1. An electrostatic latent image formed on an electrostatic latent image carrier is visualized by developing using a developer layer carried on the developer carrier of a developing device, and the visualized image is transferred. After the transfer to the recording medium by the device, the transfer residual developer on the electrostatic latent image carrier is removed by the cleaning device, and the developer removed by the cleaning device is returned to the developing device main body to repeatedly perform image formation. In the image forming apparatus, a developer charging addition device is installed between the transfer device and the cleaning device, and the charge having the charging polarity of the developer charging addition device is added to the transfer residual developer. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the developer charging device is a corona discharge device. 3. The image forming apparatus according to claim 1, wherein the developer charging device is a conductive roller contact charging device. 4. The image forming apparatus according to claim 1, wherein the developer charging device is a conductive brush contact charging device. 5. The image forming apparatus according to claim 1, wherein the developer charging adding device is a magnetic brush contact charging device. 6. The electrostatic latent image formed on the electrostatic latent image carrier is visualized by using a developer layer carried on the developer carrier of a developing device, and the visualized image is transferred. After the transfer to the recording medium by the device, the transfer residual developer on the electrostatic latent image carrier is removed by the cleaning device, and the developer removed by the cleaning device is returned to the developing device main body to repeatedly perform image formation. In the image forming apparatus, after the cleaning by the cleaning device, a developer charging adding device is installed in the developer conveying path returned to the developing device main body, and charging of the charging polarity of the developer charging adding device is performed. An image forming apparatus which is added to the transfer residual developer. 7. The image forming apparatus according to claim 6, wherein the developer charging device is a conductive roller contact charging device. 8. The image forming apparatus according to claim 6, wherein the developer charging adding device is a conductive brush contact charging device. 9. The image forming apparatus according to claim 6, wherein the developer charging device is a magnetic brush contact charging device.