JP2001013836A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device and an image forming method having a simple cleaning means without needing almost the correction control and correction mechanism for application of a bias to a cleaning auxiliary means and highly stable in cleaning performance. SOLUTION: This image forming device has, at least, an image carrier, a development means for developing an electrostatic latent image formed on the image carrier with toner, a transfer means for transferring the developed toner image to transfer paper, and a cleaning means for clearing away toner remaining on the image carrier. In this case, the cleaning means is composed of a cleaning blade and a cleaning auxiliary member made of a non-insulating material, and has an application means for applying a constant current bias to the cleaning auxiliary member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method with improved cleaning means for removing residual toner remaining on an image carrier after transferring a toner image onto transfer paper. Here, the transfer paper is in the form of a sheet on which a toner image is transferred, and includes not only a paper sheet but also a plastic sheet.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a charging means, a writing means, a developing means, a transferring means, a cleaning means, and a pre-charging exposure means are provided at a peripheral portion of a photosensitive member as a rotating image carrier. After the surface of the photoreceptor is uniformly charged by the means, image exposure is performed by the writing means to form a latent image, and the latent image is developed by the developing means to form a toner image on the surface of the photoreceptor. On the other hand, the transfer paper fed from the transfer paper storage means or the like is sent to the transfer position, where the toner image is transferred onto the transfer paper at the transfer position. Further, the residual toner is removed from the surface of the photoreceptor after passing the transfer means by the cleaning means, the remaining charge is erased by the pre-charging exposure means, and the next cycle starts with uniform charging by the charging means. It is repeated.

When an image is formed by using an analog image forming apparatus, a document is placed at a predetermined position on a platen glass and scanned from one end to the other end of the document using a scanning optical system. By performing the above, a latent image is formed by irradiating the original image onto the rotating photosensitive member via the imaging optical system.

On the other hand, when copying is performed using a digital image forming apparatus, the read image data is temporarily stored in a memory, and the image data is read out of the memory at the time of printing and written on a photosensitive member by a writing means. The writing of the latent image of the image is performed.

The cleaning means comprises a blade for scraping residual toner and a non-insulating cleaning auxiliary member, to which a constant voltage bias having a polarity opposite to that of the toner is applied.

[0006]

As described above, in a method of applying a bias having a polarity opposite to that of toner to a cleaning auxiliary member of a non-insulating material, a cleaning electric field is generally applied by a constant voltage control. However, the effective cleaning electric field is reduced due to the resistance fluctuation of the cleaning auxiliary member (resistance change due to deterioration of energization of the auxiliary member itself, resistance change due to environmental conditions), dirt, or transfer conditions, and the cleaning performance itself is reduced. For
Some kind of correction control and correction mechanism was required depending on the energization time, the detection value of the temperature and humidity sensor, and the like.

Particularly, in recent years, in consideration of the demand for higher image quality, the adoption of a small-diameter and nearly spherical polymerized toner, which is liable to cause cleaning failure, has been studied, and securing and stabilizing the cleaning performance has become an important development issue. ing.

The present invention eliminates such a problem, and provides an image forming apparatus and an image forming apparatus having a simple and stable cleaning means having a high cleaning performance and requiring almost no correction control of a bias application to a cleaning auxiliary means or a correction mechanism. It is an object to provide a forming method.

[0009]

This object can be achieved by any of the following technical means (1) to (14).

(1) At least an image carrier, developing means for developing an electrostatic latent image formed on the image carrier with toner, transfer means for transferring the developed toner image to a transfer paper, and an image carrier An image forming apparatus comprising: a cleaning unit for cleaning remaining toner, wherein the cleaning unit includes at least a cleaning blade and a cleaning auxiliary member made of a non-insulating material, and applies a constant current bias to the cleaning auxiliary member. An image forming apparatus comprising:

(2) The image forming apparatus according to item (1), wherein the constant current bias is changed and applied based on the number of images to be formed.

(3) The image forming apparatus according to (1) or (2), wherein the constant current bias is changed based on environmental conditions.

(4) The cleaning auxiliary member is a cleaning roller (1) to (3).
The image forming apparatus according to claim 1.

(5) The image forming apparatus according to any one of (1) to (3), wherein the cleaning auxiliary member is a fur brush.

(6) The constant current bias is 1 in absolute value.
The image forming apparatus according to any one of (1) to (5), wherein the image forming apparatus has a current of not less than μA.

(7) The constant current bias is 5 in absolute value.
The image forming apparatus according to any one of (1) to (5), wherein the image forming apparatus has a current of not less than μA.

(8) A developing step of developing at least an electrostatic latent image formed on the image carrier with toner, a transfer step of transferring a toner image developed on the image carrier to a transfer paper, and an image carrier An image forming method for forming an image on transfer paper by repeating a cleaning step of cleaning toner remaining on the transfer paper, wherein the cleaning step is constituted by at least a cleaning blade and a cleaning auxiliary member of a non-insulating material; An image forming method, wherein a constant current bias is applied to a cleaning auxiliary member.

(9) The image forming method according to the above mode (8), wherein the constant current bias is changed based on the number of images to be formed.

(10) The constant current bias is changed based on environmental conditions (8) or (9).
Item.

(11) The cleaning auxiliary member is a cleaning roller, (8) to (1).
The image forming method according to any one of the above items 0).

(12) The image forming method according to any one of (8) to (10), wherein the cleaning auxiliary member is a fur brush.

(13) The image forming method according to any one of (8) to (12), wherein the constant current bias is 1 μA or more in absolute value.

(14) The image forming method according to any one of (8) to (12), wherein the constant current bias has an absolute value of 5 μA or more.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the image forming apparatus according to the present invention will be described first with reference to the schematic diagram shown in FIG.

The image forming apparatus shown in FIG. 1 is an image forming apparatus of a digital system, and includes an image reading section A, an image processing section B (not shown), an image forming section C, and transfer paper transfer as transfer paper transfer means. It is composed of a section D.

An automatic document feeder for automatically transporting a document is provided above the image reading section A.
The original placed on the original 1 is moved by the original transport roller 12 to the original
The sheets are separated and conveyed, and the image is read at the reading position 13a. The document for which the reading of the document has been completed is discharged onto the document discharge tray 14 by the document conveying roller 12.

On the other hand, the image of the original when placed on the platen glass 13 is read in a V-shape by a reading operation at a speed v of a first mirror unit 15 comprising an illumination lamp and a first mirror constituting a scanning optical system. Reading is performed by moving the second mirror unit 16 including the second mirror and the third mirror located at the speed v / 2 in the same direction.

The read image is formed on the light receiving surface of an image sensor CCD, which is a line sensor, through a projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (brightness signal), and then A
After performing the / D conversion and performing processing such as density conversion and filter processing in the image processing unit B, the image data is temporarily stored in the memory.

In the image forming section C, a drum-shaped photosensitive member 21 serving as an image carrier and a charger 22 serving as charging means, a developing device 23 serving as developing means, and a transfer means are provided as image forming units. A transfer unit 24, a separator 25 as a separating unit, a cleaning unit 26, and a PCL (precharge lamp) 27 are arranged in the order of operation. The photoconductor 21 is formed by applying a photoconductive compound on a drum substrate, and uses, for example, an organic photoconductor (OPC) and is driven and rotated clockwise in the drawing.

After the rotating photoreceptor 21 is uniformly charged by the charger 22, image exposure is performed by the exposure optical system 30 based on an image signal called out from the memory of the image processing unit B and recorded. . The exposure optical system 30 serving as a writing unit uses a laser diode (not shown) as a light emitting source, passes through a rotating polygon mirror 31, an fθ lens (no sign), and a cylindrical lens (no sign), and the optical path is bent by a reflection mirror 32 to perform main scanning. The image exposure is performed at the position Ao on the photoconductor 21.
A latent image is formed by rotation (sub-scan) of the photoconductor 21. In one example of the present embodiment, a character portion is exposed to form a reversal latent image.

The latent image on the photosensitive member 21 is subjected to reversal development by the developing device 23, and a visible toner image is formed on the surface of the photosensitive member 21. In the transfer paper transport section D, paper feed units 41 (A) and 41 serving as transfer paper storage means in which transfer papers P of different sizes are stored below the image forming unit.
(B) and 41 (C) are provided, and a manual paper feed unit 42 for performing manual paper feed is provided on the side, and the transfer paper P selected from any of them is supplied to a guide roller 43.
The transfer paper P is fed along the transport path 40, and the transfer paper P is temporarily stopped and then re-fed by a pair of registration rollers 44 for correcting the inclination and deviation of the fed transfer paper.
The toner image on the photoconductor 21 is transferred to the transfer paper P by the transfer device 24 at the transfer position Bo, being guided by the transport path 40, the pre-transfer roller 43a, and the transfer entry guide plate 46,
Next, the charge is removed by the separator 25, and the transfer paper P is separated from the surface of the photoconductor 21, and is conveyed to the fixing device 50 by the conveying device 45.

The fixing device 50 has a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is heated and pressurized to transfer toner. Weld. The transfer paper P on which the toner image on one side has been fixed is subjected to double-sided image formation for forming a toner image on the other side according to a mode described below, or is discharged onto the paper output tray 64 in a state of a single-sided image.

When the double-sided image forming mode is selected,
The transfer paper P after the image fixing on the front surface is guided by the conveyance direction switching member 62 and descends along the reverse conveyance path 60,
After being once carried into the switchback path 60a, it is carried out and reversed between the front surface and the back surface.
Is further re-fed along the conveyance path 40 by the guide roller 43, and the transfer paper P is temporarily stopped by the registration roller pair 44 for correcting the inclination and deviation of the transfer paper. After that, re-feeding is performed, and the toner image of the back surface image formed on the photoreceptor 21 is transferred to the back surface of the transfer paper P by the transfer device 24 at the transfer position Bo, then separated and conveyed, and fixed. The paper is discharged onto the paper discharge tray 64.

When the one-sided image forming mode is selected,
The transfer paper P on which the front surface image has been fixed proceeds straight and is discharged onto the paper discharge tray 64, or is guided to the reversing conveyance path 60 by the conveyance direction switching member 62, and then the upper and lower surfaces are reversed by switchback. The paper is discharged onto the paper discharge tray 64.

Hereinafter, the cleaning means 26 which is a major feature of the present invention will be described in detail.

A) First, as shown in a partially enlarged view of FIG. 2A, a new (NEW) cleaning roller 26B using conductive polyurethane as a cleaning auxiliary member for a non-insulating material in the cleaning means 26 and its use process. An article (OLD) is attached to the cleaning means 26, and the result of comparing the influence of the resistance change between the two is described. As compared with a new article, the used article undergoes a change in resistance, the resistance value increases, and the applied voltage value for obtaining the same current value also increases. As shown in the VI characteristic diagram of FIG. appear.

As described above, the new cleaning roller 26
The cleaning performance (toner removal rate) was compared using B and the cleaning roller having changed resistance, and the results shown in the following graph of FIG. 4 were obtained. As a confirmation pattern, a solid image having a toner adhesion amount M / A of 0.23 to 0.35 mg / cm ² was passed through the cleaning roller 26B without being transferred in the middle of the transfer pole. Thus, the cleaning roller 2 applied to obtain a sufficient toner removal rate of 80% or more due to the resistance fluctuation of the cleaning roller 26B.
It can be seen that the voltage value of 6B changes greatly.

B) Next, the effect of the transfer conditions will be described with reference to experiments with and without transfer.

The same conductive polyurethane as described above was used for the cleaning roller 26B.

The environmental conditions were considered to be a steady state at a temperature and humidity of 20 ° C. and 50% RH.

1) No transfer: A solid image having a toner adhesion amount M / A of 0.23 to 0.35 mg / cm ² was passed in a check pattern.

2) When there is a transfer: a solid image having a toner adhesion amount of secondary color M / A = 1.5 mg / cm ² is formed by a confirmation pattern, and the toner adhesion amount M / A = 0.2 to
The residual toner of 0.22 mg / cm ² was passed through the cleaning roller 26B.

The results show that the voltage value of the cleaning roller 26B applied to obtain a necessary toner removal rate greatly changes depending on the presence or absence of the transfer step as shown in the graph of FIG.

The present inventors have found that even if there is the above-mentioned disturbance, it is possible to obtain a stable and high cleaning characteristic by using constant current control. This is shown in the following sections 3) and 4).

3) Controllability in the case where constant current bias control is performed on the cleaning roller 26B as a cleaning auxiliary means will be described.

The cleaning roller 26B was experimentally manufactured using conductive polyurethane and used as a cleaning roller.

At that time, the environmental condition is considered to be a steady state. The temperature and humidity are 20 ° C. and 50% RH. When the transfer pattern is not transferred (no transfer step), the toner adhesion amount M / A = 0.23-0.35 mg / cm ² solid image was passed.

When there is a transfer (with a transfer step), a solid image with a secondary color toner adhesion amount M / A = 1.5 mg / cm ² is formed, and the toner adhesion amount M / A = 0.2 ~
The residual toner having reached 0.22 mg / cm ² was continuously passed through a cleaning roller.

Cleaning roller 26 without transfer
B is new (NEW) and in use (OL)
D), and when there is a transfer, using only a new one, current was applied by a constant current device, and the toner removal rate with respect to each current value was plotted to obtain a graph shown in FIG.

Thus, even if the resistance of the cleaning roller 26B fluctuates or disturbances occur in the transfer process, the bias of the cleaning roller 26B is set to a constant current control and the bias current is set to the cleaning roller 26B, whereby a stable and good toner removal rate is obtained. Is obtained. When the bias current is set to 5 μA or more, a high toner removal rate of 80% or more can be obtained stably.

4) As shown in a partially enlarged view of FIG. 2B, a fur brush 26C as a cleaning auxiliary means
The controllability in the case where control is performed by applying a constant current bias to is described.

The fur brush 26C is (300/100
D / F 224 kF / inch ² , conductive rayon) with a bite amount of 1.0 mm.

The environmental conditions at that time are as follows: temperature and humidity are 25 ° C., 2
It was in a state of normal temperature and low humidity at 0% RH.

As a confirmation pattern at this time, a solid image having a toner adhesion amount M / A of 0.24 to 0.92 mg / cm ² was formed on the photosensitive member 21 and passed through the position of the fur brush 26C.

The fur brush 26C without transfer is used to apply a current by constant current control using a new brush (NEW) and a brush that has been used (OLD), and plots the toner removal ratio for each constant current value. Thus, a graph shown in FIG. 7 was obtained.

As a result, even when the resistance of the fur brush 26C fluctuates, if the bias of the fur brush 26C is set to the constant current control and the bias current is set to the fur brush 26C, a stable and excellent toner removal rate can be obtained. I understand. When the bias current is set to 5 μA or more, a high toner removal rate of 80% or more can be obtained stably.

By the way, to ensure the cleaning characteristics so that the residual toner does not slip under the blade until after the running deterioration due to wear or chipping of the cleaning blade 26A, the following Konica experimental machine was used to guarantee the cleaning characteristics. As a result of an experiment using the cleaning roller 26B and the fur brush 26C as auxiliary means, data shown in Table 1 was obtained.

The image forming apparatus used in the experiment was a "model modified from a KL-3010 color laser printer manufactured by Konica Corporation", and was changed between the NEW state and the OLD state (after passing 20k print in the single color mode). Tested. The environmental condition at that time was a steady state, that is, 20 ° C., 50
% Is RH, the toner is polymerized toner diameter 6.5 [mu] m, the cleaning roller 26B is intended diameter conductive polyurethane 16 mm, resistivity of 10 ⁷ ~10 ⁸ Ω, fur brush 26C is conductive Rayon (300/1
00 D / F 224 kF / inch ² ).

The evaluation criteria in Table 1 were as follows.

The patch pattern is continuously printed 10 times in the single color mode.
The evaluation was made based on the state of occurrence of toner slippage from the cleaning blade when sheets were passed. That is, ○ indicates that the occurrence of slip-through was zero and no cleaning failure occurred.

[Delta] indicates that only one of the 40 sheets is slightly slipped through.
Although it occurs about the number of sheets, there is almost no practical problem.

X: Clear passing was 1 in 40 sheets
More than one sheet occurs, and there is a practical problem.

[0063]

[Table 1]

As a result, the current value applied to the auxiliary means is 1
It can be seen that the setting should be at least μA, preferably at least 5 μA.

Although the above-described apparatus and method have no practical problem, if the current of the cleaning roller 26B is finely adjusted according to changes in running or environmental conditions from the viewpoint of further securing a margin of cleaning performance, more stable cleaning performance can be obtained. I knew it would be possible.

That is, as a cause of slightly changing the cleaning performance, there is a change in the toner charge amount due to a change in running or environmental conditions. Originally, the toner charge amount is affected by deterioration of the carrier surface due to running, deterioration of the toner itself (for example, embedding of an external additive on the surface of toner particles due to stress), and moisture content of the atmosphere. When the toner charge amount changes, the electrostatic force applied to the toner changes, and the cleaning performance fluctuates.

Then, it is examined how the toner charge amount changes with respect to the number of copies or the number of prints, and how the toner charge amount shifts due to temperature and humidity under environmental conditions. A table is prepared so that the optimum constant current value for the cleaning roller 26B can be set in advance according to environmental conditions such as the number of copies or the number of prints, temperature and humidity, etc. It can be seen that appropriate control is effective. An example of this is shown in Table 2.

[0068]

[Table 2]

That is, it can be seen that when the environmental conditions of both the cleaning roller 26B and the fur brush 26C become high humidity (NH), the margin to a usable bias current becomes small. Therefore, here, constant current control is performed on the humidity, and in the low humidity (NL), the lower limit is 1 μA, and the high humidity (N
The lower limit was set to 1.5 μA as H), and between low humidity and high humidity was set by linear interpolation to stabilize the margin.

The experimental machine used in this experiment was the same as the above-mentioned "Modified KL-3010 Color Laser Printer".
Those after running for 10,000 sheets were used. The environmental conditions at this time are NL (25 ° C., 20% RH), NH (25 ° C., 70% RH).
% RH), a 6.5 μm polymer toner is used as the toner, the cleaning roller 26B is made of conductive polyurethane (diameter 16 mm, resistivity 10 ⁷ to 10 ⁸ Ω), and the fur brush is made of conductive rayon (300 mm). / 100D / F
224 kF / inch ² ).

The evaluation criteria in Table 2 were the same as those in Table 1.

From the above experimental results, the bias current controlled by the constant current for the cleaning assisting means was set to 1 μA or more,
Preferably, if a voltage of 5 μA or more is applied, the cleaning roller 2
6B resistance fluctuation, transfer effect and cleaning roller 26
It can be seen that stable cleaning performance can be obtained even if there is disturbance such as contamination of B and cleaning performance is deteriorated due to running deterioration of the cleaning blade 26A.

In the embodiment of the present invention, the applied voltage of the charger 22 to the photosensitive member 21 and the bias applied voltage of the developing device 23 are (-), and the toner used is (-).
The voltage applied to the transfer pole 24 and the constant current applied to the cleaning roller 26B and the fur brush 26C are treated as (+). However, the present invention is not limited thereto. It has been confirmed that the reverse is also true.

Further, in the present invention, the applied constant current values are limited to the lower limit values of only 1 μA and 5 μA. The upper limit value is a considerably increased value, for example, 50 μA, and extremely 1A.
The effect was as good as that of 5 μA.

[0075]

According to the present invention, there is provided an image forming apparatus and an image forming method having a simple, high-performance, low-cost, and stable cleaning means which does not require correction control of bias application to the cleaning auxiliary means and almost no correction mechanism. Obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a partially enlarged view of a cleaning unit in the image forming apparatus of the present invention.

FIG. 3 is a VI characteristic diagram showing resistance fluctuation due to deterioration of a cleaning roller.

FIG. 4 is a graph illustrating a toner removal rate according to a voltage applied to a cleaning roller.

FIG. 5 is a graph showing that cleaning performance differs depending on the presence or absence of a transfer step.

FIG. 6 is a graph showing that cleaning performance differs depending on whether or not a transfer process is performed and deterioration of a cleaning roller.

FIG. 7 is a graph showing a state of a toner removal rate when a fur brush is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Photoreceptor 22 Charger 23 Developing device 24 Transfer device 25 Separator 26 Cleaning means 26A Cleaning blade 26B Cleaning roller 26C Fur brush 30 Exposure optical system

Claims (14)

[Claims] An image bearing member, developing means for developing at least an electrostatic latent image formed on the image bearing member with toner, transfer means for transferring the developed toner image to transfer paper, and remaining on the image bearing member An image forming apparatus having at least a cleaning blade and a cleaning auxiliary member made of a non-insulating material, wherein the cleaning unit is configured to apply a constant current bias to the cleaning auxiliary member. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the constant current bias is changed based on the number of formed images. 3. The image forming apparatus according to claim 1, wherein the constant current bias is changed based on environmental conditions. 4. The image forming apparatus according to claim 1, wherein the cleaning auxiliary member is a cleaning roller. 5. The image forming apparatus according to claim 1, wherein the cleaning auxiliary member is a fur brush. 6. The image forming apparatus according to claim 1, wherein the constant current bias has an absolute value of 1 μA or more. 7. The image forming apparatus according to claim 1, wherein the constant current bias has an absolute value of 5 μA or more. 8. A developing step of developing at least an electrostatic latent image formed on the image carrier with toner, a transfer step of transferring a toner image developed on the image carrier and formed on a transfer paper, and on the image carrier. And an image forming method for forming an image on transfer paper by repeating a cleaning step of cleaning the toner remaining on the transfer paper, wherein the cleaning step is constituted by at least a cleaning blade and a cleaning auxiliary member of a non-insulating material. An image forming method, wherein a constant current bias is applied to an auxiliary member. 9. The image forming method according to claim 8, wherein the constant current bias is changed based on the number of formed images. 10. The image forming method according to claim 8, wherein the constant current bias is changed based on environmental conditions. 11. The image forming method according to claim 8, wherein the cleaning auxiliary member is a cleaning roller. 12. The method according to claim 8, wherein the cleaning auxiliary member is a fur brush.
Item. 13. The constant current bias is 1 μA in absolute value.
The method according to any one of claims 8 to 12, wherein
Item. 14. The constant current bias is 5 μA in absolute value.
The method according to any one of claims 8 to 12, wherein
Item.