JPH04331970A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent cleaning failure by switching cleaning bias to low bias during time of operation for a cleaning blade to be separated from a photosensitive body while soiled toner is passed through a fur brush. CONSTITUTION:At the time of taking the first copy, generation of staining on the copy is caused by the soiled toner sticking to the nearest downstream side of the cleaning blade in a state of high bias. Therefore, the staining on the first copy can be prevented by switching the cleaning bias to the low bias and maintaining the same state during the time the soiled toner is passed through the fur brush 2. The cleaning bias is controlled by a power pack control circuit 23.

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 applicable to a dry two-component copying machine.

0002

2. Description of the Related Art In a copying machine shown in FIG. 5, numeral 7 is a transfer charger, numeral 8 is a separation charger, numeral 9 is a charger, numeral 10 is a static elimination charger, numeral 11 is a static elimination lamp, numeral 12 is a charging charger, and numeral 13 14 is an eraser, 14 is a developing device, 15 is a paper transport path, and L is an exposure light.

Furthermore, reference numeral 1 denotes a photoreceptor, and a fur brush 2 and a cleaning blade 3 are provided around the photoreceptor in contact with the photoreceptor to remove residual toner on the photoreceptor. A contact object such as a bristle brush 4
. It is known to have a cleaning device that removes fur with a fur brush (for example, Japanese Patent Publication No. 2
(Refer to Publication No.-11912).

[0004] In an image forming apparatus including such a copying machine,
When the image forming process is performed, the cleaning blade 3 is pressurized against the photoreceptor 1, but when the image forming process is not performed, the cleaning blade 3 is pressed to remove foreign substances such as toner and paper powder adhering to the cleaning blade 3. , the pressure contact is released.

In other words, after the transfer process, the toner remaining on the photoreceptor 1 is removed in the cleaning process, but the edge 3e of the cleaning blade 3 is
As shown in (a), toner T is deposited.

As shown in FIG. 6(b), when the photoreceptor 1 is stopped and the cleaning blade is released along the blade release path indicated by reference numeral 17, the edge of the blade is provided in contact with the cleaning blade. Mylar 16
As a result of the rubbing, dirt caused by toner, paper powder, etc. adhering to the edge is repelled onto the photoreceptor 1. At this time, the objects that are thrown away adhere to the downstream side of the contact position of the cleaning blade on the photoreceptor.

[0007] In addition to the cause caused by mylar,
While the photoreceptor is rotating, the cleaning blade is in a pressurized state (see Figure 7(a)), but when the photoreceptor stops and the cleaning blade is in the released state (see Figure 7(b)), , because the contact position of the blade on the photoconductor is shifted from the position where the photoconductor starts to be driven again and the cleaning blade is also in a re-pressurized state (see FIG. 7(c)).
It adheres to the downstream side of the contact position of the cleaning blade on the photoreceptor.

Next, when the photoreceptor with the toner adhered to the downstream side of the cleaning blade begins to rotate, the toner on the photoreceptor is sent to the next process as it is, but there are various places around the photoreceptor. Hair brushes 4 and 5 to prevent scattering
are attached, and if the toner on the photoreceptor is transferred to these bristle brushes and the dirt accumulates, an abnormal image will appear on the transfer paper due to the dirt on the bristle brushes.

Therefore, in order to prevent the bristle brush from getting dirty, when the dirt on the photoreceptor passes through the charger 12, corona discharge is generated to reduce the adhesion between the photoreceptor and the toner, which is the main component of the dirt. The brush was strengthened to prevent dirt from transferring to the bristle brush.

0010

[Problem to be Solved by the Invention] However, in order to charge the toner in this way, when the dirt is sent to the cleaning section again as the photoreceptor rotates,
Under normal cleaning conditions, the fur brush 2 cannot sufficiently remove toner and transfers the toner to the cleaning blade 3, making it impossible to reduce edge stains on the cleaning blade and gradually accumulating toner on the edge. The problem is that the number of particles increases, which ultimately leads to poor cleaning and image stains on the transfer paper.

Accordingly, it is an object of the present invention to provide an image forming apparatus capable of eliminating cleaning defects.

0012

[Means for Solving the Problems] In order to achieve the above object, in the present invention, when the photoconductor is stopped and the cleaning blade moves away from the photoconductor, the cleaning blade moves to the downstream side of the cleaning blade. Only when the photoreceptor rotates and the toner enters at least the fur brush, the bias is set to be different from that during normal image area cleaning.

[0013] Here, as a mode of making the bias different from that when cleaning an image area normally, it is preferable to set the bias lower than when cleaning an image area normally.

In addition, the toner remaining on the photoreceptor is carried downstream of the cleaning blade together with the photoreceptor, and before it passes through other contact objects placed around the photoreceptor, it is corona-charged and removed from other contact objects. It is also possible to perform optical static elimination after passing through an object.

[0015]

According to claims 1 and 2, the cleaning performance of the fur brush can be achieved by controlling the bias. As for claim 3, the dirty toner is removed before reaching the cleaning means.

[0016]

【Example】

Example 1 (corresponding to claims 1 and 2) As already mentioned, residual toner, paper dust, etc. are firmly attached to the photoreceptor, and there is a large amount of it, so the fur brush should be repositioned. When the time comes, it cannot be removed sufficiently using normal cleaning conditions. Therefore, an experiment was conducted using a copying machine to determine the ability to remove the toner adhering to the blade edge by changing the bias of the bias roller 6, and the results shown in FIG. 8 were obtained.

In FIG. 8, low bias means a bias lower than that during normal image area cleaning, and high bias means a higher bias. "Dirty cleaning performance when the cleaning blade is released" refers to the ability to remove toner and the like transferred to the downstream side when the cleaning blade is released. "Transfer residue cleaning performance" refers to the ability to remove toner, etc. remaining on the photoreceptor after transfer. "Untransferred cleaning performance" refers to the cleaning performance of untransferred toner images. Further, the mark ◯ indicates good cleaning performance, and the mark x indicates poor cleaning performance.

[0018] Here, when the copying machine is stopped, the cleaning blade is released, that is, the cleaning blade is separated from the photoreceptor, so the ``stains when the blade is released'' appear on the first sheet of transfer paper. However, "untransferred toner", "untransferred toner", etc. appear on the second and subsequent sheets of transfer paper.

In other words, the lower the cleaning bias, the better the ability to clean the dirt on the photoreceptor when the cleaning blade is released. However, if the image area is cleaned with the bias kept low, cleaning defects will occur for untransferred images.

This is schematically shown in FIG. 9, in which (a) shows the state when the bias is low, (b) shows the state when the bias is high, and (c) shows the state when the bias is switched. In the figure, the hatched area at the bottom of the original is the image area, and for each transfer paper from the first copy to the second copy, the area shown by the two-dot chain line is cut to remove the effects of dirt. It is made to stand out clearly.

In FIG. 9, when the same document is cleaned with a low bias, the dirt when the cleaning blade is released will not appear on the first copy, but on the second and subsequent copies, the untransferred and untransferred parts will be cleaned. This results in defects (FIG. 9(a)). Further, when cleaning is performed with a high bias, dirt appears on the first copy when the cleaning blade is released, but no cleaning failure occurs on the second and subsequent copies (FIG. 9(b)).

[0022] Therefore, in order to efficiently perform cleaning with a fur brush so that cleaning defects do not always occur,
Lower the cleaning bias when dirt enters the fur brush when the cleaning blade is released, and switch the bias so that when cleaning the image area, apply enough bias to at least clean the remaining transfer and untransferred toner. , No cleaning failure occurred for any of the first and second sheets (FIG. 9(c)).

From the above, the cleaning of the photoreceptor that became dirty during the creation of the first image was performed at a low bias, and the cleaning of the photoreceptor that became dirty during the creation of the second image was performed using a low bias. It turns out that it is better to use a high bias. By switching the bias in this way, good cleaning can be achieved in all cases, as shown in the rightmost column of FIG. It was also found that the lower the cleaning bias, the better the performance of cleaning dirt on the photoreceptor when the cleaning blade is released.

Regarding the timing for switching the bias,
This will be explained with reference to FIG. In FIG. 1, when the photoconductor 1 moves from a stopped state to a rotating state, the cleaning blade 3, which had been in the released state until then, is re-pressurized. The contact position of the brush 2 is indicated by arrow I, and the contact position of the fur brush when the photoreceptor comes around next is indicated by arrow II, and similarly by arrow III.
IV, etc.

In the image forming process of this copying machine, the copying machine rotates idly during the first rotation without performing image formation. It is the smudged toner adhering immediately downstream of the cleaning blade downstream of arrow I under high bias that causes the smearing on the first copy. Due to the idle rotation, this dirty toner is carried over without being transferred to the transfer paper during the first rotation of the photoreceptor, and the dirty toner approaches the fur brush 2 during the second rotation. By switching and maintaining the cleaning bias to a low bias while this dirty toner passes through the fur brush, this dirty toner will not appear on the first copy. The reason for this is not clear, but as a result, stains do not occur.

A high bias is applied to areas other than the low bias section. As a result, the cleaning performance of the fur brush 2 is improved, so that the second and subsequent copies do not become smudged. Regarding the switching of the cleaning bias, it is also possible to maintain the cleaning bias in a low state for one round of idle rotation, as shown by the two-dot chain line in FIG.

Next, the cleaning bias switching control means will be explained with reference to FIG. In FIG. 2, the photoreceptor is driven by a photoreceptor drive motor 20, and the timing for stopping the photoreceptor drive motor 20 is determined by a photoreceptor drive control circuit 22 based on a command from the main body CPU 21 of the copying machine. It is done after a while.

The main body CPU 21 also controls a bias application power pack 24 via a power pack control circuit 23 to apply a bias to the bias roller 6. As a result, bias control as shown in FIG. 1 is performed under unified information from the main body CPU.

Example 2 (corresponding to a part of claims 2 and 3) In this example, when the cleaning blade is released and pressurized again, the toner remaining on the photoreceptor is removed. As it rotates, it is carried downstream of the cleaning blade, and before it reaches the developing sleeve and passes through a contact object placed around the photoconductor, it is corona charged, and after passing through the contact object, it is photo-neutralized.

In FIG. 3, which is an enlarged view of the developing device 14, the bristle brush 4, which is an inlet seal, corresponds to other contact objects arranged around the photoreceptor. A developing sleeve 14a is provided downstream of the bristle brush 4. In this example, a static elimination lamp 25 for optical static elimination is provided so as to irradiate the photoreceptor between the developing sleeve 14a and the bristle brush 4.

In order to make the bristle brush less likely to stain the dirty toner adhering to the immediate downstream side of the cleaning blade 3, the charger 12 applies corona discharge to strengthen the adhesion to the photoreceptor. However, if left as is, the inlet seal becomes difficult to get dirty because the adhesion between the photoreceptor and the toner is strong, but it becomes difficult to remove the dirty toner from the photoreceptor in the developing sleeve section.

However, by doing as in this example, since the adhesion between the toner and the photoreceptor is strong after the toner on the photoreceptor passes through the charger, it can pass through the inlet seal without contaminating it. In addition, since the potential of the photoreceptor is removed by the charge removal lamp 25 before reaching the developing sleeve 14a, the adhesion force between the toner and the photoreceptor is weakened, and the charge can be removed by the development sleeve.

The relationship between the static elimination lamp 25 and other members is shown in FIG. 4 regarding the timing of operation.

[0034] In the above description, the inlet seal was used as an example, but it is assumed that the member with which the dirty toner on the photoreceptor comes into contact first, that is, the other contact object, is located upstream of the charger. In such a case, a corona discharger may be placed upstream of the other contact object.

In this way, in order to perform corona charge on the dirty toner on the photoconductor and perform photostatic charge removal after passing through the contact object around the photoconductor and before reaching the developing sleeve, the contact object It is hard to get dirty and is easily removed by the developing sleeve, which in turn reduces the burden on the cleaning means and contributes to eliminating cleaning defects.

[0036]

According to the present invention, poor cleaning can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a timing chart illustrating an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an embodiment of the present invention.

FIG. 3 is a configuration diagram of a developing device portion explaining an embodiment of the present invention.

FIG. 4 is a timing chart illustrating an embodiment of the present invention.

FIG. 5 is a configuration diagram of a copying machine suitable for implementing the present invention.

FIG. 6 is a diagram illustrating a problem in the prior art.

FIG. 7 is a diagram illustrating a problem in the prior art.

FIG. 8 is a table explaining experimental results.

FIG. 9 is a diagram schematically showing experimental results.

[Explanation of symbols]

1 Photoreceptor 2 Fur brush 3 Cleaning blade

Claims (3)

[Claims] 1. A fur brush, a cleaning blade, and other contact objects are provided around the photoreceptor in order to remove residual toner on the photoreceptor, and the fur brush is provided in contact with the photoreceptor to remove residual toner on the photoreceptor. A cleaning device that brings a metal roller into contact with the brush, applies a bias to the metal roller, creates a potential difference between the fur brush and the photoreceptor, and electrostatically removes toner on the photoreceptor with the fur brush. When the image forming process is performed, the cleaning blade is pressed against the photoreceptor, but when the image forming process is not performed, the cleaning blade is released, so that no residual pressure remains on the photoreceptor. In an image forming apparatus in which toner is carried downstream of the cleaning blade together with the photoconductor and performs corona charging before passing through the other contact object arranged around the photoconductor,
When the photoconductor stops and the cleaning blade moves away from the photoconductor, the toner transferred to the downstream side of the cleaning blade enters at least the fur brush when the photoconductor rotates next. only,
An image forming apparatus characterized in that the bias is different from that when cleaning an image area. 2. The image forming apparatus according to claim 1, wherein the manner in which the bias is made different from that during normal image area cleaning is lower than that during normal image area cleaning. 3. According to claim 1, the toner remaining on the photoreceptor is carried downstream of the cleaning blade together with the photoreceptor, and before passing through the other contact object disposed around the photoreceptor, An image forming apparatus characterized by performing corona charging and photostatic discharge after passing through the other contact object.