JPH11119626A - Cleaning method in image forming apparatus - Google Patents

Abstract

An object of the present invention is to provide a cleaning method in an image forming apparatus capable of appropriately supplying toner in accordance with a sliding load of a cleaning blade, and preventing entangling of the blade and belt filming. A cleaning blade (16a, 15d) is brought into contact with an image carrier (11) and / or a transfer body (15a), and a contact angle of the cleaning blade is detected by sensors (25, 31). If the distance is out of the range, the amount of toner stained between the papers on the image carrier 11 is increased or decreased to control the amount of toner supplied to the cleaning blade. The control of the toner adhesion amount between sheets is performed by changing the developing bias value or changing the transfer bias value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a contact transfer apparatus and a cleaning method in an image forming apparatus using the same.

[0002]

2. Description of the Related Art In recent years, a contact transfer method has been increasingly used as a transfer device of an image forming apparatus using an electrophotographic method. This method is advantageous over a conventional scorotron method in that there are advantages such as generation of a small amount of ozone, no trouble due to leakage, and good transferability of transfer.

In an electrophotographic process using this contact transfer method, a bias voltage is usually applied to a sheet interval (a non-image area on a photosensitive drum) under the same conditions as during transfer. This is because most of the toner that adheres to the space between the photoconductors is opposite-polarity toner due to the relationship between the photoconductor potential and the inter-sheet development bias. This is to prevent the transfer to the transfer body (or the intermediate transfer body).

However, depending on the type of toner used and the same toner that has passed the initial stage and time, the toner on the sheet interval may have both positive and reverse polarities, or
The polarity was not always reverse, such as when most of the positive polarity toner was used. For this reason, conventionally, the background soil toner adhered between the papers is reversely adhered to the belt surface from the photoconductor side by a contact transfer unit (transfer belt, intermediate transfer belt, or the like).
As a result, the amount of toner input to the cleaning blade in the space between the sheets is extremely reduced, and the margin for initial winding of the cleaning blade and damage to the edge of the cleaning blade is reduced, and the space between the sheets on the belt surface is reduced. Because of the fine powder toner adsorbed and accumulated from the belt, the cleaning ability of the belt cannot keep up, and belt toner filming in which the belt is covered with the toner occurs, and as a result, the life of the belt may be shortened.

Conversely, if the toner between the sheets adheres to and collects only on the photoreceptor side, toner input to the cleaning blade on the transfer body hardly occurs, and the blade edge on the belt side is damaged or turned up. It was also done. Therefore, it has been difficult to satisfy the best conditions with respect to all conditions such as the environment and the change over time of the toner.

On the other hand, a cleaning blade supporting method adopted for removing residual toner on a photosensitive member or a transfer member includes a blade supporting member for covering accuracy of the blade supporting member and rotation fluctuation of the photosensitive member itself. Is supported on the frame by a rotatable shaft,
There are a type in which the tip of the blade abuts on the photoreceptor by a pressing means such as a spring or a weight, and a type in which the blade bracket is directly fixed to the frame so that the tip of the blade abuts on the photoreceptor.

The former method, in which the bracket is rotatable, has an advantage in accuracy that severe accuracy is not required, and is mainly used for machines of a wide, medium, and high-speed layer.
On the other hand, if the frictional resistance between the photosensitive member, which is the member to be cleaned, and the cleaning blade edge changes, there is a disadvantage that the contact angle of the blade changes accordingly. As a problem caused by this, the coefficient of friction between the member to be cleaned and the blade increases due to a high temperature and high humidity environment or a decrease in toner input, and if the contact angle of the blade becomes too large, the edge may be damaged or turned up. It was easy to happen.

On the other hand, when acidic paper containing a large amount of talc as a paper additive or neutral paper containing a large amount of additives such as calcium carbonate is used, fine particles of paper components adhere to the surface of the blade edge. As a result, the coefficient of friction between the photosensitive member and the blade is reduced, and the blade tends to be stomach-like, causing a problem that toner or the like slips through.

From the above, the optimum blade conditions are:
It depends on various conditions such as the use condition, installation environment, and use size of the image forming apparatus, and it is difficult to cover all the use conditions with one setting.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, the present invention provides a photoreceptor for transferring a background toner adhered between papers on an image carrier in accordance with a sliding load of a cleaning blade. It is an object of the present invention to provide a cleaning method in an image forming apparatus that can appropriately supply cleaning media to both transfer members, set appropriate cleaning conditions for each, and prevent the initial blade entanglement and belt filming.

[0011]

According to the present invention, there is provided a cleaning method for an image forming apparatus in which a cleaning blade is brought into contact with an image carrier and / or a transfer body. The sliding load is measured by a sensor, and if the sliding load is out of a predetermined range, the amount of background toner adhering between the papers on the image carrier is increased or decreased, and the toner supplied to the cleaning blade is increased. It is characterized in that the amount is controlled and an appropriate sliding load is maintained.

Further, the control of the amount of toner adhering to the sheet interval can be performed by changing a developing bias value. Alternatively, the method may include changing the transfer bias value of the toner attached between the papers to control the amount of transfer of the toner to the transfer body. Further, the control of the toner adhesion amount may be performed by switching the shape of a density pattern created between sheets on the image carrier.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In this image forming apparatus, a charging roller 12 as a contact charging rotator, a writing optical system (only a final sixth mirror 13 is shown), and a developing device are provided on the surface of a photoreceptor 11 as an image carrier. 14 and transfer device 15
And a cleaning unit 16 and a neutralization lamp 17. Although the photoconductor 11 rotates clockwise in FIG. 1, an eraser 18 is provided in front of the developing device 14, and a PTL 19 is provided behind the developing device 14. A paper feed tray 20 is located below these, a fixing roller 21 is on the left, and a registration roller 22 is located between the paper feed tray 20 and the photoconductor 11.

The photoconductor 11 is an image carrier having a photoconductive layer such as OPC, and rotates clockwise during image formation. A high voltage is applied to the charging roller 12 during image formation, and the photosensitive member 1
The surface is uniformly charged and charged.

An original (not shown) illuminated by the halogen lamp is projected onto a photosensitive member 11 from a first mirror (not shown) by a sixth mirror 13 and an optical system. Then, due to the intensity of the light, the negative charges on the photoconductor 11 disappear, and an electrostatic latent image is formed.

The electrostatic latent image is generated as the photosensitive member 11 rotates.
The developing device 14 is reached. The developing device 14 contains toner therein, and the rotation of the developing sleeve 14a causes the toner to adhere to the electrostatic latent image on the photosensitive drum 11, and visualizes the electrostatic latent image formed thereon as a toner image. I do.

The toner image formed on the photoreceptor 11 is
The photoreceptor 11 is rotated toward the transfer device 15 by rotation, and immediately before that, the PTL 19 removes the electric charge to improve the transfer efficiency.

Next, the sheet is conveyed to the registration roller 22,
The transfer paper T waiting here is sent out to the photoconductor 11 at the same time as the toner image on the photoconductor 11.

A transfer bias is applied to the bias roller 15b at the same time as the leading end of the transfer paper T enters the nip portion of the transfer member 15a formed of a transfer belt, and a charge having a polarity opposite to that of the toner on the photosensitive member is applied to the transfer member 15a. Then, the toner image is transferred from the photoconductor 11 to the transfer paper T and is transferred.

The tip of a cleaning blade 15d is in contact with the drive roller 15f side of the transfer member 15a. This is made of polyurethane rubber like the cleaning blade 16a provided in the cleaning device 16. The surface of the transfer body 15a is coated with fluorine (polyvinylidene fluoride), and the friction coefficient μ (for cleaning blade) is set sufficiently low. Then, foreign matters (toner, paper powder, etc.) remaining on the belt are removed and stored in a receiving portion located below.

The toner and the like remaining on the photoreceptor 11 without being transferred onto the transfer paper T are peeled off by a cleaning blade 16a of a cleaning device 16 and conveyed through a conveying pipe (not shown) by a conveyor device using a spiral 16b. It is returned to the developing device 14 and reused. Finally, the entire surface of the photoreceptor 11 is exposed by the discharge lamp 17 to remove residual charges, and prepares for the next copy.

FIG. 2 shows the cleaning blade 16a of FIG.
And FIG. 15D is a diagram showing a detailed structure of a portion 15d. The cleaning blade 16 a for cleaning the toner remaining on the photoconductor 11 has one end held by a bracket 23, and the edge of the tip can contact the photoconductor 11. The bracket 23 is rotatably supported by a frame (not shown) with the shaft 23a as a support shaft.
As a result, the tip of the cleaning blade 16a is
It comes into contact with 1 under pressure. The cleaning blade 16a is made of polyurethane rubber and has a protrusion amount of 10 mm, a width of 326 mm, and a rubber hardness of 70 degrees. A sensor 25 is arranged at the movable end of the bracket 23, and the attitude of the bracket 23 can be detected by the sensor 25.

The signal from the sensor 25 is amplified by the amplifier 26 and input to the main control panel 28 as a substitute value for the current cleaning blade load. When the transition of the load was monitored, it became smaller with time as shown in FIG. This is considered to be caused by edge filming, edge abrasion, roughening of the surface of the photoreceptor, settling of the blade, and the like due to toner passing through the blade edge.

During the copying operation, the attitude of the bracket 23 is different between the image area of the transfer paper and the non-image area (between the sheets).
It can be confirmed that the sliding loads differ. Compared with the position of the bracket 23 in the transfer paper image area, the balance of the bracket 23 is balanced at a position (upward position) shifted clockwise about the support shaft 23a between the sheets.

On the other hand, a cleaning blade 15d for cleaning the surface of the transfer member 15a is held by a bracket 30, and the bracket 30 rotates about a support shaft 30a, and is rotated by a coil spring (not shown).
The ridge line at the edge tip of d is pressed against the transfer body 15a with a predetermined pressing force.

The length, protrusion, and hardness of the cleaning blade 15d in the longitudinal direction are the same as those of the cleaning blade 16a. This cleaning blade 15
The bracket 30 supporting d is also detected by the sensor 31,
The signal is amplified by the amplifier 32 and input to the main control panel 28.

When the copying operation is started, the photoreceptor 11 is charged to about -900 V, but between the sheets, the charge is erased by irradiation of the PTL 19, and the potential becomes almost 0 V. In this area, a bias of -200 V is applied to the developing sleeve 14a, and the opposite polarity toner (in the case of this system, negative toner) in the developing device 14 is caused to adhere between the sheets of the photoconductor 11.

However, when the toner of the embodiment of the present invention was actually examined, it was found that the toner and the toner aggregate transferred by the reverse bias were also positively charged. This is because the toner type and the same toner are considered to be different between the initial stage and the aging.

Therefore, even if the same bias (in the opposite direction to the toner polarity) as that of the image area is applied to the bias roller 15b between the papers as in the related art, even the positively charged toner between the papers on the photosensitive member 11 is transferred. The cleaning member 15a may be electrostatically attracted to the transfer member 15a and may exceed the cleaning ability of the cleaning blade 15d on the transfer member 15a side.
5a resulted in toner filming.

Therefore, in the apparatus of the present invention, the signals from the sensor 25 and the amplifier 26 are used for the cleaning blade 16.
When the angle of contact a becomes larger than a predetermined range (the bracket 23 is raised), it is determined that the sliding load is large, and the developing sleeve 1 is connected via the high-voltage power supply 33.
The inter-sheet bias of 4a is switched, and the potential is changed from -200V to-
The voltage is set to 300 V to increase the amount of toner between the sheets and the amount of toner supplied to the cleaning blade 16a to reduce the sliding load.

Alternatively, the transfer bias value of the bias roller 15b is set to 0 V (the transfer current is 0 μA in the case of constant current control) via the high-voltage power supply 34, and the paper-to-paper background toner adsorbed on the transfer body 15a is transferred to the photosensitive body 11 To the cleaning blade 16a to reduce the sliding load on the edge of the blade 16a.

When the bracket 30 is operated to be deviated by a predetermined amount counterclockwise about the support shaft 30a by the signals of the sensor 31 and the amplifier 32, the sliding resistance of the cleaning blade 15d is too high (sliding). It is determined that the dynamic load is too large, and the output value of the high voltage power supply 34 is switched to increase the transfer bias between sheets. In the embodiment, the transfer current was changed from 30 μA to 40 μA for constant current control. Then
A larger amount of the positively-charged background toner between the sheets of the photoconductor 11 is electrostatically transferred from the photoconductor 11 to the transfer body 15a, so that the sliding load of the cleaning blade 15d is reduced, and Damage can be prevented beforehand.

The same effect can be expected by feeding back this signal to the high voltage power supply 33, switching the developing bias value, and increasing the background toner between sheets.

On the other hand, if the cleaning load of the cleaning blade 15d is too large (the sliding load is too small), the cleaning blade 15d tends to touch the transfer member 15a, that is, the bracket 30 is attached to the support shaft 3.
When the sensor 31 and the amplifier 32 detect the position, the bias applied to the bias roller 15b via the high-voltage power supply 34 is set to 0V. I do. In the case of the embodiment, by setting the transfer current to 0 μA, the background toner adhered between the sheets of the photoconductor 11 is removed from the transfer body 15a to the photoconductor 11
, And the transfer member 15a can be prevented from being stained. Alternatively, it is also possible to reduce the cleaning load of the transfer member 15a by changing the inter-sheet developing bias of the developing sleeve 14a to, for example, -200V → 0V and reducing the amount of positively charged toner adhering between the sheets. However, in this case, only when the sliding load of the cleaning blade 16a is not large. If the sliding load of the cleaning blade 16a is large, the photosensitive member 11
The amount of toner adhering between the sheets may be increased, and the amount of toner transferred to the transfer member 15a may be reduced.

By the above operation, the background toner between the papers is appropriately input to the cleaning blade 16a or the cleaning blade 15d to reduce or increase the sliding load of each cleaning blade, thereby maintaining the cleaning property. It is.

Next, a description will be given of an embodiment of the present invention in which a paper containing a large amount of paper additives such as talc and calcium carbonate is used for the transfer paper.

In this case, contrary to the above embodiment, the photosensitive member 11
Alternatively, when the paper additive adheres to the transfer member 15a, the additive enters between the blade and the blade edge, and the friction coefficient is extremely reduced. As a result, for example, the operation posture of the bracket 23 is
The rotation of the cleaning blade 16a largely rotates counterclockwise around the center a, and the contact angle of the cleaning blade 16a becomes small (anti-node direction).
When this state continues, the filming of the fine powder to the edge is further accelerated, and eventually, the cleaning blade 16a is brought into a state of contact with the antinode, so that the toner passes through the edge of the blade.

As a preventive measure against this, the bracket 2
If the displacement of No. 3 is detected by the sensor 24 and the bracket 23 is lowered too much, as shown in FIG. 4, the width of the pattern 38 of the density sensor formed on the photoconductor 11 between the sheets is increased.
In the embodiment, the 35 × 35 shown in FIG.
mm pattern 38 once per 10 sheets (job is 1
The image density is created at the end of the job if the number is zero or more, and the density pattern is detected by a density sensor (not shown) to control the image density.

When the pattern 38 is formed, the transfer member 15a lowers the bias roller 15b by a solenoid (not shown), and separates the transfer member 15a from the photosensitive member 11. When it is detected from the signal of the sensor 25 that the posture of the bracket 23 has become lower than the predetermined position, the pattern of the density sensor is changed from 35 × 35 in FIG.
× 300, and new toner is positively input to the blade edge. By this operation, the fine powder of the paper component accumulated on the blade edge can be attached to the toner particles for cleaning.

This is effective even when the blade load is initially large. In other words, when the cleaning blade 16a and the photoconductor 11 are new and the sliding load is unstable or too large, the bracket 23 operates while balancing in the clockwise direction around the support shaft 23a. Then, the position is detected by the sensor 25, and if the position is equal to or more than the predetermined position, the density sensor pattern 38 is increased in the longitudinal direction from 35 × 35 to 35 × 300 mm as described above. As a result, the lubricating effect of the blade is improved, and blade entrainment and edge damage can be prevented. Further, it is more effective if the timing of generating the inter-sheet density pattern is switched from once every ten sheets to once every five sheets.

[0041]

According to the present invention as described above,
The sliding load of the cleaning blade is detected by a sensor, and when the sliding load deviates from a predetermined range, the amount of background toner adhered between the papers on the image carrier is increased or decreased and supplied to the cleaning blade. Since the toner amount is controlled to maintain an appropriate friction coefficient, the sliding load (friction coefficient) between the cleaning blade and the image carrier can always be kept within a certain range. Or turning over can be prevented.

Further, if the transfer amount of the toner attached to the paper is changed by controlling the transfer bias value to control the transfer amount of the toner to the transfer member, the transfer amount of the toner to the transfer member can be controlled. The coefficient of friction between the body and its cleaning blade can be kept within a certain range. The same effect as described above can also be obtained by controlling the toner adhesion amount by switching the shape of the density pattern created between the papers on the image carrier.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus using a method of the present invention.

FIG. 2 is a diagram illustrating a configuration around a cleaning blade in the image forming apparatus.

FIG. 3 is a diagram showing transition of a sliding load between a photosensitive member and a cleaning blade.

FIG. 4 is a diagram showing a density sensor pattern.

[Explanation of symbols]

 11 Image Carrier 14a Developing Sleeve 15a Transfer Body 16a, 15d Cleaning Blade 25, 31 Sensor 15b Bias Roller

Claims (4)

[Claims] In a cleaning method in an image forming apparatus in which a cleaning blade is brought into contact with an image carrier and / or a transfer body, a sliding load of the cleaning blade is measured by a sensor, and the sliding load is set to a predetermined value. When the value is out of the range, the amount of background toner adhered between the papers on the image carrier is increased or decreased to control the amount of toner supplied to the cleaning blade and to maintain an appropriate sliding load. Cleaning method in an image forming apparatus. 2. The cleaning method according to claim 1, wherein the control of the amount of toner adhering to the sheet interval is performed by changing a developing bias value. 3. The cleaning method according to claim 1, further comprising controlling a transfer amount of the toner attached to the paper by changing a transfer bias value to control a transfer amount of the toner to the transfer member. 4. The cleaning method according to claim 1, wherein the control of the toner adhesion amount is performed by switching a shape of a density pattern created between papers on the image carrier. .