JPH0553413A - Image forming device - Google Patents

Abstract

PURPOSE:To perform uniform electrification throughout the whole surface of a photosensitive drum by preventing adhesion of a foreign matter, such as a toner, on the surface of an electrically changed roller. CONSTITUTION:After a photosensitive drum 1 is started to rotate, it is rotated and moved until a position Poi corresponding to a cleaning blade 8 on the surface of the photosensitive drum 1 during the starting of driven passes a position corresponding to an electrically charged roller 2. In this case, by controlling the electrically charged roller 2 by a control device 10 so that the electrically charged roller 2 is shifted from a separating state to a state that it is brought into pressure contact with the photosensitive drum 1, the electrically charged roller 2 is brought into contact with the part, constantly cleaned by a cleaning blade 8, of the photosensitive drum 1, and a foreign matter, such as a toner, is prevented from adhering on the surface of the electrically charged roller 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image formation provided with a contact type charging roller which charges a surface of a photoconductor drum in contact with the surface of the photoconductor drum and a cleaning device for cleaning the surface of the photoconductor drum after image transfer. Regarding the device.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine or a printer using an electrophotographic method is disclosed in, for example, Japanese Patent Laid-Open No. 136068/1993.
As can be seen in the publication, there is a charging device that charges the surface of the photosensitive drum using a contact type charging roller which is low in ozone and saves energy.

Such a charging roller is preferably detachable with respect to the main body of the apparatus together with a cleaning blade of a cleaning device for cleaning the surface of the photosensitive drum, for easy maintenance. When these are constantly in pressure contact with the photoconductor drum, the characteristics of the contact part may deteriorate depending on the photoconductor, so this charging roller and cleaning blade can be brought into contact with and separated from the photoconductor drum. With such a configuration, it is preferable to separate them from the surface of the photoconductor when the photoconductor is stopped.

As the charging roller, there is, for example, one in which a cored bar is made of metal and the roller surface is made of a conductive rubber roller, and a voltage is applied between the cored bar and the base of the photoconductor. The electric charge is mainly applied to the photoconductor by discharging.

[0005]

However, in the case of the method of charging such a charging roller by bringing the charging roller into contact with the photosensitive drum, the uniformity of the resistance layer on the surface of the charging roller and the charging roller and the photosensitive member are The charging state of the photoconductor drum is apt to change due to the uniformity of the contact state with the drum, and if it is not uniform, it may not be possible to uniformly charge the entire surface of the photoconductor drum. It was

Further, when foreign matter such as toner adheres to the surface of the charging roller, the electric discharge at that portion becomes insufficient, so that only a low potential may be obtained. The present invention has been made in view of the above problems, and an object of the present invention is to prevent foreign matter such as toner from adhering to the surface of the charging roller so that uniform charging can be performed over the entire surface of the photosensitive drum. And

[0007]

In order to achieve the above object, the present invention provides an image forming apparatus such as that described above, in which the surface of the photoconductor drum is started at the start of driving after the photoconductor drum starts rotating. There is provided roller pressure contact timing adjusting means for pressing the charging roller from the separated state to the photosensitive drum when the position corresponding to the cleaning member has passed the position corresponding to the charging roller. Then, in the image forming apparatus, a cleaning member is provided so as to be able to come into contact with and separate from the photoconductor drum, and after the cleaning member comes into pressure contact with the photoconductor drum, the roller pressure contact timing adjusting means brings the charging roller into pressure contact with the photoconductor drum. Good.

At the start of driving the photosensitive drum, the cleaning member, which is separated from the surface of the photosensitive drum, is pressed against the photosensitive drum after the photosensitive drum is reversely rotated by a predetermined amount. A control means for rotating the drum in the forward direction may be provided. The cleaning member of the cleaning device is a first cleaning member that can be brought into contact with and separated from the surface of the photosensitive drum, and the first cleaning member and the photosensitive member are exposed to the downstream side of the first cleaning member in the rotation direction of the photosensitive drum. It is more effective if the second cleaning member is provided so as to close the space between the body drum and the body drum.

[0009]

According to the image forming apparatus having the above structure, when the photosensitive drum starts rotating, the charging roller is separated from the photosensitive drum at that time, and the cleaning member for the surface of the photosensitive drum is started at the start of driving. When the position corresponding to is rotated until it passes the position corresponding to the charging roller, the charging roller in the separated state comes into pressure contact with the photosensitive drum, so that the charging roller is cleaned by the cleaning member of the photosensitive drum. Since it comes into contact with the portion, foreign matter such as toner does not adhere to the surface of the charging roller.

If a cleaning member is provided so as to be able to come into contact with and separate from the photosensitive drum, and the charging member is brought into pressure contact with the photosensitive drum, the charging roller is brought into pressure contact with the photosensitive drum. The charging roller can be brought into contact with the cleaned portion by the, and the cleaning member can be separated from the photosensitive drum when the photosensitive drum is stopped. It is possible to prevent the resulting deterioration of the characteristics of the pressure contact portion.

Further, when the photosensitive drum is driven, the photosensitive drum is rotated in the reverse direction by a predetermined amount, the cleaning member is pressed against the photosensitive drum, and then the photosensitive drum is normally rotated. Even if toner adheres to the downstream side of the member in the rotation direction of the photosensitive drum, the toner moves to the upstream side of the cleaning member in the separated state due to the reverse rotation of the photosensitive drum by a predetermined amount. At the position, the cleaning member is brought into pressure contact with the photosensitive drum to rotate the photosensitive drum in the forward direction, so that the toner is cleaned by the cleaning member, so that the charging roller comes into contact with the cleaned portion on the photosensitive drum. ..

When the cleaning member of the cleaning device is composed of the first and second cleaning members, even if the toner is scattered to the downstream side of the first cleaning member in the rotation direction of the photosensitive drum, Is cleaned by the second cleaning member, the charging roller comes into contact with the cleaned portion of the photosensitive drum.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic view showing the periphery of a photosensitive drum of an image forming apparatus which is an embodiment of the present invention. In this image forming apparatus, a photosensitive drum 1 is provided substantially in the center of an apparatus main body (not shown), a charging roller 2 is provided around the photosensitive drum 1 so as to be contactable with and separable from the surface of the photosensitive drum 1, and the charging roller 2
An optical system 3 as an exposing means for exposing the surface of the photoconductor charged by the above, and a developing device 4 for forming a visible image of the latent image formed on the photoconductor drum 1 by the exposure by the optical system 3 are formed. A transfer roller 5 as a transfer unit that transfers the visible image to the sheet P, and a cleaning process for cleaning the surface of the photosensitive drum 1 by the fur brush 7 and the cleaning blade 8 that is a cleaning member after the transfer roller 5 finishes the transfer. A device 6 and a quenching lamp 9 are provided.

Further, this image forming apparatus controls the driving of various drive systems in the apparatus main body, and after the photosensitive drum 1 starts rotating, the cleaning blade for the surface of the photosensitive drum 1 is started at the start of the driving. When the position Poi corresponding to 8 is rotated until it passes the position corresponding to the charging roller 2 as shown in FIG. 2, the charging roller 2 is moved from the separated state to the photosensitive drum 1 as shown in FIG. For example, the control device 10 is provided that also functions as a roller pressure contact timing adjusting unit that drives a solenoid to press the roller. The control device 10 will be described in detail later,
The cleaning blade 8 provided so as to be able to come into contact with and separate from the position shown by a solid line and an imaginary line in FIG. 2 is pressed against the photosensitive drum 1 by driving, for example, a solenoid, and then the charging roller 2
Is controlled so as to be pressed against the photosensitive drum 1.

The charging roller 2 has a cored bar portion 2a made of metal and a roller surface side made of a conductive rubber roller 2b. The charging roller 2 is mainly driven by a voltage applied between the cored bar portion 2a and the photosensitive drum 1. The photosensitive drum 1 is charged by electric discharge, and the electroconductive rubber roller 2b is brought into contact with and separated from the surface of the photosensitive drum 1 by a mechanism using a solenoid, a lever, or the like (not shown).

Further, the cleaning device 6 is formed in a unit shape, and a tip portion 8a is provided in the unit casing 11 so as to be able to come into contact with and separate from the surface of the photosensitive drum 1 by a fur brush 7 and a mechanism (not shown). Further, a cleaning blade 8 and a toner recovery coil 12 are provided, and after the transfer is completed, the fur brush 7 and the cleaning blade 8 scrape off the residual toner on the surface of the photosensitive drum 1 into the unit casing 11 to remove the toner. The collection coil 12 collects the collected product in a collection bottle (not shown) provided outside the unit.

By the way, in such an image forming apparatus, if the charging roller 2 and the cleaning blade 8 contact the surface of the photosensitive drum 1 at the same timing at the same time when the driving of the photosensitive drum 1 is started, a problem may occur. There is. That is, in the cleaning device 6, even if the residual toner or the like on the surface of the photoconductor drum 1 is scraped off by the cleaning blade 8, as shown in FIG. 1, it is on the downstream side in the rotation direction of the photoconductor drum 1 (direction indicated by an arrow A). In some cases, scattered toner T or the like remains attached to the photosensitive drum 1 in the unit casing 11, and when the portion where the scattered toner adheres reaches the position of the charging roller 2, it is charged. Since it adheres to the surface of, the electric discharge at that portion becomes insufficient.

However, in this embodiment, since each part is operated at the timing shown in FIG. 3, the above inconvenience does not occur. That is, when the print button is pressed by the image forming operation by the operator, the cleaning blade 8 is first driven by a mechanism (for example, the solenoid is turned on) not shown,
As shown in FIG. 1, the tip portion 8 a contacts the surface of the photosensitive drum 1.

Next, the photosensitive drum 1 is driven to move the arrow A.
To start rotating in the direction. Then, after the time t1 shown in FIG. 3 has elapsed since the photosensitive drum 1 started to be driven, the charging roller 2 is pressed against the photosensitive drum 1 as shown in FIG. 2, and thereafter, charging, exposure, development and transfer are performed. Each operation is performed at the timing shown in FIG.

As shown in FIG. 1, the time t1 during which the charging roller 2 is in pressure contact with the photosensitive drum 1 is between the position where the cleaning blade 8 contacts L on the surface of the photosensitive drum and the position where the charging roller 2 contacts L. When the distance (mm) and v are linear velocities (mm / sec) of the photoconductor drum, t1> (L / v), and this time is after the photoconductor drum 1 starts rotating. This is the time when the position Poi corresponding to the cleaning blade 8 on the surface of the photosensitive drum 1 at the start of the driving is rotationally moved until it passes the position corresponding to the charging roller 2 (state in FIG. 2).

By doing so, the charging roller 2
Comes into contact with the portion of the photosensitive drum 1 that is cleaned by the cleaning blade 8, so that foreign matter such as toner does not adhere to the surface of the charging roller 2.

The series of controls are all performed by the controller 10 shown in FIG. The control device 10 is a central processing unit (CPU) having various judgment and processing functions.
And a ROM that stores each processing program including various programs and fixed data, a RAM that is a data memory that stores the processing data, and an input / output circuit (I / O).

FIG. 4 is a schematic view similar to FIG. 1 showing the periphery of a photosensitive drum showing another embodiment of the image forming apparatus, and FIG. 5 shows the cleaning blade 8 of the image forming apparatus on the surface of the photosensitive drum 1. 6 is a schematic diagram showing a state in which the image forming apparatus is in contact with FIG. 6, and FIG. 6 is a timing chart showing the operation timing of each unit of the image forming apparatus. The same reference numerals are given to the portions corresponding to FIG. This image forming apparatus includes a photosensitive drum 1
5 shows the cleaning blade 8 which is in a state of being separated from the surface of the photoconductor drum 1 after the photoconductor drum 1 is reversely rotated by a predetermined amount in the direction of the arrow B as shown in FIG. As described above, the photosensitive drum 1 is brought into pressure contact with the photosensitive drum 1, and thereafter, the photosensitive drum 1 is normally rotated in the arrow A direction.

That is, in this embodiment, when the print button is pressed, the photosensitive drum 1 first rotates in the reverse direction for the time t2 shown in FIG. 6 (in the direction of arrow B in FIG. 4). As shown, the surface portion of the photosensitive drum 1 on which the foreign matter such as the scattered toner T adheres is the cleaning blade 8.
Move to the upstream side (lower side in the figure). Then, at the timing of completion of the movement, the cleaning blade 8 in the separated state is brought into pressure contact with the surface of the photoconductor drum 1, and then the photoconductor drum 1 is normally rotated in the forward direction indicated by the arrow A.

Even in this case, since the charging roller 2 comes into contact with the portion of the photosensitive drum 1 cleaned by the cleaning blade 8, foreign matter such as toner adheres to the surface of the charging roller 2. Disappears.

The time t2 is determined in consideration of the area where the toner T or the like that is normally scattered is likely to adhere to the surface of the photosensitive drum 1 and the linear velocity v (mm / sec) of the photosensitive drum 1. Further, the rotational driving of the photoconductor drum 1 in both the forward and reverse directions can be easily performed by using a special stepping motor having a drive control circuit, and its control is similar to that of the control device 10 in FIG. It is performed by the control device 20 (FIG. 4) which is a microcomputer of the configuration.

FIG. 7 is a schematic view showing the periphery of a photosensitive drum of still another embodiment of the image forming apparatus.
The same reference numerals are given to the portions corresponding to. In this image forming apparatus, the cleaning member of the cleaning device 13 serves as a first cleaning member that can be brought into contact with and separated from the surface of the photoconductor drum 1, and a downstream of the cleaning blade 8 in the rotation direction of the photoconductor drum 1. And a cleaning blade 15 serving as a second cleaning member which is provided on the side thereof so as to close the space between the cleaning blade 8 and the photosensitive drum 1 so that the tip thereof is always in contact with the surface of the photosensitive drum 1. ing.

According to this embodiment, when the cleaning blade 8 which can be brought into contact with and separated from the photosensitive drum 1 is in the separated state shown by the solid line, the scattered toner T is scattered between the tip portion of the cleaning blade 8 and the photosensitive drum 1. Even if it leaks to the downstream side in the rotation direction of the drum 1, the cleaning blade 15 that is always in contact with the surface of the photosensitive drum 1 is provided on the downstream side (upper side in FIG. 7) of the cleaning blade 8, so that the scattering thereof occurs. The toner T does not leak to the downstream side of the photosensitive drum 1 in the rotation direction. Therefore, as in the above-mentioned embodiments,
Since the charging roller 2 is always in contact with the portion of the photosensitive drum 1 that is cleaned by the cleaning blade 15, foreign matter such as toner does not adhere to the surface of the charging roller 2.

Next, the results of confirmation tests actually conducted to confirm the effects of the above-mentioned respective examples will be described. First, in a test conducted on the image forming apparatus according to the embodiment of FIG. 1, a drum having an outer diameter of φ80 (a-si system) is used as the photosensitive drum 1, and the linear velocity of the drum is set to 1.
It is set to 80 mm / sec, and the charging roller 2 is a conductive rubber roller having a high-resistance protective layer on the roller surface, which is about 1.2K.
A voltage of V 2 was applied to obtain a photoconductor potential of 550 V, and the charging roller 2 and the cleaning blade 8 were separated from the surface of the photoconductor drum when the apparatus was stopped.

When the print button is pressed to start, the cleaning blade 8 first contacts the photosensitive drum 1 according to the timing chart shown in FIG. 3, and then the photosensitive drum 1 rotates at a drum linear velocity of 180 mm / sec. From the start of rotation, t1 = 0.4 sec (L =
After the elapse of 50 mm, t1> “L / v = 0.27 sec”), the charging roller 2 is brought into pressure contact with the photosensitive drum 1, and then the surface of the photosensitive drum 1 is uniformly charged.
In this way, after the formation of three images, the presence or absence of charging unevenness due to the effect of dirt on the charging roller 2 was confirmed, and no problem was found.

Further, in the test conducted corresponding to the embodiment of FIG. 4, the drum linear velocity was set to 120 mm / sec by using the photosensitive drum 1 of φ80 similar to the above, and the charging roller 2 similar to the above was used. A voltage of about -1.4 KV is applied to obtain a photoconductor potential of -750 V, and the charging roller 2 and the cleaning blade 8 are connected to the photoconductor drum 1 when the apparatus is stopped as in the above confirmation test. It was separated from the surface.

In this test, when the print button is pressed and started, the photosensitive drum 1 is first moved in the direction of arrow B in FIG. 4 for 0.2 sec, that is, about 25 mm (L / L) in accordance with the timing chart shown in FIG. 2) The cleaning blade 8 was rotated in the reverse direction, and then the cleaning blade 8 was brought into pressure contact with the photosensitive drum 1, and at the same time, the photosensitive drum 1 was rotated in the normal direction (in the direction of arrow A in FIG. 5). In this way, after the formation of three images, the presence or absence of charging unevenness due to the effect of dirt on the charging roller 2 was confirmed, and no problem was found.

Further, in the image forming apparatus of FIG. 1, only the cleaning device of FIG. 7 is used, and the photosensitive drum 1 and the charging roller 2 are tested under the same conditions as the latter of the above two confirmation tests. As a result, when the cleaning blade 8 serving as the first cleaning member is in the separated state, the scattered toner leaked from the cleaning blade 8 is removed by the cleaning blade 15 serving as the second cleaning member on the downstream side thereof, which is in constant contact. Therefore, since the surface of the portion of the photosensitive drum 1 in contact with the charging roller 2 was always kept in the cleaning state, no uneven charging due to the influence of dirt on the charging roller was found on the three sheets of paper on which images were formed. ..

[0034]

As described above, according to the present invention, since the charging roller is always in contact with the portion of the photosensitive drum that is cleaned by the cleaning member, foreign matter such as toner adheres to the surface of the charging roller. Since this is not the case, uniform charging can be carried out over the entire surface of the photosensitive drum, so charging unevenness can be prevented.

Further, if the cleaning member is provided so as to be able to come into contact with and separate from the photosensitive drum, and the charging roller is brought into pressure contact with the photosensitive drum after the cleaning member is brought into pressure contact with the photosensitive drum, when the photosensitive drum is stopped. Since the cleaning member can be placed in the separated state, it is possible to use it even if the photoconductor has a large property change that is likely to change its properties due to constant pressure contact.

Further, when the photosensitive drum is started to rotate, the photosensitive drum is reversely rotated by a predetermined amount, the cleaning member is pressed against the photosensitive drum, and then the photosensitive drum is normally rotated. Since the charging roller can be brought into contact with the constantly cleaned portion of the photoconductor drum while being kept in pressure contact with the photoconductor drum at all times, there is no need for a mechanism for allowing the charge roller to be brought into contact with or separated from the photoconductor drum. It will be easy.

[Brief description of drawings]

FIG. 1 is a schematic view showing the periphery of a photosensitive drum of an image forming apparatus which is an embodiment of the present invention.

FIG. 2 is a schematic view showing a state in which the photosensitive drum rotates and the position Poi corresponding to the cleaning blade on the surface of the photosensitive drum has passed the position corresponding to the charging roller and the charging roller is in pressure contact. is there.

FIG. 3 is a timing chart showing the operation timing of each unit of the image forming apparatus.

FIG. 4 is a schematic view similar to FIG. 1 showing the periphery of a photosensitive drum showing another embodiment of the image forming apparatus.

FIG. 5 is a schematic view showing a state in which the cleaning blade of the image forming apparatus is in contact with the surface of the photosensitive drum.

FIG. 6 is a timing chart showing the operation timing of each unit of the image forming apparatus.

FIG. 7 is a schematic view showing the periphery of a photosensitive drum of still another embodiment of the image forming apparatus.

[Explanation of symbols]

1 Photoconductor drum 2 Charging roller 3 Optical system (exposure means) 4 Developing device 5 Transfer roller (transfer means) 6,13 Cleaning device 7 Fur brush 8,15 Cleaning blade 10,20 Control device

Claims (4)

[Claims] 1. A photosensitive drum, a charging roller provided on the surface of the photosensitive drum so as to be able to come into contact with and separate from the surface of the photosensitive drum, an exposing means for exposing the surface of the photosensitive body charged by the charging roller, and a latent image formed by the exposure. An image including a developing device for forming a visible image, a transfer unit for transferring the formed visible image onto a sheet, and a cleaning device for cleaning the surface of the photosensitive drum with a cleaning member after the transfer by the transfer unit is completed. In the forming apparatus, after the photosensitive drum starts rotating, when the position corresponding to the cleaning member on the surface of the photosensitive drum at the start of driving is rotationally moved until it passes the position corresponding to the charging roller. An image forming apparatus comprising a roller pressure contact timing adjusting means for contacting the charging roller with the photosensitive drum in a separated state. 2. The image forming apparatus according to claim 1,
The cleaning member is provided so as to be able to come into contact with and separate from the photoconductor drum, and after the cleaning member comes into pressure-contact with the photoconductor drum, the roller pressure contact timing adjusting means brings the charging roller into pressure contact with the photoconductor drum. Image forming apparatus. 3. A photosensitive drum, a charging roller for charging the surface of the photosensitive drum, an exposing unit for exposing the surface of the photosensitive member charged by the charging roller, and a latent image formed by the exposure to a visible image. Image forming provided with a developing device, a transfer device for transferring the formed visible image to a sheet, and a cleaning device for cleaning the surface of the photosensitive drum with a cleaning member capable of contacting and separating after the transfer by the transfer device is completed. In the apparatus, at the start of driving the photoconductor drum, the photoconductor drum is reversely rotated by a predetermined amount, and then the cleaning member separated from the surface of the photoconductor drum is pressed against the photoconductor drum, and then the cleaning member is pressed. An image forming apparatus comprising a control means for rotating a photosensitive drum in a forward direction. 4. A photosensitive drum, a charging roller for charging the surface of the photosensitive drum, an exposing unit for exposing the surface of the photosensitive member charged by the charging roller, and a latent image formed by the exposure to a visible image. An image forming apparatus comprising: a developing device; a transfer device that transfers the formed visible image to a sheet; and a cleaning device that cleans the surface of the photosensitive drum with a cleaning member after the transfer by the transfer device is completed. A cleaning member of a cleaning device is a first cleaning member that can be brought into contact with and separated from the surface of the photoconductor drum, and the first cleaning member and the photoconductor are located downstream of the first cleaning member in the rotation direction of the photoconductor drum. An image forming apparatus comprising a second cleaning member provided so as to close a space between the drum and the drum.