JPH08220846A - Electrifying device - Google Patents

Abstract

PURPOSE: To prevent an abnormal image from being formed because the surface of an electrifying roller is stained by toner and normal electrification can not be performed. CONSTITUTION: The quantity of the toner adhering to the surface of the electrifying roller 2 is detected by a sensor 51, and a control means 60 drives a separation mechanism 20 in accordance with the detected value corresponding to the stain by the toner so as to separate the roller 2 from a photoreceptor drum 1 and bring the roller 2 into contact with a cleaning member 22, then, the roller 2 is rotated in such a state, whereby the surface of the roller 2 is cleaned. By making the sensor 51 movable in the shaft direction of the roller 2 or plurally disposing the sensor 51 in the shaft direction thereof so that the quantity of toner may be detected at plural spots in the shaft direction of the roller 2, the irregular electrification in the shaft direction of the roller 2 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member that rotates while contacting a rotating photosensitive member to charge the photosensitive member, and a cleaning means for cleaning a surface of the charging member that contacts the photosensitive member. The present invention relates to a charging device including.

[0002]

2. Description of the Related Art For example, in the case of a contact type charging device having a charging roller (charging member) that rotates while contacting the surface of a rotating drum-shaped photosensitive member, the charging Since the roller is in contact with the surface of the photoconductor, the residual toner cannot be completely cleaned from the surface of the photoconductor by the cleaning unit that cleans the surface of the photoconductor after the transfer of the image. There is a possibility that an abnormal image may be generated in which the toner adheres to the surface of the sheet, the normal charging operation cannot be performed, and streaks are formed on the image transferred to the transfer sheet. Therefore, in the case of a contact type charging device in which such a charging roller is brought into contact with the surface of the photoconductor, a cleaning member for cleaning the surface of the charging roller in contact with the photoconductor is provided.

[0003]

However, if the surface of the charging roller is constantly cleaned with such a cleaning member, excessive cleaning causes damage to the surface of the charging roller, which causes abnormalities. Secondary problems such as images are likely to occur.

Therefore, for example, in Japanese Unexamined Patent Publication No. 5-188738, a swingingly supported charging roller is separated from the surface of the photosensitive member by turning on a solenoid at a predetermined timing when the copying process is completed. Cleaning member whose surface is formed of a porous member (cleaning member)
There is disclosed a contact type charging device in which the charging roller is brought into contact with the surface of the charging roller and the charging roller is rotated to clean the surface of the charging roller. According to this charging device,
Since the surface of the charging roller is not constantly cleaned, it is possible to prevent the surface from being scratched.

However, in such a charging device, even if the charging roller suddenly becomes dirty during image formation, the charging operation is continued in the dirty state. Therefore, there is a problem that an abnormal image occurs. Such a problem similarly occurs in the charging device in which the cleaning operation of the charging roller is performed every predetermined number of image formations.

That is, when the image forming operation is started after cleaning the charging roller and the charging roller is abruptly soiled at a relatively early stage after that, the next cleaning time (predetermined image Since the charging operation is continued until the number of formed sheets reaches), there is a problem that an abnormal image occurs. And
In the case of such a charging device, when the image forming operation is stopped while the charging roller soiled with the toner is left as it is for a long time as described above, the toner adhered to the surface of the charging roller is left behind. However, since it becomes difficult to perform cleaning, the deterioration of the charging roller is accelerated due to this.

The present invention has been made in view of the above problems, and it is an object of the present invention to prevent the occurrence of an abnormal image because normal charging cannot be performed due to the surface of a charging member being soiled with toner. To do.

[0008]

In order to achieve the above object, the present invention provides a toner amount detecting means for detecting the amount of toner adhering to the surface of a charging member in a charging device as described above, and a toner amount detecting means therefor. The control means controls the cleaning operation of the cleaning means according to the detection value of the detection means. Further, in the above charging device, means for moving the sensor portion of the toner amount detecting means in the axial direction of the charging member is provided, and the sensor portion is moved by the means so that the toner amount is measured at a plurality of positions in the axial direction of the charging member. Should be detected.

Further, a plurality of sensor portions of the toner amount detecting means are arranged in the axial direction of the charging member, and the toner amount detecting means detects the toner amount at a plurality of positions in the axial direction of the charging member. Good. In any one of the above charging devices, the control means applies a voltage to the charging member when the detection value of the toner amount detection means continuously exceeds a predetermined value a predetermined number of times or more during an image forming operation. And a means for starting the cleaning operation by the cleaning means.

Alternatively, in the charging device, when the detection value of the toner amount detecting means exceeds a predetermined value continuously for a predetermined number of times or more, the charging member is separated from the photoconductor to stop the image forming operation. Should be provided. further,
In any one of the above charging devices, the sensor unit of the toner amount detecting means is a reflection type photo sensor that detects the amount of toner adhering to the surface of the charging member by a change in the reflected light amount of the light irradiated on the surface. It is good to do so.

[0011]

In the charging device constructed as described above, the cleaning operation by the cleaning means is controlled according to the amount of dirt due to the toner adhering to the surface of the charging member detected by the toner amount detecting means, so that the surface of the charging roller is controlled. Since it is not excessively cleaned, scratches on the surface can be prevented and stable charging can be performed. Further, even if the surface of the charging member is abruptly contaminated with toner during the image forming operation, the cleaning operation can be performed immediately after the contamination is detected. The deterioration of the member can be suppressed.

Further, means for moving the sensor portion of the toner amount detecting means in the axial direction of the charging member is provided, and the sensor portion is moved by the means to detect the amount of toner at a plurality of positions in the axial direction of the charging member. By doing so, it is possible to prevent uneven charging in the axial direction of the charging member and to uniformly charge the entire area of the photosensitive member. Also, a plurality of sensor units of the toner amount detecting means may be arranged in the axial direction of the charging member, and the toner amount detecting means may detect the toner amount at a plurality of positions in the axial direction of the charging member. In addition, it is possible to prevent uneven charging in the axial direction of the charging member and to uniformly charge the entire area of the photosensitive member.

Further, the control means stops the voltage application to the charging member when the detection value of the toner amount detecting means exceeds a predetermined value continuously a predetermined number of times during the image forming operation, and the cleaning means. If the charging member is abruptly contaminated with the toner during the image forming operation, the voltage application to the charging member is stopped and the charging member is started. Since the cleaning is started, it is possible to prevent the occurrence of an abnormal image.

Further, if a means for separating the charging member from the photoconductor and stopping the image forming operation is provided when the detection value of the toner amount detecting means exceeds the predetermined value continuously a predetermined number of times or more, Even if there is a problem with the device that cleans the surface of the photoconductor and the surface of the photoconductor is not cleaned and a large amount of residual toner adheres to the surface of the charging roller, Since it is possible to detect the stain caused by the above and stop the image forming operation, it is possible to minimize the abnormal charging operation.

Further, the sensor portion of the toner amount detecting means is
If a reflection type photo sensor that detects the amount of toner adhering to the surface of the charging member by the change in the reflected light amount of the light irradiated on the surface is used, the amount of toner adhering to the surface of the charging member By detecting the amount by the change in the amount of reflected light, the amount of the toner can be accurately detected, and the charging member can be cleaned with high accuracy corresponding thereto.

[0016]

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 diagram showing a part of a charging device and a control system thereof according to an embodiment of the present invention, and FIG. 2 is an overall configuration diagram showing an entire image forming apparatus equipped with the charging device. The image forming apparatus shown in FIG. 2 includes a contact charging type charging device 10 including a charging roller 2 that is a charging member that charges a photosensitive drum (image carrier) 1 in a contact state.
The charging roller 2 of the charging device 10 is driven at a constant speed in the arrow B direction by contacting with the photosensitive drum 1 rotating in the arrow A direction at a predetermined peripheral speed as shown by the solid line in FIG. By rotating, the surface 1a of the photosensitive drum 1 is uniformly charged to a predetermined potential.

The photoconductor drum 1 is driven by a photoconductor drive system including a drum drive timing belt, a drum drive pulley, a motor for driving them (all are not shown), and a surface 1a thereof is driven. Charging roller 2
However, due to the urging force of a spring provided in a mechanism to be described later, for example, the contact pressure is 10 g / cm (substantially linear contact). Around the photosensitive drum 1, an eraser 18 in addition to the charging roller 2, a developing device 6, a contact type transfer device 7 having an endless belt 7a, and a cleaning unit 8 are provided.
And a static eliminator 21 are provided respectively.

The light from the exposure device 9 (only the mirror portion is shown) is incident on the surface 1a of the photosensitive drum 1, and the charging surface uniformly charged by the charging roller 2 is exposed. An electrostatic latent image is formed on the electrostatic latent image. The electrostatic latent image is removed (trimmed) from an electrostatic charge in an area outside the size of the transfer paper P used by the eraser 18, and the remaining electrostatic latent image is The toner is developed by the toner supplied by the developing sleeve 6a of the developing device 6 to form a toner image (visible image).

On the other hand, the transfer paper P in a paper feed cassette (not shown) is sent out one by one by a paper feed roller which rotates at a predetermined timing, and the transfer paper P is pressed by the registration roller 13 and the pressure roller 14 which rotates in pressure contact therewith. Then, after being temporarily stopped and the timing is adjusted, the sheet is conveyed toward the transfer portion provided with the transfer device 7 at an accurate timing that matches the toner image on the photosensitive drum 1. A transfer device 7 applies a transfer bias to the transfer paper P to transfer a toner image to the upper surface side in FIG. 2, and the toner image is separated from the photosensitive drum 1 and conveyed to a fixing device (not shown), where the toner is fixed. After being discharged, the sheet is discharged to a discharge tray or the like outside the apparatus.

After the transfer, the photosensitive drum 1
Foreign matter such as residual toner and paper dust remaining on the cleaning blade 8 is provided in the cleaning unit 8.
The residual potential removed by a and remaining on the photosensitive drum 1 is removed by the static eliminator 21 to prepare for the next charging by the charging roller 2.

As shown in FIG. 1, the charging roller 2 has an elastic layer 16 made of a medium resistance material such as rubber or resin integrally mounted on the outside of a conductive core metal 15 made of iron or the like, and its surface is The surface is covered with a surface layer for the purpose of protecting a very thin high resistance thin film having a thickness of only 4 μm to a dozen μm.
It is held so that it can be moved toward and away from.

Both ends of the electrically conductive cored bar 15 of the charging roller 2 are rotatably supported by electrically conductive bearings 17, 17, and the electrically conductive bearings 17 are made of a conductive material and are tensioned. It is constantly urged by the biasing spring 12 in a direction away from the photosensitive drum 1, and the charging roller 2 is in the spaced position shown by the solid line in the figure when charging is not performed. Four
Reference numeral 0 denotes a fixing member made of an insulating material, and the tension urging spring 12
Fasten one end of. When the charging roller 2 is in contact with the surface 1a of the photoconductor drum 1, the conductive core metal 1
5 from the high voltage generating circuit 50 through the tension biasing spring 12 and the conductive bearing 17 to the charging bias voltage (for example, -500).
V) is applied so that the surface 1a of the photosensitive drum 1 is uniformly charged.

The contacting / separating mechanism 20 for contacting / separating the charging roller 2 with respect to the photosensitive drum 1 is obtained by fixing a conductive bearing 17 to one end of an arm 23 whose center is swingably supported by a shaft 24. Holds the charging roller 2 rotatably,
The movable shaft 26 of the solenoid 26 is attached to the other end of the arm 23.
The a is attached via the spring 25. A pair of arms 23 are provided to support both ends of the charging roller 2 by fixing the conductive bearings 17 on both sides of the charging roller 2 to them.

The main body of the solenoid 26 is fixed to the fixed portion of the apparatus, and the tension urging spring 12 is the solenoid 2.
6 is in the off state, the arm 23 is swung counterclockwise to the position shown by the solid line in FIG.
Is set to a position separated from the photosensitive drum 1. When the solenoid 26 is turned on, the arm 23 swings in the clockwise direction in FIG. 3 against the tension urging force of the tension urging spring 12 and moves to the position indicated by the phantom line. Two
The charging roller 2 comes into contact with the surface 1a of the photoconductor drum 1 at a predetermined contact pressure suitable for charging due to a slight extension of 5.

A cleaning member 22 made of a porous material such as a sponge is provided close to the charging roller 2 to clean the surface of the charging roller 2 that contacts the photosensitive drum 1. Then, when the solenoid 26 is in the off state, as shown by the solid line in FIG.
Is brought into contact with the cleaning member 22 at a predetermined contact pressure suitable for cleaning by the tension urging force of the tension urging spring 12, and the charging roller 2 is rotated in that state to clean the surface.

When the charging roller 2 is in pressure contact with the surface 1a of the photosensitive drum 1, the charging roller 2 is rotated by the rotational force received from the photosensitive drum 1, as shown by the phantom line in FIG. At a position where the roller drive gear 58 is separated from the photoconductor drum 1 and comes into contact with the cleaning member 22, a roller drive gear 58 correspondingly engaged with a gear (not shown) integrally fixed to the conductive core metal 15. hand,
It is rotated independently.

A sensor 51, which serves as a sensor portion of toner amount detecting means for detecting the amount of toner adhering to the surface of the charging roller 2 in proximity to the charging roller 2, for example, the charging device 10 is used as a photosensitive drum. It is fixed to a cartridge case 52 that is integrally held together with the roller 1 with a distance G from the surface of the charging roller 2.

As shown in FIG. 4, the sensor 51 is composed of a light emitting element 51a and a light receiving element 51b. The light emitting element 51a irradiates the surface of the charging roller 2 with a constant amount of light, The reflected light is received by the light receiving element 51.
b is a reflection type photo sensor that detects the amount of toner adhering to the surface of the charging roller 2 based on the change in the amount of reflected light.

Since the sensor 51 is always opposed to the surface of the charging roller 2 as shown in FIG. 1, when the charging roller 2 is in contact with the surface 1a of the photosensitive drum 1, The amount of toner adhering to the surface of the charging roller 2 can be detected regardless of the state of being separated from the surface 1a. The control unit 60 controls the cleaning operation of the charging roller 2 by the cleaning member 22 according to the detected value corresponding to the detected amount of toner.

The control means 60 includes a central processing unit (CPU) 61 having various judgment and processing functions, and processing programs including programs necessary for controlling the cleaning operation of the charging roller 2 by the cleaning member 22 and fixed processing programs. It is a microcomputer including a ROM 62 that stores data, a RAM 63 that is a data memory that stores processed data, an input interface 64, and an output interface 65.

The control means 60 inputs from the sensor 51 a signal which changes according to the amount of toner adhering to the surface of the charging roller 2 and performs a predetermined image forming operation on each part of the image forming apparatus. For this purpose, various signals are respectively input from various sensors that are respectively provided. Then, a signal for bringing the charging roller 2 into and out of contact with the photosensitive drum 1 is output to the contacting / separating mechanism 20, and the high voltage generating circuit 50 is driven to drive the charging roller 2 into the photosensitive member. A signal for charging the drum 1 is output, and various drive signals and the like are also output to various other loads at a predetermined timing.

Charging roller 2 detected by sensor 51
Data indicating the amount of toner adhering to the surface of the
Once stored in 63, the toner amount is detected again based on the signal from the sensor 51 after the lapse of the predetermined time (or after the completion of the predetermined number of image forming operations), and the toner amount and the RAM 63. The amount of dirt on the surface of the charging roller 2 is determined by comparing the difference with the data indicating the amount of toner stored in the above.

That is, as shown in FIG. 5, the charging roller 2
Let a be the amount of reflected light when toner hardly adheres to the surface of the sheet, and b be the amount of reflected light under certain conditions where the toner has adhered to the surface of the charging roller 2, which is stored in the ROM 62 of the control means 60. In accordance with the data showing the relationship between the amount of reflected light and the amount of dirt on the charging roller shown in the figure, the amount of dirt on the surface of the charging roller 2 due to toner (b′−
Calculate with a ').

If the difference (b'-a ') is larger than a preset value, the control means 60 determines that the surface of the charging roller 2 needs to be cleaned, and will be described with reference to FIG. The contacting / separating mechanism 20 is operated to separate the charging roller 2 from the surface 1a of the photoconductor drum 1 and bring it into contact with the cleaning member 22. Then, the charging roller 2
Is rotated for a cleaning time which is stored in advance in the ROM 62 and corresponds to the amount of dirt on the surface of the charging roller 2 over time, and the surface of the charging roller 2 is cleaned for a predetermined time.

6 and 7 are schematic views showing an embodiment in which a sensor for detecting toner on the surface of the charging roller is arranged so as to be movable in the axial direction of the charging roller. In this embodiment, one sensor 51 is arranged so as to be movable along the guide member 54 in the axial direction of the charging roller 2, and the toner adhered to the surface of the charging roller 2 at a plurality of positions in the axial direction. The amount of each is detected. Then, when the main switch is turned on or at a predetermined time interval, the sensor moving means 70 causes the sensor 51 to move the shaft of the charging roller 2 according to a program stored in advance in the ROM of the control means (see ROM 62 of FIG. 1). Direction (left and right in FIG. 6).

The sensor moving means 70, for example, attaches a wire between pulleys provided rotatably in proximity to both ends of the charging roller 2 and attaches the sensor 51 to a part of the wire to attach the sensor 51. To reciprocate linearly, or to screw a female screw member integrally fixing the sensor 51 into a male screw arranged in parallel over substantially the entire axial length of the charging roller 2 and rotate the male screw. Although a mechanism for linearly moving the sensor 51 back and forth is used according to the above, other known linear movement mechanism may be used.

Also in this embodiment, like the charging device 10 described with reference to FIGS. 1 to 5, the charging roller 2 is rotated together with the photosensitive drum during the image forming (copying) operation. By moving the sensor 51 in the axial direction of the charging roller 2 while rotating,
The amount of adhered toner can be detected over the entire surface of the charging roller 2.

In this embodiment, for example, the sensor 5
While moving 1 in the axial direction of the charging roller 2 once (moving from one end to the other end), the toner amount is detected n times as shown in FIG. When there is a section in which the amount of stains equal to or more than the amount (toner adhesion amount) c is detected, the cleaning operation is executed. The control is performed by the control means, which is a microcomputer similar to the control means 60 described in FIG. 1, but the configuration thereof is the same as that of the control means 60 described above, and therefore its illustration is omitted here.

As another control method, control may be performed such that when the deviation of n data exceeds a predetermined deviation, it is determined that the amount of dirt on the charging roller 2 has increased. . Further, the axial distance of the charging roller 2 is divided into n sections, and the charging roller 2 in each section is divided.
RA data in the control means based on the data of the dirt on the surface of the
It may be stored in M (see RAM 63 in FIG. 1) and the increase in the amount of dirt may be detected based on the difference between the (m-1) th data and the mth data.

FIG. 8 is a schematic view showing an embodiment in which a plurality of sensors for detecting toner on the surface of the charging roller are arranged in the axial direction of the charging roller. In this embodiment, a plurality of sensors 51 for detecting the toner on the surface of the charging roller 2 are arranged at equal intervals in the axial direction of the charging roller 2.
When any one or more of the plurality of sensors 51 detects the dirt due to the toner having a predetermined value or more, the control means (similar to the control means 60 in FIG. 1 and shown in FIG. 8). Is omitted) starts the cleaning operation. The method of detecting the amount of dirt on the surface of the charging roller 2 due to the toner is the same as in the embodiment described with reference to FIGS. 6 and 7.

When the detection value detected by the sensor 51 during the image forming operation continuously exceeds the predetermined value a predetermined number of times or more, the voltage application to the charging roller 2 is stopped and the cleaning member 22 is used. The cleaning operation of the charging roller 2 may be started. By doing so, for example, when the image forming operation (copying operation) is continuously performed for a long time, the sensor 51 is used to detect the surface of the charging roller 2 by any one of the above-described embodiments. When the amount of dirt due to toner is detected and the dirt exceeds a predetermined value for a predetermined number of times or more in succession, the voltage application to the charging roller 2 is stopped and the contact / separation mechanism 20 (FIG. 3) causes the charging roller 2 to move. Is separated from the surface of the photoconductor drum 1 and the cleaning operation is started by the rotation of the charging roller 2 (state shown by a virtual line in FIG. 1), so that an abnormal image is prevented from occurring and the image quality is always stable. Image is obtained.

If the amount of dirt (detection value) detected by the sensor 51 exceeds a predetermined value continuously for a predetermined number of times or more, the charging roller 2 is moved to the surface 1a of the photosensitive drum 1.
Alternatively, the image forming operation may be stopped. By doing this, as shown in FIG. 9, when a considerable amount of toner is detected to be attached over the entire section (1, 2, ... N) of each detection position along the axial direction of the charging roller 2, or It is considered that a failure has occurred in the cleaning unit (see the cleaning unit 8 in FIG. 2) for cleaning the surface of the photosensitive drum 1 as when it is detected that the amount of adhered toner exceeds the predetermined number of times continuously. In such a case, the image forming (copying) operation can be immediately stopped and the serviceman call can be displayed. Therefore, it is possible to detect dirt on the charging roller 2 at an early stage and replace or maintain it, so that abnormal operation can be minimized. In addition, by responding early, it is possible to prevent adverse effects on other units.

[0043]

As described above, according to the present invention, the following effects can be obtained. According to the charging device of the first aspect, since the amount of dirt due to the toner adhering to the surface of the charging member is detected and the charging member is cleaned according to the amount of dirt, the surface of the charging roller is excessively cleaned. As a result, the surface of the charging member is not damaged, so that the surface of the charging member can be prevented from being damaged and stable charging can be performed.

According to the charging device of the second and third aspects, since the stains due to the toner adhering to the surface of the charging member can be detected over the entire surface of the charging member, the charging unevenness in the axial direction of the charging member can be detected. It is possible to prevent the above-mentioned phenomenon and obtain uniform charging over the entire area of the photoconductor.

According to the charging device of claim 4, even when the charging member is abruptly soiled with the toner while the image forming operation is continuously performed for a long time, the contamination is set to a predetermined value or more a predetermined number of times or more. When the voltage is continuously exceeded, the voltage application to the charging member is stopped and the cleaning of the charging member is started. Therefore, it is possible to prevent the occurrence of an abnormal image and always obtain an image with stable image quality. Further, if toner is left on the surface of the charging member and left as it is, stains that would be difficult to clean later are found and cleaned early. Can be prevented.

According to the charging device of the fifth aspect, a device for cleaning the surface of the photoconductor may have a problem, or a large amount of residual toner on the surface of the photoconductor that has not been cleaned may adhere to the surface of the charging roller. Even in such a case, the stain on the charging roller due to the toner can be found early and replaced or maintained, so that the abnormal charging operation can be minimized. In addition, since the above-mentioned problem can be found early, it is possible to prevent adverse effects on other units.

According to the charging device of the sixth aspect, since the amount of toner adhering to the surface of the charging member is detected by the change amount of the reflected light amount, the amount of toner is accurately detected and the accuracy corresponding thereto is detected. It is possible to clean the surface of the charging member having a high charge.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a part of a charging device according to an embodiment of the present invention and a control system thereof.

FIG. 2 is an overall configuration diagram showing an entire image forming apparatus equipped with the charging device.

FIG. 3 is a schematic configuration diagram showing a contacting / separating mechanism for contacting / separating the charging roller of the charging device with respect to the surface of the photosensitive drum.

FIG. 4 is a schematic view showing how a light receiving element detects reflected light of light emitted from a light emitting element toward a charging roller by a reflection type photo sensor which is a sensor portion of a toner amount detecting means of the charging device. is there.

5 is a diagram showing the relationship between the amount of reflected light from the sensor and the amount of dirt on the charging roller stored in the ROM of the control system shown in FIG.

FIG. 6 is a schematic view showing a state in which a sensor for detecting toner on the surface of the charging roller is movably arranged in the axial direction of the charging roller, and the surface of the charging roller is not contaminated with the toner.

FIG. 7 is a schematic view showing a state in which the surface of the charging roller is also soiled with toner.

FIG. 8 is a schematic view showing an embodiment in which a plurality of sensors for detecting toner on the surface of the charging roller are arranged in the axial direction of the charging roller.

FIG. 9 is a schematic view similar to FIGS. 6 and 7, showing a case where a considerable amount of toner is detected to be detected over the entire section of each detection position along the axial direction of the charging roller.

[Description of Reference Signs] 1: Photosensitive drum 2: Charging roller (charging member) 10: Charging device 20: Contact / separation mechanism 22: Cleaning member 51: Sensor (sensor part) 51a: Light emitting element 51b: Light receiving element 54: Guide member 60: Control means

Claims (6)

[Claims] 1. A charging device comprising: a charging member that rotates while contacting a rotating photosensitive member to charge the photosensitive member; and a cleaning unit that cleans a surface of the charging member that contacts the photosensitive member. In the above, a toner amount detecting means for detecting the amount of toner adhering to the surface of the charging member and a control means for controlling the cleaning operation by the cleaning means according to the detection value of the detecting means are provided. Characteristic charging device. 2. The charging device according to claim 1, further comprising means for moving a sensor portion of the toner amount detecting means in an axial direction of the charging member, the means moving the sensor portion to cause the charging member to move. A charging device, wherein the amount of toner is detected at a plurality of positions in the axial direction. 3. The charging device according to claim 1, wherein a plurality of sensor portions of the toner amount detecting means are arranged in the axial direction of the charging member, and a plurality of sensor portions in the axial direction of the charging member are provided by the toner amount detecting means. A charging device, wherein the amount of the toner is detected at a location. 4. The charging device according to claim 1, wherein the control unit continuously sets a detection value of the toner amount detection unit to a predetermined value a predetermined number of times or more during an image forming operation. The charging device is a means for stopping the voltage application to the charging member and starting the cleaning operation by the cleaning means when the voltage exceeds. 5. The charging device according to claim 1, wherein when the detection value of the toner amount detecting means exceeds a predetermined value continuously for a predetermined number of times or more, the charging member. A charging device, which is provided with means for separating the image forming device from the photoconductor to stop the image forming operation. 6. The charging device according to claim 1, wherein the sensor unit of the toner amount detecting unit irradiates the surface of the charging member with the amount of toner adhering to the surface. A charging device, which is a reflective photosensor that detects a change in the amount of reflected light.