JPH09297456A - Cleaning device for electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent photoreceptor electrification irregularity right after cleaning a discharge wire for the removal of its soiling. SOLUTION: This device is equipped with a cleaning drive means 116 for pressing cleaning members Cp, which are brought into contact with an electrifying member 115 and separated therefrom, against the electrifying member and drives the ones Cps in relation to the other 115, and a control means for testingly electrifying and energizing the electrifying member 115 for the stabilization of electrification right after cleaning. Further, by providing a detection means for detecting the presence or absence of photoreceptor electrification irregularity, the control means testingly electrifies and energizes the electrifying member 115 right after cleaning until the detection means detects the absence of the electrification irregularity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called electrophotographic system in which a photoconductor is charged and a charged surface is exposed to image light to form an electrostatic latent image, and the electrostatic latent image is visualized by a developing device. Image forming apparatus, and more particularly, to a cleaning device for cleaning a charging member that charges a photoconductor for high quality image formation.

[0002]

2. Description of the Related Art Charging members include a corona charger and a contact charger (for example, a charging roller), but they are contaminated by toner used for development and discharge products generated when the photosensitive member is charged by the charging member. It is known. Therefore,
Cleaner for cleaning the charging member (discharge wire, charging roller)
Various charging devices have been devised and implemented, and the charging device is mainly used to regularly clean the charging member.

For example, Japanese Patent Application Laid-Open No. 4-86766 discloses that
In order to reliably remove the stain on the discharge wire of the corona charger, cleaning control for changing the number of times of wire cleaning according to the stain on the wire has been proposed. Japanese Utility Model Laid-Open No. 62-69259 discloses a discharge wire. Cleaning control is proposed in which a large number of current distribution detecting means are juxtaposed to detect the current distribution, and when the variation in the current distribution becomes large, the cleaning is started assuming that there is contamination.

[0004]

The charging member, for example, the discharge wire of the corona charger, is gradually soiled and deteriorated by the discharge, so that the soiling of the wire gradually progresses before the discharge unevenness becomes apparent. At the initial stage, the wire is only contaminated on the surface, and if the adhered substance can be removed by cleaning the surface, the original uniform discharge state can be maintained.

However, as the discharge time and the leaving time become longer, the adhered substances on the surface gradually start to fuse to the wire, and the stains that cannot be removed at the initial stage and remain on the wire also fuse. To go. Since it becomes difficult to remove the fused soil from the wire over time, it is desirable to remove the fused soil as early as possible.However, once the fused soil is removed, the portion is removed from the surface of the wire. The properties may change, the discharge may be temporarily unstable, and cleaning may rather cause uneven discharge. In order to return to a uniform discharge state, it is necessary to discharge for a while.

If an image is formed in a state where this discharge is unstable, the photosensitive member is not uniformly charged, and charging unevenness appears in the image. Also, if you perform process control in this state,
There is a possibility that the discharge state is stable during the process control and the image does not become apparent, but there is a risk that the wrong process setting will be made visible in the subsequent image formation, or the process control will be disturbed. is there. For example, a test pattern image is projected on a photoreceptor to detect a potential at the site, and adjust a charging voltage applied to a discharge wire.
Alternatively, in the case of a process control for generating a visualized image of a test pattern on a photoreceptor and adjusting or controlling a developing bias or toner replenishment of a developing device in accordance with the visualized image density, the photoreceptor potential or visualization due to charging unevenness is obtained. The process parameters (charging voltage, developing bias, toner replenishment) are erroneously set due to the high and low image densities.

The present invention aims to solve this problem.

[0008]

The cleaning device of the present invention comprises a cleaning member (Cp) which comes in contact with and separates from a charging member (115) connected to a charging power source for charging the photoconductor (9). ); The cleaning member (Cp) is applied to the charging member (115) and one of them (C
Cleaning drive means for driving (p) relative to the other (115)
(116 to 118); and immediately after the cleaning of the charging member (115) by the cleaning member (Cp) and the cleaning driving means (116 to 118), the charging member (115) is tentatively charged and biased in order to stabilize the charging. Control means (69) for controlling. In addition, in order to facilitate understanding, the reference numerals of the corresponding elements in the embodiments shown in the drawings and described later are added for reference in parentheses.

According to this, during the trial charging bias of the charging member (115) immediately after cleaning the charging member (115), the charging member (115) is
The charging characteristics of the image are stabilized, the charging unevenness is reduced when the charging force is applied for the subsequent image formation, and the image density unevenness is reduced.
Disturbance does not occur in the process control.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The cleaning device of the present invention further includes a detection means (13) for detecting the presence or absence of charging unevenness of the charging of the photoconductor (9) by the charging member (115), The means (69), immediately after cleaning the charging member (115), urges the charging member (115) by trial charging to stabilize the charging, and detects the detecting means (13).
When it detects that there is no charging unevenness, the trial charging bias is ended.

According to this, since the charging unevenness is actually measured and the trial charging bias is terminated when the charging unevenness disappears, there is no charging unevenness at the time of charging bias for the subsequent image formation, and the waiting time is eliminated. Is the shortest.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0013]

FIG. 1 shows an outline of the mechanism of a color copying apparatus equipped with a cleaning device according to an embodiment of the present invention, and FIG. A color image reading device (hereinafter, referred to as a color scanner) 1 forms an image of a document 3 on a color sensor 7 (7R, 7G, 7B) through an illumination lamp 4, a mirror group 5, and a lens 6, and
The color image information of the original is read for each of red (Red), green (Green), and blue (Blue) color separation lights, and is converted into an electric image signal.

The color sensor 7 includes R, G, and
The B color separation filters 72R, 72G, and 72B (FIG. 6) and the CCDs 7R, 7G, and 7B (photoelectric conversion elements) perform three-color simultaneous reading. Then, based on the R, G, and B color separation image signal intensity levels obtained by the color scanner 1, color conversion processing is performed by the image processing units 33 and 67 (FIG. 6), and black (Black, hereinafter Bk) , Yellow (hereinafter referred to as Y), magenta (Magenta, hereinafter referred to as M) and cyan (Cyan, hereinafter referred to as C) color image data are obtained.

By using a color image recording device (hereinafter referred to as a color printer) 2 described below, Bk,
The visualization of Y, M, and C is performed to obtain a final color copy. The operation of the color scanner 1 for obtaining the image data of Bk, Y, M, and C is such that the illumination / mirror optical system shown in FIG. Scans the document in the direction of the left arrow, and obtains one color image data for each scan. By repeating this operation a total of four times, sequential four-color image data is obtained. Then, each time, while being visualized sequentially by the color printer 2, the images are superimposed on the transfer belt 19 to form a full-color image of four colors and transferred to transfer paper (recording paper).

Next, the outline of the color printer 2 will be described. The writing optical unit 8 converts color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to a document image, and forms an electrostatic latent image on the photosensitive drum 9. The unit 8 includes a laser 8-1, a light emission drive control unit (not shown), a polygon mirror 8-2, a rotation motor 8-3, an f / θ lens 8-4, a reflection mirror 8-5, and the like. Have been.

The photoconductor drum 9 rotates counterclockwise as indicated by the arrow, around which a photoconductor cleaning unit (including a pre-cleaning static eliminator) 10, a static elimination lamp 11, a charger 12, and a potential sensor 13 are provided. , Bk developing device 1
4, a C developing device 15, an M developing device 16, a Y developing device 17, a developing density pattern detector 18, an intermediate transfer belt 19 and the like are arranged.

Each developing device rotates a developing sleeve (14-1, 15-1, 16-1, 17-) by bringing a brush of the developer into contact with the surface of the photosensitive member 9 to develop the electrostatic latent image. 1)
And a developing paddle (14-2, 15-2, 16-2, 17-2) which rotates to pump and agitate the developer, and a toner concentration detection sensor (14-3, 15) for the developer.
-3, 16-3, 17-3).

Now, in the standby state, all the four developing devices are
Although the agent on the developing sleeve is in the state of cutting off (development inoperative), the order of the developing operation (color image forming order) is
An example of Bk, C, M, and Y will be described below (however, the image forming order is not limited to this).

When the copy operation is started, the color scanner 1 starts to read Bk image data at a predetermined timing, and optical writing / latent image formation by laser light is started based on the image data (hereinafter referred to as Bk image data). The electrostatic latent image by Bk is referred to as a Bk latent image. The same applies to C, M, and Y). Before the latent image front end reaches the developing position of the Bk developing device 14 so that development can be performed from the front end of the Bk latent image, the rotation of the developing sleeve 14-1 is started to spike the agent, and the Bk latent image is formed. The image is developed with Bk toner.

Thereafter, the developing operation of the Bk latent image area is continued, but when the trailing edge of the latent image passes the Bk developing position,
The cutting of the agent on the Bk developing sleeve 14-1 is promptly performed, and the developing operation is stopped. This is at least the following C
This is completed before the leading end of the C latent image based on the image data arrives. The ear cutting is performed by switching the rotation direction of the developing sleeve 14-1 to a direction opposite to that during the developing operation.

The Bk toner image formed on the photosensitive drum 9 is transferred to the surface of the intermediate transfer belt 19 which is driven at the same speed as the photosensitive member (hereinafter, toner image transfer from the photosensitive member to the intermediate transfer belt). Is called the belt transfer). The belt transfer is performed by applying a predetermined bias voltage to the transfer bias roller 20 while the photoconductor 9 and the intermediate transfer belt 19 are in contact with each other. Note that Bk, C, M, and Y toner images sequentially formed on the photoconductor 9 are formed on the intermediate transfer belt 19.
A four-color superimposed belt transfer image is formed by sequentially aligning the belt on the same surface, and thereafter, batch transfer is performed on transfer paper.

By the way, on the side of the photosensitive member 9, the Bk process is followed by the C process, but C image data reading by the color scanner 1 starts at a predetermined timing, and a C latent image is formed by writing laser light by the image data. To do.

The C developing device 15 starts rotating the developing sleeve 15-1 with respect to the developing position after the trailing edge of the previous Bk latent image has passed and before the leading edge of the C latent image reaches. The agent is raised and the C latent image is developed with C toner. Hereafter, C
The development of the latent image area is continued, but when the rear end of the latent image passes, the C developing sleeve 15
-1. This is also completed before the leading end of the next M latent image arrives. In addition, regarding the processes of M and Y, image data reading, latent image formation,
Since the developing operation is the same as the above-described Bk and C steps, the description is omitted. Next, the intermediate transfer belt unit will be described. The intermediate transfer belt 19 is stretched around a drive roller 21, a belt transfer bias roller 20, and a group of driven rollers, and is driven and controlled by a drive motor (not shown). The belt cleaning unit 22 includes a brush roller 22-1, a rubber blade 22-2, a mechanism 22-3 for contacting and separating from the belt, and the like.
After the k image is transferred to the belt, the second, third, and fourth colors are separated from the belt surface by the contact / separation mechanism 22-3 during the belt transfer. The paper transfer unit 23 includes a paper transfer bias roller 23-1, a roller cleaning blade 23-2, and a mechanism 23-3 for contacting and separating from the belt.

The bias roller 23-1 is usually separated from the surface of the belt 19, but the bias roller 23-1 is contacted with a timing when the superimposed images of four colors formed on the surface of the intermediate transfer belt 19 are collectively transferred to the transfer paper. The roller 23-1 is pressed by the separating mechanism 23-3 and a predetermined bias voltage is applied to the roller 23-1 to perform transfer to the paper. The transfer paper 24 is fed by the feed roller 25 and the registration roller 26 at the timing when the leading end of the four-color superimposed image on the intermediate transfer belt surface reaches the paper transfer position. The intermediate transfer belt 19 can be moved in one of the following three ways after the transfer of the first color Bk toner image to the rear end is completed. , According to the copy size (in terms of copy speed, etc.).

1) Constant speed forward movement method Even after the Bk toner image is transferred on the belt, the forward movement is continued at a constant speed.

When the front end position of the Bk image on the surface of the belt 19 reaches the belt transfer position of the contact portion with the photosensitive member 9 again, the front end portion of the next C toner image on the photosensitive member 9 side is just at that position. The image is formed at the right time. As a result, the C image is accurately aligned with the Bk image and transferred onto the intermediate transfer belt 19 in a superimposed manner. Thereafter, by the same operation, the process proceeds to the M and Y image processes.
Obtaining a four-color superimposed belt transfer image. Following the fourth color Y toner image belt transfer step, the four-color superimposed toner image on the belt surface is
Batch transfer to the transfer paper 24 is performed as described above.

2) Skip Forwarding Method After the belt transfer of the Bk toner image is completed, the belt 19 is separated from the surface of the photoconductor 9 and is skipped at high speed in the forward direction as it is, and when the predetermined amount is moved, the initial forward movement is performed. Return to speed. After that, the belt 19 is brought into contact with the photosensitive member 9 again. When the leading end position of the Bk image on the surface of the belt 19 reaches the belt transfer position again, the leading end portion of the next C toner image is placed on the photosensitive member 9 side. The image is formed at a timing so as to be exactly at that position. As a result, the C image becomes Bk
The belt is transferred while being superimposed exactly on the image. Thereafter, the same operation is performed to proceed to the M and Y image processes,
A four-color superimposed belt transfer image is obtained. Following the fourth color Y toner image belt transfer step, the four-color superimposed toner image on the surface of the belt 19 is collectively transferred onto the transfer paper 24 at the same forward movement speed.

3) Reciprocating (quick return) system When the belt transfer of the Bk image is completed, the belt 19 is separated from the surface of the photosensitive member 9, and the forward movement is stopped, and at the same time, the belt 19 is returned at a high speed in the opposite direction. Return is belt 1
The front end position of the Bk image on the ninth surface passes through the position equivalent to the belt transfer in the reverse direction, and after moving a predetermined distance, stops and goes into a standby state. When the leading end of the C toner image reaches a predetermined position before the belt transfer position, the intermediate transfer belt 19 is restarted in the forward movement direction. Further, the belt 19 is brought into contact with the surface of the photoconductor 9 again. Again,
The C image is transferred to the belt 19 under the condition that it exactly overlaps Bk on the belt 19 surface. Thereafter, the same operation is performed to proceed to the M and Y image processes.
Obtain a four-color superimposed belt transfer image. Following the belt transfer process of the fourth color Y toner image, the four-color superimposed toner image on the surface of the belt 19 is moved forward without returning and the transfer paper 24. Batch transfer.

The transfer paper 24 on which the four-color superimposed toner images are collectively transferred from the surface of the intermediate transfer belt is the paper transport unit 2
7, the toner image is melted and fixed by the fixing roller 28-1 and the pressure roller 28-2, which are controlled to a predetermined temperature, and carried out to the copy tray 29 to obtain a full-color copy. The photoconductor 9 after the belt transfer
The surface is cleaned by a photoreceptor cleaning unit 10 (a pre-cleaning static eliminator 10-1, a brush roller 10-2, and a rubber blade 10-3), and the static elimination lamp 11 uniformly eliminates static electricity. After the transfer of the toner image onto the transfer paper 24, the surface of the intermediate transfer belt 19 is cleaned by pressing the cleaning unit 22 again by the contact / separation mechanism 22-3.

At the time of repeat copying, the color scanner 1
The operation of (1) and the image formation on the photoconductor 9 are performed on the first sheet Y (4
Subsequent to the (color) image process, the process proceeds to a second Bk (first color) image process at a predetermined timing. The intermediate transfer belt 19 has a cleaning unit 22 that cleans the surface of the intermediate transfer belt 19 following the batch transfer process of the first four-color superimposed image onto transfer paper.
The second Bk toner image is belt-transferred to the area cleaned in step. Thereafter, the operation is the same as that of the first sheet. The transfer paper cassettes 30, 31, 32,
Transfer papers of various sizes are stored in the storage paper 33, and are fed and conveyed in the direction of the registration rollers 26 with a timing from a storage cassette of the paper size specified by an operation panel (not shown). Reference numeral 34 denotes a manual paper feed tray for OHP paper and thick paper.

Up to this point, the description has been given of the copy mode in which four full colors are obtained. However, in the case of the three-color copy mode and the two-color copy mode, for the designated color and the number of times,
The same operation as described above is performed. Further, in the case of the single-color copy mode, only the developing device of the color is set in the developing operation (spring) until the predetermined number of sheets is completed, and the intermediate transfer belt 19 is kept in contact with the surface of the photoconductor 9. Driving is performed at a constant speed in the forward direction, and the copying operation is performed with the belt cleaner 22 still in contact with the belt 19.

FIG. 3 shows the positional relationship among the photosensitive drum 9, the charger 12 and the surface electrometer 13. A charger 12 is arranged at a position keeping a certain distance on the photosensitive drum 9, and the charger 12 uniformly charges the surface of the photosensitive drum 9. As a result, the charger 12 is charged. 3 in the downstream side of the charger 12 with respect to the rotation direction of the photosensitive drum 9.
The surface potential meters 13 are arranged, and these measure the surface potential of the photosensitive drum 9.

The discharge wire of the charger 12 is regularly and occasionally cleaned. Immediately after the discharge wire is cleaned, the discharge is unstable, so discharge (trial discharge) is always performed to stabilize the discharge.

Discharge unevenness after normal cleaning occurs due to discharge or non-discharge of the wire surface.
This discharge unevenness directly appears as unevenness of the surface potential of the photoconductor. Therefore, during this discharge, the surface potential meter 13 arranged on the downstream side of the charger 12 continuously monitors the potential of the surface of the photoconductor, and the fluctuation width within a certain time (for example, 5 seconds) is set to a predetermined threshold value ( For example, the discharge is continued while the voltage is higher than 5 V), the discharge is terminated when the voltage is lower than 5 V, and the next operation (copy standby state or image formation) is started. In FIG.
The portion of the charger 12 is shown in an enlarged manner, and the front surface of the holding member when the cleaning pad holding members 116A and 116B are in the end region and the intermediate region (5A- in FIG. 4A).
5A line direction and 5B-5B line direction), respectively.
(A) and (b). Cleaning pad Cp
The spiral feed shaft 116 for reciprocating the
It is arranged parallel to charger wire 115. At the driving end of the feed shaft 116, four grooves are formed on the peripheral surface.
A grooved shaft 117 having a pointed conical tip, which is carved at a pitch of 100 degrees, is fixed.

A drive shaft 118 is provided at a position for receiving the tip of the grooved shaft 17, and a hole into which the tip of the grooved shaft 117 is inserted is formed in the tip surface of the drive shaft 118. There are four protrusions that fit into the groove of the grooved shaft 117, the tip of the grooved shaft 117 enters the hole of the drive shaft 118, and when the drive shaft 118 rotates, the grooved shaft 117 (feed shaft 116) Rotates. The copying machine body has an electric motor 119 for driving the drive shaft 118 in forward and reverse directions through a reduction mechanism.
(Not shown).

The feed shaft 116 has a pair of holding members 116.
A and 116B (Fig. 5) are screwed (screwed together). When the electric motor 119 rotates in the forward direction, the feed shaft 116 rotates in the forward direction, and the holding members 116A and 116B move from the home position to the reverse position.

The cleaning pad Cp for cleaning the charger wire 115 is attached to the tips of the holding members 116A and 116B which move along the feed shaft 116. The holding members 116A and 116B have a cavity width of a groove for guiding the holding member of the casing of the charger,
As shown in FIG. 4A, the width becomes wider as it approaches the end block Eb in the termination region (reversal region).
Similarly, in the starting end area (home position area),
It becomes wider as it approaches the end block Ef. When the holding members 116A and 116B enter the end region (reversal region) or the start end region (home position region), the holding members 116A and 11 approach the end block Eb or Ef.
6B can be opened relatively. When opened relatively, the cleaning pad Cp separates from the charger wire 115.

The front surface of the holding member when the holding members 116A and 116B are in the end region and the intermediate region (5A-5A line direction and 5B-5B line direction in FIG. 4A).
Are shown in (a) and (b) of FIG. 5, respectively. When the holding members 116A and 116B are in the end region ((a) of FIG. 5), the holding members 116A and 116B have a large gap width of the guide groove of the casing, and the guide member Gp exerts a force to spread from the inside to the outside. The cleaning pad Cp is expanded because it is received, and the cleaning pad Cp is separated from the charger wire 115.
The same applies when in the start end area (home position area). Since the width of the guide groove of the casing is narrow when it is in the intermediate region, the holding members 116A and 116B are not shown in FIG.
It is closed as shown in FIG. That is, in the cleaning area, the holding members 116A and 116B move forward while sandwiching the charger wire 115 in the cleaning pad Cp, as shown in FIG. 5B. Then, when reaching the inversion region of the holding members 116A and 116B, the groove width of the casing for guiding the holding members 116A and 116B becomes wider again, so that the char of the holding members 116A and 116B is changed.
The restraint force on the jar wire 115 becomes weaker and the guide wire Gp expands it (a in FIG. 5).

FIG. 6 shows an electrical system configuration of the copying machine shown in FIG. The document reading unit 33, the image processing unit 67, and the printer unit 40 are sequentially connected. The document reading unit 33, the image processing unit 67, the printer unit 8, and the operation unit 68 are connected to a system controller 69 via a bus line. I have. The system controller 69 includes the document reading unit 33
, A start signal, a synchronizing signal, and a magnification specifying signal to the image processing unit 67, and an image processing mode specifying signal (monochromatic or two-color mode specifying signal, etc.) to the image processing unit 67. The entire system is controlled by an abnormal signal or an operation status signal (wait, ready, busy, stop).

The original reading unit 33 scans the original at a scanning speed corresponding to the magnification specified by the print start signal sent from the system controller 69, and the image information of the original is read in R (red) and G (green). ), And B (blue) filters 72R, 72G, and 72B, three solid-state imaging devices 7R, which convert and read electrical signals corresponding to respective colors,
7G and 7B are provided. These solid-state imaging devices 7
On the output side of R, 7G, 7B, three A / D converters 73 provided for each color of R, G, B are connected. , A shading correction circuit 74 and a buffer memory 75 are sequentially connected. Then, the image information read by the solid-state imaging devices 7R, 7G, and 7B is converted into digital image data by the A / D converter 73, subjected to shading correction, and then temporarily stored in the buffer memory 75. This buffer memory 7
By 5, image data in which each color is synchronized is output to the next-stage image processing unit 67.

At the input stage of the image processing section 67, there is provided a γ correction circuit 76 for changing the gradation of the image data sent from the document reading section 33 according to the developing characteristics of the photoconductor and the developing device. There is. The correction processing of the γ correction circuit 76 is switched by the mode designation from the system controller 69. The output data of the gamma correction circuit 76 is sent to the black separation / color generation circuit 77. The black separation / color generation circuit 77 generates image data according to information (mode information) from the system controller 69 and outputs the image data to the gradation processing circuit 78. The gradation processing circuit 78 performs gradation correction processing according to the characteristics of the developing device based on information from the system controller 69. Here, the information of the system controller 69 is a single color recording, a two-color recording, a three-color recording or a four-color recording as a color selection mode.
Examples of the color recording and image processing modes include “character mode”, “photo mode”, “text / photo mode”, and “magnification”.

The system controller 69 checks the number of copies (the number of image formations) from the end of the previous cleaning of the charger immediately after the power of the copying machine is turned on, and if it exceeds the set value, the charger is cleaned. That is, the cleaning of the charger 12 is performed to initialize the number of copies. In other words, the charger cleaning is executed for every approximately predetermined number of copies. in addition,
Even when the charger cleaning instruction key on the operation unit 68 is pressed, one charger cleaning is executed for each pressing.

FIG. 7 shows the contents of the "charger cleaning" executed by the system controller 69. Upon proceeding to this processing, the controller 69 initializes the value n of the number of reciprocations of the pad 115 (one reciprocation is once) (step 1) and clears the maximum and minimum values of the memory (register) (step 2). ). Hereinafter, in the parentheses, the word “step” is omitted, and step No. Write only numbers.

The controller 69 then holds the retaining member 116.
A and 116B (Fig. 5) are driven forward from the home position to the reversal position (3), and then driven backward at the reversal position to return to the home position (4). That is, the holding members 116A, 11
6B is driven back and forth once. This allows the discharge wire 115
Is wiped with the pad Cp. Next, the controller 69
Execute "Check for uneven discharge" (5).

The contents of "Check for uneven discharge" (5) are shown in FIG. In this, the controller 69 is the pad 1
The number of reciprocating movements of 15 is incremented by 1 (1), the photosensitive drum 9 is rotationally driven, and the charge eliminating lamp is turned on (5).
2), a charging voltage is applied to (the discharging wire 115 of) the charger 12 (53), and a photoconductor drum synchronization pulse (drum 9) is applied.
The counting of the number of occurrences of one electric pulse per rotation of a predetermined small angle is started (54), and measurement of elapsed time (time A) is started (55). Then, the position charged by the charger 12 on the photoconductor drum 9 is the potential sensor 13A,
At the timing when it reaches just below 13B and 13C, a timer t whose time limit value is t is started (56, 57) in order to determine the charging unevenness determination region (56, 57), and the potential sensors 13A, 13B,
The detected potential (V) of 13C is read (58). Then, the highest value and the lowest value are detected (59) (59). This detection potential is read (58) and the maximum and minimum values are detected (5
9) is repeated in a predetermined short period until the timer t times out (58-60). In the detection of the maximum value and the minimum value (59), regarding the potential sensor 13A, the latest read value is compared with the data of the highest value register A and the lowest value register A, and the latest read value is the highest value register A. If the value is larger than the data of the above, the read value is updated and written in the highest value register A. When the latest read value is smaller than the data in the lowest value register A, the read value is updated and written in the lowest value register A. The same applies to the other potential sensors 13B and 13C.

When the timer t time-overs, that is, when the time t elapses, the controller 69 causes the maximum value (1 for each of 13A, 13B and 13C) of the measured values of the potential sensors 13A, 13B and 13C.
The maximum value and the minimum value out of the minimum value (3 in total) and the minimum value (similarly 3 in total) are extracted, and as the surface potential unevenness, the extracted maximum value-extracted minimum value is calculated, and this is the set value. It is checked whether it is Av or less (no discharge unevenness) (discharge unevenness) (61). If the value is equal to or less than the set value Av, the post-processing (62) is executed. In this post-treatment (62), the application of the charging voltage to the charger 12 is stopped, the rotation drive of the photoconductor drum 9 is stopped and the discharge lamp is turned off when the last charged portion passes through the discharge lamp.

When the surface potential unevenness (maximum value-minimum value) exceeds the set value Av (with discharge unevenness) in the check at step 61, the controller 69 determines that the measured value of the time A is the set value Tp. Check (63) whether or not it has become longer than (for example, 5 seconds), and if not (because the uneven surface potential may stabilize), start the timer t again and restart the surface potential again. Detection of unevenness (58 to 61) is executed.

If the surface potential unevenness (maximum value-minimum value) exceeds the set value Av even when the measured value of the time count A exceeds the set value Tp, the number of times of cleaning n of the charger is set to the set value np.
(64), if not, execute "charger cleaning" (CC: Fig. 7) again,
The holding members 116A and 116B are driven back and forth once (2 to
4), "Check for uneven discharge" (5) shown in FIG. 8 is executed again.

Even when the number of times of cleaning of the charger n reaches the set value np, the surface potential unevenness (highest value-lowest value) still shows the set value Av.
If it is over the range, it is impossible to remove dirt (the cause of uneven charging) by wire cleaning by cleaning the charger, so "error processing" (65) is executed.
Then, the process proceeds to "post-processing" (62). In the error processing (65), the information indicating the main charger abnormality is written in the abnormality monitoring table (one area of the memory) and displayed on the operation unit 68.

When the "post-processing" (62) is executed, the controller 69 displays "ready" on the operating section 68 and indicates that the image forming elements other than the charger 12 are in a normal state, and the operating section 6 is displayed.
When the copy start key 8 is pressed, the above-mentioned process control for image formation is started.

As described above, when the discharge wire 115 is cleaned, the discharge wire 115 is automatically pre-discharged by the trial charging bias (step 53 in FIG. 8), and the image formation is performed after the discharge is stabilized. An image without density unevenness can be obtained. The presence or absence of discharge unevenness (charged potential unevenness) is determined based on the measured potentials of the potential sensors 13A, 13B, 13C, and pre-discharge is performed until the discharge unevenness disappears, so that unevenness remains or wasteful discharge is performed. It is possible to efficiently complete the pre-discharge without doing so. A plurality of potential sensors 13A, 13B, 13C are arranged in the drum axis direction, and the maximum and minimum values (in the drum circumferential direction) of the measured potential of each potential sensor in time series are detected. Since the difference between the highest value and the highest value and the lowest value among the lowest values of the three sets is obtained as the surface potential unevenness and the presence or absence of the unevenness is determined based on this, the two-dimensional direction of the surface of the photosensitive drum 9 (the rotation axis is It is the determination of the presence / absence of unevenness in the extending direction and the circumferential direction). As a result, the accuracy of determining the presence or absence of unevenness is high. In addition, the discharge sensor can be fixed without moving the potential sensor to detect uneven discharge, and the configuration is simple.

Although the embodiment described above is for cleaning the discharge wire 115 of the corona discharger (12), the present invention is also applicable to a cleaning device for a contact charging member such as a charging roller. , Can be implemented.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a mechanism of a copier equipped with an embodiment of the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing a photosensitive drum 9 and its surroundings shown in FIG. 1;

FIG. 3 is an enlarged perspective view showing a photosensitive drum 9, a charger 12 and a surface electrometer 13 shown in FIG.

FIG. 4 is an enlarged view showing one end of the charger 12 shown in FIG. 1, in which (a) is a plan view and (b) is a front view.

5 is an enlarged cross-sectional view of the charger 12 shown in FIG. 4, and FIG. 5A is an enlarged view of line 5A-5A in FIG. 4A when the holding members 116A and 116B are in the home position region. A sectional view, (b) shows the holding members 116A and 116B.
FIG. 5B is an enlarged cross-sectional view taken along line 5B-5B of FIG. 4A when it is in a position advanced from the m-position region toward the intermediate portion.

FIG. 6 is a block diagram showing a schematic configuration of an electric system of the copying machine shown in FIG. 1;

FIG. 7 is a flowchart showing a control operation for cleaning the charger of the system controller 69 shown in FIG. 6;

FIG. 8 is a flowchart showing the contents of “Check for uneven discharge” (5) shown in FIG. 7.

[Explanation of symbols]

1: color image reading device 2: color image recording device 3: original 4: illumination lamp 5: mirror group 6: lens 7: photoelectric conversion element 8: writing optical unit 8-1: laser 8-2: polygon mirror 8-3 : Polygon motor 8-4: f /
Theta lens 8-5: Reflection mirror 9: Photosensitive drum 10: Photosensitive drum cleaning unit 11: Static elimination lamp 12: Charger 13: Potential sensor 14: Bk developing device 15: C developing device 16: M developing device 17: Y developing Device 18: Development density pattern detector 19: Intermediate transfer belt 14-1: Bk development sleeve 15-1: C
Developing sleeve 16-1: M developing sleeve 17-1: Y
Development sleeve 14-2: Bk development paddle 15-2: C
Development paddle 16-2: C development paddle 17-2: Y
Development paddle 14-3: Bk toner concentration detection sensor 15-3: C
Toner density detection sensor 16-3: M toner density detection sensor 17-3: Y
Toner density detection sensor 20: Belt transfer bias roller 21: Belt drive roller 22: Belt cleaning unit 22-1: Brush roller 22-2: Rubber blade 22-3: Contact / separation mechanism 23: Paper transfer unit 23-1: Paper Transfer bias roller 23-2: Cleaning blade 23-3: Contact / separation mechanism 24: Transfer paper 25: Feed roller 26: Registration roller 27: Paper transport unit 28: Fixing device 28-1: Fixing roller 28-2: Pressurization Roller 29: Copy tray 10-1: Static eliminator before cleaning 10-2: Brush roller 10-3: Rubber blade 30-33:
Transfer paper cassette 34: Manual paper feed tray

Claims (4)

[Claims] 1. A cleaning member that contacts and separates a charging member connected to a charging power source to charge a photosensitive member; the cleaning member is applied to the charging member, and one of them is relative to the other. A cleaning device for a charging member, comprising: a cleaning driving device for driving; and a control device for urging the charging member by trial charging to stabilize the charging immediately after the cleaning member and the cleaning driving device clean the charging member. . 2. The apparatus further includes a detection means for detecting the presence or absence of charging unevenness of the charging of the photosensitive member by the charging member; the control means is provided immediately after cleaning the charging member for stabilizing the charging. 2. The cleaning device for the charging member according to claim 1, wherein the trial charging is terminated and the trial charging is terminated when the detecting means detects that there is no uneven charging. 3. The detecting means includes a potential sensor for measuring the surface potential of the photoconductor and a variation value calculating means for obtaining a potential variation value on the surface of the photoconductor on the basis of the potential measured by the potential sensor. The cleaning device for a charging member described above. 4. The charging member is a corona charger having a discharge wire inside the casing, and the cleaning member is a cleaning pad for wiping the discharge wire. Cleaning device for charging member.