JP3480782B2 - Cleaning device for charging member - Google Patents

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 photosensitive member 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. More particularly, the present invention relates to a cleaning apparatus for cleaning a charging member for charging a photoreceptor for high quality image formation.

[0002]

2. Description of the Related Art A charging member includes a corona charger and a contact charger (for example, a charging roller). However, the charging member is contaminated with a toner used for development or a discharge product generated when the photosensitive member is charged by the charging member. It is known. Therefore,
Cleaner for cleaning charged members (discharge wire, charged roller)
Various types of cleaning devices are devised and mounted, and are used to mainly periodically 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. detecting the current distribution provided in parallel many of the current distribution detecting means, a cleaning control to start the cleaning as there is dirty when the variation of the current distribution increases is presented.

[0004]

The discharge wire of a charging member, for example, a corona charger, is gradually stained and deteriorated by discharging, so that the stain on the wire gradually progresses before it becomes apparent as discharge unevenness. 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 deposits on the surface gradually begin to fuse to the wire, and the dirt that could not be removed in the initial stage and remained remains similarly fused to the surface of the wire. 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. property changes, discharge is temporarily unstable, rather uneven discharge by performing cleaning might occur <br/>. In order to return to a uniform discharge state, it is necessary to discharge for a while.

When an image is formed in a state where the discharge is unstable, the photosensitive member is not uniformly charged, and appears as an uneven charging 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.

An object of the present invention is to solve this problem.

[0008]

Means for Solving the Problems (1) The cleaning apparatus of the present invention is a cleaning device which contacts and separates from a charging member (115) connected to a charging power source for charging the photosensitive member (9). Material (C
p); said cleaning member (one of them Cp) against the charging member (115) (Cp) cleaning drive means for relatively driving to the other (115) (116 to 118); wherein the rotating Rotation axis direction of photoconductor (9)
Potential sensor for measuring a surface potential of several points of direction (13) and
Rotation on the photoreceptor surface based on the measured potential of the potential sensor
Calculates fluctuation values to find potential fluctuation values in the direction and rotation axis direction
Means (69) of the photoreceptor by the charging member (115)
Means for detecting the presence or absence of uneven charging of the charge (13,69); and,
Immediately after the cleaning of the charging member by the cleaning member and the cleaning driving unit , the drive of the photoconductor is started to stabilize charging.
The trial charging bias setting period of the charging member (Tp) starts Te, before
The detection means detects that there is no charging unevenness in the trial charging area on the photoconductor.
Terminating the attempt charging bias and detect, before within the set time period
If the detecting means does not detect no charging unevenness, trial charging is activated.
Is stopped and the charging by the cleaning member and the cleaning driving means is stopped.
Control means (69 : 51-64 in FIG. 8-FIG. 7) for re-cleaning the member
2 ) to 4 ); a charging device cleaning apparatus comprising: 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 of the charging member (115) immediately after the cleaning of the charging member (115), the charging member (115) is
Stabilizes the charging characteristics, reduces charging unevenness during energizing for subsequent image formation, reduces image density unevenness,
Process control - not Na disturbed in Le. On the photoconductor surface
The charge unevenness in the rotation direction and the rotation axis direction is measured, and when the charge unevenness disappears, the trial charging energization is terminated. Therefore, there is no charge unevenness during the subsequent charge energization for image formation and the waiting time Is the shortest.

[0010]

(2) The control means (69) is a charging device.
Cleaning of the charging member was repeated without detecting
When the number (n) reaches the set value (np), cleaning of the charging member is repeated.
Stop Return generates abnormality information (64-65 of FIG. 8), the
The cleaning device for a charging member according to (1).

(3) The potential sensor (13) is provided for rotating the photosensitive member.
A plurality of distributed the rolling axis (13A, 13B, 13C), the
The cleaning device for a charging member according to (1) or (2) .

(4) The charging member has a discharge wire inside the casing.
Corona charger having ear (12) der is, the cleaning member is dissipating
The above (1), which is a cleaning pad for wiping an electric wire.
(2) or (3) the cleaning device for a charging member.
Place.

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

[0014]

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 an original 3 on a color sensor 7 (7R, 7G, 7B) via an illumination lamp 4, a mirror group 5, and a lens 6, and
The color image information of the original is read for each red (Red), green (Green), and blue (Blue) color separation light, and is converted into an electric image signal.

The color sensor 7 includes R, G,
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.

A color image recording apparatus (hereinafter, referred to as a color printer) 2 described below converts this into Bk,
The visualization of Y, M, and C is performed to obtain a final color copy.

The operation system of the color scanner 1 for obtaining the image data of Bk, Y, M, and C receives a scanner start signal which is timed with the operation of the color printer 2 and, as shown in FIG. The mirror optical system scans the original in the direction of the left arrow, and obtains one color image data for each scan. By repeating this operation four times in total,
Successive four-color image data is obtained. Then, each time the color image is sequentially visualized by the color printer 2, this is transferred to the transfer belt 1.
9, a four-color full-color image is formed and transferred to transfer paper (recording paper).

Next, an 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 photosensitive drum 9 rotates in the counterclockwise direction as shown by the arrow, and around it, a photosensitive member cleaning unit (including a pre-cleaning neutralizer) 10, a neutralizing lamp 11, a charger 12, a potential sensor 13 , Bk developing unit 1
4, a C developing device 15, an M developing device 16, a Y developing device 17, a development 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, 17-17) which rotates by bringing a developer spike into contact with the surface of the photoreceptor 9 to develop an 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 four developing units
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 copying operation is started, reading of Bk image data is started at a predetermined timing by the color scanner 1, and light writing / latent image formation by laser light is started based on the image data (hereinafter, Bk image data). 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. When the rear end of the latent image passes the Bk developing position,
The cutting of the agent on the Bk developing sleeve 14-1 is immediately 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 driven at a constant speed with the photosensitive member (hereinafter, the toner image is transferred from the photosensitive member to the intermediate transfer belt). Is referred to as a 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.

On the photosensitive member 9 side, the process proceeds to the step C after the step Bk. At a predetermined timing, the reading of the C image data by the color scanner 1 starts, and the formation of the C latent image is performed by writing the laser light based on the image data. Do.

The C developing device 15 starts rotating the developing sleeve 15-1 with respect to the developing position after the rear end of the preceding Bk latent image has passed and before the leading end of the C latent image has arrived. The agent is spiked 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 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 normally separated from the surface of the belt 19, but it contacts with a timing when the superimposed images of four colors formed on the surface of the intermediate transfer belt 19 are collectively transferred to transfer paper. Pressed by the release mechanism 23-3, a predetermined bias voltage is applied to the roller 23-1 to perform transfer to 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 belt transfer of the Bk toner image, the forward movement is continued at a constant speed. Then, 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 photoconductor 9 again, the front end portion of the next C toner image on the photoconductor 9 side is exactly at that position. Then, an image is formed at a certain timing. As a result, the C image is transferred onto the intermediate transfer belt 19 while being accurately aligned with the Bk image. Thereafter, by the same operation, the process proceeds to the M and Y image processes, and a belt transfer image of four-color superposition is obtained. Following the step of transferring the Y toner image belt of the fourth color, the toner image of the four-color superimposed toner image on the belt surface is transferred to the transfer paper 24 as described above while moving forward.
Batch transfer. 2) When the belt transfer of the Bk toner image is completed, the belt 19 is separated from the surface of the photoreceptor 9 and skipped at a high speed in the forward movement direction. . Thereafter, the belt 19 is brought into contact with the photoconductor 9 again. When the front end position of the Bk image on the surface of the belt 19 reaches the belt transfer position again, the photosensitive member 9 forms an image at a timing such that the front end portion of the next C toner image is exactly at that position. Have been. As a result, the C image becomes B
The belt is transferred in a superimposed manner while being accurately aligned with the k image. Thereafter, by the same operation, the process proceeds to the M and Y image processes, and a belt transfer image of four-color superposition is obtained. Subsequent to the fourth-color Y toner image belt transfer step, the four-color superimposed toner image on the belt 19 surface is collectively transferred to the transfer paper 24 at the same forward movement speed. 3) When the belt transfer of the reciprocating (quick return) type Bk image is completed, the belt 19 is separated from the surface of the photoreceptor 9, and the forward movement is stopped, and at the same time, the high speed return is performed in the reverse direction. Return is belt 19
The front end position of the Bk image on the surface passes through the position equivalent to the belt transfer in the reverse direction, and after moving a predetermined distance, stops and enters a standby state. Next, when the leading end of the C toner image on the photoconductor 9 reaches a predetermined position before the belt transfer position, the intermediate transfer belt 19 is started again in the forward movement direction. Further, the belt 19 is brought into contact with the surface of the photoconductor 9 again. Also in this case, the belt transfer is performed under the condition that the C image is accurately overlapped with Bk on the belt 19 surface. Thereafter, by the same operation, the process proceeds to the M and Y image processes, and a belt transfer image of four-color superposition is obtained. Subsequent to the belt transfer process of the Y toner image of the fourth color, the toner is moved forward at the same speed without returning, and the four-color superimposed toner image on the surface of the belt 19 is collectively transferred to the transfer paper 24.

The transfer paper 24 on which the four-color superimposed toner image has been collectively transferred from the intermediate transfer belt surface is transferred to 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 paper feeder 33, and are fed and conveyed in the direction of the registration rollers 26 from the storage cassette of the size paper specified by the operation panel (not shown) at a certain timing. Reference numeral 34 denotes a manual paper feed tray for OHP paper and thick paper.

The copy mode for obtaining four full colors has been described above. However, in the case of the three-color copy mode and the two-color copy mode, the number of specified colors and the number of times are limited.
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 voltmeter 13. A charger 12 is disposed at a position at a certain distance from the photosensitive drum 9, and the charger 12 uniformly charges the surface of the photosensitive drum 9. As a result, the photosensitive drum 9 is charged. Three surface voltmeters 13 are arranged downstream of the charger 12 with respect to the rotation direction of the photoconductor drum 9 and measure the surface potential of the photoconductor drum 9.

The discharge wire of the charger 12 is cleaned periodically and as needed. Immediately after the discharge wire is cleaned, the discharge is unstable, so a discharge (trial discharge) is always performed to stabilize the discharge.

Usually, uneven discharge after cleaning is caused by discharge or non-discharge of the wire surface.
This discharge unevenness appears as unevenness of the surface potential of the photoconductor as it is. Therefore, during this discharge, the potential of the photoconductor surface is continuously monitored by the surface voltmeter 13 disposed downstream of the charger 12, and the fluctuation width within a certain time (for example, 5 seconds) is determined ( For example, the discharge is continued while the voltage is larger than 5 V), the discharge is terminated after the voltage becomes smaller, and the next operation (copy standby state or image formation) is started.

FIG. 4 is an enlarged view of a portion of the charger 12 and includes cleaning pad holding members 116A and 116B.
Is the front surface of the holding member when it is in the terminal region and the intermediate region (the direction of the line 5A-5A and the direction of the line 5B-5B in FIG.
5 (a) and 5 (b), respectively. A spiral feed shaft 116 for reciprocatingly driving the cleaning pad Cp includes a charger wire 115.
And are arranged in parallel. At the drive-side end of the feed shaft 116, a grooved shaft 117 having four concavities formed on the peripheral surface at a 90-degree pitch and having a sharply pointed tip is fixed.

A driving shaft 118 is provided at a position for receiving the leading end of the grooved shaft 17. A hole for receiving the leading end of the grooved shaft 117 is formed in the leading end surface of the driving shaft 118. There are four ridges that fit into the groove of the grooved shaft 117, and the tip of the grooved shaft 117 enters the hole of the drive shaft 118. When the drive shaft 118 rotates, the grooved shaft 117 (feed shaft 116). Rotates. An electric motor 119 for driving the drive shaft 118 forward and reverse through a speed reduction mechanism is provided in the copying machine main body.
(Not shown).

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

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

Front view of the holding members when the holding members 116A and 116B are in the terminal region and the intermediate region (the direction of the line 5A-5A and the direction of the line 5B-5B in FIG. 4A).
Are shown in FIGS. 5A and 5B, respectively. When the holding members 116A and 116B are in the terminal region (FIG. 5A), the holding members 116A and 116B have a large gap width of the guide groove of the casing, and the force for expanding the guide member Gp from inside to outside. The cleaning pad Cp is separated from the charger wire 115 by being spread.
The same applies to the case in the start end area (home position area). When in the intermediate region, the width of the guide groove of the casing is narrow, so that 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 advance with the charger wire 115 sandwiched between the cleaning pads Cp as shown in FIG. 5B. Then, when reaching the reversal area of the holding members 116A and 116B, the width of the groove of the casing for guiding the holding members 116A and 116B is widened again.
The binding force on the jar wire 115 is weakened, and the jar wire 115 is expanded by the guide member Gp (FIG. 5A).

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 section 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 converts the image information of the original into R (red) and G (green). ), B (blue) filters 72R, 72G, and 72B, and converts them into electric signals corresponding to the respective colors and reads the signals.
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.

The input stage of the image processing section 67 is provided with a gamma correction circuit 76 for changing the gradation of the image data sent from the document reading section 33 in accordance with the development characteristics of the photosensitive member and the developing device. I have. 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) since the previous cleaning of the charger immediately after the power of the copier is turned on, and if the number exceeds the set value, cleaning of the charger is performed. That is, cleaning of the charger 12 is executed, and the number of copies is initialized. 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. When proceeding to this processing, the controller 69 initializes the number n of reciprocating movements of the pad 115 (one reciprocation is once) (step 1), and clears the highest value and the lowest value 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 moves to the holding member 116.
A and 116B (FIG. 5) are forward driven from the home position to the reverse position (3), and are driven backward at the reverse position to return to the home position (4). That is, the holding members 116A, 11
6B is driven one round trip. Thereby, the discharge wire 115
Is wiped with the pad Cp. Next, the controller 69
"Check for uneven discharge" (5) is executed.

FIG. 8 shows the contents of "check for discharge unevenness" (5). In this case, the controller 69 is connected to the pad 1
The number of reciprocations of 15 is incremented by one ( 51 ), the photosensitive drum 9 is driven to rotate, and the neutralization lamp is turned on (5).
2) A charging voltage is applied to (the discharge wire 115 of) the charger 12 (53), and the photosensitive drum synchronous pulse (drum 9) is applied.
The counting of the number of occurrences of one electrical pulse per rotation of the predetermined small angle is started (54), and the measurement of elapsed time (timekeeping A) is started (55). The position on the photosensitive drum 9 charged by the charger 12 is a potential sensor 13A,
At a timing immediately below 13B, 13C, a timer t with a time limit of t is started (56, 57) to determine the charging unevenness determination area, 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). Reading of the detected potential (58) and detection of the highest value and the lowest value (5)
Step 9) is repeated with a predetermined short period until the timer t expires (58-60). In the detection of the highest value and the lowest value (59), the latest read value of the potential sensor 13A is compared with the data of the highest value register A and the lowest value register A, and the latest read value becomes the highest value register A. If the value is larger than the data, the read value is updated and written to the highest value register A. If the latest read value is smaller than the data of the lowest value register A, the read value is updated and written to the lowest value register A. The same applies to the other potential sensors 13B and 13C.

When the timer t has timed out, that is, when the time t has elapsed, the controller 69 sets the maximum value of the measured values of the potential sensors 13A, 13B and 13C (one for each of the potential sensors 13A, 13B and 13C).
And the lowest value (three in total) were extracted and the highest value minus the lowest value was calculated as the surface potential unevenness, and this was the set value. It is checked whether it is less than Av (there is no discharge unevenness) or not (there is discharge unevenness) (61). If the value is equal to or smaller than the set value Av, the post-processing (62) is executed. In this post-process (62), the application of the charging voltage to the charger 12 is stopped, and when the last charged portion has passed through the discharge lamp, the rotation drive of the photosensitive drum 9 is stopped and the discharge lamp is turned off.

If it is determined in step 61 that the surface potential unevenness (highest value-lowest value) exceeds the set value Av (there is discharge unevenness), the controller 69 sets the timed value of the timed A to the set value Tp. It is checked whether it has reached (for example, 5 seconds) or more (63). Otherwise (because there is a possibility that the surface potential unevenness is stabilized), the timer t is started again, and the surface potential is once again set. The unevenness is detected (58 to 61).

Even if the time value of the time A exceeds the set value Tp, if the surface potential unevenness (highest value-lowest value) exceeds the set value Av, the number n of times of cleaning the charger is reduced to the set value np.
Is checked (64), and if it is not reached, "charger cleaning" (CC: FIG. 7) is executed again.
The holding members 116A and 116B are driven one reciprocation (2 to
4), “Check for uneven discharge” (5) shown in FIG. 8 is executed again.

Even if the number n of times of charger cleaning reaches the set value np, the surface potential unevenness (highest value-lowest value) still shows the set value Av.
If it exceeds the threshold value, it is impossible to remove dirt (the cause of uneven charging) by wire cleaning by cleaning the charger, so that "error processing" (65) is executed.
Then, the process proceeds to “post-processing” (62). In the error processing (65), information indicating a main charger abnormality is written in an 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 operation section 68 when the state of the image forming elements other than the charger 12 is normal, and the operation section 6
When the copy start key 8 is pressed, the above-described 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 is formed after the discharge is stabilized. Thus, an image without density unevenness can be obtained. The presence / absence of discharge unevenness (charge potential unevenness) is determined based on the measured potentials of the potential sensors 13A, 13B, and 13C, and pre-discharge is performed until the discharge unevenness is eliminated, so that unevenness remains or wasteful discharge occurs. And the pre-discharge can be completed efficiently. A plurality of potential sensors 13A, 13B, 13C are arranged in the direction of the drum axis to detect the maximum value and the minimum value (in the drum circumferential direction) of the time series of the measured potential of each potential sensor. The difference between the maximum value and the minimum value among the maximum value and the three minimum values is obtained as surface potential unevenness, and the presence or absence of unevenness is determined based on the unevenness. Therefore, the two-dimensional direction of the surface of the photosensitive drum 9 (rotation axis is This is a non-uniformity determination in the extending direction and the circumferential direction). Thereby, the accuracy of the unevenness determination is high. In addition, it is possible to detect discharge unevenness by fixing the potential sensor without moving it, 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 the 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 voltmeter 13 shown in FIG.

4 is an enlarged view showing one end of the charger 12 shown in FIG. 1, (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, wherein FIG. 5A is an enlarged view taken along line 5A-5A of FIG. 4A when the holding members 116A and 116B are in the home position area. FIG. 3B is a sectional view, and FIG.
FIG. 5A is an enlarged cross-sectional view taken along line 5B-5B of FIG.

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 content of “check for discharge unevenness” (5) shown in FIG. 7;

[Explanation of symbols]

1: Color image reading device 2: Color image recording device 3: Manuscript 4: Lighting 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 / θ lens 8-5: Reflection mirror 9: Photoconductor drum 10: Photoconductor 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 developer 18: Development density pattern detector 19: Intermediate transfer belt 14-1: Developing sleeve for Bk 15-1: Developing sleeve for C 16-1: Developing sleeve for M 17-1: Developing sleeve for Y 14-2: Development paddle for Bk 15-2: Development paddle for C 16-2: Development paddle for C 17-2: Y development paddle 14-3: Toner concentration detection sensor for Bk 15-3: C toner concentration detection sensor 16-3: M toner density detection sensor 17-3: Y toner concentration 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: Paper feed roller 26: Registration roller 27: Paper transport unit 28: Fixing unit 28-1: Fixing roller 28-2: Pressure 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)

(57) [Claims] A cleaning member that contacts and separates from a charging member connected to a charging power source to charge the photosensitive member; Cleaning driving means for driving; the surface potentials of a plurality of points in the rotation axis direction of the rotating photoreceptor,
A potential sensor to be measured and a potential based on the potential measured by the potential sensor.
The potential on the photoreceptor surface in the direction of rotation and the direction of the axis of rotation.
A fluctuation value calculating means for calculating a fluctuation value;
Means for detecting the presence or absence of uneven charging of the photosensitive member;
And, wherein immediately after the cleaning of the charging member by the cleaning member and the cleaning driving unit, the driving of the photosensitive member starts to charge stabilization
The trial charging bias setting period of the charging member starts Te, said analyzing
Detection means detects no charging unevenness in the trial charging area on the photoconductor
Then, the trial charging is terminated, and the detection is performed within the set period.
If the output means does not detect no charging unevenness, the trial charging is stopped.
Stopping and charging member by the cleaning member and cleaning driving means
Control means for re-cleaning the charging member. 2. The control means does not detect absence of uneven charging.
The number of times of cleaning of the charging member repeated at reaches the set value.
Stop the repeated cleaning of the charging member and generate abnormal information
To, according to claim 1, wherein the charging member chestnut - training apparatus. 3. The electric potential sensor according to claim 1, wherein said electric potential sensor is provided in
A plurality of distribution, according to claim 1 or claim 2 wherein,
Cleaning device for charging member. 4. The charging member according to claim 1, wherein 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 a charging member.