JPH0882965A - Image forming device - Google Patents

Abstract

PURPOSE: To provide a means capable of surely and easily detecting the staining of the surface part of a photoreceptor in an image forming device having a developing device developing an electrostatic latent image formed on a latent image carrier with plural colors of developer at least containing toner and a means for detecting a specified developed image pattern formed on the latent image carrier by the use of an optical sensor. CONSTITUTION: This device is provided with a 1st surface detecting means 100A detecting the surface part of the latent image carrier by the optical sensor 414P in a state where the developer is in non-contact with the latent image carrier, a 2nd surface detecting means 100A detecting the surface part of the latent image carrier by the optical sensor 414P in a state where the developer is in contact with the latent image carrier, a detected voltage comparison means 100A comparing the detected voltage by the 1st surface detecting means with that by the 2nd surface detecting means, and a control means 100A controlling image forming actions in accordance with the compared result of the detected voltage by the detected voltage comparison means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile or a printer, and more specifically, it detects the surface potential of a latent image carrier by an optical sensor facing the surface of the latent image carrier. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art A developing device for developing an electrostatic latent image formed on a latent image carrier with a developer of a plurality of colors containing at least toner, and a predetermined visible image formed on the latent image carrier. In an image forming apparatus having means for detecting a pattern by an optical sensor, as means for detecting the background stain on the photoconductor, when the rotation of the developing sleeve is stopped, the portion of the photoconductor facing the developing sleeve at that time is detected by the optical sensor. It is known that the sensor detects the background, and based on the background detection information and the detection information of the predetermined visible image pattern, determines the appropriateness of image forming conditions such as the necessity of toner replenishment and performs the necessary control. Has been.

As described above, the background detection information is the basic information for controlling the image forming conditions. Therefore, if there is an error in the background detection information, the image forming conditions can be held properly. It will be difficult.

[0004]

In the above-mentioned prior art, when the toner concentration of the developer is high, the toner is in contact with the photoconductor even if the rotation of the developing sleeve is stopped, so that the photoconductor is soiled. In some cases, the toner concentration of the developer fluctuates, so that the background detection method of the related art including such a variation factor does not correctly detect the background,
If the image forming operation is controlled based on such erroneous detection information, there is a problem that the image quality is significantly deteriorated.

An object of the present invention is to provide a means for accurately and easily detecting the background stain on the background portion of the photoconductor.

[0006]

In order to achieve the above object, the present invention is configured as follows. (1). A developing device that visualizes the electrostatic latent image formed on the latent image carrier with a developer of a plurality of colors containing at least toner, and a predetermined visible image pattern formed on the latent image carrier is detected by an optical sensor. In the image forming apparatus having the means, a first background detecting means for detecting a background portion of the latent image carrier by an optical sensor when the developer is not in contact with the latent image carrier, and a latent image carrier. On the other hand, when the developer is in contact, the second background detecting means for detecting the background portion of the latent image carrier by the optical sensor and the detecting voltage comparing means for comparing the detecting voltages by the first and second background detecting means. And the control means for controlling the image forming operation according to the comparison result of the detection voltages by the detection voltage comparison means (claim 1).

(2). The image forming apparatus according to (1), wherein a predetermined visible image pattern formed on the latent image carrier is detected by an optical sensor, and the detected value is compared with a reference value to control toner replenishment. In the image forming apparatus, the detection voltage of the background portion of the latent image carrier by the optical sensor when the developer is not in contact with the latent image carrier, and the optical voltage when the developer is in contact with the latent image carrier A means for comparing and determining the detection voltage of the background portion of the latent image carrier by the sensor to correct the reference value is provided (claim 2). (3). The image forming apparatus according to (1), wherein a predetermined visible image pattern formed on the latent image carrier is detected by an optical sensor, and the detected value is compared with a reference value to control toner replenishment. In an image forming apparatus having a variable unit capable of changing at least one of a charging potential and a light amount of a latent image carrier and a developing bias, a latent image formed by an optical sensor when the developer is not in contact with the latent image carrier. The detection voltage of the latent image bearing member is compared and determined by comparing the detection voltage of the background portion of the latent image bearing member with the detection voltage of the latent image bearing member by the optical sensor when the developer is in contact with the latent image bearing member. A means for variably controlling at least one of the charging potential, the amount of light and the developing bias is provided (Claim 3). (4). In the image forming apparatus according to (1), (2) or (3), the detection voltage and the latent image of the background portion of the latent image carrier by the optical sensor when the developer is not in contact with the latent image carrier. A means for comparing and determining the detection voltage of the background portion of the latent image carrier by the optical sensor when the developer is in contact with the carrier, and stopping the copying operation when it is determined that the background stain is above a predetermined level It was decided to have (Claim 4).

(5). In the image forming apparatus according to (1) or (2) or (3) or (4), when comparing the detection voltages by the first and second background detection means, the detection voltages are compared for each color. (Claim 5).

[0009]

Function: The background detection voltage when the developer is not in contact with the latent image carrier is compared with the background detection voltage when the developer is in contact.

[0010]

【Example】

(I) Image forming apparatus suitable for carrying out the present invention FIG. 7 shows a color image forming apparatus suitable for carrying out the present invention.
Will be described with reference to. This color image forming apparatus is composed of a mechanical component such as a color image reading device, a color image recording device, a paper feeding bank, and a control unit for controlling these mechanical components.

(A) First, the mechanical components will be described. A color image reading device (hereinafter, referred to as a color scanner) 200 displays an image of an original 180 on a contact glass 202 with an illumination lamp 205 and a mirror group 204.
Color sensor 20 via A, B, C and lens 206
An image is formed on the sheet 7, and color image information of the original is read for each color separation light of, for example, blue, green, and red, and converted into an electric image signal.

In this example, the color sensor 207 is composed of blue, green, and red color separation means and a photoelectric conversion element such as a CCD (charge coupled device), and simultaneously reads three colors. And this color scanner 20
Based on the blue, green, and red color-separated image signal intensity levels obtained in 0, color conversion processing is performed by an image processing unit (not shown), and black (hereinafter referred to as Bk), cyan (hereinafter, referred to as Bk). Color image data of C), magenta (hereinafter referred to as M), and yellow (hereinafter referred to as Y) are obtained.

This color image data is used as a color image recording device (hereinafter referred to as a color printer) 4 described below.
00 to visualize with Bk, C, M, and Y colors to obtain a final color copy. The operation method of the color scanner 200 for obtaining Bk, C, M, and Y images is as follows. In FIG. 7, when the illumination / mirror optical system receives a scanner start signal in time with the operation of the color printer 400. Scan the original in the direction of the left arrow, and set 1 for each scan.
Get color image data.

By repeating this operation four times in total, sequential four-color image data is obtained. And each time,
The four color full-color images are formed by sequentially superimposing the images on the color printer 400 while visualizing the images.

Next, an outline of the color printer 400 will be described. The writing optical unit converts the color image data from the color scanner into an optical signal and performs optical writing corresponding to the original image to form an electrostatic latent image on the drum-shaped photoconductor 414 as a latent image carrier. To do.

The writing optical unit is composed of a laser emission means 441, an emission drive control section (not shown) thereof, a polygon mirror 443, a rotation motor 444 thereof, an fθ lens 442, a reflection mirror 446 and the like. ing.

The photoconductor 414 rotates in a counterclockwise direction as shown by the arrow, around which the photoconductor cleaning unit 421, a charge eliminating lamp 414M, a charger 419, a potential sensor 414D, and a revolver developing device. Four
Twenty selected developing devices, an optical sensor 414P as a developing density pattern detector, an intermediate transfer belt 415, and the like are arranged.

Here, the optical sensor 414P includes a first background detecting means for detecting the background portion of the photoconductor when the developer is not in contact with the photoconductor, and the developer for the photoconductor. It also serves as second background detecting means for detecting the background portion of the photoconductor in the contact state.

The Bk image is formed as follows.
The charger 419 uniformly charges the photoconductor 414 with a negative charge to about −700 V by corona discharge. Then, the laser light emitting means 441 performs raster exposure based on the Bk signal. In this way, when the raster image is exposed, the charge in proportion to the amount of exposure light disappears in the exposed portion of the photoconductor 414 that is initially uniformly charged, and an electrostatic latent image is formed. This electrostatic latent image is developed by the revolver developing device 420.

The revolver developing device 420 includes a Bk developing device 420K, a C developing device 420C, an M developing device 420M, a Y developing device 420Y, and a revolver rotation drive for rotating each developing device in a counterclockwise direction as shown by an arrow. (Not shown).

In order to develop the electrostatic latent image, each developing device is
The developing sleeves 420KS, 420CS, 420MS, which rotate by bringing the ears of the developer into contact with the surface of the photoconductor 414,
420YS and a developing paddle that rotates to scoop up and agitate the developer.

In the standby state, the revolver developing device B
When the copy operation is started, the color scanner 200 sets Bk at a predetermined timing.
The reading of the image data is started, and based on the image data, the optical writing by the laser beam and the latent image formation are started (hereinafter, the electrostatic latent image by the Bk image data is referred to as Bk latent image. C, M and Y are also referred to. the same.).

In order to enable development from the front end of the Bk latent image, the developing sleeve 420KS is started to rotate before the front end of the latent image reaches the developing position of the Bk developing device, and the Bk latent image is transferred with the Bk toner. develop. After that, the developing operation of the Bk latent image area is continued, but when the leading edge of the latent image passes the Bk developing position, the revolver developing device rapidly rotates from the Bk developing unit developing position to the next color developing position. This is completed at least before the leading edge of the latent image by the next image data arrives.

When the image forming cycle is started, the photoreceptor 4
14 is rotated counterclockwise as indicated by an arrow, and the intermediate transfer belt 415 is rotated clockwise by a drive motor (not shown). This intermediate transfer belt 4
With the rotation of 15, the Bk toner image is formed, the C toner image is formed, the M toner image is formed, and the Y toner image is formed. Finally, in the order of Bk, C, M, and Y, the intermediate transfer belt is formed. A toner image is formed on 415 in an overlapping manner.

The toner in the developing device 420 is negatively charged by stirring with the ferrite carrier, and
The Bk developing sleeve 420KS of the present developing device is the photosensitive member 41.
The metal base layer 4 is biased by a power supply means (not shown) to a potential in which a negative DC potential and an alternating current are superposed.

As a result, the toner does not adhere to the portion of the photoconductor 414 where the electric charge remains, and the Bk toner is adsorbed to the non-charged portion, that is, the exposed portion, and the Bk toner that is similar to the latent image can be formed. A visual image will be formed.

The intermediate transfer belt 415 is connected to the driving roller 41.
5D, a transfer counter roller 415T, a cleaning counter roller 415C, and a driven roller group are stretched and controlled by a drive motor (not shown). The material of the belt is ETFE (ethylene tetrafluoroethylene),
The electric resistance is a surface resistance and is called a medium resistance of 10 ⁸ to 10 ¹⁰ Ω / cm ² .

The Bk toner image formed on the photoconductor 414 is transferred by a belt transfer corona discharger (hereinafter referred to as a belt transfer device) 416 onto the surface of an intermediate transfer belt 415 which is driven at a constant speed in contact with the photoconductor. Transcribed. Less than,
The toner image transfer from the photoconductor 414 to the intermediate transfer belt 415 is called belt transfer.

A small amount of untransferred residual toner on the photoconductor 414 is cleaned by the photoconductor cleaning unit 421 in preparation for reuse of the next color of the photoconductor 414. The toner collected by the photoconductor cleaning unit 421 is stored in an exhaust toner tank (not shown) via the collection pipe.

The intermediate transfer belt 415 has a photosensitive member 414.
The Bk, C, M, and Y toner images sequentially formed on the sheet are sequentially aligned on the same surface to form a belt transfer image of four-color superimposition, and then collectively transferred onto a transfer paper by a corona discharge transfer device. To do.

On the side of the photoconductor 414, after the Bk step, C
As the process proceeds, the C image data starts to be read by the color scanner at a predetermined timing, and the C latent image is formed by laser writing using the image data.

The C developing device rotates the revolver developing device with respect to the developing position after the trailing end of the previous Bk latent image has passed and before the leading end of the C latent image has arrived. C
Develop the latent image with C toner.

After that, the development of the C latent image area is continued, but when the trailing edge of the latent image passes, the rotation of the C developing unit is performed as in the case of the Bk developing device. This is also completed before the leading edge of the next M latent image reaches. It should be noted that the M and Y steps are the same as the steps Bk and C described above in respect of the operations of reading image data, forming a latent image, and developing, and therefore a description thereof will be omitted.

Under the condition where the developing roller faces the photoconductor 414, the toner on the developing roller is in contact with the photoconductor 414, and the toner may adhere to the background portion of the photoconductor.
On the other hand, since the revolver developing device rotates due to the change of the color to be developed and moves from the developing roller currently facing the developing roller to the developing roller of the next color, the photosensitive member 414 has no developing roller facing the developing roller. The toner is not in contact with the photoconductor 414.

In the invention of this application, as will be described later, it is possible to accurately detect the background of the photoconductor when the developer is in contact with the photoconductor and when the photoconductor is not in contact, and compare the detection voltages. Performs smooth background detection.

The belt cleaning device 415E is composed of an entrance seal, a rubber blade, an ejection coil and an entrance seal, and a blade contact / separation mechanism. While the color is transferred to the belt, the inlet seal and the blade are separated from the belt surface by the blade contacting / separating mechanism.

The paper transfer corona discharger 417 (hereinafter referred to as a paper transfer machine) applies AC + DC or DC component by a corona discharge method to transfer the superimposed toner image on the intermediate transfer belt onto the transfer paper. . Transfer papers of various sizes are stored in the transfer paper cassette 482 in the paper feed bank, and the paper feed roller 483 is transferred from the specified size paper storage cassette.
The paper is fed and conveyed in the registration roller direction by A, B, and C. Reference numeral 412B2 indicates a manual feed tray for OHP paper, thick paper, or the like.

When the image formation is started, the transfer paper 190
Is fed from any one of the above-mentioned sheet feeding ports, and stands by at the nip portion of the registration roll pair 418R. Paper transfer device 417
When the front end of the toner image on the intermediate transfer belt 421 is approaching, the registration roller pair 418R is driven so that the front end of the transfer paper 190 exactly coincides with the front end of the image, and the registration of the paper and the image is performed.

In this way, the paper transfer device 41 in which the transfer paper 190 is superposed on the intermediate transfer belt image and connected to the positive potential
Pass over 7. At this time, the transfer paper is positively charged by the corona discharge current, and most of the toner image is transferred onto the transfer paper.

Subsequently, when passing through a separation static eliminator by an AC + DC corona (not shown) arranged on the left side of the paper transfer device 417, the transfer paper is statically discharged, separated from the intermediate transfer belt and transferred onto the conveyor belt 422.

The transfer paper on which the four-color superposed toner images are collectively transferred from the surface of the intermediate transfer belt is conveyed to the fixing device 423 by the paper conveying belt 422, and the nip between the fixing roller 423A and the pressure roller 423B controlled at a predetermined temperature. The toner image is melted and fixed in a portion, sent out of the main body by a pair of discharge rolls 424, and is stacked face up on a copy tray (not shown) to obtain a full-color copy.

The surface of the photoconductor 414 after the belt transfer is cleaned by the photoconductor cleaning unit 421 including a brush roller, a rubber blade, etc., and the charge is uniformly discharged by the charge removing lamp 414M. The surface of the intermediate transfer belt 415 after the toner image is transferred onto the transfer paper is cleaned by pressing the belt cleaning device 415E again by the blade contacting / separating mechanism to press the blade.

In the case of repeat copying, the operation of the color scanner and the image formation on the photoconductor are carried out in the second (first color) image process at a predetermined timing after the first (fourth color) image process. move on. In addition, the intermediate transfer belt 41
In the case of No. 5, following the batch transfer process of the first four-color superimposed image onto the transfer paper, the second Bk toner image is belt-transferred to the area where the surface is cleaned by the belt cleaning device. To do. After that, the same operation as the first sheet is performed.

The above is the description of the copy mode for obtaining four full colors of A4 size horizontal feed, but in the case of the three-color copy mode and the two-color copy mode, the designated color and the number of times are the same as above. The operation will be performed.

In the case of a single-color copy, only the developing device of the predetermined color of the revolver developing device 420 is in the developing operation (developing position of the predetermined color) state until the predetermined number of sheets is completed, and the blade of the belt cleaning device 415E is moved. The copying operation is continuously performed with the belt pressed.

A method of stirring the developer will be described. FIG.
Reference numeral 0 indicates a cross section of the revolver developing device 420, and in the state of the drawing, the Bk developing device 420K is located facing the photoconductor 414. The revolver developing device 420 is
By the developing casing 420A, each developing device 420Bk,
It is divided into four parts 420C, 420M and 420Y.

Since the developing units have the same structure as each developing unit, the Bk developing unit 420K will be described. In the developing casing, a developing roller 420KS that includes a magnet roller (not shown), a developing doctor 420KD that regulates the amount of developer drawn up when the developer on the developing roller is guided to the photoconductor 414, and a developer agitator Paddle 420KP and screw paddle 420KSP
And a screw 420KS '. Code 4
20KC indicates a screw case covering a screw 420KS '. As for the developer, a lid 420K for collecting the developer is appropriately used.
Recovered from Z.

As shown in FIG. 11, these screws 420KS ', developing doctor 420KD, paddle 420K.
P and the like are provided between the front side plate 420FF and the rear side plate 420RR of the revolver developing device. Front side plate 420FF
The section between the rear side plate 420RR and the rear plate 420RR substantially matches the length of the photoconductor 414.

A cartridge for replenishing toner is provided as a toner replenishing portion outside the front side plate 420FF (see FIG. 12). The toner from the cartridge is supplied to the screw paddle 420KSP as indicated by the arrow Q, and the paddle 420KP and the screw 4 as indicated by the arrow.
It is circulated and conveyed between 20 KS 'and agitated so that there is no deviation in the toner concentration of the developer.

As described above, the screw case 420
The developer in the KC is conveyed from the rear to the front by the screw 420KS ', passes through the front plate 420FF and drops to the lower screw paddle 420KSP, and by the screw paddle 420KSP, this time from the front to the rear,
It is conveyed through the front side plate 420FF.

The developing roller 420KS is a paddle 420K.
The developer existing on P is pumped up and conveyed to the developing area. The developer regulated by the partial developing doctor 420KD drops into the screw case 420KC. In this way, the developer circulates.

Toner supply will be described. As shown in FIG. 12, a toner cartridge for each color is installed in the toner supply section. The toner cartridges for Bk, C, M, and Y are designated as 420KT and 420C, respectively.
It is shown by T, 420MT, and 420YT. Here, the Bk toner cartridge 420KT is installed at the center (rotation center) of the revolver developing device 420 because the Bk developer is frequently used, and has a long capacity in the direction perpendicular to the paper surface of FIG. With the rotation of the revolver developing device, as shown by an arrow R, through an opening not shown,
Toner is supplied to the Bk toner hopper 420KTH.

Between the Bk toner hopper 420KTH and the screw paddle 420KSP which conveys the replenishment toner, the replenishment roller 420KR regulates the replenishment roller 4K.
A replenishment motor 420HM that rotates 20 KR is installed.

When replenishing toner, the replenishing motor 420HM is rotated to drop the toner in the toner cartridge or the toner hopper onto the screw paddle, and the toner is conveyed along with the rotation of the screw paddle. While being mixed and agitated at the developing dropping portion from the 420 KC to the screw paddle, it is fed into the developing device through the front side plate 420FF.

(B) The control section will be described. In FIG. 8, reference numeral 100 indicates the configuration of the entire control unit. According to a predetermined program stored in the internal memory of the control unit 100, the color scanner 200 and the color printer 4
00, paper feed bank, etc. are controlled. Control unit 100
Can output a signal for forming a predetermined visible image pattern, which will be described later, by the laser emission drive unit 105, and, for example, a value corresponding to the gradation “6” shown in FIG. 9 is assigned.

The control section 100 has a microcomputer 100A for performing arithmetic control processing. Connected to the microcomputer 100A are a basic program for arithmetic control processing, a ROM 100B that stores basic data for these processing, and a RAM 100C for loading various data.

In this microcomputer 100A,
An external device is connected via the I / O interface 100D, and an optical sensor 414P is connected to the input side of the I / O interface 100D.

The output side of the I / O interface 100D is connected to a developing bias control drive unit 102, a charge control drive unit 103, a toner replenishment drive unit 104, and a laser emission drive unit 105.

(Ii) Description Corresponding to Claims 1 and 5 In this example, when the developer is not in contact with the photoconductor 414, the optical sensor 414P detects the background portion of the photoconductor 414. Background detection means for detecting the background portion of the photoconductor by the optical sensor 414P when the developer is in contact with the photoconductor 414, and the first and second background detection It has a detection voltage comparison means for comparing the detection voltages by the means, and a control means for controlling the image forming operation according to the comparison result of the detection voltages by the detection voltage comparison means.

The control procedure in this example is performed as follows. In FIGS. 1, 7, and 13, the print switch is turned on (step A1), the grid bias is turned on, the charger 419 is turned on (step A2), and the drum motor for driving the photoconductor 414 is turned on. The developing bias is turned on (step A3) and the developing bias voltage is applied to the developing roller (step A3).
4), the developing motor is turned on (step A5), and the developing roller starts rotating.

Next, in step A6, with respect to the Bk developing unit, the optical sensor 414P detects the background when the developer on the developing roller is in contact with the photoconductor.
Obtain the detection voltage V _SG *.

The detection by the optical sensor 414P is L
The light emitted from the ED is reflected by the photoconductor, and the voltage is detected when the optical sensor that receives the reflected light receives the voltage.

Further, the optical sensor 414P detects the background of the photoconductor in the non-contact state between the developing roller and the photoconductor when the developing device is already switched, and the detection voltage V _{SG +} and the detection voltage V _{SG are} detected. * Is compared with each other, and toner replenishment control is performed based on the background detection information in which the influence of the contact of the toner on the developing roller with the photoconductor is eliminated.

Here, the detection of the detection voltage V _{SG +} of the background portion when the developer is not in contact with the photosensitive member will be described. The detection voltage V _{SG +} is, as shown in FIG. 5, until the toner on the developing roller leaves the contact with the photoconductor when the revolver developing device rotates, until the toner on the developing roller of the next color comes into contact with the photoconductor. This is performed by detecting the background of the photoconductor by the optical sensor during the period in which the developer is not in contact with the photoconductor at all.

At that time, considering the unevenness of the circumference of the photosensitive member,
In this embodiment, as shown in the flow chart of FIG. 4, the detection voltage V _{SG +} is calculated by taking the moving average of the past 5 times. In this method, since it is possible to detect the toner in a state where the toner is not adhered to the photoconductor at all times, not only the correction for the background stain when the toner is in contact, but also the improvement in the accuracy of the pattern detection,
It is possible to correct deterioration of the optical sensor, decrease of detection output due to toner scattering, and deterioration of the surface of the photoconductor with time.

At step A7, when the revolver developing device is rotated by the drive of the revolver motor and the developing roller is switched, the background is detected by the optical sensor when the toner on the developing roller and the photoconductor are not in contact with each other. 414P, and the detection voltage V _{SG +} used in step A6 is detected.

Thereafter, in steps A8 to A13, the above Bk for each of the C, M and Y developing devices is described.
The flow of the procedure similar to that in the developing device of is executed.
These operations are repeatedly executed by step A14.

When the predetermined copying operation is completed, the developing motor is turned off (step A15), the developing bias is turned off (step A16), the drum motor for driving the photoconductor 414 is turned off (step A17), and the grid bias is applied. Is turned off and the charger 419 is turned off (step A8), and the process ends.

Steps A6, A8, A10, A12
FIG. 2 shows a detailed flow of toner replenishment and background stain detection in FIG. As described based on the flow of FIG. 1, after the copy switch is pressed to turn on the grid bias, the drum motor, the developing motor, and the developing bias, the LED of the optical sensor 414P is turned on at a predetermined timing (step B1). , B2), first, the background portion where the Bk toner is in contact with the photoconductor is detected. This detection value is taken in as the background portion (white portion) detection voltage V _SG during toner contact (steps B3, 4).

For comparison with the detection voltage V _{SG +} ,
As shown in the flow of FIG. 3, leave the memory data of the past eight V _SG, and calculates an average detection voltage V _SG * (moving average) of V _SG.

In FIG. 2, after the background portion (white portion) detection voltage V _SG during toner contact is detected, the toner replenishment control is performed with a predetermined exposure amount, here, the sixth laser power in FIG. 9 described above. A pattern is developed and this pattern is detected by an optical sensor. This detection value is set to V _SP (steps B5 and B6), and is standardized by the detection value V _{SG +} to V _SP / V _SG +
Then, V _SP / V _{SG +} is compared with the reference value V _TC (step B12). If the detected value of the toner replenishment control pattern portion is larger than the reference value, that is, V _SP / V _{SG +} > V _TC
In this case, the toner replenishing motor is rotated at a predetermined timing for a predetermined time to replenish the toner (steps B13, B).
14, B15, B16).

Further, V _SP / V _{SG +} is compared with the reference value V _TC, and when the density of the toner replenishment control pattern portion is equal to or smaller than the reference value, that is, when V _SP / V _{SG +} ≤V _TC Indicates that toner replenishment is not performed (No in step B12).

Detection value V _SP , detection voltage V _SG , detection voltage V
_{The SG +} detection timing is as shown in the timing chart of FIG.

In this example, when the toner is not in contact with the photoconductor, the first background detecting means for detecting the background portion of the photoconductor 414 by the optical sensor 414P, and when the toner is in contact with the photoconductor 414 A second background detecting means for detecting the background portion of the photoconductor by the optical sensor 414P, a detecting voltage comparing means for comparing the detecting voltages by the first and second background detecting means, and further this detecting voltage comparing means. The control means for controlling the image forming operation in accordance with the comparison result of the detection voltage by is included in the microcomputer 100A (see FIG. 8) that executes the flow of FIGS. 1 and 2.

The image forming operation according to the present embodiment is defined in claim 2.
Correction of the reference value in claim 3, variably controlling at least one of the charging potential, the amount of light, and the developing bias in claim 3, and the operation of stopping the copy operation in claim 4.

(Iii) Claims 1, 4 and 5
2. In the flow shown in FIG. 2, the difference between the detection voltage V _{SG +} and the average detection voltage V _SG *, V _{SG +} −V _SG *, is calculated (steps B7 and B8) and is larger than the predetermined value (α). In this case, it is determined that the background stain is remarkably large, and the copy operation is ended (step B9). It also issues a warning. In this example, in step B8, α = 0.5 V was set and implemented.

In this example, the detection voltage of the background portion of the photoconductor 414 by the optical sensor 414P when the toner is not in contact with the photoconductor 414 and the optical sensor 414P when the toner is in contact with the photoconductor 414 are used. Photoconductor 4
When the detection voltage of the background portion 14 is compared / determined and it is determined that the background stain is equal to or more than a predetermined value, the means for stopping the copy operation is the microcomputer 10 that executes the flow of FIG.
0A (see FIG. 8).

(Iv) Description Corresponding to Claim 1, Claim 2, and Claim 5 In the flow of FIG. 2, in step B8, V _{SG +} −V _SG
When * is not larger than the predetermined value (α) and it is determined that the background stain is small, the process proceeds to the next step B10.

At step B8, V _{SG +} −V _SG
When it is determined that * is larger than the predetermined value (β), that is, when β <V _{SG +} −V _SG * <α, it is determined that the background stain has occurred, and the reference value V _TC is increased. (Step B11). By changing the reference value V _TC , the toner density can be suppressed to a low level. In this example,
In step B10, β = 0.15V was set and implemented.

In this example, the detection voltage of the background portion of the photoconductor by the optical sensor 414P when the toner is not in contact with the photoconductor 414 and the photosensitivity by the optical sensor 414P when the toner is in contact with the photoconductor. Means for comparing / determining the detection voltage of the background portion of the body to correct the reference value for toner replenishment control is included in the microcomputer 100A (see FIG. 8) that executes the flow of FIG.

(V) Description Corresponding to Claims 3 and 5 With reference to the description of the flow of FIG. 2 in the above (iv),
Instead of changing the reference value as in step B11, as shown in the flow of FIG.
_B can be changed to V _B + ΔV _B , or in accordance therewith, either the charging potential of the charger 419 or the writing light quantity by the laser emitting means 441 can be changed.

In the present embodiment, when the developing bias voltage is changed, the developing potential is −700 V and the developing bias is −520 V. When the developing bias is corrected, ΔV _B = 16.
Performed at V.

In this example, the detection voltage of the background portion of the photoconductor by the optical sensor 414P when the toner is not in contact with the photoconductor 414 and the photosensing by the optical sensor 414P when the toner is in contact with the photoconductor. The means for variably controlling at least one of the charging potential and the light amount of the photoconductor 414 and the developing bias by comparing and determining with the detection voltage of the background portion of the body 414 is a microcomputer 100A (FIG. 8)).

[0084]

According to the present invention, the background stain on the background portion of the photoconductor can be detected accurately and easily.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an embodiment of the present invention.

FIG. 3 is a flowchart illustrating an embodiment of the present invention.

FIG. 4 is a flowchart illustrating an embodiment of the present invention.

FIG. 5 is a flowchart illustrating an embodiment of the present invention.

FIG. 6 is a flowchart illustrating an embodiment of the present invention.

FIG. 7 is a front view illustrating a schematic configuration of an image forming apparatus suitable for implementing the present invention.

FIG. 8 is a block diagram illustrating means for implementing the present invention.

FIG. 9 is a graph illustrating the relationship between writing intensity and optical sensor output.

FIG. 10 is a cross-sectional view of essential parts of a revolver developing device.

FIG. 11 is a cross-sectional view illustrating the supply and circulation paths of the developer in the revolver developing device.

FIG. 12 is a side view of the main part of the revolver developing device in which the developing roller is at the Bk developing position, as viewed from the developer storage portion side.

FIG. 13 is a timing chart illustrating an example of the present invention.

[Explanation of symbols]

 414P optical sensor

Claims (5)

[Claims] 1. A developing device for visualizing an electrostatic latent image formed on a latent image carrier by a developer of a plurality of colors containing at least toner, and a predetermined visible image formed on the latent image carrier. An image forming apparatus having means for detecting a pattern by an optical sensor, wherein the optical sensor detects a background portion of the latent image carrier when the developer is in a non-contact state with the latent image carrier. A detection means and a second means for detecting the background portion of the latent image carrier by the optical sensor when the developer is in contact with the latent image carrier.
Background detection means, detection voltage comparison means for comparing the detection voltages by the first and second background detection means, and control means for controlling the image forming operation according to the comparison result of the detection voltages by the detection voltage comparison means. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein:
In an image forming apparatus for controlling a toner replenishment by detecting a predetermined visible image pattern formed on a latent image carrier by an optical sensor and comparing the detected value with a reference value, The detection voltage of the background portion of the latent image carrier by the optical sensor when the developer is not in contact with the latent image carrier of the latent image carrier by the optical sensor when the developer is in contact with the latent image carrier. An image forming apparatus comprising: a unit that compares and determines a detection voltage of a background portion to correct the reference value. 3. The image forming apparatus according to claim 1, wherein:
A predetermined visible image pattern formed on the latent image carrier is detected by an optical sensor, toner detection is controlled by comparing the detected value with a reference value, and the charging potential and light amount of the latent image carrier and the developing bias are controlled. An image forming apparatus having at least one changeable variable means, the detection voltage of the background portion of the latent image carrier by the optical sensor when the developer is in a non-contact state with the latent image carrier,・ Compare with the detection voltage of the background portion of the latent image carrier by the optical sensor when the developer is in contact with the latent image carrier.
An image forming apparatus comprising: a unit that makes a determination and variably controls at least one of a charging potential, a light amount, and a developing bias of the latent image carrier. 4. The image forming apparatus according to claim 1, 2, or 3, wherein the latent image carrier is detected by the optical sensor when the developer is not in contact with the latent image carrier. The detection voltage of the background portion and the detection voltage of the background portion of the latent image bearing member by the optical sensor when the developer is in contact with the latent image bearing member are compared / determined to determine that the background stain is not less than a predetermined value. An image forming apparatus having a means for stopping the copying operation when a judgment is made. 5. In the image forming apparatus according to claim 1, claim 2, claim 3, or claim 4, when the detection voltages of the first and second background detection means are compared, the detection voltage for each color is compared. An image forming apparatus, characterized in that