JP3217252B2 - Image forming device - Google Patents

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 electrophotography and electrostatic recording, and more particularly to an image forming apparatus in which a so-called toner image having resin, carbon, pigment, dye, etc. is fixed on a recording material to form an image. The present invention relates to a forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a laser beam printer, a toner image formed on a photosensitive drum serving as an image carrier through processes such as charging, exposure and development is recorded on paper or the like by a transfer means. The image is transferred onto a recording material, and then heated and pressed by a fixing roller, a pressure roller, or the like of a fixing unit, and is fixed on the recording material as a permanent image.

A multicolor image forming apparatus, for example, 4
In a full-color image forming apparatus, four different color toners are used, and these four color toners are sequentially transferred so as to be superimposed on a recording material wound around a transfer drum as transfer means. The fixing is performed by a heat fixing device as a fixing unit.

In order to obtain a high-quality full-color image, a high density contrast is required. That is, it is necessary to increase the maximum image density.

[0005] The image density is, for example, X-Ri
The reflection density value measured with an image density measuring instrument manufactured by TE Co., Ltd., model number 418, 938, etc. is 1.5 or more, more preferably 1.
It is preferably eight or more.

[0006]

However, in order to obtain an image density of 1.5 or more with a toner having a volume average particle diameter of about 8 μm, for example, a toner having a volume average particle size of 7.5 to 8.0 × 10 ⁻³ kg / m ² or more is required. Is required, a toner amount of 10.0 × 10 ⁻³ kg / m ² or more is required to obtain an image density of 1.8 or more. In addition, in the solid portion, not only a large amount of toner is formed on the recording material as described above, but also in the case of using the digital system as well as the analog system, the developed toner of adjacent pixels is stuck together. ing. Therefore, when the toner once melted in the fixing process cools and solidifies again, volume contraction occurs,
Since adjacent pixels are attached to each other, they are strongly attracted to each other, which may cause curl.

In particular, when a four-color full-color image is formed, about four times as much toner as a single-color image is formed on a recording material in a portion having a high density. The curl in such a case depends on the stiffness of the recording material to be used, but it may be completely curled with a commonly used paper of 80 g / m ² , which may make handling very difficult.

On the other hand, as a method for solving the problem of curling of a recording material after passing through a heat fixing device, Japanese Patent Laid-Open Publication No.
Japanese Patent Application Laid-Open No. 0-182460-182470 discloses that an imbalance in the amount of water evaporation on the front and back surfaces of a recording material in a heat fixing device causes curling. No mention is made of the occurrence of curl due to volume shrinkage when the toner once melted cools and solidifies again in the fixing process as described above.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of excellently handling a recording material without generating a large curl after fixing when forming a high density image, particularly in a full color image. It is to be.

[0010]

According to a first aspect of the present application Means for Solving the Problems] The object is an image bearing member, a charging means for uniformly charging said image bearing member, corresponding to the image density signal The image charged by the charging means to form an electrostatic latent image
Exposure means for exposing the surface of the carrier, developing means for developing the electrostatic latent image on the image carrier with a developer to form a developer image, and heating and heating the developer image transferred onto the recording material. in the image forming apparatus having a fixing unit for fixing on the recording material by applying, the total amount of the developer in the developer image you formed on the recording material is given
Judgment to judge whether the value exceeds the value according to the image density signal
Means and, if the total amount of the developer is determined to exceed the predetermined value by the determining means, the current total amount of the developer is less than a predetermined value
It is achieved by having a correction means for correcting the light <br/> beam emission time length by the exposing unit to form an image agent image on the recording material.

[0011] Further, according to the second invention of the present application, the object is an image bearing member, and <br/> charging means for uniformly charging said image bearing member, corresponding to the image density signal Form an electrostatic latent image
The surface of the image carrier charged by the charging means
Exposure means for exposing, and developing the electrostatic latent image on the image carrier
Yusuke and developing means for developing, and fixing means for fixing onto a heated pressurized recording material a developer <br/> image transferred onto the recording material by agents
That in the image forming apparatus, whether an image density signal amount of the developer in the developer image you formed on the recording material exceeds a predetermined value
Determining means for determining according to the condition, and developing by the determining means.
If it is determined that the total amount of the developer exceeds a predetermined value ,
To form a developer image having a total amount equal to or less than a predetermined value on a recording material
Is achieved by having a correction means for correcting the difference between the by <br/> developing bias charging bias and the developing unit by the charging unit.

Therefore, according to the first aspect of the present invention, the total amount of the developed image formed on the recording material is predicted, and when the total amount exceeds a predetermined value, the total amount of the developed image corresponding to the recording image signal is predicted. The light emission time length of the light source controlled by the control means is corrected to keep the image density within a predetermined value, so that the total amount of the developed image developed on the image carrier and transferred onto the recording material is a predetermined amount. It does not exceed the value and does not cause curling after fixing.

According to the second aspect of the present invention, the total amount of the developed image formed on the recording material is predicted, and when the total amount exceeds a predetermined value, the potential contrast by the charging means is corrected. Then, since the image density is kept within a predetermined value,
The total amount of the developed image developed on the image carrier and transferred onto the recording material does not exceed a predetermined value, and no curling occurs after fixing.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram showing an electrophotographic color printer which is an embodiment of the image forming apparatus according to the present invention. This printer includes an electrophotographic photosensitive drum 1 as an image carrier that rotates in the direction of an arrow. Around the photosensitive drum 1, a charger 2 serving as a charging unit, developing units 4c, 4m, 4y, and 4B
k, a rotary developing device 4 serving as a developing unit, a transfer drum 5 serving as a transfer unit having a transfer discharger 5b, a cleaning unit 6, and a laser beam scanner LS which constitutes an exposure unit disposed above the photosensitive drum 1. And the like.

In the present embodiment, the developer supplied to the photosensitive drum 1 from each developing device is a two-component developer containing toner particles and carrier particles. The developing device 4m has a magenta toner, the developing device 4y has a yellow toner, and the developing device 4B
The developer of k contains a black toner, and a full-color image can be formed.

A document to be copied is read by a document reading device (not shown).
And the like, and outputs an image signal corresponding to each of cyan, magenta, yellow, and black-and-white image information of the document. The semiconductor laser incorporated in the printer is controlled in accordance with these image signals, and emits a laser beam E. The output signal from the computer can be printed out.

Hereinafter, the sequence of the entire apparatus according to the present embodiment will be briefly described by taking a full color mode as an example. First, the photosensitive drum 1 is uniformly charged by the charger 2. Next, scanning exposure is performed by a laser beam E modulated by a cyan image signal, and an electrostatic latent image is formed on the photosensitive drum 1. This latent image is inverted by a cyan developing device 4c previously set at a developing position. Developed.

On the other hand, the recording material P such as paper taken out of the cassette 7 and advanced through a paper feed guide (not shown) and a paper feed roller 8 is supplied with a suction roller 5g of the transfer drum 5 and a suction charger 5c. Is electrostatically wound by the action of
The transfer drum 5 rotates in the direction of the arrow in synchronization with the photosensitive drum 1, and after the cyan-developed image developed by the cyan developing device 4 c is uniformly charged by the post-charging device 101, it is transferred at the transfer portion. The image is transferred onto the recording material P by the charger 5b. The transfer drum 5 continues to rotate, and prepares for transfer of an image of the next color (magenta in FIG. 2).

On the other hand, the photosensitive drum 1 is cleaned by the cleaning means 6, is charged again by the charger 2, receives the above-described exposure by the laser beam E modulated by the next magenta image signal, and forms an electrostatic latent image. Is formed. During this time, the developing device 4 rotates, and the magenta developing device 4m is fixed at a predetermined developing position, performs reversal development of the latent image corresponding to magenta, and forms a magenta visible image.

Subsequently, the above-described steps are performed on the yellow image signal and the black image signal, respectively. When the transfer of the four-color image (toner image) is completed, the recording material P is discharged by the charger 5h. Then, the toner image is separated from the transfer drum 5 by a separation claw (not shown), and is sent to a hot-press roller fixing device 9 as a fixing unit. Then, in the hot-press roller fixing device 9, the four colors of visible images overlapping the recording material P are fixed on the recording material P by heating and pressing, and discharged,
A series of full-color print sequences is completed, and a required full-color print image is formed.

As shown in FIG. 3, the exposing means comprises a semiconductor laser unit 102, a polygon mirror 10 rotating at a high speed.
5, a f-θ lens group 106 and the like. The semiconductor laser unit 102 outputs a laser beam E modulated in accordance with a time-series digital pixel signal calculated and output by an image reading device, an electronic computer or the like. Oscillates to expose the surface of the photosensitive drum 1. Each of the developing units performs reversal development in which toner charged to the same polarity as the charging polarity of the charger 2 is applied to the bright portion potential portion of the latent image. Is exposed.

More specifically, in FIG. 3, the semiconductor laser section 102 as a light source section is connected to a laser driver 500 as a light emission signal generator for sending a light emission signal (drive signal) for generating a laser beam. It flashes according to the light emission signal of the laser driver 500. A laser beam E emitted from the semiconductor laser unit 102 is converted into substantially parallel light by a collimator lens system 103. The collimator lens system 103 is moved in the direction of the arrow A, which is the optical axis direction of the laser beam, by a focus adjusting means 104 including a rack to which the collimator lens system 103 is fixed, a pinion meshing with the rack, a motor for driving the pinion, and the like. It is possible to move to.

A polygon mirror, ie, a rotating polygon mirror 105
Scans parallel light emitted from the collimator lens system 103 in the direction of the arrow by rotating at a constant speed in the direction of the arrow B. An f-θ lens group 106 (106a, 106b, 106) provided in front of the rotating polygon mirror 105
In (c), the laser beam deflected by the rotary polygon mirror 105 is formed into a spot on the surface to be scanned, that is, the photosensitive drum 1, and the scanning speed is made constant on the surface to be scanned.

The direction in which the laser beam E moves on the photosensitive drum 1 by the rotary polygon mirror 105, that is, the direction indicated by the arrow C, is called the main scanning direction. The main scanning direction is a direction in which the photosensitive drum 1 moves in the exposure unit, that is, a direction substantially perpendicular to the direction in which the recording material moves.

On the other hand, the moving direction of the photosensitive drum 1 in the exposure section is called a sub-scanning direction. The surface of the photosensitive drum 1 is raster-scanned by a laser beam by main scanning and sub-scanning.

The laser beam E is adjusted for focus adjustment before the modulation is started in accordance with the image signal to be recorded.
The light is guided via a reflecting mirror 107 onto a CCD (solid-state imaging device) 108 serving as detecting means. The CCD 108 is configured by arranging a large number of photoelectric conversion elements in a direction optically substantially equivalent to the surface of the photosensitive drum 1 in the direction of arrow C. The detection result is obtained by a laser driver 500 and a focus adjustment unit 104. Is transmitted to the control unit 100 for controlling.

Further, a signal processing unit 111 is connected to the laser driver 500 and the control unit 100. When a desired image is to be formed, the signal processing unit 11
From 1, an image output signal P is input to the control unit 100, and an image signal S is input to the laser driver 500, and the semiconductor laser unit 102 blinks in response to the image signal S. The image output signal P is output from the signal processing unit 111 before the image signal S, and the output ends after the output of the image signal S ends. The control unit 100 stops the operation of the focus adjustment unit 104 while the image output signal P is input from the signal processing unit 111.

The exposure distribution for the main scanning is formed on the surface of the photosensitive drum 1 by the scanning of the laser beam E, and the photosensitive drum 1 is rotated by a predetermined amount for each main scanning, and the image is formed on the photosensitive drum 1. A latent image having an exposure distribution according to the signal S is formed.

Next, a PWM circuit of the signal processing unit 111 which is an exposure control method used in the present embodiment will be described with reference to FIG. This PWM circuit generally includes TTL latch circuits 401 and T for latching an 8-bit image signal.
A level converter 402 for converting the TL logic level to a high-speed ECL logic level, a D / A converter 403 for converting the ECL logic level to an analog signal, an ECL comparator 404 for generating a PWM signal, and a TTL for the ECL logic level
A level converter 405 for converting to a logical level, a clock oscillator 406 for generating a clock signal 2f having a frequency twice as high as the image clock signal f, a triangular wave generator 407 for generating a substantially ideal triangular wave signal in synchronization with the clock signal 2f, and It has a 1/2 frequency divider 408 for dividing the clock signal 2f by 1/2. ECL is used everywhere to operate the circuit at high speed.
A logic circuit is provided.

The operation of the PWM circuit having the above configuration will be described with reference to FIG. 5 showing signal waveforms. The signal (a) indicates the clock signal 2f, and the signal (b) indicates the pixel clock signal f having a double period, which is related to the image signal as shown in the figure. Also, the clock signal 2 is maintained inside the triangular wave generator 407 in order to maintain the duty ratio of the triangular wave signal at 50%.
f is once frequency-divided by か ら before generating a triangular wave signal (c). Further, this triangular wave signal (c) is converted into an ECL level (0 to -1 V) to become a triangular wave signal (d).

On the other hand, the pixel signals are 00H (white) to FFH
It changes at 256 gradation levels up to (black). The symbol H is in hexadecimal. Then, the image signal (e) is
The A-converted ECL voltage is shown. In FIG. 5, for example,
The first pixel is the highest density pixel level FFH, the second pixel is a halftone level 80H, the third pixel is a halftone level 40H lower in density than the second pixel, and the fourth pixel is a halftone level lower than the third pixel. Each voltage of the adjustment level 20H is shown.

Accordingly, the comparator 404 has a pulse width corresponding to the pixel density to be formed by comparing the triangular wave signal (d) with the image signal (e) (in FIG. 5, for example, T, t ₂ , t ₂₎ . _3, t has a width such as ₄₎ to generate a PWM signal. Here, T, t ₂ , t ₃ , and t ₄ are T>
It is assumed that t ₂ > t ₃ > t ₄ .

This PWM signal is converted to a TTL level of 0 V or 5 V to become a PWM signal (f) (laser driving pulse signal having a width including 0), and is input to the laser driver circuit 500. Thus, the semiconductor laser unit 10
Numeral 2 emits light for a time corresponding to each pulse width of the signal f for each unit pixel, and scans and exposes the photosensitive drum 1. In the printer, since the reversal development is performed, the higher the density of the pixel, the longer the laser emission time.

As described above, the image density is determined by the irradiation time of the laser beam E. In this embodiment, as shown in FIG. 1, the latch circuit 40 shown in FIG.
A look-up table 400 is provided at the front stage of the image data 1 to perform gamma correction (gradation correction) of image data. The look-up table 400 is a memory in which the data of the result of the γ correction is stored, accesses the memory using an image signal of 8 bits per pixel as address data, and outputs the image signal of the desired γ corrected data. Normally, one specific gamma correction table is used in one pixel, but a plurality of types of gamma correction tables can be switched and used in one pixel as needed. In other words, for example, three types of tables are sequentially and repeatedly used for each line scan by the laser beam E, and the gamma correction in the sub-scanning direction is changed for each line to perform gradation correction.

When the density of the toner is low so that the density is not influenced by the density of the toner of each color, for example, yellow, magenta, cyan and black, the look-up table has a so-called standing γ curve. When the table is set and the density is high, a γ table having the opposite characteristic is set and provided for each formed color. A non-linear color masking circuit, for example, a secondary color masking circuit, can be provided for correction.

In the color printer shown in FIG. 2, the PWM circuit shown in FIG. 4 sequentially receives image signals of cyan, magenta, yellow, and black for each page (one page of each of a manuscript and a copy). Each time, laser modulation is performed sequentially, and one color copy is obtained by four rotations of the photosensitive drum 1.

Therefore, in the case of forming a full-color image of four colors, in a portion where the image density is high, a large amount of toner is loaded on the recording material, and curling is likely to occur.

Therefore, in the present embodiment, while the maximum image density is increased to about 1.8 in order to form a high-quality image, in order to suppress such curling after fixing,
Means are provided so that the riding amount per vehicle does not exceed a predetermined value.

Hereinafter, details of the means will be described. As a result of various experiments, the curl of the recording material has the largest effect on how many g of toner is applied per sheet, and what kind of image (whether the image is half-toned uniformly or dispersed) Riding) is not as much affected.

Further, although the amount of toner causing curl varies depending on the binder constituting the toner, in the present embodiment, if 8.0 × 10 ⁻³ kg / m ² or more of toner per unit area is applied, It was found that the curl was out of tolerance.

Therefore, the relationship between the image signal data for each color and the amount of toner applied thereto is stored in the CPU 302 in advance.

In the circuit shown in FIG.
1, an adder 301 is provided in the preceding stage, the image signal data is integrated during the pre-scan, and the integrated value is stored in the CPU 30.
The average value of the toner ride amount obtained by converting the toner ride amount through 2 and adding the four colors is 8.0 × 10 ⁻³ kg per unit area.
/ M ² or less, the image is output as it is. if,
If the average ride amount of toner exceeds 8.0 × 10 ⁻³ kg / m ² , the above-described lookup table 400 is used.
Give feedback to.

As an example, for example, when the average amount of toner applied is 8.8 × 10 ⁻³ kg / m ² , all data are multiplied by 0.9 as the correction value of the lookup table. . In this case, the value of Dmax is also 1.8 to 1.62.
However, there is almost no inferiority on the image and no curling occurs.

As described above, when the correction value of the look-up table was corrected to a maximum of 0.75, there was no inferiority in the image and no curling occurred.

By the way, the toner includes colored resin particles (containing a binder resin, a colorant, and other additives as needed) and colored resin particles to which an external additive is externally added.

Examples of the binder resin used in the toner include a styrene polymer or a polyester resin such as a styrene-acrylate resin or a styrene-methacrylate resin. In particular, when considering the color mixing at the time of fixing the color toner,

[0048]

Embedded image

Wherein R is an ethylene or propylene group, x and y are each a positive integer of 1 or more;
The average value of + y is 2 to 10), and a diol component such as a bisphenol derivative or a substituted product thereof;
A carboxylic acid component such as a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, etc.) is at least co-condensed. Polyester resins are more preferred because they have sharp melting properties.

The volume distribution and the volume average particle diameter of the toner are measured, for example, by the following measuring methods. A Coulter Counter TA-II type (manufactured by Coulter) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-i personal computer (manufactured by Canon) were connected. Prepare a 1% NaCl aqueous solution using primary sodium chloride.

The measuring method is as follows.
In 50 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added.

The electrolyte in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the particle size of 2 to 40 μm was measured using the Coulter Counter TA-II using a 100 μm aperture as an aperture. The distribution is measured to determine the volume distribution. The volume average particle size of the sample is obtained from the obtained volume distribution.

When an image was formed by the image forming means of the present invention using the above-mentioned toner, high image quality was obtained stably, and the occurrence of curling could be greatly reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

In this embodiment, an image is formed in the same manner as the image forming apparatus shown in FIG. 2, but the signal from the CPU 302 is fed back to the potential contrast without feeding back to the look-up table 400, and Dmax is used as it is. Is changed to make correction.

Specifically, the relationship between the grid bias value of the charger 2, the charging potential, the required contrast, and the maximum image density is stored in the CPU 302 every time the potential control is performed.
Normally, image formation is performed at a potential at which Dmax 1.8 is obtained.

The average running amount of toner is the same as that of the first embodiment.
8.0 × 10 per unit area ^-3kg / m^Twomore than
If it is determined that the
By changing the grid bias and development bias
Changes the development contrast and lowers the maximum image density
To prevent curling.

[0058]

As described in the foregoing, according to the first aspect, the determination according to whether the total amount of the developer in the developer image you formed on the recording material exceeds a predetermined value in the image density signal Judgment
Means and the determining means determine that the total amount of developer exceeds a predetermined value.
If the total amount of the developer is less than the predetermined value,
Correction means for correcting the luminous flux emission time length by the exposure means in order to form an image on the recording material.
The curl that can be greatly reduced.

[0059] According to the second invention, the total amount of the developer in the developer image you formed on the recording material whether exceeds a predetermined value image
A judgment means for judging according to the density signal and a judgment means
If it is determined that the total amount of the developer exceeds a predetermined value,
Forming a developer image on a recording material having a total amount of developer not more than a predetermined value
Correction means for correcting the difference between the charging bias by the charging means and the developing bias by the developing means.
The curl generated in the recording material can be greatly reduced .

[Brief description of the drawings]

FIG. 1 is a block diagram around a means for suppressing an image density within a predetermined value of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an image forming apparatus according to the present invention.

FIG. 3 is a configuration diagram illustrating an exposure unit of the image forming apparatus of FIG. 2;

FIG. 4 is a PWM circuit used in the image forming apparatus of FIG. 2;

FIG. 5 is a general example of a waveform of the PWM circuit of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (image carrier) 2 charger (charging means) 4 rotary developing device (developing means) 5 transfer drum (transfer means) 9 heat-pressure roller fixing device (fixing means) E laser beam (light beam of light source) LS laser Scanner (exposure means)

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI G03G 15/043 G03G 15/08 502 15/06 101 15/20 101 15/08 502 15/04 120 15/20 101 (56) JP-A-5-265297 (JP, A) JP-A-5-188677 (JP, A) JP-A-7-85269 (JP, A) JP-A-63-52170 (JP, A) JP-A-7-85170 -273935 (JP, A) JP-A-5-107857 (JP, A) JP-A-6-348095 (JP, A) JP-A-6-175446 (JP, A) JP-A-4-125254 (JP, A) JP-A-63-53569 (JP, A) JP-A-8-217313 (JP, A) JP-A-7-199721 (JP, A) JP-A-7-25539 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/00 303 G03G 15/01 113 G03G 15/02 102 G03G 15/04-15/04 120 G03G 15/06 101 G03G 15/08 502 G03G 15/20 101 G03G 21/00 370-512

Claims (5)

(57) [Claims] And 1. A image bearing member, uniformly charging the image bearing member
And an electrostatic latent image corresponding to the image density signal
The image bearing member surface charged by the charging means
Exposure means for exposing a surface, and an electrostatic latent image on the image carrier
A developing means for developing with a developer to form a developer image, in the image forming apparatus having a fixing unit for fixing on heating and pressing the recording material was transferred onto a recording material a developer image, on a recording material the total amount of the developer in the developer image you formed has a predetermined value
Judging means for judging whether or not to exceed according to the image density signal
The total amount of the developer exceeds a predetermined value by the determination means.
If it is determined that the total amount of the developer is below a predetermined value developer
An image forming apparatus, comprising a correction means for correcting the light beam emission time length by the exposing unit to form an image on a recording material. (2) The total amount of developer is determined by the determination means
If it is determined that the value is equal to or less than the value,
According to the image density signal without correcting the bundle emission time length
A developer image is formed on a recording material.
2. The image forming apparatus according to 1. (3) For each pixel of the image according to the image density signal
The formation of an electrostatic latent image by controlling the light emission time length
The image forming apparatus according to claim 1 or 2, wherein
Place. 4. An image bearing member, and said image bearing member is uniformly charged.
And an electrostatic latent image corresponding to the image density signal
The image bearing member surface charged by the charging means
Exposure means for exposing a surface, and an electrostatic latent image on the image carrier
A developing means for developing with a developer, the current that has been transferred onto the recording material
Fixing means for fixing the image material image on the recording material by heating and pressing.
In the image forming apparatus having the total amount of the developer in the developer image you formed on the recording material is a predetermined value
Judging means for judging whether or not to exceed according to the image density signal
The total amount of the developer exceeds a predetermined value by the determination means.
If it is determined that the total amount of the developer is below a predetermined value developer
The charging means is used to form an image on a recording material.
Correct the difference between the bias and the developing bias by the developing means.
An image forming apparatus, comprising a correction means for. (5) The total amount of developer is determined by the determination means
Below If it is determined, the correction means
On the recording material according to the image density signal without correcting
5. The method according to claim 4, wherein a developer image is formed on the surface.
Image forming apparatus.