JPH0540408A - Method and device for forming image and method for controlling toner replenishment - Google Patents

Abstract

PURPOSE:To decide the replenishment quantity of toner by considering that the toner sticking quantity on one dot is changed by the toner concentration of developer, in a device which calculates the replenishment quantity of the toner according to the sum of the digital data of an image. CONSTITUTION:The toner concentration TC' is obtained by detecting a reference toner image every prescribed number of sheets by an optical sensor and corrected by the sum LDCNT of the digital data concerned to copying just before as necessary. Then, the toner concentration TC is obtained. Toner attachment ratio MA per unit area is calculated based on the TC and stored in a register. Besides, the TC is compared with the TC concerned to the detection of a former time. Then, variable GAIN is calculated from the transition of the toner concentration and stored in the register. The replenishment quantity of the toner is calculated by multiplying the LDCNT counted every copying by the MA read out from the register and the GAIN and the toner is replenished every copying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and the like in an image forming apparatus for performing image exposure on an image bearing member by scanning a light beam according to an image information signal.

[0002]

2. Description of the Related Art As is well known, in an image forming apparatus such as a copying machine or a printer which performs image exposure on an image carrier by scanning a light beam according to an image information signal, an optical image formed on the image carrier is known. By developing, the toner in the developing device is consumed. Therefore, in this type of image forming apparatus, in order to prevent a decrease in copy image density due to the toner consumption,
It is necessary to successively supply the developing device with a new toner in an amount commensurate with the amount of toner consumed by the development, so that the toner concentration in the developing device is always kept constant.

As a conventional toner density control method for keeping the toner density in the developing device constant at all times, the number of signals representing the characters of the original is counted, and when the coefficient value reaches a predetermined predetermined value. Method for replenishing toner (Japanese Patent Publication No. 50-30463), first detecting means for counting the image forming signal to detect the amount of toner consumed, and toner consumed by scattering by obtaining the operating time of the developing roller. There is known a method (Japanese Patent Publication No. 63-33704) for replenishing toner according to a detection signal from a second detecting means for detecting the amount.

[0004]

By the way, in the image forming apparatus using the electrophotographic system, the image density formed on the image bearing member is maintained at a constant density, and the low contrast character portion of the image information is displayed. Good reproduction and clear reproduction of the background part are required to obtain a high quality copy. In particular, in an image forming apparatus equipped with a developing device that uses a two-component developer composed of a carrier and toner, it is necessary to control the toner density well. Therefore, various toner concentration sensors for controlling the toner concentration have been put into practical use in the field of this type of image forming apparatus. Further, even if such a toner concentration sensor is not used, it is possible to control the toner concentration of the image by replenishing the developing device with an amount of toner corresponding to the amount of toner consumed by the development. In addition, a fixed amount replenishment method that replenishes the developing device with an amount of toner proportional to the number of copies. A method of counting the area ratio of the image area of the original and supplying a toner in an amount proportional to the area ratio. Have been proposed in the past.

However, in the former method, since the amount of toner consumed per copy varies depending on the type of original, there is a problem that a difference occurs between the amount of consumed toner and the amount of replenishment toner. In the latter method, in the case of an image forming apparatus such as a printer without a document image scanner, or a pattern such as a reference toner image other than a black-and-white inverted image of a document or a developed image is formed on an image carrier. In this case, there is a problem that the toner consumption of the developing device cannot be accurately counted.

As a means for solving such a problem, there is known a method of integrating the light emission time of the light beam and supplying the developing device with toner in an amount corresponding to the light emission time. However, this method actually causes an error in the relationship between the light emission time of the light beam and the toner consumption amount due to the photoconductor characteristics of the image carrier, the fluctuation of the exposure amount, the development characteristics, the developer characteristics, and the like. There is a problem that the image quality cannot be maintained as the number of images formed increases.

Further, in an image forming apparatus that forms an image based on image data, toner consumption based on image data is assumed on the assumption that a proportional relationship is established between the total number of dots of the image and the toner consumption amount. It is known to calculate the amount and replenish the developing device with toner corresponding to the toner consumption amount obtained by this calculation (for example, JP-A-62-1090).
78, JP-A-62-116973, and JP-A-1-108070).

However, even if an image having the same total number of dots is used, only the total number of dots of the image is used because the toner consumption amount greatly varies depending on the toner concentration of the developer in the developing device when the latent image is developed. However, there is a problem that an accurate toner consumption amount cannot be obtained.

Further, even if the toner consumption amount can be accurately obtained, the calculated toner replenishment amount and the toner amount actually replenished in the developing device do not match for the following reason. There was a problem that was changing.
That is, in the case where the toner supply amount is controlled by the operation time of the toner supply mechanism, the delay time of the drive source,
Due to the connection time and the stop time, the operating time varies between machines, and the calculated toner replenishment amount and the actually replenished toner amount differ depending on the machine. Also, when replenishing toner with a replenishment roller, etc., the fluidity of the toner itself changes due to environmental changes and the amount of toner actually replenished changes. The amount of toner used is different.

The present invention has been made in view of the above points, and a first object thereof is to provide an image forming method by highly accurate toner density control which can prevent deterioration of image quality. A second object thereof is to provide a toner replenishment control method and an image forming apparatus using the method, which can accurately predict the toner consumption amount and perform proper toner replenishment.

[0011]

In order to achieve the first object, the invention of claim 1 is an image forming apparatus for performing image exposure on an image carrier by scanning a light beam according to an image information signal. , Integrating the light emission time of the light beam, supplying toner to the developing device in an amount corresponding to the light emission time, forming a reference toner image on the image carrier, and detecting the density of the reference toner image. The toner replenishment control to the developing device is performed based on the detection signal of the optical detection means.

According to a second aspect of the present invention, in an image forming apparatus for performing image exposure on an image carrier by scanning a light beam according to an image information signal, the light emitting time of the light beam is integrated,
The developing device is replenished with an amount of toner corresponding to the light emission time, a reference toner image is formed on the image carrier, and the above-mentioned detection signal is detected by an optical detection means for detecting the density of the reference toner image. The toner supply amount to the developing device is variable.

According to a third aspect of the present invention, in the image forming method according to the second aspect, the relationship between the light emission time of the light beam and the toner replenishment amount is changed based on the detection signal of the optical detecting means.

According to a fourth aspect of the present invention, in the image forming method according to the second aspect, the relationship between the light emission time of the light beam and the toner replenishment amount is changed stepwise based on the detection signal of the optical detecting means. To do.

According to a fifth aspect of the present invention, in an image forming apparatus for performing image exposure on an image carrier by scanning a light beam according to an image information signal, the light emission time of the light beam is integrated,
A reference toner image is formed on the image carrier according to the light emission time, and toner replenishment control to the developing device is performed based on a detection signal of an optical detection unit that detects the density of the reference toner image. To do.

According to a sixth aspect of the present invention, in the image forming method according to the fifth aspect, the toner is replenished to the developing device according to the light emission time of the light beam.

In order to achieve the second object, the invention of claim 7 calculates the total area of the toner adhering area on the image carrier using the image data in the image area, and calculates the total area according to the total area. In a toner replenishment control method for replenishing toner to a developing device, a toner adhesion amount per unit area of a toner adhesion region on an image carrier is detected, and based on the toner adhesion amount per unit area and the total area. The toner supply amount to the developing device is calculated.

According to an eighth aspect of the present invention, in the toner replenishment control method according to the seventh aspect, the toner adhesion amount per unit area is calculated based on the density of the reference toner image formed on the image carrier. To do.

According to a ninth aspect of the present invention, in the toner replenishment control method according to the seventh aspect, the toner replenishment amount to the developing device is calculated based on the product of the toner adhesion amount per unit area and the total area. And

According to a tenth aspect of the present invention, in the toner replenishment control method according to the eighth aspect, the detection of the density of the reference toner image is executed for each predetermined image forming operation, and the developing device is supplied with the change in the density. The toner supply amount is corrected.

According to an eleventh aspect of the present invention, in the toner replenishment control method according to the eighth aspect, the total area of the toner adhering regions in the image forming operation one or more times before the timing of forming the reference toner image is a predetermined area. A comparison is made, and the toner supply amount to the developing device is corrected based on the comparison result.

According to a twelfth aspect of the present invention, area calculating means for calculating the total area of the toner adhering area on the image carrier using the image data in the image area, and the density of the reference toner image formed on the image carrier. A light detection means for detecting the toner adhesion amount, an adhesion amount calculation means for calculating the toner adhesion amount per unit area of the toner adhesion region on the image carrier based on the output of the light detection means, and a calculation result of the area calculation means. First replenishment amount calculation means for calculating the toner replenishment amount to the developing device based on the calculation result of the adhesion amount calculation means, and discrimination means for discriminating whether or not the output of the light detection means is within a predetermined range, A second replenishment amount calculation unit for calculating a toner replenishment amount based on the calculation result of the area calculation unit and a predetermined toner adhesion amount per unit area according to the discrimination result by the discrimination unit; To do.

[0023]

According to the first aspect of the present invention, the developing device is replenished with toner in an amount corresponding to the integrated emission time of the light beam, and the density of the reference toner image formed on the image carrier is also increased. The toner replenishment control to the developing device is performed based on the detection signal of the optical detection means for detecting

According to the second aspect of the present invention, the developing device is replenished with an amount of toner corresponding to the integrated light emission time of the light beam, and the density of the reference toner image formed on the image carrier is also increased. The amount of toner replenished to the developing device is varied based on a detection signal of an optical detection unit that detects

According to the third aspect of the invention, in the image forming method of the second aspect, the relationship between the light emission time of the light beam and the toner replenishment amount is varied based on the detection signal of the optical detecting means.

According to the invention of claim 4, in the image forming method of claim 2, the relationship between the light emission time of the light beam and the toner replenishment amount is changed stepwise based on the detection signal of the optical detection means. .

According to the fifth aspect of the present invention, the reference toner image is formed on the image carrier according to the integrated light emission time of the light beam, and the optical detecting means detects the density of the reference toner image. The toner replenishment control to the developing device is performed based on the detection signal of.

According to the invention of claim 6, in the image forming method of claim 6, the toner is replenished to the developing device according to the light emission time of the light beam.

According to the seventh aspect of the invention, the total area of the toner adhering area on the image carrier is calculated using the image data in the image area, and at the same time, the unit area of the toner adhering area on the image carrier is calculated. The amount of toner adhering to the developing device is calculated based on the amount of toner adhering per unit area and the total area. The replenishment toner amount is determined in consideration of the fluctuation of the toner adhesion amount per unit area of the toner adhesion region on the image carrier.

According to an eighth aspect of the present invention, in the toner replenishment control method according to the seventh aspect, the toner adhesion amount per unit area is calculated based on the density of the reference toner image formed on the image carrier. To be done.

According to a ninth aspect of the present invention, in the toner replenishment control method according to the seventh aspect, the toner replenishment amount to the developing device is calculated based on the product of the toner adhesion amount per unit area and the total area. To be done.

According to the tenth aspect of the present invention, in the toner replenishment control method according to the eighth aspect, the density of the reference toner image is detected every predetermined image forming operation, and the developing device is operated according to the change of the density. The amount of toner supplied to the printer is corrected.

According to the eleventh aspect of the present invention, in the toner replenishment control method according to the eighth aspect, the total area of the toner adhering regions in the image forming operation one or more times before the timing at which the reference toner image is formed is Compared to a given area,
The toner supply amount to the developing device is corrected based on the comparison result.

According to the twelfth aspect of the present invention, the area calculation means calculates the total area of the toner adhesion area on the image carrier using the image data in the image area, and the adhesion amount calculation means calculates the image carrier. The toner adhesion amount per unit area of the toner adhesion region on the image carrier is calculated based on the output of the light detection unit that detects the density of the reference toner image formed on the body, and the first replenishment amount calculation unit calculates the toner adhesion amount. The toner supply amount to the developing device is calculated based on the calculation result of the area calculation means and the calculation result of the adhesion amount calculation means. Then, the discriminating means discriminates whether or not the output of the light detecting means is within a predetermined range, and according to the discriminating result by the discriminating means, the second replenishment amount calculating means determines the arithmetic result of the area calculating means and the predetermined result. The toner supply amount is calculated based on the toner adhesion amount per unit area.

[0035]

Embodiments of the present invention will now be described in detail with reference to the drawings. However, for the purpose of avoiding complication of the description, the drawings and the disclosure of the configurations and operations within the scope that can be clearly assumed from the description of the present specification, and the above and other objects and novel features of the present invention will be described. Omit or simplify.

FIG. 1 is a schematic view of the essential parts of a laser beam writing type image forming apparatus utilizing the present invention.
In this embodiment, a reversal development system is used in which a negatively charged organic photoconductor is used as an image carrier and a two-component developer containing a negatively charged toner is used as a developer. In FIG. 1, the photoconductor 1 first rotates in the direction of the arrow and is uniformly charged by the charger 2. Next, by the laser beam L corresponding to the image information of the original (not shown),
The photosensitive member 1 is scanned and exposed in a direction perpendicular to the rotating direction of the photosensitive member 1. The electrostatic latent image formed on the photoconductor 1 by this is visualized by the developing unit 4. The visible toner image formed on the photoconductor 1 is transferred onto the transfer material fed by the registration roller 10 onto the transfer charger 5a of the transfer separation unit 5.
And the transfer material separated from the photoconductor 1 by the separation static eliminator 5b of the unit 5 together with the fixing device 96.
The fixing device 9 is conveyed to the fixing device 9 by the conveying device 95.
It is fixed on the transfer material by 6. On the other hand, after the above transfer,
The toner remaining on the photoconductor 1 is removed by the cleaning unit 6
Are removed from the photoreceptor 1. After this cleaning, the electric charge remaining on the photoconductor 1 is removed by the discharge light of the lamp of the charge eliminating device 7. After the photoconductor 1 is thus cleaned, the above-mentioned steps are repeated again, and the image forming operation of the next image information is executed.

Here, in the image forming area of the photoconductor 1, the dark portion potential (background potential) VD is -800V,
The exposed portion potential (image portion potential) VL is set to −100 V, and the exposed portion potential (image portion potential) VL (−10).
0 V) and the potential difference VB (−600 V) of the developing roller 41 (see FIG. 2) of the developing device 4 VL−VB =
The electrostatic latent image formed on the photoconductor 1 is developed by 500V.

The developing unit 4 for developing the electrostatic latent image formed on the photoconductor 1 is, as shown in FIG. 2, a developing device 21 having an opening facing the surface of the photoconductor 1 and the developing device 21. Two
1 and a toner cartridge 94 containing new toner to be replenished. In the developing device 21, a developing roller 20 for supplying toner to the photoconductor 1 and a developing device 21.
An agitating roller 90 for agitating the developer contained therein,
An agitating separator 91 for transferring the agitated developer toward the developing roller 20, a conveying screw 92 for making the toner and carrier distribution of the developer uniform, a doctor 93 for thinning the toner supplied to the developing roller 20, A replenishing roller 24 for replenishing the toner in the toner cartridge 94 into the developing device 21 is provided. Then, in the toner cartridge 94, the agitator 2 for stirring the toner
3 is provided. Replenishing roller 24 in this embodiment
Is configured such that its rotation amount is proportional to the toner replenishment amount.

In the image forming apparatus of this embodiment having the above-described structure, when the laser diode as the exposing means for forming the electrostatic latent image on the photoconductor 1 is driven, the laser beam L The light emission time is integrated, and the amount of toner consumed during this light emission time is calculated. The amount of toner that adheres to and is consumed by the portion of the photoconductor that has been irradiated with the laser beam L for a unit emission time can be determined in advance by experiments. Therefore, the replenishment roller 24 is driven (the rotation amount is controlled) so that the toner is replenished in an amount corresponding to the consumed toner amount calculated based on the integrated value of the light emission time of the laser beam L, thereby developing the toner. A predetermined amount of toner is replenished in the unit 4, and the toner concentration in the developer contained in the developing unit 4 is maintained substantially constant.

FIGS. 3 and 4 show the relationship between the integrated value of the light emission time of the laser beam L and the toner consumption amount, and the relationship between the rotation time of the replenishing roller 24 and the toner replenishment amount in the above embodiment, respectively. It is a thing. In this example,
The integrated value of the emission time of the laser beam L is 0.2 which is a predetermined value.
When the time reaches sec, a toner replenishment signal is output from the control means (not shown), and the replenishment roller 24 is in a predetermined time of 0.5 sec.
Driven only by the toner cartridge 94 to the developing device 2
Toner 1 is replenished with new toner. Here, it is also possible to control the drive of the replenishment roller 24 according to the integrated value of the light emission time of the laser beam L within a predetermined time when the image information is formed on the photoconductor 1.

On the other hand, in this image forming apparatus, a patterned reference toner image P for controlling the toner density in the developing device 21 is formed at a predetermined timing on a portion other than the image forming area of the photoconductor 1. Is configured. As the reference toner image P, an image pattern that becomes a solid image after the development of the electrostatic latent image of the image information formed on the photoconductor 1 can be effectively used, and the toner per unit area on the photoconductor 1 can be used. It is desirable that the adhesion amount be about 0.3 to 0.7 mg / cm ² . Therefore, in this embodiment, the latent image potential VP of the reference toner image P is set to about −300V, and the potential difference VP from the bias potential VB (−600V) of the developing roller 20 is set.
With −VB = 300V, the reference toner image P is formed.

As shown in FIG. 5, the reference toner image P for controlling the toner density formed outside the image forming area of the photoconductor 1 is detected by the optical detecting means which is arranged close to the photoconductor 1 so as to be opposed thereto. Detected. As shown in FIG. 6, this optical detecting means is composed of a light emitting element 14a such as a light emitting diode having an emission wavelength peak of 950 nm and a reflection type optical sensor 25 including a light receiving element 14b such as a phototransistor. The detection signal voltage Vsp corresponding to the reflectance of the reference toner image P and the detection signal voltage Vsg corresponding to the reflectance of the surface of the photoconductor 1 without the reference toner image P are output.

FIG. 7 shows the relationship between the toner adhesion amount per unit area of the reference toner image P and the output of the optical sensor 25. Based on this relationship, in the present embodiment, the output voltage ratio between the detection signal voltage Vsg on the surface of the photoconductor 1 without the reference toner image P and the detection signal voltage Vsp of the reference toner image P is 0.
When it becomes 5 or less, a toner replenishment signal is output, the replenishment roller 24 is driven, and toner is replenished to the developing device 21 at a predetermined rate until the next reference toner image P detection timing. ing.

FIG. 8 shows the integrated value A of the light emission time of the laser beam L and the detection signal voltages Vsp and V of the optical sensor 25.
9 is a flowchart showing a flow of toner replenishment control procedure of this embodiment by sg. In FIG. 8, first, in the normal mode, the emission time of the laser beam L is integrated, and when the integrated value reaches 0.2 sec, a toner replenishment signal is output (steps 13 and 14). Next, the toner replenishment signal drives the replenishment roller 24 for 0.5 seconds to replenish the developing device 21 with toner, and the integrated value of the emission time of the laser beam L is cleared (step 15, 16). In this way, the toner replenishment control within the normal image forming time is repeated (if N in step 14 or N in step 17 returns to step 13).

However, in the image forming apparatus shown in this embodiment, after the power switch or the front cover switch (neither is shown) of the apparatus main body is turned on, and the number of images formed is a predetermined number (in this embodiment, It is set so that the reference toner image P is formed every 10 sheets (step 3,
4). When the reference toner image P is formed, as described above, the detection signal voltage Vsp corresponding to the reflectance of the reference toner image P and the reflectance of the surface of the photoconductor 1 without the reference toner image P are obtained. The corresponding detection signal voltage Vsg is output from the optical sensor 25 (step 5).

As a result, the calculation result of the output voltage ratio of each detection signal voltage and Vsp / Vsg is obtained by comparing the toner adhesion amount per unit area of the reference toner image P and the output of the optical sensor 25 as shown in FIG. From the relationship, 0.7 / 0.4 ≧ Vsp / Vsg
It is determined whether or not ≧ 0.5 / 4.0 (step 6). The result of this determination is Vsp / Vsg <0.5 /
If it is 4.0, it is determined that the toner density in the developing device 21 is normal, and toner is not replenished (step 2
Return to).

On the other hand, the result of this determination is that the above relation, 0.
If 7 / 4.0 ≧ Vsp / Vsg ≧ 0.5 / 4.0, it is determined that the toner density in the developing device 21 is low, and the detection signal voltage Vsg of the surface of the photoconductor 1 having no reference toner image P is detected. And the output voltage ratio of the detection signal voltage Vsp of the reference toner image P to 0.5 or less, a toner replenishment signal is output to drive the replenishment roller 24 (step 7), and the next reference toner image P The toner is replenished to the developing device 21 at a predetermined rate until the detection timing of.

Furthermore, the result of this determination is that Vsp / V
When sg> 0.7 / 4.0 (N in step 8), it is determined that the toner density in the developing device 21 is abnormally low, and the maximum amount of toner replenishment to the developing device 21 is maximized. The replenishment rate is set (step 9), the toner replenishment signal is output, the replenishment roller 24 is driven (step 7), and the toner is replenished to the developing device 21 at the maximum replenishment rate until the next reference toner image P detection timing. Done. When the result of this determination is Vsp / Vsg> 0.7 / 4.0 twice in succession (N in step 8), toner near end display is performed (step 10). After the toner near end display, the toner end display is made when the number of copies of the image forming apparatus reaches a preset predetermined number (50 sheets in this embodiment) (steps 11 and 12).

In this embodiment, since the toner density control is executed as described above, stable toner density control is possible for a long time even under a wide range of environmental conditions, and a stable high-quality image is obtained. Obtainable.

Next, another embodiment of the present invention will be described. However, regarding the standard conditions, the configuration, the operation, and the like in this embodiment, a detailed description of the same parts as those in the above-described embodiment shown in FIGS. Only parts different from the example will be described in detail.

In this embodiment, the light emission time of the laser beam L is integrated, toner of an amount corresponding to the light emission time is replenished to the developing device 21, and a reference is made on the photoreceptor 1 in the same manner as in the above embodiment. A toner image P is formed and the reference toner image P is formed.
The toner supply amount to the developing device 21 is variable based on the detection signal of the optical sensor 25 for detecting the density of the toner. Further, this embodiment is characterized in that the relationship between the light emission time of the laser beam L and the toner replenishment amount is varied based on the detection signal of the optical sensor 25. further,
This embodiment is characterized in that the relationship between the emission time of the laser beam L and the toner replenishment amount is changed stepwise based on the detection signal of the optical sensor 25.

That is, in this embodiment, the output voltage ratio between the detection signal voltage Vsg on the surface of the photosensitive member 1 without the reference toner image P and the detection signal voltage Vsp of the reference toner image P is 0.6 /.
When it becomes 4.0 or more, the relationship between the light emission time of the laser beam L and the toner replenishment amount is changed, and when the integrated value of the light emission time of the laser beam L reaches 0.15 sec, the toner replenishment signal is output and the replenishment roller is supplied. 24 is a predetermined time (0.5se
c) The toner is supplied to the developing device 21 by being driven.

Here, when the integrated value of the light emission time of the laser beam L reaches 0.02 sec during the predetermined value, the toner replenishment signal is similarly output and the replenishment roller 24 is 0.5 sec.
It may be changed to be driven during c.

Further, in this embodiment, contrary to the above, the detection signal voltage Vsg on the surface of the photoconductor 1 without the reference toner image P is obtained.
And the output voltage ratio of the detection signal voltage Vsp of the reference toner image P to 0.4 / 4.0 or less, the relationship between the emission time of the laser beam L and the toner replenishment amount is changed, and the emission time of the laser beam L is changed. When the integrated value reaches 0.25 sec, a toner replenishment signal is output and the replenishment roller 24 is driven for a predetermined time (0.5 sec) to replenish toner to the developing device 21.

Here, when the integrated value of the light emission time of the laser beam L reaches a predetermined value of 0.02 sec, a toner replenishment signal is similarly output and the replenishment roller 24 is 0.3 sec.
It may be changed to be driven during the period.

FIG. 9 shows the integrated value A of the light emission time of the laser beam L and the detection signal voltages Vsp and V of the optical sensor 25.
9 is a flowchart showing a flow of toner replenishment control procedure of this embodiment by sg. In FIG. 9, first, 0.2 sec is set as the comparison value A ₀ when the main switch is turned on (steps 1 and 2). Then, in the normal mode, the emission time of the laser beam L is integrated, the integrated value A is compared with the comparison value A _0, and when the comparison value A _0, that is, 0.2 sec is reached, a toner replenishment signal is output (step 15, 16).
Then, the toner replenishment signal drives the replenishment roller 24 for 0.5 seconds to replenish the toner to the developing device 21, and the integrated value A of the light emission time of the laser beam L is cleared (step 17, 18). In this way, the toner replenishment control within the normal image forming time is repeated (if N in step 16 or N in step 19 returns to step 15).

However, in this image forming apparatus, after the power switch or the front cover switch (neither is shown) of the apparatus main body is turned on, and the number of images formed is a predetermined number (every 10 sheets in this embodiment). Is set so that the reference toner image P is formed (steps 4 and 5). Then, when the reference toner image P is formed, as described above, the detection signal voltage V corresponding to the reflectance of the reference toner image P is generated.
The detection signal voltage Vsg corresponding to sp and the reflectance of the surface of the photoconductor 1 without the reference toner image P is output from the optical sensor 25 (step 6).

As a result, the calculation result of the output voltage ratio of each detection signal voltage and Vsp / Vsg is obtained by comparing the toner adhesion amount per unit area of the reference toner image P and the output of the optical sensor 25 shown in FIG. From the relationship, 0.6 / 4.0 ≧ Vsp / Vsg
It is determined whether or not ≧ 0.4 / 4.0 (step 7).

The result of this judgment is Vsp / Vsg>
If 0.6 / 4.0, it is determined that the toner density in the developing device 21 is low, and the comparison value A ₀ is corrected to a value smaller by 0.05 sec (step 8). The relationship between the emission time of the laser beam L and the toner replenishment amount is changed so that the toner replenishment amount becomes larger than the normal condition.

On the other hand, this determination result shows that Vsp / Vsg <0.
If it is 4 / 4.0, it is determined that the toner density in the developing device 21 is high, and the comparison value A ₀ is corrected to a value larger by 0.05 sec (step 14). The relationship between the emission time of the laser beam L and the toner replenishment amount is changed so that the toner replenishment amount becomes smaller than the condition.

If the determination result is in the relationship shown in FIG. 9, it is determined that the toner density in the developing device 21 is in an appropriate state, and the standard condition is not changed (return to step 3). .

Further, when the determination result of Vsp / Vsg> 0.6 / 4.0 continues twice (steps 9 and 10), the toner near end display is made (step 1).
1). After the toner near end display, the toner end display is made when the number of copies of the image forming apparatus reaches a preset predetermined number (50 sheets in this embodiment) (steps 12 and 13).

By the above control, stable toner density control is possible over a long period of time even under a wide range of environmental conditions, and a stable and high quality image can be obtained. That is, in this embodiment, by integrating the light emission time of the light beam (laser beam) and performing the toner replenishment control, it is possible to replenish the toner in real time, and the response characteristic of the toner replenishment is improved. It can correspond to various images. Further, an optical detection means (optical sensor) outputs a detection signal of the reference toner image,
By performing the toner replenishment control together, it is possible to maintain an appropriate toner concentration by absorbing the error that occurs in the relationship between the light beam emission time and the toner replenishment amount over time and in any surrounding environment. Therefore, a stable and high-quality image can be obtained over a long period of time.

Next, still another embodiment of the present invention will be described. However, regarding the standard conditions, the configuration, the operation, etc. in the present embodiment, a detailed description of the same parts as those in the above-described embodiment shown in FIGS. Only parts different from the embodiment will be described in detail.

In this embodiment, the light emission time of the laser beam L is integrated, a reference toner image P is formed on the photosensitive member 1 according to this light emission time, and this reference toner image P The toner is supplied to the developing device 21 based on the detection signal of the optical sensor 25 that detects the density of the toner. In addition, this embodiment is characterized in that the toner is replenished according to the light emission time of the laser beam L.

That is, in this embodiment, when the laser diode as the exposure means for forming the electrostatic latent image on the photoconductor 1 is driven, the emission time of the laser beam L is integrated, and this emission time Reaches a predetermined value, a reference toner image P is formed and toner replenishment control is performed.

Here, as in the case of the above-described embodiment, the replenishment roller 2 is responsive to the integrated value of the light emission time of the laser beam L within a predetermined time when the image information is formed on the photoconductor 1.
It is also possible to perform drive control of No. 4.

FIG. 10 is a flow chart showing the flow of the toner replenishment control means based on the integrated value of the light emission time of the laser beam L and the detection signal voltages Vsp and Vsg of the optical sensor 25 in this embodiment. In FIG. 10, in the normal mode, the emission time of the laser beam L is integrated, and when the integrated value reaches 0.2 sec, the reference toner image forming signal is output (steps 3 and 4). As a result, after the image formation during image formation is completed, the reference toner image P is formed, and the integrated value of the emission time of the laser beam L is cleared (steps 5 and 6).

When the reference toner image P is formed, as described above, the detection signal voltage Vsp corresponding to the reflectance of the reference toner image P and the surface of the photoconductor 1 without the reference toner image P are formed. The detection signal voltage Vsg corresponding to the reflectance is output from the optical sensor 25 (step 7).

As a result, the calculation result of the output voltage ratio of each detection signal voltage and Vsp / Vsg is obtained by comparing the toner adhesion amount per unit area of the reference toner image P and the output of the optical sensor 25 shown in FIG. From the relationship, 0.7 / 4.0 ≧ Vsp / Vsg
It is determined whether or not ≧ 0.5 / 4.0 (step 8).

The result of this judgment is Vsp / Vsg <
If it is 0.5 / 4.0, it is determined that the toner density in the developing device 21 is normal, and toner replenishment is not performed (return to step 2).

On the other hand, the result of this judgment is 0.
If 7 / 4.0 ≧ Vsp / Vsg ≧ 0.5 / 4.0, it is determined that the toner density in the developing device 21 is low, and the detection signal voltage Vsg of the surface of the photoconductor 1 having no reference toner image P is detected. And the output voltage ratio of the detection signal voltage Vsp of the reference toner image P to 0.5 or less, a toner replenishment signal is output and the replenishment roller 24 is driven (step 9), and the next reference toner image P The toner is replenished to the developing device 21 at a predetermined rate until the detection timing of.

Further, as a result of this judgment, Vsp / Vsg> 0.
When 7 / 4.0 continues twice, toner near end display is made (steps 10 and 12). After the toner near end display, the toner end display is performed when the number of copies of the image forming apparatus reaches a preset predetermined number (50 sheets in this embodiment) (steps 13 and 14).

However, in the image forming apparatus shown in this embodiment, it is set so that the reference toner image P is formed even after the power switch or the front cover switch (neither is shown) of the apparatus main body is turned on. There is.

According to this embodiment, by performing the toner density control as described above, it is possible to greatly reduce the number of times the reference toner image P is formed, and it is possible to prevent wasteful toner consumption. The load on the cleaning device 6 can be reduced. Further, according to the present embodiment, the toner replenishment control is performed according to the emission time of the laser beam L, that is, the proper toner consumption amount, so that the responsiveness of toner replenishment is enhanced and a stable toner concentration is maintained. be able to.

FIG. 11 is a flow chart showing another flow of the toner replenishment control procedure based on the integrated value of the light emission time of the laser beam L and the detection signal voltages Vsp and Vsg of the optical sensor 25 in this embodiment.

In FIG. 11, in the normal mode, the emission time of the laser beam L is integrated by the first counter, and when the integrated value reaches 0.2 sec, the toner replenishment signal is output (steps 2 and 3). .

Then, the toner replenishing signal drives the replenishing roller 24 for 0.5 sec to replenish the developing device 21 with toner (step 4). At this time,
The integrated value of the first counter is added to the second counter, and the integrated value of the first counter is cleared (steps 5 and 6).

In this way, the toner replenishment control is repeated within the normal image forming time (when N in step 3 or N in step 7 returns to step 2), and the second
When the integrated value of the counter reaches a predetermined value of 2.0 seconds, the reference toner image forming signal is output, whereby the reference toner image P is formed after the image formation during image formation is completed,
The integrated value of the second counter is cleared (steps 8, 9, 10).

When the reference toner image P is formed, as described above, the detection signal voltage Vsp corresponding to the reflectance of the reference toner image P and the surface of the photoconductor 1 without the reference toner image P are formed. The detection signal voltage Vsg corresponding to the reflectance is output from the optical sensor 25 (step 11).

As a result, the calculation result of the output voltage ratio of each detection signal voltage and Vsp / Vsg is obtained by comparing the toner adhesion amount per unit area of the reference toner image P and the output of the optical sensor 25 as shown in FIG. From the relationship, 0.7 / 4.0 ≧ Vsp / Vsg
It is determined whether or not ≧ 0.5 / 4.0 (step 12).

The result of this judgment is Vsp / Vsg <
If it is 0.5 / 4.0, it is determined that the toner density in the developing device 21 is normal, and toner replenishment is not performed (return to step 1).

On the other hand, the result of this determination is that the above relation, 0.
If 7 / 4.0 ≧ Vsp / Vsg ≧ 0.5 / 4.0, it is determined that the toner density in the developing device 21 is low, and the detection signal voltage Vsg of the surface of the photoconductor 1 having no reference toner image P is detected. And the output voltage ratio of the detection signal voltage Vsp of the reference toner image P to 0.5 or less, a toner replenishment signal is output to drive the replenishment roller 24 (step 13), and the next reference toner image P The toner is replenished to the developing device 21 at a predetermined rate until the detection timing of.

Further, as a result of this judgment, Vsp / Vsg> 0.
When 7 / 4.0 continues twice, toner near end display is made (steps 14 and 16). After the toner near end display, the toner end display is made when the number of copies of the image forming apparatus reaches a preset predetermined number (50 sheets in this embodiment) (steps 17 and 18).

However, in the image forming apparatus shown in this embodiment, the reference toner image P is set to be formed even after the power switch or the front cover switch (neither is shown) of the apparatus main body is turned on. There is.

According to the present embodiment, as described above, the reference toner image is formed according to the light emission time of the light beam (laser beam) to control the toner density, so that the reference toner image is adjusted according to the toner consumption amount. Thus, the number of times the reference toner image is formed can be suppressed to the necessary minimum. As a result, wasteful toner consumption can be prevented and the load on the cleaning device 6 can be reduced. Further, according to the present embodiment, the responsiveness of toner supply is improved,
It is possible to maintain a stable toner concentration and obtain a high-quality image for a long period of time. Further, according to the present embodiment, the toner replenishment control is performed according to the emission time of the laser beam L, that is, the proper toner consumption amount, so that the responsiveness of toner replenishment is further enhanced.

Next, in the toner replenishment control method of calculating the total area of the toner adhering area on the photoconductor using the image data in the image area and replenishing the toner to the developing device according to the total area, An embodiment in which the toner adhesion amount per unit area of the upper toner adhesion region is detected, and the toner replenishment amount to the developing device is calculated based on the toner adhesion amount per unit area and the total area. Will be described.

The digital copying machine according to the present embodiment is composed of a reading device (scanner) which is a document reading means and a copying device (printer) which executes a series of processes for copying the read document information on paper. be able to. As the reading device, for example, a document on the contact glass is sub-scanned by a moving optical system having a document illumination lamp arranged below the contact glass, and is reflected on the lower surface of the document according to the density of the document image. Light is incident on a one-dimensional image sensor through a mirror and a lens, and while this one-dimensional image sensor detects one line in the main scanning direction on the original image, the two-dimensional image of the original is obtained by sub-scanning by a moving optical system. Can be used.

FIG. 12 shows a schematic structure of the mechanical portion of the copying apparatus in this embodiment. In FIG. 12, the photosensitive drum 1
A charging charger 2, a writing unit (not shown), a developing unit 4, a transfer / separation unit 5, a cleaning unit 6, a charge eliminating device 7 and the like are provided around the area. First, the surface of the photosensitive drum 1 is uniformly charged to a high potential by the corona current generated by the charging charger 2.
The surface is irradiated with laser light from the writing unit, the charging potential changes according to the intensity of the light, and a potential distribution is formed according to the presence or absence of laser light irradiation. The writing unit is equipped with a semiconductor laser (hereinafter referred to as writing LD) as a laser light source, and the laser light emitted from the semiconductor laser is irradiated onto the surface of the photoconductor drum 1 through an optical system such as a rotary multi-facet, a lens, and a mirror. However, as this rotary polygon mirror, one that performs main scanning on the photoconductor by being driven to rotate at a constant speed by an electric motor can be used. Then, a position signal for each pixel (recording / not recording) to be recorded by the control device is applied to the writing LD so that each pixel position is synchronized with the rotation position of the rotary polygon mirror, and each scanning position of the image. Then, the laser light is turned on / off according to the density of the pixel (recording / non-recording). As a result, the potential distribution formed on the photosensitive drum 1 corresponds to the light and shade of the original image and forms an electrostatic latent image. The electrostatic latent image is visualized by the toner supplied by the developing unit 4 arranged downstream of the writing unit. The developing unit 4 is composed of a developing device 21 having a developing roller 20 for supplying the toner onto the photoconductor and a toner hopper 22 containing the toner to be supplied to the developing device 21. An agitator 23 and a replenishing roller 24 are provided. On the other hand, the transfer paper fed from a cassette (not shown) is sent to the surface of the photoconductor drum 1 via the registration roller 9, and after the toner image is transferred by the transfer separation unit 5, it is separated from the surface of the photoconductor drum 1. .. The transfer paper onto which the toner image has been transferred has the toner image fixed thereon when passing through a fixing device (not shown), and is discharged to a discharge tray (not shown). An optical sensor 25 is provided on the surface of the photoconductor drum 1 between the developing unit 4 and the transfer separation unit 5 to detect the amount of light reflected from the photoconductor surface.

FIG. 13 shows a schematic structure of an electric component section of the digital color copying machine. In the housing of the reading device 10,
Reading control circuit 20, reading drive device 30, image reading circuit 4
0 and the image processing circuit 50 are accommodated, and the copying apparatus 90 is also included.
An image information storage device 60, a copying circuit 70, which is storage means for storing the read document information,
A system control device 61 and an operation device 80 which is an operation means for performing a key input to the system control device 61 are housed. The information storage device 60 includes an image memory unit 62 and the system control device 61. The read control circuit 20, the write drive control circuit 71 included in the copy circuit 70, and the operating device 80 are connected to the system control circuit 61 by signal lines L1, L2, and L3, and perform data transmission with each other. ing.

The reading control circuit 20 receives a signal from the system control circuit 61 via L1, and the scanner motor 31
Rotation speed control, heater control of the fluorescent lamp 32, lighting instruction of the fluorescent lamp 32, control of the filter solenoid 33 for detecting the document size, control of the scanner power supply cooling fan, and the like. The image reading circuit 40 divides the signal from the CCD 41, which converts the reflected light from the original document into an analog signal of 80 dpi, into an odd number (ODD) and an even number (EVEN) and amplifies it. Therefore, it is divided into two according to the performance of the amplifier), the switching element 43 and the switching element 43 that combine the ODD and EVEV signals from the amplifier 42 into a serial analog signal.
The analog signal from the fluorescent lamp 3 from the image processing circuit 50.
Amplification degree instruction data A for correcting the fluctuation of the brightness of 2
A variable amplifier 44 that amplifies by the GC, an A / D converter 45 that converts an analog signal from the variable amplifier 44 into a digital signal, and the like are provided. The image processing circuit 50 includes five gate arrays 51 to 55 and a clock generation circuit 5 for processing the image signal sent from the image reading circuit 40.
6, ROM 57, RAM 58 and the like. The gate array 51 detects the light amount, shading correction, timing control, command control, data editing / output, CCD drive clock generation, etc.
In the main scanning direction, the gate array 53 performs halftone processing,
The binarization process, the document size detection, the gate array 54 is in charge of character / halftone separation, blank editing, and the gate array 55 is in charge of mark area detection. The image memory unit 62 is composed of a memory board and a memory control board. A system control circuit 61 controls the entire system and gives instructions for reading and writing image data. To control the whole system, monitor the system ready status,
Includes detection of transfer paper size / remaining amount, original reading and feeding start instruction, control of scanner copy mode and printer copy mode, etc., and grasps the remaining amount of memory when instructing reading and writing of image data. Are doing.
The copying circuit 70 includes a line driver circuit 72 for receiving the image data from the image memory unit 62, a laser driver circuit 73 for amplifying the image data signal from the line driver circuit 72, and a semiconductor laser (LD) driven by the laser driver circuit 73. ) 74, a read drive control circuit 75, a write drive control circuit 71, a drive device 76 and the like.
The operation device 80 includes an operation panel 81 provided with a display device for displaying various information and input keys, and an operation control circuit 82.

FIG. 14 shows a detailed structure of the write drive control circuit. 390 includes an actuator group (pickup solenoid, paper feeding clutch, tray lock solenoid, lifting motor) of the paper feeding device, a serial / parallel receiver, and the like, and is connected to the output port of the CPU 703. The sensor group 390a connected to the input gate array 701 includes a sensor group (paper size detection sensor, paper end detection sensor, tray set detection sensor, connection detection sensor) in the paper feeding device. A conversion table 801 is connected to the video controller 800, and also video data (VIDEO DAT)
A) is also input. The video controller 800 is configured as a part of the CPU 810 as shown in FIG. 18, and video data (EXTERNAL VIDEO DAT) from the outside is input from the input port of the CPU 810.
A) is read and a conversion table 80 composed of P-ROM
It is configured to output to 1. Input gate array 70
The sensor group 705 connected to No. 2 includes various sensors for sheet feeding and conveyance, a main body door open detection sensor, an optical sensor (analog), etc., and a write LD feedback output (analog) and a write synchronization detection signal. Is also input to the input gate array 702. The actuator group 707 connected to the output gate array 706 includes various clutches for feeding and feeding, a main drive motor, a cleaning blade solenoid, a toner replenishing solenoid, a rotary polygon mirror motor, a fixing heater, and a charging high voltage. A power supply circuit, a high-voltage power supply circuit for transfer, a charge eliminating lamp, an optical sensor 25 (see FIG. 12) and the like are included, and the LD output adjustment output of the optical sensor 25 is also output from this output gate array 706.

Next, the toner replenishment control in this embodiment will be described. In this embodiment, the image data in the image area is used to calculate the total area of the toner adhering area on the photoconductor, and the toner supply amount to the developing device is calculated according to the total area. The toner adhering amount per unit area of the toner adhering area is detected, and the toner replenishing amount to the developing device is calculated based on the toner adhering amount per unit area and the total area.

First, the calculation of the total area of the toner adhesion area will be described. Conventionally, toner adheres to a portion (hereinafter referred to as a dot) corresponding to black data on the photoconductor, and the fact that the number of this black data is related to the toner consumption is used to calculate the toner density in the developing device. In order to control (hereinafter, referred to as toner density) to be constant, it has been proposed to calculate the total number of black data in one image and obtain the toner replenishment amount based on the total number of black data. This is based on the assumption that the toner adhesion amount per dot is constant.
The toner consumption amount for forming one image is obtained by the total number of dots in one image. However, the amount of adhered toner per dot differs depending on the writing conditions such as the amount of light when writing one dot and the toner density. For example, in the graph of FIG. 15, the vertical axis represents the toner adhesion amount per unit area, assuming that the dots are densely packed in a unit area of 1 cm ² , and the horizontal axis represents the pulse width of the writing LD. The toner density is 3.2.
% And 2.5% 1.8%, the toner adhesion amount per unit area is shown. The lower part of the horizontal axis of the figure shows the correspondence between specific multi-valued data of black data (hereinafter referred to as LD multi-valued data) and the pulse width of the writing LD. As can be seen from this figure, even with one dot developed with the developer having the same toner concentration, the toner adhesion amount differs depending on the pulse width of the writing LD (determined by the concrete multi-valued data of black data), and Even for one dot having the same writing LD pulse width, the toner adhesion amount differs depending on the toner concentration. Further, in this example, since the LD multi-valued data and the pulse width of the writing LD are not in a proportional relationship, the relationship between the LD multi-valued data and the toner adhesion amount is not linear. The toner adhesion amount of the data 0001 is 1/1 of the toner adhesion amount of the LD multi-valued data 1111.
It does not correspond to the quantity of 6. Therefore, generally, the toner adhesion amount is determined by the pulse width of the LD and the toner density, and can be expressed by the following formula (1) using the function F that defines the correspondence relationship. (Toner adhesion amount) = F [(LD multi-valued data), (toner density data)] (1) The correspondence represented by the function F can be obtained as follows, for example.

FIG. 16 shows LD multivalued data on the vertical axis,
The toner adhesion amount per unit area is taken on the horizontal axis 1,
6 is a graph showing a corresponding curve a of LD multi-valued data and a toner adhesion amount per unit area when the toner density is 2.5%, which is obtained by an experiment. The horizontal axis 2 below the horizontal axis 1
Is for reading the value of the consumption data corresponding to the toner adhesion amount. On the horizontal axis 2, the scale of the point b ′ on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area (value indicated by the point b) corresponding to the LD multi-valued data 1111 is set to 15, for example. Horizontal axis 2 corresponding to adhesion amount 0
The scale of the upper point a ′ is set to 0, for example, and the scale between the points b ′ (15) and a ′ (0) is divided at the same interval. Using the vertical axis, the horizontal axis 2 and the corresponding curve a, read the scale of the horizontal axis 2 corresponding to LD multi-valued data,
The correspondence relationship shown in Table 1 below can be obtained as the correspondence relationship between the LD multi-valued data and the consumption data (multi-valued data) when the toner density is 2.5%. Here, the LD multi-valued data 11
Although the scale of the point b ′ on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area (the value indicated by the point b) corresponding to 11 is set to 15, the scale is not limited to this. A constant larger than 15 may be used when it is desired to detect the toner adhesion amount per unit surface more accurately than in the example, and a smaller constant may be used when the accuracy is detected lower than this. . For other toner densities, instead of the corresponding curve a, a corresponding curve of LD multi-value data experimentally obtained for each toner density and the toner adhesion amount per unit area is used, and it corresponds to the LD multi-value data 1111. The scale of the point b ′ on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area (the value indicated by the point b) is the scale (15) in the case of the toner density of 2.5%. Is set to be the same as the ratio between the maximum value of the toner adhesion amount at this toner density and the maximum value at the toner density of 2.5%, and the LD multi-value is similarly set. Obtain the correspondence between data and consumption data (multivalued data). (Hereafter, margin)

[0096]

By the way, in the present embodiment, the shape of the curve corresponding to the LD multi-valued data and the toner adhesion amount per unit area does not differ greatly for each toner concentration as shown in FIG. Ratio between consumption data in toner concentration (for example, if the toner concentration is 2.5%, 15: 1)
5: 14: 13: 11: 10: 10: 8: 7: 6: 4: ...)
However, as shown in Table 2, it can be approximated so that the toner densities are the same. The constants Mi and Mj exemplified in Table 2 are the maximum value of the toner adhesion amount per unit area when the toner concentrations are 1.8% and 3.2% and the unit area when the toner concentration is 2.5%. It is a ratio with the maximum value of the toner adhesion amount per hit.

[0098]

That is, in the present embodiment, the above equation (1)
As a special case of, the value can be approximated as a product of the function MA and the function F ₁ as shown in the following expression (2). (Toner adhesion amount) = MA [(toner density data)] F
₁ [(LD multi-valued data)] (2) Here, the function F ₁ is the writing L as the writing condition for 1 dot.
The pulse width of D is changed (for example, LD multi-valued data 00
The pulse width is 0 to 50 nse according to 00 to 1111.
(change to c) changes the potential on the photoconductor and the area of one dot, which is related to the change in the toner adhesion amount. This change in the potential on the photoconductor is the same as the change in the area of one dot in that the amount of toner adhered per dot is changed.
It can be treated as a change in the toner adhesion area per dot. Therefore, the consumption data can be handled as data relating to the toner adhesion area. on the other hand,
The function MA can be handled as a value representing the toner adhesion amount per unit area, that is, the toner adhesion rate.

Therefore, in the present embodiment, instead of simply calculating the total number of black data to obtain the toner consumption amount in one image as in the prior art, the correspondence relationship and the function MA corresponding to the function F ₁ are replaced. The correspondence corresponding to is experimentally obtained, and the correspondence corresponding to this function F ₁ is used to obtain 1
The LD multi-valued data is converted into consumption data for each dot in one image, and the total sum of the consumption data in one image is calculated to obtain the total toner adhesion area in one image. The density is detected, the toner adhesion rate is calculated from the toner density by using the correspondence relationship corresponding to the function MA, and the total toner adhesion area is multiplied by the toner adhesion rate to obtain the toner consumption amount in one image.

First, the calculation for obtaining the total toner adhesion area using image data will be described. FIG. 17 shows a counting circuit for converting LD multi-valued data into consumption data for this purpose. This circuit is mainly a conversion table 8 for converting LD multi-valued data into consumption data.
10. An adder 811, a flip-flop 812 for position adjustment, a counter 813, and the like for counting the consumption data and calculating the sum of the toner adhesion areas. This adder 811, the flip-flop 8 for adjusting the position
12, the counter 813, etc. are the video controller 80
0 (see FIG. 13). The conversion table 810 is composed of the P-ROM 801 which is connected to the CPU 810 which constitutes the video controller 800 shown in FIG. 18 as described above. Then, as external video data, the video controller 800 (CPU 80
The LD multi-valued data input to 1) is output from the video controller 800 (CPU 801) to the conversion table 810, and the consumption data from this conversion table 810 is input to the video controller 800 (CPU 801) to perform counting. .

In FIG. 17, first, the conversion table 810.
The LD multi-valued data is converted into consumption data, latched by the flip-flop 814 at the first stage, and then added by the adder 811.
Data is sent to. The adder 811 calculates the sum of the input data and the previous remaining data, and outputs the result as a key to the counter in the next stage. This adder 8
The performance of 11 is determined by the consumption data (multilevel data level) of the input. For example, if the consumption data is 3 to 4 values, 2 bits and 2 bits are used, and if the consumption data is 5 to 8 values, 3 is used.
Bits and 3 bits are used, and further, 4 bits and 4 bits are used for 9 to 16 values. In this way, the size of the adder 811 is determined by the number of bits of data. FIG. 19
Is a timing chart showing the timing at which carry occurs, and the consumption data is 4-bit data (0000-11
This is an example in the case of 11). The counter increments the count each time a carry is input, counts this carry, and obtains total toner adhesion area data as the sum of consumption data. Then, this counter is a signal FGA which is turned on during the writing period of the effective image area.
Counts up only when TE is in the ON state, which is O
Cleared when falling to FF state. The output of the counter is latched by the flip-flop at the fall of FGATE, and the CPU reads it. The toner adhesion area data read here is represented by the upper 8 bits.

From the above, it is possible to obtain the total area of the toner adhering area in consideration of the size of the toner adhering area per dot according to the LD multi-valued data. In the configuration of this example, counting can be performed in the same manner regardless of whether the conversion table is input as code data or binary data (0000 or 1111).

In this example, the total sum of the consumption data is converted into the consumption data of the LD multi-valued data 1111 and the converted upper 8 bits are read by the CPU as the toner adhesion area data. Here, for example, A3 size (420
X297), the total number of dots is 1 according to the following formula (1).
110110000000101000011110B
Therefore, the upper 8 bits are 0 eCH, and the total sum of the image data is 111111010011111111100111101 from the following equation (2) except for each end 2 mm.
It becomes B and the upper 8 bits become 0e6H.
If the toner adhesion area data read into PU is 0e6H, LD is applied on the entire A3 (excluding 2 mm from the end).
This corresponds to the image written with the multivalued data 1111. (Total number of dots) = 420 × (400 / 25.4) × 297 × (400 / 25.4) = 30935582 (dots) = 1110110000000000101000011110B (1) (total image data) = (420-4) × (400 / 25.4) × (297-4) × (400 / 25.4) = 30228285 (dots) = 1110011010011111100111101B (2)

FIG. 20 is a flow chart of the reading control of the output of the counter latched by the flip-flop by the CPU. In step 1, the toner adhesion area data (LDCNT) output from the counter latched by the flip-flop is read. Since only the upper 8 bits of this LDCNT can be read as described above, it is determined whether the LDCNT read in step 2 is 0, and 0
If it is, LDCN is set in the register LDCNT in step 3.
After storing 1 as T data, this LD is stored in step 4.
The CNT data is stored in the register LDONCT. On the contrary, if it is not 0, the read LDCNT is stored in the register LDONCT as it is.

Next, the detection of the toner density for calculating the toner adhesion rate will be described. The toner density detection in this embodiment does not directly detect the toner density in the developing device, but a predetermined electrostatic latent image (hereinafter referred to as a reference pattern latent image) is formed on the photoconductor, The optical density of a visible image (hereinafter referred to as a reference pattern toner image) obtained by developing the pattern latent image with a developing device is detected, and the toner density in the developing device is calculated from the detected optical density. Specifically, it is detected as follows. First, a reference pattern is written on the photoconductor in the non-image area by the same laser light used for writing the image area to form a reference pattern latent image. The reference pattern latent image is conveyed to the developing unit by the rotation of the photoconductor and is developed, and then is opposed to the optical sensor 25. The light receiving portion of the optical sensor 25 is turned on, the non-pattern portion (photosensitive material background portion) is read by the light receiving element, and the reference pattern toner image portion is also read in the same manner. At this time, the developing device 21
The toner density is detected by utilizing the fact that the lower the toner density inside, the smaller the amount of toner that adheres to the reference pattern toner image, and conversely the higher the toner density, the greater the amount of toner that adheres to the reference pattern toner image. Here, the background portion is also detected in order to cancel the influence of the eccentricity of the photosensitive drum and the toner stain of the optical sensor 25 by taking the ratio of the detection value of the background portion and the detection value of the reference pattern toner image portion. Is.

First, the circuit configuration of the optical sensor 25 and the output adjustment of the optical sensor 25 will be described with reference to FIGS. 22 and 23. FIG. 22A shows a schematic circuit configuration of an optical sensor 25 including an LED 90, which is a light emitting element, and an optical transistor 91, which is a light receiving element, which are arranged so as to face the surface of the photosensitive drum. The LED 90 is connected to the power supply line Vcc (+ 5V) at the node, and the cathode is connected to the timer I (not shown) via the phototransistor driver 92.
22 (b), which is connected to the LED lighting circuit composed of C etc.
The low-active PWM waveform as shown in FIG. This PWM is about 20 KHz, 8-bit resolution (0
~ 255). The emitter of the phototransistor 91 is connected to the analog input port of the main control board. Since the ratio of the detection output of the reference pattern toner image and the detection output of the background portion is used as described above, if each detection output is appropriate, the eccentricity of the photosensitive drum included in both detection outputs Therefore, the effects of the above can be canceled out, and the toner concentration can be controlled appropriately. However, the output of the photodetector is, for example, as shown in FIG. 23, even if the amount of received light is increased (the horizontal axis of FIG. 23 is the ON bit number that determines the PWM duty that determines the light emission amount of the LED 90. Therefore, the larger the number of ON bits, the larger the amount of light emission, and the larger the amount of light received by the phototransistor 91. Accordingly, there is a saturation region (4.7 V in FIG. 23) in which the detection output does not change. When the distance between the surface of the photoconductor drum 1 and the optical sensor 25 becomes small due to eccentricity or the like, and the detection output of the background portion, which has a relatively high output, falls within this range, It becomes impossible to accurately detect the density of the reference pattern toner image. Further, when the light receiving surface of the optical sensor 25 is contaminated with the toner and the output becomes low, the erroneous detection due to the existence of the saturated region as described above does not occur, but the output itself becomes small, so that the A / D conversion is performed. , The resolution of the reference pattern toner image decreases, and the accuracy of the density detection of the reference pattern toner image decreases. In addition, in FIG. 23, the range a is the upper limit of the background detection output V _SG (hereinafter, referred to as output V _SG ) capable of relatively accurate detection due to variations in the light receiving and emitting sensitivities between the optical sensors 25. It shows the range of variation in the number of ON bits when 0 V is detected, and the number of ON bits is 20.
It varies in the range of -40. As described above, the slopes of the characteristics corresponding to the output V _SG and the PWM are different between the optical sensors 25, but each product has a certain slope.
In addition, by increasing the duty of PMW by 1 bit, the output V _SG is 0.1 to 0.1 in a range where relatively accurate detection is possible.
It can be increased by 0.2V. Therefore, in this example, the output of the optical sensor 25 is set to the duty of the PMW so that the output V _SG that becomes a relatively high output does not fall in the saturation region and is in an advantageous range from the viewpoint of resolution. To adjust. Specifically, the output V _SG is within a range in which relatively accurate detection can be performed, but the output V _SG is larger than 2.5 V and smaller than 3.0 V, which has a relatively low output and deteriorates resolution. In this case, the PWM duty is adjusted so that the output V _SG is 4.0 V, which is an appropriate value.

Next, the control when the detection output of the background portion or the reference pattern toner image portion is an abnormal value will be described. If toner, paper powder, or the like adheres to the surface of the optical sensor 25 over time, the sensor output decreases, and sufficient SN characteristics cannot be obtained, resulting in erroneous detection of toner concentration.
A sudden change in toner density due to excessive toner replenishment or the like, and the toner density largely deviates from the target toner density.
A runaway of toner concentration may occur. As mentioned above,
The use of the ratio of the output V _SG and the detection output V _SP of the reference pattern toner image portion (hereinafter referred to as the output V _SP ) or the adjustment of the output of the optical sensor 25 prevents the occurrence of such a situation. Although it contributes to this, there is a limit to this, and if a large amount of toner or the like adheres, it cannot be dealt with and the above-mentioned problem occurs. Therefore, in the present embodiment, if the output of the optical sensor 25 is not within the preset range, it is determined to be abnormal, and the output is not used for the calculation of the toner concentration, but instead of this, Then, the toner density is calculated using the preset data. Specifically, the output V
_SG is less than 2.5 or output V _SP is 2.5V
In the above case, it is determined that the toner is abnormal, and the toner density is calculated using preset data.

Specific control of reading the detection output of the optical sensor 25 including the above-described output adjustment of the optical sensor 25 and control in the case where the detection output is abnormal will be described with reference to FIG. First, in step 1, it is determined whether or not the detection of the background portion of the photoconductor and the reference pattern toner image portion by the optical sensor 25 is completed. Judgment, judgment as to whether or not the detected output is abnormal are executed. The determination as to whether or not the detection output is abnormal is made in steps 2 and 3 according to the above criteria.
Then, when it is determined that there is an abnormality, the routine proceeds to the fifth step, and the subroutine CHKV shown in FIG. 25 is executed.

In the subroutine CHKV shown in FIG. 25,
The data table is looked up using the variable GAIN, and the predetermined data preset in the data table is stored in the register V _SG , which stores the output V _SG and the output V _SP ,
Update to V _SP and store. The variable GAIN corresponds to the ratio of the toner replenishment amount and the toner consumption amount described later, as will be described later, and when this is 1.0, the toner replenishment amount and the toner consumption amount become equal. When the latest detected toner concentration is lower than the target toner concentration, this variable GAI
N is made larger than 1.0 to increase the toner density, and this increase is determined in consideration of the transition of the toner density. Similarly, when the latest detected toner concentration is higher than the target toner concentration, this variable GAIN is made smaller than 1.0 to lower the toner concentration, and
This amount of decrease is determined in consideration of the transition of the toner density. The variable GAIN used here relates to the detection one time before the current detection. Specifically, when the variable GAIN is 1.0, step B1
From step B5, the register V _SG stores 4.0 V and the register V _SP stores 0.25 V, and the variable GAIN is 1.
If it is smaller than 0, steps B2 to B4
To register V _SG to 4.0 V and register V _SP to 0.
When 30V is stored and the variable GAIN is larger than 1.0, the process proceeds from step B2 to step B3 to store 4.0V in the register V _SG and 0.20V in the register V _SP . The value of 4.0 V stored in the register V _SG is an appropriate value for output as described above. The value stored in the register V _SP is selected in accordance with the transition of the toner density represented by the variable GAIN, and the toner replenishment amount is set to be small so as to prevent excessive replenishment of toner.
It should be noted that such replacement of V _SG and V _SP may be performed even when a sudden change in the output V _SP occurs.

Returning to FIG. 21, after the subroutine CHKV is executed in step 5, or in step 4, the output V _SG is smaller than 3.0 V (because it is judged to be Y in steps 2 and 3, If it is determined to be 2.5 V or more), the procedure proceeds to step 6 and the subroutine c shown in FIG.
Execute onvv.

In the subroutine convv, the output of the light emitting element optical sensor 25 of the optical sensor 25 is adjusted. Specifically, it is an appropriate value of the output V _{SG in} step A1.
The difference between 0 V and the output V _SG is stored in the register A bit by bit. Next, in step A2, this difference is converted by the constant 10 into the difference of the ON bit from the PWM output characteristic shown in FIG. Here, the constant 10 is a coefficient of the above conversion when the optical sensor 25 has an output characteristic in which the inclination in FIG. 23 is maximized, and the PWM is based on the output characteristic in which the inclination is maximized in this way. This is to prevent excessive adjustment of. Next, in step A3, the above ON bit difference is added to the ON bit of the current PWM duty, and then in step A4, the PWM duty is 25
If it is larger than 5, the PMW duty is set to 255 in step A5 if it is larger, and then the subroutine is ended. Conversely, if it is not larger, the subroutine is ended as it is.

Returning to FIG. 21, after the subroutine convv is executed in step 6, or when it is determined in step 4 that the output V _SG is 3.0 V or more, the latest output V in steps 7 and 8 is obtained. _SG, registers register DVGNEW the V _SP is stored, the contents of DVPNEW, output V _SG according to the detection of one time before, V _SP is stored DVGOL
After updating to D, DVPOLD and storing, step 8,
At 9, the contents of the registers V _SG and V _SP related to the current detection are updated and stored in the registers DVGNEW and DVPNEW. This completes reading the outputs V _SP and V _SG .

Next, the above registers DVGNEW, DVP
The calculation of the toner density using the outputs V _SG and V _SP stored in NEW will be described. In this example, the output V _SG
(V) and output V _SP (V) ratio V _SP / V _SG , and developing device 21
There is a certain relationship with the toner density in the inside as shown in the first quadrant of FIG. Therefore, this relationship is stored in the RAM as a data table, and the optical sensor 25
After reading the outputs V _SG and V _{SP at} , the toner density of the developing device 21 can be obtained by looking up this data table with V _SP / V _SG .

In the second quadrant of FIG. 26, the horizontal axis represents the toner adhesion amount with the unit area described above, and shows the corresponding characteristics of the toner density and the toner adhesion amount per unit area. From the characteristics, the function MA in the equation (2), that is, the correspondence relationship between the toner density and the toner adhesion rate can be obtained. The correspondence relationship between the toner density and the toner adhesion rate is stored in the data table.

Here, in the present embodiment, when an image having a large toner consumption amount such as a black solid image is formed, the toner is replenished according to the toner consumption amount as will be described later. Toner may be replenished in an amount that temporarily exceeds the developer stirring ability. If the reference pattern toner image is read by the optical sensor 25 (the reference latent image is developed for that purpose) immediately after replenishing such an amount of toner, the developer (carrier) and the toner are temporarily agitated due to insufficient stirring. Due to insufficient toner charging, the amount of toner adhered to the reference latent image is reduced as compared with the case of an appropriate amount of toner charge. For this reason, the optical density of the reference pattern toner image becomes lighter than in the case where the toner is developed with an appropriate toner charge amount, and as shown in FIG. 27, the output V _SP of the optical sensor 25 becomes high. In FIG. 27, the horizontal axis represents the area ratio ({toner adhesion area / A3
(420 × 297) area} × 100%), and the output V _SP at the time of reading the sensor is plotted on the vertical axis, and the actual toner concentration is 1.8%, 2.0%, 2.7% Regarding the area ratio of the image relating to the copy operation immediately before the sensor reading timing and the output V _SP at the time of reading the sensor. It can be seen that the output V _SP increases as the area ratio increases at any toner concentration.
Therefore, in the present embodiment, when the sum total of consumption data of images relating to image formation immediately before the optical sensor read timing, that is, the sum total of toner adhesion areas is a certain value or more, the read V _SP is as shown in FIG. Correct to. It should be noted that the read V _SP is corrected using not only the sum of the consumption data of the images related to the image formation immediately before the optical sensor reading timing, that is, the sum of the toner adhering areas, but also the sum of the toner adhering areas from a plurality of sheets before. You may do so.

In FIG. 28, the horizontal axis shows the area ratio obtained from the toner adhesion area data relating to the copy operation immediately before the sensor reading timing, and the vertical axis shows the correction bit number of the V _SP data. One bit of this correction bit number corresponds to about 0.02 V of the output of the optical sensor 25 (5 V / 25
5). This correction bit number is obtained in advance by an experiment. Correcting the V _SG data makes it possible to obtain an accurate toner concentration (toner concentration after sufficient stirring operation).

Specific control of the above calculation of the toner density and the calculation of the toner adhesion rate MA will be described with reference to FIG. First, the output V _SP read from the register DVPNEW in step 1 is set to the register DV
Using the output V _SG read from the GNEW, the output V _SG is converted into V _SP data when the output V _SG is 4.0 V, and the register A is converted.
To store. Here, V _SP when the output V _SG is 4.0 V
The reason why the output V _SP is multiplied by the constant 204 in order to be converted into data is that the data of the optical sensor 25 is read from the analog port of 8 bits and the upper limit of 5V as described above (255 × 4V / 5V = 204). Next, in step 2, it is judged whether or not it is larger than 40 which is this V _SP data value, and if it is larger than this, register A is set to 4
It is corrected to 0 (step 3). This is because the V _SP data is 4 because the size of the data table for obtaining the toner density from the V _SP data, that is, the ratio of the output V _SP and V _SG.
Those of 0 or more are collectively approximated as V _SP data 40. Next, in steps 4 and 5, it is judged whether or not the V _SP data is 0, and if it is 0, it is corrected to 1 (step 5). This is also approximated from the size relation of the data table. Then, in steps 6 to 10, the V _SP data shown in FIG. 28 is corrected using LDCNT. Here, the LDCNT 184 has an area ratio of 80 in the image.
%, LDCNT138 to 60%, LDCNT69
Correspond to the same 30% respectively. Although not shown in the flowchart, 1 is set when the result of the subtraction processing in steps 9 to 11 becomes smaller than 1. next,
In step 12, the V _SP data is used to search the data table in which the correspondence between the V _SP data, that is, the ratio between the output V _SP and the output V _SG and the toner concentration is stored, and the toner concentration data is read. After storing in the register A, it is stored in the register DBTDEN in step 13. Next, in step 14, the toner density data stored in the register A is used to search the data table in which the correspondence between the toner density and the toner adhesion rate is stored, and the toner adhesion rate data is read. After storing this in register A,
In step 15, the data in register A is transferred to register DBTN
Store in MA.

Using the toner adhesion area and the toner adhesion rate for one image obtained as described above, the toner consumption amount consumed by this one image is calculated. Specifically, the product of the toner adhesion area data and the toner adhesion rate data is calculated to obtain the toner consumption amount per one image formation.

Next, the calculation of the toner supply amount will be described. Ideally, if the replenishment conditions of the toner replenishment mechanism are controlled so that the toner replenishment amount matches the toner consumption amount obtained by the above calculation, the toner density should be kept constant. In addition to the fact that the toner replenishment amount calculated due to variations in the mechanical feel of the toner replenishment mechanism and environmental changes do not always match the amount of toner actually replenished, in this example Will be misaligned. That is, in this example, the toner concentration of the developer in the developing device 21 is set to the photoconductor 1
Since it is determined by detecting the optical density of the reference pattern toner image obtained by developing the reference latent image formed above, the toner is consumed to form the reference pattern toner image, and the cleaning unit 6 is used. The burden of cleaning the reference pattern toner image also arises. For this reason,
As described above, the toner density is detected every 10th image formation, and during the 10th image formation after the detection, the toner adhesion ratio MA obtained using the detected toner density and the image formation operation are calculated. The toner consumption amount per one image formation is calculated from the sum of the toner adhesion areas obtained as described above. However, since the toner density changes during the formation of 10 images after the toner density is detected, an error occurs between the toner consumption amount and the actual toner consumption amount, resulting in the toner concentration. Is out of the target toner density.

Therefore, in this embodiment, in addition to the latest toner density detection result, the toner density related to this latest toner density detection is compared with the toner density related to the previous toner density detection, The toner replenishment amount is determined in consideration of the transition of the toner concentration, and if the actual toner concentration deviates from the target toner concentration,
The target toner density should be quickly converged.

That is, from the latest toner density detection result, when the detected toner density is higher than the target toner density, the toner replenishment amount is made smaller than the toner consumption amount, and conversely, the detected toner density is lower than the target toner density. If the toner detection amount is lower than the latest detection toner concentration (if the toner concentration tends to decrease), the toner is replenished more than the toner consumption amount. If the replenishment amount is larger than the toner consumption amount, and conversely, the previously detected toner concentration is higher than the latest detected toner concentration (when the toner concentration tends to increase), the toner replenishment amount is larger than the toner consumption amount. The amount of toner replenishment is determined from the viewpoint of reducing the amount of toner.

In order to determine the toner replenishment amount from the above viewpoints, the variable GA in the toner replenishment amount calculation is used in this example.
IN is used. Below, the variable GAIN in this example
Will be specifically described. The variable GAIN corresponds to the ratio between the toner replenishment amount and the toner consumption amount, and when this is 1.0, the toner replenishment amount and the toner consumption amount are equal. And
When the latest detected toner density is lower than the target toner density, this variable GAIN is made larger than 1.0 to increase the toner density, and this increase is taken into consideration in the transition of the toner density. Make a decision. Similarly, when the latest detected toner density is higher than the target toner density, this variable GAIN is made smaller than 1.0 to lower the toner density, and this decrease is changed to the above toner density transition. Make decisions in consideration.

The specific value of the variable GAIN varies depending on the characteristics of the developing device 21 and the toner replenishment method, and is experimentally obtained. An example will be shown below. If the latest detected toner concentration is lower than the target toner concentration and the previously detected toner concentration is also lower than the target toner concentration, the GAIN value is 1.4 to 2.3.
The latest detected toner concentration is lower than the target toner concentration,
In addition, when the previous detected toner concentration is higher than the target toner concentration, the GAIN value is 1.3 to 3.0, the latest detected toner concentration is higher than the target toner concentration, and the previous detected toner concentration is Is 0.5 to 0.8 when the toner density is lower than the target toner density, the latest detected toner density is higher than the target toner density, and the previous detected toner density is also higher than the target toner density. GAI when high
The value of N is set in the range of 0.6 to 1.0. Specifically, it is set as shown in Table 3 below. In addition, A in the vertical direction in Table 3 below
= 0 to 4 correspond to the latest detected toner density, and lateral tables 1 to 5 correspond to the previously detected toner density. The A = 0 to 4 and the tables 1 to 5 correspond to the categories of the detected toner density, as shown in the flowcharts of FIGS. 30 and 31 showing the specific control. Of these, tables 1 to 5 correspond to data tables for searching GAIN data from the respective A categories.

Specific control for obtaining GAIN will be described with reference to FIGS. 30 and 31. First, in step 1, as in step 1 in the flowchart of FIG. 29 described above, the output V _SP read from the register DVPNEW is
Using the output V _SG read from the register DVGNEW, the output V _SG is converted into V _SP data when the output V _SG is 4.0 V and stored in the register A. In step 2, this is stored in the register DBPNEW. Before the storage in the register DBPNEW, the correction process of steps 6 to 11 in the flowchart of FIG. 29 may be performed. Then, in steps 3 and 4, similarly, the output V _SP read from the register DVPOLD is used with the output V _SG read from the register DVGOLD to output V _SG when the output V _SG is 4.0 volts.
_It is converted into _SP data, stored in the register A, and stored in the register DBPOLD. And steps 5-13
Then, first, using the V _SP data at the time of the previous detection read from the register DBPOLD, which of the data tables in Table 3 to use is selected. Then step 14
.About.19, the classification of A in the above Table 3 is determined using the latest detected V _SP data read from the register DBP NEW. Then, in step 23, the data table selected as described above is searched using the determined section A, and the searched GAIN data is stored in the register A,
In step 24, this is stored in the register DBGAIN.

FIG. 32 shows the toner replenishment amount calculation using GAIN and the like obtained as described above. 32, the toner consumption data is calculated by calculating the product of the toner adhesion rate data read from the register DBTNMA and the toner adhesion area data read from the register LDCNT in step 1.
This is stored in the register DBADDT. Next, in step 2, the toner consumption data read from the register DBADDT is multiplied by the GAIN data read from the register DBGAIN to obtain toner replenishment amount data, which is stored in the register DBADDL / H. In this example, the toner replenishment amount is obtained by the product of DBADDT and GAIN which is the toner consumption amount data for one sheet, but it may be obtained by the following equation (3) instead. DBADDT + (1-GAIN) × A (3) However, A is a constant also in the calculation of this expression (3), the difference between the toner consumption amount and the toner replenishment amount is calculated in accordance with the detected toner concentration and the transition of the toner concentration. The target toner concentration is set and the operation is performed to bring it closer to the target toner concentration.

Next, the toner supply operation will be described.
The toner is replenished according to the toner consumption amount. The amount of replenishment toner is set according to the rotation driving time of the replenishment roller 24. The toner consumption amount per one image is the product of the toner consumption area and the toner adhesion rate as described above, and is specifically expressed by the following formula (4). (Toner consumption amount) = LDCNT × 2 ¹⁷ × MA × 1 / (400 / 2.54) ² ≈LDCNT × MA × 655/124 (4) Here, the unit of (toner consumption) is mg, LDCNT ×
The unit of 2 ¹⁷ is dot, the unit of MA is mg / cm ² , 1 /
The unit of (400 / 2.54) ² is cm ² / dot.
It should be noted that the reason why LDCNT is multiplied by 2 ¹⁷ is that the toner adhesion area data LDCNT is represented by the upper 8 bits as described above. On the other hand, toner replenishment in this example is performed by rotating the replenishment roller 24 by driving the clutch, and as shown in FIG. 33, in the area A where the toner replenishment amount per unit time is stable, 300 mg / second Replenishment is done. In FIG. 33, the vertical axis is 30
The relationship between the remaining amount in the toner hopper 22 and the toner replenishment amount is shown by taking the toner replenishment amount per second and the horizontal axis representing the remaining amount of toner in the toner hopper 22. Then, the toner replenishment amount by the above calculation is obtained by multiplying the toner consumption amount by GAIN and converted into a replenishment time (rotation time of the replenishment roller 24), the following formula (5) is obtained. (Replenishment time) = (toner consumption amount) × GAIN × 1/300 ≈LDCNT × MA × 131/124 × 60 (5) The unit of this (replenishment time) is seconds. Only during this replenishment time, the clutch is turned on to replenish the toner.
In the above flowchart, constant processing (× 131, 124 × 60) for matching the above unit system is performed.
Etc.) are omitted.

When the drive source for the image forming operation (the motor for driving the drum 1 and the registration roller 9) and the drive source for the developing unit 4 (the motor for driving the mag roller and the replenishing roller 24) are independently provided. , An electromagnetic clutch for replenishment at an arbitrary timing of feeding of each recording sheet, for a time corresponding to DBADDL, DBADDH which is replenishment amount data O
N As a result, the agitator 23 and the replenishing roller 24 in the toner hopper 22 are driven to replenish the developing device 21 with toner. Further, when the above-mentioned drive sources are the same, the toner replenishing operation is performed at the time of recording or at the timing when the transfer of the toner image on the photoconductor 1 is completed in order to prevent image deterioration due to load variation of the drive source. Is preferred.

As described above, in this embodiment, the toner density TC 'is determined by detecting the reference toner image by the optical sensor for each predetermined number of sheets.
Is calculated and, if necessary, the toner density TC is obtained by correcting this with the sum LDCNT of the toner adhesion area data relating to the immediately preceding copy. With this TC, the toner adhesion rate MA per unit area is calculated and stored in the register. Further, this TC is compared with the TC related to the previous detection, and the variable GAIN is calculated from the transition of the toner density and stored in the register. Then, the LDCNT counted for each copy is multiplied by MA and GAIN read from the register to calculate the toner replenishment amount, and the toner is replenished for each copy. As a result, the toner density can be converged to the target toner density, and the stable visualization ability of the developing unit 4 can be obtained.

Incidentally, FIG. 34 shows the timing of execution of each control and the use relation of each operation result in the above-mentioned embodiment with reference to the timing of the copy operation. In the figure, “Δ” indicates the sensor check timing, which is set for the first sheet after the main switch of the image forming apparatus is turned on and for every tenth sheet thereafter. At this timing, the pattern on the photoconductor 1 is read by the optical sensor 25 to obtain outputs V _SG and V _SP . “TC ′” indicates toner concentration calculation, and the toner concentration (TC) in the developing device 21 is calculated from the output ratio of the output V _SG and the output V _SP . “TC” indicates toner concentration correction, which is performed by checking the toner adhesion area (LDCNT) of the recording paper immediately before the sensor check timing, and a certain value or more (when the adhesion amount is large, the stirring of the developing device 21 is insufficient. In this case), the toner density is corrected to a value higher than TC '. The corrected toner density is designated as TC. "M
“A” indicates the calculation of the toner adhesion rate. Since the toner adhesion amount per unit area on the photoconductor 1 varies depending on the toner concentration even under the same process condition, the adhesion rate MA is obtained from the value of TC in the data table. “LDCNT” indicates the calculation of the toner adhesion area, which is image data (multivalued data, etc.)
To the toner adhesion area using the data table,
The total toner adhesion area LDCNT per recording paper is obtained. “UT.” Indicates the calculation of the toner consumption amount, which is the product of the adhesion rate MA and the toner adhesion area LDCNT. To calculate. “GAIN” indicates the calculation of the variable GAIN, and the detected V _SG , V _SP and the previously detected V _SG ,
V _SP is compared, and a variable GAIN for adjusting the replenishment amount so as to obtain the target toner concentration TC (V _SG , V _SP ) is obtained. “ADDT” indicates the toner replenishment amount calculation, and the consumed toner amount uT. The toner replenishment amount is calculated as the product of the variable GAIN and the variable GAIN. Through the above flow, the toner replenishment amount is obtained for each recording sheet and the toner replenishment is executed. However, the variable GAIN is changed at each sensor check timing.

As described above, in this embodiment, in order to detect the toner adhering rate, which is the toner adhering amount per unit area on the photoconductor 1, the toner density of the developer in the developing device 21 is detected by using the optical sensor 25. However, instead of this, a toner concentration sensor may be provided in the developing device 21. Further, although the toner density is detected every predetermined number of sheets, instead of this, it may be detected every time. Further, when the output of the optical sensor 25 is not within the predetermined range, the value of the preset data table is read (step 5 in the flowchart of FIG. 21 and the subroutine CHKV of FIG. 25), and this value is read by the optical sensor 25. The toner adhesion rate is calculated by using it as substitute data in place of the data (V _SG data, V _SP data) corresponding to the output of the above (flow chart in FIG. 29), and toner is supplied based on this toner adhesion rate and toner adhesion area. The amount of toner is calculated, and the second replenishment amount calculation means is constituted by this, but instead of this, when the output of the optical sensor 25 is not within the predetermined range, the toner adhesion rate corresponding to the output of the optical sensor 25. The value used as the substitute data in place of the above data is preset in the data table, and when the output of the optical sensor 25 is not within the predetermined range, this data table is set. Alternatively, the second replenishment amount calculation means may be configured by reading out the substitute data in place of the data of the toner attachment ratio and calculating the toner replenishment amount based on the substitute data and the toner attachment area. .. Further, in the above-mentioned embodiment, the above equation (2) is established as a special case of the above equation (1) as described above, but such equation (2) is not established,
As a result, when it is necessary to convert the toner consumption amount per dot to consumption data using both the image multi-value data and the toner density, the data for retrieving the consumption data from the image multi-value data A table may be provided for each toner concentration. Then, the toner density data for this purpose may be obtained by detecting the toner density each time, or when the toner density is detected at a predetermined interval as in the above embodiment, the latest toner density may be used. good. Further, in the above-described embodiment, since the toner adhesion area varies depending on the pulse width of the writing LD, multivalued data of an image is converted into consumption data, and the sum of the consumption data per image is one image. The toner adhesion area of
Even if the pulse width of is constant, if the toner adhesion amount changes depending on the density of dots in the image, for example,
Even when the toner adhesion rate changes depending on whether the distance between dots is close enough to increase the toner adhesion amount due to the edge effect in development, the relationship between the dot distance and the toner adhesion amount is Obtained in advance, this relationship is used as a conversion table from image multi-valued data to consumption data, the image multi-valued data is once converted into consumption data, and the consumption data is summed up per image. The toner adhesion area per image is obtained. Further, in the above embodiment, various data tables are used, but those replaced by the internal arithmetic expression are replaced with the arithmetic expression and the arithmetic processing of this arithmetic expression is executed instead of the search of the data table. Is also good.

[0132]

According to the present invention, the light emitting time of the light beam (laser beam) is integrated and the toner replenishment control is performed, whereby the toner replenishment can be performed in real time. Since the response characteristic of is improved, it can be applied to any image. Further, by outputting the detection signal of the reference toner image with the optical detection means (optical sensor) and performing the toner replenishment control together, it is possible to reduce the time and any environment.
It is possible to absorb an error that occurs in the relationship between the light emitting time of the light beam and the toner replenishment amount, maintain an appropriate toner concentration, and always obtain a stable and high-quality image.

According to the invention of claim 7, the total area of the toner adhesion area on the photoconductor is calculated using the image data in the image area, and the toner adhesion area per unit area of the toner adhesion area on the photoconductor is calculated. The amount of toner replenished to the developing device is calculated based on the toner adhesion amount per unit area and the total area. Since the amount of replenishment toner is determined in consideration of the fluctuation of the toner adhesion amount per unit area of the above toner adhesion region, the toner consumption amount is accurately predicted,
Proper toner supply can be performed.

According to the eighth aspect of the present invention, the toner adhesion amount per unit area is calculated based on the density of the reference toner image formed on the image carrier, so that the characteristic change of the image carrier may occur. It is possible to accurately detect the toner adhesion amount per unit area in consideration of the change in the toner adhesion amount.

Further, according to the invention of claim 9, the toner replenishment amount to the developing device is calculated based on the product of the toner adhesion amount per unit area and the total area, so that the toner on the image bearing member is calculated. The calculation of the total area of the adhesion region and the calculation of the final toner replenishment amount can be executed by a relatively simple calculation process.

According to the tenth aspect of the present invention, since the density of the reference toner image is detected for each predetermined image forming operation, the toner consumption and the load on the cleaning device due to the formation of the reference toner image are reduced. Since the toner replenishment amount to the developing device is corrected according to the change of the density, the deviation from the target toner density occurs during the image forming operation in which the density of the reference toner image is not detected. Even if
This deviation can be suppressed to be relatively small, and at the same time, the target toner concentration can be quickly converged.

Further, according to the invention of claim 11, the total area of the toner adhering region in the image forming operation one or more times before the timing of forming the reference toner image is compared with the predetermined area. In the forming operation, it is possible to determine whether the toner charge amount is insufficient due to insufficient developer agitation due to excessive toner replenishment, and the toner replenishment amount to the developing device is corrected based on the comparison result. It is possible to prevent further excessive replenishment of toner due to erroneous detection of the toner adhesion amount per unit area due to insufficient charging. Even when the detected density of the reference toner image is used for the toner near-end detection for determining whether there is a remaining amount of replenishment toner, even if the toner charge amount is insufficient due to insufficient developer agitation due to excessive toner replenishment, It is possible to prevent the toner near end detection.

According to the twelfth aspect of the invention, the area calculating means for calculating the total area of the toner adhering area on the image carrier using the image data in the image area, and the reference formed on the image carrier. Light detection means for detecting the density of the toner image, adhesion amount calculation means for calculating the toner adhesion amount per unit area of the toner adhesion area on the image carrier based on the output of the light detection means, and the area calculation means. The first replenishment amount calculation means for calculating the toner replenishment amount to the developing device based on the calculation result of 1) and the calculation result of the adhesion amount calculation means, and whether or not the output of the light detection means is within a predetermined range. A discriminating unit, and a calculation result of the area calculating unit and a predetermined value according to the discrimination result by the discriminating unit.
Since the second replenishment amount calculation means for calculating the toner replenishment amount based on the toner adhesion amount per unit area is provided, when the light detection means makes an erroneous detection due to toner stain or the like, a rapid toner concentration Fluctuations can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus in which an image forming method of the present invention is implemented.

FIG. 2 is a schematic sectional view of a developing device in the image forming apparatus.

FIG. 3 is a diagram showing a relationship between an integrated value of a laser beam emission time and a toner consumption amount in the image forming apparatus.

FIG. 4 is a diagram showing a relationship between a rotation time of a supply roller and a toner supply amount in the image forming apparatus.

FIG. 5 is a schematic diagram of an optical sensor arrangement portion in the image forming apparatus.

FIG. 6 is a schematic explanatory view of the optical sensor.

FIG. 7 is a diagram showing the relationship between the toner adhesion amount per unit area of the reference toner image and the output of the optical sensor.

FIG. 8 is a flowchart showing the flow of a toner replenishment control procedure based on the integrated value of the laser beam emission time and the detection signal voltage of the optical sensor in the embodiment of the invention.

FIG. 9 is a flowchart showing the flow of a toner replenishment control procedure based on the integrated value of the laser beam emission time and the detection signal voltage of the optical sensor in another embodiment of the present invention.

FIG. 10 is a flowchart showing a flow of a toner replenishment control procedure based on an integrated value of laser beam emission time and a detection signal voltage of the optical sensor in still another embodiment of the present invention.

FIG. 11 is a flowchart showing a flow of a toner replenishment control procedure based on an integrated value of laser beam emission times and a detection signal voltage of the optical sensor in still another embodiment of the present invention.

FIG. 12 is a schematic configuration diagram around a photoconductor of a digital copying machine according to another embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of an electric component section of the copying machine.

14 is a block diagram showing the configuration of the write drive control circuit of FIG.

FIG. 15 is a characteristic diagram showing a relationship between a writing LD pulse width and a toner adhesion amount in the copying machine.

FIG. 16 is a characteristic diagram showing a relationship between LD multi-valued data and a toner deposition amount of the copying machine.

FIG. 17 is a configuration diagram of a counter circuit for calculating a toner adhesion area of the copying machine.

FIG. 18 is a circuit diagram showing a CPU and peripheral circuits in which the counter circuit is configured.

FIG. 19 is a timing chart of the counter circuit.

FIG. 20 is a flow chart of reading control of toner adhesion amount data of the copying machine.

FIG. 21 is a flowchart of reading control of an optical sensor output of the copying machine.

22A is a circuit diagram of an optical sensor of the copying machine, and FIG. 22B is a waveform diagram of an input signal to the circuit.

FIG. 23 is a characteristic diagram of the optical sensor.

FIG. 24 is a flowchart of a subroutine executed in the flowchart of FIG.

FIG. 25 is a flowchart of another subroutine executed in the flowchart of FIG.

FIG. 26 is another characteristic diagram of the optical sensor.

FIG. 27 is a characteristic diagram showing a relationship between an image area ratio and an output V _SP related to image formation immediately before detection by an optical sensor.

FIG. 28 is a graph showing the relationship between the number of correction bits of the output of the optical sensor and the area ratio.

FIG. 29 is a flowchart of control of optical sensor output correction and toner adhesion amount calculation of the copying machine.

FIG. 30 is a part of a flowchart of control for calculating variable GAIN of the copying machine.

FIG. 31 is the remaining part shown in FIG. 19 of the flowchart of the control for calculating the variable GAIN of the copying machine.

FIG. 32 is a flowchart of a control for calculating both toner supply in the copying machine.

FIG. 33 is a characteristic diagram of the toner supply mechanism of the copying machine.

FIG. 34 is a timing chart showing execution timings of various controls of the copying machine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 photoconductor drum, 4 developing unit 6 cleaning device, 21 developing device 22, toner hopper, 23 agitator 24 replenishing roller, 25 optical sensor 41 developing roller, 800 video controller 801 P-ROM (conversion table), 811 adder 813 counter, 815 Latch circuit P Reference toner image, L Laser beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number of the agency FI Technical display location G03G 15/08 112 11222-2H // G03G 15/04 116 (72) Inventor Hisao Murayama Ota, Tokyo 1-3-6 Nakamagome-ku, Ricoh Co., Ltd. (72) Inventor Mayumi Yoshida 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Yuko Harazawa 1-chome, Nakamagome, Ota-ku, Tokyo 3-6, Ricoh Co., Ltd. (72) Shinji Kato 1-3-6, Nakamagome, Ota-ku, Tokyo Tokyo Ricoh Co., Ltd.

Claims (12)

[Claims] 1. An image forming apparatus for performing image exposure on an image bearing member by scanning a light beam according to an image information signal,
An optical system that integrates the light emission time of the light beam, supplies toner to the developing device in an amount corresponding to the light emission time, forms a reference toner image on the image carrier, and detects the density of the reference toner image. An image forming method, characterized in that the toner replenishment control to the developing device is performed based on the detection signal of the static detection means. 2. An image forming apparatus for performing image exposure on an image bearing member by scanning a light beam according to an image information signal,
An optical system that integrates the light emission time of the light beam, supplies toner to the developing device in an amount corresponding to the light emission time, forms a reference toner image on the image carrier, and detects the density of the reference toner image. An image forming method characterized in that the amount of toner replenished to the developing device is varied based on a detection signal of a static detection means. 3. The image forming method according to claim 2, wherein the relationship between the light emission time of the light beam and the toner replenishment amount is varied based on the detection signal of the optical detection means. 4. The image forming method according to claim 2, wherein the relationship between the light emission time of the light beam and the toner replenishment amount is varied stepwise based on the detection signal of the optical detection means. 5. An image forming apparatus for performing image exposure on an image carrier by scanning a light beam according to an image information signal,
The light emission time of the light beam is integrated, a reference toner image is formed on the image carrier according to the light emission time, and the development is performed based on a detection signal of an optical detection unit that detects the density of the reference toner image. An image forming method characterized by controlling toner supply to a container. 6. The image forming method according to claim 5, wherein toner is replenished to the developing device according to the light emission time of the light beam. 7. A toner replenishment control method for calculating a total area of a toner adhering area on an image carrier using image data in an image area and replenishing toner to a developing device according to the total area. A toner characterized in that the toner adhesion amount per unit area of the toner adhesion region on the body is detected, and the toner replenishment amount to the developing device is calculated based on the toner adhesion amount per unit area and the total area. Supply control method. 8. The toner replenishment control method according to claim 7, wherein the toner adhesion amount per unit area is calculated based on the density of the reference toner image formed on the image carrier. 9. The toner replenishment control method according to claim 7, wherein the toner replenishment amount to the developing device is calculated based on a product of the toner adhesion amount per unit area and the total area. 10. The density of the reference toner image is detected every predetermined image forming operation, and the toner replenishment amount to the developing device is corrected according to the change of the density.
The toner replenishment control method described. 11. A toner replenishment amount to a developing device is compared with a predetermined area by comparing a total area of a toner adhering area in an image forming operation one or more times before the timing of forming the reference toner image with a predetermined area. 9. The toner replenishment control method according to claim 8, further comprising: 12. Area calculating means for calculating the total area of a toner adhering area on an image carrier using image data in the image area, and light detection for detecting the density of a reference toner image formed on the image carrier. Means, an adhesion amount calculation means for calculating the toner adhesion amount per unit area of the toner adhesion region on the image carrier based on the output of the light detection means, the calculation result of the area calculation means, and the adhesion amount calculation means. First replenishment amount calculation means for calculating the amount of toner replenishment to the developing device based on the calculation result, discrimination means for discriminating whether the output of the light detection means is within a predetermined range, and discrimination result by the discrimination means In accordance with the above, the image forming apparatus is provided with a second replenishment amount calculation unit for calculating the toner replenishment amount based on the calculation result of the area calculation unit and a predetermined toner adhesion amount per unit area. ..