JP3474475B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a copying machine or a printer. More specifically, the present invention relates to a two-component developer by controlling toner replenishment. The present invention relates to an image forming apparatus that controls toner density and image density.

[0002]

2. Description of the Related Art Generally, a developing device included in an electrophotographic or electrostatic recording type image forming apparatus is a one-component developer containing only non-magnetic toner or magnetic toner, or
A two-component developer including a non-magnetic toner and a carrier is used. Particularly, in a color image forming apparatus that forms a full-color image or a multi-color image by an electrophotographic method, most developing apparatuses use a two-component developer from the viewpoint of image tint and the like.

As is well known, the toner concentration of this two-component developer (ratio of toner weight to the total weight of carrier and toner) is an extremely important factor in stabilizing image quality.

Since the toner in the two-component developer is consumed by the development, the toner density of the two-component developer decreases as the development is performed, and the image density decreases accordingly. Therefore, it is necessary to control the toner density or the image density at appropriate times to maintain the image quality.

Therefore, conventionally, the toner density control for detecting the toner density of the two-component developer and controlling the toner replenishment so that the toner density of the two-component developer is always constant according to the change, and Image density control is performed in which the image density is detected and toner replenishment is controlled so that the image density is always constant according to the change.

As a conventional toner density control method, for example, a magnetic permeability sensor method is known. The magnetic permeability sensor method utilizes the fact that the magnetic permeability of a two-component developer consisting of toner and magnetic carrier changes according to the toner concentration, and the magnetic permeability sensor allows the magnetic permeability of the two-component developer in the developing device. Is detected, and based on the detection result, toner is replenished from the toner replenishing tank so that the magnetic permeability becomes a predetermined concentration, so that the toner concentration is kept constant. In this method, since the toner concentration of the two-component developer in the developing device is directly detected, it is possible to keep the toner concentration of the two-component developer constant.

On the other hand, as a conventional image density control method, the density information (image area, black solid ratio) of the original image is converted into a video count number, and the toner consumption amount is predicted from this value to estimate the initial toner density. A video counter method is known in which settings are made and toner supply is controlled.

As a conventional image density control method,
The electrostatic latent image of the patch image for image density control formed on the photoconductor is developed by developing with a developing device, and the density of the developed patch image is detected by the image density sensor, and it is determined according to the patch image density. There is also known a patch detection method in which the image density is kept constant by controlling toner replenishment.

[0009]

However, the conventional toner density control and image density control have the following problems.

First, in the magnetic permeability sensor method, the toner concentration of the two-component developer is kept constant, but the triboelectric charge amount (tribo) of the toner is changed by the deterioration of the carrier in the two-component developer and the environmental change. descend. As a result, the developability of the two-component developer is also lowered, and the image density is lowered. Therefore, in the magnetic permeability sensor method, although the toner density of the two-component developer can be maintained constant, there is a problem that the image density decreases when the quality of the carrier changes or the environment changes. there were.

Further, in the video counter system, when the toner consumption amount of the consuming system or the toner replenishing amount of the replenishing system varies, the toner density deviates from the initial set value by the variation.

Further, in the patch detection method, the image density can be kept constant, but when a low patch image density is obtained due to the deterioration of the developing property due to the change of the triboelectric charge amount of the toner, the toner replenishment is excessive. However, there is a problem in that the toner density is increased and toner scattering, fogging, and charging failure occur. This is a serious problem because the toner concentration of the two-component developer cannot be easily dropped once it has risen. Further, excessive replenishment of toner causes a situation in which the two-component developer fills the developing device and overflows from the developing device.

On the other hand, when a high patch image density is obtained due to an increase in developability associated with a change in the triboelectric charge amount of the toner, the toner replenishment stop state is continued, so that the toner amount in the developing device decreases, which causes There is a serious problem that the toner density of the two-component developer decreases and the coating amount of the developing sleeve (on the two-component developer decreases, which causes image deterioration. In addition, the reduction of the toner amount reduces the consumption of the carrier. And the load on the two-component developer is increased, and the life of the two-component developer is shortened.

The patch detection method is basically a method in which the toner density is controlled so as to cancel out all the changes in the conditions that cause changes in the image density, such as changes in the potential of the photosensitive member and changes in the characteristics of the developer. Therefore, the range of toner density used becomes inevitably large, and the load on the two-component developer becomes large.

Further, according to the study by the inventors of the present application, the toner concentration control such as the magnetic permeability sensor method is performed when the printing rate of the document to be copied is low, that is, the toner consumption is small and the toner is gradually added. It turned out to be particularly difficult when replenishing.

When an image having a low printing rate (image area, black solid ratio) is continuously formed, the replenishment amount and the consumption amount of the toner are small, so that the toner has properties such as storability, fluidity and chargeability. An external additive such as silica, which is added to the toner in a large amount for the purpose of improvement, has a great influence on the detection value of the magnetic permeability sensor, and the apparent toner concentration tends to be higher than the actual toner concentration. That is, even if the two-component developer is agitated, the carrier density changes due to the repulsion of the charged two-component developer, and as a result, the magnetic permeability changes even with the same toner concentration, so an accurate toner concentration can be detected. Hateful.

As a result, an excessively small amount of toner is replenished and the toner density in the developing device becomes insufficient. This not only increases carrier consumption and causes image defects, but also
The deterioration of the two-component developer is promoted and the life of the two-component developer becomes short.

Further, in Japanese Patent Laid-Open No. 9-127757, image forming is provided with a developing means for developing with a color two-component developer and a developing means for developing with a black two-component developer. In the apparatus, a first control device that determines the toner replenishment amount by detecting the density of a reference image for density detection formed on the image carrier, and the developer density of the developing means that uses the color developer are detected. It is disclosed that a second control device that obtains the toner replenishment amount and a third control device that obtains the toner replenishment amount from the digital image signal for each pixel of the reference image are provided.

In the image forming apparatus, for the three color developers, the toner replenishment control calculated by the second control unit is corrected using the toner replenishment amount obtained by the first control unit as the correction toner amount, and black is obtained. With respect to the developer, the toner replenishment control is corrected by the third control device with the toner replenishment amount obtained by the first control device as the correction toner amount.

However, the image forming apparatus described in the above publication does not control the toner replenishment according to the amount of toner consumed. Therefore, even when a large amount of toner is consumed and a good result can be obtained only by controlling the toner density, complicated toner replenishment control is performed by a plurality of control devices, so that a reference image for density detection and The image forming speed is reduced by the time required for density detection and the like.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an image forming apparatus capable of stably obtaining a high quality image and having an excellent operating speed and a low running cost. To provide.

[0022]

In order to solve the above-mentioned problems, an image forming apparatus according to a first aspect of the present invention has an image carrier capable of holding an electrostatic latent image on its surface, and an input image. Latent image forming means for forming an electrostatic latent image according to information on the surface of the image carrier, and developing means for developing the electrostatic latent image with a two-component developer composed of toner and carrier to form a toner image. An image forming apparatus comprising: a toner replenishing means for replenishing the developing means with toner; a toner concentration detecting means for detecting a toner concentration in a two-component developer in the developing means; Image density detecting means for detecting the image density of the reference toner image, print rate calculating means for obtaining the print rate of the image from the input image information, and toner consumption is detected based on the calculation result of the print rate calculating means, Of detected toner And money amount, based on the detection result of the detection result and the image density detecting means of the toner concentration detection means,
A toner replenishment control means for controlling toner replenishment by the toner replenishment means , wherein the toner replenishment control means is a toner replenishment control means.
-Detection result of density detection means and detection of image density detection means
Whether to perform toner replenishment control based on both knowledge results
In other words, it is possible to
Based on the detected toner consumption.
Toner replenishment control method
It is characterized by changing .

According to the above construction, the toner consumption is detected based on the printing rate obtained based on the document image information (image area, black solid coverage, etc.), and the toner consumption is detected accurately from the detected toner consumption. The method of toner replenishment control can be changed by determining whether or not toner replenishment control is necessary.

When precise toner replenishment control is required, the image density detection is performed without detecting the amount of replenishment toner held based on only the detection result of the toner concentration detection means such as the magnetic permeability sensor. The amount of replenishment toner held can also be detected by using the detection result of the means in combination. This allows
The toner replenishment control can be precisely performed based on both the detection result of the toner density detecting means and the detection result of the image density detecting means. Therefore, the toner density can be controlled to be constant on the basis of the detection result of the toner density detecting means, and the developer overflow, fog, and developing roller that occur due to excessive toner replenishment despite the low density of the original image. It is possible to prevent problems such as defective coating on the sleeve. Further, since the image density can be controlled to be constant from the initial stage of image formation based on the detection result of the image density detecting means,
Even if the characteristics of the two-component developer change due to environmental changes or the amount of toner consumption changes, the toner density can be controlled to an appropriate density at which a toner image having an appropriate image density can be obtained. With these, a high quality image is obtained.

On the other hand, when precise toner replenishment control is not required, it is possible to use only the detection result of the toner density detecting means and not use the image density detection result. This makes it possible to omit the formation of the reference toner image. Therefore, it is possible to suppress the decrease in the operation speed (job speed) of the image forming apparatus due to the formation of the reference toner image, and it is possible to quickly shift to the image forming operation. Further, since it is possible to prevent wasteful toner consumption for forming the reference toner image, it is possible to effectively utilize the toner that is a consumable item, and it is possible to suppress the running cost. Further, it is possible to suppress the number of times of starting and stopping the toner replenishing means, and it is possible to prevent the toner replenishing means from frequently repeating start / stop due to excessive toner replenishment control to lower the image forming efficiency. Further, it is possible to prevent the toner from sticking in the toner tank, suppress the load for driving the member that stirs the toner, and prolong the life of the apparatus.

As described above, according to the first aspect of the present invention, it is possible to suppress the decrease of the operating speed and the running cost while being influenced by the variation of the printing rate judgment and the change of the environmental conditions. Highly accurate toner density control can be realized. Therefore, even if the developability of the toner, the toner consumption amount, and the like change due to environmental changes, the toner density of the two-component developer is kept constant, and the image density is kept constant, so that high-quality images can be stably obtained. It is possible to provide an image forming apparatus which can obtain an image and which is excellent in operation speed and low in running cost.

In the present specification, "to detect the density of the reference toner image formed on the surface of the photoconductor" only means to directly detect the density of the reference toner image formed on the surface of the photoconductor. Instead, it also includes detecting the density of the reference toner image formed on the surface of the photoconductor by detecting the density of the reference toner image transferred on the transfer body after being formed on the surface of the photoconductor.

The image forming apparatus according to claim 2 of the present invention is
In order to solve the above problems, an image carrier capable of holding an electrostatic latent image on its surface, and a latent image forming means for forming an electrostatic latent image according to input image information on the surface of the image carrier. An image forming apparatus comprising: a developing unit that develops the electrostatic latent image with a two-component developer including toner and a carrier to form a toner image; and a toner replenishing unit that replenishes the developing unit with toner. Toner density detecting means for detecting the toner density in the two-component developer in the developing means, image density detecting means for detecting the image density of the reference toner image formed on the surface of the image carrier, and operating states of the toner replenishing means. And a toner replenishment operation detection unit that detects the toner consumption amount based on the detection result of the toner replenishment operation detection unit, and the detected toner consumption amount, the detection result of the toner concentration detection unit, and the image density. Based on the detection result of knowledge means comprising a toner supply control means for controlling the supply of toner by the toner replenishing means, the toner supply control unit, the toner density detection
Of the detection results of the knowledge means and the image density detection means
Toner replenishment control is performed based on both
Toner replenishment based only on the detection result of the toner density detection means
Determine whether to perform control based on the detected toner consumption
It is characterized in that the method of toner replenishment control is changed by the setting.

According to the above arrangement, the toner consumption is detected based on the operating state of the toner replenishing means, and it is determined from the detected toner consumption whether or not precise toner replenishment control is necessary. The method of toner replenishment control can be changed.

As a result, when precise toner replenishment control is required as in the case of the first aspect of the invention, it is based on both the detection result of the toner density detecting means and the detection result of the image density detecting means. , Both the image density and the toner density can be made proper, and a high quality image can be obtained. On the other hand, when precise toner replenishment control is not required, it is possible to omit the formation of the reference toner image by using only the detection result of the toner concentration detection means, and it is possible to speed up the image forming operation and The running cost can be suppressed.

Therefore, even if the developability of the toner, the toner consumption amount, and the like change due to environmental changes, the toner density of the two-component developer is kept constant, and the image density is also kept constant to stabilize. It is possible to provide an image forming apparatus that can obtain a high quality image and that has a high running speed and a low running cost.

The image forming apparatus according to claim 3 of the present invention is
In order to solve the above-mentioned problems, in the image forming apparatus according to claim 1 or 2, the toner replenishment control unit, when the detected toner consumption amount is less than a preset reference amount, the toner concentration detection unit. The toner replenishment means controls the toner replenishment based on both the detection result of the image density detection means and the detection result of the image density detection means, and when the detected toner consumption amount is larger than the reference amount, only the detection result of the toner concentration detection means It is characterized in that the replenishment of toner by the toner replenishing means is controlled based on the above.

According to the above configuration, when the toner characteristic changes greatly and the toner consumption amount that requires precise detection of the amount of replenishment toner to be retained is smaller than the reference amount, the toner concentration detection means detects the result. Since the toner replenishment control is precisely performed based on both the detection result of the image density detection means, it is possible to control the image density constant while controlling the toner density constant. Therefore, problems such as developer overflow, fogging, and defective coating of the developing roller on the sleeve can be prevented, and a toner image having an appropriate image density can be obtained. As a result, it becomes possible to form a high quality image even when the toner consumption amount is small.

On the other hand, when the consumption amount of toner is larger than the reference amount, the change in the toner characteristics is small, and the toner replenishment control is performed only on the basis of the detection result of the toner concentration detecting means to obtain an appropriate image density. A high quality image can be formed. By not using the detection result of the image density, the formation of the reference toner image can be omitted. Therefore, it is possible to suppress a decrease in the operating speed of the image forming apparatus, prevent wasteful toner consumption for forming the reference toner image, and suppress a running cost. Further, the number of times of starting and stopping the toner replenishing means can be suppressed, and a decrease in image forming efficiency can be prevented.

The image forming apparatus according to claim 4 of the present invention is
In order to solve the above problems, in the image forming apparatus according to any one of claims 1 to 3, the toner replenishing means conveys the replenishment toner held in the toner tank to the developing means. And a toner amount detecting means for detecting the amount of the replenishment toner held in the toner tank based on the detected toner consumption amount, the detection result of the toner concentration detecting means, and the detection result of the image density detecting means. Is further provided.

According to the above construction, the amount of toner consumed is detected based on the operating state of the toner replenishing means, and it is determined whether or not it is necessary to precisely detect the amount of replenishment toner to be held based on the detected amount of toner consumed. It is possible to change the method for detecting the amount of replenishment toner to be held.

When it is judged from the detected toner consumption that it is necessary to accurately detect the holding amount of the replenishment toner, only the detection result of the toner concentration detecting means such as the magnetic permeability sensor is used. It is possible to detect the holding amount of the replenishment toner by also using the detection result of the image density detecting means without detecting the holding amount of the replenishment toner. This allows
It becomes possible to accurately determine the necessity of toner replenishment (toner filling) based on the combination condition of the detection result of the toner density detection means and the detection result of the image density detection means. Therefore, effective toner replenishment can be performed at an appropriate timing without being affected by changes in developer characteristics due to environmental changes and changes in toner consumption of the toner consumption system. Therefore, it is possible to surely prevent the decrease in the image density caused by the decrease in the toner replenishment amount due to the toner exhaustion, and obtain a high quality image.

On the other hand, when it is judged that it is not necessary to accurately detect the holding amount of the replenishment toner from the detected toner consumption amount, only the detection result of the toner concentration detecting means is used and the image density detection result is determined. It is possible not to use the detection result. This eliminates the need to form the reference toner image, so that wasteful toner consumption for forming the reference toner image can be prevented and running cost can be suppressed.

As the toner amount detecting means, for example, there is a toner out detecting means for detecting a toner out state (toner empty) in which there is no supply toner in the toner tank.

The image forming apparatus according to claim 5 of the present invention is
In order to solve the above-mentioned problems, in the image forming apparatus according to claim 4, the toner amount detecting means detects the toner concentration detecting means when the detected toner consumption amount is smaller than a preset reference amount. While the amount of replenishment toner is detected based on both the result and the detection result of the image density detection unit, when the detected toner consumption amount is larger than the reference amount, replenishment is performed based on only the detection result of the toner concentration detection unit. The feature is that the amount of toner for use is detected.

According to the above arrangement, it is difficult to accurately detect the amount of replenishment toner only by the detection result of the toner concentration detecting means. When the consumption amount of toner is less than the reference amount, the detection result of the toner concentration detecting means is obtained. Since the amount of replenishing toner is detected based on the detection result of the image density detecting means and the image density detecting means, it becomes possible to accurately determine whether or not toner replenishment is necessary. Therefore, effective toner replenishment can be performed at an appropriate timing without being affected by changes in developer characteristics due to environmental changes and changes in toner consumption of the toner consumption system.
Therefore, it is possible to surely prevent the decrease in the image density caused by the decrease in the toner replenishment amount due to the toner exhaustion, and obtain a high quality image.

Further, according to the above construction, when the toner consumption amount is larger than the reference amount, only the detection result of the toner density detecting means is used, so that it is not necessary to form the reference toner image. Therefore, it is possible to speed up the image forming operation, prevent wasteful toner consumption for forming the reference toner image, and suppress the running cost.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] The following will describe one embodiment of the present invention with reference to FIGS. 1, 4 to 6 and 8 to 10. In the present embodiment, the case where the image forming apparatus of the present invention is applied to an indirect electrophotographic color digital copying machine including image forming units for cyan, magenta, yellow, and black will be described. To do. The image forming units for the respective colors have the same configuration except that the toner color is different and the magnitude relationship between the patch density and the reference voltage is different (described later). Therefore, in the following description, In order to simplify the description, only the configuration related to one image forming unit in the color digital copying machine will be described.

The color digital copying machine of this embodiment is
CCD (Charg that reads the image of the original 21 to be copied
e Coupled Device) 1 and photoconductor drum (image carrier) 4
0, an exposure device (latent image forming means) 10 for forming an electrostatic latent image according to document image information, a developing device (developing means) 44 for developing the electrostatic latent image to form a toner image, Transfer drum 47 for transferring the toner image onto a transfer paper (not shown)
It has and.

The CCD 1 is for reading the image of the original 21 to be copied and supplying the original image information to the exposure device 10. The photoconductor drum 40 has a photoconductor layer made of amorphous silicon, selenium, organic photoconductor (OPC) or the like on the drum surface, and holds an electrostatic latent image on the surface thereof, and is indicated by an arrow in FIG. It is designed to rotate in the direction. Instead of the photoconductor drum 40, another transfer body, a dielectric, or the like may be used.

The exposure device 10 forms an electrostatic latent image on the surface of the photoconductor drum 40 by exposing the surface of the photoconductor drum 40 according to document image information. As the exposure device 10, for example, a pulse width modulation circuit for pulse width modulating an analog image signal to output a laser driving pulse having a width corresponding to the level of each pixel image signal of the analog image signal, and the laser driving pulse are supplied. And a semiconductor laser that emits light for a time corresponding to the pulse width of the laser driving pulse, and an optical system that guides the laser light emitted from the semiconductor laser to the surface of the photosensitive drum 40 (rotating polygon mirror, f / θ lens, fixed mirror, etc.) Those with and can be used.

The developing device 44 conveys the two-component developer 43 composed of toner and carrier held therein onto the photosensitive drum 40 by the developing roller 44a, thereby forming an electrostatic latent image on the photosensitive drum 40. Two-component developer 4
It is designed to be developed in 3. The developing roller 44a is
A developing area which is arranged so as to face the photoconductor drum 40 and rotates in the opposite direction to the photoconductor drum 40 while carrying the two-component developer 43 on the surface thereof so that the two-component developer 43 faces the photoconductor drum 40. It is to be transported to. Further, the developing device 44 includes the replenishment toner 63 supplied from a toner hopper (toner tank) 60 described later and the developing device 4.
The two-component developer 43 in 4 is agitated and mixed to make the toner concentration of the two-component developer 43 uniform.

As shown in FIG. 1, a toner hopper 60 having a predetermined internal capacity for containing replenishment toner 63 is attached to the upper part of the developing device 44, and a toner conveying screw is provided in the lower part of the toner hopper 60. A (toner supply means) 62 is installed. Toner transport screw 6
2 is rotationally driven by the toner replenishment motor 28 connected to the toner conveying screw 62, and thereby the replenishment toner 63 in the toner hopper 60 is supplied into the developing device 44. The toner replenishment motor 28 is
Electric power is supplied from the motor drive circuit 8 so that the motor drive circuit 8 is driven to rotate.
Under control of a PU (Central Processing Unit) 6, electricity is supplied only when necessary.

The transfer drum 47 abuts the transfer sheet conveyed from a sheet feeding device (not shown) on the surface of the transfer sheet while adsorbing the transfer sheet, so that the toner image on the surface of the transfer drum 40 is transferred onto the transfer sheet. It is to be transcribed. In addition,
Instead of the transfer drum 47, another transfer body such as a transfer belt may be used.

Next, an image forming method in the color digital copying machine of the present embodiment will be described. First, the image of the original 21 to be copied is read by the CCD 1, and the analog image signal is output from the CCD 1. Next, the analog image signal output from the CCD 1 is amplified by the amplifier 2 to a predetermined level, and A / D (Analog to
Digital) converter 3 converts the digital image signal.

Further, the digital image signal output from the A / D converter 3 transfer drum 47 is γ-corrected by a γ converter (not shown), and D / A (Digital to Analog).
It is converted into an analog image signal again by a converter (not shown) and then input to the exposure device (latent image forming means) 10.

Next, while the surface of the photosensitive drum 40 moves from the position facing the transfer drum 47 to the position contacting the developing roller 44a of the developing device 44, it is uniformly charged by a charger (not shown). After that, the exposure device 10 exposes according to the analog image signal. As a result, an electrostatic latent image corresponding to the image information signal is formed. This electrostatic latent image is developed by the two-component developer conveyed onto the photosensitive drum 40 by the developing roller 44a and is visualized as a toner image.

When the toner image formed on the photosensitive drum 40 reaches the position facing the transfer drum 47, it is transferred onto the transfer paper attracted to the surface of the transfer drum 47. After that, the transfer paper is peeled off from the transfer drum 47 and conveyed to a fixing device (not shown), and the toner image is fixed as a permanent image by the fixing device. Further, the residual toner remaining on the photosensitive drum 40 after the transfer is removed by a cleaner (not shown) before reaching the charging position by the charger (not shown). An image is formed on the transfer paper as described above.

In the color digital copying machine of the present embodiment, three kinds of detection are performed in order to control the amount of toner replenished from the toner hopper 60 to the developing device 44. That is, the color digital copying machine according to the present embodiment exposes the toner concentration sensor 23 (toner concentration detecting means) for detecting the toner concentration in the two-component developer 43 held in the developing device 44 and the reference toner image. An image density sensor (image density detection means) 73 which is formed on the surface of the body drum 40 and directly or indirectly detects the image density of the reference toner image, and a counter (which determines the print ratio of the image from the document image information). Printing rate calculation means) 4.

The toner concentration sensor 23 detects the toner concentration in the two-component developer 43 in the developing device 44 (ratio of the weight of toner to the total weight of the two-component developer 43), and outputs a detection signal indicating the detection result. It is what is output. Here, as the toner concentration sensor 23, the two-component developer 4 is used.
A magnetic permeability sensor for detecting the magnetic permeability of No. 3 is used. Therefore, the output of the toner concentration sensor 23 is equal to that of the two-component developer 4
It changes in proportion to the carrier concentration in 3. Therefore,
The output of the toner concentration sensor 23 decreases as the toner concentration in the two-component developer 43 increases.

The image density sensor 73 is the photosensitive drum 40.
The density of the toner image on the photosensitive drum 40 is indirectly detected by reading the reflectance of the patch image transferred onto the transfer drum 47 from above, and a detection signal indicating the reflectance of the patch image is output. is there.

The patch image is a toner image having a predetermined printing rate such as a solid image formed under the same conditions as the copy image (toner image corresponding to the original image), and is a copy on the surface of the photosensitive drum 40. The image is formed outside the area where the image is to be formed, for example, on the surface of the side end portion of the photosensitive drum 40. The method of forming the patch image is not particularly limited, but here, a predetermined patch image signal output from the patch image signal source 72 is applied to the digital image signal output from the A / D converter 3. Is used.

Since the output of the image density sensor 73 indicates the reflectance of the patch image, when the toner is color toner (chromatic toner), the output increases as the density of the patch image increases, while the toner becomes black. In the case of toner (achromatic toner), it decreases as the density of the patch image increases.

The image density sensor 73 may directly detect the density of the toner image on the photosensitive drum 40 by detecting the potential of the patch image on the photosensitive drum 40.

The counter 4 calculates the print rate of the image, that is, the ratio of print pixels (pixels in which toner dots should be formed) to all the pixels of the image, based on the density information (image area, black solid ratio) of the original image. To do. Counter 4
Converts the digital signal representing the density information of the original image output from the A / D converter 3 into a video count number representing the image printing rate, and uses CP as a prediction signal representing the image printing rate.
Output to U6.

In the color digital copying machine of the present embodiment, the toner consumption amount is predicted based on the image print ratio obtained by the counter 4, and the predicted toner consumption amount is calculated.
CP for controlling the feeding of the replenishment toner 63 by the toner feeding screw (toner replenishing means) 62 based on the output of the toner density sensor 23 and the output of the image density sensor
A U (toner supply control means, toner amount detection means) 6 is provided.

The CPU 6 outputs to the toner density sensor 23 a prediction signal indicating the printing rate of the image output from the counter 4.
The first comparison signal generated based on the output of 1 and the second comparison signal generated based on the output of the image density sensor 73 are input. The first comparison signal is generated by comparing the toner concentration detection signal output from the toner concentration sensor 23 by the comparator 77 and the toner concentration reference voltage (reference signal) output from the reference voltage signal source 78. And represents the magnitude relationship between the toner concentration detection signal and the toner concentration reference voltage. Further, the second comparison signal is obtained by comparing the signal representing the detection result of the image density output from the image density sensor 73 in the comparator 75 with the reference voltage of the image density output from the reference voltage signal source 76. It is generated, and represents the magnitude relationship between the image density detection signal and the image density reference voltage.

A memory 7 storing control data for toner replenishment control is connected to the CPU 6,
The control data is read from the memory 7 as needed.

The CPU 6 makes a comprehensive judgment from the predicted signal representing the image printing rate, the first comparison signal and the second comparison signal, and according to the control data read from the memory 7, the toner hopper 60 to the developing device. The control of toner replenishment to 44 is executed. That is, the CPU 6 controls the rotation driving of the toner feeding screw 62 by the toner replenishment motor 28 by controlling the energization of the motor driving circuit 8 and thereby controls the rotation of the toner feeding screw 62, so that the toner hopper 60 develops. The amount of the replenishment toner 63 replenished to the device 44 is adjusted.

The CPU 6 also has a function of detecting that the replenishment toner 63 held in the toner hopper 60 has run out. When the CPU 6 detects that the replenishment toner 63 has run out, the display device 5 A display indicating that the replenishment toner 63 has run out (hereinafter referred to as toner empty display) is displayed.

As described in the section of the prior art, the toner replenishment control is difficult and the toner empty detection is difficult only when the toner consumption amount is small, based only on the detection result of the magnetic permeability sensor. Therefore, in the CPU 6 of the color digital copying machine of the present embodiment, when the toner consumption amount is smaller than the preset reference amount, the transfer is performed in addition to the output of the toner density sensor 23 indicating the magnetic permeability detected by the magnetic permeability sensor. Considering the output of the image density sensor 73 representing the reflectance of the patch image formed on the drum 47, the toner replenishment operation is executed depending on which of the four combination conditions described below satisfies the combination of these two outputs. The presence / absence of toner is detected, and toner out (toner empty) is detected.

Next, the toner replenishment control and toner depletion detection in the color digital copying machine of this embodiment will be described with reference to FIG.
It will be described in detail with reference to the flowchart of FIG.
Note that, here, a case where a color toner (chromatic color toner) is used will be described.

In the following description, the toner concentration detection result output from the toner concentration sensor 23 (two-component developer 43
Of the image density sensor 73 is referred to as "toner density detection signal" or "ATC output", and a signal representing the image density detection result (patch image reflectance) output from the image density sensor 73 is referred to as "image density detection". Signal ”or“ patch output ”
Is written. Further, the reference voltage (reference signal) of the toner concentration output from the reference voltage signal source 78 is referred to as “toner concentration reference signal” or “reference output”, and the reference voltage signal source 76
The reference voltage (reference signal) of the image density output from is referred to as "image density reference signal" or "reference output".

In the toner supply control of this embodiment, first,
The printing rate of the original image is read by the counter 4 (S1),
The CPU 6 determines whether the printing rate of the original image is the low printing rate or not depending on whether the printing rate of the original image is lower than a predetermined threshold value (S2). Then, the CPU 6 determines that the predicted toner consumption amount is smaller than the preset reference amount if the printing rate of the original image is lower than the preset threshold value.

If it is determined in S2 that the printing rate is not low, that is, the printing rate is high, the subroutine 1 shown in FIG. 5 is executed (S3), and then the standby mode is restored (S3).
4).

In the subroutine 1, first, the toner density sensor 23 detects the toner density (S31).
After that, the CPU 6 determines whether the toner concentration detection signal (ATC output) is larger than the toner concentration reference signal.
The determination is made based on the first comparison signal from S7 (S3
2). When it is determined in S32 that the toner concentration detection signal (ATC output) is not larger than the toner concentration reference signal, the CPU 6 determines that the toner amount is sufficient (S3
3) Return to the normal mode (S34).

On the other hand, in S32, the toner concentration detection signal (A
If it is determined that (TC output) is larger than the toner concentration reference signal, the CPU 6 causes the toner conveying screw 62 to execute toner supply (S37). After the toner is supplied, the toner density sensor 23 detects the toner density (S38), and the CPU 6 detects the toner density detection signal (AT
If it is determined that the C output) is less than the toner concentration reference signal (S39), it is determined that the toner amount is sufficient (S3).
3) Return to the normal mode (S34).

Then, toner supply is executed in S37, S38
When the toner concentration detection signal (ATC output) becomes less than the toner concentration reference signal due to the toner replenishment less than three times in the CPU 6, the toner amount is detected. It is determined that there is enough (S33) and the normal mode is restored (S34), while the toner concentration detection signal (ATC
If the output) is larger than the toner concentration reference signal, it is determined that the replenishment toner 63 held in the toner hopper 60 has run out (S42), and the toner empty display is displayed on the display device 5 (S43).

In order to repeat the loop of S37 to S39 up to three times, the CPU 6 resets its internal counter before executing toner replenishment (S3
5), the count number n is set to 1 (S36), and S37 to S3
If the count number n is 2 or less after execution of 9, the count number n is incremented by 1 (S41). If the count number n is 3 after execution of S37 to S39, the loop of S37 to S39 is exited and the process proceeds to S42. .

On the other hand, when it is determined in S2 that the printing rate is low, the toner density sensor 23 detects the toner density (S5), and then the CPU 6 sends the toner density detection signal (ATC output) to the toner density reference signal. Whether or not it is larger is determined based on the first comparison signal from the comparator 77 (S6).

When it is determined in S6 that the toner density detection signal (ATC output) is larger than the toner density reference signal, the image density detection is performed by the image density sensor 73 (S7), and then the CPU 6 detects the image density detection signal. Whether (patch output) is larger than the image density reference signal is determined based on the second comparison signal from the comparator 75 (S
8). When the image density detection signal (patch output) is larger than the image density reference signal, the CPU 6 causes the toner feeding screw 62 to execute "intermittent toner replenishment" (S9), while the image density detection signal (patch output). Is not larger than the image density reference signal, the toner carrying screw 62 is caused to execute "continuous toner supply" (S).
10).

Note that the "continuous toner replenishment" and the "intermittent toner replenishment" are the same in that both of them result in toner replenishment as a result, but the "continuous toner replenishment" is to continuously replenish toner. Yes The replenishment toner 63 is replenished in a larger amount, and "intermittent toner replenishment" is to replenish toner intermittently, and the replenishment toner 63 is replenished in a smaller amount.

On the other hand, in S6, the toner concentration detection signal (AT
If it is determined that C output) is not larger than the toner density reference signal, the image density detection is performed by the image density sensor 73 (S11), and then the CPU 6 sends the image density detection signal (patch output) to the image density reference signal. Whether or not it is larger is determined based on the second comparison signal from the comparator 75 (S12). When the image density detection signal (patch output) is larger than the image density reference signal, the CPU 6 stops the toner feeding screw 62 to stop the toner supply (S13) and returns to the standby mode (S4). If the image density detection signal (patch output) is not larger than the image density reference signal, the toner feeding screw 62 is caused to execute "intermittent toner supply" (S).
14).

The toner replenishment control in S5 to 14 is summarized as follows. (1) When ATC output> reference output and patch output <reference output, “continuous toner supply” is executed, and (2) when ATC output <reference output and patch output <reference voltage. "Intermittent toner replenishment" is executed. (3) If ATC output> reference output and patch output> reference output, "intermittent toner replenishment" is executed, and (4) ATC output <reference If the output and the patch output> reference output, the process proceeds to S4 without supplying toner, and returns to the standby mode (standby state).

As described above, the CPU 6 predicts the toner consumption amount from the output of the counter 4, and when the toner consumption amount is small, the toner density detection signal (ATC output) and the image density detection signal (patch output). By controlling the rotation of the toner conveying screw 62 based on the above, it is possible to stably obtain a high quality image. On the other hand, when the toner consumption amount is large, the patch image formation can be omitted by controlling the rotation of the toner carrying screw 62 based only on the toner concentration detection signal (ATC output). It is possible to speed up the process and reduce the running cost.

The above "(1)" Continuous toner supply "(S1)
0) and the "intermittent toner replenishment" of the above (2) are executed, then the subroutine 2 shown in FIG.
After the toner is supplied in (S15), the toner empty detection routine (S16 to S20) executes the toner empty display, the re-execution of the subroutine 2 and the toner empty detection routine, and the return to the standby mode according to the following conditions. Decide which one to do.

(5) If ATC output> reference output and patch output <reference output, the toner hopper 60
The display device 5 is caused to perform a toner empty display indicating that the supply toner 63 held therein has run out (S2).
1).

(6) If ATC output <reference output and patch output <reference voltage, subroutine 2 (S
15) and empty detection routine (S16 to S2)
Re-execute 0).

(7) If ATC output> reference output and patch output> reference output, subroutine 2 (S
15) and empty detection routine (S16 to S2)
Re-execute 0).

(8) If ATC output <reference output and patch output> reference output, the process proceeds to S4 without toner supply and returns to the standby mode (standby state).

In the above cases (6) and (7), there is a high possibility that the toner hopper 60 is out of toner (toner empty) without the replenishment toner 63 in comparison with the case (8). . Therefore, in the cases of (6) and (7), the empty detection routine is re-executed to detect the toner empty more reliably.

Next, the subroutine 2 and the toner empty detection routine will be described. In the subroutine 2, as shown in FIG. 6, execution of toner supply (S53) is repeated twice. That is, the CPU 6
First resets the internal counter (S5
1) The count number n is set to 1 (S52), and the toner feeding screw 62 is caused to execute toner supply (S53).
Then, it is determined whether the count number n is 2 (S5
4) If the count number n is not 2, 1 is added to the count number n (S55), and if the count number n is 2, the toner empty detection routine is started.

In the toner empty detection routine, first, the CPU 6 determines whether the toner density detection signal (ATC output) is larger than the toner density reference signal.
The determination is made based on the first comparison signal from S7 (S1
6).

When it is determined in S16 that the toner density detection signal (ATC output) is larger than the toner density reference signal, the image density detection is performed by the image density sensor 73 (S17), and then the CPU 6 detects the image density detection signal. Whether (patch output) is larger than the image density reference signal is determined based on the second comparison signal from the comparator 75 (S
18). If the image density detection signal (patch output) is larger than the image density reference signal, the CPU 6 executes S15.
On the other hand, when the image density detection signal (patch output) is not larger than the image density reference signal, it is determined that the toner is empty, and the toner empty display is displayed on the display device 5 (S21).

On the other hand, in S32, the toner concentration detection signal (A
If it is determined that the TC output) is not larger than the toner density reference signal, the image density sensor 73 detects the image density (S19), and then the CPU 6 sends the image density detection signal (patch output) to the image density reference signal. Whether or not it is larger is determined based on the second comparison signal from the comparator 75 (S20). When the image density detection signal (patch output) is larger than the image density reference signal, the CPU 6 determines that the toner amount is sufficient and returns to the standby mode (S4), while the image density detection signal (patch output) is output. ) Is not larger than the image density reference signal, the process returns to S15.

As described above, the CPU 6 predicts the toner consumption amount from the output of the counter 4, and when the toner consumption amount is small, the toner density detection signal (ATC output) and the image density detection signal (patch output). By causing the display device 5 to display the toner empty based on the above, it becomes possible to replenish the toner at an appropriate timing, and it is possible to surely prevent the decrease in the image density due to the toner exhaustion. Therefore, an effect of obtaining a high quality image can be obtained. On the other hand, when the toner consumption amount is large, by causing the display device 5 to display the toner empty based on only the toner concentration detection signal (ATC output),
Since the formation of the patch image can be omitted, the image forming operation can be speeded up and the running cost can be suppressed.

The above description relates to the case where the color toner is used, but when the black toner is used,
As described above, since the relationship between the reflectance and the density of the toner image is reversed, control may be performed with the magnitude relationship between the patch density and the reference voltage reversed.

That is, when the color toner is used, as shown in FIGS. 8A and 8B and Tables 1 and 2, the output of the toner density sensor 23 increases as the toner density in the two-component developer 43 increases. While the (ATC output) decreases, the output of the image density sensor 73 (patch output) increases as the density of the patch image increases. Therefore, toner replenishment is performed when the output of the toner density sensor 23 (ATC output) is higher than the reference output or when the output of the image density sensor 73 (patch output) is lower than the reference output.

[0094]

[Table 1]

[0095]

[Table 2]

On the other hand, when the black toner is used, as shown in FIGS. 9A and 9B and Tables 3 and 4, the toner concentration sensor 23 increases as the toner concentration in the two-component developer 43 increases. Output (ATC output) decreases, the output of the image density sensor 73 (patch output) decreases as the density of the patch image increases. Therefore, toner replenishment may be performed when the output of the toner density sensor 23 (ATC output) is higher than the reference output or when the output of the image density sensor 73 (patch output) is higher than the reference output.

[0097]

[Table 3]

[0098]

[Table 4]

Next, in the color digital copying machine of this embodiment, the toner replenishment control and the toner exhaustion detection when black toner (achromatic toner) is used will be described with reference to FIGS.
And it demonstrates in detail using the flowchart of FIG.

First, similarly to the case of using the color toner (chromatic color toner), the printing rate of the original image is read by the counter 4 (S1), and it is determined whether the original image printing rate is low. Is determined (S2).

When it is determined in S2 that the print coverage is not low, the subroutine 1 shown in FIG. 5 is executed (S3).
It returns to the standby mode (S4). On the other hand, if it is determined in S2 that the printing rate is low, the toner density sensor 23 detects the toner density (S5), and then the CPU 6 determines whether the toner density detection signal (ATC output) is larger than the toner density reference signal. Whether or not it is determined based on the first comparison signal from the comparator 77 (S6). The above points are the same as in the case of using color toner.

Next, at S6, the toner concentration detection signal (AT
When it is determined that C output) is larger than the toner density reference signal, the image density sensor 73 detects the image density (S7), and then the CPU 6 outputs the image density detection signal (patch output) smaller than the image density reference signal. Whether or not it is determined based on the second comparison signal from the comparator 75 (S
108). When the image density detection signal (patch output) is smaller than the image density reference signal, the CPU 6 causes the toner feeding screw 62 to execute "intermittent toner replenishment" (S9), while the image density detection signal (patch output). )
Is smaller than the image density reference signal, the toner feeding screw 62 is caused to execute "continuous toner supply" (S10).

On the other hand, in S6, the toner concentration detection signal (AT
If it is determined that C output) is not larger than the toner density reference signal, the image density detection is performed by the image density sensor 73 (S11), and then the CPU 6 sends the image density detection signal (patch output) to the image density reference signal. Whether or not it is smaller is determined based on the second comparison signal from the comparator 75 (S112). When the image density detection signal (patch output) is smaller than the image density reference signal, the CPU 6 stops the toner feeding screw 62 to stop the toner supply (S13) and returns to the standby mode (S4). If the image density detection signal (patch output) is not smaller than the image density reference signal, the toner feeding screw 62 is caused to execute "intermittent toner supply" (S).
14).

S5 to 7.9 to 11 to 13 to 14 and 108
The 112 toner supply control is summarized as follows. (1) When ATC output> reference output and patch output> reference output, “continuous toner supply” is executed, and (2) when ATC output <reference output and patch output> reference voltage For (3) ATC output> reference output and patch output <reference output, (intermittent toner supply) is performed, and (4) ATC output <reference When the output and the patch output <the reference output, the process proceeds to S4 without supplying the toner, and returns to the standby mode (standby state).

The above "(1)" continuous toner supply "(S1)
0) and the "intermittent toner replenishment" of (2) above are executed, then the subroutine 2 (S1 shown in FIG. 6) is executed.
After replenishing the toner in 5), in the toner empty detection routine (S16 to 17, 19, 118, 120), the toner empty display, the subroutine 2 and the toner empty detection routine are re-executed according to the following conditions.
And whether to return to standby mode.

(5) If ATC output> reference output and patch output> reference output, toner hopper 60
The display device 5 is caused to perform a toner empty display indicating that the supply toner 63 held therein has run out (S2).
1).

(6) If ATC output <reference output and patch output> reference voltage, subroutine 2 (S
15) and empty detection routine (S16-17.
19 ・ 118 ・ 120) is re-executed.

(7) If ATC output> reference output and patch output <reference output, subroutine 2 (S
15) and empty detection routine (S16-17.
19 ・ 118 ・ 120) is re-executed.

(8) If ATC output <reference output and patch output <reference output, the process proceeds to S4 without toner supply and returns to the standby mode (standby state).

In the above cases (6) and (7), there is a high possibility that the toner hopper 60 is out of toner (toner empty) without the replenishment toner 63, compared to the case (8). . Therefore, in the cases of (6) and (7), the empty detection routine is re-executed to detect the toner empty more reliably.

Next, the toner empty detection routine will be described. In the toner empty detection routine, first, the CPU 6 determines whether the toner density detection signal (ATC output) is larger than the toner density reference signal.
The determination is made based on the first comparison signal from S7 (S1
6).

When it is determined in S16 that the toner density detection signal (ATC output) is larger than the toner density reference signal, the image density is detected by the image density sensor 73 (S17), and then the CPU 6 detects the image density detection signal. Whether or not (patch output) is smaller than the image density reference signal is determined based on the second comparison signal from the comparator 75 (S
118). Then, the CPU 6 executes S1 when the image density detection signal (patch output) is smaller than the image density reference signal.
On the other hand, when the image density detection signal (patch output) is not smaller than the image density reference signal while returning to step 5, it is determined that the toner is empty, and the toner empty display is displayed on the display device 5 (S21).

On the other hand, in S32, the toner density detection signal (A
If it is determined that the TC output) is not larger than the toner density reference signal, the image density sensor 73 detects the image density (S19), and then the CPU 6 sends the image density detection signal (patch output) to the image density reference signal. Whether or not it is smaller is determined based on the second comparison signal from the comparator 75 (S120). When the image density detection signal (patch output) is smaller than the image density reference signal, the CPU 6 determines that the toner amount is sufficient and returns to the standby mode (S4), while the image density detection signal (patch output). ) Is not smaller than the image density reference signal, the process returns to S15.

As described above, when the black toner is used, the toner replenishment control and the toner empty detection are performed by reversing the magnitude relationship between the patch density and the reference voltage as compared with the case where the color toner is used. As a result, the same effect as when the color toner is used can be obtained.

[Second Embodiment] The following will describe another embodiment of the present invention in reference to FIGS. 2, 5 to 7 and 11. For convenience of description, members having the same functions as the members shown in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

In the first embodiment, the toner consumption amount is predicted from the printing rate of the original image, whereas in the present embodiment, the toner consumption amount is detected from the driving state of the toner hopper. 1 and the basic operation is the same as that of the first embodiment.

That is, in the color digital copying machine of the present embodiment, as shown in FIG. 2, instead of the counter 4 in the color digital copying machine of the first embodiment, the toner feeding screw is changed from the energized state of the motor drive circuit 8. A drive state determination unit (replenishment operation detection unit) 9 that detects the replenishment operation of the replenishment toner 63 by detecting the drive state of 62 is provided. Then, in the present embodiment, the CPU 6
The toner consumption amount is detected based on the drive state of the toner conveying screw 62 detected by the drive state determination means 9, and the predicted toner consumption amount and the output of the toner density sensor 23 and the image density sensor are output. Based on this, the feeding of the replenishment toner 63 by the toner feeding screw 62 is controlled.

Next, in the color digital copying machine of the present embodiment, toner replenishment control and toner out detection when color toner (chromatic toner) is used will be described with reference to the flowcharts of FIGS.

In the toner replenishment control using the color toner and the toner exhaustion detection, first, the drive state determination means 9 detects the drive state of the toner carrying screw 62 (S6).
1) The CPU 6 determines whether the toner consumption amount is smaller than a preset reference amount based on the driving state of the toner conveying screw 62 (S62). This determination may be made based on whether the operation time of the toner transport screw 62 is longer than a predetermined time.

When it is determined in S2 that the toner consumption amount is larger than the preset reference amount, the subroutine 1 shown in FIG. 5 is executed (S63), and then the standby mode is restored (S64). On the other hand, if it is determined in S2 that the toner consumption amount is less than the preset reference amount, S65
Perform ~ 81. S65 to 81 are S5 to 21 of FIG.
Is the same as The contents of the subroutine 2 of S75 are as shown in FIG. 6, and are the same as the contents of the subroutine 2 of S15 of FIG.

Next, in the color digital copying machine of this embodiment, the toner replenishment control and the toner exhaustion detection when black toner (achromatic toner) is used will be described with reference to FIGS.
And it demonstrates using the flowchart of FIG.

First, as in the case of using color toner, the driving state determining means 9 causes the toner carrying screw 62 to be used.
Is detected (S61), and the CPU 6 determines whether the toner consumption amount is less than a preset reference amount based on the driving state of the toner carrying screw 62 (S6).
2).

When it is determined in S2 that the toner consumption amount is larger than the preset reference amount, the subroutine 1 shown in FIG. 5 is executed (S63), and then the standby mode is restored (S64).

On the other hand, if it is determined in S2 that the toner consumption amount is less than the preset reference amount, S65-
67.69-71.73-77.79.81.168.
172/178/180 is executed. S65-67.6
9 ~ 71 ・ 73 ~ 77 ・ 79 ・ 81 ・ 168 ・ 172 ・
178 and 180 are S5 to 7.9 to 11 and 13 in FIG.
~ 17, 19, 21, 108, 112, 118, 120
Is the same as The contents of the subroutine 2 of S75 are as shown in FIG. 6, and are the same as the contents of the subroutine 2 of S15 of FIG.

In the present embodiment, as described above, the toner replenishment control and the toner exhaustion detection are performed based on the toner consumption amount detected from the driving state of the toner conveying screw 62. Thereby, the same effect as that of the first embodiment can be obtained.

[Third Embodiment] The following will describe still another embodiment of the present invention in reference to FIG. For convenience of description, members having the same functions as the members shown in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

In the first and second embodiments, the transfer drum 4
Although the indirect method electrophotographic color digital copying machine using No. 7 has been described, the image forming apparatus of the present embodiment is, as shown in FIG. 3, a direct method electrophotographic color digital copying machine using no transfer member. It is an opportunity.

That is, in the color digital copying machine of the present embodiment, the transfer drum 47 in the color digital copying machine of the first embodiment is omitted, and instead of the image density sensor 73,
An electric potential sensor (image density detecting means) 27 for detecting the density of the patch image by detecting the electric potential of the patch image formed on the photosensitive drum 40 is provided, and the basic operation is the first embodiment. Is the same as

In the toner replenishment control and the toner exhaustion detection of this embodiment, the output of the potential sensor 27 is used instead of the output of the image density sensor 73 in the generation of the second comparison signal in the comparator 75. The other points are the same as those in the first embodiment. With the toner replenishment control and the toner exhaustion detection, it is possible to obtain the same effect as that of the first embodiment.

The image forming apparatus of the present invention is not limited to the color digital copying machine of each of the above-mentioned embodiments, and an electrophotographic method or an electrostatic image may be formed on an image carrier such as a photoconductor or a dielectric. An electrostatic latent image is formed in accordance with the input image information by a recording method or the like, and this electrostatic latent image is developed by a developing means using a two-component developer composed of a non-magnetic toner and a carrier, and a toner image ( Any image forming apparatus having a configuration for forming a visible image) can be applied. Therefore, the image forming apparatus of the present invention can be used in copiers other than color digital copiers,
It is also applicable to printers, facsimile machines and the like.

[0131]

As described above, in the image forming apparatus according to the first aspect of the present invention, the toner concentration detecting means for detecting the toner concentration in the two-component developer in the developing means and the surface of the image carrier are formed. An image density detection unit that detects the image density of the formed reference toner image, a printing rate calculation unit that obtains an image printing ratio from input image information, and a toner consumption amount that is detected based on the calculation result of the printing ratio calculation unit. the consumption of the sensed toner, based on the detection result of the detection result and the image density detecting means of the toner concentration detection means, and a toner replenishment control means for controlling the supply of toner by the toner replenishing means, the toner The replenishment control means is the toner concentration detection means.
Based on both the detection result and the detection result of the image density detection means.
Toner replenishment control based on
Toner replenishment control is performed only based on the detection results of the detection means.
Whether the toner consumption is detected or not.
The toner replenishment control method is changed according to the above.

According to the above-mentioned structure, the toner consumption amount is detected based on the image printing rate, and the toner replenishment control is performed depending on whether or not precise toner replenishment control is necessary based on the detected toner consumption amount. The method can be changed.

When precise toner replenishment control is required, a high-quality image can be stably obtained based on both the detection result of the toner density detecting means and the detection result of the image density detecting means. On the other hand, when precise toner replenishment control is not required, the formation of the reference toner image can be omitted by using only the detection result of the toner concentration detection means, and the image forming operation can be speeded up and running. The cost can be suppressed.

Therefore, the above-described structure has an effect that a high-quality image can be stably obtained, and an image forming apparatus having an excellent operating speed and a low running cost can be provided.

The image forming apparatus according to claim 2 of the present invention is
As described above, the toner density detecting means for detecting the toner density in the two-component developer in the developing means, the image density detecting means for detecting the image density of the reference toner image formed on the surface of the image carrier, and the toner A toner replenishment operation detection unit that detects the operation state of the replenishment unit, and the toner consumption amount is detected based on the detection result of the toner replenishment operation detection unit, and the detected toner consumption amount and the detection result of the toner concentration detection unit and image based on the density sensing means detection result includes a toner replenishment control means for controlling the supply of toner by the toner replenishing means, the toner supply control unit, a toner concentration detecting hands
Both the step detection result and the image density detection means detection result
Toner replenishment control based on the
Toner replenishment control based only on the detection result of the density detection means
To determine whether to perform
By doing so, the toner replenishment control method is changed .

According to the above arrangement, the toner consumption is detected based on the operating state of the toner replenishing means, and the toner replenishment is determined based on whether or not precise toner replenishment control is necessary based on the detected toner consumption. The control method can be changed.

When precise toner replenishment control is required, a high-quality image can be stably obtained based on both the detection result of the toner density detecting means and the detection result of the image density detecting means. On the other hand, when precise toner replenishment control is not required, the formation of the reference toner image can be omitted by using only the detection result of the toner concentration detection means, and the image forming operation can be speeded up and running. The cost can be suppressed.

Therefore, the above-described structure has an effect that a high-quality image can be stably obtained, and an image forming apparatus having an excellent operating speed and a low running cost can be provided.

The image forming apparatus according to claim 3 of the present invention is
As described above, when the detected toner consumption amount is less than the preset reference amount, the toner replenishment control unit is based on both the detection result of the toner density detection unit and the detection result of the image density detection unit. While controlling the toner replenishment by the toner replenishing means, when the detected toner consumption amount is larger than the reference amount, the toner replenishing means controls the toner replenishment based on only the detection result of the toner concentration detecting means. .

According to the above construction, when the toner consumption amount is smaller than the reference amount, a high quality image is stably obtained based on both the detection result of the toner density detecting means and the detection result of the image density detecting means. On the other hand, when the toner consumption amount is larger than the reference amount, it is possible to omit the formation of the reference toner image by using only the detection result of the toner concentration detection means, and it is possible to speed up the image forming operation. The running cost can be suppressed.

Therefore, the above-described structure has an effect that a high-quality image can be stably obtained, and an image forming apparatus having an excellent operating speed and a low running cost can be provided.

The image forming apparatus according to claim 4 of the present invention is
As described above, the toner replenishing means conveys the replenishment toner held in the toner tank to the developing means, and the detected toner consumption amount, the detection result of the toner concentration detecting means, and the image density detection The toner amount detecting means for detecting the amount of the replenishment toner held in the toner tank based on the detection result of the means is further provided.

According to the above arrangement, the toner consumption amount is detected based on the operating state of the toner replenishing means, and it is determined whether or not it is necessary to accurately detect the amount of toner to be replenished from the detected toner consumption amount. It is possible to change the method for detecting the amount of replenishment toner to be held.

When it is judged from the toner consumption amount that the accurate holding amount of the replenishment toner is required to be detected, based on the detection result of the toner density detecting means and the detection result of the image density detecting means. By detecting the amount of replenishment toner to be retained, it becomes possible to accurately determine whether toner replenishment is necessary and replenish toner at an appropriate timing.
Therefore, it is possible to surely prevent the image density from being lowered due to the toner exhaustion, and it is possible to obtain a high quality image.

On the other hand, when it is judged from the toner consumption that it is not necessary to accurately detect the holding amount of the replenishment toner, it is necessary to form the reference toner image by using only the detection result of the toner density detecting means. Disappears. Therefore, it is possible to suppress a decrease in the operating speed of the image forming apparatus, prevent unnecessary toner consumption for forming the reference toner image,
There is also an effect that the running cost can be suppressed.

The image forming apparatus according to claim 5 of the present invention is
In order to solve the above-mentioned problems, in the image forming apparatus according to claim 4, the toner amount detecting means detects the toner concentration detecting means when the detected toner consumption amount is smaller than a preset reference amount. While the amount of replenishment toner is detected based on both the result and the detection result of the image density detection unit, when the detected toner consumption amount is larger than the reference amount, replenishment is performed based on only the detection result of the toner concentration detection unit. The feature is that the amount of toner for use is detected.

According to the above construction, when the toner consumption amount is smaller than the reference amount, the amount of replenishment toner is detected based on the detection result of the toner density detecting means and the detection result of the image density detecting means. Therefore, it becomes possible to replenish the toner at an appropriate timing, and it is possible to surely prevent the decrease in the image density due to the toner exhaustion. Therefore, an effect of obtaining a high quality image can be obtained.

Further, according to the above construction, when the toner consumption amount is larger than the reference amount, only the detection result of the toner density detecting means is used, so that it is not necessary to form the reference toner image. Therefore, it is possible to obtain an effect that the image forming operation can be speeded up, useless toner consumption for forming the reference toner image can be prevented, and running cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a schematic view showing another embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a schematic view showing still another embodiment of the image forming apparatus according to the present invention.

FIG. 4 is a flowchart showing a flow of toner replenishment control and toner depletion detection when color toner is used in the image forming apparatus shown in FIG.

5 is a flowchart showing the contents of subroutine 1 in FIG.

FIG. 6 is a flowchart showing the contents of subroutine 2 in FIG.

FIG. 7 is a flowchart showing a flow of toner replenishment control and toner depletion detection when color toner is used in the image forming apparatus shown in FIG.

FIG. 8 is a graph showing the relationship between ATC output and patch output and toner density and image density when color toner is used, FIG. 8A is a graph showing the relationship between ATC output and toner density, and FIG. Is a graph showing the relationship between patch output and image density.

9A and 9B are graphs showing the relationship between ATC output and patch output and toner density and image density when black toner is used, FIG. 9A is a graph showing the relationship between ATC output and toner density, and FIG. Is a graph showing the relationship between patch output and image density.

10 is a flowchart showing a flow of toner replenishment control and toner depletion detection when black toner is used in the image forming apparatus shown in FIG.

11 is a flowchart showing a flow of toner replenishment control and toner depletion detection when black toner is used in the image forming apparatus shown in FIG.

[Explanation of symbols]

1 CCD 2 amplifier 3 A / D converter 4 counter (printing ratio calculation means) 5 display device 6 CPU (toner supply control means, toner amount detection means) 7 memory 8 motor drive circuit 9 drive state determination means 10 exposure device (latent device) Image forming means) 21 Original document 23 Toner density sensor (toner density detecting means) 27 Potential sensor (image density detecting means) 28 Toner supply motor 40 Photoreceptor drum (image carrier) 43 Two-component developer 44 Developing device (developing means) 44a Developing roller 47 Transfer drum 60 Toner hopper (toner tank) 62 Toner conveying screw 63 Replenishment toner 72 Patch image signal source 73 Image density sensor (image density detecting means) 75 Comparator 76 Reference voltage signal source 77 Comparator 78 Reference voltage signal source

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-320285 (JP, A) JP-A-3-41488 (JP, A) JP-A-2-50183 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/08 112 G03G 15/08 114 G03G 15/08 115 G03G 15/00 303

Claims (5)

(57) [Claims] 1. An image carrier capable of holding an electrostatic latent image on its surface, a latent image forming means for forming an electrostatic latent image according to input image information on the surface of the image carrier, and the static image forming means. An image forming apparatus comprising: a developing unit that develops an electrostatic latent image with a two-component developer including a toner and a carrier to form a toner image; and a toner replenishing unit that replenishes the developing unit with toner. Toner density detecting means for detecting the toner density in the component developer, image density detecting means for detecting the image density of the reference toner image formed on the surface of the image carrier, and obtaining the image print rate from the input image information The toner consumption amount is detected based on the print ratio calculation means and the calculation result of the print ratio calculation means, and the detected toner consumption amount and the detection result of the toner density detection means and the image density detection means are detected. Based Te, and a toner replenishment control means for controlling the supply of toner by the toner replenishing means, the toner supply control hand
The step indicates the detection result of the toner density detection means and the image density detection.
Toner replenishment control is performed based on both detection results of the knowledge means.
Or only the detection result of the toner concentration detection means
Based on whether the toner replenishment control is performed based on the detected toner
By deciding based on the amount of consumption,
An image forming apparatus characterized by changing a control method . 2. An image bearing member capable of holding an electrostatic latent image on its surface, a latent image forming means for forming an electrostatic latent image according to input image information on the surface of the image bearing member, and said static image. An image forming apparatus comprising: a developing unit that develops an electrostatic latent image with a two-component developer including a toner and a carrier to form a toner image; and a toner replenishing unit that replenishes the developing unit with toner. Toner density detecting means for detecting the toner density in the component developer, image density detecting means for detecting the image density of the reference toner image formed on the surface of the image carrier, and toner for detecting the operating state of the toner replenishing means The toner consumption amount is detected based on the detection result of the replenishment operation detection means and the toner replenishment operation detection means, and the detected toner consumption amount, the detection result of the toner density detection means and the detection of the image density detection means Toner replenishment control means for controlling replenishment of toner by the toner replenishment means based on the result is provided .
The means is the detection result of the toner density detecting means and the image density.
Toner replenishment control based on both detection results of the detection means
Or only the detection result of the toner concentration detection means
Toner replenishment control based on
-Toner replenishment by deciding based on consumption
An image forming apparatus characterized by changing a control method . 3. The toner replenishment control means, based on both the detection result of the toner density detection means and the detection result of the image density detection means when the detected toner consumption amount is smaller than a preset reference amount. While controlling the toner replenishment by the toner replenishing means, when the detected toner consumption amount is larger than the reference amount, the toner replenishing means controls the toner replenishment based on only the detection result of the toner concentration detecting means. The image forming apparatus according to claim 1 or 2. 4. The toner replenishing means conveys the replenishment toner held in the toner tank to the developing means, and the detected toner consumption amount, the detection result of the toner density detecting means, and the image density detection. Based on the detection result of the means,
4. The image forming apparatus according to claim 1, further comprising toner amount detection means for detecting the amount of replenishment toner held in the toner tank. 5. The toner amount detecting means, based on both the detection result of the toner density detecting means and the detection result of the image density detecting means when the detected toner consumption amount is smaller than a preset reference amount. The amount of replenishment toner is detected, and when the detected amount of consumed toner is larger than a reference amount, the amount of replenishment toner is detected only based on the detection result of the toner concentration detection means. 4. The image forming apparatus according to item 4.