JPH1039608A - Picture image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-grade color image, in which the concentration of the image is constant from the begining of the image formation, by detecting the concentration of a reference image in order to obtain the quantity of the supply of the toner and feeding back this result to other controllers, thereby maintaining the concentration of the toner at a constant value. SOLUTION: A patch image as a reference image for detecting the concentration is formed on a photo sensitive material drum 40. The light is irradiated from a light emitting part 73a of an LED of a concentration sensor 73, and the reflected light received by a light receiving part 73b made up of a photoelectric transfer element or the like in order to detect the actual concentration of the patch image. The output signal thus detected is supplied to an input port on one side of a comparator 75 and compared with the standard signal, which comes from a standard voltage signal source 76, which corresponds to the standard concentration of the patch image, and which is supplied to the other side of the comparator 75, in order to obtain the difference between the two and to supply the output signal on the difference of the concentration to the CPU 67. The output signal on the difference of the concentration is used for the control of the supply of the toner to a developer 43 within a developing machine 44, which is conducted by both a developer reflecting ATR and a video-count ATR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer of an electrophotographic system or an electrostatic recording system, and more particularly to a toner density or image of a developer through a toner supply control of a two-component developer. The present invention relates to an image forming apparatus including a density control device for controlling a density.

[0002]

2. Description of the Related Art Generally, a developing device included in an electrophotographic or electrostatic recording type image forming apparatus includes a one-component developer containing a magnetic toner as a main component, or a non-magnetic toner and a magnetostatic carrier as a main component. Is used. In particular, in an image forming apparatus that forms a full-color or multi-color image by an electrophotographic method, most developing devices use a two-component developer from the viewpoint of the color of the image.

As is well known, the toner concentration (the ratio of the weight of the toner to the total weight of the carrier and the toner) of the two-component developer is a very important factor in stabilizing image quality. The developer toner is consumed during development, and the toner concentration of the developer decreases. Therefore, the developer density or the image density is detected at appropriate times using a development density control device or an image density control device, and the toner is replenished in accordance with the detected change. It is necessary to maintain the image quality.

FIG. 8 shows an example of the overall configuration of an image forming apparatus provided with a conventional density controller, in this embodiment, an electrophotographic digital copying machine.

[0005] First, an image of a document 21 is read by a CCD 1, and an obtained analog image signal is amplified to a predetermined level by an amplifier 2, and an analog-to-digital converter (A / D)
A converter 3 converts the digital image signal into a digital image signal of, for example, 8 bits (0 to 255 gradations). Next, this digital image signal is supplied to a γ converter 5 (a converter composed of a 256-byte RAM and performing a density conversion by a look-up table method in this example). The data is input to a converter (D / A converter) 9.

[0006] The digital image signal is again converted into an analog image signal by the converter 9 and supplied to one input of a comparator 11. The other input of the comparator 11 is supplied with a triangular wave signal of a predetermined cycle generated from the triangular wave generating circuit 10. The analog image signal supplied to one input of the comparator 11 is compared with the triangular wave signal. Pulse width modulation. The pulse-modulated binary image signal is directly input to the laser drive circuit 12 and used as an on / off control signal for emission of the laser diode 13. The laser beam emitted from the laser diode 13 is scanned in the main scanning direction by a well-known polygon mirror 14, passes through an f / θ lens 15, and a reflection mirror 16, and rotates as indicated by an arrow. Irradiation is performed on the drum 40 to form an electrostatic latent image.

On the other hand, the photosensitive drum 40 is uniformly discharged by the exposure device 18 and is uniformly charged, for example, negatively by the primary charger 19. Thereafter, an electrostatic latent image corresponding to the image signal is formed by receiving the above-described laser light irradiation. This electrostatic latent image is developed into a visible image (toner image) by the developing device 20. A toner replenishing tank 8 containing a replenishing toner 29 is attached to an upper portion of the developing device 20.
A toner conveying screw 30 that conveys the toner 29 by being rotationally driven by the motor 28 and supplies the toner 29 to the inside of the developing device 20 is installed in a lower part of the inside.

The toner image formed on the photosensitive drum 40 is transferred by the transfer charger 22 onto the transfer material P conveyed to the photosensitive drum 40 by the transfer material carrying belt 17. The transfer material carrying belt 17 has two rollers 25.
The transfer material P, which is stretched between a and 25b and is driven in the direction of the drawing arrow, is conveyed to the photosensitive drum 40 held thereon. The transfer residual toner remaining on the photosensitive drum 40 is thereafter scraped off by the cleaner 24.

For simplicity of explanation, only a single image forming station (including a photosensitive drum 40, an exposing unit 18, a primary charging unit 19, a developing unit 20, etc.) is shown, but a color image forming apparatus is shown. In the case of (1), for example, image forming stations for cyan, magenta, yellow, and black are sequentially arranged on the transfer material carrying belt 17 along the moving direction.

The image forming apparatus controls the supply of toner to the developer 21 in the developing device 20 in which the toner density is reduced by the above-described development, so as to control the toner density of the developer or the image density to be constant. , Various types of concentration control devices (AT
R) is installed.

More specifically, a method of detecting and controlling the toner density of the developer 21 in the developing device 20 by the amount of reflected light by a toner density sensor 23 provided in the developing device 20 (developer reflection ATR), A method in which a patch image 26 is formed on the body drum 40 for reference, and the image density is detected and controlled by a sensor 23 such as a potential sensor installed opposite to the photosensitive drum 40 (patch detection ATR); There is a method (video count ATR) of calculating and controlling a necessary toner amount from an output level of a digital image signal for each pixel from the camera.

In each case, the CPU 6 controls the rotation of the motor 28 via the motor drive circuit 7 based on the information obtained by each method, thereby controlling the supply of toner to the developer 21 in the developing container 20. And the toner density of the developer or the density of the image is kept constant.

[0013]

However, the conventional concentration control device has the following problems.

In the developer reflection ATR, since the toner concentration of the developer 21 in the developing device 20 is directly detected, the toner concentration of the developer 21 can be kept constant. However, the triboelectric charge amount (tribo) of the toner changes due to the deterioration of the magnetic carrier in the developer and the fluctuation of the environment, and the developability changes. For this reason, even if the toner concentration of the developer 21 can be maintained constant, if there is a change in the quality of the carrier or a change in the environment,
There is a disadvantage that the image density changes.

In the video count ATR, the density information of the original image is converted into a video count number, the toner consumption is predicted from this value, the toner density is initialized, and the toner supply of the consumption system is performed in order to supply the toner. When the amount fluctuates, there is a disadvantage that the toner density deviates from the initial set value by the amount of the fluctuation.

Further, in the patch detection ATR, since the density of the patch image 26 on the photosensitive drum 40 is detected, the image density can be kept constant. When a low patch image density is obtained due to a decrease in the toner density, the ATR determines this and continues the toner replenishment state, so that the toner is filled in the developing device 20 and the developer overflows or fogs. In addition, a high patch image density is obtained due to an increase in developability due to a change in the triboelectric charge amount of the toner, and when this is determined by the ATR,
Since the toner supply stop state is continued, the amount of toner in the developing device 20 is reduced, so that the amount of the developer coating on the developing sleeve is reduced, and there is a serious disadvantage that image deterioration is caused.

Accordingly, an object of the present invention is to maintain a constant toner concentration of a developer even when a change in toner developability due to an environmental change or a change in toner consumption of a toner consuming system occurs. An object of the present invention is to provide an image forming apparatus capable of obtaining a high-quality color image having a constant image density from the beginning.

[0018]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image carrier, a latent image forming means for digitally forming an electrostatic latent image corresponding to each color component of an image on the image carrier, and an electrostatic latent image formed on the image carrier. Developing an image using a two-component developer to form a toner image, a toner replenishing unit for replenishing toner to the developing unit, and a toner replenishing control for the developing unit provided for the developing unit. In an image forming apparatus including two or more density control devices for controlling a toner density of a developer or an image density of a toner image, at least a reference image for density detection is formed on an image carrier as the density control device. A control device for determining the toner supply amount by detecting the reference image density;
The image forming apparatus is characterized in that another control device for actually performing toner control based on the toner supply amount calculated by the control device is provided for the developing means.

[0019]

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

In the following description, a plurality of latent image forming means for forming an electrostatic latent image on a plurality of image carriers in a digital manner correspond to the electrostatic latent images formed on the image carrier. The image forming apparatus is provided with a plurality of developing means for developing using a two-component developer of a color and a plurality of toner replenishing means for replenishing toner to the developing means. It goes without saying that the present invention is equally applicable to a system in which one developing unit is opposed to a system in which a plurality of developing units are opposed to one image carrier.

(Embodiment 1) First, an overall configuration of an embodiment of an image forming apparatus according to the present invention will be described with reference to FIG. In this embodiment, a case where the present invention is applied to an electrophotographic digital copying machine will be described. However, it goes without saying that the present invention can be equally applied to various other image forming apparatuses of the electrophotographic type and the electrostatic recording type.

In FIG. 1, an image of a document 31 to be copied is projected by a lens 32 onto an image sensor 33 such as a CCD. The image sensor 33 decomposes an original image into a number of pixels and generates a photoelectric conversion signal corresponding to the density of each pixel. The analog image signal output from the image sensor 33 is sent to an image signal processing circuit 34, where the analog image signal is converted into a pixel image signal having an output level corresponding to the density of the pixel. Sent.

The pulse width modulation circuit 35 has a width (time width) corresponding to the level of each input pixel image signal.
Is formed and output. That is, as shown in FIG. 3A, a wider drive pulse W is applied to a high-density pixel signal, and an intermediate-width drive pulse I is applied to a low-density pixel image signal. Form.

The laser drive pulse output from the pulse width modulation circuit 35 is supplied to the semiconductor laser 36 and causes the semiconductor laser 36 to emit light for a time corresponding to the pulse width. Therefore, the semiconductor laser 36 is driven for a longer period of time for the high-density pixels, and is driven for a shorter period of time for the low-density pixels. Therefore, the photosensitive drum 40
With the optical system described below, a longer range is exposed in the main scanning direction for high density pixels, and a shorter range is exposed in the main scanning direction for low density pixels. That is, the dot size of the electrostatic latent increase differs according to the pixel density. Therefore, it is needless to say that the toner consumption corresponding to the high density pixel is larger than that of the low density pixel. In FIG. 3D, the electrostatic latent images of the low, medium and high density pixels are indicated by L, M and H, respectively.

The laser light 36a emitted from the semiconductor laser 36 is swept by a rotary polygon mirror 37, and a lens 38 such as an f / θ lens and a fixed mirror for directing the laser light 36a toward the photosensitive drum 40 as an image carrier. With 39, the photosensitive drum 40 is scanned in a direction substantially parallel to the rotation axis (main scanning direction), and an electrostatic latent image is formed.

The photoreceptor drum 40 is an electrophotographic photoreceptor drum having a photoreceptor such as amorphous silicon, selenium, or OPC on its surface and rotating in the direction of the arrow. It is uniformly charged by the charger 42. Thereafter, exposure scanning is performed with laser light modulated in accordance with the above-described pixel information signal, whereby an electrostatic latent image corresponding to the image information signal is formed. This electrostatic latent image is reversely developed by a developing device 44 using a two-component developer 43 in which toner and carrier are mixed, and is visualized as a toner image. Here, the reversal development means that the photosensitive drum 4
This is a developing method in which a toner charged to the same polarity as the latent image is attached to an area exposed to light 0, and this is visualized.

This toner image is transferred by the transfer charger 49 onto the transfer material P conveyed to the photosensitive drum by the transfer material carrying belt 47. The transfer material carrying belt 47 is stretched between the two rollers 45a and 45b, and is driven endlessly in the direction of the arrow in the figure to hold the transfer material held thereon.
P is conveyed to the photosensitive drum 40. The transfer material P to which the toner image has been transferred is separated from the transfer material carrying belt 47, conveyed to a fixing device (not shown), and fixed to a permanent image. Further, the residual toner remaining on the photosensitive drum 40 after the transfer is removed by the cleaner 50 thereafter.

Although only a single image forming station (including a photosensitive drum 40, an exposing unit 41, a primary charging unit 42, a developing unit 44, and the like) is shown in FIG. For example, a color image forming apparatus including image forming stations for cyan, magenta, yellow, and black, and the image forming stations are sequentially arranged on the transfer material carrying belt 47 along the moving direction, and each color is formed. An electrostatic latent image for each color (after each color component of the image) obtained by decomposing the image of the original is sequentially formed on the photosensitive drum of the image forming station, and is developed by a developing device having a toner of a corresponding color, and the transfer material is developed. Carry belt 4
The transfer material P is sequentially superimposed and transferred onto the transfer material P conveyed by.

FIG. 2 shows an example of the developing unit 44. As shown in the figure, the developing device 4 is arranged to face the photosensitive drum 40, and the inside thereof is a partition wall 51 extending in the vertical direction.
Thus, the first chamber (developing chamber) 52 and the second chamber (stirring chamber) 5
It is divided into three. A non-magnetic developing sleeve 54 that rotates in the direction of the arrow is disposed in the first chamber 52, and a magnet 55 is fixedly disposed in the developing sleeve 54.

As shown in FIG. 1, a toner replenishing tank 60 containing a replenishing toner 63 is mounted on the upper part of the developing unit 44, and a toner conveying screw 62 is installed in the lower part of the toner replenishing tank 60. Have been. A motor 70 connected via a gear train 71 allows the toner conveying screw 62
Is rotated, so that the toner 63 in the replenishing tank 60 is rotated.
Is transported and supplied into the developing device 44. The supply of toner by the transport screw 62 is controlled by controlling the rotation of a motor 70 by a CPU 67 via a motor drive circuit 67. Control data and the like supplied to the motor drive circuit 69 are stored in a RAM 68 connected to the CPU 67.

The first chamber 52 and the second chamber 53 are provided with developer stirring screws 58 and 59, respectively. The screw 58 stirs and conveys the developer in the first chamber 52, and the screw 59 and the toner 63 supplied by the rotation of the conveyance screw 62 from the toner supply tank 60 in FIG. 1 are already in the developing device 44. The developer 43 is agitated and conveyed to make the toner concentration of the developer 43 uniform. A developer passage (not shown) for connecting the first chamber 52 and the second chamber 53 to each other is formed in the partition 51 at the front and rear ends in FIG.
Due to the conveying force of 59, the developer in the first chamber 52 whose toner concentration has been reduced due to the toner consumption due to the development moves from one of the passages to the second chamber 53, and the toner concentration in the second chamber 53 recovers. The developer is configured to move from the other passage into the first chamber 52.

The two-component developer 43 in the developing device 44 is carried on the developing sleeve 54 by the magnetic force of the magnet 55, and the thickness of the layer is regulated by the blade 56. Is transported to the developing area opposite to. Then, in the development area, the developer 43 is used for developing the latent image on the photosensitive drum 40. A power supply 57 applies a developing bias voltage obtained by superimposing a DC voltage on an AC voltage from a power source 57 in order to improve the development efficiency, that is, the toner application rate to the latent image.

Since the toner density of the developer 43 in the developing device 44 decreases due to the development of the electrostatic latent image, the density controller controls the toner supply tank 60 to supply the toner 63 from the toner replenishing tank 60 to the developing device 44. The toner density of the agent 43 is controlled to be constant, or the image density is controlled to be constant.

In the image forming apparatus according to the present invention, as a density control device, a patch image is formed on the photosensitive drum 40 for reference, and the image density is set to a light emitting section 73a and a light receiving section which are installed opposite to the photosensitive drum 40. A method of detecting and controlling with a density sensor 73 having a sensor 73b (patch detection ATR), the developing device 4
A method of detecting and controlling the toner density of the developer 43 in the developing device 44 by a density sensor 77 having a light emitting part 77a and a light receiving part 77b installed in the developer 4 (developer reflection ATR)
And a method (video count ATR) of calculating and controlling a necessary toner amount from an output level of a digital image signal for each pixel from the video counter 66.

In the present invention, the output signal of the toner supply control by the patch detection ATR, which is the first density control device, is output to the second,
One feature is the use of a third toner supply control device, a developer reflection ATR and a video count ATR. Hereinafter, this will be described in detail with reference to the flowcharts of FIGS.

First, the patch detection ATR is operated at a predetermined timing to form a patch image on the photosensitive drum 40 as a reference image for density detection. That is, as shown in FIG. 1, a patch image signal generating circuit 72 for generating a patch image signal having a signal level corresponding to a predetermined density is provided, and the patch image signal from this generating circuit 72 is supplied to the pulse width modulation circuit 35. And generates a laser drive pulse having a pulse width for the predetermined concentration. The laser drive pulse is supplied to the semiconductor laser 36, the laser 36 emits light for a time corresponding to the pulse width, and the photosensitive drum 40 is scanned. At this time, the counter 66 is not operated. As a result, a patch electrostatic latent image having a predetermined density is formed on the photosensitive drum 40, and the patch electrostatic latent image is developed by the developing device 44.

Next, the patch image (toner image) obtained in this manner is attached to the LED of the density sensor 73 of the patch detection ATR.
Light is emitted from a light emitting unit 73a, and the reflected light is received by a light receiving unit 73b such as a photoelectric conversion element, and the actual patch density of the patch image is detected. The detected patch density corresponds to the actual image density of the developer 43 in the developing device 44.

An output signal from the light receiving section 73b which detects the actual patch image density is supplied to one input of a comparator 75. The other input of the comparator 75 receives a specified density (initial density) of the patch image from the reference voltage signal source 76.
Is input. The comparator 75 compares the patch image density with the initial image density to determine the density difference, and supplies an output signal of the density difference to the CPU 67. The output signal of the density difference is used for toner supply control to the developer 43 in the developing device 44 by the developer reflection ATR and the video count ATR.

The image forming apparatus of the present invention includes image forming stations for four colors, for example, yellow, magenta, cyan, and black. The density difference between the actual density of the patch image of each color and the initial density is obtained, and an output signal of the density difference is supplied to the CPU 67.

In the present invention, the toner replenishment control by the developer reflection ATR and the video count ATR is performed separately for the chromatic developer (color developer) and the achromatic black developer.

That is, the yellow, magenta, and cyan color developers can detect a change in color by the amount of reflected light.
It is possible to maintain the developer density at a certain level by using the developer reflection ATR by the density sensor 77 installed in the developing device 44. However, when the amount of frictional charge of the toner changes due to a change in the temperature and humidity of the environment, the image density fluctuation due to the change in the amount of toner charge cannot be followed.

Therefore, for the color developer, the developer reflection ATR
Is controlled by the CPU 67 at this time.
Calculates the amount of toner excess or deficiency (toner replenishment amount) of the color developer required to return the above-described patch image density to the initial density, and converts the toner replenishment amount as a toner correction amount to a signal level corresponding thereto. To each developing unit 44. This will be specifically described with reference to FIG. FIG. 5 shows a patch detection signal for a patch image density using the developer density as a parameter. That is, the signal level (SgnlInit) for a predetermined patch image density (here, 0.5) is stored in the CPU 67, and is compared with an output signal (Sgnl) that actually detects the patch image density. Is calculated to calculate the amount of toner required to return to the initial density.

Required toner amount = (SgnlInit−Sgnl) / (Signal level difference Δ of developer 1%) * (Toner amount for developer 1%) −

Thereafter, the toner replenishment amount calculated above is used as a toner correction amount, and the corresponding signal level (hereinafter referred to as X)
To obtain the feedback amount.

Next, correction is performed using a coefficient (hereinafter referred to as a developer characteristic coefficient α) corresponding to the development characteristic, which is one of the features of the present invention. In this embodiment, the developing characteristic coefficient α is changed according to the developing contrast potential (Vcont) of the two-component developing toner (yellow, magenta, cyan, and black). Feedback to each replenishment control device.

Specifically, the change was made based on the development contrast potential determined for each color during image formation.

FIG. 6 shows how the image density changes with Vcont using the color difference of the developer as a parameter.

Here, a method of changing the development characteristic coefficient will be described. Specifically, the characteristic coefficient of the developer black shown in FIG. 6 was set to α (K) = 1, and α was changed by the following equation.

Α (color) = Vcont (color) / Vcont (K)

In the first embodiment, the maximum density (Dmax) of each color
Development contrast potential that can guarantee 1.6 is yellow 2
50V, magenta 300V, cyan 350V, black 4
00V, α (Y) = 0.625, α
(M) = 0.75, α (C) = 0.875, and α (K) = 1. The toner replenishment signal level is multiplied by the obtained development characteristic coefficient α, a correction signal (α · X) is calculated, and the signal level with respect to the target density of the developer reflection ATR as the toner replenishment control device is calculated using the following equation. (Hereinafter referred to as Target (n)) is added and subtracted to provide feedback.

Target (n + 1) = Target
t (n) + α · X

The actual replenishment was calculated from the difference from the developer concentration signal level (ATR Sgnl) when the agent reflection ATR was performed next (the following formula), and toner replenishment was performed.

Toner supply amount = 量 (Target (n +
1) ー ATR Sgnl)

For a carbon black-based developer,
Since it is impossible to apply the developer reflection ATR, in the present invention, the video counter 66 integrates the required toner amount from the output level of the digital image signal for each pixel, and controls the toner supply by the video count ATR. At this time, the CPU 67 calculates the toner excess / deficiency (toner replenishment amount) of the black developer necessary for returning the patch image density to the initial image density from the output signal of the density difference of the patch image (black), The toner replenishment amount is used as a correction toner amount, and a signal level (hereinafter, referred to as Y) corresponding thereto
And feeds it back to the counter 66.

At this time, the signal (α · Y) of the toner correction amount corrected by using the developer characteristic coefficient α (K) of the black developer obtained above is used as a video count ATR using the following equation.
Is corrected by adding and subtracting a signal of a corrected toner amount to a signal of a video count value (hereinafter referred to as vcnt) obtained by integrating a required toner amount in the control by the control by the video count ATR method. Vcnt).

Vcnt = vcnt + α (K) · Y

As described above, according to the present invention, when performing the toner supply control of the two-component developer of yellow, magenta, cyan, and black, the toner supply amount in the toner supply control by the respective patch detection ATRs is obtained. , Magenta, and cyan developer, the toner replenishment amount is calculated as a feedback amount in accordance with the development characteristics, the correction toner amount is calculated by the developer characteristic coefficient α, and the toner replenishment control by the developer reflection ATR is corrected. For the developer, the toner replenishment control by the video count ATR is corrected based on the corrected toner amount, so the feedback amount can be changed following the change (γ) in the development characteristics due to the development contrast potential during image formation. Became.
As a result, it is possible to alleviate sudden toner replenishment and stoppage in a state where the development characteristics are suddenly changed, and to form a high-quality color image with appropriately controlled image density.

(Embodiment 2) In this embodiment, when the toner supply control of the two-component developer of each color is performed in the first embodiment, the amount of toner excess / deficiency (toner supply amount) by each patch detection ATR is obtained. In response to the results, the development characteristic coefficient α was changed according to the environment in the image forming apparatus, and the results were fed back to the respective replenishment controllers.

More specifically, the development characteristic coefficient was changed from an environment sensor (not shown) provided in the image forming apparatus based on the amount of water. Water content (steam pressure per kg
FIG. 7 shows how the image density changes due to the laser level (up to 256 gradations) with (g) shown as a parameter.
Shown in

Here, a method of changing the development characteristic coefficient will be described. Specifically, the γ of the water content shown in FIG.
(1) was set to α = 1, and α was changed by the following equation.

Α = γ (z) / γ (1)

After multiplying the development characteristic coefficient α by the toner correction signal level calculated after performing the patch detection ATR,
Feedback was performed to the signal level determined from the developer reflection ATR and video count ATR. Therefore, the feedback amount changes following the change (γ) in the development characteristic due to the environmental change in the image forming apparatus, so that the image density increases due to abrupt toner supply or the color change based on the image density decrease due to the stop of the supply. Could be minimized.

(Embodiment 3) In this embodiment, when performing toner supply control of the two-component developer of each color in Embodiment 2, the amount of toner excess / deficiency (toner supply amount) by each patch detection ATR is obtained. In response to the results, the development characteristic coefficient α (color) of each color was changed according to the amount of water in the yellow, magenta, cyan, and black developers and fed back to each replenishment control device.

More specifically, a development characteristic coefficient was changed from an environment sensor (not shown) installed in the developing device based on the amount of water.

Accordingly, since the feedback amount changes following the change (γ) in the development characteristics due to the change in the environment of each developer, a more favorable and stable image can be provided.

(Embodiment 4) In this embodiment, when the toner replenishment control of the two-component developer of each color is performed in the first embodiment, the toner replenishment control device is set to the video count ATR for all the colors.
This is the case where the control is performed only by the control. In this embodiment, each video count ATR is compared with the result of obtaining the toner excess / deficiency amount (toner supply amount) by each patch detection ATR.
Is fed back to the video count amount used in.

In the case of this embodiment, since the toner consumption amount is predicted and the toner is replenished by the consumption amount, the agent reflection AT
There is no time lag from when toner is supplied to when it reaches the sensor as in R. Thereby, good control with very little interference between sensors can be performed. Furthermore, in this system, the developer characteristic coefficient α is changed according to the characteristic difference of each developer (agent difference / environmental difference / developing contrast potential difference), and then it is fed back to the replenishment signal of the video count ATR to achieve higher reliability. We were able to.

[0068]

As described above, in the image forming apparatus of the present invention, when performing the toner supply control of the two-component developer of a plurality of colors, the toner supply amount in the toner supply control by the patch detection ATR is obtained. The amount of toner replenishment is calculated by changing the gain according to the color of each material and the environmental difference, and the corrected toner amount is calculated. Even if the toner consumption of the toner varies, the toner density of each developer can be controlled to a density at which an appropriate image density can be obtained for the toner image, and the image density of the toner image of each color is appropriately controlled. A high-quality color image can be obtained stably from the beginning of image formation. Of course, there is no overflow of the developer, no fogging, and no defective coating of the developer on the developer carrying member.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory view illustrating a schematic configuration of a developing device included in the image forming apparatus of FIG. 1;

3 is a waveform diagram illustrating a method of counting density information of an image information signal in the image forming apparatus of FIG.

FIG. 4 is a flowchart illustrating density control in the image forming apparatus according to the first exemplary embodiment.

FIG. 5 is an explanatory diagram showing a signal level of a patch detection sensor with respect to an image density due to a developer density change.

FIG. 6 is an explanatory diagram showing a change in image density due to Vcont using the type of developer as a parameter.

FIG. 7 is an explanatory diagram showing a change in image density with respect to a laser level due to a change in water content.

FIG. 8 is an explanatory diagram showing an entire configuration of an example of a conventional image forming apparatus.

[Explanation of symbols]

 Reference Signs List 40 photosensitive drum 43 two-component developer 44 developing device 60 toner replenishing tank 62 toner transport screw 63 replenishing toner 66 counter 67 CPU 69 motor driving circuit 70 motor 72 patch image signal generating circuit 73 density sensor 75 comparator 76 reference voltage signal Source 77 Concentration sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Sakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shigeru Matsuzaki 3-30-2 Shimomaruko, Ota-ku, Tokyo (72) Inventor ▲ Yoshi ▼ Tadanobu Kawano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takao Ogata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside (72) Inventor Kunihiko Kitayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. A latent image forming means for digitally forming an electrostatic latent image on at least one image carrier, and developing the electrostatic latent image formed on the image carrier using a two-component developer. Developing means for forming a toner image; toner replenishing means for replenishing toner to the developing means; and at least two density control devices installed for the developing means for controlling the toner density of the developer or the image density of the toner image. An image forming apparatus comprising the above, wherein a control parameter of another control device is changed by a signal from at least one control device. 2. A latent image forming means for digitally forming an electrostatic latent image on at least one image carrier, and developing the electrostatic latent image formed on the image carrier using a two-component developer. Developing means for forming a toner image, toner replenishing means for replenishing toner to the developing means, and toner density of the developer or image density of the toner image through control of toner replenishment to the developing means provided for the developing means And a density control device for controlling the image forming apparatus, wherein at least a reference image for density detection is formed as the density control device, and a toner replenishment amount is determined by detecting the reference image density. And a second control device for detecting the concentration of the developer in the developing means and performing toner replenishment control.
An image forming apparatus that corrects a toner replenishment signal calculated from a reference image density of a control device, and feeds it back to a control parameter of a second control device. 3. A latent image forming means for digitally forming an electrostatic latent image on at least one image carrier, and developing the electrostatic latent image formed on the image carrier using a two-component developer. Developing means for forming a toner image, toner replenishing means for replenishing toner to the developing means, and toner density of the developer or image density of the toner image through control of toner replenishment to the developing means provided for the developing means And a density control device for controlling the image forming apparatus, wherein at least a reference image for density detection is formed as the density control device, and a toner replenishment amount is determined by detecting the reference image density. And a second control device for performing toner supply control based on a digital image signal for each pixel of the reference image, and compensating for the toner supply signal calculated from the reference image density of the first control device. An image forming apparatus, comprising: feeding back to a control parameter of a second control device after performing a correction. 4. When a signal obtained by correcting a toner replenishment signal from a first control device for obtaining a toner replenishment amount by detecting the reference image density is fed back to another control device, chromatic color development is performed. For the developer, the second controller controls the toner replenishment by detecting the concentration of the developer installed in the developing means. For the achromatic developer, the toner replenishment is performed from the digital image signal for each pixel of the reference image. The image forming apparatus according to claim 2, wherein the control is performed by a third control device that performs control. 5. An image forming apparatus according to claim 2, wherein a correction coefficient used for feeding back to said toner replenishment control device is changed according to development characteristics. 6. The image forming apparatus according to claim 2, wherein a correction coefficient used for feedback to said toner supply control device is changed according to an environment (temperature / humidity / moisture content). 7. The method according to claim 2, wherein the correction coefficient used for feedback to said toner replenishment control device is changed by a development contrast potential (difference between a bright portion potential on an image carrier and a development potential). Or the image forming apparatus of 3.