JPH0611965A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image of stable concentration even at outputting a continuous image due to excellent development by stably controlling toner concentration of developer of two components in a developing device. CONSTITUTION:A video count type ATR (developer concentration detecting and controlling device) containing a video counter 23 and the like and a patch detecting type ATR containing a toner concentration detecting sensor and the like constituted of a photoelectric transfer element 28 and the like are provided, a supply quantity of toner 7 from a hopper 6 to a developing vessel 4 by means of a toner carrying screw 61 is previously detected, toner is supplied by operating the screw 61 on the basis of the detected toner supply quantity and an image forming information signal, and operation of the screw 61 is corrected by toner concentration of the developer in the vessel 4 detected by the detecting sensor. Hereby, the developer 5 can be accurately controlled in its toner concentration, and an image of stable concentration can be obtained even at forming a continuous image.

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 using an electrophotographic system, and more particularly to a two-component developer in which a developing device for developing a latent image formed on an image bearing member is mixed with toner and carrier. The present invention relates to an image forming apparatus using.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, it is known that a latent image formed on an image bearing member is developed with a developer in a developing device and visualized as a toner image. However, in a developing device that uses a two-component developer,
Mixing ratio of developer toner (T) and carrier (C) T /
(T + C) (The toner concentration of the developer. Below, T /
It is important to keep (T + C) ratio) constant,
Therefore, several methods such as a light reflection detection method have been proposed as a developer concentration detection / control device (ATR).

When the toner of the developer uses a colorant such as carbon showing the same optical characteristics as the carrier as the pigment, it is necessary to detect the mixture ratio of the carrier and the toner by the difference in the light reflection intensity of the developer. Is impossible. For this reason,
As a method of detecting the toner concentration of a developer using such a toner having carbon as a pigment, a change in magnetic permeability in a unit volume of the developer, that is, a density of carriers in the unit volume is obtained, and then T It is common to use a so-called inductance method for calculating the / (T + C) ratio.

However, in order to improve the image quality, when the charge amount of the toner is increased and the fluidity is improved, the carrier is repelled by the charged developer even if the developer is stirred. However, since the magnetic permeability of the developer changes even with the same T / (T + C) ratio, there is a problem that an accurate T / (T + C) ratio cannot be detected.

Therefore, the T / (T +
C) As a method of measuring the ratio, a latent image having a fixed potential is formed on the photosensitive drum in advance, and the latent image is directly developed to form a patch image having a pattern of the reference density, and the image density Is used to detect the T / (T + C) ratio (patch detection method).

On the other hand, in an image forming apparatus for forming a full-color image at high speed by a digital method, a patch image is formed on a photosensitive drum and the density is detected every time an individual image is formed during continuous image formation. Then, the copying speed becomes slow and the inside of the apparatus is adversely affected.

Therefore, in the case of such a digital image forming apparatus, during continuous image formation, the image information signal is added to predict the toner consumption amount, and toner is sequentially replenished by the so-called video count. Toner is replenished by the method ATR.

That is, as shown in FIG. 6, an input image signal from a reader 13 'composed of an image pickup device or the like is A / D converted, and the output level of the digital pixel signal is integrated for each pixel to obtain a video counter. 23, and the CPU 24 converts this video count into a toner replenishment amount, and sends a signal as a replenishment signal to the drive circuit of the toner hopper (toner replenishing device) of the image forming apparatus (printer) 32. The toner is supplied to the developing device.

According to the above video count type ATR, the toner is replenished at the time of continuous image output in accordance with the image signal output. Therefore, T / T is supplied in accordance with the actual toner replenishment amount into the developing device. The accuracy of the (T + C) ratio is determined. Therefore, it is important to replenish the toner with an accurate replenishment amount.

However, when a toner hopper using a normal screw as a toner feeding member is used, the toner replenishment amount greatly varies depending on the toner state in the width direction of the hopper, and the toner replenishment amount with respect to the reference amount. ±
It may fluctuate by 20% or more.

For this reason, in continuous formation of an image such as a full-color image, which has a large toner consumption amount and a correspondingly large toner replenishment amount, the fluctuation of the replenishment amount with respect to the reference value exceeds the worst ± 20%. Image output is 10
The T / (T + C) ratio fluctuates by as much as several percentages when the number of printed sheets reaches almost 0, which causes a problem that the image density greatly changes during continuous image output.

[0012]

Therefore, during continuous image formation, toner is replenished by the video count type ATR, and at the end of continuous image formation, the toner density of the developer is detected by the patch detection system, and the T of the developer is detected. /
A proposal to correct the (T + C) ratio has also been made recently.

According to such a method, good toner replenishment control can be performed and a stable image can be obtained if continuous image formation is performed on several tens of sheets. That is, the following may be done. First, as described above, during the continuous image forming sequence, the toner is replenished by the video count type ATR. At the end of continuous image formation, the patch detection method A
Switch to TR, form a patch image on the photosensitive drum,
From the toner concentration, the toner concentration of the developer in the developing container is measured.

Based on the measured toner density, it is determined whether or not the toner is replenished to the developing device by the toner replenishing operation during continuous image formation. If it is determined that the toner is not overreplenished, the toner hopper is used. The feeding screw is driven at the required number of revolutions to replenish the developing device with the insufficient toner from the hopper. Further, the toner replenishment amount is corrected by the video count number and is fed back to the next toner replenishment amount. If the toner is replenished in an appropriate amount, the toner replenishment amount for the shortage is zero, and the replenishment amount is not corrected by the video count number. Further, when it is determined that the amount of toner is excessively replenished, the amount of replenishment of the video count is corrected and fed back to the next amount of toner replenishment.

As described above, an image having a stable density can be obtained by forming several tens of continuous images. However, it is very difficult to keep the amount of toner replenished from the hopper accurately within a fixed amount range at all times. Therefore, in continuous copying of several hundred sheets or more, copying of images such as full color, which consumes a large amount of toner, is particularly difficult. However, during image formation, due to large fluctuations in the toner replenishment amount that was replenished with the video count number-based replenishment amount (correction by the patch detection method has not yet been performed), the toner will exceed the stable control range and over-replenish toner The T / (T + C) ratio of the agent becomes high, or the toner replenishment amount is too small and the T / (T + C) ratio is lowered, so that an extremely low density of the image occurs. Especially when you want to output full color images at high speed,
Since it is often done by continuous copying of several hundred sheets,
The tendency is great.

Therefore, an object of the present invention is to stably control the toner density of the two-component developer in the developing device and to obtain an image having a stable density even during continuous image output by good development. Is to provide.

[0017]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
A latent image forming unit that forms an electrostatic latent image corresponding to an image information signal on an image carrier, a developing unit that develops the electrostatic latent image using a two-component developer, and a toner replenisher that supplies toner to the developing unit. Means, a density detecting means for detecting the toner density of the developer, and a replenishing amount detecting means for detecting the toner replenishing amount by the replenishing means, and the replenishing amount detecting means replenishes the toner by the replenishing means at a predetermined timing. Detect the amount,
The replenishing means is operated based on the detected toner replenishment amount and the image information signal, and the operation of the replenishing means is corrected based on the toner density detected by the density detecting means. The image forming apparatus.

Another embodiment of the present invention is a latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, and a developing means for developing the electrostatic latent image with a two-component developer. A toner replenishing means for replenishing the developing means with toner, and a density detecting means for detecting the toner density of the developer. The replenishing means is operated based on the image forming information signal and detected by the detecting means. In the image forming apparatus that corrects the operation of the replenishing means based on the toner concentration that is obtained, during execution of a predetermined sequence portion in the image forming sequence according to the replenishment amount based on the image information signal, or the image information signal. The image forming apparatus corrects the operation of the replenishing means when the amount of replenishment based on the number reaches a certain number during continuous image formation or when it is predicted that the amount of replenishment will be changed. A. Preferably, the predetermined sequence part is a post-rotation at the end of image formation or a pre-rotation at the start of image formation.

Still another embodiment of the present invention is a latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, and a developing for developing the electrostatic latent image using a two-component developer. Means, a toner replenishing means for replenishing toner to the developing means, and a density detecting means for detecting the toner density of the developer, and actuating the replenishing means on the basis of the image forming information signal. In an image forming apparatus that corrects the operation of the replenishing device based on the detected toner concentration, the operation of the replenishing device is corrected during execution of a predetermined sequence portion in the image forming sequence of the image or at a predetermined timing. The image forming apparatus is characterized by performing. Preferably, the predetermined sequence portion is a post-rotation at the end of image formation, and the predetermined timing is a predetermined number of image formations and a document replacement.

Still another embodiment of the present invention is a latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, and a developing for developing the electrostatic latent image using a two-component developer. Means, a toner replenishing means for replenishing the toner to the developing means, and a density detecting means for detecting the toner density of the developer by a change in magnetic permeability, and actuating the replenishing means based on the image forming information signal, Further, in an image forming apparatus that detects the toner concentration of the developer by the detecting unit at a predetermined timing and operates the replenishing unit based on the toner concentration, the toner of the developer after the replenishing unit operates based on the toner concentration. In the image forming apparatus, the density is detected and a reference value when the replenishing means is operated based on the toner density is changed to the detected value. The reference value can be changed in consideration of humidity.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a block diagram showing Embodiment 1 of the image forming apparatus of the present invention. In FIG. 1, reference numeral 1 is an electrophotographic photosensitive drum which has amorphous silicon, selenium, OPC, etc. on its surface and rotates in the arrow direction. The photosensitive drum 1 is first uniformly charged by the primary charger 2 and then exposed and scanned by a laser beam modulated in accordance with a recorded image information signal as described later, whereby an electrostatic latent image is formed on the photosensitive drum 1. Is formed. This latent image is reversely developed by the developing device 4 using a two-component developer in which a non-magnetic toner and a carrier are mixed, and a toner image is formed on the photosensitive drum 1. The reversal development is a developing method in which a latent image is formed as an exposed region of the photoconductor on the surface of the photosensitive drum 1 and toner charged to the same polarity as the latent image is attached to the region to visualize the latent image. is there.

The toner image is held on an endless transfer belt 9 which is wound between pulleys 91 and 92 and driven endlessly in the direction of the arrow, and is transferred onto a transfer sheet (not shown) by a transfer charger 8. Transcribed. The transfer paper on which the toner image has been transferred is separated from the transfer belt 9 and conveyed to a fixing device (not shown), where the toner image is fixed on the transfer paper. On the other hand, the toner remaining on the photosensitive drum 1 due to the transfer is removed by the cleaner 10.

An example of the developing device 4 is shown in FIG. In FIG. 2, the inside of the developing device 4 is divided by a partition wall 43 into a first developing chamber 41 and a second stirring chamber 42. The developing chamber 41 includes a non-magnetic developing sleeve 44 that rotates in the direction of the arrow.
And the magnet 4 fixedly arranged in the developing sleeve 44.
5 are arranged. The two-component developer 5 in the developing device 4 is
The developing sleeve 44 is carried by the action of the magnet 45 in the developing sleeve 44, and is formed into a thin layer by the layer thickness regulation by the blade 46 disposed above the developing sleeve 44 with a narrow gap therebetween, while the developing sleeve is formed. By the rotation of 44, the toner is conveyed toward the developing area facing the photosensitive drum 1. Then, in the developing area, toner is applied to the electrostatic latent image on the photosensitive drum 1 from the developer on the developing sleeve 44 and developed, and the electrostatic latent image is visualized as a toner image. In order to improve the developing efficiency at this time, that is, the rate of applying toner to the latent image, a developing bias voltage in which a DC voltage is superimposed on an AC voltage is applied from a power source 47 to the developing sleeve 44.

In the developing chamber 41 and the agitating chamber 42, first and second screws 48 and 49 for agitating and conveying the developer are respectively provided.
Are arranged. The first screw 48 conveys the developer in the developing chamber 41 while stirring it, and the second screw 49
From the toner hopper 66 of FIG.
Thus, the toner 67 supplied into the stirring chamber 42 through the toner discharge port 62 and the developer 5 in the stirring chamber 42 are conveyed while being stirred, and the toner concentration of the developer 5 is made uniform. The developing chamber 41 and the stirring chamber 42 are provided on the front side and the back side of the partition wall 43 in the figure.
An opening (not shown) communicating with the inside is provided, and the developer 5 in which the toner density is lowered due to the consumption of toner by the development due to the conveying force of the first and second screws 48 and 49 is discharged from the developing chamber 41 to the above-mentioned state. The developer 5 that has moved to the inside of the stirring chamber 42 through one of the openings and has recovered the toner concentration in the stirring chamber 42
Moves into the developing chamber 41 through the other opening.

Now, the image pickup device 13 such as CCD shown in FIG.
A reader (image reading device) is configured to include a video count system ATR100 by combining the reader 13 'with a video counter 23 as shown in FIG.
Are formed. In addition, a patch detection type ATR 101 is formed including a toner concentration detection sensor including a light source 27 such as an LED and a photoelectric conversion element 28.
The light source 27 and the photoelectric conversion element 28 are arranged at positions immediately downstream of the developing device 4 in the rotation direction of the photosensitive drum 1.

As shown in FIG. 1, the copy original 11 is projected on the lens 12 of the reader by the image pickup device 13.
The image pickup device 13 decomposes the original image into a large number of pixel portions and outputs a photoelectric conversion signal corresponding to the density of each pixel. Image sensor 1
3 is transmitted to the image signal processing circuit 14, and this image signal processing circuit 14 forms a pixel image signal having an output level corresponding to the density of the pixel for each pixel.

The pixel image signal is a pulse width modulation circuit 15
Be transmitted to. This circuit forms a laser drive pulse having a width (time length) corresponding to the level for each pixel image signal. That is, as shown in (a) of FIG. 3, a wider drive pulse d is applied to high density pixels, a narrower drive pulse 1 is applied to low density pixels, and a narrower drive pulse 1 is applied to low density pixels. A drive pulse h having an intermediate width is formed.

The semiconductor laser 17 is driven by point reduction by the drive pulse. Therefore, the laser 17 is turned on for a high density pixel for a longer period of time and for a low density pixel for a shorter period of time. Therefore, the photosensitive drum 1
The optical system described below exposes a long range in the main scanning direction for high density pixels and a short range in the main scanning direction for low density pixels. That is, the dot size of the latent image differs depending on the density of the pixel. Therefore, as a matter of course, the toner consumption amount for the high-density pixels is larger than that for the low-density pixels.
Incidentally, in FIG. 3D, the latent images of low, medium and high density pixels are shown by L, H and D, respectively.

The output beam 3 of the semiconductor laser 17 is swept by the rotary polygon mirror 18 shown in FIG. 1, passes through a lens 19 such as an fθ lens and a fixed mirror 20 which directs it toward the photosensitive drum 1, and the beam 3 is directed to the photosensitive drum 1. A spot image is formed on the surface. Thus, the laser beam 3 scans the photosensitive drum 1 in a direction (main scanning direction) substantially parallel to the rotation axis of the photosensitive drum 1 to form an electrostatic latent image on the surface of the photosensitive drum 1.

In order to control the amount of toner supplied to the developing device 4 by the video counting method, the image signal processing circuit 14 is used.
The level of the output signal of is counted for each pixel. This counting is performed as follows in this embodiment.

That is, the output of the pulse width modulation circuit 15 is applied to the AND gate 21, while the clock pulse generated by the clock pulse oscillator 22 ((b) in FIG. 3) is also applied to the AND gate 21. . Therefore, from the AND gate 21, as shown in FIG. 3C, a number of clock pulses corresponding to each width of the laser driving pulse,
That is, the number of clock pulses corresponding to the density of each pixel is output. This clock pulse number is integrated by the counter 23. This integrated signal (the number of integrated clock pulses C
₁ ) corresponds to the amount of toner consumed by the developing device 4 to form one image (toner image) of the original 11.

The integrated signal C ₁ is applied to the CPU 24 and stored in the RAM 25. This CPU 24
Calculates the rotational drive time of the conveying screw 61 required to supply the toner 7 in an amount commensurate with the amount of toner consumed in the developing device 4 from the hopper 6 to the developing device 4 based on the integrated signal C _1. Control the drive circuit 26 of 64,
The motor 64 is driven for the above time. Therefore, generally, when the integrated value is large, the driving time of the motor 64 is longer, and when the integrated value is smaller, the driving time of the motor 64 is shorter.

The driving force of the motor 64 is transmitted to the conveying screw 61 via the gear train 63, and the screw 6
1 conveys the toner 7 in the hopper 6 and supplies it to the developing device 4. This toner replenishment is performed every time the development of one image is completed.

By the way, the toner is supplied to the developing device based on the density information obtained by photoelectrically converting the image of the copy original as described above. The toner is supplied based on the actual toner density of the developer being detected. As described above, the hopper 6 to the developing device 4 is used because it is a kind of speculative supply.
If the amount of toner replenished from the developing device 4 or the expected amount of toner consumption in the developing device 4 changes, the developer 5 in the developing device 4
Toner density changes from the specified value.

Therefore, in the present embodiment, in order to solve this problem, after the image formation of the set number N of the same original document is completed and before the image formation of the next original document is started, the photosensitive member is exposed. A patch image is formed as a reference image on the drum 1, and the actual toner concentration of the developer in the developing device 4 is obtained. Thereby, the toner replenishment amount at the time of image formation for the next document is corrected, and the toner hopper 6 The object is achieved by measuring the toner replenishment amount from the above in advance and further correcting the replenishment amount.

More specifically, a patch image signal generation circuit 16 having a signal level corresponding to a predetermined density applies the same signal to a pulse width modulation circuit 15, and a drive signal having a pulse width corresponding to the above density is applied. By laser 1
7 is driven in a decelerating manner to scan the photosensitive drum 1 (at this time, the counter 23 is not operated). As a result, an electrostatic latent image of the patch image corresponding to the specified density is formed on the photosensitive drum 1, and the electrostatic latent image is developed by the developing device 4,
As shown in FIG. 2, the patch image Q is formed on the photosensitive drum 1. The patch image Q formed on the photosensitive drum 1
On the other hand, light is emitted from the light source 27 that constitutes the toner concentration detection sensor, and the reflected light is received by the photoelectric conversion element 28.
Since the output signal of the element 28 corresponds to the density of the reference toner image, this output signal eventually corresponds to the actual toner density of the two-component developer 5 in the developing device 4.

The output signal of the element 28 is applied to the comparator 29. On the other hand, the comparator 29 has a reference voltage signal source 3
From 0, a reference signal corresponding to the specified toner density of the developer is also applied. Therefore, the comparator 29 compares the output signal of the element 28 with the reference signal to form a signal indicating whether the actual toner concentration of the developer in the developing device 4 is equal to or higher than a specified value or lower than the specified value.

The output signal of the comparator 29 thus formed is applied to the CPU 24, and the CPU 24 runs short when the actual toner concentration of the developer 5 detected by the element 28 is smaller than the specified value. The screw 61 is operated so as to supply the toner of the amount to the developing device 4. That is, CPU
Reference numeral 24 calculates the shortage toner amount based on the signal from the comparator 29, calculates the screw rotation time required to supply this to the developing device 4, and controls the motor drive circuit 26 for that time. The motor 64 is driven to rotate.

If the actual toner density detected by the element 28 is higher than the specified toner density value or is lower as described above, the CPU 24 uses the counter 23 to perform the next toner replenishment. The operation is corrected as follows.

First, when the actual toner density detected by the element 28 is the same as the specified toner density, the RAM 2
The integrated signal C ₁ stored in 5 is canceled, and the toner replenishing operation associated with the next image forming operation is performed as described above.

On the other hand, when the actual toner density detected by the element 28 is lower than the specified toner density,
In addition to supplying the shortage toner as it is as described above, the CPU 24 generates the shortage toner amount M during the formation of N images. Insufficient toner amount (M / N) is calculated.
In other words, the CPU 24 calculates the clock pulse number C ₂ corresponding to the insufficient toner amount (M / N). And CPU2
Reference numeral 4 calculates the correction coefficient (C ₁ + C ₂ ) / C ₁ using the integrated clock pulse number C ₁ and this clock pulse number C ₂ , and stores this in the RAM 25.

On the other hand, when the actual toner density detected by the element 28 is higher than the specified toner density, the CPU 24
Calculates the excess toner amount M ′ in the developer, and since this excess toner amount M ′ was generated during the formation of N images, the excess toner amount when forming next one image Calculate (M '/ N). In other words, the CPU 24 determines the clock pulse number C corresponding to the excess toner amount (M '/ N).
₃ , and using the clock pulse number C ₁ and this clock pulse number C ₃ , a correction factor (C ₁ −C ₃ ) /
C ₁ is calculated and stored in the RAM 25.

When forming an image with the next original, the number of clock pulses C ₄ counted by the counter 23 is RA when the original is used for the image information signal obtained by photoelectric conversion.
In addition to being stored in M25, the CPU 24 calculates the toner replenishment time per image corresponding to the number of clock pulses obtained by multiplying C ₄ by the correction coefficient, and the screw 61 is incremented by the above time at the end of each image formation. To replenish the toner.

That is, when the toner supply amount is not enough at the time of the previous image formation, the number of clock pulses C ₄ × {(C ₁ + C ₂ ) / C ₁ } corresponds to the current image formation. Replenish toner to the developing device for time. In other words,
The toner is replenished to the developing device 4 for a time longer than the toner replenishment time corresponding to the clock pulse number C ₄ counted by the counter 23 using the image information signal.

On the other hand, if the toner replenishment amount is excessive at the time of the previous image formation, then at the time of the current image formation,
Toner is supplied to the developing device 4 for a time corresponding to the number of clock pulses C ₄ × {(C ₁ -C ₃ ) / C ₁ }. In other words, the toner is replenished to the developing device 4 for a time shorter than the toner replenishment time corresponding to the clock pulse number C ₄ counted by the counter 23 using the image information signal.

After the set number of copies of the same image have been completed, the reference toner image is formed again and the reflection density of the reference toner image is detected by the element 28. Using this detection value and the count value C ₄ ,
It may be controlled in the same manner as described above.

A flow chart of the above control is shown in FIG. As shown in FIG. 4, after the machine start-up mode is selected, the toner replenishment amount is measured in step S100 (which will be described later) and then copying is started, and then in step S101, the original is read and photoelectrically converted as described above. . In S102, the level of each pixel of the document image information signal is counted (in the embodiment, the counter 23 counts clock pulses). In step S103, the toner supply amount per image, that is, the rotation speed of the screw 61 is determined based on the count signal and the correction coefficient. In S104, a latent image is formed and developed, and if necessary, further transferred.
After the formation of one toner image in S105 and before the formation of the next toner image of the same image, the screw 61 is rotated by the number of rotations determined as described above to replenish the toner. This toner image formation and toner supply are repeated for the number of copies selected and set by the operator, and when this is completed (S106),
In S107, the actual toner concentration of the developer 5 in the developing device 4 is measured as described above.

Based on this toner density measurement, it is determined in S108 whether or not the toner has been excessively replenished to the developing device by the toner replenishing operation so far. If it is determined in S108 that the toner is not over-replenished, the screw 61 is driven at the required number of revolutions based on the measured toner concentration in S109, and the insufficient toner is replenished to the developing device. And S11
The correction coefficient is calculated at 0 and fed back to the next toner replenishment amount correction (feedback operation (1)). However, when the proper amount of toner is replenished, the toner replenishment amount in S109 is zero, and the correction coefficient calculated in S110 is 1. If it is determined in S108 that the supply is excessive, the correction coefficient is calculated in S111,
Feedback is made to the next toner supply amount correction (feedback operation (2)).

In the above, even if the toner is oversupplied in the previous image forming step, the toner is further supplied to the developing device in the next image forming step. However, the above-mentioned excess supply is
Actually, it is a small amount, and does not become an abnormally large amount. In reality, the toner replenishment amount is not exactly the same each time, and a variation larger or smaller than the target value occurs each time. Therefore, even if more toner is replenished to the above-mentioned excess replenishment amount, it is averaged due to variations in the above-mentioned toner replenishment amount, and when the target value of the further replenishment toner amount is corrected as described above, The toner concentration of the agent actually approaches the specified value in a short time, and the toner concentration does not gradually increase and is left alone.

The correction coefficient obtained in the first image forming operation is K ₁ , the correction coefficient obtained in the second image forming operation is K ₂ , ..., And the correction coefficient obtained in the nth image forming operation. If the correction coefficient is K _n , (K ₁ × K ₂ × ... × K _n ) may be used as the correction coefficient in the (n + 1) th image forming operation.

As described above, if a correction term is added to the toner replenishment amount and the toner replenishment amount or the toner replenishment amount is changed for each set number N in accordance with a change from the expected value of the toner replenishment amount, The toner density is stable during continuous image formation. However, as described above, the replenishment amount of the toner largely changes depending on the state of the toner in the toner hopper, and the change due to the leaving is also very large. In particular, the toner whose fluidity is improved for the purpose of improving the image quality has a noticeable difference in state when left standing, and the change in the replenishment amount is large.

Therefore, in the present invention, the toner replenishment amount is accurately detected in advance at a predetermined timing for the purpose of suppressing the fluctuation of the T / (T + C) ratio due to the toner replenishment only from the image information during continuous copying. It is possible to improve the accuracy of the replenishment amount by further providing a means and correcting the replenishment amount for each set number N of sheets, and it is possible to make the fluctuation of the T / (T + C) ratio extremely small even during continuous copying. It was done.

The method of measuring the toner supply amount may be as follows. For example, the transfer is turned off, and about 10 high density solid images corresponding to A3 are formed on the photosensitive drum to form a latent image and the latent image is developed to form an image, thereby consuming the toner. The image density at that time is always detected by the light source 27 and the photoelectric conversion element 28. Since the relationship between the toner concentration and the toner amount per unit area of the image is obtained, the consumed toner amount can be detected.

Further, the replenishment of the toner at this time is carried out in accordance with the consumption amount of the A3 high density solid image formation.
When 10 high-density solid images equivalent to A3 are formed, the toner consumption is about 12 g, and the amount of developer is 60
When the amount is 0 g, about 2% of toner is consumed and replenished. When the toner density of the developer changes by 1%, the image density changes by about 0.2 around 1.5. Therefore, when the toner replenishment amount deviates from the reference value by about 5%, it is converted to 10 solid images corresponding to A3, and the amount of 12 g of 0.
At 5%, the deviation is about 0.6 g. This is T / (T +
The C) ratio is 0.1%, and the image density is 0.
If the toner replenishment amount deviates by 5% or more, the image density changes by 0.02 or more. Therefore, the deviation of the toner replenishment amount can be detected by detecting the change amount of the density of the initial image. Is possible.

By calculating the replenishment amount per unit time from the deviation of the replenishment amount detected in the above process and determining the replenishment time, it becomes possible to maintain the error of the replenishment amount to 5% or less, and it is always stable. The obtained image is obtained. After the amount of replenishment is calculated, the amount of replenishment is replenished to restore the original T / (T + C) ratio. Explaining with the flow chart of FIG. 4, the toner supply amount is measured every time the main switch of the machine is turned on at a predetermined timing in step 100, and thereafter, the toner supply amount is corrected every N sheets.
A stable image is always obtained.

Embodiment 2 FIG. 5 is a sectional view showing a developing unit in Embodiment 2 of the image forming apparatus of the invention. In this embodiment, the lower surface of the toner conveying passage 74 from the toner hopper 6 of FIG. 1 in which the conveying screw 61 is installed and the upper portion of the stirring chamber 42 of the developing device 4 are connected by a bypass passage 75, and the conveying passage 74 is formed. An opening 74a that can be opened and closed by a lid 71 is provided at the connecting portion of the bypass passage 75 on the lower surface, and a weighing plate 72 in which the weighing pan 73 is inserted into the bypass passage 75 below the opening 74a is installed.

Then, the opening 74a of the toner conveying passage 74 is opened at a predetermined timing by the lid 71, and the screw 61 is rotated for a predetermined time so that the toner conveyed in the passage 74 passes through the opening 74a and is placed on the weighing pan 73. To
The weight of the dropped toner is measured and measured with 72. The measured toner weight is sent to the CPU 24 shown in FIG.
Then, the toner replenishment amount per unit time was calculated and measured from the rotation time of the conveying screw 61 at that time.

In this embodiment, the toner replenishment amount measurement in step S100 of FIG. 4 is completed in this way, and thereafter, as in the first embodiment, copying is started and step S10 is performed.
In the sequence of 1 or less, an image was formed while correcting the toner supply amount every N sheets. Similarly, a stable image was always obtained.

The method of measuring the toner replenishment amount according to the present invention is not limited to the above method, but the following method can be used. That is, the toner replenishment amount has a correlation with the torque of the replenishment motor 64 that drives the screw 61 that conveys the toner from the toner hopper 6 in FIG. 1. The larger the replenishment motor torque, the larger the toner replenishment amount. Less. Therefore, the relationship between the torque of the replenishment motor 64 and the toner replenishment amount may be obtained in advance, the torque of the replenishment motor 64 may be measured when replenishing the toner with the screw 61, and then the toner replenishment amount may be obtained.

As described above, according to the first and second embodiments, the actual toner replenishing amount of the toner replenishing means for replenishing the toner into the developing device is obtained in advance, and the toner replenishing amount and the image information signal are obtained. And to activate the toner replenishment means,
Moreover, since the toner concentration of the developer in the developing device is detected by the toner concentration detecting means and the operation of the toner replenishing means is corrected, the toner concentration of the developer in the developing device can be controlled with high accuracy, and the density is stable. Images can be acquired continuously.

In the above, the transfer belt 8 for conveying the recording material
On the other hand, the image forming apparatus in which one image forming unit such as the photosensitive drum 1 is provided has been described as an example, but the present invention is not limited to this, and a plurality of similar image forming units are arranged in parallel along the transfer belt. The present invention can be similarly applied to the existing color image forming apparatus.

Embodiment 3 In the above Embodiments 1 and 2, the video count type ATR is used.
The toner replenishment is corrected by detecting the toner density by the patch image, the toner replenishment amount from the toner hopper is measured in advance, and the toner replenishment amount is further corrected by the measured replenishment amount.

In this embodiment, since the toner replenishment of the hopper has a characteristic, the replenishment characteristic is utilized to enable continuous copying of several hundred sheets in the case of an image with a small amount of toner replenishment. .

First, FIG. 7 shows an example of the variation of the actual replenishment amount with respect to the set replenishment amount of the toner replenished from the toner hopper, which will be described. As a result of many experiments, the amount of fluctuation of the actual toner supply amount from the set supply amount is
There is a linear relationship in a portion where the replenishment amount is small. For example, when the set replenishment amount is y (g), the variation amount of the toner replenishment amount is a coefficient α.
As αy (g). When the set replenishment amount exceeds a certain amount, the variation amount converges to a constant amount. For example, when the set replenishment amount is b (g) or more, the variation amount takes a value αb (g) constant.

In the case of continuous image formation, image formation is performed within a range in which the amount of fluctuation of the actual amount of replenishment from the set amount of replenishment is added for the number of times of replenishment, that is, the cumulative amount of variation of toner replenishment does not exceed the position. Needed, T / (T + C) of developer
The maximum allowable amount of cumulative variation is determined from the allowable range of the ratio and the amount of the developer. In the present embodiment, the maximum allowable amount of this cumulative fluctuation amount is assumed to be D. If the number of image formations is N, for example, when the replenishment amount is small, if the feedback operation is performed in the range of N × α × y <D, the T / (T + C) ratio does not fall outside the allowable range and a stable image is obtained. Is obtained. Further, when the image density is high and the replenishment amount is large, a stable image can be obtained by performing the feedback operation in the range of N × α × b <D.

8 to 11 are flow charts showing an algorithm for toner replenishment in this embodiment. Figure 8 ~
In FIG. 11, the allowable value C is represented by C = D / α, and the timing of performing the feedback operation in some cases is described.

First, as shown in FIG. 8, when the operator turns on the copy button, the reader 13 scans the document 1 in step S101 to read the document, and the document image image information signal A is sent from the reader 13. / D
It is converted and output.

Next, in order to perform toner supply by the ATR of the video count system, the level of each pixel of the original image information signal is counted in S102, and specifically, the video counter 23 counts clock pulses. S1
In step 03, the toner supply amount y per image, that is, the number of rotations of the toner conveying screw 61 of the hopper 6 is determined based on the count signal and the correction coefficient.

Next, in step S201, it is determined whether the toner replenishment amount y is equal to or greater than the set replenishment amount point b shown in FIG. If the replenishment amount y is not greater than or equal to b, it is determined in step S202 whether Ny (N is the set number of copies) is greater than the above-described allowable value C (= D / α), and if the replenishment amount Ny is greater than or equal to b. Is
Similarly, in S203, it is determined whether Nb is larger than the allowable value C (= D / α). If it is not large, it is not necessary to correct the toner replenishment amount during continuous image formation.
From S203 to S104 shown in FIG. 9, the continuous image forming operation is performed.

The continuous image formation when the image density is high depends on the amount of the developer, but the limit is usually about 100 sheets,
When the number of sheets for continuous image formation exceeds this number, the T / (T + C) ratio exceeds the permissible range due to fluctuations in the toner replenishment amount. For this reason, conventionally, the number of continuous image formations was limited to about 100, and the same was used regardless of whether the image density was high or low. However, by using the algorithm of this embodiment, the image density can be reduced. When it was low, continuous image formation of several hundred sheets or more became possible.

First, as shown in FIG. 9, image formation (copying) is started in S104, and latent images are formed, developed, and, if necessary, further transferred. Next, in S105, after one toner image is formed and before the next toner image of the same image is formed, the screw 61 is rotated by the number of rotations determined as described above to replenish the developing container 4 with the toner 7. The formation of the toner image and the replenishment of the toner are repeated by the set number N selected and set by the operator, and when this is completed (S10).
6) Then, it is determined whether or not the next original is on the feeder (S204).

If the original document is on the feeder, the original document is sent to the reader unit and read at the same time, and the cumulative replenishment amount including the replenishment amount up to the present is calculated by the above-described procedure (S205). When it is determined that the allowable range C is not exceeded even when the image is formed on S, S101 to S10
6 through S101 'to S106' similar to 6 and then S104 again.
The following operations are continuously performed.

When the original is not on the feeder or when the cumulative replenishment amount exceeds the allowable range C, the process proceeds to S107 shown in FIG. 11 and the actual toner concentration of the developer in the developing device 4 is measured by the patch detecting means. To be done. Then, based on this, in S108, it is determined whether or not the toner has been over-replenished by the toner replenishing operation so far. S1
If it is determined that the toner is not over-replenished in 08, the screw 61 is driven at the required number of revolutions in S109 to replenish the insufficient toner to the developing device. Then, in S110, the correction coefficient of the toner replenishment amount is calculated and fed back to the next toner replenishment amount correction (feedback operation (1)), and S101 and subsequent steps are performed as shown in FIG. However, if the proper amount of toner has been supplied, the toner supply amount in S109 is zero,
The correction coefficient calculated in SS110 is the same as the previous correction coefficient and does not change. If it is determined in S108 that the toner supply amount is excessive, a correction coefficient of the toner supply amount is calculated in S117 and is fed back to the next toner supply amount correction (feedback operation (2)). To do.

In the above, even if the toner is oversupplied in the previous image forming step, the toner is further replenished in the developing device in the next image forming step. However, the excessive replenishment is actually small. It is a quantity, not an abnormally large quantity. In reality, the toner replenishment amount is not exactly the same each time, and a variation larger or smaller than the target value occurs each time. Therefore, even if more toner is replenished to the excessive replenishment amount, the toner concentration of the developer is averaged due to the above variation and the target value of the further replenishment toner amount is corrected as described above. As described in the first embodiment, in reality, the toner concentration does not approach the specified value within a short period of time and the toner concentration does not gradually increase.

Next, when Ny and Nb are respectively larger than the allowable value C in S202 and S203 of FIG.
The image formation is started by going to S104 ′ shown in
After forming one toner image at 05 ', and before forming the next toner image of the same image, the screw 61 is rotated by the number of rotations determined as described above to replenish the toner. Then S104 "
Then, it is determined whether the replenishment amount y is equal to or greater than the set replenishment amount point b in FIG. If the supply amount y is not greater than or equal to b, S10
At 5 ", it is determined whether or not ny (n is the number of image formation after feedback back) is larger than the above-described allowable value C (= D / α). If the replenishment amount is y or more, S106"
Similarly, it is determined whether nb is larger than the allowable value C (= D / α). If it is not large, it is not necessary to correct the replenishment amount during continuous image formation. Therefore, it is judged whether or not the set number N has been reached (S206). If the set number has not been reached, the process returns to S104 'to form an image. If it is reached, the process proceeds to S107 and the toner density measurement and the following steps are performed.

If ny and nb exceed the permissible value C in S105 "and S106", the image forming operation is stopped even during continuous image formation, and S107 'to S111' similar to S107 to S117 described above are executed. Take action. That is, S10
Starting from the toner concentration measuring operation 7 ', it is judged whether or not there is excessive replenishment (S108'), toner replenishment based on toner concentration (S109 '), feedback operation (1) (S1).
10 ') or from S105' to feedback operation (2) (S111 ') to S103 "to determine the toner replenishment amount per sheet to adjust the image density, and then return to S104'. Further, the image forming operation is continuously performed.

In this embodiment, since the image formation is performed by using the algorithm as described above, even when the continuous image formation of 100 sheets or more, the speed hardly decreases and the image having the good density is stable. I got it.

Fourth Embodiment FIG. 12 is a schematic configuration diagram showing a fourth embodiment of the image forming apparatus of the present invention.

In the present embodiment, as shown in FIG. 12, in order to separate the light source 27 and the photoelectric conversion element 28, which constitute the toner density detection sensor of the patch detection type ATR, from the developing device 4, the transfer drum of the photosensitive drum 1 is separated. It was installed on the downstream side of the image transfer section facing 50. The patch image Q formed on the photosensitive drum 1 is detected after the toner image on the photosensitive drum 1 is transferred. Therefore, when the patch image Q passes through the image transfer portion, the transfer drum 50 of the image transfer portion is transferred. The transfer drum 50 is installed by the brush-type charge removing means 93 installed in the transfer drum 50.
Is removed and the transfer drum 50 is separated from the photosensitive drum 1, so that the patch image Q is not transferred onto the transfer drum 50.

As a result, the toner concentration of the patch image can be stably detected without soiling the detection surface of the toner concentration detection sensor means.

The present embodiment is the same as the third embodiment except that the toner density detection side of the patch image has passed through the transfer drum 50, and the video count type AT is used.
By using the ATR of the R and patch detection method and performing the image formation while performing the toner density detection and the feedback by the algorithm shown in FIGS. 8 to 11, even if the continuous image formation of 100 sheets or more, the image of the good density is stable. I got it.

Fifth Embodiment FIG. 13 is a configuration diagram showing a fifth embodiment of the image forming apparatus of the present invention. The image forming apparatus of this embodiment is provided with the first, second, third, and fourth image forming portions Pa, Pb, Pc, and Pd so that a full-color image can be formed at high speed.

The image forming portions Pa, Pb, Pc and Pd are
Electrophotographic photosensitive drums 1a, 1b, 1c and 1d, respectively
It is equipped with. Photosensitive drums 1a, 1b, 1c, 1d
Have their surfaces respectively covered by primary chargers 2a, 2b, 2c,
Laser light emitted from a light source device (not shown) is uniformly charged by 2d and then scanned by a polygon mirror 16 and condensed on a generatrix of the photosensitive drums 1a, 1b, 1c, 1d via a reflection mirror and an fθ lens. Then, a latent image corresponding to the image signal is formed.

The latent images formed on the photosensitive drums 1a, 1b, 1c and 1d are developed by developing units 4a, 4b, 4c and 4 respectively.
By using the two-component developer of cyan, magenta, yellow, and black, the photosensitive drums 1a, 1b, 1
Cyan, magenta, yellow, and black toner images are formed on c and 1d.

The cyan, magenta, yellow and black toner images on the photosensitive drums 1a, 1b, 1c and 1d are transferred from the cassette 80 through the registration roller 81 and the transfer belt 9.
It is transferred and attracted onto the recording material P that is conveyed by the transfer belt 9 and transferred onto the recording material P by the action of the transfer chargers 8a, 8b, 8c, and 8d, and cyan, magenta, and
A full-color image in which toner images of four colors of yellow and black are superimposed is obtained.

The recording material P, on which the transfer of the black toner image in the fourth image forming portion Pd has been completed, is separated from the transfer belt 9 by the action of the separation charging device 82 and is conveyed to the fixing device 83, where the fixing roller 83a is provided. By applying pressure and heat with the pressure roller 83b, the four color toner images are mixed and fixed on the recording material P to form a full-color permanent image, which is then discharged outside the image forming apparatus. It

On the other hand, the photosensitive drum 1 on which the toner image is transferred
The toners a, 1b, 1c, and 1d are prepared for the subsequent latent image formation and subsequent image formation by removing the toner remaining thereon by the respective cleaners 5a, 5b, 5c, and 5d. The toner remaining on the transfer belt 9 is scraped off by a rotating fur brush 84 provided near the downstream end of the transfer belt 9.

According to this embodiment, the patch detection type AT is used.
R patch image toner concentration detection sensors 31a, 31
b, 31c and 31d are transfer chargers 8a and 8d, respectively.
b, 8c, 8d and cleaners 10a, 10b, 10c, 1
It is provided between 0d and AT of the video count system.
In addition to the toner replenishment by R, the toner can be replenished by the patch detection type ATR.

Further, a charge eliminating means (not shown) of the transfer belt 9 is provided near the image transfer portion, and as in the case of the fourth embodiment.
By removing the charge from the transfer belt 9 when the toner density of the patch image is detected, the transfer of the patch image to the transfer belt 9 is prevented. In this case, even if the transfer belt 9 is contaminated by patch images, the fur brush 84 scrapes off the toner during post-rotation after the first image formation, and then the next image formation sequence starts. There is no problem because the recording material P is not soiled by the toner on the back.

Also in this embodiment, similar to the third embodiment, the video count ATR and patch detection ATR are used.
By performing image formation while performing toner density detection and feedback with the algorithm shown in FIGS. 8 to 11 by using the above, it is possible to stably obtain an image of good density even when 100 or more continuous images are formed. .

As described above, according to the third to fifth embodiments, when the operation of the replenishing means for replenishing the toner in the developing device is corrected based on the result of detecting the toner concentration of the developer in the developing device, When the original image density is high when the toner supply amount by video count reaches a certain value during continuous image formation during a predetermined sequence operation depending on the toner replenishment amount by the original image density, or when the original image density is low, Since it is performed when the number of images to be formed reaches a certain number during continuous image formation, toner is satisfactorily replenished during continuous image formation operation to control the toner concentration of the developer in the developing device.
A stable image can always be obtained.

Sixth Embodiment FIG. 14 and FIG. 15 are flowcharts showing an algorithm for toner replenishment in this embodiment.
Shows the case where the number of image formations per original is 100 or less and the feeder is used, and FIG. 15 shows the case where the number of image formations per original is 100 or more.

First, the case where the number of images formed per original is 100 or less will be described with reference to FIG. 15. First, in step S101, the reader scan operation for reading the original is performed along with the image forming start operation. Then, the input image signal from the reader 13 'of FIG. 2 is A / D converted.

Next, in S102, the level of each pixel of the original image information signal is counted, and specifically, the video counter 23 of the video count type ATR 100 counts the clock pulse. In step S103, the toner supply amount per image, that is, the number of rotations of the toner conveying screw 61 of the hopper 6 in FIG. 1 is determined based on the count signal and the correction coefficient. Then, in S104, a latent image is formed, developed to form a toner image, and further transferred if necessary. S10
In step 5, after the formation of one toner image described above and before the formation of the next toner image of the same image, the toner conveying screw is rotated by the number of rotations determined as described above to replenish the developing container 4 with the toner 7. This toner image formation and toner supply are repeated for the number of image formation sheets selected by the operator.

When this is completed (S106), it is determined whether or not the next original is on the feeder (S20).
1). The original is on the feeder and the sum of the number of image formations selected and set by the operator and the number of image formations after the feedback operation for replenishing the toner to the present is 1
If it is 00 or less, the next document is conveyed to the document table (S202), and the operations from S101 onward are continuously performed again.

If the original is not on the feeder, or if the sum of the number of image formations after feedback back is 100 or more, the actual toner density of the developer 5 in the developing device 4 is detected by means such as patch detection in S107. Is measured. Then, based on this, in S108, it is determined whether or not the toner has been over-replenished by the toner replenishing operation so far. If it is determined in S108 that the supply is not excessive, the screw 61 is driven at the required rotation speed in S109,
The insufficient toner is replenished in the developing device 4. And S11
A correction coefficient of the toner replenishment amount is calculated with 0 and is fed back to the next correction of the toner replenishment amount (feedback operation (1)). However, when the proper amount of toner has been replenished, the toner replenishment amount in S109 is zero, and the correction coefficient calculated in S110 is the same as the previous correction coefficient and remains unchanged. If it is determined in S109 that the supply is excessive, S111
Then, the correction coefficient of the toner replenishment amount is calculated and fed back to the next toner replenishment amount correction (feedback operation (2)).

In the above, as in the case of the first embodiment and the like, even when the excessive replenishment was made in the previous image forming step,
Toner is further replenished to the developing device in the next image forming step, but the excessive replenishment is actually a small amount,
There is no abnormally large amount, and it is not true that the toner replenishment amount is exactly the same each time, and there is a variation that is larger or smaller than the target value each time. Even if the toner is further replenished, it is averaged due to the above variations and the like, and when the target value of the further replenishment toner amount is corrected as described above, the toner concentration of the developer is actually short. In the meantime, the toner concentration does not gradually increase and the toner concentration does not gradually increase.

As described above, when 100 or less image forming sheets are continuously image-formed using a feeder or the like, the continuous image forming operation is performed until the number of image forming sheets exceeds 100. If it is determined that the number of sheets exceeds the limit, for example, when replacing the original, the actual toner concentration of the developer in the developing device is measured by means such as patch detection, the video count replenishment amount is corrected, and the next toner replenishment is performed. By feeding back the amount, the image having a stable density can be continuously obtained even if the replenishment amount of the hopper is changed, without substantially reducing the image forming speed.

Further, the number of image formations selected and set is 100.
It is the case of more than one sheet. In this case, when 100 or more images are continuously formed after the feedback operation, the image forming operation is interrupted even during continuous image formation, and the above-described steps S107 to S107 are performed.
Go to S107 'to S111' which is the same as 111, and go to S10
Starting from the toner concentration measuring operation 7 ', it is judged whether or not there is excessive replenishment (S108'), toner replenishment based on toner concentration (S109 '), feedback operation (1) (S1).
10 ') or the feedback operation (2) from S108' (S111 ') to determine the toner replenishment amount per sheet to adjust the image density, and then to S103.
The amount of replenishment per sheet is fed back and the image forming operation is further continuously performed.

As a result, even if the number of images formed is 100 or more, images having a stable density can be continuously obtained with almost no decrease in the image forming speed.

In this embodiment, the feedback operation is performed with 100 or more sheets. However, since the predetermined number is set according to the capacity of the toner hopper, the set number may be set accordingly.

Example 7 In this example, the toner replenishment control method performed in Example 6 was applied to the image forming apparatus shown in FIG. As described above, the image forming apparatus of FIG.
The light source 27 and the photoelectric conversion element 28 forming the toner concentration detection sensor of TR are installed on the downstream side of the image transfer portion facing the transfer drum 50 of the photosensitive drum 1, and the patch detection sensor surface is not polluted and a stable patch image is obtained. The toner density of the image can be read, and when the patch image Q passes through the image transfer portion, the photosensitive drum 16 of the image transfer portion can be read.
The transfer means 93 installed therein is neutralized by the neutralization charger 94 so that the patch image Q is not transferred.

In the present embodiment, while the transfer means 93 is being removed every 100 sheets, the ATR of the video count system and the ATR of the patch detection system are used as in the case of the sixth embodiment, and the number of continuous image formation is reduced. 100 or less when 100 or less
When the number of sheets is equal to or more than the number of sheets, toner density detection and feedback are performed by the algorithms shown in FIGS.
As a result, similarly, an image having a good density can be stably obtained with almost no decrease in image forming speed.

Example 8 In this example, the toner replenishment control method performed in Example 6 was applied to the image forming apparatus shown in FIG.

In the image forming apparatus of FIG. 13, as described above, the toner concentration detection sensors 31a, 31b, 31c, 31d of the patch detection type ATR patch image are transferred to the transfer chargers 8a, 8b, 8c, 8d, respectively. Cleaner 10
It is provided between a, 10b, 10c, and 10d. In addition to the toner replenishment by the video count type ATR, the toner replenishment can be performed by the patch detection type ATR. A charge removing unit (not shown) is provided on the transfer belt 9, and the transfer belt 9 is discharged when the toner density of the patch image is detected, thereby preventing the transfer of the patch image to the transfer belt 9.

Also in this embodiment, as in the case of the seventh embodiment, the static electricity of the transfer belt 9 is removed every 100 sheets, and the video counting system A is used as in the case of the sixth embodiment.
Using ATR of TR and patch detection method, when the number of continuous image formation is 100 or less, or 100 or more, the image formation is performed while toner density detection and feedback are performed by the algorithms shown in FIGS. 14 and 15, respectively. As a result, an image having a good density can be stably obtained with almost no decrease in image forming speed.

As described above, according to the sixth to eighth embodiments, when continuous image formation is performed when the number of sheets exceeds a predetermined number,
By measuring the toner concentration of the developer in the developing device at a predetermined timing and by feeding back to the replenishment amount of the video count, a stable image can be formed even when a large number of continuous images are formed, and the image forming speed is hardly reduced. I got it.

Ninth Embodiment FIG. 16 is a configuration diagram showing a ninth embodiment of the image forming apparatus of the present invention. In this embodiment, in the image forming apparatus of FIG. 13, toner image density detecting sensors 31a, 31b for patch images are provided at the image forming stations Pa, Pb, Pc, Pd.
Instead of providing 31c and 31d, those developing devices 4
Inductance sensors 33a, 33b, 33 that form an ATR of an inductance type in a, 4b, 4c, and 4d.
c and 33d are provided. The other configuration of this embodiment is shown in FIG.
16 is basically the same as that of the image forming apparatus shown in FIG. 16, and the same reference numerals as those in FIG. 16 denote the same members.

As described above, an inductance type ATR is also known in which the toner density is detected by utilizing the change in the apparent magnetic permeability depending on the mixing ratio of the non-magnetic toner of the developer and the magnetic carrier. The method is disadvantageous in that it is susceptible to output fluctuations due to continuous stirring over a long period of time, such as changes in charge amount, fluidity and density of toner, and fluctuations in output due to suspension of stirring. Further, in the video count type ATR, since there are many fluctuation factors such as fluctuations in the toner feed amount from the toner hopper and toner scattering, it is difficult to use them alone as described above.

Therefore, in this embodiment, the toner concentration of the developer is detected and controlled by the video count type ATR, the toner concentration is confirmed at a predetermined timing by the inductance type ATR, and a concentration changing means is further provided. By changing the reference density value when the toner density is controlled by the inductance type ATR, the advantages of the video count and inductance type ATR are utilized to stain the members such as the transfer belt 9 of the image forming apparatus. Toner control can be performed without any need.

The ATR mechanism in this embodiment will be described by taking the first station Pa as an example. FIG. 17 is a block diagram showing the ATR mechanism in this embodiment.

In FIG. 17, an inductance sensor 33a is provided to control the toner concentration of the developer 5 in the developing device 4a by an inductance type ATR, and is a magnetic carrier of the developer 5 and a non-magnetic material. The toner density of the developer 5 is detected by utilizing the apparent change in the magnetic permeability due to the change in the toner mixing ratio. The reference density value is preset in the RAM 102 according to the output of the initial developer (starter), and the toner is replenished by comparing it with the detection signal value.

Further, the video count type ATR including the video counter 23 and the like integrates the output level of the digital image signal for each pixel and predictably supplies toner. According to the video count type ATR, first, the image of the original 11 is read by the CCD 13 constituting the image input system, and the obtained analog image signal is amplified to a predetermined level by the amplifier 34, and the analog-digital converter is used. (A / D converter) The converter 35 converts the digital image signal into, for example, 8-bit (0 to 255 gradations).

The output level of the image signal converted into a digital signal is integrated for each pixel, and this is converted into a video count number by the video counter 23.
Send to PU24. The CPU 24 converts the video count number into a toner replenishment amount and sends it as a toner replenishment signal to the motor drive circuit 26. The motor drive circuit 26 drives the motor 64 for a time corresponding to the toner replenishment signal, rotates the conveying screw 61 of the toner hopper 6 for the above predetermined time, and replenishes the toner 7 from the toner hopper 6 to the developing device 4a in an appropriate amount. The toner concentration of the developer 5 in the developing device 4a is kept constant.

Next, the algorithm for toner replenishment of this embodiment will be described with reference to FIG.

First, in step S101, the image forming operation of each station is started. That is, the first station P
Taking magenta of a as an example, a voltage of -4 to -9 KV is applied to the primary charger 2a which is a corona charger, and the surface of the photosensitive drum 1a is uniformly charged with a charging current of -300 to 900 μA. Then, based on the image signal from the image input system described above, a latent image is formed on the photosensitive drum 1a by the scanning optical device 103 including the polygon mirror 18 and the like. During this period, in S102, the video count number is determined based on the original reading signal in the image input system, and the CPU 24 further converts it into the toner replenishment time.

In S103, the stirring and conveying screw (not shown) in the developing device 4a which started with the image forming operation (see FIG. 2).
The stirring operation by the screws 48, 49) is started, and the output value of the inductance method ATR is detected at a timing when a predetermined time has elapsed, and the RAM 102 is determined in S104.
It is automatically adjusted so as to be converted into the reference signal value of the previous image forming operation stored in. This compensates for the fact that the output fluctuation value due to the compression of the developer, which is caused by the change in leaving the developer, cannot be completely restored.

In the present embodiment, as the developer 5, a toner having an average particle size of 6 to 12 μm in which a pigment is dispersed in a polyester resin and 0.1% or less of titanium dioxide as an external additive is added, and a ferrite magnetic material are used. A carrier having an average particle size of 30 to 70 μm was used.

Next, in S105, an image forming operation (copying) after development and transfer is started, and in S106, toner is replenished between images (paper) based on the video count number. S
If the image formation is completed in 107 and it is completed (Yes), the output is detected by the inductance ATR in S108 to check the toner density, and if there is a difference from the reference signal value, it is based on that. Toner is supplied to restore the standard density.

In S109, the inductance ATR output signal value after the density adjustment is updated as the reference signal value, and the RAM is updated.
It is stored in the memory 102.

As described above, in the present embodiment, the toner replenishment control is performed by the video count type ATR, and the toner concentration is confirmed by the inductance type ATR at a predetermined timing to check the inductance type AT.
The toner is replenished by R for correction, and the reference density value when toner is replenished by the inductance ATR is updated and corrected, so that the advantages of each ATR can be further utilized regardless of the restrictions on the apparatus configuration. It became possible to control the toner density stably.

In the above, the toner is replenished every time one image is formed. However, the toner may be replenished collectively when a certain number of image formations or a certain number of video counts are reached. According to this, the toner replenishment error can be made less likely to enter than when a small amount of toner is replenished, so that replenishment accuracy can be further improved.

Example 10 As shown in FIG. 19, the output value of the ATR output of the inductance type shifts depending on the humidity of the surrounding environment. Therefore, in this embodiment, a humidity sensor is provided, and when the inductance ATR output value is adjusted before the image forming operation, the adjustment is performed in consideration of the relationship between the humidity and the inductance output.

For example, referring to FIG. 19, the humidity ranges from 20% to 60%.
A 40% change in% changes the inductance output from 3V to 2.15V by 0.75V, so the humidity correction value is 0.75 / 40≈0.019V /%. Therefore, if the humidity at the time of adjusting the inductance output value is 40% lower than that at the time of the previous memory, the output value is adjusted and set so that the output value becomes 0.75V higher.

In this embodiment, when the inductance ATR output value is adjusted, the AT of the humidity and inductance type is adjusted.
Since the inductance ATR output value is adjusted in consideration of the R output relationship, the toner replenishment accuracy is further improved.

As described above, according to the ninth to tenth embodiments, the video count type ATR, the inductance type ATR, and the means for changing the reference density value when performing the toner density control by the inductance ATR are provided. Since it is provided, it is possible to control the toner density in a stable manner by further utilizing the advantages of each ATR, regardless of the restrictions on the apparatus configuration.

[0128]

As described above, according to the present invention,
The actual toner replenishing amount of the toner replenishing means for replenishing the toner into the developing device is obtained in advance, the toner replenishing means is operated using the toner replenishing amount and the image information signal, and the toner concentration detecting means develops. Since the toner concentration of the developer in the container is detected and the operation of the toner replenishing means is corrected, the toner concentration of the developer in the developer can be controlled with high accuracy, and images with stable density can be continuously obtained. It became so.

According to another aspect of the present invention, when the operation of the replenishing means for replenishing the toner in the developing device is corrected based on the result of detecting the toner concentration of the developer in the developing device, the toner based on the original image density is used. During a predetermined sequence operation depending on the replenishment amount, or when the document image density is low, the toner replenishment amount by video count reaches a certain value during continuous image formation, and when the document image density is high, the image is generated during continuous image formation. Since it is performed when the number of formed sheets reaches a certain number,
Even during the continuous image forming operation, the toner concentration is controlled well by supplying the toner well, and the stable image can be obtained at all times.

According to still another aspect of the present invention, when continuous image formation is performed over a predetermined number of sheets, the toner concentration of the developer in the developing device is measured at a predetermined timing, and the video count type ATR is used. By feeding back the toner replenishment by the method described above, a stable image can be obtained even when a large number of continuous images are formed with almost no decrease in the image forming speed.

According to still another aspect of the present invention, the toner replenishment control by the video count type ATR is performed, and the toner concentration is confirmed by the inductance type ATR at a predetermined timing to confirm the inductance type AT.
The toner is replenished by R for correction, and the reference density value when toner is replenished by the inductance ATR is updated and corrected, so that the advantages of each ATR can be further utilized regardless of the restrictions on the apparatus configuration. It became possible to control the toner density stably.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an image forming apparatus of the present invention.

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

FIG. 3 is an explanatory diagram showing an example of a counting method of density information of an image information signal in a video counting system ATR provided in the image forming apparatus of FIG.

4 is a flowchart showing an algorithm of toner supply control in the image forming apparatus of FIG.

FIG. 5 is a sectional view showing a developing device in Embodiment 2 of the image forming apparatus of the invention.

FIG. 6 is a block diagram showing a concept of toner replenishment by a video count type ATR, which is performed in a conventional digital image forming apparatus.

FIG. 7 is a graph showing toner replenishment characteristics of the toner hopper attached to the developing device in Embodiment 3 of the image forming apparatus of the present invention.

FIG. 8 is a part of a flowchart showing an algorithm of toner replenishment control in Embodiment 3 of the image forming apparatus of the invention.

FIG. 9 is another part of the flowchart.

FIG. 10 is still another part of the flowchart.

FIG. 11 is still another part of the flowchart.

FIG. 12 is a configuration diagram showing an embodiment 4 of the image forming apparatus of the invention.

FIG. 13 is a configuration diagram showing a fifth embodiment of the image forming apparatus of the invention.

FIG. 14 is a part of a flowchart showing an algorithm of toner replenishment control in Embodiment 6 of the image forming apparatus of the invention.

FIG. 15 is another part of the flowchart.

FIG. 16 is a configuration diagram showing an embodiment 9 of the image forming apparatus of the invention.

17 is a block diagram showing an ATR mechanism installed in the image forming apparatus of FIG.

18 is a flowchart showing an algorithm of toner supply control in the image forming apparatus of FIG.

FIG. 19 is a graph showing humidity-dependent output characteristics of the inductance type ATR used in Example 10 of the image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 1a-1d Photosensitive drum 4 Developing device 4a-4d Developing device 5 Developer 6 Toner hopper 7 Toner 13 Imaging device 13 'Reader 23 Video counter 24 CPU 27 Light source 28 Photoelectric conversion device 31a-31d Density sensor 33a-33d Inductance Sensor 61 Toner transport screw 100 Video counter system ATR 101 Patch detection system ATR

Claims (8)

[Claims] 1. A latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, a developing means for developing the electrostatic latent image with a two-component developer, and a toner for the developing means. A toner replenishing unit for replenishing the toner, a concentration detecting unit for detecting the toner concentration of the developer, and a replenishing amount detecting unit for detecting the toner replenishing amount by the replenishing unit. The toner replenishing amount by the replenishing device is detected, the replenishing device is operated based on the detected toner replenishing amount and the image information signal, and the replenishing device is based on the toner density detected by the density detecting device. An image forming apparatus that corrects the operation of the image forming apparatus. 2. A latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, a developing means for developing the electrostatic latent image with a two-component developer, and a toner for the developing means. A toner replenishing means for replenishing the toner, and a density detecting means for detecting the toner density of the developer. The replenishing means is operated based on the image forming information signal, and based on the toner density detected by the detecting means. In an image forming apparatus that corrects the operation of the replenishing means, a predetermined sequence portion in an image forming sequence is being executed according to the replenishing amount based on the image information signal, or the replenishing amount based on the image information signal is continuous. An image forming apparatus, which corrects the operation of the replenishing means when a predetermined number of sheets are reached during image formation or when a document that is expected to reach a certain number is replaced. 3. The image forming apparatus according to claim 2, wherein the predetermined sequence portion is a post-rotation at the end of image formation or a pre-rotation at the start of image formation. 4. A latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, a developing means for developing the electrostatic latent image with a two-component developer, and a toner for the developing means. A toner replenishing means for replenishing the toner, and a density detecting means for detecting the toner density of the developer. The replenishing means is operated based on the image forming information signal, and based on the toner density detected by the detecting means. In the image forming apparatus for correcting the operation of the replenishing means, the operation of the replenishing means is corrected during execution of a predetermined sequence portion in the image forming sequence of the image or at a predetermined timing. Image forming apparatus. 5. The image forming apparatus according to claim 4, wherein the predetermined sequence portion is during post-rotation at the end of image formation. 6. The image forming apparatus according to claim 5, wherein the predetermined timing is when image formation has reached a predetermined number of sheets and a document is replaced. 7. A latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, a developing means for developing the electrostatic latent image with a two-component developer, and a toner for the developing means. A toner replenishing means for replenishing the toner, and a density detecting means for detecting the toner concentration of the developer based on a change in magnetic permeability. The replenishing means is operated based on the image forming information signal, and the detection is performed at a predetermined timing. In the image forming apparatus, the toner concentration of the developer is detected by the means, and the replenishing means is operated based on the toner concentration, the toner concentration of the developer after the replenishing means is operated based on the toner concentration is detected, and An image forming apparatus, wherein a reference value when the replenishing means is operated based on a toner concentration is changed to a detection value thereof. 8. The image forming apparatus according to claim 7, wherein the reference value is changed in consideration of humidity.