JPH11295976A - Density controller for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically replace new toner for deteriorated toner at appropriate time by comparing the density of a developed real image with previously predicted limit density. SOLUTION: The image density is detected by an image density detecting device 134 composed of a capacitor 132 and a counter. A controller 114 inspects the deterioration state of the toner retaining in a developing device main body based on a detection signal by the device 134 at the intervals of the acting time of a rotary developing device 42, and performs the replacement of the toner as necessary. The previously predicted limit image density is stored in the ROM 122 of the controller 114. When the integrated value of the image density within specified acting time is under the limit image density, the controller 114 judges that the deterioration of the toner is accelerated, and designates to perform action that one part or all of the toner in the developing device main body is discharged and the toner is supplied from a toner cartridge by nearly the same quantity as the quantity of the discharged toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a developing device for containing a two-component developer containing at least a carrier and a toner.
The present invention relates to a density control device for controlling the density of a developed image in an image forming apparatus having a developing unit for developing a latent image written on an image carrier.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus in which a photosensitive drum is charged and exposed, toner contained in a developing unit is charged to a carrier, taken out by a developing roll, and developed by applying toner to the photosensitive drum. In addition,
The carrier is collected in the developing device. To prevent a decrease in density due to a decrease in toner or the like, a so-called patch or band-like density pattern is periodically formed in a non-image area of the photosensitive drum, and the patch or the density pattern is read by a densitometer, and I try to compare with the value.

When the value is lower than the reference value, the density is restored by additionally supplying new toner (for example, see Japanese Patent Application Laid-Open No. 4-39679).

[0004] Further, although similar to the above-mentioned prior art in that a patch or a density pattern is read by a densitometer and compared with a reference value, the subsequent control is not to supply toner but to a photosensitive drum. Output during image writing (eg current)
There is also disclosed a technique for preventing a decrease in concentration by increasing the density (see, for example, JP-A-1-295281).

[0005] By using the above-mentioned means, it is possible to recover the concentration temporarily.

[0006]

However, when a character or the like is recorded, that is, when an image in which an area where toner is actually applied is very small in the image recording area is continuously output, the toner and the carrier are charged. May increase or decrease at an accelerating rate. To explain this in detail, if the time during which the toner contained in the developer (toner and carrier) stays in the developer becomes longer, the amount of charge rises abnormally due to the stirring action, and thereafter, it becomes difficult to charge. After that, a phenomenon that abnormal charge reduction occurs may occur.

Here, if the development is performed when the charge amount is abnormally increased, the carrier may be developed together with the toner during the development. Also, aggregation between toners occurs,
This aggregated toner may also be developed.

In such a state, for example, when the image is transferred to an intermediate transfer member, a color point is generated, and the image quality is reduced. If there is no transfer, color points are missing. In addition, toner whose charge amount has abnormally increased (highly charged toner)
And the toner whose charge amount is abnormally reduced (low-charged toner), the density unevenness occurs in the image after the transfer process, which also causes the deterioration of the image quality.

As described above, the density unevenness that occurs after the transfer cannot be detected by forming a patch or a density pattern on the photosensitive drum and measuring the density as in the above-described prior art. No measures have been taken.

In view of the above facts, the present invention is directed to a density of an image forming apparatus which can automatically replace a deteriorated toner with a new toner at an appropriate time based on an appropriate parameter caused by density unevenness. The aim is to obtain a control device.

[0011]

According to a first aspect of the present invention, there is provided a developing device for storing a two-component developer containing at least a carrier and a toner, and a latent image written on an image carrier is visualized. An image forming apparatus having a developing unit for performing a developing operation, wherein the density control unit controls a density of the visualized image, and a developing operation integrating unit that integrates a time during which the developing unit operates; Image density integrating means for integrating the density of a visualized real image for the entire image area written to the image carrier during the operating time of the developing means, and an image integrated by the image density integrating means. Comparing means for comparing the density with a predicted critical density; and determining whether the image density integrated by the image density integrating means by the comparing means is lower than the predicted critical density. To have a toner replacement means for supplying a predetermined amount of discharging the toner, and the toner of approximately the same amount in the developing device.

According to the first aspect of the present invention, it is possible to recognize the actual amount of toner used during a predetermined operation time of the developing means by integrating the image density.

The reason that the amount of toner used is small despite the operation of the developing means is that the toner remains in the developing device for a long time. During the long-term stay, the charge amount of the toner abnormally increases due to the stirring action. Also,
Thereafter, the charge amount is abnormally reduced. In any case, the high-charged toner, the low-charged toner, or a mixture of these, causes the occurrence of density unevenness, for example, on the intermediate transfer member or the recording paper after development. Please refer to the subject).

Therefore, the integrated image density is compared with a pre-estimated limit density by comparing means, and the comparison result indicates that the integrated image density is lower than the pre-estimated limit density. Is determined, the deterioration of the toner is determined, the toner remaining in the developing device is discharged by the replacement means, and substantially the same amount of toner is supplied.

Thus, the newly supplied toner has an appropriate charge amount and can eliminate density unevenness.

That is, as long as the density unevenness is measured by a density pattern or the like on the image carrier, the density unevenness as a final image which could not be recognized can be eliminated.
Deterioration in image quality can be reliably suppressed.

According to a second aspect of the present invention, in the first aspect of the invention, apart from the operation time of the developing device for integrating the image density, the comparison means is shorter than the operation time. Setting means for setting the interval time of
It is further characterized by having.

According to the invention described in claim 2, for example,
Assuming that the operation time of the developing device for integrating the image density is A, the intermediate point where the time A has elapsed is the start of the next time A. As a result, the interval at which the comparison is performed by the comparison means is A / 2. In this way, the toners to be compared are compared in a partially overlapped state, and more accurate monitoring can be performed.

According to a third aspect of the present invention, in the first or second aspect of the present invention, after the replacement of the toner by the toner replacement means, the prohibiting means for prohibiting the replacement of the next toner for a predetermined time, It is further characterized by having.

According to the third aspect of the invention, the toner replacement control based on the density determination for a predetermined time, that is, once to several times, is prohibited by the prohibition means. After replacing the toner,
During a certain period (operating time A of the developing device), the newly supplied toner remains sufficiently, and it is not necessary to replace the toner even if the image density is low. Can be prevented.

According to a fourth aspect of the present invention, the amount of toner discharged and supplied, or the operating time, based on the absolute amount of image density compared by the comparing means according to the second or third aspect of the present invention. Or changing means for changing at least one of the prohibition times prohibited by the prohibition means.

According to the fourth aspect of the present invention, as a result of the comparison by the comparing means, even if the density is of the acceptable level, the density is determined depending on whether the density is close to or far from the limit density predicted in advance. Different levels when rejected. Conversely, at the reject level, the reject level differs depending on whether the density is close to or lower than the limit density. Therefore, at least one of the discharge amount and the supply amount of the toner, the operation time, or the prohibition time prohibited by the prohibition unit is changed based on the absolute amount of the image density.

For example, when the density is judged to be acceptable at a density close to the critical density, the rejection level is determined in a state close to the critical density by shortening the operation time and making a pass / fail decision with a fine stance. Can be.

For example, when the density is rejected at a density far from the limit density, the amount of the discharged toner and the amount of the supplied toner can be increased to further reduce the deteriorated developer in the developer.

According to a fifth aspect of the present invention, there is provided the method according to any one of the first to fourth aspects.
5. The image forming apparatus according to claim 1, wherein the developing unit of the image forming apparatus includes at least two color developing units, and each developing unit is independently controlled. The density control device for an image forming apparatus according to any one of claims 1 to 4, wherein:

According to the fifth aspect of the present invention, the present invention is applicable even if the present image forming apparatus is, for example, a color image forming apparatus. And control.

[0027] According to a sixth aspect of the present invention, in the first aspect of the present invention, the image density is a value of a visualized real image with respect to the total number of pixels in the image area. It is characterized by being obtained based on the ratio of the number of pixels.

According to the present invention, an accurate image density can be obtained by obtaining the image density by the number of pixels. That is, if the total number of pixels in the image area is Pma
x (typically tens of millions of pixels) and the pixel developed as an image is Pg, the image density Rg (%) is (Pg / Pmax
) × 100.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the image density is obtained by obtaining an image signal when writing an image on the image carrier. Is obtained based on the ratio of the current value based on the image signal to the maximum value of the current value of the current value.

An image is recorded based on a predetermined image signal. In order to output this image signal, a current flows.
Therefore, the image density can be obtained by integrating the current values.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects of the present invention, the operating time of the developing means is a rotational driving time of the developing device. I have.

According to the eighth aspect of the invention, when the developing means is operating, it is always when the developing device is rotating, and the rotational driving time may be set as the operating time.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the image forming apparatus converts the actual image visualized on the image carrier into an actual image. The image forming apparatus further includes a transfer unit that transfers the image to the loop-shaped intermediate transfer body that is repeatedly contacted with the image carrier, wherein the operation time of the developing unit is determined based on the number of rotations of the intermediate transfer body. I have.

According to the ninth aspect of the present invention, for example,
When a color image is transferred to a recording paper, a plurality of colors (three colors or three colors + black) are sequentially transferred onto the intermediate transfer body in a superimposed manner, and thereafter, are collectively transferred to the recording paper. In such a configuration, the number of rotations of the intermediate transfer member when the corresponding color is transferred to the intermediate transfer member can be used as the operation time of the corresponding color developing device.

The tenth aspect of the present invention is the first aspect.
10. The image forming apparatus according to claim 1, wherein the image bearing member is a photosensitive member, and the photosensitive member is charged by a charging roll, and toner is adhered by a potential difference between the photosensitive member and a developing roll of a developing device. The toner is discharged by the replacement means by a potential difference between the surface potential of the photoconductor, which has not been neutralized after being charged by the charging roll, and the developing roll of the developing device to which the voltage is applied. It is characterized by development.

According to the tenth aspect of the present invention,
The image bearing member is a photosensitive member, and the photosensitive member is charged to create a potential difference between the photosensitive member and a developing roll of a developing device. This potential difference causes the toner to adhere to the photoconductor.

Therefore, when the toner is discharged by the replacement means, it is possible to utilize the carry-out of the toner to the photosensitive member due to the potential difference. In other words, the toner can be discharged by the same operation as the normal image formation, so that it is not necessary to provide a special toner discharging mechanism.

The eleventh aspect of the present invention relates to the first aspect.
11. The image forming apparatus according to claim 1, wherein the image bearing member is a photosensitive member, and the photosensitive member is charged by a charging roll, and toner is adhered by a potential difference between the developing roll of the developing device. The development is performed by a potential difference between a developing roll of a developing device to which a surface electrode voltage of an area where the image is removed by the image writing unit after being charged by the charging roll is applied. The image to be performed is a striped image having a predetermined interval and a predetermined width.

According to the eleventh aspect of the present invention, the image at the time of discharging the toner is a striped image having a predetermined interval and a predetermined width, so that the potential of both the image portion and the non-image portion can be reduced. The peak value can be overshoot, the ratio of the deteriorated developer in the discharged developer increases, and the charging state during the subsequent development can be further stabilized.

According to a twelfth aspect of the present invention, in the first aspect,
The invention according to any one of claims 11 to 11, further comprising a selection unit for selecting whether to perform or not to perform the toner replacement.

According to the twelfth aspect of the present invention, the replacement of the toner promotes the consumption of the toner. Therefore, the execution or non-execution of the toner replacement can be selected so as to be executed only when the priority is given to the image quality. I did it.

According to a thirteenth aspect of the present invention, in the first aspect,
13. The method according to claim 12, wherein after discharging the toner and supplying the toner, a predetermined image is formed on the photosensitive member before the next image formation is performed, and the image density is detected. If the image density is not within the set range, a predetermined amount of toner is discharged or supplied so as to fall within the set range.

According to the thirteenth aspect of the present invention, even if the toner is replaced (discharged and supplied), the density may still be reduced (density unevenness). After that, before forming the next image, a predetermined image is formed on the photoreceptor, and the image density is detected by the detecting means. If necessary, toner discharge or toner supply is repeated based on the detected density.
Thereby, an appropriate concentration can be obtained.

[0044]

FIG. 1 shows an image forming apparatus 10 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 10 is covered with a casing 12 and formed in a substantially box shape.

Below the image forming apparatus 10, a plurality of paper trays 16 (three paper trays 16A, 16B and 16C are shown in the present embodiment) are provided. Each of the sheet trays 16A, 16B, and 16C is provided with sheets 18 having different sizes such as, for example, B5 size, B4 size, A4 size, and A3 size. A half-moon roller 20 is provided in the vicinity of the paper discharge section of the paper tray 16, and the paper 1 is transferred from the designated paper tray 16.
8 are fed one by one, and are transported in a predetermined direction by a plurality of transport roller pairs 22. When the image forming apparatus 10 instructs image formation on both sides (front and back) of the sheet 18, the sheet 18 on which image formation on the front side has been completed is performed.
Is provided with a sheet reversing unit 17 for reversing the front and back.

On one side of the image forming apparatus 10, a manual feed tray 24 into which paper 18 is manually inserted as necessary.
Are arranged. A half-moon roller 20 is provided near the paper discharge section of the manual feed tray 24 in the same manner as the above-mentioned paper tray 16, so that the paper 18 can be sent out one by one.

The fixing device 1 is provided above the image forming apparatus 10.
4 is provided with a discharge tray 26 from which the sheet 18 on which a desired image is fixed is discharged.

Paper tray 16 in image forming apparatus 10
On the upper part, a photoreceptor 30 as an image carrier, a charger 38 disposed around the photoreceptor 30, a belt-shaped intermediate transfer member 42, a photoreceptor cleaner 44, and an unillustrated static elimination lamp are provided. Charging device 128, rotary developing device 40, and image data obtained by reading an original with a scanner and performing various types of image processing (the image forming apparatus 10 in the present embodiment is intended for a color image, so 4 for yellow, magenta, cyan, and black
An optical scanning device 32 that irradiates a light beam to the photosensitive member 30 as an image carrier based on the
And an image forming apparatus 28 including the fixing device 14 for fixing a desired image on the paper 18.

The light scanning device 32 includes a light source, a rotating polygon mirror 3
4. fθ lens, cylindrical mirror, reflection mirror 3
6 and the like. A laser beam emitted from a light source (not shown) is deflected by a rotating polygon mirror 34 and fθ lens, cylindrical mirror, reflection mirror 36
Irradiation is performed on the photoreceptor 30 via the like.

The photosensitive member 30 rotates at a constant speed in the direction of arrow A shown in FIG. The charging member 38 negatively charges the photoconductor 30 uniformly. The rotary developing device 40 includes four color toners 46Y of yellow, magenta, cyan, and black.
46M, 46C and 46Bk are supplied. The intermediate transfer body 42 is wound around a plurality of rollers 48, and the rotation of the rollers 48 causes an arrow B shown in FIG.
Move at a constant speed in the direction. Photoreceptor cleaner 44
Removes toner remaining on the photoreceptor 30 without being transferred to the intermediate transfer body 42. Further, the charge removing lamp removes the charge of the photosensitive member 30 after the residual toner is removed by the photosensitive member cleaner 44.

Further, around the intermediate transfer member 42, an image detection sensor 51 and an intermediate transfer member cleaner 50 are provided. The image detection sensor 51 is provided upstream of the transfer unit 52 in the rotation direction of the intermediate transfer body 42, and detects the presence or absence of a toner image formed on the intermediate transfer body 42. The intermediate transfer body cleaner 50 is provided downstream of the transfer unit 52 in the rotation direction of the intermediate transfer body 42, and after the transfer of the toner image from the intermediate transfer body 42 to the sheet 18 is completed, the intermediate transfer body 42 The toner remaining on the surface is removed.

The photosensitive member 30 rotating in the direction of arrow A is uniformly negatively charged by the charger 38, and
First, a first-color black latent image is formed on the photoreceptor 30 by the laser light emitted from the photoreceptor 2. This latent image is developed with black toner by the black developing device of the rotary developing device 40. The developed black toner image is transferred to the intermediate transfer member 42.
Is transferred to The toner remaining on the photoconductor 30 without being transferred is removed by a cleaner (not shown), and the photoconductor 30 is discharged by a discharge lamp.

Then, the photosensitive member 30 is uniformly negatively charged again by the charger 38, and the second color yellow image is formed. In this manner, a total of four color toner images are sequentially transferred to the intermediate transfer member 42 from the third color magenta to the fourth color cyan (primary transfer). When the transfer of the four color toner images to the intermediate transfer member 42 is completed, a final toner image is formed on the surface of the intermediate transfer member 42.

Below the intermediate transfer member 42, the intermediate transfer member 4
A transfer section 52 for transferring the final toner image formed on the sheet 2 to the sheet 18 is provided. The paper 18 is transported from the paper tray 16 provided with the paper 18 of the designated size to the transfer unit 52 by the transport roller pair 22 as described above, and the image on the intermediate transfer body 42 is transferred to the paper 18. (Secondary transfer).

The fixing device 14 is provided downstream of the transfer unit 52 in the transport direction of the sheet 18. In the fixing device 14, a predetermined image is formed on the sheet 18 by performing a fixing process on the sheet 34 onto which the final toner image has been transferred.

FIG. 2 shows the developing device main bodies 40Y, 40M, 40C, 4C of the respective colors provided in the rotary developing device 40.
0k (FIG. 2 shows the developing device main body 40C)
It is shown.

The developing device main body 40C contains the toner 46C.
And a carrier (not shown) constituting a two-component developer. A pair of agitating / conveying rolls 100 are arranged in the developing device main body 40C, and are configured to convey the two-component developer in the developing device main body 40C toward the developing roll 102 while agitating.

In the vicinity of the peripheral surface of the developing roll 102, a layer thickness limiting plate 104 is provided.
The amount of toner magnetically attracted to the toner is limited.

The toner 46C is supplied to the toner cartridge 10
6 and is sequentially sent to the developing device main body 40C via the guide path 108. Also,
A toner supply pipe 110 is provided adjacent to the toner cartridge 106, and a toner supply roll 112 is detachably mounted on the toner supply pipe 110.

That is, when the amount of toner in the toner cartridge 106 is reduced or exhausted, the toner 46C can be supplied to the toner cartridge 106 by loading the toner supply roll 112 into the toner supply pipe 110. It has a structure.

FIG. 3 is a control block diagram of the image forming apparatus 10 according to the present embodiment.

The operation of each section is controlled by the controller 114. The controller 114 includes a microcomputer 116. The microcomputer 116 includes a CPU 118, a RAM 120,
A ROM 122, an input / output device (I / O) 124, and a bus 12 such as a data bus or a control bus for connecting these components;
6.

The I / O 124 includes a charging device 1 including an optical scanning device 32, a charging member 38, a photosensitive member cleaner 44, and the like.
28 and each of the rotary developing devices 40 are connected, and operate based on a control signal from the controller 114. Further, the I / O 124 is connected to a transport device 130 that controls a transport system (rotation driving of the photoconductor 30, transport of the intermediate transfer body 42, transport of the sheet 18, rotation of the fixing device 14). Note that a high-voltage power supply 125 supplies a high-voltage power to the optical scanning device 32, the charging device 128, the rotary developing device 40, and the fixing device 14.

The detection of the image density is performed by the image density detecting device 1 comprising a capacitor 132 and a counter (not shown).
34.

The capacitor 132 stores a current of an ON signal at the time of writing an image in the optical scanning device 32 as a charge, and when the charge reaches a predetermined amount, sends a signal to a counter to discharge the stored charge. The counter accumulates this signal. Also,
The controller 114 counts the rotational drive time of the developing roll 102 provided on each of the developing device main bodies 40C, 40M, 40Y, and 40k in the rotary developing device 40, and calculates the operation time of the rotary developing device 40. .

Here, in the controller 114, at predetermined operation time intervals of the rotary developing device 40, based on the detection signal from the image density detecting device 134, etc.
The deterioration state of the toner 46C (46M, 46Y, 46k) staying in the toner main body 40C (40M, 40Y, 40k) is inspected, and if necessary, the developing device main body 40C (40M, 40k) is checked.
(Y, 40k).

That is, the ROM 1 of the controller 114
22 stores a predicted limit image density in advance, and the controller 114 promotes the deterioration of the toner when the integrated value of the image density within a predetermined operation time is lower than the limit image density. Is determined, the part of or all of the toner in the developing device main body 40C (40M, 40Y, 40k) is discharged, and an amount of toner substantially equal to the discharged toner amount is supplied from the toner cartridge 106. It is designed to be instructed.

In the present embodiment, the toner is discharged from the photosensitive member 30 based on a predetermined image signal in the same manner as in actual development. The image based on the image signal at this time is a striped image having a predetermined interval and a predetermined width (see FIG. 8).

FIG. 4 is a characteristic diagram showing the relationship between the image density and the number of missing images, and it is known that the lower the image density, the greater the number of missing images. This means that the amount of toner used within a predetermined operation time is extremely small, and the amount of toner 46C
(46M, 46Y, 46k) are the developing device main body 40C (40
M, 40Y, 40k).

Further, the occurrence of the missing is caused by the toner 46C.
(46M, 46Y, 46k).

FIG. 5 shows a toner charge amount and a toner number distribution characteristic for each charge amount.

In FIG. 5, a characteristic line A indicates a normal toner, and in the normal state, a characteristic B indicates that the toner having a high charge amount tends to increase (first toner deterioration).
The characteristic C has a tendency to be dispersed from a toner having a low charge amount to a toner having a high charge amount (second stage).

In any case, if the charge amount is not appropriate,
The amount of toner 46C (46M, 46Y, 46k) adhering to the photoreceptor 30 during development increases or decreases, resulting in uneven density.

Therefore, in the present embodiment, the toner 46C (46
M, 46Y, and 46k) are replaced beforehand to suppress the occurrence of density unevenness.

The operation of the present embodiment will be described below with reference to the flowchart of FIG. 6 and the time chart of FIG.

In step 200, first, the counter, timer t ₁ and average density Ms of the image density detecting device 134 are cleared (initial setting).

In the next step 202, the timer t ₁ is incremented. Next, in step 204, it is determined whether or not the timer t ₁ has reached a predetermined time T. This predetermined time T is 1/1 of a predetermined operation time of the corresponding color developing device in the rotary developing device 4 for integrating the image density.
Equivalent to 2.

If a negative determination is made in step 204, the process returns to step 202,
By repeating step 04, the timer is counted.
If an affirmative determination is made in step 204, that is, if it is determined that the timer t ₁ has reached T, the process proceeds to step 206, where the integrated value of the counter of the image density detecting device 134 is read. From the average density Me ₁ . The average density Me ₁ is an integrated value during a half of a predetermined operation time of the corresponding color developing device in the rotary developing device 40.

In the next step 210, the timer t ₁ is cleared, and the routine proceeds to step 212. Step 20 above
Steps 0 to 210 are initial operations and are performed only at the start of control, for example, after power-on.

At step 212, the timer t ₁ is incremented. Then, at step 214, it is determined whether or not the timer t ₁ has reached a predetermined time T. The predetermined time T corresponds to half the predetermined operation time of the corresponding color developing device in the rotary developing device 40 for integrating the image density.

If a negative determination is made in step 214, the process returns to step 212,
By repeating step 14, the timer is counted.
If an affirmative determination is made in step 214, that is, if it is determined that the timer t ₁ has reached T, the process proceeds to step 216 to read a signal (charge amount of the capacitor 132) from the image density detecting device 134, and then in step 218 The average density Me ₂ is calculated from the charge amount of this capacitor. The average density Me ₂ is determined by a predetermined rotary developing device 4.
It is an integrated value during 1/2 of the operation time of 0.

In the next step 220, the average density Me ₁ of the _first half of the predetermined operation time and the average density Me _{2 of the second} half are added, and the predetermined color developing device of the rotary developing device 40 is added. The average density Ms during the operation time is determined.

In the next step 222, the average density Me ₂ , which was the average density of the latter half, is replaced with the average density Me ₁ in order to obtain the average density of the _first half of the next time.
Migrate with.

In step 224, a double value (hereinafter, simply referred to as a critical average density) M _{L of} the critical average density predicted in advance is used.
Is read, and in step 226, the limit average density ML is compared with the average density Ms.

If it is determined in step 226 that M _L <Ms, it is determined that there is no deterioration of the toner.
After clearing the timer t ₁ is shifted to 28, step 2
The process proceeds to step 12 and the above steps are repeated.

In step 226, M _L ≧ M
s, the charge amount of the toner is high or the distribution is expanded, and it is determined that deterioration has occurred.
Then, the process proceeds to 30 to issue a toner replacement operation instruction.

When there is an instruction for the toner replacement operation,
The controller reads a predetermined image signal (in the present embodiment, a striped image having a predetermined interval and a predetermined width), and performs a normal developing operation based on the image signal.
As a result, the toner adheres to the photoconductor 30,
The toner can be discharged from the developing device main body 40C (40M, 40Y, 40k). The toner attached to the photoconductor 30 can be discarded by using a cleaning mechanism of the photoconductor 30. The adhering portion of the intermediate transfer member can be discarded by using a cleaning mechanism for the intermediate transfer member.

Next, based on the image signals, the toner cartridge 1 supplies substantially the same amount of toner as the amount of toner taken out from the developing device main body 40C (40M, 40Y, 40k).
06, the operation based on the toner replacement operation instruction in step 230 of FIG. 6 is completed.

[0089] In the next step 232, after storing the limit mean density M _L to the average density of Me _1, the process proceeds to step 228. As a result, in the next average density determination, M _L
<Since the Ms = Me ₁ + Me _2, during the advance the rotary developing device 40 of the corresponding-color development device operating time (double T) is
The toner replacement operation can be prohibited.

Thus, after the toner replacement operation is performed once, while the replacement is not required (twice T), the toner replacement operation is prohibited, and the toner deterioration determination can be performed with a fineness every time T. it can.

Although the description in the above flowchart has been omitted, the image density is measured after the toner replacement during the toner replacement operation (in the case of the present embodiment, it is possible to use a striped image). )), As a result of this measurement,
If the image density does not reach the predetermined density range, the method may include discharging or supplying toner until the image density falls within the predetermined density range.

As described above, in the present embodiment, the operation time of the corresponding color developing device in the rotary developing device 40 is determined in advance, and during this operation time, images having a low image density are continuously processed. Accordingly, in order to suppress density unevenness caused by deterioration of the toner staying in the developing device main body for a long time, the integrated image density during the predetermined operation time and the previously estimated limit average density are determined for a predetermined time (the Since the determination is made every） of the operation time, the deterioration of the toner can be quickly recognized. Further, when the toner deterioration is recognized, the toner in the developing device main body is discharged, and the same amount of toner as the discharged toner is supplied, so that the subsequent uneven density can be suppressed.

In the present embodiment, the time image density at which the image density is compared with the limit average density is set to の of the time required to integrate the image density, but the determination interval may be further narrowed. . Further, the time may be the same. Further, the replacement amount of the toner may be changed based on the integrated image density. Further, the next determination time may be changed based on the integrated image density. Further, the prohibition time after the toner replacement operation may be changed based on the integrated image density.

In the present embodiment, an apparatus for forming a color image has been described as an example. However, an apparatus for forming a monochrome image is not limited as long as it is an apparatus for forming an image using toner. Absent.

Further, in the present embodiment, as the image density detecting device, the current value based on the image signal is obtained from the charge amount of the capacitor for charging, but the number of pixels obtained based on the image signal may be counted. .

The operating time of the corresponding color developing device in the rotary developing device 40 is defined as the rotational driving time of the corresponding color developing device in the rotary developing device 40. , Or from the number of output sheets 15.

Further, the operation time of the corresponding color developing device in the rotary developing device 40 may be obtained from the voltage application time of the transfer device 52 for the corresponding color.

Further, the toner is discharged in the toner replacing operation by developing based on a predetermined image signal of a stripe pattern. Then, the potential difference between the surface potential that has not been neutralized and the developing roll to which the voltage is applied may be developed.

[0099] Further, in this embodiment, by setting the 0 to M _L, so does not become Ms> M _L, it can be set not to implement the toner replacement.

Further, since independent control is performed for each color, the limit image density can be set to an appropriate value for each of the CMYk colors. In addition, replacing unwanted colors may be set to 0 M _L.

[0101]

As described above, the density control device of the image forming apparatus according to the present invention automatically replaces deteriorated toner with new toner at an appropriate time based on an appropriate parameter caused by density unevenness. It has an excellent effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment.

FIG. 2 is an enlarged view around a developing device main body.

FIG. 3 is a control block diagram of the image forming apparatus according to the embodiment.

FIG. 4 is a characteristic diagram showing a relationship between an image density and the number of occurrences of missing images.

FIG. 5 is a characteristic diagram illustrating a toner charge amount distribution in a normal state, an abnormal initial stage, and an abnormal end stage.

FIG. 6 is a control flowchart for a toner deterioration inspection according to the embodiment.

FIG. 7 is a time chart of image storage and determination.

FIG. 8 is a schematic diagram showing a relationship between an actual image at the time of toner discharge and an image signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image forming apparatus 40 Rotary developing device 40Y, 40M, 40C, 40k Developing device main body 46Y, 46M, 46C, 46k Toner 114 Controller 132 Capacitor 134 Image density detecting device

Continued on the front page (72) Inventor Yusuke Kitagawa 3-7-1, Fuuchi, Iwatsuki-shi, Saitama Prefecture Fuji Xerox Co., Ltd. Iwatsuki Office (72) Inventor Hideo Nakura 3-7-1, Fuchu, Iwatsuki-shi, Saitama Fujize Rocks Co., Ltd. Iwatsuki Office (72) Inventor Shigeki Nishimura 3-7-1, Fuchu, Iwatsuki City, Saitama Prefecture Fuji Xerox Co., Ltd. Iwatsuki Office

Claims (13)

[Claims] 1. An image forming apparatus comprising: a developing device for containing a two-component developer containing at least a carrier and a toner; and a developing unit for visualizing a latent image written on an image carrier. What is claimed is: 1. A density control device for controlling the density of a visualized image, comprising: a developing operation integrating means for integrating a time during which the developing means operates; and a developing operation integrating means for performing a predetermined operating time of the developing means. Image density integrating means for integrating the density of the visualized real image with respect to the entire image area written on the carrier; comparing the actual image density integrated by the image density integrating means with a previously predicted limit density And a predetermined amount of toner in the developing device when it is determined that the actual image density integrated by the image density integrating means by the comparing means is lower than a predicted limit density. It was drained and the concentration control device of an image forming apparatus having a toner replacement means for supplying toner approximately the same amount. 2. The image processing apparatus according to claim 1, further comprising: a setting unit that sets an interval time shorter than the operation time, which is shorter than the operation time, for the comparison by the comparison unit. The density control device for an image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, further comprising a prohibition unit for prohibiting a next toner replacement for a predetermined time after the toner replacement by the toner replacement unit.
3. A density control device for an image forming apparatus according to claim 2. 4. A method for changing at least one of a discharge amount and a supply amount of the toner, an operation time, and a prohibition time prohibited by a prohibition unit, based on an absolute amount of an image density compared by the comparison unit. 4. The density control device for an image forming apparatus according to claim 2, further comprising a change unit that changes the density. 5. The image forming apparatus according to claim 1, wherein the developing unit of the image forming apparatus includes developing units for at least two colors, and each developing unit is independently controlled. A density control device for an image forming apparatus according to claim 1. 6. The image density according to claim 1, wherein the image density is obtained based on a ratio of a pixel number of a visualized real image to a total pixel number of the image area. Item 2. A density control device for an image forming apparatus according to Item 1. 7. The image density according to claim 1, wherein the image density is obtained based on an integrated value of a current value according to an image signal when writing an image on the image carrier. 2. A density control device for an image forming apparatus according to claim 1. 8. The density control device for an image forming apparatus according to claim 1, wherein the operation time of the developing unit is a rotation driving time of a developing device. 9. The image forming apparatus further includes a transfer unit that transfers a real image visualized on the image carrier to a loop-shaped intermediate transfer body that repeatedly contacts the image carrier. 9. The density control device according to claim 1, wherein the operation time of the developing unit is determined based on the number of rotations of the intermediate transfer member. 10. The replacement means, wherein the image bearing member is a photosensitive member, the photosensitive member is charged by a charging roll, and toner is attached by a potential difference between the photosensitive member and a developing roll of a developing device. Wherein the toner is discharged by a development performed by a potential difference between a surface potential of the photoreceptor, which has not been neutralized after being charged by the charging roll, and a developing roll of a developing device to which the voltage is applied. A density control device for an image forming apparatus according to claim 1. 11. The image bearing member is a photoreceptor, and the photoreceptor is charged by a charging roll, and the toner is attached by a potential difference between the photoreceptor and a developing roll of a developing device. After being charged, the development is performed by a potential difference between a developing roller of a developing device to which a surface electrode voltage of a region where a charge is removed by an image writing unit is applied. The density control device for an image forming apparatus according to claim 1, wherein the image is a striped image having a width. 12. The density control device for an image forming apparatus according to claim 1, further comprising a selection unit for selecting whether to perform the toner replacement. 13. After the toner has been discharged and supplied, a predetermined image is formed on a photoreceptor before the next image formation, and the image density is detected by a detecting means, and the image density is set. If it is not within the range, it will be within the set range,
13. The density control device for an image forming apparatus according to claim 1, wherein a predetermined amount of toner is discharged or supplied.