JPH11295940A - Density controlling device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and correctly recognize the density reduction or the like in consequence of insufficient residual toner. SOLUTION: When images of high density are successively processed, the residual toner becomes below the predicted value. In this case, such phenomena exerting adverse influence to the density that the toner in a developing device main body is reduced to a small quantity causing abnormal high static charge, and subsequently, the charge quantity distribution is diffused. Accordingly, after a warning of the above toner replenishment, the controlling device is made possible to quickly recognize the occurrence of the density unevenness by shortening a period of the density measuring, the phenomena being liable to occur in consequence of the little residual toner quantity can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer, and more particularly to a density control of an image forming apparatus which controls image density by detecting empty toner and measuring the density of a pattern image. Related to the device.

[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 This value is compared with the value (for example, see Japanese Patent Application No. 8-355072).

Here, when the value is lower than the reference value, the operator is informed of this and a new toner is additionally supplied to recover the density.

[0004]

However, when image formation is continued in a state where the image formation amount is large (image density is high), the toner consumption increases at an accelerated rate.

In such a case, immediately before the toner remaining amount is detected to be empty, that is, when the toner remaining amount is small, if the density pattern forming cycle is long, the toner empty detection is delayed. This will cause a decrease in density.

Further, if the amount of toner in the two-component developer is too small, the charge amount becomes abnormally high, and thereafter, the charge amount changes greatly. A large variation is observed, which also causes a color point or a missing color point, which is one of the density reductions.

[0007] The cause is that if development is performed when the charge amount is abnormally increased, the carrier may be developed together with the toner during development. Further, aggregation of the toner may occur, and the aggregated toner may 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, it is an object of the present invention to provide a density control device for an image forming apparatus capable of quickly and reliably recognizing a decrease in density due to a small amount of remaining toner.

[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 density control device for controlling the density of the visualized image, wherein a density measurement pattern is formed on the image carrier at predetermined intervals. The image forming apparatus includes a density inspection unit that forms and performs a density measurement inspection, and a cycle changing unit that changes an execution cycle of the density inspection unit based on a predetermined condition based on a used amount of toner.

According to the first aspect of the invention, the cycle of the density measurement inspection by the density inspection means is changed based on the amount of toner used, so that the density measurement inspection is performed at the cycle optimal for the remaining amount of toner. Can be. For example, when the amount of remaining toner is large, the period may be long because the toner does not run out immediately. On the other hand, when the remaining amount of toner is small, the toner may be emptied immediately, so that the cycle is shortened.

As described above, by changing the period,
It is possible to eliminate wasteful time of the density measurement inspection by the density inspection unit and quickly recognize a decrease in density due to a decrease in the remaining amount of toner.

According to a second aspect of the present invention, there is provided a developing device for containing a two-component developer containing at least a carrier and a toner, and a developing means for visualizing a latent image written on an image carrier. An image forming apparatus having a density control device for controlling the density of the visualized image,
Integrating means for integrating the toner supply time to the image carrier in the developing means, and alarm means for issuing an alarm for urging toner replenishment when the toner supply time integrated by the integrating means reaches a time to supply toner. Pattern image forming means for forming a pattern image for density measurement on the image carrier at predetermined intervals, and pattern density measurement for measuring the density of the pattern for density measurement formed by the pattern image forming means Means, a comparing means for comparing a density value measured by the pattern density measuring means with a reference value, and a toner replenishing means for replenishing toner when toner empty is recognized based on a comparison result by the comparing means And after confirming that at least one of the time exceeding the predetermined time of the toner supply time integrated by the integration means or the alarm by the alarm means is confirmed, A cycle changing unit for a period of performing serial pattern image forming means and a period shorter than the normal period,
have.

According to the second aspect of the present invention, the toner supply time to the image carrier in the developing means is integrated. When the accumulated time reaches a predetermined time, it is determined that the remaining amount of toner is almost empty, and an alarm is issued by an alarm means to urge the operator to supply toner. This allows the operator to replenish the toner, thereby increasing the remaining amount of toner. Note that it is also possible to temporarily replenish the spare toner in consideration of the case where there is no operator.

In addition, a pattern for density measurement is formed on the image carrier at predetermined intervals, and the density is measured by a pattern density measuring means.

The measured density value is compared with a reference value,
When it is determined that the density is lower than the reference value, the toner is forcibly supplied.

However, if this cycle is long, the remaining amount of toner is small, and if images having a high image density are successively processed, the toner becomes empty before the next density measurement time, or The state becomes almost empty, and there may be cases where a decrease in density cannot be prevented beforehand.

Therefore, after it is confirmed that the toner supply time integrated by the integrating means exceeds a predetermined time or at least one of the warnings by the warning means is confirmed, the period for performing the pattern image forming means is set to a normal cycle. By setting the cycle to be shorter than the cycle, a decrease in density can be detected early, and as a result, a decrease in image quality can be prevented.

According to a third aspect of the present invention, in the invention according to the second aspect, when the cycle changing means is performed when an alarm is issued by the alarm means, the toner supply is completed after the alarm is issued. It is characterized in that it is executed after execution.

According to the third aspect of the present invention, the operation is performed after the toner is replenished after the warning by the warning means. At this time, if the toner is replenished in a state in which the toner is extremely empty, the remaining amount is small even after the toner is replenished. Therefore, by performing the density measurement after the toner replenishment, the remaining toner state can be recognized.

According to a fourth aspect of the present invention, in the first aspect of the present invention, it is preferable that the period is determined based on a count value of the number of recordings on recording paper. Features.

According to the fourth aspect of the present invention, the density measurement period is a count value of the number of recording sheets. For example, when the normal period is set to A4, the short period is set to A4. There are five cards. For counting the number of sheets, an existing counter or the like may be used.

According to a fifth aspect of the present invention, in the density control device of the image forming apparatus according to any one of the first to fourth aspects, the developing means uses toner of at least two colors. An intermediate transfer member, which is provided with a developing device for developing, and rotates so that a part of the image carrier is brought into contact, and a toner image for each color formed by the image carrier can be transferred in a superimposed manner. It is characterized by:

According to the fifth aspect of the present invention, when the image forming apparatus is an apparatus capable of forming two or more colors, for example, a full-color image, the image carrier is provided with each color in each color unit. Is formed, and the toner image is sequentially transferred to the intermediate transfer member. As a result, an image of each color (cyan, magenta, yellow, black) is superimposed on the intermediate transfer member. By transferring this superimposed image to recording paper, a full-color image can be obtained.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the period is determined based on the number of rotations of the intermediate transfer member.

According to the sixth aspect of the invention, since the density measurement cycle is set to the number of rotations of the intermediate transfer body, size conversion and the like become unnecessary.

[0028]

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 this 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.

A 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
A photoreceptor 30 as an image carrier, a charger 38 disposed around the photoreceptor 30, an intermediate transfer member 42 composed of an IBT belt, and a photoreceptor cleaner 44
And a charging device 128 including a static elimination lamp (not shown)
And image data obtained by reading an original with a scanner and performing various image processing (the image forming apparatus 10 according to the present embodiment is intended for a color image, so that yellow, magenta , Which is converted into image data of four colors of cyan and black), an optical scanning device 32 for irradiating a light beam to a photoconductor 30 as an image carrier, and a fixing device 14 for fixing a desired image on the paper 18. An image forming apparatus 28 including:
Is provided.

The optical 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 photoconductor 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 disposed 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 developing device main bodies 40Y, 40M, 40C, 4C of 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 that are rotated by a driving force of a dispensing motor (not shown) are provided in the developing device main body 40C, and convey the two-component developer in the developing device main body 40C toward the developing roll 102 while agitating. It has become. For this reason, there is a correlation between the on-time of the dispense motor and the toner supply amount, and it is possible to obtain the toner supply amount described later by the count value of the on-time of the dispense motor.

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 stored in 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 unit 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 is connected to the fixing device 14, the optical scanning device 32, each part of the charging device 128 composed of the charging member 38, the photosensitive member cleaner 44 and the like, and the rotary developing device 40, respectively. It operates based on a control signal from the controller 114. Also, I
The / O 124 is connected to a transport device 130 that controls a transport system (rotational drive of the photoreceptor 30, transport of the intermediate transfer member 42, transport of the paper 18, and rotational drive of the fixing device 14).
Note that the optical scanning device 32, the charging device 128, the rotary developing device 42, and the fixing device 14
5, a high-voltage power supply is supplied.

The operation time of the rotary developing device 42 is as follows.
It is counted by the counter 132, and when a predetermined count value (predetermined time) elapses, it is determined that the toner consumption becomes empty on average, a signal is output to the alarm unit 134, and it is time to replace the toner. Warning (warning).

Further, simultaneously with the alarm, the rotary developing device 42
Of the developing device main body 4 by operating a predetermined amount of toner 46C (46M, 46Y, 46k).
0C (40M, 40Y, 40k).

Here, in the image forming apparatus 10 according to the present embodiment, the density measurement pattern is
As shown in FIG. 4, a point patch 136 is formed on the photoreceptor 30.
And the band patch 138 are formed by the same processing as the normal image formation.

The point patch 136, as shown in FIG.
Photoconductor 30 charged to a surface potential VL of -650 volts
Above, are exposed so that the exposed portion potential V _D of -200 volts on the basis of the image signal. Here, the developing bias VB of -500 volts between the surface potential V _L and the exposure unit potential V _D is located.

Since the toner is negatively charged, the difference between the exposed portion potential V _D and the developing bias V _B , that is, the contrast potential, causes the photosensitive drum 3
Move to 0 and develop.

On the other hand, the band patch 138 is
36 (including a normal image) is formed under a condition different from the potential condition when forming.

[0054] As shown in FIG. 6, the surface potential V _L is lower-level than the formation point patch 136 (normal image) on the photosensitive member 30, that is lower than the developing bias V _B level (e.g. -470 volts) Is set. Then, the portion of the photosensitive member 30 is charged to a level lower than this usually then developed by adhering toner in contrast potential between the surface potential V _L and the developing bias V _B.

As shown in FIG. 3, the point patch creation instructing section 140 outputs a point patch creation instruction each time a predetermined number of images (20 sheets in A4 format) are recorded.
In step 2, a point patch 136 is created in response to this instruction.

On the other hand, the band patch creation instructing section 142 outputs a band patch creation instruction each time a predetermined number of images (20 sheets in A4 format) are recorded, and in response to this, the charging roller 38 and the developing roll 102 are output. A predetermined voltage is applied to create a band patch 138.

A density sensor 144 is provided on a part of the peripheral surface of the photoreceptor 30 to detect the densities of the dot patch 136 and the band patch 138, and a reference value stored in the ROM 122 in advance as a table. Then, based on the comparison result, the voltage applied to the charging roll 38 and the scanning exposure device 32
Is calculated.

Based on this correction value, the voltage applied to the charging roll 38 and the output intensity of the scanning exposure device 32 are corrected.

The density of the band patch 138 is determined by the CPU 1
At 18, toner empty detection control is executed to determine whether the remaining amount of toner is empty (or nearly empty) based on the input density fluctuation state, and as a result of the determination, the remaining amount of toner is empty (or low). ), The alarm unit 134 is activated (empty alarm).

Here, the point patch 136 and the band patch 13
As described above, normally, as described above, the density is measured by periodically forming the photoconductor 30 every 20 sheets in A4 format, but after the dispense motor has been turned on for a predetermined time, this cycle is changed to It is being shortened.

That is, after the operation time of the rotary developing device 42 elapses a predetermined time, a predetermined amount of toner 46C (46
M, 6Y, and 46k), the developing device main body 40C (40M, 40K) depends on the image recording densities before and after the replenishment (when images with high image densities are continuously processed).
(Y, 40k) may be short of toner. This toner shortage causes a change in the charge amount, and is a state in which density unevenness is likely to occur. For this reason, the concentration measurement cycle is shortened in order to quickly detect a decrease in concentration. The operation of the present embodiment will be described below with reference to the flowcharts of FIGS.

In the controller 114 of the present embodiment,
All the controls such as the normal operation control of the image forming apparatus 10 and the creation control of the point patch 136 and the band patch 138 are collectively monitored.
2. The individual operation control of each unit such as the transport device 130 is controlled by a sequencer provided for each unit.

In the following, the toner empty detection control routine (FIG. 7) and the density patch creation / density measurement control routine (FIG. 8), which are the points of the present invention, will be described, and the other controls will be omitted. FIG. 7 shows a toner empty detection control routine.

In step 200, first, the toner empty detection count value Cc is cleared (the counter 132 is cleared). Next, in step 202, it is determined whether or not the rotary developing device 42 is operating. That is, in the present embodiment, attention is paid to the fact that toner is used during the on-time of the dispense motor, and the amount of toner consumption is predicted by counting the on-time.

In the next step 204, the count value is incremented, and then in step 206,
The toner empty detection count value Cc is compared with a preset empty count value Cs.

If a negative determination is made in step 206, that is, if it is determined that Cc <Cs, it is determined that the remaining amount of toner is sufficient, and the routine proceeds to step 202.

In step 206, an affirmative decision is made.
That is, when it is determined that Cc ≧ Cs, it is determined that the remaining amount of toner is small (close to empty), and a warning to supply toner is issued (warning).

In the next step 212, the count value Cc for toner empty detection is cleared.
Then, the flag F is set (1), and this routine ends.

The flag F is used for changing the creation timing of the density patch described below. FIG. 8 shows a density patch creation / density measurement control routine.

In step 250, it is determined whether or not the flag F has been reset (0). If a negative determination is made, it is determined that no empty has been detected in the toner empty detection of FIG. Then, the count value Ts corresponding to the cycle of density patch creation and density measurement described below is set to 20. In the present embodiment, the count value Ts is the number of processed sheets in A4 size conversion.

If a negative determination is made in step 250, it is determined that the toner is empty in the toner empty detection of FIG. 7 (see step 214), and the flow proceeds to step 254 to set the count value Ts to 5. .

That is, when the empty toner is detected, the period (Ts) shorter than the normal period (Ts = 20) is used.
= 5).

When the count value Ts is set in step 252 or step 254, the flow advances to step 256 to read the actual processed sheet count value Tc, and then to step 258, where the actual count value Tc and the set count value are set. The value Ts is compared.

As a result of this comparison, if it is determined that Tc <Ts, it is determined that it is not time to create a density patch, and this routine ends. If it is determined that Tc ≧ Ts, it is determined that it is time to create a density patch, and the process proceeds to step 260 where the point patch 136 and the band patch 138 are formed.
Is formed on the photoconductor 30 (see FIGS. 4, 5 and 6).

In the next step 261, the densities of the created point patch 136 and band patch 138 are measured by the density sensor 144.
Only when the flag F is set in the next step 262, that is, when the empty detection is performed, the recovery operation is executed in the step 263 and the process proceeds to the step 264 (in the case of a negative determination in the step 262, The process moves from step 261 to step 263.) The above recovery operation is performed when the toner 4
6C (46M, 46Y, 46k) to the developing machine main body 40C
(40M, 40Y, 40k).

If a negative determination is made in step 262 or the recovery operation ends in step 263, then the measured value is compared with a reference in step 264. As a result of this comparison, if it is determined that the determination is OK, it is determined that the remaining amount of toner is sufficient, and the routine proceeds to step 266, where the flag F is reset, and this routine ends.

If it is determined in step 264 that the amount of toner is NG, it is determined that the remaining amount of toner is small, and the flow advances to step 268 to issue a toner empty warning. In step 270, the apparatus is shut down.
This routine ends.

According to the present embodiment, since the remaining toner amount determination is based on the premise that processing is performed at a normal image density, an image having an extremely low image density or an image having an extremely high image density is continuously processed. If the processing is performed in this way, an error may occur in the determination.

In particular, when images having a high image density are continuously processed, a situation occurs in which the remaining amount of toner is smaller than the predicted value.

In this case, the developing device main body 40C (40M, 4
0Y, 40k), a phenomenon that adversely affects the density, such as causing abnormally high charge and then spreading the charge amount distribution, may occur.

Therefore, after the above-described toner replenishment warning, the period of the density measurement that is periodically performed is changed to be short, and the occurrence of the density unevenness is quickly recognized. A possible phenomenon can be prevented beforehand.

In the present embodiment, the toner empty detection is performed based on the on-time of the dispense motor. However, the number of rotations of the photosensitive drum 30, the number of rotations of the intermediate transfer body 42, the number of processed sheets of the recording paper 16, and the like. The value is not limited to the above as long as it changes according to the processing.

Also, the density patch (point patch 136, band patch 138) is created, and the period for performing density measurement is set to the number of processed A4 converted recording papers 16. Number of rotations of 42, rotary developing device 42
The cycle may be set by other means, such as the operation time of.

Further, in the present embodiment, the image forming apparatus 10 for forming a full-color image has been described as an example.
The present invention is also applicable to a single color (monochrome etc.) image forming apparatus.

[0085]

As described above, the density control apparatus for an image forming apparatus according to the present invention has an excellent effect that a reduction in density due to a small amount of remaining toner can be quickly and reliably recognized. Have.

[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 perspective view of the photosensitive drum on which dot patches and band patches are formed.

FIG. 5 is a characteristic diagram showing a toner potential for creating a point patch.

FIG. 6 is a characteristic diagram illustrating a toner potential for creating a band patch.

FIG. 7 is a control flowchart showing a toner empty detection control routine.

FIG. 8 is a control flowchart showing a density patch creation / density measurement control routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image forming apparatus 30 Photosensitive drum (image carrier) 40 Rotary developing device 40Y, 40M, 40C, 40k Developing device main body 46Y, 46M, 46C, 46k Toner 114 Controller 132 Counter 134 Alarm unit 140 point patch creation instructing unit 142 Band patch Creation instruction section 144 Density sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/14 G03G 21/00 386 21/00 386 372

Claims (6)

[Claims] 1. An image forming apparatus, comprising: a developing device for storing 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. A density control device for controlling the density of a visualized image, a density inspection unit that forms a density measurement pattern on the image carrier at predetermined intervals, and performs a density measurement inspection, A density control device for an image forming apparatus, comprising: a period changing unit that changes an execution period of the density inspection unit based on a predetermined condition based on an amount of toner used. 2. 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. A density control device for controlling the density of a visualized image, comprising: an integration unit that integrates a toner supply time to an image carrier in the developing unit; and a toner supply time integrated by the integration unit. An alarm unit for issuing an alarm for urging toner replenishment when it is time to supply the toner; a pattern image forming unit for forming a pattern image for density measurement on the image carrier at a predetermined cycle; Pattern density measuring means for measuring the density of the pattern for density measurement formed by the image forming means, and comparing the density value measured by the pattern density measuring means with a reference value Comparing means, a toner replenishing means for replenishing toner when the empty toner is recognized based on the comparison result by the comparing means, or a time exceeding a predetermined time of the toner supply time integrated by the integrating means, or the alarm A period changing unit that sets a period for performing the pattern image forming unit shorter than a normal period after at least one of the alarms is confirmed by the unit. 3. The image forming apparatus according to claim 2, wherein when the alarm is issued by the alarm unit, the period change unit is executed after the alarm and after toner supply is completed. Concentration control device. 4. The density control device for an image forming apparatus according to claim 1, wherein the cycle is determined based on a count value of the number of sheets recorded on a recording sheet. 5. The image forming apparatus according to claim 1, wherein the developing unit includes a developing unit that develops using at least two or more colors of toner. 5. The apparatus according to claim 1, further comprising an intermediate transfer member capable of superimposing and transferring toner images of respective colors. 6. The apparatus according to claim 5, wherein the period is determined based on the number of rotations of the intermediate transfer member.