JP2920326B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an image forming apparatus that forms a toner image on an image forming body by an electrophotographic method, and transfers the toner image onto a transfer material to obtain an image.

BACKGROUND OF THE INVENTION

Electrophotographic image formation involves forming and developing a latent image according to an original image or image data on an image forming body, forming a toner image on the image forming body, and then transferring the toner image onto a transfer material. In this way, an image is obtained. The developing means for visualizing the latent image formed on the image forming body contains a one-component developer composed of only toner or a two-component developer composed of toner and carrier,
When each image is visualized, only the toner moves from the developing means to the image forming body to form a toner image on the image forming body. Generally, in both the one-component developer and the two-component developer, stirring is performed in order to sufficiently triboelectrically charge the developer contained in the developing means. In a one-component developer, the amount of toner as a developer is detected by a sensor, and control is performed such that a constant amount of toner is always contained in the developing unit. In the case of the two-component developer, a toner density, which is a ratio of toner and carrier, is measured by a toner density sensor as a toner density measuring unit. If the toner concentration sensor detects that the toner concentration in the developing means is low, a new supply toner is supplied into the developing means. In this way, the control is performed so that the toner concentration in the developing unit is always constant. As described above, the reason why the toner amount is controlled in the one-component developer and the toner concentration is controlled in the two-component developer is that if the toner amount or the toner concentration fluctuates, the developing performance changes, and good development cannot be performed. That's why.

[Object of the invention]

However, since the toner amount in the one-component developer or the toner concentration in the two-component developer is always kept constant, the consumption amount of the toner contained in the developing means is small (image formation with a small visualized area). In this case, a large amount of toner stays in the developing means, and therefore, the stirring time is long and the load on the developer is large, that is, the deterioration of the developer is caused as seen in an increase in the amount of charge and a decrease in fluidity. Will be. Such deterioration of the developer is not considered at all in the conventional image forming apparatus. Therefore, when the developer deteriorates, the movement from the developing unit to the image forming body becomes unstable due to the decrease in the fluidity, and the toner image density decreases, the toner image density increases,
Image fogging and thickening of characters, especially in the case of a color image, extremely deteriorates color reproducibility, resulting in a reduction or instability in developing performance and a decrease in image quality. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of forming an image by always supplying a stable developer without a deteriorated developer in a developing unit. In addition, since the developer contained in the developing means is prevented from deteriorating, it is possible to prevent problems associated with the deterioration of the developer, such as a decrease in development performance and a decrease in development quality, so that an image that can always form a stable image can be prevented. An object of the present invention is to provide a forming apparatus. Another object of the present invention is to provide an image forming apparatus capable of forming an image having excellent color reproducibility, since the developing performance of each color developing means is not different from the expected performance in a color image.

[Means for solving the problems]

An object of the present invention is to provide an image forming apparatus that has an image forming unit that forms an electrostatic latent image on an image forming body and visualizes the electrostatic latent image by a developing unit to form an image. Is compared with a predetermined reference value, and when the consumption amount of the developer is lower than the reference value, it is determined that the developer is deteriorated, so that the deterioration of the developer in the developing unit is detected. Detecting means, and control means for controlling the image forming means to form an image on a non-image portion on the image forming body when deterioration of the developer is detected by the deterioration detecting means, Image forming apparatus.

【Example】

Next, the present invention will be described based on an embodiment shown in the accompanying drawings.
I will tell. FIG. 1 shows a color composite incorporating one embodiment of the present invention.
FIG. 2 is a main cross-sectional view of a color image forming apparatus as a copying machine. This
Color copiers are roughly divided into image reading systems A and
The writing system B, the image forming system C and the paper feeding system D
Color image is formed by the following process.
It is. First, in the image reading system A,
The document placed on the carriage 12 that slides horizontally.
Irradiated by the attached halogen lamp 121. Yes
The mirrors 131 and 132 are attached to the moving mirror unit 13.
And slide it in the horizontal direction,
Combination with mirror 122 attached to cartridge 12
The light image of the document is led out to the image reading unit 14 by. The carriage 12 and the movable mirror unit 13 are
Wire connected to the motor (all shown
) And driven at speeds of V and 1 / 2V respectively
Are slid in the same direction. The image reading unit 14 includes a lens 141 and a camera
Mirror 142, and the mirrors 121, 131, 13
The light image of the original transmitted by 2 is collected by the lens 141.
They are bundled and imaged on the light receiving surface of the color CCD 142, respectively. The original is blue image data by the color CCD 142
(B), green image data (G), and red image data (R).
Color separation into color image data and image processing means (not shown)
Yero (Y), magenta (M), cyan
(C), the toner housed in the black (Bk) developing means.
A color signal corrected in accordance with the toner color is output, and the exposure means
Is input to the laser writing system B. In the laser writing system B, a semiconductor laser (not shown)
The laser beam generated by the
Is rotated and scanned by the polygon mirror 16 which is rotated
After passing through a θ lens 17 and a cylindrical lens 18, a mirror 19
The optical path is bent by the
Image-formed body uniformly charged to a predetermined charge by
Projected on the peripheral surface of the photosensitive drum 20 to form a bright line. On the other hand, the specific position of the photosensitive drum 20 in the sub-scanning direction
The index provided in the photo sensor
(Not shown), and the image signal is
The modulation of the semiconductor laser by the signal starts and the main scanning direction is determined.
Is determined. When scanning is started, the laser is scanned in the main scanning direction.
Laser beam is indexed by an index sensor (not shown)
The detected and modulated laser beam is applied to the photosensitive drum 20.
Scan on the peripheral surface. Therefore, main scanning by laser beam
And the photosensitive drum 20 by sub-scanning by rotation of the photosensitive drum 20
A latent image corresponding to the first color is formed on the peripheral surface of the program 20.
In this embodiment, the latent image is, for example, one of a plurality of developing units.
Developed by developing unit 22Y containing yellow (Y) toner
As a result, a Y toner image is formed on the surface of the photosensitive drum 20.
You. The obtained toner image is held on the photosensitive drum 20.
With the screen separated from the peripheral surface of the photoreceptor drum 20,
Passing under the cleaning means 23 and continuing to copy the second color.
-Enter the cycle. That is, the photosensitive drum 20 on which the Y toner image is formed
Is charged again by the charger 21 and then the image is read.
The second color signal output from the laser system A
B, and the same as in the case of the first color signal described above.
Writing on the surface of the photoreceptor drum 20
It is formed. The latent image is, for example, magenta as the second color.
(M) Developed by developing unit 22M containing toner
You. This M toner image is the already formed Y toner
Formed in the presence of an image. Similarly, the latent image formed by the image signal of the third color.
The image is developed with a developing device 22C containing cyan (C) toner.
C toner image is formed, and furthermore, by the fourth color image signal
Developing the formed latent image containing black (Bk) toner
And develops a Bk toner image on the surface of the work drum 20
The color toner image is superimposed on the surface of the photosensitive drum 20
Formed on top. The developing sleeve 221 of each of these developing units 22Y, 22M, 22C, 22Bk
DC or further AC bias is applied to
Reversal development without contact with the photoconductor drum 20 where the body is installed
(Jumping development). What
In the case of developing devices not related to development, the rotation of the developing sleeve
Stop the photosensitive drum 20 by cutting the bias, etc.
Prevents damage to the toner image formed on the
Not supply the toner to the latent image. The color formed on the surface of the photosensitive drum 20 as described above
-The toner image is transferred to a transfer unit 24 provided as a transfer unit.
And the timing supplied by the feeding belt 25 of the feeding system D
The timing is synchronized with the color toner image by the
It is transferred to the transferred transfer material. The transfer unit 24 is opposite in polarity to the toner.
Transfer is performed by applying a high-voltage power supply having a high voltage. Thus, the transfer material on which the color toner image has been transferred is separated.
The photoconductor drum is separated from the surface of the photosensitive drum by the
The color toner image is carried into the fixing device 29 through the
After fixing is performed, the sheet is discharged. On the other hand, the transfer and separation of the color toner image to the transfer material were completed.
The photosensitive drum 20 further rotates clockwise to
Blade 231 of the lining means 23 remains in the pressed state
Removal and cleaning of the toner are performed. After cleaning
Again, the blade 231 is separated from the photosensitive drum 20 again,
Enter a new copy process. Next, the structure and function of the developing means will be described with reference to FIG.
This will be described with reference to the cross-sectional view of the container 22. In this embodiment,
The developing units 22Y, 22M, 22C, and 22Bk all have the same configuration function.
Since an imager is used, the developing device 22 is used here as an example.
It will be described as. Inside the developing device 22, a developing sleeve 221 and a stirring screw are provided.
Queues 222 and 223, magnet roller 224, thin layer forming member 22
5, a scraper 226 and the like are provided. Developing sleeve 22
The gap between 1 and the photosensitive drum 20 is coaxial with the developing sleeve 221.
Constantly fixed by the abutting rollers (not shown)
The gap (0.3-1mm, preferably about 0.5mm) is maintained
You. The stirring screws 222 and 223 are turned in opposite directions.
The agitating member rotates, and is used as a toner supply unit (not shown).
Therefore, the toner supplied from the supply port 227 is transferred to the magnetic carrier.
And a member for sufficiently stirring and mixing. That is, the toner
Two-component developer consisting of a carrier and a stirring screw
With sufficient stirring and mixing by 222 and 223, friction band
After the electric charge is applied to make the developer homogeneous, the developing sleeve 221 is used.
Supplied to The developing sleeve 221 has a fixed magnet roller 224
Enclose and surround the thin layer forming member 225 and scraper 226
Are arranged. The magnet roller 224 has an N pole and
And S poles are alternately arranged at equal intervals.
It is composed of stone, but contacts the scraper 226
Forming a repulsive magnetic field at the part where
In order to achieve this, one pole is missing to make seven poles. The book
In the embodiment, a magnet roller composed of 8 pole magnets
224 was used, but in general, the developer
Keep the spikes low while ensuring proper magnetic force
For this purpose, it is preferable to use a magnet with 300 to 900 Gause and 8 to 16 poles.
Use a trawler. The thin layer forming member 225 is rigid and magnetic
With no developer interposed in the developing sleeve 221
It is pressed with a predetermined load in a state. The developer supplied from the stirring screws 222 and 223
It adheres to the peripheral surface of the image sleeve 221 and forms a thin layer forming member 225.
It is formed into a thin layer of about 300 μm. This developer
Is transported together with the developing sleeve 221 and is
The latent image on the peripheral surface of the photoreceptor drum 20 and the developing interval described above.
And non-contact reversal development to form a toner image. During this non-contact development, a DC component is supplied from a power supply (not shown).
A developing bias including an AC component in addition to the developing sleeve.
221 so that the developer is
Only the toner selectively migrates to and adheres to the surface of the latent image.
You. The carrier ratio of the developer that consumed the toner component has increased.
The scraper 226
The developer is separated and recovered by the
Are combined. Further, the developing device 22 has a toner / carrier ratio.
Toner concentration measurement for measuring toner concentration (wt%)
Setting means 1S is provided below the stirring screw 223.
You. The toner density sensor S1 as the toner density measuring means
Are magnetic permeability detection sensors, capacitance detection sensors, reflection densitometers, etc.
Any existing toner density sensor can be used. Next, with respect to toner supply and density control,
A description will be given with reference to FIGS. FIG. 3 shows the output voltage of the toner density sensor S1 and the toner density.
It is a figure showing the relation of a degree. Thus, the toner density and
There is a correlation between the output voltage of the toner density sensor S1
In this embodiment, the output voltage of the toner concentration sensor S1 is
The toner density is controlled based on the density. That is, the toner density
If the toner supply amount is adjusted according to the output of the sensor S1,
Adjustment of the toner density can be easily performed. The same
When the straight line area in the figure is used for adjusting the toner density,
The adjustment can be made more easily and accurately. FIG. 4 is a block diagram showing the adjustment of the toner density.
You. The toner control unit 50 includes a level dividing unit 501, a memory unit 5
02, etc., output from toner density sensor S1
The level is divided into several levels based on the voltage value.
The amount of toner supply is controlled according to. First, the level dividing unit 501 of the toner control unit 50
-The output voltage input from the concentration sensor S1 is
, I.e., i.e., i (i = 0, 1, 2, 3...). This
The level division of the output voltage in the bell division section 501 is the third
The approximate straight line area in the figure is used, and this level
The more precise the control, the more precise the toner density
I can do it. On the other hand, the memory section 502 of the toner control means 50 has
At the time of driving the toner level i and the toner replenishing means 51 shown in FIG.
Between t _i (I = 0,1,2,3 ...) is stored in advance.
Level is determined by the level dividing unit 501 of the toner control unit 50.
Based on the divided toner level i.
The stage 50 outputs a drive signal for controlling the toner replenishment drive means 51 as described above.
Drive time t _i Output only. Note that the data stored in the memory
The relationship between the driving time of the toner supply means 51 and the toner
Not only the relationship with the feeding amount, but also the toner density
The relationship with the output voltage of the
Is determined in consideration of the circulation time of the developer
You. Therefore, the output voltage of the toner concentration sensor S1 is low (toner
-High density), the toner control means 50 drives the toner supply
The time for outputting the drive signal to the means 51 is shortened.
If the voltage is high (toner density is low), a drive signal is output.
Longer time. Here, the drive of the toner replenishment drive unit 51 is performed.
The amount of toner replenishment per unit time of movement should be constant
It is designed in advance to control the drive time.
The toner supply amount can be controlled more, and the toner density
You can control it. Toner supply hand driven by toner supply drive means 51
The tray is, for example, a supply tray stored in a toner hopper.
Toner by a toner conveying screw (neither is shown)
Is supplied from the supply port 227 of the developing device to the developing device.
is there. This toner conveying screw is driven by a pulse motor.
And the supply amount is designed in advance.
In addition, by controlling the driving time of the pulse motor,
-Supply the correct amount of toner to maintain the density.
Can be. The toner supply means is limited to the above-described configuration.
It goes without saying that it is not something that can be done. Table 1 shows the output obtained by the toner density sensor S1.
Based on voltage, toner density, level classification, toner supply
Of the driving time of the moving means 51 and the supply amount of the supply toner.
It is the table | surface which showed an example of the relationship. In the table, toner
The output voltage of 2V in the embodiment with the concentration of 7%,
In the linear area in the relational expression of toner density (FIG. 3), about
Voltage set to have a slope of −0.35 V /%
Using a toner sensor with a control adjustment function (manufactured by TDK),
The output voltage of the toner density sensor S1 is supplied to the level dividing section 501.
Divided into seven toner levels (level 0 to level 6)
The replenishing capacity of the toner replenishing means is designed to be 100 mg / sec.
Shows the case where This relationship, besides the above considerations,
In consideration of the characteristics of the developer and the capabilities of the developer itself,
is there. FIG. 5 shows the detection timing of the toner concentration sensor and the toner timing.
6 is a timing chart showing replenishment timing.
In the figure, each means is driven at a high level.
Are shown. The display is synchronized with the electrostatic latent image formed on the photosensitive drum 20.
When the image sleeve 221 is driven, the toner density sensor S1
To measure the toner density. One second before this drive
In addition, the stirring screws 222 and 223 are driven,
When the toner concentration is measured, the mixture is sufficiently stirred. Soshi
The toner density sensor obtained by measuring the toner density.
The output voltage of the sensor S1 is adjusted based on the relationship shown in Table 1 above.
The supply driving unit 51 is driven. In FIG. 5, the toner density
Is the toner density level measured by sensor S1 before?
Shows the case of Level 6, Level 1 and Level 2, respectively
The drive signal is generated for the time corresponding to the level (see Table 1).
Has been output. In this embodiment, as shown in FIG.
Measure the toner concentration at the start of development and every 2 seconds thereafter,
Measurement of toner density by three measurements on one screen
Shows the case where it has finished, but is not limited to this
It goes without saying that it is not. As described above, it is detected by the toner concentration sensor S1.
Control the supply amount of supply toner based on the toner concentration
The toner concentration should always be constant in the developing unit.
Can be. Further, the control of the toner density is performed in one screen.
Perform density measurement multiple times during image formation, or
The toner concentration with higher accuracy
Because it is possible to always perform stable image formation
Can be. Next, detection of deterioration of the developer will be described with reference to FIGS. 4 and 6.
It will be described based on. By adjusting the toner concentration of the developer as described above,
Supply toner is supplied, and the toner density is
Control. In other words, the supplied to
Toner amount can be estimated to be the amount of toner consumed.
Wear. Therefore, when detecting the deterioration of the developer, first, the toner
The output voltage measured by the density sensor S1 is
Toner classified by the level dividing unit 501 of the stage 50
Histogram of level i and frequency of measurement (see Fig. 6)
Is created in the calculating section 521 of the toner deterioration detecting means 52.
You. Then, after completion of predetermined image formation (the number of density measurements)
In addition, the calculation unit 521 calculates the histogram
Based on the toner level i and its frequency and measurement
From the number of times, Is used to estimate the toner consumption. That is, on
The formula is weighted according to the toner level (replenishment amount)
The number of times of toner supply is integrated, and a predetermined number of toner
Calculate the total consumption (supply) and calculate the total toner consumption (supplementation).
Is divided by the number of measurements to give
Calculates the toner consumption (replenishment amount) as the consumption value
It is. In other words, the calculation unit 521 performs the toner density measurement 1
Average toner consumption (replenishment) per cycle? Also calculate
It is. In this embodiment, the toner level is multiplied by the frequency.
However, the output value and frequency of toner concentration sensor S1 are
It goes without saying that it may be allowed. That is, the level
Without passing through the separation unit 531, the obtained toner density sensor S 1
The average output value is calculated from the output value to the average consumption (toner density sensor
Since the relationship between S1 and toner supply is known in advance, the output value
Needless to say, it may be calculated as
Nor. The determining unit 522 of the toner deterioration detecting means 52
The consumption value calculated in is compared with a preset reference value.
To determine whether the toner consumption is low.
That is, the smaller the consumption value is, the more the developing device 22
Consumption of the toner inside the developing unit 22 is small.
The toner is agitated and the stirring time of the toner is prolonged.
This leads to the deterioration of Conversely, the consumption value
Is large, toner consumption is large and stays in the developing unit 22
Therefore, the problem of toner deterioration does not occur. Note that the reference values are based on the characteristics of the developer, the performance of the developing device, and the characteristics.
The value is set in consideration of various factors such as gender. FIG. 6 shows the detection of the deterioration of the developer.
This will be specifically described using a gram. FIG. 6 shows one screen as in the case of the toner density adjustment.
During the measurement, the toner density was measured three times, and five screens were continuously displayed.
Obtained by the operation unit 521 when copying to the transfer material
FIG. Created after 5 screens are formed
From the histogram shown in the figure, the frequency of toner level 0 is 3,
Level 1 frequency is 7, Level 2 frequency is 4, Level 3 frequency
The frequency is 1, the frequency of level 4 is 0, the frequency of level 5 is 0,
The frequency of level 6 is 0. Therefore, the calculation is performed by the calculation unit 521.
Consumption value is Becomes The consumption value 1.2 calculated by the calculation unit 521 is
Input to the judgment unit 522 of the
Compared to the value 1.4. That is, the consumption value is 12 and the standard
In this case, the consumption value is smaller than 1.4.
In the cutting section 522, it is determined that the toner consumption is low.
You. Therefore, assuming that the toner in the developing device has deteriorated,
The toner deterioration detecting means 52 includes a toner deterioration preventing means 53 described later.
To output a deterioration signal to prevent toner deterioration. The above-mentioned reference value 1.4 is obtained by experiments.
According to this, the blackening rate of the original (black
Ratio of line drawing part: However, this is limited to black
There is no line drawing part for each color component.
If you repeat about 2% of copies,
Effects of developer deterioration such as deterioration of image quality and image density
Therefore, as mentioned earlier, the characteristics of the developer and the
It is determined in consideration of various factors such as characteristics. Only
However, the present invention is not limited to the numerical values shown in the present embodiment.
Needless to say. This reference value is
Screen size (transfer material size)
It is desirable. For example, A-3 is twice as large as A-4.
The reference value is also doubled to 2.8,
It may be changed by the area ratio of the screen size. In this embodiment, the toner consumption per unit measurement is
The amount (replenishment amount) was calculated, but only for these
Not consumption, for example, consumption per copy.
In addition, the amount consumed per unit operation time of the developing unit may be sufficient.
Needless to say. Furthermore, in this embodiment, after 5 copies
Was calculated, but the present invention is not limited to this.
Any number of copies, such as copy, 10 copy, 100 copy
Often, the operator sets up for continuous copying.
Calculates the average of the specified number of copies until the last image formation
After the specified time, not the number of copies
May be calculated. Next, the toner deterioration preventing means 53 will be described. The toner deterioration preventing means 53 is provided with the toner deterioration detecting means 52.
Is determined that the amount of toner in the developing device 22 is low.
Driven when As a specific means, the photosensitive drum
A belt-like latent image and toner are formed on the non-image portion of the
This toner image is transported without being transferred onto the transfer material, and is cleared.
Removed on the photosensitive drum 20 by the cleaning means 31
As a result, the deteriorated toner remaining in the developing device 22 is
Is used (abandoned). FIG. 7 shows the timing chart of the toner deterioration prevention means 53.
FIG. However, the figure shows only one
Focusing on the developing device 22 of the
Light, development, transfer and cleaning after completion of each color development
The dashed-dotted line indicates the end of the image area,
The dotted line indicates the rear end of the image area, and the mark indicates the toner density sensor S1.
The measurement timing of the toner density is shown. The surface of the photosensitive drum 20 is uniformly charged by the charger 21,
Image exposure with first color signal by laser writing system B
After the image latent image formation is performed by performing
If the toner is deteriorated, for example, from the rear end of the image area
A part of the non-image part separated by about 20mm is in the laser writing system B
More strip exposure is performed to form a strip latent image. On the other hand, the developing device 22 reversely develops the image latent images sequentially.
At that time, the toner concentration was measured and the result was described above.
The toner density is adjusted as follows. Also, a toner deterioration detecting unit
If the toner is judged to be deteriorated by 52,
The above-described belt-shaped latent image is formed. Conversely, if the toner has not
If it is determined that the belt-shaped latent image is not formed, the belt-shaped latent image is not formed. And
The band-shaped latent image is developed by the developing unit 22 and subsequently visualized.
And then developed (so-called solid image) and visualized. The toner image of the image portion visualized as described above is transferred to a transfer device.
The image is transferred onto a transfer material separately transported by 24. band
The transfer of the transfer toner 24 is stopped for the toner
In the state of being held on the photosensitive drum 20
It is carried out to the cleaning means 23 as it is. The cleaning unit 23 removes residual toner in the image area and
Until then, remove the belt-like toner from the photoconductor drum 20
The cleaning blade 231 that was separated is the photosensitive drum 2
Contact 0 and clean. In experiments, the formation of the band-like latent image was approximately 40 mg of toner.
Is formed so as to adhere as the belt-like toner.
As a result, the deteriorated toner remaining in the developing device 22 can be sufficiently reduced.
It was confirmed that it could be removed by
Needless to say, it is not. As described above, adjustment of toner concentration, detection of toner deterioration and
The prevention of toner deterioration is achieved by the developing units 22Y, 22M, 22C, and 22Bk shown in FIG.
Since both have the same configuration and functions,
One developing unit 22 has been described.
For each of 22Y, 22M, 22C, 22Bk, each color toner
Adjust the density, detect deterioration of each color toner, and
It is controlled with respect to the prevention of conversion. FIG. 8 shows an image of a document in the color copying machine shown in FIG.
4 shows a timing chart for obtaining an image by copying.
In the figure, the one-dot chain line indicates the tip of the image portion, and the two-dot chain line
Indicates the rear end of the image area.
-Make sure that each means is
Are shown. Also, in FIG.
Only one copy of the placed document is copied, and the toner density is detected as 1
Three times for the image, detection of toner deterioration and prevention of deterioration are 1
This is a case where it is performed for each pixel. First, place a document on the platen 11, and copy it from the operation panel.
-Button (neither is shown)
The ram 20 rotates, and the charger 21 cleans the surface of the photosensitive drum 20.
Likewise charged. On the other hand, the photoreceptor to be charged
The cleaning means 23 cleans the surface of the drum 20
Is As described above, the photoconductor drum 20 is provided at a specific position.
Detected index and drive image reading system A
The image of the original is read by the color CCD 142, and
The corresponding yellow image signal is generated by the laser writing system B.
Exposed on the photosensitive drum 20 charged uniformly
Perform formation. The developing device 22Y sequentially starts from the leading edge of the image on which the latent image was formed.
Thus, a toner image is formed on the photosensitive drum 20. this
At the position indicated by the mark in the figure,
The toner concentration is detected by the toner concentration sensor S1Y.
According to the detected value, the yellow toner for supply is supplied into the developing device 22Y.
Is replenished. This density detection was performed three times, and
Weighted by the toner deterioration determination means 52
The toner consumption is calculated and set in advance in the determination unit 522.
Then, the toner deterioration is determined by comparing with the reference value. No.
In FIG. 8, the supply amount (consumption amount) of the yellow toner is small.
The case where there is no image is shown.
Strip exposure (solid image exposure)
U. This belt-shaped exposed portion is developed by the developing 22Y and is a belt-shaped
A toner image is formed on the photosensitive drum 20. Yellow tona
The image and the belt-shaped toner image are held on the photosensitive drum 20.
Cree that is transported as is and is separated from the photosensitive drum 20
Of the magenta toner image passing under the
Get started. The image formation of the magenta toner image is performed by the yellow toner described above.
-Similar to image formation, charge, exposure and development
Magenta in synchronization with the yellow toner image in the presence of the toner image
A toner image is formed. During this development, magenta toner
Density measurement, supply of magenta toner for supply,
Detects toner deterioration and takes measures to prevent toner deterioration if necessary.
Drive stage 53. It should be noted that in FIG.
-Since the consumption is more than the reference value, the laser writing system B
No band exposure is performed. Photoconductor
When the magenta toner image is formed on the ram 20, the next image
Get started. Following magenta toner image formation, cyan toner image
The formation of the black toner image is the same as the yellow toner described above.
Image and magenta toner images are formed in the same manner. In addition,
The consumption amount of the cyan toner is determined by the toner deterioration determination unit 52.
Because it was less than the reference value, the rear end of the cyan toner image
Belt exposure at a position distant from the
Formed so as to prevent toner deterioration. B
For rack toner, the consumption is higher than the reference value.
No belt toner image is formed. Therefore, yellow and magenta
Black, cyan, and black toner images
Thus, a color toner image is formed. This colortona
-The image is separately transported in synchronization with the photosensitive drum 20.
The image is transferred by the transfer device 24 onto the transferred transfer material. On the other hand,
-Toner degraded at a position away from toner image
Yellow and cyan belt-shaped toner images
However, the charger 24 operates for this belt-like toner image.
Not like that. Therefore, the photoconductor at the end of the transfer
The residual toner after the transfer of the color toner image is
These are belt-shaped toner images, which are
And a new image is formed. Note that the toner deterioration preventing unit 53 is driven as in the present embodiment.
Timing, i.e., a belt-like latent image
The timing for forming the toner image is determined based on the image signal.
Performed for each color toner immediately after image formation, but limited to this
For example, Y, M, C toner based on image signals
-BK latent image after image formation
An image may be formed to prevent toner deterioration.
No. In this case, the latent image formation corresponding to each color toner
The latent image formation position is changed for each toner, and each
What is necessary is just to drive the developing devices 22Y, 22M, 22C, and 22BK. Further, in this embodiment, it is composed of a toner and a carrier.
The case where a two-component developer is used has been described.
It is also possible to use a one-component developer consisting of
Needless to say.

【The invention's effect】

As described in detail above, in the present invention, the supply amount of the supply developer supplied to the developing unit is defined as the consumption amount of the developer, the deterioration amount of the developer in the developing unit is detected based on the consumption amount, and the developer amount is determined. An object of the present invention is to provide an image forming apparatus for removing a deteriorated developer in a developing unit from a developing unit by forming a band-like image on a non-image portion on the image forming body when deterioration is detected. As a result, the image forming apparatus of the present invention has an effect that there is no deteriorated developer in the developing means, and a stable developer is always supplied to form an image. Also, to prevent the developer contained in the developing means from deteriorating, it is possible to prevent problems associated with the deterioration of the developer such as a decrease in developing performance and image quality, and to always form a stable image, Further, in a color image, since the developing performance of each color developing means is not different from the expected performance, an effect that an image having excellent color reproducibility can be formed can be obtained.

[Brief description of the drawings]

FIG. 1 is a main cross-sectional view of a color image forming apparatus as a color copying machine in which one embodiment of the present invention is incorporated. Second
The figure is a cross-sectional view of the developing means of the device. FIG. 3 is a diagram showing a relationship between an output voltage of a toner density sensor and a toner density.
FIG. 4 is a block diagram showing adjustment of toner concentration and detection of toner deterioration. FIG. 5 is a timing chart showing the detection timing of the toner density sensor and the timing of toner replenishment. FIG. 6 is a histogram created when toner deterioration is detected. FIG. 7 is a timing chart schematically showing the driving of the toner deterioration preventing means. FIG. 8 is a timing chart showing image formation by a color copying machine to which the present invention is applied. 20 photoconductor drum 21 charging device 22Y, 22M, 22C, 22Bk developing device 23 cleaning device 24 transfer device 50 toner control device 51 toner supply driving device 52 Toner deterioration detecting means 53 Toner deterioration preventing means 221 Developing sleeves 222, 223 Stirring screw A A: Image reading system B Laser writing system C Image forming system D Paper feeding system S1 Toner density sensor

Continuation of the front page (56) References JP-A-1-170971 (JP, A) JP-A-63-146087 (JP, A) JP-A-3-91782 (JP, A) JP-A-54-7348 (JP) , A) Japanese Utility Model 63-180866 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08

Claims (2)

(57) [Claims] 1. An image forming apparatus comprising: an image forming unit that forms an electrostatic latent image on an image forming body and visualizes the electrostatic latent image by a developing unit to form an image; The amount of the developer is compared with a preset reference value, and when the consumption of the developer is lower than the reference value, the deterioration of the developer is determined to detect the deterioration of the developer in the developing unit. Deterioration detection means, when deterioration of the developer is detected by the deterioration detection means,
An image forming apparatus comprising: a control unit that controls an image forming unit so that an image is formed on a non-image portion on the image forming body. 2. A developing device comprising: a density detecting means for detecting a concentration of a developer in the developing means; and a developer replenishing means for replenishing the developing means with the developer based on a detection result by the density detecting means. 2. The image forming apparatus according to claim 1, wherein the deterioration detecting unit calculates a consumption amount of the developer based on a detection result by the density detecting unit.