JP5068041B2 - Image forming method and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming method using an electrophotographic system such as a copying machine, a printer, and a facsimile machine, which forms an image with stable toner density (TC) over time, and image formation.

2. Description of the Related Art Conventionally, image forming apparatuses such as digital copying machines and laser beam printers that use electrophotography have been widely used. In such an image forming apparatus, an electrostatic latent image is formed with a laser beam on a photoreceptor serving as an image carrier, developed with toner, and a toner image is directly or indirectly formed on a recording member such as recording paper. An image is formed by transferring.
In recent years, high image quality is also required in electrophotographic image forming methods, but the image quality varies greatly depending on the toner concentration of the developer (hereinafter referred to as TC). For example, at a high TC, the developer volume increases and a strip-like white-out image is generated due to poor circulation of the developer. Also, the high TC transition is disadvantageous for toner scattering.
Conversely, low TC is disadvantageous for density unevenness because the toner amount is insufficient. Further, in the system in which the developer is conveyed by the agitation / conveyance screw, the developer bulk is reduced and the pumping to the developing sleeve is caused to be unsatisfactory, resulting in unevenness of the agitation / conveyance screw pitch in the image.
As described above, in order to obtain high image quality in image formation, it is desirable to control the TC within a certain range. However, in the control for keeping the image density constant, it is necessary to keep the toner charge amount constant.

It has been confirmed that the toner charge amount varies depending on the conditions under which the developer is used. When the amount of toner consumed per unit time is small, the amount of toner that passes through the doctor increases and the charge amount increases. Conversely, when the amount of toner consumed per unit time is large, the toner is transferred to the carrier. Adhesion of the additive is promoted, and the charge amount is reduced.
As described above, in the two-component developer, the direction in which the toner charge amount increases or decreases with time changes depending on the toner consumption amount per unit time. The reason why the charge amount of the toner increases is that if the toner consumption amount per unit time is small, there is a toner having a long contact time with the carrier, and in this case, the TC is increased when trying to obtain the target image density. Need arises.
The reason why the toner charge amount decreases is that if the toner consumption amount per unit time is large, the charging ability of the carrier is lowered due to adhesion of the toner additive to the carrier, and TC is lowered when trying to obtain the target image density. Need arises.
This means that there is a range of toner consumption per unit time in which the toner charge amount can be kept constant, and within this range, the toner charge amount is stabilized over time, and as a result, TC Can be stabilized over time to stabilize the image quality.

The effect on the image when TC changes will be described. First, when TC increases too much, a dispersion failure in the developing device due to an increase in the developer bulk occurs, and a white belt may be generated. It is also disadvantageous for toner scattering.
On the other hand, if the amount is too low, there will be no margin of density unevenness due to the lack of absolute toner amount, and the developer volume will be reduced, resulting in poor pumping to the sleeve, and the image will be uneven due to the stirring / conveying screw pitch. May occur. As described above, TC needs to be used within a certain range, but it is difficult to keep the charge amount within a certain range including the environment and time.
The change in developer charge amount due to the environment can be dealt with by correcting it from information such as temperature / humidity detection elements, but the change over time is controlled because the tendency changes depending on the situation where the developer is used. Is difficult.
As an example, the amount of charge increases under the condition that a low image area ratio image is output one by one in one image forming operation, and 100 high image area ratio images are output in one image forming operation. Under the output condition, the charge amount decreases. That is, it is impossible to control based on the number of sheets or the development driving time.

Here, in order to maintain the toner charge amount within a certain range, it is necessary to adjust the time for driving the developing device and the amount of toner consumed so that the toner consumption amount per unit time falls within the certain range. Many proposals have been made for this problem (see, for example, Patent Document 1).
Patent Document 1 proposes a technique for measuring the surface potential of toner developed on an image carrier and controlling the charge amount within an appropriate range by driving the developer or forcibly consuming the toner in comparison with a reference value. Yes.
JP-A-6-186856

However, this technique has a problem that a means for measuring the surface potential of the toner is required, and a detection means is required because the charge amount of the toner changes depending on humidity and TC, and the control becomes complicated. .
In view of the above situation, the object of the present invention is to take advantage of the fact that the toner charge amount change rate has a strong correlation with the toner consumption amount of the developing device driving time unit, and the toner charge amount fluctuation range with time is reduced. To provide a two-component electrophotographic image forming method and an image forming apparatus that maintain a good image quality by keeping the fluctuation range of TC in a developer within an appropriate range where abnormal images do not occur by controlling to a certain range. is there.

In order to solve the above problems, the invention described in claim 1 is a two-component development type image forming method comprising a toner and a carrier, and detects the developer agitation time and the toner consumption amount at the start of image formation. In the image forming step, α is below the lower limit of setting so that the range of α representing the toner consumption amount per stirring time of the developer falls within a predetermined range. The first correction control for forcibly consuming the toner is performed, and the second correction control for driving the developing device and agitating the developer is performed when α exceeds a set upper limit. To do.
According to a second aspect of the present invention, there is provided the image forming method according to the first aspect, wherein the first and second correction controls are periodically performed based on the stirring time of the developer .
According to a third aspect of the present invention, there is provided the image forming method according to the first aspect, wherein the first and second correction controls are periodically performed on a toner consumption basis.
According to a fourth aspect of the present invention, as the range of α, the range of α in which the variation in charge amount is within ± 10 μC / g is used with reference to the value of the charge amount at which an appropriate toner concentration is obtained. The image forming method according to Item 1, is characterized.
According to a fifth aspect of the present invention, there is provided the image forming method according to the first aspect, wherein the lower limit of the target range of α is set so that the blur of the image falls within an allowable range.

The invention according to claim 6 is characterized in that when performing the second correction control, the driving speed of the developing device is made faster than that during the image forming operation.
The invention according to claim 7 is the image forming method according to claim 1, wherein the first correction control is performed by creating a pattern during image formation.
According to an eighth aspect of the present invention, when there are a plurality of the developing devices, the first and second correction controls calculate the α in each developing device and satisfy the correction condition. The image forming method according to claim 1, wherein the first and second correction controls are performed only on the image.
The invention described in claim 9 is characterized in that the first and second correction controls are performed simultaneously with the image density adjustment and the alignment operation.
According to a tenth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to ninth aspects, wherein the image forming apparatus performs image formation using a two-component developer comprising a toner and a carrier . The image forming apparatus includes a control unit that realizes each process .

  According to the present invention, when the toner consumption amount per unit time is small, it is possible to eliminate the need to increase the TC by forcibly consuming the toner and reducing the total toner charge amount. If α is large, the developing device is driven and agitated to remove additives adhering to the carrier and increase the chance of contact between the toner and the carrier, thereby increasing the overall charge amount and reducing TC. Can be suppressed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of a color image forming apparatus to which the present invention is applied, specifically, a tandem indirect transfer type image forming apparatus. FIG. 2 is an enlarged schematic view showing the periphery of the image forming means of the tandem image forming unit in FIG.
1 and 2, the image forming apparatus includes an image forming apparatus main body 1, a paper feed table 2 on which the image forming apparatus main body 1 is mounted, a scanner (reading optical system) 3 mounted on the image forming apparatus main body 1, and It consists of an automatic document feeder (ADF) 4 mounted thereon.
An endless belt-like intermediate transfer member 10 extending in the lateral direction is provided at the center position of the image forming apparatus main body 1. In the illustrated example, the intermediate transfer member 10 is wound around three support rollers 14, 15, and 16 so as to be able to rotate and convey clockwise in the drawing.
In the illustrated example, an intermediate transfer body cleaning device 17 that removes residual toner remaining on the intermediate transfer body 10 after image transfer is provided to the left of the second support roller 15 among the three support rollers 14, 15, and 16. Provided.
Further, among the three support rollers 14, 15, 16, the intermediate transfer member 10 that is stretched between the first support roller 14 and the second support roller 15 is black / yellow along the transport direction. The tandem image forming unit 20 is configured by arranging four image forming units 18 of magenta and cyan side by side.

An exposure device 21 is further provided immediately above the tandem image forming unit 20 as shown in FIG. On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer body 10 from the tandem image forming unit 20.
In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24, which is an endless belt, between two rollers 23, and is pressed against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to the sheet from the paper feed table.
A fixing device 25 for fixing the transferred image on the sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 which is an endless belt. The secondary transfer device 22 described above also has a sheet transport function for transporting the image-transferred sheet to the fixing device 25.
In the illustrated example, a sheet reversing device 28 for reversing the sheet to record images on both sides of the sheet in parallel with the above-described tandem image forming unit 20 below the secondary transfer device 22 and the fixing device 25. It has.

Now, when making a copy using this color electrophotographic apparatus, a document is set on the document table 30 of the automatic document feeder 4. Alternatively, the automatic document feeder 4 is opened, a document is set on the contact glass 32 of the scanner 3, and the automatic document feeder 4 is closed to hold the document.
When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 4, the document is transported and moved onto a reading glass 32 (not shown), and then on the contact glass 32. When the document is set on the scanner 3, the scanner 3 is immediately driven to travel on the first traveling body 33 and the second traveling body 34.
Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.
When a start switch (not shown) is pressed, one of the support rollers 14, 15 and 16 is rotationally driven by a drive motor (not shown) and the other two support rollers are driven to rotate. 10 is rotated and conveyed.
At the same time, the individual image forming means 18 rotates the photoconductor 40 to form black, yellow, magenta, and cyan monochrome images on each photoconductor 40. Then, along with the conveyance of the intermediate transfer member 10, the single color images are sequentially transferred to form a composite color image on the intermediate transfer member 10.

On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 2 is selectively rotated, and the sheet is fed out from one of paper feed cassettes 44 provided in multiple stages in the paper bank 43.
The fed sheets are separated one by one by a separation roller 45 and put into a paper feed path 46, conveyed by a conveyance roller 47 and guided to a paper feed path 48 in a copying machine (image forming apparatus) main body 1, and a registration roller 49 Stop by hitting.
Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet.
The sheet after image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25. After fixing the transferred image by applying heat and pressure with the fixing device 25, it is switched with the switching claw 55, discharged with the discharge roller 56, and stacked on the discharge tray 57.
Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56.

On the other hand, the intermediate transfer member 10 after the image transfer is prepared by removing residual toner remaining thereon after the image transfer by the intermediate transfer member cleaning device 17 to prepare for the image formation by the tandem image forming unit 20 again.
As shown in FIG. 2, which shows an enlarged view of the periphery of two image forming units of the tandem image forming unit in FIG. 1, in the tandem image forming unit 20, the individual image forming units 18 (only two are shown in FIG. 2). More specifically, for example, a charging device 60, a developing device 61, a primary transfer device 62, a photoconductor cleaning device 63, a charge removal device 64, and the like are provided around the drum-shaped photoconductor 40.
The developing device 61 includes a developer agitating / conveying screw 66a of a first developer agitating unit (toner replenishing side) 66 as a developer agitating / conveying means, a second developer agitating unit ( A developer carrying body 67) stirring / conveying screw 67a and a developer carrying body (developing roller, developing sleeve) 68 are provided.

A replenishing port (not shown) is provided on the outer wall of the developer container 65 of the first developer stirring section 66, and toner is supplied from a toner replenishing device (not shown). The toner replenishment side developer stirring screw 66a stirs and conveys the toner replenished from the toner replenishing device and the developer in the developer container 65 (two-component developer having magnetic particles and toner).
Further, the agitation screw 67a of the second developer agitation unit (developer carrier side) 67 agitates and conveys the developer in the developer container 65. The first developer agitator 66 and the second developer agitator 67 are partitioned by a partition wall 69, and there are openings (not shown) for delivering the developer at both ends. In FIG. 2, reference numeral 10 denotes an intermediate transfer member, 71 denotes a toner density sensor, 73 denotes a developer blade, 75 denotes a cleaning blade, and 76 denotes a cleaning roller.

Next, a color image forming process of the image forming apparatus used in the present invention will be described. When forming a color image, first, in the first image forming unit 18, the surface of the rotating photosensitive drum 40 is uniformly charged by the charging roller 60 that is a charging device, and is uniformly charged to about −650V. .
Thereafter, image exposure is performed by a laser optical system as an exposure device, and an electrostatic latent image is formed on the photoconductive layer on the surface of the photosensitive drum 40. The electrostatic latent image is developed using a yellow developer from a developing sleeve 68 provided in the developing device 61, and the latent image is visualized as a yellow toner image.

The development process will be described. The developing device 61 includes a developing container 65 containing a two-component developer and a developing sleeve 68, stirring screws 66a and 67a, and a doctor blade 73 that forms a toner thin layer on the surface of the developing sleeve 68. .
The developing sleeve 68 is arranged close to the photosensitive drum 40 at least at the time of development, and is set so that development can be performed while the developer is in contact with the photosensitive drum 40.
The two-component developer used in this embodiment is configured by mixing a negatively charged toner having an average particle diameter of 6 to 7 μm manufactured by a pulverization method and a magnetic carrier having an average particle diameter of 35 μm. In this embodiment, at the time of development, -500v is applied to the development sleeve 68 as a development bias and development is performed.

The transfer process will be described. The toner image visualized on the photosensitive drum 40 is transferred to the intermediate transfer belt by the first intermediate transfer unit, and then the respective photosensitive drums in the order of the second, third, and fourth image forming means 18. The toner image on 40 is transferred to the intermediate transfer belt 10, whereby a color-superimposed image is formed on the intermediate transfer belt 10.
The toner image formed by superimposing colors on the intermediate transfer belt is transferred onto the transfer paper by the secondary transfer belt 24, and then the toner image is thermally fixed onto the transfer paper by the fixing device 25, and the image is transferred. The fixed transfer paper is output to the paper discharge unit 57.

Image density control will be described. In the electrophotographic system, when the amount of toner to be developed is calculated from the amount detected by the optical element while changing the development potential stepwise, the relationship between the development potential and the adhesion amount shows linearity. The inclination is called development γ, and the value of the development potential when the amount of toner to be developed becomes 0 is called development start voltage: Vk.
A developing potential for obtaining a desired toner adhesion amount is calculated from the values of developing γ and Vk, and the charging potential Vc, the developing potential Vb, and the laser light quantity are selected from a preset table. .
A change in TC will be described. In this method, a target development γ value is set, and the toner replenishment amount is controlled so that the development potential falls within a certain range. Considering only within the range of developer, this means that the charge amount of the developer falls within a certain range, and the charge amount adjustment by changing the TC for the change in the charge amount of the developer over the environment or over time Is done. As a result, TC decreases when the charge amount decreases, and TC increases when the charge amount increases.

FIG. 3 is a flowchart for explaining the flow of developer control in the image forming method according to the present invention. As shown in FIG. 3, at the start of image formation, the toner consumption amount α per driving time of the developing device is detected to determine whether α is within the reference range (S1).
In this case, if α is below the reference range, toner is forcibly consumed (S2), potential control is performed (S3), and image formation preparation is started. If α exceeds the reference range, a drive motor (not shown) of the developing sleeve 68 (FIG. 2) is driven (S4), potential control is performed (S3), and image formation preparation is started. Further, in step (S1), if α is within the reference range, the potential control is performed as it is (S3) and the image formation preparation is started.
As described above, the image forming method according to the present invention detects the developing device driving time and the toner consumption amount so that the value of α representing the toner consumption amount per developing device driving time is within a certain range during the image forming process. On the other hand, when α falls below the set lower limit, toner is forcibly consumed. Conversely, when α exceeds the set upper limit, the developing device is driven and the developer is stirred. Yes.
A control circuit for performing this control is incorporated in the overall configuration of the tandem type indirect transfer type image forming apparatus using the present invention, and is included in the developing device of the tandem image forming unit, so that it is not particularly shown as a control circuit.

FIG. 4 is a graph showing a toner consumption amount (= α) per unit time and a charge amount (= DA) change amount normalized by the initial TC. FIG. 5 is a graph showing the TC transition (with / without correction) when toner consumption per unit time is large. FIG. 6 is a graph showing the TC transition (with / without correction) when the toner consumption amount per unit time is small.
The first embodiment of the present invention will be described with reference to FIGS. FIG. 4 shows the amount of change in charge amount from the beginning: ΔDA converted to TC 7 wt% when the amount of toner consumed: α is changed in the developing device 61 (FIG. 2).
([DA] = [Q / M] × [TC] / 7)
It can be confirmed that the charge amount increases when α <15 [mg / sec] and the charge amount decreases when α> 25 [mg / sec]. Here, it is assumed that 15 <α <25 [mg / sec], and the operation when out of this range is as follows:
α <15 [mg / sec]... forcibly consumes the toner so as to be within α. α> 25 [mg / sec]... to drive the developing device 61 so as to be within α and stir the developer. Set to do.

5 and 6 show the results of examining the transition of TC with and without correction in the first embodiment of the present invention. It was confirmed that the TC transition could be stabilized regardless of the toner consumption per development driving time by adding the correction.
FIG. 7 is a graph showing the TC transition of the sheet number reference correction. FIG. 8 is a graph showing the TC transition of the developer driving time reference correction. FIG. 9 is a graph showing the TC transition of the developer drive time reference correction, with the number of sheets on the horizontal axis.
As an example in which the correction according to the first embodiment of the present invention is installed, the second embodiment uses 100 sheets under the condition that the toner consumption is small and the image density adjustment and alignment operations enter every fixed number of image formations. The TC transition reflecting the correction of the present invention is shown in FIG.
It can be seen that TC increases over time with respect to the number of images formed. This is because the image density adjustment and alignment operations are image forming operations, and the developing device is driven, but the number of sheets is zero. For this reason, the number of images formed, the developing device drive time, and the number of images are not necessarily in a linear relationship, and it is considered that the toner charge amount increases because the developing device drive time is longer than expected.
From this, it can be said that the number of formed images is not suitable for correction in actual use. This is also a factor that does not establish a linear relationship between the developing device driving time and the number of image formations, such as the number of sheets output in one image formation operation (job) and the paper size.

Here, FIG. 8 shows the TC transition when the paper is passed under the same conditions with the main correction being performed every 100 minutes with the developing device driving time as a reference. It was confirmed that the TC increase was suppressed more than the image forming number reference, and that the TC control could be performed stably by using the developing device driving time as a reference. As shown in FIG. 9, even when compared with the same number of sheets, the increase in TC is still suppressed.
In order to keep TC constant, it is necessary to periodically perform the control shown in the first embodiment. Here, by using the developing device drive time as a reference, accurate correction is possible because the drive time not only during the printing operation but also during the image density adjustment operation and the alignment operation is taken into consideration.

FIG. 10 is a graph showing the TC transition based on the developing device driving time. In the second embodiment, correction is performed on the basis of the developing device drive time. The transition of TC when the sheet is passed under the condition that the amount of toner consumption is large with this control included is shown as a circle in FIG. 10 as the third embodiment. A TC decrease accompanying a decrease in the charge amount is observed.
This is because a large amount of toner is consumed within a certain developing device driving time, and the amount of charge is reduced before correction is performed. In view of this, the transition of TC under the condition that the correction is made for each constant toner consumption amount in consideration of the toner consumption amount is shown by ■. In this case, it can be confirmed that the correction is performed before the charge amount decreases, and the decrease in TC is suppressed.
In the correction of the developing device agitation time reference shown in the second embodiment, when a large amount of toner is consumed during the correction, the charge amount greatly decreases, and the agitation time in the correction operation increases. End up. Here, by using the toner consumption amount as a reference, it is possible to suppress a significant decrease in the charge amount between corrections and to shorten the stirring time.

FIG. 11 is a graph showing the TC transition based on the developing device drive time reference when the toner consumption is large. FIG. 12 is a graph showing the TC transition based on the developing device driving time reference when the toner consumption is small.
The fourth embodiment defines the range of α in which correction according to the present invention is performed. If the range of α is too large, correction is not performed and the effect is almost the same as in the prior art.
The range of α to be corrected is desirably set so as to fall within a certain range of charge amount fluctuation with reference to the point where the amount of change in DA in the first embodiment is zero.

FIG. 11 shows the transition of TC when image formation is repeated under the following conditions while changing the range of α. Here, the toner consumption amount per unit time in which the change amount of DA in the first embodiment is 0 is α0, and the range in which the correction according to the present invention is included is a variation in DA in the first embodiment. Comparison is made with consumption per unit time of 10, 15, and 20 μC / g: α0 ± 5, 10, and 15 mg / second.
When the correction range is α = 0 ± 15 mg / second (DA fluctuation ± 20 μC / g), the effect of the correction cannot catch up, and when α is large, the charge amount decreases, and as a result, TC decreases. Further, when α is small, the charge amount increases, and as a result, TC also increases, and the effect of this correction is not obtained.
From these results, it can be confirmed that it is effective to use the range of α in which the change amount of the charge amount is within ± 15 μC / g in order to shift the charge amount within a certain range.
The transition of the toner charge amount varies depending on the toner consumption amount per unit time, and there is a range in which the increase and decrease of the charge amount can be balanced. By using α in which the rate of change of the charge amount with respect to the developing device drive time is in the range of ± 10 μC / g, the charge amount can always be maintained in an appropriate range.

FIG. 13 is a graph showing the transition of the rank rank according to the fourth embodiment. In the fifth embodiment, attention is focused on suppressing the blur of the image when the toner consumption amount per unit time is small, that is, the density unevenness of the solid portion on the image.
When the toner consumption per unit time is small, the image may become blurred. One reason for this is that there is a large amount of toner whose charge amount is increased by being stirred for a long time in the developing device, and transfer becomes difficult.
Here, in this control, the lower limit of the toner consumption per unit time in which the blur is within the allowable range is checked in advance, and the toner is consumed when the lower limit is exceeded, so that the image quality without blur can be maintained. Thought.
FIG. 13 shows the transition of the ranking of image blur when the toner consumption amount of the fourth embodiment is small. It was confirmed that good image quality was maintained by setting the threshold for toner consumption to 10 mg / second.

FIG. 14 is a graph showing the time taken for correction when changing the developing device drive speed during correction. In the sixth embodiment, when performing correction for driving the developing device when the amount of toner consumption per unit time is large, the time required for correction is shortened by making the developing device drive speed faster than that during the image forming operation. I am interested in that.
In FIG. 14, the developing device drive time is the same as that at the time of image formation, 1.5 times the time of image formation, and twice the time of image formation, and the toner consumption per unit time is 40 mg / second. The time taken for the correction when the continuous image forming operation is performed is shown below. It can be confirmed that the correction time is shortened by making the developing device drive speed during the correction operation faster than during the image formation.

FIG. 15 is a graph showing the time taken to output a certain number of sheets depending on the toner consumption timing. The seventh embodiment is interested in performing correction based on toner consumption without stopping the image forming operation when the toner consumption per unit time is small.
FIG. 15 shows the time when a predetermined number of sheets are passed between the toner consumption operations performed after the fixed number of images are formed and between the image forming operations (between sheets). It was possible to reduce the time required to pass the paper by correcting between the image formation.
As described above, when the amount of toner consumed per unit time is less than a certain amount, the toner in the developing device is consumed. However, the time required for correction can be shortened by creating a consumption pattern during image formation.

FIG. 16 is a graph showing a difference in developer deterioration (amount of carrier film shaving) due to a difference in operation target. In the eighth embodiment, when there are a plurality of developing devices, α is calculated for each developing device, and only necessary items are corrected simultaneously by toner consumption and developing device driving, and those that do not need to be operated are operated. By not doing so, it is intended to suppress the deterioration of the developer by correction.
FIG. 16 shows a case where all units are operated at the time of correction and a case where only the units that need correction are operated. The degree of deterioration of the carrier is represented by the total amount of carrier film scraping of each developing device. .
Since all the developing devices are operated, some of them need not be corrected, so that the total carrier deterioration is progressing, and the carrier deterioration is suppressed by operating only the units that need correction.

FIG. 17 is a graph showing the difference in sheet passing time depending on whether correction is performed during image density adjustment and alignment. In the ninth embodiment, the time is further reduced by performing the correction according to the present invention at the time of image density adjustment and alignment operation that are performed periodically.
The developing device agitating operation when the toner consumption per unit time is small is performed simultaneously with the image density adjustment and the alignment operation. In addition, when the amount of toner consumed per unit time is large, the consumption can be performed simultaneously by creating a consumption pattern in the present invention at a position that does not interfere with the pattern created during image density adjustment or alignment operation. You can save time.
FIG. 17 shows the time required to pass a certain number of sheets, with or without performing the correction according to the present invention at the time of image density adjustment and alignment. By performing the correction of the present invention at the time of image density adjustment and alignment, the time required for correction can be shortened.
Accordingly, a special pattern is formed in each of the density adjustment operation and the alignment operation, but a correction is made when a consumption pattern is created at a position that does not interfere with the pattern and toner consumption is performed. By performing the adjustment at the same time as the density adjustment and alignment, the time required for correction can be shortened.

FIG. 18 is a graph showing a difference in time required for correction depending on whether or not correction is performed at the fixing device startup time. The tenth embodiment aims to further shorten the time by performing correction according to the present invention while the temperature of the fixing device rises.
According to the tenth embodiment, the startup time of the fixing device is required from the time when the machine power is turned off to the standby in order to reduce energy, but it is efficient by performing this correction using that time. Can be corrected.
FIG. 18 shows the time required for the correction in 10 days with and without the correction according to the present invention when the fixing device is started up. By performing the correction according to the present invention at the time of starting the fixing device, it is possible to reduce the time for performing only the correction, reduce the time required for the correction, and perform the correction efficiently.

1 is a schematic diagram illustrating an overall configuration of a color image forming apparatus to which the present invention is applied, specifically, an image forming apparatus of a tandem type indirect transfer system. FIG. 2 is an enlarged schematic view illustrating the periphery of an image forming unit of the tandem image forming unit in FIG. 1. 6 is a flowchart illustrating a developer control flow of the image forming method according to the present invention. FIG. 5 is a graph showing a toner consumption amount (= α) per unit time and a charge amount (= DA) change amount normalized by an initial TC. FIG. 6 is a graph showing a TC transition (with / without correction) when toner consumption per unit time is large. FIG. 6 is a graph showing a TC transition (with / without correction) when toner consumption per unit time is small. It is a figure which shows TC transition of sheet number reference | standard correction | amendment with a graph. It is a figure which shows TC transition of developing device drive time reference | standard correction with a graph. It is a figure which shows TC transition of developing device drive time reference | standard correction | amendment on a horizontal axis | shaft, and shows a number of sheets by a graph. It is a figure which shows TC transition of developing device drive time reference | standard with a graph. FIG. 6 is a graph showing a TC transition based on a developing device driving time reference when a toner consumption amount is large. FIG. 6 is a graph showing a TC transition based on a developing device driving time reference when a toner consumption amount is small. It is a figure which shows the bullet rank transition in 4th Embodiment with a graph. FIG. 7 is a graph showing the time taken for correction when changing the developing device drive speed during correction. FIG. 6 is a graph showing a time taken for a constant sheet output depending on toner consumption timing. It is a figure which shows the difference of the developer deterioration (carrier film scraping amount) by the difference of the object made to operate | move by a graph. It is a figure which shows the difference in the paper passing time by the presence or absence of the correction | amendment at the time of image density adjustment and alignment. FIG. 9 is a graph showing a difference in time required for correction depending on whether or not correction is performed at the fixing device startup time.

Explanation of symbols

20 tandem image forming unit, 40 drum-shaped photoreceptor, 60 charging device, 61 developing device, 62 primary transfer device, 66a developer stirring / conveying screw, 67a developer stirring / conveying screw, 68 developer carrier (development) sleeve)

Claims (10)

In a two-component development image forming method comprising a toner and a carrier,
At the start of image formation, the developer agitation time and the toner consumption amount are detected. During the image formation process, the range of α representing the toner consumption amount per agitation time of the developer is a predetermined change amount of the charge amount. The first correction control for forcibly consuming the toner is performed when α is below the set lower limit so that the range falls within the range, and the developing device is driven when α exceeds the set upper limit. A second correction control for stirring the developer is performed. The image forming method according to claim 1, wherein the first and second correction controls are periodically performed based on a stirring time of the developer .   The image forming method according to claim 1, wherein the first and second correction controls are periodically performed on a toner consumption basis.   2. The image formation according to claim 1, wherein the range of α is such that the variation in charge amount is within ± 10 μC / g with reference to the value of the charge amount at which an appropriate toner density is obtained. Method.   The image forming method according to claim 1, wherein the lower limit of the target range of α is set so that the blur of the image falls within an allowable range.   The image forming method according to claim 1, wherein when performing the second correction control, the driving speed of the developing device is made faster than that during the image forming operation.   The image forming method according to claim 1, wherein the first correction control is performed by creating a pattern during image formation.   In the first and second correction controls, when there are a plurality of the developing devices, the α is calculated in each developing device, and only the developing devices satisfying the correction condition are subjected to the first and second correction controls. The image forming method according to claim 1, wherein correction control is performed.   The image forming method according to claim 1, wherein the first and second correction controls are performed simultaneously with image density adjustment and alignment operation. In an image forming apparatus that forms an image using a two-component developer composed of a toner and a carrier,
An image forming apparatus comprising a control means for realizing each step of the image forming method according to claim 1.

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