JP3503914B2 - Image forming device - Google Patents

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 a copying machine, a facsimile, a printer, etc.
The present invention relates to an image forming apparatus that can prevent unnecessary agitation when agitating a developer for the purpose of stabilizing the charging of the developer supplied to an image carrier.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus,
It is known that a charged developer is attracted onto an image bearing member by magnetic force to perform development. In order to favorably replenish the image bearing member with the developer, it is required that the developer be well charged. Further, particularly when a two-component developer is used, it is required that the toner is uniformly mixed in the developer. Therefore, conventionally, there has been proposed a method of stirring the developer before being supplied to the image carrier. In an image forming apparatus that agitates the developer, the degree of agitation of the developer affects the charge amount of the developer and the mixing degree of the toner in the developer (hereinafter, referred to as developer characteristics), so that a good image is obtained. In order to obtain the above, it is required to properly agitate the developer.

For example, in an image forming apparatus using a two-component developer, it is necessary to stabilize the developer characteristics in the developing device at an appropriate level while developing the image density. Toner replenishment, which is performed to maintain the toner concentration in the developer, is usually performed during the developing operation, immediately before and after the developing operation, or when the apparatus is warmed up. The toner was incorporated into the developer, and the developer characteristics were improved.

However, how much the stirring of the developer is sufficient depends on the toner concentration in the developer immediately before the stirring, the developer characteristics, etc., and the usage condition of the image forming apparatus, etc. It must be considered that it changes depending on.

Various methods have been proposed as simple means for this. For example, JP-A-3-29338
According to Japanese Unexamined Patent Publication No. 3 (1994), a method is proposed in which the stirring time is controlled according to the information detected by the developer concentration detection sensor in the developing device after toner supply. In addition, a method of controlling the stirring time according to the toner replenishment amount, or a constant stirring time for obtaining a sufficient developer characteristic to obtain a stable and good image in any case, the toner replenishment is performed. A method of carrying out each time is also known.

On the other hand, the stirring of the developer cannot always obtain stable image quality unless the developer characteristics that have changed with time / environment are taken into consideration. As means for dealing with this, for example, according to Japanese Patent Laid-Open No. 2-125275, the density detecting means detects the density of the non-image portion on the image carrier, and when the detection result of the density exceeds a certain value, the developing means. It has been proposed that the toner supply to the toner is stopped and the stirring member is driven to prevent the toner from scattering and the image from cracking.

[0007]

In the method of controlling the stirring time according to the detection result of the developer concentration detecting sensor and the method of controlling the stirring time according to the toner replenishment amount, the object to be detected is to be detected. It is necessary to accurately grasp the developer characteristics of the developer that becomes However, in a unique situation, this precise grasp is difficult, so there is a problem of lacking flexibility in control, and in order to accurately perform control according to a unique situation, advanced technology is required. Because it was difficult. Therefore, if the reliability of stirring control according to the developer characteristics is required, it is safe to adopt a method of stirring the developer for a sufficiently long time.

From the above, in the conventionally proposed image forming apparatus, in order to stably obtain a good image, it is required to set the developer stirring operation in advance for a long time. However, if the stirring time of the developer is increased, not only the deterioration of the developer will be accelerated, but also depending on the control method, useless downtime of the image forming apparatus may occur or work may be delayed.

The present invention has been made in view of the above problems, and an object of the present invention is to perform stirring for a minimum time necessary for stably obtaining a good image even in a unique situation. And an image forming apparatus that does not continue stirring unnecessarily.

[0010]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention appropriately drives a developer agitating means in a developing device for developing a latent image on an image carrier, In an image forming apparatus that stabilizes the charging of the developer in the developing device, an image is formed of a potential portion for measurement, which is at least one of a potential portion corresponding to a white portion and a potential portion to which toner adheres, under a predetermined image forming condition. An image forming means including the developing device, which is formed on a carrier and exerts a developing action on the measuring potential part by the developing device, and on the measuring potential part subjected to the developing action. Density detecting means for detecting the density of the developer, and the toner adheres based on the detection result of the density detecting means
Density detection of halftone pattern formed as potential part
The value has been repeated multiple times and is within the predetermined appropriate range.
The density detection value of the potential part corresponding to the white part is equal to or higher than a predetermined appropriate value.
When both of the above are satisfied, a means for stopping the driving of the developer agitating means is provided.

Here, the electric potential corresponding to the white portion is the electric potential of the photosensitive member portion which is not intended to adhere toner in a normal image forming process. It is the potential of the photoconductor portion where all the charges are removed, and the potential of the photoconductor portion that is charged by uniform charging in reversal development.

Further, it intends in particular line potential portion formed density detection is repeated a plurality of times of halftone patterns toner adheres as potential portion for the measurement. According to this, Ru can appropriately determine whether the toner distribution becomes uniform in the developing device.

[0013] In the image forming apparatus according to claim 1, while stirring the developer, a predetermined image forming condition, a <br/> potential portion of the halftone pattern potential portion of the corresponding white portion and the toner adheres Both potential portions for measurement are formed on the image carrier, and the concentration of the developer on the potential portion for measurement is detected . Then, it is formed as a potential portion to which the toner is attached.
The density detection value of the halftone pattern is repeated multiple times.
Within a predetermined proper range and the potential equivalent to the above white area
Both the density detection value of the part has exceeded a predetermined appropriate value
When the above condition is satisfied, the driving of the developer stirring means is stopped .

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, in which a toner replenishing means for replenishing the developer with toner is provided, and the driving of the developer agitating means is started during or immediately after replenishing the toner. It is characterized by that.

According to another aspect of the image forming apparatus of the present invention, when the developer and the toner are not uniformly mixed during or immediately after the toner is replenished to the developer by the toner replenishing means.
The stirring of the developer is started, and the potential portion for measurement, which is at least one of the potential portion corresponding to the white portion and the potential portion to which the toner adheres, is formed on the image bearing member according to the predetermined image forming conditions formed on the image bearing member. When the toner is replenished or immediately after replenishment, the toner is formed on the toner, and the developer characteristics are substantially judged by the detection result of the concentration of the developer on the potential portion for measurement to control the continuation and stop of the stirring of the developer. Good developer characteristics can be obtained even when the developer is agitated.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect, further comprising environmental condition detecting means for detecting an environmental condition, and the environment of use is suitable for use of the image forming apparatus by the environmental condition detecting means. It is characterized in that the drive of the developer agitating means is started when it is detected that it is out of the range of various environments.

Here, the developer characteristics are affected by the use environment conditions such as time and environment. For example, in the case of a developer highly dependent on the environment due to humidity, if the temperature inside the device is substantially constant, within a certain range of absolute humidity, the developer will have an appropriate humidity with suitable developer characteristics for image formation. Even if it deviates from the above range, there is an image formable range at a humidity close to the proper humidity. Then, when the humidity is out of the image-formable range, the developer characteristics are not suitable for image formation.

In the image forming apparatus according to claim 3, when the use environment is out of the range of the environment suitable for use of the image forming apparatus and it is judged that the developer characteristics are unsuitable for image formation, the development The stirring of the agent is started, and a potential portion for measurement, which is at least one of the potential portion corresponding to the white portion and the potential portion to which the toner adheres, is formed on the image carrier under predetermined image forming conditions, and the measurement potential portion is formed. When the developer characteristics are substantially judged from the detection result of the concentration of the developer on the potential portion of the toner, the stirring and continuing of the developer are controlled to be stopped, and the developer is stirred at the time of toner supply or immediately after the supply Also makes it possible to obtain good developer characteristics.

Here, in addition to the insufficient stirring, the degree of deterioration of the developer also affects the detection result of the density in the potential portion corresponding to the white portion. No matter how much the deteriorated developer is stirred, good developer characteristics cannot be obtained. In this case, the stirring operation may continue and the control unit may run away.

Conventionally, various methods for detecting the degree of deterioration of the developer have been proposed. For example, JP-A-59-038
According to Japanese Patent No. 767, the optical sensor detects the density of the pattern image formed on the image carrier under a predetermined image forming condition, and the life of the developer is determined based on the edge effect strength of the detection result. It is known how to do it. And, Japanese Patent Laid-Open No. Hei 5
No. -80655 discloses an optical sensor for detecting the density of a non-image portion of a pattern image formed on an image carrier, and the life of the developer is determined based on the degree of background stain based on the detection result. .

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

DETAILED DESCRIPTION OF THE INVENTION

[Embodiment 1] An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a copying machine according to this embodiment. The copying machine includes a scanner unit 20 for reading a document, an image processing unit 21 for electrically processing a digital signal output from the scanner unit 20,
The printer unit 22 forms an image on a transfer sheet based on a digital signal output from the image processing unit.

In the scanner section 20, the image of the original placed on the original placing table is read by an image reading device (not shown) via an irradiation lamp, a mirror and a lens (not shown), and the data is read. Image processing unit 21
Sent to. In the image processing unit 21, this data is subjected to necessary processing, converted into an image signal, and sent to the printer unit 22.

In the printer unit 22, the surface of the photosensitive drum 1 as an image carrier, which is driven to rotate in the direction of arrow A in the figure, is uniformly charged by the charger 2. And
A latent image corresponding to the image of the original is formed on the surface of the photoconductor drum 1 by the exposure device 3 including a semiconductor laser, a polygon mirror, a reflection mirror, and the like, based on the image signal from the image processing unit 21. The latent image on this photosensitive drum 1 is
At the portion facing the developing device 4, the image is developed by the developer supplied from the developing roller 41 as the developer carrying member of the developing device 4. Here, the developing device 4 will be described in detail later. Then, the visualized image is placed on a belt-shaped conveying device 7 from the paper feeding tray 5 at timing by the registration rollers 6 and is conveyed to a portion facing the photosensitive drum 1, for example, transfer paper (see FIG. (Not shown) is transferred by the transfer device 8. The transfer sheet onto which the visible image has been transferred is conveyed by the conveying device 7, and when passing through the fixing device 9, the visible image is fixed and discharged onto the paper discharge tray 10. Here, the untransferred toner remaining on the photosensitive drum 1 after the transfer of the visible image is cleaned by the cleaning device 1.
The photosensitive drum 1 is cleaned by 1 and collected by the cleaning device 11. Then, the surface of the photosensitive drum 1 after cleaning is provided with a discharge lamp (not shown).
The residual charge is removed by.

FIG. 2 is a plan view of the developing device used in the copying machine having the above structure. The developing device 4 develops using a two-component developer composed of toner and carrier, and is mainly composed of a developer stirring tank 42 and a toner storage tank 43 provided above the developer stirring tank 42. The toner storage tank 4 is provided between the toner storage tank 43 and the developer stirring tank 42.
3 is provided with a toner replenishing roller 44 for replenishing the developer agitating tank 42 with toner.
An agitating roller 45 as an agitating means for agitating the developer is provided at the bottom of the casing, and a developing roller 41 for carrying the developer on the surface is provided at an opening of the casing facing the photosensitive drum 1. The agitating roller 45 supplies the developer consisting of toner and carrier to the developing roller 41 while mixing and agitating the developer consisting of the toner and the carrier. The developer replenished on the developing roller is regulated to have a predetermined thickness and then conveyed to a developing area opposite to the photosensitive drum.

In the copying machine of this embodiment, the optical sensor 30 for detecting the amount of toner adhering to the photoconductor is located at a position facing the photoconductor drum on the downstream side of the developing area in the rotation direction A of the photoconductor drum. It is provided to detect the toner adhesion state on the photoconductor. A method for determining whether to continue or stop the stirring of the developer based on this detection signal will be described in detail later.

By the way, the stirring and mixing of the developer and the toner in the developer stirring tank by the stirring roller is carried out for the purpose of uniformly mixing the developer and the toner and appropriately raising the charge amount of the developer. Is performed immediately after the start-up, during the developing operation, during the developing operation, immediately before and immediately after the developing operation, and the like. When the toner consumption in the developing device drops significantly from the appropriate value, such as when a large number of images with large image area and large toner consumption are formed, the next image forming work command is issued. The toner replenishment work is performed in order to raise the toner concentration in the developer to an appropriate value before the occurrence of. At this time, the developer in the developer agitation tank, in which the required amount of toner has been replenished from the toner storage tank, has a non-uniform toner concentration and chargeability. Stirring is started.

In this embodiment, a halftone pattern as a potential portion to which the toner having sufficient detection sensitivity adheres is formed in parallel with the stirring work by using a charger and an exposure device, and a photoconductor is used by a developing device. After visualizing on the drum, the image density of the halftone pattern is read by an optical sensor. Then, based on the output value of the optical sensor, the voltage applied to the charger grid (not shown), the LD voltage applied to the exposure device, and the voltage applied to the developing roller are controlled to maintain the image quality. The optical sensor not only detects the density of the halftone pattern, but also detects the density of the white potential portion as the potential portion corresponding to the white portion.
The detection of the density of the halftone pattern and the density of the white potential portion are alternately performed, and the image formation cycle of the halftone pattern is set so that each detection cycle is an integral multiple of the rotation pace of the stirring roller.

3 (a) and 3 (b) are diagrams showing the detection results of the halftone pattern and the white potential portion by the optical sensor, where the horizontal axis shows the stirring time and the vertical axis shows the detection value of the optical sensor. ing. In FIG. 3A, when the detected value of the halftone pattern falls within the area l surrounded by the broken line, it can be determined that the density of the halftone pattern is stable within the proper range and the developer is uniformly mixed. On the other hand, FIG. 3 (b)
In the above, when the detected value of the white portion potential portion is stable at a value larger than the value m indicated by the broken line, it can be determined that the density of the white portion potential portion is stable at an appropriate value or more and the developer reaches a desired charge amount. Therefore, after the stirring of the developer is started, the detection result of the halftone pattern is stabilized several times continuously in the region l, and the detection result of the white potential portion is experimentally obtained in advance. When the value is larger than the appropriate value m in the white area, h1
Then, the density of the halftone pattern is stable within the proper range, and the density of the white potential portion is stable at the proper value m or more, and it is determined that the image is good, and the stirring is stopped. Here, the criterion for determining the stability of the density of the halftone and white potential areas depends on the system of the copying machine, the accuracy and stability of the detection value by the optical sensor, and the characteristics of the supply such as the photosensitive drum developer used. Routinely and, in some cases, need to change depending on the history of supply usage.

Further, control of continuation and stop of the above stirring is
As described above, instead of using the detection results of the densities of both the halftone and white part potential parts, it is also possible to make the judgment only by the detection result of the halftone pattern or only the detection result of the white part potential part. it can.

According to the above construction, the developer characteristics such as the uniform mixing of toner in the developer and the charge amount are detected by the image density while stirring the developer, so that the state of the image can be accurately detected. can do. Also, if the image density is not good, stirring is continued, and when it becomes good, it stops, so it is possible to accurately grasp the time when the image becomes good, and stop stirring immediately when the image becomes good. Also, it is possible to prevent the developer from being unnecessarily continuously stirred to accelerate the deterioration of the developer. Further, it is possible to prevent wasteful downtime of the copying machine and delay of image forming work. Further, if the detection result of the halftone pattern is stabilized within a desired range several times in a row, it is determined that the image is good, so that the detection accuracy of the sensor is unstable or the image density is temporarily good. It is possible to prevent the stirring from being stopped by mistake in the case of deterioration. Further, according to the configuration that determines whether the stirring is continued or stopped based on the detected values of the densities of both the halftone pattern and the white potential portion, the density of only the halftone pattern or the white potential portion is detected. From the result, it is possible to more accurately detect that the developer characteristics are in a state suitable for image formation, as compared with the configuration that determines whether stirring is continued or stopped.

On the other hand, the control for continuing and stopping the agitation is
In the case of judging only by the detection result of the halftone pattern or only the detection result of the white potential part, the configuration for deciding whether to continue or stop the stirring as compared with the case of detecting both is provided. Can be simplified.

Further, in particular, when the developer is agitated in a state where the toner is extremely unevenly distributed in the developer at the time of replenishing the toner or immediately after the replenishment of the toner, by controlling the continuation and stoppage of the agitation as described above. However, it is not necessary to continue stirring for a sufficiently long time when the developer characteristics are expected to be in a state suitable for image formation, and good developer characteristics can be obtained with almost the minimum necessary stirring time. Therefore, it is possible to prevent a defective formed image due to insufficient agitation of the developer, and to prevent excessive agitation to accelerate the deterioration of the developer.

In the copying machine of the present embodiment, when the environment in which the copying machine is used is greatly changed and the developer characteristics are affected, and there is a possibility that the formed image is deteriorated, the occurrence of this problem is prevented. It has an anticipatory and preventative structure. That is, as shown in FIG. 2, the humidity sensor 31 for detecting the use environment information is provided above the developing device at a position separated from the developing device. If a humidity sensor detects that the environment in which the copier is to be used has changed significantly, and if it is expected that the charge amount of the developer in the developing device is partially reduced, the next image forming operation is performed. Until the command is issued, the stirring of the developer by the rotation of the stirring roller is started in order to make the charge amount of the developer in the developing device uniform and restore the developer characteristics. Also in this stirring work, as in the above stirring work, in parallel with this, various controls in the formation of the halftone pattern on the photosensitive drum, the reading of the halftone pattern density and the white part potential part density by the optical sensor, Also, control the continuation and stop of the stirring work. Regarding the control of continuation and stop of stirring during this stirring work, as in the case of the stirring work described above, the judgment control of the stirring continuation or the stop is performed only by the detection result of the halftone pattern or only the detection result of the white potential part. You can go.

According to the above construction, when the use environment of the copying machine is detected, the developer characteristics are adversely affected, and when it is determined that the developer is unsuitable for image formation, stirring of the developer is started, The developer properties on the image bearing member are substantially judged to control the continuation and stop of the stirring of the developer so that good developer properties can be obtained, so that the developer properties are not suitable for image formation. When the operating environment is set to, the occurrence of defects in the formed image due to insufficient stirring of the developer during the developing operation,
This can be prevented with the minimum stirring time, and it is possible to prevent the stirring of the developer excessively and accelerate the deterioration of the developer.

[Embodiment 2] Next, another embodiment of the present invention will be described. In the copying machine of the first embodiment, if the developer characteristics do not reach the desired level even if the stirring is continued, the cause may be deterioration of the developer. In the case of this cause, even if the stirring is continued, the stirring is unnecessarily continued. In view of this, the present embodiment employs a configuration that avoids runaway of the developer agitation work control unit due to developer deterioration in the copying machine of the first embodiment. The basic structure of the copier, the formation of a halftone pattern on the photoconductor drum, various controls for reading the halftone pattern density and the white part potential part density with an optical sensor, and the control method for continuing and stopping the stirring operation are basically The same as the first embodiment. Further, similarly to the above-described embodiment, the control for continuing and stopping the stirring may be determined only by the detection result of the halftone pattern or only the detection result of the white potential portion. The difference is that the upper limit time of the stirring work is set, and when the upper limit time is reached, the stirring is stopped regardless of the reading result by the optical sensor.

FIG. 4 shows an example of the detection result of the white potential portion by the optical sensor while stirring, when the developer is deteriorated. The horizontal axis shows the stirring time and the vertical axis shows the stirring time. The detection value of the optical sensor is shown. The white circles in the figure are examples of the developer with a relatively small degree of deterioration of the developer, and the circles filled with black are examples of the developer with a relatively large degree of deterioration of the developer. Further, at the time h2, in consideration of various copying machine use conditions, if the developer is not deteriorated to the extent that it needs to be replaced, the optical sensor detection value of the white portion potential portion is surely the above-mentioned white portion appropriate value. It is time to reach m or more. Even when this time h2 is reached, if the optical sensor output of the white portion potential portion has not reached the white portion proper value m, it can be determined that the developer has deteriorated. Further, in the figure, the output level of the optical sensor indicated by n is the optical sensor output level of the white part on the photoconductor corresponding to the abnormal image in which the white background stain is recognized on the transfer paper. The NG line is set with this level n as the upper limit value n of the developer life.

In the present embodiment, from the start of stirring to the above-mentioned upper limit time h2, as in the case of the above-described first embodiment, the control for continuing and stopping the stirring is performed by detecting the detection results of both the halftone pattern and the white potential portion. To judge. Then, when the upper limit time h2 elapses in the state where the stirring is continued, the stirring is stopped at that time. Then, the state of deterioration of the developer is determined based on the detection value of the white potential portion by the optical sensor at this time.

When the detected value of the white potential portion at the time when the upper limit time h2 is reached is smaller than the NG line, it is determined that the image quality cannot be maintained any more due to the deterioration of the developer. Then, the user is made aware that the developer needs to be replaced by turning on a toner replacement warning lamp provided on the operation unit or the like, and the copying machine is disabled.

On the other hand, when the upper limit time h2 is reached, the detected value of the white potential portion is on the NG line or the NG line.
Area p sandwiched by the line and the lower limit line of the detection value proper range
When it is settled inside, the background stain on the image is not remarkable, but it is judged that the fatigue deterioration of the developer is advanced. Then, the toner concentration control level of the developer is changed to the lowest level at which the required image density can be obtained, and the user is notified that the developer needs to be replaced by turning on the toner replacement warning lamp provided on the operation unit etc. Let Although the image density is reduced by lowering the toner density control level of the developer, it is possible to temporarily avoid the occurrence of background stains on the image and fluctuations in the image density. Therefore, it is possible to secure a grace time until such an abnormal image is generated, and during this time, the operation of the copying machine is not stopped. Therefore, by replacing the developer during the grace time, useless downtime is generated. Can be prevented.

Here, in the toner density control, usually, a pattern image formed on the image carrier under a predetermined image forming condition is detected by an optical sensor, and the detection result is set in advance as a toner replenishment determination threshold value. When it is judged that the toner adhesion amount of the pattern image is small as compared with, the toner is replenished to increase the toner density. That is, the toner replenishment determination threshold value determines the toner concentration control level of the developer. Therefore, in the present embodiment, the delay time is generated by changing the toner replenishment determination threshold value to a value corresponding to the minimum toner adhesion amount that can obtain a density that does not deteriorate the image quality.

The set value of the upper limit time of the stirring work is determined by the characteristics of the supply such as the charging ability of the developer used and the stirring ability of the developing device, and depending on the case,
Depends on supply usage history.

Further, as means for discriminating the state of deterioration of the developer in order to avoid runaway of the control portion, instead of means for using the detection results of the densities of both the halftone and white portion potential portions as described above. Alternatively, it is possible to make the determination based only on the detection result of the white potential portion. Further, only the halftone potential part is used for the judgment control of the stirring continuation and the stop until the upper limit time h2 comes, and the optical sensor output of the white part potential is output only when the upper limit time is reached while the stirring is continued. It may be used to detect the degree of developer deterioration.

According to the above construction, by setting the upper limit on the stirring operation time of the developer, the stirring of the developer becomes unnecessary when the developer characteristics do not reach the desired level due to the deterioration of the developer. It is possible to avoid a runaway of the control unit that continues.

In each of the above embodiments, the optical sensor 30 directly detects the toner concentration on the photoconductor in order to detect the toner concentration on the measurement potential portion. However, instead of this, The toner on the potential portion for measurement may be transferred onto a transfer paper or a conveyor belt of the transfer device 7, and then the optical density thereof may be detected. In this case, the output level of the optical sensor on the photoconductor does not match the output level of the optical sensor on the transfer paper due to the transferability when the toner on the photoconductor is transferred to the transfer paper or the like. Therefore, the optical sensor output level corresponding to each is used.

[0052]

Effects of the Invention] According to the image forming apparatus according to claim 1, while stirring the developer, both the potential of the halftone pattern the potential of the corresponding white portion on the image bearing member and the toner is deposited
The concentration of the developer in the measuring potential portion is detected .
Then, the half formed as the potential portion on which the toner adheres
The density detection value of the tone pattern is repeated multiple times
It is within the proper range and the density of the potential part corresponding to the white part is detected.
If both of the values have exceeded the prescribed appropriate value,
The case, it is determined to have become the desired developer properties, so to stop the agitation of the developer, an excellent effect of being able to maintain a good image while suppressing to a minimum the stirring time of the current image agent is there.

[0053] Incidentally, if performing the detection to stir controlling the concentration of both users of a potential portion where the potential of the white portion corresponds and toner adheres is the developer properties determined by the two, either one However, if the detection result is not good, it is possible to continue stirring the developer and stop the stirring after both are in a good state, so it is better to grasp the accurate image state. There is an advantage that it is possible to grasp the time when the developer characteristics return to a state where a good image can be reliably formed.

According to the image forming apparatus of the second aspect, even if the developer is agitated when the developer and the toner are not uniformly mixed during or immediately after the toner is replenished to the developer, the image is formed. By detecting the density of the pattern image, non-image area, or both of them on the carrier, the developer characteristics are substantially judged, and the continuous and stopped stirring of the developer is controlled to obtain good developer characteristics. Thus, there is an excellent effect that it is possible to prevent a defective formed image due to insufficient agitation of the developer at the time of replenishing the toner and to prevent excessive agitation to accelerate the deterioration of the developer.

According to the image forming apparatus of the third aspect, when it is determined that the use environment makes the developer characteristics unsuitable for image formation, stirring of the developer is started, and development on the image carrier is started. It is an environment where the developer properties are not suitable for image formation because the developer properties are substantially judged to control the continuation and stop of the developer agitation to obtain good developer properties. In this case, there is an excellent effect that it is possible to prevent a defective formed image due to insufficient stirring of the developer at the time of development, and to prevent excessive stirring to accelerate deterioration of the developer.

[0056]

[0057]

[0058]

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic copying machine according to an embodiment.

FIG. 2 is a plan view showing the developing device in FIG. 1 and its vicinity.

FIG. 3 is a diagram showing a detection result of each part by an optical sensor.

FIG. 4 is a diagram showing a detection result of a white potential portion by an optical sensor.

[Explanation of symbols]

1 photoconductor drum 2 charger 3 exposure equipment 4 Developing device 5 paper feed tray 6 Registration roller 7 Conveyor 8 Transfer device 9 Fixing device 10 Output tray 11 Cleaning device 20 Scanner section 21 Image processing unit 22 Printer 30 Optical sensor 31 Humidity sensor 41 developing roller 42 developer stirring tank 43 toner storage tank 44 Toner supply roller 45 stirring roller A. Photosensitive drum rotation direction l Appropriate range of halftone pattern detection values m Lower limit of appropriate value of detection value of white potential part h1 Output timing of stirring end command h2 Upper limit of stirring time

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Claims (3)

(57) [Claims] 1. An image forming apparatus for driving a developer agitating means in a developing device for developing a latent image on an image carrier to stabilize the charging of the developer in the developing device according to a predetermined image forming condition. , A potential portion for measurement, which is at least one of a potential portion corresponding to a white portion and a potential portion to which toner adheres, is formed on the image carrier, and a developing action is performed on the potential portion for measurement by the developing device. Based on the detection result of the image forming means including the developing device, the density detecting means for detecting the density of the developer on the measuring potential portion to which the developing action is applied, , The potential to which the above toner adheres
The density detection value of the halftone pattern formed as a part is
Repeated multiple times and within the prescribed appropriate range
The density detection value of the potential area equivalent to the white area is above the specified proper value.
An image forming apparatus comprising: means for stopping the driving of the developer stirring means when both of the above are satisfied . 2. The image forming apparatus according to claim 1, further comprising: a toner replenishing means for replenishing the developer with toner, and driving of the developer stirring means is started during or immediately after replenishing the toner. apparatus. 3. The image forming apparatus according to claim 1, further comprising environmental condition detecting means for detecting humidity, wherein the environmental condition detecting means detects that the humidity is out of the range of humidity suitable for use of the image forming apparatus. The image forming apparatus is characterized in that the drive of the developer agitating means is started in the case of the occurrence.