JPH0844175A - Image forming device - Google Patents

Abstract

PURPOSE:To appropriately judge the necessity of the execution of a stirring mode where developer is stirred at the inside of a developing device and the electrifying state of toner is stabilized in an electrophotographic image forming device using two-component developer. CONSTITUTION:This device is provided with a timer 52 measuring the stopping time of a developing device 37, a humidity sensor 44 measuring humidity near the developing device 37, and a storing device 53 storing the output value of the humidity sensor 44 at every image forming operation. When the time measured by the timer 52 is equal to or longer than a reference at the time of starting the image forming operation, a CPU 56 reads in the output Hum (on) of the humidity sensor 44 and compares it with the humidity Hum (end) at the time of a previous image forming stored in the storing device 53. In the case that a difference is equal to or higher than a specified value, the driving motor 43 of the developing device 37 is driven and the stirring mode of the developer is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for obtaining a visible image by using a two-component developer in which a toner and a magnetic carrier are mixed, and a control method thereof,
The present invention relates to an image forming apparatus and a control method thereof that can appropriately determine whether or not to perform a stirring mode for stirring a two-component developer in a developing device to stabilize a charged state of toner.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus using a two-component developer is well known. The two-component developer is a mixture of a magnetic carrier such as ferrite and a toner in which carbon or the like is dispersed in a dispersion medium made of resin. In an image forming apparatus using this two-component developer, The toner is charged by stirring the contained two-component developer, and then the toner is made to adhere to the electrostatic latent image due to the difference in the charging potential to visualize the latent image. Further, at the time of development, in order to supply the toner of uniform density to the latent image, the two-component developer is conveyed while being stirred in the developing device. In such an image forming apparatus, if the power source is stopped for a long time or if the image is formed without forming an image even when the power source is turned on, there is a problem in that an image formed thereafter has a light and shade. This is because the charging characteristics of the toner change when the humidity changes while the power is off or while the developing device is stopped.
This is because the charge amount of the toner changes abruptly due to the agitation during the subsequent developing operation. This will be described in more detail with reference to FIG.

FIG. 3 is a diagram showing changes with time in the charging characteristics and the charging amount of the toner when the power supply to the image forming apparatus is stopped at night. The toner charging characteristics have a low maximum charge amount in a high humidity environment (a charge amount when a stable state is obtained by stirring under a predetermined humidity) and a high charge amount in a low humidity environment. When it changes as shown, the maximum charge amount of the toner changes as shown by the broken line in FIGS. However, the charge amount of the toner does not change immediately with a change in humidity, but changes only when the toner is stirred, and reaches the maximum charge amount and stabilizes. The solid line graphs in FIGS. 7 (b) to 7 (d) show this state. In FIG. 7 (b), image formation is performed while the humidity decreases the previous day, the developer is stirred, and the toner is charged. The amount increases. However, the amount of charge does not change while the power supply is stopped, and there is a difference between the amount of charge and the maximum amount of charge that further increases as the humidity changes. Then, when the developer is agitated at the time of image formation the next morning, the charge amount of the toner sharply increases, and the charge amount becomes the maximum charge amount in humidity at that time and becomes stable. Further, in the cases shown in FIGS. (C) and (d), even if the humidity decreases and the charging characteristic of the toner increases on the previous day, an image is not formed and the toner is not stirred during the period, so that the charge amount of the toner is Does not increase. Therefore, there is a larger difference between the maximum charge amount of the toner and the actual charge amount than in the case shown in FIG. Then, when the image is formed the next morning, the amount of charge is agitated longer than in the case of FIG.

When an image is formed when there is a difference between the maximum charge amount of the toner and the actual charge amount, as in the image formation after the rest shown in FIGS. The amount of toner charge changes abruptly, and as a result, the amount of toner attached in one image changes, resulting in light and shade. Therefore, it is necessary to agitate the two-component developer that has been left for a long time in advance before forming an image to keep the charge amount of the toner constant.

Further, in an image forming apparatus using a two-component developer, a patch having a predetermined potential is formed on an image carrier on which a latent image is formed, and the toner adhesion amount to this patch is detected. Is used as a standard for detecting whether or not the toner concentration in the two-component developer is appropriate and replenishing the toner in the developing device. In this type of image forming apparatus, when the toner adhesion amount is detected while the toner charge amount is decreasing, the toner density is detected to be lower than the actual value. For this reason, the toner is replenished in an excessive amount, and the background is smeared in the image after the charge amount of the toner is restored by stirring during development. From this point as well, it is important to stir the developer in advance when an image is formed after being left for a long time.

On the other hand, if the developer is agitated more than necessary, it deteriorates the toner and shortens the service life of the carrier, which is not desirable. Therefore, it is necessary to properly judge the necessity of stirring the developer and the stirring time and appropriately control the stirring mode for stirring the developer in advance.

As a technique for accurately determining whether or not the developer needs to be stirred and the stirring time, there has been a conventional technique as disclosed in JP-A-2-56.
The techniques described in Japanese Patent No. 578 and Japanese Patent Laid-Open No. 4-258581 are proposed. The technique disclosed in Japanese Patent Laid-Open No. 2-56578 detects the temperature of a predetermined portion of the image forming apparatus main body as a measure of the elapsed time after the image forming apparatus is stopped, and based on this temperature, the developer stirring time is determined. To control. That is, for example, by detecting the temperature of the fixing roller,
If the temperature is 50 C or higher, the power of the device is turned off.
If not so much time has passed since
After stirring the toner for 2 seconds, the toner density is controlled. If the temperature is 50 C or less, it is assumed that a considerable amount of time has passed since the power was turned off, and the toner concentration is controlled after 10 seconds of toner stirring.

The technique disclosed in Japanese Unexamined Patent Publication No. H4-255881 counts the rest time of the developing device by a built-in clock, and controls the necessity of stirring and the time based on this time.

[0009]

However, in the prior art as described above, the necessity or agitation time of the agitation is judged only on the basis of the stop time or the rest time of the image forming apparatus or the developing apparatus. The control of the stirring mode corresponding to the changing charging characteristics of the toner is not performed. Therefore, even if the humidity does not change and there is not much difference between the charging characteristics of the toner and the actual charge amount, the stirring is performed, or the stirring is not sufficiently performed despite the large difference. there is a possibility. In addition, in the technique disclosed in Japanese Patent Application Laid-Open No. 2-56578, the time after the power supply to the image forming apparatus main body is stopped is used as a standard, so that stirring is necessary when image formation is not performed while the power is on. It may not be judged.

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of accurately determining whether or not stirring of a two-component developer before image formation is necessary, and It is to provide a control method of an image forming apparatus.

[0011]

In order to solve the above problems, the invention according to claim 1 is an image carrier in which a latent image due to a difference in charging potential is formed by irradiation of image light after uniform charging. A body, a developing device that visualizes the latent image by attaching toner to the image carrier, and a stirring mode that stirs the two-component developer housed in the developing device and stabilizes the electric charge of the toner. In an image forming apparatus having a control means for controlling the developing device so as to be carried out, a humidity measuring means for measuring the humidity in the image forming apparatus, and a humidity measuring means for measuring the humidity every time an image forming operation is performed. And a storage unit for newly storing the output value, wherein the control unit detects the output of the humidity measuring unit before starting the image forming operation, and outputs the output value and the latest value stored in the storage unit. And the output value of the humidity measuring means of Comparison, assumed to be set to determine whether the implementation of the agitation mode based on the comparison result.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, there is provided a time measuring means for measuring an elapsed time from the end of each image formation, When starting the image formation, the control means determines whether or not the stirring mode is performed when the elapsed time from the end of the latest image formation is equal to or longer than a predetermined time set in advance. Is set to.

According to a third aspect of the invention, after uniform charging,
An image carrier on which a latent image due to a difference in charging potential is formed by irradiation of image light, a developing device that visualizes the latent image by attaching toner to the image carrier, and humidity near the developing device is detected. A method for controlling an image forming apparatus, comprising: a humidity measuring unit; and a stirring mode for stirring a two-component developer housed in the developing device to stabilize the electric charge of the toner. Each time it is performed, the output value of the humidity measuring unit is stored, and after the rest, the output of the humidity measuring unit is detected before starting the image forming operation. The method further includes the step of comparing the output value of the humidity measuring means stored at the time of the most recent image formation and determining whether or not the stirring mode is performed based on the comparison result.

In the agitation mode, a two-component developer contained in the developing device or a two-component developer replenished from a toner supplier is agitated by a stirring means such as a screw auger provided in the developing device. Is. The stirring mode may be performed only for the purpose of stabilizing the charge amount of the toner, or may be performed for other purposes such as conveyance and supply of the developer. The agitation mode may be set so that the image forming operation is performed at the same time while the two-component developer is agitated, but the agitation mode is set to be performed independently of the image forming operation. Is desirable.

The control means not only controls the execution of the stirring mode, that is, the driving of the stirring means, but also controls each part of the image forming apparatus such as the developing device and the image carrier so as to perform the image forming operation. You can

The storage means is capable of holding the input and read data during power-on or power-off of the apparatus body. As the data stored in the storage unit for each image formation, the output value from the humidity measuring unit detected by the control unit before starting the image forming operation may be used as it is, or after the image formation is completed, a new humidity value may be used. What read the output value from the measuring means may be used.

[0017]

In the image forming apparatus according to the first aspect, the humidity in the apparatus is measured by the humidity measuring means every time the image forming operation is performed, and the output value is stored in the storage means. And
When the image forming operation is restarted after the image forming operation is stopped, the control means detects the output value of the humidity measuring means, and this output value and the humidity measurement at the time of the most recent image forming stored in the storage means. The output value from the means is compared to determine whether or not the stirring mode is performed. Therefore, when the maximum charge amount of the toner changes due to a change in humidity during rest, and the difference between the maximum charge amount of the toner and the actual charge amount occurs, the stirring mode is executed, and when the change in humidity is small, the stirring mode is performed. Do not implement. Therefore, it is possible to reduce the deterioration of the developer by executing the stirring mode only when truly stirring is required.

Further, since the control means judges the necessity of performing the stirring mode by comparing the humidity at that time and the humidity at the time of the previous image formation for each image forming operation, the case where the power supply is turned off and the operation is stopped. Not only when the power is on, even if the image forming operation is not performed and the humidity changes and the charging characteristics of the toner change, the stirring mode is executed if necessary. can do.

In the image forming apparatus according to the second aspect of the invention, the stirring is performed in the same manner as the image forming apparatus according to the first aspect, only after a preset time has elapsed since the last image formation was completed. Determine whether the mode is implemented. Therefore,
If the developing device has a short downtime and the change in humidity does not affect the change in the toner charging characteristics, the agitation mode is not executed.If the downtime is long, not only the humidity but also the length of the downtime. It is possible to determine whether or not the stirring mode is performed in consideration of the above.

If a predetermined time or more has elapsed from the end of the previous image formation, the agitation mode is executed in advance even if the image formation is not started, and the actual image formation is started after the image formation is started. It is also possible to reduce the time lag until the image formation is performed and to efficiently form the image.

In the control method of the image forming apparatus according to the third aspect of the present invention, the same steps as those of the operation of the image forming apparatus according to the first aspect are performed and the same effect can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention will be specifically described below with reference to FIGS. FIG. 1 is a block diagram showing a copying machine which is an embodiment of an image forming apparatus according to the invention described in claim 1 or 2. The copying machine according to the present embodiment includes an image reading unit 1 that exposes and scans a document and converts the image signal into an image signal, and an image signal processing that performs processing such as digitization and gradation analysis of the image signal output from the image reading unit 1. A unit 2 and an image forming unit 3 that forms an image based on the processed image signal,
The image forming unit 3 includes a control unit 5 that controls each device. The image reading unit 1 includes a platen glass 11 on which a document D is placed, an exposure lamp 12 that illuminates the document D on the platen glass 11 while traveling along the platen glass 11, and reflected light from the document D. (Image light) is incident,
An image sensor 13 for converting the image light into an image signal and outputting the image signal to the image processing unit 2 is provided.

The image forming section 3 generates a laser beam based on the output from the laser driving circuit 31 and the laser driving circuit 31 which controls the emission of the laser beam based on the processed image signal from the image signal processing section 2. A laser generator 32, a polygon mirror 33 for deflecting the laser beam from the laser generator 32, a mirror 34 for reflecting the deflected laser light to an image carrier 35, and a photoconductor on the surface by a charger 36 while rotating. After the layer is uniformly charged, the image carrier 35 in which a latent image is formed due to the difference in electrostatic potential by the irradiation of the laser beam and the two-component developer including the carrier and the toner are accommodated. A developing device 37 that supplies toner to the upper latent image to form a toner image;
A transfer material conveying path 38 that feeds a transfer material such as paper so as to face the toner image, a transfer device 39 that transfers the toner image on the image carrier 35 to the opposite transfer material, and an image carrier 35 that is not transferred. A cleaning device 40 for cleaning the toner remaining on the upper side and a discharging lamp 41 for discharging the surface of the image carrier 35 after the residual toner is cleaned by exposure are charged. Further, in the vicinity of the developing device 37, a toner supply device 42 for supplying toner into the developing device 37, and the developing device 3
Developing device drive motor 43 for driving 7 and developing device 3
Humidity sensor 44 that outputs a signal based on the humidity in the vicinity of 7
And a density sensor 45 for detecting the density of the toner image formed on the image carrier 35.

The control unit 5 is a timer (measuring means) 52 for measuring the time during which the developing device driving motor 43 is stopped.
The storage device 53 stores the output value output from the humidity sensor 44, and the CPU 56 that controls the operation of each device of the image forming unit 3. The CPU 56 includes a stirring control circuit 51 that controls the developing device driving motor 43, and a toner replenishment control circuit 54 that controls the toner supply device 42 based on the output from the density sensor 45.

Next, an embodiment of the control method of the image forming apparatus according to the invention of claim 3 in the flow of the operation of the above-mentioned copying machine will be described. FIG. 2 is a flow chart showing the flow of the operation of the copying machine described above. When the power of the apparatus main body is turned on, the time from the end of the previous image formation is read by the CPU 56 from the timer 52. If the read time is longer than the reference time, the humidity sensor 4
4 and the output value H from the humidity sensor 44 during the previous image formation from the storage device 53.
um (end) is read and these values are compared. Then, the stirring flag is turned on only when the difference between the output values Hum (on) and Hum (end) before and after the suspension is greater than or equal to the reference value. When the time read from the timer 52 is shorter than the reference time, the image forming operation can be performed as it is. After that, when the image formation is not started, the time from the timer is read again and the subsequent operations are repeated.

When the image formation is started and the stirring flag is turned on, the developing device drive motor 43 is used.
Thus, the developer in the developing device 37 is agitated. Therefore, the toner is charged according to the charging characteristics at this point and is in a stable charged state. After that, the image carrier 3
5 starts rotating, and the image forming operation is started. On the other hand, when the stirring flag is off, the developer is not stirred and the image forming operation is started as it is.

When the image forming operation is started, the image carrier 3
5 starts rotating, and the charger 36 uniformly charges the surface of the image carrier 35. Then, a preset patch forming signal is output from the laser driving circuit 31 to the laser generator 32, and the laser light from the laser generator 32 is carried on the rear image through the polygon mirror 33, the fθ lens 46, and the mirror 34. The surface of the body 35 is irradiated, and a patch for density detection is formed on the surface of the image carrier 35. Then, the developing device 37 supplies the toner, which is sufficiently agitated and has a stable charged state, to the density detecting patch for development. The density sensor 45 detects the toner density of the density detection patch to which the toner adheres. The output value from the density sensor 45 is input to the CPU 56, and when the density is low, toner is replenished from the toner supply device 42 into the developing device 37 based on the signal output from the toner replenishment control circuit 54. On the other hand, when the density is high, a toner consuming patch is formed on the image carrier 35, and the toner in the developing device 37 is transferred to this patch and collected, whereby the toner is consumed.

After that, the exposure lamp 12 exposes and scans the original D on the platen glass 11, and the image light is reflected by the polygon mirror 3.
3 and the mirror 34, and enters the image sensor 13. The image sensor 13 outputs an image signal based on the image light to the image signal processing unit 2, and the image signal processing unit 2 performs digitization, gradation processing, etc. on the image signal and outputs the image signal to the laser drive circuit 31. The laser generator 32 generates a laser beam based on the image signal from the laser drive circuit 31. Laser light is polygon mirror 33
After being deflected to, the surface of the image carrier 35 uniformly charged by the charger 36 is irradiated through the fθ lens 46 and the mirror 34, and a latent image is formed on the image carrier 35. Toner is attached to the latent image from the developing device 37 to form a toner image. At this time, in the developing device 37, in order to supply the developer having a constant toner concentration to the entire latent image, the developer is conveyed while being stirred. At this time, the charge amount of the toner is already in a stable state according to the charging characteristics and does not change due to stirring, and the toner having a constant charge is evenly attached to the latent image, resulting in a toner image with no shading. It is formed. The toner image faces the transfer material conveyed through the paper conveyance path 38 and is transferred to the transfer material by the transfer device 39. After that, the cleaning device cleans the toner remaining on the surface of the image carrier 35 without being transferred, and then the charge eliminating lamp 41 irradiates the surface of the image carrier 35 to eliminate the charge. Further, the output value from the humidity sensor 44 is read by the CPU 56 and rewritten as a new Hum (end) value in the storage device 53. This stored value is maintained even when the power of the main body device is turned off. The steps from uniform charging are repeated,
A new image is formed.

The correlation between the difference in humidity before or after the pause of the image forming operation or the pause time and the required stirring time is set in advance, and the stirring time is set to the humidity value before or after the pause, that is, the output value. Hum (on) and Hum (e
nd) or the rest time.

[0030]

As described above, in the image forming apparatus according to the first aspect of the present invention, it is determined whether or not the stirring mode should be performed based on the difference in humidity before and after the suspension. The stirring mode can be executed only when the amount of charge in the stable state based on the above and the actual amount of charge are different from each other and stirring is truly required. Therefore, it is possible to avoid deterioration of the developer without stirring the developer more than necessary. In addition, since it is determined whether or not the stirring mode should be performed for each image forming operation,
When the humidity of the main body is changed during the operation of the main body, this can be detected and the stirring mode can be executed.

In the image forming apparatus according to the second aspect of the present invention, the elapsed time from the time when the previous image formation is completed is counted, and the stirring mode is executed only after the preset time has elapsed. Since the presence / absence is determined, the presence / absence of the stirring mode or the stirring time can be determined in consideration of both the change in humidity and the elapsed time when the down time is long.

In the control method of the image forming apparatus according to the third aspect of the present invention, the same steps as the operation of the image forming apparatus according to the first aspect are performed, and the same effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a copying machine which is an embodiment of the invention described in claim 1 or claim 2.

FIG. 2 is a flowchart showing a control method which is a part of the control operation in the embodiment of FIG. 1 and is an embodiment of the invention described in claim 3;

FIG. 3 is a graph showing changes in the charging characteristics of the developer and the actual charge amount when the humidity changes with time.

[Description of Reference Signs] 1 image reading unit 2 image signal processing unit 3 image forming unit 5 control unit 11 platen glass 12 exposure lamp 13 image sensor 31 laser drive circuit 32 laser generator 35 image carrier 37 developing device 39 transfer device 42 toner Supplying device 43 Developing device driving motor 44 Humidity sensor 45 Concentration sensor 51 Stirring control circuit 52 Timer 53 Storage device 56 CPU

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 15/09 Z

Claims (3)

[Claims] 1. An image carrier on which a latent image due to a difference in charging potential is formed by irradiation of image light after uniform charging, and a developing device which visualizes the latent image by attaching toner to the image carrier. An image forming apparatus having a control means for controlling the developing device so that a stirring mode for stirring the two-component developer housed in the developing device and stabilizing the electric charge of the toner is carried out, The image forming apparatus has a humidity measuring unit that measures the humidity, and a storage unit that newly stores the output value of the humidity measuring unit each time the image forming operation is performed. The output of the humidity measuring means is detected before starting, and this output value is compared with the latest output value of the humidity measuring means stored in the storage means, and the stirring mode is calculated based on the comparison result. To determine whether or not An image forming apparatus characterized in that it is urchin set. 2. The image forming apparatus according to claim 1, further comprising a time measuring unit that measures an elapsed time from the end of each image formation, and the control unit starts the image formation. When performing the above, when the elapsed time from the end of the most recent image formation is equal to or longer than a preset predetermined time, it is set to determine whether or not to perform the stirring mode. Image forming apparatus. 3. An image carrier on which a latent image due to a difference in charging potential is formed by irradiation of image light after uniform charging, and a developing device which visualizes the latent image by attaching toner to the image carrier. A humidity measuring means for detecting the humidity in the vicinity of the developing device and stirring the two-component developer housed in the developing device to carry out a stirring mode for stabilizing the electric charge of the toner. In the control method, the output value of the humidity measuring means is stored every time the image forming operation is performed, and after the rest, the output of the humidity measuring means is detected before the image forming operation is started. A step of comparing the output value of the humidity measuring means stored at the time of the most recent image formation among the image formation performed previously and determining whether or not the stirring mode is performed based on the comparison result. Of the image forming apparatus characterized in that Your way.