JPH0683154A - Humidity control device - Google Patents

Abstract

PURPOSE:To prevent fluctuation caused by the humidity of each characteristic in an electrophotographic process and to stabilize image quality to be kept high by simple and inexpensive device by appropriately controlling the humidity around an image forming mechanism without delay corresponding to a humidity state which actually influences each characteristic in the electrophotographic process just by detecting one characteristic in the electrophotographic process of the image forming mechanism. CONSTITUTION:The density ID of a developed image which is formed and developed on a photosensitive drum 41 and actually influenced by the humidity is detected by an AIDC sensor 300, and the humidity in a copying part 200 is controlled by a humidity controlling device 400 in accordance with the detected result. The AIDC sensor 300 is an image density detecting sensor used in the case of automatically correcting the secular change by feeding back the image density to the control of developing bias and exposure, and it is provided before the transfer part of the drum 41 and used in common.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity control device, and more particularly to a humidity control device for controlling the humidity around an image forming mechanism by an electrophotographic process.

[0002]

2. Description of the Related Art Humidity affects characteristics such as charging, exposure, development and transfer in an electrophotographic process, and makes image quality such as image density unstable.

In order to solve this problem, conventionally, the amount of toner adhered on the photosensitive member is detected and fed back to the developing bias and the exposure amount for control.

Further, the toner supplied to the developing unit is dehumidified through a hygroscopic agent, and the adsorbent is regenerated by a heater and a fan, and ultrasonic waves are radiated during the first image formation in the morning, and the fan is exhausted and dried. It is also done.

On the other hand, in Japanese Utility Model Laid-Open No. 53-128748, a dehumidifying means using a reproducible dehumidifying agent is provided in the copying machine to perform dehumidification. A technique is disclosed in which reproduction is performed so that image formation is performed stably.

Further, Japanese Patent Laid-Open No. 58-33271 discloses a technique of detecting humidity in a copying machine using an electrophotographic process with a humidity sensor and correcting an automatic toner density adjusting function according to the output of the humidity sensor. Disclosure.

Further, Japanese Laid-Open Patent Publication No. 3-123374 discloses a technique for correcting the developing condition according to the output of the humidity sensor.

[0008]

However, if the developing bias and the exposure amount are controlled from the toner adhesion amount on the photoconductor,
For example, it is not possible at least to cope with other electrophotographic process characteristics such as transfer characteristics that vary with humidity. Therefore, fluctuations in image quality due to humidity cannot be sufficiently suppressed.

When the toner in the developing device is dehumidified, it is possible to avoid that the charging characteristics of the toner fluctuate due to humidity. However, it cannot cope with the characteristic changes of other electrophotographic processes.

If the inside of the copying machine is simply dehumidified by the dehumidifying function of the desiccant, it is difficult to cope with sudden changes and large changes in environmental conditions, and it is difficult to keep the inside of the copying machine at a predetermined humidity accurately. Therefore, fluctuations in image quality due to humidity cannot be sufficiently suppressed.

When the humidity in the copying machine is detected to correct the toner density or the developing characteristic, it is possible to cope with the change in the characteristic of other electrophotographic process such as the change of the transfer characteristic. Can not.

Therefore, it is possible to individually correct each characteristic of the electrophotographic process according to the output of the humidity sensor. However, the device is extremely complicated and expensive, and is not practical.

Further, even if the characteristics of the electrophotographic process are corrected according to the output of the humidity sensor, there is an inherent delay in the fluctuation of each characteristic of the electrophotographic process of the image forming mechanism due to humidity, so that accurate correction is possible. However, there is a problem in that it is difficult to suppress fluctuations in image quality due to humidity.

In view of the above points, the present invention detects the characteristics affected by humidity in the electrophotographic process, and adjusts the humidity around the image forming mechanism in accordance with the detection result to obtain the above-mentioned characteristics. It is an object of the present invention to provide a humidity control device capable of solving various problems.

[0015]

In order to achieve the above-mentioned objects, the present invention provides a means for adjusting the humidity around an image forming means by an electrophotographic process and an electrophotography related to the humidity of the image forming means. It is characterized in that it is provided with means for detecting characteristics and control means for operating the humidity adjusting means in accordance with the detected electrophotographic characteristics.

The humidity adjusting means preferably utilizes the freezing function of the Peltier element.

[0017]

According to the above construction of the present invention, the characteristic of the electrophotographic process affected by the humidity of the image forming mechanism is detected by the detecting means, and the characteristic of the electrophotographic process resulting from the effect of the humidity is detected. Depending on the result, the control unit activates the humidity adjusting unit to regulate the humidity around the image forming mechanism, so that the humidity around the image forming mechanism is delayed according to the humidity condition that is actually affecting the electrophotographic process of this mechanism. It can be adjusted properly without any problems.

When the humidity adjusting means utilizes the cooling function of the Peltier element, the humidity can be adjusted by directly providing the heat exchanging section at the low temperature section and the high temperature section of the Peltier element.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the overall construction of the digital color copying machine of the first embodiment.

The digital color copying machine is roughly divided into an image reader section 100 for reading an original image and a copying section 200 for reproducing an image read by the image reader section.

In the image reader unit 100, the scanner 10 includes an exposure lamp 12 for irradiating a document, a rod lens array 13 for condensing the reflected light from the document, and a contact type for converting the condensed light into an electric signal. The CCD color image sensor 14 of FIG. The scanner 10 is driven by the motor 11 at the time of reading an original, moves in the direction of the arrow (sub scanning direction), and scans the original placed on the platen 15. The image on the document surface illuminated by the exposure lamp 12 is photoelectrically converted by the image sensor 14.

R obtained by the image sensor 14,
The multi-valued electrical signals of G and B are converted into 8-bit gradation data of any one of yellow (Y), magenta (M), cyan (C), and black (K) by the read signal processing unit 20. It is converted and stored in the synchronization buffer memory 30.

Next, in the copying section 200, the print head section 31 performs gradation correction (γ correction) on the input gradation data according to the gradation characteristics of the photoconductor, and then the corrected image. Data is D / A converted to generate a laser diode drive signal, and the semiconductor laser is caused to emit light by this drive signal.

The print head unit 3 corresponding to the gradation data
The laser beam emitted from the laser beam No. 1 exposes the photosensitive drum 41, which is rotationally driven, via the reflecting mirror 37. The photoconductor drum 41 is irradiated with an eraser lamp 42 before being exposed for each copy, and is uniformly charged by a charging charger 43. When exposed in this state, an electrostatic latent image of the original is formed on the photosensitive drum 41. Cyan, magenta, yellow, and black toner developing devices 45
Only one of a to 45d is selected and the electrostatic latent image on the photosensitive drum 41 is developed. The developed toner image is transferred by the transfer charger 46 onto the copy paper wound around the transfer drum 51.

After four colors are transferred to the copy paper, the transfer drum 5
It is separated from 1 and sent to the fixing unit 60. Then, after the fixing process is performed here, the sheet is discharged to the tray 61. Reference numeral 62 is a paper feeding unit.

Changes in environmental humidity have a great influence on image formation by the electrophotographic process in the copying section 200.

For example, FIG. 7 shows the tendency of developing characteristics to depend on humidity. From FIG. 7, when the humidity becomes high, the photosensitive drum 41
The amount M of the developer attached to the toner increases, and the image density increases.
This is because the charge amount of the developer changes mainly with humidity,
For this reason, it is caused by the change in the adhesion amount characteristic with respect to the developing potential ΔV (developing bias potential V _B −latent image potential V _i ).

Utilizing this, in the present embodiment, the density (ID) of the developed image formed on the photosensitive drum 41 by the development, which is actually affected by the humidity, is measured by the AIDC sensor 30.
0, and the humidity inside the copying section 200 is adjusted by the humidity adjuster 400 according to the detection result.

As a result, the humidity in the copying section 200 is
It can be adjusted properly without delay based on one of the characteristic values of the electrophotographic process that is actually affected by humidity, and by adjusting the proper humidity, all of the characteristics that are affected by the humidity of the electrophotographic process can be controlled. Can be stabilized.

The AIDC sensor 300 is an image density detection sensor used when the image density is fed back to the control of the developing bias and the exposure amount and the change of the image density over time is automatically corrected. It is provided in front of the transfer portion of the drum 41 and is used in common.

The detection and correction of the image density are performed, for example, by forming a visible image of the test pattern on the non-image portion of the photosensitive drum 41 and detecting the density of the image.

The humidity adjustment may be performed together with this or at an appropriate timing independently.

The humidity controller 400 comprises a dehumidifying unit 401 as shown in FIG. 2 and a humidifying unit 40 as shown in FIG.
2 and.

The dehumidifying unit 402 includes a Peltier element 40.
I am using 3.

As shown in FIG. 2, the Peltier element 403 has a low temperature portion 403b and a high temperature portion 403c on both sides of the P / N junction portion 403a, and a cooling fin 405 is provided in the low temperature portion 403b and the high temperature portion 403c. The radiation fins 406 are separately coupled.

In the dehumidifying unit 401, the air 411 in the copying section 200 containing moisture is blown by the blower fan 407.
Are introduced into the dehumidifying unit 401. Peltier element 40
Cooling fin 405 attached to the low temperature section 403b of No. 3
At this time, the humidity in the air is condensed to form water droplets, and the collected water receiver 4
It falls to 08. The dehumidified air 412 is discharged to the outside of the dehumidifying unit 401.

At this time, the high temperature portion 40 of the Peltier element 403
By cooling 3c by the blower fan 409 via the radiation fins 406 attached thereto, the cooling efficiency of the low temperature portion 403b of the Peltier element 403 is increased, and as a result, the dehumidification efficiency is increased.

As shown in FIG. 3, the humidifying unit 402 keeps water in the water storage tank 422 so that the cloth film 423 soaked in water is maintained in a wet state. Therefore, the wind 424 sent by the blower fan 421 passes through the cloth film 423 to become moist air 425. The moist air 425 is sent into the copying section 200 to humidify it.

In this embodiment, as shown in FIG.
The CPU 500 for controlling the operation of the copying machine shown in FIG.

Therefore, in addition to the start signal, the output of the AIDC sensor 300 and other inputs are input to the CPU 500. In addition, the Petzche element 40 of the humidity controller 400
3, the operation signal and other outputs of the humidity controller driver 501 that drives the dehumidifying unit 401 and the humidifying unit 402 are output.

FIG. 5 is a flow chart showing the main contents of the humidity adjustment control by the control circuit of FIG.

According to this, if the output Vs when the image density of the visible image of the test pattern is detected by the AIDC sensor 300 is larger than a predetermined value, for example, 3.5 V, it is determined that the image density is high due to high humidity. , The dehumidifying unit 401 is driven and the process returns.

On the contrary, if the output Vs is smaller than a predetermined value, for example, 2.5 V, it is determined that the image density is low due to the low humidity, and the humidifying unit 402 is driven and the process returns.

As a result, the humidity of the copying section 200 is adjusted so as to obtain an image density within a certain range. By this humidity adjustment, it is possible to suppress fluctuations due to humidity in all of the characteristics that are affected by humidity in the electrophotographic process.

Experimental data on the change in humidity and the change in the charge amount of the developer when the high humidity state is automatically adjusted to the room temperature state by such control are shown by the solid and phantom lines in FIG.

In FIG. 7, the characteristic of the change in the charge amount with respect to the change in humidity when the conventional humidity is detected and the humidity is adjusted based on the detection result is shown by a chain line.

As is apparent from FIG. 7, the conventional humidity detection,
For the humidity control, the charge amount Q of the developer at t ₂ 'off switch is normal humidity condition at t _2. On the other hand, in the case of the present embodiment, since the humidity is adjusted until Q reaches the normal humidity state, Q at t ₂ "
Is stable. Therefore, in the case of this embodiment (t ₂ '-t ₂ "), the time lag can be shortened.

FIG. 8 shows a flow chart of the humidity adjustment control as the second embodiment of the present invention. In this embodiment, the AIDC sensor 300 provided in front of the transfer section and the AIDC sensor 300 shown in FIG. 1 provided after the transfer section.
The image density of the test pattern before and after the transfer is detected by a, and the transfer efficiency Tef is calculated from the image density data before and after the transfer.

Only when the transfer efficiency Tef of the calculation result is smaller than the predetermined value 0.70, the dehumidifying unit 40
1 is driven.

However, when the humidity is below normal humidity, there is not much difference in transfer efficiency. Therefore, in the present embodiment, the dehumidifying unit 401 is driven only when the humidity is high and the transfer efficiency is 70% or less.

FIG. 9 shows a flow chart of the humidity adjustment control as the third embodiment of the present invention.

In this embodiment, the residual potential V of the photosensitive drum 41 is
The characteristic that the fluctuation width ΔVr of r increases when the humidity is high is used. In the example, when ΔVr> 50, the dehumidifying unit 40
The flow for operating (dehumidifying) No. 1 is shown.

As a result, the same effect as in the case of using the AIDC sensor 300 could be obtained. In this case, in order to detect the surface potential of the photosensitive drum 41, the surface potential sensor 300b shown in FIG. 1 is provided.

Further, the AIDC sensor 300 and the surface potential sensor 300b are used in combination, and the humidity is adjusted based on the detection results of these, so that the effect of stabilizing the image quality is further improved.

10 to 13 show a fourth embodiment of the present invention. In the copying machine of this embodiment, magnetic type ATDC sensors 601a to 601d for detecting the bulk density of the two-component developer are provided in the developing devices 45a to 45d as shown in FIG. The humidity is adjusted according to the detection result in.

As shown in FIGS. 11 and 12, the bulk density (A.D.) of the developer changes with the change in humidity, and the magnetic ATDC sensors 601a to 601 for detecting the magnetic permeability of the developer.
The output V _{MA of} 1d also changes. This embodiment utilizes this characteristic, and as shown in FIG.
When the output V _{MA of a} to 601d is larger than a predetermined value 2.8, the humidifying unit 402 is driven to return, and when it is smaller than the predetermined value 2.6, the dehumidifying unit 401 is driven to return.

The accuracy of the value of the output V _MA of the ATDC sensors 601a to 601d is increased by taking the average value of the developing devices 45a to 45d.

According to this embodiment, it is possible to obtain an effect such as improvement in accuracy uptime lag as in the case of using the AIDC sensor described above. Further, in the case of this embodiment, it is not necessary to develop the test pattern, so that it is possible to suppress the extra toner consumption.

FIG. 14 shows a fifth embodiment of the present invention, in which the amount of dust emitted from the developing device is detected and the humidity is adjusted accordingly.

This is based on the fact that humidity affects the generation of toner dust from the developing device.

As for the relationship between humidity and dust, generally speaking, as humidity increases, the amount of toner charge decreases and inquiries with the carrier weaken, so the amount of toner dust increases. It mainly occurs during the rotation of the developing sleeve for carrying out the developer from the developing device and developing it.

When the amount of smoke is increased, color mixing and stains inside the developing device occur, deteriorating the image quality.

On the contrary, if it is prevented that the vicinity of the developing device is in a high humidity state, the smoke can be suppressed.

Humidity is related to developer life.
Explaining this point, in general, when a developer is used in a high humidity state, its deterioration progresses faster than when it is used in normal humidity or low humidity, which leads to a shortened life of the developer.

On the contrary, if the humidity is controlled so that the vicinity of the developing device does not become high in humidity, the developing life can be extended.

Humidity is also related to the amount of developer conveyed on the developing sleeve. The higher the humidity, the worse the fluidity of the developer and the smaller the amount conveyed. As a result, the development efficiency is lowered and the graininess is deteriorated.

Further, the humidity is related to the residual potential Vr, and the higher the humidity, the more the fluctuation of Vr (ex. With respect to the number of copies).
Is big. As a result, the image density is not stable.

Therefore, it is preferable to adjust the humidity to keep it low.

In this embodiment, since the humidity is adjusted according to the detection result of the amount of dust, the unit 701 for detecting the amount of dust is installed, and the dust is introduced into the unit 701 by the fan 702 or the like. The difference from the first embodiment is that the humidity controller 400 is driven according to the detection result.

Here, the dust amount detection unit 701 is for irradiating, for example, a laser beam to detect diffraction and scattering by the dust toner and calculate the dust amount. Since the amount of dust and the humidity have the above-described correlation, by operating the humidity controller 400 according to the detected value of the amount of dust, the above-mentioned magnetic AT
Similar to the case of using the DC sensor, it is possible to obtain effects such as performing humidity control and improving the accuracy of image stabilization without consuming extra toner.

FIG. 15 shows a sixth embodiment of the present invention, which utilizes the fact that the developer carrying amount Ms on the developing sleeve of the developing device is affected by the humidity as described above. The humidity controller 400 is operated according to Ms.

Here, the conveyance amount Ms can be detected, for example, by combining the light emitting diode and the photosensors 300d to 300g in the developing sleeves 702a to 702d of the developers 45a to 45d as shown in FIG. When the carry amount Ms becomes smaller, more light emitted from the light emitting diode and irradiated on the developer layer on the developing sleeve is reflected by the developing sleeve. Therefore, if the correlation that the incident light on the photo sensor 300d increases is used. Good. The accuracy of the transport amount Ms is improved by using the average value of the developing devices 45a to 45d.

According to this embodiment, as in the case of the above-mentioned embodiments, the accuracy and time lag can be improved, the dehumidification efficiency can be improved and the size can be reduced by using the Peltier device as compared with the conventional image stabilizing system.

If a humidity sensor is provided and its output is combined with the detected values of the bulk density of the developer and the amount of dust,
It is also possible to judge the abnormality of the ratio of the toner and the carrier of the developer and the life of the developer.

In each of the above embodiments, only the case where the Peltier element is used for the humidity controller has been described, but the present invention is not limited to this, and various conventionally known humidifying, dehumidifying, and drying means may be appropriately adopted. Of course.

[0077]

According to the present invention, by detecting the humidity around the image forming mechanism by only detecting one characteristic of the electrophotographic process of this mechanism, it is possible to cope with the humidity condition that actually affects each characteristic of the electrophotographic process. Since it is adjusted appropriately without delay or the like, a simple and inexpensive device can prevent fluctuations in each characteristic of the electrophotographic process due to humidity and stabilize the image quality.

When the humidity adjusting means uses the cooling function of the Peltier element, it is possible to achieve dehumidification with a small and quiet one.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a digital color copying machine showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a dehumidifying unit.

FIG. 3 is a sectional view of a humidifying unit.

FIG. 4 is a block diagram of a main part of a control circuit.

5 is a flowchart showing control contents of humidity adjustment by the control circuit of FIG.

FIG. 6 is a graph showing a temporal relationship between a humidity change due to humidity control and a charge amount of a developer in comparison between the case of the first embodiment and the case of humidity detection and humidity control.

FIG. 7 is a graph showing the relationship between humidity and image density.

FIG. 8 is a flowchart showing contents of humidity adjustment control as a second embodiment of the present invention.

FIG. 9 is a flowchart showing contents of humidity adjustment control as a third embodiment of the present invention.

FIG. 10 is an overall configuration diagram of a digital color copying machine showing a fourth embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the bulk density of the developer and the magnetic ATDC sensor output.

FIG. 12 is a graph showing the relationship between humidity and bulk density.

FIG. 13 is a flowchart showing the content of control for adjusting humidity in accordance with the detected bulk density of the developer.

FIG. 14 is an overall configuration diagram of a digital color copying machine showing a fifth embodiment of the present invention.

FIG. 15 is an overall configuration diagram of a digital color copying machine showing a sixth embodiment of the present invention.

[Explanation of symbols]

 200 Copying unit 300, 300a to 300g Sensor 400 Humidity controller 401 Dehumidifying unit 402 Humidifying unit 403 Peltier element 500 CPU 601a to 601d Sensor 701 Dust amount detecting unit

Claims (2)

[Claims] 1. A means for adjusting the humidity around an image forming means by an electrophotographic process, a means for detecting an electrophotographic characteristic relating to the humidity of the image forming means, and a humidity adjustment according to the detected electrophotographic characteristic. A humidity control apparatus comprising: a control unit that operates the unit. 2. The humidity control apparatus according to claim 1, wherein the humidity adjusting means uses the freezing function of the Peltier element.