JPH0683152A - Humidity control device - Google Patents

Abstract

PURPOSE:To keep proper humidity without being affected by a time lag in controlling humidity, to restrain fluctuation caused by the humidity of each characteristic of an electrophotographic process and to stabilize image quality by averagely controlling the humidity around an image forming mechanism by using history data on the humidity in specified time units at each time. CONSTITUTION:The humidity in a copying part 200 is detected by a humidity sensor 300 so as to obtain the history data on the humidity in specified time units at each time, and the humidity in the copying part 200 is controlled by a humidity controlling device 400 according to the history data. Therefore, not only a start signal but also output from the sensor 300 and other input are inputted in a CPU 500. An operation signal for a humidistat driver driving the dehumidifier unit 401 and the humidifier unit 402 of the device 400 and other output are outputted from the CPU 500. Then, a memory 502 for forming the history data on the humidity is connected to the CPU 500. The sensor 300 is installed near a photosensitive drum 41 being a trouble, especially, when the fluctuation caused by the humidity of the characteristic of the electrophotographic process is caused.

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.

Japanese Unexamined Patent Publication No. 58-33271 discloses a technique of detecting humidity in a copying machine using an electrophotographic process by a humidity sensor and correcting an automatic toner density adjusting function according to the output of the humidity sensor. is doing.

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.

On the other hand, JP-A-52-134733 discloses
Disclosed is a technique of detecting the humidity of a specific portion around a photoconductor in a copying machine and adjusting the humidity of the specific portion in the copying machine according to the detection result.

[0006]

However, when the humidity in the copying machine is detected and the toner density is corrected or the developing characteristic is corrected, other electrophotography which is said to be a change in transfer characteristic. It cannot respond to changes in process characteristics.

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.

Further, if the humidity of a very limited specific part in the copying machine is detected and the humidity of this specific part is adjusted according to the detection result, the humidity can be adjusted relatively responsively. .

However, if this is performed in each part having the characteristic of being affected by humidity in the electrophotographic process, the structure becomes too complicated, and the cost is also impractical.

When this is applied to control the humidity of the entire copying machine to try to solve the above problem, a time lag occurs from the detection of the humidity until the inside of the copying machine reaches a predetermined humidity, resulting in each electrophotographic process. It is not possible to sufficiently suppress the fluctuation of the characteristics due to humidity.

In view of the above points, the present invention can solve the above problems by adjusting the humidity around the image forming mechanism in accordance with the humidity history data of a predetermined time unit from time to time. It is an object of the present invention to provide a humidity control device that can be used.

[0013]

In order to achieve the above-mentioned object, the present invention detects the environmental humidity of the image forming means by adjusting the humidity around the image forming means by an electrophotographic process, It is characterized in that it is provided with means for creating history data in a predetermined time unit at that time and control means for operating the humidity adjusting means in accordance with the history data.

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

[0015]

According to the above-mentioned structure of the present invention, the history data of the humidity around the image forming mechanism for each predetermined time unit is created by the history data creating means, and the control means operates the humidity adjusting means in accordance with the history data of the humidity. To adjust the humidity around the image forming mechanism, the humidity around the image forming mechanism can be adjusted on average, and the humidity can be kept at an appropriate level without being affected by the time delay of the humidity adjustment.

[0016]

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.

This 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.

The change in environmental humidity has a great influence on the image formation by the electrophotographic process in the copying section 200.

For example, FIG. 8 shows the tendency of the developing characteristics to depend on humidity. As shown in FIG. 2, when the humidity is high, the amount M of the developer attached to the photosensitive drum 1 is increased and the image density is increased. This is because the charge amount of the developer changes mainly depending on the humidity, which changes the adhesion amount characteristic with respect to the development potential ΔV (developing bias potential V _B −latent image potential V _i ).

In order to prevent the characteristics of these electrophotographic processes from changing depending on the ambient humidity, in this embodiment, the humidity sensor 300 detects the humidity in the copying section 200 to detect the humidity of a predetermined time unit. Get historical data,
The humidity inside the copying section 200 is adjusted by the humidity adjuster 400 according to the history data.

As a result, the humidity in the copying section 200 is
Since it is adjusted on average and is kept at an appropriate humidity without being affected by the time delay of humidity adjustment, all of the characteristics affected by humidity of the electrophotographic process can be stabilized.

As shown in FIG. 1, the humidity sensor 300 is provided in the vicinity of the photosensitive drum 1 where the variation of the characteristics of the electrophotographic process due to humidity is a particular problem.

The humidity controller 400 includes 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 402, the air 411 in the copying section 200 containing moisture is blown by the blower fan 407.
Are introduced into the dehumidifying unit 402. 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 402.

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 404 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 humidity sensor 300 and other inputs are input to the CPU 500. A humidity controller driver 501 that drives the dehumidifying unit 401 and the humidifying unit 402 of the humidity controller 400.
, And other outputs are output. CPU5
A memory 502 for making humidity history data is connected to 00. However, instead of this, the memory function of the CPU 500 may be used.

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

According to this, the humidity sensor 300 detects the detected data, and the detected data is the memory 50 for storing the humidity data for a predetermined time, for example, 3 hours, for which history data should be obtained.
Sequentially stored in 2 and sequentially updated with the latest data. Then, from the data in the memory 502, the average humidity in a predetermined time unit at any time is recorded as the history data Have. Created as.

FIG. 6 shows a method of storing the history data of humidity detected by the humidity sensor 300. In the figure, the sampling interval is T ₀ , and the target period of history data calculation is T. Here, when the humidity at t _n is sensed,
Humidity data after t ₁ (= t _n −T) is stored in the memory. The average humidity at that time can be expressed as in equation (1).

[0040]

[Equation 1]

After that, until T ₀ seconds later (t _{n + 1} ), the Have. Is effective.
However, H _{n + 1} is sensed at t _{n + 1} , and the oldest data H ₁ HA is deleted at the same time as being saved in the memory. That is in the memory t ₂ subsequent humidity data (H _2, H _3,
...... H _{n + 1} ) has been saved. At this time (t = t _{n + 1}
) Have. Can be expressed as in equation (2).

[0042]

[Equation 2]

This cycle is repeated thereafter, and the history data is updated.

The above history data Have. Is higher than a predetermined humidity of 60% RH, it is determined that the humidity is high, the dehumidifying unit 401 is driven, and the process returns.

On the contrary, the return Have. Has a predetermined humidity of 40
If it is smaller than% RH, it is determined that the humidity is low, the humidifying unit 402 is driven, and the process returns.

As a result, the humidity of the copying section 200 can be maintained properly, fluctuations of various characteristics of the electrophotographic process due to humidity can be prevented, and the image quality can be stabilized.

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 line and phantom line A in FIG. .

In FIG. 7, the characteristic B of the change in the amount of charge 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 one-dot chain line.

Both A and B follow the same trajectory until t _2, but in the case of B, dehumidification stops at t ₂ , so it takes time for Q to reach the normal humidity state. On the other hand, in case of A, t ₂
Since the historical data indicates high humidity at the time point, by continuing the dehumidification, Q reaches the normal humidity state at t ₂ ".
It can be seen that the humidity control characteristics of No. ₂ improved only (t ₂ '-t ₂ ").

Here, the charge amount Q can be controlled more accurately by providing a weighting function based on time instead of a simple average humidity as the humidity history data.

Further, the output level of the humidity controller 400 is
By switching according to the humidity data, it is possible to further reduce the ripple of fluctuations in the charge amount Q.

Here, as the output level switching method, the input current value to the Peltier element, the air volume of the blower fan, etc. are effective.

Further, in order to minimize the trouble of the humidity controller 400, it is better to provide a means for giving a warning to the user when the stop of the blower fan or the abnormal temperature of the fin is detected. Further, when the above abnormality is detected and the humidity exceeds a predetermined range, the copying machine is stopped to prevent the occurrence of miscopy.

The relationship between humidity and dust will now be described. Generally, as humidity increases, the amount of toner charge decreases and the inquiries with the carrier weaken, so the amount of toner dust increases.

This 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 dust increases, color mixing and stains inside the developing device occur, deteriorating the image quality.

On the contrary, if the vicinity of the developing device is prevented from being in a high humidity state, the dust can be suppressed.

Humidity is also 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.

Conversely, 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 of conveyance. 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 is, the more the fluctuation of Vr (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.

[0062]

According to the present invention, by utilizing the historical data of the humidity in a predetermined time unit at each time, the humidity around the image forming mechanism is adjusted evenly, and the influence of the time delay of the humidity adjustment is eliminated. Since the humidity is maintained at an appropriate level, it is possible to suppress fluctuations in various characteristics of the electrophotographic process due to humidity and stabilize the image quality.

[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 an explanatory diagram of a memory method of history data of humidity.

FIG. 7 is a graph showing a temporal relationship between a change in humidity due to humidity control and a charge amount of a developer, comparing the case of the example of the present invention and the case of the conventional example.

FIG. 8 is a graph showing the relationship between humidity and image density.

[Explanation of symbols]

 200 Copying Part 300 Humidity Sensor 400 Humidity Controller 401 Dehumidifying Unit 402 Humidifying Unit 403 Peltier Element 500 CPU 502 Memory

Claims (1)

[Claims] 1. A means for adjusting the humidity around the image forming means by an electrophotographic process, a means for detecting the environmental humidity of the image forming means, and creating history data in a predetermined time unit at that time, and the history data. And a control means for operating the humidity adjusting means according to the above.