JPH04335663A - Image forming device - Google Patents

Abstract

PURPOSE:To detect humidity without using a dedicated humidity sensor by using the detected result of the surface potential of a photosensitive body as data for calculating the humidity. CONSTITUTION:In an image forming device which forms an electrostatic latent image on a photosensitive drum, which is electrostatically charged by an electrostatic charger, by executing exposure corresponding to image information and transfers a visible image, which is obtained by toner-developing the electrostatic latent image by a developing device, on a transfer paper by a transfer charger 5, the surface potential of the photosensitive drum is detected by a potential sensor 2. Besides, the detected value is converted to a digital signal and fetched in a CPU 16. By the potential data, tables 18a and 18b set in a ROM 18 is referred and the humidity of an installing atmosphere is calculated so as to be used for controlling image forming conditions or the like.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is used in facsimiles, printers, etc., and controls the humidity in the installation atmosphere as one of the control elements.
This invention relates to an image forming apparatus using an electrophotographic method.

0002

[Prior Art] A latent image is formed on a photoreceptor based on image information, this latent image is developed with toner to become a visible image, this visible image is transferred to plain paper, and the transferred image is further fixed. Some electrophotographic image forming apparatuses that form images using a humidity detection value of the installation atmosphere as one of the transfer conditions. That is, the moisture content of the paper varies depending on the ambient humidity, and the resistance value of the transfer paper itself changes, which weakens the transfer electric field and makes it difficult to obtain a stable image. For this reason, for example, a control method is adopted in which the humidity of the installation atmosphere is detected and the transfer current of the transfer charger is changed in accordance with this detected value. Similarly, when separating transfer paper, the electric field of the separation charger is affected by humidity, which affects the separation situation. Furthermore, the influence of humidity is not limited to the transfer conditions, but also affects the development conditions, and influences the amount of toner adhesion to the latent image, that is, the image density. Therefore, it is important to detect the humidity of the installation atmosphere and reflect this detected value in the control of each charger. Regarding this type of technology, for example, there are techniques described in Japanese Patent Application Laid-open No. 62-287271 and Japanese Patent Application Laid-Open No. 64-81972.

0003

[Problems to be Solved by the Invention] However, the above-mentioned conventional techniques all use a dedicated sensor for detecting humidity, which increases the cost of the device. Therefore, an object of the present invention is to provide an image forming apparatus that can detect humidity without using a dedicated humidity sensor.

0004

[Means for Solving the Problems] In order to achieve the above object, the first means includes a charging means for charging the surface of a photoreceptor and a latent image on the charged photoreceptor according to image information. an exposure means for forming a latent image; a developing means for developing a latent image exposed by the exposure means; a transfer means for transferring the developed image onto a transfer medium; and a separation means for separating the transfer medium to which the image has been transferred from the photoreceptor. An image forming apparatus comprising:
surface potential detection means for detecting the surface potential of the photoreceptor;
The apparatus further includes a humidity calculating means for calculating the humidity of the installation atmosphere based on the surface potential detected by the surface potential detecting means. Further, the second means includes a surface potential detection means for detecting the surface potential of the photoreceptor, a temperature detection means for detecting the surface temperature of the photoreceptor, and a surface potential detection means for detecting the surface potential of the photoreceptor in a similar image forming apparatus. The apparatus is configured to include a humidity calculation means for calculating the humidity of the installation atmosphere from the surface potential and the detection value detected by the temperature detection means. In these cases, the apparatus may be configured to further include image forming condition control means for controlling image forming conditions based on the calculated value calculated by the humidity calculating means.

[0005]

According to the first means described above, a pre-stored table is referred to based on the surface potential of the photoreceptor detected by the surface potential detecting means, and the corresponding humidity value is determined. Therefore, humidity can be determined without providing a separate humidity sensor. According to the second means, the surface potential of the photoreceptor detected by the surface potential detection means;
A pre-stored table is referred to based on the surface temperature of the photoreceptor detected by the temperature detection means, and the corresponding humidity value is determined with higher accuracy.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an electrical system of an embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a schematic configuration diagram showing a mechanical section of the image forming apparatus according to the present invention. First, the configuration of FIG. 2 will be explained. A photosensitive drum 1, which is a cylindrical photosensitive member on which a latent image is formed, rotates counterclockwise in the figure. Near the drum surface after the exposure position, there is a potential sensor 2 as a surface potential detection means for detecting the surface potential of the photoreceptor drum 1, and a developing means for developing a latent image formed by exposure with toner through the exposure means. a developing device 3 for controlling the toner image on the photoreceptor drum 1; A transfer charger 5 serves as a transfer means for electrostatically transferring to a transfer paper as a transfer medium, a separation charger 6 serves to peel off the transferred transfer paper from the surface of the photoreceptor drum 1, and a toner remaining on the surface of the photoreceptor drum 1 is removed. A cleaning device 7 removes charges from the surface of the photoreceptor drum 1, a static elimination lamp 8 removes charges from the surface of the photoreceptor drum 1, a drum thermistor 9 serves as a temperature detection means for detecting the surface temperature of the photoreceptor drum 1, and the surface of the photoreceptor drum 1 is cleaned prior to exposure. A charger 10 serving as a charging means for uniformly charging the photosensitive drum 1 and an eraser 11 that brings the surface of the photoreceptor drum 1 from which electricity has been removed to a ground potential are installed in sequence. Further, a conveyor belt 12 for conveying the transferred transfer paper is disposed adjacent to the separation charger 6, and a fixing device 13 is installed at the rear end for fixing the toner image on the transfer paper by applying pressure and heat. ing.

Next, the configuration of FIG. 1 will be explained. An analog/digital converter (hereinafter referred to as an A/D converter) 14 for converting its analog output into a digital signal is connected to the potential sensor 2, and similarly, an A/D converter is connected to the drum thermistor 9. 15 are connected. Each A/D
A CPU 16 is connected to the converters 14 and 15.
The U16 includes a RAM (random access memory) 17 that stores data and processing results, and a ROM (read read memory) that stores programs for operating the CPU 16.
only memory) 18 is connected. This ROM
18 is a table (A) 18 corresponding to the characteristics shown in FIG.
a and a table (B) 18b with the contents shown in FIG. Furthermore, a pulse width modulation circuit (hereinafter referred to as PWM) 19 is connected to the CPU 16, and a high voltage generation circuit (H.V.) 20 for supplying a high voltage to the transfer charger 5 is connected to this PWM 19. ing.

[0008] In the case of a photoreceptor drum in which a selenium-based charged substance is used and its surface is coated with a thin resin, the residual potential changes almost uniquely depending on the humidity near the photoreceptor when the drum temperature is constant. do. For this reason, Figure 3
As shown, the drum surface temperature (℃) and residual potential (V)
The relationship changes depending on the humidity. Therefore, this relationship is set as table (A) 18a. here,
Preparations are made for humidity (15%, 30%, 60%, 90%). In addition, as shown in FIG. 4, table (B) 1
In 8b, transfer current (μA) values are set for each of a plurality of (five in this embodiment) environmental conditions.

Next, the operation of the embodiment having the above configuration will be explained. In the configuration of FIG. 2, when forming an image, the photosensitive drum 1 is rotated and a voltage is applied to each charger. As a result, the exposed portion of the photoreceptor drum 1 is charged in advance by the charger 10 . This charged area is exposed to light according to image information by an exposure means (not shown), and a latent image is formed by this exposure. The latent image is continuously formed as the photosensitive drum 1 rotates. At this time, if the amount of light from the eraser 11 is sufficient, the potential will almost completely drop to the ground potential by the time it reaches the position of the potential sensor 2. However, in the case of a selenium-based photoreceptor drum, depending on the environmental conditions, it may exceed 200 V. remains. Potential V that could not be completely eliminated by the eraser 11
The potential sensor 2 detects ==.

As the photosensitive drum 1 rotates, the latent image reaches a position facing the developing device 3, toner development is performed, and a developed image is formed. This developed image is processed by the pre-transfer charger 4 to suppress leakage of toner charge, and then
Move to the transfer position. At the same time that the developed image reaches the transfer position, the transfer paper is carried to the transfer position by a paper feeding means (not shown), and the toner image on the photoreceptor drum 1 is electrostatically transferred to the transfer paper by the transfer charger 5. will be held. After the transfer, the transfer paper is separated from its leading edge by the separation charger 6 and sent onto the conveyor belt 12. The conveyor belt 12 feeds the transfer paper between a pair of rollers of a fixing device 13, and the fixing device 13 that receives the toner image fixes the toner image onto the transfer paper.The transfer paper after the fixing is discharged from the device.

During the process of sequential image formation, the surface temperature of the photosensitive drum 1 increases. As is clear from FIG. 3, as the drum temperature changes, the potential (residual potential) V== which could not be completely eliminated also changes, which affects the image density. By detecting the residual potential, it is possible to know the relative humidity, which is related to the moisture content of the transfer paper, but by detecting the drum temperature Td with the drum thermistor 9, it is possible to know the absolute humidity (which affects, for example, image blurring). give)
can be known. Further, the detection output of the drum thermistor 9 can also be used for control so as not to allow copying unless V== becomes low to some extent.

The residual potential V=
= and the drum temperature Td are converted into digital signals by A/D converters 14 and 15, and taken into the CPU 16. From the two detection results, the CPU 16 determines in which region of FIG. 3 the humidity and drum temperature are stored in the ROM 18, and a signal is transmitted according to the table (B) shown in FIG. A signal with a predetermined duty is sent to the voltage generation circuit 20, and a predetermined transfer current is supplied to the transfer charger 5.

FIG. 5 is a transfer current-transfer rate characteristic diagram for determining table (B). That is, the table (B) shown in FIG. 4 is created based on the relationship between the transfer current, humidity, and transfer rate when the drum humidity is constant.

In the above explanation, the control conditions were limited to the transfer current, but image forming conditions whose optimum value changes depending on the humidity (for example, image density fluctuations due to changes in toner charge amount, poor cleaning, changes in the moisture content of transfer paper) It is also possible to control (for example, change the control value of the image density sensor, change the separation current, etc.) (for example, change the control value of the image density sensor, change the separation current, etc.).

[0015]

[Effects of the Invention] Since the present invention is constructed as described above, it achieves the following effects. According to the invention described in claim 1, there are provided a surface potential detection means for detecting the surface potential of the photoconductor, and a humidity calculation means for calculating the humidity of the installation atmosphere based on the detected value of the surface potential obtained by the detection means. Since it is equipped with a humidity sensor, humidity values can be obtained without providing a dedicated humidity sensor, and costs can be reduced. According to the second aspect of the invention, the surface potential detection means for detecting the surface potential of the photoreceptor, the temperature means for detecting the surface temperature of the photoreceptor, and the humidity calculation means for calculating the humidity from the detected values of both are provided. Since it is equipped with a humidity sensor, it is possible to obtain a more accurate humidity value without providing a dedicated humidity sensor. According to the invention described in claim 3, since the image forming conditions are controlled based on the calculated value of humidity, it is possible to take appropriate correction means for changes in humidity, and it is possible to obtain stable images. can. According to the fourth aspect of the invention, since the image forming condition is the transfer current of the transfer charger, it is possible to perform current control that corresponds to changes in the resistance value of the transfer paper, which is susceptible to changes in humidity, and to achieve stable transfer. It becomes possible to do this.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an electrical system of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a front view showing a mechanical section of the image forming apparatus according to the present invention.

FIG. 3 is a characteristic diagram showing the relationship between drum surface temperature (° C.) and residual potential (V).

FIG. 4 is an explanatory diagram showing a table (B) according to the present invention.

FIG. 5 is a transfer current-humidity-transfer rate characteristic diagram used to create table (B) in FIG. 4;

[Explanation of symbols]

1 Photoreceptor drum 2 Potential sensor 3 Developing device 5 Transfer charger 6 Separate charger 8 Removal lamp 9 Drum thermistor 10　Electrical charger 11 Eraser 13 Fixing device 16 CPU 18 ROM 18a Table (A) 18b Table (B) 19 Pulse width modulation circuit 20 Voltage generation circuit

Claims (4)

[Claims] [Claim 1] Charging means for charging the surface of a photoreceptor;
An exposure device that forms a latent image on a charged photoreceptor according to image information, a development device that develops the latent image exposed by the exposure device, and a transfer device that transfers the developed image onto a transfer medium. and a separation means for separating a transfer medium onto which an image has been transferred from a photoreceptor, a surface potential detection means for detecting a surface potential of the photoreceptor, and a surface potential detection means for detecting a surface potential detected by the surface potential detection means. An image forming apparatus comprising: humidity calculation means for calculating humidity of an installation atmosphere based on a surface potential. [Claim 2] Charging means for charging the surface of the photoreceptor;
An exposure device that forms a latent image on a charged photoreceptor according to image information, a development device that develops the latent image exposed by the exposure device, and a transfer device that transfers the developed image onto a transfer medium. and a separation means for separating a transfer medium onto which an image has been transferred from a photoreceptor, a surface potential detection means for detecting a surface potential of the photoreceptor, and a surface potential detection means for detecting a surface temperature of the photoreceptor. The device is characterized by comprising a temperature detection means, and a humidity calculation means for calculating the humidity of the installation atmosphere from the surface potential detected by the surface potential detection means and the detected value detected by the temperature detection means. Image forming device. 3. The apparatus according to claim 1, further comprising image forming condition control means for controlling image forming conditions based on the calculated value calculated by the humidity calculating means. The image forming apparatus according to any one of the above. 4. The image forming apparatus according to claim 3, wherein the image forming condition controlled by the image forming condition control means is a transfer current used in a transfer means.