JPH11167239A - Color electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image of an excellent image quality on a recording medium. SOLUTION: This device is provided with a photoreceptor belt that the toner image is formed thereon, and an intermediate transfer belt on which the toner image is successively formed so as to overlap the other. Moreover, the color electrophotographic device is composed by equipping media transfer roller 7 being applied with voltage in polarity opposite to the toner for transferring the synthetic image on the paper sheet, the temp./humidity sensor 16 for detecting the temp./humidity of the device outside atmosphere, voltage information storing means 32 in which data of the application voltage on the media transfer roller 7 deduced from the printing condition and the temp./humidity of the device outside atmosphere, and a CPU 30 for applying the voltage of the value obtained from voltage information storing means 32 on the media transfer roller 7 based on the printing condition and the temp./humidity at right before executing the transfer of the composing image being detected by the temp./humidity sensor 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic image forming apparatus, and more particularly to a technique which is effective when applied to improvement of image quality in a color electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art In recent years, in a color electrophotographic image forming apparatus, in order to obtain stable transfer quality in various environments, an optimum value of a transfer voltage applied to a transfer roller based on humidity detected by a humidity sensor is used. To adjust.

That is, the transfer voltage at which the multi-layer toner portion is transferred well is different from the transfer voltage at which the single-layer toner portion is transferred well. Therefore, multilayer (two or more layers)
In order to transfer a composite image in which a toner image superimposed on a toner image and a single-layer toner image are simultaneously present on a recording medium so as to obtain good transfer quality, it is necessary to set a transfer voltage according to each environment. .

Therefore, an optimum transfer voltage according to each environment, which is experimentally obtained in consideration of the volume resistance and the surface resistance of the recording medium (paper or plastic film), is set, and the recording medium is accommodated. In addition, a sensor capable of detecting environmental conditions in the vicinity is attached, and the voltage applied to the transfer roller is controlled to a set transfer voltage corresponding to the detection value of the sensor. It should be noted that other printing conditions of the image forming section such as the developing bias are not changed.

[0005]

However, even in such a conventional color electrophotographic image forming apparatus, the image quality may slightly fluctuate due to a change in the environment. Not good.

It is considered that the cause is as follows. First, since the vicinity of the recording medium containing the sensor is inside the apparatus, a subtle change in the environment is detected under the influence of heat generated from a power supply, a fixing device, and the like installed in the apparatus. Difficult to do.

Second, when the amount of the recording medium used is large, the recording medium stored in the cassette of the apparatus is used up at an early stage, and the recording medium stored outside the apparatus is used. Therefore, the actual water content of the recording medium differs from the water content of the recording medium detected by the apparatus.

Third, since the transfer quality is strongly affected not only by the moisture content of the recording medium but also by a short-time change outside the apparatus, it is difficult to measure the humidity of the stagnant atmosphere near the recording medium storage section. , Sometimes not in time. vice versa,
When reflecting the detection information in real time, the voltage control value changes during printing due to a momentary environmental change,
Printing unevenness occurs.

Fourth, since the absolute moisture content in the air is different in different temperature ranges, if the optimum value of the transfer voltage is determined using only the relative humidity as a parameter as in the prior art, it is possible to accurately cope with the temperature change. The water content of the recording medium cannot be measured.

Fifth, conventionally, for example, a high-voltage power supply of constant current control using a change in current resistance according to a change in water content of a recording medium is used, and the current control value is changed based on environmental information. For example, since the optimum value of the transfer voltage is determined by a logical method, it is impossible to cope with a change in the chemical condition of the recording medium.

Sixth, since the water content according to the environment differs depending on the type of recording medium and the optimum value of the transfer voltage differs, for example, even if the same paper category is used, different brands, different thicknesses and different manufacturing methods will provide good transfer. No image is obtained.

Accordingly, an object of the present invention is to provide a color electrophotographic image forming apparatus capable of forming an image of good image quality on a recording medium.

[0013]

In order to solve this problem, a color electrophotographic image forming apparatus according to the present invention provides a toner image formed by attaching toner to an electrostatic latent image formed in accordance with image data. A photosensitive member to be formed, an intermediate transfer member in which toner images of different colors sequentially formed on the photosensitive member are transferred so as to overlap each other to form a composite image, and a voltage having a polarity different from that of the toner are applied. A transfer roller for transferring the composite image formed on the intermediate transfer member to the recording medium while rotating in contact with the recording medium; a temperature / humidity detecting means for detecting the temperature / humidity of the external atmosphere of the apparatus; printing conditions and the temperature of the external atmosphere of the apparatus; A voltage information storage unit in which data of an applied voltage to the transfer roller calculated from the humidity is stored, and a printing condition and a temperature and humidity immediately before executing transfer of the composite image detected by the temperature and humidity detecting unit. Is obtained by a configuration in which a control means for applying a voltage value obtained from the pressure information storage means to the transfer roller.

Thus, a color electrophotographic image forming apparatus capable of forming an image of good image quality on a recording medium can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a photoconductor in which toner is formed by attaching toner to an electrostatic latent image formed in accordance with image data, and An intermediate transfer body in which toner images of different colors sequentially formed on the body are transferred so as to overlap each other to form a composite image, and a voltage having a polarity different from that of the toner is applied to the intermediate transfer body while rotating in contact with the recording medium. A transfer roller for transferring the composite image formed on the transfer body to a recording medium; a temperature and humidity detecting means for detecting the temperature and humidity of the external atmosphere of the apparatus; and a transfer roller calculated from the printing conditions and the temperature and humidity of the external atmosphere of the apparatus. A voltage information storage unit storing data of the applied voltage, and a value obtained from the voltage information storage unit based on the printing conditions and the temperature and humidity immediately before the transfer of the composite image detected by the temperature and humidity detecting unit is performed. The voltage of A color electrophotographic image forming apparatus having control means for applying a voltage to a roller, wherein the temperature and humidity detecting means detects atmosphere information outside the apparatus, and the temperature and humidity detecting means detects immediately before the start of transfer of a composite image. Since the transfer voltage is determined from the data in the voltage information storage means according to the information, the moisture content of the recording medium can be estimated without being affected by the heat source inside the apparatus, and the optimum applied voltage is applied to the transfer roller. This makes it possible to stably form an image of good image quality on a recording medium in all environments.

According to a second aspect of the present invention, in the first aspect of the invention, the data of the voltage applied to the transfer roller stored in the voltage information storage means is set to a temperature of 0 for one type of recording medium. The temperature range is divided into at least two regions within a range of ~ 33 ° C, and a humidity of 0 to 1
This is a color electrophotographic image forming apparatus provided in a range of at least three areas within a range of 00% RH. In this way, two or more and three or more kinds of transfer voltage information are respectively corresponding to temperature and humidity. By providing the transfer roller, it is possible to apply an optimum applied voltage to the transfer roller, and it is possible to form an image of good image quality on a recording medium.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the data of the voltage applied to the transfer roller stored in the voltage information storage means is for at least two types of recording media. A given color electrophotographic image forming apparatus has an effect that it is possible to finely control a voltage applied to a transfer roller depending on a type of a recording medium.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, the data of the voltage applied to the transfer roller stored in the voltage information storage means is a color value which is an experimental value. This is an electrophotographic image forming apparatus, which is determined in consideration of the phenomenon that the actual ambient environment and the water content of the recording medium are different, especially in a low humidity environment, and more stably forms an image of good image quality on the recording medium. Has the effect that it becomes possible to

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is an explanatory view showing the internal structure of a color electrophotographic image forming apparatus according to one embodiment of the present invention, and FIG. 2 shows a temperature and humidity sensor attached to the color electrophotographic image forming apparatus of FIG. FIG. 3 is a perspective view, and FIG. 3 is a block diagram showing a control structure of a voltage applied to the transfer roller.

In FIG. 1, a photoreceptor belt (photoreceptor) 3 on which a photosensitive receptive layer such as an organic photoconductor (OPC) is applied in a thin film form has three photoreceptor belt support / conveyance rollers 3a.
3b and 3c are band-tuned and supported so as to form a horizontal plane on one side, and are rotated circumferentially along photoreceptor belt supporting and conveying rollers 3a, 3b and 3c by a drive motor (not shown). Black (B), cyan (C), magenta (M),
A developing device 2B for storing toner of each color of yellow (Y);
2C, 2M, and 2Y are provided. On the side of the photoreceptor belt 3, a photoreceptor cleaning device 12 for removing the toner remaining on the photoreceptor belt 3, a static eliminator 9 in which an LED lamp is arranged in parallel to eliminate the charge on the photoreceptor belt 3, a photoreceptor belt by corona discharge A charging device 10 for charging 3 is provided, and a laser unit 1 is further provided.

The charger 10 includes a charging wire 10a made of a tungsten wire or the like and a shield plate 10 made of a metal plate.
b, the grid plate 10c. When a high voltage is applied to the charging line 10a, the charging line 10a causes a corona discharge, and the photosensitive belt 3 is uniformly charged via the grid plate 10c. The laser light emitted from the laser unit is controlled by a signal from a host computer (not shown), and a plurality of color components corresponding to a specific component among a plurality of predetermined color components on the photoreceptor belt 3. An electrostatic latent image is formed.

The developing units 2B, 2C, 2M and 2Y for each color are
The developing units are arranged at equal intervals and detachably in predetermined storage sections provided in the apparatus main body, and the inside of each developing unit has the same configuration except for the type of the stored toner.

The developing units 2B, 2C, 2M, and 2Y are brought into contact with the photosensitive belt 3 when developing an electrostatic latent image of a predetermined color corresponding to the developing units 2B, 2C, 2M, and 2Y. The developing units 2B, 2C, 2M, and 2Y are provided with contact cams 5B, 5C, 5M, and 5Y.
When it is not pushed in the direction of the photoreceptor belt 3 by M and 5Y, it is held at a standby position separated from the photoreceptor belt 3.

The intermediate transfer member unit includes an intermediate transfer member belt (intermediate transfer member) 4 made of a conductive resin and the like, and three intermediate transfer member belt supporting / conveying rollers 4a for adjusting the intermediate transfer member belt 4. 4b and 4c. In order to transfer the toner image on the photoconductor belt 3 onto the intermediate transfer belt 4, an intermediate transfer roller 13 is disposed to face the photoconductor belt 3 with the intermediate transfer belt 4 interposed therebetween.

Here, the surface circumference of the intermediate transfer belt 4 is set to be equal to the surface circumference of the photosensitive belt 3. In order to scrape off residual toner on the intermediate transfer belt 4, an intermediate transfer belt cleaning device 15 is installed near the intermediate transfer belt support and transport roller 4c. The intermediate transfer member belt cleaning device 15 is separated from the intermediate transfer member belt 4 while forming a composite image on the intermediate transfer member belt 4, and comes into contact with the intermediate transfer member belt 4 only when it is used for cleaning.

A paper cassette (not shown) for storing paper (recording medium) 14 is provided below the apparatus. Then, the paper 14 is sent out from the paper cassette to the paper transport path one by one by the paper feed roller 17. In order to match the position of the sheet 14 with the composite image formed on the intermediate transfer belt 4, a registration roller 18 for temporarily stopping and waiting the sheet 14 is provided in pressure contact with a driven roller 19. Further, a medium transfer roller (transfer roller) 7 for transferring a composite image formed on the intermediate transfer belt 4 to a sheet 14 by applying a voltage having a polarity different from that of the toner is provided on the sheet transport path. And put the composite image on paper 1
Only when the image is transferred to the intermediate transfer belt 4, the intermediate transfer belt 4 is rotated. The medium transfer roller 7 is made of, for example, conductive foamed polyurethane. In addition, other than the paper 14, for example, an OHP film or the like can be applied to the recording medium.

In order to fix the composite image transferred to the paper 14, a fixing device 8 including a heat roller 8a having a heat source therein and a pressure roller 8b is disposed. And
The paper 14 passes through the heat roller 8 when passing through the fixing device 8.
The composite image transferred by the pressure and heat is fixed by the pinching rotation of the pressure roller 8a and the pressure roller 8b, and a color image is formed.

Here, a temperature / humidity detecting sensor (temperature / humidity detecting means) 16 for detecting the temperature and humidity (relative humidity -RH-) of the atmosphere outside the device is attached to the present apparatus.

As shown in FIG.
Is installed in an intermediate chamber 23 formed inside the housing 22 and separated from other portions by the partition wall 20 and the lid 21. The intermediate chamber 23 is configured to have the same environment as the outside air atmosphere by a slit 24 formed in the housing 22. Further, a slit 25 is also formed in the partition wall, and the outside air introduced from the slit 24 into the intermediate chamber 23 is guided through the slit 25 to the inside of the apparatus which is under negative pressure due to the effect of the fan. Therefore, the temperature and humidity detection sensor 16 can accurately detect the environmental condition of the outside air without being affected by the heat generated inside the apparatus.

As shown in FIG.
Are converted into digital signals by A / D converters 26 and 27, output to I / O ports 28 and 29, and input to CPU (control means) 30. This CPU 30 has condition information storage means 3
1 is connected, and from the condition information storage means 31,
Condition information data such as the type of recording medium (type of paper and plastic film, specifications such as thickness), device operation status information (process speed, single-color printing or multicolor printing, double-sided printing or single-sided printing), etc. It is being sent. Further, a voltage information storage means 32 is connected to the CPU 30, and data of the voltage applied to the medium transfer roller 7 stored in the voltage information storage means 32 (Tables 1 to 3).
Is sent.

The CPU 30 outputs an optimum voltage applied to the medium transfer roller 7 based on these data. The output signal is converted from the I / O port 33 into an analog signal by the D / A converter 34 and input to the high-voltage power supply 35, whereby the voltage determined by the CPU 30 is supplied to the medium transfer roller 7. Here, in the present specification, “optimal” does not mean that it is most appropriate in objective judgment, but it is sufficient to make subjective judgment.

The temperature and humidity data to be used are those immediately before the composite image is transferred onto the paper 14. As a result, the temperature and humidity detection sensor 16
The transfer voltage does not change even if the detection value changes due to.

Here, the data stored in the voltage information storage means 32 are shown in (Tables 1 to 3).

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

As shown in these tables, the type of recording medium (A to E, plain paper) and the process speed (96 mm / sec)
47 mm / sec), printing color (single color / color), printing surface (both sides / single side), and is divided into 16 cases. Are divided into 10 regions between 0 and 100% RH, and an applied voltage to the transfer roller 7 corresponding to the temperature and the humidity in the divided regions is given. Here, it is considered that the minimum image quality can be ensured if the temperature is divided into at least two regions and the humidity is divided into at least three regions, and 5 and 1 as in the present embodiment.
It is not necessary to divide into 0 areas. In addition, in the numbers in the voltage values in these tables, for example, “35 (10
36) "means the number outside the parentheses (here," 3
5 ”) indicates a quote price, and the number in parentheses (here,“ 10 ”)
36 ") indicates the voltage. Therefore, a voltage of 1036 V is applied by the numeral “35”.

All of these voltage values are obtained by experiments. In the experiment, several types of recording media with different characteristics among the categories shown in the table were evaluated based on the moisture content that could exist in different environments, and a voltage area with no problem on the image was obtained. I went in. Then, similar experiments were performed for all recording media categories in all environments.

As a result, a common optimum transfer voltage is obtained even for recording media having different characteristics such as resistance values even when the moisture content is the same due to the difference in chemical composition, and an image of good image quality can be stably formed on the recording medium. It can be formed. In addition, the phenomenon that the actual ambient environment and the water content of the recording medium are different from each other in a low humidity environment is prevented, and an image of good image quality can be more stably formed on the recording medium. Further, it is possible to finely control the voltage applied to the transfer roller depending on the type of the recording medium.

However, some of the voltage values in the table may be experimental values and others may be theoretical values. Further, all of them can be theoretical values. Further, instead of such various types of recording media, only data for one recording medium may be included.

The operation of the electrophotographic apparatus configured as described above will be described below. In FIG. 1, after the charged photoreceptor belt 3 is uniformly discharged by a discharger 9, a charging line 10a in a charger 10 connected to a high-voltage power supply is provided.
To apply corona discharge to the photosensitive belt 3
Is uniformly charged to about -500v to -650v.

Next, the photoreceptor belt 3 is rotated by a driving device (not shown) so that a predetermined color of a plurality of color components, for example, black, is formed on the uniformly charged surface of the photoreceptor belt 3. A laser beam corresponding to the image shown in FIG. As a result, the portion of the photoreceptor belt 3 irradiated with the laser beam loses its charge and an electrostatic latent image is formed. on the other hand,
The developing device 2B containing the black toner contributing to the development is brought into contact with the photoreceptor belt 3 by the contact cam 5B being rotated half a time by a color selection signal from a host computer (not shown). . Then, a thin layer of toner to which a predetermined voltage is applied adheres to the electrostatic latent image to form a toner image.

The developing device 2B having completed the development in this way
When the contact cam 5B is further rotated by a half turn, the contact cam 5B moves from the contact position with the photosensitive belt 3 to the standby position. While the developing device 2B is developing, the other developing devices 2C, 2C
M and 2Y are separated from the photoreceptor belt 3.

Next, when, for example, the color of cyan (C) is selected, the developing device 2C is brought into contact with the photoreceptor belt 3, and starts the development of cyan by the same operation as described above. When four colors are used, such a developing operation is sequentially repeated four times, and the four colors B, C, M, and Y on the intermediate transfer belt 4.
The toner images of the layers are transferred so as to overlap each other, and a composite image is formed here. In the case of one color, a single-layer toner image is formed, in the case of two colors, two layers are formed, and in the case of three colors, a three-layer toner image is formed.

A small amount of toner remaining on the photoreceptor belt 3 without being transferred is cleaned by the photoreceptor cleaning device 12 and prepared for the next process.

When a high voltage having a polarity opposite to that of the toner is applied to the medium transfer roller 7, the composite image thus formed is
The sheet is collectively transferred to the sheet 14 sent from the sheet cassette along the sheet transport path.

Here, the value of the voltage applied to the transfer roller is determined as follows. That is, the type of recording medium that is currently set (referred to as “recording medium A”), the process speed (referred to as “96 mm / sec”), the printing color (referred to as “color”), and the printing surface (referred to as “color”). When the temperature and humidity ("25 ° C." and "50%") are input to the CPU 30, a table is referred to from these data and the applied voltage value is "28 (898)".
Is obtained. As a result, a voltage of 898 V is output from the high-voltage power supply 35 according to the nominal value 28 and applied to the medium transfer roller 7, and the composite image is transferred under an optimum applied voltage.

The sheet 14 onto which the composite image has been transferred is subsequently sent to the fixing device 8. And here, heat and heat roller 8
a and the pressure roller 8b is fixed by the pinching force, and a color image is formed. The sheet 14 that has passed through the fixing device 8 is discharged to a discharge tray.

The small amount of toner remaining without being transferred onto the intermediate transfer belt 4 is cleaned by the intermediate transfer belt cleaning device 15 being brought into contact by an electromagnetic clutch (not shown) to be prepared for the next process. .

As described above, according to the color electrophotographic image forming apparatus of the present embodiment, the voltage information storage means is provided by the detection information immediately before the start of the transfer of the composite image by the temperature and humidity detection sensor 16 which has detected the atmosphere information outside the apparatus. Since the optimum transfer voltage is applied to the medium transfer roller 7 based on the data of No. 32, an image of good image quality can be stably formed on the paper 14 in all environments.

[0052]

As described above, according to the present invention, the optimum transfer voltage is obtained from the data in the voltage information storage means by the detection information immediately before the start of the transfer of the composite image by the temperature and humidity detection means which has detected the atmosphere information outside the apparatus. Is applied to the transfer roller, so that an effective effect of stably forming an image of good image quality on the recording medium in all environments can be obtained.

The data of the voltage applied to the transfer roller stored in the voltage information storage means is divided into at least two areas within a temperature range of 0 to 33 ° C. for one type of recording medium. 0-100% humidity for the area
By dividing and giving at least three areas in the range of RH, it is possible to apply an optimum applied voltage to the transfer roller, and it is possible to form an image with good image quality on a recording medium. Is obtained.

By applying the data of the voltage applied to the transfer roller stored in the voltage information storage means to at least two types of recording media, it is possible to finely control the voltage applied to the transfer roller depending on the type of recording medium. Is obtained.

By using the data of the voltage applied to the transfer roller stored in the voltage information storage means as experimental values, the data is determined in consideration of the phenomenon that the actual ambient environment and the water content of the recording medium are different in a low humidity environment. Therefore, an effective effect that an image of good image quality can be more stably formed on the recording medium can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an internal structure of a color electrophotographic image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a temperature and humidity detection sensor attached to the color electrophotographic image forming apparatus of FIG.

FIG. 3 is a block diagram illustrating a control structure of a voltage applied to a transfer roller.

[Explanation of symbols]

 Reference Signs List 3 photoreceptor belt (photoreceptor) 4 intermediate transfer member (intermediate transfer member belt) 7 medium transfer roller (transfer roller) 14 paper (recording medium) 16 temperature and humidity detecting means (temperature and humidity detecting sensor) 30 CPU (control means) 32 Voltage information storage means

Claims (4)

[Claims] An image forming apparatus according to claim 1, wherein a toner image is formed by attaching toner to an electrostatic latent image formed in accordance with image data, and a toner image of a different color sequentially formed on said photoconductor is mutually reciprocated. An intermediate transfer member on which a composite image is formed by being transferred so as to overlap with each other; and a voltage having a polarity different from that of the toner is applied, and the composite image formed on the intermediate transfer member is rotated while contacting and rotating with a recording medium. A transfer roller for transferring to a medium, temperature and humidity detecting means for detecting the temperature and humidity of the outside atmosphere of the apparatus, and data of a voltage applied to the transfer roller determined from printing conditions and temperature and humidity of the outside atmosphere of the apparatus are stored. A voltage information storage unit, and converts the voltage of the value obtained from the voltage information storage unit based on printing conditions and the temperature and humidity immediately before executing the transfer of the composite image detected by the temperature and humidity detection unit. Color electrophotographic image forming apparatus characterized by a control means for applying to the roller. 2. The data of the voltage applied to the transfer roller stored in the voltage information storage means is divided into at least two areas within a temperature range of 0 to 33 ° C. for one type of the recording medium. Humidity 0
2. The color electrophotographic image forming apparatus according to claim 1, wherein said color electrophotographic image forming apparatus is divided into at least three regions within a range of 100% RH. 3. The color printer according to claim 1, wherein the data of the voltage applied to the transfer roller stored in the voltage information storage means is provided for at least two types of recording media. Electrophotographic image forming apparatus. 4. A color electrophotographic image forming apparatus according to claim 1, wherein the data of the voltage applied to said transfer roller stored in said voltage information storage means is an experimental value.