JPH08202171A - Electrophotographic recording device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide an electrophotographic recording device that can evenly charge a toner by supplying an appropriate electric current to a photoconductor and stably obtain a high-quality image. . The electrophotographic recording apparatus includes a charging unit 11 that uniformly charges the surface of a photoconductor 10, an exposure unit 12 that forms an electrostatic latent image according to image information, and a toner that has a different charging polarity. Developing means 13 and 14 for developing to form a toner image, pre-transfer charging means 17 for aligning the charging polarities of the toner images, and recording medium 31.
And a transfer means 41 for transferring the toner image to the pre-transfer charging means 17. The pre-transfer charging means 17 is an ammeter 2a for detecting the amount of current flowing through the charging wire 1a, which is one discharge electrode, and the other discharge electrode. An ammeter 2b for detecting the amount of current flowing through the shield member 1b, and a power supply controller 3 for controlling the power supply 4 supplied to the charging wire 1a so that the difference between one current amount and the other current amount becomes constant. I have.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus such as a printer, a copying machine or a FAX, which records an image by an electrophotographic method, and more particularly to a pre-transfer charging device in the electrophotographic recording apparatus.

[0002]

2. Description of the Related Art Electrophotographic recording devices such as copiers and printers that obtain color images by electrophotography are widely used. As an image printing method by this recording device, an evenly charged surface of the photoconductor is exposed based on image information to form an electrostatic latent image having a printing level and a non-printing level, and the electrostatic latent image is formed. A method of developing an electric latent image to obtain an image (two-level printing method) is generally used. To obtain a full-color image by this printing method, charging,
It is necessary to repeat exposure and development four times.

For the purpose of further increasing the printing speed or downsizing the recording apparatus, the electrostatic latent image composed of two printing potential levels and a non-printing potential level can be obtained by one exposure. A method for forming an image and developing for two colors (three-level printing method) is disclosed in US Pat. No. 4,078,929. In this method, the surface of the photoconductor is uniformly charged by a charger, and then the photoconductor is irradiated with light modulated based on image information to form an electrostatic latent image having three potential levels. To form. Regarding the potential of the electrostatic latent image, the part where the initial charging potential is maintained without being exposed by the exposure device, the part where the photosensitive member surface potential is reduced by strong exposure, and the weakly exposed photosensitive member surface potential is initially charged. It consists of a part that is approximately the middle value of the potential. This electrostatic latent image is developed by using two developing devices in which one developing device contains positively charged toner and the other developing device contains negatively charged toner, and an appropriate developing bias voltage is applied to the developing roll. Upon application, the electrostatic latent image is developed to obtain a color image. The portion where the surface potential of the photoconductor is weakly exposed and has an intermediate value of the initial charging potential is a portion (background portion) to which neither toner adheres. After the toner image is formed on the photoreceptor, the polarity of the toner is made uniform by the charging device, and the toner image is transferred to the recording medium (cut paper, continuous paper, OHP sheet, etc.) by the transfer device. After that, the toner image is fused on the recording medium by heat in the fixing device. In this way, two-color printed images are obtained on the recording medium.

The feature of the three-level printing method is that latent images of two colors can be formed by one exposure,
That is, it is possible to perform two-color printing at the same printing speed as that of a one-color machine without misalignment. However, on the other hand, since the development is performed using two color toners having polarities different from each other, it is necessary to make the charging polarities of the toner uniform before transferring the toner image to the recording paper. This is done by charging the toner by corona discharge of the charger.

Japanese Patent Publication No. 6-3557 discloses an example of applying an electric charge to the toner on the photosensitive member. According to this publication, when applying a charge to the toner on the photoreceptor, the charge is applied to the toner by simultaneously irradiating light, and the efficiency is improved.

[0006]

However, in the above-mentioned three-level printing method, even if the current flowing through the discharge electrode of the charger is constant, the conductive medium is air, so that the shield member and the photoconductor are not affected. The ratio of the flowing current is not always constant, and if the wall surface of the shield member becomes dirty, the electrical resistance increases, making it difficult for the current to flow through the shield member, and it is not possible to obtain stable and high-quality images. There is.

Further, in order to control the charge amount of the toner on the photoconductor, it is expected that it is more effective to control the current amount flowing to the photoconductor than the current flowing to the discharge electrode. The technology does not consider proper control of the current through the photoreceptor. Besides, in order to control the current, it is necessary to remove the factors that disturb the current amount,
That is, in particular, among the contamination of the electrode of the charger, the change of environment, the distortion of the charger, etc. as a factor that disturbs the current amount in the charger, the influence of the contamination of the electrode is the largest, and the charger including the electrode Although it is important to clean the components of (1), since no consideration is given to this, there is also a problem that a stable image cannot be obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic recording apparatus capable of stably obtaining a high quality image by setting the charge amount of the toner on the photosensitive member to an appropriate value.

[0009]

The above-described object is to discharge the corona discharge to the pre-transfer charging means for charging the toner image before transfer formed on the surface of the photoconductor by corona discharge to make the charge polarity of the toner image uniform. This is achieved by providing current amount detection means for detecting the amount of current flowing through the electrodes and power supply control means for controlling the power supply for the corona discharge based on the amount of current detected by the current amount detection means.

Further, charging means for uniformly charging the surface of the photoconductor, exposure means for forming an electrostatic latent image on the surface of the photoconductor by image information, and the electrostatic latent image formed on the surface of the photoconductor. Developing means for developing a toner image with toners having different charging polarities, pre-transfer charging means for aligning the charging polarity of the toner image on the surface of the photoconductor, and transfer means for transferring the toner image to a recording medium. In the electrophotographic recording apparatus configured to include, the pre-transfer charging means is a corotron, and a current amount for detecting a current amount flowing in one discharge electrode of the corotron and a current amount flowing in the other discharge electrode of the corotron. This can also be achieved by including a detection unit and a power supply control unit that controls the power supply to the discharge electrode so that the difference between the one current amount and the other current amount becomes constant.

Further, when the pre-transfer charging means is a scorotron, the amount of current flowing through one discharge electrode of the scorotron, the amount of current flowing through the other discharge electrode, and the amount of current flowing through the grid of the scorotron are detected. A current amount detecting means, and a power source controlling means for controlling the power source supplied to the discharge electrode so that a value obtained by subtracting the sum of the other current amount and the current amount flowing in the grid from the one current amount becomes constant. And may have.

[0012]

According to the above structure, the power supply control means calculates the difference in current amount between the current flowing through one of the discharge electrodes and the current flowing through the other discharge electrode, and the current is supplied to the photoconductor corresponding to the difference in current amount. The power supply supplied to the discharge electrode is controlled so that the current becomes constant. As a result, even when the discharge electrode or the like becomes dirty or the electric resistance of the air changes due to a change in the environment and the current flowing through the discharge electrode changes, the current amount difference, that is, the current flowing through the photoconductor is always Be constant. When the current flowing through the photoconductor becomes constant, the amount of charge of the toner attached to the photoconductor becomes substantially uniform, and a high-quality image can be printed stably.

Further, since it is determined from the change in the amount of current flowing through the discharge electrode that the discharge electrode or the like is contaminated, the cleaning means may be driven based on the determination to clean the discharge electrode or the like. A stable image can be printed.

[0014]

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

[Embodiment 1] When a full-color image is printed by an electrophotographic recording apparatus, image information for each pixel is transmitted from the host computer to the recording apparatus to form the entire image. Each print pixel has eight types of white (W), magenta (M), red (R), green (G), cyan (C), blue (B), yellow (Y), and black (K). Printed in color. The intermediate color can be expressed by setting an appropriate toner mixing ratio among M, C, and Y.

FIG. 2 is a diagram showing the structure of an electrophotographic recording apparatus according to an embodiment of the present invention. The configuration and operation of the first embodiment will be described below with reference to FIGS. Around the first photoconductor 10 along the rotation direction,
First charging means 11, first main exposure means 12, first developing means 13, second developing means 14, first toner adhesion amount sensor 15, auxiliary exposure means 16, first pre-transfer charging means 17,
The first static eliminator 18 and the first cleaner 19 are arranged.

Similarly, around the second photoconductor 20, the second charging means 21, the second main exposure means 22, the third developing means 23,
Fourth developing means 24, second toner adhesion amount sensor 25, second
Pre-transfer charging means 27, second charge eliminating means 28, and second cleaner 29 are arranged.

First developing means 1 near the first photoconductor 10
3 and the toner contained in the second developing means 14 are any two kinds of M, C and Y, one of which is a positively charged toner and the other of which is a negatively charged toner. In this embodiment, the first developing means 13 contains a developer containing M toner which is positively charged, and the second developing means 14 is negatively charged C.
It contains a developer containing toner. As the developer, a one-component developer which has been conventionally used, or 2
Any of the component developers may be used.

The image signal sent from the host computer consists of eight types of basic color data and halftone data. The halftone data is data that represents the amount of each toner attached and data that determines the electrostatic latent image potential during exposure. The electrostatic latent image potential is determined by changing the exposure amount during exposure. The relationship between the exposure amount and the electrostatic latent image potential after exposure is measured and set in advance using a photoconductor and an optical system to be used, and is stored in the exposure amount calculation means in the first main exposure means 12.

FIG. 3 is a diagram showing the surface potential distribution on the photoconductor after exposure. That is, it is a potential diagram of an electrostatic latent image when image data for two colors is recorded on a photoconductor by one exposure. On the surface of the photoreceptor, there are a portion where the initial charging potential V1 is maintained, a portion where the surface potential is V2 after weak exposure and a portion where the surface potential is V3 after strong exposure. Development is performed by setting appropriate development bias potentials Vb1 and Vb2. The portion where the surface potential is V2 becomes the background portion of the image to which toner does not adhere. The largest amount of toner adheres to the areas where the surface potentials are V1 and V3. When printing an image in full color, the exposure amount at the time of exposure is changed to set the surface potential within the range of V1 to V3, and an appropriate amount of toner is exposed by the first developing means 13 and the second developing means 14. The image is attached to the body.

In this method, since two kinds of toner (C, M) cannot be attached to the same pixel, blue (B)
Cannot be expressed. However, since the two types of toner have different charging polarities, the charge on the surface of the first photoconductor 10 is appropriately removed (or reduced). As a result, the toner can be mixed by the electrostatic force of the electric charge of the toner itself.
As a specific method, the auxiliary exposure means 16 is used to irradiate the first photoconductor 10 with light to remove (or reduce) the charges on the photoconductor, and the two types of toner are mixed to produce blue (B). A method of expressing is conceivable. As the auxiliary exposure means 16, similar to the first main exposure means 12, a laser light source, a lens system, an optical system including a polygon motor, an LED array and the like can be mentioned.

Returning to FIG. 1, after the auxiliary exposure, the charging polarity of the toner image formed from the two types of toner is adjusted to one polarity by the pre-transfer charging means 17, and the toner image is electrostatically charged by the charger 34. Is transferred onto the intermediate transfer body 40 as a transfer means. After the toner image is transferred to the intermediate transfer body 40, the surface of the first photoconductor 10 is discharged by the first charge removing unit 18 and cleaned by the first cleaner 19.

Before transfer to the intermediate transfer member 40, changing the charging polarity of the toner is performed on the surface of the photosensitive member by a corona charger as a pre-transfer charging means so that the toner has one polarity. This can be achieved by corona-discharging the toner image. Corona discharge by the corona charger includes direct current corona discharge and alternating current corona discharge. Corona discharge by direct current is indispensable to give electric charge to the toner by discharge. Although it is possible to sufficiently reverse the charging polarity of the toner only by corona discharge by direct current, if the corona discharge by alternating current is added to the direct current and the corona discharge by alternating current is also added, the charging polarity of the toner can be more efficiently reversed. it can.

That is, the corona discharge by alternating current is
Since the discharge is started at a voltage smaller than that of the direct current, the corona current is stable. Therefore, it is possible to uniformly and stably reverse the charge polarity of the toner by performing the pre-transfer charging using a current containing an AC component.

In this case, the AC component of the current supplied to the corona charger (that is, pre-transfer charging means) such as a corotron or scorotron is preferably about 300 to 700 μA. Desirably, it is about 400 to 650 μA. The reason for this is that the alternating current is
If it is less than 300 μA, it becomes difficult to flow DC current stably, and if it is more than 700 μA, when the shield member or wire becomes dirty, a spark discharge will occur from the wire toward the shield member. Because it does.

On the other hand, by applying a high voltage to the wire of the corona discharger, the corona current flows through the shield member and the photoconductor. Even when the same voltage is applied to the wire, the current flowing through the wire changes depending on the structure of the charger and the environment in which the charger is placed. Further, the toner may adhere to the wire or the shield member to increase their electric resistance and reduce the amount of current. Further, if toner adheres partially to the longitudinal direction of the wire or shield member, a distribution of the amount of current is generated. As described above, the current flowing through the photoconductor changes due to various factors.

Therefore, when the toner charge amount is changed by the pre-transfer charging, the change amount is expected to depend on the charge amount flowing into the photosensitive member per unit area. The amount of charge flowing per unit area of the photoconductor is defined by the difference between the current flowing through the wire of the corona charger and the current flowing through the shield member and the moving speed of the photoconductor (process speed of the electrophotographic recording apparatus).

FIG. 4 is a diagram showing the relationship between the amount of charge applied to the photoconductor and the amount of toner charge on the photoconductor. That is, when the charging polarity of the toner is inverted from positive to negative by the pre-transfer charging means, the relationship between the charge amount of the DC component applied to the photoconductor and the toner charge amount of the solid image existing on the photoconductor is shown. ing. In the figure, when the process speed is changed from 90 to 270 mm / s, it is converted into the amount of charge given per unit area from the energizing current and speed and displayed.

Regardless of the process speed, the toner charge amount after pre-transfer charging depends on the charge amount given per unit area. It was found that when a charge of 0.04 μC per cm ² is applied, the charge polarity of the toner is inverted from positive to negative, and when a charge of 0.1 μC is applied, the charge amount of the toner reaches a saturation value and stabilizes. And the amount of charge given per unit area is 0.
It has also been found that when it exceeds 25 μC, toner having a particularly high charge amount is generated in spots, and unevenness occurs in the toner image after transfer. Therefore, when pre-transfer charging is performed, it can be said that it is desirable to set the amount of electric charge applied to the photoconductor as described above so as to give the amount of electric charge of the direct current component in the range of 0.1 to 0.25 μC / cm ² .

As described above, it is effective to flow an appropriate amount of charge, that is, an appropriate current of an alternating current component and a direct current component, to the photosensitive member during pre-transfer charging. Therefore, the power supply control means has a current control means for making the current flowing through one of the discharge electrodes a current obtained by folding the alternating current into the direct current, and the alternating current component of the current flowing through one of the discharge electrodes is , 300 to 700 μA, and the DC component has a current control means for controlling the current to be in the range of 0.1 to 0.25 μC per 1 cm ² of the printing area of the photoconductor.

Since the process speed of the electrophotographic recording apparatus is known in advance, it can be said that the current flowing through the photoconductor should be detected and controlled in order to flow an appropriate current through the photoconductor. However, a current has flowed into the first photoconductor 10 from the first charging unit 11, the intermediate transfer body 40, and the like. Therefore, it is difficult to directly detect only from the current flowing from the pre-transfer charging unit 17 to the first photoconductor 10, and it is necessary to detect indirectly.

For example, as a method of indirectly obtaining the amount of current, a method of obtaining it from the value of the current flowing through the discharge electrode of the corona charger can be considered. Then, it is important to properly detect the amount of current flowing through the photoconductor and appropriately control the amount of current in order to obtain a stable image. The method will be described with reference to the following figure.

FIG. 1 is a diagram showing the structure of a pre-transfer charging means of one embodiment according to the present invention. In the figure, the case where the pre-transfer charging means is a corona charger and the corona charger is a corotron is shown. The structure of the corotron is the charging wire 1 which is one of the discharge electrodes of the corotron.
a, a shield member 1b which is the other discharge electrode, ammeters 2a and 2b as current amount detecting means, a power supply control device 3, and a power supply 4. Incidentally, the current amount detecting means may be a single integrated ammeter.

The operation is as follows. The charging wire 1a of the corotron is supplied from the power source 4 with a current obtained by folding the alternating current into the direct current. The current flowing through the charging wire 1a is divided into the photoconductor 10 and the shield member 1b. Charging wire 1
The current flowing in a is detected by the ammeter 2a as current amount detecting means for detecting the amount of current flowing in one discharge electrode, and the current flowing in the shield member 1b is detected as current amount detecting means for detecting the current amount flowing in the other discharge electrode. Ammeter 2b
Is detected by The power supply control device 3 includes an ammeter 2a,
The amount of current flowing through the photoconductor 10 is calculated from the current value measured by 2b, and for example, the amount of current flowing through the charging wire 1a is subtracted from the amount of current flowing through the shield member 1b to obtain an appropriate current. The amount of current flowing through the charging wire 1a is controlled so that the current flows in the direction. That is, the power supply control device 3 is a power supply control means that controls the power supply supplied to the discharge electrodes so that the difference between the one current amount and the other current amount becomes constant.

In summary, the pre-transfer charging means for charging the toner image before transfer formed on the surface of the photoconductor by corona discharge to make the charging polarity of the toner image uniform is the amount of current flowing through the discharge electrode for corona discharge. It can be said that it has a current amount detecting means for detecting the above, and a power source controlling means for controlling the power supply for corona discharge based on the current amount detected by the current amount detecting means.

Generally, in charging, it is important to give an appropriate amount of charge per unit area of the photoconductor. Then, an appropriate value of the current flowing through the photoconductor depends on the width of the photoconductor and the process speed. From the results shown in FIG. 4, a stable image can be obtained if the current amount is 0.1 to 0.25 μA per 1 cm ² of the printing area of the photoconductor. The amount of current is
0.15-0.25 μA is more desirable.

By doing so, it is possible to control so that an appropriate current always flows through the photosensitive member, so that a stable image can be obtained. The ammeters 2a and 2b here detect the DC component of the current flowing through the wire and the shield member.

By the way, when an image is printed by the electrophotographic recording apparatus, toner scattered from the developing means adheres to the inner surfaces of the charging wire 1a and the shield 1b of the corona charger arranged around the photoconductor. Come on. When the toner adheres to the inner surfaces of the charging wire 1a and the shield 1b, the electric resistance increases, so that the current flowing through the charging wire 1a decreases even when the same voltage is applied to the charging wire 1a. Since the toner adhesion to the charging wire 1a is not uniform in the longitudinal direction, a large amount of current flows from the portion with a small toner adhesion (the portion having a low electric resistance) to the photoconductor or the shield member. Uneven charging of the toner occurs and the image quality deteriorates. Therefore, it is necessary to regularly clean the corona charger.

As described above, when toner adheres to the charging wire 1a, it becomes difficult for current to flow in the charging wire 1a.
From this, the contamination of the discharge electrode can be detected from the "change in the relationship between the voltage applied to the discharge electrode and the current flowing through the discharge electrode". Further, when the toner adheres to the shield member 1b, the current flowing into the shield member 1b decreases. Therefore, the contamination of the discharge electrode can also be detected from the "ratio between the current flowing through one discharge electrode and the current flowing through the other discharge electrode". The detection of the current for detecting the dirt may be detected by either an AC component or a DC component.

When dirt is detected, the current flowing in the photoconductor can be stabilized by controlling the discharge electrode such as the wire and the shield member inside the corotron, so that the current can be stabilized for a long period of time. It is possible to maintain a stable and high-quality image throughout.

FIG. 5 is a view showing the arrangement of a pre-transfer charging means with a cleaning means according to an embodiment of the present invention. A corona charger having a cleaning means for cleaning the wire and the shield member of the corona charger, for example, the first pre-transfer charging means 17 in FIG.
Is shown. The configuration of the present embodiment is the charging wire 1a,
Shield member 1b, cleaning member 51, spring 53, pulley 5
5, a drive wire 56. The shape of the cleaning member 51 is designed to contact the charging wire 1a stretched by the spring 53 and the inner surface of the shield member 1b to clean them.

The operation is as follows. When the current flowing through the charging wire 1a or the shield member 1b becomes abnormal, for example, the power supply control device 3 in FIG. 1 detects a change in the amount of current. Further, when the power supply control device 3 determines from the change that the discharge electrodes or the like are contaminated, the drive device (not shown) is activated and the pulley 55 is rotated. And the drive wire 5
6 moves left and right. As a result, the cleaning member 51 that is connected to the drive wire 56 and is in contact with the charging wire 1a and the shield member 1b also moves to the left and right, and the charging wire 1a
Clean the shield member 1b. During normal printing, the cleaning member 51 is installed at a position where charging before transfer is not hindered.

FIG. 6 is an enlarged view of the cleaning member 51 shown in FIG. The illustrated cleaning member 51 is made of a soft material such as sponge or felt. And, for example, the charging wire 1
In this structure, the charging wire 1a is passed through a hole 58 formed in the central portion of the cleaning member 51 so that the charging wire 1a can be cleaned.

Therefore, according to the embodiment shown in FIGS. 5 and 6, the pre-transfer charging means determines the contamination inside the corotron from one current amount and the other current amount, and the inside of the corotron based on the determination. It can be said that it has a cleaning means for cleaning the. Then, in the above example, the determination means is the power supply control device 3. The cleaning means has the same structure as that shown in FIG. 5 including a driving device (not shown).

In other words, the pre-transfer charging device used in the electrophotographic recording device has a judging means for judging the contamination of the discharge electrode from the change of the amount of current flowing through the discharging electrode of the charging device, and a judgment means based on the judgment. Cleaning means for cleaning the discharge electrode.

Returning to FIG. 1 again, even around the second photoconductor 20, the surface of the second photoconductor 20 is uniformly charged by the second main charging means 21 as in the case of the first photoconductor 10. The second main exposure unit 22 performs exposure with a preset exposure amount. The toner contained in the third developing means 23 and the fourth developing means 24 is a combination of black (K) toner and yellow (Y) toner, and these do not have to be mixed with each other. Auxiliary exposure means is not required around the. If the K toner and the Y toner have different charging polarities, they may be stored in either the third developing unit 23 or the fourth developing unit 24.

Finally, the toner image on the second photoconductor 20 is transferred onto the surface of the intermediate transfer body 40 by the charger 35 without any positional deviation. The toner image on the intermediate transfer member 40 is recorded on the recording medium 31 conveyed by the conveying unit 32.
(Cut paper, continuous paper, OHP sheet, or the like is used) A voltage is applied to the surface, and further transfer is performed by a transfer roll 41 as a transfer unit. After that, the recording medium 31 is conveyed to the fixing means 37, and the toner image is fixed on the surface of the recording medium 31 by heat and pressure to complete a full-color image. On the other hand, the toner remaining on the intermediate transfer body 40 is cleaned by the intermediate transfer body cleaner 42.

[Embodiment 2] FIG. 7 is a diagram showing the structure of a pre-transfer charging means according to another embodiment of the present invention. This is the case where the corona charger is a scorotron.

In the scorotron, a grid 1c is provided on the opening surface of the corotron shown in FIG. 1, and a Zener diode 5 and an ammeter 2c are connected to the grid 1c kept at a constant potential. It is a composition.
Others are the same as the corotron, and the description is omitted.

The operation will be described. The current flowing from the charging wire 1a to the photoconductor 10 is a flow of electric charges passing through the space portion of the grid 1c. Therefore, the amount of charge passing through the space of the grid 1c kept at a constant potential is
It is also uniform with respect to the surface of the grid 1c. Therefore, uniform charges can be supplied to the surface of the photoconductor. As in the case of the corotron, the charging wire 1a of the scorotron is supplied from the power source 4 with a current obtained by folding the alternating current into the direct current. The current flowing through the charging wire 1a is applied to the photoconductor 10, the shield member 1b,
Divide into the grid 1c.

The current flowing through the charging wire 1a is detected by the ammeter 2a, the current flowing through the shield member 1b is detected by the ammeter 2b, and the current flowing through the grid 1c is detected by the ammeter 2c. Power control device 3
Is the current amount detected by the ammeter 2a, the ammeter 2b, and the ammeter 2c.
Charging wire 1 so that an appropriate current flows to photoreceptor 10.
Controls the amount of current flowing through a. If the pre-transfer charging means is a scorotron, the number of parts will increase and the circuit configuration will become slightly more complicated, but compared to the corotron,
Since the current can be controlled to flow uniformly through the photoconductor, there is an effect that a stable image with less density unevenness can be obtained.

[Third Embodiment] FIG. 8 is a view showing the arrangement of an electrophotographic recording apparatus according to another embodiment of the present invention. Example 1 is a recording apparatus having a different printing process, specifically, a method of transferring a toner image directly from the photoconductor 10 to the recording medium 31 without using the intermediate transfer body 40 shown in Example 1. It is an electrophotographic recording device.

The configuration and operation will be described together. The surface of the photoconductor 10 is uniformly charged by the first charging means 11 and exposed by the first main exposure means 12 to form an electrostatic latent image. Then, the electrostatic latent image is developed by the first developing means 13 and the second developing means 14 to form a toner image. Subsequently, the surface of the photoconductor 10 is charged by the second charger 21 on the developed toner image.

After that, the second main exposure means 22 exposes to form an electrostatic latent image. The electrostatic latent image is developed by the third developing means 23 and the fourth developing means 24. Here, the conditions that the toner contained in the first developing unit 13, the second developing unit 14, the third developing unit 23, and the fourth developing unit 24 should have are the same as those in the first embodiment.

The pre-transfer charging means 17 according to the present invention
By this, appropriate pre-transfer charging control is performed. Uniformly
Further, after the charge polarities of the toner are stably aligned, the toner image is transferred onto the recording medium 31 and fixed by the fixing means 37. The surface of the photoconductor 10 is neutralized by the static eliminator 18 for irradiating light, and the toner remaining on the surface of the photoconductor 10 is cleaned by the cleaner 19.

In the case of the third embodiment, since a toner image is formed on one photosensitive member 10, there is an advantage that the positional deviation is less likely to occur as compared with the first embodiment, and since the intermediate transfer member is not used, the apparatus is The advantage of small size is taken advantage of by the present invention.

[0057]

EFFECT OF THE INVENTION In an electrophotographic recording apparatus for obtaining a color image by using plural kinds of toners having different charging polarities, an appropriate current is applied at the time of pre-transfer charging in which the charging polarities of the toners are made uniform before being transferred onto a recording medium. Since it can be controlled so as to flow to the photoconductor, it is possible to provide a high-quality image having a constant density.

Further, it becomes possible to detect the contamination of the pre-transfer charging means from the current flowing through the wire, the shield member, the grid, etc., which is the discharge electrode of the pre-transfer charging means, and the cleaning and repair of the pre-transfer charging means (handlability) ) Becomes easy. Then, by detecting the dirt and cleaning the pre-transfer charging means, there is an effect that a more stable image can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a pre-transfer charging device according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electrophotographic recording apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a surface potential distribution on a photoconductor after exposure.

FIG. 4 is a diagram showing the relationship between the amount of charge applied to a photoconductor and the amount of toner charge on the photoconductor.

FIG. 5 is a diagram showing a configuration of a pre-transfer charging unit with a cleaning unit according to an exemplary embodiment of the present invention.

6 is an enlarged view of the cleaning member 51 of FIG.

FIG. 7 is a diagram showing a configuration of a pre-transfer charging device according to another embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of an electrophotographic recording apparatus of another embodiment according to the present invention.

[Explanation of symbols]

1a ... Charging wire, 1b ... Shield member, 1c ... Grid, 2a, 2b, 2c ... Ammeter, 3 ... Power supply control device, 4 ...
Power supply, 5 ... Zener diode, 10 ... First photoconductor, 1
1 ... 1st charging means, 12 ... 1st main exposure means, 13 ... 1st
Developing means, 14 ... Second developing means, 15 ... First toner adhesion amount sensor, 16 ... Auxiliary exposure means, 17 ... First pre-transfer charging means, 18 ... First charge eliminating means, 19 ... First cleaner, 20
... second photoconductor, 21 ... second charging means, 22 ... second main exposure means, 23 ... third developing means, 24 ... fourth developing means, 25
... second toner adhesion amount sensor, 27 ... second pre-transfer charging means, 28 ... second charge eliminating means, 29 ... second cleaner, 31 ...
Recording medium, 32 ... Conveying means, 34, 35 ... Charging device, 37
... fixing means, 40 ... intermediate transfer body, 41 ... transfer roll, 4
2 ... Intermediate transfer member cleaner.

Claims (8)

[Claims] 1. A pre-transfer charging means for charging a toner image before transfer formed on a surface of a photoconductor by corona discharge to detect the amount of current flowing through the discharge electrode for corona discharge. An electrophotographic recording apparatus comprising: a current amount detecting means; and a power supply control means for controlling a power supply for the corona discharge based on a current amount detected by the current amount detecting means. 2. A charging means for uniformly charging the surface of the photoconductor,
An exposure unit that forms an electrostatic latent image on the surface of the photoconductor by image information, and a developing unit that develops the electrostatic latent image formed on the surface of the photoconductor using toners having different charging polarities to form a toner image. In the electrophotographic recording apparatus, a pre-transfer charging unit that aligns the charging polarities of the toner images on the surface of the photoconductor and a transfer unit that transfers the toner images onto a recording medium are provided. A current amount detecting means for detecting a current amount flowing in one discharge electrode of the corotron and a current amount flowing in the other discharge electrode of the corotron, and a difference between the one current amount and the other current amount. And a power supply control means for controlling the power supply supplied to the discharge electrode so that the discharge amount becomes constant. 3. A charging means for uniformly charging the surface of the photoconductor,
An exposure unit that forms an electrostatic latent image on the surface of the photoconductor by image information, and a developing unit that develops the electrostatic latent image formed on the surface of the photoconductor using toners having different charging polarities to form a toner image. In the electrophotographic recording apparatus, a pre-transfer charging unit that aligns the charging polarities of the toner images on the surface of the photoconductor and a transfer unit that transfers the toner images onto a recording medium are provided. A scorotron, a current amount detecting means for detecting a current amount flowing through one discharge electrode of the scorotron, a current amount flowing through the other discharge electrode, and a current amount flowing through the grid of the scorotron, and the one current amount. From the other current amount and the current amount flowing in the grid is subtracted, the power supply control means for controlling the power supplied to the discharge electrode is constant. Electrophotographic recording apparatus characterized by. 4. The power supply control means according to claim 2 or 3, wherein the power supply control means has a current control means for making the current flowing through the discharge electrode a current obtained by folding a direct current into an alternating current. Electrophotographic recording device. 5. The power source control means according to claim 2, wherein the AC component of the current flowing through the discharge electrode is in the range of 300 to 700 μA, and the DC component is the printing of the photoconductor. An electrophotographic recording apparatus comprising a current control means for controlling a current in the range of 0.1 to 0.25 μC per 1 cm ^{2 of} area. 6. The determination means according to claim 2, which determines contamination of the inside of the corotron from the one current amount and the other current amount, and cleaning means for cleaning the inside of the corotron based on the determination. An electrophotographic recording device characterized by being provided. 7. The method according to claim 3, wherein the one current amount, the other current amount, and the current amount flowing in the grid.
An electrophotographic recording apparatus, comprising: a determination unit that determines the dirt inside the scorotron, and a cleaning unit that cleans the inside of the scorotron based on the determination. 8. An electrophotographic recording apparatus, comprising: a determining unit that determines the contamination of the discharge electrode based on a change in the amount of current flowing through the discharging electrode of the charging device; and a cleaning unit that cleans the discharge electrode based on the determination. Pre-transfer charging device.