JPH10161406A - Color electrophotographic equipment - Google Patents

Abstract

(57) Abstract: An object of the present invention is to perform high-speed printing with high printing quality without contaminating the periphery of a developing tank. SOLUTION: In a printing area, as shown in (a), a developer is uniformly applied on a developing roller 31 and is subjected to a developing process. The developing bias voltage applied to the roller 31 is changed. Then, as shown in FIG. 2B, the developer portion cut by the spike cutting member 32 is
After the contact with the photosensitive member 15, as shown in FIG. 4C, the developing roller 31 with almost no remaining developer is opposed to the photoconductor 15.
Stop the rotation of.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
The present invention relates to a color electrophotographic apparatus capable of high-speed printing with high printing quality suitable for a copier, a laser fax, and a composite device thereof.

[0002]

2. Description of the Related Art In recent years, demand for color printing technology has increased,
Further, high quality printing is required. Various types of color electrophotographic apparatuses capable of performing color printing have been proposed and put to practical use. As a typical example, there is one that has a plurality of developing tanks having developers of different colors from each other, and further performs multicolor printing by a two-component developing method in which a developer for each developing tank is configured by a two-component developer. is there. In this case, the developing process is performed for each of the selected developing tanks, and the other developing tanks do not mix colors with the selected developing tanks.

As a method for avoiding the color mixture, a method of mechanically retracting the developing tank itself to prevent the developing tank from coming into contact with the photosensitive member, and a method of stopping the rotation of the developing roller without moving the developing tank itself are considered. . However, in a method in which the developing tank itself is mechanically retracted so as not to come into contact with the photoconductor, the carrier may adhere to the photoconductor due to vibration during the movement of the developing tank. Further, in the method of stopping the rotation of the developing roller, the carrier rises due to the vibration when the rotation of the developing roller is stopped.

When the carrier sticks to the photoreceptor and rises, it causes contamination in the apparatus, not only damages the fixing roller and the like, but also adheres to the developed portion of the photoreceptor. In addition, image loss may occur, causing image quality degradation.

In order to solve this problem, for example, Japanese Unexamined Patent Publication No.
The apparatus disclosed in Japanese Patent Application Laid-Open No. 1-250665 solves the above problem by stopping the driving of the developing roller during non-development and applying a bias voltage to the developing roller to remove a part of the developer on the surface of the developing roller. Trying to solve.

[0006]

However, in the apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-250665,
Even if the rotation of the developing roller is stopped, the developer is in contact with the photoconductor, so even if the bias voltage is adjusted, the carrier rises from the developer in contact with the photoconductor to a considerable extent.

Further, in the color electrophotographic apparatus, there is a demand for downsizing of the apparatus and higher speed of printing, and it is necessary to rotate a developing roller at a high speed in order to cope with the demand. In particular, in an electrophotographic apparatus of a reversal developing system, rising of a carrier has a great effect on image quality deterioration.

FIG. 10 shows the relationship between the photosensitive member surface potential and the developing bias voltage applied to the developing roller in the electrophotographic apparatus of the reversal developing system. In this apparatus, toner fogging, in which toner is originally attached to a white background during development, and carrier rising, in which the carrier adheres to the photoconductor, are opposite phenomena. Therefore, the developing bias voltage is optimized. That is, the outer peripheral surface of the photoreceptor is charged to the reference potential V0 and irradiated with a laser beam or the like to obtain the light portion potential VL.

In actual image formation, in order to prevent toner fogging, a developing bias voltage VB which is a potential between V0 and VL is applied to the developing roller, and a developing contrast (VB
-VL) to form a toner image to make it a visible image. However, when the development contrast (VB-VL) is small, that is, when (V0-VB) is large, carrier rising easily occurs. This is because the developer carrier on the developing roller is easily attracted electrostatically by the surface charge of the photoconductor.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and controls the developing operation so as not to contaminate the periphery of the developing tank, thereby enabling high-speed printing with high printing quality. An object is to provide a color electrophotographic apparatus.

[0011]

In order to solve the above-mentioned problems, a color electrophotographic apparatus according to claim 1 of the present invention is provided.
In a color electrophotographic apparatus having an ear cutting member in each color developing tank, after the end of development of a printing area in each color developing tank, an ear cutting control means for closing the ear cutting member so as to be in contact with a photoconductor, A bias power source for applying a developing bias voltage to a developing roller of each of the color developing tanks; and a bias control unit for changing a voltage of the bias power source after development of a printing area is completed in each of the color developing tanks. The configuration has

According to a second aspect of the present invention, in the color electrophotographic apparatus according to the first aspect of the present invention, the bias control means increases a developing contrast in a reversal developing method. It is characterized in that the developing bias voltage is changed.

According to a third aspect of the present invention, in the color electrophotographic apparatus according to the first aspect, the bias power source is configured by using a power source for charging a photosensitive member. It is characterized by having.

According to the above configuration, in the color electrophotographic apparatus according to the first aspect of the present invention, after the development of the printing area is completed in each color developing tank, the spike cutting member is closed so as to be in contact with the photosensitive member, and a bias power supply is provided. , The flow of the developer after the completion of the development of the print area can be suppressed, and the amount of carrier rise from the developer or the amount of toner fogging can be controlled.

In the color electrophotographic apparatus according to the second aspect of the present invention, since the developing bias voltage is changed so as to increase the developing contrast in the reversal developing method, it is possible to prevent the carrier from rising from the developer.

In the color electrophotographic apparatus according to the third aspect of the present invention, since the bias power supply is configured to use the power supply for charging the photosensitive member together, it is possible to prevent a delay in switching timing of the developing bias power supply and to further improve the timing. It is possible to reliably prevent the carrier from rising from the developer.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a color electrophotographic apparatus according to an embodiment of the present invention. The color electrophotographic apparatus according to the present embodiment includes a paper feeding unit 1 for stocking and supplying a transfer paper on which an image is formed with toner, a developing unit 2 for forming a toner image, and a transfer for transferring the toner image to the transfer paper. And a fixing unit 4 for fusing and fixing the toner image transferred to the transfer paper.

The paper feeding section 1 is detachably disposed at the lowermost stage of the main body, and is provided on the front side of the main body with a paper feeding cassette 5 for stocking the transfer paper and supplying it to the transfer section 3. A manual supply unit 6 for manually supplying the sheets one by one is provided. Further, a pickup roller 7 for sending out the transfer sheets one by one from the uppermost portion of the paper feed cassette 5 and a P for conveying the transfer sheet sent from the pickup roller 7
An F roller 8; a manual roller 9 for conveying the transfer paper from the manual feed unit 6; a PF roller 8 and a manual roller 9
And a pre-curl roller 10 for curling the transfer paper conveyed by the printer. The transfer paper supplied from the manual paper feed unit 6 is also conveyed to the pre-curl roller 10 by the manual feed roller 9.

The developing section 2 is provided with an image carrier drum 15 which is a photosensitive member.
It is made of a grounded conductive aluminum tube, and an OPC (Organic Photoconductor) film or selenium is formed on the surface thereof. Around the image carrier drum 15, developing units 16, 17, 18, and 19 containing yellow, magenta, cyan, and black color toners are radially arranged. A charger 20 for charging the surface of the image carrier drum 15; a cleaning blade 21 for scraping and removing residual toner on the surface of the image carrier drum 15
Is installed. Then, a toner image is formed on the surface of the image carrier drum 15 for each color toner.

The transfer section 3 is provided with a transfer drum 11 which is in pressure contact with the image carrier drum 15. Around the transfer drum 11, a ground roller 12 serving as a grounded electrode, a guide 13 for guiding the transfer paper so as not to fall off the transfer drum 11, and a peeling for forcibly peeling the transfer paper attracted to the transfer drum 11 Claws 14 and the like are arranged.
The peeling claw 14 is detachably attached to the surface of the transfer drum 11.

The image carrier drum 15 repeats charging, exposure, development, and transfer for each color by the above-mentioned sheet feeding unit 1, developing unit 2, and transfer unit 3. That is, in the case of color printing, a single color toner image is transferred onto the transfer paper every time the transfer drum 11 makes one rotation with respect to the transfer paper electrostatically attracted to the transfer drum 11, and one color image is formed at a maximum of four rotations. obtain.

Next, a fixing roller 23 for fusing the toner image at a predetermined temperature and pressure to fix the toner image on the transfer paper is provided on the fixing unit 4.
And a fixing guide 22 that guides the transfer paper separated from the transfer drum 11 by the separation claw 14 to the fixing roller 23 after the transfer of the toner image. A discharge roller 24 is provided downstream of the transfer of the transfer paper by the fixing unit 4, and discharges the transfer paper after the fixing onto the discharge tray 25 from the apparatus main body.

Next, the operation of the color electrophotographic apparatus having the above configuration will be described. The image carrier drum 15 is a motor (not shown)
Is rotated in the direction of arrow A by the driving of the outer peripheral photoconductor layer at the charging position by the charger 20 at a predetermined potential (for example, V0
= Near -700 V), the surface potential of the image carrier drum 15 is reduced by laser exposure of a laser optical unit (not shown) (for example, near VL = -50 V), and an electrostatic latent image is formed in the image forming area. An image is formed. This electrostatic latent image is
At the developing position, a toner having a negative charge is supplied by a developing roller of a developing device to form a toner image and visualize the toner image. In normal visualization, a developing bias remote signal is input to a developing bias power supply, and a predetermined developing bias voltage (for example, near VB = −500 V) is output.

FIG. 2 is a detailed structural view of the developing device.
(A) shows a state in which the spike cutting member 32 is not in contact with the developing roller 31, and (b) shows a state in which the spike cutting member 32 is in contact with the developing roller 31. Hot standing cutting member 3
The direction in which the developing roller 31 is closed and comes into contact with the developing roller 31 is a direction at which the developing roller 31 comes into contact with the developing roller 31 at an acute angle to the rotation direction B. This is because, if the contact is made in the opposite direction, there is a possibility that the developer may get on the ear cutting member 32. The material used for the ear-cutting member 32 may be an elastic material such as urethane rubber or a metal such as aluminum, and has a shape that can block the developer.

FIGS. 3A and 3B are detailed structural views of a developing device according to another embodiment, wherein FIG. 3A shows a state in which the spike cutting member 32a is not in contact with the developing roller 31, and FIG. The state where the cutting member 32a is in contact with the developing roller 31 is shown.
The developing device of FIG. 2 is the same as the developing device of FIG. In the developing device shown in FIGS. 2 and 3, both the cutting-edge cutting members 32 and 32a have a shape capable of blocking the developer.

FIG. 4 shows the structure of the developing bias power supply 43 and the control device 41 for controlling the same. Hot standing cutting member 3
Shortly before or at the start of scraping of the developer on the developing roller 31 by the closing of the developing roller 2, or at the same time, a developing bias remote signal for changing the developing contrast is input from the controller 41 to the developing bias power supply 43. Then, a developing bias voltage of −600 V is applied to the developing roller 31 from the developing bias power supply 43, and the developing contrast is expanded. In order to change the developing bias voltage, a D / A converter 42 is provided between the control device 41 and the developing bias power supply 43. An output voltage control signal is output from the control device 41 to the D / A converter 42, and the output of the power supply 43 is changed based on the control signal. As a result, the carrier of the developer, which is generated by stopping the rotation of the developing roller 31, is prevented.

FIG. 5 shows a configuration of a developing bias power supply 43 and a control device 41a according to another embodiment. In the present embodiment, the developing bias voltage is supplied by using a charging power supply 44 that supplies a voltage to the charger 20. By using two developing bias power supplies, it is possible to prevent a delay in the timing of switching the developing bias voltage and more reliably prevent a carrier rise that occurs when each developing device narrows the developing contrast.

Next, the drive timing of the rising cutting member 32 and the developing bias voltage in one developing device will be described with reference to the operation explanatory diagram of the rising cutting member 32 in FIG.

First, in the printing area, as shown in FIG. 6A, the developer is uniformly attached on the developing roller 31, and the developing process is performed. After passing the printing area, the spike cutting member 32 starts closing and comes into contact with the developing roller 31 under the control of the control unit (not shown). Thereafter, as shown in FIG. 6B, the developer portion cut by the spike cutting member 32 comes into contact with the photoconductor 15. This state is not a normal ear, but an unstable ear that is magnetically and mechanically weak. Therefore, the carrier easily rises due to centrifugal force or mechanical force. For this reason, the developer portion cut by the spike cutting member 32 is
It is necessary to widen the development contrast during non-development before contacting No. 5, that is, to change the development bias voltage.

After a further elapse of time, as shown in FIG. 6 (c), the developing roller 31 having almost no developer is left.
Becomes opposed to the photoconductor 15, and the rotation of the developing roller 31 is stopped in this state. In this state, the developer does not come into contact with the surface of the photoreceptor 15, so that the carrier does not rise in principle.

Before the spike cutting member 32 is closed by the above operation, it is necessary to end the printing area without fail. If the print area is slightly touched, development failure occurs at the leading or trailing end of the print area. For this reason, the control unit:
Control is performed so that the spike cutting member 32 starts closing after the printing area has passed.

The timing for stopping the rotation of the developing roller 31 is as follows:
It is necessary to keep it after the developer portion cut in step 2 passes through the photoconductor. Actually, the ear standing cut member 3
It takes only a few milliseconds for the developing roller 31 to rotate from 2 to the surface of the photoreceptor, but if the timing is too short, the carrier rises.

Next, the relationship between the above-described operations in the developing tanks 1, 2, 3, and 4 of the respective colors (corresponding to the developing units 16, 17, 18, and 19 in FIG. 1, respectively) will be described with reference to the timing chart of FIG. I do. FIG. 7A shows the timing of rotation and stop of the developing roller in each developing tank. The developing roller of one developing tank stops, and after a predetermined time, the developing roller of the next developing tank rotates.

FIG. 7B shows the length of the developer on the developing roller in each developing tank. The portion a where the developer normally adheres to the developing roller in the developing tank 1 corresponds to a state where the developer in the printing area shown in FIG. 6A is uniformly adhered to the developing roller. Further, a portion b where the developer is normally cut from the portion a where the developer is normally adhered is the developer portion cut by the spike cutting member shown in FIG. Corresponds to the contact state. A portion c where the developer hardly adheres to the developing roller corresponds to a state where the portion where the developer hardly remains as shown in FIG.

FIG. 7C shows the timing at which the spike cutting member opens and closes and separates from or contacts the developing roller.

FIG. 7D shows the timing of changing the developing bias voltage when two developing bias power supplies are used, and V1, V2, V3, and V4 denote the developing bias voltages in each developing tank when the developing is not performed. Is shown. In each developing tank,
After the end of the printing area, the developing bias voltage is increased, that is, set to V1, V2, V3, and V4, so that the developing contrast is expanded. After a predetermined time, the developing bias voltage is returned to the original value. The timing of changing the developing bias voltage may be synchronized with the opening / closing timing of the ear cutting member.

It is desirable to use individual developing bias power supplies for each developing tank. However, since the number of developing bias power supplies increases, one developing bias power supply is used.
The contrast at the time of development (the state where the developing roller is rotating) and the contrast at the time of non-developing (the state where the developing roller is not rotating) may be switched. In this case, switching control of the developing bias voltage is required. For example, at the time point d after the development in the developing tank 1 is completed in FIG. 7D and before the developing tank 2 starts the development, the developing bias voltage is returned to the original state, and the developing contrast is set to the contrast at the time of development. Need to be kept.

FIG. 8 shows a timing chart of another embodiment, and is different from the timing chart of FIG.
Only the opening / closing timing of the spike cutting member shown in FIG. 8C is different. That is, the spike cutting member is kept closed even after the development of one developing tank is completed, and the spike cutting member is opened before the development of the next cycle is started after the development of each developing tank is completed. Even when the developing roller is not in contact, no problem occurs because the developing roller is not rotating.
The timings of FIGS. 8A, 8B, and 8D are shown in FIG.
This is the same as each timing of (a), (b) and (d).

Next, the development contrast at the time of non-development after the ear-cutting member is closed is the same in the developing tank of each color.
Alternatively, the development contrast may be changed according to each developer. That is, when the developing bias voltage at the time of development of each color developing tank is set to −500 V, the developing bias voltage at the end of development may be set to −600 V in all the developing tanks. An optimal value may be set.

FIG. 9 shows an example of the relationship between the developing bias voltage of each color developing tank during non-development, carrier rise, and toner fog. In the black developing tank, V1 = −580 V to −600 V, the center value is −590 V. In the cyan developing tank, V2 = −600 V to −620 V, the center value is −6 V.
In a magenta developing tank, the optimum value is V3 = −600 V to −640 V, and the central value is −620 V. In a yellow developing tank, V4 = −600 V to −620 V, and the central value is −610 V. . This is because the main colorants of the black toner and the color toner are carbon black and pigment, respectively, which are different from each other.

As described above, in the color electrophotographic apparatus of the present invention, when each color developing tank has completed development of the printing area, the flow of the developer is suppressed using After changing the contrast, the rotation of the developing roller is stopped. As a result, it is possible to prevent carrier rising and toner fogging caused by electrostatic attraction of the developer to the photoconductor. In particular, in an electrophotographic apparatus of the reversal development system, the rising of the carrier has a great effect on the deterioration of the image quality, so that the development contrast is expanded when the image is not developed.

[0042]

As described above, in the color electrophotographic apparatus according to the first aspect of the present invention, after the development of the printing area is completed in each color developing tank, the spike cutting member is closed so as to be in contact with the photoreceptor. Since the voltage of the bias power supply is changed, the flow of the developer after the development of the printing area is completed is suppressed, and even if the developing roll is rotated at high speed to support high-speed printing, the amount of carrier rising from the developer or toner fogging You can control the amount.

In the color electrophotographic apparatus according to the second aspect of the present invention, since the developing bias voltage is changed so as to widen the developing contrast in the reversal developing method, carrier rise from the developer can be prevented, and high-speed printing can be performed. And high printing quality.

In the color electrophotographic apparatus according to the third aspect of the present invention, since the bias power supply is configured in combination with the power supply for charging the photosensitive member, the switching timing of the developing bias power supply can be prevented from being delayed, and moreover. It is possible to reliably prevent the carrier from rising from the developer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a color electrophotographic apparatus according to an embodiment of the present invention.

FIGS. 2A and 2B are detailed configuration diagrams of a developing device, wherein FIG. 2A shows a state in which an ear-cutting member is not in contact with a developing roller;
FIG. 4 is a diagram illustrating a state in which the ear-cutting member is in contact with the developing roller.

3A and 3B are detailed configuration diagrams of a developing device according to another embodiment, in which FIG. 3A shows a state in which an ear cutting member is not in contact with a developing roller, and FIG. It is a figure showing the state where it contacted.

FIG. 4 is a diagram illustrating a configuration of a developing bias power supply and a control device.

FIG. 5 is a diagram illustrating a configuration of a developing bias power supply and a control device according to another embodiment.

FIG. 6 is an explanatory view of the operation of the ear standing cutting member,
(A) is a state in which the developer is uniformly attached to the developing roller,
FIG. 2B is a diagram illustrating a state in which the developer portion cut by the spike cutting member is in contact with the photosensitive member, and FIG. 2C is a diagram illustrating a state in which the portion of the developing roller where the developer hardly remains is opposed to the photosensitive member. .

FIGS. 7A and 7B are timing charts showing the relationship between the operations in the developing tanks 1, 2, 3, and 4, wherein FIG. 7A shows the operation timing of the developing roller, and FIG. (C) is a chart showing the timing at which the spike cutting member opens and closes, and (d) is a chart showing the timing at which the developing bias voltage is changed.

FIGS. 8A and 8B are timing charts showing the operation of another embodiment in the developing tanks 1, 2, 3, and 4, wherein FIG. 8A shows the operation timing of the developing roller, and FIG. 7C is a chart showing the timing of opening and closing of the spike-cutting member, and FIG. 7D is a chart showing the timing of changing the developing bias voltage.

FIG. 9 shows a developing bias voltage of each color developing tank during non-development,
FIG. 3 is a diagram illustrating a relationship between carrier rise and toner fog.

FIG. 10 is a diagram illustrating a relationship between a photoconductor surface potential and a developing bias voltage in a reversal developing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper feed part 2 Developing part 3 Transfer part 4 Fixing part 5 Paper feed cassette 6 Manual feed part 7 Pickup roller 8 PF roller 9 Manual feed roller 10 Precurl roller 11 Transfer drum 12 Ground roller 13 Guide 14 Peeling claw 15 Image carrier drum (Photoconductor) 16, 17, 18, 19 Developing device 20 Charging device 21 Cleaning blade 22 Fixing guide 23 Fixing roller 24 Discharge roller 25 Discharge tray 31 Developing roller 32, 32a Spike cut member 41 Control device 42 D / A converter 43 Power supply for developing bias 44 Power supply for charging

Claims (3)

[Claims] 1. A color electrophotographic apparatus having an ear-cutting member in each color developing tank, wherein the ear-cutting member is closed so as to be in contact with a photoreceptor after development of a printing area in each of the color developing tanks. Cut control means, a bias power supply for applying a developing bias voltage to the developing roller of each color developing tank, and a bias control means for changing the voltage of the bias power supply after the development of the printing area in each color developing tank is completed. A color electrophotographic apparatus. 2. The color electrophotographic apparatus according to claim 1, wherein said bias control means changes a developing bias voltage so as to increase a developing contrast in a reversal developing method. 3. The color electrophotographic apparatus according to claim 1, wherein said bias power source is configured by using a photoconductor charging power source in combination.