JPH0433031B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a color electrophotographic apparatus capable of forming monochrome, multicolor, and natural color images.

[Prior art]

As a method for forming color images, the electrostatic latent image formed on the electrostatic latent image carrier by operations such as charging and exposure in each process is repeated three or four times, and the electrostatic latent image formed on the electrostatic latent image carrier is colored yellow, cyan, etc. A color electrophotographic method is known in which three or four colors are superimposed to obtain a natural-color copy by developing with , magenta, and, if necessary, black developers.

In a conventional color electrophotographic apparatus using such a color electrophotography method, the yellow, cyan, magenta, and optionally Depending on the situation, three or four developing devices each individually containing each type of black developer are arranged, and the electrostatic latent image formed on the photoreceptor drum is exposed to light through a blue filter in the first process. The image is developed by rubbing using a developing roll of a developing device containing yellow developer. At this time, other developing devices containing cyan, magenta, and other developers are retreated from the vicinity of the photoreceptor drum so as not to rub the photoreceptor drum.

Next, the electrostatic latent image formed on the photosensitive drum by exposure through a red filter is developed by sliding with a developing roll of a developing device containing cyan developer. In this second process,
Before the development, the developing device containing the yellow developer developed in the first process is withdrawn from the vicinity of the photoreceptor drum, and the developing device containing the cyan developer is replaced with the photoreceptor drum. are set at regular intervals in the vicinity of .

In the third process, the electrostatic latent image formed on the photosensitive drum by exposure through a green filter is rubbed and developed by a developing roll of a developing device containing magenta developer. During this third process as well, before the development, the developing device containing the cyan developer developed in the second process is evacuated from the vicinity of the photoreceptor drum, and the magenta developer is used instead. A developing device containing the image is set.

Further, when black development is performed as necessary, operations similar to these processes are performed.

A color image is formed by performing the copying process three or four times in this manner and sequentially transferring the monochromatic image developed in each process onto the transfer paper.

As explained above, in the conventional color electrophotographic apparatus, the operation of setting and retracting each developing device in the vicinity of the photoreceptor drum, that is, the developing position, is repeated in each copying process as described above. However, during development, the distance between the photosensitive drum and the developing roll of the developing device must be set to always be a constant distance.

However, as each developing device is repeatedly set or retracted, the distance between the photoreceptor drum and the developing roll may shift, resulting in image distortion and density unevenness.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and it is possible to prevent image distortion and density unevenness in a color electrophotographic apparatus using a plurality of developing devices, and to produce high-quality color. The purpose is to form an image.

[Structure of the invention]

To achieve this objective, the present invention provides a color electrophotographic recording device that forms a multicolor image by repeating a unit copying process two or more times, and a natural color image by repeating a unit copying process three or four times. , a plurality of developing devices each containing two or more color developers are arranged along the outer circumferential surface of an electrostatic latent image carrier rotating at a constant speed, and each developing device is located between a certain distance from the electrostatic latent image carrier. A developing roll facing each other with a radial angle, a developer storage tank containing the developer, an opening for discharging and collecting the developer, and a total length in the axial direction of the sleeve of the developing roll at a position opposite to the opening. The developing roll includes a cylindrical sleeve made of non-magnetic material, and a permanent magnet provided within the sleeve. It has a structure in which a plurality of N poles and S poles are separately magnetized in the direction, and the sleeve and the permanent magnet are relatively rotatable, and during development, the developing roll of the developing device corresponding to the color to be developed is By rotating the sleeve in a certain direction at high speed and rotating the permanent magnet in the same direction at low speed, development is carried out between the electrostatic latent image carrier and the developing roll from inside the developer storage tank through the opening. The upper layer of developer supplied to the area is conveyed from the opening to the stopper, and the lower layer of developer is conveyed from the stopper to the opening, so that the upper layer of developer is applied to the electrostatic latent image carrier. The formed electrostatic latent image is developed by rubbing in the development area between the electrostatic latent image carrier and the developing roll, and the developing device that does not correspond to the color to be developed is in a state where the sleeve of the developing roll is rotated. Then, by lowering or stopping the rotation speed of the permanent magnet, or increasing the rotation speed of the sleeve while keeping the permanent magnet rotation, the developer can be collected into the developer storage tank or remain in the developer storage tank. It is characterized by the following.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 1 is a sectional view showing the structure of a developing device used in the present invention. In the figure, numeral 1 indicates an electrostatic latent image carrier, ie, a photosensitive drum, made of a photosensitive material such as selenium.

A developing roll 2 is installed to face the photosensitive drum 1 at a constant distance, and this developing roll 2 has a cylindrical sleeve 2a made of a non-magnetic material.
and a cylindrical permanent magnet 2b disposed within the sleeve 2a, and the permanent magnet 2b has a structure in which a plurality of N poles and S poles are alternately divided and magnetized in the circumferential direction. Furthermore, the sleeve 2a and the permanent magnet 2b are designed to be able to rotate independently and relative to each other.

3 is a developer storage tank, the developer roll 2 is attached near the bottom of the developer storage tank 3, and a stopper made of a flexible material such as sponge is provided at the bottom of the developer storage tank 3. 4 is provided, and this stopper 4 stops the sleeve 2 of the developing roll 2.
It is in contact with a over its entire axial length.

5 is an opening provided between the developing roll 2 and the developer storage tank 3, and is provided on the opposite side of the stopper 4; 6 is an opening provided between the developer roll 2 and the developer storage tank 3; It is.

In the developing device with such a configuration, when the permanent magnet 2b of the developing roll 2 is rotated in the direction of arrow A, the developer 6 becomes a chain magnetic brush, and the rotation direction of the permanent magnet 2b is rotated along the direction of magnetic flux flow. It rotates on the sleeve 2a in the opposite direction. Therefore, the developer 6 in the developer storage tank 3 is sent in the direction of arrow C and is discharged from the opening 5 to the outside of the developer storage tank 3, and reaches the area where the development roll 2 and the photoreceptor drum 1 face each other, that is, the development area. and is conveyed to the stopper 4 position.

Furthermore, when the sleeve 2a of the developing roll 2 is rotated in the direction of arrow B (the same direction as the permanent magnet 2b), the developer 6 on the sleeve 2a outside the developer storage tank 3 is moved in the same direction as the arrow B. The developer is transported in the D direction, passes through the development area, and is collected into the developer storage tank 3 through the opening 5.

Now, when the electrostatic latent image formed on the photoreceptor drum 1 is developed using the above-mentioned developing device, the permanent magnet 2b is rotated at high speed in the direction of arrow A, and the sleeve 2a is moved in the same direction as the arrow A. When the developer 6 is rotated at a low speed in the direction B, the developer 6 passes through the opening 5 from inside the developer storage tank 3, passes through the development area, and reaches the stopper 4.
The sleeve 2 is conveyed to the position shown in FIG.
The length of the magnetic brush of the developer 6 formed on a is balanced.

Therefore, when we observed the conveyance state of the developer 6 in this balanced state, we found that the lower layer of the layer of developer 6 was conveyed mainly depending on the rotation of the sleeve 2a, and the conveyance direction was in the direction of arrow D. This is the direction in which the developer 6 is collected into the developer storage tank 3 as described above.

On the other hand, the transport of the upper layer mainly depends on the rotation of the permanent magnet 2b, and the transport direction is the direction of arrow C, which is the direction in which the developer 6 is discharged to the outside of the developer storage tank 3.

Further, in the vicinity of the stopper 4, the developer 6 in the upper layer, which was conveyed in the direction of arrow C depending on the rotation of the permanent magnet 2b, moves to the lower layer in a U-turn, and here, depending on the rotation of the sleeve 2a, the developer 6 in the upper layer is transported in the direction of arrow C. It was confirmed that the paper was transported in the D direction.

In this manner, the conveyance state of the developer 6 becomes balanced, and the electrostatic latent image formed on the photoreceptor drum 1 is developed by rubbing.

Even if the developer 6 adheres to the photoreceptor drum 1 due to development and the developer 6 in the development area is consumed, the developer 6 is sequentially supplied from the developer storage tank 3, and the number of revolutions of the sleeve 2a and the number of revolutions of the sleeve 2a are always maintained. The height of the magnetic brush is balanced by the number of magnetic poles and the number of rotations of the permanent magnet 2b.

During non-development, the rotation of the sleeve 2a of the developing roll 2 can be kept as it is and the rotation speed of the permanent magnet 2b can be lowered or stopped, or the rotation of the permanent magnet 2b can be kept as it is and the rotation speed of the sleeve 2a can be increased. , developer 6 between the opening 5 and the stopper 4
is collected into the developer storage tank 3. Therefore, the developer 6 does not rub against the photoreceptor drum 1, and no development is performed.

FIG. 2 is a schematic side view showing an embodiment of a color electrophotographic apparatus according to the present invention. In the figure, reference numeral 1 denotes a photosensitive drum, which rotates at a constant speed in the direction of the arrow shown in the figure. 7 is a corona charger, 8 is an exposure device, 9 is a color separation filter device, 1
0 to 13 are developing devices, 14 is a transfer sheet, 15 is a transfer drum, 16 is a corona transfer charger, and 17 is a static eliminating and cleaning device, each of which is arranged at a predetermined position along the outer peripheral surface of the photosensitive drum 1. has been done.

Here, the developing devices 10 to 13 each have the configuration explained in FIG. 1, and the developing device 10 stores yellow developer, 11 stores cyan developer, 12 stores magenta developer, and 13 stores black developer. . These developing devices 10 to 13 are arranged in order along the outer peripheral surface of the photoreceptor drum 1, and each developing roller 2
is opposed to the photoreceptor drum 1 at a constant distance.

FIG. 3 is an explanatory diagram of the drive mechanism of the developing devices 10 to 13 described above, and 18 to 21 are each of the developing devices 10.
- 13 are gears provided at one end of the permanent magnet 2b, 22-25 are idle gears meshing with the gears 18-21, 26-29 are electromagnetic clutches, 30
-33 are drive gears connected to idle gears 22-25 via electromagnetic clutches 26-29, respectively.

Next, the operation of the color electrophotographic apparatus having the above-described configuration will be explained.

First, a preliminary operation will be described. The photosensitive drum 1 is rotated at a constant speed in the direction of the arrow by a motor (not shown) via a connecting member (also not shown). Further, the sleeve 2a of each developing roll 2 in the developing devices 10 to 13 is also rotated in synchronization with the photoreceptor drum 1 via a transmission member (not shown) as explained in FIG. 3
0 to 33 rotate in synchronization with the photosensitive drum 1 via a transmission member (not shown).

At this time, the electromagnetic clutches 26 to 29 do not operate, and each developing roll 2 in the developing devices 10 to 13
The permanent magnet 2b does not rotate. Therefore, the developing device 1
Developers 6 0 to 13 are each stored in the developer storage tank 3 and are not discharged to the outside, so that the photoreceptor drum 1 is not rubbed by the developer 6.

After the above preliminary operations are performed, the next printing operation begins.

First, as a first copying process, the blue filter of the color separation filter device 9 is set. In synchronization with this, the electromagnetic clutch 26 connected to the permanent magnet 2b of the developing device 10 equipped with the yellow developer 6 operates, and the rotation of the drive gear 30 is transmitted to the idle gear 22.
A permanent magnet 2b is integrated with the gear 18 meshing with the permanent magnet 2b.
rotates. As a result, the developer 6 is discharged from the developer storage tank 3 as shown in FIG. 6 rubs the photosensitive drum 1.

In this state, the surface of the photoreceptor drum 1 rotating at a constant speed is uniformly charged by the corona charger 7, and is then passed through the blue filter of the color separation filter device 9 to the photoreceptor drum 1 by the exposure device 8. An electrostatic latent image is formed, and this electrostatic latent image is further rubbed by the magnetic brush-shaped yellow developer 6 in the development area.

On the other hand, the transfer paper 14 is wound around the outer peripheral surface of the transfer drum 15 and set, and when the electrostatic latent image developed with the yellow developer 6 as described above moves to the position of the transfer drum 15, The yellow developer 6 on the photoreceptor drum 1 is sequentially transferred onto the transfer paper 14 by the corona transfer charger 16 disposed within the transfer drum 15, and after the transfer, the photoreceptor drum 1 is charged by a static eliminating and cleaning device. The residual developer is cleaned and static electricity is removed.

In this way, the first copying process ends.

Next, in the second copying process, the red filter of the color separation filter device 9 is set. In synchronization with this, the operation of the electromagnetic clutch 26 connected to the permanent magnet 2b of the developing device 10 equipped with the yellow developer 6 stops, and the rotation of the drive gear 30 is no longer transmitted to the idle gear 22. The rotation of magnet 2b is stopped. Therefore, the yellow developer 6 that was rubbing against the photosensitive drum 1 in the first copying process is transferred to the developer storage tank 3 of the developing device 10.
will be collected within.

At the same time, the electromagnetic clutch 27 connected to the permanent magnet 2b of the developing device 11 equipped with the cyan developer 6 operates, and the drive gear 31
The rotation of the permanent magnet 2b is transmitted to the idle gear 23, and the permanent magnet 2b rotates together with the gear 19 meshing with the idle gear 23. Therefore, the cyan developer 6 is discharged from the developer storage tank 3 and transferred to the sleeve 2.
A magnetic brush is formed on the surface a, and the photosensitive drum 1 is rubbed by this cyan developer 6.

In this state, a process similar to the first copying process is performed, and the cyan developer 6 is transferred onto the transfer paper 14 onto which the yellow developer 6 was transferred in the first copying process.

Similarly, in the third copying process, the magenta developer 6 is transferred onto the transfer paper 14, and if necessary, in the fourth process, the black developer 6 is transferred onto the transfer paper 14. The developer 6 is finally fixed on the transfer paper 14 by a fixing device (not shown) to form a color image.

Note that although this embodiment is a case where a natural color image is formed by repeating the unit copying process three or four times, it is possible to form a multicolor image by repeating the unit copying process two or more times, and it is also possible to form a multicolor image by repeating the unit copying process once or more. It is also possible to form monochromatic images in the copying process.

Further, in the above-described embodiment, by stopping the rotation of the permanent magnet of the developing device that does not perform development among the plurality of developing devices, the developer of each of these developing devices is collected into the developer storage tank. However, as explained in Figure 1, the developer can be collected by lowering the rotation speed without stopping the rotation of the permanent magnet, or by increasing the rotation speed of the sleeve without stopping the rotation of the permanent magnet. No matter which method is used, only the developer of a desired color can be rubbed onto the photoreceptor drum.

〔Effect of the invention〕

As explained above, the present invention rotates the sleeve of the developing roll of the developing device corresponding to the color to be developed out of a plurality of developing devices at high speed in a certain direction, and rotates the permanent magnet in the same direction at low speed. By rotating, the upper layer of the developer supplied from the developer storage tank through the opening to the development area between the electrostatic latent image carrier and the development roll is conveyed from the opening to the stopper, and the developer is developed. The lower layer of developer is conveyed from the stopper to the opening, and the electrostatic latent image formed on the electrostatic latent image carrier by the upper layer of developer is transferred between the electrostatic latent image carrier and the developing roll. For developing devices that carry out frictional development in the developing area and that do not correspond to the color to be developed, lower or stop the rotation speed of the permanent magnet while the sleeve of the developing roll is rotating.
Alternatively, the developer may be collected or retained in the developer storage tank by increasing the number of rotations of the sleeve while keeping the rotation of the permanent magnet unchanged.

Therefore, unlike conventional methods, there is no need to move the developing device to set and retreat the electrostatic latent image carrier, and the distance between the developing roll of each developing device and the electrostatic latent image carrier can always be kept constant. At the same time, the rotation of the sleeve and permanent magnet and the action of the stopper make it possible to easily and reliably always make the layer of developer conveyed to the developing area uniform on each developing roll, which is different from that seen in conventional devices. It is possible to prevent such image disturbances and density unevenness from occurring, and it is possible to obtain the effect that high-quality color images can always be formed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a single developing device used in the present invention, FIG. 2 is a schematic side view showing an embodiment of a color electrophotographic apparatus according to the present invention, and FIG.
The figure is an explanatory view showing the drive mechanism of the developing device used in the present invention. 1... Electrostatic latent image carrier (photosensitive drum), 2...
Developing roll, 2a...Sleeve, 2b...Permanent magnet, 3...Developer storage tank, 4...Stopper, 5...
...opening, 6...developer, 7...corona charger,
8... Exposure device, 9... Color separation filter device, 1
0 to 13...Developing device, 14...Transfer paper, 15
...Transfer drum, 16...Corona transfer charger, 1
8-21... Gear, 22-25... Idle gear, 26-29... Electromagnetic clutch, 30-33...
...Drive gear.

Claims (1)

[Claims] 1. A multicolor image is produced by repeating the unit copying process two or more times, and a multicolor image is produced by repeating the unit copying process three or four times.
A color electrophotographic recording device that forms a natural color image by repeating the process several times, in which a plurality of developing devices containing two or more color developers are arranged along the outer peripheral surface of an electrostatic latent image carrier that rotates at a constant speed. Each developing device includes a developing roll facing the electrostatic latent image carrier with a certain distance, a developer storage tank containing the developer, and an opening for discharging and collecting the developer. , a stopper that abuts over the entire axial length of the sleeve of the developing roll at a position opposite to the opening; This permanent magnet has a structure in which a plurality of N poles and S poles are separately magnetized in the circumferential direction, and the sleeve and permanent magnet are relatively rotatable. At the time of development, the sleeve of the developing roll of the developing device corresponding to the color to be developed is rotated at high speed in a certain direction, and the permanent magnet is rotated at low speed in the same direction. The upper layer of the developer supplied from the opening to the developing region between the electrostatic latent image carrier and the developing roll is conveyed from the opening to the stopper, and the lower layer of the developer is conveyed from the stopper to the opening. While being conveyed, the electrostatic latent image formed on the electrostatic latent image carrier by the upper layer developer is rubbed and developed in a development area between the electrostatic latent image carrier and the developing roll. For developing devices that do not correspond to the desired color, the rotation speed of the permanent magnet may be lowered or stopped while the sleeve of the developing roll is rotating, or the rotation speed of the sleeve may be increased while the permanent magnet continues to rotate. A color electrophotographic recording apparatus characterized in that the developer is collected into a developer storage tank or remains in the developer storage tank.