JP2000352868A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain density difference between respectively adjoining images, in the image forming device. SOLUTION: This image forming device is provided with a belt electrophotographic photoreceptor 1 in a closed loop shape being peripherally rotated by plural rollers 2a and 2b that the electrostatic latent image is formed thereon, the developing roller 7b that the number of rotation at one round of developing operation is made to be an integer, and forming the toner image 7c by feeding the toner 7a on the electrostatic latent image, and moreover the transfer counter roller 8 arranged inner peripheral position of the belt electrophotographic photoreceptor 1 being movably along the recording medium 9, for transferring the toner image 7c on the recording medium 9 by pressing the belt electrophotographic photoreceptor 1 on the recording medium 9 that the toner image 7c is formed thereon and the peripheral rotation is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a toner image by bringing a developing roller into contact with an electrostatic latent image formed on a belt-shaped electrophotographic photosensitive member, and transferring the toner image to a recording medium. The present invention relates to an image forming apparatus that forms an image.

[0002]

2. Description of the Related Art In recent years, in a toner type image forming apparatus capable of forming a clear image with excellent resolution, as represented by a laser printer, particularly, a developing roller is brought into direct contact with a belt-shaped electrophotographic photosensitive member. 2. Description of the Related Art A contact development type image forming apparatus that performs development has been widely used. Among such image forming apparatuses, an orthogonal transfer type image forming apparatus in which a toner image carrier is moved in a direction orthogonal to a conveying direction of a recording medium and a toner image is transferred step by step in small steps is known. Due to its configuration, it is very suitable for promoting miniaturization of products.

A conventional image forming apparatus for transferring a toner image formed on a belt-shaped electrophotographic photosensitive member to a recording medium by continuous pressing of a transfer plate by a transfer opposing roller will be described below.

[0004] The belt-shaped electrophotographic photosensitive member is supported by a driving roller and a displacement roller, and is rotated in a predetermined direction. The height of the displacement roller is higher than the height of the drive roller, and the belt-shaped electrophotographic photosensitive member has a predetermined inclination angle. Around the belt-shaped electrophotographic photosensitive member, a cleaning device, a static eliminator, a charging device, and a developing device are sequentially arranged. An exposure unit (LSU) for forming an electrostatic latent image on the belt-shaped electrophotographic photosensitive member is disposed above the belt-shaped electrophotographic photosensitive member.

The recording medium is supported on a transfer plate, and is conveyed in a direction orthogonal to the direction in which the belt-shaped electrophotographic photosensitive member rotates. Further, a transfer opposing roller that moves along the recording medium is provided near the drive roller in the belt-shaped electrophotographic photosensitive member.

In such an image forming apparatus of the orthogonal transfer system, when an image forming operation is instructed, the belt-shaped electrophotographic photosensitive member starts rotating around and is uniformly charged by the charger. Then, the potential of the portion irradiated with the laser beam from the exposure device changes, and an electrostatic latent image is formed.

When the developing roller of the developing device comes into contact with the belt-like electrophotographic photosensitive member, the electrostatic latent image is developed by the toner attached to the surface of the developing roller, and a toner image appears.

When the formation of the toner image is completed, the rotation of the belt-shaped electrophotographic photosensitive member and the conveyance of the recording medium are temporarily stopped, and the belt-shaped electrophotographic photosensitive member is rubbed on the recording medium by the movement of the transfer opposing roller. Displace. As a result, the toner image is transferred to the recording medium.

When the transfer of the toner image is completed, the recording medium is fed intermittently by the width of the developing area. Further, the belt-shaped electrophotographic photosensitive member starts rotating again, is cleaned by the cleaning device, and the electric charge is eliminated by the static eliminator.

[0010]

FIG. 4 is an explanatory view showing an output image of image data of uniform density recorded by a conventional image forming apparatus.

FIG. 4 shows an output image recorded by repeating image formation and transfer operations three times on one recording medium. Accordingly, one image is formed such that three images are adjacent to each other in the feed direction of the recording medium.

As described above, the toner layer is formed on the surface of the developing roller in the developing device, whereby the toner is supplied to the belt-shaped electrophotographic photosensitive member. At this time, the thickness of the toner layer formed on the developing roller may be uneven due to the surface condition of the developing roller, the fluctuation of the outer diameter, or the like. Then, the amount of toner supplied to the belt-shaped electrophotographic photosensitive member varies, and a density difference occurs in the output image in the rotation cycle of the developing roller.

As a result, since the three images are not images formed continuously, there arises a problem that the density difference between the three images is conspicuous as shown in FIG. That is, in FIG. 4, since the densities of the mutually adjacent images are different, there is a problem that the densities change rapidly and the boundaries of the images can be clearly seen.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of suppressing a density difference between mutually adjacent images.

[0015]

In order to solve this problem, an image forming apparatus according to the present invention comprises a closed-loop belt-shaped electrophotographic photosensitive member on which an electrostatic latent image is formed by being rotated by a plurality of rollers. And a developing roller for supplying a toner to the electrostatic latent image to form a toner image, and a developing roller for supplying a toner to the electrostatic latent image and disposed at an inner peripheral position of the belt-shaped electrophotographic photosensitive member. A transfer opposing roller that is provided movably along the recording medium, presses the belt-shaped electrophotographic photosensitive member on which the toner image is formed and stops rotating around the recording medium, and transfers the toner image to the recording medium. It is configured.

Accordingly, the position angle when the developing roller is stationary is always the same, so that the developing roller always starts developing the electrostatic latent image from the same position, and the image between adjacent images is It is possible to suppress the density difference.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a closed-loop belt-shaped electrophotographic photosensitive member on which an electrostatic latent image is formed by being rotated by a plurality of rollers, and a single development operation. The number of rotations during the operation is an integer, and a developing roller that supplies toner to the electrostatic latent image to form a toner image is disposed at an inner peripheral position of the belt-shaped electrophotographic photosensitive member and along a recording medium. An image forming apparatus having a transfer opposing roller that is provided movably, presses the belt-shaped electrophotographic photosensitive member on which the toner image has been formed and has stopped rotating around the recording medium, and transfers the toner image to the recording medium, Since the developing roller always starts developing the electrostatic latent image from the same position, it has an effect that it is possible to suppress the density difference between mutually adjacent images.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is an explanatory view showing the structure of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a schematic view showing a transfer mechanism of the image forming apparatus shown in FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing an output image from the device.

As shown in FIGS. 1 and 2, a belt-shaped electrophotographic photosensitive member 1, which is a closed-loop toner image carrier whose surface is coated with a layer of an organic photoconductive material, comprises a driving roller 2a and a displacement roller. 2b, and is adapted to rotate in the direction of arrow A. By setting the height of the displacement roller 2b for applying a constant tension to the belt-shaped electrophotographic photosensitive member 1 higher than the height of the driving roller 2a for driving the belt-shaped electrophotographic photosensitive member 1, the belt-shaped electrophotographic photosensitive member 1 is given a predetermined inclination angle.

Around the belt-shaped electrophotographic photosensitive member 1, a cleaning device 3, a static eliminator 4,
A charging device 5 and a developing device 7 having a developing roller 7b are arranged in order, and a toner 7a is stored in the developing device 7. An exposing unit (LSU) 6 that irradiates a laser beam 6 a to form an electrostatic latent image on the belt-shaped electrophotographic photosensitive member 1 is disposed above the belt-shaped electrophotographic photosensitive member 1. Here, the developing roller 7b in one developing operation
Is an integer, so that the position angle when the developing roller 7b stops is always the same.

A recording medium 9 such as paper is provided on a transfer plate 10.
The belt-shaped electrophotographic photosensitive member 1 is transported in a direction orthogonal to the direction in which the belt-shaped electrophotographic photosensitive member 1 rotates.

Further, in the vicinity of the driving roller 2a in the belt-shaped electrophotographic photosensitive member 1, a transfer opposing roller 8 which moves along the recording medium 9 is provided.

Next, the operation of the image forming apparatus having the above configuration will be described.

When an image forming operation is instructed, the drive roller 2a and the displacement roller 2b rotate, and the belt-shaped electrophotographic photosensitive member 1 starts to rotate in the direction indicated by the arrow A. Then, the portion passing through the charger 5 is uniformly charged to about -600V. Thereafter, the potential of the part irradiated with the laser beam 6a irradiated based on the image signal from the exposure unit 6 becomes -1.
The voltage rises to about 00 V, and an electrostatic latent image is formed on the charged portion.

Since the developing roller 7b is constantly pressed against the belt-shaped electrophotographic photosensitive member 1, the developing roller 7b of the developing device 7
When b comes into contact with the belt-shaped electrophotographic photosensitive member 1, the electrostatic latent image is developed by the negative polarity toner 7a attached to the surface of the developing roller 7b, and a toner image 7c appears.

When the formation of the toner image 7c is completed, the rotation of the belt-shaped electrophotographic photosensitive member 1 and the recording medium 9 are completed.
Is temporarily stopped, and the belt-shaped electrophotographic photosensitive member 1 is rubbed and displaced on the recording medium 9 stopped on the transfer plate 10 by the movement of the transfer opposing roller 8. This allows
The toner image 7c on the belt-shaped electrophotographic photosensitive member 1 is transferred to the recording medium 9. At this time, in order to eliminate the slack of the belt-shaped electrophotographic photosensitive member 1, the displacement roller 2b is displaced following the movement of the transfer opposing roller 8.

During the transfer step, the toner image 7c may be shifted and transferred unless the floating of the recording medium 9 from the transfer plate 10 at the time of transfer is prevented to prevent the recording medium 9 from skidding. is there. Therefore, in order to prevent such a recording deviation, a positive voltage having a polarity opposite to that of the toner image 7c is applied to the transfer plate 10 to charge positive charges. Then
The static electricity generated on the surface of the transfer plate 10 causes the recording medium 9
Is electrostatically attracted to the transfer plate 10 and temporarily bound on the transfer plate 10. Then, the transfer plate 10 having a positive charge attracts the negatively charged toner image 7 c from the surface of the belt-shaped electrophotographic photosensitive member 1, peels it, and transfers it to the recording medium 9.

The belt-shaped electrophotographic photosensitive member 1 is separated from the recording medium 9 by moving the transfer opposing roller 8 past the recording medium 9 and out of the area of the recording medium 9 each time the transfer for one process is completed. I do. Immediately before the belt-shaped electrophotographic photosensitive member 1 is separated from the recording medium 9, the transfer plate 10
Since the application of the voltage to the recording medium 9 has been stopped, the recording medium 9 that has been electrostatically attracted to the transfer plate 10 has been released.

When the transfer of the toner image 7c is completed, the conveyance of the recording medium 9 is started in order to proceed to the next transfer step, and the conveyance distance (conveyance amount) of the recording medium 9 is the same as that of the belt-shaped electrophotographic photosensitive member 1. It is only the width of the development area (recording area). Accordingly, the recording medium 9 is intermittently fed to the fixing device (not shown) by the width of the developing area. On the other hand, the belt-shaped electrophotographic photosensitive member 1 starts rotating again, and the toner remaining on the portion of the belt-shaped electrophotographic photosensitive member 1 on which the toner image 7c has been transferred is removed by the cleaning device 3, and thereafter,
The charge on the belt-shaped electrophotographic photosensitive member 1 is eliminated by the neutralizer 4.

Then, such an image forming operation is sequentially repeated, and a predetermined image such as a character or a figure is formed on one recording medium 9.

Here, in the present embodiment, as described above, the number of rotations of the developing roller 7b during one developing operation is an integer, and the position angle when the developing roller 7b is stationary is always constant. It is the same.

In the image forming apparatus, writing of an electrostatic latent image on the belt-shaped electrophotographic photosensitive member 1 is always performed at the same timing in order to align the positions between adjacent images.

Therefore, assuming that the number of rotations during one development operation of the developing roller 7b is an integer and the stationary position angle is always the same, the developing roller 7b always starts developing the electrostatic latent image from the same position. Will be. That is, the electrostatic latent image is developed at the same position on the developing roller 7b.

FIG. 3 shows an output image of such an image forming apparatus. In FIG. 3, the output image is an image formed on one recording medium by repeating the image forming and transferring operations three times. For convenience, each image has an outer frame.

As shown in the figure, in this embodiment, since the adjacent images are developed by the same portion of the developing roller 7b, the density difference between the mutually adjacent images is largely suppressed.

[0037]

As described above, according to the present invention, the position angle when the developing roller is stationary is always the same.
The developing roller always starts developing the electrostatic latent image from the same position, and an effective effect that it is possible to suppress a density difference between mutually adjacent images can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating a transfer mechanism of the image forming apparatus of FIG. 1;

FIG. 3 is an explanatory diagram illustrating an output image of the image forming apparatus of FIG. 1;

FIG. 4 is an explanatory diagram showing an output image of image data of uniform density recorded by a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 belt-shaped electrophotographic photosensitive member 2 a drive roller 2 b displacement roller 7 a toner 7 b developing roller 7 c toner image 8 transfer opposing roller 9 recording medium

Claims (1)

[Claims] A closed loop belt-shaped electrophotographic photosensitive member which is rotated around by a plurality of rollers to form an electrostatic latent image; and the number of rotations during one development operation is an integer. A developing roller for supplying a toner to the latent image to form a toner image; a developing roller disposed at an inner peripheral position of the belt-shaped electrophotographic photosensitive member and movably provided along a recording medium to form the toner image. An image forming apparatus, comprising: a transfer opposing roller that presses the belt-shaped electrophotographic photosensitive member, which has stopped circumferential rotation, onto the recording medium to transfer the toner image onto the recording medium.