JPH0545957A - Image forming device - Google Patents

Abstract

PURPOSE:To form an image with an overall normal density by forming an electrostatic latent image stretched in a subscanning direction on a surface of a photosensitive body moving while carrying out subscanning, and visualizing this by carrying out powder developing. CONSTITUTION:Laser beam modulated corresponding to an image signal is allowed to reflect and deflected through a deflector of a polygon mirror, etc., and made to carry out image exposure over the photosensitive drum 4 and to carry out main scanning in the axial direction by a laser scanning unit 31 provided in a loading part of an image forming cartridge 1. Rotation of the photosensitive drum 4 is made to be the sub scanning movement, and the electrostatic latent image just similar to the image signal is formed by the main scanning. Furthermore, paper feeding path 33 is provided in a bottom part of the loading part of the image forming cartridge 1 to transfer a transfer sheet 32. Then, the electrostatic latent image formed on the photosensitive drum 4 is left as an image stretched in the direction of the subscanning direction, and since the visual image powder developed by a developing roll 11 is transferred to the transfer sheet 32 shrunk to an appropriate size, the developer is condensed and the image density is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a facsimile,
The present invention relates to an image forming apparatus that forms an image by an electrophotographic method such as a laser beam printer.

[0002]

2. Description of the Related Art An image forming apparatus of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-279870.

Among conventionally known image forming apparatuses, in the case of using a one-component non-magnetic developer, the developer is carried on the surface of the developing roller and conveyed toward a portion facing the photoconductor, and comes into contact with the photoconductor. Alternatively, a method of developing the electrostatic latent image on the photoconductor in a non-contact state is adopted.

In the non-contact development, the layer thickness of the developer is set larger than that in the contact development in order to stably supply the developer. In contact development, the thickness of the image is reduced by suppressing the layer thickness,
Highly reproducible changes are said to be thin.

[0005]

Incidentally, the developing roller and the photoconductor may be eccentric. Especially in the case of non-contact development, the eccentricity causes a variation in the development gap set between the developing roller and the photoconductor.

As shown in FIG. 5, due to the potential difference between the charge on the surface of the photosensitive drum a on which the electrostatic latent image is formed and the bias charge on the surface of the developing roller b, the potential difference between the photosensitive drum a and An electric field c is generated between the developing roller b and the developing roller b.

The electric field c spreads in a ripple shape as shown in FIG. 5, but as the developing gap increases from g ₁ to g ₂ , the electric field spreads around, and the developing roller b of the developer spreads from the electric field to that extent. The suction force of the developer to a is weakened.

Therefore, when the developing gap changes as described above, the developing characteristics also change. When the fluctuation of the developing characteristics is caused by the eccentricity, the fluctuation appears in a wavy shape, and a striped density unevenness occurs in the formed image.

Even if the layer thickness of the developer carried on the surface of the developing roller is increased, the striped density unevenness due to the fluctuation of the developing gap cannot be eliminated.

Further, when the layer thickness of the developer is large, layer unevenness having large unevenness is likely to occur on the layer surface of the developer d as shown in FIG. 6, which causes density unevenness or disturbance of the edge portion of the image. This causes scattering, and as shown in FIG. 6, the developer d excessively adheres to the electrostatic latent image in the form of thin lines, which causes the image to become thick.

When the developing agent is a thin layer formed by contact development, the developing roller comes into contact with the photosensitive drum, which affects the material of the developing roller. For example, in the case of a rubber developing roller, a plasticizer or other Additives, etc. are emitted, which contaminate the surface of the photosensitive drum a and impair the image quality.
May shorten the life of the.

Therefore, it is an object of the present invention to provide an image forming apparatus capable of solving the above problems by a simple improvement.

[0013]

The first invention of the present application is a means for forming an electrostatic latent image extending in the sub-scanning direction on the surface of a photosensitive member which moves in the sub-scanning direction, and a means for powdering the electrostatic latent image. It is characterized by comprising means for developing and visualizing, and means for shrinking and transferring the elongated visible image formed on the photoreceptor in the sub-scanning direction.

In a second aspect of the present invention, in addition to the first aspect, the electrostatic latent image forming means makes the speed of the sub-scanning movement of the photoconductor larger than that at the same magnification, and the transfer means uses a transfer sheet. The transfer is performed at a speed lower than the sub-scanning moving speed of the photoconductor.

The third invention of the present application is characterized in that, in the second invention, the following relationship is satisfied: sub-scanning moving speed: transfer sheet conveying speed = sub-scanning direction image elongation: main scanning speed. ..

The fourth invention of the present application is the third invention, wherein the transfer means electrostatically carries the transfer sheet for transfer, and at the same time electrostatically transfers the visible image on the photoreceptor to the transfer sheet. It is characterized by that.

The fifth invention of the present application is the same as the fourth invention, wherein the electrostatic latent image forming means uses a one-component non-magnetic developer.
It is characterized in that it is developed in a non-contact manner with a photoconductor under a DC bias.

[0018]

According to the structure of the first invention of the present application, an electrostatic latent image extending in the sub-scanning direction is formed on the surface of the photosensitive member which moves in the sub-scanning direction by the electrostatic latent image forming means, and the electrostatic latent image is developed by the developing means. As a result, the image is developed by powder development by means of the developing means, regardless of whether it extends in the scanning direction. Can be formed.

The image on the photoconductor is contracted and transferred onto the transfer sheet in the sub-scanning direction by the transfer means, so that an image of a normal size is formed on the transfer sheet, and also the developing powder due to the contraction in the sub-scanning direction. It is possible to increase the density by concentrating and even if there is density unevenness in the visible image before transfer, it can be formed by averaging it.

According to the above configuration of the second invention of the present application,
In the invention, the electrostatic latent image extending in the sub-scanning direction on the photoconductor is formed by moving the photoconductor in the sub-scanning direction by the electrostatic latent image forming means faster than at the same magnification. The transfer is performed only by speed control such that the transfer image is transferred to the transfer sheet at a speed lower than the sub-scanning speed of the photoconductor by transferring the developed image developed by the developing means to the transfer sheet in the sub-scanning direction. The required image formation and transfer can be achieved.

According to the above configuration of the third invention of the present application, the first
Alternatively, in the second aspect of the invention, further, the relationship of sub-scanning moving speed: transfer sheet conveying speed = sub-scanning direction image elongation rate: main scanning speed may be satisfied, and necessary image formation and transfer are performed by sub-scanning of the photoconductor. This can be achieved by increasing the speed of movement only.

According to the fourth invention of the present application, in any one of the first to third inventions, the transfer means electrostatically carries the transfer sheet to be used for transfer and transfers the visible image on the photoreceptor. Therefore, the transfer sheet is provided for transfer at a speed different from the sub-scanning speed of the photoconductor without increasing the number of parts,
Also, transfer can be performed.

According to the fifth invention of the present application, in any one of the first to fourth inventions, the image forming means uses a one-component non-magnetic developer, which is DC biased in non-contact with the photoconductor. Since it is used for development, it is possible to prevent density unevenness, image edge portion disorder, and developer scattering due to eccentricity of the developer bearing member provided in the photoconductor or the image forming unit.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus as an embodiment to which the present invention is applied will be described below.

FIG. 1 shows a schematic structure of the image forming apparatus in which a one-component non-magnetic developer is used.

A developing device casing 2 and a waste toner casing 3 are arranged on both sides of the photosensitive drum 4. The photosensitive drum 4 is formed by forming a photoconductive layer such as selenium or an organic photoconductive material on the surface of a metal base such as aluminum. The surface of the photosensitive drum 4 is uniformly charged by the charging charger 5 on the upper side and is indicated by an arrow 6. As described above, an electrostatic latent image is formed by receiving image exposure.

This electrostatic latent image is developed by the developer supplied from the developing device casing 2 and becomes a visible image.

A developing roller 11 for developing the electrostatic latent image formed on the photosensitive drum 4 is provided at the toner supply port 2a of the developing device casing 2 facing the photosensitive drum 4.
It is axially supported on the side wall of the developing device casing 2.

A developing gap is provided between the developing roller 11 and the photosensitive drum 4 for non-contact development with a one-component non-magnetic developer.

A developer supplying paddle 15 for stirring the developer in the developing device casing 2 while supplying the developer in the developing device casing 2 to the fur brush 13 is provided in the developing device casing 2, and a stirring blade 17 for preventing the toner from blocking. Is installed.

At the upper edge of the toner supply port 2a of the developing device casing 2, there is provided a developing blade 21 which extends to the peripheral surface of the developing roller 11 and comes into pressure contact with it.

The developing blade 21 is for making the developer supplied by the fur brush 13 on the developing roller 11 into a thin layer having a predetermined thickness, and a rubber blade such as urethane rubber or silicone rubber is preferable. In some cases, metal blades such as phosphor bronze for springs and spring steel are also useful.

The developing blade 21 has an upper end attached to the metal support member 22 spanned between the side walls of the developing device casing 2 by adhesion or the like, and a lower end pressed against the surface of the developing roller 11.

A seal piece 25 is provided on the lower edge of the toner supply port 2a of the developing device casing 2, and the developing roller 11
It extends upward and is in pressure contact. The seal piece 25 is made of polyethylene terephthalate (PET) or the like, and allows the residual toner after being carried on the developing roller 11 and subjected to development on the photosensitive drum 4 to pass through the toner supply port 2a, but the toner supply port Preventing the developer from coming off from 2a.

By the way, the developing roller 11 is made of aluminum or stainless steel, and the portion of the developer carrying region on the central side in the longitudinal direction facing the toner supply port 2a is formed on the matte surface by sandblasting or the like to carry and carry the developer. It is made to be advantageous to do.

The above-mentioned image forming mechanism constitutes the image forming cartridge 1 which is attached to and detached from the apparatus main body.

A laser scan unit 31 for exposing the image is provided above the portion where the image forming cartridge 1 is mounted. The laser scan unit 31 reflects the laser light modulated according to an image signal by a deflector such as a polygon mirror and deflects it to expose the photosensitive drum 4 with an image as shown by an arrow 6 to mainly perform an axial direction. To scan. On the other hand, the rotation of the photosensitive drum 4 becomes a sub-scanning movement, and an electrostatic latent image according to an image signal is formed by the main scanning.

A paper passing path 33 for transferring the transfer sheet 32 is provided below the portion where the image forming cartridge 1 is mounted.

The sheet passing path 33 is formed by a pickup roller 35, and the transfer sheets 3 are sent one by one from a sheet feeding cassette 34 which is also detachably attached to the apparatus main body.
2 is formed between the photosensitive drum 4 and the conveyor belt 36 that sucks and conveys 2.

The conveyor belt 36 is made of, for example, a dielectric material,
The transfer sheet 32 is stretched by three rollers 37 to 39 and given a predetermined charge by being charged by a charging charger 41 provided on the back surface side, and the transfer sheet 32 is adsorbed and conveyed as shown in FIG. Further, the transport belt 36 attracts the visible image formed on the photosensitive drum 4 to the transfer sheet 32 side by the charge and transfers the image onto the transfer sheet 32 which is attracted to the transport belt 36 and is transported. In order for this transfer to be properly performed in the area of the transfer sheet 32, the conveyor belt 36 must be
It is necessary to be charged more than the area where 2 is carried.

One roller 3 for tensioning the conveyor belt 36
The transfer belt 32 is arranged so as to face the photosensitive drum 4 in a state where the conveyor belt 36 is pulled up in a mountain shape and curved, and the transfer sheet 32 adsorbed and carried on the surface of the conveyor belt 36 is in line contact with the photosensitive drum 4. ..

This is to transfer the image without damaging the image even if there is a difference in peripheral speed between the photosensitive drum 4 and the conveying belt 36, as will be described later.

A timing roller 42 is brought into pressure contact with the conveyance start end portion supported by the roller 37 of the conveyance belt 36. Then, the skew of the transfer sheet 32 is corrected by receiving the fed transfer sheet 32 between the timing roller 42 and the conveyance belt 36 in the stopped state and aligning the leading ends thereof. Also, the conveyor belt 3 after that
The transfer sheet 32 and the visible image formed on the photosensitive drum 4 are aligned with each other at the drive start timing of 6 and the timing roller 42, and the transfer sheet 32 is conveyed and transferred.

A static eliminating charger 43 is provided inside the conveyance belt 36 near the conveyance end portion supported by the rollers 39, and neutralizes and removes the electric charges of the conveyance belt 36 by AC charges.

The transfer sheet 32 reaching the charge eliminating charger 43 is released from the electrostatic holding on the conveying belt 36 by the charge eliminating, and when it reaches the conveying end portion of the conveying belt 36, the transfer sheet 32 is separated by the separating claw 44. It is separated from 36 without difficulty and is sent to the fixing roller 45.

By the way, the electrostatic latent image formed on the photosensitive drum 4 is set as an image extending in the sub-scanning direction, and the developed image is powder-developed by the developing roller 11.
The image is transferred to the upper side by shrinking to the proper size in the sub-scanning direction.

As a result, the developer forming the visible image on the photosensitive drum 4 is concentrated in the sub-scanning direction when it is transferred onto the transfer sheet 32, and the image density is improved. Therefore, the development on the photosensitive drum 4 may be performed at a required density or less.

Further, even if the density of the developed image developed in the sub-scanning direction on the photosensitive drum 4 is slightly uneven, the development in the sub-scanning direction when the developed image is transferred onto the transfer sheet 32 is performed. Averaged by concentration of agent.

As a result, the developing characteristics required in accordance with the required image quality can be made lower than in the conventional case, and the layer thickness of the developer formed on the developing roller 11 is a thickness advantageous for development. By setting the layer thickness between the layer and the thin layer, you can obtain the required density evenly without problems such as non-contact development in the thick layer and contact development in the thin layer, and obtain a high quality image. Can be formed.

The formation of the electrostatic latent image extending in the sub-scanning direction and the contraction of the visible image on the photosensitive drum 4 onto the transfer sheet 32 in the sub-scanning direction are the photosensitive drum 4 in this embodiment.
Is set at a speed higher than the sub-scanning speed at the same magnification.

Image exposure by the laser scanning unit 31 is performed at a scanning speed v ₁ required to form a ₁ × image.
2 (FIG. 2), the photosensitive drum 4 is rotationally driven at a speed v ₂ (FIG. 2) faster than that by the image expansion ratio x.

As a result, an electrostatic latent image which extends x times in the sub-scanning direction is formed on the photosensitive drum 4 by ordinary image exposure.

The peripheral speed v ₃ (FIG. 2) of the developing roller 11 for developing the electrostatic latent image extending in the sub-scanning direction is set to be the same as the peripheral speed v ₂ of the photosensitive drum 4.

As a result, the electrostatic latent image extended in the sub-scanning direction can be subjected to the same degree of development as in the conventional case by the developer on the developing roller 11 which is conveyed at the same speed for each portion.

Therefore, a visible image extending in the sub-scanning direction is formed on the photosensitive drum 4 with a normal density even if no special developing condition is set.

The conveying speed v ₄ (FIG. 2) of the transfer sheet 32 for transferring this visible image on the photosensitive drum 4 is set equal to the scanning speed v ₁ at the same magnification. This is just a value obtained by dividing the peripheral velocity v ₂ of the photosensitive drum 4 by the expansion ratio x of the image.

As a result, the visible image extending in the sub-scanning direction on the photosensitive drum 4 has a transfer sheet 32 having a slow speed of v ₂ / x.
The image is contracted upward in the sub-scanning direction and transferred to form a non-scaled image.

When the visible image is contracted and transferred in the sub-scanning direction, the developers forming the visible image extending in the sub-scanning direction are gathered up to the same size and concentrated. Therefore, the image density is improved, and even if there is density unevenness in the visible image extending in the sub-scanning direction on the photosensitive drum 4, this is averaged.

From the above speed relationship, v ₁ = v ₄ , v ₂ = v ₃ = v ₁ x (1)

Considering the magnification M when the image formation is performed by reducing or enlarging, v ₁ M = v ₄ M, v ₂ = v ₃ = v ₁ x (2)

Further, the image density can be adjusted by utilizing the fact that the image density is increased by contracting and transferring the visible image extending in the sub-scanning direction.

Specifically, x in the equation (2) may be corrected by the density correction coefficient m. The speed relationship in this case is v ₁ M = v ₄ M, v ₂ = v ₃ = v ₁ xm ... (3).

In order to carry out the above-mentioned image formation, a speed change mechanism required for each is provided between the main motor and the like.

For controlling the image forming operation as described above, the microcomputer 100 for operation control provided in the image forming apparatus shown in FIG. 3 is used.

A print signal 101, a magnification setting signal 102, a density setting signal 103 and other inputs are connected to the input side of the microcomputer 100.

The magnification M is set in the range of 0.5 to 2, and the density correction coefficient m is set in the range of 0.5 to 1.5, for example.

The output side of the microcomputer 100 is connected with a main motor drive signal 201, a scan speed signal 202, a photosensitive drum / developing roller speed signal 203, a conveyor belt speed signal 204, and other outputs.

The specific image forming process is performed by the flowchart shown in FIG. 4, for example. This will be described. When the magnification setting key is operated, the magnification M corresponding to the operation is read and stored as magnification information. If the magnification setting key is not operated, M = 1 is set. This can be done by default.

Next, when the density setting key is operated, the density correction coefficient m corresponding to the operation is read and stored as density correction information. If there is no operation of the magnification setting key, m
Set to = 1. This can be done by default.

Subsequently, the necessary speed setting is performed based on the equation 3 from the magnification information and the density correction information.

Next, when the print key is operated, an image forming operation is performed at the speed relationship set as described above, and an image having a predetermined magnification is formed with a predetermined density.

Finally, other necessary processing is performed and the process returns to the main routine of the operation control (not shown).

[0073]

According to the first invention of the present application, an electrostatic latent image extending in the sub-scanning direction is formed by the electrostatic latent image forming means on the surface of the photosensitive member which moves in the sub-scanning, and this is formed by the developing means. By developing the image with powder to visualize it, each image is developed by the developing means equally regardless of whether the image extends in the scanning direction to obtain an image having normal density as a whole. The image on this photoreceptor that can be formed,
By shrinking and transferring the image on the transfer sheet in the sub-scanning direction by the transfer means, a normal size image is formed on the transfer sheet, and the density of the developer powder is increased by the contraction in the sub-scanning direction to increase the density. Even if there is density unevenness in the visible image, it can be formed by averaging, so that it is possible to form a high-quality image with sufficient and uniform density without setting development conditions with disadvantages. it can.

According to the above configuration of the second invention of the present application, the first
In the invention, the electrostatic latent image extending in the sub-scanning direction on the photoconductor is formed by moving the photoconductor in the sub-scanning direction by the electrostatic latent image forming means faster than at the same magnification. The transfer is performed only by speed control such that the transfer image is transferred to the transfer sheet at a speed lower than the sub-scanning speed of the photoconductor by transferring the developed image developed by the developing means to the transfer sheet in the sub-scanning direction. The required image formation and transfer can be easily achieved.

According to the above configuration of the third invention of the present application, the first
Alternatively, in the second aspect of the invention, further, the relationship of sub-scanning moving speed: transfer sheet conveying speed = sub-scanning direction image elongation rate: main scanning speed may be satisfied, and necessary image formation and transfer are performed by sub-scanning of the photoconductor. This can be achieved more easily by increasing the speed of movement only.

According to the fourth invention of the present application, in addition to any one of the first to third inventions, the transfer means electrostatically carries the transfer sheet for electrostatic transfer, and at the same time, transfers the visible image on the photosensitive member. Therefore, the transfer sheet is provided for transfer at a speed different from the sub-scanning speed of the photoconductor without increasing the number of parts,
In addition, transfer can be performed, and the configuration is simplified.

According to the fifth invention of the present application, in any one of the first to fourth inventions, the image forming means further comprises a one-component non-magnetic developer, which is DC-biased in non-contact with the photoconductor. Since it is used for development, it is possible to prevent density unevenness due to eccentricity of the developer carrier provided in the photoconductor or the image forming unit, disturbance of the image edge portion, and scattering of the developer, and a thin layer. It is possible to form higher quality images without the disadvantages of contact development.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus as an embodiment to which the present invention is applied.

FIG. 2 is a partial perspective view showing an image forming state of the apparatus of FIG.

3 is a block diagram of a control circuit of the device of FIG.

FIG. 4 is a flowchart showing an image forming processing subroutine by the control circuit of FIG.

FIG. 5 is an explanatory diagram showing a state of non-contact development with a one-component non-magnetic developer.

FIG. 6 is an explanatory diagram showing a developing state with a developer set in a thick layer.

[Explanation of symbols]

 2 developing device casing 4 photosensitive drum 11 developing roller 31 laser scanning unit 32 transfer sheet 36 conveyor belt 41 charger 100 microcomputer 202 scan speed signal 203 photosensitive drum / developing roller speed signal 204 conveyor belt speed signal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 15/16 7818-2H

Claims (5)

[Claims] 1. A means for forming an electrostatic latent image extending in the sub-scanning direction on the surface of a photosensitive member which moves in the sub-scanning direction, a means for developing the electrostatic latent image by powder development to visualize the latent image. An image forming apparatus, comprising: a unit configured to shrink and transfer the expanded visible image formed on the body in the sub-scanning direction. 2. The electrostatic latent image forming means makes the speed of the sub-scanning movement of the photoconductor larger than that at the same magnification, and the transfer means makes the transfer sheet move at a speed lower than the sub-scanning movement speed of the photoconductor. Transfer is performed. 3. Sub-scanning moving speed: transfer sheet conveying speed =
The image forming apparatus according to claim 1 or 2, wherein a relationship of sub-scanning direction image expansion ratio: main scanning speed is satisfied. 4. The image according to any one of claims 1 to 3, wherein the transfer means electrostatically carries a transfer sheet to be used for transfer and electrostatically transfers a visible image on the photoconductor onto the transfer sheet. Forming equipment. 5. The image according to claim 1, wherein the electrostatic latent image forming means uses a one-component non-magnetic developer and develops it under non-contact with a photoconductor under a direct current bias. Forming equipment.