JPH075755A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image of satisfactory quality by securely holding toner, carried by means of a magnet roller, on the surface of a photosensitive drum. CONSTITUTION:The photosensitive drum 12 is electrically grounded, and composed of a magnetic, conductive base material drum 24 in the form of a cylinder, and a photoconductive layer 26 applied on the surface of the drum. Because it is necessary that the base material drum 24 be magnetic, a nickel-plated iron pipe with a proper diameter is used. A developing container 30 storing toner 28 is provided with the magnet roller 32 for holding the toner 28 on its surface, and a controlling blade 34 for controlling the thickness of a layer of the toner 28, held on the surface of the magnet roller 32, on this side of a development area. The center shaft 36 of the magnet roller 32 is rotatably attached to the developing container 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Usually, a portion which is arranged around a photosensitive drum and which forms an image by sequentially acting on the photosensitive drum is called a process portion, and various parts such as a copying machine and a laser printer are formed. It is used in office machines.

A general structure of this process section will be described with reference to FIG.

The photosensitive drum 100 is rotatably supported by a device body (not shown) about its central axis. Around the photoconductor drum 100, the charging device 102, the image exposing device 103, and the developing device 1 are arranged along the rotation direction.
04, a transfer device 106, and a cleaner 108 are arranged in that order.

The photoconductor drum 100 has a structure in which a resin having photoconductivity is applied on a drum tube by dipping, and is generally called an OPC drum.

More specifically, the photosensitive drum 100 has a base coat layer, a charge generation layer, and a charge transport layer on the surface of an aluminum tube whose surface is polished to have a surface roughness of about 0.8 s. It is manufactured by forming and in that order. The undercoat layer is made of an insulating layer such as an anodized film or a resin film, and restricts charge transport to some extent to maintain the charged state of the surface of the photoconductor to suppress dark decay, and to reduce surface energy more than metal surface. Is provided for the purpose of facilitating application of the charge generation layer by providing an insulating layer having a small thickness. The charge generation layer is a charge generation material dispersed in a binder resin. The charge generating substance to be dispersed varies depending on the wavelength of light used for exposing the photoreceptor, and in the case of using a wavelength of 450 to 600 nm as in a copying machine, azo, perylene, anthanthrone pigment, thiapyrylium dye, etc. are used, and laser light is used. For printers that use wavelengths in the infrared region, phthalocyanine pigments and trisazo pigments are used. As the charge transport layer, a layer in which oxadiazole, oxazole, pyrazoline or the like is dispersed in a binder resin is used.

Next, the structure of the developing device 104 will be described. The developing container 110 containing the toner 112 has a developing roller 114 having a magnet material 124 for carrying the toner 112 on the surface thereof, and a layer thickness of the toner 112 carried on the developing roller 114 in front of the developing area. A regulating blade 118 for regulating is provided.

FIG. 4 shows a sectional view of the developing roller 114 cut in the longitudinal direction. The developing roller 114 includes a rod-shaped central shaft 122 made of a material such as stainless steel, a magnet material 124 having a cylindrical outer periphery formed around the central shaft 122, and a magnetic material 124 covering the periphery thereof, such as aluminum. The sleeve 1 is provided with a cylindrical sleeve 125 made of a conductive and non-magnetic material, and flanges 126 and 127 provided at both ends of the sleeve 125.
25 is supported by a bearing 128 so as to be rotatable relative to the central shaft 122. In addition, the magnetic material 124
The central shaft 122 provided with is fixed to the side plate of the developing container 110 so as not to rotate.

The toner 112 stored in the developing device 104 is made of a binder resin in which magnetic powder, a charge control agent, or the like is dispersed, and is made of hydrophobic silica for the purpose of imparting fluidity or a toner having transferability. Various external additives are added for the purpose of adjusting the characteristics of the toner such as improvement.

The operation of the process unit having such a configuration will be described. The surface of the photoconductor drum 100 is uniformly charged to about -700V by the charger 102 in contact with the surface. The surface of the charged photosensitive drum 100 is exposed by the exposure device 103 according to image information to form an electrostatic latent image. The toner 112 conveyed by the developing device 104 is transferred to the surface of the photoconductor drum 100 by electrostatic force, and visualizes the electrostatic latent image. Photoconductor drum 100
The upper toner 112 is transferred to the paper 130 by the transfer device 106.
Transcribed on. The toner 112 remaining on the photosensitive drum 100 after the transfer is removed by the cleaning blade 109 that constitutes the cleaner 108. In this process section, the above process is repeated to sequentially form images on the paper 130.

Further, the operation of the developing device 104 for developing the electrostatic latent image on the photosensitive drum 100 into a visible image will be described in detail. Toner 112 is caused by the magnetic force of the magnetic material 124 in the developing roller 114 to cause the sleeve 125 to move. The toner adheres to the surface of the sheet and is conveyed to the developing area as the sleeve 125 rotates. Then, the toner 112 attached in front of the developing area
The layer thickness is regulated by the regulation blade 118, and the electrostatic latent image formed on the surface of the photosensitive drum 100 in the developing area is developed into a visible image.

[0012]

However, the image forming apparatus provided with the developing device having the above configuration has the following drawbacks.

In a developing system using a magnetic toner containing only one component, triboelectrification of the toner is carried out by friction with a regulating blade, but toner charged to a predetermined polarity is
Of the toner layers adhering to the surface of the developing roller, only the toner of the very surface layer is limited, and the toner is insufficiently charged. That is, in the above-described developing device, since the toner layer is mixed between the regulation blade and the developing region, the charge distribution of the toner contacting the photosensitive drum becomes non-uniform, and the uncharged toner that causes the background fog is uncharged. Toner will increase. Therefore, the obtained image also has a large amount of unnecessary toner scattered around the characters, and the image quality deteriorates.

Further, in the above developing device, since the spikes of toner are formed in the central portion of the magnet material, it has the ability to visualize the electrostatic latent image on the photosensitive drum. Depending on the arrangement of the rollers, magnetic lines of force may run parallel to the sleeve surface between the magnet materials. In such a state, the ears of the toner are not formed, so that part does not contribute to the visualization of the electrostatic latent image. Therefore, horizontal stripes appear in the developed image, and the quality of the output image is significantly deteriorated.

The present invention has been made to solve the above-mentioned problems, and the developer conveyed by the developer conveying means can be surely carried on the surface of the image carrier, and as a result, good image quality can be obtained. It is an object of the present invention to provide an image forming apparatus capable of obtaining an image.

[0016]

In order to achieve this object, an image forming apparatus of the present invention has an image bearing member for bearing an electrostatic latent image on its surface and a magnet inside, and has the above-mentioned image bearing member. An image forming apparatus, comprising: a developer transporting unit that transports a developer to a vicinity thereof, which visualizes an electrostatic latent image on the image carrier into a visible image by the developer, wherein the image carrier is , A magnetic conductive base, and a photoconductive layer which covers the surface of the base and carries the electrostatic latent image.

[0017]

In the image forming apparatus of the present invention having the above-mentioned structure, the developer carried by the developer carrying means follows the magnetic lines of force generated between the magnet of the developer carrying means and the base of the image carrying body. Move to the surface of. Then, the developer visualizes the electrostatic latent image formed on the surface of the image carrier into a visible image.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, in the image forming apparatus 10 of the present embodiment, the photosensitive drum 12 as an image carrier is supported by a device body (not shown) so as to be rotatable about its central axis. Has been done. Around the photosensitive drum 12, along the rotation direction thereof, the charging roller 14, the exposure device 16, the developing device 18, the transfer roller 20, and the cleaner 22.
Are arranged in that order.

The photosensitive drum 12 is electrically grounded,
A cylindrical base drum 24 having magnetism and conductivity,
It is composed of a photoconductive layer 26 applied on the surface thereof. Since the base material drum 24 is required to have magnetism, an iron pipe having an appropriate diameter plated with nickel is used. The composition of the photoconductive layer 26 is the same as the composition of the photoconductive layer of the photosensitive drum in the conventional example, and will not be described in detail here.

Next, the structure of the developing device 18 will be described. In the developer container 30 that stores the toner 28 as a magnetic developer, the layer thickness of the toner roller 28 on the surface of the mag roller 32 as the developer conveying means for supporting the toner 28 on the surface. And a regulating blade 34 for regulating the above in front of the developing area. The center shaft 36 of the mag roller 32 is rotatably attached to the developing container 30, and the center shaft 36 and the rotation shaft of the photosensitive drum 12 are positioned parallel to each other. Further, the gap between the surface of the mag roller 32 and the surface of the photosensitive drum 12 is positioned so as to be 200 to 500 μm.

The structure of the mag roller 32 will be described with reference to FIG. The mag roller 32 has a central shaft 36 made of a conductor.
A magnet 38 that is formed in a cylindrical shape around the magnet 38 and is magnetized eight-pole isotropically in the circumferential direction of the central axis 36; and a sleeve 40 that is provided so as to cover the circumference of the magnet 38 as a conductive portion. It consists of Further, the magnet 38 and the sleeve 40 are fixed to the central shaft 35 and are configured to be rotatable integrally with the rotation of the central shaft 36. Further, the sleeve 40 is made of a conductive material such as aluminum, and a power source 42 for applying a voltage as a developing bias is connected to the central shaft 36.

The charging roller 14 is a core material 13 made of a conductor.
A urethane foam rubber 15 is formed around the
The urethane urethane rubber 15 has a resistance value of 10 ³ to 10 ¹⁵ Ωc.
It is about m. The core material 13 is connected to a power source (not shown), and the surface of the photosensitive drum 12 in contact with the surface of the charging roller 14 is charged by the voltage supplied from the power source. According to this charging method, the charging roller 14
Since the surface of the photosensitive drum 12 and the surface of the photosensitive drum 12 are in contact with each other, there is an advantage that the amount of ozone generated by corona discharge is extremely small.

The exposure device 16 comprises a laser oscillator such as a laser diode and various optical elements for guiding the laser beam emitted from the laser oscillator to the surface of the photosensitive drum 12. The laser oscillator is the image forming apparatus 1
By repeating blinking according to the image data input to 0, an electrostatic latent image is formed on the photosensitive drum 12.

The transfer roller 20 is also a photosensitive drum 12.
Is placed in contact with the surface of. Then, when the sheet 44 passes between the transfer roller 20 and the photosensitive drum 12, the toner 28 on the surface of the photosensitive drum 12 adheres to the sheet 44 due to the pressure contact force of the transfer roller 20 against the photosensitive drum 12. .

The cleaner 22 is the cleaning box 2
3 and a cleaning blade 25.
The cleaning blade 25 is for scraping off the toner 28 remaining on the surface of the photosensitive drum 12 after the transfer is completed, and is fixed to the cleaning box 23. Further, the cleaning box 23 stores the toner 28 scraped by the cleaning blade 25.

Next, the image forming apparatus 10 having such a configuration.
The operation of will be described.

First, the surface of the photosensitive drum 12 is uniformly charged to about -700 V by applying a voltage to the charging roller 14. Then, the surface of the photoconductor drum 12 can be exposed by blinking the laser diode constituting the exposure device 16 based on the image information. Then, the electric charge at the exposed position of the photosensitive drum 12 disappears, so that a potential distribution called an electrostatic latent image is formed on the surface of the photosensitive drum 12. The electrostatic latent image is visualized as a visible image by the toner 28 attached by the developing device 18. The toner 28 forming the visible image is transferred onto the sheet 44 by the transfer roller 20. The toner 28 remaining on the photosensitive drum 12 after the transfer is removed by the cleaning blade 25 and stored in the cleaning box 25. By repeating the above process, images are sequentially formed on the paper 44.

The sheet 44 on which the image is formed is conveyed to a well-known fixing device (not shown). In the fixing device, when the paper 44 is pressed and heated, the toner 28 is melted and fixed on the surface of the paper 44. After that, the paper 44 is discharged to the outside of the apparatus.

Next, the operation of the developing device 18 will be described in detail. Since the toner 28 in the developing container 30 is magnetic, it adheres to the surface of the sleeve 40 by the magnetic force generated by the magnet 38 forming the mag roller 32. Then, the attached toner 28 is carried by the rotation of the mag roller 32, the layer thickness thereof is regulated by the regulation blade 34, and the toner 28 is frictionally charged to a predetermined polarity. And mag roller 3
Due to the rotation of 2, the toner 28 is transferred to the photosensitive drum 12.
And the mag roller 32 are close to each other in the developing area, they adhere to the portion of the electrostatic latent image formed on the surface of the photoconductor drum 12 to form a visible image.

Here, in the developing device 18 having the above-described structure, the sleeve 40 and the magnet 38 constituting the mag roller 32 rotate integrally, so that the layer of toner 28 is formed between the regulating blade 34 and the developing area. Since the toner 28 that has been charged to the surface of the photosensitive drum 12 remains in contact with the photoconductive layer 26 on the surface of the photosensitive drum 12 without changing its relative position, the toner 28 that has not been charged remains on the surface of the photosensitive drum 40. As a result of less chance of contact with the photoconductor drum 12, image quality deterioration such as background fogging and toner 28 around characters is less likely to occur. Therefore,
It is possible to obtain a high-quality image while keeping the advantage of using the developer having a simple structure, that is, the magnetic toner 28 composed of one component.

Further, in the image forming apparatus of this embodiment, the base material drum 24 constituting the photoconductor drum 12 is manufactured from a magnetic material such as iron in order to promote the rising of the toner 28 in the developing area. There is. FIG. 3 shows the appearance of the spikes of the toner 28 in the developing area and the distribution of magnetic force lines. Since the base material drum 24 is made of a magnetic material and the magnetic force lines are concentrated on the material having high magnetic permeability, the magnetic force lines emitted from the magnet 38 of the mag roller 32 in the developing region are easily oriented toward the photoconductor drum 12. And as a result,
Since the area where the spikes of the toner 28 are formed becomes large, it is possible to obtain sufficient image quality with a smaller number of rotations of the mag roller 32.

The image forming apparatus of the present invention is not limited to the above-described embodiments, and changes can be made without departing from the spirit of the invention.

For example, although the toner 28 is a one-component magnetic toner in the above embodiment, a developer containing a carrier or an additive similar thereto may be used. Further, the photoconductive layer 26 of the photoconductor drum 12 is not limited to the organic photoconductor as described above, and a material such as a selenium compound or amorphous silicon may be used.

[0035]

As is apparent from the above description, in the image forming apparatus of the present invention, the image carrier is composed of the magnetic substrate, so that the charged toner is surely carried by the image carrier. It comes in contact with the body and can obtain high quality images.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an image forming apparatus embodying the present invention.

FIG. 2 is a cross-sectional view showing a state in which a mag roller used in the image forming apparatus of this embodiment is cut in the longitudinal direction.

FIG. 3 is a diagram showing details in the vicinity of a developing area in the image forming apparatus of this embodiment.

FIG. 4 is a sectional view of a conventional image forming apparatus.

FIG. 5 is a sectional view showing a state in which a developing roller used in an example of a conventional image forming apparatus is cut in a longitudinal direction.

[Explanation of symbols]

 10 Image Forming Device 12 Photoreceptor Drum 24 Base Material Drum 26 Photoconductive Layer 28 Toner 32 Mag Roller

Claims (1)

[Claims] 1. An image carrier for carrying an electrostatic latent image on its surface,
And a developer transporting means for transporting the developer to the vicinity of the image carrier, the electrostatic latent image on the image carrier being visualized by the developer. The image forming apparatus is characterized in that the image carrier comprises a magnetically conductive substrate and a photoconductive layer that covers the surface of the substrate and carries the electrostatic latent image. Image forming apparatus.