JPH11174794A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of obtaining the output image of high resolution by concentrately performing the developing process in a nip position on a developing sleeve, in which the potential distribution becomes sharpest. SOLUTION: As for this device, the developer carrier 42 in developing means 42, provided with a fixedly arranged insulating cylindrical member 43, and the cylindrical member 43 is, provided with the developing area image forming member 45 composed of a conducting material, extend/located in a straight line state in the lengthwise direction of the cylindrical member 43 in parallel with the photoreceptor drum 1 on the closest position to the photoreceptor drum 1. The conducting film 44 is arranged on the periphery of the cylindrical member 43 and the developing area image forming member 45.

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 such as an electrophotographic copying machine and a laser beam printer.

[0002]

2. Description of the Related Art FIG. 1 shows an example of an electrophotographic image forming apparatus. In this example, the image forming apparatus has a drum-shaped electrophotographic photoconductor rotatably supported, that is, a photoconductor drum 1. The photosensitive drum 1 is charged to a predetermined potential by a charging unit 2 such as a charging roller, and is exposed to a desired pattern by, for example, irradiating a laser beam corresponding to image information by an exposure unit 3. An electrostatic charge image (electrostatic latent image) is formed on the surface. The electrostatic charge image is developed by a developing unit 4 having a developer (hereinafter, referred to as “toner”) to form a toner image that follows the potential distribution created by the electrostatic charge image.

That is, the developing means 4 includes a developing container 41 containing a toner, and a developing sleeve 42 as a developer carrying member for carrying and transporting the toner in the developing container 41. Toner is supplied from the developing sleeve 42 to the photosensitive drum 1 in accordance with the electrostatic latent image, and a toner image is formed on the photosensitive drum 1 as described above to obtain an output image.

The developing process at this time is performed by a developing sleeve 42.
Process in which the electrostatic charge image on the photosensitive drum 1 is conveyed to the transfer position, centered on the closest position (nip position) of the distance (distance between S-D) between the photosensitive drum 1 and the photosensitive drum 1 Then, the distance between SD becomes longer, and the developing process ends at the limit position where the toner can fly.

[0005] The toner image on the photosensitive drum 1 is transferred to a transfer material P supplied at a predetermined timing from a paper feed cassette (not shown) by a transfer means 5 such as a transfer roller. The unfixed toner image transferred onto the transfer material P is
The recording medium is heated and pressed by the fixing unit 6 and is permanently fixed to the transfer material P. Thereafter, the transfer material P is discharged out of the image forming apparatus.

On the other hand, the toner and paper dust remaining on the photosensitive drum 1 at the time of transfer are removed by the cleaning means 7, and the photosensitive drum 1 is subjected to the next image forming process.

[0007]

In the image forming apparatus having the above-described structure, the potential distribution formed by the electrostatic charge image on the photosensitive drum 1 depends on the electrode effect of the developing sleeve 42 and the photosensitive drum 1 and the developing sleeve 5. Becomes sharpest at the closest position of, and becomes broader as the distance between SD becomes longer. Therefore, the actual output image reflects not the sharp potential distribution near the nip but the broad potential distribution at the limit position where the toner can fly, making it difficult to obtain a high-resolution image. .

On the other hand, with the spread of digital images in recent years,
Improvement in the reproducibility of dot images is required, but for that purpose, it is necessary to end the developing process at the closest position between the photosensitive drum and the developing sleeve, where the potential distribution is sharper.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of obtaining a high-resolution output image by intensively performing a developing process at a nip position of a developing sleeve where a potential distribution is sharpest. It is to be.

[0010]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
Image carrier, charging means for uniformly charging the image carrier,
An image forming apparatus comprising: an exposure unit that exposes the charged image carrier to form an electrostatic latent image; and a developing unit that attaches toner to the electrostatic latent image to form a toner image. An image forming apparatus is characterized in that a spatial range in which development is performed is limited. According to an embodiment of the present invention, the developing unit includes a developer carrier for supporting and transporting the developer, and the developer carrier has a conductive member partially disposed on an insulating member. Formed by
Preferably, the conductive member is arranged at a position closest to the image carrier.

According to a preferred embodiment of the present invention, the developing means includes a developer carrier for supporting and transporting the developer, and the developer carrier includes a fixedly disposed insulating cylindrical member. A developing area defining member provided on the cylindrical member and arranged in parallel with the image carrier at a position closest to the image carrier and made of a conductive material; An endless conductive film that stretches and rotates on the outer peripheral surface of the component member and carries and transports the developer,
Having.

According to another preferred embodiment of the present invention,
The developing means includes a developer carrying member for carrying and transporting a developer, and the developer carrying member is provided with an endless conductive film that carries and transports the developer, and a developer carrier that is closest to the image carrier. A cylindrical or elliptical developing area defining member made of a conductive material, having a curved portion disposed in a position parallel to the image carrier and having a curvature having a greater curvature than the image carrier; And at least one columnar member for stretching the conductive film in cooperation with the columnar development area defining member.

According to another preferred embodiment of the invention,
The developing means includes a developer carrier for supporting and transporting the developer, and the developer carrier is separated from the rotating insulating cylindrical member by a predetermined width on the outer peripheral surface of the cylindrical member. And a developing area defining member, which is made of a conductive material and is held in a floating state, is provided on the image carrier. An electric current is applied to the developing area defining member that comes near to apply a developing bias.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 The image forming apparatus of the present invention can be the electrophotographic image forming apparatus described above with reference to FIG.

That is, also in this embodiment, the image forming apparatus has a drum-shaped electrophotographic photosensitive member rotatably supported, that is, a photosensitive drum 1, as schematically shown in FIG. The photosensitive drum 1 is charged to a predetermined potential by the charging unit 2 and is exposed to a desired pattern by the exposure unit 3.
An electrostatic charge image is formed on the surface of the photosensitive drum. This electrostatic charge image forms a toner image by the developing unit 4.

More specifically, the photoreceptor drum 1 may be a photoreceptor having a support such as aluminum as a lowermost layer, and may be a function-separated type having a charge generation layer and a charge transport layer, or a charge transfer layer. A single layer type in which the generation layer and the charge transport layer are the same layer can be used. As the charge generation layer, for example, selenium-tellurium, pyrylium-based pigments, phthalocyanine-based pigments, azo pigments, and the like can be used. As the charge transport layer, poly-N-
A high molecular compound having a heterocyclic or condensed polycyclic aromatic such as vinylcarbazole or polystyreneanthracene, or a low-molecular heterocyclic compound such as pyrazoline, imidazole or oxazole can be used.

As the charging means 2 used for the primary charging, a non-contact type using a corona charger or a contact type using a charging roller as shown in the figure can be used.

The exposure means 3 is a scanner type combining a semiconductor laser with a lens and a rotating mirror,
Exposure means such as a binary recording method using ON / OFF of a laser and a PWM method in which each pixel is time-resolved to form a halftone by using a line type in which an optical shutter is combined with D and the like can be used.

As the developing means 4, toner particles charged by a charging means such as frictional charging are restrained on a developing sleeve 42 as a developer carrier by a mechanical force, and are brought into non-contact with the photosensitive drum 1. An electric field may be applied to the arranged developing sleeve 42 to fly toner particles and form a toner image corresponding to the potential distribution or the electric field distribution on the photosensitive drum.

Since the configuration and operation of the image forming apparatus of the present invention having the above configuration are as described above, further detailed description will be omitted, and the characteristic portions of the present invention will be described in detail.

First, a principle for outputting a high-resolution image in the image forming apparatus of the present invention will be described with reference to FIGS.

In FIG. 2, the electrostatic charge image C present on the surface of the cylindrical electrophotographic photosensitive member, that is, the photosensitive drum 1 is
Corresponding to the distance (G) between S and D determined by the relationship of curvature with the developing sleeve 42 which is the opposite electrode, as shown in FIG. 3, a different potential distribution (E) depending on the position from the nip.
To form In a developing method using an electric field as a driving force, the potential distribution or the electric field distribution on the surface of the photosensitive drum is directly reflected on the toner image on the photosensitive drum 1 to determine the quality of an output image.

Therefore, the present invention restricts the spatial range in which development is performed, that is, concentrates development at the position where the potential distribution is sharpest in the vicinity of the nip, so that a sharp potential distribution is obtained. High-resolution images can be output by reflecting the results in the development process.

FIG. 4 shows a configuration near the nip of a developing area in which the image bearing member constructed according to the present embodiment, that is, the photosensitive drum 1 and the developing means 4 are arranged to face each other.

According to the present invention, in the present embodiment, the developer carrier 42 has an insulating cylindrical member 43 fixedly disposed, and the cylindrical member 43 is provided at a position closest to the photosensitive drum 1. A developing area defining member 45 extending linearly along the longitudinal direction of the cylindrical member 43 in parallel with the photosensitive drum 1 and made of a conductive material is provided. The outer surface 45a of the developing area defining member 45 facing the photoconductor drum 1 is formed in a curved shape, and has a larger curvature than the photoconductor drum 1. In this embodiment, the photosensitive drum 1 has a diameter of 3 cm, and the cylindrical member 43 is made of a synthetic resin having a diameter of 1 to 3 cm, specifically, polyester, polycarbonate, polyamide, or the like. Set the radius of the curved portion to 0.
SUS (or aluminum,
(Brass).

A conductive film 44 is disposed on the outer peripheral surfaces of the cylindrical member 43 and the developing area defining member 45. The conductive film 44 rotates in the direction of the arrow, carries the developer (toner) contained in the developing container 41, and transports the developer toward the photosensitive drum 1. In this embodiment, a magnetic one-component toner was used as a developer. As the conductive film 44, natural rubber, butadiene rubber having a thickness of 0.3 to 3 mm,
A film mixed with carbon black using isoprene rubber or resin as a binder component can be suitably used. A developing bias of a predetermined magnitude is applied to the developing area defining member 45, and the toner conveyed by the conductive film 44 flies to the photosensitive drum 1 and The electrostatic charge image is developed into a toner image.

According to this embodiment, the curvature of the developing sleeve 42 near the nip can be increased by providing the developing area defining member 45 on the cylindrical member 43 of the developer carrying member 42 located in the developing area. . Therefore, in this embodiment,
By limiting the spatial range in which development is performed, the development process can be intensively performed near the nip, and the development process can be terminated at a position where a sharp potential distribution can be obtained. Can be output.

Embodiment 2 FIG. 5 shows a schematic configuration of an image forming apparatus according to a second embodiment of the present invention. According to the present embodiment, the developing unit 4 applies the developing area defining member 45 formed of a columnar conductive material whose diameter is smaller than that of the photosensitive drum 1 to a position closest to the photosensitive drum 1. The photosensitive drum 1 is arranged parallel to the body drum 1 in the longitudinal axis direction. In this embodiment, the development area defining member 45 is made of SUS (or aluminum or brass) having a diameter of 0.2 to 1 cm.

The developing means 4 further includes the developing area defining member 4
5 and columnar members 46 and 47 arranged in a triangular shape with the member 45, and around the developing area defining member 45 and the cylindrical members 46 and 47. A conductive film 44 similar to that used in Example 1 was stretched, and the conductive film 44 was configured to rotate in the direction of the arrow.

In the present embodiment, a developing container 41 containing toner is provided adjacent to the columnar member 46, and supplies the toner to the conductive film 44. The conductive film 44 carries the toner, transports the toner toward the photosensitive drum 1, and applies a developing bias to the developing area defining member 45 to fly the toner on the film toward the photosensitive drum 1. Then, a developing process is performed.

Also in this embodiment, the spatial range in which development is performed is limited by increasing the curvature of the toner transport film near the nip by providing the development area defining member 45 located in the development area. , The developing process can be performed intensively in the vicinity of the nip, the developing process can be terminated at a position where a sharp potential distribution can be obtained, and a high-resolution image can be output.

Third Embodiment FIG. 6 shows a schematic configuration of an image forming apparatus according to a third embodiment of the present invention. According to the developing means of the present embodiment,
, The developing area defining member 45 formed of an elliptical conductive material is used instead of the developing area defining member 45 formed of a cylindrical conductive material disposed closest to the photosensitive drum 1. A member 45 is arranged parallel to the longitudinal axis direction of the photosensitive drum 1. At this time, the elliptical member 45 is arranged such that the end of the elliptical member 45 having a large curvature is located closest to the photosensitive drum 1.

The developing means 4 further includes, similarly to the second embodiment,
The image forming apparatus further includes columnar members 46 and 47 arranged in parallel with the developing area defining member 45 and in a triangular shape with the developing area defining member 45. The developing area defining member 45 and the cylindrical members 46 and 47 are provided.
The conductive film 44 similar to that of the first embodiment is stretched around the conductive film 44, and the conductive film 44 is rotated in the direction of the arrow.

Also in the present embodiment, a developing container 41 containing toner is provided near the columnar member 46, and supplies toner to the conductive film 44. Conductive film 4
4 carries the toner and transports it toward the photosensitive drum 1;
By applying a developing bias to the developing area defining member 45, the toner on the film 44 flies toward the photosensitive drum 1 to perform a developing process.

Also in this embodiment, the developing area defining member 45 which is located in the developing area and is made of a conductive material having a large curvature is used.
By increasing the curvature of the toner transport film 44 in the vicinity of the nip, the spatial range in which development is performed can be limited, and the development process can be intensively performed in the vicinity of the nip. The development process can be terminated at the position where is obtained, and a high-resolution image can be output.

Embodiment 4 FIG. 7 shows a schematic configuration of an image forming apparatus according to a fourth embodiment of the present invention. The developing means 4 of the present embodiment is a circle arranged in parallel with the developing area defining member 45 disposed closest to the photosensitive drum 1 in the second embodiment, and furthermore, forming a triangle with the member 45. Instead of the columnar members 46 and 47, one columnar member 46 is disposed on the side opposite to the photosensitive drum 1, and the developing area defining member 45 and the columnar member 4 are arranged.
6, a conductive film 44 similar to that of the first embodiment is stretched, and the conductive film 44 is rotated in the direction of the arrow.

In this embodiment, a developing container 41 containing toner is provided near the columnar member 46, and supplies toner to the conductive film 44. The conductive film 44 carries the toner, is conveyed toward the photosensitive drum 1, and applies a developing bias to the developing area defining member 45 to transfer the toner on the film 44 toward the photosensitive drum 1. And the developing process.

Also in this embodiment, the spatial range in which development is performed is limited by increasing the curvature of the toner transport film near the nip by providing the development area defining member 45 located in the development area. , The developing process can be performed intensively in the vicinity of the nip, the developing process can be terminated at a position where a sharp potential distribution can be obtained, and a high-resolution image can be output.

Embodiment 5 FIG. 8 shows a schematic configuration of an image forming apparatus according to a fifth embodiment of the present invention. In the developing means 4 of the present embodiment, the developer carrier 42 opposed to the photosensitive drum 1 includes a cylindrical member 43 made of an insulating material, and the outer peripheral surface thereof has a photosensitive drum. A plurality of developing area defining members 45 made of a conductive material and extending in the longitudinal axis direction of the photosensitive drum 1 are provided in parallel with the photosensitive drum 1. In the present embodiment, the cylindrical member 43 is made of a synthetic resin such as polyester, polycarbonate, or polyamide, and has an outer diameter of 1 to 3 cm. Also, the developing area defining member 45
Was made of SUS (or aluminum or brass), the width W was 0.5 to 3 mm, and good results could be obtained by providing the outer periphery of the cylindrical member 43 at intervals of 0.5 to 2 mm.

According to the present embodiment, each of the conductive developing region defining members 45 is maintained in a floating state, and only the developing region defining member 45 which has reached the closest position to the photosensitive drum 1 is maintained.
, And a developing bias of a predetermined magnitude is applied. Therefore, when the toner carried by the developer carrying member 42 and conveyed toward the photosensitive drum 1 reaches the position closest to the photosensitive drum 1, a developing bias is applied to the developing area defining member 45. As a result, it flies toward the photosensitive drum 1 and performs a developing process.

Also in this embodiment, by applying a developing bias only to the developing area defining member 45 which has reached the closest position to the photosensitive drum 1, the spatial range in which development is performed is limited. The development process can be performed intensively near the nip, and the development process can be terminated at a position where a sharp potential distribution can be obtained, so that a high-resolution image can be output.

In each of the above embodiments, the image bearing member 1 is described as a photosensitive drum, but the same result can be obtained with a belt-shaped photosensitive member.

[0044]

As described above, the image forming apparatus of the present invention comprises an image carrier, charging means for uniformly charging the image carrier, and exposing the charged image carrier to form an electrostatic latent image. In an image forming apparatus including an exposing unit for forming a toner image and a developing unit for forming a toner image by attaching toner to an electrostatic latent image, the spatial range in which development is performed is limited. The development process can be performed intensively at the nip position of the developing sleeve where the potential distribution is the sharpest, and an output image with higher resolution can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating a configuration of a developing space formed by a photosensitive drum and a developer carrier.

FIG. 3 is a diagram showing a potential distribution generated on the surface of a photosensitive drum in a developing space formed by the photosensitive drum and a developer carrier.

FIG. 4 is a schematic configuration diagram of an embodiment of a developing unit configured according to the present invention.

FIG. 5 is a schematic configuration diagram of another embodiment of a developing unit configured according to the present invention.

FIG. 6 is a schematic configuration diagram of another embodiment of a developing unit configured according to the present invention.

FIG. 7 is a schematic configuration diagram of another embodiment of a developing unit configured according to the present invention.

FIG. 8 is a schematic configuration diagram of still another embodiment of a developing unit configured according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier (photoreceptor drum) 2 Charging means 3 Exposure means 4 Developing means 41 Developing container 42 Developer carrier 43 Insulating cylindrical member 44 Conductive film 45 Developing area defining member 46, 47 Columnar member

Claims (6)

[Claims] 1. An image carrier, a charging unit for uniformly charging the image carrier, an exposure unit for exposing the charged image carrier to form an electrostatic latent image, and the electrostatic latent image An image forming apparatus comprising: a developing unit configured to form a toner image by attaching toner to the image forming apparatus; wherein a spatial range in which development is performed is limited. 2. The image forming apparatus according to claim 1, wherein the developing unit includes a developer carrier for carrying and transporting the developer, and the developer carrier is formed by partially disposing a conductive member on an insulating member. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 2, wherein the conductive member is arranged at a position closest to the image carrier. 4. The image forming apparatus according to claim 1, wherein the developing unit includes a developer carrier for supporting and transporting the developer, and the developer carrier is formed between a fixedly arranged insulating cylindrical member and the image carrier. At the contact position, the developing member is provided on the cylindrical member so as to be parallel to the image carrier, and is formed on the outer peripheral surface of the developing region defining member made of a conductive material. 2. The image forming apparatus according to claim 1, further comprising: an endless conductive film that is disposed and rotated to carry and transport the developer. 5. The developing means includes a developer carrier for carrying and transporting a developer, the developer carrier having an endless conductive film for carrying and transporting the developer, and the image carrier. A cylindrical or elliptical shape made of a conductive material, which is arranged in parallel with the image carrier at a position closest to the body, and has a curved portion having a larger curvature than the image carrier. 2. The developing area defining member according to claim 1, further comprising: a developing area defining member; and at least one cylindrical member for stretching the conductive film in cooperation with the cylindrical developing area defining member. Image forming device. 6. The developing means includes a developer carrier for supporting and transporting the developer, the developer carrier having a rotating insulating cylindrical member, and a predetermined width formed on an outer peripheral surface of the cylindrical member. A plurality of developing region defining members, which are arranged apart from each other and extend along the longitudinal direction of the cylindrical member and are made of a conductive material and held in a float state, 2. The image forming apparatus according to claim 1, wherein a current is applied to the developing area defining member closest to the image carrier to apply a developing bias.