JPH09269650A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a satisfactory image free from image irregularity resulting from shaft displacement of a developing roller and others which is caused during manufacture, or warps in them, in an image forming device for use as an output device as for computer. SOLUTION: The device is equipped with a pressure roller 29 made of a rigid material, which brings the developing roller 10 into pressure contact with a photoreceptor 1, and the shaft centers of the photoreceptor 1, developing roller 10, and pressure roller 29 are on a straight line. A bearing 30 at each end of the core metal of the pressure roller 29 is pressed by a pressure spring 31, and stops by striking against an abutting face formed on the chassis of a developing unit 5 which supports the photoreceptor 1. Thus, the pressure roller 29 made of the rigid material maintains a nip of a fixed width in its axial direction, and by pressing the entire surface of the developing roller 10 to the photoreceptor 1 uniformly on both right and left sides, a satisfactory image free of image irregularity and density irregularity can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus or an electrostatic recording apparatus, which relates to an image forming apparatus which visualizes an electrostatic latent image formed on a photosensitive member with toner.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic apparatus has mainly been a device using a dry toner, and has been put into practical use as many copying machines, laser printers, plain paper facsimiles, etc., and has made remarkable progress. This electrophotographic device is a device to which electrophotographic process technology is applied.After the electrostatic latent image formed on the photoconductor is visualized with toner particles, it is transferred to recording paper and printing is completed after the fixing process. To do.

A conventional image forming apparatus will be described below. FIG. 6 is a schematic sectional view of a conventional image forming apparatus, FIG. 7 is a plan view of the photoconductor and the developing roller, and FIG. 8 is a front view of the photoconductor showing the nip width of the photoconductor and the developing roller. . In FIG. 6, a metal drum such as aluminum is used as a base material, and a photosensitive receiving layer such as selenium (Se) or an organic photoconductor (hereinafter referred to as OPC) is applied in a thin film on the outer peripheral surface thereof to form an electrostatic latent image. The charger 2 arranged in the vicinity of the photoreceptor 1 which is an image carrier is a charging wire 2 such as a tungsten wire.
a, a metal shield plate 2b, and a grid plate 2c. The charging line 2a causes corona discharge to uniformly charge the photoconductor 1 through the grid plate 2c. The exposure light beam 4 emitted from the exposure optical system 3 is obtained by subjecting an image signal to light intensity modulation or pulse width modulation by a laser driving circuit (not shown), and forms an electrostatic latent image on the photoconductor 1.

Next, the developing device 5 will be described. The toner supply roller 6, which is a toner supply member, is provided with a toner hopper 7.
It is for supplying the toner 9 stirred and conveyed by the toner stirring member 8 which is rotatably supported at both ends to be bent and formed into a rectangular shape to the surface of the developing roller 10 which is a toner carrier. Toner supply bias power supply 11 is connected to the shaft-making part through a protective resistor 12. The layer thickness regulating blade 13 comprises a metal spring plate member 13a and a layer thickness regulating member 13b which contacts the developing roller 10, and the layer thickness regulating member 13b has an elastic member such as silicone or urethane at one end of the metal spring plate member 13a. It is integrally formed.

The developing roller 10 and the toner supplying roller 6 are
An elastic member such as urethane or silicon is formed in layers on the outer peripheral surface of a metal such as stainless steel as a base material, and is rotatably supported at both ends of the toner hopper 7. The toner stirring member 8 draws a circular locus along with the rotation of the toner supply roller 6, stirs to prevent the toner 9 contained in the toner hopper 7 from aggregating, and conveys the toner 9 to the toner supply roller 6. The toner 9 supplied from the toner supply roller 6 has its toner layer thickness regulated by the layer thickness regulating blade 13 and is triboelectrically charged to form a thin layer state on the outer peripheral surface of the developing roller 10. After that, the developing roller 10 comes into contact with or close to the photoconductor 1,
By the bias voltage applied from the developing bias power source 14, the toner 9 is transferred and adhered to the portion of the photoconductor 1 where the electrostatic latent image is formed to visualize the electrostatic latent image. The layer thickness regulation blade 13 is attached by a blade holder 15 with screws.

The recording paper 17 stored in the recording paper cassette 16 is sent from the recording paper cassette 16 one by one to a conveying roller 19 by a half-moon shaped paper feed roller 18. The fed recording paper 17 is conveyed in the direction indicated by the arrow A by the conveying roller 19. Registration roller 2
0 is provided to make the recording paper 17 and the toner image formed on the photosensitive member 1 coincident with each other, so that the recording paper 17 is temporarily stopped and waited, and is in contact with the driven roller 21. The transfer device 22 includes a transfer line 22a made of a tungsten wire or the like and a shield plate 22b made of a metal plate. When a high voltage is applied to the transfer line 22a, the transfer line 22a causes corona discharge, and the recording paper 17
The toner image on the photoconductor 1 is transferred onto the surface. The toner image transferred onto the recording paper 17 is pressed by the fixing device 25 including a heat roller 23 and a pressure roller 24 having a heat source inside, as the heat roller 23 and the pressure roller 24 are nipped and rotated. The heat fixes the recording paper 17 and the printing is completed.

The cleaner portion is composed of a cleaning blade 26 for scraping off the residual toner on the photoconductor 1 and a toner collecting container 27 for storing the scraped residual toner. A static eliminator 28 for effective cleaning is provided.

[0008]

However, in the above-described conventional structure, as shown in FIGS. 7 and 8, the nip portion of the photoconductor 1 or the developing roller 10 is deviated due to axial misalignment or bending. The hatched portion in FIG. 8) will vary, and image unevenness will occur. As described above, since the accuracy is improved so that the developing roller is not misaligned, the cost is increased. Similarly, there is a problem in that unevenness in processing due to variations in manufacturing accuracy of the charging roller and the layer-thickness regulating roller causes axial unevenness, which causes uneven charging and unevenness in the image due to uneven toner layer thickness on the developing roller. Had.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an image forming apparatus capable of obtaining a high-quality image without image unevenness.

[0010]

According to a first aspect of the present invention, there is provided a developing roller carrying a toner for developing an electrostatic latent image formed on a photoconductor, a toner hopper for storing the toner, An image forming apparatus, comprising: a layer thickness regulating member that is parallel to a developing roller and regulates a toner layer thickness of the developing roller, comprising a pressing roller that presses the developing roller against a photoconductor, and the nip portion thereof is an axis. It is constant in the direction.

According to a second aspect of the present invention, there is provided a photoconductor, a charging roller which is brought into pressure contact with the photoconductor, and a pressing roller which is brought into pressure contact with the photoconductor, and the nip portions are made constant in the axial direction. .

According to a third aspect of the present invention, there is provided an image forming apparatus including a layer thickness regulating roller which regulates the layer thickness of the toner by pressing it against the developing roller, wherein the layer thickness regulating roller is pressed against the developing roller. A pressure roller is provided, and these nip portions are made constant in the axial direction.

[0013]

According to the first aspect of the present invention, an image forming apparatus can be obtained in which a developing roller can be uniformly pressed against a photoconductor and the nip portions thereof can be made constant in the axial direction. It is possible to obtain a high quality image without unevenness and density unevenness.

According to the second aspect of the invention, it has an effect of uniformly charging the photoconductor in the axial direction and reducing unevenness of the surface potential.

According to the invention of claim 3, the toner layer thickness on the developing roller can be made uniform in the axial direction.

(First Embodiment) The first embodiment of the present invention will be described below. 1 is a schematic cross-sectional view of a developing roller and its periphery in an image forming apparatus according to Embodiment 1 of the present invention, FIG. 2 is a plan view of the same photosensitive member, developing roller and pressing roller, FIG.
FIG. 4 is a front view of the photoconductor showing the nip width between the photoconductor and the developing roller. Since the configuration other than the periphery of the developing roller is the same as that of the conventional image forming apparatus, the same reference numerals are given and detailed description will be omitted.

The photosensitive member 1 is a negative charging type OPC in which an aluminum drum is used as a base material and an organic photoconductor is applied in a thin film on the outer peripheral surface thereof. The developing roller 10 has a single-layer structure in which a metal shaft is used as a base material and silicon rubber, which is a conductive elastic member having a resistance value of 106 Ωcm, is formed on the outer peripheral surface thereof. A developing bias power source 14 is connected to the metal shaft of the developing roller 10. The developing roller 10 preferably has a rubber hardness in the range of 30 to 60 degrees, and the surface roughness is preferably 7 μmRz or less because the higher the surface smoothness is, the more uniform the toner thin layer can be formed.

The pressing roller 29 is formed of a metal roller made of a rigid material such as aluminum or SUS, and the shaft centers of the photosensitive member 1, the developing roller 10 and the pressing roller 29 are aligned with each other. Has been done. The pressure springs 31 press the bearings 30 arranged at both ends of the core metal of the pressing roller 29, and the pressing roller 29 formed of a rigid material causes the developing roller 10 to uniformly move to the photosensitive member 1 in the entire axial direction. It is configured to press with a nip width of. Therefore, as shown in FIGS. 2 and 3, the developing roller 10 is exactly pressed against the photoconductor 1 by the pressing roller 29, and the nip width (portion indicated by hatching in FIG. 3) becomes constant in the axial direction. The bearing 30 is a developing device 5 that supports the photoconductor 1.
Since it abuts on the contact surface 32 formed on the chassis of the developing roller 10 and stops, the pressing roller 29 is evenly distributed in the axial direction on the left and right sides.
The entire surface is pressed against the photoconductor 1.

Further, by roughening the surface of the pressing roller 29 by sandblasting or the like, the developing roller 10 is pressed against the photosensitive member 1 and the toner 9 is supplied to the developing roller 10 so that the toner 9 is triboelectrically charged and is not developed. It also has a function of scraping off the toner 9 remaining on the developing roller 10. The toner supply bias power source 11 is connected to the metal shaft of the pressing roller 29 via a protective resistor 12.

The layer thickness regulating roller 33 uses a silicone rubber having a resistance value of 106 Ωcm on the outer circumference of a metal shaft so that the linear pressure on the developing roller 10 is 60 to 100 g / cm, preferably 70 to 90 g / cm. Pressure is applied. Thereby, the layer thickness of the toner 9 on the developing roller 10 can be regulated with high accuracy. The layer thickness of the toner 9 on the developing roller 10 is set to 0.2 to 1.0 mg / cm ² , preferably 0.4 to 0.6 mg / cm ² . As the layer thickness exceeds 0.6 mg / cm ² , the variation in the charge amount of the toner 9 tends to increase, particularly 1.0 m.
If it exceeds g / cm ² , this tendency becomes remarkable, which is not preferable. On the other hand, if it is less than 0.4 mg / cm ² , the image density in the printed image tends to be reduced, and particularly if it is less than 0.2 mg / cm ² , the image density is rapidly reduced, which is not preferable.

The transfer unit 22 is composed of a transfer wire 22a made of a tungsten wire and a metallic shield plate 22b, and the cleaner section is composed of a cleaning blade 26 and a toner recovery container 27.

Toner 9 is a non-magnetic one-component toner,
Negatively-charged toner is used by uniformly dispersing carbon, wax, charge control agent, etc. in polyester resin. The bias voltage value of the developing bias power source 14 is -300 V, and the bias voltage value of the toner supply bias power source 11 is -400 V.
V, the resistance value of the protection resistor 12 is 22 MΩ.

The operation of the image forming apparatus configured as described above will be described. Process speed is 96mm /
sec, the peripheral speed of the developing roller 10 is 192 mm / sec
Therefore, the peripheral speed ratio with respect to the photoconductor 1 is double. The layer thickness regulating roller 29 has a linear pressure of 80 g / cm with respect to the developing roller 10.
It is fixed in contact with. The peripheral speed of the pressing roller 29 is 132 mm / sec. The rotation directions of the photoconductor 1, the developing roller 10, and the pressing roller 29 are in the directions of the arrows shown in FIG. 1, and the respective contact portions are in a frictional contact state.

The photoreceptor 1 is uniformly charged to -700 V by the charger 2, and the photoreceptor 1 is exposed to the optical system 3 according to the image signal.
By selectively exposing it with the exposure light beam 4 emitted from, the potential of the unexposed portion becomes -700V, the potential of the exposed portion becomes approximately -100V, and an electrostatic latent image is formed on the photoconductor 1. To be done.

After being stirred and conveyed by the toner stirring member 8, the toner 9 supplied to the surface of the developing roller 10 as a toner carrier and conveyed is regulated in toner layer thickness by the layer thickness regulating roller 33. Frictionally charged with
A thin layer state is formed on the outer peripheral surface of the developing roller 10. After that, the toner 9 is transferred and adhered to the portion of the photoconductor 1 where the electrostatic latent image is formed by the bias voltage applied from the developing bias power source 14 to visualize the electrostatic latent image.

Next, a voltage of 1 kV is applied to the transfer line 22a made of a tungsten wire to cause corona discharge, and the toner image on the photoconductor 1 is transferred onto the recording paper 17. The toner image transferred onto the recording paper 17 is fixed on the recording paper 17 by pressure and heat by the fixing device 25 composed of the heat roller 23 and the pressure roller 24, and the printing is completed.

(Second Embodiment) The second embodiment of the present invention will be described below. FIG. 4 is a schematic cross-sectional view of the periphery of the photoconductor of the image forming apparatus according to the second embodiment of the present invention.
Since the configuration other than the periphery of the photoconductor is the same as that of the image forming apparatus of the first embodiment, the same reference numerals are given and detailed description thereof will be omitted.

The pressing roller 29 is formed of a metal roller such as aluminum or SUS, and the shaft centers of the photoconductor 1, the charging roller 34 and the pressing roller 29 are aligned with each other. The pressure springs 31 press the bearings 30 arranged at both ends of the core of the pressing roller 29, and the pressing roller 29 formed of a rigid material causes the charging roller 34 to uniformly move to the photoreceptor 1 in the entire axial direction. It is configured to abut with a nip width of. Since the bearing 30 stops against the contact surface 32 formed on the chassis of the developing device 5 that supports the photoconductor 1, the pressing roller 29 presses the charging roller 34 against the photoconductor 1 uniformly in the left and right in the axial direction. .

Further, by roughening the surface of the pressing roller 29 by sandblasting or the like, it has a function of pressing the charging roller 34 against the photosensitive member 1 and cleaning the toner 9 adhering to the charging roller 34. Therefore, also in the second embodiment, the same operational effect as in the first embodiment can be obtained.

(Third Embodiment) The third embodiment of the present invention will be described below. FIG. 5 is a schematic sectional view around a developing roller of an image forming apparatus according to Embodiment 3 of the present invention. Since the configuration other than the periphery of the developing roller is the same as that of the image forming apparatus of the first embodiment, the same reference numerals are given and detailed description will be omitted.

The pressing roller 29 is formed of a metal roller such as aluminum or SUS, and the developing roller 10, the layer thickness regulating roller 33, and the pressing roller 29 are arranged such that their axial centers are aligned with each other. There is. The pressure springs 31 press the bearings 30 arranged at both ends of the core metal of the pressure roller 29, and the pressure roller 29 formed of a rigid material causes the layer thickness regulating roller 33 to uniformly move in the axial direction over the developing roller 10. The contact is made with a constant nip width. Since the bearing 30 comes into contact with the contact surface 32 formed on the chassis of the developing device 5 that supports the developing roller 29 and stops, the pressing roller 29 is pressed.
Means that the layer thickness regulating roller 33 is pressed against the developing roller 10 uniformly in the left and right in the axial direction. Therefore, also in the third embodiment, the same operational effect as in the first embodiment can be obtained.

By roughening the surface of the pressing roller 29 by sandblasting or the like, the layer thickness regulating roller 33 is pressed against the developing roller 10 and the layer thickness regulating roller 3 is pressed.
It also has a function of cleaning the toner 9 attached to the toner 3.

[0033]

As described above, according to the present invention, the developing roller carrying the toner for developing the electrostatic latent image formed on the photosensitive member, the toner hopper for storing the toner, and the developing roller in parallel with each other. In the image forming apparatus, which is provided with a layer thickness regulating member that regulates the toner layer thickness of the developing roller, by providing a pressing roller made of a rigid material that presses the developing roller against the photoconductor, these nip portions are axially moved. It can be kept constant, and a high-quality image without image unevenness and density unevenness can be obtained. Moreover, by roughening the surface of the pressing roller and rotating it in the same direction as the developing roller, the toner is supplied to the developing roller, and the triboelectric charging of the toner between the developing roller and the pressing roller is made uniform in the axial direction. Therefore, a stable and high-quality image can be obtained, and an image forming apparatus with improved reliability can be obtained.

Further, by providing a charging roller that is in pressure contact with the photosensitive member and a pressing roller made of a rigid material that presses the charging roller in contact with the photosensitive member, it is possible to make the nip portion of them uniform in the axial direction, and It is possible to uniformly charge in the axial direction and reduce unevenness of the surface potential.

Further, in the image forming apparatus provided with the layer thickness regulating roller which is brought into pressure contact with the developing roller to regulate the layer thickness of the toner, by providing the pressing roller made of a rigid material for bringing the layer thickness regulating roller into pressure contact with the developing roller. The nip portions can be made uniform in the axial direction, and the toner layer thickness on the developing roller can be made uniform in the axial direction.

[Brief description of drawings]

FIG. 1 is a schematic sectional view around a developing roller of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of a photosensitive member, a developing roller, and a pressing roller of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a front view of the photoconductor showing the nip width between the photoconductor and the developing roller of the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a schematic sectional view of the periphery of a photoconductor of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view around a developing roller of an image forming apparatus according to a third embodiment of the present invention.

FIG. 6 is a schematic sectional view of a conventional image forming apparatus.

FIG. 7 is a plan view of a photoconductor and a developing roller of a conventional image forming apparatus.

FIG. 8 is a front view of the photoconductor showing the nip width between the photoconductor and the developing roller of the conventional image forming apparatus.

[Explanation of reference numerals] 1 photoconductor 2 charging device 3 exposure optical system 4 exposure light beam 5 developing device 6 toner supply roller 7 toner hopper 8 toner stirring member 9 toner 10 developing roller 11 toner supply bias power supply 12 protective resistance 13 layer thickness regulating blade 14 Development Bias Power Supply 15 Blade Holder 16 Recording Paper Cassette 17 Recording Paper 18 Paper Feeding Roller 19 Conveying Roller 20 Registration Roller 21 Driven Roller 22 Transfer Device 23 Heat Roller 24 Pressure Roller 25 Fixing Device 26 Cleaning Blade 27 Toner Collection Container 28 Static Eliminator 29 Pressing roller 30 Bearing 31 Pressure spring 32 Contact surface 33 Layer thickness regulating roller 34 Charging roller

Claims (3)

[Claims] 1. A developing roller carrying a toner for developing an electrostatic latent image formed on a photoconductor, a toner hopper for storing the toner, and a toner of the developing roller positioned in parallel with the developing roller. An image forming apparatus having a layer thickness regulating member for regulating the layer thickness, comprising a pressing roller that presses the developing roller against the photoconductor, and makes the nip portion constant in the axial direction. Image forming apparatus. 2. A developing roller carrying toner for developing an electrostatic latent image formed on a photoconductor, a toner hopper for storing toner, and toner of the developing roller positioned in parallel with the developing roller. An image forming apparatus comprising a layer thickness regulating member for regulating the layer thickness, comprising: a charging roller that comes into pressure contact with the photoconductor, and a pressing roller that comes into pressure contact with the photoconductor with the charging roller, and these nip parts are provided. An image forming apparatus characterized by making it constant in the axial direction. 3. A developing roller carrying a toner for developing an electrostatic latent image formed on a photoconductor, a toner hopper for storing the toner, and a toner layer thickness regulated by being in pressure contact with the developing roller. An image forming apparatus, comprising: a layer thickness regulating roller for controlling the layer thickness regulating roller; and a pressing roller for pressing the layer thickness regulating roller to the developing roller, wherein the nip portions are made constant in the axial direction. apparatus.