JP2002162824A - Developing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of reducing the variance of image density in the longitudinal direction of a latent image carrier as compared with that in a conventional manner by suppressing so that a distance between a developer carrier and the latent image carrier at both longitudinal end parts of the developer carrier may differ from that at the central part of the developer carrier and to provide an image forming device using the developing device. SOLUTION: As for the developing device provided with the developer carrier 71 for carrying the developer and supplying the developer to the latent image on the latent image carrier 1, and at least one abutting member 73 and 74 coming into contact with the developer carrier, the abutting members are arranged in contact with the developer carrier so as to eliminate distortion generated in the longitudinal center part of the developer carrier.

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 a printer, a copying machine, a facsimile and the like.

[0002]

2. Description of the Related Art FIG. 5 is a schematic configuration diagram of a developing device 107 using a one-component non-magnetic developer (hereinafter, toner) according to a conventional example. The developing device includes a photoconductor 10 as a latent image carrier.
A developing tank portion 108 which is open to the first and contains toner therein; and a developing roll 109 provided in the opening portion
And agitator members 110 and 111 provided in the developing tank unit to convey the toner to the developing roll 109 side;
9, and is supplied to the developing roll 109 by contacting the developing roller 109 with a toner supply roll 112 for supplying toner to the developing roll 109 and a developing roller 109 at a position upstream of the developing region facing the photoconductor in the rotation direction. A thin-layer blade 113 for forming the toner into a certain amount of toner layer. A toner supply roll 112 as a developer supply member and a thin layer blade 113 as a developer regulating member for forming toner in a certain amount of toner layer are supplied to the development roll 109 at a predetermined pressure.
It is arranged in contact with

[0003]

The above-mentioned developing roll 109
Tries to deflect under its own weight in the direction of gravity so that its central part falls down. The magnitude and direction of the deflection to be caused by its own weight are shown in the figure as a vector V1. Also,
By the contact pressures P2 and P3 of the toner supply roll 112 and the thin layer blade 113 which are in contact with the developing roll 109, the developing roll is caused to bend in a direction opposite to the contact direction. The magnitude and direction of the deflection to be caused by these are shown in the figure as V2 and V3. Due to these causes, the central portion of the developing roll 109 is deflected by the combined vector V of V1, V2, and V3. In the illustrated conventional device, the composite vector V has a component VG of a distance method between the developing roll 109 of the developing device 107 and the photoconductor. As a result, the developing gap at the center of the developing roll 109 becomes narrower by VG than the developing gaps at both ends.

The image width is about 350 m corresponding to the A3 vertical width.
With a developing roll of m, the deflection is insignificant. However, recent printers and copiers have become wider,
There is a demand for miniaturization, and the width of developing devices and developing rolls has been increased.
A smaller diameter is required. The deflection at the center of the wide developing roll is considered with an equal load distribution. For example, a diameter of 30 mm,
A developing roll made of a stainless steel pipe material having a length of 970 mm is bent by its own weight at a central portion of about 0.04 mm. When the contact pressure of the thin layer blade is 50 g / cm, the deflection of the central portion of the developing roll due to the contact pressure of the thin layer blade is about 0.19 mm. Set the contact pressure of the toner supply roll to 6
If it is 0 g / cm, the central part of the developing roll will be bent about 0.22 mm. Therefore, in the configuration shown in FIG. 5, the deflections of the three members are combined, so that the central portion of the developing roll 109 is bent by about 0.3 mm in the V direction, and the center of the developing roller 109 is shifted by about 0.1 mm in the direction of the photoconductor. The developing gap of the portion fluctuates.

Further, the developing device is pressed in the direction of the photoreceptor, a gap holding member having an outer diameter slightly larger than that of the developing roll provided coaxially with the developing roll is brought into contact with the photoreceptor, and the developing gap is set at a predetermined distance. In the non-contact non-magnetic one-component developing device, the developing roll tends to bend because the pressure applied to the developing device is applied to the developing roll shaft. For example, when the shaft of the developing roll is attached to both side walls of the developing tank via bearings and the developing tank itself is urged toward the photoconductor,
If the spacing member is attached to the developing roll shaft axially inside the side walls, the developing roll tends to bend so that the central portion of the developing roll is separated from the photoconductor. Conversely, if the spacing member is attached to the developing roller shaft at an axially outer side of the side wall portions, the developing roller tends to bend so that the central portion of the developing rule approaches the photoconductor.

[0006] Because of the various forces acting on the developing roll including the above-described attractive force, the developing roll bends so that the distance between the developing roll at both ends and the center of the developing roll is different from the photosensitive drum. The gap differs between both ends and the center of the developing roll. As a result, the density of the image varies depending on the size of the developing gap. Non-contact non-magnetic one-component developing device Since the development gap is 0.1 to 0.3 mm, the width of the non-contact non-magnetic one-component developing device is increased,
Miniaturization is difficult. Further, even in a one-component developing apparatus in which a developing roll and a photoreceptor are brought into contact with each other to perform development, since the contact pressure between the two is different at both ends of the developing roll and at the center, there is a possibility that the density of the image may vary. is there. Furthermore, even in a developing device using a two-component developer, the distance between the developing roll and the photoconductor is different at both ends and the central portion of the developing roll, regardless of whether the system is a contact or non-contact system. There is a possibility that shading will occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object the distance between the developer carrier and the latent image carrier at both ends and the center in the longitudinal direction of the developer carrier. It is an object of the present invention to provide a developing device and an image forming apparatus using the same, which can suppress the occurrence of a difference in image density and reduce the density of image density in the same direction as compared with the related art.

[0008]

According to one aspect of the present invention, there is provided a developer carrying member for carrying a developer and supplying the latent image to a latent image on the latent image carrying member. In a developing device having at least one contact member that comes into contact with the body, the corresponding contact member is disposed in contact with the developer carrier so as to cancel a deflection generated in a central portion in a longitudinal direction of the developer carrier. It is characterized by having done. Claim 2
The present invention relates to a developing device having a developer carrier that carries a developer and supplies the latent image to the latent image carrier, and at least one contact member that contacts the developer carrier. The direction of deflection occurring at the center in the longitudinal direction of the body is within 30 degrees with respect to the direction perpendicular to the distance direction between the latent image carrier and the developer carrier. The contact member is provided in contact with the contact member. According to a third aspect of the present invention, in the developing device according to the first or second aspect, the contact member rotationally rubs the developer carrier to supply a one-component non-magnetic developer;
It is a developer regulating member that comes into contact with the developer carrier and regulates the developer. According to a fourth aspect of the present invention, in the developing device of the first, second, or third aspect, the developer carrier that contacts the surface of the latent image carrier to maintain an interval between the surface of the latent image carrier and the developer carrier. A gap holding member having a diameter larger than the body is provided at both ends coaxial with the developer carrying member, and a pressurizing means for pressing the shaft toward the latent image carrier is provided. A longitudinal center portion of the developer carrier, including a bending force of the developer carrier caused by a positional deviation in the axial direction from a point of application of a drag from the latent image carrier received via the spacing member; The bending direction occurring at the central portion in the longitudinal direction of the developer carrier is within 30 degrees with respect to the direction perpendicular to the distance direction between the latent image carrier and the developer carrier. The relevant contact member is brought into contact with the developer carrier so that It is characterized in that the. According to a fifth aspect of the present invention, in the developing device of the first, second, third or fourth aspect, an alternating electric field is used at the time of development. According to a sixth aspect of the present invention, there is provided an image forming apparatus having a latent image carrier and a developing device for developing a latent image formed on the latent image carrier. Or 5
Wherein the developing device is used.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine as an image forming apparatus will be described below. FIG. 1 is a cross-sectional view illustrating a schematic configuration of the electrophotographic copying machine according to the embodiment. This image forming apparatus has two developing devices that use different toner colors, and can form an image of two colors. The reversal developing method (N / P developing method) is also used for image formation for two colors. More specifically, a photosensitive member 1 as an image carrier that is uniformly charged negatively
An electrostatic latent image is formed on the surface by laser exposure, and development is performed with negatively charged toner.

The image of the original placed on the original placing table is 1
A portion of the same color as the color toner (for example, a black portion) and a portion of the same color as the second color toner (for example, a red portion) are separately and simultaneously separated via a filter by the two image pickup devices (C
CD) 13. Black image signal 131 and red image signal 13 from each image pickup device
2 is sent to the image memory / control units 13a and 13b.

The photosensitive member 1 driven to rotate in the direction of arrow A in FIG. 1 is uniformly charged to approximately -900 V by a first scorotron charger 2 as a first charging means. Then, an electrostatic latent image is formed on the surface of the photoconductor 1 by the laser writing device 3 as the first exposure unit with respect to the black portion of the document determined by the reading device 13. The potential of the electrostatic latent image is -100V. The electrostatic latent image on the photoconductor 1 is
At a portion opposed to the first developing device 4 having black toner, the negative polarity toner in the developer is supplied from the developing rolls 41 and 42 of the first developing device 4 to form a toner image by a two-component magnetic brush developing method. I do. The developing bias of the first developing device is -550V.

Subsequently, the process proceeds to an image forming process for a second color.
Is recharged. Then, with respect to the red portion read by the reading device 13, a second color electrostatic latent image is formed on the surface of the photoreceptor by the LED array 6 as the second exposure means. The potential of the electrostatic latent image of the second color also becomes -100V. This electrostatic latent image is subjected to non-contact development by the second developing device 7 having red toner, which is a one-component non-magnetic toner, to form a toner image. The developing gap of the second developing device is 0.1 m
m to 0.3 mm, and the developing bias is a DC bias of -750 V or an AC bias capable of superimposing development. The black toner image portion of the first color is
Is higher than the electrostatic latent image of the second color image, so that mixing of the black toner image and the red toner image is prevented.

The toner images of the two colors formed on the photoconductor 1 are transferred by a registration roll 19 at a nip portion where a dielectric belt 21 of a transfer device 20 as a transfer unit is in contact with the photoconductor 1. At the same time, the toner image is transferred onto the transfer paper conveyed in the direction of arrow B in FIG. 1, and then conveyed to the fixing device 10, where the toner image on the transfer paper is fixed. After the fixing, the transfer paper is discharged out of the image forming apparatus.
The toner remaining on the photoreceptor 1 after the transfer of the toner image is scraped off by a cleaning brush roll 81 and a cleaning blade 82 of the cleaning device 8 and collected in the cleaning device 8. Further, the residual charge is removed from the surface of the photoreceptor 1 after cleaning by the charge removing lamp 9 to prepare for the next image formation.

FIG. 2 shows the area around the developing roll 71 of the developing device 7 for the second color. The developing device 7 for the second color is a one-component non-magnetic developing device. The developing roll 71 is a cylindrical member made of metal such as aluminum or stainless steel. In the case of the present embodiment, the developing roll 71 has an outer diameter of φ30 and a thickness of 1.5.
A stainless steel pipe having a length of 970 mm and a length of 970 mm was used. The toner is supplied to the developing roll 71 by being rubbed and rotated by a rotatable toner supply roll 74 which is in pressure contact with the developing roll 71. The toner supply roll 74 is formed by winding an elastic member such as foamed polyurethane around a metal core. In front of the developing area of the developing roll 71, there is a thin layer blade 73 provided so as to contact the developing roll 71. The thin layer blade 73 is made of an elastic metal plate or urethane rubber, and regulates the amount of toner on the developing roller 71 to a constant value. The toner supply roll 74 and the thin layer blade 73 are disposed so as to be substantially opposed to each other with the development roll 71 as a center.

The central portion of the developing roller 71 has V due to its own weight.
1 deflection, by the contact pressure P2 of the toner supply roll 74,
The central portion of the developing roll 71 bends by V2. Further, due to the contact pressure P3 of the thin layer blade 73, the central portion of the developing roll 71 is V
3 bends. For example, the components are arranged and arranged as shown in the figure, and the contact pressure P2 of the toner supply roll 74 is set to about 40 gf / cm.
When the contact pressure P3 of the thin layer blade 73 was set to about 30 gf / cm, the resultant deflection V at the center of the developing roll 71 was V = V1.
+ V2 + V3 = 0. Therefore, the developing roll 71
A developing gap D, which is a gap between the developing roller 71 and the photosensitive member 1, is equal at both ends and the center of the developing roll 71.

[Modification 1] FIG. 3 shows the periphery of the developing roll 71 of the developing device 7 for the second color according to a modification. The components are the same as described above. As shown in FIG.
4 and the thin layer blade 73 are arranged so as to be substantially opposed to each other with the developing roller 71 as a center. The central portion of the developing roll 71 is bent by V1 due to its own weight, and the central portion of the developing roll 71 is bent by V2 due to the contact pressure P2 of the toner supply roll 74. Further, the central portion of the developing roll 71 is bent by V3 due to the contact pressure P3 of the thin layer blade 73. For example, the components are arranged as shown in the figure, and the contact pressure P2 of the toner supply roll 74 is set to about 3
0 gf / cm, the contact pressure P3 of the thin blade 73 is about 60
At gf / cm, the combined deflection V (= V1 + V2 + V3) at the center of the developing roll 71 was 90 degrees with respect to the line connecting the developing roll 71 and the center of the photosensitive member 1 as shown in the figure. For this reason, the developing gap D, which is the gap between the developing roll 71 and the photoconductor 1, was substantially equal at both ends and the center of the developing roll 71.

[Modification 2] FIG. 4 shows a developing device 7 for a second color according to another modification. The components are the same as described above. As shown, the toner supply roll 74 and the thin layer blade 7
Reference numeral 3 is disposed so as to be substantially opposed to the developing roller 71 as a center. The developing device 7 is pressed in the direction of the photoconductor 1 by a pressing member 75 as a pressing unit of the image forming apparatus main body. The pressing member 75 is made of an elastic metal leaf spring member. Rollers 72 are provided on both end shafts of the developing roll 71 as coaxial rotatable members that are rotatable with the developing roll 71. The outer diameter of the roller 72 is slightly larger than the outer diameter of the developing roller 71, and when the developing device 7 is pressed in the direction of the photoconductor 1, the roller 72 hits the photoconductor. The developing gap, which is the gap between the developing roller 71 and the photoconductor 1, is determined by the rollers 72. The roller 72 is made of a resin material having a sliding property with respect to both the shaft and the photoconductor surface.

Due to the pressure P4 applied by the pressing member 75, the developing roll 71 bends by V4 in a direction in which the center of the developing roll 71 is separated from the photosensitive member. This is the developing roll 71
This is because the shaft is mounted on both side walls of the developing tank via bearings, and the roller 72 is mounted on the developing roll shaft axially inside the side walls. And
As in the above-described embodiment, the central portion of the developing roll 71 is bent by V1 due to its own weight, and the contact pressure P2 of the toner supply roll 74 is changed.
As a result, the central portion of the developing roll 71 is bent by V2. Further, the central portion of the developing roll 71 is bent by V3 due to the contact pressure P3 of the thin layer blade 73. For example, the components are arranged and arranged as shown in the figure, and the contact pressure P2 of the toner supply roll 74 is set to about 30 gf.
/ Cm, the contact pressure P3 of the thin layer blade 73 is about 60 gf /
cm, the combined deflection V (= V1 + V2 + V3 + V4) at the center of the developing roll 71 was 90 degrees with respect to the line connecting the developing roll 71 and the center of the photosensitive member 1 as shown in the figure. For this reason, the developing gap D, which is the gap between the developing roll 71 and the photoconductor 1, was substantially equal at both ends and the center of the developing roll 71. If the angle is set in the range of ± 30 degrees with respect to the 90-degree direction, preferably in the range of ± 15 degrees, and more preferably in the range of ± 5 degrees, better results can be obtained as compared with the related art.

For example, as shown in FIG. 4, by using an AC bias capable of superimposing the developing bias applied to the developing roll 71, the density unevenness can be largely reduced. In order to prevent the black toner image of the first color from being disturbed, the AC bias capable of superimposing development has a frequency of 500 Hz to 2 KHz with an amplitude of -500 V to -1500 V, and a duty ratio at which the toner tries to travel to the photoconductor 1 at a duty ratio of 50. % Or less is desirable.

[0020]

According to the first to sixth aspects of the present invention, the developer carrying member has no bending, the developing gap with the image carrying member is uniform at both ends and the center in the longitudinal direction, and the developing efficiency is stabilized. Image density unevenness can be suppressed. Alternatively, since the bending direction generated at the central portion in the longitudinal direction of the developer carrier is substantially perpendicular to the direction of the distance between the image carrier and the developer carrier, even if the amount of deflection at the central portion of the developer carrier is large. In addition, the fluctuation of the developing gap between both ends and the center of the developer carrier can be reduced. Therefore, unevenness in image density in the longitudinal direction of the developing carrier can be suppressed, and the width and size of the apparatus can be reduced. In particular, according to the fifth aspect of the invention, when developing the latent image on the image carrier, the latent image is developed while forming an alternating electric field by using, for example, an oscillating bias voltage obtained by superimposing an AC voltage on a DC voltage. A high-definition image with no image is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment.

FIG. 2 is an explanatory diagram of a developing device of the copying machine.

FIG. 3 is an explanatory diagram of a developing device according to a modification.

FIG. 4 is an explanatory diagram of a developing device according to another modification.

FIG. 5 is an explanatory view of a conventional example.

[Explanation of symbols]

 1 Photoconductor 71 Developing Roll 72 Roller 73 Thin Blade 74 Toner Supply Roll 75 Pressing Member

Claims (6)

[Claims] An image forming apparatus comprising: a developer carrying member for carrying a developer and supplying the latent image to a latent image carrier; and at least one contact member contacting the developer carrying member. A developing device, wherein a corresponding contact member is abutted against a developer carrier so as to cancel a deflection generated at a central portion in a longitudinal direction of the carrier. 2. A developing apparatus comprising: a developer carrier for carrying a developer and supplying the latent image to a latent image carrier; and at least one contact member abutting on the developer carrier. The direction of deflection occurring at the center in the longitudinal direction of the carrier is within 30 degrees with respect to the direction perpendicular to the distance direction between the latent image carrier and the developer carrier. A developing device, wherein the contact member is disposed in contact with the contact member. 3. A developing device according to claim 1, wherein said contact member is a developer supply member for supplying a one-component non-magnetic developer by rotating and rubbing said developer carrier. A developing device, which is a developer regulating member that contacts the body to regulate the developer. 4. The developing device according to claim 1, wherein:
A gap holding member having a diameter larger than that of the developer carrying member that is in contact with the surface of the latent image carrying material and maintains a distance between the surface of the latent image carrying material and the developer carrying member. A pressure means for pressing the shaft toward the latent image carrier, and a point of action of a pressing force by the pressure means and a point of action of a drag from the latent image carrier received via the spacing member. To cancel the bending generated at the central portion in the longitudinal direction of the developer carrying member, including the bending force of the developer carrying member caused by the positional deviation in the axial direction, or the central portion in the longitudinal direction of the developer carrying member. The contact member is brought into contact with the developer carrier so that the bending direction generated in the direction is within 30 degrees with respect to the direction perpendicular to the distance direction between the latent image carrier and the developer carrier. A developing device, wherein the developing device is disposed. 5. The developing device according to claim 1, wherein an alternating electric field is used during development. 6. An image forming apparatus having a latent image carrier and a developing device for developing a latent image formed on the latent image carrier, wherein the developing device is used as the developing device. An image forming apparatus using the developing device of (1).