JP2001343816A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where toner pooling in the vicinity of a layer thickness restricting plate can be prevented, sufficient image density can be obtained and image failure is hardly generated. SOLUTION: In the image forming device where a photoreceptor drum 1, a developing sleeve 2 and the layer thickness restricting plate 3 are provided and a toner image is formed by developing a latent image on the photoreceptor drum 1 by applying alternating bias between the photoreceptor drum 1 and the developing sleeve 2, frequency 'f' of the alternating bias and/or maximum bias difference Vpp are varied and applied to the layer thickness restricting plate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer, an FA
More particularly, the present invention relates to an image forming apparatus that forms an image using toner.

[0002]

2. Description of the Related Art A conventional image forming apparatus develops an electrostatic latent image on a photoreceptor with toner charged by a developing device to form a toner image. In general, as shown in FIG. 4, a one-component developing device includes a toner support member 22, a layer thickness regulating plate 23, a toner storage space 24, and a toner stirring rod 25. The toner which is charged by being stirred by the toner 25 and adheres to the surface of the toner supporting member 22 while forming a thin toner layer of a predetermined thickness on the layer thickness regulating plate 23 is developed on the electrostatic latent image carrier (photoconductor) 21. It can be developed by being transported to the area. At this time, an alternating bias is applied between the electrostatic latent image carrier 21 and the toner supporting member 22 to develop the latent image on the electrostatic latent image.

[0003]

However, in many conventional image forming apparatuses, conduction is established to the layer thickness regulating plate 23 in consideration of cost and toner durability. When passing through, the toner adheres to the layer thickness regulating plate 23 having the same potential as the alternating bias, and the toner stays there. The problem is that image defects such as fogging and reduced density occur due to the generation of the toner layer or the disturbance of the toner layer on the toner support member 22. It is easy to occur at the time and high temperature and high humidity environment.

[0004] Such problems are caused by devising the surface shape and material of the toner supporting member 22, forming an insulating thin layer on the toner supporting member 22 for performing alumite treatment, and developing time of an alternating bias. It is also conceivable to change the ratio of the reverse development time and
The purpose is to provide a sufficient solution.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an electrostatic latent image carrier on which an electrostatic latent image is formed, and an electrostatic latent image carrier facing the electrostatic latent image carrier. A toner supporting member for forming a thin layer of toner on the surface and transporting the toner to a developing area of the electrostatic latent image carrier; and a layer thickness regulation for forming a predetermined thin layer of toner on the toner supporting member. A toner image is formed by applying an alternating electric field between the electrostatic latent image carrier and the toner supporting member to develop a latent image on the electrostatic latent image carrier to form a toner image. In the image forming apparatus for obtaining an image by transferring an image to a transfer material, the layer thickness regulating member is made of a conductive material, and the frequency f of the alternating electric field and / or the maximum potential difference Vpp are applied to the layer thickness regulating member by changing it. Image forming apparatus.

[0006]

Embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. It's just

FIG. 1 is a schematic sectional view of an image forming apparatus showing an embodiment of the present invention. In the figure, a-Si
A charger 6, an exposure unit 7, a developing device 8 having a developing sleeve 2, a transfer roller 10, and a cleaning blade 11 are arranged around the photosensitive drum 1 (electrostatic latent image carrier) formed by the above. . The photosensitive drum 1 and the developing sleeve 7 rotate in the directions of the arrows in the figure, respectively, to form images.

An a-Si photosensitive drum 1 is charged by a charger 2.
The upper portion is uniformly charged to about +240 [V], and the exposure unit 7 forms an electrostatic latent image on the photoconductor based on image data from the outside. At this time, the photoconductor surface potential after exposure is about +10 [V].

An alternating electric field (Vdc = 160) as a developing bias is applied between the a-Si photosensitive drum 1 and the developing sleeve 2.
[V], Vpp = 1.8 [kV], f = 2.4 [kHz]) to cause the toner to jump to the exposed portion of the photoconductor to develop the toner image. FIG. 2 shows the waveform of the developing bias used in the present embodiment. Note that the alternating electric field may be any other electric field in which a DC voltage is superimposed with a rectangular, triangular, or sine wave AC component.

The developed toner image on the photosensitive drum 1 is
The image is transferred onto the recording material P by the transfer roller 10 and is fixed by a fixing device (not shown) arranged on the downstream side in the recording material conveyance direction. At this time, a negative high-voltage bias is applied to the transfer roller 10, though it differs depending on the environment, the type and resistance of the recording medium, and the like. The residual toner on the photosensitive drum 1 after the transfer is removed by the cleaning blade 11. As the toner, a positively charged magnetic toner is used, and the average particle diameter d of the toner is 5.0 to 8.0 [μm].

FIG. 3 is a diagram showing a detailed configuration of the developing device 8, which comprises a developing sleeve (toner supporting member) 2, a layer thickness regulating plate 3, a toner storage space 4, and a toner stirring rod 5, and The toner in the storage space 4 is charged by being stirred by the toner stirring rod 5, and the toner attached to the surface of the developing sleeve 2 while forming a thin toner layer of a predetermined thickness by the layer thickness regulating plate 3 Is developed by being transported to the current area.

The present invention is characterized in that a bias whose frequency f and / or maximum bias difference Vpp of the alternating bias is changed by the bias converting means 9 is applied to the layer thickness regulating plate 3, and a bias different from the alternating bias is applied to the layer thickness regulating plate 3. By applying the voltage to the regulating plate 3, the toner is jumped between the layer thickness regulating plate 3 and the developing sleeve 2 so as to eliminate toner stagnation.

For example, a bias (Vdc = 160 [V], Vpp = 1.8 [kV], f = 1.8 [kHz]) having a frequency different from the alternating bias is applied to the layer thickness regulating plate 3 of the image forming apparatus under the above conditions. The developing device A to which the applied bias, the developing device B to which the bias having the maximum bias difference different from the alternating bias (Vdc = 160 [V], Vpp = 1.5 [kV], f = 2.4 [kHz]) and the conventional developing device C ( When the printing rate was 1% and the number of printed sheets was 10,000, the image density of the developing unit A was ID 1.35, the image density of the developing unit B was ID 1.33, and development was performed. The image density of the developing device C was ID 1.03, and it was found that the developing devices A and B could obtain a sufficient image density while the developing device C had a reduced image density. In the image density ID, 0.0 means white and 1.8 means black in reflection density.

[0014]

As described above, according to the present invention, the layer thickness regulating member is made of a conductive material, and the frequency f of the alternating bias and / or the maximum bias difference Vpp are applied to the layer thickness regulating member while being changed. , The toner stagnation near the layer thickness regulating plate is prevented, and a sufficient image density can be obtained;
An image forming apparatus in which an image defect is less likely to occur can be provided.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an alternating bias used in the image forming apparatus of the present invention.

FIG. 3 is a schematic sectional view showing a developing device of the image forming apparatus of the present invention.

FIG. 4 is a diagram illustrating a conventional image forming apparatus.

[Explanation of symbols]

 1, 21: photosensitive drum (electrostatic latent image carrier) 2, 22: developing sleeve (toner support member) 3, 23: layer thickness regulating plate 4, 24: toner storage space 5, 25: stirring bar 6: charging Unit 7: Exposure unit 8: Developing unit 9: Bias conversion unit 10: Transfer roller 11: Cleaning blade

Claims (1)

[Claims] An electrostatic latent image carrier on which an electrostatic latent image is formed;
A toner support member that faces the electrostatic latent image carrier, forms a thin layer of toner on the surface, and conveys the toner to a development area of the electrostatic latent image carrier; A layer thickness regulating member for forming a thin layer, and developing an latent image on the electrostatic latent image carrier by applying an alternating bias between the electrostatic latent image carrier and the toner supporting member. Forming an image by transferring the toner image to a transfer material to obtain an image, wherein the layer thickness regulating member is a conductive member, and the layer thickness regulating member has a frequency f and And / or changing and applying the maximum bias difference Vpp.