JPH03170978A - Developing device - Google Patents

Abstract

PURPOSE:To obtain an image whose picture quality is satisfactory without using an expensive developer, etc. by setting a circumferential speed ratio of a photosensitive drum and a developing sleeve and a main magnetic pole angle to satisfy a specific relation. CONSTITUTION:A developing sleeve 33 is placed in parallel to a rotation axis of a photosensitive drum 20, and the developing sleeve 33 is mainly constituted of a sleeve body 35 and a magnet roll 36. The magnet roll 36 has plural fixed magnets 37 opposed to the inside peripheral surface of the sleeve body 35, and one of them is set as a main magnetic pole 38. In such a state, in a developing device 22, a peripheral speed ratio (S/D) of a circumferential speed (D) of the photosensitive drum 20 and a circumferential speed (S) of the sleeve body 35 of the developing sleeve 33, and a main magnetic pole angle (N) are set so as to satisfy a relation of 3.5<=N/(S/D)<=7.0. In such a way, by only adjusting the developing device 22, an image whose picture quality is satisfactory can be obtained, and it becomes unnecessary to use an optical system and a developer of a high cost in order to improve the picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application ￥f'J The present invention relates to a developing device, particularly an image forming device that forms an image using a photosensitive drum. This article relates to a developing device for developing latent images. [Prior art and its problems] In a 100-image forming device that forms an image using a photoreceptor drum, a developing device is used to obtain a toner image from an electrostatic latent image formed on the photoreceptor drum. It is being done. The developing device includes a developing sleeve placed close to the photoreceptor drum. The developing sleeve is equipped with a plurality of fixed magnets inside, and the magnetic force of the developing sleeve attracts the developer onto the surface and transports it to the photoreceptor drum, thereby developing the electrostatic latent image on the photoreceptor drum. ing.

In such developing devices, adjustments are made mainly on image density, so image defects such as blurring at the trailing edge of the developed image (i.e., the trailing edge in the same way the image is formed) may occur. be. As means for improving such image defects and obtaining images of good quality, for example, improvements in the optical system for reading originals and improvements in the developer used in the development device are known. However, although these methods improve image quality, there is a problem in that the entire image forming device or developer becomes expensive. SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that can produce images of good quality just by adjusting the developing device itself, without using expensive developers. [Means for Solving the Problems] A developing device according to a first invention is for developing an electrostatic latent image on a photosensitive drum in an image forming apparatus that forms an image using a photosensitive drum. ．． This developing device includes a developing sleeve that is disposed adjacent to the photosensitive drum and has a main magnetic pole angle (N) exceeding 1°. Then, the circumferential speed CD of the photoreceptor drum and the circumferential speed S of the developing sleeve
) and the main magnetic pole angle (N) are 3
．． It is set to satisfy the relationship 5≦N/(S/D)≦7.0.

The developing device of the second invention is for developing an electrostatic latent image on a photosensitive drum in an image forming apparatus that forms an image using a photosensitive drum.

This developing device is arranged adjacent to the photoreceptor drum.
It is equipped with a developing sleeve having a main magnetic pole angle (N) of 0° to 1°. The peripheral speed ratio (S/D) between the peripheral speed (D) of the photoreceptor drum and the peripheral speed (S) of the developing sleeve is 3.5.
It is set to satisfy the relationship ≦1/(S/D)≦7.0.

[Effect]

In the first and second inventions, the circumferential speed ratio between the circumferential speed of the photosensitive drum and the circumferential speed of the developing sleeve and the main magnetic pole angle are set so as to satisfy the above-mentioned relationship. For this reason, the first
In the second aspect of the present invention, images with good quality can be obtained without using expensive developers or the like.

〔Example〕

FIG. 2 shows an example of a copying machine employing an embodiment of the present invention.

In FIG. 2, 4. of the copying machine main body l1. There is a manuscript table 1 on the side.
2 is fixed, and a document holder l3 is placed on the document table 12.
are arranged so that they can be opened and closed freely. On the right side of the main body 1l of the copying machine, paper cassettes 14 and 15 are removably attached. On the left side of the copying machine main body 11 in the figure, there is installed a paper discharge tray l8 from which copied sheets are discharged. Inside the copying machine main body 11, an exposure device 19 for reading originals is provided at the top. This exposure device 19 consists of a light source, a mirror, etc. Further, a photosensitive drum 20 on which an electrostatic latent image is formed is arranged in the center of the main body 1l of the copying machine. Photosensitive drum 20
Around the , there are a {W electric device 21 for charging the photoreceptor drum 20 to a predetermined charge, a developing device 22 for developing the electrostatic latent image, and a transfer device 23 for transferring the toner image onto the paper. , a paper separating device 24 for separating paper from the photosensitive drum 20, and a cleaning device 25 for removing residual toner on the photosensitive drum 20. Between the paper feeding force set 14.15 and an image forming section formed by the photosensitive drum 20, etc., and downstream from the image forming section, there are paper feeding conveyance paths 2 for conveying the paper, respectively.
7 and υF paper conveyance path 28 are provided. A fixing device 30 is arranged between the JF paper transport path 28 and the paper discharge tray l8 to fix the transferred image on the transported paper. FIG. 1 shows details of the developing device 22. In the figure, the developing device 22 includes a developing device main body 22a and a developing device main body 22a.
It consists of a 1/ner hopper 22b placed above the hopper 2a. Toner T to be supplied to the developing device body 22a is stored in the toner hopper 22b. This toner T is supplied into the developing device body 22a by a supply roller 3l disposed at the lower end of the toner hopper 22b. The developing device body 22a is disposed adjacent to the photosensitive drum 20 that rotates in the direction of arrow a. Developer main body 22
a has a stirring roller 32 and a developing sleeve 33. The agitation supply roller 32 is disposed below the supply roller 31 and is driven to rotate in the direction of arrow b in the figure.

fli! The stirring supply roller 32 has a large number of blades 34 extending in the radial direction. The blade 34 is slightly bent in the direction of rotation so that the toner T from the toner hopper 22b can be easily stirred and conveyed toward the developing sleeve 33.

The developing sleeve 33 is arranged parallel to the rotation axis of the photoreceptor drum 20, and faces the photoreceptor drum 20. The developing sleeve 33 is mainly composed of a sleeve body 35 and a magnet roll 36. The sleeve body 35 is rotated in the direction shown by arrow C in the opposite direction to the rotational direction of the photoreceptor drum 20.
It is designed to be rotated in the direction. therefore,
At the opposing portions of the photosensitive drum 20 and the sleeve body 35, both move in the same direction. The magnet roll 36 is arranged inside the sleeve body 35. This magnet roll 36 has a plurality of fixed magnets 37 facing the inner peripheral surface of the sleeve body 35. One of these is set as the main magnetic pole 38. The main magnetic pole 38 is connected to the developing sleeve 33 on the photosensitive drum 2.
0 and is located above a line connecting the center of the photosensitive drum 20 and the center of the developing sleeve 33 at a predetermined main pole angle (N). The main magnetic pole 38 is mounted so that the sleeve body 35 side is the north pole. Further, the other fixed magnets 37 are attached so that their polarities alternate in order from the 3rd main magnetic pole. However, one set of fixed magnets 37 adjacent to each other at the bottom of the magnet roll 36
Both are attached so that the sleeve body 35 side is the south pole. A regulating plate 39 is arranged on the -E side of the developing sleeve 33. The regulating plate 39 is configured such that the distance between its tip and the developing sleeve 33 can be adjusted in order to regulate the flow rate of the toner T from the agitation supply roller 32 by 11 sections. Further, above the developing sleeve 33 and the Vjl agitation supply roller 32, a guide plate 40 is arranged for causing the toner T regulated by the regulation temporary 39 to flow back to the agitation supply roller 32 side again. In the developing device 22, the circumferential speed (D) of the photoreceptor drum 20
The circumferential speed ratio (S/D) of the circumferential speed (S) of the sleeve body 35 of the developing sleeve 33 and the main magnetic pole angle (N) are 3.5.
The value of N/(S/D) is set to satisfy the relationship of ≦N/(S/D)≦7.0. If the value of N/(S/D) is not set within the above range, the developing device 22 The toner image formed on the body drum 20 is prone to image defects, especially blurring at the rear end of the toner image. Furthermore, the image density tends to become unstable. In addition, the main magnetic pole angle (N) is 20
゜ or less is desirable. If the main magnetic pole angle (N) exceeds 20 degrees, image density tends to become unstable. Further, the circumferential speed ratio (S/D) is preferably 1.0 or more and 3.0 or less. If the circumferential speed ratio is not set within the above range, toner is likely to scatter and the photosensitive drum 20 is likely to be damaged. Next, the operation of the above embodiment will be explained. When copying, open the document holder l3 and place the document on the document table 12.
Place the original on top and close the original holder 13. When a start button (not shown) is pressed, the original is read by the exposure device 19, and its image is formed as an electrostatic latent image on the 'ζ photoreceptor drum 20.

The photosensitive drum 20 on which the electrostatic latent image is formed is rotating in the direction of arrow a in FIG. The electrostatic latent image then moves to the ゜ζ developing device 22 as the photosensitive drum 20 rotates.

In the developing device 122, the toner T supplied into the developing device main body 22a from the toner hopper 22b is agitated by the rotation of the agitation supply roller 32 and is frictionally charged. Furthermore, the rotation of the agitation supply roller 32 transports the toner T to the upper side of the developing sleeve 33. The flow rate of the transported toner T is controlled by a regulating plate 39, and the toner T is held on the developing sleeve 33 at a constant rfj+\- by the magnetic force of the main magnetic pole 38 and the fixed electrode 37. As a result, the surface of the sleeve body 35 of the developing sleeve 33 is coated with the magnetic brush B.
will be given form. In addition, the flow NiA is controlled by the regulation plate 39.
The aligned toner T flows above the guide plate 40 and is guided by the guide plate 40 to return to the agitation supply roller 32 side. The electrostatic latent image formed on the photosensitive drum 20 is developed by a magnetic brush 1 formed on a developing sleeve 33. As a result, a toner image is obtained on the photoreceptor drum 20. After developing the static TMWJ image, the developer constituting the magnetic brush B separates from the sleeve 35 between the fixed magnets 37 attached to the lower part of the magnet roll 36 and whose polarity is in the same direction, and moves to the stirring roller 32. The flow returns to. On the other hand, paper is conveyed to the photosensitive drum 20 from either the paper feed cassette 14 or f5 via the paper feed conveyance path 27. *The toner image on the photoreceptor drum 20 is transferred onto the fed paper by the transfer device 23. The paper onto which the toner image has been transferred is separated from the photoreceptor drum 20 by a paper separation device 24 and sent to the fixing device 3 via a stray paper conveyance path 28.
0, and the transferred toner image is fixed there.

The paper on which the image has been fixed is ejected from the fixing device 30 to the ejection tray l8. As a result, it is possible to obtain paper on which a predetermined image is imprinted.

For the paper obtained in this way, the peripheral speed ratio (S/D) and the main 6n pole angle (N) in the developing device 22 are set so as to satisfy the above-mentioned relationship, so that the image quality can be improved. A good copy image is formed. As described above, in this embodiment, an image with good image quality is obtained by setting the relationship between the angle (N) and the circumferential speed ratio (S/D) of the main group of the developing device 22 to a constant relationship. be able to. In other words, it is possible to obtain a high-quality image simply by adjusting the imaging device 22.

Therefore, according to this embodiment, there is no need to use an expensive optical system or developer to improve image quality.

[Other Examples]

In the above embodiments, the case where the main magnetic pole angle (N) exceeds 1° has been described, but the main magnetic pole angle (N) may also be between 0° and 1°. However, in this case, the peripheral speed ratio (S/D)
must be set to satisfy the relationship 3.5≦1/(S/D)≦7.0. If the circumferential speed ratio (S/D) does not satisfy the above relationship, the trailing edge of the developed image will be misaligned and the image density will also become unstable. [Experimental Example] A manuscript was copied using a copying machine employing the above-described embodiment. Copying was performed under the following conditions, and the resulting copied images were evaluated. The results are shown in Table 1. View-1 East ≦ 1 Tsubai ◎ Photoreceptor drum type: Organic photoreceptor (OPC) ◎ Developer:
2 commandments ferrite developer ◎Developing sleeve diameter: 31ttrta ◎Photoreceptor drum diameter: 78nym ◎Main magnetic pole angle (N): As shown in Table 1. ◎Developing sleeve peripheral speed (S): As shown in Table 1. ◎Photoconductor drum circumferential speed (D): As shown in Table 1.

◎Distance M between photoreceptor drum and developing sleeve (D-S): As shown in Table 1.

◎Magnetic brush thickness (H): As shown in Table 1. ◎Main magnetic pole strength: 850 Gauss ◎Photoconductor drum initial surface potential: -750V ◎Bias potential: -220V 5K negative O: Good. ×: Fading is observed at the rear end of the image.

Δ: Image density is uneven.

From the results of the first behind-the-scenes experiment, we found that the experimental examples (experiment Nos. 9, 10, 11, 12, 13,
14, 15 and 16), it can be seen that images with good image quality can be obtained.

In Table 1, D-S is the drum-to-sleeve distance, and I1 is the ear cutting dimension.

〔Effect of the invention〕

In the present invention, the peripheral speed ratio between the peripheral speed of the photoreceptor drum and the peripheral speed of the developing sleeve and the main magnetic pole angle are set so as to satisfy the above-mentioned relationship. Therefore, according to the present invention,
It is possible to obtain high-quality images without using expensive developers.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical cross-sectional view of an embodiment of the present invention, and FIG. 2 is a schematic vertical cross-sectional view of a copying machine employing the embodiment. 20... Photosensitive drum, 22... Developing device, 33...
...Developing sleeve, 38...Main magnetic pole.

Claims (2)

[Claims] (1) In an image forming apparatus that forms an image using a photoreceptor drum, a developing device for developing an electrostatic latent image on the photoreceptor drum, the developing device being disposed adjacent to the photoreceptor drum. , a developing sleeve having a main magnetic pole angle (N) exceeding 1°, a peripheral speed ratio (S/D) of the peripheral speed (D) of the photoreceptor drum and the peripheral speed (S) of the developing sleeve; The main magnetic pole angle (N
) is set to satisfy the relationship of 3.5≦N/(S/D)≦7.0. (2) In an image forming apparatus that forms an image using a photoreceptor drum, a developing device for developing an electrostatic latent image on the photoreceptor drum, the developing device being disposed adjacent to the photoreceptor drum. , a developing sleeve having a main magnetic pole angle (N) of 0° to 1°, and a peripheral speed ratio (S/D) of the peripheral speed (D) of the photosensitive drum and the peripheral speed (S) of the developing sleeve. is 3.5≦1/(S/
D) A developing device that is set to satisfy the relationship of ≦7.0.