JPH0485573A - Developing device - Google Patents

Abstract

PURPOSE:To eliminate defective development on an electrostatic latent image formed on a photosensitive drum which occurs on a downstream side in a rotating direction by specifying the circumferential speed of a developing roller, a gap between the photosensitive drum and the developing roller and the particle size of carrier. CONSTITUTION:The circumferential speed of the developing roller 142 is set once to twice as high as the circumferential speed of an image carrier, the gap between the roller 142 and the image carrier 13 is set once to 1.3 times as large as the gap between a developer regulating means 146 and the roller 142, and the average particle size of the carrier particle is set at 20mum to 80mum. By making the circumferential speed of the roller 142 once to twice as high as the circumferential speed of the photosensitive drum 13, an action that the developer on the developing roller is scraped by a magnetic brush and the photosensitive body is reduced in such constitution. Then, by making the gap between the image carrier 13 and the roller 142 equal to or 1.3 times as large as the gap between the means 146 and the roller 142, the developer on the developing roller is electrostatically charged by the tip of the bristle of the magnetic brush and the stagnation of the developer on an upstream side in the rotating direction on the developing roller is prevented from occurring. As a result, the defective development on the trailing edge part of the image is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device provided in, for example, an electrophotographic image forming apparatus, and particularly relates to a two-component developing device.

(Prior Art) For example, an image forming apparatus such as an electronic copying machine or a laser beam printer includes a developing device that visualizes an electrostatic latent image formed on a photoreceptor drum as an image carrier by developing toner. It is provided. There are two types of development methods: a two-component system in which the toner is attached to carrier particles and transported onto the photoreceptor drum, and the toner is separated from the carrier particles by the Coulomb force of the latent image, and a one-component system in which the toner is transported alone and applied to the latent image. It is broadly divided into

The former two-component developing method is widely used because it provides high-quality copied images and is superior to the one-component developing method in terms of reliability. Although the latter one-component developing method is inferior to the two-component developing method in terms of image quality and reliability, it has the advantage that the developing device can be made smaller. Also, among the two-component developing methods, the with mode method, in which the photoreceptor drum and the developing roller rotate in parallel in the same direction, is the mainstream, and this method improves the density of the solid areas of the copied image. Fogging can be reduced. .

(Problems to be Solved by the Invention) However, there is a problem in that a developing device using a conventional two-component developing system) causes poor development. 4. The rear edge of this image θ) The developing defect is caused by the trailing edge being missing. During development, 1.2 stagnation occurs in the direction of rotation of the image roller - 6.° on the downstream side, and as a result, the magnetic grip on the downstream side becomes sparse, so a6+1: occurs.

The present invention is based on point j4), - In view of this, thing C
To provide a developing device that can eliminate developing defects that occur on the downstream side in the rotational direction of a T-electrostatic latent image formed on a photoreceptor drum 6. The purpose is ゛ and i.

[Structure of the invention]

(σ to solve RM) - TI father) In order to achieve the above object, the present invention provides an image t.

Developing device 1 installed near the special holiday and at the same rotation speed::
: ff--, this development ci~u human blood size I2, t, consisting of carrier powder and toner, the composition of the component system, developer regulations that regulate the thickness of the plaster. ""Two-stage,! :
, 1 In the developing device on the right, the circumferential speed of the development I] is $-nii Htu image 1tj: 1 to 2 times the special holiday circumferential speed, ',, i, ,,,, , front 51L', visual 1 image 11
Xj-7, 1πL The gap between the image carrier 2 is set to 10; 3 Haku, -I, ka-> Said 1
1.97 grains F・I-□-uniform grain row"f',) f
t m 7'ノj・8[1μm 2-L, T, -2・R Features, 5, (Function) 1, Structure 1. According to this, the current circumferential speed of 4 * [1 - LA is reduced.

1 to 2 times (3/-4) the circumferential speed of the optical drum. 0 for scraping more, 8 for reduction, 5 for 5 zeru.'' Or round pa, 'l!lru 4゜mano 2, image carrier,!
- Development fR [7-Ra +gy gap: h ru Gap between image side regulation f stage and development rT-Ra 11- and r 7, Toni J, Su, Development 11 U ↓, the developer of magnetic brush tip B, charging 1'S: Seven Ro upper Ushi, development 1'L-A' in the direction of rotation of the developer. Preventing stagnation on the flow side (L4 Ru1, 4
As a result of 1, °, there was no development failure at the rear end of the image, and 41 pages were -2.

In addition, if the circumferential speed of the developing roller is made faster than the circumferential speed of the image carrier, the image density of the discarded image will be lowered, but by reducing the diameter of the 4" particles by 20 μm to 80 μm,・Increase S-11 (12, low image density F)
can be prevented.

(Example) Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view showing the configuration of a developing device to which this embodiment is applied, FIG. 2 is an explanatory diagram similarly showing the overall configuration of the image forming apparatus, and FIG. 3 is an external perspective view of FIG. 2. .

′! The image forming apparatus shown in FIG. s2 and FIG. 2
The upper iM [covering the document cover] is removably loaded in the soil F on one side of the main body 1, and the paper feed force sensor I/4.5 of the upper F protrudes from the - side, and the other side of the main body 1. It consists of a tray 6 protruding from the paper discharge end of the section.

Inside the main body 1, there is an arrow 1]
A direction I, reciprocating exposure exposure 5: if "7', J", 8.9. Optical system consisting of '10 2. , Light 1: Exposure travel of light & l: , J:: Reflected light for magnification 1/Nzuno'' II jitter 11 and 12 PAl: T image-forming image carrier and photoreceptor drano at 1・ ] 2. An electrostatic latent image 15 formed on the surface of the photoreceptor 113,
Tonneau I-1 wear I-F: ' mi1 Visualization development 8
1214, and in synchronization with the rotation of the photoreceptor dom 13 by arrow C (indicated by 4 degrees), the camera is set 1-11, and the height 1 is I.

Storage 1. t: , 71-paper 1) is fed through a feeding mechanism 15 or 16 and a guide path 1'l' or 18, a fluorophore 20 for turning the sheet 1) and a kidney for peeling. : The surface of the photoreceptor drum 1B (1.
4゛Intermediate 11, (Tocar image transfer 12, ka) Peeling charger S , conveyor belt 2
The terminal end 1 of 3 is ``set ζ'', and the fixing row that defines the image on the copy paper P) is paired with 24? "1. Fixing" A pair of paper ejecting rollers 25 is provided adjacent to the pair of Y-ra 24, and the copy paper P l,i : is ejected onto the tray 6 in a red color from the pair of rollers 25 .

Further, on the peripheral edge of the photoreceptor drum 13, a charger 26 for removing electricity is provided along the rotational direction to remove electricity from the drum 13 after transfer.
A cleaner 27 that removes toner adhering to the surface of the drum 3 after static electricity removal, a static removal lamp 28 that erases afterimages on the drum 13, and a static removal lamp 28 that charges the surface of the photoreceptor drum 13 to form an electrostatic latent image during exposure. Charger 2 for forming an image
9 is placed.

Furthermore, there is a cooling fan 30 in the main body 1 to prevent temperature rise, and a cooling fan 30 located at the insertion tip of the cassette 4.5.
A cassette size detector 31, 32 consisting of a plurality of microswitch groups for detecting the cassette size is provided.

FIG. 1 shows the configuration of the developing device 14. Inside the case 141, a developing roller 142 is arranged parallel to the axial direction of the photoreceptor drum 13.
and agitation rollers 143 and 144 are rotatably provided, each driven by a drive system (not shown) to move arrows A, B, and C.
It is rotated in the direction shown. and photosensitive drum 13
and the developing roller 142 are opposed to each other with a gap d interposed therebetween. Further, a toner concentration sensor 145 is provided in the lower part of the case 141 facing the stirring roller 144, and a developer regulating blade 146, which is a developer regulating means, is provided in the upper part of the case 141 facing the developing roller 142. It is being The toner concentration sensor detects the toner concentration of a developer (not shown) filled in the case 141. Further, the developer regulating blade 146 faces the outer periphery of the developing roller 142 with a gap d2 in between, and regulates the thickness of the developer layer formed on the developing roller 142 to be constant. Further, a magnetic brush 147 is provided at the upper part of the case 141 so as to face the developing roller 142, and its tip contacts the developer layer formed on the developing roller 142 to triboelectrically charge the toner.

Next, the results of an experiment in which the level of trailing edge defects and image density were measured using the developing device 14 according to this embodiment will be explained with reference to FIGS. 4 to 7.

The experiment was conducted under the following conditions.

The particle size of the toner is 11 μm, the toner concentration is 6.0% by weight, and the average particle size of the carrier particles is 75 μm to 15 μm.
The developer having a particle size of 0 μm is referred to as developer D1. The particle size and concentration of the toner are the same as above, and the average particle size of the carrier particles is 2.
The developer having a thickness of 0 μm to 80 μm is referred to as developer D2.

Further, the surface potential when the photoreceptor drum 13 is charged by the charger 29 is -700V, and the gap d1 between the photoreceptor drum 13 and the developing roller 42 in the development area is 0.
7m+w, developer regulating blade 146 and developing roller 14
The gap d2 between 2 and 2 is variable in three stages: 0.4 fin, 0.5 fin, and 0.6 fin.

In addition, the circumferential speed of the photosensitive drum 13 is determined by the vp1 developing roller 142.
When the circumferential speed of is Vm, the circumferential speed ratio V m / Vp is 0
, 5 to 2.5. Furthermore, developing roller 1
The bias voltage applied to 42 is -200V DC.

V m using developer D1 in FIGS. 4 and 5, respectively.
/ V p is changed to show the results of measuring the trailing edge level and image density. Similarly, FIGS. 6 and 7 show the results of measurements using developer D2, respectively. In these figures, the solid line is d2-Q.

4 dragons, the broken line is d2-. 0.5mm, dashed line is d2-0
．． This is the case with 6 questions.

In FIG. 4, in the case of d2-0.4 dragon, the level of rear end missing is the lowest, and among them, V m / V p <2.
The best result is 0. This is because the gap between the developing roller 142 and the developer regulating blade 146 is small and the thickness of the developer layer formed on the developing roller 142 is thin, and the circumferential speed Vm of the developing roller 142 is lower than the photoreceptor drum. 13, the scraping action of the magnetic brush becomes smaller, and the developing roller 142
This is because the stagnation on the upstream side in the direction of rotation is reduced and the downstream side does not become sluggish.

On the other hand, when developer D2 was used, similar results were obtained regarding the level of trailing edge defects as shown in FIG. However, as shown in Figures 5 and 7, the image density is higher when using developer D2, in which the average particle size of carrier particles is smaller, than when using developer D1. Obtainable.

When L oak V' rn / V' p is 1.0 or more,
In either case, the level of the trailing edge is good, but the image density is i.
&5N's Iku 1゛r is Na・Naru 1, Sub-3"' (T
], , 0 $ V n1/Vp≦2.0 can be said to be the optimum value. The photoreceptor tram 1 is supplied from the developing roller 142 to the photoreceptor tram 1'', and a high quality copy image is obtained.
3 and the development τ]-ra 142, the gap d between the development T'I
・Equivalent to the gap d2 between the blade 142 and the developer regulating blade 146. ．． About 3 times more rfk: ,! - It is desirable to do so, 1.1., Ob V'
+11 / V p 52 , 01d2≦d, ≦1
．． ．． 3d2 and jl, carrier particle j′1・diameter is 2
0 It ni By using a developer with a diameter of 7″I to 80 μm at 41°, there is no trailing edge defects and high image density.
High quality duplicate images can be obtained.

〔Effect of the invention〕

As explained above, 1: According to the present invention, the development defect at the rear end of the image is eliminated. It is possible to obtain both images of excellent quality with high softness.

[Brief explanation of drawings]

FIG. 1 is a longitudinal section B of the present invention (not shown). I...
,, Figure z is an explanatory diagram of the overall configuration of the 119 image forming apparatus according to this embodiment. -Tg4''[,,ine This example;,-4,L test II, Diagram showing the 1i prefecture゛C
A) 1,'' 3... Image carrier (photoreceptor i'> 1-
)14...Developing device 142...Developing roller

Claims (1)

[Claims] Regulation of the thickness of a two-component developer consisting of a developing roller rotatably disposed close to an image carrier, and carrier particles and toner attached to the surface of the developing roller. In the developing device, the peripheral speed of the developing roller is set to be 1 to 2 times the peripheral speed of the image bearing member, and the gap between the developing roller and the image bearing member is set to be the same as that of the developing roller. A developing device characterized in that the gap between the agent regulating means and the developing roller is 1 to 1.3 times, and the average particle size of the carrier particles is 20 to 80 μm.