JPS63208867A - Developing method - Google Patents

Abstract

PURPOSE:To prevent fluctuation in image density occurring in a machine difference by setting a specific developer packing ratio at the time of development to be executed by conveying a developer consisting of a magnetic carrier and toner. CONSTITUTION:The developer packing ratio PD (%) in a developing part defined by the equation PD=M/(rhoXDs)X100 is set at 20-50% at the time of the development to be executed by fixing an internal pole 3 and conveying the developer consisting of the magnetic carrier 4 and toner 5 in the rotation of a nonmagnetic material sleeve 2. In the equation, M (g/cm<2>) signifies the amt. of the developer past a nap height control part 6 on the sleeve; rho (g/cm<3>) signifies the true sp. gr. of the developer; Ds (cm) signifies the spacing between the developing sleeve 2 and an electrostatic latent image recording body 7. The contact ratio of the developer and photosensitive body is satd. and the influence of the fluctuation in Db and Ds is decreased when the development is executed by setting the developer packing ratio at the high value in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrophotographic copying machine or an electrostatic copying machine.
The present invention relates to a method of developing using a two-component developer consisting of a magnetic carrier and a toner. More specifically, the present invention relates to a developing method that reduces "variations" in image density related to machine differences.

Conventional electrophotographic copying machines use a developing device to supply toner to the surface of a photoreceptor bearing an electrostatic latent image, and after development, the resulting toner image is transferred to a transfer material such as paper. .

In order to obtain images with stable density in such a developing device, it is necessary to supply toner to the photoreceptor by the developing device under constant conditions.

FIG. 1 is a schematic cross-sectional view showing a developing method using a conventional two-component developing device. In FIG. 1, a developing sleeve 2 of a developing device 1 has a magnet 3 therein, and while rotating in the direction of the arrow, attracts a magnetic carrier 4 to its surface to form magnetic spikes. The carrier 4 on which the spikes are formed moves in the same direction as the developing sleeve 2 while carrying the toner 5 on its surface. As the developing sleeve 2 rotates, the ears of the magnetic carrier 4 hit the height regulating plate 6 and are regulated to a height Db, and then reach the developing area X between the developing sleeve 2 and the photoreceptor 7, which is set at the developing gap Ds. The toner 5 moves based on the electrostatic latent image on the surface of the photoreceptor 7, and development is performed.

Problems to be Solved by the Invention However, both the regulation gap (distance between the regulation blade and the developing sleeve: Db) and the development gap (the interval of 20 seconds between the developing sleeve and the photosensitive drum) require mechanical precision. Based on 0.05-0. There is a tolerance of l0mm. In the conventional developing method using a two-component developer, the image density is easily affected by changes in Db and Ds, and therefore there is a large "variation" in the image density due to machine differences.

Note that in order to prevent the development of spike marks, where marks caused by rubbing with the developer appear on the screen, D has been added to the value of such areas.
It has been proposed to set b/Ds (Japanese Unexamined Patent Publication No. 1983
1387.57), there is no attempt to eliminate machine differences in image density by regulating Db/Ds within a specific range.

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above circumstances, and have found that Db,
Developer filling rate in the developing section determined by Ds 1) D is related to the contact ratio between the developer and the photosensitive drum (the ratio of the area where the developer ear contacts the latent image surface) and affects the amount of development. After learning about this, he was able to complete his invention.

That is, the present invention provides a developing method in which the inner pole is fixed and a developer consisting of a magnetic carrier and toner is conveyed by rotation of a non-magnetic sleeve to perform development, in which the developer in the developing section defined by the following formula is used. Filling rate PD (%): PD = M/(1)XDS)X100 [where M(g
/am3) is the amount of developer after passing through the height regulating section on the sleeve, ρ (g/cm3) is the true specific gravity of the developer, Ds (cm)
means the distance between the developing sleeve and the electrostatic latent image recording member] is set to 20 to 50%.

If the PD value is less than 20%, the image R density varies depending on the PD, and if it changes due to machine differences (Db, Ds), the image density will vary according to the PD. %, there is no effect on further stabilizing the image density, and developer clogging is likely to occur.

In the present invention, the image density was saturated and stabilized by setting the PD value high. It is more preferable to set the PD value to 30 to 40%.

Next, the results of a test regarding the relationship between the PD and image density ID will be shown.

〔Measuring method〕

Developer ffi on the sleeve after passing through the height regulating section (M)
The measurement was carried out as follows.

FIG. 2 is a perspective view showing a method for measuring M. As shown in FIG. 2, a masking plate IO having an opening 9 of a predetermined area is placed on the thin film of the developer 8 after it has passed through the height regulating plate 6.

Next, the developer 8 in the opening 9 is adsorbed and removed using a magnet (not shown), and its weight, fftm, is measured and divided by the area S of the opening 9 to obtain M (g/am).

Further, the true specific gravity ρ (g/cm 3 ) of the developer was measured using an air comparison hydrometer (manufactured by Beckman).

A gap gauge was used to measure the distance Ds (cm) between the developing sleeve and the electrostatic latent image carrier.

From these, the developer filling rate PD (%) in the developing section X was determined by the following formula.

PD = M/(ρxDs)xlooo The image density ID was measured using a Sakura reflection densitometer (manufactured by Konishiroku Photo Industry Co., Ltd.).

[Test I]

Under the following conditions, change the settings of the head height regulation plate 6 to obtain various Db
Perform operations using the values, and check the PD value and image density (ID) at this time.
I sought a relationship with. The results are shown in Figure 3.

(Test conditions) Photosensitive drum (OPC): l 50pP/am'80I
IIIφ, circumferential speed 15cm/sea, charging potential knee 60
0V Ds: 0.65mm Developing bias knee 150V Developing sleeve: 31mmφ, main pole strength 800 Gauss, circumferential speed 30cm/sea, Rz#10μ shoulder developer: MC-
41&M-21 toner (manufactured by Minolta Camera Co., Ltd.), toner mixing ratio 8% by weight, toner charge amount 12 μC/g As is clear from Figure 3, stable image density was obtained in the PD value range of 20 to 50%. It will be done.

[Test Example 2] The relationship between PD and ID was determined in the same manner as Test Example 1 except that Ds was set to 0.55 mm. The results are shown in Figure 4. As in Test Example 1, stable image density is obtained when the PD value is in the range of 20 to 50%.

By performing development with a high developer filling rate (FD = 20 to 50%), the contact ratio between the developer and the photoreceptor is saturated, and the influence of "variations" in Db and Ds is reduced. became.

Effects of the Invention According to the method of the present invention, the influence of components and assembly tolerances of the developing device on image density is reduced, and "variations" in image density due to machine differences are prevented.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view showing development using a two-component developer, Figure 2 is a perspective view showing a method for measuring the amount of developer on the sleeve, and Figures 3 and 4 are developer filling ratios. 3 is a graph showing the relationship between image density and image density. The main symbols in the figure are as follows. l: developing device, 2: developing sleeve, 6: height regulating plate, 8
:Developer.

Claims (1)

[Claims] (1) In a developing method in which the inner pole is fixed and development is carried out by transporting a developer consisting of a magnetic carrier and toner by rotation of a non-magnetic sleeve, the developer filling rate of the developing section is defined by the following formula: PD (%): PD=M/(ρ×Ds)×100 [In the formula, M (g/cm^2) is the amount of developer after passing through the height regulating section on the sleeve, ρ (g/cm^3) is the true specific gravity of the developer, and Ds (cm) is the distance between the developing sleeve and the electrostatic latent image recording member] is set to 20 to 50%.