JPS63305373A - Developing device - Google Patents

Abstract

PURPOSE:To develop a toner image with high picture quality by arranging a thin layer forming blade for forming a thin layer of a two-component developer on a developing roller opposed to an image supporting body and arranging a peeling blade for peeling developer formed as a thin layer in the vicinity of the developing roller on the downstream side of a developing area. CONSTITUTION:The thin layer forming blade 8 for forming the thin layer of the two-component developer on the developing roller 2 including a magnet roll oppositely to an image supporting body 1 and the peeling blade 10 consisting of an elastic body to peel the developer formed as a thin layer is arranged in the vicinity of the roller 2 on the downstream side of the developing area. The blade 10 is arranged between the roller 2 and stirring members 2, 4 for stirring the developer and pressed from the reverse direction against the rotating direction of the roll 2. Thereby, new two-component developer with regulated toner density is always fed to the developer on the periphery of the roller 2 and a uniform thin layer appropriate for developing processing can be formed. Consequently, stable development can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides electrostatic recording Ml! The present invention relates to an improvement of a developing device using a two-component developer installed in Wt.

[Background of the invention]

A developing device that uses a two-component developer is equipped with a developing sleeve, which is a non-magnetic rotating body containing a magnetic roller, at a position opposite to the image support, and the developing sleeve is a non-magnetic rotating body that is positioned opposite to the image support, and the toner powder and magnetic carrier are mixed at a constant rate during the rotation period. A uniform layer of the developer is formed by magnetically adsorbing the developer mixed at the same ratio on the circumferential surface of the developer, which is further made into a thin layer by a cutter plate, and then a developing agent is applied between the developer and the image support. The image is developed by transferring only the toner powder to the electrostatic image on the image support by means of a bias voltage.

In addition, the present applicant has proposed that, in place of the conventional honing board, for example, if
IB? ? 61-34318 No. 7) Ruiha! J [1986
By providing a developer layer forming means proposed in Japanese Patent Application No. 31319, etc., in which a thin plate fixed at one end and given elasticity is pressed against a rotating developing sleeve at a surface near the other end. Furthermore, we have proposed a developing method for obtaining a thin layer of developer on a developing sleeve.

When a thinner developer layer is formed on the circumferential surface of the developing sleeve by such means, development can be carried out under conditions in which a high frequency developing bias is applied without contact between the image support and the developer layer on the developing sleeve. It will be done.

During development, toner powder adheres to the latent image area, and new toner powder and magnetic carrier are mixed in the thin layer of developer on the surface of the developing sleeve where the mixing ratio of toner powder has decreased after the rotation of the circumference. It is necessary to adsorb the developer and restore the mixing ratio of toner powder in the thin layer that is formed again so that electrostatic images with constant density can be continuously obtained.

[Problem that the invention seeks to solve]

However, when development is continued, the developer remaining on the peripheral surface of the developing sleeve after developing the electrostatic latent image with high image density contains almost no toner powder, so new developer is added. Even if a new developer layer is formed on the circumferential surface of the developing sleeve by adsorption and addition, it is difficult to restore the developer layer to the specified toner ratio, and the density of the electrostatic image that is subsequently developed will decrease. It is inevitable that the image quality will be lower than that developed previously.

In order to solve this problem, for the developing sleeve,
A magnetic roller is provided close to the developing sleeve at the position where the development is completed, and the magnetic roller attracts and peels off the developer with a low mixing ratio of toner powder, and adsorbs new developer to the developing sleeve again to produce the specified toner. There are examples of methods that maintain the density, but this method requires a strong driving force to apply strong braking to the developing roller, and also has problems such as collecting the developer that has been attracted and peeled off by the magnetic roller. There are problems, the structure becomes complicated and the developing device becomes large. There is also a method in which a porous rubber roller is brought into sliding contact with the developing sleeve to replace the developer on the circumferential surface of the developing sleeve, but when using this method, the developer scraped off during use Since some of the developer adheres to the rubber roller, there is a problem in that the developer exchange efficiency decreases. As a result of solving this problem and improving the present invention, the load caused by braking is small regardless of the type and size of the developing roller, and the developing roller is always supplied with developer having a specified content ratio of toner powder. However, it is an object of the present invention to provide a developing device that can always develop toner images of sufficient quality and sufficient toner density even when continuous copying is performed.

[Means for solving problems]

The present invention aims to achieve the above object, and includes a thin layer forming blade that forms a thin layer of a two-component developer on a developing roller facing an image support and containing a magnetic roller, and a developing area downstream side. In the vicinity of the developing roller, the r
This invention provides a developing device characterized in that it is equipped with a stripping blade made of an elastic material that strips off developer waste.

〔Example〕

An embodiment of the present invention is shown in Figures #&1.

FIG. 1 shows the structure of a developing device 9 of the present invention, which is installed facing the circumferential surface of a photosensitive drum 1, which is an image support.

The developing device 9 is composed of a developing section 9A that supplies developer to the electrostatic image formed on the photoreceptor drum 1, and a replenishing section 9B that supplies toner powder to the developing section 9A, both of which are integrated. The photoreceptor drum 1 is housed in a unitized state in a container, and is fixed to the peripheral edge of the photoreceptor drum 1.

Developing roller 2 is mounted in the developing section 9A at a predetermined distance from the surface of the photosensitive drum 1. Magnet rows 27 whose outer circumferential surfaces are alternately polarized are housed inside the developing roller 2. Both the developing sleeve 2 and the magnet roller 7, which constitute the developing roller, are rotated by power at respective predetermined speeds. On the other hand, the magnet row 27 is rotated in the opposite direction.

Reference numerals 3 and 4 denote a pair of stirring members that rotate in opposite directions, and the toner powder carried out from the replenishing section 9B by the rotation of the toner replenisher 5 adheres to the sponge roller 6 and is sent to the developing section 9A. Then, the stirring members 3 and 4 mix the toner powder with the magnetic carrier held in the developing section 9A and distribute it uniformly, and at the same time, the toner powder is attached to the magnetic carrier due to the charging action caused by stirring, resulting in two components. It is designed to compose a developer.

The thin layer forming blade 8 is the above-mentioned developer layer forming means, and in this embodiment has a thickness of 1. Ozr phosphor bronze plate and 1! !
-fio, 5zz urethane rubber bonded together, and is attached so as to constantly press against the circumferential surface of the developing sleeve 2 with a predetermined pressure contact force, but the pressure contact force is The strength is set to such an extent that a non-uniform layer of developer adsorbed on the circumferential surface of the roller 2 can be changed into a thin layer of about 0.3zz by compression and pressure.

The peeling elastic blade 10 is newly provided near the developing roller 2 on the downstream side of the developing area according to the present invention, and is made of an elastic blade made of, for example, urethane rubber, and as shown in FIG. It is held by adhesive with double-sided tape or by adhesive. The holding member 1
1, as shown in the second figure, a shaft 12 is fixedly installed, and both ends of the shaft are rotatably fitted into pivot holes 13 provided in a caning side wall 15 of the developing device 9. .

Furthermore, an arm 14 is fixedly attached to the end along the side wall 15 of the developer casing, and a spring 16 provided at the end allows the peeling elastic blade 10 to rotate about the pivot shaft 13 as shown in the second figure. Forced clockwise. Reference numeral 17 is an eccentric cam for adjusting the pressing force of the peeling elastic blade 10 against the developing sleeve 2 to an optimum state. The peeling elastic blade 10 forcibly peels off the developer, which has consumed toner powder after the development process has been completed as described above, from the circumferential surface of the developing sleeve 2. New developer containing a prescribed amount of toner powder is supplied from the toner stirring member 3 to the peeled portion onto the circumferential surface of the developing sleeve 2.

Further, the thin layer forming blade 8 flattens the new developer layer supplied from the stirring members 3 and 4 formed on the peripheral surface of the developing roller 2, and at the same time forms a thin layer of the most suitable thickness for the developing process. It is designed to have the effect of changing the The attachment angle θ of the peeling elastic blade to the developing sleeve 2 and the pressing pressure FN are θ in the counter type shown in FIG.
= 15~20°FN = 10~20g/cm, in the trail method shown in Figure 4, when force is applied in the direction of the spring load and the elastic blade is brought into contact as in the case of (,), θ = 60~70
°Spring load = 40~60g/cm, when force is applied in the direction of F around point ^ as in case (b) and the elastic blade is brought into contact, θ = 60~70°FN = 15~25H /a
About m is good. However, the mounting angle θ is shown as the angle of attack as shown.

The purpose of the peeling elastic blade 10 is to scrape off the toner-deficient developer remaining on the developing sleeve 2 after development, so the blade may contact the developing sleeve 2 in a trail manner or a counter manner, but preferably in a trail manner or a counter manner. It is preferable to attach the developing sleeve 2 from the opposite direction to the rotating direction of the developing sleeve 2, that is, in a counter manner, so that the developing sleeve 2 contacts the developing sleeve 2 at an angle.

The properties required of the stripping elastic blade 10 in order to scrape off the developer lacking toner on the developing sleeve 2 are that the edge of the stripping elastic blade 10 contacts the surface of the developing sleeve 2 with uniform force, and It is necessary that the developer does not slip through, and that it also has the force (appropriate contact pressure) to scrape off the developer. For each type of blade installation, if the angle is within the specified angle θ, if the contact pressure is small, developer scraping failure will occur, and if it is too large, the elastic blade 1
The edge portion of 0 rolls up, and the same problem as described above occurs in scraping off the developer. Poor scraping here refers to the inability to scrape off 70% or more of the developer per unit area of the sleeve.The contact pressure varies depending on the material composition of the elastic blade, so it is true! ! It is desirable to set the elastic blade 10 appropriately according to 1F, and it is necessary to select a material that will not allow the developer to stick to the blade during long-term use. For example, it is preferable to use polyurethane rubber. In the affected areas, sufficient developer is not supplied and the image appears as a white smudge. Further, if the hardness of the blade is too hard, there is a risk of damaging the developing sleeve, and if the blade is too soft, the ability to scrape off the developer will decrease, so the rubber hardness is preferably about 60° to 70°.

As a specific example, on the circumferential surface of the photosensitive drum 1,
250 per minute with an outer diameter of 201φ arranged by a gap of
When image formation was carried out at the contact angle mentioned above with a polyurethane rubber stripping elastic blade manufactured by Hokushin Industries with a thickness of 3 and a hardness of 70 degrees and a size of 315 Soso x 18 Soron against a rotating stainless steel developing sleeve 2, an image was formed at the above contact angle. Even after copying a sheet, there was no density unevenness in the image and no scratches were observed on the developing sleeve. The pressing pressure FM of the elastic blade 10 used in this experiment (method shown in FIG. 3) was 10 to 20 g/am, and the surface roughness of the developing sleeve 2 used was 3S.

The developing roller used in this example includes a magnet roller 27 that rotates at 800 revolutions per minute and has 12 poles magnetized to 600 G on the circumferential surface of the developing sleeve 2, and the photosensitive drum 1 facing this developing roller is It is rotated at a circumferential surface potential of 600 μ and a circumferential speed of 70 m/s, and a bias in which an alternating current of 2 K V p-p 4 KIIZ and a direct current voltage of toov are superimposed is installed between it and the developing roller. A developing process was performed by applying a voltage.

Experiments have shown that if the surface roughness of the developing sleeve 2 is too large, a large amount of toner-deficient developer passes through the contact area between the stripping elastic blade 10 and the developing sleeve 2, and the replacement of new developer is not performed sufficiently, resulting in a decrease in the number of copies. As the number increases, there is a tendency for the density of the copied image to decrease. The relationship between the surface roughness of the developing sleeve 2 and the image density under the above experimental conditions is shown in the table below. To determine 0 image quality, form a solid image of 20 x 200 mm size and measure the image density with a reflection densitometer (manufactured by Konishiroku Photo Industry). After copying 5,000 copies, those with no decrease in image density are marked O, those with a decrease of about 0.1 to 0.2 are marked Δ, and those with a greater decrease in density are marked X. . In actual use, those marked with ○ to Δ are desirable as copy images.The surface roughness S is in accordance with the surface finish roughness display for parts determined by JIS (Japanese Industrial Standards), and the reference surface is as shown in Figure 5. The height of the uneven peaks and valleys is expressed in μl relative to the length of .

From the above, it has been found that the surface roughness of the developing sleeve 2 is desirably 48 or less when producing a copy image, and that when the roughness is 3S or less, the developer can be replaced satisfactorily by the peeling elastic blade 10.

〔Effect of the invention〕

According to the present invention, the developer on the circumferential surface of the developing roller is constantly replenished with fresh two-component developer having a specified toner concentration, and is formed into a uniform thin layer suitable for development processing. It is now possible to provide a developing device that has a stable developing ability without changing the image tone even when developing high-density images is performed continuously.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional configuration diagram of a developing device according to the present invention, Fig. 2 is a partial cross-sectional perspective view of an elastic stripping blade, and Fig. 3 and Fig. 4 are angular illustrations of attachment of the elastic stripping blade to a developing sleeve. , FIG. 5 is an explanatory diagram of component surface roughness. 1-m-photosensitive drum 2--one developing sleeve 9A-
--Developing section 10-m-Elastic blade for peeling

Claims (6)

[Claims] (1) A thin layer forming blade that faces the image support and forms a thin layer of a two-component developer on a developing roller containing a magnetic roller; A developing device comprising a stripping blade made of an elastic material that strips off layers of developer. (2) The developing device according to claim 1, wherein the stripping blade is disposed between the developing roller and a stirring member that stirs the developer. (3) The developing device according to claim 1 or 2, wherein the peeling blade is pressed against the rotational direction of the developing roller from a direction opposite to the rotating direction of the developing roller. (4) The developing device according to any one of claims 1 to 3, wherein the peeling blade is a rubber blade. (5) The developing device according to any one of claims 1 to 4, wherein the developing roller has a surface roughness of 4S or less. (6) The developing device according to claim 5, wherein the surface roughness of the developing roller is preferably 3S or less.