JPH0350536Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Purpose [Field of industrial application] This invention relates to a developing device for an electronic copying machine, and mainly uses a rotating non-magnetic sleeve and a magnet roll fixed inside the sleeve. The present invention relates to a developing device using a magnetic brush developing method.

[Prior art]

Prior art related to this invention is disclosed in, for example, Japanese Patent Publication No. 40024/1983 and Japanese Patent Publication No. 13948/1983. That is, the former improves the contact action of the magnetic brush by arranging magnetic poles of different polarities close to the main developing pole of the magnet roll, while the latter improves the contact action of the magnetic brush by arranging magnetic poles of different polarities in close proximity to the main developing pole of the magnet roll. Between the magnetic poles, magnetic poles of the same polarity are added at both ends of the magnet roll to prevent the developer from moving on the sleeve.

[Problem that the invention attempts to solve]

Generally, PPC (Plain Paper Copier) dry development methods are classified into one-component development and two-component development. Two-component development uses a powder mixture of toner and carrier as a developer, and the carrier (magnetic material) with toner attached is attracted to the surface of a non-magnetic cylindrical sleeve with a magnet roll placed inside and transported to the photosensitive drum. The latent image on the drum is developed by electrostatically attracting only the toner by the latent image charge on the drum. Here, the sleeve containing this magnet roll first adsorbs (picks up) new developer, keeps the adhesion thickness constant, and transports it to the developing section.In the developing section, the developer is made to stand up like a brush. It has the function of separating the developer from the sleeve after development. The characteristics of each of these functions are mainly controlled by the action of the magnetic force of the magnet roll within the sleeve, so the distribution of magnetic lines of force on the sleeve surface due to the magnetic poles magnetized by the magnet roll determines the development performance. Determine. Especially when the magnet roll is fixed and only the sleeve is rotated, each magnetic pole of the magnet roll has its own role in controlling the state of the developer conveyed on the sleeve, and the other magnetic poles have their own roles. Compared to component development and magnet roll rotation methods, the distribution of magnetic lines of force, that is, the strength and positional relationship of each magnetic pole, is incomparably more important.

However, although the local strength of the magnetic field and its effects have been disclosed as described above, the distribution of the magnetic field lines on the sleeve is
Since each magnetic pole of the internal magnet roll influences each other and changes slightly, it is not easy to distribute the magnetic field lines conveniently for each part function on the sleeve. The relationship with the function is not disclosed.

This idea was devised in view of these circumstances, and by using an integrally molded magnet roll, we considered the relationship between its cross-sectional shape, the position of the magnetic poles, and each function on the sleeve, and created a high-performance developing function. The present invention provides a developing device having the following features.

(b) Structure of the invention The developing device of this invention includes a non-magnetic sleeve that rotates in one direction and a magnet roll fixed in the sleeve, and applies developer to the outer periphery of the non-magnetic sleeve. A pick-up section that introduces and adsorbs the developer, a thickness regulating section that regulates the thickness of the developer using a blade, a developing section that causes the developer to stand up in the vicinity of the developing drum, and a conveyor that transports the developer that has been developed. In a developing device in which a part and a separating part for removing developer are arranged in the direction of rotation of the sleeve, the magnet roll is formed of a pentagonal prism body formed by integral molding and having one groove extending in the axial direction on the outer periphery. The four planes of the outer periphery face the pick-up section, the development section, the conveyance section, and the separation section, and the concave groove faces the thickness regulating section, and the planes facing the pick-up section and the conveyance section are at the same polarity. This is a developing device in which the flat surfaces facing the developing section are magnetized with different polarities.

The pick-up portion has the role of attracting the mixed developer onto the sleeve, and if the magnetic force in this portion is weak, the developer will remain partially and the uniformity will be disturbed.

In the thickness regulating section, the thickness of the developer is kept constant using a blade provided close to the sleeve.
To convey developer with even thickness to a holding section. The developer is most densely adsorbed in this area, but since the developer is likely to slip, conventional measures have been taken to make the sleeve surface rough.

The degree of this slip is also greatly influenced by the state of the magnetic field on the sleeve surface. The distance between this blade and the sleeve surface is: - 1 to 2 mm when using a resin carrier - 2 to 4 mm when using an iron carrier - 1 mm or less when using one-component toner, and the error is within ±5%. It is preferable that it fits.

The above-mentioned developing section connects the developer in a thread-like manner in the direction of magnetic lines of force using the magnetic field of the magnet roll to form brush-like vertical spikes, and by stroking the photosensitive drum with the tips of the tips, toner is applied to the drum. to be absorbed. If the brush width in the circumferential direction of the sleeve in contact with the photosensitive drum is narrow, the developed image will be thin, and if it is too wide, fogging (white background will turn black) will occur.

The separating portion has the role of reducing the magnetic adsorption force of the developer and separating the developer using the centrifugal force generated by rotation of the sleeve.

[Example 1] In a two-component developing type PPC developing device whose partial configuration is shown in FIG. 1, 1 is a developing drum rotating in the direction of arrow A, and 2 is a non-magnetic body rotating in the direction of arrow B Sleeve, 3 is shaft 1 inside sleeve 2
a magnetic roll concentrically fixed by 0;
4 is a developer containing a mixture of toner and carrier; 5 is a stirring roller that stirs the developer; 6 is a case side plate;
7 is a blade. Further, 8 is a pick-up part that introduces and adsorbs the developer 4 onto the sleeve, 9 is a thickness regulating part that regulates the thickness of the developer by the blade 7, and 11 is a part that causes the developer to stand up in the vicinity of the developing drum 1. The developing section 12 is a separating section from which the developer is removed. Furthermore, 13 is a first magnetized section that is magnetized opposite to the developing section 11, and 14 is a pickup section 8.
A second magnetized part 15 is magnetized opposite to the first magnetized part 13 and has a different polarity, and 15 is a third magnetized part that is magnetized adjacent to and has a different polarity from the first magnetized part 13. . 16 is a flat surface formed facing the developing section 11; 17 is a groove formed facing the thickness regulating section 9; 18;
Reference numeral 19 denotes a flat surface formed to face the separation section 12 and the pickup section 8, respectively.

The magnet roll 3 is made of a mixture of magnetic powder and synthetic resin powder and is integrally molded by extrusion using a mold having the cross section shown in FIG.

The molded magnet roll 3 is housed in a magnetizing device, and the magnetic poles corresponding to each position on its outer circumference are magnetized as shown in FIG. After the stainless steel shaft 10 is press-fitted into the magnet roll 3 which has been magnetized,
It is housed and fixed inside the sleeve 2 as shown in FIG.

FIG. 3 shows an example of the results of measuring the distribution of magnetic flux density on the circumferential surface of the sleeve 2 in which the magnetized magnet roll 3 is fixed, in correspondence with the arrangement of the developing device. According to this, first, the developing section 11 exhibits a magnetic flux density distribution N ₁ with a maximum N pole value of 800 Gauss, a substantially uniform width, and a sharp rise.
Magnetic flux density distribution of S pole corresponding to pick-up part 8
S ₁ is adjacent to the developing section 11 and has an S-pole magnetic flux density distribution.
S ₂ are formed with maximum values of 600 and 500 Gauss, respectively.

Then, the magnetic flux density distribution U corresponding to the thickness regulating portion decreases to almost zero Gauss, and the separation portion 12
The magnetic flux density distribution W corresponding to
Most of them are zero Gaussian.

When using a developing device configured in this way,
In the pick-up section 8, the developer 4 is evenly attracted onto the sleeve by the strong magnetic force shown by the magnetic flux density distribution _S1 , and in the thickness regulating section 9, the attracting force is reduced by the weak magnetic force shown by the density distribution U. The thickness of the developer is easily controlled without becoming a rotational load on the sleeve 2, and the developer does not slip on the sleeve 2. Furthermore, in the developing section 11, the developer 4 that was attracted by the weak magnetic force shown in the density distribution U of the thickness regulating section 9 is removed from the developing section 11.
When the toner is introduced into the drum ₁ , the developer forms soft brush-like spikes due to the wide and strong magnetic force shown by the density distribution N1, and an appropriate amount of toner is attracted to the drum 1. The developer that has been developed is transported to the separation section 12 by the magnetic force shown by the density distribution _S2 . Since the corresponding density distribution V in the separation section 12 is very small, the developer is separated from the surface of the sleeve 2 due to the rotational centrifugal force of the sleeve 2. The detached developer 4 is stirred by the stirring roller 5 and adsorbed to the pickup section 8 again. Note that a scraping plate (not shown) may be provided at the separation portion 12 to more completely remove the developer.

In this way, the distribution state of the lines of magnetic force on the circumferential surface of the sleeve is optimally controlled in accordance with the function, and high-performance development processing is performed.

Furthermore, the magnet roll of this embodiment can also be integrally molded by injection molding.

(C) Effect According to this invention, by making the cross-sectional shape of the integrally molded magnet roll and the magnetized position on its outer periphery correspond to each function of the developing process, the lines of magnetic force on the surface of the sleeve that conveys the developer can be reduced. Since the distribution is appropriately controlled, a developing device with excellent developing performance is provided.

Moreover, since the magnet roll has an extremely simple shape of a pentagonal prism with only one groove, it not only reduces the manufacturing cost of the mold for integral molding, but also simplifies the processing process. , machining accuracy becomes easier to manage.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of this invention, Fig. 2 is an explanatory diagram showing the magnetization of the magnet roll in Fig. 1, and Fig. 3 is a graph showing the magnetic flux density distribution in Fig. 1. . 1...Developing drum, 2...Nonmagnetic sleeve,
3...Magnetrol, 4...Developer, 7...
Blade, 8...Pickup part, 9...Thickness regulation part, 11...Development part, 12...Separation part, 13
...First magnetized part, 14... Second magnetized part, 15...
Third magnetized portion, 16, 18, 19...Flat surface, 17
...concave groove.

Claims (1)

[Claims for Utility Model Registration] A pick-up device comprising a non-magnetic sleeve that rotates in one direction and a magnet roll fixed within the sleeve, and which introduces and attracts developer to the outer periphery of the non-magnetic sleeve. a thickness regulating section that regulates the thickness of the developer with a blade; a developing section that causes the developer to stand up in the vicinity of the developing drum; a transport section that transports the developer after development; In a developing device in which a detachable part is arranged in the direction of rotation of the sleeve, the magnet roll is formed by integral molding and is a pentagonal prism body having one groove extending in the axial direction on the outer periphery, and has four flat surfaces on the outer periphery. The flat surfaces facing the pick-up section, developing section, conveyance section, and separation section, respectively, and the concave grooves facing the thickness regulating section, and facing the pick-up section and the conveyance section, are magnetized to the same polarity, and are magnetized to the same polarity. A developing device in which opposing planes are magnetized with different polarities.