JPH0628862U - Development cylinder - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a developing cylinder that has both electrical conductivity and adhesive force between a flange and a sleeve and that does not cause defects such as white spots in an image. .. A developing cylinder used in a dry electrophotographic developing device is characterized in that a conductive adhesive is used for adhering a flange and a cylindrical sleeve.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a developing cylinder used in a dry electrophotographic developing device such as a copying machine, a facsimile, and a laser beam printer, and ensures electrical continuity between a flange and a sleeve, resulting in white spots in an image. The present invention relates to a developing cylinder that does not cause the above problems.

[0002]

[Prior art]

 FIG. 2 shows an axial sectional view of a developing cylinder used in a developing device of a copying machine or a facsimile machine, in which a magnet sleeve is covered with a metal sleeve. A cylindrical sleeve S, which is usually made of a non-magnetic material and has a conductive property, is provided outside the magnet roll M, which is composed of shafts 1 and 2 projecting from both ends of a cylindrical magnet having a plurality of magnetic poles. The both ends are sealed by the flanges 3 and 4, and the shaft 1 projecting from one end of the magnet roll M is rotatably supported, and the shaft 2 projecting from the other end is passed through the flange 4. The magnet roll M is housed in the sleeve S in a non-contact state by projecting it to the outside of the sleeve S and fixing and supporting the shaft 2. By rotating the sleeve S with respect to the magnet roll M, the developer made of a magnetic material is magnetically attracted to the surface of the sleeve S, and is controlled to have a constant thickness by a developer passage amount regulating plate (doctor blade). It is transferred onto the electrostatic latent image formed above.

In the electrostatic latent image, for example, a black portion has a negative charge remaining on the surface of the photosensitive drum, and a toner image is transferred to the charged portion to obtain a developed image. The toner is positively charged by the friction between the toners, and is transferred to the surface of the photosensitive drum by Coulomb attraction with the negative electric charge on the surface of the photosensitive drum. For example, in the case of jumping development, the movement of the positively charged toner is controlled by applying a voltage to the sleeve via a flange. For example, when a positive voltage is applied to the sleeve surface, the positively charged toner repels from the sleeve surface due to Coulomb repulsion and jumps toward the negative charge on the photosensitive drum. Conversely, when a negative voltage is applied to the sleeve surface, the positively charged toner does not separate from the sleeve surface due to Coulomb attractive force, and the toner on the photosensitive drum surface is also pulled back to the sleeve side. That is, the amount of toner transferred onto the surface of the photosensitive drum is controlled by the voltage applied to the sleeve to express the shade and halftone of the image.

As described above, since the voltage is applied to the sleeve through the flange, the flange 3 or 4 shown in FIG. 2 is also made of a conductive material such as polyacetal or ABS resin, carbon, or the like. The one in which metal powder or the like is dispersed and blended is used. In addition to the synthetic resin, a metal may be used.

[0005]

[Problems to be solved by the device]

 Since the fitting part of the flange to the sleeve also serves as the driving force transmission part to the sleeve, it is necessary to firmly fix it to the inner peripheral surface of the sleeve. It is considered that the slightly larger flange is press-fitted into the sleeve, but such a method is not preferable because the end of the sleeve bulges as shown in FIG. Against this background, a method has been generally adopted in which the outer diameter of the flange is usually set to be substantially equal to or slightly smaller than the inner diameter of the sleeve, and a strong adhesive is used.

However, the use of the adhesive has the following problems. Adhesives with various compositions such as thermosetting and thermoplastic can be used, but usually they are insulators in the hardened state, and they are used in the fitting part to firmly bond the flange and the sleeve. Along with the uniform formation of the adhesive layer, there has been a problem that electrical connection between the flange and the sleeve cannot be established. In order to obtain a good quality image, it is desirable that the electric resistance between the flange and the sleeve is 10 ⁸ Ω or less, preferably 10 ⁶ Ω or less, but it is easy to form a uniform adhesive. Since it was 10 ⁸ Ω or more, the desired voltage was not applied to the sleeve, the amount of toner transferred onto the photosensitive drum could not be controlled, and as a result, defects such as white spots occurred in the image. That is, in the prior art, the electrical connection between the flange and the sleeve and the adhesive force are contradictory to each other, and there is a drawback that the image and the mechanical adhesive force cannot be compatible with each other.

[0007]

[Means for Solving the Problems]

 The present invention has been devised in view of the above problems, and provides a developing cylinder that eliminates image defects such as white spots while maintaining the adhesive force between the flange and the sleeve. What is done is that a conductive adhesive is used to bond the flange and the sleeve in the developing cylinder.

[0008]

[Action]

 When the developing cylinder according to the present invention is used, a conductive adhesive is used to bond the flange and the sleeve, so that reliable electrical continuity can be obtained while maintaining a strong adhesive force. There is no variation in voltage or no voltage is applied.

[0009]

【Example】

 Next, an embodiment of the present invention will be described in detail. 1 (a) to 1 (c) show a fitting portion between the flange portion F and the sleeve S in the developing cylinder of the present invention, (a) only the end surface of the sleeve, (b) only the sleeve inner diameter portion (c). Shows the case where the adhesive B is used for both the sleeve end surface and the inner diameter portion. The outer diameter of the flange is preferably set to be smaller than the inner diameter of the sleeve by about 0.03 mm to 0.06 mm. As the material of the flange F, polyacetal, ABS resin, polyamide, polycarbonate, polyphenylene oxide, So-called engineering plastics such as polyphenylene sulfide, polysulfone, and polyethylene terephthalate, and thermosetting resins such as phenolic resins, in which a conductive dispersion material such as carbon or metal powder is dispersed can be used.

As the base material of the conductive adhesive, a phenolic resin, an epoxy resin, a polyurethane resin, a cyanoacrylate resin, a nitrile rubber resin, or the like can be used. A metal powder such as silver or copper, which has a low electric resistivity and is advantageous in terms of cost, may be used. The powder may be mainly in the form of flaky powder or atomizer granular powder, but since the bulk specific gravity of both is different, the amount that can be dispersed in a certain amount of adhesive base material is different. It suffices to adjust the optimum mixing ratio in the shape.

Next, a first embodiment will be described. Adhesive base material: copper powder was mixed and kneaded in a weight ratio of 1: 2, using a one-liquid epoxy resin as an adhesive base material and atomizer copper powder as a conductive dispersant, and adjusted with butyl cellosolve acetate. As shown in FIG. 1 (a), it was applied only to the end face of the sleeve and cured by heating at 150 ° C. After curing, the electrical resistance between the central part of the sleeve and the flange was measured at room temperature and found to be 10 ⁵ Ω, and an adhesive strength with no practical problem was obtained. The sleeve used was an aluminum tube having an outer diameter of 18 mm and a total length of 240 mm, and the flange was made of ABS resin in which carbon powder was dispersed.

Next, a second embodiment will be described. Adhesive base material: silver powder was mixed and kneaded in a weight ratio of 2: 1 using a one-component epoxy resin as an adhesive base material and scale-like silver powder as a conductive dispersant, and then adjusted with butyl cellosolve acetate. As shown in FIG. 1C, the coating was applied to the sleeve end surface and the inner diameter portion and heat-cured at 150 ° C. When the electrical resistance between the central portion of the sleeve and the flange was measured at room temperature after curing, it was 10 ⁵ Ω, and an adhesive force with no practical problem was obtained. As in the first embodiment, the sleeve was an aluminum tube having an outer diameter of 18 mm and a total length of 240 mm, and the flange was made of ABS resin in which carbon powder was dispersed.

[0013]

[Effect of device]

 As described above, in the present invention, by using the conductive adhesive for the adhesion between the flange and the metal sleeve in the developing cylinder, it becomes possible to easily establish the electrical conduction between the flange and the sleeve. As seen in the figure, the electrical connection between the flange and sleeve does not conflict with the adhesive force, and a strong adhesive force can be obtained while maintaining the electrical connection. If such a developing cylinder is used, the voltage applied to the sleeve does not fluctuate, and the amount of toner jumping to the photosensitive drum can be reliably controlled, so that defects such as white spots do not occur in the image. A good image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an adhesive application part in a fitting part of a flange and a sleeve.

FIG. 2 is an explanatory view showing a sectional structure of a developing cylinder.

FIG. 3 is an explanatory view showing a state where a flange having a fitting portion having an outer diameter slightly larger than the inner diameter of the sleeve is strongly pressed into the sleeve in the conventional developing cylinder.

[Explanation of symbols]

 B Adhesive F Flange M Magnet roll S Sleeve

Claims (1)

[Scope of utility model registration request] 1. A developing cylinder for use in a dry electrophotographic developing device, wherein a magnet roll having a plurality of magnetic poles formed on its outer peripheral surface is rotatably housed in a cylindrical sleeve whose both ends are closed by flanges. 2. A developing cylinder, wherein a conductive adhesive is used to bond the flange and the cylindrical sleeve.