JPS61145570A - Dry type developing device - Google Patents

Abstract

PURPOSE:To obtain an image having high quality by an electronic copying machine which uses a dry type developing device by blocking a gap between the upper end part of a peripheral wall and a photosensitive drum with a seal material and preventing toner from scattering, and forming air vents with a filter nearby a doctor blade for controlling a developer and releasing interval pressure. CONSTITUTION:The gap G between the upper end part of a casing member 12 and a photosensitive drum 2 is blocked with a seal material 22, such as 'Mylar(R)', fixed to a casing member 12. Plural air vents 23 which are arrayed in the axial direction of a developing roller 13 are formed above the doctor 15 of the casing member 12, but the respective vents 23 are blocked with filters 24. Thus, the gap G is blocked with the seal material 22 to confine suspended toner N which is generated nearby the doctor 15 in a developing tank. Thus, the gap G is blocked to reduce a rise in the internal pressure generated by the casing member 12 and developer effectively through the air vents 23.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a dry developing device used in electronic copying machines and the like.

<Summary of the Invention> The present invention closes the gap between the upper end of the peripheral wall of the developing device and the photoreceptor drum with a sealing material to prevent toner from scattering to the outside from the developing tank. A ventilation hole with a filter is formed in the circumferential wall of the developing tank to allow internal pressure to escape.

<Prior Art and Its Disadvantages> A conventional developing device of this type applied to an electronic copying device will be described with reference to FIGS. 5 and 6 as an example.

In the figure, a photosensitive drum 2 disposed within a copying apparatus main body 1 rotates, for example, in the direction of the arrow during copying. A charging charger 3 , a pre-transfer static elimination charger 4 , a developing device 5 , a transfer charger 6 , a peeling charger 7 , a cleaning device 8 , and a static elimination charger 9 are arranged around the photosensitive drum 2 .

The developing tank 1o in the developing device 5 is composed of a developing case 1) and a casing member 12, and inside includes a developing roller 13 that rotates close to the photosensitive drum 2, an agitation roller 14, and a roller that regulates the height of the developer M. A doctor 15 and the like are provided. At the open end of the toner supply port 16 of the developer tank 10, there is a toner supply device 20 that includes an agitator 17, a toner scraping shaft 18, a toner hopper 19, and the like.
is connected.

In the above configuration, the toner N in the toner hopper 19 is constantly stirred, and any toner shortage on the developer tank 10 side is replenished through the toner supply port 16. In the developing tank IO, the developer M stirred by the stirring roller 14 is attracted by the magnetic force of the developing roller 13 to form a magnetic brush. This magnetic brush sequentially moves toward the photoreceptor on the surface of the photoreceptor drum 2 as the developing roller 13 rotates, and along the way, the height of the developer M is regulated by the doctor 15 and used for development.

The conventional method described above has the following drawbacks.

Since there is a gap G between the upper end of the casing member 12, which forms an opening facing the photoreceptor drum 2, and the photoreceptor drum 2, the toner N is separated by the broken line in FIG. It tends to be scattered outside by the current. If this toner N scatters to the outside and adheres to the optical system 21 (Fig. 5) due to the wind flow generated in the copying machine main body 1, it will cause deterioration of image quality, and the bearing of the rotating body disposed inside the copying machine (not shown) will cause bearing lock, etc. This scattering of the toner N is likely to occur in a floating state when the physical bond between the toner and the carrier is broken during the movement of the developer M.

If the gap G is closed with a sealing material, the fear of toner scattering will be eliminated, but an increase in the internal pressure of the developer tank 2 will cause new toner generation. That is, the developing roller 13
Since the photosensitive drum 2 and the developer M are in contact with each other in the central region in the axial direction, a sealing effect by the developer M appears, but in both end regions beyond the magnet width of the developing roller 13, the developer M and the photosensitive Since there is no contact with the body drum 2, the sealing performance is poor. Therefore, the pressure inside the developing tank 10 causes air to be blown out through the gaps between the end areas, and if the toner is multiplied by this and scattered, the image quality will further deteriorate.

<Object of the Invention> An object of the present invention is to eliminate the above-mentioned drawbacks and provide a dry developing device that can effectively suppress toner scattering.

<Structure of the invention> This invention is constructed as follows.

A gap between the upper end of the peripheral wall of the developer tank and the photosensitive drum is closed with a sealing material. A vent hole is formed in the peripheral wall of the developer tank near the developer regulating doctor. This vent is blocked with a filter.

<Embodiment> FIG. 1 is a side cross-sectional view of a dry type developing device according to an embodiment of the present invention, and the same parts as in the conventional one are given the same reference numerals and the explanation thereof will be omitted.

In the figure, a gap G between the upper end of the casing member 12 and the photosensitive drum 2 is closed with a sealing material 22 such as mylar fixed to the casing member 12. A plurality of ventilation holes 23 arranged in a row in the axial direction of the developing roller 13 are formed above the doctor 15 in the casing member 12 . Each ventilation hole 23 is closed with a filter 24 as shown in FIG.

Since the gap G is closed with the sealing material 22 in this manner, the floating toner N generated near the doctor 15 can be confined within the developer tank 10. That is, scattering of the toner N to the outside from the gap G is prevented, and there is no fear of the toner N adhering to the optical system, thereby ensuring a proper image.

By closing the gap G, the casing member 12
The internal pressure in the closed space formed by the developer tends to rise, but the air flow shown by the dotted line in FIG. Can be done. Of course, the ventilation hole 23
Since the filter 24 covers the floating toner N, the floating toner N does not fly away due to the airflow.

Both end areas of the developing roller 13 beyond the magnet width (third
Although the portion B in the figure) is a region where the sealing effect of the sealing material 22 is low, since the increase in the internal pressure is suppressed, no air is blown out from the both end regions. Furthermore, together with the provision of the sealing material 22, the developing roller 1
3 and photoreceptor drum 5 Opposing portion of drum 2 (part A in Fig. 3)
As the rotation of the roller 13 causes a flow of air into the developer tank 10, there is also the effect that the toner N floating around this area can be forcibly drawn into the developer tank 10.

In addition, paper dust or insufficiently charged toner collected by magnetic cleaning is blown up by the air flow toward the ventilation hole 23, but the filter 24 prevents these paper dust W from scattering to the outside. Furthermore, the base 15a of the doctor 15 directly below the filter 24 serves as a catch for objects that fall from the filter 24 due to their own weight, and accumulates thereon, thereby preventing image deterioration due to the scattering of paper dust W, etc. . Of course, the tray for receiving paper powder W etc. does not have to be used as a tray at the base 15a of the doctor 15 as described above, but a separate tray can be used as a tray member 25 in accordance with the formation position of the ventilation hole 23 as shown in FIG. It is also possible to provide

<Effects of the Invention> As described above, according to the present invention, it is possible to prevent toner from scattering from the gap between the upper end of the circumferential wall of the developer tank and the photoreceptor drum, and also to prevent an increase in the internal pressure of the developer tank. This eliminates toner scattering from both ends of the roller, and has the effect of guaranteeing high-quality images with stable copying operations.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a dry developing device according to an embodiment of the present invention, FIG. 2 is a perspective view of the main parts of the device, FIG. 3 is an explanatory diagram of the gap in the axial direction of the developing roller, and FIG. 4 FIG. 2 is a side view of a dry developing device according to another embodiment of the present invention. 5 and 6 are a schematic diagram of a conventional electronic copying apparatus and a side sectional view of a dry developing device, respectively. 2-photosensitive drum, 10-developing tank, 13-developing roller, 15-doctor, 22-sealing material, 23-ventilation hole, 24-filter, G-gap, M-developer.

Claims (1)

[Claims] (1) A developing roller provided in a developing tank and rotating close to the photosensitive drum; a doctor disposed above the developing roller to regulate the height of the developer in the developing tank; and the developing roller. a sealing material that closes a gap between an upper end of the peripheral wall of the tank and the photoreceptor drum; a vent hole located near the doctor and formed in the peripheral wall of the developer tank; and a filter that closes the vent hole. , a dry developing device.