JPH04298772A - Developing device - Google Patents

Abstract

PURPOSE:To prevent developer stored in the housing of a developing device from blowing out by adjusting pressure in the housing so that it may be constant even when the housing is deformed. CONSTITUTION:A vent 15 is formed on the upper part of the housing 14a of the developing device 14, and a porous film 16 made of PTFE having many holes whose diameter is smaller than the particle size of the developer 20 is stuck to the vent 15 as a filter, so that the film 16 constitutes a pressure adjusting means for adjusting the pressure in the housing 14a so that it may be constant. Therefore, even when the housing 14a is deformed and the pressure in the housing 14a becomes higher by the deformation, only air in the housing 14a flows out to the outside through the vent 15 and the porous film 16, so that the pressure in the housing 14a is adjusted to be constant and the developer 20 is surely prevented from blowing out.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus using electrophotographic technology, such as a copying machine or a laser beam printer.

0002

2. Description of the Related Art A conventional example of a color image forming apparatus applying electrophotographic technology is shown in FIG. In the figure, 1 is a photosensitive drum which is an electrostatic latent image carrier, 2 is a charging device for charging the photosensitive drum 1, and 3 is a latent image forming means for forming a latent image on the photosensitive drum 1 using laser light or the like. It is.

Further, around the photosensitive drum 1, there are yellow, magenta, cyan, and black developing devices 14 (4Y , 4M, 4C, 4B) are arranged. In addition, 5 is a cleaner.

In such a color image forming apparatus, sheets of paper are fed one by one from a paper feed cassette 6 by a paper feed roller 7, and then transferred to a transfer drum 8 by a gripper (not shown) or the like.
The material is held by the material and transported while being wrapped around it. Thereafter, developed images of yellow, magenta, cyan, and black are transferred to the paper between the photosensitive drum 1 and the photosensitive drum 1 four times, and the paper is finally guided to the fixing section 9 and discharged outside the machine.

In the above configuration, the developing devices 14 (4Y, 4M, 4C, 4B) are configured to be detachable from the main body of the image forming apparatus as cartridges in the direction of the arrow shown in the figure, and are housed inside them. When the developer of each color is used up, the user can replace it with a new unit.

FIG. 7 is a sectional view showing the structure of the developing device 14. It is assumed that the developing device 14 uses a non-magnetic one-component developer.

In the figure, 10 is a developing roller which is a developer carrier rotatably supported by a housing 14a, and 11 is a developing roller.
a and 11b transfer the developer in the developing device 14 to the developing roller 1.
0, which is also rotatable.

The developer conveyed by the developer conveying members 11a and 11b electrostatically adheres to the surface of the developing roller 10, and the elastic rubber blade 12 biased against the developing roller 10 makes the layer thickness uniform. It is sheared and flies by the voltage applied to the photosensitive drum 1 to develop the electrostatic latent image formed on the photosensitive drum 1.

By the way, the developer seal around the developing roller 10 is usually made of an elastic rubber blade 12 and a film-like lower seal 13, as well as felt-like sealing materials at both ends of the developing roller 10, called end seals. (not shown), etc., to prevent developer from leaking around the rotating developing roller 10.

0010

However, with the conventional developing device 14, if the operator grips the developing device 14 with more force than necessary, as shown in FIG. 8, when replacing the developing device 14, The grip force causes the housing 14a to elastically deform inward, and the internal pressure increases by the amount of deformation, causing the developer stored inside to leak between the developing roller 10 and the sealing material such as the elastic blade 12 and the lower seal 13. Problems such as ballooning and staining the inside of the image forming apparatus were occurring. In particular, in a color image forming apparatus that uses developers of multiple colors, the blown out developer often stains the developing rollers of other developing devices, causing color mixing. Further, such color image forming apparatuses do not have a magnet in the developing roller and often use a non-magnetic one-component developer, so the binding force of the developer to the developing roller is weak and the developer is likely to scatter.

The present invention has been made in view of the above-mentioned problems, and its purpose is to maintain the pressure inside the housing at a constant level even if the housing is deformed for some reason. An object of the present invention is to provide a developing device that can prevent blowing out of agents.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a developing device that is detachable from an image forming apparatus main body and that stores a developer in a housing, even if the housing is deformed. A feature of the present invention is that a pressure adjusting means is provided for adjusting the pressure inside the housing to a constant level without discharging the developer stored inside the housing.

[0013]

According to the present invention, even if the casing of the developing device is deformed when the developing device is replaced, the pressure inside the casing is kept constant by the pressure adjusting means provided in the developing device. Blowing out of the developer inside the housing to the outside is reliably prevented.

[0014]

Embodiment A first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a sectional view of a developing device 14 according to the present invention. The developing device 14 is attached to and detached from an image forming apparatus (not shown), and a developer 20 and a developer 20 are contained in a housing 14a of the developing device 14. Developer conveying members 11a and 11b for supplying developer to the developing roller 10 are housed. In FIG. 1, 12 and 13 are an elastic blade and a lower seal, respectively.

A ventilation hole 15 is formed in the upper part of the housing 14a, and the developer 20 is inserted into the ventilation hole 15.
A porous membrane 16 made of PTFE having a large number of pores with a diameter smaller than the particle size of is pasted as a filter, and the porous membrane 16 constitutes a pressure adjustment means for adjusting the pressure inside the housing 14a to a constant There is.

That is, for example, when an operator operates the developing device 14
When attaching and detaching, the housing 14a is deformed by the grip force, and even if the internal pressure of the housing 14a increases due to this deformation, the air inside the housing 14a flows out through the ventilation hole 15 and the porous membrane 16. Therefore, the internal pressure of the housing 14a is adjusted to a constant level, and since the pore diameter of the porous membrane 16 is smaller than the particle size of the developer 20 as described above, the developer 2
0 does not pass through the porous membrane 16 and flow out to the outside, and only air passes through the porous membrane 16. If the pore diameter of the porous membrane 16 is set to 5 μm or less, the porous membrane 16
also performs a waterproof function, and the problem of water intrusion due to the provision of the ventilation holes 15 does not occur.

Next, a second embodiment of the present invention will be explained based on FIG. 2.

In this embodiment, a filter 19 is constructed by laminating a polyester woven fabric base material 17 as a protective layer to the front and back surfaces of the porous membrane 16 in the first embodiment.

[0020] Usually, the porous membrane 16 has a thickness of 10 to 15 μm.
Because it is extremely thin (m), it is difficult to handle and easily damaged in its original state. Therefore, considering that the porous membrane 16 may be accidentally damaged by an operator or may be contacted by the developer conveying member 11a (see FIG. 1), for example, the base material 17 may be attached to the front and back surfaces of the porous membrane 16 as in this embodiment. It is desirable to bond them together to form the filter 19, and if the filter 19 is adhered to the housing 14a with an adhesive 18 such as double-sided tape, handling during production will also be improved.

Furthermore, if the base material 17 is waterproofed, the waterproofness of the filter 19 is increased, and water intrusion into the housing 14a through the vent hole 15 can be reliably prevented in a high humidity environment or the like.

FIG. 3 shows a third embodiment of the present invention.

In this embodiment, a foamed resin body 21 made of maltplane or the like having a thickness of several mm is fitted into the ventilation hole 15 as a protective layer. No adverse effects.

[0024] Thus, the housing 14 is formed by the foamed resin body 21.
This prevents developer from adhering to the base material 17 and the porous membrane 16, and prevents the permeability of the porous membrane 16 (filter 19) from decreasing due to developer adhesion and the filter 19 from coming into contact with the developer conveying member. Damage is prevented.

Next, a fourth embodiment of the present invention is shown in FIG.

In the first, second and third embodiments, the effect is influenced by the relationship between the air permeability of the porous membrane 16 (filter 19) and the airtightness of the area where the developer is likely to blow out. That is, the porous membrane 16 (
The air permeability of the developing roller 10 (Fig. 1
(See) If the airtightness of the surrounding seal is poor, there is a risk that the developer may blow out along with the air from the poor airtightness.

Therefore, as shown in FIG. 4, a protrusion 14a-1 is formed on the housing 14a, an opening 15 is formed in the protrusion 14a-1, and the opening 15 is closed with a thin film member 16. . The thin film member 16 may be a porous film made of PTFE similar to those in the first, second and third embodiments, or a thin film with no air permeability, which is given slack as shown in the figure. It is glued. In FIG. 4, reference numeral 21 designates a foamed resin body such as Moltoprene, similar to that described above, for protecting the thin film member 16.

In the above configuration, even if the volume of the casing 14a is reduced due to deformation of the casing 14a, the air within the casing 14a corresponding to the volume reduction causes the thin film member 16 to expand as shown in FIG. Therefore, an increase in the internal pressure of the housing 14a is suppressed, and the air inside the housing 14a does not flow out to the outside, so even if the sealing performance around the developing roller is poor, it can be removed from the area with poor sealing performance. This effectively prevents developer from blowing out. Note that the amount of slack in the thin film member 16 is determined in consideration of the maximum amount of deformation of the housing 14a.

[0029]

Effects of the Invention As is clear from the above description, according to the present invention, in a developing device which is attached to and detached from the main body of an image forming apparatus and which stores a developer in a housing, even if the housing is deformed, Since a pressure adjustment means is provided to adjust the pressure inside the housing to a constant level without discharging the developer stored inside the housing, even if the housing of the developing unit is deformed when replacing the developing unit, the developing The pressure adjustment means provided in the apparatus maintains the pressure inside the housing constant, thereby reliably preventing the developer inside the housing from blowing out to the outside.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a pressure regulating means according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a pressure regulating means according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a pressure regulating means according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view showing the operation of a pressure regulating means according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of a conventional color image forming apparatus.

FIG. 7 is a sectional view of a conventional developing device.

FIG. 8 is a cross-sectional view showing how developer comes out from a conventional developing device.

[Explanation of symbols]

14 Developing device 14a Housing 15 Vent hole (opening) 16 Porous membrane (thin film member) 19
Filter 20 Developer 21 Foamed resin body

Claims (2)

[Claims] Claim 1: Attached to and detached from the main body of the image forming apparatus,
A developing device comprising a developer stored in a housing is provided with a pressure adjustment means for adjusting the pressure inside the housing to a constant level without discharging the developer stored inside the housing even if the housing is deformed. A developing device characterized by: 2. The pressure adjusting means is configured by covering a ventilation hole opening in the housing with a filter having a large number of holes having a diameter smaller than the particle size of the developer. developing device.