JPS646509Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an electrostatic latent image developing device that develops an electrostatic latent image carried on the surface of an electrostatic latent image carrier. More specifically, the present invention relates to an electrostatic latent image developing device equipped with an improved developer replenishment mechanism.

Prior Art In an electrostatic latent image developing device, as the electrostatic latent image is developed, the developer in the developer tank is consumed and decreased. Therefore, in the developing device, it is necessary to replenish the developer tank with replenishment developer in accordance with the decrease in the amount of developer in the developer tank. For this reason, electrostatic latent image developing devices are widely known that are equipped with a developer replenishment mechanism that appropriately replenishes replenishment developer stored in a replenishment developer tank into the developer tank.

Typical examples of the developer replenishment mechanism include:
One example includes a developer replenishment roller having a developer replenishment notch on the circumferential surface, and the replenishment is carried out by appropriately rotating and driving this replenishment roller. By the way, when the inventor of the present invention repeatedly conducted many experiments on this developer replenishment mechanism, it was confirmed that lumps of developer were often present in the replenishment developer replenished in the developer tank. ing. Although such lump-like developer is not solidly agglomerated, if it is mixed into the developer in the developer tank, it will remain in the form of a lump when an electrostatic latent image is developed. It adheres to the surface of the image carrier and causes deterioration in the quality of the developed image. Specifically, such bulky developer adheres to the surface of the electrostatic latent image carrier corresponding to the area image portion of the electrostatic latent image,
This produces black spots in the area image portion of the developed image.

Purpose of the invention The purpose of the present invention is to eliminate the above-mentioned mixture of lumps of developer into the developer in the developer tank. In other words, it is an object of the present invention to provide an electrostatic latent image developing device equipped with an improved developer replenishment mechanism that does not involve the mixing of lumps of developer into the developer in the developer tank as described above.

Summary of the invention The summary of the invention is that the electrostatic latent image developing device according to the invention has the following two points: (a) The developer supply roller is conductive.

(b) The supply roller is grounded.

The invention is characterized by an improved developer replenishment mechanism.

Although the details of the reason have not been clearly elucidated, the above-mentioned (a) and (b) sufficiently eliminate the contamination of the lumped developer as described above in the developer replenishment mechanism.

Embodiment An embodiment of the electrostatic latent image developing device according to the present invention will be described below in a form that is incorporated into a toner image transfer type electrophotographic copying machine.

In FIG. 1, an electrophotographic photosensitive drum 1 is rotationally driven in the direction of arrow a upon the start of a copying operation, and an electrostatic latent image forming means (not shown) forms an electrostatic latent image on its surface corresponding to an original image. A latent image is formed. This electrostatic latent image is developed by an electrostatic latent image developing device 2 while being carried on the surface of the electrophotographic photosensitive drum 1, and is visualized as a toner image.

The electrostatic latent image developing device 2 is divided into a developing unit 2A and a developer replenishing unit 2B, each of which can be easily attached to and detached from the main body of the copying machine. That is, the developing unit 2A is slidably placed on guide rails 3a and 3b fixed inside the copying machine main body, and can be pulled out to the front side of the copying machine main body (the front side in Fig. 1) as necessary. It is possible to remove it. Incidentally, a part of the guide rail 3a is designed to perform the function of guiding the transfer paper to the transfer section, which will be described later. Furthermore, the developer replenishment unit 2B is also placed on mounting plates 3c and 3d fixed inside the copying machine main body, and can be removed by lifting it to the top of the copying machine main body (upper side in Figure 1) if necessary. It is becoming.

Here, the developing unit 2A is mainly composed of a developer tank 4, a developing sleeve 5, and a bucket roller 6. The developer tank 4 contains a two-component magnetic developer, specifically, a developer containing a mixture of an insulating toner with an average particle size of 11 μm and a small-diameter magnetic carrier with an average particle size of 21 μm and a resistance value of 10 ¹⁴ Ωcm. It houses the developer and rotatably supports the developing sleeve 5 and the bucket roller 6. The developing sleeve 5 attracts the developer in the form of a brush on its circumferential surface by the magnetic action of a magnetic roller 7 rotatably provided therein. The electrostatic latent image carried on the surface of the photoreceptor drum 1 is developed. During development, both the developing sleeve 5 and the magnetic roller 7 are driven to rotate in the direction of the arrow b, thereby transporting the brush-shaped developer along the circumferential surface of the developing sleeve 5 in the opposite direction of the arrow b. It's becoming like this. However, the rotational driving speed of the developing sleeve 5 is set to a low speed, and the rotational driving speed of the magnetic roller 7 is set to a high speed. The bucket troller 6 is rotated in the direction of arrow c to sequentially supply the developer contained in the developer tank 4 onto the circumferential surface of the developing sleeve 5.

As will be explained in detail later, the developer tank 4 is
It is made of ABS resin and has a rib 4a for guiding the transfer paper on its bottom surface. On the other hand, a lid 4b is screwed onto the top thereof. This lid 4b has an opening 4b' for receiving the developer to be replenished by the developer replenishment unit 2B into the developer tank 4.

Next, the developer replenishment unit 2B will be explained. The developer replenishment unit 2B is mainly composed of a replenishment developer tank 8, a developer replenishment roller 9, and a developer stirring rod 10. The replenishment developer tank 8 contains therein a replenishment developer De, more specifically, an average particle diameter which is a consumed component of the two-component magnetic developer.
A replenishment developer made of 11 μm insulating toner can be stored therein, and a replenishment roller 9 and a stirring rod 10 are rotatably or swingably supported.
The replenishment developer tank 8 has a developer replenishment opening 8 at the bottom.
a, and has an opening for loading replenishment developer, which is normally closed by a lid 8b, in its upper part. This lid 8b can be opened from the outside of the copying machine main body, and developer can be replenished into the tank 8 from the outside.
Loading the De is now easier.

The developer replenishment roller 9 is connected to the developer replenishment opening 8.
A is rotatably mounted on shaft 9', and is driven by an unillustrated driving source when replenishing developer to move arrow d around shaft 9'.
The replenishment developer De stored in the tank 8 is replenished into the developer tank 4 by being rotated in the direction. This replenishment roller 9 is made of FRP (glass fiber reinforced plastic) material subjected to conductive treatment, and has a diameter of 22 mm and an electrical resistance value (volume resistance value) of 10 ³ Ωcm. Further, as shown in FIG. 3, on the outer peripheral surface of the replenishment roller 9, developer replenishment notches 9a for filling the replenishment developer De are provided at intervals of 90 degrees in the circumferential direction. It is provided in an open manner in the axial direction. This arrangement of the notch 9a stabilizes the amount of replenishment developer De filled in the notch 9a, and furthermore,
This is extremely advantageous because it facilitates uniform dispersion of the replenishment developer De replenished into the developer tank 4.

On the other hand, the developer replenishing roller 9 is grounded via a bearing (not shown) that supports its shaft 9'. This configuration is extremely important for preventing lumps of developer from being mixed into the replenishment developer De supplied to the developer tank 4. This is because, according to what the present invention has determined based on experiments, the replenishment roller 9 has a configuration capable of retaining electric charge, specifically, a configuration in which the replenishment roller 9 is insulatively supported with respect to the ground, or This is because in the structure where the replenishment roller 9 is made of an insulating material with a resistance of 10 ⁵ Ωcm or more, the above-mentioned contamination may occur, whereas in the above-mentioned structure, the above-mentioned contamination is eliminated. In order to eliminate the above-mentioned contamination, at least the electrical resistance value of the surface of the developer replenishing roller 9 must be 10 ⁴ Ωcm or less, preferably 10 ³ Ωcm or less, and the surface of the developer replenishing roller 9 must be It is sufficient if the developer roller 9 is grounded, and the developer roller 9 may be coated with a conductive material on its surface. That is, as the developer roller 9, in addition to one made of conductive resin such as polycarbon resin or metal such as aluminum, it is also possible to use one made of an insulating material with metal plating on the surface. It is.

The developer stirring rod 10 is driven to swing in the direction of arrow e around a shaft 10', and is driven to swing in synchronization with the rotation of the developer replenishment roller 9, and is replenished in the replenishment developer tank 8. It is designed to prevent the occurrence of crosslinking of the developer De. The developer measuring blade 11 measures the outer circumferential surface of the replenishing roller 9 in a region where the outer circumferential surface of the replenishing roller 9, which is rotated and driven with most of the outer circumferential surface buried in the replenishing developer De, is slightly elevated from the bottom. light pressure contact is made. This metering blade 11 only allows the replenishment developer De filled in the notch 9a of the replenishment roller 9 to reach the opening 8.
This allows the liquid to pass through a and be guided out of the tank 8. The arrangement of the metering blade 11 as described above is advantageous in stabilizing the amount of replenishment developer De filled in the notch 9a even in a high humidity environment.

The developer scraping blade 13 is in light pressure contact with the outer peripheral surface of the supply roller 9 exposed to the outside of the tank 8 . This blade 13 is the supply roller 9
The replenishment developer De guided out of the tank 8 due to the rotational drive of the developer is scraped downward from inside the notch 9a. As shown in FIG. 3, the tip of this blade 13 is cut into a strip so that the tip spans the entire width of the notch 9a and adapts to the depression to achieve a good developer scraping effect. It's summery. Further, a developer leakage prevention pad 12 is provided on the outer peripheral surface of the replenishment roller 9 that moves from outside the tank 8 into the tank 8.
is in light pressure contact.

The blades 11 and 13 are made of mylar sheets with a thickness of about 180 μm, and the pads 12
is made of polyurethane foam. Although there are no particular restrictions on these materials,
In order to further ensure that lumps of developer are not mixed into the replenishment developer De supplied in the developer tank 4, the material of the developer replenishment roller 9 is made of a material that is difficult to be triboelectrically charged. If so, it is desirable that they be located close to each other on the triboelectrification series. Furthermore, it is also desirable that the material be a conductive material. In this case, the surface of the supply roller 9 can also be grounded via these members.

The developer shutter 14 is normally biased in the direction of arrow f by a spring (not shown), and automatically moves in the direction of arrow f when the developing unit 2A and developer replenishing unit 2B are removed from the copying machine main body. , the replenishment developer De is prevented from dropping unnecessarily downward from the developer unit 2B. In addition,
The developer leakage prevention pads 21 and 22 are connected to the developer tank 4.
It is attached around the opening 4b' of the lid 4b, and when replenishing the developer, the replenishment developer De scraped off the outer peripheral surface of the replenishment roller 9 flows to the outside of the electrostatic latent image developing device 2. It is designed to prevent leakage.

On the other hand, the toner image obtained as a result of developing the electrostatic latent image by the electrostatic latent image developing device 2 is transferred to the transfer charger 15 installed as the photoreceptor drum 1 is rotated in the direction of arrow a. The image is transferred to the surface of the transfer paper in the section, and fixed to the surface of the transfer paper by a fixing means (not shown). Then, the transfer paper with the toner image fixed thereon is discharged as a copy from the copying machine main body to an external discharge tray.

The toner image transfer type electrophotographic copying machine shown in FIG. Any of the sheets of paper 17 stored in the cassette is used as transfer paper, and a special transfer paper feeding mechanism is provided for this purpose.

Here, to explain the copy paper feeding mechanism, the pair of conveyance rollers 18 are constantly driven to rotate, and the paper inserted into the main body of the copying machine along the manual feed table 16 is fed to the timing roller 1.
This leads to 9. The timing roller 19 is driven to rotate in synchronization with the rotation of the photoreceptor drum 1 when the copying operation starts, and is driven to rotate only after the leading edge of the paper reaches between the timing rollers 19. There is. Further, the paper feed roller 20 is rotated at the start of the copying operation, and guides the paper 17 in the cassette to the timing roller 19. A particularly noteworthy feature of this transfer paper feeding mechanism is that a portion of the transfer paper conveyance path is formed at the bottom of the developer tank 4 of the developing device 2. That is, as shown in FIG. 4, the developer tank 4 has a rib 4a on its bottom surface that widens toward the end in the transfer paper conveyance direction indicated by arrow B.
This means that the paper inserted into the main body of the copying machine along the manual feed table 16 is guided to the timing roller 19 by the rib 4a.

The ribs 4a are integrally formed when the developer tank 4 is molded with resin, specifically, ABS resin, and are formed at a distance h, specifically 3 mm, from the bottom surface of the developer tank 4. It has a height of Further, the rib 4a has an inclination of θ, specifically 30°, with respect to the transfer paper conveyance direction B, and has a shape that is itself inclined in the transfer paper conveyance direction B.

In the transfer paper transport mechanism having such a configuration, if a paper jam or the like occurs in the transfer paper transport path, the passage can be easily opened by removing the developer tank 4 from the copying machine main body. Advantageously, the removal of paper jams is simple.
Further, since the bottom surface of the developer tank 4 forms a part of the passage, the number of structural parts can be reduced, and the internal space of the copying machine can be used extremely effectively, which is advantageous.

Effects of the Invention In the developer replenishment mechanism of the electrostatic latent image developing device according to the present invention, replenishment developer without lump-like developer is replenished into the developer tank. For this reason,
Problems such as image quality deterioration of developed images that may occur in conventional electrostatic latent image developing devices can be solved by the electrostatic latent image developing device according to the present invention.

According to the present inventor's confirmation, when the developer replenishment roller in the electrostatic latent image developing device is insulatively supported with respect to the ground, or
It has been revealed that when the developer replenishment roller is changed to one made of an insulating material, the above-mentioned effects cannot be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the internal structure of an embodiment of the electrostatic latent image developing device according to the present invention, FIG. 2 is a diagram showing an enlarged main part thereof, FIG. FIG. 4 is a diagram showing the structure of the bottom surface of the developer tank (a diagram showing a part of the bottom surface of the developer tank from the direction of line A--A in FIG. 1). 2...Electrostatic latent image developing device, 2A...Developing unit,
2B...Developer supply unit, 4...Developer tank, 8...
Replenishment developer tank, 8a...Developer replenishment opening, 9
...Developer supply roller, 9a...Developer supply notch,
De...Replenishment developer.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A replenishment developer tank that stores replenishment developer therein and has a developer replenishment opening at the bottom, and a replenishment developer tank that is rotatably provided in the opening and has a developer replenishment tank on its circumferential surface. In an electrostatic latent image developing device comprising a replenishment roller having a notch and means for rotationally driving the replenishment roller in a fixed direction when replenishing developer, the replenishment roller is electrically conductive and grounded. An electrostatic latent image developing device characterized by: 2. The electrostatic latent image developing device according to claim 1, wherein the supply roller is made of a material having a volume resistivity of 10 ⁴ Ωcm or less.