JP3217169B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine, and more particularly to a vertical developing device used for a color copying machine.

[0002]

Conventionally, the current image using the two-component developer in an electrophotographic image forming apparatus is carried out using a vertical development apparatus as shown in FIG. In the figure,
A developing device 1 is disposed in proximity to a photosensitive drum 2 serving as an image carrier, and the developing device 1 includes a replenishing tank 3 for storing replenished toner 11 and a developing tank 4. In the supply tank 3, a supply roller 6 and a thin layer blade 7 which are in contact with the supply roller 5 are arranged. A bias circuit 20 for applying a bias voltage is connected to each of the supply roller 5, the supply roller 6, and the thin layer blade 7, and the bias circuit 20 is connected to a reference density pattern 21 formed on the photosensitive drum 2. The amount of charge of the replenishment toner 11 is corrected according to.

A developing sleeve 8 is disposed in the developing tank 4, and a plurality of magnets 8a including a magnet constituting a main developing pole are provided inside the developing sleeve 8 in a support plate 8a.
b, and this developing main pole is set at a position facing the photosensitive drum 2. Then, an upper stirring screw 12 for stirring the developer and a lower stirring screw 14
Is arranged. In the above configuration, the replenishment toner 11 stored in the replenishment tank 3 is rubbed against the surface of the replenishment roller 5 by the supply roller 6 and is carried on the surface, and the thickness of the toner layer is made uniform by the thin layer blade 7. It is transported in the direction of the developing sleeve 8. Then, the toner carried to the developing tank 4 and carried on the surface of the developing sleeve 8 forms a magnetic brush by a plurality of magnets 8a, which is exposed from the opening of the developing tank 4 and is already formed on the photosensitive drum 2. By contacting the electrostatic latent image, the image is visualized and developed.

[0004]

However, in the above-mentioned conventional developing device, it is very difficult to stir and mix the toner and the carrier of the developer magnetically adhered on the developing sleeve 8. This is remarkable in the vertical developing device having a developer agitating section above the developing sleeve 8. In the developing device having this configuration, if the stirring and mixing are insufficient, the toner density of each copy fluctuates, the pitch of the spiral pitch of the upper and lower stirring screws 12 and 14 becomes uneven, and the front and rear density unevenness due to poor lateral stirring of the developer is caused. Would. Also, the developing sleeve 8 is used to improve the image quality.
If the linear speed of rotation is reduced, the stirring and mixing (particularly, the horizontal stirring ability) is necessarily reduced, so that there is a problem that high image quality cannot be expected. Accordingly, the present invention solves the above-mentioned conventional problems, and can perform good stirring and mixing of the toner and the carrier of the developer on the developing sleeve, and also has a horizontal stirring ability, thereby enabling high image quality HR development. It is an object to provide a developing device having a simple structure.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a developing sleeve for carrying a two-component developer comprising a toner and a carrier, an upper stirring screw and a lower stirring screw for mixing the toner and the carrier. Screw and surface of two-component developer carrying toner on the developing sleeve
And a developing roller having a magnet inside thereof for supplying the toner to the developing roller.
Transport to remove the developer on the leave and transport it upward
A developing apparatus comprising feed and roller, and arranged close to the stirring screw to the upper side of the developing sleeve,
The transport roller is provided so as to have a central axis above the central axis of the lower stirring screw, and the upper stirring screw is disposed so as to have a central axis above the central axis of the transport roller, and the developing sleeve 2 supported on
The supply roller in the moving direction of the developer
The rollers and the development area are arranged in this order.
is there. Further, a stirring guide member is provided so as to surround at least the lower half portion of the upper stirring screw in close proximity, and to assist lateral conveyance and stirring of the developer by the upper stirring screw.

[0006]

[Action] Thus, toner is f on the developing sleeve provided by the auxiliary supply roller. The developer (toner and carrier) on the developing sleeve is all stripped off by a transport roller and transported upward, and thereafter the developer drops to a guide member by gravity and is temporarily held here. At this time, the developer is conveyed in the horizontal direction by the upper stirring screw, and sufficient horizontal stirring is performed, and the developer falls downward from the rear end portion or the like of the stirring guide member. Then, the dropped developer is sufficiently mixed and supplied to the developing sleeve while being laterally conveyed by the lower stirring screw.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a developing device 1 is arranged close to a photosensitive drum 2 serving as an image carrier, and the developing device 1 includes a supply tank 3 for storing a supply toner 11 and a developing tank 4. In the supply tank 3, a supply sponge roller 6 and a thin layer blade 7 which are in contact with the supply roller 5 are arranged. In the developing tank 4, a developing sleeve 8 and its developing doctor 15, an upper conveying roller 10, a lower conveying roller (conveying roller) 9, an upper conveying screw 12, a screw casing 13 serving as a stirring guide member, and a lower conveying screw 14 are arranged. Have been. Inside the developing sleeve 8, a plurality of magnets (not shown) including a magnet constituting a developing main pole are attached, and the developing main pole is set at a position facing the photosensitive drum 2. Above the developing sleeve 8, there is disposed a lower transport roller 9 provided with a block magnet having two poles of NS.
An upper transport roller 10 having the same internal structure as that of the above is disposed. An upper stirring screw 12 and a screw casing 13 are provided at a substantially intermediate position between the upper conveying roller 10 and the lower conveying roller 9, and the lower stirring screw 1 is provided below these.
4 are provided. The screw casing 13 has a slit opening (not shown).

In this configuration (claims 3 and 2), the replenishment toner 11 stored in the replenishment tank 3 is rubbed against the surface of the replenishment roller 5 by the supply sponge roller 6, and is carried on the surface and the thin layer blade 7 Thereby, the thickness of the toner layer is made uniform, and the toner layer is conveyed in the direction of the developing sleeve 8. Then, the toner carried to the developing tank 4 and carried on the surface of the developing sleeve 8 forms a magnetic brush by a plurality of magnets 8a, which is exposed from the opening of the developing tank 4,
By coming into contact with the electrostatic latent image already formed on the photosensitive drum 2, the image is visualized and development is performed.

After the development by the developing sleeve 8 is completed, the lower transport roller 9 removes the developer supplied from the replenishing roller 5 by one.
00% is peeled off and pumped up toward the upper transport roller 10, and the upper transport roller 10 also pumps the supplied developer upward. The rotation directions of the developing sleeve 8, the upper transport roller 10, and the lower transport roller 9 are all counterclockwise. Then, the developer pumped up by the upper transport roller 10 reaches a portion above the developing tank 4 which is not affected by the magnetic force, drops by the gravity below the developing tank 4, is received by the screw casing 13, and It is conveyed from the near side in the figure to the far side by the upper stirring screw 12 rotating in the direction.
At this time, the developer that has overflowed while being conveyed in the screw casing 13 falls downward from the slit opening, and all falls downward from a release port provided near the rear end of the screw casing 13. . The shape of the screw casing 13 enables efficient cross-mixing. The developer that has fallen from the slit opening and the release opening of the screw casing 13 is sufficiently mixed with the developer accumulated therearound while being conveyed from the back side in the figure to the front side by the lower stirring screw 14. Is supplied to the developing sleeve 8.

Next, another embodiment (claim 1) will be described with reference to FIG. The configuration of this embodiment is substantially the same as that of the above-described embodiment, except that the upper transport roller 10 is omitted and only the lower transport roller (transport roller) 9 is provided. With this configuration, a sufficient developer transfer (pumping) volume cannot be ensured, but the apparatus becomes simpler and the entire apparatus becomes more compact. The shape of the screw casing 13 has a function of allowing the developer conveyed by the conveying roller 9 to be filled by gravity dropping and peeling and filling. As described above, the developer on the developing sleeve 8 is completely stripped off by the transport roller (lower transport roller) 9 and vertically transported (including the upper transport roller 10), and then dropped onto the screw casing 13 by gravity. To hold the developer once, and the upper stirring screw 11
To perform sufficient horizontal stirring. At this time, the developer overflowing in the screw casing 13 escapes from the slit opening, and the developer conveyed laterally drops from the release port. Then, while being laterally conveyed by the lower stirring screw 14, the developer is sufficiently mixed with the developer and supplied to the developing sleeve 8.

[0011]

As described above, according to the first and second aspects, the lower stirring screw is arranged close to the upper side of the developing sleeve, and the transport roller for transporting the developer upward is provided with the lower stirring screw. The upper stirring screw is provided so as to have a center axis above the center axis of the stirring screw, and the upper stirring screw is arranged so as to have a center axis above the center axis of the conveyance roller, and at least a lower half of the upper stirring screw is provided. Since the guide member is provided so as to surround the toner in close proximity, the toner of the developer on the developing sleeve and the carrier can be satisfactorily stirred and mixed, and the lateral stirring ability can be improved. Therefore, deterioration of the image repeat variation or uneven pitch of the image shading can be prevented, compact, it is possible to perform the current image of high quality at low cost. Even if the linear velocity of the developing roller is reduced to achieve high image quality, a sufficient stirring effect can be expected. Also,
According to the third aspect, since the upper transport roller separate from the transport roller is disposed so as to have a central axis above the central axis of the upper stirring screw, the developer transport volume to the guide member can be sufficiently increased. To improve the stirring and mixing properties of the developer.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional developing device.

[Explanation of symbols]

 Reference Signs List 5 supply roller 6 supply roller 8 developing sleeve 9 transport roller (lower transport roller) 10 upper transport roller 11 toner 12 upper stirring screw 13 stirring guide member 14 lower stirring screw

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Maruta 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Kaoru Yoshimatsu 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Takuji Yoneda 1-3-6 Nakamagome, Ota-ku, Tokyo; Ricoh Co., Ltd. (72) Inventor Kazuo Nojima 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Katsuji Watanabe 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (56) References JP-U 2-107164 (JP, U) Kaisho 63-70567 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08-15/095

Claims (3)

(57) [Claims] A developing sleeve for carrying a two-component developer comprising a toner and a carrier; an upper stirring screw and a lower stirring screw for mixing the toner and the carrier;
Toner of the two-component developer carried on the developing sleeve
A replenishing roller for replenishing the surface and a magnet inside
To peel off the developer on the image sleeve and transport it upward
A developing apparatus comprising: a conveying roller, and the stirring screw are arranged close to the upper side of the developing sleeve, wherein the conveying roller, the center axis above the center axis of the stirring screw provided so as to have a, and the upper mixing screw is arranged to have a central axis above the center axis of the conveying roller, said current
In the moving direction of the two-component developer carried on the image sleeve
The supply roller, the transport roller and the developing area
A developing device, which is arranged in the following order . 2. An agitating guide member which is disposed so as to closely surround at least a lower half of the upper agitating screw, and which assists lateral conveyance and agitation of the developer by the upper agitating screw. The developing device according to claim 1. 3. The developing device according to claim 1, wherein an upper transport roller separate from said transport roller is disposed so as to have a central axis higher than a central axis of said upper stirring screw.