JPH09114210A - Developing device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the amount of developer to be stored in a developing device, to prolong the life of the developer and to eliminate the need of changing the material of the shaft of a stirring member to hard material by making a hole on the surface of the shaft of the stirring member. SOLUTION: The stirring member 1 is provided with many rectangular holes 4 on the outer periphery of the shaft 2, and the storing amount of the developer is increased by as much as the holes 4 in comparison with the conventional developing device. Namely, since the hole 4 is only made on the surface of the shaft 2, the stirring member 1 is formed nearly at equal cost to the conventional member. Furthermore, the size of the shaft 2 does not differ from the conventional shaft of the stirring member and the strength thereof does not differ. In the case a magnetic permeability sensor 7 is provided, the holes 4 are not made on the surface of a part 5 on the member 1 opposed to the sensor 7. Therefore, the amount of the developer stored just before the sensor 7 becomes constant, output from the sensor 7 becomes stable, and ripple is rest-rained to be small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus, and more particularly to a developing device for an image forming apparatus which uses a two-component developer and uses a magnetic permeability sensor to control the toner density of the two-component developer.

[0002]

2. Description of the Related Art In recent years, there has been a demand for downsizing and cost reduction of an image forming apparatus, and accordingly, a developing device of low cost and small size is also required. As a low-cost and small-sized developing device, two stirring members each having a spiral blade provided on its shaft are rotatably provided in the developing device, and the shafts of the stirring members are rotated in opposite directions to each other in two different directions. 2. Description of the Related Art A developing device is known which mixes and agitates component developers and conveys them in one direction along an axis. Then, a magnetic permeability sensor is installed in the middle of the developer transport path, and toner concentration control of the two-component developer is also performed using the magnetic permeability sensor.

FIG. 6 is a schematic view of a general image forming apparatus. The cylindrical image carrier 8 or the photosensitive drum is rotatably supported by the main body of the image forming apparatus. Around the image carrier 8, a charging device 9, an exposure optical system (not shown), an eraser (not shown), a developing device 10, a transfer unit 12 and a cleaning unit 13 are arranged counterclockwise in order. The developing device 10 is made into a cartridge, two stirring members 1 are axially supported in parallel, and a magnetic permeability sensor 7 is arranged on the side of the stirring member 1. A developing sleeve 11 is axially supported in parallel with the stirring member 1. Further, a cleaning blade 15 is attached to the cleaning unit 13 so as to support a cleaning toner conveying screw 14 and contact the surface of the image carrier 8.

The operation of such a general image forming apparatus during image formation will be described. After the image carrier 8 is charged by the charger 9, an electrostatic latent image is formed on the image carrier 8 by an exposure optical system (not shown). And by an eraser not shown,
Unnecessary charges are removed in the non-image area such as the inter-transfer material area and both ends of the transfer material on the surface of the image carrier 8. Next, toner is supplied to the electrostatic latent image on the surface of the image carrier 8 from the developing sleeve 11 of the developing device 10 which is made into a cartridge, and a toner image is formed on the surface of the image carrier 8. Then, the transfer material is charged by the transfer portion 12 and the toner image on the image carrier 8 is transferred to the transfer material. After that, the transfer material is conveyed to a fixing device (not shown), and the toner image is fixed on the transfer material by heat and pressure. On the other hand, the toner remaining on the image carrier 8 without being transferred to the transfer material is scraped off by the cleaning blade 15.

FIG. 7 is a schematic side view of a stirring member and a magnetic permeability sensor included in a conventional developing device of this type. The stirring member 1 is configured by providing a blade 3 in a spiral shape on the surface of a shaft 2 having a round bar shape. When the agitating member 1 is rotated around the shaft 2, the blade 3 conveys the developer around the shaft 2 in the longitudinal direction of the shaft 2 while mixing and stirring the developer.

Further, a magnetic permeability sensor 7 is installed on the side of the stirring member 1, and the magnetic permeability of the two-component developer near the magnetic permeability sensor 7 is measured to determine the toner concentration of the two-component developer. Have control.

[0007]

However, the conventional developing device has a problem that a sufficient amount of developer cannot be stored in the developing device. Moreover, in the conventional developing device,
There is a problem in that the mounting position of the magnetic permeability sensor is limited, the amount of the developer near the magnetic permeability sensor is not stable, and it is difficult to correctly control the toner concentration. Further, the conventional developing device has a problem that the life of the developer is short because the amount of the developer stored is small.

Therefore, the present invention solves the above problems in a developing device having two agitating members, and provides a developing device of an image forming apparatus capable of correctly and simply controlling toner concentration. To aim.

[0009]

A developing device for an image forming apparatus according to a first aspect of the present invention incorporates two stirring members each having a spiral blade provided on a peripheral surface of a shaft, and a toner and a carrier. In a developing device of an image forming apparatus in which a two-component developer consisting of is mixed and agitated by the blade and conveyed in the axial direction of the stirring member, a hole is provided on the surface of the shaft of the stirring member. .

In the developing device of the image forming apparatus according to the second aspect of the present invention, a magnetic permeability sensor is provided in the vicinity of the stirring member, and the hole is formed in a portion of the shaft of the stirring member facing the magnetic permeability sensor. The feature is that it is not provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a developing device of an image forming apparatus according to the present invention will be described below with reference to the drawings. In the following description, the same parts as those in the conventional example are designated by the same reference numerals, and the duplicated description will be omitted.

FIG. 1 is a schematic side view of an agitating member of a developing device according to a first embodiment of the present invention, and FIG. 3 is a first view of the present invention.
FIG. 6 is a perspective view of a stirring member of the developing device according to the exemplary embodiment. The stirring member 1 of this embodiment has a rectangular hole 4 on the outer peripheral surface of the shaft 2.
A large number of holes are provided, and the amount of developer stored is increased by the amount of the holes 4 as compared with the conventional developing device. Moreover, a hole 4 is formed on the surface of the shaft 2.
Since it is simply provided, the stirring member 1 can be produced at a cost similar to the conventional one. Further, the thickness of the shaft 2 is the same as the shaft of the conventional stirring member, and the strength is the same.

FIG. 4 is a graph comparing the output of the magnetic permeability sensor when the conventional stirring member is used and when the stirring member of this embodiment is used. The vertical axis represents the permeability sensor output, and the horizontal axis represents time. The permeability sensor output 16 when the conventional stirring member shown in FIG. 7 is used has less ripple or fluctuation than the permeability sensor output 17 when the stirring member of the embodiment shown in FIG. 1 is used. You can see from the graph.

In the magnetic permeability sensor output 17 when the stirring member of this embodiment is used, the peak 18 of the magnetic permeability sensor output is the same as the peak 18 of the other magnetic permeability sensor outputs.
This is the output at the time when the hole 4 provided in the shaft 2 reaches the position immediately before the magnetic permeability sensor, and since the developer is also stored in the hole 4 of the shaft 2, the amount of the developer immediately before the magnetic permeability sensor. It corresponds to the time when the number is increasing. That is, it can be seen from the graph of FIG. 4 that the output is not constant unless the amount of the developer immediately before the magnetic permeability sensor is kept constant.

FIG. 2 is a schematic side view of the stirring member of the developing device according to the second embodiment of the present invention. As in the first embodiment, the stirring member 1 is provided with the hole 4 in the round rod-shaped shaft 2, but the hole 5 is formed on the surface of the portion 5 facing the magnetic permeability sensor 7.
Is not provided. For this reason, the amount of the developer immediately before the magnetic permeability sensor 7 becomes constant, the output of the magnetic permeability sensor becomes stable, and the ripple can be suppressed to a small level.

FIG. 5 is a graph showing the relationship between the magnetic permeability sensor output and toner concentration. A solid line 19 shows the relationship between the magnetic permeability sensor output and the toner concentration when the amount of developer is large,
The broken line 20 shows the relationship between the magnetic permeability sensor output and the toner concentration when the amount of developer is small. It can be seen from the graph in FIG. 5 that the output of the magnetic permeability sensor increases as the toner concentration decreases, regardless of whether the amount of developer is large or the amount of developer is small.
Further, it can be seen from the graph of FIG. 5 that the output of the magnetic permeability sensor is smaller when the developer is less, at the same toner concentration.

[0017]

According to the developing device of the image forming apparatus of the first aspect, since the hole is provided on the surface of the shaft of the stirring member, the amount of the developer to be stored in the developing device is increased and There is an effect that the life can be extended. Also, since the shaft of the stirring member is simply provided with holes, the thickness of the shaft of the stirring member is the same as the conventional one, and there is no great influence on the strength of the shaft required for mixing, stirring, and conveying the developer. It is not necessary to change the shaft of the stirring member to a hard material such as metal, and it is not necessary to change or increase the manufacturing process of the shaft of the stirring member, and the shaft of the stirring member can be kept at the conventional cost. There is also an effect that it can be reused by making a slight modification to the creation process of.

According to the developing device of the image forming apparatus of the second aspect, since no hole is provided in the portion of the shaft of the agitating member facing the magnetic permeability sensor, in addition to the above-mentioned common effect, immediately before the magnetic permeability sensor. There is an effect that the amount of the developer existing in can be kept constant even if the shaft of the stirring member rotates, and the output of the magnetic permeability sensor becomes stable.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a stirring member of a developing device according to a first embodiment of the present invention.

FIG. 2 is a schematic side view of a stirring member of a developing device according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a stirring member of the developing device according to the first embodiment of the present invention.

FIG. 4 is a graph comparing the outputs of magnetic permeability sensors when a conventional stirring member is used and when the stirring member of the present invention is used.

FIG. 5 is a graph showing the relationship between magnetic permeability sensor output and toner concentration.

FIG. 6 is a schematic diagram of a general image forming apparatus.

FIG. 7 is a schematic side view of a conventional stirring member and a magnetic permeability sensor.

[Explanation of symbols]

1 Stirring member 2 Shaft 3 Blade 4 Hole 5 Part 6 Part 7 Permeability sensor 8 Image carrier 9 Charger 10 Developer 11 Development sleeve 12 Transfer unit 13 Cleaning unit 14 Cleaning toner conveying screw 15 Cleaning blade 16 Conventional stirring member Magnetic permeability sensor output when used 17 Magnetic permeability sensor output when using the stirring member of the present invention 18 Peak of magnetic permeability sensor output

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Yuki 1-3-3 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (2)

[Claims] 1. A shaft of the stirring member, wherein two stirring members each having a spiral blade provided on the peripheral surface of the shaft are incorporated, and a two-component developer consisting of toner and carrier is mixed and stirred by the blade. A developing device for an image forming apparatus, wherein a hole is provided on a surface of a shaft of the stirring member in the developing device for the image forming apparatus conveyed in a predetermined direction. 2. The image forming apparatus according to claim 1, wherein a magnetic permeability sensor is provided near the stirring member, and the hole is not provided in a portion of the shaft of the stirring member facing the magnetic permeability sensor. Developer.