JP3008590B2 - 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 a developing device which is used in an image forming apparatus such as an electrophotographic copying machine and a printer, and which makes a developer adhere to an electrostatic latent image for visualization. The present invention relates to a developing device.

[0002]

2. Description of the Related Art Conventionally, as a developing device using a magnetic developer, a developer carrier that adsorbs the developer on the surface and rotates and conveys the developer, and a developing device that is adsorbed on the developer carrier There is known a developer regulating member that regulates a developer to form a thin layer of developer, and a developer transport unit that transports the developer while stirring the developer and supplies the developer to a developer carrier. I have.

[0003] In such a developing device, a developer carrier is provided so as to face an electrostatic latent image carrier capable of forming an electrostatic latent image on the surface, and the developer carrier is provided inside the developer carrier. A plurality of magnets are provided so as to be stationary, so that the magnetic developer can be attracted to the surface and conveyed. A first developer agitating chamber is provided in the housing accommodating the developer carrier along the axial direction of the developer carrier, and a second developer agitating chamber is provided in parallel with the first developer agitating chamber. A developer stirring chamber is provided, and both developer stirring chambers communicate with each other at both ends in the axial direction of the developer carrier. In the first developer agitating chamber, there is provided a first developer transport unit that transports the developer in the axial direction of the developer carrier and supplies the developer to the developer carrier. A second developer transport unit that transports the developer in a direction opposite to the first developer transport unit is provided in the developer stirring chamber. As the developer conveying means, a screw auger having a good developer agitating property is generally used.

In such a developing device, the developer is agitated by a second developer conveying means provided in a second developer agitating chamber and is conveyed in the axial direction of the developer carrier.
It is fed into the first developer stirring chamber from a communication portion with the first developer stirring chamber at the end. In the first developer stirring chamber, the developer is transported in the reverse direction by the first developer transporting means, and the developer is supplied to the developer carrier together with the transport. The developer conveyed to the opposite end in the first developer agitating chamber is fed into the second developer agitating chamber from a portion communicating with the second developer agitating chamber, and the second developer transporting means is provided. Is transported in the reverse direction. As described above, the developer is transported so as to circulate through the first developer stirring chamber and the second developer stirring chamber, and is sufficiently stirred. On the other hand, the developer supplied to the developer carrier is formed into a uniform thin layer by the developer regulating member, and the developer carrier is conveyed to a development area which is in close proximity to the electrostatic latent image holding member and is moved to the electrostatic latent image holding member. Image development takes place.

[0005]

However, in the above-described developing device, when the developer is consumed and the amount of the developer in the developer stirring chamber is reduced, the supply of the developer to the developer carrier is reduced. It becomes worse, and stripe-like unevenness due to the structure of the screw auger occurs in the thin layer of the developer formed on the surface of the developer carrier. This is because the developer is conveyed by the rotation of the blades of the screw auger 106 as shown in FIG. 5, and a portion where a large amount of the developer is deposited and a portion where only a small amount of the developer are deposited are generated with respect to the position of the blade. It is considered that the supply of the developer to the developer carrier 101 becomes uneven. If there is unevenness in the thin layer thickness of the developer on the developer carrying member, there is a problem that when developing the electrostatic latent image, stripe-shaped density unevenness occurs in the image, and a good image cannot be obtained.

Further, in the above-described developing device, the developer is transported so as to circulate between the first developer stirring chamber and the second developer stirring chamber, and along the axial direction of the developer carrier. The developer is substantially evenly distributed in the two developer stirring chambers provided. For this reason, even though a large amount of the developer still remains in the entire housing of the developing device, the amount of the developer in the first developer stirring chamber is small, and the above-described stripe-shaped This causes density unevenness.

As a means for eliminating such stripe-like density unevenness, a paddle roller may be used instead of a screw auger as a member for supplying a developer. However, the paddle roller has poor stirring performance of the developer, and the paddle roller alone may not sufficiently stir the developer. In particular, when a two-component developer in which a toner and a carrier that is a magnetic particle are mixed is used as a developer, sufficient stirring is necessary because only the toner is consumed in the development and only the toner is supplied. For this reason, a screw auger is required in addition to the paddle roller, and there is a problem that the developing device becomes large.

The present invention has been made in view of the above-mentioned problems, and stabilizes the supply of the developer to the developer carrying member by effectively utilizing the stored developer to reduce the amount of the developer. An object of the present invention is to provide a developing device capable of obtaining a high-quality image by expanding the range of the amount of residual developer in which stripe-shaped density unevenness due to the decrease is not generated.

[0009]

In order to solve the above-mentioned problems, a developing device of the present invention has a built-in magnet and a developer carrying member capable of adsorbing and transporting a developer on a surface thereof; A first developer stirring chamber provided along the axial direction of the developer carrier at a position facing the developer carrier;
A second developer stirring chamber that is provided substantially parallel to the first developer stirring chamber and communicates with the first developer stirring chamber at both ends; and the first developer stirring chamber or the second developer stirring chamber. A third developer agitating chamber communicating with the developer agitating chamber at one end thereof; and a third developer agitating chamber provided in the first developer agitating chamber for agitating the developer and conveying the developer in the axial direction of the developer carrier. A first developer conveying unit that is provided in the second developer stirring chamber, and conveys the developer in a direction opposite to the first developer conveying unit; 3 is provided in the developer stirring chamber, and the third
And a third developer conveying means is a developer stirring chamber for conveying the first developer stirring chamber or the second developer stirring chamber and the developer toward a position communicating said first developing Agent transport
Means and the second developer conveying means, the first developer
The developer is circulated and transported in the developer stirring chamber and the second developer stirring chamber.
Wherein the first developer stirring chamber has a discharge section for discharging a certain amount of the developer stored in the first developer stirring chamber to the third developer stirring chamber. .

Further, in the above-mentioned developing device,
It is preferable that the developer transport amount of the developer transport unit is set to be larger than the developer transport amount of the first developer transport unit.

Preferably, the first, second and third developer conveying means are screw-type conveying means. Further, the first developer conveying means and the second developer conveying means have a wing shape,
The pitch or the size of the screw may be different so that the amount of developer transported by the second developer transport unit may be larger, or the rotation speed of the second developer transport unit may be increased by the first developer transport. It may be made larger than the means, so that the developer transport amount is increased.

[0012]

In the developing device constructed as described above, the first and second developer stirring chambers provided in parallel communicate with each other at both ends, and the first developer conveying means and the second developer stirring means are connected to each other. Is arranged to transport the developer in the first developer agitating chamber and the second developer agitating chamber in opposite directions to each other, so that the developer is agitated in the first developer agitating chamber and the second developer agitating chamber. Is transported so as to circulate through the developer stirring chamber and the second developer stirring chamber. In addition, the third developer stirring chamber
Is arranged to convey the developer toward the communicating portion with the first developer stirring chamber or the second developer stirring chamber. Is carried into the first developer stirring chamber through the communication section or through the communication section and the second developer stirring chamber. Therefore, in addition to the developer circulating between the first developer stirring chamber and the second developer stirring chamber, the developer is carried into the first developer stirring chamber from the third developer stirring chamber. However, the first developer stirring chamber is provided with a developer discharge section. When the amount of the developer stored in the first developer stirring chamber exceeds a certain amount, the developer is discharged to the third developer stirring chamber. The discharged amount of the developer in the first developer stirring chamber is maintained at a constant amount.

The developer is supplied from the first developer stirring chamber to the developer carrier, and a thin layer of the developer is formed on the surface of the developer carrier. Since the amount of the developer is kept almost constant, the supply of the developer to the developer carrier is stabilized, and the thin layer on the developer carrier does not have stripe-like density unevenness. Even when the amount of developer stored in the developing device is reduced by performing the repetitive development, while the developer is being supplied from the third developer stirring chamber to the first developer stirring chamber, The amount of developer in the first developer stirring chamber is kept constant.

In a developing device in which the amount of developer transported by the second developer transporting means is larger than the amount of transported developer by the first developer transporting means, the developer is transported by the first developer transporting means.
The developer is conveyed by the second developer conveying means so that the amount of the developer carried into the second developer agitating chamber from the developer agitating chamber through the communicating part at the end is connected to the communicating part at the opposite end. From first
The amount of the developer carried into the developer stirring chamber is increased. Therefore, the amount of developer stored in the first developer stirring chamber is larger than the amount of developer stored in the second developer stirring chamber. Therefore, the developer is consumed and decreases, the developer is not supplied from the third developer stirring chamber to the first developer stirring chamber, and the amount of the developer stored in the second developer stirring chamber is reduced. The developer amount in the first developer agitating chamber is kept substantially constant until. As described above, even if the amount of developer stored in the developing device decreases, the amount of developer in the first developer stirring chamber for supplying the developer to the developer carrier is kept constant, and good development is performed. The range of the residual developer amount in the developing device that can be expanded.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a configuration of a developing device according to one embodiment of the present invention, and shows a cross section of a developer carrier and a developer conveying unit in a direction perpendicular to an axis. FIG. 2 is a schematic sectional view of the developing device taken along line II in FIG. 1, and FIG. 3 is a schematic sectional view taken along line II-II in FIG. The developing device is provided to face the electrostatic latent image holding member 20 and is capable of adsorbing and transporting the developer on the surface thereof, and a developer amount on the developer holding member 1. And a developer regulating member 2 for regulating the pressure and forming a thin layer of developer is disposed in the housing. Further, inside the housing, a first developer stirring chamber 3 provided along the developer carrier 1 for stirring and transporting the developer,
A second developer stirring chamber 4 is provided substantially parallel to the first developer stirring chamber and partitioned by a partition, and a third developer stirring chamber provided below the first and second developer stirring chambers. And a developer stirring chamber 5.

The first developer stirring chamber 3 contains a developer carrier 1
And a first screw auger 6 serving as a first developer conveying means is rotatably provided therein. The screw auger 6 is configured to stir the developer by rotating, and to convey the stirred developer to the developer carrier 1 while conveying the developer in the direction of arrow B.

The second developer stirring chamber 4 is provided substantially in parallel with the first developer stirring chamber 3 at the same length. This second
Is provided with a second screw auger 7 which is a second developer conveying means, and the arrow A which is in the opposite direction to the first screw auger 6 while stirring the developer. Can be conveyed in the direction of. At this time, the second screw auger 7 has the same developer conveying force as the first screw auger 6. The first
The developer agitating chamber 3 and the second developer agitating chamber 4 are open at both ends to a first communication chamber 10 and a second communication chamber 11, respectively. A communicating portion is configured to transfer the developer from the first developer stirring chamber to the second developer stirring chamber or from the second developer stirring chamber to the first developer stirring chamber. .

The third developer stirring chamber 5 is provided below the first developer stirring chamber 3 and the second developer stirring chamber 4 substantially in parallel with the developer stirring chamber. A third screw auger 8 serving as a third developer conveying means therein;
Is provided. By rotating the third screw auger 8, the developer can be conveyed in the same direction as the second screw auger 7, that is, in the direction of arrow C shown in FIG. The end of the third developer stirring chamber 5 on the downstream side in the transport direction is open to the third communication chamber 12,
The partition between the communication chamber 12 and the second communication chamber 11 is provided with an opening 13 through which the developer can be loaded. The first developer stirring chamber 3 is provided with a developer discharge section 9 at the upper portion of the side wall. When the amount of the developer stored in the first developer stirring chamber 3 exceeds a certain amount, the first developer stirring chamber 3 overflows. 9 to the third developer stirring chamber 5.

In such a developing device, the developer is conveyed in the direction of arrow A by the rotation of the second screw auger 7 in the second developer stirring chamber 4 and is sent into the second communication chamber 11. From the second communication chamber 11, the first screw auger 6 rotates to carry the developer into the first developer stirring chamber 3. In the first developer stirring chamber 3, the developer is indicated by an arrow B.
And is supplied to the developer carrier 1. The developer transported to the opposite end of the first developer stirring chamber 3 is sent to the first communication chamber 10 and is carried into the second developer stirring chamber 4 by the second screw auger 7. . As described above, the developer is conveyed so as to circulate through the first developer stirring chamber 3 and the second developer stirring chamber 4.

In the third developer stirring chamber 5, the third developer
Of the developer by the rotation of the screw auger 8
And is sent into the third communication chamber 12.
Further, the rotation of the third screw auger 8 causes the third
Through the opening 13 from the communication chamber 12 of the second communication chamber 11
Sent to. From the second communication chamber 11, the developer is carried into the first developer stirring chamber 3 by the first screw auger 6. Therefore, the developer is carried into the first developer stirring chamber 3 from the second developer stirring chamber 4 and the third developer stirring chamber 5, and is carried into the first developer stirring chamber 3. The amount of developer to be carried out is larger than the amount of developer carried out from the first developer stirring chamber 3 to the second developer stirring chamber 4. For this reason, the amount of the developer in the first developer stirring chamber increases, but the developer that has exceeded a certain amount overflows from the discharge section 9 provided in the upper part of the side wall, and enters the third developer stirring chamber 5. Is discharged.

When the developer is conveyed as described above, the amount of the developer stored in the developing device decreases due to the consumption of the developer. The developer is replenished into the developer stirring chamber 3 and the first developer until the developer from the first developer stirring chamber 3 no longer overflows and the developer in the third developer stirring chamber 5 runs out. The stirring chamber 3 holds a substantially constant amount of developer. If a sufficient amount of developer is stored in the first developer stirring chamber, unevenness in thickness does not occur in a thin layer of developer formed on the surface of the developer carrier, and unevenness in density also occurs in a developed image. Does not occur. Therefore, the range of the amount of the residual developer in the developing device in which good development can be performed is expanded.

In the above-described embodiment, the first screw auger 6 and the second screw auger 7 have the same developer conveying force. Can be larger than the screw auger 6. In such a developing device, the developer is transported by the first screw auger 6,
The amount of the developer transferred from the first developer stirring chamber 3 to the second developer stirring chamber 4 through the first communication chamber 10 at the end is conveyed by the second screw auger 7 and opposite thereto. The amount of the developer carried into the first developer stirring chamber 3 from the second communication chamber 11 at the end on the side increases. Therefore, the first
The amount of the developer stored in the developer stirring chamber 3 becomes larger than the amount of the developer stored in the second developer stirring chamber 4, and the developer is consumed and the second developer stirring chamber 4 is consumed. The amount of developer in the first developer stirring chamber 3 can be kept constant until the amount of developer stored in the third developer stirring chamber 5 becomes small. As a result, the range of the amount of the residual developer in the developing device that can perform satisfactory development without density unevenness is expanded, and development without density unevenness can be performed even when the developer is consumed.

FIG. 4 is a schematic cross-sectional view showing the structure of a developing device according to another embodiment of the present invention, and shows a cross section of the developer carrying member and the developer conveying means in a direction perpendicular to the axis. In this developing device, the third developer agitating chamber 5 is installed below the second developer agitating chamber 4, and the size of the blades of the second screw auger 7 and the third screw auger 8 is made the same. It was done. Thus, the size of the developing device can be reduced without changing the effects of the embodiment shown in FIG.

The development is repeatedly performed by the developing device as described above, and the amount of the developer stored in the developing device when the stripe-shaped density unevenness starts to occur in the image is measured to confirm the effect of the present invention. The results obtained are shown below. Table 1 shows that the initial developer volume stored in the entire developing device is 450 ml.
And, when the stripe-shaped unevenness starts to occur, the developing device according to the present invention, the developer volume stored in the entire developing device,
This is shown in comparison with a conventional developing device. The developing device according to the present invention and the conventional developing device shown here both have a developer storage capacity of the entire developing device of 450.
ml, and is set such that the amount of developer transported by the first screw auger 6 and the amount of developer transported by the second screw auger 7 are the same. The conventional developing device has two developer stirring chambers as described above, and can transport the developer so as to circulate through these developer stirring chambers.

[0025]

[Table 1]

From this table, it can be seen that in the conventional developing device, the developer volume at which the occurrence of stripe-like unevenness of the image is 360 ml, whereas in the developing device according to the present invention, it is 280 ml, and the residual development which does not cause the stripe-like unevenness. The range of dosage is expanded by 80 ml.

Table 2 shows that in the developing device according to the present invention, the ratio of the number of rotations of the first screw auger 6 to the number of rotations of the second screw auger 7 was changed, and the conveying force of the second screw auger 7 was changed. To the first screw auger 6
The graph shows the developer volume at the time when stripe-shaped unevenness starts to occur when the width is larger than the above.

[0028]

[Table 2]

According to this table, the first screw auger 6
When the rotational speed ratio between the first screw auger 7 and the second screw auger 7 is 1: 2, the range of the amount of the residual developer in which the striped unevenness does not occur is further expanded by 40 ml as compared with the case where the rotational speed ratio is 1: 1. It is recognized that. In the conventional developing device, even if the conveying force of the second screw auger is made larger than the conveying force of the first screw auger, the effect of expanding the range in which the striped unevenness does not occur is recognized. When the rotational speed ratio between the auger and the second screw auger is 1: 2, the amount of developer at which stripe-shaped unevenness starts to be generated is 320 ml.

[0030]

As described above, in the developing device of the present invention, the first developer is agitated and conveyed in a circulating manner.
A third developer stirring chamber is provided in addition to the developer stirring chamber and the second developer stirring chamber, and the developer is supplied from the third developer stirring chamber to the first developer stirring chamber or the second developer stirring chamber. The amount of developer stored in the first developer stirring chamber is maintained at a sufficient amount even if the amount of developer in the developing device decreases. You. In addition, the discharge amount of the developer exceeding a certain amount in the first developer stirring chamber is discharged to the third developer stirring chamber, so that the amount of the developer in the first developer stirring chamber is substantially constant. Will be kept. Accordingly, as the amount of the developer in the developing device decreases, the range in which the substantially constant amount of the developer is maintained in the first developer stirring chamber is expanded, and the amount of the developer in the developing device decreases and the remaining amount of the developer decreases. A developing device in which stripe-like unevenness does not occur in the image until the amount becomes small. Further, the above effect can be further enhanced by making the conveying force of the second developer conveying means in the second developer stirring chamber larger than the conveying force of the first developer conveying means in the first developer stirring chamber. Can be significant.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a developing device according to an embodiment of the present invention, illustrating a cross section of a developer carrier and a developer conveying unit in a direction perpendicular to an axis.

FIG. 2 is a schematic cross-sectional view showing a configuration of a developing device according to an embodiment of the present invention, and shows a cross-section at a position indicated by line II in FIG.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of a developing device according to one embodiment of the present invention, and illustrates a cross-section at a position indicated by line II-II in FIG.

FIG. 4 is a schematic cross-sectional view illustrating a configuration of a developing device according to another embodiment of the present invention, illustrating a cross section of the developer carrier and the developer conveying unit in a direction perpendicular to the axis.

FIG. 5 is a schematic diagram illustrating a problem that occurs when a developer is supplied to a developer carrier by a screw auger.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developer carrier 2 developer regulating member 3 first developer stirring chamber 4 second developer stirring chamber 5 third developer stirring chamber 6 first developer conveying means 7 second developer conveying means Reference Signs List 8 third developer conveying means 9 discharge section 10 first communication chamber 11 second communication chamber 12 third communication chamber 13 opening A, B, C Arrows indicating the direction in which developer is conveyed

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiro Yamaguchi 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Ebina Works (56) References JP-A-3-180876 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/08-15/09

Claims (2)

(57) [Claims] 1. A developer carrying member having a built-in magnet and capable of adsorbing and transporting a developer on its surface, and provided along a direction of an axis of the developer carrying member at a position facing the developer carrying member. A first developer stirring chamber provided; a second developer stirring chamber provided substantially parallel to the first developer stirring chamber and communicating with the first developer stirring chamber at both ends; A third developer stirring chamber communicating with one end of the first developer stirring chamber or the second developer stirring chamber, and a third developer stirring chamber provided in the first developer stirring chamber to stir the developer. A first transporting member in the axial direction of the developer carrying member
A second developer conveying means provided in the second developer stirring chamber, for conveying the developer in a direction opposite to the first developer conveying means, and the third developing means. A third developer conveying means provided in the developer stirring chamber, for conveying the developer toward a position where the third developer stirring chamber communicates with the first developer stirring chamber or the second developer stirring chamber; And the first developer conveying means and the second developer conveying means.
Means the first developer stirring chamber and the second developer stirring chamber
Is intended to circulate conveying the developer in the inner, the first developer stirring chamber, to discharge the developer exceeds a predetermined amount is stored in the first developer stirring chamber into the third developer stirring chamber A developing device comprising a discharge unit. 2. The developing device according to claim 1, wherein the amount of developer transported by said second developer transporting means is equal to said first developer transport amount.
A developing device that is set to be larger than the amount of developer transported by the developer transporting means.