JPH03269558A - Developing device - Google Patents

Abstract

PURPOSE:To improve the mixing and electrification importing properties of a developer and the quality of an image by providing a major axis part where a distance from the center of a rotary shaft is set at a prescribed value, and a minor axis part where the distance from the center of the rotary shaft is set at a value shorter than the prescribed one, on the spiral blade of a developer carrying member, on a face perpendicular to a developer carrying direction. CONSTITUTION:The rotary shaft 31 of the developer carrying member 3 is eccentrically pro vided, the spiral blade 5 of the developer carrying member 3 has the major axis part 51 where the distance from the center of the rotary shaft 31 is set to the prescribed value and the minor axis part 52 where the distance from the center of the rotary shaft 31 is set at the value shorter than the prescribed one on the face perpendicular to the developer carrying direction. Therefore, the developer inside the developer carrying path 9 is carrying in a state where the developer is biased to the side of the major axis part 51 compared with the side of the minor axis part 52 of the spiral blade 5 by the rotation of the developer carrying member 3, and the quantity of the developer in the vicinity of a sidewall surface is reduced according to the passing through the major axis part 51. When the minor axis part faces to the sidewall surface, the developer in the upper part drops the bottom surface side of the lower part through a gap formed between the minor axis part and the sidewall surface, and is mixed with the developer of the lower part. Thus, the mixing and the electrifica tion imparting properties of the developer and the quality of the image are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device used in an image forming apparatus such as an electrophotographic copying machine and a printer. The present invention relates to a developing device that can improve the mixing properties of developer in the developing device.

(Prior Art) Generally, in an electrophotographic copying machine, a developing device is used to visualize an electrostatic latent image formed on a photoreceptor.

Hereinafter, a conventional developing device will be explained based on FIG. 3. Here, FIG. 3 is a sectional view showing a conventional developing device.

In the figure, l indicates a developing device, and inside this developing device 1, with a partition wall 2 in between, there are spiral blades 5, an agitation conveying spiral 3 (rotary shaft 31) as a developer conveying member, and a spiral blade. The supply conveyance spiral 4 (rotary shaft 41) for applying developer to the developing roller 7 has a substantially U-shaped developer formed by the side wall surface of the partition wall 2 and the inner surface of the developing device 1. They are arranged in parallel on the conveyance path 9. This agitation conveyance spiral 3 rotates counterclockwise in FIG. 3. It rotates clockwise in Figure 3 to convey the developer in the back direction perpendicular to the plane of the paper. Furthermore, the partition wall 2 facing both ends of the agitation conveyance spiral 3 and the supply conveyance spiral 4 is provided with developer from the supply conveyance spiral 4 to the agitation conveyance spiral 3 and vice versa. The receiver is formed with a notch (not shown) for passing the developer, and is configured to circulate and transport the developer within the developing unit 1. Note that a developer detector is provided in a part of the developer conveyance path of the agitation conveyance spiral 3, and the concentration (or amount of developer) of the developer being conveyed is detected. When the developer concentration (or developer amount) is low, new developer is replenished onto the agitation conveyance spiral 3 from the replenishment port 10 of the developing device 1 .

However, with the developer transport device described above, a situation has occurred in which the quality of the obtained image deteriorates with time.

In this regard, the inventor of the present invention discovered the phenomenon that causes this through observation.

That is, for example, when forming an image using a document with a large amount of image information, the amount of developer consumed increases, and the amount of developer (TI) that is newly replenished also increases accordingly. When the replenished developer (T1) is deposited on the upper layer of the old developer (TO), it may be deposited above the rotation locus of the helical blade 50 of the agitation conveyance spiral 3.

As a result, a situation arises in which the developer is not easily mixed into the old developer (TO) despite the rotational drive of the agitation conveyance spiral 3, and as a result, poor mixing of the developer is caused and the developer In some cases, the amount of charge was insufficient, resulting in image capri.

Therefore, in order to solve the above-mentioned problems, for example, it is possible to prevent the replenishment developer (T1) from accumulating above the spiral blades 5 by increasing the size of the spiral blades 5 of the stirring conveyance spiral 3. It will be done.

(Problems to be Solved by the Invention) However, in this case, the developer conveyance path 9 of the developing device 1 also becomes wide, resulting in an increase in the size of the developing device 1 itself, which is not very desirable in terms of space saving. I can't say that.

As a result of intensive study of the above-mentioned developing device, the inventors of the present invention found that by eccentrically providing the rotating shaft of the agitation conveyance spiral, which is normally provided to pass through the center of the helical blade, It has been discovered that the deposited developer can be completely and reliably mixed with the old developer.

In other words, an object of the present invention is to improve the mixing property while mixing the developer extremely smoothly without increasing the size of the developing device and its components by eccentrically disposing the rotating shaft of the agitation conveyance spiral. The object of the present invention is to provide a developing device that can perform the following steps.

(Means for Solving the Problems) The developing device of the present invention includes a developer transporting member having a spiral blade for agitating and transporting developer in one direction, and a developer transported by the developer transporting member. A developing device comprising a developer transport path having a side wall surface and a bottom surface for guiding a developer transport member and in which a developer transport member is rotatably disposed, the rotation axis of the developer transport member being eccentrically arranged. The spiral blade of the developer conveying member has a long diameter portion whose distance from the center of the rotation axis is set to a predetermined value in a plane perpendicular to the developer conveyance direction, and a distance from the center of the rotation axis. The short diameter portion is set to be shorter than a predetermined value.

(Function) According to the developing device of the present invention, in a plane perpendicular to the developer conveying direction, the spiral blade of the developer conveying member has a major diameter portion whose distance from the center of the rotation axis is set to a predetermined value; Since the developer in the developer transport path has a short diameter part whose distance from the center of the rotation axis is set shorter than a predetermined value, the developer in the developer transport path is transferred to the short diameter part of the helical blade as the developer transport member rotates. It is conveyed in a state where it is biased towards the long diameter side rather than the side.

As a result, the amount of developer present in the vicinity of one side wall surface of the developer transport path decreases as the long diameter portion passes, and when the short diameter portions eventually face each other, the side wall surface and Through the gap formed between them, the upper developer reliably falls to the lower bottom side and is mixed with the lower developer. The mixed developer on the bottom surface is conveyed by the long diameter portion.

In addition, the developer in the developer transport path does not always have a constant length in the plane perpendicular to the developer transport direction, but has different lengths (longer diameter part and shorter diameter part). It is easier to receive vibrations, which improves the mixing properties of the developer.

(Example) An example of the developing device of the present invention will be described below with reference to FIGS. 1 and 2.
This will be explained based on the diagram.

Here, FIG. 1 is a sectional view of essential parts showing one embodiment of the developing device of the present invention, and FIG. 2 is a sectional view for explaining the operation of the developing device of this embodiment.

Hereinafter, the same components as those of the conventional example will be indicated by the same reference numerals, and the explanation thereof will be omitted, and only the feature points of this embodiment that are different from the conventional example will be described.

In the figure, 3 indicates an agitation conveyance spiral, and a rotating shaft 31 of this agitation conveyance spiral 3 is eccentrically attached to one side from the center of the spiral blade 5.

As a result, the spiral blades 5 of the stirring conveyance spiral 3
is a long diameter portion 51 whose distance from the center of the rotating shaft 31 is set to a predetermined value R1 in a plane perpendicular to the developer conveying direction, and a distance from the center of the rotating shaft 31 that is shorter than the predetermined value R1. It has a short diameter portion 52 set to R2.

At this time, the predetermined value R1 is determined by the long diameter portion 51 of the spiral blade 5.
and the developer transport path 9, so as to have a length capable of transporting all the developer present in the gap Sl between the transport surface 8 of the developer transport path 9.
That is, the gap S1 generally has a gap length (0.5 to 1.5 mm) formed between the spiral blade 5 and the conveying surface 8.
(about an). On the other hand, the distance R2 of the short diameter portion 52 from the center of the rotating shaft 31 is determined by the gap S2 formed between the short diameter portion 52 of the spiral blade 5 and the side wall surface of the conveyance surface 8 of the developer conveyance path 9. The length of the gap S2 is such that the developer can fall from above to below through the gap S2.
The length is set to be slightly larger (about 2.0 Illflll to 2.5 circles) than (about 0.5 mm to 1.5□□□).

Continuing on, the operation of this embodiment will be explained. As the agitation conveyance spiral 3 rotates, the developer in the developer conveyance path 9 is moved closer to the major diameter portion 5 of the spiral blade 5 than to the minor diameter portion 52 side.
It is transported in a state where it is biased towards one side.

As a result, on the partition wall 2 side of the developer transport path 9, the amount of old developer (T O) existing near the partition wall 2 decreases as the long diameter portion 51 passes, and eventually the short diameter When the parts 52 face each other, the replenishment developer (TI) on the upper side reliably falls to the lower bottom side through the gap S2 created between the parts 52 and the partition wall 2, and is sucked into the old developer (TO) on the lower side. mixed. The mixed developer on the bottom surface side is completely conveyed by the long diameter portion 51.

When this example was observed through experiments, it was found that the unmixed phenomenon in which the new developer (T1) was deposited on top of the old developer (TO) no longer occurred as in the conventional case, and the miscibility of the developer was further improved. was confirmed to have improved. The reason for this is that the developer in the developer transport path 9 is arranged so that the rotating shaft 31 is eccentric from the center of the spiral blade 5, and the spiral blade 5 is perpendicular to the developer transport direction. Since the surface does not always have a constant length but always has different lengths, it can be assumed that vibrations are easily received during the conveyance process and the mixing properties of the developer are improved.

(Effects) According to the developing device of the present invention, in a plane perpendicular to the developer conveying direction, the spiral blade of the developer conveying member has a long diameter portion whose distance from the center of the rotation axis is set to a predetermined value; Since the developer in the developer transport path has a short diameter part whose distance from the center of the rotation axis is set shorter than a predetermined value, the developer in the developer transport path is transferred to the short diameter part of the helical blade as the developer transport member rotates. It is conveyed in a state where it is biased towards the long diameter side rather than the side.

As a result, the amount of developer present in the vicinity of one side wall surface of the developer transport path decreases as the long diameter portion passes, and when the short diameter portions eventually face each other, the side wall surface and Through the gap formed between them, the upper developer reliably falls to the lower bottom side and is mixed with the lower developer. The mixed developer on the bottom surface is conveyed by the long diameter portion. In addition, the developer in the developer transport path is susceptible to vibrations because the spiral blades do not always have a constant length in a plane perpendicular to the developer transport direction, but always have different lengths. This improves the mixing properties of the developer, making it possible to impart a predetermined amount of charge to the developer, resulting in good image quality.

Furthermore, it is only necessary to set the rotating shaft of the developer conveying member eccentrically, and there is no need to increase the size of the developing device and its components.

[Brief explanation of drawings]

FIG. 1 is a sectional view of essential parts showing an embodiment of the developing device of the present invention, FIG. 2 is a sectional view for explaining the operation of the developing device of this embodiment, and FIG. 3 is a sectional view of a conventional developing device. FIG. 1...Developer, 3...Agitation conveyance spiral, 31.
... Rotating shaft, 5... Spiral blade, 51... Long diameter part,
52...Short diameter part

Claims (1)

[Scope of Claims] A developer transporting member having a spiral blade for agitating and transporting developer in one direction, and a side wall surface and a bottom surface for guiding the developer transported by this developer transporting member. and a developer conveyance path in which a developer conveyance member is rotatably disposed, wherein a rotation axis of the developer conveyance member is eccentrically provided, and a spiral of the developer conveyance member is arranged eccentrically. In a plane perpendicular to the developer conveyance direction, the shaped blade has a long diameter part whose distance from the center of the rotation axis is set to a predetermined value, and a short diameter part whose distance from the center of the rotation shaft is set to be shorter than a predetermined value. A developing device comprising: