JP3458095B2 - Transport blade and developing device including the same - 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 for an image forming apparatus such as a copying machine, a printer and a facsimile. In particular, Japanese Industrial Standards A row No. 0 (A0) size and A
The present invention relates to a developing device for an image forming apparatus capable of forming an image on a large size sheet such as a first row (A1) size.

[0002]

2. Description of the Related Art For example, in a copying machine, an electrostatic latent image is formed on the surface of a photoconductor by exposing the surface of the photoconductor which is uniformly charged. It becomes a toner image, and an output image is obtained by transferring the toner image onto the paper. The development of the electrostatic latent image with the toner is performed by a developing device that electrostatically attaches the toner to the surface of the photoconductor. In the two-component developer, the carrier and the toner exist in the developing tank of the developing device, but when the development is repeated, the amount of the carrier in the developing tank does not change and the amount of the toner decreases. as a result,
Image density changes.

Therefore, in order to control the toner content in the developer, conventionally, the toner content sensor is used to detect the toner content in the developer. The toner concentration sensor detects magnetic permeability due to a carrier that is a magnetic material, and indirectly detects a toner content rate in the developer. It is preferable that the toner concentration sensor is attached to a portion in front of the detection surface where the amount of the developer is always stable. This is because even if the toner content in the developer is constant, if the amount of the developer existing in front of the detection surface of the toner concentration sensor changes, the magnetic permeability detected by the toner concentration sensor changes, and This is because it is erroneously determined that the toner content rate has changed.

As a mounting position of the toner concentration sensor satisfying such a condition, there may be a case where the vicinity of the conveying blade for stirring and transferring the developer in the developing tank is selected. At such a mounting position, a stable amount of developer always occupies the front side of the detection surface of the toner concentration sensor, so that the change in magnetic permeability due to the change in the amount of developer can be reduced.
Regarding the material and structure of the conveying blade, a metal stirring blade is welded around a metal shaft (metal conveying blade), a resin stirring blade is insert-molded with a metal shaft (insert molding resin conveying blade). ), And a resin-conveying blade integrally formed of resin.

By the way, in a large-sized copying machine or the like that uses A0 size paper, the conveying blades are very long (for example, 1 m). For this reason, in the insert-molded resin conveying blade, the resin contracts strongly during molding, and the shaft is likely to warp. Further, in the resin conveying blade, the load applied to the conveying blade is large and there is a problem in strength. For the above reasons, metal transport blades are generally used for such large-sized copying machines.

[0006]

However, when the metal conveying blade is used, the toner concentration sensor mounted in the vicinity of the conveying blade detects the magnetic permeability of the metal conveying blade to accurately detect the toner content in the developer. It may not be detected. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a conveying blade whose toner concentration sensor can detect the toner content rate.

Another object of the present invention is to provide a carrier blade having a sufficiently high strength. Still another object of the present invention is to provide a developing device in which the toner concentration sensor can correctly detect the toner content rate and control the image concentration.

In order to achieve the above-mentioned object, the invention according to claim 1 is a carrying blade for carrying a developer, which is housed in a developing tank of a developing device, from one end to the other end of the developing tank. A metal shaft of a predetermined length that extends, a metal spiral blade that is attached to the shaft and that extends spirally from the shaft except a predetermined range of the shaft , and a flat plate that is mounted in the predetermined range of the shaft. look contains a stirring blade of a non-magnetic with Jo unit, when driving the developing device, the stirring blade near
The conveyance blade is configured such that the developer stays nearby .

According to the present invention, since the shaft of the conveying blade is made of metal, even a long conveying blade for an image forming apparatus using a large size sheet such as A0 size and A1 size,
Sufficient strength is maintained. Further, the carrying blade includes a non-magnetic stirring blade, and the range in which the non-magnetic stirring blade is attached is a position facing the toner concentration sensor when the carrying blade is housed in the developing tank of the developing device. Can be set to. The non-magnetic stirring blade does not affect the magnetic permeability detected by the toner concentration sensor. Therefore,
By using such a conveyance blade, the toner concentration sensor can detect.

The invention according to claim 2 is the conveying blade according to claim 1, wherein the predetermined range of the shaft is a range including a substantially central portion in the longitudinal direction of the shaft.
In the image forming apparatus, the toner concentration sensor is usually attached to the developing tank at a substantially central portion in the longitudinal direction. Therefore, the non-magnetic stirring blade is attached to the central portion of the axis of the conveying blade as in the present invention, so that when the conveying blade is housed in the developing tank of the developing device, the non-magnetic stirring blade is The stirring blade and the toner concentration sensor face each other.

According to a third aspect of the present invention, the developing tank, the conveying blade according to the first or second aspect housed in the developing tank, and the developing tank so as to face the non-magnetic stirring blade of the conveying blade. And a toner concentration sensor for detecting the toner content rate in the developer attached to the developing device. In such a developing device, a non-magnetic stirring blade is attached to the shaft of the conveying blade at a position facing the toner concentration sensor, so that the toner concentration sensor can detect the toner concentration. Therefore, in such a developing device, the image density can be controlled correctly.

[0012]

1 is a sectional view showing the overall construction of a copying machine in which a developing device according to an embodiment of the present invention is adopted. The copying machine 1 includes a paper storage unit 2 for storing roll paper or cut paper, a transport mechanism 3 for feeding paper to the image forming mechanism 5, an optical system 4 for reading a document, and an optical system 4. An image forming mechanism 5 for forming an image based on the given light and transferring the image onto a sheet, a fixing device 6 for fixing the image transferred onto the sheet, and the like are provided.

The image forming mechanism 5 includes a photosensitive drum 7, a charger 8 for charging the photosensitive drum 7, and a developing device 9 for developing the electrostatic latent image formed on the photosensitive drum 7 into a toner image. , And a cleaner 10 for cleaning residual toner. FIG. 2 is a sectional view of the developing device 9 of the copying machine 1. Hereinafter, the structure and operation of the developing device 9 will be described with reference to FIG. The developing device 9 is a unit for developing the electrostatic latent image formed on the photosensitive drum 7 into a toner image with a two-component developer having toner and a carrier that is a magnetic material. The developing device 9 includes a developing tank 20, a hopper 27 that stores toner to be supplied to the developing tank 20, and a replenishing roller 28 that supplies the developer of the hopper 27 to the developing tank 20.

At the bottom of the developing tank 20, there is arranged an agitating paddle 21 having spiral blades around the shaft and blades oriented perpendicular to the shaft. On the left side of the stirring paddle 21, a conveyance blade 22 having spiral blades around the shaft is arranged. A toner concentration sensor 25 is attached to the wall surface of the developing tank 20 on the left side of the transport blade 22, with the detection surface D facing the transport blade 22.
A cylindrical supply roller 23 is provided on the upper right of the stirring paddle 21.
Are arranged. The supply roller 23 is arranged in close contact with the photosensitive drum 7 outside the developing tank 20 in parallel. The supply roller 23 is provided with a rotatable cylindrical sleeve, and a magnet whose relative position with respect to the apparatus is fixed therein.

A regulating plate 24 made of a non-magnetic material, such as aluminum, is arranged on the upper left side of the supply roller 23. The regulation plate 24 includes a regulation portion 24a having a flat plate shape, and a partition portion 24b located on the left side of the regulation portion 24a and having a bottom portion having a cross-sectional shape and an upwardly convex mountain shape. Regulation section 24a
Are disposed above the supply roller 23 with a constant distance from the peripheral surface of the supply roller 23. The partition portion 24b is arranged above the stirring paddle 21 and the supply roller 23 and at a position straddling them. A guide plate 26 is arranged above the stirring paddle 21 and between the stirring paddle 21 and the regulation plate 24. The guide plate 26 is inclined so that the conveying blade 22 descends in a certain direction.

When the developing device 9 is driven, the developer is agitated by the agitating paddle 21 and the conveying blade 22. The toner concentration sensor 25 detects the toner content rate in the developer by detecting the magnetic permeability of the developer flowing and passing through the front surface of the conveying blade 22 by the action of the conveying blade 22. Stirring paddle 21
From, the developer is also supplied to the supply roller 23.
The carrier, which is a magnetic material, is attracted by the magnetic field of the supply roller 23, so that the developer is attached to the peripheral surface of the supply roller 23. The sleeve of the supply roller 23 rotates in a direction in which the developer supplied from the stirring paddle 21 is carried upward along the peripheral surface of the supply roller 23 while the magnet inside the supply roller 23 is kept in the relative position. The developer adhering to the peripheral surface of the supply roller 23 is scraped off by the restricting portion 24a of the restricting plate 24 and is restricted so as not to exceed the desired amount of adhesion.

The developer that has been scraped off and separated from the supply roller 23 is dammed by the restricting portion 24a of the restricting plate 24, the traveling direction is changed along the partition portion 24b, and the developer is supplied toward the guide plate 26. The developer flows on the guide plate 26 and drops toward the conveying blade 22. The developer returned to the portion of the conveying blade 22 circulates again between the conveying blade 22 and the stirring paddle 21, and a part of the developer is supplied to the supply roller 23. When the toner in the developer is consumed by the supply roller 23 and the toner content rate in the developer decreases, the toner concentration sensor 25 detects the magnetic permeability corresponding to it and outputs a corresponding voltage. The replenishing roller 28 is operated so that the output voltage becomes the target output, and the toner is supplied from the hopper 27 to the developing tank 20, so that the toner content rate in the developer is kept constant.

Since the portion of the developing tank 20 where the conveying blade 22 exists is almost filled with the developer, the amount of the developer existing in front of the detection surface D of the toner concentration sensor 25 is stable. Therefore, by mounting the toner concentration sensor 25 at such a position, it is possible to reduce a change in magnetic permeability due to a change in the amount of the developer to be detected. FIG. 3 shows the developing tank 20, the conveying blades 22, the toner concentration sensor 25, the stirring paddle 21,
7 is a plan view showing the arrangement of a supply roller 23. FIG. The toner concentration sensor 25 is attached near the center of the developing tank 20 in the longitudinal direction. That is, the distances L1 and L2 from both end surfaces of the developing tank 9 to the toner concentration sensor 25 are substantially equal.

The conveying blade 22, the stirring paddle 21, and the supply roller 23 are arranged in parallel with each other at a constant interval. When the developing device 9 is driven, the developer is conveyed to the conveying blade 22.
By the rotation of the stirring paddle 21 and the stirring paddle 21, the stirring paddle 21 is conveyed in the direction along the respective axes, and is moved from the conveying blades 22 toward the stirring paddle 21 at one end and the stirring paddle 2 at the other end.
It moves from 1 to the conveying blade 22 and circulates. The supply of the developer from the stirring paddle 21 to the supply roller 23 occurs over almost the entire area in the longitudinal direction of the stirring paddle 21 and the supply roller 23.

FIG. 4 is a schematic perspective view showing the structure of the conveying blade 22 according to the embodiment of the present invention. FIG. 5 is a schematic perspective view showing the shape of the non-magnetic stirring blade 32 used for the conveying blade 22. The transport blades 22 are
A non-magnetic stirring blade 32 is attached around a shaft 30 made of metal in a certain range defined in the center of the shaft 30, and spiral blades 31A and 31B made of metal are provided on both sides of the non-magnetic stirring blade 32. It has a structure with blades attached. The metallic spiral blades 31A and 31B have a continuous spiral shape in the same rotation direction, and they are fixed to the shaft 30 by welding, brazing, or the like.

The non-magnetic stirring blade 32 has a shape in which the vicinity of the central axis of a rectangular plate is curved into a ½ cylindrical shape. That is, the non-magnetic stirring blade 32 has a semi-cylindrical portion 32a and two flat plate portions 32b. The non-magnetic stirring blade 32 is fitted onto the shaft 30 by the semi-cylindrical portion 32a,
The shaft 30 is fixed to the shaft 30 through a hole 32h. The material of the non-magnetic stirring blade 32 is resin,
Ceramic or the like can be used. The metallic spiral blades 31A and 31B also use the toner concentration sensor 25.
, So that it does not affect the magnetic permeability detected by SUS3
It is preferably made of a weak magnetic material such as 04. The screw for fixing the non-magnetic stirring blade 32 is preferably made of a non-magnetic material.

Since the transport blades 22 use the shaft 30 made of metal, sufficient strength can be maintained even when applied to an image forming apparatus using large size sheets such as A0 size and A1 size. In the developing device 9 to which the transport blade 22 is attached, the toner concentration sensor 25 is
It is arranged near the center of the shaft 30 in the longitudinal direction.
Therefore, the toner concentration sensor 25 and the non-magnetic stirring blade 32 face each other. When the developing device 9 is driven, the tip of the non-magnetic stirring blade 32 passes near the toner concentration sensor 25 by the rotation of the conveying blade 22, but does not affect the magnetic permeability detected by the toner concentration sensor 25. Therefore, by using such a conveyance blade 22, the toner content rate in the developer can be correctly obtained from the magnetic permeability detected by the toner concentration sensor 25.

Further, when the transport blade 22 having the non-magnetic stirring blade 32 having such a shape is used, the developer is transported laterally in the portion of the non-magnetic stirring blade 32, that is, near the toner concentration sensor 25. Since the action is poor, retention of the developer occurs. Therefore, a sufficient amount of the developer is always present in front of the toner concentration sensor 25, and it is possible to further reduce the change in magnetic permeability due to the change in the amount of the developer. FIG. 6 is a schematic perspective view showing a modified example of the non-magnetic stirring blade attached to the shaft 30.

The non-magnetic stirring blade 33 may have a shape including a spiral blade 33c formed on the semi-cylindrical portion 33a in addition to the flat plate portion 33b as shown in FIG. The non-magnetic stirring blade 33 having such a shape is
Spiral blades 33c are formed to be continuous when these two are combined with the flat plate-shaped portions 33b facing each other. At this time, the rotation direction of the spiral is the same as the rotation direction of the spiral of the metallic spiral blades 31A and 31B. The two non-magnetic stirring blades 33 having such a shape are fixed so as to be wrapped from both sides with respect to the metal shaft 30 by screws and the like through the holes 33h.

The spiral of the non-magnetic stirring blade 33 is in the same direction as the spiral of the metallic spiral blades 31A and 31B. That is, in such a conveying blade, since the spiral in the same direction is formed in all parts, the developer can be laterally transferred with an appropriate stagnation. FIG. 7 shows the toner when the developing device 9 is driven for each of the case of using the conveying blade 22 shown in FIG. 4 and the case of using the conveying blade in which the metal spiral blade is formed over the entire length around the metal shaft. It is a characteristic view which shows the result of having measured the output voltage of a density sensor.
Resin is used as the material of the non-magnetic stirring blade 32.

When the carrier blade having the metallic spiral blade is used, the output voltage fluctuates greatly in synchronization with the rotation period of the carrier blade, but the carrier blade 22 shown in FIG.
When using, the fluctuation of the output voltage is suppressed to be small. FIG. 8 is a schematic diagram showing the structure of a modified example of the transport blade according to the present invention. When it is desired to arrange the toner concentration sensor 40 at the end of the developing tank 9, as shown in FIG. 8, a non-magnetic stirring blade 42 is provided within a certain range of the end of the metal shaft 41.
And the transport blade 44 having the metallic spiral blade 43 provided on the other portion may be used. In this case, the toner concentration sensor 40 and the non-magnetic stirring blade 42 face each other.

FIG. 9 is a schematic diagram showing the structure of another modification of the conveying blade according to the present invention. When the two toner concentration sensors 45A and 45B are used, as shown in FIG. 9, a metal spiral blade 47, a non-magnetic stirring blade 48, and a metal spiral blade are provided around the metal shaft 46 from the end. 49, a non-magnetic stirring blade 50, and a conveying blade 52 provided with a metallic spiral blade 51 may be used. In this case, the toner concentration sensor 45A faces the non-magnetic stirring blade 48, and the toner concentration sensor 45B faces the non-magnetic stirring blade 50.

The above is an example of the embodiment of the present invention, and various design changes can be made within the scope of the matters described in the claims.

[Brief description of drawings]

FIG. 1 is a sectional view showing an overall configuration of a copying machine in which a developing device according to an embodiment of the present invention is adopted.

FIG. 2 is a sectional view of a developing device according to an embodiment of the present invention.

FIG. 3 is a plan view showing an arrangement of a developing tank, a conveying blade, a toner concentration sensor, a stirring paddle, and a supply roller of the developing device.

FIG. 4 is a schematic perspective view showing a structure of a conveyance blade according to the embodiment of the present invention.

FIG. 5 is a schematic perspective view showing a shape of a non-magnetic stirring blade used for the conveying blade.

FIG. 6 is a schematic perspective view showing a shape of a modified example of a non-magnetic stirring blade that constitutes the conveying blade of FIG.

FIG. 7 is a characteristic diagram showing a result of measuring an output voltage of the toner concentration sensor when the developing device is driven.

FIG. 8 is a schematic diagram showing the structure of a modified example of the conveying blades according to the present invention.

FIG. 9 is a schematic diagram showing the structure of another modification of the conveying blades according to the present invention.

[Explanation of symbols]

9 developing device 20 developing tanks 22, 44, 52 conveying blades 25, 40, 45A, 45B toner concentration sensors 30, 41, 46 metal shafts 31A, 31B, 43, 47, 49, 51 metal spiral blades 32, 33, 42, 48, 50 Non-magnetic stirring blade

Continuation of the front page (56) References JP-A-61-151579 (JP, A) Actually open 62-94356 (JP, U) Actually open 4-75356 (JP, U) (58) Fields investigated (Int .Cl. ⁷ , DB name) G03G 15/08 1105 G03G 15/08 115

Claims (3)

(57) [Claims] 1. A transport blade for transporting a developer housed in a developing tank of a developing device, comprising a metal shaft of a predetermined length extending from one end to the other end of the developing tank, and A metal spiral blade that is attached and extends in a spiral shape from the shaft except a predetermined range of the shaft, and a flat plate-shaped part that is attached to the predetermined range of the shaft.
Look contains a stirring blade of a non-magnetic, at the time of driving the developing apparatus, the developer in the stirring blade near the residence of
Conveying blades characterized by being configured to . 2. The conveying blade according to claim 1, wherein the predetermined range of the shaft is a range including a substantially central portion in the longitudinal direction of the shaft. 3. A developing tank, a carrying blade according to claim 1 or 2 housed in the developing tank, and a developing device mounted in the developing tank so as to face a non-magnetic stirring blade of the carrying blade. A developing device, comprising: a toner concentration sensor for detecting a toner content rate in the agent.