JPH11167258A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of preventing lowering of an image density, fog, vertical white stripes, unevenness, or the like from occurring. SOLUTION: This device 3, provided with developer containing means 309 containing the insulating powder developer, developer carry/transporting means 301 supported by the developer containing means 309 freely rotationally, while carry/transporting the developer on a surface thereof, and developer layer forming means 302 forming the developer layer on the developer carry/ transporting means 301, is not provided with developer transport/applying means coming into contact with the developer carry/transporting means 301, and moreover, is constituted so that the lowermost part of the developer carry/ transporting means 301 is located above the lowermost part of the internal surface of the developer containing means 309 on the vertical line. In such a case, the developer containing means 309 is provided with developer fall retarding means (310a to 310c) retarding the fall of the developer from the vicinity of the developer carry/transporting means 301 toward the lowermost part on the inside surface of the developer containing means 309.

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 developing an electrostatic latent image formed on an image carrier by an electrophotographic system or an electrostatic recording system with an insulating powder developer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus or the like which forms an image by an electrophotographic system or an electrostatic recording system, as shown in FIG. 9, an electrostatic latent image formed through a predetermined process is carried. The image carrying means 1 and the developer carrying /
An appropriate developing bias voltage E was applied between the conveying means 301 and the electrostatic latent image on the image carrier 1 was developed by the insulating powder developer t (FIG. 9).

Incidentally, the position of the developer carrying / transporting means 301 in the developing device 3 is generally
9 is lower than or approximately equal to the bottom surface 309B. This is based on the technical idea of actively using gravity when the developer in the developer accommodating section 309 moves toward the developer carrying / transporting means 301.

However, in recent years, after a user of the image forming apparatus issues an image output command (such as pressing a copy button or a control unit of the image forming apparatus giving the image forming command to the image forming unit), image information is printed on paper. From when the image is printed on a recording medium such as the printer and discharged from the image forming apparatus (hereinafter referred to as _TFP).
And However, it does not include so-called warm-up time of the image forming apparatus) that is short has come to be emphasized in this T _FP.

As an effective means for shortening the _TFP , the conveying direction of a recording medium such as paper inside the image forming apparatus is changed from a substantially horizontal direction shown in FIG. 10 to a substantially vertical direction shown in FIG. It is conceivable to reduce the distance from the paper feeding device 2 to the fixing device 4. In FIGS. 10 and 11, reference numeral 1 denotes an image carrier, and 3 denotes a developing device.

By the way, when the above configuration is adopted, it is often necessary that the position of the developer carrying / transporting means in the developing device is considerably higher than the developer accommodating portion.

In such a developing device, gravity cannot be used when the developer in the developer accommodating portion moves toward the developer carrying / transporting means, and the developer that has been pumped up is rather developed due to gravity. It returns in the direction of the agent storage means.

Further, even when the developer in the developer accommodating section reaches the vicinity of the developer carrying / transporting means, since the compressive force due to gravity does not act, the developer comes into contact with the developer carrying / transporting means 301 as shown in FIG. A roller-like developer conveying / applying means 308 made of sponge rubber or the like has been required. In particular, when a non-magnetic developer to which a magnetic attraction does not act is used, the developer transport / coating unit 308 is indispensable.

[0009]

However, in the case of using the developer conveying / applying means in contact with the developer carrying / conveying means, as the process speed (ie, image forming speed) increases, the developer conveying / applying means increases. Coating means and developer carrying /
Problems such as abrasion of the conveying means and deterioration of the developer itself occur. As a result, there is a problem that the output image quality is deteriorated due to a decrease in image density, fog, vertical white stripes, unevenness, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to pump up a developer without using a developer carrying / applying means in contact with the developer carrying / transporting means. Another object of the present invention is to provide a developing device capable of preventing the occurrence of image density reduction, fog, vertical white stripes, unevenness, and the like.

[0011]

In order to achieve the above-mentioned object, according to the present invention, there is provided a developer accommodating means for accommodating an insulating powdery developer, and a rotatably supported by the developer accommodating means. A developer carrying / transporting means for carrying / transporting a developer on the surface thereof; and a developer layer forming means for forming a developer layer on the developer carrying / transporting means. No developer transport / application means in contact with the transport means,
In the developing device, in the developing step, the lowermost part of the developer carrying / transporting means is located vertically above the lowermost part of the inner surface of the developer accommodating means. The developer storage means is provided with developer drop obstruction means for obstructing the developer from dropping toward the lowermost portion of the inner surface of the storage means.

According to a second aspect of the present invention, in the first aspect of the present invention, the developer falling obstruction means is constituted by a plate-like member having a free end provided on a lower wall of the developer accommodating means. Features.

According to a third aspect of the present invention, in the first aspect of the invention, the developer falling obstruction means is a plate-like member having a free end provided between an upper wall and a lower wall of the developer accommodating means. It is characterized by comprising.

According to a fourth aspect of the present invention, in the first aspect of the invention, the developer drop obstructing means is constituted by a magnetic field generating means provided near a wall of the developer accommodating means.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a sectional view of a developing device according to a first embodiment, FIG. 2 is a partially enlarged sectional view of the developing device, and FIG. 3 is a developer carrying / transporting means of the developing device. FIG. 4 is an enlarged sectional view of a portion, and FIG. 4 is a perspective view of a plate-like member.

The developer carrying / transporting means 301 of the developing device 3 according to the present embodiment is constituted by an aluminum cylinder having a diameter of 24.5 mm, and has aluminum rotating support shafts at both ends thereof to accommodate the developer. It is rotatably supported on the side wall of the means 309 via a bearing (not shown). The developer carrying / transporting means 301 rotates at a peripheral speed of 470.4 mm / sec in the direction of arrow A in the figure.

The distance between the developer carrying / transporting means 301 and the latent image carrying means 1 is set at 210-250 μm, and the developer carrying / transporting means 301 has an amplitude of 1350-1650 V,
A rectangular AC voltage with a frequency of 2400-3000 Hz is 0V-
The voltage is superimposed on a DC voltage that is variable between +600 V and applied.

The outer surface of the developer carrying / transporting means 301 is firstly subjected to a surface roughening treatment by spraying spherical glass particles and then irregular alumina particles, and has a center line average roughness of 0.25 to 0.5. It is 40 μm Ra.

In the above configuration, the rotation of the developer carrying / transporting means 301 causes the magnetic field generating means 303 to pump up the S1 pole (the vertical component magnetic flux density on the surface of the developer carrying / transporting means 301 is 600 Gauss to 700 Gauss). The component magnetic developer t is regulated and thinned by the developer layer forming member 302. Next, the N2 electrode (developer loaded /
The vertical component magnetic flux density on the surface of the conveying means 301 is 950 Gauss
s to 1050 Gauss), the developer t develops the electrostatic latent image on the latent image holding means 1, and the developer t which has not been subjected to development is thereafter returned to the developer accommodating means 309 again. .

In the present embodiment, the developer layer forming member 302 comes into contact with the developer carrying / transporting means 301, which is made of urethane rubber (0.9 to 1.2 mm in thickness,
Hardness 60-70 °), width 16mm, length 298-3
It is formed into a rectangular shape of 07 mm, and its long side F is clamped with a width of about 5 mm as shown in FIG. The free end M of the developer layer forming member 302 protrudes upstream in the rotation direction (the direction of arrow A) of the developer carrying / transporting means 301. The width of the pressure contact area between the rubber surface of the developer layer forming member 302 and the developer carrying / transporting means 301 is about 0.
5 mm, the developer carrying / transporting means 3 in the center P of the pressure contact area.
01 is the developer carrying / transporting means 3 from above the vertical line.
The angle is about 100 ° upstream of the rotation direction 01 (direction of arrow A) (see FIG. 3).

In the developing device 3 according to the present embodiment, the height difference H between the lowermost part of the developer carrying / transporting means 301 and the lowermost part of the inner surface of the developer accommodating means 309 is set to 35 mm. .

On the other hand, three developer stirring / transporting means 305a, 305b, 305c are provided in the developing device 3, and each of the developer stirring / transporting means 305a to 305c is a non-developer as shown in FIG. A plastic arm portion 305-2 is attached to a rotating shaft 305-1 of a magnetic metal rod, and a plastic foil 305-3 having high wear resistance and elasticity is attached to the arm portion 305-2.

Thus, three developer stirring and conveying means 305
a to 305c rotate in the same direction (the direction of arrow C in FIG. 1) at the same angular velocity ω (about 0.262 rotations / sec). or,
Rotation radius R of each developer stirring and conveying means 305a to 305c
Are set to 9 mm, 7 mm, and 17 mm, respectively.
The angle α (see FIG. 2) formed by the bottom surface 309A of the first device and the horizontal line is set to 32 °.

At the bottom of the developer carrying / transporting means 301 of the developer accommodating means 309, three plate-like members 310a, 310b, 310c are provided as developer drop obstructing means, all of which are the same. It has a shape, and its protruding height h (see FIG. 2) is all set to 7 mm.
Note that the plate members 310a to 310c interfere with the plastic foil 305-3 (see FIG. 4) of the developer stirring and transporting means 305a to 305c, and the developer stirring and transporting means 305a to 305c.
When 5c further rotates and the plastic foil 305-3 returns to the original shape, the developer is jumped up. Further, a plate-like member 306 having an opening is provided on the upper wall of the developer accommodating means 309, and this plate-like member 306 also functions as a developer drop obstruction means. The average charge amount q of the developer on the developer carrying / transporting means 301 at normal temperature and normal humidity by a suction method is -9 to-
12 μC / g, application amount m is 0.8 to 1.0 mg / cm ²
And the initial weight average particle size of the developer is 6.2 to 6.8 μm.
m.

In the present embodiment, when a solid black image (in the case where the JIS row 4 size paper is fed sideways: the developer amount is about 0.5 g / sheet) is continuously output, 95 sheets are output. No white spots occurred in the image up to the eyes. The stable image density after output of about 300,000 sheets was 1.29, and the vertical white streaks after the developer supplementation were 4 to 5 lines.

On the other hand, a conventional developing device (conventional example 1)
In this case, when solid black images were continuously output, white spots occurred on the 25th sheet. The stable image density after outputting about 300,000 sheets is 1.22, and the vertical white streak after replenishing the developer is several tens.
There were zero.

The developing apparatus according to the prior art 1 has the same construction as that of the first embodiment except that it does not include a means for hindering the developer from dropping and a means for transporting / applying the developer in contact with the developer carrying / transporting means. This is the same as the developing device according to the embodiment.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. 5 is a sectional view of a developing device according to Embodiment 2 of the present invention, FIG. 6 is a partially enlarged sectional view of the developing device, and FIG. 7 is an enlarged sectional view of a developer carrying / transporting unit of the developing device. It is.

In the developing device 3 according to the present embodiment,
The developer carrying / transporting means 301 is constituted by a hollow cylinder made of aluminum having a diameter of 16 mm, and has a rotating support shaft made of aluminum at both ends thereof, and is rotatable via a bearing on a side wall of the developer accommodating means 309. Supported. The developer carrying / transporting means 301 rotates at a peripheral speed of 138 mm / sec in the direction of arrow A in FIG.

The distance between the developer carrying / transporting means 301 and the latent image carrying means 1 is set at 270 to 330 μm, and the developer carrying / transporting means 301 has an amplitude of 1250 to 1350.
V, a rectangular wave AC voltage having a frequency of 1750 to 1800 Hz is applied so as to be superimposed on a DC voltage variable between -400 and -600 V.

The outer surface of the developer carrying / transporting means 301 is subjected to a blasting treatment by spraying spherical glass particles, and then coated with a phenol resin, crystalline graphite and carbon and having a volume resistance of 100 Ωcm or less (film thickness of 10 μm to 10 μm). 14 μm) with an average roughness of 0.70 to 0.90 μm Ra.

In this embodiment, since the developer is a one-component non-magnetic developer exhibiting red, no magnetic field generating means is provided inside the developer carrying / transporting means 301. In this embodiment, the developer layer forming member 30 is also used.
2 is in contact with the developer carrying / transporting means 301.

As shown in FIG. 7, the developer layer forming member 302 has a rectangular phosphor bronze plate 302-2 (having a thickness of 0.12 mm) having a width of 16 mm and a length of 298 to 307 mm and a width of 6 mm.
mm, urethane rubber 302- having a length of 298 to 307 mm
It has a two-layer structure of 1 (0.9 mm thickness), and one long side of the phosphor bronze plate 302-1 is fixed by screws 315. The urethane rubber 302-1 is located only in the vicinity of the pressure contact portion with the developer carrying / transporting means 301.

The free end M of the developer layer forming member 302 is 0.5 to 1 m upstream of the developer carrying / transporting means 301 in the rotation direction.
m. The width of the pressure contact area between the developer layer forming member 302 and the developer carrying / transporting means 301 is about 0.5 m.
m, the developer carrying / transporting means 3 at the center P of the contact portion between the developer carrying / transporting means 301 and the developer layer forming member 302.
The position above the vertical line 01 is about 11 degrees upstream of the vertical line in the rotational direction (the direction of arrow A in the figure) of the developer carrying / transporting means 301.
This is the position at 0 ° (see FIG. 7).

The developer carried at normal temperature and normal humidity by the suction method
The average charge amount q of the developer on the conveying means 301 is +12 to +
15 μC / g, application amount m is 0.7 to 0.9 mg / cm ²
And the initial weight average particle size of the developer is 7.4 to 7.8 μm.
m.

In this embodiment, the height difference H between the lowermost part of the developer carrying / transporting means 301 and the lowermost part of the inner surface of the developer accommodating means 209 is 25 mm. Further, three developer stirring and transporting means 305a, 305b, 3
The developer agitating / conveying means 305a to 305c are provided with a plastic arm 305-2 attached to a rotating shaft 305-1 of a metal rod.
2. Plastic foil 305 having high wear resistance and elasticity
-3 (see FIG. 4).

Then, three developer stirring and conveying means 305
a to 305c are rotating at the same angular velocity ω (about 0.092 rotation / s) in the same direction (the direction of arrow C in FIG. 5). still,
The rotation radii R of the developer stirring and conveying means 305a to 305c are set to 3 mm, 4 mm, and 12 mm, respectively.
The angle α (see FIG. 6) formed by the bottom surface of the developer accommodating means 209 on the developer carrying / transporting means 301 side is set to 45 °.

In this embodiment, a plate-like member 310 is provided at the bottom of the developer accommodating means 209 on the side of the developer carrying / transporting means 301 as a developer drop obstructing means. The plate member 310 has an opening in the center, and the opening is formed in the opening as shown in FIG.
1 is provided. The developer check valve 311 is made of an elastic material such as rubber, and the developer can move only in the direction of arrow K in FIG. However, the space L shown in FIG. 5 (the space surrounded by the walls of the developer carrying / transporting means 301, the developer layer forming member 302, and the plate member 310)
When the amount of the developer existing in the space reaches a predetermined amount (100 to 120 g), the further developer does not enter the space L.

The average charge q of the developer on the developer carrying / transporting means 301 at normal temperature and normal humidity by the suction method is -1.
8 to -25 μC / g, and the coating amount m is 0.7 to 0.9 mg / g.
cm ² , and the initial weight average particle size of the developer is 8.2 to
It is 8.8 μm.

In this embodiment, when continuously outputting a solid red image (in the case where the paper of the JIS column No. 4 is fed sideways: the amount of developer is about 0.5 g / sheet), 35 sheets are output. No white spots occurred in the image up to the eyes. The image density after outputting about 20,000 sheets was 1.29, and the number of vertical white streaks was 4 to 5.

On the other hand, a conventional developing device (conventional example 2)
In this case, when a solid red image was continuously output, white spots occurred in the fifth sheet. The image density after outputting about 20,000 sheets was 1.12, and the number of vertical white stripes was several tens.

The developing apparatus according to the prior art 2 has the same construction as that of the present embodiment except that it does not have the developer drop obstructing means and that it has the developer carrying / applying means in contact with the developer carrying / transporting means. This is the same as the developing device according to the embodiment.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a sectional view of a main part of the developing device according to the present embodiment.

The configuration of the developing device according to the embodiment of the present invention is the same as that of the developing device according to the first embodiment except that the developer falling obstruction means is a magnetic field generating means 312 provided near the wall of the developer accommodating means 309. The configuration is the same as that of the device.

The magnetic field generating means 312 has a length of 300 m.
It is composed of a rectangular rubber magnet having a width of 5 mm, a width of 5 mm, and a thickness of 1 mm, and N poles and S poles are alternately magnetized, and the magnetic flux density of each pole is 80 to 120 Gauss. A total of three magnetic field generating means 312 are provided at intervals of 5 mm.
09 on the inner wall.

Thus, when solid black images are continuously output in the present embodiment, no white spots occur in the image up to the 55th sheet. The stable image density after output of about 300,000 sheets was 1.26, and the number of vertical white stripes after the replenishment of the developer was 4 to 5.

Although the above-described three embodiments have been described, it is possible to make small changes within the scope of the present invention, and it is also possible to prevent the developer layer forming means from contacting the developer carrying / transporting means. Device, a developing device having a plurality of developer layer forming means and a plurality of developer carrying / transporting means, a developing device in which the developer carrying / transporting means is in contact with the image carrier means, and a two-component developer composed of toner and carrier. Of course, the present invention can be applied to a developing device to be used, a developing device having a belt-like developer carrying / conveying unit, or a belt-like developing layer forming unit.

[0049]

As is apparent from the above description, according to the present invention, the developer obstructing the developer from dropping from the vicinity of the developer carrying / transporting means toward the lowermost part of the inner surface of the developer accommodating means. Since the drop obstructing means is provided in the developer accommodating means, the developer can be pumped up without using the developer conveying / applying means which comes into contact with the developer carrying / conveying means, thereby lowering image density, fogging, and vertical white stripes. , Unevenness and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a developing device according to a first embodiment of the present invention.

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

FIG. 3 is an enlarged sectional view of a developer carrying / transporting unit of the developing device according to the first embodiment of the present invention.

FIG. 4 is a perspective view of a plate member provided in the developing device according to the first embodiment of the present invention.

FIG. 5 is a sectional view of a developing device according to a second embodiment of the present invention.

FIG. 6 is a partially enlarged sectional view of a developing device according to a second embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view of a developer carrying / transporting unit of a developing device according to a second embodiment of the present invention.

FIG. 8 is a sectional view of a main part of the developing device according to the exemplary embodiment.

FIG. 9 is a sectional view of a conventional developing device.

FIG. 10 is a cross-sectional view of an image forming apparatus having a horizontal path.

FIG. 11 is a cross-sectional view of an image forming apparatus having a vertical path.

[Explanation of symbols]

3 Developing device 301 Developer carrying / transporting means 302 Developer layer forming member (developer layer forming means) 305a to 305c Developer stirring and conveying means 309 Developer storing means 310a to 310c Plate member (developer drop obstructing means) 312 Magnetic field generation means (developer drop obstruction means)

Claims (4)

[Claims] A developer accommodating means for accommodating an insulative powder developer; a developer carrying / transporting means rotatably supported by the developer accommodating means and carrying / conveying the developer on its surface; A developer layer forming means for forming a developer layer on the developer carrying / transporting means, and no developer carrying / applying means in contact with the developer carrying / transporting means; In a developing device, a lowermost part of the developer carrying / transporting unit is located vertically above a lowermost part of an inner surface of the developer accommodating unit in the step, A developing device, wherein a developer drop obstructing means for obstructing the developer from falling toward the lowermost portion of the inner surface is provided in the developer accommodating means. 2. The developing device according to claim 1, wherein said developer drop obstructing means is constituted by a plate-like member having a free end provided on a lower wall of said developer accommodating means. 3. The device according to claim 1, wherein said developer drop obstructing means is formed of a plate-like member having a free end provided between an upper wall and a lower wall of said developer accommodating means. Developing device. 4. The developing device according to claim 1, wherein said developer drop obstructing means comprises a magnetic field generating means provided near a wall of said developer accommodating means.