JPH11143236A - Image forming device - Google Patents

Abstract

(57) Abstract: In an image forming apparatus provided with a developing device using a two-component developer containing a resin toner and a magnetic carrier having an average particle diameter of 20 to 40 μm, a layer regulation in a developer layer regulating section is performed. Perform well. SOLUTION: The average particle diameter of the magnetic carrier is r (μm),
Let the closest distance between the developer carrier and the developer layer regulating member be l
(Μm), assuming that the magnetic flux density in the direction perpendicular to the surface of the developer carrier of the magnetic pole of the magnetic field generating means facing the developer layer thickness regulating member is Br (Gauss), Br / r ≧ 20 (Gauss /
μm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine
An electrophotographic or electrostatic recording type image forming apparatus such as a BP or a facsimile is characterized by a dry two-component type developing device.

[0002]

2. Description of the Related Art Conventionally, for example, as a full-color image forming apparatus, various apparatuses having a photosensitive drum as an electrostatic latent image carrier and a transfer material carrier for carrying paper as a transfer material have been proposed and implemented. ing.

FIG. 4 illustrates an example of such a general full-color image forming apparatus.

In FIG. 4, in this full-color image forming apparatus, a photosensitive drum 1, which is an image carrier, is rotatably arranged in the direction of an arrow.
Optical system 3, four developing units 4Y, 4M, 4C with different colors
4K, a transfer device 5, and a cleaning device 6 are arranged.

The optical system 3 comprises a document scanning section and a color separation filter. The optical system 3 irradiates the photosensitive drum 1 with a color-separated light image or a light image E corresponding thereto by, for example, a laser beam exposure apparatus as shown in FIG. is there.

The photosensitive drum 1 uniformly charged by the corona charger 2 is irradiated with a light image E for each of the separated colors to form a latent image.

[0007] The latent image formed on the photosensitive drum 1 is developed by the developing devices 4Y, 4M, 4C, and 4K, and an image is formed on the photosensitive drum 1 using a resin-based toner.

Further, the toner image on the photosensitive drum 1 is transferred from a transfer material cassette 7a, 7b or 7c to a transfer material supplied to a position facing the photosensitive drum 1 via a transfer system and a transfer device 5. .

In the present embodiment, the transfer device 5 includes a transfer drum 5a,
Transfer brush charger 5b, suction brush charger 5c for electrostatically adsorbing a transfer material, and suction roller 5 opposed thereto
g, inner corona charger 5d, and outer corona charger 5e
Transfer drum 5 which is rotatably driven
a transfer material carrying sheet 5 made of a dielectric material
f is integrally stretched in a cylindrical shape.

As the transfer drum 5a rotates, the toner image on the photosensitive drum 1 is sequentially transferred onto the transfer material carried on the transfer material carrying sheet 5f by the transfer brush charger 5b. A desired number of color images are transferred to the transfer material sucked and conveyed to the transfer material carrying sheet 5f, and a full-color image is formed.

When the transfer of the desired number of toner images is completed in this way, the transfer material is separated from the transfer drum 5a by the separation charger 5
j and separated by separation means 8 a and 8 b, and discharged to a tray 10 via a heat fixing device 9.

On the other hand, after the transfer, the photosensitive drum 1 and the transfer material supporting sheet 5f are cleaned by a cleaning device 6 and a transfer cleaner 14, which are the cleaning means, respectively, and then subjected to the image forming process again. Can be done.

Here, the developing device in the conventional example will be described with reference to FIG. 5 taking the developing device 4Y for yellow toner as a representative. The developing device 4Y includes a developing container 406 containing a two-component developer 40Y containing a resin toner and a carrier. At the opening of the developing container 406, a hollow non-magnetic sleeve 401 serving as a developer carrier is indicated by an arrow. It is rotatably supported in the C direction. Inside thereof, a magnet roller 402 as a magnetic field generating means magnetized to five poles is fixedly arranged on a shaft.

In the developing container 406, two screws 405A and 405B are disposed in parallel with the sleeve 401, rotate in the directions of arrows A and B, and transport the developer 40Y while stirring. During this stirring operation, the toner takes on a desired triboelectric charge due to friction with the carrier.

The agitated developer 40Y is carried on the surface of the sleeve 401 by the magnetic force of the magnetic pole S3 of the magnet roller. As the sleeve 401 rotates in the direction of arrow C, the non-magnetic regulating blade 40, which is a developer layer regulating member, is used.
The toner is conveyed to a developer regulating portion, which is the closest portion between the sleeve 3 and the sleeve 401, and is regulated to a desired layer thickness while standing up by the magnetic force lines of the magnetic pole N1. At this time, in this example, the magnetic pole N1
The magnetic plate 404 is disposed on the upstream side in the sleeve rotation direction of the regulating blade 403 in order to concentrate and effectively use the magnetic lines of force. The distance between the magnetic plate 404 and the sleeve 401 is the distance between the regulating blade 403 and the sleeve 401. It is arranged so that it becomes above.

The developer 40Y thus regulated to a desired layer thickness is further conveyed to the developing section by rotating in the direction of arrow C, and as described above, the latent image on the photosensitive drum 1 is visualized. . Further, the regulated remaining developer 40Y flows in the direction of arrow D according to the lines of magnetic force created by the magnetic poles N1 and S3 along the inner surface of the developing container 406, and is again conveyed to the developer regulating section.

After the development, the remaining toner and the carrier are continuously rotated by the sleeve 401 in the direction of arrow C to cause the developing container 40 to rotate.
After being taken in, the repelling magnetic field formed between the magnetic poles S2 and S3 leaves the sleeve 401 and is again subjected to the developer agitation and conveyance formed by the screws 405A and 405B. The desired toner is replenished by a toner replenishing means that is not in use, and the toner concentration of the developer 40Y is kept constant.

In recent years, toner, which is a developer, has been reduced in particle size in order to achieve high image quality and high definition, and from the viewpoint of increasing the contact area in order for the toner to obtain a sufficient triboelectric charge, the toner has a small particle size. Also tends to be smaller.

In this conventional example, the average particle diameter of the toner is 8 μm and the average particle diameter of the carrier is 50 μm. However, it is considered that it is essential to further reduce the particle diameter in the future. .

As a method of measuring the toner particle size, a small amount of the toner to be measured is put into water, sufficiently stirred using an ultrasonic vibrator or the like, and the energized measuring aperture is put into water. A method is used in which a change in current value when toner passes through the aperture is measured, and a resistance value is calculated therefrom to calculate an average particle diameter.

As a method for measuring the carrier particle size,
Since the specific gravity is larger than the toner and the dispersion in water is not successful, while suctioning the carrier to be measured by air, when the carrier comes to the measurement location, shine light from behind, measure the light-scattered projection, A method of calculating as an average particle diameter radius is employed.

[0022]

However, in the conventional developing apparatus, the conditions for using a carrier having an average particle diameter of 20 to 40 .mu.m and having a small particle diameter are not sufficiently reduced. With regard to the regulation of the developer layer, under the conditions in the conventional example, the developer layer was not uniform in the longitudinal direction, resulting in image unevenness.

The cause of the non-uniformity of the developer layer was examined. As the carrier particle size was reduced, the amount of magnetization decreased and the amount density of the developer increased. It was found to be due to a decrease in flowability.

That is, since the amount of magnetization of the carrier is reduced, the magnetic restraining force at the magnetic pole N1 is reduced, so that the developer is not sufficiently raised in the developer regulating portion, and the developer conveyed to the developer regulating portion is not sufficiently raised. Layer regulation is not performed well. As a countermeasure, the gap between the sleeve 401 and the regulating blade 403 in the developer regulating section was narrowed. However, since the amount density of the developer has increased, the fluidity of the developer has decreased, and The flow in the direction of arrow D was poor, and similarly good regulation of the developer layer could not be performed.

The present inventors have found that the major factor that regulates the developer layer is the ratio l of the closest distance l between the sleeve and the developer layer regulating member, which is a mechanical regulation factor, to the average particle diameter r of the magnetic carrier. / R and the magnetic flux density gradient in the vertical direction magnetic flux density Br on the sleeve surface of the magnetic pole of the magnet roller facing the developer layer regulating member, which is a physical regulating factor, at the closest portion between the sleeve and the developer layer regulating member. Br / l
(Gauss / μm), and by examining the conditions for obtaining a good developer layer without unevenness even when the carrier particle size is reduced by defining these two factors. Then, the present inventors have come to a conclusion.

Accordingly, a main object of the present invention is to provide an image forming apparatus provided with a developing device using a two-component developer containing a resin toner and a magnetic carrier having an average particle diameter of 20 to 40 μm. An object of the present invention is to provide an image forming apparatus capable of satisfactorily regulating layers in the above.

Another object of the present invention is to provide an image forming apparatus provided with a developing device using a two-component developer containing a resin toner and a magnetic carrier having an average particle size of 20 to 40 μm. r (μm), the closest distance between the developer carrier and the developer layer regulating member is 1 (μm), and the magnetic flux in the direction perpendicular to the surface of the developer carrier of the magnetic pole of the magnetic field generating means facing the developer layer thickness regulating member Density is Br (Gauss
), It is intended to provide an image forming apparatus capable of favorably regulating the layer in the developer layer regulating section by setting Br / r ≧ 20 (Gauss / μm).

Another object of the present invention is to provide an image forming apparatus provided with a developing device using a two-component developer containing a resin toner and a magnetic carrier having an average particle size of 20 to 40 μm. The diameter is r (μm), the closest distance between the developer carrier and the developer layer regulating member is l (μm),
The perpendicular magnetic flux density of the magnetic pole of the magnetic field generating means facing the developer layer thickness regulating member with respect to the surface of the developer carrier is Br (Gauss).
s), Br / r ≧ 20 (Gauss / μm), 30 ≧ l / r ≧ 15, and 2 ≧ Br / l
An object of the present invention is to provide an image forming apparatus capable of favorably regulating a layer in a developer layer regulating section by setting (Gauss / μm) ≧ 1.

[0029]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A two-component developer having a resin toner and a magnetic carrier having an average particle diameter of 20 to 40 μm is used. The developer is carried and the developer is transported to a development area facing the image carrier. A developing device having a rotatable hollow non-magnetic developer carrier having generating means, and a developer layer regulating member for regulating a layer thickness of the developer on the developer carrier conveyed to a developing area. In the image forming apparatus provided, the developing device sets the average particle size of the magnetic carrier to r (μ).
m) When the magnetic pole of the magnetic field generating means facing the developer layer regulating member has a magnetic flux density perpendicular to the surface of the developer bearing member, Br / Ga ≧ 20 (Gauss). An image forming apparatus characterized in that:

When the closest distance between the developer carrier and the developer layer regulating member is 1 (μm), it is possible that 30 ≧ l / r ≧ 15 and 2 ≧ Br / l ≧ 1. preferable. It is preferable that the resin toner has an average particle size of 10 μm or less.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the following description, the present invention relates to the image forming apparatus shown in FIG.
Of the developing device. Therefore, a detailed description of the configurations and functions of the image forming apparatus and the developing apparatus will be omitted, and only the features of the present invention will be described.

Example 1 First, Table 1 below shows the average particle diameter r (μm) of the magnetic carrier in the developing device used in the present example and the conventional example, and the closest distance l between the sleeve and the developer layer regulating member. (Μm),
The magnetic flux density Br (Gauss) in the perpendicular direction to the sleeve surface of the magnetic pole of the magnet roller facing the developer layer regulating member,
The magnetic flux density gradient Br / l (Gauss / μm), the ratio 1 / r of the closest distance l between the sleeve and the developer layer thickness regulating member to the average particle diameter r of the magnetic carrier, and the developer layer in each case studied. Shows uniformity.

The symbols relating to the uniformity of the developer layer in Table 1 have the following meanings. ：: The movement of the developer is good, the thickness of the developer layer in the developing section is uniform in the longitudinal direction, and the image is good without causing image unevenness. Δ: Although the movement of the developer layer in the direction of arrow D in FIG. 5 is slow, the thickness of the developer layer in the developing portion is uniform in the longitudinal direction, and there is no image unevenness and there is no practical problem. ×: The movement of the developer layer in the direction of arrow D in FIG. 5 is poor, and the thickness of the developer layer in the developing portion is not uniform in the longitudinal direction, and image unevenness occurs, which is a practical problem.

[0034]

[Table 1]

The factors l / r and Br / l are the major factors regulating the developer layer thickness.
Focusing on the two factors, FIG. 1 plots the results shown in Table 1 on a graph.

In the graph of FIG. 1, the vertical axis represents the ratio l / r of the closest distance l between the sleeve and the developer layer thickness regulating member to the average particle diameter r of the magnetic carrier, and the horizontal axis represents the developer layer regulating member. A magnetic flux density gradient Br / l (Gau
ss / μm), and the curve f is 1 / r = 2
0 / Br / l, that is, a curve showing Br / r = 20 (Gauss / μm).

From the results of this graph, it was found that a correlation of 1 / r ≧ 20 / Br / l was obtained between 1 / r and Br / r. If 1 is eliminated from this relationship, Br / r ≧
20 (Gauss / μm), which is a condition for exhibiting the effect of the present invention.

That is, when the carrier particle diameter r is 20 to 40 μm, by setting Br / r ≧ 20 (Gauss / μm), the thickness of the developer layer is regulated without unevenness in the longitudinal direction of the sleeve, and A good image without unevenness was obtained.

The method of measuring the carrier employs a method of calculating the average particle diameter by using a light scattering method as in the description of the conventional example.

As shown in FIG. 2, the measurement method of Br (magnetic flux density in the direction perpendicular to the sleeve surface of the magnetic pole of the magnet roller facing the developer layer regulating member) is to measure the magnetic flux density measurement probe 50 having a cylindrical shape. The portion is pressed onto the sleeve 401 so as to be perpendicular to the center of the sleeve 401, and the sleeve 4 is fixed while the sleeve 401 is fixed.
This is a method of measuring the magnetic flux density while rotating the magnet 402 which is coaxial with the 01.

Embodiment 2 Next, Embodiment 2 according to the present invention will be described with reference to FIG.

From the results of the study in Example 1, when the average particle size r of the magnetic carrier is 20 to 40 μm, Br / r ≧
Although a result of 20 (Gauss / μm) was obtained, an appropriate range is actually provided for the closest distance 1 between the sleeve and the developer layer regulating member.

Therefore, the present inventors have focused on only the above range of l and examined the relationship between l / r, Br / l, and the regulation of the thickness of the developer layer. As a result, when r is 20 to 40 μm, 30 ≧
1 / r ≧ 15 and 2 ≧ Br / l (Gauss / μm) ≧
As a result of the examination, it was obtained that it is desirable to use it under the condition 1.

FIG. 3 shows an appropriate l value including the result of the first embodiment.
5 is a graph illustrating the range of / r and Br / l.

In the graph of FIG.
・ Classified as IV, but inappropriate for each reason.

I: 1 / r> 30 The distance between the sleeve and the regulating blade is too large,
The developer layer could not be regulated sufficiently by increasing Br, and the developer was stagnated particularly in the developing section, causing image unevenness and image fogging.

II: 1 / r <15 The distance between the sleeve and the regulating blade is too small,
Even when Br was reduced, the developer layer clogged with the developer regulating portion, resulting in image unevenness and low image density.

III: Br / l <1 Br is small, so that the developer does not stand sufficiently and mechanical regulation can be performed, but the thickness of the developer layer becomes non-uniform. Further, since the developer holding force up to the developer regulating portion is weak, the transportability is also unstable.

IV: Br / l> 2 Since Br was large, the magnetic restraining force in the developer regulating portion was strong, and the developer layer was clogged with the developer regulating portion, resulting in image unevenness and low image density. .

As a result of this study, the average particle diameter r of the carrier was 2
Br / r ≧ 20 in case of 0 to 40 μm (Gauss / μm)
In the range, 30 ≧ l / r ≧ 15 and 2 ≧
By defining each factor so as to be used under the condition of Br / l (Gauss / μm), the development layer thickness without unevenness in the longitudinal direction was regulated, and a good image without image unevenness was obtained.

[0051]

As is apparent from the above description, according to the present invention, the average particle size of the magnetic carrier is r (μm), and the magnetic pole of the magnetic field generating means facing the developer layer regulating member is connected to the developer carrier. Assuming that the magnetic flux density in the vertical direction with respect to the surface is Br (Gauss), Br / r ≧ 20 (Gauss) allows the developer layer thickness to be regulated without unevenness in the longitudinal direction of the developer carrier. A good image without unevenness was obtained.

In addition to the above conditions, the closest distance between the developer carrier and the developer layer regulating member is 1 (μm).
Where 30 ≧ l / r ≧ 15 and 2 ≧ Br / l
When ≧ 1, the same effect as above could be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the correlation between Br / l and l / r in Example 1 according to the present invention.

FIG. 2 is an explanatory diagram for explaining a method for measuring Br.

FIG. 3 is an explanatory diagram for explaining a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 5 is a schematic configuration diagram of the developing device of FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive column (image carrier) 4 developing device 40Y two-component developer 401 sleeve (developer carrier) 402 magnet roller (magnetic field generating means) 403 regulating blade (developer layer regulating member) 404 magnetism regulating auxiliary blade

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shigeo Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the company

Claims (3)

[Claims] 1. A two-component developer containing a resin toner and a magnetic carrier having an average particle diameter of 20 to 40 .mu.m, carrying the developer and transporting the developer to a development area facing an image carrier. A rotatable hollow non-magnetic developer carrier having a magnetic field generating means therein, and a developer layer regulating member for regulating a layer thickness of the developer on the developer carrier conveyed to a developing area. In the image forming apparatus provided with a developing device having the following formula, the developing device sets an average particle diameter of the magnetic carrier to r (μ
m): Br / r ≧ 20 (Gauss), where Br (Gauss) is the perpendicular magnetic flux density of the magnetic pole of the magnetic field generating means facing the developer layer regulating member with respect to the surface of the developer carrying member. An image forming apparatus comprising: 2. When the closest distance between the developer carrier and the developer layer regulating member is 1 (μm), 30 ≧ l / r ≧ 15 and 2 ≧ Br / l ≧ 1. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 1, wherein said resin toner has an average particle diameter of 10 μm or less.