JPH0194365A - Developing device - Google Patents

Abstract

PURPOSE:To improve conveyance performance and to eliminate the staying, leak, and scattering of a developer by arranging a magnetic member at the opening part of a developer storage container on an entrance-side part viewed from a developer carrier. CONSTITUTION:The magnetic member 10 is installed on the bisector Z between the N and S poles of a magnet roll 3 or on a downstream side about the bisector and on the upstream side of the N pole in the rotating direction of a developing sleeve 2. The magnetic member 10 is arranged under the developer container 4 opposite the developing sleeve 2 and then part of lines of magnetic force of the N pole is converged on the magnetic member 10 under the developer container 4. The lines of magnetic force are high in density at the periphery of the magnetic member between both poles and extend along the surface of the developing sleeve 2. Consequently, the attractive force of the developer to the developing sleeve 2 is high, the conveyance performance of the developer is improved, and the staying leak, scattering etc., of the developer are precluded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is utilized in the technical field of developing devices used in electronic copying devices, and is particularly applicable to various types of display devices for image recording, printers, and facsimile electrophotographic devices. Applicable to the device (related to my developing device).

(Prior Art and Problems) A fixed magnetic field generating means is disposed inside a rotatable cylindrical developer carrier made of a non-magnetic material, and the magnetic force generated by the magnetic field generating means is applied onto the developer carrier. The developer transported toward the developing section while being held by the developer is regulated to a predetermined layer thickness by the contact pressure of a thin rubber plate, etc., and then transferred to the latent image carrier in the developing section. Developing devices that develop latent images are known.

In this type of device, the developer carrying member rotates and after passing through the developing section, the developer in the developer container is transferred again by magnetic force.
C is held and transported to the developing section. that time,
In order to ensure that the developer is retained until it reaches the developing section, a magnetic field must be formed all around the developer carrier, at least in the range from the developer container to the developing section.

Therefore, conventionally, the magnetic field generating means has usually been made of four poles or more than four poles. Therefore, it was expensive. If the developer carrier is made small in diameter, the magnetic field generating means will also be made small in diameter, and the number of poles can be reduced. However, even if the number of poles is simply reduced by making the diameter smaller, the magnetic force will decrease, resulting in poor developer conveyance and phenomena such as fog.

As described above, in conventional developing devices that use multi-polar magnet rollers, in order to generate sufficient magnetic force to obtain high-quality images, magnetic field generating means with a diameter larger than a certain degree or with a small number of poles are used. The only way to do this is to use an expensive magnet with extremely strong magnetic force as a magnetic field generating means, which poses a major problem in manufacturing a small and inexpensive developing device.

Furthermore, when the developer carrier returns to the developer container after passing through the developing section, the developer is prevented from leaking from the gap on the entrance side between the developer container and the developer container as seen from the developer carrier. In order to prevent this, one pole of the plurality of poles of the magnetic field generating means is provided with a sealing function at the position of the gap. For this reason as well, the magnetic field generating means must have four or more magnetic poles.

(Means for Solving the Problems) An object of the present invention is to solve the problems of a developing device having a multipolar magnetic field generating means as described above, and to provide a small, inexpensive, and good developing device using a bipolar magnetic field generating means. It is an object of the present invention to provide a developing device which can obtain an image and also has a sufficient sealing function in the above-mentioned gap.

In order to achieve the above object, the present invention provides a rotatable developer carrier that transports developer on its surface by the magnetic force of a magnetic field generating means fixedly arranged in an internal space.
5. The developer is placed inside the developer container so as to partially protrude from the front opening of the developer container in which the developer is stored. In a developing device in which the developer carrier and the latent image carrier are installed together with the protruding portion of the developer carrier in close proximity to or in contact with the latent image carrier, the developer carrier has a length of 5 mm or more and 25 mm. The magnetic field generating means has a cylindrical outer diameter of less than a millimeter, and has magnetic poles at two positions around the periphery, one pole is at a position facing the latent image carrier, and the other pole is at a position in the internal space of the developer container. a regulating member disposed on the outlet side portion of the developer carrier at the opening of the developer container that contacts the surface of the developer carrier to regulate the thickness of the developer layer on the surface; The developer is placed at the entrance side of the developer carrier at the opening of the developer container, within the magnetic field region of the other pole, and at a position upstream in the direction of movement of the developer carrier than the position of the maximum magnetic force line of the other pole. The magnetic member is arranged to face the agent carrier with a gap therebetween.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a developing device according to a most preferred embodiment of the present invention. The developing device according to this embodiment will be explained by taking a developing device using Carlson electrophotography as an example, and the overall configuration thereof is already well known. The developing device and the like provided near the outer periphery of the photosensitive drum are illustrated in detail, and illustrations of the primary charging means, exposure means, cleaning means, etc. in the Carlson process are omitted.

In FIG. 1, a latent image carrier, that is, a photoreceptor drum l, is rotatably supported in the direction of the arrow, and a developing device is disposed near the outer edge of the photoreceptor drum l. The surface photoreceptor of the photoreceptor drum l is a known photoreceptor such as OPC, and a latent image is formed on the photoreceptor by a known charging means and image exposure means. It is beginning to form.

The developing device has a developer container 4 having an opening 4a on the front surface and containing a one-component or two-component developer therein, and is arranged so as to partially protrude from the developer container 4 with a gap on the photoreceptor drum l. A developing sleeve 2, which is a rotatable developer carrier facing the opening, and a regulating member 5 made of, for example, urethane rubber, made of a non-magnetic thin plate and elastically in contact with the developing sleeve 2; A magnet roll 3 as a magnetic field generating means having two magnetic poles 3a and 3b is fixedly arranged inside the sleeve 2.

Such bipolar magnet rolls are: Unlike multipolar magnet rolls, which are made by pasting multiple magnets together, they can be made from a single magnet, so they are easy to manufacture, and the magnetism exerted by the magnetic poles is The force is much stronger than the magnetic force exerted by the magnetic poles of a multipolar magnet roll of the same diameter.

The developing sleeve 2 as described above rotates in the direction of arrow B (counterclockwise), and the one-component or two-component developer is attached to the surface of the developing sleeve 2 by the magnetic force of the magnet roll 3, and the developing sleeve 2 is rotated in the direction of arrow B (counterclockwise). It is designed to be carried out toward the outside of the container, that is, to the developing area. In this embodiment, an example in which a predetermined gap is set between the developing sleeve and the photoreceptor drum is explained, but if the two are in contact, even if a so-called elastic developing sleeve is used. It is computable.

A developing bar asumi source is connected to the developing sleeve 2. That is, by forming an alternating electric field in which a DC component is superimposed between the developing sleeve 2 and at least the image portion of the latent image carrier, the developing sleeve 2 is closely opposed to the outer peripheral surface of the photoreceptor drum 1. The developer is transferred onto the photoreceptor drum 1 and the latent image formed on the photoreceptor drum 1 is developed.

Next, a description will be given of the magnet roll, which is a magnetic field generating means fixedly disposed within the developing screen 2, and in particular, the position of its magnetic pole.

31 of the two poles 3a and 3b of the magnet roll 3
) is located in the developing section closest to the photoreceptor tram l, while 3a is located at the opening 4a of the developer container 4. That is, the poles 3a and 3b are located on opposite sides of the center of the magnet roll 3, or preferably located on substantially one diameter line of the magnet roll 3. By doing so, the magnetic field range of one and both magnetic poles is utilized to the maximum extent possible, and a sufficient amount of developer is deposited on the developing sleeve 2. If the magnetic pole 3a is not within the opening 4a of the container 4, the amount of developer adhering to the developing sleeve will be insufficient, causing image unevenness during development.

However, even if the bipolar McNet roll 3 as described above is employed in a conventional relatively large-diameter one, the developing device tends to have poor developer conveyance. This is because conventionally, by adopting a multi-polar magnet roll, there are multiple magnetic poles that contribute to developer conveyance in addition to the magnetic pole for the developing section, whereas with the above-mentioned bipolar magnet roll, there are multiple magnetic poles that contribute to the transportability of the developer. This is because there is only one magnetic pole. Also, due to this, the developer container 4
Since there is no seal member on the inlet side (lower side in the figure) of the opening 4a, this may cause leakage of the developer.

However, it has been found that if the diameter of the developing sleeve 2 is made smaller, the developer can be sufficiently transported and a high-quality image can be obtained even with the bipolar magnetic roll 3, even though there is a problem regarding the transportability of the developer. . This point is a characteristic feature of the present invention. In particular, it was confirmed that the outer diameter of the developing sleeve was excellent when it was 5 to 25 mm. Further, a magnetic member 10 is disposed on the developer container 4 in order to promote the above-mentioned transportability and prevent leakage of the developer from the developer container. The position of the magnetic member 10 is within the magnetic field region of the magnetic pole 3a of the two poles of the magnet roll 3, which is directed toward the inside of the developer container 4, and is located further than the maximum magnetic force line position of the magnetic pole 3a on the developing sleeve 2. is set on the upstream side of

For example, in FIG. 1, the magnetic member 10 is located on the bisector Z of the N and S poles of the magnet roll 3 or on the developing sleeve 2.
It is installed downstream of the bisector and upstream of the north pole with respect to the rotational direction of.

The magnetic member 10 is attached to the developing sleeve 2 at the lower part of the developer container 4.
At the lower part of the developer container 4,
A part of the magnetic lines of force of the north pole will be concentrated on the magnetic member 10. Comparing this with the case of a conventional two-pole magnet roll, 1. In a case where there is no magnetic member, as in the case of a particular conventional device shown in FIG. It's going around a lot outside. For this reason, the adhesion of the developer to the developing sleeve is weak, and the transportability of the developer is also reduced, resulting in retention, leakage, and scattering of the developer. In contrast, in this example, the second
As shown in Figures (A) and (R).

When the magnetic member 10 is provided, the lines of magnetic force are located between the two poles, have a high density around the magnetic member, and extend along the surface of the developing sleeve 2. Therefore, the adhesion of the developer to the developing sleeve 2 is strong, the transportability of the developer is improved, and it is possible to prevent retention, leakage, scattering, etc. of the developer. Here, in FIG. 2(A), the magnetic force between the S developing pole and the magnetic plate IO is stronger than that between the N pole and the magnetic plate IO.
, the magnetic plate 10 is arranged upstream of the bisector of the two poles of N in the rotational direction of the developing sleeve 2. Therefore, some of the developer remains on the developing sleeve 2 at the C part in FIG. As the sleeve 2 rotates, the developer is transported toward the developer container 4 side. In addition, in FIG. 2(B), the developer does not stagnate on the upstream side of the magnetic member IO, and is transported satisfactorily.

Next, while comparing the apparatus of this embodiment with other conventional apparatuses, an experiment was conducted regarding its image gradation, and the results will be shown with reference to FIG.

In Figure 3, the surface voltage value of the photoreceptor drum (hereinafter abbreviated as SD bias) after subtracting the DC component voltage value applied to the developing sleeve is plotted on the horizontal axis, and the image density value after copying is plotted using Macbeth RD514 (registered trademark). The vertical axis is the result of measuring the reflection density using a 3D printer, and the outer diameter of the developing sleeve is shown as a parameter. Note that in this experiment, development was performed using a jumping development method.

In the jumping development method, a latent image potential of -700 V in the dark area and -200 V in the bright area is formed on the OPC photoreceptor drum by a known method, and the distance between the developing sleeve and the photoreceptor drum is set to about 300 V in this example. A DC current of -zsov is applied between the developing sleeve and the photoreceptor drum.
3KV Te1.5KII (73) This is a method in which the developer, for example, the -component magnetic toner, is ejected from the development sleeve to the latent image on the photoreceptor drum by superimposing them with an alternating bias.

The experimental conditions for each curve shown in FIG. 3 are as follows.

song! lI: The outer diameter of the developing sleeve is 321 m, and a quadrupole magnet roll is fixed in its inner space to generate an external magnetic field of 1000 G (Gauss) on the surface of the developing sleeve.

Curve (2): The outer diameter of the developing sleeve is 20 mm, and a quadrupole magnet roll that generates an external magnetic field of 800 G (Gauss) on the surface of the developing sleeve is fixed in its inner space.

Curve ■: The outer diameter of the developing sleeve is 10+a■, and a quadrupole magnet roll that generates an external magnetic field of 500 G (Gauss) on the surface of the developing sleeve is fixed in its inner space.

Wave curve ■: The outer diameter of the developing sleeve is IOmo+, and the inner space has a force of 750 G (
A two-pole McNet roll that emits an external magnetic field (Gauss) is fixed.

That is, the curved line ~■ is the result of an experiment using a conventional multi-pole (quadripolar) magnet roll, and the broken curve (2) is the experimental result for a developing device using the two-pole magnetic roll of this embodiment.

From the results in Figure 3.

■ At SD bias or Ov, curve ■ has a higher density than other curves.

■ The curve ■ and the broken curve ■ are gentler than the other curves.

I can say this clearly.

The above-mentioned phenomenon (2) is so-called fog, and in terms of the image quality at curve m, the adhesion of developer to the white background portion of the copied image becomes noticeable, which poses a problem in use.

Further, the above-mentioned development (■) indicates good gradation properties. The steeper the rise of the curve, the harder it is to bring out the gradation of the image.On the other hand, the broken curve in the homeland ■ has a gentle slope and is excellent for bringing out the gradation of the image. It can be said.

Overall, from the above experimental results, it can be said that in the case of curve (2), an image with no scattering or fogging, sufficient Dmax, no unevenness, and very rich gradation can be obtained.

Note that this tendency occurs when the outer diameter of the developing sleeve is 5 to 25II1.
It was also confirmed that the same was true in the range of 1.

Furthermore, in the embodiment of the present invention, the non-magnetic thin plate 5 having elasticity is provided so that one side thereof contacts the developing sleeve, and the opening of the developer container is made smaller than in the case of regulating members disposed at intervals. A wider configuration can be adopted, and the design specification range of the developing base configuration can be expanded. the result,
Since the developer sleeve and the developer can be transported sufficiently long to the regulating member, the frictional electrification of the developer is also sufficient and stable.

The darning effect can be obtained even if the magnetic member is included.

In addition to the case where the non-magnetic thin plate contacts in the subordinate direction with respect to the rotational direction of the developing sleeve as in the above-described embodiment, the present invention also provides contact with the non-magnetic thin plate in the opposite direction to the rotational direction of the developing sleeve. This applies even if there is contact. FIG. 4 shows an embodiment in which a non-magnetic thin plate is brought into contact with the developing sleeve in a direction opposite to the rotating direction. In this example as well, the same effect as when the contact shape 7g of the non-magnetic thin plate is made in the subordinate direction with respect to the direction of rotation of the sleeve is exhibited, there is no scattering or fogging, Dmax is sufficiently obtained, and there is no unevenness. Images with extremely rich gradation can be obtained.

Further, the non-magnetic thin plate may be a thin plate of phosphor bronze or stainless steel, or may have rubber fixed to the contact portion with the developing sleeve.

In addition, the surface of the developing sleeve is coated with 0.5 to 5 p by a known method to improve frictional charging of toner and conveyance of developer.
It is preferable to provide m unevenness. In this example #40
A sandblasted aluminum sleeve was used for the mouth.

(Effect of the invention) As described above, according to the present invention, as a magnetic field generating means,
By using a small-diameter bipolar magnet roll instead of a large-diameter or expensive magnet roll, you can not only obtain images with excellent gradation without scattering or fogging, but also in the position opposite to the developing section. The magnetic pole for taking in the developer is placed at the top, and the magnetic force of the bipolar magnet roll is utilized to the maximum extent to supply the developer, resulting in a good image with no roughness or unevenness. equipment can be provided. Moreover, it contributes to miniaturization of the entire device. Alternatively, the above-mentioned magnetic member may be disposed at the opening of the developer storage container on the entrance side when viewed from the developer carrier, and the developer may be restrained at this portion to improve its transportability. As a result, there is an effect that developer retention, leakage, and scattering in the above-mentioned portions are eliminated.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a schematic configuration of an embodiment of the present invention;
Figures 2 (A) and (B) are diagrams showing the state of magnetic lines of force around the magnetic members of the apparatus shown in Figure 1, and Figure 3 is a diagram showing experimental results using the apparatus shown in Figure 1 compared with conventional ones. FIG. 4 is a longitudinal cross-sectional view showing a schematic configuration of another embodiment of the present invention. l...Latent image carrier (photosensitive drum) 2.
......Developer carrier (development sleeve) 3...
......Magnetic field generating means (Macnet roll) 3a
, 3b...Magnetic pole 4...Developer container 4a...Opening 5...Regulating member 10... ...Representative of Canon Co., Ltd., magnetic member patent applicant
Person Patent Attorney Fujioka Microbacteria 1 Figure 3 Figure 3 Surface voltage of photoreceptor drum (V) Figure 4 Procedural amendment (method) % formula % 1. Indication of the incident 1985 Patent application No. 251631 2. Invention Name Development Device 3, Relationship with the person making the amendment Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (100) Canon Co., Ltd. Representative Kaku
Ryu Sanbu 4, Agent 150 Phone: 03-770-904
05, date of amendment order: December 2, 1986 (Shipping date: December 2, 1988)
2) 6. In column 7 of "Brief explanation of drawings" of the specification to be amended, "It is a longitudinal sectional view" on page 19, line 5 of the statement of contents of the amendment was changed to "Longitudinal sectional view. 5 is a diagram showing the state of magnetic lines of force in the conventional device.''

Claims (3)

[Claims] (1) A rotatable developer carrier, which conveys developer on its surface by the magnetic force of a magnetic field generating means fixedly arranged in the internal space, is moved from the front opening of the developer container containing the developer. A developing device in which the developer carrier and the latent image carrier are disposed in the container so as to partially protrude, and the developer carrier and the latent image carrier are installed in parallel, with the protruding portion of the developer carrier being close to or in contact with the latent image carrier. The developer carrier has a cylindrical outer diameter of 5 mm or more and 25 mm or less, the magnetic field generating means has magnetic poles at two positions around the periphery, and one pole is located at a position facing the latent image carrier, The other electrode is disposed at a position in the internal space of the developer container, and contacts the surface of the developer carrier at the outlet side portion of the developer carrier at the opening of the developer container to form a layer of developer on the surface. a regulating member for regulating the thickness of the developing material, the developing material being located within the magnetic field region of the other pole and below the maximum magnetic force line position of the other pole at the entrance side portion of the developer carrier at the opening of the developer container. A developing device characterized in that a magnetic member is disposed at an upstream position in the moving direction of the developer carrier, facing the developer carrier with a gap therebetween. (2) The developing device according to claim (1), wherein the two poles of the magnetic field generating means are located approximately on one diameter line of the developer carrier. (3) The developing device according to claim (1), wherein the regulating member is formed of a non-magnetic thin plate that has elasticity and comes into contact with the developer carrier.