JPS6022362Y2 - magnetic brush developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing device for developing an electrostatic latent image carried on the surface of an electrostatic latent image carrier.

The above-mentioned magnetic brush developing device is widely used in electrophotographic copying machines and the like, and includes a developing sleeve provided facing the surface of a photoreceptor, which is an electrostatic latent image carrier, and a developing device provided inside the developing sleeve. a developing magnet, a developer circulation means for circulating the developer contained in the device in the longitudinal direction of the developing sleeve, and a toner replenishing means for replenishing the developer with toner. It is known that it has the following.

Incidentally, such a magnetic brush developing device is used to develop an electrostatic latent image, and the toner replenishing means appropriately replenishes the developer whose toner concentration has decreased. The developer and the newly replenished toner need to be thoroughly mixed and stirred before being used to develop the electrostatic latent image.

This is because, if the developer is used to develop an electrostatic latent image without being sufficiently mixed and stirred, significant fogging etc. will occur in the developed image.

For this reason, a developer stirring mechanism consisting of rotating blades or the like is usually incorporated into the magnetic brush developing device.

However, it is not easy to mix and stir the developer, etc., which is a fine powder, and in order to mix and stir to a sufficient degree, the developer stirring mechanism must be large and complex. I have no choice but to do so.

Therefore, at present, this developer agitation mechanism is a major obstacle to miniaturization of the developing device.

On the other hand, in connection with the developer stirring mechanism, when the developer is mixed and agitated by a rotating blade or the like, the developer in a stagnant state is forcibly stirred by the rotating blade with a strong force. A large mechanical stress is applied to the developer, and this causes a situation in which the developer deteriorates early.

This invention was made in view of these points,
A novel developer stirring mechanism capable of sufficiently performing the mixing and stirring without being large and complicated in itself, and as a result, making it possible to downsize the developing device, further comprising: It is an object of the present invention to provide a magnetic brush developing device equipped with a developer stirring mechanism capable of carrying out the mixing and stirring described above without substantially causing early deterioration of the developer.

Hereinafter, one embodiment of the magnetic brush developing device according to the present invention will be described with reference to FIGS. 1 to 6.

FIG. 1 is a drawing showing the internal structure of an embodiment of the magnetic brush developing device according to the present invention, and FIG.
It is a sectional view taken along the line -■.

In FIG. 1, an electrophotographic photosensitive drum 1 is rotatably provided in the direction of arrow A by a drive device (not shown).

Around the photoreceptor drum 1, there is a charger 2 for uniformly charging the surface of the photoreceptor drum 1, and a charger 2 for exposing an image of a document (not shown) to form an electrostatic latent image on the surface of the drum 1. An exposure section 3 and a magnetic brush developing device 4 for developing the electrostatic latent image carried on the surface of the drum 1 into a visible image are provided.

Furthermore, a transfer charger, a cleaning device, an eraser, etc. (not shown) are provided around the drum 1.

A developing sleeve 6 made of a non-magnetic material is provided within the frame 5 of the developing device 4 so as to be rotatable about a shaft 7, with a portion of the sleeve facing the surface of the drum 1.

As shown in FIG. 2, the width of the sleeve 6 is set wider than the width of the drum 1, and a portion of the sleeve 6 is arranged so as to extend to the left and right sides of the drum 1.

Inside the sleeve 6, there are provided developing devices 8, 9, and 10 divided into three parts, one on the top, one on the bottom, and on the side of the drum 1.

These magnets 89.10 are provided in the longitudinal direction of the sleeve 6 over a developing section B where the sleeve 6 faces the surface of the drum 1 and a portion C where the sleeve 6 protrudes longer than the drum 1. It is being

18 for the circumference of the sleeve 6 facing the surface of the drum 1
As shown in FIG. 3, with respect to the circumferential surface of the sleeve 6 which is 0 degrees apart, a first screw 11 for conveying developer having a width approximately equal to the width of the sleeve 6 is rotatable around a shaft 12. It is provided.

Below this first screw 11, B of the sleeve 6,
A control plate 15 is installed with a narrow gap 13 between it and the sleeve 6 at the part facing the C part, and a wide gap 14 at the protruding part of the sleeve 6 opposite to the C part, and is adjustable with respect to the frame 5. It is installed.

A second screw 16 for conveying the developer is provided below the sleeve 6 at a position facing the magnet 9 so as to be rotatable about a shaft 17 .

As shown in FIGS. 2 and 3, this second screw 16 is integrally attached with a supply blade 18 located at the developer mixing section E in the 0 part, and the C part excluding the mixing part E. That is, the peripheral surfaces located only at the developer stirring portions F1, B, and D are formed in a screw shape.

In these sections F, B, and D, the developer is rotationally driven so as to be conveyed in a direction opposite to the direction in which the first screw 11 conveys the developer.

A shielding plate 19 is provided between the second screw 16 and the sleeve 6 at the B portion, and the second screw 16
Neighboring developer is prevented from being magnetically attracted to the circumferential surface of the sleeve 6.

However, in the F section, a portion of the shielding plate 19 is cut out so that the developer that is not affected by the magnet 9 falls into the vicinity of the second screw 16.

Further, a developer scraping plate 20 whose tip 20a is pressed against the circumferential surface of the sleeve 6 is in the D section, and a regulating plate 21 having a slight gap with the circumferential surface of the sleeve 6 is in the E section. are provided for each.

On the other hand, in the developer conveyance direction along the circumferential surface of the sleeve 6, the developer 22 magnetically attracted to the circumferential surface of the sleeve 6 is placed on the circumferential surface of the sleeve 6 on the near side that approaches the surface of the drum 1. Height regulating plates 23 are provided at regular intervals and are adjustable for regulating the amount.

Further, below the surface of the developing device 4 that directly faces the photoreceptor drum 1, a developing device is provided to prevent the developer 22 housed in the developing device 4 from scattering outward from the inside of the frame 5. A chemical scattering prevention plate 24 is attached.

This anti-scattering plate 24 is made of an insulating material such as thin polyurethane rubber, and its tip is pressed against the surface of the drum 1.

Further, a toner tank 26 filled with replenishment toner 25 is installed above the frame 5 located in the mixing section E, and at the bottom of this toner tank 26 there are two replenishment toner sheets with hole positions different from each other. The plates 28 and 29 are provided so as to be able to slide integrally into a large number of holes 27 provided in the frame 5 from above and below.

The replenishment plates 28, 29 are provided with knobs 30 for sliding movement, and these replenishment plates 28.
29 is slid manually or automatically by being connected to a drive source as appropriate.

Furthermore, in portions C and D of the developing device 4, the sleeve 6 does not directly face the surface of the photoreceptor drum 1, so there is a possibility that the developer 22 may scatter and leak toward the drum 1 side.

Therefore, in the C9D section, a scattering prevention plate 31 is provided in order to completely prevent such scattering and leakage.

Next, the operation of the magnetic bush developing device 4 will be explained.

First, the surface of the photoreceptor drum 1 is uniformly charged with a charge 2, and imagewise exposed in an exposure section 3 to form an electrostatic latent image.

When this electrostatic latent image passes through the developing device 4, it is rubbed by the magnetic brush of the developer 22 formed on the circumferential surface of the sleeve 6 due to the magnetic action of the magnet 10, and the toner 25 in the developer 22 is rubbed. It is visualized by being attached.

This developed image is transferred onto the surface of a transfer paper (not shown) by a transfer charger and fixed by a fixing device.

Toner remaining on the surface of the photosensitive drum 1 without being transferred during transfer is wiped off from the surface of the drum 1 by a cleaning device.

After being cleaned, the surface of the drum 1 is uniformly irradiated with light by an eraser to discharge the charges, and is ready for the next copying cycle.

In the developing device 4, the developer 22 after being used for the electrostatic latent image is spread along the circumferential surface of the sleeve 6 as the sleeve 6 is rotated counterclockwise in FIGS. After being conveyed in this direction, it is dropped onto the control plate 15 from the circumferential surface of the sleeve 6 .

The dropped developer 22 is guided by the control plate 15 together with the developer 22 already accumulated on the control plate 15 and is moved to the first
As the screw 11 is rotated, it is transported backward with respect to the plane of the paper in FIG. 1, that is, in a direction from section B to section D in FIG.

Note that a portion of the developer 22 is distributed between the control plate 15 and the sleeve 6.
Then, it falls downward from the gap 13.

The developer 22 dropped in this way reaches the shielding plate 19 and is magnetically attracted onto the circumferential surface of the sleeve 6 by the magnet 9 on the shielding plate 16.
The magnetic brush of the developer 22 formed at the closest position to the surface of the photoreceptor drum 1, that is, on the circumferential surface of the sleeve 6, can rub the surface of the photoreceptor drum 1 while the amount of the developer 22 is regulated. The image is transported to the development position.

The conveyance speed of the developer 22 conveyed on the control plate 15 as the first screw 11 is rotated, and the developer 22 falls through the gap 13 between the control plate 15 and the sleeve 6 and is magnetically attracted onto the circumferential surface of the sleeve 6. The amount of developer 22 can be controlled by moving control plate 15 relative to frame 5 and adjusting gap 13.

As shown in FIG.
It is dropped onto the second screw 16 through the wide gap 14 between the control plate 15 and the circumferential surface of the sleeve 6 .

At this time, the developer 2 adhering to the circumferential surface of the sleeve 6
2, the second screw 16 is removed by the action of the scraping plate 20.
It will fall on top.

Thereafter, the dropped developer 22 is conveyed from the D section to the B section to the 0 section as the second screw 16 is rotated. 19, these developers 22 are not magnetically attracted onto the circumferential surface of the sleeve 6 and are not transported to the developing position.

The developer 22 conveyed to the E section is pumped upward by the supply blade 18 and is magnetically attracted onto the circumferential surface of the sleeve 6 by the magnetic force of the magnet 9 .

The developer 22 magnetically attracted in this manner is conveyed while receiving the magnetic force of the magnet 10.8 as the sleeve 6 is rotated, and falls onto the control plate 15 again.

The dropped developer 22 is conveyed from the E part to the F part on the control board 15 along with the toner 25 which is replenished by falling from the toner tank 26 as the first screw 11 is driven to rotate.

At this time, the developer 22 and the toner 25 are mixed and agitated to some extent by the rotational action of the first screw 11 in the E section, but the toner 25 is not completely divided into small pieces, and the toner 25 is not completely divided in the developer 22. Development may occur in which particles are electrostatically attracted to the surface of the carrier in bulk.

When a developer in such a state is used for development, the toner is not uniformly charged and the toner scatters significantly, causing the toner to adhere in spots to the non-image areas of the electrostatic latent image. ,
Fog and dirt will occur in the developed image.

In order to prevent such a situation from occurring, the following measures are taken in the developing device 4.

That is, before the developer 22 transported from the E section to the F section is used for developing the electrostatic latent image, it falls from the gap 14 onto the shielding plate 19 as shown in FIG. The toner electrostatically attracted to the carrier in the agent 22 is magnetically attracted to the circumferential surface of the sleeve 6 by the magnetic force of the magnet 9 together with the carrier.

On the other hand, the toner that is not electrostatically attracted to the carrier falls onto the second screw 16.

The toner and carrier in the developer 22 magnetically attracted onto the circumferential surface of the sleeve 6 are conveyed through the magnets 9, 10, 8 as the sleeve 6 is rotated.

At this time, in the developer 22, the carrier rotates under the action of a plurality of magnetic fields whose directions change, so that no large mechanical stress is applied to the developer 22, and magnetically In other words, developing magnets 8, 9
．． Uniform dispersion, mixing and agitation of carrier and toner is ensured by the magnetic field action of 10.

This mixing and agitation has the function of dividing the toner particles into individual particles and electrostatically adhering them to the surface of the carrier particles as a single layer, as well as uniforming the charges of the toner particles.

The developer 22 that has been conveyed once on the circumferential surface of the sleeve 6 is
The developer falls from the circumferential surface of the sleeve 6 onto the control plate 15 again and is mixed with the developer 22 on the control plate 15. Some of the developer falls through the gap 13 and is again subjected to the mixing and agitation, but some of it is mixed with the developer 22 on the control plate 15. The first screw 11 transports it to section B.

In this way, the developer 22 is circulated through the loop from the first screw 11 via the second screw 16 and returned to the first screw 11 as the sleeve 6 is driven to rotate, and is applied to the surface of the photoreceptor drum 1. Since the developer 25 is magnetically mixed and stirred with the toner 25 on the circumferential surface of the sleeve 6 located in the F section, which does not face the developer, the developer 22 supplied onto the circumferential surface of the sleeve 6 in the B section, that is, the developer immediately before being used for development. The amount and toner concentration of the developer are uniform in the longitudinal direction of the sleeve 6, and the toner and carrier are sufficiently mixed and stirred in the developer 22, so that no fogging or the like occurs in the developed image. It is.

On the other hand, the toner 25 stored in the toner tank 20
The developer 2 near the sleeve 6 located in the F section is replenished.
It is only necessary to perform this for toner tank 20.
The width itself is small and approximately equal to the width of the F section.

Further, the developer 22 includes toner 25 replenished on the peripheral surface of the end portion of the developing sleeve 6 that does not face the surface of the photoreceptor drum 1.
At the same time, the mixture is sufficiently mixed and stirred by changes in the magnetic field formed by the plurality of magnetic poles of the magnets 8, 9, and 10, and then the first screw 11 is applied onto the circumferential surface of the sleeve 6 in the portion facing the surface of the photoreceptor drum 1. transported.

Therefore, the flow of the developer 22 in the axial direction of the first screw 11 becomes smooth, and the toner concentration of the developer 22 magnetically attracted onto the circumferential surface of the sleeve 6 is reduced in the axial direction of the first screw 11, that is, in the sleeve 6. Since it becomes uniform in the longitudinal direction, uneven development in the axial direction of the photoreceptor drum 1 can also be prevented.

Note that the magnets 8, 9, and 10 within the sleeve 6 may extend to the D portion.

It goes without saying that the developing device 4 may be incorporated into a device such as a facsimile machine in which an electrostatic latent image is formed on a dielectric sheet instead of the photosensitive drum 1.

Further, the mixing section E and a part of the stirring section F may be provided so as to protrude outward from the casing of the main body of the copying machine.

In this case, it is advantageous that the toner 25 can be loaded into the developing device 4 without pulling out the developing device 4 from the main body of the copying machine.

As is clear from the above description, in the magnetic brush developing device according to the present invention, the mixing and agitation of the developer and the newly replenished toner is carried out on the part of the developing sleeve that does not face the surface of the electrostatic latent image carrier. Since this is carried out using the peripheral surface, the developer stirring mechanism itself is small and simple.

Therefore, the entire developing device is also miniaturized.

Further, the developer and the newly replenished toner are mixed and stirred on the circumferential surface of the developing sleeve in the above portion before being used to develop the electrostatic latent image, and then transferred to the developing section by the developer circulation conveyance means. The developer and the newly replenished toner are sufficiently mixed and agitated because of the fact that the developer and the newly replenished toner are mixed and agitated, and the mixing and agitation is highly efficient magnetic mixing and agitation using a developing magnet. Moreover, it is done reliably,
As a result, there is no possibility that fog or the like will occur in the developed image.

Furthermore, unlike the case of conventional mixing and agitation using rotating blades, etc., the magnetic mixing and agitation does not apply large mechanical stress to the developer, etc., and as a result, the developer deteriorates early. There's nothing like it happening.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the internal structure of an embodiment of the magnetic brush developing device according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line ■-■ in FIG. Cross section, 4th
The figure is a sectional view taken along the IV-TV line in Figure 2, and Figure 5 is a cross-sectional view of the line IV-TV in Figure 2.
■-V line sectional view in the figure, Figure 6 is the V line in Figure 2.
It is a sectional view taken along the line I-VI. 1...Photosensitive drum, 4...Magnetic brush developing device, 6...Developing sleeve, 8, 9, 1
0... Developing magnet, 11... First screw for developer transport 16... Second screw for developer transport, 18... Supply vane , 22...
...Developer, 25...Replenishment toner 26...
...Toner tank, B...Development section, C9D
...Protruding part, E...Developer mixing part, F
...Developer stirring section.

Claims (1)

[Claims for Utility Model Registration] 1. A developing sleeve provided facing the surface of the electrostatic latent image carrier, a developing magnet provided inside the developing sleeve, and a developer contained in the device. In a magnetic brush developing device, the width of the developing sleeve is The width is set wider than the width of the electrostatic latent image carrier, and there is a portion at the end of the developing sleeve that does not face the surface of the electrostatic latent image carrier, and the developer conveyed by the developer circulation conveyance means By replenishing toner by the toner replenishing means to the developer located near the developing sleeve in the portion, the developer is newly replenished with the developer on the circumferential surface of the developing sleeve in the portion. A magnetic brush developing device characterized in that, before being used to develop an electrostatic latent image, the toner and toner are mixed and stirred by the magnetic field action of a developing magnet, and then transported to a developing section by the developer circulation transport means. . 2. The magnetic brush developing device according to claim 1, wherein the developing magnet has a plurality of magnetic poles. 3. The magnetic brush developing device according to claim 2, wherein the developing sleeve is rotationally driven.