JPH06214464A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a miniaturized developing device which can excellently form an image and which is easily exchanged by arranging a developing grid provided with many holes between a vibration magnet and a latent image forming body and integrally providing it with a developer housing part. CONSTITUTION:The developing grid 15 provided with many holes is arranged between the vibration magnet 14 and the latent image forming body 6. Besides, the grid 15 and the developer housing part 9a housing magnetic developer are integrally provided so that they can be simultaneously exchanged. As for the magnet 14, it is good that it is integrally provided with the grid 15 and the housing part 9a so that they can be simultaneously exchanged or it is provided so that it can be separated from them. Pressure when the magnetic developer (toner) flows out from the housing part 9a is distributed to a magnetic brush carried by the magnet 14 and the grid 15. As the result, since the receiving force of the flowing-out pressure of the toner becomes very strong in comparison with the case that it is received only by the magnetic brush, the wasteful flowing-out of the toner is eliminated and the toner is prevented from being leaked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine, a facsimile or a printer,
More specifically, it relates to improvement of a magnetic brush developing type developing device using a vibrating magnet.

[0002]

2. Description of the Related Art As is well known, in a developing device in an image forming apparatus such as a copying machine, a facsimile or a printer, an electrostatic latent image formed on a photoconductor, which is a latent image carrier, by an exposure process is used. Visible image processing is performed with a developer. Therefore, in the developing section, for example, when a dry developer is used, the developing sleeve carrying the developer on the surface is brought close to the photoconductor, and the developer on the surface is applied to the electrostatic latent image on the photoconductor. It is designed to be electrostatically adsorbed. As the developer, there are a two-component type developer in which a toner made of dielectric particles is attached to a carrier such as a carrier, and a one-component type developer without using a carrier or the like.

Of these developers, the two-component type developer is
For example, in the case of a magnetic developer, since the carrier holding property with respect to the toner is good, a relatively stable toner supply can be performed, which has an advantage that the toner supply control necessary for stabilizing the image density can be easily performed. On the other hand, since the deterioration of the carrier and the mixing ratio with the toner are likely to change, it is difficult to manage the characteristics of the developer, or the toner replenishing section is additionally provided, which tends to increase the size of the developing device.

On the other hand, the one-component type developer does not contain a carrier and therefore does not have the above-mentioned drawbacks. Further, the one-component type developer includes a toner only and a toner to which an auxiliary agent is added or mixed if necessary, and the toner is a magnetic toner in which a magnetic material is kneaded and included in the toner particles themselves. And non-magnetic toner containing no magnetic substance.

Among them, the magnetic brush developing method using magnetic toner has an advantage that a peripheral image called edge effect is less emphasized and a uniform image can be obtained. Further, the developing method using the magnetic toner has the advantages that the apparatus can be simplified and that a high-quality image can be stably obtained. However, the conventional developing device using the magnetic brush developing method has a drawback in that the toner replenishing mechanism and the like are mechanically complicated, and that when the device is operated, a load is applied to the toner, which accelerates the deterioration of the toner.

As an example of such a developing device, a magnetic powder developer is held on the surface of a non-magnetic cylinder having a magnetic means inside and conveyed to the electrostatic image holding surface for development, and at that time, a carrier is used. A seal member prevents the developer from scattering from both ends of the developer and the scooping member collects the developer into the area for development to contribute to the development. (Japanese Patent Laid-Open No. 54-59943), or one in which the setting relationship between the developer application area of the developing magnet roll and the image area is determined in order to prevent abnormal images (JP-A-4-16).
No. 5377).

Further, in a general two-component developing device, a magnetic brush developing device which continuously carries out a cycle of absorbing a developer, developing and releasing the developer is a magnet, a sleeve, a bearing and a driving means. As for the positional relationship in the direction of the rotation axis, it was inevitable that the bearing was on the outside of the magnet, the end of the sluve was on the outside of the bearing, and the supporting portion of the shaft or the connecting portion with the driving means was further outside thereof (Japanese Examined Patent Publication). 41-3
428). Such a relationship cannot be changed because the basic structure of the magnetic brush developing device that continuously performs the developing cycle even if the one-component system has become the mainstream as the developing system in recent years. In other words, due to the basic structure for practical use of the developing magnet roll for a general one-component magnetic toner, the widthwise dimension of this one-component developing device necessarily requires a dimension much larger than the image width. I was there.

Incidentally, with the recent tendency toward downsizing (downsizing) of office equipment, so-called downsizing of device cross-sections has been actively carried out in image forming apparatuses as the material technology has advanced. For example, the diameter of the photosensitive drum may be changed from 40 mm in the past to 30 mm, or 20 m
m is done. However, even in such a tendency, it was difficult to reduce the size of the developing device in the width direction. This is because the basic structure of the magnetic brush developing device that continuously performs the developing cycle is restricted as described above.

On the other hand, Japanese Patent Publication No. 37-12640 discloses that "a developing operation is performed by sliding on a photosensitive paper while shaking a magnetic brush having magnetic powder adsorbed and formed on a magnet". It is widely known as a method of shaking and developing a magnetic brush that has been adsorbed and formed on. In this system, the bearing is located outside the magnet, the end of the sleeve is located outside the bearing, and the shaft is located outside the shaft, as in the positional relationship of the magnet, the sleeve, the bearing, and the driving means in the rotation axis direction of the magnetic brush developing device as described above. The supporting portion or the connecting portion with the driving means is further expected to replace the basic structure on the outside thereof and to reduce the width direction of the developing device. However,
Since this method uses two components, problems such as toner scattering and toner leakage occur. Furthermore, as the magnet, an electromagnet is used to change the trapped state of the magnetic powder or exchange the magnetic powder depending on whether the voltage supplied to the magnet is stopped or stopped. Therefore, miniaturization is restricted in this respect.

Japanese Patent Publication No. 39-8149 discloses that an oscillating cylindrical sleeve containing a rotating columnar magnet having a plurality of poles reciprocates in a direction perpendicular to the photographic paper transporting direction even at a relatively low speed. By giving the movement, uneven development is eliminated,
Although it shows the point of obtaining a clear image, the device itself is long in the horizontal direction and is not suitable for miniaturization. Further, since the magnetic brush is separated from the magnet, it has a drawback that it slips on the sleeve and its reliability is low.

JP-A-52-23349 and JP-A-53-23
Japanese Patent Publication No.-40533 discloses a developing device provided with means for vibrating a magnet having a magnetic brush made of magnetic toner. Although these developing devices have the advantage of not having a movable part, it cannot be said that the toner scattering due to vibration is always sufficient, and contamination of the periphery of the device occurs.

Japanese Patent Publication No. 40-17227 discloses that a net of a non-magnetic material is arranged between the electrostatic latent image forming surface and the magnet of the magnetic brush, and the developer of the magnetic brush is mixed or shaken by the vibration of the net or the magnet. What stirs is disclosed. This publication describes that the brush can be vibrated at a high frequency by this means, and the hardness of the brush portion can be adjusted by changing the size of the mesh. However, since this method is a two-component method that uses a carrier with a strong magnetic force, the net is required to be non-magnetic in order to reduce the drive load due to the resistance of the net. There was a drawback that the toner was heavily scattered.

In Japanese Utility Model Application Laid-Open No. 53-16441, a non-magnetic electrode having an insulating surface is disposed between the surface of the latent image carrier and the one-component magnetic toner carrier, and a developing bias voltage is applied to the electrode. It is disclosed that the voltage can be applied. However, because of the structure with the developing sleeve, the device is
There were obstacles to the complexity and miniaturization.

[0014]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic brush developing type developing device, which can improve the image formation during the developing operation and can easily replace the developing device. Furthermore, it is to make it possible to reduce the size of the entire apparatus.

[0015]

In order to achieve such an object, the present invention develops an electrostatic latent image on an electrostatic latent image forming body by causing a magnetic brush on a magnetic developer by vibrating a vibrating magnet. In the developing device, a developing grid having a large number of holes is arranged between the vibrating magnet and the electrostatic latent image forming body, and at least the developing grid and the developer accommodating portion accommodating the magnetic developer can be simultaneously replaced. It is characterized by being integrally provided.

In the present invention, the vibrating magnet may be provided integrally with the developing grid and the developer accommodating portion so as to be simultaneously replaceable, or may be separable from the developing grid and the developer accommodating portion.

The developing grid is preferably provided below the discharge port of the developer accommodating portion so as to cover the front portion of the vibrating magnet.

[0018]

According to the present invention, the pressure when the magnetic developer (hereinafter referred to as toner) flows out from the developer accommodating portion is dispersed between the magnetic brush carried by the vibrating magnet and the developing grid. As a result, the receiving force becomes much stronger than the case where the magnetic brush only receives the outflow pressure of the toner, so that wasteful toner outflow is eliminated and toner leakage is prevented. Also, since a magnetic brush of toner is formed through the developing grid and then the electrostatic latent image is developed using this magnetic brush, the magnetic brush is intermittently cut by the developing grid by the vibration of the vibrating magnet that directly carries the toner. It Therefore, the cut magnetic brush is temporarily carried on the developing grid or floats there. As a result, the toner consumed during the developing operation can be brought into soft contact with the electrostatic latent image, so that a good image can be obtained. Moreover, since the magnetic developer, that is, the one-component toner is used, the driving load is much smaller than that of the two-component toner, and the toner is not scattered. Therefore, the reliability of the toner can be increased.

Further, according to the present invention, the image width can be satisfied by the length of the vibrating magnet plus the amplitude of the vibration, so that the lateral width of the developing device exceeds the lateral width of the photosensitive drum. Can be made much smaller than the conventional device. In addition, since the developing grid and the vibrating magnet can be replaced at the same time as the developer storage portion that stores the magnetic developer, they can be easily replaced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an image forming apparatus 1 to which the present invention is applied.
Shows the appearance of. The operation portion of the upper surface of the image forming apparatus 1 is covered by a lid 2 that can be opened and closed. Figure 3
Shows the state when the lid 2 is opened. At this time, the lid 2
The front side of the sheet also serves as a guide member for the print sheet P, and the print sheet P is inserted from above to a predetermined position along the lid 2 to prepare for printing. Then, by an operation such as giving a predetermined instruction on the operation display unit 3,
Data output from a personal computer (not shown) is printed, and the print paper P is ejected from the front surface of the image forming apparatus 1. Further, by depressing the button 4, the upper housing of the image forming apparatus 1 can be opened, and various parts therein can be taken out of the image forming apparatus 1.

FIG. 4 shows a vertical section of the image forming apparatus 1.
The printing paper P inserted along the lid 2 is transported inside the apparatus at a predetermined timing at the position of the registration roller 5, and the toner image formed on the surface of the photosensitive drum 6 is transferred. The photoconductor drum 6 is, for example,
A surface potential of 700 V is applied. Then, the exposure means 8
Is exposed by a laser beam or the like by
The surface potential is 00V. This electrostatic latent image is visualized by being subjected to reversal development with the negatively charged toner T of the developing device 9. At the time of development, in order to prevent background stains, for example, -5
A developing bias of 00V is applied to the developing device 9. The developed toner image is transferred onto the printing paper P by the transfer means 10. The print sheet P is fixed on the fixing unit 11
The toner image is fixed by passing between the heat roller and the pressure roller and is discharged to the front surface of the image forming apparatus 1. The photosensitive drum 6 repeats the same operation after the residual toner on the photosensitive drum 6 is removed by the cleaning means C.

FIG. 1 shows a state in which the upper housing of the image forming apparatus 1 is opened and the developing device 9 is taken out. Developing device 9
Can be disconnected from the magnet drive motor M by pulling out the image forming apparatus 1 almost vertically.

FIG. 5 is an overall perspective view of the developing device 9.
The image forming apparatus 1 is provided on the side surface of the frame 9b of the developing device 9.
A guide means 12 is provided which allows the developing device 9 to be housed in a predetermined position by engaging with a convex positioning member provided inside the main body when mounted inside. In addition, the front surface of the developer accommodating portion 9a (right front in the figure)
A horizontally long discharge port 13 for discharging the toner T is provided on the lower side. A horizontally long vibrating magnet 14 and a developing grid 15 are provided below the discharge port 13, and these can be integrally replaced with the developer accommodating portion 9a as shown in FIG. The vibrating magnet 14 is attached to the frame 9b so as to be able to vibrate left and right, and the developing grid 15 is fixed to the frame 9b by curving its entire length into a C-shape so as to cover the front portion of the vibrating magnet 14 at intervals. There is. The developing grid 15 is provided with a large number of hexagonal holes, for example.

The developing device 9 is not limited to this example, but may be integrated with the photosensitive drum 6, the cleaning means C and the like so as to be taken out together with them. In addition, the developing device 9
Alternatively, the developer accommodating portion 9a for accommodating the toner T may be separable from the developing mechanism portion so that only the developer accommodating portion can be replaced. FIG. 6 shows only the developing grid 15 of the vibrating magnet 14 and the developing grid 15 in the developer accommodating portion 9a.
The vibrating magnet 14 is left in the image forming apparatus 1 for economic reasons when the developing device 9 is replaced.

FIG. 7 shows a mechanism for vibrating the vibrating magnet 14. A cam follower 16 is fixed to the center of the back surface of the vibrating magnet 14, and a concave portion 16a of the cam follower 16 is slidably fitted to an eccentric cam 17 fixed to the rotation shaft of the magnet drive motor M. Swing levers 18 are attached to the left and right ends of the vibrating magnet 14. In the swing lever 18, a thick portion 18a and a thin portion 18b are connected in a U shape, and the thick portion 18a is connected to the frame 9b and the thin portion 18b.
b are each fixed to the vibrating magnet 14 via a fixing member. Since the thin portion 18b can be freely deformed in the direction perpendicular to the surface (length direction of the vibrating magnet 14), when the eccentric cam 17 rotates, the vibrating magnet 14 vibrates left and right according to the amount of eccentricity. Becomes Cam follower 1
The concave portion 16a of 6 and the eccentric cam 17 are fitted by setting the developing device 9 at a predetermined position in the image forming apparatus 1 by the guide action of the guide means 12.

FIG. 8 shows the vibrating magnet 14 and the developing grid 15.
And the action. Since the developing grid 15 covers the vibrating magnet 14 below the discharge port 13, the toner T attached to the surface of the vibrating magnet 14 passes through the hole of the developing grid 15 to form the magnetic brush B. When the vibrating magnet 14 is stationary, the magnetic brush B is prevented from moving in the direction orthogonal to the magnetic field by the resistance of the holes of the developing grid 15. Therefore, the magnetic brush B cannot move freely, and the discharge port 13
Is blocked, and the toner T is prevented from leaking out as shown by the arrow. This blocking force is so strong that the toner leakage prevention is sufficiently maintained even if a slight impact is applied from the outside. This is because the pressure when the toner T flows out from the discharge port 13 is received not only by the magnetic brush B but also by the developing grid 15. That is, since the developing grid 15 having high rigidity reinforces the magnetic brush B from the inside, the receiving force becomes much stronger than in the case where the flexible magnetic brush B alone receives the toner outflow pressure.

Further, during the developing operation, that is, when the vibrating magnet 14 vibrates due to the rotation of the magnet driving motor M, the toner T is quickly supplied to the vibrating magnet 14. In this case as well, the pressure when the toner T flows out from the discharge port 13 is received not only by the magnetic brush B but also by the developing grid 15, so that wasteful outflow is prevented. Then, the electrostatic latent image is developed by using the magnetic brush B of the toner T formed through the developing grid 15. In this case, if the vibrating magnet 14 that directly carries the toner T vibrates, the magnetic brush B
Are intermittently cut by the developing grid 15. As a result, the cut magnetic brush B is temporarily removed from the developing grid 1.
5. Hold on 5 and repeat floating around it. Due to this phenomenon, the magnetic brush B is transferred to the electrostatic latent image during the developing operation.
Since the toner T supplied from the toner is assured of soft contact with the electrostatic latent image, a good image having excellent gradation can be obtained. The magnet drive motor M is, for example, 1.
As long as the motor operates with two 5V AA batteries, there is no problem in performing the developing operation.

The arrangement of the developing grid 15 in FIG.
Although the example in which the upper end portion 15a is provided below the discharge port 13 has been described, the discharge grid 13 may be arranged so as to be covered with the developing grid 15. In this case, the outlet 13
The toner T flowing out of the vibrating magnet 14 is immediately captured by the vibrating magnet 14 to form the magnetic brush B, and is interrupted by the developing grid 15 in the front and stopped. Next, when the vibrating magnet 14 vibrates, the magnetic brush B extends outside through the holes of the magnetic developing grid 15 to perform the developing operation. In any case, the pressure when the toner T flows out from the discharge port 13 is
Since it is received not only by the magnetic brush B but also by the developing grid 15, useless outflow is prevented.

The material of the developing grid 15 may be magnetic or non-magnetic as long as it is conductive. However, when using a magnetic material, make sure that the magnetic shield action does not become too strong.
The thickness is preferably 0.5 mm or less, and particularly preferably 0.2 mm or less. Development grid 15
The representative diameter of the holes is 3 mm or less, preferably 2 mm or less. Further, the ratio of this hole to the entire area of the developing grid 15, that is, the opening ratio,
It is preferably 30% or more, and particularly preferably 60% or more in order to further improve the image quality. Further, the shape of this hole is not limited to a hexagon, and can be arbitrarily selected.

As an example using the developing grid 15, an electroformed nickel plate having a thickness of 0.1 mm provided with holes having a typical diameter of about 2 mm and having an aperture ratio of about 90% was used. When the amplitude was 2 mm and the frequency was 45 Hz, good image quality could be obtained.

FIG. 9 is a diagram for explaining the relationship between the image width and the length of the vibrating magnet 14. In this figure, the vibrating magnet 1
The length of 4 (magnet width) is shorter than the image area which is the maximum length for forming the toner image on the printing paper. The amplitude (magnet amplitude) of the vibrating magnet 14 is, for example, 2 mm. The practical amplitude is 5 mm or less, preferably 3 mm or less.

The maximum paper passing width is now A4 size (210 mm
X297 mm), the width of the photosensitive drum is naturally selected to be a value exceeding 210 mm. If a blank portion having a width of 5 mm is provided on both sides of the A4 size and the rest is the image width, the value is 200 mm. Since the magnet amplitude is 2 mm as described above, the magnet width is a value obtained by subtracting 2 mm from 200 mm, that is, 198 mm.
The image area can then be completely covered. Usually, the vibrating magnet 14, its drive mechanism, and the developer accommodating portion 9a.
Since the above is integrated into a developing device, the entire width thereof is slightly increased from the above 198 mm. Generally, a resin material having a thickness of about 1 mm is often used as the exterior member of the developing device. Further, a toner leak preventing seal member such as a sponge is disposed in the gap between the exterior member and the vibrating magnet 14. Even if these are combined, the length added to the magnet width and the magnet amplitude is about several mm. In this example, the width of the developing device can be set to be approximately equal to the maximum sheet passing width. That is, there is no need for a length exceeding the width of the photosensitive drum, unlike the conventional device. In this way, the length obtained by adding the amplitude to the length of the vibrating magnet is set to satisfy the image width, so that the lateral width thereof can be particularly minimized as compared with the conventional developing device.

Even when the entire sheet passing width is used as the image area, the length obtained by adding the magnet amplitude to the magnet width is the same as above. In this case, a developing device having a width obtained by adding a few millimeters to the maximum paper passing width can be obtained, but it is still much smaller than the conventional developing device.

[0034]

As described above, according to the present invention, the toner pressure when flowing out from the developer accommodating portion is received not only by the magnetic brush carried by the vibrating magnet but also by the developing grid, so that only the magnetic brush is used. As compared with the case of receiving the outflow pressure of the toner, the receiving force becomes much stronger, so that the wasteful outflow of toner is eliminated and the toner leakage is prevented. Also, since a magnetic brush of toner is formed through the developing grid and then the electrostatic latent image is developed using this magnetic brush, the magnetic brush is intermittently cut by the developing grid by the vibration of the vibrating magnet that directly carries the toner. The cut magnetic brush is temporarily carried on the developing grid or floats there. As a result, the toner consumed during the developing operation can be brought into soft contact with the electrostatic latent image, so that a good image can be obtained. Moreover,
Since the one-component toner is used, the driving load is much smaller than that of the two-component toner, and the toner is not scattered. Therefore, the reliability of the toner can be increased.

Since the image width can be satisfied by the length of the vibrating magnet plus the amplitude of the vibration,
The width of the developing device can be made much smaller than that of the conventional device which has a width exceeding the length of the photosensitive drum.

Further, the development grid, or claim 2
In the one described in (1), the vibrating magnet is further provided integrally with the developer accommodating portion for accommodating the magnetic developer so as to be simultaneously replaceable,
These can be easily replaced. Further, according to the third aspect of the present invention, since the developer accommodating portion and the developing grid can be separated from the vibrating magnet having a longer life than them, the vibrating magnet can be replaced while being left in the image forming apparatus. And can be economical.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a developing device according to the present invention taken out of an image forming apparatus.

FIG. 2 is an external perspective view of the image forming apparatus of the above.

FIG. 3 is a perspective view showing a state in which printing paper is set in the image forming apparatus.

FIG. 4 is a cross-sectional view showing a state in which the developing device is set in the image forming apparatus.

FIG. 5 is a sectional view of the developing device.

FIG. 6 is a sectional view of an image forming apparatus using a developing device that is replaceable except for a vibrating magnet.

FIG. 7 is a perspective view of a vibrating magnet drive mechanism of the developing device.

FIG. 8 is an enlarged cross-sectional view of a developing device.

FIG. 9 is a diagram illustrating a relationship between an image width and a width of a vibrating magnet.

[Explanation of symbols]

 B magnetic brush C cleaning means M magnet drive motor P printing paper T toner 1 image forming apparatus 2 lid 3 operation display section 4 button 5 registration roller 6 photoconductor drum (electrostatic latent image forming body) 7 charging means 8 exposure means 9 development Device 9a Developer storing portion 9b Frame 10 Transfer means 11 Fixing means 12 Guide means 13 Discharge port 14 Vibrating magnet 15 Development grid 15a Development grid upper end 16 Cam follower 16a Recess 17 Eccentric cam 18 Swing lever 18a Thick portion 18b Thin portion

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Fumihiro Kitahara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] 1. A developing device for developing a latent electrostatic image on an electrostatic latent image forming member by causing a magnetic brush to a magnetic developer by vibrating the vibrating magnet, wherein a developing grid having a large number of holes is provided with the vibrating magnet. A developing device, which is disposed between the electrostatic latent image forming body and at least the developing grid and a developer storage portion for storing the magnetic developer are integrally replaceable. 2. The developing device according to claim 1, wherein the vibrating magnet is integrally provided so as to be simultaneously replaceable with the developing grid and the developer accommodating portion. 3. The developing grid and the developer accommodating portion are integrally provided so as to be simultaneously replaceable, and the vibrating magnet is separable from the developing grid and the developer accommodating portion. Item 1. The developing device according to Item 1. 4. The developing device according to claim 1, wherein the developing grid is provided below an outlet of the developer accommodating portion so as to cover a front portion of the vibrating magnet.