JPS61175661A - Forming device for thin layer of developer - Google Patents

Abstract

PURPOSE:To prevent the fogging and white absence of a developed image by circulating magnetic particles and taking a nonmagnetic developer through the rotation of a circulation magnet and securing the triboelectrification of the nonmagnetic developer. CONSTITUTION:Magnetic particles 27 are circulated as shown by an arrow (c) as the circulation magnet 35 rotates as shown by an arrow (d). The magnetic particles 27, therefore, receive a moving force in the direction of the arrow (c) by friction against a developing sleeve 22 and receives a moving force as shown by the arrow (c) when the circulation magnet 35 rotates as shown by an arrow (d). The magnetic field established by the circulation magnet 35 extends to not only magnetic particles contacting a developing sleeve 22, but also magnetic particles outside it, so the force of the circulation operates on the whole of the magnetic particle layer, so that the circulation becomes stable extremely.

Description

[Detailed description of the invention] 1st Duke The present invention relates to an apparatus for forming a thin layer of an image agent.

The present invention further relates to a thin layer forming device for non-magnetic developer.

¥tJLJM Conventionally, various devices have been proposed and put into practical use as dry-component developing devices. However, in any of the development methods, it is extremely difficult to form a thin layer of dry-component developer, and for this reason, a developing device has been constructed by forming a relatively thick layer. However, as improvements in the clarity, resolution, etc. of developed images are currently being sought, it is essential to develop a method for forming a thin layer of a dry component developer and an apparatus therefor.

As a method of forming a thin layer of a conventionally known dry component developer, Japanese Patent Application Laid-Open No. 54-43037 has been proposed and has been put into practical use. However, this concerned the formation of a thin layer of magnetic developer. In order to make magnetic developers magnetic, a magnetic material must be added inside them, which causes poor fixing properties when heat fixing the developed image transferred to transfer paper.
Since a magnetic material (the magnetic material is usually black) is added to the developer itself, there are problems such as poor color reproduction during color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer, there are two methods: using a cylindrical brush made of soft bristles like beaver's hair, and applying the developer to the brush. A method of coating the developing roller with a doctor blade or the like has been proposed. However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to regulate the amount of developer, but uniform application is not achieved, and the Ta of the brush is reduced by simply rubbing the fiber brush on the developing roller. Since no triboelectric charge is imparted to the developer existing between the fibers, there is a problem in that fogging and the like are likely to occur. Furthermore, since the device includes a non-magnetic developer, it is difficult to prevent the developer from leaking from the device.

As a novel thin layer forming method that is completely different from the conventional method described above, a magnetic brush made of magnetic particles is formed on the upstream side of the magnetic particle restraining member with respect to the moving direction of the surface of the developer holding member.
A method has already been proposed in which a thin layer of non-magnetic developer is formed on a developer holding member using this magnetic brush. However, in this developing device, magnetic particles are not sufficiently circulated within the container. Since the developer is not sufficiently replenished to the magnetic particle layer, unevenness occurs in the thin layer formed on the developer holding member, thereby causing uneven development.

In addition, when the circulation of magnetic particles is inhibited by vibrations from the image forming apparatus main body, and the circulation of magnetic particles becomes insufficient or stops, the amount of developer held on the developer holding member The amount of electrification due to friction increases, and even if a normal developing bias is applied, the developer does not fly to the image carrier, which may cause problems such as inability to develop (so-called white spots).

Therefore, the present invention provides an apparatus for forming a thin layer of non-magnetic developer on a developer holding member using magnetic particles confined within a container, in which the magnetic particles are stably and sufficiently circulated within the container over a long period of time. An object of the present invention is to provide a developer thin layer forming device.

According to the present invention, there is provided a developer supply container having an opening, a non-magnetic member for holding developer which is provided in the opening and is movable endlessly inside and outside the container, and the holding member. a fixed magnetic field generating means provided inside; a magnetic particle restraining member provided outside the developer holding member and restraining the magnetic particle layer within the developer supply container together with the fixed magnetic field generating means;
Since there is provided a developer thin layer forming device characterized by having a magnetic field generating means provided inside the holding member and capable of rotating once, stable circulation of the magnetic particles is ensured.

real jl example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a developer thin layer forming apparatus described in Japanese Patent Application No. 58-205189 filed by the present applicant. This developer thin layer forming device forms a magnetic brush made of magnetic particles on the upstream side of a magnetic particle restraining member with respect to the moving direction of the surface of the developer holding member, and develops a thin layer of non-magnetic developer with this magnetic brush. It is formed on the agent holding member.

The apparatus shown in FIG. 1 includes a developer supply container 21 and a developing sleeve 22 as a developer holding member. Developing sleeve 22
is a non-magnetic sleeve made of aluminum or the like, and its right half-circumferential surface is inserted into the container zl through a horizontally long opening formed in the lower part of the left side wall of the developer supply container 21 in the longitudinal direction of the container, and its left half-circumferential surface is inserted into the container zl. It is mounted horizontally on a bearing that is exposed to the outside and can freely rotate, and is driven to rotate counterclockwise as shown by the arrow. The developer holding member 22 is not limited to the above-mentioned cylindrical body (sleeve).
The surface of the developing sleeve 22 exposed outside the container, which may be in the form of an endless belt that is rotationally driven, has a very small surface on the surface of the latent image holding member 3, such as a photoreceptor, which is driven to move in the direction of arrow a. They face each other with a gap between them.

A magnet 23 is provided inside the developing sleeve 22, and this is a fixed permanent magnet (magnet) as a fixed magnetic field generating means that is positioned and held in the illustrated position and orientation, and when the developing sleeve 22 is rotationally driven. Moko's magnet 2
3 is fixedly held in the position and posture shown in the figure. This magnet 23 has a north pole 23a and a south pole 23b. As the magnet 23, an electromagnet may be provided instead of a permanent magnet.

A magnetic blade as a magnetic particle restraining member is provided on the upper edge side of the opening of the developer supply container in which the developing sleeve 22 is disposed. It is arranged along the length of the upper edge of the opening so as to protrude into the inside of the opening, and is made by, for example, bending a steel plate into a simple cross-sectional shape.

A magnetic particle circulation area limiting member 26 is provided with its lower surface in contact with the upper surface of the magnetic blade 24, and its front end surface 26a is undercarved.

Reference numerals 27 and 28 indicate magnetic particles and non-magnetic developer which were sequentially accommodated in the developer supply container 21.

The bottom plate of the developer supply container 21 is extended below the developing sleeve 22, which is a developer holding member, to prevent the developer from leaking to the outside. In addition, in order to further ensure the prevention of leakage of this developer to the outside, the extended bottom plate 2
A leaked developer collecting container 29 for receiving and restraining leaked developer is disposed on the upper surface of 1a, and a scattering prevention member 30 is disposed along the length of the distal end edge of the extended bottom plate 21a.

A voltage, which will be described later, is applied to this member 30.

The magnetic particles 27 have a particle size of 30 to 200 JL, preferably 7
It is 0 to 150p. Each magnetic particle may be made of only a magnetic material, a combination of a magnetic material and a non-magnetic material, or a mixture of two or more types of magnetic particles. In order to prevent leakage of magnetic particles or developer from the developer supply container 21 in which the sleeve 22 is disposed, that is, the area where the magnetic particles 27 face the inside of the container 21. The magnetic particle layer is attracted to each part of the sleeve surface area from the magnetic member 31 to the tip of the magnetic blade 24, which is a magnetic particle restraining member, by the magnetic field of the magnet 23 in the sleeve 22, and completely covers the sleeve surface area as a magnetic particle layer. The state will be as follows. When the non-magnetic developer 28 is put into the container 21 after the magnetic particles 27 are put therein, a large amount of the non-magnetic developer 28 is stored outside the magnetic particle layer as the first layer with respect to the sleeve 22 and exists as a second layer.

The first magnetic particles 27 preferably contain non-magnetic developer 28 in an amount of about 2 to 70% (by weight) of the magnetic particles, but may be composed of only magnetic particles. Furthermore, once the magnetic particles 27 are adsorbed and held as a magnetic particle layer in the visible area of the sleeve surface, they will not substantially drift to one side even if the device is vibrated or the device is tilted considerably.
The sleeve surface area is kept completely covered.

When the magnetic particles 27 and the non-magnetic developer 28 are sequentially placed in the container 21 as described above, the magnet 23
A magnetic brush 27a of magnetic particles is formed in a portion of the magnetic particle layer near the sleeve surface corresponding to the position of the magnetic pole 23a by the strong magnetic field of the magnetic pole 23a.

Further, even when the sleeve 22 is rotated in the direction indicated by the arrow, the magnetic particle layer near the tip of the magnetic blade 24, which is a magnetic particle restraining member, is affected by gravity, magnetic force, and the magnetic blade 24.
Due to the balance between the restraint force based on the effect of the presence of 4 and the conveyance force in the moving direction of the sleeve 22, the sleeve 22 is restrained at the point 25 on the surface thereof, forming a stationary layer 27b that can move to some extent but is almost immobile. .

Also, when the sleeve 22 is rotated in the direction shown by the arrow, the magnetic pole 2
4 and the fluidity and magnetic properties of the magnetic particles 27, the magnetic brush 27a can be set to the magnetic pole 2.
3a, it circulates in the direction of arrow C, forming a circulation layer 27c. In the circulation layer 27C, the magnetic particles relatively close to the sleeve 22 are moved to the magnetic pole 23 by the rotation of the sleeve 22.
The stationary layer 2 located on the rotationally downstream side of the sleeve from the vicinity of a
It rises to the top of 7b. In other words, it receives a force that pushes it upward. Since the upper limit of the circulation area of the pushed-up magnetic particles is determined by the magnetic particle circulation area limiting member 26 provided on the upper part of the magnetic blade 24, the magnetic particles do not climb onto the magnetic blade 24 and are , and returns to the vicinity of the magnetic pole 23a again. In this case, magnetic particles that are located far from the sleeve surface and receive a small push-up force may fall before reaching the magnetic particle circulation area limiting member 26. In other words, in the circulation layer 27c, the magnetic brush 2 of the magnetic particles moves as shown by the arrow C due to the magnetic force and frictional force due to gravity and magnetic poles, and the fluidity (viscosity) of the magnetic particles.
7a is performed, and during this circulation, the magnetic brush sequentially takes in the non-magnetic developer 28 from the developer layer above the magnetic particle layer and returns to the lower part of the developer supply container 21, and then the sleeve 22. This cycle is repeated as the motor rotates. The magnetic blade 24 does not directly participate in this circulation.

The non-magnetic developer that is successively taken in and mixed into the magnetic particle layer on the surface of the sleeve 22 is charged by friction with the magnetic particles due to the flow of the magnetic particles, friction with the surface of the developing sleeve, etc. In this case, it is preferable to apply an insulating treatment such as an oxide film or a resin that is electrostatically at the same level as the non-magnetic developer to the surface of the magnetic particles, to reduce the transfer of tripod from the magnetic particles, and to transfer the necessary charge to the developing sleeve. By applying the developer to the developing sleeve 22, it is possible to prevent the influence of deterioration of the magnetic particles, and the application of the developer to the developing sleeve 22 is stabilized. Since this charged developer is non-magnetic, it is not restrained by the magnetic field of the magnetic pole 24, and the sleeve surface is the magnetic member 3 at the lower edge of the container opening where the sleeve 22 is disposed.
During the rotational movement from the magnetic blade 1 to the tip of the magnetic blade 24, the surface of the sleeve is uniformly and thinly coated at each part due to the mirroring force.

Even when the sleeve 22 is rotating, the magnetic particles in the magnetic particle stationary layer 27b near the tip of the magnetic blade 24 are affected by the binding force based on the effects of gravity, magnetic force, and the presence of the magnetic blade 24, as described above, and the sleeve 22. The thin coating of the non-magnetic developer formed on the surface of the sleeve 22 does not pass through the gap d between the tip of the magnetic blade 24 and the sleeve 22 due to the balance with the conveyance force in the moving direction of the magnetic blade 22. As the sleeve 22 rotates, only the layer passes through the gap d and is rotationally conveyed to the latent image carrier 3 side, and comes close to the surface of the latent image carrier 3. 28a is the developing sleeve 22
A thin coating layer of non-magnetic developer formed on the surface of the developing sleeve 22 and a close facing portion of the latent image carrier 11 on which the thin layer of non-magnetic developer is formed is referred to as a developing section 32.

Incidentally, reference numeral 33 in the figure denotes a developer blocking member provided at both ends of the sleeve 22 in the longitudinal direction, and prevents the non-magnetic developer from being applied to both ends of the sleeve.

In the developing section 32, the non-magnetic developer layer 28a on the surface side of the developing sleeve 22 is coated with a developing bias voltage obtained by applying a voltage in which alternating current and direct current are superimposed by a bias power source 34 between the latent image holder 3 and the developing sleeve 22. The electric field selectively transfers and adheres to the three surfaces of the latent image carrier in accordance with the latent image pattern, and the latent images are sequentially developed (this developing method is described in, for example,
8-32375), the bias power supply 34 may be an alternating current or a direct current.

The surface of the developing sleeve that has passed through the developing section 32 and been consumed as the developer layer is selectively developed is returned to the developer supply container 21 by the subsequent rotational drive of the sleeve, and comes into contact with the magnetic particle layer again. The cycle of being coated with the non-magnetic developer contained in the layer is repeated, and the surface of the latent image holding member 3 is continuously developed. As described above, the magnetic particle layer is naturally replenished by successively taking in developer from the non-magnetic developer 28 storage layer located outside of the magnetic particle circulation layer 27c. In order to prevent the so-called ghost image phenomenon of the developing sleeve, the developer layer that has not been subjected to development is scraped off from the surface of the developing sleeve that has been rotated back into the container 21 using a -H scraper means (not shown). It is also preferable to bring the developer layer scraping sleeve surface into contact with the magnetic particle layer so that the developer is coated.

The non-magnetic developer 28 may be externally supplemented with silica particles to increase fluidity, or abrasive particles to polish the surface of the photoreceptor, which is the latent image holding member 3, in a transfer image forming system, for example. Alternatively, a non-magnetic developer 28 containing a small amount of magnetic particles may be used.

With the above configuration, a highly satisfactory developer thin layer forming apparatus can be obtained. However, when the developing device is used for a long period of time, the circulation layer 27c is damaged due to mechanical vibrations that the developing device receives from the main body of the image forming apparatus, or vibrations and shocks that occur when replacing the developing device as the image is colored. Circulation may be impaired. As described above, the non-magnetic developer 28 present outside the circulating layer 27c of magnetic particles is taken into the magnetic particle layer and naturally replenished.

Therefore, if the circulation in the circulation layer 27c deteriorates, the replenishment of the non-magnetic developer 28 to the magnetic particle layer is delayed, resulting in uneven thickness of the thin layer of the non-magnetic developer 28 formed on the developing sleeve 22. , causing density unevenness in the formed image.
Further, as described above, the circulation of the circulation layer 27c is inhibited by mechanical vibrations applied to the developing device from the outside. Alternatively, in an extreme case, when stopped, the amount of triboelectric charge of the non-magnetic developer 22 formed into a thin layer on the developing sleeve 22 increases,
There are disadvantages such as so-called white spots.

FIG. 2 is a sectional view of a developer thin layer forming apparatus according to an embodiment of the present invention that solves this problem. A seal bag net 36 for restraining magnetic particles is fixed at a position facing the magnetic blade 24. The magnetic pole facing the magnetic blade 24 is
The strength is about 400G, and in this example it is the S pole, but the N pole is
This magnet 36 and magnetic blade 2 can be used as poles.
4 prevents the magnetic particles 27 from leaking outside the developing container 21 and being transported to the developing area 32.

A circulation magnet 35 is provided upstream of the magnet 36 in the direction of rotation of the sleeve 22. More specifically, the circulation magnet 35 is a 0m ring magnet/ ) is a rotatable magnet having a plurality of magnetic poles, and in this embodiment is a magnet roller, which rotates in the direction of arrow d. The magnet roller 35 has magnetic poles arranged alternately in the same direction. The magnetic particles 27 are caused by the rotation of the circulating magnet 35 in the direction of arrow d.
It circulates in the direction of arrow C. Therefore, the magnetic particles 27 receive a force to move in the direction of arrow C due to the frictional force of the developing sleeve 22, and simultaneously receive a force to move in the direction of arrow C as the circulating magnet 35 rotates in the direction of arrow d. become. In the configuration shown in FIG. 1 which does not use the present invention, the magnetic particles 27 are circulated only by the frictional force generated by the rotation of the developing sleeve 22 in the direction of the arrow. Therefore, since the direct circulation force only reaches the magnetic particles 27 in contact with the developing sleeve 22, the circulation of the magnetic particle layer tends to become unstable.In contrast, in the case of the present invention shown in FIG. According to the embodiment, the magnetic field of the circulating magnet 35 reaches not only the magnetic particles in contact with the developing sleeve 22 but also the magnetic particles outside the developing sleeve 22, so the force exerted by this magnetic field causes a circulating force to be applied to the entire magnetic particle layer. The circulation becomes extremely stable.

In Fig. 2, the circulating magnet 35 has a 4-pole structure with N-5 alternating, but the number of poles may be 2 or 4 or more.The size of the FM pole is approximately 400 to 800G. It is desirable that the rotational speed of the circulating magnet is about 1.5 to 3 times the sleeve speed.

FIG. 3 shows another embodiment of the invention.

In the embodiment shown in FIG. 2, the developing sleeve 22 and the circulation magnet 35 are driven separately from the outside, but with this configuration, the driving section becomes complicated and large. Therefore, in this embodiment, the external drive is applied to the developing sleeve 22, and the circulation magnet 35 is configured to follow the developing sleeve 22 within the developing sleeve 22.

An internal gear is formed inside the developing sleeve 22, and a gear is formed outside the circulation magnet 35, and a gear 37 is fitted into both teeth. The shaft of the gear 37 is attached to the main body.

In FIG. 3, when the developing sleeve 22 is rotated in the direction indicated by the arrow by an external drive mechanism (not shown), the gear 37 is rotated in the direction indicated by the arrow e.
The circulating magnet 35 rotates in the direction of arrow d. By providing the intermediate gear in the sleeve 22 in this manner, it is possible to rotate the circulation magnet 36 without increasing the size of the drive system. That is,
There are gears 37 and 35 on the inner surface of the developing sleeve 22,
All gear systems are housed within the sleeve 22, and there is no need to provide a gear train in the depth direction, so the drive system does not become large.

As explained above, according to the present invention, the rotation of the circulation magnet 36 sufficiently circulates the magnetic particles and takes in the non-magnetic developer. Since charging is ensured, there will be no fogging or white spots in the developed image.

Furthermore, according to an embodiment in which an intermediate gear is provided within the sleeve,
It has become possible to rotate the circulation magnet 36 with a simple configuration, and it has become possible to prevent white spots and the like without increasing the size of the device, and to maintain stable high image quality over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a thin developer layer forming apparatus that does not use the present invention, and FIG. 2 is a cross-sectional view of a thin developer layer forming apparatus according to an embodiment of the present invention. FIG. 3 is an enlarged view of the vicinity of the developing sleeve of a developer thin layer forming device according to another embodiment of the present invention. 1 Dotate 1" 3φ・Fist photosensitive drum, 24...Magnetic particle restraining member, 2
2...Developer holding member, 23・◆・Internal magnet,
27・Sakaki・Magnetic particles, 28-・Non-magnetic developer, 36・
...Fixed magnet, 35...Circulating magnet, 37
11-・Intermediate gear. Figure 1 Figure 2

Claims (1)

[Scope of Claims] A developer supply container having an opening; a developer holding non-magnetic member provided in the opening and movable endlessly inside and outside the container; and a fixing member provided inside the holding member. a magnetic field generating means; a magnetic particle restraining member provided outside the developer holding member and restraining the magnetic particle layer inside the developer supply container together with the fixed magnetic field generating means; a magnetic particle restraining member provided inside the holding member and rotating. A developer thin layer forming device comprising: magnetic field generating means capable of generating a magnetic field.