JPH04365071A - Formation of developer thin layer and device thereof - Google Patents

Abstract

PURPOSE:To prevent the reduction of the image density and realize high durability even when the diameter of a developing sleeve is reduced or when the grain size of toner is reduced. CONSTITUTION:A toner feed roller 18 is arranged in contact with a developing sleeve 12 in a hopper 14, and a preset quantity of magnetic grains 16 is held by the magnetic pole 17 of a magnet 13 and a nonmagnetic member 19 on the downstream side in the rotating direction of the developing sleeve 12 from the contact position.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forming a thin layer of developer used in a dry development system in which toner particles are used as a developer.

0002

2. Description of the Related Art Conventionally, various apparatuses using a dry developing method have been proposed and put into practical use. However, in any of the development methods, it is extremely difficult to form a thin layer of dry developer, and therefore a relatively thick layer has been formed for development. 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 dry developer and an apparatus therefor.

As a conventionally known method for forming a thin layer of dry type developer, one proposed in Japanese Patent Laid-Open No. 43037/1983 has been put into practical use. However, this concerns the formation of a thin layer of magnetic developer. In order to make magnetic developers magnetic, it is necessary to add a magnetic substance to the developer, and this poses a problem of poor fixing properties when thermally fixing a developed image transferred to a transfer paper. Furthermore, since a black magnetic material is usually added to the developer itself, poor color reproduction has been a problem.

[0004] For this reason, methods for forming a thin layer of non-magnetic developer include a method in which soft hair like beaver hair is used as a cylindrical brush and the developer is adhered to the brush, and the surface is made of fibers such as velvet. A method has been proposed in which a doctor blade or the like is used to coat the developed roller.

However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, although it is possible to regulate the amount of developer, uniform application is not achieved, and the developer is simply rubbed by the fiber brush on the developing roller. Since the developer existing between the fibers of the brush is not triboelectrically charged, there is a problem that fogging is likely to occur.

Furthermore, in Japanese Patent Publication No. 60-42768, as shown in FIG.
It has been proposed that the developing sleeve is restrained on the developing sleeve 2 and the toner 15, which is a developer, is applied onto the developing sleeve. Although it was possible to apply a thin toner layer using the above method, this method requires that the toner be taken into the magnetic particle circulation by the circulation movement of the magnetic particles 16 (arrow C in the figure), and if insufficient take-up occurs, However, there is a problem in that the amount of toner applied decreases and the image density decreases. Since this problem largely depends on the circulation of the magnetic particles 16, the magnetic field generating means 1
It is necessary to carefully set the magnetic field pattern of No. 7, and it is highly dependent on the environment (temperature, humidity), so the above method has problems with stability.

On the other hand, as a simple one-component developing device, for example, as shown in JP-A-54-43038, a rubber or metal elastic blade is brought into light pressure contact with a developing sleeve, and toner is passed through this contact nip. A method has been proposed in which a thin layer of toner is formed on the developing sleeve, and friction thereon provides sufficient triboelectricity to the toner. However, when regulating the application of non-magnetic toner with the above configuration, a separate toner supply member is required. Although magnetic toner can be supplied onto the developing sleeve by the magnetic force of a magnet within the developing sleeve, non-magnetic toner requires a mechanical supply means. Therefore, the present applicant has proposed a developing device (Japanese Patent Application Laid-Open No. 116559/1983) shown in FIG. In this invention, the developing sleeve 12 of the elastic blade 40
A roller 50 is disposed on the upstream side in the rotational direction in contact with the developing sleeve 12 to strip off undeveloped toner on the developing sleeve 12 and supply toner to the developing sleeve 12. The above configuration makes it possible to simplify the apparatus, faithfully reproduce a solid black image with high density and a wide area, and always provide a stable image without sleeve ghost.

[0008]

[Problems to be Solved by the Invention] However, due to the trend toward smaller particle diameters of developers due to the recent improvement in the quality of copied images and the trend toward smaller diameter developing sleeves due to thinner and smaller developing devices, it has become difficult to When applied to an apparatus configuration, it is not always possible to obtain a sufficiently good image. This is because in the case of one-component insulating toner, toner tribo is applied from the surface of the developing sleeve, but when a small-diameter sleeve is used as the developing sleeve, the surface area of the developing sleeve decreases, and the degree of contact between the developing sleeve surface and the toner decreases. This is because the amount of charge on the toner tends to be insufficient. Particularly, when applying toner onto a developing sleeve using an elastic member, the width of contact between the elastic member and the developing sleeve decreases as the diameter of the developing sleeve decreases, making it easy to reduce and unevenly charge the toner by friction. Further, the fluidity of small particle size toner as a developer is poorer than that of normal particle size toner, which also causes non-uniform toner reloading from the surface of the developing sleeve.

As described above, according to the conventional example described above, image deterioration was easily noticeable in non-contact development, particularly in non-contact development under alternating electric fields.

Furthermore, according to the above-mentioned conventional example, since the elastic blade is brought into pressure contact with the developing sleeve, wear of the elastic blade is unavoidable, and addition to the toner is large, so there is a problem in durability.

The present invention solves the above-mentioned problems and provides a thin developer layer that does not reduce image density even when the diameter of the developing sleeve is made smaller or the particle size of the toner is made smaller, and that can realize high durability. The object of the present invention is to provide a forming method and an apparatus therefor.

0012

[Means for Solving the Problems] According to the present invention, the above-mentioned object is first achieved by a developer supplying means that contacts a developer carrier and is rotatably disposed within a developer supply container. Supplying the developer in the developer supply container onto the developer carrier, downstream in the rotational direction of the developer carrier from the contact position between the developer supply means and the developer carrier,
restraining magnetic particles in a predetermined area on the surface of the developer carrier by a magnetic pole of a magnetic field generating means inside the developer carrier and a non-magnetic member disposed at a predetermined interval on the surface of the developer carrier; This is achieved by transporting the developer on the developer carrier to the constrained region of the magnetic particles, thereby charging the developer and forming it into a predetermined thin layer, and then allowing the device to contain the developer. a developer supply container, a developer carrier rotatably disposed in an opening of the developer supply container, and a magnetic field generating means disposed inside the developer carrier;
In the developer thin layer forming device, the developer supplying means is rotatably supported within the developer supplying container and is disposed so as to come into contact with the developer carrier, at least one of the magnetic poles of the magnetic field generating means. one of the magnetic poles is disposed at a predetermined position downstream in the rotational direction of the developer carrier from the contact position between the developer carrier and the developer supplying means, and is substantially opposed to the magnetic pole disposed at the predetermined position. A non-magnetic member is disposed at a predetermined interval on the surface of the developer carrier, and magnetic particles are restrained and held in a predetermined area of the developer carrier surface sandwiched between the non-magnetic member and the magnetic pole. This is achieved by

[0013]

According to the present invention, the developer in the developer supply container is supplied to the developer carrier by the developer supply means and conveyed by the developer carrier. The transported developer is
When the non-magnetic member contacts the magnetic particles bound by the magnetic poles of the magnetic field generating means, the non-magnetic member is triboelectrically charged, and is formed into a predetermined thin layer by passing through the magnetic particles.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments of the present invention will be explained based on the drawings.

<First Embodiment> First, a first embodiment of the present invention will be described based on FIG. 1.

FIG. 1 is an explanatory diagram showing the basic configuration of the present invention. In FIG. 1, 11 is a cylindrical electrophotographic photoreceptor that moves in the direction of arrow a. A non-magnetic developing sleeve 12, which is a developer carrier, is provided at a predetermined distance from the photoreceptor 11. The developing sleeve 12 rotates in the direction of arrow b as the photoreceptor 11 moves. A fixed magnet 13 is provided within the developing sleeve 12 as a magnetic field generating means. Further, 14 is a hopper as a developer supply container, which accommodates toner 15 as a non-magnetic developer and magnetic particles 16 together with the developing sleeve 12.

The toner 15 is applied onto the developing sleeve 12 by a toner supplying roller 18, which is a developer supplying means and rotates in contact with the developing sleeve 12 in the hopper 14. On the other hand, a small amount of magnetic particles 16 are held near the surface of the developing sleeve 12 on the downstream side in the rotational direction of the developing sleeve 12 and corresponding to the magnetic pole 17 of the magnet 13 . The magnetic particles 16 are transferred to the hopper 14 by the balance between the magnetic force, gravity, and the conveying force in the moving direction of the developing sleeve 12.
The developing sleeve 12 is restrained by a non-magnetic member 19 attached to the surface of the developing sleeve 12 . The coated toner 15 is regulated to a predetermined layer thickness by the bound magnetic particles 16, but is not restrained by the magnetic field of the magnetic pole 17 because it is non-magnetic. Therefore, the toner 15 has magnetic particles 1
6, the surface of the developing sleeve 12 is uniformly and thinly coated by mirror force, and is conveyed as the developing sleeve 12 rotates, and is subjected to development on the surface of the photoreceptor 11.

Next, the constraint conditions for the magnetic particles 16 will be explained in detail. For the magnetic particles 16, about 1 g of iron powder with a particle size of about 50 μm is used. The appropriate amount is about 1 to 3 g; if it is too small, gaps will form between the magnetic particles, making it impossible to coat the toner uniformly, and if it is too large, the binding properties will be poor.

The magnetic pole of the magnet 13 in the developing sleeve 12 must have a strength of 600G or more, and if it is too weak, the restraint will be poor. Further, it is preferable that the number of poles is only one near the restraining part; if there are multiple poles, the magnetic particles will stand up, and the restraint will deteriorate. Furthermore, the angle of the magnetic pole with respect to the vertical direction (θ in the figure) is shown in Figure 4.
Since there is no need to consider the circulation of magnetic particles as in the conventional example shown in FIG. 1, there is no particular restriction, but the binding property is better as θ is larger in the + direction (clockwise direction in the figure). Further, the magnetic particles 16 may be either paramagnetic or ferromagnetic, but the more easily magnetized, the better the binding property will be.

The non-magnetic member 19 is a non-magnetic metal plate and is provided in contact with the magnetic particles 16 but not in contact with the developing sleeve 12. This member not only enhances the restraint of the magnetic particles 16 but also has the effect of sealing to prevent toner from flowing out from the hopper 14. If this non-magnetic member 19 is made of a magnetic material, the magnetic particles 16 on the developing sleeve 12 will stand up, and the restraint of the magnetic particles 16 will deteriorate, so it is necessary to use a non-magnetic member.

It is necessary to sufficiently take in the toner 15 to the magnetic particles 16 restrained as described above, and this function is reliably performed by the toner supply roller 18.

The toner supply roller 18 is preferably made of an elastic material such as urethane foam or sponge with a rubber skin layer covered thereon. In this embodiment, urethane foam is used, and the toner supply roller 18 is brought into pressure contact with the developing sleeve 12 and used for development. It rotates with a difference in circumferential speed from the rotation of the sleeve. In this embodiment, the pressing width is 1 mm, and the developing sleeve is rotated in the same direction (c in the figure) as the developing sleeve rotation direction (b in the figure) at 150% of the circumferential speed of the developing sleeve.

As described above, according to the apparatus of this embodiment, since the magnetic particles 16 are restrained in the region between the non-magnetic member 19 and the surface of the developing sleeve 12 relative to the magnetic pole 17, the toner 15 and the magnetic The friction with the particles 16 is ensured, and the toner 15 is more fully and uniformly charged than in the conventional example using an elastic blade. Therefore, the developing sleeve 12
Even when the toner 15 is made smaller in diameter or the toner 15 is made smaller in particle size, a uniform image with high density can be stably obtained even if the environment such as temperature and humidity fluctuates.

Furthermore, by using the toner supply roller 18, the toner 15 is not insufficiently taken in as in the conventional example, and the toner is sufficiently supplied.

[0025] Therefore, a sufficiently supplied toner 15
is sufficiently charged by the magnetic particles 16 and regulated to a predetermined layer thickness by the magnetic particles 16, so that the surface of the developing sleeve 12 is coated with a uniform and thin toner layer. As a result, an image with high clarity and resolution can be obtained.

Furthermore, in this embodiment, since it is not necessary to circulate the magnetic particles, the magnetic poles can be easily set, and the magnetic particles can be stably restrained by the magnetic poles 17 and the non-magnetic member 19.

Furthermore, since an elastic blade is not used as in the conventional method, there is no wear of the elastic blade, less addition to toner is achieved, and high durability can be achieved. In addition, the non-magnetic member 19 can prevent the toner 15 from leaking from the hopper 14, making it possible to provide a simple and inexpensive developing device with excellent durability and stability.

<Second Embodiment> Next, a second embodiment will be explained based on FIG. 2. Note that the same reference numerals are given to the same parts as in the first embodiment, and the explanation thereof will be omitted.

In this embodiment, a non-magnetic elastic member 20 is used in place of the metal non-magnetic member 19 of the first embodiment.

The non-magnetic elastic member 20 is made of P with a thickness of 500 μm.
ET is used to contact the magnetic particles 16 but not the developing sleeve 12. This elastic member has magnetic particles 16
Since the magnetic particles 16 are firmly restrained and the magnetic particles are pressed against the developing sleeve to some extent, the triboelectric effect on the toner by the magnetic particles 16 becomes even more reliable. Further, the above-mentioned sealing effect is further enhanced, and a simple and inexpensive developing device with excellent durability and stability can be provided.

<Third Embodiment> Next, a third embodiment will be described based on FIG. 3. The same reference numerals are given to the same parts as in the first embodiment, and the explanation thereof will be omitted.

In this embodiment, magnetic toner is used. Similar to the first embodiment, the magnetic toner is supplied to the toner supply roller 18.
It is applied to the developing sleeve 12 by a small amount of magnetic particles 16, and is applied in a thin layer by a minute amount of magnetic particles 16, and then conveyed to a portion facing the photoreceptor 11. The magnetic pole of the magnet 13 inside the developing sleeve 12 is an N pole 17 corresponding to a portion where a small amount of magnetic particles 16 are restrained.
In addition, an S pole 21 is arranged at a portion corresponding to the opposing portion of the photoreceptor 11. As a result, a force acts in a direction that prevents the magnetic toner from flying during development, and this force and the photoreceptor 1
The magnetic toner is developed into a latent image in balance with the latent image No. 1 and the force due to the electric field of the developing bias. The non-magnetic member 19 can ensure the restraint of the magnetic particles 16 without attracting the magnetic toner 15 and can seal the magnetic toner 15.

According to this embodiment, as in the first embodiment, it is possible to realize a uniform and thin layer of toner coating with stable charging, and to improve gradation by magnetic force, resulting in a high-quality image without fogging. can be obtained.

[0034]

[Effects of the Invention] As explained above, according to the present invention,
The developer is supplied to the developer carrier by a developer supply means brought into contact with the developer carrier, and the developer is supplied by the magnetic particles bound by the non-magnetic member and the magnetic pole in the developer carrier. Since the charging and layer thickness are controlled, the developer can be sufficiently and uniformly charged. Therefore, even when the diameter of the developer carrier is reduced or the particle size of the developer is reduced, or even when the environment such as temperature and humidity fluctuates, images with high density, sharpness, and resolution can be stably maintained. You can get it.

Furthermore, since there is no need to use an elastic blade, addition to the developer, wear of members, and rotational torque can be reduced easily and inexpensively.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic configuration of a first embodiment of the device of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a schematic configuration of a device according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a schematic configuration of a conventional device.

FIG. 5 is a sectional view showing a schematic configuration of another conventional device.

[Explanation of symbols]

12 Developer carrying member (developing sleeve) 13 Magnetic field generating means (magnet) 14 Developer supply container (hopper) 15 Developer (toner) 16 Magnetic particles 17 Magnetic pole (N pole) 18 Developer supply means (toner supply roller) 19
non-magnetic material

Claims (2)

[Claims] 1. A developer supplying means that is in contact with the developer carrier and rotatably disposed within the developer supply container supplies the developer in the developer supply container onto the developer carrier. The magnetic pole of the magnetic field generating means inside the developer carrier and the developer carrier are located downstream of the contact position between the developer supply unit and the developer carrier in the rotational direction of the developer carrier. Magnetic particles are restrained in a predetermined area on the surface of the developer carrier by non-magnetic members arranged at predetermined intervals on the surface, and the developer on the developer carrier is transported to the constrained area of the magnetic particles. A method for forming a thin layer of developer, which comprises charging the developer to form a predetermined thin layer. 2. A developer supply container for containing a developer, a developer carrier rotatably disposed in an opening of the developer supply container, and a magnetic field disposed inside the developer carrier. In a developer thin layer forming device comprising: a generating means; and a developer supplying means rotatably supported within the developer supply container and disposed so as to come into contact with the developer carrier, the magnetic field generating means may include a magnetic field generating means; At least one of the magnetic poles is disposed at a predetermined position downstream in the rotational direction of the developer carrier from a contact position between the developer carrier and the developer supply means, and the magnetic pole disposed at the predetermined position and Non-magnetic members are disposed at a predetermined interval on the surface of the developer carrier so as to substantially face each other, and magnetic particles are restrained in a predetermined region of the surface of the developer carrier sandwiched between the non-magnetic member and the magnetic pole. A developer thin layer forming device characterized in that: