JPH0527576A - Developing device - Google Patents

Abstract

PURPOSE:To obtain the uniform high quality image of a high density with development by sufficiently supplying the toner of one-component and two- component developers onto a developer carrier to carry it thereon by means of a developer supplying means such as an elastic roller, simultaneously, regulating the toner excellently, and forming a uniform thin layer sufficiently electrified on the developer carrier. CONSTITUTION:A magnet 13 is provided inside a developing sleeve 12 carrying the nonmagnetic toner 15 of the one-component developer supplied by the supplying roller 18 of the elastic roller, the magnetic pole N of the magnet 13 is located on the downstream side than the supplying roller 18, a magnetic grain 24 is restricted on the sleeve 12 by the magnetic pole N, to form a toner regulating layer 26, and the toner 15 on the sleeve 12 is regulated. Since the toner 15 is regulated by the magnetic grain 24 restricted on the sleeve 12, the toner 15 is sufficiently electrified, the uniform thin toner layer can be formed, and the aimed performance image can be obtained by the development.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing a latent image formed on an image bearing member with a toner or a developer composed of toner and magnetic particles to visualize it as a toner image.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic system or the like, a latent image formed on an image carrier is developed with a developer and visualized as a toner image.

Conventionally, a developing device using a one-component developer made of toner has been known as one of such developing devices, and various types of devices have been proposed and put into practical use. However, in any type of developing device, it is extremely difficult to form a thin layer of toner, which is a one-component developer, on the image bearing member. Therefore, it is necessary to form a relatively thick toner layer for development. Had to be forced. However, at the present time when improvements in the sharpness and resolution of a developed image are required, development of a toner thin layer forming method and its apparatus is essential.

As a conventionally known method for forming a thin layer of toner, Japanese Patent Laid-Open No. 54-43037 has been proposed and put into practical use. However, this relates to the formation of a thin layer of magnetic toner which is a one-component magnetic developer.
In the first place, in magnetic toner, a magnetic substance must be internally added to the toner in order to give it magnetism. Therefore, when the toner image transferred onto the transfer paper is heat-fixed, the fixing property is poor, and the magnetic substance is attached to the toner itself. However, there is a problem in that the color reproduction is poor (the magnetic substance is usually black).

As a method for forming a thin layer of a magnetic toner which is a one-component non-magnetic developer, soft hair such as beaver hair is made into a cylindrical fiber brush, which is used as a toner carrier, and the toner is formed on it. Has been proposed, and a method of applying the same to a toner carrier whose surface is made of fibers such as velvet by a doctor blade or the like has been proposed.
However, when the above-mentioned fiber brush is used in combination with a doctor blade, the amount of toner applied on the fiber brush can be regulated, but uniform application is not performed, and the doctor blade simply rubs the fiber brush. Since the triboelectric charge is not applied to the toner existing between the fibers, there is a problem that fog or the like is likely to occur.

Further, the method described in Japanese Patent Publication No. 60-42768 has been proposed. In this method, as shown in FIG. 4, the magnetic force of the magnet 13 and the magnetic particles 16 of the magnetic field generating means installed in the developing sleeve 12 as the developer carrying member.
Due to the effect of the gravity of the developing sleeve 1 on the magnetic particles 16 constituting the two-component developer 20 contained in the developing container 14.
The toner 15 is constrained on the developing roller 12 and applied on the developing sleeve 12 to form a thin layer of the toner 15.
Although the layer of the toner 15 can be thinly formed on the developing sleeve 12 by the above method, the toner 15 is taken into the inside of the magnetic particles 16 by the circulating movement of the magnetic particles 16 as shown by an arrow d in the figure. When the magnetic particles 16 are insufficiently taken in between the magnetic particles 16, the amount of toner coated on the developing sleeve 12 decreases, and the density of the image obtained by the development decreases. Since the intake of the toner 15 inside the magnetic particles 16 depends largely on the circulation of the magnetic particles 16, it is necessary to strictly set the magnetic field pattern of the magnet 13, and the temperature and humidity greatly depend on the environment. Therefore, the method proposed above has a problem in stability of formation of a thin toner layer.

On the other hand, as a developing device employing a one-component developer, for example, as shown in JP-A-54-43038, an elastic blade made of rubber or metal is brought into light contact with the developing sleeve to develop with this elastic blade. It is known that toner is allowed to pass through the nip portion in contact with the sleeve to form a thin layer of toner on the developing sleeve, and the friction there provides sufficient triboelectric charge to the toner. .. However, when using non-magnetic toner, a toner supply member for supplying toner to the developing sleeve is required separately. With magnetic toner, the toner can be supplied onto the developing sleeve by the action of the magnetic field generating means built in the developing sleeve, but with non-magnetic toner this cannot be done.
Therefore, a mechanical toner supply means is required.

[0008]

Therefore, the applicant of the present invention is
A developing device disclosed in Japanese Patent Laid-Open No. 58-116559 is proposed. In this proposed developing device, a developer supply roller composed of an elastic roller in contact with the developing sleeve is arranged on the upstream side of the elastic blade in the rotating direction of the developing sleeve, and the undeveloped toner on the developing sleeve is peeled off by the roller. The new toner is supplied onto the developing sleeve. With the above configuration, the developing device can be simplified and a solid black image of high density and area can be faithfully reproduced, and an image without sleeve ghost can always be stably obtained.

However, recently, there has been a tendency for the particle size of the toner to become smaller as the image quality of the copied image becomes higher, and the developing sleeve to become smaller as the developing device becomes smaller and thinner, and these are realized by the developing device proposed above. Attempting to do so, it is not always possible to obtain good quality images. This is because the insulating toner of the one-component developer imparts a triboelectric charge to the toner from the surface of the developing sleeve, and when a developing sleeve having a small diameter is used, the surface area of the developing sleeve is small, so that the surface of the developing sleeve and the toner are not separated from each other. This is because the degree of contact of the toner is reduced, and the triboelectric charge application to the toner tends to be insufficient. In particular, when the toner on the developing sleeve is regulated by the elastic blade, the contact width between the elastic blade and the developing sleeve is reduced due to the reduction of the diameter of the developing sleeve, and the triboelectric charge of the toner is likely to be reduced and non-uniform.

Further, the toner having a small particle size has a fluidity worse than that of a toner having a normal particle size, and this also causes nonuniformity of charge imparting from the developing sleeve surface to the toner. Therefore, when non-contact development, especially non-contact development under an alternating electric field of development bias, image deterioration is apt to be noticeable.

Further, since the elastic blade is pressed against the developing sleeve, abrasion of the developing sleeve and the elastic blade cannot be avoided, and there is a problem in terms of durability and torque of the developing sleeve and the like.

From the above, the developer supplying means such as a developer supplying roller composed of an elastic roller can sufficiently supply the toner of the one-component developer or the toner constituting the two-component developer onto the developing sleeve. , While supporting it, the toner is well regulated without using an elastic blade or the like,
It is desired to develop a developing device capable of forming a uniform thin toner layer with sufficient toner charge on the developing sleeve and easily obtaining a high density and uniform high quality image by development. A developing device having such characteristics has not been proposed yet.

Accordingly, it is an object of the present invention to provide a developing device having the above characteristics.

[0014]

The above object can be achieved by the developing device according to the present invention. In summary, the present invention relates to the toner on the developer carrier provided in the developing container by the developer supplying means provided in the developing container containing the toner or the developer containing the toner and the magnetic particles. Is supplied and supported, and the toner carried on the developer carrying member is regulated to form a thin layer of toner, and the toner formed on the thin layer is imaged by the rotation of the developer carrying member. In a developing device which conveys to a developing unit facing a carrier and is used for development, magnetic field generating means is installed in the developer carrier in a non-rotating manner, and the magnetic field generating means is rotated with respect to the rotating direction of the developer carrier. A magnetic particle restraining magnetic pole is arranged at a position upstream of the supply means, and a developer regulating layer made of magnetic particles restrained by the magnetic pole is formed on the developer carrying member, and the regulation is performed. On the developer carrier by layers A developing apparatus is characterized in that by regulating the supported toner to form a thin layer of the toner.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic structural view showing an embodiment of the developing device of the present invention. In FIG. 1, reference numeral 11 is a cylindrical electrophotographic photosensitive member of the image forming apparatus, and the photosensitive member 11 is adapted to rotate in the direction of arrow a. The developing device of this embodiment includes a developing container 14 in which a non-magnetic toner 15 of a one-component non-magnetic developer is stored.
A non-magnetic developing sleeve 12 serving as a developer bearing member is provided in the opening facing the photoconductor 11 with a gap therebetween. The developing sleeve 12 is adapted to rotate in the direction of arrow b by a driving means (not shown).

Further, in the developing container 14, the developing sleeve 1
Developing sleeve 1 on the side opposite to the side facing the photoconductor 11
A toner supply roller 18 that is an elastic roller that abuts 2 and rotates in the direction of arrow c is provided, and the toner 15 in the developing container 14 is supplied to the developing sleeve 12 by the supply roller 18.
It is supplied on and supported on it.

The toner supply roller 18 is preferably an elastic roller such as urethane foam or sponge covered with a rubber skin layer. In this embodiment, the supply roller 18 is made of urethane foam. .. The supply roller 18 is rotated in a state of being pressed against the developing sleeve 12 with a peripheral speed difference from the rotational speed of the developing sleeve 12. In this embodiment, the pressure contact width of the supply roller 18 with the developing sleeve 12 is set to 1
mm, the rotation direction was the direction c facing the rotation direction b of the developing sleeve 12 at its pressure contact portion, and the peripheral speed was 150% of the peripheral speed of the developing sleeve 12.

With such a supply roller 18, sufficient toner 15 can be supplied onto the developing sleeve 12 and can be carried on the developing sleeve 12.

According to the present invention, the magnet 13 of the magnetic field generating means is installed in the developing sleeve 12 so as not to rotate, and the magnet 13 is located upstream of the supply roller 18 in the rotating direction of the developing sleeve 12. In the position
A magnetic pole N for restraining magnetic particles is arranged. By applying a small amount of magnetic particles 24 to the position corresponding to the magnetic pole N on the developing sleeve 12, a toner regulation layer 26 made of the magnetic particles 24 is provided. The small amount of magnetic particles 24 is retained by the magnetic force of the magnetic pole N, and the magnetic particles 2
The balance between the gravity of 4 itself and the action of the conveying force in the rotating direction by the developing sleeve 12 balances the developing sleeve 12
The toner regulation layer 26 is formed by being restrained at the above position.

The non-magnetic toner 15 carried on the developing sleeve 12 by being supplied by the supplying roller 18 is regulated by the magnetic particles 24 while passing through the regulating layer 26 on the developing sleeve 12, and a triboelectric charge is imparted. And it is formed in a thin layer. At this time, since the triboelectric charge imparting ability of the magnetic particles 24 is larger than that of the elastic blade, the toner 1
The charge of 5 becomes sufficient and uniform, and the toner 15 adheres to the surface of the developing sleeve 12 by the mirroring force due to the charge to form a toner layer, so that the toner layer becomes uniform and thin.

The toner 15 thus charged and formed into a thin layer is conveyed to the developing section facing the photoconductor 11 as the developing sleeve 12 rotates, and the electrostatic latent image on the surface of the photoconductor 11 is conveyed. Used for image development.

The toner regulation layer 26 composed of the magnetic particles 24 will be further described. In this embodiment, as the magnetic particles 24, about 1 g of iron powder of about 50 μm was used. A proper amount of the magnetic particles 24 is about 1 to 3 g. If the amount is too small, a gap is formed between the magnetic particles 24 forming the regulation layer 26 and the magnetic particles 24 are carried on the developing sleeve 12. The toner 15 cannot be regulated so as to form a uniform thin layer, and if it is more than this, the restraint of the magnetic particles 24 on the developing sleeve 12 deteriorates, and the regulation layer 26
Is difficult to form, and the magnetic particles 24 adhere to the photoconductor 11 to cause image contamination.

The magnetic pole N of the magnet 13 in the developing sleeve 12 needs to be 600 gauss or more, and if it is too weak, the restraint of the magnetic particles 24 is deteriorated. Further, the number of poles of the magnet 13 is preferably only one such as the magnetic pole N in the formation portion of the regulation layer 26, and when there are a plurality of poles in the formation portion of the regulation layer 26, the magnetic particles 24 stand and the restraint property is similarly deteriorated. To do. Further, unlike the conventional developing device shown in FIG. 4, the angle θ of the magnetic pole N with respect to the vertical direction is not particularly limited because the magnetic particles 24 do not need to circulate. However, the angle θ is a clock in the figure. The larger in the circumferential direction, the better the restraint of the magnetic particles 24.
The magnetic particles 24 may be a paramagnetic material or a ferromagnetic material, but if they are easily magnetized, the restraint property increases.

With such a structure, the toner 15 carried on the developing sleeve 12 is regulated by the toner regulating layer 26 of the magnetic particles 24 so that the toner 15 is sufficiently charged and is evenly distributed on the developing sleeve 12. In addition, it is possible to form a sufficiently thin toner thin layer. Further, since the regulation layer 26 is formed by satisfactorily restraining the magnetic particles 24 at the position on the developing sleeve 12 corresponding to the magnetic pole N of the magnet 13, it can be made stable.

Therefore, according to the present developing device, since the developing sleeve 12 can be developed using a thin layer of the toner 15 having a sufficient charge, a uniform layer thickness, and a thin layer, a uniform image with high density can be stably obtained. Obtained. Also, there is little environmental dependency such as temperature and humidity. That is, in the case of the conventional developing device of FIG. 4, in order to form a thin toner layer on the developing sleeve 12 with the toner 15 of the two-component developer 20, first, the toner 15 is used.
Needs to be taken into the inside of the magnetic particles 16 and the taking-in largely depends on the circulation of the magnetic particles 16, so that it is necessary to strictly set the magnetic field pattern of the magnet 13 or the environment of temperature and humidity. Although there is a drawback that the dependence is large, this developing apparatus does not have such a drawback because the magnetic particles 24 are not circulated.

Further, in the present developing device, the regulation of the toner 15 does not depend on the elastic blade, so that the structure is simple and inexpensive, and the problem itself such as abrasion of the developing sleeve 12 and the elastic blade and torque increase does not occur. Excellent durability.

FIG. 2 is a schematic diagram showing another embodiment of the developing device of the present invention. In this embodiment, a two-component developer 20 composed of a toner 15 and magnetic particles 16 is used as a developer, and 20 magnetic brushes 20a of the developer are formed on a toner supply roller 22 which is an inelastic roller. , The toner 15 from the magnetic brush 20a by an electric field to the developing sleeve 1
It is characterized in that the toner 5 is made to fly onto the developing sleeve 12 and the toner 5 is supplied and carried on the developing sleeve 12.

Inside the supply roller 22, in order to carry the developer 20 on the supply roller 22 to form the magnetic brush 20a, the four-pole magnet 19 of the magnetic poles S ₁ , N ₁ , S ₂ and N ₂ is formed. Is provided so as not to rotate, and a power source 21 for applying an electric field between the supply roller 22 and the developing sleeve 12 is provided in order to fly the toner 15 from the magnetic brush 20a. In order to stably fly and supply the toner 15 onto the developing sleeve 12, it is effective to apply an AC bias from the power source 21, and in this embodiment, DC 300V _DC , AC 1kHz, 1500Vp.
A bias with p superimposed was applied.

Toner 1 carried on the developing sleeve 12
The regulation by the regulation layer 26 composed of the magnetic particles 24 constrained on the developing sleeve 12 after 5 is the same as in the previous embodiment, whereby the toner 15 is charged and formed into a thin layer. Then, it is conveyed to a developing unit facing the photoconductor 11 and used for developing the latent image on the photoconductor 11.

According to the present embodiment, as described above, since the toner 15 flies onto the developing sleeve 12 by the electric field, only the toner having a large charge amount can be supplied and carried on the developing sleeve 12. Therefore, in combination with the charging due to the regulation by the toner regulation layer 26, the developing sleeve 1
It is possible to more reliably form a thin layer on the toner layer 2 with sufficiently charged toner.

FIG. 3 is a schematic structural view showing still another embodiment of the developing device of the present invention. In this embodiment, in the developing device of FIG. 1, as shown in FIG. 3, a magnetic toner 15 of a one-component magnetic developer is used as the developer, and the developing sleeve 1 is used.
The feature is that the magnetic pole S is provided at the position of the developing portion of the inner magnet 13 facing the photoconductor 11. Magnetic toner 15
Developing sleeve 1 after carrying the toner on the developing sleeve 12.
Toner regulating layer 2 composed of magnetic particles 24 constrained on
The regulation by 6 is the same as that in the previous embodiment.

Also in this embodiment, since the toner 15 carried on the developing sleeve 12 is regulated by the toner regulation layer 26 composed of the magnetic particles 24, the toner 15 is similarly charged sufficiently and uniformly, and That toner 15
Can form a uniform and sufficiently thin toner thin layer on the developing sleeve 12, and a highly dense and uniform image can be stably obtained by the development, and its environmental dependency such as temperature and humidity is small.

Further, in this embodiment, as described above, since the S pole is arranged at the position of the developing portion of the magnet 13, the toner 15 on the developing sleeve 12 is formed by the S pole in the developing portion.
On the other hand, a magnetic force acts in a direction not to fly, and this magnetic force and the electrostatic force of the latent image on the photoconductor 11 and the electrostatic force of the electric field due to the developing bias applied to the developing sleeve 12 interact with each other, resulting in weak static electricity. It is possible to cause the toner 15 to fly to the photoconductor 11 by electric power and be used for development. Therefore, there is an advantage that it is possible to obtain a high-quality image with good gradation and no fog.

[0034]

As described above, according to the developing device of the present invention, the toner of the one-component developer or the two-component developer is constituted by the developer supplying means such as the developer supplying roller composed of the elastic roller. The magnetic field generating means is installed in the developer carrier when the toner is sufficiently supplied to and carried on the developer carrier and the toner is regulated to form a thin layer of toner on the developer carrier. , A magnetic pole for restraining magnetic particles is arranged at a position upstream of the supply means with respect to the rotating direction of the developer carrier of the magnetic field generation means, and the magnetic particles restrained by the magnetic pole on the developer carrier are A developer regulating layer is formed, and a developer regulating layer composed of magnetic particles bound to the magnetic poles is formed on the developer carrying body, thereby regulating the toner carried on the developer carrying body. , Toner on the developer carrier Charging can form a sufficient and uniform toner thin layer, a high-quality image can be easily obtained by development. Further, since the elastic blade or the like is not used to regulate the toner, the developing device has a simple structure and is inexpensive, and the problem itself such as abrasion of the developing sleeve 12 and the elastic blade and increase in torque does not occur, and the durability is excellent.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a developing device of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the developing device of the invention.

FIG. 3 is a schematic configuration diagram showing still another embodiment of the developing device of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional developing device.

[Explanation of symbols]

 11 Photosensitive Drum 12 Developing Sleeve 13, 19 Magnet 15 Toner 18, 22 Supply Roller 24 Magnetic Particle 26 Toner Regulation Layer

Claims (1)

Claim: What is claimed is: 1. A developer carrying member installed in the developing container by a developer supply means provided in a developing container containing a toner or a developer composed of toner and magnetic particles. The toner is supplied and supported on the developer carrying member, and the toner carried on the developer carrying member is regulated to form a thin layer of the toner. In a developing device which is conveyed to a developing unit facing the image carrier by rotation and is used for development, a magnetic field generating means is installed in the developer carrying body in a non-rotating manner, and the magnetic field generating means rotates the developer carrying body. A magnetic pole for restraining magnetic particles is arranged at a position upstream of the supply means with respect to the moving direction, and a developer regulating layer made of magnetic particles restrained by the magnetic pole is formed on the developer carrier, Due to the formed regulatory layer, Developing apparatus is characterized in that to form a thin layer of the toner to regulate the toner carried on the carrying member.