JP2000181229A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device in which the wear of the outside surface of a developer carrier is suppressed, the damage of a magnetic field generation means by the inside surface of the developer carrier is prevented from occurring and an excellent image can be stably outputted over a long term. SOLUTION: This developing device is provided with a cylindrical developing sleeve (developer carrier) 13 consisting of a nonmagnetic metallic material and a magnet roller (magnetic field generation means) 14 arranged inside the sleeve 13. Besides, it is constituted so that developer carried on the sleeve 13 is fed to a developing part opposed to an image carrier and a latent image formed on the surface of the image carrier is developed by the developer. Then, metallic plated layers 15 and 16 are formed at the whole of the inside and outside surfaces of the sleeve 13.

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 an electrostatic latent image formed on an image carrier such as a photoreceptor, and an image forming apparatus provided with the developing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic system, an electrostatic latent image is formed on an image carrier such as a photoreceptor.
This electrostatic latent image is developed by a developing device. Here, as the developing device, a non-magnetic developing sleeve containing a magnet roller for transporting the developer is used.

FIG. 7 is a cross-sectional view of a conventional developing sleeve 113. The illustrated developing sleeve 113 is made of a non-magnetic metal such as aluminum or SUS, and has a magnetic field generating means inside thereof. Are included. This developing sleeve 11
Reference numeral 3 denotes a developing device which is rotatably disposed around a magnet roller 114.
14 is fixed non-rotatably.

[0004] As the outer diameter of the magnet roller 114 approaches the inner diameter of the developing sleeve 113, the magnitude of the magnetic force measured outside the developing sleeve 113 increases. Roller 114
Performance can be efficiently exhibited.

[0005]

However, in the prior art, the inner surface treatment of the developing sleeve 113 has not been clarified, and if the outer diameter of the magnet roller 114 is too large, the developing sleeve 113 will not be covered. The magnet roller 114 may be damaged by minute projections or the like inside, and a desired magnetic force may not be obtained outside the developing sleeve 113, thereby hindering the transportability of the developer and consequently causing a defect in a copied image. was there. In particular, plastic magnets, which are cheaper in cost than so-called ferrite magnets, are soft as a material and are easily damaged by protrusions and the like inside the developing sleeve, and the magnetic force outside the developing sleeve may be disturbed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to suppress wear of the outer surface of a developer carrying member and to prevent damage to a magnetic field generating means by an inner surface of the developer carrying member. It is an object of the present invention to provide a developing device and an image forming apparatus capable of stably outputting a good image over a long period of time.

[0007]

In order to achieve the above object, the present invention is directed to a cylindrical developer carrier made of a non-magnetic metal material, and a magnetic field generator disposed in the developer carrier. Means for transporting the developer carried on the developer carrier to a developing section facing the image carrier, and developing the latent image formed on the surface of the image carrier with the developer. A metal plating layer is formed on the entire inner surface and outer surface of the developer carrier.

According to a second aspect of the present invention, in the first aspect of the invention, the magnetic generating means is formed of a plastic magnet.

According to a third aspect of the present invention, in the first or second aspect, the hardness Hv of the metal plating layer is set to 45.
It is characterized by being set to 0 to 1000.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, the metal plating layer is made of an electroless Ni.
-P plating, electroless Ni-B plating or electroless Pd-P
It is characterized by being formed by plating.

According to a fifth aspect of the present invention, in the first, second or third aspect of the present invention, the metal plating layer is formed by electric Cr plating.

According to a sixth aspect of the present invention, in the first to fourth or fifth aspects, the metal plating layer is constituted by a plurality of layers.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the metal plating layer comprising the plurality of layers is constituted by a layer obtained by applying an electric Cr plating on an electric Cu plating. .

According to an eighth aspect of the present invention, there is provided an image carrier having a photosensitive layer on a surface, a cylindrical developer carrier made of a non-magnetic metal material, and a magnetic field generating means disposed in the developer carrier. A developing device that transports the developer carried on the developer carrying member to a developing section facing the image carrying member, and develops a latent image formed on the surface of the image carrying member with the developer; Wherein a metal plating layer is formed on the entire inner surface and outer surface of the developer carrying member of the developing device.

Therefore, according to the present invention, since the metal plating layer is formed on the entire inner surface and outer surface of the developer carrier of the developing device, wear of the outer surface of the developer carrier is suppressed, and
It is possible to prevent the magnetic field generating means from being damaged by the inner surface of the developer carrying member, and to stably output a good image over a long period of time.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the basic configuration of an image forming apparatus according to the present invention. In FIG. 1, reference numeral 50 denotes a photosensitive drum (usually an electrophotographic photosensitive drum) as an image carrier on which an electrostatic latent image is formed. ), A latent image forming portion 51 for forming an electrostatic latent image on the photosensitive drum 50 by a laser beam or the like;
Reference numeral 2 denotes a developing device according to the present invention for visualizing the electrostatic latent image on the photosensitive drum 50 as a toner image, and 53 denotes a transfer material using the toner image on the photosensitive drum 51 visualized by the developing device 52. A transfer separation unit 54 for transferring and separating the transfer material from the photosensitive drum 50 is a cleaning unit for cleaning untransferred toner on the photosensitive drum 50.

The photosensitive drum 50 of the latent image forming section 51
A primary charger (not shown) is disposed at an upstream portion in the rotation direction. The transfer material onto which the toner image has been transferred is conveyed to a fixing unit (not shown), and the toner image is fixed on the transfer material by heat or pressure.

Next, the developing device 52 will be described with reference to FIG.

FIG. 2 is a sectional view of the developing device 52. In the developing container 52 of the developing device 52, a magnetic toner 12 is accommodated as a one-component developer. Particles having a particle size of about 5 to 15 μm obtained by kneading and pulverizing a resin are formed. A developing sleeve 13 as a developer carrier is rotatably disposed at the opening of the developing container 11, and a fixed magnet roller 14 is included in the developing sleeve 13. The developing sleeve 13 has a metal plating layer having a predetermined hardness and thickness formed on the inner and outer surfaces.

Reference numeral 5 denotes a magnetic blade as a developer regulating member for regulating the thickness of the toner layer.
Is made of a magnetic member.

Here, an example of the magnetic poles of the magnet roller 14 will be described.

The magnetic force of each magnetic pole of the magnet roller 14 measured on the surface of the developing sleeve 13 is as follows.

N1 = 950 Gauss, S1 = 1020 Gauss, N2 = 1000 Gauss N2 = 680 Gauss, N3 = 630 Gauss, S3 = 9
Next, the functions of the magnetic poles N1 to N3 and S1 to S3 will be described.

The N1 pole is located at a position facing the magnetic blade 5 and is called a cut pole, and contributes to the charge application to the magnetic toner 12.

The developing sleeve 13 is made of a non-magnetic member, is rotatable in the direction of arrow a in FIG. 2, and has a magnet roller 14 fixedly disposed therein. The magnetic blade 5 is arranged so that the distance from the developing sleeve 13 is a constant value W.
It is often set to a value in the range of μm to 1 mm.

As shown in FIG. 3, an area where the magnetic flux density is concentrated near the developing sleeve 13 and the magnetic blade 5 by the magnetic roller 5 and the magnetic blade 5 made of a magnetic member disposed to face the magnetic pole. G is formed.

FIG. 4 is an enlarged view of the area G. As shown in FIG. 4, the magnetic toner 1 supplied from the developing container 11
No. 2 forms ears (state B) in the direction from the developing sleeve 13 to the magnetic blade 5 by the N1 pole of the magnet roller 14, and subsequently reaches the area G and is magnetically restricted. That is, the area G is a toner restricted area. Charge is applied to the constrained magnetic toner 12 by frictional charging between the rotating developing sleeve 13 and the magnetic blade 5.

The magnetic toner 12 charged by the frictional charging receives the image force from the developing sleeve 13 by the charge obtained by itself. This becomes a conveying force to the magnetic toner 12, and the magnetic toner 12 is conveyed with the rotation of the developing sleeve 13. A portion where the conveying force acting on the charged magnetic toner 12 overcomes the binding force due to the magnetic force (that is, the portion where the conveying force acts on the charged magnetic toner 12)
At the position indicated by the cut line L), the ears of the magnetic toner 12 are cut off, and the magnetic toner 12 remaining on the developing sleeve 13 is conveyed in the rotation direction of the developing sleeve 13.

Next, the N2 pole will be described.

The N2 pole is located at the closest part of the photosensitive drum 50 (see FIG. 1) and is called a developing pole. Magnetic toner 1
Numeral 2 forms ears by the magnetic field formed by the N2 pole, and the magnetic toner 12 having formed the ears forms an electrostatic latent image on the photosensitive drum 50 by a developing bias applied to the developing sleeve 13 by a high-voltage power supply (not shown). Develop as an image.

The other poles S1, S2, N3, and S3 are called transport poles and have a function of transporting the magnetic toner 12 on the developing sleeve 13.

Here, the developing sleeve 13 will be described with reference to FIGS. FIG. 5 shows the developing sleeve 13.
6 is an enlarged detail view of a portion A in FIG.

The base 13a of the developing sleeve 13 is made of a non-magnetic metal material such as SUS or aluminum.
The surface may be roughened as shown in detail in FIG. 6 in order to enhance toner transportability. Developing sleeve 13
Although the surface can be roughened by various methods, a sandblasting process will be described below as an example.

As the abrasive grains as the blast material, regular abrasive grains (preferably spherical or flat particles having a smooth surface) are preferable, and glass beads having a particle size of # 100 to # 600 are preferably used. The blast nozzle is at a distance of 7 mm from the developing sleeve 13.
While the developing sleeve 13 is rotated at 12 rpm, the glass beads are blown from the blast nozzle at an air pressure of 3 kg.
Sprayed with / m ^2. During the spraying, the blast nozzle is moved along the surface of the developing sleeve 13 by a distance of 30 cm in 1 to 2 minutes parallel to the axis. Thus, the surface of the developing sleeve 13 is blasted to obtain a rough surface. After the blast processing is completed, the developing sleeve 13 is dried after its surface is cleaned.

In the developing sleeve 13, the base 1
A metal plating layer 15 is formed on the inside of the surface 3a, and a metal plating layer 16 is formed on the outside.

The outer metal plating layer 16 has a role of preventing wear of a relatively soft metal having a Vickers hardness (Hv) of less than 200, such as aluminum or SUS, constituting the base 13a of the developing sleeve 13. Therefore, the hardness Hv of the metal plating layer 15 is preferably 450 or more.
The higher the hardness Hv of the metal plating layer 15 is, the better. However, if annealing, which is a commonly used means of increasing the metal hardness, is performed, the developing sleeve 13 will be warped, and the rotation during rotation will be large, causing a problem on the image. Hardness Hv
Is practically about Hv = 1000.

The metal plating layers 15 and 16 formed on the developing sleeve 13 are preferably non-magnetic like aluminum or SUS constituting the base 13a. For example, electroless Ni-P plating, electroless Ni- B plating, electroless Pd-P plating, etc. are performed favorably. For example, Ni (nickel) is a ferromagnetic substance by itself, but is electroless Ni-P,
In the Ni-B plating layer, it becomes amorphous and becomes non-magnetic by being combined with P (phosphorus) or B (boron). The P content in the Ni-P plating film required for such demagnetization is 8 to 10 wt%, and the B content in the Ni-B plating film is 5 to 7 wt%.

However, if the metal plating layers 15 and 16 formed on the surface of the developing sleeve 13 are made as thin as several μm, they may be somewhat magnetized but may be subjected to electro-Cr plating which is characterized by being hard. . In addition, in order to improve the adhesion of the electric Cr plating, an electric Cu plating
r plating may be performed.

Next, the inner metal plating layer 15 smoothes the inside of the developing sleeve 13 so that the magnet roller 14 fixed inside is not damaged by minute projections 17 inside the developing sleeve 13. Plays a role.
Here, the internal magnet roller 14 is
In order not to be damaged by minute projections inside the developing roller 3, it is conceivable to make the outer diameter of the magnet roller 14 inside the developing sleeve 13 sufficiently smaller than that inside the developing sleeve 13. Has a developing sleeve 13
In order to obtain a desired magnetic force outside the above, the magnetic force of the internal magnet roller 14 must be increased, which may be technically difficult and may increase the cost.

Therefore, it is necessary to make the outer diameter of the magnet roller 14 close to the inner diameter of the developing sleeve 13 in order to minimize the magnetic force of the inner magnet roller 14.

However, if there are minute projections inside the developing sleeve 13, manufacturing variations in the diameters of the developing sleeve 13 and the magnet roller 14 may overlap, and the magnet roller 14 may be damaged.

Therefore, in the present invention, a metal plating layer 15 is also formed inside the developing sleeve 13 to make the inner surface of the developing sleeve 13 smooth,
4 was not damaged. Note that, in order to smooth the inner surface of the developing sleeve 13, the metal plating layer 15 is used.
The plating can be multilayered to increase the thickness of the plating.

As shown in FIG. 5, the developing sleeve 13 in which the center value of the inner diameter of the base 13a in manufacturing is 31.32 mm and the outer diameter of the magnet roller 14 is 30.32 mm.
Were manufactured in large numbers. Here, the entire surface of the developing sleeve 13 was plated with 2 μm of electric Cr. These developing sleeves 13 were assembled into a copying machine and subjected to a durability test of one million sheets on a multi-developing sleeve over a long period of time. At this time, the gap between the inside of the developing sleeve 13 and the magnet roller 14 is only about 0.5 mm as the central value in manufacturing, and the inside magnet roller 14
It has been found that the magnetic force of can be measured externally with little loss.

[0045]

As is apparent from the above description, according to the present invention, since the metal plating layer is formed on the entire inner surface and outer surface of the developer carrier of the developing device, wear of the outer surface of the developer carrier is reduced. In addition to this, it is possible to prevent the magnetic field generating means from being damaged by the inner surface of the developer-carrying body, and it is possible to stably output a good image over a long period of time.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of a developing device according to the present invention.

FIG. 3 is a cross-sectional view illustrating a toner restricted area of the developing device according to the present invention.

FIG. 4 is an enlarged detailed view of a toner restricted area of the developing device according to the present invention.

FIG. 5 is a transverse sectional view of a developing sleeve of the developing device according to the present invention.

FIG. 6 is an enlarged detail view of a portion A in FIG. 5;

FIG. 7 is a cross-sectional view of a developing sleeve of a conventional developing device.

[Explanation of symbols]

 Reference Signs List 12 magnetic toner 13 developing sleeve (developer carrier) 14 magnet roller (magnetic field generating means) 15, 16 metal plating layer 50 photosensitive drum (image carrier) 52 developing device

Claims (8)

[Claims] An image forming apparatus comprising: a cylindrical developer carrier made of a non-magnetic metal material; and a magnetic field generating means disposed in the developer carrier. The developer carried on the developer carrier is imaged. In a developing device that conveys to a developing unit facing the carrier and develops a latent image formed on the surface of the image carrier with a developer, a metal plating layer is formed on the entire inner surface and outer surface of the developer carrier. A developing device, characterized in that: 2. The developing device according to claim 1, wherein said magnetism generating means comprises a plastic magnet. 3. The hardness Hv of the metal plating layer is 450 to 450.
The developing device according to claim 1, wherein the number is set to 1,000. 4. The developing device according to claim 1, wherein the metal plating layer is formed by electroless Ni-P plating, electroless Ni-B plating, or electroless Pd-P plating. 5. The developing device according to claim 1, wherein said metal plating layer is formed by electro-chromium plating. 6. The developing device according to claim 1, wherein said metal plating layer is composed of a plurality of layers. 7. The developing device according to claim 6, wherein said metal plating layer comprising a plurality of layers is formed by a layer obtained by applying an electric Cr plating on an electric Cu plating. 8. An image carrier having a photosensitive layer on a surface thereof, a cylindrical developer carrier made of a non-magnetic metal material, and a magnetic field generating means disposed in the developer carrier, the developer comprising: A developing device that transports the developer carried on the carrier to the developing unit facing the image carrier, and develops the latent image formed on the surface of the image carrier with the developer. An image forming apparatus, wherein a metal plating layer is formed on the entire inner surface and outer surface of a developer carrier of the developing device.