JPH08179630A - Developing magnet and developing device - Google Patents

Abstract

PURPOSE: To reduce the weight of a developing magnet and to realize a cost reduction by providing a developing magnet with a cylindrical body made of a thermoplastic resin and nonmetallic bearings or nonmetallic bearings for capping both right and left openings. CONSTITUTION: The magnet part is constituted of the cylindrical body 30 made of the thermoplastic resin contg. magnetic material powder by extrusion molding, by which the magnet part is provided with rigidity. The developing magnet which is approximately uniform in magnetic force in a longitudinal direction and is reducible to a lighter weight is obtd. by using the non-metallic through- bearings 21 penetrating the inside of the cylinder. The developing magnet magnetized to multiple poles in a circumferential direction by the magnetic powder contained in the cylindrical body 30 made of the thermoplastic resin. In such a case, a rigid nylon is used as the resin of the cylindrical body 30 made of the thermoplastic resin and oxide magnetic powder, such as barium or strontium ferrite, is used as its magnetic material in actuality and a POM made of a resin is used for the through-bearings 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing magnet and a developing device used in an image forming apparatus utilizing electrophotography such as a copying machine and a printer.

[0002]

2. Description of the Related Art A conventional example of the present invention is shown in FIGS.

In an image forming apparatus using an electrophotographic system such as a copying machine or a laser beam printer, a latent image formed on an image carrier is developed by a developing device and visualized as a toner image. As such a developing device, a developing device using a dry one-component magnetic toner as a developer is known.

FIG. 2 is a sectional view of an example of a conventional developing device.

In a developing container 4 of a developing device, a cylindrical non-magnetic metal developer carrier 2 such as aluminum which rotates in the direction of arrow B and faces the image carrier 1 which rotates in the direction of arrow A (hereinafter referred to as "development"). Sleeve) is provided. Inside the developing sleeve 2 rotating in the direction of arrow B, a developing magnet 3 magnetized with multiple poles in the circumferential direction is fixedly arranged. In addition, the magnetic poles magnetized in multiple directions in the circumferential direction are usually S-poles and N-poles alternately magnetized, and the vertical magnetic force on the sleeve surface is 500 to 90.
It is about 0G.

Fine irregularities are formed on the surface of the developing sleeve by sandblasting or the like, and by coating a conductive thin layer of a composite material composed of a binder resin, carbon black, and carbon graphite, the magnetic toner T of the developing sleeve is formed. In addition to improving the carrying force, an elastic blade 5 made of an elastic member such as urethane rubber is arranged, and a magnetic toner T is formed as a thin layer on the developing sleeve 2 at a nip portion formed between the developing sleeve 2 and the elastic blade 5. By coating, the magnetic toner T is stably charged.

FIG. 3 shows an example of a conventional developing magnet.

Conventionally, as shown in FIG. 3 (a), a developing magnet 3 has a cylindrical developing sleeve 2 in which a soft magnet portion 3b formed by extrusion molding and a magnet bearing using a metallic penetrating shaft such as iron. It is composed of the part 3a.

The developing magnet 3 is disposed inside the developing sleeve 2 and is composed of a sleeve flange 10 made of POM or the like.
As a sleeve unit to which a gear 11 for rotating the developing sleeve is added, it is attached to the developing device, and both ends of the magnet bearing portion 3a are fixedly supported by the developing device.

Further, as shown in FIG. 3 (b), the developing magnet 3 is also known as a hard plastic magnet in which all of the magnet portion and the magnet bearing portion are integrally molded by resin with a magnetic material by molding. Has been.

[0011]

The conventional hard plastic magnet has poor productivity due to molding and tends to have unevenness in the magnetic force in the longitudinal direction, but has an advantage that the number of parts is small. Also, with soft magnets, because they are extruded like chikuwa, they have good productivity and uniform magnetic force in the longitudinal direction,
Since strong bearings such as iron are used for the bearing, it is difficult to reduce the weight, and both have advantages and disadvantages.

In a hollow magnet of a thermoplastic resin cylindrical body made of hard nylon or the like containing a magnetic material that solves the above problems, when a bearing is connected to both ends,
It is necessary to combine them so as not to affect the magnetic force.

It has been desired that the developing magnet satisfy the conditions such as good productivity, little magnetic force unevenness in the longitudinal direction, light weight and small size, and a small number of parts.

[0014]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is a developing device which is inexpensive, can achieve weight reduction in a process cartridge system, and can always form a stable and clear image. Or to provide a developing magnet for providing an image forming apparatus.

A movable image carrier having a photoconductor layer on a conductive substrate is charged, exposed, and developed by a developing device to form a toner image on the image carrier, and then an image is formed on a transfer material. In an image forming apparatus that transfers a toner image on a carrier and permanently fixes the toner image on the transfer material to the transfer material by a fixing device, a non-magnetic metal hollow containing a developing magnet for carrying toner as a developer. With a developing sleeve that is a cylindrical member, the developing magnet structure is provided with a thermoplastic resin cylindrical body formed by extrusion molding, and a non-metallic bearing penetrating the inside of the cylinder, and by the magnetic powder contained in the thermoplastic resin cylindrical body, By using a developing magnet that is magnetized in multiple poles in the circumferential direction, it is possible to provide a developing device that is extremely inexpensive, lightweight, and has less magnetic unevenness in the longitudinal direction.

The developing magnet structure includes a thermoplastic resin cylindrical body formed by extrusion molding, and a non-metallic bearing that covers the left and right openings of the cylindrical body, so that the developing magnet has a hollow portion and the thermoplastic resin cylinder is formed. By using a developing magnet that is magnetized in the circumferential direction in multiple poles by the magnetic powder contained in the body, it is possible to provide a developing device that is much cheaper and lighter and that has less uneven magnetic force in the longitudinal direction. .

The notch of the non-metallic bearing insertion portion that covers both the left and right openings of the thermoplastic resin cylindrical body is provided outside the image forming area, and more preferably outside the maximum sheet passing width, so that the bearing insertion portion is formed. Since it is not affected by the decrease in magnetic force at the end portion of the developing magnet due to the notch, it is possible to obtain a substantially uniform magnetic force in the longitudinal direction within the image forming area, and it is possible to secure a uniform image density.

Development is made by forming notches in the non-metallic bearing insertion portion that covers both the left and right openings of the thermoplastic resin cylindrical body between magnetic poles arranged in multiple poles in the circumferential direction of the thermoplastic resin cylindrical body. By using a magnet, it is possible to obtain a substantially uniform magnetic force in the longitudinal direction of the developing magnet in the image forming area and the entire sheet passing width, and to obtain a uniform image density.
Also, it is possible to ensure the prevention of fogging in the margin portion outside the image forming area, and further, it is possible to shorten the developing magnet length to the maximum paper passing width at the shortest, and to realize the downsizing and weight saving of the developing device. You can

Further, the thermoplastic resin cylindrical body,
By using a developing magnet provided with a notch of a non-metallic bearing insertion portion penetrating the inside of the cylinder between magnetic poles arranged in the circumferential direction of the thermoplastic resin cylindrical body in the same manner as described above, the thermoplastic resin It is possible to prevent the circumferential displacement between the cylindrical body and the penetrating resin bearing, and to prevent the magnetic force from being reduced due to the notch, so that a substantially uniform magnetic force can be obtained in the longitudinal direction of the developing magnet, and a uniform image density can be obtained. Can be secured.

The developing magnet is only a thermoplastic resin cylinder formed by extrusion molding, and the bearing portion is formed by cutting both ends of the thermoplastic resin cylinder to reduce the outer diameter. The number of parts is reduced by using a developing magnet that has a hollow part not only inside the magnet but also inside the bearing and is magnetized in multiple poles in the circumferential direction by the magnetic powder contained in the thermoplastic resin cylinder. As a result, the cost and weight can be reduced, and the coaxiality of the magnet portion and the magnet bearing portion can be improved by the integral structure.

[0021]

【Example】

(Embodiment 1) FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention.

Conventionally, as shown in FIG. 3 (b), a plastic magnet in which a magnet portion and a bearing portion are integrally molded has a problem that productivity is poor due to molding and magnetic force in the longitudinal direction becomes uneven. It was Further, as shown in FIG. 3 (a), in the developing magnet in which the bearing portion 3a is made of a rigid metallic penetrating bearing such as iron, and the magnet portion 3b is made of a fluffy soft magnet, the magnet portion 3b is pushed Because of the molding, the productivity is good, and the magnet length can be easily changed simply by changing the cutting length, and the magnetic force in the longitudinal direction can be easily molded uniformly, but because the soft magnet is used. Since a rigid metal bearing is used for the bearing, it has been difficult to reduce the weight.

In this embodiment, as shown in FIG. 1, the magnet portion is formed of a thermoplastic resin cylindrical body 30 containing magnetic powder by extrusion molding so that the magnet portion has rigidity and the inside of the cylinder is made to have rigidity. By using the non-metallic penetrating bearing 21 that penetrates through the developing magnet, it is possible to obtain a developing magnet that has a substantially uniform magnetic force in the longitudinal direction and can achieve weight reduction.

Actually, hard nylon was used as the resin of the thermoplastic resin cylindrical body 30, oxide magnetic powder such as barium or strontium ferrite was used as the magnetic material, and resin POM was used for the penetrating bearing 21.

(Second Embodiment) FIG. 4 is an explanatory view of a second embodiment of the present invention.

In the first embodiment, the non-metallic penetrating bearing is used as the bearing, but in the present embodiment, the thermoplastic resin cylindrical body 30 of the magnet portion and the non-metallic bearing 22 that covers the left and right openings thereof are used. By using the hollow portion, the weight of the developing magnet can be further reduced by using the hollow portion.

The magnet portion 30 and the non-metallic bearing 22 for covering both the left and right openings may be joined to the inside of the cylinder as it is.
As shown in (a), the bearing 22 may be coupled by cutting the inner diameter of the cylinder. Further, it is possible to cover the outer diameter of the cylinder with the bearing 22, but in this case, the developing magnet is included in the developing sleeve.
It is preferable to combine them as in (b). FIG. 4
As shown in (c), when the perpendicularity between the cut surface 31a of the thermoplastic resin cylindrical body 30 and the outer peripheral surface of the thermoplastic resin cylindrical body 30 is high, the positioning provided on the cut surface 31a The bearing 22 may be connected by a hole.

Further, the joining may be performed by adhesion, press fitting, or patching.

Actually, hard nylon was used as the resin of the thermoplastic resin cylindrical body 30, oxide magnetic powder such as barium or strontium ferrite was used as the magnetic material, and resin POM was used for the bearing 22.

(Third Embodiment) FIGS. 5 and 6 are explanatory views of a third embodiment of the present invention.

In the second embodiment, in the notch 23 of the insertion portion of the non-metal bearing 22 that covers both the left and right openings of the thermoplastic resin cylindrical body 30 of the developing magnet, the magnetic force is reduced, so that the notch 23 When the image forming area is provided in the image forming area, there occurs a problem that the image density becomes uneven at the end portion of the image.

Therefore, in this embodiment, as shown in FIGS. 5 (a) and 5 (b), the bearing insertion portion notch 23 is disposed outside the image forming area, so that the bearing inserting portion notch 23 is formed in the image forming area. It is possible to eliminate unevenness in magnetic force in the longitudinal direction and prevent unevenness in image density.

Further, in the above structure, there is a concern that the edge of the paper outside the image forming area may be fogged due to a decrease in the magnetic force in the cutout portion 23. It should be placed outside the width of the paper.

(Fourth Embodiment) FIGS. 7 and 8 are explanatory views of a fourth embodiment of the present invention.

In this embodiment, as shown in FIG.
Notch 2 at the insertion portion of the non-metallic bearing 22 that covers the left and right openings of the thermoplastic resin cylindrical body 30 that is the developing magnet
3 is a cylindrical body 3 made of a thermoplastic resin as shown in FIG.
By providing between the magnetic poles arranged in a multi-pole in the circumferential direction of 0, even if the notch 23 of the bearing insertion portion is arranged in the image forming area, there is no occurrence of magnetic force unevenness in the longitudinal direction and uneven image density. It becomes possible to prevent it. Therefore, the length of the magnet portion can be set to be the shortest and the maximum sheet passing width, so that the size and weight of the developing magnet can be reduced.

Further, it is not necessary to provide the notches between all the magnetic forces as shown in FIG. 7B, but it is also possible to provide only one notch as shown in FIG. 7C.

Also, as shown in FIG. 8, even if the notches provided between the magnetic poles are provided in the entire area of the thermoplastic resin cylindrical body 30, there is no reduction in the magnetic force due to the notches, and the magnetic force in the longitudinal direction is not generated. Can be uniform.

Further, by applying the embodiment shown in FIG. 8 to the thermoplastic resin cylindrical body 30 which is a developing magnet and the notch of the insertion portion of the non-metallic bearing 21 penetrating the inside of the cylinder, the embodiment is realized. In the 1 developing magnet,
It is possible to prevent the magnetic portion 30 and the penetrating bearing 21 from being displaced in the circumferential direction, to prevent the occurrence of magnetic force unevenness in the longitudinal direction, and to prevent the image density unevenness.

(Fifth Embodiment) FIG. 9 is an explanatory view of a fifth embodiment of the present invention.

In the above-mentioned four embodiments, the magnet portion is the thermoplastic resin cylindrical body, and the non-metallic bearing which is a separate member is used for the bearing portion, but in this embodiment, it is shown in FIG. 9 (a). As described above, both ends of the thermoplastic resin cylindrical body 30 are cut to reduce the outer diameter to form a bearing shape, thereby reducing the number of constituent parts of the developing magnet, thereby reducing the cost and making the bearing hollow. As a result, it is possible to reduce the weight, and at the same time, by integrally forming the bearing portion, it becomes easy to make the coaxiality of the magnet portion and the bearing portion highly accurate.

FIG. 9B is a sectional view showing a state in which the developing magnet 30 used in this embodiment is incorporated in the developing sleeve.

[0042]

As described above, according to the present invention, the developing magnet structure is provided with the thermoplastic resin cylindrical body and the non-metal bearing penetrating the inside of the cylinder, or the non-metal bearing that covers the left and right openings thereof. By providing a metal bearing, it is possible to reduce the weight and cost of the developing magnet, and by disposing the notch of the bearing insertion portion between the magnetic poles,
It is possible to further reduce the size and weight of the developing magnet.

Further, by integrally forming the magnet portion and the bearing portion with the thermoplastic resin cylindrical body, the coaxiality between the bearing portion and the magnet portion is improved, and the bearing is hollow so that the weight is further reduced.

Further, the weight reduction and downsizing of the developing magnet leads to the weight reduction and downsizing of the developing device. In particular, when the developing magnet is applied to the process cartridge which can be attached to and detached from the main body of the image forming apparatus, the handling becomes easy and the transportation cost is reduced. Is also effective.

In this embodiment, the dry one-component magnetic toner has been described, but the present invention can be applied to a two-component toner, and not only hard nylon but also resin for the thermoplastic resin cylindrical body is used.
Other thermoplastic resins such as polyamide may be used, and the magnetic substance contained may be magnetic powder other than barium or strontium ferrite. In addition, the bearing is made of resin POM
Not only that, but when another resin is applicable and a bearing having high strength and light weight is used, ceramic or the like may be used.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a conventional developing device.

FIG. 3 is an explanatory diagram of a conventional developing magnet and a developing sleeve.

FIG. 4 is an explanatory diagram of the second embodiment.

FIG. 5 is an explanatory diagram of a third embodiment.

FIG. 6 is an explanatory diagram of the third embodiment.

FIG. 7 is an explanatory diagram of the fourth embodiment.

FIG. 8 is an explanatory diagram of the fourth embodiment.

FIG. 9 is an explanatory diagram of the fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Development sleeve 3 Development magnet 21 Penetration bearing 22 End cover bearing 30 30 Thermoplastic resin cylinder

Claims (6)

[Claims] 1. A transfer material after a movable image carrier having a photoconductor layer on a conductive substrate is charged, exposed, and developed by a developing device to form a toner image on the image carrier. In an image forming apparatus for transferring a toner image on an image carrier to a toner image and for permanently fixing the toner image on the transfer material to the transfer material by a fixing device, a non-development magnet for carrying the toner as the developer is incorporated. A developer carrying member which is a magnetic metal hollow cylindrical member, wherein the developing magnet structure comprises a thermoplastic resin cylindrical body formed by extrusion molding, and a non-metallic bearing penetrating the inside of the cylinder, and the thermoplastic resin cylinder. A developing magnet and a developing device, wherein the magnetic powder contained in the body is magnetized into multiple poles in the circumferential direction. 2. A transfer material after a movable image carrier having a photoreceptor layer on a conductive substrate is charged, exposed, and developed by a developing device to form a toner image on the image carrier. In an image forming apparatus for transferring a toner image on an image carrier to a transfer medium and permanently fixing the toner image on the transfer material to the transfer material by a fixing device, a non-development magnet for carrying the toner as the developer is incorporated. The developer magnet is a magnetic metal hollow cylindrical member, and the developing magnet structure is provided with a thermoplastic resin cylindrical body formed by extrusion molding and a non-metallic bearing that covers both left and right openings of the developing magnet. A developing magnet and a developing device, which have a hollow portion and are magnetized in the circumferential direction in multiple poles by the magnetic powder contained in the thermoplastic resin cylindrical body. 3. The developing magnet according to claim 2, wherein the notch of the non-metallic bearing insertion portion that covers both the left and right openings of the thermoplastic resin cylindrical body is provided at least outside the image forming area. 4. A notch of a non-metallic bearing insertion portion that covers both left and right openings of the thermoplastic resin cylindrical body is provided between magnetic poles arranged in multiple poles in the circumferential direction of the thermoplastic resin cylindrical body. The developing magnet according to claim 2, wherein: 5. A notch of a non-metallic bearing insertion portion penetrating the inside of the thermoplastic resin cylinder is provided between magnetic poles arranged in multiple poles in the circumferential direction of the thermoplastic resin cylinder. The developing magnet according to claim 1, wherein: 6. A transfer material after a movable image carrier having a photoconductor layer on a conductive substrate is charged, exposed, and developed by a developing device to form a toner image on the image carrier. In an image forming apparatus for transferring a toner image on an image carrier to a toner image and for permanently fixing the toner image on the transfer material to the transfer material by a fixing device, a non-development magnet for carrying the toner as the developer is incorporated. It has a developer carrying member which is a magnetic metal hollow cylindrical member, the developing magnet is only a thermoplastic resin cylindrical body by extrusion molding, and the bearing portion cuts both ends of the thermoplastic resin cylinder, Since it has a small diameter, it has a hollow portion inside the developing magnet and inside the bearing, and is magnetized in the circumferential direction in multiple poles by the magnetic powder contained in the thermoplastic resin cylindrical body. Developing magnet and the developing device and said.