JP2906211B2 - Magnet roll molding method and molding die - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a magnet roll used in a developing section of an electrophotographic image forming apparatus such as a copying machine, a facsimile, a laser beam, and the like, and a mold for forming a magnet roll.

[0002]

2. Description of the Related Art As is well known, a magnet roll used in an electrophotographic image forming apparatus has an outer peripheral portion of 4 to 1 mm.
It has zero magnetic poles. Therefore, the charged toner is attracted to the magnet roll together with the carrier, which is a magnetic material. Therefore, when a cylinder made of a nonmagnetic material called a sleeve on the outer periphery of the magnet roll is rotationally driven, the toner adsorbed on the magnet roll is transported to a predetermined position. The toner conveyed by suction is electrostatically attracted to, for example, a photosensitive drum to form a latent image, and excess toner is scraped off together with the carrier. in this way,
Since the magnet roll is required to have a complicated function of adsorbing, transporting, and releasing the charged toner, the distribution of the magnetic poles is also complicated. Such a magnet roll is generally formed by injecting a mixed material of a magnetic powder and a synthetic resin such as a polyamide resin into a mold.

A mold for forming a magnet roll is composed of a pair of molds divided at a parting line or a parting surface. A cylindrical cavity for forming the outer peripheral surface of the magnet roll is formed therein, and 4 to 10 permanent magnets are provided on the outer peripheral portion of the cavity. Therefore, when the above-described material is injected and filled into the cavity by closing the mold with the parting surfaces together, a magnet roll having magnetic poles of a desired distribution is formed. Open the mold and take out the magnet roll. Alternatively, molding can be performed by injection-filling a similar material into a mold having no parting surface, that is, a cylindrical mold. According to this molding method, since the mold is not separated, it is cooled and solidified after injection filling to reduce the volume or volume of the magnet roll, and then the magnet roll is withdrawn from the mold in the axial direction.

[0004]

According to the former molding method of performing injection molding using a pair of molds divided at a parting surface, the mold is opened and taken out in the radial or lateral direction of the magnet roll. Since there is no need to cool until the volume of the magnet roll is sufficiently reduced,
The molding cycle can be shortened. However, there are problems. For example, since the parting line or parting surface must be formed in the diameter direction of the cavity to remove the formed magnet roll,
There is a disadvantage that the arrangement of the magnetic poles is restricted. More specifically, assuming that a cavity C for forming a magnet roll is formed in a pair of dies A and B as shown in FIG. 4, a parting line L is indicated by a solid line. Must be formed in the diameter direction of the cavity C. On the other hand, when the parting line L ′ is appropriately deviated from the diameter as shown by the dotted line,
Since the part formed by the mold B has a large diameter, it cannot be taken out in the radial direction or the lateral direction even when the molds A and B are opened. On the other hand, the magnet roll is required to have a complicated function as described above, and the magnetic field distribution is, for example, as shown in FIG.
As shown in the figure, the cross section is not uniform and has a complicated pattern. By the way, since the parting line L of the mold cannot be deviated from the diameter direction as described above, and the permanent magnet cannot be arranged on the parting line L, conventionally, the arrangement of the magnetic poles or the magnetic field distribution is sacrificed. Therefore, they are arranged so as to avoid the parting line L. Therefore, the magnetic field distribution of the magnet rolls formed by the dies A and B differs from the design or theoretical arrangement, and sufficient performance is not obtained.

[0005] When a mold having no parting surface is used, there is an advantage that the permanent magnet can be arranged as designed since there is no parting surface. However, when using a cylindrical mold without a parting surface, it is necessary to cool and reduce the volume in order to extract the formed magnet roll from the cavity in the axial direction. This occupies 60 to 70% of the cycle, and there is a disadvantage that the molding efficiency is reduced. Accordingly, an object of the present invention is to provide a magnet roll forming method capable of obtaining a high quality magnet roll, and a magnet roll forming die used for carrying out the method.

[0006]

According to the present invention, in order to achieve the above object, a plurality of permanent magnets are arranged at predetermined intervals on the outer peripheral portion of a pair of mold cavities, and a plurality of permanent magnets are arranged therein. At least one permanent magnet is divided and arranged at the same polarity with the parting surfaces of the pair of molds interposed therebetween, and the pair of molds is operated so that the divided permanent magnets act as one permanent magnet. The mold is clamped, and a material composed of a synthetic resin such as a polyamide resin and magnetic powder is injected into the cavities of the pair of molds to form a magnet roll. The invention according to claim 2 is a magnet roll forming mold in which a cylindrical cavity is formed in a pair of molds, and a plurality of permanent magnets are arranged at predetermined intervals on an outer peripheral portion of the cavity. In this case, at least one of the permanent magnets is divided and arranged in the same polarity close to the parting surface with the parting surface interposed therebetween.

[0007]

[Function] A pair of molds are clamped by a mold clamping machine. As a result, the permanent magnets arranged in the same polarity in proximity to the parting surface across the parting surface in a divided manner act as one magnet. A material composed of a resin and magnetic powder is kneaded and melted, for example, in a cylinder barrel. Then, the cavity of the clamped mold is injection-filled. The magnetic powder in the material is magnetized in a predetermined distribution by the permanent magnet of the mold.
Open the pair of molds and take out the formed magnet roll.

[0008]

Embodiments of the present invention will be described below. FIG. 3 is a radial cross-sectional view of the magnet roll, and it is assumed that the magnet roll exhibits an ideal magnetic field distribution. In order to form a magnet roll having such a magnetic field distribution, permanent magnets 4 to 8 are provided around the cavity 3 of the mold K in FIG.
Must be arranged as shown in the figure. By the way, as is clear from FIG. 2, when the permanent magnets 4 to 8 are arranged in this way, the permanent magnets 4 to 8 pass through the diameter of the cavity 3,
Moreover, the parting surface cannot be provided without touching the permanent magnets 4 to 8. Therefore, in this embodiment, the permanent magnet 8 is divided into two as described later. Thereby, the parting surface can be formed in the diameter direction of the cavity. As shown in FIG. 1, the mold according to the present embodiment includes, for example, a fixed mold 1 formed of a non-magnetic material and a movable mold 2 similarly formed of a non-magnetic material. It is composed of Inside the dies 1 and 2, a cavity 3 for determining the outer peripheral surface of a magnet roll having a predetermined length is formed. The diameter direction of the cavity 3 is a parting plane P.

The permanent magnets 4 to 8 provided on the outer periphery of the cavity 3 have different sizes or different magnet strengths in order to obtain a magnetic field distribution as shown in FIG. The permanent magnets 4 to 8 have substantially the same length as the length of the cavity 3 in the axial direction.
A long hole for embedding a permanent magnet is formed in the outer periphery of the cavity 3, and the S pole or the N pole is arranged so as to face the axis of the cavity 3. At least one of the permanent magnets 8 of the permanent magnets 4 to 8 is divided into two in the axial direction, and one of the permanent magnets 8a is disposed along the parting line or parting plane P of the fixed mold 1 and the other permanent magnet. 8
b is provided near the parting surface P along the parting surface P of the movable mold 2 in the same manner. These permanent magnets 8a and 8b are arranged so as to face each other when the mold is clamped, and so that the same poles coincide. At this time, the distance between the permanent magnets 8a and 8b is large enough that the wall between the parting surface P and the hole for burying the permanent magnets 8a and 8b can hold the permanent magnets 8a and 8b. If it has mechanical strength, it will act as one magnet if it is arranged closer. The permanent magnets 8a and 8b thus divided are provided close to the parting surface P, but do not adhere to each other even if the molds 1 and 2 are clamped. Permanent magnets 8a, 8b when clamped
When the distance between the permanent magnets 8 is large, the permanent magnet 8
Since the peak values of the magnetic poles a and 8b decrease, a larger or stronger magnet may be used in total of the permanent magnets 8a and 8b as compared with the case where one permanent magnet 8 is provided.

Next, an example in which a magnet roll is formed using the dies 1 and 2 will be described. Although not shown in the drawing, the movable mold 2 is clamped to the fixed mold 1 by a mold clamping device. On the other hand, a material composed of a synthetic resin such as a polyamide resin and magnetic powder is kneaded and melted in a cylinder barrel, for example.
Then, the cavities 3 of the clamped dies 1 and 2 are injection-filled. Then, the magnetic powder in the material is magnetized in a predetermined distribution by the permanent magnets 4 to 7, 8a, and 8b of the molds 1 and 2. The movable mold 2 is opened, and the formed magnet roll is taken out in the radial direction or the lateral direction.

[0011]

As described above, according to the present invention, at least one of the permanent magnets is divided and arranged in the same polarity with the parting line interposed therebetween. Since one magnetic pole is formed, the arrangement of the permanent magnets is not limited, and the permanent magnets can be arranged in the mold as designed. Therefore, the magnetic field distribution of the formed magnet roll is as designed and a high quality magnet roll can be obtained. In addition, since there is no restriction on the arrangement of the permanent magnets, an effect of facilitating the design and manufacture of a mold for forming a magnet roll can be obtained. Furthermore, since the mold is composed of a pair of molds, the mold roll can be opened and the magnet roll can be taken out after molding, and the cooling and solidifying time is shorter than that of a cylindrical mold that cannot be opened. Therefore, the effect that the molding cycle is short and the productivity is improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a mold for forming a magnet roll according to the present invention, and is a schematic cross-sectional view in a mold-clamped state.

FIG. 2 is a schematic cross-sectional view of a mold, showing an example of arrangement of permanent magnets applied to the present embodiment.

FIG. 3 is a schematic cross-sectional view of a mold showing an example of distribution of a magnetic field applied to the present embodiment.

FIG. 4 is a schematic sectional view of a mold for explaining a parting line of the mold for forming a magnet roll.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed mold 2 Movable mold 3 Cavity 4-7 Permanent magnet 8a, 8b Permanent magnet (divided permanent magnet) P Parting surface

Claims (2)

(57) [Claims] 1. A plurality of permanent magnets (4 to 8) are arranged at predetermined intervals on the outer periphery of a cavity (3) of a pair of molds (1, 2), and at least one of the permanent magnets is arranged. And the pair of molds (1, 2)
The pair of molds (1, 2) are arranged at the same polarity with the parting surface (P) of the pair interposed therebetween so that the divided permanent magnets (8a, 8b) act as one permanent magnet (8). Forming a magnet roll by injecting a material comprising a synthetic resin and a magnetic powder into a cavity (3) of the pair of molds (1, 2) to form a magnet roll. Method. 2. A cylindrical cavity (3) is formed in a pair of molds (1 and 2), and a plurality of permanent magnets (4 to 8) are formed at predetermined intervals around the outer periphery of the cavity (3). ) Is arranged, wherein at least one magnet (8) of the permanent magnets (4 to 8) is divided in the form of the parting surface (1). A magnet roll forming die, which is arranged at the same polarity in close proximity to the surface with P) interposed therebetween.