JPH0372445B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection molding machine for manufacturing a ring-shaped anisotropic plastic magnet.

(Prior art and its problems) Conventionally, in this type of injection molding machine that uses a repulsive radial magnetic field mold, the ring-shaped cavity 13 is inserted into the radial yoke 10' from the inside, as shown by the arrow in FIG. A magnetic force is applied by an electromagnetic coil so that magnetic flux passes in the radial direction, and a mixture of ferromagnetic powder and molten resin (hereinafter simply referred to as magnetic material) is injected and filled into the cavity 13, and the The ferromagnetic particles are radially aligned along the magnetic flux and solidified to obtain a ring-shaped molded product.

However, the mold used in the past was designed as a single-cavity mold, which was theoretically advantageous for magnetic circuits.
Since the center of the cavity 13 and the centers of the mold 2 and the electromagnetic coil are on the same axis, the spool 18 occupies a fairly large area near the movable core pin 12 of the magnetic material that guides the magnetic flux inside the ring-shaped cavity 13. In addition, since a gap occurs between the runner 19 and the movable core pin 12, magnetic flux cannot be guided sufficiently and efficiently from the fixed side (nozzle side), and this disadvantage is particularly noticeable in small-diameter ring-shaped molded products. It was hot.

(Object of the Invention) The present invention was made to solve the above-mentioned conventional problems, and even if the target molded product has a small diameter, it can efficiently guide magnetic flux inside the molding cavity.
The purpose is to improve the quality of molded products.

(Means for Solving the Problems) The plastic magnet injection molding machine of the present invention is provided with an electromagnetic coil for applying magnetic force, and when the coil is energized, magnetic flux is transferred from the fixed platen side and the movable platen side to the molding machine. It flows inside the mold to the inside of the ring-shaped cavity, changes direction by 90 degrees, and flows in the radial direction.
In a plastic magnetic injection molding machine equipped with a repulsive radial magnetic field mold that forms a closed magnetic path that separates the flow around the outer periphery of the radial yoke and returns to the fixed platen side and the movable platen side, the radial yoke is connected to the fixed side mold and the movable side mold. The radial yoke is formed into a plate shape to be sandwiched between the side mold and the radial yoke, and a plurality of holes for forming the outer peripheral surface are provided at positions offset from the center of the electromagnetic coil of the radial yoke. The present invention is characterized in that the ring-shaped cavity is formed by inserting a core pin for forming the peripheral surface.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3.

In the figure, reference numeral 1 denotes a fixed platen made of a magnetic material, and a mold 2 made of a magnetic material and a mold 3 made of a non-magnetic material fitted around the mold are attached to the fixed platen 1. , an electromagnetic coil 4 is attached to the outer periphery of these molds 2 and 3.

A movable platen 5 made of a magnetic material is fitted into a diver 6 made of a magnetic material by a mold clamping device (not shown), and is capable of moving forward and backward relative to the fixed platen 1.

This movable platen 5 has a mold 7 made of magnetic material.
A mold 8 made of a non-magnetic material is fitted around the mold, and an electromagnetic coil 9 is mounted around the outer periphery of these molds 7 and 8.

A radial yoke 10 is made of a magnetic material and is slidably inserted through the tie bar 6. This radial yoke 10 is formed into a plate shape so as to be sandwiched between the fixed side mold 3 and the movable side mold 8 during mold clamping, and is located at a position offset from the center of the electromagnetic coils 4 and 9 of the radial yoke 10. Holes 11 for molding the outer peripheral surface of the molded product are provided at positions (in the example, two symmetrical positions with the center of the coil in between).

Further, a core pin 12 made of a magnetic material for forming the outer peripheral surface of the molded product is connected to the movable mold 7, and the outer peripheral surface forming hole 11 is connected to the movable mold 7 when the mold is clamped.
inserted within.

Reference numeral 13 denotes a ring-shaped cavity, which is composed of the fixed mold 3, the movable mold 8, the hole 11 of the radial yoke 10, and the core pin 12 of the movable mold 7 during mold clamping.

An ejector pin 14 is movably inserted into the movable molds 7 and 8 with one end facing inside the cavity 13, and the other end is connected to the ejector plate 15. 17.

A sprue 18 is provided at the center of the coil of the stationary mold 3. 19 is a runner, and 20 is a side gate, which is provided between the stationary mold 3 and the radial yoke 10. A plasticizing device 21 is capable of injecting and filling a magnetic material into the cavity 13 via a spray 18, a runner 19, and a side gate 20.

(Function) The electromagnetic coil 4,
9, the magnetic flux flows in opposite directions through the fixed platen 1, mold 2, movable platen 5, and mold 7, as shown in FIGS. The movable side core pin 12 changes the direction by 90 degrees, and as shown in FIG. They return to form a closed magnetic path. In this case, the sprue 18 is located on the central axis of the electromagnetic coil 4, but each cavity 13
The center is offset from the sprue extension line. Moreover, since the cavity 13 is filled with magnetic material through the side gate 20 on one side, the sprue 18 and the runner 19 do not become an obstacle to guiding the magnetic flux inside the cavity 13, and the flow of the magnetic flux is prevented. is not cut off by Runner 19. Therefore, the magnetic flux φ along the radial direction in the cavity 13
Since the magnetic force is applied uniformly, the ferromagnetic particles in the magnetic material filling the cavity 13 are efficiently oriented so that the crystal axes, which are easy to magnetize, are aligned radially along the magnetic flux. The molded article is solidified while maintaining its radial orientation.

In this embodiment, the tie bar 6 is used as a return yoke for magnetic flux. The same effect can be achieved even if the forming piece is placed across the fixed platen 1 and the movable platen 5. In addition, although the example in which the radial yoke 10 is attached to the tie bar 6 has been described, it can also be attached to the fixed side molds 2 and 3 or the movable side molds 7 and 8 and slidably contact the return yoke of the diver 6, etc. It has the same effect.

(Effects of the Invention) As described above, the present invention has no spray or runner in the magnetic mold that guides the magnetic flux inside the ring-shaped cavity, and can efficiently guide the magnetic flux. Since both molds can be made to have almost the same shape, a well-balanced radial magnetic field is generated, and even small-diameter ring-shaped molded products can obtain uniform and sufficient magnetic flux, making it possible to manufacture molded products with excellent radial orientation. At the same time, it becomes possible to produce multiple pieces.

[Brief explanation of drawings]

Fig. 1 is a plan sectional view showing an embodiment of the present invention, Fig. 2 is an enlarged view of the main part of Fig. 1, Fig. 3 is a sectional view taken along the - line in Fig. 1, and Fig. 4 is a conventional example. FIG. 1... Fixed platen, 2, 3, 7, 8... Mold, 4, 9... Electromagnetic coil, 5... Movable platen, 6... Tie bar, 10... Radial yoke,
11...Outer peripheral surface forming hole, 12...Core pin, 1
3...Cavity, 18...Sprue, 19...
Runner, 20...side gate.

Claims (1)

[Claims] 1. An electromagnetic coil for applying magnetic force is provided, and when the coil is energized, magnetic flux flows from the fixed platen side and the movable platen side inside the mold to the inside of the ring-shaped cavity, changes direction by 90 degrees, and flows in the radial direction. ,
In a plastic injection molding machine equipped with a repulsive radial magnetic field mold that forms a closed magnetic path that separates the flow around the outer periphery of the radial yoke and returns to the fixed platen side and the movable platen side, the radial yoke is connected to the fixed side mold and the movable side mold. Formed into a plate shape that is sandwiched between the mold and
A plurality of holes for forming the outer circumferential surface are provided at positions offset from the center of the electromagnetic coil of the radial yoke, and core pins for forming the inner circumferential surface provided on the mold side are inserted into the holes to form the ring-shaped cavity. A plastic magnet injection molding machine characterized by: