JPH0372446B2 - - 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.

(Conventional technology and its problems) Generally, in this type of injection molding machine, a repulsive radial magnetic field mold is designed so that magnetic flux passes radially from the inside of the cavity for the ring-shaped molded product when magnetic force is applied, and the mold is fixed. In order to narrow and guide the magnetic flux from the platen side and the movable platen side to the inside of the cavity, the outer surface of the mold made of magnetic material is narrowed as it approaches the cavity. For this reason, the ejector mechanism provided in the movable mold obstructs the flow of magnetic flux guided inside the cavity.
A small diameter pin was used for the ejector pin, or a stripper plate was used.

However, when using a small-diameter ejector pin, a return pin is required, which increases the size of the ejector mechanism, and it is not easy to select the material of the return pin, and there is an unavoidable problem that pin marks are left on the side of the molded product after the mold is released. .

On the other hand, when using a stripper plate, the ejector mechanism becomes larger, which narrows the magnetic path inside the mold, and increases the air gap between the mold mounting plate and the mold, resulting in a deterioration of magnetic efficiency. I couldn't escape it.

(Objective of the Invention) The present invention was made to solve the above-mentioned conventional problems, and has an object to efficiently guide magnetic flux to the inside of the cavity and to prevent protrusion marks from being left on the molded product. With the goal.

(Means for Solving the Problems) The plastic magnet injection molding machine of the present invention has an ejector sleeve, one end of which is fixed to the ejector plate, on the movable side of the magnetic field mold, which is movable concentrically with the cavity. The distal end on the cavity side of the ejector sleeve is made of a non-magnetic material, and the proximal end is made of a magnetic material. It is characterized in that it is fixed to the movable mold mounting plate by passing through it.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

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 tie bar 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. Furthermore, a mold 7 made of a magnetic material and a mold 8 made of a non-magnetic material fitted around the mold are attached to the movable platen 5.
An electromagnetic coil 9 is attached to the outer periphery of these molds 7 and 8.

The molds 2 and 7 are narrowed as the outer surfaces of the molds approach the cavity 10 in order to guide magnetic flux from the fixed platen 1 side and the movable platen 5 side to the inside of the cavity 10 for the ring-shaped molded product.

11 is the ejector sleeve, cavity 10
It is movably inserted into the movable side molds 7 and 8 with its tip facing toward the cavity 10 and concentric with the cavity 10, and its base end is fixed to the ejector plate 12.
Ejector cylinder 13 removes ejector rod 1.
Projected through 4.

This ejector sleeve 11 has a cavity 1.
It has an outer diameter slightly larger than the outer circumferential forming surface of the molded product No. 0, and an inner diameter that is approximately the same as the inner circumferential forming surface of the molded product, and the tip end surface is used as the side surface for molding the molded product. Further, the distal end portion on the cavity side of the ejector sleeve 11 is made of a non-magnetic material, and the proximal end portion is made of a magnetic material. The boundary surface B between the non-magnetic material and the magnetic material is narrowed so as to be continuous with the outer surface shape of the mold 7 made of the magnetic material.

Reference numeral 15 denotes a core pin for molding the inner peripheral surface of a molded product made of a magnetic material, which passes through the ejector sleeve 11 and is fixed to the movable mold mounting plate 16.

A radial yoke 17 is made of a magnetic material and is slidably inserted through the tie bar 6. The radial yoke 17 is formed into a plate shape so as to be sandwiched between the fixed mold 3, the movable mold 8, and the ejector sleeve 11 during mold clamping, and the electromagnetic coil 4 of the radial yoke 17 , 9 are provided with holes 18 for forming the outer peripheral surface of the molded product. Therefore, the cavity 10 is connected to the stationary side molds 2 and 3 and the ejector sleeve 11 during mold clamping.
, a core pin 15 and a radial yoke 17.

A sprue 19 is provided at the center of the coil of the stationary mold 3. 20 is a runner, and 21 is a side gate, which is provided between the stationary mold 3 and the radial yoke 17. A plasticizing device 22 is capable of injecting and filling a magnetic material into the cavity 10 via a sprue 19, a runner 20, and a side gate 21.

Note that 23 is an ejector pin made of a non-magnetic material.

(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 FIG. After changing the direction by 90 degrees, both of them pass radially through the cavity 10, branch off at the outer periphery, return to the fixed platen 1 and the movable platen 5 using the tie bar 6 as a return yoke, and form a closed magnetic path, respectively. At this time, ejector sleeve 11
is composed of a non-magnetic material and a magnetic material, and the boundary surface thereof is narrowed to a shape that is continuous with the mating surfaces of the movable side molds 7 and 8, and a core pin 15 made of a magnetic material is passed through the ejector sleeve 11. Because I let it happen,
The flow of magnetic flux is not hindered by the ejector mechanisms 11 to 14, and the magnetic flux efficiently flows through the cavity 10.
guided inside. Therefore, since the magnetic force of the magnetic flux φ along the radial direction is uniformly applied to the cavity 10, the ferromagnetic particles in the magnetic material filled in the cavity 10 are aligned in the direction of the crystal axis in which magnetization is easy. The molded product is efficiently oriented so as to be radially aligned along the magnetic flux, and the molded product is solidified while maintaining its radial orientation, and after the mold is opened, it is ejected by the ejector sleeve 11. At this time, since the movable side side surface of the molded product is molded by the ejector sleeve 11 which is thicker and concentric, the ejector sleeve 11 does not cause protrusion marks on the molded product.

(Effects of the Invention) As described above, the present invention comprises an ejector sleeve made of a non-magnetic material and a magnetic material so as to constrict and guide magnetic flux from the movable platen side to the inside of the cavity together with the movable mold, and Since the core pin made of magnetic material is passed through the sleeve, the magnetic flux can be efficiently guided inside the cavity, and the ejector sleeve can also be used as a return pin, simplifying and downsizing the ejector mechanism. Magnetic efficiency can be surely improved. Also,
Since ejection is performed by the ejector sleeve forming the side surface of the molded product, it is easy to release the mold, and there are no ejection marks on the molded product, making it possible to improve the quality of the molded product.

[Brief explanation of drawings]

Fig. 1 is a plan sectional view showing one embodiment of the present invention, Fig. 2 is an enlarged sectional view of a repulsive radial magnetic field mold, and Fig. 3 is an enlarged sectional view of a repulsive radial magnetic field mold.
The figure is an enlarged view of the core pin in the same mold. 2, 3, 7, 8... Mold, 10... Cavity, 11... Ejector sleeve, 15... Core pin, 16... Mold mounting plate, 17... Radial yoke.

Claims (1)

[Claims] 1. A repulsive radial magnetic field mold is provided that allows magnetic flux to pass radially from the inside of the cavity for a ring-shaped molded product by applying magnetic force, and a magnetic material is used to guide the magnetic flux from the fixed platen side and the movable platen side to the inside of the cavity. In a plastic magnet injection molding machine in which the outer surface of the mold is narrowed as it approaches the cavity, an ejector sleeve, one end of which is fixed to the ejector plate, is movable concentrically with the cavity on the movable side of the magnetic field mold. The distal end on the cavity side of the ejector sleeve is made of a non-magnetic material, and the proximal end is made of a magnetic material, and a core pin for molding the inner peripheral surface of the molded product made of the magnetic material is inserted into the ejector sleeve.
A plastic magnet injection molding machine characterized in that the ejector sleeve is passed through and fixed to a movable mold mounting plate.