JPS63130315A - Injection molding machine for plastic magnet - Google Patents

Abstract

PURPOSE:To constitute the title machine so that ejection marks are not left behind by leading the magnetic flux efficiently to a cavity, by a method wherein an ejector sleeve is inserted into a cavity concentrically, the tip part and a base end side are constituted of a nonmagnetic material and magnetic material respectively, through which a core pin composed of the magnetic material is penetrated. CONSTITUTION:An ejector sleeve 11 is constituted of a nonmagnetic material and magnetic material. A boundary surface between them is narrowed into a form which continues to a mating surface between movable molds 7, 8. Then a core pin 15 composed of the magnetic material is penetrated through the inside of the said ejector sleeve 11. Therefore, magnetic flux is led to the inside of cavity 10 efficiently and magnetic force of the magnetic flux phi running along the cavity in a radial direction is applied evenly to the inside of the cavity. A crystal axis of ferromagnetic particles in, a filling magnetic material in the cavity 10 is in a direction to be stretched after the magnetic flux efficiently. A molding is soldiplied while a radially stretched state is kept as it is and the molding is ejected by an ejector sleeve 11 after mold break. In this instance, as a movable side of the molding is molded with the thick and concentric ejector sleeve 11 with this construction, it does not happen that ejection marks are left on the molding through the ejection.

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) In general, this type of injection molding machine uses a repulsive radial magnetic field mold so that magnetic flux passes radially from the inside of the cavity for the ring-shaped molded product when magnetic force is applied.

In order to narrow and guide the magnetic flux from the fixed 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, so conventionally, a small diameter pin or a stripper plate has been used as the ejector pin.

However, when using a small-diameter ejector pin, a return pin is required, making the ejector mechanism thicker, and it is not easy to select the material for the return pin, and there is no need to avoid the inconvenience of leaving pin marks on the side of the molded product after the mold is released. There wasn't.

On the other hand, when using a stripper plate, the ejector mechanism becomes large, so the magnetic path inside the mold is narrowed, and the air gap between the mold mounting plate and the mold 1jfl becomes large.
However, the inconvenience of deterioration in magnetic efficiency could not be avoided.

(Object of the Invention) The present invention has been 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 movably inserts an ejector sleeve, one end of which is fixed to an ejector plate, into the movable side of the magnetic field mold 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, and a core pin for molding the inner peripheral surface of the molded product made of the magnetic material is passed through the inside of the ejector sleeve to form the movable side. It is characterized by being fixed to the mold mounting plate.

(Example) Hereinafter, one embodiment 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.

Reference numeral 5 denotes a movable platen made of a magnetic material; 1 is fitted into a tie bar 6 made of a magnetic material by a mold clamping device (not shown);
゛It can move 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, and the outer peripheries of these molds 7 and 8 are is equipped with an electromagnetic coil 9.

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.

Reference numeral 11 denotes an ejector sleeve, which has its tip facing the cavity 10 and is concentric with the cavity 10, and is attached to the movable side molds 7 and 8.
The ejector plate 12 is movably inserted into the ejector plate 12 .
The proximal end is fixed to , and is projected through the nitrogen ejector 14 by an ejector cylinder 13 .

This ejector sleeve 11 has an outer diameter slightly larger than the molding surface on the outer peripheral surface of the molded product of the cavity 10, and an inner diameter that is approximately the same as the molding surface on the inner peripheral surface of the molded product.

The tip surface is used as the side surface for molding the molded product. Further, the cavity-side distal end of the ejector sleeve 11 is made of a non-magnetic material, and the proximal end is made of a magnetic material. The boundary 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 magnetic material.

Reference numeral 15 denotes a core pin for molding the inner circumferential surface of the 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. This radial yoke 17 is formed in a plate shape so as to be sandwiched between the fixed side mold 3, the movable side mold 8, and the ejector sleeve 11 during mold clamping, and the electromagnetic coil 4, A hole 18 for forming the outer peripheral surface of the molded product is provided at a position offset from the center of the molded product.

Therefore, the cavity 10 is used as the stationary side mold 2 during mold clamping.
, 3, an ejector sleeve 11, 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. 22 is a plasticizing device, and sprue 19. The magnetic material can be injected and filled into the cavity 10 via the runner 20 and the side gate 2I.

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

(Operation) When the electromagnetic coil 4°9 is energized to generate magnetic force in the opposite direction, the magnetic flux flows in the opposite direction through the fixed platen 1, mold 2, movable platen 5, and mold 7, as shown in Figure 1. After that, both magnetic fluxes are connected to the movable core pin 15 inside the cavity 10.
0', both of them pass through the cavity 10 radially, 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, the ejector sleeve 11 is swept with a non-magnetic material and a magnetic material, and the boundary surface thereof is narrowed to a shape that is continuous with the mating surface of the movable mold 7.8.
Since the core pin 15 made of a magnetic material is passed through the ejector sleeve 11, the flow of magnetic flux is caused by the ejector mechanism 1.
The magnetic flux is efficiently guided to the inside of the cavity 10 without being hindered by the elements 1 to 14. Therefore, cavity 10
Since the magnetic force of the magnetic flux φ along the radial direction is uniformly applied to the ferromagnetic particles in the magnetic material filled in the cavity 10, the crystal axes of the ferromagnetic particles in the magnetic material filled in the cavity 10 are aligned radially along the magnetic flux. The molded product is efficiently oriented and solidified while maintaining its radial orientation, and after opening the mold,
It is projected by the ejector sleeve 11. At this time, since the movable side side surface of the molded product is formed by the ejector sleeve 11 which is thicker and compliant with this, 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 narrow and guide magnetic flux from the movable platen side to the inside of the cavity together with the movable side mold, and inside the ejector sleeve. Since a core pin made of magnetic material is passed through the core pin, the magnetic flux can be guided inside the cavity efficiently, and the ejector sleeve can also be used as a return pin, simplifying and downsizing the ejector mechanism, improving magnetic efficiency. Improvements can definitely be made. Further, since ejection is performed by the ejector sleeve forming the side surface of the molded product, it is easy to release the mold, and the molded product does not have any ejection marks, making it possible to improve the quality of the molded product.

[Brief explanation of the drawing]

FIG. 1 is a plan sectional view showing an 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 view of a core pin in the mold. 2.3, 7.8... Mold, 1o... Cavity 11... Ejector sleeve, 15... Core pin 16... Mold mounting plate, 17... Radial yoke.

Claims (1)

[Claims] A repulsive radial magnetic field mold is provided that allows magnetic flux to pass radially from the inside into a cavity for a ring-shaped molded product by applying magnetic force, and a magnetic material that guides magnetic flux from the fixed platen side and the movable platen side to the inside of the cavity is provided. 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 having one end fixed to an ejector plate is movably inserted on the movable side of the magnetic field mold 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, and a core pin for molding the inner peripheral surface of the molded product made of the magnetic material is passed through the ejector sleeve and attached to the movable side metal. A plastic magnet injection molding machine characterized by being fixed to a mold mounting plate.