JPS6144614A - Mold for injection molding resin magnet - Google Patents

Abstract

PURPOSE:To cause the magnetic characteristics of a product to be sufficient by providing the exciting coils giving the magnetic fields with mutually opposite directions to the upper and lower yorks connected to an inner pole, and so on. CONSTITUTION:At the mold for injection molding a plurality of ring shape resin magnets with radical and anisotropic properties, the exciting coil 40 for magnetizing the inner pole 12 and the outer pole 10 defining a ring like space 50, is arranged at the outer periphery of the mold. The exciting coils 40, 40' giving the magnetic fields with mutually opposite directions to the upper and lower yorks 32, 32' connected, as a magnetic circuit, respectively to the upper and lower part of the inner pole 12, are provided. The exciting coils 60, 60' generating the magnetic fields with the directions opposite to at least one of the exciting coil 40, 40', are arranged onto the mold of the portion becoming almost symmetrical axis of a plurality of ring like spaces 50, and the yorks 62, 62' connected to at least one of the upper and lower yorks 32, 32', as a magnetic circuit, are provided in the exciting coils 60, 60'.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold used when injection molding a plurality of resin magnets having radial anisotropy.

(Prior art) A method of imparting magnetic anisotropy in the radial direction to resin magnets by injection molding is to apply ferromagnetic The basic method is to inject a resin mixed with substances into a cavity. When molding ring-shaped resin magnet products that can be given radial magnetic anisotropy, it is not always necessary to design the magnetic circuit of the mold in such a way that the magnetic field is evenly applied to each product when making multiple pieces. Because it is not easy, it is difficult to obtain the desired magnetic anisotropy. On the other hand, in the case of one piece,
Although the magnetic properties were sufficient, it was disadvantageous in terms of productivity. Conventional radial anisotropy, a problem with multi-cavity resin magnet molds, is that the magnetic properties vary between individual products, and even within a single product, the strength of anisotropy varies depending on its position. In order to prevent the occurrence of the It was discovered in 1983 that the mold was configured to apply a magnetic field to the inner and outer poles.
It is described in the publication No.-7633.

According to such a mold configuration, since the inner pole is magnetized from only one direction, the total amount of magnetic flux applied to the inner pole is insufficient, resulting in a problem that the magnetic properties of the product are insufficient.

Furthermore, according to the mold configuration described in the above-mentioned Japanese Utility Model Publication No. 58-7633, the same number of outer poles as the number of products is required, so it is difficult to manufacture a multi-cavity mold of, for example, four or more. In this case, the number of man-hours for manufacturing the outer electrode increases, resulting in a significant disadvantage in terms of cost. Furthermore, when assembling the mold, it is necessary to arrange as many outer poles as the number of products concentrically with the inner pole, which increases the time and man-hours for assembling the mold.

(Problems to be Solved by the Invention) In a mold, an excitation coil is applied to the inner pole (core) and the cylindrical outer pole (mold) that constitute the ring-shaped mold space in one direction from the upper and lower sides of the mold. According to the conventional mold configuration configured to magnetize the inner and outer poles by applying a magnetic field to the inner and outer poles, the total amount of magnetic flux applied to the inner poles is insufficient, resulting in insufficient magnetic properties of the product. This was done in an attempt to solve the problem.

In order to solve the above problems, the present inventors manufactured a mold as schematically shown in FIG. 2 and performed injection molding of a resin magnet.

In FIG. 2, 10 is an outer pole, 12 is an inner pole, 21 is a movable yoke plate, 31 is a fixed yoke plate, 32 is a fixed yoke, 32' is a movable yoke, 35 is an injection hole, and 36 is a passage. , 40 , 40 ′ are exciting coils, and 50 is a ring-shaped space. The exciting coils 40 , 40 ′ generate magnetic fields H, H′ in opposite directions, respectively.
are applied to the inner pole 12 via the fixed yoke 32 and the movable yoke 32', respectively.

Note that the arrows in the figure indicate the direction of magnetization in each member that is a ferromagnetic material. In the mold configuration shown in FIG. 2,
Since magnetic fields were applied to the inner pole 12 from above and below, the total amount of magnetic flux applied to the inner pole increased.

However, as shown in the plan view of FIG.
The problem is that the flow of magnetic flux flowing out from the inner pole (core) located symmetrically to the injection hole 35 is disturbed, and the magnetic flux becomes an unrestrained value in the portion of the ring-shaped space 50 that faces the ring-shaped space 50 located symmetrically. was derived.

The present invention solves both of the above-mentioned problems.

(Means for Solving the Problems) The present invention provides a method for injection molding a plurality of ring-shaped resin magnets having radial anisotropy. In a mold that is magnetized by excitation coils arranged on the outer periphery of the mold, upper and lower yokes each connected to the upper and lower sides of the inner pole in a magnetic circuit manner are provided with excitation coils that apply a magnetic field with a reflective force of 1ii1 to each other, and a plurality of rings are provided. Another excitation coil that generates a magnetic field in the opposite direction to at least one of the excitation coils is disposed in a part of the mold that is approximately the axis of symmetry of the shaped space, and is connected to at least one of the upper and lower yokes in a magnetic circuit. The present invention is characterized in that a yoke is provided within the separate excitation coil.

(Function) Figures 1 (A) and 1 (B) are drawings showing an example of the mold according to the present invention, which correspond to Figures 2 and 3, respectively. The main difference from the figure is that another excitation coil 60 that generates a magnetic field in the opposite direction to the magnetic field H of the excitation coil 40 is provided at a portion of the four ring-shaped spaces 50 that is substantially symmetrical, and the excitation coil 60 The yoke 62 is disposed inside the yoke 62 and is connected to the fixed yoke vi31 in a magnetic circuit manner. By configuring the mold in this way, two ring-shaped spaces 50 located at axially symmetrical positions can be created.
At the intermediate position, the magnetic flux flows from the outer pole 10 to the fixed yoke plate 31 via the yoke 62, so that the radial magnetic flux flow is not disturbed at this intermediate position.

Note that in FIGS. 1A and 1B, the radial magnetic field is strengthened in the ring-shaped space 50 because the inner pole 12 is magnetized from both sides of the fixed yoke 32 and the movable yoke 32'.

(Means for solving the problem - Part 2) In a mold for injection molding a plurality of ring-shaped resin magnets having radial anisotropy, a ring-shaped space into which the resin is press-fitted is formed. If the poles and outer poles are each composed of a ferromagnetic material corresponding to the number of products and a ferromagnetic continuum that is shared by each product, there is no need to use the same number of outer poles as the number of products in a multi-cavity mold. The magnetic circuit is simplified because the outer pole acts as a single magnetic body with north or south pole. Moreover, if a predetermined number of holes are formed between the products in the ferromagnetic material serving as the outer pole in an appropriate arrangement in terms of the magnetic circuit, the magnetic flux density can be easily made more uniform within the mold.

(Example) An example of the present invention is shown in FIGS. 4(A) and 4(A) of the attached drawings.
B) Explain based on the diagram. This example shows a multi-cavity mold for molding eight ring-shaped resin magnets.

As shown in the drawings, an outer pole 10 having cylindrical holes substantially close to the outer circumference of the cavity, which are arranged on the same circumference at equal intervals radially with respect to the mold center axis XX, is shown in FIG. 4(B). It consists of one continuous ferromagnetic material. Here, "continuous" means continuous in terms of magnetic circuit, and includes not only a completely integrated structure but also a continuous structure in which several ferromagnetic materials are integrated by appropriate bonding means. Eight cylindrical inner poles 12 are held coaxially with the pole 10 at a certain distance from the inner circumferential surface thereof, and in such a manner that their end faces are in the same plane as the end face of the outer pole 10, in predetermined mutual positions as will be described later. .

The mold according to the embodiment of the present invention includes a movable mold 20, a fixed mold 30, and an excitation coil 40 disposed around the outer periphery of these molds.
, 40'.

The movable mold 20 supports a movable yoke 32' by a movable yoke plate 31 and a hollow box-shaped magnetic bottom plate member 29 fixed to its inner surface, and further supports the inner pole 10 on its upper surface.

Nonmagnetic backup members 25 and 25' are provided to surround the movable yoke 32' of the movable mold 20 to close the bottom of the ring-shaped space 50 and close the magnetic circuit between the inner pole 12 and the outer pole 10. It's blocked.

Further, in the hollow part of the movable side yoke 22, extrusion bottle stands 26, 26' are accommodated so as to be movable in the direction away from the movable side yoke plate 21, and several extrusion pins 27 are attached to this. , 27' are advanced into corresponding holes drilled in the wall surface of the movable side yoke 22 and the magnetic bottom plate members 29, 29' by an extrusion drive means (not shown). Magnetic bottom plate members 29 , 29
The movable yoke 32 placed thereon is configured such that its outer diameter substantially matches the outer diameter of the inner pole 12. With this configuration, 29.29', 32'
, 12 is formed.

In the fixed side mold 30, eight approximately cylindrical fixed side yokes 32 are arranged to face a fixed side yoke plate 31 having almost the same shape as the movable side yoke plate 21.
is further arranged to face the inner pole 12, and the end face of the fixed side yoke 32 is made to correspond to the end face of the inner pole 12, and a magnetic field is formed between the outer surface and the inner surface of the fixed side yoke plate 31. The inner pole 12 and the outer pole 10 are firmly fixed via the fixed side yoke plate 31 by a non-magnetic fixed backup member 33 which is connected in a circuit and whose outer surface is a flat surface that matches the end surface of the fixed side yoke 32. ing.

In the above-mentioned member, in order to generate radial anisotropy, the inner pole 12 and the outer pole 10 must be ferromagnetic, and if the backup member is ferromagnetic, the radial magnetic field will be disturbed. This is not desirable because

Further, the injection port 35 formed at the center of the fixed side yoke plate 31 connects to the passage 36, the outer pole 10 and the fixed backup member 33.
It communicates with each ring-shaped space 50 via a runner 28 between them.

The excitation coils 40 and 40' have a shape that completely surrounds the outer peripheries of the movable mold 20 and the fixed mold 30 when the movable mold 20 and the fixed mold 30 are connected in a manner suitable for resin injection. Coils 41, 41' having
It consists of a cover 42 that covers the outer peripheral surface.

Note that the cover 42 is preferably made of a ferromagnetic material.

According to the present invention, additional excitation coils 60 and 60' are provided concentrically with respect to the mold center axis XX, which is the axis of symmetry of the eight ring-shaped spaces 50.

Inside this additional excitation coil 60, a yoke 62 made of a cylindrical ferromagnetic material is in contact with the fixed side yoke 31 and has an outer pole 1.
A yoke 62' made of a cylindrical ferromagnetic material is provided inside the other additional excitation coil 60' so as to be in contact with the outer pole 10 and the movable side fixed plate 2.
It is provided so as to be in contact with 1. These yokes 62
, 62', the magnetic field of the additional excitation coils 60, 60' causes the magnetic circuit formed by the excitation coils 40, 40
' flows in the opposite direction.

FIG. 5 shows the magnetic circuit of the mold shown in FIG. 4(A).

As can be seen from FIG. 5, the magnetic flux of the outer pole 10 passes through the yokes 62 and 62', and the strength of the magnetic field of the movable yoke plate 21 and the fixed excitation coils 60 and 60' is controlled by the magnetic flux of the excitation coils 40 and 40'. It is desirable that the strength be equal to or higher than that of the magnetic field.

Furthermore, a mold in which more than two ring-shaped spaces are arranged in a straight line is also conceivable. In this case, it is desirable to provide four additional excitation coils at approximately axially symmetrical positions in each adjacent ring-shaped space.

(Effects) According to the present invention, in a multi-cavity mold in which the inner pole is magnetized from both sides, magnetic flux easily and regularly flows out of the mold in the middle of the ring-shaped space forming portion of the continuous outer pole. Since the ζ resin magnet is released, the radial anisotropy of the ζ resin magnet is homogenized. In particular, with a mold that magnetizes the inner pole from one side than the above-mentioned type, the total amount of magnetic flux applied to the inner pole is determined by the area of the fixed plate side yoke, and this volume is the area of the outer pole. If it is smaller, there is a problem that the strength of the radial magnetic field in the ring-shaped space is limited by the inner pole (fixed plate side yoke), but according to the present invention, there is no such limitation, and the radial magnetic field is reduced as described above. Since the directional anisotropy is homogenized, a mold that is extremely advantageous for molding multiple pieces is provided.

Furthermore, according to a preferred embodiment of the present invention, when a predetermined number of perforations are provided in one ferromagnetic material, the ferromagnetic material for the outer pole can be considered as one magnetic pole, that is, the outer pole is composed only of the ferromagnetic material. Therefore, by securing only the area of the outer pole necessary for the magnetic circuit, it is possible to manufacture any number of products, for example, eight or more. On the other hand, in a method in which independent outer poles are installed individually in a non-magnetic material, if the number of products is large, the area of the non-magnetic part is required in addition to the outer poles required for the magnetic circuit. A larger mold is required compared to In particular, if a large number of outer poles are forced to be placed in a narrow space, the magnetic resistance at that part will increase, making it impossible to obtain an optimal state for the magnetic circuit, and the strength of the magnetic field in the ring-shaped space will decrease. A problem occurs.

In this respect, since the outer pole in the present invention is a ferromagnetic continuum, it has the advantage that the area of the mold can be reduced.

[Brief explanation of the drawing]

Figure 1 (A) is a sectional view of a mold according to an embodiment of the present invention, Figure 1 (B) is the mold ring-shaped space in Figure 1 (A), Figures 2 and 3 are respectively A cross-sectional view and a plan view showing the magnetic circuit of the mold used by the present inventors in the experiment, FIG. 4(A) is a cross-sectional view of the mold according to the embodiment of the present invention, and FIG. 4(B) is the 4(A) is a plan view seen from the outer pole surface, and FIG. 5 is a drawing showing the magnetic circuit of the mold shown in FIG. 4(A). 10...outer pole, 12...inner pole, 20...
・Movable side mold, 21...Movable side yoke plate, 22・
...Movable side yoke, 26...Extrusion pin stand, 30.
...Fixed side mold, 31...Fixed side yoke plate, 32
...Fixed side yoke, 50...Ring-shaped space, 6
0...Additional excitation coil. Figure 1A Figure 18 Figure 2 Figure 3 Figure 4B Figure 1a) '62'

Claims (1)

[Claims] 1. A ring-shaped space (50 mm
) in which an inner pole (12) and an outer pole (10) are magnetized by an excitation coil (40) disposed around the outer periphery of the mold. The connected upper and lower yokes (32, 32') are provided with excitation coils (40, 40') that apply magnetic fields in opposite directions, and the molds are provided with excitation coils (40, 40') that apply magnetic fields in mutually opposite directions. , another excitation coil (60, 60') that generates a magnetic field in the opposite direction to at least one of the excitation coils (40, 40'), and the upper and lower yokes (32
, 32') connected in a magnetic circuit to at least one of the excitation coils (60, 62').
A mold for injection molding a resin magnet, characterized in that the mold is provided in a mold for injection molding of a resin magnet.