JPH09239786A - Mold for resin mold rotor and resin mold rotor molding thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of appearance inferiority in a weld line part by effectively allowing the air in a cavity or the gas due to a molten resin therein to escape out of the cavity and releasing the internal stress of a middle flange part. SOLUTION: In a mold for the injection molding of a resin mold rotor 63 having a shaft arranged to the center thereof and constituted so that the boss part 65 around the shaft and an outer peripheral cylindrical part 66 are connected by a disc-shaped middle flange part 67 and a thick-walled part 67a and a thin-walled part 67b are provided to the middle flange part 67, an air vent 3 consisting of a hole 4 bored in an axial direction so as to be opened to a cavity at one end thereof and the metal pin 5 inserted into the hole 4 so as to provide a predetermined gap with respect to the hole 4 is arranged to a mold core part 2. The metal pin 5 is arranged to the mold core part 2 so as to protrude into the cavity. The air vent 3 or the metal pin 5 is provided, for example, to the weld line part of the thick-walled part 67a of the middle flange part 67.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for a resin mold rotor used for, for example, a stepping motor, and a resin mold rotor molded with this die.

[0002]

2. Description of the Related Art Generally, a stepping motor used for a power unit of an office automation equipment or the like is constructed as shown in FIG. 9, for example. That is, the stepping motor 50 is
It has a stator 51 and a rotor 52 supported by the stator 51. The stator 51 includes two yoke units 5
3, 54 and bearing support plates 55, 5 fixed to the side surfaces thereof
6 and bearings 57 and 58 attached to the bearing support plates 55 and 56. Further, the yoke units 53 and 54 have an inner yoke 59 and an outer yoke 60, respectively.
It is formed by sandwiching the exciting coil 61 between them.

On the other hand, as the rotor 52, for example, FIG.
A resin mold rotor 63 having the shape shown in is used. The resin mold rotor 63 includes an output shaft 64 rotatably supported by bearings 57 and 58, a boss portion 65 formed around the output shaft 64, an outer peripheral cylindrical portion 66 on which magnetic poles are formed, and a boss. It has a disk-shaped middle collar portion 67 that connects the portion 65 and the outer peripheral cylindrical portion 66. The middle brim portion 67 has a thick wall portion 67a formed on the boss portion 65 side and a ring-shaped thin wall portion 67b formed on the outer peripheral cylindrical portion 66 side.

The resin mold rotor 63 is
Conventionally, it is molded by a molding die shown in FIG.
In this molding die K, three gates G (see FIG. 12) are provided at equal positions in the circumferential direction at positions corresponding to the middle flange portion 67, and the output shaft 64 is inserted into the cavity Y. In this state, from the gate G to the cavity Y of the molding die K
The resin mold rotor 63 shown in FIG. 12 is molded by injecting the resin P into the inside. An air vent V is provided on the resin injection side of the output shaft 64 for discharging the air existing in the cavity Y to the outside when the resin is injected.

[0005]

However, in this molding die K, the air vent V provided on the resin injection side of the output shaft 64 is different from the resin injection direction by 180 degrees, so that the resin P has a cavity Y. When injected into the resin mold rotor 6, air cannot be completely removed from the air vent V.
There is a case where it is caught in the middle brim portion 67 of No. 3.

Then, the air is driven into the weld line portion, and the strength of the weld line portion of the resin mold rotor 63 is lowered, and as shown in FIG. 11, inside the thick portion 67a of the middle flange portion 67 and the boss portion. There are problems that a nest S may be formed in the inner wall 65, a recess Q may be formed on the back surface of the middle brim portion 67, or a crack R1 may be formed in the weld line portion.

Further, in order to improve the roundness and strength of the outer peripheral cylindrical portion 66 of the resin mold rotor 63, since the thick portion 67a and the thin portion 67b are provided in the middle brim portion 67, the middle brim portion 67 is provided.
Where the wall thickness becomes uneven, the thick wall portion 6 of the middle brim portion 67
Air or resin molten gas in the cavity is accumulated in the weld line portion of 7a, the strength of the weld line portion is reduced, and a radial crack R2 is formed in the boundary portion between the boss portion 65 and the middle flange portion 67 (see FIG. 12). ) May occur.

Further, the resin P is the thick portion 67 of the middle brim portion 67.
Since it spreads in a ring shape from a to the thin portion 67b,
When the strength of the resin P is weak due to variations in molding conditions, stress easily accumulates in the thick portion 67a of No. 7, and circumferential cracks R3 (see FIG. 12) occur in the weld line portion due to internal stress after shrinkage of the molded product. There was also a problem that there were cases.

The present invention has been made in view of the above circumstances, and an object thereof is to effectively escape the air in the cavity and the gas due to the molten resin to the outside of the cavity and release the internal stress of the middle flange portion. Accordingly, it is an object of the present invention to provide a molding die for a resin mold rotor and a resin molding rotor molded by this mold, which can prevent the appearance of a poor appearance in the weld line portion.

[0010]

In order to achieve the above object, a molding die for a resin-molded rotor according to claim 1,
A molding die for injection-molding a resin-molded rotor having a shaft disposed in the center, the boss portion around the shaft and the outer peripheral cylindrical portion are connected by a disk-shaped middle flange portion, and the middle flange portion has a thick portion and a thin portion. In the mold, an air vent having a hole axially bored so that one end is open to the cavity side and a metal pin inserted into the hole with a predetermined gap from the hole are provided in the mold core portion. It is characterized by

According to this molding die for the resin mold rotor, when the resin is injected from the gate into the cavity, the air generated in the cavity or the molten resin is air vent provided in the die core portion. Escape to the outside of the cavity from the gap between the hole and the metal pin. As a result, the formation of cavities, dents, and cracks due to the entrainment of gas and air in the resin mold rotor is prevented.

Further, the molding die according to claim 2 is characterized in that the air vent is arranged so as to be located at the weld line portion of the resin mold rotor, and the molding die according to claim 3 Is characterized in that the air vent is arranged so as to be located in the middle flange portion of the resin mold rotor. According to these molding dies, the strength of the middle brim thick portion that becomes the weld line portion of the resin mold rotor is improved, and the occurrence of cracks or the like in the weld line portion is prevented.

Further, the molding die according to claim 4 is characterized in that the length of the metal pin of the air vent is such that it projects into the cavity from the end face of the mold core portion. According to this, the stress in the middle flange portion of the resin-molded rotor can be released by the metal pin, and the occurrence of cracks or the like in the weld line portion can be prevented.

Further, the molding die according to claim 5 is characterized in that the metal pin of the air vent moves up and down in synchronization with the eject mechanism of the injection molding machine. According to this molding die, the metal pin is By moving up and down, burrs and the like of resin adhering to the inner wall of the hole of the air vent through which the metal pin is inserted are automatically removed.

The molding die according to claim 6 is characterized in that the metal pin of the air vent is formed by a stepped pin and the hole is formed by a counterbore corresponding to the metal pin. The die prevents the metal pin from coming off the hole.

According to a seventh aspect of the present invention, there is provided a molding die for a resin mold rotor, wherein a shaft is arranged at a center, a boss portion around the shaft is connected to a peripheral cylindrical portion by a disc-shaped middle collar portion, and a middle collar is formed. In a molding die for injection-molding a resin-molded rotor having a thick portion and a thin portion in a portion, a metal pin is disposed in the die core portion so as to project in the axial direction from an end surface of the cavity side. To do.

According to this resin mold rotor molding die, the metal pin projects in the cavity in the axial direction, and the metal pin forms an axial hole in the thick part of the flange of the resin mold rotor. At the time of molding this hole, the stress in the middle flange portion of the resin mold rotor can be released, and cracks and the like of the resin mold rotor after molding can be prevented.

Further, the molding die according to claim 8 is characterized in that the metal pin is arranged so as to be positioned at the weld line portion of the resin mold rotor, and the molding die according to claim 9 is The metal pin is provided in the thick wall portion of the middle flange portion of the resin mold rotor. According to these molding dies, the stress in the thick portion of the middle flange, which is the weld line portion of the resin mold rotor, is released, and the occurrence of cracks or the like in the weld line portion is prevented.

According to a tenth aspect of the present invention, in the resin-molded rotor according to the tenth aspect, a shaft is arranged in the center, the boss portion around the shaft is connected to the outer peripheral cylindrical portion by the disk-shaped middle flange portion, and the middle flange portion is thick-walled. In a resin mold rotor having a hollow portion and a thin portion, a hole penetrating in the axial direction is formed in the weld line portion in the thick portion of the middle flange portion. According to this resin-molded rotor, when forming a hole in the thick portion of the middle collar portion, the stress in the middle collar portion is released, and the occurrence of cracks and the like in the weld line portion after molding is prevented.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 3 show a first embodiment of a molding die for a resin mold rotor according to the present invention, FIG. 1 is a sectional view of a main part thereof, FIG. 2 is an enlarged view of an A part of FIG.
FIG. 3 is a plan view of a resin-molded rotor molded by this molding die. In each of the following molding dies, the case of molding the resin mold rotor 63 having the shape shown in FIG. 10 will be described as an example, and the molding dies K of FIG.
The same parts as those of the above are denoted by the same reference numerals, and detailed description thereof will be omitted.

The molding die 1 of the first embodiment comprises a die core portion 2
An air vent 3 is arranged in the mold, and the air vent 3 has a hole 4 axially bored in the mold core portion 2 and a metal pin 5 inserted in the hole 4. The hole 4 is formed as a stepped hole (counterbore hole) having three hole portions that gradually increase in diameter from the upper portion to the lower portion, that is, a first hole portion 4a, a second hole portion 4b, and a third hole portion 4c. The upper end of the first hole 4a opens to the cavity Y side.

On the other hand, the metal pin 5 is formed by cutting a cylindrical metal rod so that the diameter increases stepwise from the upper part to the lower part, that is, the first pin part 5.
a, a second pin portion 5b, and a third pin portion 5c. The stepped shape of the metal pin 5 and the hole 4 prevents the metal pin 5 from coming out of the hole 4 toward the cavity Y.

The upper end of the metal pin 5 is usually the first.
The first pin portion 5a is located inside the cavity Y as indicated by the chain double-dashed line in FIG. 2 by being substantially aligned with the opening end of the hole 4a and rising in synchronization with the ejection mechanism (not shown) of the mold core portion 2. It is configured to project a predetermined length.

As shown in FIG. 3, the air vents 3 composed of the holes 4 and the metal pins 5 are provided at three positions equally divided in the circumferential direction, that is, at the substantially central portion between the adjacent gates G. Has been. The outer diameter of the first pin portion 5a of the metal pin 5 is set to, for example, 1 mm, and the gap 6 between the outer peripheral surface of the first pin portion 5a and the inner surface of the first hole portion 4a (see FIG. 2).
The dimension t1 of the reference) is, for example, 10 to 15 microns (μ
m).

The second pin portion 5b of the metal pin 5 and the second
The size t2 (see FIG. 2) of the gap 7 between the holes 4b is 100.
The thickness is set to about micron, and further, the thick portion 67a of the middle brim portion 67 of the resin mold rotor 63 (hereinafter, the middle brim thick portion 6
7a) has a wall thickness h1 (see FIG. 1) of 2.8 mm,
The shape of the cavity Y is set such that the thickness h2 (see FIG. 1) of the thin wall portion 67b of the middle brim portion 67 (hereinafter referred to as the middle brim thin portion 67b) is 2.0 mm.

According to the molding die 1 of the first embodiment, when the resin P (see FIG. 1) is injected into the cavity Y, first, the boss portion 65, the middle brim thin portion 67b, the outer peripheral cylindrical portion 66, The resin P is filled in the order of the middle brim thick part 67a, and the middle brim thin part 67a is filled.
The air in the cavity Y that cannot pass through b flows as shown by the solid arrow in FIG. 3 and is collected in the weld line portion of the middle flange thick portion 67a.

The collected air is collected by the metal pins 5 of the three air vents 3 provided in the mold core 2.
From the gaps 6 and 7 of the holes 4 and the like, they are expelled to the outside of the cavity Y as indicated by arrows in FIG. At this time, by setting the dimension t1 of the gap 6 as described above, the resin P does not flow out from the gap 6 and the resin mold having the shape shown in FIG. The rotor 63 is molded.

Thus, the molding die 1 according to the first embodiment described above.
According to this, in addition to the conventional air vent V, since the air vent 3 is separately provided in the weld line portion of the middle brim thick portion 67a between the adjacent gates G, it is present in the cavity Y without coming off from the air vent V. The air that is generated and the air that is trapped in the molten resin P can escape from the air vent 3 to the outside of the cavity Y. As a result, there is no generation of cavities in the middle brim thick portion 67a and the boss portion 65 due to air, and no dents in the back surface of the middle brim thick portion 67a, and the weld line portion of the resin mold rotor 63. The molding strength is improved, and the occurrence of cracks at this position is prevented.

Further, by appropriately setting the dimension t1 of the gap 6 between the first pin portion 5a and the first hole portion 4a of the air vent 3 according to the characteristics of the resin P, only the air can escape from the gap 6. It is possible to prevent the resin P from flowing out from the gap 6. Further, since the metal pin 5 is moved up and down in synchronization with the ejecting mechanism of the mold core portion 2, the burr U of the resin P attached to the inner wall of the first hole portion 4a (FIG. (See) can be automatically removed, and maintenance of the molding die 1 becomes easy.

Since the hole 4 and the metal pin 5 are formed in a stepped shape, the cavity Y from the hole 4 of the metal pin 5 is formed.
It is possible to reliably prevent slipping out to the side. Although the resin mold rotor 63 molded by the molding die 1 of the first embodiment does not have a large change in appearance structure as compared with the conventional one, as shown in the experimental results described later, the appearance defect is significantly large. Will decrease.

FIGS. 4 to 6 show a second embodiment of a molding die for a resin mold rotor according to the present invention. FIG. 4 is a sectional view of an essential part of the molding die, and FIG. 5 is a resin molded by this molding die. FIG. 6 is a plan view of the mold rotor, and FIG. 6 is a sectional view taken along line BB of FIG. The characteristic of the molding die 11 of this second embodiment is that
In the embodiment, the length of the metal pin is increased so that the upper end of the metal pin projects into the cavity Y during molding.

That is, the metal pin 15 is inserted into the hole 14 of the air vent 13 provided in the mold core portion 12,
The first pin portion 15a of the metal pin 15 extends upward and protrudes from the end surface of the mold core portion 12 on the cavity Y side for a predetermined length (for example, about 2.75 mm). Also,
The third hole portion 14c of the hole 14 is opened, for example, on the lower surface side of the mold core portion 12 in order to facilitate the discharge of the air in the cavity Y. The other parts of the configuration are similar to those of the first embodiment, and therefore corresponding parts are designated by corresponding reference numerals and detailed description thereof is omitted.

According to this molding die 11, the metal pin 15
The gaps 16 and 17 between the holes 14 and the holes 14 allow the air in the cavity Y to flow as shown by the solid arrows in FIGS. 4 and 5 and escape to the outside of the cavity Y, and the same effect as the first embodiment can be obtained. can get. Moreover, the through hole 20 can be formed in the middle flange portion 67 of the resin mold rotor 63 by the upper portion of the first pin portion 15a of the metal pin 15, and the stress inside the middle flange portion 67 can be released. Can also be obtained.

That is, the first pin portion 15a is provided at the weld line portion of the thick wall portion 67a of the middle brim of the resin mold rotor 63.
When the resin mold rotor 63 is molded, the stress in the middle collar portion 67 is divided and the stress concentrated in the weld line portion is released when the resin mold rotor 63 is molded. The release of the stress prevents the occurrence of cracks in the weld line portion of the resin mold rotor 63 in the circumferential direction or the radial direction due to stress concentration.

7 and 8 show a third embodiment of a molding die for a resin mold rotor according to the present invention. FIG. 7 is a cross-sectional view of an essential part thereof, and FIG. 8 is a resin molded by this molding die. It is a top view of a mold rotor. The molding die 21 of the third embodiment is erected on the die core portion 22 at a position corresponding to the middle brim thick portion 67a of the resin mold rotor 63 so that the metal pin 23 projects in the cavity Y in the axial direction. It is set up.

The metal pin 23 is erected by press-fitting into the three holes 25 (see FIG. 7) formed at the substantially center position between the gates G on the end surface of the mold core portion 22 on the cavity Y side. The metal pin 23 has the same function as the first pin portion 15a of the metal pin 15 of the second embodiment. The outer diameter of the metal pin 23 is set to, for example, about 1.2 mm, and the protruding dimension from the end surface of the mold core portion 22 is set to about 2.75 mm.

According to this molding die 21, by injecting the resin P from the gate G, the resin mold rotor 63 having the through hole 20 in the axial direction in the middle brim thick portion 67a is injected as in the second embodiment. Is molded. During this molding,
As indicated by the dotted arrow, the stress in the middle brim portion 67 of the resin mold rotor 63 contracts, and the stress concentrated in the weld line portion of the middle brim portion 67 is released. This prevents cracks in the weld line portion of the resin mold rotor 63 in the circumferential direction and the radial direction due to stress concentration.

Next, the experimental results of actually molding the resin mold rotor 63 using the molding dies of the above-mentioned respective examples will be described. The following Table 2 is a list showing the results of this experiment, and this experiment was carried out by using as the resin P, a nylon 12-based ferrite magnet powder-containing plastic magnet having the characteristics shown in Table 1 below.

[0039]

[Table 1]

[0040]

[Table 2]

From the results, in the case of the molding die 1 of the first embodiment, the defective appearance rate such as dents and cracks of the resin mold rotor 63 after molding is reduced by 23% as compared with the conventional example, and the thermal shock test. The occurrence rate of cracks after the environmental test such as 5% was also reduced, and it became clear that the appearance defect was significantly reduced.

In the case of the molding die 21 of the third embodiment,
The resin-molded rotor is strong in environmental tests, that is, durable because the appearance defect rate after molding is reduced by 16% compared to the conventional example, cracks do not occur even after environmental tests, and internal stress is released. It was revealed that 63 was obtained. By the way, although the experimental result by the molding die 11 of the second embodiment is not described in Table 2, the result equivalent to that of the first embodiment and the third embodiment is obtained also in this second embodiment. It has been confirmed.

The shape of the resin mold rotor 63 (the shape of the cavity Y) in each of the above embodiments is merely an example, and the resin mold rotor of any shape having the thick wall portion 67a and the thin wall portion 67b in the middle brim portion 67 is used. 67 can be applied. Further, the structure of the molding die such as the position and the number of the gates G is also an example, and molding dies having various forms and structures can be used.

Furthermore, the air vents 3 and 13 and the metal pin 2
The number of 3 is also increased / decreased according to the number of gates G,
Further, the shapes of the holes 4, 14 of the air vents 3, 13 and the metal pins 5, 15 and the shape of the metal pins 23 are not limited to those in the above embodiments, and may be appropriately determined according to, for example, the characteristics of the resin used. It goes without saying that various changes such as setting can be made without departing from the scope of the present invention.

[0045]

As described above in detail, according to the molding die for the resin mold rotor of the present invention and the resin molding rotor molded by the molding die, the air vent consisting of the hole and the metal pin is formed in the die core portion. By arranging, even if the thickness of the middle flange of the resin mold rotor is set to be thick, the air in the cavity and the gas due to the molten resin can be effectively released to the outside of the cavity when the resin is filled. Further, by disposing a metal pin for stress relaxation in the mold core part and forming a hole in the middle flange part, the stress depending on the thick part and the thin part having different wall thicknesses of the resin mold rotor is released. be able to.

From the above, it is possible to prevent the occurrence of cracks in the weld line portion of the resin mold rotor, the formation of cavities in the middle flange portion and the boss portion, the formation of recesses in the middle flange portion, and the like. As a result, the moldability of the resin-molded rotor is improved, and at the same time, it is possible to obtain a resin-molded rotor of high quality and high reliability in which the defective appearance ratio is significantly reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a first embodiment of a molding die for a resin mold rotor according to the present invention.

FIG. 2 is an enlarged view of part A of FIG.

FIG. 3 is a plan view of a resin-molded rotor molded by this molding die.

FIG. 4 is a cross-sectional view of essential parts of a second embodiment of a molding die for a resin mold rotor according to the present invention.

FIG. 5 is a plan view of a resin-molded rotor molded by this molding die.

6 is a sectional view taken along line BB of FIG.

FIG. 7 is a cross-sectional view of an essential part of a third embodiment of a molding die for a resin mold rotor according to the present invention.

FIG. 8 is a plan view of a resin-molded rotor molded by this molding die.

FIG. 9 is a sectional view showing an example of a stepping motor.

FIG. 10 is a perspective view showing an example of the resin-molded rotor.

FIG. 11 is a sectional view of a main part of a conventional molding die for a resin mold rotor.

FIG. 12 is a plan view of a resin-molded rotor molded by this molding die.

[Explanation of symbols]

 1, 11, 21 ... Molds 2, 12, 22 ... Mold core parts 3, 13 ... Air vents 4, 14 ... Holes 5, 15 ...・ ・ Metal pin 6,16 ・ ・ ・ ・ ・ ・ Gap 7,17 ・ ・ ・ ・ Gap 20 ・ ・ ・ ・ ・ ・ Through hole 23 ・ ・ ・ ・ ・ ・ Metal pin 50 ・ ・ ・・ ・ ・ ・ ・ Stepping motor 63 ・ ・ ・ ・ ・ ・ Resin mold rotor 64 ・ ・ ・ ・ ・ ・ Output shaft 65 ・ ・ ・ ・ ・ ・ Boss 66 ・ ・ ・Outer cylindrical portion 67 ・ ・ ・ ・ ・ ・ ・ ・ Middle brim portion 67a ・ ・ ・ ・ ・ ・ Thick wall portion 67b ・ ・ ・ ・ ・ ・ Thin wall portion Y ・ ・ ・ ・ ・ ・ ・ Cavity G ・ ・・ ・ ・ ・ Gate P ・ ・ ・ ・ ・ ・ ・ Resin

Claims (10)

[Claims] 1. A resin-molded rotor having a shaft at its center, a boss portion around the shaft and an outer peripheral cylindrical portion are connected by a disk-shaped middle flange portion, and the middle flange portion has a thick portion and a thin portion. In a molding die for injection-molding, a hole formed in the mold core portion in the axial direction so that one end is open to the cavity side, and a metal pin inserted in the hole with a predetermined gap from the hole. A molding die for a resin mold rotor, characterized in that an air vent having the above is arranged. 2. The molding die for a resin mold rotor according to claim 1, wherein the air vent is arranged so as to be located at a weld line portion of the resin mold rotor. 3. The molding die for a resin mold rotor according to claim 1, wherein the air vent is arranged so as to be located at a central flange portion of the resin mold rotor. 4. The metal pin of the air vent has a length that protrudes into the cavity from the end surface of the mold core portion, according to any one of claims 1 to 3. Mold for resin mold rotor. 5. The molding die for a resin mold rotor according to claim 1, wherein the metal pin of the air vent moves up and down in synchronization with an eject mechanism of an injection molding machine. Type. 6. The air vent metal pin is formed of a stepped pin, and the hole is formed of a counterbore corresponding to the metal pin. A molding die for a resin-molded rotor according to item. 7. A resin-molded rotor having a shaft at its center, a boss portion around the shaft and an outer peripheral cylindrical portion are connected by a disk-shaped middle flange portion, and the middle flange portion has a thick portion and a thin portion. In a molding die for injection-molding, a molding die for a resin mold rotor, characterized in that a metal pin is axially protruded from the cavity-side end surface of the molding core portion. 8. The molding die for a resin mold rotor according to claim 7, wherein the metal pin is arranged so as to be located at a weld line portion of the resin mold rotor. 9. The metal pin is arranged in a thick wall portion of a middle flange portion of the resin molded rotor,
A molding die for a resin mold rotor according to claim 7 or 8. 10. A resin-molded rotor having a shaft at its center, a boss portion around the shaft and an outer peripheral cylindrical portion are connected by a disk-shaped middle flange portion, and the middle flange portion has a thick portion and a thin portion. The resin-molded rotor according to claim 1, wherein a hole penetrating in the axial direction is formed in the weld line portion at the thick portion of the middle flange portion.