JP2002254474A - Method and mold for insert molding of fragile ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a mold for accurately injection-molding a fragile ring by injection pressure without damaging the same in a method for the insert molding of a resin on the inner surface side of the fragile ring like a ferrite sintered magnet ring. SOLUTION: A chuck 2 expanded and contracted equally in a radial direction is provided to a first mold 3 and the fragile ring 1 is inserted in the chuck 2. A clamping member 5 is provided to a second mold 4 and a molten plastic material is injection-molded in the fragile ring in a such state that the chuck 2 is clamped and held by the clamping member 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a mold for producing an insert molded product in which a brittle ring mainly composed of a cylindrical ferrite sintered magnet ring is located on the outer periphery and a plastic resin is molded inside the brittle ring. About.

[0002]

2. Description of the Related Art A ferrite sintered magnet ring is often inserted into a mold for injection molding and a plastic material is molded therein. FIG. 8 shows an example in which a plastic material is insert-molded inside a brittle ring 1 having a diameter of about 1 cm, and a gear portion 36 is provided on the outer periphery of a shaft portion. After the insert molding, the ferrite sintered magnet ring is magnetized to form a rotor such as a motor or an instrument. Such a ferrite sintered magnet ring has
It has the following features. The ferrite sintered magnet ring is relatively strong against an external force from the outer peripheral direction toward the center in the radial direction. However, it is easily damaged by an external force radially outward from the center of the ring. In addition, since it is a sintered magnet, the dimensional accuracy of the product is generally low, and its tolerance is about 0.1 mm.

[0003] Insert molding of such a ferrite sintered magnet which has a relatively large tolerance and is easily damaged by an external force from the center to the outside has conventionally been performed as follows. A ferrite sintered magnet ring is mounted in the cavity of the mold, and the inside thereof is filled with a molten plastic material. At this time, the filling of the resin is stopped just before the resin material is completely filled, so that a large injection pressure is not applied to the sintered magnet. Then, the product was taken out, and all cracks and the like were inspected. The reason why the injection pressure is not completely applied is that the sintered magnet ring cannot withstand the injection pressure from the inside and breaks. In particular, since the tolerance of the gripping sintered magnet is relatively large, it is difficult to completely align the outer periphery of the sintered magnet with the fitting recess of the mold. Has a slight gap. Then, an injection pressure is applied from the inside in a state in which the outer periphery is not gripped, and it is extremely easily broken. Moreover,
This is because, even if there is no gap between the sintered magnet ring and the mold, the sintered magnet ring may be damaged by the internal pressure of the injection molding.

[0004]

When a brittle ring such as a sintered ferrite magnet ring is insert-molded by a conventional method, if the resin material is not completely filled, the molding accuracy becomes poor. With it
Since the molding becomes unstable, it is necessary to inspect all the insert molded products. Accordingly, it is an object of the present invention to provide a product having high molding accuracy by completely filling a brittle ring with a molten resin, and to provide an insert molding method in which a brittle ring does not crack and a mold therefor.

[0005]

According to the present invention, there is provided a brittle ring made of a brittle material formed in an annular shape.
(1) In an insert molding method of a brittle ring in which at least a part of its outer periphery is exposed to the outer surface after molding, and a molten plastic material is injection-molded on its inner peripheral side, a chuck that is uniformly expanded and contracted in the radial direction is used. (2) is placed in a molding die, and the brittle ring is placed in the chuck (2).
Inserting (1) and applying external force to the chuck (2) in the direction of the center so that the brittle ring (1) is not damaged during injection, while holding the outer circumference of the brittle ring (1) fastened, This is an insert molding method for a brittle ring in which a molten plastic material is injection-molded on the inner peripheral side of the ring (1).

According to a second aspect of the present invention, there is provided a first mold (3) and a second mold (4) for molding which are arranged so as to be openable and closable so as to be in contact with and separated from each other. Chuck for holding brittle ring (2) arranged in (3) and uniformly expanded and contracted in the radial direction
And a fastening member (5) provided on the second mold (4) or the first mold (3), for pressing the outer periphery of the chuck (2) and holding the outer periphery radially inward. A mold having a configuration in which a molten plastic material is injection-molded on the inner surface side of the brittle ring (1) in a state in which a circular annular brittle ring (1) is fastened and held to the chuck (2). It is.

According to a third aspect of the present invention, in the second aspect, the chuck (2) comprises a collet chuck having a tapered frustoconical portion (7) at a tip end in the axial direction. A chuck release ring that springs outward in the radial direction
(8) is arranged, and a fastening member (5) having a cylindrical concave portion (9) aligned with the truncated conical portion (7) is attached to the second mold (4), and the fastening member (5) Is a mold configured to be pressed in the axial direction by fluid pressure.

According to a fourth aspect of the present invention, in the second or third aspect, one side of the brittle ring (1) in the axial direction is the first positioning means (11) of the first mold (3). And the other side is positioned by the second positioning means (12) of the second mold (4), and the second positioning means (1
2) is constituted by a pressing surface (14) of an insert press (13) provided slidably in the axial direction in a second mold (4) and abutting against the brittle ring (1). The presser (13) is a mold configured to press the presser surface (14) against the brittle ring (1) by the injection pressure of the molten plastic.

According to a fifth aspect of the present invention, in the fourth aspect, the slide bush (19) is movably disposed on the insert holder (13) or the slide core (17) which slides integrally therewith. , Its slide bush (19)
The slide bush (19) is configured to be retracted by the injection pressure of the molten plastic, and to be positioned and fixed by abutting against the bush positioning surface (41). Mold.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part of a mold according to the present invention, and shows a state in which a first mold 3 on a movable side and a second mold 4 on a fixed side are slightly separated. 2 is an explanatory view of the fastening operation of the brittle ring 1, and FIG. 3 shows a closed state of the same mold. FIG. 4 is an enlarged view of a main part of the mold, and FIG. 5 is a longitudinal sectional view of a main part of the injection molding machine. FIG. 6 is a side view of the fixed mounting receiving plate 22, and FIG. 7 is an explanatory view showing a state in which the injection molding machine is opened. This mold is for molding the plastic molded article 35 shown in FIG. The brittle ring 1 is made of a short cylindrical ferrite sintered magnet ring, and its tolerance is about 0.1 mm in each of the diameter direction and the axial direction. On the other hand, the axial length L of the plastic molded product 35 is about 0.05 mm, which is smaller than the tolerance of the brittle ring 1. That is, the tolerance from the end face of the brittle ring 1 to the tip of the shaft must be maintained at 0.05 mm. 8A is a longitudinal sectional view of the plastic molded product 35, and FIG. 8B is a left side view.

In the mold of the present invention, as shown in FIG. 1, a movable core insert 42 is inserted into a through hole provided in the movable first mold 3, and a chuck 2 for holding a brittle ring 1 is provided on the outer periphery thereof. Has been fitted. The chuck 2 is formed of a well-known commercially available collet chuck, and is formed in a cylindrical shape having a taper as shown in FIG. In addition, each slit is formed so as to leave a slightly non-slit portion at the end thereof, thereby having a structure that can be expanded and contracted in the radial direction. The outer periphery of the front end portion of the chuck 2 is formed in a truncated conical portion 7, and the middle portion and the rear end portion are formed in a gentle frustoconical taper.

The chuck 2 thus formed is fitted on the outer periphery of the movable core insert 42 as described above, and has a radius formed by the chuck opening ring 8 arranged in the annular groove on the outer periphery of the movable core insert 42. It is urged outward in the direction and slightly expanded. As the chuck opening ring 8, an elastic rubber ring having a circular cross section can be used. The ejector 18 is inserted through the center of the movable core insert 42 via an ejector sleeve 18a. Ejector
The tip of 18 has a shaft-shaped projection 18b that matches the shaft hole of the plastic molded product 35. The first cavity 15 is formed between the distal end of the ejector 18, the distal end of the movable insert 42, and the distal end of the chuck 2.

Next, the through hole of the second mold 4 on the fixed side is
A tubular fastening member 5 for fastening the chuck is inserted.
The fastening member 5 is formed as shown in FIG. 2, in which an insert holder 13, a slide core 17, and a slide bush 19 (FIG. 1) are sequentially fitted on the center side thereof.
On the inner peripheral surface of the distal end portion of the fastening member 5, a tapered cylindrical concave portion 9 matching the frustoconical portion 7 of the chuck 2 is formed. A pair of holes is formed in the fastening member 5 on the diameter line, and a slide pin 32 is inserted therethrough. The intermediate portion of the slide pin 32 is slightly enlarged to have a large diameter, and the enlarged portion contacts the edge of the hole of the fastening member 5. Further, the left end face of the slide pin 32 is aligned with the end face of the hydraulic input slide pin holder 40 inserted through the fixed mounting plate 21.

The insert retainer 13 provided inside the fastening member 5 is formed in a tubular shape with one end closed, has a center hole at the center of the closed portion, and has a second hole at the inner periphery and at the end of the center hole. A cavity 16 is provided. The insert retainer 13 is slightly movable in the axial direction with respect to the inside of the fastening member 5. A cylindrical slide core 17 is fitted inside the insert holder 13. The distal end surface of the slide core 17 is in contact with the closed surface of the insert retainer 13. An annular groove 26 is formed on the rear end surface of the slide core 17, and a spool path extends in the axial direction from the annular groove 26 to the second cavity 16.
27 are drilled. A spool runner passage 37 is formed radially outside the annular groove 26 to the outer surface of the mold. The center of the slide core 17 has a stepped hole through which a slide bush 19 is inserted. The slide bush 19 is slightly movable in the axial direction. Further, a pin retaining collar 6 is pressed into the rear end of the center hole of the sliding core 17 to form a retaining of the slide bush 19.

Next, a fixed mounting plate which can be freely attached to and detached from the second mold 4.
In FIG. 1, a pin holder 20 is inserted through the center hole in FIG. 1, and a bush positioning surface 41 is provided at the tip thereof.
The rear end surface of the slide bush 19 abuts on the bush positioning surface 41 via the internal pressure of the cavity. Fixed mounting plate
A pair of core holders 29 and runner lock pins 39 are inserted through 21 and are provided so as to be slightly movable in the axial direction. Also, the core holder 29 and the runner lock pin 39
A pressing coil spring 30 is seated on the rear end face of the supporting member, thereby urging the core pressing member 29 and the runner lock pin 39 to the right. Furthermore, core holder 29 and runner lock pin 39
A pair of hydraulic input slide pin holders 40 is inserted through the outside of the slide pin 32, and the end faces thereof abut the end faces of the slide pins 32.
The tip surface of the slide bush 19 is in the second cavity 16.
It is exposed to.

Next, the fixed mounting plate 21 is fixed to the fixed mounting receiving plate 38 and the fixed die plate 22 as shown in FIG. The fixed attachment receiving plate 38 is provided with a chuck fastening hydraulic cylinder 33a, in which a piston 33 is housed. Then, the rear end surfaces of the pair of hydraulic input slide pin holders 40 come into contact with the front end surfaces of the pistons 33. A pair of hydraulic hose connectors 31 project from the rear end of the fixed mounting receiving plate 38, and the hydraulic hose connectors 31 communicate with the chucking hydraulic cylinder 33a. The first mold 3 includes a movable receiving plate 10 and a movable mounting plate 23.
Fixed to. Note that the tip surface of the insert retainer 13 is a retainer surface 14 constituting the second positioning means 12 of the brittle ring 1, and the end surface of the movable core insert 42 forms the first positioning means 11 of the brittle ring 1. And brittle ring 1
Are sandwiched between both end faces.

[0017]

[Usage Method] A method of using an injection molding machine having a mold as described above will be described. In a state where the molds are opened as shown in FIG. 7, the first mold 3 and the second mold 4 are separated from each other, and the second mold 4 and the fixed mounting plate 21 are also separated from each other. That is, the second mold 4 is guided by the guide shaft 43 from the fixed mounting plate 21 and moves rightward and stops at the end of the stopper 44. At this time, the spool runner 45 is separated from the second mold 4. Then, when the runner separating plate 46 moves rightward, the spool runner 45 comes off the runner lock pin 39 and falls downward. The chuck 2 of the first mold 3 is slightly expanded outward in the radial direction by the chuck release ring 8. And by ejecting the ejector 18 to the left,
The plastic molded article 35 can be taken out and dropped. With the ejector 18 pulled back, a new brittle ring 1 is inserted into the chuck 2 by a robot (not shown).

Next, the mold is closed at a low pressure as shown in FIG. At this time, the elastic force of the holding coil spring 30 is
29, is transmitted to the insert retainer 13 through the slide core 17, and the retainer surface 14 provided on the tip surface thereof is the brittle ring 1
And the other end surface is in contact with the end surface of the movable core insert 42. Next, the mold is clamped at a high pressure, and the hydraulic pressure is supplied to the chuck fastening hydraulic cylinder 33a shown in FIG. 5 to press the piston 33 rightward. Then
In FIG. 3, the fastening member 5 moves rightward via the hydraulic input slide pin holder 40 and the slide pin 32. Thereby, the outer periphery of the chuck 2 is reduced, and the brittle ring 1 is fastened and gripped. At this time, the axis of the brittle ring 1 and the axis of the chuck 2 are aligned.

Next, the injection cylinder 24 of FIG. 5 moves downward,
The nozzle 25 touches the mold and the inside thereof communicates with the spool runner path 37. Then, the molten plastic is filled into the cavity via the spool runner path 37, the annular groove 26, and the spool path 27. At this time, the injection pressure is transmitted to the slide core 17 via the annular groove 26, which presses the brittle ring 1 to the right via the insert retainer 13 and prevents the brittle ring 1 from moving in the axial direction. . The molten resin in the cavity reaches the end face of the slide bush 19, moves the slide bush 19 slightly to the left, and positions the left end of the slide bush 19 in contact with the end face of the pin retainer 20. Thereby, the axial distance between the right end of the slide bush 19 and the set surface 11a of the movable core insert 42 is accurately specified. Thus, the axial length L of the plastic product
(FIG. 8) can be held accurately.

Then, the mold is opened through a pressure holding step and a cooling measurement step. That is, the mold is opened as shown in FIG. 7, and the spool runner 45 is pulled out from the runner lock pin 39 and dropped. At this time, the slide bush 19 is prevented from falling off by the pin retaining collar 6. Then, the ejector 18 is advanced to push out the plastic molded product 35, and the above-described steps are repeated.

[0021]

[Modification] The present invention is not limited to the above-described embodiment. For example, instead of providing the fastening member 5 of the chuck 2 in the second mold 4, the fastening member is provided in the first mold 3. You may. In that case, in FIG.
Has a structure in which a slide member having an inner surface aligned with the outer periphery of the tapered surface having a gentle inclination on the right side is moved from right to left in the axial direction.

[0022]

According to the insert molding method and the mold of the present invention, the brittle ring 1 formed in an annular shape is
The outer periphery of the brittle ring 1 is fastened and held by the chuck 2 which is uniformly expanded and contracted in the radial direction at the time of injection.
Since the injection molding of the molten plastic material is performed on the inner peripheral side of the above, it is possible to reliably prevent the brittle ring 1 from being damaged by the injection pressure of the molten plastic. Further, since the chuck 2 on which the brittle ring 1 is fastened and held is uniformly expanded and contracted in the radial direction, even if the accuracy of the outer diameter of the brittle ring 1 varies, the axis of the brittle ring 1 is surely aligned. The axis of the chuck 2 can be aligned, and as a result, the axis of the brittle ring 1 can be aligned with the axis of the plastic molded product.

According to the second aspect of the present invention, since the brittle ring 1 is fastened and held by pressing the outer periphery of the chuck 2 by the fastening member 5, the plastic molding metal having a simple structure and high accuracy is provided. We can provide the mold. According to the third aspect of the present invention, the fastening member 5 is configured to be pressed in the axial direction by the fluid pressure, the structure is simple, and the fastening force is adjusted to a predetermined value by adjusting the fluid pressure. It becomes easy to hold. Thereby, the brittle ring 1
Can be prevented from being damaged.

According to the present invention, the brittle ring 1 is provided.
The first side of the first mold 3 in the axial direction of the first mold 3 is
And the other side is positioned by the second positioning means 12 of the second mold 4. The second positioning means 12 is constituted by a pressing surface 14 of an insert holder 13 provided on the second mold 4 so as to be slidable in the axial direction, against the brittle ring 1. As a result, the pressing surface 14 is pressed against the brittle ring 1, so that the brittle ring 1 can be prevented from being damaged by the pressure for pressing the brittle ring 1. That is, since the brittle ring 1 is pressed by the injection pressure in a state where it is abutted against the first positioning means 11 of the first mold 3, the brittle ring 1 is not damaged by the injection pressure. Further, since the brittle ring 1 is configured to be pressed by the pressing surface 14 by the injection pressure of the molten plastic, the mold can be simplified and easily manufactured.

According to the fifth aspect of the present invention, the slide bush 19 is movably disposed on the insert holder 13 or the slide core 17, and the end surface of the slide bush 19 is exposed in the cavity and is filled therein. It is retracted by the injection pressure of the molten plastic, comes into contact with the bush positioning surface 41, and is stopped and fixed. Therefore, even if the axial dimension of the brittle ring 1 varies, the position of the end face of the bush positioning surface 41 is always kept constant, and the axial dimension of the molded product can be accurately formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a mold according to the present invention, showing a state in which a movable first mold 3 and a fixed second mold 4 are slightly separated from each other.

FIG. 2 is an explanatory view of a chuck 2 and a fastening member 5 used in the mold.

FIG. 3 is a longitudinal sectional view of the same mold, showing a closed state of the mold.

FIG. 4 is an enlarged view of a main part of the mold.

FIG. 5 is a longitudinal sectional view of a main part of an injection molding machine having the mold.

FIG. 6 is a left side view in FIG. 5;

FIG. 7 is a vertical sectional view of a main part showing a mold opening state of the injection molding machine having the same mold.

FIG. 8 is a longitudinal sectional view and a left side view showing an example of a plastic molded product 35 produced by the mold of the present invention.

[Explanation of symbols]

 Reference Signs List 1 brittle ring 2 chuck 2a slit 3 first mold 4 second mold 5 fastening member 6 pin retaining collar 7 frustoconical part 8 chuck opening ring 9 cylindrical recess 10 movable receiving plate 11 first positioning means 11a set surface 12 Second positioning means 13 Insert holder 14 Pressing surface 15 First cavity 16 Second cavity 17 Slide core 18 Ejector 18a Ejector sleeve 18b Shaft type projection 19 Slide bush 20 Pin holder 21 Fixed mounting plate 22 Fixed die plate 23 Movable mounting Plate 24 Injection cylinder 25 Nozzle 26 Annular groove 27 Spool path 29 Core holder 30 Holding coil spring 31 Hydraulic hose connector 32 Slide pin 33a Hydraulic cylinder for chucking 33 Piston 34 Tie bar 35 Plastic molded product 36 Gear part 37 Spool runner path 38 Fixed mounting Receiving plate 39 Runner lock pin 40 Hydraulic input slide Pin retainer 41 bushing positioning surface 42 movable core nest 43 guide shaft 44 stopper 45 spool runner 46 runner separating plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeki Totsuka 1-7-1 Yokoi, Shimada-shi, Shizuoka Yazaki Keiki Co., Ltd. F-term (reference) 4F202 AD02 AH04 CA11 CB01 CB12 CK42 CK64 CQ05 4F206 AD02 AH04 JA07 JB12 JQ81

Claims (5)

[Claims] A brittle ring (1) made of a brittle material formed in an annular shape is injection molded with a molten plastic material on its inner peripheral side so that at least a part of its outer periphery is exposed after molding. In the insert molding method for a brittle ring, a chuck (2) uniformly expanded and contracted in the radial direction is arranged in a molding die, and the brittle ring (1) is placed in the chuck (2).
Insert external force to the chuck (2) in the direction of the center so that the brittle ring (1) is not damaged during injection.
A method of insert-molding a brittle ring, wherein a molten plastic material is injection-molded on the inner circumferential side of the brittle ring (1) while fastening and holding the outer circumference of (1). 2. A first mold (3) and a second mold (4) for molding, which are arranged so as to be openable and closable so as to be in contact with and separated from each other, and have a radius arranged on the first mold (3). A chuck (2) for holding a brittle ring that is uniformly expanded and contracted in the direction, and a second mold (4) or a first mold (3). And a fastening member (5) for fastening and holding the inside of the chuck in the radial direction. A circular annular brittle ring is attached to the chuck (2).
A mold configured such that a molten plastic material is injection-molded on the inner surface side of the brittle ring (1) while (1) is held and fastened. 3. The chuck according to claim 2, wherein said chuck (2) comprises a collet chuck having a tapered frustoconical portion (7) at an axial end thereof, and a radially outwardly resilient chuck on an inner peripheral surface thereof. A fastening member (5) having an opening ring (8) disposed therein and having a cylindrical concave portion (9) aligned with the truncated conical portion (7) is attached to the second mold (4). (5) A mold configured to be pressed in the axial direction by fluid pressure. 4. The first mold according to claim 2, wherein one side of the brittle ring (1) in the axial direction is the first mold.
(3) is positioned by the first positioning means (11), the other side is positioned by the second positioning means (12) of the second mold (4), and the second positioning means (12) is a second mold. (4) The presser surface (14) of the insert presser (13) slidably provided in the axial direction is configured to abut against the brittle ring (1), and the insert presser (13) is made of molten plastic. A mold configured to press the holding surface (14) against the brittle ring (1) by the injection pressure of the mold. 5. The slide bush (19) according to claim 4, wherein the slide bush (19) is movably disposed on the insert holder (13) or the slide core (17) that slides integrally therewith. The end face is exposed in the cavity for filling the molten plastic,
A mold configured such that the slide bush (19) is retracted by the injection pressure of the molten plastic, abuts on the bush positioning surface (41) and is positioned and fixed.