JP2001246641A - Method for injection molding multicolored molded article and rotor of pm type stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for injection molding a multicolored molded article including a process injection molding a cylindrical part constituting the outside of the molded article having a cylindrical shape by a primary molding process and injection molding the molded part constituting the inside of the cylindrical part by a secondary molding process and to prevent trouble such that cracking/deformation is generated in the cylindrical part by the pressure of the molding resin in the cylindrical part in the secondary molding process simply, economically and certainly. SOLUTION: At a time of primary molding, a mold piece 4 is used in opposed relation to a fixed attaching plate 3a to constitute a primary mold. After the completion of primary molding, the molded cylindrical part 53 is not detached from the mold piece 4 and the mold piece 4 is fed to a secondary injection molding apparatus to be opposed to a cavity 17. The cylindrical part 53 is placed on the mold piece 4 through primary and secondary molding processes and the generation of a gap between the outer periphery of the cylindrical part 53 and the inner periphery of the mold piece 4 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a multicolor molded article manufactured by a plurality of injection molding steps, and to a P-type wherein the outer periphery of a rotor portion is injection-molded with a magnetic material.
The present invention relates to a rotor of an M type (Permanent Magnet Type) stepping motor.

[0002]

2. Description of the Related Art Here, as an example of a multicolor molded product, a rotor of a generally used PM type stepping motor will be described.

[0003] A PM type stepping motor uses a permanent magnet multipolarized on a cylindrical surface of a rotor portion constituting the motor, and provides a driving field corresponding to pulse power around the permanent magnet to perform a stepping rotation operation. This is one type of stepping motor to perform. FIG. 6 is a perspective view showing the appearance of the rotor of the PM type stepping motor. Reference numeral 50 denotes a rotor body, reference numeral 51 denotes a rotating shaft made of a metal material, and reference numeral 52 denotes a thermoplastic resin formed by injection molding. A hub 53 indicates a magnet portion formed by injection molding from a plastic magnet material. FIG. 7 is a sectional view taken along line xx in FIG. 6 and shows a state where the rotor 50 is in a secondary molding die 54 for molding the hub 52.

Next, the manufacturing process of the rotor 50 will be described. Generally, the manufacturing process of the rotor 50 includes two injection molding processes of a first injection molding process of injection-molding the magnet portion 53, a second injection molding process of injection-molding the hub 52, and a magnet. A magnetizing step of multipole magnetizing the portion 53 is performed, but the description of the magnetizing step is omitted here. First, the magnet part 53 is formed by the primary injection molding process.
Is molded. Here, the magnet part 53 is molded using a plastic magnet that can be injection molded. Magnets used for injection molding include ferrites such as value ferrite and rare earths such as samarium cobalt. Recently, neodymium-iron-boron (Nd ₂ Fe ₁₄ B) has a large magnetic energy. Commonly used from The magnet is powdered to be a fine magnetic material using a thermoplastic resin such as a plastic as a binder, and is used for injection molding as a plastic magnet. However, the plastic magnet is expensive among molding materials constituting the rotor 50. Therefore, it is required that the magnet portion 53 be made as thin as possible a cylinder as long as it does not affect the magnetic force characteristics, and the amount of molding material used is suppressed.

Next, a magnet part 5 formed into a cylindrical shape
Reference numeral 3 denotes a hub that is taken out of the movable-side primary molding die, which forms the primary molding die in the primary injection molding step, through a mold opening step, and after the runner is removed, in the secondary injection molding step. Is inserted together with the rotary shaft 51 into a movable-side secondary molding die that constitutes a secondary molding die for performing the molding. Then, the movable side secondary molding die,
The fixed-side secondary molding die used in opposition to the movable-side secondary molding die is united and clamped, and the secondary molding resin for molding the hub 52 passes from the injection device through the spool and gate. Is injected into the cavity. The molding resin injected from the gate flows into the inner peripheral portion of the magnet part 53, and the hub 52 is formed through a pressing step, a pressure holding step, and a cooling step.
The rotor 50 before magnetization is completed.

In the secondary molding step, the hub 52 is used.
When molding the magnet part 5 as shown by the arrow in FIG.
3 receives a resin pressure from the inside thereof, so that a tensile stress is generated in the magnet portion 53 in the circumferential direction during the secondary molding process. A magnet 53 is provided between the outer periphery of the magnet 53 and the inner periphery of the secondary molding die 54.
In order to easily insert into the next molding die 54,
As a result, some clearance 55 when inserted
The design is such that For this reason, at the time of molding, the magnet portion 53 does not receive an auxiliary pressure from the inner periphery of the secondary molding die 54 in a direction that cancels the resin pressure, and the resin pressure remains unchanged in the circumferential direction of the magnet portion 53. It will appear as stress. Accordingly, the magnet portion 53 is distorted in the radial direction due to the tensile stress in the secondary forming step, that is, it tends to expand outward.

[0007]

However, when the clearance 55 exists as described above and the radial thickness of the magnet portion 53 is small and the strength is low, that is, when the allowable stress is low, the magnet pressure is reduced by the resin pressure. The portion 53 is distorted in the circumferential direction, and may crack or crack beyond the elastic deformation range and the plastic deformation range. Also, the magnet part 5
Even if the thickness of the material 3 in the radial direction is relatively large, the same problem as described above will occur if the material characteristics itself after molding have a low allowable stress. Therefore, two means have conventionally been used to solve the above problem, but have the following problems.

First, even when the clearance 55 is reduced as much as possible and the magnet portion 53 expands outward due to the resin pressure from the inside, the magnet portion 53 must not be moved beyond the elastic deformation region and the plastic deformation region. The outer periphery of the magnet 53 is precisely polished so that the outer periphery of the magnet 53 does not contact the inner periphery of the secondary molding die 54 and cause any further deformation.
Means for reducing the clearance 55 has been used.
However, in this case, the magnet part 5 is attached to the secondary molding die 54.
The insert No. 3 is very tight and has poor workability.
Further, in this means, a polishing step for the outer periphery of the magnet portion 53 is additionally required, and thus there is a problem in cost.

Secondly, the molding resin in the secondary molding step is injected not only into the inner periphery of the magnet portion 53 but also into the outer periphery at the same time, that is, into the clearance 55, so that the molding resin is simultaneously injected from the outside of the magnet portion 53. Means has been used in which a resin pressure is applied and the resin pressure from the inside of the magnet part 53 is reduced by the resin pressure from the outside. But,
In this means, the tensile stress generated in the circumferential direction of the magnet portion 53 is relieved, and the occurrence of cracks and cracks described above is reduced. However, when the resin pressure from the outside is not uniform in the circumferential direction, the magnet portion 53 is There was a problem that the roundness was reduced due to deformation.

The present invention has been made in view of such a situation, and an object of the present invention is to injection-mold a cylindrical portion constituting the outer side of a molded product having a cylindrical shape by a primary molding step.
In a method for injection-molding a multicolor molded article, which comprises a step of injection-molding a molding part constituting the inside of the cylindrical part by a secondary molding step, the molding resin injected inside the cylindrical part in the secondary molding step An object of the present invention is to reliably and easily and economically prevent the cylindrical portion from being cracked, cracked, or deformed by resin pressure.

[0011]

According to a first aspect of the present invention, there is provided a method for injection-molding a multi-color molded article, comprising: a cylindrical portion forming an outer side of a cylindrical molded article; In a primary molding step, and injecting a molded portion constituting the inside of the cylindrical portion by a secondary molding step. Injection molding machine having a movable-side primary molding die and a fixed-side primary molding die constituting a secondary molding die, and a movable-side secondary molding die and a fixed side 2 constituting a secondary molding die
A secondary injection molding machine having a secondary molding die is independent and independent, and after the primary molding, the cylindrical portion molded into an easily removable mold piece constituting the movable-side primary molding die is removed. The mold piece is removed from the movable-side primary molding die while remaining in the mold piece, and the removed mold piece is fitted into the mold piece in the secondary injection molding machine. The secondary molding step is performed by fitting the movable-side secondary molding die having a concave portion.

According to the first aspect of the present invention, the cylindrical portion molded into a removable mold piece constituting a movable-side primary molding die for performing a primary molding step is combined with the primary molding die. With the mold piece remaining, the mold piece is moved to the movable side 1.
Take out from the next molding die, take out the above-mentioned mold piece,
In the secondary injection molding machine, the secondary molding step is performed by fitting the movable piece to a movable secondary molding die having a concave portion into which the mold piece is fitted, so that the cylindrical portion is subjected to a primary molding step and a secondary molding step. Through the same mold piece.
That is, conventionally, the cylindrical portion is taken out of the movable-side primary mold by itself after the primary molding is completed, and
The secondary molding process is performed by being transported and inserted into the movable-side secondary molding die for performing the next molding process. According to the present invention, the transporting and inserting can easily constitute the movable-side primary molding die. This is performed for each removable mold piece. For this reason, in the secondary molding step, the molding resin is injected into the cylindrical portion in a state where the gap between the outer periphery of the cylindrical portion and the inner periphery of the mold for performing the secondary molding is extremely small or completely absent. The cylindrical portion receiving the resin pressure cannot be deformed beyond the elastic deformation region and the plastic deformation region by the resin pressure,
No cracks or cracks occur. In this case, as described above, an additional step such as a polishing step of polishing the outer periphery of the cylindrical portion so as to reduce the clearance between the outer periphery of the cylindrical portion and the inner periphery of the mold for performing the secondary molding step is not required.
The problem can be easily and economically prevented, and furthermore, as in the case of simultaneously injecting resin also to the outer peripheral portion of the cylindrical portion in order to reduce the resin pressure received from the inside of the cylindrical portion,
There is no possibility that the roundness of the cylindrical portion is reduced due to the unevenness of the resin pressure.

[0013] In the secondary molding step, the outer periphery of the cylindrical portion is moved by the resin pressure received from the inside to the movable side 1.
The roundness of the outer periphery of the cylindrical portion always depends on the roundness of the inner periphery of the movable-side primary molding die because the outer periphery of the cylindrical portion is always pressed against the inner periphery of the next die. Therefore, if the roundness of the inner periphery of the movable-side primary molding die is within a desired range, the roundness of the outer periphery of the cylindrical portion is always within the desired range without lowering, and between products. The variation in roundness can be suppressed.

Further, in the present invention, since the injection molding machine for performing the primary molding step and the injection molding machine for performing the secondary molding step are independent and independent, the following advantages are provided.

For example, one unit including both a primary molding die and a secondary molding die, and a moving device for making the movable primary molding die face the fixed secondary molding die. When performing injection molding with an injection molding machine, the structure of the injection molding machine is complicated, so once the injection molding machine is manufactured, the mold is fixed and can only be used as a dedicated machine. Becomes

On the other hand, in the present invention, a general-purpose molding machine can be used, and a product having a distinct shape can be formed easily and easily by exchanging only the mold piece. Therefore, it is possible to reduce capital investment and increase the efficiency of the manufacturing process.

According to a second aspect of the present invention, there is provided an injection molding machine having a primary molding die for injection-molding the cylindrical portion according to the first aspect, wherein the primary molding die is provided. Is characterized by comprising a fixed-side primary molding die and a movable-side primary molding die having a removable mold piece.

According to the injection molding machine according to the second aspect of the present invention, since the movable-side primary molding die having the detachable die top is provided, the cylindrical portion is connected to the mold as described above. With the mold pieces remaining on the mold pieces, the mold pieces can be conveyed to an injection molding machine that performs a secondary molding step, so that the same function and effect as the first aspect of the invention can be obtained.

An injection molding machine according to a third aspect of the present invention is an injection molding machine provided with a secondary molding die for injection-molding a molding portion forming the inside of the cylindrical portion. The molding die is composed of a fixed-side secondary molding die and a movable-side secondary molding die having a concave portion for fitting a mold piece in which the cylindrical portion formed in the primary molding step remains. It is characterized by the following.

According to the injection molding machine according to the third aspect of the present invention, the movable secondary having a concave portion for fitting the mold piece in which the cylindrical portion formed in the primary molding step remains. The invention according to claim 1, wherein the mold has a molding die, and as described above, the mold piece having the cylindrical portion remaining in the primary molding step can be used as it is in the secondary molding step. The same operation and effect as described above can be obtained.

According to a fourth aspect of the present invention, there is provided a die top for forming the cylindrical portion according to the first aspect, wherein the die top is a movable side constituting a primary forming die. It is characterized in that it can be removed from the primary molding die.

According to the invention described in claim 4 of the present application, the mold piece is detachable from the movable-side primary molding die constituting the primary molding die. The same operation and effect as described above can be obtained.

The rotor of the PM type stepping motor according to the invention of claim 5 of the present application has a cylindrical portion that is injection-molded in a primary molding step, and a rotary member that is injection-molded inside the cylindrical portion in a secondary molding step. P having a shaft support
A rotor of an M-type stepping motor, wherein the outer circumference roundness of the cylindrical portion in a state integrated with the rotary shaft support portion is easily removed from the mold piece for performing the injection molding of the cylindrical portion. It is characterized by being dependent on the inner roundness.

According to the fifth aspect of the present invention, the roundness of the outer circumference of the cylindrical portion depends on the roundness of the inner circumference of the easily removable mold piece for performing the injection molding of the cylindrical portion. As a result, the variation in roundness of the outer periphery of the rotor manufactured by injection molding between products is small. Further, since the mold piece can be easily removed from the injection molding machine, it is possible to use the same mold piece even when the molding machine must be frequently changed due to manufacturing equipment. Accordingly, the lot quantity of the rotor can be increased under any circumstances, and therefore, there is an advantage that the variation between products is further reduced.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an injection molding method for a multicolor molded article and a rotor of a PM type stepping motor according to the present invention. still,
Here, in order to explain the injection molding method of multicolor molded products,
An example of the injection molding method of the rotor of the PM type stepping motor having the structure shown in FIG. 6 will be described, but the present invention is not limited to the injection molding method of the rotor of the PM type stepping motor.

FIGS. 1 to 4 are views for explaining the injection molding process of the rotor of the PM type stepping motor using the sectional structure of the injection molding die. First, referring to these drawings, the injection molding die will be described. And an outline of the injection molding process.

FIG. 1 is a sectional view showing a state in which a primary molding resin is injected into an injection-molded mold that has been clamped in a primary molding step, and the resin is filled in a mold cavity. In FIG. 1, reference numeral 1a indicates a primary molding die (hereinafter, the suffix "a" indicates a primary molding die, and "b" indicates a secondary molding die or a component constituting these dies. ,
Each of these shall be mounted on a separate injection molding machine).

The mold 1a is attached to a primary injection molding machine for performing a primary molding step. The mold 1a includes a fixed mold part (hereinafter, referred to as “primary upper mold”) 13a and a movable mold part (hereinafter, referred to as “primary lower mold”) 14a. Further, the primary lower mold is movable in the vertical direction in the figure so that the mold 1 can be clamped and opened.

The primary lower mold 14a includes a mold piece 4 and a core 6a for molding the cylindrical portion 53, a movable mold plate 5a for attaching the same, a cylindrical portion 53 and a mold frame formed at the end of the primary molding. Ejector pins 9a, 1 for simultaneously removing the 4
0a, an ejector plate 11a for driving the ejector pins 9a, 10a, a spacer block 8a for forming a drive space for the ejector plate 11a, and a movable-side mounting plate 12a serving as a base for these. Is composed of only the fixed side mounting plate 3a.

Reference numeral 2a denotes a plastic magnet (neodymium-iron-boron (Nd ₂ Fe ₁₄ B) using nylon as a binder), which is a primary molding resin, which is melted in a heating cylinder (not shown). 1 to supply to 1a
The following shows an injection device. The molten resin injected from the primary injection device 2a passes through the fixed-side mounting plate 3a and fills a molding space provided by the mold pieces 4, the core 6a, and the fixed-side mounting plate 3a. When the filling of the molding resin is completed, the filled molten resin is cooled and solidified after passing through a pressure step and a pressure holding step.

FIG. 2 shows a state in which the mold 1a is opened from the step shown in FIG. After cooling and solidifying, lower mold 14
is retracted, the primary upper die 13a and the primary lower die 14a are separated from each other and stopped. Next, the ejector plate 12a is driven to eject the ejector pins 9a and 10a upward to take out the molded cylindrical portion 53 and the mold piece 4 at the same time, and remove the spool runner 56 remaining in the cylindrical portion 53.

Next, while the injection-molded cylindrical portion 53 remains without being taken out of the mold piece 4, the mold piece 4 in which the cylindrical portion 53 remains is conveyed to a secondary injection molding machine. It is inserted into a recess provided in the movable mold plate 5b constituting the secondary molding die 1b shown.

FIG. 3 shows a state in which the mold 1 is clamped from the step shown in FIG. 2, the secondary molding resin is injected, and the cavity is filled with the secondary molding resin. In the forming step, the hub 52 shown in FIG. 6 is formed. Code 2b
Shows an injection device that supplies PBT (polybutylene terephthalate) as a secondary molding resin, which is melted in a heating cylinder (not shown), to a secondary molding die.
The secondary molding resin injected from the injection device 2b passes through the spool bush 15 and the cavity 17, the mold top 4,
The molding space provided by the core 6b is filled. 2
When the filling of the next molding resin is completed, the filled molten resin is cooled and solidified after passing through a pressure step and a pressure holding step.

FIG. 4 shows the secondary lower mold 14 from the process shown in FIG.
b is retracted and the secondary upper mold 13b and the secondary lower mold 14b are separated from each other. At this time, the secondary upper mold 13
b, the fixed side mounting plate 3b and the stripper plate 1
6. Separate the fixed mold plate 18 and remove the spool runner 57. The ejector plate 11b is driven to eject the ejector pins 9b, thereby taking out the molded rotor 50 from the mold piece 4. At this time, the ejector pin 10b projects and the mold piece 4 is simultaneously removed from the movable mold plate 5b.
The ejector pin 9b contacts the rotor 50 and the rotor 5
0 is pushed up from the mold piece 4 by a certain amount.
The length has been adjusted to abut the.

Next, the operation and effect of this manufacturing method will be described with reference to FIG.
This will be described with reference to FIG. 5A and 5B are schematic diagrams in which the rotor molding of the PM type stepping motor described above is simplified by enlarging a portion where the rotor 50 is molded in the cross section of the mold, and FIG. (B) is a state in which the plastic magnet resin is filled in the mold in a primary molding step in which the molding is performed, and (B) is a state in which the PBT resin is filled in the mold in a secondary molding step in which the hub 52 is molded. Is shown.

In FIG. 5A, the fixed-side mounting plate 3a and the mold piece 4 constitute a primary molding mold in a state where they are pressed against each other.
The cylindrical part 53 is formed. Next, after the fixed-side mounting plate 3a and the mold piece 4 are separated by opening the mold, the mold piece 4 is taken out with the cylindrical portion 53 remaining on the mold piece 4, and a secondary molding process is performed. It is transported to the molding machine,
Insert into the next molding die. As a result, FIG.
As shown in the figure, the mold piece 4 constitutes a secondary molding mold together with the cavity 17. That is, the cylindrical portion 53
Since the molding is performed without being removed from the mold piece 9 through the primary molding step and the secondary molding step, in the secondary molding step, is the gap between the outer periphery of the cylindrical portion 53 and the inner periphery of the mold piece 4 extremely small? Or, in the state where there is no cylinder 53
Since the PBT resin is injected into the inner periphery, the cylindrical portion 53 receiving the resin pressure from the inside cannot be deformed beyond the elastic deformation region and the plastic deformation region by the resin pressure, and cracks and cracks may occur. Absent. In this case, the cylindrical portion 53
Since an additional step such as a polishing step of polishing the outer periphery of the cylindrical portion 53 to reduce the clearance between the outer periphery and the inner periphery of the mold for performing the secondary molding step is not required, the above-described effects can be obtained simply and economically. Further, as in the case of simultaneously injecting resin also to the outer peripheral portion of the cylindrical portion 53 in order to relieve the resin pressure received from the inside of the cylindrical portion 53, the perfect circular shape of the cylindrical portion 53 due to unevenness of the resin pressure There is no danger that the degree will decrease.

During the secondary molding process, the outer circumference of the cylindrical portion 53 is always pressed against the inner circumference of the mold piece 4 by the resin pressure received from the inside, so that the roundness of the outer circumference of the cylindrical portion 53 is always gold. It depends on the roundness of the inner circumference of the mold piece 4. Therefore, if the roundness of the inner circumference of the mold piece 4 is within the desired range, the roundness of the outer circumference of the cylindrical portion 53 of the rotor 50 manufactured according to the present embodiment is always within the desired range without lowering. In addition, it is possible to maintain stable quality with small roundness variation between products.

Further, an injection molding machine for performing a primary molding step;
Since the injection molding machine that performs the secondary molding process is separate and independent,
As a general-purpose molding machine can be used as compared with a dedicated two-color molding machine that performs two processes with one unit, it is possible to reduce capital investment and increase the efficiency of the manufacturing process.

[0039]

As described above, according to the present invention,
A multi-color molded article including a step of injection-molding a cylindrical portion constituting the outer side of a molded article having a cylindrical shape by a primary molding step, and an step of injection-molding a molded section constituting the inside of the cylindrical section by a secondary molding step; In the injection molding method, it is possible to easily, economically and surely prevent the cylindrical portion from being cracked, cracked or deformed by the resin pressure of the molding resin injected into the cylindrical portion in the secondary molding step. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold, showing one embodiment of a method for injection molding a multicolor molded article according to the present invention.

FIG. 2 is a mold sectional view showing one embodiment of a method for injection molding a multicolor molded product according to the present invention.

FIG. 3 is a mold sectional view showing one embodiment of the injection molding method for a multicolor molded article according to the present invention.

FIG. 4 is a mold sectional view showing one embodiment of the method for injection-molding a multicolor molded article according to the present invention.

FIG. 5 is an enlarged schematic view of a mold cross section showing one embodiment of the injection molding method of a multicolor molded article according to the present invention.

FIG. 6 is a perspective view of a rotor of a PM stepping motor.

FIG. 7 is a sectional view showing an xx section in FIG. 6;

[Explanation of symbols]

 1a, 1b Mold 2a, 2b Injection device 3a, 3b Fixed side mounting plate 4 Mold top 5a, 5b Movable side plate 6a, 6b Core 7a, 7b Receiving plate 8a, 8b Spacer block 9a, 9b Ejector pin 10a, 10b Ejector pin 11a, 11b 	 Ejector plate 12a, 12b 	 Movable mounting plate 13a, 13b 	 Fixed mold part 14a, 14b 	 Movable mold part 15 Spool bush 16 Ejector plate 17 Cavity 18 Fixed side template

[Procedure amendment]

[Submission date] March 6, 2000 (200.3.6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold, showing one embodiment of a method for injection molding a multicolor molded article according to the present invention.

FIG. 2 is a mold sectional view showing one embodiment of a method for injection molding a multicolor molded product according to the present invention.

FIG. 3 is a mold sectional view showing one embodiment of the injection molding method for a multicolor molded article according to the present invention.

FIG. 4 is a mold sectional view showing one embodiment of the method for injection-molding a multicolor molded article according to the present invention.

FIG. 5 is an enlarged schematic view of a mold cross section showing one embodiment of the injection molding method of a multicolor molded article according to the present invention.

FIG. 6 is a perspective view of a rotor of a PM stepping motor.

FIG. 7 is a sectional view showing an xx section in FIG. 6;

[Description of Signs] 1a, 1b Molds 2a, 2b Injection device 3a, 3b Fixed-side mounting plate 4 Mold top 5a, 5b Movable-side plate 6a, 6b Core 7a, 7b Receiving plate 8a, 8b Spacer block 9a, 9b Ejector pin 10a, 10b Ejector pin 11a, 11b Ejector plate 12a, 12b Movable mounting plate 13a, 13b Fixed mold parts 14a, 14b Movable mold part 15 Spool bush 16 Ejector plate 17 Cavity 18 Fixed mold plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 9:00 B29L 9:00 31:08 31:08 31:32 31:32 F term (Reference) 4F202 AG03 AG07 AG08 AH04 AH33 CA11 CB01 CB22 CB28 CK06 CK17 CK25 CK42 CK52 CK54 4F206 AG03 AG07 AG08 AH04 AH33 JA07 JB22 JB28 JL02 JM13 JM16 JN12 JN25 JN33 JQ81

Claims (5)

[Claims] A step of injection-molding a cylindrical portion constituting the outside of a molded article having a cylindrical shape by a primary molding step, and a step of injection-molding a molded portion constituting the inside of the cylindrical portion by a secondary molding step. A primary injection molding machine having a movable primary molding die and a fixed primary molding die constituting a primary molding die, and a secondary molding die. The secondary injection molding machine having the movable secondary molding die and the fixed secondary molding die constituting the mold is independent and independent. After the primary molding, the removal forming the movable primary molding die is performed. With the cylindrical portion formed into a possible mold piece remaining in the mold piece, the mold piece is moved to the movable side 1.
A secondary molding step is performed by taking out the mold piece taken out from the next molding die and fitting it to a movable secondary molding mold having a concave portion into which the mold piece is fitted in the secondary injection molding machine. An injection molding method for a multicolor molded article, characterized in that: 2. An injection molding machine comprising a primary molding die for injection-molding the cylindrical portion according to claim 1, wherein the primary molding die is detachable from a fixed-side primary molding die. An injection molding machine, comprising: a movable-side primary molding die having a flexible mold piece. 3. An injection molding machine provided with a secondary molding die for injection-molding a molding portion constituting the inside of the cylindrical portion according to claim 1, wherein the secondary molding die is a fixed secondary mold. Injection molding, comprising: a molding die; and a movable-side secondary molding die having a concave portion for fitting the die piece in which the cylindrical portion formed in the primary molding step remains. Machine. 4. The die piece for molding the cylindrical portion according to claim 1, wherein the die piece is detachable from a movable-side primary molding die constituting a primary molding die. Die top featured. 5. A PM type stepping motor rotor comprising: a cylindrical portion injection-molded in a primary molding step; and a rotary shaft support portion injection-molded in a secondary molding step inside the cylindrical portion, The outer periphery roundness of the cylindrical portion in a state of being integrated with the rotating shaft support portion was made to depend on the inner periphery roundness of the easily removable mold piece for performing the injection molding of the cylindrical portion, A rotor for a PM type stepping motor.