JPH0948047A - Mold and manufacture of molding using the mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a moldeding with surface and inside defects reduced extremely, and provide further a mold to be employed therefor. SOLUTION: This mold includes a moving part 52 being movable within the cavity 51 and urging means of an air cylinder or the like for urging the moving part, and the urging means operates to urge the moving part to be retreated after an elongated material injected within the cavity is blocked by the moving part 52 and becomes a mass, and as the mass of molten material becomes large, injection of material is contemned, while retreating the moving part 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold suitable for manufacturing a vibration-proof member, an intermediate member for manufacturing mechanical structural parts, or a molded body such as a cylindrical or cylindrical member. The present invention relates to a method for manufacturing a molded body using a mold.

[0002]

2. Description of the Related Art In general, an injection molding method is known as a method for producing a molded body made of a material such as a thermoplastic resin, a thermosetting resin, or rubber. In the injection molding method, the material melted in the cylinder is injected from the gate into the product cavity of the mold in which the shape of the molded body is formed in advance, and after the material is hardened in the product cavity, it is demolded and molded. It is a way to get a body.

Referring to FIG. 16, a conventional injection molding method will be described by taking the production of a resin roller as an example. FIG. 16 is a cross-sectional view showing a state in which a molten resin material is injected into a mold 100 for injection molding composed of fixed molds 101 and 102 to hold the pressure. The fixed molds 101 and 102 are provided with roller product cavities 104 substantially in half, and the mold temperature is kept constant by a cooling pipe (not shown). One of the fixed molds 101 and 102 is attached to a molten resin material injection molding machine (not shown) as a fixed part, and the other as a movable part. The injection molding machine is provided with a nozzle 105.

When a resin roller is molded by an injection molding method, as shown in FIG. 16, a mold 100 on the fixed part side and a mold on the movable part side are clamped with a parting line 107 as a boundary.
And the molten resin material 10 is formed from the injection hole 102A.
Injection injection. Then, after the cold storage time elapses, the mold 100
Open and take out the resin roller which is the molded body.

[0005]

However, in the conventional method for producing a molded article, defects such as "flow marks" occur on the outer surface of the resulting molded article, and defects such as "air entering" occur inside the product. However, there are problems such as occurrence of defects and defects such as "sinks" when the thickness of the molded body is increased.

FIG. 17 is a general explanatory view of "flow mark" and "air containing" which are product defects that occur in an injection molded product. As schematically shown in FIG. 17A, a wrinkled pattern 111 may be formed on the surface of the molded product 110. This is a product defect called "flow mark". Further, as schematically shown in the cross-sectional view of FIG. 17 (B), bubbles 112 may be included inside the molded product. This is a product defect called "air containing".

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a mold capable of producing a molded product in which defects on the surface and inside are significantly reduced. To do. It is another object of the present invention to provide a method for producing a molded product in which defects on the surface and inside are significantly reduced.

[0008]

[Means for Solving the Problems] A molded article manufactured by a conventional injection molding method has a defect such as "filled with air" inside or a defect such as "flow mark" on the surface. This is because the molten material such as molten resin or molten rubber injected into the mold as described above fills the product cavity of the mold in a string shape. The present inventors have clarified the details of the process of forming this defect by repeating various experiments. The process of defect formation clarified by the present inventors will be described with reference to FIG.

At the initial stage of filling, the molten material such as molten resin or molten rubber becomes a string-like shape 118, and the gate 116 causes the mold 1 to move.
It is injected into 15 product cavities 117. As shown in FIG. 15 (A), the molten material 118 injected in a string shape is gently stacked from the bottom to the top of the mold 11.
5 The product cavity 117 of 5 is filled up. At this time, a force for fusing the molten material 118 injected in a string shape to densely fill the product cavity 117 does not act, and the molten material 118 stacked in a string shape contains a large amount of air between them. It is in the state of being. String-like molten material 118 filled in the product cavity 117 while containing air between them.
When the top of the stack reaches near the gate 116, the molten material injected from the gate 116 is
Since there is no space below 6 to form a string-like shape, as shown in FIG. 15B, the product cavity 117 is placed in the upper part, that is, the gate 11 as shown in FIG.
It will be filled from the 6 side.

Continuing to inject molten material further, FIG.
As shown in FIG. 5 (C), the molten material 119 grown in a lump shape.
Crushes the string-shaped molten material 118 accumulated under the product cavity 117 by the filling pressure, and the filling of the molten material into the product cavity 117 is completed. Molten material 118 filled in a string with air in the initial stage of filling
Is compressed in the lower portion of the product cavity 117 at the end of filling, and fusion occurs between the string-like molten materials 118. The trace of fusion at this time becomes a "flow mark", and the air bubbles contained between the string-like molten materials and remaining inside the molded body become "air-containing" defects.

That is, the conventional injection molding method has a problem in that the molten material injected into the product cavity of the mold is allowed to form a cord and gently fill the product cavity. Therefore, it is considered that it is possible to suppress the occurrence of product defects in the central portion and the surface portion of the molded product by uniformly and densely filling the molten material into the product cavity of the mold.

The present invention has been made on the basis of the recognition of such a problem and the investigation into the cause of the conventional injection molding method. A movable member is provided in a product cavity of a mold, and a gate is used at an initial stage of filling. By damming the molten material to be injected with this movable member, it prevents the molten material from becoming a string shape, and enables the uniform and dense filling of the molten material into the product cavity from the initial stage of injection molding. By doing so, the above object is achieved.

That is, the present invention provides a movable part movable in the cavity and a biasing means for biasing the movable part in a mold for injecting a molten material into the cavity to obtain a molded body, The urging means is characterized by urging the movable portion such that the string-shaped material injected into the cavity is stopped by the movable portion and becomes a lump, and then the movable portion retracts.

Further, according to the present invention, in a method for manufacturing a molded body, in which a molten material is injected into a cavity of a mold to manufacture a molded body, a mold having a movable portion in the cavity is used as a mold. It is characterized in that, as the string-shaped material injected into the cavity of the mold is stopped by the mold and becomes a lump, the movable part is retracted and the material is continuously injected.

FIG. 1 is a diagram for explaining a process of filling a product cavity with a molten material in the injection molding method of the present invention. The mold 50 according to the present invention includes a product cavity 5
The movable part 52 which moves in 1 is provided. The movable portion 52 shown in FIG. 1 is an example in which the surface 53 forms part of the cavity wall surface.

First, as shown in FIG. 1 (A), the movable part 5
2 is brought close to the gate 54, the distance between the gate 54 and the surface 53 of the movable part 52 is set to be equal to or less than the maximum distance h at which the molten material 55 can form a mass, and injection is started. The maximum distance h between the gate 54 and the movable part 52 where this molten material can be a lump is
It is determined by the viscosity of the molten material at the time of injection and the diameter of the gate 54. The movable portion 52 is urged toward the gate 54 by urging means such as an air cylinder and a coil spring. The urging means urges the movable part 52 toward the gate 54 with a predetermined force so that the movable part 52 retracts when the injection filling pressure of the molten material exceeds it. Molten material 5
As shown in FIG. 1 (A), the sample No. 5 becomes a lump from the beginning of filling. When the filling is continued, as shown in FIG. 1B, the molten material 55 overcomes the urging force of the movable part 52 and moves the movable part 5.
While pushing 2 downward, the product cavity 51 is filled downward from above. Finally, as shown in FIG. 1C, the entire product cavity 51 is filled and the filling is completed. The molded body is taken out by using the movable portion 52 as an ejector and extruding the molded body from below.

The movable portion 52 shown in FIG. 1 has a surface 53.
Form a wall surface of the product cavity, the surface of the movable part does not necessarily have to form the wall surface of the product cavity. FIG. 2 is a diagram illustrating an example in which the surface of the movable portion does not form the wall surface of the product cavity and moves without contacting the wall surface of the product cavity. FIGS. 2B and 2C are cross-sectional views of a mold 60 for manufacturing the kamaboko-shaped molded body 66 schematically shown in FIG. A gate 64 for injecting a molten material is provided above the mold 60, and a movable portion 62 is provided inside the product cavity 61 so as to face the gate 64.
The movable portion 62 is arranged at a position closest to the gate 64 in the initial state by an urging means such as an air cylinder or a coil spring, and thereafter moves in a direction away from the gate 64 as the injection amount of the molten material increases. As is clear from the figure, in the case of this example, the surface 63 of the movable portion 62 does not always contact the wall surface of the product cavity 61 during the movement of the movable portion 63, and the movable portion 62 does not always contact the wall surface of the product cavity 61. The surface 63 of 62 does not form one wall of the product cavity.

FIG. 3 is a view for explaining how the molten material is filled in the product cavity of the mold shown in FIG.
Similar to the case of FIG. 1, first, as shown in FIG.
The movable part 62 is brought close to the gate 64, the distance between the gate 64 and the surface 63 of the movable part 62 is set to be equal to or less than the maximum distance at which the molten material 65 can form a lump, and injection is started. Moving part 6
2 is biased toward the gate 64 by biasing means such as an air cylinder or a coil spring. The urging means urges the movable portion 62 with a predetermined force toward the gate 64,
When the injection filling pressure of the molten material exceeds it, the movable part 6
Make sure that 2 moves backwards.

Also in this case, the movable portion 6 is provided directly below the gate 64.
Since the second surface 63 is located, the molten material 65 injected from the gate 64 cannot be in the form of a string, but is in the form of a lump from the beginning of filling, as shown in FIG. 3 (A). If the filling of the molten material 65 is continued in this state, as shown in FIG. 3B, the molten material 65 overcomes the urging force of the movable portion 52 and pushes the movable portion 62 downward to fill the product cavity 61. To go. And finally, as shown in FIG.
The entire product cavity 61 is filled and the filling is completed. However, in the case of this mold, the molten material 65 is prevented so that the molten material 65 does not penetrate into the clearance 67 on the lower surface which constitutes the movable portion 62 and the product cavity 61.
Injection speed and retreat speed of the movable part 62 or the movable part 62
It is necessary to adjust the timing of retreat.

In the present invention, the molten material used to form the molded article may be a thermoplastic resin, a thermosetting resin, or various rubbers. Specifically, polyethylene, polypropylene, polyvinyl chloride, polystyrene, ABS resin, AS resin, polymethyl methacrylate, polyvinyl acetate, polyvinylidene chloride,
Fiber-based resin, nylon (polyamide), polyurethane, polyacetal (polyoxymethylene), polycarbonate, modified polyphenylene ether, polypropylene terephthalate, polyethylene terephthalate, ultra high molecular weight polyethylene, polyphenylene sulfide, polysulfone, polyether sulfone, polyether ether ketone , Thermoplastic resins including polyarylate, liquid crystal polymer, olefin vinyl alcohol copolymer, polyamideimide, polyetherimide, polytetrafluoroethylene, phenol resin, urea resin, amino resin such as melamine resin, epoxy resin, unsaturated Polyester resin, diallyl phthalate resin, polyimide resin, silicone resin, polyurethane, silicone elastomer, sheet molding co Thermosetting resin including compound, bulk molding compound, styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber, nitrile rubber, chloroprene rubber, synthetic rubber such as fluororubber, silicone rubber, urethane rubber and natural rubber. A rubber or the like containing the same can be used.

According to the present invention, by filling the movable material in the product cavity while retreating the movable part together with the molten material filling speed, the molten material becomes a lump from the beginning of filling, and a lump filling form from the beginning to the end of filling. The product cavity is densely packed with. Therefore, there is a problem with conventional injection molding methods, such as "flow mark" and "air flow".
It is possible to obtain a molded product excellent in strength without causing product defects such as.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 4 and 5 are cross-sectional views showing an example of an injection molding die used for manufacturing a resin roller, FIG. 4 shows an injection operation state of a molding cycle, and FIG. 5 shows a holding pressure operation state. Represent

The injection molding die 20 is composed of a fixed die 1, a fixed die 2 and a movable die 3 which form a product cavity 4. The movable die 3 is incorporated in the fixed die 2. Has been. The movable mold 3 is made of a cylindrical body such as metal or resin, and at least one O-ring 3E such as rubber for preventing the outflow of the molten resin material is provided on the outer peripheral surface. The fixed mold 1 is attached to the movable part of the injection molding machine (not shown) and the fixed mold 2 is similarly attached to the fixed part with the parting line 7 as a boundary. Although not shown, cooling pipes for controlling the temperature of the mold are incorporated, and the temperatures of the mold 1 and the mold 2 are preferably maintained at 100 to 110 ° C. An injection hole 2A into which a nozzle 5 of an injection molding machine for injecting a resin material is fitted is provided above the molds 1 and 2.

The movable mold 3 constitutes a part of the wall surface of the product cavity 4, and specifically has the roller product cavity wall surfaces 4B, 4C and 4D. Movable mold 3
Is movable by freely sliding in the vertical direction on the mold wall surface 4E formed by the molds 1 and 2. The rear end of the movable mold 3 is connected to the slide rod 3A, and the slide rod is urged by the air cylinder 21 toward the injection hole 2A. The urging force by the air cylinder 21 is 5 when the injection pressure of the resin material is, for example, 500 kgf.
It is about kgf.

Next, a method of filling the product cavity 4 with the molten resin material while moving the movable mold 3 will be described. When the injection molding die 20 is clamped, the movable die 3 is moved to the air cylinder 2 via the slide rod 3A.
It is arranged toward the injection hole 2A along the mold wall surface 4E so as to project into the mold space 14 by the urging force of 1, and the product cavity wall surface 4B of the movable mold 3 and the mold 1,
The second product cavity wall surface 4B is close to or abuts. Therefore, the volume of the product cavity 4 when the slide rod 3A is biased by the air cylinder 21 is determined by the product cavity wall surfaces 4C of the fixed molds 1 and 2 and the product cavity wall surfaces 4C and 4D of the movable mold 3. It is the enclosed volume, and this state is the substantially minimum volume.

As shown in FIG. 4, the product cavity wall surfaces 4B, 4C, 4D of the mold 3 are passed through the nozzle 5 in this state.
The molten resin material 10 is injected and injected as shown by arrow A. The flow pressure F of the molten resin material 10 is the movable mold 3
It is received by the product cavity wall surfaces 4B, 4C, 4D.

When the injection of the molten resin material 10 is further continued, the flow pressure due to the injection is further increased. While balancing with the urging force of the cylinder 21, a backward movement is started in the opposite direction (downward direction in FIG. 4) of the urging force by the increased amount (volume) of the molten material, and the product cavity wall surface 4A increases. In this manner, when the injection of the molten resin and the backward movement of the movable mold 3 are simultaneously continued to perform molding, the resin material 10 is uniformly and densely filled in the product cavity as shown in FIG.

After the filling is completed, the molds 1 and 2 are cooled at a constant speed to mold the resin roller 12. After a lapse of a predetermined time, the mold 20 is divided and the molded shaft-integrated resin roller 12 shown in FIG. 6 is taken out. The resin roller 12 shown in FIG.
6B is molded integrally with the roller main body 25 using a resin composition.

The shaft portion of the roller may be a metal cored bar 27 that penetrates the roller body 25 along the axial direction as shown in FIG. 7A, or as shown in FIG. 7B. In addition, the metal shafts 28A and 28B may be embedded in the roller body 25 so as to project from both ends of the roller body 25 along the axial direction without penetrating the roller body 25. Alternatively, as shown in FIG. 7C, the shaft 29A on one side may be integrally formed with the roller body 25, and the other shaft 29B may be a metal shaft embedded in the roller body 25. Furthermore, these shafts (or cores) 26A, 26B, 27, 28A, 2
8B, 29A, 29B may be provided with a driving gear for rotating the rollers.

In the injection molding mold shown in FIGS. 4 and 5, a coil spring 8 as shown in FIG. 8 may be used instead of the air cylinder as the biasing means for biasing the movable mold 3. it can. In this case, the slide rod 3A connected to the rear end of the movable mold 3 is slidably supported by the bush 9 incorporated in the mold 2, and the end of the slide rod 3A is attached to the movable mold 3. It is supported by the biasing coil spring 8.

FIG. 9 is a sectional view for explaining another example of the injection molding die according to the present invention. The mold 30 of this example is provided with a plurality of movable molds (two in FIG. 9) made of a cylindrical body such as metal or resin, and the movable molds 3B and 3C are symmetrical with respect to the inlet 2A. The structure is such that it moves forward or backward by distance. The rear ends of the movable molds 3B and 3C are connected to the slide rod 3A, and the end of the slide rod 3A is supported by the coil spring 8.

In the engaged state of the die 30 composed of the fixed dies 1 and 2, the movable dies 3B and 3C are urged by the coil spring 8 in the direction of approaching each other, and the volume of the product cavity 4 is minimized. Has become. In this state, the molten resin material is injected and injected into the product cavity 4 of the mold 30 through the nozzle 5. The flow pressure of the molten resin material is received by the wall surfaces of the product cavities of the movable molds 3B and 3C. When the injection of the molten resin material is further continued, the flow pressure due to the injection is further increased.
C moves backward in the opposite direction of the urging force (left and right direction in FIG. 9) by an amount (volume) of the molten resin material while balancing with the urging force of the coil spring 8 via the slide rod 3A.
The volume of the product cavity 4 increases.

In this way, when the injection of the molten resin material and the backward movement of the movable molds 3B and 3C are simultaneously and continuously performed for molding, the resin material is uniformly and densely filled in the product cavity. After that, when the molds 1 and 2 are cooled at a constant speed, the resin roller is molded. Then, after a predetermined time has passed, the mold 30 is divided to obtain the molded shaft-integrated resin roller 12 shown in FIG. Although the coil spring 8 is used as the urging means for the movable molds 3B and 3C in FIG. 9, other urging means such as an air cylinder may be used instead of the coil spring.

FIGS. 10, 11 and 12 are sectional views for explaining another example of the injection mold according to the present invention. The mold 40 of this example is for manufacturing a shaft-integrated roller in which a roller body 25 made of a resin material and a metal cored bar 27 are integrally molded as shown in FIG. 7 (A).
FIG. 10 is a sectional view of the injection-molding die in a clamped state, and FIGS. 11 and 12 are sectional views of the die during resin roller molding.

The injection molding die 40 is composed of a fixed die 1, a fixed die 2 and a movable die 3 which form the product cavity 4. The fixed mold 1 and the fixed mold 2 can be fixed by clamping a metal cored bar 27 in the center of the mold space 14 during mold clamping. The movable mold 3 is a core metal 27
Is formed of a columnar body such as metal or resin having a through hole 3D through which is inserted, and at least one O-ring 3E such as rubber for preventing the outflow of the molten resin material is provided on the outer peripheral surface. The movable mold 3 is a cored bar 2 fixed to the fixed molds 1 and 2.
7 is slidable along the mold wall surface 4E so that the fixed molds 1 and 2 can freely move from one end to the other end of the product cavity wall surface 4B.

One fixed mold 1 is attached to the movable part of the injection molding machine (not shown) and the other fixed mold 2 is similarly attached to the fixed part with the parting line 7 as a boundary. Although not shown, the fixed molds 1 and 2 have cooling pipes incorporated therein for controlling the temperature of the molds. An injection hole 2A into which a nozzle 5 of an injection molding machine for injecting a resin material is fitted is provided above the mold 2.

In the mold clamping state of the mold 40, as shown in FIG. 10, the movable mold 3 is placed on the product cavity wall surface 4B on the injection hole 2A side so that the product cavity 4 has a substantially minimum volume. Keep it close. In this state, as shown in FIG. 11, the molten resin material 10 is injected and injected into the product cavity wall surface 4B of the mold 3 through the nozzle 5 as shown by an arrow A. The flow pressure F of the melted resin material 10 is received by the product cavity wall surface 4B of the movable mold 3. When the injection of the molten resin material 10 is further continued, the flow pressure due to the injection further increases, but in response to the increase of the flow pressure, that is, the increase of the molten resin material, the movable mold 3 includes the O-ring 3E and the molds 1 and 2. While balancing the frictional force of the mold wall surface 4E,
The increased amount (volume) of the molten resin material 10 moves backward toward the end of the mold space 14 on the side opposite to the injection hole 2A (downward direction in FIG. 11), and the product cavity wall surface 4A increases.

In this way, when injection molding of the molten resin material and backward movement of the movable mold 3 are simultaneously continued to perform molding,
As shown in FIG. 12, the resin material is uniformly and densely filled in the product cavity 4. After that, when the fixed molds 1 and 2 are cooled at a constant speed, the resin roller is molded. After a lapse of a predetermined time, the mold 40 is divided and the molded shaft-integrated roller shown in FIG. 7A is taken out.

Next, an example in which a shock absorbing rubber body is manufactured by using the injection molding die according to the present invention will be described. FIG.
FIG. 14 is a perspective view of a shock absorbing rubber body, and FIG. 14 is an explanatory view of an injection molding die used for manufacturing. The shock-absorbing rubber body 79 manufactured here has a hollow cylindrical shape with an inner diameter of 16 mm, an outer diameter of 65 mm, and a height of 80 mm.
It is possible to provide vibration insulation when attaching mechanical instruments such as precision instruments and instruments to the floor surface or when suspending and fixing the blower from the ceiling.

FIG. 14B is a sectional view of the injection molding die, and FIG. 14A is a sectional view taken along the line AA of FIG. 14B. The mold 70 has a cylindrical product cavity 71 inside, and the NR-based molten rubber material injected from the nozzle of the injection molding machine passes through four runners 78A, 78B, 78C, 78D and at four locations. It is injected into the product cavity 71 from the gates 74A, 74B, 74C and 74D. Inside the product cavity 71, an annular movable mold 81 that is moved by the bias of the air cylinder 80 is provided. The upper surface 76 of the movable mold 81 is an annular flat surface that serves as one wall surface of the product cavity, and by driving the movable mold 81 by the air cylinder 80, the upper surface 76 of the movable mold 81 is different from the product cavity 71. It is possible to move inside the product cavity 71 by sliding on the wall surface of the product. In addition, the movable mold 8
Instead of the air cylinder 80, other means, for example, a coil spring, may be used as a means for urging 1.

Before the injection of the molten rubber material 75 into the product cavity 71 is started, the movable mold 81 is brought close to or abutted against the gates 74A to 74D by the bias of the air cylinder 80. In this state, the volume of the product cavity 71 is
Vertical product cavity wall surface and upper surface 76 of movable mold 81
The volume is surrounded by, and this state is substantially the minimum volume. In this state, the molten rubber material 75 is injected and injected into the product cavity 71 of the mold 70 from the four gates 74A to 74D through the runners 78A to 78D. The flow pressure of the molten rubber material 75 is the upper surface 76 of the movable mold 81.
Can be accepted by. The molten rubber material 75 injected from the four gates 74A to 74D into the product cavity of the minimum volume spreads around the gates 74A to 74D to fill the product cavity 71, and the molten rubber material injected from different gates. Welds are welded to each other in the circumferential direction of the product cavity 71 and weld fusion occurs immediately after the start of injection.

Here, when the movable mold 81 is lowered by starting the injection of the molten rubber material 75, the initial internal pressure of the air cylinder 80 is increased by the rising force of the movable mold 81 to about 1 point per gate.
It is set so as to apply more than kg, and it is lowered when the injection filling pressure of the molten rubber material exceeds its rising force. If the raising force of the movable die 81 by the air cylinder 80 is too strong, there is a problem that the molten rubber material enters the clearance between the wall surface of the product cavity 71 and the movable die 81, and the raising force of the movable die 81 is increased. If it is too weak, the molten rubber material 75 injected from each gate 74A to 74D
The fusion timing of the welds in which the lumps of the two contact with each other in the circumferential direction and fuse together is delayed, and the merit of increasing the weld strength is reduced.

When the injection of the molten rubber material 75 is further continued, the flow pressure due to the injection is further increased.
1 starts retreating in the direction opposite to the urging force by the increasing volume of the molten rubber material 75 while balancing with the urging force of the air cylinder 80, and the volume of the product cavity 71 increases. In this manner, injection molding of the molten rubber material 75 and backward movement of the movable mold 81 are continuously performed at the same time so that the molten rubber material 75 is uniformly distributed in the product cavity 71 as in the above-described respective examples. And densely packed. After that, when heat-vulcanized in the mold 70, the shock absorbing rubber body shown in FIG. 13 is molded. After a lapse of a predetermined time, the mold is divided and the movable mold 81 is driven upward by the air cylinder 80, so that the movable mold 81 urged by the air cylinder 80 is used as a mold ejector. The molded impact absorbing rubber body is taken out of 70.

For comparison, a shock absorbing rubber body for comparison was manufactured by using a conventional injection mold similar to the injection mold 70 shown in FIG. 14 except that the movable mold 81 was not used. The appearance of a shock-absorbing rubber body manufactured using the injection mold shown in FIG. 14 (hereinafter referred to as the product of the present invention) and the shock-absorbing rubber body for comparison (hereinafter referred to as the comparative product), containing air, and bare. The defective rate and 0 to 50% compression durability were compared.

Here, the bare defect refers to a rubber chipping defect caused in the outer shape of the product by the air remaining between the cavity wall and the rubber, because the air in the product cavity is not discharged when the molten rubber material is injected. For air-containing and bare defect rate, bare (rubber missing)
Also, it was measured by a method of counting those with blisters (containing air). For 0 to 50% compression durability, the impact absorbing rubber body is continuously subjected to repeated compression of 0% (not compressed) and 50% in the height direction at a frequency of 1 Hz, and the number of times until a crack is generated in the product is measured. I asked.

When the appearance was compared by visual observation, a slight weld mark was recognized in the product of the present invention, but no flow mark was found. On the other hand, weld marks and flow marks were clearly recognized in the comparative product. The defective rate of the product of the present invention containing air and bare was less than 1/10 of that of the comparative product.
Further, when the compression durability was compared with 0 to 50%, the product of the present invention showed a compression durability almost four times that of the comparative product.

[0047]

According to the present invention, the product defects on the surface and inside of the molded product manufactured by the injection molding method can be remarkably reduced, and a molded product excellent in strength can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a process of filling a product cavity with a molten material in the injection molding method of the present invention.

FIG. 2 is an explanatory view of an injection molding die in which a surface of a movable portion does not form a wall surface of a product cavity.

FIG. 3 is a diagram for explaining how the molten material is filled in the product cavity of the mold shown in FIG.

FIG. 4 is a sectional view showing an example of an injection molding die according to the present invention.

FIG. 5 is a cross-sectional view of an injection molding die during a pressure holding operation.

FIG. 6 is a sectional view of a shaft-integrated roller.

FIG. 7 is a cross-sectional view illustrating the structure of a magnet roller.

FIG. 8 is a cross-sectional view showing another example of the injection molding die according to the present invention.

FIG. 9 is a cross-sectional view showing another example of the injection molding die according to the present invention.

FIG. 10 is a sectional view showing another example of an injection molding die according to the present invention.

FIG. 11 is a cross-sectional view of an injection molding die during roller molding.

FIG. 12 is a cross-sectional view of an injection molding die during roller molding.

FIG. 13 is a perspective view of a shock absorbing rubber body.

FIG. 14 is an explanatory view of an injection molding die used for manufacturing a shock absorbing rubber body.

FIG. 15 is an explanatory diagram of a process in which a defect is formed by a conventional injection molding method.

FIG. 16 is a sectional view of a mold during molding of a conventional roller.

FIG. 17 is an explanatory diagram of flow marks and air entering.

[Explanation of symbols]

20, 30, 40, 50, 60, 70, 100, 115
Mold 1, 2, 101, 102 Fixed mold 2A, 102A Injection hole 3, 3B, 3C, 81 Movable mold 3A Slide rod 3D Through hole 3E O-ring 4, 51, 61, 71, 117 Product cavity 4A , 4B, 4C, 4D Product cavity wall surface 4E Mold wall surface 5,105 Nozzle 7,107 Parting line 8 Coil spring 9 Bracket 10 Resin magnetic material 12 Resin roller 14 Mold space 21,80 Air cylinder 25 Roller body 27 Core Gold 52,62 Movable part 53,63 Movable part surface 54,64,74A to 74D, 116 Gate 55,65 Melt material 75 Molten rubber material 78A to 78D Runner 79 Impact absorbing rubber body 111 Flow mark 112 Air entry defect A Flow direction F Flow pressure

Claims (4)

[Claims] 1. A mold for injecting a molten material into a cavity to obtain a molded body, comprising: a movable part movable in the cavity, and an urging means for urging the movable part. The die is characterized in that the urging means urges the movable portion so that the movable portion retracts after the material injected into the cavity is blocked by the movable portion and becomes a lump. 2. The mold according to claim 1, wherein the urging means is a coil spring or an air cylinder. 3. The mold according to claim 1, wherein a surface of the movable portion forms at least a part of a wall surface of the cavity. 4. A method for manufacturing a molded body, comprising manufacturing a molded body by injecting a molten material into a cavity of a mold, wherein the mold is a mold according to any one of claims 1 to 3. The injection of the molten material is continued while retracting the movable portion as the mass of the molten material formed by being injected into the cavity of the mold and stopped by the movable portion becomes larger. And a method for producing a molded article.