JP7488755B2 - Foam molding mold and method for manufacturing foam molded product using the same - Google Patents

Description

The present invention relates to a foam molding mold in which foaming raw material such as polyurethane is injected into a mold to form a foam molded product, and a method for manufacturing a foam molded product using the same.

For example, there is a foam molded rigid urethane product 6 (Fig. 3A) that is placed inside a vehicle door and absorbs the energy of a collision by collapsing by itself in the event of a side impact, and a foam molded armrest 6 (Fig. 3B) made of soft urethane foam that can be tilted in the center of the rear seat of a vehicle so that when it is tilted down, an elbow can be rested on it or a drink can be placed on it. These foam molded products 6 are generally made by injecting a predetermined amount of foaming material into a lower mold 2B as shown in Fig. 8, closing the lower mold 2B and the upper mold 3B, and then foam molding.
However, it was difficult to close and seal the lower mold 2B and the upper mold 3B, and the foaming raw material leaked from the mating surface of the lower mold 2B and the upper mold 3B, which tended to cause burrs on the foam-molded product 6 obtained by foam molding. The task of removing the burrs in post-processing was troublesome, and the workload increased as the number of pieces increased.
For this reason, several inventions have been proposed that aim to minimize the occurrence of burrs (for example, Patent Document 1).

JP 2006-35590 A

However, as described in claim 1 of Patent Document 1, "...an annular recess is formed so as to surround the cavity, a synthetic resin seal member is provided in the annular recess so as to be capable of contacting and releasably contacting the split surface of the second split mold, an annular groove is formed in the end of the seal surface of the seal member, and a packing material that is in close contact with the split surface of the second split mold is fitted into the groove," which places a burden on the user of having to periodically replace the packing material. In addition, there is a risk that the foaming material may get in between the packing material and the split mold, and once it gets in, it is difficult to remove.

The present invention aims to solve the above problems by providing a foam molding die that can minimize the occurrence of burrs in foam molded products without using packing material, and a method for manufacturing foam molded products using the same.

In order to achieve the above object, the gist of the invention as set forth in claim 1 is an expansion molding die having a lower die and an upper die, which forms a cavity for an expansion molded product by closing the die, the lower die has a die mating surface that spreads outwardly upward from the periphery of the opening of the cavity surface that forms a recess, the die mating surface comes into contact with the die mating surface of the upper die by closing the die, and a frame-shaped portion including an outer peripheral side surface that connects at least each side surface of the lower die with the opening of the recessed cavity surface on the upper side has a linear expansion coefficient smaller than that of the upper die. The expansion molding die as set forth in claim 2 is the expansion molding die as set forth in claim 1, which is characterized in that the upper die is made of an aluminum material, and the frame-shaped portion is made of a metal material having a linear expansion coefficient smaller than that of the aluminum material. The foam molding mold according to claim 3 is the foam molding mold according to claim 1 or 2, characterized in that the material of the main part of the lower mold that forms the cavity surface and the mold mating surface of the lower mold is an aluminum material, and the material of the frame-shaped part surrounding the main part of the lower mold is a metal material having a linear expansion coefficient smaller than that of the aluminum material. The gist of the invention according to claim 4 is a foam molding mold that includes a lower mold and an upper mold, and forms a cavity for a foam molding product by closing the mold, the lower mold has a mold mating surface that spreads outwardly upward from the opening periphery of the cavity surface that forms the recess, and the mold mating surface comes into contact with the mold mating surface of the upper mold by closing the mold, and the mold material that forms the cavity surface of the lower mold has a linear expansion coefficient relatively smaller than that of the mold material that forms the cavity surface of the upper mold. The foam molding mold according to claim 5 is the foam molding mold according to claims 1 to 4, characterized in that the linear expansion coefficient of the entire lower mold including the frame-shaped part is smaller than that of the upper mold. The foam molding die of the invention of claim 6 is any of claims 1 to 5, characterized in that a holding member passes through a through hole provided in a support member, and its tip is fixed to the upper surface of the upper mold so that the upper mold is held by the support member, and the through hole is set larger than the shaft diameter of the holding member, so that the upper mold can move freely in the horizontal direction, forward and backward and left and right, in a plan view, in response to temperature changes. The foam molding die of the invention of claim 7 is any of claims 1 to 6, characterized in that the foam molding die is a die for producing a foam-molded product of polyurethane foam.
The gist of the invention described in claim 8 is a method for producing a foam-molded product, which is characterized in that a foaming raw material for a foam-molded product is injected onto the cavity surface of a lower mold using a foam molding mold described in any one of claims 1 to 7, the mold is closed, foam molding is performed, and then the foam-molded product is removed from the mold and taken out.

(Action)
When the lower mold has a mold mating surface that spreads outward from the opening periphery of the cavity surface that forms the recess, and the mold mating surface comes into contact with the mold mating surface of the upper mold by closing the mold, and when the second component is provided, the frame-shaped portion including the outer peripheral side surface that connects at least each side surface of the lower mold with the opening of the recessed cavity surface on the upper side surface has a linear expansion coefficient smaller than that of the upper mold, the cavity surface of the upper mold becomes larger than the opening of the lower mold as the temperature rises. Furthermore, when the foam molding mold is closed in this state, the upper mold cavity surface comes to the lower mold mating surface that is higher than the opening periphery, and the upper mold mating surface comes into contact with the lower mold mating surface in a manner that the upper mold mating surface is securely placed on the lower mold mating surface, which leads to suppression of burrs. Furthermore, when the mold mating surface is made of aluminum material, the mold mating surface is plastically deformed by the mold closing, and a better zero-touch seal surface with a burr suppression effect is quickly formed.

As in the foam molding mold of the present invention and the manufacturing method of foam molded products using the same, when the configuration of the mold mating surface of the lower mold that spreads outward toward the top is added with a configuration that suppresses thermal expansion of the lower mold side compared to the upper mold when the foam molding mold is heated from the room temperature at the time of mold production to the high temperature of foam molding, the contact seal when the mold is closed is improved without the help of a separate member such as a packing material, and the occurrence of burrs in the foam molded product can be minimized, which is an excellent effect.

FIG. 2 is a partially sectional perspective view of the foam molding mold of the present invention. 2 is a vertical cross-sectional view of the foam molding mold of FIG. 1 at or near room temperature upon completion of fabrication. FIG. FIG. FIG. 2 is a longitudinal cross-sectional view of a foaming mold in which foaming raw material is injected in an open state during foam molding. FIG. 5 is a vertical cross-sectional view of the foam molding mold after closing from the state shown in FIG. 4 . FIG. 6 is a plan view taken along line VI-VI of FIG. 5 . FIG. 4 is a vertical cross-sectional view of a foam molding mold according to another embodiment. FIG. 6 is a longitudinal sectional view corresponding to FIG. 5 in the case where a conventional foam molding die is used. 9A is a partially enlarged view of FIG. 8, and FIG. 9B is a view of another embodiment replacing FIG. FIG. 7 is a vertical sectional view of a foam molding mold of another embodiment, which is an alternative to those shown in FIGS. 1 to 6.

The foam molding mold according to the present invention and the manufacturing method of the foam molded product using the same will be described in detail below. Figures 1 to 10 show one embodiment of the foam molding mold and the manufacturing method of the foam molded product using the same, where Figure 1 is a partial cross-sectional perspective view of the foam molding mold, Figure 2 is a vertical cross-sectional view of the foam molding mold of Figure 1 at room temperature, Figure 3 is a perspective view of the foam molded product, Figure 4 is a vertical cross-sectional view of the foaming raw material being injected into the lower mold in the open state, Figure 5 is a vertical cross-sectional view of the foam molding mold closed from the state of Figure 4, Figure 6 is a plan view of Figure 5, Figure 7 is a cross-sectional view of another embodiment of the foam molding mold, Figure 8 is a vertical cross-sectional view corresponding to Figure 5 of the conventional foam molding mold, Figure 9 (A) is a partially enlarged view of Figure 8, (B) is another embodiment instead of (A), and Figure 10 is a vertical cross-sectional view of a different embodiment of the foam molding mold. Note that each figure is simplified and the essential parts of the invention are emphasized for ease of understanding. Parts that are not directly related to the present invention are omitted, and the connection means 2J is not illustrated in any figures other than Figure 1, and the support member 4 and holding member 5 are not illustrated in any figures other than Figure 5 and Figure 6.

(1) Foam molding mold This foam molding mold 1 is a metal mold that has a lower mold 2 and an upper mold 3, and forms a cavity C for a foam molded product 6 by closing the mold (Figs. 1 to 6). The cavity C is where the foam molded product 6 as shown in Fig. 3(a) is foam molded, but here the cavity C is illustrated simply as a roughly rectangular body for the sake of convenience.

The lower mold 2 has a mold mating surface 22 that spreads outward from the opening periphery 211 of the cavity surface 21 that forms the recess. In the present invention, "upward" literally refers to the upper side of the paper in the front view of the cross-section shown in Figure 2. The mold mating surface 22 spreads outward in a trumpet shape as shown in Figure 1, but it is sufficient if it is an inclined surface that spreads outward from the opening periphery 211 of the lower mold cavity surface 21 toward the opposing upper mold 3. This mold mating surface 22 and the mold mating surface 32 on the upper mold 3 side are abutted by mold closing. The lower mold 2 has a frame-shaped portion 2F that includes an outer peripheral side surface 2b that connects at least each side surface 2b of the lower mold 2 with the opening 20 of the recessed cavity surface 21 on the upper surface 2a side, and the linear expansion coefficient of the frame-shaped portion 2F is set to be smaller than the linear expansion coefficient of the upper mold 3.

The frame-shaped portion 2F and the lower mold 2 including the frame-shaped portion 2F can be made of the same material so that the linear expansion coefficient of the entire lower mold 2 is smaller than the linear expansion coefficient of the upper mold 3.
However, the lower mold 2 of this embodiment is made of different materials, that is, a main part 2M in which a cavity C of an upper surface opening 20 is formed by cutting a solid rectangular block by an end mill or the like, and a frame-shaped part 2F of a thickness t including an outer peripheral side surface 2b, which surrounds each side surface 2Mb of the main part 2M as shown in Figs. 2 and 6. The material of the lower mold main part 2M which forms the cavity surface 21 and the mold mating surface 22 of the lower mold 2 is aluminum material, and the frame-shaped part 2F surrounding the lower mold main part 2M is made of a metal material having a linear expansion coefficient smaller than that of the aluminum material. The material of the frame-shaped part 2F which surrounds the outer peripheral side surface 2Mb of the lower mold main part 2M in close contact with it is an inorganic material such as a metal (here, structural steel) having a linear expansion coefficient smaller than that of aluminum shown in Table 1. The inner side surface 2Fb of the frame-shaped part 2F is welded at necessary places so as to be in close contact with and integrated with the main part side surface 2Mb. Although the reference symbol 2J indicates the welded part, other joining means may be used.

Table 1. Linear expansion coefficients of various metals

The upper mold 3 is a split mold of the foam molding mold 1 having a mold mating surface 32 which comes into contact with the mold mating surface 22 of the lower mold 2 when the mold is closed.
The upper mold 3 is made of the same aluminum material as the lower mold main part 2M. The mold mating surface 32 of the upper mold 3 is finished so that it comes into intimate contact with the mold mating surface 22 of the lower mold 2 when the mold is closed under the normal temperature environment during mold production, as shown in Fig. 2. The periphery 311 of the upper mold cavity surface 31 and the opening periphery 211 of the lower mold cavity surface 21 coincide with each other. The mold mating surface 32 of the upper mold 3 tapers gradually toward the bottom end so that the lower mold mating surface 22, which spreads out upward from the lower mold opening periphery 211 like a trumpet, can come into contact with the substantially entire area of the mold mating surface 32 of the upper mold 3 when the mold is closed (Fig. 1).
At least one of the mating surfaces 22, 32 of the lower mold 2 and the upper mold 3 is provided with a degassing groove (not shown) for releasing excess gas during foam molding. When the mold is closed at room temperature during mold production, the entire area of the upper mold mating surface 32 except for the degassing groove is in contact with the lower mold mating surface 22.

However, the temperature in the foam molding process for producing the foam molded product 6 is higher than room temperature. For example, the polyurethane foam molded product 6 shown in Fig. 3 is produced in an environment of about 60°C. Therefore, when the temperature changes from room temperature or a temperature close to room temperature at which the foam molding die 1 is produced to the high temperature during foam molding, the lower die 2 and upper die 3 made of the same material undergo thermal expansion (linear expansion). In Fig. 1, the transverse distance L2 of the lower die opening periphery 211 and the transverse distance L3 of the cavity surface 31 of the upper die 3 corresponding to the transverse distance L2 extend due to thermal expansion.
At room temperature, the mold mating surfaces 22, 32 are adjusted to form a tight seal when the molds are closed, but when exposed to the temperature of about 60°C during foam molding, the shapes of the lower mold 2 and upper mold 3 are different even if they are made of the same material (for example, aluminum), so if the conventional type lower mold 2B and upper mold 3B shown in Figure 8 are used, they will deform individually, and this deformation will lead to the generation of burrs. When the temperature changes from room temperature to the temperature during foam molding, the lower mold 2B and upper mold 3B will not expand to a similar shape while maintaining their shape, but will deform as shown by the chain line in Figure 8, for example. Different changes will occur even if the lot of the foam molding mold is different.
If the upper mold 3B warps or the opening periphery 211 of the cavity surface 21 of the lower mold 2B widens, a gap ε is created when the upper mold 3B descends to close the mold (Fig. 9(A)). During foam molding, the foaming raw material g leaks out from the gap ε. Even if the upper mold 3 is lowered further than the lowest point, the mold mating surfaces 22, 32 do not form a tight seal surface as shown in Fig. 9(B), and a lot of burrs are generated.

The foam molding die 1 solves the problem of burrs by selecting a metal material having a smaller linear expansion coefficient than the aluminum material for the material forming the frame-like portion 2F surrounding the lower mold main portion 2M, even if the material for forming the lower mold main portion 2M that forms the cavity surface 21 and mold mating surface 22 of the lower mold 2 is the same aluminum material as the upper mold 3. Here, structural steel SS400 is used for the material forming the frame-like portion 2F.
The foam molding mold 1 is completed at room temperature 23°C, and then the temperature is raised to 60°C for foam molding. Then, in FIG. 1, if the distance L between both sides of the lower mold main part 2M made of aluminum (aluminum A2017 in Table 1) is 500 mm at room temperature, it will expand by about 0.44 mm, but the length L between the inner sides of the frame-shaped part 2F made of structural steel will only expand by 0.21 mm. As a result, in FIG. 1, the frame-shaped part 2F holds down the expansion of the lower mold main part 2M from the left and right outer sides of the paper toward the opening 20 side. When the temperature rises from room temperature to 60°C for foam molding, the horizontal length L of the lower mold main part 2M is held down from both sides by the frame-shaped part 2F and the expansion becomes smaller than 0.44 mm, while the upper mold 3 side is not restricted by the frame-shaped part 2F and can expand freely as it is.
Therefore, when the foam molding mold 1 aligned at room temperature as shown in Fig. 2 is opened and then closed at the high temperature of foam molding, the relationship will inevitably be {transverse distance L3 of upper mold cavity surface 31>transverse distance L2 of lower mold opening periphery 211}. As shown in Fig. 5, periphery 311 of upper mold cavity surface 31 comes onto mold matching surface 22, which is higher than opening periphery 211 of lower mold 2, and mold matching surface 22 of lower mold 2 and mold matching surface 32 of upper mold 3 come into contact. The gap ε seen in Fig. 9(a) no longer occurs, and mold matching surface 32 of upper mold 3 reliably comes into contact with mold matching surface 22 of lower mold 2.

Moreover, the material forming the upper mold 3 and the lower mold main part 2M is aluminum, which is a soft material among metal materials. In the initial downward movement of the upper mold 3 as shown in FIG. 5, the periphery 311 of the upper mold cavity surface 31 stops at the mold mating surface 22 at an intermediate position higher than the opening periphery 211 of the lower mold 2. The upper mold 3 hits the mold mating surface 22 with the downward dynamic pressure that still has some reserve and has not yet reached the original bottom position. As the number of mold closings increases, the contact surfaces of the upper mold mating surface 32 and the lower mold mating surface 22 become familiar with each other, and the contact surface smoothly transitions to a tight seal. Furthermore, if both parts of the lower mold 2 and the upper mold 3 that form the mold mating surfaces 22 and 32 are made of a soft metal material such as aluminum, as in this embodiment, the contact surfaces become familiar with each other quickly, and the contact seal is accelerated.
Furthermore, when the mold mating surfaces 22, 32 are formed by cutting using an end mill or the like as described above, it is difficult to make the mold mating surfaces 22, 32 into a zero-touch tight seal surface, and when viewed under a microscope, there are irregularities caused by the end milling that can lead to burrs. As the number of mold closing cycles increases, the irregularities caused by the end milling are smoothed out, and the contact surfaces of the mold mating surfaces 22, 32 of the upper mold 3 and the lower mold 2 become more compliant, resulting in a convenient foam molding mold 1 that eliminates the irregularities.

The present invention is not limited to the above embodiment, and many modifications are possible within the technical concept of the present invention. The present invention is not limited to the foam molding mold 1 shown in Figs. 1 to 6 of the embodiment, and may be, for example, a foam molding mold 1 in which the linear expansion coefficient of the entire lower mold 2 is smaller than that of the upper mold 3. The foam molding mold 1 may be a foam molding mold 1 in which the linear expansion coefficient of the bottom surface portion including the bottom surface 2c of the lower mold 2 is smaller than that of the upper mold 3, in addition to the frame portion 2F including the outer peripheral side surface that connects at least each side surface 2b of the lower mold 2 and goes around once. This produces the same action and effect as the present embodiment.
In addition, in the foam molding mold 1 in which the lower mold mating surface 22, which spreads outwardly upward from the opening periphery 211 of the cavity surface 21 forming the recess, and the upper mold mating surface 32 come into contact with each other, if the mold material forming the cavity surface 21 of the lower mold 2 has a linear expansion coefficient relatively smaller than that of the mold material forming the cavity surface 31 of the upper mold 3, the requirements of the foam molding mold 1 are satisfied. For example, as shown in FIG. 7, the mold material portion of the lower mold main part 2K forming the cavity surface 21 has a linear expansion coefficient relatively smaller than that of the mold material forming the cavity surface 31 of the upper mold 3. In addition, in the foam molding mold 1 in which each side surface of the lower mold main part 2K is surrounded by an enclosure 29 and adopted as the lower mold 2. The enclosure 29 may be omitted, and even if it is present, the linear expansion coefficient does not matter. The lower mold 2 and the upper mold 3 are not limited to those in which the cavity C is formed by cutting a massive block, but may be those formed by casting processing as shown in FIG. 10.

In addition, the upper mold 3 of this embodiment has a support member 4 attached to its upper surface 3a as shown in Figures 5 and 6. An actuator (not shown) moves the upper mold 3 up and down via the support member 4 to open and close the mold with the lower mold 2, and the upper mold 3 is attached so that it can linearly expand in the up, down, left and right directions (arrows in the figure) on the paper as viewed from above in Figure 6 as the temperature rises.
In detail, the holding member 5 passes through a through hole 40 provided in the support member 4, and its tip portion is fixed to the upper surface 3a side of the upper die 3, so that the upper die 3 is held by the support member 4. The through hole 40 is set larger than the shaft diameter of the holding member 5, so that the upper die 3 can freely move back and forth and left and right in the horizontal direction of the paper in the plan view of Fig. 6 due to temperature changes. The support member 4 here is a grooved steel 4A as shown in Fig. 5, and the holding member 5 is a bolt 5A. The grooved steel 4A has upright portions 42 standing on both sides of a base portion 41, and the base portion 41 that abuts against the upper surface 3a of the upper die 3 is provided with a through hole 40 with a hole diameter larger than the shaft portion 52 of the bolt 5A.
In Fig. 5, after the groove steel 4A is positioned and set on the upper surface 3a of the upper die, the bolt shank 52 passes through the through hole 40 from above the base portion 41 and is screwed and fixed to the upper die 3, so that the upper die 3 is held by the groove steel 4A. Because the through hole 40 is set larger than the shank diameter of the bolt 5A, in the plan view of Fig. 6, the upper die 3 can freely move forward, backward, left and right in the horizontal direction on the page relative to the bolt 5A and the groove steel 4A. When the temperature rises to the foam molding temperature, the groove steel 4A of the support member 4 does not hinder the thermal expansion (linear expansion) of the upper die 3 in the horizontal direction on the page.

In this way, frame portion 2F, which has a linear expansion coefficient smaller than that of lower mold main part 2M, limits the thermal expansion (linear expansion) of lower mold main part 2M at high temperatures. This restriction ensures that upper mold mating surface 32 is always placed on lower mold mating surface 22 when the mold is closed. Furthermore, when the temperature rises, support members 4 and holding members 5 allow upper mold 3 to be freely expandable in a plan view, resulting in a foam molding mold 1 that does not impede the thermal expansion (linear expansion) of upper mold 3. The desired foam molding mold 1 is completed, which has the effect of suppressing the generation of burrs during foam molding.
Reference numeral 3 b denotes a side surface of the upper mold, reference numeral 35 denotes a screw hole for a bolt which is a holding member 5 , and reference numeral 51 denotes a bolt head 51 of the holding member 5 .

(2) Manufacturing method of foam-molded article using a foam molding mold The manufacturing method of a foam-molded article uses the foam molding mold 1 of (1). First, an insert item 8, if any, is set in the mold. Then, foaming raw material g is injected and the mold is closed to produce a foam-molded article 6 such as a soft or hard polyurethane foam.
Here, we will describe one manufacturing method for molding the rigid urethane foam molded product 6 in Figure 3(A) using the foam molding die 1 in Figures 1 to 6. The upper die 3 and the main part 2M of the lower die are made of aluminum, and the frame-shaped part 2F is made of a metal material (structural steel SS400, etc.) that has a smaller linear expansion coefficient than the aluminum. The rigid urethane foam molded product 6 is an impact absorbing material that is installed inside a vehicle door, and in the event of a side collision, it collapses by itself to absorb the collision energy and protect the occupants.

First, the foam molding mold 1 as shown in Fig. 2, in which the opening periphery 211 of the lower mold cavity surface 21 is aligned with the periphery 311 of the upper mold cavity surface 31, is placed under the environmental temperature (about 60°C) for foam molding. Then, this foam molding mold 1 is brought into the open state as shown in Fig. 4.
When the foam molding mold 1 is placed under a temperature ranging from room temperature to about 60°C, the lower mold main part 2M tries to expand outwardly toward the side surface 2Mb as shown by the arrow in Figure 4. However, the frame-shaped part 2F, which has a smaller linear expansion than the main part 2M, is already tightly attached to and surrounds the main part side surface 2Mb at room temperature during mold production, so that the expansion of the main part 2M outwardly toward the side surface 2Mb is suppressed (the x on the arrow in Figure 4).

Next, an insert 8 (not shown) is set on the lower mold cavity surface 21 or the upper mold cavity surface 31 while the mold is open. Next, with the mold open, a predetermined amount of foaming raw material g for the foamed molded body 7 is injected onto the lower mold cavity surface 21 using an injection hose NL or the like.

After that, the upper mold 3 is operated to close the mold (FIG. 5). When the upper mold 3 moves downward by closing the mold, the main part side surface 2Mb is clamped by the frame-shaped part 2F as described above, so that the part of the opening periphery 211 of the upper mold cavity surface 31 that has freely expanded under the temperature of the foam molding environment stops at a point on the lower mold mating surface 22 above the opening periphery 211 of the lower mold cavity surface 21 that it reached at room temperature. When the upper mold 3 moves downward by closing the mold, the periphery 31 of the upper mold cavity surface 31 abuts against the lower mold mating surface 22 above before it reaches the opening periphery 211 of the lower mold cavity surface 21. The upper mold 3 moves downward by the force of the actuator (not shown), but since it has not yet reached the bottom, the upper mold 3 strongly abuts against the lower mold mating surface 22 and comes into close contact.
In addition, the upper mold 3 is held by the support member 4 with the holding member 5 passing through a through hole 40 provided in the support member 4 and its tip fixed to the upper surface 3a of the upper mold, and the through hole 40 is set to be larger than the shaft diameter of the holding member 5. Therefore, the upper mold 3 can move freely and expand back and forth and left and right in the horizontal direction of the paper surface of Fig. 6 in accordance with the rise in temperature. When the mold is closed, the peripheral edge 311 of the upper mold cavity surface 31 that has moved downward, i.e., the lower edge of the upper mold mating surface 32, can be reliably abutted against the lower mold mating surface 22 that spreads upward from the lower mold opening peripheral edge 211.
In this embodiment, the mold is closed after the foaming raw material g is injected, but the foaming raw material g can also be injected after the mold is closed.

Next, with the mold closed, the process moves to foam molding of the foam molded product 7. The mold closed state shown in Fig. 5 is maintained for a predetermined time, and the foam molded product 7 integrated with the insert item 8 is foam molded, to produce the foam molded product 6 as shown in Fig. 3(a).
At this time, the foaming raw material g foams and hardens, but the heat generated by the foaming and hardening reaction may further increase the temperature of the foam molding die 1. In that case, the upper die 3 becomes relatively larger, so that the adhesion between the upper die mating surface 32 and the lower die mating surface 22 is further increased.
After the foam molding is completed and the foamed product 6 is demolded, the foamed product 6 is obtained with minimal flash. The foam molding process is then repeated to produce the desired foamed products 6 of the energy absorbing material.
In particular, when the mold is closed as described above, the upper mold 3 does not move downward completely due to the force generated by the actuator, and the upper mold 3 strongly abuts against the lower mold mating surface 22. If the mold is closed repeatedly, the aluminum material, which is soft as a metal material, undergoes plastic deformation, and the mating surfaces 22, 32 of both molds form a zero-touch seal surface at a relatively early stage. At an early stage after the start of foam molding, the desired foam molded product 6 that is free of burrs or has remarkably little burrs is removed by demolding.

In the foam molded product 6 of this embodiment, a hard polyurethane foam shown in Fig. 3(A) is used for the foam molded body 7, but a soft polyurethane foam such as an armrest shown in Fig. 3(B) can also be used for the foam molded body 7. For armrests, seat cushions, etc., which are larger than the small ones shown in Fig. 3(A), a cast foam molding die 1 as shown in Fig. 10 is appropriately used.
In Fig. 3, 7a denotes the upper surface of the foamed molded body 7, 70 denotes a recess, 71 denotes a base end, 72 denotes a tip end, and in Fig. 10, 27 denotes a recess, and 28 denotes a rib. The other configurations are the same as in (1), and the explanations thereof will be omitted. The same reference numerals as in (1) denote the same or corresponding parts.

(3) Effect According to the foam molding mold configured in this manner and the manufacturing method of a foam molded product using the same, the lower mold 2 has a mold mating surface 22 that extends upward and outward from the opening periphery 211, and when the mold is closed, the mold mating surface 22 abuts the upper mold mold mating surface 32, and the linear expansion coefficient of at least the frame-shaped portion 2F is made smaller than the linear expansion coefficient of the upper mold 3. Therefore, the mold can be closed reliably even if the foam molding mold 1 thermally expands as the temperature changes from the room temperature during mold production to the high temperature during foam molding.

In conventional foam molding dies, the difference in shape between the lower die 2B and the upper die 3B caused by thermal expansion accompanying the rise in temperature during foam molding could lead to individual deformation, resulting in defects such as a gap ε being formed between the mating surfaces 22, 32 of the two dies (FIG. 9A) or insufficient contact between the mating surfaces 22, 32 (FIG. 9B).
In contrast, in the present lower mold 2, the frame-shaped portion 2F, which has a smaller linear expansion coefficient than the upper mold 3, surrounds the side surface 2Mb of the lower mold main portion 2M and presses down the horizontal outward thermal expansion of the main portion 2M, thereby suppressing the horizontal outward expansion of the lower mold main portion 2M. Naturally, expansion around the opening 20 of the lower mold 2 is also suppressed. Even when not only the frame-shaped portion 2F but the entire lower mold 2 is made smaller in linear expansion coefficient than the upper mold 3, expansion around the lower mold opening 20 is suppressed by the entire lower mold 2, and is therefore reduced.
On the other hand, when the temperature is raised from room temperature to a high temperature state for foam molding, the upper mold 3 is not restricted by the frame-shaped portion 2F. Therefore, when the mold is closed, the periphery 311 of the upper mold cavity surface 31 hits a point of the lower mold mating surface 22 above the opening periphery 211 as shown in Fig. 5, and both mold mating surfaces 22, 32 are surely brought into contact with each other. By the operation of the actuator, the upper mold 3 is originally lowered to a point where the periphery 311 of the upper mold cavity surface 31 matches the opening periphery 211 of the lower mold cavity surface 21, but it hits the lower mold mating surface 22 just before that point and is stopped from descending. Since the mold is closed by adding the downward pressure still remaining in the upper mold 3, both mold mating surfaces 22, 32 are more closely attached to each other.

In addition, the lower die mating surface 22 is cone-shaped from above toward the bottom surface 2c where the cavity surface 21 is located, and the upper die mating surface 32 is tapered to match the shape of the lower die mating surface 22. Therefore, when the mold is closed, the upper die 3, which is accompanied by a downward pressure, tightly plugs the lower die 2, and the upper die mating surface 32 seals tightly against the cone-shaped lower die mating surface 22.

Furthermore, if the upper mold 3 is made of aluminum, which is soft among metal materials, even if the upper mold mating surface 32 has microscopic irregularities, the upper mold mating surface 32 will quickly conform to the lower mold mating surface 22 as the number of mold closings increases, forming a tight seal. If the cavity surface 21 of the lower mold 2 and the lower mold main part 2M forming the mating surface 22 are both made of aluminum, the mating will proceed more smoothly when the mold is closed, and the sealing will be more perfect. When the temperature is shifted from room temperature to the high temperature of the foam molding process, the cross-sectional distance L3 of the upper mold cavity surface becomes larger than the cross-sectional distance L2 of the lower mold opening periphery, causing interference between the upper mold 3 and the lower mold 2 when the mold is closed, but the soft aluminum material is plastically deformed to achieve good sealing when the mold is closed.
Furthermore, the mold closing force when closing the foam molding die 1 to produce the foam molded product 6 is weaker than the clamping force of an injection molding die, which makes burrs more likely to occur during foam molding in the first place. In this situation, by satisfying the above-mentioned configurations, the foam molded product 6 can be demolded with minimal burrs. Even after many years of taking various measures, the amount of burrs that occurs on the foam molded product 6 after demolding is dramatically reduced. Reducing the amount of burr removal work contributes to a significant reduction in the labor burden of post-processing and cost reduction.

5 and 6, if the upper mold 3 is held by the support member 4 and the through hole 40 is set larger than the shaft diameter of the holding member 5, the upper mold 3 can expand and contract due to thermal expansion when there is a temperature change. It can move freely in the horizontal direction (arrow direction in FIG. 7) when viewed from above, and the support member 4 and holding member 5 do not hinder the thermal expansion of the upper mold 3 in the horizontal direction when the temperature rises from room temperature to the high temperature during foam molding. When the mold is closed, the periphery 311 of the upper mold cavity surface 31 abuts against a point on the lower mold mating surface 22 above the opening periphery 211 described above, helping the two mold mating surfaces 22, 32 to abut against each other.
Thus, the foam molding die 1 and the method for producing the foam molded article 6 using the same exhibit the various excellent effects described above and are extremely useful.

The present invention is not limited to the above embodiment, and can be modified in various ways within the scope of the present invention depending on the purpose and application. The shape, size, number, material, etc. of the lower mold 2, lower mold main part 2M, frame-shaped part 2F, upper mold 3, support member 4, holding member 5, foam molded product 6, etc. can be selected appropriately according to the application.

1 Foam molding mold 2b Side surface (outer peripheral side surface)
2F: Frame-shaped part 2M: Main part (lower mold main part)
20 Opening 21 Cavity surface (lower mold cavity surface)
211: Opening edge of cavity surface 22: Mold mating surface (lower mold mating surface)
3 Upper mold 31 Mold mating surface 4 Support member 5 Holding member 6 Foam-molded product g Foaming raw material

Claims (8)

In a foam molding mold having a lower mold and an upper mold, a cavity for a foam molded product is formed by closing the mold.
A foam molding mold characterized in that the lower mold has a mold mating surface that extends upward and outward from the periphery of the opening of the cavity surface that forms the recess, and when the mold is closed, the mold mating surface abuts against the mold mating surface of the upper mold, and a frame-shaped portion that includes an outer peripheral side surface that connects at least each side surface of the lower mold, with the opening of the recessed cavity surface facing upward, has a linear expansion coefficient that is smaller than the linear expansion coefficient of the upper mold. The foam molding mold according to claim 1, wherein the upper mold is made of aluminum, and the frame portion is made of a metal material having a linear expansion coefficient smaller than that of the aluminum. The foam molding mold according to claim 1 or 2, wherein the material forming the lower mold main part that forms the cavity surface and mold mating surface of the lower mold is an aluminum material, and the material forming the frame-shaped part surrounding the lower mold main part is a metal material having a linear expansion coefficient smaller than that of the aluminum material. In a foam molding mold having a lower mold and an upper mold, a cavity for a foam molded product is formed by closing the mold.
The lower mold has a mold mating surface that spreads outwardly and upwardly from an opening periphery of a cavity surface that forms a recess, and the mold mating surface comes into contact with a mold mating surface of the upper mold by closing the mold,
A foam molding mold, characterized in that the mold material forming the cavity surface of the lower mold has a relatively smaller linear expansion coefficient than the mold material forming the cavity surface of the upper mold. 4. The foam molding mold according to claim 1, wherein a linear expansion coefficient of the entire lower mold including the frame portion is smaller than a linear expansion coefficient of the upper mold. The foam molding mold according to any one of claims 1 to 5, in which a holding member passes through a through hole provided in the support member, and the tip of the holding member is fixed to the upper surface side of the upper mold so that the upper mold is held by the support member, and the through hole is set larger than the shaft diameter of the holding member, so that the upper mold can move freely in the horizontal direction, forward and backward, and left and right, in a plan view, expanding and contracting in response to temperature changes. The foam molding mold according to any one of claims 1 to 6, wherein the foam molding mold is a metal mold for producing foam molded polyurethane foam products. Using the foam molding mold according to any one of claims 1 to 7,
A method for producing a foam-molded product, comprising injecting a foaming raw material for a foam-molded product onto a cavity surface of a lower mold, closing the mold, foam-molding, and then demolding the foam-molded product to remove it from the mold.

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