Sandwich molded product and its manufacturing method

Abstract

To provide a sandwich molded article that has a rib-like protrusion, is capable of suppressing occurrence of a sink mark on a surface opposite to a surface on which the protrusion is formed, has few restrictions on a size and shape of the protrusion, and is capable of suppressing a complicated manufacturing process and an increase in a manufacturing cost.SOLUTION: There is provided a sandwich molded article 1 composed of a core material 2 that is a fiber-containing resin and skin materials 3 that are fiber-free resins arranged on both sides of the core material 2. The sandwich molded article comprises: a plate-like portion 5; a rib-like protrusion 6 formed on one surface 5a of the plate-like portion 5; and at least three small ribs 7 adjacent to the protrusion 6 and is separated from the protrusion 6. The small ribs 7 are parallel to each other and extend in a direction B orthogonal to a direction A in which the protrusion 6 extends. A thickness TB of the small rib 7 is smaller than a thickness TC of the plate-like portion 5 and a thickness TA of the protrusion 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sandwich molded product. and its manufacturing method Regarding. [Background technology]

[0002] In order to achieve both a good surface appearance and high overall rigidity in resin molded products, sandwich molded products having a hard core material inside and skin materials located on both sides of the core material are sometimes used. Patent Document 1 discloses a sandwich molded product provided with ribs for engaging mounting fixtures such as metal fittings and screws. Patent Document 2 discloses a sandwich molded product provided with reinforcing ribs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-16876 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-125139 Summary of the Invention [Problem to be solved by the invention]

[0004] As shown in FIG. 6, in a resin molded product provided with a rib-shaped protrusion P, a depression (so-called sink mark) R may occur in part of the surface opposite the surface on which the protrusion P is formed. For example, when such a resin molded product is used as an exterior panel member of an automobile, the protrusion P is generally formed on a surface that is not visible to the occupants or bystanders. Therefore, the sink mark R occurs on the surface that is visible to the occupants and bystanders, and this sink mark R mars the aesthetic appearance and becomes a design problem. Furthermore, there are design constraints, such as adjusting the formation position of the protrusion P so that the sink mark R occurs in a less noticeable position, which limits the degree of freedom in design.

[0005] One way to prevent the occurrence of sink marks R is to reduce the thickness (plate thickness) of the protruding portions P. However, reducing the thickness of the protruding portions P reduces the strength, which places greater restrictions on the dimensions and shape of the protruding portions P, such as not being able to make the height of the protruding portions P too high. Furthermore, for example, when using the protruding portions P as reinforcing material, it is possible to increase the number of protruding portions P instead of reducing the thickness of the protruding portions P, but this does not necessarily result in an adequate reinforcing effect being obtained in areas that require reinforcement, and ingenuity is required in arranging the multiple protruding portions P.

[0006] Even if the thickness of the base portion of the protrusion P is reduced to prevent the occurrence of sink marks R, it is possible to prevent a decrease in the reinforcing effect by increasing the thickness of the tip portion of the protrusion P. However, in order to form a protrusion P that is thin at the base and thick at the tip, slide molding is required using a complex mold with a slide mechanism, which makes the manufacturing process complicated and increases manufacturing costs.

[0007] Therefore, an object of the present invention is to provide a sandwich-molded product having rib-like protrusions, which can suppress the occurrence of sink marks on the surface opposite to the surface on which the protrusions are formed, and which has few restrictions on the size and shape of the protrusions, and which suppresses the complexity of the manufacturing process and increases in manufacturing costs. and its manufacturing method The purpose is to provide [Means for solving the problem]

[0008] The sandwich-molded product of the present invention is a sandwich-molded product made of a core material which is a fiber-containing resin and skin materials which are fiber-free resins and which are located on both sides of the core material, and has a plate-shaped portion, a rib-like protruding portion formed on one side of the plate-shaped portion, and at least three small ribs provided adjacent to the protruding portion but separated from the protruding portion, the plate-like portion has a gate mark, the small rib is disposed between the gate mark and the protruding portion, and the extending direction of the protruding portion is substantially perpendicular to a straight line connecting the gate mark and the protruding portion at the shortest distance; The small ribs are parallel to each other and extend in the same direction as the protrusion. omitted They extend in perpendicular directions, The length of the small rib is greater than the thickness of the protrusion, The thickness of the small rib is smaller than the thickness of the plate-like portion and the thickness of the protrusion.

[0009] The thickness of the protrusion may be equal to or greater than the thickness of the plate-like portion, and the thickness of the small rib may be equal to or less than one-third the thickness of the plate-like portion. The protrusion may consist of only the skin material. The multiple fibers contained in the core material are typically aligned in approximately one direction along the MD direction (the direction of flow of the molten resin during molding), and each of the small ribs may extend in a direction approximately parallel to the longitudinal direction of the fibers. Each of the small ribs may extend in a direction substantially parallel to the MD direction (direction of resin flow). Each of the small ribs may extend in a direction substantially parallel to a straight line connecting the gate mark on the plate-shaped portion and the protrusion at the shortest distance. The height at which the small ribs protrude from the one surface of the plate-like portion may be smaller than the height at which the protruding portions protrude from the one surface of the plate-like portion. The small rib may include a portion whose height protruding from the one surface of the plate-like portion decreases from the protruding portion side toward the opposite side. The small ribs may be positioned parallel to each other, and the extension length of the small ribs located farther from the gate mark on the plate-shaped portion may be shorter than the extension length of the small ribs located closer to the gate mark. The small ribs may be positioned parallel to one another, and the extension length of the small ribs positioned on the outer side may be shorter than the extension length of the small ribs positioned on the central side. [Effects of the Invention]

[0010] According to the present invention, the rib-shaped protrusions can be formed, and the occurrence of sink marks on the surface opposite to the surface on which the protrusions are formed can be suppressed. In addition, there are few restrictions on the size and shape of the protrusions, and the manufacturing process can be simplified. Sandwich molding that reduces the complexity of the process and increases in manufacturing costs and its manufacturing method can be provided. [Brief explanation of the drawings]

[0011] [Figure 1]1A is a cross-sectional view of one embodiment of the sandwich molded product of the present invention, and FIG. 1B is a perspective view thereof. [Figure 2] 1 is a schematic cross-sectional view for explaining the principle of occurrence of sink marks in a resin molded product. FIG. [Figure 3] FIG. 2 is a schematic plan view illustrating the relationship between the longitudinal direction of fibers in a fiber-containing resin and the ease of shrinkage. [Figure 4] 1A and 1B are schematic perspective views for explaining the ease with which a fiber-containing resin penetrates into a protruding portion of a resin molded product. [Figure 5] 1A is a cross-sectional view of another embodiment of the sandwich molded product of the present invention, and FIG. 1B is a perspective view thereof. [Figure 6] FIG. 1 is a cross-sectional view schematically showing a part of a conventional sandwich-molded product in which a sink mark has occurred. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows one embodiment of a sandwich-molded product 1 of the present invention. FIG. 1(A) is a cross-sectional view of the sandwich-molded product 1 of this embodiment cut along the longitudinal direction of a small rib 7, and FIG. 1(B) is a perspective view of the sandwich-molded product 1. As shown in FIG. 1(A), the sandwich-molded product 1 of this embodiment comprises a core material 2 and skin materials 3 positioned on both sides of the core material 2. The core material 2 is a fiber-containing resin containing fibers 4, such as glass fibers or carbon fibers. Examples of resins contained in the core material 2 include thermoplastic resins typically used in injection molding, preferably propylene-based resins. The propylene-based resin may contain a propylene-based resin modified with an unsaturated carboxylic acid, such as maleic anhydride, fumaric acid, or (meth)acrylic acid, or a derivative thereof. Examples of fibers 4 that can be used as raw materials include chopped carbon fiber, chopped glass fiber, or fiber-reinforced resin pellets. Within the core material 2, the fibers 4 are aligned substantially in one direction. The skin material 3 is a fiber-free resin that does not contain fibers, and is usually a thermoplastic resin, preferably a propylene-based resin, and more preferably homopolypropylene.

[0013] As shown in FIG. 1(B), a sandwich-molded product 1 made of such a core material 2 and skin material 3 is injection-molded to have a flat, large-area plate-like portion 5 and rib-like protrusions 6 and small ribs 7 formed on one surface 5a of the plate-like portion 5. Both the rib-like protrusions 6 and small ribs 7 are elongated members extending in specific directions on one surface 5a of the plate-like portion 5. The protrusions 6 extend in direction A shown in FIG. 1(B). The multiple small ribs 7 are parallel to each other and extend in direction B, which is perpendicular to direction A in which the protrusions 6 extend. At least three small ribs 7 are provided for one protrusion 6.

[0014] The protrusions 6 are reinforcing ribs for reinforcing the strength of the plate-like portion 5, or are portions that form part of the walls of pockets for mounting or holding various components. The direction in which the protrusions 6 extend (direction A) is a direction that is approximately perpendicular to an imaginary line E that connects the gate mark 5c of the plate-like portion 5 (the position that faced the gate through which resin was injected during molding) and the protrusions 6 at the shortest distance, in other words, a direction that is approximately perpendicular to the MD direction (the direction in which resin flows during molding). Therefore, the direction in which the protrusions 6 extend (direction A) is a direction that is approximately perpendicular to the longitudinal direction of the fibers 4 that are aligned in approximately one direction (MD direction) inside the core material 2. The thickness T of the protrusions 6 A is, for example, the thickness T of the plate-shaped portion 5 so as to have sufficient strength to reinforce the plate-shaped portion 5. C That is all. In this specification, the thickness T A ,T B ,T C means the plate thickness perpendicular to the main surface (plate surface) of the plate-shaped portion. A ,H B is the dimension of the protrusion 6 and the small rib 7 projecting from one surface 5a of the plate-shaped portion 5, and is the dimension in the direction perpendicular to the one surface 5a. A ,L B is the dimension in the longitudinal direction (the direction in which the protrusions 6 and small ribs 7 extend on one surface 5a of the plate-like portion 5) in the planar shape seen in a direction perpendicular to the plate-like portion 5. The thickness T of the protrusions 6 and small ribs 7 A ,TB is the dimension in the short direction (direction perpendicular to the longitudinal direction) in the planar shape.

[0015] In this embodiment, a plurality of (at least three) small ribs 7 are provided to prevent the occurrence of sink marks due to the provision of the protruding portions 6. The plurality of small ribs 7 are provided adjacent to the protruding portions 6 on one surface 5a of the plate-like portion 5, but are separated from the protruding portions 6, and are parallel to each other and extend in a direction (direction B) perpendicular to the direction (direction A) in which the protruding portions 6 extend. Therefore, the direction (direction B) in which the small ribs 7 extend is substantially parallel to the imaginary straight line E and substantially parallel to the MD direction (direction of resin flow). Therefore, the direction (direction B) in which the small ribs 7 extend is substantially parallel to the longitudinal direction of the fibers 4 inside the core material 2. The thickness T of the small ribs 7 is B is the thickness T of the protrusion 6 A and the thickness T of the plate-shaped portion 5 C is smaller than the thickness T C This is less than one-third of the total.

[0016] As a specific example, the thickness T of the plate-shaped portion 5 C and the thickness T of the protrusion 6 A are 2 mm to 3 mm, and the thickness T B The height H of the protruding portion 6 protruding from one surface 5a of the plate-like portion 5 is about one third of the above, that is, 0.6 mm to 1 mm. A is 20 mm or less, and the height H of the small rib 7 protruding from one surface 5a of the plate-like portion 5 B is H A (20mm) or less.

[0017] According to this embodiment, the occurrence of sink marks on the other surface 5b of the plate-shaped portion 5 (the surface opposite to the surface 5a on which the protrusions 6 and small ribs 7 are formed) is suppressed. The reason for this is explained below. FIG. 2 schematically illustrates the principle behind the occurrence of sink marks in a resin molded product. Generally, when protrusions P are formed on one surface Sa of the plate-shaped portion S, shrinkage occurs in a direction parallel to the plate surface of the plate-shaped portion S and in the protruding direction of the protrusions P due to temperature changes and other factors after molding, as shown by the arrows in FIG. 2. As a result, sink marks occur at the base portions C of the protrusions P. A common method for suppressing the occurrence of sink marks is to reduce the thickness of the protrusions P (at least the thickness of the base portions of the protrusions P). By reducing the thickness of the protrusions P, the change in cross section caused by forming the protrusions P is minimized, which suppresses a decrease in resin pressure and density, and as a result, the occurrence of sink marks can be suppressed.

[0018] It is known that a fiber-containing resin such as the core material 2 of the sandwich-molded product 1 of this embodiment is unlikely to shrink in a direction D1 parallel to the longitudinal direction (MD) of the fibers F, as shown schematically in Fig. 3, but is likely to shrink in a direction D2 perpendicular to the longitudinal direction (MD) of the fibers F. Furthermore, as shown schematically in Fig. 4(A), the fibers F easily penetrate into the elongated rib-like protrusions P extending in the direction D1 parallel to the longitudinal direction (MD) of the fibers F, and therefore the fiber-containing resin easily penetrates. In contrast, as shown schematically in Fig. 4(B), the fibers F hardly penetrate into the elongated rib-like protrusions P extending in the direction D2 perpendicular to the longitudinal direction (MD) of the fibers F, and therefore the fiber-containing resin hardly penetrates.

[0019] Considering the relationship between the longitudinal direction of the fibers F of the fiber-containing resin and the ease of shrinkage as shown in Fig. 3 and the ease of penetration of the fiber-containing resin into the protruding portions P as shown in Figs. 4(A) and 4(B), in this embodiment, as shown in Fig. 1, protruding portions 6 used as reinforcing ribs, for example, are arranged to extend in a direction (direction A) perpendicular to the longitudinal direction (MD direction) of the fibers 4 of the core material 2. Furthermore, a plurality of small ribs 7 intended to suppress sink marks are arranged between the gate marks 5c and the protruding portions 6 to extend in a direction (direction B) parallel to the longitudinal direction (MD direction) of the fibers 4 of the core material 2.

[0020] When molding a sandwich-molded product 1 having such a configuration, resin injected from a gate of a mold (not shown) spreads from the gate mark 5c to the surrounding area to form the plate-like portion 5. During this process, when the resin reaches the portion (recess) of the mold (not shown) where the small ribs 7 are to be formed, the small ribs 7 extend in a direction (direction B) parallel to the longitudinal direction (MD) of the fibers 4 of the core material 2. This allows the resin to smoothly penetrate not only the skin material 3, which is a fiber-free resin, but also the core material 2, which is a fiber-containing resin. As a result, as shown in FIG. 1(A), the small ribs 7 of a sandwich structure consisting of the skin material 3 and the core material 2 are formed. After passing through the portion where the small ribs 7 are to be formed, the resin reaches the portion (recess) of the mold (not shown) where the protrusions 6 are to be formed. Because the protrusions 6 extend in a direction (direction A) perpendicular to the longitudinal direction (MD) of the fibers 4 of the core material 2, the fiber-containing resin is less likely to penetrate the core material 2. In particular, since the core material 2 penetrates into the small ribs 7 before reaching the position where the protrusions 6 are formed, the timing at which the core material 2 reaches the portion where the protrusions 6 are formed is delayed, and the core material 2 is hardly contained in the protrusions 6. In other words, as shown in FIG. 1(A), the protrusions 6 are formed substantially only by the skin material 3. In other words, the shape and dimensions of the small ribs 7 (particularly the height H of the small ribs 7) are adjusted so that a large amount of the core material 2 is contained in the small ribs 7 and the core material 2 is not contained in the protrusions 6. B and length L B ) is set. However, as mentioned above, the thickness T of the small rib 7 B is the thickness T of the plate-shaped portion 5 C It is set to one-third or less.

[0021] As described above, in this embodiment, the shape and dimensions of the small ribs 7 (particularly the height H B and length L B ) controls the speed and amount of the core material 2 reaching the portion where the protrusion 6 is to be formed, thereby making it easy to form the protrusion 6 using only the skin material 3. As an example, the length L of the small rib 7 at a position close to the gate mark 5c (a position close to the imaginary straight line E connecting the gate mark 5c and the protrusion 6 at the shortest distance) is B and height HB The length L of the small rib 7 at a position farther from the gate mark 5c (a position farther from the imaginary straight line E) B and height H B Generally, the imaginary straight line E passes through the center of the protrusion 6 in the direction A or in the vicinity thereof, so that the length L of the small rib 7 located in the center among the plurality of small ribs 7 positioned parallel to each other is B and height H B The length L of the small rib 7 located on the outside B and height H B However, the length of the small rib 7, L B and height H B is determined depending on the distance between the gate mark 5c and the protrusion 6, and the length L of the plurality of small ribs 7 B and height H B may be made substantially constant.

[0022] As described above, the small ribs 7 of the sandwich structure consisting of the skin material 3 and the core material 2 have a thickness T B is thin (thickness T C Therefore, sink marks due to the small ribs 7 are unlikely to occur. Because the protrusions 6 are essentially composed of the skin material 3, which is a fiber-free resin, there is no direction in which they are particularly likely to shrink, as shown in Figure 3. Furthermore, because the protrusions 6 extend elongated in a direction in which the core material 2 is less likely to shrink, the contractile force acting on the protrusions 6 is small in the plate-like portion 5 surrounding the protrusions 6. Therefore, sink marks are unlikely to occur on the surface 5b opposite the protrusions 6 at the positions where the protrusions 6 are formed. Because the present invention can suppress the occurrence of sink marks, restrictions on the shape and dimensions of the protrusions 6 are reduced, allowing protrusions 6 with sufficient strength to be easily formed, and there is no need to increase the number of protrusions 6. Furthermore, because there is no need to consider the occurrence of sink marks, the positions at which the protrusions 6 are formed can be freely determined, improving design flexibility. Furthermore, slide molding is not required to manufacture the sandwich-molded product 1 of the present invention, which does not result in complex manufacturing processes or increased manufacturing costs.

[0023] Another embodiment of the sandwich molded product 1 according to the present invention is shown in Fig. 5. In this embodiment, the shape of the small ribs 8 is different from that of the embodiment shown in Fig. 1. That is, the small ribs 8 of this embodiment protrude from one surface 5a of the plate-like portion 5 by a height H B The small ribs 8 have a generally triangular shape that includes a portion that narrows from the protrusion 6 side toward the opposite side (the gate mark 5c side). When the small ribs 8 have a shape that widens from the gate mark 5c side toward the protrusion 6 side, the core material 2, which is a fiber-containing resin, can more smoothly infiltrate into the small ribs 8. This makes it easier to control the speed and amount of the core material 2 that reaches the position where the protrusion 6 is formed. The other configurations and effects are the same as those of the embodiment shown in FIG. 1, so a description thereof will be omitted. [Explanation of symbols]

[0024] 1. Sandwich molding 2 Core material 3 Skin material 4. Fiber 5 Plate-shaped part 5a One side 5b The other side 5c Gate remains 6 Rib-like protrusions 7,8 Small ribs

Claims

1. A sandwich molded product comprising a core material that is a fiber-containing resin and skin materials that are fiber-free resins located on both sides of the core material, a plate-shaped portion; a rib-shaped protruding portion formed on one surface of the plate-shaped portion; and at least three small ribs provided adjacent to the protruding portion and separated from the protruding portion, the plate-shaped portion has a gate mark, the small rib is disposed between the gate mark and the protrusion, the direction in which the protrusion extends is substantially perpendicular to a straight line connecting the gate trace and the protrusion at the shortest distance; The small ribs are parallel to each other and extend in a direction substantially perpendicular to the direction in which the protrusion extends, The length of the small rib is greater than the thickness of the protrusion, A sandwich-molded product, characterized in that the thickness of the small rib is smaller than the thickness of the plate-shaped portion and the thickness of the protrusion.

2. the thickness of the protruding portion is equal to or greater than the thickness of the plate-shaped portion, 2. The sandwich molded product according to claim 1, wherein the thickness of the small rib is one-third or less of the thickness of the plate-like portion.

3. 3. The sandwich molded product according to claim 1, wherein the protrusion is made of the skin material alone.

4. The sandwich-molded product according to claim 1 , wherein each of the small ribs extends in a direction substantially parallel to a straight line connecting the gate mark of the plate-shaped portion and the protrusion in the shortest distance.

5. A sandwich-molded product according to any one of claims 1 to 4, wherein the height at which the small rib protrudes from the one surface of the plate-shaped portion is lower than the height at which the protruding portion protrudes from the one surface of the plate-shaped portion.

6. The sandwich-molded product according to any one of claims 1 to 5, wherein the small rib includes a portion whose height protruding from the one surface of the plate-shaped portion decreases from the protruding portion side toward the opposite side.

7. The small ribs are positioned parallel to each other, and the extension length of the small ribs located farther from the gate mark on the plate-shaped portion is shorter than the extension length of the small ribs located closer to the gate mark on the plate-shaped portion. A sandwich-molded product according to any one of claims 1 to 6.

8. The sandwich molded product according to any one of claims 1 to 7, wherein the small ribs are positioned parallel to each other, and the extension length of the small ribs located on the outer side is shorter than the extension length of the small ribs located on the central side.

9. A method for manufacturing a sandwich molded product comprising a core material that is a fiber-containing resin and skin materials that are fiber-free resins and are located on both sides of the core material, a core material injection step of injecting the core material into a mold having a shape corresponding to the sandwich molded product; The sandwich molded product is a plate-shaped portion; a rib-shaped protruding portion formed on one surface of the plate-shaped portion; and at least three small ribs provided adjacent to the protruding portion and separated from the protruding portion, The small ribs are parallel to each other and extend in a direction substantially perpendicular to the direction in which the protrusion extends, The length of the small rib is greater than the thickness of the protrusion, the thickness of the small rib is smaller than the thickness of the plate-like portion and the thickness of the protrusion, A method for manufacturing a sandwich molded product, characterized in that the core material injection process is a process of injecting the core material so that the core material reaches the portion of the mold that forms the small rib before reaching the portion of the mold that forms the protrusion, and so that the core material that has reached the portion of the mold that forms the protrusion flows in a direction approximately perpendicular to the direction in which the protrusion extends.

Images