Cooling passage and injection molding die having cooling passage

Abstract

To provide a cooling passage for improving cooling efficiency of a thermoplastic material by a refrigerant in injection molding, and an injection molding die having the cooling passage.SOLUTION: Provided are: a cooling passage is constituted by a hollow cylindrical tube body which forms a refrigerant flow passage by surrounding a molding area of an injection molding die, and has a protruding part formed orthogonally to a flow direction of a laminar flow boundary layer generated by inflow of a refrigerant, on an internal wall surface of the tube body; and an injection molding die having the cooling passage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The disclosure in this specification relates to an injection molding die having cooling passages that form a flow path for a refrigerant that cools a thermoplastic material injected into the injection molding die, and a cooling portion constituted by the cooling passages. [Background technology]

[0002] In injection molding, a molded product is formed by cooling and solidifying a high-temperature thermoplastic material injected into a mold. If the thermoplastic material in the mold is not cooled uniformly, the molded product removed from the mold will shrink unevenly, causing molding defects. Therefore, the cooling process in injection molding is an important process that determines the quality of the molded product.

[0003] Typically, an injection mold has cooling passages arranged around the cavity space. In the cooling process, a refrigerant is sent to the cooling passages to cool the thermoplastic material. Since the thermoplastic material to be injected is at a high temperature, if the refrigerant stagnates in the cooling passages, the material will reach thermal equilibrium in a short time, reducing the cooling effect. Therefore, in the cooling process, it is necessary to continuously send the refrigerant to the cooling passages to cool the material.

[0004] In order to improve the durability of the cooling effect of the refrigerant, it is conceivable to devise measures such as increasing the flow rate of the refrigerant or increasing the diameter of the cooling passage, but each of these has physical limitations.

[0005] In view of this, conventionally, for example, an injection molding die has been proposed in which a convex rib is provided on the inner surface of the cooling passage to expand the surface area (i.e., the heat transfer area) and improve the cooling effect (see, for example, Patent Document 1).

[0006] Also, an injection molding die has been proposed in which cooling is performed by a parallel spiral flow flowing through a cooling bush having a spiral cooling groove formed in the wall surface forming the cooling bush hole of the core body (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2-106314 [Patent Document 2] Japanese Patent Application Publication No. 9-262870 Summary of the Invention [Problem to be solved by the invention]

[0008] However, even if the surface area of ​​the cooling passage is increased as in the above-mentioned conventional technology, the flow of the refrigerant is affected by the damping effect due to viscosity, and a low-speed boundary layer is formed near the inner surface, resulting in a problem that the cooling effect is significantly reduced compared to the main flow in the axial center of the cooling passage.

[0009] Incidentally, there are two cooling methods for injection molding dies: a water-cooling type that uses water as a refrigerant, and an air-cooling type that uses air. In the case of a water-cooling type, if the temperature inside the pipe exceeds 100 degrees, the internal pressure increases and steam may leak to the outside. In addition, when the clamped die is separated after molding, if the water remaining inside the pipe adheres to the molded product or the die, it may damage the molded product and cause rusting of the die. In order to avoid such inconvenience, an air-cooling type is adopted, but from the viewpoint of thermal conductivity, the cooling effect of the air-cooling type is lower than that of the water-cooling type. Therefore, the air-cooling type requires even more efficient cooling than the water-cooling type.

[0010] The disclosure in this specification is intended to solve the above-mentioned problems, and has an object to provide a cooling passage that improves the efficiency of cooling a thermoplastic material by a refrigerant in injection molding, and an injection molding die having such a cooling passage. [Means for solving the problem]

[0011] In order to solve the above problems, one embodiment of a cooling passage disclosed in this specification is composed of a hollow cylindrical tube that surrounds the molding area of ​​an injection molding die to form a refrigerant flow path, and has a convex portion formed on the inner wall surface of the tube perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant.

[0012] According to this configuration, a low-speed boundary layer that develops toward the downstream of the flow passage repeatedly separates and reattaches due to the convex parts provided in the flow direction, generating turbulence, which results in frequent heat exchange with the main flow passage in the center of the flow passage.

[0013] Moreover, one aspect of the injection molding die disclosed in this specification has a cooling passage that forms a cooling flow path for a coolant that cools a thermoplastic material, and the cooling flow path has a convex portion formed on an inner wall surface perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the coolant.

[0014] In addition, the cooling section of the injection molding die may be composed of two circuits: an air-cooling circuit into which a gas-phase refrigerant flows as the refrigerant, and a water-cooling circuit into which a liquid-phase refrigerant flows, and at least the air-cooling circuit may be composed of the cooling passage. Effect of the Invention

[0015] The cooling passage of the present invention has an effect of improving the efficiency of cooling a thermoplastic material by a refrigerant during injection molding. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a partial side cross-sectional view of a cooling passage according to this embodiment, in which (A) shows a state in which a backflow region occurs at a convex portion, (B) shows a state in which a boundary layer separates at a convex portion, and (C) shows a state in which the boundary layer separates at a convex portion and then reattaches. [Diagram 2] FIG. 2 is a diagram showing a cooling passage according to the first embodiment, where (A) is a perspective view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line II'. [Diagram 3]FIG. 3 is a diagram showing a cooling passage according to the second embodiment, where (A) is a perspective view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line II-II'. [Figure 4] FIG. 4 is a diagram showing a cooling passage according to a third embodiment, where (A) is a perspective view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line III-III'. [Diagram 5] FIG. 5 shows a cooling passage according to a fourth embodiment, where (A) is a perspective view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line IV-IV'. [Figure 6] FIG. 6 is a diagram showing a cooling passage according to a fifth embodiment, in which (A) is an oblique view, (B) is a side cross-sectional view, (C) is a conceptual diagram showing the flow lines of the boundary layer, and (D) is a view from the arrow V. [Figure 7] FIG. 7 is a diagram showing a cooling passage according to a sixth embodiment, in which (A) is a perspective view, (B) is a side cross-sectional view, (C) is a conceptual diagram showing the flow lines of the boundary layer, and (D) is a view from the arrow VI. [Figure 8] FIG. 8 is a diagram showing a cooling passage according to the seventh embodiment, where (A) is a perspective view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line VII-VII'. [Figure 9] FIG. 9 is an explanatory diagram showing an injection molding die according to this embodiment, where (A) is an oblique view, (B) is a top view showing a state in which the movable core and the slide core are joined, and (C) is a top view showing a state in which the slide core is separated from the movable core. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments for carrying out the disclosure of this specification will be described with reference to the drawings. When a subsequent embodiment has a component corresponding to an embodiment described earlier, the same reference numerals are used and duplicated description is omitted. In addition, when only a part of the configuration is described in each embodiment, the reference numerals of the previously described embodiment may be used for the other parts of the configuration. Even if it is not clearly stated that each embodiment can be specifically combined, it is also possible to partially combine the embodiments as long as there is no particular problem with the combination. In addition, the size of each member and component in the drawings is appropriately emphasized to facilitate explanation, and does not indicate the actual dimensions or the ratio between members and components.

[0018] 1 is a partial side cross-sectional view of a cooling passage 11 of an injection molding die according to this embodiment. The cooling passage 11 is composed of a hollow cylindrical pipe body 113 surrounding the molding area (near the cavity) of the injection molding die. That is, the pipe body 113 is disposed so as to run parallel to the periphery of the molding area (not shown) into which high-temperature molding resin (plastic resin) flows. The hollow internal space of the pipe body 113 forms a refrigerant flow path for a refrigerant that cools the plastic resin.

[0019] 1(A), a refrigerant flows into a refrigerant flow passage 111 surrounded by an inner wall surface 112 of a pipe body 113. The refrigerant that flows in exchanges heat with a high-temperature thermoplastic resin to be cooled, and the temperature of the refrigerant rises. In this embodiment, the refrigerant may be in either a gas phase or a liquid phase, unless otherwise specified.

[0020] In the refrigerant flow passage 111, the flow of the refrigerant forms two layers with different flow velocities: a mainstream layer M in an area centered on the axis of the pipe body 113, and a laminar boundary layer B in the vicinity of the inner wall surface 112. Friction occurs between the laminar boundary layer B and the inner wall surface 112 due to the viscosity of the refrigerant, and kinetic energy is lost. Therefore, the flow velocity of the boundary layer side streamline F1 of the laminar boundary layer B is lower than the flow velocity of the mainstream layer side streamline F2 of the mainstream layer M. In the laminar boundary layer B where the flow velocity of the refrigerant is lowered, the refrigerant whose temperature has increased due to the heat exchange remains there, and the cooling efficiency gradually decreases.

[0021] In this embodiment, the cooling passage 11 has a convex portion 114 formed perpendicular to the flow direction of the boundary layer side flow line F1 on an inner wall surface 112 of the refrigerant flow path 111. That is, the convex portion 114 is provided at a position where it blocks the flow of the boundary layer side flow line F1 of the laminar boundary layer B of the refrigerant.

[0022] As described above, the convex portion 114 is formed in the laminar boundary layer B with a gentle velocity gradient, so that the frictional resistance of the refrigerant decreases when the refrigerant reaches the convex portion 114. Meanwhile, as the refrigerant continues to flow in, it is subjected to the action of an adverse pressure gradient at the convex portion 114, and a reverse flow region A is formed. In the reverse flow region A, the refrigerant cannot flow along the inner wall surface 112, and forms a separation space S at the convex portion 114 and the inner wall surface 112, as shown in Fig. 1(B), and proceeds in the flow direction of the boundary layer flow line F1 while forming a turbulent flow.

[0023] On the other hand, by continuously flowing in the coolant, new coolant flows into the separated space S, and a reattachment region R is formed as shown in Fig. 1(C) . By providing multiple protrusions 114 in the flow direction of the boundary layer side flow line F1, the stagnation state is eliminated, and separation and reattachment of the coolant is repeated at each of the protrusions 114 on the inner wall surface 112, improving the cooling efficiency.

[0024] The spacing between the multiple protrusions 114 is not particularly limited, but if they are formed at least in the section of the flow where the velocity distribution of the injection molding die no longer changes, i.e., before the flow reaches a fully developed state, the separation and reattachment of the refrigerant can be effectively repeated.

[0025] First Embodiment

[0026] 2A and 2B are diagrams showing a cooling passage 12 according to the first embodiment, in which FIG. 2A is a perspective view of the cooling passage 12, FIG. 2B is a side cross-sectional view of the cooling passage 12, and FIG. 2C is a vertical cross-sectional view taken along line II' in FIG. 2B.

[0027] In this embodiment, the pipe body 123 constituting the cooling passage 12 has a circular cross-sectional shape in a direction perpendicular to the flow direction of the refrigerant (the flow direction of the boundary layer flow line F1 and the main layer flow line F2). The first convex portion 124 and the second convex portion 125 are formed by steps on the inner wall surface 122 formed by bending a cut-out wall portion having a predetermined thickness in the flow direction of the refrigerant flow path 121 so as to protrude in the radial direction of the circle. In other words, if the cut-out pieces are formed so that the axis C of the refrigerant flow path 121 is eccentric, the first convex portion 124 and the second convex portion 125 will have steps on the inner wall surface 122. In this embodiment, the first convex portion 124 has an axis C that is eccentric to a first eccentric position E1, and the second convex portion 125 has an axis C that is eccentric to a second eccentric position E2, so that the appearance of the tube body 123 is a bent shape that protrudes in the radial direction of the circle, and the first convex portion 124 and the second convex portion 125 are formed on the inner wall surface 122 by steps.

[0028] In addition, when the bending portions are provided at a plurality of locations in the radial direction, it is preferable that at least adjacent convex portions (the first convex portion 124 and the second convex portion 125 in this embodiment) have the bending radial direction in different directions (angles). By protruding in this manner, the boundary layer side flow lines F1 flowing at different positions in the circumferential direction are repeatedly subjected to the separation and reattachment action depending on the respective positions where the first convex portion 124 and the second convex portion 125 are formed. Therefore, the cooling effect of the first convex portion 124 and the second convex portion 125 is uniformly exerted over the entire circumference of the pipe body 123, and the occurrence of molding defects such as warping can be suppressed. However, when it is necessary to increase the cooling efficiency of the boundary layer side flow lines F1 flowing exclusively at a predetermined position in the circumferential direction, it is preferable to make the bending direction (angle) the same.

[0029] 2(B) shows a state in which the first convex portion 124 is subjected to the action of a reverse pressure gradient and a backflow region A is formed, but as explained in FIG. 1, by continuously flowing in the refrigerant, the formation of the separated space S and the reattachment region R is repeated. In the following embodiments, too, only the state in which the backflow region A is formed is shown, and the action of the repeated formation of the separated space S and the reattachment region R is omitted because it is the same as in the first embodiment.

[0030] <Second embodiment>

[0031] Figure 3 shows a cooling passage 13 in a second embodiment, where Figure 3(A) is an oblique view of the cooling passage 13, Figure 3(B) is a side cross-sectional view of the cooling passage 13, and Figure 3(C) is a vertical cross-sectional view taken along line II-II' in Figure 3(B).

[0032] In the cooling passage 13 according to this embodiment, similarly to the first embodiment, the first convex portion 134 and the second convex portion 135 formed on the inner wall surface 132 are formed by cut-out wall portions having a predetermined thickness in the flow direction of the refrigerant. However, while in the first embodiment, the cross-sectional shape in the direction perpendicular to the flow direction of the refrigerant (the flow direction of the boundary layer flow line F1 and the main stream layer flow line F2) is circular, in the second embodiment, the cross-sectional shape of the pipe body 133 is elliptical.

[0033] The first convex portion 134 and the second convex portion 135 are formed by steps on the inner wall surface 132 formed by bending a cut-out wall portion having a predetermined thickness in the flow direction of the refrigerant flow passage 131 (the flow directions of the boundary layer flow line F1 and the main layer flow line F2) so as to protrude by rotating the cut-out wall portion at a predetermined angle in the circumferential direction of the ellipse around the axis of the tube body 133. That is, the first convex portion 134 and the second convex portion 135 are formed by the difference between the length in the minor axis direction and the length in the major axis direction of the ellipse, so that the rotation gives the tube body 133 an external shape that is bent so as to protrude, similar to the first embodiment, and the first convex portion 134 and the second convex portion 135 are formed by steps on the inner wall surface 132.

[0034] Furthermore, similarly to the first embodiment, when multiple bending portions are provided, it is preferable that at least adjacent convex portions (in this embodiment, first convex portion 134 and second convex portion 135) are rotated at different angles.

[0035] <Third embodiment>

[0036] 4A and 4B are diagrams showing a cooling passage 14 according to a third embodiment, in which FIG. 4A is a perspective view of the cooling passage 14, FIG. 4B is a side cross-sectional view of the cooling passage 14, and FIG. 4C is a vertical cross-sectional view taken along line III-III' in FIG. 4B.

[0037] The cooling passage 14 according to this embodiment is a modification of the second embodiment, and the cross section of the pipe body 143 in the direction perpendicular to the flow direction of the refrigerant is a star-shaped polygon.

[0038] The first convex portion 144 and the second convex portion 145 are formed by steps on the inner wall surface 142 formed by bending a cut-out wall portion having a predetermined thickness in the flow direction of the refrigerant flow passage 141 (the flow directions of the boundary layer flow line F1 and the main layer flow line F2) at a predetermined angle in the circumferential direction of the star-shaped polygon around the axis of the tube body 143 to protrude. That is, the first convex portion 144 and the second convex portion 145 are formed by rotating the star-shaped polygon with radial concaves and convexes alternately in the circumferential direction, so that the tube body 143 appears to have a protruding bent shape as in the first embodiment, and the first convex portion 144 and the second convex portion 145 are formed by steps on the inner wall surface 142.

[0039] Furthermore, similarly to the first embodiment, when multiple bending portions are provided, it is preferable that at least adjacent convex portions (in this embodiment, first convex portion 144 and second convex portion 145) are rotated at different angles.

[0040] The shape according to this embodiment has a larger surface area of ​​the inner wall surface 142 than a cylindrical round tube. The larger the surface area, the better the cooling effect. Therefore, the expansion of the surface area, together with the provision of the first convex portion 144 and the second convex portion 145, produces a synergistic cooling effect.

[0041] 4 shows a star-shaped polygon with four vertices, but this is not intended to be limiting. In this embodiment, a star-shaped polygon includes all figures obtained by connecting the intersections obtained by extending each side of a polygonal planar geometric figure, and includes so-called pointed star figures.

[0042] <Fourth embodiment>

[0043] FIG. 5 is a diagram showing a cooling passage 15 according to a fourth embodiment, in which FIG. 5(A) is a perspective view of the cooling passage 15, FIG. 5(B) is a side cross-sectional view of the cooling passage 15, and FIG. 5(C) is a vertical cross-sectional view taken along line IV-IV' in FIG. 5(B).

[0044] The cooling passage 15 in this embodiment is a modified example of the second and third embodiments, and the cross-sectional shape of the tube body 153 in a direction perpendicular to the flow direction of the refrigerant is formed into a radial asterisk shape by intersecting multiple rectangular bodies at the axis.

[0045] The first convex portion 154 and the second convex portion 155 are formed by steps on the inner wall surface 152 formed by bending a cut-out wall portion having a predetermined thickness in the flow direction of the refrigerant flow passage 151 (the flow directions of the boundary layer flow line F1 and the main layer flow line F2) at a predetermined angle in the circumferential direction of the asterisk shape around the axis of the tube body 153 so as to protrude. That is, the first convex portion 154 and the second convex portion 155 are formed by rotating the asterisk shape so that radial concaves and convexes are alternately formed in the circumferential direction, so that the appearance of the tube body 153 is bent so as to protrude, similarly to the first embodiment, and the first convex portion 154 and the second convex portion 155 are formed by steps on the inner wall surface 152.

[0046] The asterisk shape, like the star polygon, provides a synergistic effect due to the expansion of the surface area. In particular, the asterisk shape has a rectangular tip, which provides a greater effect of expanding the surface area than the star polygon, which has a pointed tip.

[0047] Although FIG. 5 shows an asterisk shape with eight radial apexes, the number of apexes is not limited to this.

[0048] <Fifth embodiment>

[0049] 6A and 6B are diagrams showing a cooling passage 16 according to a fifth embodiment, in which FIG. 6(A) is an oblique view of the cooling passage 16, FIG. 6(B) is a side cross-sectional view of the cooling passage 16, FIG. 6(C) is a conceptual diagram showing the flow lines of the boundary layer, and FIG. 6(D) is a vertical cross-sectional view seen from the V direction of FIG. 6(B).

[0050] In the cooling passage 15 according to this embodiment, like the third embodiment, the cross section of the pipe body 163 in the direction perpendicular to the flow direction of the refrigerant is a star-shaped polygon.

[0051] Unlike the third embodiment, the convex portion 164 is formed by twisting the tube 163 in the flow direction of the refrigerant flow passage 161 (the flow direction of the boundary layer flow line F1 and the main layer flow line F2) to form a plurality of spiral ribbing on the inner wall surface 162, and is constituted by rib-like steps formed between adjacent ribbing. That is, by rotating both ends of the tube 163 in mutually opposite directions to form a twisted shape, the inner wall surface 162 is formed with a spiral groove (rifling) along the twisted shape. The groove is a single groove or a plurality of parallel grooves depending on the angle of the rotation, and the rib-like convex portion 164 is formed adjacent to the groove.

[0052] The adjacent convex portions described in the first to fourth embodiments, i.e., the first convex portion 124 and the second convex portion 125, the first convex portion 134 and the second convex portion 135, the first convex portion 144 and the second convex portion 145, and the first convex portion 154 and the second convex portion 155, are structured to be discretely arranged in the flow direction, but the convex portion 164 in this embodiment is structured to be continuously arranged in the flow direction. Therefore, as shown in FIG. 6C, the boundary layer flow line F1 in this embodiment has a reaching distance to the convex portion 164 that differs depending on the position on the inner wall surface 162, and the separation and reattachment of the refrigerant that occurs at the convex portion 164 occurs at different positions depending on the position on the inner wall surface 162.

[0053] When observing the behavior of the refrigerant near the convex portion 164 in a cross section of the pipe 162 perpendicular to the flow direction of the laminar boundary layer B, the boundary layer flow line F1 that abuts against the convex portion 164 forms a layer where the refrigerant does not move. On the other hand, the boundary layer flow line F1 that is adjacent to the boundary layer flow line F1 of the non-moving layer and does not abut against the convex portion 164 forms a layer where the refrigerant moves. The refrigerant that constitutes the moving layer acts to separate the refrigerant from the non-moving layer.

[0054] The internal space of the tube body 163 in which the rifling is formed applies a swirling motion to the refrigerant flow in the refrigerant flow passage 161, thereby improving linearity and ensuring a stable flow. Ensuring a stable refrigerant flow with high linearity accelerates the separation and reattachment actions. Therefore, the protrusions 164 in this embodiment combine the separation and reattachment actions with the action of increasing the linearity of the refrigerant to further improve the cooling efficiency.

[0055] Sixth embodiment

[0056] 7A and 7B are diagrams showing a cooling passage 17 according to a sixth embodiment, in which FIG. 7(A) is a perspective view of the cooling passage 17, FIG. 7(B) is a side cross-sectional view of the cooling passage 17, FIG. 7(C) is a conceptual diagram showing flow lines of the boundary layer, and FIG. 7(D) is a vertical cross-sectional view seen from direction VI of FIG. 7(B).

[0057] In the cooling passage 17 of this embodiment, like the fourth embodiment, the cross-sectional shape of the pipe body 173 in the direction perpendicular to the flow direction of the refrigerant is formed into a radial asterisk shape by intersecting multiple rectangular bodies at the axis.

[0058] Unlike the fourth embodiment, the convex portion 174 is formed by twisting the tube 173 in the flow direction of the refrigerant flow passage 171 (the flow direction of the boundary layer flow line F1 and the main layer flow line F2) to form a plurality of spiral ribbing on the inner wall surface 172, and is constituted by rib-like steps formed between adjacent ribbing. That is, by rotating both ends of the tube 173 in mutually opposite directions to form a twisted shape, the inner wall surface 172 is formed with a spiral groove (rifling) along the twisted shape. The groove is a single groove or a plurality of parallel grooves depending on the angle of the rotation, and the rib-like convex portion 164 is formed adjacent to the groove.

[0059] In the cross section of pipe 172 perpendicular to the flow direction of laminar boundary layer B, the behavior of the refrigerant near convex portion 174 is such that, similar to embodiment 5, a boundary layer flow line F1 that abuts against convex portion 174 forms a layer where the refrigerant does not move, and a boundary layer flow line F1 that is adjacent to the boundary layer flow line F1 of the non-moving layer and does not abut against convex portion 174 forms a layer where the refrigerant moves. The refrigerant that constitutes the moving layer acts to separate the refrigerant in the non-moving layer.

[0060] The internal space of the tube body 173 in which the rifling is formed provides a swirling motion to the refrigerant flow in the refrigerant flow passage 171, thereby improving linearity and ensuring a stable flow. Ensuring a stable refrigerant flow with high linearity accelerates the separation and reattachment actions. Furthermore, by forming the cross-sectional shape into an asterisk shape, the surface area of ​​the inner wall surface 172 is also expanded. Therefore, the protrusions 174 in this embodiment can further improve the cooling efficiency by combining the separation and reattachment actions, the action of improving the linearity of the refrigerant, and the expansion of the surface area.

[0061] Seventh embodiment

[0062] Figure 8 shows a cooling passage 18 according to the seventh embodiment, where Figure 8(A) is an oblique view of the cooling passage 18, Figure 8(B) is a side cross-section 8 of the cooling passage 12, and Figure 8(C) is a vertical cross-section taken along line VII-VII' in Figure 8(B).

[0063] The pipe body 183 constituting the cooling passage 18 according to this embodiment has a circular cross section in a direction perpendicular to the flow direction of the refrigerant (the flow direction of the boundary layer flow line F1 and the main laminar flow line F2). The first convex portion 184 and the second convex portion 185 are formed by a lattice plate formed on the whole or part of the cross section of the refrigerant flow passage 181 in the direction perpendicular to the flow direction of the refrigerant (FIG. 8 shows an example in which the lattice plate is formed on the whole cross section, but it may be formed in a ring shape in a range perpendicular to the flow direction of the laminar boundary layer B generated by the inflow of the refrigerant from the inner wall surface 182). The refrigerant passes between the meshes of the lattice plate, but the lattice portion acts to block the flow of the boundary layer side flow line F1 of the laminar boundary layer B of the refrigerant. Therefore, the lattice portion plays the role of the first convex portion 184 and the second convex portion 185, and the separation and reattachment are repeated.

[0064] The mesh size of the lattice plate is not particularly limited, but for example, the mesh size may be set small in a range perpendicular to the flow direction of the laminar boundary layer from the inner wall surface 182 (not shown). By making the mesh size small in such a range, the separation and reattachment are promoted more effectively.

[0065] <Injection mold>

[0066] 9A and 9B are explanatory diagrams showing an injection molding die 2 according to this embodiment, in which FIG. 9A is an oblique view, FIG. 9B is a top view showing a state in which the movable core and the slide core are joined, and FIG. 9C is a top view showing a state in which the slide core is separated from the movable core.

[0067] The injection mold 2 according to this embodiment includes a fixed core 21, a movable core 22, and a slide core 23. As shown in FIG. 9B, the injection mold 2 has an air-cooling circuit 10a into which a gas-phase refrigerant flows and a water-cooling circuit 10w into which a liquid-phase refrigerant flows. The air-cooling circuit 10a and the water-cooling circuit 10w are provided with any of the cooling passages 11, 12, 13, 14, 15, 16, 17, and 18 described in the first and second embodiments. The air-cooling circuit 10a is provided in the movable core 22 and the slide core 23, and the water-cooling circuit 10w is provided in the fixed core 21.

[0068] As shown in FIG. 9C, when the slide core 23 is separated from the movable core 22, the air-cooling circuit 10a arranged in the slide core 23 is also separated from the movable core together with the slide core 23. At this time, the connection port 10c of the air-cooling circuit 10a of the movable core 22 is in an open state. When performing injection molding, the slide core 23 is assembled into the movable core 22, and the air-cooling circuit 10a on the slide core 23 side is connected to the air-cooling circuit 10a of the movable core 22 via the connection port 10c. On the other hand, the water-cooling circuit 10w of the fixed core 21 is arranged independently of the air-cooling circuit 10a. Therefore, in this embodiment, there are two independent circuits, the water-cooling circuit 10w of the fixed core 21 and the air-cooling circuit 10a of the movable core 22 and the slide core 23.

[0069] Generally, water has a thermal conductivity about 20 times higher than air, so water cooling is selected from the viewpoint of cooling efficiency. However, in the case of water cooling, if the refrigerant leaks, rust will form on the injection mold 2. If rust occurs, it will be mixed in during injection molding and cause molding defects. Also, if the temperature inside the pipes of the water cooling circuit 10w exceeds 100°C, it will boil, and the pressure inside the pipes will increase, which may cause damage.

[0070] Due to their structure, the movable core 22 and the slide core 23 require a process of connecting them through the connection port 10c during injection molding. Therefore, if water cooling is selected, the water (coolant) remaining in the pipes leaks out when the movable core 22 and the slide core 23 are attached and detached, which causes the above-mentioned rust. Therefore, the air-cooling circuit 10a is selected for the movable core 22 and the slide core 23. However, if water cooling is selected for the fixed core 21 from the viewpoint of cooling efficiency, uneven cooling occurs between the fixed core 21 and the movable core 22 and the slide core 23, which causes molding defects. Therefore, it is sufficient to provide any one of the cooling passages 11, 12, 13, 14, 15, 16, 17, and 18 in both or either of the air-cooling circuit 10a and the water-cooling circuit 10w. EXAMPLES

[0071] In the following experiment, a refrigerant (air) was flowed into steel specimens (cooling passages) having various shapes under the following conditions, and the difference in cooling efficiency was confirmed. <Experimental conditions> Specimen length: 50mm -Cross-sectional area of ​​specimen: φ3 - Sample heating temperature: 130℃ Air temperature: 35℃ Measurement position: 13mm from the center of the specimen

[0072] To ensure a stable temperature rise for the specimen (instead of using thermoplastic resin), four cartridge heaters were placed at equal distances from the outer periphery of the specimen, and at equal intervals in the circumferential direction between each cartridge heater. The experiment measured the time required for the temperature to change from 130°C to 125°C (a 5°C drop) at the heater control temperature (a thermocouple was used at a position 13 mm from the center of each specimen). The above experiment was repeated 10 times, and the measured value was the average value.

[0073] The specimens were of nine different cross-sectional shapes, as shown in Table 1. The pipe cross sections of the straight pipes, which were circular (φ3), straight pipes with star-shaped polygonal shapes (φ3-1), and straight pipes with asterisk shapes (φ3-6), were all pipes that did not have any protrusions formed on the inner wall surface of the pipes perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant, and were measured as comparative data.

[0074] The star-shaped polygonal pipe cross section with a twist of 180° (No. 418) and a twist of 360° (No. 419) are shapes described in FIG. 6. No. 418 has a twist rotation angle of 180°, and No. 419 has a twist rotation angle of 360°. The asterisk-shaped pipe cross section with a twist of 180° (No. 420) and a twist of 360° (No. 421) are shapes described in FIG. 7. No. 420 has a twist rotation angle of 180°, and No. 421 has a twist rotation angle of 360°. The asterisk-shaped pipe cross section with three shape changes (No. 422) and seven shape changes (No. 423) are shapes described in FIG. 5. No. 422 has three convex portions formed from the steps described in FIG. 5, and No. 423 has seven convex portions formed from the steps.

[0075] The vertical axis of Table 1 is the time (seconds) required for a 5°C temperature change (cooling) from 130°C to 125°C, and the horizontal axis is the cross-sectional shape of each specimen.

[0076] According to Table 1, the time required for cooling for each comparison data was 40.9 seconds for φ3, 32.4 seconds for φ3-1, and 23.4 seconds for φ3-6. The difference in time between each comparison data is due to the difference in surface area. It can be seen that compared to φ3, the cooling time was shortened by approximately 21% for φ3-1 and approximately 43% for φ3-6.

[0077] The time required for cooling for the shapes explained in Figure 6 was 25.9 seconds for No. 418 and 26.1 seconds for No. 419. Therefore, compared to φ3, it can be seen that No. 418 achieved a reduction of approximately 37% and No. 419 achieved a reduction of approximately 36%. Also, when comparing the same star-shaped polygonal cross-sectional shape, it can be seen that No. 418 achieved a reduction of approximately 21% and No. 419 achieved a reduction of approximately 20% compared to φ3-1.

[0078] The time required for cooling for the shapes explained in Figure 5 was 23.4 seconds for No. 422 and 21.6 seconds for No. 423. Therefore, compared to φ3, it can be seen that No. 422 achieved a shortening effect of approximately 43% and No. 423 achieved a shortening effect of approximately 47%. Also, when comparing with the asterisk shapes, which have the same cross-sectional shape, it can be seen that compared to φ3-6, No. 422 required the same time, but No. 423 achieved a shortening effect of approximately 8%.

[0079] The time required for cooling for the shapes explained in Figure 7 was 22.5 seconds for No. 420 and 21.1 seconds for No. 421. Therefore, compared to φ3, it can be seen that No. 420 achieved a shortening effect of approximately 45% and No. 421 achieved a shortening effect of approximately 48%. Also, when comparing the same asterisk shape cross-sectional shape, it can be seen that No. 420 achieved a shortening effect of approximately 4% and No. 421 achieved a shortening effect of approximately 10% compared to φ3-6.

[0080] [Table 1]

[0081] The technology disclosed in this specification is not limited to the above-mentioned embodiment. That is, it includes the embodiment shown as an example and the modification by a person skilled in the art based on them. It also includes the replacement or combination of parts or elements between one embodiment and another embodiment. Furthermore, the disclosed technical scope is not limited to the description of the embodiment. The disclosed technical scope is indicated by the description of the claims, and further includes all modifications within the meaning and scope equivalent to the description of the claims. [Explanation of symbols]

[0082] 2 Injection mold 21 Fixed core 22 Movable core 23 Slide Core 10a Air cooling circuit 10c Connection port 10w water cooling circuit 11, 12, 13, 14, 15, 16, 17, 18 Cooling passage 111, 121, 131, 141, 151, 161, 171, 181 Coolant flow path 112, 122, 132, 142, 152, 162, 172, 182 Inner wall surface 113, 123, 133, 143, 153, 163, 173, 183 Body 114, 164, 174 Convex 124, 134, 144, 154, 184 First convex part 125, 135, 145, 155, 185 Second convex part A Backflow area B laminar boundary layer C axis center E1 1st eccentric position E2 2nd eccentric position F1 boundary layer streamline F2 mainstream laminar streamline M Mainstream layer R Reattachment area S Separation space

Claims

1. A cooling passage comprising a hollow cylindrical tube surrounding a molding area of ​​an injection molding die to form a refrigerant flow path, the tube having an inner wall surface having a convex portion formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant.

2. 2. The cooling passage according to claim 1, wherein a cross-sectional shape of the pipe perpendicular to the flow direction of the refrigerant in the refrigerant flow path is circular, and the convex portion is constituted by a step on the inner wall surface formed by bending the pipe so that a cut-out wall portion having a predetermined thickness in the flow direction protrudes in a radial direction of the circle.

3. 2. The cooling passage according to claim 1, wherein a cross-sectional shape of the pipe in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path is elliptical, and the convex portion is constituted by a step on the inner wall surface formed by bending a cut-out wall portion having a predetermined thickness in the flow direction so as to protrude by rotating the wall portion at a predetermined angle in the circumferential direction of the ellipse around an axis of the pipe.

4. 4. A cooling passage according to claim 3, wherein the cross-sectional shape of said tube in a direction perpendicular to said flow direction is a star-shaped polygon.

5. 4. A cooling passage according to claim 3, wherein a cross-sectional shape of said pipe in a direction perpendicular to said flow direction is a radial asterisk shape formed by intersecting a plurality of rectangular bodies at said axis.

6. 5. The cooling passage according to claim 4, wherein the cross-sectional shape of the convex portion is a star-shaped polygon, the tube is twisted in the flow direction to form a plurality of spiral ribbings on the inner wall surface, and the convex portion is configured by rib-like steps formed between adjacent ribbings.

7. 6. The cooling passage according to claim 5, wherein the cross-sectional shape of the convex portion is the asterisk shape, the tube body is twisted in the flow direction to form a plurality of spiral ribbings on the inner wall surface, and the convex portion is configured by rib-like steps formed between adjacent ribbings.

8. 2. The cooling passage according to claim 1, wherein the convex portion is constituted by a lattice plate formed on the whole or part of a cross section of the coolant flow passage in a direction perpendicular to the flow direction of the coolant.

9. The cooling passage according to claim 1 , wherein the protrusions are formed at a plurality of positions at predetermined intervals in a flow direction of the refrigerant flow passage.

10. An injection molding die comprising a hollow cylindrical tube surrounding a molding area of ​​the injection molding die to form a refrigerant flow path, the inner wall surface of the tube being provided with a cooling passage having a protrusion formed perpendicular to the flow direction of a laminar boundary layer generated by the inflow of the refrigerant.

11. 11. The injection molding die according to claim 10, wherein the cooling passage comprises two circuits: an air-cooling circuit into which a gas-phase refrigerant flows as the refrigerant, and a water-cooling circuit into which a liquid-phase refrigerant flows as the refrigerant.

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