JP7702158B2 - Cooling passage and injection mold having cooling passage - Google Patents

Description

The disclosure in this specification relates to a cooling passage that forms a flow path for a refrigerant that cools a thermoplastic material injected into an injection mold, and an injection mold having a cooling section composed of the cooling passage.

In injection molding, hot thermoplastic material is injected into a mold and then cooled and solidified to form a molded product. If the thermoplastic material in the mold is not cooled uniformly, the molded product will shrink unevenly when removed from the mold, resulting in molding defects. Therefore, the cooling process in injection molding is an important process that determines the quality of the molded product.

Typically, an injection mold has cooling passages around the cavity space. In the cooling process, a refrigerant is sent to the cooling passages to cool the thermoplastic material. Because the thermoplastic material to be injected is at a high temperature, if the refrigerant stagnates in the cooling passages, it 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.

In order to increase the durability of the cooling effect of the refrigerant, it is possible to consider measures such as increasing the flow rate of the refrigerant or increasing the diameter of the cooling passage, but there are physical limitations to each of these.

Therefore, in the past, for example, an injection molding die was proposed that improves the cooling effect by providing convex ribs on the inner surface of the cooling passage to expand the surface area (i.e., the heat transfer area) (see, for example, Patent Document 1).

In addition, an injection molding die has been proposed in which cooling is performed by a parallel spiral flow through a cooling bush having a spiral cooling groove on the wall surface that forms the cooling bush hole of the core body (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2-106314 Japanese Patent Application Publication No. 9-262870

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

There are two cooling methods for injection molding dies: water-cooled, which uses water as a refrigerant, and air-cooled, which uses air. In the case of water-cooled dies, if the temperature inside the pipes exceeds 100 degrees, the internal pressure increases and there is a risk of steam leaking to the outside. In addition, when the clamped die is separated after molding, if the water remaining inside the pipes adheres to the molded product or die, it may damage the molded product and cause the die to rust. In order to avoid such inconveniences, air-cooled dies are adopted, but from the perspective of thermal conductivity, air-cooled dies have a lower cooling effect than water-cooled dies. Therefore, air-cooled dies require even more efficient cooling than water-cooled dies.

The disclosure in this specification is intended to resolve the above-mentioned problems, and aims to provide a cooling passage that improves the efficiency of cooling a thermoplastic material by a refrigerant during injection molding, and an injection molding die having such a cooling passage.

In order to solve the above problems, one embodiment of a cooling passage disclosed in this specification is, for example, composed of a hollow cylindrical tube that surrounds a molding area of an injection molding die to form a refrigerant flow path, and the cross-sectional shape of the tube perpendicular to the flow direction of the refrigerant in the refrigerant flow path is circular, and a cut-out piece-shaped wall portion having a predetermined thickness in the flow direction is formed by bending the tube to protrude radially of the circle, thereby forming a step on the inner wall surface of the tube, and the inner wall surface has a convex portion formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant.

With this configuration, the low-speed boundary layer that develops toward the downstream of the flow path repeatedly separates and reattaches due to the protrusions provided in the flow direction, generating turbulence, which frequently exchanges heat with the main flow path in the center of the flow path.

Moreover, one aspect of the injection molding die disclosed in this specification has a cooling passage that forms a cooling flow path for a refrigerant that cools a thermoplastic material, the cooling flow path being constituted by a hollow cylindrical tube surrounding a molding area of the injection molding die, the cross section of the tube in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path being made asterisk-shaped, the tube being twisted in the flow direction to form a plurality of spiral ribbing on the inner wall surface of the tube, and rib-like steps formed between adjacent ribbings provide a convex portion on the inner wall surface of the tube that is formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant .

The cooling section of the injection mold may be configured with two circuits: an air-cooled circuit that introduces a gas-phase refrigerant as the refrigerant, and a water-cooled circuit that introduces a liquid-phase refrigerant, and at least the air-cooled circuit may be configured with the cooling passage.

The cooling passage of the present invention has the effect of improving the cooling efficiency of the thermoplastic material by the refrigerant during injection molding.

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 a boundary layer separates at a convex portion and then reattaches. 2A and 2B are diagrams showing the cooling passage according to the first embodiment, in which (A) is an oblique view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line I-I'. 3A is a perspective view of a cooling passage according to the second embodiment, FIG. 3B is a side cross-sectional view, and FIG. 3C is a vertical cross-sectional view taken along line II-II'. 4A is a perspective view of a cooling passage according to the third embodiment, FIG. 4B is a side cross-sectional view, and FIG. 4C is a vertical cross-sectional view taken along line III-III'. 5A and 5B are diagrams showing a cooling passage according to a fourth embodiment, in which (A) is an oblique view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line IV-IV'. 6A and 6B are diagrams 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 as viewed from the arrow V. 7A and 7B are diagrams showing a cooling passage according to a sixth 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 VI. 8A and 8B are diagrams showing a cooling passage according to the seventh embodiment, in which (A) is an oblique view, (B) is a side cross-sectional view, and (C) is a vertical cross-sectional view taken along line VII-VII'. 9A and 9B are explanatory diagrams showing an injection molding die according to this embodiment, in which (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.

Below, the embodiments for implementing the disclosure of this specification will be described with reference to the drawings. When a subsequent embodiment has components corresponding to the previously described embodiments, the same reference numerals will be used and duplicated descriptions will be omitted. In addition, when only a portion of the configuration is described in each embodiment, the reference numerals of the previously described embodiment may be used for other portions of the configuration. Even if it is not clearly stated that specific combinations are possible in each embodiment, it is possible to partially combine the embodiments together, provided that there is no particular problem with the combination. In addition, the size of each member and component in the drawings has been appropriately exaggerated to facilitate explanation, and does not indicate the actual dimensions or the ratio between members and components.

Figure 1 is a partial cross-sectional side 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 tube 113 that surrounds the molding area (near the cavity) of the injection molding die. That is, the tube 113 is arranged 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 tube 113 forms a refrigerant flow path for a refrigerant that cools the plastic resin.

As shown in FIG. 1(A), a refrigerant flows into a refrigerant flow passage 111 surrounded by an inner wall surface 112 of a tube body 113. The refrigerant that flows in exchanges heat with the 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.

In the refrigerant flow path 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 tube body 113, and a laminar boundary layer B near 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 reduced, the refrigerant whose temperature has increased due to the heat exchange accumulates, and the cooling efficiency gradually decreases.

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

As described above, the convex portion 114 is formed in a laminar boundary layer B with a gentle velocity gradient, so when the refrigerant reaches the convex portion 114, frictional resistance decreases. Meanwhile, as the refrigerant continues to flow in, it is subjected to 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 as shown in FIG. 1B, a separation space S is formed between the convex portion 114 and the inner wall surface 112, and the refrigerant proceeds in the flow direction of the boundary layer flow line F1 while forming a turbulent flow.

On the other hand, by continuously flowing in the refrigerant, new refrigerant flows into the separation 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 the refrigerant repeatedly separates and reattaches at each of the protrusions 114 on the inner wall surface 112, improving the cooling efficiency.

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

<First embodiment>

Figure 2 shows the cooling passage 12 according to the first embodiment, where Figure 2(A) is a perspective view of the cooling passage 12, Figure 2(B) is a side cross-sectional view of the cooling passage 12, and Figure 2(C) is a vertical cross-sectional view taken along line I-I' in Figure 2(B).

In this embodiment, the tube 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 form steps on the inner wall surface 122. In this embodiment, the axis C of the first convex portion 124 is eccentric to the first eccentric position E1, and the axis C of the second convex portion 125 is eccentric to the second eccentric position E2, so that the external appearance of the tube body 123 is bent so as to protrude in the radial direction of the circle, and the first convex portion 124 and the second convex portion 125 are formed by steps on the inner wall surface 122.

When the bending is performed at multiple 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 different radial bending 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 locations 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 tube 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 specific position in the circumferential direction, it is preferable to make the bending direction (angle) the same.

Figure 2 (B) shows the state where the first protrusion 124 is subjected to the action of a reverse pressure gradient and a reverse flow region A is formed, but as explained in Figure 1, the refrigerant is continuously introduced, so the formation of the separation space S and the reattachment region R is repeated. In the following embodiments, only the state where the reverse flow region A is formed is shown, and the action of the repeated formation of the separation space S and the reattachment region R is omitted because it is the same as in the first embodiment.

<Second embodiment>

Figure 3 shows the cooling passage 13 according to the second embodiment, where Figure 3(A) is a perspective 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).

In the cooling passage 13 according to this embodiment, as in 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 layer flow line F2) is circular, in the second embodiment, the cross-sectional shape of the tube body 133 is elliptical.

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 path 131 (the flow direction 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 steps on the inner wall surface 132 ...

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

<Third embodiment>

Figure 4 shows the cooling passage 14 according to the third embodiment, where Figure 4(A) is a perspective view of the cooling passage 14, Figure 4(B) is a side cross-sectional view of the cooling passage 14, and Figure 4(C) is a vertical cross-sectional view taken along line III-III' in Figure 4(B).

The cooling passage 14 in this embodiment is a modified version of the second embodiment, in which the cross-sectional shape of the tube 143 in a direction perpendicular to the flow direction of the refrigerant is a star-shaped polygon.

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 path 141 (the flow direction of the boundary layer flow line F1 and the main layer flow line F2) by rotating the cut-out wall portion at a predetermined angle in the circumferential direction of the star-shaped polygon around the axis of the tube body 143. That is, the first convex portion 144 and the second convex portion 145 are formed by rotating the star-shaped polygon so that the appearance of the tube body 143 is bent to protrude, 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.

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

The shape of this embodiment has a larger surface area for 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 provides a synergistic cooling effect with the provision of the first convex portion 144 and the second convex portion 145.

Note that while FIG. 4 shows a star polygon with four vertices, this is not intended to be limiting. In this embodiment, a star polygon includes any figure formed by connecting the intersections obtained by extending each side of a polygonal planar geometric figure, including so-called pointed star figures.

<Fourth embodiment>

Figure 5 shows the cooling passage 15 according to the fourth embodiment, where Figure 5(A) is a perspective view of the cooling passage 15, Figure 5(B) is a side cross-sectional view of the cooling passage 15, and Figure 5(C) is a vertical cross-sectional view taken along line IV-IV' in Figure 5(B).

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

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 path 151 (the flow direction of the boundary layer flow line F1 and the main layer flow line F2) by rotating the cut-out wall portion at a predetermined angle in the circumferential direction of the asterisk shape around the axis of the tube body 153. That is, the first convex portion 154 and the second convex portion 155 are formed by rotating the asterisk shape so that the tube body 153 has an external shape that is bent to protrude, similar 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.

The asterisk shape, like the star polygon, provides a synergistic effect by expanding the surface area. In particular, the asterisk shape has a rectangular radiating tip, so it has a greater effect in expanding the surface area than the star polygon, which has a pointed tip.

Note that in Figure 5, an asterisk shape with eight radial apexes is shown, but this is not intended to be limiting.

<Fifth embodiment>

Figure 6 shows the cooling passage 16 according to the fifth embodiment, where Figure 6(A) is a perspective view of the cooling passage 16, Figure 6(B) is a side cross-sectional view of the cooling passage 16, Figure 6(C) is a conceptual diagram showing the flow lines of the boundary layer, and Figure 6(D) is a vertical cross-sectional view seen from the V direction of Figure 6(B).

In the cooling passage 15 of this embodiment, as in the third embodiment, the cross-sectional shape of the tube 163 in the direction perpendicular to the flow direction of the refrigerant is a star-shaped polygon.

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 multiple 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 opposite directions to each other to form a twisted shape, a spiral groove (rifling) is formed on the inner wall surface 162 along the twisted shape. The groove is a single groove or multiple parallel grooves depending on the angle of the rotation, and a rib-like convex portion 164 is formed adjacent to the groove.

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 arranged discretely in the flow direction, but the convex portion 164 in this embodiment is structured to be arranged continuously in the flow direction. Therefore, as shown in FIG. 6(C), the boundary layer flow line F1 in this embodiment has a different reach to the convex portion 164 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 locations depending on the position on the inner wall surface 162.

When looking at the behavior of the refrigerant near the convex portion 164 in a cross section of the tube 162 perpendicular to the flow direction of the laminar boundary layer B, the boundary layer flow line F1 that abuts the convex portion 164 forms a layer in which 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 this immobile layer and does not abut the convex portion 164 forms a layer in which the refrigerant moves. The refrigerant that constitutes the moving layer acts to separate the refrigerant from the immobile layer.

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

<Sixth embodiment>

Figure 7 shows the cooling passage 17 according to the sixth embodiment, where Figure 7(A) is a perspective view of the cooling passage 17, Figure 7(B) is a side cross-sectional view of the cooling passage 17, Figure 7(C) is a conceptual diagram showing the flow lines of the boundary layer, and Figure 7(D) is a vertical cross-sectional view seen from the VI direction of Figure 7(B).

In the cooling passage 17 of this embodiment, as in the fourth embodiment, the cross-sectional shape of the tube 173 in the direction perpendicular to the flow direction of the refrigerant is a radial asterisk shape formed by intersecting multiple rectangular bodies at the axis.

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 multiple spiral ribbing on the inner wall surface 172, and is constituted by rib-like steps formed between adjacent ribbing. In other words, by rotating both ends of the tube 173 in opposite directions to each other to form a twisted shape, a spiral groove (rifling) is formed on the inner wall surface 172 along the twisted shape. The groove is a single groove or multiple parallel grooves depending on the angle of the rotation, and a rib-like convex portion 164 is formed adjacent to the groove.

In the cross section of the tube 172 perpendicular to the flow direction of the laminar boundary layer B, the behavior of the refrigerant near the convex portion 174 is the same as in the fifth embodiment, where the boundary layer flow line F1 abutting the convex portion 174 forms a layer in which the refrigerant does not move, and where the boundary layer flow line F1 adjacent to the boundary layer flow line F1 of the immobile layer that does not abut the convex portion 174 forms a layer in which the refrigerant moves. The refrigerant that constitutes the moving layer acts to separate the refrigerant from the immobile layer.

The internal space of the tube body 173 in which the rifling is formed imparts a swirling motion to the flow of the refrigerant in the refrigerant flow passage 171, thereby improving linearity and ensuring a stable flow. Ensuring a stable flow of the refrigerant with high linearity accelerates the separation and reattachment action. Furthermore, by making the cross-sectional shape 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 action, the action of increasing the linearity of the refrigerant, and the expansion of the surface area.

<Seventh embodiment>

Figure 8 shows a cooling passage 18 according to the seventh embodiment, where Figure 8(A) is a perspective 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).

The tube 183 constituting the cooling passage 18 in this embodiment 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 laminar flow line F2). The first convex portion 184 and the second convex portion 185 are formed by a lattice plate formed on the entire or part of the cross section of the refrigerant flow path 181 in a direction perpendicular to the flow direction of the refrigerant (FIG. 8 shows an example in which the lattice plate is formed on the entire 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 peeling and reattaching are repeated.

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 more effectively promoted.

<Injection mold>

Figure 9 is an explanatory diagram showing an injection molding die 2 according to this embodiment, where Figure 9(A) is a perspective view, Figure 9(B) is a top view showing the movable core and the sliding core joined together, and Figure 9(C) is a top view showing the sliding core separated from the movable core.

The injection molding die 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 molding die 2 has an air-cooling circuit 10a through which gas-phase refrigerant flows and a water-cooling circuit 10w through which 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.

9(C), 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.

Generally, water has a thermal conductivity about 20 times higher than air, so water cooling is the method of choice from the viewpoint of cooling efficiency. However, when using water cooling, if the refrigerant leaks, rust will form on the injection molding die 2. If rust forms, it can become 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, the pipes will boil, and the pressure inside the pipes will rise, which may cause damage.

The movable core 22 and the slide core 23 require a process of connecting them through the connection port 10c during injection molding due to their structure. Therefore, if water cooling is selected, the water (refrigerant) remaining in the pipes will leak out when the movable core 22 and the slide core 23 are attached and detached, causing the above-mentioned rust. Therefore, the air-cooled circuit 10a is selected for the movable core 22 and the slide core 23. However, from the viewpoint of cooling efficiency, if water cooling is selected for the fixed core 21, uneven cooling will occur between the fixed core 21 and the movable core 22 and the slide core 23, causing molding defects. Therefore, it is sufficient to arrange any one of the cooling passages 11, 12, 13, 14, 15, 16, 17, and 18 in both or either of the air-cooled circuit 10a and the water-cooled circuit 10w.

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>
・ Length of specimen: 50 mm
Cross-sectional area of specimen: φ3
Sample heating temperature: 130°C
Air temperature: 35°C
Measurement position: 13 mm from the center of the specimen

To ensure a stable temperature (instead of using thermoplastic resin), the specimens were heated using four cartridge heaters positioned at equal distances from the outer periphery of the specimen, and each cartridge heater was spaced equally circumferentially. 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 taken as the average.

The specimens had nine different cross-sectional shapes, as shown in Table 1. The pipe cross sections were a straight circle (φ3), a straight star-shaped polygon (φ3-1), and a straight asterisk (φ3-6). None of these pipes had protrusions on the inner wall surface of the pipe that were perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant, and were measured as comparative data.

The star-shaped polygonal 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 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 cross section with three shape changes (No. 422) and seven shape changes (No. 423) are shapes described in FIG. 5. No. No. 422 has three protruding parts formed from the steps described in FIG. 5, and No. 423 has seven protruding parts formed from the steps.

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

According to Table 1, the time required for cooling 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.

The time required for cooling for the shapes described in Figure 6 was 25.9 seconds for No. 418 and 26.1 seconds for No. 419. Therefore, compared to φ3, No. 418 achieved a reduction in time of approximately 37% and No. 419 achieved a reduction in time of approximately 36%. Also, when comparing the cross-sectional shapes of the same star-shaped polygon, No. 418 achieved a reduction in time of approximately 21% and No. 419 achieved a reduction in time of approximately 20% compared to φ3-1.

The time required for cooling for the shapes described in Figure 5 was 23.4 seconds for No. 422 and 21.6 seconds for No. 423. Therefore, compared to φ3, No. 422 achieved a reduction in time of approximately 43%, and No. 423 achieved a reduction in time of approximately 47%. Also, when comparing with the asterisk shape, which has the same cross-sectional shape, compared to φ3-6, No. 422 required the same time, but No. 423 achieved a reduction in time of approximately 8%.

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

The technology disclosed in this specification is not limited to the above-mentioned embodiment. In other words, it includes the embodiments shown as examples and modifications made by those skilled in the art based on them. It also includes the substitution 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.

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 refrigerant flow path 112, 122, 132, 142, 152, 162, 172, 182 inner wall surface 113, 123, 133, 143, 153, 163, 173, 183 tube 114, 164, 174 convex portion 124, 134, 144, 154, 184 first convex portion 125, 135, 145, 155, 185 second convex portion A reverse flow region B laminar boundary layer C Axial center E1 First eccentric position E2 Second eccentric position F1 Boundary layer streamline F2 Mainstream laminar streamline M Mainstream layer R Reattachment area S Separation space

Claims (10)

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 a circular cross-sectional shape perpendicular to the flow direction of the refrigerant in the refrigerant flow path, the tube having a cut-out piece-like wall portion having a predetermined thickness in the flow direction formed by bending the tube so as to protrude in a radial direction of the circle , and a protrusion formed on the inner wall surface perpendicular to the flow direction of a laminar boundary layer generated by the inflow of the refrigerant . 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 elliptical cross-sectional shape in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path, and a cut-out piece-like wall portion having a predetermined thickness in the flow direction is bent by rotating a predetermined angle in the circumferential direction of the ellipse about the axis of the tube so as to protrude, thereby forming a step on the inner wall surface of the tube , the step having a convex portion formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant . 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 a star-shaped polygonal cross section in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path, the tube having a cut-out piece-like wall portion having a predetermined thickness in the flow direction, the wall portion being bent so as to protrude by rotating a predetermined angle in the circumferential direction of the star-shaped polygon about the axis of the tube, thereby forming a step on the inner wall surface of the tube, the step forming a protrusion being formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant . A cooling passage comprising a hollow cylindrical tube surrounding a molding area of an injection molding die to form a refrigerant flow path, the cross-sectional shape of the tube in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path being formed by intersecting a plurality of rectangular pieces at the axis of the tube , the cross-sectional shape of the tube being formed into a radial asterisk shape, and a cut-out piece-like wall portion having a predetermined thickness in the flow direction is bent so as to protrude by rotating the axial center of the tube at a predetermined angle in the circumferential direction of the asterisk shape, the step on the inner wall surface of the tube being formed so as to protrude, the step having a convex portion formed on the inner wall surface perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant. 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 a star -shaped polygonal cross section in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path, the tube being twisted in the flow direction to form a plurality of spiral ribbing on an inner wall surface of the tube , and rib-like steps formed between adjacent ribbings to form convex portions on the inner wall surface perpendicular to the flow direction of a laminar boundary layer generated by the inflow of the refrigerant . 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 asterisk- shaped cross section in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path, the tube being twisted in the flow direction to form a plurality of spiral ribbing on an inner wall surface of the tube , and rib-like steps formed between adjacent ribbings to form convex portions on the inner wall surface perpendicular to the flow direction of a laminar boundary layer generated by the inflow of the refrigerant . A cooling passage which is composed of a hollow cylindrical tube surrounding a molding area of an injection molding die to form a refrigerant flow path, and which has a lattice plate having a predetermined mesh size formed in a ring shape on an inner wall surface of the tube over the entire cross section or part of the cross section of the refrigerant flow path in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path, and which has a convex portion on the inner wall surface which is perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant and which blocks the flow of the refrigerant. 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. 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 tube having an asterisk-shaped cross section in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path, the tube being twisted in the flow direction to form a plurality of spiral ribbing on an inner wall surface of the tube, and a cooling passage having a convex portion formed perpendicular to the flow direction of a laminar boundary layer generated by an inflow of the refrigerant on the inner wall surface of the tube by rib-like steps formed between adjacent ribbings. 10. The injection mold according to claim 9 , 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.