Cooling passage and injection mold having the 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 mold having a cooling passage that forms a flow path for a refrigerant for cooling a thermoplastic material injected into the injection mold and a cooling part composed of the cooling passage.

Background Art

[0002] Injection molding forms a molded product by cooling and solidifying a high-temperature thermoplastic material injected into a mold. When the cooling of the thermoplastic material in the mold is uneven, the molded product taken out of the mold shrinks unevenly, which causes molding defects. Therefore, the cooling process in injection molding is an important process that affects the quality of the molded product.

[0003] Normally, in an injection mold, cooling passages are piped 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 injection-molded is at a high temperature, if the refrigerant stays in the cooling passages, it will reach a thermal equilibrium state in a short time and the cooling effect will decrease. Therefore, in the cooling process, it is necessary to continuously send a refrigerant to the cooling passages for cooling.

[0004] In order to enhance the sustainability of the cooling effect of the refrigerant, measures such as increasing the flow rate of the refrigerant and thickening the pipe diameter of the cooling passages can be considered, but all have physical limitations.

[0005] Therefore, conventionally, for example, an injection mold has been proposed in which convex ribs are provided on the inner surface of the cooling passage to increase the surface area (i.e., the heat transfer area) and improve the cooling effect (see, for example, Patent Document 1).

[0006] Also, an injection mold has been proposed in which cooling is performed by a spiral parallel flow flowing through a cooling bushing provided with spiral cooling grooves on the wall surface forming the cooling bushing hole of the core body (see, for example, Patent Document 2).

Prior Art Documents

Patent Document

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, even if the surface area of the cooling passage is increased as in the prior art, when 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, there has been a problem that the cooling effect is significantly reduced compared to the main flow at the axial center of the cooling passage.

[0009] By the way, the cooling method of the injection mold has a water-cooling type using water as the refrigerant and an air-cooling type using air. In the case of the water-cooling type, when the temperature inside the pipe exceeds 100 degrees, the internal pressure rises and there is a risk of steam leaking to the outside. Also, when the mold that has been clamped is divided after molding, if the water remaining in the pipe adheres to the molded product or the mold, it may damage the molded product and cause rusting of the mold. In order to avoid such inconveniences, the air-cooling type will be adopted. However, from the viewpoint of thermal conductivity, the air-cooling type has a lower cooling effect than the water-cooling type. Therefore, in the case of the air-cooling type, further improvement in cooling efficiency is required compared to the water-cooling type.

[0010] The disclosure in this specification is for solving the above problems, and an object is to provide a cooling passage for improving the cooling efficiency of a thermoplastic material by a refrigerant and an injection mold having such a cooling passage in injection molding.

Means for Solving the Problems

[0011] In order to solve the above problems, one aspect of the cooling passage disclosed in this specification is For example, It is composed of a hollow cylindrical tube that surrounds the molding area of the injection molding die and forms a refrigerant flow path. 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 a step on the inner wall surface of the tube formed by bending the tube so as to protrude in the radial direction of the circle, 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.

[0012] According to this configuration, the low-speed boundary layer that develops toward the downstream of the flow path repeatedly peels off and reattaches due to the convex portion provided in the flow direction, generating turbulent flow, so that heat exchange with the mainstream in the center of the flow path occurs frequently.

[0013] Also, 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 it is composed of a hollow cylindrical tube surrounding the molding area of the injection molding die, the cross-sectional shape of the tube in a direction perpendicular to the flow direction of the refrigerant in the refrigerant flow path is asterisk-shaped, and the tube is twisted in the flow direction to form a plurality of spiral ribs on the inner wall surface of the tube, and by the rib-shaped steps formed between adjacent ribs, the has on the inner wall surface , cold a convex portion formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the medium.

[0014] Further, the injection molding die may be configured such that the cooling section is composed of two systems of circuits, an air-cooling circuit that allows a vapor-phase refrigerant to flow in as the refrigerant and a water-cooling circuit that allows a liquid-phase refrigerant to flow in, and at least the air-cooling circuit is composed of the cooling passage.

Advantages of the Invention

[0015] The cooling passage of the present invention has the effect of improving the cooling efficiency of the thermoplastic material by the refrigerant in injection molding.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments for implementing the disclosure according to this specification will be described with reference to the drawings. When subsequent embodiments have components corresponding to those described above, the same reference numerals are given and duplicate descriptions are omitted. Also, when only a part of the configuration is described in each embodiment, reference numerals of the embodiments described above may be used for other parts of the configuration. Even when it is not explicitly stated that specific combinations are possible in each embodiment, as long as there is no particular problem with such combinations, it is also possible to partially combine the embodiments. In addition, the sizes of the members and components in the drawings are appropriately emphasized for ease of explanation and do not indicate actual dimensions, ratios between members, and ratios between components.

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

[0019] As shown in FIG. 1(A), the refrigerant flows into the refrigerant flow path 111 surrounded by the inner wall surface 112 of the tube 113. The refrigerant that has flowed 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 the gas phase or the liquid phase unless otherwise particularly limited.

[0020] In the refrigerant flow path 111, two layers with different flow velocities are formed: a main flow layer M in a region centered on the axis of the tube 113 and a laminar boundary layer B near the inner wall surface 112. Due to the viscosity of the refrigerant, friction occurs between the laminar boundary layer B and the inner wall surface 112, 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 main flow layer side streamline F2 of the main flow layer M. The laminar boundary layer B with a reduced flow velocity of the refrigerant gradually decreases in cooling efficiency because the refrigerant whose temperature has risen due to the heat exchange stays.

[0021] In the present embodiment, the cooling passage 11 has a convex portion 114 formed on the inner wall surface 112 of the refrigerant flow path 111 so as to be orthogonal to the flow direction of the boundary layer side streamline F1. That is, the convex portion 114 is provided at a position that blocks the flow of the boundary layer side streamline F1 of the laminar boundary layer B of the refrigerant.

[0022] Since the convex portion 114 is formed in the laminar boundary layer B with a gentle velocity gradient as described above, when the refrigerant reaches the convex portion 114, the frictional resistance becomes small. On the other hand, by continuously flowing in the refrigerant, a reverse pressure gradient acts on 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. As shown in FIG. 1(B), a separation space S is formed by the convex portion 114 and the inner wall surface 112, and while forming a turbulent flow, it proceeds in the flow direction of the boundary layer streamline F1.

[0023] On the other hand, by continuously flowing in the refrigerant, new refrigerant flows into the separation space S, and as shown in FIG. 1(C), a reattachment region R is formed. By providing a plurality of convex portions 114 in the flow direction of the boundary layer side streamline F1, the stagnant state is eliminated, and the separation and reattachment of the refrigerant are repeated at each location where the convex portion 114 of the inner wall surface 112 is provided, improving the cooling efficiency.

[0024] The arrangement interval of the plurality of convex portions 114 is not particularly limited. However, if it is formed at least in a section before reaching a flow in which the velocity distribution of the injection mold does not change, that is, a fully developed flow, the separation and reattachment of the refrigerant are effectively repeated.

[0025] <First Embodiment>

[0026] FIG. 2 is a diagram showing the cooling passage 12 according to the first embodiment. FIG. 2(A) is a perspective view of the cooling passage 12, FIG. 2(B) is a side sectional view of the cooling passage 12, and FIG. 2(C) is a vertical sectional view taken along line I-I' of FIG. 2(B).

[0027] In the present embodiment, the tubular body 123 constituting the cooling passage 12 has a circular cross-sectional shape in a direction orthogonal to the flow direction of the refrigerant (the flow directions of the boundary layer streamline F1 and the mainstream layer streamline F2). The first convex portion 124 and the second convex portion 125 are constituted by steps on the inner wall surface 122 formed by bending a cut-out piece-shaped 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. That is, if the cut-out piece is formed so that the axis C of the refrigerant flow path 121 is eccentric, a step is formed on the inner wall surface 122. In the present embodiment, the first convex portion 124 has the axis C eccentric to the first eccentric position E1, and the second convex portion 125 has the axis C eccentric to the second eccentric position E2, so that on the outer appearance of the tubular body 123, it has a shape bent so as to protrude in the radial direction of the circle, and on the inner wall surface 122, the first convex portion 124 and the second convex portion 125 are formed by steps.

[0028] Regarding the radial direction, when providing the bending portions at a plurality of locations, at least adjacent convex portions (the first convex portion 124 and the second convex portion 125 in the present embodiment) preferably have different directions (angles) in the radial direction to be bent. By protruding in this way, the action of peeling and reattachment is repeated by the boundary layer side streamline F1 flowing at different positions in the circumferential direction at each location where the first convex portion 124 and the second convex portion 125 are formed. Therefore, the cooling effect by the first convex portion 124 and the second convex portion 125 is uniformly exerted over the entire circumference of the tubular body 123, and the occurrence of molding defects such as warping can be suppressed. However, when it is necessary to specifically increase the cooling efficiency of the boundary layer side streamline F1 flowing at a predetermined position in the circumferential direction, it is preferable to make the bending direction (angle) the same.

[0029] Fig. 2(B) shows a state in which a reverse pressure gradient acts on the first convex portion 124 and a reverse flow region A is formed. However, as described with reference to Fig. 1, by continuously flowing the refrigerant, the formation of the separation space S and the formation of the reattachment region R are repeated. Hereinafter, in each embodiment, only the state in which the reverse flow region A is formed is shown, and the description of the action in which the formation of the separation space S and the formation of the reattachment region R are repeated is omitted because it is the same as that in the first embodiment.

[0030] <Second Embodiment>

[0031] FIG. 3 is a view showing the cooling passage 13 according to the second embodiment. FIG. 3(A) is a perspective view of the cooling passage 13, FIG. 3(B) is a side cross-sectional view of the cooling passage 13, and FIG. 3(C) is a vertical cross-sectional view taken along line II-II' of FIG. 3(B).

[0032] Similar to the first embodiment, the first convex portion 134 and the second convex portion 135 formed on the inner wall surface 132 of the cooling passage 13 according to the present embodiment are formed by cut-out piece-shaped wall portions having a predetermined thickness in the flow direction of the refrigerant. However, in the first embodiment, the cross-sectional shape in the direction orthogonal to the flow direction of the refrigerant (the flow directions of the boundary layer streamline F1 and the main flow layer streamline F2) is circular, while 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 configured by steps on the inner wall surface 132 formed by bending a cut-out piece-shaped wall portion having a predetermined thickness in the flow direction of the refrigerant flow path 131 (the flow directions of the boundary layer streamline F1 and the main flow layer streamline F2) so as to protrude by rotating at a predetermined angle in the circumferential direction of the ellipse around the axis of the pipe body 133. That is, due to the difference in the length in the minor axis direction and the length in the major axis direction of the ellipse, by rotating the first convex portion 134 and the second convex portion 135, on the outer appearance of the pipe body 133, similar to the first embodiment, it has a shape bent so as to protrude, and on the inner wall surface 132, the first convex portion 134 and the second convex portion 135 are formed by steps.

[0034] Also, similar to the first embodiment, when providing the bending portions at a plurality of locations, at least the adjacent convex portions (the first convex portion 134 and the second convex portion 135 in the present embodiment) are preferably rotated at different angles.

[0035] <Third Embodiment>

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

[0037] The cooling passage 14 according to the present embodiment is a modification of the second embodiment, and the cross-sectional shape of the pipe body 143 in the direction orthogonal 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 of the inner wall surface 142 formed by bending a cut-out piece-shaped wall portion having a predetermined thickness in the flow direction of the refrigerant flow path 141 (the flow direction of the boundary layer streamline F1 and the main flow layer streamline F2) so as to protrude by rotating at a predetermined angle in the circumferential direction of the star-shaped polygon around the axis of the pipe body 143. That is, the first convex portion 144 and the second convex portion 145 are formed by the fact that the star-shaped polygon has radially alternating concavities and convexities in the circumferential direction, and by rotating, the outer appearance of the pipe body 143 has a shape bent so as to protrude, similar to the first embodiment, and on the inner wall surface 142, the first convex portion 144 and the second convex portion 145 are formed by steps.

[0039] Also, similar to the first embodiment, when providing the bending portions at a plurality of locations, at least the adjacent convex portions (the first convex portion 144 and the second convex portion 145 in the present embodiment) are preferably rotated at different angles.

[0040] The shape according to the present embodiment has a larger surface area of the inner wall surface 142 than a cylindrical round pipe. If the surface area increases, the cooling effect also improves. Therefore, by expanding the surface area, a synergistic cooling effect is achieved with the provision of the first convex portion 144 and the second convex portion 145.

[0041] In addition, in FIG. 4, a star-shaped polygon with four vertices is shown, but it is not intended to be limited thereto. In the present embodiment, the star-shaped polygon includes all the figures obtained by connecting the intersection points obtained by extending each side of the plane geometric figure of the polygon, including the so-called star figure.

[0042] <Fourth Embodiment>

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

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

[0045] The first convex portion 154 and the second convex portion 155 are constituted by steps on the inner wall surface 152 formed by bending a cut-out piece-shaped wall portion having a predetermined thickness in the flow direction of the refrigerant flow path 151 (the flow direction of the boundary layer streamline F1 and the main flow layer streamline F2) so as to protrude by rotating at a predetermined angle in the circumferential direction of the asterisk shape around the axis of the pipe body 153. That is, the first convex portion 154 and the second convex portion 155 are formed by the fact that the asterisk shape has radially alternating concavities and convexities in the circumferential direction, and by rotating, the outer appearance of the pipe body 153 has a shape bent so as to protrude, similar to the first embodiment, and on the inner wall surface 152, the first convex portion 154 and the second convex portion 155 are formed by steps.

[0046] Similar to the star-shaped polygon, the asterisk shape can obtain a synergistic effect by expanding the surface area. In particular, since the radial tip portion of the asterisk shape is rectangular, the surface area expansion effect is higher than that of the star-shaped polygon with a pointed tip portion.

[0047] In addition, in FIG. 5, an asterisk shape with 8 radial tops is shown, but it is not intended to be limited thereto.

[0048] <Fifth Embodiment>

[0049] FIG. 6 is a view showing the cooling passage 16 according to the fifth embodiment, FIG. 6(A) is a perspective view of the cooling passage 16, FIG. 6(B) is a side sectional view of the cooling passage 16, FIG. 6(C) is a conceptual diagram showing the streamlines of the boundary layer, and FIG. 6(D) is a vertical sectional view seen from the V direction of FIG. 6(B).

[0050] Similar to the third embodiment, the cooling passage 15 according to the present embodiment has a star-shaped polygon as the cross-sectional shape of the pipe body 163 in the direction orthogonal to the flow direction of the refrigerant.

[0051] Different from the third embodiment, the convex portion 164 is formed by twisting the pipe body 163 in the flow direction of the refrigerant flow path 161 (the flow direction of the boundary layer streamline F1 and the main flow layer streamline F2) to form a plurality of spiral ridges on the inner wall surface 162, and is constituted by rib-shaped steps formed between adjacent ridges. That is, by rotating both ends of the pipe body 163 in opposite directions to form a twisted shape, a spiral groove (rifling) is formed on the inner wall surface 162 along the twisted shape. The groove is formed as a single groove or a plurality of parallel grooves according to the angle of rotation, and a rib-shaped convex portion 164 is formed adjacent to the groove.

[0052] The adjacent convex portions described in the first to fourth embodiments, that is, 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, the first convex portion 154 and the second convex portion 155, are structured to be discretely arranged with respect to the flow direction. However, the convex portion 164 in the present embodiment has a structure that is continuously arranged with respect to the flow direction. Therefore, as shown in FIG. 6(C), the reaching distance of the boundary layer streamline F1 in the present embodiment to the convex portion 164 differs depending on the position of the inner wall surface 162, and the action of peeling and reattachment of the refrigerant generated at the convex portion 164 occurs at different locations depending on the position of the inner wall surface 162.

[0053] In the cross-section of the pipe body 162 perpendicular to the flow direction of the laminar boundary layer B, looking at the behavior of the refrigerant near the convex portion 164, in the boundary layer streamline F1 that contacts the convex portion 164, a layer where the refrigerant does not move is formed. On the other hand, in the boundary layer streamline F1 that does not contact the convex portion 164 adjacent to the boundary layer streamline F1 of this non-moving layer, a layer where the refrigerant moves is formed. The refrigerant constituting the moving layer exerts an effect of peeling off the refrigerant in the non-moving layer.

[0054] In addition, since the internal space of the pipe body 163 formed with the rifling gives a swirling motion to the flow of the refrigerant in the refrigerant flow path 161, the straightness can be enhanced and a stable flow can be ensured. By ensuring a highly straight and stable flow of the refrigerant, the actions of peeling and reattachment are accelerated. Therefore, the convex portion 164 in the present embodiment can further improve the cooling efficiency by combining the actions of peeling and reattachment and the action of enhancing the straightness of the refrigerant.

[0055] <Sixth Embodiment>

[0056] FIG. 7 is a view showing a cooling passage 17 according to the sixth embodiment. 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 the streamlines of the boundary layer, and FIG. 7(D) is a vertical cross-sectional view seen from the VI direction of FIG. 7(B).

[0057] Similar to the fourth embodiment, the cooling passage 17 according to the present embodiment has a cross-sectional shape of a pipe body 173 in a direction perpendicular to the flow direction of the refrigerant as a radial asterisk shape formed by intersecting a plurality of rectangular bodies at the axis.

[0058] Unlike the fourth embodiment, the convex portion 174 is formed by twisting the tubular body 173 in the flow direction of the refrigerant flow path 171 (the flow directions of the boundary layer streamline F1 and the mainstream layer streamline F2) to form a plurality of spiral ridges on the inner wall surface 172, and is constituted by rib-shaped steps formed between adjacent ridges. That is, by rotating both ends of the tubular body 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 formed as a single groove or a plurality of parallel grooves according to the angle of rotation, and a rib-shaped convex portion 164 is formed adjacent to the groove.

[0059] In the cross-section of the tubular body 172 perpendicular to the flow direction of the laminar boundary layer B, the behavior of the refrigerant in the vicinity of the convex portion 174 is the same as that in the fifth embodiment. In the boundary layer streamline F1 that contacts the convex portion 174, a layer in which the refrigerant does not move is formed, and in the boundary layer streamline F1 that does not contact the convex portion 174 adjacent to the boundary layer streamline F1 of this non-moving layer, a layer in which the refrigerant moves is formed. The refrigerant constituting the moving layer has an effect of peeling off the refrigerant in the non-moving layer.

[0060] Note that the internal space of the tubular body 173 in which the rifling is formed can give a swirling motion to the flow of the refrigerant in the refrigerant flow path 171, so that the straightness can be enhanced and a stable flow can be ensured. By ensuring a highly straight and stable refrigerant flow, the actions of peeling and reattachment are accelerated. Furthermore, by making the cross-sectional shape asterisk-shaped, the surface area of the inner wall surface 172 is also expanded. Therefore, the convex portion 174 in the present embodiment can further improve the cooling efficiency by combining the actions of peeling and reattachment, enhancing the straightness of the refrigerant, and expanding the surface area.

[0061] <Seventh Embodiment>

[0062] FIG. 8 is a view showing a cooling passage 18 according to the seventh embodiment. FIG. 8(A) is a perspective view of the cooling passage 18, FIG. 8(B) is a side cross-section 8 of the cooling passage 12, and FIG. 8(C) is a vertical cross-sectional view taken along line VII-VII' of FIG. 8(B).

[0063] The tubular body 183 that constitutes the cooling passage 18 according to this embodiment has a circular cross-sectional shape in a direction orthogonal to the flow direction of the refrigerant (the flow directions of the boundary layer streamline F1 and the mainstream layer streamline F2). The first convex portion 184 and the second convex portion 185 are constituted by a lattice plate formed on the whole or a part of the cross-section of the refrigerant flow path 181 in a direction orthogonal to the flow direction of the refrigerant (in FIG. 8, an example in which the lattice plate is formed on the whole of the cross-section is shown, but it may be formed in a ring shape within a range orthogonal to the inner wall surface 182 with respect to the flow direction of the laminar boundary layer B generated by the inflow of the refrigerant). The refrigerant passes between the meshes of the lattice plate, and the lattice portion functions to block the flow of the boundary layer side streamline F1 of the laminar boundary layer B of the refrigerant. Therefore, the lattice portion serves as the first convex portion 184 and the second convex portion 185, and repeats the peeling and reattachment.

[0064] Note that the mesh size of the lattice plate is not particularly limited. For example, the mesh size in the range orthogonal to the inner wall surface 182 may be set to be small with respect to the flow direction of the laminar boundary layer (not shown). By reducing the mesh size within such a range, the peeling and reattachment are more effectively promoted.

[0065] <Injection mold>

[0066] FIG. 9 is an explanatory view showing the injection mold 2 according to this embodiment. FIG. 9(A) is a perspective view, FIG. 9(B) is a top view showing a state in which the movable side core and the slide core are joined, and FIG. 9(C) is a top view showing a state in which the slide core is separated from the movable side core.

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

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

[0069] By the way, generally, since water has a thermal conductivity about 20 times that of air, water cooling is selected from the viewpoint of cooling efficiency. On the other hand, in the case of water cooling, if the refrigerant leaks, rust will occur on the injection mold 2. When rust occurs, it will cause molding defects due to the mixing of rust during injection molding. Also, when the temperature inside the pipe of the water-cooling circuit 10w reaches 100°C or higher, it will be in a boiling state, and the pressure inside the pipe may increase and cause damage.

[0070] The movable core 22 and the slide core 23 structurally require a process of connection via the connection port 10c during injection molding. Therefore, when water cooling is selected, the water (refrigerant) remaining in the pipe may leak when the movable core 22 and the slide core 23 are detached, which causes rusting. Thus, the movable core 22 and the slide core 23 will select the air cooling circuit 10a. However, from the perspective of cooling efficiency, if water cooling is selected for the fixed core 21, cooling unevenness will occur between the fixed core 21, the movable core 22, and the slide core 23, which causes molding defects. Therefore, any one of the cooling passages 11, 12, 13, 14, 15, 16, 17, 18 may be arranged in either or both of the air cooling circuit 10a and the water cooling circuit 10w.

Example

[0071] In the following experiment, refrigerant (air) was introduced into steel specimens (cooling passages) having various shapes under the following conditions to confirm the difference in cooling efficiency. <Experimental Conditions> ·Length of specimen: 50 mm ·Cross-sectional area of specimen: φ3 ·Temperature rise of specimen: 130 °C ·Air temperature: 35 °C ·Measurement position: 13 mm from the center of the specimen

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

[0073] The cross-sectional shapes of the specimens were nine types as shown in Table 1. The pipe cross-sections, namely circular straight (φ3), star-shaped polygon straight (φ3-1), and asterisk-shaped straight (φ3-6), are all pipe bodies that do not have convex portions formed orthogonally to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant on the inner wall surface of the pipe body, and were measured as comparative data.

[0074] The pipe cross-sections of star-shaped polygon with 180° twist (No.418) and 360° twist (No.419) are the shapes explained in Fig. 6. For No.418, the rotation angle of the twist is 180°, and for No.419, the rotation angle of the twist is 360°. Also, the pipe shapes of asterisk-shaped with 180° twist (No.420) and 360° twist (No.421) are the shapes explained in Fig. 7. For No.420, the rotation angle of the twist is 180°, and for No.421, the rotation angle of the twist is 360°. The pipe shapes of asterisk-shaped with 3 shape changes (No.422) and 7 shape changes (No.423) are the shapes explained in Fig. 5. For No.422, the number of convex portions composed of the steps explained in Fig. 5 is 3, and for No.423, the number of convex portions composed of the steps is 7.

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

[0076] According to Table 1, the time required for cooling each comparative 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 comparative data is due to the difference in surface area. It can be seen that compared with φ3, φ3-1 had a cooling time shortening effect of about 21%, and φ3-6 had a cooling time shortening effect of about 43%.

[0077] Regarding the shape described in Fig. 6, the time required for cooling was 25.9 seconds for No. 418 and 26.1 seconds for No. 419. Therefore, it can be seen that compared with φ3, No. 418 had a shortening effect of about 37% and No. 419 had a shortening effect of about 36%. Also, even when comparing star polygons with the same cross-sectional shape, it can be seen that compared with φ3-1, No. 418 had a shortening effect of about 21% and No. 419 had a shortening effect of about 20%.

[0078] Regarding the shape described in Fig. 5, the time required for cooling was 23.4 seconds for No. 422 and 21.6 seconds for No. 423. Therefore, it can be seen that compared with φ3, No. 422 had a shortening effect of about 43% and No. 423 had a shortening effect of about 47%. Also, when comparing asterisk shapes with the same cross-sectional shape, compared with φ3-6, No. 422 had the same required time, but it can be seen that for No. 423, a shortening effect of about 8% was obtained.

[0079] Regarding the shape described in Fig. 7, the time required for cooling was 22.5 seconds for No. 420 and 21.1 seconds for No. 421. Therefore, it can be seen that compared with φ3, No. 420 had a shortening effect of about 45% and No. 421 had a shortening effect of about 48%. Also, even when comparing asterisk shapes with the same cross-sectional shape, compared with φ3-6, it can be seen that No. 420 had a shortening effect of about 4% and No. 421 had a shortening effect of about 10%.

[0080]

Table 1

[0081] The technology disclosed in this specification is not limited to the above embodiments. That is, it includes the illustrated embodiments and modifications by those skilled in the art based on them. Also, it includes the replacement or combination of parts and elements between one embodiment and another. Furthermore, the disclosed technical scope is not limited to the description of the embodiments. The disclosed technical scope is indicated by the description of the claims and further includes all changes within the meaning and scope equivalent to the description of the claims.

Explanation of Reference Numerals

[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 Passages 111, 121, 131, 141, 151, 161, 171, 181 Refrigerant Flow Paths 112, 122, 132, 142, 152, 162, 172, 182 Inner Wall Surfaces 113, 123, 133, 143, 153, 163, 173, 183 Pipe Bodies 114, 164, 174 Protrusions 124, 134, 144, 154, 184 First Protrusions 125, 135, 145, 155, 185 Second Protrusions A Countercurrent Region B Laminar Boundary Layer C Axis E1 First Eccentric Position E2 Second Eccentric Position F1 Boundary Layer Streamlines F2 Mainstream Layer Streamlines M Mainstream Layer R Reattachment Region S Separation Space

Claims

Claim 1: A cooling passage comprising a hollow cylindrical tube that surrounds a molding area of an injection molding die and forms a refrigerant flow path. The cross-sectional shape of the tube perpendicular to the flow direction of the refrigerant in the refrigerant flow path is circular. A cut-out piece-shaped wall portion having a predetermined thickness in the flow direction is formed by bending the tube so as to project in the radial direction of the circle. By means of a step on the inner wall surface of the tube thus formed, 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. Claim 2: A cooling passage comprising a hollow cylindrical tube that surrounds a molding area of an injection molding die and forms 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 is elliptical. A cut-out piece-shaped wall portion having a predetermined thickness in the flow direction is formed by bending the tube so as to project by rotating it at a predetermined angle in the circumferential direction of the ellipse about the axis of the tube. By means of a step on the inner wall surface of the tube thus formed, 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. Claim 3: A cooling passage comprising a hollow cylindrical tube that surrounds a molding area of an injection molding die and forms 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 is a star polygon. A cut-out piece-shaped wall portion having a predetermined thickness in the flow direction is formed by bending the tube so as to project by rotating it at a predetermined angle in the circumferential direction of the star polygon about the axis of the tube. By means of a step on the inner wall surface of the tube thus formed, 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. Claim 4: A cooling passage comprising a hollow cylindrical tube that surrounds a molding area of an injection molding die and forms 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 is a radial asterisk shape formed by intersecting a plurality of rectangular bodies at the axis of the tube. A cut-out piece-shaped wall portion having a predetermined thickness in the flow direction is formed by bending the tube so as to project by rotating it at a predetermined angle in the circumferential direction of the asterisk shape about the axis of the tube. By means of a step on the inner wall surface of the tube thus formed, 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. Claim 5: A cooling passage is formed by a hollow cylindrical tube that surrounds the molding area of an injection molding die and forms 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 is a star-shaped polygon. The tube is twisted in the flow direction to form a plurality of spiral ribs on the inner wall surface of the tube. Due to the rib-shaped steps formed between adjacent ribs, the inner wall surface has convex portions formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant. Claim 6: A cooling passage is formed by a hollow cylindrical tube that surrounds the molding area of an injection molding die and forms 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 is an asterisk shape. The tube is twisted in the flow direction to form a plurality of spiral ribs on the inner wall surface of the tube. Due to the rib-shaped steps formed between adjacent ribs, the inner wall surface has convex portions formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant. Claim 7 A cooling passage is formed by a hollow cylindrical tube that surrounds the molding area of an injection molding die and forms a refrigerant flow path. A grid plate with a predetermined mesh size formed in a ring shape on the inner wall surface of the tube by all 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 has convex portions on the inner wall surface that are perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant and block the flow of the refrigerant. Claim 8 The convex portions are formed at a plurality of locations at predetermined intervals in the flow direction of the refrigerant flow path, and the cooling passage according to any one of Claims 1 to 7 is provided. Claim 9 An injection molding die is provided with a cooling passage formed by a hollow cylindrical tube that surrounds the molding area of an injection molding die and forms 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 is an asterisk shape. The tube is twisted in the flow direction to form a plurality of spiral ribs on the inner wall surface of the tube. Due to the rib-shaped steps formed between adjacent ribs, the inner wall surface of the tube has convex portions formed perpendicular to the flow direction of the laminar boundary layer generated by the inflow of the refrigerant. Claim 10 The injection mold according to claim 9, wherein the cooling passage is composed of two systems of circuits, an air-cooling circuit into which a vapor-phase refrigerant flows as the refrigerant and a water-cooling circuit into which a liquid-phase refrigerant flows.

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