Method for manufacturing injection molds and resin molded products

Abstract

To adjust the temperature of a mold surface.SOLUTION: An injection mold 20 injects resin into a cavity 26 to form resin molded products 10. The injection mold 20 is equipped with a nesting 28 consisting of a plurality of plates 42 stacked on top of each other. The nest 28 has an air distribution channel 46 between adjacent plates 42, 42 that directs air supplied from an air supply section 48 toward the cavity 26. The air distribution channel 46 may be formed by recessing a portion of the overlapping surfaces of the plates 42.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to an injection mold and a method for manufacturing a resin molded product.

Background Art

[0002] An injection mold for molding a resin molded product controls the temperature of the mold surface by passing cooling water through a cooling passage (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an injection mold, for the convenience of controlling the temperature of the mold surface, it is preferable to arrange the cooling passage at a position as close as possible to the mold surface. However, depending on the shape of the cavity (the shape of the resin molded product), etc., the cooling passage may only be arranged at a position far from the mold surface. In this case, temperature unevenness may occur on the mold surface, and there is a risk of poor quality of the resulting resin molded product.

[0005] In view of the above problems in the prior art, the present invention is proposed to preferably solve these problems, and an object thereof is to provide an injection mold capable of controlling the temperature of the mold surface.

Means for Solving the Problems

[0006] A first aspect of the injection mold according to the present invention is an injection mold for injecting resin into a cavity to mold a resin molded product, comprising a nested structure in which a plurality of plate-like bodies are stacked, The essence of the nesting structure is that it has an air passage between the plate-like bodies that directs air supplied from the air supply unit towards the cavity.

[0007] A second embodiment of the injection mold according to the present invention is, in the first embodiment, The cavity is formed between a convex shape and a concave shape, The aforementioned insert may constitute the mold surface that forms the curved portion of the cavity in the convex mold.

[0008] A third aspect of the injection mold according to the present invention is, in the first or second aspect, The air passage may be formed by recessing a part of the overlapping surface of the plate-like bodies.

[0009] One embodiment of the method for manufacturing a resin molded article according to the present invention is: The gist of the invention is to fill the cavity formed by the injection mold according to any of the first, second, and third embodiments with resin, and then cool the resin filled in the cavity by passing air through the air passage. [Effects of the Invention]

[0010] According to the first embodiment of the injection molding die according to the present invention, the temperature of the mold surface can be controlled by air passing through an air passage. According to one embodiment of the method for manufacturing resin molded articles according to the present invention, the quality of the resulting resin molded article can be improved because it is molded using an injection mold in which the temperature of the mold surface is controlled. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view showing an example of a resin molded product formed using an injection mold according to an embodiment of the present invention. [Figure 2] (a) is a cross-sectional view of the injection mold of the embodiment, shown in the closed state. Note that the cut is made at the location of the air passage. (b) is a cross-sectional view taken along line AA of (a). [Figure 3]This is a cross-sectional view of the injection molding die of the embodiment, shown in the open state. The cut is made at the location of the air passage. [Figure 4] This is a cross-sectional view of the injection molding die of the embodiment, shown in the closed state. Note that the cut is made at the attachment point to the nesting matrix. [Figure 5] This is a perspective view showing the nesting of the embodiment. [Figure 6] This is a perspective view showing the nested structure of the embodiment in disassembled form. [Figure 7] This is a plan view showing another example of an airflow passage. [Modes for carrying out the invention]

[0012] Next, a preferred example of the injection mold and resin molded product manufacturing method according to the present invention will be described below with reference to the attached drawings. [Examples]

[0013] The resin molded product 10 shown in Figure 1 has a curved, concave edge. More specifically, the resin molded product 10 comprises a base portion 12, a first wall portion 14 rising from the base portion 12, and a second wall portion 16 rising from the base portion 12. The resin molded product 10 has a pair of first wall portions 14, 14 arranged on either side of the base portion 12. In addition, the second wall portion 16 of the resin molded product 10 has a smaller projection dimension from the base portion 12 than the first wall portion 14. The resin molded product 10 can be used in various parts, such as interior vehicle components like instrument panels and door trims, exterior vehicle components, and even residential components, not limited to vehicle components.

[0014] As shown in FIGS. 2 and 3, an injection mold 20 according to an embodiment for manufacturing a resin molded product 10 includes a first mold part 22 and a second mold part 24. When the first mold part 22 and the second mold part 24 are closed, molten synthetic resin is injected (filled) into a cavity 26 formed between the first mold part 22 and the second mold part 24, and the synthetic resin is cooled and cured to form the resin molded product 10. In the embodiment, the first mold part 22 is a convex mold that defines the back surface of the resin molded product 10. Also, the second mold part 24 is a concave mold that defines the front surface (design surface) of the resin molded product 10.

[0015] As shown in FIGS. 2 to 4, the first mold part 22 includes an insert 28. One surface of the insert 28 (when particularly distinguished, it is referred to as an insert mold surface 28a) is a part of the mold surface that forms the cavity 26 in the first mold part 22. The insert 28 may be disposed at an appropriate position in consideration of temperature adjustment in the first mold part 22. In particular, it is preferable that the insert mold surface 28a forms a curved portion of the cavity 26 in the first mold part 22. In the embodiment, at the curved portion of the cavity 26, a bent portion that bends from the base portion 12 to the first wall portion 14 in the resin molded product 10 is formed. In other words, the insert 28 is preferably disposed at a corner portion that bends from the top portion to the bottom portion of the convex portion in the first mold part 22. In the embodiment, the base portion 12 of the resin molded product 10 is formed by the top portion of the convex portion, the first wall portion 14 of the resin molded product 10 is formed by the bottom portion of the convex portion, and a bent portion that bends from the base portion 12 to the first wall portion 14 is formed by the corner portion of the convex portion.

[0016] In FIGS. 2 to 4, it is an example in which the insert 28 is disposed in the left curved portion of the cavity 26 corresponding to the bent portion from the base portion 12 to the left first wall portion 14. However, the insert 28 may also be disposed in the right curved portion of the cavity 26 corresponding to the bent portion from the base portion 12 to the right first wall portion 14, or the insert 28 may not be disposed in the right curved portion. Also, the insert 28 may be disposed in the curved portion of the cavity 26 corresponding to the bent portion from the base portion 12 to the second wall portion 16, or the insert 28 may not be disposed in the curved portion.

[0017] The first mold part 22 may arrange the nested mold surface 28a of the insert 28 corresponding to the entire width direction of the curved part of the cavity 26, or may arrange the nested mold surface 28a of the insert 28 corresponding to a partial range in the width direction of the curved part of the cavity 26. In the embodiment, one insert 28 is arranged, but a plurality of inserts 28 may be arranged side by side in the width direction of the curved part of the cavity 26.

[0018] As shown in FIGS. 2 to 4, the insert 28 is fitted into the installation recess 32 formed in the master mold 30. A fastening element 36 such as a bolt (referred to as a master mold fastening element when particularly distinguished) passed through the through hole portion 34 formed in the master mold 30 is fitted (screwed) into the fastening hole 38 provided in the insert 28, and the insert 28 is fixed to the master mold 30 (see FIG. 4). In the master mold 30, the through hole portion 34 through which the master mold fastening element 36 passes is formed larger than the outer diameter of the master mold fastening element 36, and the gap between the master mold fastening element 36 and the through hole portion 34 becomes the master mold exhaust passage 40.

[0019] As shown in FIGS. 2 to 6, the insert 28 is configured by stacking a plurality of plate-like bodies 42. The plurality of plate-like bodies 42 are fixed to each other by a fastening element 44 such as a bolt (referred to as an insert fastening element when particularly distinguished) (see FIG. 6). The plurality of plate-like bodies 42 are arranged in the direction from the top portion to the bottom portion of the convex portion in the first mold part 22. One surface of each plate-like body 42 faces the cavity 26 and constitutes the nested mold surface 28a.

[0020] As shown in Figures 2 and 3, the nest 28 has an air passage 46 between adjacent plate-like bodies 42. Air supplied from the air supply unit 48 passes through the air passage 46 and is directed toward the cavity 26. One end of the air passage 46 opens into the space 32a formed between the bottom surface of the installation recess 32 and the nest 28. The other end of the air passage 46 opens into the nest mold surface 28a, and the air passage 46 is connected to the cavity 26. It is preferable to set the opening width of the outlet that opens into the nest mold surface 28a of the air passage 46 to, for example, about 0.02 mm to 0.05 mm. By supplying air to the air passage 46, the intrusion of resin into the air passage 46 can be suppressed, but by setting the opening width of the outlet to be narrow, it becomes more difficult for resin to enter from the outlet. The air passage 46 may be formed with dimensions equal to the opening width of the outlet in the portion other than the outlet, or with dimensions different from the opening width of the outlet.

[0021] As shown in Figures 5 and 6, the air passage 46 is formed by recessing a part of the overlapping surface of the plate-like body 42. Here, it is acceptable to recess only one overlapping surface of adjacent plate-like bodies 42 (see Figures 5 and 6), or to recess both overlapping surfaces of adjacent plate-like bodies 42 (see Figure 7). Furthermore, the air passage 46 may be formed by recessing only one of adjacent plate-like bodies 42 (see Figures 5 and 6), or by combining recesses provided on both adjacent plate-like bodies 42 (see Figure 7). In addition, the air passage 46 may be slit-shaped, with an opening width in the width direction of the plate-like body 42 being wider than the opening width in the overlapping direction of the plate-like body 42 (see Figure 5), or it may be pore-shaped, with an opening width in the overlapping direction of the plate-like body 42 being approximately the same as the opening width in the width direction of the plate-like body 42 (see Figure 7). Furthermore, the air passage 46 provided between adjacent plate-like bodies 42 may be a single passage (see Figures 5 and 6), or it may be a plurality of air passages 46 provided between adjacent plate-like bodies 42 in the width direction of the plate-like bodies 42 (see Figure 7).

[0022] As shown in Figure 2, the air supply unit 48 is equipped with an air supply means 48a, such as a blower. Air sent from the air supply means 48a is supplied to the space 32a through a passage 30a provided in the main mold 30 of the first mold unit 22. The air supply unit 48 may also be equipped with an air temperature control means 48b for adjusting the temperature of the supplied air. As the air temperature control means 48b, for example, a vortex cooler that cools the passing air by the vortex effect, or other means can be used. For example, supplying cooled air can improve the cooling efficiency of the mold surface.

[0023] As shown in Figures 5 and 6, the insert 28 may be provided with an insert exhaust passage 50 for discharging air. In this embodiment, the insert exhaust passage 50 is connected upstream to the air passage 46 and downstream to the main mold exhaust passage 40. More specifically, the upstream end of the insert exhaust passage 50 is connected to the vicinity of the outlet of the air passage 46. The insert exhaust passage 50 is connected to the fastening hole 38 by passing through the outer surface of the insert 28 from between adjacent plate-like bodies 42, 42. Since the fastening hole 38 is connected to the main mold exhaust passage 40, the air that has passed through the insert exhaust passage 50 is discharged outside the injection mold 20 via the main mold exhaust passage 40 (see Figure 4).

[0024] A method for manufacturing a resin molded product 10 using the injection mold 20 described above will now be explained. In the injection mold 20, the first mold section 22 and the second mold section 24 are closed, resin is injected into the cavity 26, the closed state is maintained for a holding pressure period and a cooling period, and then the mold is opened to remove the resin molded product 10. The timing of starting air supply by the air supply unit 48 may be before closing the first mold section 22 and the second mold section 24, after closing the first mold section 22 and the second mold section 24 but before resin injection, during resin injection (filling period), or during the holding pressure period or cooling period after the completion of resin injection. However, the cooling period after the completion of resin injection is preferred because air can be directly applied to the resin molded product 10. The period during which air is supplied by the air supply unit 48 may be a part of the molding cycle consisting of the mold closing period, resin filling period, holding pressure period, cooling period, mold opening period, and resin molded product removal period 10, or air may be supplied for the entire duration of the molding cycle.

[0025] In the injection mold 20, air supplied from the air supply unit 48 is sent to the cavity 26 through the air passage 46 of the insert 28. The insert 28 and the insert mold surface 28a are cooled by heat exchange with the air passing through the air passage 46. As the insert mold surface 28a is cooled in this way, the resin in contact with the insert mold surface 28a can be cooled. In addition, the resin can also be directly cooled by the air that reaches the outlet of the air passage 46. Thus, with the injection mold 20, the temperature of the insert mold surface 28a can be controlled by the air passing through the air passage 46. In this way, temperature unevenness in the cavity 26 can be suppressed, preventing molding defects in the resin molded product 10 molded in the injection mold 20, and enabling the production of high-quality resin molded products 10.

[0026] In the injection mold 20, temperature control is performed using air, so problems do not arise from contact with the resin as with water. Moreover, using air allows for greater freedom in path selection in the first mold section 22 than with water. Therefore, with the injection mold 20, the insert 28 can be placed in positions that could not be accommodated with a cooling structure using cooling water, and the mold surface temperature of the first mold section 22 can be appropriately adjusted.

[0027] The injection mold 20 facilitates the formation of the air passage 46 by providing it in the insert 28. By providing the air passage 46 between the plate-like bodies 42 in the insert 28, the degree of freedom in the shape, path, and size of the air passage 46 is increased, making it possible to form the air passage 46 with a very small opening width as described above. In particular, by forming the air passage 46 by recessing a part of the overlapping surface of the plate-like bodies 42, an air passage 46 with a very small opening width can be easily set.

[0028] When a cooling structure using cooling water is set in the injection mold 20 of the embodiment, the cooling pipes must be passed above the upper end of the cavity 26 in the first mold section 22. Therefore, even if the cooling pipes are in a baffle structure, it is difficult to bring the cooling pipes close to the curved portion of the cavity 26. In the injection mold 20 of the embodiment, the mold surface of the first mold section 22 can be formed with an insert 28 provided with an air passage 46, and the temperature of the mold surface can be controlled more efficiently than with a cooling structure using cooling water. In particular, since the insert 28 forms the mold surface that forms the curved portion of the cavity 26 in the first mold section 22, the curved portion from the base 12 to the first wall 14 of the resin molded product 10 can be cooled by the insert 28. As a result, the occurrence of molding defects in which the first wall 14 collapses inward from the specified position due to molding shrinkage can be suppressed, and a high-quality resin molded product 10 can be manufactured.

[0029] The injection mold 20 in this embodiment has a discharge structure that discharges air to the outside of the injection mold 20 via the insert exhaust passage 50. This improves the cooling efficiency of the insert 28 by the air passing through the air passage 46.

[0030] According to the method for manufacturing a resin molded product 10 using the injection mold 20 described above, the quality of the resulting resin molded product 10 can be improved because the molding is performed using an injection mold 20 in which the temperature of the mold surface is controlled.

[0031] (Example of change) In addition to the matters mentioned above, the following may also be applied, for example. Furthermore, the present invention is not limited to the specific descriptions of the examples and the following modifications. (1) In this embodiment, the first mold part (convex) is positioned on the upper side and the second mold part (concave) is positioned on the lower side of the first mold part. However, the embodiment is not limited to this, and the first mold part (convex) may be positioned on the lower side and the second mold part (concave) may be positioned on the upper side of the first mold part (convex), or the first mold part (convex) and the second mold part (concave) may be positioned in the lateral direction. (2) The orientation in which the plate-like bodies constituting the nesting are stacked is not limited to the embodiment, but for example, multiple plate-like bodies may be stacked in an orientation corresponding to the width direction of the first wall. (3) A nested structure may be placed on a movable slide core. (4) The injection molding die may have only an air cooling structure that passes air through an internal air passage, but it may also have a water cooling structure using cooling water in addition to the air cooling structure. (5) In the embodiment, air was discharged to the outside of the injection molding die using through-holes through which fastening elements that fix the insert to the main mold pass. However, for example, the downstream of the insert exhaust passage may be connected to the joint between the first mold section (convex mold) and the second mold section (concave mold), and the air may be released from the joint between the first mold section (convex mold) and the second mold section (concave mold). The discharge structure may be omitted. [Explanation of Symbols]

[0032] 10 Resin molded product, 20 Injection mold, 22 First mold section (convex mold), 24 Second mold section (concave), 26 Cavity, 42 Plate-like body, 46 Air passage

Claims

1. An injection mold for forming a resin molded product by injecting resin into a cavity, It has a nesting structure made up of multiple plate-like bodies stacked on top of each other, The nesting element has an air passage between the plate-like bodies that directs air supplied from the air supply unit toward the cavity. The air passage leads to the cavity. An injection molding die characterized by the following.

2. The cavity is formed between a convex shape and a concave shape, The injection molding die according to claim 1, wherein the insert constitutes a mold surface that forms the curved portion of the cavity in the convex mold.

3. The injection molding die according to claim 1 or 2, wherein the air passage is formed by recessing a part of the overlapping surface of the plate-like bodies.

4. After filling the cavity formed by the injection mold according to claim 1 with resin, air is passed through the air passage to cool the resin filled in the cavity. A method for manufacturing a resin molded product characterized by the following:

Images