JP2004358884A - Injection press molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection press molding method capable of allowing a resin to spread throughout a cavity in proper quantities in a relatively simple manner. <P>SOLUTION: This injection press molding method has a mold arranging process for demarcating the cavity 6 by the mold surfaces 40 and 50 of a plurality of molds 4 and 5 and arranging a narrow part 61, wherein the distance D3 between the mold surfaces is short, and a wide part 62, wherein the distance D4 between the mold surfaces is longer than the narrow part 61, in the cavity 6, a resin injection process for injecting a resin 7 in the cavity 6 and allowing the resin 7 to flow in the shape almost similar to the whole shape of the cavity 6 by the respective different flow speeds of the resin 7 in the narrow and wide parts 61 and 62, and a pressing process for compressing the cavity 6 to allow the resin 7, which is allowed to flow in the almost similar shape, to spread throughout the cavity 6 by compression pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection press molding method used for manufacturing, for example, a fuel tank.
[0002]
[Prior art]
For example, a resin molded product such as a fuel tank is manufactured by an injection press molding method. The injection press molding method has a mold arrangement step, a resin injection step, and a press step. FIG. 7 shows a schematic diagram of a mold disposing step and a resin injecting step in manufacturing a fuel tank. As shown in the figure, in the mold arrangement step, the movable upper mold 100 and the fixed lower mold 101 are arranged so as to face up and down. At this time, the division plane PL is slightly opened. Then, a cavity 102 is formed between the mold surfaces of both molds. The cavity 102 has the same shape as the lower divided body of the fuel tank.
[0003]
In the resin injection step, a molten resin 104 is injected into the cavity 102. The resin 104 is injected into the cavity 102 from the gate 103 opened almost at the center of the fixed lower mold 101. The resin 104 spreads in the cavity 102 substantially concentrically around the gate 103.
[0004]
FIG. 8 shows a schematic diagram of a pressing process at the time of manufacturing a fuel tank. As shown in the figure, in the pressing step, the movable upper mold 100 is lowered to perform mold clamping. The cavity 102 is compressed by the mold clamping. Due to this compression pressure, the resin 104 that has spread substantially concentrically in the previous step spreads over the entire cavity 102.
[0005]
Thereafter, the lower divided body of the fuel tank is manufactured through mold cooling and demolding. The lower fuel tank split is thermally welded to the upper fuel tank split manufactured in a similar manner. Thus, the fuel tank is completed.
[0006]
[Patent Document 1]
JP-A-8-258100
[Problems to be solved by the invention]
However, according to the above manufacturing method, in the resin injection step, the resin spreads substantially concentrically around the gate. FIG. 9 shows a perspective view of a lower mold used in the resin injection step. Parts corresponding to those in FIG. 7 are denoted by the same reference numerals. As shown in the figure, in the resin injecting step, the resin 104 spreads substantially concentrically around the gate 103. The resin 104 spreads over the entire cavity 102 in a subsequent pressing step.
[0008]
However, the fuel tank lower divided body, that is, the cavity 102, which is a resin molded product, has a rectangular parallelepiped box shape whose upper surface is open. That is, the concentric resin 104 and the entire cavity shape are not similar. Therefore, the portion L1 where the distance from the end of the resin 104 to the end of the cavity 102 (hereinafter, referred to as “reach distance”) is short and the portion L2 where the reach is long is mixed.
[0009]
At the end of the cavity 102 in the portion L1 where the reaching distance is short, the resin 104 is excessively supplied in the pressing step. On the other hand, at the end of the cavity 102 at the portion L2 where the reach distance is long, the resin 104 may not sufficiently spread in the pressing step. For this reason, there is a possibility that molding failure may occur in the molded resin article after molding. In addition, since molding accuracy is poor, it is disadvantageous for manufacturing a resin molded product having a complicated shape.
[0010]
To avoid this problem, Patent Literature 1 discloses an injection molding method for controlling the flow of resin by inserting and removing pins from a mold surface into and out of a cavity. However, according to the injection molding method described in the document, it is necessary to arrange the pins so that the pins can be taken in and out of the mold surface. This complicates the structure of the mold. Further, in the pressing step in which the pressure in the cavity becomes high, the resin may leak from the cavity through the gap between the pin and the pin hole. Further, according to the injection molding method described in the document, a control device for controlling the insertion and removal of the pin is separately required. For this reason, there is a possibility that the cost of the mold and the production cost of the resin molded product will increase.
[0011]
The injection press molding method of the present invention has been completed in view of the above problems. Accordingly, an object of the present invention is to provide an injection press molding method that can relatively easily spread resin throughout the entire cavity without excess or shortage.
[0012]
[Means for Solving the Problems]
(1) In order to solve the above-mentioned problems, an injection press molding method of the present invention defines a cavity by a plurality of mold surfaces, and forms a narrow portion having a short distance between mold surfaces in the cavity, and a narrower portion than the narrow portion. A mold disposing step of disposing a wide portion having a long distance between mold surfaces, and injecting a resin into the cavity, wherein the flow rates of the resin in the narrow portion and the wide portion are different from each other. A resin injecting step of flowing the resin into a substantially similar shape of the entire cavity shape, and a pressing step of compressing the cavity and spreading the resin that has flowed into the substantially similar shape to the entire cavity by a compression pressure, I do.
[0013]
The injection press molding method of the present invention has a mold arrangement step, a resin injection step, and a press step. In the mold arrangement step, a plurality of molds are provisionally clamped to define cavities between mold surfaces. The cavity has a narrow portion and a wide portion. The distance between the mold surfaces of the wide portion is set longer than the distance between the mold surfaces of the narrow portion.
[0014]
In the resin injection step, a molten resin is injected into the cavity. The flow resistance of the resin in the narrow portion is large. In the narrow portion, the surface area of the mold surface relative to the volume of the resin is relatively large. Therefore, the resin easily loses heat to the mold surface. That is, the resin is easily solidified. For these reasons, the flow speed of the resin in the narrow portion is low.
[0015]
On the other hand, the flow resistance of the resin in the wide part is small. In the wide part, the area of the mold surface with respect to the volume of the resin is relatively small. Therefore, the resin is less likely to lose heat to the mold surface. That is, the resin is hardly solidified. For these reasons, the flow speed of the resin in the wide part is high. In this step, the resin is caused to flow into the cavity so as to have a shape substantially similar to the entire shape of the cavity by utilizing the difference in the flow speed of the resin between the narrow portion and the wide portion.
[0016]
In the pressing step, the cavity is compressed. Then, the resin that has flowed in a substantially similar shape in the previous step is spread over the entire cavity by the cavity compression pressure.
[0017]
According to the injection press molding method of the present invention, the shape of the resin after the completion of the resin injection step is substantially the same as the shape of the entire cavity, that is, the shape of the resin molded product. Therefore, in the pressing step, the resin can be spread over the entire cavity without excess or shortage. Therefore, molding defects are less likely to occur. Further, since the molding accuracy is good, even a resin molded product having a complicated shape can be easily manufactured. In addition, weld that tends to occur in the resin injection step can be removed by resin reflow in the pressing step. In this regard, molding defects are unlikely to occur.
[0018]
Further, according to the injection press molding method of the present invention, it is possible to spread the resin over the entire cavity relatively easily without inserting and removing pins and the like in the cavity.
[0019]
(2) Preferably, the narrow portion is formed between a ridge and a groove arranged opposite to the ridge and symmetrical with the ridge, and in the pressing step, It is preferable that the difference between the distance between the mold surfaces of the narrow portion and the distance between the mold surfaces of the wide portion is set to be small by compressing the cavity.
[0020]
The difference between the distance between the mold surfaces of the narrow portion and the distance between the mold surfaces of the wide portion is ununiform in the wall thickness and manifests itself in the resin molded product. In this regard, according to this configuration, in the pressing process, the difference between the distance between the mold surfaces of the narrow portion and the distance between the mold surfaces of the wide portion is set to be small. Therefore, unevenness in the thickness of the resin molded product can be suppressed.
[0021]
Hereinafter, the operation will be specifically described with reference to examples. FIG. 10 is an enlarged view showing an example of the arrangement of the ridges and the grooves. The solid line in the figure shows the arrangement of the ridges and grooves in the resin injection step. On the other hand, the one-dot chain line in the figure shows the arrangement of the ridges and grooves in the pressing step.
[0022]
The ridge portion 205 is provided to project from the mold surface of the fixed lower mold 201 toward the inside of the cavity 202. On the other hand, the groove 206 is formed to be depressed from the mold surface of the movable upper mold 200. A narrow portion 203 is formed between the ridge 205 and the groove 206. A wide portion 204 is formed between the fixed lower mold 201 and the movable upper mold 200.
[0023]
In the pressing step, when the movable upper mold 200 is lowered by the press width D, the distance D2 between the mold surfaces of the wide portion 204 is reduced by the press width D. On the other hand, when the intersecting angle between the compression direction and the extending direction of the narrow portion 203 is α, the distance D1 between the mold surfaces of the narrow portion 203 becomes narrower by Dsinα.
[0024]
That is, when the cavity 202 is compressed in the pressing step, the shortening width of the narrow portion 203 between the mold surfaces D1 is smaller than the shortening width of the wide portion 204 of the mold surface distance D2. For this reason, the difference between the mold surface distance D2 and the mold surface distance D1 in the pressing step is smaller than the difference between the mold surface distance D2 and the mold surface distance D1 in the resin injection step. Therefore, according to this configuration, it is possible to prevent the thickness of the resin molded product from becoming uneven.
[0025]
(3) Preferably, in the configuration of the above (2), an intersection angle between an extending direction of the narrow portion and a compression direction in the pressing step is set to 5 ° or more and 55 ° or less. Is good.
[0026]
That is, in this configuration, the intersection angle α is set within 30 ° ± 25 ° in FIG. Here, the reason why the intersection angle α is set to 5 ° or more is that when the intersection angle α is less than 5 °, the compression direction and the extending direction of the narrow portion 203 become almost parallel. In other words, the narrow portion 203 and the wide portion 204 are arranged so as to form a substantially right angle. For this reason, the flow resistance of the resin in the pressing step increases. And there is a possibility that the resin may not spread to the entire cavity.
[0027]
On the other hand, the reason why the intersection angle α is set to 55 ° or less is that, when the intersection angle α exceeds 55 °, the reduced width Dsinα of the mold surface distance D1 of the narrow portion 203 and the reduced width D2 of the mold surface distance D2 of the wide portion 204 are reduced. And are close to each other.
[0028]
That is, in the resin injection step, it is necessary to flow the resin into a shape substantially similar to the entire cavity shape. Therefore, it is preferable that the flow control of the resin is easy. Therefore, it is preferable that the difference between the mold surface distance D1 of the narrow portion 203 and the mold surface distance D2 of the wide portion 204 is large. On the other hand, in the pressing step, it is necessary to suppress the thickness of the resin molded product from becoming uneven. Therefore, it is preferable that the difference between the mold surface distance D1 of the narrow portion 203 and the mold surface distance D2 of the wide portion 204 is small. That is, in the resin injection step, the difference between the mold face distance D1 and the mold face distance D2 is large, and in the press step, the difference between the mold face distance D1 and the mold face distance D2 is small. I want to set the distance between faces.
[0029]
However, when the intersection angle α exceeds 55 ° and the reduced width Dsinα of the inter-mold distance D1 and the reduced width D of the inter-mold distance D2 are close to each other, the inter-mold distance D1 and the inter-mold distance in the pressing process are close to each other. D2 is similarly shortened. For this reason, it is difficult to perform the above setting. For such a reason, the intersection angle α is set to 55 ° or less.
[0030]
(4) Preferably, the distance between the mold surfaces of the narrow portion is set so that the resin can be blocked in the resin injection step. That is, in the present configuration, the distance between the mold surfaces of the narrow portion is set so that the resin is completely blocked by the narrow portion in the resin injection step. According to this configuration, in the resin injection step, there is no possibility that the resin flows beyond the narrow portion. Therefore, it becomes easy to flow the resin into a shape substantially similar to the entire shape of the cavity. That is, it becomes easier to control the flow of the resin.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the injection press molding method of the present invention will be described. In the present embodiment, the injection press molding method of the present invention is embodied as a method for manufacturing a fuel tank.
[0032]
First, the configuration of the fuel tank manufactured by the manufacturing method of the present embodiment will be described. FIG. 1 shows a partially transparent view of the fuel tank. As shown in the figure, the fuel tank 1 includes an upper split body 2 and a lower split body 3. The upper split body 2 is made of resin and has a rectangular parallelepiped box shape that opens downward. On the other hand, the lower divided body 3 is made of resin and has a rectangular parallelepiped box shape opened upward. The lower divided body 3 and the upper divided body 2 are integrated by heat-welding the opening edges of each other. A rib 30 having a triangular cross section protrudes from the inner surface of the bottom wall of the lower divided body 3. The ribs 30 are arranged in a total of two rows. The two rows of ribs 30 are arranged substantially in parallel so that the steep slopes 300 face each other.
[0033]
Next, the manufacturing method of this embodiment will be described step by step. The manufacturing method of the present embodiment includes a mold arrangement step, a resin injection step, and a pressing step. First, the mold arrangement step will be described. FIG. 2 shows a schematic view of the mold arrangement step and the resin injection step. As shown in the drawing, in the mold arrangement step, the movable upper mold 4 and the fixed lower mold 5 are arranged so as to face up and down, and temporary mold clamping is performed. The movable upper die 4 is made of metal and has a rectangular parallelepiped convex shape. A groove 41 having a triangular cross section is formed in the mold surface 40 of the movable upper mold 4. The grooves 41 are arranged in a total of two rows substantially parallel to the longitudinal direction of the cavity 6 described later. The fixed lower die 5 is made of metal and has a rectangular parallelepiped concave shape. The movable upper die 4 is inserted into the fixed lower die 5 at a predetermined interval. At this time, the division plane PL is slightly opened. From the mold surface 50 of the fixed lower mold 5, a ridge 51 having a triangular cross section is provided so as to project therefrom. The ridges 51 are arranged substantially in parallel in a total of two rows. A gate 60 is opened at the center of the two rows of ridges 51. The gate 60 communicates with an injection molding machine (not shown). FIG. 3 shows an enlarged view of the inside of the circle A in FIG. As shown in the figure, the ridge portion 51 and the groove portion 41 are vertically opposed. The ribs 30 of the lower divided body 3 shown in FIG. 1 are formed by the ridges 51 and the grooves 41. A narrow portion 61 is defined between the steep slope 510 of the ridge 51 and the steep slope 410 of the groove 41. A wide portion 62 is defined between the mold surface 50 on which the ridge portion 51 is provided and the mold surface 40 on which the groove portion 41 is provided. The distance between the mold surfaces (the distance between the steep slope 410 and the steep slope 510) D3 of the narrow portion 61 is shorter than the distance between the mold surfaces (the distance between the mold surface 40 and the mold surface 50) D4 of the wide portion 62. Is set. Specifically, the inter-mold-surface distance D3 is set to be equal to or less than an upper limit distance (hereinafter, referred to as a “limit distance”) at which the resin can be blocked in a resin injection step which is a subsequent step. Returning to FIG. 2, a cavity 6 is defined between the mold surface 40 of the movable upper mold 4 and the mold surface 50 of the fixed lower mold 5. The cavity 6 has the same shape as the lower divided body 3 of FIG.
[0034]
Next, the resin injection step will be described. In this step, the molten resin 7 is injected into the cavity 6 through the gate 60 from the injection molding machine. The injected resin 7 initially diffuses substantially concentrically around the gate 60. That is, the wide portion 62 is concentrically diffused. However, two rows of narrow portions 61 are arranged at both ends of the wide portion 62. The distance D3 between the mold surfaces of these narrow portions 61 is set to be equal to or less than the limit distance. Therefore, the flow resistance of the resin 7 in the narrow portion 61 is large. Further, the surface area of steep slope 410 and steep slope 510 is relatively large with respect to the volume of resin 7 in narrow portion 61. Therefore, the resin 7 is easily deprived of heat by the steep slope 410 and the steep slope 510. That is, the resin 7 is easily solidified. For these reasons, the flow speed of the resin 7 in the narrow portion 61 is low. Therefore, as shown in FIG. 3, the resin 7 is completely blocked at the narrow portion 61. FIG. 4 is a perspective view of a lower mold used in the resin injection step. As shown in the figure, the resin 7 flowing in the direction in which the ridges 51 (that is, the narrow portions) are arranged is blocked by the narrow portions 61. On the other hand, the resin 7 flowing in the direction in which the narrow portion 61 is not disposed is not blocked. Therefore, after the completion of this step, the resin 7 has a shape substantially similar to the entire shape of the cavity 6.
[0035]
Next, the pressing process will be described. FIG. 5 shows a schematic diagram of the pressing process. FIG. 6 is an enlarged view of the inside of a circle B in FIG. As shown in the figure, in the pressing step, the movable upper mold 4 is lowered to perform complete mold clamping. The cavity 6 is compressed by the mold clamping. Due to the compression pressure, the distance D3 between the mold surfaces of the narrow portion 61 and the distance D4 between the mold surfaces of the wide portion 62 are substantially the same. Then, the resin 7 that has been blocked by the narrow portion 61 in the previous process flows as shown by a white arrow in FIG.
[0036]
Thereafter, the lower divided body 3 shown in FIG. 1 is manufactured through mold cooling and demolding. The lower divided body 3 is thermally welded to the upper divided body 2 also manufactured by injection press molding. Thus, the fuel tank 1 is completed.
[0037]
Next, effects of the manufacturing method of the present embodiment will be described. According to the manufacturing method of the present embodiment, the narrow portion 61 and the wide portion 62 are arranged in the cavity 6. In the resin injection step, the distance D4 between the mold surfaces of the wide portion 62 is set longer than the distance D3 between the mold surfaces of the narrow portion 61. Therefore, in the resin injection step, the resin 7 can be caused to flow so as to have a substantially similar shape to the entire shape of the cavity 6. Therefore, the L3 reach distance and the L4 reach distance in FIG. For this reason, in the post-pressing process, the resin 7 can be spread over the entire cavity 6 without excess or shortage.
[0038]
In addition, according to the manufacturing method of the present embodiment, the resin 7 can be spread over the entire cavity 6 relatively easily without inserting and removing pins and the like into and from the cavity 6.
[0039]
Further, according to the manufacturing method of the present embodiment, the distance D3 between the mold surfaces of the narrow portion 61 in the resin injection step is set to be equal to or less than the limit distance. Therefore, in the resin injection step, the resin 7 can be completely blocked by the narrow portion 61. Therefore, it becomes easy to flow the resin 7 into a shape substantially similar to the entire shape of the cavity 6.
[0040]
Further, according to the manufacturing method of the present embodiment, the narrow portion 61 is formed between the ridge 51 and the groove 41. Therefore, the narrow portion 61 can be relatively easily arranged.
[0041]
Further, according to the manufacturing method of the present embodiment, in the pressing step, the difference between the mold surface distance D3 of the narrow portion 61 and the mold surface distance D4 of the wide portion 62 is set to be substantially zero ( 3 and 6 described above). For this reason, the thickness of the lower divided body 3 of the fuel tank 1 becomes substantially uniform. That is, there is no possibility that the resin 7 filling the narrow portion 61 is solidified as a thin portion in the lower divided body 3. Therefore, the characteristics such as mechanical strength and fuel permeability resistance required for the fuel tank 1 can be sufficiently ensured.
[0042]
Further, according to the manufacturing method of the present embodiment, the intersection angle β between the extending direction of the narrow portion 61 and the compression direction in the pressing step (see FIGS. 3 and 6 described above) is set to 30 °. Therefore, the fluidity of the resin 7 in the pressing step is good. Further, in the resin injection step, the difference between the mold surface distance D3 and the mold surface distance D4 can be set large. In addition, in the pressing step, the difference between the inter-mold surface distance D3 and the inter-mold surface distance D4 can be made substantially zero.
[0043]
The embodiment of the injection press molding method of the present invention has been described above. However, the embodiments are not particularly limited to the above embodiments. Various modifications and improvements that can be made by those skilled in the art are also possible.
[0044]
For example, in the above embodiment, the groove 41 is arranged on the movable upper die 4. Further, the ridge portion 51 is arranged on the fixed lower mold 5. However, this arrangement may be reversed. Further, the groove and the ridge may be arranged on the movable upper mold 4, and the ridge and the groove may be arranged on the fixed lower mold 5. Then, the groove of the movable upper die 4 and the ridge of the fixed lower die 5 may be opposed to each other. In addition, the protrusion of the movable upper mold 4 and the groove of the fixed lower mold 5 may be opposed to each other. Further, in the above embodiment, two dies, that is, the movable upper die 4 and the fixed lower die 5 are arranged, but the number of dies is not particularly limited.
[0045]
In the above embodiment, the groove 41 and the ridge 51 are both triangular in cross section. However, the groove 41 and the ridge 51 do not have to have a symmetrical shape. Further, the cross-sectional shape does not have to be a triangle. For example, it may be a polygon such as a square or a pentagon, or a circle or an ellipse.
[0046]
In the resin injection step of the above embodiment, the resin 7 is completely blocked at the narrow portion 61, but the resin 7 does not have to be completely blocked in the same step. It suffices if the flow of the resin 7 can be suppressed by the narrow portion 61.
[0047]
In the above embodiment, the lower split body 3 is manufactured by the injection press molding method of the present invention, but the upper split body 2 may be manufactured by the injection press molding method of the present invention. Further, the injection press molding method of the present invention is not limited to the fuel tank manufacturing method described above, and includes, for example, door trims, dashboards, meter panels, dampers for car air conditioners, automobile-related members such as air ducts, personal computer housings, personal computers. It can also be embodied as a method for manufacturing a disc tray for a vehicle. In particular, it is advantageous for a resin molded product requiring high molding accuracy and uniform thickness.
[0048]
In the above embodiment, the inter-mold distance D3 is set to be equal to or less than the limit distance. However, the inter-mold surface distance D3 may be set so as to exceed the limit distance. The limit distance is determined based on the type of resin used, the resin temperature, the injection pressure in the resin injection step, the injection time, the heat transfer coefficient of the mold, the total length of the narrow portion in the resin flow direction, and the like.
[0049]
【The invention's effect】
According to the injection press molding method of the present invention, the resin can be spread over the entire cavity relatively easily without excess or shortage.
[Brief description of the drawings]
FIG. 1 is a partial perspective view of a fuel tank manufactured by a manufacturing method according to an embodiment of the present invention.
FIG. 2 is a schematic view of a mold arrangement step and a resin injection step in the manufacturing method according to one embodiment of the present invention.
FIG. 3 is an enlarged view inside a circle A in FIG. 2;
FIG. 4 is a perspective view of a lower mold used in a resin injection step of the manufacturing method according to one embodiment of the present invention.
FIG. 5 is a schematic view of a pressing step in the manufacturing method according to one embodiment of the present invention.
6 is an enlarged view inside a circle B in FIG. 5;
FIG. 7 is a schematic view of a mold disposing step and a resin injecting step at the time of manufacturing a conventional fuel tank.
FIG. 8 is a schematic view of a conventional press process at the time of manufacturing a fuel tank.
FIG. 9 is a perspective view of a lower mold used in a resin injection step of a conventional fuel tank manufacturing method.
FIG. 10 is an enlarged view showing an example of the arrangement of ridges and grooves in the injection press molding method of the present invention.
[Explanation of symbols]
1: fuel tank, 2: upper split body, 3: lower split body, 30: rib, 300: steep slope, 4: movable upper mold, 40: mold face, 41: groove, 410: steep slope, 5: fixed lower mold, 50: mold surface, 51: ridge, 510: steep slope, 6: cavity, 60: gate, 61: narrow, 62: wide, 7: resin.

Claims (4)

A cavity is defined by the mold surfaces of a plurality of molds, a narrow portion having a short distance between mold surfaces in the cavity, and a wide portion having a long distance between mold surfaces than the narrow portion.
A resin injecting step of injecting a resin into the cavity, wherein the flow rates of the resin in the narrow portion and the wide portion are different from each other, so that the resin flows in a shape substantially similar to the overall shape of the cavity;
A pressing step of compressing the cavity and spreading the resin, which has flowed into a substantially similar shape, over the entire cavity by a compression pressure;
An injection press molding method having the following. The narrow portion is formed between a ridge and a groove that is arranged to face the ridge and is symmetrical with the ridge.
The injection according to claim 1, wherein in the pressing step, a difference between a distance between the mold surfaces of the narrow portion and a distance between the mold surfaces of the wide portion is set to be small by compressing the cavity. Press molding method. The injection press molding method according to claim 2, wherein an intersection angle between an extending direction of the narrow portion and a compression direction in the pressing step is set to 5 ° or more and 55 ° or less. The injection press molding method according to claim 1, wherein a distance between the mold surfaces of the narrow portion is set so that the resin can be blocked in the resin injection step.

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