JP5923638B2 - Mold for molding - Google Patents

Description

  The present invention relates to a molding die provided with a die cooling passage for compressed gas.

  2. Description of the Related Art Conventionally, a molding die for a molded product having an undercut, for example, a resin molded product such as an automobile bumper, often has an undercut that hinders release from the molding die. This is because when the bumper is mounted on the vehicle body, a boss-like part with a concave surface whose inner surface is undercut is formed on the vehicle body side of the bumper, that is, inside, and the mounting bracket on the vehicle body side is connected to the boss-like part It can be done.

  As a molding die capable of undercutting a molded product in which such an undercut exists, a molding die provided with a slide core that can be slid in the die by a pin or the like is representative. An injection mold having a slide core includes a fixed mold and a movable mold, and the cavity is inserted into the undercut portion when the mold is clamped. The molten resin is injected into the inside and cooled and solidified to obtain a molded product having a predetermined shape. On the other hand, when the mold is opened, the molded product is ejected by an ejector pin after the slide core comes out of the undercut portion.

  Note that a cooling water channel is normally formed in the fixed mold and the movable mold, and by passing cooling water through the cooling water channel, the fixed mold and the movable mold are cooled with water. It has become.

JP 2000-52384 A

  In the prior art, a part of the cavity is formed by the slide core. Therefore, a part of the inner surface of the bumper is formed by the part of the slide core. For this reason, if the slide core is not provided with a cooling means such as a movable mold, a relatively large temperature difference occurs between the movable mold and the slide core. As a result, the molded product is cooled. Due to the difference in shrinkage of the resin at the time, not only does the sink mark appear on the back of the molded product (bumper), but the effect of the sink mark also causes the sink on the surface of the molded product (bumper). Even if given, it has a problem that the aesthetics are slightly inferior.

  In order to solve such a problem, in the prior art, although the stationary mold and the movable mold are water-cooled, it is conceivable to adopt a water-cooling structure for the slide core. However, even if a water channel is formed in the slide core, the slide core is movable so that it can be taken in and out of the undercut portion, so the water channel joint must be surely watertight. For this reason, the structure of the joint is complicated and difficult to miniaturize, and it is difficult to adopt it for a relatively small-sized slide core.

  On the other hand, it is conceivable to employ air cooling instead of water cooling for the slide core. In air cooling, even if there is some air leakage at the joint or the like, the possibility of adversely affecting the molded product is low. However, in the case of air cooling, the cooling capacity is lower than that of water cooling. For this reason, for example, a cooler that circulates a heat medium using a motor or a pump is adopted, and the primary air temperature of the air passage is lowered by the cooler. Conceivable. Although it is certainly effective to lower the air temperature using a cooler, even if there are multiple relatively small slide cores, the cooling capacity is relatively small, and a dedicated cooler should be installed. Must modify the existing injection molding machine.

  The problem to be solved is that, in the molding die of the molding die in which the die cooling passage for compressed gas is arranged inside the die, the temperature of the gas flowing through the die cooling passage for compressed gas is determined. It is a point which improves cooling capacity by lowering without using a cooler.

The molding die according to claim 1 is a molding die in which a die-cooling passage for compressed gas is arranged inside a nest arranged in a die used for molding a molded product made of thermoplastic resin. A gas supply path is provided at the inlet of the mold cooling passage, a gas discharge path is provided at the outlet of the mold cooling passage, and the tip of the gas supply path is tapered to cut off the ventilation. A nozzle whose area gradually decreases is provided, an expansion chamber in which compressed gas ejected from the nozzle expands is provided on the inlet side of the mold cooling passage, and the mold is provided between the expansion chamber and the outlet. A branch passage formed by branching a plurality of cooling passages is provided, and a fin-like portion is formed between the branch passages by the material of the nesting, and the nozzle, the gas supply passage, and the expansion chamber are blocked from ventilation. The area ratio is 1: 2 to 5: 4 to 13 To.

According to the invention of claim 1, by expanding the compressed air, it is possible to flow through the mold cooling passage in a state where the gas temperature is lowered according to the Boyle-Charles principle.

It is a perspective view of a bumper showing Example 1 of the present invention. It is a perspective view of the same metal mold | die. It is sectional drawing around the slide core of a reference example. It is a disassembled perspective view of the slide core. It is sectional drawing of the slide core. It is sectional drawing which shows Example 1 of this invention.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below do not limit the contents of the present invention described in the claims. In addition, all of the configurations described below are not necessarily essential requirements of the present invention.

  1 and 2 show Example 1, FIGS. 3 to 5 show reference examples, and the Example shows a case of a molding die for an automobile bumper. As shown in FIG. A boss 3 having a concave surface 2 whose inner surface is formed as an undercut is formed inside 1. A mounting bracket (not shown) on the vehicle body side can be connected to the boss 3.

  As shown in FIGS. 2 and 3, the molding die includes a fixed side die 4 and a movable side die 5 that can be brought into and out of contact with the fixed side die 4, and these fixed side molding surfaces 6. Bumper molding cavity 8 is formed between the movable molding surface 7 and the movable side molding surface 7. The movable mold 5 includes a movable mold plate 9 that forms a movable molding surface 7, and an injection molding machine (not shown) provided on the rear side of the movable mold plate 9 via a support material 10. A sliding plate 12, also referred to as a protruding plate that slides along the support wall 10, is provided between the movable side mold plate 9 and the mounting plate 11. A water-cooling cooling path (not shown) is formed in the movable side template 9 by holes. The sliding plate 12 is connected to a proximal end of a protruding pin (not shown) whose distal end appears on the movable molding surface 7. The fixed-side mold 4 is similarly provided with a cooling path for water cooling.

  A slide core 14 for molding the boss 3 is fitted in the recess 13 of the movable molding surface 7. When the mold is closed, the top surface 15 side of the slide core 14 protrudes slightly from the movable molding surface 7, and the concave surface 2 formed as an undercut on one side of the top surface 15 side. A projection 16 is formed on which the molding surface portion is formed. The tip 18F of the pin 18 is connected to the bottom surface 17 on the side opposite to the top surface 15 side of the slide core 14, that is, the mounting plate 11 side, and slidably penetrates the through hole 19 of the movable side mold plate 9. The base end 18B of the pin 18 is pivotally connected to the sliding plate 12 side, and the center axis direction of the pin 18 is relative to the contact / separation direction of the movable mold 5 with the fixed mold 4. It is provided diagonally. Therefore, when shifting from the mold closed state to the mold open state, the sliding plate 12 advances toward the movable side mold plate 9, so that the pin 18 is slidably guided through the through hole 19 and the pin 18 is centered on the base end 18B. As a result, the slide core 14 can move backward. In addition, when shifting from the mold open state to the mold closed state, the mold is set so as to move forward and enter the molded state.

  As shown in FIGS. 4 and 5, a mold cooling passage 20 for compressed gas, in the embodiment, compressed air, is provided inside the slide core 14. An inlet 22 serving as the primary side 21 of the compressed air in the mold cooling passage 20 and an outlet 24 serving as the secondary side 23 of the compressed air are provided on the bottom surface 17 of the slide core 14, and the center of these inlet 22 and outlet 24 The axis line substantially coincides with the contact / separation direction. A flexible pipe-like gas supply path 25 is provided at the inlet 22, and a gas discharge path 26 is also connected to the outlet 24. The gas discharge path 26 may be formed by a flexible pipe shape. A flexible protective pipe 27 for the gas supply path 25 is connected to the inlet 22, and the gas supply path 25 is built in the protective pipe 27.

  The mold cooling passage 20 for the compressed air is arranged on the primary side 21 side and is coaxial with the jet direction X of the compressed air from the tip 25F of the gas supply path 25, that is, the flow of the compressed air is parallel to the contact and separation direction. Forward section 28, intermediate section 29 connected to forward section 28 and intersecting with forward section 28 in an orthogonal direction and substantially parallel to top surface 15, and connected to intermediate section 29 and orthogonal to the intermediate section And a return path portion 30 arranged on the secondary side 23 side in parallel with the forward path portion 28 and compressed air from the middle of the forward path portion 28 to the middle portion 29 and further to the middle of the return path portion 30. The mold cooling passage 20 is branched and formed. In the embodiment, five branch paths 31 are formed in the mold cooling passage 20 for compressed air, and a thin fin-shaped portion 32 is formed between the branch paths 31 by the material of the slide core 14.

  It should be noted that the total cross-sectional area of the forward passage portion 28, the total cross-sectional area of the intermediate portion 29 (that is, the total area of the ventilation areas of the plurality of branch paths 31), and the total cross-sectional area of the return passage portion 30 are substantially the same area. Is formed.

  The front end 25F of the gas supply path 25 is disposed in an end surface so as to be orthogonal to the ejection direction X so as to face the start end 31F of the branch path 31, and the front end 25F of the gas supply path 25 is tapered. As a result, the nozzle 33 is formed in a round hole having a gradually reduced ventilation cross-sectional area. Thus, a compressed air expansion chamber 34 having a larger ventilation cross-sectional area than the nozzle 33 is provided at a position in the ejection direction X facing the nozzle 33. Is formed by the primary side 21 of the forward path portion 28. That is, an expansion chamber 34 in which the compressed air ejected from the nozzle 33 expands is formed in the gas supply path 25 between the nozzle 33 and the start end 31F of the branch path 31, that is, the primary side 21 of the forward path portion 28 of the gas supply path 25. Thus, the compressed air ejected from the nozzle 33 can be immediately expanded at the tip 25F. For this reason, each ventilation | gas cross-sectional area is formed large in order of the nozzle 33, the gas supply path 25, and the expansion chamber 34, and the ratio is formed about 1: 2-5: 4-13. . Further, the ventilation length L of the expansion chamber 34, that is, the length L from the nozzle 33 to the start end 31F of the branch path 31, is about 0.5 to 5 times the diameter D when the expansion chamber 34 is cylindrical. Is formed. In addition, when the said ratio remove | deviates from the said numerical value, a temperature fall may be a little inferior with expansion.

  Further, as shown in FIG. 2, mold closing detection means 35 is provided on the movable mold 5. The mold closing detection means 35 is composed of a limit switch 36 fixed to the support wall 10 or the mounting plate 11, and an operating piece 37 provided on the sliding plate 12 for pressing the limit switch 36 when the mold is closed. Yes. Further, when mold closing is detected by the mold closing detecting means 35, a compressed air source 38 such as an air compressor with a tank or a compressed air tank is connected to the base end 25B of the gas supply path 25, and the tip 25F side of the gas supply path 25 is connected. An automatic open / close valve 39 such as an electromagnetic open / close valve is interposed between the base end 25B and the base end 25B, and the mold close detecting means 35, the automatic open / close valve 39, etc. are electrically connected to a control device (not shown). Z)).

  As shown in FIG. 4, the slide core 14 is manufactured in such a manner that one side formed with a mold cooling passage 20 and the like, which are divided into two parts, and the other side formed with a protrusion 16, an inlet 22, an outlet 24, and the like are brought into contact with each other. It shows what has become.

  Next, the operation of the above configuration will be described. In the mold open state, the movable side mold 5 is separated from the fixed side mold 4, and the slide core 14 in the movable side mold 5 is movable side molding surface 7 of the movable side mold plate 9. Rather than the movable mold 5 side.

  Next, the movable mold 5 is advanced by an injection molding machine. At this time, while the movable side mold 5 is in contact with the fixed side mold 4 and enters the mold closed state, the mounting plate 11 side moves forward, and the sliding plate 12 relatively approaches the mounting plate 11, so that the pin 18 Slides through a through-hole 19 provided obliquely in the movable mold 5 and rotates around the base end 18B side, and the slide core 14 is set on the movable mold plate 9 in the mold closed state. In this set state, as shown in FIG. 3, a space S in which the boss-like portion 3 that is the concave surface 2 is formed is formed between the protrusion 16 and the movable-side molding surface 7. Yes. Further, cooling water is supplied to the cooling water channel, and the movable side template 9 and the like are cooled to a predetermined temperature.

  Then, the mold 8 is filled with the molten resin in the cavity 8, and the molten resin is solidified to form the bumper 1 integrally formed with the boss 3 having the undercut portion.

  When the mounting plate 11 side moves forward and the sliding plate 12 relatively approaches the mounting plate 11 side, the operating piece 37 comes into contact with the limit switch 36 of the mold closing detection means 35 and operates, thereby controlling the control device. Accordingly, the automatic opening / closing valve 39 is opened, and the compressed air is jetted from the air source 38 through the gas supply path 25 to the expansion chamber 34 from the nozzle 33 at the tip 25F. In this way, the compressed air introduced from the forward path portion 28 on the primary side 21 side is discharged from the return path portion 30 on the secondary side 23 side to the gas discharge path 26 through the intermediate portion 29 of the mold cooling passage 20. The air is finally released from the gas discharge path 26 to the atmosphere. At this time, the compressed air is expanded from the tip 25F having a small diameter of the nozzle 33 into the expansion chamber 34 having a space having a large diameter. As a result, the air temperature is lowered, and the reduced air is converted into gold. By passing through the branch path 31 of the mold cooling passage 20, heat exchange is performed between the air and the fin-like portion 32, and the slide core 14 heated by the top surface 15 in contact with the molten resin can be cooled. . The fact that the temperature of the compressed air decreases as it expands is based on Boyle-Charles' law relating to the volume, pressure, and temperature of the ideal gas.

  When molding is performed in this manner, the mold moves to a mold open state in which the movable mold 5 is retracted. At the time of this mold opening transition, the mounting plate 11 is retracted, so that the sliding plate 12 is relatively separated from the mounting plate 11. Therefore, when the movable side mold plate 9 is retracted, the pin 18 is inclined through the through hole 19. , And the pin 18 rotates in the direction opposite to the protrusion 16 with the base end 18B as the center of rotation, whereby the protrusion 16 is extracted from the concave surface 2 of the boss 3. When the movable mold 5 continues to retreat, the projecting pin projects from the movable molding surface 7 so that the bumper 1 as a molded product projects from the movable molding surface 7 and is released from the mold. When the mold is opened, the operating piece 37 is separated from the limit switch 36 and the automatic closing valve 39 is closed via the control device in response to the mold closing detection means 35 detecting the mold opening. Stop supplying.

Hereinafter, experimental examples will be described. As a precondition, when the air temperature is 20 ° C., the temperature of the compressed air of the air source is 20 ° C., the pressure is 0.4 MPa, and the air passage cross-sectional area of the first space is 30 mm ² , compression is performed without providing a nozzle at the tip. When the temperature of the top surface 15 part of the slide core 14 when supplying air to the gas supply path 25 was 76 ° C., a nozzle was provided at the tip, and the diameter of the nozzle-shaped gas supply path 25 ( a) 2 mm (air passage sectional area 3.14 mm ² ), (b) 3 mm (air passage sectional area 7.07 mm ² ), (c) 4 mm (air passage sectional area 12.56 mm ² ), (d) 5 mm (air) When the passage cross-sectional area is 19.63 mm ² ), the cooled temperature of the expanded air in the first space portion is approximately 12 ° C., and the temperature of the top surface 15 portion of the slide core 14 is 51 to 65 degrees. The temperature can be reduced to about 11-25 ° C. It came.

  Thus, when the air passage cross-sectional area of the diameter of the nozzle-like gas supply passage 25 is smaller than 2/3 (≈ 19.63 / 30) of the air passage cross-sectional area of the first space portion, the air temperature And the compressed gas can flow into the mold cooling passage 20.

  As described above, in the reference example, a molding die in which a die cooling passage 20 for compressed air is disposed inside the slide core 14 disposed in the die used for molding the bumper 1. The gas supply passage 25 is provided at the inlet 22 of the mold cooling passage 20, the gas discharge passage 26 is provided at the outlet 24 of the mold cooling passage 20, and the tip of the gas supply passage 25 is tapered. A nozzle 33 with a gradually reduced cross sectional area is provided, and an expansion chamber 34 in which compressed gas ejected from the nozzle 33 expands is provided on the inlet 22 side of the mold cooling passage 20, and the expansion chamber 34 and the outlet 24 A branch passage 31 formed by branching the mold cooling passage 20 into a plurality of portions is provided, and a fin-like portion 32 is formed between the branch passages 31 by the material of the slide core 14, and the nozzle 33, gas Since the ratio of the ventilation cross-sectional area of the supply passage 25 and the expansion chamber 34 is 1: 2 to 5: 4 to 13, the primary side 21 side Then, by expanding the compressed air in the expansion chamber 34, the air temperature on the secondary side 23 side is made lower than the air temperature on the primary side 21 side and is passed through the mold cooling passage 20 to cool the slide core 14. As a result, the cooling efficiency of the slide core 14 can be increased by flowing air having a temperature lower than the temperature of the compressed air supplied from the compressed air source 38 to the mold cooling passage 20. In addition, since the temperature of the air passing through the mold cooling passage 20 does not need to use a device such as a cooler, the size of the injection molding machine does not increase.

  Further, the top surface 15 of the slide core 14 forms a part of the cavity 8 provided in the movable mold 5 so that a part of the bumper 1 is formed by the top surface 15. The temperature of the top surface 15 can be lowered to, for example, the same level as that of the movable molding surface 7 by lowering the temperature of the air flowing through the mold cooling passage 20. The entire cooling state of the molded product can be made uniform, and a high-quality molded surface that does not show sink marks on the molded surface can be molded.

  FIG. 6 shows Embodiment 1, and the same parts as those in the reference example are denoted by the same reference numerals, and detailed description thereof is omitted. In the first embodiment, a nest 41 is provided on the movable side template 9 ′, and the top surface 15 ′ of the nest 41 is aligned with the movable side molding surface 7 ′. Formed with a molding surface. The bottom surface 17 'of the insert 41 is provided with a primary side 21' that is an inlet 22 'for compressed air and a secondary side 23' that is an outlet 24 'for heat-exchanged air. Between the secondary side 23 ', there is provided a die cooling passage 20' for compressed air, which is composed of an outward passage portion 28 ', an intermediate portion 29' branched by a fin-like portion 32 'and a return passage portion 30'. It has been.

  The forward path 28 'is provided with a nozzle 33', and a compressed air expansion chamber 34 'is provided on the secondary side 23' of the nozzle 33 '. The nozzle 33 ′ is formed in the insert 41 itself, and the tip 25F ′ of the gas supply path 25 ′ is orthogonal to the ejection direction X ′.

  Therefore, when compressed air is supplied when the mold is closed, the compressed air ejected from the nozzle 33 'expands in the expansion chamber 34', so that the air temperature decreases. Then, the temperature-decreased air passes through the intermediate portion 29, so that the temperature of the entire nesting and consequently the top surface 15 'can be lowered.

  In this way, in this embodiment, molding is used for molding the bumper 1 which is a molded product made of a thermoplastic resin, and a mold cooling passage 20 'for compressed gas is disposed inside the mold having the insert 41. A gas supply path 25 ′ is provided at the inlet 22 ′ of the mold cooling passage 20 ′, and a gas discharge path 26 ′ is provided at the outlet 24 ′ of the mold cooling passage 20 ′. The tip of the supply path 25 ′ is tapered, and a nozzle 33 ′ is provided which has a gradually reduced vent cross-sectional area. The compressed gas ejected from the nozzle 33 ′ expands on the inlet 22 ′ side of the mold cooling passage 20 ′. An expansion chamber 34 ′ is provided, and a plurality of fin-shaped portions 32 ′ are provided in the mold cooling passage 20 ′ between the expansion chamber 34 ′ and the outlet 24 ′. Since it is made of a material, air having a temperature lower than that of the compressed air supplied from the compressed air source 38 is allowed to flow through the mold cooling passage 20 '. It can be increased cooling efficiency of the nested 41. Further, since the temperature of the air passing through the mold cooling passage 20 'does not need to use a device such as a cooler, the size of the injection molding machine does not increase.

  In this way, in this embodiment, the ratio of the cross-sectional area of the nozzle 33 ′, the gas supply path 25 ′, and the expansion chamber 34 ′ is 1: 2 to 5: 4 to 13.

As described above, in this embodiment, in accordance with the first aspect of the present invention, a compressed gas mold is placed inside the insert 41 disposed in the mold used to mold the bumper 1 which is a molded product made of a thermoplastic resin. A molding die provided with a cooling passage 20 ', wherein a gas supply path 25' is provided at an inlet 22 'of the mold cooling passage 20' and an outlet 24 'of the mold cooling passage 20'. A gas discharge path 26 ′ is provided, a nozzle 33 ′ having a tapered tip and a gradually reducing cross-sectional area is provided at the tip of the gas supply path 25 ′, and a nozzle is provided on the inlet 22 ′ side of the mold cooling path 20 ′. An expansion chamber 34 ′ in which compressed gas ejected from 33 ′ expands is provided, and a branch path 31 ′ formed by branching the mold cooling passage 20 ′ into a plurality of portions is formed between the expansion chamber 34 ′ and the outlet 24 ′. A fin-like portion 32 ′ is formed between the branch paths 31 ′ by the material of the nesting 41, and the ventilation cross-sectional areas of the nozzle 33 ′, the gas supply path 25 ′, and the expansion chamber 34 ′ are formed. Ratio is 1: 2 to 5: is 4-13.

  As described above, the molding die according to the present invention can be applied to various uses.

1 Bumper (molded product)
5 Movable mold
20´ Mold cooling passage
21´ Primary side
22´ entrance
23´ Secondary side
24´ Exit
25´ Gas supply path
31´ branch
33´ nozzle
34´ expansion chamber
41 Nesting

Claims (1)

A molding die having a mold cooling passage for compressed gas disposed inside a nest disposed in a mold used for molding a molded product made of a thermoplastic resin, the mold cooling A gas supply path is provided at the inlet of the passage, a gas discharge path is provided at the outlet of the mold cooling passage, a tip is provided with a nozzle that tapers at the tip of the gas supply path, and a ventilation cross-sectional area is gradually reduced. An expansion chamber in which compressed gas ejected from the nozzle expands is provided on the inlet side of the mold cooling passage, and the mold cooling passage is divided into a plurality of branches between the expansion chamber and the outlet. The fins are formed by the material of the nesting between these branch paths, and the ratio of the ventilation cross-sectional areas of the nozzle, the gas supply path, and the expansion chamber is 1: 2-5. : Mold for molding characterized by being 4-13.

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