JP2007083582A - Manifold for hot runner type injection-molding die, and heater for manifold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To unify the temperature balance of a manifold for a hot runner type injection-molding die. <P>SOLUTION: In this manifold 10, the manifold 10 is divided into specified regions, and heaters 30A, 30B and 30C are provided for respective regions A, B and C. An electric energy regulator regulates an electric energy amount to each heater 30 in such a manner that the temperature of the whole of the manifold 10 may become uniform based on a detecting signal of a temperature sensor which is provided at a specified location. Thus, a temperature difference for the whole of the manifold 10 can be made small, and as a result, the temperature can be unified. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a manifold for a hot runner type injection mold and a heater for the manifold for the hot runner type injection mold, and more particularly to an improvement for reducing the temperature difference of the entire manifold.

  The hot runner type injection molding mold heats the manifold with a heater, that is, heats the resin path of the molten resin derived from the injection molding machine with the heater, and fills the cavity with the molten resin while maintaining the molten state of the molten resin. . The hot runner type injection mold is effective for mass production, advanced product accuracy, resource saving, cost reduction, etc., because the product in the cavity can be taken out while leaving the resin path of the molten resin, that is, the molten resin. And widely used in resin injection molding.

  FIG. 9 is a schematic cross-sectional view of a general hot runner type injection mold 50. As shown in FIG. 9, an injection molding machine (not shown) is mounted on the upper side of the manifold 52 via a sprue 54, and the molten resin melted by the injection molding machine passes through the sprue 54 and the runner 56 of the manifold 52. To be derived. This runner 56 branches in two directions toward the respective gates 60 of the cavity 58 in the left and right directions in the figure) and opens at the lower surface of the manifold 52. Hot nozzles 62 communicating with the runners 56 are fixed to the lower surface of the manifold 52, and a gate 60 that opens to the cavity 58 is formed at the lower end of the hot nozzle 62. The molten resin derived from the injection molding machine flows in the order of the sprue 54, the runner 56, the hot nozzle 62, and the gate 60, and is filled in the cavity 58. Each of the sprue 54, the runner 56, and the hot nozzle 62 is provided with heating means such as a heater, and circulates to the cavity 58 while maintaining a molten state of the molten resin.

  FIG. 10 is a cross-sectional perspective view taken along the line AA in FIG. 9 and shows an example of a heater arranged in the manifold.

  As shown in FIG. 10A, through holes 64 are formed at the four corners of the manifold 52 (or at two places in the center of the vertical side), and the cartridge heater 66 is inserted into the through holes 64 with a heat insulating material 68 interposed therebetween. Be placed. The cartridge heater 66 is a linear heater having a circular cross section, and is disposed substantially parallel to the length direction of the manifold 52.

  10B, cross-sectional U-shaped grooves 70 are formed at the four corners of the manifold 52, and a sheathed heater 72 is disposed in the cross-sectional U-shaped groove 70 with a heat insulating material 68 interposed therebetween. Similar to the cartridge heater 66, the sheath heater 72 is also arranged substantially parallel to the length direction of the manifold 52.

Japanese Patent Application No. 9-185574

  However, when molding a large product such as a bumper of a vehicle, the gate from the molten resin inlet of the manifold to the cavity becomes longer, and there are places where the runner becomes longer.

  When such a long runner is heated with the heater arrangement described above, the central portion (slightly downstream) of the runner 56 becomes high temperature, and the end of the manifold 52, in other words, the vicinity of the upper portion of the hot nozzle 62 becomes low temperature. There is a problem that occurs. For example, when the length of the runner is about 70 cm, the temperature difference may be about 30 ° C.

  The reason why such a temperature difference occurs is as follows. Due to the low thermal conductivity and heating capacity of the cartridge heater 66 and the sheathed heater 72, heat cannot be efficiently transferred from the heaters 66 and 72 to the manifold 52. Therefore, the heater itself does not become a thermal circuit, and heat is gradually transferred from the manifold 52 to the low temperature portion of the manifold 52, so that it is considered that heat concentrates in the central portion of the runner 56 after all. In addition, since the shape of the outlet of the runner 56, that is, the end of the manifold 52 (near the upper part of the hot nozzle 62) is generally larger than that of the central portion of the runner 56, the heating target per unit area of the heater is increased. The temperature drops. Further, the heat is transferred to the hot nozzle 62 and the temperature is lowered.

  Such a poor thermal balance of the manifold 52 may cause a temperature change in the molten resin flowing through the runner 56 and cause the resin to deteriorate. Further, if the temperature of the molten resin when it is led out to the cavity 58 is low or the temperature is not uniform between the gates 60, the molten resin does not solidify at a uniform speed in the cavity 58, and the product accuracy is deteriorated. There is a problem.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to reduce the temperature difference of the entire manifold.

  The manifold of the hot runner type injection mold of the present invention is a manifold of the hot runner type injection mold that is stretched toward each gate to the cavity around the introduction port through which the molten resin from the injection molding machine is introduced. A runner that penetrates the inside of the manifold and circulates the molten resin, and is extended and branched from the introduction path through which the molten resin from the injection molding machine is introduced to each gate of the cavity. A runner consisting of a flow passage, a lead-out path communicating with the flow passage to lead the molten resin to the gate of the cavity, and a heating wire supported by an insulating support in the hollow outer tube are inserted, and the heating wire A heater having both ends electrically connected to lead terminals fixed to both ends of the hollow outer tube, heating the molten resin flowing through the runner, and at least one flow passage; In the lead-out path communicating with the passage, individual heaters are arranged while being bent along the runner path, and the detection signal of the temperature sensor provided at a predetermined position of the manifold is supplied to the electric energy regulator. The manifold is characterized in that the power amount to each heater is adjusted by the power amount regulator so that the temperature of the manifold becomes uniform.

  Further, in the manifold of the hot runner type injection mold according to the present invention, the area of the manifold around each lead-out path is configured to have substantially the same shape, and each heater around the respective lead-out path has almost individual heaters. It is provided with the same arrangement | positioning form.

  Furthermore, in the manifold of the hot runner type injection mold of the present invention, the hollow outer tube of the heater is made of aluminum in the shape of a square tube, and the heater has a curvature on its center line when the outer width of the square tube is w. It has a flexibility that can be freely deformed up to w and is pressed in close contact with a square groove formed on the surface of the manifold.

  The manifold heater of the present invention is a heater for a manifold that heats a molten resin flowing through a runner formed in a manifold of a hot runner type injection mold, and is a heating wire supported by an insulating support in a hollow outer tube Is inserted, and both ends of the heating wire are electrically connected to lead terminals fixed to both ends of the hollow outer tube, the hollow outer tube is made of square-shaped aluminum, and the outer width of the square tube is set to w. At this time, it is characterized in that it has flexibility so that it can be freely deformed up to the curvature w on its center line.

  According to the manifold of the hot runner type injection mold of the present invention, the heaters for heating the runner flow passage and the outlet passage region are individually provided, and the temperature is controlled for each heater. The temperature difference can be reduced.

  According to the manifold heater of the present invention, the hollow outer tube is made of square tube-shaped aluminum and has an excellent flexibility, so that the heating efficiency to the manifold can be increased and the temperature of the manifold can be accurately controlled. it can.

  FIG. 1 is a plan view of a manifold (hereinafter simply referred to as a manifold) of a hot runner type injection mold according to this embodiment, and FIG. 2 is a schematic cross-sectional view of the hot runner type injection mold according to this embodiment. is there.

  The manifold of the present embodiment can be suitably used for large resin molded products, for example, vehicle bumpers, instrument panels, large television frames, and the like. Further, it can be used for processing thermoplastic resins such as plastics and engineering plastics, and is also suitably used for processing engineering plastics that require high-precision temperature control.

  As shown in FIG. 1, the manifold 10 according to the present embodiment has a shape that is extended toward each of the four gates of the cavity around a molten resin inlet 12 from an injection molding machine (not shown). Yes. This is a so-called four-point mold with a four-point gate. The manifold 10 of this embodiment can be used for manufacturing a bumper for a vehicle. As shown in FIG. 2, a sprue 14 to which an injection molding machine (not shown) is connected is mounted on the upper side of the inlet 12 of the manifold 10. A runner 20 penetrating the inside of the manifold 10 is formed from the inlet 12 toward the gate 18 to the cavity 16. The runner 20 opens on the lower surface of the manifold 10, and the hot nozzles 22 are respectively fixed to the openings. The gate 18 is formed at the lower end of the hot nozzle 22. The molten resin derived from the injection molding machine flows in the order of the sprue 14, the runner 20, the hot nozzle 22, and the gate 18, and is filled in the cavity 16. At this time, the sprue 14, the manifold 10, the hot nozzle 22, and the like are each provided with heating means such as a heater, and the molten resin is filled into the cavity 16 while maintaining a molten state.

  The runner 20 of the present embodiment includes an introduction path 24 that is connected to the introduction port 12 and into which the molten resin from the injection molding machine is introduced, and a flow path 26 that is branched and extended from the introduction path 24 toward each gate 18 of the cavity 16. And a lead-out path 28 that communicates with the flow path 26 and leads the molten resin to the gate 18 of the cavity 16. As shown in FIG. 2, the introduction path 24 extends downward from the introduction port 12, and the flow path 26 is bent at the position where the introduction path 24 is substantially at the center of the height of the manifold 10. It extends in parallel with the length direction, and the outlet path 28 extends downward from the end portion of the flow path 26. In the present embodiment, the flow passage 26 has a long flow passage 26A and a short flow passage 26B. In the present embodiment, the configuration (capacity) of the manifold 10 in the lead-out path region C is the same (or substantially the same).

  Characteristic points in the present embodiment are the arrangement of heaters and the heater structure provided in the manifold 10, which will be described in detail sequentially.

  3 is a cross-sectional view taken along line BB in FIG. As shown in FIG. 3, the heater 30 has a rectangular tube shape and is pressed into close contact with square grooves 32 formed at two locations on the upper and lower surfaces of the manifold 10. A characteristic point in the present embodiment is that the manifold 10 of the present embodiment is divided into predetermined areas, and heaters 30 are provided for each of which are individually temperature-controlled. FIG. 4 is a schematic diagram in which the manifold 10 is divided into predetermined regions. As shown in FIG. 4, in this embodiment, the area around the introduction path 24 is the introduction path area A, the area around the long flow path 26A is the long flow path area B, and the area around the lead-out path 28 is derived. The road area C is divided. A heater 30A is provided in the introduction path area A, a heater 30B is provided in the long flow path area B, and a heater 30C is provided in the lead-out path area C. 1 and 4 show the arrangement on the upper surface side, and the rear surface side is arranged in the same manner as this upper surface side. In the present embodiment, a total of 14 heaters 30 are arranged. As shown in FIGS. 1 and 4, the heaters 30 </ b> A, 30 </ b> B, and 30 </ b> C are arranged while being bent along the path of the runner 20. For example, the heat capacity of each region A, B, C may be calculated to adjust the amount of bending. As understood from FIG. 1, in this embodiment, the heater 30 </ b> B is arranged in the long flow passage region B and the heater 30 </ b> C is arranged individually in the lead-out passage region C. In addition, the individual heaters 30C are provided in each of the lead-out path regions C. However, since the lead-out path regions C are configured in substantially the same shape, the heaters 30C have the same length and substantially the same arrangement form. Can be provided. Thereby, design can be performed easily.

  These 14 heaters 30 have their electric power adjusted individually. That is, the manifold 10 is provided with a temperature sensor 34 (indicated by a circle S in the figure) at a predetermined location, and a detection signal of the temperature sensor 34 is input to the power amount adjuster 36. Based on the detection signal of the temperature sensor 34, the power amount adjuster 36 adjusts the amount of power to each heater 30 so that the temperature of the entire manifold 10 becomes uniform.

  As described above, in the present embodiment, the manifold 10 is divided into desired regions, and the heaters 30A, 30B, and 30C are provided for each region, and the temperatures of these heaters are individually controlled. Thereby, the temperature difference of the whole manifold can be reduced with high accuracy, and the temperature can be made uniform. In particular, since the heater 30B is disposed in the long flow passage region B and the heater 30C is disposed in the lead-out passage region C, the temperature can be individually controlled, and the temperature difference between the long runner portions can be reduced. Further, since the configuration (capacity) of the manifold 10 in the lead-out path region C is the same (or almost the same), the length and arrangement of the heater 30C can be made the same, and the temperature of the lead-out path region C can be controlled with high accuracy. can do. Further, since the heater 30C arranged in the lead-out path region C can be standardized (length, etc.), the manufacturing cost can be reduced. The temperature control may be performed by adjusting the amount of electric power for each of the heaters 30A, 30B, and 30C for each of the regions A, B, and C. That is, when the number of gates increases, the shape of the manifold in the lead-out path region C is the same even if the temperature of the other heater 30C is controlled based on the detection signal of a certain heater 30C. Can do.

  Next, the configuration of the manifold heater 30 will be described in detail.

  FIG. 5 is a schematic cross-sectional view illustrating a schematic configuration of the manifold heater 30 according to the present embodiment, and FIG. 6 is a diagram illustrating a bent state of the manifold heater 30. The heater 30 includes a hollow outer tube 40 that is in contact with an object to be heated (manifold 10), a coiled heating element wire 42 that is inserted into the hollow outer tube 40 and generates heat when a current is applied from a power source, and an electrical insulating property. An insulating support 44 that is made of a material (for example, magnesium oxide) that supports the heating element wire 42 and is fixed to both ends of the hollow outer tube 40, and both ends of the heating element wire 42 are electrically connected by spot welding or the like. Connected lead terminals 46.

  The hollow outer tube 40 is made of a metal having excellent flexibility and thermal conductivity. In the present embodiment, the hollow outer tube 40 is made of aluminum, which is a material having flexibility that can be bent freely and having excellent thermal conductivity. Yes. As shown in FIG. 6, when the outer width of the hollow outer tube 40 is w, the heater 30 preferably has a flexibility that can be freely deformed up to the curvature w on the center line. This flexibility can be obtained by selecting aluminum as a highly flexible material and applying a heat treatment such as the thickness of the hollow outer tube 40 or known annealing. By having such flexibility, it can be bent and deformed by hand, for example, without using a processing device, and the manifold 10 can be easily pushed into the square groove 32. The hollow outer tube 40 may be made of a material having high flexibility and good thermal conductivity, such as an aluminum alloy, nickel, copper, silver, or the like.

  FIG. 7 is an enlarged cross-sectional view showing a state in which the heater 30 is pushed into the square groove 32 of the manifold 10. As described above, the heater 30 is formed in a rectangular tube shape (the cross-sectional shape is square or rectangular). For example, the outer width w is 6.3 mm, the inner width w1 is 4.3 mm, and the thickness t of the hollow outer tube 40 is 1 mm. It is (degree). The thickness t of the hollow outer tube 40 is preferably about 8 to 20% with respect to the outer width. One side of the square groove 32 is about 6.6 mm in consideration of the thermal expansion of the heater 30. As described above, the heater 30 is pressed in close contact with the square groove 32, and three sides are in close contact with and in contact with the square groove 32 of the manifold 10. In FIG. 7, a gap is shown, but when the heater 30 is pushed into the square groove 32, the heater 30 is pushed in slightly so as to be in close contact with the square groove 32. As a result, the aluminum in the hollow outer tube 40 becomes a heat dissipation layer and can efficiently transfer heat to the manifold 10. Further, since the three sides are in close contact with and in contact with the square groove 32 of the manifold 10, the contact area is larger than the cross-sectional circular shapes of the cartridge heater 66 and the sheathed heater 72 shown in FIG. Therefore, heating efficiency can be improved. Further, in the present embodiment, the heater 30 is in direct contact with the manifold 10 without using a heat insulating material, so that the heat transfer efficiency is also improved in this respect.

  The heater 30 having an outer width of 7.3 mm, an inner width of 5.8 mm, and a hollow outer tube 40 having a thickness of about 1 mm can be suitably used.

  Hereinafter, the thermal conductivity of the heater and the manifold of this embodiment will be compared.

[Table 1]
Temperature Thermal conductivity (1) Heater of this embodiment 20 ° C. 204 W / mK
300 ° C 230W / mK
(2) SUS seed heater 20 ° C 16W / mK
(3) Nickel sheathed heater 20 ° C 59W / mK
(4) 73 brass (copper 30%, zinc 70%) square heater 20 ° C 99W / mK
(5) Manifold (hot plate) of this embodiment
ACD37 20 ℃ 46W / mK
300 ° C 41.8W / mK

  For example, the conventional (2) sheathed heater made of SUS has low thermal conductivity, so heat is not efficiently transferred from the sheathed heater to the manifold, and heat is transferred from the manifold to the low temperature portion of the manifold. It will be. Therefore, a temperature difference occurred in the entire manifold, and the temperature difference was about 30 ° C. to 40 ° C. for a runner of about 70 cm. Further, this delay in heat transfer results in heat radiation from the surface from the manifold, and the thermal efficiency is about 20% to 30% including the initial stage of heating.

  In contrast, in the heater 30 of the present embodiment, the aluminum hollow outer tube 40 functions as a heat dissipation layer, and the heat of the heater 30 is quickly transmitted to each part of the manifold 10. In other words, the heater itself becomes part of the thermal circuit. Also, this heat transfer speed prevents excessive heat dissipation. With such a configuration of the heater 30 and the arrangement of the heaters of the manifold 10 of the present embodiment described above, a temperature difference of about 3 to 5 ° C. can be achieved with a 70 cm runner. In addition, this heat transfer speed prevented excessive heat dissipation, and the thermal efficiency including the initial stage of heating was able to achieve 60% or more and about 66%.

  Next, the operation of this embodiment will be briefly described.

  Electric power is supplied to each heater 30 and the manifold 10 is heated. The power amount adjuster 60 adjusts the power amount of each heater 30 based on the detection signal of the temperature sensor 34. Thereby, the temperature balance of the manifold 10 can be made uniform.

  In the present embodiment, in particular, since the heaters 30 in the long flow passage region B and the lead-out passage region C are individually provided, the temperature control when the runner 20 becomes long can be performed efficiently. Further, since the heaters 30C in the lead-out path region C corresponding to the respective gates are also individually provided, the temperature of the molten resin led out from the runner 20 can be controlled with high accuracy.

  Further, since the hollow outer tube 40 of the heater 30 of the present embodiment is made of aluminum having flexibility that can be bent freely and having excellent thermal conductivity, the heating efficiency is good, and as a result, temperature control is performed with high accuracy. can do.

<Other examples>
FIG. 8 is a diagram illustrating a heater arrangement example of another manifold. Members that are the same as or equivalent to those in the first embodiment are given the same reference numerals, and descriptions thereof are omitted. Further, points not particularly described are the same as those in the first embodiment.

  As shown in FIG. 8, the manifold 48 is a six-piece mold having a six-point gate that extends toward the six gates. The manifold 48 is divided into predetermined regions, and the heaters 30 described above are arranged, and these heaters 30 are individually controlled. In this example, the area around the introduction path 24 is the introduction path area A, the area around the upper long flow path 26A in the figure is the long flow path area B1, and the area around the lower long flow path 26C in the figure is the area. The area around the long flow path area B2 and the outlet path 28 is divided into sections of the outlet path areas C and 11. A heater 30D is provided in the introduction path area A, a heater 30E is provided in the long flow path area B1, a heater 30F is provided in the long flow path area B2, and a heater 30G is provided in the discharge path area C. Similarly, the heater 30 is arranged on the back side, and a total of 22 heaters are arranged.

  In the manifold 48, the arrangement form of the heaters 30D, 30E, and 30F is different from that in the first embodiment shown in FIG. Thus, the arrangement of the heaters 30 may be changed in consideration of the heat capacity of each region.

It is a top view of the manifold of the hot runner type injection mold of an embodiment. It is a sectional view of the whole hot runner type injection mold of an embodiment. It is the BB sectional view taken on the line of FIG. It is the schematic diagram which divided the manifold of this embodiment into the predetermined area | region. It is a schematic sectional drawing which shows schematic structure of the heater for manifolds of embodiment. It is a figure which shows the bent state of the heater for manifolds. It is an expanded sectional view showing the state where the heater was pushed into each groove of the manifold. It is a figure which shows the heater arrangement | positioning example of another manifold. It is a schematic cross section showing a general hot runner type injection mold. It is sectional drawing of the AA line of FIG.

Explanation of symbols

  10 manifold, 12 inlet port, 14 sprue, 16 cavity, 18 gate, 20 runner, 22 hot nozzle, 24 inlet channel, 26 flow channel, 28 outlet channel, 30 heater (heater for manifold), 32 square groove, 34 temperature sensor 36, electric energy regulator, 40 hollow outer tube, 42 heating element wire, 44 insulation support, 46 lead terminal.

Claims (4)

It is a manifold of a hot runner type injection mold that is stretched toward each gate to the cavity around the introduction port into which the molten resin from the injection molding machine is introduced,
A runner penetrating the inside of the manifold and through which the molten resin flows, an introduction path through which the molten resin from the injection molding machine is introduced, and a flow path branched and extended from the introduction path toward each gate of the cavity A runner comprising a lead-out path that communicates with the flow path and leads the molten resin to the gate of the cavity;
A heating element wire supported by an insulating support is inserted into the hollow outer tube, and both ends of the heating element wire are electrically connected to lead terminals fixed to both ends of the hollow outer tube, and melted through the runner. A heater for heating the resin;
At least one of the flow passages and the lead-out passage communicating with the flow passage, each individual heater is disposed while being bent along the route of the runner,
A detection signal of a temperature sensor provided at a predetermined position of the manifold is input to an electric energy adjuster, and the electric energy to each heater is supplied to the manifold so that the manifold temperature becomes uniform by the electric energy adjuster. Hot runner type injection mold manifold characterized by being adjusted. A hot runner type injection mold manifold according to claim 1,
The area of the manifold around each lead-out path is composed of almost the same shape,
A manifold of a hot runner type injection mold, wherein individual heaters are provided in substantially the same arrangement form in the manifold region around each outlet path. A hot runner type injection mold manifold according to claim 1 or 2,
The hollow outer tube of the heater is made of aluminum in the shape of a square tube,
The heater has flexibility that can be freely deformed up to a curvature w on the center line when the outer width of the square tube is w, and is pressed in close contact with a square groove formed on the surface of the manifold. A hot runner type injection mold manifold. A heater for a manifold that heats a molten resin flowing through a runner formed on a manifold of a hot runner type injection mold,
A heating element wire supported by an insulating support is inserted into the hollow outer tube, and both ends of the heating element wire are electrically connected to lead terminals fixed to both ends of the hollow outer tube,
The hollow outer tube is made of aluminum in a rectangular tube shape, and has a flexibility that can be freely deformed to a curvature w on the center line when the outer width of the rectangular tube is w.

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