JPH0333087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electromagnetic induction heating injection molding method and an apparatus therefor used, for example, in runnerless synthetic resin injection molding.

[Conventional technology]

Conventionally, this type of electromagnetic induction heating injection molding method and apparatus include those disclosed in, for example, Japanese Unexamined Patent Publication No. 180811/1983.

This will be explained with reference to FIG.

Reference numeral 1 denotes a chip incorporated in the mold 2, 3 a high-frequency electromagnetic induction heating coil wound near the tip of the chip 1, 4 a gate hole communicating with the hole 5 opened at the tip of the chip 1, and a cavity. It communicates with 6. Reference numeral 7 indicates a resin inflow portion that contacts a nozzle (not shown) of an injection molding machine, 8 indicates a manifold, and each of the divided resin flow paths 9 has an opening 10 opened at the rear end of each chip 1. is connected to.

The chip 1 has a pipe structure with a circulation hole 11 passing through the center thereof, and constitutes the heated material of the wound high frequency electromagnetic induction heating coil 3,
A shield cover 12 is disposed around the outer periphery, and a temperature sensor 13 is embedded in the tip of the chip 1 to sense and measure the temperature of the chip 1.

This injection molding method and apparatus is characterized in that a high frequency electromagnetic induction heating coil 3 is used instead of the commonly known heater system using Joule heat, and the resin temperature near the gate hole 4 of the mold 2 is The purpose is to control with high precision. Specifically, the difference between the temperature measured by the temperature sensor 13 and the set temperature is supplied to the highly responsive high-frequency electromagnetic induction heating coil 3 by changing the high-frequency oscillation frequency, so that the temperature fluctuations at the tip of the chip 1 are constantly adjusted to the optimum molding temperature. Holds conditions. In addition, problems such as stringiness, separation, and gate clogging that occur from the gate hole can be solved by high frequency control of the resin temperature near the gate hole, without using mechanical valves or complicated mechanisms such as intermittent temperature control to open and close the gate. This is avoided by maintaining good gate balance using a highly accurate control means called electromagnetic induction heating.

[Problem that the invention seeks to solve]

By the way, in such a conventional injection molding method and apparatus, the gate hole 4 is provided separately from the hole 5 of the chip 1, and the required length to communicate with the cavity 6 is essential, so that it is not as good as the conventional gate hole. However, even if high-frequency electromagnetic induction heating, which has excellent responsiveness, is used, it is difficult to control subtle changes in the raw resin phase, such as softening, solidification, or melting of a small amount of resin in the gate hole 4. It is extremely difficult to avoid inconveniences such as string pulling, sagging, and gate clogging, and it is difficult to achieve the intended purpose.

Moreover, since the chip 1 communicating with the gate hole 4 has a pipe-like shape, if the amount of channel resin is increased, the diameter of the communication hole 11 must be increased. If this hole diameter is increased, the high-frequency electromagnetic induction coil will also have to be increased in size, including the number of windings, the thickness of the coil itself, and the high-frequency oscillation device. Therefore, the heating effect on the raw material resin at the center of the pipe-shaped chip 1 is gradually reduced, and on the other hand, as the size increases, the overall heat capacity also increases, so the responsiveness of temperature control inevitably decreases. Therefore, even if a heat generating means with excellent responsiveness such as a cut-angle, high-frequency electromagnetic induction coil is used, it can only be used for small-sized, small-volume injection molding means.

[Means for solving problems]

The electromagnetic induction heating injection molding method of the first invention includes forming an annular tubular flow path P in at least the runner process of the runner process following the gate A leading to the cavity 6, one or more resin dividing processes, and the plasticizing process. The purpose is to provide a high-frequency electromagnetic induction heating means capable of heating this annular tubular flow path P, melt the raw resin, and intermittently perform injection molding.

In addition to the above-mentioned method, the electromagnetic induction heating injection molding method of the second invention includes independently providing a high-frequency electromagnetic induction heating means for heating the gate A in the gate step of injecting the molten resin into the cavity 6, and in particular, The purpose is to locally heat A to melt the raw material resin within the gate A and intermittently perform injection molding.

Furthermore, the electromagnetic induction heating injection molding apparatus of the third invention is an apparatus for implementing the methods of the first and second inventions, and includes a runner mechanism B, a manifold mechanism C, and a gate A leading to the cavity 6. Form the flow path of the raw material resin in at least one of the plasticizing mechanisms D, starting from the side closer to the gate A, into a ring-tubular flow path P of a desired shape by arranging an inclusion X such as a core. Furthermore, a high frequency electromagnetic induction heating mechanism Q is provided which can heat the mechanism and/or the inclusion X as a heated material provided along the annular tubular flow path P.

The high-frequency electromagnetic induction heating mechanism Q is designed to freely change the frequency of high-frequency waves using a desired high-frequency oscillation control circuit 18 to obtain a desired temperature.

[Effect]

Among the flow paths through which the raw material resin passes, a ring tubular flow path P is formed at least in the runner process following the gate A leading to the cavity 6, and a heating mechanism Q as a high-frequency electromagnetic induction heating means is provided on the outer periphery of the flow path P. When the heating mechanism Q is energized, the inclusions X such as a core as a material to be heated and/or the runner mechanism B forming the runner process exhibit a heat generating effect and the raw resin in the annular tubular flow path P is heated by electromagnetic induction. can be melted.

Furthermore, an inclusion X such as a core is disposed in one or both of the manifold mechanism C and the plasticization mechanism D, which constitute the resin division process and the plasticization process other than the runner process, respectively, and communicates with the annular tubular flow path P. Even if the annular tubular flow path P is formed, the respective mechanisms C, D or/and the inclusions
acts as a heat-receiving material, a heat generating effect based on an electromagnetic induction effect is generated, and the raw resin in the annular tubular flow path P can be melted.

In particular, the molten resin is transferred from gate A to cavity 6.
If a high frequency electromagnetic induction heating mechanism (not shown) that can locally heat the gate A based on an electromagnetic induction effect independent of other processes such as the runner process is also provided in the gate process for injecting into the inside, By energizing this mechanism, the raw resin in gate A is rapidly heated and melted, and when the power is removed, the raw resin in gate A is rapidly cooled and solidified, so-called gate A.
can be turned on and off. Note that the heating temperature can be freely varied up and down by changing the frequency of the high-frequency oscillation control circuit.

〔Example〕

Embodiments of the method and apparatus according to the present invention will be described below with reference to the explanatory diagram in FIG. 1 and the partial structural cross-sectional diagram in FIG. 2.

Reference numeral 6 denotes a cavity which can be opened and closed each time a molding operation is performed to take out a molded product, similar to the mold of a conventional injection molding apparatus, and has substantially the same structure as shown in FIG. 4. Reference numeral A denotes a gate which communicates with the cavity 6 and operates in the gate process to form a hole as small and short as possible to inject the raw material resin in a semi-molten or molten state. B is a runner mechanism that operates during the runner process and constitutes the final stage in which the molten resin can be supplied to the gate A. C is a manifold mechanism, which keeps the raw material resin in a molten state and can be divided and transferred to one or more required number of locations (in the figure, four locations) to perform the so-called resin division process. It is connected in communication with the raw material supply mechanism E that is metered and supplied according to the quantity.
Together with this mechanism E, a plasticizing process and a raw material supply process can be performed. F is an injection mechanism composed of a desired type such as a plunger or an in-line screw, and is operable each time an injection operation is performed.

X is an inclusion corresponding to a core, and the illustration shows an inclusion that is integrally configured across runner mechanism B, manifold mechanism C, and plasticizing mechanism D, but only runner mechanism B or runner It may be configured to include only two mechanisms, mechanism B and manifold mechanism C, and this configuration may be provided at least in runner mechanism B (not shown).

P is a ring tubular flow path formed between the inclusion X and each of the mechanisms, and serves as a passage through which the raw resin can be transferred. The annular tubular flow path P shown in FIGS. 1 and 2 has an annular shape based on a double circular structure, but is not necessarily limited to the illustrated shape. For example, it is possible to make it into a desired shape such as an ellipse, a triangle, or a square, and this annular tubular flow path P has the smallest diameter in the runner mechanism B closest to each cavity 6, and in turn in the manifold mechanism C, the plastic The diameter is increased as the molding mechanism D and the cavity 6 are separated from each other, so that it can be adapted to the production of a large number of molded products or the size of the capacity.

To explain the annular tubular flow path P having a double circular structure in FIG. 3, when the wall thickness l of the annular tubular flow path P is constant,
As the diameter r becomes smaller, the cross-sectional area S of the annular tubular flow path P becomes smaller, but as the diameter r becomes larger, the cross-sectional area S becomes larger. In short, it can be seen that the cross-sectional area S of the annular tubular flow path P having the same wall thickness l increases or decreases as the square of the radius r.

Therefore, while the wall thickness l of the annular tubular flow path P is maintained in a thin layer, the amount of raw resin can be heated and melted and transferred very effectively.

Moreover, this relationship is maintained in exactly the same way no matter what shape the annular tubular flow path P has. Q indicates a high frequency electromagnetic induction heating mechanism; high frequency electromagnetic induction coils q1, q wound around any one of the mechanisms B to D provided with the annular tubular flow path P or the required number of mechanisms;
Similarly, although not shown, a high-frequency electromagnetic induction coil can be wound around the gate A as well, if necessary. In this high-frequency electromagnetic induction coil, the number of windings, the wire diameter, and the frequency to be applied can be varied depending on the size and wall thickness of the annular flow path P. In the illustration, high-frequency electromagnetic induction coils q1, q2, and q3 are continuously wound around the runner mechanism B, the manifold mechanism C, and the plasticizing mechanism D, but they may be provided independently for each mechanism. Further, it may be provided only in the runner mechanism B or only in the gate A and the runner mechanism B, and the others may be heated by a conventional cartridge heater or the like.

By the way, these high frequency electromagnetic induction coils q1, q
The high frequency electromagnetic induction heating mechanism Q based on 2,q3 is
It is preferable that each of the mechanisms B, C, and D including the gate A is itself a heated material, and at the same time, it is also possible to use the aforementioned inclusion X itself as a heated material.
If the material to be heated is a magnetic material, the hysteresis loss will work synergistically and the heating effect will be good, but a non-magnetic material such as ceramics may also be used.

Although the high frequency oscillation control circuit 18 for operating the high frequency electromagnetic induction heating mechanism Q is shown as a block circuit in FIG. 1, this circuit 18 can be operated on each mechanism simultaneously or separately.

In Fig. 2, inclusions X are
Although a slanted cross-sectional view is shown in which the integrally formed inclusion X and at least two recesses having a shape similar to that of the inclusion X are shown, The above-described split molds 14 and 15 are formed, and the recess has a size equal to the wall thickness l of the annular tubular flow path P added to the diameter r of the inclusion X in the split molds 14 and 15, and The inclusion
can be held between the split molds 14 and 15 while being supported between the two concave portions, and a tightening metal wire 17 can be wound around it, or it can be fixed with screws or made of carbon fiber (not shown). It can be formed by any suitable means, such as a material that shrinks when heated. In addition, high frequency electromagnetic induction coil q
1, q2, and q3 are wrapped around each other, but a shield case (not shown) for shielding may be placed on the outer periphery.

Then, the annular tubular flow path P is formed using two or more split molds 14,1.
5, gas is effectively vented during injection molding, and there is no problem of resin leakage.

Although not shown in the figure, the inclusion Although cooling methods can be used,
A high frequency electromagnetic induction coil or other heating element (not shown) for heating the annular channel P can also be incorporated.

Incidentally, although not explicitly shown, the mold structure may be integrated over the entire area from the gate A to the injection mechanism F, or it is also possible to separate the necessary mechanisms.

With the configuration described above, the runner mechanism B or plasticizing mechanism D leading to the gate A is rapidly heated to the required temperature by the action of the high frequency electromagnetic induction heating mechanism Q, and the raw material passing through the annular tubular flow path P is The resin can be melted effectively, and the necessary amount of molten resin can be injected into the cavity 6 through the gate A by the function of the injection mechanism F to perform the molding operation.

In particular, when the high-frequency electromagnetic induction coil q1 wrapped around the runner mechanism B or the high-frequency electromagnetic induction coil wrapped around the gate A as needed is intermittently turned on and off each time the molding operation is performed, The small amount of resin in the gate A portion can be heated and melted and cooled and solidified very effectively and quickly, so that the so-called opening and closing operations of the gate can be performed reliably.

〔Effect of the invention〕

In this invention, the flow path through which the raw material resin passes is a ring-tubular flow path, and a high-frequency electromagnetic induction heating method is used as the heating means, and the necessary mechanisms of the runner process, resin dividing process, and plasticizing process are operated by energization. As a result, the thin-walled raw material resin in the ring-tubular flow path can be instantly and extremely efficiently heated and melted, making it possible to perform injection molding operations of the raw material resin efficiently. Become.

Further, the flow path of the raw material resin is a ring tubular flow path,
Even if the thickness of the wall is made thin, the cross-sectional area of the annular tubular channel can be freely adjusted by freely changing the diameter, which increases the diameter of the annular tubular channel. Also, simply by increasing the winding diameter of the high-frequency electromagnetic induction coil, the raw material resin can be effectively heated and melted without losing the immediate heating effect that acts on the raw material resin, making it possible to perform not only small-sized molding but also large-sized molding. has.

Furthermore, by providing a high-frequency electromagnetic induction heating means in the gate or runner mechanism and intermittently turning on and off the power to the high-frequency electromagnetic induction coil each time injection molding is performed, the melting and solidification of the raw material resin in the gate part can be repeated and continued. This allows the gate to be opened and closed using the same method, making so-called high-precision molding possible. When a high-frequency electromagnetic induction coil is wound around the gate and the gate portion is intermittently heated during the gate process, it can work effectively even if the gate itself is long.

In general, when the gate is short, the gate can be opened and closed effectively by intermittently turning on and off the energization of the runner mechanism and the high-frequency electromagnetic induction heating means during the runner process.

Note that the annular tubular channel can be formed by incorporating it into the members constituting each mechanism using an intervening material such as a core, but its shape and size are free, and the location where it is formed can be changed depending on the location, except for the runner mechanism. It has an effect that can be implemented in any individual place without any problem.

Furthermore, since the flow path is annular and tubular, the bent portion does not form an acute angle as in the conventional case.
Therefore, the bent portions are bent as much as possible to eliminate places where the raw resin accumulates, and this has the effect of facilitating smooth injection molding operations.

[Brief explanation of drawings]

FIG. 1 is a principle explanatory diagram showing an embodiment of the electromagnetic induction heating injection molding method and apparatus according to the present invention; FIG. FIG. 3 is an explanatory enlarged sectional view of the same as the above, and FIG. 4 is an explanatory sectional view of the main part of the conventional example. 6... Cavity, A... Gate, B... Runner mechanism, C... Manifold mechanism, D... Plasticizing mechanism, E... Raw material supply mechanism, F... Injection mechanism,
X...Inclusion, P...Annular tubular channel, Q...High frequency electromagnetic induction heating mechanism.

Claims (1)

[Claims] 1. A raw material supply step for supplying a desired raw material resin;
It consists of a plasticizing process in which the raw resin can be softened and melted, a resin dividing process in which the molten resin can be divided into one or more required numbers, and a runner process in which the molten resin leading to the cavity accumulates each time the molding operation is performed. At least in the runner process, an annular tubular channel is formed with an inclusion such as a core and heated by high frequency electromagnetic induction heating means, and the raw resin is melted and the molten resin is passed through the annular tubular channel. An electromagnetic induction heating injection molding method characterized in that the injection operation is performed intermittently into a cavity through a gate by a desired injection means. 2. The high-frequency electromagnetic induction heating means is disposed so as to be able to operate continuously or separately in the resin dividing step and the plasticizing step following the runner step, and each of the steps includes:
An annular tubular flow path is formed through which the raw material resin passes, and the raw material resin passing through this annular tubular flow path is intermittently injected into the cavity via a gate by a desired injection means that softens and melts the raw material resin. An electromagnetic induction heating injection molding method according to claim 1, characterized in that: 3. The high-frequency electromagnetic induction means, which operates at least in the runner process, is operated intermittently during each molding operation to soften and melt a small amount of solidified raw material resin that mainly accumulates in the gate part, and to open the gate. The electromagnetic induction heating injection molding method according to claim 1, characterized in that the molding member is opened to enable injection. 4 a raw material supply step of supplying the desired raw material resin;
A plasticizing process that can soften and melt the raw resin, a resin dividing process that can divide the molten resin into one or more required numbers, a runner process where the molten resin leading to the cavity accumulates each time the molding operation is performed, and a runner process that allows the molten resin to flow into the cavity. It consists of a gate step of injecting, and in the gate step of the steps, a high frequency electromagnetic induction heating means is provided to heat the gate, and at least in the runner step, an inclusion such as a core is arranged and formed. A ring tubular flow path heated by a high frequency electromagnetic induction heating means that is continuous or independent of the heating means is provided to melt the raw resin, and this molten resin is intermittently injected into the cavity through the gate and the ring tubular flow path. An electromagnetic induction heating injection molding method, characterized in that the method comprises the steps of: 5. The high-frequency electromagnetic induction heating means operates at least in the gate process intermittently during each molding operation to soften and melt a small amount of solidified raw material resin that mainly accumulates in the gate area. 5. The electromagnetic induction heating injection molding method according to claim 4, wherein the molding member is opened to enable injection. 6. The raw resin to be melted by a desired injection mechanism consisting of a raw material supply mechanism for supplying the desired raw material resin in a fixed amount, a plasticizing mechanism, a manifold mechanism having one or more divided flow paths, and a runner mechanism leading to the gate. In an injection molding device that is capable of injecting into a cavity via Electromagnetic induction heating characterized by having an annular tubular flow path formed by arranging inclusions such as children, and a high frequency electromagnetic induction heating mechanism disposed in a mechanism along the annular tubular flow path. Injection molding equipment. 7. Electromagnetic induction heating injection according to claim 6, characterized in that the high frequency electromagnetic induction heating mechanism disposed at least in the runner mechanism is configured to control opening and closing of electric circuits in connection with the injection molding operation. Molding equipment. 8. The high-frequency electromagnetic induction heating mechanism installed in the runner mechanism is divided into a high-frequency electromagnetic induction heating mechanism for the gate that can locally heat the gate and a mechanism that can heat the annular tubular flow path of the runner mechanism. 7. The electromagnetic induction heating injection molding apparatus according to claim 6, wherein the electromagnetic induction heating mechanism is configured to control opening and closing of an electric circuit in conjunction with an injection molding operation.