JP3214090B2 - Polymer material molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding apparatus for polymer materials, and more particularly to a new proposal relating to a molding apparatus having a conductor winding inside using a thermosetting resin such as an epoxy resin. .

[0002]

2. Description of the Related Art Generally, when a polymer material undergoes a curing reaction to change from a liquid state to a solid state, it involves volume shrinkage. For this reason, even if a polymer material in a fluid state is injected into a mold and an attempt is made to mold the same shape as the mold cavity, local shrinkage and other defects are generated due to the volume shrinkage accompanying the curing reaction. May accompany. The occurrence of this kind of defect becomes particularly remarkable when the reactivity of the resin is increased and the molding is performed in a short time.

In order to prevent the occurrence of these defects, various means have been devised to control the curing of the polymer material and to compensate for the above-mentioned volume shrinkage. As an example of these, Japanese Patent Publication No.
And -31904. This is because, while setting the mold temperature higher than the resin temperature and pressing the resin from the injection port, the curing reaction proceeds from the portion farther from the injection port toward the injection port, and the curing that occurs at that time The shrinkage is dealt with by pushing the liquid resin from the injection port side.

[0004]

However, even when the thickness of the molded product is considerably different, the above-mentioned defect cannot be prevented even by such a method. This is because when the thermosetting resin is cured, it contracts in volume and emits curing reaction heat. This is because, when the resin thickness is considerably different, the principle of the progress of the curing reaction as described above is broken due to the rise in the resin temperature due to the reaction heat, and the resin cannot be supplied from the injection port side. When resin supply becomes impossible,
The hardened volume shrinkage of the remaining portion is concentrated in a local area solidified at the end of the portion, and becomes a defect. This phenomenon becomes more serious as the curing proceeds in a shorter time, and is an obstacle to mass production.

[0005] Further, even when a mold has a dangling conductor inside a mold such as a molded coil, a defect often occurs. This is due to the fact that there are few portions where the conductor is in contact with the mold and the supply of heat from the mold to the conductor is poor. If the preheating temperature of the coil conductor is low, or if the temperature once drops after contacting with a resin having a low temperature at the time of injection, it is difficult to quickly increase the conductor temperature even if the temperature of the mold is controlled thereafter. In this case, the curing reaction in the vicinity of the conductor is delayed, and the volume shrinkage of the cured body is the last in the vicinity of the conductor, so that the defect occurs inside the vicinity including the coil conductor, and there is a concern that this is particularly harmful in terms of insulation. .

As a method of preventing such a defect, there is a method of energizing a conductor (Japanese Patent Application Laid-Open No. 3-190155). In this method, the coil conductor must be completely insulated from the mold. There is a drawback that the device becomes complicated, for example, the device and its control device are required.

An object of the present invention is to prevent the occurrence of defects in a molded product in short-time molding, which is a drawback of the prior art, by improving a simpler apparatus.

[0008]

In the present invention, attention is paid to the fact that the generation of defects in the prior art is due to local concentration of volumetric shrinkage due to the curing reaction of the resin, I tried to solve it by dispersing it. As a means for achieving this, in the present invention, a thin plate that has appropriate rigidity and is capable of deforming in a necessary place of the mold (a place where the above-mentioned defect is expected to occur such as a large change in wall thickness) is airtightly sealed. In addition to mounting, a means is provided for controlling the deformation of the thermosetting resin in accordance with the progress of the curing reaction.

[0009]

In this case, since the volume shrinkage of the resin is uniformly dispersed in a controlled shape over a wide range, the resin does not become a defect in the molded product.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1 is an embodiment of the present invention for a molded product including a coil conductor.

The mold 1 is divided into three parts as shown in the figure, between which a thin plate 4 having a moderate rigidity and being deformable, which is a main element of the present invention, is installed. In the cavity of the mold, the coil conductor 2 is disposed at substantially the center of the cavity via an appropriate insulating spacer (not shown). The coil conductor is usually formed by coating a copper or aluminum wire with an insulating layer or winding a predetermined number of times while interposing an interlayer insulating layer. The space between the mold and the thin plate is hermetically sealed by an O-ring 5.

In the figure, an O-ring on the mold cavity side of a thin plate is a hermetic seal for preventing leakage of resin and reducing the pressure inside the mold as required. The O-ring on the opposite side prevents leakage of gas or liquid when controlling deformation of the thin plate 4 by applying pressure from the pressurizing port 6 using gas or liquid, as described later. This leak prevention is replaced with an O-ring.
As shown in FIG. 2, a thin plate may be directly welded to a mold to maintain airtightness.

In this case, it is not necessary to divide the mold into three parts as shown in FIG. In the molding of the thermosetting resin, an appropriate temperature is controlled by means such as providing a heating means such as a heater directly in the mold or putting the entire mold in a heating furnace, but in this embodiment,
The heating means is not shown in the drawings including FIG. After setting the mold and the coil conductor as described above and raising the temperature to a predetermined temperature, the mold cavity in which the coil conductor is installed is filled with a mold resin. As a molding resin, an epoxy resin is usually mixed with inorganic powder such as quartz powder, alumina powder, calcium carbonate powder, etc. for the purpose of improving thermal conductivity, reducing thermal expansion coefficient and curing shrinkage rate, and further reducing cost. The combined one is used. Then, at the stage where volume shrinkage occurs due to the curing reaction of the resin,
By detecting this, the pressure from the pressurizing port is changed (normally, the pressing force is gradually increased) to control the thin plate. By controlling the thin plate to be pushed into the mold cavity in accordance with the volume shrinkage of the resin in this way, the resin thickness on the outer surface is slightly reduced as shown in FIG.
Is exaggerated for the sake of clarity). Since the curing shrinkage of a normal epoxy resin alone is about 2% or less, the volume shrinkage of the mold resin containing about 50% by volume of the inorganic powder is about 1%.
Therefore, even if there is no resin replenishment from other parts, the reduction of the resin thickness by pushing the thin plate is only about 1% of the actual resin thickness. Further, since the thin plate has appropriate rigidity, its deformation does not concentrate locally. For example, for an insulating layer thickness of 10 mm,
This is a smooth decrease of about 0.1 mm, and in many cases, there is no problem.

FIGS. 4 and 5 show embodiments in which the present invention is applied to a race track coil and a circular coil having a thick resin portion, respectively. The present invention may be applied to the entire area where the coil conductor exists, or may be applied to a portion where a defect is expected to occur as shown in FIGS.
FIG. 4 shows an example in which the present invention is applied to a lower part of a coil which is farthest from the resin injection port 14 and in which resin supply is difficult to be performed.

FIG. 5 shows an example in which the present invention is applied to a coil leg having an extremely thick resin layer. Each is a cross-sectional view when the coil conductor is viewed from the front, and the cross-sectional structure in which the coil conductor is sliced is substantially the same as FIG. 1 or FIG. The thin plate 4 is pushed in a direction perpendicular to the plane of the drawing.

The method of controlling the pressure from the outside of the thin plate in accordance with the progress of the curing shrinkage of the resin has been described so far. However, the dimensions of the thin plate are properly selected and the atmospheric pressure is applied to the outside of the thin plate. In this case, substantially the same effects as described above can be obtained without particularly controlling the pressure.

For example, in FIG. 4, the thickness of the thin plate is d, the length in the lateral direction is a, the width of the deformable portion is b, the Young's modulus of the thin plate is E, and the external pressure applied to the thin plate is p. Assuming that the pressure inside the cavity is reduced, the maximum deflection δmax of the thin plate can be expressed by the following equation (such as a mechanical engineering handbook).

[0018]

(Equation 1)

Β is a constant determined by the length / width ratio a / b and the material of the thin plate. Thin plate is steel plate, a is 500mm, b is 1
FIG. 6 shows the relationship between the thickness of the thin plate calculated with 00 mm and p as the atmospheric pressure and the maximum deflection δmax. From the figure, set the plate thickness to 1.
If it is selected to be about 5 mm, if the inside of the cavity is decompressed, it will be deformed to about 0.4 mm according to its size.
If a thin plate manufactured under such conditions is used, the control of the progress of the curing reaction described in the section of the prior art is lost, and even if the resin cannot be supplied to the lower part of the coil from the injection port side, the following operation is performed. The generation of defects can be suppressed. That is, if the volume of the resin shrinks in a state where the resin is not supplied, the inside of the cavity is decompressed, and the thin plate is drawn into the cavity correspondingly, so that the deformation of the thin plate described with reference to FIG. 1 occurs. In this case as well, the volume shrinkage is dispersed over a wide range and the thickness of the insulating layer is slightly reduced, so that it does not become a defect. It is better that the thickness of the thin plate in an actual case is selected to be thinner than the above value so that it can follow a small pressure change caused by volume shrinkage. When designed thinly, in Fig. 6,
Although it appears that excessive deformation occurs, the resin is actually full, and only deformation due to curing shrinkage occurs.
However, if the thickness of the plate is made too thin, the rigidity of the thin plate becomes insufficient, and the deformation of the plate follows the local change in the volume of the resin. Will be lost. It is necessary to appropriately select the thickness and material of the thin plate in consideration of the dimensions of the thin plate portion, the insulating thickness of the portion, the resin volume of the portion where it is considered difficult to supply the resin, the curing shrinkage of the resin, and the like.

In FIG. 5, the same principle can be applied to the case where the resin is not sufficiently supplied from the injection port side to the thick portion only by slightly deforming the surface layer by deformation of the thin plate. No defects occur.
The degree of deformation of the plate in this case can be calculated by the following equation.

[0021]

(Equation 2)

However,

[0023]

(Equation 3)

In the above equation, R is the radius of the deformable portion of the thin plate, and ν is the Poisson's ratio of the thin plate. Other symbols are
This is the same symbol as (1). Referring to these results, FIG.
An appropriate thin plate thickness may be selected in the same procedure as described above.

Next, the means for monitoring the curing process of the resin will be specifically described with reference to FIGS. These figures are intended for circular or oval coils, and the coil conductors and resin in the figures are connected at portions not shown. Illustration of sealing means such as an O-ring is omitted. FIG. 7 shows a method of measuring and utilizing a change in the dielectric properties of the resin itself as a monitor of the curing process. When a coil conductor is provided as shown in FIG. 7, the dielectric properties can be measured using the coil conductor 2 as one electrode and the mold as another electrode. In that case, an insulating layer 21 for insulating the lead terminal 14 and the mold 2 is required in the terminal portion. The dielectric properties are guided to a measuring device 24 through coil conductors and leads 22 and 23 from the mold. The dielectric properties for monitoring the curing of the resin include insulation resistance Z, dielectric loss tan δ, capacitance C, and the like. Changes in the insulation resistance and tan δ during the curing reaction are shown in FIG.
Shown in FIG. 9 shows the rate of change with respect to the initial value. The peak of tan δ almost coincides with the point of gelation of the resin (change from liquid to solid). In the change of insulation resistance,
Significant changes of several orders of magnitude can be seen. Since these characteristics differ depending on the resin used, it is possible to monitor the curing of the resin by grasping the characteristics peculiar to them in advance and comparing them. These processes can be easily performed recently using a personal computer or the like.

FIG. 8 shows an index of the resin curing monitor.
This is an example in the case where deformation and temperature of a thin plate are used. In the drawing, the cavity between the thin plate and the outer mold is drawn large for the purpose of making the drawing easy to see, and a large space is not necessarily required as long as the sensor can be mounted. The deformation of the thin plate can be easily measured by attaching a strain gauge 31 to the opposite side of the resin of the thin plate as shown in FIG. Further, it is desirable that the thermocouple 33 for measuring the temperature be attached to a portion that better reflects the change in the resin temperature.
Attaching to a thin plate as shown in the figure is one powerful method. FIG. 9 shows the deformation of the thin plate and the change in temperature during the resin curing process. As described above, the change in the strain of the thin plate is caused by the fact that the inside is decompressed when the cured volume shrinkage of the resin cannot be compensated for. The change in temperature is caused by the heat of curing reaction of the resin. In FIG. 9, the time when the deformation of the thin plate is almost eliminated and the time when the temperature shows a peak substantially correspond to the gelation time of the resin. As in the case of the dielectric properties, by measuring these properties while comparing them with properties grasped in advance, it is possible to monitor the progress of resin curing. Based on such information from the resin curing progress monitoring means, the deformation of the thin plate may be controlled accordingly. For example, when a pressure is applied to the thin plate from the time when the deformation of the thin plate is observed, a molded product having no defects can be obtained.

In the above embodiment, the pressure applied to the thin plate is applied from the time when the curing shrinkage starts.
After the resin fills the cavity, the resin injection port may be sealed and pressurized from the beginning.

Further, if the present invention is used in combination with the means for applying pressure to the resin in the mold cavity as described in the prior art, it is possible to achieve more rapid curing. FIG. 10 is an embodiment for such an example. The mold and the target coils in the figures have almost the same configuration as those shown in FIGS. However, with respect to the attachment of the thin plate 4, an example of the method of welding to the mold of FIG. 2 has been described. The thin plate 4 is also partially divided and attached. Each thin plate 4 is provided with a strain gauge 31 for monitoring deformation. A decompression port 41 for depressurizing a cavity in the mold is provided at the upper part of the mold, and is connected to a vacuum pump 43 via a valve 53. However, these are not necessarily required except for high-voltage equipment that does not allow the generation of small defects inside the resin. In that case, a means for preventing the resin filled from below from overflowing may be taken. After mixing the epoxy resin and the inorganic powder, the mold resin that has been well kneaded and defoamed is poured into the pressure tank 42. The pressure supplied from the pressure device 44 via the valve 50 is applied to the pressure tank. An injection port is provided at the lower part of the mold, and is connected to a pressurized tank by piping. In the vicinity of the pressure reducing port 41 and the injection port, a means (not shown) for separating the mold and the pipe after the resin is cured is provided. Further, the respective pressurizing ports 6 are collectively connected via a valve 52 which can be remotely controlled by sending a control signal,
The pressurizing device 4 is further connected via a remotely controllable valve 51.
Connected to 4.

The signals of the respective strain gauges provided on the thin plate 4 are led to the measurement control device 45 by the lead wires 32. The measurement control device 45 also includes a device that returns a signal of the strain gauge to a strain. It is also desirable that each valve other than 52 has a structure that can be remotely operated by a control signal from the measurement control device. 55 is a signal lead wire for that purpose.

In such a configuration, after the mold temperature is maintained at a predetermined temperature by a heating means (not shown), the resin is cured in the following procedure.

The valve 53 provided at the pressure reducing port is opened, and the inside of the mold cavity in which the coil conductor 2 is set is reduced in pressure by the vacuum pump 43. In this case, since atmospheric pressure is applied to the thin plate from the outside and deformation occurs before resin injection, the valves 52 and 54 are opened (the valve 51 is closed) and the outside of the thin plate needs to be maintained at the same pressure as the inside of the mold cavity. There is.

The resin is filled into the mold cavity by opening the valve 50 and applying an appropriate pressure to the resin in the pressurized tank.

When the resin is filled in the mold, the valve 53 is closed, and the pressure applied to the pressurized tank is increased to apply pressure to the resin in the mold. The same pressure as the pressurized tank is applied to the outside of the thin plate.

In this state, while monitoring the strain of the strain gauge, the curing was advanced and if the strain fluctuation shown in FIG. 9 was recognized, the pressure outside the thin plate was further increased to make it impossible to supply from the inlet. Deformation of a thin plate due to hardening shrinkage
(Push inside) to supplement. : After a predetermined period of time when the mechanical strength of the resin becomes the strength required for dismantling the mold, the pressure is released and the mold is dismantled to complete the molding.

In principle, the pressure adjustment in these moldings can be manually performed by a valve. However, when the structure shown in FIG. 10 is employed, extremely short and short molding is required. Such a configuration using computer control is indispensable. According to such a method, a product having no defect can be molded in an extremely short time.

The description so far has been based on the use of epoxy resin,
In addition, the case where a coil conductor is provided has been described as an example, but it goes without saying that the present invention can be applied even when another thermosetting resin is used or when no coil conductor is provided. Further, the concept of the present invention can be applied to molding of a thermoplastic resin.

[0037]

As described above, according to the present invention, molding without defects can be performed in a very short time, and mass production can be performed with a small number of devices.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the embodiment showing a sealing structure different from that of FIG. 1;

FIG. 3 is an explanatory view showing a deformed state of a thin plate of the present invention.

FIG. 4 is a longitudinal sectional view showing a specific application example of the present invention.

FIG. 5 is a longitudinal sectional view showing a specific application example of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between a plate thickness for determining a thickness of a thin plate described in the present invention and a maximum deflection amount.

FIG. 7 is a longitudinal sectional view showing a means for monitoring the progress of curing of a resin.

FIG. 8 is a longitudinal sectional view showing another example of a means for monitoring the progress of curing of a resin.

FIG. 9 is a characteristic diagram showing changes over time of various monitor quantities.

FIG. 10 is a system diagram showing another embodiment of the present invention in which a molding device and a control device are combined.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Die, 2 ... Coil conductor, 3 ... Mold resin, 4 ... Thin plate, 5 ... O-ring, 6 ... Pressing port, 7 ... Welded part, 13 ... Terminal part, 14 ... Terminal, 15 ... Injection port, 21 ... Terminal insulator,
22 and 23: measurement lead wire, 24: dielectric property measuring device, 31: strain gauge, 32: lead wire, 33: thermocouple, 40: injection port, 41: decompression port, 42: pressurized tank,
43: Vacuum pump, 44: Pressurizing device, 45: Measurement control device, 51 to 55: Valve, δmax: Dielectric loss, d: Thin plate thickness, Δ: Change amount, t: Elapsed time, Z: Insulation resistance, T ... Temperature, ε: strain of thin plate.

──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Hirokazu Takasaki 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. Hitachi, Ltd. Hitachi Plant (56) References JP-A-4-325211 (JP, A) JP-A-54-148055 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 39 / 02-39/12 B29C 39/22-39/44 B29C 33/20-33/28 B29C 33/38-33/42 B29C 43/02-43/20 B29C 43/36-43/58 B29C 45/70 B29D 11 / 00,17 / 00,31 / 00

Claims (1)

(57) [Claims] In a molding apparatus of a polymer material for flowing a flowable polymer material into a mold and performing reaction hardening, a deformable thin plate is hermetically attached to at least a part of a mold surface in contact with the polymer material. And a means for controlling deformation of a thin plate on a side not in contact with the polymer material.