JP2006231604A - Molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly suppress the positional shift of a component in the case of the insert molding of the component without using a fixing pin or the like. <P>SOLUTION: When the component 2 arranged in the cavity of a mold 1 is subjected to insert molding using a resin, the component 2 is positioned by the guide 3 provided to a predetermined molding surface 1a and a resin is injected so as to apply the force caused by the flow resin to the component 2 in the direction going toward the molding surface 1a provided with the guide 3. Specifically, the surface, which is opposed to the molding surface 1a provided with the guide 3, is set to a basis h<SB>0</SB>in a height direction to inject the resin from the position not less than the height of the center of gravity of the component 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molding method in which various parts are insert-molded in a resin, and more particularly, to a technique for preventing positional displacement of the parts.

  In the field of resin molded products, insert molding of electronic components and mechanical components is widely performed, and by incorporating these components integrally, various functions can be added to the resin molded products. Here, insert molding requires only placing the parts in the mold and injecting the resin, making it possible to easily produce resin molded products that integrate electronic parts and mechanical parts, reducing man-hours. This is an effective method for reducing costs.

  In recent years, with the progress of miniaturization of electronic devices and the like, miniaturization is required for components incorporated in the device, and the resin molded product is no exception. In order to reduce the size of the resin molded product, it is necessary to reduce the resin thickness of the molded product as much as possible. In the molding, first, ensuring the strength is an issue.

From such a situation, for example, an attempt has been made to ensure the strength of the resin molded product by adding a filler to the resin (see Patent Document 1). Patent Document 1 relates to molding of a lens holder. The lens holder is molded with a resin containing filler having shape anisotropy, and the filler is oriented in the axial direction of the central axis. Thereby, it is said that it is possible to provide a lens holder which is excellent in dimensional accuracy and is thin and light but has high mechanical rigidity.
JP-A-6-27360

  By the way, in the insert molding, the problem of component misalignment remains as a major problem. Since the viscosity of the resin at the time of insert molding is high, a large force is applied to the insert part due to the flow of the resin, and as a result, the displacement often occurs. Usually, in order to prevent displacement of the insert part, for example, a guide is provided on the mold, and the insert part is arranged here to perform molding, but the guide that simply supports one side of the insert part is arranged. Then, as a result of applying stress due to the viscosity of the resin to the insert part, the insert part is lifted from the guide and is likely to be displaced.

  Therefore, in order to reliably prevent displacement of the insert part, it is not sufficient to provide the guide. For example, a fixing pin is inserted from the outside, and the insert part is sandwiched between the fixing pin and the guide and fixed. In order to prevent the resin from being lifted by the force caused by the flow of the resin, measures such as preventing positional displacement have been made.

  However, when fixing the insert part by inserting a fixing pin from the outside, very high pressure is applied to the inside of the mold, and it is necessary to devise measures that do not hinder the flow of the resin so that the resin is evenly filled Therefore, the implementation is accompanied with great difficulty.

  For example, when the insert part is fixed with the tip of the fixing pin, it is necessary to apply a large force against the pressure applied to the inside of the mold. However, since the insert part has a certain amount of dimensions, excessive force is required. However, there is a problem that the insert part is damaged by being added to the insert part, or that a sufficient force is not applied to the insert part and the position is shifted as a result.

  In particular, in resin molded products using magnets such as rare earth metal magnets as insert parts, they are often used for sensors and actuators using their characteristics, and the positional deviation of the magnets as insert parts causes variations in magnetic characteristics, As a result, there is a big problem that it causes variations in characteristics of applied products.

  Alternatively, when the insert part is lifted, a problem of degassing in the case of using a thermosetting resin becomes a problem. When a thermosetting resin is used, a reaction gas is generated as the resin hardens. Normally, this reaction gas is used along the guides or the like, for example, using a micro space between the insert part and the mold. Escaped to the outside. Here, when the insert part is lifted, a film is formed by the encircling resin, and a minute space along the guide is closed by the film. As a result, it becomes impossible to degas the reaction gas, resulting in problems such as dissociation between the resin and the insert parts, or gas accumulation and deformation of the resin. Further, when the insert part is misaligned and the resin enters the resulting gap or the like, the inserted resin becomes a burr. When the burr is generated, the electric circuit and the mechanical sliding portion may not operate. Also, when burrs occur in other parts, they may fall off during use of the product and adhere to the electric circuit or sliding part. Therefore, for example, burrs must be removed by post-processing, which is complicated in the process.

  Furthermore, when fixing an insert part by inserting a fixing pin from the outside, an opening (hole) is formed in the resin portion after the fixing pin is pulled out, which may cause a decrease in strength. In particular, after molding, stress is suddenly released at the opening, and cracks and the like are likely to occur. When these cracks occur, they cannot be provided as a product, and therefore, a decrease in yield due to the occurrence of defective products becomes a major problem.

  The present invention has been proposed in view of such a conventional situation. That is, an object of the present invention is to provide a molding method capable of reliably preventing the displacement of a component without necessarily using a fixing pin inserted from the outside when the component is insert-molded. It is another object of the present invention to provide a molding method that can eliminate a decrease in strength caused by inserting a fixing pin into a mold and that can also achieve smooth gas venting.

  The present inventor has intensively studied for a long time to achieve the above object. As a result, when insert molding a part, it came to the conclusion that the position shift of a part can be avoided without necessarily using a fixing pin by pressing down a part using the flow of resin.

  The present invention has been devised based on such knowledge, and when the parts placed in the cavity of the mold are insert-molded with resin, the parts are provided by a guide provided on a predetermined mold surface. In addition, the resin is injected so that a force due to the flow of the resin is applied to the mold surface on which the guide is provided with respect to the component.

  In the present invention, a component to be inserted is pressed against a guide provided on a predetermined mold surface by utilizing the force of resin flow. Therefore, even if a fixing pin or the like is not inserted from the outside, the positioning state of the component is maintained by the guide, and the occurrence of the positional deviation due to floating or the like is eliminated. At this time, even if there is a dimensional variation in the parts, a certain force is applied to the parts due to the flow of the resin. For example, the parts may be damaged due to excessive force or the parts may be lifted due to excessive force. There is no.

  In addition, since the lift of the component is surely suppressed, the minute space for degassing is not blocked by the wraparound of the resin, and the resin and the component are not dissociated by the reaction gas or the resin is not deformed. . Furthermore, since it is not always necessary to insert the fixing pin, the formation of the opening of the resin molded product to be molded is minimized, and the occurrence of cracks is suppressed. The present invention does not exclude the case where the fixing pin is inserted. For example, in the case where the fixing pin is used to the extent that the flow of the resin is not disturbed or cracks are generated, By applying the present invention in combination, the floating and misalignment of the parts are more effectively eliminated, and a stable molding state is realized.

  According to the present invention, when a part is insert-molded, the positional deviation of the part can be surely eliminated without necessarily using a fixing pin inserted from the outside, and variation in the part arrangement in the resin molded product can be suppressed. it can. Further, according to the present invention, for example, burrs generated around the fixed pin can be prevented, and a post-process for removing the burrs is not necessary. Furthermore, according to the present invention, it is possible to suppress the dissociation of the resin and parts, the deformation of the resin, the occurrence of cracks, and the like, and the generation of defective products can be suppressed and the yield can be improved.

  Hereinafter, a molding method to which the present invention is applied will be described in detail with reference to the drawings.

  Actual resin molded products have various shapes and various arrangements of components, but in this embodiment, the basic concept will be described using the simplest model.

  First, FIG. 1 shows an example of insert molding when the component 2 is arranged in the cavity of a mold 1 having a substantially rectangular parallelepiped shape. In the case of this example, a plurality of guides 3 are provided on the bottom surface 1a of the mold 1, and the guides 3 position the component 2 in the in-plane direction on the bottom surface 1a.

  In this example, the guides 3 are provided at four locations corresponding to the four corners of the component 2, and each guide 3 is a rising wall 3 a that supports the peripheral surface of the component 2, for example, as shown in FIG. 2. And a mounting surface 3 b that supports the bottom surface of the component 2. Accordingly, the inserted component 2 is positioned in the height direction by the mounting surface 3b of the guide 3, and the movement in the in-plane direction is restricted by the rising wall 3a.

  However, since the component 2 is only placed on the placement surface 3b of the guide 3, it can move upward. Therefore, there is a concern about the position shift due to the floating of the component 2. In addition, as described above, particularly when a thermosetting resin is used, a reaction gas is generated along with the curing. Usually, this reaction gas uses a minute space between the insert part and the mold, For example, it escapes to the outside along the guide or the like. Here, when the insert part is lifted, a film is formed by the encircling resin, and a minute space along the guide is closed by the film. As a result, it becomes impossible to degas the reaction gas, resulting in problems such as dissociation between the resin and the insert parts, or gas accumulation and deformation of the resin. Therefore, in the present invention, the component 2 is prevented from being lifted by utilizing the flow of resin.

  Specifically, in the mold 1, a gate 4 is provided at a position higher than the part 2, and the resin is injected therefrom. As described above, when the resin is injected from the gate 4 provided at a position higher than the part 2, the flow of the resin becomes a so-called down flow, and as shown by an arrow in FIG. . In addition, a part of the resin flow passes over the component 2.

  Due to such resin flow, a force in the direction indicated by the arrow F is applied to the component 2, and as a result, the component 2 is placed on the mold surface 1 a on which the guide 3 of the mold 1 is formed, that is, the placement of the guide 3. It will be pressed toward the surface 3b. Therefore, the component 2 does not float when the resin is injected, the positioning state by the guide 3 is maintained, and the component 2 can be molded without any positional deviation.

In this case, the height of the resin injection port (gate 4) with respect to the component 2 is important. Specifically, first, the bottom surface 2a of the component 2 whose height is determined by the mounting surface 3b of the guide 3 is used as a reference. The bottom surface 2a is a surface facing mold surface which has guide 3 provided with (bottom 1a), in the height direction, the bottom surface 2a based h _0, position the height of the upper surface 2b of the part 2 h It turns out that. In addition, the height direction said here is not restricted to a perpendicular direction. For example, as shown in FIG. 3A, when the guide 3 is provided on the bottom surface 1a of the mold 1 and the component 2 is placed thereon, the vertical direction becomes the height direction. ), When the guide 3 is provided on the side surface 1b of the mold 1, the horizontal direction (in this case, the left direction) is the height direction, which is shown in FIG. 3 (c). As described above, when the guide 3 is provided on the upper surface 1c of the mold 1, the direction in which it hangs down is the height direction.

In the present invention, the bottom surface 2a based h _0, it is necessary to provide the gate 4 at a position higher than the height of the center of gravity of the part 2. When the component 2 has a vertically symmetrical shape, it is necessary to provide the gate 4 at a position higher than ½ of the height h. If the gate 4 is provided at a position lower than this, the flow of the resin rises with respect to the component 2 and the possibility of the component 2 being lifted increases. Preferably, the gate 4 is provided at a position higher than the height h of the component 2.

  Further, when the cavity, which is a space in which the component 2 is arranged, is composed of a plurality of cavities at least partially partitioned by a partition wall, the mold surface in which the guide 3 is provided for the component 2 in all the cavities It is necessary to inject the resin so that a force due to the flow of the resin is applied toward 1a.

  FIG. 4 shows an example in which the component 2 is placed in each of a plurality (two) of cavities C1 and C2 partitioned by a partition wall, and molding is performed by injecting resin. As shown in FIG. 4A, when the cavities C1 and C2 communicate with each other at the lower position, when resin is injected from the gate 4 provided in one of the cavities C1, the component 2 disposed in the cavity C1. Is applied with a downward force F1 due to the flow of the resin. Therefore, the component 2 is pressed against the guide 3 side, and no positional deviation occurs. On the other hand, in the cavity C2, the resin is injected from the communicating portion, that is, from below the cavity C2, and the flow of the resin is directed from the bottom to the top. As a result, a force F2 is applied in the direction of lifting with respect to the component 2, and there is a high possibility of causing a positional shift.

  In order to solve this problem, for example, as shown in FIG. 4B, gates 4 may be provided in both cavities C1 and C2, and resin may be injected therefrom. In this case, the resin flows down in the cavities C1 and C2, and downward forces F1 and F2 are applied.

  Alternatively, as shown in FIG. 4C, the resin flow from the cavity C1 toward the cavity C2 may be once guided upward, and the resin may be introduced into the cavity C2 from here. In this case as well, the resin flows down in the cavities C1 and C2, and downward forces F1 and F2 are applied.

  The above is the basic idea regarding the flow of the resin in the molding method of the present invention. In addition to this, for example, the substantially longitudinal direction of the component 2 is formed so that the resin flow is formed along the longitudinal direction of the component 2, for example. It is preferable to inject the resin. When the resin is injected from the substantially longitudinal direction, the parts are not easily tilted, which is effective from the viewpoint of preventing misalignment, and further, an effect of preventing cracks can be obtained. This is due to the following reasons.

For example, when the component 2 is insert-molded, the resin thickness of the portion formed along the longitudinal direction of the component 2 may be thin in the molded resin molded product. FIG. 5 shows a typical shape example of the resin molded product when the component 2 is arranged in the mold 1. This resin molded product has resin parts A, B, C, and D corresponding to the four sides of the part 2, and the thicknesses of the resin parts A, B, C, and D are t ₁ , t _{2, respectively.} , T ₃ , t ₄ . Then, t ₁ , t ₂ , t ₃ > t ₄ , and the portion with the smallest resin thickness is defined as a resin portion D. Therefore, the resin part D has the weakest strength in the molded resin product to be molded.

  When a resin molded product having such a shape is molded, for example, as shown in FIG. 6A, when resin is injected from the resin portion C side, the flow of the resin is as indicated by arrows in the figure. That is, the flow of resin injected into the mold cavity 1 from the resin part C side is blocked by the component 2 and moves while avoiding the component 2. And about the resin part D, after flowing around the resin part A and the resin part B, the flow of resin arrives. At this time, in the resin part D, the flow of the resin divided by the component 2 joins, and as a result, a so-called weld is caused at the position indicated by w in the figure. The weld causes a significant decrease in strength, and if this occurs in the resin portion D having the weakest strength, it leads to the occurrence of cracks in this portion and remarkably deteriorates the reliability.

  On the other hand, as shown in FIG. 6B, when the resin is injected from the resin portion A side, the flow of the resin is also divided along the component 2 by the component 2, and the end of the component 2, in this case, the resin portion B Join at. Accordingly, weld occurs in the resin part B, but the resin part B is thick in resin, and even if the weld occurs, the influence of the strength reduction is slight, and no cracks are caused due to this. Further, regarding the resin portion D having the thinnest resin, a flow of the resin that moves while avoiding the component 2 is formed in this portion, and the weld does not become a joint of the resin flow. There is no. Therefore, the strength does not decrease in the resin part D, which is the most problematic in terms of strength, and the occurrence of cracks can be suppressed.

  As described above, the flow of the resin around the component 2 varies depending on the resin injection direction. Accordingly, when molding the resin molded product, as shown in FIG. 6B, the resin flow is formed in parallel along the resin portion D having the smallest thickness of the resin and causing a problem in strength. That is, it is preferable to inject the resin from the resin part A side (or the resin part B side).

  In addition, when a fibrous filler is added to the resin in order to improve the strength of the resin molded product, or when a rare earth metal magnet having a negative coefficient of thermal expansion is used for the component 2, the resin is changed accordingly. It is preferable to consider the injection direction.

  For example, when molding the resin molded product, it is necessary to insert-mold the component 2, but when the component 2 is insert-molded in this way, it is necessary to consider the difference in the thermal expansion coefficient between the component 2 and the resin. is there. Since the component 2 and the resin to be incorporated usually have different coefficients of thermal expansion, cracks are likely to occur after integral molding. In particular, when the component 2 is a rare earth metal magnet having anisotropy, the above tendency is remarkable. This is because the rare earth metal magnet has a negative thermal expansion coefficient in a direction orthogonal to the orientation direction. When insert molding a rare earth metal magnet, the resin surrounding the rare earth metal magnet shrinks during cooling after integral molding due to the thermal expansion coefficient, whereas the rare earth metal magnet surrounded by the resin expands. To do. As a result, a large stress is generated. Therefore, when the rare earth metal magnet is integrated with another substance such as a resin, it is susceptible to a stress generated when the temperature changes, and therefore, the rare earth metal magnet is liable to crack. Therefore, it is necessary to design the process in consideration thereof. Further, when resin molding is performed, gas may be generated. In this case, the generated gas may not be discharged to the outside due to wraparound of the resin or the like, and may accumulate at the interface between the resin and the magnet. In such a case, at the time of cooling, the resin contracts while the magnet expands, and the interface gas is crushed to generate a high internal pressure. Therefore, it is also necessary to design the process so that the gas can be quickly degassed. For these reasons, it is preferable to optimize the process in consideration of these matters when molding a resin molded product.

  As described above, when the component 2 is insert-molded, it is necessary to appropriately control the injection direction of the resin, thereby suppressing the displacement of the component, and further, the generation of burrs and cracks. It is possible to reliably suppress the occurrence of defects, suppress the occurrence of defective products, and greatly improve the yield of resin molded products.

  In the following, a resin molded product was actually molded to confirm the effect of the present invention.

Example 1
The shape of the resin molded product produced in the present example is shown in FIGS. This resin molded product 11 is obtained by insert molding two rare earth metal magnets 13 in a resin portion 12. The resin molded product 11 has a structure in which a resin portion 12 is roughly divided into two parts and these are connected in a casing shape, and one rare earth metal magnet 13 is inserted into each of the divided resin portions 12. Molded. The rare earth metal magnet 13 is positioned by a guide provided in the mold. Therefore, a guide hole 14 is formed in the resin portion 12 corresponding to the guide.

  The rare earth metal magnet 13 inserted into the resin molded product 11 has a size of 10 mm × 10 mm × 3 mm, and was produced by an ordinary powder metallurgy technique. The orientation direction in the rare earth metal magnet 13 is the thickness direction [vertical direction in FIG. The horizontal direction in FIG.7 (c). The surface was subjected to Ni plating. As the resin to be injected, a thermosetting phenol resin (novolak) filled with 40% by mass of a glass filler was used.

  The resin molded product was molded by injecting resin from the same direction as in the example shown in FIG. 1 and further in the examples shown in FIG. 4B and FIG. 6B. That is, in FIG. 7, two gates were provided on the left end side in the drawing corresponding to the two divided parts, and resin was injected from here (from the direction of arrow J). The position of each gate was set higher than the height of the rare earth metal magnet 13. As a result, a resin flow is formed so that a force is applied downward to the rare earth metal magnet 13, and the rare earth metal magnet 13 does not float from the guide. The number of produced resin molded products is 200.

  About each resin molded product, after resin solidified, it took out from the metal mold | die and performed aging at 180 degreeC for 3 hours. Thereafter, it was visually observed and evaluated whether or not the guide pin hole was blocked with the resin around. In other words, a case where no resin wraparound was observed in all the guide pin holes was regarded as a non-defective product, and if there was even one guide pin hole blocked by the resin, it was interpreted as a positional deviation and was regarded as a defective product. The number of resin molded products in which positional deviation occurred was divided by the number of molded products (200), and the defective product occurrence rate was determined and evaluated. As a result, in this example, a resin molded product causing a positional shift was not recognized, and a very good result was obtained. (Defect occurrence rate 0%)

Example 2
A resin molded product was produced in the same manner as in Example 1. However, a thermosetting phenol resin (resole) was used as the resin. When the same evaluation as in Example 1 was performed, the occurrence rate of positional deviation was 0%, which was a favorable result.

Comparative Example A resin molded product similar to that in Example 1 was molded, but the resin injection direction was the same as in FIG. That is, in FIG. 7, one gate was provided at the center position on the upper end side in the figure so as to face the rare earth metal magnet 13, and resin was injected from here (from the direction of arrow H). In this case, the resin flow is the same as in FIG. In this case, the occurrence rate of misalignment was 97%, which was a significantly large value compared to the example. The positional deviation occurred in all of the magnets on the resin part 12A side without a gate opening.

It is a schematic diagram which shows the flow of the resin at the time of providing a gate above. It is a principal part schematic perspective view which shows the example of a shape of the guide provided in the metal mold | die. It is a schematic diagram which shows the reference plane and height of components, (a) is the case where a guide is provided on the bottom surface of the mold, and (c) is the case where the guide is provided on the side surface of the die. In the case (c), the guide is provided on the upper surface of the mold and the parts are arranged. It is a schematic diagram which shows the example of the flow of the resin at the time of arrange | positioning components in a some cavity, (a) is a case where resin is inject | poured from one cavity with respect to the cavity connected below, (b) Is the case where resin is injected from both cavities, and (c) is the case where the resin injected from one cavity is guided above the other cavity. It is a top view which shows the example of arrangement | positioning of components in a metal mold | die cavity. (A) is a schematic diagram showing the flow of resin when the resin is injected from the direction orthogonal to the longitudinal direction of the component, and (b) is the resin flow when the resin is injected from the direction parallel to the longitudinal direction of the component. It is a schematic diagram which shows a flow. The shape of the resin molded product produced in the Example is shown, (a) is a plan view, (b) is a side view, and (c) is a front view.

Explanation of symbols

1 Mold, 1a Mold surface, 2 parts, 3 guide, 3a rising wall, 3b mounting surface, 4 gate, 11 resin molded product, 12 resin part, 13 rare earth metal magnet, 14 guide hole

Claims (7)

When insert-molding parts placed in the mold cavity with resin,
Positioning the part with a guide provided on a predetermined mold surface, and injecting resin so that a force by the flow of the resin is applied to the part toward the mold surface provided with the guide A characteristic molding method.   The molding method according to claim 1, wherein the resin is injected from a position equal to or higher than the height of the center of gravity of the part, with a surface facing the mold surface provided with the guide as a reference in the height direction.   The molding method according to claim 2, wherein the resin is injected from a position higher than the height of the component. The mold has a plurality of cavities at least partially partitioned by a partition wall, and each component is disposed in each cavity,
4. The resin is injected into all the cavities so that a force due to the flow of the resin is applied toward the mold surface on which the guide is provided for the component. 5. The forming method as described.   The molding method according to claim 1, wherein the component has shape anisotropy, and a resin is injected from a substantially longitudinal direction of the component.   The molding method according to claim 1, wherein the component is a rare earth metal magnet.   The molding method according to claim 1, wherein the resin is a thermosetting resin.

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