JP2008252666A - Method of manufacturing helical antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a helical antenna that can be formed by a die of a simple structure, has excellent appearance, and reduces manufacturing cost. <P>SOLUTION: A helical coil 10 is attached to a primary cavity 21 of a die 20 for primary molding. A primary slide core 23 is inserted into the inner periphery of the tip of the helical coil 10 by a length determined by a prescribed ratio to the length of the helical coil 10 via a primary through hole 22 formed at the die 20 for primary molding. The primary cavity 21 is filled with resin. At the tip, a primary molding 30 having a recess 31 with a prescribed depth is formed. The primary molding 30 is attached to a secondary cavity 51 of a die 50 for secondary molding. A secondary slide core 55 is inserted into the recess 31 formed at the tip of the primary molding 30 via a secondary through hole 54 formed at the die 50 for secondary molding before the secondary cavity 51 is filled with resin to form a secondary molding 70. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a helical antenna by resin molding.

Conventionally, as a method for manufacturing a helical antenna, a method for manufacturing a helical antenna by resin molding is known.
In this type of helical antenna manufacturing method, resin molding is divided into two stages of primary molding and secondary molding. In the primary molding, a primary molded product is formed by integrally molding a helical coil and an insulating resin by insert molding. In manufacturing and secondary molding, there is a manufacturing method in which the outer periphery of the primary molded product is further covered with resin to produce a secondary molded product having the final antenna shape.

When performing the secondary molding, as a method of positioning the primary molded product in the mold for secondary molding, a plurality of projections are provided on the outer periphery of the primary molded product, and these projections are formed on the secondary molding die. A method of positioning (for example, refer to Patent Document 1) (hereinafter referred to as “Method 1”) while supporting the primary molded product by contacting the inner periphery of the cavity, or from the distal end to the proximal end. A hollow part extending in the axial direction is formed, and in the secondary molding, a support bar is inserted into the hollow part to the back and the primary molded product is supported by the support bar. A method of positioning a primary molded product while supporting it (see, for example, Patent Document 2) (hereinafter referred to as “Method 2”) is known.
JP 2004-179791 A JP-A-10-215116

However, in Method 1, it is necessary to mold a plurality of protrusions on the primary molded product, and there is a problem that a mold for temporary molding becomes complicated. In addition, when the resin molding is biased during the primary molding and a projection larger than expected is formed, a convex portion appears at a location corresponding to the projection during the secondary molding, and the appearance of the antenna is remarkably increased. There was a problem of being damaged.
In addition, since the secondary molded product manufactured by Method 2 has a hollow center and is weak against shearing force, a resin center rod is inserted into the hollow to reinforce the strength of the secondary molded product. There is a need to. For this reason, there has been a problem that the manufacturing cost is increased by the need to prepare the center bar.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a method for manufacturing a helical antenna that can be molded with a mold having a simple structure, has an excellent appearance, and has a low manufacturing cost. .

In order to achieve the above object, the present invention attaches a helical coil to a primary cavity of a primary molding die, and a primary molding slide core via a through-hole formed in the primary molding die. The helical coil is inserted into the inner periphery of the tip of the helical coil by a length determined at a predetermined ratio with respect to the length of the helical coil, the primary cavity is filled with resin, and the tip has a predetermined depth. A primary molded product having a recess is molded, the primary molded product is mounted in a secondary cavity of a secondary molding die, and a secondary molding slide core is formed through the secondary molding die. After inserting into the concave part formed in the front-end | tip part of the said primary molded product through a hole, the secondary cavity is filled with resin and a secondary molded product is shape | molded.
When a helical antenna is manufactured by this manufacturing method, a concave portion is formed at the tip of the primary molded product formed in the manufacturing process. During secondary molding, a slide core is inserted into the recess, and the primary molded product is supported by the slide core while the primary molded product is supported in the secondary molding die. It is not necessary to provide projections for the primary molding, the structure of the mold for primary molding can be simplified, and the convex antenna due to the projections does not appear during secondary molding, and the helical antenna has an excellent appearance. Can be manufactured. Moreover, since it is not necessary to insert a resin center rod into the secondary molded product, the cost can be reduced accordingly.

In this invention, the secondary molding slide core is energized, and the secondary cavity is filled with resin while the secondary molding is pressed in the axial direction to mold the secondary molding. May be.
According to this, the primary molded product can be firmly positioned and supported in the secondary cavity, and when the resin is injected into the secondary cavity during the secondary molding, the tension acting in the direction opposite to the molding pressure The displacement of the shape of the primary molded product is kept.

In the present invention, the primary molding slide core may be inserted into the inner circumference of the tip of the helical coil by a length of 3% to 5% of the free length of the helical coil.
When a helical antenna is manufactured by this manufacturing method, a hollow portion is hardly formed on the inner periphery of a primary molded product formed in the manufacturing process. Furthermore, when supporting in the secondary molding die, the secondary molding slide core can reliably support the primary molded product via the recess formed at the tip of the primary molded product.

In the present invention, a normal winding portion formed by winding a conductor at a predetermined pitch on the proximal end side of the helical coil is formed, and the normal winding portion is formed on the distal end side of the helical coil. Forming a tightly wound portion formed by winding a conductor at a pitch smaller than the pitch of the portion, and the primary molding slide core corresponding to the densely wound portion on the inner periphery of the tip of the helical coil May be inserted.
When a helical antenna is manufactured by this manufacturing method, the densely wound portion is formed at a location corresponding to the concave portion formed at the tip portion of the primary molded product formed in the manufacturing process. For this reason, a thin recessed part is reinforced by this tightly wound part, and the length of the primary molded product is not expanded or contracted by contraction of the resin during the primary molding, or is not deformed by an external force.

Further, in the present invention, the primary cavity is filled with resin via a primary molding inlet provided on the base end side or the tip end side of the primary molding die, and the base end of the secondary molding die The secondary cavity may be filled with resin through a secondary molding inlet provided on the side or the tip side.
In this case, during resin molding, the resin smoothly flows from the proximal end to the distal end in the mold cavity or from the distal end to the proximal end, and the primary molded product and the secondary molded product without warping or bending. The product can be molded.

In the present invention, the primary cavity and the secondary cavity may be filled with a resin having insulating properties and thermoplasticity.
According to this, a high performance helical antenna can be easily resin-molded.

  According to the present invention, it is not necessary to provide a protrusion on the primary molded product, so that the structure of the mold for primary molding can be simplified, and a convex portion due to the protrusion appears in the secondary molding. Therefore, a helical antenna with an excellent appearance can be manufactured. In addition, according to the present invention, it is not necessary to insert a resin center rod into the secondary molded product, so that the cost can be reduced accordingly.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a state in which a helical antenna 1 according to the present embodiment is attached to a roof 3 of an automobile 2. The helical antenna 1 is attached to the outside of an automobile and detects radio waves related to radio broadcasts and television broadcasts in a predetermined frequency band. A helical helical coil 10 (see FIG. 2) is provided inside the helical antenna 1, and the helical antenna 1 has a predetermined resonance frequency based on the overall length and pitch of the helical coil 10.

  As shown in FIG. 1, a helical antenna base 5 is attached to a roof 3 of an automobile 2 via a packing sheet 4, and a base end portion of the helical antenna 1 is vertically moved within a predetermined range on the helical antenna base 5. It is supported so that it can swing. Since the helical antenna 1 is attached to the roof 3 of the automobile 2, it receives various external forces such as air resistance during traveling, dust in the air, and wind and rain. At this time, the helical coil 10 is covered with a resin so that the shape of the helical coil 10 is deformed by the external force and the predetermined resonance frequency mounted on the helical antenna 1 is not changed accordingly. Thus, the shape is fixed, and the structure is not exposed to wind and rain or foreign matter.

Next, a method for manufacturing the helical antenna 1 according to this embodiment will be described.
The helical antenna 1 according to the present embodiment is manufactured by resin molding. In this resin molding, a primary molded product 30 (FIG. 4) in which the helical coil 10 and an insulating resin are integrally molded by insert molding. And a secondary molded product 70 (see FIG. 6) having the final shape of the helical antenna 1 is formed by covering the outer periphery of the primary molded product 30 with an insulating resin. For the secondary molding.

FIG. 2 is a view showing the helical coil 10 before the primary molding.
As shown in this figure, the helical coil 10 is formed by winding a conductor spirally, and is formed on the base end side, and a normal winding portion 11 in which the conductor is wound at a substantially constant pitch; A densely wound portion 12 formed on the front end side and having a conductor wound at a pitch smaller than the pitch of the normal wound portion 11. The pitch of the helical coil 10 is fixed by the resonance frequency that the helical antenna 1 should have.
In the present embodiment, the free length L1 of the helical coil 10 is 160 mm, the outer diameter L3 is 6 mm, and the length L2 in the axial direction of the closely wound portion 12 is 6.4 mm. The length L2 is desirably 3% to 5% of the free length L1.
A conductive connection fitting 13 is connected to the seat on the proximal end side of the helical coil 10, and a male screw portion 14 is formed on the proximal end side of the connection fitting 13.

FIG. 3 is a view showing a state in which the helical coil 10 is disposed in the primary molding die 20. The primary molding die 20 has an upper primary molding die 20A shown in the upper part of FIG. 3 and a lower primary molding die 20B shown in the lower part. A primary cavity 21 is formed between the molds 20A and 20B, and a connection fitting 13 is clamped and fixed to the primary molding dies 20A and 20B at the base end of the primary cavity 21. The helical coil 10 is supported and positioned in the primary cavity 21.
In the primary cavity 21, the total axial length L4 of the portion where the helical coil 10 is disposed is 158.4 mm, which is 1.6 mm shorter than the free length L1 (160 mm) of the helical coil 10. The total length L4 is desirably 98% to 99% of the free length L1. Moreover, in the primary cavity 21, the diameter L5 of the location where the helical coil 10 is disposed is 5.94 mm, which is 0.06 mm smaller than the outer diameter L3 (6 mm) of the helical coil 10. The diameter L5 is desirably 98% to 99% of the outer diameter L3.
Due to such a configuration, when the helical coil 10 is arranged in the primary cavity 21, the helical coil 10 is compressed in the axial direction and the circumferential direction by the primary cavity 21, and the free length L1 and the outer diameter L3 are reduced. Is done. At this time, since the degree of compression is very small, the pitch of the helical coil 10 hardly changes.

A primary through hole 22 is formed at the tip of the primary molding die 20 so as to penetrate the primary molding die 20 in the axial direction. After the helical coil 10 is disposed in the primary molding die 20, The slide core 23 passes through the primary through hole 22 and is inserted into the inner periphery at the tip of the helical coil 10. The primary slide core 23 is for forming a concave portion 31 that is recessed in the axial direction at a position corresponding to the closely wound portion 12 of the helical coil 10 at the tip of the primary molded product 30 in the primary molding (FIG. 4). Reference), one end 24 of the primary slide core 23 is inserted about 6.4 mm from the distal end of the helical coil 10 toward the proximal end of the inner peripheral portion of the helical coil. The length inserted here is preferably 3% to 5% of the free length L1 of the helical coil 10.
Reference numeral 25 in the figure indicates an injection port for injecting resin. As shown in this figure, the injection port 25 is provided on the base end side of the primary molding die 20. The injection port 25 may be provided on the distal end side of the primary molding die 20.

At the time of primary molding, a molten resin having insulating properties and thermoplasticity is injected into the primary cavity 21 through the injection port 25 at a pressure of about 40 to 60 tons / square centimeter. At that time, a molding pressure is applied to the helical coil 10 to displace the helical coil 10 toward the tip in the axial direction. However, in this embodiment, since the outer periphery of the helical coil 10 is in contact with the inner periphery of the primary cavity 21, friction force is generated between the outer periphery of the helical coil 10 and the inner periphery of the primary cavity 21. The helical coil 10 is kept from being displaced by the molding pressure.
Further, the helical coil 10 is in a state of being pressed in the axial direction in the primary cavity 21, and constantly applies tension toward the axial front end and the axial base end. For this reason, when a molding pressure is applied to the helical coil 10 so as to displace the helical coil 10 toward the tip in the axial direction, the shape of the helical coil 10 is displaced by a tension acting in the direction opposite to the molding pressure. The thing is stopped.
After the above operations, the resin filled in the primary cavity 21 is cooled and cured, the primary slide core 23 is removed from the primary molding die 20, and the upper and lower primary molding dies 20A and 20B are split vertically. The primary molded product 30 is molded.

FIG. 4 is a view showing the primary molded product 30 formed by the primary molding described above.
As shown in this figure, in the primary molded product 30, the helical coil 10 and the resin are integrally molded in a state where the entire helical coil 10 is covered with resin, and even if an external force is applied to the primary molded product 30. The shape of the helical coil 10 is not displaced. Further, a concave portion 31 is formed by a primary slide core 23 described above at a location corresponding to the densely wound portion 12 at the tip of the primary molded product 30. Note that the outer surface of the helical coil 10 is exposed on the outer periphery of the primary molded product 30.

  In the present embodiment, in the primary molded product 30, the concave portion 31 is formed at a location corresponding to the densely wound portion 12 in which the conductor is wound at a pitch smaller than a normal pitch. Here, in the primary molded product 30, the portion corresponding to the concave portion 31 (hereinafter referred to as “the concave portion corresponding portion 32”) is thinner than the portion corresponding to the normal winding portion 11, and the strength is low. Low. For this reason, compared with other portions, the recess-corresponding portion 32 easily expands and contracts due to the shrinkage of the resin during primary molding, and easily deforms due to external force. However, in this embodiment, since the conductor corresponding to the thin concave portion 32 is wound more than usual, the strength of this portion is reinforced, and the length is expanded and contracted by the resin contraction during the primary molding. In addition, the recess-corresponding portion 32 is not deformed by an external force. Accordingly, the recess-corresponding portion 32 of the primary molded product 30 is deformed, and the primary molded product 30 cannot be stored in the secondary molding die 50 (see FIG. 5) due to this deformation. The shape of the finished product is not distorted due to the deformation of 32. Further, the pitch of the helical coil 10 is not deformed in accordance with the deformation of the recess corresponding portion 32.

FIG. 5 is a view showing a state in which the primary molded product 30 is disposed in the secondary molding die 50.
The secondary molding die 50 has an upper secondary molding die 50A shown in the upper part of the drawing and a lower secondary molding die 50B shown in the lower part. A secondary cavity 51 is formed between 50 </ b> A and 50 </ b> B, and the primary molded product 30 is disposed in the secondary cavity 51. A fixing piece 52 for fixing and supporting the base end of the primary molded product 30 is provided at the base end portion of the secondary cavity 51, and a female screw portion 53 is formed at the distal end side of the fixing piece 52. ing. When the primary molded product 30 is disposed in the secondary cavity 51, the male screw portion 14 at the base end of the primary molded product 30 is screwed into the female screw portion 53.

A secondary through hole 54 that penetrates the secondary molding die 50 in the axial direction is formed at the tip of the secondary molding die 50, and the primary molded product 30 is a secondary part of the secondary molding die 50. After being arranged in the next cavity 51, the secondary slide core 55 passes through the secondary through hole 54 and is inserted into the recess 31 of the primary molded product 30. The secondary slide core 55 is constantly urged in the direction of the arrow Y1 in the drawing by a spring mechanism 58 disposed on the base end side of the secondary molding die 50, and one end 56 of the secondary slide core 55. Continuously presses the bottom of the recess 31 in the direction of the arrow Y1. When the secondary slide core 55 urges the primary molded product 30, the length L6 of the location where the helical coil 10 is present in the primary molded product 30 is compared with L4 shown in FIG. The primary molded product 30 is energized to such an extent that it shrinks slightly.
In this way, the primary molded product 30 is firmly supported in the secondary cavity 51 by supporting the base end by screwing and supporting the front end by being biased toward the base end side by the secondary slide core 55. While being positioned.

The secondary molding die 50 is provided with a pair of injection ports 57, 57 sandwiching the front end side of the fixed piece 52, and at the time of secondary molding, molten resin having insulating properties and thermoplasticity is injected into the injection port. Injected into the secondary cavity 51 at a pressure of about 40 to 60 tons / square centimeter through 57 and 57. In the present embodiment, the inlets 57, 57 are provided on the proximal end side of the secondary molding die 50, but this may be provided on the distal end side.
At this time, a molding pressure is applied to the primary molded product 30 toward the distal end in the axial direction. However, in this embodiment, the base end of the primary molded product 30 is supported by screwing, and the distal end thereof is a secondary slide. Since the primary molded product 30 is firmly positioned in the secondary cavity 51 by being urged and supported by the core 55, the primary molded product in the secondary cavity 51 is formed by the molding pressure during the secondary molding. The position of 30 does not shift.
Further, the primary molded product 30 is urged in the direction of the arrow Y1 by the secondary slide core 55, and a tension is always applied in this direction. For this reason, when a molding pressure is applied to the primary molded product 30 during secondary molding, the shape of the primary molded product 30 is kept from being displaced by a tension acting in a direction opposite to the molding pressure.
Further, the inside of the primary molded product 30 is molded in a state filled with resin except for the concave portion 31. For this reason, the strength of the primary molded product 30 is high, and warping and bending of the primary molded product 30 hardly occur due to the molding pressure during the secondary molding.

  After the above operation, after the resin filled in the secondary cavity 51 is cooled and hardened, the bias to the secondary slide core 55 by the spring mechanism 58 is released, and the secondary slide core 55 is used for secondary molding. The upper and lower secondary molding dies 50A and 50B are cut up and down and the secondary molded product 70 is molded.

FIG. 6 is a side view of the secondary molded product 70 molded by secondary molding.
As shown in this figure, in the secondary molded product 70, a tip recess 71 is formed at a location where the secondary slide core 55 was present, and a cap 72 is press-fitted into the tip recess 71. . The cap 72 closes the tip recess 71 to prevent intrusion of foreign matters and enhance the appearance of the secondary molded product 70.
The secondary molded product 70 is integrally formed while the primary molded product 30 is covered with resin. In the primary molded product 30, the outer surface of the helical coil 10 is exposed. However, in the secondary molded product 70, the exposed portion of the helical coil 10 disappears, and the helical coil 10 is entirely covered and the shape of the helical coil 10 is caused by collision of foreign matter. Will not be deformed. Further, the secondary molded product 70 has a structure that is stronger against external force by covering the primary molded product 30 with resin.

As described above, according to the present embodiment, since the outer periphery of the helical coil 10 is in contact with the inner periphery of the primary cavity 21 during the primary molding, the outer periphery of the helical coil 10 and the primary coil are in contact with each other. A frictional force acts between the inner periphery of the cavity 21 and the displacement of the shape of the helical coil 10 by the molding pressure is stopped. Further, the helical coil 10 is in a state of being compressed in the axial direction within the cavity, and constantly applies tension toward the axial front end and the axial base end. For this reason, when a molding pressure is applied to the helical coil 10 so as to displace the helical coil 10 toward the tip in the axial direction, the shape of the helical coil 10 is displaced by a tension acting in the direction opposite to the molding pressure. The thing is stopped.
For this reason, the helical coil 10 is primarily molded while maintaining a predetermined pitch, and the helical coil 10 can be surely provided with a desired resonance frequency. For this reason, the helical antenna 1 including the helical coil 10 according to the present embodiment can stably detect radio waves related to radio broadcasting, television broadcasting, and the like.
In addition, when the helical coil 10 is not manufactured with a predetermined pitch, the primary molded product 30 is bent or warped, which adversely affects the appearance of the helical antenna 1. In the present embodiment, the helical coil 10 is Since the primary molding is performed while maintaining a predetermined pitch, the primary molded product 30 is not bent or warped, and the appearance of the helical antenna 1 is not impaired.
Further, it is not necessary to form a spiral groove for fixing the helical coil 10 in the primary molding die 20, the structure of the primary molding die 20 can be simplified, and the manufacturing cost of the primary molding die 20 can be simplified. Can be reduced.

  Further, according to the present embodiment, the total length L4 is 98% to 99% of the free length L1, and the diameter L5 is 98% to 99% of the outer diameter L3. For this reason, when the helical coil 10 is mounted in the primary cavity 21, the helical coil 10 is pressed into the primary cavity 21 and mounted in the primary molding die 20 with almost no deformation of its shape.

  Further, according to the present embodiment, the length in which the primary slide core 23 is inserted from the distal end of the helical coil 10 toward the proximal end and the length in the axial direction of the recess 31 in the primary molding are as follows: It is 3% to 5% of the 10 free lengths L1. For this reason, a hollow part is hardly formed in the inner periphery of the primary molded product 30, and further, the secondary slide core 55 is formed through the recess 31 formed at the tip of the primary molded product 30 during the secondary molding. The primary molded product 30 can be reliably supported.

  In addition, according to the present embodiment, since the conductor is wound more than usual in the concave portion corresponding portion 32 of the primary molded product 30, the strength of this portion is reinforced, and the resin in the primary molding is strengthened. The length does not expand and contract due to the contraction, and is not deformed by an external force. Accordingly, the recess-corresponding portion 32 of the primary molded product 30 is deformed, and the primary molded product 30 cannot be stored in the secondary molding die 50 due to this deformation, or is derived from the deformation of the recess-corresponding portion 32. As a result, the shape of the finished product is not distorted. Further, the pitch of the helical coil 10 is not deformed in accordance with the deformation of the recess corresponding portion 32. For this reason, the helical antenna 1 including the helical coil 10 according to the present embodiment can stably detect radio waves related to radio broadcasting, television broadcasting, and the like.

Further, according to the present embodiment, there is no need to form protrusions on the outer periphery of the primary molded product 30, and therefore, there is no need for the primary molding die 20 to have a structure for forming the protrusions. The structure of the mold 20 is simplified. Furthermore, the convex part derived from the said protrusion does not appear in the outer peripheral surface of the secondary molded product 70, and the external appearance of the helical antenna 1 is not impaired. Further, since the protrusion is for positioning the primary molded product 30 in the secondary cavity 51 of the secondary molding die 50, the size and shape of the projection are so that the primary molded product 30 can be accurately positioned. Although very high accuracy is required, considerable labor is required for molding the primary molded product 30, and the number of man-hours for manufacturing has increased. However, in this embodiment, it is not necessary to mold the protrusions. Labor is reduced and man-hours for production are reduced.
Further, in the conventional secondary molding, there is a projection on the outer periphery of the primary molded product 30, and this projection contacts the inner periphery of the secondary cavity 51, and the primary molded product 30 is positioned in the cavity. However, in this configuration, when the resin is injected at the time of the secondary molding, this protrusion becomes an obstacle, the flow of the resin in the secondary cavity 51 is disturbed, and the secondary molded product 70 is moved from the base end to the front end. As a result, the secondary molded product 70 was easily bent and deformed and the tip portion contracted easily. However, in this embodiment, the flow of the resin is not disturbed in the secondary cavity 51, and therefore, the secondary molded product 70 is sequentially cured from the proximal end to the distal end, and bending deformation and distal end contraction change do not occur.

  Further, in other conventional secondary molding, a hollow exists in the primary molded product 30 from the front end to the base end, and a support rod is inserted into the hollow portion to position the primary molded product 30. However, in the case of this configuration, when the resin is injected during the secondary molding, the resin flows into the gap interposed between the hollow portion and the support rod, and the inside of the secondary molding die 50 The flow of the resin was disturbed, and the secondary molded product 70 was not sequentially cured from the proximal end to the distal end, and bending deformation and distal end shrinkage change were likely to occur. However, in the present embodiment, only the concave portion 31 has a hollow structure inside the primary molded product 30, and most of the hollow portion is not hollow. Therefore, when the resin is injected during the secondary molding, The flow of the resin is not disturbed in the secondary cavity 51 due to a gap interposed between the secondary slide core 55 and the like, and therefore the secondary molded product 70 is sequentially cured from the proximal end to the distal end, and is bent and deformed. Shrinkage change does not occur.

Further, according to the present embodiment, it is not necessary to form a hollow portion extending in the axial direction from the distal end to the proximal end in the primary molded product 30, and in the secondary molding, a secondary molding metal A support bar for positioning the primary molded product 30 in the secondary cavity 51 of the mold 50 is not necessary. For this reason, primary molding and secondary molding become simple.
Moreover, the hollow part extended in an axial direction from the front-end | tip to the base end is not formed in the secondary molded article. For this reason, it is not necessary to insert a resin center rod for reinforcing the strength of the secondary molded product 70 into the secondary molded product 70 as in the prior art, and the manufacturing cost can be reduced accordingly. Furthermore, in the conventional configuration in which the center rod is inserted into the hollow portion to increase the strength, an abnormal noise is generated when the hollow portion and the center rod collide with each other. Although the coil 10 has been deteriorated, there is no such concern in this embodiment.

  In the present embodiment, since the injection port 25 of the primary molding die 20 exists on the proximal end side, the resin smoothly flows from the proximal end to the distal end in the primary cavity 21 in the primary molding. And the primary molded product 30 without a curvature and a curve can be shape | molded. Similarly, since the injection port 57 of the secondary molding die 50 exists on the proximal end side, the resin smoothly flows from the proximal end to the distal end in the secondary cavity 51 in the secondary molding. Further, the secondary molded product 70 with less warping and bending and excellent in appearance can be formed.

  In the present embodiment, in the secondary molding, the primary molded product 30 is supported by screwing in the secondary cavity 51 of the secondary molding die 50, and the distal end is the secondary slide core 55. By being biased and supported by the base end side, the positioning is performed while being firmly supported in the secondary cavity 51. For this reason, the position of the primary molded product 30 does not shift in the secondary cavity 51 due to the molding pressure. Further, the primary molded product 30 is urged in the proximal direction by the secondary slide core 55, and is always in a tensioned state in this direction. For this reason, when a molding pressure is applied to the primary molded product 30 during secondary molding, the shape of the primary molded product 30 is kept from being displaced by a tension acting in a direction opposite to the molding pressure.

  In the present embodiment, the primary cavity 21 and the secondary cavity 51 are filled with a resin having insulating properties and thermoplasticity. For this reason, a high-performance helical antenna can be easily molded with resin.

  In addition, embodiment mentioned above shows the one aspect | mode of this invention to the last, and a deformation | transformation and application are arbitrarily possible within the scope of the present invention. For example, in the present embodiment, specific lengths are described with reference symbols L1 to L6, but this length is merely an example and can be arbitrarily designed.

It is a figure which shows a state when the helical antenna which concerns on this embodiment is attached to the roof of a motor vehicle. It is a figure which shows the helical coil before primary shaping | molding. It is a figure which shows the state with which the helical coil was mounted | worn with the metal mold | die for primary molding. It is a figure which shows a primary molded product. It is a figure which shows the state with which the primary molded product was mounted | worn with the metal mold | die for secondary molding. It is a figure which shows a secondary molded product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Helical coil 11 Normal winding part 12 Closely wound part 20 Primary molding die 21 Primary cavity 22 Primary through-hole 23 Primary slide core 25 Inlet 30 Primary molded product 31 Concave part 50 Secondary molding die 51 Secondary cavity 52 Fixed Piece 54 Secondary through-hole 55 Secondary slide core 57 Inlet 70 Secondary molded product 71 Tip recess L1 Free length

Claims (6)

Install the helical coil in the primary cavity of the primary mold,
A length determined by a predetermined ratio with respect to the length of the helical coil on the inner periphery of the tip of the helical coil via the through hole formed in the primary molding die, the slide core for primary molding Insert only minutes
Filling the primary cavity with resin, forming a primary molded product having a concave portion of a predetermined depth at the tip,
The primary molded product is mounted in a secondary cavity of a secondary molding die,
After inserting the slide core for secondary molding into the concave portion formed at the tip of the primary molded product through the through hole formed in the mold for secondary molding, resin is put into the secondary cavity. A method for manufacturing a helical antenna, comprising filling and forming a secondary molded product. Energizing the slide core for secondary molding,
2. The helical antenna according to claim 1, wherein in the secondary cavity, the secondary molded product is molded by filling the secondary cavity with resin while pressing the primary molded product in the axial direction. Method. The primary molding slide core is inserted into the inner periphery of the tip of the helical coil by a length of 3% to 5% of the free length of the helical coil. Method for manufacturing a helical antenna. On the base end side of the helical coil, a normal winding portion formed by winding a conductor substantially constant at a predetermined pitch is formed,
On the front end side of the helical coil, a densely wound portion formed by winding a conductor at a pitch smaller than the pitch in the normal winding portion is formed,
The method of manufacturing a helical antenna according to any one of claims 1 to 3, wherein the primary molding slide core is inserted into a portion corresponding to the densely wound portion on an inner periphery of a tip portion of the helical coil. . Filling the primary cavity with resin through the primary molding inlet provided on the base end side or the tip side of the primary molding die,
5. The resin is filled in the secondary cavity through a secondary molding inlet provided on a base end side or a distal end side of the secondary molding die. The manufacturing method of the helical antenna of description. The method for manufacturing a helical antenna according to claim 1, wherein the primary cavity and the secondary cavity are filled with a resin having an insulating property and thermoplasticity.

Images