JP2011167900A - Structure of thermal caulking part and method for thermally caulking the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal caulking structure and a method for thermally caulking the same capable of preventing separation of excess resin (weld flash) leaked to the outside of a weld chip from a caulking part without having influence on strength of the weld chip in thermal caulking. <P>SOLUTION: A plurality of small holes 12 or notches 13 are provided around a fixing hole 11 for thermal caulking provided on a fixed article 10, and an excess molten resin bypass guide flow passage 12 communicated with a recessed part 36 of the weld chip 30 and the outside of the weld chip 30 is formed. As a result, the caulking part 38 and an annular body 50 as the excess resin 37 are connected by the effect of the small hole 12, and the excess molten resin passes through it, and flows to the outside, and is solidified integrally with a weld boss 21 side, and therefore, the excess resin 37 is not unstably formed in the form of the weld flash, which is different from the conventional thermal caulking method. As a result, the situation that the weld flash is separated from the caulking part and is scattered in the product as a foreign matter can be prevented. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

In the present invention, when fixing an object to be fixed to a thermoplastic resin molded article, a welded or deformed portion called a welding boss is formed in advance on a part of the thermoplastic resin molded article, and the welding boss is fixed. Passing through the fixed hole on the object side and protruding its tip from inside the fixed hole, and by melting or deforming this protruding tip side with heat, a heat caulking fixing part for crimping the object to be fixed to the thermoplastic resin molded product And a heat caulking method thereof.

As a method of fixing an object to be fixed to a molded product formed of a thermoplastic resin, first, a welding boss integrally formed with the molded product is passed through a fixing hole formed on the fixed object side.
Next, the tip of the welding boss protruding from the fixing hole is pressed against an electrothermal welding tip (hereinafter referred to as “welding tip”) to fill the recess formed at the tip of the welding tip with the molten resin, and further cooled. Thus, there is known a thermal caulking method in which a crimping portion like a mushroom umbrella larger than the fixing hole is formed, and an object to be fixed is caulked (fixed) to a molded product by the caulking fastening portion.

However, when the thickness of the object to be fixed varies, for example, in a printed board on which an electrical component is mounted, the thickness of the printed board may vary depending on the production lot.
Examples of this are shown in FIGS. FIG. 16 is a cross-sectional view in which the crimping portion 2 is formed as set, and FIG. 17 is a cross-sectional view when the molten resin flows out of the welding tip 7.

For example, when the thickness of the printed circuit board 1 is thin, since the welding boss 4 integrally formed with the molded product 3 is long (high) and the welding boss 4 protrudes from the fixing hole 5, the amount of resin to be melted increases. There is a case where it cannot be accommodated in the recess and flows out of the welding tip 7 from the tip of the welding tip 7 as shown in FIG. The resin that has flowed out is commonly called a burr 6, and when incorporated in the product, the burr 6 is detached from the caulking portion 2 as shown in FIG. 17 (b) and mixed into the incorporated product. Cause inconvenience.
Further, the leaked molten resin adheres to the outer side surface of the welding tip 7, and as a result, the welding tip 7 may become dirty, which may adversely affect the crimping quality.

Therefore, as a bonding method that does not generate burrs, Japanese Patent Application Laid-Open No. 2004-262041 introduces an ultrasonic bonding method.
That is, a notch is formed in the tip portion of the ultrasonic welding horn, and the surplus resin at the tip portion of the welding protrusion generated during the ultrasonic welding passes through the notch and the back surface of the trim member on the opposite side of the ultrasonic welding horn. It is an ultrasonic bonding method for resin parts, characterized in that it is guided to

However, if a notch is formed in the tip portion of the ultrasonic welding horn, the strength of the tip portion is lowered, which may adversely affect the life of the expensive ultrasonic welding horn.

Japanese Patent Laid-Open No. 2004-262041

The purpose of the present invention is to eliminate the disadvantages of the above-mentioned known examples, and the purpose is to have no influence on the strength of the welding tip (ultrasonic welding horn) in heat caulking, and the outside of the welding tip. It is to provide a structure of a heat caulking fastening portion in which surplus resin (burrs) leaking into the seam does not separate from the caulking fastening portion and a caulking fastening method.

In order to achieve the above object, according to the present invention, a welding boss is provided on a resin base material, and the welding boss is passed through a fixing hole formed on the fixed object side. The tip is protruded from the fixing hole, and the concave contact surface formed on the tip surface of the welding tip is pressed against the tip of the protruding welding boss to heat and melt the portion where the welding boss protrudes from the fixing hole. In a caulking fastening structure for fixing an object to be fixed to a resin base by forming a caulking part having a diameter larger than the diameter of the fixing object, the welding chip is pressed around the fixing hole in the object to be fixed. When the tip of the peripheral wall of the concave contact surface comes into contact with the object to be fixed, surplus welding resin flows out of the peripheral wall so as to bypass the tip and solidifies integrally with the caulking portion of the welding boss. Forming a detour guide passage for resin It is characterized in.

According to this invention, when the welding tip continues to melt the welding boss and finally the tip of the peripheral wall of the welding tip comes into contact with the surface of the object to be fixed, the excess molten resin is welded via the detour channel portion. The excess molten resin that has flowed out can be cooled and solidified together with the crimping portion.

Furthermore, in the invention according to claim 2, in the heat caulking part structure according to claim 1, the molten resin bypass guide flow path part is formed as a hole or a groove formed intermittently around the fixed hole. It is a feature.

  According to the present invention, it is possible to form the bypass induction flow path portion of the excess molten resin by a simple processing technique.

Furthermore, in invention of Claim 3, when the said to-be-fixed object which has the said heat caulking fastening structure of Claim 1 and Claim 2 is heat caulked to a resin-made base material, it protrudes in the said base material. After the welded boss is passed through the fixing hole, the welded boss is melted while pressing the welded tip against the welded boss, and is further formed of a molten resin around the concave contact surface of the welded boss. The excess resin protruding from the space surrounded by the peripheral wall is caused to flow out from the front end of the peripheral wall formed at the front end of the weld tip via the surplus resin bypass guide flow path portion, and the crimped portion of the weld boss This is a heat caulking method in which surplus resin is processed by solidifying it integrally.

According to this invention, the molten resin of the welding boss melted by the heat of the welding tip flows out from the tip of the welding tip via the detour guide channel portion, and is cooled and solidified integrally with the caulking fastening portion. Therefore, unlike the conventional thin burrs, the burrs are securely connected to the caulking portions, and are not easily separated from the caulking portions and scattered as foreign matters in the product.
In addition, since the object to be fixed is fixed to the welding boss by the action of the excess molten resin solidified in the detour guide flow path portion, particularly when there is only one welding boss, the object to be fixed is centered on the welding boss. Rotation can be prevented.

In the present invention, as described above, the excess molten resin that protrudes from the contact surface of the welding tip is solidified integrally with the crimping portion, so that the excess resin is scattered in the product as burrs or the like. There is nothing to do.
Moreover, since the to-be-fixed object is connected with the caulking part by the action of the solidified surplus resin, the to-be-fixed object does not rotate around the welding boss. Moreover, the surplus resin does not adhere to the side surface of the welding tip, and the number of cleanings of the welding tip can be reduced.

Plan view of printed circuit board Explanatory drawing of the heat caulking fastening part structure in Example 1 It is explanatory drawing of a welding chip | tip, Comprising: (a) is a perspective view, (b) is a front view, (c) is A-A 'line sectional drawing. Explanatory drawing of position and dimensional relationship between contact surface of welding tip and small hole Explanatory drawing of the heat caulking fastener structure in Example 2 It is explanatory drawing of the heat crimping process of Example 3, Comprising: Explanatory drawing just before crimping It is explanatory drawing of the heat crimping process of Example 3, Comprising: Explanatory drawing in the middle of crimping It is explanatory drawing of the heat crimping process of Example 3, Comprising: Explanatory drawing at the time of completion | finish of crimping Top view of caulking part of Example 3 BB 'sectional view of the caulking portion of Example 3 CC 'sectional view of the caulking part of Example 3 It is explanatory drawing of the heat crimping process of Example 4, Comprising: Explanatory drawing just before crimping It is explanatory drawing of the heat crimping process of Example 4, Comprising: Explanatory drawing in the middle of crimping It is explanatory drawing of the heat crimping process of Example 4, Comprising: Explanatory drawing at the time of completion | finish of crimping Sectional drawing of the crimping part of Example 4 Sectional view in a conventional example in which the crimped portion is formed as set It is explanatory drawing of a comparative example, (a) is explanatory drawing at the time of crimping end, (b) is explanatory drawing of the condition where the excess resin is scattered

  The structure of the heat caulking fastening portion and the method of heat caulking fastening according to the present invention is such that the tip of the welding tip is fastened by a plurality of small holes or notches around the fixing hole for heat caulking fastened in the fixed object. A flow channel portion is formed in which the inside and outside of the welding tip communicate with each other when contacting the object, and the object is achieved by the action of the flow channel portion.

Note that the relationship between the volume of the welding boss protruding from the object to be fixed and the capacity of the welding tip recess requires that the volume of the welding boss be larger than the capacity of the welding tip recess. The volume of the welding boss may be designed to be 1.3 to 1.5 times the capacity of the concave portion of the chip.

In the first embodiment, the structure of the heat crimping portion described in claim 1 will be described.
FIG. 1 is a plan view of a printed circuit board 10 which is an object to be fixed, FIG. 2 is an explanatory view of a circular small hole 12 drilled in the printed circuit board 10, and FIG. 3 is an explanatory view of a welding tip 30 used in this embodiment. 3 (a) is a perspective view seen from the contact surface 31, FIG. 3 (b) is a front view of the welding tip 30 seen from the contact surface 31, and FIG. 3 (c) is A in FIG. 3 (b). It is -A 'part sectional drawing.

Describing in detail based on each drawing, the fixed object 10 shown in FIG. 1 is a printed circuit board on which electronic components are mounted, and is formed by melting a welding boss 21 protruding from a resin base material 20. The caulking fastening portion 38 is solidified and caulked to the resin base material 20. The thickness of the printed circuit board 10 is 1.6 mm. The printed circuit board 10 is provided with four fixing holes 11 through which the welding bosses 21 are passed, and circular small holes 12 are formed around the four peripheral holes. In this embodiment, the diameter L1 of the fixing hole 11 is 3.8 mm, and the diameter L2 of the small hole L2 is 2.0 mm.
In this embodiment, the number of small holes 12 is four, but the number can be arbitrarily selected.
39 is an imaginary line which shows the position of the contact surface of a welding tip.

FIG. 3 shows the welding tip 30 used in this embodiment. FIG. 3A is a perspective view seen from the contact surface 31, and the contact surface 31 is formed with a welding surface 32 that is recessed in a concave shape. A slit 33 is cut in a position facing the side surface 44 of the welding tip 30, and an electric wire (not shown) is electrically connected to the opening side wall 44 of the welding tip 30 divided by the slit 33. A voltage can be applied to the welding tip 30 to generate heat.
The wall thickness t of the distal end side wall 34 of the welding tip 30 in FIG. 3C is 0.6 mm.

FIG. 4 shows a state in which the welding chip 30 is brought into contact with the printed circuit board 10 with respect to the position and dimensional relationship between the contact surface 31 of the welding chip 30 and the small hole 12 that forms the bypass guide flow path of the excess molten resin. Explain (the welding boss is not shown).

The position of the small hole 12 is arranged around the fixing hole 11 so that the welding tip 30 reaches almost the center of the small hole 12. Further, regarding the relationship between the diameter of the small hole 11 and the thickness t of the welding tip 30, the molten resin in the concave portion 36 of the welding tip 30 is not welded unless the diameter dimension of the small hole 12 is at least as large as the thickness t. It is impossible to flow outside through the small hole 12 due to the clearance 40 and the clearance 41 between the thickness t of the small hole 12 and the diameter of the small hole 12.

The clearance between the welding tip 30 and the small hole 12 can be selected in view of the type of resin (fluidity), the size of the welding boss (amount of molten resin), the temperature of the welding tip, and the like.
In this embodiment, the small hole 12 penetrates the object to be fixed, but may have a bottom, and the shape of the small hole 12 is not limited to a circle but may be a square shape.
Moreover, although the number of the small holes 12 is arbitrary, since the intensity | strength of the fixing hole 11 by the side of the to-be-fixed object 10 will be reduced when there are too many, it is good to restrain in the range of 2 or more and about 6 pieces.

In the first embodiment, the small holes 12 formed in the printed circuit board 10 have a circular shape in the heat caulking fastening structure, but in the second embodiment, a surplus is provided by a plurality of radial cutouts 13 continuous with the fixing holes 11. An example of forming a resin bypass guide channel is introduced. FIG. 5 is an explanatory diagram of the notch 13 formed in the printed circuit board 10.
In the present embodiment, notches 13 each having a shape of a long hole radially in four directions are provided around the fixing hole 11 at intervals of 90 degrees. As described in Example 1, the length from the center of the notch 13 is selected so that the opening of the welding tip 30, the notch, and 13 does not interfere with the resin flow.

In Example 3, a heat caulking method for fixing to the resin base material 20 using the printed circuit board 10 having the structure of the heat caulking portion described in Example 1 will be described with reference to FIGS.
The small hole 12 in the present embodiment has a penetrating shape.
6 is an explanatory view showing a state in which the welding tip 30 is pressed against the tip surface 22 of the welding boss 30, FIG. 7 is an explanatory view showing a state in which the welding boss 21 starts to melt due to the heat of the welding tip 30, and FIG. FIG. 9 is a top view of the caulking portion 38 after the heat caulking process is completed, and FIG. 10 is a cross-sectional view taken along the line BB ′ in FIG. 11 is a cross-sectional view taken along the line CC ′ in FIG.

First, as shown in FIG. 6, a welding boss (φ3.4 mm) 21 formed integrally with a resin base material (made of ABS resin) 20 is formed in a fixing hole (φ3.8 mm) 11 formed in the printed board 10. And put it on the upper surface of the resin base material 20.
Next, the welding tip 30 is pressed against the tip surface 22 of the welding boss 21, and the welding boss 21 is melted by the heat of the welding tip 30. The timing of applying voltage to the welding tip 30 to generate heat can be either when the heat is generated and then pressed, or when the heat is generated after pressing.
By heating the welding boss 21 while further pressurizing with the welding tip 30, as shown in FIG. 7, the melted resin is filled in the concave portion (contact surface) 36 of the welding tip 30.

FIG. 8 shows a state in which the contact surface (tip of the peripheral wall) 31 of the welding chip 30 is in contact with the surface of the printed circuit board 10 by continuing the pressurization.
The surplus resin 37 that is melted more than the volume of the recess 36 enters the small hole 12 from the clearance 40 (width: 0.7 mm) between the contact surface 31 of the welding tip 30 and the small hole 12, and the small hole 12 has an excess resin. It will be filled with. Thereafter, when the inside of the small hole 12 is filled with surplus resin, it flows out of the welding chip 30 from the clearance 41 (width: 0.7 mm) between the side surface of the welding chip 30 and the small hole.

Thereafter, the welding tip 30 is cooled and detached from the caulking fastening portion 38, or after the welding tip 30 is detached, the caulking fastening portion 38 is cooled to complete the thermal caulking process.
As shown in FIG. 9, which is a plan view of the caulking fastening portion 38, an excess molded body 50 formed by solidifying the excess resin 37 connected to the caulking fastening portion 38 is formed by the above heat caulking operation.

10 and 11 are sectional views of the caulking fastening portion 38. FIG. As can be seen from FIG. 10, the caulking fastening portion 38 and the surplus molded body 50, which is the surplus resin 37, are connected by the effect of the small holes 12. As a result, it is not formed stably, and as a result, it does not separate from the caulking fastening portion and is not scattered as foreign matter in the product.
In addition, since the surplus resin 37 enters the small holes 12, an effect of suppressing the printed circuit board (fixed object) 10 from rotating around the welding boss 21 is also obtained.

Table 1 shows data obtained by measuring the anti-rotation strength.
In addition, in the heat caulking method using the to-be-fixed object which formed the radial notch described in Example 2, since it is the same as the method described in Example 3, description is abbreviate | omitted.

In Example 4, a heat caulking method using a bottomed type in which only about 1/3 of the wall thickness of the fixed object is formed as the shape of the small hole formed in the printed circuit board will be described with reference to FIGS. .

12 is an explanatory view showing a state in which the welding tip 30 is pressed against the front end surface 22 of the welding boss 30, FIG. 13 is an explanatory view showing a state in which the welding boss 21 has started to melt due to the heat of the welding tip 30, and FIG. FIG. 15 is a cross-sectional view of the caulking portion 38 in which the heat caulking process has been completed, and FIG. 15 is a diagram illustrating a state in which the molten resin flows to the outside through the small holes 12.
The shape of the bottom of the small hole 12 is bowl-shaped so that the surplus resin flows smoothly.

A heat caulking method will be described. This is basically the same as in the third embodiment, and the welding tip 30 is pressed against the top surface 22 of the welding boss 21 to melt the welding boss as shown in FIG.

Further, as shown in FIG. 13, when the concave portion 36 of the welding tip 30 is filled with the molten resin, the excess resin 37 is melted more than the volume of the concave portion 36 when coming into contact with the surface of the fixed object 10. 30 enters the small hole from the clearance 40 between the contact surface 31 and the small hole 12, and then goes to the outside of the welding chip 30 from the clearance 41 between the side surface and the small hole of the welding tip 30 along the bowl shape of the bottom surface of the small hole 12. It flows out (FIG. 14).

Thereafter, the welding tip 30 is cooled and detached from the caulking fastening portion 38, or after the welding tip 30 is detached, the caulking fastening portion 38 is cooled to complete the thermal caulking process.
As shown in FIG. 15, which is a cross-sectional view of the caulking fastening portion 38, an excess molded body 50 formed by solidifying the excess resin 37 connected to the caulking fastening portion 38 is formed by the above heat caulking operation.
Table 1 shows data obtained by measuring the anti-rotation strength.

As Comparative Example 1, a heat caulking method was performed without forming a small hole or notch around a conventional fixing hole.
As a result, as shown in FIG. 17 (a), burrs 6 that are surplus resin are generated around the caulking fastening portions 2, and the burrs 6 are detached as shown in FIG. The inconvenience of mixing occurred.
Further, the anti-rotation was measured in the same manner as in Example 3. However, the fixed object easily rotated around the welding boss.

Table 1 shows data obtained by measuring the anti-rotation strength.

DESCRIPTION OF SYMBOLS 10 Printed circuit board 11 Fixing hole 12 Small hole 20 Base material 21 Welding boss 30 Welding chip 37 Excess resin 40, 41 Clearance 50 Excess molding

Claims (3)

A welding boss is protruded from the resin base material, and the tip of the welding boss protrudes from the fixing hole by passing the welding boss through a fixing hole formed on the fixed object side, and a welding tip is attached to the tip of the protruding welding boss. The concave contact surface formed on the front end surface of the resin is pressed against the resin base material by forming a crimped portion having a diameter larger than the diameter of the fixed hole by heating and melting the portion where the welding boss protrudes from the fixed hole. In the caulking fastening structure for fixing the fixed object, when the tip of the peripheral wall of the concave contact surface is in contact with the fixed object around the fixing hole in the fixed object and pressing the welding tip, A heat caulking fastening structure in which a surplus molten resin flows out of the peripheral wall so as to bypass its tip and solidifies integrally with a caulking portion of the welding boss to form a bypass guiding passage portion of surplus molten resin. The heat caulking structure according to claim 1, wherein the molten resin bypass guiding flow path is a hole or groove formed intermittently around the fixing hole. When the object to be fixed having the heat caulking structure according to claim 1 or 2 is heat caulked to a resin base material, a welding boss protruding from the base material is passed through the fixing hole. Then, the welding boss is melted while pressing the welding tip against the welding boss, and is further melted and protrudes from a space surrounded by a peripheral wall formed around the concave contact surface of the welding boss. The excess resin is caused to flow out from the front end of the peripheral wall formed at the front end of the welding tip via the surplus resin bypass guide flow path portion and solidify integrally with the caulking portion of the welding boss. Heat caulking method to process.