JPH1044246A - Heat-fusion of thermoplastic resin and resistance heating element used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase fusion strength while enhancing the hermetical sealability of a fused part and to prevent that the end of a resistance heating element or conductor is exposed to the outside of a product to deteriorate appearance and to omit the labor for the post-processing of an exposed part. SOLUTION: A ring-shaped resistance heating element 40 having the same shape as a bonding surface is held between a case main body 20 and a cover 30 and voltage is applied to the resistance heating element 40 while appropriate force applied to the case main body 20 and the cover 30 to fuse both of them. At this time, small diameter holes 24 in which voltage applying terminals are inserted are provided to the molded product part so as to arrive at the resistance heating element 40 and the voltage applying terminals are inserted in the small diameter holes 24 from the outside to apply voltage to the resistance heating element 40. The resistance heating element 40 is formed in a ring shape while voltage applying points are set to two points almost 1/2 with respect to length. When the small diameter holes 24 are desired to be closed, protruded step parts are formed to the peripheries of them and subsequently collapsed by fusion chips to fill the small diameter holes 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article molded from a thermoplastic resin, for example, a battery case to be mounted on an electronic device or the like. The present invention relates to a method of applying a voltage to a body to generate heat, thereby melting and welding a resin on a bonding surface, and a resistance heating body used in the method.

[0002]

2. Description of the Related Art In a case where electronic components are built in a case main body and a cover formed of a thermoplastic resin, and the case main body and the cover are connected to each other, a method using ultrasonic waves, high-frequency electromagnetic induction or an adhesive is known. ing.

[0003]

However, this coupling method using ultrasonic waves or high-frequency electromagnetic induction has a risk of inducing a failure factor in the built-in electronic components and the like. In addition, in the case of bonding with an adhesive, it takes a long time to fix, and the adhesive leaks out from the joint to cause dirt or deteriorate the appearance. Therefore, JP-A-58-59050 and JP-A-62-288029 disclose a heating element based on electric resistance (hereinafter referred to as a "resistance heating element") between a case body and a cover to be fused. A method has been proposed in which the thermoplastic resin is melted by this heat generation to fuse the thermoplastic resins together. Since this method is an instantaneous fusion method by heat, it is an effective joining method without affecting the internal parts and appearance.

However, in any case, in the case of an electrode for supplying a voltage to the resistance heating element, or in the case of a wire-shaped resistance heating element, this conductor protrudes out of the case, and the case is connected to another case. It is an obstacle for incorporation into the body. In addition, the case alone may cause a problem in appearance. For this reason, processing for cutting the protruding portion is required as necessary. Further, it is conceivable that any liquid enters between the resistance heating element and the thermoplastic resin from the outside and penetrates into the case to affect the internal components. In addition, since the resistance heating element is not ring-shaped, there is a portion that is not welded somewhere, and when it is desired to seal the product, the conventional resistance heating element cannot cope.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a case for an electronic component, particularly in a case for an electronic component, in which no electrode or conductive wire comes out of the case, no liquid permeates between the resistive heating element and the resin, and a sealable welding is performed. The present invention provides a method and a resistance heating element used in the welding method, and has the following configuration. 1. When heat-welding molded products molded with thermoplastic resin,
The resistance heating element is formed in a ring shape in a method of welding a molded article by applying a voltage to the resistance heating element to generate heat while holding the resistance heating element between the joining surfaces and pressing with an appropriate force. At the same time, small-diameter holes for inserting voltage application terminals are opened at two points corresponding to approximately one half of the length of the resistance heating element so as to reach the resistance heating element at the corresponding formed product part, A method for heat-welding a thermoplastic resin in which a voltage application terminal is inserted into the small-diameter hole from the outside and a voltage is applied to the resistance heating element, thereby causing the resistance heating element to generate heat and welding a bonding surface.

[0006] 2. 2. The method for heat-welding a thermoplastic resin according to the above item 1, wherein a plurality of electrodes for contacting a voltage application terminal are provided on the resistance heating element. 3. 3. The heat as described in 1 or 2, wherein the projecting step is provided around the small diameter hole for inserting the voltage application terminal, and after the welding of the molded product is completed, the step is crushed using a welding tip to seal the small diameter hole. Heat welding method of plastic resin. 4. A resistance heating element used for heat welding a thermoplastic resin formed by punching a thin plate into a ring shape. 5. A plastic case formed by heat-sealing a case body and a cover with a ring-shaped resistance heating element interposed between joint surfaces.

[0007]

A ring-shaped resistance heating element is sandwiched between resin fusion surfaces, and a voltage application terminal connected to a power supply device is inserted into a small-diameter hole opened in either the case body or the cover to contact the resistance heating element. When brought into contact, the resistance heating element generates heat due to its electrical resistance and melts the surrounding resin.

When the molten metal is sufficiently melted, the voltage is stopped, the voltage application terminal is disconnected, and when the resin is cooled, the resin in the molten portion is hardened and the case body and the cover are fused. Thereafter, when the stepped portion protruding around the small-diameter hole is crushed by a welding tip, the small-diameter hole is closed, so that the resistance heating element cannot be seen from the outside and a sealed case is completed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of thermoplastic resins for heat fusion include, for example, polyethylene, polypropylene, polystyrene, AS resin, ABS resin, methacrylic resin, polyvinyl chloride and the like. In the case of a product molded from such a thermoplastic resin, for example, a battery case, a groove is formed in a fusion surface on the case body side, and furthermore, a resistance heating element for dividing a ring-shaped resistance heating element into approximately two equal parts. At two points on the body, small-diameter holes for inserting voltage application terminals are formed in the corresponding case body. This small diameter hole may be on the cover side. If necessary, a projecting step is formed around the small diameter hole.

As the resistance heating element, for example, a nickel-chromium alloy, an iron-chromium alloy, an iron-nickel alloy or the like can be used. As a means for forming the resistance heating element in a ring shape, both ends of a single wire may be connected, or for example, a thin resistance heating plate may be punched out with a press or the like. In the resistance heating element, the ring shape means an endless body, and since the shape is adapted to the shape of the joining surface,
There are various shapes such as a circle and a square.

A resistance heating element is incorporated in the groove, a cover is put on the resistance heating element, its lower edge (fusion surface) is aligned with the fusion surface on the case body side, and the resistance heating element is sandwiched between both fusion surfaces. Press the case body and cover. 2 in that state
After inserting a voltage application terminal into each of the small-diameter holes and bringing the terminal into contact with the resistance heating element, when a voltage is applied to cause the resistance heating element to generate heat, the surrounding resin melts. After this state, when the voltage is stopped, the voltage application terminal is pulled out, and the molten portion is cooled naturally or forcibly, the molten resin is cured. As a result, the case body and the cover are fused, that is, joined.

Next, after the welding connection, a welding tip having a cup-shaped contact surface at one end for heating and melting the projecting step portion protruding around the small diameter hole is brought into contact with the projecting step portion. By melting and further crushing, an enormous portion is formed so that the small-diameter hole can be closed. However, when it is not necessary to close the small-diameter hole, the formation of the projecting step and the crushing using the welding tip are not performed. As a result, the entire circumference of the case is completely welded by the ring-shaped resistance heating element, so that the adhesive strength is improved, and a sealed case in which the resistance heating element is not visible from the outside of the case is completed.

[0013]

FIG. 1 is a completed perspective view of a battery case 10 according to the present invention. The battery case 10 has a shape in which a cover 30 is put on the case body 20. FIG. 2 is an assembled perspective view of the battery case 10. Case body 20 and cover 3
Numeral 0 is a plastic molded product molded with a thermoplastic resin, and reference numeral 40 is a ring-shaped resistance heating element formed of a nickel-chromium alloy. A lower fitting edge 31 is formed on the lower edge of the cover 30.

The resistance heating element 40 has the same shape as the joint surface, and has a ring shape. In this embodiment, SUS3
No. 03 material, thickness 0.15 mm, width 0.5
mm, and two circular electrodes 41 are provided at opposing points of the resistance heating element 40 that are almost equally divided. A fitting recess 21 is provided at the upper edge of the case body 20, and a round 22 having substantially the same shape as the two electrodes 41 provided on the resistance heating element 40 at two places of the fitting recess 21.

FIG. 3 is a sectional view taken along the line AA 'of the round portion 22. As shown in FIG. A terminal guide hole 23 is opened on the back side of the round 22 toward the bottom surface of the case body 20, and a small-diameter hole 24 is formed in the center of the round 22 toward the bottom surface of the case body 20 like the terminal guide hole 23. Further, a protruding step 25 integrally formed is provided around the small diameter hole 24 on the terminal guide hole 23 side. In addition, only the small-diameter hole 24 of the terminal guide hole 23 may be formed at the time of forming the case main body 20 or may be formed by processing later.

The method of incorporating the resistance heating element is shown in Round 22.
The description will be made with reference to FIGS. 4, 5, 6, and 7, which are enlarged views of the section taken along the line AA '. FIG. 4 is a diagram showing the preparation for welding. The resistance heating element 40 is incorporated into the fitting recess 21 so that the electrode 41 of the resistance heating element 40 is fixed to the round 22 formed in the fitting recess 21, and the cover 30 is placed on the fitting and the lower edge (fused surface) thereof. To the case body 20 side with the fusion surface, and the resistance heating element 40 is sandwiched between both fusion surfaces. Then, using a pressing device (not shown), an appropriate force is applied to the case body 2.
0 and the cover 30 are pressed in the joining direction.

Next, as shown in FIG. 5, a voltage application terminal 502 connected to a voltage supply controller (not shown)
Each of the books is inserted into the terminal guide hole 23, and is further brought into contact with the electrode 41 of the resistance heating element 40 through the small-diameter hole 24, and then a voltage of AC4V (100 A) is applied for 2.5 seconds to apply the resistance heating element 40. To generate heat. Since the heating conditions vary depending on the resin used and the size of the case, it is preferable to set the conditions in advance in the voltage supply controller.

The surrounding resin is melted by the heat generated by the resistance heating element 40. That is, the molten resins on the case body 20 side and the cover 30 side fuse together. This fusion zone is a portion surrounded by an outer dotted line in FIG. Then, when the voltage is stopped in a state of sufficient fusion, the voltage application terminal 50 is pulled out, and when cooled, the molten resin is cured and the case body 20 and the cover 3 are hardened.
0 is fused and bonded.

If it is not desired to show the resistance heating element 40 from the outside of the case 10, or if the case 10 is to be hermetically sealed, the following method may be added. Figure 6 shows the situation.
FIG.

First, as shown in FIG. 6, a welding tip 60 having a cup-shaped contact surface is inserted into the terminal guide hole 23 and is brought into contact with the protruding step 25 protruding around the small diameter hole 24. Let it. Then, the resin of the protruding step 25 is melted, and is further crushed by the welding tip 60 to melt the protruding step 25.
Are mixed and integrated. Next, the welding tip 60 is released,
When cooled, the enlarged portion 26 is formed as shown in FIG. 7, the small-diameter hole 24 is closed, the electrode 41 (the resistance heating element 40) cannot be seen, and the case 10 is hermetically closed. The welding tip 60 may be a hot rod, but a good finish is obtained by using a welding tip having a structure in which a voltage is applied to the metal piece, and after the welding, the coolant is sprayed on the metal piece to forcibly cool the metal piece.

In this embodiment, the small-diameter hole 24 is provided on the case body 20 side, and the voltage application terminal 50 contacts the electrode 41 of the resistance heating element 40 from the back side of the case body 20. The small-diameter hole 24 may be provided, and the position of the small-diameter hole 24 can be arbitrarily selected depending on the shape of the case, the manufacturing process, and the like. Although the electrodes are provided on the resistance heating element, the electrodes need not be provided if the structure is such that the voltage application terminal is surely in contact with the resistance heating element.

[0022]

Embodiment 2 As another bonding method, there is a method in which a voltage applying terminal is brought into contact with a resistance heating element sandwiched between a case body and a cover from the side. 8 to 10 are cross-sectional views of the main parts, and FIG. 11 is a completed perspective view of the case 10. On the fusion surface on the case body 20 side, a ring-shaped resistance heating element 40
Half-shaped concave portions 28 are formed from the surface of the rib 27 toward the outside of the case body 20 at two points corresponding to the opposing point positions of the resistance heating element 40 which are substantially equally divided by two.

As a welding method, as shown in FIG. 8, a resistance heating element 40 is fixed in a fitting recess 21 formed in the case body 20, a cover 30 is put on the resistance heating element 40, and a lower edge of the cover 30 is attached to the case body 20 side. In addition to the fusion surface, the resistance heating element 40
Is sandwiched between both fusion surfaces. Further, the process is the same as that of the first embodiment until the case body 20 and the cover 30 are pressed in the connecting direction by an appropriate force using a pressing device (not shown).

At this time, the resistance heating element 40 sandwiched inside the case 10 is exposed at two places of the half-shaped concave portion 28 provided in the case body 20. Therefore, the voltage application terminal 50 can be brought into contact with the exposed portion of the resistance heating element 40, and when a voltage is applied to the resistance heating element 40 by the voltage application terminal 50 as shown in FIG. Heat is generated, and a fusion region surrounded by a dotted line is generated. If the mixture is further cooled, the case body 20 and the cover 30 are welded. FIG. 10 is a cross-sectional view showing a fusion region at a place other than the half-shaped concave portion 28. FIG.
8 is shown.

Comparative Example A comparison was made of the tensile strength between the conventional ultrasonic welding method, which is often used for welding thermoplastic resins, and the welding method using the thin ring-shaped resistance heating element of the present invention. However, the resistance heating element was not in the shape of a ring but in the form of a thin strip. Table 1 shows the results.

As a test piece, a molded piece shown in FIG. 12 molded of ABS resin was used. In the method (1) using the resistance heating element R, in the test piece A, the resistance heating element R using the material SUS304 is sandwiched on one of the joining surfaces, and a voltage of AC4V, (6A) is applied thereto to generate heat welding. did. In the method (2) using ultrasonic welding, a welding rib S having a triangular cross section is integrally formed on one joint surface of the test piece A, and welding is performed by bringing both surfaces into contact. FIG.
, The unit of the number indicating the dimension is mm.

The tensile direction at the time of measuring the tensile strength is shown in (3). The measurement results were almost the same in both methods. Therefore, it is recognized that the present invention which is capable of instantaneously and safely welding using a resistance heating element is an excellent method, as compared with the ultrasonic welding method which has a risk of inducing a cause of failure in a built-in electronic component or the like.

[0028]

[Table 1]-Tensile strength tester Toyo Seiki Seisakusho Co., Ltd. Universal tensile tester V10-C type-Material of test piece (A) ABS resin

[0029]

As described above, the present invention incorporates a ring-shaped resistance heating element into a molded article to be heat-welded, and inserts a voltage application terminal into the molded article through a small-diameter hole provided in the molded article to form the resistance heating element. Since this is a heat welding method in which the heat is welded by heat contact, the following effects are obtained. 1. Since the electrode for voltage application does not come out of the molded product, there is no need for secondary processing such as cutting the electrode after welding.
5). 2. Since the resistance heating element has a ring shape, the entire joining surface can be welded, and the joining strength and the sealing property can be improved (claims 1 to 5). 3. A step is provided around the small diameter hole for voltage application,
After welding, the step is melted to close the small-diameter hole, whereby a sealed plastic case can be manufactured (claims 1 to 5). 4. By pressing the resistance heating thin plate to form a ring-shaped resistance heating element, it is possible to efficiently produce a resistance heating element of the same standard (claim 4).

[Brief description of the drawings]

FIG. 1 is a completed perspective view of a battery case using the method of the present invention.

FIG. 2 is an explanatory view of a state in which a resistance heating element of the present invention is used when a case body and a cover are thermally welded to each other in a battery case.

FIG. 3 is a cross-sectional view taken along line AA ′ of a round portion.

FIG. 4 is a round cross-sectional view in which a resistance heating element is incorporated in a fitting recess, and the resistance heating element is sandwiched between a case body and a cover.

FIG. 5 is a round sectional view in which a resin is melted by bringing a voltage application terminal into contact with an electrode of a resistance heating element.

FIG. 6 is a round sectional view in which a welding tip is applied to a step and the step is melted.

FIG. 7 is a round cross-sectional view showing a state where an enlarged portion is formed and a small-diameter hole is closed.

FIG. 8 is an explanatory view of an embodiment in which a voltage application terminal is inserted from a half-shaped concave portion formed on a side surface of a case body and a cover to apply a voltage to a resistance heating element.

FIG. 9 is an explanatory diagram showing a state in which a voltage is applied from the side to generate heat in a resistance heating element and the resistance heating element is melted.

FIG. 10 is an explanatory view of a fusion state at a portion other than a voltage application point.

FIG. 11 is a perspective view of a case completed by the method of the second embodiment.

FIG. 12 is an explanatory diagram of a test piece and a test method used in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Battery case 20 Case main body 21 Fitting concave part 24 Small diameter hole 25 Projection step part 26 Enlarged part 27 Rib 28 Half-shaped concave part 30 Cover 40 Resistance heating element 41 Electrode 50 Voltage application terminal 60 Welding chip

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Michio Haga 1-11-1, Horaicho, Fukushima City, Fukushima Prefecture Tohoku Munekata Corporation

Claims (5)

[Claims] When a molded article formed of a thermoplastic resin is heat-welded, a resistance heating element is sandwiched between joining surfaces thereof, and a voltage is applied to the resistance heating element to generate heat while applying an appropriate force. Thereby, in the method of welding a molded product,
The resistance heating element is formed in a ring shape, and a voltage is applied to two points corresponding to approximately one-half of the length of the resistance heating element so as to reach the resistance heating element at a corresponding formed part. A small-diameter hole for terminal insertion is opened, and a voltage application terminal is inserted from the outside into the small-diameter hole to apply a voltage to the resistance heating element, thereby causing the resistance heating element to generate heat and welding a thermoplastic resin. Heat welding method. 2. The method according to claim 1, wherein a plurality of electrodes for contacting a voltage application terminal are provided on the resistance heating element. 3. The small-diameter hole is sealed by providing a projecting step around the small-diameter hole for inserting a voltage application terminal and crushing the step using a welding tip after welding of the molded product. 3. The method for heat-welding a thermoplastic resin according to 1 or 2. 4. A resistance heating element used for heat welding a thermoplastic resin formed by punching a thin plate into a ring shape. 5. A plastic case obtained by thermally welding a case body and a cover with a ring-shaped resistance heating element interposed between joint surfaces.