Patent Application
20170141483
Field of the Invention
The present invention relates to a terminal for aluminum electric wire connection and a method for producing the same.
Description of Related Art
In recent years, there are increasing demands for an aluminum electric wire, which is light in weight and low in cost, for the purpose of achieving both an improvement of energy efficiency and a reduction of cost. In a case where this electric wire having the above characteristics is connected to an electric apparatus, means for connecting copper and aluminum is needed because a wire in the electric apparatus is copper in many cases, and a copper-alloy terminal is often used as such means. Various methods such as a method using soldering, a method using an ultrasonic wave, a method using fusing, and a method using laser have been proposed as a method for the terminal connection. Especially soldering is an excellent method that provides reliable joining because soldering makes it possible to firmly connect an entire connection part in a case where a large number of aluminum wires are connected.
However, in general, in a case where an aluminum electric wire is connected to a copper-alloy terminal, an aluminum wire in the terminal does not reach a predetermined necessary temperature due to low heat conductivity of the copper-alloy terminal even when the terminal is heated in soldering. It is therefore undesirably hard to introduce a flux or molten solder into the whole of the inside of the terminal. This results in formation of voids in the solder and parts that are not soldered, thereby causing a problem that the reliability of electrical joining becomes low. The voids can be a cause of discharge, occurrence of electric erosion, an increase of electric resistance, generation of heat during application of electricity, and the like and are therefore not desirable. Furthermore, the voids easily include air and moisture, and thermal conductivity decreases due to the presence of air and moisture. This leads to less certainty of joining. Meanwhile, in a case where the terminal and an end of the electric wire are compressed by swaging with great force in order to reduce voids and improve thermal conductivity, there is a risk of damaging of the electric wire and even breaking of the electric wire.
Techniques concerning joining between an electric wire and a terminal are, for example, disclosed in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a technique concerning a connection terminal for ultrasonic wave joining between an aluminum electric wire and a terminal made of copper using an ultrasonic horn chip, and Patent Document 2 discloses a technique concerning a terminal metal fitting including a pipe-like conductor connection part that is integral with a plate member main body made of aluminum and into which a twisted-wire conductor is inserted, and a dissimilar-metal layer that is made of a metal that is not aluminum and is provided on a bottom surface of the plate member main body.
[Patent Document 1] JP Laid-open Patent Publication No. 2007-12329
[Patent Document 2] JP Laid-open Patent Publication No. H09-204947
In view of the circumstances, the applicant of the present application has conceived of a terminal joining structure for an electric wire end portion illustrated in
The terminal joining structure for an electric wire end portion illustrated in
A plurality of linear heat transmitting members 13 are inserted into the electric wire end portion 12a so as to be apart from one another by an appropriate interval. Each of the heat transmitting members 13 forms a high-temperature passage for solder introduction in the electric wire end portion 12a during soldering. In this state, for soldering, first and second electrodes 14a and 14b are disposed on an outer side in a radial direction of the terminal main part 11a so as to face each other, and third and fourth electrodes 15a and 15b are disposed on an outer side in a radial direction of the terminal piece 11b so as to face each other.
Next, as illustrated in
In this state, the terminal main part 11a, the terminal piece 11b, and the electric wire end portion 12a are heated by applying an electric current between the first and second electrodes 14a and 14b and between the third and fourth electrodes 15a and 15b. Heating of the electric wire end portion 12a by the third and fourth electrodes 15a and 15b is transmitted to the electric wire end portion 12a via the heat transmitting members 13 in the terminal main part 11a. As a result, the electric wire end portion 12a in the terminal main part 11a is evenly heated. This allows a flux and solder to be efficiently introduced into the electric wire end portion 12a in the terminal main part 11a, thereby accomplishing soldering with certainty.
However, in a case where the electric wire end portion 12a exposed on the terminal piece 11b is temporarily sectioned to a first end 12a1 that is close to the terminal main part 11a and a second end 12a2 that is far from the terminal main part 11a, the first end 12a1 is not pressed against the inside of the terminal piece 11b by the third electrode 15a, but the second end 12a2 is pressed against the inside of the terminal piece 11b by the third electrode 15a.
This creates a sharp difference in height between the first end 12a1 and the second end 12a2. Furthermore, since the electric wire end portion 12a is an aluminum wire and is therefore hard to heat, an electric current applied between the third and fourth electrodes 15a and 15b becomes excessively large. Accordingly, the end 12a2 is heated to an excessively high temperature, and stress acts between the end 12a1 and the end 12a2. This undesirably increases the possibility of damaging of the electric wire end portion 12a.
In view of this, a main purpose of the present invention is to provide a terminal connection structure in which the aforementioned sharp difference in height is not present and the shape of a third electrode is improved, and a method for producing such a terminal connection structure.
In order to attain the purpose, a terminal connection structure according to the present invention is a terminal connection structure for an electric wire end portion in which the electric wire end portion is soldered being exposed on a flat-plate terminal piece out from inside of a terminal main part, the terminal piece being continuous with a front end of the terminal main part, wherein the electric wire end portion exposed on the terminal piece from the terminal main part includes a first end section that is close to the terminal main part and a second end section that is far from the terminal main part, and the electric wire end portion has a shape, in side view, such that the first end section is compressed to have a gentle curved surface that approaches the terminal piece toward the second end section.
In the terminal connection structure according to the present invention, the electric wire end portion exposed on the terminal piece has a shape, in side view, such that the first end section is compressed to have a gentle curved surface that approaches the terminal piece toward the second end section. This allows stress acting between the first end section and the second end section to be dispersed, thereby preventing the electric wire end portion from being broken at a part where the electric wire end portion is exposed on the terminal piece from the terminal main part. It is therefore possible to provide a terminal connection structure that has high mechanical reliability.
In one embodiment of the present invention, an inclination angle θ of an intermediate part of the first end section in a longitudinal direction is 20° to 70° on an upper side that is a side far from a soldering surface on which the electric wire end portion on the terminal piece is soldered.
In another embodiment of the present invention, a recess having a gently inclined side wall surface is provided in a soldering surface on which the electric wire end portion on the terminal piece is soldered. It is preferable that a protrusion that promotes thermal conduction between the electric wire end portion and the terminal piece or a protrusion around which the electric wire end portion is wound is provided in the recess.
In a further embodiment of the present invention, a pair of restricting walls that regulate spread of the electric wire end portion on a soldering surface on which the electric wire end portion on the terminal piece is soldered are provided along respective side edges of the soldering surface.
A method for producing a terminal connection structure according to the present invention is a method in which an electric wire end portion is soldered being exposed on a flat-plate terminal piece from inside of a terminal main part, the terminal piece being continuous with a front end side of the terminal main part, the method including the steps of: heating the terminal piece and the electric wire end portion by applying an electric current between a pair of electrodes in a state where the terminal piece and the electric wire end portion exposed on the terminal piece are pressed from both sides thereof in a radial direction by the pair of electrodes; and introducing a flux and then solder into the inside of the terminal main part and onto the terminal piece in a state where the terminal piece and the electric wire end portion are heated, wherein one of the pair of electrodes that presses the electric wire end portion has a curved surface shape or a tapered surface shape at an edge part thereof that is on a radially inner side and on a terminal main part side.
In the method for producing a terminal connection structure according to the present invention, one of the pair of electrodes that presses the electric wire end portion has a curved surface shape or a tapered surface shape at an edge part thereof that is on a radially inner side and on a terminal main part side. Accordingly, when the pair of electrodes are pressed against the terminal piece and the electric wire end portion exposed on the terminal piece from both sides thereof in the radial direction, the electric wire end portion exposed on the terminal piece is pressed so that the first end section is compressed to have, in side view, a gentle curved surface that approaches the terminal piece toward the second end section. This allows stress acting between the first end section and the second end section to be dispersed, thereby preventing the electric wire end portion from being broken at a part where the electric wire end portion is exposed on the terminal piece from the terminal main part.
Furthermore, in a case where the terminal piece and the electric wire end portion are heated by applying an electric current between the electrodes, the electric current flows in a scattered manner throughout the electric wire end portion from the first end section side to the second end section side. Thus, a rise in temperature caused by heating of the electric wire end portion becomes gentle, leading to improvement in performance of a subsequent soldering process in which a flux and solder are introduced. Furthermore, since the electric wire end portion is heated by applying an electric current between the third electrode and the fourth electrode in a state where the electric wire end portion is nipped by the pair of third and fourth electrodes that face each other in the radial direction and the electric wire end portion is soldered by introducing solder and a flux into the terminal main part, the electric wire end portion and the terminal are soldered onto each other without creating voids in the terminal. As a result, it is possible to provide a terminal connection structure that is free from troubles caused by voids and that accomplishes a good solder connection state.
One embodiment of the method according to the present invention further includes the step of heating the terminal main part and the electric wire end portion inside the terminal main part by applying an electric current between a pair of first and second electrodes in a state where the terminal main part is pressed from both sides thereof in the radial direction by the pair of first and second electrodes.
Another embodiment of the method according to the present invention further includes the step of inserting, into the electric wire end portion, a plurality of heat transmitting members each having a wire shape and being made of a metal having higher thermal conductivity than the electric wire end portion.
A further embodiment of the method according to the present invention is arranged such that a recess having a gently inclined side wall surface is provided in a surface of the terminal piece on which the electric wire end portion is soldered; and the other one of the pair of electrodes that presses the terminal piece presses part of the terminal piece that is located out of the recess on a side opposite to the terminal main part.
A still further embodiment of the method according to the present invention is arranged such that a pair of restricting walls are provided along respective side edges of the terminal piece; and the steps are performed in a state where spread of the electric wire end portion exposed on the terminal piece is restricted by the pair of restricting walls.
Any combination of at least two constructions, disclosed in the appended claims and/or the specification and/or the accompanying drawings should be construed as included within the scope of the present invention. In particular, any combination of two or more of the appended claims should be equally construed as included within the scope of the present invention.
In any event, the present invention will become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:
A method for producing a terminal connection structure for an electric wire end portion and the terminal connection structure according to an embodiment of the present invention are described below. A terminal 11 in the terminal connection structure is described with reference to
A side wall surface 11g of the recess 11e is a gentle slope, as illustrated in the enlarged view of
A plurality of protrusions 110 are provided on a bottom surface of the recess 11e. Each of the protrusions 110 has an elongated shape extending in the longitudinal direction C, which is an axial direction, as is clear from
The restricting walls 11f rise in a direction of the soldering surface 11d and thus restrict spread of the overall width of the electric wire end portion 12a as illustrated in
In the terminal 11 configured as above, an electric wire 12 made of aluminum, copper, or the like is mounted from an opening of the terminal main part 11a on one side, and an end 12a, which is a front end portion of the electric wire 12, is soldered inside the terminal main part 11a and on the soldering surface 11d which is a top surface of the terminal piece 11b, as illustrated in
A plurality of linear heat transmitting members 13 are inserted into the electric wire end portion 12a inside the terminal main part 11a so as to be disposed apart from one another by a predetermined interval in parallel with the longitudinal direction C of the electric wire end portion 12a. The heat transmitting members 13 are inserted into the electric wire end portion 12a while keeping the linear shape so as to form high-temperature passages in the electric wire end portion 12a during soldering, and in this state, solder (not illustrated) is introduced to the inside of the terminal main part 11a through the high-temperature passages. The heat transmitting members 13 also have a function of promoting flow of the solder and flux in the electric wire end portion 12a. The number of heat transmitting members 13 inserted into the electric wire end portion 12a may be more than one or may be one.
The heat transmitting members 13 are made of a metal (e.g., copper) having higher thermal conductivity than the electric wire end portion 12a, and a metal plating layer having a thickness of approximately 6μ to 10μ and made of a material such as tin or solder is provided on a surface of each of the heat transmitting members 13. The metal plating layer (not illustrated) on the surface of the terminal 11 and the metal plating layer on the surfaces of main body of the heat transmitting members 13 melt due to high heat applied to the terminal 11 during soldering. This makes it easier to form the high-temperature passages.
The electric wire end portion 12a is aligned along the pair of restricting walls 11f without spreading the overall width on the soldering surface 11d of the terminal piece 11b because of the pair of restricting walls 11f, as illustrated in
Next, a soldering method according to the embodiment is described with reference to
In this case, each of the first and second electrodes 14a and 14b and the fourth electrode 15b has a cubic shape, whereas the third electrode 15a has a shape such that an edge part thereof on the radially inner side and on the terminal main part 11a side has a shape of a predetermined curved surface bulging toward the terminal main part 11a as illustrated in
The shape of the curved surface S3 includes not only a partial cylindrical surface, but also a shape that changes in an exponential manner or in a parabolic manner. In this case, the third electrode 15a may have a curved surface S4 obtained by curving the entire surface facing the electric wire end portion 12a while eliminating the side surface S1, as illustrated in
Next, as illustrated in
Similarly, the third and fourth electrodes 15a and 15b are pressed against the terminal piece 11b outside the terminal main part 11a and against the electric wire end portion 12a on the terminal piece 11b from both sides thereof in the radial direction, so that the electric wire end portion 12a and the terminal piece 11b are nipped by the third and fourth electrodes 15a and 15b. In this state, the terminal piece 11b and the electric wire end portion 12a are heated by applying an electric current between the third and fourth electrodes 15a and 15b. A method for applying an electric current is not limited in particular.
In this case, an edge part 15a1 (
That is, the electric wire end portion 12a is gently curved between a rear edge 121 which is the highest portion of the curved first end section 12a1 on an upper side (side far from the terminal piece 11) of the first end section 12a1, and a rear edge 122 of the second end section 12a2 at which the curve ends and a straight part starts, and a ratio (L/H) of a dimension L in the longitudinal direction between the rear edges 121 and 122 to a height difference H between the rear edges 121 and 122 is 0.4 to 2.8, preferably 0.7 to 2.5, more preferably 1.0 to 2.0. The above three ranges of the ratio L/H are 20° to 70°, preferably 20° to 55°, more preferably 25° to 45° when expressed by an inclination angle θ of a longitudinal-direction intermediate part 12m of the first end section 12a1 with respect to the longitudinal direction C. In a case where the inclination angle θ is 70° or more, the first end section 12a1 is steeply curved, and the electric wire end portion 12a is more likely to be damaged. In a case where the inclination angle θ is less than 20°, the first end section 12a1 becomes too long, and the size of the terminal connection structure becomes large.
Furthermore, since a part of the terminal piece 11b in which the recess 11e is not provided is pressed by the third and fourth electrodes 15a and 15b with the electric wire end portion 12a interposed therebetween, a sufficient amount of electric current flows on the second end section 12a2 side of the electric wire end portion 12a so as to heat the second end section 12a2 side, whereas the temperature inside the recess 11e does not become high, and heat is gradually transmitted. This heat gradually evaporates the flux accumulated in the recess 11e and allows solder introduced from the second end section 12a2 to the first end section 12a1 to be sufficiently introduced into the electric wire end portion, whereby the electric wire end portion is soldered. In this case, because of the recess 11e, gentle inclination of the side wall surface 11g of the recess 11e, and taper of the edge part 15a1 of the third electrode 15a, damage of the electric wire end portion 12a caused by heat is small, and since excessive stress does not act, mechanical damage of the electric wire end portion 12a is also small.
The above configuration prevents formation of a sharp difference in height between the first end section 12a1 and the second end section 12a2 of the electric wire end portion 12a outside the terminal main part 11a. Thus, during soldering, the electric wire end portion 12a is hard to be broken, and owing to the recess 11e, a flux is less apt to evaporate and is maintained for a long period. As a result, the electric wire end portion 12a can be soldered onto the soldering surface 11d of the terminal piece 11b with high reliability.
In the electric wire end portion 12a, the heat transmitting members 13 are almost parallel with the twisted wires of the electric wire end portion 12a. Upon application of heat to the terminal main part 11a from outside, high heat is transmitted to the heat transmitting members 13. This melts the metal plating layer provided on each of the heat transmitting members 13, thereby forming a high-temperature passage around each of the heat transmitting members 13. In this state, a flux and molten solder such as aluminum solder are introduced into the terminal main part 11a from above. The flux introduced into the terminal main part 11a flows into the electric wire end portion 12a along the heat transmitting parts 13 having a high temperature and expands to the inside of the terminal main part 11a.
Furthermore, the flux is absorbed into the electric wire end portion 12a due to a capillary action caused by gaps around each of the heat transmitting members 13. As a result, the flux acts on the surface of the electric wire end portion 12a and removes an oxide film formed on the surface of the electric wire end portion 12a. Next, the introduced molten solder flows into the electric wire end portion 12a while being guided by the heat transmitting members 13, as in the flux. As a result, the solder spreads inside the terminal main part 11a and connects the twisted wires of the electric wire end portion 12a to one another and connects the electric wire end portion 12a and the terminal main part 11a. In this way, inside the terminal main part 11a, the flux acts on the surface of the electric wire end portion 12a, and the molten solder makes contact with the electric wire end portion 12a from which the oxide film has been removed by the flux, thus forming a good soldered part having no void inside the terminal main part 11a.
The electric wire end portion 12a may be divided into two parts in a width direction orthogonal to the longitudinal direction C, and the divided parts may be wound around the protrusion 112, as illustrated in
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings which are used only for the purpose of illustration, those skilled in the art will readily conceive numerous changes and modifications within the framework of obviousness upon the reading of the specification herein presented of the present invention. Accordingly, such changes and modifications are, unless they depart from the scope of the present invention as delivered from the claims annexed hereto, to be construed as included therein.
This application is a continuation application, under 35 U.S.C. §111 (a) of international application No. PCT/JP2014/070260, filed Jul. 31, 2014.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/070260 | Jul 2014 | US |
| Child | 15418852 | US |
