JP2008078052A - Design method of plate thickness of electric wire crimping part and terminal having electric wire crimping part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a design method capable of clarifying specifications of materials which can be changed without the need of trial production evaluation or the like at the time of correspondence for thinning of terminals with wire crimping parts of the same shapes. <P>SOLUTION: A reinforced α brass material is used for manufacturing a terminal with a wire crimping part, and when a 0.2% yield strength of a non-reinforced α brass material (I) conventionally used is σ<SB>0.2-I</SB>(MPa), and a plate thickness is t<SB>I</SB>(mm), a reinforced α brass material (F) satisfying a constant relation between a 0.2% yield-strength σ<SB>0.2-F</SB>(MPa) and a plate thickness t<SB>F</SB>(mm) is selected. Then, the reinforced α brass material used is to be composed of copper by 62 to 71.5 wt.% and the rest of zinc, and a crystal particle size is to be aligned at 1 to 2 μm, and the 0.2% yield strength to be 300 to 700 MPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for designing a material plate thickness to achieve thinning without reducing the crimping strength (wire holding strength) of a wire crimping portion when manufacturing a terminal having a wire crimping portion, and the material The terminal which has an electric wire crimping part obtained using is provided.

  Conventionally, brass materials have been widely used for electronic members and mechanism parts such as terminals and connectors because they have relatively high mechanical strength, relatively good electrical conductivity, and are inexpensive. As the types of these terminals, there are plate terminals including battery terminals and LA terminals when the plate thickness is thick, and fitting terminals having male and female members when the plate thickness is thin. Moreover, in many terminals, joining with an electric wire is essential, and a crimping method is often used as a joining method. Therefore, a brass material has been used as a material used for a terminal having a crimped portion unless particularly high strength, electrical conductivity, and stress relaxation properties are required.

  With the recent trend of thinning and thinning, there is an increasing need to reduce the thickness of parts, contribute to weight reduction, and reduce material costs. Therefore, Patent Document 1 proposes to increase the strength of the brass material by miniaturizing the crystal grains to reduce the size and weight of the product.

JP 2004-292875 A

  According to the above-mentioned Patent Document 1, a method of manufacturing a reinforced brass material that can contribute to weight reduction of a component is publicly known, and at the time of designing a new component, it is a general procedure to evaluate the suitability of the material by trial manufacture. No problem. However, when a reinforced α brass material is considered as an alternative material in conventional applications such as terminals, the criteria for selection differ depending on the type of terminal to determine how strong the reinforced α brass material is appropriate. For example, when the plate thickness is thick and the molding process is complicated like a battery terminal, securing the molding processability is regarded as important. And in the case of round terminals, it is only necessary to ensure the strength of the crimping part, and in the case of complicated processing such as mating terminals that combine male and female, forming workability such as bending workability Is important. Therefore, in order to know the strength level, a mold using a non-reinforced α brass material is used, various thicknesses of reinforced α brass materials having the same thickness as the non-reinforced brass but different strength levels are selected, and the appropriate strength level is selected. It will be trial and error as much as possible. Alternatively, for example, when 90-degree bendability becomes an index, for example, a reinforced α-brass material may be selected so that the 90-degree bendability is equivalent to the currently used non-reinforced α-brass material. And even if the strength level of the reinforced α brass material is determined in this way, it is necessary to make trial and error by trial manufacture of crimped parts with various plate thicknesses, how much thinning of the crimped parts by reinforcement is possible Become.

  Therefore, as a result of diligent research, the present inventor has selected a reinforced α brass material as a material for a terminal having a wire crimping portion, and a thickness design method for reducing the thickness while maintaining the wire holding strength of the wire crimping portion. I came up with this. According to the method of the present invention, if the strength of the reinforced α brass material is determined from the function required for the terminal (such as not affecting the moldability), how much thinning can be achieved, Easy to determine.

Method for designing wire crimping portion plate thickness when manufacturing a terminal having a wire crimping portion according to the present invention: The method for designing wire crimping portion plate thickness when producing a terminal having a wire crimping portion according to the present invention is a crystal A method for designing the thickness of a wire crimping portion when manufacturing a terminal having a wire crimping portion with a reinforced α brass material whose particle size is refined to 1 μm to 2 μm, and 0.2% of the reinforced α brass material (F) When the proof stress is σ _0.2-F (MPa) and the 0.2% proof stress of the non-reinforced α brass material (I) is σ _0.2-I (MPa), the reinforced α brass material (F) to be used It is characterized in that the thickness t _F (mm) is prepared so as to satisfy the following formula 2 with respect to the thickness t _I (mm) of the non-reinforced α brass material (I).

The non-reinforced α brass material has a 0.2% yield strength (σ _0.2-I ) of 200 MPa to 540 MPa, and the reinforced α brass material has a 0.2% yield strength (σ _0.2-F ) of 300 MPa to 700 MPa. Preferably there is.

  The reinforced α brass material is preferably 62 wt% to 71.5 wt% of copper, and the balance other than inevitable impurities is made of zinc.

Terminal having electric wire crimping portion according to the present invention: The terminal having the electric wire crimping portion according to the present invention uses a reinforced α brass material having a plate thickness selected by the above-described method for designing the electric wire crimping portion plate thickness. It is said.

  The method for designing a terminal having a wire crimping portion according to the present invention is characterized by using a reinforced α brass material as a raw material. And when the said reinforced alpha brass material (F) is used as a terminal material, compared with the terminal which uses the non-reinforced alpha brass material (I), it is easy to estimate how much the material thickness can be reduced. Become. As a result, since it is possible to easily estimate an appropriate thickness that can be thinned, it is possible to obtain a terminal having a wire crimping portion that is designed with fine adjustment according to a required level such as weight reduction.

  Hereinafter, the present invention will be described in more detail through embodiments and examples.

Form of wire crimping part plate thickness design method when producing a terminal having a wire crimping part according to the present invention: The design method of wire crimping part plate thickness when producing a terminal having a wire crimping part according to the present invention is as follows: A method for designing the thickness of a wire crimping portion when a terminal having a wire crimping portion is manufactured from a reinforced α brass material having a crystal grain size refined to 1 μm to 2 μm, which is a 0. When the 2% proof stress is σ _0.2-F (MPa) and the 0.2% proof stress of the non-reinforced α brass material (I) is σ _0.2-I (MPa), the reinforced α brass material (F ) thickness t _{F (mm)} of the to prepare to satisfy Equation 3 below is with respect to the thickness t _{I (mm)} of unreinforced α brass (I).

  In order to secure the wire holding strength of the crimping part, it is necessary not only to determine the reinforcement level of the reinforced α brass material, but also to prototype the crimping part with reinforced α brass material with different plate thickness and conduct a practical test. It was. However, in the present invention, it is possible to estimate the amount of reduction in thickness due to the improvement in strength by applying the above formula, and if the 0.2% proof stress is 1.2 times, the thickness can be reduced by about 9%. It turns out that it becomes. Furthermore, it can be seen that when the 0.2% proof stress is 1.5 times, the level of thinning is about 20%.

  However, when the shape of the wire crimping portion is not changed at all, it is preferable to use the following formula 4 instead of the above formula 3.

  When molding the terminal, if only the plate thickness is reduced using the same mold, when the electric wire is crimped using the obtained terminal, the pushing of the brass piece on the upper part of the crimping part becomes tight and the electric wire is damaged. There is a trend. Therefore, when the molding die is the same, it is preferable to reduce the thickness to 20%.

  The reinforced α brass material used here maintains the moldability while increasing the mechanical strength by refining the crystal grain size to 1 μm to 2 μm. When the crystal grain size exceeds 2 μm, the mechanical strength cannot be increased while maintaining the moldability. Therefore, it becomes impossible to design the plate thickness using the method of the present invention. Even if the crystal grain size is smaller than 1 μm, the effect of improving the moldability is saturated. At the current technical level, the lower limit of crystal refinement is considered to be about 0.5 μm, and the level at which industrialization is possible is about 0.8 μm. Therefore, the lower limit is set to 1 μm with the idea of rounding off after the decimal point.

In the present invention, as described above, in the terminal molding, it is an object to facilitate selection of the material thickness when replacing the non-reinforced α brass material with the reinforced α brass material. However, when the strength level of the reinforced α brass material is not determined, the 0.2% proof stress of the non-reinforced α brass material (I) to be substituted is σ _0.2-I (MPa). In addition, by making the 0.2% proof stress σ _0.2-F (MPa) of the reinforced α brass material (F) to satisfy the following formula 5, high strength is obtained without affecting the moldability. The inventor of the present invention has also conceived that it is possible to achieve the above-mentioned and has applied for a patent.

  By using the above formula 5, it is possible to estimate to what extent it is appropriate to obtain a material with increased mechanical strength. Therefore, it is possible to save materials and time, and contribute to resource and energy savings.

The non-reinforced α brass material has a 0.2% yield strength (σ _0.2-I ) of 200 MPa to 540 MPa, and the reinforced α brass material has a 0.2% yield strength (σ _0.2-F ) of 300 MPa to 700 MPa. Preferably there is. As described above, α brass materials of 1 / 2H to EH are generally used for terminals, but their 0.2% proof stress (σ _0.2-I ) is 200 MPa to 540 MPa. . And the 0.2% yield strength ((sigma) _0.2-F ) of reinforced alpha brass material is 300 MPa-700 MPa. The portion below the lower limit of the reinforced α brass material is in a range where there is no problem in moldability even with the non-reinforced α brass material, and there is no need to use the reinforced α brass material. When the upper limit is exceeded, although the crystal grains are refined, there is a problem in the bending workability, which causes a problem in the bending workability and the bending becomes substantially impossible.

  The reinforced α brass material used here is one in which the crystal grain size is refined to 1 μm to 2 μm so as not to impair the moldability, and can be adjusted to the target mechanical strength by employing the following steps. First, the ingot used for rolling casts the molten metal adjusted to the composition range mentioned later by a continuous casting method. First, the ingot is hot-rolled and faced by a regular method. Thereafter, cold rolling with a working rate of 40% to 90% and subsequent annealing are repeated as necessary to obtain a brass strip having a Vickers hardness adjusted to 130 to 170. Furthermore, after subjecting the strip to cold rolling at a processing rate of 0% to 25%, low-temperature annealing is performed as necessary to adjust the 0.2% proof stress to 90% of the maximum value, and reinforced α brass The strip is prepared. According to this manufacturing method, a reinforced α brass material excellent in moldability and mechanical strength can be obtained.

  The reinforced α brass material is preferably 62 wt% to 71.5 wt% of copper and the balance other than unavoidable impurities is made of zinc. The composition of the α brass material according to the present invention is a range that covers C2600, C2680 and C2720 as defined by JIS standards. The reason why the composition range is defined as the reinforced α brass material in the present invention will be described. In a copper-zinc alloy, if the amount of the copper component exceeds 71.5 wt%, the mechanical strength level becomes low, and if the mechanical strength is forcibly increased, the tendency for workability to deteriorate becomes remarkable. Moreover, if the amount of copper component is less than 62 wt%, a β phase appears, and a single phase structure of an α phase cannot be obtained. When the β phase appears, it becomes a crystal structure in which two phases coexist, and electrochemically, the phase interface becomes a starting point of corrosion, which causes anxiety factors such as deterioration of stress corrosion cracking property.

Form of a terminal having a wire crimping portion according to the present invention: A terminal having a wire crimping portion according to the present invention is made of a reinforced α brass material (F) having a thickness selected by the above-described method for designing a wire crimping portion plate thickness. It is characterized by the use. As described above, when the 0.2% proof stress becomes 1.2 times, it becomes possible to reduce the thickness by about 9%, and when the 0.2% proof stress becomes 1.5 times, the level of thinning becomes about 20%. . Therefore, the terminal manufactured using the material design method according to the present invention described above is 9% lighter if 0.2% proof stress is 1.2 times as the material. If the 0.2% proof stress is 1.5 times, the weight will be reduced by 20%. In addition, in order to improve the reliability of electrical connection, it is preferable that the terminal having the wire crimping portion according to the present invention is subjected to Sn plating on the surface, like the conventional terminal.

  Furthermore, as will be apparent from the examples described later, the influence of the crimp height on the wire holding strength is reduced by using a material having a high mechanical strength. Therefore, the range in which the crimp height can be selected during the crimping operation is widened, and the occurrence of defects due to operational errors can be suppressed. Certainly, when a large amount of terminal processing is performed, since it is connected by an automatic machine, the occurrence of problems is considered rare. However, when a crimping operation is carried out for repairing or the like, it is possible to connect the terminal to the electric wire with stable quality even when the skill level of the operator is low.

  Hereinafter, the present invention will be described in more detail through examples. In the present invention, the crimping level of an electric wire that does not impede practical use is a level close to the maximum strength obtained when the electric wire is crimped to a crimp terminal shape, and the crimping strength within a range that takes into account a certain variation. That's it. The ease of disconnection after wire crimping is also affected by the shape design such as inserting ribs. Therefore, the simplest terminal shape that conforms to 2 mm square thickness of the wire was adopted and evaluated. FIG. 1 shows the shape of the terminal, FIG. 2 shows a photograph of the actual appearance, FIG. 3 shows a state in which the electric wire is properly crimped, and FIG. 4 shows a cross section taken along the line AB in FIG. And since crimp height is set too high, the crimping | compression-bonding of an electric wire is not performed sufficiently, but the cross section of the crimping | compression-bonding part in a state with insufficient electric wire holding strength is shown in FIG. Moreover, although thinning was implemented to 20%, the crimping | compression-bonding part when an electric wire holding strength did not fall is shown in FIG.

  The α brass material for forming the terminal is made of a material having a proof stress of 380 MPa, 490 MPa, 580 MPa, 650 MPa, and thicknesses of 0.40 mm, 0.45 m, 0.50 mm, 0.55 mm, and 0.60 mm. The type was used. And since it is clear that the crimpability varies depending on the setting of the crimping jig to be used, for the purpose of enabling comparison under the optimum conditions, an experiment was conducted in which the crimp height was changed for each terminal. The electric wire holding strength of the portion was obtained, and data on the minimum plate thickness indicating the optimum crimping strength was obtained.

  Here, the criteria for determining whether or not the crimped state is good in an actual test will be described. When the crimp height is set to be smaller than the range in which the electric wire disconnection occurs, the crimping property is seemingly good even if the mechanical strength of the material is insufficient, and no electric wire disconnection is observed, and the electric wire holding strength in the vicinity of about 300 N is shown. However, if the crimp height is set too low, the brass piece of the terminal bites into and damages the electric wire at the time of crimping, and thus a phenomenon that the electric wire is easily broken at the crimping portion is observed. Therefore, in the present invention, the electric wire holding strength (N) obtained when the crimp height is optimally prepared is referred to as “crimping strength (N)”. Below, the material with the minimum 0.2% yield strength is the non-reinforced α brass material, and the material with the maximum 0.2% yield strength is the reinforced α brass material, and the test results are compared.

<Non-reinforced α brass material>
Fig. 3 shows the results of a test conducted on an unreinforced α brass material (I) having a 0.2% proof stress of 380 MPa, a composition of 65.1 wt% copper and the balance zinc, and a crystal grain size of 10 to 15 µm. 7 shows. As is apparent from FIG. 7, the terminal having a thickness of 0.6 mm shows a maximum wire holding strength of 322 N near the crimp height of 1.97 mm. In the case of a material having a plate thickness of 0.55 mm, the crimp height indicating the maximum value of the wire holding strength is as low as 1.82 mm as much as the plate thickness is reduced, but the maximum value indicates 326N. Therefore, the minimum thickness that can be used for the material used in this example was evaluated to be 0.55 mm. By the way, in the material with a plate thickness of 0.6 mm, when the crimp height is lowered to 1.94 mm, a sharp decrease in the wire holding strength is observed. And even with a material of 0.55 mm, the wire holding strength sharply decreases at a crimp height of 1.80 mm, and the material used here has a tendency to decrease the wire holding strength when the crimp height is lowered from the optimum value. Are commonly seen. And from the above result, the minimum value of the crimping | compression-bonding intensity | strength which does not have a practical problem in the Example which concerns on this invention was set to 320N.

<Reinforced α brass material>
And the result of having implemented the test with respect to the reinforced alpha brass material (F) whose material 0.2% proof stress is 650MPa, has a composition of copper 65.2wt% and the balance zinc, and the crystal grain size is 1.4μm. As shown in FIG. As is clear from FIG. 8, the maximum value of the wire holding strength is 320 N or more in the whole range of the plate thickness from 0.4 mm to 0.6 mm, and even if the plate thickness is 0.4 mm, it is sufficiently practical. It was something to endure. Therefore, the minimum usable thickness is 0.4 mm. However, when the crimp height is changed from the optimum value to the high side or the low side using the same thickness material as seen in the non-reinforced α brass material (I), the wire holding strength changes rapidly. The phenomenon of doing is not seen.

  From the above two examples, when using a material with low mechanical strength, such as the above-mentioned non-reinforced α brass material (I), if the crimp height is high, the crimping becomes weak and the wire holding strength becomes insufficient. If the crimp height is made too low in order to increase the strength, the folded brass piece will damage the electric wire. In this case, since the durability until the wire breaks is reduced, the setting of the crimp height is important in order to obtain a stable wire holding strength. However, when a reinforced α-brass material with higher mechanical strength is used, there is no abrupt decrease in wire holding strength corresponding to changes in the crimp height. Therefore, it is clear that the advantage of using a reinforced α brass material having high mechanical strength and good workability is not only to make the material thin and lightweight. In other words, even if the optimally thin material is used, the failure of the crimping operation is reduced, the occurrence of defects can be suppressed even if the skill of the operator for the wire crimping operation is shallow, and the setting of the crimp height can be widened. Work efficiency is improved.

  Furthermore, as two types of reinforced α brass materials having different preparation levels, the composition is the same as the material having a 0.2% proof stress of 650 MPa, the crystal grain sizes are 1.4 μm and 1.5 μm, respectively, and the 0.2% proof stress is Tests were similarly performed on materials set to 490 MPa and 580 MPa. As a result, when a material having a 0.2% proof stress of 490 MPa was used, the minimum plate thickness for obtaining a practically unobstructed crimp strength was 0.50 mm, and a material having a 0.2% proof stress of 580 MPa was used. In this case, the minimum plate thickness at which the pressure-bonding strength without any practical problem was obtained was 0.45 mm. Table 1 shows the relationship between the 0.2% proof stress of the material and the minimum plate thickness, and the error from the plate thickness obtained in the calculation.

As shown in Table 1, the crimping strength obtained regardless of the plate thickness was 326N to 337N, and the wire holding strength was sufficient with the wire gradually breaking. The relationship between the 0.2% proof stress and the minimum thickness of the material shown in Table 1 is shown in FIG. As a correlation equation of the relationship between the 0.2% proof stress σ _0.2 (MPa) and the plate thickness t (mm) shown in FIG. 8, the following equation 6 having a constant of 15 is obtained.

In this equation, it can be considered that the constant is determined according to the shape of the crimping portion. Therefore, when replacing the non-reinforced α brass material (I) with the reinforced α brass material (F), the 0.2% proof stress σ _0.2-I (MPa) of the non-reinforced α brass material (I) and the plate By using the thickness t _I (mm), the 0.2% proof stress σ _0.2-F (MPa) of the reinforced α brass material (F) and the plate thickness t _F (mm), material replacement at individual crimping parts In the case of thinking, by setting the constant to be the same, the following equation 7 with an error of ± 10% is derived.

  Table 1 compares the plate thickness calculated using Equation 7 and the minimum plate thickness obtained in the example. According to the calculation according to the present invention, it is clear that an appropriate plate thickness can be determined without performing a test in which the plate thickness of the crimping portion is changed. In addition, the crimping part of the terminal using the reinforced α brass material has sufficient wire holding strength equivalent to or better than that of the crimping part using the non-reinforced α brass material, even though it is thin. ing.

  The method for designing a terminal having a wire crimping portion according to the present invention is characterized by using a reinforced α brass material as a raw material. By using the reinforced α brass material as a terminal material, it becomes easy to design the material to what extent the thickness of the material can be reduced as compared with the conventional terminal using the α brass material. As a result, it is possible to easily estimate the appropriate plate thickness that can be thinned, so that it is possible to obtain a terminal having a crimped portion with guaranteed electric wire holding strength without repeating trial and error according to the required level such as weight reduction. Become. Conventionally, since this trial and error is cumbersome and unrecognizable, it is also true that the use of reinforced brass has been postponed, and the significance of the present invention is also great in this respect.

  Depending on the degree of thinning, if the thickness is about 10%, there is no need to change the mold used for the molding process. Such thinning can obviously reduce the weight of parts, and at the same time, saves material, and has a great economic effect.

It is a manufacture figure of the terminal which has the electric wire crimping part manufactured in the Example. It is a terminal which has the electric wire crimping | crimped part manufactured in the Example. . It is the figure which crimped | bonded the electric wire favorably to the terminal which has the electric wire crimping part manufactured in the Example. It is a figure which shows the cross section in the arrow view (AB) of the crimping | compression-bonding part in FIG. It is a crimping | compression-bonding cross section at the time of crimping | bonding an electric wire by crimp height excess using unreinforced alpha brass material (I) in an Example. It is the crimping | compression-bonding part cross section of the terminal which obtained appropriate crimping strength with the reinforcement | strengthening (alpha) brass material with a board thickness of 0.4 mm using the metal mold | die for board thickness of 0.5 mm created in the Example. It is a figure which shows the result of having evaluated the electric wire holding strength using the terminal which has the electric wire crimping part manufactured with the material whose 0.2% yield strength is 380 Mpa. It is a figure which shows the result of having evaluated the electric wire holding strength using the terminal which has the electric wire crimping part manufactured with the material whose 0.2% yield strength is 650 MPa. It is a figure which shows the relationship between the 0.2% yield strength of material and minimum board thickness which can ensure crimping | compression-bonding strength.

Claims (4)

A method for designing a wire crimping portion plate thickness when manufacturing a terminal having a wire crimping portion with a reinforced α brass material whose crystal grain size is refined to 1 μm to 2 μm,
The 0.2% proof stress of the reinforced α brass material (F) is σ _0.2-F (MPa), and the 0.2% proof stress of the non-reinforced α brass material (I) is σ _0.2-I (MPa). The thickness t _F (mm) of the reinforced α brass material (F) used is adjusted so as to satisfy the following formula 1 with respect to the thickness t _I (mm) of the non-reinforced α brass material (I). A method for designing a thickness of a wire crimping portion, characterized by:
The non-reinforced α brass material has a 0.2% yield strength (σ _0.2-I ) of 200 MPa to 540 MPa, and the reinforced α brass material has a 0.2% yield strength (σ _0.2-F ) of 300 MPa to 700 MPa. The method for designing the thickness of the wire crimping portion according to claim 1. 3. The method for designing the thickness of a wire crimping portion according to claim 1, wherein the reinforced α brass material is composed of 62 wt% to 71.5 wt% of copper and the remainder other than inevitable impurities is made of zinc. The terminal which has an electric wire crimping part using the reinforcement | strengthening (alpha) brass material of the plate thickness selected by the design method of the electric wire crimping | compression-bonding board thickness in any one of Claims 1-3.