Evaluation and prediction method for insulated wire with terminal

Abstract

The present invention addresses the problem of providing a method whereby it is possible to easily predict the result of a free drop test of an insulated wire with a terminal. The evaluation and prediction method for solving the problem is an evaluation and prediction method when a free drop test is performed on an insulated wire (20) with a terminal, the insulated wire (20) with the terminal having an insulated wire (1) and a terminal (10) connected to at least one end of the insulated wire (1). An evaluation and prediction method for an insulated wire with a terminal, the insulated wire (1) having a conductor (2) formed by twisting a plurality of bare wires and a coating layer (3) that coats the conductor, the evaluation and prediction method having a step for checking whether the tensile strength of the conductor and the 3% endurance of the coating layer satisfy the following equation.

Description

Technical Field

[0001] The present invention relates to an evaluation prediction method for an insulated electric wire with a terminal. Background Art

[0002] Insulated wires having a conductor and a coating covering the conductor have long been used as power lines or signal lines for vehicles or industrial use. Recently, with the complex control and automation of vehicles and industrial machinery, there is a demand for thinner and stronger wires. As insulated wires for vehicles, it has been proposed to set the cross-sectional area of ​​the conductor to approximately 0.22 mm. 2 Various insulated wires are disclosed, such as an insulated wire having an oil content of 0.0447 W (Patent Document 1), an insulated wire in which the amount of oil adhering to the conductor is adjusted to suppress buckling (Patent Document 2), and the like.

[0003] Generally speaking, insulated wires are rarely used alone, and terminals are connected to both ends of the insulated wires, and various devices are connected via these terminals. In addition, when assembling automobiles or industrial machinery, or when using automobiles or industrial machinery, the equipment may fall while the various devices are connected to the wires. As a result, stress in the direction of free fall is applied to the insulated wires instantly, and the wires may break. If such a break occurs, the equipment may be damaged or sufficient conduction may not be achieved between the equipment.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent No. 61 34103.

[0007] Patent document 2: Japanese Patent No. 6864856. Summary of the invention

[0008] Problem that the invention aims to solve

[0009] The resistance of an insulated wire to a free fall of the above-mentioned equipment is generally evaluated by a free fall test. Moreover, when selecting the material of the conductor or coating layer of the above-mentioned insulated wire or evaluating the performance of the insulated wire with a terminal, a free fall test needs to be performed each time, which is very troublesome. Therefore, it is desired to provide a method for evaluating the results of a free fall test more simply.

[0010] A main object of the present invention is to provide a method capable of easily predicting the evaluation of a free drop test of an insulated wire with a terminal.

[0011] Solutions to the problem

[0012] According to one aspect of the present invention, there is provided an evaluation prediction method for an insulated wire with a terminal, which is an evaluation prediction method when a free drop test is performed on the insulated wire with a terminal, wherein the insulated wire with a terminal comprises an insulated wire and a terminal connected to at least one end of the insulated wire, the insulated wire comprises a conductor formed by twisting a plurality of bare wires and a coating covering the conductor,

[0013] The evaluation prediction method of the insulated wire with a terminal includes a step of confirming whether the tensile strength of the conductor and the 3% proof stress of the coating layer satisfy the following formula.

[0014] 100[N]≤(tensile strength of conductor[N]×0.7)+(3% endurance of coating[N])

[0015] According to another aspect of the present invention, there is provided an evaluation prediction method for an insulated wire with a terminal, which is an evaluation prediction method for a free drop test of an insulated wire with a terminal, wherein the insulated wire with a terminal comprises an insulated wire and a terminal connected to an end of the insulated wire, the insulated wire comprises a conductor formed by twisting a plurality of bare wires and a coating covering the conductor,

[0016] The evaluation prediction method of the insulated wire with a terminal comprises:

[0017] A step of determining a minimum value of the terminal fixing force required to achieve a 100% pass rate in the free drop test; and

[0018] A step of confirming whether the minimum value, the tensile strength of the conductor, and the 3% proof stress of the coating layer satisfy the following formula.

[0019] Minimum value [N] ≤ (tensile strength of conductor [N] × 0.7) + (3% endurance of coating [N])

[0020] Effects of the Invention

[0021] According to the evaluation prediction method of the insulated wire with a terminal of the present invention, the result of the free drop test of the insulated wire with a terminal can be easily predicted. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a side view showing an example of an insulated wire with a terminal.

[0023] Figure 2A It is a schematic cross-sectional view showing an example of an insulated wire.

[0024] Figure 2B It is a schematic cross-sectional view showing another example of the insulated wire.

[0025] Figure 3This is a flowchart showing the steps of an evaluation prediction method for an insulated wire with a terminal according to one embodiment.

[0026] Figure 4 This is a flowchart showing the steps of an evaluation prediction method for an insulated wire with a terminal according to another embodiment.

[0027] Figure 5 This is a graph showing the correlation between the terminal fixing force of the insulated wire with terminal and the pass rate of the free drop test.

[0028] Figure 6 This is a graph showing the relationship between the tensile strength of a conductor, the fixing force when the conductor is fixed to a terminal, and the cross-sectional area of ​​the conductor. DETAILED DESCRIPTION

[0029] First, an insulated wire with a terminal, which is a target of the evaluation prediction method of the present invention, will be described, and then the evaluation prediction method will be described.

[0030] 1. About insulated wires with terminals

[0031] exist Figure 1 1 shows the shape of one end of an insulated wire 20 with a terminal according to one embodiment of the present invention. In the insulated wire 20 with a terminal according to the present embodiment, the terminal 10 may be connected to only one end of the insulated wire 1 or to both ends. Specific examples of the insulated wire 1 and the terminal 10 are shown below, but the insulated wire 1 and the terminal 10 of the insulated wire 20 with a terminal are not limited to these, and the evaluation prediction method described below can also be applied to wires with terminals other than the wires with terminals shown below.

[0032] (1) Insulated wire

[0033] exist Figure 2A A cross-sectional view of an insulated wire 1 according to this embodiment is shown in FIG. Figure 2B 2 is a cross-sectional view of an insulated wire 1 according to another embodiment. The insulated wire 1 includes a conductor 2 formed by twisting a plurality of bare wires 2 a and 2 b , and a coating 3 covering the conductor 2 .

[0034] exist Figure 2A and Figure 2B In the insulated wire 1 shown in the figure, the conductor 2 is composed of a central bare wire 2a and six concentric bare wires 2b that concentrically surround the central bare wire 2a. The number of bare wires 2a and 2b is appropriately selected according to the purpose of the insulated wire 1 (insulated wire 20 with terminal). In addition, the conductor 2 can be as follows: Figure 2A The non-compressed conductor shown is formed by twisting a plurality of bare wires 2a and 2b together, or it may be formed by twisting a plurality of bare wires 2a and 2b together. Figure 2BThe compressed conductor shown is a plurality of bare wires 2a and 2b twisted and compressed into a desired shape. It should be noted that when the conductor 2 is a compressed conductor, the compression rate is preferably 3% to 4%. The compression rate of the conductor 2 is derived from the following formula.

[0035] Compression ratio = (conductor cross-sectional area before compression - conductor cross-sectional area after compression) / conductor cross-sectional area before compression × 100%

[0036] The cross-sectional area and diameter of each bare wire 2a, 2b constituting the conductor 2 are not particularly limited, but the total cross-sectional area of ​​each bare wire 2a, 2b, that is, the cross-sectional area of ​​the conductor 2 is preferably 0.16 mm 2 The cross-sectional area of ​​the conductor 2 is more preferably 0.120 mm 2 Above and 0.16mm 2 Below, more preferably 0.125 mm 2 Above and 0.16mm 2 The following evaluation prediction method can also be applied to the following 2 Insulated wire 20 with terminal having a conductor with a large cross-sectional area. However, in recent years, it has been required to reduce the cross-sectional area of ​​conductor 2. In the development of the conductor 2, the cross-sectional area of ​​conductor 2 is 0.16mm 2 The following insulated wire 1 can be particularly suitably used. It should be noted that the cross-sectional shape of the conductor 2 can be a substantially circular shape or an elliptical shape, or a polygonal shape, etc. The thickness of each bare wire 2a, 2b constituting the conductor 2 can be the same or different, but is usually the same.

[0037] In addition, the conductor 2 is preferably a central bare wire 2a and concentric bare wires 2b arranged around the central bare wire 2a, which are twisted in a certain direction with the central bare wire 2a as the axis. The twist pitch at this time is not particularly limited and can be appropriately selected according to the desired performance of the insulated wire 1. It is usually preferably 5 mm or more and 10 mm or less, and more preferably 6 mm or more and 8 mm or less. "Twisting pitch" refers to the length of the conductor 2 required for the conductor 2 to rotate 360° with the central bare wire 2a as the axis.

[0038] In addition, untempered bare wires are used as the bare wires 2a and 2b of the conductor 2. In addition, the amount of oil adhering to the bare wires 2a and 2b of the conductor 2 may be adjusted.

[0039] Here, the metal of each bare wire 2a, 2b constituting the conductor 2 is not particularly limited, and is the same as the metal contained in the conductor of the known insulated wire. The metal may be a metal monomer or an alloy. In particular, from the viewpoint of conductivity and processability, copper alloys are preferably used. Examples of copper alloys include alloys containing one or more additive elements selected from the group consisting of Fe, Ti, Mg, Sn, Ag, Ni, In, Zn, Cr, Al, P, Be, Co and Si, and the remainder consisting of Cu and unavoidable elements. The additive elements are preferably Mg and / or Sn. The above-mentioned additive elements may be one or a combination of two or more. Usually, there are three or less.

[0040] The amount of the additive element in the copper alloy can also be appropriately selected according to the desired performance of the insulated wire. For example, it is preferably 0.2 mass % or more and 0.4 mass % or less, more preferably 0.25 mass % or more and 0.35 mass % or less, and further preferably 0.28 mass % or more and 0.32 mass % or less. If the amount of the additive element in the copper alloy is 0.2 mass % or more, there is a tendency that the strength of the conductor 2 is improved and the tensile strength becomes stronger. On the other hand, if the amount of the additive element in the copper alloy is 0.4 mass % or less, there is a tendency that the conductivity of the conductor 2 is easily improved.

[0041] In addition, the conductivity of the conductor 2 is not particularly limited, but if it is 75% IACS or more, the insulated wire 1 can be used for various purposes, so it is preferably 80% IACS or more. The conductivity of the conductor 2 is a value calculated from the resistance value according to Japanese Industrial Standard JIS H 0505. The resistance value is measured by the double bridge method using a conductor with a length of 500 mm. The conductivity of the conductor 2 can be adjusted by, for example, the type or amount of the above-mentioned additive element.

[0042] On the other hand, the coating layer 3 is a layer of the insulating coating conductor 2, and is usually composed of a resin alone or a combination of a resin and other components. The type of the resin is not particularly limited, and for example, as shown in the embodiments described below, it can be a polyvinyl chloride or polyphenylene ether resin. In addition, it can also contain an olefin resin such as polyethylene or polypropylene. In addition, the coating layer 3 can also contain any components such as a plasticizer, a filler, a stabilizer, and a processing aid in addition to the resin.

[0043] The thickness of the coating layer 3 is not particularly limited, but is preferably 0.15 mm or more and 0.25 mm or less, and more preferably 0.15 mm or more and 0.20 mm or less. If the thickness of the coating layer 3 is 0.15 mm or more, sufficient insulation is easily obtained. On the other hand, if the thickness of the coating layer 3 is 0.25 mm or less, the insulated wire 1 can be made thinner. However, the evaluation prediction method described later can also be applied to the insulated wire 20 with a terminal having a coating layer 3 having a thickness of less than 0.15 mm or a thickness of more than 0.25 mm.

[0044] The manufacturing method of the insulated wire 1 having the conductor 2 and the coating layer 3 is not particularly limited, and the evaluation prediction method described below can be applied to the insulated wire 1 regardless of the manufacturing method. Generally, a plurality of bare wires 2a and 2b are prepared and twisted to a desired cross-sectional area to form a conductor 2. Thereafter, an insulating material is extruded and coated around the conductor 2 to form the coating layer 3, thereby obtaining the insulated wire 1.

[0045] (2)Terminal

[0046] The shape and type of the terminal 10 are not particularly limited, and can be appropriately selected according to the use of the electric wire 20 with a terminal.

[0047] exist Figure 1 The terminal 10 shown is provided with a female or male fitting portion 11 for connecting to various devices, a wire barrel portion 12 for fixing the conductor 2 of the insulated wire 1, and an insulating barrel portion 13 for supporting the coating 3 of the insulated wire 1 in this order.

[0048] The shape of the fitting portion 11 may be selected as appropriate in accordance with the type of device as long as it can be connected to various devices.

[0049] The wire barrel portion 12 is a portion for reliably electrically or mechanically connecting the conductor 2 and the terminal 10 , and has a structure for compressing and fixing the conductor 2 .

[0050] The insulating tube 13 has a structure for compressing and fixing the coating layer 3. These structures are the same as those of a general terminal.

[0051] The method for connecting the terminal 20 and the insulated wire 1 is not particularly limited, and the connection can be performed by, for example, the following method.

[0052] First, the coating layer 3 is stripped from the end of the insulated wire 1 to expose the conductor 2. The conductor 2 can be exposed by a general method, or the conductor 2 can be exposed by a dedicated tool such as a stripper.

[0053] Next, the terminal 10 is connected to the exposed conductor 2. Specifically, a method can be used in which the coating 3 of the insulated wire 1 is fixed to the insulating barrel 13 of the terminal 10 and the wire barrel 12 is pressed to crimp the exposed conductor 2 to the wire barrel 12.

[0054] 2. Evaluation and prediction method for insulated wires with terminals

[0055] The evaluation prediction method of the above-mentioned insulated wire with terminal (hereinafter, also simply referred to as “evaluation prediction method”) will be described.

[0056] An evaluation prediction method according to an embodiment of the present invention can predict the evaluation result of the following test (free fall test): a test in which a weight is added to one end of an insulated wire with a terminal including an insulated wire with a length of 300 mm, and the other end of the insulated wire with the terminal is fixed to a specified height (for example, a height of 1000 mm), and the weight is allowed to fall freely from the other end. Specifically, it is possible to predict whether the insulated wire will break when the weight is allowed to fall freely. In addition, the above-mentioned prediction result is the result when the weight is installed in a manner that a load is applied to the wire barrel portion and the insulating barrel portion of the terminal. The method is described below.

[0057] exist Figure 3 The steps of the evaluation prediction method of this embodiment are shown in the flowchart.

[0058] First, the tensile strength A [N] of the conductor of the insulated wire of the wire with terminal to be evaluated and the 3% proof stress B [N] of the coating layer of the insulated wire are determined ( S1 ).

[0059] The "tensile strength A of the conductor" in this specification refers to the tensile strength of the conductor in the same state as in the insulated wire, that is, the tensile strength of the conductor in a state where multiple bare wires are twisted in a certain direction. It should be noted that the tensile strength of the conductor may vary depending on the presence or absence of compression of the bare wire, the compression rate, the cross-sectional area of ​​the conductor, the twisting pitch of the conductor, and the amount of oil attached to the bare wire. Therefore, the "tensile strength A of the conductor" is preferably a value obtained by actually making an insulated wire, taking out the conductor from it and measuring the tensile strength, or a value obtained by only making a conductor in the same steps as when making an insulated wire and measuring the tensile strength of the conductor. The tensile strength of the conductor can be determined by a universal testing machine (Autograph) manufactured by Shimadzu Corporation, etc.

[0060] On the other hand, "3% proof strength B of the coating layer" refers to the 3% proof strength of the coating layer in the same state as that in the insulated wire, that is, the 3% proof strength of the coating layer in a tubular shape with a predetermined thickness. "3% proof strength B of the coating layer" is preferably a value obtained by measuring the 3% proof strength of the coating layer after the coating layer is stripped from the insulated wire, or a value obtained by measuring the 3% proof strength of the coating layer after only the coating layer is produced in the same steps as when the insulated wire is produced. The 3% proof strength of the coating layer is measured in accordance with the JASO D618 standard.

[0061] Next, it is examined whether the "tensile stress A of the conductor" and the "3% proof stress B of the coating layer" determined in the above satisfy the following formula (S2).

[0062] 100[N]≤(conductor tensile strength A[N]×0.7)+(3% endurance of coating B[N])

[0063] The right side of the above formula is equivalent to the terminal fixing force of the insulated wire with terminal, as verified in the examples described later. In addition, the value (100N) on the left side of the above formula is the minimum value of the terminal fixing force that can ensure a 100% pass rate when the free drop test is performed, as verified in the examples described later. This value is derived from the examples described later.

[0064] Then, when the above formula is satisfied, it is determined to be acceptable (S3), and when the above formula is not satisfied, it is determined to be unacceptable (S4).

[0065] It should be noted that, as required, the thickness and composition of the coating layer can be changed, or the composition, diameter, compression rate, twist pitch and other conditions of the conductor can be changed, and the above evaluation prediction method can be repeatedly performed to determine the best type and structure of the conductor and coating layer. In other words, according to this evaluation prediction method, even if the insulated wire is not actually produced or the free drop test is not actually performed, the evaluation result of the free drop test can be easily predicted. Therefore, it is very useful when developing a new insulated wire or changing the specifications. In addition, the above evaluation prediction method can be used not only in the case of newly developing an insulated wire, but also in quality management.

[0066] Furthermore, the above evaluation prediction method is useful in any field as long as the above free fall test is performed. For example, it is useful in the development and quality management of insulated wires used in various electrical equipment such as automobiles and airplanes, and control equipment for industrial robots, etc. It is particularly useful in the evaluation of insulated wires with terminals for automobile wiring harnesses.

[0067] (Other embodiments)

[0068] The evaluation prediction method described above can be applied to a free fall test in which the weight of the weight is 400g and the length of the insulated wire is 300mm. However, in the case where the conditions of the free fall test are changed, it is preferable to perform the evaluation prediction method in the following manner. Figure 4 The steps of the evaluation prediction method are shown in the flowchart of FIG.

[0069] First, determine the minimum value C (S11) of the terminal fixing force of the insulated wire with terminals required to make the pass rate 100% in the desired free drop test. Specifically, prepare a plurality of insulated wires with terminals including insulated wires with arbitrary conductors and arbitrary coating layers. And, measure the terminal fixing force of these insulated wires with terminals by type. And, perform the desired free drop test on these insulated wires with terminals, and calculate the pass rate of each type. Then, compare the above-mentioned terminal fixing force with the pass rate of the free drop test, and determine the minimum value C of the terminal fixing force for which the pass rate is definitely 100%. For example, in the case where there are a mixture of examples with a pass rate of 100% and examples with a pass rate lower than 100% for the same terminal fixing force, it is inappropriate to use the terminal fixing force as the above-mentioned minimum value C. The minimum value among the terminal fixing forces for which the pass rate is definitely 100% is selected as the above-mentioned minimum value C.

[0070] Next, similarly to the above-described embodiment, the tensile strength A[N] of the conductor of the insulated wire with a terminal and the 3% proof strength B[N] of the coating layer, the evaluation results of which are to be predicted, are determined by a desired free drop test ( S12 ).

[0071] Thereafter, it is examined whether the “tensile stress A of the conductor”, “3% proof stress B of the coating layer”, and “minimum value C” determined above satisfy the following formula (S13).

[0072] Minimum value C[N]≤(conductor tensile strength A[N]×0.7)+(3% endurance B[N] of coating)

[0073] Then, when the above formula is satisfied, it is determined to be acceptable (S14), and when the above formula is not satisfied, it is determined to be unacceptable (S15).

[0074] According to this evaluation prediction method, it is possible to easily predict the evaluation result of the desired free drop test without actually manufacturing the insulated wire or actually performing the free drop test, just by setting the minimum value C at the beginning. Therefore, it is very useful when developing a new insulated wire or changing the specification. In addition, the above evaluation prediction method can be used not only in the case of newly developing an insulated wire, but also in quality management.

[0075] [Example]

[0076] The above-mentioned evaluation prediction method is derived based on the following verification: In addition, verification is also performed to determine whether the evaluation result derived by the above-mentioned evaluation prediction method is consistent with the actual result (verification 3).

[0077] Verification 1 (Confirmation of the correlation between terminal fixing force and free drop test evaluation)

[0078] (1) Sample preparation

[0079] Ten samples 1 to 11 were prepared in each case by the following method.

[0080] (1.1) Preparation of Sample 1

[0081] A copper alloy containing 0.3 mass % Sn and the remainder consisting of Cu and inevitable elements was continuously cast using a horizontal continuous casting machine with a graphite mold having a water cooling jacket on the outer periphery to produce a cast rod with a diameter of 12 mm. The cast rod was cold worked to obtain a plurality of bare wires with a diameter of about 0.16 mm.

[0082] Then, seven bare wires are prepared, one of which is used as the central bare wire, and the remaining six are used as concentric bare wires arranged concentrically around the central bare wire. The cross-sectional area of ​​the conductor is 0.155mm 2 The way these will be twisted.

[0083] Polyvinyl chloride resin (PVC1) manufactured by Mitsubishi Chemical Corporation was extruded from the die of an extruder so as to cover the periphery of the conductor, thereby forming a coating layer around the conductor to produce an insulated wire. The coating layer had a thickness of 0.2 mm.

[0084] Then, install the insulated wire at one end thereof. Figure 1 Such a terminal makes an insulated wire with a terminal.

[0085] (1.2) Preparation of Sample 2

[0086] The coating layer was formed using resin composition 1 composed of a mixture of polyvinyl chloride resin, plasticizer, heavy calcium carbonate filler, Ca / Zn stabilizer, and acrylic processing aid (see Table 2 for the compounding ratio). An insulated wire with a terminal was prepared in the same manner as Sample 1 except for this.

[0087] (1.3) Preparation of Sample 3

[0088] The coating layer was formed using polyvinyl chloride resin (PVC2) manufactured by RIKEN TECHNOS Co., Ltd. An insulated wire with a terminal was produced in the same manner as Sample 1 except for the above.

[0089] (1.4) Preparation of Sample 4

[0090] Seven bare wires were prepared in the same manner as in Sample 1 so that the cross-sectional area of ​​the conductor was 0.160 mm 2 Then, a modified polyphenylene ether resin (m-PPE) manufactured by SABIC Corporation was used to form a coating layer and attach a terminal in the same manner as in Sample 1 to produce an insulated wire with a terminal.

[0091] (1.5) Preparation of Sample 5

[0092] The coating layer was formed using the same resin composition 1 as that of Sample 2. An insulated wire with a terminal was produced in the same manner as Sample 4 except for the above.

[0093] (1.6) Preparation of Sample 6

[0094] Seven bare wires were prepared in the same manner as in Sample 1 so that the cross-sectional area of ​​the conductor was 0.137 mm 2 These were compressed and twisted in a manner. Thereafter, a coating layer was formed and a terminal was attached in the same manner as in Sample 1 to produce an insulated wire with a terminal.

[0095] (1.7) Preparation of samples 7 to 11

[0096] The material of the coating layer was changed as shown in the following Table 1. Insulated wires with terminals were produced in the same manner as Sample 6 except for the above.

[0097] It should be noted that the resin composition 2 and the resin composition 3 in Table 1 are obtained by changing the compounding ratio of the resin composition 1, and the compounding ratio is shown in Table 2.

[0098]

Table 1

[0099]

[0100]

Table 2

[0101] Resin composition Resin composition 1 Resin composition 2 Resin composition 3 Polyvinyl chloride resin 100 parts by mass 100 parts by mass 100 parts by mass Plasticizers 25 parts by mass 28 parts by mass 30 parts by mass Heavy calcium carbonate filler 6 parts by mass 6 parts by mass 6 parts by mass Ca / Zn stabilizer 4 parts by mass 4 parts by mass 6 parts by mass Acrylic Processing Aids - - 8 parts by mass

[0102] (2) Free drop test

[0103] A 400g weight was added to the front end of the terminal to apply a load to the wire barrel and insulating barrel of each of the above-mentioned insulated wires with terminals (the length of the insulated wire is 300mm). Then, the end of the side where the terminal is not installed was fixed at a height of 1000mm. Then, the weight was allowed to fall freely from a height of 1000mm, and it was visually confirmed whether the insulated wire was broken. Evaluation was performed according to the following criteria. In addition, the pass rate of the free fall test was calculated for each sample.

[0104] Pass: No breakage of insulated wire

[0105] Failure: Insulated wire is broken

[0106] (3) Terminal fixing strength

[0107] The terminal fixing force (N) of the insulated wire with terminal of each sample was measured in the following manner. The coating was peeled off at one end of the insulated wire to expose the conductor, and the terminal was installed at one end of the conductor. Here, a commercially available crimping terminal was used as the terminal and crimped to the conductor. The appropriate installation height was adjusted according to the combination of the conductor and the coating. After that, the maximum load (N) at which the terminal does not fall off when stretched at a speed of 100 mm / min was measured using a universal tensile testing machine. This maximum load is taken as the terminal fixing force.

[0108] (4) Correlation between terminal fixing force and free drop test evaluation

[0109] A graph was created with the terminal fixing force as the horizontal axis and the pass rate of the free drop test as the vertical axis. Figure 5 The diagram is shown in . Figure 5 It can be seen that when the terminal fixing force increases, the pass rate of the free drop test increases, and it can be seen that there is a correlation between the two. In addition, according to the test results, the minimum value of the terminal fixing force that must achieve 100% pass in the above free drop test is 100N.

[0110] Verification 2 (Relationship between the terminal bonding strength, the conductor bonding strength, and the coating bonding strength)

[0111] As described above, there is a correlation between the terminal fixing force of the insulated wire with a terminal and the evaluation result of the free drop test. It can be seen that if the terminal fixing force exceeds 100N, the result of the free drop test must be good. However, when selecting the material of the insulated wire with a terminal, it is cumbersome to make the insulated wire with a terminal and measure its terminal fixing force separately. Here, the connection of the terminal to the insulated wire is performed by pressing the wire barrel part of the conductor of the insulated wire and the insulating barrel part of the coating. That is, the terminal fixing force can be expressed by the following formula that sums the fixing force of the conductor to the terminal and the fixing force of the coating to the terminal. Based on such a prediction, the following verification was performed.

[0112] Terminal bonding strength = conductor bonding strength to terminal + coating bonding strength to terminal

[0113] ·About the conductor's fixed connection strength based on the terminal

[0114] For the three conductors used in each sample (the cross-sectional area of ​​the conductor is 0.155 mm 2 、0.160mm 2 , and 0.137mm 2), and the tensile strength of each was determined by a universal testing machine (Autograph) manufactured by Shimadzu Corporation.

[0115] Next, (only) these conductors were connected to the above terminals, and the bonding strength was measured by the same method as above. The cross-sectional area of ​​the conductor was taken as the horizontal axis and the strength was taken as the vertical axis. Figure 6 It should be noted that Figure 6 In the figure, the black dots represent the tensile strength of the conductor, and the white dots represent the connection strength with the terminal. Figure 6 In the diagram, the gray dots indicate how the strength is reduced by fixing the conductor to the terminal. Figure 6 As shown in the figure, for conductors of any cross-sectional area, a decrease in strength of about 25% to 30% can be observed by fixing the conductor to the terminal. In other words, it can be seen that the fixing force between the conductor and the terminal is greater than "the tensile strength of the conductor × 0.7". Figure 6 In FIG. 1 , the tensile strength, the fixing force to the terminal, and the reduction ratio of the strength are shown as average values.

[0116] ·About the fixing force of the coating layer based on the terminal

[0117] The covering layers of the 11 types of insulated wires with terminals used in each sample were measured using the following methods: "Adhesion strength between the conductor and the covering layer" which can predict the correlation with the terminal fixing force, the tensile property of the covering layer, namely "yield point strength", and the tensile property of the covering layer, namely "3% yield strength".

[0118] (Measurement of Adhesion Strength of Coating Layer)

[0119] The close contact strength of the coating layer was measured based on JASO D618. Specifically, an insulated wire with a length of 100 mm was prepared in the same manner as the above-mentioned sample, and the coating layer at one end thereof was removed to expose a 25 mm portion of the conductor, while a 25 mm portion of the other end was cut off and discarded. The insulated wire with a total length of 75 mm was used as the measurement object, and the exposed conductor was inserted through the through hole of the retaining member (a hole with a diameter larger than the outer diameter of the conductor and smaller than the outer diameter of the insulated wire). The retaining member was fixed, and one end of the conductor protruding from the retaining member was stretched. Moreover, the minimum load when the coating layer was stripped from the conductor and the conductor was pulled out was used as the close contact strength. The measuring device used a universal testing machine (Autograph) made by Shimadzu Corporation.

[0120] (Determination of yield point strength and 3% proof stress of coating layer)

[0121] The yield strength and 3% yield strength of the coating layer were measured based on JASO D618. Specifically, a tubular test piece having a length of about 150 mm was used from the above-mentioned sample, and the yield strength and 3% yield strength were measured for the tubular test piece using a universal testing machine (Autograph) manufactured by Shimadzu Corporation.

[0122] (analyze)

[0123] Only the coating layer of each sample was fixed to the terminal, and the bonding strength was measured by the same method as above. Moreover, the bonding strength of the coating layer was used as the horizontal axis, and the close contact strength, yield point strength, and 3% endurance obtained in the above test were used as the vertical axis, respectively, and a graph was made (not shown), and the relationship between each characteristic (close contact strength, yield point strength, 3% endurance) and the bonding strength of the insulated wire with the terminal was shown as a linear function (approximate formula). The calculated linear function is shown in Table 3. In addition, for each approximate formula, the determination coefficient R 2 The results are shown in Table 3. From the value of the determination coefficient, it can be seen that the correlation between the 3% proof stress and the bonding strength of the coating layer is very high, and that the value of the 3% proof stress is substantially equivalent to the bonding strength of the coating layer to the terminal.

[0124]

Table 3

[0125] Close contact Yield strength 3% Stamina Approximate formula y=1.4271x-6.3342 y＝0.9293+0.2069 y＝1.0106-2.8301 <![CDATA[Coefficient of determination R 2 > 0.6906 0.4454 0.7568

[0126] ·result

[0127] From the above results, it can be seen that the minimum value predicted as the value of the terminal fixing force of the insulated wire with a terminal can be expressed by the following formula.

[0128] Terminal fixing force (predicted minimum value) = conductor tensile strength × 0.7 + 3% endurance of coating

[0129] Verification 3 (Verification of the correlation between terminal fixing force (predicted value) and free drop test)

[0130] Verification 1 shows that when the free drop test is performed, there is a correlation between the evaluation result and the terminal fixing force of the insulated wire with terminal, and the terminal fixing force that ensures 100% pass in the free drop test is 100N.

[0131] On the other hand, from Verification 2, it is found that the minimum value predicted as the terminal fixing force of each insulated wire with a terminal is "conductor tensile strength × 0.7 + 3% proof strength of coating layer".

[0132] In summary, it can be considered that when manufacturing an insulated wire with a terminal, if the tensile strength of the conductor and the coating layer satisfy the following formula, the result of the free drop test will definitely be acceptable.

[0133] 100[N]≤(tensile strength of conductor[N]×0.7)+(3% endurance of coating[N])

[0134] Therefore, the value calculated from this formula was compared with the test result of the free fall test performed in the above-mentioned Verification 1, and the validity of the above-mentioned formula was confirmed. The results are shown in Table 4.

[0135]

Table 4

[0136]

[0137] ※(The upper column of data is the calculated terminal fixing force, and the lower column is the actual pass rate of the drop impact test)

[0138] As shown in Table 4 above, when the above formula (100[N]≤(tensile strength of conductor [N]×0.7)+(3% endurance of coating [N]) is satisfied, the pass rate of any free fall test is 100%, confirming that the above evaluation prediction method is useful.

[0139] It should be noted that, when the above formula is not satisfied, the pass rate may not be 100%. Therefore, it is considered that in order to achieve 100% pass, the above formula must be satisfied.

[0140] Industrial Applicability

[0141] According to the evaluation prediction method of the present invention, even without actually manufacturing the insulated wire with a terminal, the result of the free drop test of the insulated wire with a terminal, which has a conductor formed by twisting a plurality of bare wires and a coating layer covering the conductor, can be predicted. Therefore, it is very useful in the development and quality management of the insulated wire.

[0142] Description of Reference Numerals

[0143] 1 Insulated wire

[0144] 2 Conductors

[0145] 2a Center bare wire

[0146] 2b Concentric bare wire

[0147] 3. Coating

[0148] 10 terminals

[0149] 11 Chimeric part

[0150] 12. Wire bobbin

[0151] 13 Insulation tube

[0152] 20 Insulated wire with terminal

Claims

1. An evaluation prediction method for an insulated wire with a terminal, the evaluation prediction method being a method for evaluating the insulated wire with a terminal when a free drop test is performed on the insulated wire with a terminal, the insulated wire with a terminal comprising an insulated wire and a terminal connected to at least one end of the insulated wire, the insulated wire comprising a conductor formed by twisting a plurality of bare wires and a coating covering the conductor, The evaluation prediction method of the insulated wire with a terminal comprises: A step of confirming whether the tensile strength of the conductor and the 3% yield strength of the coating layer satisfy the following formula: 100[N]≤(tensile strength of conductor [N]×0.7)+(3% endurance of coating layer [N]).

2. The evaluation prediction method of the insulated wire with a terminal according to claim 1, wherein: The free fall test is a test in which a 400 g weight is added to one end of the insulated wire with a terminal having a length of 300 mm, the other end of the wire with a terminal is fixed, and the weight is allowed to fall freely from the other end.

3. The evaluation prediction method of the insulated wire with a terminal according to claim 1, wherein: The cross-sectional area of ​​the conductor is 0.16 mm 2 Below, and The coating layer has a thickness of 0.15 mm or more and 0.25 mm or less.

4. An evaluation prediction method for an insulated wire with a terminal, the evaluation prediction method being an evaluation prediction method when a free drop test is performed on the insulated wire with a terminal, the insulated wire with a terminal having an insulated wire and a terminal connected to an end of the insulated wire, the insulated wire having a conductor formed by twisting a plurality of bare wires and a coating covering the conductor, the evaluation prediction method for the insulated wire with a terminal comprising: A step of determining a minimum value of the terminal fixing force required to achieve a 100% pass rate in the free drop test; and A step of confirming whether the minimum value, the tensile strength of the conductor, and the 3% proof stress of the coating layer satisfy the following formula, Minimum value [N] ≤ (tensile strength of conductor [N] × 0.7) + (3% proof strength of coating layer [N]).

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