Connection structure

Abstract

This connection structure has a terminal. The terminal has a first surface and a second surface. The first surface is provided with a plurality of ridges. Each of the plurality of ridges extends along an imaginary line. Each of the plurality of ridges has a first wall surface and a second wall surface. A first angle is defined as the inclination angle of the first wall surface with respect to the second surface in a cross-section perpendicular to the imaginary line. A second angle is defined as the inclination angle of the second wall surface with respect to the second surface in a cross section perpendicular to the imaginary line. The second angle is greater than the first angle. The second angle is greater than 20° and less than or equal to 85°.

Description

Connection structure

[0001] The present disclosure relates to a connection structure. This application claims priority based on Japanese Patent Application No. 2024-156663, a Japanese patent application filed on September 10, 2024. All the descriptions contained in the Japanese patent application are incorporated herein by reference.

[0002] Japanese Unexamined Patent Application Publication No. 2023-082637 (Patent Document 1) describes a fastening structure having a first fastened member and a second fastened member. According to the fastening structure, the first fastened member contains aluminum or an aluminum alloy. The second fastened member contains a metal. A protrusion protruding toward the second fastened member is integrally formed on the surface of the first fastened member facing the second fastened member.

[0003] Japanese Unexamined Patent Application Publication No. 2023-082637

[0004] The connection structure according to the present disclosure includes a terminal, an attachment target, and an attachment member. The terminal is formed of aluminum or an aluminum alloy. The attachment target is formed of a metal. The attachment member connects the terminal and the attachment target. The terminal includes a first surface and a second surface. The second surface is opposite to the first surface. A plurality of ridges are provided on the first surface. Each of the plurality of ridges extends along a virtual line. In a state where the terminal is connected to the attachment target, the plurality of ridges contact the attachment target. Each of the plurality of ridges has a first wall surface and a second wall surface. The second wall surface is opposite to the first wall surface. In a cross-section perpendicular to the virtual line, the inclination angle of the first wall surface with respect to the second surface is a first angle. In a cross-section perpendicular to the virtual line, the inclination angle of the second wall surface with respect to the second surface is a second angle. The second angle is larger than the first angle and is greater than 20° and less than or equal to 85°.

[0005] Figure 1 is a schematic side view showing the configuration of the connection structure according to this embodiment. Figure 2 is a schematic bottom view showing the configuration of the terminal and electric wire according to this embodiment. Figure 3 is an enlarged schematic bottom view showing region III of Figure 2. Figure 4 is a schematic cross-sectional view showing the configuration of multiple protrusions. Figure 5 is a schematic side view illustrating the coating layer of the object to be attached. Figure 6 is a schematic diagram showing how the terminal and the object to be attached slide when the terminal and the object to be attached are connected according to a comparative example. Figure 7 is a schematic diagram showing how the sliding between the terminal and the object to be attached is suppressed when the terminal and the object to be attached are connected according to a comparative example. Figure 8 is a schematic diagram showing how the protrusions deform when the terminal and the object to be attached according to this embodiment are connected. Figure 9 is a schematic cross-sectional view showing the configuration of the terminal according to the first modified example of this embodiment. Figure 10 is a schematic bottom view showing the configuration of the terminal according to the second modified example of this embodiment. Figure 11 is a schematic cross-sectional view showing the configuration of multiple protrusions according to the second modified example of this embodiment. Figure 12 is a schematic cross-sectional view showing the configuration of the terminal according to the third modified example of this embodiment. Figure 13 is a schematic cross-sectional view showing the configuration of the terminals related to the sample and the mounting object. Figure 14 is a schematic plan view showing the configuration of the terminals related to the sample and the mounting object. Figure 15 is a schematic cross-sectional view illustrating the method for measuring contact resistance. Figure 16 is a diagram showing the contact resistance of a sample with a changed second angle. Figure 17 is a diagram showing the contact resistance of a sample with a changed ratio of the length of the top surface to the width of the top surface. Figure 18 is a diagram showing the contact resistance of a sample with a changed ratio of the distance between two adjacent protrusions to the average width of the top surface. Figure 19 is a diagram showing the contact resistance of a sample with a changed height of each of the multiple protrusions. Figure 20 is a diagram showing the contact resistance of a sample with a changed first angle. Figure 21 is a diagram showing the contact resistance of a sample with a changed Vickers hardness. Figure 22 is a diagram showing the contact resistance of a sample with a planar top surface and a changed width of the top surface. Figure 23 is a diagram showing the contact resistance of a sample with a convex curved top surface in cross-sectional view and a changed radius of curvature of the top surface. Figure 24 shows the contact resistance of samples in which the top surface is convex and curved in cross-sectional view, and the width of the top surface is varied.

[0006] In connection structures where a terminal is connected to an object to be attached, if the terminal is made of aluminum or an aluminum alloy, the contact resistance between the terminal and the object to be attached may increase due to the aluminum oxide film formed on the surface of the terminal. In particular, the contact resistance may become excessively high when sliding at the interface between the terminal and the object to be attached is suppressed during fastening.

[0007] This disclosure has been made in view of the above-mentioned problems, and its purpose is to provide a connection structure that can reduce contact resistance even when sliding at the interface between the terminal and the object to be attached is suppressed.

[0008] According to this disclosure, a connection structure is available that can reduce contact resistance even when sliding at the interface between the terminal and the object to be attached is suppressed.

[0009] Embodiments of the present disclosure will be listed and described first. (1) The connection structure according to the present disclosure comprises a terminal, a mounting object, and a mounting member. The terminal is made of aluminum or an aluminum alloy. The mounting object is made of metal. The mounting member connects the terminal and the mounting object. The terminal has a first surface and a second surface. The second surface is opposite to the first surface. The first surface is provided with a plurality of protrusions. Each of the plurality of protrusions extends along a virtual line. When the terminal is connected to the mounting object, the plurality of protrusions are in contact with the mounting object. Each of the plurality of protrusions has a first wall surface and a second wall surface. The second wall surface is opposite to the first wall surface. In a cross section perpendicular to the virtual line, the inclination angle of the first wall surface with respect to the second surface is a first angle. In a cross section perpendicular to the virtual line, the inclination angle of the second wall surface with respect to the second surface is a second angle. The second angle is greater than the first angle. The second angle is greater than 20° and less than or equal to 85°. This reduces the contact resistance between the terminal and the mounting object, even when sliding at the interface between the terminal and the mounting object is suppressed.

[0010] (2) According to the connection structure described in (1) above, each of the multiple protrusions may have a top surface. The top surface may connect the first wall surface and the second wall surface.

[0011] (3) According to the connection structure described in (2) above, the length of the top surface in the direction in which the imaginary line extends may be 1.5 times or more the width of the top surface in the direction perpendicular to the direction in which the imaginary line extends when viewed from the first surface toward the second surface. This effectively reduces the contact resistance between the terminal and the object to be attached.

[0012] (4) According to the connection structure described in (2) or (3) above, the distance between two adjacent protrusions among the multiple protrusions may be 3.0 times or more and 200 times or less the average width of the top surfaces of the multiple protrusions. This effectively reduces the contact resistance between the terminal and the object to be attached.

[0013] (5) In the connection structure according to any of (1) to (4) above, the height of each of the multiple protrusions may be 0.01 mm or more and 0.5 mm or less. This effectively reduces the contact resistance between the terminal and the object to be attached.

[0014] (6) In the case of the connection structure according to any of (1) to (5) above, the first angle may be 4° or more and 45° or less.

[0015] (7) In the case of the connection structure according to any of (1) to (6) above, the object to be attached may be made of one of the following materials: aluminum, aluminum alloy, copper, and copper alloy. This prevents galvanic corrosion from occurring when water adheres to the connection part between the terminal and the object to be attached.

[0016] (8) In the case of the connection structure according to any of (1) to (7) above, the mounting member may have a bolt.

[0017] (9) In the connection structure according to any of (1) to (8) above, the Vickers hardness of the terminal may be 50 HV or more and 160 HV or less. A Vickers hardness of 50 HV or more of the terminal prevents a decrease in the connection strength between the terminal and the object to be attached. A Vickers hardness of 160 HV or less of the terminal prevents an excessive decrease in the bendability of the terminal.

[0018] (10) In the connection structure according to any of (2) to (4) above, the top surface may be planar. In a cross section perpendicular to the dashed line, the width of the top surface may be 0.02 mm or more and 0.5 mm or less. By having a top surface width of 0.02 mm or more, it is possible to prevent the cost required to form multiple protrusions from becoming excessively high. By having a top surface width of 0.5 mm or less, the contact resistance between the terminal and the object to be attached can be effectively reduced.

[0019] (11) According to the connection structure relating to any of (2) to (4) above, in a cross section perpendicular to the imaginary line, the top surface may be a curved shape that is convex in the direction from the second surface toward the first surface. The radius of curvature of the top surface may be 0.05 mm or more. The width of the top surface may be 0.02 mm or more and 0.5 mm or less. By having a top surface width of 0.02 mm or more, it is possible to prevent the cost required to form multiple protrusions from becoming excessively high. By having a top surface width of 0.5 mm or less, the contact resistance between the terminal and the object to be attached can be effectively reduced.

[0020] (12) According to the connection structure described in (1) above, the terminal may be made of any one of 5052, 6101, and 6061 in the International Registered Alloy Numbers. The Vickers hardness of the terminal may be 50 HV or more and 160 HV or less. The mounting object may be made of any one of aluminum, aluminum alloy, copper, and copper alloy. The mounting member may have a bolt. Each of the multiple protrusions may have a top surface that connects the first wall surface and the second wall surface. The length of the top surface in the direction in which the imaginary line extends may be at least twice the width of the top surface in the direction perpendicular to the direction in which the imaginary line extends when viewed from the first surface toward the second surface. The distance between two adjacent protrusions among the multiple protrusions may be at least three times and no more than seventy times the average width of the top surfaces of the multiple protrusions. The height of each of the multiple protrusions may be at least 0.05 mm and no more than 0.2 mm. The first angle may be at least 10° and no more than 45°. In a cross-section perpendicular to the imaginary line, the width of the top surface may be 0.05 mm or more and 0.5 mm or less. This effectively reduces the contact resistance between the terminal and the object to be mounted.

[0021] (13) According to the connection structure described in (12) above, the object to be mounted may have a main body and a covering layer. The main body may be made of either copper or a copper alloy. The covering layer may cover the portion of the main body facing the first surface. The covering layer may be made of either tin, an alloy containing tin and copper, silver, or an alloy containing silver and copper. This effectively reduces the contact resistance between the terminal and the object to be mounted.

[0022] Hereinafter, embodiments of the present disclosure (hereinafter also referred to as "these embodiments") will be described based on the drawings. In the following drawings, identical or corresponding parts will be given the same reference numerals, and their descriptions will not be repeated.

[0023] First, the configuration of the connection structure 1 according to this embodiment will be described. As shown in Figure 1, the connection structure 1 mainly comprises a terminal 2, a mounting object 3, a mounting member 4, and an electric wire 5. The terminal 2 and the mounting object 3 are connected by the mounting member 4. In this specification, when two parts are said to be connected, it means that the two parts are electrically connected by contact or joining. The electric wire 5 is connected to the terminal 2. The terminal 2 and the electric wire 5 form an electric wire with a terminal.

[0024] Terminal 2 has a first surface 21 and a second surface 22. When terminal 2 is connected to the mounting object 3, the first surface 21 faces the mounting object 3. The second surface 22 is opposite to the first surface 21. The direction from the first surface 21 to the second surface 22 is called the first direction 101. Conversely, the direction from the second surface 22 to the first surface 21 is called the second direction 102.

[0025] The terminal 2 is provided with, for example, a first through-hole 2h. The first through-hole 2h penetrates the first surface 21 and the second surface 22. The mounting member 4 is placed inside the first through-hole 2h. The terminal 2 is, for example, a CB type terminal. However, the terminal 2 may also be a U type terminal, a Y type terminal, or an R type terminal.

[0026] The terminal 2 has a plate portion 28 and a wire barrel 29. The plate portion 28 forms a first surface 21 and a second surface 22, respectively. The thickness of the plate portion 28 is, for example, 0.1 mm or more and 7 mm or less. The thickness of the plate portion 28 is the distance between the first surface 21 and the second surface 22 in the first direction 101.

[0027] The wire barrel 29 is connected to the plate portion 28. The wire barrel 29 grips the electric wire 5. The terminal 2 and the electric wire 5 are connected by the wire barrel 29 gripping the electric wire 5.

[0028] Terminal 2 is made of aluminum or an aluminum alloy. An aluminum alloy is an alloy in which aluminum is the main component. The main component is the component that is present in the largest quantity by mass among the constituent components. Details of the material of terminal 2 will be described later.

[0029] The mounting target 3 is configured to be connectable to the terminal 2 by a mounting member 4. The shape of the mounting target 3 is not particularly limited, but for example, it is plate-shaped. The mounting target 3 is, for example, a different terminal from the terminal 2. The mounting target 3 is made of metal. Details of the material of the mounting target 3 will be described later.

[0030] As shown in Figure 1, the mounting target 3 has a third surface 31 and a fourth surface 32. When the terminal 2 is connected to the mounting target 3, the third surface 31 faces the terminal 2. The fourth surface 32 is opposite to the third surface 31. A second through hole 3h is provided in the mounting target 3. The second through hole 3h penetrates the third surface 31 and the fourth surface 32. The mounting member 4 is placed inside the second through hole 3h.

[0031] The mounting member 4 has a bolt 41 and a nut 43. The mounting member 4 fastens the terminal 2 and the object to be mounted 3. By fastening the mounting member 4 to the terminal 2 and the object to be mounted 3, the terminal 2 and the object to be mounted 3 are connected.

[0032] The bolt 41 has, for example, a flange portion 42. On the second surface 22, the flange portion 42 contacts the terminal 2. A nut 43 is attached to the bolt 41. On the fourth surface 32, the nut 43 contacts the mounting object 3. The flange portion 42 of the bolt 41 and the nut 43 sandwich the terminal 2 and the mounting object 3. If the bolt 41 does not have a flange portion 42, a washer (not shown) is placed between the bolt 41 and the terminal 2.

[0033] The bolt 41 is formed of, for example, steel. The bolt 41 may be formed of, for example, an aluminum alloy, or of SNB7 steel as specified in JIS (Japanese Industrial Standards) G 4107:2010.

[0034] The electric wire 5 is connected to the terminal 2, for example, on the second surface 22. The electric wire 5 has a conductor 50 and an insulating sheath 51. The conductor 50 is held by the wire barrel 29 of the terminal 2. The conductor 50 is, for example, a stranded wire made by twisting together multiple strands. The outer diameter of the conductor 50 is, for example, 0.1 mm or more and 50 mm or less. The conductor 50 is made of, for example, copper, copper alloy, aluminum, or aluminum alloy.

[0035] The insulating coating 51 covers the outer circumference of the conductor 50. The thickness of the insulating coating 51 is, for example, 0.1 mm or more and 10 mm or less. The main component of the insulating coating 51 is, for example, a polyolefin resin. The polyolefin resin is, for example, polyethylene or polypropylene. The insulating coating 51 may also be formed of a silicone resin.

[0036] Figure 2 shows the configuration of the terminal 2 and the electric wire 5 as viewed in the first direction 101. As shown in Figure 2, the first surface 21 is formed by a first portion 26 and a second portion 27. The first portion 26 is provided with a plurality of protrusions 6, which will be described later. In Figure 2, the area with multiple dots indicates the first portion 26. When the terminal 2 is connected to the mounting target 3 (see Figure 1), the first portion 26 is in contact with the mounting target 3. When viewed in the first direction 101, at least a part of the first portion 26 overlaps with the mounting target 3.

[0037] Viewed in the first direction 101, the first portion 26 surrounds the first through hole 2h. Viewed in the first direction 101, the outer circumferential contour of the first portion 26 is, for example, rectangular. Viewed in the first direction 101, the inner circumferential contour of the first portion 26 is circular. The inner circumferential contour of the first portion 26 overlaps with the edge of the first through hole 2h, for example.

[0038] The second portion 27 is connected to the first portion 26. The second portion 27 is, for example, planar. When the terminal 2 is connected to the mounting object 3, at least a portion of the second portion 27 does not overlap with the mounting object 3. In other words, when the terminal 2 is connected to the mounting object 3, at least a portion of the second portion 27 is exposed from the mounting object 3.

[0039] Viewed in the first direction 101, the first through-hole 2h is, for example, circular in shape. The inner diameter of the first through-hole 2h is, for example, 4 mm to 20 mm. Viewed in the first direction 101, the shape of the first surface 21 is, for example, rectangular. The size of the terminal 2 is determined according to the application of the terminal 2. Viewed in the first direction 101, the length of the first surface 21 in the longitudinal direction is, for example, 5 mm to 200 mm.

[0040] Figure 3 shows an enlarged schematic diagram of the bottom of the first portion 26 of the first surface 21. Figure 4 shows a cross-section that is parallel to the first direction 101 and intersects the first portion 26. The cross-section shown in Figure 4 is a cross-section along the line IV-IV in Figure 3.

[0041] As shown in FIGS. 3 and 4, a plurality of ridges 6 are provided on the first surface 21 of the terminal 2. In a state where the terminal 2 is connected to the mounting target 3 (see FIG. 1), each of the plurality of ridges 6 contacts the mounting target 3. The plurality of ridges 6 are formed, for example, by cutting or forging. Note that the number of the ridges 6 is not particularly limited.

[0042] As shown in FIG. 3, each of the plurality of ridges 6 extends along the virtual line 90. In other words, the extending direction of each of the plurality of ridges 6 is the same as the extending direction of the virtual line 90. The virtual line 90 is a straight line extending along a direction perpendicular to the first direction 101. Note that the cross section shown in FIG. 4 is a cross section perpendicular to the virtual line 90. Note that the shape of the virtual line 90 is not particularly limited. The virtual line 90 may be a straight line extending along a radial direction from the center of the first through hole 2h. The virtual line 90 may be a curve. For example, the virtual line 90 may be a concentric curve that is point-symmetrical with respect to the center of the first through hole 2h.

[0043] The extending direction of the virtual line 90 is defined as the third direction 103. A direction perpendicular to each of the first direction 101 and the third direction 103 is defined as the fourth direction 104. The fourth direction 104 may be the same as, for example, the extending direction of the portion of the conductor 50 (see FIG. 1) gripped by the wire barrel 29.

[0044] As shown in FIG. 4, each of the plurality of ridges 6 is convex in the second direction 102. In a cross section perpendicular to the virtual line 90 (hereinafter also referred to as a cross-sectional view), the shape of each of the plurality of ridges 6 is, for example, trapezoidal. Each of the plurality of ridges 6 has a first wall surface 61, a second wall surface 62, and a top surface 63. The first wall surface 61 and the second wall surface 62 form the side surface of the ridge 6. The top surface 63 connects the first wall surface 61 and the second wall surface 62. The second wall surface 62 is in the fourth direction 104 with respect to the first wall surface 61.

[0045] In the cross-sectional view, the connection point between the first wall surface 61 and the top surface 63 is defined as the first connection point 81. In the cross-sectional view, the connection point between the second wall surface 62 and the top surface 63 is defined as the second connection point 82. In the ridge 6, the second wall surface 62 is on the opposite side of the first wall surface 61. From another viewpoint, on the top surface 63, the second connection point 82 is on the opposite side of the first connection point

[0045] 81.

[0046] As shown in FIG. 3, each of the plurality of ridges 6 extends, for example, to connect two different points on the contour of the first portion 26. In other words, when viewed in the first direction 101, both ends of each of the plurality of ridges 6 overlap, for example, the contour of the first portion 26. The length L of the top surface 63 in the third direction 103 may be the same as the length of the first portion 26 in the third direction 103. The length L of the top surface 63 in the third direction 103 is, for example, 0.03 mm or more and 50 mm or less.

[0047] A part of the plurality of ridges 6 extends, for example, from the edge of the first through-hole 2h to the outer peripheral contour of the first portion 26. From another perspective, a part of the plurality of ridges 6 forms a part of the inner peripheral surface of the first through-hole 2h. The extending directions of each of the plurality of ridges 6 are parallel to each other. The plurality of ridges 6 are arranged along the fourth direction 104 and are located around the first through-hole 2h.

[0048] As shown in FIGS. 3 and 4, the first portion 26 has a bottom surface 64. The bottom surface 64 is located between two adjacent ridges 6 among the plurality of ridges 6 or between the plurality of ridges 6 and the contour of the first portion 26. The first portion 26 is formed by the plurality of ridges 6 and the bottom surface 64. As shown in FIG., in a cross-sectional view, the connection point between the bottom surface 64 and the first wall surface is the third connection point 83, and the connection point between the bottom surface 64 and the second wall surface 62 is the fourth connection point 84.

[0049] As shown in FIG. 4, the top surface is, for example, planar. The top surface 63 may be parallel to the second surface 22 or may be inclined with respect to the second surface 22. The inclination angle of the top surface 63 with respect to the second surface 22 is, for example, 0° or more and 20° or less.

[0050] In a cross-sectional view, as the distance from the bottom surface 64 increases along the second direction 102, the width of each of the plurality of ridges in the fourth direction 104 decreases. The straight line 91 shown in FIG. 4 is a straight line parallel to the second surface 22 and passing through the third connection point 83. In a cross-sectional view, the first wall surface 61 is inclined in the second direction 102 with respect to the straight line 91. In other words, the first wall surface 61 is inclined with respect to the second surface 22.

[0051] The inclination angle of the first wall surface 61 with respect to the second surface 22 is defined as the first angle θ1. The first angle θ1 is the angle between the straight line 91 and the first wall surface 61. The first angle θ1 may be, for example, 1° or more and less than 85°, 4° or more and 60° or less, 4° or more and 45° or less, 10° or more and 45° or less, or 10° or more and 30° or less.

[0052] In Figure 4, the straight line 91 is parallel to the second surface 22 and passes through the fourth connection point 84. In cross-sectional view, the second wall surface 62 is inclined in the second direction 102 with respect to the straight line 91. In other words, the second wall surface 62 is inclined with respect to the second surface 22.

[0053] The inclination angle of the second wall surface 62 with respect to the second surface 22 is defined as the second angle θ2. The second angle θ2 is the angle between the straight line 91 and the second wall surface 62. The second angle θ2 is greater than the first angle θ1. The second angle θ2 is greater than 20° and less than or equal to 85°. The second angle θ2 may be, for example, 35° or more, 50° or more, or 65° or more. The second angle θ2 may be, for example, 83° or less, or 81° or less. The second angle θ2 may be, for example, 50° or more and less than or equal to 85°, 65° or more and less than or equal to 85°, or 75° or more and less than or equal to 83°.

[0054] The width W of the top surface 63 in the fourth direction 104 is, for example, 0.02 mm or more and 0.5 mm or less. The width W of the top surface 63 is the distance in the fourth direction 104 between the edge line between the top surface 63 and the first wall surface 61 and the edge line between the top surface 63 and the second wall surface 62.

[0055] The width W may be, for example, 0.05 mm or more, or 0.15 mm or more. The width W may be, for example, 0.4 mm or less, or 0.3 mm or less. The width W may be 0.03 mm or more and 0.5 mm or less, or 0.05 mm or more and 0.5 mm or less, or 0.1 mm or more and 0.4 mm or less.

[0056] The length L of the top surface 63 in the third direction 103 (see Figure 3) is 1.5 times or more the width W of the top surface 63 in the fourth direction 104. The length L may be, for example, 2 times or more the width W, 5 times or more, or 10 times or more. The length L may be, for example, 200 times or less the width W.

[0057] The sum of the widths W of the top surfaces 63 of each of the multiple protrusions 6, divided by the number of multiple protrusions 6, is considered the average width of the top surfaces 63 of the multiple protrusions 6. Note that the width W of each of the top surfaces 63 of the multiple protrusions 6 may be the same as the average width of the top surfaces 63.

[0058] The distance P between two adjacent protrusions 6 is between 3.0 and 200 times the average width of the top surfaces 63 of the multiple protrusions 6. The distance P is the distance in the fourth direction 104 between the first connection points 81 of each of the two adjacent protrusions 6 along the fourth direction 104.

[0059] The interval P may be four times or more the average width of the top surface 63, or five times or more. The interval P may be 150 times or less the average width of the top surface 63, or 80 times or less. The interval P may be three times or more and 150 times or less the average width of the top surface 63, or 3.0 times or more and 70 times or 4 times or more and 50 times or less the average width of the top surface 63.

[0060] The height H of each of the multiple protrusions 6 is between 0.01 mm and 0.5 mm. The height H is the longest distance in the second direction 102 between the top surface 63 of the protrusion 6 and the bottom surface 64 adjacent to the protrusion 6.

[0061] The height H may be 0.05 mm or more, or 0.1 mm or more. The height H may be 0.45 mm or less, or 0.3 mm or less. The height H may be 0.03 mm or more and 0.35 mm or less, or 0.05 mm or more and 0.2 mm or less, or 0.1 mm or more and 0.18 mm or less. The first angle θ1, the second angle θ2, the width W, the length L, the spacing P, and the height H can each be measured using a contact-type three-dimensional shape measuring machine. Alternatively, they can be measured, for example, by embedding the terminal in resin, mirror-polishing its cross-section, and observing it using a metal microscope.

[0062] <Material of Terminals> Next, the aluminum or aluminum alloy forming terminal 2 will be described in detail. Terminal 2 is formed of, for example, one of the internationally registered alloy numbers 5052, 6101, and 6061. Each of the registered alloy numbers 5052, 6101, and 6061 is an aluminum alloy. The internationally registered alloy numbers 5052, 6101, and 6061 correspond to the alloy numbers 5052, 6101, and 6061 specified in JIS H 4000:2014, respectively.

[0063] In the aluminum alloy forming terminal 2, the aluminum content may be, for example, 80% by mass or more, or 99% by mass or more. The aluminum alloy forming terminal 2 may contain unavoidable impurities.

[0064] The aluminum alloy may contain silicon and magnesium. For example, the silicon content in the aluminum alloy is 0.01% by mass or more and 1.50% by mass or less, and the magnesium content in the aluminum alloy is 0.01% by mass or more and 2.00% by mass or less.

[0065] Aluminum alloys may contain one or more additive elements selected from the group consisting of copper, manganese, iron, chromium, zirconium, and titanium. The copper content in the aluminum alloy is, for example, 0% to 1.2% by mass, or 0.1% to 1.2% by mass. The manganese content in the aluminum alloy is, for example, 0% to 1.5% by mass. The iron content in the aluminum alloy is, for example, 0% to 0.8% by mass.

[0066] The chromium content in aluminum alloys is, for example, 0% by mass or more and 0.4% by mass or less. The zirconium content in aluminum alloys is, for example, 0% by mass or more and 0.8% by mass or less. The titanium content in aluminum alloys is, for example, 0% by mass or more and 0.2% by mass or less. The total content of titanium and zirconium in aluminum alloys is, for example, 0% by mass or more and 0.3% by mass or less.

[0067] At least a portion of the first part 26 of the first surface 21 may have the aluminum or aluminum alloy, which is the material of the terminal 2, exposed to the outside. In other words, at least a portion of the first part 26 does not need to have an artificially formed coating covering the aluminum or aluminum alloy. The coating serves to reduce the contact resistance between the terminal 2 and the mounting object 3. According to the terminal 2 of this embodiment, the contact resistance between the terminal 2 and the mounting object 3 can be reduced even without a coating. Therefore, the cost required to form a coating in the manufacture of the terminal 2 can be reduced.

[0068] <Vickers hardness of terminals> The Vickers hardness of terminal 2 is, for example, 50 HV or more and 160 HV or less. The Vickers hardness is measured in accordance with JIS Z 2244-1:2020. The Vickers hardness of terminal 2 may be, for example, 55 HV or more, or 60 HV or more. The Vickers hardness of terminal 2 may be, for example, 140 HV or less, or 120 HV or less. The Vickers hardness of terminal 2 may be, for example, 50 HV or more and 150 HV or less, or 55 HV or more and 130 HV or less, or 60 HV or more and 110 HV or less.

[0069] <Conductivity of the terminal> The conductivity of terminal 2 is, for example, 30% IACS or more and 63% IACS or less. This reduces the amount of heat generated by terminal 2 when energized. Therefore, the thermal stress applied to the electric wire 5 connected to terminal 2 and the mounting object 3 can be reduced. Aluminum alloys containing silicon and magnesium are more likely to satisfy the above conductivity. Conductivity is measured in accordance with JIS H 0505:1975.

[0070] <Material of the mounting target> Mounting target 3 is formed of one of the following materials, for example, aluminum, aluminum alloy, copper, and copper alloy. Mounting target 3 may be formed of one of the following materials, for example, 5052, 6101, and 6061 in the International Register of Alloys, or it may be formed of C1020, a copper alloy as defined in JIS H 3100:2018.

[0071] The material of terminal 2 and the material of the mounting object 3 may be the same or different. If both the material of terminal 2 and the material of the mounting object 3 are aluminum alloys, the composition of the aluminum alloy forming terminal 2 and the composition of the aluminum alloy forming mounting object 3 may be the same or different.

[0072] At least a portion of the surface of the mounting target 3 facing the first surface 21 (the third surface 31) may have aluminum or an aluminum alloy exposed to the outside. In other words, at least a portion of the third surface 31 does not need to have an artificially formed coating covering the aluminum or aluminum alloy. The entire third surface 31 may have aluminum or an aluminum alloy exposed to the outside. According to the terminal 2 of this embodiment, even if the mounting target 3 does not have a coating, the increase in contact resistance between the terminal 2 and the mounting target 3 can be suppressed. Therefore, the cost required to form a coating in the manufacturing of the mounting target 3 can be reduced.

[0073] Figure 5 is a schematic side view illustrating the coating layer of the mounting target 3. Although Figure 1 shows a configuration in which the mounting target 3 does not have a coating layer, as shown in Figure 5, the mounting target 3 may have a coating layer 37 covering its surface. Specifically, the mounting target 3 may have a main body portion 36 and a coating layer 37. The main body portion 36 corresponds to the mounting target 3 shown in Figure 1. The main body portion 36 is formed of, for example, one of aluminum, aluminum alloy, copper, and copper alloy. The main body portion 36 may also be formed of, for example, one of copper and copper alloy.

[0074] The coating layer 37 is a metal layer formed, for example, by plating. The coating layer 37 is provided on the portion of the mounting object 3 that contacts the terminal 2. Specifically, the coating layer 37 covers the portion of the main body 36 that faces the first surface 21. As a result, the coating layer 37 fills the gap at the interface between the terminal 2 and the mounting object 3 when the terminal 2 and the mounting object 3 rub against each other. Therefore, oxidation of the newly formed surface of the aluminum or aluminum alloy forming the terminal 2 can be prevented. This prevents an increase in contact resistance between the terminal 2 and the mounting object 3. The coating layer 37 forms, for example, a third surface 31. The thickness of the coating layer 37 is, for example, 2 μm. The coating layer 37 may cover the entire main body 36. The coating layer 37 may form a fourth surface 32. In this specification, when it is stated that the mounting object 3 is formed of a specific material, this includes the case where the main body 36 is formed of the specific material and the coating layer 37 is formed of a material other than the specific material.

[0075] The coating layer 37 may contain at least one selected from the group consisting of gold, silver, tin, and nickel. The coating layer 37 is formed of, for example, one of tin, an alloy containing tin and copper, silver, and an alloy containing silver and copper. By having a coating layer 37 formed of one of these metals on the mounting target 3, surface oxidation of the mounting target 3 can be suppressed compared to when the mounting target 3 does not have a coating layer 37. Therefore, it is possible to prevent an increase in coating resistance due to the surface oxide film on the mounting target 3. In addition, the contact resistance between the terminal 2 and the mounting target 3 can be reduced by increasing the true contact area between the terminal 2 and the mounting target 3, which makes it easier to reduce concentrated resistance. The Vickers hardness of the coating layer 37 may be lower than the Vickers hardness of the main body 36. Also, the oxide film present on the surface of the coating layer 37 may be more easily broken than the base surface of the mounting target. These factors prevent an increase in contact resistance between the terminal 2 and the mounting target 3.

[0076] The Vickers hardness of mounting target 3 is, for example, 50 HV or more and 160 HV or less. The Vickers hardness of mounting target 3 may be 55 HV or more, or 60 HV or more. The Vickers hardness of mounting target 3 may be 110 HV or less, or 80 HV or less.

[0077] If the Vickers hardness of the mounting target 3 is 50 HV or higher, each of the multiple protrusions 6 will deform more easily when connecting the terminal 2 and the mounting target 3. If the Vickers hardness of the mounting target 3 is 160 HV or lower, the multiple protrusions 6 will bite into the mounting target 3 more easily. The biting of the multiple protrusions 6 into the mounting target 3 will allow the terminal 2 and the mounting target 3 to be mechanically fixed more firmly.

[0078] Next, the effects of the connection structure 1 according to this embodiment will be explained. A film of aluminum oxide (native oxide film) is formed on the surface of aluminum and aluminum alloy. The electrical resistivity of aluminum oxide is higher than the electrical resistivity of aluminum and aluminum alloy, respectively. Therefore, when connecting the terminal 2, which is made of aluminum or aluminum alloy, to the mounting target 3, it is required that the native oxide film be destroyed so that the newly formed surface of the aluminum or aluminum alloy comes into contact with the mounting target 3.

[0079] One way to break down the natural oxide film is to provide a projection on the surface of the terminal 2 that contacts the mounting object 3. When the terminal 2 and the mounting object 3 are connected using a bolt, fastening torque is usually transmitted from the bolt to the terminal 2 and the mounting object 3. In this case, due to this fastening torque, the terminal 2 and the mounting object 3 slide along the tangential direction of the interface between the terminal 2 and the mounting object 3.

[0080] Figure 6 shows how terminal 2 and mounting target 3 slide when connected, according to a comparative example. As shown in Figure 6, when terminal 2 and mounting target 3 are connected, an axial force F is applied to terminal 2 and mounting target 3. Due to the application of the axial force F and fastening torque to terminal 2 and mounting target 3, terminal 2 and mounting target 3 slide along arrow S at the interface between terminal 2 and mounting target 3. As a result, a shear force is applied to the native oxide film 9 at the tip of the projection 8 provided on terminal 2. This destroys the native oxide film 9. Consequently, the newly formed surface of the aluminum and aluminum alloy forming terminal 2 comes into contact with mounting target 3. As a result, the contact resistance between terminal 2 and mounting target 3 is reduced. However, even when projection 8 is provided on the surface of terminal 2, the contact resistance between terminal 2 and mounting target 3 was not always sufficiently reduced.

[0081] Figure 7 shows how sliding between terminal 2 and mounting target 3 is suppressed when terminal 2 and mounting target 3 are connected in the comparative example. For example, if terminal 2 and mounting target 3 are firmly fixed by other parts, terminal 2 and mounting target 3 will not slide when fastening torque is applied. In this case, as shown in Figure 7, only an axial force F is applied to the native oxide film 9. In other words, near the interface between terminal 2 and mounting target 3, terminal 2 and mounting target 3 are uniaxially compressed. In this case, the native oxide film 9 is not sufficiently destroyed. As a result, the contact resistance between terminal 2 and mounting target 3 is not sufficiently reduced.

[0082] According to the connection structure 1 of this embodiment, a plurality of protrusions 6 extending along the imaginary line 90 are provided on the first surface 21 of the terminal 2. Each of the plurality of protrusions 6 has a first wall surface 61 and a second wall surface 62. In a cross section perpendicular to the imaginary line 90, the inclination angle of the second wall surface 62 with respect to the second surface 22 of the terminal 2 (second angle θ2) is greater than the inclination angle of the first wall surface 61 with respect to the second surface 22 (first angle θ1). The second angle θ2 is greater than 20° and 85° or less.

[0083] As a result, as shown in Figure 8, when the terminal 2 and the mounting object 3 are connected, the axial force F causes the tip of each of the multiple protrusions 6 to deform. Specifically, the tip of each protrusion 6 can be deformed to tilt in the direction from the first wall surface 61 toward the second wall surface 62. Therefore, each of the multiple protrusions 6 slides along the arrow S on the mounting object 3. Consequently, a shear force is applied to the native oxide film 9. This causes the native oxide film 9 to be sufficiently destroyed. As a result, even when sliding at the interface between the terminal 2 and the mounting object 3 is suppressed, the contact resistance between the terminal 2 and the mounting object 3 can be reduced.

[0084] According to the connection structure 1 of this embodiment, each of the multiple protrusions 6 has a top surface 63. The length L of the top surface 63 in the third direction 103 is 1.5 times or more the width W of the top surface 63 in the fourth direction 104. Therefore, when connecting the terminal 2 and the mounting object 3, deformation of each of the multiple protrusions 6 along the longitudinal direction of the top surface 63 (third direction 103) can be suppressed. From another point of view, the anisotropy of the rigidity of each of the multiple protrusions 6 can be increased. Specifically, when connecting the terminal 2 and the mounting object 3, the tip of each of the multiple protrusions 6 becomes more likely to deform only in the direction from the first wall surface 61 to the second wall surface 62. Therefore, the amount of deformation in the shear direction of each of the multiple protrusions 6 can be increased. Consequently, the natural oxide film 9 can be effectively destroyed. As a result, the contact resistance between the terminal 2 and the mounting object 3 can be effectively reduced.

[0085] According to the connection structure 1 of this embodiment, the distance P between two adjacent protrusions 6 among the plurality of protrusions 6 is 3.0 times or more the average width of the top surface 63 of the plurality of protrusions 6. This reduces the apparent contact area between the terminal 2 and the mounting object 3 when connecting the terminal 2 and the mounting object 3. Consequently, the contact pressure applied to each of the plurality of protrusions 6 increases. This effectively destroys the natural oxide film 9. As a result, the contact resistance between the terminal 2 and the mounting object 3 can be effectively reduced.

[0086] According to the connection structure 1 of this embodiment, the height H of each of the multiple protrusions 6 is 0.01 mm or more. This effectively reduces the contact resistance between the terminal 2 and the object to be attached 3.

[0087] According to the connection structure 1 of this embodiment, both the terminal 2 and the mounting object 3 may be made of aluminum or an aluminum alloy. This prevents galvanic corrosion from occurring when water adheres to the connection portion between the terminal 2 and the mounting object 3.

[0088] According to the connection structure 1 of this embodiment, the Vickers hardness of the terminal 2 is 50 HV or higher. This makes it easier for each of the multiple protrusions 6 to bite into the mounting object 3 when the terminal 2 and the mounting object 3 are connected. As a result, the terminal 2 and the mounting object 3 can be mechanically fixed firmly. Therefore, it is possible to prevent a decrease in the connection strength between the terminal 2 and the mounting object 3 due to thermal shock, vibration, etc.

[0089] According to the connection structure 1 of this embodiment, the Vickers hardness of the terminal 2 is 160 HV or less. This makes each of the multiple protrusions 6 more easily deformed when the terminal 2 and the mounting object 3 are connected. Therefore, the natural oxide film 9 can be effectively destroyed. As a result, the contact resistance between the terminal 2 and the mounting object 3 can be reduced more reliably. In addition, because the Vickers hardness of the terminal 2 is 160 HV or less, it is possible to prevent the bendability of the terminal 2 from being excessively reduced. For this reason, terminals 2 with complex shapes can be easily formed.

[0090] If the width W of the top surface 63 is excessively small, the cost required to form multiple protrusions 6 becomes excessively high. According to the connection structure 1 of this embodiment, the width of the top surface 63 is 0.02 mm or more. This prevents the cost required to form multiple protrusions 6 from becoming excessively high.

[0091] According to the connection structure 1 of this embodiment, the width of the top surface 63 is 0.5 mm or less. This reduces the apparent contact area between the terminal 2 and the mounting object 3 when connecting the terminal 2 and the mounting object 3. Consequently, the contact pressure applied to each of the multiple protrusions 6 increases. This effectively destroys the natural oxide film 9. As a result, the contact resistance between the terminal 2 and the mounting object 3 can be effectively reduced.

[0092] (First Modified Example) Figure 9 is a schematic cross-sectional view showing the configuration of the terminal 2 according to the first modified example of this embodiment. The cross-section shown in Figure 9 corresponds to the cross-section shown in Figure 4. In Figure 9, for the sake of explanation, the first connection point 81 and the second connection point 82 are each shown as black dots.

[0093] As shown in Figure 9, in cross-sectional view, the top surface 63 may be a curved shape convex in the second direction 102. When the top surface 63 is curved in cross-sectional view, the first connection point 81 and the second connection point 82 are inflection points. In other words, the first connection point 81 and the second connection point 82 are points where the change in the slope of the tangent line becomes zero when the point of contact between the tangent line to the top surface 63 and the top surface 63 moves along the top surface 63.

[0094] If the top surface 63 is curved in cross-sectional view, the first connection point 81 and the second connection point 82 can be identified using the following procedure. Specifically, a curve showing the shape of the protrusion in cross-sectional view is obtained using a contact-type three-dimensional shape measuring machine. Along this curve, the point of contact between the tangent to the top surface 63 and the top surface 63 is moved from the vertex of the top surface 63 in the fourth direction 104. The point where the change in the slope of the tangent becomes 0 is identified as the first connection point 81. Similarly, the second connection point 82 can be identified by moving the point of contact between the tangent to the top surface 63 and the top surface 63 in the opposite direction to the fourth direction 104 from the vertex of the top surface 63. Note that the tangent to the top surface 63 is a straight line passing through two points that lie on the above curve and are 0.001 mm apart in the fourth direction 104.

[0095] The radius of curvature R of the top surface 63 is 0.05 mm or more. If the radius of curvature R is excessively small, the cost required to form multiple protrusions 6 becomes excessively high. By having a radius of curvature R of 0.05 mm or more, it is possible to prevent the cost required to form multiple protrusions 6 from becoming excessively high.

[0096] In a cross-sectional view, the radius of curvature R is defined as the radius of a circle passing through three points: the first connection point 81, the second connection point 82, and a point (not shown) that coincides with the top surface 63 and is located midway between the first connection point 81 and the second connection point 82 in the fourth direction 104.

[0097] The radius of curvature R may be, for example, 0.15 mm or more, or 0.25 mm or more. There is no particular upper limit to the radius of curvature R. When the radius of curvature R is infinite, the top surface 63 becomes planar as shown in Figure 4.

[0098] (Second Modification) Figure 10 is a schematic bottom view showing the configuration of the terminal 2 according to the second modification of this embodiment. As shown in Figure 10, each of the multiple protrusions 6 may be island-shaped. The multiple protrusions 6 are arranged along the third direction 103 and the fourth direction 104, respectively. The length L of the top surface 63 in the third direction 103 is shorter than the length of the first portion 26 in the third direction 103. The bottom surface 64 is located between two adjacent protrusions 6 in the third direction 103. When viewed in the first direction 101, the bottom surface 64 is grid-shaped.

[0099] The distance D between two adjacent protrusions 6 along the third direction 103 is not particularly limited. The distance D is, for example, 0.5 times or less the length L of the top surface 63. The distance D is 0 mm or more. The distance D may be 0 mm.

[0100] Each of the multiple protrusions 6 is shaped like a truncated square pyramid. Each of the multiple protrusions 6 has a first end face 65 and a second end face 66. The first end face 65 and the second end face 66 are connected to the first wall 61, the second wall 62, and the top face 63, respectively. The first end face 65 and the second end face 66 may also be connected to the bottom face 64, or to the face of the terminal 2 connected to the first face 21. The second end face 66 is located in a third direction 103 relative to the first end face 65.

[0101] Figure 11 shows a cross-section parallel to the third direction 103 and intersecting the projection 6. As shown in Figure 11, the length of the projection 6 in the third direction 103 decreases as it moves away from the bottom surface 64 along the second direction 102. The first end face 65 and the second end face 66 are inclined with respect to the second surface 22.

[0102] The inclination angle of the first end face 65 with respect to the second face 22 (third angle θ3) may be the same as the first angle θ1 (see Figure 4). The third angle θ3 is smaller than the second angle θ2. The third angle θ3 is, for example, 4° or more and 45° or less.

[0103] The inclination angle of the second end face 66 with respect to the second face 22 (fourth angle θ4) may be the same as the first angle θ1 (see Figure 4). The fourth angle θ4 is smaller than the second angle θ2. The fourth angle θ4 is, for example, between 4° and 45°.

[0104] (Third Modification) As shown in Figure 12, in cross-sectional view, the bottom surface 64 may be a concave curve in the first direction 101. When the bottom surface 64 is curved in cross-sectional view, the third connection point 83 and the fourth connection point 84 are inflection points.

[0105] If the bottom surface 64 is curved in cross-sectional view, the third connection point 83 and the fourth connection point 84 can be identified using the same procedure as for identifying the first connection point 81 and the second connection point 82 as described above. As shown in Figure 12, if both the top surface 63 and the bottom surface 64 are curved in cross-sectional view, in the measurement of the first angle θ1, the straight line passing through the first connection point 81 and the third connection point 83 is identified as the first wall surface 61. In the measurement of the second angle θ2, the straight line passing through the second connection point 82 and the fourth connection point 84 is identified as the second wall surface 62.

[0106] (Other variations) The electric wire 5 may be connected to the first surface 21 or to another surface of the terminal 2. In the above, the terminal 2 and the electric wire 5 were separate parts, but the terminal 2 and the electric wire 5 may be a single component. Specifically, the electric wire 5 may be a single-core wire, and the terminal 2 may be a part of the single-core wire. The terminal 2 may be manufactured by forming the tip of the single-core wire into a terminal shape. The terminal 2 may be, for example, a part of a busbar. The terminal 2 may be manufactured by forming a part of a busbar into a terminal shape. The terminal 2 may have an insulation barrel. The insulation barrel grips the insulating coating 51 of the electric wire 5.

[0107] In the above description, the configuration in which the terminal 2 and the electric wire 5 are connected by the wire barrel 29 of the terminal 2 has been explained. However, the electric wire 5 may also be connected to the terminal 2 by welding or solid-state bonding, for example. Specifically, the electric wire 5 may be connected to the terminal 2 by resistance welding, laser welding, ultrasonic welding, or friction stir welding, for example.

[0108] In the above description, a configuration in which the second surface 22 of the terminal 2 is flat was explained, but the second surface 22 may have a curved portion. In this case, the "angle of inclination with respect to the second surface 22," such as the first angle θ1 and the second angle θ2, is the angle of inclination with respect to the portion of the second surface 22 that the mounting member 4 contacts. Specifically, for example, if the mounting member 4 has a bolt 41 as shown in Figure 1, the angle of inclination of the first wall surface 61 with respect to the portion that the flange portion 42 (or washer) of the bolt 41 contacts is defined as the first angle θ1.

[0109] The shape of the first through-hole 2h is not particularly limited. When viewed in the first direction 101, the first through-hole 2h may be an elongated hole. In the terminal 2, a slit may be provided instead of the first through-hole 2h. The slit extends, for example, to the left end of the terminal 2 in Figure 2.

[0110] Multiple protrusions may be provided on the mounting target 3. Specifically, multiple protrusions may be provided on the third surface 31. The configuration of the multiple protrusions provided on the mounting target 3 may be the same as the configuration of the multiple protrusions 6 provided on the terminal 2. When the terminal 2 and the mounting target 3 are connected, the top surfaces 63 of the multiple protrusions 6 provided on the terminal 2 and the top surfaces of the multiple protrusions provided on the mounting target 3 come into contact.

[0111] In the above description, the outer contour of the first part 26 was rectangular, but the outer contour of the first part 26 may be circular. In other words, the first part 26 may be annular. The outer contour of the first part 26 may be elliptical.

[0112] The inner circumferential contour of the first portion 26 does not have to overlap with the edge of the first through hole 2h. When viewed in the first direction 101, the inner circumferential contour of the first portion 26 may be a larger circle than the edge of the first through hole 2h.

[0113] In the second direction 102, the top surface 63 of each of the multiple protrusions 6 may be at the same height as the second portion 27 or at a different height. In the second direction 102, the top surface 63 of each of the multiple protrusions 6 may be located between the second portion 27 and the second surface 22. From another point of view, the multiple protrusions 6 may be formed by forming multiple recesses in the first portion 26 of the first surface 21.

[0114] Each of the multiple protrusions 6 may project in the second direction 102 relative to the second portion 27. In the second direction 102, the bottom surface 64 of the first portion 26 may be at the same height as the second portion 27.

[0115] The first part 26 does not necessarily have a bottom surface 64. From another point of view, two adjacent protrusions 6 among the multiple protrusions 6 may be connected. In other words, the first wall surface 61 of a protrusion 6 may be connected to the second wall surface 62 of an adjacent protrusion 6.

[0116] The mounting member 4 may have, for example, a rivet. The terminal 2 and the mounting object 3 may be connected by crimping the rivet.

[0117] (Sample Preparation) The effect of the shape of multiple protrusions 6 on the contact resistance between the terminal 2 and the mounting object 3 was investigated. First, terminals 2 and mounting objects 3 related to samples 1 to 28, 101, and 102 were prepared. Samples 1 to 28 are examples. Samples 101 and 102 are comparative examples.

[0118] As shown in Figures 13 and 14, the shape of the terminal 2 for all samples was rectangular and plate-like. The thickness of the terminal 2 was 2 mm. The length of the terminal 2 in the short direction was 14 mm. The length of the terminal 2 in the long direction was 70 mm. Multiple protrusions 6 were provided on the first surface 21 of the terminal 2. A first through hole 2h was provided in the center of the terminal 2. The inner diameter of the first through hole 2h was 7 mm.

[0119] In all samples, the first angle θ1 of each of the multiple protrusions 6 varied between 5° and 45°. In samples 1 to 28, the second angle θ2 of each of the multiple protrusions 6 varied between 45° and 85°. In sample 101, the second angle θ2 of each of the multiple protrusions 6 was 20°. In sample 102, the second angle θ2 of each of the multiple protrusions 6 was 88°.

[0120] In samples 1 to 14, 23 to 26, 101, and 102, the shape of the top surface 63 was planar. On the other hand, in samples 15 to 22, 27, and 28, the shape of the top surface 63 in cross-sectional view was curved and convex in the second direction 102.

[0121] In all samples, the length L of each top surface 63 of the multiple ridges 6 varied between 0.2 mm and 14 mm. The width W of each top surface 63 of the multiple ridges 6 varied between 0.03 mm and 0.55 mm. In samples where the shape of the top surface 63 in cross-sectional view was convex (samples 15 to 22, 27, and 28), the radius of curvature R of the top surface 63 varied between 0.1 mm and 4.8 mm.

[0122] In all samples, the length L of the top surface 63 in the third direction 103 varied between 1 and 466.7 times the width W of the top surface 63 in the fourth direction 104. The spacing P between two adjacent protrusions 6 varied between 1.8 and 100 times the average width of the top surfaces 63 of the multiple protrusions 6. In all samples, the average width of the top surfaces 63 of the multiple protrusions 6 was the same as the width W. The height H of each of the multiple protrusions 6 varied between 0.009 mm and 0.4 mm.

[0123] In samples 1 to 20, 22 to 27, 101, and 102, the material of terminal 2 was 6061 according to the International Registered Alloy Number. The Vickers hardness of terminal 2 was 95 HV. The Vickers hardness was measured in accordance with JIS Z 2244-1:2020. The cross section of terminal 2 at a position not in contact with the mounting object 3 was mirror-polished until the effect of the processed altered layer was eliminated and then used for measurement. The measurement load for Vickers hardness was 50 gf (≒0.49 N). The Vickers hardness was the median value of 20 measured points. In sample 21, the material of terminal 2 was 6101 according to the International Registered Alloy Number. The Vickers hardness of terminal 2 was 60 HV. In sample 28, the material of terminal 2 was 1050 according to the International Registered Alloy Number. The Vickers hardness of terminal 2 was 45 HV.

[0124] As shown in Figures 13 and 14, the shape of the mounting object 3 for all samples was a rectangular plate. The thickness of the mounting object 3 was 1.5 mm. The length of the mounting object 3 in the short direction was 14 mm. The length of the mounting object 3 in the long direction was 70 mm. A second through hole 3h was provided in the center of the mounting object 3. The inner diameter of the second through hole 3h was 7 mm.

[0125] In samples 1 to 21, 23 to 28, 101, and 102, the material of the mounting target 3 was C1020. In sample 22, the material of the mounting target 3 was 6101 according to the International Registered Alloy Number. In sample 22, the third surface 31 of the mounting target 3 had multiple protrusions. The shape of the multiple protrusions on the mounting target 3 was the same as the shape of the multiple protrusions 6 on the terminal 2.

[0126] (Evaluation Method) In all samples, the contact resistance between terminal 2 and mounting object 3 was measured. Specifically, as shown in Figure 14, terminal 2 and mounting object 3 were positioned so that the longitudinal direction of terminal 2 and the longitudinal direction of mounting object 3 were perpendicular when viewed in the thickness direction of terminal 2. As shown in Figure 15, terminal 2 and mounting object 3 were positioned so that the first surface 21 of terminal 2 and the third surface 31 of mounting object 3 faced each other.

[0127] The terminal 2 and the mounting object 3 were sandwiched between two jigs 95. The shape of the jigs 95 was cylindrical. The outer diameter of the jigs 95 was 13 mm. The inner diameter of the jigs 95 was 7 mm. The jigs 95 were positioned so that the central axis of the first through hole 2h of the terminal 2, the central axis of the second through hole 3h of the mounting object 3, and the central axes of each of the two jigs 95 overlapped.

[0128] The contact resistance between terminal 2 and mounting target 3 was measured when both terminal 2 and mounting target 3 were compressed uniaxially. In other words, the contact resistance was measured when sliding between terminal 2 and mounting target 3 was suppressed. Specifically, a load A was applied to terminal 2 and mounting target 3 via two jigs 95 along the direction in which the central axis extends. The magnitude of load A was 3000 N. With load A applied, the contact resistance between terminal 2 and mounting target 3 was measured using the four-terminal method. For the measurement of contact resistance, electrode terminals of the measuring device were attached to both ends of the longitudinal direction of terminal 2 and both ends of the longitudinal direction of mounting target 3. The measurement current was set to a maximum of 1 A.

[0129] (Evaluation results)

[0130]

[0131] Table 1 shows the measurement results of contact resistance for each sample. The evaluation results will be explained below using Table 1 and Figures 16 to 24. In Figures 16 to 24, the number following "P" indicates the sample number. Specifically, for example, points labeled "P1" indicate the measurement results for sample 1.

[0132] <Second Angle> Figure 16 shows the contact resistance of samples (samples 1 through 4, 11, 101, and 102) with varying second angles θ2. As shown in Table 1, the samples shown in Figure 16 had the same parameters other than the second angle θ2.

[0133] As shown in Figure 16 and Table 1, in samples where the second angle θ2 was greater than 20° and 85° or less (samples 1 to 4 and 11), the contact resistance was 0.36 mΩ or less. Also, in samples where the second angle θ2 was between 73° and 85° (samples 1 to 3), the contact resistance was 0.1 mΩ or less. On the other hand, in sample 101, where the second angle θ2 was 20°, the contact resistance was 0.78 mΩ. In sample 102, where the second angle θ2 was 88°, the contact resistance was 1.28 mΩ.

[0134] From the above, it was confirmed that, compared to the terminal 2 in the comparative example, the terminal 2 in the embodiment can reduce contact resistance even when sliding between the terminal 2 and the mounting object 3 is suppressed. In particular, it was confirmed that contact resistance can be effectively reduced when the second angle θ2 is 73° or more and 85° or less.

[0135] <Length / Width> Figure 17 shows the contact resistance of samples (Samples 5, 9, and 25) in which the ratio of the length L of the top surface 63 to the width W of the top surface 63 (length / width) was varied. As shown in Table 1, the samples shown in Figure 17 had the same parameters except for the length L of the top surface 63 and the ratio of the length L of the top surface 63 to the width W of the top surface 63.

[0136] As shown in Figure 17 and Table 1, in samples (Samples 5 and 9) where the length L of the top surface 63 was 1.5 times or more the width W of the top surface 63, the contact resistance was 0.25 mΩ. In sample 25, where the length L of the top surface 63 was 1 time the width W of the top surface 63, the contact resistance was 0.52 mΩ. From the above, it was confirmed that the contact resistance can be effectively reduced by making the length L of the top surface 63 1.5 times or more the width W of the top surface 63.

[0137] <Spacing / Average Width> Figure 18 shows the contact resistance of samples (samples 5 to 8, 23, and 24) in which the ratio of the spacing P between two adjacent protrusions to the average width of the top surface 63 (spacing / average width) was varied. As shown in Figure 18 and Table 1, in samples (samples 5 to 8) where the spacing P was 3.0 times or more the average width of the top surface 63, the contact resistance was 0.4 mΩ or less. Also, in samples (samples 7 and 8) where the spacing P was 10 times or more the average width of the top surface 63, the contact resistance was 0.12 mΩ or less. On the other hand, in samples (samples 23 and 24) where the spacing P was 2.9 times or less the average width of the top surface 63, the contact resistance was 0.51 mΩ or more.

[0138] From the above, it was confirmed that contact resistance can be effectively reduced when the spacing P is 3.0 times or more the average width of the top surface 63. In particular, it was confirmed that contact resistance can be effectively reduced when the spacing P is 10 times or more the average width of the top surface 63.

[0139] <Height of the protrusions> Figure 19 shows the contact resistance of samples (samples 4, 13, 14, and 26) in which the height H of each of the multiple protrusions 6 was varied. As shown in Figure 19 and Table 1, the contact resistance was 0.4 mΩ or less in the samples (samples 4, 13, and 14) where the height H was 0.01 mm or more. On the other hand, in sample 26, where the height H was 0.009 mm, the contact resistance was 0.54 mΩ. From the above, it was confirmed that the contact resistance can be effectively reduced by having a height H of 0.01 mm or more.

[0140] <First Angle> Figure 20 shows the contact resistance of samples (samples 10 to 12) with varying first angles θ1. As shown in Table 1, the samples shown in Figure 20 had the same parameters other than the first angle θ1.

[0141] As shown in Figure 20 and Table 1, the contact resistances of samples 10 to 12 were between 0.26 mΩ and 0.27 mΩ. Therefore, it was confirmed that contact resistance can be reduced even when the first angle θ1 is changed.

[0142] <Vickers Hardness> Figure 21 shows the contact resistance of samples with varying Vickers hardness (Samples 16, 21, and 28). As shown in Table 1, the samples shown in Figure 21 had the same parameters except for the terminal material and Vickers hardness.

[0143] As shown in Figure 21 and Table 1, the contact resistance was 0.45 mΩ or less in the samples with a Vickers hardness of 50 HV or higher (Samples 16 and 21). On the other hand, the contact resistance of Sample 28, which had a Vickers hardness of 45 HV, was 0.61 mΩ. From the above, it was confirmed that contact resistance can be effectively reduced by having a Vickers hardness of 50 HV or higher.

[0144] <Width of the planar top surface> Figure 22 shows the contact resistance of samples (samples 5, 7, and 23) in which the top surface 63 is planar and the width W of the top surface 63 is varied. As shown in Figure 22 and Table 1, the contact resistance was 0.25 mΩ or less for samples with a width W of 0.5 mm or less (samples 5 and 7). On the other hand, the contact resistance was 0.69 mΩ for sample 23, which had a width W of 0.55 mm. From the above, it was confirmed that the contact resistance can be effectively reduced by having a width W of 0.5 mm or less.

[0145] <Radius of curvature of the top surface> Figure 23 shows the contact resistance of samples (samples 15 to 18) in which the top surface 63 is convex in cross-sectional view and the radius of curvature R of the top surface 63 is varied. As shown in Table 1, the samples shown in Figure 23 had the same parameters other than the radius of curvature R.

[0146] As shown in Figure 23 and Table 1, the contact resistance was 0.22 mΩ or less for samples with a radius of curvature R of 0.05 mm or more (samples 15 to 18). Furthermore, the contact resistance was 0.1 mΩ or less for samples with a radius of curvature R of 0.3 mm or less (samples 15 and 16).

[0147] From the above, it was confirmed that contact resistance can be reduced when the radius of curvature R is 0.05 mm or greater. In particular, it was confirmed that contact resistance can be effectively reduced when the radius of curvature R is 0.3 mm or less.

[0148] <Width of a convex curved plane> Figure 24 shows the contact resistance of samples (samples 16, 19, 20, 27) in which the top surface 63 is convex curved in cross-sectional view and the width W of the top surface 63 is varied. As shown in Table 1, the samples shown in Figure 24 had the same parameters except for the width W, the ratio of length L to width W, and the ratio of spacing P to average width.

[0149] As shown in Figure 24 and Table 1, for samples with a width W of 0.5 mm or less (samples 16, 19, and 20), the contact resistance was 0.35 mΩ or less. Also, for samples with a width W of 0.2 mm or less (samples 16 and 20), the contact resistance was 0.11 mΩ or less. On the other hand, for sample 27 with a width W of 0.55 mm, the contact resistance was 0.68 mΩ.

[0150] From the above, it was confirmed that contact resistance can be reduced by having a width W of 0.5 mm or less. In particular, it was confirmed that contact resistance can be effectively reduced by having a convex curved top surface 63 in cross-sectional view and a width W of 0.2 mm or less.

[0151] <Material and Shape of Mounting Object> As shown in Table 1, samples 16 and 22 had the same parameters except for the material of the mounting object 3. In sample 16, where the material of the mounting object 3 was C1020, the contact resistance was 0.1 mΩ. In sample 22, where the material of the mounting object 3 was 6101 and the mounting object 3 had multiple protrusions, the contact resistance was 0.49 mΩ.

[0152] From the above, it was confirmed that contact resistance can be reduced by using C1020 material for mounting target 3 compared to the case where the material of mounting target 3 is 6101. Furthermore, compared to the comparative examples (samples 101 and 102), it was confirmed that contact resistance can be sufficiently reduced by using 6101 material for mounting target 3 and by providing multiple protrusions on mounting target 3.

[0153] (Sample Preparation) Next, the effect of the coating layer 37 of the mounting target 3 on the contact resistance between the terminal 2 and the mounting target 3 was investigated. First, the terminal 2 and mounting target 3 for samples 31 to 56 and 103 were prepared. Samples 31 to 56 are examples. Sample 103 is a comparative example.

[0154] In all samples, the terminal 2 and mounting target 3 were prepared using the same method as the corresponding sample shown in Table 1 above. A coating layer 37 was formed on the surface of the prepared mounting target 3. Therefore, in all samples, the configuration of the terminal 2 was the same as the configuration of the terminal 2 of the corresponding sample shown in Table 1 above. The configuration of the mounting target 3 was the same as the configuration of the mounting target 3 of the corresponding sample shown in Table 1 above, except that it had a coating layer 37. The coating layer 37 was made of tin. The thickness of the coating layer 37 was 2 μm.

[0155] (Evaluation Method) For all samples, the contact resistance between terminal 2 and mounting target 3 was measured. The measurement method described above was used for measuring the contact resistance.

[0156] (Evaluation results)

[0157]

[0158]

[0159] Tables 2 and 3 show the configuration of each sample and the measurement results of the contact resistance. In the "Corresponding No." column of Tables 2 and 3, the corresponding sample number in Table 1 is shown for each sample. From another perspective, the configuration of each sample was the same as the configuration of the sample number indicated in the "Corresponding No." column, except that the mounting target 3 had a coating layer 37.

[0160] As shown in Tables 2 and 3, the contact resistance was 0.10 mΩ or less in samples 31 to 56. In sample 101, the contact resistance was 0.28 mΩ. From the above, it was confirmed that, compared to the connection structure 1 according to the comparative example, the connection structure 1 according to the embodiment can reduce contact resistance even when the mounting target 3 has a coating layer 37.

[0161] As shown in Tables 1 to 3, the contact resistances of samples 31 to 56 and 103 were lower than those of the corresponding samples in Table 1. Therefore, it was confirmed that the presence of the coating layer 37 on the mounting target 3 reduces contact resistance.

[0162] It should be understood that at least one configuration and feature described in each embodiment and example can be combined with other embodiments and examples, or modified in various ways.

[0163] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0164] 1 Connection structure, 2 Terminal, 2h First through hole, 3 Mounting target, 3h Second through hole, 4 Mounting member, 5 Electric wire, 6 Protrusion, 8 Projection, 9 Natural oxide coating, 21 First surface, 22 Second surface, 26 First part, 27 Second part, 28 Plate part, 29 Wire barrel, 31 Third surface, 32 Fourth surface, 36 Main body part, 37 Coating layer, 41 Bolt, 42 Flange part, 43 Nut, 50 Conductor, 51 Insulating coating, 61 First wall surface, 62 Second wall surface, 63 Top surface, 64 Bottom surface, 65 First end surface, 66 Second end surface, 81 First connection point, 82 Second connection point, 83 Third connection point, 84 Fourth connection point, 90 Imaginary line, 91 Straight line, 95 Jig, 101 First direction, 102 Second direction, 103 Third direction, 104 Fourth direction, A Load, D Distance, F Axial force, P Spacing, R Radius of curvature, S Arrow, W Width, θ1 First angle, θ2 Second angle, θ3 Third angle, θ4 Fourth angle.

Claims

1. A connection structure comprising: a terminal formed of aluminum or an aluminum alloy; a mounting object formed of metal; and a mounting member connecting the terminal and the mounting object, wherein the terminal includes a first surface and a second surface opposite to the first surface, and the first surface is provided with a plurality of protrusions extending along a virtual line and in contact with the mounting object when the terminal is connected to the mounting object, each of the plurality of protrusions having a first wall surface and a second wall surface opposite to the first wall surface, and in a cross section perpendicular to the virtual line, if the angle of inclination of the first wall surface with respect to the second surface is taken as the first angle, and the angle of inclination of the second wall surface with respect to the second surface is taken as the second angle, then the second angle is greater than the first angle, and the second angle is greater than 20° and less than or equal to 85°.

2. The connection structure according to claim 1, wherein each of the plurality of protrusions has a top surface that connects the first wall surface and the second wall surface.

3. The connection structure according to claim 2, wherein the length of the top surface in the direction in which the imaginary line extends is 1.5 times or more the width of the top surface in a direction perpendicular to the direction in which the imaginary line extends, as viewed from the first surface toward the second surface.

4. The connection structure according to claim 2 or 3, wherein the distance between two adjacent protrusions among the plurality of protrusions is 3.0 times or more and 200 times or less the average width of the top surfaces of the plurality of protrusions.

5. The connection structure according to any one of claims 1 to 4, wherein the height of each of the plurality of protrusions is 0.01 mm or more and 0.5 mm or less.

6. The connection structure according to any one of claims 1 to 5, wherein the first angle is 4° or more and 45° or less.

7. The connection structure according to any one of claims 1 to 6, wherein the object to be attached is formed of one of aluminum, an aluminum alloy, copper, and a copper alloy.

8. The connection structure according to any one of claims 1 to 7, wherein the mounting member includes a bolt.

9. The connection structure according to any one of claims 1 to 8, wherein the Vickers hardness of the terminal is 50 HV or more and 160 HV or less.

10. The connection structure according to any one of claims 2 to 4, wherein the top surface is planar, and in a cross section perpendicular to the dashed line, the width of the top surface is 0.02 mm or more and 0.5 mm or less.

11. The connection structure according to any one of claims 2 to 4, wherein in a cross section perpendicular to the dashed line, the top surface is a curved shape that is convex in the direction from the second surface toward the first surface, the radius of curvature of the top surface is 0.05 mm or more, and the width of the top surface is 0.02 mm or more and 0.5 mm or less.

12. The terminal is formed of one of the internationally registered alloy numbers 5052, 6101, and 6061, the Vickers hardness of the terminal is 50 HV or more and 160 HV or less, the mounting object is formed of one of aluminum, aluminum alloy, copper, and copper alloy, the mounting member includes a bolt, each of the plurality of protrusions has a top surface connecting the first wall surface and the second wall surface, the length of the top surface in the direction in which the imaginary line extends is at least twice the width of the top surface in a direction perpendicular to the direction in which the imaginary line extends when viewed from the first surface toward the second surface, the distance between two adjacent protrusions of the plurality of protrusions is 3.0 times or more and 70 times or less the average width of the top surfaces of the plurality of protrusions, the height of each of the plurality of protrusions is 0.05 mm or more and 0.2 mm or less, the first angle is 10° or more and 45° or less. The connection structure according to claim 1, wherein in a cross section perpendicular to the dashed line, the width of the top surface is 0.05 mm or more and 0.5 mm or less.

13. The connection structure according to claim 12, wherein the object to be attached comprises a main body made of either copper or a copper alloy, and a covering layer covering the portion of the main body facing the first surface, and the covering layer is made of either tin, an alloy containing tin and copper, silver, or an alloy containing silver and copper.

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