Inter-terminal connection structure

Abstract

The present invention discloses an inter-terminal connection structure capable of suppressing the occurrence of galvanic corrosion while maintaining good manufacturability. An inter-terminal connection structure (10) is provided with: a first terminal (12); a second terminal (14) connected to the first terminal (12); a relay terminal (18) for conductively connecting the first terminal (12) and the second terminal (14); and a fastening bolt (16) for bolting the first terminal (12) and the second terminal (14) to each other in a state in which the relay terminal (18) is sandwiched between the first terminal (12) and the second terminal (14). In a plurality of members fixed by fastening of the fastening bolt (16), the difference between the natural potentials of respective metal materials in members in contact with each other is 300 mV or less in each case.

Description

Inter-terminal connection structure

[0001] The present disclosure relates to an inter-terminal connection structure.

[0002] Patent Document 1 discloses an inter-terminal connection structure, which is one of electrical connection structures adopted in automobiles, in which a terminal provided at an end of a wire harness is bolted to a terminal provided on an electric unit side by a fastening bolt. Such an inter-terminal connection structure can easily and firmly realize connection between terminals in a vehicle.

[0003] Japanese Patent Laying-Open No. 2016-159814

[0004] Incidentally, in the structure of Patent Document 1, for example, when a terminal provided at an end of a wire harness is made of aluminum and a terminal on an electric unit side is made of a copper alloy or the like, resulting in a connection between dissimilar metals, if water or the like enters between the two terminals, galvanic corrosion may occur between the terminals due to a difference in ionization tendency between the two. In order to suppress the occurrence of such galvanic corrosion, the periphery between the contact surfaces of both terminals is covered with a corrosion preventive material to prevent water from entering. However, since a separate step of applying the corrosion preventive material is required, there has been an inherent problem that deterioration in manufacturability is unavoidable.

[0005] Therefore, the present disclosure discloses an inter-terminal connection structure capable of suppressing the occurrence of galvanic corrosion while maintaining good manufacturability.

[0006] The inter-terminal connection structure of the present disclosure includes: a first terminal; a second terminal connected to the first terminal; a relay terminal electrically connecting between the first terminal and the second terminal; and a fastening bolt that bolts the first terminal and the second terminal to each other in a state where the relay terminal is sandwiched between the first terminal and the second terminal, wherein among a plurality of members fixed by fastening of the fastening bolt, a difference in natural potential between respective metal materials of mutually contacting members is 300 mV or less in all cases.

[0007] According to the inter-terminal connection structure of the present disclosure, the occurrence of galvanic corrosion can be suppressed while maintaining good manufacturability.

[0008] Figure 1 is a perspective view showing the terminal-to-terminal connection structure according to Embodiment 1, with the first terminal and the second terminal bolted together. Figure 2 is a plan view of the terminal-to-terminal connection structure shown in Figure 1. Figure 3 is a longitudinal cross-sectional view showing an enlarged view of the III-III cross-section in Figure 2. Figure 4 is a longitudinal cross-sectional view showing an enlarged view of the IV-IV cross-section in Figure 2. Figure 5 is a cross-sectional view showing the V-V cross-section in Figure 3. Figure 6 is a perspective view showing the terminal-to-terminal connection structure shown in Figure 1 before the first terminal and the second terminal are bolted together. Figure 7 is an exploded perspective view showing the terminal-to-terminal connection structure shown in Figure 1 in an exploded state.

[0009] <Description of Embodiments of the Disclosure> First, embodiments of the Disclosure will be listed and described. The terminal connection structure of the Disclosure comprises (1) a first terminal, a second terminal connected to the first terminal, an intermediate terminal providing an electrical connection between the first terminal and the second terminal, and a fastening bolt that bolts the first terminal and the second terminal together with the intermediate terminal sandwiched between them, wherein in a plurality of members fixed by fastening the fastening bolt, the difference in the natural potential of the respective metal materials in the members that are in contact with each other is 300 mV or less in all cases.

[0010] According to the terminal connection structure of this disclosure, in multiple members fixed by fastening fastening bolts, the difference in the natural potential of each metal material between members in contact with each other (for example, the fastening bolt and the first terminal, the first terminal and the intermediate terminal, the intermediate terminal and the second terminal, and the second terminal and the fastening bolt) is 300 mV or less in all cases. As a result, even when the contact surfaces of each component are in contact with dissimilar metals, the difference in the natural potential of the metal materials constituting them is 300 mV or less, so even if water adheres to the contact surfaces, the occurrence of galvanic corrosion can be suppressed. Therefore, the corrosion-preventive material that surrounds the contact surfaces, which was required in conventional structures, can be eliminated, and a terminal connection structure can be provided that suppresses the occurrence of galvanic corrosion while maintaining good manufacturability.

[0011] (2) In the above (1), it is preferable that the fastening bolt has a first bolt insertion hole that penetrates the first terminal, an intermediate through hole that penetrates the intermediate terminal and communicates with the first bolt insertion hole, and a second bolt insertion hole that penetrates the second terminal and communicates with the intermediate through hole, and the head of the fastening bolt inserted by sequentially inserting it through the first bolt insertion hole, the intermediate through hole and the second bolt insertion hole abuts against the first terminal and the tip of the fastening bolt is screwed into the threaded portion of the second terminal, so that the first terminal, the intermediate terminal and the second terminal are in close contact with each other by the axial force of the fastening bolt. By using a fastening bolt, the first terminal and the second terminal, which are electrically connected to each other via an intermediate terminal, can be inserted into the fastening bolt and brought into close contact with each other all at once by the axial force of the fastening bolt. This makes it possible to achieve both further improvement in manufacturability and prevention of galvanic corrosion. Furthermore, since the tip of the fastening bolt is screwed into the threaded portion of the second terminal, even if an oxide film is formed between the contact surfaces of the fastening bolt and the second terminal, the screwing process removes the oxide film, ensuring a good connection between the fastening bolt and the second terminal.

[0012] (3) In the above (2), it is preferable that the relay terminal has a mounting cylinder portion that is assembled to the inner circumferential surface of the first bolt insertion hole of the first terminal, and has a plurality of press-fit ribs on the outer circumferential surface of the mounting cylinder portion that are press-fitted into the inner circumferential surface of the first bolt insertion hole. Since a plurality of press-fit ribs are provided on the outer circumferential surface of the mounting cylinder portion that is the contact area between the first terminal and the relay terminal, the press-fit ribs of the mounting cylinder portion of the relay terminal can bite into the inner circumferential surface of the bolt insertion hole of the first terminal. As a result, even if an oxide film is formed between the contact surfaces of the first terminal and the relay terminal, the oxide film can be removed by the biting of the press-fit ribs, and a good connection state between the first terminal and the relay terminal can be achieved.

[0013] (4) In (2) or (3) above, it is preferable that the relay terminal has a cylindrical projection that protrudes toward the second terminal, a part of the relay through hole is partitioned by the inner surface of the cylindrical projection, a housing space is formed by the radial gap between the fastening bolt inserted through the relay through hole and the inner surface, the second terminal is held by the second terminal holding part, the second terminal holding part has a finger-prevention rib that covers the inner surface of the second bolt insertion hole of the second terminal and protrudes toward the first terminal, and the finger-prevention rib is housed in the housing space of the relay terminal so that the first terminal, the second terminal and the relay terminal can be bolted together with the fastening bolt. With the recent increase in the current of in-vehicle equipment, in terminal connection structures, when exposed terminals become live parts, measures are required to prevent workers' fingers from coming into contact with live parts. For example, if a finger-prevention rib is provided on the second terminal, a cylindrical projection can be provided on the intermediate terminal that electrically connects the first and second terminals. By cleverly utilizing this cylindrical projection, the bolt fastening of the first terminal, intermediate terminal, and second terminal can be achieved simply and compactly while accommodating the finger-prevention rib.

[0014] <Details of Embodiments of the Disclosure> Specific examples of the terminal connection structures of the Disclosure will be described below with reference to the drawings. However, the Disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the Claims as indicated by the Claims.

[0015] <Embodiment 1> Hereinafter, the terminal connection structure 10 of Embodiment 1 of the present disclosure will be described with reference to Figures 1 to 7. This terminal connection structure 10 is used in vehicles such as electric vehicles and hybrid vehicles, and is a structure in which a first terminal 12, which is a battery-side component as a power source, and a second terminal 14, which is a motor-side component as a load, are bolted together with fastening bolts 16. By bolting together the first terminal 12 and the second terminal 14, they are electrically connected, and the battery and the motor are electrically connected. The first terminal 12 and the second terminal 14 constituting the terminal connection structure 10 can be arranged in any orientation within the vehicle, but hereafter, "upper" will be described as the upper part in Figure 3, "lower" as the lower part in Figure 3, "left" as the upper part in Figure 2, "right" as the lower part in Figure 2, "front" as the left in Figure 2, and "rear" as the right in Figure 2. In addition, in the following description, for multiple identical components, only some components may be given reference numerals, and the reference numerals for other components may be omitted.

[0016] <Terminal Connection Structure 10> The terminal connection structure 10 includes a first terminal 12, a second terminal 14 connected to the first terminal 12, an intermediate terminal 18 that electrically connects the first terminal 12 and the second terminal 14, and a fastening bolt 16 that bolts the first terminal 12 and the second terminal 14 together with the intermediate terminal 18 sandwiched between them. In the multiple members fixed by fastening the fastening bolt 16, the difference in the natural potential of each metal material in the members that are in contact with each other is set to 300 mV or less. Specifically, as will be described later, the difference in the natural potential of each metal material in the fastening bolt 16 and the first terminal 12, the first terminal 12 and the intermediate terminal 18, the intermediate terminal 18 and the tin plating provided on the second terminal 14, the tin plating and the second terminal 14, and the second terminal 14 and the fastening bolt 16 that are in contact with each other is set to 300 mV or less.

[0017] <First Terminal 12> As shown in Figure 6 and other figures, the first terminal 12 is generally rectangular and flat, and is provided with a first bolt insertion hole 20 that penetrates the first terminal 12 in the thickness direction (vertical direction). In Embodiment 1, the first terminal 12 is made of aluminum alloy. Specifically, the first terminal 12 has a portion in the front part where the width dimension (left-right dimension) decreases towards the tip side (front end side), and the front end portion of the first terminal 12 is offset to one side in the width direction (to the right in Embodiment 1) relative to the rear part. The first bolt insertion hole 20 is formed in the portion of the front end portion of the first terminal 12 that is offset to the right. A synthetic resin insulating coating 22 is fixed to the rear part of the first terminal 12. In other words, the first terminal 12 can be understood as a single-core wire made of aluminum alloy, and the first bolt insertion hole 20 is formed in the portion of the front end portion of this wire where the insulating coating 22 has been removed. Furthermore, the first terminal 12, having the structure described above, is held by a first terminal holding portion (not shown). In the terminal connection structure according to this disclosure, the structure of the first terminal holding portion is not limited.

[0018] <Second Terminal 14> As shown in Figures 3 and 4, the second terminal 14 has a substantially cylindrical shape that extends vertically as a whole, and a second bolt insertion hole 24 is formed in the central part of the second terminal 14 that penetrates vertically and communicates with the relay through hole 78 described later. In Embodiment 1, the second terminal 14 is made of pure copper. Specifically, the second terminal 14 has substantially constant outer and inner diameter dimensions along its substantially entire length in the vertical direction, but at the upper end portion, a large-diameter portion 26 is formed in which the outer and inner diameter dimensions are larger than those of other parts. As shown in Figure 4, through holes 27 are formed on both the front-rear and rear-facing sides of the large-diameter portion 26 in the front-rear direction in the upper-rear intermediate portion of the large-diameter portion 26.

[0019] The upper end surface of the large-diameter portion 26 is an annular surface 28, and as will be described later, the annular surface 28 is exposed to the outside in the radial direction between the inner cylinder portion 36 of the second terminal holding portion 32 and the finger-preventing rib 40. As a result, when the fastening bolt 16 is fastened, the annular surface 92 at the lower end of the intermediate terminal 18 and the annular surface 28 at the upper end of the second terminal 14 come into contact, and the intermediate terminal 18 and the second terminal 14 are electrically connected. In particular, in Embodiment 1, the annular surface 28 of the second terminal 14, or the surface including the annular surface 28, is tin-plated as a surface treatment, so that the annular surface 92 of the intermediate terminal 18 and the annular surface 28 of the second terminal 14 come into contact via the tin plating and are electrically connected. In addition, in the second bolt insertion hole 24, a female thread 30 is formed on the inner circumferential surface below the large-diameter portion 26, which serves as a threaded portion into which the male thread 46 of the fastening bolt 16 is screwed.

[0020] <Second Terminal Holding Part 32> The second terminal 14 is held by a second terminal holding part 32 made of synthetic resin. The second terminal holding part 32 has a base plate portion 34 that extends horizontally (in a direction perpendicular to the vertical direction), and the second terminal 14 protrudes from the base plate portion 34 on both sides in the vertical direction. A substantially cylindrical inner cylinder portion 36 is integrally formed on this base plate portion 34, covering the outer peripheral surface of the second terminal 14 over substantially its entire length in the vertical direction. That is, the inner cylinder portion 36 protrudes from the base plate portion 34 on both sides in the vertical direction, and the inner peripheral surface of the inner cylinder portion 36 is fixed to the outer peripheral surface of the second terminal 14.

[0021] Furthermore, an outer cylinder portion 38 is integrally formed on the outer circumference of the inner cylinder portion 36, projecting upward from the base plate portion 34. These inner cylinder portion 36 and outer cylinder portion 38 are arranged concentrically, separated from each other in the radial direction. That is, the annular space between the inner cylinder portion 36 and outer cylinder portion 38 in the radial direction opens upward. In this annular space, for example, when fastening the fastening bolt 16, a cylindrical portion projecting downward from the first terminal holding portion is inserted, so that the first terminal holding portion and the second terminal holding portion 32 are positioned relative to each other in the radial direction.

[0022] <Finger-proof rib 40> The second terminal holding portion 32 is equipped with a finger-proof rib 40 that covers the inner circumferential surface of the second bolt insertion hole 24 in the second terminal 14 and protrudes toward the first terminal 12 side (upwards). Specifically, the finger-proof rib 40 is substantially cylindrical in shape as a whole and is provided protruding upward from the boundary portion (a tapered surface that gradually slopes toward the outer circumference upwards) between the large diameter portion 26 and the portion below it on the inner circumferential surface of the second terminal 14 (the inner circumferential surface of the second bolt insertion hole 24). As a result, the finger-proof rib 40 covers the inner circumferential surface of the second bolt insertion hole 24, in particular the inner circumferential surface of the large diameter portion 26. The female thread 30, which is the threaded portion described above, is formed on the inner circumferential surface of the second bolt insertion hole 24 in the portion below the finger-proof rib 40. In Embodiment 1, the resin material constituting the second terminal holding portion 32 is also filled into each through hole 27 provided in the large-diameter portion 26 of the second terminal 14. Therefore, the inner cylindrical portion 36 that covers the second terminal 14 from the outer circumference and the finger-preventing rib 40 that covers the second terminal 14 (especially the large-diameter portion 26) from the inner circumference are connected and integrally formed by the resin filled into each through hole 27.

[0023] These inner cylinder portion 36 and finger-prevention rib 40 protrude upward by a predetermined distance from the annular surface 28, which is the upper end surface of the second terminal 14. In short, an annular space is formed radially between the inner cylinder portion 36 and the finger-prevention rib 40, opening upward, and the annular surface 28 of the second terminal 14 is exposed to the outside through this annular space. The inner cylinder portion 36 and the finger-prevention rib 40 have a predetermined radial distance from each other, and the annular space between them has a predetermined depth dimension (vertical dimension). By providing such a finger-prevention rib 40, for example, when fastening the fastening bolt 16, it is prevented that the worker's fingers will unintentionally enter the inner cylinder portion 36 and come into contact with the annular surface 28 of the second terminal 14.

[0024] Therefore, the second terminal holding portion 32 is configured as a triple-cylinder structure, with an inner cylinder portion 36, an outer cylinder portion 38, and a finger-touch prevention rib 40, all of which are substantially cylindrical, arranged concentrically inside and outside in the radial direction. This second terminal holding portion 32 is formed as an integrally molded product with the second terminal 14 by molding it with the second terminal 14 set in the molding cavity of the second terminal holding portion 32. Multiple collars 42 are provided in a substantially embedded state on the outer circumference of the second terminal holding portion 32, and the second terminal holding portion 32 that holds the second terminal 14 is fixed to a motor-side member (not shown) by bolts (not shown) inserted through each collar 42.

[0025] <Fastening Bolt 16> The fastening bolt 16 of Embodiment 1 is composed of multiple members, as shown in Figures 6 and 7, and includes a bolt body 48 in which a male thread 46 is formed on the outer circumferential surface of the tip portion (lower end portion) 44. An insertion hole 52 is formed on the lower end surface of the tip portion 44 of the bolt body 48, opening downwards, into which a synthetic resin tip cap 50 is inserted. The tip cap 50 is a substantially cylindrical member integrally equipped with an insertion portion 54 that is inserted into the insertion hole 52. In Embodiment 1, the tip cap 50 is attached to the bolt body 48 by press-fitting the insertion portion 54 into the insertion hole 52. The tip cap 50 may be bonded or welded to the bolt body 48 as needed.

[0026] In Embodiment 1, the outer diameter of the tip cap 50 is slightly smaller than the outer diameter of the tip portion 44 of the bolt body 48, so that the tip cap 50 does not cover the outer circumferential surface of the tip portion 44. By providing the tip cap 50 on the tip portion 44 of the fastening bolt 16 (bolt body 48) in this way, the tip portion 44 can be stably guided into the second bolt insertion hole 24 when fastening the fastening bolt 16, as described later, and the male thread 46 can be prevented from being damaged by contact with other members (for example, the relay terminal 18). In addition, by covering the tip surface (lower end surface) of the tip portion 44 with the tip cap 50, it is possible to prevent electric shock by an unintentional contact between the worker and the lower end surface of the tip portion 44.

[0027] Furthermore, the upper portion of the head 56 of the bolt body 48 is covered by an insulating cap 58. As shown in Figures 3 and 4, the head 56 of the bolt body 48 is provided with an upwardly projecting portion 60, which is embedded in the operating portion 62 of the insulating cap 58. When fastening the fastening bolt 16, the operator can avoid electric shock to the worker through the tool by gripping the operating portion 62 with a tool or the like while performing the fastening work. In Embodiment 1, the insulating cap 58 is formed as an integrally molded product comprising the bolt body 48, and the outer circumferential surface of the upwardly projecting portion 60 is fixed to the operating portion 62 of the insulating cap 58.

[0028] In particular, in Embodiment 1, the outer diameter of the upper projection 60 differs in the vertical direction, with the intermediate portion in the vertical direction having a smaller diameter than the other portions. Furthermore, the operating portion 62 of the insulating cap 58 is provided with a part that protrudes inward and fits into the smaller diameter portion of the upper projection 60, thereby preventing the insulating cap 58 from falling off the bolt body 48, for example, when fastening or unfastening the fastening bolt 16. In addition, the upper projection 60 is provided with a plurality of outer peripheral projection ribs 61 that protrude outward at predetermined intervals in the circumferential direction. Furthermore, the part that protrudes inward from the operating portion 62 fits into the circumferential space between each of these outer peripheral projection ribs 61, thereby preventing the operating portion 62 (insulating cap 58) from rotating only in the circumferential direction relative to the upper projection 60 (bolt body 48) when fastening the fastening bolt 16.

[0029] Furthermore, a cylindrical portion 64, which is generally cylindrical in shape, is integrally formed on the outer circumference of the operating portion 62 of the insulating cap 58. Multiple positioning protrusions 66 and locking protrusions 68 are provided on the outer circumference of the cylindrical portion 64. These positioning protrusions 66 and locking protrusions 68 allow the insulating cap 58 and the retainer 72 to be positioned in the circumferential direction and then fixed together when the retainer 72 is assembled to the insulating cap 58, as will be described later.

[0030] An annular sealing member 70 and a retainer 72 that prevents the sealing member 70 from falling off the cylindrical portion 64 are externally fitted to the cylindrical portion 64 of the insulating cap 58. When the fastening bolt 16 is tightened, the sealing member 70 is compressed radially between the first terminal holding portion that holds the first terminal 12 and the outer circumferential surface of the cylindrical portion 64, thereby creating a liquid-tight seal between the first terminal holding portion and the fastening bolt 16. The sealing member 70 is externally fitted to the cylindrical portion 64 from below, and the annular retainer 72 is further externally fitted to the cylindrical portion 64 below the sealing member 70. On the inner circumferential surface of the retainer 72, positioning recesses 74 and lock recesses 76 are provided at positions corresponding in the circumferential direction to the positioning protrusions 66 and lock protrusions 68 on the cylindrical portion 64, respectively. As a result, when assembling the retainer 72 to the cylindrical portion 64, the cylindrical portion 64 and the retainer 72 are positioned relative to each other in the circumferential direction by the positioning protrusions 66 and positioning recesses 74, and the retainer 72 is fixed to the cylindrical portion 64 by the locking protrusions 68 engaging with the locking recesses 76.

[0031] In this bolt body 48, which has an insulating cap 58 integrally provided, the sealing member 70 and retainer 72 are assembled to the insulating cap 58, and the tip cap 50 is assembled to the bolt body 48, thereby forming the fastening bolt 16 of Embodiment 1. In this fastening bolt 16, the bolt body 48 is made of carbon steel, which is an alloy of iron and carbon.

[0032] <Intermediate Terminal 18> As shown in Figure 7 and other figures, the intermediate terminal 18 has a roughly stepped cylindrical shape that extends vertically as a whole, and an intermediate through-hole 78 is formed in the central part of the intermediate terminal 18 that penetrates vertically and communicates with the first bolt insertion hole 20 mentioned above. In Embodiment 1, the intermediate terminal 18 is made of an aluminum and copper alloy (aluminum bronze). The upper part of this intermediate terminal 18 has a smaller diameter than the lower part, and a stepped plate portion 80 in the shape of a roughly annular plate is provided between the lower part and the upper part.

[0033] In short, the intermediate portion of the relay terminal 18 is provided with a stepped plate portion 80 that extends horizontally, and cylindrical portions protrude from both the vertical and horizontal sides of the stepped plate portion 80. The cylindrical portion that protrudes upward from the stepped plate portion 80 is the mounting cylinder portion 82 that is assembled to the inner circumferential surface of the first bolt insertion hole 20 in the first terminal 12, and the cylindrical portion that protrudes downward from the stepped plate portion 80 toward the second terminal 14 is the cylindrical projection portion 84. In Embodiment 1, the stepped plate portion 80 protrudes further outward than both the mounting cylinder portion 82 and the cylindrical projection portion 84. The inner holes of the mounting cylinder portion 82, the stepped plate portion 80, and the cylindrical projection portion 84 are all connected to form the relay through hole 78.

[0034] Furthermore, the inner circumference end of the stepped plate portion 80, which has a roughly annular plate shape, is provided with an annular inner circumference projection 86 that protrudes inward from the mounting cylinder portion 82 that protrudes upward from the stepped plate portion 80. When the fastening bolt 16 is fastened, the inner circumference projection 86 is positioned to contact or face with a small gap the outer circumference surface of a relatively small diameter portion in the middle of the vertical direction of the bolt body 48 of the fastening bolt 16 when the fastening bolt 16 is inserted through the intermediate through hole 78 of the intermediate terminal 18. This prevents the fastening bolt 16 from tilting relative to the intermediate terminal 18 after it has been fastened, and also prevents the fastening bolt 16 from unintentionally coming out of the intermediate terminal 18 by contacting the male thread 46 at the tip 44 of the bolt body 48.

[0035] <Mounting cylinder portion 82> As described above, the mounting cylinder portion 82 is generally cylindrical in shape and is formed protruding upward from the inner circumferential end of the stepped plate portion 80, which is generally annular in shape. In Embodiment 1, press-fit ribs 88 are provided on the outer circumferential surface of the mounting cylinder portion 82, which are press-fitted into the inner circumferential surface of the first bolt insertion hole 20. In particular, in Embodiment 1, a plurality of press-fit ribs 88 are provided, and these plurality of press-fit ribs 88 are spaced apart from each other in the circumferential direction. Specifically, the virtual outer diameter of the portion of the mounting cylinder portion 82 where no press-fit ribs 88 are provided is equal to or slightly smaller than the inner diameter of the first bolt insertion hole 20, and the virtual outer diameter of the portion of the mounting cylinder portion 82 where each press-fit rib 88 is provided is slightly larger than the inner diameter of the first bolt insertion hole 20. As shown in Figure 5, each press-fit rib 88 has a generally trapezoidal cross-section, but the embodiment is not limited to this, and it may have a triangular or semicircular cross-section.

[0036] In Embodiment 1, the first terminal 12 is made of an aluminum alloy, and in the air, an oxide film may form on the surface of the first terminal 12, including the inner circumferential surface of the first bolt insertion hole 20. In such cases, each press-fit rib 88 is press-fitted into the inner circumferential surface of the first bolt insertion hole 20, thereby peeling off and breaking the oxide film formed on the inner circumferential surface of the first bolt insertion hole 20 and making contact with the first terminal 12, thereby electrically connecting the first terminal 12 and the mounting cylinder portion 82 (relay terminal 18).

[0037] <Cylindrical projection 84> As described above, the cylindrical projection 84 is generally cylindrical in shape and is formed to protrude downward from the stepped plate portion 80, which is roughly annular in shape. In Embodiment 1, the cylindrical projection 84 has a larger diameter than the mounting cylinder portion 82, and the cylindrical projection 84 protrudes downward from the radially intermediate portion of the stepped plate portion 80. The inner circumferential surface of the cylindrical projection 84 partitions a part of the relay through hole 78. In addition, the inner circumferential surface of the cylindrical projection 84, which has a larger diameter than the mounting cylinder portion 82, is spaced outward from the outer circumferential surface of the bolt body 48 when the fastening bolt 16 is inserted through the relay terminal 18. The radial gap between these cylindrical projections 84 and the bolt body 48 constitutes an annular housing space 90.

[0038] In particular, in Embodiment 1, the outer diameter of the cylindrical projection 84 is equal to or slightly smaller than the inner diameter of the inner cylinder portion 36 in the second terminal holding portion 32, while the inner diameter of the cylindrical projection 84 is equal to or slightly larger than the outer diameter of the finger-touch prevention rib 40 in the second terminal holding portion 32. As a result, when fastening with the fastening bolt 16, the cylindrical projection 84 that protrudes downward from the intermediate terminal 18 can be inserted into the annular space radially between the inner cylinder portion 36 and the finger-touch prevention rib 40 in the second terminal holding portion 32. In other words, the finger-touch prevention rib 40 is housed in the accommodation space 90 formed radially between the cylindrical projection 84 and the bolt body 48, so that the first terminal 12 and the second terminal 14 can clamp the intermediate terminal 18 and fasten with the fastening bolt 16. Furthermore, the downward projection dimension of the cylindrical projection 84 is equal to or slightly larger than the depth dimension (vertical dimension) of the annular space provided radially between the inner cylinder 36 and the finger-prevention rib 40.

[0039] In other words, in Embodiment 1, the mounting cylinder portion 82 of the relay terminal 18 is press-fitted into the first bolt insertion hole 20, so that the first terminal 12 and the relay terminal 18 are assembled together, and the first bolt insertion hole 20 and the relay through hole 78 are in communication with each other. Then, the cylindrical projection 84 of the relay terminal 18 is inserted into the annular space radially between the inner cylinder portion 36 of the second terminal holding portion 32 and the finger-touch prevention rib 40, so that the relay through hole 78 and the second bolt insertion hole 24 are in communication with each other. The fastening bolts 16 are sequentially inserted into the first bolt insertion hole 20, the relay through hole 78 and the second bolt insertion hole 24, which are in communication with each other. At that time, the head 56 of the fastening bolt 16 abuts against the portion surrounding the first bolt insertion hole 20 in the first terminal 12, and the male thread 46 at the tip 44 of the fastening bolt 16 is screwed into the female thread 30 which is the threaded portion of the second terminal 14.

[0040] As a result, the axial force of the fastening bolt 16 causes the portion of the first bolt insertion hole 20 in the first terminal 12 to rest on and be in close contact with the stepped plate portion 80 of the intermediate terminal 18, and the annular surface 92 at the lower end of the cylindrical projection 84 of the intermediate terminal 18 and the annular surface 28 at the upper end of the second terminal 14 to be in close contact with each other. This electrically connects the first terminal 12 and the second terminal 14, creating electrical conductivity between the battery on the first terminal 12 side and the load (e.g., a motor) on the second terminal 14 side.

[0041] In the terminal connection structure 10 of Embodiment 1, which has the structure described above, the material of the fastening bolt 16 (particularly the bolt body 48) is carbon steel, and the material of the first terminal 12 is an aluminum alloy. In addition, the material of the intermediate terminal 18 is an aluminum-copper alloy, and the material of the second terminal 14 is pure copper. Furthermore, the second terminal 14 is tin-plated, and the intermediate terminal 18 and the second terminal 14 come into contact with each other via this tin plating. As a result, the difference in natural potential between the metal materials that are fixed and in contact with each other by the fastening bolt 16, such as the fastening bolt 16 (bolt body 48) and the first terminal 12, the first terminal 12 and the intermediate terminal 18, the intermediate terminal 18 and the tin plating, the tin plating and the second terminal 14, and the second terminal 14 and the fastening bolt 16 (bolt body 48), is all 300 mV or less. As a result, corrosion that occurs due to a relatively large potential difference is prevented between each component constituting the terminal connection structure 10, even without providing corrosion inhibitors to each component. Therefore, the manufacturing process for each component can be made more complicated, and the conductivity of the terminal connection structure 10 can be maintained over a long period of time.

[0042] A head 56 of a fastening bolt 16 (bolt body 48) inserted sequentially through the first bolt insertion hole 20, the relay through hole 78, and the second bolt insertion hole 24 abuts against the first terminal 12, and a tip end portion 44 (male screw 46) of the fastening bolt 16 (bolt body 48) is screwed into a screw portion (female screw 30) of the second terminal 14, whereby the first terminal 12 and the relay terminal 18, as well as the relay terminal 18 and the second terminal 14, are brought into close contact with each other by the axial force of the fastening bolt 16. Accordingly, the first terminal 12 and the relay terminal 18, as well as the relay terminal 18 and the second terminal 14, can be brought into contact more reliably, and the conduction performance between the first terminal 12 and the second terminal 14 is improved.

[0043] A plurality of press-fitting ribs that are press-fitted into the inner peripheral surface of the first bolt insertion hole 20 are provided on the outer peripheral surface of the mounting cylinder portion 82 of the relay terminal 18. Accordingly, the relay terminal 18 can be easily assembled to the first terminal 12, and electrical connection between the first terminal 12 and the relay terminal 18 can also be realized more reliably. In particular, when the first terminal 12 is formed of an aluminum alloy as in the first embodiment, an oxide film may also form on the inner peripheral surface of the first bolt insertion hole 20. By providing each press-fitting rib 88 on the outer peripheral surface of the mounting cylinder portion 82, each press-fitting rib 88 can break through the oxide film and stably abut against the inner peripheral surface of the first bolt insertion hole 20.

[0044] An accommodation space 90 is formed between the cylindrical protrusion 84 and the fastening bolt 16 in the radial direction in the relay terminal 18, and the second terminal holding portion 32 includes a finger contact prevention rib 40. The finger contact prevention rib 40 is accommodated in the accommodation space 90, so that the first terminal 12, the second terminal 14, and the relay terminal 18 can be bolt-fastened by the fastening bolt 16. Providing the finger contact prevention rib 40 in this manner prevents an operator from unintentionally contacting the second terminal 14 and getting an electric shock. Even when the second terminal 14 is exposed in an annular shape between the finger contact prevention rib 40 and the inner cylinder portion 36, adopting a configuration in which the cylindrical protrusion 84 of the relay terminal 18 fits between the finger contact prevention rib 40 and the inner cylinder portion 36 allows stable electrical connection between the second terminal 14 and the relay terminal 18 to be realized.

[0045] <Modifications> Although Embodiment 1 has been described in detail above as a specific example of the present disclosure, the present disclosure is not limited by this specific description. Modifications, improvements, etc., to the extent that they can achieve the purpose of the present disclosure are included in the present disclosure. For example, the following modifications of the embodiments are also included in the technical scope of the present disclosure.

[0046] (1) In the above embodiment, the material of the first terminal 12 was an aluminum alloy, the material of the second terminal 14 was pure copper, the material of the fastening bolt 16 (bolt body 48) was carbon steel, and the material of the intermediate terminal 18 was an aluminum-copper alloy (aluminum bronze), but the embodiment is not limited to this. That is, in a plurality of members fixed by fastening fastening bolts, the difference in the natural potential of each metal material in the members that come into contact with each other (including the fastening bolts) is 300 mV or less, and for example, the materials of the first terminal, second terminal, fastening bolt (bolt body) and intermediate terminal are not limited to those described above. The above-mentioned "members that come into contact with each other in a plurality of members fixed by fastening fastening bolts" may include a plating layer such as the tin plating provided on the annular surface 28 of the second terminal 14 in the above embodiment. Also, even when a plating layer is provided on the annular surface of the second terminal, the material is not limited to tin.

[0047] Furthermore, separate components may be placed between the head of the fastening bolt (bolt body) and the first terminal, or between the intermediate terminal and the second terminal. In this case, the difference in the natural potential of each metal material in the components that come into contact with each other, including this separate component, should be 300 mV or less. Therefore, for example, the difference in natural potential between the fastening bolt and the first terminal may be greater than 300 mV, and the difference in natural potential between the intermediate terminal and the second terminal may also be greater than 300 mV. In this case, the natural potential of the separate component may be set to an intermediate value between the fastening bolt and the first terminal, or between the intermediate terminal and the second terminal.

[0048] (2) The shape of the second terminal holding portion that holds the second terminal is not limited to the aspect described in the above embodiment. For example, in the second terminal holding portion, a plurality of second terminals may be held in parallel, and in such a case, it is only required that the first terminal is bolted to at least one second terminal by the inter-terminal connection structure according to the present disclosure. Further, in the inter-terminal connection structure according to the present disclosure, the second terminal holding portion may not be provided with a finger contact prevention rib.

[0049] (3) The shape of the fastening bolt employed in the inter-terminal connection structure according to the present disclosure is not limited to the aspect described in the above embodiment. For example, the tip cap provided at the tip portion of the bolt body may have a shape that covers the outer peripheral surface of the tip portion of the bolt body. Note that, in the fastening bolt, the insulating cap fixed to the head of the bolt body and the tip cap fixed to the tip portion of the bolt body may not be provided.

[0050] 10 Inter-terminal connection structure 12 First terminal 14 Second terminal 16 Fastening bolt 18 Relay terminal 20 First bolt insertion hole 22 Insulating coating 24 Second bolt insertion hole 26 Large diameter portion 27 Through hole 28 Annular surface (at the upper end of the second terminal) 30 Internal thread (thread portion) 32 Second terminal holding portion 34 Base plate portion 36 Inner cylindrical portion 38 Outer cylindrical portion 40 Finger contact prevention rib 42 Collar 44 Tip portion 46 External thread 48 Bolt body 50 Tip cap 52 Insertion hole 54 Insertion portion 56 Head 58 Insulating cap 60 Upper protruding portion 61 Outer peripheral protruding rib 62 Operation portion 64 Cylindrical portion 66 Positioning convex portion 68 Locking convex portion 70 Seal member 72 Retainer 74 Positioning concave portion 76 Locking concave portion 78 Relay through hole 80 Step plate portion 82 Mounting cylindrical portion 84 Cylindrical protruding portion 86 Inner peripheral side protruding portion 88 Press-fit rib 90 Accommodating space 92 Annular surface (at the lower end of the relay terminal)

Claims

1. A terminal-to-terminal connection structure comprising: a first terminal; a second terminal connected to the first terminal; an intermediate terminal providing an electrical connection between the first and second terminals; and a fastening bolt that bolts the first and second terminals together with the intermediate terminal sandwiched between them, wherein, in a plurality of members fixed by the fastening bolt, the difference in the natural potential of the metal materials in the members that are in contact with each other is 300 mV or less in all cases.

2. The terminal connection structure according to claim 1, comprising: a first bolt insertion hole passing through the first terminal; an intermediate through hole passing through the intermediate terminal and communicating with the first bolt insertion hole; and a second bolt insertion hole passing through the second terminal and communicating with the intermediate through hole, wherein the head of the fastening bolt inserted by sequentially passing through the first bolt insertion hole, the intermediate through hole, and the second bolt insertion hole abuts against the first terminal and the tip of the fastening bolt is screwed into the threaded portion of the second terminal, so that the first terminal, the intermediate terminal, and the second terminal are in close contact with each other by the axial force of the fastening bolt.

3. The terminal-to-terminal connection structure according to claim 2, wherein the relay terminal has a mounting cylinder portion that is assembled to the inner circumferential surface of the first bolt insertion hole of the first terminal, and the outer circumferential surface of the mounting cylinder portion has a plurality of press-fit ribs that are press-fitted into the inner circumferential surface of the first bolt insertion hole.

4. The terminal connection structure according to claim 2 or 3, wherein the relay terminal has a cylindrical projection that protrudes toward the second terminal, a portion of the relay through-hole is partitioned by the inner circumferential surface of the cylindrical projection, a housing space is formed by the radial gap between the fastening bolt inserted through the relay through-hole and the inner circumferential surface, the second terminal is held by the second terminal holding portion, the second terminal holding portion has a finger-prevention rib that covers the inner circumferential surface of the second bolt insertion hole of the second terminal and protrudes toward the first terminal, and the finger-prevention rib is housed in the housing space of the relay terminal, so that the first terminal, the second terminal and the relay terminal can be bolted together with the fastening bolt.

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