Bushing for lead-acid battery and lead-acid battery

Abstract

This bushing (40A) for a lead storage battery includes: a cylindrical bushing body part (41) that can be fitted in a pole column (45); and a columnar terminal part (50) that is situated at a location offset from the bushing body part (41) in a plan view, wherein the terminal part (50) includes a pedestal portion (52) integrally connected to the bushing body part (41) via a connection portion, and a connection portion (51) which is located on the pedestal portion (52) and to which an external terminal is connected, and the pedestal portion (52) has a concave cavity portion (53) on the bottom surface of the pedestal portion (52).

Description

Technical Field

[0001] The present invention relates to a bushing used in a lead-acid battery.

Background Art

[0002] As a structure of a bushing for a lead-acid battery, a structure in which an external terminal is coaxially attached to a bushing through which a terminal post penetrates is known (Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When offsetting the terminal portion with respect to the bushing main body portion, it is conceivable as an idea to integrally connect the bushing main body portion and the terminal portion with a connecting portion. If the stress remaining inside the bushing is large, the strength of the bushing decreases, and the bushing is likely to break when an external force is applied to the bushing.

[0005] The present invention has been completed based on the above circumstances, and discloses a technique for reducing the stress remaining in a bushing for a lead-acid battery and increasing the strength of the bushing.

Means for Solving the Problems

[0006] A bushing for a lead-acid battery includes a cylindrical bushing main body portion that can be fitted with a terminal post, and a columnar terminal portion that is offset from the bushing main body portion in a plan view. The terminal portion includes a pedestal portion integrally connected to the bushing main body portion via a connecting portion, and a connection portion located on the pedestal portion to which an external terminal is connected. The pedestal portion has a concave cavity portion on the bottom surface of the pedestal portion.

[0007] This invention can be applied to lead-acid batteries.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0009] <Overview of the Bushing for Lead-Acid Batteries> The bushing for lead-acid batteries disclosed in this specification includes a cylindrical bushing main body that can be fitted with a terminal post, and a columnar terminal portion located at a position offset from the bushing main body portion in a plan view. The terminal portion includes a pedestal portion integrally connected to the bushing main body portion via a connecting portion, and a connecting portion located on the pedestal portion to which an external terminal is connected. The pedestal portion has a concave cavity on the bottom surface of the pedestal portion.

[0010] Since the bushing is embedded in the middle cover except for a part as described later, it is fixed to the middle cover. When an external force is applied to the connection part, stress concentrates on the pedestal part of the terminal part, and there is a concern that the bushing may break. When a concave cavity is provided on the bottom surface of the pedestal part, the residual stress of the pedestal part is relaxed compared to the case where there is no cavity, and the strength of the pedestal part can be increased. By increasing the strength of the pedestal part, it is possible to suppress the breakage of the bushing when an external force is applied to the terminal part. By providing the cavity, the amount of material used can be reduced, and the cost reduction and weight reduction of the bushing can be achieved.

[0011] The ceiling surface of the cavity may be located below the connection part. Since the cavity does not overlap the connection part in the vertical direction, the strength of the connection part can be increased compared to the case where the cavity overlaps the connection part. Thereby, the deformation of the connection part when an external force is applied can be suppressed.

[0012] On the current path from the terminal part via the connecting part to the bushing main body part, when comparing the cross-sectional areas of the current path, the cross-sectional area of the connecting part may be made smaller than the cross-sectional areas of other parts.

[0013] By fusing the connecting part, overcurrent can be interrupted to protect the lead-acid battery. Since the connecting part is located outside the lead-acid battery, it is possible to prevent fragments associated with fusing from entering the inside of the lead-acid battery. In addition, the presence or absence of fusing can be easily visually confirmed from the outside of the lead-acid battery.

[0014] The terminal part (the connection part and the pedestal part) may be a stepped cylindrical shape, and the diameter of the pedestal part may be larger than the diameter of the connection part. By making the diameter of the pedestal part larger than the diameter of the connection part, the strength of the pedestal part can be increased, and the breakage of the bushing can be suppressed. If the diameter of the pedestal part is large, the volume of the space of the cavity can be increased, so that the residual stress can be reduced. Furthermore, by increasing the volume of the space of the cavity, the amount of material used can be further reduced, and further cost reduction and weight reduction of the bushing can be achieved.

[0015] The lead storage battery may include the bushing for the lead storage battery. Further, the hollow portion of the pedestal portion of the lead storage battery may be fitted with the boss portion of the lid member of the lead storage battery.

[0016] <Embodiment> One embodiment of the present invention will be described with reference to FIGS. 1 to 8.

[0017] 1. Structure of Lead Storage Battery 10 As shown in FIGS. 1 to 3, the lead storage battery 10 includes an electrolytic cell 20, a plate group 30 as a power generation element, an electrolytic solution U, and a lid member 70. In the following description, the lateral width direction (the arrangement direction of the bushings 40A and 40B) of the electrolytic cell 20 is defined as the X direction, the height direction of the electrolytic cell 20 is defined as the Y direction (vertical direction), and the depth direction is defined as the Z direction. The XZ plane is a horizontal plane.

[0018] The electrolytic cell 20 is made of synthetic resin, has four outer walls 21 and a bottom wall 22, and is in a box shape with an open top surface. The inside of the electrolytic cell 20 is partitioned into a plurality of cell chambers 25 by a partition wall 23 as shown in FIG. 2. A plurality of cell chambers 25 are provided in six rows in the lateral width direction (X direction in FIG. 2) of the electrolytic cell 20, and a plate group 30 is accommodated in each cell chamber 25 together with the electrolytic solution U.

[0019] As shown in FIG. 3, the plate group 30 includes a positive electrode plate 30A, a negative electrode plate 30B, and a separator 30C that separates both electrode plates 30A and 30B. Each of the electrode plates 30A and 30B has a grid body filled with an active material, and ear portions 31A and 31B are provided at the upper portions of the respective electrode plates 30A and 30B. The ear portions 31A and 31B are provided for connecting the electrode plates 30A and 30B of the same polarity in the cell chamber 25 via a strap 32.

[0020] The strap 32 is, for example, a plate shape long in the X direction, and a positive electrode use and a negative electrode use are provided for each cell chamber 25. By electrically connecting the positive and negative straps 32 of adjacent cell chambers 25 via a strap connection portion 33 formed on the strap 32, the plate groups 30 of each cell chamber 25 are connected in series.

[0021] The lid member 70 includes an intermediate lid 60 and an upper lid 100. The intermediate lid 60 is made of synthetic resin and has a size capable of sealing the upper surface of the battery case 20. On the back surface of the intermediate lid 60, a lid partition (not shown) corresponding to the partition wall 23 is formed. The intermediate lid 60 is attached so as to overlap the battery case 20, seals the upper surface of the battery case 20, and has a structure that makes each cell chamber 25 in the battery case 20 airtight and watertight. The upper lid 100 is also made of synthetic resin like the intermediate lid 60 and is attached so as to overlap the upper surface of the intermediate lid 60. The upper surface 100A of the upper lid 100 is located below the upper end of the bushing 40A as shown in FIG. 3.

[0022] The intermediate lid 60 is heat-welded to the battery case 20. The upper lid 100 is heat-welded to the intermediate lid 60.

[0023] 2. Regarding the bushings 40A and 40B for lead-acid batteries The lead-acid battery 10 has two bushings 40A and 40B. The bushing 40A is for the negative electrode, and the bushing 40B is for the positive electrode. Since the structures of the two bushings 40A and 40B are the same, the structure will be described below taking the negative electrode side bushing 40A as an example.

[0024] Also, in the following description, the shapes of the bushing main body 41, the terminal part 50, etc. are described as cylindrical or columnar, but the outer peripheral surface is tapered for the purpose of improving formability.

[0025] As shown in FIGS. 4 and 5, the negative electrode side bushing 40A includes a bushing main body 41, a connecting part 55, and a terminal part 50.

[0026] The bushing main body 41 is cylindrical with the vertical direction as the axis and has an annular groove on the outer periphery. The bushing main body 41 has an axial hole 42 that penetrates the center part vertically. Inside the axial hole 42, a columnar pole 45 is located. The pole 45 is made of a metal such as lead alloy.

[0027] The terminal post 45 is inserted into the shaft hole 42 of the bushing main body 41 from below, and there is no step between the upper end portion 46 of the terminal post 45 and the upper end portion 43 of the bushing main body 41, and they are in a substantially flat state. The terminal post 45 and the bushing main body 41 are welded, and the molten lead alloy flows into the space between the bushing main body 41 and the terminal post 45, and the two are joined without a gap. The terminal post 45 is longer than the bushing main body 41, and the lower part of the terminal post 45 protrudes downward from the lower surface 41A of the bushing main body 41. The base end portion 47 of the terminal post 45 is joined to the strap 32 of the electrode plate group 30.

[0028] The terminal portion 50 has a two-stage cylindrical shape with different diameters. The lower stage is the pedestal portion 52, and the upper stage is the connection portion 51. An external terminal (not shown) provided at the end of the wire harness is assembled to the connection portion 51, so that electric power can be supplied from the lead storage battery 10 to the load via the wire harness.

[0029] The pedestal portion 52 has a larger diameter than the connection portion 51 and has a circular bottom surface 52A. The pedestal portion 52 has a cavity portion 53 in the bottom surface 52A. The cavity portion 53 is located at the center portion (axial center portion) of the bottom surface 52A and is a concave space extending upward from the bottom surface 52A. The cross-sectional shape of the cavity portion 53 is circular. The inner diameter of the cavity portion 53 decreases from bottom to top. The cavity portion 53 is tapered in the same manner as the connection portion 51 and the like. The ceiling surface 53A of the cavity portion 53 is located below the lower end 51A of the connection portion 51, and the cavity portion 53 does not overlap the connection portion 51 in the vertical direction.

[0030] As shown in FIGS. 4 and 5, in a plan view (when viewed from the B direction in FIGS. 4 and 5), the terminal portion 50 is offset in the Z direction (right direction in FIG. 5) from the bushing main body 41. The B direction is a direction parallel to the protruding direction of the terminal portion 50 and is a direction parallel to the connection direction between the connection portion 51 and the pedestal portion 52. Also, in the present embodiment, the B direction corresponds to the Y direction (vertical direction).

[0031] The connecting portion 55 is oval in shape and long in the Z direction. One arc of the connecting portion 55 coincides with the center of the terminal portion 50, and the other arc coincides with the center of the bushing main body portion 41. The connecting portion 55 overlaps the entire pedestal portion 52 and the entire bushing main body portion 41 in plan view, integrally connecting the pedestal portion 52 and the bushing main body portion 41. When viewed from the horizontal direction, with the connecting portion 55 as the boundary, the terminal portion 50 protrudes upward almost entirely including the pedestal portion 52, and the bushing main body portion 41 protrudes downward.

[0032] Also, a flange 56 that protrudes horizontally is provided on the entire outer peripheral surface of the connecting portion 55. Protrusions 57 are provided on both sides in the Z direction of the lower surface of the flange 56. These protrusions 57 are provided to prevent the bushing 40A from rotating with respect to the middle cover 60.

[0033] The entire bushing 40A is made of a metal such as a lead alloy, and the bushing main body portion 41, the connecting portion 55, and the terminal portion 50 are integrated. The bushing 40A can be integrally formed by casting, for example.

[0034] As shown in FIG. 1, the middle cover 60 has attachment portions 61 on both sides in the X direction of the upper surface. The two attachment portions 61 are long oval-shaped depressions in the Z direction, and the bushings 40A and 40B are located inside. The bottom wall 63 of the attachment portion 61 has a boss portion 63A that fits into the cavity portion 53 and an enclosing portion 63B that surrounds the outer surface of the bushing main body portion 41, covering the lower outer periphery of the bushing 40A without a gap.

[0035] The middle cover 60 is integrally formed by flowing molten resin into a mold in which the bushings 40A and 40B are inserted, and the two bushings 40A and 40B are fixed to the middle cover 60. As shown in FIG. 5, among the bushings 40A, only the terminal portion 50 protrudes from the upper surface of the middle cover 60, and the other portions are located inside the attachment portion 61, making it difficult for hands to touch the portions of the bushing 40A other than the terminals.

[0036] When charging the lead storage battery 10, as shown by the arrow in FIG. 6, current flows through the terminal portion 50 (connection portion 51 and pedestal portion 52), the connection portion 55, and the bushing main body portion 41 in the bushing 40A. During discharge, current flows in the reverse path. The direction of the current in the terminal portion 50 and the bushing main body portion 41 is the Y direction, and in the connection portion 55, it is the Z direction.

[0037] When comparing the cross-sectional areas of the current paths, by making the cross-sectional area of the connection portion 55 between the terminal portion 50 and the bushing main body portion 41 smaller than the cross-sectional areas of the other parts (terminal portion 50 and bushing main body portion 41), when an overcurrent flows, the connection portion 55 can be blown and the overcurrent can be cut off.

[0038] Hereinafter, the cross-sectional areas of each part of the current path will be specifically described. As shown in FIG. 7, let the cross-sectional area of the cross-section in the direction orthogonal to the direction of the current (Y direction) in the terminal portion 50 be S1.

[0039] Among the terminal portions 50, the connection portion 51 has a cylindrical shape with the Y direction as the axis, and the cross-sectional shape is circular. Since a taper in the direction where the upper part narrows is provided on the side surface of the connection portion 51, the diameter of the circle becomes smaller as the cross-sectional position goes upward, and the cross-sectional area S1A of the connection portion 51 becomes smaller. The magnitude of the cross-sectional area S1A is determined by the diameter of the cylinder forming the connection portion 51. When changing the cross-sectional position along the Y direction, the minimum value among the values that the cross-sectional area S1A can take is defined as the minimum cross-sectional area S1Amin.

[0040] Among the terminal portions 50, the pedestal portion 52 is generally cylindrical, but a concave cavity portion 53 is provided on the bottom surface 52A. The cross-section at the position including the cavity portion 53 is the remaining part obtained by removing the concentric cavity portion 53 from the outer peripheral circle of the pedestal portion 52, and its shape is an annular shape. The cross-sectional area S1B of the pedestal portion 52 is the area of this annulus. The cross-sectional area S1B is determined by the two values of the outer diameter of the pedestal portion 52 and the outer diameter of the cavity portion 53. When changing the cross-sectional position along the Y direction, the minimum value among the values that the cross-sectional area S1B can take is defined as the minimum cross-sectional area S1Bmin.

[0041] Of the minimum cross-sectional area S1Amin. of the connection part 51 and the minimum cross-sectional area S1Bmin. of the pedestal part 52, the smaller one is defined as the minimum cross-sectional area S1min. of the terminal part 50.

[0042] Next, let the cross-sectional area of the cross-section in the direction orthogonal to the direction (Z direction) of the current in the connecting part 55 be S2. In the connecting part 55, when the position of the cross-section is changed along the Z direction between the terminal part 50 and the bushing main body part 41, the minimum value among the values that the cross-sectional area S2 can take is defined as the minimum cross-sectional area S2min.

[0043] Next, let the cross-sectional area of the cross-section in the direction orthogonal to the direction (Y direction) of the current in the bushing main body part 41 be S3.

[0044] The current flows not only through the bushing main body part 41 but also through the pole piece 45 welded to the bushing main body part 41. The cross-sectional area S3 of the bushing main body part 41 as the current path is the total cross-sectional area of the bushing main body part 41 and the pole piece 45 welded to the bushing main body part 41. When the position of the cross-section is changed along the Y direction, the minimum value among the values that the cross-sectional area S3 can take is defined as the minimum cross-sectional area S3min.

[0045] When comparing the cross-sectional areas of the current paths, by determining the cross-sectional shape of the connecting part 55 so that the minimum cross-sectional area S2min. of the connecting part 55 is smaller than the minimum cross-sectional areas S1min. and S3min. of the other parts 41 and 50, the connecting part 55 is blown when an overcurrent flows.

[0046] 3. Explanation of Effects As shown in FIG. 5, the bushing 40A is embedded in the middle cover 60 except for a part and is fixed to the middle cover 60. As shown in FIG. 8, when a horizontal external force F is applied to the connection part 51, stress is concentrated on the pedestal part 52. Due to the concentration of stress, the vicinity of the center of the bottom of the pedestal part 52 (near part A in FIG. 8) is deformed, and there is a concern about the breakage of the bushing 40A. This problem applies not only when the external force F is applied to the left outer peripheral surface of the connection part 51 from the left direction in FIG. 8, but also when the horizontal external force F is applied to the right outer peripheral surface from the right direction in FIG. 8.

[0047] To increase the strength of the terminal portion 50 and suppress the breakage of the bushing 40A, it is effective to reduce the stress (residual stress) remaining inside the pedestal portion 52. As shown in FIG. 7, by providing a concave cavity portion 53 on the bottom surface 52A of the pedestal portion 52, the residual stress of the pedestal portion 52 is relaxed compared to the case where there is no cavity portion 53 (see FIG. 8). Therefore, when a horizontal external force F is applied, the pedestal portion 52 is less likely to deform, and breakage of the bushing 40A can be suppressed. In addition, by providing the cavity portion 53, the amount of material used can be reduced, and cost reduction and weight reduction of the bushing 40A can be achieved.

[0048] The reason why the residual stress is relaxed by providing the cavity portion 53 is as follows.

[0049] When the bushing 40A is formed by casting, the molten metal (lead alloy) poured into the mold is sequentially cooled from the surface toward the inside and solidifies. Since the volume of the lead alloy decreases as the temperature drops, strain caused by the temperature difference between the surface and the inside occurs inside the pedestal portion 52 during the cooling process, and stress remains inside (residual stress). In particular, the vicinity of the center of the bottom of the pedestal portion 52 (near portion A in FIG. 8) is far from the surface, so it cools more slowly than other parts and residual stress is likely to remain.

[0050] By providing the cavity portion 53 in the pedestal portion 52, the entire pedestal portion 52 can be cooled uniformly, and the temperature difference between the surface and the inside during cooling becomes smaller. Therefore, the residual stress of the pedestal portion 52 can be reduced. Note that the manufacturing method of the bushing 40A is not limited to casting, and any other manufacturing method may be used as long as it causes residual stress in the pedestal portion 52.

[0051] When the diameter of the outer peripheral circle of the pedestal portion 52 is R1 and the diameter of the cavity portion 53 is R2, the value of R2 / R1 at which the residual stress can be reduced is in the range of 0.25 to 0.40.

[0052] When assembling an external terminal to the connection part 51, since the connection part 51 is strongly tightened from the outside, the connection part 51 is required to have a predetermined strength so as not to be deformed or damaged. In the bushing 40A according to the present embodiment, the ceiling surface 53A of the cavity 53 is located below the connection part 51.

[0053] In this configuration, the cavity 53 is not formed inside the connection part 51, and the connection part 51 and the cavity 53 do not overlap in the vertical direction. Since there is no cavity inside the connection part 51, the strength of the terminal part 50 can be ensured so as not to be deformed or damaged even when tightened from the outside by an external terminal or the like.

[0054] When an overcurrent flows through the lead storage battery 10, the connecting part 55 is blown and the overcurrent is cut off. Therefore, the lead storage battery 10 can be protected from the overcurrent. Since the connecting part 55 is located outside the lead storage battery 10, it is possible to suppress fragments associated with the fusing from entering the inside of the lead storage battery 10. Further, the presence or absence of fusing can be easily visually recognized from the outside of the lead storage battery 10.

[0055] <Other Embodiments> The present invention is not limited to the embodiments described above and by the drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, various modifications can be made and implemented without departing from the gist other than the following.

[0056] (1) In the above embodiment, the ceiling surface 53A of the cavity 53 is located below the lower end 51A of the connection part 51, but the ceiling surface 53A may be located above the lower end 51A.

[0057] (2) The bushing 40A may have any shape as long as it includes a cylindrical bushing main body part 41 into which the terminal post 45 is fitted and a terminal part 50 located at a position offset from the bushing main body part 41 in a plan view. Further, the cavity 53 may be provided on the bottom surface 52A of the pedestal part 52, and the position and shape are not limited.

[0058] (3) In the above-described embodiment, the case where the material of the bushing 40A is a lead alloy has been described. However, any electrical conductor such as a metal or alloy other than a lead alloy is included in the technical scope of the present invention.

Explanation of Reference Numerals

[0059] 40A: Bushing (an example of a bushing for a lead storage battery) 41: Bushing main body 45: Terminal post 50: Terminal portion 51: Connection portion 51A: Lower end 52: Base portion 53: Cavity portion 53A: Ceiling surface 55: Connecting portion S1, S1A, S1B, S2, S3: Cross-sectional area

Claims

1. A bushing for a lead-acid battery, comprising: a cylindrical bushing body portion that can be fitted with a terminal post; a columnar terminal portion located at a position offset from the bushing body portion in a plan view; The terminal portion includes: a pedestal portion integrally connected to the bushing body portion via a connecting portion; a connection portion located on the pedestal portion to which an external terminal is connected; The pedestal portion has a concave cavity on the bottom surface of the pedestal portion; The terminal portion is a stepped cylindrical shape; The diameter of the pedestal portion is larger than the diameter of the connection portion; A bushing for a lead-acid battery.

2. The bushing for a lead-acid battery according to Claim 1, wherein the ceiling surface of the cavity is located below the connection portion; A bushing for a lead-acid battery.

3. The bushing for a lead-acid battery according to Claim 1 or Claim 2, wherein on the current path from the terminal portion through the connecting portion to the bushing body portion, when comparing the cross-sectional areas of the current path, the cross-sectional area of the connecting portion is smaller than the cross-sectional areas of other portions; A bushing for a lead-acid battery.

4. A lead-acid battery having the bushing for a lead-acid battery according to any one of Claims 1 to 3. A lead-acid battery.

5. The lead-acid battery according to Claim 4, wherein the cavity of the pedestal portion is fitted with a boss portion of a lid member of the lead-acid battery; A lead-acid battery.

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