Lead-acid battery plug and lead-acid battery

Abstract

A vent plug (18) is provided with: a head part (35); a cylindrical part (36) extending from the head part (35); and a filter (34) provided inside the cylindrical part (36), wherein the cylindrical part (36) is provided with a through-hole (43) which causes the interior and exterior of the cylindrical part (36) to be in communication with each other, the through-hole (43) has an opening in the circumferential surface of the cylindrical part (36), and the filter (34) is provided so as to close the opening of the through-hole (43).

Description

[Technical field]

[0001] The present invention relates to a lead-acid battery vent plug and a lead-acid battery. [Background technology]

[0002] Lead-acid batteries are used in various applications, including automotive and industrial use. Lead-acid batteries include a plate group in which positive and negative plates are alternately stacked with separators between them. In addition, in lead-acid batteries, the plate group is immersed in an electrolyte held in a battery case, and the opening of the battery case is sealed with a lid. Some of these lead-acid batteries have a liquid port plug on the lid for refilling the electrolyte. The liquid port plug includes a cylindrical body with an open lower end and a head that seals the upper end of the cylindrical body. In addition, some of the liquid port plugs have a through hole formed therein for connecting to an exhaust passage that communicates with an exhaust hole provided in the lid. The through hole, the exhaust passage, and the exhaust hole have the function of discharging oxygen gas and hydrogen gas generated on the plates in the battery case when the lead-acid battery is charged to the outside of the lead-acid battery.

[0003] In lead-acid batteries, a phenomenon in which the water content in the electrolyte is reduced (hereinafter referred to as "liquid reduction") may occur. Possible causes of this liquid reduction include, for example, the following. When a lead-acid battery is used in a high-temperature environment such as an engine room, some of the water in the electrolyte evaporates, generating water vapor that is released outside the cell chamber through the exhaust hole of the electrolyte plug, or the electrolyte becomes mist-like and is released outside the cell chamber through the exhaust hole of the electrolyte plug. This causes liquid reduction in each cell chamber. When liquid reduction occurs, problems such as a decrease in battery capacity and corrosion of the current collector connected to the electrode plate group may occur.

[0004] For example, Patent Document 1 discloses a lead-acid battery that includes a vent plug attached to a liquid port provided on the exterior of the lead-acid battery and a sheet that covers the vent port of the vent plug. By providing a sheet that covers the vent hole of the vent plug in this way, water vapor is not easily released from inside the battery, and reduction in electrolyte due to the release of water vapor from inside the battery is suppressed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-276741 A Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors of the present application have focused on the fact that loss of electrolyte in a lead-acid battery occurs when water vapor or mist is released to the outside through the electrolyte vent plug, and have arrived at the present invention. That is, an object of the present invention is to provide a electrolyte vent plug for a lead-acid battery and a lead-acid battery that can suppress loss of electrolyte. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a lead-acid battery vent plug comprising a head, a cylindrical portion extending from the head, and a filter provided inside the cylindrical portion, wherein the cylindrical portion has a through hole connecting the inside and outside of the cylindrical portion, the through hole has an opening on the inner surface of the cylindrical portion, and the filter is provided to block the opening of the through hole. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a lead-acid battery 100 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of a vent plug 18 according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a front view of the vent plug 18 shown in FIG. 2. [Figure 4] FIG. 3 is a rear view of the vent plug 18 shown in FIG. 2. [Diagram 5] 3 is a cross-sectional view taken along line AA in FIG. 2, showing the internal structure of a vent plug 18. FIG. [Figure 6] 3 is a diagram showing a state in which the vent plug 18 shown in FIG. 2 is attached to the lid 15. FIG. [Figure 7] 1A and 1B are diagrams showing a liquid vent plug 181 according to a modified example of the present invention, where (a) is a front view and (b) is a rear view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0010] [General configuration of lead-acid battery 100] Fig. 1 is a perspective view showing a lead-acid battery 100 according to an embodiment of the present invention. As shown in Fig. 1, the lead-acid battery 100 includes a plurality of plate groups (not shown), an electrolyte (not shown), a battery case 12 that contains the plate groups and the electrolyte and is open at the top, and a lid 15 that seals the opening of the battery case 12.

[0011] The battery case 12 is a container having a substantially rectangular parallelepiped shape with an opening on the top surface, and is made of, for example, synthetic resin. The battery case 12 has a partition wall. The interior of the battery case is divided by the partition wall into a plurality of cell chambers arranged in a predetermined direction. A group of electrodes is arranged in each of the plurality of cell chambers.

[0012] The opening of the battery case 12 is sealed with a lid 15 having a shape corresponding to the opening. More specifically, the peripheral portion of the lower surface of the lid 15 and the peripheral portion of the opening of the battery case 12 are joined by, for example, thermal welding. The lid 15 includes a base 19 and a platform portion 20 protruding from the base 19. A negative electrode terminal 16 and a positive electrode terminal 17 are provided on the base of the lid 15.

[0013] The pedestal portion 20 of the lid 15 includes a first protruding portion 21 protruding between the positive electrode terminal 17 and the negative electrode terminal 16, and a second protruding portion 22 extending parallel to the arrangement direction of the positive electrode terminal 17 and the negative electrode terminal 16. The pedestal portion 20 includes a handle 23 for allowing a user of the lead-acid battery 100 to hold the lead-acid battery 100.

[0014] Further, the second protruding portion 22 is provided with a water refill port 25 (see FIG. 7) at a position corresponding to each cell chamber, and the lid 15 is provided with a liquid refill port plug 18 that seals the water refill port 25. In the example shown in FIG. 1, the lid 15 is provided with six liquid refill port plugs. When refilling the lead-acid battery 100 with water, the liquid refill port plugs 18 are removed and refilling liquid is supplied.

[0015] Additionally, exhaust holes 24 are provided on the side surface of second protruding portion 22 of lid 15. Exhaust holes 24 are connected to an exhaust path (not shown) provided in lid 15, and exhaust gas generated in each cell chamber to the outside. Additionally, exhaust holes 24 are provided at the end in the arrangement direction in which vent plugs 18 are arranged when lid 15 is viewed from above. In other words, exhaust holes 24 are provided so that vent plugs 18 and exhaust holes 24 are in a straight line.

[0016] [General configuration of the liquid outlet plug 18] Fig. 2 is a perspective view of the vent plug 18 according to the embodiment of the present invention. Fig. 3 is a front view of the vent plug 18, and Fig. 4 is a rear view of the vent plug 18. Fig. 5 is a cross-sectional view taken along line AA in Fig. 2, showing the internal structure of the vent plug 18.

[0017] As shown in FIGS. 2 to 5, the liquid vent plug 18 includes a main body 31, a packing 32, a splash guard 33, and a filter .

[0018] The main body 31 of the vent plug 18 includes a circular, plate-like head 35 and a tubular portion 36 that extends from the head 35 and has a generally cylindrical shape. A tool hole 41 is formed in the head 35 of the vent plug 18. A screw thread portion 42 having a helical screw thread is formed on the outer periphery of the tubular portion 36. The vent plug 18 is fixed to the water refill port 25 provided in the lid 15 by screwing the screw thread portion 42 into the tool hole 41. The lead-acid battery 100 allows the vent plug 18 to be attached and detached by inserting a coin, a screwdriver, or the like having a shape corresponding to the tool hole 41 into the tool hole 41 and rotating the vent plug 18.

[0019] The cylindrical portion 36 includes a cylindrical portion 40, a thread portion 42, a restricting portion 44, and a flange portion 46. Here, the end of the cylindrical portion 36 on the head 35 side is referred to as a first end portion 50, and the end opposite to the first end portion 50 is referred to as a second end portion 51. That is, the cylindrical portion 36 is connected to the head 35 at the first end portion 50 and is integrated with the head 35. The head 35 seals the first end portion 50 of the cylindrical portion 36. The cylindrical portion 40 of the cylindrical portion 36 is a hollow cylindrical member whose end opposite to the head 35 is open. The cylindrical portion 36 holds the filter 34 and the splash guard 33 inside the cylindrical portion 40. The cylindrical portion 40 also includes a through hole 43 and a slit 45. Hereinafter, the central axis of the cylindrical portion 36 is referred to as the central axis L, and the direction parallel to the central axis L is referred to as the "axial direction of the cylindrical portion 36". In addition, in the axial direction of the tubular portion 36, the direction from the second end portion 51 to the first end portion 50 is defined as the upward direction, and the direction from the first end portion 50 to the second end portion 51 is defined as the downward direction.

[0020] The restricting portion 44 is a ring-shaped member with a portion cut out, and protrudes outward from the tubular portion 40. The packing 32 is a ring-shaped member made of, for example, synthetic rubber. The packing 32 ensures a tight seal between the lid 15 and the liquid outlet plug 18 when the liquid outlet plug 18 is attached to the water refill port 25. The packing 32 is fitted between the head 35 and the restricting portion 44. The packing 32 is arranged so that its outer diameter is smaller than that of the head 35 and larger than that of the restricting portion 44, and is held in a predetermined position by the restricting portion 44 and the head 35.

[0021] The through hole 43 includes an opening formed on the inner peripheral surface of the cylindrical portion 36 and an opening formed on the outer peripheral surface of the cylindrical portion 36, and is provided so as to connect the opening formed on the inner peripheral surface of the cylindrical portion 36 and the opening formed on the outer peripheral surface of the cylindrical portion 36. Therefore, the through hole 43 communicates the inside and the outside of the cylindrical portion 40 (cylindrical portion 36). The through hole 43 is also provided so as to extend in the radial direction of the cylindrical portion 36. The through hole 43 is connected to an exhaust passage (not shown) provided in the lid 15. Gas generated in each cell chamber of the lead-acid battery 100 escapes from the inside of the cylindrical portion 40 to the exhaust passage through the through hole 43 and is discharged to the outside through the exhaust hole 24. The through hole 43 is provided at two positions facing each other across the central axis L of the cylindrical portion 36.

[0022] The slit 45 is provided so as to extend from the second end 51 of the cylindrical portion 36 toward the first end 50. In the example shown in Figs. 2 to 5, the slit 45 is provided at two positions facing each other across the central axis L of the cylindrical portion 36. The width of the slit 45 is approximately uniform over the entire length in the vertical direction. Since the slit 45 is provided in the liquid outlet plug 18, even if the liquid level of the electrolyte rises above the second end, which is the lowest part of the cylindrical portion 36, the gas escapes through the slit 45 to the through hole 43 and the exhaust path, so that overflow can be suppressed.

[0023] As shown in Figs. 2 to 5, the through hole 43 and the slit 45 are formed at the same position in the circumferential direction of the outer circumferential surface of the cylindrical portion 36. In addition, the end of the slit 45 on the first end 50 side is referred to as end 45a. In this embodiment, the liquid vent plug 18 is shown in which the through hole 43 and the slit 45 are formed at the same position in the circumferential direction of the outer circumferential surface of the cylindrical portion 36. However, the positional relationship between the through hole 43 and the slit 45 in the liquid vent plug 18 is not limited to this. That is, the through hole 43 and the slit 45 may be formed at different positions in the circumferential direction of the outer circumferential surface of the cylindrical portion 36.

[0024] The thread portion 42 is a helical thread provided on the outer circumferential surface of the tubular portion 40 and protruding outward from the tubular portion 40. The end of the thread portion 42 on the second end 51 side is referred to as a starting end 42a. The end of the thread portion 42 on the first end 50 side is referred to as a terminal end 42b. In other words, the starting end 42a and the terminal end 42b are the starting end and the terminal end of the thread portion 42 provided on the outer circumferential surface of the tubular portion 40 so as to draw a spiral from the second end 51 side to the first end 50 side.

[0025] 2 to 5, in the liquid vent plug 18, the slit 45 and the thread portion 42 are provided in an overlapping region of the outer circumferential surface of the cylindrical portion 40. That is, the thread portion 42 is provided with a discontinuous thread.

[0026] The flange portion 46 is provided on the outer circumferential surface of the cylindrical portion 36. The flange portion 46 protrudes outward from the cylindrical portion 36 in the circumferential direction of the cylindrical portion 36. In the direction of the central axis L of the cylindrical portion 36, the cylindrical portion 36 is provided closer to the first end portion 50 than the thread portion 42. As shown in FIGS. 2 to 5, the flange portion 46 includes a ring portion 46a and a flange portion 46b.

[0027] The ring portion 46a is a ring-shaped member that protrudes from the cylindrical portion 36 outward in the circumferential direction of the cylindrical portion 36. The ring portion 46a is provided so that the amount of protrusion (distance from the outer peripheral surface of the cylindrical portion 36) from the outer peripheral surface of the cylindrical portion 36 is approximately the same as the amount of protrusion of the top of the thread portion 42. The flange portion 46b is a ring-shaped member that protrudes further outward in the radial direction of the cylindrical portion 36 from the ring portion 46a. Therefore, the amount of protrusion of the flange portion 46 from the outer peripheral surface of the cylindrical portion 36 is greater than the amount of protrusion of the thread portion 42.

[0028] The filter 34 is a porous body made of a sintered body of ceramics such as alumina or a sintered body of resin particles such as polypropylene. The filter 34 is an explosion-proof filter, and prevents sparks and the like generated outside from penetrating into the battery case 12. As shown in Figs. 3 to 5, the filter 34 is held inside the cylindrical portion 40 of the cylindrical portion 36.

[0029] FIG. 6 is a diagram showing a state in which the vent plug 18 is attached to the water refill port 25 of the lid 15. As shown in FIG. 6, the vent plug 18 is attached to the water refill port 25 of the lid 15 by screwing the threaded portion 25a provided on the water refill port 25 with the threaded portion 42a of the vent plug 18. As shown in FIG. 7, the filter 34 is disposed at a position where the through hole 43 is provided in the axial direction of the cylindrical portion 36. The filter 34 is provided to block the opening of the through hole 43. That is, the filter 34 is provided so as to abut against the opening on the inner peripheral surface side of the cylindrical portion 36 in the through hole 43 that communicates between the inside and the outside of the cylindrical portion 36.

[0030] As shown in FIG. 5, the splash guard 33 is held inside the cylindrical part of the cylindrical part 36. The splash guard 33 is integrally formed, for example, from resin. As shown in FIG. 5, the splash guard 33 includes a bottom part 60, a support part 61, a first splash guard plate 62, a second splash guard plate 63, a third splash guard plate 64, a fourth splash guard plate 65, and a fifth splash guard 66. The splash guard 33 includes the first splash guard plate 62 to the fifth splash guard plate 66, so that the gas exhaust path inside the cylindrical part 36 is labyrinth-shaped. As a result, the gas generated inside the battery container 12 is exhausted to the outside through the inside of the cylindrical body 36, while the electrolyte is not easily leaked out. In the following, the first splash guard plate 62 to the fifth splash guard plate 66 may be collectively referred to as a plurality of splash guard plates.

[0031] The bottom 60 is a circular plate-like member and is provided to seal the second end 51 of the cylindrical part 36. The diameter of the bottom 60 is slightly larger than the inner diameter of the cylindrical part 36 at the second end 51, and the bottom 60 of the splash protector 33 is press-fitted into the second end 51 of the cylindrical part 36. As a result, the splash protector 33 is locked inside the cylindrical part 36. In addition, a convex part 60a that protrudes outward in the circumferential direction is formed on the outer circumferential surface of the bottom 60 at a position corresponding to the slit 45. The convex part 60a is formed in two places at a position corresponding to the slit 45. In the liquid outlet plug 18, the splash protector 33 is press-fitted into the cylindrical part 36 so that the convex part 60a is inserted into the slit 45, thereby defining the direction (orientation) in which the splash protector 33 is held by the cylindrical part 36. The support portion 61 is a rod-shaped body that extends from the center of the bottom portion 60 in parallel with the axial direction of the cylindrical portion 36 toward the first end side.

[0032] The first splash protection plate 62 is the splash protection plate located closest to the second end 51 among the multiple splash protection plates included in the splash protection body 33. The first splash protection plate 62 is formed as a pair facing each other across the central axis L of the cylindrical portion 36. The first splash protection plate 62 has a substantially semicircular plate shape, with a straight portion of the semicircular shape connected to the support portion 61 and an arc facing outward. The first splash protection plate 62 is also arranged to extend obliquely upward from the support portion 61.

[0033] In the first splash protection plate 62, the lowermost part connected to the support portion 61 is the base portion 62a. In addition, in the first splash protection plate 62, the uppermost end portion 62b (closer to the first end portion 50) is located above (closer to the first end portion 50) the end portion 45a of the slit 45. Here, if the distance in the direction of the central axis L of the cylindrical portion 36 from the second end portion 51 to the upper end portion 62b of the first splash protection plate 62 is set to a distance h2, the distance h2 satisfies the following relational expression between the distance h1 representing the depth of the slit 45 and the pitch α of the thread portion 42 (see FIG. 3). h1 < h2 < h1 + α (1)

[0034] Consider the case where the distance h2 is equal to or less than the distance h1, that is, the depth of the slit 45 is equal to or shorter than the distance to the upper end 62b of the first splash plate 62. In such a case, the end 45a of the slit 45 is located closer to the first end 50 than the upper end of the first splash plate 62, so that the electrolyte easily infiltrates into the inside of the cylindrical body 36 from above the first splash plate 62 due to vibration or the like. The electrolyte that has infiltrated into the inside of the cylindrical body 36 may creep up inside the cylindrical body 36 and overflow due to further vibration or the like being applied to the lead-acid battery 100.

[0035] When the distance h2 is h1+α or more, the distance in the axial L direction from the upper end 62b of the first splash plate 62 to the end 45a of the slit 45 becomes large. Therefore, compared with the case where the distance h2 is less than h1+α, the electrolyte that has infiltrated into the inside of the cylindrical body 36 due to vibration or the like is more likely to hit the inner wall of the cylindrical body 36, and the electrolyte that has infiltrated into the inside of the cylindrical body 36 is less likely to be discharged to the outside of the cylindrical body 36. In this case, as in the above case, when vibration or the like is further applied to the electrolyte that has infiltrated into the cylindrical body 36, the electrolyte may creep up inside the cylindrical body 36 and overflow.

[0036] In this way, since the vent plug 18 satisfies the above relational expression (1), the vent plug 18 is less susceptible to overflowing due to vibrations or the like (it has excellent dynamic overflowing performance).

[0037] In addition, in the vent plug 18, the upper end 62b of the first splash plate 62 is located closer to the first end 50 (higher) than the starting end 42a of the thread portion 42.

[0038] The second splash protection plate 63 is provided above (toward the first end portion 50) the first splash protection plate 62 and has a generally rectangular flat plate shape. The second splash protection plates 63 are formed as a pair facing each other across the central axis L of the cylindrical portion 36, and are disposed to extend obliquely downward from the support portion 61.

[0039] The third splash protection plate 64 is provided above the second splash protection plate 63 and has approximately the same shape as the first splash protection plate 62. That is, the third splash protection plate 64 is formed as a pair so as to face each other across the central axis L of the cylindrical portion 36. The third splash protection plate 64 has an approximately semicircular plate shape, with a chord connected to the support portion 61 and an arc facing outward. The third splash protection plate 64 is also disposed so as to extend obliquely upward from the support portion 61. Similarly to the first splash protection plate 62, the lowest portion of the third splash protection plate 64 connected to the support portion 61 is called the base, and the uppermost portion (on the first end portion 50 side) is called the upper end portion.

[0040] The fourth splash protection plate 65 is provided so as to extend downward from between the base and the upper end of the third splash protection plate 64. The fourth splash protection plate is a substantially rectangular flat plate. The fourth splash protection plate 65 is formed as a pair so as to face each other across the central axis L of the cylindrical portion 36.

[0041] The fifth splash protection plate 66 is provided above the third splash protection plate 64 and is connected to the top of the support column 61. The upper end 66a, which is the end of the fifth splash protection plate 66 on the first end 50 side, is the end of the splash protection body 33 on the first end 50 side. The upper end 66a is located closer to the first end 50 than the upper end 42b of the threaded portion 42.

[0042] [Modifications] Hereinafter, modified examples of the present invention will be described with reference to the drawings. For the sake of convenience, the same reference numerals will be used to designate members having the same functions as those described in the embodiment, and the description thereof will be omitted.

[0043] Fig. 7 shows a vent plug 181 according to a modified example, where (a) of Fig. 7 is a plan view of the vent plug 181 and (b) of Fig. 7 is a rear view. As shown in Fig. 7, in the vent plug 181 according to this modified example, the thread portion 421 and the flange portion 461 are provided so as to be integrated. That is, in the vent plug 18 according to the above-mentioned embodiment, the terminal end 42a of the thread portion 42 and the flange portion 46 are arranged to be spaced apart in the direction of the central axis L of the cylindrical portion 36. On the other hand, in the vent plug 181 according to this modified example, the terminal end 421a of the thread portion 421 is connected to the flange portion 461.

[0044] In this way, it is sufficient that the flange portion 451 is provided closer to the first end portion 50 than the thread portion 421, and the thread portion 421 and the flange portion 451 may be provided integrally. Even if the vent plug 181 has such a configuration, it has the same effect as the vent plug 18 according to the embodiment.

[0045] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0046] 〔summary〕 (1) A lead-acid battery vent plug according to one embodiment of the present invention is a lead-acid battery vent plug 18, 181 comprising a head 35, a cylindrical portion 36 extending from the head 35, and a filter 34 provided inside the cylindrical portion 36, wherein the cylindrical portion 36 has a through hole 43 connecting the inside and outside of the cylindrical portion 36, the through hole 43 has an opening on the inner circumferential surface of the cylindrical portion 36, and the filter 34 is provided to block the opening of the through hole 43.

[0047] Here, consider a case where a part of the moisture in the electrolyte held in the battery case 12 evaporates, and the water vapor generated by the evaporation is discharged to the outside of the lead-acid battery 100 through the through hole 43 of the vent plug. In the vent plug 18, 181 according to one embodiment of the present invention, the opening on the inner circumferential surface side of the through hole 43 provided in the tubular portion 36 of the vent plug 18, 181 is blocked by the filter 34. Therefore, gas containing water vapor is less likely to be discharged from the through hole 43 to the outside of the vent plug 18, 181 compared to a case where the filter 34 does not block the through hole 43. That is, the ventilation resistance of the gas flowing from the inside of the tubular portion 36 through the through hole 43 to the exhaust path is higher than a case where the filter 34 does not block the through hole 43, and as a result, the loss of the liquid can be suppressed.

[0048] (2) In one embodiment of the lead-acid battery liquid pressurizing port plug (liquid port plug 18, liquid port plug 181) of the present invention, the cylindrical portion 36 may have a thread portion 42, 421 provided on the outer circumferential surface, and the cylindrical portion 36 may have a flange portion 46, 461 that protrudes radially outward from the cylindrical portion 36 beyond the thread portion 42, 421.

[0049] Since the opening on the inner peripheral surface side of the through hole 43 is blocked by the filter 34, it is considered that the gas containing water vapor passes between the thread portion 42, 421 of the vent plug 18, 181 and the thread portion 25a of the water refill port 25 and is discharged to the outside of the lead-acid battery 100 without passing through the inside of the vent plug 18, 181. According to the above configuration, since the flange portion 46, 461 that protrudes radially outward of the cylindrical portion 36 beyond the thread portion 42, 421 is provided, it is possible to prevent the gas containing water vapor from passing between the thread portion 42, 421 of the vent plug 18, 181 and the thread portion 25a of the water refill port 25 and being discharged to the outside of the lead-acid battery 100. That is, by providing the flange portion 46, 461, it is possible to seal the gap between the outer peripheral surface of the cylindrical portion 36 and the water refill port 25. Therefore, it is possible to provide a vent plug for a lead-acid battery that can further suppress loss of liquid.

[0050] (3) In the lead-acid battery vent plug (vent plug 181 ) according to one aspect of the present invention, the flange portion 461 may be provided integrally with the thread portion 421 .

[0051] (4) The lead-acid battery vent plug (vent plug 18, 181) according to one aspect of the present invention may have a plurality of through holes 43 provided at opposing positions.

[0052] (5) The lead-acid battery 100 according to an aspect of the present invention may include the vent plugs 18, 181 described above. [Explanation of symbols]

[0053] 18: Vent plug (Vent plug for lead-acid battery), 34: Filter, 36: Cylindrical part, 42: Thread part, 43: Through hole, 100: Lead-acid battery, 181: Vent plug, 421: Thread part, 461: Flange part

Claims

1. A vent plug for a lead-acid battery comprising a head portion, a cylindrical portion extending from the head portion, and a filter provided inside the cylindrical portion, The cylindrical portion includes a through hole that communicates between the inside and the outside of the cylindrical portion, The through hole has an opening on an inner circumferential surface of the cylindrical portion, The filter is arranged so as to close the opening of the through hole with a peripheral side surface abutting against an inner peripheral surface of the cylindrical portion.

2. The cylindrical portion has a screw thread portion provided on an outer circumferential surface, The cylindrical portion includes a flange portion that protrudes radially outward from the cylindrical portion beyond the thread portion, With the lead-acid battery fluid port plug attached to the water refill port of the lead-acid battery, The threaded portion is screwed into a threaded portion provided on an inner peripheral surface of the water refill port, 2. The lead-acid battery port plug according to claim 1, wherein the flange portion is located above the thread portion provided on the cylindrical portion and protrudes toward an inner peripheral surface of the water refill port.

3. 3. The lead-acid battery vent plug according to claim 2, wherein the flange portion is formed integrally with the screw thread portion.

4. 4. The lead-acid battery vent plug according to claim 1, wherein a plurality of the through holes are provided at opposing positions.

5. A lead-acid battery comprising the lead-acid battery vent plug according to any one of claims 1 to 4.

Images