Lead-acid battery

Abstract

A lead-acid battery 1 comprises: a battery case 20; an electricity storage element 30 and an electrolyte 35 which are housed in the battery case 20; a lid member 50 for sealing the upper surface of the battery case 20; and a vent plug 70 attached to the lid member 50. A plug body 71 of the vent plug 70 includes: a head portion 73 having an exhaust hole 73B; and a cylindrical portion 75 which protrudes downward from the head portion 73 and has an opening 76 at a tip. When the lead-acid battery 1 is in the upright or inverted position, the opening 76 at the cylinder tip of the cylindrical portion 75 of the vent plug 70 is positioned above a liquid surface of the electrolyte 35, and the opening 76 at the cylinder tip is closed by a wall.

Description

lead acid battery

[0001] The present invention relates to a technique for suppressing overflow of an electrolyte.

[0002] Lead-acid batteries contain dilute sulfuric acid (hereinafter referred to as electrolyte) as a reactive material. Because lead-acid batteries generate gases due to chemical reactions, some batteries have a vent hole in the vent plug to allow the gas to escape. Lead-acid batteries are sometimes transported in an inverted position (hereinafter referred to as an inverted position). If electrolyte seeps into the vent plug during transportation, the electrolyte may leak out through the vent hole.

[0003] One document that discloses a technique for suppressing electrolyte leakage when the battery is in an inverted position is Patent Document 1. Patent Document 1 discloses that in a lead-acid battery equipped with an exhaust cylinder that hangs down from the top surface of the battery into the battery, the tip of the cylinder is located above the electrolyte level when the lead-acid battery is in an upright position, and is also located above the electrolyte level when the battery is in an inverted position.

[0004] Japanese Patent Application Laid-Open No. 2002-352787

[0005] However, in the inverted state, the electrodes and separator are located above the exhaust cylinder (hereinafter referred to as the vent plug), so there is a possibility that the electrolyte dripping from these may enter the vent plug and leak out through the exhaust hole. The object of the present invention is to enhance the function of suppressing the overflow of the electrolyte in the inverted state.

[0006] A lead-acid battery includes a battery case, an electric storage element and an electrolyte contained in the battery case, a lid member that seals the top of the battery case, and a vent plug attached to the lid member. The plug body of the vent plug has a head portion having a vent hole and a cylindrical portion that protrudes downward from the head portion and has an opening at its tip. When the lead-acid battery is in an upright position or an inverted position, the opening at the tip of the cylindrical portion is located above the liquid level of the electrolyte, and the opening at the tip of the cylindrical portion is closed by a wall.

[0007] The function of suppressing overflow of the electrolyte in the inverted state can be strengthened.

[0008] Perspective view of a lead-acid battery Perspective view of a battery case Cross-section of a lead-acid battery Perspective view of a vent plug Cross-section of a vent plug Enlarged view of a portion of Figure 5 Cross-section of a lead-acid battery in an upright position Cross-section of a lead-acid battery in an inverted position Cross-section of a vent plug

[0009] (Summary of this embodiment) (1) A lead-acid battery includes a battery case, an electric storage element and an electrolyte housed in the battery case, a lid member that seals the top of the battery case, and a vent plug attached to the lid member. The plug body of the vent plug has a head portion having an exhaust hole and a cylindrical portion that protrudes downward from the head portion and has an opening at its tip. When the lead-acid battery is in an upright position or an inverted position, the opening at the tip of the cylindrical portion of the vent plug is positioned above the liquid level of the electrolyte, and the opening at the tip of the cylindrical portion is closed by a wall. In (1), any configuration other than the above is optional and may be used.

[0010] According to the configuration (1), even if electrolyte drips from the storage elements such as the electrodes and separators in an inverted lead-acid battery, the opening at the tip of the tube is blocked by a wall, so that the electrolyte is prevented from entering the inside of the plug body through the opening. Therefore, the function of suppressing the overflow of electrolyte in an inverted state can be strengthened.

[0011] (2) In the lead-acid battery described in (1), the storage element may include positive and negative electrode plates and a separator separating the positive and negative electrode plates. The separator may be a mat separator made of glass fiber.

[0012] According to (2), when a lead-acid battery equipped with a mat separator is inverted, the mat separator, which holds a large amount of electrolyte, is positioned above the vent plug, causing the electrolyte held in the mat separator to fall toward the vent plug. The lead-acid battery described in (2) can solve a unique problem: even when equipped with a mat separator, electrolyte falling from the mat separator is blocked by the wall at the end of the tube when the battery is in an inverted position, making it prone to entering the vent plug and increasing the risk of overflow. Furthermore, the vent plug configured as described in (1) tends to have a longer tubular portion than conventional vent plugs, and in a lead-acid battery placed upright, the opening at the end of the tube is likely to be closer to the electrolyte level. In this case, if free electrolyte is present, it is likely to enter the vent plug. According to (2), in a lead-acid battery equipped with a mat separator, the mat separator holds a large amount of electrolyte and there is little free electrolyte. Therefore, in a lead-acid battery placed upright, even with a vent plug having the configuration of (1), the wall at the tip of the tube can adequately block the electrolyte, making it difficult for the electrolyte to enter the vent plug.

[0013] (3) In the lead-acid battery according to (1) or (2), the vent plug may have a filter with a valve body built in the plug body. According to (3), the electrolyte is more likely to remain inside the vent plug than in a configuration without a built-in valve body, so that the function of preventing the electrolyte from overflowing can be further strengthened.

[0014] (4) In the lead-acid battery according to any one of (1) to (3), the vent plug may have a splash guard inside the plug body. The opening may be closed by a bottom wall of the splash guard.

[0015] According to (4), the splash guard creates a labyrinth-like gas exhaust path inside the plug body, preventing electrolyte spillage due to vibration. In addition, the bottom wall of the splash guard closes the opening of the plug body, eliminating the need for a separate wall to close the opening, and reducing the number of parts.

[0016] <Embodiments> 1. Structure of lead-acid battery Fig. 1 is a perspective view showing a lead-acid battery 1 according to an embodiment of the present invention. Fig. 2 is a perspective view of a battery case 20. Fig. 3 is a cross-sectional view taken along line AA in Fig. 1.

[0017] 1 to 3, the lead-acid battery 1 includes a battery case 10, a plate pack 30 as an electricity storage element, and an electrolyte 35. In the following description, when the battery case 10 is placed horizontally without tilting relative to a mounting surface, the width direction of the battery case 10 (the direction in which the external terminals 53A, 53B are arranged) is defined as the X direction, the up-down direction (height direction) of the battery case 10 is defined as the Z direction, and the depth direction is defined as the Y direction.

[0018] The battery case 10 includes a battery case 20 and a lid member 50. The battery case 20 is made of synthetic resin and has four outer walls 21, a bottom wall 22, and a box shape with an open top.

[0019] As shown in Fig. 2, the interior of the battery case 20 is divided into a plurality of cell chambers 25 by partition walls 23. Six cell chambers 25 are provided in the width direction of the battery case 20 (the X direction in Fig. 2), and each cell chamber 25 contains a plate assembly 30 together with an electrolyte 35 made of dilute sulfuric acid.

[0020] 3, the electrode plate assembly 30 is composed of a positive electrode plate 30A, a negative electrode plate 30B, and a separator 30C. Each of the electrode plates 30A, 30B is composed of a grid filled with an active material.

[0021] The separator 30C is a mat separator made of glass fiber, and serves to separate the adjacent positive electrode plate 30A and negative electrode plate 30B, and to retain the electrolyte 35.

[0022] The lead-acid battery 1 including the mat separator 30C has the feature that the amount of free electrolyte 35 (fluid electrolyte) is small because the mat separator 30C holds a large amount of electrolyte 35.

[0023] The cover member 50 is made of synthetic resin and includes a flat plate portion 51 and an outer peripheral wall 54. The flat plate portion 51 is large enough to seal the top surface of the battery case 20. The outer peripheral wall 54 extends downward from the outer peripheral edge of the flat plate portion 51.

[0024] A lid partition (not shown) corresponding to the partition 23 is formed on the back surface of the lid member 50. The lid member 50 is attached so as to overlap the battery case 20 and is heat-welded to the battery case 20. The lid member 50 seals the top surface of the battery case 20.

[0025] The lead-acid battery 1 is provided with a positive external terminal 53A and a negative external terminal 53B. As shown in Fig. 1 , the positive external terminal 53A and the negative external terminal 53B are disposed on both sides of the cover member 50 in the X direction.

[0026] The lead-acid battery 1 further includes vent plugs 70. The vent plugs 70 are attached to the vents 55 of the lid member 50. Six sets of vents 55 and vent plugs 70 are provided corresponding to the six cell chambers 25.

[0027] The lead-acid battery 1 has a stepped portion 52 elongated in the X direction on the flat plate portion 51 of the lid member 50 , and six vent plugs 70 are installed on the stepped portion 52 .

[0028] The step portion 52 is closed by a sheet member of the same type (not shown), and the gas exhausted from each liquid vent plug 70 is concentrated and exhausted from a concentrated exhaust portion 52A formed on the outer wall 54 of the lid member 50.

[0029] 2. Explanation of the Structure of the Vent Plug Figure 4 is a perspective view of the vent plug 70, Figure 5 is a cross-sectional view of the vent plug 70, and Figure 6 is an enlarged view of Figure 5. As shown in Figures 3 to 6, the vent plug 70 comprises a plug body 71, a packing 79, a splash guard 80, and a filter 100.

[0030] The plug body 71 of the vent plug 70 is made of, for example, synthetic resin and includes a circular plate-shaped head portion 73 and a cylindrical portion 75. A tool hole 73A and an exhaust hole 73B are formed in the head portion 73. The exhaust hole 73B passes through the head portion 73 and communicates with a hollow portion V within the cylindrical portion 75 (see FIG. 6 ).

[0031] The cylindrical portion 75 extends downward from the head portion 73. The cylindrical portion 75 is a hollow cylindrical member whose central axis is the straight line L. A tip end 75A of the cylindrical portion 75 forms an opening 76.

[0032] The cylindrical portion 75 has a screw thread portion 78 on its outer periphery. The vent plug 70 is fixed by screwing the screw thread portion 78 onto the vent 55 provided in the lid member 50.

[0033] The packing 79 is located below the head 73. The packing 79 is a ring-shaped member made of, for example, synthetic rubber. The packing 79 ensures a tight seal between the cover member 50 and the vent plug 70 when the vent plug 70 is attached to the vent 55.

[0034] The cylindrical portion 75 has slits 77. The slits 77 extend upward from a tip end 75A of the cylindrical portion 75. The slits 77 are provided in two locations on opposite sides of the central axis L of the cylindrical portion 75.

[0035] By providing the slit 77 in the liquid vent plug 70 , the gas G generated in each cell chamber 25 of the battery case 20 can pass through the slit 77 and circulate into the internal space of the cylindrical portion 75 .

[0036] The cylindrical portion 75 holds therein a splash guard 80 and a filter 100. Specifically, the splash guard 80 is held in the lower portion of the cylindrical portion 75, and the filter 100 is held in the upper portion of the cylindrical portion 75.

[0037] The splash guard 80 is integrally formed from, for example, resin, and includes a bottom wall 90, a support column 91, a first splash guard plate 92, a second splash guard plate 93, a third splash guard plate 94, a fourth splash guard plate 95, and a fifth splash guard 96.

[0038] The bottom wall 90 is disk-shaped and fits snugly around the inner periphery of the vent plug 70 , closing the opening 76 at the tip 75 A of the vent plug 70 .

[0039] Since the splash guard 80 has the first splash guard plate 92 to the fifth splash guard plate 96, the exhaust path for the gas G inside the cylindrical portion 75 is maze-shaped, so that the electrolyte 35 does not easily leak out.

[0040] The filter 100 is an explosion-proof filter that removes electrolyte spray from the gas G generated inside the battery case 20 and prevents sparks and the like generated outside from penetrating into the battery case 10.

[0041] Specifically, the filter 100 includes a filter body 110, a filter case 120, and a valve body 130. The filter body 110 is disk-shaped and is a porous body made of a sintered body of ceramic such as alumina or a sintered body of resin particles such as polypropylene.

[0042] The filter case 120 is made of a resin such as polypropylene. The filter case 120 is disk-shaped and slightly larger than the filter body 110, and includes a bottom wall 121 and an outer peripheral wall 125. The filter case 120 can accommodate the filter body 110 in the upper part.

[0043] An air vent 123 is formed in the center of the bottom wall 121 of the filter case 120. The valve body 130 is, for example, a resin plate, and is located on the upper surface of the bottom wall 121 of the filter case 120 to close the air vent 123.

[0044] The pressure of the gas G causes the valve element 130 to lift from the lower wall 121, thereby opening the vent hole 123. As a result, as shown by the dashed line F in Figures 5 and 6, the gas G generated inside the battery case passes through the vent hole 123 and the filter body 110 and is exhausted from the exhaust hole 73B. The dashed line F in Figures 5 and 6 indicates the exhaust path of the gas G.

[0045] Furthermore, by providing the valve body 130, the air flow resistance R of the vent plug 70 can be increased, and the performance of suppressing loss of the lead-acid battery 1 can be improved.

[0046] 3. Positional Relationship between Electrolyte Liquid Level and Tip of Vent Plug <Normal Installation State> Figure 7 is a cross-sectional view of the lead-acid battery 1 when the lead-acid battery 1 is in the normal installation state. The normal installation state means a state in which the battery case 10 is placed horizontally without tilting relative to the installation surface.

[0047] As shown in Figure 7, when the height position H1 of the liquid level of the electrolyte 35 is compared with the height position H2 of the tip 75A of the liquid outlet plug 70 in the upright position, the height position H2 of the tip 75A of the liquid outlet plug 70 is located higher than the height position H1 of the liquid level of the electrolyte 35.

[0048] 8 is a cross-sectional view of the lead-acid battery 1 when the lead-acid battery 1 is in an inverted state. The inverted state refers to a state in which the lead-acid battery 1 is turned 180 degrees from the normal position (with the lid member 50 on the bottom and the battery case 20 on the top).

[0049] As shown in Figure 8, when the height position H3 of the liquid level of the electrolyte 35 is compared with the height position H4 of the tip 75A of the liquid outlet plug 70 in the inverted state, the height position H4 of the tip 75A of the liquid outlet plug 70 is located higher than the height position H3 of the liquid level of the electrolyte 35.

[0050] Thus, in both the upright and inverted positions of the lead-acid battery 1, the height positions H2 and H4 of the tip 75A of the vent plug 70 are located higher than the height positions H1 and H3 of the liquid surface of the electrolyte 35. In other words, the overall length HZ of the cylindrical portion 75 is determined based on the shape of the battery case 10 and the amount of free electrolyte 35 so that the relationships H2 > H1 and H4 > H3 always hold (see FIG. 5 ).

[0051] By determining the overall length HZ of the cylindrical portion 75 as described above, the free electrolyte 35 in the battery case 10 will not enter the inside of the vent plug 70 through the opening 76, regardless of whether the lead-acid battery 1 is in an upright or inverted position, thereby reducing the risk of the free electrolyte 35 leaking to the outside through the exhaust hole 73B.

[0052] Furthermore, when providing a slit 77 in the cylindrical portion 75, it is desirable to form the slit 77 at a position higher than the liquid level of the electrolyte 35 in both the upright and inverted positions so that the electrolyte 35 does not enter through the slit 77.

[0053] In addition, in the lead-acid battery 1, the opening 76 at the tip 75A of the vent plug 70 is closed by the bottom wall 90 of the splash guard 80. Therefore, as shown in Figures 8 and 9, even if the electrolyte 35 drips from the storage elements 30, such as the electrodes and separators, located above the vent plug in the inverted state, the electrolyte 35 can be prevented from entering the inside of the vent plug 70 through the opening 76. This strengthens the function of preventing the electrolyte 35 from spilling when the battery is in the inverted state.

[0054] Furthermore, by incorporating the valve body 130 in the filter 100, the electrolyte 35 is more likely to remain inside the vent plug 70, so that the function of preventing the electrolyte 35 from spilling can be further strengthened.

[0055] <Other Embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0056] (1) In the above embodiment, the opening 76 at the tip of the vent plug is closed using the splash guard 80, but the opening 76 may be closed with a separate member. Also, the splash guard 80 may be omitted.

[0057] (2) In the above embodiment, the separator 30C is a mat separator capable of holding the electrolyte 35. However, the separator 30C need only be capable of separating at least the positive and negative electrode plates 30A and 30B, and may not be designed to hold the electrolyte.

[0058] (3) In the above embodiment, the filter 100 is provided with the valve 130, but the valve 130 may be omitted.

[0059] (4) In the above embodiment, the slit 77 is provided in the cylindrical portion 75 of the vent plug 70, but the slit 77 may be omitted.

[0060] REFERENCE SIGNS LIST 1 Lead-acid battery 10 Battery case 20 Battery case 30 Plate group (electricity storage element) 30A, 30B Electrode plate 30C Mat separator 50 Lid member 70 Vent plug 71 Plug body 75 Cylindrical portion 75A Tip portion 76 Opening 80 Splash guard 90 Bottom wall 100 Filter 130 Valve body

Claims

1. A lead-acid battery comprising: a battery case; an electricity storage element and an electrolyte contained in the battery case; a lid member that seals the top of the battery case; and a vent plug attached to the lid member, wherein the plug body of the vent plug has a head portion having an exhaust hole, and a cylindrical portion that protrudes downward from the head portion and has an opening at its tip, and wherein the opening at the tip of the cylindrical portion of the vent plug is positioned above the liquid surface of the electrolyte when the lead-acid battery is in an upright position or an inverted position, and the opening at the tip of the cylindrical portion is closed by a wall.

2. A lead-acid battery according to claim 1, wherein the storage element includes positive and negative electrode plates and a separator separating the positive and negative electrode plates, and the separator is a mat separator made of glass fiber.

3. A lead-acid battery according to claim 1 or 2, wherein the liquid vent plug has a filter with a valve body built into the plug body.

4. A lead-acid battery according to claim 1 or 2, wherein the vent plug has a splash guard inside the plug body, and the opening is closed by the bottom wall of the splash guard.

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