JPH11329399A - Lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of corrosion in a connection part between a shelf-like portion and a lug portion of a negative electrode strap by performing construction such that the lug portion partially remains at the shelf portion in the connection part between the lug portion and the shelf portion of the negative electrode lattice body, a connection boundary surface between an exposed portion on its surface and the shelf-like portion is provided with a thick lead-tin alloy layer, and a part of the surface of the lug portion has no alloy layer containing high density tin. SOLUTION: A lug portion 1 made of lead-calcium alloy is collected by a shelf-like portion 2 made of lead-tin alloy or lead-antimony alloy, and welded to form a negative electrode strap. The lug portion 1 is burried in the shelf-like portion 2. The dimension A is ensured to attain the strength and corrosion resistance of the strap itself. A lead-tin alloy layer 3 is formed on a surface of the lug portion 1, and the connection part extending from the lug portion 1 ensures the dimension B for attaining a high thickness. The content of tin is made higher density than that of the shelf-like portion 2 and the lugportion 1. A portion 4 which is not covered with the lead-tin alloy layer is provided on the surface of the lug portion 1 burried in the shelf-like portion 2. Accordingly, it is possible to generate a gap at the connection part between the portions 2, 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead storage battery.

[0002]

2. Description of the Related Art A lead-acid battery used for starting an automobile engine or the like is usually filled with a dilute sulfuric acid electrolyte in a battery container so that the electrolyte falls within a certain range. When water is reduced by electrolysis or the like, water is replenished. In order to suppress this decrease in the electrolyte, a battery using a lead-calcium-based alloy substantially free of antimony in place of the lead-antimony-based alloy conventionally used for the negative electrode grid or both the positive and negative electrode grids has been developed. Is becoming commonplace. In such a lead-acid battery, when the electrolyte is abnormally reduced and the electrode group constituting the lead-acid battery main body or the shelf connecting the electrodes of the same polarity is exposed from the electrolyte, the negative electrode shelf is abnormally corroded. It has been found that battery failure can occur. This is also due to the fact that the battery operating environment temperature is increasing year by year.

One of the causes of such abnormal corrosion is a slight gap between the lug and the shelf which is produced when the grating lug and the shelf are manufactured by burning or caston welding. The presence of. If there is such a gap, the sulfuric acid content in the gap reacts with lead, and the subsequent supply of sulfuric acid is cut off.Therefore, a mechanism such as an increase in the pH in the gap and the promotion of the lead dissolution reaction accompanying it, It is considered that the corrosion in this part progresses abnormally.

Therefore, it is one of the measures for improving the corrosion resistance of the strap to prevent such a gap from being generated during the production of the strap. As a specific means therefor, for example, Japanese Patent Application Laid-Open No. 58-225568 discloses a negative electrode. There is disclosed a technique in which a lead alloy containing high concentration of tin, that is, solder is applied in advance to the surface of a lattice ear to form a strap.

However, as the operating environment such as the operating temperature of the battery becomes more severe, the lead-tin alloy itself provided for the purpose of suppressing the generation of the gap between the shelf and the ear is corroded by the corrosion of the lead-tin alloy itself. It has been found that it is necessary to consider the distribution state of the lead-tin alloy at the joint between the shelf and the ear, since the battery may fail due to the detachment.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress corrosion occurring at the junction between the shelf and the ear in the negative electrode strap portion and the occurrence of battery failure.

[0007]

According to the present invention, there is provided a negative electrode comprising a lug of a negative electrode grid made of a lead-calcium alloy and a shelf for collecting and welding the lugs. A lead-acid battery including a strap portion, wherein a part of the ear portion remains on the shelf portion at the junction between the shelf portion and the ear portion, and a portion and a shelf portion exposed from the shelf portion on the surface of the ear portion. Is provided with a lead-tin alloy layer containing tin at a higher concentration than the shelf, and the joining interface between the ear and the shelf is thicker than the other ears. A lead-acid battery in which the lead-tin alloy layer containing high-concentration tin does not exist on at least a part of the surface of the ear part that remains.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to suppress the corrosion of the strap portion of the lead storage battery, it is important to first suppress the occurrence of a gap at the joint between the shelf and the ear. In this configuration, a solder alloy having a relatively low melting point, that is, a lead-tin alloy needs to be interposed in a portion where a gap is generated as described in the related art. However, a lead-tin alloy containing a relatively high concentration of tin, such as a solder alloy, is more susceptible to corrosion than a lead alloy in a shelf or ear, and therefore, the joining between the shelf and the ear. It is not preferable to make it exist all around the part. Therefore, in order to avoid such an undesired structure, the configuration of the present invention provides a portion where the lead-tin alloy layer does not exist in at least a part of the joining portion between the shelf and the ear. It is.

The lead-acid battery according to the present invention has lead-
An expanded lattice of a calcium alloy, for example, a tin alloy containing 0.07% by weight of lead and 0.3% by weight of calcium is used. About the ear part, beforehand thickness 10μ
The lead alloy was provided with a 50% tin alloy by cladding. The application of a lead alloy containing a high concentration of tin as described above, that is, a solder alloy, to the surface of the ear portion has already been widely used to secure the welding stability of the strap portion. A lead-tin alloy or a lead-antimony alloy was used as an alloy for forming the ledges by assembling and welding the lugs having such a configuration. Here, it is necessary that the tin content of the lead-tin alloy applied to the surface of the ear portion be higher than that of the alloy forming the shelf portion and the ear portion in order to suppress the gap between the shelf portion and the ear portion. is there.

FIG. 1 shows the structure of the shelf and ears of the negative electrode strap part in the lead storage battery of the present invention.

Ear 1 made of the above-mentioned lead-calcium alloy
Are assembled and welded together by a ledge 2 made of a lead-tin alloy or a lead-antimony alloy to form a negative electrode strap. Here, the ear 1 is configured to be embedded in the shelf 2. That is, it is necessary to secure the dimension A in FIG. 1 in order to secure the strength and corrosion resistance of the strap itself. A lead-tin alloy layer 3 is formed on the surface of the ear 1, and its thickness is larger at the joint exposed from the shelf of the ear, as shown by the dimension B in FIG. The configuration is as follows. Here, an alloy non-coating portion 4 where no lead-tin alloy layer is present is provided on the surface of the ear portion buried in the shelf. The tin content of the lead-tin alloy layer 3 is configured to be higher than that of the shelf 2 and the ear 1 as described above. In addition, it is desirable to form a fillet 5 at a portion where the ear 1 is exposed from the shelf 2 at the joint between the shelf 2 and the ear 1 in order to obtain the effect of the present invention.

[0012]

Embodiments of the present invention will be described below.

First, a negative electrode plate was prepared using a tin alloy expanded lattice containing 0.07% by weight of lead and 0.3% by weight of calcium. A tin alloy having a thickness of 10 μm and 50% by weight of lead in advance, that is, a solder layer provided with a clad and a negative electrode plate not provided with the solder layer were prepared on the surface of the ear portion. Each of these negative electrode plates was formed into a shelf in units of six sheets to form a negative electrode strap. The alloys on the shelves were a tin alloy containing 2.5% by weight of lead and an arsenic alloy containing 2.7% by weight of lead and 0.3% by weight of antimony. The shelf was formed by using the Caston method together with the above-described burning method. Here, the Caston method is a method in which a lug is inserted into a mold from above, a molten lead alloy is poured into the mold, and then solidified to form a shelf. A negative electrode strap was formed using these two types of negative electrode plates, two types of shelf alloys, and two types of welding methods in combinations shown in Table 1.

[0014]

[Table 1]

Here, prior to the formation of the straps other than the straps A and D, a rosin-based flux was applied to the ears so that the welding condition was good.

Each of the straps welded with the configuration shown in Table 1 was cut in the longitudinal direction of the strap, and the welding state of the cross section was confirmed. The results are shown in FIG.

Among them, C, C 'and F correspond to the configuration of the present invention shown in FIG. The difference in the configuration of each strap will be described. For straps A and D, there is no lead-tin alloy layer 3 on the surface of ear 1 and no fillet is formed at the welding interface between shelf 2 and ear 1. , Straps B and E, ears 1 remaining inside shelf 2
The lead-tin alloy layer 3 is formed almost uniformly on the entire surface (excluding the cut surface of the ears) even after the strap is formed.

A strap according to the present invention as shown in FIGS. 2 and 1 is formed under certain welding conditions. That is, first, when the burning welding is started, the burning flame melts the strap shelf. The molten lead alloy flows into the portion that forms the shelf, and the amount of heat causes the ear or the lead-tin alloy layer applied to the surface of the ear to fuse and solidify together when fused and solidified, respectively. At this time, since the melting point of the lead-tin alloy layer is much lower than that of the alloys forming the other shelves or the ears, the lead-tin alloy layer is first melted first at the start of melting and the ears are melted. It melts in such a manner that a part of the upper part of the lead-tin alloy layer provided in the part is cut off. Moreover, a considerable part of the molten lead-tin alloy layer descends by gravity along the ears without being mixed with the alloy that forms the already molten shelf, and the welding interface between the shelf and the ears Are arranged in such a way that they gather in a lot. Since the lead-tin alloy layer thus arranged has a surface tension reduced by the action of the flux, the shelf and the ear are arranged so as to form a fillet with the lead-tin alloy layer. . A fillet is thus formed by the lead-tin alloy layer when all parts forming the strap are melted and solidified. As described above, since the melting point of the lead-tin alloy layer is low, solidification is finished at last, and a fillet 5 having a shape like the strap C shown in FIG. At this time, the contact angle of the lead-tin alloy layer with the shelf and the ear is 90 ° or less, and it can be said that the fillet 5 is formed in a good shape.

Next, in order to evaluate the corrosion resistance of the various straps thus manufactured, 12V48Ah automotive lead-acid batteries having the various straps shown in Table 2 were manufactured.
The electrolyte surface was kept at a position 5 mm from the lower surface of the shelf, and a constant voltage overcharge was performed at 13.8 V in an environment of 75 ° C. until the joint between the shelf and the ear of the strap came off due to corrosion. I checked the time.

The results are shown in Table 2.

[0021]

[Table 2]

Straps A and D corroded in the shortest time. When the state of this corrosion was observed in detail, no fillet was formed at the weld interface between the ledge and the ear of the strap, and so-called crevice corrosion proceeded early from the gap formed between the ledge and the ear. I think that the. Also, straps B and E had a relatively long time until corrosion. Observation of the condition suggests that a fillet is formed by the lead-tin alloy layer at the weld interface between the ledge and the ear of the strap, which seems to have suppressed early corrosion. However, the lead-tin alloy layer itself contains high-concentration tin, so the corrosion resistance of the alloy itself cannot be said to be high. At the time of final corrosion, corrosion proceeds along the lead-tin alloy layer and the final Ears came off the shelves. However, in the case of the straps C and F according to the structure of the present invention, as in the case of the straps B and E, a fillet was formed at the welding interface between the shelf portion and the ear portion of the strap by the lead-tin alloy layer at the time of the strap production. Was suppressed. Further, although this portion gradually corroded, it is presumed that the corrosion rate was considerably slowed down even if the amount of corrosion was the same as that of fillets B and E because the lead-tin alloy layer was concentrated on this portion. Is done. More importantly, corrosion is
Uncoated portion 4 directly welded without the interposition of a lead-tin alloy layer inside the welding interface between the shelf and the ear as shown in FIG.
No corrosion progressed at all. This is considered to be because the corrosion rate itself is slower than that of the lead-tin alloy layer when there is no factor for accelerating corrosion such as a gap in the alloy itself of the shelf and ears.

[0023]

As described above, according to the present invention, there is provided a lead-acid battery having extremely excellent corrosion resistance in a situation where the electrolyte surface is abnormally lowered and the negative electrode strap is exposed in the gas phase. And its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing a state of a cross section of a negative electrode strap portion in the configuration of the present invention. FIG. 1B is an enlarged view of a dotted line portion in FIG.

2A is an explanatory diagram of a negative electrode strap A in a conventional example. FIG. 2B is an explanatory diagram of a strap B. FIG. (C'2) Enlarged view of dotted line portion of (c'1) (d) Illustration of strap D in conventional example (e) Illustration of strap E (f) Illustration of strap F in the configuration of the present invention

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ear part 2 Shelf part 3 Lead-tin alloy layer 4 Alloy uncoated part 5 Fillet

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masashi Izawa 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A lead-acid battery comprising a negative electrode grid made of a lead-calcium alloy and a negative electrode strap having a shelf for burying the tip of the ear, the lead storage battery comprising: A portion exposed from the shelf and a bonding interface between the shelf and the shelf are provided with a lead-tin alloy layer containing a higher concentration of tin than the shelf and the ear, and the ears remaining on the shelf are provided. A lead-acid battery, wherein at least a part of the surface is provided with an alloy non-coating portion in which the lead-tin alloy layer containing high-concentration tin does not exist. 2. The lead-tin alloy layer at a portion located on the lower surface of the shelf at the joint interface between the ear and the shelf is thicker than the surface of the other ear. Item 7. The lead storage battery according to Item 1. 3. The lead-acid battery according to claim 1, wherein a fillet is formed at a junction between the shelf and the ear by a lead-tin alloy component. 4. The lead-acid battery according to claim 1, wherein the shelf is made of a lead-tin alloy. 5. The lead storage battery according to claim 1, wherein the shelf is made of a lead-antimony alloy.