JPH0654660B2 - Method of manufacturing prismatic battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a prismatic battery in which a metal case and a lid are welded by a pulse type laser welding machine.

2. Description of the Related Art With the miniaturization of electronic devices, smaller and higher-performance batteries have been required for power supplies used in them. Under such circumstances, the rectangular battery, which does not waste the storage space in the device, is rapidly replacing the conventional cylindrical battery, especially in the fields of nickel-cadmium battery and lithium battery.

These prismatic batteries are manufactured by welding a lid to the opening of a case made of stainless steel or a nickel-plated steel plate that houses the power generating element.

Conventionally, arc welding and gas welding have been widely used as welding methods, but for welding small prismatic batteries, the positioning accuracy of the weld is high and the thermal effect on the periphery of the weld is small, and mass productivity is excellent. The method using a pulse type laser welding machine in combination with an XY table is the most suitable, and the prismatic battery obtained by these methods has a high welding machine accuracy, and the appearance is beautiful that cannot be imitated by other welding methods. You can get the finish. In this case, the YAG laser welder is most suitable for the pulse type laser welder because of its easy oscillation energy and easy control method.

There is also a seam welding (continuous welding) method as another welding method, but the thermal effect on the periphery of the weld is greater than that of the pulse method, and there is a risk of deformation and deterioration of resin parts, electrodes, electrolyte, etc. Not suitable for use due to its high price.

Problems to be Solved by the Invention In a small rectangular battery, a lid made of the same material is opened in a rectangular case molded from nickel-plated steel plate or stainless steel in consideration of mechanical strength and chemical resistance. A method is adopted in which the parts are fitted and the fitting parts are welded to seal them. As mentioned above, the pulse type laser welding machine is widely used for this welding.

However, there often occurred a problem that the solution in the battery leaked from the welded portion. Therefore, as a result of detailed observation by the present inventors, it was found that this leakage was concentrated around the start point and the end point during welding. The cause will be described below.

FIG. 1 shows a schematic view of a prismatic battery welding method using a pulse laser welder. As can be seen from FIG. 1, while the case (1) is fed horizontally using an XY table so that the laser beam (4) is focused on the fitting part (3) of the rectangular case (1) and the lid (2). A indicated by the symbol in the figure →
Welding is performed in the order of B, B → C, C → D, D → A. At this time, the following relationship is established between the oscillation frequency n of the pulse laser, the feed rate V of the case, and the bead density generated by welding.

d = n / V ([N / l]) ... 1st Formula d: The number of beads per length of a welding part n: N / t. V = 1 / t N: Number of pulses, t: Time l: Welding distance For example, to set the bead density to 3 [pieces / mm], if the pulse oscillation frequency of the laser is 60 [pulses / second], the feed rate Must be set to 20 [mm / sec].

However, as shown in FIG. 2, the movement of the XY table starts from the point A, starts from the point A in the section ending at the point B, goes through the acceleration section S ₁ and moves at the constant speed Vs in the constant speed section S. Next, the speed is gradually reduced in the deceleration section S ₂ that fluctuates in the B direction, stops at the point B, and the speed becomes zero. In this way, near the feed start point and the feed end point, there are an acceleration section and a deceleration section where the feed rate (V) becomes smaller than the set speed. On the other hand, the number n of oscillations of the laser is constant, so that the bead density shown in the first equation inevitably swells over the original set number in this section.

Since the bead density and the energy received by the weld are in a proportional relationship, the start point and end point where the bead density is large are irradiated with laser energy that is larger than necessary compared to the constant speed section, and the welding machine in this part Dislocations and the like were generated at the points due to abnormal thermal influences, which were the cause of welding defects such as cracks.

Means for Solving Problems As a method of eliminating welding defects in prismatic batteries welded with a pulse laser welder, instead of the conventional welding method, the bead density was made uniform over the entire welded area. It was found that extremely stable welding with no cracks was possible. Furthermore, the present inventors have established the following two types of methods to realize it.

[Method A] First, the first method is to provide an extra feed section before the start point and after the end point with respect to the necessary welding section so that the feed speed V is always constant in the welding section. The method is shown in FIG. The laser oscillation is linked to the feed and oscillates only in the welding section. As a result, if the number n of oscillations of the laser is constant, it is possible to obtain a constant bead density, as can be seen from the first equation shown above. This method is called method A.

[Method B] In the second method, the case feeding method is the same as the conventional method, and the pulse oscillation number n is synchronized with the feeding speed to control the bead density to be constant. FIG. 4 shows the method. That is, while detecting the feed speed V of the XY table, the number of oscillations n is controlled so that the bead density given by the first equation becomes constant according to this feed speed V. This method is called method B.

Example A steel plate having a thickness of 0.4 mm is molded, and consists of a nickel-plated case and lid. Width 16.4 mm, thickness 5.6 mm, height
Welding is carried out using a prismatic alkaline storage battery with 67 mm nickel-cadmium as the active material, and the presence or absence of leakage of alkaline electrolyte from the weld is checked by red litmus test paper to check for defects in the weld. It was

The laser welding machine used was a pulse type YAG laser welding machine with an output of 150 W, and the case was sent by an XY table joined to an NC controller. The bead density in the welded part was set to 3 [pieces / mm].

Sample A was prepared by the method A according to the present invention. That is, the distance between the front and rear of the welding section was increased by 3 mm, the feed rate in the welding section was kept constant at 20 [mm / sec], and the laser oscillation frequency was 60 at the same time. Welding was performed under the condition of [pulse / second].

Sample B is the above method B according to the present invention, the case feed is only in the welding section, the speed is based on 20 [mm / sec], and the laser oscillation frequency is based on [60 pulses / sec] as the starting point. The acceleration and deceleration sections at the end point were automatically controlled according to the respective speeds, and welding was performed so that the bead density became constant over the entire welded portion. In addition,
The detection of the feed rate and the control of the laser oscillation frequency related to it were carried out by incorporating a computer.

Sample C was produced by the conventional method, and the bead density inevitably exceeded 3 [pieces / mm] at the welding start point and welding end point.

After welding, 50 cells of each of these batteries were left in a high temperature tank at 60 ° C. and 95 RH%, and the leakage occurrence rate of the electrolytic solution from the joint was examined. The results are shown in Table 1.

As shown in Table 1, leakage was detected from 12% of the batteries in Sample C according to the conventional method at 180 days after standing, but was not detected at all in Samples A and B according to the present invention. There were no liquid leaks or welding defects.

EFFECTS OF THE INVENTION According to the present invention, it is possible to make the bead density of the laser welded portion uniform near the start point and the end point of welding, eliminate the welding defects caused by the conventional excessive density, and achieve extremely high reliability. It is possible to obtain a high rectangular battery. At the same time, since the total number of laser oscillations per battery can be reduced, the life of expensive laser-excited lamps can be extended and the production cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of a method for welding a prismatic battery using a laser, and FIGS. 2 to 4 are pattern diagrams of pulsed laser welding, of which FIG. 2 is a conventional method, FIGS. The figure shows the method according to the invention. 1 ... Case, 2 ... Lid 3 ... Fitting part, 4 ... Laser 5 ... Bead

 ─────────────────────────────────────────────────── --Continued from the front page Judgment panel for referees Judge Kozo Matsuura Judge Nakajima Kiyoshi Judge Mitsuo Sugaya (56) )

Claims (2)

[Claims] 1. A step of welding a fitting part with a pulse type laser welding machine while fitting a lid in an opening of a rectangular case and moving it with an XY table, wherein in the step, distances of all the welding parts are provided. This is a method of manufacturing a prismatic battery in which the number of laser irradiations per hit is constant, and in order to keep the number of laser irradiations per distance at all the welded parts constant, the extra feed section of the XY table is set to the starting point of the welding section. By providing it at the front and after the end point, the movement speed of the XY table is controlled to be constant at all the welded parts, and the laser oscillation ratio with time of the pulse laser welder is made constant. Battery manufacturing method. 2. A step of welding the fitting portion with a pulse type laser welding machine while fitting a lid in the opening of the rectangular case and moving the lid with an XY table, wherein in the step, distances of all the welding portions are provided. A method of manufacturing a prismatic battery in which the number of laser irradiations per hit is constant, and in order to keep the number of laser irradiations per distance across all welded parts constant, a pulse laser welder is used in proportion to the movement distance of the XY table. A method of manufacturing a prismatic battery, which is characterized by controlling the laser oscillation frequency.