Welding method and laser device

Abstract

The invention is suitable for the technical field of laser processing, and provides a welding method and a laser device.According to the welding method, a flat nail is welded to a cover plate of a battery cell through annular laser beams emitted by the laser device, the annular laser beams comprise the first laser beam and the second laser beam, the first laser beam is a center point laser beam, and the second laser beam is a center point laser beam; the second laser beam is a hollow ring laser beam, and the first laser beam is located in the second laser beam; the first laser beam and the second laser beam emit light periodically and synchronously, and the peak pulse width of the second laser beam is larger than that of the first laser beam. According to the embodiment, the surface cracking probability of the flat nail can be reduced, the number of cracks generated in the welding process is reduced, and the welding quality is improved.

Description

Technical Field

[0001] The present application relates to the field of laser processing technology, and in particular to a welding method and a laser device. Background Art

[0002] With the rapid development of new energy vehicles, the market demand for power batteries that power new energy vehicles is also increasing.

[0003] When producing power batteries, it is necessary to inject electrolyte into the battery cell through the injection hole, then put the flat nail into the injection hole, and then weld the flat nail to the battery cell. However, when welding the flat nail, the thermal stress generated by welding cannot be released in time, resulting in cracks when welding the flat nail, affecting the welding quality of the flat nail, and thus affecting the production quality of the power battery. Summary of the invention

[0004] The embodiments of the present application provide a welding method and a laser device, which can reduce cracks generated when welding flat nails.

[0005] In a first aspect, an embodiment of the present application provides a welding method, which welds a flat nail to a cover plate of a battery cell by using an annular laser beam emitted by a laser device; the annular laser beam includes a first laser beam and a second laser beam, the first laser beam is a center point laser beam, the second laser beam is a hollow ring laser beam, and the first laser beam is located within the second laser beam; the first laser beam and the second laser beam emit light periodically and synchronously, and the peak pulse width of the second laser beam is greater than the peak pulse width of the first laser beam.

[0006] In some possible implementations of the first aspect, within the same light emission period, the pulse width of the first laser beam includes a first rising pulse width t1, a first peak pulse width t2, a first falling pulse width t3, and a second falling pulse width t4 in sequence; the first peak pulse width t2 corresponds to a first peak power p1;

[0007] The pulse width of the second laser beam includes a second rising pulse width T1, a second peak pulse width T2 and a third falling pulse width T3 in sequence; the second peak pulse width T2 corresponds to a second peak power P1;

[0008] Among them, t1+t2+t3<T1+T2, p1<P1.

[0009] In some possible implementations of the first aspect, t1+t2+t3+t4<T1+T2+T3.

[0010] In some possible implementations of the first aspect, the difference between the peak pulse width of the second laser beam and the peak pulse width of the first laser beam is 1 ms-3 ms.

[0011] In some possible implementations of the first aspect, a ratio of a scanning speed of the first laser beam to an emission frequency of the first laser beam is 1:1.67-1:3.

[0012] In some possible implementations of the first aspect, a scanning speed of the first laser beam is 10 mm / s-60 mm / s, and a light emission frequency of the first laser beam is 20 Hz-100 Hz.

[0013] In some possible implementations of the first aspect, a ratio of the power of the first laser beam to the power of the second laser beam is 1:1.5-1:3.

[0014] In some possible implementations of the first aspect, the power of the first laser beam is 600W-1400W, and the power of the second laser beam is 1000W-1800W.

[0015] In some possible implementations of the first aspect, the emission frequency of the second laser beam is an integer multiple of the emission frequency of the first laser beam.

[0016] In some possible implementations of the first aspect, the emission frequency of the second laser beam is twice the emission frequency of the first laser beam.

[0017] In a second aspect, an embodiment of the present application provides a laser device, which is used to weld the flat nail to the cover plate of the battery cell by a welding method as described in any of the above technical solutions.

[0018] In some possible implementations of the second aspect, the collimation focal length of the laser device is 100 mm, and the focusing focal length of the welding method is 200 mm; the laser device comprises:

[0019] An inner core, the core diameter of the inner core is 30 μm or 50 μm, and the inner core is used to emit the first laser beam;

[0020] The outer core has a core diameter of 300 or 460 μm and is used to emit the second laser beam.

[0021] The welding method and laser device provided in the embodiment of the present application, the annular laser beam includes a first laser beam and a second laser beam; the first laser beam is a center point laser beam, the second laser beam is a hollow ring laser beam, and the first laser beam is located in the second laser beam; the first laser beam and the second laser beam emit light periodically and synchronously, and the peak pulse width of the second laser beam is greater than the peak pulse width of the first laser beam; so that when the flat nail is laser welded to the cover of the battery cell, when the power of the first laser beam decreases or is zero, the second laser beam still has a relatively high power, so that the second laser beam plays a role of slow cooling; thereby, the existence time of molten metal during welding can be extended, the temperature gradient can be reduced, and thermal stress can be reduced; therefore, the probability of cracking on the surface of the flat nail can be reduced, the number of cracks generated during welding can be reduced, and the welding quality can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0023] Figure 1 A pulse waveform diagram of the first laser beam and the second laser beam in an embodiment of the welding method of the present application;

[0024] Figure 2 This is a pulse waveform diagram of the first laser beam and the second laser beam in another embodiment of the welding method of the present application.

[0025] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0027] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0028] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0029] It should be understood that the term “and / or” used in the specification and appended claims of this application refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0031] The embodiments of the present application provide a welding method and a laser device for solving the technical problem of many welding cracks when welding flat nails to battery cells.

[0032] In an embodiment of the present application, the welding method welds the flat nail to the cover plate of the battery cell by an annular laser beam emitted by a laser device. The annular laser beam includes a first laser beam and a second laser beam, the first laser beam is a center point laser beam, the second laser beam is a hollow ring laser beam, and the first laser beam is located in the second laser beam. The first laser beam and the second laser beam periodically emit light synchronously, and the peak pulse width of the second laser beam is greater than the peak pulse width of the first laser beam.

[0033] In the process of producing battery cells, a liquid injection hole is opened on the cover of the battery cell to inject electrolyte into the battery cell through the liquid injection hole. After the liquid injection is completed, a flat nail needs to be inserted into the liquid injection hole, and then the laser device emits a first laser beam and a second laser beam to weld the flat nail to the cover of the battery cell to achieve the sealing of the battery cell.

[0034] In this embodiment, the laser device may be a ring laser.

[0035] The laser device of the embodiment of the present application is used to emit an annular laser beam, which includes a first laser beam and a second laser beam; the first laser beam is a center point laser beam, the second laser beam is a hollow ring laser beam, and the first laser beam is located in the second laser beam; the first laser beam and the second laser beam emit light periodically and synchronously, and the peak pulse width of the second laser beam is greater than the peak pulse width of the first laser beam; so that when the flat nail is laser welded to the cover of the battery cell, when the power of the first laser beam decreases or is zero, the second laser beam still has a relatively high power, so that the second laser beam plays a role of slow cooling; thereby, the existence time of the molten metal during welding can be extended, and the temperature gradient can be reduced, so as to reduce thermal stress; therefore, the probability of cracking on the surface of the flat nail can be reduced, the number of cracks generated during welding can be reduced, and the welding quality can be improved.

[0036] In one embodiment, if Figure 1 As shown, in the same light emission period, the pulse width of the first laser beam includes the first rising pulse width t1, the first peak pulse width t2, the first falling pulse width t3, and the second falling pulse width t4 in sequence; the first peak pulse width t2 corresponds to the first peak power p1. The pulse width of the second laser beam includes the second rising pulse width T1, the second peak pulse width T2, and the third falling pulse width T3 in sequence; the second peak pulse width T2 corresponds to the second peak power P1. Among them, t1+t2+t3<T1+T2, p1<P1.

[0037] like Figure 1 As shown, Figure 1 The pulse waveform diagram of the first laser beam and the second laser beam when the first laser beam and the second laser beam emit light synchronously. Between t1+t2 and t1+t2+t3, the first peak power p1 of the first laser beam begins to decrease. The power of the second laser beam does not change, and is still the second peak power P1; and p1<P1. Therefore, between t1+t2 and t1+t2+t3, the second laser beam has a slow cooling effect, which can reduce the temperature gradient and thus reduce thermal stress.

[0038] In one embodiment, if Figure 1 and Figure 2 As shown, t1+t2+t3+t4<T1+T2+T3. After t1+t2+t3+t4, the power of the first laser beam is zero, that is, the first laser beam does not emit light at this time. However, the power of the second laser beam is not zero, that is, the second laser beam continues to emit light. Therefore, the second laser beam has a slow cooling effect, which can reduce the temperature gradient and thus reduce thermal stress.

[0039] In this embodiment, Figure 2 The pulse waveform diagram of the first laser beam and the second laser beam when the first laser beam and the second laser beam emit light periodically and synchronously, and the emission frequency of the second laser beam is twice the emission frequency of the first laser beam.

[0040] In one embodiment, the difference between the peak pulse width of the second laser beam and the peak pulse width of the first laser beam is 1ms-3ms. When the difference in the peak pulse width is within the range of 1ms-3ms, the probability of cracking on the flat nail surface can be further reduced, the number of cracks generated during welding can be reduced, and the welding quality can be improved.

[0041] In one embodiment, the ratio of the scanning speed of the first laser beam to the light emission frequency of the first laser beam is 1:1.67-1:3. When the ratio is within the range of 1:1.67-1:3, the probability of cracking on the flat nail surface can be further reduced, the number of cracks generated during welding can be reduced, and the welding quality can be improved.

[0042] It can be understood that the relative position of the light spot of the first laser beam and the light spot of the second laser beam remains unchanged, so the scanning speed of the first laser beam is the same as the scanning speed of the second laser beam.

[0043] In one embodiment, the scanning speed of the first laser beam is 10 mm / s-60 mm / s, and the light emission frequency of the first laser beam is 20 Hz-100 Hz, which can reduce the probability of cracking on the flat nail surface, reduce the number of cracks generated during welding, and improve welding quality.

[0044] In one embodiment, the ratio of the power of the first laser beam to the power of the second laser beam is 1:1.67-1:3. When the ratio is within the range of 1:1.5-1:3, the probability of cracking on the flat nail surface can be further reduced, the number of cracks generated during welding can be reduced, and the welding quality can be improved.

[0045] In one embodiment, the power of the first laser beam is 600 W-1400 W, and the power of the second laser beam is 1000 W-1800 W. The probability of cracking on the flat nail surface can be reduced, the number of cracks generated during welding can be reduced, and the welding quality can be improved.

[0046] In one embodiment, the emission frequency of the second laser beam is an integral multiple of the emission frequency of the first laser beam, which can reduce the probability of cracking on the flat nail surface, reduce the number of cracks generated during welding, and improve welding quality.

[0047] In one embodiment, the emission frequency of the second laser beam is twice the emission frequency of the first laser beam, which can further reduce the probability of cracking on the flat nail surface, reduce the number of cracks generated during welding, and improve welding quality.

[0048] like Figure 2 As shown in FIG. 1 , after t1+t2+t3+t4, the power of the first laser beam is zero, that is, the first laser beam does not emit light at this time. However, the power of the second laser beam is not zero, that is, the second laser beam continues to emit light, so the second laser beam has a slow cooling effect, which can reduce the temperature gradient and thus reduce thermal stress.

[0049] In addition, an embodiment of the present application further provides a laser device, which is used to weld the flat nail to the cover plate of the battery cell by a welding method as described in any of the above embodiments.

[0050] In one embodiment, the collimation focal length of the laser device is 100 mm, and the focusing focal length of the laser device is 200 mm. The laser device includes an inner core and an outer core, the core diameter of the inner core is 30 μm or 50 μm, and the inner core is used to emit a first laser beam. The core diameter of the outer core is 300 μm or 460 μm, and the outer core is used to emit a second laser beam. The probability of cracking on the surface of the flat nail can be reduced, the number of cracks generated during welding can be reduced, and the welding quality of welding the flat nail to the battery core can be improved.

[0051] The above description is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural changes made by using the contents of the present application specification and drawings under the inventive concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A welding method, characterized in that: The welding method welds a flat nail to a cover plate of a battery cell by using an annular laser beam emitted by a laser device; the annular laser beam includes a first laser beam and a second laser beam, the first laser beam is a center point laser beam, the second laser beam is a hollow ring laser beam, and the first laser beam is located within the second laser beam; the first laser beam and the second laser beam emit light periodically and synchronously, and the peak pulse width of the second laser beam is greater than the peak pulse width of the first laser beam.

2. The welding method according to claim 1, characterized in that In the same light emission period, the pulse width of the first laser beam includes a first rising pulse width t1, a first peak pulse width t2, a first falling pulse width t3, and a second falling pulse width t4 in sequence; the first peak pulse width t2 corresponds to a first peak power p1; The pulse width of the second laser beam includes a second rising pulse width T1, a second peak pulse width T2 and a third falling pulse width T3 in sequence; the second peak pulse width T2 corresponds to a second peak power P1; Among them, t1+t2+t3<T1+T2, p1<P1.

3. The welding method according to claim 2, characterized in that: t1+t2+t3+t4<T1+T2+T3.

4. The welding method according to claim 1, characterized in that: The difference between the peak pulse width of the second laser beam and the peak pulse width of the first laser beam is 1 ms-3 ms.

5. The welding method according to claim 1, characterized in that: The ratio of the scanning speed of the first laser beam to the light emission frequency of the first laser beam is 1:1.67-1:

3.

6. The welding method according to claim 5, characterized in that: The scanning speed of the first laser beam is 10 mm / s-60 mm / s, and the light emission frequency of the first laser beam is 20 Hz-100 Hz.

7. The welding method according to claim 1, characterized in that: The ratio of the power of the first laser beam to the power of the second laser beam is 1:1.5-1:

3.

8. The welding method according to claim 7, characterized in that: The power of the first laser beam is 600W-1400W, and the power of the second laser beam is 1000W-1800W.

9. The welding method according to claim 1, characterized in that: The emission frequency of the second laser beam is an integer multiple of the emission frequency of the first laser beam.

10. The welding method according to claim 9, characterized in that: The emission frequency of the second laser beam is twice the emission frequency of the first laser beam.

11. A laser device, characterized in that: The laser device is used to weld the flat nail to the cover plate of the battery cell by the welding method according to any one of claims 1 to 10.

12. The laser device according to claim 11, characterized in that The collimation focal length of the laser device is 100 mm, and the focusing focal length of the welding method is 200 mm; the laser device comprises: An inner core, the core diameter of the inner core is 30 μm or 50 μm, and the inner core is used to emit the first laser beam; The outer core has a core diameter of 300 or 460 μm and is used to emit the second laser beam.

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