JP4346464B2 - Leak detection device - Google Patents

Description

  The present invention relates to an apparatus that acquires fluorescence obtained from plasma and identifies the type of an inspection object, and more particularly to a leak detection apparatus that detects whether or not an element having a small element number has leaked from a sealed structure.

  In general, a lithium (Li) secondary battery is known as a product containing a liquid in a container. When manufacturing a lithium secondary battery, a lithium electrolyte is accommodated in a container, and the container containing the lithium electrolyte is welded and sealed. Thereafter, the weld is inspected for leakage of the lithium electrolyte. When the inspection is performed, a microscope or the like is used, and a large number of personnel are used to determine the presence or absence of visual solution leakage. By performing the inspection as described above, it is required to provide a lithium secondary battery that does not leak.

On the other hand, it has been proposed to analyze elements from the emission of plasma generated by condensing and irradiating a sample with a laser, for example, in the analysis of flue gas from industrial plants and harmful substances contained in wastewater (for example, patent documents) 1).
JP 2000-310596 A

By the way, in the case of performing the above-described inspection, there are a large number of manufactured products in addition to visually determining the presence or absence of solution leakage. For this reason, the labor cost increases due to the prolonged inspection time, and the determination of the presence or absence of liquid leakage occurs. Here, since the leakage itself may be due to a change with time, it does not matter that it needs to be left to some extent.
The present invention has been made in view of the above points, and an object thereof is to provide a leak detection apparatus having excellent leak detection accuracy.

In order to solve the above-described problems, a leak detection apparatus according to an aspect of the present invention includes a YAG laser oscillator that outputs pulsed laser light, the pulsed laser light is condensed, and an energy density of 5 J / cm ² to 25 J / cm ^2. the converging and irradiating means for irradiating power intensity to 0.83GW / cm ² without the pulsed laser beam with 4.2GW / cm ² in a rechargeable lithium battery table surface, included in the irradiated rechargeable lithium battery lithium Hara and fluorescence condensing means for fluorescence condensing light emitted from the child, and fluorescence spectrometry means for quantifying the elements contained in the prior SL lithium secondary battery from the wavelength and intensity that the condensing fluorescence that, has, before Symbol rechargeable lithium battery is sealable lithium electrolyte therein, the pulsed laser beam is irradiated to the lithium secondary battery table surface, presence or absence of leakage of the lithium electrolyte It is characterized by sensing.

  According to the present invention, it is possible to provide a leak detection device with excellent leak detection accuracy.

Hereinafter, an embodiment in which the leakage detection device of the present invention is used for detection of leakage of a lithium secondary battery will be described with reference to the drawings.
As shown in FIG. 1, the leak detection apparatus includes a condensing irradiation unit 1, a fluorescence condensing unit 2, and a fluorescence spectroscopic measurement unit 3. The focused irradiation means 1 irradiates an Ed: YAG laser oscillator 10 as an oscillator, a laser transmission means 20 for transmitting pulse laser light output from the YAG laser oscillator to the surface of the inspection object, and the surface of the inspection object. It has a slider 30 as scanning means for scanning the condensing point of the pulse laser beam.

  The laser transmission means 20 includes a transmission mirror 21 serving as a distribution optical system that distributes the pulse laser light output from the YAG laser oscillator 10, and the pulse laser light is incident on the transmission laser 21 through the transmission mirror. The incident optical system 22 for condensing, the laser transmission optical fiber 23 for transmitting the pulse laser beam condensed by the incident optical system to the surface of the inspection object, and the pulse laser beam transmitted by the laser transmission optical fiber for inspection It has the condensing optical system 24 which condenses and irradiates the object surface.

  Here, the pulse laser beam is generated at a predetermined timing by a main controller (not shown), and is output from the YAG laser oscillator 10 with a predetermined pulse width based on the drive pulse. In this embodiment, the condensing irradiation means 1 has a plurality of laser transmission means 20, for example, eight sets. From the above, the pulsed laser light is collected by the focused irradiation means 1 and irradiated onto the surface of the inspection object. Further, the pulse laser beam is branched by the transmission mirror 21 and irradiated to a plurality of locations.

  The fluorescence condensing means 2 atomizes and plasmas the inspection object, and condenses unique fluorescence (spectrum including fluorescence) emitted (radiated) from each element present in the inspection object. Here, the operation of the fluorescence condensing means 2 is controlled by a timing adjustment mechanism (not shown). For this reason, the fluorescence emitted from the atoms contained in the irradiated inspection object is collected by the fluorescence collecting means 2.

  The fluorescence spectroscopic measuring means 3 separates the fluorescence (light) into spectral components and the like, measures the spectrum specific to the element contained in the inspection object, etc., and photoelectrically converts the measured spectrum, and the fluorescence condensing means 2 has a fluorescence transmission optical fiber 40 that transmits the fluorescence collected in 2 to the spectroscope, and a determination device 60 that is supplied with the spectrum photoelectrically converted by the spectroscope and quantifies the elements contained in the inspection object. . For this reason, the element contained in the test object can be quantified by the fluorescence spectroscopic measuring means 3 from the wavelength of the condensed fluorescence and the intensity at the wavelength.

  Next, the configuration of the lithium secondary battery will be described. As shown in FIG. 2, a lithium secondary battery 100 as a casing has a container 101 made of aluminum and a lid 102 made of aluminum, and these containers and the lid are welded along a weld line A which is a welded portion. ing. That is, the lithium electrolyte solution can be sealed inside the lithium secondary battery 100. The lithium secondary battery 100 contains a lithium electrolyte as a liquid.

  Here, when there is an insufficiently welded portion such as a crack or a pinhole at the joint portion of the lithium secondary battery 100 described above, the lithium electrolyte inside the lithium secondary battery may leak. When the lithium electrolyte leaks to the outside, white powder adheres to the location along the weld line A on the surface of the lithium secondary battery 100 due to the leaked lithium electrolyte. Moreover, when the location where welding is insufficient is small, white powder may not be confirmed.

Next, a method for inspecting a lithium secondary battery by detecting leakage of the lithium electrolyte in the lithium secondary battery 100 as the inspection object using the above-described leakage detection device will be described.
As shown in FIGS. 1 and 2, after the lithium secondary battery 100 is set at a predetermined position, the YAG laser oscillator 10 of the focused irradiation means 1 outputs a pulse laser beam. The output pulse laser beam is branched by each laser transmission means 20 and transmitted to the surface of the lithium secondary battery 100 by the laser transmission optical fiber 23.

  Thereafter, the pulsed laser light is condensed on the surface of the lithium secondary battery 100 by each condensing optical system 24 and irradiated to a plurality of locations. More specifically, the pulse laser beam is irradiated along the weld line A on the surface of the lithium secondary battery 100. Here, when the lithium electrolyte is leaking to the irradiation area along the weld line A, the lithium electrolyte that has leaked to the outside of the lithium secondary battery 100 and the aluminum on the surface of the lithium secondary battery 100 are turned into plasma by pulse laser light. Is done.

  The plasma starts recombination with the end of irradiation with the pulsed laser beam, and the constituent elements of the irradiated lithium secondary battery 100 become excited atoms for several μs to several tens of μs. When atoms in this excited state transition to the lower level, the atoms emit fluorescence proportional to the number of atoms.

  Thus, the laser transmission means 20 irradiates the pulse laser beam and scans the laser transmission means by the slider 30. For this reason, the pulse laser beam irradiated from the laser transmission means 20 is temporally scanned in the area along the welding line A on the surface of the lithium secondary battery 100 in the direction of an arrow, for example. More specifically, the pulse laser beam branched by each laser transmission means 20 is condensed and irradiated at a plurality of locations, and scanned by the pulse repetition frequency of these pulse laser beams.

  Further, when the fluorescence is emitted from the region along the weld line A on the surface of the lithium secondary battery 100, the fluorescence condensing means 2 is moved to the fluorescence condensing region to condense the fluorescence. The spectrum of the fluorescence condensed by the fluorescence condensing means 2 is measured by the spectroscope 50 via the fluorescence transmission optical fiber 40 of the fluorescence spectroscopic measuring means 3, and the element contained in the substance that has emitted the fluorescence by the determination device 60 is detected. Quantify. That is, when the lithium electrolyte leaks outside the lithium secondary battery 100, a spectrum unique to lithium contained in the lithium electrolyte is obtained.

  Then, all the regions along the weld line A on the surface of the lithium secondary battery 100 are irradiated with pulsed laser light, and the spectrum of the fluorescence emitted thereby is acquired by the determination device 60, and a spectrum unique to lithium is obtained. In this case, it can be seen that leakage of the lithium electrolyte occurs. Moreover, when the spectrum peculiar to lithium is not obtained, it turns out that the leakage of lithium electrolyte has not arisen. From the above, it is possible to detect the presence or absence of leakage of the lithium electrolyte. Note that the lithium secondary battery 100 in which leakage of the lithium electrolyte has occurred is discarded.

  According to the leakage detection apparatus configured as described above, the surface of the lithium secondary battery 100 is irradiated with pulsed laser light to detect the presence or absence of lithium electrolyte leakage. Thus, even when a technique for measuring the fluorescence generated by the pulse laser beam is applied, leakage of the lithium electrolyte from the welded portion of the lithium secondary battery 100 can be detected. Since lithium has good sensitivity and strong fluorescence, even a slight leakage of lithium electrolyte can be detected with high accuracy.

  Since the measurement method requires almost no pretreatment, it is more efficient than the case where leakage of the lithium electrolyte is detected by visual observation with a microscope. Moreover, the method can test | inspect the soundness of many lithium secondary batteries 100 in a short time, and can test | inspect continuously per one lithium secondary battery within several seconds.

The pulsed laser light is condensed and irradiated at a plurality of locations, and the surface of the lithium secondary battery 100 is temporally scanned. More specifically, scanning is performed for the pulse repetition frequency of these pulsed laser beams. For this reason, leakage of the lithium electrolyte can be detected more efficiently.
As described above, the leakage of the lithium electrolyte that occurs in the lithium secondary battery can be performed inexpensively and efficiently with high sensitivity and high accuracy.

Furthermore, the inventor of the present application investigated the accuracy of leakage detection of the lithium secondary battery 100 when the irradiation condition of the pulse laser beam was changed.
As shown in FIG. 3, it can be seen that the measurement sensitivity of the fluorescence intensity is low when the pulse laser beam with a condensing diameter of φ0.5 mm is irradiated and the irradiation energy of the pulse laser beam is less than 20 mJ. This is because the background strength is high. Further, it is clear that when the irradiation energy of the pulse laser beam exceeds 50 mJ, the container 101 and the lid 102 made of aluminum constituting the lithium secondary battery 100 are seriously damaged. From the above, the irradiation energy of the condensed pulsed laser light is selected from 20 mJ to 50 mJ based on the measurement sensitivity of the fluorescence intensity, the background intensity, and the damage of the lithium secondary battery 100.

As described above, if 20mJ to 50mJ was selected as the irradiation energy, irradiation energy density condensed from Atsumariko径0.5 mm in diameter, to 5 J / cm ² without the 25 J / cm ^2. The power intensity of the pulsed laser light is from 0.83 GW / cm ² to 4.2 GW / cm ² from a pulse width of 6 sec ^.
As shown in FIG. 4, the condensing diameter of the pulsed laser beam is reduced and irradiated to a large number of locations along the weld line A of the lithium secondary battery 100, and the fluorescence emitted from these numerous locations is measured. In this case, it is understood that useless irradiation energy from the weld line in the width direction can be reduced.

Next, a case where the condensed diameter of the pulse laser beam is changed will be described.
The condensed diameter D of the pulsed laser light is expressed by the following relational expression (1) from the inspection length L necessary for leakage detection, the repetition frequency Q of the YAG laser oscillator, the detection determination time S, and the number of branches (number of condensed light) n. Can be shown.
L = Q × S × D × n ------ (1)
For example, when the inspection length L required for leakage detection is 40 mm, the frequency Q is 10 Hz, and the detection determination time S is 1 sec, the number of branches n is 10 (units), the condensing diameter D is φ0.4 mm, and the irradiation energy is 12.8mJ is required. It can be seen that if the condensing diameter D is reduced, the number of branches n or the frequency Q needs to be increased, which is expensive.

Here, FIG. 4 shows the relationship among the irradiation energy, the total irradiation energy, the number of branches (number of branches) n, and the light collection area with respect to the light collection diameter Q when the frequency Q is 10 Hz.
As shown in this figure, for example, if the condensing diameter is ½, φ0.2 mm, it is necessary to double the number of branches n or the frequency Q, and when only the number of branches is increased, 20 (units). Become. If the condensing diameter D is 1.5 times as large as φ0.6 mm, the number of branches n can be reduced to 7 (units) of 1 / 1.5, but the required irradiation energy is about 2.25 times 29 mJ, The total irradiation energy is 193 mJ, which is about 1.5 times as much. Here, when the light collection diameter D is φ0.5 mm, the number of branches n is 8, the irradiation energy is about 20 mJ, and the total irradiation energy is 160 mJ, which is about 1.25 times.

  Further, when the frequency Q is 20 Hz, there is an advantage that the number of branches n can be reduced. However, it has been found that this increase in frequency makes the YAG laser oscillator 10 expensive. Furthermore, a YAG oscillator that generally obtains a large output at a high repetition rate of 10 Hz or more requires a new development technique such as cooling and becomes expensive.

  From the above, if the condensing diameter D is selected to be 0.2 mm or more, the number of branches n is 20 (units) or less, and the total irradiation energy (oscillator output) is 250 mJ or less, the condensing diameter D is 0.2 mm or less. A range of 0.8 mm is selected.

Further, when the required total irradiation energy is P and the irradiation energy density required for measurement using the spectroscope 50 is E, it can be expressed by the following relational expression (2).
P = E × D ² × π / 4 × n ------ (2)
If the required irradiation energy density E is 15 J / cm2, the condensing diameter D is 0.4 mm, and the number of branches n is 10 (units), the total irradiation energy P is about 190 mJ. When the irradiation energy density E is increased in order to increase the intensity of the fluorescence, it is necessary to increase the total irradiation energy P, which is expensive. From the above, it can be seen that the optimum system for detecting the leakage of lithium electrolyte is selected according to the required irradiation energy density E and the like.

  Next, the range in which the pulse laser beam is irradiated will be described. As shown in FIG. 2, in the region along the weld line A of the lithium secondary battery 100, when the leakage of the lithium electrolyte is very small, a trace of leakage is seen in a range R within about 1 mm from the weld line. For this reason, it is understood that it is best to irradiate the pulse laser beam in a range R within 2 mm from the weld line A.

Next, the number of times of irradiation with pulsed laser light will be described.
As shown in FIG. 6, when the pulse laser beam was irradiated to the same location, it became clear that the fluorescence intensity of lithium fell. That is, this decrease in fluorescence intensity is because the amount of leaked lithium electrolyte solution is small, and therefore, if the pulse laser beam is irradiated much, the lithium electrolyte solution disappears due to evaporation or scattering. From the above, it is important to irradiate the same location within 10 times with the pulse laser beam.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention. For example, as shown in FIG. 7, the leakage of the lithium electrolyte may be detected by using a leakage detection device having a configuration in which two sets of the YAG laser oscillator 10 and the fluorescence condensing means 2 described above are provided. By configuring the leak detection device as described above, the soundness of a large number of lithium secondary batteries 100 can be inspected in a shorter time.

  The laser transmission optical fiber 23 and the fluorescence transmission optical fiber 40 described above are configured by optical fibers. However, the present invention is not limited to this, and the same effect (system) as that of the above-described embodiment can be obtained as long as other transmission optical systems are used. It is done. The focused irradiation means 1 only needs to have at least one set of laser transmission means 20. Moreover, although the leak diameter apparatus mentioned above demonstrated the case where it used for the detection of the leak of the lithium electrolyte solution of the lithium secondary battery 100, it is not restricted to lithium, Na, Mg, Al, K, Ca, Mn, Ga , Sr, Y, In, Ba, Pt, Pb, and the like can detect these leaks satisfactorily.

1 is a schematic diagram of a leak detection apparatus according to an embodiment of the present invention. The figure which showed the lithium secondary battery test | inspected using the leak detection apparatus shown in FIG. The figure which showed the change of the fluorescence intensity with respect to the irradiation energy of a pulse laser. Schematic which showed the condensing point of the condensed pulse laser. The figure which showed each change of the total irradiation energy of a pulse laser with respect to the condensing diameter of the condensing location of a pulse laser, the irradiation energy of a pulse laser, the number of branches of a pulse laser, and the condensing area of a pulse laser. The figure which showed the fluorescence intensity with respect to the frequency | count of irradiation of a pulse laser. Schematic of the leak detection apparatus which concerns on other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Condensing irradiation means, 2 ... Fluorescence condensing means, 3 ... Fluorescence spectroscopy measurement means, 10 ... YAG laser oscillator, 20 ... Laser transmission means, 21 ... Transmission mirror, 22 ... Incident optical system, 23 ... Laser transmission optical fiber 24 ... Condensing optical system, 30 ... Slider, 40 ... Fluorescence transmission optical fiber, 50 ... Spectroscope, 60 ... Determination device, 100 ... Lithium secondary battery, A ... Welding line.

Claims (8)

A YAG laser oscillator that outputs pulsed laser light;
The pulsed laser beam is condensed, to no 5 J / cm ² energy density 25 J / cm ^2, 2 batteries Table lithium said pulsed laser beam to 0.83GW / cm ² no was 4.2GW / cm ² power intensity Condensing irradiation means for irradiating the surface;
A fluorescence condensing means for fluorescence condensing light emitted from the lithium atom of the Ru contained in irradiated lithium secondary battery,
Anda fluorescence spectrometry means for quantifying the elements contained in the previous SL lithium secondary battery from the wavelength and intensity thereof of the fluorescence, which is the focused beam,
Before SL rechargeable lithium battery is sealable lithium electrolyte therein, the pulsed laser beam is irradiated to the lithium secondary battery table surface, and detecting the presence or absence of leakage of the lithium electrolyte Leak detection device. The leak detection apparatus according to claim 1, wherein a condensed diameter of the pulsed laser light that is condensed and irradiated is 0.2 mm or more . The leak detection device according to claim 2, wherein a condensed diameter of the pulsed laser light that is condensed and irradiated is 0.8 mm or less . The leakage detection apparatus according to claim 1, wherein the irradiation energy of the pulsed laser light that is condensed and irradiated is 20 mJ to 50 mJ . 2. The leakage according to claim 1 , wherein the pulsed laser beam having a welded portion on the surface of the lithium secondary battery is irradiated within the range of 2 mm from the welded portion. Detection device. The focused irradiation means has a plurality of laser transmission optical fibers,
2. The leakage according to claim 1, wherein the pulse laser beam is branched and irradiated to a plurality of locations, and each pulse laser beam is transmitted to the surface of the lithium secondary battery by the laser transmission optical fiber. Detection device. Further comprising scanning means;
The condensing irradiation means has a distribution optical system for branching the pulsed laser light and condensing and irradiating a plurality of places.
The inspection length required for detecting the leakage of the lithium secondary battery surface is L, the detection judgment time is S, the number of branches of the pulse laser beam is n, the focused diameter of the pulse laser beam is D, and the YAG laser oscillator is repeated. If the frequency is Q,
L = Q × S × D × n,
The leakage detection apparatus according to claim 1, wherein the scanning unit sequentially irradiates the pulse laser beam to a plurality of locations on the surface of the lithium secondary battery so as to satisfy the relational expression . The leak detection apparatus according to claim 1, wherein the pulse laser beam that is condensed and irradiated is irradiated to the same portion within 10 times .

Images