Title of Invention: Welding Condition Inspection Device
technical field
[One]
This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0026135 dated March 2, 2020, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification.
[2]
The present invention relates to an apparatus for inspecting a welding state in a welding part for electrical connection or mechanical fastening in a lithium secondary battery, and more particularly, to a weak welding of a welding part of an electrode tab and an electrode tab or a welding part of an electrode tab and an electrode lead It relates to a device for checking whether or not
background
[3]
In general, a secondary battery means a battery that can be charged and discharged, unlike a primary battery that cannot be charged, and is widely used in electronic devices such as mobile phones, notebook computers, camcorders, etc. or electric vehicles. In particular, since the lithium secondary battery has a larger capacity than a nickel-cadmium battery or a nickel-hydrogen battery and has a high energy density per unit weight, the degree of its utilization is rapidly increasing.
[4]
On the other hand, lithium secondary batteries are classified according to the structure of the electrode assembly of the positive electrode/separator/negative electrode structure. Typically, a jelly-like structure in which a long sheet-type positive electrode and negative electrode are wound with a separator interposed therebetween. A roll electrode assembly, a stacked electrode assembly in which a plurality of positive and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, a bi-cell in which positive and negative electrodes of a predetermined unit are stacked with a separator interposed therebetween; or and a stack/folding type electrode assembly having a structure in which full cells are wound.
[5]
Recently, a pouch-type battery having a structure in which a stack-type or stack/folding-type electrode assembly is embedded in a pouch-type battery case of an aluminum laminate sheet has attracted a lot of attention due to low manufacturing cost, small weight, easy deformation, etc. and its use is gradually increasing.
[6]
Such a lithium secondary battery mainly uses a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. A lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate to which the positive electrode active material and the negative electrode active material are applied, respectively, are disposed with a separator interposed therebetween, and a packaging material for sealing and housing the electrode assembly together with an electrolyte.
[7]
At this time, a plurality of positive electrode tabs extending from the plurality of positive electrode plates and a plurality of negative electrode tabs extending from the plurality of negative electrode plates are formed in the electrode assembly, and the plurality of positive electrode tabs and the plurality of negative electrode tabs are respectively a positive electrode lead and a negative electrode The lead is welded together. Here, a plurality of positive electrode tabs and a plurality of negative electrode tabs constitute an electrode tab, and a positive electrode lead and a negative electrode lead constitute an electrode lead.
[8]
In this way, when welding the electrode tab and the electrode lead, if the welding between the electrode tab and the electrode tab and between the electrode tab and the electrode lead is weakly performed, a welding defect occurs. process is needed
[9]
As a method for inspecting weak welding defects of a weld, conventionally, a method of measuring the tensile strength by pulling the welded part in the opposite direction with respect to the welded object was used. However, in this method, since the electrode tab or the electrode lead is damaged in the process of measuring the tensile strength, there is a limit in which full investigation is impossible.
[10]
Accordingly, there is a need to develop a technology for an inspection device with excellent detection power while allowing full investigation in inspecting whether a weld is weakly welded.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[11]
Accordingly, the present invention has been devised to solve the above problems, and in detecting weak welding defects of the welded part, it is to provide an inspection apparatus excellent in defect detection power while allowing full investigation.
means of solving the problem
[12]
The welding state inspection apparatus of the present invention for achieving the above object is an apparatus for inspecting a welding state in a welding part for electrical connection or mechanical fastening in a lithium secondary battery, and by contacting a resistance measuring probe on the welding part to a measurement unit for obtaining data for deriving a resistance value; and a control unit communicating with the measuring unit, receiving data obtained from the measuring unit, determining a resistance value in the welding unit, and comparing the determined resistance value with a critical resistance value to determine whether or not welding is weak, wherein the measuring unit comprises: , characterized in that the resistance measuring probe is configured to be in contact with one end and the other end of the welding part.
[13]
In one specific example, when the determined resistance value exceeds the threshold resistance value, the control unit determines that the welding is weak.
[14]
In one specific example, the measuring unit, a flat-type cradle on which the subject is mounted; an upper plate having a predetermined separation distance from the cradle and having a plurality of through-holes through which a resistance measuring probe can be inserted; a lower plate positioned at a lower portion having a predetermined separation distance from the cradle and having a plurality of through-holes through which a resistance measuring probe can be inserted; a coupling unit for coupling the cradle, the upper plate and the lower plate; and a pair of resistance measuring probes for contacting on the weld and acquiring data for determining a resistance value.
[15]
In one specific example, one resistance measuring probe includes a current probe and a resistance probe.
[16]
In one specific example, an upper guide member and a lower guide member for allowing the resistance measuring probe to be inserted into the proper position are coupled on the upper plate and the lower plate, respectively.
[17]
In one specific example, the upper guide member and the lower guide member each have a through hole through which a resistance measuring probe can be inserted, and the through hole of the upper guide member and the through hole of the upper plate are in a straight line. location, the resistance measuring probe is configured to penetrate them at the same time to access the upper surface of the weld, and the through-hole of the lower guide member and the through-hole of the lower plate are located in a straight line, so that the resistance measuring probe penetrates them and the lower surface of the weld configured to be accessible.
[18]
In one specific example, the coupling portion includes a coupling rod and a defective screw.
[19]
In one specific example, the holder, the upper plate, and the lower plate, each of which has a coupling hole formed in four corners, the coupling rod, the upper plate, the holder and the lower plate by sequentially passing through the respective coupling holes formed on the By being inserted, the upper plate, the cradle and the lower plate are configured to be engageable.
[20]
In one specific example, further comprising a compression spring for adjusting the separation distance between the holder and the upper plate and the separation distance between the holder and the lower plate, wherein the coupling rod is inserted into the hollow portion of the compression spring configured to be possible.
[21]
In one specific example, the control unit includes a threshold resistance value setting program for setting the threshold resistance value by processing the data obtained by the measurement unit for the sample group in a statistical manner.
[22]
In one specific example, resistance values ​​determined from data obtained for the sample group form a normal distribution curve.
[23]
In one specific example, the inspection apparatus of the present invention further includes an output unit for displaying the data obtained from the measurement unit and the resistance value of the welding unit determined by the control unit.
[24]
In one specific example, the test apparatus of the present invention further includes a power supply for applying power to the measurement unit, wherein the power supply is a DC power supply and is controlled by the control unit.
Effects of the Invention
[25]
The welding state inspection apparatus of the present invention measures the resistance of a sample group, sets a critical resistance value from a normal distribution curve of the measured resistance value, and when measuring the resistance of the sample group and the welding part to be inspected, the resolution is nanoohm It is possible to measure the fine resistance of the ohm level, so it has a very excellent effect in detecting weak welding defects.
Brief description of the drawing
[26]
BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the measuring part which comprises the welding state inspection apparatus of this invention.
[27]
FIG. 2 is a plan view of a cradle constituting the measurement unit of FIG. 1 .
[28]
3 is a plan view of an upper plate constituting the measurement unit of FIG. 1 .
[29]
4 is a coupling view of an upper plate and an upper guide member according to an embodiment of the present invention.
[30]
FIG. 5 is a front view of FIG. 1 ;
[31]
6 is a schematic diagram of a resistance measuring probe according to an embodiment of the present invention.
[32]
7 is a graph showing the correlation between welding strength and resistance.
[33]
8 is a schematic diagram illustrating a resistance measurement method according to an embodiment of the present invention.
[34]
9 is a schematic diagram illustrating a resistance measurement method according to another embodiment of the present invention.
Best mode for carrying out the invention
[35]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention.
[36]
Accordingly, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical spirit of the present invention, so at the time of the present application, various It should be understood that there may be equivalents and variations.
[37]
Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components unless otherwise stated.
[38]
[39]
The welding state inspection apparatus of the present invention is an apparatus for inspecting a welding state in a welding part for electrical connection or mechanical fastening in a lithium secondary battery, and data for deriving the resistance value of the welding part by contacting a resistance measuring probe on the welding part measuring unit to acquire; and a control unit communicating with the measuring unit, receiving data obtained from the measuring unit, determining a resistance value in the welding unit, and comparing the determined resistance value with a critical resistance value to determine whether or not welding is weak, wherein the measuring unit comprises: , characterized in that it is configured to be able to contact the resistance measuring probe to one end and the other end of the welding part.
[40]
6 is a schematic diagram of a resistance measuring probe according to an embodiment of the present invention. Referring to FIG. 6 , the resistance measuring probes 150 and 150 ′ of the present invention are configured as a pair, and a pair of current probes and Includes a pair of voltage probes. That is, one resistance measuring probe 150 includes a current probe 151 and a voltage probe 152 , and the other resistance measuring probe 150 ′ also includes a current probe 151 ′ and a voltage probe 152 ′. Therefore, it is possible to measure the resistance of the welded part using the 4-wire measurement method. The current probe applies a current to a welding part to be measured, and the voltage probe measures a voltage. Accordingly, the resistance value of the welding portion can be determined.
[41]
According to the present invention, data for determining a resistance value is obtained by bringing a pair of resistance measuring probes into contact with a welding part, and thus, it is possible to measure the resistance of the welding part by a four-wire measurement method. Since the 4-wire resistance measurement method is not affected by the contact resistance compared to the 2-wire resistance measurement method, it is possible to measure the fine resistance more precisely.
[42]
1 is a schematic diagram of a measuring unit 100 constituting a welding state inspection apparatus according to an embodiment of the present invention. Referring to FIG. 1 , the measuring unit 100 of the present invention includes a flat plate-type cradle 110 on which a subject is mounted; an upper plate having a predetermined separation distance from the cradle and having a plurality of through-holes through which a resistance measuring probe can be inserted; a lower plate 130 positioned at a lower portion having a predetermined separation distance from the cradle and having a plurality of through-holes through which a resistance measuring probe can be inserted; a coupling unit 140 for coupling the cradle, the upper plate and the lower plate; and a pair of resistance measuring probes 150 and 150' contacting on the weld and acquiring data for determining a resistance value.
[43]
The cradle 110 is a rectangular plate-shaped member on which an object to be inspected including a welding part to be inspected is seated, and the object to be inspected is mounted in a central portion. 2 is a plan view of a holder 110 according to an embodiment of the present invention. Referring to FIG. 2, the holder 110 of the present invention has a plurality of coupling holes 111 through which a coupling rod to be described later can be inserted, and And, these coupling holes are formed in the four corners of the cradle. In addition, a rectangular through-hole 112 is formed in the thickness direction of the cradle in a portion corresponding to the welding part of the subject so that the resistance measuring probe can contact the top and bottom surfaces of the welding part, A welding portion is positioned in the through hole 112 region.
[44]
The upper plate 120 is located at a point having a predetermined separation distance from the holder 110 in the vertical upper direction. The upper plate has a flat plate shape like the cradle, and has a plurality of through-holes through which a resistance measuring probe including a current probe and a voltage probe can be inserted. 3 is a plan view of an upper plate 120 according to an embodiment. Referring to FIG. 3 , the upper plate 120 of the present invention is a rectangular plate-shaped member, and coupling holes 121 are provided at each of the four corners. is formed, and a coupling rod (not shown) to be described later is inserted into these coupling holes. The upper plate 120 also has through-holes 122 into which a resistance measuring probe can be inserted. The plurality of through-holes are formed in portions corresponding to one end and the other end of the welding portion, and accordingly, the resistance measuring probe is accessible to the one end and the other end of the welding portion. In addition, the resistance measuring probe inserted into the upper plate may access the top of the welding part.
[45]
The lower plate 130 is positioned at a point having a predetermined separation distance from the holder 110 in the vertical lower direction. The lower plate is a rectangular flat member, and has a plurality of through-holes through which a resistance measuring probe can be inserted, like the upper plate. Each of the four corners of the lower plate is formed with coupling holes, and a coupling rod to be described later is inserted into these coupling holes. Like the upper plate, the lower plate has a plurality of through-holes into which the resistance measuring probe can be inserted, and these through-holes may be formed in portions corresponding to one end and the other end of the welding part. Thereby, the resistance measuring probe becomes accessible to one end and the other end of a welding part. And, the resistance measuring probe inserted into the lower plate may access the lower surface (back) of the welding part.
[46]
As described above, since the upper plate and the lower plate each include a plurality of through-holes into which the resistance measuring probe can be inserted, there is an advantage in that the insertion position of the resistance measuring probe can be appropriately adjusted according to the inspection position of the welding part.
[47]
Referring to FIG. 1 , an upper guide member 160 and a lower guide member (not shown) are respectively coupled to the upper plate 120 and the lower plate 130 . The upper guide member 160 and the lower guide member (not shown) function to allow the resistance measuring probe to be inserted into the correct position.
[48]
Hereinafter, the upper guide member will be described. 4 is a coupling view of an upper plate and an upper guide member according to an embodiment of the present invention. Referring to FIG. 4 , the upper guide member 160 includes a plurality of through-holes 161 through which a resistance measuring probe can be inserted. According to the embodiment shown in FIG. 4 , the number of the through-holes is two, and the resistance measuring probe 150 may be inserted into each of the through-holes. The through-holes are formed in portions corresponding to one end and the other end of the welding part, and the resistance measuring probe may be inserted into both the one and the other ends of the welding part, and the resistance measuring probe may be inserted only in one of the one end and the other end of the welding part. .
[49]
Meanwhile, a plurality of through-holes 122 are also formed in the upper plate 120 , and the resistance measuring probe 150 includes the through-hole 161 of the upper guide member 160 and the through-hole 161 of the upper plate 120 . It is configured to sequentially penetrate through the through-holes 122 to allow access to the upper surface of the welding part of the subject on the cradle 110 . At this time, in order for the resistance measuring probe to pass through both the through hole 161 of the upper guide member and the through hole 122 of the upper plate, these through holes are placed on a straight line in the insertion direction of the resistance measuring probe as shown in FIG. 4 . do. Accordingly, when the resistance measuring probe is inserted in the thickness direction of the upper plate, the upper guide member 160 can be inserted without being inclined, and has a function of fixing the resistance measuring probe.
[50]
Although not shown in FIG. 4 , a lower guide member is coupled to the lower plate, and the lower guide member, like the upper guide member, has a plurality of through-holes through which the resistance measuring probe can be inserted. In addition, the number of the through-holes may be two, and a resistance measuring probe may be inserted into each of the through-holes. A through hole is formed in the lower plate like the upper plate, and the resistance measuring probe sequentially passes through the through hole of the lower guide member and the through hole of the lower plate, and is placed on the lower surface of the welding part of the subject on the cradle. configured to be accessible. At this time, in order for the resistance measuring probe to pass through both the through hole of the lower guide member and the through hole of the lower plate, the through hole of the lower guide member and the through hole of the lower plate corresponding thereto are in a straight line in the insertion direction of the resistance measuring probe. will be raised The lower guide member, like the upper guide member, allows the resistance measuring probe to be inserted without being inclined, and serves to fix the resistance measuring probe at the same time.
[51]
The cradle, the upper plate, and the lower plate constituting the measuring part of the present invention have a structure coupled by a coupling part. As described above, the cradle, the upper plate, and the lower plate each have coupling holes at four corners, and the coupling part includes a coupling rod and a coupling screw.
[52]
1 and 5, in the coupling portion 140 of the present invention, the coupling rod 141 is each coupling hole formed on the upper plate 120, the cradle 110 and the lower plate 130. By being inserted through them sequentially, the upper plate, the cradle and the lower plate are configured to be coupled.
[53]
In addition, the measuring unit 100 of the present invention is a compression spring for adjusting the separation distance between the holder 110 and the upper plate 120 and the separation distance between the holder 110 and the lower plate 130 . Further comprising 170, the compression spring 170 is configured to enable the insertion of the coupling rod 141 inside the hollow portion. Due to the elasticity of the compression spring 170 , the upper plate 120 and the lower plate 130 are movable in the vertical direction along the coupling rod 141 , respectively, and the upper plate 120 and/or the lower plate 130 are movable. ) by applying a load in the direction of the cradle 110 , after positioning them at a desired point, the upper plate and the lower plate can be fixed to the desired point using the coupling screw 142 . And the compression spring 170 may have the length of the distance from the upper plate to the lower plate corresponding to one coupling rod 141, but one coupling rod 141 may pass through the two compression springs. have. In this case, one compression spring has a length corresponding to between the upper plate 120 and the holder 110 , and the other compression spring has a corresponding length between the lower plate 130 and the holder 110 . will have
[54]
In one specific example, the welding state inspection apparatus of the present invention further includes an output unit for displaying the data obtained from the measurement unit, the resistance value of the welding unit determined by the control unit. Through the output unit, the inspector may check the resistance value of the welding part to be inspected.
[55]
In one specific example, the welding state inspection apparatus of the present invention further includes a power supply for applying power to the measurement unit. Preferably, the power source is a direct current power source. This is because the DC method has the advantage of being able to measure resistance with high precision compared to the AC method. The magnitude of the current applied to the measuring unit, the current application time, the current application time, and the like are controlled by the control unit.
[56]
The control unit of the present invention will be described in detail.
[57]
The control unit of the present invention communicates with the measurement unit, receives data obtained from the measurement unit, determines a resistance value in the welding unit, and compares the determined resistance value with a threshold resistance value to determine whether weak welding is performed.
[58]
The test apparatus of the present invention is characterized in that the control unit includes a threshold resistance value setting program for setting the threshold resistance value by processing the data obtained by the measurement unit with respect to the sample group in a statistical manner.
[59]
The inventors of the present invention have found that, when the electrical resistance of a weld having weak welding strength is measured, it is greater than the electrical resistance value of a weld having normal welding strength, and led to the present invention. Referring to FIG. 7 , it can be seen that the resistance value of the normal weld with a welding strength of 22 kgf or more is smaller than the resistance value of the weak weld with a welding strength of less than 22 kgf. Conventionally, there has been a technique of measuring the resistance of a welded part and comparing the measured resistance value with a critical resistance value to determine a welding defect. Since correlation is used, a separate process for measuring the tensile strength of the weld was required.
[60]
However, the inspection apparatus of the present invention, in deriving the critical resistance value, does not depend on the correlation between the tensile strength and resistance of the weld, but introduces a statistical method and collects data for determining the resistance value of the weld. Therefore, it is characterized in that the resistance is precisely measured by measuring the micro-resistance in the nano-ohm to the micro-ohm unit by increasing the resolution.
[61]
In general, resistance values ​​form a normal distribution curve from data acquired for a large sample group. Since an individual with a large deviation from the normal distribution curve can be estimated as defective in terms of statistical probability, a predetermined deviation is set as the threshold resistance value. , and this method is based on the premise that the data on the sample group is reliable, so in the process of setting the critical resistance value, it is possible to precisely measure the resistance to the unit of nanoohm to microohm for the sample group. It is to use the measuring unit of the present invention that can precisely measure resistance in nano-ohm to micro-ohm units even when measuring the resistance of an object to be inspected by using the measuring unit of the present invention. As described above, the control unit constituting the test apparatus of the present invention includes a threshold resistance value setting program for setting the threshold resistance value by processing the data obtained by the measurement unit for the sample group in a statistical manner. Otherwise, there is no need to separately measure the tensile strength of the weld to set the critical resistance value.
[62]
A welding defect inspection method using the inspection apparatus of the present invention will be described in detail. A welding defect inspection method according to an embodiment of the present invention includes: a threshold resistance setting step (S100) of measuring the resistance of a welding part of a sample group and deriving a threshold resistance value that is a criterion for determining weak welding; A resistance measurement step of measuring the resistance value of the welding part to be inspected (S200); and when the resistance value measured in the resistance measurement step exceeds the threshold resistance value, determining as weak welding (S300), wherein the threshold resistance setting step (S100) and the resistance measurement step (S200) are , using the above-described measurement unit.
[63]
First, the threshold resistance setting step ( S100 ) will be described.
[64]
The threshold resistance setting step (S100) includes a data construction step (S110) of determining the resistance value of the welding part of the sample group and storing it; and a threshold resistance value deriving step (S120) of deriving a threshold resistance value by processing the data accumulated by the data building step (S110) in a statistical manner.
[65]
In the data building step (S110), data for determining the resistance of the welded part is obtained with respect to a large number of objects constituting the sample group using the measuring unit constituting the inspection device of the present invention, and the resistance value based on the obtained data includes the process of determining A pair of resistance measuring probes constituting the measuring part of the present invention are brought into contact with the welding part, and one resistance measuring probe includes a current probe and a voltage probe, so that the pair of resistance measuring probes includes a pair of current probes and a single resistance measuring probe. A pair of voltage probes are included, and thus, a 4-wire resistance measurement is possible. Compared to the two-wire resistance measurement method, the 4-wire resistance measurement method has an advantage in that data can be acquired more precisely because the contact resistance is small.
[66]
The number of individuals in the sample group in the data building step S110 is at least 100,000, preferably 200,000, and it is preferable in terms of reliability that the number of possible sample groups is large.
[67]
In the step of deriving the threshold resistance value (S120), the data accumulated by the data building step (S110) is processed in a statistical manner to derive the threshold resistance value. The control unit constituting the inspection apparatus of the present invention includes a program for setting a threshold resistance value by processing data in a statistical manner. In one specific example, the program may be to obtain a normal distribution curve of individual resistance values ​​of the individuals in the sample group, and to set a value of +6δ in the normal distribution curve as a threshold resistance value.
[68]
When a sample group shows a normal distribution curve, most individuals have a value close to the mean value (u), and there are few individuals with a large deviation from the mean value (u). Therefore, from a probabilistic point of view, an individual with a large deviation from the average value can be estimated as defective. Specifically, the probability that an individual with a deviation of 1δ (standard deviation) appears is about 32%, the probability that an individual with a deviation of 2δ appears is about 5%, and the probability that an individual with a deviation of 3δ appears is about 0.3%, and the probability of an individual with a deviation of 3δ is about 0.3%, of 4δ. It is known that the probability that an individual with a deviation appears is about 0.01%, the probability that an individual with a deviation of 5δ appears is about 0.001%, and the probability that an individual with a deviation of 6δ appears is about 0.0000001%. Therefore, a value obtained by adding a value of 6δ to an average value is set as a critical resistance value, and having a resistance value greater than this value is highly reliable even if it is estimated as defective due to weak welding.
[69]
Hereinafter, the resistance measurement step ( S200 ) will be described in detail. The resistance measurement step (S200) is to acquire data for determining the resistance value of the welding part to be inspected by the measuring unit constituting the inspection apparatus of the present invention.
[70]
The measuring unit of the present invention includes two resistance measuring probes, and obtaining data for deriving a resistance value by contacting the two resistance measuring probes to a welding part. 8 is a schematic diagram illustrating a process of acquiring data using a resistance measuring probe according to an embodiment of the present invention. Referring to FIG. 8 , one resistance measuring probe 150 is brought into contact with one end 31 of the welding unit 30 , and the other resistance measuring probe 150 ′ is connected to the other end 32 of the welding unit 30 . It is made to contact, and the resistance of the welding part 30 whole is measured. And in the embodiment of FIG. 8 , two resistance measuring probes 150 and 150 ′ are located on the upper surface of the welding part. As shown in FIG. 8 , the welding part 30 may be divided into a welding part 33 of the electrode tab 20 part and a welding part 34 of the electrode lead 10 part, and both of the two resistance measuring probes are connected to the electrode tab part. It can be made to contact the welding part (33). Alternatively, both of the two resistance measuring probes may be brought into contact with the welding part 34 of the electrode lead part.
[71]
9 is a schematic diagram illustrating a process of acquiring data using a resistance measuring probe according to another embodiment of the present invention. Referring to FIG. 9 , one resistance measuring probe 150 may contact the welding portion 33 of the electrode tab portion and the other resistance measurement probe 150 ′ may contact the welding portion 34 of the electrode lead portion to measure resistance. have. Among the various embodiments, it was most preferable in terms of detection power for detecting weak welding to measure resistance in a manner that both of the two resistance measuring probes were in contact with the welding part 33 of the electrode tab part.
[72]
The welding condition inspection apparatus and welding defect inspection method of the present invention can be widely applied to a welding part of a secondary battery, and can be applied to a welding part according to various welding methods. That is, the welding defect inspection method of the present invention can be applied to the welding part between the electrode tab and the electrode tab, the welding part between the electrode tab and the electrode lead, the welding part between the electrode lead and the bus bar in the battery pack, etc., and the welding part by ultrasonic welding, laser welding, etc. It can be applied to all welding parts, etc.
[73]
The welding state inspection apparatus according to the present invention measures the resistance of the sample group in the critical resistance setting step, sets the critical resistance value from the normal distribution curve of the measured resistance value, and measures the resistance of the sample group and the welding part to be inspected Since the resolution is in the range of nano ohms to mine, the resistance is precisely measured by using an ohm-level micro resistance measuring instrument, so that the detection power of weak welding defects is very excellent.
Claims
[Claim 1]
An apparatus for inspecting a welding state in a welding part for electrical connection or mechanical fastening in a lithium secondary battery, comprising: a measurement unit for obtaining data for deriving a resistance value of the welding part by contacting a resistance measuring probe on the welding part; and a control unit communicating with the measuring unit, receiving data obtained from the measuring unit, determining a resistance value in the welding unit, and comparing the determined resistance value with a critical resistance value to determine whether or not welding is weak, wherein the measuring unit comprises: , Welding state inspection apparatus, characterized in that configured to be able to contact the resistance measuring probe to one end and the other end of the weld.
[Claim 2]
The welding state inspection apparatus according to claim 1, wherein the control unit determines that the welding is weak when the determined resistance value exceeds a threshold resistance value.
[Claim 3]
The method of claim 1, wherein the measuring unit comprises: a plate-type cradle on which the subject is mounted; an upper plate having a predetermined separation distance from the cradle and having a plurality of through-holes through which a resistance measuring probe can be inserted; a lower plate positioned at a lower portion having a predetermined separation distance from the cradle and having a plurality of through-holes through which a resistance measuring probe can be inserted; a coupling unit for coupling the cradle, the upper plate and the lower plate; and a pair of resistance measuring probes contacting the welding part to acquire data for determining a resistance value.
[Claim 4]
The welding condition inspection apparatus according to claim 1, wherein one resistance measuring probe includes a current probe and a voltage probe.
[Claim 5]
The welding state inspection apparatus according to claim 3, wherein an upper guide member and a lower guide member for allowing the resistance measuring probe to be inserted into the proper position are respectively coupled to the upper plate and the lower plate.
[Claim 6]
The method of claim 5, wherein the upper guide member and the lower guide member each have a through hole through which a resistance measuring probe can be inserted, and the through hole of the upper guide member and the through hole of the upper plate are in a straight line. location, the resistance measuring probe is configured to penetrate them at the same time to access the upper surface of the weld, and the through-hole of the lower guide member and the through-hole of the lower plate are located in a straight line, so that the resistance measuring probe penetrates them and the lower surface of the weld Welding condition inspection device, characterized in that configured to be accessible to.
[Claim 7]
[4] The welding state inspection apparatus according to claim 3, wherein the coupling part includes a coupling rod and a coupling screw.
[Claim 8]
The method of claim 7, wherein the holder, the upper plate and the lower plate, each of which has a coupling hole formed in four corners, the coupling rod, the upper plate, the holder and the lower plate by sequentially passing through the respective coupling holes formed on the By being inserted, the welding state inspection device, characterized in that configured to be coupled to the upper plate, the cradle and the lower plate.
[Claim 9]
The method of claim 7, further comprising a compression spring for adjusting the separation distance between the holder and the upper plate and the separation distance between the holder and the lower plate, wherein the coupling rod is inserted into the hollow portion of the compression spring. Welding condition inspection device, characterized in that configured to be possible.
[Claim 10]
The welding state inspection apparatus according to claim 1, wherein the control unit includes a threshold resistance value setting program configured to set the threshold resistance value by processing the data obtained by the measurement unit for the sample group in a statistical manner.
[Claim 11]
11. The apparatus of claim 10, wherein the resistance values ​​determined from the data obtained for the sample group form a normal distribution curve.
[Claim 12]
The welding state inspection apparatus according to claim 1, further comprising a power source for applying power to the measurement unit, wherein the power source is a DC power source and is controlled by the control unit.