JP2018010770A - Inspection method of battery module and inspection apparatus of battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method and an inspection apparatus of battery module which allow for non-destruction detection of a defective part existing between a battery cell and a heat transmission member.SOLUTION: In an inspection method of battery module, a battery module 10 includes multiple battery cells 2, a heat transmission member 4 to which the multiple battery cells 2 are attached, and a heat transmission layer 6 placed between the multiple battery cells 2 and heat transmission member 4. This inspection method includes a step of heating the surface 4s of the heat transmission member 4 on the side opposite to the heat transmission layer 6, while placing the heat transmission layer 6 between the multiple battery cells 2 and heat transmission member 4, a step of imaging the surface 4s of the heat transmission member 4 by using an infrared imaging apparatus 30 after heating the surface 4s of the heat transmission member 4, and a step of detecting a defective part based on an infrared image obtained from the infrared imaging apparatus 30.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a battery module inspection method and a battery module inspection apparatus.

  For example, a battery module including an array formed by arranging a plurality of battery cells such as a lithium ion secondary battery is known. In such a battery module, a heat dissipation structure is provided for releasing heat generated in the battery cell to the housing. For example, in the battery module described in Patent Document 1, a heat transfer plate is disposed between battery cells, and one end side of the heat transfer plate is in contact with the housing. Thereby, the heat generated in the battery cell is released to the casing.

JP-T 8-506205

  In order to improve heat transfer between the battery cell and a heat transfer member (for example, a casing) to which the battery cell is attached, a heat transfer layer may be interposed between the two. In this case, when the battery cell is bonded to the heat transfer layer, air bubbles may be mixed between the battery cell and the heat transfer layer. Or when a heat-transfer layer peels from a heat-transfer member, a space | gap may arise between a heat-transfer layer and a heat-transfer member. Alternatively, the heat transfer layer may be broken to generate voids in the heat transfer layer. In either case, a gap exists between the battery cell and the heat transfer member.

  If a defective portion such as the above-described gap exists between the battery cell and the heat transfer member, improvement in heat transfer between the battery cell and the heat transfer member is hindered. In addition, detecting defective parts such as foreign matters in the battery module also contributes to improving the quality of the battery module.

  An object of one aspect of the present invention is to provide a battery module inspection method and a battery module inspection apparatus capable of nondestructively detecting a defective portion that may exist between a battery cell and a heat transfer member.

  In the battery module inspection method according to one aspect of the present invention, the battery module includes a plurality of battery cells, a heat transfer member to which the plurality of battery cells are attached, the plurality of battery cells, and the heat transfer member. A heat transfer layer disposed between the heat transfer layer and the heat transfer layer in a state where the heat transfer layer is disposed between the plurality of battery cells and the heat transfer member. From the step of heating the surface opposite to the thermal layer, the step of imaging the surface of the heat transfer member using an infrared imaging device after heating the surface of the heat transfer member, and the infrared imaging device Detecting a defective portion based on the obtained infrared image.

  In this battery module inspection method, when the surface of the heat transfer member is heated, heat is transferred from the heat transfer member to the plurality of battery cells via the heat transfer layer. Here, when a defective part exists in either (1) between the heat transfer member and the heat transfer layer, (2) inside the heat transfer layer, or (3) between the heat transfer layer and the plurality of battery cells. There is. The defective part has a thermal conductivity different from the thermal conductivity of the heat transfer layer. As such a defective portion, for example, air bubbles mixed during manufacturing of the battery module, voids generated by peeling or tearing of the heat transfer layer generated when the battery module is used, and the like can be considered. In this case, heat transfer from the heat transfer member to the plurality of battery cells is insufficient at the location where the defective portion exists. For this reason, in the obtained infrared image, a portion where a defect portion exists appears as a spot having a higher temperature than the surroundings.

  When the defective part is a foreign substance such as a conductive particle, for example, if the foreign substance has a thermal conductivity larger than the thermal conductivity of the heat transfer layer, from the heat transfer member to the plurality of battery cells in the place where the defective part exists. The heat conductivity is excessively high. For this reason, in the obtained infrared image, a portion where a defect portion exists appears as a spot having a lower temperature than the surroundings.

  Therefore, when the inspection method of the battery module is used, a defective portion that may exist between the battery cell and the heat transfer member can be detected in a nondestructive manner.

  The inspection method further includes a step of performing resolution enhancement processing of the infrared image after imaging the surface of the heat transfer member, and in the step of detecting the defective portion, the infrared light after the resolution enhancement processing is performed. The defective portion may be detected based on the image.

  In this case, the defective portion can be detected with high accuracy even if the defective portion is a gap having a minute diameter.

  The inspection method may further include a step of compressing the heat transfer layer with the plurality of battery cells before imaging the surface of the heat transfer member.

  When the heat transfer layer is compressed, a temperature change corresponding to the stress fluctuation occurs due to the thermoelastic effect. The distribution of the residual stress generated by compressing the heat transfer layer becomes non-uniform when there is a defect. It is because the temperature of the gas in a space | gap rises by adiabatic compression when a defect part is a space | gap. As a result, in the infrared image, the location where the defect portion exists appears as a spot having a higher temperature than the surroundings. Therefore, a defective part can be detected with high accuracy.

  In the inspection apparatus for a battery module according to one aspect of the present invention, the battery module includes a plurality of battery cells, a heat transfer member to which the plurality of battery cells are attached, the plurality of battery cells, and the heat transfer member. A heat transfer layer disposed between the heat transfer member and a heating device for heating the surface of the heat transfer member opposite to the heat transfer layer, and the surface of the heat transfer member. An infrared imaging device for imaging, and a defect detection device for detecting a defect based on an infrared image obtained from the infrared imaging device.

  In this battery module inspection apparatus, the battery module inspection method can be suitably implemented. Therefore, it is possible to nondestructively detect a defective portion that may exist between the battery cell and the heat transfer member.

  According to one aspect of the present invention, a battery module inspection method and a battery module inspection apparatus capable of nondestructively detecting a defective portion that may exist between a battery cell and a heat transfer member can be provided.

It is a side view which shows typically the battery module of a test object. It is a figure which shows typically the inspection apparatus of the battery module which concerns on embodiment. It is a figure which shows typically the inspection apparatus of the battery module which concerns on embodiment. It is a flowchart which shows the inspection method of the battery module which concerns on embodiment. It is a figure which shows an example of a thermography image.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and redundant descriptions are omitted.

  FIG. 1 is a side view schematically showing a battery module to be inspected. A battery module 10 shown in FIG. 1 includes a plurality of battery cells 2, a heat transfer member 4 to which the plurality of battery cells 2 are attached, and heat transfer disposed between the plurality of battery cells 2 and the heat transfer member 4. Layer 6.

  The plurality of battery cells 2 are arranged in one direction. A plurality of heat transfer plates 8 may be attached to each of the plurality of battery cells 2. Each heat transfer plate 8 includes a first plate-like portion 8 a arranged between adjacent battery cells 2 and a second plate-like portion 8 b arranged between the heat transfer layer 6 and the battery cell 2. Have. However, the 1st plate-shaped part 8a of the heat-transfer plate 8 located in the end of the arrangement direction of the battery cell 2 is arrange | positioned between the battery cell 2 and the end plate 12 mentioned later. The end of the second plate-like portion 8b is connected to the end of the first plate-like portion 8a and extends in a direction intersecting with the extending direction of the first plate-like portion 8a. Each heat transfer plate 8 is, for example, a metal plate.

  Each battery cell 2 is held by a battery holder that forms a frame. The battery cell 2 is a secondary battery such as a lithium ion secondary battery, for example, and houses an electrode assembly in a case. The battery cell 2 is provided with a positive electrode terminal and a negative electrode terminal.

  Each battery cell 2 is arranged so that terminals having different polarities are adjacent to each other, and are electrically connected in series by a bus bar. A pair of end plates 12 that can restrain the plurality of battery cells 2 in the arrangement direction are provided at the arrangement ends of the battery cells 2. Each end plate 12 has a plate-like portion 12 a that presses the plurality of battery cells 2, and a bracket portion 12 b for fixing the end plate 12 to the heat transfer member 4. The end plate 12 is fixed to the heat transfer member 4 via a bracket portion 12b by a fastening member such as a bolt, for example.

  The heat transfer member 4 may be, for example, a housing that houses the plurality of battery cells 2 or a part of the housing. The heat transfer member 4 is a metal plate such as an iron plate, for example.

  The heat transfer layer 6 may have elasticity. The heat transfer layer 6 is, for example, a gel-like resin layer. The heat transfer layer 6 may be a solid layer formed by curing a liquid heat conductive material (TIM: Thermal Interface Material). The heat transfer layer 6 has a thermal conductivity of, for example, 1.5 W / m · K or more. The thermal conductivity of the heat transfer layer 6 may be 2 W / m · K or more, 2.5 W / m · K, or 3.0 W / m · K or more. Examples of the heat conductive material of the heat transfer layer 6 include elastically deformable materials such as polyurethane resin, silicone gel, rubber, and resin sponge.

  In the battery module 10, the battery cell 2 generates heat due to charging / discharging of the battery cell 2, and the heat reaches the heat transfer member 4 from the battery cell 2 via the heat transfer plate 8 and the heat transfer layer 6. Thereby, heat is radiated from the heat transfer member 4 to the outside air. That is, the heat transfer member 4 functions as a heat dissipation member. When the gap V exists between the heat transfer layer 6 and the heat transfer plate 8, improvement in heat transfer between the battery cell 2 and the heat transfer member 4 is hindered. Such voids V are, for example, bubbles mixed when the heat transfer plate 8 is bonded to the heat transfer layer 6, peeling of the heat transfer layer 6 caused by expansion and contraction of the battery cell 2 due to charging / discharging of the battery cell 2. Or it is caused by tearing. The air gap V can be detected by an inspection device and an inspection method for the battery module 10 described below.

  FIG.2 and FIG.3 is a figure which shows typically the inspection apparatus of the battery module which concerns on embodiment. The inspection apparatus 100 shown in FIGS. 2 and 3 can inspect the battery module 10. FIG. 2 shows the inspection apparatus 100 in the heating process described later, and FIG. 3 shows the inspection apparatus 100 in the imaging process described later.

  The inspection device 100 includes a heating device 20 for heating the surface 4s of the heat transfer member 4 opposite to the heat transfer layer 6, an infrared imaging device 30 for imaging the surface 4s of the heat transfer member 4, and an infrared ray. A defect detection device 40 for detecting a defect based on an infrared image obtained from the imaging device 30. The inspection device 100 may include a pair of rails 50 as a transport device for transporting the battery module 10 from the heating device 20 to the infrared imaging device 30.

  The heating device 20 may include a drive device that drives the heat source such that the heat source is brought into contact with the surface 4 s of the heat transfer member 4 and the heat source is separated from the surface 4 s of the heat transfer member 4. The driving device can drive the heat source in the crossing direction (for example, the vertical direction) of the surface 4 s of the heat transfer member 4.

  The infrared imaging device 30 is an infrared camera, for example. An infrared image of the surface 4 s of the heat transfer member 4 is obtained by the infrared imaging device 30.

  The defect detection device 40 includes a computer 42 that receives an infrared image obtained from the infrared imaging device 30 and a monitor 44 that displays a detection result of the defect based on the infrared image. The computer 42 can process infrared images. The infrared image can be displayed on the monitor 44 as a thermographic image as shown in FIG.

  The computer 42 can also perform high resolution processing of an infrared image obtained from the infrared imaging device 30 as follows, for example. First, the brightness curve data of the infrared image obtained from the infrared imaging device 30 is digitized to create a first digital image including discrete values averaged by the pixel width. Next, the same luminance curve data is digitized at a pixel position shifted by ½ pixel with respect to the pixel position where the first digital image is created, and a second digital image is created. Thereafter, by calculating an average value of the value of the first digital image and the value of the second digital image, a digital image subjected to the high resolution processing is obtained. By performing such processing two-dimensionally, high resolution processing can be performed on the entire infrared image of the surface 4 s of the heat transfer member 4.

  The pair of rails 50 can transport the battery module 10 in the direction A in which the rail 50 extends while supporting both ends of the battery module 10. The heat source of the heating device 20 can be driven so as to approach the battery module 10 or move away from the battery module 10 through the space between the pair of rails 50.

  In the inspection apparatus 100, a method for inspecting the battery module 10 described later can be suitably implemented. Therefore, a defective portion that can exist between the battery cell 2 and the heat transfer member 4 can be detected in a nondestructive manner.

  FIG. 4 is a flowchart illustrating the battery module inspection method according to the embodiment. The method for inspecting a battery module according to the embodiment may be performed as follows using the inspection apparatus 100, for example.

(Compression process)
First, the battery module 10 of FIG. 1 is prepared. For example, the heat transfer layer 6 provided on the heat transfer member 4 and the heat transfer plate 8 attached to the battery cell 2 are bonded together. Thereafter, the bracket portions 12b of the pair of end plates 12 are fixed to the heat transfer member 4 by fastening members such as bolts, for example. As a result, the heat transfer layer 6 is compressed by the dead weight of the battery cell 2 and the heat transfer plate 8 (step S1).

(Heating process)
Next, as shown in FIG. 2, the surface 4s of the heat transfer member 4 is heated in a state where the heat transfer layer 6 is disposed between the plurality of battery cells 2 and the heat transfer member 4 (step S2). . FIG. 2A is a plan view of the inspection apparatus 100, and FIG. 2B is a side view of the inspection apparatus 100. The heat source of the heating device 20 may be brought into contact with the surface 4s of the heat transfer member 4 for 3 to 60 seconds, for example. Further, the surface 4s of the heat transfer member 4 may be heated by radiant heat from the heat source. The temperature of the heat source may be 50 to 70 ° C, 55 to 65 ° C, or 59 to 61 ° C. The heating process also corresponds to an aging test of the battery module 10. After the heating, the battery module 10 is cooled by separating the heat source of the heating device 20 from the surface 4 s of the heat transfer member 4. Thereby, since the state at the time of use of the battery module 10 can be reproduced, peeling or tearing of the heat transfer layer 6 caused by expansion and contraction of the battery cell 2 accompanying charging / discharging of the battery cell 2 can be reproduced.

(Imaging process)
Next, for example, after the battery module 10 is conveyed by the rail 50, as shown in FIG. 3, the surface 4s of the heat transfer member 4 is imaged using the infrared imaging device 30 (step S3). FIG. 3A is a plan view of the inspection apparatus 100, and FIG. 3B is a side view of the inspection apparatus 100.

(High resolution process)
Next, the high resolution processing of the infrared image obtained from the infrared imaging device 30 is performed as necessary (step S4).

(Defect detection process)
Next, a defective part is detected based on the infrared image obtained from the infrared imaging device 30 (step S5). In the case of performing the high resolution processing of the infrared image, the defective portion is detected based on the infrared image after the high resolution processing. When the high resolution processing of the infrared image is performed, a thermographic image as shown in FIG. 5 is obtained, for example. In this thermographic image, when the defective portion is the gap V, the portion where the defective portion exists appears as a spot H having a higher temperature than the surroundings.

  The defective part detection device 40 has a product standard in which the defective part is set in advance (for example, when the dimension of the defective part is equal to or less than a threshold, and when the defective part is a gap V, the temperature of the defective part is equal to or lower than the threshold, In the case of a foreign substance having a large thermal conductivity, it may be determined as a non-defective product if the temperature of the defective portion satisfies the threshold) or higher, and may be determined as a defective product if the product standard is not satisfied. In the case of a defective product, the bracket portion 12b of the pair of end plates 12 is removed from the heat transfer member 4 and the bracket portion 12b is fixed to the heat transfer member 4 again. Alternatively, the heat transfer layer 6 may be peeled off from the heat transfer member 4 after the bracket portions 12 b of the pair of end plates 12 are removed from the heat transfer member 4. In this case, after the new heat transfer layer 6 is formed on the heat transfer member 4, the bracket portion 12 b is fixed to the heat transfer member 4.

  In the inspection method of the battery module 10, when the surface 4 s of the heat transfer member 4 is heated, heat is transferred from the heat transfer member 4 to the plurality of battery cells 2 via the heat transfer layer 6 and the heat transfer plate 8. Here, (1) between the heat transfer member 4 and the heat transfer layer 6, (2) the inside of the heat transfer layer 6, and (3) the defective portion between the heat transfer layer 6 and the heat transfer plate 8. May exist. The defective part has a thermal conductivity different from the thermal conductivity of the heat transfer layer. As such a defective portion, for example, air bubbles mixed during the manufacture of the battery module 10, a void V generated by peeling or tearing of the heat transfer layer 6 generated when the battery module 10 is used, and the like can be considered. In this case, the heat transfer from the heat transfer member 4 to the plurality of battery cells 2 is insufficient at the location where the defective portion exists. For this reason, in the obtained infrared image, a portion where a defect portion exists appears as a spot having a higher temperature than the surroundings.

  When the defective part is a foreign substance such as conductive particles, for example, if the foreign substance has a thermal conductivity larger than the thermal conductivity of the heat transfer layer 6, a plurality of batteries are transferred from the heat transfer member 4 at the location where the defective part exists. The heat transfer to the cell 2 becomes excessively high. For this reason, in the obtained infrared image, a portion where a defect portion exists appears as a spot having a lower temperature than the surroundings.

  Therefore, if the inspection method for the battery module 10 is used, a defective portion that may exist between the battery cell 2 and the heat transfer member 4 can be detected in a nondestructive manner.

  Furthermore, in the inspection method of the battery module 10, not only the defective portion existing before the heating but also the defective portion that is not present before the heating and is generated for the first time by the heating can be detected.

  When detecting a defect part based on the infrared image after high resolution processing, the heat conductivity of the heat transfer layer 6 is low (for example, more than 0 W / mK and 1.0 W / mK or less, more preferably 0.2 W / mK or more. 1.0 W / mK or less), even if the defect portion is a gap V having a minute diameter (for example, 0.5 to 5.0 mm, more preferably 0.5 to 1.5 mm), the defect portion is detected with high accuracy. can do.

  When the heat transfer layer 6 is compressed, a temperature change corresponding to the stress fluctuation occurs due to the thermoelastic effect. The distribution of the residual stress generated by compressing the heat transfer layer 6 becomes non-uniform when a defect exists. It is because the temperature of the gas in the space | gap V rises by adiabatic compression that a defect part is the space | gap V. As a result, in the infrared image, the location where the defect portion exists appears as a spot having a higher temperature than the surroundings. Therefore, a defective part can be detected with high accuracy.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment.

  For example, the compression step S1 and the high resolution processing step S4 may not be performed. The compression step S1 may be performed between the heating step S2 and the imaging step S3.

  In addition, the defective portion can be detected by performing the compression step S1 without performing the heating step S2. In this case, when the heat transfer layer 6 is compressed in the compression step S1, a temperature change corresponding to the stress fluctuation occurs due to the thermoelastic effect. The distribution of the residual stress generated by compressing the heat transfer layer 6 becomes non-uniform when a defect exists. It is because the temperature of the gas in the space | gap V rises by adiabatic compression that a defect part is the space | gap V. As a result, in the infrared image, the location where the defect portion exists appears as a spot having a higher temperature than the surroundings. Therefore, a defective part can be detected.

  2 ... Battery cell, 4 ... Heat transfer member, 4s ... Surface, 6 ... Heat transfer layer, 10 ... Battery module, 20 ... Heating device, 30 ... Infrared imaging device, 40 ... Defect detection device, 100 ... Inspection device.

Claims (4)

A battery module inspection method comprising:
The battery module includes a plurality of battery cells, a heat transfer member to which the plurality of battery cells are attached, and a heat transfer layer disposed between the plurality of battery cells and the heat transfer member,
The inspection method is:
Heating the surface of the heat transfer member opposite to the heat transfer layer in a state where the heat transfer layer is disposed between the plurality of battery cells and the heat transfer member;
Imaging the surface of the heat transfer member using an infrared imaging device after heating the surface of the heat transfer member;
Detecting a defective portion based on an infrared image obtained from the infrared imaging device;
A method for inspecting a battery module. After imaging the surface of the heat transfer member, further comprising the step of performing a high resolution processing of the infrared image,
The battery module inspection method according to claim 1, wherein in the step of detecting the defective portion, the defective portion is detected based on the infrared image after the high resolution processing.   The battery module inspection method according to claim 1, further comprising a step of compressing the heat transfer layer with the plurality of battery cells before imaging the surface of the heat transfer member. A battery module inspection device,
The battery module includes a plurality of battery cells, a heat transfer member to which the plurality of battery cells are attached, and a heat transfer layer disposed between the plurality of battery cells and the heat transfer member,
The inspection device includes:
A heating device for heating the surface of the heat transfer member opposite to the heat transfer layer;
An infrared imaging device for imaging the surface of the heat transfer member;
A defect detection device for detecting a defect based on an infrared image obtained from the infrared imaging device;
A battery module inspection apparatus comprising: