How to evaluate the airtightness of a case

Abstract

To provide a method for evaluating the airtightness of a case, which can reduce the time required to evaluate the airtightness of a plurality of cases while saving space and reducing costs. [Solution] The method for evaluating the airtightness of a case of the present invention includes a first pressurization / depressurization step of operating a first pump connected to the first case via a first pipe to reduce or increase the pressure inside the first case, a first pressure change measurement step of measuring the amount of pressure change inside the first case using an evaluation device connected to the first case via a second pipe after stabilizing the pressure inside the first case, and a first evaluation step of evaluating the airtightness of the first case using the evaluation device based on the amount of pressure change inside the first case, wherein the first pressurization / depressurization step is performed by opening a first valve provided on the first pipe and closing a second valve provided on the second pipe, and the first pressure change measurement step is performed by closing the first valve and opening the second valve.

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the airtightness of a case. [Background technology]

[0002] Patent document 1 discloses a method for evaluating the airtightness of a battery pack case by evacuating the gas inside the case using a vacuum pump to reduce the pressure, stabilizing the pressure inside the case, and then measuring the amount of pressure change inside the case using an evaluation device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-117088 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method for evaluating the airtightness of a battery case disclosed in Patent Document 1 requires a long time to exhaust gas from the battery pack case using a vacuum pump, which results in a long time required to evaluate the airtightness of multiple battery pack cases. It is also possible to provide a vacuum pump and evaluation device for each of the multiple cases and perform depressurization and airtightness evaluation of the multiple cases in parallel. However, in this case, the number of vacuum pumps and evaluation devices required is equal to the number of cases for which depressurization and airtightness evaluation are performed in parallel, resulting in increased installation space and higher costs. Furthermore, when evaluating the airtightness of a battery pack case by introducing and pressurizing gas into the case using a pump or the like, the long time required to introduce the gas into the case also results in the same problems as those described above.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a method for evaluating the airtightness of cases that can reduce the time required to evaluate the airtightness of multiple cases while saving space and reducing costs. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the method for evaluating the airtightness of a case of the present invention includes a first pressurization / depressurization step of operating a first pump connected to a first case via a first pipe to reduce or increase the pressure inside the first case, a first pressure change measurement step of measuring the amount of pressure change inside the first case using an evaluation device connected to the first case via a second pipe after stabilizing the pressure inside the first case, and a first evaluation step of evaluating the airtightness of the first case using the evaluation device based on the amount of pressure change inside the first case, and is characterized in that the first pressurization / depressurization step is performed with a first valve provided on the first pipe in an open state and a second valve provided on the second pipe in a closed state, and the first pressure change measurement step is performed with the first valve in a closed state and the second valve in an open state.

[0007] As a result, in the case airtightness evaluation method according to the present invention, the process of depressurizing or pressurizing the inside of the case and the process of evaluating the airtightness of the case can be separated, and by switching each valve between an open state and a closed state, it is possible to perform the depressurization or pressurization and the airtightness evaluation of multiple battery packs in parallel. Therefore, the case airtightness evaluation method according to the present invention can shorten the time required to evaluate the airtightness of multiple cases, including the first case. Furthermore, in the case airtightness evaluation method according to the embodiment, a common vacuum pump and evaluation device are used to depressurize or pressurize the multiple battery cases and evaluate their airtightness, so the number of vacuum pumps and evaluation devices can be reduced, thereby saving space and reducing costs.

[0008] Furthermore, in the above, a first pressure adjustment step may be provided between the first pressurization / depressurization step and the first pressure change measurement step, in which the first valve is switched from the open state to the closed state and the second valve is switched from the closed state to the open state, and the pressure inside the first case is adjusted using a second pump provided in the evaluation device.

[0009] This improves the accuracy of measuring the amount of pressure change inside the first case, allowing for a more accurate evaluation of the first airtightness.

[0010] In the above, the method further comprises a second pressurizing / depressurizing step of operating the first pump to depressurize or pressurize the inside of a second case connected to the first pump via a third pipe; a second pressure change measuring step of measuring a pressure change amount in the second case by the evaluation device connected to the second case via a fourth pipe after the pressure in the second case has been stabilized; and a second evaluation step of evaluating the airtightness of the second case by the evaluation device based on the pressure change amount in the second case. When the first pressurizing / depressurizing step is performed, at least the third pipe is operated. a third valve provided on the fourth pipe is closed, and when performing the first pressure change measurement step and the first evaluation step, at least a fourth valve provided on the fourth pipe is closed, and after performing the first pressurization / depressurization step, the third valve is opened and the fourth valve is closed to perform the second pressurization / depressurization step, and after performing the first evaluation step to complete the evaluation of the airtightness of the first case, the third valve is closed and the fourth valve is opened to perform the second pressure change measurement step and the second evaluation step.

[0011] This allows for space saving and cost reduction by using a vacuum pump and evaluation device that are common to both the first and second cases, while also shortening the time required to evaluate the airtightness of the second case.

[0012] Furthermore, in the above, a second pressure adjustment step may be provided between the second pressurization / depressurization step and the second pressure change measurement step, in which the third valve is switched from the open state to the closed state and the fourth valve is switched from the closed state to the open state, and the pressure inside the second case is adjusted using a second pump provided in the evaluation device.

[0013] This improves the accuracy of measuring the amount of pressure change inside the second case, allowing for a more accurate evaluation of the airtightness of the second case. [Effects of the Invention]

[0014] The method for evaluating the airtightness of a case according to the present invention has the effect of reducing the time required to evaluate the airtightness of a plurality of cases while saving space and reducing costs. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an evaluation device, a first vacuum pump, and the like used in a method for evaluating the airtightness of a case according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of the main part of the evaluation device according to the embodiment. [Figure 3] FIG. 3 is a block diagram illustrating an example of a functional configuration of a control device included in the evaluation device according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of the flow of processing executed by the control device of the evaluation device according to the embodiment. [Figure 5] FIG. 5 is a diagram showing the open / closed states of the valves when the step of reducing the pressure inside the first battery case is performed. [Figure 6] FIG. 6 is a diagram showing the open / closed states of each valve when performing the step of evaluating the airtightness of the first battery case and the step of reducing the pressure inside the second battery case. [Figure 7] FIG. 7 is a diagram showing the open / closed states of the valves when the step of evaluating the airtightness of the second battery case and the step of reducing the pressure inside the third battery case are performed. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the method for evaluating the airtightness of a case according to the present invention will be described, although the present invention is not limited to this embodiment.

[0017] Fig. 1 is a diagram showing a schematic configuration of an evaluation device 1 and a first vacuum pump 12 used in a method for evaluating the airtightness of a case according to an embodiment. Fig. 2 is a block diagram showing the configuration of a main part of the evaluation device 1 according to an embodiment. Fig. 3 is a block diagram showing an example of the functional configuration of a control device 13 provided in the evaluation device 1 according to an embodiment.

[0018] The method for evaluating the airtightness of a case according to the embodiment uses an evaluation device 1 and a first vacuum pump 12. As shown in FIG. 1 , the evaluation device 1 according to the embodiment includes a leak tester 10, a master chamber 11, a control device 13, and a second vacuum pump 14. The evaluation device 1 is an apparatus for evaluating the airtightness of a battery case using the method for evaluating the airtightness of a case according to the embodiment. For example, in FIG. 1 , the evaluation device 1 is used to evaluate the airtightness of a first battery case 411 in a first battery pack 41 and the airtightness of a second battery case 412 in a second battery pack 42. Note that in FIG. 1 , the first vacuum pump 12 corresponds to the first pump of the present invention, and the second vacuum pump 14 corresponds to the second pump of the present invention. Also, in FIG. 1 , the first battery case 411 corresponds to the first case of the present invention, and the second battery case 412 corresponds to the second case of the present invention.

[0019] The first battery pack 41 and the second battery pack 42 are mounted, for example, under the floor of the vehicle and supply power to a motor that drives the vehicle. In the first battery pack 41 and the second battery pack 42, a plurality of battery modules (not shown), a battery ECU (Electronic Control Unit), a thermistor, etc. (not shown) are housed in a first battery case 411 and a second battery case 412 that are flat and long boxes. Each battery module is configured by electrically connecting a plurality of batteries (battery cells), such as lithium-ion batteries, to each other. In order to grasp the status of each battery module, the battery ECU measures the voltage, current, temperature, etc. of each battery module and monitors the input / output to each battery module.

[0020] The first battery case 411 and the second battery case 412 each include a lower case that is box-shaped and open at the top, and an upper case that is box-shaped and open at the bottom. The lower case is made of a light metal such as an aluminum alloy. The upper case is made of a resin, for example. The lower and upper cases are fitted together with flanges at the open ends, and the flanges are fastened together by bolts or the like.

[0021] The leak tester 10, the master chamber 11, and the second vacuum pump 14 constitute a pressure measurement unit in the evaluation device 1. In the evaluation device 1, a pressure measurement process is carried out using the leak tester 10, the master chamber 11, and the second vacuum pump 14. The leak tester 10 is connected to the master chamber 11 via a pipe 20. The master chamber 11 has a highly airtight structure. The leak tester 10 is also connected to the second vacuum pump 14 via a pipe 21.

[0022] Furthermore, one end of a pipe 22 that communicates with the pipe 20 via the leak tester 10 is connected to the leak tester 10. The other end of the pipe 22 is connected to a first work connection jig 51. A second valve 62 is provided midway along the pipe 22. The first work connection jig 51 is configured to be connected to, for example, a first battery case 411, which is the first work. In the present embodiment, as an example, the first work connection jig 51 is connected to one longitudinal end of a lower case of the first battery case 411.

[0023] One end of a pipe 25 is connected to the first vacuum pump 12. The other end of the pipe 25 is connected to the pipe 22 at a position closer to the first workpiece connecting jig 51 than the second valve 62. A first valve 61 is provided in the middle of the pipe 25. One end of a pipe 26 is connected to the first vacuum pump 12. The other end of the pipe 26 is connected to the second workpiece connecting jig 52. A third valve 63 is provided in the middle of the pipe 26. The second workpiece connecting jig 52 is configured to be connected to, for example, a second battery case 412, which is the second workpiece. In the present embodiment, as an example, the second workpiece connecting jig 52 is connected to one longitudinal end of a lower case of the second battery case 412.

[0024] Furthermore, one end of a pipe 23 that communicates with the pipe 21 via the leak tester 10 is connected to the leak tester 10. The other end of the pipe 23 is connected to a pipe 24. One end of the pipe 24 is connected to the pipe 22 at a position closer to the leak tester 10 than the second valve 62. The other end of the pipe 24 is connected to the pipe 26 at a position closer to the second work connection jig 52 than the third valve 63. A fourth valve 64 is provided midway along the pipe 24, at a position closer to the pipe 26 than the connection point with the other end of the pipe 23.

[0025] In this embodiment, the first valve 61 corresponds to the first valve of the present invention, the second valve 62 corresponds to the second valve of the present invention, the third valve 63 corresponds to the third valve, and the fourth valve 64 corresponds to the fourth valve of the present invention.

[0026] Furthermore, valves, differential pressure sensors, and the like (not shown) are provided within the leak tester 10. The leak tester 10 is electrically connected to a control device 13 via wiring 30 so as to be able to communicate with the control device 13. As shown in Fig. 2, the control device 13 includes a CPU (Central Processing Unit) 131, a ROM (Read Only Memory) 132, a RAM (Random Access Memory) 133, a storage unit 134, and an input / output I / F (Interface) 135. The CPU 131, ROM 132, RAM 133, storage unit 134, and input / output I / F 135 are connected to each other via a bus 136 so as to be able to communicate with each other.

[0027] The CPU 131 is a central processing unit that executes various programs and controls each component. That is, the CPU 131 reads programs from the ROM 132 and executes the programs using the RAM 133 as a work area. This causes the control device 13 to function as the evaluation unit 1301 shown in FIG. 3. The evaluation unit 1301 evaluates the airtightness (air leakage) of the battery case based on a pressure change amount ΔP, which is the differential pressure between the pressure inside a battery case, such as the first battery case 411, and the pressure inside the master chamber 11, measured using a differential pressure sensor or the like in the leak tester 10. The evaluation unit 1301 evaluates the airtightness (air leakage) of the battery case by determining whether the pressure change amount ΔP inside the battery case is less than a predetermined value. Specifically, if the pressure change amount ΔP is less than the predetermined value, the evaluation unit 1301 evaluates that the airtightness of the battery case is ensured. On the other hand, if the pressure change amount ΔP is equal to or greater than the predetermined value, the evaluation unit 1301 evaluates that the airtightness of the battery case is not ensured.

[0028] In this embodiment, various programs and various data are stored in the ROM 132. The storage unit 134 is configured with an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs including an operating system and various data.

[0029] The input / output I / F 135 is electrically connected to the leak tester 10, the first vacuum pump 12, the second vacuum pump 14, the user I / F 137, the first valve 61, the second valve 62, the third valve 63, and the fourth valve 64. The user I / F 137 includes, for example, a display which is a display device (not shown) and a keyboard which is an input device (not shown). Note that the user I / F 137 is not shown in FIG. 1.

[0030] Fig. 4 is a flowchart showing an example of the flow of processing executed by the control device 13 of the evaluation device 1 according to the embodiment. Fig. 5 is a diagram showing the open / closed states of the valves 61, 62, 63, and 64 when performing the step of depressurizing the inside of the first battery case 411. Fig. 6 is a diagram showing the open / closed states of the valves 61, 62, 63, and 64 when performing the step of evaluating the airtightness of the first battery case 411 and the step of depressurizing the inside of the second battery case 412. Fig. 7 is a diagram showing the open / closed states of the valves 61, 62, 63, and 64 when performing the step of evaluating the airtightness of the second battery case 412 and the step of depressurizing the inside of the third battery case 413.

[0031] Next, the control flow in the control device 13 will be described with reference to Fig. 4. The CPU 131 of the control device 13 starts executing a program when, for example, a switch (not shown) provided in the user I / F 137 is turned on. In this program, the CPU 131 executes each step and process of the control flow shown in Fig. 4.

[0032] First, in step S1, as shown in Fig. 5, the CPU 131 opens at least the first valve 61 and closes at least the second valve 62 and the third valve 63. Note that in Fig. 5, the fourth valve 64 may be either open or closed. This forms a path L1 shown by a dashed line in Fig. 5, which connects the first battery case 411 and the first vacuum pump 12 via the piping 25. Then, the CPU 131 operates the first vacuum pump 12 to discharge air from the first battery case 411 and perform a decompression step (first pressurization / decompression step) in which the pressure inside the first battery case 411 is reduced.

[0033] Next, in step S2, as shown in Fig. 6, the CPU 131 closes the first valve 61 and the fourth valve 64 and opens the second valve 62 and the third valve 63. As a result, a path L2 shown by a dashed line in Fig. 6 is formed, which connects the first battery case 411 and the evaluation device 1 via the pipes 20, 21, 22, and 23. Furthermore, a path L3 shown by a dotted line in Fig. 6 is formed, which connects the second battery case 412 and the first vacuum pump 12 via the pipe 26. Then, the CPU 131 executes a pressure adjustment process (first pressure adjustment process) in which the pressure inside the first battery case 411 is adjusted using the second vacuum pump 14 so that the pressure inside the first battery case 411 is stabilized.

[0034] Next, in step S3, the CPU 131 controls and closes a valve (not shown) that the leak tester 10 has, thereby isolating the first battery case 411 and the master chamber 11 from the second vacuum pump 14. As a result, in step S3, the CPU 131 executes a pressure equalization process (first pressure equalization process) to equalize the pressure in the first battery case 411 and the pressure in the master chamber 11.

[0035] Next, in step S4, the CPU 131 controls and closes a valve (not shown) of the leak tester 10 to isolate the interior of the first battery case 411 from the interior of the master chamber 11. As a result, in step S4, the CPU 131 executes an equilibration process (first equilibration process) in which the CPU 131 waits until the pressure inside the first battery case 411 stabilizes. At this time, if there is an air leak in the first battery case 411, the air inside the first battery case 411 will escape from that leak point, causing the pressure inside the first battery case 411 to decrease.

[0036] Next, in step S5, the CPU 131 executes a pressure change measurement process (first pressure change measurement process) to measure the differential pressure between the pressure inside the first battery case 411 and the pressure inside the master chamber 11, i.e., the pressure change amount ΔP inside the first battery case 411, using the differential pressure sensor of the leak tester 10.

[0037] Next, in step S6, the CPU 131 executes a process to complete the measurement of the pressure change amount ΔP.

[0038] Next, in step S7, the CPU 131 determines whether the pressure change amount ΔP is less than a preset specified value, and executes an evaluation step (first evaluation step) to evaluate the airtightness of the first battery case 411. When the processing in step S7 is completed, execution of the program is terminated. In the method for evaluating the airtightness of a case according to the embodiment, the first work connecting jig 51 is removed from the first battery case 411 whose airtightness evaluation has been completed, and as shown in FIG. 7, the first work connecting jig 51 is connected to the third battery case 413 of the third battery pack 43, which is a third workpiece whose airtightness is to be newly evaluated.

[0039] 4, while the first pressure adjustment process is being performed on the first battery case 411, the CPU 131 executes a depressurization process (second pressurization / depressurization process) of step S1 on the second battery case 412. That is, as step S1 on the second battery case 412, the CPU 131 operates the first vacuum pump 12 to discharge the air inside the second battery case 412 connected to the pipe 26, thereby executing a depressurization process (second pressurization / depressurization process) to depressurize the inside of the second battery case 412.

[0040] Next, after the evaluation of the airtightness of the first battery case 411 is completed, the CPU 131 closes the second valve 62 and the third valve 63 and closes the first valve 61 and the fourth valve 64, as shown in FIG. 7. This forms a path L4 shown by a dotted line in FIG. 7, which connects the second battery case 412 and the evaluation device 1 via pipes 20, 21, 22, 23, 24, and 26. Furthermore, a path L5 shown by a dashed line in FIG. 7 is formed, which connects the third battery case 413 and the first vacuum pump 12 via pipe 25. Then, as step S2 for the second battery case 412, the CPU 131 executes a pressure adjustment process (second pressure adjustment process) in which the pressure inside the second battery case 412 is stabilized using the second vacuum pump 14.

[0041] 4 (second equalization step, second equilibration step, second pressure change measurement step, measurement completion process, and second evaluation step) for the second battery case 412, in the same manner as for the first battery case 411, to evaluate the airtightness of the second battery case 412. Note that the explanation of the steps and processes for the second battery case 412 from step S3 onwards is omitted here because it is sufficient to replace the first battery case 411 with the second battery case 412 in the explanation of the steps and processes for the first battery case 411 from step S3 onwards.

[0042] Furthermore, in the case airtightness evaluation method according to the embodiment, the CPU 131 executes a depressurization step (third pressurization / depressurization step) of step S1 for the third battery case 413 while executing the second pressure adjustment step for the second battery case 412. That is, as step S1 for the third battery case 413, the CPU 131 executes a depressurization step (third pressurization / depressurization step) of operating the first vacuum pump 12 to exhaust air from the third battery case 413 connected to the pipe 25 and depressurize the third battery case 413. Next, after the evaluation of the airtightness of the second battery case 412 is completed, the CPU 131 opens at least the fourth valve 64 and closes the second valve 62 and the third valve 63. Then, as step S2 for the third battery case 413, the CPU 131 executes a pressure adjustment step (third pressurization / depressurization step) of adjusting the pressure in the third battery case 413 using the second vacuum pump 14 so that the pressure in the third battery case 413 is stabilized.

[0043] 4 (third equalization step, third equilibration step, third pressure change measurement step, measurement completion process, third evaluation step) for the third battery case 413, in the same way as for the first battery case 411 and the second battery case 412, to evaluate the airtightness of the third battery case 413. Note that the explanation of the steps and processes for the third battery case 413 from step S3 onwards can be omitted because it is sufficient to replace the first battery case 411 with the third battery case 413 in the explanation of the steps and processes for the first battery case 411 from step S3 onwards.

[0044] As described above, in the case airtightness evaluation method according to the embodiment, by incorporating a pressure adjustment process after the depressurization process, it is possible to separate the process of depressurizing the battery case from the process of evaluating the airtightness by detecting gas leaks from the battery case. As a result, in the case airtightness evaluation method according to the embodiment, by switching the first valve 61 to the fourth valve 64 between the open and closed states, it is possible to perform depressurization and evaluation of the airtightness of multiple battery cases in parallel using a common vacuum pump and a common evaluation device. Therefore, the case airtightness evaluation method according to the embodiment can prevent the time required to evaluate the airtightness of multiple battery cases from increasing, thereby improving the productivity of battery packs. Furthermore, in the case airtightness evaluation method according to the embodiment, because a common vacuum pump and evaluation device are used to depressurize and evaluate the airtightness of multiple battery cases, the number of vacuum pumps and evaluation devices can be reduced, thereby saving space and reducing costs.

[0045] Furthermore, in the method for evaluating the airtightness of a case according to the embodiment, the first valve 61 to the fourth valve 64 are switched between the open state and the closed state by controlling the first valve 61 to the fourth valve 64 by the CPU 131, but this is not limiting. That is, an operator may manually switch at least one of the first valve 61 to the fourth valve 64 between the open state and the closed state.

[0046] Furthermore, in the method for evaluating the airtightness of a case according to the embodiment, a decompression step is performed as the first pressurization / decompression step and the second pressurization / decompression step, in which a pump is operated to exhaust gas from the battery case or the like and reduce the pressure, but this is not limited to this. That is, in the method for evaluating the airtightness of a case according to the embodiment, a pressurization step may be performed as the first pressurization / decompression step and the second pressurization / decompression step, in which a pump is operated to introduce gas into the battery case or the like and pressurize it. [Explanation of symbols]

[0047] 1 Evaluation device 10 Leak Tester 11 Master Chamber 12 First vacuum pump 13 Control device 14 Second vacuum pump 20, 21, 22, 23, 24, 25, 26 Piping 41 First battery pack 42 Second battery pack 43 Third battery pack 51 First workpiece connection jig 52 Second workpiece connection jig 61 First Valve 62 Second valve 63 Third Valve 64 Fourth Valve 131 CPU 132 ROM 133 RAM 134 Storage section 135 Input / Output Interface 136 Bus 137 User Interface 1301 Evaluation Department 411 First battery case 412 Second battery case 413 Third battery case

Claims

1. a first pressurization / depressurization step of depressurizing or pressurizing the inside of the first case by operating a first pump connected to the first case via a first pipe; a first pressure change measuring step of measuring a pressure change amount in the first case by an evaluation device connected to the first case via a second pipe after stabilizing the pressure in the first case; a first evaluation step of evaluating the airtightness of the first case by the evaluation device based on the amount of pressure change inside the first case; A method for evaluating the airtightness of a case having performing the first pressurization / depressurization step by opening a first valve provided in the first pipe and closing a second valve provided in the second pipe; The first pressure change measuring step is performed with the first valve in a closed state and the second valve in an open state. A method for evaluating the airtightness of a case, comprising:

2. a first pressure adjustment step, between the first pressurizing / depressurizing step and the first pressure change measuring step, of switching the first valve from the open state to the closed state and switching the second valve from the closed state to the open state, and adjusting the pressure in the first case using a second pump provided in the evaluation device; 2. The method for evaluating the airtightness of a case according to claim 1.

3. a second pressurizing / depressurizing step of operating the first pump to reduce or increase the pressure in a second case connected to the first pump via a third pipe; a second pressure change measuring step of measuring a pressure change amount in the second case by the evaluation device connected to the second case via a fourth pipe after stabilizing the pressure in the second case; a second evaluation step of evaluating the airtightness of the second case by the evaluation device based on the amount of pressure change inside the second case; It has When the first pressurizing / depressurizing step is performed, at least a third valve provided in the third pipe is closed, When the first pressure change measuring step and the first evaluation step are performed, at least a fourth valve provided in the fourth pipe is kept in a closed state, After the first pressurization / depressurization step is performed, the third valve is opened and the fourth valve is closed, and the second pressurization / depressurization step is performed; after the first evaluation step is performed to complete the evaluation of the airtightness of the first case, the third valve is closed, the fourth valve is opened, and the second pressure change measuring step and the second evaluation step are performed.

3. The method for evaluating the airtightness of a case according to claim 1 or 2.

4. a second pressure adjustment step, between the second pressurizing / depressurizing step and the second pressure change measuring step, of switching the third valve from the open state to the closed state and switching the fourth valve from the closed state to the open state, and adjusting the pressure in the second case using a second pump provided in the evaluation device; 4. The method for evaluating the airtightness of a case according to claim 3.

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