How to evaluate the airtightness of a case

Abstract

A method for evaluating the airtightness of a case is provided that can reduce measurement errors in the amount of pressure change inside the case due to the temperature inside the case and perform a more accurate evaluation of the airtightness. [Solution] The method for evaluating the airtightness of a case of the present invention includes a pressure measurement process in which the pressure inside the case is reduced or increased and the pressure inside the case is stabilized, and then the amount of pressure change inside the case is measured; a temperature acquisition process in which the temperature inside the case is acquired while the amount of pressure change is being measured; a process in which the measured amount of pressure change is corrected based on the acquired temperature; and an evaluation process in which the airtightness of the case is evaluated based on the corrected amount of pressure change.

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 leak inspection device that exhausts gas from within a workpiece to reduce the pressure, measures the temperature of the gas exhausted from within the workpiece, and after stabilizing the pressure and temperature within the workpiece, measures the amount of pressure change within the case to inspect for gas leaks from the workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-111716 Summary of the Invention [Problem to be solved by the invention]

[0004] When evaluating the airtightness of a battery pack case as a workpiece, there is room for improvement in the airtightness evaluation method because measurement errors occur in the amount of pressure change inside the case due to the temperature (gas temperature) inside the case.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a method for evaluating the airtightness of a case that reduces measurement errors in the amount of pressure change inside the case due to the temperature inside the case and enables more accurate evaluation of airtightness. [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 according to the present invention is characterized by comprising a pressure measurement step of reducing or pressurizing the inside of the case and measuring the amount of pressure change inside the case after stabilizing the pressure inside the case; a temperature acquisition step of acquiring the temperature inside the case while measuring the amount of pressure change; a step of correcting the measured amount of pressure change based on the acquired temperature; and an evaluation step of evaluating the airtightness of the case based on the corrected amount of pressure change.

[0007] As a result, in the method for evaluating the airtightness of a case according to the present invention, it is possible to evaluate the airtightness of the case using the amount of pressure change inside the case corrected using the temperature inside the case when the pressure inside the case is stable, thereby enabling a more accurate evaluation of the airtightness of the case.

[0008] In addition, in the above, a jig having a connector in which a metal terminal is inserted into a resin housing and the resin housing and the metal terminal are sealed with a sealing member may be connected to the case, and a temperature sensor provided in the case may be electrically connected to an inspection device having a temperature acquisition unit that acquires the temperature via wiring electrically connected to the connector, so that the temperature may be acquired in the temperature acquisition process.

[0009] This allows electrical connection while suppressing gas leakage from the jig, thereby improving the accuracy of evaluation of the airtightness of the case. [Effects of the Invention]

[0010] The method for evaluating the airtightness of a case according to the present invention makes it possible to evaluate the airtightness of a case using the amount of pressure change inside the case corrected using the temperature inside the case when the pressure inside the case is stable. Therefore, the method for evaluating the airtightness of a case according to the present invention has the effect of reducing measurement errors in the amount of pressure change inside the case caused by the temperature inside the case, and enabling a more accurate evaluation of the airtightness. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an evaluation device to which a method for evaluating the airtightness of a battery case according to an embodiment is applied. [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 showing an example of the functional configuration of an inspection 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 inspection device of the evaluation device according to the embodiment. [Figure 5] FIG. 5 is a diagram showing the sealing structure of the workpiece connecting jig. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] Fig. 1 is a diagram showing a schematic configuration of an evaluation device 1 to which a method for evaluating the airtightness of a battery case 40 according to an embodiment is applied. 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 an inspection device 13 included in the evaluation device 1 according to an embodiment.

[0014] 1, an evaluation device 1 according to the embodiment includes a leak tester 10, a master chamber 11, a vacuum pump 12, and an inspection device 13. The evaluation device 1 is a device that evaluates the airtightness of a battery case 40 of a battery pack 4 using the method for evaluating the airtightness of a case according to the embodiment. In this embodiment, the evaluation device 1 is used to evaluate the airtightness of the battery case 40 of the battery pack 4.

[0015] The battery pack 4 is mounted, for example, under the floor of the vehicle and supplies power to a motor that drives the vehicle. The battery pack 4 contains a plurality of battery modules (not shown), a battery ECU (Electronic Control Unit), a thermistor 42, and other components housed within a flat, long, box-shaped battery case 40. Each battery module is formed by electrically connecting a plurality of batteries (battery cells), such as lithium-ion batteries. To grasp the status of each battery module, the battery ECU measures the voltage, current, temperature, and other parameters of each battery module and monitors the input and output to each battery module.

[0016] The battery case 40 includes a lower case having a box-like shape with an open top and an upper case having a box-like shape with an open 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 case and the upper case have flanges at the open ends thereof that overlap each other, and the flanges are fixed to each other by bolts or the like. One longitudinal end of the lower case (the front end when mounted on a vehicle) is provided with a plurality of connectors 41. These connectors 41 are, for example, female connectors. When evaluating the airtightness of the battery case 40, a jig manufactured using a male connector is attached to each of the connectors 41. This seals each connector 41.

[0017] The leak tester 10, the master chamber 11, and the vacuum pump 12 constitute a pressure measurement unit in the evaluation device 1. In the evaluation device 1, a pressure measurement process is performed using the leak tester 10, the master chamber 11, and the vacuum pump 12. The leak tester 10 is connected to the master chamber 11 via a pipe 20. The master chamber 11 is configured to be highly airtight. The leak tester 10 is also connected to the vacuum pump 12 via a pipe 21. 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 work connection jig 5. The work connection jig 5 is configured to be connected to a battery case 40, which is a work. In the present embodiment, as an example, the work connection jig 5 is connected to one longitudinal end of a lower case of the battery case 40. One end of a pipe 23 that communicates with the pipe 21 via the leak tester 10 is also connected to the leak tester 10. The other end of the pipe 22 is connected to the pipe 22 .

[0018] Furthermore, valves, differential pressure sensors, and the like (not shown) are provided within the leak tester 10. When using the leak tester 10 or the like to test the airtightness (air leakage) of the battery case 40, the vacuum pump 12 is first operated to exhaust the air from the battery case 40 and the master chamber 11, thereby reducing the pressure within the battery case 40 and the master chamber 11. Next, the vacuum pump 12 is isolated from the battery case 40 and the master chamber 11, respectively, and the pressure within the battery case 40 and the master chamber 11 is stabilized. Next, the battery case 40 is isolated from the master chamber 11, and the test is held until the pressure within the battery case 40 stabilizes. Next, the differential pressure between the pressure within the battery case 40 and the pressure within the master chamber 11 is measured by a differential pressure sensor provided in the leak tester 10. The differential pressure measured by the differential pressure sensor is recognized as the amount of pressure change within the battery case 40.

[0019] Then, if the differential pressure is ΔP [Pa], the time taken for measuring the differential pressure by the differential pressure sensor is t [sec], and Ve is the equivalent internal volume [mL], the amount of air leaking from the battery case 40, Q [mL / min], can be calculated using the following equation (1):

[0020] Q=Ve×{ΔP / (1.012×105)}×(60 / t)···(1)

[0021] The equivalent internal volume Ve is a coefficient that takes into consideration the influence of pressure fluctuation factors (volume changes due to the internal pressure of the battery case 40 and the differential pressure sensor) in the entire measurement system, including the workpiece battery case 40 and the leak tester 10. This equivalent internal volume Ve is measured, for example, by a dedicated measuring unit provided in the leak tester 10.

[0022] The leak tester 10 is electrically connected to an inspection device 13 via wiring 30. As shown in Fig. 2, the inspection 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, the ROM 132, the RAM 133, the storage unit 134, and the input / output I / F 135 are connected via a bus 136 so as to be able to communicate with each other.

[0023] The CPU 131 is a central processing unit that executes various programs and controls each part. That is, the CPU 131 reads the programs from the ROM 132 and executes the programs using the RAM 133 as a work area. As a result, the inspection device 13 functions as a temperature acquisition unit 1301, a correction unit 1302, and an evaluation unit 1303 shown in FIG. 3. In this embodiment, various programs and various data are stored in the ROM 132. The storage unit 134 is configured by an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs including an operating system and various data.

[0024] The input / output I / F 135 is electrically connected to the leak tester 10, the vacuum pump 12, the user I / F 137, the thermistor 42, and the like. 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. Also, in FIG. 1, the inspection device 13 and the leak tester 10 are electrically connected by wiring 30. Also, in FIG. 1, the inspection device 13 and the thermistor 42 are electrically connected by wiring 31 or the like via the work connection jig 5.

[0025] The CPU 131 executes a program, causing the inspection device 13 to function as a temperature acquisition unit 1301, a correction unit 1302, and an evaluation unit 1303. The temperature acquisition unit 1301 performs a temperature acquisition process, the correction unit 1302 performs a correction process, and the evaluation unit 1303 performs an evaluation process. Specifically, the temperature acquisition unit 1301 acquires the temperature (gas temperature) inside the battery case 40 while the leak tester 10 (pressure measurement unit) is measuring the differential pressure (amount of pressure change). The correction unit 1302 corrects the amount of pressure change measured by the leak tester 10 based on the temperature inside the battery case 40 acquired by the temperature acquisition unit 1301. The evaluation unit 1303 evaluates the airtightness (air leakage) of the battery case 40 based on the amount of pressure change corrected by the correction unit 1302.

[0026] The correction unit 1302 calculates a corrected pressure change amount by subtracting a value obtained by multiplying the temperature inside the battery case 40 acquired by the temperature acquisition unit 1301 by a predetermined correction coefficient from the pressure change amount (pressure fluctuation) measured by the leak tester 10. Specifically, if the pressure change amount measured by the leak tester 10 is ΔP, the temperature acquired by the temperature acquisition unit 1301 is T, the corrected pressure change amount is ΔP', and the correction coefficient is α, the correction unit 1302 calculates the corrected pressure change amount ΔP' by ΔP' = ΔP - α × T. The correction coefficient α is determined by confirming the correlation between the pressure change amount inside the battery case 40 and the temperature inside the battery case 40, for example, by measuring the actual battery case 40. This correction coefficient α is calculated, for example, as the slope of a graph plotting data on the pressure change amount inside the battery case 40 and the temperature inside the battery case 40, obtained by measuring the actual battery case 40.

[0027] The evaluation unit 1303 evaluates the airtightness (air leakage) of the battery case 40 by determining whether the corrected pressure change amount ΔP' is less than a preset specified value. Specifically, if the corrected pressure change amount ΔP' is less than the specified value, the evaluation unit 1303 evaluates that the airtightness of the battery case 40 is ensured. On the other hand, if the corrected pressure change amount ΔP' is equal to or greater than the specified value, the evaluation unit 1303 evaluates that the airtightness of the battery case 40 is not ensured.

[0028] Fig. 4 is a flowchart showing an example of the flow of processing executed by the inspection device 13 of the evaluation device 1 according to the embodiment. Next, the flow of control in the inspection device 13 will be described with reference to Fig. 4. The CPU 131 of the inspection 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 performs a pressure measurement process in steps S1 to S4, a temperature acquisition process in step S5, a correction process in step S7, and an evaluation process in step S8 in the control flow shown in Fig. 4.

[0029] First, in step S1, the CPU 131 activates the vacuum pump 12 to exhaust the air in the battery case 40 and the air in the master chamber 11, thereby reducing the pressure inside the battery case 40 and the master chamber 11.

[0030] Next, in step S2, CPU 131 controls and closes valves (not shown) of leak tester 10 to isolate the interior of battery case 40 and the interior of master chamber 11 from vacuum pump 12. As a result, in step S2, the pressure in battery case 40 and the pressure in master chamber 11 are equalized (stabilized).

[0031] Next, in step S3, the CPU 131 controls and closes a valve (not shown) of the leak tester 10, disconnecting the interior of the battery case 40 from the interior of the master chamber 11, and waits until the pressure inside the battery case 40 stabilizes (reaches an equilibrium state). At this time, if there is an air leak in the battery case 40, the air inside the battery case 40 will escape from that leak point, causing the pressure inside the battery case 40 to decrease.

[0032] Next, in step S4, the CPU 131 measures the differential pressure between the pressure inside the battery case 40 and the pressure inside the master chamber 11, that is, the amount of pressure change ΔP (pressure change) inside the battery case 40, using the differential pressure sensor provided in the leak tester 10.

[0033] Next, in step S5, the CPU 131 acquires the temperature T inside the battery case 40 while measuring the amount of pressure change ΔP. Specifically, the CPU 131 acquires the temperature (gas temperature) T inside the battery case 40 detected by the thermistor 42, which is a temperature sensor provided inside the battery case 40, while measuring the amount of pressure change ΔP.

[0034] Next, in step S6, the CPU 131 completes the measurement of the pressure change amount ΔP and the acquisition of the temperature T inside the battery case 40.

[0035] Next, in step S7, the CPU 131 calculates a corrected amount of change in pressure ΔP′ by subtracting a value obtained by multiplying the temperature T by the correction coefficient α from the amount of change in pressure ΔP.

[0036] Next, in step S8, the CPU 131 determines whether the corrected pressure change amount ΔP′ is less than a preset specified value, and evaluates the airtightness of the battery case 40. When the processing in step S8 is completed, the execution of this program is terminated.

[0037] As described above, in the method for evaluating the airtightness of the battery pack 4 according to the embodiment, it is possible to evaluate the airtightness of the battery case 40 using the corrected pressure change amount ΔP′ inside the battery case 40, which is corrected using the temperature inside the battery case 40 when the pressure inside the battery case 40 is stable. Therefore, the method for evaluating the airtightness of the battery pack 4 according to the embodiment reduces measurement errors in the pressure change amount ΔP inside the battery case 40 caused by the temperature inside the battery case 40, and enables more accurate evaluation of the airtightness of the battery pack 4.

[0038] Furthermore, in the above embodiment, the pressure measurement process is configured to reduce the pressure by discharging gas from the battery case 40, etc., but this is not limited to this. The pressure measurement process may also be configured to introduce gas into the battery case 40, etc., using a pump or the like to pressurize it.

[0039] FIG. 5 is a diagram showing the sealing structure of the work connection jig 5. The work connection jig 5 has a jig case that is fitted into and connected to a jig connection portion (not shown) provided on a battery case 40, which is the work. The jig case is provided with a male connector 500 that is fitted into and connected to a female connector (not shown) provided on the other end of the wiring 31 that is electrically connected to the inspection device 13. The male connector 500 has a resin housing 510 and a metal terminal 511. By fitting the female connector of the wiring 31 into the male connector 500 of the work connection jig 5, a concave metal electrode provided on the female connector comes into contact with and is electrically connected to the metal terminal 511 provided on the male connector 500. In addition, when the work connection jig 5 is connected to the battery case 40, for example, an electrode of a wiring (not shown) that is electrically connected to a thermistor 42 in the battery case 40 is connected to the other end of the metal terminal 511 located within the jig case 50.

[0040] Metal terminal 511 is integrally formed with rod-shaped portion 511a and plate-shaped portion 511b. Rod-shaped portion 511a is provided so as to penetrate resin housing 510. Resin housing 510 is partially exposed to the outside of jig case 50 in the axial direction (longitudinal direction) of rod-shaped portion 511a, with one end of rod-shaped portion 511a located outside jig case 50 and the other end of rod-shaped portion 511a located inside jig case 50. Plate-shaped portion 511b is provided on the other end side of rod-shaped portion 511a.

[0041] Furthermore, within the jig case 50 of the workpiece connecting jig 5, the plate-shaped portion 511b is fastened and fixed to the resin housing 510 by a plurality of screws 62 so that an O-ring 61, which is a rubber sealing member passed through the rod-shaped portion 511a, is sandwiched between the resin housing 510 and the rod-shaped portion 511a. As a result, even if a gap is formed between the resin housing 510 and the rod-shaped portion 511a of the metal terminal 511 due to a difference in linear thermal expansion between the resin housing 510 and the metal terminal 511, the seal structure formed by the plate-shaped portion 511b of the metal terminal 511 and the O-ring 61 can improve airtightness. Therefore, the method for evaluating the airtightness of a battery case 40 according to this embodiment can suppress air leakage from the workpiece connecting jig 5 while enabling electrical connection, thereby improving the accuracy of evaluating the airtightness of the battery case 40. [Explanation of symbols]

[0042] 1 Evaluation device 4 Battery pack 5 Workpiece connection jig 10 Leak Tester 11 Master Chamber 12 Vacuum pump 13 Inspection equipment 20, 21, 22, 23 Piping 30,31 Wiring 40 Battery case 41 Connector 42 Thermistor 50 Jig Case 61 O-ring 62 screws 131 CPU 132 ROM 133 RAM 134 Storage section 135 Input / Output Interface 136 Bus 137 User Interface 500 male connector 510 Resin housing 511 Metal terminal 511a Rod-shaped part 511b Plate-shaped part 1301 Temperature acquisition section 1302 Correction Unit 1303 Evaluation Department

Claims

1. a pressure measurement step of reducing or increasing the pressure inside the case, stabilizing the pressure inside the case, and then measuring a pressure change amount inside the case; a temperature acquisition step of acquiring a temperature inside the case while measuring the amount of pressure change; correcting the measured amount of pressure change based on the acquired temperature; an evaluation step of evaluating the airtightness of the case based on the corrected amount of pressure change; A method for evaluating the airtightness of a case, comprising:

2. A method for evaluating the airtightness of a case as described in claim 1, characterized in that a jig having a connector in which a metal terminal is inserted into a resin housing and the resin housing and the metal terminal are sealed with a sealing member is connected to the case, and a temperature sensor provided inside the case is electrically connected to an inspection device having a temperature acquisition unit that acquires the temperature via wiring electrically connected to the connector, and the temperature is acquired in the temperature acquisition process.

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