Method for calculating ejection rate of solid object and device for calculating ejection rate of solid object

Abstract

To provide a method for calculating the ejection rate of a solid object which can easily determine the rate of an ejection object which is ejected from a battery.SOLUTION: The method for calculating the rate of ejection of a solid object according to an embodiment of the present disclosure is a method for calculating the rate of a solid object in an ejection material ejected from a battery which has become hot, and the method includes the steps of: causing the battery to generate heat or heating the battery and rising the temperature; continuously taking an image of an ejection object ejecting from an ejection part of the battery which has become hot, by the imaging unit; specifying a solid object dispersed in the imaged ejection object; and calculating the rate of the specified solid object.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method and an apparatus for calculating the ejection velocity of a solid object. [Background technology]

[0002] In recent years, the use of batteries has been increasing in many fields, such as portable terminals, automobiles, and renewable energy. Batteries generate heat depending on the environment and conditions of use, and this heat can become uncontrollable, causing the contents to erupt (also known as thermal runaway). Simulations of battery thermal runaway are being carried out to ensure safety even when such thermal runaway occurs. One of the important parameters in this simulation is the speed of the erupted contents (ejected material). Non-Patent Document 1 is known as a method for calculating the speed of this ejected material. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Gongquan Wang, Depeng Kong, Ping Ping, Jennifer Wen, Xiaoqin He, Hengle Zhao, Xu He, Rongqi Peng, Yue Zhang, Xinyi Dai, “Revealing particle venting of lithium-ion batteries during thermal runaway: A multi-scale model toward multiphase process,” eTransportation 16 (2023) 100237, p.1-20 Summary of the Invention [Problem to be solved by the invention]

[0004] In Non-Patent Document 1, a rectifier is provided in the safety valve of the storage battery, and a pitot tube is disposed adjacent to the rectifier to measure the pressure difference of the ejected material and calculate the speed of the ejected material. Since the ejected material that passes through the rectifier rapidly diffuses, the measurement method of Non-Patent Document 1 cannot measure the pressure difference with high accuracy, and there is a risk that it will be difficult to obtain the accurate speed of the ejected material.

[0005] Although a method of calculating the speed of the ejected material by simulation is known, the inventors of the present invention have intensively studied a method of calculating the speed of the ejected material experimentally. The ejected material includes gas (vapor), liquid, and solid (granular material), and among these, the ejected solid material may damage the battery itself or the peripheral members of the battery. In addition, in the all-solid-state battery which is expected to be widespread in the future, it is expected that the amount of ejected solid material due to thermal runaway will increase, and the degree of the damage may be large. From the viewpoint of ensuring safety, it is required to calculate the ejection speed of the ejected solid material.

[0006] In consideration of these circumstances, an object of the present disclosure is to provide an ejection velocity calculation method that can easily determine the velocity of solid matter in ejection material ejected from a battery. [Means for solving the problem]

[0007] A method for calculating the ejection velocity of solid objects according to one embodiment of the present disclosure, devised to solve the above problems, is a method for calculating the velocity of solid objects in ejection material ejected from a battery whose temperature has increased, and includes the steps of generating heat in the battery or heating the battery to increase its temperature, continuously capturing images of the ejection material ejected from the ejection portion of the battery whose temperature has increased using an imaging unit, identifying solid objects scattered in the ejection material that has been imaged, and calculating the velocity of the identified solid objects. Effect of the Invention

[0008] The calculation of the ejection velocity of solid objects according to one embodiment of the present disclosure makes it easy to determine the velocity of solid objects in the ejection material ejected from the battery. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic plan view showing a solid object ejection velocity calculation device and a battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described.

[0011] (1) A method for calculating the ejection velocity of solid matter according to one embodiment of the present disclosure is a method for calculating the velocity of solid matter in ejection material ejected from a battery whose temperature has increased, the method comprising the steps of generating heat in the battery or heating the battery to increase its temperature, continuously capturing images of the ejection material ejected from the ejection portion of the battery whose temperature has increased with an imaging unit, identifying solid matter scattered in the ejection material that has been imaged, and calculating the velocity of the identified solid matter.

[0012] The method for calculating the ejection velocity of solid objects (hereinafter also referred to as "the calculation method") captures an image of the ejected object ejected from a battery, and identifies the solid object in the ejected object from the captured image. This makes it easy to identify the solid object. In addition, since the ejected object is continuously imaged, the movement of the identified solid object can be easily tracked. This makes it easy to calculate the velocity of the identified solid object, and therefore makes it easy to estimate the velocity of the ejected object immediately after ejection.

[0013] (2) In the above (1), the imaging step may capture images using a plurality of the imaging units. In this way, the movement of the identified solid object can be tracked three-dimensionally, and the speed of the identified solid object can be calculated with high accuracy.

[0014] (3) In the above (2), at least two imaging units may capture images from two different directions perpendicular to the ejection direction of the ejected object. In this way, the three-dimensional movement of the ejected object can be easily tracked.

[0015] (4) In the above (3), the two directions may be perpendicular to each other. In this way, the three-dimensional movement of the solid object can be tracked more easily.

[0016] (5) In any of (1) to (4) above, the method may further include a step of observing the ejection state of the ejection material from the image captured in the imaging step. That is, the ejection state, such as the ejection direction of the entire ejection material including gas and liquid, the spread after ejection, and the speed of this spread, may be observed from the captured image.

[0017] (6) A solid object ejection velocity calculation device according to one embodiment of the present disclosure is a device for calculating the velocity of ejection material ejected from a battery whose temperature has increased, and includes a temperature increasing means for generating heat in the battery or heating the battery, an imaging unit for continuously capturing images of the ejection material ejected from the battery whose temperature has increased, and a calculation unit for identifying solid objects scattered within the captured ejection material and calculating the velocity of the solid objects.

[0018] The solid object ejection velocity calculation device includes an imaging unit that captures the ejection object ejected from the battery, so that the solid object in the ejection object can be easily identified from the captured image. In addition, since the imaging unit continuously captures the ejection object, the movement of the identified solid object can be easily tracked. Therefore, the velocity of the identified solid object can be easily calculated.

[0019] (7) In the above (6), a casing may be further provided to house the imaging unit. In this way, the imaging unit can be easily protected from the ejected matter.

[0020] Here, "orthogonal" generally means within the range of 90°±10°.

[0021] [Details of the embodiment of the invention] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0022] <Gushing speed calculation device> The ejection velocity calculation device 100 (hereinafter, simply referred to as "the device 100") that calculates the velocity of solid matter in the ejection material ejected from the battery B whose temperature has increased includes a temperature increasing means (not shown) that generates heat in the battery B or heats the battery B, an imaging unit that continuously images the ejection material ejected from the battery B whose temperature has increased, and a calculation unit that calculates the velocity of solid matter scattered in the imaged ejection material, as shown in Fig. 1. The device 100 of this embodiment also includes a display unit that displays the image captured by the imaging unit, and an illumination unit that irradiates the ejection material.

[0023] 〔battery〕 The battery B is not particularly limited as long as it ejects (releases) the contents by thermal runaway, and examples thereof include storage batteries such as lithium ion batteries. The battery B may have a housing of a substantially rectangular parallelepiped or cylindrical shape, or may be formed into a bag shape by laminating sheet-like members. The ejected matter (contents of the battery B) is mainly gas (vapor) and includes liquid and solid (particulate solid matter). The gas includes, for example, carbon oxide and flammable gas. In this embodiment, the battery B has a substantially rectangular parallelepiped housing and has a safety valve S as an ejection part that ejects (releases) the contents by thermal runaway, which is formed between a pair of electrodes B1 and B2 provided on one surface (top surface). The battery B is placed on the mounting table 150 so that the safety valve S faces upward (opposite to the direction of gravity). The solid matter is, for example, fragments of the electrodes B1 and B2 that are broken inside the battery B.

[0024] [Temperature increasing means] The temperature increasing means increases the temperature of battery B by generating heat in battery B or by heating battery B. The temperature increasing means may be, for example, a heater such as an electric heater that heats battery B from the outside by contacting a heating surface with battery B, a power source that supplies excess electricity to battery B (putting it into an overcharged state) to generate heat, or a sharp conductive material such as a nail that is pierced into battery B to short-circuit it internally.

[0025] [Imaging unit] The imaging unit continuously captures images of the ejection material ejected from the battery B whose temperature has risen. The imaging unit is not particularly limited, and may be, for example, a camera. The ejection material is preferably captured by a plurality of imaging units. By capturing images by a plurality of imaging units, the ejection state of the ejection material can be captured stereoscopically (three-dimensionally). The device 100 includes two cameras, a first camera 110 and a second camera 111.

[0026] The two cameras 110, 111 are preferably arranged so that the imaging direction (normal direction at the center of the imaging area (image)) of the cameras 110, 111 is approximately 90° (approximately horizontal in this embodiment) with respect to the ejection direction (upward in this embodiment) of the ejection material, and the two cameras 110, 111 are arranged so that the imaging directions are different, and the ejection material is imaged. In this manner, one camera (first camera 110) can image the ejection state of the ejection material in one direction, while the other camera (second camera 111) can image the ejection state in a direction different from the one direction, so that the ejection state can be captured three-dimensionally.

[0027] Moreover, it is more preferable that the two directions are perpendicular to each other. That is, it is more preferable that the two cameras 110, 111 are arranged so that their imaging directions intersect at approximately 90° on the safety valve S. In this way, it is possible to image the jetting condition in the one direction (X direction) and a direction perpendicular to the one direction (Y direction), which improves the ease of capturing the jetting condition three-dimensionally.

[0028] The height at which the cameras 110, 111 are placed (the vertical distance from the installation surface of the camera to the center of the imaging area) is not particularly limited, but it is preferable that the cameras are placed at a height such that a part of the battery B is captured in a part of the imaging area of ​​the cameras 110, 111. For example, it is preferable that the cameras are placed at a height such that a part of the battery B including the top surface is captured in an area of ​​30% or less, or 20% or less, below the imaging area of ​​the cameras 110, 111. In this way, the above-mentioned ejection state from the safety valve S can be captured.

[0029] The device 100 preferably includes a casing that houses the imaging unit. That is, the cameras 110, 111 are preferably housed in casings 112, 113, respectively. In this way, the cameras 110, 111 can be protected from the ejected material. The casings 112, 113 are not particularly limited, and may be, for example, boxes made of metal, resin, or the like, with one surface of the cameras 110, 111 facing the imaging direction being made of a transparent plate.

[0030] [Display] The display unit displays the images captured by the cameras 110 and 111. The display unit is not particularly limited, and may be a known monitor 120. By providing the monitor 120 in the device 100, the ejection state can be visually observed.

[0031] [Lighting section] The illumination unit is a light source that irradiates the ejection with light. The illumination unit is not particularly limited, and known LED (Light Emitting Diode) illumination or the like can be used. By providing the device 100 with LED illumination, the cameras 110 and 111 can clearly capture the ejection. The device 100 of this embodiment has a first LED illumination 130 arranged between the two cameras 110 and 111, a second LED illumination 131 arranged so that the first camera 110 is located between the first LED illumination 130, and a third LED illumination 132 arranged so that the second camera 111 is located between the first LED illumination 130.

[0032] [Calculation section] The calculation unit calculates the speed of solid objects scattered in the ejected material captured. Specifically, the calculation unit identifies solid objects in the ejected material from a plurality of images captured in succession, and calculates the speed from the distance traveled by the solid objects. The calculation unit is not particularly limited, and a known personal computer 140 can be used. The personal computer 140 is electrically connected to the cameras 110 and 111. The cameras 110 and 111 transmit the captured images to the personal computer 140. The personal computer 140 identifies solid objects in the ejected material from the received images. The number of solid objects to be identified may be one, but is preferably multiple.

[0033] The velocity is calculated, for example, as follows: First, from multiple images captured by the first camera 110, the position (coordinate) lx0 of the identified solid object in the left-right direction (X direction) of the image at time t0 and the position lx1 at time t1 are confirmed, and the velocity Vx of the identified solid object in the X direction is calculated using the following formula (1).

number

[0034] Next, from multiple images captured by the second camera 111, the position ly0 at time t0 and the position ly1 at time t1 of the identified solid object in the left-right direction (Y direction) of the image are confirmed, and the velocity Vy of the identified solid object in the Y direction is calculated using the following equation (2).

number

[0035] Furthermore, from multiple images captured by either the first camera 110 or the second camera 111, the position lz0 of the identified solid object at time t0 in the vertical direction (Z direction) of the image and the position lz1 at time t1 are confirmed, and the velocity Vz of the identified solid object in the Z direction is calculated using the following equation (3).

number

[0036] The velocity V of the above-specified solid object is calculated using the following formula (4).

number

[0037] <Ejection velocity calculation method> The method for calculating the ejection speed of solid objects includes a step of increasing the temperature by generating heat in the battery B or by heating the battery B, a step of continuously capturing images of the ejection material ejected from the ejection portion of the battery B whose temperature has increased with an imaging unit, a step of identifying solid objects scattered in the captured ejection material, and a step of calculating the speed of the identified solid objects. The calculation method may further include a step of observing the ejection state of the ejection material in the image captured in the imaging step.

[0038] [Step of increasing temperature] In the temperature increasing step, the battery B is caused to generate heat or is heated to increase the temperature of the battery B, thereby causing the battery B to transition to a thermal runaway state. The temperature of the battery B may be increased by supplying excess electricity from a power source to the electrodes B1 and B2 to generate heat from within the battery, or by heating the battery from the outside using a heater or the like.

[0039] [Image capture process] In the imaging step, the imaging unit continuously images the ejection material ejected from the ejection portion of the battery B whose temperature has risen. That is, the cameras 110 and 111 continuously image the ejection material ejected from the safety valve S of the battery B that has gone into thermal runaway. The lower limit of the number of images (frames) per second of the ejection material continuously captured may be, for example, 100 fps, 200 fps, 500 fps, 1000 fps, 2000 fps, 5000 fps, or 10000 fps. The upper limit of the number of frames is not particularly limited and may be, for example, 20000 fps. By keeping the number of frames within the above range, the calculation accuracy of the speed of the solid object can be improved. The number of frames may be variable so that imaging can be performed according to the ejection situation.

[0040] [Specifying step] In the identification step, solid objects scattered in the imaged ejection material are identified. Specifically, images captured by the cameras 110, 111 are transmitted to the personal computer 140, and the solid objects are identified by image analysis by the personal computer 140. The solid objects may be identified by an operator visually from the image displayed on the monitor 120 and instructed to the personal computer 140.

[0041] [Calculation step] In the calculating step, the velocity of the identified solid object is calculated. Specifically, the velocity of the solid object is calculated using the above formulas (1) to (4).

[0042] [Observation step] In the observing step, the ejection state of the ejection material is observed from the image captured in the imaging step. The observation method is not particularly limited, and examples include a method of visually observing the spread (width, height, angle, etc.) and speed of the ejection material by displaying the captured image on a monitor 120, or a method of converting the image into data by image processing using a personal computer 140.

[0043] <Advantages> The device 100 and the calculation method continuously capture images of the ejection material ejected from the battery B, and therefore can identify solid objects in the ejection material and easily track the movement of the identified solid objects. This makes it easy to calculate the speed of the identified solid objects. Since the change in speed of the ejected solid object between immediately after ejection and a certain time after ejection is relatively small, the speed of the ejection material immediately after ejection can be easily estimated by calculating the speed of the solid object.

[0044] By determining the speed of the ejected material immediately after ejection, it is possible to perform various simulations with high accuracy regarding the safety of Battery B, such as the energy released by Battery B going into thermal runaway.

[0045] [Other embodiments] The above-mentioned embodiment does not limit the configuration of the present disclosure. Therefore, the above-mentioned embodiment may omit, replace, or add components of each part of the above-mentioned embodiment based on the description in this specification and common technical knowledge, and it should be construed that all of them belong to the scope of the present disclosure.

[0046] In batteries in which the location from which the ejection material will be discharged is predicted (batteries in which an ejection portion is formed), such as batteries having the above-mentioned safety valve, it is preferable that the camera of the imaging unit is positioned so as to capture an image of a portion of the battery including the ejection portion as described above, and in batteries in which the location from which the ejection material will be discharged is unpredictable (batteries in which the ejection material will be discharged from any location, and the ejection location is the ejection portion), the camera may be positioned so as to capture an image of the entire battery.

[0047] The number of cameras may be one. When calculating the speed of a solid object using one camera, the speed of the solid object can be obtained by using the above formulas (1), (3), and (4). The number of cameras may be three or more. [Industrial Applicability]

[0048] The solid object ejection velocity calculation device and solid object ejection velocity calculation method disclosed herein can determine the velocity of objects ejected from a battery, and are therefore suitable for use in various simulations of thermal runaway of batteries, such as simulating the safety of a battery pack having multiple batteries connected together. [Explanation of symbols]

[0049] 100 Ejection velocity calculation device 110 Camera No. 1 111 Second Camera 112,113 Casing 120 monitors 130 No. 1 LED Lighting 131 2nd LED Lighting 132 3rd LED lighting 140 Personal Computer 150 Placement table B battery B1,B2 electrode S Safety valve

Claims

1. A method for calculating the velocity of solid matter in a jet ejected from a battery at an elevated temperature, comprising the steps of: generating heat in the battery or heating the battery to increase its temperature; A step of continuously capturing images of ejected material ejected from the ejection portion of the battery whose temperature has increased, using an imaging unit; identifying solid objects dispersed within the imaged ejecta; calculating the velocity of the identified solid object; A method for calculating the ejection velocity of a solid object comprising:

2. 2. The method for calculating the ejection velocity of a solid object according to claim 1, wherein said imaging step comprises imaging using a plurality of said imaging units.

3. 3. The method for calculating the ejection velocity of a solid object according to claim 2, wherein at least two image capturing units capture images from two different directions perpendicular to the ejection direction of the ejected object.

4. The method for calculating the ejection velocity of solid objects according to claim 3, wherein the two directions are perpendicular to each other.

5. The method for calculating the ejection velocity of solid objects according to claim 1 , further comprising the step of observing an ejection state of the ejected objects from an image captured in the imaging step.

6. An apparatus for calculating the velocity of solid matter in ejection material ejected from a battery whose temperature has increased, comprising: A temperature increasing means for generating heat in the battery or for heating the battery; an imaging unit that continuously images the ejection material ejected from the battery whose temperature has increased; a calculation unit that identifies solid objects scattered within the imaged ejecta and calculates the speed of the solid objects; A solid object ejection velocity calculation device comprising:

7. The apparatus for calculating the ejection velocity of a solid object according to claim 6 , further comprising a casing that houses the imaging unit.

Images