Battery abnormality detection device

Abstract

This invention provides a battery abnormality detection device that detects cell swelling by measuring fluctuations in the cell's vibration response due to cell swelling and changes in spatial characteristics associated with changes in the spatial volume within the package. [Solution] The battery abnormality detection device comprises a battery 1 containing cells in a package, a vibration source 2 that applies vibration to the battery 1 from outside the battery 1, and a vibration sensor 3 that measures the vibration generated in response to the vibration applied by the vibration source 2. The device determines the state of the battery 1 based on the vibration generated in response to vibration under normal conditions and the vibration measured by the vibration sensor 3.

Description

Technical Field

[0001] Embodiments of the present invention relate to a battery abnormality detection device for detecting battery abnormalities.

Background Art

[0002] Generally, as an abnormal state of a battery, there is battery swelling. This battery swelling occurs when gas is generated by an internal chemical reaction in a structure having a sealed container that seals an electrolyte, and the expansion of the cell occurs due to an increase in pressure inside the sealed container. When the cell expands, it causes damage to the structure around the battery, such as rupture and ignition, so it is necessary to take measures such as detecting the expansion. However, there is a problem that it is difficult to discriminate from electrical characteristics. In addition, since the cell is usually housed in a package, it is difficult to determine the presence or absence of swelling by visually checking the appearance.

[0003] Therefore, a method of detecting cell expansion by attaching a pressure sensor that detects a pressure change to the surface of the cell housed in the package is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method of attaching a pressure sensor to the surface of the cell housed in the package, it is necessary to attach the sensor in advance, and it cannot be applied to batteries that are already in use.

[0006] Furthermore, if the method focuses on detecting deformation of the package rather than the cell itself, it is possible to detect this by attaching a sensor to the package afterwards, or by detecting changes in its appearance. However, this method cannot detect the cell until it bulges significantly, collides with the package, and the bulging of the cell progresses to the point where it can be observed in the package.

[0007] The present invention has been made in view of the above, and aims to provide a method for detecting cell swelling by measuring the fluctuations in the vibration response of the cell due to cell swelling and the changes in spatial characteristics associated with changes in the spatial volume within the package. [Means for solving the problem]

[0008] The battery abnormality detection device of this embodiment includes a battery in which cells are housed in a package, an excitation source that applies vibration to the battery from outside the battery, and a vibration sensor that measures the vibration generated in response to the excitation applied from the excitation source. The device determines the state of the battery based on the vibration generated in response to excitation under normal conditions and the vibration measured by the vibration sensor. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram showing the configuration of the battery abnormality detection device according to the first embodiment. [Figure 2] Figure 2 is a flowchart for measuring normal battery values. [Figure 3] Figure 3 is a flowchart for diagnosing battery abnormalities. [Figure 4] Figure 4 shows the frequency analysis waveform in response to excitation. [Figure 5] Figure 5 shows the damping waveform of the vibration amplitude in response to excitation. [Figure 6] Figure 6 is a diagram showing the configuration of the battery abnormality detection device according to the second embodiment. [Figure 7] Figure 7 is a diagram showing the configuration of the battery abnormality detection device according to the third embodiment. [Figure 8]Figure 8 is a three-view drawing of the cell. [Modes for carrying out the invention]

[0010] The embodiments will be described below with reference to the drawings. Figure 1 is a configuration diagram of the battery abnormality detection device according to the first embodiment. The battery abnormality detection device comprises a battery 1, a vibration source 2, and a vibration sensor 3. Battery 1 has a plurality of cells and a package that houses the plurality of cells. A cell is also called a battery cell, single cell, or battery, etc. A cell is, for example, a non-aqueous electrolyte secondary battery such as a lithium-ion battery, and comprises a flat or substantially rectangular parallelepiped outer container made of aluminum or an aluminum alloy, and a non-aqueous electrolyte, a positive electrode, a negative electrode, a separator, etc. inside the outer container. The package is made of, for example, a flame-retardant resin material.

[0011] The vibration generator 2 performs vibration by making contact with the battery 1. For example, vibration can be applied using an impulse hammer with a hammer or steel ball. In other words, vibration is generated by creating an impact load by colliding an element with a certain amount of mass. The waveform of the vibration is an impulse. The vibration force is adjusted by the speed at which the object is hit and the height from which it is dropped. Alternatively, a load sensor may be attached to measure the vibration force. The magnitude of the input is determined by adjusting or measuring the vibration force, and data is acquired in the form of the response (vibration) to the input (vibration force).

[0012] Furthermore, vibration can be applied using a vibrator or similar device. That is, an exciter is attached to the object, and an arbitrary vibration is generated using electromagnetic force, hydraulic pressure, etc., to excite the object. The excitation force is adjusted by adjusting the current value or hydraulic pressure. Alternatively, acceleration or load sensors may be attached to measure the excitation force (exciter mass × acceleration). The magnitude of the input is determined by adjusting or measuring the excitation force, and data is acquired in the form of the response (vibration) to the input (excitation force).

[0013] The vibration sensor 3 is configured to detect vibrations with respect to the vibration force applied by the vibration source 2 while being in contact with the battery 1. For example, it is an acceleration sensor that measures the acceleration in vibrations, and a piezoelectric acceleration sensor, a strain - type acceleration sensor, a MEMS acceleration sensor, etc. can be used.

[0014] Next, the method for detecting abnormalities in the battery in this embodiment will be described. Figures 2 and 3 are flowcharts for measuring the swelling abnormality of the battery. Figure 2 is a flowchart for measuring the normal value of the battery, and Figure 3 is a flowchart for diagnosing the abnormality of the battery.

[0015] First, as shown in Figure 2, in measuring the normal value of the battery, the vibration source 2 is attached to one position of the battery 1, and the vibration sensor 3 is attached to the other position (S001). Next, an impact or a vibration waveform is applied to the battery 1 by the vibration source 2 (S002), and the response waveform with respect to the applied impact or vibration waveform is detected by the vibration sensor 3 (S003).

[0016] The response waveform detected by the vibration sensor 3 is stored in a storage device (not shown) (S004). As the response waveform to be stored, it may be the vibration waveform itself detected by the vibration sensor 3, or for example, the peak value of the vibration, the frequency - analysis waveform, the decay waveform of the vibration amplitude, etc. Furthermore, when measuring by a method where the vibration force is not stable (impact hammer), a load cell is attached to the vibration source to measure the vibration force in parallel, and by normalizing with the vibration force, it becomes possible to remove the influence of the variation of the vibration force during abnormality diagnosis.

[0017] Also, as shown in Figure 3, in diagnosing the abnormality of the battery, the vibration source 2 is attached to one position of the battery 1, and the vibration sensor 3 is attached to the other position (S101). Next, an impact or a vibration waveform is applied to the battery 1 by the vibration source 2 (S102), and the response waveform with respect to the applied impact or vibration waveform is detected by the vibration sensor 3 (S103).

[0018] When the deviation is large compared to the normal value measured during normal operation of the response waveform detected by the vibration sensor 3, it is determined as abnormal (S104). As methods for abnormal determination, the coincidence rate of vibration waveforms, the magnification of vibration peak values, the coincidence rate of frequency analysis waveforms, and the coincidence rate of vibration amplitude decay waveforms can be used. For calculating this coincidence rate, cross-correlation or an autoencoder using machine learning can be used.

[0019] Figure 4 shows the frequency analysis waveform for vibration excitation. As abnormal determination, it is performed based on the deviation of the coincidence rate of this frequency analysis waveform. Figure 4 shows the waveforms of frequency responses in the normal state and the abnormal state. Generally, in a cell, a positive electrode, a negative electrode, a separator, and an electrolyte are filled in an outer container, and there is almost nothing other than solids and liquids. However, when gas is generated inside the cell and swelling due to an increase in internal pressure occurs, a space containing gas is generated. When a space containing gas is generated, the restraint of the cell surface is reduced, and larger vibrations are more likely to occur with respect to external forces.

[0020] Therefore, in many frequency bands, the response to external forces tends to be larger compared to the normal state. Also, since the internal volume changes due to expansion, the frequency of acoustic resonance determined depending on the space changes, so the peak value of the frequency obtained by measurement changes. Therefore, by obtaining the coincidence rate of the frequency analysis waveform and determining that there is a large deviation, it can be determined that the cell has swelled and is in an abnormal state.

[0021] [[ID=1�]] Also, Figure 5 shows the vibration amplitude decay waveform for vibration excitation. Figure 5 shows the waveforms of vibration amplitude responses in the normal state and the abnormal state when impulse vibration excitation is applied. Here, the vibration amplitude is a waveform normalized by dividing by the maximum value of the amplitude.

[0022] As explained in Figure 4, the creation of a space containing gas reduces the constraint on the cell surface. Compared to the normal state, the initial vibration amplitude is larger, the initial amplitude decrease is greater, and after the initial amplitude decay, the amplitude decay decreases and the time it takes for the decay to subside is longer. Therefore, by determining the agreement rate between the damped waveform of the vibration amplitude and the cell, it can be determined that an abnormal condition has occurred, such as swelling of the cell, when the discrepancy becomes large.

[0023] Similarly, the agreement rate of other vibration waveforms and the magnification of the vibration peak values ​​will also differ between normal and abnormal states due to the presence of gas-filled spaces, making it possible to determine abnormal states. While it is possible to use any excitation method to determine abnormal states because the response waveforms will differ, in terms of computational cost, it is possible to reduce the calculation processing of waveforms by using frequency analysis waveforms for excitations applying arbitrary waveforms and by using the damping characteristics of vibration amplitudes for excitations applying impulse waveforms.

[0024] As described above, the battery abnormality detection device can determine the abnormal state of a battery by detecting fluctuations in the vibration response due to cell swelling and comparing them with the normal state. Furthermore, it can be applied to batteries already in use by performing vibration excitation and detection from an external source.

[0025] Next, a second embodiment will be described. Figure 6 is a configuration diagram of the battery abnormality detection device according to the second embodiment. The same reference numerals are used for parts that are the same as in the first embodiment, and their detailed descriptions are omitted. In Figure 6, the difference from the first embodiment is that the excitation source 2 and the vibration sensor 3 are provided in a non-contact manner with respect to the battery 1.

[0026] The vibration generator 2 performs vibrations on the battery 1 without contact. For example, a laser irradiator can generate an impact load on an object and generate vibration by laser ablation, which obtains an excitation force by melting and evaporating the surface of the object by laser irradiation, or by laser irradiation-induced plasma, which obtains an excitation force by focusing a laser near the surface of the object to be vibrated and generating plasma.

[0027] Furthermore, since excitation using a laser irradiator utilizes the localized pressure increase caused by a rapid increase in volume as the excitation force, the excitation waveform is basically an impulse waveform. The magnitude of the input is determined by adjusting or measuring the excitation force using the laser output, and data is acquired in the form of the response (vibration) to the input (excitation force). In non-contact shock excitation sources, non-contact excitation is possible while maintaining a certain level of excitation force, but it is not possible to input arbitrary excitation waveforms; only impulses are accepted.

[0028] The vibration sensor 3 detects vibrations in response to the excitation force applied to the battery 1 by the excitation source 2 in a non-contact manner. For example, there are laser Doppler and eddy current sensors. Laser Doppler measures the absolute value of vibration from the change in the optical path length of the laser caused by the vibration of the object. Eddy current sensors generate a high-frequency magnetic field using a coil, which generates eddy currents in the target metal, and measures the absolute value of distance by changing the impedance of the sensor coil. Laser Doppler has the advantage of enabling highly accurate measurements, and eddy current sensors have the advantage of being able to measure cell swelling without removing the cells from the package, as battery packages are generally made of resin.

[0029] With the above configuration, similar to the first embodiment, the battery abnormality detection device can determine the abnormal state of the battery by detecting fluctuations in the vibration response due to cell swelling and comparing them with the normal state. Furthermore, it can be applied to batteries already in use by performing vibration excitation and detection from an external source. In addition, compared to the first embodiment, vibration excitation and measurement are performed without contact, so abnormality detection can be performed safely when the battery is energized.

[0030] Next, a third embodiment will be described. Figure 7 is a configuration diagram of the battery abnormality detection device according to the third embodiment. The same reference numerals are used for parts identical to those in the first embodiment, and their detailed descriptions are omitted. In Figure 7, the difference from the first embodiment is that the excitation source 2 and vibration sensor 3 are provided non-contact with the battery 1 and perform excitation and measurement using pressure waves.

[0031] The vibration generator 2 performs vibrations on the battery 1 without contact. For example, a pressure wave generator uses a coil or similar device to vibrate an internal diaphragm, thereby irradiating an object with a desired pressure wave and exciting it. The excitation force is adjusted by the output of the power source used to vibrate the diaphragm. Non-contact pressure wave generators can accept any excitation waveform as input, but the excitation force is smaller compared to other methods. In particular, when using a commonly available cone-shaped pressure wave source, the excitation force decreases with the square of the distance, so it is desirable to place it as close as possible to the object to be excited. The magnitude of the input is determined by adjusting or measuring the excitation force using the output of the pressure wave generator, and data is acquired in the form of the response (vibration) to the input (excitation force).

[0032] The vibration sensor 3 detects vibrations in response to the excitation force applied to the battery 1 by the excitation source 2 in a non-contact manner. For example, a pressure sensor such as a microphone measures pressure fluctuations in the air caused by vibrations generated by excitation by capturing the vibration of a diaphragm. Pressure sensors such as microphones cannot measure the DC component of pressure, but this is not a problem in this method because it does not use the DC component and only the fluctuation value needs to be acquired.

[0033] Furthermore, in configurations where a pressure wave measurement sensor is used in response to excitation by a pressure wave source, it is possible to measure the pressure wave input for excitation rather than the pressure wave caused by the vibration of the object being measured. By arranging multiple pressure wave measurement sensors, it is possible to exclude pressures other than those caused by the vibration of the object being measured through calculation, or by giving directionality to the pressure wave to be measured, it is possible to measure the pressure wave caused by the vibration of the object being measured. In addition, as shown in Figure 3, it is also effective to prevent the pressure output from the source from directly hitting the measurement sensor by placing a package or cell between the pressure wave source and the measurement sensor.

[0034] With the above configuration, similar to the first embodiment, the battery abnormality detection device can determine the abnormal state of the battery by detecting fluctuations in vibration response due to cell swelling and changes in spatial characteristics due to changes in the spatial volume within the package, and comparing them with the normal state. Furthermore, it can be applied to batteries that are already in use by performing vibration excitation and detection from the outside. In addition, compared to the first embodiment, vibration excitation and measurement are performed without contact, so abnormality detection can be performed safely when the battery is energized.

[0035] As described above, according to each embodiment, the battery abnormality detection device can determine the abnormal state of the battery by detecting fluctuations in the vibration response due to cell swelling and comparing them with the normal state. Furthermore, the excitation source and vibration sensor of each embodiment are not limited to a single combination; they can also be used in combination with contact-based excitation and non-contact-based measurement, among other methods.

[0036] Furthermore, the excitation source and vibration sensors may be configured to increase the excitation force or limit the excitation location by using multiple excitation sources, or to improve the accuracy of measurement or limit the measurement location by using multiple vibration sensors in an array system. Furthermore, as shown in the three-view drawing of the cell in Figure 8, the surface of the cell that is most affected by the pressure increase within the cell is the surface with the largest area. Therefore, it is desirable to apply excitation from a direction perpendicular to the target surface so that vibration occurs in the direction of the surface with the largest area.

[0037] Furthermore, the measurement of the normal value for a battery's normal state may be performed on all items undergoing abnormality diagnosis, or it may be performed on only a few items and applied to the same product. Alternatively, an analytical model may be created to estimate the normal value without relying on measurements.

[0038] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0039] 1. Battery 2. Kaburihara 3. Vibration sensor

Claims

1. A battery with cells housed within a package, A vibration source that applies vibration to the battery from outside the battery, It has a vibration sensor that measures vibrations generated in response to excitation applied from the aforementioned excitation source, A battery abnormality detection device that determines the state of the battery based on the vibration generated in response to excitation under normal conditions and the vibration measured by the vibration sensor.

2. The battery abnormality detection device according to claim 1, wherein the vibration source is provided in contact with the battery.

3. The battery abnormality detection device according to claim 1, wherein the vibration sensor is provided in contact with the battery.

4. The battery abnormality detection device according to claim 1, wherein the vibration source is provided at a distance from the battery.

5. The battery abnormality detection device according to claim 1, wherein the vibration sensor is provided at a distance from the battery.

6. The battery abnormality detection device according to claim 1, wherein the vibration source and the vibration sensor are provided facing the surface having the largest area among the surfaces of the cell.

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