JP2020181777A - Battery pack abnormality detection device - Google Patents

Abstract

To provide a battery pack abnormality detection device that can detect abnormality in a battery cell with a simpler configuration.SOLUTION: A battery pack abnormality detection device includes a weight sensor 13 that measures the weight of a battery cell 3, a weight change detection unit 12 that detects a weight change in the battery cell 3 when the weight measured by the weight sensor 13 is equal to or less than a predetermined threshold value, and an abnormality detection unit 14 that detects abnormality in the battery cell 3 on the basis of the weight change detected by the weight change detection unit 12.SELECTED DRAWING: Figure 1

Description

The present invention relates to a battery pack abnormality detection device that detects an abnormality in a vehicle battery pack.

Electric vehicles such as electric vehicles and hybrid vehicles equipped with an electric motor as a power source are equipped with a battery pack for supplying electric power to the electric motor. The battery pack includes a plurality of battery cells and a case for accommodating the plurality of battery cells, and each battery cell is electrically connected in the case.

There are various structures of each battery cell, and for example, there is one in which a power generation element including a positive electrode plate, a negative electrode plate, and a separator is housed in a container together with an electrolytic solution, and the container is sealed by a lid member. In such a battery cell, for example, if foreign matter such as metal dust is mixed in the container, there is a possibility that an internal short circuit (short circuit) may occur due to the foreign matter.

When an internal short circuit occurs, the temperature inside the container rises and gas is generated, which may increase the pressure inside the container. For this reason, the battery cell is generally provided with a safety valve that opens when the pressure in the container rises to a predetermined value to suppress bursting due to the pressure rise.

Further, in a battery pack in which a plurality of battery cells are sealed in a container, when the safety valve is opened due to an internal short circuit, the internal pressure rises even in adjacent normal battery cells due to the influence of the heat of the battery cells. As a result, there is a risk of falling into a situation where the safety valve opens (so-called heat chain). Therefore, in the battery pack, it is preferable to appropriately detect an abnormality in each battery cell (opening of the safety valve) and take an early action.

In the technique proposed in Patent Document 1, the internal pressure of the battery cell rises when an abnormality such as deterioration or short circuit of the battery occurs, and the abnormality of the battery is detected by monitoring the internal pressure.

However, a sensor for detecting the internal pressure must be arranged inside the battery cell, which complicates the configuration.

JP-A-2002-289265

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a battery pack abnormality detection device capable of detecting an abnormality in a battery cell with a simpler configuration.

A first aspect of the present invention for solving the above problems is an abnormality detecting device for detecting an abnormality in a battery pack in which a plurality of battery cells provided with a safety valve that opens when an internal pressure rises are housed inside a battery case. It is characterized by including a weight change detecting means for detecting a weight change of the battery cell and an abnormality detecting means for detecting an abnormality of the battery cell based on the weight change detected by the weight change detecting means. It is in the abnormality detection device of the battery pack.

In the first aspect, it is possible to detect an abnormality in the battery cell by detecting a weight change with a simple configuration without changing the configuration of the battery cell.

A second aspect of the present invention is the battery pack abnormality detecting device according to the first aspect, wherein the weight change detecting means is measured by a weight sensor for measuring the weight of the battery cell and the weight sensor. The battery pack abnormality detection device includes a weight change detection unit that detects a weight change of the battery cell when the weight is equal to or less than a predetermined threshold value.

In the second aspect, the weight of the battery cell can be directly measured to detect a more accurate weight change.

A third aspect of the present invention is the battery pack abnormality detecting device according to the first aspect, wherein the weight change detecting means includes a weight sensor for measuring the weight of the battery pack including the battery cell, and the weight. The battery pack abnormality detection device includes a weight change detection unit that detects a weight change of the battery cell when the weight measured by the sensor is equal to or less than a predetermined threshold value.

In the third aspect, the number of weight sensors can be reduced and the cost can be reduced as compared with measuring each battery cell with a weight sensor.

A fourth aspect of the present invention is the battery pack abnormality detecting device according to any one of the first to third aspects, wherein the weight change detecting means includes a vibration sensor provided in the battery cell and the vibration sensor. When the resonance frequency of the actuator that vibrates the battery cell and the battery cell obtained from the vibration sensor when the battery cell is vibrated at its natural frequency by the actuator is different from the natural frequency of the battery cell. The battery pack abnormality detecting device includes a weight change detecting unit for detecting a weight change of the battery cell.

In the fourth aspect, even if it is difficult to detect the weight change by the weight sensor, the weight change of the battery cell can be detected if the resonance frequency is different from the natural frequency.

According to the present invention, there is provided an abnormality detection device for a battery pack that can more reliably detect an abnormality in a battery cell.

It is the schematic of the abnormality detection apparatus which concerns on Embodiment 1. FIG. This is a flow showing the operation of the abnormality detection device. It is the schematic of the abnormality detection apparatus which concerns on Embodiment 2. FIG. It is the schematic of the abnormality detection apparatus which concerns on Embodiment 2. FIG. It is the schematic of the abnormality detection apparatus which concerns on Embodiment 3. It is a figure which shows the frequency of an actuator and a battery cell.

<Embodiment 1>
An abnormality detection device for a battery pack will be described with reference to FIG.
As shown in FIG. 1, the abnormality detection device 10 of the present embodiment targets a battery pack (not shown) mounted on an electric vehicle as an abnormality detection target. The battery pack 1 has a case (not shown) below the floor of an electric vehicle (not shown) and a plurality of battery cells 3 housed in the case (the figure shows only one battery cell). It has).

Each battery cell 3 is a sealed secondary battery such as a lithium ion battery. The battery cell 3 includes a container and a lid member for sealing the container, and an electrode body (none of which is shown) including a positive electrode plate, a negative electrode plate, and a separator is housed inside the container together with an electrolytic solution. .. Since the electrode body has a known structure, the description thereof is omitted here.

The lid member is provided with a positive electrode terminal and a negative electrode terminal (neither shown) connected to the positive electrode plate or the negative electrode plate of the electrode body housed in the container, respectively. The lid member is further provided with a safety valve 6 between the positive electrode terminal and the negative electrode terminal.

The safety valve 6 is formed to be relatively fragile compared to other parts of the lid member. For example, when an internal short circuit occurs in the container, the valve opens when the internal pressure of the container reaches a predetermined value. It is configured to do. As a result, even if the internal pressure of the container rises, the gas in the container is ejected to the outside from the opened safety valve 6. Therefore, it is possible to suppress the rupture of the container due to the increase in internal pressure.

The abnormality detecting device 10 includes a weight change detecting means for detecting a weight change of the battery cell 3. In the present embodiment, as an example of the weight change detecting means, a weight change detecting unit 12 provided in the control device 11 and a weight sensor 13 provided in the battery cell 3 are provided.

Since the weight sensor 13 is a sensor for measuring the weight and is a known device, detailed description thereof will be omitted. A battery cell 3 is mounted on the weight sensor 13. Such a weight sensor 13 is provided for each of the plurality of battery cells 3. Of course, it is not necessary to have one weight sensor 13 for each battery cell 3, and one weight sensor 13 may be provided for each of the plurality of battery cells 3.

The control device 11 is an ECU (Electronic Control Unit) mounted on an electric vehicle, and is a ROM that stores and stores a CPU, a control program, and the like, a RAM as an operating area of the control program, and an EEPROM that rewritably holds various data. , An interface unit that interfaces with peripheral circuits, etc. is included. The control device 11 controls each part of the vehicle via the interface unit to realize various controls such as running, braking, and charging / discharging of the electric vehicle.

As one function of the control device 11, a change in the weight measured by the weight sensor 13 is detected, and an abnormality detection of the battery cell 3 is performed based on the change. The functions of detecting the weight change and detecting the abnormality are realized by the weight change detecting unit 12 and the abnormality detecting unit 14 implemented as a control program. The abnormality detection unit 14 is an example of the abnormality detection means according to the claim.

The weight change detection unit 12 acquires the weight from the weight sensor 13 and detects the change in the weight. Specifically, a threshold value smaller than the weight of the battery cell 3 in the normal state is stored in advance in the storage device of the control device 11. If the weight acquired from the weight sensor 13 is equal to or less than the threshold value, the weight change detection unit 12 detects the change in the weight of the battery cell 3.

The threshold value used for the weight change detection unit 12 can be obtained by actual measurement. For example, by placing the battery pack 1 in an environment where the safety valve 6 opens and measuring the weight of the battery cell 3 when the safety valve 6 actually opens with the weight sensor 13, the weight can be used as a threshold value.

If the weight change is detected by the weight change detection unit 12, the abnormality detection unit 14 detects an abnormality that the battery cell 3 is thermally runaway. The mechanism by which thermal runaway of the battery cell 3 can be detected from the weight change is as follows. When the battery cell 3 is thermally runaway to generate gas and is released from the safety valve 6 to the outside, the battery cell 3 becomes lighter by the amount of the gas. That is, the battery cell 3 at the time of thermal runaway is lighter than the battery cell 3 at the time of normal operation. Therefore, as described above, it is possible to detect an abnormality that the battery cell 3 is thermally runaway and the safety valve 6 is opened based on the weight change of the battery cell 3.

The abnormality detection unit 14 is not limited to the method of detecting an abnormality as soon as a weight change is detected. For example, it may be determined that an abnormality has occurred in the battery cell 3 when the weight is equal to or less than the threshold value for a predetermined time. As a result, the influence of the vibration of the vehicle body on the weight sensor 13 can be reduced.

Further, when the abnormality detection unit 14 detects an abnormality in the battery cell 3, the abnormality detection device 10 may be provided with an alarm system that warns the passenger that the abnormality has occurred. The warning system includes, for example, a device for transmitting information such as a liquid crystal display and a speaker provided in an electric vehicle, and information (characters, images, figures, sounds) indicating that an abnormality has occurred in the battery cell 3 in such a device. Etc.) can be mentioned as one function (program) of the control device 11 for presenting.

Further, the abnormality detection of the battery cell 3 by the abnormality detection unit 14 may always function, or may function when a specific condition is satisfied. The state in which the abnormality detection unit 14 detects the abnormality of the battery cell 3 is referred to as a monitoring mode, and the state in which the abnormality detection is not performed is referred to as a non-monitoring mode. The determination of switching between the monitoring mode and the non-monitoring mode will be described with reference to FIG.

First, the abnormality detection unit 14 determines whether the ignition switch of the vehicle is ON (step S1). If the ignition switch is ON (step S1: Yes), the abnormality detection unit 14 shifts to the monitoring mode (step S5).

If the ignition switch is off (step S1: No), it is determined whether or not an occupant is in the vehicle (step S2). Whether or not the occupant is on board can be obtained by, for example, a seat sensor that detects whether or not the occupant is on board. In addition, it is possible to determine whether or not an occupant is in the vehicle by analyzing the image obtained by the camera provided in the vehicle.

When the occupant is on board (step S2: Yes), the abnormality detection unit 14 shifts to the monitoring mode (step S5). Even if the ignition switch is off, if an occupant is in the vehicle, the monitoring mode is set, so that the safety can be further improved.

If the occupant is not on board (step S2: No), the abnormality detection unit 14 determines whether the manual button is on (step S3). The manual button is a switch for forcibly shifting to the monitoring mode on the abnormality detection unit 14. If the manual button is on (step S3: Yes), the abnormality detection unit 14 shifts to the monitoring mode (step S5).

If the manual button is off (step S3: No), the abnormality detection unit 14 shifts to the non-monitoring mode (step S4).

By setting the monitoring mode when such specific conditions (steps S1 to S3) are satisfied, it is possible to detect an abnormality in the battery cell 3 when it is necessary to ensure safety for the occupant. As described above, the monitoring mode may be set when any of the specific conditions is satisfied, or the constant monitoring mode may be set regardless of the specific conditions.

The abnormality detection device 10 of the present embodiment can detect an abnormality in the battery cell 3, that is, a state in which the battery cell 3 is thermally runaway and the safety valve 6 is opened, based on the weight change of the battery cell 3. The weight change is performed by measuring the weight of the battery cell 3 with the weight sensor 13 and comparing the value with the threshold value. That is, there is no need to process the battery cell 3 or attach a sensor. As described above, the abnormality detection device 10 of the present embodiment can detect the abnormality of the battery cell 3 by detecting the weight change with a simple configuration without changing the configuration of the battery cell 3.

Further, the abnormality detection device 10 of the present embodiment detects the weight change of the battery cell 3 by the weight sensor 13 and the weight change detection unit 12. In this way, the weight of the battery cell 3 can be directly measured to detect a more accurate weight change.

<Embodiment 2>
Although the weight sensor 13 for measuring the weight of the battery cell 3 has been described in the first embodiment, the present invention is not limited to such a configuration. In this embodiment, a configuration in which a plurality of battery cells 3 are collectively measured in weight will be described.

FIG. 3 is a schematic view of the abnormality detection device 10 according to the present embodiment. The same components as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted.

A battery case 2 is attached to the floor surface 20 of the electric vehicle below the floor surface 20. The battery case 2 is a box-shaped member, and a plurality of battery cells (not shown) are modularized and housed therein. Specifically, the battery case 2 is attached to the floor surface 20 via a load meter 15 such as a spring. The battery case 2 does not have to be attached to the floor surface 20 only via the load meter 15, and may be attached to the floor surface 20 via the load meter 15 and stays.

The load meter 15 is an example of the weight sensor according to the claim, and can transmit the measured weight of the battery case 2 to the control device 11. The weight measured by the load meter 15 is the weight of the battery pack 1 including all the battery cells 3.

The weight change detection unit 12 acquires the weight from the load meter 15 and detects the change in the weight. Specifically, the storage device of the control device 11 stores in advance a threshold value smaller than the weight of the battery pack 1 containing the battery cell 3 in the normal state. If the weight obtained from the load meter 15 is equal to or less than the threshold value, the weight change detection unit 12 detects that the weight of at least one battery cell 3 has changed.

Further, the weight change may be detected for each of the plurality of load meters 15, or the change may be detected for the total value of the plurality of load meters 15. In this case, the weight change detection unit 12 can detect that the weight of the battery cell 3 has changed when all the weights obtained by the individual load meters 15 have changed and the total value has also changed. ..

The threshold value used for the weight change detection unit 12 can be obtained by actual measurement. For example, the battery pack 1 is placed in an environment where the safety valve 6 is opened, and the weight of the battery pack 1 including the battery cell 3 when the safety valve 6 is actually opened is measured by the load meter 15, and the weight is used as a threshold value. Can be used.

The abnormality determination by the abnormality detection unit 14 detects the abnormality of the battery cell 3 when the weight change is detected, as in the first embodiment. Of course, it is not limited to such a method. It may be determined that an abnormality has occurred in the battery cell 3 when the weight is equal to or less than the threshold value for a predetermined time. As a result, the influence of the vibration of the vehicle body on the weight sensor 13 can be reduced.

The abnormality detection device 10 of the present embodiment does not detect the weight change of the battery cell 3 individually, but detects the weight change of the battery pack 1. In other words, it is possible to detect that a weight change has occurred in at least one battery cell 3. As a result, the number of weight sensors can be reduced and the cost can be reduced as compared with the case where each battery cell 3 is measured by the weight sensor.

Further, FIG. 4 illustrates another aspect of measuring the weight of the battery pack 1. The weight sensor shown in FIG. 3 was a load meter 15 arranged so as to suspend the battery pack 1, but the weight sensor shown in FIG. 4 is a pressure sensitive sheet 16. Specifically, the floor surface 20 is provided with a support portion 21 that supports the battery pack 1 from the lower surface side. A pressure-sensitive sheet 16 is arranged on the support portion 21, and the battery pack 1 is placed on the pressure-sensitive sheet 16.

Even with such a configuration, an abnormality in the battery cell 3 can be detected based on the weight of the battery pack 1 as in the configuration shown in FIG.

<Embodiment 3>
In the first embodiment, the weight change of the battery cell 3 is directly detected by the weight sensor 13, but the embodiment is not limited to this.

FIG. 5 is a schematic view of the abnormality detection device 10 according to the present embodiment. The same components as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The abnormality detection device 10 of the present embodiment includes a vibration sensor 17, an actuator 18, and a weight change detection unit 12 as weight change detection means.

The vibration sensor 17 is a device attached to the battery cell 3 and detects the vibration of the battery cell 3. The vibration of the battery cell 3 detected by the vibration sensor 17 is transmitted to the control device 11.

The actuator 18 is a device that applies vibration to the battery cell 3. The actuator 18 can vibrate at a frequency given by the weight change detection unit 12. By vibrating the actuator 18, the battery cell 3 mounted on the actuator 18 can be vibrated. The actuator 18 may be configured to vibrate a plurality of battery cells 3 together, or may be configured to vibrate the battery cells 3 individually.

With reference to FIG. 6, the detection of the weight change of the battery cell 3 by utilizing the vibration by the abnormality detecting unit 14 will be described.
FIG. 6A shows the vibration of the actuator 18 and its amplitude. The abnormality detection unit 14 vibrates the actuator 18 at the natural frequency f0 of the battery cell 3.

FIG. 6B shows the vibration of the battery cell 3 detected by the vibration sensor 17 in the normal state. The vibration of the actuator 18 causes the battery cell 3 to resonate, and the resonance is detected by the vibration sensor 17. In the normal state (when there is no abnormality in the battery cell 3), the resonance frequency of the battery cell 3 is the natural frequency f0.

FIG. 6C shows the vibration of the battery cell 3 detected by the vibration sensor 17 during the thermal runaway of the battery cell 3. At the time of thermal runaway, the safety valve 6 of the battery cell 3 is opened to release gas, and the weight of the battery cell 3 is reduced. As the weight of the battery cell 3 decreases, its natural frequency changes. Let f1 be the frequency after the change. Therefore, at the time of thermal runaway, the resonance frequency of the battery cell 3 becomes a frequency f1 different from the natural frequency f0 at the normal time, and the amplitude becomes smaller than at the normal time.

Based on the above-mentioned principle, the weight change can be indirectly detected by the vibration of the battery cell 3. Specifically, the abnormality detection unit 14 vibrates the actuator 18 at the normal natural frequency f0 and compares it with the resonance frequency obtained from the vibration sensor 17. If the resonance frequency is the natural frequency f0, it is detected that no weight change has occurred in the battery cell 3. On the other hand, if the resonance frequency is different from the natural frequency f0, it is detected that the battery cell 3 has a weight change.

Whether or not the resonance frequency is different from the natural frequency f0 may have a certain range, for example, on the condition that the resonance frequency is not within a predetermined range from the natural frequency f0. Such conditions can be obtained by actual measurement.

The abnormality detection device 10 of the present embodiment does not directly detect the weight change of the battery cell 3, but indirectly detects it based on the resonance frequency of the battery cell 3. Thereby, for example, even if it is difficult to detect the weight change by the weight sensor, the weight change of the battery cell 3 can be detected if the resonance frequency is different from the natural frequency f0.

<Other Embodiments>
Although one embodiment of the present invention has been described above, the present invention is, of course, not limited to the above-described embodiment. In the first embodiment, the weight change is directly detected by the weight sensor, and in the third embodiment, the weight change is indirectly detected by using the resonance frequency, but they may be used in combination. Examples of the abnormality detection means include the abnormality detection unit 14 which is a program executed by the control device 11, but the abnormality is not limited thereto. The abnormality detecting means may be, for example, an electronic circuit that realizes the same function as the abnormality detecting unit 14.

1 ... Battery pack, 2 ... Battery case, 3 ... Battery cell, 6 ... Safety valve, 10 ... Abnormality detection device, 11 ... Control device, 12 ... Weight change detection unit, 13 ... Weight sensor, 14 ... Abnormality detection unit, 15 ... Load meter, 16 ... pressure sensitive sheet, 17 ... vibration sensor, 18 ... actuator

Claims (4)

An abnormality detection device that detects an abnormality in a battery pack in which a plurality of battery cells provided with a safety valve that opens when the internal pressure rises are housed inside the battery case.
A weight change detecting means for detecting a weight change of the battery cell,
An abnormality detecting device for a battery pack, comprising: an abnormality detecting means for detecting an abnormality in the battery cell based on a weight change detected by the weight change detecting means. In the battery pack abnormality detection device according to claim 1,
The weight change detecting means is
A weight sensor that measures the weight of the battery cell and
An abnormality detecting device for a battery pack, comprising: a weight change detecting unit for detecting a weight change of the battery cell when the weight measured by the weight sensor is equal to or less than a predetermined threshold value. In the battery pack abnormality detection device according to claim 1,
The weight change detecting means is
A weight sensor that measures the weight of the battery pack including the battery cell,
An abnormality detecting device for a battery pack, comprising: a weight change detecting unit for detecting a weight change of the battery cell when the weight measured by the weight sensor is equal to or less than a predetermined threshold value. In the battery pack abnormality detection device according to any one of claims 1 to 3.
The weight change detecting means is
The vibration sensor provided in the battery cell and
An actuator that vibrates the battery cell and
When the resonance frequency of the battery cell obtained from the vibration sensor when the battery cell is vibrated by the actuator at its natural frequency is different from the natural frequency of the battery cell, the weight change of the battery cell is detected. An abnormality detection device for a battery pack, which comprises a weight change detection unit.

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