Power supply device, and method for detecting opening of exhaust valve of power supply device

Disclosed is a power supply device including a battery having an exhaust valve that opens when an internal pressure becomes higher than a set pressure, the battery being housed in a case, a temperature sensor that detects a temperature in the case, and a detection circuit that detects opening of the exhaust valve at a detected temperature detected by the temperature sensor. In this power supply device, the detection circuit detects that a high temperature time (t1) from a timing at which a rate of rise (ΔT/Δt) of the temperature detected by the temperature sensor is higher than a rise rate set value and exceeds the rise rate set value to a timing at which the detected temperature falls to less than or equal to a reference temperature is longer than a high temperature time set value, and detects the opening of the exhaust valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of the PCT International Application No. PCT/JP2019/015052 filed on Apr. 5, 2019, which claims the benefit of foreign priority of Japanese patent application 2018-083308 filed on Apr. 24, 2018, the contents all of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a power supply device in which a rechargeable battery is disposed in a case, and relates particularly to a power supply device including an exhaust valve that opens when an internal pressure of the battery rises to an abnormal pressure, and a method for detecting opening of the exhaust valve of the power supply device.

BACKGROUND ART

In a power supply device in which a battery is built in a case, an exhaust valve is provided in the battery in order to prevent an adverse effect such as a rupture of the battery. The exhaust valve detects an internal pressure of the battery and opens. The exhaust valve opens when the internal pressure of the battery becomes higher than a set pressure, and ejects an internal high-pressure gas to prevent a rise of the internal pressure. The internal pressure of the battery rises when the battery is used in an abnormal state. The abnormal state of the battery in which the exhaust valve opens is caused by, for example, a flow of an excessive charging/discharging current or an internal short-circuit of positive and negative electrodes. Since the exhaust valve opens during abnormal use, it is important to detect the open state quickly. A power supply device that detects a temperature and determines whether the exhaust valve opens has been developed. (See PTL 1)

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

The device that detects the temperature and determines the opening of the exhaust valve determines the valve opening by detecting the battery temperature and an ambient temperature. Since the battery temperature rises when the exhaust valve opens, the valve opening can be detected by the battery temperature and the ambient temperature. However, the battery temperature fluctuates under external conditions such as the ambient temperature, and also changes with the magnitude of the current that charges and discharges the battery, so that it is difficult to detect the valve opening reliably and quickly. In addition, in the device that determines the opening of the exhaust valve based on the temperature, noise induced in the temperature sensor hinders accurate detection of the temperature, so that this also makes it difficult to detect the opening of the exhaust valve quickly and reliably.

The present invention has been developed for the purpose of eliminating the above-mentioned conventional adverse effects, and an important object of the present invention is to provide a power supply device capable of detecting a temperature and accurately and quickly detecting opening of an exhaust valve, and a method for detecting the opening of the exhaust valve.

A power supply device of the present invention includes battery1having an exhaust valve that opens when an internal pressure becomes higher than a set pressure, case3that houses battery1, temperature sensor5that detects a temperature in case3, and detection circuit7that detects opening of the exhaust valve at a detected temperature detected by temperature sensor5, in which it is detected that a high temperature time (t1) from a timing at which a rate of rise (ΔT/Δt) of the detected temperature is higher than a rise rate set value and exceeds the rise rate set value to a timing at which the detected temperature falls to less than or equal to a reference temperature is longer than a high temperature time set value, and detection circuit7detects the opening of the exhaust valve.

In the power supply device of the present invention, a plurality of temperature sensors5are provided in case3, and detection circuit7can detect the opening of the exhaust valve from the temperature detected by each of temperature sensors5. At least one of the plurality of temperature sensors5can be disposed in an exhaust gas path in case3. Furthermore, at least one of the plurality of temperature sensors can be disposed to be thermally coupled directly or indirectly to battery1, and thus to detect the battery temperature.

In the power supply device of the present invention, detection circuit7detects that a rising time (t2) from a timing at which the rate of rise (ΔT/Δt) of the detected temperature is higher than a set rate to a timing at which the rate of rise (ΔT/Δt) falls to less than or equal to the set rate exceeds a rising time set value and can detect the opening of the exhaust valve.

In the power supply device of the present invention, temperature sensor5can also be used as temperature sensor5that detects the battery temperature.

A method for detecting opening of an exhaust valve of a power supply device of the present invention is a method for detecting opening of an exhaust valve of a power supply device including battery1having an exhaust valve that opens when an internal pressure becomes higher than a set pressure, case3that houses battery1, and temperature sensor5that detects a temperature in case1, and the method includes detecting a rate of rise (ΔT/Δt) of the detected temperature detected by temperature sensor5, detecting a high temperature time (t1) from when the rate of rise exceeds a rise rate set value to when the rate of rise falls to less than or equal to a reference temperature, and determining that the exhaust valve has opened in a state in which the rate of rise (ΔT/Δt) is larger than the preset rise rate set value and the high temperature time (t1) is longer than a high temperature time set value.

In the method for detecting opening of an exhaust valve of a power supply device of the present invention, temperatures at a plurality of measurement points are detected by a plurality of temperature sensors5disposed in case3, and when it is detected that the rate of rise (ΔT/Δt) of the temperature detected by any of temperature sensors5and the high temperature time (t1) exceed the set values, it can be determined that the exhaust valve has opened.

In the method for detecting opening of an exhaust valve of a power supply device of the present invention, it is detected that a rising time (t2) from a timing at which the rate of rise (ΔT/Δt) of the detected temperature is higher than a set rate to a timing at which the rate of rise (ΔT/Δt) falls to less than or equal to the set rate exceeds a rising time set value, and it can be determined that the exhaust valve has opened.

In the method for detecting opening of an exhaust valve of the present invention, temperature sensor5can also be used as temperature sensor5that detects the battery temperature.

The power supply device and the method for detecting opening of an exhaust valve of a power supply device of the present invention are characterized in that a temperature is detected and the opening of the exhaust valve can be detected accurately and quickly. In particular, in the power supply device and the valve opening detection method described above, in addition to the rate of rise (ΔT/Δt) of the temperature detected by the temperature sensor, the high temperature time (t1) from when the rate of rise (ΔT/Δt) of the detected temperature exceeds the rise rate set value to when the detected temperature falls to less than or equal to the reference temperature is detected, and it is also detected that the high temperature time (t1) exceeds the high temperature time set value to detect the opening of the exhaust valve, so that there is a feature that the opening of the exhaust valve can be accurately detected by ignoring an influence of noise induced in the temperature sensor. Although the temperature sensor can detect, for example, the battery temperature in the case with a simple circuit configuration, the influence of noise induced in the temperature sensor cannot be eliminated. The noise of the temperature sensor is induced from a power supply circuit such as a switching power supply via a power supply line, and is further induced as radiation noise from various switching circuits. Since a detection voltage of the temperature sensor fluctuates due to both the detected temperature and noise, the voltage fluctuation due to noise causes an error in the detected temperature. Complete removal of noise is extremely difficult, and errors in the detected temperature due to noise hinder accurate detection of the opening of the exhaust valve.

The power supply device and the valve opening detection method of the present invention can accurately detect the opening of the exhaust valve even when the detected temperature fluctuates due to noise. This is because the power supply device and the valve opening detection method described above detect the opening of the exhaust valve with both the rate of rise (ΔT/Δt) of the temperature and the high temperature time (t1) to when the temperature falls. When the exhaust valve opens and high-temperature exhaust gas is ejected from the battery, the temperature inside the case rises rapidly. In addition, after the temperature rises, it takes time for the temperature to fall to the reference temperature, and the time to when the temperature falls is considerably longer than a noise cycle. Thus, the rate of rise (ΔT/Δt) is compared with the rise rate set value. In addition, the high temperature time (t1) to when the temperature falls to the reference temperature is compared with the high temperature time set value, and it is detected that both the rate of rise and the high temperature time exceed the set values, so that malfunctions due to noise that fluctuates in a short cycle are eliminated, and the opening of the exhaust valve is reliably detected.

DESCRIPTION OF EMBODIMENT

Hereinafter, the present invention will be described in detail with reference to the drawings. In the description below, the terms indicative of specific directions or positions (e.g., “upper”, “lower”, and other words including these words) are used as appropriate. The use of these terms is to make the understanding of the present invention easy with reference to the drawings, and does not limit the technical scope of the present invention by their meanings. The parts indicated with the same reference characters represented in a plurality of the drawings denote the same or equivalent parts or members.

In addition, the exemplary embodiment described below exemplifies a power supply device and a method for detecting opening of an exhaust valve of the power supply device for embodying the technical idea of the present invention, and it is not intended to limit the present invention to the following exemplary embodiment. Unless specifically stated otherwise, the dimensions, materials, shapes and relative arrangements, among others, of the components described below do not intend to limit the scope of the present invention to these dimensions, materials, shapes, and relative arrangements, etc., and intended to exemplify. Moreover, details described in one embodiment and one Example are also applicable to another embodiment and another Example. Furthermore, the sizes, positional relationship, and the like of members shown in the drawings may be exaggerated for clarity.

The power supply device of the present invention is optimal for a large-capacity power supply in which a large number of batteries are built in a case, for example, a backup power supply, and is used for various other applications such as a power supply device for a vehicle that supplies electric power to a traveling motor of a bicycle or a vehicle.

Power supply device100shown in the schematic diagrams ofFIGS. 1 and 2has a plurality of batteries1incorporated as battery unit2in case3. Case3contains battery unit2, circuit board4, and temperature sensor5connected to circuit board4. In battery unit2, a plurality of rechargeable batteries1are connected in series or in parallel via a lead plate (not shown) of a metal sheet and connected in a block shape.

Battery1is a cylindrical battery or a prismatic battery. In battery1, an electrode and an electrolyte solution are housed in a metal case having a sealed structure. In the metal case, an opening of an exterior can whose bottom is closed is airtightly fixed by a sealing plate. The exterior can is produced by pressing a metal sheet. The sealing plate is airtightly fixed by caulking at a peripheral edge of the opening of the exterior can through a packing.

Although not shown, battery1is provided with an exhaust valve in order to prevent the metal case having a sealed structure from being damaged when an internal pressure of the metal case rises. The exhaust valve is provided on the sealing plate or on a bottom surface of the exterior can. The exhaust valve opens when the internal pressure becomes higher than a set pressure, for example, 1.5 MPa, and prevents the metal case from being broken due to the rise of the internal pressure. The exhaust valve is opened in an abnormal state. Therefore, the temperature of battery1is also very high when the exhaust valve opens. Thus, a gas and an electrolyte solution (ejected substance) ejected from the exhaust valve that opens become abnormally high temperature exhaust gases. Particularly, in a battery device in which battery1is a lithium ion battery, exhaust gas has an abnormally high temperature. In addition, since the lithium ion battery is filled with a nonaqueous electrolyte solution, this becomes a combustion gas discharged at a high temperature, which may cause a more abnormally high temperature. Even in not only the lithium ion battery but also other rechargeable batteries, the exhaust valve opens in an abnormal use state, so that exhaust gas has an abnormally high temperature.

Case3is made of metal or plastic, has a sealed structure or a structure that is closed but not sealed, and is provided with an exhaust port (not shown) for discharging the exhaust gas discharged from battery1to the outside. In case3having the exhaust port, the exhaust gas ejected from battery1is discharged to the outside through the exhaust port. However, case3having a sealed structure or a closed structure does not necessarily have to be provided with a specific exhaust port, but may be provided with a partial gap to have a structure in which the exhaust gas is discharged to the outside through this gap.

In power supply device100ofFIG. 1, case3has a rectangular box shape as a whole, and battery unit2and circuit board4are disposed inside case3. In the power supply device ofFIG. 1, three sets of battery units2are disposed in case3. However, the power supply device of the present invention does not specify the number of batteries1housed in case3and the connection state.

Circuit board4is connected to temperature sensor5via lead wire6. Temperature sensor5detects the temperature of a specific portion in case3and detects that the exhaust valve of battery1has opened. It is important for the power supply device in which a plurality of batteries1are built in case3to accurately detect the opening of the exhaust valve even when the exhaust valve of any of batteries1has opened. In power supply device100ofFIGS. 1 and 2, a plurality of temperature sensors5are disposed in case3, and power supply device100detects the opening of the exhaust valve from the temperature detected by every temperature sensors5. The power supply device ofFIGS. 1 and 2is provided with temperature sensor5A that detects the battery temperature and temperature sensor5B that detects the temperature of the exhaust gas ejected from the exhaust valve that opens.

Temperature sensor5A that detects the battery temperature is disposed to be thermally coupled directly or indirectly to battery1constituting battery unit2. Battery unit2in which batteries1are connected in series or in parallel via the lead plate of the metal sheet may be disposed such that temperature sensor5A is thermally coupled to the lead plate, and may be disposed to be thermally coupled to battery1via the lead plate. Since the lead plate is connected to the plurality of batteries1, temperature sensor5A thermally coupled to battery1via the lead plate can quickly detect the temperature of the plurality of batteries1connected with the lead plate. However, temperature sensor5A can also be disposed by being thermally coupled to a surface of a battery case. In illustrated power supply device100, a plurality of temperature sensors5A that detect the battery temperature are disposed on an upper surface and a lower surface of battery unit2. Each temperature sensor5A detects the temperature of battery1thermally coupled. In illustrated power supply device100, the number of temperature sensors5A is smaller than the number of batteries1, and the temperature of specific battery1is detected. Power supply device100is designed such that each battery1is charged and discharged with the same current to reduce a temperature difference, so that the temperature of specific battery1is detected without detecting all the battery temperatures. Since power supply device100detects the battery temperature in order to protect battery1, for example, power supply device100detects the temperature of battery1in which a temperature change is large to allow battery1to be charged and discharged while protecting battery1. However, the power supply device can detect the temperature by thermally coupling temperature sensors5A to all batteries1.

Temperature sensor5B that detects the temperature of the exhaust gas is disposed between battery units2and between battery unit2and an inner surface of case3in a passage of the exhaust gas discharged from battery1. In power supply device100ofFIGS. 1 and 2, temperature sensor5B that detects the temperature of the exhaust gas is disposed between battery unit2and case3. Temperature sensor5B detects the temperature of the exhaust gas flowing along the inner surface of case3to detect the opening of the exhaust valve. Temperature sensor5B for exhaust gas is disposed by being thermally coupled to battery1, so that temperature sensor5B can also be used as temperature sensor5A that detects the temperature of battery1.

Circuit board4is mounted with detection circuit7connected to temperature sensor5via lead wire6to detect the opening of the exhaust valve, and protection circuit8connected to battery1to control charging/discharging of battery1. Detection circuit7detects the temperature of the battery in case3and the temperature of the gas passage to detect the opening of the exhaust valve. When the exhaust valve is opened, high temperature exhaust gas is ejected into case3. Therefore, the detection of the exhaust valve can be determined by detecting the temperature in case3. However, the temperature in case3fluctuates even under conditions other than the opening of the exhaust valve and, for example, fluctuates with an ambient temperature of case3and a current value for charging/discharging battery1. Thus, even when the exhaust valve does not open, if the ambient temperature rises or the current for charging/discharging battery1increases, the temperature in case3rises. The temperature in case3rises as the exhaust valve opens, and also rises due to the ambient temperature and the charging/discharging current, so that when the opening of the exhaust valve is determined by comparing the temperature in case3with a set value, accurate detection cannot be performed. This is because even when the exhaust valve does not open, if the ambient temperature is high and the charging/discharging current increases, the temperature in case3rises.

In order to overcome the drawback that the rise of the temperature due to the ambient temperature and the charging/discharging current makes it difficult to accurately determine the opening of the exhaust valve, the power supply device determines the opening of the exhaust valve by comparing a rate of rise of the detected temperature, that is, a rate of rise (ΔT/Δt) of the temperature with a preset rise rate set value, instead of comparing the temperature detected by temperature sensor5with the set value. However, although the temperature detected by temperature sensor5rises when the exhaust valve opens, the detected temperature also rises due to noise induced in temperature sensor5, so that if the opening of the exhaust valve is determined only by the rate of rise (ΔT/Δt), malfunctions due to noise occur. In order to identify a fluctuation of the temperature detected by temperature sensor5due to noise and a fluctuation of the detected temperature due to the opening of the exhaust valve, the power supply device compares a time from when the rate of rise (ΔT/Δt) of the detected temperature exceeds the rise rate set value and further exceeds the rise rate set value to when the rate of rise (ΔT/Δt) falls to less than or equal to a preset reference temperature, that is, a high temperature time (t1) when the exhaust valve opens and the temperature rises with a high temperature time set value and determines that the exhaust valve opens only when the rate of rise (ΔT/Δt) is larger than the rise rate set value and, in addition, the high temperature time (t1) is longer than the high temperature time set value.

Detection circuit7that detects the opening of the exhaust valve with both the rate of rise (ΔT/Δt) of the temperature and the high temperature time (t1) stores the rise rate set value and the high temperature time set value in a memory. The rise rate set value, the high temperature time set value, and the reference temperature forcibly cause thermal runaway of one battery1in case3to open the exhaust valve, measure the temperature detected by temperature sensor5, and further measure noise induced in temperature sensor5, and thus to be set to a value capable of accurately determining the opening of the exhaust valve without being affected by the noise.

FIG. 3shows a state in which the temperature detected by temperature sensor5changes when the exhaust valve opens.FIG. 4shows a state in which the detected temperature changes due to noise induced in temperature sensor5when the exhaust valve does not open. In these figures, the horizontal axis is a time axis, and the vertical axis is the temperature detected by temperature sensor5. Temperature sensor5uses an element whose electrical resistance changes with a temperature, such as a thermistor, and detection circuit7detects the temperature by converting the electric resistance of temperature sensor5into a voltage. InFIGS. 3 and 4, the temperature detected by temperature sensor5fluctuates up and down due to noise. In these figures, the temperature is detected and plotted in a predetermined detection cycle. The detection cycle is set to, for example, 100 msec to 500 msec such that the temperature change can be detected quickly. In addition, in order to improve temperature detection accuracy, detection circuit7detects the temperature in a cycle shorter than the set cycle, for example, a sampling cycle of 5 msec to 10 msec, and averages a plurality of detected temperatures detected in the sampling cycle to calculate the temperature change in the set cycle.

As shown inFIG. 3, the temperature detected by temperature sensor5in which noise is induced changes up and down, the detected temperature rises when the exhaust valve opens, and the detected temperature also rises due to noise. In order to accurately detect the opening of the exhaust valve while ignoring the influence of noise, detection circuit7sets the rise rate set value, the high temperature time set value, and the reference temperature. The rise rate set value is set to, for example, 1° C./sec in order to reliably detect the temperature rise due to the opening of the exhaust valve. For the high temperature time set value and the reference temperature, in consideration of a state from the opening of the exhaust valve to the fall of the temperature, for example, the high temperature time set value is set to 20 sec, and the reference temperature is set to the detected temperature when the rate of rise (ΔT/Δt) exceeds the rise rate set value. If the rise rate set value and the high temperature time set value are too small, the influence of noise is likely to be exerted. On the contrary, if these values are too large, it becomes impossible to accurately detect the opening of the exhaust valve. After the exhaust valve opens, the rate of rise of the temperature and the state of the fall of the temperature change depending on an internal volume of case3, the type and size of battery1, the number and disposition of batteries1, the disposed location of temperature sensor5, etc., so that the rise rate set value, the high temperature time set value, and the reference value are set to values that reliably detect the opening of the exhaust valve while the exhaust valve opens.

Detection circuit7does not necessarily need to set the rise rate set value for 1 sec, and can store the rate of rise of the temperature in a time period shorter than 1 sec or a time period more than or equal to 1 sec. For example, detection circuit7that stores the rise rate set value for 2 sec compares the rate of rise (ΔT/Δt) for 2 sec with the rise rate set value to determine the opening of the exhaust valve.

Furthermore, in addition to the rate of rise (ΔT/Δt), the high temperature time (t1), and the reference temperature, detection circuit7compares a rising time (t2) from a timing at which the rate of rise (ΔT/Δt) of the detected temperature is higher than a set rate to a timing at which the rate of rise (ΔT/Δt) falls to less than or equal to the set rate with the rising time set value, and detects that the rising time (t2) also exceeds the rising time set value to determine the opening of the exhaust valve, so that the opening of the exhaust valve can be determined more accurately. The rising time set value is set to, for example, 1 sec to 2 sec. However, the rising time set value also changes depending on the internal volume of case3, the type and size of battery1, the number and disposition of batteries1, the disposed location of temperature sensor5, etc., so that the rising time set value is set to a value capable of reliably determining the opening of the exhaust valve without being affected by noise.

Power supply device100ofFIGS. 1 and 2includes the plurality of temperature sensors5. Power supply device100determines that the exhaust valve has opened in the state in which the rate of rise (ΔT/Δt) of the temperature detected by any of temperature sensors5is larger than the rise rate set value and the high temperature time (t1) is longer than the high temperature time set value and the state in which the rising time (t2) is longer than the rising time set value, and the opening of the exhaust valve can be quickly and accurately determined. In addition, a power supply device including the plurality of temperature sensors5can determine the opening of the exhaust valve by providing each of temperature sensors5with the rise rate set value, the high temperature time set value, and the rising time set value separately.

INDUSTRIAL APPLICABILITY

The present invention is effectively used for a power supply device in which a plurality of batteries each of which includes an exhaust valve are disposed in a case.

REFERENCE MARKS IN THE DRAWINGS