Cell system

Abstract

To provide a battery system capable of suppressing unnecessary input / output restrictions.SOLUTION: A cell system includes charging state determination means for determining whether a present charging state is a rapid charging state, estimation means for estimating the temperature difference between the inside and outside of a battery pack, and control means for restricting the input / output of the battery pack depending on an estimation result of the estimation means. The estimation means switches information to be used for estimation depending on whether a determination result by the charging state determination means is a rapid charging state or not.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery system. [Background technology]

[0002] Patent Document 1 discloses a technique for limiting the input and output of a battery pack based on the results of estimating the maximum temperature inside the battery pack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-222133 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology disclosed in Patent Document 1, since the tendency of the internal / external temperature difference differs between the normal charging state and the rapid charging state, there is a risk that input / output limitations may be imposed even when such limitations are not necessary.

[0005] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a battery system that can suppress unnecessary input / output limitations. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the battery system of the present invention is a battery system comprising a charging state determination means for determining whether or not the current charging state is a rapid charging state, an estimation means for estimating the temperature difference inside and outside the battery pack, and a control means for restricting the input / output of the battery pack depending on the estimation result of the estimation means, wherein the estimation means switches the information used for estimation depending on whether or not the determination result by the charging state determination means is a rapid charging state.

[0007] As a result, during rapid charging when the temperature difference between the inside and outside of the battery is small, it is possible to perform an estimation of the temperature difference between the inside and outside of the battery according to the rapid charging, thereby making it possible to suppress unnecessary input / output restrictions.

[0008] In the above, the information used by the estimation means for the estimation is a map showing the relationship between the environmental temperature and the inside and outside temperature difference, and the map includes an inside and outside temperature difference map for rapid charging used during rapid charging of the battery pack, and a normal inside and outside temperature difference map for use other than during rapid charging of the battery pack.

[0009] As a result, during rapid charging when the internal and external temperature difference is small, the internal and external temperature difference map for rapid charging can be used to estimate the internal and external temperature difference according to the rapid charging, thereby suppressing unnecessary input / output restrictions. Effect of the Invention

[0010] The battery system according to the present invention is capable of estimating the internal and external temperature difference according to rapid charging during rapid charging when the internal and external temperature difference becomes small, thereby achieving the effect of suppressing unnecessary input / output restrictions. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of a battery system according to an embodiment. [Diagram 2] FIG. 2 is a flowchart showing a procedure for limiting input / output of a battery pack based on an estimate of a maximum temperature inside the battery pack in a battery system according to an embodiment. [Diagram 3] FIG. 3 is a map showing the relationship between the environmental temperature and the inside / outside temperature difference in the battery system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a battery system according to the present invention will be described, however, the present invention is not limited to the embodiment.

[0013] In the following, a lithium-ion battery pack, i.e., a battery pack made up of a combination of multiple lithium-ion unit batteries, will be described as the battery pack, but other battery packs may also be used. For example, a nickel-metal hydride battery pack may also be used. In addition, the battery pack will be described as being configured by connecting multiple unit batteries in series, but it is of course possible to configure the battery pack by connecting multiple unit batteries in parallel. Also, multiple unit batteries may be configured as one battery pack by connecting them in series and in parallel.

[0014] The number and arrangement of the various sensors described below are merely examples for the purpose of explanation, and other numbers of sensors may be used, and the arrangement of the sensors may be set arbitrarily. For example, an intake air temperature sensor will be described as detecting the environmental temperature, but sensors that detect the outside air temperature or the temperature in the vicinity of the battery pack other than the intake air temperature may be used.

[0015] Although the power supply circuit including the battery pack will be described as comprising a battery pack, a system main relay, a voltage converter, a smoothing capacitor, and an inverter, other elements may be added as necessary, for example, a DC / DC converter, a low-voltage power supply, etc.

[0016] Although the rotating electric machine connected to the power supply circuit including the battery pack is described as being one motor-generator having both a motor function and a generator function, two motor-generators may be used instead, in which case one rotating electric machine having only a motor function and one rotating electric machine having only a generator function may be used.

[0017] 1 is a diagram showing a portion of a hybrid vehicle control system that controls the operation of a hybrid vehicle equipped with a battery pack and a rotating electric machine, which is related to control of the input and output of the battery pack, as a battery system 1. This battery system 1 has a function of limiting the input and output of the battery pack based on the surface temperature of the battery pack, and in particular, has a function of estimating the maximum temperature inside the battery pack and limiting the input and output based on the estimated maximum temperature.

[0018] This battery system 1 includes a battery pack 2 formed by combining multiple battery cells 20, a system main relay 10, a battery pack side smoothing capacitor 11, a voltage converter 12, an inverter side smoothing capacitor 14, an inverter 16, a rotating electric machine 18, a current sensor 31, a temperature sensor 32, a voltage sensor 33, and an intake air temperature sensor 34 as an environmental temperature sensor provided in association with the battery pack 2, an I / V / T detection unit 41 connected to these sensors and detecting the current I, voltage V, and temperature T, respectively, a cooling air volume input unit 42 that inputs the value of the cooling air volume, and a control device 6 that controls the operation of these components as a whole. In this case, the control device 6 corresponds to a battery pack input / output control device.

[0019] The battery pack 2 is a battery pack serving as a chargeable and dischargeable secondary battery configured to obtain a desired output voltage and output current by connecting lithium ion unit batteries in series as a plurality of battery cells 20. The desired output voltage can be, for example, a terminal voltage of about 200 V. In this case, the battery pack 2 can be configured by connecting 100 or more lithium ion battery cells 20 in series.

[0020] The current sensor 31 provided in the battery pack 2 has a function of detecting input / output current of the battery pack 2, and is connected in series to at least one of both terminals of the battery pack 2. When there is one current sensor 31, the detection value of the current sensor 31 detects the current value in the battery pack 2. When a current sensor 31 is provided at each of both terminals of the battery pack 2, the I / V / T detection unit 41 obtains the difference between the detection values ​​of the two current sensors, and when the difference exceeds a predetermined allowable difference value, for example, it is detected that the current sensor 31 is abnormal.

[0021] In this way, the current sensor 31 is provided to acquire the current value input to and output from the battery pack 2. The current value input to and output from the battery pack 2 depends on the drive power and regenerative power of the rotating electric machine 18, which is the load, and so the magnitude of this value indicates the magnitude of the current load. In this way, the current value data acquired by the current sensor 31 is transmitted to the control device 6 via the I / V / T detection unit 41 as data of the current load 51. When multiple current sensors 31 are used to monitor an abnormality between them, a message to that effect is output, processing is performed to obtain a correct current value, and one correct current value data is transmitted to the control device 6.

[0022] The voltage sensor 33 provided in the battery pack 2 has a function of detecting the battery voltage of the battery cells 20 constituting the battery pack 2, and a plurality of voltage sensors 33 are used. In the example of Fig. 1, five voltage sensors 33 are shown arranged at equal intervals along the arrangement direction of the battery cells 20 constituting one battery pack 2.

[0023] In this way, the voltage sensors 33 have the function of detecting the battery voltages of the battery cells 20 at a plurality of predetermined arbitrary positions of the battery pack 2, and can therefore be called voltage detection units. The voltage sensors 33 are connected to the I / V / T detection unit 41, and data on the battery voltage value of each battery cell 20 is transmitted to the control device 6 via this unit.

[0024] The temperature sensor 32 provided in the battery pack 2 is disposed on the surface of the battery pack 2 and has the function of detecting the surface temperature of the battery pack, and a plurality of temperature sensors 32 are used. In the example of Fig. 1, three temperature sensors 32 are shown disposed at equal intervals along the arrangement direction of the battery cells 20 of one battery pack 2.

[0025] The temperature sensors 32 may be, for example, temperature-sensing elements such as thermistors. Each temperature sensor 32 is attached to the surface of the battery pack 2 by appropriate attachment means. An appropriate adhesive may be used as the attachment means. Alternatively, a molding integration technique may be used in which a temperature-sensing element such as a thermistor is molded with a resin material and integrated with the battery pack 2. In the following, a description will be given assuming that the temperature sensors 32 are attached to the battery pack 2 by the molding integration technique.

[0026] In this way, the temperature sensor 32 has a function of detecting the surface temperature of the battery pack 2, and can be called a battery surface temperature sensor or a battery temperature sensor. The temperature sensor 32 is connected to the I / V / T detection unit 41, and data on the surface temperature of the battery pack 2 is transmitted to the control device 6 via this.

[0027] The intake air temperature sensor 34 has a function of detecting the environmental temperature around the battery pack 2, and is a temperature sensor provided at the intake port when the battery pack 2 is air-cooled. As described above, the intake air temperature sensor 34 has a function of acquiring the environmental temperature of the battery pack 2, and can also be called an environmental temperature acquisition unit. The temperature value data acquired by the intake air temperature sensor 34 is transmitted to the control device 6 via the I / V / T detection unit as data of the intake air temperature 52. In the following, unless otherwise specified, the environmental temperature refers to the intake air temperature. A plurality of intake air temperature sensors 34 may be provided at the intake port. Also, in addition to the intake air temperature sensor 34, another sensor may be provided as environmental temperature detection means. In these cases, the detection values ​​of the respective sensors are averaged, and the result can be used as the environmental temperature of the battery pack 2.

[0028] The I / V / T detection unit 41 is an interface circuit provided between the various sensors and the control device 6. The detection values ​​of the various sensors are, for example, analog voltage values. The I / V / T detection unit 41 has a function of converting the analog signal levels, which vary depending on the sensor, into standardized analog signals or digital signals suitable for various processes in the control device 6.

[0029] The cooling air volume input unit 42 is an interface circuit for inputting the value of the cooling air volume, which is the volume of air passing through the air intake when air-cooling the battery pack 2, to the control device 6. Specifically, data on the cooling air volume indicated by an air volume changeover switch or an air volume setting button or the like is acquired as an input value and transmitted to the control device 6.

[0030] The system main relay 10 is a power supply switching device that can electrically connect or disconnect between the battery pack 2, which is a high-voltage secondary battery, and the load side, which includes a rotating electric machine 18. The system main relay 10 uses multiple relays that are independently provided on the positive busbar and the negative busbar to prevent welding between the terminals due to arc discharge or the like that occurs when connecting or disconnecting the high voltage. The timing of connection and disconnection of these relays is set to be appropriately staggered from each other to prevent welding between the terminals.

[0031] The voltage converter 12 is disposed between the battery pack 2 and the inverter 16, and is a circuit having a voltage conversion function. The voltage converter 12 can be configured to include a reactor, a switching element that operates under the control of the control device 6, and the like. The voltage conversion function includes a boost function that boosts the voltage on the battery pack side by utilizing the energy storage effect of the reactor and supplies it to the inverter side, and a step-down function that steps down the power from the inverter side to the battery pack side and supplies it as charging power.

[0032] The battery pack side smoothing capacitor 11, which is provided between the battery pack 2 and the voltage converter 12, and the inverter side smoothing capacitor 14, which is provided between the voltage converter 12 and the inverter 16, are capacitors that have the function of suppressing and smoothing fluctuations in voltage and current.

[0033] The inverter 16 is a circuit that performs power conversion between AC power and DC power. The inverter 16 includes a plurality of switching elements that operate under the control of the control device 6. The inverter 16 can perform both AC-DC conversion and DC-AC conversion. When the rotating electric machine 18 is made to function as a generator, the inverter 16 has an AC-DC conversion function of converting three-phase AC regenerative power from the rotating electric machine 18 into DC power and supplying it as a charging current to the battery pack side. When the rotating electric machine 18 is made to function as a motor, the inverter 16 has an AC-DC conversion function of converting DC power from the battery pack side into three-phase AC driving power and supplying it as driving power to the rotating electric machine 18 when the vehicle is powered, and has an AC-DC conversion function of converting three-phase AC regenerative power from the rotating electric machine 18 into DC power and supplying it as a charging current to the battery pack side when the vehicle is braked.

[0034] Here, the battery pack 2, system main relay 10, battery pack side smoothing capacitor 11, voltage converter 12, inverter side smoothing capacitor 14, and inverter 16 are connected to a rotating electric machine 18 to form one power supply circuit.

[0035] The rotating electric machine 18 is a motor-generator (MG) mounted on the vehicle, and is a three-phase synchronous rotating electric machine that functions as a motor when power is supplied from a power supply circuit including the battery pack 2, and functions as a generator when driven by an engine (not shown) or when the vehicle is braked.

[0036] The control device 6 has a function of controlling the overall operation of each component of the battery system 1. In particular, the control device 6 has a function of estimating the maximum temperature inside the battery pack and controlling the operation of the voltage converter 12 and the inverter 16 based on the estimated maximum temperature, thereby limiting the input / output power of the battery pack 2. The control device 6 can be configured with a computer or the like suitable for installation in a vehicle.

[0037] The control device 6 includes a maximum temperature estimation unit 60 that estimates the maximum temperature inside the battery pack 2, a temperature difference map memory unit 65 that stores a temperature difference map used in the maximum temperature estimation unit 60, and an input / output limiting unit 66 that limits the input / output power of the battery pack 2 based on the estimated maximum temperature.

[0038] The battery pack 2 can be normally charged using AC or quickly charged using DC by a charging device connected to a commercial power source. The control device 6 functions as a charging state determination means for determining whether the current charging state is a quickly charging state or not (for example, a non-charging state or a normal charging state) by, for example, communicating with the charging device.

[0039] Here, the temperature difference map memory unit 65 stores an overheat protection map, which is a map of offset temperature values ​​calculated for the temperature difference inside and outside the battery relative to the battery surface temperature, in association with at least one of the data on the intake air temperature 52, which is the environmental temperature, the data on the current load 51, and the data on the cooling air volume input and acquired from the cooling air volume input unit 42.

[0040] The maximum temperature estimation unit 60 includes an internal / external temperature difference estimation module 61 that estimates the internal / external temperature difference, which is the temperature difference between the surface temperature and internal temperature of the battery pack 2, an R-induced temperature difference estimation module 62 that estimates the temperature difference within the battery pack due to differences in the internal resistance of each battery cell 20, a contact condition-induced temperature difference estimation module 63 that estimates the temperature difference due to the contact state between the temperature sensor 32 and the battery pack 2, and a sensor-induced temperature difference estimation module 64 that estimates the temperature difference due to differences in detection characteristics between the multiple temperature sensors 32.

[0041] This function can be realized by software, specifically, by executing a battery pack input / output control program, although a part of this function may be realized by hardware.

[0042] A description will be given of the operation of this configuration, particularly each function of the control device 6. Fig. 2 is a flow chart showing a procedure for limiting the input / output of the battery pack 2 based on an estimate of the maximum temperature inside the battery pack 2.

[0043] 2 is a flow chart showing the procedure for limiting the input / output of the battery pack 2 based on the estimation of the maximum temperature inside the battery pack 2 as described above, and each procedure corresponds to each processing procedure of the battery pack input / output limiting program. To limit the input / output of the battery pack 2, first, the intake air temperature, the current load, the cooling air flow rate, the battery surface temperature, the current I, the voltage V, and the quick charge state are acquired (step S1). Specifically, the control device 6 acquires the intake air temperature 52, which is the environmental temperature, via the intake air temperature sensor 34, acquires the battery surface temperature via the temperature sensor 32, acquires the current value corresponding to the current load 51 via the current sensor 31, acquires the battery voltage of the unit battery via the voltage sensor 33, and acquires the cooling air flow rate data from the cooling air flow rate input unit 42. The control device 6 also acquires information on whether the battery pack 2 is in a quick charge state (quick charging) from the charging device.

[0044] Next, four temperature differences are estimated: an inside / outside temperature difference estimation (step S2), an R-attributed temperature difference estimation (step S7), a sensor contact state-attributed temperature difference estimation (step S8), and a sensor-attributed temperature difference estimation (step S9).

[0045] The internal / external temperature difference estimation (step S2) is a process of estimating the internal / external temperature difference of the battery, which is the difference between the internal temperature of the battery pack 2 and the battery surface temperature actually detected by the temperature sensor 32, in accordance with the environmental temperature. This process is executed by the function of the internal / external temperature difference estimation module 61 in the maximum temperature estimation unit 60 of the control device 6. The internal / external temperature difference estimation module 61 is an estimation means for estimating the internal / external temperature difference of the battery pack 2.

[0046] Specifically, the temperature difference between the battery surface temperature actually detected by the temperature sensor 32 and the internal temperature of the battery pack 2 is estimated by taking into consideration the data of the intake air temperature 52, which is the environmental temperature acquired through the intake air temperature sensor 34, the data of the current load 51 acquired through the current sensor 31, and the data of the cooling air volume acquired through the cooling air volume input unit 42. In order to estimate the temperature difference with high accuracy, it is preferable to take into consideration all of the data of the intake air temperature 52, the data of the current load 51, and the data of the cooling air volume, but when there is a margin in the input / output restrictions of the battery pack 2, for example, only the data of the intake air temperature 52 may be used. Also, both the data of the intake air temperature 52 and the data of the current load 51 may be taken into consideration.

[0047] For the estimation of the inside and outside temperature difference, a map showing the relationship between the factors to be considered and the inside and outside temperature difference can be used. For example, FIG. 3 shows a map showing the relationship between the environmental temperature and the inside and outside temperature difference in the battery system 1 according to the embodiment, where the intake air temperature 52 is the environmental temperature. The map showing the relationship between the environmental temperature and the inside and outside temperature difference as shown in FIG. 3 can be used by reading out the map stored in the temperature difference map storage unit 65. This map is a map of data previously obtained by an experiment or the like, and has the environmental temperature on the horizontal axis and the inside and outside temperature difference based on the battery surface temperature on the vertical axis, that is, the inside and outside temperature difference=(internal temperature of the battery pack 2)-(battery surface temperature actually measured by the temperature sensor 32).

[0048] The inside and outside temperature difference has a characteristic of increasing as the environmental temperature decreases from room temperature RT (Room Temperature). This characteristic is determined by the structure of the battery pack 2 and can be obtained in advance. A map of the obtained environmental temperature and the inside and outside temperature difference is stored in the temperature difference map storage unit 65 of the control device 6. Therefore, to estimate the inside and outside temperature difference, for example, the environmental temperature can be used as a search key to search the map showing the relationship between the environmental temperature and the inside and outside temperature difference, and the corresponding inside and outside temperature difference can be read out.

[0049] Furthermore, the battery system 1 according to the embodiment has, as maps indicating the relationship between the environmental temperature and the inside and outside temperature difference, an inside and outside temperature difference map for rapid charging used during rapid charging of the battery pack 2, and a normal inside and outside temperature difference map used during non-rapid charging of the battery pack 2. The inside and outside temperature difference map for rapid charging and the normal inside and outside temperature difference map are stored in a temperature difference map storage unit 65 of the control device 6. The inside and outside temperature difference estimation module 61 switches the map (information) used to estimate the inside and outside temperature difference depending on the result of determining whether or not the battery is in a rapid charging state.

[0050] The map showing the relationship between the environmental temperature and the inside / outside temperature difference may be in a format other than a map format, so long as it relates the environmental temperature to the inside / outside temperature difference. For example, it may be in a look-up table format in which the relationship between the environmental temperature and the inside / outside temperature difference is tabulated, or in a functional format in which the environmental temperature is input and the inside / outside temperature difference is output.

[0051] In FIG. 2, the inside / outside temperature difference estimation module 61 judges whether or not quick charging is in progress in the inside / outside temperature difference estimation (step S2) (step S3). When the inside / outside temperature difference estimation module 61 judges that quick charging is in progress (Yes in step S3), it selects the inside / outside temperature difference map for quick charging (step S4). Then, the inside / outside temperature difference estimation module 61 decides that the map used for the inside / outside temperature difference estimation is the inside / outside temperature difference map for quick charging (step S6). On the other hand, when the inside / outside temperature difference estimation module 61 judges that quick charging is not in progress (No in step S3), it selects the normal inside / outside temperature difference map (step S5). Then, the inside / outside temperature difference estimation module 61 decides that the map used for the inside / outside temperature difference estimation is the normal inside / outside temperature difference map (step S6). The inside / outside temperature difference estimation module 61 estimates the inside / outside temperature difference using the inside / outside temperature difference map decided in step S6 in this way.

[0052] The R-attributed temperature difference estimation (step S7) is a process of estimating the internal resistance R of each battery cell 20 from the voltage V and current I of each battery cell 20 at a plurality of arrangement positions, and estimating the temperature difference in the battery pack 2 caused by the difference in the internal resistance R of each battery cell 20. This process is executed by the function of the R-attributed temperature difference estimation module 62 of the maximum temperature estimator 60.

[0053] The sensor contact state-attributed temperature difference estimation (step S8) is a process of estimating in advance the maximum value of the deviation between the actual surface temperature of the battery pack 2 and the detection value of each temperature sensor 32, which is caused by the contact state between the multiple temperature sensors 32 and the surface of the battery pack 2. This process is executed by the function of the contact state-attributed temperature difference estimation module 63 of the maximum temperature estimator 60.

[0054] After the four temperature difference estimation processes are completed, the maximum temperature estimation unit 60 estimates the maximum temperature inside the battery pack (step S10). The maximum temperature estimation unit 60 then determines whether the estimated maximum temperature is equal to or higher than a predetermined threshold temperature (step S11). As the threshold temperature, it is preferable to use a smoke generation temperature T0, which is a characteristic of a lithium ion battery. If the battery pack 2 is a battery other than a lithium ion battery, a threshold temperature set according to the characteristics of the battery type can be used as T0. Then, if the determination in step S11 is positive, the input / output control unit of the control device 6 limits the input / output power of the battery pack 2 to prevent smoke generation (step S12). Also, if step S12 is executed or the determination in step S11 is negative, the series of battery pack input / output control processes are terminated.

[0055] The battery system 1 according to the embodiment can estimate the internal and external temperature difference according to the rapid charging during rapid charging when the internal and external temperature difference becomes small, and therefore can suppress unnecessary input / output restrictions. [Explanation of symbols]

[0056] 1 Battery System 2 Battery pack 6. Control device 10 System Main Relay 11 Battery pack side smoothing capacitor 12 Voltage converter 14 Inverter side smoothing capacitor 16 Inverter 18 Rotating Electric Machine 20 Battery Cells 31 Current Sensor 32 Temperature Sensor 33 Voltage Sensor 34 Intake Air Temperature Sensor 41 I / V / T detector 42 Cooling air volume input section 60 Maximum temperature estimation part 61 Internal and external temperature difference estimation module 62 R-induced temperature difference estimation module 63 Contact-induced temperature difference estimation module 64 Sensor-induced temperature difference estimation module 65 Temperature difference map storage section 66 Input / Output Restriction Section

Claims

1. a charging state determination means for determining whether the current charging state is a rapid charging state; An estimation means for estimating a temperature difference between inside and outside the battery pack; a control means for limiting an input / output of the battery pack in response to an estimation result of the estimation means; A battery system comprising: The battery system according to claim 1, wherein the estimation means switches information used for estimation depending on whether the result of the determination by the charge state determination means is a rapid charge state.

2. the information used by the estimation means for estimation is a map showing a relationship between an environmental temperature and an inside / outside temperature difference, 2. The battery system according to claim 1, wherein the maps include an internal and external temperature difference map for rapid charging used during rapid charging of the battery pack, and a normal internal and external temperature difference map for use other than during rapid charging of the battery pack.

Images