Battery protection control method in cold regions

Abstract

To provide a protection control method of a battery in a cold district that can protect a battery mounted on a hybrid vehicle and effectively utilize electric power generated in the vehicle.SOLUTION: In a protection control method of a battery in a cold district, a control part that controls a battery, a power generator and a power storage device controls discharge / charge amounts of the battery and protects the battery. The control part, provided in a vehicle, when estimating that the vehicle is likely to slip during travelling, on the basis of information concerning a travelling environment, measures a charge rate of the battery; when the charge rate of the battery is higher than a range of medians, stops charging of the battery by the power generator and makes the battery supply power to the power storage device until the charge rate lowers down to the range of medians; and when the charge rate is lower than the range of medians, stops output of power from the battery to an electric motor and switches travelling by the motor to travelling by an engine, and makes the power generator charge the battery until the charge rate rises up to the range of medians.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery protection control method in cold climates, and more particularly to a battery protection control method in cold climates for protecting a drive battery mounted on a hybrid vehicle in cold climates. [Background technology]

[0002] A drive battery (simply referred to as the battery) that supplies power to an electric motor installed in a hybrid vehicle along with an engine experiences a drop in battery performance, i.e., a drop in the battery's input / output power capacity, when the battery temperature drops in cold regions, such as low-temperature environments below freezing. In such a state, for example, if tire slip occurs while driving, the engine speed increases, and power generated by the generator is input to the battery. However, this power input exceeds the allowable input, potentially damaging the battery. Similarly, if the vehicle attempts to drive on an uphill road with a high grip while the battery's performance is reduced, the battery's output power exceeds the allowable output power, potentially damaging the battery.

[0003] Therefore, when the battery temperature drops in a low-temperature environment, it is necessary to warm up the battery and restore its original performance. Typically, to warm up a battery, methods include generating heat from a heater such as a resistor, or discharging the battery and using its internal resistance to generate heat. However, continuous discharge can cause an imbalance in the ions in the battery, further deteriorating its discharge capacity. Therefore, a storage device such as a capacitor is connected to the battery, and the battery and storage device are repeatedly discharged and charged. This repeated cycle causes current to flow through the battery's internal resistance, causing the battery to heat up.

[0004] Patent Document 1 discloses a power storage system applicable to a vehicle, which has a battery (secondary battery) and a capacitor, and discloses that the temperature is increased by repeatedly charging and discharging the secondary battery and the capacitor.

[0005] Patent Document 2 discloses a technology for preventing deterioration of the battery of an electric vehicle, in which regenerative power generation is prohibited in areas where slippage is predicted based on outside temperature, radar, cameras, etc., and control is performed to suppress battery deterioration, and regenerative power generation is resumed once the area where slippage is predicted has passed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-125880 [Patent Document 2] Japanese Patent Application Publication No. 2018-131097 Summary of the Invention [Problem to be solved by the invention]

[0007] The technology disclosed in Patent Document 1 shows a method for quickly and easily raising the temperature to a predetermined level by repeatedly charging and discharging between a battery (secondary battery) and a capacitor. However, it does not mention raising the temperature in a low-temperature environment such as below freezing. In other words, in a low-temperature environment, the performance of the battery is reduced, and it is unclear whether it is possible to immediately exchange power in a state where the battery would be damaged by power exceeding its allowable input / output.

[0008] Patent Document 2 only discloses that regenerative power generation is prohibited in areas where slippage is expected, but does not disclose anything about battery temperature rise.

[0009] Furthermore, Patent Documents 1 and 2 do not mention the power stored in the power storage device when it is determined that the battery has warmed up sufficiently, road conditions have improved, and the possibility of slipping has decreased.

[0010] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a battery protection control method for use in cold regions that can protect a battery mounted on a hybrid vehicle in an environment where the outside temperature is so low that the performance of the battery deteriorates, and that can effectively utilize the electricity generated by the vehicle. [Means for solving the problem]

[0011] In order to achieve the above object, the battery protection control method according to claim 1 comprises: A battery protection control method for use in cold climates includes a battery that supplies driving power to an electric motor mounted together with an engine in a hybrid vehicle, a generator that generates electric power by rotation of the engine and charges the battery, a power storage device that is connected to the battery in an electrically connectable and disconnectable manner to discharge the battery's power, and a control unit that controls the battery, the generator, and the power storage device, and protects the battery by controlling the charge / discharge amount of the battery, The control unit The aforementioned hybrid Based on environmental information from an environmental information acquisition unit that is provided in the vehicle and acquires information about the driving environment, hybrid When it is estimated that the vehicle may slip while traveling, the charging rate of the battery is measured, If the charging rate of the battery is higher than a median value range, stopping charging of the battery by the generator and supplying power from the battery to the power storage device until the charging rate falls within the median value range; When the charging rate of the battery is lower than the median range, the power output from the battery to the electric motor is stopped, and the vehicle is switched to running using the engine, and the generator charges the battery until the charging rate rises within the median range.

[0012] This method allows the battery's charging rate to be set in the median range, for example, 48-52%, in a low-temperature environment where performance is degraded, thereby preventing the battery from being damaged even if excessive power is input to or output from the battery. In other words, by setting the charging rate in the median range, a margin is provided between the input and output power values ​​that would cause damage, protecting the battery from excessive input and output of power.

[0013] The method for protecting and controlling a battery in a cold region according to claim 2 is the method for protecting and controlling a battery in a cold region according to claim 1, The aforementioned hybrid The vehicle is provided with a battery temperature detection unit that detects the temperature of the battery, and a heating means that raises the temperature of the battery, The control unit is characterized in that when it receives information from the battery temperature detection unit that the battery temperature is below a predetermined value, and when the charging rate of the battery falls within the median range through the control of claim 1, it activates the battery heating means until the temperature of the battery rises to the predetermined temperature.

[0014] With this method, when the battery temperature is below a predetermined value, for example, below a temperature at which battery performance is degraded, and the battery's charging rate is within the median range, the heating means is activated and the battery is heated. The heating means can employ various methods, such as generating heat from a resistor or repeatedly charging and discharging the battery. By heating the battery, the battery's performance is restored, allowing it to perform to its original potential.

[0015] The method for protecting and controlling a battery in a cold region according to claim 3 is Section 2 In the battery protection control method in cold climates described in The power storage device and the electric motor are connected in a manner that allows for switchable connection and disconnection; When the charging rate of the battery is within the median range by the control of claim 1 and the battery temperature is equal to or higher than a predetermined temperature by the control of claim 2, the control unit: The battery and the power storage device are connected to each other, and the power stored in the power storage device is charged to the battery, or The power storage device and the electric motor are connected to each other, and the electric power stored in the power storage device is used to drive the electric motor.

[0016] This method achieves the control described in claims 1 and 2, i.e., by keeping the charging rate within the median range and raising the battery temperature to a predetermined level, the power stored in the power storage device can be used effectively. That is, the power storage device and the battery are connected, and power is transferred from the power storage device to the battery to increase the battery's SOC, or the power storage device and the electric motor are connected, and the power stored in the power storage device can be used to drive the vehicle. [Effects of the Invention]

[0017] According to the method for protecting and controlling a battery in cold climates of the present invention, when it is estimated that a vehicle may slip while traveling, the battery's charging rate can be controlled to always be within the median range. This prevents the battery from being damaged in a situation where a slip occurs, causing the engine speed to increase and power input exceeding the allowable input to the battery, or in a situation where power output exceeding the allowable output is generated from the battery during strong grip traveling. This allows the battery of a hybrid vehicle to be protected in cold climates while maintaining safe traveling of the hybrid vehicle. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a flowchart of protection control according to a method for protecting and controlling a battery in cold climates of the present invention; [Figure 2] 3 is an explanatory diagram of the allowable input / output power of the battery in the cold region protection control method of the present invention. FIG. [Figure 3] 1 is a connection circuit diagram of a main battery and a sub-battery according to a method for protecting and controlling a battery in cold climates of the present invention; [Figure 4] 1 is a connection circuit diagram of a main battery and a sub-battery according to a method for protecting and controlling a battery in cold climates of the present invention; [Figure 5] 3 is a flow chart showing a method for controlling battery protection in cold climates according to the present invention for returning power from a sub-battery. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of a battery protection control method for cold climates according to the present invention will be described in detail with reference to the drawings. In this embodiment, the power storage device is a sub-battery, and a DC-DC converter is used to switch between connection and disconnection between the main battery and the sub-battery.

[0020] Fig. 1 is a flow diagram of protection control relating to a method for protecting and controlling a battery in cold climates according to the present invention. In this embodiment, protection control involves setting the state of charge (SOC) of the main battery to a value near the median range and raising the temperature of the main battery, which is at a low enough temperature to cause a performance degradation, to a predetermined temperature. The median range is, for example, a state of charge range of 48 to 52%. This range can be set arbitrarily depending on the capacity, characteristics, etc. of the battery.

[0021] It is estimated that the hybrid vehicle may slip while traveling (step S1). The control unit determines the possibility of the vehicle slipping based on information from an environmental information acquisition unit provided in the vehicle that acquires information about the traveling environment. The environmental information acquisition unit acquires environmental information by, for example, estimating road conditions from weather forecasts, using slip information about the vehicle itself, making judgments based on outside temperature, or acquiring information from other companies.

[0022] Next, the control unit determines whether the main battery is at a low temperature, i.e., whether the temperature is low enough to cause a deterioration in the performance of the battery (step S2). The control unit can obtain the battery temperature from a battery temperature detection unit installed in the vehicle that detects the battery temperature.

[0023] Figure 2 shows the temperature dependence of the allowable input power and allowable output power of a battery as an example. As parameters, a battery with a high SOC (SOC: 85%, shown by the dashed line), a battery with a low SOC (SOC: 25%, shown by the dashed line), and a battery with an SOC of 50% (shown by the solid line) are shown. Figure 2(a) shows the allowable input power. In the low temperature range, the allowable input power of both high and low SOC batteries is low, but the allowable input power of the high SOC battery is significantly lower, and it is necessary to actively discharge it to bring it closer to the allowable input power of a battery with an SOC of 50%.

[0024] Figure 2(b) shows the allowable output power. In the low temperature region, the allowable output power is low for both high and low SOC batteries. However, the allowable output power of a low SOC battery is significantly lower, and it is necessary to actively charge it to bring it closer to the allowable output power of a battery with an SOC of 50%.

[0025] Returning to Fig. 1, if the battery temperature is not low enough to cause a performance degradation (step S2, No), the process proceeds to heat generation control in step S9. If the battery temperature is low enough to cause a performance degradation (step S2, Yes), the control unit checks the SOC of the main battery and determines whether the SOC is in the median range, for example, 48 to 52% (step S3). The battery SOC can be estimated, for example, by the control unit measuring the battery voltage.

[0026] If the SOC is near the median, i.e., in the median region (step S3, Yes), the process proceeds to heat generation control in step S9. If it is not in the median region (step S3, No), it is determined whether the battery SOC is high or low (step S4). This determination is also made by the control unit. If the SOC is high (step S4, Yes), power input is prohibited until the SOC reaches a target SOC, for example, 48 to 52% (step S5), and power is transferred to the sub-battery (step S6). This power transfer continues until the SOC reaches the target SOC.

[0027] If the SOC is low (step S4, No), the system prohibits power output until the SOC reaches a target SOC, for example, 48 to 52% (step S7), increases the engine speed, generates power using the generator, and charges the main battery with that power (step S8). This charging continues until the SOC reaches the target SOC.

[0028] Next, the main battery is heated. In FIG. 1, this heating is referred to as heat generation control (step S9). Heat generation control can be achieved by heating the battery using a heating element such as a heater, but in this embodiment, heat generation is achieved by repeatedly charging and discharging the main battery and sub-battery, and the phenomenon of heat generation due to the internal resistance of the batteries is utilized. Since the SOC of the main battery is in the median range, power can be exchanged safely.

[0029] 3 is a circuit diagram of a connection between a main battery and a sub-battery according to the present invention, which relates to a method for protecting and controlling a battery in cold climates. In this embodiment, a sub-battery 18 is used as the power storage element. DC-DC converters 12 and 16 are connected to the main battery 14 and the sub-battery 18, respectively, and these are electrically connected in parallel.

[0030] Power from the main battery 14 is connected to a vehicle load, such as an electric motor, via an electromagnetic relay 20. In FIG. 3, the vehicle load side is indicated by an arrow. The electromagnetic relay 20 consists of a negative-side relay 20c and positive-side relays 20a and 20b, with a resistor inserted in series with relay 20a to protect the relay contacts. As a result, power is supplied to the vehicle load side by turning relay 20c and relay 20a ON, then turning relay 20b ON and relay 20a OFF.

[0031] The electrical connection between the main battery 14 and the sub-battery 18 is controlled by the converter 12 connected to the main battery 14 and the converter 16 connected to the sub-battery 18. The converter 12 of the main battery 14, the converter 16 of the sub-battery 18, and the relay 20 are controlled by a control unit (not shown) that controls the entire system.

[0032] Charging and discharging between the main battery 14 and the sub-battery 18 is performed by controlling the converters 12, 16 to repeatedly connect and disconnect the main battery 14 and the sub-battery 18. When the main battery 14 and the sub-battery 18 are connected, if the SOC of the main battery 14 is higher than the SOC of the sub-battery 18, the sub-battery 18 is discharged, and if the SOC of the main battery 14 is lower than the SOC of the sub-battery 18, the main battery 14 is charged.

[0033] That is, since the vehicle is driven by the engine and the electric motor, the generator inputs power to the main battery 14, while outputting power to the electric motor, causing the charging rate of the main battery 14 to fluctuate. For example, when the charging rate of the main battery 14 becomes higher than the median range, the sub-battery 16 can be connected to discharge the main battery 14, and when the charging rate of the main battery 14 becomes lower than the median range, the sub-battery 16 can be connected to charge the main battery 14 from the sub-battery 16. By performing such control by the control unit, the temperature of the main battery 14 can be raised.

[0034] Figure 4 shows the main battery and sub-battery connection circuit shown in Figure 3, with the converter on the main battery 14 side omitted. In this circuit, the main battery 14 and sub-battery 18 can be connected and disconnected by converter 16. Compared to Figure 3, this has the advantage of requiring fewer components, but has the disadvantage that the amount of charge to the main battery cannot be controlled as precisely as in Figure 3, because it is affected by the vehicle load when controlling the return (charging) of power stored in the sub-battery, which will be described later, to the main battery.

[0035] When the main battery 14 reaches a predetermined temperature, for example, 0°C (step S10, Yes), the heat generation control (step S9) is turned off (step S11). The temperature of the main battery is constantly monitored by the battery temperature detection unit described above.

[0036] Figure 5 shows the control that is performed after the protective control in Figure 1 is completed. It is assumed that the main battery has warmed up sufficiently and the possibility of the vehicle slipping has decreased (step S21). This control flow makes effective use of the power stored in the sub-battery.

[0037] First, the protection control described in Fig. 1 is stopped (step S22). The protection control means bringing the SOC of the main battery closer to the median value and raising the temperature of the main battery. These have already been achieved.

[0038] Next, it is checked whether power is stored in the sub-battery (step S23). This check is performed by the control unit. If power is not stored (step S23, No), the flow ends. If power is stored (step S23, Yes), it is checked whether the allowable input power (Win) of the main battery is sufficient (step S24). If the Win of the main battery is not sufficient (step S24, No), the flow ends.

[0039] If the main battery has sufficient Win (step S24, Yes), the power of the sub-battery is returned to the main battery, or the power of the sub-battery is used together with the main battery for the vehicle load (step S25). Returning power to the main battery means supplying the power of the sub-battery to the main battery and increasing the SOC of the main battery. Since the temperature is not low enough to cause performance degradation and the vehicle is not expected to slip, there is no problem in increasing the SOC of the main battery.

[0040] To return power to the sub-battery, the control unit controls the converters 12, 16 to connect the sub-battery 18 to the main battery 14. If the SOC of the sub-battery 18 is higher than the SOC of the main battery, the main battery 14 is charged. To use the power of the sub-battery together with the main battery for the vehicle load, the control unit controls the converters 12, 16 to connect both the main battery 14 and the sub-battery 18 to the vehicle load.

[0041] By performing such control after protective control, the performance of the main battery is improved, contributing to safe and secure driving of the hybrid vehicle.

[0042] According to the battery protection control method of this embodiment, when the temperature is low enough that the performance of the main battery is degraded and there is a possibility of road slippage, the SOC of the main battery is controlled to be near the median value, and the main battery and sub-battery are connected and power is repeatedly exchanged to warm up the main battery. Furthermore, when the risk of road freezing has disappeared and the temperature of the main battery has risen, the power stored in the sub-battery can be returned to the main battery or used for the vehicle load, thereby enabling effective use of the power stored in the sub-battery.

[0043] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, although the power storage device connected to the main battery and repeatedly charged and discharged is a sub-battery, this is not limited to this, but a capacitor may also be used. Furthermore, although a converter is used to connect the main battery and the sub-battery, this is not limited to this, and for example, an electromagnetic relay may be used. [Explanation of symbols]

[0044] 10 Connection circuit 12 Converter 14 Main battery 16 Converter 18 Sub-battery (power storage device) 20 Electromagnetic Relay

Claims

1. A battery protection control method for use in cold climates includes a battery that supplies driving power to an electric motor mounted together with an engine in a hybrid vehicle, a generator that generates electric power by rotation of the engine and charges the battery, a power storage device that is connected to the battery in a manner that allows electrical connection and disconnection to be switched to discharge the power of the battery, and a control unit that controls the battery, the generator, and the power storage device, and protects the battery by controlling the charge / discharge amount of the battery, The control unit measuring a charging rate of the battery when it is estimated that there is a possibility that the hybrid vehicle will slip while traveling based on environmental information from an environmental information acquisition unit that is provided in the hybrid vehicle and acquires information about a traveling environment; If the charging rate of the battery is higher than a median value range, stopping charging of the battery by the generator and supplying power from the battery to the power storage device until the charging rate falls within the median value range; A battery protection control method for use in cold climates, characterized in that, when the charging rate of the battery is lower than the median range, power output from the battery to the electric motor is stopped, and the vehicle is switched to traveling using the engine, and the generator is caused to charge the battery until the charging rate rises within the median range.

2. The hybrid vehicle is provided with a battery temperature detection unit that detects the temperature of the battery, and a heating means that raises the temperature of the battery, 2. The method for protecting and controlling a battery in cold climates according to claim 1, wherein the control unit activates the battery heating means when it receives information from the battery temperature detection unit that the battery temperature is below a predetermined value and when the charging rate of the battery falls within the median range as a result of the control of claim 1, until the temperature of the battery rises to the predetermined temperature.

3. The power storage device and the electric motor are connected in a manner that allows for switchable connection and disconnection; When the charging rate of the battery is within the median range by the control of claim 1 and the battery temperature is equal to or higher than a predetermined temperature by the control of claim 2, the control unit: The battery and the power storage device are connected to each other, and the power stored in the power storage device is charged to the battery, or 3. The method for protecting and controlling a battery in cold climates according to claim 2, wherein the power storage device and the electric motor are connected to each other, and the electric power stored in the power storage device is used to drive the electric motor.

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