JP2007151334A - Battery control device - Google Patents

Abstract

[PROBLEMS] To improve engine startability at a low temperature and prevent the occurrence of overdischarge cells.
The battery temperature at the next engine start is predicted (S1), the lowest voltage cell at which the voltage drops most at the engine start is specified (S3), the predicted battery temperature, and the internal resistance of the lowest voltage cell. Based on the above, a target SOC is set for obtaining a predetermined output from the battery without the voltage of the lowest voltage cell being lower than a predetermined overdischarge threshold at the next engine start (S4). And charging / discharging of a battery is controlled so that SOC of the lowest voltage cell becomes more than target SOC.
[Selection] Figure 10

Description

  The present invention relates to an apparatus for controlling charging / discharging of a battery.

  Conventionally, the battery temperature at the next engine start is predicted, and based on the predicted battery temperature, a target SOC is set such that a predetermined output is obtained from the battery at the engine start, and the SOC of the battery matches the target SOC A device for controlling charging / discharging of a battery is known (see Patent Document 1).

JP 11-355967 A

  However, in the conventional battery control device, depending on the state of the cells constituting the battery, there is a possibility that a cell that is in an overdischarge state may occur when the engine is started.

  The battery control device according to the present invention predicts the battery temperature at the start of the engine, specifies the lowest voltage cell at which the voltage is lowest at the start of the engine, and based on the predicted battery temperature and the state of the specified lowest voltage cell. Thus, when the engine is started, the target SOC for obtaining a predetermined output from the battery is set so that the voltage of the lowest voltage cell does not fall below the predetermined overdischarge threshold, and the SOC of the lowest voltage cell is equal to or higher than the target SOC. In addition, the battery charging / discharging is controlled.

  According to the battery control device of the present invention, the voltage of the lowest voltage cell falls below a predetermined overdischarge threshold at the time of engine start based on the predicted battery temperature at the time of engine start and the state of the cell having the lowest voltage. Without setting the target SOC for obtaining a predetermined output from the battery and controlling the charging / discharging of the battery so that the SOC of the lowest voltage cell is equal to or higher than the target SOC, Can be prevented.

  FIG. 1 is a system configuration diagram in which a battery control device according to an embodiment is applied to a hybrid vehicle. In FIG. 1, a thick solid line indicates a transmission path of mechanical force, and a broken line indicates a power line. A thin solid line indicates a control line, and a double line indicates a hydraulic system. The power train of the vehicle includes a motor 1, an engine 2, a clutch 3, a motor 4, a continuously variable transmission 5, a reduction gear 6, a differential device 7, and drive wheels 8.

  The output shaft of the motor 1, the output shaft of the engine 2, and the input shaft of the clutch 3 are connected to each other, and the output shaft of the clutch 3, the output shaft of the motor 4 and the input shaft of the continuously variable transmission 5 are connected to each other. Has been.

  When the clutch 3 is engaged, the engine 2 and the motor 4 serve as a vehicle propulsion source, and when the clutch 3 is released, only the motor 4 serves as a vehicle propulsion source. The driving force of the engine 2 and / or the motor 4 is transmitted to the drive wheels 8 via the continuously variable transmission 5, the reduction gear 6, and the differential 7. The continuously variable transmission 5 is supplied with pressure oil from the hydraulic device 9, and the belt is clamped and lubricated. An oil pump (not shown) of the hydraulic device 9 is driven by a motor 10.

  The motors 1, 4, and 10 are AC machines such as a three-phase synchronous motor or a three-phase induction motor. The motor 1 is mainly used for engine starting and power generation, and the motor 4 is mainly used for vehicle propulsion and braking. The motor 10 is a motor for driving an oil pump of the hydraulic device 9. When the clutch 3 is engaged, the motor 1 can also be used for vehicle propulsion and braking, and the motor 4 can also be used for engine starting and power generation.

  The clutch 3 is a powder clutch and can adjust the transmission torque. The continuously variable transmission 5 is a continuously variable transmission such as a belt type or a toroidal type, and can adjust the gear ratio steplessly.

  The motors 1, 4 and 10 are driven by inverters 11, 12 and 13, respectively. The inverters 11 to 13 are connected to a main battery (assembled battery) 15 via a common DC link 14, and convert direct current power stored in the main battery 15 into alternating current power. 10, AC power generated by the motors 1 and 4 is converted into DC power, and the main battery 15 is charged. The main battery 15 is configured by connecting a plurality of cells s1 to sn in series. Since the inverters 11 to 13 are connected to each other via the DC link 14, the power generated by the motor during the regenerative operation can be directly supplied to the motor during the power running operation without going through the main battery 15. .

  The controller 16 includes a microcomputer, its peripheral components, various actuators, etc., and the rotational speed, output and torque of the engine 2, the transmission torque of the clutch 3, the rotational speed and torque of the motors 1, 4 and 10, and the continuously variable transmission. 5 and the charge / discharge of the main battery 15 are controlled.

  FIG. 2 is a diagram illustrating various sensors and various devices connected to the controller 16. The controller 16 is connected to a key switch 20, a battery temperature sensor 21, an engine rotation sensor 22, a battery SOC detection device 23, an outside air temperature sensor 24, a memory 26, a fuel injection device 30, an ignition device 31, a display 32, and the like. .

  The key switch 20 is closed when a main key (not shown) of the vehicle is set to the ON position or the START position. Hereinafter, the closing of the switch is referred to as ON or ON, and the opening is referred to as OFF or OFF. The battery temperature sensor 21 detects the temperature Tb of the main battery 15, and the engine rotation sensor 22 detects the rotation speed Ne of the engine 2. The battery SOC detection device 23 detects the state of charge (SOC) of the main battery 15, and the outside air temperature sensor 24 detects the outside air temperature Ta.

  The memory 26 stores data indicating a correspondence relationship between the battery temperature and the internal resistance of the cell and the target SOC, and the battery temperature Tb and the outside air temperature Ta every time the engine is started.

  The fuel injection device 30 controls the supply, stop, and injection amount of fuel to the engine 2 in accordance with a fuel injection command output from the controller 16. The ignition device 31 ignites by driving a spark plug in accordance with an ignition command of the engine 2.

  3 shows a total voltage sensor 35 that detects the total voltage of the main battery 15, a current sensor 36 that detects the charge / discharge current of the main battery 15, and cell voltage sensors Vt1 to Vtn that detect the voltages of the cells s1 to sn. FIG. The total voltage detected by the total voltage sensor 35, the charge / discharge current detected by the current sensor 36, and the cell voltage detected by the cell voltage sensors Vt1 to Vtn are input to the controller 16.

  FIG. 4 is a diagram showing the temperature characteristics of the main battery 15, and shows the SOC for continuously obtaining the battery output (target value) required for starting the engine 2 by the motor 1 for 10 seconds. Here, the characteristics of an initial product of a lithium ion battery that can obtain an output of 25 kw at 25 ° C. will be described as an example, but other types of batteries have similar characteristics. If the SOC of the battery is constant, the output decreases as the temperature decreases. Therefore, a larger SOC is required to obtain a predetermined output as the temperature decreases. For example, if the battery output required to start the engine 2 by the motor 1 is 5 kw, it can be started at −20 ° C. if the SOC is 25%, but at −30 ° C., the SOC is required as much as 75%. become.

  In general, as the discharge proceeds, the temperature of the battery itself increases, and the output also increases. Therefore, in this embodiment, when the battery temperature is low and a predetermined output cannot be obtained, the battery is discharged until the predetermined output is obtained to raise the battery temperature. Specifically, when starting the engine at a low temperature, power is supplied from the main battery 15 to the motor 1 until the rotational speed of the engine 2 reaches a predetermined speed, and cranking is continued. As a result, the temperature Tb of the main battery 15 rises and the output increases, so that the rotational speed of the engine 2 also rises. When the rotational speed of the engine 2 reaches a predetermined speed, the fuel is injected by the fuel injection device 30 and ignited by the ignition device 31, the ignition operation of the engine 2 is started, and the start of the engine 2 is completed.

  However, if the SOC of the main battery 15 is too low, cranking of the engine 2 itself becomes impossible at low temperatures, and the engine 2 cannot be started. Therefore, it is necessary to manage the SOC of the main battery 15 so that at least an output capable of cranking the engine 2 is obtained.

  FIG. 5 is a diagram showing the SOC distribution of the plurality of cells s1 to sn constituting the main battery 15. In the three SOC distributions shown in FIG. 5, the average SOC of the cells is the same, but the minimum voltage of the cells is different due to the capacity variation between the cells. That is, the minimum cell voltage is lower in the SOC distribution with many low capacity cells than in the SOC distribution with many high capacity cells.

  FIG. 6 is a diagram showing a cell voltage distribution during no load and a cell voltage distribution during discharge. If the internal resistance of each cell is different, the voltage distribution during discharge will be different from the voltage distribution during no load. That is, the cell having the lowest voltage during no load may be different from the cell having the lowest voltage during discharge.

  FIG. 7 is a diagram for explaining a method of obtaining the internal resistance of the cell. As shown in FIG. 7, when the vehicle travels, a plurality of cell voltage and current data are acquired and linear regression calculation is performed, and the internal resistance is obtained from the slope of the obtained straight line. Note that the method for detecting the internal resistance of the cell is not limited to this method. For example, based on the total voltage and current value that is the voltage of the entire main battery 15, the internal resistance of the entire main battery is obtained, and the obtained internal resistance is divided by the number of cells to obtain the average internal resistance value of the cells. A value obtained by multiplying the average value of the internal resistance by a predetermined correction coefficient (a coefficient in consideration of variations in internal resistance) can also be used as the internal resistance of each cell. The internal resistance thus obtained is stored in the memory 26.

FIG. 8 is a diagram for explaining a method of specifying a cell having the lowest voltage when the engine is started. Before starting the engine, if the open circuit voltage of a certain cell is E0, the discharge current at the start of the engine is I, and the internal resistance is R, the cell voltage V at the start of the engine (during discharge) can be obtained by the following equation (1). . The discharge current I is a value obtained by dividing the battery output (W) during discharge by the total voltage (V) of the main battery 15.
V = E0−R × I (1)

  Based on the formula (1), the voltage of each cell at the time of engine start (during discharge) is obtained, and the cell having the lowest voltage is specified among the obtained cell voltages.

  In the battery control apparatus according to the embodiment, the battery temperature Tb at the next engine start is predicted, the lowest voltage cell having the lowest voltage is specified at the engine start, and the specified lowest voltage cell is a predetermined overdischarge. The target SOC is set so that a predetermined output can be obtained from the battery without falling below the threshold value, and charging / discharging of the main battery 15 during vehicle operation is performed so that the SOC of the lowest voltage cell is equal to or higher than the target SOC. Control. As a result, it is possible to obtain an output necessary for starting the engine and to prevent generation of cells that are in an overdischarged state.

  FIG. 9 shows the SOC (target SOC) at which the output (target value 5 kw in FIG. 4) required for starting the engine is obtained without the overdischarged state of the cell with the lowest voltage (lowest voltage cell) when the engine is started. It is the figure shown with respect to the battery estimated temperature Tb at the time of engine starting, and the internal resistance of the voltage minimum cell. As shown in FIG. 9, the lower the predicted battery temperature Tb, the higher the target SOC for obtaining the output required for starting the engine. Also, the higher the internal resistance of the lowest voltage cell, the lower the voltage during discharge. Therefore, the target SOC needs to be increased in order to prevent the lowest voltage cell from being overdischarged. Here, the target SOC corresponding to the battery temperature and the internal resistance of the cell is obtained in advance by experiments or the like, and the obtained data is stored in the memory 26.

As a method for predicting the battery temperature Tb at the next engine start, for example, there are the following methods (a) and (b).
(A) Every time the engine is started, the battery temperature Tb is stored in the memory 26, and the lowest value of the stored battery temperatures is set as the predicted value of the battery temperature Tb. However, a predetermined number of battery temperature data is stored in the memory 26. When the temperature data exceeding the predetermined number is stored, the oldest temperature data is deleted.
(B) Since the battery temperature Tb at the next engine start is considered to be close to the outside air temperature Ta, the outside air temperature Ta is used instead of the battery temperature Tb in FIG. Alternatively, in consideration of the temperature difference between the outside air temperature Ta and the installation location of the main battery 15, the battery temperature Tb at the next engine start is predicted based on the outside air temperature Ta. However, a predetermined number of outside air temperature data is stored in the memory 26. When temperature data exceeding a predetermined number is stored, the oldest temperature data is deleted.

  FIG. 10 is a flowchart showing the SOC control of the main battery 15. The SOC control according to the embodiment will be described with reference to this flowchart. The controller 16 is executed only once each time the key switch 20 of the vehicle changes from the OFF position to the ON position. Unless the vehicle is traveling for a very long distance or for a long time, the external temperature at the time of starting the engine and the internal resistance of the cell are not greatly changed from those at the next starting of the engine, but the battery temperature is charged and discharged during driving. This process is preferably performed only once every time the engine is started.

  In step S1, the battery temperature Tb at the next engine start is predicted by the method described above. When the battery temperature Tb is predicted, the process proceeds to step S2. In step S2, the open circuit voltage of each cell is detected, the internal resistance is read from the memory 26, and the process proceeds to step S3. In step S3, the lowest voltage cell with the lowest voltage is specified when the engine is started. As described above, the lowest voltage cell is specified by obtaining the voltage of each cell at the time of engine start (during discharge) based on the open voltage and internal resistance of each cell. When the lowest voltage cell is specified, the process proceeds to step S4.

  In step S4, the target SOC is determined based on the battery temperature Tb predicted in step S1 and the internal resistance of the lowest voltage cell specified in step S3. However, as the internal resistance of the lowest voltage cell used for obtaining the target SOC, a value obtained by correcting the internal resistance detected in step S2 based on the battery temperature Tb predicted in step S1 is used. That is, since the internal resistance of the cell changes according to the temperature, data in which the battery temperature is associated with the temperature correction coefficient for correcting the internal resistance is prepared in advance and stored in the memory 26. Based on this data and the battery temperature Tb predicted in step S1, a temperature correction coefficient is obtained. Then, the internal resistance of the lowest voltage cell detected in step S2 is corrected using the obtained temperature correction coefficient.

  As described above, in the memory 26, the battery temperature and the internal resistance of the cell, and the lowest voltage cell at which the voltage is lowest when the engine is started are not overdischarged, and a predetermined output can be obtained from the battery. Data associating with the target SOC is stored. Therefore, the controller 16 determines the target SOC based on the battery temperature Tb predicted in step S1, the internal resistance of the lowest voltage cell subjected to temperature correction, and the data stored in the memory 26. When the target SOC is obtained, the process proceeds to step S5.

  In step 5, charging / discharging of the main battery 15 is controlled by the inverters 11 to 13 so that the SOC of the lowest voltage cell specified in step S3 is equal to or higher than the target SOC obtained in step S4.

  FIG. 11 is a diagram for explaining a method of controlling charging / discharging of the main battery 15 so that the SOC of the cell in which the voltage decreases most at the time of engine start becomes equal to or higher than the target SOC. Fig.11 (a) is a figure which shows the charging / discharging control range at the normal time. In normal charging / discharging control, control is performed so that the SOC of the main battery 15 is within a range of about 40% to 75%. FIG. 11B is a diagram showing a charge / discharge control range when control is performed so that the SOC of the cell in which the voltage decreases most at the time of engine start becomes equal to or higher than the target SOC. In the example shown in FIG. 11B, by controlling the SOC of the main battery 15 to be in the range of 65% to 85%, the SOC of the cell in which the voltage is the lowest when the engine is started does not fall below the target SOC. Is controlling.

  That is, the lower the predicted battery temperature Tb and the higher the internal resistance of the cell whose voltage drops most at the time of engine start, the higher the target SOC, so by increasing the charge / discharge control range of the main battery 15 or By increasing the SOC control center, the SOC of the cell in which the voltage drops most when the engine is started is set to be equal to or higher than the target SOC.

  FIG. 12 is a flowchart illustrating an engine start process performed by the battery control device according to the embodiment. When the temperature of the engine 2 (engine coolant temperature) is equal to or lower than a predetermined value at the start of vehicle operation, the controller 16 shifts to a travel mode by the driving force of the engine 2, or when power generation by the motor 1 is necessary, When the engine 2 start condition is satisfied, the control program is executed to start the engine 2.

  In step S <b> 11, the motor 1 is driven to start cranking of the engine 2, and the battery temperature Tb detected by the battery temperature sensor 21 is stored in the memory 26. At this time, in order to raise the temperature of the main battery 15 quickly, it is desirable to discharge at the maximum output. Note that the power supplied from the main battery 15 to the motor 1 at the time of starting is adjusted by the inverter 11 in accordance with a command from the controller 16. Further, instead of the battery temperature Tb, the outside air temperature Ta detected by the outside air temperature sensor 24 may be stored.

  In a succeeding step S12, it is confirmed based on the engine speed Ne detected by the engine speed sensor 22 whether or not the engine cannot be started. If the fuel is injected and ignited when the engine 2 is rotating at a speed higher than a predetermined startable speed, the engine 2 shifts to an ignition operation and starts. However, when the SOC of the main battery 15 is low and the rotational speed of the engine 2 does not reach a predetermined speed at which the engine 2 can be started, the engine 2 does not start. In this embodiment, an example in which startability is determined based on the engine rotational speed Ne at the time of start is shown, but the determination method of startability is not limited to this embodiment, and for example, based on the intake pressure of the engine, etc. You may make it determine whether start is possible. If the engine rotational speed Ne is equal to or higher than a predetermined speed at which the engine can be started, the engine can be started and the process proceeds to step S13, where fuel is injected by the fuel injection device 30 and ignited by the ignition device 31, Then, the engine start process is terminated.

  If the engine speed Ne does not reach the predetermined speed at which the engine can be started, it is determined that the engine cannot be started and the process proceeds to step S14. In step S14, it is determined whether or not the key switch 20 is turned off. If it is determined that the key switch 20 is turned off, the engine start process is terminated. On the other hand, if it is determined that the key switch 20 is not turned off, the process proceeds to step S15. In step S15, “battery warming up” is displayed on the display 32. This prevents the driver from turning off the key switch 20 during engine startup.

  In step S16, the start waiting time until the engine start is completed is predicted and displayed on the display 32. The start waiting time is determined based on the battery temperature characteristic (see FIG. 4) measured in advance based on the SOC of the main battery 15 detected by the battery SOC detection device 23 and the battery temperature Tb detected by the battery temperature sensor 21. The battery output is obtained, and the time until the battery output reaches a target value at which the engine can be started is predicted from the battery output characteristics (see FIG. 13) measured in advance. The characteristic shown in FIG. 13 represents the battery output with respect to the discharge time when discharged at the maximum output of the battery.

  In step S17 subsequent to step S16, it is determined whether or not the rotational speed of the engine 2 has reached a predetermined speed at which the engine 2 can be started, that is, whether or not the engine can be started. In step S18, the fuel injection device 30 and the ignition device 31 are driven to start the ignition operation of the engine 2. On the other hand, if the rotational speed of the engine 2 does not reach the predetermined speed and it is determined that the engine cannot be started, the process proceeds to step S19.

  In step S19, it is determined whether or not the key switch 20 is turned off. If it is determined that the key switch 20 is turned off, the engine start process is terminated. If it is determined that the key switch 20 is not turned off, the process returns to step S15 to continue warming up the main battery 15.

  According to the battery control device in one embodiment, the battery temperature at the time of starting the engine is predicted, the lowest voltage cell having the lowest voltage at the time of starting the engine is specified, the predicted battery temperature, and the specified lowest voltage cell The target SOC for obtaining a predetermined output from the battery without setting the voltage of the lowest voltage cell below the predetermined overdischarge threshold at the time of starting the engine is set based on the state of the engine. The charging / discharging of the battery is controlled as described above. As a result, when the engine is started, an output necessary for starting the engine can be obtained even if the battery temperature is low, and generation of cells that are in an overdischarged state can be prevented.

  In particular, according to the battery control device in one embodiment, the target SOC is set based on the predicted battery temperature at the next engine start and the internal resistance of the lowest voltage cell. The target SOC for obtaining a predetermined output from the battery can be accurately set without the voltage falling below a predetermined overdischarge threshold. In addition, since the internal resistance of the lowest voltage cell used when setting the target SOC is corrected based on the predicted battery temperature at the time of starting the engine, a more accurate target SOC can be set and the cell is in an overdischarged state. Can be more reliably prevented.

  In addition, according to the battery control device in one embodiment, since the lowest voltage cell is specified based on the open voltage of each cell and the internal resistance of each cell, the lowest voltage cell in which the voltage is lowest when the engine is started. Can be accurately identified.

  The present invention is not limited to the embodiment described above. For example, the motors 1, 4, and 10 are not limited to AC machines, and DC motors can also be used. When a DC motor is used for the motors 1, 4 and 10, a DC / DC converter is used instead of the inverter. The clutch 3 may be a dry single plate clutch or a wet multi-plate clutch.

The method for predicting the battery temperature Tb at the next engine start is not limited to the methods (a) and (b) described above. For example, the following methods (c) to (e) are used. It can also be used.
(C) Stores yearly weather information at various points or regions on the earth, for example, outside air temperature data for the date, and stores information related to engine start, for example, battery temperature Tb at each engine start, outside air temperature Ta, etc. 26. A current location of the vehicle is detected by a GPS unit (not shown), the average value of the outside air temperature Ta before and after the current day is obtained from the above-mentioned annual weather information around the current location, and the obtained average value is used as the predicted value of the battery temperature Tb. A predicted value of the outside air temperature Ta can be obtained by a similar method.
(D) The battery temperature Tb at the next engine start is obtained from the temperature change rate between the latest detected battery temperature Tb1 and the battery temperature Tb2 detected immediately before. That is, assuming that the time from when the battery temperature Tb2 is detected until the time when the battery temperature Tb1 is detected (left time) is T1, and the past average left time is T11, the battery temperature Tb at the next engine start is Obtained by (2).
Tb = {(Tb1-Tb2) / T1} * T11 + Tb1 (2)
A predicted value of the outside air temperature Tb can also be obtained by a similar method.
(E) The battery temperature Tb at the next engine start is predicted by combining the methods (a) to (d) described above. For example, the predicted battery temperature Tb is obtained by the following equation (3).
Tb = Tb (a) * Xa + Tb (b) * Xb + Tb (c) * Xc + Tb (d) * Xd (3)
However, Tb (a) to Tb (d) are battery temperatures predicted by the methods (a) to (d), respectively, and Xa to Xd are weighting factors. In the expression (3), the four methods (a) to (d) described above are combined, but any three or two methods may be combined.

  In the above-described embodiment, an example in which the engine start waiting time is predicted based on the battery temperature and the SOC has been shown. However, the start waiting time prediction method is not limited to the above-described method. For example, the relationship between the engine rotation speed at the time of engine start and the start waiting time may be measured in advance, and the start waiting time may be predicted based on the engine rotation speed after the start of cranking.

  The target SOC for obtaining a predetermined output from the battery without causing the voltage of the lowest voltage cell to fall below a predetermined overdischarge threshold at the next engine start is determined based on the battery temperature and the internal resistance of the lowest voltage cell. However, the degree of deterioration may be used instead of the internal resistance of the lowest voltage cell.

  The correspondence between the constituent elements of the claims and the constituent elements of the embodiment is as follows. That is, the controller 16 is a temperature predicting means, a minimum voltage cell specifying means, a target SOC setting means, an internal resistance detecting means, the inverters 11 to 13 and the controller 16 are controlling means, and the cell voltage sensors Vt1 to Vtn are open voltage detecting means. The battery temperature sensor 21 constitutes battery temperature detection means, and the outside air temperature sensor 24 constitutes outside air temperature detection means. In addition, the above description is an example to the last, and when interpreting invention, it is not limited to the correspondence of the component of said embodiment and the component of this invention at all.

1 is a system configuration diagram in which a battery control device according to an embodiment is applied to a hybrid vehicle. Diagram showing various sensors and various devices connected to the controller The figure which shows the total voltage sensor which detects the total voltage of a main battery, the current sensor which detects the charging / discharging current of a main battery, and the cell voltage sensor which detects the voltage of each cell Diagram showing temperature characteristics of main battery The figure which shows SOC distribution of the some cell which comprises a main battery Diagram showing cell voltage distribution during no load and cell voltage distribution during discharge The figure for explaining the method of calculating the internal resistance of the cell The figure which shows SOC which can obtain the output which is necessary for engine starting with respect to battery temperature and internal resistance of the cell A graph showing the target SOC for obtaining an output required for starting the engine without the overdischarged state of the cell having the lowest voltage when starting the engine, with respect to the predicted battery temperature and the internal resistance of the cell when starting the engine. Flowchart showing main battery SOC control The figure for demonstrating the method to control charging / discharging of a main battery so that SOC of the cell in which a voltage falls most at the time of engine starting becomes more than target SOC. The flowchart which shows the engine starting process performed by the battery control apparatus in one embodiment The figure which shows the battery output with respect to the discharge time when discharged at the maximum output of the battery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Engine, 3 ... Clutch, 4 ... Motor, 5 ... Continuously variable transmission, 6 ... Reduction gear, 7 ... Differential gear, 8 ... Drive wheel, 9 ... Hydraulic device, 10 ... Motor, 11 ... Inverter, 12 ... Inverter, 13 ... Inverter, 15 ... Main battery, 16 ... Controller, 21 ... Battery temperature sensor, 22 ... Engine rotation sensor, 23 ... Battery SOC detector, 24 ... Outside air temperature sensor, 26 ... Memory, 30 ... Fuel injection device 31 ... Ignition device 32 ... Display 35 ... Total voltage sensor 36 ... Current sensor Vt1 to Vtn ... Cell voltage sensor

Claims (7)

In a battery control device that supplies power to a starting motor from a battery constituted by a plurality of cells to start an engine, generates power by a power generating motor, and charges the battery.
Temperature predicting means for predicting the battery temperature at engine start;
A minimum voltage cell specifying means for specifying a cell having the lowest voltage (hereinafter referred to as a minimum voltage cell) when the engine is started;
Based on the battery temperature predicted by the temperature predicting means and the state of the lowest voltage cell specified by the lowest voltage cell specifying means, the voltage of the lowest voltage cell at a start of the engine has a predetermined overdischarge threshold value. Target SOC setting means for setting a target SOC for obtaining a predetermined output from the battery without lowering,
Battery control comprising: control means for controlling charge / discharge of the battery so that the SOC of the cell specified by the lowest voltage cell specifying means is equal to or higher than the target SOC set by the target SOC setting means. apparatus. The battery control device according to claim 1,
Further comprising internal resistance detection means for detecting the internal resistance of each cell;
The target SOC setting means sets the target SOC based on the battery temperature predicted by the temperature prediction means and the internal resistance of the lowest voltage cell detected by the internal resistance detection means. Battery control device. The battery control device according to claim 2,
A temperature correction unit that corrects the internal resistance of the lowest voltage cell detected by the internal resistance detection unit based on the battery temperature predicted by the temperature prediction unit;
The target SOC setting means sets the target SOC based on the battery temperature predicted by the temperature prediction means and the internal resistance corrected by the temperature correction means. The battery control device according to claim 2 or 3,
It further comprises an open voltage detection means for detecting the open voltage of each cell,
The lowest voltage cell specifying means specifies the lowest voltage cell based on the open voltage of each cell detected by the open voltage detecting means and the internal resistance of each cell detected by the internal resistance detecting means. A battery control device. In the battery control device according to any one of claims 1 to 4,
Battery temperature detecting means for detecting the temperature of the battery;
Storage means for storing a plurality of battery temperatures detected by the battery temperature detection means when the engine is started,
The temperature predicting means predicts a temperature having the lowest value among a plurality of battery temperatures stored in the storage means as a battery temperature at the time of starting the engine. In the battery control device according to any one of claims 1 to 4,
An outside air temperature detecting means for detecting the outside air temperature;
Storage means for storing a plurality of outside air temperatures detected by the outside air temperature detecting means when the engine is started,
The temperature control means predicts a battery temperature at the time of engine start based on a plurality of outside air temperatures stored in the storage means. In the battery control device according to any one of claims 1 to 4,
It further comprises a current position detecting means for detecting the current position of the vehicle,
The temperature control means predicts a battery temperature at the time of engine start based on weather information around the vehicle position detected by the current location detection means.

Images