JP2014033571A - Power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power system having a first storage battery, a second storage battery and a connection switch for interconnecting and disconnecting both storage batteries which appropriately performs power supply to electric loads.SOLUTION: The power system includes: a generator 10; a first storage battery 20 and a second storage battery 30 each connected in parallel with the generator 10; a connection switch 50 disposed in a connection line 15 electrically connecting both storage batteries to selectively connect and disconnect the first storage battery 20 and the generator 10 to and from the second storage battery 30; and an ECU 80. On condition that an output voltage of the first storage battery 20 has dropped to a charge trigger voltage, the ECU 80 triggers power generation by the generator 10 to charge the first storage battery 20. The charge trigger voltage is set higher when the connection switch 50 is turned on than when the connection switch 50 is turned off.

Description

  The present invention relates to a power supply system including a first storage battery and a second storage battery, and a generator that charges both the storage batteries.

  For example, as a vehicle power supply system mounted on a vehicle, two storage batteries such as a lead storage battery (first storage battery) and a lithium ion storage battery (second storage battery) are used. A configuration for supplying power is known (see, for example, Patent Document 1). Specifically, the lithium ion storage battery is electrically connected to the generator and the lead storage battery via a semiconductor switch (connection switch) as an opening / closing means.

  By turning on the connection switch during regenerative power generation, power can be supplied from the generator to the lithium ion storage battery. Further, by turning off the connection switch during non-regenerative power generation, electric power is supplied from the lithium ion storage battery to the electric load connected to the lithium ion storage battery side with respect to the connection switch. By controlling the connection switch as described above, it is possible to efficiently use the electric energy generated during regenerative power generation.

JP 2012-80706 A

  If the power consumption of the electrical load suddenly increases in a short time due to the sudden drive of the electrical load on the lead storage battery while the connection switch is in the conductive state, the electrical load on the lead storage battery side is also from the lithium ion storage battery. Is supplied with power. In this case, since the connection switch is in a conductive state, the drive voltage of the lead-acid battery and the lithium-ion battery decreases as the lead-acid battery-side electric load is driven. There is concern about becoming unstable.

  The present invention has been made to solve the above-described problems, and in a power supply system including a first storage battery, a second storage battery, and a connection switch for connecting and disconnecting both the storage batteries, it is preferable to supply power to an electric load. The purpose is to be able to implement.

  The invention according to claim 1 electrically connects the generator (10), the first storage battery (20) and the second storage battery (30) connected in parallel to the generator, and both the storage batteries. A connection switch (50) provided on a connection line (15) to be connected, for switching between conduction and interruption between the first storage battery and the generator and the second storage battery, and an output voltage of the first storage battery up to a charge execution voltage It is a power supply system that performs power generation by a generator and charges the first storage battery on the condition that it has been reduced.

  And a voltage setting means (80) for setting the charging execution voltage higher when the connection switch is in a conductive state than when the connection switch is in a cutoff state. And

  In the said structure, when the connection switch is made into the conduction | electrical_connection state, the charge implementation voltage of a 1st storage battery is set high compared with the case where a connection switch is made into the interruption | blocking state. Then, power is generated by the generator, and charging is performed so that the output voltage of the first storage battery does not become lower than the charging execution voltage. In this case, since the output voltage of the first storage battery is maintained high in advance, the electrical load on the first storage battery side is suddenly driven, and the supply current to the electrical load rapidly increases in a short time, and the output of the first storage battery Even when the voltage drops, it is possible to suppress a drop in the voltage supplied to the electric load on the second storage battery side. For this reason, it can suppress that the drive state of the electric load by the side of the 2nd storage battery becomes unstable.

  In addition, when the connection switch is in the cut-off state, the first storage battery alone supplies power to the first load of the first storage battery, and the second storage battery independently supplies the second load battery side of the electric load. Supply power. For this reason, the voltage supplied to the electrical load on the second storage battery side does not change depending on the driving state of the electrical load on the first storage battery side. Therefore, when the connection switch is in the cut-off state, the charging execution voltage of the first storage battery is set lower than in the case where the connection switch is in the conductive state. Thereby, the power generation in a generator can be suppressed and power saving can be achieved.

The block diagram which shows the outline of the power supply system in this embodiment. The flowchart which shows the procedure of an internal resistance calculation process. The flowchart which shows the procedure of a charging implementation voltage setting process. The flowchart which shows the procedure of a LiSOC maintenance value calculation process. The timing chart which shows the charge / discharge control in this embodiment. The flowchart which shows the procedure of a charging implementation voltage setting process (modification).

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. The power supply system of the present embodiment is an on-vehicle power supply system mounted on a vehicle, and the vehicle travels using an engine (internal combustion engine) as a drive source. When the engine is started, initial rotation is applied to the engine by driving the starter motor.

  As shown in FIG. 1, this power supply system includes an alternator 10 (generator), a lead storage battery 20 as a first storage battery, a lithium ion storage battery 30 as a second storage battery, various electric loads 41, 42, 43, and a connection switch. MOS switch 50 and SMR switch 60 as a storage battery switch. The lead storage battery 20, the lithium ion storage battery 30, and the electrical loads 41 to 43 are electrically connected in parallel to the alternator 10 by a power supply line 15 as a connection line. The power supply line 15 forms a mutual power supply path for each of the electrical elements.

  The lead storage battery 20 is a well-known general-purpose storage battery. On the other hand, the lithium ion storage battery 30 is a high-density storage battery having higher charge / discharge energy efficiency, output density, and energy density than the lead storage battery 20. The lithium ion storage battery 30 is constituted by an assembled battery formed by connecting a plurality of single cells in series. The storage capacity of the lead storage battery 20 is set larger than the storage capacity of the lithium ion storage battery 30.

  The MOS switch 50 is a semiconductor switch made of a MOSFET, and is provided between the alternator 10 and the lead storage battery 20 and the lithium ion storage battery 30. The MOS switch 50 functions as a switch that switches conduction (ON) and interruption (OFF) of the lithium ion storage battery 30 with respect to the alternator 10 and the lead storage battery 20.

  On / off of the MOS switch 50 is controlled by the ECU 70 (electronic control unit). That is, the ECU 70 switches the MOS switch 50 between the on operation (conduction operation) and the off operation (shut-off operation).

  Similarly to the MOS switch 50, the SMR switch 60 is configured by a semiconductor switch made of a MOSFET, and is provided between the connection point (X in the figure) of the MOS switch 50 and the electric load 43 and the lithium ion storage battery 30. It has been. The SMR switch 60 functions as a switch that switches between conduction and interruption of the lithium ion storage battery 30 with respect to the connection point of the MOS switch 50 and the electric load 43.

  Switching of the SMR switch 60 between the on operation (conduction operation) and the off operation (shut-off operation) is performed by the ECU 70. The SMR switch 60 is also an emergency opening / closing means, and is normally kept in an on state by an on signal being constantly output from the ECU 70. In an emergency illustrated below, the output of the on signal is stopped and the SMR switch 60 is turned off. By turning off the SMR switch 60, overcharging and overdischarging of the lithium ion storage battery 30 are avoided.

  For example, when the regulator provided in the alternator 10 breaks down and the set voltage Vreg becomes abnormally high, there is a concern that the lithium ion storage battery 30 may be overcharged. In this case, the SMR switch 60 is turned off. Moreover, when the lithium ion storage battery 30 cannot be charged due to the failure of the alternator 10 or the failure of the MOS switch 50, there is a concern that the lithium ion storage battery 30 is overdischarged. Also in this case, the SMR switch 60 is turned off.

  The SMR switch 60 may be configured using a normally open electromagnetic relay. In this case, even if the ECU 70 breaks down and the operation of the SMR switch 60 cannot be controlled, the SMR switch 60 is automatically opened and the conduction is cut off.

  The lithium ion storage battery 30, the switches 50 and 60, and the ECU 70 are integrated by being accommodated in a casing (accommodating case) and configured as a battery unit U. The ECU 70 in the battery unit U detects the output current, output voltage, and temperature of the lithium ion storage battery 30. The ECU 70 is connected to an ECU 80 (electronic control unit) outside the battery unit. That is, these ECUs 70 and 80 are connected by a communication network such as CAN and can communicate with each other, and various data stored in the ECUs 70 and 80 can be shared with each other.

  The load indicated by reference numeral 43 among the electric loads 41 to 43 is a constant voltage required electric load in which the voltage of the supplied power is substantially constant or the voltage fluctuation is within a predetermined range and is required to be stable. The MOS switch 50 is electrically connected to the lithium ion storage battery 30 side. Thereby, the power supply to the electric load 43 which is a constant voltage required electric load is mainly shared by the lithium ion storage battery 30.

  Specific examples of the electric load 43 include a navigation device and an audio device. For example, when the voltage of the supplied power is not constant but fluctuates greatly, or fluctuates greatly beyond the predetermined range, the voltage instantaneously drops below the minimum operating voltage, and the navigation device etc. This causes a malfunction that resets the operation. Therefore, the electric power supplied to the electric load 43 is required to be stable at a constant value where the voltage does not drop below the minimum operating voltage.

  Moreover, the load shown by the code | symbol 41 among the electric loads 41-43 is a starter motor which starts an engine, and the load shown by the code | symbol 42 is general except the electric load 43 (constant voltage request | requirement electric load) and the starter 41. Electric load. Specific examples of the electric load 42 include wipers such as a headlight and a front windshield, a blower fan for an air conditioner, and a defroster heater for a rear windshield. The electric load 42 includes a driving load that is driven when a predetermined driving condition such as power steering or a power window is satisfied. The starter 41 and the electric load 42 are electrically connected to the lead storage battery 20 side with respect to the MOS switch 50. As a result, the lead storage battery 20 mainly shares power supply to the starter 41 and the electric load 42.

  The alternator 10 generates electric power using rotational energy of an engine crankshaft (output shaft). Since the configuration and the like of the alternator 10 are well known, they are not illustrated here and will be described briefly. When the rotor of the alternator 10 is rotated by the crankshaft, an alternating current is induced in the stator coil according to the exciting current flowing in the rotor coil, and is converted into a direct current by a rectifier. Then, the regulator adjusts the exciting current flowing through the rotor coil so that the voltage of the generated direct current is adjusted to the set voltage Vreg. The ECU 80 controls the alternator 10 with respect to the regulator.

  The electric power generated by the alternator 10 is supplied to various electric loads 41 to 43 and also supplied to the lead storage battery 20 and the lithium ion storage battery 30. When the drive of the engine is stopped and the alternator 10 is not generating power, power is supplied from the lead storage battery 20 and the lithium ion storage battery 30 to the electric loads 41 to 43. The amount of discharge from the lead storage battery 20 and the lithium ion storage battery 30 to the electric loads 41 to 43 and the amount of charge from the alternator 10 to each storage battery 20, 30 are the SOC (State of charge) of each storage battery 20, 30. The ratio of the actual charge amount to the charge amount) is controlled to be in a range (appropriate range) where overcharge / discharge is not caused. That is, the set voltage Vreg is adjusted by the ECU 80 and the operation of the MOS switch 50 is controlled by the ECU 70 so that excessive charging / discharging does not occur as described above.

  Further, the ECU 80 performs power generation in the alternator 10 regardless of whether or not the vehicle is in a regenerative state, on condition that the output voltage of the lead storage battery 20 has decreased to a predetermined charging execution voltage. This charging execution voltage is set so that the output voltage of the lead storage battery 20 is equal to or higher than the minimum operating voltage at which the electric load 42 is guaranteed to operate stably. Thereby, it is suppressed that the output voltage of the lead storage battery 20 becomes lower than the charge execution voltage, and the operation of the electric load 42 is suppressed from becoming unstable.

  Further, in the present embodiment, deceleration regeneration is performed in which the alternator 10 is generated by the regenerative energy of the vehicle and charged to both the storage batteries 20 and 30 (mainly the lithium ion storage battery 30). This deceleration regeneration is performed when conditions such as that the vehicle is in a decelerating state and that fuel injection to the engine is cut off are satisfied.

  Here, since the storage batteries 20 and 30 are connected in parallel, when charging is performed by the alternator 10, the alternator 10 can be used for the storage battery having a lower terminal voltage if the MOS switch 50 is turned on. The electromotive current flows in. On the other hand, when power is supplied (discharged) to the electric loads 42 and 43, if the MOS switch 50 is turned on at the time of non-power generation, the storage battery on the higher terminal voltage side is discharged to the electric load. .

  By the way, at the time of regenerative charging, the lithium ion storage battery 30 is charged with priority over the lead storage battery 20 so that the terminal voltage of the lithium ion storage battery 30 becomes lower than the terminal voltage of the lead storage battery 20. It has become. These settings can be realized by setting the open circuit voltage and internal resistance value of both storage batteries 20 and 30. The open circuit voltage can be set by selecting the positive electrode active material, the negative electrode active material and the electrolyte of the lithium ion storage battery 30. This is possible.

  The vehicle according to this embodiment automatically stops the engine when a predetermined automatic stop condition is satisfied, and automatically restarts the engine when the predetermined restart condition is satisfied with the engine being automatically stopped. The ECU 80 has a stop function, and the idling stop control is performed by the ECU 80. In this idling stop control, when the engine is automatically stopped, the MOS switch 50 is operated to be turned off (cut off). When the engine is restarted, the ECU 70 turns off (cuts off) the MOS switch 50 in order to drive the starter (electric load 41) by the lead storage battery 20 while the lead storage battery 20 and the lithium ion storage battery 30 are electrically disconnected. ) Is operated to the state.

  In addition, in order to charge the lithium ion storage battery 30 (regenerative charging) in the process of decreasing the engine speed, the ECU 70 operates the MOS switch 50 and the SMR switch 60 to turn on during regenerative charging. During traveling of the vehicle other than during regenerative charging, the ECU 70 operates the MOS switch 50 to be turned off and the SMR switch 60 to be turned on. Since the connection between the alternator 10 and the lead storage battery 20 and the electric load 43 is cut off and the connection between the lithium ion storage battery 30 and the electric load 43 is brought into conduction, the lithium ion storage battery 30 alone has power for the electric load 43. Supply is made. Thereby, at the time of regenerative power generation, the generated power can be positively charged to the lithium ion storage battery 30. Since the lithium ion storage battery 30 has higher energy efficiency at the time of charging / discharging than the lead storage battery 20, it can improve the charging / discharging efficiency as the whole power supply system.

  Further, in order to suppress overdischarge in the lithium ion storage battery 30, when the SOC of the lithium ion storage battery 30 becomes lower than the SOC to be maintained (SOC maintenance value), the ECU 70 turns on the MOS switch 50 and the SMR switch 60. Control to turn on. By this control, the connection between the alternator 10 and the lead storage battery 20 and the lithium ion storage battery 30 becomes conductive, and the lithium ion storage battery 30 is charged from the alternator 10 or the lead storage battery 20.

  Here, the SOC is calculated by the ECU 70 based on the output voltage and output current of the lithium ion storage battery 30. In addition, the SOC maintenance value is the electric load of the lithium ion storage battery 30 alone in a state where the lead storage battery 20 and the lithium ion storage battery 30 are electrically disconnected during the engine restart period (the longest period assumed in advance). 43 is set so that power can be supplied. For this reason, it becomes possible to ensure the capacity | capacitance required in the restart period of an engine for the lithium ion storage battery 30. FIG. Further, the SOC maintenance value is set so that there is a free capacity for charging the power of the regenerative power generation. Thereby, in power generation other than regenerative power generation such as power generation during normal driving, charging worthy of the lithium ion storage battery 30 is limited, and the power of regenerative power generation is charged to the lithium ion storage battery 30 for the limited free capacity. Can do. This is an advantageous configuration for utilizing the lithium ion storage battery 30 with high charge / discharge efficiency.

  Further, the maximum power (dischargeable power: Wout) that can be supplied to the electric load by the lithium ion storage battery 30 decreases as the temperature of the lithium ion storage battery 30 decreases. For this reason, even if the remaining capacity is sufficient by controlling the SOC of the lithium ion storage battery 30 to be equal to or higher than the SOC maintenance value, the Wout of the lithium ion storage battery 30 is consumed by the electric load 43 on the lithium ion storage battery 30 side. There is a possibility that the power will be lower. For this reason, if Wout of the lithium ion storage battery 30 is less than the power consumption of the electric load 43, even if the SOC is equal to or higher than the SOC maintenance value, power shortage occurs when the MOS switch 50 is turned off. An abnormality may occur in the operation of

  Therefore, Wout is calculated from the SOC and temperature of the lithium ion storage battery 30, and an independent discharge prohibition value for prohibiting discharge of the lithium ion storage battery 30 to the electric load 43 is determined for Wout of the lithium ion storage battery 30. . The single discharge prohibition value is set from the power consumption of the electric load 43. Then, when Wout falls below the single discharge prohibition value, control is performed to turn on the MOS switch 50. Thereby, it becomes possible to supply electric power from the lead storage battery 20 to the electric load 43, and the operation abnormality of the electric load 43 can be suppressed. Further, when Wout of the lithium ion storage battery 30 is below the single discharge prohibition value and regenerative power generation is not performed, control is performed to turn on the MOS switch 50 and turn off the SMR switch 60. Thereby, the discharge from the lithium ion storage battery 30 is suppressed.

  By the way, the electric load 42 includes a driving load that is driven when predetermined driving conditions such as power steering and a power window are established. Here, when driving of the electric load 42 is started, an inrush current instantaneously flows to the electric load 42. When an inrush current flows from the lead storage battery 20 to the electric load 42, a voltage drop occurs in the lead storage battery 20. In this case, when the MOS switch 50 is in the on state, the lead storage battery 20 and the electric load 43 are connected, so that the input voltage of the electric load 43 also temporarily decreases. For this reason, the input voltage of the electric load 43 may be lower than the minimum operating voltage of the electric load 43. In this case, a problem that the operation of the electric load 43 is reset occurs.

  For example, the power steering is driven based on a driver's steering operation, and the power window is driven based on a switch operation by a driver or the like. That is, the establishment of the driving condition for the electric load 42 is accidental and cannot be predicted. For this reason, it is difficult to turn off the MOS switch 50 or increase the power generation amount of the alternator 10 before and after the timing when the inrush current flows to the electric load 42.

  Therefore, in the present embodiment, the ECU 80 increases the charging execution voltage of the alternator 10 on the condition that the MOS switch 50 is turned on. That is, when the MOS switch 50 is turned on, the lower limit value of the output voltage of the lead storage battery 20 is increased. As a result, an inrush current associated with the driving of the electric load 42 occurs, and even if the output voltage of the lead storage battery 20 drops, the output voltage of the lead storage battery 20 is prevented from falling below the minimum operating voltage of the electric load 43. it can.

  Further, when the MOS switch 50 is in a conductive state and the SMR switch 60 is in a cut-off state, the lead storage battery 20 supplies power to the electric loads 41 to 43 independently. In this case, compared with the case where electric power is supplied from the lead storage battery 20 and the lithium ion storage battery 30 to the electric loads 41 to 43, the amount of current output from the lead storage battery 20, that is, the amount of current flowing through the lead storage battery 20 is increased. To do. For this reason, the fall amount of the output electric power of the lead storage battery 20 increases. Therefore, in addition to the MOS switch 50 being in the conductive state, when the SMR switch 60 is in the cut-off state, the lower limit value of the output voltage of the lead storage battery 20 is increased by increasing the charging execution voltage of the alternator 10. Raise.

  Moreover, the fall of the output voltage of the lead storage battery 20 accompanying the power supply to the electric loads 41 to 43 can be calculated as the product of the current flowing through the lead storage battery 20 and the internal resistance of the lead storage battery 20. That is, as the internal resistance of the lead storage battery 20 increases, the drop in the output voltage of the lead storage battery 20 increases. The internal resistance of the lead storage battery 20 increases as the deterioration of the lead storage battery progresses, and increases as the temperature decreases. Therefore, in the present embodiment, the internal resistance of the lead storage battery 20 is calculated, and the amount of decrease in the output voltage of the lead storage battery 20 due to the inrush current associated with the driving of the electrical load 42 is calculated in advance based on the calculated internal resistance. deep. Then, a voltage value obtained by adding the calculated output voltage drop amount to the minimum operating voltage of the electric load 43 is set as a charging execution voltage when the MOS switch 50 is turned on. Thereby, it can suppress that the output voltage of the lead storage battery 20 is less than the minimum operating voltage of the electric load 43.

  In addition, the output voltage of the storage battery is reduced due to a decrease in electromotive force due to a polarization phenomenon in addition to a voltage drop caused by current flowing through the internal resistance. Here, the decrease in the electromotive force due to polarization changes depending on the direction and magnitude of the current flowing through the lead storage battery 20, but when a large current is passed to some extent, this influence is so small that it can be ignored. In particular, when power is supplied to the starter 41, there is no problem even if the influence of the polarization of the lead storage battery 20 is not taken into consideration. Therefore, when an inrush current occurs at the start of power supply from the lead storage battery 20 to the starter 41 in the idling stop restart, an instantaneous decrease amount of the output voltage of the lead storage battery 20 due to the inrush current is acquired. By calculating the internal resistance of the lead storage battery 20 based on the decrease amount of the output voltage, the resistance value of the internal resistance can be calculated more accurately.

  In addition to acquiring an instantaneous decrease in the output voltage of the lead storage battery 20 at the start of power supply from the lead storage battery 20 to the starter 41, the current value of the discharge current flowing through the lead storage battery 20 at the time of power supply is acquired. It is good also as composition to do. Here, the internal resistance of the lead storage battery 20 can be calculated by dividing the reduction amount of the output voltage by the current value of the discharge current. Further, instead of the momentary decrease in the output voltage of the lead storage battery 20 at the start of power supply to the starter 41, the influence of the polarization phenomenon on the output voltage, in which a steady current flows from the lead storage battery 20 to the starter 41, is affected. The amount of decrease in the output voltage in the saturated state may be acquired, and the internal resistance may be calculated based on the amount of decrease in the output voltage.

  FIG. 2 is a flowchart showing an internal resistance calculation process of the lead storage battery 20, and this process is repeatedly executed by the ECU 80 at a predetermined time period.

  In FIG. 2, in step S <b> 11, it is determined whether or not idling stop restart has been performed since the previous calculation of the internal resistance. When it is determined that the idling stop restart has not been performed (S11: NO), the process ends. When it is determined that the idling stop restart has been performed (S11: YES), in step S12, the amount of decrease in the output voltage V (Pb) of the lead storage battery 20 at the time of the restart is acquired. In step S13, the internal resistance of the lead storage battery 20 is calculated based on the amount of decrease in the output voltage V (Pb) of the lead storage battery 20 acquired in step S12, and the process ends.

  FIG. 3 is a flowchart showing a charging execution voltage setting process of the lead storage battery 20, and this process is repeatedly executed by the ECU 80 at a predetermined time period.

  In FIG. 3, in step S21, it is determined whether or not the MOS switch 50 is in a conductive state and the SMR switch 60 is in a cutoff state. When the MOS switch 50 is in the cut-off state or the SMR switch 60 is in the conductive state (S21: NO), in step S22, the charge execution voltage is set to a normal charge execution voltage that does not consider the deterioration state of the lead storage battery 20. The process is terminated.

  When the MOS switch 50 is in a conductive state and the SMR switch 60 is in a cutoff state (S21: YES), in step S23, the internal resistance of the lead storage battery 20 calculated in step S12 of FIG. 2 is acquired. In step S24, the maximum value of the voltage drop of the lead storage battery 20 is obtained by integrating the acquired internal resistance of the lead storage battery 20 and the maximum value of the inrush current that is predicted to flow as the electric load 42 is driven. calculate. In step S25, the maximum value of the voltage drop amount of the lead storage battery 20 calculated in step S23 is added to the minimum operating voltage of the electric load 43, and the charge execution voltage of the lead storage battery 20 is calculated. The calculated charging execution voltage is higher than the normal charging execution voltage. Then, the calculated charging execution voltage is set as a new charging execution voltage, and the process ends.

  FIG. 4 is a flowchart showing a calculation process of the SOC maintenance value of the lithium ion storage battery 30, and this process is repeatedly executed by the ECU 70 at a predetermined time period. 4, in step S31, the internal resistance of the lead storage battery 20 calculated in step S12 of FIG. 2 is acquired. In step S32, it sets so that the SOC maintenance value of the lithium ion storage battery 30 may become large, so that internal resistance of the lead storage battery 20 is large, and a process is complete | finished.

  FIG. 5 shows a timing chart showing the progress of charge / discharge control in this embodiment.

  At time T0, charge / discharge control of the lead storage battery 20 and the lithium ion storage battery 30 is started. At T0, the SOC of the lead storage battery 20 is reduced by, for example, natural discharge, and the output voltage V (Pb) of the lead storage battery is lower than the charge execution voltage. For this reason, the power generation in the alternator 10 is performed to charge the lead storage battery 20. Further, since the SOC of the lithium ion storage battery 30 is higher than the SOC maintenance value and Wout (not shown) is larger than a predetermined value, the ECU 70 turns off the MOS switch 50 and turns on the SMR switch 60. At time T1, since V (Pb) reaches the charging execution voltage, power generation in the alternator 10 is stopped.

  At time T2, regenerative power generation is started. When the regenerative power generation is started, the ECU 70 turns on the MOS switch 50. By regenerative power generation, the lead storage battery 20 and the lithium ion storage battery 30 are charged, and V (Pb) and the SOC (LiSOC) of the lithium ion storage battery 30 rise. The fuel cut is performed at any timing from time T2 to time T3, and the idling stop automatic stop control is performed by the ECU 80. At time T3, the regenerative power generation ends, and the ECU 70 turns off the MOS switch 50.

  At time T4, idling stop restart control is performed, and power is supplied from the lead storage battery 20 to the starter 41. Since the electric power consumed by the starter 41 is larger than that of the other electric loads 42 and 43, a large current flows through the lead storage battery 20 and V (Pb) is greatly reduced. At time T5, the ECU 80 calculates the internal resistance of the lead storage battery 20 based on the voltage drop amount of V (Pb) accompanying the drive of the starter 41 at time T4. Then, based on the calculated internal resistance, ECU 70 newly calculates an SOC maintenance value.

  At time T <b> 6, the SOC of the lithium ion storage battery 30 has decreased, so that Wout becomes equal to or less than the single discharge prohibition value, and single discharge of the lithium ion storage battery 30 is prohibited. Since regenerative power generation is not performed, the ECU 70 turns the MOS switch 50 on and the SMR switch 60 off. When the MOS switch 50 is turned on and the SMR switch 60 is turned off, the ECU 80 calculates the charging execution voltage based on the internal resistance of the lead storage battery 20. Since the charging execution voltage is higher than the normal charging execution voltage, the ECU 80 controls the alternator 10 to generate power, and charges the lead storage battery 20 until V (Pb) reaches a new charging execution voltage. .

  At time T7, the driving load (for example, power steering) of the electric load 42 is driven, and an inrush current flows through the driving load. When the inrush current flows, a voltage drop occurs in the lead storage battery 20 and V (Pb) decreases, but V (Pb) is set to a voltage value higher than the charging execution voltage calculated based on the internal resistance. For this reason, the operation guarantee voltage of the electric load 43 does not fall below. Then, the ECU 80 performs power generation in the alternator 10 and charges the lead storage battery 20 so that V (Pb) has a voltage value higher than the charging execution voltage.

  Since regenerative power generation is performed at time T8, the ECU 70 turns on the SMR switch 60. Thereby, the alternator 10 and the lithium ion storage battery 30 are connected, and the lithium ion storage battery 30 is charged. At time T9, the regenerative power generation is completed, and Wout of the lithium ion storage battery 30 is a value equal to or greater than a predetermined value. Therefore, the ECU 70 turns off the MOS switch 50 and permits single discharge of the lithium ion storage battery 30.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  (1) In the above configuration, when the MOS switch 50 is in the conductive state, the charging execution voltage of the lead storage battery 20 is set higher than in the case where the MOS switch 50 is in the cutoff state. Then, power generation by the alternator 10 is performed, and charging is performed so that the output voltage of the lead storage battery 20 is higher than the charging execution voltage. Thereby, the output voltage of the lead storage battery 20 is maintained high in advance. For this reason, even when the electric load 42 on the lead storage battery 20 side is driven and the supply current to the electric load 42 increases and the output voltage of the lead storage battery 20 drops, the output voltage of the lead storage battery 20 is It is suppressed that the voltage falls below the minimum operating voltage of the electric load 43 on the lithium ion storage battery 30 side. Thereby, it can suppress that the drive state of the electric load 43 by the side of the lithium ion storage battery 30 becomes unstable.

  Further, when the MOS switch 50 is in the cut-off state, the lead storage battery 20 supplies power to the electric loads 41 and 42 on the lead storage battery 20 side alone, and the lithium ion storage battery 30 alone is the lithium ion storage battery 30. Power is supplied to the electric load 43 on the side. For this reason, the input voltage of the electric load 43 on the lithium ion storage battery 30 side does not decrease depending on the driving state of the electric loads 41 and 42 on the lead storage battery 20 side. Therefore, when the MOS switch 50 is in the cut-off state, the charge execution voltage of the lead storage battery 20 is set lower than in the case where the MOS switch 50 is in the conductive state. Thereby, the electric power generation in the alternator 10 can be suppressed and power saving can be achieved.

  (2) By controlling the energization / shut-off state of the SMR switch 60, overcharge and overdischarge in the lithium ion storage battery 30 can be prevented. Here, when the MOS switch 50 is in the conductive state and the SMR switch 60 is in the cut-off state, the lead storage battery is used for both the electrical loads 41 and 42 on the lead storage battery 20 side and the electrical load 43 on the lithium ion storage battery 30 side. 20 will supply electric power, and the electric current which flows through the lead acid battery 20 will increase. For this reason, when the SMR switch 60 is in the cut-off state, a voltage drop due to driving of the electric load 42 is larger than when the SMR switch 60 is in the conductive state. Therefore, in addition to the MOS switch 50 being in a conductive state, the charging execution voltage of the lead storage battery 20 is set high on condition that the SMR switch 60 is in a cut-off state. Thereby, the output voltage of the lead storage battery 20 is raised in an appropriate period. For this reason, the electric power generation in the alternator 10 can be suppressed and power saving can be achieved.

  (3) As the internal resistance of the lead storage battery 20 increases, the voltage drop inside the lead storage battery 20 accompanying the driving of the electric load 42 increases. In this regard, in the above configuration, the charging execution voltage is set based on the internal resistance of the lead storage battery 20. Thereby, even if the voltage drop in the lead storage battery 20 accompanying the drive of the electric load 42 increases with the increase in the internal resistance of the lead storage battery 20, the output voltage of the lead storage battery 20 is the electric load. It is possible to suppress the lowering of the minimum operating voltage of 43.

  (4) The output voltage of the lithium ion storage battery 30 is increased by increasing the SOC maintenance value that is the SOC maintenance value of the lithium ion storage battery 30 in accordance with the increase in the internal resistance of the lead storage battery 20. Thereby, even if it is a case where the output voltage of lead acid battery 20 falls with the increase in internal resistance of lead acid battery 20, it can control that the supply voltage to electric load 43 falls below the minimum operating voltage of electric load 43. . In addition, by maintaining the SOC of the lithium ion storage battery 30 at the SOC maintenance value, it is possible to secure a free capacity for charging the regenerative power generation.

  Moreover, Wout of the lithium ion storage battery 30 will also rise because the maintenance value of SOC of the lithium ion storage battery 30 rises. As a result, the Wout of the lithium ion storage battery 30 is suppressed from falling below the single discharge prohibition value, the occurrence of a situation in which the MOS switch 50 is turned on and the SMR switch 60 is turned off is suppressed. A decrease in the voltage supplied to the electric load 43 due to the driving of the load 42 can be suppressed.

  (5) The output voltage of the storage battery is reduced not only by a voltage drop due to the internal resistance of the storage battery but also by a decrease in electromotive force due to polarization of the storage battery. Here, when the current flowing through the storage battery increases with the supply of electric power to the electric load, if the increase amount is equal to or greater than a predetermined value, the influence of the polarization of the storage battery on the electromotive force of the storage battery becomes so small that it can be ignored. For this reason, by calculating the internal resistance of the lead storage battery 20 based on the output voltage of the lead storage battery 20 when the current flows through the lead storage battery 20 as the drive load is driven, the lead storage battery 20 is more accurately calculated. The internal resistance can be calculated.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In place of the charging execution voltage setting process shown in FIG. 3 in the above embodiment, the ECU 80 may perform the charging execution voltage setting process shown in FIG. In step S41 of FIG. 6, it is determined whether or not the MOS switch 50 is in an on state. When the MOS switch 50 is in the off state (S41: NO), in step S42, the charging execution voltage is set to the normal charging execution voltage (V0), and the process ends. If the MOS switch 50 is in the on state (S41: YES), in step S43, it is determined whether or not the SMR switch 60 is in the off state. When the SMR switch 60 is in the on state (S43: NO), in step S44, the charging execution voltage is set to a predetermined voltage V1 higher than the normal charging execution voltage (V0), and the process is terminated. When the SMR switch 60 is in the off state (S43: YES), in step S45, the charging execution voltage is set to a predetermined voltage V2 higher than the voltage V1, and the process is terminated.

  If the MOS switch 50 is turned on, the electric load 42 on the lead storage battery 20 side is driven, so that the input voltage of the electric load 43 is lowered. For this reason, the input voltage of the electrical load 43 is suppressed from falling below the minimum operating voltage of the electrical load 43 by raising the charging execution voltage from the voltage V0 and raising the output voltage of the lead storage battery 20. Here, when the MOS switch 50 is in the on state and the SMR switch 60 is in the off state, the inrush current associated with the driving of the electric load 42 is discharged only from the lead storage battery 20. Therefore, comparing the case where the MOS switch 50 is on and the SMR switch 60 is off with the case where the MOS switch 50 is on and the SMR switch 60 is on, the MOS switch 50 is on and the SMR switch 60 is on. The amount of voltage drop when is turned off increases. Therefore, the charge execution voltage V2 when the MOS switch 50 is on and the SMR switch 60 is off is higher than the charge execution voltage V1 when the MOS switch 50 is on and the SMR switch 60 is on. Set. Thereby, generation | occurrence | production of the condition where the input voltage of the electric load 43 is less than the minimum operating voltage of the electric load 43 can be suppressed suitably. The voltages V1 and V2 may be calculated based on the internal resistance.

  In the above embodiment, the charging execution voltage of the lead storage battery 20 when the MOS switch 50 is turned on and the SMR switch 60 is turned off is calculated from the internal resistance of the lead storage battery 20, but the open end voltage of the lead storage battery The internal resistance may be calculated from the output voltage and output current.

  In addition, the ECU 80 calculates the deterioration state of the lead storage battery 20 based on the voltage drop amount of the lead storage battery 20 accompanying the power supply to the starter 41 in the idling stop restart, and calculates the internal resistance based on the deterioration state. And it is good also as a structure which calculates charge implementation voltage based on the internal resistance. Here, the deterioration state of the lead storage battery 20 may be calculated by other methods such as the usage time of the lead storage battery 20.

  Based on the temperature of the lead storage battery 20 when the internal resistance of the lead storage battery 20 is calculated and the temperature of the lead storage battery 20 when the MOS switch 50 is turned on and the SMR switch 60 is turned off, the ECU 80 The internal resistance of the storage battery 20 may be corrected. Thereby, the maximum value of the voltage drop amount of the lead storage battery 20 can be estimated more accurately.

  In FIG. 3 steps S23 to S25 of the above embodiment, the charging execution voltage is calculated and set based on the internal resistance of the lead storage battery 20, but this is changed and the charging execution voltage is compared with the normal charging execution voltage. Thus, the voltage may be increased by a predetermined voltage value.

  DESCRIPTION OF SYMBOLS 10 ... Alternator, 15 ... Feed line, 20 ... Lead acid battery, 50 ... MOS switch, 80 ... ECU.

Claims (5)

A generator (10);
A first storage battery (20) and a second storage battery (30) respectively connected in parallel to the generator;
A connection switch (50) provided on a connection line (15) for electrically connecting both the storage batteries, and for switching between conduction and disconnection between the first storage battery and the generator and the second storage battery;
On the condition that the output voltage of the first storage battery has decreased to a predetermined charge execution voltage, in the power supply system that performs power generation by a generator and charges the first storage battery,
A power supply comprising voltage setting means (80) for setting the charge execution voltage higher when the connection switch is in a conductive state than when the connection switch is in a cutoff state. system. An electric load is connected to the second storage battery side across the connection switch to the connection line,
A storage battery switch that is provided between the connection point at which the second storage battery and the electrical load are connected to the second storage battery in the connection line, and switches between conduction and disconnection between the connection point and the second storage battery. (60)
When the connection switch is in a conductive state and the storage battery switch is in a cut-off state, the voltage setting means is more charged than in the case where the connection switch is in a conductive state and the storage battery switch is in a conductive state. The power supply system according to claim 1, wherein the working voltage is set high. An internal resistance calculating means (80) for calculating an internal resistance of the first storage battery;
The power supply system according to claim 1, wherein the voltage setting unit sets the charging execution voltage based on an internal resistance of the first storage battery calculated by the internal resistance calculation unit. When the remaining capacity of the second storage battery is equal to or less than a predetermined maintenance capacity, the connection switch is turned on to charge the second storage battery from the first storage battery or the generator, Switch control means (70) for controlling the remaining capacity of the second storage battery to be equal to or higher than the maintenance capacity;
The power supply system according to claim 3, further comprising: a maintenance capacity setting means (70) for setting the maintenance capacity based on an internal resistance of the first storage battery calculated by the internal resistance calculation means.   The internal resistance calculating means is based on a decrease in the output voltage of the first storage battery accompanying power supply to a driving load driven under a predetermined condition when the connection switch is in a cut-off state. The power supply system according to claim 3 or 4, wherein an internal resistance of the first storage battery is calculated.

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