JP2014034288A - Vehicular power source system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source system including a first storage battery, a second storage battery, and a connection switch which switches conduction and cut-off of power for both batteries, the power source system suitably supplying power to an electrical load connected to the second storage battery side via a connection switch.SOLUTION: A vehicular power source system includes an alternator 10, a lead storage battery 20, a lithium ion storage battery 30, a MOS switch 50 which switches conduction and cut-off of power for both batteries, and an ECU 70. Upon non-regenerative power generation, the ECU 70 places the MOS switch 50 in a cut-off state and causes the lithium ion storage battery 30 to supply power to an electrical load 43; upon regenerative power generation, the ECU 70 places the MOS switch 50 in a conduction state and causes lithium ion storage battery 30 to be charged. The ECU 70 calculates the dischargeable power of the lithium ion storage battery 30 using the output voltage, output current, and temperature of the lithium ion storage battery 30. When the calculated dischargeable power is equal to or less than a threshold value, the ECU places the MOS switch 50 in the conduction state to inhibit the lithium ion storage battery 30 alone from supplying power.

Description

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

  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, and power is supplied to various in-vehicle electric loads while using each of these storage batteries properly. A configuration for supplying 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 as an opening / closing means.

  By turning on the semiconductor switch during regenerative power generation, power can be supplied from the generator to the lithium ion storage battery. Further, by turning off the semiconductor switch at the time of 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 semiconductor switch. By performing the control of the semiconductor switch as described above, it becomes possible to efficiently use the electric energy generated during the regenerative power generation.

  Furthermore, in order to suppress overdischarge in the lithium ion storage battery, control is performed to turn on the connection switch when the remaining capacity of the lithium ion storage battery falls below a predetermined value. By this control, electric power is supplied from the generator or the lead storage battery to the electric load on the lithium ion storage battery side, and the discharge of the lithium ion storage battery is suppressed, so that the remaining capacity can be maintained at a predetermined value or more. .

JP 2012-80706 A

  Here, the maximum power (dischargeable power) that the lithium ion storage battery can supply to the electrical load decreases as the temperature of the lithium ion storage battery decreases. For this reason, even if it performs control which maintains the remaining capacity of a lithium ion storage battery above a predetermined value, the dischargeable electric power of a lithium ion storage battery may fall below the power consumption of the electric load by the side of a lithium ion storage battery. If the dischargeable power of the lithium ion storage battery is lower than the power consumption of the electric load on the lithium ion storage battery side, turning off the connection switch may cause power shortage and abnormal operation of the electric load.

  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 storage batteries, the second storage battery is sandwiched between the connection switches. It is an object to be able to suitably carry out power supply to an electric load connected to the side.

  Invention of Claim 1 is a power supply system for vehicles, Comprising: Compared with a 1st storage battery (20) and a said 1st storage battery respectively connected in parallel with respect to a generator (10) and the said generator. A second storage battery (30) having a high energy efficiency of discharge and a connection line (15) for electrically connecting both the storage batteries, and continuity and interruption between the first storage battery and the generator and the second storage battery. A connection switch (50) for switching between, and an electric load that is connected to the second storage battery side across the connection switch in the connection line by controlling the connection switch to a cut-off state during non-regenerative power generation of the generator (43), switch control for causing the second storage battery to be charged by supplying power from the second storage battery and controlling the connection switch to a conductive state during regenerative power generation of the generator. It comprises a stage (70), the.

  Furthermore, power calculating means (70) for calculating dischargeable power, which is the maximum power that the second storage battery can supply to the electrical load, using the output voltage, output current, and temperature of the second storage battery. And the switch control means determines that the dischargeable power of the second storage battery calculated by the power calculation means is less than or equal to a power threshold determined based on power consumption by the electric load. The power supply to the electric load by the second storage battery alone is prohibited by controlling the connection switch to be in a conductive state.

  According to the said structure, since the connection switch is made into the interruption | blocking state at the time of non-regenerative electric power generation, electric power supply will be performed with respect to an electrical load by the 2nd storage battery alone. For this reason, the electric power of a 2nd storage battery can be utilized actively, and efficient energy use is attained in combination with the charge at the time of regenerative power generation.

  In addition, by using the output voltage, output current, and temperature of the second storage battery, the dischargeable power that is the maximum power that the second storage battery can supply to the electric load is calculated. When the calculated dischargeable power becomes equal to or less than the power threshold value determined based on the power consumption of the electric load, the connection switch is turned on regardless of whether or not it is during regenerative power generation. When the connection switch is turned on, electric power is supplied from the first storage battery or the generator to the electric load on the second storage battery side with the connection switch interposed therebetween.

  As a result, even when the dischargeable power of the second storage battery is lower than the power consumption of the electrical load as a result of the temperature being lowered, power can be supplied to the electrical load, It is possible to suppress malfunction due to power shortage of the load.

The block diagram which shows the outline of the power supply system for vehicles in embodiment. The flowchart showing the calculation process of dischargeable electric power Wout. The flowchart showing charging / discharging control processing. The timing chart showing charging / discharging control.

  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 imparted to the engine by driving the starter.

  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 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 LIN 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.

  The load indicated by reference numeral 41 among the electric loads 41 to 43 is a starter for starting the engine, and the load indicated by reference numeral 42 is a general electric other than the electric load 43 (constant voltage required electric load) and the starter 41. It is a 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 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, 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. Such setting can be realized by setting the open-circuit voltage and internal resistance value of both the storage batteries 20 and 30. The open-circuit voltage is set by selecting the positive electrode active material, the negative electrode active material, and the electrolyte solution 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. At the automatic stop by the idle stop function, the MOS switch 50 is switched off. Thereby, the electric load 42 is supplied with electric power from the lead storage battery 20, and the electric load 43 is supplied with electric power from the lithium ion storage battery 30. Then, the engine is automatically restarted with the MOS switch 50 turned off. Since the starter 41 and the lithium ion storage battery 30 are disconnected and the starter 41 and the lead storage battery 20 are energized, the starter 41 is driven by power supply from the lead storage battery 20.

  Further, during non-regenerative power generation, 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. During regenerative power generation, the ECU 70 operates the MOS switch 50 to be on and the SMR switch 60 to be on. Thereby, the generated electric power is charged in 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, when the SOC of the lithium ion storage battery 30 becomes lower than the SOC to be maintained (maintenance SOC), the ECU 70 turns on the MOS switch 50 and turns on 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 open end voltage and the output current of the lithium ion storage battery 30. In addition, it is good also as a structure which correct | amends calculated SOC based on the voltage between terminals at the time of SOC calculation of the lithium ion storage battery 30. FIG. Further, the maintenance SOC is set so that the lithium ion storage battery 30 can supply power to the electric load 43 alone while the lead storage battery 20 and the lithium ion storage battery 30 are electrically disconnected during idling stop. . For this reason, it becomes possible to ensure the capacity | capacitance required in an idling stop period in the lithium ion storage battery 30. FIG. Furthermore, the maintenance SOC is set so that there is a free capacity for charging the power of the regenerative power generation. As a result, in power generation other than regenerative power generation such as power generation during normal driving, charging of the lithium ion storage battery 30 is limited to the maintenance SOC, and the regenerative power generation is used for the free capacity secured by the limitation. 30 can be charged. This is an advantageous configuration for utilizing the lithium ion storage battery 30 with high charge / discharge efficiency.

  By the way, unlike the SOC, the maximum power (dischargeable power: Wout) that the lithium ion storage battery 30 can supply to the electric load decreases as the temperature of the lithium ion storage battery 30 decreases. For this reason, control is performed to maintain the SOC of the lithium ion storage battery 30 at or above the maintenance SOC, and even if the remaining capacity is sufficient, 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 lower than the power consumption of the electric load 43, even if the SOC is equal to or higher than the maintenance SOC, turning off the MOS switch 50 causes power shortage, Abnormalities can occur in operation.

  Therefore, in the present embodiment, the ECU 70 calculates Wout of the lithium ion storage battery 30 and switches on / off a discharge prohibition flag that prohibits discharge of the lithium ion storage battery 30 to the electric load 43 based on Wout. Then, the ECU 70 controls the MOS switch 50 and the SMR switch 60 based on the discharge prohibition flag, thereby suppressing the power shortage.

  If the discharge prohibition flag is turned on during non-regenerative power generation, the ECU 70 controls the switches 50 and 60 to be in a discharge prohibition mode (MOS switch 50: on, SMR switch 60: off), and the lithium ion storage battery 30 Prohibit discharge. If the discharge prohibition flag is turned on during regenerative power generation, the ECU 70 controls the switches 50 and 60 to be in a charging mode (MOS switch 50: on, SMR switch 60: on). The ion storage battery 30 is charged.

  When the discharge prohibition flag is turned off, the ECU 70 controls the switches 50 and 60 according to whether or not regenerative power generation is performed. That is, the ECU 70 controls the switches 50 and 60 to be in a single discharge mode (MOS switch 50: off, SMR switch 60: on) at the time of non-regenerative power generation, and switches 50, 60 to the charge mode at the time of regenerative power generation. Control to turn on (MOS switch 50: on, SMR switch 60: on) is performed. Here, regardless of whether the discharge prohibition flag is on or off, when the SOC of the lithium ion storage battery 30 becomes lower than the maintenance SOC, the ECU 70 sets the switches 50 and 60 to raise the SOC of the lithium ion storage battery 30 to the maintenance SOC. Control for setting the charging mode (MOS switch 50: on, SMR switch 60: on) is performed.

  The ECU 70 determines a prohibition threshold based on the maximum power consumed by the electric load 43. Then, the ECU 70 compares Wout with the prohibition threshold when the discharge prohibition flag is off, and turns on the discharge prohibition flag when Wout is lower than the prohibition threshold. Further, the ECU 70 compares Wout with a permission threshold that is higher than the prohibition threshold by a predetermined value when the discharge prohibition flag is on, and when Wout is higher than the permission threshold, the discharge prohibition flag Turn off.

  The dischargeable power Wout is calculated by the ECU 70 from the temperature of the lithium ion storage battery 30 and the SOC of the lithium ion storage battery 30. The prohibition threshold is calculated by integrating the guaranteed voltage of the electric load 43 and the maximum current flowing through the electric load 43 when the electric load 43 is in a driving state.

  FIG. 2 is a flowchart showing Wout calculation processing. This process is repeatedly performed by the ECU 70 at a predetermined time period.

  In step S01, the temperature of the lithium ion storage battery 30 is acquired, and in step S02, the SOC of the lithium ion storage battery 30 is acquired. In step S03, the OCV of the lithium ion storage battery 30 is calculated based on the temperature of the lithium ion storage battery 30 and the SOC using the open-circuit voltage (OCV) characteristics of the lithium ion storage battery 30. Here, the open-circuit voltage refers to a battery voltage in a state where an electric load is not connected to a battery terminal.

  In step S04, the internal resistance Rbat of the lithium ion storage battery 30 during discharge is calculated based on the temperature of the lithium ion storage battery 30 and the SOC of the lithium ion storage battery 30 using the internal resistance Rbat characteristic of the lithium ion storage battery 30. The OCV and Rbat of the lithium ion storage battery 30 can be obtained from the output current and the output voltage of the lithium ion storage battery 30 instead of being obtained from the SOC.

  In step S05, the internal resistance Rbat is corrected based on the deterioration state of the lithium ion storage battery 30. The deterioration state of the lithium ion storage battery 30 is calculated by the ECU 70 based on the usage time of the lithium ion storage battery 30, the actual resistance value, and the like.

  In step S06, a maximum current value Imax that can be discharged from the lithium ion storage battery 30 to the electric load 43 is calculated. Imax can be calculated as “Imax = (OCV−guaranteed voltage) / (Rbat + Rpack)”. Here, Rpack is a resistance component that causes power loss inside the battery unit U, and is composed of a wiring resistance inside the battery unit U, an on-resistance of the SMR switch 60, and the like. Rpack is a resistance obtained by removing the internal resistance Rbat of the lithium ion storage battery 30 from the internal resistance of the battery unit U. In step S07, dischargeable power Wout is calculated. Wout is calculated as “Wout = Imax × guaranteed voltage”. Here, the guaranteed voltage is a voltage value for which the operation of the electric load 43 is guaranteed.

  FIG. 3 is a flowchart showing the charge / discharge control process. This process is repeatedly performed by the ECU 70 at a predetermined time period.

  In step S11, it is determined whether or not the discharge prohibition flag is off. When the discharge prohibition flag is off (S11: YES), in step S12, it is determined whether Wout is larger than the prohibition threshold. If the dischargeable power is less than or equal to the prohibition threshold (S12: NO), in step S13, the discharge prohibition flag is turned on and the process ends.

  When the dischargeable power is larger than the prohibition threshold (S12: YES), in step S14, it is determined whether or not the SOC (LiSOC) of the lithium ion storage battery 30 is smaller than the maintenance SOC. If the LiSOC is smaller than the maintenance SOC, the switches 50 and 60 are controlled in the charging mode (MOS switch 50: on, SMR switch 60: on) in step S15, and the process is terminated.

  If LiSOC is equal to or higher than the maintenance SOC (S14: NO), it is determined in step S16 whether or not regenerative power generation is being performed in alternator 10. If regenerative power generation is being carried out (S16: YES), the switches 50 and 60 are controlled in the charging mode (MOS switch: on, SMR switch: on) in step S15, and the process is terminated. When regenerative power generation is not performed (S16: NO), in step S17, the switches 50 and 60 are controlled to the single discharge mode (MOS switch 50: off, SMR switch 60: on), and the process ends.

  In step S11, if the discharge prohibition flag is on (S11: NO), it is determined in step S18 whether Wout is equal to or greater than a permission threshold. If Wout is equal to or greater than the permission threshold (S18: YES), in step S19, whether LiSOC has reached the upper limit value (LiSOC upper limit value) of a predetermined SOC control range determined by LiSOC in the lithium ion storage battery 30. Make a decision. Here, the LiSOC upper limit value is a value at which overcharging occurs when the lithium ion storage battery 30 is charged and the SOC is increased from the upper limit value. When Wout is equal to or greater than the permission threshold value and LiSOC has reached the LiSOC upper limit value (S19: NO), in step S20, the discharge prohibition flag is turned off and the process is terminated.

  If Wout is equal to or greater than the permission threshold value and LiSOC has not reached the LiSOC upper limit value (S19: YES), it is determined in step S21 whether the idling stop automatic stop condition is satisfied and the idling stop control is being performed. When the idling stop control is being performed (S21: YES), in step S20, the discharge prohibition flag is turned off and the process is terminated.

  When Wout is smaller than the permission threshold (S18: NO), or when Wout is equal to or larger than the permission threshold but idling stop control is not performed (S21: NO), whether or not LiSOC is smaller than the maintenance SOC in step S23. Judgment is made. If LiSOC is smaller than the maintenance SOC (S23: YES), in step S24, the switch is controlled to the charging mode (MOS switch 50: on, SMR switch 60: on), and the process is terminated. If LiSOC is equal to or higher than the maintenance SOC (S23: NO), it is determined in step S25 whether or not regenerative power generation is being performed. If regenerative power generation is being performed (S25: YES), in step S24, the switches 50 and 60 are controlled in the charging mode (MOS switch 50: on, SMR switch 60: on), and the process ends. If regenerative power generation is not performed (S25: NO), the switches 50 and 60 are controlled to the single discharge inhibition mode (MOS switch 50: on, SMR switch 60: off) in step S26, and the process is terminated.

  FIG. 4 is a timing chart showing the progress of charge / discharge control. The control when the temperature of the lithium ion battery is 30 ° C. is indicated by a solid line, and the control at 0 ° C. is indicated by a one-dot chain line.

  Based on FIG. 4, the charge / discharge control regarding this embodiment is demonstrated. First, a description will be given when the temperature of the lithium ion storage battery 30 is 30 ° C. At time T0, electric power is supplied to the ECU 70, and control by the ECU 70 is started. Prior to time T0, charge / discharge control by the ECU 70 is not performed, and Wout and SOC (LiSOC) of the lithium ion storage battery 30 are in a state of being lowered by natural discharge. For this reason, at time T0, Wout is below the prohibition threshold, and LiSOC is below the maintenance SOC.

  Since Wout is below the prohibition threshold, the ECU 70 prohibits single discharge of the lithium ion storage battery 30. Further, since LiSOC is lower than maintenance SOC, ECU 70 sets the switch in a charging mode, that is, MOS switch 50 is turned on and SMR switch 60 is turned on. Then, power is supplied from the alternator 10 or the lead storage battery 20 to the lithium ion storage battery 30 and charging is performed until the maintenance SOC is reached. Thereby, the lithium ion storage battery 30 can be charged with the remaining capacity used by the electric load 43 when the idling stop is restarted.

  At time T1, since the LiSOC reaches the maintenance SOC, the ECU 70 turns off the SMR switch 60 and stops the power supply from the alternator 10 or the lead storage battery 20 to the lithium ion storage battery 30. Here, since Wout is lower than the permission threshold value and prohibition of single discharge of the lithium ion storage battery 30 is not released, the MOS switch 50 is kept on and power is supplied from the alternator 10 or the lead storage battery 20 to the electrical load 43. Let it be done.

  At time T2, a brake operation is performed, the vehicle speed is reduced, and regenerative power generation is performed. As the regenerative power generation is performed, the ECU 70 performs control to turn on the MOS switch 50 and turn on the SMR switch 60 to charge the lithium ion storage battery 30 from the alternator 10. With the charging of the lithium ion storage battery 30, Wout reaches the permission threshold at time T3.

  At time T4, regenerative power generation is stopped, and automatic engine stop control in idling stop control is performed. Since Wout is equal to or greater than the permission threshold value and the automatic stop control of the idling stop control is performed, the discharge prohibition is canceled. Since the prohibition of discharge is released, the ECU 70 supplies power from the lithium ion storage battery 30 to the electric load 43 alone with the MOS switch 50 turned off and the SMR switch 60 turned on. As the lithium ion storage battery 30 is discharged, Wout and LiSOC decrease. Thereafter, at time T5, since regenerative power generation is performed, the ECU 70 performs control to turn on the MOS switch 50 and turn on the SMR switch 60, and charge the lithium ion storage battery 30 from the alternator 10.

  Next, the case where the temperature of the lithium ion storage battery 30 is 0 degreeC is demonstrated. The LiSOC at time T0 is the same as that at 30 ° C. described above. The control from time T0 to T3 is the same as when the temperature is 30 ° C. Here, when the temperature is 0 ° C., Wout is lower than that when the temperature is 30 ° C., so at time T3, Wout does not reach the permission threshold value, and the discharge prohibition flag remains on.

  At time T4, since regenerative power generation is stopped and single discharge of the lithium ion storage battery 30 is prohibited, the ECU 70 sets the MOS switch 50 in the on state and the SMR switch 60 in the off state, and the electric power is generated from the alternator 10 and the lead storage battery 20. Power is supplied to the load 43. For this reason, LiSOC and Wout are maintained during times T4 to T5. Since regenerative power generation is performed at time T5, the ECU 70 switches the SMR switch 60 from OFF to ON while keeping the MOS switch 50 in the ON state. Thereby, the lithium ion storage battery 30 is charged, and LiSOC and Wout rise. At time T6, Wout reaches the permission threshold. At time T7, the engine automatic stop control in the idling stop control is performed, and the ECU 70 turns off the discharge prohibition flag.

  During the period when the discharge prohibition flag is on (temperature 30 ° C .: T0 to T4, temperature 0 ° C .: T0 to T7), the MOS switch 50 is turned on by the ECU 70. For this reason, the electric load 43 is supplied with electric power from the alternator 10 or the lead storage battery 20 during a period in which Wout may be lower than the maximum electric power consumed in the electric load 43, and the electric load 43 is insufficient in electric power. Can be suppressed. Further, when the control at the temperature of 0 ° C. is compared with the control at the temperature of 30 ° C., the discharge prohibition flag is quickly turned off in the control at the high temperature of 30 ° C. For this reason, in T4 to T5, the power of the lithium ion storage battery 30 is consumed, and it is possible to secure a free capacity for charging the regenerative power generation.

  By turning off the SMR switch 60 at the time T1, the LiSOC maintains the maintenance SOC in the period from the time T1 to T2. Thereby, in the regenerative power generation at times T2 to T4, it is possible to secure a free capacity for charging the lithium ion storage battery 30 with the power generated in the alternator 10.

  At times T4 to T5, when the temperature is 0 ° C., Wout is not less than the prohibition threshold and less than the permission threshold. Wout never falls below the maximum power consumed by the electric load 43, and even if the lithium ion storage battery 30 supplies power to the electric load 43 alone, there is no power shortage. Further, when the temperature is low, Wout may be less than the prohibition threshold. In this case, the determination of steps S19 and S21 in FIG. 3 is not performed, and thus the discharge prohibition flag is not turned off.

  Hereinafter, the effect which this embodiment show | plays is described.

  (1) According to the above configuration, since the MOS switch 50 is in a cut-off state during non-regenerative power generation, power is supplied to the electric load 43 by the lithium ion storage battery 30 alone. For this reason, the electric power of the lithium ion storage battery 30 can be utilized positively, and efficient energy use is possible together with the charge at the time of regenerative power generation.

  In addition, when the Wout of the lithium ion storage battery 30 is equal to or lower than the power threshold value determined based on the power consumption of the electric load 43, the MOS switch 50 is set to the conductive state regardless of whether or not the regenerative power generation is being performed. To do. When the MOS switch 50 is turned on, power is supplied from the alternator 10 or the lead storage battery 20 to the electric load 43. As a result, the SOC and temperature of the lithium ion storage battery 30 are reduced, and as a result, even if the Wout of the lithium ion storage battery 30 is lower than the power consumption of the electric load 43, power is supplied to the electric load 43. It is possible to suppress malfunction caused by power shortage of the electrical load 43.

  (2) When the MOS switch 50 is turned on during non-regenerative power generation, the lead storage battery 20 and the lithium ion storage battery 30 can be connected. Then, charging is performed from the lead storage battery 20 to the lithium ion storage battery 30 or from the lithium ion storage battery 30 to the lead storage battery 20. Charging from the storage battery to the other storage battery means discharging the power charged in one storage battery and charging the other storage battery. That is, the number of times of charge / discharge in the storage battery is increased at least once compared to the case where the power generated in the alternator 10 is directly charged in the storage battery. As the number of times of charging / discharging increases, power loss occurs, and the power use efficiency of the power supply system as a whole decreases.

  Here, when the MOS switch 50 is turned on during non-regenerative power generation, the SMR switch 60 is turned off. This makes it possible to suppress charging of the lithium ion storage battery 30 from the lead storage battery 20 while supplying power from the alternator 10 or the lead storage battery 20 to the electric load 43, thereby improving the power use efficiency of the entire power supply system. Can be improved.

  (3) By setting the SOC maintenance value, the SOC of the lithium ion storage battery 30 is maintained in a state where the SOC has reached the SOC maintenance value. In this case, since the SOC does not increase any more, even if regenerative power generation is performed after the present time, a free capacity for charging by the regenerative power generation can be secured. This is an advantageous configuration in the present configuration using a storage battery with high charge / discharge efficiency as the lithium ion storage battery 30.

  If it is determined that the SOC and the SOC maintenance value of the lithium ion storage battery 30 are equal during non-regenerative power generation and in a state where the power supply prohibition of the lithium ion storage battery 30 alone is set, the MOS switch 50 is turned on and the SMR switch is turned off By controlling, the overload of the lithium ion storage battery 30 can be suppressed while driving the electric load 43 appropriately.

  Similarly, it is assumed that the SOC of the lithium ion storage battery 30 is determined to be less than the SOC maintenance value at the time of non-regenerative power generation and in a state where power supply prohibition by the lithium ion storage battery 30 alone is prohibited. In this case, the electric power supplied from the alternator 10 or the lead storage battery 20 is added to the drive of the electric load 43 by controlling the MOS switch 50 and the SMR switch 60 in the conductive state, and the lithium ion storage battery 30 is charged. Can also be used. Therefore, the SOC of the lithium ion storage battery 30 recovers to the SOC maintenance value.

  In the above configuration, the MOS switch 50 is controlled to be in a conductive state based on Wout, and when the MOS switch 50 is in a conductive state, switching of the SMR switch 60 is controlled based on the SOC. Thus, the SOC can be properly managed in the lithium ion storage battery 30 while suppressing excessive discharge in consideration of the temperature condition for the lithium ion storage battery 30.

  (4) As a result of frequent switching of the MOS switch 50 and the SMR switch 60, a transient current / voltage change occurs in the entire power supply system, and the elements of the electric load 43 to which power is supplied are deteriorated and the power efficiency is lowered. Will be invited. Therefore, a first power threshold (prohibition threshold) and a second power threshold (permission threshold) higher than the first power threshold are provided as power thresholds. Then, when it is determined that the dischargeable power is lower than the prohibition threshold, prohibition of power supply to the electric load 43 by the lithium ion storage battery 30 alone is started, and it is determined that the dischargeable power is higher than the permission threshold. In this case, the prohibition of power supply to the electric load 43 by the lithium ion storage battery 30 alone is lifted. Thereby, when the dischargeable power is between the prohibition threshold value and the permission threshold value, switching of the switch is suppressed, and it is possible to suppress deterioration of the element and a decrease in power efficiency.

  (5) When the idling stop control is performed, the output voltage of the lead storage battery 20 decreases as the starter 41 is driven. Therefore, when the idling stop control is performed, it is desirable that the lithium ion storage battery 30 supplies power to the electric load 43 alone with the MOS switch 50 being cut off in order to prevent the voltage supplied to the electric load 43 from being lowered.

  For this reason, it is desirable to keep the dischargeable power of the lithium ion storage battery 30 high. Therefore, in addition to the dischargeable power being equal to or higher than the permission threshold, the prohibition of discharge by the lithium ion storage battery 30 alone is canceled on condition that the engine is automatically stopped in the idling stop control. Thereby, when idling stop control is not carried out, it is possible to inhibit the discharge of the lithium ion storage battery 30 by prohibiting the discharge of the lithium ion storage battery 30 alone, and to keep the dischargeable power of the lithium ion storage battery high. become. Further, on the condition that the engine automatic stop control in the idling stop control is performed, the voltage associated with the driving of the starter 41 is set by turning off the MOS switch 50 by releasing the prohibition of discharge by the lithium ion storage battery 30 alone. The malfunction of the electric load 43 due to the decrease can be prevented.

  As described above, as conditions for releasing the discharge prohibition, the dischargeable power is equal to or higher than the discharge permission threshold (FIG. 3, step S18: YES), and the idling stop control is performed (step S21: YES). Therefore, the dischargeable power is maintained at a high level. Furthermore, since the discharge prohibition is canceled on the condition that the dischargeable power is equal to or higher than the discharge permission threshold and LiSOC has reached the LiSOC upper limit value (S19: NO), the LiSOC is prevented from excessively rising. can do.

  (6) The internal resistance Rbat of the lithium ion storage battery 30 increases as the deterioration progresses. Accordingly, the dischargeable power of the lithium ion storage battery 30 becomes smaller as the deterioration progresses. Therefore, by correcting the internal resistance Rbat and thus the dischargeable power based on the deterioration state of the lithium ion storage battery 30, more accurate dischargeable power can be obtained, and the power supply to the electric load 43 is reliably performed. It becomes possible.

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

  -ECU70 and ECU80 may be comprised as one ECU. By being configured as one ECU, a delay due to communication between the ECUs can be eliminated. Accordingly, the switches 50 and 60 can be quickly controlled based on switching between the regenerative power generation and the non-regenerative power generation of the alternator 10.

  -Other methods may be used for setting the power threshold. For example, the power consumed by the electrical load 43 may be monitored and stored, and the power threshold may be set based on the maximum amount of power actually consumed. As a result, the power charged in the lithium ion storage battery 30 can be used more, and the power use efficiency can be improved. Moreover, even if the operating / non-operating state of the electrical load 43 is acquired by a network such as CAN, the amount of power consumed by the operating electrical load 43 is calculated, and the power threshold is set based on the calculation result. Good.

  -Although it was set as the structure which provides 1st power threshold value (prohibition threshold value) and 2nd power threshold value (permission threshold value) as a power threshold value, when one power threshold value is provided and dischargeable power exceeds the said power threshold value The discharge prohibition flag may be turned off, and the discharge prohibition flag may be turned on when the dischargeable power is equal to or lower than the power threshold. Furthermore, it may be configured to prohibit the ON / OFF of the discharge prohibition flag for a predetermined time after the ON / OFF of the discharge prohibition flag is switched once. Thereby, even when one power threshold value is used, frequent switching of the switches can be suppressed.

  -In above-mentioned embodiment, although the lead storage battery 20 was used as a 1st storage battery and the lithium ion storage battery 30 was used as a 2nd storage battery, this may be changed. For example, another secondary battery such as a nickel-cadmium storage battery or a nickel hydride storage battery may be used as the second storage battery.

  -In above-mentioned embodiment, it was set as the structure which cancels | releases prohibition of discharge only by the lithium ion storage battery 30 on condition that the electric power which can be discharged becomes more than a permission threshold value, and the automatic stop conditions in idle stop control were satisfied. Instead, the prohibition of discharge by the lithium ion storage battery 30 alone may be canceled on the condition that the dischargeable power is equal to or greater than the permission threshold and the restart condition in the idle stop control is satisfied. Further, when the dischargeable power becomes equal to or higher than the permission threshold, the discharge prohibition may be canceled regardless of whether or not the idling stop control is performed.

  DESCRIPTION OF SYMBOLS 10 ... Alternator (generator), 15 ... Feed line (connection line), 20 ... Lead storage battery (1st storage battery), 30 ... Lithium ion storage battery (2nd storage battery), 43 ... Electric load, 50 ... MOS switch (connection switch) ), 70... ECU (switch control means, power calculation means).

Claims (6)

A generator (10);
A first storage battery (20) connected in parallel to each of the generators, and a second storage battery (30) having higher energy efficiency of charge and discharge compared to the first storage battery;
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;
At the time of non-regenerative power generation of the generator, the connection switch is controlled to be in a cut-off state, and the electric load (43) connected to the second storage battery side across the connection switch in the connection line is Switch control means (70) for supplying electric power from the two storage batteries, and controlling the connection switch to a conductive state during regenerative power generation of the generator to charge the second storage battery. In the power system,
Power calculating means (70) for calculating dischargeable power, which is the maximum power that the second storage battery can supply to the electrical load, using the output voltage, output current, and temperature of the second storage battery. ,
The switch control means, when it is determined that the dischargeable power of the second storage battery calculated by the power calculation means is less than or equal to a power threshold value determined based on power consumption by the electric load. A power supply system for a vehicle, wherein the power supply to the electric load by the second storage battery alone is prohibited by controlling the switch to a conductive state. A storage battery switch (60) that is provided between a connection point to which the electrical load is connected in the connection line and the second storage battery, and switches between connection and disconnection between the connection point and the second storage battery;
2. The vehicle power supply system according to claim 1, wherein the switch control unit controls the storage battery switch to be in a cut-off state during non-regenerative power generation and in a state where power supply is prohibited by the second storage battery alone. . A remaining capacity calculating means (70) for calculating a remaining capacity of the second storage battery based on an output voltage and an output current of the second storage battery;
The switch control means determines a remaining capacity maintenance value for maintaining the value of the remaining capacity for the remaining capacity of the second storage battery, and is in a state of prohibiting power supply at the time of non-regenerative power generation and the second storage battery alone. If it is determined that the remaining capacity of the second storage battery is equal to or greater than the remaining capacity maintenance value, the storage battery switch is controlled to be in a cut-off state, and regenerative power generation or a state where power supply is prohibited by the second storage battery alone 3. The vehicle power supply system according to claim 2, wherein when the remaining capacity of the second storage battery is determined to be less than a remaining capacity maintenance value, the storage battery switch is controlled to be in a conductive state. As the power threshold, a first power threshold and a second power threshold higher than the first power threshold are provided,
When the switch control means determines that the dischargeable power of the second storage battery has become equal to or less than the first power threshold, the electrical load of the second storage battery alone is set by turning on the connection switch. When it is determined that the dischargeable power of the second storage battery is higher than the second power threshold, the connection switch is turned off during non-regenerative power generation. The vehicle power supply system according to any one of claims 1 to 3, wherein the prohibition of power supply to the electric load by the second storage battery alone is canceled. The vehicle power supply system is mounted on a vehicle having an automatic stop / start function for automatically stopping the engine while the vehicle is running, and then performing cranking by a starter (41) to automatically restart the engine. ,
The starter is connected to the first storage battery side across the connection switch in the connection line,
The switch control means sets the connection switch to a cut-off state when the dischargeable power of the second storage battery is higher than the second power threshold and the engine is automatically stopped and restarted. The vehicle power supply system according to claim 4, wherein the prohibition of power supply to the electric load by the second storage battery alone is canceled.   The vehicle power supply system according to any one of claims 1 to 5, wherein the power calculation unit corrects the dischargeable power based on a deterioration state of the second storage battery.

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