JPWO2014208028A1 - Power storage system - Google Patents

Abstract

In an electricity storage system using a nickel hydride battery or a lithium ion battery and a lead battery together, the lead battery is made smaller. The power storage system (100) is mounted on a vehicle including a motor generator (200) capable of switching between a power running mode functioning as a motor and a regeneration mode functioning as a generator, and a starter (300) for starting the engine. . A nickel metal hydride battery or a lithium ion battery is used for the main battery (10). A lead battery is used for the sub-battery (20) that can be connected in parallel with the first secondary battery. When the ignition is turned on, the management unit (30, 40) supplies power from the main battery (10) to the motor generator (200) to start the engine when the temperature of the main battery (10) is higher than the set temperature. When the temperature of the battery (10) is equal to or lower than the set temperature, power is supplied from the sub battery (20) to the starter (300) to start the engine.

Description

  The present invention relates to an electricity storage system suitable for an idling stop and energy regeneration system.

  Currently, lead batteries are usually used for storage batteries used in idling stop systems and energy regeneration systems. In a lead battery, full charge maintenance is desired in order to suppress performance degradation. Since the lead battery is frequently charged and discharged in the above-described application, the performance deterioration of the lead battery is accelerated, and the battery life is shortened. Particularly in the idling stop system, a considerable amount of discharge is required when the engine is restarted from the idling stop state. Deterioration of a lead battery accelerates as the depth of discharge (DOD) increases. In general, the recommended DOD range for lead batteries is 0-10%.

  On the other hand, it is conceivable to suppress the depth of discharge from increasing by increasing the capacity of the lead battery relative to the discharge capacity necessary for power supply. However, when the capacity of the lead battery is increased, the size and mass increase, and the cost also increases.

  Nickel metal hydride batteries and lithium ion batteries have a relatively small influence of discharge depth on battery deterioration, and can be used in a wide DOD range. Generally, the recommended DOD range for nickel metal hydride batteries and lithium ion batteries is 20 to 80%. Therefore, when a nickel metal hydride battery or a lithium ion battery is used instead of the lead battery, the power storage system can be reduced in size and weight.

JP 2011-162112 A

  In recent years, there has been a demand for a power storage system having a motor assist function for assisting travel by an engine by driving a motor for power using a storage battery used in an idling stop or an energy regeneration system. However, when considering such an application, it has been found that the discharge capacity required for power supply increases remarkably, and lead batteries have limitations in terms of size, mass, and cost.

  On the other hand, when starting a vehicle engine or driving a motor, instantaneous large current discharge is required. Nickel metal hydride batteries and lithium ion batteries generally increase reaction resistance at low temperatures. Therefore, in a nickel metal hydride battery and a lithium ion battery, if the discharge voltage is lowered, sufficient starting performance may not be obtained. Therefore, when a nickel metal hydride battery or a lithium ion battery is used in the above-described power storage system, it is required to ensure starting performance at a low temperature.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power storage system having a good starting performance at a low temperature while designing a lead battery having a large environmental load as small as possible.

  In order to solve the above-described problem, a power storage system according to an aspect of the present invention includes a motor generator capable of switching between a power running mode functioning as a motor and a regeneration mode functioning as a generator, and a starter for starting the engine. A power storage system mounted on a vehicle, the first secondary battery using a nickel metal hydride battery or a lithium ion battery, and the second secondary battery using a lead battery that can be connected in parallel with the first secondary battery. When the secondary battery and the ignition are turned on, when the temperature of the first secondary battery is higher than the set temperature, the motor is supplied from the first secondary battery to the motor generator to start the engine. And a management unit that starts the engine by supplying power from the second secondary battery to the starter when the temperature is equal to or lower than the set temperature.

  ADVANTAGE OF THE INVENTION According to this invention, the starting performance at the time of low temperature can be improved, designing a lead battery with a large environmental load as small as possible.

It is a figure for demonstrating the vehicle-mounted electrical storage system which concerns on embodiment of this invention. It is a flowchart for demonstrating the operation | movement at the time of vehicle starting of the vehicle-mounted electrical storage system which concerns on embodiment of this invention. It is a flowchart for demonstrating charge control of the sub battery of the vehicle-mounted electrical storage system which concerns on embodiment of this invention.

  Hereinafter, an in-vehicle power storage system according to an embodiment of the present invention will be described. In the following description, it is assumed that the in-vehicle power storage system is mounted on a vehicle having an idling stop function, an energy regeneration function, and a motor assist function.

  The idling stop function is a function that automatically stops the engine when the vehicle stops and restarts the engine automatically when the vehicle starts. The energy regeneration function is a function that operates the alternator or motor generator without using fuel by the kinetic energy of the vehicle when decelerating, and supplies power to the in-vehicle power storage system etc. using the energy generated by the alternator or motor generator. It is. The motor assist function is a parallel-type mild hybrid system, in which the motor is connected to the crankshaft of the engine via a V-belt, and the engine torque is increased by the rotational force of the motor. The connection form of the motor and the engine is an example, and any connection form may be used as long as the connection form can increase the engine torque. Any of the idling stop function, the energy regeneration function, and the motor assist function has an effect of improving fuel consumption.

  In vehicles equipped with an idling stop function, the number of engine starts increases. The engine is usually started by a starter driven by an in-vehicle power storage system. Therefore, as the number of engine starts increases, the power consumption of the battery increases and the number of discharges increases. In addition, since a vehicle equipped with an energy regeneration function generates power intensively by an alternator or a motor generator when the vehicle is decelerated, there is a need for an in-vehicle power storage system that can efficiently charge with a large capacity. Further, even a vehicle equipped with a motor assist function requires a large-capacity on-vehicle power storage system.

  Conventionally, lead batteries are often used in in-vehicle power storage systems. When the lead battery reaches the discharge lower limit voltage due to discharge, the alternator or the motor generator is operated to charge the lead battery. Thereby, it is suppressed that the discharge depth of a lead battery becomes deep, and the deterioration of a lead battery is suppressed. However, such control shortens the idling stop time and reduces the fuel efficiency improvement effect.

  From the viewpoint of protecting the global environment, lead-free power storage systems are being studied, and nickel-metal hydride batteries, lithium ion batteries, and the like are also being considered as alternatives to lead batteries in power storage systems for vehicles. As described above, nickel metal hydride batteries and lithium ion batteries can be used up to a deeper discharge depth than lead batteries, but there is a problem in that the discharge characteristics are drastically lowered at a low temperature of 0 ° C. or lower. In in-vehicle applications, sufficient engine starting performance at low temperatures cannot be secured. Therefore, a system configuration in which a nickel-metal hydride battery or a lithium ion battery is adopted as the main battery while a lead battery having a small capacity is left as the sub battery is conceivable.

  FIG. 1 is a diagram for explaining an in-vehicle power storage system (in-vehicle power supply device) 100 according to an embodiment of the present invention. In a vehicle on which the in-vehicle power storage system 100 is mounted, a motor generator 200, an inverter 250 starter 300, an electrical component 400, and an ECU (Electronic Control Unit) 500 are mounted as members related to the in-vehicle power storage system 100.

  The motor generator 200 integrates a motor and an alternator, and is configured to be able to switch between a power running mode that functions as a motor and a regeneration mode that functions as a generator. The motor generator 200 is composed of, for example, a three-phase AC synchronous motor.

  Inverter 250 converts the DC power supplied from in-vehicle power storage system 100 to AC power and supplies it to motor generator 200 when the power running mode is designated by ECU 500. When the regeneration mode is designated by the ECU 500, the AC power generated by the motor generator 200 is converted into DC power and supplied to the in-vehicle power storage system 100 and the electrical component 400. When motor generator 200 is configured with a three-phase AC synchronous motor, inverter 250 is configured with a three-phase bridge circuit.

  In the present embodiment, in-vehicle power storage system 100 is configured with a 12V system, and the operating voltage of motor generator 200 is also set to 12V. Although a configuration in which the operating voltage of the motor generator 200 is boosted to a high voltage such as 24 V, 36 V, or 48 V is conceivable, a DC-DC converter and a boost converter must be provided between the inverter 250 and the in-vehicle power storage system 100. When the operating voltage of the motor generator is low, it is necessary to increase the current or reduce the power. In the present embodiment, by reducing the power of motor generator 200, a configuration in which the DC-DC converter and the boost converter are omitted while the enlargement of motor generator 200 is suppressed is employed.

  The starter 300 is a motor dedicated to starting the engine. The engine can be started by the motor generator 200, and a configuration without the starter 300 is also possible in principle. However, a starter with an increased capacity is used in a cold region specification vehicle. In a low temperature state, the viscosity of the engine oil is high and the internal resistance of the engine increases, so that it may be difficult to start the engine with a normal starter or motor generator.

  Also when using a remote engine starter, a starter 300 is provided separately from the motor generator 200. The remote engine starter is a starter having a function of starting and stopping the engine by remote operation from outside the vehicle. By starting the engine from outside the vehicle, it is possible to adjust the temperature inside the vehicle by operating the air conditioner before getting into the vehicle.

  The electrical component 400 is a generic name indicating various electric loads mounted in a vehicle such as a headlight, an air conditioner, a defogger, an audio, a meter, a stop lamp, a fog lamp, a winker, a power steering, a power window, and an engine electrical component. In this embodiment, for convenience of explanation, motor generator 200, inverter 250, starter 300, and ECU 500 are handled separately from electrical component 400. Electrical component 400 is driven by electric power supplied from motor generator 200 or in-vehicle power storage system 100.

  ECU 500 is connected to various auxiliary devices, sensors, and switches mounted in the vehicle, and electronically controls the engine and various auxiliary devices. When executing the idling stop function, the ECU 500 detects stop of the vehicle or deceleration to a set speed or less based on signals input from a brake, a vehicle speed sensor, and the like. When ECU 500 detects them, it stops the engine. When ECU 500 detects the release of the brake, ECU 500 determines that the vehicle has started to travel. When the start of vehicle travel is detected after the idling stop function is executed and the engine is stopped, ECU 500 restarts the engine. At that time, the motor generator 200 is controlled to the power running mode so that electric power is supplied from the in-vehicle power storage system 100 to the motor generator 200, and the motor generator 200 is operated. In the above description, it is determined that the vehicle starts to travel when the brake is released, but the determination method is an example. For example, the vehicle travel start may be determined based on the state of the vehicle speed sensor or the accelerator.

  When ECU 500 detects start and acceleration based on signals input from an accelerator, a vehicle speed sensor, etc., ECU 500 controls motor generator 200 to a power running mode and causes motor generator 200 to perform engine assist. When deceleration of the vehicle is detected based on signals input from a brake, a vehicle speed sensor, etc., the motor generator 200 is controlled to a regeneration mode, and the motor generator 200 is caused to generate power. During other normal driving, the motor generator 200 is stopped in principle. When the stored energy of the in-vehicle power storage system 100 is lower than the set lower limit value, the motor generator 200 is controlled in the regeneration mode to generate power even during normal travel. The fuel consumption improves as the power generation time of the motor generator 200 during engine running is reduced.

  The in-vehicle power storage system 100 includes a main battery 10, a sub battery 20, a first temperature sensor 15, a second temperature sensor 25, a first switch S1, a first management unit 30, and a second management unit 40. As the main battery 10, a battery that can be used up to a region with low degradation and a deep discharge depth is used. Examples of such batteries having a wider recommended DOD than lead batteries include nickel-metal hydride batteries, lithium ion batteries, and nickel-cadmium batteries. In this embodiment, an example in which a nickel metal hydride battery whose voltage / temperature management is easier than that of a lithium ion battery is considered. Since the nickel hydride battery has a relatively high charge / discharge upper limit temperature, it can be installed in an engine room.

  When constructing a general 12V system as an in-vehicle power source, for example, 10 nickel metal hydride batteries with a nominal voltage of 1.2V are connected in series, and a plurality of series circuits are connected in parallel to form the main battery 10. To do. Assuming that the capacity of one series circuit is 6 Ah, a 48 Ah main battery 10 can be configured by connecting 8 in parallel. Note that the capacity may be increased by further increasing the parallel number. The capacity of the main battery 10 can secure a dark current to the vehicle auxiliary machine when the vehicle is left. In the above description, the configuration in which the nickel-metal hydride batteries connected in series are connected in parallel is exemplified, but the storage capacity of the main battery 10 can be increased by improving the storage capacity per unit. For example, the storage capacity per piece can be increased by increasing the amount of the active material applied to the electrode.

  A lead battery is used for the sub-battery 20. As will be described later, the sub-battery 20 is basically used only for starting the engine using the starter 300 at a low temperature. Therefore, it is sufficient for the lead battery to have a capacity corresponding to the current flowing through the starter 300 at a low temperature. That is, since a usage pattern in which current is simultaneously supplied to the starter 300 and the electrical component 400 is not assumed, it can be made smaller and lighter than a conventional lead battery as a main battery.

  A first switch S1 is provided between the sub battery 20 and the power line L1. When the first switch S1 is on, the main battery 10 and the sub battery 20 are connected in parallel. In the state where the first switch S1 is OFF, the sub battery 20 is electrically disconnected from the power supply line L1. In this state, the sub battery 20 is also electrically disconnected from the main battery 10 and the electrical component 400.

  The sub battery 20 is connected to the starter 300 via the second switch S2. The second switch S <b> 2 is inserted between the connection point of the sub battery 20 and the first switch S <b> 1 and the current terminal of the starter 300. A relay or a semiconductor switch can be used for the first switch S1 and the second switch S2.

  The first temperature sensor 15 is disposed in the vicinity of the main battery 10, detects the environmental temperature of the main battery 10, and outputs it to the first management unit 30. The second temperature sensor 25 is disposed in the vicinity of the sub battery 20, detects the environmental temperature of the sub battery 20, and outputs it to the second management unit 40. In addition, when the main battery 10 and the sub battery 20 are arrange | positioned in the position which adjoined, a temperature sensor can be made common.

  The first management unit 30 manages and controls the main battery 10. Specifically, the voltage value and the current value are acquired from the main battery 10, the temperature value is acquired from the first temperature sensor 15, and the remaining capacity (SOC: State of Charge) of the main battery 10 and the presence or absence of abnormality are monitored. To do. The second manager 40 manages and controls the sub battery 20. Specifically, the voltage value and the current value are acquired from the sub battery 20, the temperature value is acquired from the second temperature sensor 25, and the remaining capacity of the sub battery 20 and the presence or absence of abnormality are monitored.

  When the main battery 10 and the sub-battery 20 are installed at positions close to each other, the first management unit 30 and the second management unit 40 may be formed on the same substrate. When the installation positions of the main battery 10 and the sub battery 20 are separated from each other, the first management unit 30 and the second management unit 40 are formed on different substrates as shown in FIG. Both are connected by CAN (Controller Area Network) and operate in cooperation. Hereinafter, in order to simplify the description, the first management unit 30 and the second management unit 40 are regarded as one control entity, and both are collectively referred to as management units 30 and 40.

  The management units 30 and 40 and the ECU 500 are connected by CAN and communicate with each other. The management units 30 and 40 notify the ECU 500 of the states of the main battery 10 and the sub battery 20. For example, normal / abnormal and remaining capacity are notified. In addition, when the remaining capacity of main battery 10 or the remaining capacity of sub battery 20 falls below the set lower limit value, management units 30 and 40 send an operation instruction of motor generator 200 to ECU 500 to charge main battery 10 or sub battery 20. Notice. Management units 30 and 400 receive vehicle information from ECU 500. For example, the operating status of the motor generator 200 is received.

  When the driver turns on the ignition switch, the ECU 500 is notified of the signal, and the ECU 500 instructs the management units 30 and 40 to turn on the ignition. The management units 30 and 40 obtain temperature values from the first temperature sensor 15. When the temperature of main battery 10 is higher than the set temperature, management units 30 and 40 supply power from main battery 10 to motor generator 200 to start the engine. Management units 30 and 40 control motor generator 200 to the power running mode via ECU 500. At this time, the management units 30 and 40 turn off the first switch S1 and the second switch S2. That is, the motor generator 200 and the electrical component 400 are driven only by the main battery 10. A temperature lower than the normal temperature is set as the set temperature. For example, 10 ° C. is set.

  When the temperature of the main battery 10 is equal to or lower than the set temperature, the management units 30 and 40 supply power from the sub battery 20 to the starter 300 to start the engine. At this time, the management units 30 and 40 control the first switch S1 to be off and the second switch S2 to be on. That is, the main battery 10 drives the electrical component 400, and the sub battery 20 drives the starter 300.

  The above engine start control is the control at the time of the first start. When returning from the idling stop state, starter 300 is not used, and management units 30 and 40 exclusively supply power from main battery 10 to motor generator 200 to restart the engine. Since the temperature of the engine room rises after the vehicle travels, the temperature of the main battery 10 is usually higher than the set temperature. Further, since the engine restart from the idling stop state is frequent, the sub battery 20 is designed not to be used for the purpose of protecting the lead battery. In the case of a vehicle with a cold district specification, the starter 300 can be a cold district starter having a capacity increased from the normal specification, and the motor generator 200 can be a normal specification motor generator. In this configuration, the cold starter 300 is used when the engine temperature is low, and the normal motor generator 200 is used when returning from the idling stop state. When the starter 300 has a cold district specification, the current required for starting the engine becomes large, so that the current can be saved by using the motor generator 200.

  The management units 30 and 40 basically control the sub battery 20 not to supply power to loads other than the starter 300. As an exception, when the main battery 10 is unusable due to a malfunction or the like, the electric component 400 and the motor generator 200 are also powered. More specific description will be given below. When power is supplied from the sub battery 20 to the starter 300 to start the engine, the management units 30 and 40 control the first switch S1 to be off and the second switch S2 to be on. When charging the sub-battery 20, the first switch S1 is turned on and the second switch S2 is turned off. In other cases, the first switch S1 is turned off and the second switch S2 is turned off. When the main battery 10 is exceptionally unavailable, the first switch S1 is turned on and the second switch S2 is turned off (except at the time of initial engine start).

  FIG. 2 is a flowchart for explaining the operation of vehicle-mounted power storage system 100 according to the embodiment of the present invention when the vehicle is started. When the ignition switch is turned on by the driver (Y in S10), the management units 30 and 40 obtain the temperature value from the first temperature sensor 15, and compare the temperature with the set temperature (S11). When the acquired temperature exceeds the set temperature (N in S11), the management units 30 and 40 control the first switch S1 and the second switch S2 to be off (S12), and control the motor generator 200 to the power running mode (S13). ). When the engine starts and the acceleration period ends, the management units 30 and 40 stop the motor generator 200 or shift to the regeneration mode to generate power.

  Returning to step S11, when the acquired temperature is equal to or lower than the set temperature (Y in S11), the management units 30 and 40 control the first switch S1 to be off and the second switch S2 to be on (S14). When engine start is confirmed (Y in S15), the second switch S2 is controlled to be turned off (S16).

  FIG. 3 is a flowchart for illustrating charging control of sub battery 20 of in-vehicle power storage system 100 according to the embodiment of the present invention. It is assumed that the first switch S1 is off during normal operation. When the voltage of the sub-battery 20 becomes equal to or lower than the lower limit voltage (Y in S20), the management units 30 and 40 control the first switch S1 to be on (S21) and charge the sub-battery 20 from the motor generator 200. When motor generator 200 is stopped, motor generator 200 is controlled in the regeneration mode. When the voltage of the sub-battery 20 reaches the upper limit voltage (Y in S22), the first switch S1 is controlled to be turned off (S23).

  As described above, according to the present embodiment, a nickel metal hydride battery and a lead battery are connected in parallel, and the lead battery is basically used only for engine start using the starter 300 at a low temperature. The lead battery can be reduced in size and weight. The frequency of lead battery replacement can also be reduced. Since the motor generator 200 is always used when returning from the idling stop state, the use frequency of the lead battery can be reduced. If the lead battery can be miniaturized in this way, the amount of lead used with a large environmental load can be reduced.

  When the nickel metal hydride battery cannot be used due to a problem or the like, the lead battery can be connected to the power supply line L1 to supply power to the electrical component 400 and the motor generator 200. Thus, the lead battery has a function of supplying power to the starter 300 when the engine is started at a low temperature and a function as a backup power source.

  As described above, the power storage system having the configuration using the lead battery as much as possible is much less likely to cause the lead battery to be in an overdischarged state as compared with the conventional configuration. Even if the voltage of the nickel metal hydride battery is lowered, if the engine can be started via the starter 300, the alternator can be moved, so that the nickel metal hydride battery can be charged.

  In the above description, the lead battery has been described based on the configuration that is used only for starting the starter 300. However, the lead battery may be configured to supply power to a vehicle auxiliary machine that is stopped. Since the power supply (dark current) to the vehicle auxiliary machine while the vehicle is stopped depends on the use conditions of the vehicle, there is a problem that power consumption is difficult to predict. In order to solve this problem, the first switch S1 can be controlled to be turned on while the vehicle is stopped, and power can be supplied to the vehicle auxiliary machine using both a lead battery and a nickel metal hydride battery. At this time, since it is desirable to stop power supply as much as possible when the ignition is off, it is preferable to use a latch-type switch as the first switch S1. The latch switch can be kept on even when power supply is stopped.

  The present invention has been described based on the embodiments. Those skilled in the art will understand that these embodiments are exemplifications, and that various modifications can be made to the combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. By the way.

  In the above-described embodiment, an example in which the power storage system is mounted on a vehicle having an idling stop function, an energy regeneration function, and a motor assist function has been described. However, the present invention is not limited to mounting on a vehicle having these functions. .

  DESCRIPTION OF SYMBOLS 100 Vehicle-mounted electrical storage system, 200 Motor generator, 250 Inverter, 300 Starter, 400 Electric component, 500 ECU, 10 Main battery, 15 1st temperature sensor, 20 Sub battery, 25 2nd temperature sensor, 30 1st management part, 40 2nd management part, S1 1st switch, S2 2nd switch, L1 power supply line.

Claims (6)

A power storage system mounted on a vehicle including a motor generator capable of switching between a power running mode functioning as a motor and a regeneration mode functioning as a generator, and a starter for starting an engine,
A first secondary battery in which a nickel metal hydride battery or a lithium ion battery is used;
A second secondary battery using a lead battery, which can be connected in parallel with the first secondary battery;
When the ignition is turned on, when the temperature of the first secondary battery is higher than a preset temperature, the motor generator is powered from the first secondary battery to start the engine, and the first secondary battery When the temperature is equal to or lower than the set temperature, a management unit for starting the engine by supplying power from the second secondary battery to the starter;
A power storage system comprising:   The power storage system according to claim 1, wherein the second secondary battery is a dedicated secondary battery that supplies power to the starter. A first switch provided between the second secondary battery and a power line;
A second switch provided between a connection point between the second secondary battery and the first switch and a current terminal of the starter;
When the management unit charges the second secondary battery by turning off the first switch and turning on the second switch when starting the engine by supplying power from the second secondary battery to the starter The power storage system according to claim 1 or 2, wherein the first switch is turned on and the second switch is turned off, and the first switch is turned off and the second switch is turned off at other times. . A first switch provided between the second secondary battery and a power line;
A second switch provided between a connection point between the second secondary battery and the first switch and a current terminal of the starter;
When the management unit charges the second secondary battery by turning off the first switch and turning on the second switch when starting the engine by supplying power from the second secondary battery to the starter The first switch is turned on and the second switch is turned off. When the ignition is turned off, the first switch is turned on and the second switch is turned off. In other cases, the first switch is turned off and the second switch is turned off. The power storage system according to claim 1, wherein the power is controlled to be turned off.   The power storage system according to claim 4, wherein the first switch is a latch-type switch. The vehicle has an idling stop function,
6. The power storage according to claim 1, wherein when the management unit returns from an idling stop state, the power is supplied from the first secondary battery to the motor generator to restart the engine. 6. system.

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