JP7334419B2 - vehicle power supply - Google Patents

Description

The present invention relates to a vehicle power supply device.

2. Description of the Related Art In recent years, hybrid vehicles that use both an internal combustion engine and a motor to drive wheels have been widely used. This type of vehicle is equipped with a storage battery (battery), and power is supplied from the storage battery to the motor. In addition, when the vehicle decelerates, a technology is used that performs regenerative charging, in which the kinetic energy of the vehicle is converted into electrical energy, recovered, and charged to a storage battery.

Patent Literature 1 describes an in-vehicle power supply system that controls regenerative charging of two types of storage batteries. Specifically, the in-vehicle power supply system of Patent Document 1 includes a rotating machine connected to an output shaft of an internal combustion engine, a first storage battery and a second storage battery connected in parallel to the rotating machine, a first storage battery and a rotating machine. a connection switch for switching between electrical connection and disconnection between the machine and the second storage battery, and when regenerative power is generated by the rotating machine, the connection switch is made conductive to charge the first storage battery and the second storage battery. A lead storage battery or the like is used as the first storage battery, a lithium ion storage battery or the like is used as the second storage battery, and the internal resistance value of the second storage battery is set lower than the internal resistance value of the first storage battery. As a result, more of the electric power generated during regenerative power generation is charged to the second storage battery with high energy efficiency, thereby improving the energy efficiency of the entire power supply system.

JP 2014-180151 A

In the technique of Patent Document 1, when charging by regenerative power generation, the second storage battery with low internal resistance and good charge acceptance is preferentially charged. Discharge becomes easy to proceed. As a result, when the depth of discharge of the first storage battery exceeds a predetermined threshold (the charging rate falls below a predetermined threshold), it is necessary to drive the internal combustion engine to generate power for charging. The frequency of recharging increases, causing deterioration in fuel consumption.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle power supply device capable of improving fuel efficiency by reducing the frequency of charging by power generation that consumes fuel.

The present invention provides an electric motor connected to an output shaft of an internal combustion engine, a first battery and a second battery having an internal resistance smaller than that of the first battery, which are connected in parallel to the electric motor, and the electric motor and the second battery. and a control unit for switching between the connected state and the disconnected state of the switching means based on the state of charge of the first battery and the state of charge of the second battery. wherein the first battery is a lead storage battery, the second battery is a lithium ion storage battery, and the control unit controls the second battery when the electric motor performs regenerative power generation for converting kinetic energy of the vehicle into electric power. When the amount of charge of the battery is higher than the target amount of charge of the second battery and the amount of charge of the first battery is lower than the target amount of charge of the first battery, the switching means is set to the disconnected state to switch off the first battery. is charged by regenerative power generation, and when the charge amount of the second battery is higher than the target charge amount of the second battery and the charge amount of the first battery is higher than the target charge amount of the first battery and charging by regenerative power generation to both the first battery and the second battery by setting the switching means to the connected state.

According to the vehicle power supply device of the present invention, when the second battery, which has a small internal resistance, has reached the target charging amount during charging by regenerative power generation, electrical connection from the electric motor to the second battery is cut off. Therefore, the first battery having a large internal resistance can be reliably charged. As a result, the frequency of charging due to power generation that consumes fuel can be reduced, and improved fuel efficiency can be achieved.

1 is a configuration diagram of a vehicle according to an embodiment; FIG. It is a figure which shows the concept of charge control by the power supply device of a vehicle. 4 is a flow chart showing the flow of charging control by the power supply device of the vehicle;

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings. First, with reference to FIG. 1, components of a vehicle according to this embodiment will be described. For convenience of explanation, FIG. 1 is simplified for explaining the technology of the present disclosure, and it is assumed that a vehicle normally has components even if they are not shown.

A vehicle 10 of the present embodiment is a hybrid vehicle that uses both an engine 13 that is an internal combustion engine and a motor generator 14 to drive wheels (driving wheels) 11 . Either one of the engine 13 and the motor-generator 14 or both the engine 13 and the motor-generator 14 is used as a drive source to drive the drive shaft 16 via the transmission 15 to rotate the wheels 11 . A control unit 17 is provided for comprehensively controlling the vehicle 10 . The control unit 17 comprehensively represents means related to control of the vehicle 10, such as an ECU (Electrical Control Unit).

The engine 13 is an internal combustion engine that burns a mixture of air and fuel in a combustion chamber (not shown) to obtain power. Air taken in from the outside is sent to the combustion chamber of the engine 13 through an intake pipe (not shown). A throttle valve (not shown) whose operation is controlled by the control unit 17 is provided in the intake pipe. By changing the opening of the throttle valve, the amount of air supplied to the combustion chamber through the intake pipe is adjusted.

An injector 20 is provided for injecting fuel into the air entering the combustion chamber. An air-fuel mixture containing the injected fuel is ignited by the ignition plug 21 and burned in the combustion chamber, thereby reciprocating a piston (not shown) within a cylinder (not shown) communicating with the combustion chamber. The control unit 17 controls the injection amount and injection timing of the fuel in the injector 20 and the ignition timing of the ignition plug 21 .

Reciprocating movement of the piston in the cylinder is converted into rotational movement of the crankshaft (output shaft) 22 . A crank angle sensor (not shown) detects the rotational state (rotational position, rotational speed) of the crankshaft 22 and sends a detection signal to the control unit 17 . The transmission 15 changes the speed of the rotation output from the crankshaft 22 and transmits it to the drive shaft 16 . A vehicle speed sensor (not shown) that detects the rotation speed of the drive shaft 16 is provided, and the vehicle speed of the vehicle 10 is calculated by the control unit 17 based on the detection signal of the vehicle speed sensor.

The vehicle 10 has an accelerator pedal 25 and a brake pedal 26 that are operated by a passenger. An accelerator opening sensor 27 detects the operation amount (accelerator opening) of the accelerator pedal 25, and a brake stroke sensor 28 detects the operation amount (brake stroke) of the brake pedal 26. sent to The control unit 17 drives the engine 13 by appropriately controlling the amount of intake air from the intake pipe, the fuel injection from the injector 20, the ignition of the spark plug 21, and the like, according to the output request based on the accelerator opening.

The brake mechanism 29 decelerates the rotation of the wheel 11 by mechanical frictional contact. A brake mechanism 29 is composed of a disc rotor provided on an axle that supports the wheel 11 and a caliper containing a brake pad that is hydraulically operated and sandwiches the disc rotor. When the brake pedal 26 is depressed, the brake mechanism 29 is hydraulically driven to decelerate the vehicle 10 .

The motor-generator 14 has a function of an electric motor that generates power from electric power supplied from a battery, which will be described later, and transmits the power to the crankshaft 22, and a function of a generator that generates power from the power input from the crankshaft 22. , a so-called motor generator. The motor-generator 14 as an electric motor performs driving assist by cranking the engine 13 from a stopped state to start the engine 13 and supplementing the power of the engine 13 to provide driving power (power to rotate the drive shaft 16). Is possible. The motor-generator 14 as a generator receives rotational force from the crankshaft 22 to generate power. More specifically, when the engine 13 consumes fuel and drives the crankshaft 22, the motor-generator 14 receives rotational force and generates power (in the following description, engine power generation); During deceleration, there is a case where the rotational energy from the drive shaft 16 is converted into electric power by the motor generator 14 by regenerative torque (referred to as regenerative power generation in the following description).

The motor-generator 14 has a rotating shaft 30 parallel to the crankshaft 22 . A pulley 31 is attached to the crankshaft 22 , a pulley 32 is attached to the rotating shaft 30 , and a transmission belt 33 is stretched between the pulleys 31 and 32 . Power can be transmitted between the crankshaft 22 and the rotary shaft 30 via the transmission belt 33 . The power transmission mechanism provided between the engine 13 side and the motor generator 14 side may be of a type other than the type using the transmission belt 33 .

When using the motor generator 14 as an electric motor, the rotating shaft 30 is rotationally driven by electric power. By rotating the rotary shaft 30 while the engine 13 is stopped, the crankshaft 22 can be initially rotated to start the engine 13 . In the driving state of the engine 13, the power from the motor-generator 14 assists the power of the engine 13 to rotate the crankshaft 22, and the power of the engine 13 and the motor-generator 14 rotates the drive shaft 16 and the wheels 11. The vehicle 10 is driven.

The vehicle 10 includes a starter 40 as a starting device for starting the engine 13 in addition to the motor generator 14 . The control unit 17 controls the motor generator 14 and the starter 40 so that they are used under suitable starting conditions. For example, the motor generator 14 is mainly used to restart the engine 13 from idling stop, and the starter 40 is mainly used to start the engine 13 from a cold state.

When the motor-generator 14 is used as a generator, the rotating shaft 30 is rotated by the rotation of the crankshaft 22 side. The motor-generator 14 incorporates a permanent magnet and a coil. One of the permanent magnet and the coil is a rotor that rotates with a rotating shaft 30, and the other is a fixed stator. When the rotating shaft 30 rotates, a current is generated in the coil by electromagnetic induction. Thus, engine power generation by consuming fuel to drive the engine 13 and regenerative power generation by converting kinetic energy into electric power by the motor generator 14 when the vehicle 10 decelerates can be performed.

The AC power generated by the motor-generator 14 is converted to DC and supplied to the electrical system of the vehicle 10 including a battery, which will be described later. The vehicle 10 includes a converter (not shown) that mutually converts an AC voltage input to and output from the motor generator 14 and a DC voltage input to and output from other electrical components.

The vehicle 10 includes a first battery 50 and a second battery 51 as onboard power sources. The first battery 50 and the second battery 51 are different types of storage batteries. In the present embodiment, the first battery 50 is a lead storage battery and the second battery 51 is a lithium ion storage battery. The lithium-ion battery used for the second battery 51 has a voltage equivalent to that of the lead-acid battery used for the first battery 50 (for example, about 12 V).

The lead-acid battery, which is the first battery 50, has the characteristic of being able to discharge a large amount of current in a short period of time. The lithium-ion storage battery, which is the second battery 51 , has characteristics such as lower internal resistance, higher charge acceptance, and superior energy efficiency than the first battery 50 . Note that the types of the two storage batteries in the present invention are not limited to this combination. For example, it is possible to use a nickel-metal hydride storage battery instead of the lithium ion storage battery.

A charge state detection sensor 52 that detects the charge state of the first battery 50 and a charge state detection sensor 53 that detects the charge state of the second battery 51 are provided. Each charge state detection sensor 52, 53 detects information such as voltage between terminals of each battery 50, 51, current input/output to/from each battery 50, 51, temperature inside or around each battery 50, 51, and the like. These detection values are sent to the control unit 17 . The control unit 17 detects the state of charge (such as the amount of charge) of the first battery 50 based on the information transmitted from the state of charge detection sensor 52, and detects the state of charge of the second battery 50 based on the information transmitted from the state of charge detection sensor 53. 51 state of charge (charge amount, etc.) is detected. In the present embodiment, the charge amount of each of the first battery 50 and the second battery 51 is defined as a state of charge (SOC), which is the remaining capacity obtained by subtracting the discharge amount from the fully charged state. Although set, the charge amount may be determined by an index other than this.

The first battery 50 and the second battery 51 are electrically connected in parallel with the motor generator 14 . A power line PS connected to the first battery 50 and the second battery 51 is shown in FIG. The power line PS is composed of a power cable and connectors for connecting or branching the power cable. A changeover switch (switching means) 54 for switching the mutual power supply between the motor generator 14 and the second battery 51 between a connected state and a disconnected state is provided in the middle of the power line PS.

In the connected state of the change-over switch 54 , the electric power is supplied from the second battery 51 to the electric motor-generator 14 to operate the electric motor-generator 14 as an electric motor, and the electric power is supplied to the second battery 51 using the electric motor-generator 14 as a generator. It can be supplied to charge the second battery 51 . It should be noted that electric power can also be supplied from the second battery 51 to the starter 40 in the connected state of the switch 54 .

In the present embodiment, first battery 50 is always electrically connected to motor generator 14 and starter 40 via power line PS. The first battery 50 capable of discharging a large current in a short period of time is suitable for power supply to the starter 40 .

In addition to the motor-generator 14 and the starter 40, electrical system components to which power is supplied from the first battery 50 and the second battery 51 are collectively shown as a first electrical load 55 and a second electrical load 56 in FIG. Power is supplied mainly from the first battery 50 to the first electrical load 55 , and power is mainly supplied from the second battery 51 to the second electrical load 56 . The first electric load 55 is suitable for those with relatively high power consumption, those with short operating times, and the like. For the second electrical load 56, a load with relatively low power consumption, a load that is used continuously, and the like are suitable.

In the vehicle 10 having the above configuration, when the passenger depresses the accelerator pedal 25, the control unit 17 responds to the output request by supplying power from the engine 13 or the motor generator 14 (in this case, the battery). function as an electric motor) to generate an output that drives the drive shaft 16 . Further, when the engine 13 is driven, the control unit 17 can cause the motor generator 14 to function as a generator to charge the batteries 50 and 51 .

Regenerative power generation is performed when an occupant of the vehicle 10 performs a predetermined deceleration operation or when the vehicle 10 satisfies predetermined operating conditions. Specifically, when the brake pedal 26 is depressed, or when the brake pedal 26 is not depressed but the accelerator pedal 25 is released, it is determined that coasting while decelerating is required. This applies to cases such as In this case, the control unit 17 can cause the motor-generator 14 to function as a generator, collect regenerative energy, and charge the batteries 50 and 51 (charging by regenerative power generation). The conditions under which the regenerative charging control is to be started are stored in advance in the memory of the control unit 17 or the like, and whether or not the conditions are met is determined according to the inputs from various sensors provided in the vehicle 10 .

Referring to FIG. 2, charging control of the power supply device in vehicle 10 will be described. FIG. 2 is a table showing the relationship between the state of charge (amount of charge) of each battery 50 and 51 and the selected charging method. The vertical axis in FIG. 2 indicates the charge amount (charging rate) of the first battery 50, and the charge amount of the first battery 50 increases (the charge rate increases) toward the top in FIG. The horizontal axis in FIG. 2 indicates the amount of charge (rate of charge) of the second battery 51, and the amount of charge of the second battery 51 increases (the rate of charge increases) toward the right in FIG.

As shown in FIG. 2, three thresholds TH1, TH2, and TH3 are set for the amount of charge of the second battery 51 (horizontal axis direction), and two thresholds TH4, TH4, and TH4 are set for the amount of charge of the first battery 50 (vertical axis direction). TH5 is set. Then, the control unit 17 selects a predetermined charging method for each of a plurality of regions divided by each threshold value and causes charging to be performed.

The threshold TH1 is a boundary value for determining whether the second battery 51 is low in charge. When the threshold TH1 is exceeded, it is determined that the second battery 51 has insufficient charge, and discharge of the second battery 51 is suppressed in order to prevent deterioration of the second battery 51 due to overdischarge. Specifically, in a state below the threshold TH1, the engine 13 is driven to positively charge the second battery 51 by engine power generation, and electric power for driving assistance is supplied from the second battery 51 to the motor generator 14. supply is prohibited.

The threshold TH2 is a value obtained by securing a predetermined amount of charge for assisting the driving of the motor-generator 14 in the second battery 51 from the threshold TH1. The predetermined amount of charge is the amount of charge required to execute driving assistance when the vehicle is accelerated multiple times. During normal vehicle running, acceleration and deceleration are repeated. Therefore, during acceleration, power is supplied from the second battery 51 to the motor-generator 14 to assist driving, and then during deceleration, the second battery 51 is expected to be charged by regenerative power generation. be able to. Therefore, if a charge amount sufficient to assist acceleration for several times is ensured, it is unlikely that the charge amount for driving assist to the motor generator 14 becomes insufficient during normal vehicle running, and charging by regeneration is not possible. A discharge cycle for driving assistance can be realized. Therefore, a threshold TH2 that allows several driving assists to be executed from the threshold TH1 is set as the target charge amount of the second battery 51 .

The threshold TH3 is a value for determining that the second battery 51 is practically fully charged. Since the deterioration of the second battery 51 is likely to progress when charging is performed beyond the threshold TH3, the threshold TH3 is set as a guideline for suppressing overcharging of the second battery 51 . Note that the practical full charge targeted by the threshold TH3 is a predetermined value lower than the specified full charge of the second battery 51 (for example, 100% state of charge in a new state). It is appropriately set according to the characteristics.

The threshold TH4 is the target charge amount of the first battery 50 . In order to suppress deterioration, the lead-acid battery applied as the first battery 50 is preferably used with a charge amount close to the full charge in the specification (for example, a charging rate of 100% in a new state). progresses more easily. Accordingly, the usage range recommended for preventing deterioration of the first battery 50 is up to a predetermined lower limit value that is not very low with respect to the full charge according to the specifications. On the other hand, the charging efficiency of a lead-acid battery decreases as it approaches full charge, and charging and discharging near full charge tends to increase energy loss. Taking these conditions into consideration, the threshold TH4 is set as a value obtained by adding a margin (charge amount) of several percent to prevent deterioration from the lower limit of the usage range of the first battery 50 .

The threshold TH5 is a boundary value for determining whether the first battery 50 is in an over-discharged state. When the threshold value TH5 is exceeded, it is determined that the first battery 50 is in an over-discharged state and the amount of charge is insufficient, and the engine 13 is driven to actively charge the first battery 50 by engine power generation.

Charging methods are divided as follows. First, there is the selection of the charging destination using the switch 54 . When the switch 54 is in the connected state, the power line PS for charging from the motor generator 14 is connected to both the first battery 50 and the second battery 51 . When the switch 54 is in the disconnected state, the power line PS for charging from the motor generator 14 is connected only to the first battery 50 and not connected to the second battery 51 . In addition, as a method of power generation, there are engine power generation that obtains electric power by driving the motor generator 14 with the power of the engine 13 by combustion of fuel, and regenerative power generation that obtains electric power by driving the motor generator 14 with regenerative energy during deceleration. There is. In other words, four charging methods can be selected depending on the combination of the charging destination and the power generation method.

In the first charging method, both the first battery 50 and the second battery 51 are electrically connected to the motor generator 14 (the changeover switch 54 is set to the connected state), and the first battery 50 and the second battery are charged by engine power generation. 51 are to be charged.

In the second charging method, only the first battery 50 is electrically connected to the motor generator 14 (the selector switch 54 is turned off), and only the first battery 50 is charged by the engine power generation. .

In the third charging method, both the first battery 50 and the second battery 51 are electrically connected to the motor generator 14 (the switch 54 is connected), and the second battery 51 and the first battery are charged by regenerative power generation. 50 are to be charged.

In the fourth charging method, only the first battery 50 is electrically connected to the motor generator 14 (the selector switch 54 is turned off), and only the first battery 50 is charged by regenerative power generation. .

Based on the state of charge detected by the state of charge detection sensor 52 and the state of charge detection sensor 53, the control unit 17 determines which of the plurality of areas in the table shown in FIG. or not, and appropriately selects the charging method.

Region A is a state in which the amount of charge of the second battery 51 is greater than the threshold TH3 and the amount of charge of the first battery 50 is greater than the threshold TH5. In the region A, the control unit 17 causes charging by the fourth charging method. That is, control is performed so that only the first battery 50 is charged by regenerative power generation.

In the fourth charging method implemented in region A, the second battery 51 is not charged when the changeover switch 54 is in the disconnected state. The kinetic energy of the vehicle 10 can be efficiently recovered to the first battery 50 while preventing deterioration due to excessive charging of the battery. As a result, fuel consumption for power generation by the engine 13 can be prevented, and fuel efficiency can be improved.

Region B is a state in which the amount of charge of first battery 50 is below threshold TH5. In the region B, the control unit 17 causes charging by the second charging method. That is, control is performed so that only the first battery 50 is charged by engine power generation.

The second charging method implemented in area B can immediately enter the charging phase of first battery 50 without waiting for regeneration due to deceleration of vehicle 10 . In addition, since the connection of the motor generator 14 to the second battery 51 with high charge acceptance is released, charging can be concentrated on the first battery 50 without causing a charging current to flow through the second battery 51 . . Therefore, the overdischarged state of the first battery 50 can be reliably and quickly eliminated. In region B, when the vehicle is running at a decelerating speed in which regenerative power generation can be performed, the control unit 17 also causes charging by the fourth charging method (charging of the first battery 50 by regenerative power generation). As a result, fuel consumption for power generation can be suppressed.

Region C is a state in which the charge amount of the second battery 51 is between the threshold TH2 and the threshold TH3, and the charge amount of the first battery 50 is between the threshold TH4 and the threshold TH5. In this region C, the control unit 17 causes charging to be performed according to the fourth charging method. That is, control is performed so that only the first battery 50 is charged by regenerative power generation.

By selecting the fourth charging method in the region C, the discharge of the first battery 50 progresses to suppress the region B in which the engine power generation is performed (below the threshold TH5), and the fuel for power generation is reduced. consumption can be prevented. In addition, since the charging efficiency decreases when the amount of charge of the first battery 50 approaches full charge, it is possible to charge the first battery 50 alone during deceleration (regeneration) on the condition that the amount falls below the threshold TH4. A decrease in efficiency can be suppressed.

On the other hand, if the second battery 51 is equal to or greater than the threshold TH2, a sufficient amount of charge for assisting the driving of the motor generator 14 can be secured, and the second battery 51 is disconnected from the motor generator 14 during regeneration. Also, it is difficult to enter the drive assist prohibition state due to insufficient charge amount. In other words, it is possible to avoid a decrease in fuel consumption of the engine 13 due to prohibition of assist. In addition, by not further charging the second battery 51 that has a sufficient amount of charge, fuel consumption for power generation can be prevented, and deterioration of the second battery 51 can be suppressed.

Region D is a range corresponding to region C in the state where the charge amount of the second battery 51 is between the threshold TH1 and the threshold TH3 and the charge amount of the first battery 50 is greater than the threshold TH5. This is the excluded area. Specifically, a state in which the charge amount of the second battery 51 is between the threshold TH1 and the threshold TH2 and the charge amount of the first battery 50 is between the threshold TH5 and the threshold TH4; Region D is a state in which the amount is between the threshold TH1 and the threshold TH3 and the charge amount of the first battery 50 is greater than the threshold TH4.

In the area D, the control unit 17 causes charging by the third charging method. That is, both the first battery 50 and the second battery 51 are controlled to be charged by regenerative power generation.

The second battery 51 has lower internal resistance and higher charge acceptance than the first battery 50 . Therefore, in the third charging scheme implemented in region D, of the two batteries 50, 51 electrically connected in parallel to the motor-generator 14, the proportion of charge current to the second battery 51 is growing. As a result, the power supply cycle of charging by regeneration and discharging for driving assistance can be performed mainly by the second battery 51 with less energy loss, and an effect of improving fuel efficiency can be obtained.

In addition, in the third charging method implemented in region D, the first battery 50 is also charged by regenerative power generation. Therefore, it is difficult for the charge amount of the first battery 50 to fall below the threshold TH5 (enter region B) to require charging by engine power generation, and fuel consumption can be suppressed.

Region E is a state in which the amount of charge of the second battery 51 is below the threshold TH1. In the area E, the control unit 17 causes charging by the first charging method. That is, both the first battery 50 and the second battery 51 are controlled to be charged by engine power generation.

If the second battery 51 is used (discharged) while the charge amount is below the threshold TH1, the deterioration of the second battery 51 is likely to progress. Overdischarge of the second battery 51 is reliably and quickly eliminated by the first charging method that can enter the charging phase. Since the second battery 51 has a higher charge acceptance than the first battery 50, the changeover switch 54 is connected to connect the first battery 50 and the second battery 51 electrically in parallel with the motor generator 14. By generating power in the connected state, it is possible to efficiently charge the second battery 51 whose charge amount is insufficient.

In region E, when the vehicle is decelerating so that regenerative power generation can be performed, the control unit 17 also performs charging by the third charging method (charging of the first battery 50 and the second battery 51 by regenerative power generation).

As described above, by using a plurality of charging methods with different combinations of power generation modes and charging targets based on the state of charge of each of the batteries 50 and 51, fuel consumption for power generation is suppressed and fuel efficiency is improved. can. In addition, when the batteries 50 and 51 tend to over-discharge, the batteries 50 and 51 can be quickly charged, and overcharging of the batteries 50 and 51 can be suppressed, thereby contributing to an improvement in battery life. Since the charging control of the present embodiment is set based only on the state of charge of each battery 50, 51 regardless of conditions such as vehicle speed, the control is not complicated and highly accurate charging management can be easily performed. be able to. Moreover, since it can be realized with a simple configuration in which the changeover switch 54 is provided on the power line PS, it is advantageous in terms of cost.

Next, with reference to FIG. 3, the control flow of this embodiment will be described. While the electrical system of the vehicle 10 is powered on, the processing of the following control flow is continuously executed at predetermined timings.

In step S<b>1 , the state-of-charge detection sensor 52 detects the voltage across the terminals of the first battery 50 , the ambient temperature, the input/output current, and the like, and transmits the detected signal to the control unit 17 . The control unit 17 calculates the amount of charge of the first battery 50 based on the signal received from the charge state detection sensor 52 .

In step S<b>2 , the state-of-charge detection sensor 53 detects the voltage across the terminals of the second battery 51 , the ambient temperature, the input/output current, and the like, and transmits the detected signal to the control unit 17 . The control unit 17 calculates the amount of charge of the second battery 51 based on the signal received from the charge state detection sensor 53 .

In subsequent step S3, the control unit 17 determines whether or not there is a request for charging. Specifically, when a request for power generation due to a decrease in the charge amount of the first battery 50 and the second battery 51 calculated in steps S1 and S2, or a request for regeneration during deceleration of the vehicle 10 occurs, it is determined that there is a request for charging. Then (YES in step S3), the process proceeds to step S4. If there is no charge request (NO in step S3), the process exits from step S4 without performing the process.

In step S4, the control unit 17 determines the charging method based on the table of FIG. 2 described above. Specifically, from the amount of charge of the first battery 50 and the amount of charge of the second battery 51 obtained in steps S1 and S2, the charging method is calculated using a predetermined parameter. Alternatively, table data indicating the relationship between the charge amount of each battery 50 and 51 and each charging method may be stored in the memory of the control unit 17 or the like, and the charging method may be determined by reading from the table data.

In step S5, the control unit 17 performs setting (switching control) of the switch 54 according to the charging method determined in step S4. If the determined charging method is the first charging method or the third charging method, the second battery 51 is included in the charging target. A charging path to the battery 51 is formed. If the determined charging method is the second charging method or the fourth charging method, the charging target is only the first battery 50, so the switch 54 is turned off to charge the second battery 51. block the route.

When the setting of the changeover switch 54 in step S5 is completed, the process proceeds to step S6, and the control unit 17 controls the motor generator 14 to perform charging by the charging method set in step S4.

As described above, in the vehicle power supply device of the present embodiment, there are a plurality of charge states (regions A to E in FIG. 2) classified by thresholds of charge amounts for the first battery 50 and the second battery 51, respectively. and select a charging method suitable for each state of charge, while suppressing fuel consumption, the first battery 50 and the second battery 51, which have different characteristics, are less likely to be over-discharged or over-charged. can be realized.

In particular, regarding the second battery 51, the target charge amount (which satisfies the predetermined charge amount for driving assist performed by the motor generator 14) is between the threshold TH1 indicating the decrease in charge amount and the threshold TH3 indicating practical full charge. is set, and a threshold TH4, which is the target charge amount, is set for the first battery 50 . In addition, in region C between threshold TH2 and threshold TH3 and less than threshold TH4, control is performed so that only the first battery 50 is charged by regenerative power generation (the fourth charging method is selected). ing). When the first battery 50 and the second battery 51 are connected in parallel to the motor-generator 14, the second battery 51 having higher charge acceptance is preferentially charged. On the other hand, in the charging control in region C, the first battery 50 is powered by the power obtained by regenerative power generation without charging the second battery 51 that has a sufficient amount of charge for driving assistance. The battery is efficiently charged up to the target charging amount (threshold TH4). Therefore, it is difficult for the first battery 50 to fall into a state in which the first battery 50 is insufficiently charged and engine power generation is required (area B in FIG. 2), and fuel consumption for power generation can be suppressed.

With a simple configuration and wiring in which the first battery 50 and the second battery 51 are connected in parallel to the motor generator 14 and a changeover switch 54 is provided at the input/output portion of the electric power to the second battery 51, the above can realize the control and effect of Therefore, the power supply device to which the present invention is applied has the advantage of requiring low costs for parts and manufacturing, and can be easily applied to many vehicles.

It should be noted that the present invention is not limited to the above embodiments, and can be implemented with various modifications. In the above embodiment, the configuration, control, and the like shown in the accompanying drawings are not limited to this, and can be changed as appropriate within the scope of exhibiting the effects of the present invention. In addition, it is possible to carry out by appropriately modifying the present invention as long as it does not deviate from the scope of the purpose of the present invention.

For example, in the above-described embodiment, only the changeover switch 54 that switches between the connection state and the disconnection state from the motor generator 14 to the second battery 51 is provided on the power line PS. A changeover switch for switching between a connection state and a disconnection state with respect to 50 may be provided separately.

When a changeover switch is provided on the first battery 50 side, the following operation is possible as an example. In the table of FIG. 2, the area D or the area E is divided into two with the threshold value TH4 as the boundary. If the charge amount of the first battery 50 is lower than the threshold value TH4 in the area D or the area E, the changeover switch on the first battery 50 side is kept in the connected state. That is, the two batteries 50 and 51 are both electrically connected to the motor-generator 14 and are in the same state (the third charging method or the first charging method) as described in the region D or region E described above. Become. If the charge amount of the first battery 50 is higher than the threshold value TH4 in the area D or the area E, the changeover switch on the first battery 50 side is turned off. Even when both the first battery 50 and the second battery 51 are connected to the motor-generator 14, the ratio of the charge flow to the second battery 51, which has high charge acceptance, increases. , the charging to the first battery 50, which has already reached a sufficient amount of charge, is completely interrupted, and the charging of the second battery 51 can be performed more reliably and efficiently.

As described above, according to the vehicle power supply device of the present invention, there is an effect that the frequency of charging by power generation that consumes fuel can be reduced, and fuel efficiency can be improved. It is useful for vehicles that require both driving efficiency.

10: Vehicle 13: Engine 14: Motor Generator (Electric Motor)
15: Transmission 16: Drive shaft 17: Control section 22: Crankshaft (output shaft)
29: brake mechanism 40: starter 50: first battery 51: second battery 52: charge state detection sensor 53: charge state detection sensor 54: changeover switch (switching means)
55 : First electric load 56 : Second electric load PS : Power line TH1 : Threshold value (boundary value for overdischarge of the second battery)
TH2: threshold (target charge amount of the second battery)
TH3: Threshold (boundary value for overcharging of the second battery)
TH4: threshold (target charge amount of the first battery)
TH5: Threshold (boundary value determined as overdischarge of the first battery)

Claims (3)

an electric motor connected to an output shaft of an internal combustion engine;
a first battery and a second battery having a lower internal resistance than the first battery, each connected in parallel to the electric motor;
a switching means for switching between an electrical connection state and a disconnection state between the electric motor and the second battery;
A power supply device for a vehicle, comprising: a control unit that switches between a connected state and a disconnected state of the switching means based on the state of charge of the first battery and the state of charge of the second battery,
The first battery is a lead-acid battery, the second battery is a lithium-ion battery,
When the electric motor performs regenerative power generation in which the kinetic energy of the vehicle is converted into electric power, the control unit controls the charge amount of the second battery to be higher than the target charge amount of the second battery, and the charge amount of the first battery to be charged. When the amount of charge is lower than the target charge amount of the first battery, the switching means is disconnected, and only the first battery is charged by the regenerative power generation, and the charge amount of the second battery is reduced. When the charging amount of the first battery is higher than the target charging amount of the second battery and the charging amount of the first battery is higher than the target charging amount of the first battery, the switching means is brought into a connected state, and the first battery and the first battery are connected. 1. A power supply device for a vehicle, wherein both of the two batteries are charged by the regenerative power generation . When the electric motor performs the regenerative power generation, the control unit controls whether the charge amount of the second battery is overcharged, including a case where the charge amount of the first battery is higher than a target charge amount of the first battery. 2. The power supply device for a vehicle according to claim 1, wherein the switching means is set to a disconnected state and only the first battery is charged by the regenerative power generation when the threshold value determined as being exceeded is exceeded. . When the charge amount of the second battery falls below a threshold value for determining that the charge amount is low, the control unit connects the switching means to cause the electric motor to generate power, and the first battery and the first battery are connected. 2. The vehicle power supply device according to claim 1, wherein both of the two batteries are charged by the engine power generation and the regenerative power generation .

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