JP6112023B2 - Vehicle power supply system - Google Patents

Description

The present invention relates to vehicle dual power system that will be installed in an electric vehicle.

  2. Description of the Related Art In recent years, electric vehicles that are equipped with electric motors that can generate electric power as driving power sources and that can be directly supplied and charged using a charging plug from a household power source or the like have been put into practical use.

In this type of vehicle, since the characteristics of the mounted the battery (secondary battery) will affect the running performance of the vehicle, the required running performance (vehicle required output, required cruising distance, etc.) the appropriate cell in accordance with the It is necessary to select. This is because when the battery is not optimal, it is necessary to increase the weight of the battery in order to satisfy all the required values, which causes an increase in vehicle weight and deterioration in fuel consumption. However, there are many cases where there is no optimal battery that can satisfy the running performance without excess or deficiency among the limited batteries available. Therefore, it is considered to use a combination of two types of power storage devices having different characteristics (for example, Patent Document 1).

JP 2003-219666 A

  In an electric vehicle, the battery is gradually deteriorated by repeatedly charging and discharging the battery at a high frequency. Specifically, the electric capacity that can be stored gradually decreases. For this reason, when the deterioration of the battery reaches a certain level, the battery is replaced in order to ensure traveling performance.

  In this case, in vehicles equipped with a combination of so-called energy batteries and power batteries, a certain level of deterioration is set, and if one of the batteries reaches a certain level of deterioration regardless of the type of battery, both batteries must be replaced. Is implemented. However, the degree of progress of deterioration differs between the power battery and the energy battery, and since the energy battery and the power battery cooperate to bear input and output of power, either one of the batteries has reached the above deterioration level. Even in this case, there are many cases where the battery can still be used as a total battery. Therefore, there is room for improvement in this respect.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a technique that enables more effective use of a battery in an electric vehicle including two types of batteries having different characteristics. And

In order to solve the above problems , a power supply system for a vehicle according to the present invention is a power supply system for a vehicle including an electric motor for traveling that can regenerate power, and includes a first secondary battery and the first second battery. A second secondary battery connected in parallel to the secondary battery, having a lower output density and a higher energy density than the first secondary battery, and a current electrical capacity relative to the initial electrical capacity of the first secondary battery And a second capacity maintenance ratio that is a ratio of the current electric capacity with respect to an initial electric capacity of the second secondary battery, and an initial value of each secondary battery. An arithmetic unit that calculates an average value according to a ratio of electric capacity as a total capacity maintenance rate, a determination device that determines a battery replacement time when the total capacity maintenance rate is equal to or less than a predetermined first reference value, and It is time to replace the batteries Having and a notification device for notifying that it has been determined, is connected in parallel to said first secondary battery, the capacity capable of storing regenerative power drive power and the electric motor generates the electric motor The capacitor and regenerative power generated by the electric motor are preferentially charged to the capacitor over the first secondary battery and the second secondary battery, and the electric power stored in the capacitor is supplied to the first secondary battery and wherein preferentially seen including a charging and discharging device supplies the electric motor than the second secondary battery, the initial electric capacity of the first secondary battery, the initial electric capacity of the second secondary battery Is also set large .
According to such a vehicle power supply system, since the battery replacement time is determined based on the total capacity maintenance rate of both the secondary batteries, the battery replacement time of the first secondary battery and the second secondary battery is appropriately set. It is possible to postpone. Therefore, the first secondary battery and the second secondary battery can be used more effectively than in the past.
Moreover, since it becomes possible to reduce the opportunity of charging / discharging of a 1st secondary battery and a 2nd secondary battery, the lifetime of a 1st secondary battery and a 2nd secondary battery can be extended substantially.
In addition, since the initial electric capacity of the first secondary battery is set to be larger than the initial electric capacity of the second secondary battery, the life of the first secondary battery is substantially extended, Reduction of the total capacity maintenance rate is suppressed. Therefore, it becomes possible to effectively postpone the battery replacement time of the first secondary battery and the second secondary battery.

In the vehicular power supply system, the determination device includes a second reference in which either one of the first capacity maintenance ratio and the second capacity maintenance ratio is a predetermined reference value that is lower than the first reference value. When the value is less than or equal to the value, it is determined that it is time to replace the battery.
According to this configuration, even if the total capacity maintenance ratio exceeds the first reference value, if either the first capacity maintenance ratio or the second capacity maintenance ratio is equal to or less than the second reference value. Is determined to be the battery replacement time. As a result, it is possible to avoid troubles caused by continuous use of both batteries in a state in which the deterioration of one of the batteries is excessively advanced, for example, ignition due to heat generation.

In the above vehicle power supply system, the first secondary battery has a ratio of output density to energy density that is a required motor output that is an output value of the electric motor and a required value of the energy capacity of the battery. The second secondary battery has a power density / energy density ratio smaller than a required battery energy capacity ratio, and is smaller than a required motor output / required battery energy capacity ratio. Is preferred.

  According to this vehicle power supply system, the total weight of the batteries (the first secondary battery and the second secondary battery) can be suppressed to a necessary minimum while satisfying both the required motor output and the required battery energy capacity. It becomes.

  In the above vehicle power supply system, various mounting examples of the electric motor, the first secondary battery, and the second secondary battery are conceivable. For example, the following configuration satisfies the traveling performance of the vehicle. This is suitable for reducing the weight of the battery and extending the life of the secondary battery. That is, the vehicle has a required motor output of 50 kW and a required battery energy capacity of 30 kWh, and the first secondary battery has an output density of 380 W / kg and an energy density of 80 Wh / kg. The second secondary battery has an output density of 40 W / kg and an energy density of 240 Wh / kg.

  As described above, according to the vehicle power supply system of the present invention, it is possible to appropriately postpone the replacement time of both batteries in an electric vehicle including two types of batteries having different characteristics. Therefore, the battery can be used more effectively.

1 is a schematic circuit diagram showing a vehicle power supply system as a basis of the present invention. It is a figure which shows the battery performance map for demonstrating the characteristic of the secondary battery employ | adopted as the power supply system for vehicles. It is a flowchart which shows an example of charge operation control at the time of electric motor regeneration. It is a flowchart which shows an example of discharge operation control at the time of an electric motor drive. It is a flowchart which shows an example of discharge operation control at the time of an electric motor drive. It is a graph which shows the relationship between the capacity maintenance rate of the secondary battery in the vehicle power supply system which concerns on this invention, and a conventional system, and the number of charging / discharging cycles. It is a flowchart which shows the modification of charge operation control at the time of an electric motor drive. 1 is a schematic circuit diagram showing a vehicle power supply system according to the present invention. It is a figure which shows the battery performance map for demonstrating the characteristic of the secondary battery (1st battery and 2nd battery) applied to the power supply system for vehicles. It is a graph which shows the relationship between the capacity | capacitance maintenance rate of a secondary battery, and the number of charging / discharging cycles with and without a capacitor module. It is a flowchart which shows an example of the lifetime management control of a secondary battery.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, first, the vehicle power supply system 1A (hereinafter referred to as the basic system 1A as appropriate) which is the basis of the present invention is described, and then the vehicle power supply system 1B and the battery life management method according to the present invention are described. Will be described.
(A) Configuration of Electric Vehicle to which Basic System 1A is Applied FIG. 1 is a schematic diagram showing a vehicle power supply system 1A that is the basis of the present invention. This vehicle power supply system 1A is mounted on an electric vehicle that drives drive wheels (not shown) using only the electric motor 2 as a power source (that is, does not use an internal combustion engine in combination).

  The electric motor 2 is a motor generator having a power generation function, and generates regenerative power by being controlled as a generator when the vehicle is decelerated.

  The vehicle power supply system 1A includes an inverter 10 for supplying electric power to the electric motor 2, a secondary battery 12 (hereinafter referred to as battery 12) and a capacitor module 14 for storing electric power used in the vehicle, And a first circuit 11 that connects the inverter 10, the battery 12, and the capacitor module 14 in parallel with each other. As the battery 12, for example, a lithium ion battery is applied.

  The battery 12 can be charged by a charger provided outside the vehicle. The vehicle power supply system 1A can be connected to the device 1A and the charger to supply power from the charger to the battery 12. A charging plug (not shown) is provided. The charging plug can be connected to a normal charger, which is a household power source, or a quick charger installed in a parking area or the like.

  The capacitor module 14 is connected to the first circuit 11 between the inverter 10 and the battery 12. In addition to the battery 12, the capacitor module 14 includes a capacitor 16 for storing electric power used in the vehicle, a DC-DC converter 18 that converts (steps up and down) the voltage of the capacitor 16, and the capacitor 16 and the DC- The circuit includes a second circuit 20 that connects the DC converter 18 in series, a bypass circuit 21 that branches from the second circuit 20 and bypasses the DC-DC converter 18, and a bypass switch 22 that opens and closes the bypass circuit 21. In the present embodiment, an electric double layer capacitor is applied as the capacitor 16.

  The bypass switch 22 is controlled to be opened and closed by a controller 30 described later. In the off (open) state of the bypass switch 22, the capacitor 16 and the inverter 10 are electrically connected via the DC-DC converter 18, and in the on (closed) state of the bypass switch 22, the DC-DC converter. By bypassing 18, capacitor 16 and inverter 10 are electrically connected.

  The vehicle power supply system 1A includes a controller 30 for controlling the inverter 10 and the capacitor module 14 (DC-DC converter 18 and switch 22), and various sensors. The controller 30 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that is configured by, for example, a RAM or a ROM and stores a program and data, an electrical signal And an input / output (I / O) bus for inputting and outputting. Various information is input to the controller 30 from the sensor. Specifically, the vehicle power supply system 1A includes an accelerator opening sensor 32 that detects the accelerator opening, a vehicle speed sensor 34 that detects the traveling speed of the vehicle, and a battery current / voltage that detects the current and voltage of the battery 12. A sensor 36, a capacitor current / voltage sensor 38 for detecting the current and voltage of the capacitor, an inverter current sensor 40 for detecting the input current of the inverter 10, and a DC-DC current sensor 42 for detecting the input current of the DC-DC converter 18. The signals from these sensors 32 to 42 are input to the controller 30.

  Further, the vehicle power supply system 1 </ b> A is provided with a third circuit 27 for supplying electric power to the vehicle electrical components 26 other than the electric motor 2, and the third circuit 27 is further provided in accordance with the type of the vehicle electrical components 26. A DC-DC converter 24 is provided for converting the voltage (step-up / step-down). Examples of the vehicle electrical component 26 include an electric air conditioner, a navigation device, an audio device, and the like, which are electric loads having a lower voltage and lower output than the electric motor 2.

  In the vehicle power supply system 1A, as will be described in detail later, when the vehicle is accelerated, the electric power stored in the capacitor 16 is preferentially supplied to the electric motor 2 rather than the battery 12, and when the vehicle is decelerated. The DC-DC converter 18 and the switch 22 are controlled so that the regenerative power generated by the electric motor 2 is charged to the capacitor 16 with priority over the battery 12. That is, the capacitor 16 mainly bears the supply of electric power to the electric motor 2 and the storage of regenerative electric power generated by the electric motor 2. Therefore, the capacitor 16 is selected to have a capacity capable of storing at least electric power for driving the electric motor 2 and regenerative electric power generated by the electric motor 2.

On the other hand, the battery 12 mainly bears the supply of electric power to the vehicle electrical components 26 such as an electric air conditioner and the storage of electric power from the charger supplied via the charging plug. However, as the battery 12, the vehicle running performance, i.e., may give to satisfy both the requirements battery energy capacity of the which is the output value of the electric motor 2 required motor output and the battery 12 (request cruising distance of the vehicle) Things are selected. By selecting the battery 12 in this way, the running performance of the vehicle can be ensured with only the battery 12 (that is, after the power of the capacitor 16 is used up), and the battery 12 can be reduced in weight. ing.

  Here, selection of the battery 12 will be described.

  In designing an electric vehicle, first, the required motor output (W) for the maximum output of the electric motor and the required battery energy capacity (Wh) for the energy capacity of the battery that supplies power to the electric motor. And the battery is selected based on these two types of required values. In the case of an electric vehicle such as the present embodiment, since the driving power source is only the electric motor 2, the required motor output is substantially equal to the output to be given to the wheels in order to realize the driving performance required for the vehicle. The same value. Further, the required battery energy capacity is obtained from the required cruising distance as to how much the vehicle can travel.

  When selecting a battery, it is ideal to select one battery that satisfies both the required motor output and the required battery energy capacity. FIG. 2 is a graph for making such a selection. The horizontal axis of this graph represents the energy density (Wh / kg) of the battery, and the vertical axis represents the output density (W / kg) of the battery. Further, in this graph, the “required P / E line” is a straight line having a certain slope that matches the value of the ratio between the required motor output and the required battery energy capacity. In addition, the “BIC line” is a limit line indicating that there is no battery having a higher output density and energy density than the line at present, and the performance of various existing batteries is plotted on a graph. It can be obtained from the distribution of each plot (BIC is an abbreviation for “Best in Class”).

  Here, assuming that there is a battery having the performance matching the point where the required P / E line and the BIC line intersect, this is plotted as A0. The battery represented by A0 is referred to as “virtual optimum battery”. If the virtual optimum battery A0 having such performance exists, the required motor output and the required battery energy capacity described above can be satisfied by using the battery A0 alone, and the weight of the battery can be satisfied. Can be minimized.

  The reason is as follows.

  Since the plot (white circle) of the virtual optimum battery A0 exists on the required P / E line as shown in the figure, the value of the ratio between the output density and the energy density of the virtual optimum battery A0 is the required P / E. Should match the slope of the line. For this reason, the relationship between the output density and energy density of the virtual optimum battery A0, the required motor output and the required cruising distance can be expressed by the following equation (1).

[Equation 1]
D _P / D _E = P / E (1)
here,
D _P : Virtual optimal battery power density (W / kg)
D _E : Energy density of virtual optimal battery (Wh / kg)
P: Required motor output (W) = Vehicle required output (W)
E: Required battery energy capacity (Wh) ∝Required cruising distance (km).

By modifying the above equation (1),
[Equation 2]
E / D _E = P / D _P (2)
Is obtained.

The unit of the left side and the right side of the formula (2) is “kg”. That is, the left side (E / D _E ) of the formula (2) corresponds to the weight (kg) of the battery that can satisfy the required battery energy capacity E, and the right side (P / D _P ) represents the required motor output P. This corresponds to the weight (kg) of the battery that can be satisfied. That the right side and the left side are equal as described above means that both of the required motor output P and the required battery energy capacity E can be satisfied without excess or shortage by using one type of battery.

Therefore, as the battery 12, the battery whose ratio of the output density and the energy density is approximately equal to the ratio of the required motor output of the vehicle and the required battery energy capacity, that is, the graph of FIG. When the value of the ratio between the power density and the energy density is a point on the required P / E line or a point in the vicinity thereof, the point closer to the point where the required P / E line and the BIC line intersect with each other The matching performance, that is, the performance closer to the virtual optimum battery A0 is selected. Thus, as the battery 12, it can be satisfied both the required motor output required battery energy capacity (required cruising distance of the vehicle), and is lightweight battery as much as possible are selected.

  For example, in this embodiment, the required motor output of the vehicle is 50 kW, the required battery energy capacity is 10 kWh (the inclination of the required P / E line is about 5.6), and the output density of the battery 12 is 1300 W / kg. A lithium ion battery having an energy density of 230 Wh / kg is applied. Further, as described above, the capacitor 16 has a maximum output of 50 kW and an energy capacity of 70 Wh so that the electric power for driving the electric motor 2 and the regenerative power generated by the electric motor 2 can be stored. Things have been applied.

(B) Charging / Discharging Operation of Vehicle Power Supply System 1A First, a charging operation (charging operation during regeneration) of the vehicle power supply system 1A will be described.

  FIG. 3 is a flowchart showing an example of charging operation control of the vehicle power supply system 1A. This control is executed when the running state of the vehicle is shifted from acceleration or constant speed to deceleration. Specifically, it is executed when the accelerator opening becomes zero. Note that when the vehicle is shifted to decelerating running in this way, the electric motor 2 is controlled as a generator (regenerative control).

  When the control of this flowchart starts, the controller 30 acquires information input from the battery current / voltage sensor 36 and the capacitor current / voltage sensor 38, that is, the voltage values of the battery 12 and the capacitor 16, and the battery voltage is the capacitor voltage. It is judged whether it is higher than (step S1, S3). If the determination here is YES, the controller 30 turns on (closes) the bypass switch 22 to charge the regenerative power generated by the electric motor 2 to the capacitor 16 by bypassing the DC-DC converter 18. (Step S5). That is, when the battery voltage is higher than the capacitor voltage, the regenerative power is naturally charged in the capacitor 16 due to the voltage difference. Therefore, in this case, the DC-DC converter 18 is bypassed, and an electric loss due to the internal resistance of the DC-DC converter 18 is avoided, so that the regenerative power is efficiently recovered.

  On the other hand, when the determination in step S3 is NO, the controller 30 turns off the bypass switch 22 and further controls the DC-DC converter 18 so that the capacitor voltage becomes lower than the battery voltage. (Step S15). Thereby, the regenerative power is charged in the capacitor 16.

  When charging of regenerative power is started, the controller 30 determines whether or not the capacitor voltage value is less than the allowable upper limit value of the capacitor 16 (steps S7 and S9). If YES is determined here, the controller 30 further determines whether or not the regeneration is continued (step S17). If YES, the charging of the regenerative power to the capacitor 16 is continued.

  On the other hand, if the determination in step S9 is NO, that is, if the capacitor voltage value is greater than or equal to the allowable upper limit value of the capacitor 16, it is further determined whether or not regeneration is continued (step S11), and the determination here is YES. In that case, the controller 30 performs step-up control of the DC-DC converter 18 (step S13). Specifically, the DC-DC converter 18 is boosted so that the capacitor voltage becomes higher than the battery voltage, and then the process proceeds to step S11. That is, switching the charging destination of the regenerative power from the capacitor 16 to the battery 12 prevents the capacitor 16 from being overcharged.

  When it is finally determined NO in step S11 or step S17, specifically, the traveling state of the vehicle is shifted from deceleration to acceleration, or the traveling speed of the vehicle becomes 0 and the electric motor 2 is regenerated. Is stopped, the controller 30 ends the flowchart.

  As described above, in this vehicle power supply system 1A, only when the regenerative power generated by the electric motor 2 is preferentially charged in the capacitor 16 and the capacitor voltage is determined to be equal to or higher than the allowable upper limit value of the capacitor 16. In addition, the regenerative power is charged in the battery 12.

  Next, the discharge (power supply) operation of the vehicle power supply system 1A will be described.

  4 and 5 are flowcharts showing an example of discharge operation control of the vehicle power supply system 1A. This control is executed when the vehicle travels by driving the electric motor 2.

  When the control of this flowchart is started, the controller 30 acquires information input from the battery current / voltage sensor 36 and the capacitor current / voltage sensor 38, that is, the current values and the voltage values of the battery 12 and the capacitor 16, and the capacitor 30 After obtaining the capacity (charge rate) of 16, it is determined whether or not the capacity is larger than a predetermined value (steps S21 and S23). If the determination here is YES, the controller 30 determines whether or not the capacitor voltage is higher than the battery voltage (step S25). If YES, the capacitor voltage further exceeds the inverter allowable upper limit value. It is judged whether it is lower than (step S27). When the determination in step S27 is YES, the controller 30 turns on the bypass switch 22 and bypasses the DC-DC converter 18 with the electric power stored in the capacitor 16, and the electric motor 2 (inverter 10). To supply. That is, when the capacitor voltage is larger than the battery voltage, the electric power of the capacitor 16 is automatically supplied (discharged) to the electric motor 2 due to the voltage difference. Therefore, in this case, the DC-DC converter 18 is bypassed, and electric loss due to the internal resistance of the DC-DC converter 18 is avoided, so that electric power is efficiently supplied to the electric motor 2.

  When power supply from the capacitor 16 to the electric motor 2 is started, the controller 30 acquires an inverter input current value and determines whether or not the inverter input current value is less than an inverter input allowable upper limit value (step S31, S33). If the determination here is YES, it is determined whether or not the discharge is continued (step S39), and if YES, the controller 30 proceeds to step S31 and starts from the capacitor 16 to the electric motor 2. Continue to supply power. On the other hand, when the determination in step S39 is NO, for example, when the traveling state of the vehicle is shifted to deceleration, the controller 30 ends the control based on the flowchart.

  If the determination in step S33 is NO, that is, if the inverter input current value is equal to or greater than the inverter input allowable upper limit value, the controller 30 determines whether or not the discharge is continued (step S35). If NO, the control based on the flowchart is terminated. On the other hand, if the determination in step S35 is YES, the controller 30 turns off the bypass switch 22, and further controls the DC-DC converter 18 so that the capacitor voltage is lower than the battery voltage (step S37). ). Thereby, the power supply from the capacitor 16 is stopped, and instead, the power supply from the battery 12 to the electric motor 2 (inverter 10) is started. That is, since the capacitor 16 has a characteristic capable of charging and discharging a large amount of power in a short time, it is conceivable that the inverter input current value becomes equal to or higher than the inverter input allowable upper limit value when power is supplied from the capacitor 16. Therefore, when the inverter input current value is equal to or greater than the inverter input allowable upper limit value, the power supply from the capacitor 16 is stopped, and the power supply is performed from the battery 12 whose output (discharge) is slow, thereby protecting the inverter 10. doing. Note that if the determination in step S23 is NO, that is, if the capacitance of the capacitor 16 is equal to or less than the predetermined value, the controller 30 similarly proceeds to step S37. This prevents the capacitor 16 from being overdischarged.

  On the other hand, when the determination in step S25 is NO, that is, when the capacitor voltage is equal to or lower than the battery voltage, the controller 30 turns off the bypass switch 22 so that the capacitor voltage becomes higher than the battery voltage. The DC-DC converter 18 is boosted (step S43). If the determination in step S27 is NO, that is, if the capacitor voltage is equal to or higher than the inverter allowable upper limit value, the controller 30 turns off the bypass switch 22, and the capacitor voltage is lower than the inverter allowable upper limit value. Further, the DC-DC converter 18 is stepped down so as to be higher than the battery voltage (step S41). Thereby, power supply from the capacitor 16 to the electric motor 2 (inverter 10) is started.

  When the power supply from the capacitor 16 to the electric motor 2 is started via the process of step S41 or S43, the controller 30 receives the input information from the DC-DC current sensor 42, that is, the input current of the DC-DC converter 18. A value is acquired, and it is determined whether or not the DC-DC input current value is less than the input allowable upper limit value of the DC-DC converter 18 (steps S45 and S47). If the determination is YES, the controller 30 further determines whether or not the discharge is continued (step S49). If YES, the process proceeds to step S45, and the electric motor 2 is transferred from the capacitor 16 to the electric motor 2. Continue to supply power to On the other hand, when the determination in step S49 is NO, for example, when the traveling state of the vehicle is shifted to deceleration, the controller 30 ends the control based on the flowchart. If the determination in step S47 is NO, that is, if the DC-DC input current value is greater than or equal to the input allowable upper limit value of the DC-DC converter 18, the controller 30 proceeds to step S35.

  As described above, in the discharging (power supply) operation in the vehicle power supply system 1A, the electric power stored in the capacitor 16 is preferentially supplied to the electric motor 2 (inverter 10), and the electric power from the capacitor 16 to the electric motor 2 is supplied. Only when the DC-DC input current value exceeds the allowable input upper limit value of the DC-DC converter 18 during supply, or when the inverter input current value becomes equal to or higher than the allowable input limit value of the inverter. Electric power is supplied to the motor 2.

(C) Effects of Charging / Discharging Operation of Vehicle Power Supply System 1A According to this vehicle power supply system 1A, as described above, when the electric motor 2 is regeneratively controlled, the regenerative power generated by the electric motor 2 is generated. Is preferentially charged to the capacitor 16, and regenerative power is charged to the battery 12 only when the capacitor voltage is determined to be equal to or higher than the allowable upper limit value of the capacitor 16. Therefore, there is almost no charging opportunity of the battery 12 except when electric power is charged from the charger through the charging plug.

  Further, when the vehicle is driven by driving the electric motor 2, the electric power of the capacitor 16 is preferentially supplied to the electric motor 2 (inverter 10), and the DC-DC input current value is increased while the electric power is supplied from the capacitor 16. The power supply from the battery 12 to the electric motor 2 is performed only when the input allowable upper limit value of the DC-DC converter 18 is equal to or greater than the inverter input current value is equal to or greater than the inverter input allowable upper limit value. Therefore, there is virtually no opportunity for the electric power of the battery 12 to be supplied to the electric motor 2 (inverter 10).

  That is, in this vehicle power supply system 1A, since the capacitor 16 mainly supplies power to the electric motor 2 (inverter 10) and charging regenerative power, the battery 12 supplies power to the electric motor 2 and charges regenerative power. There is little to do. Therefore, as compared with a system in which power is supplied from only the battery to the electric motor and regenerative power is charged only in the battery, the charge / discharge opportunities for the battery 12 are greatly reduced. Therefore, according to this vehicle power supply system 1A, it is possible to effectively suppress the deterioration of the battery 12 due to charging / discharging, thereby extending the life of the battery 12.

  For example, FIG. 6 is a graph comparing the deterioration degree of the battery 12 of the vehicle power supply system 1A and the deterioration degree of the battery of the conventional general system. The vertical axis of this graph represents the capacity retention rate (%) of the battery, and the horizontal axis represents the number of charge / discharge cycles of the entire system. The capacity maintenance rate is the ratio of the capacity of the battery that can actually be stored (currently) to the capacity of the battery that can be stored at the beginning (at the time of shipment). In addition, one cycle of charge / discharge is to perform external high-charge operation with a constant current value after a predetermined number of times of continuous high-load operation (repeat acceleration and deceleration) a predetermined number of times. The number of charge / discharge cycles is indicated by a root value (1/2 power root). The batteries used in both systems are the same.

  As shown in this graph, according to the vehicle power supply system 1A, a decrease in the capacity maintenance rate of the battery is suppressed as compared with the conventional system. This is because, as described above, in the above-described vehicle power supply system 1A, the charging / discharging opportunities for the battery 12 are reduced.

  In this vehicle power supply system 1A, as described above, the battery 12 has a ratio of the output density to the energy density that is substantially equal to the ratio of the required motor output of the vehicle to the required battery energy capacity. Some are selected. That is, the battery 12 is selected as light as possible while satisfying the running performance of the vehicle. Therefore, according to this vehicle power supply system 1A, it is possible to reduce the weight of the battery while satisfying the traveling performance of the vehicle, and further to enjoy the effect of extending the life of the battery.

(D) Modified Example of Vehicle Power Supply System 1A For example, in the flowcharts (charging operation control) shown in FIGS. 4 and 5, the capacitor voltage is determined to be equal to or higher than the allowable upper limit value of the capacitor 16, and the regenerative operation is performed. Is continued (YES in step S11), the controller 30 performs step-down control of the DC-DC converter 18 to switch the charging destination of the regenerative power from the capacitor 16 to the battery 12, but the regenerative power is charged. You may make it discharge without doing. Specifically, a discharge circuit including an open / close switch is provided in parallel to the capacitor module 14 and charging operation control is performed based on the flowchart shown in FIG. In this flowchart, steps S18 and S19 are provided instead of step S13 in the flowcharts of FIGS. That is, if the determination in step S11 is YES, the controller 30 activates a warning lamp or the like to notify the driver, and then closes the open / close switch to turn on the discharge circuit (steps S18 and S19). Thereby, regenerative electric power is given to a discharge circuit and it discharges.

  Such a configuration is advantageous in extending the life of the battery 12 because there is no opportunity to charge the battery 12 with regenerative power.

(Description of the present invention)
(A) Configuration of Electric Vehicle to which Vehicle Power Supply System 1B of the Present Invention is Applied FIG. 8 is a schematic diagram showing a vehicle power supply system 1B according to the present invention. The basic configuration of the vehicle power supply system 1B is common to the basic system 1A. Therefore, in the following description, the same reference numerals are assigned to configurations common to the basic system 1A, description thereof is omitted, and differences from the basic system 1A are mainly described in detail.

  As shown in FIG. 8, the vehicle power supply system 1B includes a first secondary battery 13a and a second secondary battery 13b as secondary batteries (hereinafter referred to as a first battery 13a and a second battery 13b). (Omitted). In this example, a lithium ion battery is used as each of the batteries 13a and 13b.

  The first battery 13a and the second battery 13b are batteries having different characteristics from each other, and are connected to the first circuit 11 in parallel with each other. Specifically, when comparing the first battery 13a and the second battery 13b, the second battery 13b has a smaller output density and a higher energy density than the first battery 13a. In other words, the output density of the first battery 13a is higher than that of the second battery 13b, and the energy density of the second battery 13b is higher than that of the first battery 13a.

  As described above, the first battery 13a having a relatively large output density is a battery that places importance on exerting a high output, and in this specification, such a type of battery is referred to as a power battery (P in FIG. 8). It is described as a battery). The second battery 13b having a relatively large energy density is a battery that places importance on securing the charge capacity. In this specification, such a type of battery is referred to as an energy battery (referred to as an E battery in FIG. 8). .

  The reason why two batteries having different characteristics are provided is that a single battery may not satisfy the required motor output of the vehicle and the required battery energy capacity. When the graph of FIG. 2 is used, the value of the ratio between the power density and the energy density of the battery is a point on or near the required P / E line, and the required P / E line and the BIC line intersect. This is the case where the weight of the battery becomes extremely large because there is no performance that matches the point closer to the point. That is, even when there is no suitable single battery such as the virtual optimum battery A0 in FIG. 2, a battery having a higher output density than the required P / E line and a battery having a higher energy density than the required P / E line If used in combination, the total weight of the battery can be reduced while satisfying the required motor output of the vehicle and the required battery energy capacity.

  In this vehicle power supply system 1B, as shown in the map of FIG. 9, as the first battery 13a, a battery having a higher output density than the required P / E line, that is, the point on the upper left side of the map than the required P / E line. The battery having the same performance as the point B1 on the BIC line is applied, and the second battery 13b has a higher energy density than the required P / E line, that is, the right side of the map than the required P / E line. A lower point that has the same performance as the point C1 on the BIC line is applied. Thus, the total weight of the batteries (first battery 13a and second battery 13b) is reduced while satisfying the required motor output and the required battery energy capacity.

  For example, in the present embodiment, the required motor output of the vehicle is 50 kW, the required battery energy capacity is 30 kWh (the inclination of the required P / E line is approximately 1.7), and the output density of the first battery 13a is 380 W / A lithium ion battery with an energy density of 80 Wh / kg is applied, and a lithium ion battery with an output density of 40 W / kg and an energy density of 240 Wh / kg is applied as the second battery 13b. Further, in order to store at least the electric power for driving the electric motor 2 and the regenerative electric power generated by the electric motor 2, the capacitor 16 having a maximum output of 20 kW and an energy capacity of 70 Wh is applied. The capacitor 16 is assumed to be a so-called small car class, and the capacitor 16 has a value corresponding to regenerative power and regenerative energy corresponding to the vehicle weight during deceleration regeneration. Is done.

  In the present embodiment, the electric capacity of the first battery 13a and the capacity ratio of the second battery 13b is 1: 1. As shown in FIG. 8, the first battery 13a is connected to the first circuit 11 on the side closer to the capacitor module 14 than the second battery 13b. In short, this means that the capacitor module 14 is provided for the first battery 13a.

  Further, in this vehicle power supply system 1B, instead of the battery current / voltage sensor 36 of the basic system 1A, a first battery current / voltage sensor 37a for detecting the current and voltage of the first battery 13a, and a second battery 13b. And a second battery current / voltage sensor 37b for detecting the current and voltage of the sensor 37, and signals from these sensors 37a and 37b are input to the controller 30.

  In this example, the controller 30 corresponds to the arithmetic device and the determination device of the present invention.

(B) Charging / Discharging Operation of Vehicle Power Supply System 1B and Its Effects The charging / discharging operation in this vehicle power supply system 1B is basically performed in the same manner as the charging operation of basic system 1A described above.

  That is, when the running state of the vehicle is shifted from acceleration or constant speed to deceleration, the controller 30 controls the regenerative power charging operation based on the flowchart of FIG.

  However, since the vehicle power supply system 1B includes the two batteries 13a and 13b, the controller 30 acquires the current value and the voltage value of both the batteries 13a and 13b in step S1. Further, the controller 30 determines whether or not the capacitor voltage is lower than the voltage values of both the batteries 13a and 13b in step S3, and in step S15, the capacitor voltage becomes lower than the voltages of both the batteries 13a and 13b. The DC-DC converter 18 is stepped down. Further, in step S13, the controller 30 performs step-down control of the DC-DC converter 18 so that the capacitor voltage is higher than the voltages of the batteries 13a and 13b.

  When the vehicle is driven by driving the electric motor 2, the controller 30 controls the power supply (discharge) operation to the electric motor 2 based on the flowcharts of FIGS. 4 and 5.

  However, since the vehicle power supply system 1B includes the two batteries 13a and 13b, the controller 30 acquires the current value and voltage value of both the batteries 13a and 13b in step S21. Further, the controller 30 determines whether or not the capacitor voltage is higher than the voltage value of both the batteries 13a and 13b in step S25, and in step S43, the capacitor voltage becomes higher than the voltage of both the batteries 13a and 13b. The DC-DC converter 18 is boosted. In step S41, the controller 30 performs step-down control of the DC-DC converter 18 so that the capacitor voltage is lower than the inverter allowable upper limit value and higher than the voltages of the batteries 13a and 13b. The DC-DC converter 18 is stepped down so that the capacitor voltage is lower than the voltages of the batteries 13a and 13b.

  Also in such a vehicle power supply system 1B, when the electric motor 2 is regeneratively controlled, the regenerative electric power generated by the electric motor 2 is preferentially charged to the capacitor 16, and the capacitor voltage has an allowable upper limit of the capacitor 16. Only when it is determined that the value is greater than or equal to the value, regenerative power is charged in the batteries 13a and 13b. Therefore, there is almost no opportunity to charge the batteries 13a and 13b except when the power is charged from the charger via the charging plug.

  Further, when the vehicle is driven by driving the electric motor 2, the electric power of the capacitor 16 is preferentially supplied to the electric motor 2 (inverter 10), and the DC-DC input current value is increased while the electric power is supplied from the capacitor 16. The power supply from the batteries 13a and 13b to the electric motor 2 is performed only when the input allowable upper limit value of the DC-DC converter 18 is exceeded or when the inverter input current value is equal to or higher than the inverter input allowable upper limit value. . Therefore, there is virtually no opportunity for the electric power of the batteries 13a and 13b to be supplied to the electric motor 2 (inverter 10).

  Therefore, also for this vehicle power supply system 1B, it is possible to effectively suppress the deterioration of the batteries 13a, 13b due to charging / discharging, and as a result, in the same manner as the basic system 1A (FIG. 1) described above, It is possible to extend the lifetime of 13b.

  For example, the graph (a) in FIG. 10 shows the degree of deterioration of the first battery 13a and the second battery 13b when the capacitor module 14 is not provided, that is, when the capacitor module 14 is removed from the configuration of FIG. Fig. 8 is a graph showing the relationship (deterioration degree) between the number of charge / discharge cycles and the capacity maintenance ratio (for convenience, here, referred to as a comparison system (in Fig. 10, a comparative example)), and (b) is shown in Fig. 8. It is a graph which shows the deterioration degree of the 1st battery 13a of the vehicle power supply system 1B, and the 2nd battery 13b.

  As shown in these graphs (a) and (b), according to the vehicle power supply system 1B, the capacity maintenance rate of the second battery 13b is almost the same as that of the comparison system, but the capacity of the first battery 13a is A decrease in maintenance rate is effectively suppressed. This is because, in the comparison system, a power battery having a smaller internal resistance than the energy battery exclusively supplies power to the electric motor 2 and charges regenerative power, but the capacitor module 14 is used for the first battery 13a. In the vehicle power supply system 1B provided with the capacitor 16, the capacitor 16 exclusively performs power supply to the electric motor 2 and charging of regenerative power. Therefore, the opportunity of charging / discharging with respect to the 1st battery 13a is reduced, As a result, the fall of the capacity maintenance rate of the 1st battery 13a is suppressed.

  In a vehicle power supply system including two batteries 13a and 13b, in order to evaluate the deterioration state of the battery in the entire system, as will be described in detail later, the capacity maintenance rate of each battery 13a and 13b is evaluated individually. However, as shown in the graphs (a) and (b) of FIG. 10, the vehicle power supply system 1B maintains the capacity of the second battery 13b. Since the decrease in the rate is suppressed, the decrease in the total battery capacity maintenance rate is suppressed compared to the comparative system. That is, according to the vehicle power supply system 1B, the lifetime of the batteries 13a and 13b can be extended as compared with the comparison system.

(C) the life management control diagram 11 of a battery is a flowchart illustrating an example of a life management control of the battery in the vehicle power supply system 1B (life management method of engaging Ru batteries in the present invention). This control is executed at a preset timing when the ignition of the vehicle is turned off.

When the control of this flowchart is started, the controller 30 determines whether or not a warning flag, which will be described later, is ON (step S51). If the determination here is NO, the controller 30 determines whether the battery current / voltage sensor 37a. , 37b, the OCV1 (open circuit voltage) of the first battery 13a and the OCV2 of the second battery 13b are obtained based on the information input from the first battery 13a, and the SOC1 and the second battery 13b of the first battery 13a are obtained based on these values. SOC2 is obtained (step S53). The controller 30, Ri Contact stored a map showing a relationship between the SOC and the OCV, the controller 30, by extracting the SOC corresponding to the value of the acquired OCV from this map, each battery 13a, 13b SOC1 , SOC2 is calculated.

Next, the controller 30 determines whether or not the vehicle is started, that is, whether or not the ignition is turned on (step S55). If the determination here is YES, the controller 30 determines whether the battery current / voltage is Based on information input from the sensors 37a and 37b, input / output current integration processing (calculation of integral values) of the batteries 13a and 13b is started (step S57). Next, it is determined whether or not the vehicle is stopped, here, whether or not the ignition is turned off (step S59). If the determination here is YES, the controller 30 determines whether or not each of the batteries 13a and 13b. The input / output current integration process is stopped, and the OCV ₁ ′ and OCV ₂ ′ of the batteries 13 a and 13 b are obtained, and the SOC ₁ ′ and SOC ₂ ′ of each battery 13 a are obtained based on the values (step S 61). Then, based on the data acquired in steps S53, S57, and S61, the capacity maintenance rate of each of the batteries 13a and 13b and the total capacity maintenance rate of the battery are obtained (step S63). The capacity maintenance rate is the ratio of the capacity of the battery that can be actually stored (currently) to the capacity of the battery that can be stored initially (at the time of shipment), as mentioned in the description of the basic system 1A.

  Using the data acquired in steps S53, S57, and S61, the capacity maintenance rates of the batteries 13a and 13b can be obtained based on, for example, the following formulas (3) and (4).

[Equation 3]
Rp = ΔE ₁ / ΔSOC ₁ · E ₁ 0 (3)
Re = ΔE ₂ / ΔSOC ₂ · E ₂ 0 (4)
here,
Rp: Capacity maintenance rate (%) of the first battery 13a (corresponding to the first capacity maintenance rate of the present invention)
Re: Capacity maintenance rate (%) of the second battery 13b (corresponding to the second capacity maintenance rate of the present invention)
ΔE ₁ : Integrated value of input / output current of first battery 13 a ΔE ₂ : Integrated value of input / output current of second battery 13 b ΔSOC ₁ : Change amount of SOC of first battery 13 a (SOC ₁ ′ −SOC ₁ )
ΔSOC ₂ : SOC change amount of first battery 13 a (SOC ₂ ′ −SOC ₂ )
E ₁ 0: Initial (shipment) capacity of the first battery 13a E ₂ 0: Initial (shipment) capacity of the second battery 13b And the total capacity maintenance rate of the first battery 13a and the second battery 13b is as follows: It is obtained based on equation (5).

[Equation 4]
R = (Rp + Re · f) / (1 + f) (5)
here,
R: Total capacity maintenance rate (%) of the battery (corresponding to the total capacity maintenance rate of the present invention)
f: initial capacity of the specific capacity retention rate R of the battery total second battery 13b when was the 1 initial capacity of the first battery 13a is in short the battery 13a, 13b mean in accordance with the ratio of the initial capacity of the Value. In this example, since the initial capacity ratio of both the batteries 13a and 13b is 1: 1 as described above, in this case, the total capacity retention rate R of the batteries is a simple average value [(Rp + Re) / 2].

  When the capacity maintenance rates Rp and Re of the batteries 13a and 13b and the total capacity maintenance rate R of the batteries 13 are obtained, the controller 30 determines whether the battery total capacity maintenance rate R is set in advance (the first standard of the present invention). (Corresponding to a value) or less, in this example, whether or not it is 80% or less is determined (step S65). That is, it is determined whether it is time to replace the battery. If the determination here is YES, the controller 30 turns on the warning flag (step S67) and ends this flowchart. On the other hand, when it is determined NO in step S65, the controller 30 sets a limit value (corresponding to the second reference value of the present invention) in which the capacity maintenance rate of either the first battery 13a or the second battery 13b is set in advance. In this example, it is determined whether it is 70% or less. If the determination here is YES, the process proceeds to step S67 to turn on the warning flag. If the determination is NO, This flowchart is terminated.

  If the determination in step S51 is YES, that is, if the warning flag is already ON, the controller 30 displays a warning display such as turning on a maintenance request lamp (corresponding to the notification device of the present invention), for example. Execute (Step S71). Then, it is determined whether or not a warning display resetting operation has been performed (step S73). If the determination here is YES, the warning flag is turned off (step S75), and then this flowchart is terminated. If the determination is NO, the process of step S75 is skipped and the present flowchart is terminated.

  In this example, the process of step S63 corresponds to the capacity maintenance rate calculation process of the present invention, and the processes of steps S65 and S69 correspond to the life determination process of the present invention.

(D) Effects of Life Management Control According to the vehicle power supply system 1B in which such life management control is performed, the warning display is executed based on the total battery capacity maintenance rate R, so the battery 13a The battery 13a and 13b can be used for a longer period by prolonging the replacement time of the battery 13b within an appropriate range. In other words, it is possible to reasonably extend the life of each battery 13a, 13b.

  That is, in a conventional system that uses a combination of an energy battery and a power battery, a certain deterioration level (capacity maintenance rate) is set, and maintenance (battery replacement) is performed when one of the batteries reaches the deterioration level. It is common. However, the power battery and the energy battery have different degrees of deterioration due to the difference in internal resistance, and the energy battery and the power battery cooperate to bear power input / output, so either one of the batteries Even when the battery reaches the degradation level, the battery as a whole is still usable in many cases. This is equivalent to shortening the life of each battery 13a, 13b.

  In this respect, according to the above-described vehicle power supply system 1B, the warning display is executed based on the battery total capacity maintenance rate R, that is, based on the evaluation of the total battery deterioration state. It becomes possible to postpone the arrival of the maintenance (battery replacement) time of the batteries 13a and 13b, that is, to extend the life of the batteries 13a and 13b.

  For example, as shown in the graph (b) of FIG. 10, in this vehicle power supply system 1B, the capacity maintenance rate Rp of the first battery 13a reaches 80 (%) when the number of charge / discharge cycles is 90. In the second battery 13b, the number of charge / discharge cycles is 20 and the capacity maintenance rate Rp has already reached 80 (%). Therefore, if the replacement reference value is assumed to be 80% capacity maintenance rate, the conventional system has 20 charge / discharge cycles and the maintenance time comes. However, according to the vehicle power supply system 1B, the charge / discharge cycle number is 36. Maintenance time can be postponed to about once. Therefore, according to the vehicle power supply system 1B, the batteries 13a and 13b can be used more effectively.

  Moreover, according to the vehicle power supply system 1B, even if the total capacity maintenance rate R of the battery is equal to or greater than the replacement reference value (80% in this example), the capacity maintenance rate of any of the batteries 13a and 13b is If it is less than the limit value (70% in this example), a warning is displayed. Specifically, for example, even if the capacity maintenance rate Rp of the first battery 13a is 95 (%), the warning display is executed when the capacity maintenance rate Re of the second battery 13b is 65 (%). Is done. Therefore, troubles caused by continuous use of the batteries 13a and 13b in a state in which the deterioration of one of the batteries 13a and 13b is excessively advanced, for example, ignition due to heat generation, can be avoided. There are also advantages.

  In this vehicle power supply system 1B, the capacity ratio of the first battery 13a and the second battery 13b is 1: 1, but the capacity of the first battery 13a is set larger than the capacity of the second battery 13b. It may be. That is, according to the vehicle power supply system 1B, the life of the first battery 13a can be effectively extended as described above (see graph (b) in FIG. 10). Therefore, if the capacity of the first battery 13a is set larger than the capacity of the second battery 13b, the total battery life can be more effectively extended.

  As mentioned above, although it demonstrated about embodiment of the vehicle power supply system 1B of this invention, these embodiment is an illustration of preferable embodiment of the vehicle power supply system which concerns on this invention, The concrete structure is The present invention is appropriately changed without departing from the gist of the present invention.

1A, 1B Vehicle power supply system 2 Electric motor 10 Inverter 12 Secondary battery 13a First secondary battery 13b Second secondary battery 14 Capacitor module 16 Capacitor 18 DC-DC converter 22 Bypass switch 36 Battery current / voltage sensor 37a First Battery current / voltage sensor 37b Second battery current / voltage sensor 38 Capacitor current / voltage sensor 40 Inverter current sensor 42 DC-DC current sensor

Claims (4)

A power supply system for a vehicle including an electric motor for traveling that can regenerate electric power,
A first secondary battery;
A second secondary battery connected in parallel to the first secondary battery, having a lower output density and a higher energy density than the first secondary battery;
A first capacity maintenance ratio that is a ratio of the current electric capacity to an initial electric capacity of the first secondary battery, and a second capacity that is a ratio of the current electric capacity to the initial electric capacity of the second secondary battery. An arithmetic device that calculates an average value as a total capacity maintenance ratio, which is an average value with the maintenance ratio and according to a ratio of the initial electric capacity of each secondary battery,
A determination device for determining a battery replacement time when the total capacity maintenance rate is equal to or less than a predetermined first reference value;
A notification device for notifying that the battery replacement time is determined by the determination device;
A capacitor connected in parallel to the first secondary battery and having a capacity capable of storing electric power for driving the electric motor and regenerative power generated by the electric motor;
The regenerative power generated by the electric motor is charged to the capacitor with priority over the first secondary battery and the second secondary battery, and the electric power stored in the capacitor is supplied to the first secondary battery and the second secondary battery. and a charge and discharge device for supplying preferentially to the electric motor than the secondary battery seen including,
An initial electric capacity of the first secondary battery is set to be larger than an initial electric capacity of the second secondary battery . The vehicle power supply system according to claim 1 ,
The determination device determines whether to replace the battery when one of the first capacity maintenance ratio and the second capacity maintenance ratio is a predetermined reference value and is equal to or lower than a second reference value lower than the first reference value. The vehicle power supply system characterized by the above-mentioned. In the vehicle power supply system according to claim 1 or 2 ,
In the first secondary battery, the value of the ratio between the output density and the energy density is greater than the value of the ratio of the required motor output that is the output value of the electric motor and the required battery energy capacity that is the required value of the energy capacity of the battery. Big
The power supply system for vehicles, wherein the second secondary battery has a ratio value between an output density and an energy density smaller than a ratio value between the required motor output and the required battery energy capacity. In the vehicle power supply system according to claim 3 ,
The vehicle has the required motor output of 50 kW and the required battery energy capacity of 30 kWh,
The first secondary battery has an output density of 380 W / kg and an energy density of 80 Wh / kg, and the second secondary battery has an output density of 40 W / kg and an energy density of 240 Wh / kg. A power supply system for a vehicle characterized by being.

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