JP6670176B2 - Power supply for vehicles - Google Patents

Description

  The present invention relates to a vehicle power supply device mounted on a vehicle.

  A generator such as a motor generator, an alternator, or an ISG (integrated starter generator) is connected to the engine mounted on the vehicle. The generator connected to the engine is not only driven to generate power by the engine power, but is often controlled to generate power even during vehicle braking or coasting from the viewpoint of improving the fuel efficiency of the vehicle. As described above, when the generator is controlled to a power generation state during vehicle braking or coast running, the generated power of the generator is stored in a power storage unit such as a battery. By the way, when charging and discharging a power storage unit such as a battery, it is required to charge and discharge in an appropriate temperature range from the viewpoint of protecting the power storage unit. When the temperature of the power storage unit rises beyond a predetermined temperature range, an excessive rise in the temperature of the power storage unit is suppressed by interrupting the charge / discharge current using a relay or the like (see Patent Document 1 and 2).

JP 2008-27826 A JP 2008-204867 A

  However, in a situation where the temperature of the power storage unit rises significantly, simply interrupting the charge / discharge current of the power storage unit is a factor for reducing the power generation opportunity of the generator. In other words, when the charge / discharge current of the power storage unit is interrupted due to the temperature rise, even if the brake pedal is depressed and the vehicle is decelerated, the generator cannot be generated and the vehicle cannot be powered. This was a factor that reduced energy efficiency. Therefore, there is a demand for improving the energy efficiency of a vehicle by securing a power generation opportunity of a power generator even in a situation where the temperature of a power storage unit increases.

  An object of the present invention is to improve the energy efficiency of a vehicle.

A vehicular power supply device of the present invention is a vehicular power supply device mounted on a vehicle, comprising: a generator connected to an engine; a first power storage unit connected to the power generator; and a first power storage unit. A second power storage unit connected to the generator in parallel, a conduction state connecting the generator and the first power storage unit, and a cutoff state separating the generator and the first power storage unit are controlled. Power switch, a temperature sensor for detecting the temperature of the first power storage unit, and a switching mode for alternately switching the power switch between a cutoff state and a conductive state when the temperature of the first power storage unit exceeds a threshold value. And a switch control unit that executes the switching mode, wherein the switch control unit is configured to execute the switching mode, wherein the temperature of the first power storage unit before the temperature of the first power storage unit reaches the threshold is determined . Based on the climb speed, Setting at least one of the cut-off time and the conduction time of the photoelectric switch.

  According to the present invention, when the temperature of the first power storage device exceeds the threshold value, the switching mode in which the energizing switch is alternately switched between the cutoff state and the conduction state is executed. Thereby, the power generation opportunity of the generator can be secured while suppressing the temperature rise of the first power storage body, and the energy efficiency of the vehicle can be improved.

1 is a schematic diagram illustrating a configuration example of a vehicle including a vehicle power supply device according to an embodiment of the present invention. FIG. 2 is a circuit diagram illustrating an example of a power supply circuit. It is a figure which shows the electric power supply situation at the time of controlling a starter generator to a power generation state. It is a figure which shows the electric power supply situation at the time of controlling a starter generator to a power generation suspension state. It is a figure which shows the electric power supply situation at the time of controlling a starter generator to a power running state. It is a figure showing an example of an execution situation of a switching mode. (A) is a diagram showing a power supply circuit in which a switch is controlled to be in a cutoff state, and (b) is a diagram showing a power supply circuit in which a switch is controlled to be in a conductive state. FIG. 5 is a comparison diagram illustrating a change in battery temperature depending on whether or not a switching mode is provided. (A) And (b) is a figure which shows an example of the opening / closing timing of a switch.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration example of a vehicle 11 including a vehicle power supply device 10 according to an embodiment of the present invention. As shown in FIG. 1, a vehicle 11 is equipped with a power unit 13 having an engine 12 as a power source. A starter generator (generator) 16 is mechanically connected to a crankshaft 14 of the engine 12 via a belt mechanism 15. A transmission mechanism 18 is connected to the engine 12 via a torque converter 17, and wheels 20 are connected to the transmission mechanism 18 via a differential mechanism 19 and the like. The engine 12 is connected to an engine controller 22 including a computer or the like for controlling various devices 21 such as an injector, an igniter, and a throttle valve.

  The starter generator 16 connected to the engine 12 is a so-called integrated starter generator (ISG) that functions as a generator and an electric motor. The starter generator 16 functions not only as a generator driven by the crankshaft 14 but also as an electric motor for starting and rotating the crankshaft 14 in so-called idling stop control. The starter generator 16 has a stator 30 provided with a stator coil, and a rotor 31 provided with a field coil. In addition, the starter generator 16 is provided with an ISG controller 32 including an inverter, a regulator, a computer, and the like in order to control an energized state of the stator coil and the field coil. By controlling the energized state of the field coil and the stator coil by the ISG controller 32, the generated torque of the starter generator 16 functioning as a generator is controlled, and the driving torque of the starter generator 16 functioning as a motor is controlled. be able to.

[Power supply circuit]
The power supply circuit 40 included in the vehicle power supply device 10 will be described. FIG. 2 is a circuit diagram showing an example of the power supply circuit 40. As shown in FIG. 2, power supply circuit 40 includes a lithium ion battery (first power storage) 41 electrically connected to starter generator 16, and a lead battery electrically connected to starter generator 16 in parallel with this. (Second power storage unit) 42. In order to positively discharge the lithium ion battery 41, the terminal voltage of the lithium ion battery 41 is designed to be higher than the terminal voltage of the lead battery 42. Further, in order to positively charge and discharge the lithium ion battery 41, the internal resistance of the lithium ion battery 41 is designed to be smaller than the internal resistance of the lead battery 42.

  A positive electrode line 43 is connected to the positive terminal 41 a of the lithium ion battery 41, a positive line 44 is connected to the positive terminal 42 a of the lead battery 42, and a positive line 45 is connected to the positive terminal 16 a of the starter generator 16. These positive electrode lines 43 to 45 are connected to each other via a connection point 46. A negative electrode line 47 is connected to the negative terminal 41 b of the lithium ion battery 41, a negative line 48 is connected to the negative terminal 42 b of the lead battery 42, and a negative line 49 is connected to the negative terminal 16 b of the starter generator 16. You. These negative electrode lines 47 to 49 are connected to a reference potential point 50.

  The negative electrode line 47 connected to the lithium ion battery 41 is provided with a switch (energizing switch) SW1 that switches between a conductive state and a cutoff state. By controlling the switch SW1 to be conductive, the starter generator 16 and the lithium ion battery 41 can be connected. On the other hand, by controlling the switch SW1 to be in the cutoff state, the starter generator 16 and the lithium ion battery 41 can be separated. In addition, a switch SW2 that switches between a conductive state and a cutoff state is provided on the positive electrode line 44 connected to the lead battery 42. These switches SW1 and SW2 may be switches configured by semiconductor elements such as MOSFETs, or may be switches that mechanically open and close contacts using electromagnetic force or the like. The switches SW1 and SW2 are also called relays, contactors, and the like.

  The power supply circuit 40 includes a battery module 51. The battery module 51 incorporates the lithium ion battery 41 and switches SW1 and SW2. Further, the battery module 51 is provided with a temperature sensor 52 for detecting the temperature of the lithium ion battery 41. Further, the battery module 51 is provided with a battery controller 53 including a computer or the like. The battery controller 53 has a function of monitoring the state of charge, current, voltage, temperature, and the like of the lithium ion battery 41, and a function of controlling the switches SW1 and SW2. That is, the battery controller 53 functions as a switch control unit that controls the switch SW1. The positive electrode line 44 is provided with a fuse 55 for protecting the electric device 54 and the like.

[Battery charge / discharge control]
The charge / discharge control of the lithium ion battery 41 will be described. In order to control charging and discharging of the lithium ion battery 41, the vehicle power supply device 10 is provided with a main controller 56 including a computer or the like. The main controller 56 and the above-described controllers 22, 32, 53 are communicably connected to each other via a vehicle-mounted network 57 such as CAN or LIN. The main controller 56 controls charging and discharging of the lithium ion battery 41 by controlling the starter generator 16 to a power generation state or a power generation pause state based on the state of charge SOC of the lithium ion battery 41. The state of charge (SOC) is the ratio of the amount of charge to the design capacity of the battery. This state of charge SOC is transmitted from the battery controller 53 to the main controller 56.

  FIG. 3 is a diagram illustrating a power supply state when the starter generator 16 is controlled to a power generation state. FIG. 4 is a diagram illustrating a power supply state when the starter generator 16 is controlled to be in the power generation suspension state. FIG. 5 is a diagram illustrating a power supply state when the starter generator 16 is controlled to the power running state. Note that the power generation state of the starter generator 16 includes a combustion power generation state in which the starter generator 16 is rotationally driven by engine power, and a regenerative power generation state in which the starter generator 16 is rotationally driven by kinetic energy during vehicle deceleration.

  As shown in FIG. 3, for example, when the charged amount of the lithium ion battery 41 is depleted, the starter generator 16 is controlled to the combustion power generation state. That is, when the state of charge SOC of the lithium ion battery 41 is lower than the predetermined lower limit, the starter generator 16 is controlled to the combustion power generation state in order to charge the lithium ion battery 41 and increase the state of charge SOC. When controlling the starter generator 16 to the combustion power generation state, the voltage generated by the starter generator 16 is raised above the terminal voltage of the lithium ion battery 41. As a result, as shown by the black arrows in FIG. 3, power is supplied from the starter generator 16 to the lithium ion battery 41, the electric device 54, the lead battery 42, and the like. 41 is charged.

  As shown in FIG. 4, for example, when the charged amount of the lithium ion battery 41 is sufficiently ensured, the starter generator 16 is controlled to be in the power generation stop state. That is, when the state of charge SOC of the lithium-ion battery 41 exceeds a predetermined upper limit, the starter generator 16 is controlled to be in a power generation pause state in order to promote the discharge of the lithium-ion battery 41 and reduce the engine load. When the starter generator 16 is controlled to be in the power generation suspending state, the voltage generated by the starter generator 16 is lower than the terminal voltage of the lithium ion battery 41. Thereby, as indicated by the black arrow in FIG. 4, power is supplied from the lithium ion battery 41 to the electric device 54 and the like, so that the power generation of the starter generator 16 can be suppressed and the engine load can be reduced. can do.

  As described above, the starter generator 16 is controlled to the combustion power generation state or the power generation stop state based on the state of charge SOC. However, from the viewpoint of improving the fuel efficiency of the vehicle 11, the starter generator 16 is switched to the regenerative power generation state during vehicle deceleration. Controlled. As a result, the kinetic energy of the vehicle can be converted into electric energy and collected, and the energy efficiency of the vehicle can be improved. Whether or not to execute the regenerative power generation of the starter generator 16 is determined based on the operation status of the accelerator pedal and the brake pedal, and the like. For example, when the depression of the accelerator pedal is released or when the brake pedal is depressed, the voltage generated by the starter generator 16 is raised above the terminal voltage of the lithium ion battery 41, and as shown in FIG. Generator 16 is controlled to a regenerative power generation state. As shown in FIGS. 3 and 4, when the starter generator 16 is controlled to the combustion power generation state, the regenerative power generation state, and the power generation suspension state, the switches SW1 and SW2 are held in the conductive state.

  As shown in FIG. 5, when controlling the starter generator 16 to the powering state, the switch SW2 is switched from the conductive state to the cutoff state. That is, when the starter generator 16 starts and rotates the engine 12 or when the starter generator 16 assists the engine 12, the switch SW2 is switched from the conductive state to the cutoff state. That is, by shutting off the switch SW2, the power supply circuit including the lead battery 42 and the electric device 54 and the power supply circuit including the lithium ion battery 41 and the starter generator 16 are separated from each other. Thereby, even when a large current is supplied from the lithium ion battery 41 to the starter generator 16, it is possible to prevent an instantaneous voltage drop, that is, an instantaneous voltage drop in the electric device 54 or the like.

[Switching mode]
Hereinafter, the switching mode of the switch SW1 will be described. If the temperature of the lithium ion battery 41 is excessively increased, the lithium ion battery 41 may be deteriorated. Therefore, the battery controller 53 executes a switching mode in which the switch SW1 is alternately switched between the cutoff state and the conduction state based on the temperature of the lithium ion battery 41. By executing this switching mode, it is possible to suppress a rise in the temperature of the lithium ion battery 41 and secure an opportunity for regeneration of the starter generator 16 as described later. Note that, in the switching mode, the switch SW2 is kept conductive.

  FIG. 6 is a diagram illustrating an example of the execution state of the switching mode. In FIG. 6, the conductive state of the switch SW1 is shown as ON, and the cutoff state of the switch SW1 is shown as OFF. FIG. 7A is a diagram illustrating the power supply circuit 40 in which the switch SW1 is controlled to be turned off, and FIG. 7B is a diagram illustrating the power supply circuit 40 in which the switch SW1 is controlled to be turned on.

  As shown in FIG. 6, in the lithium ion battery 41, an upper limit temperature Tmax is set as various temperature conditions, a first threshold (threshold) T1 lower than the upper limit temperature Tmax is set, and the first threshold T1 is lower than the first threshold T1. A second threshold T2 is set. The upper limit temperature Tmax is a temperature at which charging and discharging of the lithium ion battery 41 is prohibited from the viewpoint of protecting the lithium ion battery 41. Further, the first threshold T1 is a temperature at which the switching mode starts, and the second threshold T2 is a temperature at which the switching mode ends.

  When the temperature of the lithium ion battery 41 (hereinafter, referred to as battery temperature) is lower than the first threshold value T1, that is, when the battery temperature changes within a normal range (symbol a1), the switch SW1 is maintained in the conductive state. (Symbol b1). Thereafter, for example, when charging and discharging are repeated in a short time, the battery temperature rises, and when the battery temperature reaches the first threshold value T1 (reference a2), a switching mode for opening and closing the switch SW1 is started. As described above, the switching mode is a control mode in which the switch SW1 is alternately switched between the cutoff state and the conduction state.

  As shown in FIG. 7A, turning off the switch SW1 disconnects the lithium ion battery 41 from the power supply circuit 40. Thus, charging and discharging of the lithium-ion battery 41 can be stopped, so that a rise in battery temperature can be suppressed. On the other hand, as shown in FIG. 7B, by turning on the switch SW1, the lithium ion battery 41 is connected to the power supply circuit 40. As a result, the lithium ion battery 41 can be charged and discharged. Therefore, when a regenerative opportunity such as vehicle deceleration occurs, the lithium ion battery 41 can be charged with regenerative power. That is, by executing the switching mode, it is possible to suppress a rise in battery temperature and a decrease in energy efficiency. As described above, the switching mode for suppressing the rise in the battery temperature is executed, and thereafter, when the battery temperature decreases to the second threshold value T2 (reference numeral a3), the switching mode is terminated, and the switch SW1 is maintained in the conductive state again. (Symbol b2). When the battery temperature reaches the upper limit temperature Tmax, it is necessary to stop the temperature rise of the lithium ion battery 41, so that the switching mode is stopped and the switch SW1 is kept in the cut-off state.

  Next, a description will be given of a change in battery temperature depending on the presence or absence of the switching mode. FIG. 8 is a comparison diagram showing a change in battery temperature depending on the presence or absence of the switching mode. FIG. 8 shows the transition of the temperature when the switching mode is executed as an example using a solid line, and the transition of the temperature when the switching mode is not executed as a comparative example using a broken line.

  As shown in FIG. 8, in the embodiment, when the battery temperature reaches the first threshold value T1 (reference numeral c1), the switching mode of the switch SW1 is started. Thereby, charging and discharging of the lithium-ion battery 41 can be limited, so that an increase in battery temperature can be suppressed. On the other hand, in the comparative example, even when the battery temperature is higher than the first threshold value T1, the switch SW1 is kept conductive (reference d1). Thereafter, when the battery temperature reaches the upper limit temperature Tmax (symbol e1), the switch SW1 is switched from the conductive state to the cutoff state, and the switch SW1 is held in the cutoff state (symbol d2). As described above, in the comparative example, since the rise in the battery temperature proceeds early, the switch SW1 is easily held in the cutoff state.

  As described above, when the switch SW1 is kept in the cut-off state, the regenerative power generation of the starter generator 16 causes the lithium-ion battery Since 41 cannot be charged, the energy efficiency of the vehicle is reduced. On the other hand, as shown in the embodiment, when the switching mode of the switch SW1 is being executed, the regenerative power is limited as compared with the normal time, as indicated by reference numerals f1 and f2. The regenerative power generation can charge the lithium-ion battery 41, so that the energy efficiency of the vehicle can be improved.

[Opening / closing timing of switch SW1]
Next, a method of setting the opening / closing timing of the switch SW1 in the switching mode, that is, a method of setting the cutoff time and the conduction time of the switch SW1 in the switching mode will be described. Here, FIGS. 9A and 9B are diagrams showing an example of the opening / closing timing of the switch SW1. FIG. 9A shows the opening / closing timing when the rising speed of the battery temperature is high, and FIG. 9B shows the opening / closing timing when the rising speed of the battery temperature is low. Note that ΔTemp1 and ΔTemp2 shown in FIG. 9 indicate the amount of increase in the battery temperature during the predetermined time Δt.

  As shown in FIGS. 9A and 9B, in the switching mode, the opening and closing of the switch SW1 is repeated at a predetermined cycle Ta. Further, as shown in FIG. 9A, when the rate of increase of the battery temperature (ΔTemp1 / Δt) is large, the cutoff time Tb1 for holding the switch SW1 in the cutoff state is set long, and the switch SW1 is turned on. The conduction time Tc1 to be held is set short. On the other hand, as shown in FIG. 9B, when the rate of increase of the battery temperature (ΔTemp2 / Δt) is small, the cutoff time Tb2 for holding the switch SW1 in the cutoff state is set long, and the switch SW1 is turned on. The conduction time Tc2 to be held is set short.

  As described above, the battery controller 53 sets the cutoff time of the switch SW1 in the switching mode to be longer as the battery temperature rises faster. Further, the battery controller 53 sets the conduction time of the switch SW1 in the switching mode to be shorter as the rising speed of the battery temperature is faster. Accordingly, when the rate of rise of the battery temperature is fast, that is, when the battery temperature easily reaches the upper limit temperature Tmax, the switching mode can be appropriately controlled so as to suppress the rise of the battery temperature. On the other hand, when the rising speed of the battery temperature is slow, that is, when the battery temperature is unlikely to reach the upper limit temperature Tmax, the switching mode is appropriately controlled so that the lithium-ion battery 41 is charged with a large amount of regenerative power. I can do it.

  In the above description, both the cut-off time and the conduction time of the switch SW1 are changed based on the rising speed of the battery temperature, but the present invention is not limited to this. For example, only the cutoff time of the switch SW1 may be changed based on the rising speed of the battery temperature, and the conduction time of the switch SW1 may be kept constant. Alternatively, only the conduction time of the switch SW1 may be changed based on the rising speed of the battery temperature, and the interruption time of the switch SW1 may be kept constant. Further, in the example illustrated in FIG. 9, the cutoff time and the conduction time in the switching mode are set based on the rising speed immediately before the battery temperature reaches the first threshold value T1, but the present invention is not limited to this. For example, the cut-off time and the conduction time in the switching mode may be set based on the average value of the rising speed until the battery temperature reaches the first threshold value T1.

  In the above description, the switch SW1 is opened and closed at a constant cycle Ta. However, the present invention is not limited to this, and the opening and closing cycle of the switch SW1 may be changed. In the above description, in the process of executing the switching mode, the cut-off time and the conduction time of the switch SW1 may be changed. For example, a third threshold value is set between the first threshold value T1 and the upper limit temperature Tmax, and when the battery temperature reaches the third threshold value during the execution of the switching mode, the cutoff time is set based on the rising speed of the battery temperature. Alternatively, the conduction time may be reset.

  The present invention is not limited to the above embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention. In the above description, the switch SW1 is provided on the negative electrode line 47 of the lithium ion battery 41, but the present invention is not limited to this. For example, a switch SW1 may be provided on the positive electrode line 43 of the lithium ion battery 41 as shown by a dashed line in FIG. In the above description, the lithium ion battery 41 is used as the first power storage, and the lead battery 42 is used as the second power storage. However, the present invention is not limited to this, and other types of batteries may be used. Alternatively, a capacitor may be employed. Further, it is needless to say that the first power storage unit and the second power storage unit are not limited to different types of power storage units, and may be the same type of power storage units.

  In the above description, the starter generator 16, which is an ISG, is used as the generator. However, the present invention is not limited to this, and an alternator may be used as the generator, and the motor generator, which is the power source of the hybrid vehicle, may be used. It may be adopted as a generator. In the above description, the battery controller 53 functions as the switch control unit. However, the present invention is not limited to this, and another controller such as the main controller 56 may function as the switch control unit.

Reference Signs List 10 vehicle power supply device 12 engine 16 starter generator (generator)
41 Lithium-ion battery (first power storage)
42 Lead battery (second power storage unit)
52 temperature sensor 53 battery controller (switch control unit)
SW1 switch (power switch)
T1 First threshold (threshold)
Tb1, Tb2 cut-off time Tc1, Tc2 conduction time

Claims (5)

A vehicle power supply device mounted on a vehicle,
A generator connected to the engine,
A first power storage unit connected to the generator;
A second power storage unit connected to the generator in parallel with the first power storage unit;
An energizing switch that is controlled to a conduction state that connects the generator and the first power storage unit and a cutoff state that disconnects the generator and the first power storage unit;
A temperature sensor for detecting a temperature of the first power storage unit;
A switch control unit that executes a switching mode that alternately switches the energizing switch between a cutoff state and a conduction state when the temperature of the first power storage unit exceeds a threshold value;
Has,
The switch control unit, when executing the switching mode, based on a rising speed of the temperature of the first power storage device before the temperature of the first power storage device reaches the threshold value, a cutoff time of the energizing switch. And at least one of the conduction time is set,
Power supply for vehicles. The power supply device for a vehicle according to claim 1,
The switch control unit sets a longer cut-off time of the energizing switch in the switching mode as a temperature rising speed of the first power storage unit increases.
Power supply for vehicles. The vehicle power supply device according to claim 1 or 2,
The switch control unit sets the conduction time of the energizing switch in the switching mode to be shorter as the rate of temperature rise of the first power storage device is higher.
Power supply for vehicles. The power supply device for a vehicle according to any one of claims 1 to 3,
The switch control unit holds the energizing switch in a conductive state when the temperature of the first power storage unit is lower than the threshold.
Power supply for vehicles. The power supply device for a vehicle according to any one of claims 1 to 4,
An internal resistance of the first power storage unit is smaller than an internal resistance of the second power storage unit;
Power supply for vehicles.

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