JP7119728B2 - vehicle power supply - Google Patents

Description

The present invention relates to a vehicle power supply device.

2. Description of the Related Art In recent years, vehicles such as hybrid vehicles in which wheels are driven by both a motor and an internal combustion engine, and vehicles such as electric vehicles in which wheels are driven by a motor have been developed and put into practical use. This type of vehicle is equipped with a battery (storage battery), and power is supplied from the battery to the motor. There is known a technique for performing regenerative charging, in which the kinetic energy of the vehicle is converted into electrical energy and recovered to charge a battery when the vehicle decelerates.

In order to improve the recovery efficiency of regenerative energy, in addition to the lead-acid battery (second battery) that is often used in existing vehicles, there are cases where a lithium-ion battery or the like (first battery) with good charge acceptance is installed. be. In this case, the regenerated energy is mainly recovered by the first battery with good charge acceptance. Then, when the state of charge of the first battery becomes higher than a predetermined level, the charging destination is switched to the second battery. In order to set charging voltages suitable for these two different types of batteries, a technique has been proposed in which a DC/DC converter is provided and the voltage value is changed when the charging destination is switched (for example, Patent Document 1).

Japanese Patent No. 4839722

A power supply device that adjusts a charging voltage with a DC/DC converter has the problem that mounting the DC/DC converter increases the cost and restricts the layout. Also, the energy loss caused by voltage conversion cannot be ignored.

On the other hand, if the charging destination is switched to the second battery while the first battery is being charged at a high voltage without using the DC/DC converter, an overcurrent will flow through the second battery at the time of switching and an abnormality will occur. There is a risk of

In addition, if regeneration is interrupted without switching the charging destination to the second battery when the state of charge of the first battery exceeds a predetermined level, the deceleration torque will suddenly drop, affecting the behavior of the vehicle. may reach. In addition, energy loss occurs because the regenerative energy cannot be recovered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply device for a vehicle that is simple in structure, low in cost, and capable of switching between regeneratively charged batteries while suppressing energy loss. and

The present invention is a power supply device for a vehicle that includes a battery and an electric motor that receives power supply from the battery and generates power for driving wheels, and is capable of regeneratively charging the battery by converting rotational energy of the wheels into electric power. a first battery and a second battery having a larger internal resistance than the first battery as batteries; When the first battery reaches the first charge amount while the first battery is being charged, the electric power generation amount of the electric motor is changed to change the charge voltage from the first voltage to the second voltage lower than the first voltage. When the voltage is gradually changed and the first battery reaches the second charge amount, the second battery is charged with the second voltage via the charging branch.

Advantageous Effects of Invention According to the vehicle power supply device of the present invention, it is possible to switch batteries to be regeneratively charged with a simple configuration at low cost while suppressing energy loss.

1 is a block diagram showing a control system of a vehicle according to this embodiment; FIG. 4 is a time chart showing regenerative charging control of the power supply device of the vehicle; 4 is a flowchart showing regenerative charging control of the power supply device of the vehicle;

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

A vehicle 10 of the present embodiment is a hybrid vehicle that uses both an engine 13 that is an internal combustion engine and a motor generator 14 to drive wheels (driving wheels) 11 . Either the engine 13 or the motor-generator 14 or both the engine 13 and the motor-generator 14 drive the drive shaft 16 through the transmission 15 to rotate the wheels 11 . The starter 17 is an electric motor for starting the engine 13 and is provided separately from the motor generator 14 .

The friction brake 18 decelerates the rotation of the wheel 11 by mechanical frictional contact. A friction brake 18 is composed of a disc rotor provided on an axle that supports the wheel 11 and a caliper containing a brake pad that is hydraulically operated and sandwiches the disc rotor.

The motor generator 14 is a so-called motor generator. The motor-generator 14 functions as an electric motor that generates driving power for driving the drive shaft 16 with electric power supplied from the battery unit 20 . Also, during deceleration, it functions as a generator that converts the rotational energy of the drive shaft 16 into electric power by the regenerative torque of the motor generator 14 .

Electric power is supplied from the battery unit 20 to the motor generator 14 when the motor generator 14 functions as an electric motor. Further, when the motor generator 14 functions as a generator, the battery unit 20 is charged with electric power generated by the motor generator 14 . The motor-generator 14 and the like are provided with a conversion unit that mutually converts an AC voltage input/output to/from the motor-generator 14 and a DC voltage input/output to/from the battery unit 20 . The battery unit 20 has a first battery 21 and a second battery 22 . The first battery 21 and the second battery 22 are different types of storage batteries, and the first battery 21 has lower internal resistance than the second battery 22 and is superior in charge acceptance. As an example, a lithium ion battery can be used for the first battery 21 and a lead battery can be used for the second battery 22 . The lithium ion battery used for the first battery 21 has a voltage equivalent to that of the lead battery used for the second battery 22 (for example, about 12 V). However, the types of the two batteries are not limited to this combination. For example, it is possible to use a nickel hydrogen battery or the like instead of the lithium ion battery.

The battery unit 20 also supplies electric power to components of the electrical system other than the motor generator 14 . For example, the power supply line from the first battery 21 is connected to an ECU (Electrical Control Unit), a TCM (Transmission Control Module), a car navigation system (not shown), etc. that constitute a control device 30, which will be described later. A power supply line from the second battery 22 is connected to the starter 17 and other accessories such as a wiper (not shown).

The battery unit 20 is provided with a charging branch portion 24 that branches the charging power line between the motor generator 14 and the first battery 21 side and the second battery 22 side. Due to the difference in internal resistance between the first battery 21 and the second battery 22, the charging branch unit 24 preferentially charges the first battery 21 side, which has a smaller internal resistance (when the current from the motor generator 14 side is flowing).

The control device 30 performs overall control of the vehicle 10, and the elements appearing in FIG. It controls the operation of the unit 24 . Separate ECUs are provided for the engine 13, the motor generator 14, and the like, and a TCM is provided for controlling the transmission 15. These are collectively indicated as a control device 30. FIG.

FIG. 1 shows schematic functional blocks of a power generation control unit 31, a charge control unit 32, a brake control unit 33, and a liquid temperature calculation unit 34 that are involved in regenerative charging among the multiple elements that constitute the control device 30. rice field. The power generation control unit 31 is a functional block that controls power generation by the motor generator 14 . As one of the functions of the power generation control unit 31, when the motor generator 14 functions as a generator, the magnitude of the excitation current can be adjusted to change the amount of power generated by the motor generator 14. FIG. Thereby, the charging voltage when charging the battery unit 20 can be adjusted without permission. The charging control unit 32 is a functional block that controls the operation of the charging branch unit 24 and the like. to control. Information such as the charging rate of the first battery 21 and the second battery 22 is managed through the charging control unit 32 . The brake control unit 33 is a functional block that controls the operation of the friction brake 18, and can adjust the deceleration rate of the vehicle 10 in cooperation with the regenerative braking performed by the power generation control unit 31 controlling the motor generator 14. can. The liquid temperature calculator 34 is a functional block that calculates (estimates) the liquid temperature of the second battery 22 from the temperature in the engine room that accommodates the engine 13 and the motor generator 14 and the vehicle speed of the vehicle 10 .

Detection signals from various sensors provided in the vehicle 10 and operation signals from the operation means are input to the control device 30 . When an accelerator pedal 40 provided as an operation means is depressed, the control device 30 supplies electric power from the engine 13 or the electric motor generator 14 (in this case, the battery unit 20) in accordance with the output request. ) to generate an output that drives the drive shaft 16 . When the brake pedal 41 is depressed, in response to the deceleration request, the control device 30 operates the friction brake 18 under the control of the brake control unit 33, and operates the motor generator under the control of the power generation control unit 31. 14 functions as a generator to recover regenerated energy and charge the battery unit 20 .

Control of regenerative charging in the power supply device of vehicle 10 will be described with reference to the time chart of FIG. 2 . This regenerative charging control is performed when the occupant of the vehicle 10 performs a predetermined operation or when the vehicle 10 satisfies predetermined operating conditions. Specifically, when the brake pedal 41 is depressed, or when the brake pedal 41 is not depressed but the accelerator pedal 40 is released, it is determined that coasting while decelerating is requested. This applies to cases such as The conditions under which the regenerative charging control is to be started are stored in advance in the memory or the like of the control device 30, and it is determined whether or not the conditions are met according to the inputs from various sensors provided in the vehicle 10 or the like.

The example of control shown in FIG. 2 shows a case where the brake pedal 41 is depressed, and the friction brake 18 operates in response to the operation of the brake pedal 41 to decelerate due to mechanical frictional resistance. . The deceleration of the vehicle due to regeneration using the motor-generator 14 as a power generator is assumed to be DR1, and the deceleration of the vehicle due to the friction brake 18 is assumed to be DR2. A total deceleration DRG of the vehicle 10 is obtained by combining the deceleration DR1 and the deceleration DR2. The actual behavior of the vehicle 10 during deceleration is mainly affected by the total deceleration DRG. FIG. 2 shows the rate of change of each deceleration as a slope with respect to the horizontal axis (elapsed time). It shows a case where time has changed. That is, it shows the case where the total deceleration DRG is controlled to be constant.

Regenerative charging control is started at T1 in FIG. When entering regenerative charging control, the control device 30 controls power generation of the motor generator 14 through the power generation control section 31 . Electric power is generated by the motor generator 14 and direct current enters the charging branch 24 of the battery unit 20 . In the charging branch portion 24, current flows to the side of the first battery 21 having a smaller internal resistance, and the first battery 21 is charged first. At this stage when the first battery 21 is to be charged, the power generation control unit 31 controls the power generation amount of the motor generator 14 so as to perform regenerative charging at the first voltage V1. The first voltage V1 is a voltage for charging the first battery 21, which has a small internal resistance and a high charge acceptance, as efficiently as possible, and is higher than a second voltage V2, which will be described later.

When the first battery 21 is charged at the first voltage V1, the charge amount of the first battery 21 gradually increases. Eventually, at T2 in FIG. 2, the charge amount (charging rate) of the first battery 21 reaches a predetermined value CM1 (first charge amount). The predetermined value CM1 here is a charge amount close to the full charge CM2 (second charge amount) and smaller than the full charge CM2. In general, a secondary battery for driving a vehicle such as the first battery 21 is not charged to the maximum capacity in order to maintain a long life, and is operated within a range of a predetermined percentage of practical charging rate from the maximum capacity. . Full charge CM2 in this description means the upper limit of such a range of practical charging rates. As an example, when the fully charged CM2 is in a charged state of about 80% of the maximum capacity, the predetermined value CM1 referred to by T2 in FIG. 2 is set to about 75% of the maximum capacity.

When the charge amount of the first battery 21 reaches a predetermined value CM1, the power generation control unit 31 of the control device 30 gradually decreases the power generation amount of the motor generator 14, and the charging voltage is changed from the first voltage V1 to the second voltage V2. Charging of the first battery 21 is continued while gradually changing (gradually decreasing). As a result, the amount of charge per unit time (increase rate of the amount of charge) decreases compared to charging at the first voltage V1. The gradual change here means that the charging voltage is changed at a uniform change rate as much as possible from the first voltage V1 to the second voltage V2 without causing a sudden voltage change on the way. That is, control is performed so that the inclination angle of the graph showing the change in charging voltage is constant between T2 and T3 in FIG. Due to the correlation between the charge amount from the predetermined value CM1 to the full charge CM2 and the voltage difference from the first voltage V1 to the second voltage V2, the voltage reaches the second voltage V2 at the timing of the full charge CM2. A uniform change rate of the charging voltage can be calculated, and the voltage is gradually changed at the calculated change rate.

When the charging voltage is lowered by adjusting the amount of power generated by the motor-generator 14 in this way, the recovery efficiency of the regenerated energy gradually decreases, so the deceleration DR1 of the vehicle due to regeneration gradually decreases. If the voltage is switched from the first voltage V1 to the second voltage V2 all at once, the deceleration DR1 (and the total deceleration DRG) will change abruptly in response to this, giving the occupants of the vehicle 10 a sense of discomfort, may cause unnatural behavior. On the other hand, in the regenerative charging control of the present embodiment, the charge voltage changes gradually from the first voltage V1 to the second voltage V2. can be prevented.

Further, the brake control unit 33 of the control device 30 increases the deceleration DR2 of the vehicle by the friction brake 18 so as to offset the decreasing deceleration DR1. For example, when the brake pedal 41 is stepped on during regenerative charging, the braking force of the friction brake 18 is applied stronger than corresponding to the original stepping amount (deceleration request) of the brake pedal 41. - 特許庁Since the deceleration DR1 gradually decreases in accordance with the gradual change of the charging voltage, the deceleration DR2 by the friction brake 18 is gradually increased (not rapidly increased) accordingly. By balancing the decrease in deceleration DR1 (decrease in regenerative braking force) and the increase in deceleration DR2 (increase in friction braking force), it is possible to prevent the total deceleration DRG from changing. Yes (see FIG. 2), the vehicle can be decelerated without giving the passenger a sense of discomfort.

When it is detected at T3 in FIG. 2 that the first battery 21 is fully charged, the charging control section 32 of the control device 30 controls the charging branch section 24 so that the first battery 21 is not charged any more. . As a result, the charging destination is switched from the first battery 21 to the second battery 22 . The power generation control unit 31 of the control device 30 controls the motor generator 14 to fix the charging voltage gradually changed from T2 to T3 in FIG. 2 charging is performed with voltage V2. Since the charging destination is switched after dropping to the second voltage V2 instead of maintaining the first voltage V1 corresponding to the first battery 21 with high charge acceptance, there is no risk of overcurrent flowing to the second battery 22. - 特許庁Since the deceleration DR1 due to regeneration during charging at the second voltage V2 is lower than that during charging at the first voltage V1, the deceleration DR2 due to the friction brake 18 is maintained in a state of being increased. Compensate for the reduction.

Next, with reference to FIG. 3, the control flow of this embodiment will be described. Note that the flowchart in FIG. 3 shows an example, and can be changed as appropriate. When a predetermined operating condition that serves as a trigger, such as depression of the brake pedal 41 or release of the accelerator pedal 40, is input, the regenerative charging control flow of FIG. 3 is started.

In step S1, charging of the first battery 21 at the first voltage V1 is started. In step S2, it is determined whether or not the amount of charge of the first battery 21 has reached or exceeded a predetermined value CM1 close to the full charge CM2. to continue.

When the amount of charge of the first battery 21 reaches or exceeds the predetermined value CM1 (Yes in step S2), the process proceeds to step S3, where the liquid temperature calculator 34 of the control device 30 calculates the second battery 21 based on the temperature in the engine room and the vehicle speed. Estimate the liquid temperature of 22. The higher the liquid temperature of the lead battery that constitutes the second battery 22, the lower the appropriate voltage for charging. Therefore, an appropriate value of the second voltage V2 is set corresponding to the liquid temperature of the second battery 22 so that the higher the liquid temperature of the second battery 22, the lower the second voltage V2. The setting of the second voltage V2 may be calculated from a predetermined parameter, or may be read from table data indicating the relationship between the liquid temperature and the charging voltage stored in advance.

Subsequently, in step S4, the power generation control unit 31 of the control device 30 controls the excitation current of the motor generator 14 to change the power generation amount, thereby gradually changing the charging voltage from the first voltage V1 to the second voltage V2. (gradually lower). From the difference between the second voltage V2 and the first voltage V1 determined in step S3, the difference in voltage to be lowered can be found. Also, the charge amount from the predetermined value CM1 to the full charge CM2 in the first battery 21 is stored as a default value. Therefore, as described above, it is possible to calculate an appropriate change rate for gradually changing the voltage so that the charging voltage becomes the second voltage V2 at the timing when the full charge CM2 is reached. is gradually changed, the charging of the first battery 21 is continued.

In step S5, the brake control unit 33 of the control device 30 increases the braking force of the friction brake 18 to increase the deceleration DR2 of the vehicle in order to compensate for the reduction in the deceleration DR1 of the vehicle due to regeneration due to the decrease in charging voltage. . As a result, it is possible to prevent fluctuations in braking performance caused by a drop in the charging voltage, and maintain the total deceleration DRG so as not to cause discomfort to the occupant.

In step S6, it is determined whether or not the amount of charge of the first battery 21 has reached the full charge CM2, and if it has not reached the full charge CM2 (No in step S6), The first battery 21 is charged. When the amount of charge of the first battery 21 reaches full charge CM2 (Yes in step S6), the process proceeds to step S7 to prevent the first battery 21 from being charged any more and switch the charging destination to the second battery 22.例文帳に追加With the above, the switching control of the charging destination is completed, and the control flow of FIG. 3 is exited.

As described above, in the vehicle power supply device of the present embodiment, the first battery 21 and the second battery 22 having different internal resistances can be charged with appropriate voltages. In particular, since the charging destination is switched to the second battery 22 after dropping from the first voltage V1 that charges the first battery 21 with a small internal resistance to the second voltage V2, the second battery 22 is charged at the time of switching. An excessive current does not flow, and durability and safety of the battery unit 20 can be improved.

Further, since the charging voltage is changed from the first voltage V1 to the second voltage V2 by adjusting the power generation amount of the motor generator 14 under the control of the control device 30, a DC/DC converter or the like for adjusting the charging voltage is used. separately. As a result, effects such as cost reduction, weight reduction, and layout improvement of the power supply device can be obtained. In addition, energy efficiency is good because no loss occurs during voltage conversion by the DC/DC converter.

In addition, by adjusting the charging voltage as described above, it is possible to switch the charging destination without interrupting regeneration, so regenerative energy can be collected without waste and sudden loss of deceleration torque does not occur. Moreover, when the charging voltage is adjusted, the charging voltage is gradually lowered from the first voltage V1 to the second voltage V2 without abruptly changing. There is little possibility of giving a sense of incongruity to the occupant.

Furthermore, since the decrease in deceleration DR1 due to regeneration due to the drop in charging voltage is compensated for by the increase in deceleration DR2 due to the friction brake 18, which is a mechanical braking means, deceleration control with even higher precision and excellent drivability can be achieved. realizable.

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

For example, in the above embodiment, the charging branch unit 24 connects charging lines to both the first battery 21 and the second battery 22, and during regenerative charging, the inside of the first battery 21 and the second battery 22 is charged. Due to the difference in resistance, charging is performed sequentially from the first battery 21 . Unlike this, it is also possible to provide a switch that selects and switches the charging destination between the first battery 21 and the second battery 22 in a portion corresponding to the charging branch unit 24 . Such a switch is also included in the concept of the charging branch unit in the present invention.

It is preferable to offset the decrease in deceleration DR1 due to regeneration with the increase in deceleration DR2 due to friction brake 18, as in the above embodiment. However, since the decrease in deceleration DR1 is controlled to be a gradual change (change in charging voltage is a gradual change), compared to a sudden change in deceleration when regeneration is suddenly interrupted, Behavior stabilizes. Therefore, even if the control is performed without increasing the deceleration DR2 (step S5 in FIG. 3 is omitted), a predetermined effect can be obtained.

In the above embodiment, the friction brake 18 is used as a mechanical braking means that works separately from the regenerative braking, but it is also possible to use a mechanical braking means other than the friction brake.

In the above embodiment, the liquid temperature of the second battery 22 is estimated from the temperature in the engine room, etc., but a sensor or the like for measuring the liquid temperature of the battery may be provided separately.

Unlike the vehicle 10 of the above-described embodiment, the present invention can also be applied to a type of vehicle in which an electric motor and a generator are provided separately. Furthermore, the present invention can be applied not only to hybrid vehicles that use both an internal combustion engine and an electric motor, but also to electric vehicles that run only with the driving force of the electric motor.

INDUSTRIAL APPLICABILITY As described above, the present invention has the effect of being able to switch between regeneratively charged batteries with a simple configuration at low cost while suppressing energy loss. useful for

10: Vehicle 11: Wheel 13: Engine 14: Motor Generator (Electric Motor)
15: transmission 16: drive shaft 18: friction brake (mechanical braking means)
20: Battery unit 21: First battery 22: Second battery 24: Charging branch unit 30: Control device 31: Power generation control unit 32: Charging control unit 33: Brake control unit 34: Fluid temperature calculation unit CM1: First battery Predetermined charge value (first charge amount)
CM2: Full charge of the first battery (second charge amount)
DR1: deceleration by regeneration DR2: deceleration by friction brake DRG: total deceleration V1: first voltage V2: second voltage

Claims (5)

A power supply device for a vehicle comprising a battery and an electric motor receiving power supply from the battery to generate power for driving wheels, and capable of regeneratively charging the battery by converting rotational energy of the wheels into electric power,
a first battery and a second battery having a larger internal resistance than the first battery as the batteries;
When the first battery reaches the first charge amount while the first battery is being charged at the first voltage, the power generation amount of the electric motor is changed to increase the voltage from the first voltage to the first voltage. Gradually change the charging voltage to a lower second voltage,
A power supply device for a vehicle, wherein the second battery is charged with the second voltage via the charging branch when the first battery reaches the second charge amount. 2. The vehicle power supply device according to claim 1, wherein the second charge amount is a full charge of the first battery. 3. The vehicle power supply device according to claim 1, wherein the second voltage is set to be lower as the liquid temperature of the second battery is higher. Provided with mechanical braking means for decelerating the rotation of the wheel by applying mechanical resistance,
4. The vehicle power source according to any one of claims 1 to 3, wherein when the voltage is gradually changed from the first voltage to the second voltage, deceleration of the vehicle by the mechanical braking means is increased. Device. 5. The vehicle power supply device according to claim 1, wherein the first battery is a lithium ion battery and the second battery is a lead battery.

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