Vehicle, power source system, and control method of power source system

A second power storage device is electrically connected to a positive electrode line and a negative electrode line, and electric power for generating a driving force is directly supplied to an inverter section. A converter section supplies electric power received from the inverter section to a first power storage device. Because a backflow prevention circuit is provided, the electric power is not supplied in the direction of the second power storage device at this point. A diode of the backflow prevention circuit is connected between a system main relay and the connection node of a positive electrode line on the positive electrode line branching off from the positive electrode line and connected to the second power storage device. The diode controls the flow of a current from the positive electrode line side toward the second power storage device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national phase application based on the PCT International Patent Application No. PCT/IB2013/001957 filed Sep. 10, 2013, claiming priority to Japanese Patent Application No. 2012-225092 filed Oct. 10, 2012, the entire contents of both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vehicle, a power source system, and a control method of a power source system, and particularly relates to a start control of a power source system in an electric vehicle.

2. Description of Related Art

There is a Conventional power source system in which a main battery (hereinafter referred to, as a first power storage device) and a sub battery (hereinafter referred to as a second power storage device) are mounted on a vehicle, a step-up converter and a relay switch are disposed in paths between the first and second power storage devices and a load such as a motor or the like, and a plurality of the power storage devices are connected in parallel. Such a power source system is described in, e.g., each of Japanese Patent Application Publication No. 2009-142102 (JP-2009-142102 A) and Japanese Patent Application Publication No. 2011-199934 (JP-2011-199934 A).

In the power source system described above, in a case where the power storage devices have different output voltages, a relay switch including a limiting resistor (hereinafter referred to as a relay switch with a precharge function) is provided, and the power storage device can be connected to the load such that an inrush current does not flow into the load when the power storage device is connected to the load.

However, in the thus configured conventional power source system, it is desirable to simplify the configuration and further improve the efficiency of the power source system, and it is necessary to properly protect equipment at the time of connection of each power storage device.

SUMMARY OF THE INVENTION

In view of the above issue, the invention provides a vehicle, a power source system, and a control method of a power source system capable of properly connecting or disconnecting a plurality of power storage devices to or from each other using no-load energization or the like.

According to one aspect of the invention, there is provided a vehicle including a power source system, a drive device, and a control device. The drive device is configured to be driven with electric power supplied from the power source system. The control device is configured to control the power source system or the drive device. The power source system includes a first power storage device, a voltage conversion device, a second power storage device, a first switch, and a second switch. The voltage conversion device is configured to convert a voltage from the first power storage device. The second power storage device is configured to be electrically connected to a path supplying electric power subjected to the conversion in the voltage conversion device to the drive device and supply electric power to the drive device. The first switch is configured to switch between supply and shutoff of electric power between the first power storage device and the voltage conversion device. The second switch is configured to switch between supply and shutoff of electric power from the second power storage device to the drive device. The control device of the vehicle is configured to control the power source system or the drive device, close the first switch with activation of the power source system, and close the second switch in response to a voltage applied to the drive device being increased to a predetermined voltage.

The control device may further include a notification device configured to provide a notification that the vehicle can travel in response to the first switch being closed.

The first power storage device may further include a high-output battery, and the second power storage device may include a high-capacity battery.

The vehicle may further include a backflow prevention circuit configured to be connected between the drive device and the second switch. The backflow prevention circuit may be configured to prevent a current on a side of the drive device from flowing toward the second power storage device. The backflow prevention circuit may be configured to include a diode.

The drive device may further include a rotary electric machine as a load coupled to an engine, and the control device may be configured to prevent start of the engine until the second switch is closed.

The control device may further be configured to prevent the start of the engine by temporarily relaxing an output limit of the first power storage device.

The control device may further be configured to prevent the start of the engine by temporarily reducing an output torque upper limit value of the rotary electric machine.

According to another aspect of the invention, there is provided a power source system for supplying electric power to a load. The power source system includes a first power storage device, a voltage conversion device, a second power storage device, a first switch, a second switch, and a control device. The voltage conversion device is configured to convert a voltage from the first power storage device. The second power storage device is configured to be electrically connected to a path linking the voltage conversion device and the load and supply electric power to the load. The first switch is configured to switch between supply and shutoff of electric power between the first power storage device and the voltage conversion device. The second switch is configured to switch between supply and shutoff of electric power from the second power storage device to the load. The control device is configured to close the first switch with activation of the power source system, and close the second switch in response to a voltage applied to the load being increased to a predetermined voltage.

According to still another aspect of the invention, there is provided a control method of a power source system for supplying electric power to a load. In the control method, the power source system includes a first power storage device, a voltage conversion device, a second power storage device, a first switch, and a second switch. The voltage conversion device is configured to convert a voltage from the first power storage device. The second power storage device is configured to be electrically connected to a path linking the voltage conversion device and the load and be capable of supplying electric power to the load. The first switch is configured to switch between supply and shutoff of electric power between the first power storage device and the voltage conversion device. The second switch is configured to switch between supply and shutoff of electric power from the second power storage device to the load. The control method closes the first switch to start supply of electric power with activation of the power source system, increases a voltage given from the first power storage device by using the voltage conversion device, and closes the second switch in response to a voltage applied to the load being increased to a predetermined voltage.

According to the invention, by the control device of the vehicle, the first switch is closed when the power source system is activated, and the second switch is closed in response to the voltage applied to the drive device being increased to the predetermined voltage. As a result, it is possible to properly connect and disconnect a plurality of the power storage devices to or from each other using no-load energization or the like.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinbelow, an embodiment of the invention will be described with reference to the drawings. In the following description, the same components are designated by the same reference numerals. The names and the functions thereof are identical with each other. Consequently, the detailed description thereof will not be repeated.

First, the configuration of a vehicle will be described.FIG. 1is an entire block diagram of a hybrid vehicle on which a power source system50according to the embodiment of the invention is mounted.

Referring toFIG. 1, a hybrid vehicle100has the power source system50, a drive device90, and an electronic control unit (ECU)30as a control device for controlling the power source system50and the drive device90.

The power source system50has a first power storage device BAT1, a second power storage device BAT2, system main relays SMR1and SMR2, a converter section10, capacitors C1and C2, a backflow prevention circuit35, voltage sensors42,44,46, and48, and current sensors52,54, and56.

Among them, the first power storage device BAT1is connected to the converter section10as a voltage conversion device via the system main relay SMR1described later.

The voltage sensor42detects a voltage VB1of the first power storage device BAT1, and outputs the detected value of the voltage VB1to the ECU30. The current sensor52detects a current I1inputted to or outputted from the converter section10from or to the first power storage device BAT1, and outputs the detected value thereof to the ECU30. The values of the voltage VB1and the current I1are used for the calculation of a state of charge SOC described later in the ECU30.

The system main relay SMR1includes a contact G1connected between a negative electrode of the first power storage device BAT1and a negative electrode line NL1, a contact P1connected in series to a limiting resistor R1between the negative electrode of the first power storage device BAT1and the negative electrode line NL1, and a contact B1connected between a positive electrode of the first power storage device BAT1and a positive electrode line PL1. The ON/OFF states of the contacts G1, P1, and B1are individually controlled according to a control signal SM1given from the ECU30.

Note that, at the time of start of the hybrid vehicle100, the ECU30brings the contacts B1and P1of the system main relay SMR1into the ON state to allow conduction of electricity and thereby performs precharge of the capacitors C1and C2and, when the precharge is completed, the ECU30brings the contact P1into the OFF state to open the contact P1after bringing the contact G1into the ON state to allow the conduction of electricity. By switching between the ON/OFF states of the contacts G1, P1, and B1in this order, an inrush current can be prevented and the system main relay SMR1allows electric power to be supplied to an inverter section20.

The capacitor C1is provided between the positive electrode line PL1and the negative electrode line NL1, and reduces a voltage fluctuation between the positive electrode line PL1and the negative electrode line NL1.

The voltage sensor46detects the voltage between the contacts of the capacitor C1, i.e., the value of a voltage VL of a positive electrode line PL2with respect to the negative electrode line NL1, and outputs the detected value thereof to the ECU30. The current sensor56detects the value of a current I3flowing to a reactor15, and outputs the detected value thereof to the ECU30.

The converter section10includes upper and lower arm switching elements11and12, upper and lower arm diodes13and14, and the reactor15. The upper and lower arm switching elements11and12are connected in series between a positive electrode line PL3and the negative electrode line NL1.

To the upper and lower arm switching elements11and12, the upper and lower arm diodes13and14are respectively connected in antiparallel. The reactor15is connected between the connection node of the upper and lower arm switching elements11and12and the positive electrode line PL1.

In the present embodiment, as the switching element, it is possible to use, e.g., an insulated gate bipolar transistor (IGBT), a power metal oxide semiconductor (MOS) transistor, or a power bipolar transistor.

The converter section10is basically controlled such that the upper and lower arm switching elements.11and12are turned ON/OFF complementarily and alternately in each switching cycle. During a step-up operation, the converter section10performs the step-up operation such that direct current (DC) power having the voltage VL outputted by the first power storage device BAT1has a voltage VH. This step-up operation is performed by giving electromagnetic energy accumulated in the reactor15during the ON period of the lower arm switching element12to the positive electrode line PL3via the upper arm switching element11and the upper arm diode13connected in antiparallel thereto.

In addition, during a step-down operation, the converter section10performs the step-down operation such that the DC power having the voltage VH outputted by the inverter section20has the voltage VL. This step-down operation is performed by giving the electromagnetic energy accumulated in the reactor15during the ON period of the upper arm switching element11to the negative electrode line NL1via the lower arm switching element12and the lower arm diode14connected in antiparallel thereto. A voltage conversion ratio (a ratio between VH and VL) in each of the step-up operation and the step-down operation is controlled by an ON period ratio (a duty ratio) between the upper and lower arm switching elements11and12. For example, when the upper arm switching element11is fixed to ON and the lower arm switching element12is fixed to OFF, it is possible to satisfy VH=VL (the voltage conversion ratio=1.0).

The voltage sensor48detects the voltage between the contacts of the capacitor C2, and outputs the detected value of the voltage VH to the ECU30. The capacitor C2is provided between the positive electrode line PL3and the negative electrode line NL1, and reduces the voltage fluctuation between the positive electrode line PL3and the negative electrode line NL1.

In addition, the converter section10is electrically connected to the inverter section20with the positive electrode line PL3and the negative electrode line NL1.

The positive electrode line PL2and a negative electrode line NL2are provided with the system main relay SMR2, and the supply and the shutoff of electric power from the second power storage device BAT2to the drive device are switched.

The system main relay SMR2includes a contact G2connected between the negative electrode of the second power storage device BAT2and the negative electrode line NL2, and a contact B2connected to the positive electrode of the second power storage, device BAT2. However, the system main relay SMR2does not include the limiting resistor R1and the contact P1included in the system main relay SMR1. The ON/OFF states of the contacts G2and B2are individually controlled according to a signal SM2given from the ECU30.

To the positive electrode line PL3and the negative electrode line NL1, the second power storage device BAT2is connected via the positive electrode line PL2and the negative electrode line NL2.

When the voltage VH exceeds a voltage VB2, the control signal SM2for performing a closing operation is outputted from the ECU30, and the contacts B2and G2are closed. With this, the system main relay. SMR2supplies the current from the second power storage device BAT2to motor generators MG1and MG2.

The backflow prevention circuit35is provided on the positive electrode line PL2. The backflow prevention circuit35is configured by, e.g., a diode D3, and is connected with the direction from the positive electrode line PL2to the positive electrode line PL3serving as a forward direction.

As a result, for example, in a case where the increase of the voltage VH is required at the time of a high load, it is possible to prevent the current that should flow to the motor generator MG2from flowing in the direction of the second power storage device BAT2unintentionally. Note that, in this embodiment, although the diode D3is used as the backflow prevention circuit, the configuration of the backflow prevention circuit is not particularly limited thereto, and any circuit device may be used as long as the circuit device is configured so as not to be brought into the ON state to be closed unless the voltage VH detected by the voltage sensor48becomes a predetermined value or higher. In addition, the disposition of the circuit device for the backflow prevention, the number of switching elements, and the value of the voltage that permits or prohibits the conduction of electricity are not particularly limited.

To both ends of the second power storage device BAT2, the voltage sensor44is connected. The voltage sensor44detects the value VB2of the voltage V2of the second power storage device BAT2, and outputs the detected value to the ECU30. The current sensor54detects the value of a current I2inputted to/outputted from the second power storage device BAT2, and outputs the detected value to the ECU30. Subsequently, the ECU30compares the value of the voltage VB2with the value of the voltage VH detected by the voltage sensor48to switch between the first power storage device BAT1and the second power storage device BAT2.

The first power storage device BAT1includes a high-output battery, while the other second power storage device BAT2includes a high-capacity battery. Note that, as, the first power storage device BAT1, it is possible to use, e.g., a secondary battery having the maximum output power larger than that of the second power storage device BAT2. By using the first power storage device BAT1in HV traveling described later and configuring the first power storage device BAT1by the secondary battery capable of inputting and outputting a relatively large current, it is possible to provide sufficient output and charging performance during acceleration/deceleration traveling.

As the second power storage device BAT2, it is possible to use the secondary battery having a power storage capacity larger than that of the first power storage device BAT1. By supplying electric power directly to the inverter section20without the intervention of a power conversion device such as the converter section10, it is possible to use the secondary battery as the power source that has a small power conversion loss and excellent energy efficiency during constant speed traveling having a small change in speed when a vehicle travels on an express way.

With this, by using the first power storage device BAT1and the second power storage device BAT2appropriately, it is possible to configure the DC power source having high power and the large capacity.

In addition, the combination of the first power storage device BAT1and the second power storage device BAT2may be the combination of secondary batteries of different types, and a large-capacity capacitor may also be used in at least one of the first power storage device BAT1and the second power storage device BAT2.

The drive device90has an engine2, the motor generators MG1and MG2as rotary electric machines, the inverter section20that supplies electric power to the motor generators MG1and MG2, a power dividing mechanism4that couples the engine2and the motor generators MG1and MG2, and a wheel6that is coupled to the power dividing mechanism4and can rotate with the power from the engine2and the motor generator MG1and MG2.

The motor generators MG1and MG2are controlled by the ECU30described later. The ECU30may be divided into a plurality of ECUs, e.g., may be configured to have an engine ECU (not shown) as a result of the division, and the engine2may be controlled by an engine control signal outputted from the engine ECU.

The hybrid vehicle100travels with a driving force from at least one of the engine2and the motor generator MG2. That is, one or both of the engine2and the motor generator MG2are automatically selected as a drive source according to the traveling state.

In addition, the motor generator MG2is rotationally driven with the electric power supply from the inverter section20. The inverter section20is controlled with a control signal PWI, and adjusts the rotational torque of the motor generator MG2.

The rotational driving force of the motor generator MG2and the rotational driving force of the engine2cause the wheel6or the motor generator MG1to rotate based on torque distribution by the power dividing mechanism4adjusted by the ECU30. With this, it is possible to cause the hybrid vehicle100to travel or obtain the rotational electromotive force of the motor generator MG1.

Further, during motor traveling, in a case where the rotational torque that should be generated by the motor generator MG2is insufficient, in principle, the ECU30starts the engine2, and adds the rotational driving force of the engine2to the rotational driving force of the motor generator MG2in the power dividing mechanism4to thereby compensate for the insufficiency of the rotational torque.

Additionally, the hybrid vehicle100of the present embodiment is provided with an external charging device60that charges the second power storage device BAT2by using electric power from the electric power source outside the vehicle. The external charging device60includes a charger-side relay switch CHR, a body-side charging port61, a charger62, and a voltage sensor63.

The charger62is connected to the body-side charging port61, and is also connected to the second power storage device BAT2via the charger-side relay switch CHR. In addition, the charger62receives alternating current (AC) power transmitted to the body-side charging port61from an external power source70by using a charging cable80. Consequently, the charger62converts the received AC power to DC power, and supplies charging electric power to the second power storage device BAT2.

One terminal65of a contact BC of the charger-side relay switch CHR, is connected to the positive electrode of the second power storage device BAT2, while the other terminal is connected to an output terminal67of the charger62. In addition, one terminal of a contact GC is connected to the negative electrode of the second power storage device BAT2, while the other terminal is connected to an output terminal68of the charger62. There is provided a contact PC that is in parallel to the contact GC on the negative electrode side and is connected in series to the limiting resistor.

The voltage sensor63measures the voltage between the output terminals67and68of the charger62, and outputs the measured value VCH to the ECU30.

The charging cable80corresponds to electric vehicle supply equipment (EVSE) in Society of Automotive Engineer (SAE) Standards, and includes a connector section81. The connector section81of the charging cable80is connected to the body-side charging port61provided in the hybrid vehicle100, and electric power from the external power source70is transmitted to the hybrid vehicle100.

Although the description will be given by showing the electric vehicle having the engine2as the vehicle inFIG. 1, the configuration of the vehicle is not limited thereto and, for example, the vehicle may also be an electric vehicle that travels only with a motor or an electric vehicle that does not have the external charging device60on the body, and the vehicle may also a hybrid vehicle that uses a fuel cell together with or instead of the engine2. In addition, the shape, the type, and the number of drive sources are not particularly limited, and it is also, possible to use not only what is called a series/parallel-type plug-in hybrid vehicle in which the power dividing mechanism4is provided and the power of the engine2is distributed to the motor generator MG1and the wheel6but also what is called a series-type hybrid vehicle in which the power of the engine2is used only for electric power generation by the motor generator MG1and the driving force of the vehicle is generated by using only the motor generator MG2or hybrid vehicles of different types.

The ECU30controls the power source system50and the inverter section20to adjust the driving force when the vehicle travels. The ECU30includes a prevention control section32that prevents the start of the engine2until the system main relay SMR2is closed. In a case where the voltage VH detected by the voltage sensor48exceeds the voltage VB2, the ECU30outputs the control signal SM2for closing the circuit to the system main relay SMR2.

In addition, a memory section31with which the rating predetermined value such as the voltage or the like, vehicle information, and a notification can be written or read may be provided in the ECU30or may also be connected to the ECU30from the outside.

Further, a notification device40is connected to the ECU30. The notification device40performs an display output that uses characters, figures, and notification sound through a monitor output display section provided in a vehicle interior. The ECU30transmits an output signal for performing the display output to the notification device40. With the input of the display output, the notification device40notifies a user of a state in which the vehicle can travel visually or through audio by using an audio output and turning on an indicator lamp.

The vehicle ECU that is not shown generates a request output PR to the first power storage device BAT1and the second power storage device BAT2. The ECU30generates a control signal PWC for driving the converter section10based on the voltages VB1and VB2and the voltages VL and VH according to the depression amount of an accelerator pedal, a vehicle speed, and the request output PR, and outputs the generated control signal PWC to the converter section10.

In addition, the ECU30generates the control signal PWI based on the rotational speed current of the motor generator MG2and the voltage VH. When the generated control signal PWI is outputted to the inverter section20, the inverter section20adjusts the rotational driving force of each of the motor generators MG1and MG2.

The ECU30further determines the state of charge SOC indicative of the remaining capacity of each of the first power storage device BAT1and the second power storage device BAT2and an output power upper limit value WOUT (in watts) thereof based on the voltages VB1and VB2and the current values I1and I2detected by the current sensors52and54. The value indicative of the state of charge. SOC is defined by the ratio of an actual charge capacity to a rating capacity and, for example, the state of charge SOC is defined as 100% when the power storage device is fully charged, and the state of charge SOC is defined as 0% when the power storage device is completely discharged.

The hybrid vehicle100of the embodiment is capable of traveling while switching between what is called HV traveling in which the hybrid vehicle100travels while switching between the engine2and the motor generator MG2, and what is called EV traveling in which the hybrid vehicle100travels with the rotational driving force of the motor generator MG2.

Next, a comparative example will be described.FIG. 2is a view showing the configuration of a hybrid vehicle200on which a power source system150of the comparative example is mounted. Note that the same part as that of the embodiment is designated by the same reference numeral and the description thereof will not be repeated.

The hybrid vehicle200of the comparative example is different from the hybrid vehicle ofFIG. 1in that, as a part of the power source system150, a second converter section110that converts the voltage of electric power supplied to the inverter section20is provided on the side of the second power storage device BAT2similarly to the first power storage device BAT1.

In the thus configured hybrid vehicle200of the comparative example, in the EV traveling in which the hybrid vehicle200travels only with the driving force from each of the motor generators MG1and MG2, together with or without the supply of electric power from the converter section10, electric power of the second power storage device BAT2of which the voltage is increased by the second converter section110is supplied to the inverter section20.

FIG. 3is a time chart showing a change of each of the voltages VL1, VL2, and VH caused by closing and opening of the system main relays SMR1and SMR2at the time of activation of the power source system50in the comparative example.

In the hybrid vehicle200, during a time period from the start of the vehicle to the establishment of a Ready-ON state in which a preparation for starting control operations required for traveling in individual parts is completed, the welding check of each contact of the system main relays SMR1and SMR2is performed. For example, the welding check is performed by switching between the closed state and the opened state of each contact.

As shown inFIG. 3, before the start of the vehicle (before time t1), the converter section10and the second converter section110are gate-blocked, and the voltage VH is about 0 V, and is not increased.

At time t1, the respective contacts B1and B2of the system main relays SMR1and SMR2are closed. At this point, the voltage VH does not rise in a case where the other contacts are normal and are opened, and the voltage VH rises as indicated by a two-dot chain line d in a case where welding occurs. As a result, by using the change of the voltage VH in this state, it is possible to perform the welding check of contacts G1and G2or P1and P2.

Next, in order to perform precharge of capacitors C11and C12, the contact P1of the system main relay SMR1and the contact P2of the system main relay SMR2are closed at time t2. In a case where there is no welding at each relay contact and the connection state is normal, the voltages VL1and VL2start to rise at this point, and the voltage VH becomes equal to the higher one of the voltages VL1and VL2.

At time t3, when the precharge is ended, the respective contacts G1and G2of the system main relays SMR1and SMR2are closed, the respective contacts P1and P2of the system main relays SMR1and SMR2are opened, and the Ready-ON state is established.

In the configuration of the comparative example, by using the two converter sections of the converter section10and the second converter section110having the same configuration, electric power is supplied to the same load. The number of converter sections increases as the number of power storage devices connected in parallel to the load increases.

In a case where the power storage devices having different power storage capacities and output voltages are connected in parallel to the load, it is necessary to provide the relay switch including the limiting resistor (hereinafter referred to as a relay switch with a precharge function) such that the inrush current does not flow in.

In addition, in the welding check, in the case where the voltage VH rises as indicated by the two-dot chain line d inFIG. 3, there is a possibility that the contacts G1and G2or the contacts P1and P2of the system main relays SMR1and SMR2are welded, but it is not possible to identify the location.

If time for the welding check for the system main relay SMR1is made different from time for the welding check for the system main relay SMR2, and the welding check for the system main relay SMR1and the welding check for the system main relay SMR2are performed separately, it takes time before the precharge of the capacitors corresponding to the system main relays SMR1and SMR2is completed and the Ready-ON state that allows traveling is established.

Further, in a case where the Ready-ON state is defined as the state in which the system main relays SMR1and SMR2are closed, it requires time to increase the value of the voltage VH on the side of the first power storage device BAT1to the value of the voltage V2(VB2) on the side of the second power storage device BAT2. As a result, a time lag between the start of the vehicle and the establishment of the Ready-ON state is increased.

In addition, in each of the system main relays SMR1and SMR2, since the relay switch including the limiting resistor is used at the contact P, the number of components is increased and the configuration of the circuit becomes complicated.

In contrast to this, in the power source system50provided in the hybrid vehicle100ofFIG. 1, the second converter section110is omitted in order to reduce a switching loss to improve power supply efficiency. Then, the voltage VL2outputted from the second power storage device BAT2is set to be higher than the voltage VL1outputted from the first power storage device BAT1. For example, when the voltage VL1applied from the first power storage device BAT1is assumed to be about 200 V, the voltage VL2is set to about 450 V.

Further, when the configuration is adopted in which the power supply efficiency is improved by directly connecting the second power storage device BAT2to the inverter section20without providing the second converter section110on the side of the second power storage device BAT2, there is a possibility that the inrush current from the side of the second power storage device BAT2flows into the path to the load.

To cope with this, in the power source system50of the embodiment shown inFIG. 1, in a case where the second power storage device BAT2having a different voltage is connected in parallel to the path to which the first power storage device BAT1is connected, after properly adjusting the voltage applied between the terminals of the system main relay SMR2such that no-load energization is performed by using the converter section10on the side of the first power storage device BAT1, the second power storage device BAT2is connected. With this, the occurrence of the inrush current is prevented while the time lag at the time of start of traveling is eliminated by using the first power storage device BAT1.

Consequently, the ECU30closes the system main relay SMR1with the activation of the power source system50, and closes the system main relay SMR2in response to the voltage VH applied to the drive device90being increased to the predetermined voltage V2(VB2).

Subsequently, by using such a relay closing procedure and the diode D3as the backflow prevention circuit in combination, the second power storage device BAT2having a relatively high voltage is directly connected to the path to the load while the backflow is prevented, and the no-load energization is performed.

FIG. 4is a time chart showing the detail of the operation in a case where processing is performed by the power source system50of the embodiment.

In the hybrid vehicle100, with the control by the ECU30, at time t11, at the start of the vehicle, an activation sequence of the power source system50including the welding check is started.

In a case where charges after the previous traveling are not completely removed and the voltage VH is not lowered as indicated by a two-dot chain line a in the drawing before time t11when the contact B1of the system main relay SMR1is closed, the ECU30determines that there is a high possibility that the contact B1and the contact G1of the system main relay SMR1are welded. At time t11, when the control signal SM1is outputted from the ECU30in response to a user's activation operation, the contact B1of the system main relay SMR1is closed. At this point, in a case where the voltage VH starts to rise as indicated by a broken line b, the ECU30determines that there is a high possibility that the contact P is welded. From time t12to time t13, the contact P1is closed with the control signal SM1from the ECU30, and the precharge of the capacitor C1is performed.

As indicated by a broken line c, in a case where the precharge is not performed even when the control signal SM1for closing the contact P1is outputted from the ECU30, there is a high possibility that a broken wire or an abnormality that the contacts P1and B1of the system main relay SMR1are kept opened occurs. In the case where the possibility of the broken wire is high, it is desirable to perform an inspection with high accuracy, e.g., an inspection that uses dedicated external diagnosis equipment additionally.

The ECU30of the hybrid vehicle100closes the system main relay SMR1at the time of the activation before closing the system main relay SMR2, and monitors the voltage VH using the voltage sensor48to perform the diagnosis of the abnormality of the system main relay SMR1including the abnormality described above.

In the embodiment, at the time point when the system main relay SMR1is closed, the Ready-ON state is assumed to be established. Accordingly, when the precharge is completed at time t13and the contacts B1and G1of the system main relay SMR1are closed, the Ready-ON state can be established at time t14.

Subsequently, preliminary voltage increase is started with the control signal PWC outputted to the converter section10from the ECU30and, at the same time, an output signal for performing the display output is transmitted to the notification device40from the ECU30. With this, the notification device40notifies the user that the vehicle can travel.

At time t15, when the increased voltage VH exceeds the value of the voltage V2(VB2) of the second power storage device BAT2, the contacts B2and G2of the system main relay SMR2are closed at time t16. Thus, by defining the state in which only the system main relay SMR1is in the ON state as the Ready-ON state, it is possible to reduce time required from the start of the vehicle to the establishment of the Ready-ON state.

Furthermore, in this embodiment, since it is not necessary to perform the welding check of the system main relay SMR2before the Ready-ON state is established, it is possible to further reduce the time.

FIG. 5is a flowchart for explaining a control process of the power source system50according to the embodiment.

When the control process is started in, response to the activation operation of the user, in step S1, the ECU30outputs the control signal SM1for closing the system main relay SMR1. The individual contacts B1, G1, and P1of the system main relay SMR1are successively closed while being subjected to the above-described abnormality diagnosis.

When the system main relay SMR1is closed, the Ready-ON state is established, and a state in which the traveling can be immediately started by using electric power from the first power storage device BAT1is established. That is, it is possible to cause the vehicle to travel by the motor traveling by rotationally driving the motor generator MG2by using only electric power from the first power storage device BAT1without the supply of electric power from the second power storage device BAT2.

In step S2, the ECU30transmits the information that the system main relay SMR1is closed with the control signal SM1and the Ready-ON state is established to the notification device40.

In step S3, the ECU30generates the control signal PWC based on the given request output PR, controls the converter section10, and increases the voltage VH applied to the inverter section20.

Next, in step S4, the ECU30acquires the value of the voltage VH of the voltage sensor48and the value of the voltage VB2of the voltage sensor44. The value of the voltage V2of the second power storage device BAT2may be the value of the voltage VB2or the average value of the voltage VB2during a predetermined time period.

In step S5, the ECU30compares the values of the voltages VH and V2, and determines whether or not the value of the voltage VH exceeds the value of the voltage V2. In a case where the value of the voltage VH exceeds the value of the voltage V2(YES in step S5), the ECU30advances the process to the next step S6.

In step S6, when the control signal SM2is outputted, the contacts B2and G2are closed.

Thus, in the case where the voltage V2of the second power storage device BAT2is higher than the voltage VL, the closing of the system main relay SMR2is prohibited until the voltage VL of the positive electrode line PL3is increased to the value of the voltage VH by the converter section10, and the contacts B2and G2of the system main relay SMR2are closed with the control signal SM2in response to the voltage VH exceeding the voltage V2. With this, the first power storage device BAT1and the second power storage device BAT2are connected in parallel to the inverter section20.

In the embodiment, the value of the voltage VB2as the actually measured value sent from the voltage sensor44and the value of the voltage VH detected by the voltage sensor48are directly compared, and are used in the determination in the ECU30. With this, it is possible to perform switching excellent in responsiveness.

Between the system main relay SMR2and the inverter section20, the second converter section110shown in the comparative example is not provided. As a result, since the second power storage device BAT2can be directly connected to the inverter section20, it is possible to eliminate the switching loss in the voltage conversion operation by the second converter section110to improve the electric power efficiency. At this point, even when the system main relay SMR2is closed in the state in which the voltage VH exceeds the voltage V2, the backflow of the current to the second power storage device BAT2is blocked by the diode D3of the backflow prevention circuit35.

The user is able to know that the power supply to the motor generator MG1is allowed at the timing when the system main relay SMR1is closed to be brought into the ON state. As a result, it is possible to start the traveling of the hybrid vehicle100before the completion, of connection of the second power storage device BAT2by the system main relay SMR2.

In addition, in a case where the voltage VH does not exceed the voltage V2(NO in step S5), the ECU30advances the process to step S7. In step S7, the prevention control for preventing the start of the engine2is executed by the prevention control section32.

The output of the motor generator MG2is limited in a case where the voltage VH applied to the inverter section20is not sufficiently high, and hence, in order to compensate for the insufficiency of the output of the motor generator MG2, the engine2becomes easy to start. When the engine2is easy to start, there is a possibility that vibrations and noises involved in the engine start are generated and an emission deteriorates. Further, there is a user's request for continuing the motor traveling without starting the engine2if possible during the EV traveling.

As the countermeasure against this, the ECU30performs a control in which the start condition of the engine2is changed from the start condition thereof during normal traveling such that the engine2becomes difficult to start. Specifically, in the present embodiment, the output power upper limit value WOUT of the first power storage device BAT1is temporarily increased to be larger than a value during the normal traveling RA.

FIG. 6is a time, chart in a case where the start prevention process is executed. Note that, the section from time t21to time t24is the same as the section from time t11to time t14ofFIG. 4so that the description thereof will not be repeated.

At time t24when the system main relay SMR1is closed and the Ready-ON state is, established, the ECU30sets the output power upper limit value WOUT of the first power storage device BAT1to a value RL larger than the value during the normal traveling RA using the prevention control section32.

With this, electric power that can be outputted from the first power storage device. BAT1is temporarily increased, and hence it is possible to increase the voltage VH early, and increase the current amount supplied to the motor generator MG2.

As a result, when the hybrid vehicle100travels only with the supply of electric power by the first power storage device BAT1, in a case where the voltage applied to the inverter section20is low at the time of start of the hybrid vehicle100, the engine2usually becomes easy to start. However, even in such a case, the drive device90continues traveling only with the driving force of the motor generator MG2without starting the engine2.

During the prevention control by the ECU30, since the motor traveling is continued, the vibrations and the noises involved in the engine start are not generated and acceleration can be performed smoothly. Further, especially during the EV traveling, it is possible to continue the EV traveling state as long as possible without starting the engine2to reflect the user's request for continuing the motor traveling, and achieve excellent drivability.

At time t26, when the value of the voltage VH reaches the value of the voltage-V2of the second power storage device BAT2, the control signal SM2is outputted from the ECU30, and the contacts B2and G2of the system main relay SMR2are closed. When the system main relay SMR2is closed, the prevention control section32returns the output power upper limit value WOUT from the increased value RL to the value during the normal traveling RA. At the time of this returning, a rate limit process for preventing a sudden change is performed.

FIG. 7is a flowchart specifically showing the start prevention of the engine2of the embodiment. When the control process by the ECU30advances to step S10from step S7ofFIG. 5, the prevention control of the start of the engine2is started by the prevention control section32.

Subsequently, in step S11, in order to prevent the unintentional start of the engine2for compensating for the insufficiency of the torque of the motor generator MG2, the output power upper limit value WOUT of the first power storage device BAT1is changed to be higher than the normal value RA.

By setting the output power upper limit value WOUT to be higher than the normal value RA, the traveling range by the motor generator MG2is enlarged, and hence the start of the engine2is prevented. Note that the output power upper limit value WOUT can fluctuate depending on temperature conditions and the state of charge SOC.

In step S12, the ECU30compares the voltage VH and the voltage V2, and determines whether or not the voltage VH exceeds the voltage V2.

In a case where the voltage VH does not exceed the voltage V2(NO in step S12), the ECU30returns the process to step S10, arithmetic processing is repeated in the prevention control section32, and the prevention control of the start of the engine2by changing the output power upper limit value WOUT is continued.

In addition, in a case where the value of the voltage VH exceeds the value of the voltage V2(YES in step S12), the ECU30advances the process to step S13, and returns the output power upper limit value WOUT to the normal value RA. Subsequently, the process is returned to step S5in the main routine shown inFIG. 5.

In the present embodiment, the ECU30of the hybrid vehicle100closes the system main relay SMR1when the power source system50is activated, and closes the system main relay SMR2in response to the voltage VH applied to the drive device90being increased to the predetermined voltage V2.

As a result, it is possible to properly connect the second power storage device BAT2to the first power storage device BAT1using the no-load energization, and it is possible to omit the second converter section110or the like to simplify the configuration.

Subsequently, when the system main relay SMR1is closed, the state in which the traveling can be started by using electric power from the first power storage device BAT1is established.

The user can recognize that a state in which the motor traveling can be started by rotationally driving the motor generator MG2without the supply of electric power from the second power storage device BAT2is established using the notification device40.

Consequently, the user does not feel the time lag between the start of the hybrid vehicle100and the establishment of the state in which the hybrid vehicle100can travel, and hence the user can start the traveling smoothly.

In addition, after the start of the traveling, in response to the voltage VH applied to the drive device90exceeding the predetermined voltage V2, the system main relay SMR2is closed. As a result, it is possible to increase the cruising distance together with the first power storage device BAT1as the high-output battery on the side of the system main relay SMR1or by switching to the second power storage device BAT2as the high-capacity battery.

The backflow prevention circuit is configured to include the diode D3. As a result, it is possible to implement the configuration in which the current does not flow back to the second power storage device BAT2even when the voltage VH exceeds the predetermined voltage V2. Consequently, it is possible to reduce the frequency of the welding check of the system main relay SMR2, and further reduce the time lag from the start of the vehicle by not performing the welding check before the Ready-ON state is established.

The start of the engine2is prevented by the prevention control section32until the system main relay SMR2is closed. As a result, even in a situation in which the engine2is normally started, the drive device90can continue the traveling only with the driving force of the motor generator MG2without starting the engine2, and maintain smooth drivability by the motor traveling.

Next, a modification of the present embodiment will be described. As another example of the method of preventing the start of the engine2, there can be used a method called changing of an upper limit guard in which the value of the rotational torque of the motor generator MG2is changed to an upper limit value NL of the rotational torque lower than a normal upper limit value NA such that the rotational torque of the motor generator MG2does not become insufficient. Hereinafter, an example of the changing of the upper limit guard of the torque limit will be described in detail in the modification.

FIG. 8is a time chart in a case where the start prevention process of the modification is executed. Note that the section from time t31to time t34is the same as the section from time t11to time t14ofFIG. 4so that the description thereof will not be repeated.

At time t34when the ECU30closes the system main relay SMR1to establish the Ready-ON state, the prevention control section32reduces the upper limit value of the rotational torque indicated by a one-dot chain line inFIG. 8from the value NA during the normal traveling of the one-dot chain line to the value NL indicated by a solid line. The value NL is the value with which the output fluctuation of the first power storage device BAT1by the output torque does not exceed WOUT.

With the operation described above, the torque of the motor generator MG2is set so as not to exceed the output power upper limit value WOUT, and hence the insufficiency of the torque is not caused and the engine2is not started.

That is, as the result, the same state as the state in which the total request output PR inputted to the ECU30is limited is established, and the start of the engine2is prevented from time t34when the Ready-ON state is started to time t35when the value of the voltage VH>the value of the voltage VB is satisfied and the system main relay SMR2is closed.

When the contacts B2and G2of the system main relay SMR2are closed at time t35, the prevention control section32returns the upper limit guard of the torque limit of the motor generator MG2to the value NA as the normal upper limit value.

FIG. 9is a flowchart specifically showing the start prevention process of the modification. When NO is selected at step S5ofFIG. 5, the ECU30causes the prevention control section32to start the prevention process of the start of the engine2at step S20.

In step S21, the change control of the upper limit value of the rotational torque of the motor generator MG2is performed by the prevention control section32, and the upper limit value is changed from the normal upper limit value NA of the rotational torque to the value NL lower than the value NA.

In step S22, the ECU30determines whether or not the value of the voltage VH exceeds the value of the voltage V2using the prevention control section32.

In a case where the value of the voltage VH does not exceed the value of the voltage V2(NO in step S12), the ECU30returns the process to step S20, repeats the prevention control process, maintains the upper limit value of the rotational torque at NL, and continues the prevention of the start of the engine2.

In a case where the value of the voltage VH exceeds the value of the voltage V2(YES in step S12), the ECU30advances the process to step S23.

In step S23, the ECU30returns the torque upper limit from the value NL to the normal value NA. Subsequently, the process is returned to step S5in the main routine.

Note that, in the embodiment and its modification described above, the control in the ECU30is actually performed by a central processing unit (CPU), the CPU reads a program having the individual steps in the flowchart from a read only memory (ROM), and executes the read program to execute the process according to the flowchart. Consequently, the ROM corresponds to a recording medium allowing reading by the computer (CPU) in which the program having the individual steps in the flowchart is recorded. Note that an electronic component configured by hardware such as an application specific integrated circuit (ASIC) in which the program part is formed as a circuit may also be used.

The embodiment described thus far will be summarized again with reference to the drawings. As shown inFIG. 1, the hybrid vehicle100has the power source system50, the drive device90, and the ECU30. The drive device90is configured to be driven with electric power supplied from the power source system50. The ECU30is configured to control the power source system50and/or the drive device90.

The power source system50includes the first power storage device BAT1, the converter section10, the second power storage device BAT2, the system main relay SMR1, and the system main relay SMR2. The converter section10is configured to convert the voltage from the first power storage device BAT1. The second power storage device BAT2is configured to be electrically connected to the path supplying the electric power subjected to the conversion in the converter section10to the drive device90, and supply electric power to the drive device90. The system main relay SMR1is configured to switch between supply and shutoff of electric power between the first power storage device BAT1and the converter section10. The system main relay SMR2is configured to switch between the supply and the shutoff of electric power from the second power storage device BAT2to the drive device90.

The ECU30of the hybrid vehicle100is configured to close the system main relay SMR1with the activation of the power source system50, and closes the system main relay SMR2in response to the voltage VH applied to the drive device90being increased to the predetermined voltage V2.

Preferably, the ECU30may further include the notification device40that provides a notification that the vehicle can travel in response to the system main, relay SMR1being closed.

Further preferably, the first power storage device BAT1may include the high-output battery, and the second power storage device BAT2may include the high-capacity battery.

Further preferably, the hybrid vehicle100may further include the backflow prevention circuit35configured to be connected between the drive device90and the system main relay SMR2and prevent the current on the side of the drive device90from flowing toward the second power storage device BAT2, and the backflow prevention circuit35may be configured to include the diode D3.

Further preferably, the drive device90may be configured to include the motor generator MG1as the load coupled to the engine2, and the ECU30may be configured to prevent the start of the engine2until the system main relay SMR2is closed.

Further preferably, the ECU30may be configured to prevent the start of the engine2by temporarily relaxing the output limit of the first power storage device BAT1.

Further preferably, the ECU30may be configured to prevent the start of the engine2by temporarily reducing the upper value NL of the rotational torque that can be outputted from the motor generator MG2.

In addition, the power source system50of the hybrid vehicle100supplies electric power to the motor generators MG1and MG2. The power source system50has the first power storage device BAT1, the converter section10, the second power storage device BAT2, the system main relay SMR1, the system main relay SMR2, and the ECU30. The converter section10is configured to convert the voltage from the first power storage device BAT1. The second power storage device BAT2is configured to be electrically connected to the path linking the converter section10and the motor generators MG1and MG2, and be capable of supplying electric power to the motor generators MG1and MG2. The system main relay SMR1is configured to switch between the supply and the shutoff of electric power between the first power storage device BAT1and the converter section10. The system main relay SMR2is configured to switch between, the supply and the shutoff of electric power from the second power storage device BAT2to the motor generators MG1and MG2. The ECU30is configured to close the system main relay SMR1with the activation of the power source system50, and close the system main relay SMR2in response to the voltage applied to the motor generators MG1and MG2being increased to the predetermined voltage.