JP2007098981A - Power unit for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power unit for a vehicle for increasing a traveling distance in EV traveling, and for improving fuel costs. <P>SOLUTION: In the case of HV traveling of a vehicle, a controller 30 puts a battery B in a serial connection state. Thus, it is possible to obtain a high motor output by a high motor driving voltage, and to achieve sufficient power performance by assisting an engine ENG even in a traveling state that large vehicle driving force is required. On the other hand, in the case of EV traveling of the vehicle, the controller 30 puts the battery B in a parallel connection state. Thus, it is possible to increase a power source capacity, and to extend the traveling distance per one charge of the battery B. Also, the input voltage of an invertor 31 is made relatively smaller than that in the case of traveling when the battery is put in the serial connection state so that it is possible to reduce the switching loss of the invertor 31. Furthermore, the carryover of the power from the battery B is restricted in response to the current restriction of the battery B, so that it is possible to further increase the traveling distance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle power supply device, and more particularly to a vehicle power supply device mounted on a hybrid vehicle.

  Recently, hybrid vehicles and electric vehicles have attracted attention as environmentally friendly vehicles. A hybrid vehicle is a vehicle that uses a motor driven by a DC power source via an inverter in addition to a conventional engine as a power source. In other words, a power source is obtained by driving the engine, a DC voltage from a DC power source is converted into an AC voltage by an inverter, and a motor is rotated by the converted AC voltage to obtain a power source.

  An electric vehicle is a vehicle that uses a motor driven by a DC power supply via an inverter as a power source.

  In such a hybrid vehicle or electric vehicle, in order to improve energy efficiency while driving the vehicle appropriately, it is required to supply electric power according to the load on the motor and efficiently recover energy during regeneration. It is done.

  Recently, many studies have been made to optimize energy efficiency in order to improve vehicle fuel efficiency (system efficiency in an electric vehicle) (see, for example, Patent Documents 1 and 2).

  For example, Patent Document 1 discloses a main circuit system of an electric vehicle that improves system efficiency by lowering an input voltage of an inverter and lowering a switching loss during low output operation of the electric vehicle.

  According to this, the battery serving as the power source of the vehicle driving AC motor is composed of two battery blocks formed by dividing a plurality of unit batteries connected in series into two parts. The two battery blocks are switched between serial connection and parallel connection by operation of a changeover switch. Specifically, when the accelerator pedal depression amount, the motor output, or the brake pedal depression amount is large, the two battery blocks are connected in series by the changeover switch. On the other hand, when the accelerator pedal depression amount, the motor output, or the brake pedal depression amount is small, the two battery blocks are connected in parallel by the changeover switch.

Thereby, since the battery voltage becomes low during the low output operation of the electric vehicle, the input voltage of the inverter also becomes low. As a result, the switching loss of the inverter can be reduced and the system efficiency of the electric vehicle can be improved.
Japanese Patent Laid-Open No. 5-236608 JP 2000-59903 A JP 2004-282800 A JP 2000-92603 A JP-A-8-237811

  However, according to the above main circuit system of an electric vehicle, when the accelerator pedal depression amount, the motor output, or the brake pedal depression amount exceeds a predetermined threshold, the battery block is immediately switched from the parallel connection to the series connection. As a result, the input voltage of the inverter is doubled, resulting in an increase in switching loss. As a result, if it is attempted to improve the power performance of the electric vehicle by improving the motor output, it is difficult to improve the system efficiency. Since the system efficiency greatly affects the distance (cruising distance) that can be traveled per charge of the electric vehicle, as a result, there is a limit to the increase of the cruising distance.

  By the way, in a hybrid vehicle, as a means of improving fuel efficiency, when the vehicle is stopped or when driving at low speed with low engine efficiency, the engine is stopped and the vehicle is driven only by the driving force of the motor (hereinafter referred to as “EV driving”). There are those equipped with a function. Therefore, for the same reason as the above-described electric vehicle, if the cruising distance in EV traveling can be extended, the fuel efficiency of the vehicle can be further improved.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a vehicular power supply device that can increase a cruising distance during EV traveling and improve fuel efficiency.

  According to this invention, the vehicle power supply device includes a first travel mode in which the engine and the motor for driving the vehicle are power sources, and a second travel mode in which the engine is stopped and only the motor is the power source. It is mounted on a vehicle having The power supply device for a vehicle includes a DC power source composed of n (n is a natural number of 2 or more) unit power sources, a drive circuit that receives a DC voltage supplied from the DC power source, and a motor running on the motor. And a control device for controlling the drive circuit so as to generate the drive force required for the operation. The control device includes a first power supply unit that configures a DC power supply by connecting n unit power supplies in series, and a second power that configures a DC power supply by connecting at least two unit power supplies out of n in parallel. Power supply means and a selection means for selecting one of the first and second power supply means according to the travel mode of the vehicle.

  According to the above-described vehicle power supply device, when a vehicle using a DC power source configured by unit power sources connected in parallel is driven, the power source capacity increases, so that the cruising distance per charge of the DC power source can be increased. it can. In addition, since the DC voltage supplied to the drive circuit is relatively lower than when traveling using a DC power supply configured with unit power supplies connected in series, the switching loss generated in the drive circuit is reduced. Is done. Furthermore, taking out the electric power from the DC power supply is restricted by the limitation of the DC current flowing through the unit power supply. Thereby, the cruising range of the vehicle is further increased. As a result, the fuel consumption of the vehicle can be improved.

  In addition, when the vehicle travels using a DC power source configured with unit power sources connected in series, high output of the motor is achieved by a high motor driving voltage. Therefore, according to the present invention, the fuel efficiency of the vehicle can be improved without deteriorating the running performance of the vehicle.

  Preferably, the selection unit selects the first power supply unit when the vehicle is in the first travel mode, and selects the second power supply unit when the vehicle is in the second travel mode.

  According to the above vehicle power supply device, a sufficient motor output can be obtained as an assist for the engine output, so that the running performance of the vehicle is ensured. In addition, the cruising distance per charge of the DC power supply can be extended, and the fuel efficiency of the vehicle can be improved.

  Preferably, the control device has a predetermined reference value provided for the power that can be output from the DC power supply, and the power supplied from the DC power supply to the drive circuit when the second power supply means is selected Set so as not to exceed the reference value.

  According to the above-described vehicle power supply device, when the vehicle travels using a DC power source configured by unit power sources connected in parallel, the carry-out of power from the DC power source is restricted. Thereby, the cruising range of the vehicle can be extended.

  Preferably, the control device permits the engine start control means to start the engine from the engine stop state based on the amount of charge of the DC power source at the time of transition from the second power supply means to the first power supply means. Further included. The engine start control means prohibits starting of the engine until the charge amount of the DC power source becomes a predetermined threshold value or less.

  According to the vehicle power supply device described above, EV traveling is continued as long as the charge amount of the DC power supply does not become a predetermined threshold value or less. As a result, the cruising range of the vehicle is further increased.

  According to the present invention, the cruising distance per charge of the DC power supply can be extended by running the vehicle using the DC power supply configured by the unit power supplies connected in parallel. On the other hand, by driving the vehicle using a DC power source constituted by unit power sources connected in series, the motor drive voltage is increased and the motor output is increased. As a result, the fuel efficiency of the vehicle can be improved without degrading the running performance of the vehicle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 1 is a schematic block diagram of a vehicle power supply device according to an embodiment of the present invention.
Referring to FIG. 1, vehicle power supply device 100 is mounted on a hybrid vehicle. Vehicle power supply device 100 includes battery B, boost converter 12, capacitors C1 and C2, inverters 14 and 31, voltage sensors 10 and 20, current sensors 22, 24 and 28, and system relays SR1 and SR2. The travel mode selection unit 40, the series / parallel switching circuit 42, and the control device 30 are provided.

  The engine ENG generates driving force using combustion energy of fuel such as gasoline as a source. The driving force generated by the engine ENG is divided into two paths by the power split mechanism 50, as indicated by the thick oblique lines in FIG. One is a path that transmits to a drive shaft that drives a wheel via a reduction gear (not shown). The other is a path for transmission to motor generator MG1.

  Although motor generators MG1 and MG2 can function as both a generator and an electric motor, as will be described below, motor generator MG1 mainly operates as a generator, and motor generator MG2 mainly operates as an electric motor.

  Specifically, motor generator MG1 is a three-phase AC rotating machine, and is used as a starter that starts engine ENG during acceleration. At this time, motor generator MG1 receives the supply of electric power from battery B, drives it as an electric motor, cranks engine ENG, and starts it.

  Further, after engine ENG is started, motor generator MG1 is rotated by the driving force of engine ENG transmitted via power split mechanism 50 to generate electric power.

  The electric power generated by motor generator MG1 is selectively used depending on the driving state of the vehicle and the amount of charge of battery B. For example, during normal traveling or sudden acceleration, the electric power generated by motor generator MG1 becomes electric power for driving motor generator MG2 as it is. On the other hand, when the charge amount of battery B is lower than a predetermined value, the electric power generated by motor generator MG1 is converted from AC power to DC power by inverter 14 and stored in battery B.

  Motor generator MG2 is a three-phase AC rotating machine, and is driven by at least one of the electric power stored in battery B and the electric power generated by motor generator MG1. The driving force of motor generator MG2 is transmitted to the drive shaft of the wheel via the speed reducer. Thus, motor generator MG2 assists engine ENG to cause the vehicle to travel, or causes the vehicle to travel only by its own driving force.

  Further, at the time of regenerative braking of the vehicle, motor generator MG2 is rotated by a wheel via a speed reducer and operates as a generator. At this time, the regenerative electric power generated by motor generator MG2 is charged to battery B via inverter 31.

  System relays SR1 and SR2 are turned on / off by signal SE from control device 30.

  Boost converter 12 includes a reactor L1, NPN transistors Q1, Q2, and diodes D1, D2. Reactor L1 has one end connected to the power supply line of battery B, and the other end connected to an intermediate point between NPN transistor Q1 and NPN transistor Q2, that is, between the emitter of NPN transistor Q1 and the collector of NPN transistor Q2. . NPN transistors Q1 and Q2 are connected in series between the power supply line and the earth line. The collector of NPN transistor Q1 is connected to the power supply line, and the emitter of NPN transistor Q2 is connected to the ground line. Further, diodes D1 and D2 for flowing current from the emitter side to the collector side are connected between the collector and emitter of each NPN transistor Q1 and Q2.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17. U-phase arm 15, V-phase arm 16, and W-phase arm 17 are provided in parallel between the power supply line and the earth line.

  The U-phase arm 15 includes NPN transistors Q3 and Q4 connected in series, the V-phase arm 16 includes NPN transistors Q5 and Q6 connected in series, and the W-phase arm 17 includes NPN transistors Q7 and Q7 connected in series. Consists of Q8. Further, diodes D3 to D8 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the NPN transistors Q3 to Q8, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of motor generator MG1. In other words, motor generator MG1 is configured such that one end of three coils of U, V, and W phases is commonly connected to a neutral point, and the other end of the U phase coil is at an intermediate point between NPN transistors Q3 and Q4. The other end of the coil is connected to the intermediate point of NPN transistors Q5 and Q6, and the other end of the W-phase coil is connected to the intermediate point of NPN transistors Q7 and Q8.

The inverter 31 has the same configuration as the inverter 14.
The battery B is composed of a secondary battery such as nickel metal hydride or lithium ion. In addition, the battery B may be a fuel cell or a capacitor. The battery B is a battery module, and includes n battery units (n is a natural number of 2 or more) connected in series as shown in FIG.

  The series / parallel switching circuit 42 switches the connection of a plurality of battery units constituting the battery B in series or in parallel. The series / parallel connection switching is performed according to a signal S / P from the control device 30 by a method described later. When the connection of the plurality of battery units is switched, the DC voltage Vb output from the battery B is within the voltage range of Vbi ≦ Vb ≦ n × Vbi, where the power supply voltage per battery unit is Vbi. The variable value can be set to an integral multiple of the power supply voltage Vbi.

  Voltage sensor 10 detects DC voltage Vb output from battery B, and outputs the detected DC voltage Vb to control device 30. Current sensor 22 detects a direct current Ib flowing through battery B and outputs the detected direct current Ib to control device 30.

  Capacitor C1 smoothes DC voltage Vb supplied from battery B, and supplies the smoothed DC voltage Vb to boost converter 12.

  Boost converter 12 boosts DC voltage Vb supplied from capacitor C1 and supplies the boosted voltage to capacitor C2. More specifically, when boosting converter 12 receives signal PWMC from control device 30, boosting converter 12 boosts DC voltage Vb according to the period during which NPN transistor Q2 is turned on by signal PWMC and supplies it to capacitor C2.

  Further, when boost converter 12 receives signal PWMC from control device 30, battery 12 is charged by stepping down the DC voltage supplied from inverter 14 and / or inverter 31 via capacitor C2.

  Capacitor C 2 smoothes the DC voltage from boost converter 12 and supplies the smoothed DC voltage to inverters 14 and 31. The voltage sensor 20 detects the voltage across the capacitor C2, that is, the output voltage Vm of the boost converter 12 (corresponding to the input voltage to the inverters 14 and 31, the same applies hereinafter), and controls the detected output voltage Vm. Output to device 30.

  When a DC voltage is supplied from battery B via capacitor C2, inverter 14 converts the DC voltage to an AC voltage based on signal PWMI1 from control device 30 to drive motor generator MG1. Thereby, motor generator MG1 is driven to generate torque according to torque command value TR1.

  Inverter 14 converts the AC voltage generated by motor generator MG1 into a DC voltage based on signal PWMI1 from control device 30 during regenerative braking of the hybrid vehicle equipped with vehicle power supply device 100, and the conversion is performed. A DC voltage is supplied to the boost converter 12 via the capacitor C2. Note that regenerative braking here refers to braking that involves regenerative power generation when the driver operating the hybrid vehicle performs a footbrake operation, or regenerative braking by turning off the accelerator pedal while the vehicle is running, although the footbrake is not operated. This includes decelerating (or stopping acceleration) the vehicle while generating electricity.

  When a DC voltage is supplied from battery B via capacitor C2, inverter 31 converts DC voltage to an AC voltage based on signal PWMI2 from control device 30 to drive motor generator MG2. Thereby, motor generator MG2 is driven to generate torque according to torque command value TR2.

  Inverter 31 also converts the AC voltage generated by motor generator MG2 into a DC voltage based on signal PWMI2 from control device 30 during regenerative braking of the hybrid vehicle on which vehicle power supply device 100 is mounted. A DC voltage is supplied to the boost converter 12 via the capacitor C2.

  Current sensor 24 detects motor current MCRT1 flowing through motor generator MG1, and outputs the detected motor current MCRT1 to control device 30. Current sensor 28 detects motor current MCRT2 flowing through motor generator MG2, and outputs the detected motor current MCRT2 to control device 30.

  Traveling mode selection unit 40 selects a traveling mode DM of the hybrid vehicle and outputs the selected traveling mode DM to control device 30.

  As travel mode DM, engine ENG is assisted by the driving force of motor generators MG1 and MG2 to drive the vehicle (hereinafter also simply referred to as “HV travel mode”), engine ENG is stopped, and motor generator MG2 is stopped. A mode for driving the vehicle with only the driving force (hereinafter, also simply referred to as “EV driving mode”) is set.

  Then, the traveling mode selection unit 40 selects either the HV traveling mode or the EV traveling mode based on the vehicle speed or the accelerator opening. For example, the traveling mode selection unit 40 selects the EV traveling mode when the vehicle speed is equal to or lower than a predetermined vehicle speed threshold value. Then, in response to the vehicle speed exceeding the vehicle speed threshold, traveling mode selection unit 40 switches traveling mode DM from the EV traveling mode to the HV traveling mode. Thus, the EV traveling mode is selected when the vehicle is stopped or traveling at low speed, while the HV traveling mode is selected during traveling that requires a large driving force such as acceleration of high-speed traveling.

  The travel mode selection unit 40 may select the travel mode DM based on an operation of an EV travel selection switch (not shown) by the driver.

  Control device 30 receives torque command values TR1, TR2 and motor rotational speeds MRN1, MRN2 from an external ECU (Electrical Control Unit) (not shown), receives DC voltage Vb from voltage sensor 10, and outputs voltage boost converter 12 from voltage sensor 20. Receives voltage Vm (that is, input voltage to inverters 14 and 31), DC current Ib from current sensor 22, motor current MCRT1 from current sensor 24, motor current MCRT2 from current sensor 28, and travel mode selection The driving mode DM is received from the unit 40.

  Based on output voltage Vm, torque command value TR1 and motor current MCRT1, control device 30 performs switching control for NPN transistors Q3-Q8 of inverter 14 when inverter 14 drives motor generator MG1 by a method described later. The signal PWMI1 is generated, and the generated signal PWM1 is output to the inverter 14.

  Control device 30 also controls switching of NPN transistors Q3-Q8 of inverter 31 when inverter 31 drives motor generator MG2 by a method described later, based on output voltage Vm, torque command value TR2, and motor current MCRT2. Signal PWMI2 is generated, and the generated signal PWMI2 is output to inverter 31.

  Furthermore, when inverter 14 (or 31) drives motor generator MG1 (or MG2), control device 30 provides DC voltage Vb, output voltage Vm, torque command value TR1 (or TR2), motor rotational speed MRN1 (or MRN2). ) And the running mode DM, a signal PWMC for switching control of the NPN transistors Q1 and Q2 of the boost converter 12 is generated and output to the boost converter 12 by a method described later.

  Furthermore, control device 30 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

FIG. 2 is a functional block diagram of the control device 30 in FIG.
Referring to FIG. 2, control device 30 includes inverter control means 301 and 302, a converter control circuit 303, and battery control means 304.

  Inverter control means 301 generates signal PWMI1 based on torque command value TR1, motor current MCRT1 and input voltage Vm, and outputs the signal to NPN transistors Q3-Q8 of inverter 14.

  More specifically, inverter control means 301 calculates a voltage to be applied to each phase coil of motor generator MG1 based on input voltage Vm, motor current MCRT1 and torque command value TR1, and based on the calculated result. A signal PWMI1 for turning on / off the NPN transistors Q3 to Q8 of the inverter 14 is generated. Then, inverter control circuit 301 outputs the generated signal PWMI1 to each NPN transistor Q3-Q8 of the inverter.

  Thereby, each of the NPN transistors Q3 to Q8 of the inverter 14 is subjected to switching control, and controls a current that flows to each phase of the motor generator MG1 so that the motor generator MG1 outputs a designated torque. In this way, the motor drive current is controlled, and the motor torque corresponding to the torque command value TR1 is output.

  Further, inverter control means 301 starts engine ENG from a stopped state based on charge amount SOC of battery B by a method described later when travel mode DM from travel mode selection unit 40 in FIG. 1 is in EV travel mode. Control the timing. That is, according to the present invention, the traveling state of the hybrid vehicle shifts from EV traveling to HV traveling at the timing controlled by the inverter control means 301.

  Inverter control means 302 calculates a voltage to be applied to each phase coil of motor generator MG2 based on input voltage Vm, motor rotational speed MRN2 and torque command value TR2, and based on the calculated result, each NPN of inverter 31 is calculated. A signal PWMI1 for turning on / off the transistors Q3 to Q8 is generated. Then, inverter control circuit 302 outputs the generated signal PWMI2 to NPN transistors Q3 to Q8 of inverter 31.

  Thereby, each of the NPN transistors Q3 to Q8 of the inverter 31 is subjected to switching control, and controls a current flowing through each phase of the motor generator MG2 so that the motor generator MG2 outputs a designated torque. In this way, the motor drive current is controlled, and a motor torque corresponding to the torque command value TR2 is output.

  Based on torque command value TR1 (or TR2), motor rotational speed MRN1 (or MRN2), DC voltage Vb, DC current Ib, output voltage Vm, and travel mode DM, converter control means 303 generates signal PWMC by a method described later. The generated signal PWMC is output to NPN transistors Q1 and Q2 of boost converter 12.

  The battery control means 304 generates a signal S / P for switching the connection of n battery units in the battery B based on the driving mode DM from the driving mode selection unit 40, and uses the generated signal S / P. Output to the series-parallel switching circuit 42. When receiving the signal S / P, the series / parallel switching circuit 42 switches the connection of n battery units by the method described below. As a result, the DC voltage Vb output from the battery B becomes a variable value that changes according to the travel mode DM.

  FIG. 3 is a diagram for explaining connection switching of n battery units constituting the battery B. FIG.

  Specifically, FIG. 3A is a diagram illustrating a configuration example of the battery B when n battery units are connected in parallel. Referring to FIG. 3A, n battery units Bu1 to Bun are composed of two battery units (for example, Bu1 and Bu2) connected in parallel, and a total of n / 2 battery units are connected in series. It consists of the structure connected to. In the present invention, as shown in FIG. 3A, the connection state of the battery B configured such that at least one set of two or more battery units connected in parallel is formed is referred to as “parallel connection”. This is called “state”.

  On the other hand, FIG.3 (b) is a figure which shows the structural example of the battery B when n battery units are connected in series. Referring to FIG. 3 (b), the n battery units Bu1 to Bun are disconnected in parallel for each set of battery units, and the negative electrode of one battery unit and the positive electrode of the other battery unit are connected. Are switched as follows. In the present invention, the connection state of the battery B configured such that all of the n battery units are connected in series as shown in FIG. 3B is referred to as a “series connection state”.

  Here, when the two connection states are compared, as is apparent from FIGS. 3A and 3B, the power supply voltage of the battery B (corresponding to the DC voltage Vb) is the parallel connection state with respect to the series connection state. About 1/2. On the other hand, with respect to the battery capacity, the parallel connection state has approximately twice the capacity of the series connection state.

  These two connection states are appropriately switched by the battery control means 304 in accordance with the travel mode DM of the hybrid vehicle.

  More specifically, when the driving mode DM of the hybrid vehicle is selected as the HV driving mode, the battery control unit 304 generates a signal S / P for setting the connection state of the battery B in a series connection state, and performs serial-parallel switching. Output to the circuit 42. The series / parallel switching circuit 42 switches the connection state of the n battery units Bu1 to Bun according to the signal S / P so as to have the configuration shown in FIG.

  On the other hand, when the travel mode DM of the hybrid vehicle is selected as the EV travel mode, the battery control means 304 generates a signal S / P for setting the connection state of the battery B in the parallel connection state, and the series / parallel switching circuit 42. Output to. The series / parallel switching circuit 42 switches the connection state of the n battery units Bu1 to Bun according to the signal S / P so as to have the configuration shown in FIG.

  Here, in the actual battery B, the connection switching of the n battery units Bu1 to Bun is performed between positive electrodes for every two adjacent battery units (for example, battery units Bu1 and Bu2) as shown in FIG. First open / close means (for example, semiconductor relay Rp1) for electrically connecting the negative electrodes, second open / close means (for example, semiconductor relay Rp4) for electrically connecting the negative electrodes, and the positive electrode of one battery unit This can be realized by providing third opening / closing means (for example, semiconductor relay Rs1) for electrically connecting the negative electrode of the other battery unit. The wiring between the battery units and the first to third opening / closing means are formed in advance on a circuit board, for example, and are integrated with the battery B by installing the battery B on the upper surface of the circuit board. .

  In FIG. 4, the first to third opening / closing means (corresponding to the semiconductor relays Rp1 to Rp6, Rs1 to Rs3) are powered by an auxiliary battery provided separately from the DC power supply B, and based on the driving mode DM. Opened and closed by the generated signal. Specifically, when the traveling mode DM is selected as the EV traveling mode, the first and second opening / closing means are closed, and the third opening / closing means is opened. Thereby, two adjacent battery units are connected in parallel. On the other hand, when the traveling mode DM is selected as the HV traveling mode, all of the first to third opening / closing means are opened. Thereby, two adjacent battery units are connected in series, and all n battery units are connected in series.

  It is obvious that the configuration of the battery units Bu1 to Bun when the battery B is in a parallel connection state is not limited to the configuration of FIG. For example, as shown in FIG. 5, if the number of battery units constituting one set of battery units is increased, the power supply voltage (DC voltage Vb) of the battery B becomes lower, while the battery capacity is reduced. It can be further increased. However, when the DC voltage Vb is lowered, the DC voltage Vb is boosted to a desired target voltage corresponding to the motor required output by the boost converter 12 and input to the inverters 14 and 31.

  As described above, the vehicle power supply device 100 according to the present invention is characterized in that the connection state of the battery B is switched in accordance with the travel mode. Thereby, the DC voltage Vb output from the battery B is set to a different voltage for each traveling state. Below, the effect which this characteristic show | plays is demonstrated.

  When the vehicle is running on HV, the connection state of the battery B is in a series connection state. That is, DC voltage Vb output from battery B is set to the maximum DC voltage n × Vbi that battery B can output (hereinafter also referred to as the maximum DC voltage, where Vbi is the power supply voltage per battery unit). The

  Therefore, during HV traveling, motor generators MG1 and MG2 are driven at a high drive voltage, so that a high driving force can be output. As a result, even in a traveling state where a large vehicle driving force is required such as acceleration during high-speed traveling, the engine ENG is assisted to achieve sufficient power performance.

  On the other hand, when the vehicle is running on EV, the connection state of the battery B is a parallel connection state. Therefore, the DC voltage Vb output from the battery B is a voltage lower than the maximum DC voltage n × Vbi described above.

  Therefore, during EV travel, motor generator MG2 for driving the vehicle is driven with a drive voltage lower than in the HV travel state, and the motor output is relatively lower than during HV travel. However, in view of the fact that EV traveling is applied when the required vehicle driving force itself is relatively lower than HV traveling, such as when traveling at low speeds in urban areas, the output of motor generator MG2 is reduced. It can be said that the influence on the running performance of the vehicle is small.

  On the other hand, paying attention to the battery B, during EV traveling, the battery capacity increases as a plurality of battery units are connected in parallel. For example, in the configuration of FIG. 3A, the battery capacity is increased approximately twice by connecting two battery units in parallel. As a result, it is possible to extend the cruising distance that can travel per charge of the battery B.

  Further, during EV travel, the input voltage Vm of the inverter 31 is lower than during HV travel, so that the loss in the inverter 31 is reduced. This is because the loss in the inverter 31 (including the steady loss and the switching loss) becomes smaller as the voltage is lower. During EV traveling, these losses are reduced, so that the cruising distance can be increased.

  Here, since the DC voltage Vb output from the battery B is low during EV traveling, a desired motor in which the DC voltage Vb is determined according to the required output according to the magnitude of the output required for the motor generator MG2. It is necessary to boost the driving voltage (corresponding to the input voltage Vm of the inverter 31). That is, boost converter 12 calculates target voltage Vdc_com of output voltage Vm (= input voltage of inverter 31) based on required torque (torque command value TR2) of motor generator MG2 and motor rotation speed MRN2, and outputs It is necessary to execute the boosting operation so that the voltage Vm becomes the calculated target voltage Vdc_com.

  When the boosting operation is executed, a direct current Ib_com necessary for setting the output voltage Vm to the target voltage Vdc_com flows through the battery B. The direct current Ib_com becomes a relatively high current as the step-up ratio (Vdc_com / Vb) increases. That is, a high current flows through the battery B when the DC voltage Vb is low.

  Here, when a high current flows through the battery B, the amount of heat generated by the internal resistance increases, the battery temperature rises, and the battery B is deteriorated. Therefore, from the viewpoint of protecting the battery B from a high current, the DC current Ib of the battery B is usually provided with a predetermined current threshold value, and the DC current Ib is controlled so as not to exceed this current threshold value. Current limiting is performed.

  Therefore, when the current limitation of battery B is performed, the power taken out from battery B is suppressed to a power lower than the required output of motor generator MG2. According to this, during EV travel, the cruising distance per charge of the battery B is increased by limiting the power output from the battery B.

  As described above, according to the present invention, when the hybrid vehicle is in EV traveling, the battery B is connected in parallel, so the cruising distance per charge of the battery B can be extended. As a result, the fuel efficiency of the hybrid vehicle is improved.

  Here, the vehicle power supply device 100 of the present invention is further characterized in that a limit is imposed on the electric power output from the battery B during EV traveling in order to further increase the cruising distance during EV traveling. The output limitation of the battery B is executed by the converter control unit 303 in FIG. 2 as described below.

FIG. 6 is a functional block diagram of converter control means 303 in FIG.
Referring to FIG. 6, converter control means 303 includes a voltage command calculation unit 60, a converter duty ratio calculation unit 62, and a converter PWM signal conversion unit 64.

  The voltage command calculation unit 60 is configured to optimize the inverter input voltage based on the torque command value TR1 (or TR2) and the motor rotational speed MRN1 (or MRN2) from the external ECU and the travel mode DM from the travel mode selection unit 40. A value (target value), that is, voltage command value Vdc_com of boost converter 12 is determined, and the determined voltage command value Vdc_com is output to converter duty-ratio calculation unit 62.

  Specifically, voltage command calculation unit 60 provides a predetermined reference value Wout_std in advance for electric power (hereinafter also referred to as battery output) Wout that can be output from battery B when traveling mode DM is in EV traveling mode. The voltage command value Vdc_com is determined so that the output power Pb of B does not exceed the reference value Wout_std.

  Note that the output power Pb of the battery B corresponds to the power supplied from the battery B to the inverter 31 via the boost converter 12. Voltage command value Vdc_com is derived based on motor request output Pcom which is the product of torque command value TR2 of motor generator MG2 and motor rotation speed MRN2.

Therefore, voltage command calculation unit 60 determines voltage command value Vdc_com so that output power Pb of battery B satisfies the relationship of the following equation.
Pb ≦ Wout_std (1)
Next, converter duty-ratio calculation unit 62 receives voltage command value Vdc_com from voltage command calculation unit 60 and receives DC voltage Vb from voltage sensor 10, and based on DC voltage Vb, inverter 14 (or 31) A duty ratio DR for setting the input voltage Vm to the voltage command value Vdc_com is calculated. Then, converter duty-ratio calculation unit 62 outputs the calculated duty ratio DR to converter PWM signal conversion unit 64.

  Converter PWM signal converter 64 generates signal PWMC for turning on / off NPN transistors Q1 and Q2 of boost converter 12 based on duty ratio DR from converter duty ratio calculator 62, and the generated signal PWMC is output to boost converter 12.

  FIG. 7 is a diagram illustrating a relationship between the motor request output Pcom and the output power Pb of the battery B during EV travel.

  As is apparent from FIG. 7, as the motor request output Pcom increases, the power Pb output from the battery B increases monotonously along the straight line LN1. As a result, during EV traveling, driving force necessary for vehicle traveling is generated in motor generator MG2.

  However, when the output power Pb of the battery B exceeds the reference value Wout_std of the battery output, the output power Pb of the battery B increases to the reference value Wout_std as shown by the straight line LN2 even though the motor required output Pcom increases. Fixed. This makes it difficult to always satisfy the motor request output Pcom during EV travel. Therefore, the vehicle is restricted to travel with a high load. However, since the power take-out from the battery B is limited, the cruising distance can be increased.

  Note that when it is determined that the vehicle travel characteristics (or the driver's driving feeling) are significantly deteriorated because the output power Pb of the battery B does not satisfy the motor required output Pcom during high-load traveling, If the output restriction is removed, the cruising distance can be increased without impairing the running characteristics of the vehicle.

  In addition to the limitation of the output power Pb from the battery B, the vehicle power supply device 100 according to the present invention has a state of charge (SOC) of the battery B equal to or less than a predetermined threshold value during EV traveling. Until this time, the engine ENG is prohibited from starting, that is, switching to the HV traveling mode is prohibited. The engine start prohibition control is executed by the inverter control means 301 in FIG.

FIG. 8 is a functional block diagram of the inverter control means 301 in FIG.
Referring to FIG. 8, inverter control unit 301 includes a motor control phase voltage calculation unit 70, an inverter PWM signal conversion unit 72, and an SOC detection unit 74.

  Motor control phase voltage calculation unit 70 receives output voltage Vm of boost converter 12, that is, an input voltage to inverter 14, from voltage sensor 20, and receives motor current MCRT1 flowing in each phase of motor generator MG1 from current sensor 24. The torque command value TR1 is received from the external ECU. Then, motor control phase voltage calculation unit 70 calculates a voltage to be applied to each phase coil of motor generator MG1 based on torque command value TR1, motor current MCRT1 and voltage Vm, and uses the calculated result for the inverter. Output to the PWM signal converter 72.

  Based on the calculation result received from motor control phase voltage calculation unit 70, inverter PWM signal conversion unit 72 generates signal PWMI1 that actually turns on / off each NPN transistor Q3-Q8 of inverter 14, and generates the signal PWMI1. The signal PWMI4 is output to the NPN transistors Q3 to Q8 of the inverter 13.

  Thereby, each of the NPN transistors Q3 to Q8 of the inverter 14 is switching-controlled, and controls the current flowing through each phase of the motor generator MG1 so that the motor generator MG1 outputs the commanded torque. In this way, the motor drive current is controlled, and the motor torque corresponding to the torque command value TR1 is output.

  The SOC detection means 74 receives the driving mode DM from the driving mode selection unit 40, receives the DC voltage Vb from the voltage sensor 10, and receives the DC current Ib from the current sensor 22. Then, SOC detection means 74 calculates the SOC of battery B based on DC voltage Vb and DC current Ib when travel mode DM is in EV travel mode.

  Then, the SOC detection means 74 controls the timing for starting the engine ENG from the stop state based on the calculated SOC during EV traveling. Specifically, the SOC detection means 74 generates a signal STP for prohibiting the engine ENG from starting from a stopped state when the SOC of the battery B is larger than a predetermined threshold value set in advance. Output to the inverter PWM signal converter 72. When receiving the signal STP, the inverter PWM signal converter 72 stops generating the signal PWMI1 for turning on / off the NPN transistors Q3 to Q8 of the inverter 14.

  As a result, drive control of motor generator MG1 by inverter 14 is not performed, so that the motor torque necessary for starting engine ENG is not output, and starting of engine ENG is prohibited. As a result, the hybrid vehicle continues the EV travel until the SOC of battery B falls below a predetermined threshold value.

  Normally, in a hybrid vehicle, if the vehicle speed or the accelerator opening exceeds a predetermined threshold value while the vehicle is running on EV, the engine ENG is started from a stopped state and switched to HV running. In contrast, in the hybrid vehicle according to the present invention, even if the vehicle speed or the accelerator opening exceeds a predetermined threshold value, the engine ENG is used as long as the SOC of the battery B does not fall below the predetermined threshold value. Starting is prohibited. Therefore, the hybrid vehicle according to the present invention has a longer EV traveling period than a normal hybrid vehicle. Thereby, it becomes possible to further improve the cruising distance during EV travel.

  As described above, according to the embodiment of the present invention, when the hybrid vehicle performs EV traveling, battery B is switched from the serial connection to the parallel connection. As a result, the capacity of the battery B is increased and the loss of the inverter 31 is reduced. Therefore, the cruising distance during EV traveling can be extended, and the fuel efficiency of the vehicle is improved. In particular, by limiting the output power from battery B and controlling the timing of switching to HV traveling based on the SOC, the cruising distance during EV traveling can be further extended.

  Further, when the hybrid vehicle performs HV traveling, since the battery B is connected in series, the motor drive voltage can be increased to increase the output of the motor. Thereby, the running performance of the vehicle is ensured.

  In the present embodiment, from the viewpoint of increasing the cruising distance and improving fuel efficiency, the configuration in which the battery B is connected in series during HV traveling and the battery B is connected in parallel during EV traveling has been described. By adopting such a configuration, it is possible to newly realize the traveling of the vehicle with an emphasis on traveling performance.

  That is, since the battery B is connected in parallel during the HV traveling, the vehicle driving force depends solely on the engine output, but the battery B is connected in series during the EV traveling, so that the motor output can be increased. As a result, not only environmental performance but also traveling performance can be improved.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to a vehicle power supply device mounted on a hybrid vehicle.

1 is a schematic block diagram of a vehicle power supply device according to an embodiment of the present invention. It is a functional block diagram of the control apparatus in FIG. 4 is a diagram for explaining connection switching of n battery units constituting a battery B. FIG. 4 is a circuit diagram for explaining connection switching of n battery units constituting a battery B. FIG. It is a figure which shows the other structural example of the battery B when n battery units are connected in parallel. It is a functional block diagram of the converter control means in FIG. It is a figure which shows the relationship between the motor request | requirement output Pcom at the time of EV driving | running | working, and the output electric power Pb of the battery B. FIG. It is a functional block diagram of the inverter control means in FIG.

Explanation of symbols

  10, 20 Voltage sensor, 12 Boost converter, 14, 31 Inverter, 15 U-phase arm, 16 V-phase arm, 17 W-phase arm, 22, 24, 28 Current sensor, 30 Control device, 40 Traveling mode selection unit, 42 Parallel switching circuit, 50 power split mechanism, 60 voltage command calculation unit, 62 converter duty ratio calculation unit, 64 converter PWM signal conversion unit, 100 vehicle power supply device, 301, 302 inverter control unit, 303 converter control unit, 304 Battery control means, B battery, Bu1 to Bu6 battery unit, Rp1 to Rp6, Rs1 to Rs3 Semiconductor relay, Q1 to Q8 NPN transistor, D1 to D8 diode, C1, C2 capacitor, ENG engine, L1 inductor, MG1, MG2 motor generator , SR1, SR2 system relay.

Claims (4)

A vehicle power supply mounted on a vehicle having a first travel mode using an engine and a motor for driving the vehicle as a power source, and a second travel mode using the engine as a power source only with the motor as a power source A device,
a direct current power source composed of n (n is a natural number of 2 or more) unit power sources;
A drive circuit for driving the motor by receiving a DC voltage from the DC power supply;
A control device for controlling the drive circuit so as to generate a driving force necessary for traveling of the vehicle in the motor;
The controller is
First power supply means for connecting the n unit power supplies in series to constitute the DC power supply;
A second power supply unit configured to connect the at least two unit power sources out of the n units in parallel to constitute the DC power source;
A vehicle power supply apparatus comprising: selection means for selecting one of the first and second power supply means according to a travel mode of the vehicle.   The selection means selects a first power supply means when the vehicle is in a first travel mode, and selects the second power supply means when the vehicle is in a second travel mode. The vehicle power supply device according to 1.   The control device has a predetermined reference value provided for electric power that can be output from the DC power supply, and supplies electric power supplied from the DC power supply to the drive circuit when the second power supply means is selected. The vehicle power supply device according to claim 2, wherein the vehicle power supply device is set so as not to exceed the predetermined reference value. The control device allows the engine to be started from the engine stop state based on a charge amount of the DC power source at the time of transition from the second power supply unit to the first power supply unit. Further comprising start control means,
The vehicle power supply device according to claim 2, wherein the engine start control means prohibits starting of the engine until a charge amount of the DC power supply becomes a predetermined threshold value or less.

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