JP2017154582A - Hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid vehicle configured so that either of front wheels and rear wheels are driven by an internal combustion engine and a first electric motor and the other are driven by a second electric motor, which suppresses fuel economy from being deteriorated unexpectedly by unnecessarily maintaining a stopping state of the internal combustion engine.SOLUTION: If an engine 2 is in a stopping state and when driving force required by a vehicle exceeds a predetermined value (rated torque A of a motor generator 10) during traveling of the vehicle by the motor generator 10, when a condition for permitting decrease in charging quantities of an electrification device 16 is satisfied, an ECU 26 maintains the stopping state of the engine 2 and increases an allocation of driving force of a motor generator 28. On the other hand, unless the condition is satisfied, the ECU 26 starts the engine 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hybrid vehicle, and more particularly to a hybrid vehicle in which one of a front wheel and a rear wheel is driven by an internal combustion engine and a first electric motor, and the other is driven by a second electric motor.

  Japanese Patent Laying-Open No. 2004-162670 (Patent Document 1) discloses a hybrid vehicle in which one of a front wheel and a rear wheel is driven by an engine and a first electric motor, and the other is driven by a second electric motor. In this hybrid vehicle, the output of the second electric motor increases when the required driving force of the vehicle exceeds the output limit value of the first electric motor. The engine is started when the required driving force of the vehicle exceeds the sum of the output limit values of the first and second motors. According to this hybrid vehicle, the engine stop state can be maintained until the required driving force of the vehicle exceeds the sum of the output limit values of the first and second electric motors (see Patent Document 1).

JP 2004-162670 A

  However, in the hybrid vehicle disclosed in Patent Document 1, the engine stop state is maintained until the required driving force of the vehicle exceeds the sum of the output limit values of the first and second electric motors. The electric power consumed by the second electric motor is increased. When the SOC of the power storage device greatly decreases due to the consumption of electric power by the first and second motors, the engine frequently operates to charge the power storage device in accordance with the decrease in the SOC. As a result, fuel consumption may worsen on the contrary.

  The present invention has been made to solve such a problem, and an object thereof is to drive one of the front wheels and the rear wheels by the internal combustion engine and the first electric motor, and drive the other by the second electric motor. In the hybrid vehicle, the fuel consumption is suppressed from deteriorating by maintaining the stopped state of the internal combustion engine more than necessary.

  A hybrid vehicle according to the present invention includes an internal combustion engine and a first electric motor capable of outputting a driving force to one of a front wheel and a rear wheel, a second electric motor capable of outputting a driving force to the other of the front wheel and the rear wheel, and a power storage device. And a control device. The power storage device stores electric power for driving the first and second electric motors. The control device controls the internal combustion engine and the first and second electric motors while controlling the driving force distribution of the first and second electric motors according to the required driving force of the vehicle. When the internal combustion engine is in a stopped state and the required driving force exceeds a predetermined value while traveling by the first electric motor, a condition for allowing a reduction in the charge amount of the power storage device is satisfied Maintains the stopped state of the internal combustion engine and increases the driving force distribution of the second electric motor. When the above condition is not satisfied, the internal combustion engine is started.

  In this hybrid vehicle, when the required driving force exceeds a predetermined value, the driving force distribution of the second electric motor does not always increase, and the condition for allowing the charge amount of the power storage device to decrease is satisfied. The driving force distribution of the second electric motor increases. In the case where a reduction in the charge amount of the power storage device can be tolerated, the internal combustion engine does not operate to charge the power storage device, and the fuel consumption does not deteriorate. The internal combustion engine is started as necessary when a condition for allowing a reduction in the charge amount of the power storage device is not satisfied. Accordingly, it is possible to suppress the deterioration of fuel consumption by maintaining the stopped state of the internal combustion engine more than necessary.

  According to the present invention, in a hybrid vehicle in which one of the front wheels and the rear wheels is driven by the internal combustion engine and the first electric motor and the other is driven by the second electric motor, the stop state of the internal combustion engine is maintained more than necessary. On the other hand, it can suppress that a fuel consumption deteriorates.

It is a block diagram for demonstrating the whole structure of a hybrid vehicle. It is a figure for demonstrating CD mode and CS mode. It is a figure for demonstrating an example of the driving force distribution of a motor generator, and the change of the operating state of an engine with respect to the change of a vehicle request | requirement driving force. It is a flowchart which shows the process sequence of driving force distribution control.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals and description thereof will not be repeated.

(Embodiment 1)
[Configuration of hybrid vehicle]
FIG. 1 is a block diagram for illustrating the overall configuration of a hybrid vehicle according to the first embodiment of the present invention. Referring to FIG. 1, hybrid vehicle 100 includes an engine 2, drive devices 21 and 22, transmission gears 8 and 9, drive shafts 12 and 13, front wheels 14, rear wheels 15, and power storage device 16. Is provided. Hybrid vehicle 100 further includes a power converter 23, a connection unit 24, and an ECU (Electronic Control Unit) 26.

  In the hybrid vehicle 100, the engine 2 and the driving device 21 can output driving force (torque) to the front wheels 14, and the driving device 22 can output driving force to the rear wheels 15. The hybrid vehicle 100 is a so-called four-wheel drive vehicle (4WD vehicle) that can output a driving force to each of the front wheels 14 and the rear wheels 15.

  The engine 2 is an internal combustion engine that outputs power by converting thermal energy from combustion of fuel into kinetic energy of a moving element such as a piston or a rotor.

  Drive device 21 includes a power split device 4, motor generators 6, 10, and power converters 18, 20. Motor generators 6 and 10 are AC rotating electric machines, and are constituted by, for example, a three-phase AC synchronous motor. The motor generator 6 is used as a generator driven by the engine 2 via the power split device 4 and also as an electric motor for starting the engine 2. The motor generator 10 mainly operates as an electric motor and drives the drive shaft 12. On the other hand, when braking the vehicle or reducing acceleration on a downward slope, the motor generator 10 operates as a generator and performs regenerative power generation.

  The power split device 4 includes, for example, a planetary gear mechanism having three rotation shafts of a sun gear, a carrier, and a ring gear. Power split device 4 divides the driving force of engine 2 into power transmitted to the rotation shaft of motor generator 6 and power transmitted to transmission gear 8. The transmission gear 8 is connected to a drive shaft 12 for driving the front wheels 14. Transmission gear 8 is also coupled to the rotating shaft of motor generator 10.

  The power storage device 16 is a rechargeable DC power supply, and is configured by a secondary battery such as a nickel metal hydride battery or a lithium ion battery, for example. The power storage device 16 supplies power to the power converters 18 and 20. The power storage device 16 is charged by receiving the generated power when the motor generator 6 and / or 10 generates power. Note that a large-capacity capacitor can also be employed as the power storage device 16.

  The state of charge of the power storage device 16 is indicated by an SOC (State Of Charge) that represents the current power storage amount with respect to the fully charged state of the power storage device 16 as a percentage. The SOC is calculated based on, for example, the output voltage and / or input / output current of the power storage device 16 detected by a voltage sensor and / or current sensor (not shown). The SOC may be calculated by an ECU provided separately in the power storage device 16, or may be calculated by the ECU 26 based on the output voltage of the power storage device 16 and / or the detected value of the input / output current.

  Power converter 18 performs bidirectional DC / AC power conversion between motor generator 6 and power storage device 16 based on a control signal received from ECU 26. Similarly, power converter 20 performs bidirectional DC / AC power conversion between motor generator 10 and power storage device 16 based on a control signal received from ECU 26. Thereby, motor generators 6 and 10 can output a positive torque for operating as an electric motor or a negative torque for operating as a generator, with the transfer of electric power to and from power storage device 16. . It is also possible to arrange a boost converter for DC voltage conversion between power storage device 16 and power converters 18 and 20.

  Drive device 22 includes a motor generator 28 and a power converter 29. Motor generator 28 is an AC rotating electric machine, and is constituted by, for example, a three-phase AC synchronous motor. The motor generator 28 mainly operates as an electric motor and drives the drive shaft 13. On the other hand, when braking the vehicle or reducing acceleration on a downward slope, the motor generator 28 operates as a generator to perform regenerative power generation. The rotation shaft of the motor generator 28 is connected to the transmission gear 9, and the transmission gear 9 is connected to the drive shaft 13 for driving the rear wheel 15.

  Power converter 29 performs bidirectional DC / AC power conversion between motor generator 28 and power storage device 16 based on a control signal received from ECU 26. Thereby, motor generator 28 can output a positive torque for operating as an electric motor or a negative torque for operating as a generator, with the transfer of electric power to and from power storage device 16.

  Based on a control signal received from ECU 26, power converter 23 converts power supplied from a power source (not shown) external to the vehicle electrically connected to connection unit 24 into a voltage level of power storage device 16. Output to power storage device 16 (hereinafter, charging of power storage device 16 by a power supply external to the vehicle is also referred to as “external charging”).

  The ECU 26 includes a CPU (Central Processing Unit), a storage device, an input / output buffer, and the like (all not shown), and controls each device in the hybrid vehicle 100. Note that these controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuit).

  As a main function of the ECU 26, there is a function of distributing the required driving force (required torque) of the vehicle to the motor generators 10, 28 and the engine 2. For example, when the required driving force exceeds a predetermined value Tr1 (described later) in a state where the vehicle driving force is generated only by the motor generator 10, the amount of charge (for example, SOC) of the power storage device 16 is reduced. When permitted, ECU 26 distributes a part of the requested driving force to motor generator 28. On the other hand, when the required driving force exceeds the predetermined value Tr1, if the reduction in the charge amount of the power storage device 16 is not allowed, the ECU 26 starts the engine 2 to supplement the driving force. This function will be described in detail later.

  Further, the ECU 26 executes traveling control for controlling traveling of the vehicle by selectively applying a CD (Charge Depleting) mode and a CS (Charge Sustaining) mode. Hereinafter, the CD mode and the CS mode will be described first. Then, the distribution control of the driving force to the motor generators 10 and 28 and the engine 2 will be described.

[Description of CD mode / CS mode]
FIG. 2 is a diagram for explaining the CD mode and the CS mode. Referring to FIG. 2, for example, it is assumed that traveling is started in the CD mode after power storage device 16 is fully charged by external charging.

  The CD mode is a mode in which the SOC is consumed, and basically consumes electric power (mainly electric energy by external charging) stored in the power storage device 16. That is, the CD mode is a mode that allows a reduction in SOC. When traveling in the CD mode, the engine 2 does not operate in order to maintain the SOC. As a result, the SOC may temporarily increase due to the regenerative power collected when the vehicle decelerates or the power generated by the operation of the engine 2, but as a result, the rate of discharge rather than charging As a whole, the SOC decreases as the travel distance increases.

  The CS mode is a mode for maintaining the SOC at a predetermined level. As an example, when the SOC decreases to a predetermined value SL indicating a decrease in SOC at time t1, the CS mode is selected, and the subsequent SOC is controlled within the control range RNG. That is, the CS mode is a mode that does not allow the SOC to fall below the lower limit of the control range RNG. Specifically, the engine 2 operates when the SOC reaches the lower limit (engine start threshold value) of the control range RNG, and the engine 2 stops when the SOC reaches the upper limit of the control range RNG. Thus, the SOC is controlled within the control range RNG by appropriately repeating the operation and stop of the engine 2 (intermittent operation). As described above, in the CS mode, the engine 2 operates to maintain the SOC.

  Even in the CD mode, the engine 2 operates if a large driving force is required. On the other hand, even in the CS mode, the engine 2 stops when the SOC increases. That is, the CD mode is not limited to the EV travel that travels while the engine 2 is always stopped, and the CS mode is not limited to the HV travel that travels while the engine 2 is always operated. In both the CD mode and the CS mode, EV running and HV running are possible.

[Problems caused by maintaining the stopped state of the internal combustion engine more than necessary]
In the hybrid vehicle 100 described above, it is conceivable to keep the engine 2 stopped as long as the required driving force of the vehicle can be satisfied by the motor generators 10 and 28. This is because fuel is not consumed while the engine 2 is stopped, and it is considered that fuel efficiency is good at first glance.

  However, the amount of power consumed by motor generators 10 and 28 increases as engine 2 does not operate. When the SOC of power storage device 16 is greatly reduced due to the consumption of electric power by motor generators 10, 28, engine 2 is operated and fuel is consumed to charge power storage device 16. If the engine 2 is frequently operated to charge the power storage device 16, the fuel consumption may be deteriorated.

  For example, during the CS mode and when the engine 2 is stopped, the required driving force of the vehicle is a predetermined value Tr1 (a value obtained by subtracting the reaction torque associated with the start of the engine 2 from the rated torque of the motor generator 10). (Details will be described later)), it is assumed that a part of the required driving force is distributed to the motor generator 28 without starting the engine 2. In this case, the electric power consumed by motor generators 10 and 28 increases, and the SOC of power storage device 16 may immediately fall to the engine start threshold value. When the SOC reaches the engine start threshold value, the engine 2 is started. Electric power is also consumed for starting the engine 2. Therefore, if the engine 2 is frequently started and stopped during the CS mode, the fuel consumption deteriorates.

  Therefore, in hybrid vehicle 100 according to the first embodiment, when engine 2 is in a stopped state and the required driving force of the vehicle exceeds predetermined value Tr1 while traveling by motor generator 10, power storage device 16 In the CD mode in which a decrease in the charging amount is allowed, the ECU 26 maintains the stopped state of the engine 2 and increases the driving force distribution of the motor generator 28. On the other hand, when the engine 2 is stopped and the required driving force of the vehicle exceeds the predetermined value Tr1 while the motor generator 10 is running, the ECU 26 operates the engine 2 in the CS mode in which the decrease in the SOC is not allowed. Start.

  As described above, in hybrid vehicle 100, when the required driving force exceeds predetermined value Tr1, the driving force distribution of motor generator 28 does not always increase, and the condition for allowing a reduction in the charge amount of power storage device 16 is allowed. The driving force distribution of the motor generator 28 increases only when the above holds (during the CD mode). When the reduction in the charge amount of the power storage device 16 can be allowed, the engine 2 does not operate to charge the power storage device 16, and the fuel consumption does not deteriorate. And when the conditions which permit the fall of the charge amount of the electrical storage apparatus 16 are not satisfied (in CS mode), the engine 2 is started as needed. As a result, it is possible to prevent the fuel consumption from deteriorating by maintaining the stopped state of the engine 2 more than necessary.

  In the above description, the determination value for determining whether or not to distribute the driving force to the motor generator 28 or the engine 2 is not the rated torque of the motor generator 10 but the predetermined value Tr1 for the following reason. That is, in the configuration of hybrid vehicle 100, engine 2 is started by motor generator 6. When the motor generator 6 is driven to start the engine 2, a reaction force is generated on the drive shaft 12 through the power split device 4. In order to satisfy the required driving force, it is necessary to cancel this reaction force. In hybrid vehicle 100, the reaction force is canceled by increasing the output of motor generator 10. The torque required to cancel this reaction force is hereinafter referred to as torque A. In order to start the engine 2 as necessary, the motor generator 10 needs to be in a state where the torque A can be output at any time. Therefore, the predetermined value Tr1 is a value obtained by subtracting the torque A from the rated torque of the motor generator 10. As a result, the motor generator 10 can always output the torque A for starting the engine 2 even when the driving force is being output to the front wheels 14.

  FIG. 3 is a diagram for explaining an example of a change in driving force distribution of motor generator 28 and an operating state of engine 2 with respect to a change in required driving force of hybrid vehicle 100. Referring to FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the required driving force of the vehicle, the SOC of power storage device 16, the CD mode / CS mode, the driving force distribution of motor generator 28, and the operation of engine 2 from the top. Indicates the state.

  At times t0 to t1, the required driving force of the vehicle is equal to or less than a predetermined value Tr1. Further, since SOC of power storage device 16 has not decreased to predetermined value SL (FIGS. 2 and 3), hybrid vehicle 100 travels in the CD mode. In this case, the requested driving force is not distributed to the motor generator 28, and the engine 2 is not started. The required driving force is satisfied only by driving the motor generator 10.

  At times t1 to t2, the required driving force of the vehicle exceeds a predetermined value Tr1. Since SOC of power storage device 16 has not decreased to predetermined value SL, hybrid vehicle 100 travels in the CD mode. The CD mode is basically a mode in which SOC is consumed. In the CD mode, since the reduction of the SOC is allowed, the ECU 26 distributes a part of the required driving force to the motor generator 28. That is, the ECU 26 increases the distribution of the requested driving force to the motor generator 28.

  When the SOC of power storage device 16 decreases to a predetermined value SL at time t3, the mode of hybrid vehicle 100 is switched to the CS mode.

  From time t4 to t5, the required driving force of the vehicle again exceeds the predetermined value Tr1. When the mode of the hybrid vehicle 100 is switched to the CS mode at the time t3, the CS mode is a mode for maintaining the SOC, and therefore, a decrease in the SOC is not allowed in the CS mode. Therefore, the requested driving force is not distributed to the motor generator 28 and the engine 2 is started. As described above, in hybrid vehicle 100 according to the first embodiment, when the above-described conditions are not satisfied (in the CS mode), engine 2 is started as necessary. Hereinafter, a specific processing procedure of the driving force distribution control when the engine 2 is stopped and the hybrid vehicle 100 is traveling by the motor generator 10 will be described.

[Processing procedure for driving force distribution control]
FIG. 4 is a flowchart showing a processing procedure for driving force distribution control. This flowchart explains the operation during EV traveling by the motor generator 10 when the engine 2 is stopped.

  Referring to FIG. 4, ECU 26 determines whether or not the required driving force of the vehicle exceeds predetermined value Tr1 (step S100). If it is determined that the required driving force does not exceed predetermined value Tr1 (NO in step S100), the required driving force can be satisfied only by motor generator 10, and therefore the process proceeds to return.

  If it is determined that the required driving force exceeds predetermined value Tr1 (YES in step S100), ECU 26 determines whether the required driving force is equal to or less than predetermined value Tr2 (step S110). Predetermined value Tr2 is a value obtained by subtracting torque A (described above) from the sum of the rated torques of motor generators 10 and 28.

  If it is determined that the required driving force is equal to or less than predetermined value Tr2 (YES in step S110), ECU 26 determines whether or not the mode of hybrid vehicle 100 is the CD mode (step S130). If it is determined that the current mode is the CD mode (YES in step S130), the reduction in the amount of charge of power storage device 16 can be allowed, so ECU 26 increases the driving force distribution of motor generator 28 (step S140). Specifically, the ECU 26 increases the driving force distribution of the motor generator 28 until the driving force distributed to the motor generator 10 becomes a predetermined value Tr1 or less. Thereafter, the process proceeds to return.

  If it is determined in step S130 that the current mode is not the CD mode (the CS mode) (NO in step S130), the ECU 26 starts the engine 2 because the reduction in the charge amount of the power storage device 16 cannot be permitted. Step S120). Thereafter, the process proceeds to return.

  If it is determined in step S110 that the required driving force exceeds predetermined value Tr2 (NO in step S110), ECU 26 starts engine 2 because the required driving force cannot be satisfied by motor generators 10 and 28 alone. (Step S120). In this embodiment, the engine 2 is started when the required driving force exceeds the predetermined value Tr2, but such control is not necessarily performed. For example, the engine 2 may be started when a predetermined value smaller than the predetermined value Tr2 is exceeded.

  As described above, in hybrid vehicle 100 according to the first embodiment, when engine 2 is stopped and hybrid vehicle 100 is traveling by motor generator 10, the required driving force of the vehicle exceeds predetermined value Tr1. In this case, when the condition for permitting the decrease in the charge amount of the power storage device 16 is not satisfied (during the CS mode), the ECU 26 starts the engine 2. As a result, it is possible to prevent the fuel consumption from deteriorating by maintaining the stopped state of the engine 2 more than necessary.

(Other embodiments)
As described above, the first embodiment has been described as the embodiment of the present invention. However, the present invention is not necessarily limited to the first embodiment. Here, an example of another embodiment will be described.

  In the first embodiment, when hybrid vehicle 100 is in the CD mode, it is assumed that the condition for allowing a reduction in the charge amount of power storage device 16 is satisfied, and that the above condition is not satisfied when in CS mode. However, the conditions for allowing the charge amount of power storage device 16 to decrease are not limited to this.

  For example, when the SOC of the power storage device 16 exceeds the EV threshold, the hybrid vehicle 100 performs EV traveling. When the SOC is equal to or less than the EV threshold, the hybrid vehicle 100 performs HV traveling. The above condition may be satisfied when the SOC of the device 16 exceeds a predetermined value (> EV threshold).

  Further, assuming that the hybrid vehicle 100 includes a car navigation device (not shown), for example, when there is a downward slope on the planned route of the hybrid vehicle 100, the ECU 26 may satisfy the above condition. This is because power consumption is suppressed in this case, so that a reduction in the amount of charge of the power storage device 16 can be allowed as compared with a case where there is no downward gradient. Further, when it is determined from the output of the car navigation device that the hybrid vehicle 100 is traveling in a residential area or near the destination, the ECU 26 may satisfy the above condition. This is because when the vehicle is traveling in a residential area or near the destination, the operation of the engine 2 is suppressed to suppress noise and the like, and a reduction in the charge amount of the power storage device 16 is allowed.

  In the first embodiment, drive device 21 includes motor generators 6 and 10, and engine 2 is started by motor generator 6. However, the system configuration is not limited to this. For example, the engine 2 may be started by a starter different from the motor generator 6. In this case, when the required driving force of the vehicle exceeds the rated torque of the motor generator 10, the ECU 26 determines whether to increase the driving force distribution of the motor generator 28 or to start the engine 2. May be.

  In the first embodiment, the front wheels 14 are driven by the engine 2 and the motor generator 10, and the rear wheels 15 are driven by the motor generator 28. However, for example, the front wheels 14 may be driven only by the motor generator 10, and the rear wheels 15 may be driven by the engine 2 and the motor generator 28.

  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.

  2 engine, 4 power split device, 6, 10, 28 motor generator, 8, 9 transmission gear, 12, 13 drive shaft, 14 front wheel, 15 rear wheel, 16 power storage device, 18, 20, 23, 29 power converter, 21, 22 Driving device, 24 connecting portion, 26 ECU, 100 hybrid vehicle.

Claims (1)

An internal combustion engine and a first electric motor capable of outputting a driving force to one of the front wheels and the rear wheels;
A second electric motor capable of outputting a driving force to the other of the front wheels and the rear wheels;
A power storage device for storing electric power for driving the first and second electric motors;
A control device that controls the internal combustion engine and the first and second electric motors while controlling the driving force distribution of the first and second electric motors according to the required driving force of the vehicle,
The controller is
When the internal combustion engine is in a stopped state and the required driving force exceeds a predetermined value during traveling by the first electric motor,
When a condition for allowing a decrease in the charge amount of the power storage device is satisfied, maintaining the stopped state of the internal combustion engine and increasing the driving force distribution of the second electric motor,
A hybrid vehicle that starts the internal combustion engine when the condition is not satisfied.

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