JP2018154230A - Control system of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel economy during travel time while securing the amount of charge of a battery in a control system of a hybrid vehicle.SOLUTION: A control system 10 includes an engine 12, an electric motor, a battery 16, a driving motor, a clutch 22 and a control device. The control device travels a vehicle by switching an EV mode, a series mode, and a parallel mode as a travel mode. When the parallel mode is selected, the control device changes a selection condition of the parallel mode by operating the engine with maximum efficiency or at an operation point in a high efficient region with respect to engine speed corresponding to vehicle speed and widening a rotation number range in which the engine is operated in the parallel mode as SOC of a battery is lowered in a direction in which a lower limit of efficiency defined using heat efficiency of the engine becomes low.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control system for a hybrid vehicle.

  Patent Document 1 describes a vehicle that travels by switching an EV mode, a series mode, and a parallel mode as travel modes in a hybrid vehicle equipped with an engine and a drive motor. Here, the EV mode is a mode in which the vehicle is driven by driving the drive motor with electric power from the battery without operating the engine. The series mode is a mode in which a generator is driven by an engine to generate power and is driven to travel by a drive motor. The parallel mode is a mode that can be driven by both the engine and the drive motor.

  Patent Document 1 also describes a travel mode switching control device that includes means for detecting the travel speed of the vehicle, means for detecting the charging rate of the battery, and switching control means for switching the travel mode. . The switching control means switches from a mode other than the parallel mode to the parallel mode at a low vehicle speed when the detected charging rate is below a predetermined value, and at a high vehicle speed when the detected charging rate exceeds a predetermined value. Switch from a mode other than parallel mode to parallel mode.

JP 2014-121962 A

  In the switching control device described in Patent Document 1, switching from a mode other than the parallel mode to the parallel mode is performed according to the traveling speed of the vehicle. In this switching control device, mode switching is performed regardless of the efficiency of the engine. As a result, there is room for improvement in terms of improving fuel consumption during traveling.

  An object of the control system for a hybrid vehicle of the present invention is to improve fuel efficiency during traveling while ensuring the charge amount of the battery.

  One aspect of the present invention includes an engine, a generator driven by the engine, a battery supplied with power from the generator and charged, and driving wheels of the vehicle with the power supplied from the battery. A drive motor, a clutch for connecting / disconnecting power transmission between the engine and the drive wheel, and a control device. The control device opens the clutch and stops driving the engine as a travel mode. And an EV mode in which the drive motor is driven by the power supplied from the battery to drive the drive wheels, and the drive motor is generated by the power generated by opening the clutch and driving the generator by the engine. A series mode for driving the drive wheel by driving the engine, and connecting the clutch to drive the drive wheel by driving the engine A hybrid vehicle control system for driving a vehicle by switching between a parallel mode and a parallel drive mode, wherein the control device has a maximum efficiency or a high efficiency with respect to an engine speed corresponding to a vehicle speed when the parallel mode is selected. A rotational speed range in which the engine is operated in the parallel mode as the SOC, which is a charging ratio with respect to a set full charge amount of the battery, is decreased at an operating point in an efficiency region, and the thermal efficiency of the engine The selection condition for the parallel mode is changed by increasing the lower limit of the efficiency defined using.

  According to the present invention, in the parallel mode, the engine is operated at the operating point in the highest efficiency or high efficiency region that is efficient with respect to the engine speed corresponding to the vehicle speed. Further, the lower the SOC of the battery, the wider the rotational speed range in which the engine is operated in the parallel mode, in a direction in which the lower limit of the efficiency defined using the thermal efficiency of the engine is lowered. Thereby, when there is a margin in the SOC, the engine speed range in which the engine can be operated in the parallel mode is narrowed so that only the engine speed range in which the efficiency is high is obtained, and fuel efficiency is improved. In addition, when the SOC decreases, the charge amount of the battery can be ensured by widening the engine speed range in which the engine can be operated. Therefore, it is possible to improve fuel efficiency during traveling while ensuring the charge amount of the battery.

It is a block diagram of the control system of the hybrid vehicle of embodiment of this invention. In an embodiment, it is a figure showing the number-of-rotations range (engine drive range) of an engine operating line at the time of operating an engine in parallel mode. In embodiment, it is a figure which shows the isoefficiency line of the power generation efficiency with respect to the rotation speed and absorption torque of a generator. In an embodiment, it is a figure for explaining distribution of system efficiency and engine torque in parallel mode. In embodiment, it is a figure which shows the selection range of a parallel mode by the relationship between an engine speed and driving | running | working request torque. In embodiments, a diagram showing the relationship between system efficiency lower eta _S _ _lim for SOC. FIG. 6 is a diagram corresponding to FIG. 5 when the system efficiency lower limit η _{S — lim} is high in the embodiment. In an embodiment, it is a figure showing an operating point of vehicles and an engine according to run demand torque and engine speed in relation to a parallel mode selection area. FIG. 9 is a diagram showing the relationship of the system efficiency η _S with respect to the ratio α of the vehicle travel request output to the engine output at the two operating points B1 and B2 in FIG. In embodiments, a diagram showing the relationship between system efficiency lower eta _S _ _lim and system efficiency eta _S for SOC. 4 is a flowchart illustrating a method for selecting a travel mode in the embodiment. FIG. 7 is a diagram corresponding to FIG. 6 in another example of the embodiment. FIG. 7 is a diagram corresponding to FIG. 6 in another example of the embodiment. In another example of an embodiment, it is a figure showing operational line efficiency line L showing thermal efficiency eta on an engine operational line with respect to engine speed, and an engine drive range in parallel mode. In another example of embodiment, showing the relationship between thermal efficiency lower eta _e _ _lim engine for SOC. In another example of embodiment, showing the relationship between the heat efficiency lower eta _e _ _lim and thermal efficiency eta _e for SOC. In another example of embodiment, it is a flowchart which shows the selection method of driving mode. FIG. 13 is a diagram corresponding to FIG. 12 in another example of the embodiment. FIG. 14 is a diagram corresponding to FIG. 13 in another example of the embodiment. In another example of embodiment, it is a figure which shows the parallel mode selection area | region about a low speed stage and a high speed stage by the relationship between a vehicle speed and a vehicle request | requirement driving force.

  FIG. 1 is a configuration diagram of a control system 10 for a hybrid vehicle according to an embodiment. Below, the same code | symbol is attached | subjected and demonstrated to the same element. The hybrid vehicle includes an engine 12 and a second motor generator 14 and travels using one or both of the engine 12 and the second motor generator 14 as a drive source. The second motor generator 14 also has a function of absorbing braking force when the vehicle is decelerated and generating power as regenerative power, supplying the generated power to the battery 16, and charging the battery 16. The second motor generator 14 corresponds to a drive motor.

  Further, the hybrid vehicle includes a first motor generator 20 that is driven by the engine 12 via the speed increasing gear mechanism 18 to generate electric power. The electric power generated by the first motor generator 20 is supplied to the battery 16 and the battery 16 is charged. The first motor generator 20 is driven when electric power is supplied from the battery 16 and also functions as a motor for running or starting the engine 12. The first motor generator 20 corresponds to a generator.

  In the following, a hybrid vehicle including the first and second motor generators 20 and 14 will be described, but the hybrid vehicle is not limited to this. For example, the hybrid vehicle may include a generator that does not have a function as a drive motor, and a drive motor that does not have a function of a generator, instead of the first and second motor generators. Below, the 1st motor generator 20 may be described as 1st MG20, and the 2nd motor generator 14 may be described as 2nd MG14.

  The control system 10 includes the engine 12, the first MG 20, the battery 16, and the second MG 14, the clutch 22, the transmission 24, the main controller 26, the PCU 28, and the ECU 30. The battery 16 is charged with power supplied from the first MG 20. The second MG 14 drives the drive wheels 32 of the vehicle with electric power supplied from the battery 16. The drive wheel 32 is connected to the axle. The clutch 22 is disposed in the power transmission unit 21 between the output shaft of the engine 12 and the drive wheels 32, and connects and disconnects power transmission between the engine 12 and the drive wheels 32 under the control of a main controller 26 described later. The power transmission unit 21 includes a clutch 22, a differential gear mechanism 23, a transmission 24, and an axle. For example, the clutch 22 is controlled by a main controller 26 and includes an electric or hydraulic actuator for connecting and disconnecting the clutch 22.

  The transmission 24 is disposed between the engine 12 and the clutch 22 in the power transmission unit 21. For example, the transmission 24 includes only two speed stages, a low speed stage and a high speed stage, for the forward speed of the vehicle. The transmission 24 is controlled by the main controller 26 to select one of the low speed stage and the high speed stage and connects the engine side and the clutch side of the power transmission unit 21 at the selected gear stage. Thus, the engine 12 is connected to the axle via the transmission 24 and the clutch 22 so that power can be transmitted. The output shaft of the second MG 14 is also connected to the axle so that power can be transmitted.

  The main controller 26 includes a storage device such as a CPU and a memory. The main controller 26 corresponds to a control device. The main controller 26 is connected to the clutch 22, the transmission 24, an accelerator pedal sensor (not shown), a vehicle speed sensor, a lever sensor, a motor controller of the PCU 28, and the ECU 30, and signals representing detection values and operating states from these devices. Is entered.

  The accelerator pedal sensor detects the operation amount of the accelerator pedal of the vehicle. The vehicle speed sensor detects the speed of the vehicle.

  The main controller 26 calculates the vehicle required driving force and the travel required torque from the detected value of the accelerator pedal sensor. The vehicle request driving force and the travel request torque may be calculated based on both the detection value of the vehicle speed sensor and the detection value of the accelerator pedal sensor.

  The lever sensor detects an operation position of a speed change lever (not shown) operated by the driver. The main controller 26 outputs a control signal for shifting to the transmission 24 based on information on the operation position of the lever sensor. The main controller 26 calculates the engine speed based on the detection value of the vehicle speed sensor and the operation position of the shift lever. In the vehicle, an engine speed sensor for detecting the engine speed may be provided. At this time, a signal representing the detection value of the engine speed sensor is input to the main controller 26.

  The main controller 26 calculates the operating point of the vehicle according to a relational expression or map set in advance from the travel request torque and the detected engine speed. Further, the main controller 26 calculates an operating point of the engine 12 when the parallel mode described later is selected from a preset engine operating line and the detected engine speed.

  The main controller 26 receives a detected value of the input / output current of the battery 16 from a current sensor (not shown), and receives a detected value of the voltage across the battery 16 from a voltage sensor (not shown). The main controller 26 calculates an SOC (State Of Charge) that is a charging rate of the battery 16 using one or both of the detection values of the current sensor and the voltage sensor. The SOC is a charging ratio with respect to the full charge amount set in the battery 16. The hybrid vehicle may include a battery monitoring unit (not shown), the battery monitoring unit may detect the SOC of the battery 16, and a signal representing the detected SOC may be input to the main controller 26.

  The main controller 26 outputs control signals for driving and generating power to the first MG 20 and the second MG 14 to the PCU 28.

  Further, the main controller 26 switches the EV mode, the series mode, and the parallel mode as the travel mode and causes the vehicle to travel. This will be described later.

  The PCU 28 includes a motor controller, a first inverter, and a second inverter. Each inverter has a plurality of switching elements. The first inverter converts the direct current from the battery 16 into an alternating current by switching the switching element, supplies the alternating current to the first MG 20, and drives the first MG 20. The second inverter converts the direct current from the battery 16 into an alternating current by switching the switching element, and supplies the alternating current to the second MG 14 to drive the second MG 14. The motor controller receives the control signal from the main controller 26 and controls the driving and power generation of the first and second MGs 20 and 14 via corresponding inverters. The output of the second MG 14 is transmitted to the left and right drive wheels 32 that are front wheels or rear wheels via the differential gear mechanism 23. Thereby, the second MG 14 drives the drive wheels 32 with the electric power supplied from the battery 16. The output of the engine 12 is transmitted to the left and right drive wheels 32 via the transmission 24, the clutch 22 and the differential gear mechanism 23. Therefore, in the state where the clutch 22 is released, the output of only the second MG 14 of the engine 12 and the second MG 14 is transmitted to the drive wheels 32.

  The ECU 30 is an engine controller, and controls the operation state of the engine 12 by a control signal output from the main controller 26. The main controller 26 can be integrated with one or both of the motor controller and the ECU 30 to constitute one control device.

  Next, switching of the driving mode by the main controller 26 will be described. In the EV mode, the clutch 22 is disengaged, the driving of the engine 12 is stopped, the second MG 14 is driven by the electric power supplied from the battery 16, and the driving wheels 32 are driven to drive the vehicle.

  The series mode is a mode in which the vehicle is caused to travel by driving the driving wheels 32 by driving the second MG 14 with the electric power generated by driving the first MG 20 by the engine 12 while releasing the clutch 22. At this time, since the clutch 22 is released, the power of the engine 12 is interrupted by the clutch 22 and is not transmitted to the drive wheels 32. The electric power generated by the first MG 20 is supplied to the battery 16 and the battery 16 is charged, and electric power is supplied from the battery 16 to the second MG 14 to drive the second MG 14. In the series mode, the fuel consumption is maintained in a favorable range by rotating the engine 12 at a speed at which the engine 12 is operated with high efficiency. For example, the engine 12 has the maximum thermal efficiency at a point bp (FIG. 2) determined from the engine speed and the engine torque as will be described later. In the series mode, the engine can be rotated at a rotational speed corresponding to the point bp or a point in the vicinity of the point bp.

  In the parallel mode, the clutch 22 is connected and the driving force of the engine 12 is transmitted to the driving wheel 32 via the transmission 24, the clutch 22, and the differential gear mechanism 23, thereby driving the driving wheel 32 and driving the vehicle. This is a mode for running. At this time, the first MG 20 is driven by a part of the output of the engine 12, the generated electric power is supplied to the battery 16, and the battery 16 can be charged. In the parallel mode, the second MG 14 may be driven by the electric power supplied from the battery 16, and the driving force of the second MG 14 may be transmitted to the driving wheels 32 together with the driving force of the engine 12. In such a parallel mode, it is easy to achieve the required driving force of the vehicle.

  When the parallel mode is selected, the main controller 26 operates the engine 12 at a load point as an operating point having the highest efficiency with respect to the engine speed corresponding to the vehicle speed. FIG. 2 is a diagram illustrating an engine drive range that is a range of an engine operation line when the engine 12 is operated in the parallel mode in the embodiment. In FIG. 2, line a1 indicates the full load torque of the engine 12, and line a2 indicates the engine operating line. Further, lines b1, b2, and b3 in FIG. 2 indicate isothermal efficiency lines of the engine 12, and a point bp is a point at which the thermal efficiency of the engine 12 is maximized. As shown in FIG. 2, the engine operating line a2 includes a point bp in the engine driving range in the parallel mode, and is set to pass through a point where the thermal efficiency is highest with respect to the engine speed. In the parallel mode, the engine 12 may be operated at an operating point in a high-efficiency region having a predetermined torque width around the engine operating line a2 as indicated by a dashed-dotted line a3 in FIG.

Here, when the vehicle travel request output required for the travel of the vehicle is less than the engine output, the first MG 20 becomes a load and generates power, so that the battery 16 is charged using the surplus output during the travel of the engine 12. Done. At this time, when the ratio of the vehicle travel request output to the engine output is α, the thermal efficiency of the engine 12 is ηe, and the power generation efficiency of the first _{MG 20} is ηMG, in the parallel mode, the engine has a ratio of (1−α). Electricity is generated by a part of the output. In this case, the system efficiency η _S in the parallel mode is defined as the following equation (1).

η _S = ηe × {α + (1−α) × η _MG } (1)

(1) As understood from the equation, by multiplying the system efficiency eta _S is a multiplied by the percentage alpha thermal efficiency ηe of the engine 12, the the ratio (1-alpha) the thermal efficiency ηe of the engine 12 and the power generation efficiency eta _MG It is the sum of things. The power generation efficiency η _MG is determined from the rotational speed of the first _MG 20 and the magnitude of the absorption torque.

FIG. 3 is a diagram illustrating an isoefficiency line of power generation efficiency with respect to the rotation speed and absorption torque of the first MG 20 in the embodiment. As shown in FIG. 3, the power generation efficiency increases in the direction indicated by the arrow c. As understood from FIG. 3, the power generation efficiency η _MG is calculated from the rotation speed and absorption torque of the first _MG 20. The rotational speed of first MG 20 is obtained from the detected value of engine rotational speed.

FIG. 4 is a diagram for explaining the distribution of the system efficiency η _S and the engine torque in the parallel mode in the embodiment. As shown in FIG. 4, the output of the engine 12 is transmitted to the axle at a rate α, and is transmitted to the first MG 20 at a rate (1-α). At this time, with respect to the thermal efficiency ηe of the engine 12, the efficiency when being transmitted to the axle is ηe, and the power generation efficiency of the first _MG 20 driven by the engine 12 is ηe × ηMG. The sum of values obtained by multiplying these efficiencies by the torque distribution ratio is the system efficiency η _S in equation (1).

  The engine torque Te is divided into torque (α × Te) transmitted to the axle and torque ((1−α) × Te) transmitted to the first MG 20. Since the torque transmitted to the first MG 20 becomes the absorption torque, the power generation efficiency of the first MG 20 is obtained using the absorption torque and the rotation speed of the first MG 20.

In the control system 10 described above, the main controller 26 switches the operation between the mode other than the parallel mode and the parallel mode, and changes the rotation speed range for operating the engine 12 in the parallel mode according to the SOC of the battery 16. To control. Specifically, the main controller 26 sets the engine drive range, which is the rotational speed range in which the engine 12 is operated in the parallel mode, as the SOC of the battery 16 decreases, and the lower limit of the efficiency defined using the thermal efficiency ηe of the engine 12. Widen in the direction of lowering. Here, the efficiency defined using the thermal efficiency ηe of the engine 12 is defined as the system efficiency η _s . Thereby, the main controller 26 changes the selection condition of the parallel mode. With this configuration, as will be described later, it is possible to improve the fuel consumption during traveling while securing the charge amount of the battery 16.

  In addition, if the detected SOC is equal to or higher than the first threshold SOC1 set in advance, the main controller 26 switches the travel mode to forcibly select the EV mode. Thereby, the electric power of the battery 16 is supplied to the second MG 14 and driven, so that the battery 16 can be efficiently prevented from being overcharged.

FIG. 5 is a diagram illustrating a parallel mode selection range in relation to the engine speed and the required travel torque in the embodiment. Concerning the system efficiency η _S in the parallel mode expressed by the above equation (1), the isoefficiency lines are expressed as D1, D2, and D3 in FIG. 5 in relation to the engine speed and the required travel torque. Thus, it can be seen that it is reasonable to define the engine speed range for operating the engine 12 in the parallel mode based on the system efficiency. Specifically, when the lower limit of the system efficiency η _S is set to the system efficiency lower limit η _{S — lim} , the rotational speed range in which the engine 12 is operated in the parallel mode corresponds to the efficiency equal to or higher than the system efficiency lower limit η _{S — lim.} The rotation speed range. The upper limit of the system efficiency η _S in the parallel mode is set to a preset upper limit value η _{S — max} (see FIG. 6).

FIG. 6 is a diagram illustrating a relationship of the system efficiency lower limit η _{S — lim to} the SOC in the embodiment. Here, as shown in FIG. 6, the relationship between the system efficiency lower limit η _{S — lim} and the SOC is set in advance so that the system efficiency lower limit η _{S — lim} becomes lower as the SOC becomes smaller. This relationship is stored in the storage unit. In the relationship shown in FIG. 6, the system efficiency lower limit η _{S — lim} increases linearly as the SOC increases. The main controller 26 sets the system efficiency lower limit η _{S — lim} to be equal to or higher than the preset upper limit value η _{S — max} of the system efficiency η _S when the SOC is equal to or higher than the first threshold SOC 1 set in advance, and operates the engine 12. Is prohibited. At this time, the traveling mode is selected as the EV mode, and the vehicle is driven by the driving force of the second MG 14.

As shown in FIG. 6, a lower limit value η _{S — min} of the system efficiency in the parallel mode is set in the system efficiency lower limit η _{S — lim} . The main controller 26 calculates the system efficiency lower limit η _{S — lim} from the relationship between the SOC and the system efficiency lower limit η _{S — lim} and the detected SOC. The main controller 26 determines that the calculated system efficiency lower limit η _{S — lim} is lower than the preset lower limit value η _{S — min due} to the detected SOC being lower than the preset second threshold value SOC2. Switches the travel mode to the series mode. As a result, the vehicle can be driven in the series mode with high fuel efficiency. At this time, the lower limit value η _{S — min} is equal to the maximum value (maximum power generation efficiency) of the product of the upper limit value η _{e — max} that is the maximum efficiency of the thermal efficiency of the engine 12 and the power generation efficiency η _MG of the first _{MG 20.} It is preferable to set. According to this preferable configuration, it is compensated that the series mode is more efficient than the parallel mode.

FIG. 6 shows a case where the detected SOC matches the second threshold value SOC2. In this case, from the point E1 corresponding to the second threshold SOC2 on the system efficiency lower limit line, which is a line representing the relationship between the system efficiency lower limit η _{S — lim} and SOC in FIG. 6, the current system efficiency lower limit η _{S — lim} Is set. In FIG. 6, the system efficiency lower limit line is shown as the η _{S — lim} line (the same applies to FIG. 10). In this case, the system efficiency lower limit η _{S — lim} is the lower limit value η _{S — min} , and the parallel mode selection range is maximized. At this time, in FIG. 5, the system efficiency lower limit η _{S — lim} is D1, and the engine drive range in the parallel mode is the range indicated by the arrow in FIG. In the system efficiency lower limit line of FIG. 6, the line segment connecting the lower limit value η _{S — min} and the upper limit value η _{S — max} is below the lower limit value η _{S — min} and above the upper limit value η _{S — max} . It extends to extend in a straight line.

On the other hand, when the detected SOC becomes larger than the second threshold SOC2 in FIG. 6, the system efficiency lower limit η _{S — lim} corresponding to the SOC becomes larger than the lower limit value η _{S — min} on the system efficiency lower limit line of FIG. For example, when the detected SOC is a value corresponding to E2 (FIG. 6), the system efficiency lower limit η _{S — lim} is a value represented by an alternate long and short dash line F in FIG. In this case, the parallel mode selection area is narrower than the maximum parallel mode selection area as indicated by an arrow β.

FIG. 7 is a diagram corresponding to FIG. 5 when the system efficiency lower limit η _{S — lim} is high in the embodiment. FIG. 7 corresponds to the case where the system efficiency lower limit η _{S — lim} becomes a value represented by the alternate long and short dash line F of FIG. 6 and D3 of FIG. In this case, the parallel mode selection area is narrower than that shown in FIG. As a result, the rotational speed range (engine drive range) for driving the engine 12 in the parallel mode is also narrower than that shown in FIG. For this reason, the opportunity for selecting the parallel mode is reduced. On the other hand, in this case, the engine drive range in the parallel mode is only the rotation speed range in which the system efficiency η _S is high, so that the fuel efficiency in the parallel mode can be improved.

  FIG. 8 is a diagram illustrating operating points of the vehicle and the engine 12 according to the travel request torque and the engine speed in the embodiment in relation to the parallel mode selection area.

  The main controller 26 determines whether or not the current operating point of the vehicle falls within the parallel mode selection region based on the relationship between the engine torque when the engine 12 is driven in the parallel mode and the travel request torque. The main controller 26 selects the EV mode or the series mode when the operating point does not enter the selection area. Below, the case where the gear stage of the transmission 24 is fixed to one is demonstrated. In this case, the vehicle speed increases as the engine speed increases. In the following description, the second MG 14 is not driven in the parallel mode. However, the second MG 14 may be driven. At this time, the SOC of the battery is reduced, while the torque required for running in the engine is reduced by the driving force of the second MG 14. Alternatively, the second MG 14 can provide a running torque that is greater than the engine torque.

For example, in FIG. 8, when the vehicle operating point is at the point A1 where the required traveling torque is low on the low speed side, the system efficiency η _S is lower than the system efficiency lower limit η _{S — lim} , so that the parallel mode is not set. EV mode or series mode is selected. At this time, the system efficiency lower limit η _{S — lim} corresponding to the SOC is determined from the relationship indicated by the system efficiency lower limit line in FIG. 6 and the detected SOC. When the determined system efficiency lower limit η _{S — lim} is lower than the lower limit value η _{S — min} , that is, when the SOC is lower than the second threshold value SOC2, the series mode is selected. Selection of the series mode and the EV mode will be described later with reference to FIG.

  In FIG. 8, when the vehicle operating point is at the point A2 where the required torque for traveling is higher than the point A1 at the same engine speed as the point A1, the vehicle enters the parallel mode selection range and is operated in the parallel mode. At this time, the engine 12 is operated at an operating point A where the engine speed is the same as that of the point A1 on the highly efficient engine operating line shown as “engine torque” in FIG. In this case, of the torque generated by the engine 12, the remainder excluding the torque necessary for traveling is absorbed by the first MG 20 as absorption torque, and the first MG 20 generates power.

  In FIG. 8, when there is an operating point of the vehicle at points B1 and B2 where the vehicle speed is higher than the points A1 and A2, the vehicle is operated in the parallel mode. At this time, the engine 12 is operated at an operating point B where the engine speed is the same as that of the points B1 and B2 on a highly efficient engine operating line.

FIG. 9 is a diagram showing the relationship of the system efficiency η _S with respect to the ratio α of the vehicle travel request output to the engine output at the two operating points B1 and B2 in FIG. As shown in FIG. 9, the system efficiency increases as the travel request torque with respect to the engine torque increases.

FIG. 10 is a diagram illustrating a relationship between the system efficiency lower limit η _{S — lim} with respect to the SOC and the system efficiency η _S in the embodiment. As shown in FIG. 10, EV mode, series mode, and parallel mode selection areas are set. The sandy portion in FIG. 10 is a first EV mode selection region set based on the relationship between the system efficiency lower limit line, the SOC, the upper limit value η _{S — max,} and the upper limit SOC as the upper limit value of the SOC. The gray portion in FIG. 10 is a second EV mode selection area set based on the relationship between the system efficiency lower limit line, the system efficiency η _S , the SOC, the second threshold SOC2, and the upper limit SOC.

The hatched portion in FIG. 10 is the first series mode selection area set based on the relationship between the system efficiency lower limit line, the SOC, and the lower limit value η _{S — min} . 10 is set based on the relationship between the SOC, a lower limit SOC that is lower than the preset second threshold SOC2 and allowed in the parallel mode, and the upper limit η _{S — max.} This is the second series mode selection area. And the trapezoid white outline of FIG. 10 is a selection area in the parallel mode. The selection range of the EV mode, the series mode, and the parallel mode shown in FIG. 10 is an example, and is not limited to this.

  FIG. 11 is a flowchart illustrating a travel mode selection method in the embodiment. Selection in the selection method shown in the flowchart of FIG. 11 is executed by the main controller 26, and the ECU 30, the PCU 28, and the clutch 22 are controlled in a travel mode according to the selection.

In step S10 of FIG. 11, the system efficiency lower limit η _{S — lim} and the system efficiency η _S are calculated. Hereinafter, step S is described as S. The system efficiency η _S is calculated using equation (1). In S12, it is determined whether the system efficiency lower limit η _{S — lim} exceeds the upper limit value η _{S — max} . If the determination result is affirmative, that is, YES, the EV mode is selected in S14. The EV mode selected at this time corresponds to the first EV mode selection area.

If the determination result in S12 is negative, that is, NO, the process proceeds to S16. In S16, it is determined whether the system efficiency η _S is lower than the system efficiency lower limit line (η _{S — lim} line) and the SOC is equal to or higher than the second threshold value SOC2. If the determination result in S16 is YES, the series mode is selected in S14. The EV mode selected at this time corresponds to the second EV mode selection area.

If the determination result in S16 is NO, it is determined in S18 whether the system efficiency lower limit η _{S — lim} is lower than the lower limit value η _{S — min.} If the determination result is YES, the series mode is selected in S20. . The series mode selected at this time corresponds to the first series mode selection area.

  If the determination result in S18 is NO, the process proceeds to S22. In S22, it is determined whether or not the SOC is lower than the lower limit SOC. If the determination result is YES, the series mode is selected in S20. The series mode selected at this time corresponds to the second series mode selection area.

  If the determination result in S22 is NO, the parallel mode is selected in S24. When the selection of the mode is completed in S14, S20, and S24, the process returns to S10 again and the processes from S10 to S24 are repeated.

  According to the control system 10 described above, in the parallel mode, the engine 12 is operated at the maximum efficiency operating point that is efficient with respect to the engine speed corresponding to the vehicle speed. Further, as the SOC of the battery 16 is lowered, the rotational speed range in which the engine 12 is operated in the parallel mode is expanded in such a direction that the lower limit of the system efficiency defined using the thermal efficiency of the engine 12 is lowered. Thereby, when there is a margin in the SOC, the rotational speed range in which the engine 12 can be operated in the parallel mode is narrowed so that only the rotational speed range in which the system efficiency becomes high is obtained, and fuel efficiency is improved. Further, when the SOC decreases, the charge amount of the battery 16 can be ensured by expanding the rotation speed range in which the engine 12 can be operated even if the system efficiency decreases. At this time, switching from the parallel mode to the EV mode that consumes much power of the battery 16 is less likely to occur. In addition, since the fuel efficiency in driving in the parallel mode can be improved, inefficient driving conditions can be reduced. Therefore, it is possible to improve the fuel consumption during traveling while securing the charge amount of the battery 16.

  Further, when the SOC is high, the charging request is low. Therefore, by narrowing the drive range for the rotational speed of the engine 12 in the parallel mode, the EV mode is easily selected with more opportunities.

FIG. 12 is a diagram corresponding to FIG. 6 in another example of the embodiment. The system efficiency lower limit line representing the relationship between the SOC and the system efficiency lower limit η _{S — lim} is not limited to a straight line as shown in FIG. 6 but may be a line having a bent characteristic as shown in FIG. In the system efficiency lower limit line of FIG. 12, the system efficiency lower limit does not reach the upper limit value at the first threshold SOC1, and is maintained constant up to the vicinity of the preset upper limit SOC as the SOC increases. The system efficiency lower limit line changes stepwise so as to exceed the upper limit value η _{S — max} near the upper limit SOC. When the system efficiency lower limit line of FIG. 12 is used, the system efficiency η _S can be maintained near the maximum efficiency in the parallel mode by operating in the parallel mode with the high system efficiency from the first threshold value SOC1 to the vicinity of the upper limit SOC.

FIG. 13 is a diagram corresponding to FIG. 6 in another example of the embodiment. The system efficiency lower limit line representing the relationship between the SOC and the system efficiency lower limit η _{S — lim} may be a line having a curved characteristic as shown in FIG. In the system efficiency lower limit line of FIG. 13, the first threshold value SOC <b> 1 that is the SOC when intersecting with the upper limit value η _{S — max} approaches the upper limit SOC. Further, in this system efficiency lower limit line, the system efficiency lower limit is kept low from the second threshold value SOC2 to the vicinity of the first threshold value SOC1. Thereby, since a parallel mode selection area can be widened, an engine operation opportunity can be increased. For this reason, it is easy to perform power mode operation.

  The main controller 26 may be configured to be able to change between the upper limit SOC and the second threshold SOC2 according to the driver's selection, instead of setting the first threshold SOC1 as a fixed value. For example, when the driver of the hybrid vehicle gives an instruction for power mode operation using an operation unit (not shown), the system efficiency lower limit line shown in FIG. 13 is used. It is good also as a structure which performs normal driving | operation using an efficiency lower limit line.

  On the other hand, when the driver of the hybrid vehicle instructs the EV priority mode using the operation unit, the system efficiency lower limit line used for driving is made closer to the second threshold SOC2 from the system efficiency lower limit line of FIG. The system efficiency may be changed to the lower limit of system efficiency. In this case, the opportunity to shift to the EV mode increases due to the change in the SOC.

  As another example of the embodiment, the main controller 26 may change the first threshold value SOC1 in accordance with the history of driving conditions of the vehicle, that is, the first threshold value SOC1 may be changed by learning. For example, when the vehicle is a plug-in hybrid vehicle that can charge the battery 16 from the outside, the SOC history during driving and the frequency history of external charging may be stored in the main controller 26. The main controller 26 changes the first threshold value SOC1 from the history. For example, the first threshold value SOC1 can be made closer to the upper limit SOC side when there is one or both of a high SOC reduction frequency and a high external charging frequency during operation. As a result, engine operation opportunities in the parallel mode can be increased. On the other hand, when the SOC decreases less frequently during driving and the frequency of external charging is low, it is determined that the vehicle travel request torque is often low, and the first threshold SOC1 is brought closer to the second threshold SOC2 side. You can also. This increases the opportunity to enter the EV mode.

FIG. 14 is a diagram showing an operating line efficiency line L representing the thermal efficiency ηe on the operating line of the engine 12 with respect to the engine speed and an engine driving range in the parallel mode in another example of the embodiment. FIG. 15 is a diagram illustrating a relationship of a thermal efficiency lower limit η _{e — lim} that is a lower limit of the thermal efficiency ηe of the engine 12 with respect to the SOC in another example of the embodiment.

In another example shown in FIGS. 14 and 15, the thermal efficiency ηe of the engine 12 is used as the efficiency defined using the thermal efficiency of the engine 12 instead of the system efficiency in order to determine the parallel mode selection range. As described with reference to FIG. 2 above, in the parallel mode, the engine operating line a2 is set so as to pass through a point where the thermal efficiency ηe is highest with respect to the engine speed. In FIG. 14, the point G at which the thermal efficiency ηe becomes the upper limit value η _{e — max} , which is the maximum efficiency, corresponds to the point bp in FIG. Thus, it can be seen that it is reasonable to define the engine speed range in which the engine 12 is operated in the parallel mode by the thermal efficiency ηe. Specifically, when the lower limit of the thermal efficiency ηe is the thermal efficiency lower limit η _{e _lim} , the rotational speed range in which the engine 12 is operated in the parallel mode is the rotational speed range corresponding to the efficiency equal to or higher than the thermal efficiency lower limit η _{e _lim} ( Engine driving range).

As shown in FIG. 15, the relationship between the thermal efficiency lower limit η _{e # lim} and the SOC is preset so that the thermal efficiency lower limit becomes lower as the SOC becomes smaller, and this relationship is stored in the storage unit of the main controller 26. . In the relationship shown in FIG. 15, the thermal efficiency lower limit η _{e — lim} increases linearly as the SOC increases. The main controller 26 sets the thermal efficiency lower limit η _{e # lim} to the upper limit value η _{e — max} that is the maximum efficiency of the thermal efficiency, and prohibits the operation of the engine 12 when the SOC is equal to or higher than the preset first threshold value SOC1a. At this time, the traveling mode is selected as the EV mode, and the vehicle is driven by the driving force of the second MG 14.

As shown in FIG. 15, the lower limit value η _{e — min} of the thermal efficiency in the parallel mode is set in the lower thermal efficiency limit η _{e — lim} . The main controller 26 calculates the thermal efficiency lower limit η _{e — lim} from the relationship between the SOC and the thermal efficiency lower limit η _{e — lim} and the detected SOC. Then, the main controller 26 determines that the calculated thermal efficiency lower limit η _{e — lim} is lower than the preset lower limit value η _{e — min} when the detected SOC falls below the preset second threshold SOC 2 a. Switch the travel mode to the series mode. As a result, the vehicle can be driven in the series mode with high fuel efficiency. At this time, the lower limit value η _{e — min} may be set to be equal to the maximum value (maximum power generation efficiency) of the product of the upper limit value η _{e — max} of the thermal efficiency of the engine 12 and the power generation efficiency η _MG of the first _{MG 20.} preferable. According to this preferable configuration, it is compensated that the series mode is more efficient than the parallel mode.

FIG. 15 shows a case where the detected SOC matches the second threshold value SOC2a. In this case, the E1a point corresponding to the second threshold value SOC2a thermal efficiency lower limit line is a line representing the relationship between the heat efficiency lower eta _e _ _lim and SOC in FIG. 15, is set to the current heat efficiency lower eta _e _ _lim The In FIG. 15, the thermal efficiency lower limit line is shown as the η _{e — lim} line (the same applies to FIG. 16). In this case, the thermal efficiency lower limit η _{e — lim} becomes the lower limit value η _{e — min} , and the parallel mode selection range is maximized. At this time, in FIG. 14, the thermal efficiency lower limit η _{e # lim} is D1a, and the engine drive range in the parallel mode is the range indicated by the arrow γ1 in FIG. Thermal efficiency lower limit line in FIG. 15, the line segment of a straight line connecting the lower limit eta _e _ _min and an upper limit eta _e _ _max is lower limit value eta _e _ _min, and the upper limit value eta _e _ _max is the maximum efficiency It is extended so that it may be extended linearly on the upper side.

On the other hand, when the detected SOC becomes larger than the second threshold value SOC2a in FIG. 15, the thermal efficiency lower limit η _{e — lim} corresponding to the SOC becomes larger than the lower limit value η _{e — min} on the thermal efficiency lower limit line of FIG. In this case, in FIG. 14, the thermal efficiency lower limit η _{e — lim} is a one-dot chain line D2a. At this time, the engine speed range in the parallel mode selection range is a range indicated by an arrow γ2 in FIG. 14, and is narrower than the engine speed range (arrow γ1 range) in the maximum parallel mode selection range. Thereby, in the selection area indicated by the arrow γ2, the opportunity for selecting the parallel mode is reduced. On the other hand, in this case, the engine drive range in the parallel mode is only the rotation speed range in which the thermal efficiency η _e is high, so that the fuel efficiency in the parallel mode can be improved.

FIG. 16 is a diagram illustrating a relationship between the thermal efficiency lower limit η _{e — lim} with respect to the SOC and the thermal efficiency η _e in another example of the embodiment. As shown in FIG. 16, selection areas for the EV mode, the series mode, and the parallel mode are set. The sandy portion in FIG. 16 is a first EV mode selection area set based on the relationship between the thermal efficiency lower limit line, the SOC, the upper limit value η _{e — max,} and the upper limit SOC. The gray portion in FIG. 16 is a second EV mode selection region set based on the relationship between the thermal efficiency lower limit line, the thermal efficiency η _e , the SOC, the second threshold SOC 2a, and the upper limit SOC.

The hatched portion in FIG. 16 is the first series mode selection area set based on the relationship between the thermal efficiency lower limit line, the SOC, and the lower limit value η _{e — min} . The oblique lattice portion in FIG. 16 is a second series mode selection area set based on the relationship between the SOC and a lower limit SOC that is set in advance and lower than the second threshold value SOC2a. A trapezoidal white portion in FIG. 16 is a selection area in the parallel mode. The selection area of the EV mode, the series mode, and the parallel mode shown in FIG. 16 is an example, and the selection area is not limited to this.

FIG. 17 is a flowchart illustrating a travel mode selection method in another example of the embodiment. In S30 of FIG. 17, the thermal efficiency lower limit η _{e — lim} and the thermal efficiency η _e are calculated. The thermal efficiency η _e is calculated from the preset operating line efficiency line L (FIG. 14) and the engine speed. In S32, it is determined whether or not the thermal efficiency lower limit η _{e — lim} exceeds the upper limit value η _{e — max.} If the determination result is YES, the EV mode is selected in S34. The EV mode selected at this time corresponds to the first EV mode selection area.

If the determination result in S32 is NO, the process proceeds to S36. In S36, it is determined whether or not the thermal efficiency η _e is lower than the thermal efficiency lower limit line (η _{e — lim} line) and the SOC is equal to or higher than the second threshold SOC 2a. If the determination result in S36 is YES, the series mode is selected in S34. The EV mode selected at this time corresponds to the second EV mode selection area.

If the determination result in S36 is NO, it is determined in S38 whether the thermal efficiency lower limit η _{e — lim} is lower than the lower limit value η _{e — min.} If the determination result is YES, the series mode is selected in S40. The series mode selected at this time corresponds to the first series mode selection area.

  If the determination result in S38 is NO, the process proceeds to S42. In S42, it is determined whether or not the SOC is lower than the lower limit SOC. If the determination result is YES, the series mode is selected in S40. The series mode selected at this time corresponds to the second series mode selection area.

  If the determination result in S42 is NO, the parallel mode is selected in S44. When the selection of the mode is completed in S34, S40, and S44, the process returns to S30 again and the processes from S30 to S44 are repeated.

  Also in the case of the above configuration, in the parallel mode, similarly to the configurations of FIGS. 1 to 11, the engine 12 is operated at the maximum efficiency operating point that is efficient with respect to the engine speed. Further, as the SOC of the battery 16 becomes lower, the rotational speed range in which the engine 12 is operated in the parallel mode is expanded in such a direction that the lower limit of the thermal efficiency of the engine 12 becomes lower. As a result, when there is a margin in the SOC, the rotational speed range in which the engine 12 can be operated in the parallel mode is narrowed so that only the rotational speed range in which the thermal efficiency is increased is obtained, and fuel efficiency is improved. Further, when the SOC decreases, the charge amount of the battery 16 can be ensured by expanding the rotation speed range in which the engine 12 can operate even in the direction in which the thermal efficiency decreases. At this time, switching from the parallel mode to the EV mode is unlikely to occur. In addition, since the fuel efficiency in driving in the parallel mode can be improved, inefficient driving conditions can be reduced. Therefore, it is possible to improve the fuel consumption during traveling while securing the charge amount of the battery 16.

  Further, when the SOC is high, the charging request is low, and therefore, the EV mode is easily selected on more occasions by narrowing the driving range for the rotational speed of the engine 12 in the parallel mode.

  Further, according to the configuration of this example, unlike the case of using the system efficiency as in the configurations of FIGS. 1 to 11, it is not necessary to obtain the power generation efficiency and the required travel torque, so that the calculation can be simplified. On the other hand, the control with the configuration of FIGS. 1 to 11 may be able to maintain the vehicle efficiency higher than the control with the configuration of this example. In this example, other configurations and operations are the same as those in FIGS. 1 to 11.

FIG. 18 is a diagram corresponding to FIG. 12 in another example of the embodiment, and FIG. 19 is a diagram corresponding to FIG. 13 in another example of the embodiment. 18 and FIG. 19, the thermal efficiency lower limit line representing the relationship between the SOC and the thermal efficiency lower limit η _{e — lim} is not limited to a linear one as shown in FIG. It is good also as a line which has the characteristic bent like. The thermal efficiency lower limit line may be a line having a curved characteristic as shown in FIG. In this case, for example, in FIGS. 12 and 13, the relationship between the SOC and the system efficiency lower limit is replaced with the relationship between the SOC and the thermal efficiency lower limit. When the thermal efficiency lower limit line in FIG. 18 is used, the thermal efficiency η _e can be maintained in the vicinity of the maximum efficiency in the parallel mode by operating in the high thermal efficiency parallel mode from the first threshold SOC1a to the vicinity of the upper limit SOC. Moreover, when using the thermal efficiency lower limit line of FIG. 19, the thermal efficiency lower limit is kept low from the second threshold SOC2a to the vicinity of the first threshold SOC1a. Thereby, since the parallel mode selection area can be widened, the engine operation opportunities can be increased, and therefore, it is easy to perform the power mode operation.

  The main controller 26 may be configured to be able to change between the upper limit SOC and the second threshold SOC2a in accordance with the driver's selection, instead of setting the first threshold SOC1a as a fixed value. For example, when the driver of the hybrid vehicle instructs the power mode driving by the operation unit, the normal efficiency driving is performed using the thermal efficiency lower limit line of FIG. 19 when there is no instruction of the power mode driving. It is good also as composition which performs.

  On the other hand, when the driver of the hybrid vehicle instructs the EV priority mode using the operation unit, the thermal efficiency lower limit line used for driving is set to the thermal efficiency that brings the first threshold SOC1a closer to the second threshold SOC2a from the thermal efficiency lower limit line of FIG. It is good also as a structure changed to a lower limit line. In this case, the opportunity to shift to the EV mode increases due to the change in the SOC.

  As another example of the embodiment, the main controller 26 may change the first threshold value SOC1a by making the first threshold value SOC1a changeable according to the history of driving conditions of the vehicle. For example, when the vehicle is a plug-in hybrid vehicle, the SOC history during driving and the frequency history of external charging may be stored in the main controller 26. The main controller 26 changes the first threshold SOC1a from the history. For example, the first threshold value SOC1a can be made closer to the upper limit SOC side when there is one or both of a high SOC reduction frequency and a high external charging frequency during operation. On the other hand, when the SOC decreases less frequently during driving and the frequency of external charging is low, it is determined that the vehicle travel request torque is often low, and the first threshold SOC1a is brought closer to the second threshold SOC2a side. You can also.

  FIG. 20 is a diagram illustrating a parallel mode selection range for the low speed stage and the high speed stage in relation to the vehicle speed and the vehicle required driving force in another example of the embodiment. The configuration of this example aims to reduce the impact at the time of shifting and to improve the fuel efficiency when switching the shift stage of the transmission 24 in the configuration of FIGS. 1 to 11 described above. In the configuration of FIG. 20, the configuration of the hybrid vehicle and the control system other than the main controller 26 is the same as the configuration of FIG.

  Specifically, in the configuration in which the transmission 24 is provided in the power transmission portion between the output shaft of the engine 12 and the drive wheels 32, changing the gear position of the transmission 24 in accordance with the change in the vehicle speed may cause the vehicle to travel. From the aspect of smoothing. In this case, if the output shaft of the engine 12 and the drive wheel 32 are connected via the clutch 22 when switching the gear position of the transmission 24, a sudden acceleration / deceleration at the time of shifting is shocked, that is, a shift shock. It is transmitted to the vehicle occupants. In the case of the configuration of FIG. 20, in order to reduce this shift shock, the main controller 26 opens the clutch 22 when switching to another shift stage during traveling in the parallel mode at one shift stage, Switch to EV mode or series mode. Then, after the switching is completed, the main controller 26 switches the transmission 24 to the above-described another shift stage, and then connects the clutch 22 to switch to the parallel mode corresponding to the other shift stage.

  In order to configure in this way, the main controller 26 sets the relationship between the low speed stage and the high speed stage and the corresponding parallel mode selection area as shown in FIG. Specifically, the main controller 26 sets the first region and the second region in the relationship between the vehicle speed and the required driving force of the vehicle.

The first region is the maximum region in which the parallel mode is selected at the low speed stage in the relationship between the vehicle speed and the required driving force of the vehicle. The first region is a region surrounded by a high-efficiency engine operating line H1 at a low speed stage and a line representing a system lower limit corresponding to the low speed stage and the system efficiency at the lower limit value η _{e — min} . This is an area indicated as a mode selection area 1.

The second region is the maximum region in which the parallel mode is selected at the high speed stage in the relationship between the vehicle speed and the required driving force of the vehicle. The second region is a region surrounded by a high-efficiency high-efficiency engine operating line H2 and a line corresponding to the high-speed stage and representing a system lower limit at which the system efficiency becomes the lower limit value η _{e — min} . This is an area indicated as mode selection area 2. The first region and the second region are separated without intersecting.

  When the operating point of the vehicle calculated from the vehicle required driving force and the vehicle speed is in the first region (parallel mode selection region 1), the main controller 26 sets the gear stage of the transmission 24 to the low speed stage, and Select the parallel mode and run the vehicle. Further, when the operating point of the vehicle calculated from the vehicle required driving force and the vehicle speed is in the second region (parallel mode selection region 2), the main controller 26 sets the speed of the transmission 24 to the high speed, In addition, the vehicle is driven by selecting the parallel mode.

On the other hand, when the calculated operating point of the vehicle is in a region away from the first region and the second region, the main controller 26 selects the EV mode or the series mode and causes the vehicle to travel. At this time, the EV mode and the series mode are selected using, for example, the detected SOC and the calculated system efficiency η _S as shown in FIG. For example, when the SOC is low and the charge request is high, the series mode is selected.

  At this time, during traveling in the parallel mode of one shift stage, the driver may instruct to operate the shift lever to another shift stage. In this case, the main controller 26 causes the second MG 14 to generate the same torque as the torque generated from the engine before the shift substantially in synchronism with the release of the clutch 22, and changes the travel mode to the EV mode or the series mode. Switch. Thereafter, the main controller 26 uses the first MG 20 coupled to the engine 12 to adjust the engine speed so as to match the next high speed stage. At this time, the engine speed is decreased in the case of shifting up to the high speed stage side, and the engine speed is increased in the case of shifting down to the low speed stage side. After the rotation synchronization of the engine 12 is thus performed, the shift is completed, the EV mode or the series mode is terminated, the clutch 22 is connected, and the parallel mode is restored.

In the above operation, the EV mode or the series mode does not necessarily have to be terminated immediately after the shift, and the EV mode or the series mode may be continued until the parallel mode is selected according to the driving state of the vehicle. Also in the configuration of this example, as in the configurations of FIGS. 1 to 11, the operation in the parallel mode can be limited to high-efficiency traveling in which the system efficiency is equal to or higher than the lower limit value η _{e — min} . Further, the system efficiency in the parallel mode can be limited to a higher one as the SOC becomes higher. For this reason, the fuel consumption in the driving | operation in parallel mode can be improved, and the charge amount of the battery 16 can be ensured. By improving fuel efficiency in the parallel mode, inefficient driving conditions can be reduced. Further, since the EV mode or the series mode is set before shifting from the parallel mode to the parallel mode corresponding to another gear stage at the time of shifting, the shift shock can be reduced. As a result, the shift shock can be reduced and the efficiency can be improved. Other configurations and operations are the same as those in FIGS. 1 to 11.

  Further, since the transmission 24 includes only two speed stages, a low speed stage and a high speed stage, for the forward speed of the vehicle, the transmission 24 can be reduced in size and cost. Note that the forward speed of the transmission is not limited to two, and may be three or more. In the configurations of the examples in FIGS. 1 to 19, the transmission 24 may have only one speed as a forward speed.

  DESCRIPTION OF SYMBOLS 10 Control system, 12 Engine, 14 2nd motor generator (2nd MG), 16 Battery, 18 Speed-up gear mechanism, 20 1st motor generator (1st MG), 21 Power transmission part, 22 Clutch, 23 Differential gear mechanism, 24 Transmission, 26 Main controller, 28 PCU, 30 ECU, 32 Drive shaft.

Claims (14)

Engine,
A generator driven by the engine;
A battery to be charged by being supplied with electric power from the generator;
A drive motor for driving the drive wheels of the vehicle with electric power supplied from the battery;
A clutch for connecting and disconnecting power transmission between the engine and the drive wheel;
A control device,
The control device, as a running mode,
EV mode for releasing the clutch and stopping driving of the engine, and driving the driving wheel by driving the driving motor with electric power supplied from the battery;
Series mode for driving the drive wheels by driving the drive motor with electric power generated by opening the clutch and driving the generator by the engine;
A control system for a hybrid vehicle for driving the vehicle by switching between a parallel mode in which the clutch is connected and the drive wheels are driven by driving the engine,
When the parallel mode is selected, the control device causes the engine to operate at an operating point in the highest efficiency or high efficiency region with respect to the engine speed corresponding to the vehicle speed, and the battery is fully charged. By increasing the rotational speed range in which the engine is operated in the parallel mode as the SOC, which is the charging ratio with respect to the amount, decreases in the direction in which the lower limit of the efficiency defined using the thermal efficiency of the engine decreases, the parallel mode A hybrid vehicle control system that changes the selection conditions. In the hybrid vehicle control system according to claim 1,
Wherein the control device, the ratio of vehicle travel request output of the engine output and alpha, the thermal efficiency of the engine and .eta.e, the power generation efficiency of the generator as eta _MG, with an efficiency which is defined by using the thermal efficiency .eta.e of the engine A system efficiency η _S in the parallel mode,
ηe × {α + (1−α) × η _MG },
If the lower limit of the system efficiency eta _S was system efficiency lower eta _S _ _lim,
The rotational speed range in which the engine is operated in the parallel mode is set to a rotational speed range corresponding to an efficiency equal to or higher than the system efficiency lower limit η _{S — lim} , and the system efficiency lower limit η _{S — lim as the} SOC decreases. The hybrid vehicle control system widens the engine speed range in which the engine can operate in the parallel mode by changing the system efficiency lower limit η _{S — lim} with respect to the SOC so as to decrease the engine efficiency. The hybrid vehicle control system according to claim 2,
When the SOC is equal to or higher than a first threshold SOC1 set in advance, the control device sets the system efficiency lower limit η _{S — lim} to be equal to or higher than a preset upper limit value η _{S — max of the} system efficiency η _S , A hybrid vehicle control system that prohibits engine operation. The hybrid vehicle control system according to claim 2,
The control device previously set the relationship between the the SOC system efficiency lower eta _S _ _lim, the relationship and the lower limit value the system efficiency lower eta _S _ _lim calculated from the SOC preset eta _S _ _min A hybrid vehicle control system that switches the travel mode to the series mode when the vehicle travels below. In the hybrid vehicle control system according to claim 3,
The control device is a control system for a hybrid vehicle, wherein the first threshold SOC1 can be changed according to a driver's selection. In the hybrid vehicle control system according to claim 3,
The control apparatus is a control system for a hybrid vehicle, wherein the first threshold value SOC1 can be changed according to a history of driving conditions of the vehicle. In the hybrid vehicle control system according to claim 1,
The control device includes:
When the lower limit of the thermal efficiency of the engine, which is the efficiency defined using the thermal efficiency of the engine, is the thermal efficiency lower limit η _{e _lim} ,
The rotational speed range in which the engine is operated in the parallel mode is a rotational speed range corresponding to an efficiency equal to or higher than the thermal efficiency lower limit η _{e _lim} , and the thermal efficiency lower limit η _{e _lim} decreases as the SOC decreases. As described above, the hybrid vehicle control system widens the engine speed range in which the engine can operate in the parallel mode by changing the thermal efficiency lower limit η _{e — lim} with respect to the SOC. The hybrid vehicle control system according to claim 7,
When the SOC is equal to or higher than a preset first threshold SOC1a, the control device sets the thermal efficiency lower limit η _{e — lim} to be equal to or higher than a preset upper limit value η _{e — max of the} thermal efficiency, and operates the engine. Prohibited hybrid vehicle control system. The hybrid vehicle control system according to claim 7,
The control device previously set the relationship between the SOC and the heat efficiency lower eta _e _ _lim, said calculated from the relationship and the SOC was the thermal efficiency lower eta _e _ _lim is below a predetermined lower limit value eta _e _ _min In this case, the hybrid vehicle control system switches the travel mode to the series mode. The hybrid vehicle control system according to claim 8,
The control device is a control system for a hybrid vehicle, wherein the first threshold SOC1a can be changed according to a driver's selection. The hybrid vehicle control system according to claim 8,
The control apparatus is a control system for a hybrid vehicle, wherein the first threshold SOC1a can be changed according to a history of driving conditions of the vehicle. In the hybrid vehicle control system according to claim 1,
A transmission that is disposed in a power transmission portion between the output shaft of the engine and the driving wheel, and includes a forward low speed stage and a high speed stage as a plurality of speed stages;
The control device releases the clutch and switches to the EV mode or the series mode when switching to another gear stage during traveling in the parallel mode at one gear stage, and then switches to the EV mode or the series mode. A control system for a hybrid vehicle, wherein the machine is switched to another gear, and then the clutch is connected to switch to the parallel mode corresponding to the other gear. The hybrid vehicle control system according to claim 12,
In the relationship between the vehicle speed and the driving force of the vehicle, the first region which is the maximum region of the region where the parallel mode is selected at the low speed stage, and the region away from the first region, the parallel at the high speed stage A hybrid vehicle control system in which a second region which is a maximum region of regions in which a mode is selected is set, and the EV mode or the series mode is selected in a region away from the first region and the second region . In the hybrid vehicle control system according to claim 12 or 13,
The control system for a hybrid vehicle, wherein the plurality of shift stages includes only two stages of the low speed stage and the high speed stage with respect to the forward shift stage.

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