Controlling engine speed during acceleration of a hybrid vehicle

When an acceleration request is issued, an electronic control unit for a hybrid vehicle performs control for producing an acceleration feeling of setting a target engine rotation speed to an initial rotation speed (=basic initial value+initial value correction value) which is lower than an optimal-fuel-efficiency rotation speed at which required engine power is able to be most efficiently output and increasing the engine rotation speed from the initial rotation speed to the optimal-fuel-efficiency rotation speed at a rotation speed increase rate (=basic increase rate+increase rate correction value) based on the elapse of time. When the target supercharging pressure is high, the initial value correction value is set to a greater value and the increase rate correction value is set to a greater value than when the target supercharging pressure is low.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-143334 filed on Aug. 2, 2019, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a control device for a hybrid vehicle in which power which is output from an engine with a supercharger is transmitted to driving wheels via a stepless transmission.

2. Description of Related Art

A control device for a hybrid vehicle that performs control for producing an acceleration feeling is known. An example thereof is a control device for a hybrid vehicle described in Japanese Unexamined Patent Application Publication No. 2015-128955 (JP 2015-128955 A). In the control device for a hybrid vehicle described in JP 2015-128955 A, control for producing an acceleration feeling is performed and an output shortage of engine power which is generated through the control for producing an acceleration feeling is complemented with drive power from a rotary machine. When a state of charge of a battery that drives the rotary machine decreases, control is performed such that occurrence of a shortage of vehicle drive power is curbed.

SUMMARY

In performing control for producing an acceleration feeling in response to an acceleration request, there is a likelihood that a supercharging response delay will occur in the engine with a supercharger and an output shortage of the engine for required engine power will increase. When it is intended to supplement the output shortage using the rotary machine, this supplementation may not be accomplished due to constraints of the battery and thus there is concern about a decrease in acceleration performance.

The disclosure provides a control device for a hybrid vehicle that can curb a decrease in acceleration performance which is caused by an output shortage of an engine with a supercharger due to a supercharging response delay of the engine in performing control for producing an acceleration feeling.

According to a first aspect of the disclosure, there is provided a control device for (A) a hybrid vehicle including an engine with a supercharger, a stepless transmission that is provided in a power transmission path between the engine and driving wheels, and a rotary machine that is connected to the power transmission path and using the engine and the rotary machine as drive power sources, the control device including (B) a drive control unit configured (b1) to perform control for producing an acceleration feeling of setting a target value of an engine rotation speed to an initial rotation speed which is lower than an optimal-fuel-efficiency rotation speed at which the engine is able to most efficiently output required engine power, increasing the target value of the engine rotation speed from the initial rotation speed to the optimal-fuel-efficiency rotation speed at a rotation speed increase rate based on at least one of an increase in a vehicle speed and elapse of time, and controlling the stepless transmission such that the engine rotation speed reaches the target value when an acceleration request is issued and (b2) to control the rotary machine such that an output shortage of the engine for the required engine power which is caused by the engine rotation speed becoming less than the optimal-fuel-efficiency rotation speed through the control for producing the acceleration feeling is supplemented, (C) wherein the drive control unit is configured (c1) to set the initial rotation speed or a lower limit of the initial rotation speed based on a target supercharging pressure of the engine or an amount of change of the target supercharging pressure at the time of start of the control for producing the acceleration feeling and (c2) to set the initial rotation speed or the lower limit thereof to a greater value when the target supercharging pressure is high than when the target supercharging pressure is low or when the amount of change of the target supercharging pressure is great than when the amount of change of the target supercharging pressure is small.

A second aspect of the disclosure provides the control device for a hybrid vehicle according to the first aspect, wherein the drive control unit is configured to set the initial rotation speed or the lower limit thereof to a greater value as the target supercharging pressure increases or as the amount of change of the target supercharging pressure increases.

A third aspect of the disclosure provides the control device for a hybrid vehicle according to the first or second aspect, (A) wherein the drive control unit is configured (a1) to set the rotation speed increase rate based on the target supercharging pressure or the amount of change of the target supercharging pressure and (a2) to set the rotation speed increase rate to a greater value when the target supercharging pressure is high than when the target supercharging pressure is low or when the amount of change of the target supercharging pressure is great than when the amount of change of the target supercharging pressure is small.

A fourth aspect of the disclosure provides the control device for a hybrid vehicle according to any one of the first to third aspects, wherein the drive control unit is configured to set the rotation speed increase rate to a greater value as the target supercharging pressure increases or as the amount of change of the target supercharging pressure increases.

The control device for a hybrid vehicle according to the first aspect includes (A) the drive control unit configured (a1) to perform control for producing an acceleration feeling of setting a target value of an engine rotation speed to an initial rotation speed which is lower than an optimal-fuel-efficiency rotation speed at which the engine is able to most efficiently output required engine power, increasing the target value of the engine rotation speed from the initial rotation speed to the optimal-fuel-efficiency rotation speed at a rotation speed increase rate based on at least one of an increase in a vehicle speed and elapse of time, and controlling the stepless transmission such that the engine rotation speed reaches the target value when an acceleration request is issued and (a2) to control the rotary machine such that an output shortage of the engine for the required engine power which is caused by the engine rotation speed becoming less than the optimal-fuel-efficiency rotation speed through the control for producing the acceleration feeling is supplemented. (B) The drive control unit is configured (b1) to set the initial rotation speed or a lower limit of the initial rotation speed based on a target supercharging pressure of the engine or an amount of change of the target supercharging pressure at the time of start of the control for producing the acceleration feeling and (b2) to set the initial rotation speed or the lower limit thereof to a greater value when the target supercharging pressure is high than when the target supercharging pressure is low or when the amount of change of the target supercharging pressure is great than when the amount of change of the target supercharging pressure is small. An output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur when the target supercharging pressure is high than when the target supercharging pressure is low. In addition, an output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur when the amount of change of the target supercharging pressure is great than when the amount of change of the target supercharging pressure is small. Accordingly, when an output shortage of the engine is likely to occur, the initial rotation speed of the engine in the control for producing the acceleration feeling or the lower limit of the initial rotation speed is set to a great value such that the engine rotation speed increases in an early stage. As a result, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure.

With the control device for a hybrid vehicle according to the second aspect, the drive control unit sets the initial rotation speed or the lower limit thereof to a greater value as the target supercharging pressure increases or as the amount of change of the target supercharging pressure increases. An output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur as the target supercharging pressure becomes greater. In addition, an output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur as the amount of change of the target supercharging pressure becomes greater. Accordingly, when an output shortage of the engine is likely to occur, the initial rotation speed of the engine in the control for producing the acceleration feeling or the lower limit of the initial rotation speed is set to a great value and thus it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure.

With the control device for a hybrid vehicle according to the third aspect, (A) the drive control unit (a1) sets the rotation speed increase rate based on the target supercharging pressure or the amount of change of the target supercharging pressure and (a2) sets the rotation speed increase rate to a greater value when the target supercharging pressure is high than when the target supercharging pressure is low or when the amount of change of the target supercharging pressure is great than when the amount of change of the target supercharging pressure is small. An output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur when the target supercharging pressure is high than when the target supercharging pressure is low. In addition, an output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur when the amount of change of the target supercharging pressure is great than when the amount of change of the target supercharging pressure is small. Accordingly, when an output shortage of the engine is likely to occur, the rotation speed increase rate of the engine in the control for producing the acceleration feeling is set to a great value such that the engine rotation speed increases rapidly. As a result, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure.

With the control device for a hybrid vehicle according to the fourth aspect, the drive control unit sets the rotation speed increase rate to a greater value as the target supercharging pressure increases or as the amount of change of the target supercharging pressure increases. An output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur as the target supercharging pressure becomes greater. In addition, an output shortage of the engine due to a response delay of the supercharging pressure is more likely to occur as the amount of change of the target supercharging pressure becomes greater. Accordingly, when an output shortage of the engine is likely to occur, the rotation speed increase rate of the engine in the control for producing the acceleration feeling is set to a great value and thus it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings. In the following embodiments, the drawings are appropriately simplified or modified, and dimensional ratios, shapes, and the like of constituent elements are not necessarily accurate.

FIG.1is a diagram schematically illustrating a configuration of a hybrid vehicle10in which an electronic control unit100according to a first embodiment of the disclosure is mounted and illustrating a principal part of a control function for various types of control in the hybrid vehicle10. The hybrid vehicle10(hereinafter referred to as a “vehicle10”) includes an engine12, a first rotary machine MG, a second rotary machine MG2, a power transmission device14, and driving wheels16.

FIG.2is a diagram schematically illustrating a configuration of the engine12. The engine12is a drive power source for travel of the vehicle10and is a known internal combustion engine such as a gasoline engine or a diesel engine including a supercharger18, that is, an engine with the supercharger18. An intake pipe20is provided in an intake system of the engine12, and the intake pipe20is connected to an intake manifold22which is attached to an engine body12a. An exhaust pipe24is provided in an exhaust system of the engine12and the exhaust pipe24is connected to an exhaust manifold26which is attached to the engine body12a. The supercharger18is a known exhaust-turbine supercharger, that is, a turbocharger, including a compressor18cthat is provided in the intake pipe20and a turbine18tthat is provided in the exhaust pipe24. The turbine18tis rotationally driven by exhaust gas, that is, a flow of exhaust gas. The compressor18cis connected to the turbine18t. The compressor18cis rotationally driven by the turbine18tto compress air suctioned into the engine12, that is, intake air.

An exhaust bypass28that causes exhaust gas to flow from upstream to downstream with respect to the turbine18tby bypassing the turbine18tis provided in the exhaust pipe24. A waste gate valve30(hereinafter referred to as “WGV30”) that continuously controls a ratio of exhaust gas passing through the exhaust bypass28to exhaust gas passing through the turbine18tis provided in the exhaust bypass28. A valve opening of the WGV30is continuously adjusted by causing the electronic control unit100which will be described later to operate an actuator which is not illustrated. As the valve opening of the WGV30increases, exhaust gas of the engine12is more likely to be discharged via the exhaust bypass28. Accordingly, in a supercharged state of the engine12in which a supercharging operation of the supercharger18works, a supercharging pressure Pchg [Pa] from the supercharger18decreases as the valve opening of the WGV30increases. The supercharging pressure Pchg from the supercharger18is a pressure of intake air and is an air pressure downstream from the compressor18cin the intake pipe20. A side on which the supercharging pressure Pchg is low is, for example, a side with a pressure of intake air in a non-supercharged state of the engine12in which the supercharging operation of the supercharger18does not work at all, that is, a side with a pressure of intake air in an engine without the supercharger18.

An air cleaner32is provided in an inlet of the intake pipe20, and an air flowmeter34that measures an amount of intake air of the engine12is provided in the intake pipe20downstream from the air cleaner32and upstream from the compressor18c. An intercooler36which is a heat exchanger that cools intake air compressed by the supercharger18by exchanging heat between intake air and outside air or a coolant is provided in the intake pipe20downstream from the compressor18c. An electronic throttle valve38of which opening and closing are controlled by causing an electronic control unit100which will be described later to operate a throttle actuator which is not illustrated is provided in the intake pipe20downstream from the intercooler36and upstream from the intake manifold22. A supercharging pressure sensor40that detects a supercharging pressure Pchg from the supercharger18and an intake air temperature sensor42that detects an intake air temperature which is the temperature of intake air are provided in the intake pipe20between the intercooler36and the electronic throttle valve38. A throttle valve opening sensor44that detects a throttle valve opening θth [%] which is an opening of the electronic throttle valve38is provided in the vicinity of the electronic throttle valve38, for example, in the throttle actuator.

An air recirculation bypass46that causes air to flow again from downstream to upstream with respect to the compressor18cby bypassing the compressor18cis provided in the intake pipe20. For example, an air bypass valve48that is opened to curb occurrence of a surge and to protect the compressor18cat the time of sudden closing of the electronic throttle valve38is provided in the air recirculation bypass46.

In the engine12, an engine torque Te [Nm] which is an output torque of the engine12is controlled by causing the electronic control unit100which will be described later to control an engine control device50(seeFIG.1) including, for example, the electronic throttle valve38, a fuel injection device, an ignition device, and the WGV30.

Referring back toFIG.1, the first rotary machine MG1and the second rotary machine MG2are rotary electric machines having a function of an electric motor (a motor) and a function of a power generator (a generator) and are so-called motor generators. The first rotary machine MG1and the second rotary machine MG2can serve as drive power sources for travel of the vehicle10. The first rotary machine MG1and the second rotary machine MG2are connected to a battery54which is provided in the vehicle10via an inverter52which is provided in the vehicle10. In the first rotary machine MG1and the second rotary machine MG2, an MG1torque Tg [Nm] which is an output torque of the first rotary machine MG1and an MG2torque Tm [Nm] which is an output torque of the second rotary machine MG2are controlled by causing the electronic control unit100which will be described later to control the inverter52. For example, in the case of forward rotation, an output torque of each rotary machine is a powering torque which is a positive torque on an acceleration side and is a regenerative torque which is a negative torque on a deceleration side. The battery54is a power storage device that transmits and receives electric power to and from the first rotary machine MG1and the second rotary machine MG2. The first rotary machine MG1and the second rotary machine MG2are provided in a case56which is a non-rotary member attached to the vehicle body.

The power transmission device14includes a gear shifting unit58, a differential unit60, a driven gear62, a driven shaft64, a final gear66, a differential gear68, and a reduction gear70in the case56. The gear shifting unit58and the differential unit60are arranged coaxially with an input shaft72which is an input rotary member of the gear shifting unit58. The gear shifting unit58is connected to the engine12via the input shaft72or the like. The differential unit60is connected in series to the gear shifting unit58. The driven gear62engages with a drive gear74which is an output rotary member of the differential unit60. The driven shaft64fixes the driven gear62and the final gear66such that they cannot rotate relative to each other. The final gear66has a smaller diameter than the driven gear62. The differential gear68engages with the final gear66via a differential ring gear68a. The reduction gear70has a smaller diameter than the driven gear62and engages with the driven gear62. A rotor shaft76of the second rotary machine MG2which is disposed in parallel to the input shaft72is connected to the reduction gear70separately from the input shaft72and is connected to the second rotary machine MG2in a power-transmittable manner. The power transmission device14includes an axle78that is connected to the differential gear68.

The power transmission device14having this configuration is suitably used for a vehicle of a front-engine front-drive (FF) type or a rear-engine rear-drive (RR) type. In the power transmission device14, power which is output from the engine12, the first rotary machine MG1, and the second rotary machine MG2is transmitted to the driven gear62. The power transmitted to the driven gear62is transmitted to the driving wheels16sequentially via the final gear66, the differential gear68, the axle78, and the like. In this way, the second rotary machine MG2is connected to the driving wheels16in a power-transmittable manner. In the power transmission device14, the gear shifting unit58, the differential unit60, the driven gear62, the driven shaft64, the final gear66, the differential gear68, and the axle78constitute a power transmission path PT which is provided between the engine12and the driving wheels16.

The gear shifting unit58includes a first planetary gear mechanism80, a clutch C1, and a brake B1. The first planetary gear mechanism80is a known single-pinion type planetary gear device including a sun gear S0, a carrier CA0, and a ring gear R0. The differential unit60includes a second planetary gear mechanism82. The second planetary gear mechanism82is a known single-pinion type planetary gear device including a sun gear S1, a carrier CA, and a ring gear R1.

The clutch C1and the brake B1are hydraulic frictional engagement devices including a multi-disc or single-disc clutch or brake which is pressed by a hydraulic actuator or a band brake which is tightened by a hydraulic actuator. In the clutch C1and the brake B1, operating states such as an engaged state and a disengaged state are switched based on regulated hydraulic pressures which are output from a hydraulic pressure control circuit84provided in the vehicle10by causing the electronic control unit100which will be described later to control the hydraulic pressure control circuit84.

The first planetary gear mechanism80, the second planetary gear mechanism82, the clutch C1, and the brake B1are connected to each other as illustrated inFIG.1.

In a state in which both the clutch C1and the brake B1are disengaged, a differential operation of the first planetary gear mechanism80is permitted. In this state, since a reaction torque of the engine torque Te does not appear in the sun gear S0, the gear shifting unit58is in a neutral state in which mechanical power transmission is not possible, that is, a neutral state. In a state in which the clutch C1is engaged and the brake B1is disengaged, the rotary elements of the first planetary gear mechanism80rotate integrally. In this state, rotation of the engine12is transmitted from the ring gear R0to the carrier CA at a constant speed. On the other hand, in a state in which the clutch C1is disengaged and the brake B1is engaged, rotation of the sun gear S0of the first planetary gear mechanism80is prohibited and rotation of the ring gear R0is increased to be higher than rotation of the carrier CA0. In this state, rotation of the engine12is increased and output from the ring gear R0.

In this way, the gear shifting unit58serves as a two-stage stepped transmission which can be switched, for example, between a low gear stage in a directly coupled state with a gear ratio of “1.0” and a high gear stage in an overdrive state with a gear ratio of “0.7.” In a state in which both the clutch C1and the brake B1are engaged, rotation of the rotary elements of the first planetary gear mechanism80is prohibited. In this state, rotation of the ring gear R0which is an output rotary member of the gear shifting unit58is stopped and thus rotation of the carrier CAT which is an input rotary member of the differential unit60is stopped.

In the second planetary gear mechanism82, the carrier CAT is a rotary element that is connected to the ring gear R0which is an output rotary member of the gear shifting unit58and serves as an input rotary member of the differential unit60. The sun gear ST is a rotary element that is integrally connected to the rotor shaft86of the first rotary machine MG1and is connected to the first rotary machine MG1in a power-transmittable manner. The ring gear R1is a rotary element that is integrally connected to the drive gear74and is connected to the driving wheels16in a power-transmittable manner and serves as an output rotary member of the differential unit60.

The second planetary gear mechanism82is a power split mechanism that mechanically splits power of the engine12which is input to the carrier CAT via the gear shifting unit58to the first rotary machine MG1and the drive gear74. That is, the second planetary gear mechanism82is a differential mechanism that splits and transmits the power of the engine12to the driving wheels16and the first rotary machine MG1. In the second planetary gear mechanism82, the carrier CA serves as an input element, the sun gear S1serves as a reaction element, and the ring gear R1serves as an output element. The differential unit60constitutes an electrical gear shifting mechanism, for example, an electrical stepless transmission, in which a differential state of the second planetary gear mechanism82(that is, a differential state of the differential unit60) is controlled by controlling the operating state of the first rotary machine MG1that is connected to the second planetary gear mechanism82in a power-transmittable manner. The differential unit60which is a stepless transmission is provided in the power transmission path PT. The first rotary machine MG1is a rotary machine to which the power of the engine12is transmitted. Since the gear shifting unit58is in an overdrive state, an increase in torque of the first rotary machine MG1is curbed. The differential unit60corresponds to a “stepless transmission” in the present disclosure.

FIG.3is a collinear diagram illustrating relative relationships between rotation speeds of the rotary elements in the differential unit60illustrated inFIG.1. InFIG.3, three vertical lines Y1, Y2, and Y3correspond to three rotary elements of the second planetary gear mechanism82constituting the differential unit60. The vertical line Y1represents the rotation speed of the sun gear S which is a second rotary element RE2connected to the first rotary machine MG1(see “MG1” inFIG.3). The vertical line Y2represents the rotation speed of the carrier CAT which is a first rotary element RE connected to the engine12(see “ENG” inFIG.3) via the gear shifting unit58. The vertical line Y3represents the rotation speed of the ring gear R1which is a third rotary element RE3integrally connected to the drive gear74(see “OUT” inFIG.3). The second rotary machine MG2(see “MG2” inFIG.3) is connected to the driven gear62engaging with the drive gear74via the reduction gear70or the like. The gaps between the vertical lines Y1, Y2, and Y3are determined according to a gear ratio ρ (=number of teeth of the sun gear S1/number of teeth of the ring gear R1) of the second planetary gear mechanism82. In the relationship between the vertical axes in the collinear diagram, when the gap between the sun gear S1and the carrier CAT corresponds to “1,” the gap between the carrier CAT and the ring gear R1corresponds to the gear ratio ρ.

A mechanical oil pump (see “MOP” inFIG.3) which is provided in the vehicle10is connected to the carrier CA. This mechanical oil pump is operated with rotation of the carrier CAT to supply oil which is used for engaging operations of the clutch C1and the brake B1, lubrication of the parts, and cooling of the parts. When rotation of the carrier CAT is stopped, the oil is supplied by an electrical oil pump (not illustrated) which is provided in the vehicle10.

A solid line Lef inFIG.3denotes an example of relative speeds of the rotary elements at the time of forward travel in an HV travel mode which is a travel mode in which HV travel (hybrid travel) using at least the engine12as a drive power source is possible. A solid line Ler inFIG.3denotes an example of relative speeds of the rotary elements at the time of reverse travel in the HV travel mode.

In the HV travel mode, in the second planetary gear mechanism82, for example, when an MG1torque Tg which is a reaction torque and a negative torque of the first rotary machine MG1with respect to an engine torque Te that is a positive torque which is input to the carrier CAT via the gear shifting unit58is input to the sun gear S1, a direct engine-transmitted torque Td [Nm] which is a positive torque appears in the ring gear R1. For example, when the MG1torque Tg (=−ρ/(1+ρ)×Te) which is a reaction torque with respect to the engine torque Te which is input to the carrier CA is input to the sun gear S in a state in which the clutch C1is engaged, the brake B1is disengaged, and the gear shifting unit58is in a directly coupled state with a gear ratio of “1.0,” the direct engine-transmitted torque Td (=Te/(1+ρ)=−(1/ρ)×Tg) appears in the ring gear R1. A combined torque of the direct engine-transmitted torque Td and the MG2torque Tm which are transmitted to the driven gear62can be transmitted as a drive torque Tw [Nm] of the vehicle10to the driving wheels16according to required drive power Pwdem [N].

The first rotary machine MG1serves as a power generator when a negative torque is generated at the time of forward rotation. Generated electric power Wg [W] of the first rotary machine MG1is charged in the battery54or is consumed in the second rotary machine MG2. The second rotary machine MG2outputs the MG2torque Tm using all or some of the generated electric power Wg or electric power from the battery54in addition to the generated electric power Wg. The MG2torque Tm at the time of forward travel is a powering torque which is a positive torque at the time of forward rotation, and the MG2torque Tm at the time of reverse travel is a powering torque which is a negative torque at the time of reverse rotation.

The differential unit60can operate as an electrical stepless transmission. For example, in the HV travel mode, when the rotation speed of the first rotary machine MG1, that is, the rotation speed of the sun gear S, increases or decreases with respect to an output rotation speed No [rpm] which is the rotation speed of the drive gear74which is constrained on rotation of the driving wheels16by controlling the operating state of the first rotary machine MG1, the rotation speed of the carrier CA1increases or decreases. Since the carrier CA1is connected to the engine12via the gear shifting unit58, an engine rotation speed Ne which is the rotation speed of the engine12increases or decreases with the increase or decrease in the rotation speed of the carrier CA1. Accordingly, in the HV travel, it is possible to perform control such that an engine operating point OPeng is set to an efficient operating point. This hybrid type is referred to as a mechanical split type or a split type. The first rotary machine MG1is a rotary machine that can control the engine rotation speed Ne. The engine operating point OPeng is an operation point of the engine12which is expressed by the engine rotation speed Ne and the engine torque Te.

A dotted line Lm1inFIG.3represents an example of relative speeds of the rotary elements at the time of forward travel in a single-motor-driven EV travel mode in which EV travel (motor-driven travel) using only the second rotary machine MG2as a drive power source in a state in which the operation of the engine12is stopped is possible. In the single-motor-driven EV travel mode, when both the clutch C1and the brake B1are disengaged and the gear shifting unit58is put into a neutral state, the differential unit60is also put into a neutral state. In this state, the MG2torque Tm can be transmitted as a drive torque Tw of the vehicle10to the driving wheels16. In the single-motor-driven EV travel mode, for example, the first rotary machine MG1is maintained at zero rotation in order to decrease a drag loss in the first rotary machine MG1. For example, even when control for maintaining the first rotary machine MG1at zero rotation is performed, the differential unit60is in the neutral state and thus the drive torque Tw is not affected.

A dotted line Lm2inFIG.3represents an example of relative speeds of the rotary elements at the time of forward travel in a double-motor-driven EV travel mode in which EV travel using both the first rotary machine MG1and the second rotary machine MG2as drive power sources in a state in which the operation of the engine12is stopped is possible. In the double-motor-driven EV travel mode, when both the clutch C1and the brake B1are engaged and rotation of the rotary elements of the first planetary gear mechanism80is prohibited, the carrier CAT is stopped at zero rotation. In this state, the MG1torque Tg and the MG2torque Tm can be transmitted as the drive torque Tw of the vehicle10to the driving wheels16.

FIG.4is a diagram illustrating an example of optimal engine operating points OPengf in a two-dimensional coordinate system with the engine rotation speed Ne and the engine torque Te as variables. InFIG.4, a maximum efficiency line Leng denotes a group of optimal engine operating points OPengf. An optimal engine operating point OPengf is predetermined as an engine operating point OPeng at which total fuel efficiency in the vehicle10is the best in consideration of charging/discharging efficiency in the battery54in addition to fuel efficiency of the engine12alone, for example, when required engine power Pedem [W] is realized. That is, the engine rotation speed Ne at an optimal engine operating point OPengf is an optimal fuel-efficiency rotation speed Neeff at which the engine12can most efficiently output the required engine power Pedem.

Equi-engine-power lines Lpw1, Lpw2, and Lpw3denote examples in which the required engine power Pedem is engine power Pe1, Pe2, and Pe3, respectively. A point A is an engine operating point OPengA when the engine power Pe1is realized at the optimal engine operating point OPengf, a point B is an engine operating point OPengB when the engine power Pe2is realized at the optimal engine operating point OPengf, and a point C is an engine operating point OPengC when the engine power Pe3is realized at the optimal engine operating point OPengf. The points A, B, and C are also target values of the engine operating point OPeng which is expressed by a target engine rotation speed Netgt [rpm] and a target engine torque Tetgt [Nm], that is, a target engine operating point OPengtgt. That is, the target engine rotation speed Netgt is a target value of the engine rotation speed Ne and the target engine torque Tetgt is a target value of the engine torque Te.

For example, when the target engine operating point OPengtgt changes from the point A to the point C with an increase in an accelerator opening θacc [%] (for example, an increase in the accelerator opening θacc based on an operation of a driver increasing a force of depression of an accelerator pedal, which is not illustrated), the engine operating point OPeng changes on a path a which passes over the maximum efficiency line Leng. The target engine rotation speed Netgt corresponds to a “target value” in the present disclosure.

Although not illustrated inFIG.4, the optimal engine operating points OPengf at which the fuel efficiency is the highest in the engine12with the supercharger18are stored in advance with a supercharging pressure Pchg in addition to the engine rotation speed Ne and the engine torque Te as variables. The supercharging pressure Pchg when the required engine power Pedem is realized at the optimal engine operating points OPengf is a target supercharging pressure Pchgtgt [Pa].

FIG.5is a diagram illustrating an example of a drive power source switching map which is used for switching control between EV travel and HV travel. InFIG.5, a solid line Lswp is a boundary line between an EV travel area and an HV travel area at which switching between the EV travel and the HV travel is performed. An area in which a vehicle speed V [km/h] is relatively low and a required drive torque Twdem [Nm] is relatively low (that is, required drive power Pwdem is relatively small) is defined in advance in the EV travel area. An area in which the vehicle speed V is relatively high and the required drive torque Twdem is relatively high (that is, the required drive power Pwdem is relatively great) is defined in advance in the HV travel area. When a state of charge value SOC [%] of the battery54which will be described later is less than a predetermined value or when warming-up of the engine12is necessary, the EV travel area inFIG.5may be changed to the HV travel area. The predetermined value is a predetermined threshold value for determining that the state of charge value SOC is a value at which the engine12needs to be forcibly started to charge the battery54.

FIG.6is an engagement operation table illustrating a relationship between travel modes and combinations of operating states of the clutch C1and the brake B1in the travel modes. InFIG.6, “O” denotes an engaged state, a blank denotes a disengaged state, and “A” denotes that one of the clutch C1and the brake B1is engaged at the time of additional use of an engine brake for switching the engine12in a rotation-stopped state to a corotating state. “G” denotes that the first rotary machine MG1serves mainly as a generator, and “M” denotes that the first rotary machine MG1and the second rotary machine MG2serve mainly as a motor at the time of driving and serve mainly as a generator at the time of regeneration. The vehicle10can selectively realize the EV travel mode and the HV travel mode as travel modes. The EV travel mode has two modes including the single-motor-driven EV travel mode and the double-motor-driven EV travel mode.

The single-motor-driven EV travel mode is realized in a state in which both the clutch C1and the brake B1are disengaged. In the single-motor-driven EV travel mode, the clutch C1and the brake B1are disengaged and thus the gear shifting unit58is put into a neutral state. When the gear shifting unit58is put into the neutral state, the differential unit60is put into a neutral state in which a reaction torque of the MG1torque Tg does not appear in the carrier CA1connected to the ring gear R0. In this state, the electronic control unit100causes the second rotary machine MG2to output the MG2torque Tm for travel (see a dotted line Lm1inFIG.3). In the single-motor-driven EV travel mode, reverse travel may be performed by rotating the second rotary machine MG2opposite to the rotating direction at the time of forward travel.

In the single-motor-driven EV travel mode, since the ring gear R0is corotated with the carrier CA1but the gear shifting unit58is in the neutral state, the engine12is not corotated but is stopped at zero rotation. Accordingly, when regeneration control is performed in the second rotary machine MG2during travel in the single-motor-driven EV travel mode, a large amount of regeneration is possible. When the battery54is fully charged and regenerative energy does not appear during travel in the single-motor-driven EV travel mode, additional use of the engine brake can be considered. When the engine brake is used together, the brake B1or the clutch C1is engaged (see “use of engine brake together” inFIG.6). When the brake B1or the clutch C1is engaged, the engine12is corotated and the engine brake operates.

The double-motor-driven EV travel mode is realized in a state in which both the clutch C1and the brake B1are engaged. In the double-motor-driven EV travel mode, since the clutch C1and the brake B1are engaged, rotation of the rotary elements of the first planetary gear mechanism80is stopped, the engine12is stopped at zero rotation, and rotation of the carrier CA1connected to the ring gear R0is stopped. When rotation of the carrier CA1is stopped, a reaction torque of the MG1torque Tg appears in the carrier CA, and thus the MG1torque Tg can be mechanically output from the ring gear R1and transmitted to the driving wheels16. In this state, the electronic control unit100causes the first rotary machine MG1and the second rotary machine MG2to output the MG1torque Tg and the MG2torque Tm for travel (see the dotted line Lm2inFIG.3). In the double-motor-driven EV travel mode, both the first rotary machine MG1and the second rotary machine MG2can be rotated opposite to the rotating direction at the time of forward travel to allow reverse travel.

A low state of the HV travel mode is realized in a state in which the clutch C1is engaged and the brake B1is disengaged. In the low state of the HV travel mode, since the clutch C1is engaged, the rotary elements of the first planetary gear mechanism80are integrally rotated and the gear shifting unit58is put into a directly coupled state. Accordingly, rotation of the engine12is transmitted from the ring gear R0to the carrier CA at a constant speed. A high state of the HV travel mode is realized in a state in which the brake B1is engaged and the clutch C1is disengaged. In the high state of the HV travel mode, since the brake B1is engaged, rotation of the sun gear S0is stopped and the gear shifting unit58is put into an overdrive state. Accordingly, rotation of the engine12increases and is transmitted from the ring gear R0to the carrier CA1. In the HV travel mode, the electronic control unit100causes the first rotary machine MG to output the MG torque Tg which is a reaction torque of the engine torque Te by power generation and causes the second rotary machine MG2to output the MG2torque Tm by the generated electric power Wg of the first rotary machine MG1(see a solid line Lef inFIG.3). In the HV travel mode, for example, in the low state of the HV travel mode, the second rotary machine MG2can also be rotated opposite to the rotating direction at the time of forward travel to allow reverse travel (see a solid line Ler inFIG.3). In the HV travel mode, the vehicle can travel additionally using the MG2torque Tm based on electric power from the battery54. In the HV travel mode, for example, when the vehicle speed V is relatively high and the required drive torque Twdem is relatively small, the high state of the HV travel mode is set up.

Referring back toFIG.1, the vehicle10further includes the electronic control unit100serving as a controller including a control device for the vehicle10associated with control of the engine12, the first rotary machine MG, the second rotary machine MG2, and the like. For example, the electronic control unit100is configured to include a so-called microcomputer including a CPU, a RAM, a ROM, and an input and output interface, and the CPU performs various types of control of the vehicle10by performing signal processing in accordance with a program which is stored in the ROM in advance while using a temporary storage function of the RAM. The electronic control unit100is configured to include a computer for engine control, a computer for rotary machine control, and a computer for hydraulic pressure control according to necessity. The electronic control unit100corresponds to a “control device” in the present disclosure.

The electronic control unit100is supplied with various signals (for example, a supercharging pressure Pchg, a throttle valve opening θth, an engine rotation speed Ne, an output rotation speed No corresponding to a vehicle speed V, an MG1rotation speed Ng [rpm] which is the rotation speed of the first rotary machine MG1, an MG2rotation speed Nm [rpm] which is the rotation speed of the second rotary machine MG2, an accelerator opening θacc which is an accelerator operation amount from a driver indicating the magnitude of the driver's acceleration operation, and a battery temperature THbat [° C.], a battery charging/discharging current Ibat [mA], and a battery voltage Vbat [V] of the battery54) based on detection values from various sensors (for example, a supercharging pressure sensor40, a throttle valve opening sensor44, an engine rotation speed sensor88, an output rotation speed sensor90, an MG1rotation speed sensor92, an MG2rotation speed sensor94, an accelerator opening sensor96, and a battery sensor98) which are provided in the vehicle10.

The electronic control unit100outputs various command signals (for example, an engine control command signal Se for controlling the engine12, a rotary machine control command signal Sing for controlling the first rotary machine MG1and the second rotary machine MG2, and a hydraulic pressure control command signal Sp for controlling the operating states of the clutch C1and the brake B1) to various devices (for example, the engine control device50, the inverter52, and the hydraulic pressure control circuit84) which are provided in the vehicle10.

The electronic control unit100calculates a state of charge value SOC which is a value indicating the state of charge of the battery54, for example, based on the battery charging/discharging current Ibat and the battery voltage Vbat. The electronic control unit100calculates chargeable electric power Win [W] and dischargeable electric power Wout [W] for defining a feasible range of battery power Pbat [W] which is the power of the battery54, for example, based on the battery temperature THbat and the state of charge value SOC of the battery54. The chargeable electric power Win is possible input power for defining a limitation of input electric power of the battery54and the dischargeable electric power Wout is possible output power for defining a limitation of output electric power of the battery54. For example, the chargeable electric power Win and the dischargeable electric power Wout decrease as the battery temperature THbat decreases in a low-temperature area in which the battery temperature THbat is lower than that in a normal area, and decreases as the battery temperature THbat increases in a high-temperature area in which the battery temperature THbat is higher than that in a normal area. For example, the chargeable electric power Win decreases as the state of charge value SOC increases in an area in which the state of charge value SOC is high. For example, the dischargeable electric power Wout decreases as the state of charge value SOC decreases in an area in which the state of charge value SOC is low.

The electronic control unit100includes an acceleration request determining unit102, a supercharging execution determining unit104, and a drive control unit106.

The acceleration request determining unit102determines whether there is an acceleration request. Whether there is an acceleration request is determined, for example, based on whether the required drive torque Twdem is increased by an operation of a driver increasing a force of depression of an accelerator pedal. When the required drive torque Twdem is increased, it is determined that there is an acceleration request. For example, by applying the actual accelerator opening θacc and the actual vehicle speed V to a relationship between the accelerator opening θacc and the vehicle speed V and the required drive torque Twdem (for example, a drive power map) which is calculated and stored in advance (that is, predetermined) by experiment or by design, the required drive torque Twdem which is a drive torque Tw required for the vehicle10is calculated. In other words, the required drive torque Twdem is required drive power Pwdem at the vehicle speed V. The output rotation speed No or the like may be applied to the drive power map instead of the vehicle speed V.

The supercharging execution determining unit104determines whether supercharging in the engine12is to be performed when the acceleration request determining unit102determines that there is an acceleration request. For example, when a target supercharging pressure Pchgtgt at a target engine operating point OPengtgt which is set based on the accelerator opening θacc after a driver has performed an operation of increasing a force of depression of an accelerator pedal is a value with which a supercharging operation of the supercharger18works, the supercharging execution determining unit104determines that supercharging in the engine12is to be performed, and the supercharging execution determining unit104determines that supercharging in the engine12is not to be performed otherwise. The target supercharging pressure Pchgtgt is a target supercharging pressure Pchgtgt at the time of starting of control for producing an acceleration feeling (which will be described later) which is performed in response to an acceleration request, that is, a supercharging pressure Pchg at the time of ending of the control for producing the acceleration feeling.

The drive control unit106performs the control for producing the acceleration feeling and output compensation control when the acceleration request determining unit102determines that there is an acceleration request.

A method of setting a target engine operating point OPengtgt in the control for producing the acceleration feeling when the target engine operating point OPengtgt changes from a point A to a point C inFIG.4will be described below.

Here, the required engine power Pedem immediately before the control for producing the acceleration feeling is started is referred to as starting required engine power Pesta [W] and the required engine power Pedem at the time of ending of the control for producing the acceleration feeling is referred to as final required engine power Pefin [W]. In other words, the starting required engine power Pesta is engine power Pe which is required for the vehicle10immediately before an acceleration request is issued, and the final required engine power Pefin is engine power Pe which is required for the vehicle10in response to the acceleration request. In this example, the starting required engine power Pesta is engine power Pe1and the final required engine power Pefin is engine power Pe3.

The target engine operating point OPengtgt immediately before the control for producing the acceleration feeling is started is referred to as a starting operating point OPengsta, and the target engine rotation speed Netgt at the starting operating point OPengsta is referred to as a starting rotation speed Nesta [rpm]. In this example, the starting operating point OPengsta is an engine operating point OPengA (point A).

The target engine operating point OPengtgt at the time of ending of the control for producing the acceleration feeling is referred to as a final operating point OPengfin, and the target engine rotation speed Netgt at the final operating point OPengfin is referred to as a final rotation speed Nefin [rpm]. The final rotation speed Nefin is an optimal-fuel-efficiency rotation speed Neeff [rpm] of the engine12for realizing the final required engine power Pefin. In this example, the final operating point OPengfin is an engine operating point OPengC (point C).

The target engine operating point OPengtgt immediately after the control for producing the acceleration feeling is started is referred to as an initial operating point OPengini, and the target engine rotation speed Netgt at the initial operating point OPengini is referred to as an initial rotation speed Neini [rpm]. In this example, the initial operating point OPengini is an engine operating point OPengB (point B). The initial rotation speed Neini is a rotation speed which is lower than the final rotation speed Nefin and higher than the starting rotation speed Nesta. That is, the initial rotation speed Neini is lower than the optimal-fuel-efficiency rotation speed Neeff at the final operating point OPengfin at which the engine12can most efficiently output the final required engine power Pefin (=Pe3). “Required engine power” in the present disclosure is the required engine power Pedem when there is an acceleration request, and is the final required engine power Pefin which is engine power Pe required for the vehicle10in response to the acceleration request in this example.

The drive control unit106sets the target engine operating point OPengtgt to the initial operating point OPengini at the time of starting of the control for producing the acceleration feeling. Accordingly, the target engine operating point OPengtgt changes from the starting operating point OPengsta (point A) to the initial operating point OPengini (point B). The drive control unit106starts the control for producing the acceleration feeling such that the supercharging pressure Pchg of the engine12reaches the target supercharging pressure Pchgtgt at the time of starting of the control for producing the acceleration feeling. Thereafter, the drive control unit106increases the engine rotation speed Ne from the initial rotation speed Neini to the final rotation speed Nefin, that is, the optimal-fuel-efficiency rotation speed Neeff, at a preset rotation speed increase rate μ [rpm/ms] (seeFIGS.9A to9C) with the elapse of time t [ms]. Accordingly, the target engine operating point OPengtgt changes gradually from the initial operating point OPengini (point B) to the final operating point OPengfin (point C). The elapse of time t refers to the elapse of time t from the starting time of the control for producing the acceleration feeling at which the target engine operating point OPengtgt changes to the initial operating point OPengini. The elapse of time t corresponds to the “elapse of time” in the present disclosure.

As the initial rotation speed Neini, the rotation speed increase rate μ, and the lower-limit rotation speed Nemin [rpm] when the target supercharging pressure Pchgtgt does not have a value in which a supercharging operation works and the control for producing the acceleration feeling is performed, a basic initial value I0, a basic increase rate μ0[rpm/ms], and a basic lower limit M0[rpm] are acquired in advance by experiment or by design and are stored. The basic initial value I0, the basic increase rate μ0, and the basic lower limit M0are set to values with which an output shortage of the engine power Pe for the final required engine power Pefin which is caused by the engine rotation speed Ne becoming less than the final rotation speed Nefin, that is, the optimal-fuel-efficiency rotation speed Neeff, when the control for producing the acceleration feeling is performed based thereon can be compensated for by the second rotary machine MG2.

The initial rotation speed Neini at the initial operating point OPengini is set to a sum of the basic initial value I0and an initial value correction value α [rpm]. In other words, for example, the optimal engine operating point OPengf for realizing the initial rotation speed Neini becomes the initial operating point OPengini. The rotation speed increase rate μ is set to a sum of the basic increase rate μ0and an increase rate correction value β [rpm/ms]. The lower-limit rotation speed Nemin is set to a sum of the basic lower limit M0and a lower limit correction value γ [rpm]. In this way, the initial rotation speed Neini, the rotation speed increase rate μ, and the lower-limit rotation speed Nemin can be corrected by the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ, respectively.

FIGS.7A to7Care diagrams illustrating relationships among the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ and the target supercharging pressure Pchgtgt, whereFIG.7Aillustrates a relationship between the target supercharging pressure Pchgtgt and the initial value correction value α,FIG.7Billustrates a relationship between the target supercharging pressure Pchgtgt and the increase rate correction value β, andFIG.7Cillustrates a relationship between the target supercharging pressure Pchgtgt and the lower limit correction value γ.

The drive control unit106sets the initial value correction value α (>0) based on the target supercharging pressure Pchgtgt of the engine12at the time of starting of control for producing an acceleration feeling. As illustrated inFIG.7A, the initial value correction value α is set to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. The initial value correction value α is set to a greater value as the target supercharging pressure Pchgtgt becomes higher, that is, the initial value correction value α becomes greater as the target supercharging pressure Pchgtgt becomes greater. In the example illustrated inFIG.7A, the initial value correction value α increases linearly with an increase in the target supercharging pressure Pchgtgt. By setting the initial value correction value α, the drive control unit106sets the initial rotation speed Neini in control for producing an acceleration feeling to a value w(=I0+α) which is greater by the initial value correction value α than the basic initial value I0.

The drive control unit106sets the increase rate correction value β (>0) based on the target supercharging pressure Pchgtgt of the engine12at the time of starting of control for producing an acceleration feeling. As illustrated inFIG.7B, the increase rate correction value β is set to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. The increase rate correction value β is set to a greater value as the target supercharging pressure Pchgtgt becomes higher, that is, the increase rate correction value β becomes greater as the target supercharging pressure Pchgtgt becomes greater. In the example illustrated inFIG.7B, the increase rate correction value β increases linearly with an increase in the target supercharging pressure Pchgtgt. By setting the increase rate correction value β, the drive control unit106sets the rotation speed increase rate μ of the engine rotation speed Ne in control for producing an acceleration feeling to a value w(=μ0+β) which is greater by the increase rate correction value β than the basic increase rate μ0.

The drive control unit106sets the lower limit correction value γ (>0) based on the target supercharging pressure Pchgtgt of the engine12at the time of starting of control for producing an acceleration feeling. As illustrated inFIG.7C, the lower limit correction value γ is set to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. The lower limit correction value γ is set to a greater value as the target supercharging pressure Pchgtgt becomes higher, that is, the lower limit correction value γ becomes greater as the target supercharging pressure Pchgtgt becomes greater. In the example illustrated inFIG.7C, the lower limit correction value γ increases linearly with an increase in the target supercharging pressure Pchgtgt. Through this setting of the lower limit correction value γ, the drive control unit106sets the lower-limit rotation speed Nemin of a lower limit guard process in control for producing an acceleration feeling to a value w(=M0+γ) which is greater by the lower limit correction value γ than the basic lower limit M0. The lower limit guard process is a process of setting the lower limit of the target engine rotation speed Netgt and, specifically, the target engine rotation speed Netgt is set not to be less than the lower-limit rotation speed Nemin.

Referring back toFIG.1, the drive control unit106calculates the MG1torque Tg, for example, in feedback control in which the first rotary machine MG operates such that the engine rotation speed Ne reaches the target engine rotation speed Netgt. The MG2torque Tm is calculated, for example, such that the drive torque Tw corresponding to the direct engine-transmitted torque Td and the MG2torque Tm are summed to acquire the required drive torque Twdem. That is, the drive control unit106controls the second rotary machine MG2such that an output shortage of the engine power Pe [W] for the final required engine power Pefin which is caused by the engine rotation speed Ne becoming less than the final required rotation speed Nefin, that is, the optimal-fuel-efficiency rotation speed Neeff, by control for producing an acceleration feeling is compensated for. Specifically, the second rotary machine MG2is controlled such that a shortage of the direct engine-transmitted torque Td due to the output shortage of the engine power Pe is compensated for by the MG2torque Tm. Accordingly, drive power which is required by a driver is realized. Controlling of the second rotary machine MG2such that the output shortage of the engine power Pe [W] for the final required engine power Pefin which is caused by the engine rotation speed Ne becoming less than the final required rotation speed Nefin by the control for producing an acceleration feeling is compensated for is output compensation control.

In this way, the vehicle10is a vehicle in which the MG1torque Tg which is a reaction torque of the first rotary machine MG1which is input to the sun gear S1of the differential unit60is controlled such that the engine rotation speed Ne reaches the target engine rotation speed Netgt. By controlling the engine12and the differential unit60which is a stepless transmission, the engine rotation speed Ne reaches the target engine rotation speed Netgt.

In the control for producing an acceleration feeling, an output shortage of the engine power Pe is more likely to occur as the initial rotation speed Neini is set to be lower, and a period in which the output shortage of the engine power Pe occurs is more likely to extend as the rotation speed increase rate μ becomes less. In the engine12with the supercharger18, the output shortage of the engine power Pe due to a response delay of the supercharging pressure Pchg is more likely to occur and the output shortage is more likely to increase, when the target supercharging pressure Pchgtgt at the time of acceleration of the vehicle is high than when the target supercharging pressure Pchgtgt at the time of acceleration of the vehicle is low.

Accordingly, when the initial rotation speed Neini is set to be lower in the control for producing an acceleration feeling and the target supercharging pressure Pchgtgt at the time of acceleration of the vehicle in the engine12with the supercharger18is high, the output shortage of the engine power Pe is likely to increase, compensation by the second rotary machine MG2is not sufficient due to constraints on the battery54(for example, constraints by the dischargeable electric power Wout) even when it is intended to compensate for the output shortage, that is, the shortage of the direct engine-transmitted torque Td due to the output shortage of the engine power Pe is not sufficiently compensated for by the MG2torque Tm which is the output torque of the second rotary machine MG2, and there is concern of a decrease in acceleration performance. Accordingly, in this example, the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ are set based on the target supercharging pressure Pchgtgt of the engine12at the time of starting of the control for producing an acceleration feeling as described above.

FIG.8is an example of a flowchart illustrating a principal part of the control operation of the electronic control unit100. The flowchart illustrated inFIG.8is repeatedly performed when the vehicle10is in the HV travel mode.

First, in Step S10corresponding to the function of the acceleration request determining unit102, it is determined whether there is an acceleration request. When the determination result of Step S10is positive, Step S20is performed. When the determination result of Step S10is negative, Step S80is performed.

In Step S20corresponding to the function of the supercharging execution determining unit104, it is determined whether supercharging is to be performed. When the determination result of Step S20is positive, Step S30is performed. When the determination result of S20is negative, Step S60is performed.

In Step S30corresponding to the function of the drive control unit106, the initial value correction value α is set based on the target supercharging pressure Pchgtgt at the time of starting of the control for producing an acceleration feeling. Then, Step S40is performed.

In Step S40corresponding to the function of the drive control unit106, the increase rate correction value β is set based on the target supercharging pressure Pchgtgt at the time of starting of the control for producing an acceleration feeling. Then, Step S50is performed.

In Step S50corresponding to the function of the drive control unit106, the lower limit correction value γ is set based on the target supercharging pressure Pchgtgt at the time of starting of the control for producing an acceleration feeling. Then, Step S70is performed.

The initial value correction value α which is set in Step S30, the increase rate correction value β which is set in Step S40, and the lower limit correction value γ which is set in Step S50are set such that the output shortage of the engine power Pe due to a response delay of the supercharging pressure Pchg when the control for producing an acceleration feeling is performed is compensated for by the second rotary machine MG2.

In Step S60corresponding to the function of the drive control unit106, all of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ are set to zero. Then, Step S70is performed.

In Step S70corresponding to the function of the drive control unit106, the control for producing an acceleration feeling and output compensation control are performed. In the control for producing an acceleration feeling and output compensation control, the MG1torque Tg is calculated to achieve the target engine rotation speed Netgt, the MG2torque Tm is calculated to compensate for the output shortage of the engine power Pe, and the engine12, the first rotary machine MG1, and the second rotary machine MG2are controlled. The engine12is controlled such that the supercharging pressure Pchg of the engine12reaches the target supercharging pressure Pchgtgt at the time of starting of the control for producing an acceleration feeling. Then, the flowchart is restarted.

In Step S80corresponding to the function of the drive control unit106, none of the control for producing an acceleration feeling and output compensation control are performed. For example, when the vehicle10is decelerating, the engine rotation speed Ne for realizing the required engine power Pedem during deceleration is set as the target engine rotation speed Netgt on the optimal engine operating point OPengf. Then, the flowchart is restarted.

FIGS.9A to9Care diagrams illustrating an example of a timing chart for when the control operation of the electronic control unit100illustrated inFIG.8is performed, whereFIG.9Aillustrates an example in which the initial rotation speed Neini is corrected with the initial value correction value α,FIG.9Billustrates an example in which the rotation speed increase rate μ is corrected with the increase rate correction value β, andFIG.9Cillustrates an example in which the lower-limit rotation speed Nemin is corrected with the lower limit correction value γ. The lower-limit rotation speed Nemin corresponds to a “lower limit” in the present disclosure.

InFIGS.9A to9C, the horizontal axis represents time t [ms] and the vertical axis represents the target engine rotation speed Netgt. For the purpose of easy understanding of the disclosure, inFIGS.9A to9C, a timing chart for when one of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ is set is indicated by a solid line, and a timing chart for when none of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ is set is indicated by a dotted line for the purpose of comparison. When “the initial value correction value α (or the increase rate correction value β or the lower limit correction value γ) is set,” it means that the initial value correction value α (or the increase rate correction value β for the lower limit correction value γ) is set to a value greater than 0. When “the initial value correction value α (or the increase rate correction value β or the lower limit correction value γ) is not set,” it means that the initial value correction value α (or the increase rate correction value β or the lower limit correction value γ) is set to zero.

First, the timing chart for when all of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ are zero will be described below with reference toFIG.9A. The dotted lines inFIGS.9B and9Calso indicate the timing charts when all of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ are zero. Since all of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ are zero, the initial rotation speed Neini is the basic initial value I0, the rotation speed increase rate μ is the basic increase rate μ0, and the lower-limit rotation speed Nemin is the basic lower limit M0. Since the lower-limit rotation speed Nemin (=M0) has a value less than the initial rotation speed Neini (=I0), the lower limit guard process is not performed. As indicated by the dotted line inFIG.9A, the target engine rotation speed Netgt is set to the initial rotation speed Neini (=I0) at time t0immediately after the control for producing an acceleration feeling is started. After the setting, the target engine rotation speed Netgt increases at the rotation speed increase rate μ (=μ0) with the elapse of time t. At time t2, the target engine rotation speed Netgt reaches the final rotation speed Nefin. In this way, the control for producing an acceleration feeling is performed from time t0to time t2. After time t2, the target engine rotation speed Netgt is maintained at the final rotation speed Nefin.

Then, the timing chart for when the initial value correction value α is set and the increase rate correction value β and the lower limit correction value γ are zero will be described below with reference toFIG.9A. Since the initial value correction value α is set and the increase rate correction value β and the lower limit correction value γ are zero, the initial rotation speed Neini becomes a value obtained by adding the initial value correction value α to the basic initial value I0, the rotation speed increase rate μ is the basic increase rate μ0, and the lower-limit rotation speed Nemin is the basic lower limit M0. Since the lower-limit rotation speed Nemin (=M0) has a value less than the initial rotation speed Neini (=I0+α), the lower limit guard process is not performed. As indicated by the solid line inFIG.9A, the target engine rotation speed Netgt is set to the initial rotation speed Neini (=I0+α) at time t0immediately after the control for producing an acceleration feeling is started. After the setting, the target engine rotation speed Netgt increases at the rotation speed increase rate μ (=μ0) with the elapse of time t. At time t1α, the target engine rotation speed Netgt reaches the final rotation speed Nefin. In this way, the control for producing an acceleration feeling is performed from time t0to time t1α. After time t1α, the target engine rotation speed Netgt is maintained at the final rotation speed Nefin.

Then, the timing chart for when the increase rate correction value β is set and the initial value correction value α and the lower limit correction value γ are zero will be described below with reference toFIG.9B. Since the increase rate correction value β is set and the initial value correction value α and the lower limit correction value γ are zero, the initial rotation speed Neini is the basic initial value I0, the rotation speed increase rate μ becomes a value obtained by adding the increase rate correction value β to the basic increase rate μ0, and the lower-limit rotation speed Nemin is the basic lower limit M0. Since the lower-limit rotation speed Nemin (=M0) has a value less than the initial rotation speed Neini (=I0), the lower limit guard process is not performed. As indicated by the solid line inFIG.9B, the target engine rotation speed Netgt is set to the initial rotation speed Neini (=I0) at time t0immediately after the control for producing an acceleration feeling is started. After the setting, the target engine rotation speed Netgt increases at the rotation speed increase rate μ (=μ0+β) with the elapse of time t. At time t1β, the target engine rotation speed Netgt reaches the final rotation speed Nefin. In this way, the control for producing an acceleration feeling is performed from time t0to time t1β. After time t1β, the target engine rotation speed Netgt is maintained at the final rotation speed Nefin.

Then, the timing chart for when the lower limit correction value γ is set and the initial value correction value α and the increase rate correction value β are zero will be described below with reference toFIG.9C. Since the lower limit correction value γ is set and the initial value correction value α and the increase rate correction value β are zero, the initial rotation speed Neini is the basic initial value I0, the rotation speed increase rate μ is the basic increase rate μ0, and the lower-limit rotation speed Nemin becomes a value obtained by adding the lower limit correction value γ to the basic lower limit M0. Since the lower-limit rotation speed Nemin (=M0+γ) has a value greater than the initial rotation speed Neini (=I0), the lower limit guard process is performed. As described above, the target engine rotation speed Netgt is set not to be less than the lower-limit rotation speed Nemin. Since the initial rotation speed Neini (=I0) is lower than the lower-limit rotation speed Nemin (=M0+γ), the lower limit guard process is performed and, as indicated by the solid line inFIG.9C, the target engine rotation speed Netgt is set to the lower-limit rotation speed Nemin (=M0+γ) at time t0immediately after the control for producing an acceleration feeling is started. After the setting, the target engine rotation speed Netgt is set to the lower-limit rotation speed Nemin (=M0+γ) until time t1γ at which a value increasing from the initial rotation speed Neini at the rotation speed increase rate μ (=μ) becomes the lower-limit rotation speed Nemin (=M0+γ). After time t1γ, the target engine rotation speed Netgt increases at the rotation speed increase rate μ (=μ0) with the elapse of time t. At time t2, the target engine rotation speed Netgt reaches the final rotation speed Nefin. In this way, the control for producing an acceleration feeling is performed from time t0to time t2. After time t2, the target engine rotation speed Netgt is maintained at the final rotation speed Nefin.

Although the timing charts when two or all of the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ are set is not illustrated, for example, the initial rotation speed Neini becomes the sum (=I0+α) of the basic initial value I0and the initial value correction value α, the rotation speed increase rate μ becomes the sum (=μ0+β) of the basic increase rate μ0and the increase rate correction value β, and the lower-limit rotation speed Nemin becomes the sum (=M0+γ) of the basic lower limit M0and the lower limit correction value γ. Immediately after the control for producing an acceleration feeling is started, the target engine rotation speed Netgt is set to the higher of the initial rotation speed Neini and the lower-limit rotation speed Nemin. After the setting, the target engine rotation speed Netgt is set to the higher of the rotation speed increasing from the initial rotation speed Neini at the rotation speed increase rate μ with the elapse of time t and the lower-limit rotation speed Nemin. After the target engine rotation speed Netgt reaches the final rotation speed Nefin, the target engine rotation speed Netgt is maintained at the final rotation speed Nefin.

According to this embodiment, there is provided a control device100for (A) a hybrid vehicle10including an engine12with a supercharger18, a differential unit60which is a stepless transmission that is provided in a power transmission path PT between the engine12and the driving wheels16, and a second rotary machine MG2that is connected to the power transmission path PT and using the engine12and the second rotary machine MG2as drive power sources, the control device100including (B) a drive control unit106configured (b1) to perform control for producing an acceleration feeling of setting a target engine rotation speed Netgt to an initial rotation speed Neini which is lower than an optimal-fuel-efficiency rotation speed Neeff at which the engine12is able to most efficiently output required engine power Pedem, increasing the engine rotation speed Ne from the initial rotation speed Neini to the optimal-fuel-efficiency rotation speed Neeff at a rotation speed increase rate μ with the elapse of time, and controlling the differential unit60such that the engine rotation speed Ne reaches the target engine rotation speed Netgt when an acceleration request is issued and (b2) to control the second rotary machine MG2such that an output shortage of the engine12for the required engine power Pedem which is caused by the engine rotation speed Ne becoming less than the optimal-fuel-efficiency rotation speed Neeff through the control for producing an acceleration feeling is compensated for, (C) wherein the drive control unit106is configured (c1) to set the initial rotation speed Neini or a lower-limit rotation speed Nemin which is a lower limit of the initial rotation speed Neini based on a target supercharging pressure of the engine or an amount of change of the target supercharging pressure Pchgtgt of the engine12at the time of start of the control for producing an acceleration feeling and (c2) to set the initial rotation speed Neini to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. An output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. Accordingly, when an output shortage of the engine12is likely to occur, the initial rotation speed Neini of the engine12in the control for producing an acceleration feeling or the lower limit of the initial rotation speed Neini is set to a great value such that the engine rotation speed Ne increases in an early stage. As a result, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg.

According to this embodiment, the drive control unit106sets the initial rotation speed Neini to a greater value as the target supercharging pressure Pchgtgt increases. An output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur as the target supercharging pressure Pchgtgt becomes greater. Accordingly, when an output shortage of the engine12is likely to occur, the initial rotation speed Neini of the engine12in the control for producing an acceleration feeling or the lower limit of the initial rotation speed Neini is set to a great value and thus it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg.

According to this embodiment, (A) the drive control unit106(a1) sets the rotation speed increase rate μ based on the target supercharging pressure Pchgtgt and (a2) sets the rotation speed increase rate μ to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. An output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. Accordingly, when an output shortage of the engine12is likely to occur, the rotation speed increase rate μ of the engine12in the control for producing an acceleration feeling is set to a great value such that the engine rotation speed Ne increases rapidly. As a result, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg.

According to this embodiment, the drive control unit106sets the rotation speed increase rate μ to a greater value as the target supercharging pressure Pchgtgt increases. An output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur as the target supercharging pressure Pchgtgt becomes greater. Accordingly, when an output shortage of the engine12is likely to occur, the rotation speed increase rate μ of the engine12in the control for producing an acceleration feeling is set to a great value and thus it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg.

FIG.10is a functional block diagram schematically illustrating a configuration of a hybrid vehicle210in which an electronic control unit200according to a second embodiment of the disclosure is mounted and illustrating a principal part of a control function for various types of control in the hybrid vehicle210. The hybrid vehicle210(hereinafter referred to as a “vehicle210”) includes an engine12, a first rotary machine MG1, a second rotary machine MG2, a power transmission device214, and driving wheels16. Elements of the second embodiment which are substantially common to the functions of the first embodiment will be referred to by the same reference signs and description thereof will not be repeated.

An engine torque Te of the engine12is controlled by causing an electronic control unit200which will be described later to control an engine control device50which is provided in the vehicle210.

The first rotary machine MG1and the second rotary machine MG2are connected to a battery54which is provided in the vehicle210via an inverter252which is provided in the vehicle210. In the first rotary machine MG1and the second rotary machine MG2, an MG1torque Tg and an MG2torque Tm are controlled by causing the electronic control unit200which will be described later to control the inverter252.

The power transmission device214includes an electrical stepless gear shifting unit258and a mechanical stepped gear shifting unit260which are arranged in series on a common axis in a case256that is a non-rotary member attached to the vehicle body. The stepless gear shifting unit258is connected to the engine12directly or indirectly via a damper which is not illustrated or the like. The stepped gear shifting unit260is connected to an output side of the stepless gear shifting unit258. The power transmission device214includes a differential gear68that is connected to an output shaft274which is an output rotary member of the stepped gear shifting unit260and a pair of axles78that is connected to the differential gear68. In the power transmission device214, power which is output from the engine12or the second rotary machine MG2is transmitted to the stepped gear shifting unit260. The power transmitted to the stepped gear shifting unit260is transmitted to the driving wheels16via the differential gear68or the like. The power transmission device214having this configuration is suitably used for a vehicle of a front-engine rear-drive (FR) type. The stepless gear shifting unit258, the stepped gear shifting unit260, or the like is disposed to be substantially symmetric with respect to the common axis, and a lower half with respect to the axis is not illustrated inFIG.10. The common axis is an axis of a crankshaft of the engine12, an input shaft272connected to the crankshaft, or the like. The stepless gear shifting unit258, the stepped gear shifting unit260, the differential gear68, and the axles78in the power transmission device214constitute the power transmission path PT which is provided between the engine12and the driving wheels16. The second rotary machine MG2in this embodiment corresponds to a “rotary machine” in the present disclosure.

The stepless gear shifting unit258includes a differential mechanism280which is a power split mechanism that mechanically splits power of the engine12to the first rotary machine MG1and an intermediate transmission member276which is an output rotary member of the stepless gear shifting unit258. The first rotary machine MG1is a rotary machine to which power of the engine12is transmitted. The second rotary machine MG2is connected to the intermediate transmission member276in a power-transmittable manner. Since the intermediate transmission member276is connected to the driving wheels16via the stepped gear shifting unit260, the second rotary machine MG2is a rotary machine that is connected to the driving wheels16in a power-transmittable manner. The differential mechanism280is a differential mechanism that splits and transmits power of the engine12to the driving wheels16and the first rotary machine MG. The stepless gear shifting unit258is an electrical stepless transmission in which a differential state of the differential mechanism280is controlled by controlling the operating state of the first rotary machine MG1which is connected to the differential mechanism280in a power-transmittable manner. The first rotary machine MG1is a rotary machine that can control an engine rotation speed Ne. The stepless gear shifting unit258corresponds to a “stepless transmission” in the present disclosure.

The differential mechanism280is a known single-pinion type planetary gear unit including a sun gear S1, a carrier CA, and a ring gear R1.

The stepped gear shifting unit260is a mechanical gear shifting mechanism which is a stepped transmission constituting a part of the power transmission path PT between the intermediate transmission member276and the driving wheels16, that is, an automatic transmission constituting a part of the power transmission path PT between the differential mechanism280and the driving wheels16. The intermediate transmission member276also serves as an input rotary member of the stepped gear shifting unit260. The stepped gear shifting unit260is, for example, a known planetary gear type automatic transmission including a plurality of planetary gear mechanisms including a first planetary gear mechanism282A and a second planetary gear mechanism282B and a plurality of engagement devices including a clutch C1, a clutch C2, a brake B1, a brake B2, and a one-way clutch F1. In the following description, the clutch C1, the clutch C2, the brake B1, and the brake B2are simply referred to as engagement devices CB when they are not particularly distinguished from each other. The first planetary gear mechanism282A is a known single-pinion type planetary gear mechanism including a sun gear S2, a carrier CA2, and a ring gear R2. The second planetary gear mechanism282B is a known single-pinion type planetary gear mechanism including a sun gear S3, a carrier CA3, and a ring gear R3.

The differential mechanism280, the first planetary gear mechanism282A, the second planetary gear mechanism282B, the engagement devices CB, the one-way clutch F1, the first rotary machine MG1, and the second rotary machine MG2are connected as illustrated inFIG.10. In the differential mechanism280, the carrier CA1serves as an input element, the sun gear S1serves as a reaction element, and the ring gear R1serves as an output element.

Each engagement device CB is a hydraulic frictional engagement device. An engagement torque which is a torque capacity of each engagement device CB is changed using regulated engagement oil pressures which are output from solenoid valves SL1to SL4in a hydraulic pressure control circuit284provided in the vehicle210. Accordingly, the operating state such as an engaged state or a disengaged state of each engagement device CB is switched.

In the stepped gear shifting unit260, one gear stage of a plurality of gear stages with different gear ratios γat (=AT input rotation speed Nati [rpm]/AT output rotation speed Nato [rpm]) is formed by switching a combination of operating states of a plurality of engagement devices CB. In this embodiment, a gear stage which is formed in the stepped gear shifting unit260is referred to as an AT gear stage. The AT input rotation speed Nati is an input rotation speed of the stepped gear shifting unit260and has the same value as a rotation speed of the intermediate transmission member276and the same value as an MG2rotation speed Nm. The AT output rotation speed Nato is a rotation speed of the output shaft274which is an output rotary member of the stepped gear shifting unit260and is also an output rotation speed of a composite transmission262which is a combined transmission including the stepless gear shifting unit258and the stepped gear shifting unit260.

FIG.11is an engagement operation table illustrating a relationship between a gear shifting operation of the stepped gear shifting unit260illustrated inFIG.10and a combination of operating states of the engagement devices CB which are used therein. In the stepped gear shifting unit260, for example, four AT gear stages for forward movement including a first AT gear stage (“1st” inFIG.11) to a fourth AT gear stage (“4th” inFIG.11) are formed as a plurality of AT gear stages. The gear ratio γat of the first AT gear stage is the highest and the gear ratio γat becomes lower in higher AT gear stages. An AT gear stage for reverse movement (“Rev” inFIG.11) is formed, for example, by engagement of the clutch C1and engagement of the brake B2. That is, for example, the first AT gear stage is formed at the time of reverse travel as will be described later. InFIG.11, “O” denotes an engaged state, “A” denotes an engaged state at the time of engine braking or at the time of coast downshift of the stepped gear shifting unit260, and a blank denotes a disengaged state. A coast downshift is, for example, a downshift which is performed in a decelerating travel state with an accelerator turned off out of downshifts which are performed due to a decrease in the vehicle speed V during decelerating travel with the accelerator turned off (the accelerator opening θacc is 0 or substantially 0).

In the stepped gear shifting unit260, for example, an AT gear stage which is formed according to the accelerator opening θacc which is an amount of operation of an accelerator by a driver, the vehicle speed V, or the like is switched, that is, a plurality of AT gear stages is selectively formed, by the electronic control unit200which will be described later. For example, in gear shifting control of the stepped gear shifting unit260, so-called clutch-to-clutch gear shifting in which gear shifting is performed by switching one of the engagement devices CB, that is, gear shifting is performed by switching of the engagement devices CB between engagement and disengagement, is performed.

The vehicle210additionally includes a one-way clutch F0(seeFIG.10). The one-way clutch F0is a lock mechanism that can fix the carrier CA to be non-rotatable. That is, the one-way clutch F0is a lock mechanism that can fix the input shaft272which is connected to the crankshaft of the engine12and which rotates integrally with the carrier CAT to the case256. In the one-way clutch F0, one member of two members that are rotatable relative to each other is integrally connected to the input shaft272and the other member is integrally connected to the case256. The one-way clutch F0idles in a positive rotating direction which is a rotating direction at the time of operation of the engine12and is automatically engaged in a negative rotating direction which is opposite to that at the time of operation of the engine12. Accordingly, when the one-way clutch F0idles, the engine12is rotatable relative to the case256. On the other hand, when the one-way clutch F0is engaged, the engine12is not rotatable relative to the case256. That is, the engine12is fixed to the case256by engagement of the one-way clutch F0. In this way, the one-way clutch F0permits rotation in the positive rotating direction of the carrier CAT which is a rotating direction at the time of operation of the engine12and prohibits rotation in the negative rotating direction of the carrier CA. That is, the one-way clutch F0is a lock mechanism that can permit rotation in the positive rotating direction of the engine12and prohibit rotation in the negative rotating direction of the engine12.

In the vehicle210, when the rotation speed of the sun gear S1increases or decreases by controlling the rotation speed of the first rotary machine MG1with respect to the rotation speed of the ring gear R1which is constrained on rotation of the driving wheels16by formation of an AT gear stage in the stepped gear shifting unit260, the rotation speed of the carrier CA1, that is, the engine rotation speed Ne, increases or decreases. That is, in the HV travel mode in which HV travel using at least the engine12as a drive power source is possible, the engine12can operate at an operating point with high efficiency. Accordingly, in the HV travel mode, when the required drive power Pwdem of the vehicle210changes, the target engine operating point OPengtgt can be set through the control for producing an acceleration feeling of the required engine power Pedem for realizing the required drive power Pwdem.

The vehicle210further includes an electronic control unit200which is a controller including a control device for the vehicle210associated with control of the engine12, the first rotary machine MG1, the second rotary machine MG2, and the like. The electronic control unit200has the same configuration as the electronic control unit100described above in the first embodiment. The electronic control unit200is supplied with various signals which are the same as those supplied to the electronic control unit100. Various command signals which are the same as those output from the electronic control unit100are output from the electronic control unit200. The electronic control unit200has functions equivalent to the functions of the acceleration request determining unit102, the supercharging execution determining unit104, and the drive control unit106similarly to the electronic control unit100. Accordingly, similarly to the first embodiment, an output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. Accordingly, when an output shortage of the engine12is likely to occur, the initial rotation speed Neini of the engine12in the control for producing an acceleration feeling or the lower limit of the initial rotation speed Neini is set to a great value such that the engine rotation speed Ne increases in an early stage. As a result, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg. The engine12and the differential mechanism280which is a stepless transmission are controlled such that the engine rotation speed Ne reaches the target engine rotation speed Netgt. The electronic control unit200corresponds to a “control device” in the present disclosure.

According to this embodiment, the same advantages as in the first embodiment are obtained.

FIG.12is a functional block diagram schematically illustrating a configuration of a hybrid vehicle310in which an electronic control unit300according to a third embodiment of the disclosure is mounted and illustrating a principal part of a control function for various types of control in the hybrid vehicle310. The hybrid vehicle310(hereinafter referred to as a “vehicle310”) includes an engine12, a rotary machine MG, a power transmission device314, and driving wheels16. Elements of the third embodiment which are substantially common to the functions of the first embodiment will be referred to by the same reference signs and description thereof will not be repeated.

An engine torque Te of the engine12is controlled by causing an electronic control unit300which will be described later to control an engine control device50which is provided in the vehicle310.

The rotary machine MG is a rotary electric machine having a function of an electric motor and a function of a power generator and is called a motor generator. The rotary machine MG is connected to a battery54which is provided in the vehicle310via an inverter352which is provided in the vehicle310. Regarding the rotary machine MG, an MG torque Tmg [Nm] which is an output torque of the rotary machine MG is controlled by causing the electronic control unit300which will be described later to control the inverter352. Electric power Wg which is generated by the rotary machine MG is charged in the battery54or is consumed in an auxiliary machine such as an air conditioner. The rotary machine MG outputs the MG torque Tmg using electric power from the battery54.

The power transmission device314includes a clutch K0and an automatic transmission362. An input rotary member of the automatic transmission362is connected to the engine12via the clutch K0and is directly connected to the rotary machine MG. The power transmission device314includes a differential gear68that is connected to an output side of the automatic transmission362and a pair of axles78that is connected to the differential gear68. In the power transmission device314, power of the engine12is transmitted to the driving wheels16sequentially via the clutch K0, the automatic transmission362, the differential gear68, the pair of axles78, and the like. Power of the rotary machine MG is transmitted to the driving wheels16via the automatic transmission362and the like. The engine12and the rotary machine MG are drive power sources for travel of the vehicle310that are connected to the driving wheels16in a power-transmittable manner. The clutch K0, the automatic transmission362, the differential gear68, and the axles78in the power transmission device314constitute the power transmission path PT which is provided between the engine12and the driving wheels16. The rotary machine MG also has a function of a starter that cranks the engine12in a state in which the clutch K0is engaged. The rotary machine MG in this embodiment corresponds to a “rotary machine” in the present disclosure.

The clutch K0is a hydraulic frictional engagement device that connects or disconnects the power transmission path PT between the engine12and the driving wheels16.

The automatic transmission362is, for example, a known stepless transmission such as a belt-type stepless transmission including a primary pulley, a secondary pulley, and an electric belt which is suspended between the pulleys. In the automatic transmission362, V-groove widths of the primary pulley and the secondary pulley are changed by a hydraulic pressure control circuit384which is controlled by the electronic control unit300which will be described later and a suspending distance of the electric belt (an effective distance) is changed. Accordingly, the gear ratio γat of the automatic transmission362changes in a stepless manner. The automatic transmission362corresponds to a “stepless transmission” in the present disclosure.

The vehicle310can perform EV travel in which only the rotary machine MG is used as a drive power source for travel using electric power from the battery54in a state in which the clutch K0is disengaged and operation of the engine12is stopped. The vehicle310can perform hybrid travel in which the engine12operates in a state in which the clutch K0is engaged and at least the engine12is used as a drive power source for travel.

The vehicle310includes an engine-driven travel mode using only the engine12as a drive power source and an HV travel mode using the engine12and the rotary machine MG as drive power sources in a state in which the clutch K0is engaged. When the required drive power Pwdem in the vehicle310changes in any one of the engine-driven travel mode and the HV travel mode, a target engine operating point OPengtgt is set through the control for producing an acceleration feeling on a required engine power Pedem for realizing the required drive power Pwdem.

The vehicle310further includes the electronic control unit300which is a controller including a control device for the vehicle310associated with control of the engine12, the rotary machine MG, and the like. The electronic control unit300has the same configuration as the electronic control unit100described above in the first embodiment. The electronic control unit300is supplied with various signals which are the same as those supplied to the electronic control unit100. An MG rotation speed Nmg [rpm] which is the rotation speed of the rotary machine MG which is detected by an MG rotation speed sensor which is not illustrated is input instead of the MG rotation speed Ng and the MG2rotation speed Nm. Various command signals which are the same as those output from the electronic control unit100are output from the electronic control unit300. Here, the rotary machine control command signal Sing is a command signal for controlling the rotary machine MG. The electronic control unit300has functions equivalent to the functions of the acceleration request determining unit102, the supercharging execution determining unit104, and the drive control unit106similarly to the electronic control unit100. Accordingly, similarly to the first embodiment, an output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. Accordingly, when an output shortage of the engine12is likely to occur, the initial rotation speed Neini of the engine12in the control for producing an acceleration feeling or the lower limit of the initial rotation speed Neini is set to a great value such that the engine rotation speed Ne increases in an early stage. The engine rotation speed Ne reaches the target engine rotation speed Netgt by controlling the engine12and the automatic transmission362which is an automatic transmission. The electronic control unit300corresponds to a “control device” in the present disclosure.

According to this embodiment, the same advantages as in the first embodiment are obtained.

While embodiments of the disclosure have been described above in detail with reference to the accompanying drawings, the disclosure can be applied to other aspects.

In the first to third embodiments described above, the target engine operating point OPengtgt changes on the path a passing over the maximum efficiency line Leng, but the disclosure is not limited thereto. For example, the target engine operating point OPengtgt may change along a path which is temporarily separated from the path a passing over the maximum efficiency line Leng in the control for producing an acceleration feeling.

In the first to third embodiments described above, the control for producing an acceleration feeling is performed such that the target engine rotation speed Ne is set to the initial rotation speed Neini and then increases from the initial rotation speed Neini at a rotation speed increase rate μ with the elapse of time t, but the disclosure is not limited thereto. For example, the control for producing an acceleration feeling may be performed such that the target engine rotation speed Netgt increases from the initial rotation speed Neini at a rotation speed increase rate μ* with an increase in the vehicle speed V (a rate of increase of the engine rotation speed Ne with respect to an increase of the vehicle speed V) instead of the elapse of time t. This is because a feeling of acceleration is rendered even when the target engine rotation speed Netgt increases from the initial rotation speed Neini at the rotation speed increase rate μ* with an increase in the vehicle speed V. An increase in the vehicle speed V means an increase in the vehicle speed V immediately after the control for producing an acceleration feeling in which the target engine operating point OPeng is changed to an initial operating point Opengini is started, and corresponds to an “increase in a vehicle speed” in the present disclosure. In the control for producing an acceleration feeling, the target engine rotation speed Netgt may be increased from the initial rotation speed Neini at a rotation speed increase rate μ** based on both the increase in the vehicle speed V and the elapse of time t (a rate of increase of the engine rotation speed Ne with the increase in the vehicle speed V and the elapse of time t as two variables). Accordingly, in the control for producing an acceleration feeling, the target engine rotation speed Netgt may be increased from the initial rotation speed Neini at the rotation speed increase rate μ (or μ* or μ**) based on at least one of the increase in the vehicle speed V and the elapse of time t.

In the first to third embodiments described above, as the target supercharging pressure Pchgtgt increases, the initial rotation speed Neini set to a greater value, the rotation speed increase rate μ is set to a greater value, and the lower-limit rotation speed Nemin is set to a greater value, but the disclosure is not limited thereto. For example, by increasing the initial value correction value α, the increase rate correction value β, and the lower limit correction value γ in a so-called steplike (step-shaped) manner with an increase in the target supercharging pressure Pchgtgt, the initial rotation speed Neini may be set to a greater value, the rotation speed increase rate μ may be set to a greater value, and the lower-limit rotation speed Nemin may be set to a greater value, when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low. That is, the initial rotation speed Neini, the rotation speed increase rate μ, and the lower-limit rotation speed Nemin may be set to the same value in a narrow range of the target supercharging pressure Pchgtgt, but the initial rotation speed Neini may be set to a greater value, the rotation speed increase rate μ may be set to a greater value, and the lower-limit rotation speed Nemin may be set to a greater value, when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low, in a wide range of the target supercharging pressure Pchgtgt.

In the first to third embodiments described above, the initial rotation speed Neini or the lower-limit rotation speed Nemin is set to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low, but the disclosure is not limited thereto. For example, “when an amount of change of the target supercharging pressure ΔPchgtgt is great than when an amount of change of the target supercharging pressure ΔPchgtgt is small” may be used instead of “when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low.” Here, the amount of change of the target supercharging pressure ΔPchgtgt [Pa] is a difference between the target supercharging pressure Pchgtgt at the time of starting of the control for producing an acceleration feeling (that is, the supercharging pressure Pchg at the time of ending of the control for producing an acceleration feeling) and the target supercharging pressure Pchgtgt immediately before the control for producing an acceleration feeling is started (that is, the supercharging pressure Pchg immediately before the control for producing an acceleration feeling is started). An output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur when the amount of change of the target supercharging pressure ΔPchgtgt is great than when the amount of change of the target supercharging pressure ΔPchgtgt is small. Accordingly, the initial rotation speed Neini or the lower-limit rotation speed Nemin of the engine12in the control for producing an acceleration feeling is set to a greater value when the amount of change of the target supercharging pressure ΔPchgtgt is great than when the amount of change of the target supercharging pressure ΔPchgtgt is small, and thus the engine rotation speed Ne is set to increase in an earlier stage. Accordingly, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg.

In the first to third embodiments described above, the rotation speed increase rate μ is set to a greater value when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low, but the disclosure is not limited thereto. For example, “when the amount of change of the target supercharging pressure ΔPchgtgt is great than when the amount of change of the target supercharging pressure ΔPchgtgt is small” may be used instead of “when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low.” An output shortage of the engine12due to a response delay of the supercharging pressure Pchg is more likely to occur when the amount of change of the target supercharging pressure ΔPchgtgt is great than when the amount of change of the target supercharging pressure ΔPchgtgt is small. Accordingly, the rotation speed increase rate μ of the engine12in the control for producing an acceleration feeling is set to a greater value when the amount of change of the target supercharging pressure ΔPchgtgt is great than when the amount of change of the target supercharging pressure ΔPchgtgt is small, and thus the engine rotation speed Ne is set to increase in an earlier stage. Accordingly, it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg.

In the first to third embodiments described above, when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low, the initial rotation speed Neini is set to a greater value, the rotation speed increase rate μ is set to a greater value, and the lower-limit rotation speed Nemin is set to a greater value, but the disclosure is not limited thereto. For example, one of “setting the initial rotation speed Neini to a greater value” and “setting the lower-limit rotation speed Nemin to a greater value” when the target supercharging pressure Pchgtgt is high than when the target supercharging pressure Pchgtgt is low has only to be performed. When one of “setting the initial rotation speed Neini to a greater value” and “setting the lower-limit rotation speed Nemin to a greater value” is performed, the engine rotation speed Ne increases rapidly in an earlier stage and thus it is possible to curb a decrease in acceleration performance due to a response delay of the supercharging pressure Pchg in the control for producing an acceleration feeling.

In the first embodiment, the vehicle10may be a vehicle which does not include the gear shifting unit58and in which the engine12is connected to the differential unit60. The differential unit60may be a mechanism in which a differential operation can be limited by control of a clutch or brake connected to the rotary elements of the second planetary gear mechanism82. The second planetary gear mechanism82may be a double pinion type planetary gear unit. The second planetary gear mechanism82may be a differential mechanism including four or more rotary elements by connection between a plurality of planetary gear units. The second planetary gear mechanism82may be a differential gear mechanism in which the first rotary machine MG1and the drive gear74are connected to a pinion which is rotationally driven by the engine12and a pair of bevel gears engaging with the pinion, respectively. The second planetary gear mechanism82may be a mechanism with a configuration in which some rotary elements of two or more planetary gear units are connected to each other and the engine12, the first rotary machine MG1, and the driving wheels16are connected to the rotary elements of such planetary gear units in a power-transmittable manner.

In the second embodiment, the one-way clutch F0is exemplified as a lock mechanism that can fix the carrier CAT in a non-rotatable manner, but the disclosure is not limited to the aspect. This lock mechanism may be an engagement device such as an engaging clutch, a hydraulic frictional engagement device such as a clutch or a brake, a dry engagement device, an electromagnetic frictional engagement device, or a magnetic powder type clutch which selectively connects the input shaft272and the case256. Alternatively, the vehicle210does not have to include the one-way clutch F0.

In the first to third embodiments described above, the supercharger18is a known exhaust turbine type supercharger, but the disclosure is not limited to this aspect. For example, the supercharger18may be a mechanical pump type supercharger that is rotationally driven by the engine or the electric motor. An exhaust turbine type supercharger and a mechanical pump type supercharger may be provided together as a supercharger.

The above embodiments are merely examples of the disclosure, and the disclosure can be embodied in various aspects which have been subjected to various modifications and improvements based on knowledge of those skilled in the art without departing from the gist of the disclosure.