WO2015004514A1

WO2015004514A1 - Control device and control method for vehicle

Info

Publication number: WO2015004514A1
Application number: PCT/IB2014/001171
Authority: WO
Inventors: Susumu Kojima
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-07-10
Filing date: 2014-06-25
Publication date: 2015-01-15
Also published as: JP2015017543A

Abstract

A control device for a vehicle including a multicylinder four-cycle engine includes an electronic control unit. The electronic control unit is configured to (i) acquire a crank angle of the engine based on a signal that is detected at predetermined intervals, (ii) set a restart-related control value for the engine based on an acquired engine-stop crank angle acquired by the electronic control unit, and (iii) when the acquired engine-stop crank angle falls within a predetermined range including a predetermined stop-time crank angle, sets the restart-related control value to be constant based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle.

Description

CONTROL DEVICE AND CONTROL METHOD FOR VEHICLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a control device and a control method that automatically stop and restart a multicylinder four-cycle engine of a vehicle. 2. Description of Related Art

[0002] Japanese Patent Application Publication No. 2000-265879 (JP 2000-265879 A) describes a control device for a vehicle, which automatically stops and restarts a multicylinder four-cycle engine. JP 2000-265879 A describes that, in a starting device for a direct- injection internal combustion engine, an engine-stop crank angle is detected (stored) and, at the time of a restart, fuel is injected in a fuel injection amount based on a piston position into one of the cylinders in a compression stroke during cranking and then the engine is restarted by igniting first combustion at the timing at which the combustion is allowed to be effectively converted to rotation of the engine. SUMMARY OF THE INVENTIO

[0003] As is also described in JP 2000-265879 A, the engine-stop crank angle tends to be around a specific crank angle. For example, in an automatic stop of the engine, the engine tends to stop around a position of which the angle from a top dead center (TDC) becomes an angle that is half the combustion interval of the engine. At this time, depending on the number of cylinders of the engine and a detection interval of a crank angle sensor that detects a crank angle, it may not be able to accurately detect a stop at an angle that is half the combustion interval of the engine. Specifically, when the detection interval of the crank angle sensor is 6° or 10° in an eight-cylinder engine, the combustion interval is 90°CA, and the angle that is half the combustion interval is 45°CA. In this case, even when the engine stops at 45°CA from the TDC, 45°CA is not divided by 6° or 10° that is the detection interval, and it is difficult to accurately detect the angle that is half the combustion interval of the engine even with the use of any crank angle sensor (for example, when a crank angle sensor has a detection interval of 10°, a detected value is 40°CA or 50°CA). As a result, it may not be able to appropriately execute control (for example, setting of a fuel injection amount based on a crank angle) at the time of a restart after an automatic stop of the engine. The above-described inconvenience is not known, and there has been no suggestion to appropriately execute control (at the time of a restart) after a stop irrespective of the number of cylinders of an engine and a detection interval of a crank angle sensor.

[0004] The invention provides a control device and control method for a vehicle, which are able to appropriately carry out a restart suitable for an actual engine stop position.

[0005] A first aspect of the invention provides a control device for a vehicle including a multicylinder four-cycle engine. The control device includes: a crank angle acquisition unit acquiring a crank angle of the engine based on a signal that is detected at predetermined intervals; and a restart related value setting unit setting a restart-related control value for the engine based on an engine-stop crank angle acquired by the crank angle acquisition unit, wherein, when the acquired engine-stop crank angle falls within a predetermined range including a predetermined stop-time crank angle, the restart related value setting unit sets the restart-related control value to be constant based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle.

[0006] With this configuration, even when the acquired engine-stop crank angle is acquired as a different value for substantially the same actual engine stop position, and when the acquired engine-stop crank angle falls within the predetermined range, the engine is restarted by using the constant control value. Therefore, the operating state at the time of an engine restart is stable. That is, it is possible to bring the stop position of the engine closer to an actual value than the acquired engine-stop crank angle, so the operating state at the time of an engine restart is stable. Thus, it is possible to appropriately carry out a restart suitable for an actual engine stop position.

[0007] In the control device, when the acquired engine-stop crank angle falls outside the predetermined range including the predetermined stop-time crank angle, the restart related value setting unit may set the restart-related control value based on the acquired engine-stop crank angle. With this configuration, when the acquired engine-stop crank angle falls outside the predetermined range, the engine is restarted by using the control value based on the acquired engine-stop crank angle. Therefore, it is possible to appropriately carry out a restart suitable for an actual engine stop position.

[0008] In the control device, the restart related value setting unit may include a fuel injection amount setting unit setting a fuel injection amount at the time of a restart of the engine based on the acquired engine-stop crank angle, and the fuel injection amount setting unit may set a constant fuel injection amount based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle when the acquired engine-stop crank angle falls within the predetermined range including the predetermined stop-time crank angle. With this configuration, even when the acquired engine-stop crank angle is acquired as a different value for substantially the same actual engine stop position, a constant fuel injection amount is used at the time of an engine restart. Therefore, the operating state at the time of an engine restart is stable.

[0009] In the control device, an ignition start for rotating the engine by causing any one of the cylinders to combust at the time of a start of the engine may be carried out, and the fuel injection amount setting unit may set the fuel injection amount of the cylinder that is caused to combust first at the time of a restart of the engine. With this configuration, the operating state at the time of an engine restart that accompanies an ignition start is stable.

[0010] In the control device, the vehicle may include an electric motor provided in a power transmission path between the engine and a drive wheel and a clutch connecting or disconnecting the electric motor to or from the engine, the restart related value setting unit may include a clutch engagement time, setting unit setting an engagement time or engagement timing of the clutch at the time of a restart of the engine based on the acquired engine-stop crank angle, and the clutch engagement time setting unit may set the engagement time or engagement timing of the clutch to be constant, based on the predetermined stop-time crank angle, irrespective of the acquired engine-stop crank angle when the acquired engine-stop crank angle falls within the predetermined range including the predetermined stop-time crank angle. With this configuration, even when the acquired engine-stop crank angle is acquired as a different value for substantially the same actual engine stop position, the clutch is engaged by using the constant engagement time or engagement timing of the clutch at the time of an engine restart. Therefore, clutch control is stable, and engine operation timing tends to be constant.

[0011] In the control device, the predetermined stop-time crank angle may be a value between adjacent crank angles that are acquired by the crank angle acquisition unit at the predetermined intervals, and may be a crank angle corresponding to a state where any one of the cylinders of the engine stops at a position of a top dead center or a crank angle corresponding to a state where any one of the cylinders of the engine stops at a position advanced by a crank angle, which is half a combustion interval, from the top dead center. With this configuration, when the crank angle at a stop position at which the engine tends to stop is a crank angle that cannot be acquired by the crank angle acquisition unit, it is possible to appropriately carry out a restart suitable for an actual engine stop position.

[0012] A second aspect of the invention provides a control method for a vehicle including a multicylinder four-cycle engine and an electronic control unit. The control method includes: acquiring a crank angle of the engine, by the electronic control unit, based on a signal that is detected at predetermined intervals; setting a restart-related control value, by the electronic control unit, for the engine based on an acquired engine-stop crank angle acquired by the electronic control unit; and, when the acquired engine-stop crank angle falls within a predetermined range including a predetermined stop-time crank angle, setting the restart-related control value to be constant based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle.

BRIEF DESCRIPTION OF THE DRAWINGS [0013] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a view that illustrates the schematic configuration of a powertrain provided in a vehicle according to an embodiment of the invention and is a view that illustrates a relevant portion of a control system in the vehicle;

FIG. 2 is a view that illustrates the schematic configuration of an engine shown in FIG. 1 and is a view that illustrates a relevant portion of a control system in the engine within the control system in the vehicle;

FIG. 3 is a view for illustrating the opening duration of each intake valve and the opening duration of a corresponding one of exhaust valves in the embodiment;

FIG. 4 is a functional block diagram that illustrates a relevant portion of control functions of an electronic control unit according to the embodiment;

FIG. 5 is a graph that shows an example of the fact that ECU values are different even when actual engine stop positions are the same according to the embodiment;

FIG. 6 is a chart that shows an example of the fact that ECU values are different even when actual engine stop positions are the same according to the embodiment; and

FIG. 7 is a flowchart that illustrates a relevant portion of control operations of the electronic control unit, that is, control operations for appropriately carrying out a restart suitable for an actual engine stop position, according to the embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014] In an embodiment of the invention, a vehicle includes an engine, an electric motor and a clutch. The electric motor is provided in a power transmission path between the engine and a drive wheel. The clutch connects or disconnects the electric motor to or from the engine. The vehicle includes a transmission that constitutes part of the power transmission path between the electric motor and the drive wheel. Examples of the transmission include a manual transmission, such as a known synchromesh parallel-two-shaft transmission including a plurality of pairs of constant-mesh transmission gears between the two shafts, and various automatic transmissions (a planetary gear automatic transmission, a synchromesh parallel-two-shaft automatic transmission, a DCT, a CVT, and the like). Each of the automatic transmissions is formed of an automatic transmission alone, an automatic transmission including a fluid transmission device, an automatic transmission including an auxiliary transmission, or the like. The clutch is a wet-type or dry-type engagement device that is able to disconnect the engine from the drive wheel. The engine is, for example, an internal combustion engine, such as a gasoline engine, that generates power through combustion of fuel. Particularly, the engine in the case where an ignition start accompanies an engine start is a direct-injection four-cycle gasoline engine that directly injects fuel into each cylinder.

[0015] Hereinafter, an embodiment of the invention will be described in detail with reference to the accompanying drawings.

[0016] FIG. 1 is a view that illustrates the schematic configuration of a powertrain 12 provided in a vehicle 10 to which the invention is applied and is a view that illustrates a relevant portion of a control system for various controls in the vehicle 10. FIG 2 is particularly a view that illustrates the schematic configuration of an engine 14 shown in FIG. 1 and is a view that illustrates a relevant portion of a control system for output control, and the like, in the engine 14 within the control system in the vehicle 10.

[0017] In FIG. 1, the vehicle 10 is a hybrid vehicle that includes an engine 14 and an electric motor MG as driving force sources. The powertrain 12 includes an engine separating clutch K0 (hereinafter, referred to as clutch K0), a torque converter 16, an automatic transmission 18, and the like, in order from the engine 14 side inside a transmission case 20. The transmission case 20 serves as a non-rotating member. The powertrain 12 includes a propeller shaft 26, a differential gear 28, a pair of axles 30, and the like. The propeller shaft 26 is coupled to a transmission output shaft 24 that is an output rotating member of the automatic transmission 18. The differential gear 28 is coupled to the propeller shaft 26. The pair of axles 30 are coupled to the differential gear 28. A pump impeller 16a of the torque converter 16 is coupled to an engine coupling shaft 32 via the clutch K0. The pump impeller 16a is directly coupled to the electric motor MG. A turbine impeller 16b of the torque converter 16 is directly coupled to a transmission input shaft 34 that is an input rotating member of the automatic transmission 18. A mechanical oil pump 22 is coupled to the pump impeller 16a. The mechanical oil pump 22 generates operating hydraulic pressure for carrying out shift control over the automatic transmission 18, engagement/release control over the clutch K0, and the like, by being rotationally driven by the engine 14 (and/or the electric motor MG). The thus configured powertrain 12 is, for example, suitably used in the FR vehicle 10. In the powertrain 12, the power (which is synonymous with torque and force unless otherwise distinguished) of the engine 14 is transmitted from the engine coupling shaft 32 to a pair of drive wheels 38 sequentially via the clutch K0, the torque converter 16, the automatic transmission 18, the propeller shaft 26, the differential gear 28, the pair of axles 30, and the like, when the clutch K0 is engaged. The engine coupling shaft 32 couples a crankshaft 36 (see FIG. 2) of the engine 14 to the clutch K0. In this way, the powertrain 12 constitutes a power transmission path from the engine 14 to the drive wheels 38.

[0018] The automatic transmission 18 is a transmission that constitutes part of the power transmission path between both the engine 14 and the electric motor MG and the drive wheels 38 and that transmits power from the driving force sources (the engine 14 and the electric motor MG) to the drive wheels 38 side. The automatic transmission 18 is, for example, a known planetary gear-type multi-speed transmission in which a plurality of gears having different speed ratios (gear ratios) γ are selectively established, a known continuously variable transmission in which the speed ratio γ is continuously variable in a stepless manner, or the like. The speed ratio γ is expressed by the following mathematical expression (1).

y = Nin/ out (1)

In the mathematical expression (1), Nin denotes transmission input shaft rotation speed, and Nout denotes transmission output shaft rotation speed.

[0019] The electric motor MG is a so-called motor generator having the function of a motor that generates mechanical power from electric energy and the function of a generator that generates electric energy from mechanical energy. The electric motor MG generates driving power by using electric energy that is supplied from an electrical storage device 44 via an inverter 42 instead of the engine 14 or in addition to the engine 14. The electric motor MG converts the power of the engine 14 or driven force, which is input from the drive wheels 38 side, to electric energy through regeneration, and stores the electric energy in an electrical storage device 44 via the inverter 42. The electric motor MG is provided in the power transmission path between the engine 14 and the drive wheels 38, and is coupled to a power transmission path between the clutch K0 and the torque converter 16. Power is transmitted to each other between the electric motor MG and the pump impeller 16a. Thus, the electric motor MG is coupled to the transmission input shaft 34 of the automatic transmission 18 such that power is transmittable without passing through the clutch KO.

[0020] The clutch K0 is, for example, a wet-type multi-disc friction engagement device. The clutch K0 undergoes engagement/release control from a hydraulic control circuit 40 by using hydraulic pressure that is generated by the oil pump 22 as a source pressure. In the engagement/release control, a torque capacity (hereinafter, referred to as K0 torque) of the clutch K0 is changed by regulating a linear solenoid valve, or the like, in the hydraulic control circuit 40. In the engaged state of the clutch K0, the pump impeller 16a and the engine 14 are integrally rotated via the engine coupling shaft 32. On the other hand, in a released state of the clutch K0, transmission of power between the engine 14 and the pump impeller 16a is interrupted. That is, the engine 14 and the drive wheels 38 are disconnected from each other by releasing the clutch K0. Because the electric motor MG is coupled to the pump impeller 16a, the clutch KO also functions as a clutch that is provided in the power transmission path between the engine 14 and the electric motor MG and that connects or interrupts the power transmission path, that is, a clutch that connects or disconnects the electric motor MG to or from the engine 14.

[0021] In FIG. 2, the engine 14, for example, includes a plurality of cylinders 50, and is a direct- injection four-cycle gasoline engine that directly injects fuel into those cylinders 50. The engine 14 includes combustion chambers 52, an intake pipe 54, an exhaust pipe 56, fuel injection devices 58, ignition devices 60, intake valves 62, exhaust valves 64, an intake valve drive device 66 and an exhaust valve drive device 68. Each combustion chamber 52 is provided between a cylinder head and a corresponding piston. The intake pipe 54 is connected to intake ports of the combustion chambers 52. The exhaust pipe 56 is connected to exhaust ports of the combustion chambers 52. Each fuel injection device 58 is provided at the cylinder head, and directly injects fuel F to a corresponding one of the combustion chambers 52. Each ignition device 60 ignites air-fuel mixture in a corresponding one of the combustion chambers 52. Each intake valve 62 opens or closes the intake port of a corresponding one of the combustion chambers 52. Each exhaust valve 64 opens or closes the exhaust port of a corresponding one of the combustion chambers 52. The intake valves 62 are reciprocally moved in synchronization with rotation of the crankshaft 36 by the intake valve drive device 66. Thus, the intake valves 62 are opened or closed. The exhaust valves 64 are reciprocally moved in synchronization with rotation of the crankshaft 36 by the exhaust valve drive device 68. Thus, the exhaust valves 64 are opened or closed.

[0022] An electronic throttle valve 70 is provided in the intake pipe 54 of the engine 14. The electronic throttle valve 70 is opened or closed by a throttle actuator 72. In the engine 14, air-fuel mixture is formed by injecting and supplying fuel F from each fuel injection device 58 to intake air that is taken from the intake pipe 54 into a corresponding one of the combustion chambers 52, and the air-fuel mixture is ignited by a corresponding one of the ignition devices 60 to combust. Thus, the engine 14 is driven, and combusted air-fuel mixture is delivered into the exhaust pipe 56 as emission gas.

[0023] FIG. 3 is a view for illustrating the opening duration VTin of each intake valve 62 and the opening duration VTex of a corresponding one of the exhaust valves 64. In FIG. 3, the arrow A indicates the opening duration VTin of the intake valve 62, that is, the range of a crank angle Acr at which the intake valve 62 is open. The arrow B indicates the opening duration VTex of the exhaust valve 64, that is, the range of the crank angle Acr at which the exhaust valve 64 is open. The opening duration VT in the present embodiment is a period of opening (opening period) from the timing at which the valve opens (open timing) to the timing at which the valve closes (close timing), and does not indicate the open timing.

[0024] Referring back to FIG. 1 and FIG. 2, the vehicle 10, for example, includes an electronic control unit (ECU) 90 including a control device for the vehicle 10. The control device is associated with engagement/release control over the clutch K0, starting control over the engine 14, and the like. The electronic control unit 90 is, for example, configured to include a so-called microcomputer including a CPU, a RAM, a ROM, an input/output interface, and the like. The CPU executes various controls over the vehicle 10 by carrying out signal processing in accordance with a program prestored in the ROM while utilizing the temporary storage function of the RAM. For example, the electronic control unit 90 is configured to execute output control over the engine 14, drive control over the electric motor MG, including regenerative control over the electric motor MG, shift control over the automatic transmission 18, torque capacity control over the clutch K0, and the like. The electronic control unit 90 is formed separately in a unit for engine control, a unit for electric motor control, a unit for hydraulic pressure control, and the like, as needed. As shown in FIG. 1 and FIG. 2, various signals based on detected values of various sensors are supplied to the electronic control unit 90. The various sensors, for example, include a crank position sensor 74, a turbine rotation speed sensor 76, an output shaft rotation speed sensor 78, an electric motor rotation speed sensor 80, an accelerator operation amount sensor 82, a throttle sensor 84, an air flow meter 86 and a battery sensor 88. Various signals, for example, include the crank angle Acr indicating a crank position, a crank speed corresponding to an engine rotation speed Ne, a turbine rotation speed Nt, that is, a transmission input shaft rotation speed Nin, a transmission output shaft rotation speed Nout corresponding to a vehicle speed V, an electric motor rotation speed Nm, an accelerator operation amount Oacc corresponding to a driver's drive request amount for the vehicle 10, a throttle valve opening degree Oth, an intake air amount Qair, a state of charge (level of charge) SOC of the electrical storage device 44, and the like. As shown in FIG. 1 and FIG. 2, for example, an engine output control command signal Se for output control over the engine 14, an electric motor control command signal Sm for controlling the operation of the electric motor MG, and hydraulic pressure command signals Sp for operating electromagnetic valves (solenoid valves), and the like, included in the hydraulic control circuit 40 for controlling the hydraulic actuators of the clutch K0 and automatic transmission 18, are respectively output from the electronic control unit 90 to an engine control device, such as the fuel injection devices 58, the ignition devices 60 and the throttle actuator 72, the inverter 42, the hydraulic control circuit 40, and the like.

[0025] FIG. 4 is a functional block diagram that illustrates a relevant portion of control functions of the electronic control unit 90. In FIG. 4, the electronic control unit 90 includes crank angle acquisition means, that is, a crank angle acquisition unit 92, and hybrid control means, that is, a hybrid control unit 94.

[0026] The crank angle acquisition unit 92 acquires the crank angle Acr of the engine 14 on the basis of a signal that is detected at predetermined intervals. Specifically, referring back to FIG. 2, a rotor 89, such as a rotation detection rotor and a rotation detection drum, is integrally concentrically fixed to the crankshaft 36, and rotates together with the crankshaft 36. The crank position sensor 74 is, for example, provided at a position at which the crank position sensor 74 faces a plurality of teeth 89a formed at the radially outer periphery of the rotor 89 at substantially equal intervals in the circumferential direction. For example, an electromagnetic pickup sensor, a Hall element sensor, a magnetic resistance element (MRE) sensor, or the like, is employed as the crank position sensor 74. For example, in the case of the electromagnetic pickup sensor, as the rotor 89 rotates, an air gap between the crank position sensor 74 and the teeth 89a varies, so an alternating-current voltage of which the frequency varies with the rotation speed of the rotor 89 is generated from the crank position sensor 74. The alternating-current voltage is supplied to the electronic control unit 90, and the supplied alternating-current voltage is converted to a rectangular- wave pulse signal P in the electronic control unit 90. The crank angle acquisition unit 92 counts up or counts down the crank angle Acr and then acquires the crank angle Acr on the basis of the rising (or falling) of the pulse signal P that is detected at predetermined intervals corresponding to the intervals of the plurality of teeth 89a. In order to acquire the absolute position of the crank angle Acr, for example, the rotor 89 in which any one of the plurality of teeth 89a is deficient is used or a signal of a sensor that detects the position of another rotating member (for example, camshaft) that rotates in interlocking with rotation of the crankshaft 36 is used.

[0027] The hybrid control unit 84 has the function of an engine drive control unit that executes drive control over the engine 14 and the function of an electric motor operation control unit that controls the operation of the electric motor MG as a driving force source or a generator via the inverter 42, and executes hybrid drive control, or the like, with the use of the engine 14 and the electric motor MG through those control functions. For example, the hybrid control unit 84 calculates a required driving force Fdtgt as the driver's drive request amount for the vehicle 10 on the basis of the accelerator operation amount Oacc and the vehicle speed V. In consideration of a transmission loss, an auxiliary load, the speed ratio γ of the automatic transmission 18, the level of charge SOC of the electrical storage device 44, and the like, the hybrid control unit 94 outputs the command signals (the engine output control command signal Se and the electric motor control command signal Sm) for controlling the driving force sources so as to obtain the outputs of the driving force sources (the engine 14 and the electric motor MG), which achieve the required driving force Fdtgt. Other than the required driving force Fdtgt [N] of the drive wheels 38, the drive request amount may be a required driving torque [Nm] of the drive wheels 38, a required driving power [W] of the drive wheels 38, a required transmission output torque of the transmission output shaft 24, or the like. The drive request amount may also be merely the accelerator operation amount Gacc [%] , an intake air amount Qair [g/sec], or the like.

[0028] Specifically, for example, when the required driving force Fdtgt falls within the range in which the required driving force Fdtgt can be provided by only the output of the electric motor MG, the hybrid control unit 94 carries out motor running (EV traveling) in which the vehicle travels with the use of only the electric motor MG as the driving force source in a state where the clutch K0 is released. On the other hand, for example, when the required driving force Fdtgt falls within the range in which the required driving force Fdtgt cannot be provided unless at least the output of the engine 14 is used, the hybrid control unit 94 carries out engine running, that is, hybrid traveling (EHV traveling) in which the vehicle travels with the use of at least the engine 14 as the driving force source in a state where the clutch K0 is engaged. For example, when the vehicle cannot carry out EV traveling because discharging of the electrical storage device 44 is limited on the basis of a dischargeable electric power calculated from the level of charge SOC and the electrical storage device temperature, when charging of the electrical storage device 44 is required, or when warm-up of the engine 14 or a device associated with the engine 14 is required, the hybrid control unit 94 operates the engine 14.

[0029] The hybrid control unit 94 switches between EV traveling and EHV traveling by automatically stopping the engine 14 during engine running or restarting the engine 14 after an engine stop on the basis of the required driving force Fdtgt, or the like. The hybrid control unit 94 carries out a so-called idling stop for automatically stopping the engine 14 in a predetermined traveling state, such as an accelerator off low vehicle speed state where the vehicle speed V decreases toward zero and a vehicle stopped state where a brake is on. The hybrid control unit 94 restarts the engine 14 when a predetermined condition, such as a brake off state and an accelerator on state, is satisfied during an idling stop.

[0030] The hybrid control unit 94, for example, cranks the engine 14 with the use of the electric motor MG by controlling the released clutch K0 toward engagement, and starts the engine 14 by starting supply of fuel, engine ignition, and the like (which is synonymous with a restart unless otherwise specifically distinguished from each other). In this starting method, the clutch K0 is controlled such that K0 torque for transmitting engine starting torque, which is a torque required to start the engine, to the engine 14 side is obtained. The engine starting torque corresponds to part of MG torque Tm, transmitted to the engine 14 side via the clutch K0, so the amount of MG torque Tm, transmitted to the drive wheels 38 side, is reduced accordingly. Therefore, in this starting method, in order to suppress a drop of driving torque, in addition to the MG torque Tm required to meet the required driving torque, the amount of MG torque, corresponding to the K0 torque for transmitting the engine starting torque to the engine 14 side is increased (hereinafter, the amount of increase is termed K0 compensation torque (or MG compensation torque)). [0031] In EV traveling according to the present embodiment, an EV traveling region is narrowed by the amount by which the MG compensation torque is reserved from the maximum MG torque Tm that the electric motor MG is able to output, in preparation for an engine start. In other words, if the MG compensation torque is suppressed, it is possible to expand the EV traveling region. Therefore, the hybrid control unit 94 carries out an ignition start for rotating the engine 14 by causing one of the cylinders of the engine 14 to carry out combustion at the time of an engine start in addition to the starting method for controlling the clutch K0 toward engagement. That is, the hybrid control unit 94 provides part of the engine starting torque by carrying out an ignition start. In the engine starting method through an ignition start, for example, fuel is injected into one of the cylinders of the engine 14, which is stopped in expansion stroke (that is, one of the cylinders, which is in the expansion stroke of the engine 14 of which rotation is stopped), the one of the cylinders is caused to combust through ignition, the corresponding piston is pushed downward by generated explosive torque, and the engine 14 is started by rotating the crankshaft 36.

[0032] When part of the engine starting torque is provided through an ignition start, it is suitable to carry out an ignition start for moving the stopped piston. That is, overcoming the friction torque of the engine 14 at the time of initiation of an engine start by using explosive torque resulting from an ignition start is suitable to suppress the MG compensation torque. Thus, the hybrid control unit 94 initially rotates the engine 14 through an ignition start when a restart of the engine 14 is required. After that, the hybrid control unit 94 increases the engine rotation speed Ne with the use of the electric motor MG by controlling the clutch K0 toward engagement. The hybrid control unit 94 shifts into EHV traveling by completely engaging the clutch K0 after the engine rotation speed Ne is synchronized with the electric motor rotation speed Nmg. The friction torque of the engine 14 at the time, of an engine start is a resultant torque of a compression torque, a mechanical torque and a mechanical friction torque of the intake valve drive device 66 and exhaust valve drive device 68. The compression torque corresponds to a pumping loss. The mechanical friction torque corresponds to a sliding resistance. However, the friction torque of the engine 14 at the initiation of an engine start at the time of moving the stopped piston merely becomes a mechanical friction torque of the sliding resistance, intake valve drive device 66, and the like, because the engine rotation speed Ne is significantly low.

[0033] When the crank angle Acr is acquired on the basis of the pulse signal P that is detected at predetermined intervals as in the case of the present embodiment, it may not be able to accurately detect an actual crank angle Acr (also referred to as actual position) at the time of an engine stop (that is, at the time when rotation of the engine 14 is stopped). Specifically, in an eight-cylinder engine, the combustion interval is 90°CA, and the angle of half the combustion interval is 45°CA, so the engine tends to stop at a position at which any one of the cylinders is at the TDC or at 45ATDC. At the time of an engine stop, an overshoot and a reversal may be repeated. Therefore, as shown in FIG. 5 and FIG. 6, eve when actual positions at the time of an engine stop are substantially the same, the crank angles Acr (which may also be referred to as ECU value) that are acquired by the crank angle acquisition unit 92 may vary. FIG. 5 and FIG. 6 each show an example of the case where the detection interval of the crank position sensor 74 is 10° and the engine is stopped at a position near 45ATDC in the eight-cylinder engine. In FIG. 5, where the ECU value is 40°CA or 50°CA, the average actual positions at the time of an engine stop are almost the same. In FIG. 6, as indicated by a stopping behavior A, when the engine stops at 45°CA while being rotated in the forward direction or when the engine stops at 45°CA after a reversal before 50°CA at the time of an overshoot, the ECU value is 40°CA for the actual position of 45°CA. As indicated by a stopping behavior B, when the count is increased to 50°CA at the time of an overshoot and then the engine stops at 45°CA without returning to 40°CA, the ECU value is 50°CA for the actual position of 45°CA. In this way, even when the actual positions at the time of an engine stop are the same, the ECU values may vary because of a difference in behavior at the time of an engine stop.

[0034] The electronic control unit 90 ordinarily sets a fuel injection amount at the time of an engine start on the basis of the ECU value. When the case where the ECU value is 40°CA is compared with the case where the ECU value is 50°CA, the set fuel injection amount is smaller in the case where the ECU value is 40°CA. Therefore, if the actual positions are the same 45°CA, a lean state is formed in the case where the ECU value is 40°CA; whereas a rich state is formed in the case where the ECU value is 50°CA. As a result, an operating state at the time of an engine restart may not become stable. The electronic control unit 90 operates the clutch KO in accordance with an engine start-up in an ignition start, and increases the engine rotation speed Ne with the assistance of the electric motor MG At this time, the electronic control unit 90, for example, sets the engagement timing of the clutch K0 according to initiation of rotation of the engine 14 on the basis of the ECU value. When the case where the ECU value is 40°CA is compared with the case where the ECU value is 50°CA, if the actual positions are the same 45°CA, the count is increased from 50°CA in the case where the ECU value is 40°CA and the count is increased from 60°CA in the case where the ECU value is 50°CA as also shown in FIG. 6, so an operation time up to the next count-up (that is, the timing at which initiation of rotation is detected) varies even when the actual start-up timing (rotation initiation timing) is the same. As a result, the engagement timing of the clutch K0 varies, and control over the clutch K0 may not become stable. Thus, when the actual position at the time of an engine stop is the crank angle Acr that cannot be acquired by the crank angle acquisition unit 92, control at the time of a restart after an automatic stop of the engine 14 may not be appropriately executed.

[0035] Therefore, as shown in FIG. 4, the electronic control unit 90 further includes engine state determination means, that is, an engine state determination unit 96, and restart related value setting means, that is, a restart related value setting unit 98.

[0036] The engine state determination unit 96, for example, determines whether there is an engine stop request to require a stop of the engine 14, assuming a restart. For example, the engine state determination unit 96 determines that there is an engine stop request assuming a restart, for example, when the required driving force Fdtgt falls within the range in which the required driving force Fdtgt can be provided by only the output of the electric motor MG during EHV traveling or when any one of a discharge limitation on the electrical storage device 44, a charging request for the electrical storage device 44 and a warm-up request for the engine 14, and the like, is cancelled and the vehicle carries out EV traveling.

[0037] When the engine state determination unit 96 determines that there is an engine stop request, the hybrid control unit 94 stops both fuel injection and ignition to the engine 14, and the crank angle acquisition unit 92 detects the crank angle Acr of the stopped engine 14.

[0038] The engine state determination unit 96 determines whether the crank angle Acr at the time of an engine stop (hereinafter, referred to as engine-stop crank angle Acr (ECU value)) acquired by the crank angle acquisition unit 92 falls within a predetermined range including a predetermined stop-time crank angle Acrpre obtained in advance as an actual crank angle Acr at the time when the engine 14 has stopped. The predetermined stop-time crank angle Acrpre is a value between adjacent crank angles Acr (ECU values). The predetermined stop-time crank angle Acrpre is an actual crank angle Acr at which the engine 14 tends to stop and is a crank angle Acr corresponding to a state where any one of the cylinders of the engine 14 stops at the position of the TDC or a crank angle Acr corresponding to a state where any one of the cylinders of the engine 14 stops at a position advanced by a crank angle Acr, which is half the combustion interval, from the TDC. The predetermined range includes crank angles Acr (ECU values) that may be acquired by the crank angle acquisition unit 92 for an actual position and that are obtained in advance.

[0039] Specifically, in the eight-cylinder engine, any one of the cylinders of the engine 14 tends to stop at the position of the TDC (that is, the position of 90ATDC) or the position of 45ATDC. Here, in the eight-cylinder engine, for example, the case where any one of the cylinders is at the position of 45ATDC includes eight positions, that is, 45°CA, 135°CA, 225°CA, 315°CA, 405°CA, 495°CA, 585°CA, 675°CA with reference to the TDC. In the present embodiment, for the sake of convenience, these eight positions are handled as 45°CA. Similarly, when any one of the cylinders is at the position of the TDC, for the sake of convenience, eight positions are handled as 0°CA (or 90°CA). When the crank angle Acr is acquired with reference to the TDC, if the detection interval is 10°CA, the ECU value becomes 0°CA at the actual position of 0°CA; whereas the ECU value becomes 40°CA or 50°CA at the actual position of 45°CA. Thus, in such a case, the engine state determination unit 96 determines whether the engine-stop crank angle Acr (ECU value) is 40°CA or 50°CA that falls within the predetermined range including 45°CA that is the predetermined stop-time crank angle Acrpre.

[0040] The restart related value setting unit 98 sets a restart-related control value for the engine 14 on the basis of the engine-stop crank angle Acr (ECU value). Specifically, when the engine state determination unit 96 determines that the engine-stop crank angle Acr (ECU value) falls within the predetermined range including the predetermined stop-time crank angle Acrpre, the restart related value setting unit 98 sets a constant engine restart-related control value based on the predetermined stop-time crank angle Acrpre irrespective of the engine-stop crank angle Acr (ECU value). For example, in the eight-cylinder engine, the restart related value setting unit 98 sets the engine-stop crank angle Acr to not the ECU value (= 40°CA, 50°CA) but 45°CA and sets the constant engine restart-related control value based on 45°CA. On the other hand, when the engine state determination unit 96 determines that the engine-stop crank angle Acr (ECU value) falls outside the predetermined range (that is, when the engine state determination unit 96 determines that the crank angle Acr (ECU value) does not fall within the predetermined range), the restart related value setting unit 98 sets an engine restart-related control value based on the engine-stop crank angle Acr (ECU value). For example, in the eight-cylinder engine, when the engine-stop crank angle Acr (ECU value) is not 40°CA or 50°CA, the restart related value setting unit 98 sets the engine-stop crank angle Acr to the ECU value, and sets an engine restart-related control value based on the ECU value.

[0041] The engine restart-related control value is, for example, a fuel injection amount at the time of an engine restart. The engine restart-related control value is, for example, the engagement time or engagement timing of the clutch KG at the time of an engine restart. Therefore, the restart related value setting unit 98 includes fuel injection amount setting means, that is, a fuel injection amount setting unit 100, and clutch engagement time setting means, that is, a clutch engagement time setting unit 102. The fuel injection amount setting unit 100 sets the fuel injection amount at the time of an engine restart on the basis of the engine-stop crank angle Acr (ECU value). The clutch engagement time setting unit 102 sets the engagement time or engagement timing of the clutch K0 at the time of an engine restart on the basis of the engine-stop crank angle Acr (ECU value).

[0042] When the engine state determination unit 96 determines that the engine-stop crank angle Acr (ECU value) falls within the predetermined range including the predetermined stop-time crank angle Acrpre, the fuel injection amount setting unit 100 sets a constant fuel injection amount based on the predetermined stop-time crank angle Acrpre irrespective of the engine-stop crank angle Acr (ECU value). On the other hand, when the engine state determination unit 96 determines that the engine-stop crank angle Acr (ECU value) falls outside the predetermined range, the fuel injection amount setting unit 100 sets a fuel injection amount based on the engine-stop crank angle Acr (ECU value). The fuel injection amount is, for example, a fuel injection amount of the cylinder that is caused to carry out first combustion at the time of an engine restart. That is, the fuel injection amount setting unit 100 sets a fuel injection amount of the cylinder that is caused to carry out combustion first at the time of an engine restart.

[0043] When the engine state determination unit 96 determines that the engine-stop crank angle Acr (ECU value) falls within the predetermined range including the predetermined stop-time crank angle Acrpre, the clutch engagement time setting unit 102 sets a constant engagement time or engagement timing of the clutch K0 based on the predetermined stop-time crank angle Acrpre irrespective of the engine-stop crank angle Acr (ECU value). On the other hand, when the engine state determination unit 96 determines that the engine-stop crank angle Acr (ECU value) falls outside the predetermined range, the clutch engagement time setting unit 102 sets the engagement time or engagement timing of the clutch K0 based on the engine-stop crank angle Acr (ECU value). The engagement time or engagement timing of the clutch K0 is, for example, set as engagement initiation timing after a lapse of a predetermined time from the timing at which an engine restart is determined or a transitional time from initiation of engagement to completion of engagement.

[0044] FIG. 7 is a flowchart that illustrates a relevant portion of control operations of the electronic control unit 90, that is, control operations for appropriately carrying out a restart suitable for an actual engine stop position, and is, for example, repeatedly executed at an extremely short cycle time of about several milliseconds to several tens of milliseconds. The state of the vehicle 10, assumed in FIG. 7, is, for example, in the case where the engine 14 is an eight-cylinder engine and the detection interval of the crank position sensor 74 is 10°.

[0045] In FIG. 7, initially, in step (hereinafter, step is omitted) S 10 corresponding to the engine state determination unit 96, for example, it is determined whether there is an engine stop request assuming a restart. When negative determination is made in S10, the routine is ended. When affirmative determination is made in S10, for example, both fuel injection and ignition to the engine 14 are stopped in S20 corresponding to the hybrid control unit 94. Subsequently, in S30 corresponding to the crank angle acquisition unit 92, for example, the engine-stop crank angle Acr (ECU value) is detected. Subsequently, in S40 corresponding to the engine state determination unit 96, for example, it is determined whether the engine-stop crank angle Acr (ECU value) detected in S30 is 40°CA or 50°CA. When affirmative determination is made in S40, the process proceeds to S50 corresponding to the restart related value setting unit 98 and the hybrid control unit 94. In S50, for example, the engine-stop crank angle Acr is set to not the ECU value but 45°CA, and the constant engine restart-related control value based on 45°CA is set, after which the following control is executed. On the other hand, when negative determination is made in S40, the process proceeds to S60 corresponding to the restart related value setting unit 98 and the hybrid control unit 94. In S60, for example, the engine-stop crank angle Acr is set to the ECU value, and the engine restart-related control value based on the ECU value is set, after which the following control is executed.

[0046] As described above, according to the present embodiment, even when the engine-stop crank angle Acr (ECU value) is acquired as a different value for substantially the same actual engine stop position, and when the crank angle Acr (ECU value) falls within the predetermined range including the predetermined stop-time crank angle Acrpre, the restart related value setting unit 98 sets the constant control value based on the predetermined stop-time crank angle Acrpre, and the hybrid control unit 94 restarts the engine 14 by using the control value, so the operating state at the time of an engine restart is stable. That is, the engine-stop crank angle Acr that is used in control is allowed to be brought closer to an actual value than the crank angle Acr (ECU value), so the operating state at the time of an engine restart is stable. Thus, it is possible to appropriately carry out a restart suitable for an actual engine stop position.

[0047] According to the present embodiment, when the engine-stop crank angle Acr (ECU value) falls outside the predetermined range including the predetermined stop-time crank angle Acrpre, the restart related value setting unit 98 sets the engine restart-related control value based on the crank angle Acr (ECU value), and the hybrid control unit 94 restarts the engine 14 by using the control value. Therefore, it is possible to appropriately carry out a restart suitable for an actual engine stop position.

[0048] According to the present embodiment, when the engine-stop crank angle Acr (ECU value) falls within the predetermined range including the predetermined stop-time crank angle Acrpre, the fuel injection amount setting unit 100 sets a constant fuel injection amount based on the predetermined stop-time crank angle Acrpre irrespective of the crank angle Acr (ECU value). Thus, even when the crank angle Acr (ECU value) is acquired as a different value for substantially the same actual engine stop position, a constant fuel injection amount is used at the time of an engine restart, so the operating state at the time of an engine restart is stable.

[0049] According to the present embodiment, the fuel injection amount setting unit 100 sets a fuel injection amount of the cylinder that is caused to combust first at the time of an engine restart, so the operating state at the time of an engine restart that accompanies an ignition start is stable.

[0050] According to the present embodiment, when the engine-stop crank angle

Acr (ECU value) falls within the predetermined range including the predetermined stop-time crank angle Acrpre, the clutch engagement time setting unit 102 sets the constant engagement time or engagement timing of the clutch K0 based on the predetermined stop-time crank angle Acrpre irrespective of the crank angle Acr (ECU value). Thus, even when the crank angle Acr (ECU value) is acquired as a different value for substantially the same actual engine stop position, the clutch KO is engaged by using the constant engagement time or engagement timing of the clutch KO at the time of an engine restart, so clutch control is stable, and engine operation timing tends to be constant.

[0051] According to the present embodiment, the predetermined stop-time crank angle Acrpre is a value between adjacent crank angles Acr (ECU^' values), and is a crank angle Acr corresponding to the case where any one of the cylinders of the engine 14 stops at the position of the TDC or a crank angle Acr corresponding to the case where any one of the cylinders of the engine 14 stops at a position advanced by a crank angle Acr, which is half the combustion interval, from the TDC. Thus* when an actual position at which the engine 14 tends to stop is at the crank angle Acr that cannot be acquired by the crank angle acquisition unit 92, it is possible to appropriately carry out a restart suitable for an actual engine stop position.

[0052] The embodiment of the invention is described in detail with reference to the drawings; however, the invention is also applicable to other embodiments.

[0053] For example, in the above-described embodiment, the eight-cylinder engine is illustrated as the engine 14, 10° is illustrated as the detection interval of the crank position sensor 74, and the TDC is illustrated as the reference point of the crank angle Acr. However, the invention is not limited to this configuration. For example, even when the engine 14 is a four-cylinder engine, a six-cylinder engine, or the like, the invention is applicable. Even when the detection interval of the crank position sensor 74 is 6° , 8°, or the like, the invention is applicable. Even when the reference point of the crank angle Acr is 90ATDC, BDC, or the like, the invention is applicable. In short, when two crank angles Acr (ECU values) interposing an actual crank position at which the engine 14 tends to stop are present for the actual crank position (that is, the predetermined stop-time crank angle Acrpre), the invention is applicable.

[0054] In the above-described embodiment, the fuel injection amount at the time of an engine restart or the engagement time or engagement timing of the clutch K0 is illustrated as the engine restart-related control value. However, the invention is not limited to this configuration. For example, ignition timing at the time of an engine restart, or the like, is also assumed as the engine restart-related control value.

[0055] In the above-described embodiment, an ignition start is carried out for the cylinder in the expansion stroke, and the engine 14 is started with the use of the electric motor MG. However, the invention is not limited to this configuration. For example, the cylinder that is caused to combust first or the cylinder to which fuel is injected first is not always limited to the cylinder in the expansion stroke. Alternatively, the engine 14 may be started with the use of a starter motor provided separately from the electric motor MG with the assistance of an ignition start. If the engine is allowed to be started through only an ignition start, the engine 14 does not need to be started with the use of the electric motor MG (or the starter). At the time of starting the engine 14 in a rotation stopped state, it is not always necessary to increase the engine rotation speed Ne from zero through an ignition start. The engine rotation speed Ne may be initiated to increase with the use of the starter.

[0056] In the above-described embodiment, the vehicle 10 includes the torque converter 16 and the automatic transmission 18. However, the torque converter 16 or the automatic transmission 18 does not need to be provided. The vehicle 10 includes the clutch K0 and the electric motor MG. However, the clutch K0 or the electric motor MG does not need to be provided except the mode in which the engagement time or engagement timing of the clutch K0 at the time of an engine restart is set on the basis of the engine-stop crank angle Acr (ECU value).

[0057] The above-described embodiments are only illustrative, and the invention may be implemented in modes including various modifications and improvements on the basis of the knowledge of persons skilled in the art.

Claims

CLAIMS:

1. A control device for a vehicle (10) including a multicylinder four-cycle engine (14), characterized by comprising:

a crank angle acquisition unit (92) acquiring a crank angle of the engine based on a signal that is detected at predetermined intervals; and

a restart related value setting unit (98) setting a restart-related control value for the engine based on an acquired engine-stop crank angle acquired by the crank angle acquisition unit, wherein

when the acquired engine-stop crank angle falls within a predetermined range including a predetermined stop-time crank angle, the restart related value setting unit sets the restart-related control value to be constant based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle.

2. The control device according to claim 1, wherein

when the acquired engine-stop crank angle falls outside the predetermined range including the predetermined stop-time crank angle, the restart related value setting unit sets the restart-related control value based on the acquired engine-stop crank angle.

3. The control device according to claim 1 or 2, wherein

the restart related value setting unit includes a fuel injection amount setting unit (100) setting a fuel injection amount at the time of a restart of the engine based on the acquired engine-stop crank angle, and the fuel injection amount setting unit sets a constant fuel injection amount based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle when the acquired engine-stop crank angle falls within the predetermined range including the predetermined stop-time crank angle.

4. The control device according to claim 3, wherein an ignition start for rotating the engine by causing any one of cylinders to combust at the time of a start of the engine is carried out, and the fuel injection amount setting unit sets the fuel injection amount of the cylinder that is caused to combust first at the time of the restart of the engine.

5. The control device according to claim 1 or 2, wherein the vehicle includes an electric motor (MG) provided in a power transmission path between the engine and a drive wheel (38) and a clutch (K0) connecting or disconnecting the electric motor to or from the engine,

the restart related value setting unit includes a clutch engagement time setting unit (102) setting an engagement time or engagement timing of the clutch at the time of a restart of the engine based on the acquired engine-stop crank angle, and the clutch engagement time setting unit sets the engagement time or engagement timing of the clutch to be constant, based on the predetermined stop-time crank angle, irrespective of the acquired engine-stop crank angle when the acquired engine-stop crank angle falls within the predetermined range including the predetermined stop-time crank angle.

6. The control device according to any one of claims 1 to 5, wherein

the predetermined stop-time crank angle is a value between adjacent crank angles that are acquired by the crank angle acquisition unit at the predetermined intervals, and is a crank angle corresponding to a state where any one of cylinders of the engine stops at a position of a top dead center or a crank angle corresponding to a state where any one of cylinders of the engine stops at a position advanced by a crank angle, which is half a combustion interval, from the top dead center.

7. A control device for a vehicle including a multicylinder four-cycle engine, comprising:

an electronic control unit configured to

(i) acquire a crank angle of the engine based on a signal that is detected at predetermined intervals,

(ii) set a restart-related control value for the engine based on an acquired engine-stop crank angle acquired by the electronic control unit, and

(iii) when the acquired engine-stop crank angle falls within a predetermined range including a predetermined stop-time crank angle, sets the restart-related control value to be constant based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle.

8. The control device according to claim 7, wherein

. when the acquired engine-stop crank angle falls outside the predetermined range including the predetermined stop-time crank angle, the electronic control unit is configured to set the restart-related control value based on the acquired engine-stop crank angle.

9. The control device according to claim 7, wherein

the electronic control unit is configured to set a fuel injection amount at the time of a restart of the engine based on the acquired engine-stop crank angle, and

the electronic control unit is configured to set a constant fuel injection amount based on the predetermined stop-time crank angle irrespective of the acquired engine-stop crank angle when the acquired engine-stop crank angle falls within the predetermined range including the predetermined stop-time crank angle.

10. The control device according to claim 9, wherein

the electronic control unit is configured to perform ignition start for rotating the engine by causing any one of cylinders to combust at the time of a start of the engine, and set the fuel injection amount of the cylinder that is caused to combust first at the time of the restart of the engine.

11. The control device according to claim 7, wherein the vehicle includes an electric motor provided in a power transmission path between the engine and a drive wheel and a clutch connecting or disconnecting the electric motor to or from the engine,

the electronic control unit is configured to set an engagement time or engagement timing of the clutch at the time of a restart of the engine based on the acquired engine-stop crank angle, and

the electronic control unit is configured to set the engagement time or engagement timing of the clutch to be constant, based on the predetermined stop-time crank angle, irrespective of the acquired engine-stop crank angle when the acquired engine-stop crank angle falls within the predetermined range including the predetermined stop-time crank angle.

12. The control device according to claim 7, wherein

the predetermined stop-time crank angle is a value between adjacent crank angles that are acquired at the predetermined intervals, and is a crank angle corresponding to a state where any one of cylinders of the engine stops at a position of a top dead center or a crank angle corresponding to a state where any one of cylinders of the engine stops at a position advanced by a crank angle, which is half a combustion interval, from the top dead center.

13. A control method for a vehicle including a multicylinder four-cycle engine and an electronic control unit, comprising:

acquiring a crank angle of the engine, by the electronic control unit, based on a signal that is detected at predetermined intervals;

setting a restart-related control value, by the electronic control unit, for the engine based on an acquired engine-stop crank angle acquired by the electronic control unit; and when the acquired engine-stop crank angle falls within a predetermined range including a predetermined stop-time crank angle, setting the restart-related control value to be constant based on the predetermined stop-time crank angle irrespective of the acquired engine- stop crank angle.