Vehicle drive unit

Abstract

To properly restart an engine which is stopped as an engine travel mode is changed to a motor travel mode.SOLUTION: When switching from an engine travel mode to a motor travel mode, fuel cut is performed where clutch fastening is released and fuel supply to a combustion chamber of an engine is stopped, and a valve phase is changed by a phase variable device into a target phase suitable for restart of the engine. It is determined, based on the valve phase detected by a phase detection unit after the fuel cut, whether the valve phase can be changed to the target phase before the engine stops completely. In a case where it is not possible, an engine transient drive control is performed to give transient torque to the engine so that the timing of the complete stop of the engine is postponed until after the valve phase is changed into the target phase.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a drive device for a vehicle that uses both an internal combustion engine and an electric motor as a power source. [Background technology]

[0002] Among hybrid vehicles, which use both an internal combustion engine and an electric motor as power sources, there are hybrid vehicles that can run solely on the motor. That is, hybrid vehicles can switch between an engine driving mode, in which at least a portion of the power is provided by the engine, and a motor driving mode, in which all of the power is provided by the motor. In such hybrid vehicles, control to stop the engine and control to restart the stopped engine can be repeatedly performed while the vehicle is running.

[0003] An engine for such a hybrid vehicle may be equipped with a phase-varying device that can change the phase of the intake valve or exhaust valve (hereinafter referred to as the valve phase). When using this type of engine, there may be a case where the valve phase at the time of an engine stop request accompanying a change in driving mode is significantly different from the phase suitable for restarting the engine. In such a case, if the engine is stopped with the valve phase fixed at the phase at the time of the engine stop request, the air-fuel mixture cannot be properly combusted when the engine is subsequently restarted, which may result in a failure of the restart. To avoid such a situation, it is proposed to change the valve phase to a target phase suitable for restarting between the time of the engine stop request and the time the engine is completely stopped.

[0004] Although not intended for hybrid vehicle engines, the following Patent Document 1 discloses a known valve phase control technology that takes engine startability into consideration. Specifically, Patent Document 1 discloses an engine equipped with a hydraulic variable valve timing device that changes the phase of the intake valve and a control device that changes the phase of the intake valve to the most retarded phase suitable for engine start before the engine comes to a complete stop. In more detail, the control device calculates the throttle valve opening according to the intake valve advance amount (advance amount relative to the most retarded phase) at the time the ignition switch is turned off so that the engine's inertial rotation period becomes longer the greater the intake valve advance amount, and opens the throttle valve to the calculated opening. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-286064 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the control device described in Patent Document 1, the throttle valve is opened so that the greater the intake valve advance amount, the longer the engine's inertial rotation period, which prevents the engine from stopping completely before the intake valve phase change (change to the most retarded phase) is complete. If the engine can continue to rotate until the phase change is complete, the supply of hydraulic pressure from a hydraulic supply source such as an oil pump to the variable valve timing device is prevented from stopping before the phase change is complete, which increases the possibility of changing the intake valve phase to the most retarded phase suitable for restarting, and improves engine startability.

[0007] However, in the technique disclosed in Patent Document 1, which extends the inertial rotation period of the engine by opening the throttle valve (in other words, reducing pumping loss), there is a natural limit to how far the inertial rotation period can be extended. Therefore, even if a similar method is applied to a hybrid vehicle, there is a possibility that the restartability of the engine will not be sufficiently improved. Specifically, in a hybrid vehicle in which the engine may be repeatedly stopped and restarted while the vehicle is running, depending on the conditions, the valve phase at the time of an engine stop request may be significantly different from the phase suitable for restart. Therefore, simply reducing pumping loss by opening the throttle valve, etc., may not be enough to continue engine rotation until the valve phase has completely changed to the target phase, potentially resulting in insufficient restartability.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a vehicle drive device that can properly restart an engine that has stopped due to switching from engine driving mode to motor driving mode. [Means for solving the problem]

[0009] In order to solve the above problem, a vehicle drive system according to one aspect of the present invention includes an internal combustion engine including a hydraulic phase variable device that can change a valve phase, which is the phase of an intake valve or an exhaust valve; an electric motor connected to wheels; a clutch that connects the engine and the motor in a detachable manner; a phase detection unit that detects the valve phase; and a control device that can selectively execute an engine running mode in which the clutch is engaged and the engine is driven to use the engine as a power source of the vehicle, and a motor running mode in which the clutch is released and the engine is stopped to use the motor as a power source of the vehicle, and the control device is configured to switch the engine running mode from the engine running mode to the motor running mode. When switching to the engine driving mode, the clutch is released and a fuel cut is performed to stop the supply of fuel to the combustion chamber of the engine, and the phase varying device is used to change the valve phase toward a target phase suitable for restarting the engine. Based on the valve phase detected by the phase detection unit after the fuel cut, it is determined whether or not the valve phase can be changed to the target phase before the engine comes to a complete stop, and if it is determined that this is not possible, temporary engine drive control is performed to impart a temporary rotational force to the engine so that the timing of the engine coming to a complete stop is postponed until after the change to the target phase has been completed (claim 1).

[0010] According to the present invention, when a request to switch from engine driving mode to motor driving mode is received, it is determined whether the valve phase can be changed to the target phase before the engine completely stops. If it is determined that the valve phase cannot be changed, temporary engine drive control is executed to temporarily apply a rotational force to the engine. This allows the timing of the engine completely stopping to be postponed until after the change to the target phase is complete. Moreover, because the temporary engine drive control actually applies a rotational force to the engine, by appropriately adjusting the period during which the rotational force is applied, it is possible to accurately continue the engine rotation until the change to the target phase is complete. This prevents the supply of hydraulic pressure from a hydraulic supply source, such as an oil pump, to the phase varying device from being stopped before the change to the target phase is complete, and therefore the valve phase can be changed to the target phase with a high probability. Once the valve phase is changed to the target phase, the engine can be restarted under valve timing conditions suitable for restart, thereby ensuring good engine restartability.

[0011] Preferably, the engine temporary drive control includes control to engage the clutch, and the control device engages the clutch upon determining that the valve phase cannot change to the target phase before the engine is completely stopped, and continues to engage the clutch until the change to the target phase is completed (claim 2).

[0012] According to this configuration, the motor can apply rotational force to the engine via the engaged clutch, allowing the engine to continue rotating until the change to the target phase is complete.

[0013] The temporary engine drive control may include control of supplying fuel to the combustion chamber for a predetermined period included in an engagement period of the clutch (claim 3).

[0014] With this configuration, the rotational force transmitted from the motor via the clutch and the rotational force generated by combustion energy can be applied to the engine simultaneously, and the timing of the complete stop of the engine can be reliably postponed until after the change to the target phase has been completed.

[0015] The phase varying device may vary the phase of the exhaust valve. In this case, when switching from the engine driving mode to the motor driving mode, the control device sets the target phase to a most advanced phase that is the most advanced phase within a phase adjustment range of the exhaust valve adjusted by the phase varying device (claim 4).

[0016] With this configuration, the engine is restarted with the exhaust valve sufficiently advanced, in other words, with a small amount of valve overlap between the intake valve and the exhaust valve. This prevents a large amount of burned gas from flowing back into the combustion chamber and impeding the combustion of the air-fuel mixture, ensuring good engine restartability.

[0017] Preferably, the phase varying device includes a holding mechanism that holds the phase of the exhaust valve at the most advanced phase (claim 5).

[0018] According to this configuration, after the control for changing the phase of the exhaust valve to the most advanced phase (most advanced angle control) is completed, the exhaust valve phase can be reliably maintained at the most advanced angle phase from the time the engine is completely stopped until the next restart. Therefore, the engine can be reliably restarted with the exhaust valve phase at the most advanced angle phase, thereby improving the restartability of the engine.

[0019] Preferably, when a request to switch from the engine driving mode to the motor driving mode is made when the engine speed is equal to or higher than a predetermined first speed, the control device disengages the clutch and cuts the fuel, and then, when the engine speed falls below the first speed, starts control to change the valve phase toward the target phase using the phase variable device (claim 6).

[0020] This configuration prevents the exhaust valve phase from deviating significantly from the phase appropriate for the engine speed during engine stopping, thereby suppressing noise during engine stopping. In other words, if exhaust valve maximum advance control were initiated immediately when the engine speed was equal to or greater than the first speed, the exhaust valve phase could be advanced to near the most advanced phase while the engine speed was relatively high and the piston speed was fast, resulting in a situation in which only the intake valve opens at the end of the exhaust stroke. This situation could result in increased intake and exhaust noise due to a large amount of burned gas being blown back into the intake port, potentially increasing noise during engine stopping. In contrast, the above configuration does not initiate exhaust valve maximum advance control until the engine speed falls below the first speed, thereby preventing the aforementioned increase in noise and improving vehicle quietness.

[0021] Preferably, the control device compares the valve phase detected when the engine speed after the fuel cut becomes less than a second speed that is lower than the first speed with a predetermined threshold value, thereby determining whether the valve phase can be changed to the target phase before the engine comes to a complete stop (claim 7).

[0022] By examining the valve phase at the time when the engine speed drops below the second speed, it is possible to predict whether the period required for the valve phase to change to the target phase is longer or shorter than the period until the engine comes to a complete stop, and it is possible to appropriately determine whether the valve phase can change to the target phase before the engine comes to a complete stop.

[0023] When a request to switch from the engine driving mode to the motor driving mode is made while the engine speed is less than the first speed, it is preferable that the control device releases the clutch and starts control to change the valve phase toward the target phase using the phase variable device, and executes the fuel cut when the change to the target phase is completed (claim 8).

[0024] With this configuration, the engine continues to rotate due to combustion until the change to the target phase is complete, thereby reliably preventing the engine from completely stopping before the change to the target phase is complete. Here, not cutting fuel until the change to the target phase is complete means that combustion occurs in a state where the valve phase has changed to a phase suitable for restart or close to that phase, in other words, where the valve phase is shifted from the originally desired phase. This could lead to abnormal combustion. However, in this embodiment, the control that achieves both the change to the target phase and engine combustion is performed only when the engine speed at the time of the request to switch to the motor driving mode is less than the first speed, in other words, under conditions where abnormal combustion is unlikely to occur. This prevents abnormal combustion from occurring during this control. [Effects of the Invention]

[0025] As described above, the vehicle drive device of the present invention can appropriately restart the engine that has stopped due to switching from the engine drive mode to the motor drive mode. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a system diagram showing a schematic configuration of a vehicle to which a drive device according to an embodiment of the present invention is applied; [Figure 2] FIG. 1 is a schematic cross-sectional view showing the structure of an engine. [Figure 3] FIG. 2 is a cross-sectional view showing the structure of an exhaust SVT. [Figure 4] FIG. 10 is a diagram showing the adjustment range of the phase of the exhaust valve by the exhaust SVT. [Figure 5] FIG. 2 is a functional block diagram showing a control system of the vehicle. [Figure 6] 10 is a flowchart (part 1) showing control when switching from the engine driving mode to the motor driving mode. [Figure 7] 10 is a flowchart (part 2) showing control when switching from the engine driving mode to the motor driving mode. [Figure 8]6 is a time chart showing an example of time-series changes in state quantities of various parts when a request to switch from the engine driving mode to the motor driving mode is made while the engine speed is higher than a first speed. [Figure 9] 6 is a time chart showing an example of time-series changes in state quantities of various parts when a request to switch from the engine driving mode to the motor driving mode is made while the engine speed is less than a first speed. DETAILED DESCRIPTION OF THE INVENTION

[0027] [Overall configuration of hybrid vehicle] 1 is a system diagram showing a schematic configuration of a vehicle V to which a drive device according to one embodiment of the present invention is applied. As shown in the diagram, the vehicle V includes an engine 1, a clutch 30, a motor 31, an inverter 32, a battery 33, an automatic transmission 35, a differential 36, drive wheels 37, and a PCM 50. Both the engine 1 and the motor 31 are capable of driving the drive wheels 37 as a power source for traveling. In other words, the vehicle V in this embodiment is a hybrid vehicle that uses both the engine 1 and the motor 31 as a power source.

[0028] The engine 1 is an internal combustion engine that generates power by burning fuel. There is no particular restriction on the type of engine, but in this embodiment, a four-stroke gasoline engine that uses gasoline as fuel is used as the engine 1. Details of the engine 1 will be described later.

[0029] The motor 31 is, for example, a three-phase AC synchronous electric motor, in other words, a motor generator that functions both as a motor and as a generator. The motor 31 operates as a motor when necessary, such as when the vehicle V is accelerating, and generates driving force for rotating the drive wheels 37. When the vehicle V is decelerating, the motor 31 operates as a generator and generates electricity by receiving rotational force transmitted from the drive wheels 37. In this case, a braking force (regenerative braking) corresponding to the amount of electricity generated by the motor 31 acts on the drive wheels 37.

[0030] The inverter 32 is a converter that converts AC power to DC power and vice versa. That is, when the motor 31 operates as a generator, the inverter 32 converts the three-phase AC power generated by the motor 31 into DC power and supplies it to the battery 33. On the other hand, when the motor 31 operates as a motor, the inverter 32 converts the DC power stored in the battery 33 into three-phase AC power and supplies it to the motor 31. The inverter 32 also has a function of adjusting the output or power generation amount of the motor 31 by controlling the exchange of power between the motor 31 and the battery 33.

[0031] The battery 33 is a rechargeable secondary battery. For example, a lithium ion battery or a nickel-metal hydride battery can be used as the battery 33. The battery 33 supplies driving power to the motor 31 via the inverter 32, and also receives and stores power generated by the motor 31 via the inverter 32.

[0032] The battery 33 is equipped with a battery sensor SN3 that detects the input / output current to the battery 33. The current value detected by this battery sensor SN3 is used to determine the battery SOC, that is, the ratio of the current charge amount to the charge amount when the battery 33 is fully charged. In other words, the battery sensor SN3 is a sensor for detecting the battery SOC.

[0033] The clutch 30 is a clutch that connects and disconnects the engine 1 and the motor 31. Specifically, the clutch 30 connects the output shaft of the engine 1 (crankshaft 7, described later) and the rotating shaft (rotor shaft) of the motor 31 in series, or disconnects the connection. When the clutch 30 is engaged and the engine 1 and the motor 31 are connected, the torque of both the engine 1 and the motor 31 is transmitted to the drive wheels 37 via the automatic transmission 35 or the like. On the other hand, when the clutch 30 is disengaged, the motor 31 and the engine 1 are disconnected, and only the torque of the motor 31 is transmitted to the drive wheels 37.

[0034] The automatic transmission 35 is a transmission that transmits rotation input from the engine 1 and the motor 31 to drive wheels 37 while changing the speed. The automatic transmission 35 includes an input shaft 41, a plurality of planetary gear sets 42, frictional engagement elements (not shown) including a plurality of clutches and brakes, and an output shaft 43 connected to the input shaft 41 via the planetary gear sets 42 and the frictional engagement elements. While the vehicle V is traveling, the appropriate clutches or brakes in the frictional engagement elements are selectively engaged or disengaged to switch the power transmission path through the planetary gear set 42, and the gear position is changed accordingly. The rotation of the input shaft 41 is transmitted to the output shaft 43 after being shifted at a predetermined gear ratio corresponding to the current gear position. The rotation of the output shaft 43 is transmitted to the left and right drive wheels 37 via the differential 36.

[0035] A vehicle speed sensor SN1 is attached to the automatic transmission 35. The vehicle speed sensor SN1 is a sensor that detects the rotational speed of the output shaft 43 of the automatic transmission 35 as a physical quantity that represents the traveling speed of the vehicle V. The traveling speed of the vehicle V, i.e., the vehicle speed, is determined from the rotational speed detected by the vehicle speed sensor SN1.

[0036] The vehicle V is provided with an accelerator pedal 39 that is depressed by the driver. An accelerator sensor SN2 is attached to the accelerator pedal 39 to detect the accelerator opening, which indicates the degree of depression of the accelerator pedal.

[0037] The PCM 50 is a control device whose main component is a microcomputer including a processor (CPU) that performs calculations, memories such as ROM and RAM, and various input / output buses. The PCM 50 comprehensively controls the engine 1, the motor 31, and the automatic transmission 35. Specifically, the PCM 50 controls the output of the engine 1, the output of the motor 31 via the inverter 32, and the gear position of the automatic transmission 35 so that an appropriate driving force according to the driving conditions of the vehicle V is transmitted to the drive wheels 37.

[0038] Furthermore, the PCM 50 appropriately switches the driving mode of the vehicle V depending on the driving conditions, etc. That is, the PCM 50 can switch the driving mode of the vehicle V between an engine driving mode in which the engine 1 provides at least a portion of the power required to drive the vehicle V, and a motor driving mode in which the motor 31 provides all of the power. In the motor driving mode, the PCM 50 drives the motor 31 and stops the engine 1, thereby causing the vehicle V to drive only with the driving force of the motor 31. On the other hand, in the engine driving mode, the PCM 50 drives at least the engine 1, thereby utilizing the driving force of the engine 1 to drive the vehicle V. At this time, the motor 31 is also driven as necessary. When the motor 31 is driven, the driving force required to drive the vehicle V is generated by the cooperation of the engine 1 and the motor 31.

[0039] [Engine structure] 2 is a schematic cross-sectional view showing the structure of the engine 1. In this embodiment, the engine 1 is a four-stroke gasoline engine, and includes an engine body 2, an intake passage 17, and an exhaust passage 19.

[0040] The engine body 2 is a multi-cylinder type having a plurality of cylinders 2a arranged in a direction perpendicular to the plane of the paper in Fig. 2. That is, the engine body 2 includes a cylinder block 3 and a cylinder head 4 that define the plurality of cylinders 2a therein, and a plurality of pistons 5 housed in each cylinder 2a so as to be capable of reciprocating.

[0041] A combustion chamber C is formed above the piston 5 of each cylinder 2a. Each combustion chamber C is a space defined by the lower surface of the cylinder head 4, the side circumferential surface (cylinder liner) of the cylinder 2a, and the upper surface (crown surface) of the piston 5. Fuel is injected into the combustion chamber C from an injector 8, which will be described later. The piston 5 receives expansion energy (combustion energy) due to the combustion of the fuel supplied to the combustion chamber C and reciprocates up and down.

[0042] A crankshaft 7 is disposed below the pistons 5. The crankshaft 7 is the output shaft of the engine 1 (or the engine body 2), and is rotatably supported at the bottom of the cylinder block 3. The crankshaft 7 is connected to the pistons 5 of each cylinder 2a via a crank mechanism including connecting rods 6, and rotates around its central axis in response to the reciprocating motion (up and down movement) of the pistons 5.

[0043] A crank angle sensor SN4 is attached to the cylinder block 3. The crank angle sensor SN4 is a sensor for detecting the crank angle, which is the rotation angle of the crankshaft 7, and the engine speed, which is the rotation speed of the crankshaft 7.

[0044] An injector 8 and a spark plug 9 are attached to the cylinder head 4. The injector 8 is an injection valve that injects fuel into the combustion chamber C of each cylinder 2a. The spark plug 9 is a plug that ignites the mixture of fuel and air injected from the injector 8 into the combustion chamber C. One injector 8 and one spark plug 9 are provided for each cylinder 2a.

[0045] The cylinder head 4 is formed with intake ports 11 and exhaust ports 12. The intake ports 11 are ports that communicate between the combustion chambers C of each cylinder 2a and an intake passage 17. The exhaust ports 12 are ports that communicate between the combustion chambers C of each cylinder 2a and an exhaust passage 19. An intake valve 13 is provided in the intake ports 11 of each cylinder 2a, and an exhaust valve 14 is provided in the exhaust ports 12 of each cylinder 2a.

[0046] The cylinder head 4 is equipped with an intake valve train 15 and an exhaust valve train 16. The intake valve train 15 includes an intake camshaft 15a located above the intake valves 13, and the exhaust valve train 16 includes an exhaust camshaft 16a located above the exhaust valves 14. The intake camshaft 15a, the exhaust camshaft 16a, and the crankshaft 7 are connected to each other via a power transmission mechanism such as a chain. That is, the intake valve train 15 and the exhaust valve train 16 press the intake valves 13 and the exhaust valves 14 of each cylinder 2a in conjunction with the rotation of the crankshaft 7. The intake valve 13 periodically opens and closes the opening of the intake port 11 on the combustion chamber C side in response to the drive of the intake valve train 15, and the exhaust valve 14 periodically opens and closes the opening of the exhaust port 12 on the combustion chamber C side in response to the drive of the exhaust valve train 16.

[0047] The exhaust valve train 16 is equipped with an exhaust SVT 20. The exhaust SVT 20 is a device that changes the phase (opening / closing timing) of the exhaust valve 14 by changing the rotational phase of the exhaust camshaft 16a relative to the rotational phase of the crankshaft 7. Specifically, the exhaust SVT 20 in this embodiment is a variable valve control device that changes the phase of the exhaust valve 14 while maintaining the lift amount and opening period of the exhaust valve 14 constant; in other words, it changes the opening timing and closing timing of the exhaust valve 14 by the same amount. Note that the exhaust camshaft 16a, whose phase is changed by the exhaust SVT 20, is a camshaft shared by all cylinders 2a. In other words, the exhaust SVT 20 changes the phase (opening / closing timing) of the exhaust valve 14 of each cylinder 2a collectively by changing the rotational phase of the exhaust camshaft 16a. The exhaust SVT 20 corresponds to the "phase variable device" in this invention.

[0048] A cam angle sensor SN5 for detecting the rotation angle of the exhaust camshaft 16a is attached to the cylinder head 4. Information output from the cam angle sensor SN5 is used in combination with information output from the crank angle sensor SN4 described above, for example, to check the operation of the phase change of the exhaust valve 14 by the exhaust SVT 20. The cam angle sensor SN5 corresponds to the "phase detection unit" in this invention.

[0049] The intake passage 17 is a tubular passage for introducing intake air into the combustion chamber C of each cylinder 2a. The intake passage 17 is connected to the engine body 2 so as to communicate with the combustion chamber C of each cylinder 2a via the intake port 11. A throttle valve 18 is provided in the intake passage 17 so as to be able to open and close, for adjusting the flow rate of intake air flowing through the intake passage 17.

[0050] The exhaust passage 19 is a tubular passage for discharging exhaust gas emitted from the combustion chamber C of each cylinder 2a to the outside. The exhaust passage 19 is connected to the engine body 2 so as to communicate with the combustion chamber C of each cylinder 2a via the exhaust port 12. Although details are omitted, the exhaust passage 19 is provided with a catalytic device or the like for purifying harmful components in the exhaust gas.

[0051] [Details of exhaust SVT] 3 is a cross-sectional view showing the structure of exhaust SVT 20. Exhaust SVT 20 is a hydraulic variable torque device that includes an annular housing 21, a sprocket 22 formed integrally with the outer periphery of housing 21, and a rotor 23 rotatably housed inside housing 21. A chain (not shown) that runs between crankshaft 7 and exhaust camshaft 16a is engaged with sprocket 22. Rotor 23 is fixed to one end of exhaust camshaft 16a by fixing means such as bolts.

[0052] The rotor 23 has a plurality of vanes 23a that protrude radially outward. The housing 21 has a plurality of protrusions 21a that protrude radially inward. An advance hydraulic chamber 24 and a retard hydraulic chamber 25 are formed in the gaps between the vanes 23a and the protrusions 21a. The advance hydraulic chamber 24 and the retard hydraulic chamber 25 are each connected to an oil passage leading to a hydraulic supply source. The hydraulic supply source is, for example, an oil pump driven by rotation of the crankshaft 7.

[0053] When hydraulic pressure is supplied to the advance hydraulic chamber 24, the rotor 23 rotates in the advance direction relative to the housing 21, and the rotational phase of the exhaust camshaft 16a changes accordingly to the advance side. On the other hand, when hydraulic pressure is supplied to the retard hydraulic chamber 25, the rotor 23 rotates in the retard direction relative to the housing 21, and the rotational phase of the exhaust camshaft 16a changes accordingly to the retard side. In this way, the exhaust SVT 20 can freely change the rotational phase of the exhaust camshaft 16a within a predetermined angle range by adjusting the hydraulic pressure supplied to the advance hydraulic chamber 24 and the retard hydraulic chamber 25. Adjustment of the phase (opening / closing timing) of the exhaust valve 14 is achieved by changing the rotational phase of the exhaust camshaft 16a in this way by the exhaust SVT 20.

[0054] FIG. 4 is a diagram showing the adjustment range of the phase of the exhaust valve 14 by the exhaust SVT 20 described above. In this diagram, lift curve EXa is the lift curve of the exhaust valve 14 that is realized when the rotor 23 rotates to the most advanced position, that is, the most advanced position within the permissible rotation range of the rotor 23. Also, lift curve EXr is the lift curve of the exhaust valve 14 that is realized when the rotor 23 rotates to the most retarded position, that is, the most retarded position within the permissible rotation range of the rotor 23. The phase of the exhaust valve 14 is variable over the range from lift curve EXa to EXr. Also shown in FIG. 4 is the lift curve IN of the intake valve 13. As can be seen from the relationship between these lift curves EXa, EXr, and IN, the valve overlap of the intake valve 13 and the exhaust valve 14, i.e., the period during which both the intake valve 13 and the exhaust valve 14 are open across exhaust top dead center (TDC), becomes smaller as the exhaust valve 14 is advanced, and is smallest at the phase corresponding to the most advanced position of the rotor 23 (the most advanced phase).

[0055] As shown in FIG. 3 , a lock pin 26 extending in a direction perpendicular to the plane of the drawing (axial direction) is attached to the rotor 23 of the exhaust SVT 20 so as to be movable forward and backward. The lock pin 26 is a pin for locking the rotor 23 at the most advanced position; in other words, a pin for fixing the phase of the exhaust valve 14 to a phase corresponding to the lift curve EXa indicated by the solid line in FIG. 4 . The lock pin 26 locks the rotor 23 by engaging with a cover member (not shown) that covers one end face of the housing 21. The lock pin 26 is constantly biased in the locking direction by a compression spring. When the rotor 23 rotates to the most advanced position, the lock pin 26, biased by the compression spring, moves forward and engages with an engagement groove formed in the cover member. This engagement of the lock pin 26 locks the rotor 23 and the exhaust camshaft 16a connected thereto at the most advanced position. In other words, the exhaust SVT 20 has a retention mechanism that maintains the rotational phase of the exhaust camshaft 16a, i.e., the phase of the exhaust valve 14, at the most advanced phase (see lift curve EXa in FIG. 4). A release hydraulic chamber for pressing the lock pin 26 in the counter-lock direction is formed between the housing 21 and the cover member. The lock by the lock pin 26 is released by supplying hydraulic pressure to this release hydraulic chamber.

[0056] [Control system] 5 is a functional block diagram showing the control system of vehicle V. As shown in this diagram, PCM 50 is electrically connected to the above-mentioned vehicle speed sensor SN1, accelerator sensor SN2, battery sensor SN3, crank angle sensor SN4, and cam angle sensor SN5. Information detected by each of these sensors, i.e., information corresponding to vehicle speed, accelerator pedal position, battery SOC, crank angle, engine speed, cam angle, etc., is sequentially input to PCM 50.

[0057] The PCM 50 controls the running of the vehicle V based on input information from the sensors SN1 to SN5. That is, the PCM 50 is electrically connected to the injector 8, spark plug 9, throttle valve 18, and exhaust SVT 20 of the engine 1 described above, as well as to the clutch 30, motor 31, and inverter 32 described above. The PCM 50 outputs control signals to these devices that are generated through calculations based on input information from the sensors SN1 to SN5. Note that with regard to the control of the exhaust SVT 20, the PCM 50 indirectly controls the exhaust SVT 20 by controlling a hydraulic circuit device (more specifically, a solenoid valve included in the device) that supplies hydraulic pressure to the exhaust SVT 20.

[0058] The PCM 50 calculates the required torque of the vehicle V, which is the torque to be transmitted to the drive wheels 37, each time based on, for example, the vehicle speed detected by the vehicle speed sensor SN1 and the accelerator opening detected by the accelerator sensor SN2, and controls the engine 1, clutch 30, and motor 31 (inverter 32) while determining the driving mode of the vehicle V based on the calculated required torque and the battery SOC detected by the battery sensor SN3.

[0059] For example, when the torque required by the vehicle V is relatively small and the battery SOC is relatively high, the motor driving mode is selected. In this case, the PCM 50 stops the engine 1 and disengages the clutch 30. The PCM 50 also causes the motor 31 to generate torque equivalent to the torque required by the vehicle V, thereby driving the vehicle V solely by the motor 31.

[0060] When the torque required by the vehicle V is relatively high or the battery SOC is relatively low, the engine driving mode is selected. In this case, the PCM 50 drives the engine 1 (causing combustion) and engages the clutch 30. Furthermore, for example, when the output torque of the engine 1 is insufficient for the torque required by the vehicle V, the PCM 50 drives the motor 31 and causes the motor 31 to generate an assist torque equivalent to the torque shortage. In this case, the PCM 50 controls the engine 1 and the motor 31 so that the total torque of the engine 1 and the motor 31 corresponds to the torque required by the vehicle V. On the other hand, when the motor 31 is not driven, the engine 1 generates a torque equivalent to the torque required by the vehicle V, thereby causing the vehicle V to travel using only the engine 1.

[0061] [Control action] Next, the control when switching from the engine driving mode to the motor driving mode described above, particularly the control for stopping the engine 1 in response to the switching, will be described in detail using the flowcharts of Figures 6 and 7. The control shown in these figures is executed while the vehicle V is traveling in the engine driving mode. In other words, the premise for executing this control is that the driving mode of the vehicle V is the engine driving mode.

[0062] 6 starts, the PCM 50 determines whether a request has been made to switch the driving mode of the vehicle V from the engine driving mode to the motor driving mode (step S1). That is, while the vehicle is driving in the engine driving mode, the PCM 50 checks the factor conditions (e.g., required torque and battery SOC) that determine the driving conditions of the vehicle V based on the detected values ​​of the vehicle speed sensor SN1, accelerator sensor SN2, and battery sensor SN3. Then, when the factor conditions change to conditions that are compatible with the motor driving mode, the PCM 50 determines that a request has been made to switch from the engine driving mode to the motor driving mode.

[0063] If the determination in step S1 is YES, confirming a request to switch to the motor-driven driving mode, the PCM 50 determines whether the engine speed is less than a predetermined first rotation speed N1 (step S2). That is, the PCM 50 determines the engine speed at the time when the request to switch to the motor-driven driving mode is made based on the detection value of the crank angle sensor SN4, and compares the determined engine speed with the first rotation speed N1 to determine whether the former is smaller than the latter. The first rotation speed N1 may be set to a relatively high speed, for example, around 3500 rpm.

[0064] If the determination in step S2 is YES and it is confirmed that the engine speed is less than the first speed N1, the PCM 50 releases the clutch 30 (step S3) and instructs the exhaust SVT 20 to change the phase of the exhaust valve 14 to the most advanced phase (step S4). The reason for advancing the phase of the exhaust valve 14 to the most advanced phase is to ensure the restartability of the engine 1 when the driving mode of the vehicle V is later switched to the engine driving mode.

[0065] Next, the PCM 50 determines whether or not the control for changing the phase of the exhaust valve 14 to the most advanced phase (hereinafter referred to as most advanced control) has been completed (step S5). That is, the PCM 50 checks the phase change of the exhaust valve 14 caused by the exhaust SVT 20 based on the detection value of the cam angle sensor SN5, and determines that the most advanced control has been completed when the phase has changed to a position corresponding to the lift curve EXa in FIG.

[0066] If the determination in step S5 is YES and the completion of the most advanced injection control is confirmed, the PCM 50 executes a fuel cut to stop the fuel supply (fuel injection) from the injector 8 to the combustion chamber C (step S6). Due to the cessation of combustion caused by this fuel cut, the engine 1 will soon come to a complete stop. In other words, the rotation speed of the engine 1 will drop to zero.

[0067] In parallel with the process of stopping the engine 1 as described above, the PCM 50 executes a process of switching to the motor driving mode (step S7). That is, after the clutch 30 is disengaged in step S3, the PCM 50 controls the inverter 32 so that a torque corresponding to the torque required by the vehicle V is output from the motor 31. This realizes the motor driving mode in which the vehicle V is driven only by the driving force of the motor 31.

[0068] Next, the control when the determination in step S2 is NO, that is, when the engine speed at the time when the switch to the motor driving mode is requested is equal to or higher than the first speed N1, will be described with reference to Fig. 7. In this case, the PCM 50 executes disengagement of the clutch 30 and fuel cut (steps S11 and S12).

[0069] Next, the PCM 50 determines whether the engine speed has decreased to less than the first speed N1 based on the detected value of the crank angle sensor SN4 (step S13).

[0070] If the determination in step S13 is YES and it is confirmed that the engine speed has decreased to less than the first speed N1, the PCM 50 instructs the exhaust SVT 20 to change the phase of the exhaust valve 14 to the most advanced phase (step S14).

[0071] 7, that is, when the engine speed at the time a request to switch to the motor driving mode is made is equal to or higher than the first speed N1, the order of fuel cut and maximum advance control is different from that when the engine speed is less than the first speed N1 (when the determination in S2 in FIG. 6 is YES). That is, when the engine speed at the time a request to switch is made is less than the first speed N1, fuel cut is made after maximum advance control, which changes the phase of the exhaust valve 14 to the maximum advance phase (see FIG. 6), whereas when the engine speed at the time a request to switch is made is less than the first speed N1 (FIG. 7), fuel cut is made before maximum advance control.

[0072] After issuing the command for the most advanced angle control in step S14, the PCM 50 determines whether the engine speed has decreased to less than a predetermined second speed N2 based on the detected value of the crank angle sensor SN4 (step S15). The second speed N2 is a speed lower than the first speed N1 (steps S2 and S13) and may be set to, for example, around 1500 rpm.

[0073] If the determination in step S15 is YES and it is confirmed that the engine speed has decreased to less than the second speed N2, the PCM 50 determines whether the retard amount of the exhaust valve 14 relative to the most advanced phase is less than a predetermined reference retard amount A1 based on the detection value of the cam angle sensor SN5 (step S16). This determination is made to predict whether the phase of the exhaust valve 14 can be changed to the most advanced phase (see the lift curve EXa in FIG. 4) before the engine 1 completely stops, i.e., before the engine speed drops to zero. That is, the greater the retard amount of the exhaust valve 14 at the time the engine speed falls below the second speed N2, the less likely it is that the most advanced control will be completed before the engine 1 completely stops. The smaller the retard amount, the more likely it is that the most advanced control will be completed before the engine 1 completely stops. The determination in step S16, in which the retard amount of the exhaust valve 14 is compared with the reference retard amount A1, utilizes this property and is a determination to predict whether the most advanced control will be completed before the engine 1 completely stops. The reference retard amount A1 can be set to, for example, about 10 degrees.

[0074] If the determination in step S16 is YES and it is confirmed that the retard amount of the exhaust valve 14 is less than the reference retard amount A1, that is, if it is predicted that the most advanced angle control will be completed before the engine 1 comes to a complete stop, the PCM 50 continues to release the clutch 30 and cut off the fuel (step S17). As a result, the engine 1 will soon come to a complete stop.

[0075] Thereafter, the PCM 50 causes the vehicle V to travel in the motor travel mode (step S18). That is, the PCM 50 controls the inverter 32 so that a torque corresponding to the torque required by the vehicle V is output from the motor 31, and causes the vehicle V to travel using only the driving force of the motor 31.

[0076] Next, we will explain the control when the determination in step S16 is NO, i.e., when it is predicted that the most advanced control will not be completed before the engine 1 completely stops because the retard amount of the exhaust valve 14 is equal to or greater than the reference retard amount A1. In this case, the PCM 50 engages the clutch 30 (step S20), resumes fuel supply, and causes the motor 31 to generate assist torque (step S21). That is, the PCM 50 resumes fuel injection from the injector 8, thereby returning the engine 1 to an operating state in which the air-fuel mixture is combusted in the combustion chamber C. The output torque of the engine 1 generated by this resumption of combustion is transmitted to the drive wheels 37 via the engaged clutch 30. However, this resumption of combustion is transient and does not satisfy the torque corresponding to the torque required by the vehicle V. Therefore, the PCM 50 drives the motor 31 to generate torque corresponding to the shortage of the required torque, i.e., the difference between the required torque and the output torque of the engine 1. As a result, a torque corresponding to the torque required by the vehicle V is generated by the engine 1 and the motor 31 working together.

[0077] The control of steps S20 and S21 has the effect of applying a temporary rotational force to the engine 1 that is about to be stopped, thereby postponing the timing of the complete stop of the engine 1. Therefore, hereinafter, the control of steps S20 and S21 is referred to as "temporary engine drive control."

[0078] After starting the engine temporary drive control, the PCM 50 determines, based on the detection value of the cam angle sensor SN5, whether the most advanced angle control by the exhaust SVT 20 has been completed, that is, whether the phase of the exhaust valve 14 has actually changed to the most advanced angle phase (step S22).

[0079] When it is determined as YES in the step S22 and it is confirmed that the advanced angle control is completed, the PCM 50 executes the disengagement of the clutch 30 and the fuel cut again (steps S23, S24). As a result, the engine 1 will soon come to a complete stop.

[0080] Thereafter, the PCM 50 drives the vehicle V in the motor driving mode (step S25). That is, the PCM 50 controls the inverter 32 so that the torque corresponding to the required torque of the vehicle V is output from the motor 31, and drives the vehicle V only by the driving force of the motor 31.

[0081] [Operation and Effect] As described above, in the present embodiment, when there is a request to switch from the engine driving mode to the motor driving mode while the engine speed is in a state of being equal to or higher than the first speed N1, the clutch 30 is disengaged and the fuel cut is executed (S11, S12), and the advanced angle control (S14) for changing the phase of the exhaust valve 14 to the advanced angle phase by the exhaust SVT 20 is started. Further, when the engine speed subsequently drops below the second speed N2 (<N1), the retard angle amount with respect to the advanced angle phase of the exhaust valve 14 is examined, and when the retard angle amount is equal to or more than the reference retard angle amount A1, the engine temporary drive control for applying a temporary rotational force to the engine 1 is executed (S20, S21). According to such a configuration, there is an advantage that the stopped engine 1 can be appropriately restarted when switching to the motor driving mode.

[0082] If the retard amount of the exhaust valve 14 is equal to or greater than the reference retard amount A1 when the engine speed drops below the second speed N2, it is likely that the period required to advance the phase of the exhaust valve 14 to the most advanced phase will be longer than the period required for the engine 1 to completely stop. Therefore, it can be determined that the most advanced control of the exhaust valve 14 is unlikely to be completed before the engine 1 completely stops. In such a case, in this embodiment, temporary engine drive control is executed to impart temporary rotational force to the engine 1, so that the timing of the complete stop of the engine 1 can be postponed until after the most advanced control is completed. Moreover, because the temporary engine drive control actually imparts rotational force to the engine 1, the rotation of the engine 1 can be appropriately continued until the most advanced control is completed by appropriately adjusting the duration of the rotational force imparted. This prevents the supply of hydraulic pressure from a hydraulic supply source, such as an oil pump, to the exhaust SVT 20 from being stopped before the most advanced control is completed, and the phase of the exhaust valve 14 can be changed to the most advanced phase with a high probability. If the phase of the exhaust valve 14 is shifted to the most advanced phase, the engine 1 can be subsequently restarted with a small valve overlap between the intake valve 13 and the exhaust valve 14. This reduces the amount of burned gas flowing back from the exhaust port 12 to the combustion chamber C, preventing the burned gas flowing back into the combustion chamber C from impeding the combustion of the air-fuel mixture and ensuring good restartability of the engine 1.

[0083] Furthermore, in this embodiment, the temporary engine drive control is a combination of control (S20) for engaging the clutch 30, control (S21) for restarting combustion in the engine 1 by returning fuel (S22), and control (S23) for driving the motor 31 to generate assist torque. Therefore, the rotational force transmitted from the motor 31 via the clutch 30 and the rotational force resulting from the combustion energy can be simultaneously applied to the engine 1, and the timing for completely stopping the engine 1 can be reliably postponed until after the most advanced control of the exhaust valve 14 is completed. Furthermore, during the temporary engine drive control, the engine 1 and the motor 31 can be controlled so that the total torque of the engine 1 and the motor 31 corresponds to the torque required by the vehicle V, just as in the normal engine driving mode. This means that the control logic applied in the normal engine driving mode can be used during the temporary engine drive control. This simplifies the control and reduces the load on the PCM 50.

[0084] Furthermore, in this embodiment, the lock pin 26 that maintains the phase of the exhaust valve 14 at the most advanced phase is applied to the exhaust SVT 20, so after the most advanced angle control of the exhaust valve 14 is completed, the phase of the exhaust valve 14 can be reliably maintained at the most advanced angle phase from when the engine 1 is completely stopped until the next restart. Therefore, the engine 1 can be reliably restarted with the phase of the exhaust valve 14 at the most advanced angle phase, and the restartability of the engine 1 can be improved.

[0085] In addition, in this embodiment, when a request is made to switch from the engine driving mode to the motor driving mode while the engine speed is equal to or greater than the first rotational speed N1, the clutch 30 is first disengaged and fuel is cut (S11, S12). Then, when the engine speed falls below the first rotational speed N1, the exhaust valve 14 is fully advanced (S14). This configuration prevents the phase of the exhaust valve 14 from significantly deviating from the phase appropriate for the engine speed during the engine 1 stop operation, thereby reducing noise during the engine 1 stop operation. Specifically, if the exhaust valve 14 fully advanced control were to be initiated immediately after the engine speed is equal to or greater than the first rotational speed N1, the phase of the exhaust valve 14 may be advanced to near the fully advanced phase while the engine speed is relatively high and the piston speed is fast. For example, this could result in a situation where only the intake valve 13 opens at the end of the exhaust stroke. This situation could result in increased intake and exhaust noise due to a large amount of burned gas being blown back into the intake port 11, potentially increasing noise during the engine 1 stop operation. In contrast, in this embodiment, the most advanced control of the exhaust valve 14 is not started until the engine speed becomes less than the first speed N1, so that the increase in noise as described above can be avoided and the quietness of the vehicle V can be improved.

[0086] FIG. 8 is a time chart showing an example of time-series changes in the state quantities of various components when a request to switch from the engine driving mode to the motor driving mode is made when the engine speed is higher than the first engine speed N1. In the example of FIG. 8, at time t1 immediately after the request to switch, a fuel cut (F / C) is performed and the clutch 30 is released. Before time t1, the retard amount of the exhaust valve 14 relative to the most advanced phase (retard amount = 0) is A0, which is significantly larger than the reference retard amount A1. From time t1 when the fuel cut is performed, the engine speed begins to decrease, and at time t2, which is later than time t1, it decreases to the first engine speed N1. Then, from time t2, the exhaust SVT 20 operates, and the phase of the exhaust valve 14 is advanced toward the most advanced phase. The engine speed further decreases to the second engine speed N2 at time t3, which is later than time t2. In the example of FIG. 8, the retard amount of the exhaust valve 14 at time t3 is larger than the reference retard amount A1. Therefore, at time t3, the clutch 30 is re-engaged, and combustion in the engine 1 is restarted as fuel is restored. This prevents a decrease in engine speed, and the engine 1 continues to rotate. Then, at time t4 while the engine 1 continues to rotate, the amount of retardation of the exhaust valve 14 becomes zero, and the phase of the exhaust valve 14 reaches the most advanced phase. Then, at this time t4, the clutch 30 is released, and fuel cut is executed again. As a result, the engine 1 soon comes to a complete stop. Furthermore, after time t4, the lock pin 26 locks the operation of the exhaust SVT 20, so that the phase of the exhaust valve 14 is maintained at the most advanced phase.

[0087] As described above, in this embodiment, even if the retard amount of the exhaust valve 14 when the engine speed drops to the second speed N2 (time t3) is equal to or greater than the reference retard amount A1, the engagement of the clutch 30 and the resumption of combustion impart a rotational force to the engine 1, thereby extending the rotation period of the engine 1 and shifting the timing of the complete stop of the engine 1 to later than the completion (time t4) of the most advanced angle control of the exhaust valve 14. This prevents the engine 1 from coming to a complete stop before the most advanced angle control is completed, and the engine 1 can be subsequently restarted with the phase of the exhaust valve 14 in the most advanced angle phase, ensuring good restartability of the engine 1.

[0088] As shown in FIG. 6 , in this embodiment, if the engine speed at the time of the request to switch to the motor driving mode is less than the first rotation speed N1, first, the clutch 30 is released and the most advanced control of the exhaust valve 14 is initiated (S3, S4). Then, when the most advanced control is completed, a fuel cut (S6) is executed. This configuration allows the engine 1 to continue rotating by combustion until the most advanced control is completed, thereby reliably preventing the engine 1 from completely stopping before the most advanced control is completed. Here, not cutting fuel until the most advanced control is completed means that the engine 1 is burning in a state where the phase of the exhaust valve 14 is advanced to or near the most advanced phase, in other words, with a significantly reduced valve overlap. This type of combustion occurs when the internal EGR amount is significantly reduced, which may lead to abnormal combustion. However, in this embodiment, the control that achieves both maximum advance angle control and combustion in engine 1 is performed only when the engine speed at the time of requesting switching to motor driving mode is less than the first speed N1, in other words, only under conditions where abnormal combustion is unlikely to occur even if the internal EGR amount is reduced, thereby preventing abnormal combustion from occurring during this control.

[0089] FIG. 9 is a time chart showing an example of time-series changes in the state quantities of various components when a request to switch from engine driving mode to motor driving mode is made when the engine speed is less than first rotation speed N1. In the example of FIG. 9, at time t11, immediately after the request to switch, the clutch 30 is released, and the exhaust SVT 20 starts full-advance control, advancing the phase of the exhaust valve 14 toward the full-advance phase. The amount of retardation of the exhaust valve 14 relative to the full-advance phase becomes zero at time t12, which is later than time t11, and the full-advance control is completed. Then, at time t12, a fuel cut is executed. As a result, the engine speed begins to decrease, and soon after, the engine 1 comes to a complete stop.

[0090] 9, when a request is made to switch from engine driving mode to motor driving mode while the engine speed is less than the first speed N1, the engine 1 continues to rotate by combustion until the most advanced control of the exhaust valve 14 is completed. This prevents abnormal combustion from occurring, reliably preventing the engine 1 from coming to a complete stop before the most advanced control is completed, and ensures good restartability of the engine 1.

[0091] [Variations] In the above embodiment, the temporary engine drive control for imparting temporary rotational force to the engine after a fuel cut is a combination of control for engaging the clutch 30 (S20), control for restarting combustion in the engine 1 by restoring fuel (S21), and control for driving the motor 31 to generate assist torque (S21). However, the temporary engine drive control may be any control that can impart rotational force to the engine 1, and may be modified as appropriate within that scope. For example, only a portion of the period during which the clutch 30 is engaged (the period from time t3 to time t4 in FIG. 8 ) may be set as the combustion restart period in the engine 1. Alternatively, the combustion restart in the engine 1 may be omitted altogether. In this case, the temporary engine drive control involves engaging the clutch 30 and driving the motor 31. As a result, the driving force of the motor 31 is transmitted to the engine 1 via the clutch 30, and rotational force derived solely from the motor 31 is imparted to the engine 1. Conversely, the engagement of the clutch 30 and the driving of the motor 31 may be omitted, and rotational force may be imparted to the engine 1 solely by restarting combustion.

[0092] In the above embodiment, when switching from engine driving mode to motor driving mode, the exhaust SVT 20 is used to perform most advanced angle control to change the phase of the exhaust valve 14 to the most advanced angle phase. However, the phase of the exhaust valve 14 that should be set before the engine 1 is completely stopped, i.e., the target phase, need not be the most advanced angle phase, as long as it is a phase that is suitable for restarting the engine 1.

[0093] In the above embodiment, the exhaust SVT 20, which is a phase variable device that changes the phase of the exhaust valve 14 while maintaining the lift amount and valve opening period constant, is used as the phase variable device that changes the phase of the exhaust valve 14. However, instead of this, a phase variable device that changes the lift amount or valve opening period along with the valve phase may be used.

[0094] In the above embodiment, the control for changing the valve phase to a target phase before the engine 1 comes to a complete stop is performed on the exhaust valve 14, but similar control may be performed on the intake valve 13. That is, in an engine in which a phase varying device capable of changing the phase of the intake valve is applied to the intake valve, the phase varying device may be controlled when switching to the motor driving mode so that the phase of the intake valve comes to a target phase suitable for restarting before the engine 1 comes to a complete stop.

[0095] In the above embodiment, a hybrid vehicle V is illustrated that uses both the engine 1, which is a four-stroke gasoline engine fueled by gasoline, and the electric motor 31, but the vehicles to which the present invention can be applied are not limited to this. For example, the present invention may be applied to a hybrid vehicle that uses both a four-stroke diesel engine fueled by light oil and a motor. [Explanation of symbols]

[0096] 1 engine 20 Exhaust SVT (variable phase device) 26 Lock pin (retention mechanism) 30 Clutch 31 Motor 50 PCM (controller) A1 Reference retard amount (threshold) C. Combustion chamber N1 First rotation speed N2 Second rotation speed SN5 Cam angle sensor (phase detection part)

Claims

1. an internal combustion engine including a hydraulic phase varying device capable of varying a valve phase, which is the phase of an intake valve or an exhaust valve; an electric motor coupled to the wheels; a clutch that detachably connects the engine and the motor; a phase detection unit that detects the valve phase; a control device capable of selectively executing an engine running mode in which the clutch is engaged and the engine is driven to use the engine as a power source for the vehicle, and a motor running mode in which the clutch is released and the engine is stopped to use the motor as a power source for the vehicle, The control device When switching from the engine driving mode to the motor driving mode, a fuel cut is performed to release the clutch and stop the supply of fuel to a combustion chamber of the engine, and the valve phase is changed by the phase varying device toward a target phase suitable for restarting the engine, a determination is made as to whether or not the valve phase can be changed to the target phase before the engine comes to a complete stop based on the valve phase detected by the phase detection unit after the fuel cut, and if it is determined that the valve phase cannot be changed to the target phase, a temporary engine drive control is executed to impart a temporary rotational force to the engine so that the timing of the engine coming to a complete stop is postponed until after the change to the target phase has been completed.

2. 2. The vehicle drive system according to claim 1, the engine temporary drive control includes control to engage the clutch, the control device engages the clutch upon determining that the valve phase cannot change to the target phase before the engine is completely stopped, and continues to engage the clutch until the valve phase has completely changed to the target phase.

3. 3. The vehicle drive system according to claim 2, The vehicle drive device, wherein the engine temporary drive control includes control for supplying fuel to the combustion chamber for a predetermined period included in an engagement period of the clutch.

4. The vehicle drive device according to any one of claims 1 to 3, the phase variable device changes the phase of the exhaust valve, the control device sets, when switching from the engine driving mode to the motor driving mode, a most advanced phase that is the most advanced phase within a phase adjustment range of the exhaust valve by the phase varying device as the target phase.

5. 5. The vehicle drive system according to claim 4, The vehicle drive system, wherein the phase varying device includes a holding mechanism that holds the phase of the exhaust valve at the most advanced phase.

6. The vehicle drive device according to any one of claims 1 to 3, when there is a request to switch from the engine driving mode to the motor driving mode while the engine speed is equal to or higher than a predetermined first speed, the control device executes the disengagement of the clutch and the fuel cut, and thereafter, when the engine speed falls below the first speed, starts control of the phase variable device to change the valve phase toward the target phase.

7. 7. The vehicle drive system according to claim 6, the control device determines whether the valve phase can be changed to the target phase before the engine is completely stopped by comparing the valve phase detected when the engine speed after the fuel cut becomes less than a second speed that is lower than the first speed with a predetermined threshold value.

8. 7. The vehicle drive system according to claim 6, when there is a request to switch from the engine driving mode to the motor driving mode when the engine rotation speed is less than the first rotation speed, the control device releases the clutch and starts control to change the valve phase toward the target phase using the phase varying device, and executes the fuel cut when the change to the target phase is completed.

Images