JP2011226396A - Device for control of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for control of a vehicle, the device capable of stably driving an engine in an HCCI (homogeneous charge compression ignition) combustion mode immediately after starting the engine.SOLUTION: A hybrid vehicle includes: an engine having a combustion mode that can be changed over between the HCCI combustion mode and an SI (spark ignition) combustion mode; a second injector directly injecting a fuel into the combustion chamber of the engine; and an exhaust side valve mechanism capable of changing valve timing and the valve lift amount of an exhaust valve of the engine. When the engine is to be started in the HCCI combustion mode, the control device of the hybrid vehicle performs control such that a fuel directly injected into the combustion chamber by the second injector during the compression process of the engine is ignited by an ignition plug upon starting the engine, and making the closing timing of the exhaust valve faster than the closing timing of the exhaust valve in the SI combustion mode so as to retain part of the exhaust gas in the cylinder of the engine.

Description

  The present invention relates to a control device for a vehicle provided with an internal combustion engine that switches a combustion mode between a premixed compression ignition combustion mode and a spark ignition combustion mode.

  There has been proposed an internal combustion engine capable of premixed compression ignition combustion in which fuel and air are mixed to produce a lean and uniform air-fuel mixture, and the air-fuel mixture is compressed and self-ignited. Premixed compression ignition combustion has attracted attention because it has a low emission amount of nitrogen oxides (NOx) and can be operated with high efficiency by increasing the compression ratio. However, in this premixed compression ignition combustion, for example, in a high load operation region or an extremely low load operation region such as idling, it is difficult to burn the mixture at an appropriate timing, and knocking or misfire occurs. Cheap. Therefore, in recent years, in order to compensate for the operation region in which premixed compression ignition combustion is difficult, the combustion mode is switched according to the operation region between the spark ignition combustion mode in which the air-fuel mixture is burned by the spark plug and the premixed compression ignition combustion mode. Internal combustion engines that can do this have been developed.

  As for a hybrid vehicle including an internal combustion engine capable of switching the operation mode between the spark ignition combustion mode and the premixed compression ignition combustion mode as described above, for example, Patent Document 1 discloses cooling water for an internal combustion engine when the internal combustion engine is started. When the temperature is higher than a predetermined temperature (a temperature that can be operated in the premixed compression ignition combustion mode), the internal combustion engine is increased in internal combustion engine speed in the premixed compression ignition combustion mode after increasing the rotational speed of the internal combustion engine to a predetermined rotational speed with a motor. Techniques for starting engine operation are shown.

JP 2004-52693 A

  According to the technique of Patent Document 1, when the internal combustion engine is started in the premixed compression ignition combustion mode, before the actual combustion, the rotational speed of the internal combustion engine is increased to a rotational speed that can be operated in the premixed compression ignition combustion mode. Therefore, as compared with the case where combustion is started without performing anything in advance, stable combustion can be performed immediately after starting. However, when combustion is started for the first time in the internal combustion engine, combustion is not performed during the previous cycle, so the temperature in the cylinder is low and the ignition timing is not stable, and in the worst case, there is a risk of misfire. For this reason, drivability and emission may be deteriorated.

  It is an object of the present invention to provide a vehicle control apparatus that can stably operate an internal combustion engine in a premixed compression ignition combustion mode immediately after the start of the internal combustion engine.

  In order to achieve the above object, the present invention provides a premixed compression ignition combustion mode in which an air-fuel mixture in a combustion chamber (for example, an after-mentioned combustion chamber 2a) of an internal combustion engine (for example, an after-mentioned engine 2) is subjected to compression ignition combustion, A vehicle control device that switches the operation of the internal combustion engine in accordance with a predetermined condition in a spark ignition combustion mode in which an air-fuel mixture in the combustion chamber is combusted by an ignition means (for example, an ignition plug 28 described later) provided in the combustion chamber. I will provide a. The vehicle control device includes a direct fuel injection device (for example, a second injector 27 described later) that directly injects fuel into the combustion chamber, and a valve timing of at least the exhaust valve of the exhaust valve and the intake valve of the internal combustion engine. When the variable valve mechanism that can be changed (for example, an intake side valve mechanism 29a and an exhaust side valve mechanism 29b described later) and the internal combustion engine are started in the premixed compression ignition combustion mode, From the start until a predetermined number M of combustion cycles elapses), the fuel injected by the direct fuel injection device during the compression process of the internal combustion engine is ignited by the ignition means, and the closing timing of the exhaust valve is set. Prior to the timing of closing the exhaust valve in the spark ignition combustion mode, a part of the exhaust is removed from the internal combustion engine. It includes an internal combustion engine control means for remaining in the cylinder (e.g., means according to the ECU 9, and executes the processing shown in FIGS. 13 and 14 described later), the.

  According to the present invention, when the internal combustion engine is started in the premixed compression ignition combustion mode, at the time of starting, it is directly injected into the combustion chamber during the compression process, and this is ignited by the ignition means, and the closing timing of the exhaust valve is set. Prior to the closing timing in the spark ignition combustion mode, a part of the exhaust due to the combustion is left in the cylinder. Thus, even when the internal combustion engine is started in the premixed compression ignition combustion mode, at the time of starting, it is not combusted in the previous cycle by burning under conditions different from the premixed compression ignition combustion mode. Even so, it can burn stably without misfiring. Furthermore, since the temperature in the cylinder can be raised by leaving a part of the exhaust gas from the combustion in the cylinder, for example, the internal combustion engine can be stably operated in the premixed compression ignition combustion mode after the next cycle. Can do.

  In this case, the control device for the vehicle generates a driving force that supplements the driving force of the internal combustion engine by the battery (for example, a high voltage battery 8 described later) and the electric power stored in the battery, or drives the internal combustion engine. A required value for a power plant torque generated in an electric motor (for example, a motor 5 described later) that regenerates a part of the force and charges the battery, and a power plant (for example, a power plant described later) including the internal combustion engine and the electric motor. Requested torque acquisition means for acquiring (for example, power plant required torque described later) and a required value for internal combustion engine torque (for example, engine torque described later) generated in the internal combustion engine based on a required value for the power plant torque (For example, engine required torque described later), and motor torque regenerated or generated by the motor ( For example, torque distribution means (for example, ECU 9 described later, and means for executing the processes of FIGS. 9 and 10) for setting a required value (for example, motor required torque described later) for a motor torque described later is provided. When the internal combustion engine is started in the premixed compression ignition combustion mode, the internal combustion engine at the start time (for example, from the start of the engine until a predetermined number N of combustion cycles elapses). The required value for torque is set to a predetermined median value in the premixed compression ignition combustion mode (for example, HCCI median torque described later), and depending on the excess or deficiency of the median value relative to the required value of the power plant torque, It is preferable to set a required value for the motor torque.

  According to the present invention, when the internal combustion engine is started in the premixed compression ignition combustion mode, the required value for the internal combustion engine torque is stabilized in the predetermined median value in the premixed compression ignition combustion mode, that is, the premixed compression ignition combustion mode. The internal combustion engine torque value generated when the internal combustion engine is operated is set. In addition, when the required value for the internal combustion engine torque set to the median value is excessive or insufficient with respect to the required value for the power plant torque, the required value for the generator torque that is regenerated or generated by the motor is set according to the excess or deficiency. To do. Thus, for example, when the required value for the internal combustion engine torque is larger than the required value for the power plant torque, the excess is regenerated by the electric motor to charge the battery, or the required value for the internal combustion engine torque is the required value for the power plant torque. If the value is smaller than this value, this shortage can be generated by the electric motor. As a result, the electric motor can be controlled with an appropriate distribution according to the required value for the power plant torque while the internal combustion engine is stably operated in the premixed compression ignition combustion mode immediately after starting.

  In this case, the internal combustion engine control means is configured such that the required value for the power plant torque is greater than the median value and the battery is in an overdischarged state, or the required value for the power plant torque is less than the median value and the When the battery is in an overcharged state, it is preferable to operate the internal combustion engine in the spark ignition combustion mode.

  When the power plant torque is larger than the above median value, it is preferable to generate the shortage with the electric motor while operating the internal combustion engine in the premixed compression ignition combustion mode. Therefore, it becomes difficult to generate the shortage. If the required value for the power plant torque is smaller than the above median value, it is preferable to regenerate the excess with an electric motor while operating the internal combustion engine in the premixed compression ignition combustion mode. If it exists, it will become difficult to regenerate the said excess with an electric motor. According to the present invention, when the above situation occurs in the battery, the internal combustion engine is operated in the spark ignition combustion mode, so that the torque corresponding to the required value for the power plant torque can be generated only by the internal combustion engine. . Therefore, it is possible to prevent the drivability from deteriorating without generating torque according to the required value for the power plant torque.

It is a mimetic diagram showing composition of a hybrid vehicle concerning one embodiment of the present invention. It is a schematic diagram which shows the structure of the engine concerning the said embodiment, its intake system, and an exhaust system. It is a figure which shows the operation example of the exhaust valve and intake valve in SI combustion mode. It is a figure which shows the operation example of an exhaust valve and an intake valve in HCCI combustion mode. It is a figure which shows the operation area | region which performs HCCI combustion, and the operation area which performs SI combustion in the engine concerning the said embodiment. It is a figure which shows the driving mode in the hybrid vehicle concerning the said embodiment, and its driving | operation area | region. It is a main flowchart of the process concerning the setting of the driving mode of the hybrid vehicle concerning the said embodiment, torque distribution, and the combustion mode of an engine. It is a flowchart which shows the procedure which sets the driving mode of the hybrid vehicle concerning the said embodiment. It is a flowchart which shows the procedure which sets the torque distribution of the engine and motor concerning the said embodiment. It is a flowchart which shows the procedure which sets the torque distribution of the engine and motor concerning the said embodiment. It is a figure which shows the area | region which operates an engine in HCCI combustion mode immediately after the engine start concerning the said embodiment. It is a flowchart which shows the procedure which sets the combustion mode of the engine concerning the said embodiment. It is a flowchart which shows the procedure of control of the intake and exhaust valve concerning the said embodiment. It is a flowchart which shows the procedure of control of the 1st, 2nd injector and spark plug concerning the said embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of a hybrid vehicle 1 according to the present embodiment.
The hybrid vehicle 1 is a vehicle provided with a power plant composed of two driving force generation sources of an engine 2 and a motor 5. The hybrid vehicle 1 has either or both of driving force generated by the engine 2 by burning fuel stored in the fuel tank 7 and driving force generated by the motor 5 by electric power stored in the high-voltage battery 8. Thus, the drive wheels 11 and 12 can be driven to travel.

  The crankshaft of the engine 2 is connected to the output shaft of the motor 5 via the clutch CL. Further, the output shaft of the motor 5 is connected to the drive wheels 11 and 12 via the transmission TM. Therefore, by connecting the clutch CL, the drive wheels 11 and 12 can be driven by only the torque generated by the engine 2 or by the torque generated by the engine 2 and the motor 5. Further, by disengaging the clutch CL, it becomes possible to drive the drive wheels 11 and 12 with only the torque generated by the motor 5 and to travel. The clutch CL operates based on a control signal from an electronic control unit (hereinafter referred to as “ECU”) 9, and connects and disconnects the crankshaft of the engine 2 and the output shaft of the motor 5. The detailed configuration of the engine 2 will be described later with reference to FIG.

  For example, a three-phase DC brushless motor is used as the motor 5 and is connected to a high voltage battery 8 via a power drive unit (hereinafter referred to as “PDU”) 6 including an inverter. The high voltage battery 8 is composed of, for example, a plurality of lithium ion batteries. Further, a charger 81 is connected to the high voltage battery 8, and the plug 82 of the charger 81 can be inserted into a household outlet (not shown) to charge the high voltage battery 8.

The PDU 6 operates based on a torque command signal input from the ECU 9 and generates torque with the motor 5 by the electric power of the high-voltage battery 8, or a part of the torque generated by the engine 2 or driving wheels when the vehicle 1 is decelerated. The high voltage battery 8 is caused to regenerate torque transmitted from the output shafts 11 and 12 to the output shaft. More specifically, when driving the motor 5, the PDU 6 converts the power stored in the high voltage battery 8 into three-phase AC power and supplies it to the motor 5. When the motor 5 is regeneratively operated, the three-phase AC power output from the motor 5 is converted to DC power, and the high voltage battery 8 is charged.
The ECU 9 sets a required value (hereinafter referred to as “motor required torque”) for torque generated by the motor (hereinafter referred to as “motor torque”) according to the procedure described later with reference to FIG. 9 and FIG. A torque command signal corresponding to the required torque is input to the PDU 6.

FIG. 2 is a schematic diagram showing the configuration of the engine 2 and its intake system and exhaust system.
The engine 2 is a four-cylinder engine including a plurality of, for example, four cylinders 21a, and one of these is representatively shown in FIG. The engine 2 is configured by combining a cylinder block 21 in which a cylinder 21 a is formed and a cylinder head 22. The engine 2 is provided with an intake pipe 31 through which intake air circulates, an exhaust pipe 32 through which exhaust circulates, and an exhaust gas recirculation passage 33 that recirculates part of the exhaust gas in the exhaust pipe 32 to the intake pipe 31. .

  A piston 23 is slidably provided in the cylinder 21a, and a combustion chamber 2a of the engine 2 is formed by the top surface of the piston 23 and the surface of the cylinder head 22 on the cylinder 21a side. The piston 23 is connected to the crankshaft 25 via a connecting rod 24. That is, the crankshaft 25 rotates according to the reciprocating motion of the piston 23 in the cylinder 21a.

  The cylinder head 22 is formed with an intake port 22a that connects the combustion chamber 2a and the intake pipe 31, and an exhaust port 22b that connects the combustion chamber 2a and the exhaust pipe 32. An intake opening facing the combustion chamber 2a in the intake port 22a is opened and closed by an intake valve 22c, and an exhaust opening facing the combustion chamber 2a in the exhaust port 22b is opened and closed by an exhaust valve 22d. The intake valve 22c is driven by the intake side valve mechanism 29a, and the exhaust valve 22d is driven by the exhaust side valve mechanism 29b.

  The intake side valve mechanism 29a includes an intake cam phase variable mechanism (not shown) that changes the phase of the cam shaft of the intake valve 22c with respect to the crankshaft 25, and an intake lift variable mechanism (not shown) that changes the lift amount of the intake valve 22c. And the valve lift amount and valve timing of the intake valve 22c can be changed. Similarly, the exhaust valve mechanism 29b also has an exhaust cam phase variable mechanism (not shown) that changes the phase of the cam shaft of the exhaust valve 22d relative to the crankshaft 25, and an exhaust lift variable that changes the lift amount of the exhaust valve 22d. A mechanism (not shown), and the valve lift amount and valve timing of the exhaust valve 22d can be changed. Various actuators of the valve mechanisms 29a and 29b for changing the valve lift amount and valve timing of the valves 22c and 22d are connected to the ECU 9, and operate based on control signals from the ECU 9. In addition, a known thing is used for the variable lift mechanism and the variable cam phase mechanism of these valve mechanisms 29a and 29b. More specifically, for example, the variable lift mechanism described in detail in Japanese Patent Application Laid-Open No. 2008-75614 by the applicant of the present application is used, and the variable cam phase mechanism is disclosed in Japanese Patent Application Laid-Open No. 2009 by the present applicant. -2222021 publication is used.

  A first injector 26 for injecting fuel toward the combustion chamber 2a is provided on the intake pipe 31 side of the intake port 22a from the intake opening, and the cylinder head 22 faces the combustion chamber 2a. A second injector 27 that directly injects fuel into the combustion chamber 2a is provided. The ECU 9 controls the amount of fuel injected from the first injector 26 and its fuel injection timing and the amount of fuel injected from the second injector 27 and its fuel injection timing.

  The cylinder head 22 is provided with an ignition plug 28 that faces the exhaust valve 22d side of the second injector 27 in the combustion chamber 2a. The ignition timing of the air-fuel mixture by the spark plug 28 is controlled by the ECU 9.

  The intake pipe 31 is provided with a throttle valve 34 that controls the intake amount of air that flows through the intake pipe 31 and is supplied to the combustion chamber 2 a of the engine 2. The throttle valve 34 is connected to the ECU 9 via an actuator (not shown), and the opening degree is controlled by the ECU 9.

  The exhaust pipe 32 is provided with a catalytic converter 35 that carries a three-way catalyst that purifies the exhaust of the engine 2. This three-way catalyst contains, for example, an OSC material having an oxygen storage capacity for adsorbing and storing oxygen in exhaust gas in addition to a catalyst noble metal having exhaust purification capacity, and oxidizes HC and CO in exhaust gas NOx in the exhaust is reduced.

  The exhaust gas recirculation passage 33 connects the downstream side of the catalytic converter 35 in the exhaust pipe 32 and the downstream side of the throttle valve 34 in the intake pipe 31 to recirculate a part of the exhaust discharged from the engine 2. The exhaust gas recirculation passage 33 is provided with an EGR cooler 36 that cools the exhaust gas that is recirculated and an EGR valve 37 that controls the flow rate of the exhaust gas that is recirculated. The EGR valve 37 is connected to the ECU 9 via an actuator (not shown), and the opening degree thereof is electromagnetically controlled by the ECU 9.

  The ECU 9 is connected with an air flow sensor 41, an intake air temperature sensor 46, an exhaust gas temperature sensor 43, a crank angle position sensor 44, an accelerator opening sensor 45, a coolant temperature sensor 47, and the like. The air flow sensor 41 detects the amount of air taken into the engine 2 and transmits a signal substantially proportional to the detected value to the ECU 9. The intake air temperature sensor 46 detects the temperature of air taken into the engine 2 and transmits a signal substantially proportional to the detected value to the ECU 9. The exhaust temperature sensor 43 detects the temperature of the exhaust gas flowing out from the catalytic converter 35 in the exhaust pipe 32 and transmits a signal substantially proportional to the detected value to the ECU 9.

  The crank angle position sensor 44 transmits a pulse signal indicating the rotation angle of the crankshaft 25 to the ECU 9. The rotational speed of the engine 2 is calculated by the ECU 9 based on the crank angle signal transmitted from the crank angle position sensor 44. The accelerator opening sensor 45 detects the opening of the accelerator pedal of the vehicle and transmits a signal substantially proportional to the detected value to the ECU 9. The cooling water temperature sensor 47 detects the temperature of the cooling water of the engine 2 and transmits a signal substantially proportional to the detected value to the ECU 9.

  In the engine 2 configured as described above, the combustion mode according to the operation region is divided into a premixed compression ignition combustion mode (hereinafter referred to as “HCCI (Homogeneous Charge Compression Ignition) combustion mode”) and a spark ignition combustion mode (hereinafter referred to as “HCI”). , “SI (Spark Ignition) combustion mode”).

  In the SI combustion mode, a predetermined amount of fuel is injected into the intake pipe 31 by the first injector 26 during the intake stroke, and the vicinity of the spark plug 28 is richer than the stoichiometric air-fuel ratio by the second injector 27 during the compression stroke. A predetermined amount of fuel is injected so that Then, the air-fuel mixture supplied as described above is ignited and burned with a spark emitted from the spark plug 28 at a predetermined timing. Here, in the SI combustion mode, the amount of fuel injected from the two injectors 26 and 27 is adjusted so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 2a, that is, the combustion air-fuel ratio is close to the stoichiometric air-fuel ratio.

FIG. 3 is a diagram illustrating an operation example of the exhaust valve and the intake valve in the SI combustion mode.
In the SI combustion mode, the exhaust valve is opened over the exhaust process where the top surface of the piston is directed from the bottom dead center to the top dead center, and the intake valve is opened over the intake process where the top surface of the piston is directed from the top dead center to the bottom dead center. .

  In the HCCI combustion mode, a predetermined amount of fuel is injected into the intake pipe by the first injector during the intake process, and the air-fuel mixture with the air supplied to the combustion chamber is compressed by this injection and self-ignited. Here, in the HCCI combustion mode, the amount of fuel injected from the first injector is adjusted so that the combustion air-fuel ratio is leaner than the stoichiometric air-fuel ratio.

FIG. 4 is a diagram illustrating an operation example of the exhaust valve and the intake valve in the HCCI combustion mode. In FIG. 4, for comparison, an operation example of these valves in the SI combustion mode is shown by a broken line.
In the HCCI combustion mode, the air-fuel mixture is compressed and ignited, so that the temperature in the cylinder needs to be higher than the temperature in the SI combustion mode. Therefore, in the HCCI combustion mode, during the combustion cycle, a negative overlap (NOL (Negative OverLap)) occurs between the valve opening timing of the exhaust valve and the valve opening timing of the intake valve, that is, a period in which these valves are closed together. The exhaust valve and the intake valve are driven so that the above occurs. More specifically, in the HCCI combustion mode, the valve lift amount of the exhaust valve is changed to be lower than that in the SI combustion mode, and the valve timing is further changed to the advance side so that the closing timing of the exhaust valve is changed to the SI combustion mode. Faster than. Further, by changing the valve lift amount of the intake valve to be lower than that in the SI combustion mode and further changing the valve timing to the retard side, the opening timing of the intake valve is delayed from that in the SI combustion mode. In the HCCI combustion mode, by providing the negative overlap as described above for the opening timing of the exhaust valve and the opening timing of the intake valve, a part of the exhaust remains in the cylinder, and the temperature in the cylinder is changed to the SI combustion mode. Make it higher than time.

FIG. 5 is a diagram illustrating an operation region in which HCCI combustion can be performed.
As shown in FIG. 5, HCCI combustion is performed for two parameters, a required value (hereinafter referred to as “engine required torque”) for a torque generated by the engine (hereinafter referred to as “engine torque”) and an engine speed. The operation region that can be stably performed is limited to a region with a low load and a low rotational speed. Further, HCCI combustion enables particularly stable combustion within a specific operation region (region schematically shown by hatching in FIG. 5). Hereinafter, the median value of the engine torque generated when the engine is operated in the HCCI combustion mode in such an operation region where stable combustion is possible is referred to as HCCI central torque. On the other hand, SI combustion includes the above-described operation region where HCCI combustion is possible, and basically can be performed stably over the entire operation region including the region where HCCI fuel is possible.

FIG. 6 is a diagram showing a driving mode and a driving region in the hybrid vehicle.
The traveling mode in the hybrid vehicle including the power plant composed of the two driving force generation sources of the engine and the motor as described above includes a motor traveling mode and a motor assist mode according to the control mode of the engine, the motor, and the clutch. The motor regeneration mode is roughly divided into three types of travel modes.

In the motor travel mode, the clutch is disconnected, the engine is rested, and the vehicle travels only with the torque generated by the motor.
In the motor assist mode, the vehicle is driven by the clutch and the torque generated by the engine and the torque generated by the motor to supplement the engine torque.
In the motor regeneration mode, the clutch is connected and the vehicle is driven by the torque generated by the engine, and part of the torque generated by the engine or the torque transmitted from the drive wheels is regenerated by the motor to charge the high voltage battery.

  As shown in FIG. 6, since the engine is idled in the motor travel mode, the operation range in which the vehicle travel mode can be changed to the motor travel mode is the torque generated by the power plant including the engine and the motor (hereinafter referred to as “power”). The required value (hereinafter referred to as “power plant required torque”) is small and is limited to a medium / low speed operation region. Hereinafter, the motor assist mode and the motor regeneration mode are collectively referred to as assist / regeneration mode.

FIG. 7 is a main flowchart of processing relating to setting of the travel mode of the hybrid vehicle, the torque distribution, and the combustion mode of the engine. This process is repeatedly executed by the ECU at a predetermined cycle.
First, in S1, processing for setting the traveling mode of the vehicle to one of the above-described motor traveling mode and assist / regenerative mode is performed, and the process proceeds to S2. A detailed procedure for setting the travel mode will be described later in detail with reference to FIG.
In S2, processing for setting torque distribution, that is, engine request torque and motor request torque corresponding to the power plant request torque is performed, and the process proceeds to S3. A detailed procedure for setting the torque distribution will be described in detail later with reference to FIGS.
In S3, a process for setting the combustion mode of the engine to any one of the above-described HCCI combustion mode and SI combustion mode is performed, and this process is terminated. A detailed procedure for setting the combustion mode will be described later with reference to FIG.

FIG. 8 is a flowchart showing a procedure for setting the travel mode of the hybrid vehicle.
In S11, a power plant required torque is acquired and it moves to S12. This power plant required torque is a value corresponding to the torque required for the power plant according to the operation of the vehicle by the driver and the state of the vehicle, such as the detected value of the accelerator opening sensor, the engine speed, the vehicle speed, etc. It is calculated based on the parameters.

  In S12, it is determined whether or not the driving region of the vehicle is within a motor traveling region suitable for motor traveling. This determination is made, for example, by searching a map as shown in FIG. 6 described above based on the power plant required torque and vehicle speed acquired in S11. If the determination in S12 is YES, the process proceeds to S13, where the remaining capacity of the battery (hereinafter referred to as “SOC (State Of Charge)”) is acquired, and whether or not this SOC is sufficient for running the motor. Is determined.

When the determination in S13 is YES, and it is determined that the vehicle driving range is included in the motor driving range and the SOC of the battery is sufficient, the process proceeds to S14, where the vehicle driving mode is set to the motor driving mode. The process ends.
If the determination in S12 is NO and the vehicle operating area is not included in the motor travel area, or if the determination in S13 is YES and the battery SOC is not sufficient, the process proceeds to S15 to assist / regenerate the vehicle travel mode. The mode is set and the process is terminated. In this process, in response to the vehicle travel mode being changed from the assist / regeneration mode to the motor travel mode, the engine is idled, and the vehicle travel mode is changed from the motor travel mode to the assist / regeneration mode. In response, the engine is started.

FIG. 9 and FIG. 10 are flowcharts showing the procedure for setting the torque distribution between the engine and the motor, that is, the engine request torque value and the motor request torque value.
In S21, it is determined whether or not the vehicle travel mode is a motor travel mode. If the determination in S21 is YES, in order to cover all the power plant required torque acquired in S11 described above with the motor, the process proceeds to S22, the engine required torque is set to zero, and the motor required torque is set to the power plant required torque. Set to the same value as, and this process ends.

  On the other hand, if the determination in S21 is NO and the traveling mode is the assist / regenerative mode, the process proceeds to S23, and a predetermined number N combustion cycles (the predetermined number N is set to a value of 1 or more) from the start of engine start. It is determined whether or not the above N combustion cycles have elapsed since the travel mode was changed from the motor travel mode to the assist / regenerative mode.

  If the determination in S23 is YES and N combustion cycles have already elapsed since the start of the engine, it is determined that the engine can be stably operated in both the HCCI combustion mode and the SI combustion mode, and the process proceeds to S24. Move. In S24, the engine request torque and the motor request torque are set based on a predetermined normal control algorithm so that the sum of the engine request torque and the motor request torque matches the power plant request torque, and this process is terminated.

  On the other hand, if the determination in S23 is NO and the N combustion cycle has not yet elapsed since the start of the engine, that is, immediately after the start of the engine, an algorithm different from the normal control algorithm in S24 The process proceeds to S25 in order to set the engine required torque and the motor required torque based on the above.

An outline of the processing after S25 will be described with reference to FIG. 11 before a specific procedure is described.
As will be described in detail later, in this embodiment, the engine can be stably operated in the HCCI combustion mode immediately after the start of the engine. Therefore, when the engine is just started, the engine combustion mode is preferentially set to the HCCI combustion mode, and the engine required torque is set to the above-described HCCI central torque capable of stably performing the HCCI combustion. To do. When the HCCI central torque is excessive or insufficient with respect to the power plant required torque, the motor required torque is set so that the excess and deficiency is compensated by the motor.

For example, when the power plant required torque is significantly lower than the HCCI central torque, more specifically, when the power plant required torque is smaller than the HCCI central torque width lower limit set to a value slightly smaller than the HCCI central torque, this engine torque The excess is regenerated by the motor to charge the battery.
Further, for example, when the power plant required torque greatly exceeds the HCCI central torque, more specifically, when the power plant required torque is not less than the HCCI central torque width upper limit set to a value slightly larger than the HCCI central torque, This shortage of engine torque is generated by the motor by the battery power.

  As described above, the engine can be operated in the HCCI combustion mode without greatly changing the power plant torque immediately after starting the engine, but the SOC is small and the battery is overdischarged, or the SOC is large and the battery is overcharged. In such a case, it is not preferable to use the motor as an auxiliary. Therefore, in such a case, that is, in the area indicated by hatching in FIG. 11, the engine combustion mode stably generates the engine torque according to the power plant required torque without using the motor in an auxiliary manner. Require SI combustion mode that can.

Returning to FIG. 9 and FIG. 10, a specific procedure of the processing after S25 will be described.
In S25, it is determined whether or not the power plant required torque is smaller than the above-described HCCI central torque width upper limit. If YES in S25, the process moves to S26, and it is determined whether or not the SOC of the battery is in an overcharged state.
If the determination in S25 is NO, the process moves to S27, and it is determined whether or not the power plant required torque is equal to or greater than the above-described HCCI central torque width lower limit. If the determination in S27 is YES, the process moves to S28, where it is determined whether or not the SOC of the battery is in an overdischarged state.
If the determination in S27 is NO, the process moves to S29, and it is determined whether or not the SOC of the battery is in an overcharge state or an overdischarge state.

  If the determination in S26, S28, and S29 is YES, that is, if the power plant required torque is smaller than the HCCI central torque width lower limit and the battery is in an overcharged state, the power plant required torque is greater than the HCCI central torque width upper limit and the battery is If the engine is in an overdischarged state and the power plant required torque is within the HCCI central torque range and the battery is in an overcharged or overdischarged state, the process proceeds to S30, and the SI combustion mode is requested as the engine combustion mode. Thereafter, the process proceeds to S24 described above.

  On the other hand, when the determination in S26, S28, and S29 is NO, that is, when the power plant required torque is smaller than the HCCI central torque width lower limit and the battery is not overcharged, the power plant required torque is equal to or higher than the HCCI central torque width upper limit and the battery. When the power plant is not in the overdischarged state and the power plant required torque is within the HCCI central torque range and the battery is not in the overcharged state or the overdischarged state, the process proceeds to S31.

  In S31, the engine request torque is set to the HCCI central torque, and the motor request torque is set to a value obtained by subtracting the engine request torque from the power plant request torque. If the engine required torque is larger than the power plant required torque, this means that engine torque exceeding the power plant required torque is generated. Therefore, when the motor required torque becomes negative in S31, the motor is regeneratively operated so that the excess of the engine required torque with respect to the power plant required torque is regenerated by the motor and the battery is charged.

FIG. 12 is a flowchart showing a procedure for setting the combustion mode of the engine.
First, in S41, it is determined whether or not the N combustion cycle has elapsed since the start of the engine.
When the determination in S41 is YES, the process proceeds to S42, and it is determined whether or not the engine coolant temperature is higher than the temperature TWHCCI at which HCCI combustion is possible. If the determination in S42 is YES, the process proceeds to S43, and it is determined whether or not the intake air temperature is higher than the temperature TAHCCI at which HCCI combustion is possible. When the determination in S43 is YES, the process proceeds to S44, and it is determined whether or not the exhaust gas temperature is higher than the temperature TEXHCCI at which HCCI combustion is possible. When the determination in S44 is YES, the process proceeds to S45, and it is determined whether or not it is an operation region where HCCI combustion is possible. More specifically, for example, the determination is made by searching the map shown in FIG. 5 described above based on the engine required torque and the engine speed set in S2.

If any of the determinations in S42, S43, S44, and S45 is NO, the process proceeds to S46, the engine combustion mode is set to the SI combustion mode, and this process is terminated.
When the determination in S45 is YES, the process proceeds to S47, the engine combustion mode is set to the HCCI combustion mode, and this process ends.

  On the other hand, if the determination in S41 is NO and the N combustion cycle has not yet elapsed since the start of the engine, that is, immediately after the start of the engine, the routine proceeds to S48, where the SI combustion mode is set as the engine combustion mode. Is determined to be in the requested state. If the determination in S48 is YES, the process proceeds to S46, and the engine combustion mode is set to the SI combustion mode. If the determination in S48 is NO, the process proceeds to S47, and the engine combustion mode is set to the HCCI combustion mode. The process ends.

The engine control procedure will be described below with reference to FIGS. 13 and 14.
FIG. 13 is a flowchart showing a procedure for controlling the intake and exhaust valves, and is executed by the ECU for each combustion cycle of the engine.
In S51, it is determined whether or not the vehicle travel mode is a motor travel mode. If the determination in S51 is YES and the vehicle travel mode is the motor travel mode, the process proceeds to S52, and the settings of the intake and exhaust valve timing and valve lift amount are set for a predetermined cylinder-restored operation, and the settings are made. Under control the intake and exhaust valves.

If the determination in S51 is NO and the vehicle traveling mode is not the motor traveling mode, the process proceeds to S53, and it is determined whether or not the combustion mode of the engine is the HCCI combustion mode. If the determination in S53 is NO and the combustion mode of the engine is not the HCCI combustion mode, the process proceeds to S55, and the settings of the intake valve and exhaust valve timings and valve lift amounts are for SI operation (see FIG. 3 above). The intake and exhaust valves are controlled under the setting for SI combustion.
On the other hand, if the determination in S53 is YES, the process proceeds to S54, and the settings of the valve timing and valve lift amount of the intake valve and the exhaust valve are set for HCCI combustion (see FIG. 4 above), and for the HCCI combustion. The intake and exhaust valves are controlled under the setting.

FIG. 14 is a flowchart showing a procedure for controlling the first and second injectors and the spark plug, and is executed by the ECU for each combustion cycle of the engine.
In S61, it is determined whether or not the vehicle travel mode is the motor travel mode. When the determination in S61 is YES and the travel mode is the motor travel mode, the process proceeds to S62 and the cylinder resting control, that is, the amount of injected fuel is made zero.

  If the determination in S61 is NO and not the motor travel mode, the process proceeds to S63, and it is determined whether or not the combustion mode of the engine is the HCCI combustion mode. If the determination in S63 is NO, the process moves to S66, and the injected fuel amount and the injection timing are set under the conditions for SI combustion based on a plurality of parameters such as the engine required torque and the vehicle speed. Fuel is injected and ignited and burned with a spark plug. That is, in this case, as described above, fuel is injected from the first injector during the intake process, fuel is injected from the second injector during the compression process, and this is ignited by the addition plug. Further, the amount of fuel injected by the first and second injectors at this time is adjusted so that the combustion air-fuel ratio is close to the stoichiometric air-fuel ratio.

  If the determination in S63 is YES and the combustion mode is the HCCI combustion mode, the process proceeds to S64, and the predetermined number M combustion cycles (the predetermined number M is set to a value equal to or less than the predetermined number N described above, for example, 1 from the start of engine start. It is determined whether or not it has elapsed. If the determination in S64 is YES, the process moves to S65, and the injected fuel amount and the injection timing are set under the conditions for HCCI combustion based on a plurality of parameters such as the engine required torque and the vehicle speed. Fuel is injected and compression ignition combustion is performed. That is, in this case, as described above, fuel is injected from the first injector during the intake process, and this is compressed and ignited. Further, the amount of fuel injected by the first injector at this time is adjusted so that the combustion air-fuel ratio is leaner than the stoichiometric air-fuel ratio.

  On the other hand, if the determination in S64 is NO, that is, if the engine is started in the HCCI combustion mode, the process proceeds to S67, and the amount of injected fuel and the injection timing are for stratified combustion different from the conditions for HCCI combustion in S65. Set under conditions, inject fuel under the setting, and ignite and burn with spark plug. More specifically, fuel is injected from the second injector during the compression process so that the air-fuel ratio in the vicinity of the spark plug becomes rich, and this is ignited by the spark plug. Further, the amount of fuel injected by the second injector at this time is adjusted, for example, so that the combustion air-fuel ratio is leaner than the combustion air-fuel ratio at the time of HCCI combustion.

According to this embodiment, the following effects can be obtained.
(1) When the engine is started in the HCCI combustion mode, during the compression process until the M combustion cycle elapses, it is directly injected into the combustion chamber by the second injector during the compression process, and this is ignited by the spark plug. At the same time, the exhaust valve is controlled under the setting for HCCI combustion. That is, the exhaust valve closing timing is made earlier than the closing timing in the SI combustion mode, and a part of the exhaust gas caused by the combustion is left in the cylinder. As described above, even when the engine is started in the HCCI combustion mode, the engine is misfired even when the engine is not combusted during the previous cycle by burning under a condition different from that of the HCCI combustion mode. It can be burned stably. Furthermore, by leaving a part of the exhaust gas from the combustion in the cylinder, the temperature in the cylinder can be raised, so that the engine can be stably operated in the HCCI combustion mode from the next cycle.

  (2) When the engine is started in the HCCI combustion mode, the engine required torque is set to the HCCI central torque. Further, when the engine required torque set as the HCCI central torque is excessive or insufficient with respect to the power plant required torque, the motor required torque is set according to the excess / deficiency. Thereby, for example, when the set engine required torque is larger than the power plant required torque, the excess is regenerated by the motor to charge the high voltage battery, or the set engine required torque is smaller than the power plant required torque. In some cases, this shortage can be generated by a motor. Thereby, the motor can be controlled with an appropriate distribution according to the power plant required torque while the engine is stably operated in the HCCI combustion mode immediately after the engine is started.

  (3) When the power plant required torque is larger than the HCCI central torque width upper limit and the battery is in an overdischarged state, or when the powerplant required torque is less than or equal to the HCCI central torque width lower limit and the battery is in an overcharged state, SI Since the engine is operated in the combustion mode, torque corresponding to the power plant required torque can be generated only by the engine. Therefore, it is possible to prevent the drivability from deteriorating.

DESCRIPTION OF SYMBOLS 1 ... Hybrid vehicle 2 ... Engine (internal combustion engine)
27. Second injector (direct fuel injection device)
28 ... Spark plug (ignition means)
29b ... Exhaust valve mechanism (variable valve mechanism)
45. Accelerator opening sensor (required torque acquisition means)
5. Motor (electric motor)
9. ECU (internal combustion engine control means, torque distribution means, required torque acquisition means)

Claims (3)

The premixed compression ignition combustion mode in which the air-fuel mixture in the combustion chamber of the internal combustion engine is compressed and ignited and the spark ignition combustion mode in which the air-fuel mixture in the combustion chamber is combusted by the ignition means provided in the combustion chamber. A vehicle control device that switches driving according to a predetermined condition,
A direct fuel injection device for directly injecting fuel into the combustion chamber;
A variable valve mechanism capable of changing a valve timing of at least the exhaust valve of the exhaust valve and the intake valve of the internal combustion engine;
When the internal combustion engine is started in the premixed compression ignition combustion mode, at the time of starting, the fuel injected by the direct fuel injection device during the compression process of the internal combustion engine is ignited by the ignition means, and the exhaust valve An internal combustion engine control means for making the closing timing earlier than the closing timing of the exhaust valve in the spark ignition combustion mode and causing a part of the exhaust to remain in the cylinder of the internal combustion engine. apparatus. Battery,
An electric motor that generates driving force that supplements the driving force of the internal combustion engine with electric power stored in the battery, or regenerates part of the driving force of the internal combustion engine to charge the battery;
Request torque acquisition means for acquiring a request value for power plant torque generated in a power plant including the internal combustion engine and the electric motor;
Torque distribution means for setting a required value for an internal combustion engine torque generated in the internal combustion engine based on a required value for the power plant torque, and a required value for an electric motor torque regenerated or generated in the electric motor,
When the internal combustion engine is started in the premixed compression ignition combustion mode, the torque distribution means sets the required value for the internal combustion engine torque to a predetermined median value in the premixed compression ignition combustion mode. The vehicle control device according to claim 1, wherein a required value for the motor torque is set according to an excess or deficiency of the median value with respect to the required value of the power plant torque. The internal combustion engine control means includes
When the required value for the power plant torque is larger than the median and the battery is in an overdischarged state, or when the required value for the powerplant torque is smaller than the median and the battery is in an overcharged state, The vehicle control device according to claim 2, wherein the internal combustion engine is operated in a spark ignition combustion mode.

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