JP2011179387A - Control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a vehicle, which achieves both an improvement in exhaust emission control performance and stabilization of traveling performance during a period when an engine combustion mode is switched. <P>SOLUTION: A hybrid vehicle includes: an engine with a combustion mode switched between premixed compression ignition combustion and spark ignition combustion according to an operation area; a motor generating driving force for compensating output of the engine or regenerating the output of the engine; and a catalytic convertor with a built-in three-way catalyst purifying exhaust from the engine. This control device for the hybrid device controls an exhaust air-fuel ratio of the exhaust led to flow into the three-way catalyst and the ignition timing of the engine, during a switching period when the engine combustion mode is switched from the spark ignition combustion to the premixed compression ignition combustion, based on the temperature of the three-way catalyst and determination results whether or not a state where the driving force is generated by the motor to compensate the output of the engine is established and whether or not while the output of the engine is regenerated by the motor is established. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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, it is difficult to burn the air-fuel mixture at an appropriate timing, and knocking or misfire is likely to occur. Therefore, in recent years, an internal combustion engine capable of switching between spark ignition combustion in which an air-fuel mixture is burned by a spark plug and premixed compression ignition combustion in accordance with the operation region in order to compensate for an operation region in which premixed compression ignition combustion is difficult. Has been developed.

  By the way, since the optimal in-cylinder pressure and temperature differ between premixed compression ignition combustion and spark ignition combustion, the combustion state of the internal combustion engine may become unstable when switching the combustion mode. For this reason, in an internal combustion engine that switches the combustion mode in accordance with the operating region, there is a problem of how to smoothly shift the combustion mode.

  For example, in Patent Document 1, when switching the combustion mode of an internal combustion engine from premixed compression ignition combustion to spark ignition combustion, the cylinder pressure and cylinder interior suitable for spark ignition combustion are temporarily stopped by temporarily stopping the supply of fuel. Techniques have been shown for starting spark-ignited combustion after lowering to temperature. According to this technology, it is possible to prevent the internal combustion engine from misfiring or knocking while switching the combustion mode from premixed compression ignition combustion to spark ignition combustion.

  Further, for example, Patent Document 2 discloses a technique for compensating an output that fluctuates due to a temporarily unstable combustion state of an internal combustion engine with a motor output while switching the combustion mode of the internal combustion engine. ing. As a result, even when the combustion mode is being switched, stable traveling is possible without causing a torque step.

Japanese Patent No. 3714300 Japanese Patent No. 3931744

  With the techniques disclosed in Patent Documents 1 and 2 above, although it is possible to suppress a decrease in running performance while switching the combustion mode of the internal combustion engine, a decrease in the purification performance of exhaust gas discharged from the internal combustion engine. Has not been fully studied.

  The present invention relates to a control device for a vehicle provided with an internal combustion engine that switches a combustion mode between premixed compression ignition combustion and spark ignition combustion, and stabilizes running performance and exhaust purification performance while switching the combustion mode. An object of the present invention is to provide a vehicle control device that can achieve both improvement.

  In order to achieve the above object, the present invention provides an internal combustion engine (for example, engine 2 described later) that switches the combustion mode between premixed compression ignition combustion and spark ignition combustion in accordance with the operating region, and a drive that supplements the output of the internal combustion engine. Provided is a control device for a vehicle (for example, a hybrid vehicle 1 described later) including an electric motor (for example, a motor 5 described later) that generates force or regenerates the output of the internal combustion engine. The vehicle control device is provided in an exhaust passage (for example, an exhaust pipe 32 described later) of the internal combustion engine and purifies exhaust gas of the internal combustion engine (for example, a three-way catalyst of a catalytic converter 35 described later). And a catalyst temperature acquisition means (for example, an exhaust temperature sensor 43 and an ECU 9 described later) for acquiring the temperature of the exhaust purification catalyst, and the electric motor can generate driving force to supplement the output of the internal combustion engine. Determination means for determining whether or not the electric motor can regenerate the output of the internal combustion engine (for example, an ECU 9 described later, and steps S12 and S15 in FIG. 5) And the combustion mode of the internal combustion engine from spark ignition combustion to premix compression based on the temperature acquired by the catalyst temperature acquisition unit and the determination result by the determination unit Control means for controlling the exhaust air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst and the ignition timing of the internal combustion engine (for example, ECU 9 to be described later, and steps S13, S14, S16 in FIG. 5) within the switching period for switching to fire combustion. , Means for executing S17).

  According to this invention, in addition to the temperature of the exhaust gas purification catalyst, the control means determines whether or not it is in a state in which it is possible to generate a driving force with the electric motor to supplement the output of the internal combustion engine, and the output of the internal combustion engine with the electric motor. The exhaust air-fuel ratio and the ignition timing are controlled in the switching period for switching from spark ignition combustion to premixed compression ignition combustion according to the determination result of whether or not the engine can be regenerated. Thus, the exhaust purification performance within the switching period can be improved by controlling the exhaust air-fuel ratio suitable for the exhaust purification catalyst. Further, since the exhaust air-fuel ratio and the ignition timing can be controlled in an appropriate manner according to the state of the electric motor, the running performance within the switching period can be stabilized.

  In this case, it is preferable that the exhaust purification catalyst is a three-way catalyst, and the control means controls the exhaust air / fuel ratio within the switching period to a target exhaust air / fuel ratio in the vicinity of the theoretical air / fuel ratio.

  Since the three-way catalyst exhibits high purification performance in the vicinity of the theoretical air-fuel ratio, according to the present invention, the air-fuel ratio of the exhaust gas flowing into the three-way catalyst is set in the vicinity of the theoretical air-fuel ratio within the switching period. By controlling to the target exhaust air-fuel ratio, the exhaust purification performance can be maintained high.

  In this case, when the temperature acquired by the catalyst temperature acquisition unit is equal to or higher than a predetermined threshold value and the determination unit determines that the output of the internal combustion engine can be regenerated by the electric motor, The control means controls the combustion air-fuel ratio of the internal combustion engine to be close to the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio coincides with the target exhaust air-fuel ratio, and controls the ignition so that the output of the internal combustion engine becomes maximum. It is preferable to control the timing and regenerate a part of the output of the internal combustion engine with the electric motor.

  According to the present invention, by controlling the combustion air-fuel ratio close to the stoichiometric air-fuel ratio, the exhaust air-fuel ratio can be controlled to the target exhaust air-fuel ratio set near the stoichiometric air-fuel ratio. Decline can be prevented. At this time, while controlling the ignition timing of the internal combustion engine to maximize the output, a part of the output is regenerated by the electric motor. That is, by recovering part of the energy of the fuel provided to bring the exhaust air / fuel ratio close to the stoichiometric air / fuel ratio as electric energy, the internal combustion engine between the switching period and before entering the switching period It is possible to improve the energy efficiency of the entire vehicle while suppressing fluctuations in output combined with the electric motor and stabilizing the traveling of the vehicle.

  In this case, when it is determined that the temperature acquired by the catalyst temperature acquisition unit is smaller than a predetermined threshold value and the determination unit can generate a driving force that supplements the output of the internal combustion engine with the electric motor. The control means controls the combustion air-fuel ratio of the internal combustion engine to be leaner than the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio, and performs additional injection during the expansion stroke of the internal combustion engine. It is preferable to generate a driving force that supplements the output of the internal combustion engine with the electric motor.

  According to this invention, by controlling the combustion air-fuel ratio to be leaner than the stoichiometric air-fuel ratio and performing additional injection during the expansion stroke, the exhaust air-fuel ratio is set to the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio. Since it can be controlled, it is possible to prevent the exhaust purification performance from being lowered. Here, by controlling the exhaust air / fuel ratio to the target exhaust air / fuel ratio by performing additional injection, the temperature of the exhaust purification catalyst can be raised quickly, so that the exhaust purification performance of the exhaust purification catalyst can be improved. Further, at this time, by generating the driving force with the electric motor, it is possible to compensate for the output of the internal combustion engine that is decreased by making the combustion air-fuel ratio lean as described above, so that the switching period and the switching period are entered. It is possible to suppress fluctuations in the output of the internal combustion engine and the motor combined with the previous motor and to stabilize the traveling of the vehicle.

  In this case, the determination means determines that the electric motor is not in a state where the output of the internal combustion engine can be regenerated, or that the electric motor does not generate a driving force that supplements the output of the internal combustion engine. In this case, the control means controls the combustion air-fuel ratio of the internal combustion engine to be close to the theoretical air-fuel ratio so that the exhaust air-fuel ratio coincides with the target exhaust air-fuel ratio, and during the switching period and the switching period. It is preferable to control the ignition timing so as to suppress the output fluctuation of the internal combustion engine before entering.

  According to the present invention, by controlling the combustion air-fuel ratio close to the stoichiometric air-fuel ratio, the exhaust air-fuel ratio can be controlled to the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio. Can be prevented. Further, at this time, by controlling the ignition timing of the internal combustion engine so as to suppress the output fluctuation of the internal combustion engine between the switching period and before entering the switching period, the traveling of the vehicle can be stabilized. it can.

It is a mimetic diagram showing the composition of the hybrid vehicle concerning one embodiment of the present invention. It is a schematic diagram which shows the structure of the engine which concerns on the said embodiment, its intake system, and an exhaust system. 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 which concerns on the said embodiment. It is a flowchart which shows the engine air-fuel ratio and ignition timing in the switching period which switches the combustion form of the engine which concerns on the said embodiment from HCCI combustion to SI combustion, and the control procedure of a motor. It is a flowchart which shows the procedure of the control of an engine and a motor in the switching period which switches the combustion form of the engine which concerns on the said embodiment from SI combustion to HCCI combustion.

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 two driving force generation sources of an engine 2 and a motor 5. The hybrid vehicle 1 is driven by both or either of the output generated by the engine 2 by burning the fuel stored in the fuel tank 7 and the output generated by the motor 5 by the electric power stored in the high-voltage battery 8. The 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 output generated by the engine 2 or by the outputs 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 only by the output generated by the motor 5 and to travel. The clutch CL operates based on a control signal output 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 PDU 6 operates based on a control signal from the ECU 9 and generates a driving force by the motor 5 by the electric power of the high-voltage battery 8 or from a part of the output of the engine 2 or from the driving wheels 11 and 12 when the vehicle 1 is decelerated. The transmitted driving force is regenerated in the high voltage battery 8. More specifically, when driving the motor 5, the PDU 6 converts the electric 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 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.

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.

  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 for injecting fuel into the combustion chamber 2a is provided. The fuel injection amount and fuel injection timing from these injectors 26 and 27 are controlled by the ECU 9. 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 electromagnetically 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. In this three-way catalyst, the air-fuel ratio of the inflowing exhaust (hereinafter referred to as “exhaust air-fuel ratio”) is close to the theoretical air-fuel ratio, and the amount of oxygen stored (hereinafter referred to as “oxygen storage amount”). It is possible to efficiently purify the above three of HC, CO, and NOx when is an appropriate amount. Examples of the catalyst noble metal contained in the three-way catalyst include rhodium, palladium, and platinum. Examples of the OSC material include cerium and zirconium.

  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 to an air flow sensor 41, an air-fuel ratio sensor 42, an exhaust temperature sensor 43, a crank angle position sensor 44, an accelerator opening sensor 45, a cylinder internal pressure sensor (not shown), 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 air-fuel ratio sensor 42 detects the air-fuel ratio of the exhaust discharged from the engine 2 and flowing into the catalytic converter 35 (hereinafter referred to as “exhaust air-fuel ratio”), and transmits a signal substantially proportional to the detected value to the ECU 9. Further, the oxygen storage amount of the three-way catalyst of the catalytic converter 35 is sequentially calculated by the ECU 9 based on the detected value of the air-fuel ratio sensor 42. 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 temperature of the three-way catalyst of the catalytic converter 35 is calculated by the ECU 9 based on the output value of the exhaust temperature sensor 43.

  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 driver's required torque is calculated by searching a predetermined map based on the rotational speed of the engine 2 and the output value of the accelerator opening sensor 45. The cylinder pressure sensor detects the cylinder pressure 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 is premixed compression ignition combustion (hereinafter referred to as “HCCI (Homogeneous Charge Compression Ignition) combustion”) and spark ignition combustion (hereinafter referred to as “SI”) according to the operation region. (Spark Ignition) ”).

  In SI combustion, a predetermined amount of fuel is injected from the two injectors 26 and 27 at a predetermined timing in the combustion cycle. The air-fuel mixture supplied to the combustion chamber 2a in the intake process is compressed in the compression process, and the compressed air-fuel mixture is ignited by sparks emitted from the spark plug 28 at a predetermined timing in the combustion cycle. Burn. In particular, in this SI combustion, the fuel injection amounts from the two injectors 26 and 27 are adjusted so that the air-fuel ratio of the air-fuel mixture, that is, the combustion air-fuel ratio becomes close to the stoichiometric air-fuel ratio.

  In the HCCI combustion, a predetermined amount of fuel is injected from the two injectors 26 and 27 at a predetermined timing in the combustion cycle. Then, the air-fuel mixture with the air supplied into the combustion chamber 2a in the intake process is compressed in the compression process so as to have a high temperature and self-ignited. In particular, in this HCCI combustion, the fuel injection amounts from the two injectors 26 and 27 are adjusted so that the combustion air-fuel ratio is leaner than the stoichiometric air-fuel ratio.

FIG. 3 is a diagram illustrating an operation region in which HCCI combustion is performed and an operation region in which SI combustion is performed.
As shown in FIG. 3, the combustion mode of the engine is switched between HCCI combustion and SI combustion in accordance with two parameters of the engine speed indicating the operating state of the engine and the driver's required torque. HCCI combustion is performed when the operating state of the engine is in a low speed and low load operating region. In contrast, SI combustion is performed when the operating state of the engine is in a relatively high rotational speed and high load operating region.

  By the way, since the air-fuel mixture is compressed and ignited during HCCI combustion, the temperature of the combustion chamber is higher than the temperature suitable for SI combustion. Therefore, for example, when the combustion mode of the engine is switched from HCCI combustion to SI combustion, control is performed to lower the temperature of the combustion chamber to a temperature suitable for SI combustion. On the other hand, when the combustion mode of the engine is switched from SI combustion to HCCI combustion, control for increasing the temperature of the combustion chamber to a temperature suitable for HCCI combustion is performed. For example, this is performed by leaving a part of the exhaust in the combustion chamber by closing the exhaust valve earlier than the time of SI combustion.

  FIG. 4 is a flowchart showing an engine exhaust air-fuel ratio, ignition timing, and motor control procedures within a switching period in which the engine combustion mode is switched from HCCI combustion to SI combustion. The flowchart shown in FIG. 4 starts when it is determined to switch to SI combustion by a process (not shown) while the engine is operated by HCCI combustion.

  In step S1, the oxygen storage amount of the three-way catalyst of the catalytic converter is acquired, and the process proceeds to step S2. As described above, the oxygen storage amount is sequentially calculated based on the detection value of the air-fuel ratio sensor. In step S2, the target exhaust air / fuel ratio of the exhaust air / fuel ratio in the switching period for switching the engine combustion mode from HCCI combustion to SI combustion is set, and the process proceeds to step S3. In this step S2, in order to reduce the oxygen stored excessively in the three-way catalyst during the HCCI combustion and to make the oxygen storage amount of the three-way catalyst appropriate when the SI combustion is started, the above target The exhaust air-fuel ratio is set to a value that is richer than the stoichiometric air-fuel ratio and that corresponds to the acquired oxygen storage amount. More specifically, in step S2, the target exhaust air-fuel ratio is set to the rich side as the oxygen storage amount increases.

  In step S3, it is determined whether or not the temperature of the three-way catalyst of the catalytic converter is equal to or higher than a predetermined threshold based on the detected value of the exhaust temperature sensor. The determination in step S3 is a process for determining whether or not the three-way catalyst is in an activated state based on the temperature of the three-way catalyst. The threshold value is set based on the activation temperature of the three-way catalyst or the like. Set based on.

  If the determination in step S3 is YES, it is determined that the three-way catalyst is in an activated state, and the process proceeds to step S4. In step S4, it is determined whether or not the motor can regenerate part of the engine output to the high voltage battery.

  If the determination in step S4 is YES, that is, if it is determined that the three-way catalyst is in an activated state and a part of the engine output can be regenerated in the high-voltage battery by the motor, the process proceeds to step S5. . In step S5, the combustion air-fuel ratio is controlled to be richer than the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in step S2, and the engine output is maximized. The ignition timing is controlled as follows. By the way, by controlling the ignition timing so that the combustion air-fuel ratio is made richer than the stoichiometric air-fuel ratio and the output is maximized, the engine output during the switching period becomes larger than before entering the switching period. Therefore, in this step S5, the amount of the output generated by the engine that has been increased before entering the switching period is regenerated to the high-voltage battery by the motor.

  If the determination in step S4 is NO, that is, if it is determined that the three-way catalyst is in an activated state and a part of the engine output cannot be regenerated to the high-voltage battery by the motor, the process proceeds to step S6. In step S6, the combustion air-fuel ratio is controlled to be richer than the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in step S2. The ignition timing is controlled so as to suppress engine output fluctuations before the engine enters.

  On the other hand, if the determination in step S3 is NO, the process proceeds to step S7 to perform control giving priority to the activation of the three-way catalyst. In step S7, it is determined whether or not the motor can assist the engine output, that is, whether or not the motor can generate driving force to supplement the engine output. More specifically, for example, it is possible to assist the motor by determining whether or not the remaining battery capacity calculated based on the battery voltage, discharge current, temperature, etc. is greater than a predetermined threshold. It is determined whether or not the current state is correct.

  If the determination in step S7 is YES, that is, if it is determined that the three-way catalyst is not in an activated state and the engine output can be assisted by the motor, the process proceeds to step S8. In step S8, the combustion air-fuel ratio is controlled to be leaner than the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in step S2, and additional injection is performed during the expansion stroke. Do. By the way, by performing additional injection during the expansion stroke, the temperature of the three-way catalyst can be raised while controlling the exhaust air-fuel ratio to the rich side, but the fuel provided in the additional injection does not contribute to combustion in the engine. . Therefore, the output of the engine during the switching period is smaller than before entering the switching period. Therefore, in this step S8, the motor generates a driving force that compensates for a decrease in the output generated by the engine before entering the switching period.

  If the determination in step S7 is NO, that is, if it is determined that the three-way catalyst is not in an activated state and the motor output cannot be assisted by the motor, the process proceeds to step S9. In step S9, the combustion air-fuel ratio is controlled to be richer than the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in step S2, and during the switching period and during this switching period. The ignition timing is controlled so as to suppress the engine output fluctuation with the engine before entering.

  FIG. 5 is a flowchart showing a procedure for controlling the engine and the motor within a switching period in which the combustion mode of the engine is switched from SI combustion to HCCI combustion. The flowchart shown in FIG. 5 starts when it is determined to switch to HCCI combustion by a process (not shown) while the engine is operated by SI combustion.

  In step S11, it is determined whether the temperature of the three-way catalyst of the catalytic converter is equal to or higher than a predetermined threshold based on the detected value of the exhaust temperature sensor. The determination in step S11 is a process for determining whether or not the three-way catalyst is in an activated state based on the temperature of the three-way catalyst, similarly to the determination in step S3.

  If the determination in step S11 is YES, it is determined that the three-way catalyst is in an activated state, and the process proceeds to step S12. In step S12, it is determined whether or not the motor can regenerate a part of the engine output to the high voltage battery.

  If the determination in step S12 is YES, that is, if it is determined that the three-way catalyst is in an activated state and a part of the engine output can be regenerated by the motor, the process proceeds to step S13. In step S13, the combustion air-fuel ratio is controlled in the vicinity of the theoretical air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio, and the engine output is maximized. The ignition timing is controlled as follows. By the way, by controlling the combustion air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio and controlling the ignition timing so that the output is maximized, the engine output during the switching period becomes larger than before entering the switching period. Therefore, in this step S13, the increased amount of the output generated by the engine before entering the switching period is regenerated to the high voltage battery by the motor.

  If the determination in step S12 is NO, that is, if it is determined that the three-way catalyst is in an activated state and a part of the engine output cannot be regenerated in the high-voltage battery by the motor, the process proceeds to step S14. In step S14, the combustion air-fuel ratio is controlled to be close to the theoretical air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio. The ignition timing is controlled so as to suppress engine output fluctuations before entering the period.

  On the other hand, if the determination in step S11 is NO, the process proceeds to step S15 to perform control giving priority to the activation of the three-way catalyst. In step S15, as in step S7, it is determined whether or not the motor output can be assisted by the motor.

  If the determination in step S15 is YES, that is, if it is determined that the three-way catalyst is not in an activated state and the engine output can be assisted by the motor, the process proceeds to step S16. In step S16, the combustion air-fuel ratio is controlled to be close to the theoretical air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio, and additional injection is performed during the expansion stroke. I do. At this time, similarly to step S8, the motor generates a driving force that compensates for a decrease in the output generated by the engine before entering the switching period.

  If the determination in step S15 is NO, that is, if it is determined that the three-way catalyst is not in an activated state and the engine output cannot be assisted by the motor, the process proceeds to step S17. In step S17, the combustion air-fuel ratio is controlled to be close to the theoretical air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio. The ignition timing is controlled so as to suppress the engine output fluctuation with the engine before entering the engine.

According to this embodiment, the following effects can be obtained.
(1) According to this embodiment, in addition to the temperature of the three-way catalyst, whether or not the motor 5 can generate a driving force to supplement the output of the engine 2 and whether the motor 5 The exhaust air-fuel ratio and the ignition timing are controlled within the switching period for switching from SI combustion to HCCI combustion according to the determination result of whether or not the output of the engine can be regenerated. Thereby, by controlling the exhaust air / fuel ratio suitable for the three-way catalyst, it is possible to improve the exhaust purification performance within the switching period. Further, since the exhaust air / fuel ratio and the ignition timing can be controlled in an appropriate manner according to the state of the motor 5, the running performance within the switching period can be stabilized.

  (2) Since the three-way catalyst exhibits high purification performance in the vicinity of the stoichiometric air-fuel ratio, according to the present embodiment, the three-way catalyst flows into the three-way catalyst within the switching period for switching the combustion mode from SI combustion to HCCI combustion. By controlling the air-fuel ratio of the exhaust gas to the target exhaust air-fuel ratio set in the vicinity of the stoichiometric air-fuel ratio, the exhaust purification performance can be maintained high.

  (3) According to the present embodiment, in step S13 of FIG. 5, the exhaust air-fuel ratio is set to the target exhaust air-fuel ratio set in the vicinity of the theoretical air-fuel ratio by controlling the combustion air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio. Since it can be controlled, it is possible to prevent a decrease in exhaust purification performance. At this time, a part of the output is regenerated by the motor 5 while controlling the ignition timing of the engine 2 so as to maximize the output. That is, by recovering a part of the energy of the fuel supplied to bring the exhaust air-fuel ratio close to the stoichiometric air-fuel ratio as electric energy, during the switching period in which the combustion mode is switched from SI combustion to HCCI combustion, and this switching period It is possible to improve the energy efficiency of the entire vehicle 1 while suppressing fluctuations in the output of the engine 2 and the motor 5 combined before entering the vehicle and stabilizing the traveling of the vehicle 1.

  (4) According to the present embodiment, in step S16 in FIG. 5, the combustion air-fuel ratio is controlled to be leaner than the stoichiometric air-fuel ratio, and additional injection is performed during the expansion stroke, so that the exhaust air-fuel ratio is the stoichiometric air-fuel ratio. Therefore, it is possible to prevent the exhaust purification performance from being deteriorated. Here, by controlling the exhaust air / fuel ratio to the target exhaust air / fuel ratio by performing the additional injection, the temperature of the three-way catalyst can be increased quickly, so that the exhaust purification performance of the three-way catalyst can be improved. Further, at this time, by generating the driving force by the motor 5, it is possible to compensate for the output of the engine 2 that is reduced by making the combustion air-fuel ratio lean as described above, so the combustion mode is changed from SI combustion to HCCI combustion. It is possible to suppress the fluctuation of the output of the engine 2 and the motor 5 combined during the switching period before and before entering the switching period, and to stabilize the traveling of the vehicle 1.

  (5) According to the present embodiment, in steps S14 and S17 in FIG. 5, the target exhaust gas whose exhaust air-fuel ratio is set in the vicinity of the theoretical air-fuel ratio is controlled by controlling the combustion air-fuel ratio in the vicinity of the theoretical air-fuel ratio. Since the air-fuel ratio can be controlled, it is possible to prevent a reduction in exhaust purification performance. At this time, the ignition timing of the engine 2 is controlled so as to suppress fluctuations in the output of the engine 2 during the switching period in which the combustion mode is switched from SI combustion to HCCI combustion and before entering the switching period. The travel of the vehicle 1 can be stabilized.

1 ... Hybrid vehicle (vehicle)
2. Engine (internal combustion engine)
5. Motor (electric motor)
9 ... ECU (exhaust air / fuel ratio acquisition means, oxygen storage amount acquisition means, setting means, control means, catalyst temperature acquisition means, determination means)
32 ... Exhaust pipe (exhaust passage)
35 ... Catalytic converter (exhaust gas purification catalyst)
42: Air-fuel ratio sensor (exhaust air-fuel ratio acquisition means)
43. Exhaust temperature sensor (catalyst temperature acquisition means)

Claims (5)

An internal combustion engine that switches the combustion mode between premixed compression ignition combustion and spark ignition combustion according to the operating region;
A control device for a vehicle, comprising: a driving force that supplements the output of the internal combustion engine; or an electric motor that regenerates the output of the internal combustion engine,
An exhaust purification catalyst that is provided in an exhaust passage of the internal combustion engine and purifies exhaust of the internal combustion engine;
Catalyst temperature acquisition means for acquiring the temperature of the exhaust purification catalyst;
It is determined whether or not the electric motor can generate a driving force to supplement the output of the internal combustion engine, and whether or not the electric motor can regenerate the output of the internal combustion engine. A determination means;
Based on the temperature acquired by the catalyst temperature acquisition means and the determination result by the determination means, the combustion mode of the internal combustion engine flows into the exhaust purification catalyst within a switching period for switching from spark ignition combustion to premixed compression ignition combustion. And a control means for controlling the exhaust air-fuel ratio of the exhaust gas and the ignition timing of the internal combustion engine. The exhaust purification catalyst is a three-way catalyst,
2. The vehicle control apparatus according to claim 1, wherein the control means controls the exhaust air-fuel ratio within the switching period to a target exhaust air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio. When the temperature acquired by the catalyst temperature acquisition means is equal to or higher than a predetermined threshold value and the determination means determines that the output of the internal combustion engine can be regenerated by the electric motor,
The control means controls the combustion air-fuel ratio of the internal combustion engine to be close to the theoretical air-fuel ratio so that the exhaust air-fuel ratio coincides with the target exhaust air-fuel ratio, and the output of the internal combustion engine becomes maximum. The vehicle control device according to claim 2, wherein ignition timing is controlled, and further, a part of the output of the internal combustion engine is regenerated by the electric motor. When it is determined that the temperature acquired by the catalyst temperature acquisition unit is smaller than a predetermined threshold and can be generated by the determination unit with a driving force that supplements the output of the internal combustion engine with the electric motor,
The control means controls the combustion air-fuel ratio of the internal combustion engine to be leaner than the stoichiometric air-fuel ratio so that the exhaust air-fuel ratio matches the target exhaust air-fuel ratio and performs additional injection during the expansion stroke of the internal combustion engine. The vehicle control device according to claim 2, further comprising: generating a driving force that supplements the output of the internal combustion engine with the electric motor. When it is determined by the determination means that the electric motor is not capable of regenerating the output of the internal combustion engine, or when the electric motor is determined not to be capable of generating a driving force that supplements the output of the internal combustion engine,
The control means controls the combustion air-fuel ratio of the internal combustion engine to be close to the theoretical air-fuel ratio so that the exhaust air-fuel ratio coincides with the target exhaust air-fuel ratio, and during the switching period and before entering the switching period. The vehicle control device according to any one of claims 2 to 4, wherein the ignition timing is controlled so as to suppress an output fluctuation of the internal combustion engine.

Images