JP6897275B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

It is an internal combustion engine that is connected to the axle so that torque can be transmitted, and the combustion mode is divided into a lean combustion mode that burns under a lean air-fuel ratio and a stoichiometric combustion mode that burns under a nearly theoretical air-fuel ratio. In a so-called hybrid vehicle equipped with an internal combustion engine that can be switched between and an electric motor that is connected to the axle so that torque can be transmitted, when the combustion mode of the internal combustion engine should be switched from lean combustion mode to stoichiometric combustion mode, internal combustion The air-fuel ratio is almost the same as the lean air-fuel ratio, with the output of the internal combustion engine temporarily reduced and the output of the electric motor temporarily increased while maintaining the total of the engine output and the electric motor output constant. A hybrid vehicle that switches to the stoichiometric air-fuel ratio in steps is known (see, for example, Patent Document 1). According to Patent Document 1, in this way, the torque fluctuation of the internal combustion engine that occurs when the combustion mode is switched is reduced.

In addition, the combustion mode of the internal combustion engine is the first combustion mode in which compression self-ignition combustion is performed under a relatively large amount of EGR gas and lean air-fuel ratio, and a relatively small amount of EGR gas and almost theoretical air-fuel ratio. There is also known a vehicle that can be switched between a second combustion mode in which spark ignition combustion is performed in (see, for example, Patent Document 2). In the first combustion mode, reduction of fuel consumption, reduction of NOx generation, and the like can be expected.

Japanese Unexamined Patent Publication No. 2008-08802 Japanese Unexamined Patent Publication No. 2014-173532

In Patent Document 1, if the above-mentioned first combustion mode is performed as the lean combustion mode and the above-mentioned second combustion mode is performed as the stoichiometric combustion mode, it occurs when switching from the first combustion mode to the second combustion mode. It may be possible to enjoy the benefits of the first combustion mode while reducing torque fluctuations. However, when switching from the first combustion mode to the second combustion mode, it is necessary to significantly reduce the amount of fresh air and the amount of EGR gas. However, even if the throttle opening and the opening of the EGR control valve are reduced in steps, the amount of fresh air may not be immediately reduced in steps. Further, even if the opening degree of the EGR control valve is reduced in steps, the amount of EGR gas or the intake carbon dioxide concentration may not immediately decrease in steps. Therefore, combustion may occur in a state where the fresh air amount and the intake carbon dioxide concentration deviate from the target amounts. As a result, good combustion may not be obtained.

According to the present invention, it is an internal combustion engine that is connected to an axle so that torque can be transmitted, and has an EGR passage that connects an engine intake passage and an engine exhaust passage downstream of the throttle valve to each other, and an EGR gas that is arranged in the EGR passage. The EGR control valve is configured so that the intake carbon dioxide concentration can be changed by changing the amount, and the combustion mode is the first combustion mode in which compression self-ignition combustion is performed under a lean air-fuel ratio. An internal combustion engine configured to be switchable between a second combustion mode in which spark ignition combustion is performed under a substantially theoretical air-fuel ratio, and a motor generator connected to the axle so as to be able to transmit torque. A motor generator configured to be capable of performing a power running operation that increases the torque of the axle and a regenerative operation that regenerates electric energy from the torque of the axle, and the motor generator when the motor generator executes the power running operation. A battery configured to supply electric energy to the motor generator to store the regenerated electric energy when the motor generator executes the regenerative operation, and a combustion mode of the internal combustion engine according to the engine operating state. An electronic control unit configured to switch between the first combustion mode and the second combustion mode is provided, and the combustion mode is changed from the first combustion mode to the second combustion mode. In the engine operating state to be switched to, the target value of the fresh air quantity in the second combustion mode is less than the target value of the fresh air quantity in the first combustion mode, and the intake air in the second combustion mode is The target value of the carbon dioxide concentration is lower than the target value of the intake carbon dioxide concentration in the first combustion mode, and the electronic control unit further charges the battery more than a predetermined set amount. Sometimes when the combustion mode should be switched from the first combustion mode to the second combustion mode, the air-fuel ratio is maintained, the amount of fresh air is reduced, the intake carbon dioxide concentration is reduced, thereby the internal combustion engine. The second combustion mode is started by temporarily shorting the output of the engine with respect to the required output of the engine, and then changing the air fuel ratio to almost the theoretical air fuel ratio in a stepwise manner and starting spark ignition combustion. The temporary shortage of the output of the internal combustion engine at this time is compensated by the power running operation of the motor generator, and when the charge amount of the battery is smaller than the set amount, the combustion mode is changed from the first combustion mode to the above. Second combustion engine When the air-fuel ratio should be switched to, the air-fuel ratio should be reduced within the lean air-fuel ratio, the amount of fresh air should be reduced, and the intake carbon dioxide concentration should be maintained substantially, so that the output of the internal combustion engine is temporarily relative to the engine required output. The second combustion mode is started by gradually changing the air-fuel ratio to the stoichiometric air-fuel ratio and starting spark ignition combustion, and then the output of the internal combustion engine at this time. Provided is a vehicle control device configured to absorb the temporary excess of the motor generator by regenerative operation of the motor generator.

Good combustion can be ensured while limiting torque fluctuations when switching the combustion mode.

It is the whole view of the control device of a vehicle. It is a partial cross-sectional view of an internal combustion engine. It is a diagram which shows the 1st region R1, the 2nd region R2 and the 3rd region R3. It is a diagram which shows an example of a setting rate dOPETX. It is a diagram which shows an example of the lower limit value SOCL. It is a time chart explaining the 1st switching control. It is a diagram which shows the relationship between the operating point determined by the ignition timing θ and the intake carbon dioxide concentration CCO2 in the 2nd combustion mode, and various limits. It is a time chart explaining the 2nd switching control. It is a diagram which shows the relationship between the operating point determined by the ignition timing θ and the intake carbon dioxide concentration CCO2 in the 2nd combustion mode, and various limits. It is a flowchart for executing the switching control of the combustion mode of the Example by this invention. It is a flowchart for executing the first switching control. It is a flowchart for executing the second switching control.

FIG. 1 shows an overall view of a vehicle control device according to an embodiment of the present invention. Referring to FIG. 1, the vehicle control device includes an internal combustion engine 1. The internal combustion engine 1 includes an engine body 2 having a plurality of cylinders 2a. The cylinder 2a is connected to the surge tank 4 via the intake branch pipe 3, and the surge tank 4 is connected to the outlet of the compressor 6c of the exhaust supercharger 6 via the intake duct 5. The inlet of the compressor 6c is connected to the air cleaner 8 via the intake air introduction pipe 7. An air flow meter 9 configured to detect the amount of intake air is arranged in the intake introduction pipe 7. In the intake duct 5, a cooler 10 configured to cool the intake air and a throttle valve 11 are sequentially arranged. The throttle valve 11 is configured so that the amount of fresh air can be changed. On the other hand, a carbon dioxide sensor 12 configured to detect the carbon dioxide concentration in the intake air is arranged downstream of the throttle valve 11, for example, the surge tank 4.

Further, the cylinder 2a is connected to the inlet of the turbine 6t of the exhaust supercharger 6 via the exhaust manifold 13. The outlet of the turbine 6t is connected to the catalyst 15 via the exhaust pipe 14. An air-fuel ratio sensor 16 configured to detect the air-fuel ratio is arranged in the exhaust pipe 14. The surge tank 4 and the exhaust manifold 13 are connected to each other by an exhaust gas recirculation (hereinafter referred to as EGR) passage 17. In the EGR passage 17, an EGR control valve 18 configured to change the carbon dioxide concentration in the intake air by controlling the amount of EGR gas, and a cooler 19 configured to cool the EGR gas. Is placed.

The crankshaft 20 of the internal combustion engine 1 and the motor generator 21 are connected to the axle 22 so as to be able to transmit torque. Specifically, in the embodiment according to the present invention, the crankshaft 20 is connected to the axle 22 via the power split mechanism 23 and the speed reducer 24. On the other hand, the motor generator 21 of the embodiment according to the present invention includes a first motor generator 21a and a second motor generator 21b. The first motor generator 21a is connected to the axle 22 via the speed reducer 24. The second motor generator 21b is connected to the power split mechanism 23. Therefore, the torque of the internal combustion engine 1 can be transmitted to at least one of the axle 22 and the second motor generator 21b. In another embodiment (not shown), the motor generator 21 comprises a single motor generator.

The first motor generator 21a and the second motor generator 21b are electrically connected to the battery 27 via the inverter 26. A charge amount sensor 28 configured to detect the charge amount of the battery 27 is attached to the battery 27. In FIG. 1, 29 shows a wheel.

In the embodiment according to the present invention, the motor generator 21 performs a power running operation that functions as an electric motor to increase the torque of the axle 22 and a regenerative operation that functions as a generator and regenerates electric energy from the torque of the axle 22. It is configured to be executable. On the other hand, the battery 27 supplies electric energy to the motor generator 21 when the motor generator 21 executes the power running operation, and stores the regenerated electric energy when the motor generator 21 executes the regenerative operation. It is configured. In the embodiment according to the present invention, the first motor generator 21a mainly performs power running operation, and the second motor generator 21b mainly performs regenerative operation.

FIG. 2 shows in detail the internal combustion engine 1 of the embodiment according to the present invention. Referring to FIG. 2, 30 is a cylinder block, 31 is a cylinder head, 32 is a piston, 33 is a combustion chamber, 34 is an intake port, 35 is an intake valve, 36 is an intake valve 35 valve mechanism, and 37 is an exhaust port. 38 is an exhaust valve, 39 is a valve mechanism of the exhaust valve 38, 40 is a fuel injection valve arranged substantially in the center of the combustion chamber 33, and 41 is an ignition plug arranged adjacent to the fuel injection valve 40. The fuel injection valve 40 is configured so that the amount of fuel can be changed. The spark plug 41 is configured so that the ignition timing can be changed.

Referring again to FIG. 1, the electronic control unit 50 comprises a digital computer, ROM (read-only memory) 52, RAM (random access memory) 53, CPU (microprocessor) 54, which are connected to each other by a bidirectional bus 51. It includes an input port 55 and an output port 56. The output voltages of the air flow meter 9, the carbon dioxide sensor 12, the air-fuel ratio sensor 16, and the charge amount sensor 28 are input to the input port 55 via the corresponding A / D converter 57, respectively. Further, a load sensor 60 that generates an output voltage proportional to the amount of depression of the accelerator pedal 59 is connected to the accelerator pedal 59, and the output voltage of the load sensor 60 is input to the input port 55 via the corresponding AD converter 57. To. Further, a crank angle sensor 61 that generates an output pulse every time the crankshaft 20 rotates, for example, 30 degrees is connected to the input port 55. The CPU 54 calculates the engine speed based on the output pulse from the crank angle sensor 61. On the other hand, the output port 56 passes through the corresponding drive circuit 58, and the fuel injection valve 40 and the spark plug 41 (FIG. 2), the actuator of the throttle valve 11, the EGR control valve 18, the motor generator 21, the power split mechanism 23, and Each is connected to the inverter 26.

The internal combustion engine 1 of the embodiment according to the present invention has a first combustion mode in which compression self-ignition combustion is performed under a lean air-fuel ratio and a second combustion mode in which spark ignition combustion is performed under a substantially stoichiometric air-fuel ratio. It is configured to be switchable between the combustion mode of. In the first combustion mode, for example, fuel injection is performed at the end of the compression stroke, whereby a premixture is formed in a part of the combustion chamber 33. This premixture is then compressed, self-ignited and combusted. The air-fuel ratio in this case is a lean air-fuel ratio AFL (for example, 30 to 40) that is leaner than the theoretical air-fuel ratio. On the other hand, in the second combustion mode, fuel injection is performed in the intake stroke, whereby a substantially homogeneous premixture is formed in the combustion chamber 33. The premixture is then ignited by the spark plug 41 and flame propagated and burned. The air-fuel ratio in this case is almost the stoichiometric air-fuel ratio.

When the first combustion mode is performed, the air-fuel ratio can be made significantly lean, so that the fuel consumption can be reduced. Moreover, since the compression ratio can be increased, the thermal efficiency can be increased. Further, since the combustion temperature is lower than that of the second combustion mode, the generation of NOx can be reduced. Further, since sufficient oxygen is present around the fuel, the generation of unburned HC can be reduced.

In compression self-ignition combustion, knocking is more likely to occur than in spark ignition combustion. Therefore, in the embodiment according to the present invention, the first combustion mode is performed under a relatively large amount of EGR gas, and the second combustion mode is performed under a relatively small amount of EGR gas.

In the embodiment according to the present invention, as shown in FIG. 3, the first region R1, the second region R2, and the third region R3 are in the engine operating state region determined by the engine torque TQE and the engine speed NE, respectively. It is partitioned. The first region R1 includes a predetermined lower limit limit rotation speed NEL, a predetermined upper limit threshold rotation speed NEU, a predetermined lower limit threshold torque TQEL, and a predetermined upper limit threshold torque. Defined by TQEU. The third region R3 is defined by a lower limit threshold rotation speed NEL, an upper limit threshold rotation speed NEU, a second lower limit threshold torque TQEL2, and a lower limit threshold torque TQEL. On the other hand, the second region R2 is a region other than the first region R1 and the third region R3. In the example shown in FIG. 3, the second region R2 is divided into a higher torque side and a higher rotation speed side than the first region R1. In FIG. 3, the curve TQEF represents the total load.

In the example shown in FIG. 3, the lower limit threshold rotation speed NEL is set as a constant value that does not depend on the engine torque TQE from the second lower limit threshold torque TQEL2 to the upper limit threshold torque TQEU. Further, the upper limit threshold rotation speed NEU is set as a constant value that does not depend on the engine torque TQE from the second lower limit threshold torque TQEL2 to the upper limit threshold torque TQEU. On the other hand, the lower limit threshold torque TQEL is set as a value determined according to the engine speed NE from the lower limit threshold rotation speed NEL to the upper limit threshold rotation speed NEU. Further, the upper limit threshold torque TQEU is set as a value determined according to the engine speed NE from the lower limit threshold rotation speed NEL to the upper limit threshold rotation speed NEU. Further, the second lower limit threshold torque TQEL2 is set as a constant value, for example, zero, which does not depend on the engine speed NE from the lower limit threshold rotation speed NEL to the upper limit threshold rotation speed NEU. The lower limit threshold rotation speed NEL, the upper limit threshold rotation speed NEU, the lower limit threshold torque TQEL, the upper limit threshold torque TQEU, and the second lower limit threshold torque TQEL2 are stored in advance in the ROM 52, respectively.

In one example, the line segment (NEL, NEU, TQEL, TQEU) that divides the first region R1 belongs to the first region R1. In another example, the line segment (NEL, NEU, TQEL, TQEU) dividing the first region R1 belongs to the second region R2 or the third region R3 adjacent to the first region R1. Further, in one example, the line segment (NEL, NEU, TQEL2, TQEU) that divides the third region R3 belongs to the third region R3. In another example, the line segment (NEL, NEU, TQEL2, TQEU) dividing the third region R3 belongs to the first region R1 or the second region R2 adjacent to the third region R3.

In the embodiment according to the present invention, when the steady engine operating state belongs to the first region R1, the combustion mode of the internal combustion engine 1 is set to the first combustion mode, and the engine operating state belongs to the second region R2. Sometimes the combustion mode of the internal combustion engine 1 is the second combustion mode. Further, in the embodiment according to the present invention, when the steady engine operating state belongs to the third region R3, the combustion mode of the internal combustion engine 1 is different from the first combustion mode and the second combustion mode. It is said to be the combustion mode of. In the third combustion mode, in one example, compression self-ignition combustion is performed under a relatively small amount of EGR gas and lean air-fuel ratio. Since the engine torque TQE of the third region R3 is lower than that of the first region R1, knocking is less likely to occur. Therefore, the third combustion mode is performed under a relatively small amount of EGR gas. In another example, spark ignition combustion takes place under a lean air-fuel ratio.

Therefore, generally speaking, the electronic control unit 50 switches the combustion mode of the internal combustion engine 1 between the first combustion mode, the second combustion mode, and the third combustion mode according to the engine operating state. It means that it is composed of. Further, the electronic control unit 50 is configured to switch the combustion mode of the internal combustion engine 1 between the first combustion mode and the second combustion mode according to the engine operating state.

Now, when the combustion mode is the first combustion mode, for example, when the engine required torque exceeds the upper limit torque TQEU, the combustion mode is switched to the second combustion mode. In the embodiment according to the present invention, as described above, the first combustion mode is performed under a lean air-fuel ratio, and the second combustion mode is performed under a substantially stoichiometric air-fuel ratio. Further, the first combustion mode is performed under a relatively large amount of EGR gas, and the second combustion mode is performed under a relatively small amount of EGR gas. Therefore, in the engine operating state in which the combustion mode should be switched from the first combustion mode to the second combustion mode, the target value of the fresh air quantity in the second combustion mode is the target value of the fresh air quantity in the first combustion mode. And the target value of the intake carbon dioxide concentration in the second combustion mode is lower than the target value of the intake carbon dioxide concentration in the first combustion mode.

Therefore, in order to switch the combustion mode from the first combustion mode to the second combustion mode, it is necessary to significantly reduce the amount of fresh air and the intake carbon dioxide concentration. However, even if the opening degree of the throttle valve 11 is reduced in a stepped manner, the fresh air amount may not be immediately reduced in a stepped manner. Further, even if the opening degree of the EGR control valve 18 is reduced in steps, the amount of EGR gas or the intake carbon dioxide concentration may not immediately decrease in steps. Therefore, combustion may occur in a state where the fresh air amount and the intake carbon dioxide concentration deviate from the target amounts. As a result, combustion fluctuations and emissions may worsen.

Therefore, in the embodiment according to the present invention, the combustion mode of the internal combustion engine 1 is switched from the first combustion mode to the second combustion mode as follows. That is, in the embodiment according to the present invention, first, when the combustion mode of the internal combustion engine 1 is the first combustion mode, it is determined whether or not the combustion mode should be switched to the second combustion mode. In the embodiment according to the present invention, it is determined that the combustion mode should be switched to the second combustion mode when the increase rate dOPT of the engine required output OPET is higher than the predetermined set rate dOPTEX, and otherwise the combustion mode is set. It is determined that the first combustion mode should be maintained. In other words, if the rapid acceleration operation is performed while the combustion mode of the internal combustion engine 1 is the first combustion mode, it is determined that the combustion mode should be switched to the second combustion mode.

FIG. 4 shows an example of the setting rate dOPETX. In the example shown in FIG. 4, the set rate dOPTEX decreases as the engine required output OPT increases from the engine required output OPTL corresponding to the lower limit threshold torque TQEL to the engine required output OPTU corresponding to the upper limit torque TQEU. Become. In FIG. 4, dOPEM indicates the maximum engine required output increase rate dOPET that the internal combustion engine 1 can take. Therefore, in other words, the operating point determined by the engine required output OPT and the engine required output increase rate dOPTE belongs to the area RX defined by the set rate dOPTEX, the engine required output increase rate maximum value dOPETM, the engine required output OPENTL, and OPENTU. Occasionally, it is determined that the combustion mode should be switched from the first combustion mode to the second combustion mode, and the combustion mode is changed from the first combustion mode to the second combustion mode when the operating point does not belong to the region RX. It is determined that switching should not be done. The setting rate dOPETX and the engine request outputs OPENTL and OPENTU are stored in the ROM 52 in advance.

Combustion mode When it is determined that the first combustion mode should be switched to the second combustion mode, it is then determined whether or not the charge amount of the battery 27 is larger than the predetermined set amount. In the embodiment according to the present invention, when the SOC of the battery 27 (for example, the remaining charge of the battery with respect to the full charge capacity of the battery) is larger than the predetermined lower limit value SOCL, the charge amount of the battery 27 is the power running of the motor generator 21. It is determined that the battery 27 is sufficient for operation, and when the SOC is equal to or less than the lower limit value SOCL, the charge amount of the battery 27 is determined to be insufficient for the power running operation of the motor generator 21. FIG. 5 shows an example of the lower limit value SOCL. The lower limit value SOCL increases as the engine required output OPT increases from the engine required output OPTL corresponding to the lower limit threshold torque TQEL to the engine required output OPTU corresponding to the upper limit threshold torque TQEU. The lower limit value SOCL is stored in the ROM 52 in advance.

When it is determined that the charge amount of the battery 27 is sufficient for the power running operation of the motor generator 21, the first switching is performed to switch the combustion mode of the internal combustion engine 1 from the first combustion mode to the second combustion mode. Control is done. Next, the first switching control will be described with reference to FIG.

In FIG. 6, the engine output OPE, the air-fuel ratio AF, the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ in the first switching control are shown by solid lines, respectively. In FIG. 6, the broken line indicates the air-fuel ratio AF, the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the assumption that the second combustion mode is started at time ta1 and the engine operation is in a steady state. The target values of the ignition timing θ are shown respectively. Further, the dotted line indicates the ignition timing θTS required to eliminate the torque step, assuming that the second combustion mode is started at the time ta1.

With reference to FIG. 6, the time ta1 indicates the time when the first switching control should be started. In the first switching control, even if it is determined that the combustion mode should be switched, the second combustion mode is not immediately started, and the first combustion mode is continued. In this case, the air-fuel ratio AF is maintained at a relatively large lean air-fuel ratio AFL. On the other hand, at time ta1, the throttle opening is reduced. As a result, the fresh air volume QAE gradually decreases. Further, at time ta1, the opening degree of the EGR control valve 18 is reduced. As a result, the intake carbon dioxide concentration CCO2 decreases with a delay. Since the first combustion mode, that is, the compression self-ignition combustion is continued, the ignition action of the spark plug 41 is not performed.

Then, at time ta2, when the intake carbon dioxide concentration CCO2 becomes lower than the predetermined set value CCO2X, the combustion mode is switched to the second combustion mode. That is, the air-fuel ratio AF is stepwise reduced to the theoretical air-fuel ratio AFS. Further, the ignition action of the spark plug 41 is started. In this case, the ignition timing θ is set on the retard side of the target value (broken line).

After that, transient control is performed to bring the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ closer to their respective targets (broken lines). Then, at time ta3, when the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ match the respective target values, the transient control is terminated, that is, the first switching control is terminated. After that, a normal second combustion mode is performed.

On the other hand, as shown in FIG. 6, when the air-fuel ratio AF, the fresh air quantity QAE, and the intake carbon dioxide concentration CCO2 are controlled as described above, the output OPE of the internal combustion engine 1 is temporarily set with respect to the engine required output OPT. Is insufficient. The shortfall at this time is shown by SH in FIG. In the first switching control, this shortage SH is compensated by the power running operation of the motor generator 21. Therefore, the engine request output OPET is maintained and good drivability is ensured. The above-mentioned lower limit value SOCL is set so that power running operation at this time is possible.

FIG. 7 shows the relationship between the operating point determined by the ignition timing θ and the intake carbon dioxide concentration CCO2 in the second combustion mode and various limits. In FIG. 7, KN indicates the knocking limit. That is, knocking occurs when the ignition timing θ is on the advance side of the knocking limit KN or when the intake carbon dioxide concentration CCO2 is lower than the knocking limit KN. Further, in FIG. 7, CF indicates a combustion fluctuation limit. That is, when the ignition timing θ is on the retard side of the combustion fluctuation limit CF, or when the intake carbon dioxide concentration CCO2 is higher than the combustion fluctuation limit CF, the combustion fluctuation deteriorates beyond the permissible level. Further, in FIG. 7, the MF shows the misfire limit. That is, if the ignition timing θ is on the retard side of the misfire limit MF, or if the intake carbon dioxide concentration CCO2 is higher than the misfire limit MF, misfire occurs. Therefore, in FIG. 7, the dot-dotted region RD2 represents a region where good combustion is obtained when the second combustion mode is performed.

A1 shown in FIG. 6 indicates an operating point determined by the ignition timing θ and the intake carbon dioxide concentration CCO2 when it is assumed that the second combustion mode is started at the time ta1. This operating point A1 is outside the region RD2 in FIG. Therefore, in the first switching control, the second combustion mode is not performed at the operating point A1. On the other hand, A2 shown in FIG. 6 indicates an operating point in the first switching control at time ta2. The operating point A2 belongs to the region RD2 in FIG. Further, A3 shown in FIG. 6 indicates an operating point in the first switching control at time ta3. The operating point A3 also belongs to the region RD2 in FIG. Therefore, good combustion can be obtained at operating points A2 and A3.

As described above, in the first switching control, the second combustion mode is started with the fresh air quantity QAE reduced, and the ignition timing θ is retarded at this time, so that the torque fluctuation at the time of switching the combustion mode Is reduced. At the same time, knocking is avoided, combustion fluctuation is suppressed, and misfire is avoided. Moreover, since the air-fuel ratio AF is not changed between the lean air-fuel ratio AFL and the theoretical air-fuel ratio AFS, the generation of NOx is limited. Therefore, the first switching control can ensure good combustion while limiting torque fluctuations when switching the combustion mode.

On the other hand, when it is determined that the charge amount of the battery 27 is insufficient for the power running operation of the motor generator 21, the combustion mode of the internal combustion engine 1 is switched from the first combustion mode to the second combustion mode. Switching control of 2 is performed. Next, the second switching control will be described with reference to FIG.

In FIG. 8, the engine output OPE, the air-fuel ratio AF, the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ in the second switching control are shown by solid lines, respectively. In FIG. 8, the broken line indicates the air-fuel ratio AF, the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the assumption that the second combustion mode is started at time tb1 and the engine operation is in a steady state. The target values of the ignition timing θ are shown respectively.

With reference to FIG. 8, the time tb1 indicates the time when the second switching control should be started. In the second switching control, even if it is determined that the combustion mode should be switched, the second combustion mode is not immediately started, and the first combustion mode is continued. In this case, at time tb1, the air-fuel ratio AF is gradually reduced from the lean air-fuel ratio AFL within the range of the lean air-fuel ratio, that is, within the range smaller than the lean air-fuel ratio AFL and larger than the theoretical air-fuel ratio. Further, at time tb1, the throttle opening degree is reduced. As a result, the fresh air volume QAE gradually decreases. Further, at time tb1, the opening degree of the EGR control valve 18 is reduced. As a result, the intake carbon dioxide concentration CCO2 decreases with a delay. That is, after the time tb1, the intake carbon dioxide concentration CCO2 is almost maintained for a while. Since the first combustion mode, that is, the compression self-ignition combustion is continued, the ignition action of the spark plug 41 is not performed.

Then, at time tb2, when the intake carbon dioxide concentration CCO2 begins to decrease, the combustion mode is switched to the second combustion mode. That is, the air-fuel ratio AF is stepwise reduced to the theoretical air-fuel ratio AFS. Further, the ignition action of the spark plug 41 is started. In this case, the ignition timing θ is set on the advance angle side of the target value (broken line).

After that, transient control is performed to bring the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ closer to their respective targets (broken lines). Then, at time tb3, when the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ match the respective target values, the transient control is terminated, that is, the second switching control is terminated. After that, a normal second combustion mode is performed.

On the other hand, as shown in FIG. 8, when the air-fuel ratio AF, the fresh air quantity QAE, and the intake carbon dioxide concentration CCO2 are controlled as described above, the output OPE of the internal combustion engine 1 is temporarily set with respect to the engine required output OPT. To be excessive. The excess at this time is shown by EX in FIG. In the second switching control, this excess EX is absorbed by the regenerative operation of the motor generator 21. Therefore, the engine request output OPET is maintained and good drivability is ensured. The above-mentioned lower limit value SOCL is set so that the battery 27 can store the electric energy regenerated by the regenerative operation at this time.

FIG. 9 is a diagram similar to FIG. 7 showing the relationship between the operating point determined by the ignition timing θ and the intake carbon dioxide concentration CCO2 in the second combustion mode and various limits. In FIG. 9, KN is the knocking limit, CF is the combustion fluctuation limit, MF is the misfire limit, and the dot-dotted region RD2 is the region where good combustion is obtained when the second combustion mode is performed. , Representing each.

B1 shown in FIG. 8 indicates an operating point in the second switching control at time tb2. The operating point B1 belongs to the region RD2 in FIG. Further, B2 shown in FIG. 8 indicates an operating point in the second switching control at the time tb2. The operating point B2 also belongs to the region RD2 in FIG. Therefore, good combustion can be obtained at operating points B1 and B2.

As described above, in the second switching control, the second combustion mode is started in a state where the fresh air quantity QAE is reduced, so that the torque fluctuation at the time of switching the combustion mode is reduced. Moreover, since the engine output OPE is temporarily increased when the combustion mode is switched, the retardation requirement for the ignition timing θ is relaxed. Further, since the fresh air quantity QAE is reduced, the retardation request for the ignition timing θ from knocking and suppression of torque fluctuation is relaxed. As a result, knocking is avoided, combustion fluctuation is suppressed, and misfire is avoided. Further, since the compressed self-ignition combustion is continued while the intake carbon dioxide concentration CCO2 is maintained, misfire is avoided. Further, by continuing the compression self-ignition combustion, the increase in NOx generation due to the change of the air-fuel ratio AF between the lean air-fuel ratio AFL and the theoretical air-fuel ratio AFS is limited. Therefore, the second switching control can ensure good combustion while limiting torque fluctuations when switching the combustion mode.

If the second switching control is performed when the charge amount of the battery 27 is relatively large, the electric energy regenerated by the regenerative operation in the second switching control may not be stored in the battery 27. In this case, the excess EX of the engine output OPE may not be sufficiently absorbed. Further, if the first switching control is performed when the charge amount of the battery 27 is relatively small, the battery 27 may not be able to supply the electric energy required for the power running operation in the first switching control. In this case, the shortage SH of the engine output OPE may not be sufficiently compensated. On the other hand, in the embodiment according to the present invention, the first switching control is performed when the charge amount of the battery 27 is relatively large, and the second switching control is performed when the charge amount of the battery 27 is relatively small. .. Therefore, the engine output OPE can be reliably maintained at the engine required output OPET regardless of the charge amount of the battery 27.

Therefore, conceptually, when the electronic control unit 50 should switch the combustion mode from the first combustion mode to the second combustion mode when the charge amount of the battery 27 is larger than a predetermined set amount, Maintaining the air-fuel ratio AF, reducing the fresh air quantity QAE, and lowering the intake carbon dioxide concentration CCO2, thereby causing the output OPE of the internal combustion engine 1 to be temporarily short of the engine required output OPT, and then empty. The second combustion mode is started by changing the fuel ratio AF to almost the stoichiometric air-fuel ratio AFS in a stepwise manner and starting spark ignition combustion, and the temporary shortage SH of the output OPE of the internal combustion engine 1 at this time is motorized. Compensated by the power running of the generator 21
When the combustion mode should be switched from the first combustion mode to the second combustion mode when the charge amount of the battery 27 is less than the set amount, the air-fuel ratio AF is reduced within the range of the lean air-fuel ratio, and the fresh air amount QAE. To maintain the intake carbon dioxide concentration CCO2 almost, thereby causing the output OPE of the internal combustion engine 1 to be temporarily excessive with respect to the engine required output OPT, and then change the air-fuel ratio AF to almost the theoretical air-fuel ratio AFS. The second combustion mode is started by changing in steps and starting spark ignition combustion, and the temporary excess EX of the output OPE of the internal combustion engine 1 at this time is absorbed by the regenerative operation of the motor generator 21. It is configured as follows.

FIG. 10 shows a routine for executing the combustion mode switching control of the embodiment according to the present invention. Referring to FIG. 10, in step 100 (FIG. 10), the engine required load is acquired. The engine required load is calculated based on, for example, the amount of depression of the accelerator pedal 59. In the following step 101, the engine request output OPET is calculated based on the engine request load. In the following step 102, it is determined whether or not the combustion mode of the internal combustion engine 1 should be switched from the first combustion mode to the second combustion mode. That is, it is determined whether or not the operating point determined by the engine-requested output OPT and the engine-requested output increase rate dOPTE belongs to the region RX shown in FIG. The processing cycle is terminated when the combustion mode should not be switched. When the combustion mode should be switched, the next step is step 103, and the SOC of the battery 27 is acquired. In the following step 104, the lower limit value SOCL is calculated using the map of FIG. In the following step 105, it is determined whether or not the SOC of the battery 27 is larger than the lower limit value SOCL. When SOC> SOCL, the process proceeds to step 106, and the first switching control is executed. The routine that executes the first switching control is shown in FIG. On the other hand, when SOC ≦ SOCL, the process proceeds to step 107, and the second switching control is executed. The routine that executes the second switching control is shown in FIG.

With reference to FIG. 11, which shows a routine for executing the first switching control, in step 110, the fresh air quantity QAE is reduced and the intake carbon dioxide concentration CCO2 is lowered. In the following step 111, it is determined whether or not the intake carbon dioxide concentration CCO2 is lower than the set value CCO2X. When CCO2 ≧ CCO2X, the process proceeds to step 112, and power running operation of the motor generator 21 is performed to make up for the shortage SH of the engine output OPE. In the following step 113, it is determined whether or not the control parameters such as the fresh air amount QAE, the intake carbon dioxide concentration CCO2, and the ignition timing θ match the respective target values of the second combustion mode. When the control parameter does not match the target value, the process returns to step 111. Then, when CCO2 <CCO2X, the process proceeds from step 111 to step 114, and the second combustion mode is started. That is, the air-fuel ratio AF is set to almost the stoichiometric air-fuel ratio, and spark ignition combustion is performed. In the following step 115, the above-mentioned transient control is performed. Then, the process proceeds to step 112, and the power running operation of the motor generator 21 is performed. Then, the process proceeds to step 113, and when the control parameters do not match the target value, the process returns to step 111, and when they match, the processing cycle ends. That is, the first switching control is terminated.

Referring to FIG. 12, which shows a routine for executing the second switching control, in step 120, the air-fuel ratio AF is reduced, the fresh air quantity QAE is reduced, and the intake carbon dioxide concentration CCO2 is reduced. In the following step 121, it is determined whether or not the intake carbon dioxide concentration CCO2 has started to decrease. When the intake carbon dioxide concentration CCO2 is substantially maintained, the next step is step 122, and the regenerative operation of the motor generator 21 is performed in order to absorb the excess EX of the engine output OPE. In the following step 123, it is determined whether or not the control parameters match the respective target values of the second combustion mode. When the control parameter does not match the target value, the process returns to step 121. Then, when the intake carbon dioxide concentration CCO2 begins to decrease, the process proceeds from step 121 to step 124, and the second combustion mode is started. That is, the air-fuel ratio AF is set to almost the stoichiometric air-fuel ratio, and spark ignition combustion is performed. In the following step 125, the above-mentioned transient control is performed. Then, the process proceeds to step 122, and the regenerative operation of the motor generator 21 is performed. Then, the process proceeds to step 123, and when the control parameters do not match the target value, the process returns to step 121, and when they match, the processing cycle ends. That is, the second switching control is terminated.

1 Internal combustion engine 11 Throttle valve 17 EGR passage 18 EGR control valve 21 Motor generator 22 Axle 27 Battery 41 Spark plug 50 Electronic control unit

Claims (1)

An internal combustion engine that is connected to the axle so that torque can be transmitted, by changing the EGR gas amount arranged in the EGR passage and the EGR passage that connect the engine intake passage and the engine exhaust passage downstream of the throttle valve to each other. It is equipped with an EGR control valve that is configured to be able to change the intake carbon dioxide concentration, and has a combustion mode of the first combustion mode that performs compression self-ignition combustion under a lean air-fuel ratio, and an almost theoretical air-fuel ratio. An internal combustion engine that is configured to be switchable between a second combustion mode that performs spark ignition combustion with and
A motor generator that is connected to the axle so that torque can be transmitted, and is configured to be capable of performing power running operation that increases the torque of the axle and regenerative operation that regenerates electrical energy from the torque of the axle. When,
It is configured to supply electric energy to the motor generator when the motor generator executes the power running operation, and to store the regenerated electric energy by the motor generator when the motor generator executes the regenerative operation. With the battery
An electronic control unit configured to switch the combustion mode of the internal combustion engine between the first combustion mode and the second combustion mode according to the engine operating state.
With
In the engine operating condition to switch the combustion mode from the first combustion mode to the second combustion mode, the target value of the air volume in the second combustion mode the amount of fresh air in the first combustion mode The target value of the intake carbon dioxide concentration in the second combustion mode is lower than the target value of the intake carbon dioxide concentration in the first combustion mode.
The electronic control unit further
When the combustion mode should be switched from the first combustion mode to the second combustion mode when the charge amount of the battery is larger than a predetermined set amount, the air-fuel ratio is maintained and the fresh air amount is reduced. Then, the EGR control valve is controlled to reduce the intake carbon dioxide concentration so that the output of the internal combustion engine is temporarily insufficient with respect to the required output of the engine, and then the air-fuel ratio is stepped to almost the stoichiometric air-fuel ratio. The second combustion mode is started by changing the shape and starting spark ignition combustion, and the temporary shortage of the output of the internal combustion engine at this time is compensated by the power running operation of the motor generator.
When the combustion mode should be switched from the first combustion mode to the second combustion mode when the charge amount of the battery is less than the set amount, the air-fuel ratio is reduced within the range of the lean air-fuel ratio. The air volume is reduced and the EGR control valve is controlled to nearly maintain the intake carbon dioxide concentration so that the output of the internal combustion engine is temporarily excessive with respect to the engine required output, and then the air-fuel ratio is adjusted. The second combustion mode is started by changing the air-fuel ratio to almost the stoichiometric air-fuel ratio in a stepwise manner and starting spark ignition combustion, and the temporary excess of the output of the internal combustion engine at this time is regenerated by the motor generator. Absorb by
A vehicle control device that is configured to.

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