JP4946345B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable as an apparatus for controlling an internal combustion engine having a variable valve mechanism that can change the opening and closing timing of intake and exhaust valves.

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine including a variable valve timing device that makes the valve timing of intake and exhaust valves variable. In this conventional apparatus, the in-cylinder temperature is controlled by varying the closing timing of the exhaust valve with respect to the top dead center and the opening timing of the intake valve with respect to the top dead center according to the operating state of the internal combustion engine.

JP 2001-355462 A JP 2002-227680 A Japanese Utility Model Publication No. 5-96444 Japanese Patent Publication No. 7-3200

  If the exhaust valve is closed early with respect to the top dead center (exhaust valve early closing control), the internal EGR gas amount can be secured. Such exhaust valve early closing control is an effective technique for reducing NOx emissions and increasing exhaust temperature. Further, increasing the pump loss by opening the intake valve late with respect to the top dead center (intake valve slow open control) is an effective technique for increasing the exhaust temperature. However, the above conventional technique does not disclose a control method in which the internal EGR for reducing the NOx emission amount satisfies the demand for increasing the exhaust gas and the request for raising the exhaust temperature at the same time.

  The present invention has been made to solve the above-described problems, and when executing the early closing control of the exhaust valve and the slow opening control of the intake valve, the internal EGR increase request for reducing the NOx emission amount is required. It is an object of the present invention to provide a control device for an internal combustion engine that can satisfy both the exhaust gas temperature increase request and the exhaust temperature increase request at the same time without waste or shortage.

The first aspect of the present invention is an exhaust variable valve mechanism that can change at least the closing timing of the exhaust valve, an intake variable valve mechanism that can change at least the opening timing of the intake valve, and exhaust purification that purifies the exhaust gas. An internal combustion engine control device comprising:
A temperature increase request detecting means for detecting a temperature increase request of exhaust gas;
An exhaust valve closing timing determining means for determining an advance amount of the closing timing of the exhaust valve with respect to the top dead center based on the required internal exhaust gas recirculation amount when a temperature increase request of the exhaust gas is detected;
Calculation of predicted exhaust gas temperature for calculating a predicted value of exhaust gas temperature rise when the exhaust valve closing timing is controlled to be the advance amount of the exhaust valve closing timing determined by the exhaust valve closing timing determining means Means,
Whether the exhaust temperature is still insufficient with respect to the target temperature rise even when the exhaust valve closing timing is set so as to be the advance amount of the exhaust valve closing timing based on the predicted value of the exhaust temperature rise Exhaust temperature determination means for determining whether or not,
Wherein when the exhaust temperature to the heating target value is determined not to be missing by the exhaust temperature determining means, the advance of the closing timing of the exhaust valve retard amount of the opening timing of the intake valve with respect to the top dead center was determined to be the amount and the same amount, wherein when the exhaust temperature to the heating target value is determined to be missing still by the exhaust temperature determining means, an exhaust to the heating target value as the temperature is insufficient to determine the retard amount of the opening timing of the exhaust valve closing timing of the advance amount of the intake valve so that the difference increases by subtracting from the retard amount of the opening timing of the intake valve intake Means for determining the valve opening time;
It is characterized by providing.

Further, the second invention purifies exhaust gas, an exhaust variable valve mechanism that can change at least the closing timing of the exhaust valve, an intake variable valve mechanism that can change at least the opening timing of the intake valve, and the exhaust gas. An internal combustion engine control device comprising exhaust purification means,
A temperature increase request detecting means for detecting a temperature increase request of exhaust gas;
An exhaust valve closing timing determining means for determining an advance amount of the closing timing of the exhaust valve with respect to the top dead center based on the required internal exhaust gas recirculation amount when a temperature increase request of the exhaust gas is detected;
When the exhaust gas temperature rise request is detected, it is equal to or greater than the advance amount at the closing timing of the exhaust valve, and when the exhaust gas temperature rise request is high, it is lower than when it is low. The intake valve opening timing is determined so that the difference obtained by subtracting the advancement amount of the exhaust valve closing timing from the delay amount of the intake valve opening timing with respect to the top dead center becomes large. Means for determining the valve opening time;
It is characterized by providing.

The third invention further comprises exhaust temperature acquisition means for acquiring the temperature of the exhaust gas in the first or second invention,
It said timing determining means opens the intake valve, if the exhaust temperature at the point of time before the temperature increase request of the exhaust gas is detected is not high, as compared with the case where the exhaust temperature is low, advance the opening timing of the intake valve The correction is made to the corner side.

Further, a fourth aspect of the invention is the first or second aspect of the invention, further comprising operating state acquisition means for acquiring the operating state of the internal combustion engine,
The intake valve opening timing determining means corrects the opening timing of the intake valve to the advance side when the operating state of the internal combustion engine at a time point before the exhaust gas temperature increase request is detected is a high load state. It is characterized by doing.

According to a fifth invention, in the first or second invention, based on the environmental conditions surrounding the internal combustion engine, at least the advance amount of the exhaust valve closing timing and the retard amount of the intake valve opening timing are determined. One is corrected.

  According to the first invention, when the exhaust gas temperature increase request is issued, the closing timing of the exhaust valve is determined based on the required internal exhaust gas recirculation (EGR) amount, and then the required exhaust gas is determined. It is possible to compensate for the exhaust temperature rise margin that is insufficient to raise the temperature by adjusting the opening timing of the intake valve. Therefore, it is possible to control the temperature rise of the exhaust gas without waste or shortage while reliably reducing the NOx emission amount.

  According to the second invention, when the exhaust gas temperature raising request is issued, the advance amount of the exhaust valve closing timing is determined based on the required internal exhaust gas recirculation (EGR) amount, and the intake valve The delay amount of the opening timing is determined so as to be equal to or larger than the advance amount of the opening timing of the exhaust valve based on the degree of required temperature increase of the exhaust gas. For this reason, it is possible to control the temperature rise of exhaust gas without waste or shortage while reliably reducing the NOx emission amount.

According to the third aspect of the invention, according to the exhaust gas temperature at the time before the exhaust gas temperature increase request is detected, not the delay of the exhaust valve closing timing, but the advance timing of the intake valve opening timing, The temperature of the exhaust gas is adjusted. For this reason, it is possible to achieve a good balance between the temperature rise of the exhaust gas and the suppression of deterioration in fuel consumption while ensuring the suppression of the NOx emission amount.

According to the fourth aspect of the present invention, when the operating state of the internal combustion engine at the time point before the exhaust gas temperature increase request is detected is a high load state, the intake valve is not the retarded timing of the closing timing of the exhaust valve. The temperature for raising the exhaust gas is adjusted by the advance angle of the opening timing of the exhaust gas. For this reason, it is possible to achieve a good balance between the temperature rise of the exhaust gas and the suppression of deterioration in fuel consumption while ensuring the suppression of the NOx emission amount.

According to the fifth aspect of the present invention, it is possible to control the temperature rise of exhaust gas without waste or deficiency while reliably reducing the NOx emission amount regardless of changes in environmental conditions surrounding the internal combustion engine.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 is a four-cycle diesel engine (compression ignition internal combustion engine). Each cylinder of the internal combustion engine 10 is provided with an injector 12 that directly injects fuel into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. Fuel in a fuel tank (not shown) is pressurized to a predetermined fuel pressure by a supply pump 16, stored in the common rail 14, and supplied from the common rail 14 to each injector 12.

  An exhaust passage 18 of the internal combustion engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port of each cylinder. The internal combustion engine 10 of the present embodiment includes a turbocharger 22. The exhaust passage 18 is connected to the exhaust turbine of the turbocharger 22.

  On the downstream side of the turbocharger 22 in the exhaust passage 18, an exhaust purification device 24 for purifying exhaust gas is provided. As the exhaust purification device 24, for example, one of an oxidation catalyst, a storage reduction type or selective reduction type NOx catalyst, a DPF (Diesel Particulate Filter), a DPNR (Diesel Particulate-NOx-Reduction system), or a combination thereof Etc. can be used. Further, an exhaust temperature sensor 26 for detecting the exhaust gas temperature is installed in the exhaust passage 18 on the downstream side of the turbocharger 22.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the internal combustion engine 10. The air sucked through the air cleaner 30 is compressed by the intake compressor of the turbocharger 22 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed to the intake port of each cylinder by the intake manifold 34.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  One end of the external EGR passage 40 is connected to the intake passage 28 in the vicinity of the intake manifold 34. The other end of the external EGR passage 40 is connected to the vicinity of the exhaust manifold 20 of the exhaust passage 18. In the present system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the external EGR passage 40, that is, external EGR (Exhaust Gas Recirculation) can be performed. Hereinafter, the exhaust gas recirculated through the external EGR passage 40 is referred to as “external EGR gas”.

  An EGR cooler 42 for cooling the external EGR gas is provided in the middle of the external EGR passage 40. An EGR valve 44 is provided downstream of the EGR cooler 42 in the external EGR passage 40. As the opening degree of the EGR valve 44 is increased, the amount of exhaust gas passing through the external EGR passage 40, that is, the amount of external EGR can be increased.

  An intake pressure sensor 46 that detects the intake pressure is installed downstream of the intake throttle valve 36 in the intake passage 28. The system further includes an accelerator opening sensor 48 that detects the amount of depression of the accelerator pedal (accelerator opening) of the vehicle on which the internal combustion engine 10 is mounted.

  The system according to this embodiment includes an ECU (Electronic Control Unit) 50. In addition to the various sensors described above, the ECU 50 is connected to an outside air temperature sensor 52 for detecting the outside air temperature, and is also connected to the actuator described above. The ECU 50 controls the operating state of the internal combustion engine 10 by driving each actuator according to a predetermined program based on those signals and information.

  FIG. 2 is a view showing a cross section of one cylinder of the internal combustion engine 10 in the system shown in FIG. Hereinafter, the internal combustion engine 10 will be further described. As shown in FIG. 2, a crank angle sensor 62 that detects a rotation angle (crank angle) of the crankshaft 60 is attached in the vicinity of the crankshaft 60 of the internal combustion engine 10. The crank angle sensor 62 is connected to the ECU 50. The signal from the crank angle sensor 62 can detect the engine speed and the like.

  Further, the internal combustion engine 10 includes an intake variable valve mechanism 66 that continuously varies the valve timing of the intake valve 64 and an exhaust variable valve mechanism 70 that continuously varies the valve timing of the exhaust valve 68. Is provided. These intake variable valve mechanism 66 and exhaust variable valve mechanism 70 are connected to the ECU 50. Specific configurations of the intake variable valve mechanism 66 and the exhaust variable valve mechanism 70 are not particularly limited. For example, the phase of a cam (not shown) that drives the intake valve 64 and the exhaust valve 68 is continuously variable. A mechanical mechanism such as a mechanism that performs the above can be used. Alternatively, an electromagnetically driven valve that can be opened and closed at an arbitrary timing can be used.

[Characteristics of Embodiment 1]
FIG. 3 is an enlarged PV diagram showing the relationship between the in-cylinder pressure P and the in-cylinder volume V in the intake / exhaust stroke. In the internal combustion engine 10, a request for raising the exhaust gas temperature may be issued for the purpose of raising the temperature of the catalyst of the exhaust gas purification device 24 in the light load region. A waveform indicated by a solid line in FIG. 3 is obtained when the exhaust valve early closing control for closing the exhaust valve 68 earlier than the top dead center is executed. Here, the amount of early closing of the exhaust valve 68 relative to the top dead center is referred to as “EX early closing degree X”.

If the early closing control of the exhaust valve 68 is executed, the exhaust gas can be confined in the cylinder for the next cycle, and the required amount of internal EGR gas according to the magnitude of the EX early closing degree X Can be secured. And by such a method, the compression end temperature of the next cycle can be raised by ensuring a high internal EGR gas amount. When the compression end temperature increases, the exhaust temperature can be increased. Further, when the compression end temperature becomes high, the fuel injection timing can be retarded without retarding the combustion, so that the exhaust gas temperature when the exhaust valve is opened becomes high. For this reason, the exhaust temperature can be further increased effectively, and the exhaust temperature can also be increased by increasing the fuel injection amount in order to ensure the same torque as when not retarded.
Furthermore, if the early closing control of the exhaust valve 68 is executed, the NOx emission amount can be reduced well by the fact that the EGR gas amount is increased and the fuel injection timing is retarded. it can.
Further, when the early closing control of the exhaust valve 68 is performed using a variable valve mechanism (VVT mechanism) that can change the phase of the exhaust valve 68, in addition to the early closing of the exhaust valve 68, the exhaust valve 68. This is a more effective method for raising the exhaust temperature.

A waveform indicated by a broken line in FIG. 3 is obtained when the intake valve slow-opening control that opens the intake valve 64 late with respect to the top dead center is performed in addition to the early closing control of the exhaust valve 68. Here, the slow opening amount of the intake valve 64 with respect to the top dead center is referred to as “IN delay opening Y”. If this IN delay opening Y is made larger than the above-mentioned EX early closing degree X, the pump loss can be increased as shown in FIG. When the pump loss increases, the fuel injection amount is increased in order to ensure the same torque as before the pump loss increases, whereby the exhaust temperature can be raised.
In addition, when the slow opening control of the intake valve 64 is performed using a variable valve mechanism (VVT mechanism) that can change the phase of the intake valve 64, in addition to the slow opening of the intake valve 64, the intake valve 64 This is accompanied by the slow closing of the oil, and the compression end temperature decreases. When the compression end temperature decreases, the effect of increasing the exhaust temperature is diminished. For this reason, the slow opening control of the intake valve 64 uses a variable valve mechanism that can change the operating angle, and is preferably delayed by the opening timing of the intake valve 64.

  As described above, the early opening control of the exhaust valve 68 is an effective technique for reducing the NOx emission amount and increasing the exhaust temperature, and increasing the pump loss by the slow opening control of the intake valve 64 This is an effective technique for increasing the temperature. In the present embodiment, in order to satisfy both the request for increasing the internal EGR gas for reducing the NOx emission amount and the request for raising the exhaust gas temperature at the same time without waste or deficiency, the following method is used. The closing degree X and the IN slow opening degree Y are determined.

  That is, in this embodiment, first, the EX early closing degree X is determined based on the required internal EGR gas amount. The IN delay opening Y is determined based on the exhaust temperature increase request degree ΔT (= exhaust temperature increase target value−actual exhaust temperature) after being set to the EX early closing degree X or more. I tried to do it. In other words, in this embodiment, first, the EX early closing degree X is determined so that the required internal EGR gas amount can be obtained, and then the IN delay opening Y is controlled to be equal to or higher than the EX early closing degree X. In addition, the difference between the IN slow opening degree Y and the EX early closing degree X is controlled by the opening timing of the intake valve 64 according to the magnitude of the EX early closing degree X.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the first embodiment to realize the above function. This routine is executed when a temperature increase request of the catalyst (exhaust temperature) of the exhaust purification device 24 is detected based on the exhaust temperature or the like. In the routine shown in FIG. 4, first, the current actual exhaust temperature is acquired based on the output of the exhaust temperature sensor 26 (step 100).

  Next, based on the temperature increase target value of the exhaust temperature required to raise the temperature of the catalyst to the predetermined activation temperature and the current actual exhaust temperature acquired in step 100, the temperature increase target value is determined. It is determined whether or not the exhaust temperature is insufficient (step 102).

  As a result, when it is determined that the exhaust gas temperature is insufficient, an internal EGR gas amount necessary to keep the NOx emission amount below a specified value is calculated (step 104). The ECU 50 stores a map (not shown) in which the relationship between the required internal EGR gas amount and the NOx required value is determined for each operation region of the internal combustion engine 10, and according to such a map, the required internal EGR gas amount is stored. Is calculated.

  Next, the EX rapid closing degree X required to obtain the required internal EGR gas amount calculated as described above is determined (step 106). The ECU 50 stores a map (not shown) in which the EX rapid closing degree X is determined in relation to the required internal EGR gas amount, and the EX rapid closing degree X is calculated according to such a map.

  Next, a predicted value of the exhaust gas temperature rise when the closing timing of the exhaust valve 68 is controlled so as to achieve the EX early closing degree X determined as described above is calculated (step 108). Such a predicted value can be calculated according to a map based on experimental data stored in the ECU 50 or a predetermined relational expression.

  Next, based on the predicted value of the exhaust gas temperature rise calculated in step 108, the temperature increase target in step 102 may be performed by performing the early closing control of the exhaust valve 68 using the EX rapid closing degree X. It is determined whether the exhaust temperature is still insufficient for the value (step 110).

  As a result, when it is determined that the exhaust temperature is not insufficient with respect to the temperature increase target value, that is, by performing the early closing control of the exhaust valve 68 using the EX rapid closing degree X, the temperature increase target value is obtained. If it can be determined that the exhaust temperature can be raised to the maximum, the retard amount by the IN retard opening Y is determined to be the same as the advance amount by the EX rapid closing degree X (step 112). .

  On the other hand, if it is determined in step 110 that the exhaust temperature is still insufficient with respect to the target temperature increase value by only the early closing control of the exhaust valve 68 using the EX rapid closing degree X, the exhaust temperature The pump loss required to raise the exhaust gas temperature by the shortage is calculated (step 114). The ECU 50 stores a map (not shown) in which such required pump loss is determined in relation to the exhaust gas change amount Δexhaust temperature, and the required pump loss is calculated according to such a map.

  Next, the IN delay opening Y required to cause the necessary pump loss is determined (step 116). The ECU 50 stores a map (not shown) that defines the IN slow opening Y in relation to the required pump loss, and the IN slow opening Y is calculated according to such a map.

  Next, the valve timing of the intake and exhaust valves is controlled by the exhaust variable valve mechanism 70 and the intake variable valve mechanism 66 so that the EX early closing degree X and the IN slow opening degree Y determined in the above steps are obtained. At the same time, in response to such a change in the valve timing of the intake / exhaust valves, the retard of the fuel injection timing and the increase of the fuel injection amount are executed (step 118).

  According to the routine shown in FIG. 4 described above, when there is a catalyst temperature increase request at a light load or the like, if the current exhaust gas temperature is insufficient with respect to the exhaust gas temperature increase target value, The EX early closing degree X is determined so that an internal EGR gas amount that satisfies the NOx emission reduction requirement is obtained. Even when the temperature rise control of the catalyst is performed at a light load, it is essential to suppress the NOx emission amount to a specified value or less. For this reason, first, as described above, the EX rapid closing degree X is determined based on the request for reducing the NOx emission amount.

In addition, the temperature rise target value is satisfied only by raising the exhaust temperature using the exhaust valve early closing control in which the closing timing of the exhaust valve 68 is the EX early closing degree X (heating by increasing the internal EGR gas amount). When this is not possible, the IN delay opening Y is determined in accordance with the temperature difference ΔT corresponding to the target temperature increase value. In addition, the method of increasing the pump loss by the slow opening control of the intake valve 64 can increase the exhaust temperature, but causes a deterioration in fuel consumption. On the other hand, if the early closing control of the exhaust valve 68 is used, the amount of internal EGR gas is increased while avoiding an increase in pump loss by making the IN delay opening Y the same as the EX early closing degree X. By increasing the amount of NOx, it is possible to reduce NOx emissions and raise the exhaust temperature. For this reason, in the routine processing, the adjustment of the EX early closing degree X is given priority over the adjustment of the IN slow opening degree Y as described above.
Further, in the above routine, the IN slow opening degree Y is determined so that the IN slow opening degree Y ≧ EX the early closing degree X is always satisfied. For this reason, it is possible to avoid exhaust gas remaining in the cylinder as internal EGR gas from being blown back to the intake system.

  As described above, since the EX early closing degree X is determined with priority over the IN slow opening degree Y, it is possible to avoid an increase in exhaust temperature accompanied by unnecessary fuel consumption deterioration. Then, only when the exhaust temperature cannot be increased to the target temperature rise only by the early closing control of the exhaust valve 68, the shortage of the exhaust temperature in the case where the early closing control of the exhaust valve 68 is performed is determined as the IN delay opening degree. Since the compensation is made by setting Y, it is possible to control the temperature rise of the exhaust gas without causing the temperature rise to be insufficient. Thus, according to the system of the present embodiment, it is possible to satisfactorily ensure the temperature rise performance of the exhaust gas while suppressing NOx emission.

  In the first embodiment described above, the ECU 50 detects the exhaust temperature rise request based on the exhaust temperature or the like before the routine shown in FIG. The “temperature rise request detecting means” in the above executes the processes in steps 104 and 106, so that the “exhaust valve closing timing determining means” in the first or second invention executes the processes in steps 110 to 116. Thus, the “intake valve opening timing determining means” in the first or second invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 5 and FIG.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 6 described later instead of the routine shown in FIG. 4 using the hardware configuration shown in FIGS. 1 and 2.

[Features of Embodiment 2]
FIG. 5 is a diagram for explaining a characteristic determination method of the EX early closing degree X and the IN slow opening degree Y in the present embodiment, and shows the relationship between the load of the internal combustion engine 10 and the engine speed. It is. As shown in FIG. 5, the exhaust temperature of the internal combustion engine 10 is high in the high rotation high load region and low in the low rotation light load region. Therefore, in the present embodiment, the EX early closing degree X and the IN slow opening degree Y are varied by the following method in accordance with the operating region of the internal combustion engine 10.

  Specifically, in the present embodiment, when there is a catalyst temperature increase request in a low rotation light load region where the exhaust temperature is low, that is, when the exhaust gas temperature increase request is large, priority should be given to the increase of the exhaust temperature. The IN slow opening Y is adjusted so that the difference of the IN slow opening Y with respect to the EX early closing degree X determined by the relationship with the required internal EGR gas amount is increased (control A shown in FIG. 5). On the other hand, when there is a catalyst temperature increase request in a high engine speed and high load range where the exhaust temperature is high, that is, when the exhaust gas temperature increase request is small, the EX rapid closing is performed to reduce fuel consumption and reduce NOx emissions. The degree X is adjusted so that the difference of the IN slow opening Y with respect to the EX quick closing degree X is small without changing the value determined by the relationship with the required internal EGR gas amount (Fig. Control B) shown in 5.

[Specific Processing in Second Embodiment]
FIG. 6 is a flowchart of a routine executed by the ECU 50 in the second embodiment to realize the above function. This routine is executed when a catalyst temperature increase request of the exhaust purification device 24 is detected. In the routine shown in FIG. 6, first, the current operating region (load and engine speed) of the internal combustion engine 10 is acquired (step 200).

  Next, the base values of the EX early closing degree X and the IN slow opening degree Y corresponding to the current operation region are acquired (step 202). These base values are values stored in the ECU 50 as valve timings of the intake / exhaust valves used when a catalyst temperature increase request is issued. More specifically, the base value of the EX early closing degree X is determined according to the operating region of the internal combustion engine 10 as a value that can obtain the necessary internal EGR gas amount for suppressing the NOx emission amount to a predetermined value or less. It is what was done. Further, the base value of the IN slow opening degree Y is determined according to the operation region of the internal combustion engine 10 as a value within a range that does not become smaller than the EX early closing degree X.

  Next, based on the current operating region acquired in step 200, it is determined whether or not the current exhaust gas temperature increase request is relatively small (step 204). As a result, if it is determined that the current operation range is in the high rotation and high load range and the exhaust temperature increase request is relatively small, the EX rapid closing degree X is not changed from the base value, and the EX rapid closing degree X is not changed. The IN slow opening Y is corrected with respect to the base value so that the difference of the IN slow opening Y with respect to the closing degree X becomes small (step 206).

  On the other hand, if it is determined in step 204 that the current operation region is in the low rotation light load region and the exhaust temperature rise request is relatively large, the EX rapid closing degree X is not changed from the base value. Furthermore, the IN slow opening degree Y is corrected with respect to the base value so that the difference of the IN slow opening degree Y with respect to the EX early closing degree X becomes large (step 208).

  According to the routine shown in FIG. 6 described above, when the temperature increase request for the exhaust temperature is small, the advance timing of the opening timing of the intake valve 64 is prioritized over the delay timing of the closing timing of the exhaust valve 68. More specifically, according to the above routine, according to the degree of required temperature increase of the exhaust temperature, the IN early opening degree Y is corrected while the EX early closing degree X remains a fixed value. According to such a method, while suppressing the NOx emission amount by not changing the EX rapid closing degree X, the exhaust gas temperature increase and the fuel consumption deterioration suppression are suppressed according to the level of the exhaust gas temperature increase request. Can be realized in a well-balanced manner.

  By the way, in the above-described second embodiment, when the temperature increase request for the exhaust gas temperature is relatively small, the IN early opening degree Y with respect to the EX early closing degree X is not changed from the base value. The IN delay opening Y is corrected with respect to the base value so as to reduce the difference. However, in the present invention, the control of the EX early closing degree X and the IN slow opening degree Y when the request for raising the exhaust gas temperature is relatively small is not limited to such a method. That is, if the exhaust temperature increase request is relatively small, for example, if the base value of the EX early closing degree X is set as a value having a sufficient margin for the required internal EGR gas amount First, priority may be given to reducing the IN delay opening degree Y, and then correction may be made so that the EX early closing degree X is also reduced.

  In Embodiment 2 described above, when the temperature increase request for the exhaust temperature is relatively large, the EX early closing degree X is not changed from the base value, and the IN late opening degree Y with respect to the EX early closing degree X is not changed. The IN delay opening Y is corrected with respect to the base value so as to increase the difference. However, in the present invention, the control of the EX early closing degree X and the IN slow opening degree Y when the exhaust temperature increase request is relatively large is not limited to such a method. That is, if the exhaust temperature rise request is relatively large, for example, the EX rapid closing degree X and the IN slow opening degree Y are maintained constant or increased, and then the EX rapid closing is performed. The absolute values of the degree X and the IN delay opening Y may be increased.

  In the second embodiment described above, the “intake valve control priority means” according to the third aspect of the present invention is realized by the ECU 50 executing the processing of steps 204 and 206 described above.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 7 described later instead of the routine shown in FIG. 6 using the hardware configuration shown in FIGS.

[Features of Embodiment 3]
Even if the current operation region (operation state) of the internal combustion engine 10 is a light load region in which the exhaust gas needs to be heated for catalyst control, the internal combustion engine before the exhaust gas temperature increase request is issued When the 10 operating state (previous state) is a high load state, the exhaust temperature increases due to the influence of the previous state. In such a case, the required temperature increase degree ΔT of the exhaust temperature becomes small. Therefore, in the present embodiment, the IN delay opening degree Y is based on the operating state of the internal combustion engine 10 before the exhaust gas temperature increase request is issued (in other words, the exhaust temperature state before the temperature increase request). The value was corrected.

[Specific Processing in Embodiment 3]
FIG. 7 is a flowchart of a routine executed by the ECU 50 in the third embodiment to realize the above function. This routine is executed when a catalyst temperature increase request of the exhaust purification device 24 is detected. In FIG. 7, the same steps as those shown in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 7, after the base values of the EX early closing degree X and the IN slow opening degree Y are acquired as values corresponding to the current operation region (step 202), the current gas temperature with catalyst is then entered. It is determined whether or not (exhaust temperature) is higher than a predetermined determination value, in other words, whether or not the front state of the internal combustion engine 10 is a high load state (step 300). The determination in step 300 can be performed based on the output of the exhaust temperature sensor 26, or can be performed by acquiring the front state of the internal combustion engine 10 (the relationship between the load and the engine speed).

  If it is determined in step 300 that the current catalyst-containing gas temperature is higher than the determination value, that is, if it can be determined that the front state of the internal combustion engine 10 is a high load state, the EX rapid closing degree X is determined as the base. Without changing from the value, the IN slow opening degree Y is corrected with respect to the base value so that the difference in the IN slow opening degree Y with respect to the EX early closing degree X becomes small (step 206).

  On the other hand, if it is determined in step 300 that the current catalyst-containing gas temperature is equal to or lower than the determination value, that is, if it can be determined that the previous state of the internal combustion engine 10 is not a high load state, the EX early closing degree X is not changed from the base value, and the IN slow opening Y is corrected with respect to the base value so that the difference of the IN slow opening Y with respect to the EX early closing degree X becomes large (step 208).

  According to the routine shown in FIG. 7 described above, the EX speed is increased according to the operating state of the internal combustion engine 10 before the exhaust gas temperature increase request is issued (in other words, the exhaust temperature state before the temperature increase request). While the closing degree X remains a fixed value, the IN delay opening degree Y is corrected. According to such a method, the temperature of the exhaust gas and the suppression of deterioration of fuel consumption are balanced according to the front state of the internal combustion engine 10 while ensuring the suppression of the NOx emission amount by not changing the EX rapid closing degree X. Can be realized well.

In the third embodiment described above, the “exhaust temperature acquisition means” in the third invention or the “operating state acquisition means” in the fourth invention is realized by the ECU 50 executing the processing of step 300. Has been.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 8 described later instead of the routine shown in FIG. 6 using the hardware configuration shown in FIGS. 1 and 2.

[Features of Embodiment 4]
The base values of the EX early closing degree X and the IN slow opening degree Y when there is a request for raising the exhaust gas temperature are determined according to the operating region of the internal combustion engine 10 as described above. More specifically, these base values are predetermined under basic conditions where the outside air temperature is in a predetermined standard state. By the way, when there is a change in the environment surrounding the internal combustion engine 10, specifically, for example, when the outside air temperature is low, the exhaust temperature does not easily rise. Therefore, in the present embodiment, the EX early closing degree X and the IN slow opening degree Y are corrected with respect to the respective base values based on environmental conditions (outside air temperature conditions).

[Specific Processing in Embodiment 4]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in the fourth embodiment in order to realize the above function. This routine is executed when a catalyst temperature increase request of the exhaust purification device 24 is detected. In FIG. 8, the same steps as those shown in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 8, after the base values of the EX early closing degree X and the IN slow opening degree Y are acquired as values corresponding to the current operation region (step 202), then the EX early closing degree X and It is determined whether or not the current outside air temperature is low with respect to the above basic condition of the outside air temperature that defines the base value of each of the IN retarded opening Y (step 400).

  As a result, when it is determined that the outside air temperature is lower than the basic condition, the EX early closing degree X is corrected to a value larger than the base value, and the IN slow opening Y and the EX early closing are corrected. The IN slow opening Y is corrected to a value larger than the base value so that the difference from the degree X becomes large (step 402). If the outside air temperature is not far away from the basic condition, the EX early closing degree X may be a fixed value as long as it can be handled only by adjusting the IN slow opening degree Y.

  On the other hand, if it is determined in step 400 that the outside air temperature is higher than the basic condition, the EX early closing degree X is not changed from the base value, and the IN late opening degree Y with respect to the EX early closing degree X is not changed. The IN delay opening Y is corrected with respect to the base value so that the difference between the two becomes smaller (step 206).

According to the routine shown in FIG. 8 described above, when the outside air temperature is low, compared to the EX rapid closing degree X (base value) that can satisfy the required internal EGR gas amount based on the request to reduce the NOx emission amount. IN delay opening Y so that the EX rapid closing degree X is corrected to be large and the difference from the corrected EX rapid closing degree X is larger than the difference between the respective base values. Is corrected. For this reason, the exhaust temperature can be reliably and quickly raised under a low outside air temperature condition in which the exhaust temperature does not easily rise. Further, when the outside air temperature is high, the EX early closing degree X is kept at a fixed value, and the IN delay opening degree Y is corrected to be small. For this reason, it is possible to control the exhaust temperature while ensuring the suppression of the NOx emission amount and suppressing the deterioration of the fuel consumption.
As described above, according to the method of the present embodiment, the NOx emission amount can be reliably reduced and exhaust gas that is not wasted or insufficient can be reduced regardless of changes in the environmental conditions (outside air temperature conditions) surrounding the internal combustion engine 10. Temperature rise control is possible.

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 11 described later instead of the routine shown in FIG. 4 using the hardware configuration shown in FIGS.

[Internal EGR with valve overlap]
In the internal combustion engine 10 of the present embodiment, the magnitude of the negative valve overlap between the intake valve 64 and the exhaust valve 68 can be continuously changed by the intake variable valve mechanism 66 and the exhaust variable valve mechanism 70. . FIG. 9 is a diagram for explaining negative valve overlap. As shown in FIG. 9, the negative valve overlap is a state where both the intake valve 64 and the exhaust valve 68 are closed after the exhaust valve 68 is closed until the intake valve 64 is opened.

  The thin curve in FIG. 9 is a valve lift diagram of the intake valve 64 and the exhaust valve 68 when no negative valve overlap is provided. From this state, the closing timing of the exhaust valve 68 is advanced and the opening timing of the intake valve 64 is delayed, so that a negative valve overlap can be caused. A thick curve in FIG. 9 is a valve lift diagram of the intake valve 64 and the exhaust valve 68 when a negative valve overlap is generated. The magnitude (period) of the negative valve overlap can be changed by changing the closing timing of the exhaust valve 68 and the opening timing of the intake valve 64.

  When a negative valve overlap is generated, the exhaust valve 68 is closed before the burned gas in the cylinder completely flows out to the exhaust port. The burned gas that has not been discharged to the exhaust port remains in the cylinder as it is, or once discharged to the intake port as the intake valve 64 is opened, and then sucked into the cylinder together with new air by lowering the piston. Is done. When a negative valve overlap occurs, internal EGR can be performed in this way.

  The magnitude of the negative valve overlap has a correlation with the internal EGR amount or the internal EGR rate (the ratio of the internal EGR gas in the gas flowing into the cylinder). That is, as the negative valve overlap is increased, the internal EGR amount and the internal EGR rate can be increased. For this reason, in the system of this embodiment, the internal EGR amount and the internal EGR rate can be controlled by adjusting the magnitude of the negative valve overlap.

  In the present embodiment, as shown in FIG. 9, the opening timing of the exhaust valve 68 and the closing timing of the intake valve 64 are also changed as the magnitude of the negative valve overlap is changed. The magnitude of the negative valve overlap may be changed without changing the opening timing of the exhaust valve 68 and the closing timing of the intake valve 64. In the present embodiment, the magnitude of the negative valve overlap is changed by changing both the closing timing of the exhaust valve 68 and the opening timing of the intake valve 64. However, the closing timing of the exhaust valve 68 is changed. The magnitude of the negative valve overlap may be changed by changing either the opening timing of the intake valve 64 or the intake valve 64. In this case, the internal combustion engine 10 may include only one of the intake variable valve mechanism 66 and the exhaust variable valve mechanism 70. Furthermore, in the present invention, internal EGR is performed by generating a normal valve overlap (positive valve overlap) in which both the intake valve 64 and the exhaust valve 68 are opened, and the magnitude of the positive valve overlap. The internal EGR gas amount may be adjusted by changing the length. Further, the internal EGR gas amount may be adjusted by the early closing control of the exhaust valve 68, as in the first embodiment described above, even if the magnitude of the valve overlap is not changed. .

[Compatibility between internal EGR control and fuel injection timing retard control]
FIG. 10 is a diagram comparing the retard limit of the fuel injection timing and the exhaust gas temperature with or without the introduction of internal EGR control. If the fuel injection timing is retarded, the exhaust temperature can be raised as described above. By the way, the exhaust gas introduced into the cylinder by the external EGR control has a lower temperature than the exhaust gas introduced by the internal EGR control. Therefore, if the fuel injection timing is to be retarded in a situation where external EGR control is being executed, the introduced EGR gas is at a low temperature and the introduction of EGR gas reduces the oxygen concentration in the cylinder. For this reason, there is a possibility that unburned HC emissions will increase or misfire will occur.

  Therefore, as shown by a thin line in FIG. 10, it is conceivable to retard the fuel injection timing without executing the EGR control. According to such a method, since sufficient oxygen is present in the cylinder, the fuel injection timing can be sufficiently retarded until a time that is restricted by the relationship with the unburned HC emission amount. The exhaust temperature can be raised by the retard. However, in this method, since the EGR control is not executed, the NOx emission amount increases and the noise worsens.

  Therefore, in the present embodiment, the internal EGR control realized by the control of the valve timing of the intake and exhaust valves described above is combined with the retard control of the fuel injection timing. According to such a method, the oxygen concentration in the cylinder is reduced by the execution of the EGR control, but the compression end temperature is increased by supplying the EGR gas having a higher temperature than the external EGR control into the cylinder. be able to. For this reason, as shown by a thick line in FIG. 10, the fuel injection timing can be retarded to the same extent as when EGR control is not performed. In other words, if internal EGR control is combined with retard control of fuel injection timing, the introduction of EGR control can reduce NOx emissions and suppress noise, while ensuring a sufficient retard amount of fuel injection timing. . Since the compression end temperature is increased by internal EGR control, the exhaust temperature can be raised by the increase in the compression end temperature itself, and the fuel injection timing is retarded (torque reduction) because the compression end temperature is high. Accordingly, the fuel injection amount can be greatly increased, so that the exhaust temperature can be raised synergistically to a temperature higher than the light-off temperature (activation temperature) of the catalyst (see FIG. 10). Note that the method of advancing the phase of the exhaust valve 68 as shown in FIG. 9 is a more excellent method in that the exhaust temperature rises because the exhaust valve 68 is quickly opened.

[Features of Embodiment 5]
As described above, the internal EGR control and the retard control of the fuel injection timing are a highly compatible combination for increasing the exhaust temperature while reducing the NOx emission amount and suppressing the noise. Therefore, in the present embodiment, when there is a catalyst temperature increase request in the light load region, the internal EGR control and the retard control of the fuel injection timing are executed in combination, and in this case, in the cylinder The amount of retarded fuel injection was determined according to the amount of internal EGR gas introduced.

[Specific Processing in Embodiment 5]
FIG. 11 is a flowchart of a routine executed by the ECU 50 in the fifth embodiment in order to realize the above function. In the routine shown in FIG. 11, first, whether or not the current actual exhaust temperature is lower than a predetermined determination value, that is, whether or not the operating region of the internal combustion engine 10 is in a light load region where the temperature of the catalyst needs to be raised. Is discriminated (step 500). As a result, when it is determined that the exhaust gas temperature is lower than the predetermined determination value, a series of steps shown below is executed to increase the temperature of the catalyst.

  First, the introduction of external EGR gas is cut (step 502). Next, an internal EGR gas amount necessary to keep the NOx emission amount below a specified value is calculated (step 504). Next, a negative valve overlap amount necessary to obtain such a required internal EGR gas amount is calculated (step 506).

  FIG. 12 is a diagram showing the negative valve overlap amount in relation to the internal EGR gas amount, the compression end temperature, and the retard amount at the fuel injection timing. As shown in FIG. 12, the amount of internal EGR gas increases as the negative valve overlap amount increases. Along with this, the compression end temperature also increases as the negative valve overlap amount increases. The retard amount at the fuel injection timing also increases as the internal EGR gas amount increases, that is, as the negative valve overlap amount increases. Further, since the compression end temperature increases as the fuel injection amount increases, the retard amount at the fuel injection timing also increases as the fuel injection amount increases.

  The ECU 50 stores the relationship between the negative valve overlap amount and the internal EGR gas amount as shown in FIG. 12, and in this step 506, in accordance with such a relationship, a negative value corresponding to the internal EGR gas amount is stored. The valve overlap amount is acquired.

  Next, the retard amount of the fuel injection timing is acquired based on the required valve overlap amount (step 508). The ECU 50 stores the relationship between the negative valve overlap amount as shown in FIG. 12 and the retard amount of the fuel injection timing. In this step 508, the negative valve overlap amount ( The retard amount at the fuel injection timing according to the internal EGR gas amount) is acquired.

  Next, the intake variable valve mechanism 66 and the exhaust variable valve mechanism 70 are driven so that the negative valve overlap amount determined in step 506 is obtained, whereby internal EGR gas is introduced into the cylinder. (Step 510).

  Next, it is determined whether or not a predetermined time has passed to determine that the in-cylinder temperature has increased by a predetermined temperature due to the introduction of the internal EGR gas (step 512). As a result, when it can be determined that the in-cylinder temperature has risen after a predetermined time has elapsed, the fuel injection timing is retarded using the retard amount determined in step 508 (step 514).

  According to the routine shown in FIG. 11 described above, the retard amount of the fuel injection timing is determined according to the negative valve overlap amount, that is, according to the internal EGR gas amount. According to such a method, the amount of retarded fuel injection is appropriately adjusted so that the fuel stability during the retarding of the fuel injection timing is well maintained while reducing the NOx emissions by introducing the internal EGR gas. Can be determined. When an exhaust gas temperature increase request is issued, the amount of internal EGR gas determined as described above is first introduced. Next, the fuel injection timing is retarded by the amount determined as described above, so that the fuel is maintained in a state where the fuel stability is well maintained (a situation where unburned HC emissions and misfires can be reliably prevented). It is possible to execute the retard of the injection timing and further increase the fuel injection amount associated therewith, which makes it possible to raise the exhaust temperature sufficiently and to achieve both reduction of NOx emissions It becomes.

  Further, according to the above routine, the execution of the external EGR control is prohibited when the retard control of the fuel injection timing at a value corresponding to the internal EGR gas amount is executed. Thereby, the introduction of the external EGR gas having a relatively low temperature into the cylinder is cut, so that the effect of increasing the compression end temperature can be improved.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the cross section of one cylinder of the internal combustion engine in the system shown in FIG. FIG. 5 is a P-V diagram showing an enlarged relationship between the in-cylinder pressure P and the in-cylinder volume V in the intake / exhaust stroke. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the characteristic determination method of EX early closing degree X and IN late opening degree Y in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a figure for demonstrating a negative valve overlap. It is the figure which compared the retard limit of fuel injection timing, and the exhaust temperature with and without the introduction of internal EGR control. It is a flowchart of the routine performed in Embodiment 5 of this invention. FIG. 6 is a diagram showing a negative valve overlap amount in relation to an internal EGR gas amount, a compression end temperature, and a retard amount at fuel injection timing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Injector 18 Exhaust passage 24 Exhaust gas purification device 26 Exhaust temperature sensor 28 Intake passage 40 External EGR passage 46 Intake pressure sensor 48 Accelerator opening sensor 50 ECU (Electronic Control Unit)
52 Outside air temperature sensor 62 Crank angle sensor 64 Intake valve 66 Intake variable valve mechanism 68 Exhaust valve 70 Exhaust variable valve mechanism

Claims (5)

An internal combustion engine comprising: an exhaust variable valve mechanism that can change at least the closing timing of the exhaust valve; an intake variable valve mechanism that can change at least the opening timing of the intake valve; and an exhaust purification means that purifies exhaust gas A control device of
A temperature increase request detecting means for detecting a temperature increase request of exhaust gas;
An exhaust valve closing timing determining means for determining an advance amount of the closing timing of the exhaust valve with respect to the top dead center based on the required internal exhaust gas recirculation amount when a temperature increase request of the exhaust gas is detected;
Calculation of predicted exhaust gas temperature for calculating a predicted value of exhaust gas temperature rise when the exhaust valve closing timing is controlled to be the advance amount of the exhaust valve closing timing determined by the exhaust valve closing timing determining means Means,
Whether the exhaust temperature is still insufficient with respect to the target temperature rise even when the exhaust valve closing timing is set so as to be the advance amount of the exhaust valve closing timing based on the predicted value of the exhaust temperature rise Exhaust temperature determination means for determining whether or not,
Wherein when the exhaust temperature to the heating target value is determined not to be missing by the exhaust temperature determining means, the advance of the closing timing of the exhaust valve retard amount of the opening timing of the intake valve with respect to the top dead center was determined to be the amount and the same amount, wherein when the exhaust temperature to the heating target value is determined to be missing still by the exhaust temperature determining means, an exhaust to the heating target value as the temperature is insufficient to determine the retard amount of the opening timing of the exhaust valve closing timing of the advance amount of the intake valve so that the difference increases by subtracting from the retard amount of the opening timing of the intake valve intake Means for determining the valve opening time;
A control device for an internal combustion engine, comprising: An internal combustion engine comprising: an exhaust variable valve mechanism that can change at least the closing timing of the exhaust valve; an intake variable valve mechanism that can change at least the opening timing of the intake valve; and an exhaust purification means that purifies exhaust gas A control device of
A temperature increase request detecting means for detecting a temperature increase request of exhaust gas;
An exhaust valve closing timing determining means for determining an advance amount of the closing timing of the exhaust valve with respect to the top dead center based on the required internal exhaust gas recirculation amount when a temperature increase request of the exhaust gas is detected;
When the exhaust gas temperature rise request is detected, it is equal to or greater than the advance amount at the closing timing of the exhaust valve, and when the exhaust gas temperature rise request is high, it is lower than when it is low. The intake valve opening timing is determined so that the difference obtained by subtracting the advancement amount of the exhaust valve closing timing from the delay amount of the intake valve opening timing with respect to the top dead center becomes large. Means for determining the valve opening time;
A control device for an internal combustion engine, comprising: It further comprises exhaust temperature acquisition means for acquiring the temperature of the exhaust gas,
It said timing determining means opens the intake valve, if the exhaust temperature at the point of time before the temperature increase request of the exhaust gas is detected is not high, as compared with the case where the exhaust temperature is low, advance the opening timing of the intake valve 3. The control apparatus for an internal combustion engine according to claim 1, wherein the control is performed to the corner side. An operation state acquisition means for acquiring the operation state of the internal combustion engine;
The intake valve opening timing determining means corrects the opening timing of the intake valve to the advance side when the operating state of the internal combustion engine at a time point before the exhaust gas temperature increase request is detected is a high load state. 3. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   3. The internal combustion engine according to claim 1, wherein at least one of the advance amount at the closing timing of the exhaust valve and the retard amount at the opening timing of the intake valve is corrected based on an environmental condition surrounding the internal combustion engine. Engine control device.

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