WO2008156157A1

WO2008156157A1 - Torque control system for internal combustion engine

Info

Publication number: WO2008156157A1
Application number: PCT/JP2008/061288
Authority: WO
Inventors: Daichi Imai; Takeshi Hashizume
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-06-21
Filing date: 2008-06-13
Publication date: 2008-12-24
Also published as: JP2009002232A

Abstract

When a compression ignition type internal combustion with a centrifugal supercharger is operated under low atmospheric pressure, a decrease in torque produced by the engine is minimized as much as possible. To achieve this, when the engine is operated under low atmospheric pressure, a fuel injection valve performs after-injection to minimize a decrease in supercharge pressure. In this process, the timing of the after-injection and/or the amount of the after-injection can be feedback-controlled based on a difference between an actual supercharge pressure and a target supercharge pressure.

Description

Technical field of torque control system for internal combustion engine

The present invention relates to a technique for controlling the torque of an internal combustion engine, and more particularly to a technique for suppressing a decrease in torque under low atmospheric pressure. Background art

Light

When an internal combustion engine equipped with a centrifugal supercharger (turbocharger) is operated under low atmospheric pressure (eg, high altitude), the supercharging pressure is difficult to reach the target supercharging pressure. For this reason, there is a possibility that the torque generated by the internal combustion engine will not reach the required torque.

On the other hand, Japanese Patent Application Laid-Open No. 2006-29279 discloses a technique for suppressing a decrease in the output of an internal combustion engine by adjusting a target supercharging pressure based on an actual air density.

Japanese Patent Application Laid-Open No. 8-303290 discloses a technique for performing sub fuel injection after main fuel injection (first half of the expansion stroke) when the exhaust gas temperature is lower than a predetermined temperature.

In Japanese Patent Laid-Open No. 2004-28030, when the sub fuel injection is performed after the main fuel injection (the period from the expansion stroke to the exhaust stroke), the amount of the sub injection is determined based on the measured value of the exhaust temperature sensor. Japanese Laid-Open Patent Publication No. 2004-162675, which discloses a technique for feedback control of timing, discloses a technique for increasing the amount of EGR gas and performing sub fuel injection after main fuel injection when the exhaust gas temperature is low. It is disclosed.

Japanese Patent Laid-Open No. 2005-54607 discloses that when the exhaust gas temperature is lower than a predetermined temperature, the valve opening timing of the exhaust valve is advanced, and after the main fuel injection and before the valve opening timing of the exhaust valve. A technique for performing sub fuel injection is disclosed.

Japanese Patent Laid-Open No. 2005-291 1 75 discloses that when the sub fuel injection is performed after the main fuel injection, the capacity of the variable displacement turbocharger is increased and / or the opening of the waste gate valve is increased. Technology is disclosed. Disclosure of the invention

By the way, the exhaust energy decreases as the atmospheric pressure decreases. For this reason, even if the technique disclosed in Japanese Patent Laid-Open No. 2006-29279 is used, the output of the centrifugal supercharger may decrease. As a result, the boost pressure may not increase to the target boost pressure. In such a case, the internal combustion engine cannot generate the required torque. On the other hand, a method of increasing exhaust energy by retarding the fuel injection timing is also conceivable. However, the increase in exhaust energy due to the retarded fuel injection timing is slight. There is also a concern that the torque generated by the internal combustion engine may decrease due to the retarded fuel injection timing.

An object of the present invention is to provide a technology capable of suppressing a torque decrease due to a decrease in atmospheric pressure as much as possible in a torque control system for an internal combustion engine equipped with a centrifugal supercharger (turbocharger).

In order to solve the above-mentioned problems, the present invention performs after injection from a fuel injection valve when a compression ignition type internal combustion engine equipped with a centrifugal supercharger is operated under low atmospheric pressure. The exhaust energy is increased without causing a decrease in torque of the internal combustion engine.

Specifically, the present invention relates to a torque control system for a compression ignition type internal combustion engine equipped with a centrifugal supercharger, an acquisition means for acquiring atmospheric pressure, and an atmospheric pressure acquired by the acquisition means is a standard atmospheric pressure ( And a control means for performing after-injection from the fuel injection valve when the pressure is lower than 1 atm).

According to the knowledge of the present inventor, the amount of increase in exhaust energy due to after injection greatly exceeds the amount of increase in exhaust energy due to retardation of the main injection timing. For this reason, if after-injection is performed when the internal combustion engine is operated under a low atmospheric pressure such as a high altitude, a decrease in the output of the centrifugal supercharger can be suppressed.

Therefore, the actual supercharging pressure cannot be separated from the target supercharging pressure. As a result, it is possible to prevent the generated torque of the internal combustion engine from becoming excessively lower than the required torque. That is, when the internal combustion engine is operated under a low atmospheric pressure, it is possible to suppress as much as possible a decrease in torque generated by the internal combustion engine.

The after injection amount and / or the after injection timing may be determined according to the atmospheric pressure acquired by the acquisition means. Exhaust energy decreases with decreasing atmospheric pressure. On the other hand, the exhaust energy increases as the after injection amount and the retard amount of the after injection timing increase. Therefore, as the atmospheric pressure acquired by the acquisition means becomes lower, the after injection amount and / or the retard amount of the after injection timing may be increased.

The torque control system for an internal combustion engine according to the present invention may further comprise first detection means for detecting the pressure of the intake air supercharged by the centrifugal supercharger. In this case, the control means may increase the after-injection amount and / or retard the after-injection timing as the pressure detected by the first detecting means becomes lower than the target boost pressure. Yo!

The exhaust energy of the internal combustion engine increases as the after injection amount increases and / or as the after injection timing is retarded. For this reason, if the after injection amount and the retard amount of the after injection timing increase as the actual boost pressure becomes lower than the target boost pressure, the actual boost pressure approximates the target boost pressure. It is possible to let Become.

In addition, when combining the change of the after-injection amount and the change of the after-injection time, it is preferable to give priority to the retard of the after-injection timing over the increase in the after-injection amount. This is because an increase in after-injection amount causes a deterioration in fuel consumption.

For example, when the actual boost pressure is lower than the target boost pressure, the control means first delays the after injection timing while keeping the after injection quantity constant. If the actual boost pressure does not increase to the target boost pressure even if the retard amount of the after injection timing reaches the limit, the control means may increase the after injection amount.

Further, when the difference between the actual boost pressure and the target boost pressure is not more than a predetermined value, the control means may increase the exhaust energy by retarding the after injection timing. On the other hand, when the difference between the actual supercharging pressure and the target supercharging pressure exceeds a predetermined value, the control means is based on the increase in the after injection amount (or the increase in the after injection amount and the delay in the after injection timing). You can try to increase the exhaust energy.

In this way, if the delay of the after injection timing is prioritized over the increase in the after injection amount, the increase in fuel consumption can be minimized as much as possible.

Next, the internal combustion engine torque control system according to the present invention may further include second detection means for detecting the temperature of the atmosphere. In this case, the control means may decrease the retard amount of the after injection timing as the temperature detected by the second detection means becomes lower.

When the atmospheric temperature is low, after-injected fuel (hereinafter referred to as “after-injected fuel”) tends to misfire. This phenomenon becomes more prominent as the after injection timing is retarded. Therefore, if the after injection timing is significantly retarded when the atmospheric temperature is low, the amount of unburned fuel discharged from the internal combustion engine increases. On the other hand, if the retard amount of the after injection timing is limited to a lower level as the atmospheric temperature becomes lower, misfire of the after-injected fuel can be prevented.

Also, if the after-injection amount is increased when the ambient temperature is low, the amount of fuel discharged into the exhaust system will remain unburned. Therefore, when the atmospheric temperature is low, it is preferable that the increase amount of the after-injection amount is limited to be small. Brief Description of Drawings

FIG. 1 is a diagram showing a schematic configuration of a torque control system for an internal combustion engine.

Figure 2 shows the correlation between atmospheric pressure and supercharging pressure.

FIG. 3 is a diagram showing the correlation between the main injection timing and the exhaust temperature.

Fig. 4 shows the correlation between after injection timing and exhaust temperature.

FIG. 5 is a flowchart showing a torque control routine in the first embodiment.

FIG. 6 is a diagram showing a map for determining the basic after injection timing. FIG. 7 is a flowchart showing the feedback control routine in the first embodiment. Yat.

FIG. 8 is a diagram showing a map for determining the feedback correction coefficient in the first embodiment.

FIG. 9 is a diagram showing a map for determining the retard angle limit value of the after injection timing.

FIG. 10 is a graph showing the correlation between the after injection amount and the exhaust temperature.

FIG. 11 is a flowchart showing a torque control routine in the second embodiment.

FIG. 12 is a diagram showing a map for determining the basic after-injection amount. FIG. 13 is a flowchart showing a feedback control routine in the second embodiment.

FIG. 14 is a diagram showing a map for determining the feedback correction coefficient in the second embodiment.

Fig. 15 is a diagram showing a map for determining the upper limit amount of the after-injection amount

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a torque control system for an internal combustion engine according to the present invention. An internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) having a plurality of cylinders. Each cylinder 2 of the internal combustion engine 1 is provided with a fuel injection valve 3 that can inject fuel directly into each cylinder 2. The fuel injection valve 3 injects fuel boosted in the common rail 30 into the cylinder 2.

An intake passage 4 communicates with each cylinder 2. In the middle of the intake passage 4, a compressor housing 50 and an intercooler 6 of a centrifugal supercharger (turbocharger) 5 are arranged. An intake throttle valve 7 is provided in the intake passage 4 downstream of the intercooler 6. In addition, an exhaust passage 8 communicates with each cylinder 2. In the middle of the exhaust passage 8, a turbine housing 5 1 of the turbocharger 5 and an exhaust purification device 9 are arranged.

Air (intake air) drawn into the intake passage 4 is compressed by the compressor housing 50. The intake air compressed by the compressor housing 50 is cooled by the intercooler 6 and then introduced into each cylinder 2. The intake air introduced into each cylinder 2 is ignited and burned in the cylinder 2 together with the fuel injected from the fuel injection valve 3. The gas burned in the cylinder 2 (burned gas) is discharged to the exhaust passage 8. The exhaust discharged into the exhaust passage 8 is discharged into the atmosphere via the turbine housing 51 and the exhaust purification device 9. The internal combustion engine 1 has an EGR (Exhaust Gas Recirculation) mechanism. The EGR mechanism changes the cross-sectional area of the EGR passage 10 and EGR passage 10 that guide part of the exhaust from the exhaust passage 8 upstream from the turbine housing 51 to the intake passage 4 downstream from the intercooler 6. EG R EGR cooler 12 that cools the exhaust gas (high pressure EGR gas) flowing through valve 11 and EGR passage 10 is provided.

The internal combustion engine 1 configured as described above is provided with an ECU 13. The ECU 13 is an electronic control unit composed of a CPU, ROM, RAM, knock-up RAM, and the like. Various sensors such as an air flow meter 14, an intake air temperature sensor 15, an intake air pressure sensor 16, a crank position sensor 17 and an atmospheric pressure sensor 18 are electrically connected to the ECU 13.

The air flow meter 14 is disposed in the intake passage 4 upstream from the compressor housing 50 and measures the amount of air flowing into the intake passage 4 from the atmosphere. The intake air temperature sensor 15 is disposed in the intake passage 4 near the air flow meter 14 and measures the temperature of the air flowing into the intake passage 4 from the atmosphere. The intake pressure sensor 16 is disposed in the intake passage 4 downstream of the intake throttle valve 7 and measures the pressure in the intake passage 4 (internal pressure). The crank position sensor 17 measures the rotational position of the crankshaft of the internal combustion engine 1. The atmospheric pressure sensor 18 measures atmospheric pressure.

The atmospheric pressure sensor 18 is an embodiment of the acquisition means according to the present invention. The intake pressure sensor 16 is an embodiment of the first detection means according to the present invention. The intake air temperature sensor 15 is an embodiment of the second detection means according to the present invention.

The ECU 17 performs known fuel injection control and EGR control based on the measured values of the various sensors described above, and performs torque control that is the gist of the present invention. Hereinafter, torque control in this embodiment will be described.

When the internal combustion engine 1 is operated under a low atmospheric pressure such as a high altitude, the generated torque of the internal combustion engine 1 may be lower than the required torque. This is thought to be due to the fact that the intake supercharging pressure falls below the target intake pressure due to a decrease in atmospheric pressure.

Figure 2 shows the relationship between atmospheric pressure and supercharging pressure. The supercharging pressure shown in Fig. 2 was measured under conditions where conditions other than atmospheric pressure were equivalent. In Fig. 2, the supercharging pressure decreases as the atmospheric pressure decreases. Therefore, when the internal combustion engine 1 is operated under an atmospheric pressure lower than the standard atmospheric pressure, the generated torque of the internal combustion engine 1 decreases due to a decrease in the supercharging pressure.

On the other hand, in the torque control of this embodiment, when the measured value of the atmospheric pressure sensor 18 is lower than the standard atmospheric pressure, the exhaust energy of the internal combustion engine 1 is increased to suppress the decrease in the supercharging pressure. .

As a method of increasing the exhaust energy of the internal combustion engine 1, a method of retarding the main injection timing of the fuel injection valve 3 can be considered. By the way, as shown in Fig. 3, the amount of increase in exhaust temperature due to the delay of the main injection timing is small. For this reason, in order to increase the exhaust temperature significantly, it is necessary to significantly retard the main injection timing. However, if the main injection timing is significantly retarded, fuel can misfire. If the fuel is misfired, the exhaust temperature and the torque generated by the internal combustion engine 1 decrease. Further, the amount of unburned fuel discharged from the internal combustion engine 1 may increase. Therefore, in the torque control of this embodiment, the ECU 13 performs after injection without retarding the main injection timing when the internal combustion engine 1 is operated under low atmospheric pressure.

FIG. 4 is a graph showing the relationship between the after injection timing and the exhaust temperature when the after injection amount is constant. Point X in FIG. 4 indicates the exhaust temperature when the after injection is not performed (hereinafter referred to as “base exhaust temperature”).

As shown in FIG. 4, when the fuel injection valve 3 performs the after injection after the main injection, the unburned residue of the main injected fuel burns together with the after injected fuel. As a result, the exhaust temperature rises significantly above the base exhaust temperature. The amount of increase in exhaust temperature at that time increases as the after injection timing is retarded.

Therefore, it is desirable that the ECU 13 delays the after injection timing as the measured value (atmospheric pressure) of the atmospheric pressure sensor 18 becomes lower. When the after injection timing is determined in this way, the decrease in supercharging pressure due to the decrease in atmospheric pressure is suppressed. As a result, the generated torque of the internal combustion engine 1 does not significantly decrease under low atmospheric pressure.

Further, E C U 13 may perform feedback control of the after injection timing based on the actual supercharging pressure (measured value of the intake pressure sensor 16) after execution of the after injection. In other words, the ECU 1 3 corrects the after injection timing so that the actual boost pressure after the after injection is executed (hereinafter referred to as “actual boost pressure”) matches the target boost pressure. Good.

Specifically, E C U 13 increases and corrects the retard amount of the after injection timing when the actual boost pressure after execution of the after injection is lower than the target boost pressure. On the other hand, if the actual supercharging pressure after execution of after injection is higher than the target supercharging pressure, E C U 13 may correct the amount of retard of the after injection timing by decreasing. The correction amount at that time is preferably determined according to the difference between the actual boost pressure and the target boost pressure.

As described above, when the after-injection timing is feedback controlled in accordance with the difference between the actual supercharging pressure and the target supercharging pressure, the difference between the actual supercharging pressure and the target supercharging pressure becomes as small as possible. As a result, the difference between the generated torque of the internal combustion engine 1 and the required torque becomes as small as possible. By the way, if the after-injection timing is significantly retarded when the intake air temperature (atmospheric temperature) is low, the after-injected fuel may misfire. If the after-injected fuel misfires, the amount of unburned fuel emitted from the internal combustion engine 1 increases. As a result, exhaust emissions may increase.

Therefore, it is preferable that the retard amount of the after injection timing is limited by a retard angle limit value (guard value) corresponding to a measured value (atmospheric temperature) of the intake air temperature sensor 15. If the retard amount of the after injection timing is limited in this way, it becomes possible to increase exhaust energy as much as possible while avoiding deterioration of exhaust emission. Hereinafter, the execution procedure of torque control in the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing a torque control routine. The torque control routine is stored in advance in the ROM of the ECU 13 and is periodically executed by the ECU 13.

In the torque control routine of FIG. 5, the ECU 13 first executes the process of S101. In S 101, the ECU 13 reads the measured value (atmospheric pressure) AP of the atmospheric pressure sensor 18.

In S102, the ECU 13 determines whether or not the atmospheric pressure AP read in S101 is lower than the standard atmospheric pressure SAP. If a negative determination is made in S102 (AP = SAP), the ECU 13 ends the execution of this routine. On the other hand, if an affirmative determination is made in S102 (AP <SAP), the process proceeds to S103.

In S103, the ECU 13 determines the basic after-injection timing T ain j b (CAATDC) using the atmospheric pressure AP read in S101 as a parameter. At that time, the ECU 13 may determine the basic after-injection period Tai j b based on a map as shown in FIG. The map shown in Fig. 6 shows that when the atmospheric pressure AP is the standard atmospheric pressure SAP, after-injection is not performed, and when the atmospheric pressure AP is lower than the standard atmospheric pressure SAP, the lower the atmospheric pressure AP, the lower the basic after-injection timing Tainjb. Is set to be retarded.

In S104, the ECU 13 calculates a feedback correction coefficient Δ ひ. Specifically, ECU 1 3 calculates the feedback correction coefficient delta _alpha based on the feedback control routine as shown in FIG.

In the feedback control routine, the ECU 13 first executes the process of S201. In S201, the ECU 13 determines whether or not the after injection is being executed. If a positive determination is made in S201, the ECU 13 proceeds to S202.

In S 202, E C U 1 3 reads the measured value (actual boost pressure) C P of the intake pressure sensor 16.

In S203, the ECU 13 determines whether or not the actual boost pressure CP read in S202 is lower than the target boost pressure CPrtg. If an affirmative determination is made in S203 (CP <CPtrg), the ECU 13 proceeds to S204.

In S204, the ECU 13 calculates the feedback correction coefficient Δα based on the difference between the target boost pressure CP tr rg and the actual boost pressure CP (= CP tr rg−CP). For example, the ECU 13 may obtain the feedback correction coefficient Δα based on a map as shown in FIG. The map shown in FIG. 8 is determined such that the feedback correction coefficient Δα becomes larger as the difference between the target boost pressure CP tr g and the actual boost pressure CP (= CP tr g_CP) increases.

If a negative determination is made in S201 or S203, the ECU 13 sets the feedback correction coefficient Δα to “0” in S205. Returning to the torque control routine of FIG. 5, the ECU 13 corrects the basic after-injection timing Tainjb in S105 by the feedback correction coefficient Δ «calculated in S104. Specifically, the ECU 13 adds the feedback correction coefficient to the basic after injection timing Tainjb.

In S106, the ECU 1 3 detects the measured value of the intake air temperature sensor 15 (atmospheric temperature) Tm pa ¾rgjc: Ι ¾_Ρ ₀

In S107, the ECU 13 obtains a retard limit value (upper limit value of the retard amount) Tma X (CAA TDC) of the after injection timing based on the atmospheric temperature Tm pa read in S106. At that time, the ECU 13 may determine the retardation limit value Tma X based on a map as shown in FIG. The map shown in Fig. 9 is set so that the retard angle limit value Tmax becomes smaller (the retard amount decreases) as the atmospheric temperature Tmp a becomes lower. It is preferable that the relationship between the retardation limit value Tma X and the atmospheric temperature Tmp a is experimentally obtained in advance.

In S 108, E C U 13 compares the basic after-injection period T a iin j b obtained in S 105 with the retardation limit value Tma x obtained in S 107. That is, the ECU 13 determines whether or not the basic after injection timing T ainjb is less than or equal to the retard limit value Tma X (in other words, the basic after injection timing Tainjb is before the retard limit value Tma X). Whether or not).

If an affirmative determination is made in S 108 (T a i n j b ≤ Tma X), the ECU 13 proceeds to S 109. In S 109, E C U 13 determines the basic after-injection time Tainjb obtained in S105 as the after-injection time Tainj.

On the other hand, when a negative determination is made in S 108 (T a i n j b> Tmax), E C U 13 proceeds to S 1 10. In S 110, E C U 13 determines the retard angle limit value Tmax obtained in S 107 as the after injection timing T a i n j. Thus, the control means according to the present invention is realized by the ECU 13 executing the routines of FIGS. Therefore, according to the present embodiment, when the internal combustion engine 1 is operated under a low atmospheric pressure such as a high altitude, it is suppressed that the boost pressure of the intake air is significantly reduced from the target boost pressure. As a result, the generated torque of the internal combustion engine 1 does not drop significantly from the required torque. Further, since the retard amount of the after injection timing is limited according to the atmospheric temperature Tmp a, it is possible to prevent the deterioration of exhaust emission due to the decrease in the atmospheric temperature Tmp a.

In this embodiment, when the internal combustion engine 1 is operated under a low atmospheric pressure, an example in which after-injection is performed without delaying the main injection period has been described. However, torque is increased by delaying the after-injection timing. If it is not possible to compensate for this drop, the delay of the main injection timing may be used together.

Example 2>

Next, a second embodiment of the present invention will be described with reference to FIGS. This Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

In the first embodiment described above, an example in which the actual boost pressure is brought close to the target boost pressure by changing the after injection timing according to the atmospheric pressure has been described. In contrast, in this example, an example in which the actual boost pressure is brought close to the target boost pressure by changing the after-injection amount according to the atmospheric pressure will be described.

FIG. 10 is a graph showing the relationship between the after-injection amount and the exhaust temperature when the after-injection timing is constant. Point Y in Fig. 10 indicates the exhaust temperature (base exhaust temperature) when after-injection is not performed.

As shown in FIG. 10, the amount of increase in the exhaust gas temperature due to after-injection increases as the after-injection amount increases. Therefore, when the after-injection amount increases as the measured value (atmospheric pressure) of the atmospheric pressure sensor 18 decreases, the decrease in the supercharging pressure due to the decrease in atmospheric pressure is suppressed. As a result, the generated torque of the internal combustion engine 1 does not drop significantly at low atmospheric pressure.

Further, E C U 13 may perform feedback control of the after injection amount based on the actual supercharging pressure after the execution of after injection. That is, E C U 13 may correct the after-injection amount so that the actual boost pressure after the after injection is executed matches the target boost pressure.

Specifically, E C U 13 may correct the increase in the after injection amount when the actual boost pressure after the after injection is performed is lower than the target boost pressure. On the other hand, if the actual supercharging pressure after execution of after injection is higher than the target supercharging pressure, E C U 13 may correct the after injection amount to decrease. The amount of correction at that time is preferably increased as the difference between the actual boost pressure and the target boost pressure increases.

Thus, when the after-injection amount is feedback controlled according to the difference between the actual boost pressure and the target boost pressure, the difference between the actual boost pressure and the target boost pressure becomes as small as possible. As a result, the difference between the generated Tonlek and the required Tonlek of the internal combustion engine 1 becomes as small as possible.

The after-injection amount can be minimized.

By the way, if the after-injection amount is significantly increased when the intake air temperature (atmospheric temperature) is low, the after-injected fuel cannot be burned and is easily discharged from the internal combustion engine 1 without being burned. As a result, the exhaust emission of the internal combustion engine 1 may increase. For this reason, it is preferable that the after-injection amount is limited by the upper limit amount corresponding to the measured value (atmospheric temperature) of the intake air temperature sensor 15. If the after-injection amount is limited in this way, it is possible to increase exhaust energy as much as possible while avoiding deterioration of exhaust emission.

Hereinafter, the execution procedure of torque control in the present embodiment will be described with reference to FIG. FIG. 11 is a flowchart showing a torque control routine. In FIG. 11, the same reference numerals are assigned to the same processes as those in the torque control routine (see FIG. 5) of the first embodiment described above. In the torque control routine of FIG. 11, the ECU 13 proceeds to S301 when an affirmative determination is made in S102. In S 301, the ECU 13 calculates the basic after-injection amount Q ainjb using the atmospheric pressure AP read in S 101 as a parameter. At that time, the ECU 13 may determine the basic after-injection amount Qa injb based on a map as shown in FIG. The map shown in Fig. 12 shows that when the atmospheric pressure AP is the standard atmospheric pressure SAP, after-injection is not performed. When the atmospheric pressure AP is lower than the standard atmospheric pressure SAP, the lower the atmospheric pressure AP, the lower the basic after-injection amount Q. It is determined that ainjb increases.

The ECU 13 proceeds to S302 after executing S301. In S302, the ECU 13 calculates a feedback correction coefficient Δ] 3. Specifically, the ECU 13 calculates a feedback correction coefficient Δ] 3 based on a feedback control routine as shown in FIG. In FIG. 13, the same processes as those in the feedback control routine (see FIG. 7) of the first embodiment described above are denoted by the same reference numerals. In the feed pack control routine, the ECU 13 proceeds to S 401 when an affirmative determination is made in S 203. In S 401, the ECU 13 calculates a feedback correction coefficient based on the difference between the target boost pressure CPrtg and the actual boost pressure CP (= CPtrg_CP). For example, the ECU 13 may obtain the feedback correction coefficient Δ] 3 based on a map as shown in FIG. The map shown in FIG. 14 is determined such that the feedback correction coefficient Δ] 3 becomes larger as the difference between the target boost pressure CP trg and the actual boost pressure CP (= CP tr g-CP) increases. .

Further, if the negative determination is made in S201 or S203, the ECU 13 proceeds to S402. In S 402, the ECU 13 sets the feedback correction coefficient Δ] 3 to “0”.

Returning to the torque control routine of FIG. 11, the ECU 13 corrects the basic after-injection amount Q a i n j b in S 303 by the feedback correction coefficient Δ] 3 calculated in S 302. Specifically, the ECU 13 adds a feedback correction coefficient Δ; 3 to the basic after-injection amount Q a i n j b.

When the ECU 13 executes the process of S303, the ECU 13 proceeds to S106. Next, the EC U13 proceeds to S304 after executing the process of S106.

In S 304, the ECU 13 obtains the upper limit amount Q a ma X of the after injection amount based on the atmospheric temperature Tm pa read in S 106. At that time, the ECU 13 may determine the upper limit amount Q a max based on a map as shown in FIG. The map shown in Fig. 15 is set so that the upper limit amount Q a ma X decreases as the atmospheric temperature Tmp a decreases. It should be noted that the relationship between the upper limit amount Q a ma X and the atmospheric temperature Tmp a is preferably obtained experimentally in advance.

When the ECU 13 finishes executing the process of S304, the ECU 13 proceeds to S305. In S 305, the ECU 13 compares the basic after-injection amount Q ainjb obtained in S 303 with the upper limit amount Q am ax obtained in S 304. That is, ECU 13 determines whether or not the basic after-injection amount Q ainjb is less than or equal to the upper limit amount Q amax. '

When an affirmative determination is made in S 305 (Q a i n j b ≤ Q a ma X), the ECU 13 proceeds to S 306. In S 306, the ECU 13 determines the basic after-injection amount Q a i n j b obtained in S 303 as the after-injection amount Q a i n j.

On the other hand, if a negative determination is made in S 305 (Qa i n j b> Qama x), E C U 13 proceeds to S 307. In S 307, E C U 13 determines the upper limit amount Q a max obtained in S 30 4 as the after injection amount Q a i n j.

When the ECU 13 executes the routines of FIGS. 11 and 13 in this way, when the internal combustion engine 1 is operated under a low atmospheric pressure such as a high altitude, the intake supercharging pressure is significantly reduced from the target supercharging pressure. Disappear. As a result, the generated torque of the internal combustion engine 1 does not drop significantly from the required torque. In addition, since the after-injection amount is limited according to the atmospheric temperature Tmp a, it is possible to prevent the exhaust emission from deteriorating.

The first and second embodiments described above can be combined as much as possible. At this time, it is preferable that the ECU 13 increases the supercharging pressure only by retarding the after injection timing as much as possible.

For example, when the actual boost pressure is lower than the target boost pressure stage, the ECU 13 first retards the after injection timing while keeping the after injection quantity constant. If the actual boost pressure does not increase to the target boost pressure even when the after injection timing reaches the retard limit value, the ECU 13 may increase the after injection amount.

In addition, when the difference between the actual boost pressure and the target boost pressure is less than the predetermined value, the ECU 13 increases the actual boost pressure only by retarding the after injection timing. When the difference from the pressure exceeds a predetermined value, the actual supercharging pressure may be increased by increasing the after injection amount.

In this way, when the retard of the after-injection timing is prioritized over the increase in after-injection amount, it is possible to suppress as much as possible the deterioration of fuel consumption due to the execution of after-injection.

Note that the ECU 19 may delay the main injection timing when the decrease in torque cannot be compensated for by the delay of the after injection timing and the increase in the after injection amount.

Claims

The scope of the claims

1. In a torque control system of a compression ignition internal combustion engine equipped with a centrifugal supercharger, an acquisition means for acquiring atmospheric pressure;

Control means for performing after injection from the fuel injection valve when the atmospheric pressure acquired by the acquisition means is lower than the standard atmospheric pressure;

A torque control system for an internal combustion engine, comprising:

2. The control unit according to claim 1, wherein the control unit increases the after-injection amount and / or retards the after-injection timing as the atmospheric pressure acquired by the acquiring unit becomes lower than the standard atmospheric pressure. A torque control system for an internal combustion engine.

3. In claim 1 or 2, further comprising first detection means for detecting the pressure of the intake air compressed by the centrifugal supercharger,

The torque control system for an internal combustion engine, wherein the control means increases the after-injection amount as the pressure detected by the first detection means becomes lower than a target boost pressure.

4. In claim 1 or 2, further comprising first detection means for detecting the pressure of the intake air compressed by the centrifugal supercharger,

The torque control system for an internal combustion engine, wherein the after-injection timing is retarded as the pressure detected by the first detection means becomes lower than the target boost pressure.

5. In claim 1 or 2, further comprising first detection means for detecting the pressure of the intake air compressed by the centrifugal supercharger,

The control means increases the after-injection amount and increases the retard amount of the after-injection timing as the pressure detected by the first detecting means becomes lower than the target boost pressure. Torque control system for internal combustion engines.

6. In any one of claims 2, 4, and 5, further comprising second detection means for detecting the temperature of the atmosphere,

The torque control system for an internal combustion engine, wherein the control means decreases the retard amount of the after-injection timing as the temperature detected by the second detection means becomes lower.

7. In any one of claims 2, 3, and 5, further comprising a second detection means for detecting the temperature of the atmosphere, The internal combustion engine torque control system characterized in that the control means decreases the increase amount of the after-injection amount as the temperature detected by the second detection means becomes lower.