JP2008121494A - Controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of an internal combustion engine capable of surely suppressing the instability of burning when a vehicle travels on high altitudes. <P>SOLUTION: The penetrating force of a fuel spray is relatively increased, and the amount of adhesion of the fuel to the wall surface of a combustion chamber is increased since cylinder pressures (pressures at the ends of compressions) are lowered at high altitudes. Therefore, the combustion becomes instable. The instability of combustion is compensated by combining the reduction of a fuel injection pressure with the increase of an internal EGR amount. First, the fuel injection pressure is lowered according to the lowering of the atmospheric pressure. When the atmospheric pressure is further lowered, the increase of the internal EGR amount is combined therewith. The fuel injection pressure and the internal EGR amount are controlled according to the atmospheric pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  When traveling on high altitudes with a vehicle equipped with a diesel engine, the following problems may occur. Since the atmospheric pressure is low at high altitudes, the pressure of the air sucked into the cylinder is lowered, and the compression end pressure is also lowered. If it does so, the penetration force of the fuel spray injected in the cylinder will become relatively large. For this reason, since fuel spray spreads too much and collides with a combustion chamber wall surface, fuel becomes easy to adhere to a combustion chamber wall surface. As a result, the air-fuel mixture is less likely to be generated satisfactorily and combustion tends to become unstable. In particular, at the time of a light load or an idling state where the fuel injection amount is small, the in-cylinder atmosphere temperature is low, so that the fuel spray is hardly easily vaporized. For this reason, combustion tends to be particularly unstable at light loads in high altitude or at idle (hereinafter referred to as “high altitude light loads”). When the combustion fluctuation increases, misfire or torque fluctuation occurs, or the HC emission amount increases.

  Japanese Patent Application Laid-Open No. 6-299894 discloses a fuel injection control device in which the fuel injection pressure is reduced as the atmospheric pressure decreases. When the fuel injection pressure is lowered, the penetration force of the fuel spray is suppressed, so that the fuel wall surface adhesion can be suppressed.

  Japanese Patent Application Laid-Open No. 2000-120457 discloses a technique for controlling the internal EGR amount and evading misfire by variably controlling the closing timing of the intake valve and the exhaust valve according to the atmospheric pressure. .

JP-A-6-299894 JP 2000-120457 A JP 2002-129991 A JP 2003-286879 A

  However, as the altitude increases, it is actually possible to sufficiently improve combustion instability at high altitudes and light loads only with one of the method of reducing the fuel injection pressure and the method of controlling the internal EGR amount. It can be difficult. Further, when the internal EGR amount is controlled by controlling the closing timing of the intake valve and the exhaust valve, there is a problem that the fuel consumption is likely to deteriorate due to an increase in pump loss or the like.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a control device for an internal combustion engine that can reliably suppress the instability of combustion during traveling at a high altitude.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
First atmospheric pressure reduction compensation means for compensating the influence of the decrease in atmospheric pressure on the combustion stability by changing the fuel injection conditions;
A second atmospheric pressure lowering compensation means for compensating for the influence of the lowering of the atmospheric pressure on the combustion stability by increasing the internal EGR amount;
Control means for controlling the compensation amount by the first atmospheric pressure decrease compensation means and the compensation amount by the second atmospheric pressure drop compensation means based on atmospheric pressure;
It is characterized by providing.

The second invention is the first invention, wherein
The first atmospheric pressure decrease compensation means performs at least one of decreasing the fuel injection pressure in response to a decrease in atmospheric pressure and increasing the number of fuel injections in one cycle in response to a decrease in atmospheric pressure. Thus, it is characterized in that the influence of the decrease in the atmospheric pressure on the combustion stability is compensated.

The third invention is the first or second invention, wherein
The control means executes the compensation by the first atmospheric pressure decrease compensating means in preference to the compensation by the second atmospheric pressure reduction compensating means.

According to a fourth invention, in any one of the first to third inventions,
The control means executes compensation by the first atmospheric pressure decrease compensation means without executing compensation by the second atmospheric pressure decrease compensation means in a range where the atmospheric pressure decrease amount is relatively small, and further increases the atmospheric pressure decrease amount. When the pressure drop amount becomes large, the compensation by the second atmospheric pressure drop compensation means starts to be executed.

According to a fifth invention, in any one of the first to fourth inventions,
When the internal EGR amount is increased by the second atmospheric pressure decrease compensation means, the smoke emission amount may exceed the allowable level, and the internal EGR amount is further increased to suppress the combustion temperature and soot generation. It is further characterized by further comprising a low-temperature combusting means for lowering the temperature to be lower than or equal to the temperature.

According to a sixth invention, in any one of the first to fifth inventions,
The control means includes
In-cylinder gas viscosity required value calculation means for calculating a required value of in-cylinder gas viscosity based on the atmospheric pressure and the fuel injection pressure;
A required internal EGR amount calculating means for calculating a required internal EGR amount based on the in-cylinder gas viscosity required value;
The internal EGR amount is controlled based on the required internal EGR amount.

  According to the first aspect of the present invention, the effect of the decrease in the atmospheric pressure on the combustion stability is compensated by combining the change in the fuel injection conditions and the increase in the internal EGR amount. Based on this, it can be controlled appropriately. For this reason, it is possible to reliably avoid instability of combustion in a high altitude with a low atmospheric pressure, and to reduce adverse effects such as deterioration of fuel consumption as much as possible.

  According to the second invention, as changes in the fuel injection conditions, the fuel injection pressure is decreased in accordance with a decrease in atmospheric pressure, and the number of fuel injections in one cycle is increased in accordance with a decrease in atmospheric pressure. Do at least one. Thereby, since the penetration force of fuel spray can be made small, the fuel adhesion to a combustion chamber wall surface can be suppressed, and it can prevent that fuel spray spreads excessively. For this reason, the influence which the fall of atmospheric pressure has on combustion stability can be compensated effectively.

  According to the third aspect of the invention, the atmospheric pressure compensation by changing the fuel injection condition can be executed with priority over the atmospheric pressure compensation by increasing the internal EGR amount. An increase in the internal EGR amount is accompanied by a loss such as a pump loss, whereas a change in the fuel injection condition hardly involves a loss. For this reason, by executing the atmospheric pressure compensation by changing the fuel injection condition in preference to the atmospheric pressure compensation by increasing the internal EGR amount, the deterioration of fuel consumption is minimized in order to stabilize combustion at high altitudes. be able to.

  According to the fourth invention, in a range where the atmospheric pressure decrease amount is relatively small, the atmospheric pressure compensation by changing the fuel injection condition is executed without executing the atmospheric pressure compensation by increasing the internal EGR amount, and further the atmospheric pressure When the decrease amount becomes large, the atmospheric pressure compensation by increasing the internal EGR amount is started to be executed. Thereby, according to the atmospheric pressure decrease amount, combustion can be reliably stabilized, and deterioration of fuel consumption can be minimized.

  According to the fifth aspect of the present invention, when there is a risk that the smoke emission amount may exceed the allowable level due to the atmospheric pressure compensation due to the increase in the internal EGR amount, the combustion temperature is generated by further increasing the internal EGR amount. It is possible to perform low temperature combustion by lowering the temperature to below the temperature at which the above is suppressed. Thereby, in order to stabilize combustion at high altitudes, smoke emission can be more reliably suppressed.

  According to the sixth invention, when the atmospheric pressure compensation is performed by increasing the internal EGR amount, the required value of the in-cylinder gas viscosity is calculated based on the atmospheric pressure and the fuel injection pressure, and the in-cylinder gas viscosity required value is calculated. The required internal EGR amount can be calculated based on the internal EGR amount, and the internal EGR amount can be controlled based on the required internal EGR amount. As a result, an optimum internal EGR amount necessary and sufficient for stabilizing combustion at high altitudes can be calculated, so that deterioration in fuel consumption accompanying an increase in internal EGR can be minimized.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

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 a four-cycle diesel engine 10. It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source. Although the diesel engine 10 of the present embodiment is an in-line four-cylinder type, the number of cylinders and the cylinder arrangement of the diesel engine in the present invention are not limited to this.

  Each cylinder of the diesel engine 10 is provided with an injector 12 that injects fuel directly into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. In the common rail 14, high-pressure fuel pressurized by the supply pump 16 is stored. Then, fuel is supplied from the common rail 14 to each injector 12.

  The injector 12 can inject the fuel into the cylinder at an arbitrary timing a plurality of times during one cycle. That is, the injector 12 can perform pilot injection once or a plurality of times prior to main fuel injection (main injection) during one cycle. Further, the injector 12 may be capable of performing after injection, post injection, and the like after the main injection.

  An exhaust passage 18 of the diesel engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port 22 (see FIG. 2) of each cylinder. The diesel engine 10 of this embodiment includes a turbocharger 24. The exhaust passage 18 is connected to the exhaust turbine of the turbocharger 24.

  A catalyst (exhaust gas purification device) 26 for purifying exhaust gas is provided in the exhaust passage 18 downstream of the turbocharger 24. Examples of the catalyst 26 include an oxidation catalyst, a NOx 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. Can be used.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air drawn through the air cleaner 30 is compressed by the intake compressor of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by the intake manifold 34 to the intake ports 35 (see FIG. 2) of the respective cylinders.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. 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 an 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 this 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.

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

  In this system, the external EGR amount can be adjusted not only by the opening degree of the EGR valve 44 but also by the opening degree of the intake throttle valve 36. When the intake throttle valve 36 is reduced in opening to throttle the intake air, the pressure in the intake manifold 34 (intake pipe pressure) decreases, so the differential pressure from the back pressure (exhaust pipe pressure) increases. That is, the differential pressure before and after the external EGR passage 40 increases. For this reason, the amount of external EGR can be increased.

  The system of this embodiment further includes an accelerator opening sensor 48 that detects the amount of depression of the accelerator pedal (accelerator opening), an ECU (Electronic Control Unit) 50, and an atmospheric pressure sensor 68 that detects atmospheric pressure. I have. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 controls the operating state of the diesel engine 10 by operating each actuator according to a predetermined program based on the output of each sensor.

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

  Further, the diesel engine 10 is provided with an intake variable valve mechanism 54 that varies the valve timing of the intake valve 52 and an exhaust variable valve mechanism 58 that varies the valve timing of the exhaust valve 56. The intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are each connected to the ECU 50.

  Specific structures of the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are not particularly limited. For example, a phase variable mechanism that continuously varies the central phase of the valve operating angle, and a continuous valve operating angle. Various known mechanisms such as a variable operating angle variable mechanism, a mechanism having both of them, and an electromagnetically driven valve can be used as the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58.

[Features of Embodiment 1]
As described above, when the light load operation or the idle operation is performed at a high altitude with a low atmospheric pressure (hereinafter referred to as “light load” including the idling time), the fuel injected from the injector 12 is It tends to adhere to the wall surface of the combustion chamber, and as a result, combustion tends to become unstable. Therefore, in the present embodiment, in order to stabilize combustion at high altitude light load, the injection pressure suppression control for lowering the fuel injection pressure than when on a flat ground (low ground) and the amount of internal EGR more than when on a flat ground. Internal EGR increase control was performed.

  In the present embodiment, the pressure in the common rail 14 (rail pressure) is equal to the fuel injection pressure from the injector 12. Therefore, in order to reduce the fuel injection pressure, the supply pump 16 and the like may be controlled so that the rail pressure decreases. When the fuel injection pressure is lowered at the time of high altitude load, the penetration force of the spray becomes small, so that fuel adhesion to the combustion chamber wall surface can be suppressed. Therefore, combustion can be stabilized.

  The internal EGR can be performed, for example, by a method of providing a positive or negative valve overlap during the opening period of the intake valve 52 and the exhaust valve 56. Hereinafter, an example in which a negative valve overlap is provided will be described with reference to FIG. The thin line in FIG. 3 is a normal valve lift, and the thick line is a valve lift when a negative valve overlap is provided. The larger the negative valve overlap, the greater the amount of internal EGR. In the example shown in FIG. 3, the working angle of the exhaust valve 56 is constant and the central phase is advanced, and the working angle of the intake valve 52 is constant and the central phase is retarded. You may let them. Further, it is not always necessary to change the valve timings of both the exhaust valve 56 and the intake valve 52, and a negative valve overlap may be provided by changing one of the valve timings.

  When internal EGR is performed, high-temperature burned gas remains in the cylinder, so that the in-cylinder gas temperature before the start of the compression stroke increases, and thus the compression end temperature (in-cylinder gas temperature near the compression top dead center) also increases can do. For this reason, the ignitability of the fuel can be improved. Further, as the compression end temperature increases, the viscosity of the in-cylinder gas also increases. For this reason, overdiffusion of the fuel spray can be suppressed, and fuel adhesion to the combustion chamber wall surface can be suppressed. For this reason, combustion can be stabilized by increasing the amount of internal EGR during high-altitude light loads.

  FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to stabilize combustion at a high altitude light load. This routine is executed every predetermined time. According to the routine shown in FIG. 4, first, the atmospheric pressure detected by the atmospheric pressure sensor 68 is acquired (step 100). Next, injection pressure suppression control for reducing the rail pressure (fuel injection pressure) is performed (step 102).

  FIG. 5 is a diagram in which the horizontal axis represents the altitude of the vehicle travel point, and the vertical axis represents the rail pressure and the internal EGR amount at light load. In FIG. 5, the left end of the horizontal axis is an altitude corresponding to a flat ground (lowland). In step 102, the rail pressure is controlled according to the map stored in advance in the ECU 50 based on the atmospheric pressure acquired in step 100 so that the rail pressure as shown in FIG. That is, when the altitude gradually increases from the flat ground and the atmospheric pressure gradually decreases, the rail pressure is gradually decreased accordingly. And when rail pressure falls to a predetermined lower limit, even if altitude rises further, rail pressure is maintained at the lower limit. The lower limit value of the rail pressure is determined according to the characteristics of the fuel injection system such as the injector 12.

  According to the routine shown in FIG. 4, the combustion stability is determined following the process of step 102 (step 104). The stability of combustion can be determined, for example, by detecting rotational fluctuations (engine rotational speed fluctuations) based on the output of the crank angle sensor 62. That is, it can be determined that the combustion is stable if the value of the rotational fluctuation is smaller than the allowable value, and that the combustion is unstable if it is larger than the allowable value.

  If it is determined in step 104 that the combustion is stable, the current processing cycle is terminated without introducing the internal EGR. When the atmospheric pressure drop is relatively small, combustion can be sufficiently stabilized by reducing the fuel injection pressure (rail pressure) without introducing the internal EGR. For this reason, in this embodiment, as shown in FIG. 5, the internal EGR is not introduced when the atmospheric pressure decrease amount is relatively small, that is, up to a certain altitude.

  On the other hand, when it is determined in step 104 that the combustion is unstable, the internal EGR increase control for introducing the internal EGR is performed as follows. In order to stabilize the combustion, it is necessary to suppress the excessive diffusion of the fuel spray injected from the injector 12 and to make the diffusion of the fuel spray moderate. Therefore, a process of calculating the spray diffusion suppression force necessary for that is first performed (step 106). Specifically, the penetration force of fuel spray is calculated from the current rail pressure and atmospheric pressure, and the necessary spray diffusion suppression force is calculated according to the penetration force.

  Subsequently, the viscosity of the in-cylinder gas required to obtain the necessary spray diffusion suppression force calculated in step 106 is calculated (step 108). The higher the viscosity of the in-cylinder gas, the greater the spray diffusion suppression force. Here, the required value of in-cylinder gas viscosity is calculated using this relationship.

  Then, based on the required value of in-cylinder gas viscosity calculated in step 108, the internal EGR is introduced as follows (step 110). Since there is a relationship that the in-cylinder gas viscosity increases as the compression end temperature increases, first, the necessary compression end temperature is obtained from the required value of the in-cylinder gas viscosity. The compression end temperature is obtained by calculating the adiabatic compression change to the in-cylinder temperature before starting compression. The in-cylinder temperature before starting compression is correlated with the internal EGR amount. Therefore, the required internal EGR amount can be obtained by calculating backward from the required compression end temperature. In step 110, the intake variable valve mechanism 54 and the exhaust variable valve mechanism 58 are realized so that the valve timings of the intake valve 52 and the exhaust valve 56 are obtained so that the required internal EGR amount thus obtained can be obtained. Is controlled. Thereby, the necessary amount of internal EGR is actually introduced, and as a result, the necessary spray diffusion suppression force calculated in step 106 can be obtained. Therefore, overspreading of fuel spray is reliably prevented, and fuel adhesion to the combustion chamber wall surface is suppressed. In addition, the ignitability is improved due to the increase in the compression end temperature. From these things, combustion can be stabilized.

  According to the routine processing shown in FIG. 4 described above, the amount of decrease in the combustion injection pressure and the amount of increase in the internal EGR amount can be accurately controlled according to the atmospheric pressure. For this reason, combustion can be reliably stabilized even at the time of high altitude light load by the synergistic effect of both. Therefore, misfire, increase in torque fluctuation, HC emission, etc. can be reliably suppressed.

  By the way, when carrying out internal EGR, it usually involves some loss (for example, pump loss if a negative valve overlap is provided). In the present embodiment, the internal EGR amount can be controlled to an appropriate amount according to the atmospheric pressure, so that combustion stabilization can be achieved while minimizing loss. In particular, in the present embodiment, as described above, when the atmospheric pressure decrease amount is relatively small, that is, when the altitude is not so high, the internal EGR is not introduced and only the fuel injection pressure is decreased. It is said. For this reason, combustion at high altitudes can be stabilized while minimizing deterioration of fuel consumption.

  As shown in FIG. 5, in the present invention, low temperature combustion may be achieved by increasing the internal EGR amount further than the amount calculated in step 110 above a certain altitude. In this embodiment, in addition to the increase in the spray particle size due to a decrease in the fuel injection pressure, the higher the altitude, the less oxygen in the cylinder and the greater the amount of internal EGR. It becomes easy. For this reason, in the routine processing shown in FIG. 4, if the altitude exceeds a certain altitude, the smoke discharge amount may not be within an allowable level. Therefore, in such a case, it is preferable to further increase the internal EGR amount and further increase the specific heat of the in-cylinder gas, so that the combustion temperature is lowered to a temperature at which soot formation is suppressed or less. By achieving low-temperature combustion in this way, smoke emission can be reliably suppressed even when the altitude is particularly high. In addition, since this embodiment is intended for combustion stabilization at a light load, it is possible to perform a large amount of internal EGR necessary for low-temperature combustion.

  FIG. 6 is a diagram for explaining the in-cylinder gas amount in the flatland and the highland. Hereinafter, the effects of the present embodiment will be further described with reference to FIG. As shown in FIG. 6, on the flat ground, the inside of the cylinder is occupied by air and external EGR gas. On the other hand, when the same control as that on a flat ground is performed without any correction at high altitude, the air in the cylinder and the external EGR gas decrease at the same rate as shown in the second bar graph from the left. , Lack of air. Therefore, conventionally, as shown in the second bar graph from the right, by reducing the external EGR rate, an air amount equivalent to that of the flat ground is secured to stabilize combustion. However, in this case, the NOx emission amount increases due to the reduction in the external EGR, and the overdiffusion of the spray is promoted due to the decrease in the in-cylinder gas density, so that a sufficient combustion stabilization effect cannot be obtained. On the other hand, in this embodiment, as shown in the rightmost bar graph, by introducing the internal EGR instead of the external EGR, the compression end temperature can be increased, and the ignitability is improved and the in-cylinder gas is increased. Since the spray overdiffusion prevention effect by increasing the viscosity can be obtained, combustion can be reliably stabilized. In the present embodiment, the external EGR is reduced (or zero), so that the intake air temperature can be lowered, and as a result, the charging efficiency can be improved. For this reason, as shown in FIG. 6, the amount of in-cylinder gas can be increased as compared with the above-described conventional example, and overspreading of fuel spray can be more effectively prevented. Furthermore, when the internal EGR is introduced, if the negative valve overlap is set and the intake valve opening timing is after top dead center, the intake valve 52 can be opened when the piston speed is fast. Inhalation can be promoted dynamically, and the charging efficiency can be further increased.

  By the way, in Embodiment 1 described above, spray overdiffusion is prevented by lowering the fuel injection pressure, but spray overdiffusion is also prevented by increasing the number of fuel injections in one cycle. can do. That is, by dividing and injecting the fuel required for one cycle into a plurality of times, the injection amount per time is reduced, so that the spray penetration force can be reduced. In the present invention, this may be utilized to suppress spray overdiffusion and stabilize combustion. That is, in step 102 described above, the number of fuel injections in one cycle may be increased instead of lowering the fuel injection pressure or simultaneously with lowering the fuel injection pressure. For example, as the altitude rises, the number of injections is increased to 1 (only main injection), 2 (pilot injection + main injection), 3 times (2 pilot injections + main injection). Also good.

  In the first embodiment described above, the ECU 50 executes the process of step 102, whereby the “first atmospheric pressure decrease compensating means” in the first and second inventions performs the process of step 110. By executing the processing of the routine shown in FIG. 4, the “second atmospheric pressure decrease compensating means” in the first invention by executing the “in the first to fourth and sixth inventions” The "control means" increases the internal EGR amount at a certain altitude or higher than the amount calculated in step 110 to achieve low-temperature combustion, thereby realizing the "low-temperature combustion means" in the fifth invention. ing.

  Moreover, although the case where the present invention is applied to control of a diesel engine (compression ignition internal combustion engine) has been described in the above-described embodiment, the present invention is not limited to control of a diesel engine. Spark ignition internal combustion engine) It can be applied to control of various other internal combustion engines.

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 diesel engine in the system shown in FIG. It is a figure which shows the valve lift in the case of providing a negative valve overlap. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is the figure which took the altitude of the vehicle travel point on the horizontal axis, and took the rail pressure and internal EGR amount at the time of light load on the vertical axis. It is a figure for demonstrating the gas amount in a cylinder in a flat ground and a highland.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 18 Exhaust passage 20 Exhaust manifold 22 Exhaust port 24 Turbocharger 26 Catalyst 28 Intake passage 34 Intake manifold 35 Intake port 36 Intake throttle valve 38 Air flow meter 40 External EGR passage 44 EGR valve 50 ECU
52 Intake valve 54 Intake variable valve mechanism 56 Exhaust valve 58 Exhaust variable valve mechanism 62 Crank angle sensor 64 Piston

Claims (6)

First atmospheric pressure reduction compensation means for compensating the influence of the decrease in atmospheric pressure on the combustion stability by changing the fuel injection conditions;
A second atmospheric pressure lowering compensation means for compensating for the influence of the lowering of the atmospheric pressure on the combustion stability by increasing the internal EGR amount;
Control means for controlling the compensation amount by the first atmospheric pressure decrease compensation means and the compensation amount by the second atmospheric pressure drop compensation means based on atmospheric pressure;
A control device for an internal combustion engine, comprising:   The first atmospheric pressure decrease compensating means performs at least one of decreasing the fuel injection pressure in accordance with a decrease in atmospheric pressure and increasing the number of fuel injections in one cycle in response to a decrease in atmospheric pressure. The control apparatus for an internal combustion engine according to claim 1, wherein an influence of a decrease in atmospheric pressure on combustion stability is compensated for.   3. The control of the internal combustion engine according to claim 1, wherein the control means causes the compensation by the first atmospheric pressure decrease compensation means to be executed in preference to the compensation by the second atmospheric pressure decrease compensation means. apparatus.   The control means executes compensation by the first atmospheric pressure decrease compensation means without executing compensation by the second atmospheric pressure decrease compensation means in a range where the atmospheric pressure decrease amount is relatively small, and further increases the atmospheric pressure decrease amount. 4. The control apparatus for an internal combustion engine according to claim 1, wherein when the pressure drop amount becomes large, the compensation by the second atmospheric pressure drop compensation means starts to be executed.   When the internal EGR amount is increased by the second atmospheric pressure lowering compensation means and the smoke emission amount may exceed the allowable level, the internal EGR amount is further increased to suppress the combustion temperature and soot generation. The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising a low-temperature combustion means for reducing the temperature to a temperature equal to or lower than a predetermined temperature. The control means includes
In-cylinder gas viscosity required value calculation means for calculating a required value of in-cylinder gas viscosity based on the atmospheric pressure and the fuel injection pressure;
A required internal EGR amount calculating means for calculating a required internal EGR amount based on the in-cylinder gas viscosity required value;
5. The internal combustion engine control device according to claim 1, wherein the internal EGR amount is controlled based on the required internal EGR amount.

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