JP2001090525A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely suppress generation of sulfates and to reduce an emission of NOX while preventing a hydrocarbon(HC) emission from increasing, without providing a special device. SOLUTION: In this controller for an internal combustion engine provided indise an exhaust passage with an exhaust emission purifying catalyst 19 and a supercharger 9 for supercharging an intake, a supercharge pressure controlling means 52 conducts control for raising supercharge pressure by the supercharger 9 to suppress generation of the sulfates, when a sulfate generation predicting means 51 determines that an exhaust temperature is a prescribed temperature or more where a prescribed amount of the sulfates is generated based on a parameter correlative to an exhaust temperature, and the NOX is reduced when control is conducted additionally to increase an exhaust circulating amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine having an exhaust gas purifying catalyst, a supercharger (turbocharger), and an exhaust gas recirculation device (exhaust gas recirculation means).

[0002]

In recent years, HC, there is a need to reduce the emission of harmful substances such as NO _X to develop friendly environment engine environment. Therefore, an exhaust gas purifying catalyst (for example, an oxidation catalyst) is conventionally provided in an exhaust passage of an internal combustion engine (for example, a diesel engine), and the exhaust gas purifying catalyst is used to remove HC or particulate matter (PM) in exhaust gas. Of SOF (soluble organic component) is oxidized and purified. Further, a technique has been proposed in which the exhaust gas temperature is controlled so that a high HC purification rate can be maintained while suppressing a sulfate generation rate.

As such a technique, for example, Japanese Patent Laid-Open No.
There is a technique disclosed in US Pat. In this technique, the temperature of exhaust gas is reduced to suppress the generation of sulfate.

[0004]

However, in such a conventional technique, cooling air is applied from the outside to the exhaust passage in order to lower the exhaust gas temperature. It is necessary to provide a cooling fan or the like, which increases costs. In addition, power for driving such a cooling fan or the like is required, and if engine output is used for this, fuel efficiency will be deteriorated.

[0005] In this technique, when the temperature of the exhaust gas falls below a specific temperature, the exhaust gas downstream of the catalyst is recirculated to maintain the temperature of the exhaust gas above the specific temperature. However, in this technique, since the EGR control is performed by focusing only on the exhaust gas temperature, a large amount of the exhaust gas may be recirculated, and in this case, the excess air ratio λ becomes too low and the HC becomes excessive. May be discharged to

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it has been proposed that the production of sulfate can be reliably suppressed without increasing the amount of HC emission without providing a special device. An object of the present invention is to provide a control device for an internal combustion engine, which is capable of reducing the amount of NO _X emissions.

[0007]

Therefore, in the control apparatus for an internal combustion engine according to the first aspect of the present invention, the sulfate generation predicting means determines whether the temperature of the exhaust gas is higher than the predetermined temperature based on a parameter correlated with the temperature of the exhaust gas. If it is predicted that a predetermined amount or more of the sulfate will be generated, the supercharging pressure control means for controlling the supercharging pressure by the supercharger for supercharging the intake air performs control to increase the supercharging pressure. As a result, the intake air amount of fresh air increases, the exhaust gas temperature decreases, the exhaust gas temperature approaches the predetermined temperature, and the HC purification rate of the exhaust gas purification catalyst provided in the exhaust passage is prevented from decreasing. In addition, the production of sulfate is surely suppressed.

Further, in the control device for an internal combustion engine according to the present invention, the exhaust gas recirculation amount control means generates the sulfate having the exhaust gas temperature equal to or higher than the predetermined temperature and the predetermined amount or higher by the sulfate generation predicting means. Is performed, control is performed to increase the amount of exhaust gas recirculation by the exhaust gas recirculation means. Thus, it reduced exhaust gas temperature, while so as not to lower the HC purification rate by the exhaust gas purifying catalyst provided in an exhaust passage, thereby reliably reduce NO _X emissions.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. A control device for an internal combustion engine according to one embodiment of the present invention will be described with reference to FIGS. The internal combustion engine according to the present embodiment is configured as a direct injection type diesel engine (in-cylinder injection type internal combustion engine) 1, as shown in FIG.

In the diesel engine 1, an intake passage 3 and an exhaust passage 4 are connected to a combustion chamber 2. The intake passage 3 and the combustion chamber 2 are controlled to communicate with each other by an intake valve 5.
The communication between the exhaust passage 4 and the combustion chamber 2 is controlled by an exhaust valve 6. Further, a fuel injection nozzle 7 is also provided so as to face the combustion chamber 2, and fuel is supplied to the fuel injection nozzle 7 from a fuel injection pump in accordance with an operating position of a rack controlled by a rack actuator (not shown). It has become so. The fuel injection device is
The present invention is not limited to the above-described one, but is a pressure-accumulation chamber fuel injection device (common rail type fuel injection device) configured to store high-pressure fuel in a pressure-accumulation chamber and inject the high-pressure fuel from a nozzle by switching control of an electromagnetic valve. There may be.

An intake throttle valve 8 is provided in the intake passage 3. Then, by reducing the opening degree of the intake throttle valve 8, an EGR amount described later can be increased. Further, an exhaust gas purifying catalyst 19 is provided in the exhaust passage 4. The exhaust gas purifying catalyst 19 is constituted by, for example, an oxidation catalyst that purifies by oxidizing CO and HC in the exhaust gas. As shown in FIG. 4, the HC purification rate characteristics of the exhaust gas purifying catalyst 19 show the highest HC purification rate when the exhaust gas temperature (here, the exhaust gas temperature at the catalyst inlet) is about 300 ° C. The lower the exhaust gas temperature, the lower the HC purification rate by the exhaust gas purifying catalyst 19.

The diesel engine 1 is provided with a turbocharger (turbocharger) 9. In the turbocharger 9, the exhaust turbine is interposed in the exhaust passage 4, and a compressor connected to and driven by the exhaust turbine is interposed in the intake passage 3, and transmits the driving force of the exhaust turbine to the compressor. The intake air is pressurized. An intercooler 10 is provided downstream of the compressor in the intake passage 3 in order to reduce the temperature of the air pressurized by the compressor.

Here, the turbocharger 9 is shown in FIG.
As shown in (A) and (B), a turbocharger with a variable nozzle vane (also referred to as a variable capacity turbocharger or VG turbo)
The nozzle vanes 9c are arranged at equal intervals around a turbine blade 9b of the exhaust turbine 9a. Each nozzle vane 9c is connected to an annular ring 9d, and when the annular ring 9d rotates in the direction of the arrow in the drawing, the angle of the nozzle vanes 9c, that is, the opening degree is changed. That is, the nozzle vane 9c
The supercharging pressure (in manifold pressure) decreases as the opening degree of the nozzle vane 9c decreases, and increases as the opening degree of the nozzle vane 9c decreases.

FIG. 3A shows a case where the opening of the nozzle vane 9c is fully opened. When the opening of the nozzle vane 9c is fully opened, the supercharging pressure (in-manifold pressure) becomes minimum. . On the other hand, FIG. 3B shows a case where the opening degree of the nozzle vane 9c is fully closed.
When the opening of c is fully closed, the supercharging pressure (in-manifold pressure) becomes maximum.

Here, as shown in FIGS. 2, 3A and 3B, a VG turbo actuator 11 is connected to the annular ring 9d. Here, the VG turbo actuator 11 is an actuator whose operating position can be variably controlled by, for example, a built-in spring 11b and vacuum (negative pressure), and is moved from the tank 12 to the control room 11a of the VG turbo actuator 11. The operation position is controlled by switching the supply state of the vacuum by the electromagnetic valves 13 and 14, whereby the opening degree of the nozzle vane 9c is controlled to open and close so that a required supercharging pressure is obtained. The tank 12 is supplied with vacuum by a vacuum pump.

The VG turbo actuator 11
Is not limited to such a configuration,
A device that can adjust the operating position stepwise may be used. Further, the VG turbo actuator 11 is not limited to the one that operates according to the supply state of the vacuum, but may be another configuration as long as it is connected to the annular ring 9d to adjust the opening of the nozzle vane 9c. May be used.

This VG turbo actuator 11 is
It is connected to a controller (ECU) 50 to be described later, and its operation is controlled based on a control signal from the controller 50. That is, the operation of the solenoid valves 13 and 14 of the VG turbo actuator 11 is controlled based on a control signal from the controller 50 according to the operation state of the diesel engine 1.

The diesel engine 1 is also provided with an exhaust gas recirculation device (exhaust gas recirculation means, EGR device) 15 for recirculating a part of the exhaust gas discharged to the exhaust passage 4 to the intake passage. . The EGR device 15 includes an exhaust gas recirculation passage (EGR passage) 1 provided to connect the intake passage 3 and the upstream side of the exhaust passage 4.
5a and an EGR attached to the EGR passage 15a.
It comprises a valve 15b and an EGR cooler 15c provided to lower the temperature of the recirculated exhaust gas. In the present embodiment, the EGR valve 15b is
It is not a mere on-off valve, but a valve whose opening itself can be changed.

The EGR valve 15b is connected to the EGR actuator 16, and the operation of the EGR actuator 16 is controlled by a controller 50 described later, whereby the opening of the EGR valve 15b is adjusted and the EGR valve 15b is connected to the intake passage 3. The flow rate of the recirculated exhaust gas (hereinafter, referred to as EGR gas or recirculated gas) is adjusted.

Here, the EGR actuator 16 is
From the vacuum pump 17 to the control chamber 15b of the EGR valve 15b
The operation position is controlled by switching the supply state of the vacuum (negative pressure) into the solenoid valve a by solenoid valves (solenoid valves) 18a and 18b.
The EGR actuator 16 is not limited to the one having such a configuration, and may be one that can adjust the operating position stepwise (for example, a stepper motor type). Also, the EGR actuator 1
6 is not limited to the one that operates according to the supply state of the vacuum, but may have another configuration as long as the opening of the EGR valve 15b can be adjusted.

The EGR actuator 16 is connected to a controller (ECU) 50 described later, and its operation is controlled based on a control signal from the controller 50. That is, based on the control signal from the controller 50 according to the operating state of the engine 1, the electromagnetic valves 18a,
The operation of 18b is controlled.

In the present embodiment, the supercharging pressure control is performed by controlling the opening degree of the nozzle vane 9c of the turbocharger 9 in order to suppress the production of sulfate (sulfate such as SO _X ) while preventing the HC emission from increasing. performs a, so HC emissions reduce nO _X emissions while not increase, and thereby performing opening control of the EGR valve 15b, further EGR valve 15b
Fine adjustment of the excess air ratio λ is also performed by controlling the opening degree.

For this reason, as shown in FIG. 1, a controller (ECU, electronic control unit) 50
Sulfate generation prediction means 51, supercharging pressure control means 52
Exhaust gas recirculation amount control means (EGR amount control means) 53,
A target excess air ratio setting unit 54 and an actual excess air ratio estimation unit 55 are provided. Here, sulfate generation prediction means 51, based on the parameters that are correlated with the exhaust gas temperature, exhaust gas temperature is equal to or a predetermined temperature T ₀ or more, when the exhaust gas temperature is the predetermined temperature T ₀ or more Is expected to generate a predetermined amount or more of sulfate.

For this reason, the engine 1 is provided with an exhaust gas temperature sensor 36 at a predetermined location (for example, at the catalyst inlet). The exhaust gas temperature sensor 36 is connected to the controller 50, and a detection signal from the exhaust gas temperature sensor 36 is sent to the sulfate generation predicting means 51 of the controller 50. Here, the parameter having a correlation with the exhaust gas temperature includes, for example, a sulfate generation rate characteristic.

As shown in FIG. 4, for example, the sulfate generation rate characteristic changes abruptly with a change in the exhaust gas temperature (exhaust gas temperature at the catalyst inlet) when the exhaust gas temperature is equal to or higher than the predetermined temperature T ₀ . On the other hand, HC purification rate characteristics, for example, as shown in FIG. 4, not much change in the temperature region where the exhaust gas temperature is predicted to predetermined temperature T ₀ or more more than a predetermined amount of sulfate is generated.

Therefore, the temperature at which sulfate is generated
Determine the lowest temperature of the area (eg, about 250 ° C)
Temperature T₀And a predetermined temperature T as described later.₀Less than
Turbocharge to increase boost pressure when above
Exhaust gas temperature by controlling the opening degree of nozzle vane 9c
, While purifying HC efficiently,
Sulfate generation can be reliably suppressed. What
In fact, the production of sulfate can be tolerated to some extent
If the temperature is higher than the predetermined temperature T ₀As
May be set.

Since the exhaust gas temperature is high in the medium-speed, high-load operation region, it is necessary to suppress the generation of sulfate while efficiently purifying HC.
It is sufficient to raise the supercharging pressure to lower the exhaust gas temperature,
In the operating range where other exhaust gas temperatures are low,
When the exhaust gas temperature is lower than the predetermined temperature T ₀ , on the contrary, the supercharging pressure is decreased to increase the exhaust gas temperature, and thus the HC
The production of sulfate can be surely suppressed while efficiently purifying the wastewater.

The supercharging pressure control means 52 uses the supercharging pressure map at normal temperature (normal supercharging pressure map) as shown in FIG. 5 based on the engine speed Ne and the average effective pressure Pme. The supply pressure is set, and the opening degree of the nozzle vane 9c of the turbocharger 9 is controlled so that the current actual supercharge pressure (actual supercharge pressure) matches the target supercharge pressure.

For this reason, the engine 1 is provided with a crank angle sensor 34 and a load sensor 35 for detecting the load of the engine 1 at predetermined locations. These sensors are connected to the controller 50, and detection signals from the sensors are sent to the supercharging pressure control means 52 of the controller 50. The detection signals from these sensors are also sent to the EGR amount control means 53.

Since the engine speed Ne can be calculated based on the crank angle sensor 34, the crank angle sensor 34 is referred to as an engine speed sensor (engine speed detecting means, engine speed sensor) for convenience. Also,
As the load sensor 35, an accelerator opening sensor (APS) that detects the opening of an accelerator pedal (or the amount of depression of the accelerator) (not shown) is used. The load sensor 35
May use a rack position sensor that detects a rack position of a fuel injection pump (not shown).

In this case, the supercharging pressure control means 52 determines that the exhaust gas temperature is equal to or higher than the predetermined temperature T ₀ by the sulfate generation predicting means 51 in the medium-to-high rotation speed and high load operation range at the time of the hot state. When it is predicted that the above-mentioned sulfate is generated, the opening degree of the nozzle vane 9c of the turbocharger 9 is controlled in the closing direction to control the supercharging pressure (in-manifold pressure) to increase.

For this reason, as shown in FIG. 5, the supercharging pressure map at the time of the hot state is set in consideration of fuel efficiency in order to suppress the generation of sulfate in the normal operation range, that is, in the medium-speed, high-load operation range. The map value is set such that the supercharging pressure is higher in the medium-speed, high-load operation range than the map value of the supercharging pressure map to be performed. In other words, the supercharging pressure map at the time of the warm state is higher in the middle-high-speed, high-load operation range with the increase of the supercharging pressure than in the supercharging pressure map set in consideration of the fuel efficiency. The map value is set so that is larger.

As described above, the reason why the opening degree of the nozzle vane 9c of the turbocharger 9 is controlled to be closed in the middle, high speed, and high load operation range at the time of a warm state is as follows. That is, S in particulates (PM) contained in exhaust gas
An oxidation catalyst is used to reduce the OF content (soluble organic component; mainly HC). However, in a medium-speed, high-load operation range at a hot state, the exhaust gas temperature is high, so the sulfur (S) content in the fuel is reduced. The amount of sulfate generated by the action of the oxidation catalyst is increased, and the amount of IN in particulates (PM) is increased.
SOL content (insoluble organic components; mainly soot and sulfate) increases. Therefore, the oxidation catalyst
Although the OF component is reduced, the INSOL component is increased, so that the particulate matter (PM) is equal to or increased as a whole.

For this reason, in a middle-speed, high-load operating range at a hot state, the exhaust gas temperature is sufficient to reduce the SOF component. Therefore, it is necessary to lower the exhaust gas temperature so as not to generate sulfate in this operating range. is important. In this case, as can be seen from the example of the sulfate generation rate characteristics of the oxidation catalyst in FIG. 4, even if the amount of decrease in the exhaust gas temperature is not so large, there is a sufficient effect in suppressing the generation of sulfate. That is, as can be seen from the example of the sulfate generation rate characteristic of the oxidation catalyst as shown in FIG. 4, the sulfate generation rate characteristic changes rapidly with the change in the exhaust gas temperature.
Even if the amount of temperature decrease is not so large, for example, about 20 ° C., the effect of suppressing the formation of sulfate is large.

Here, as shown by the solid line A in FIG. 6, if the opening of the nozzle vane 9c of the turbocharger 9 is reduced (closed), the supercharging pressure increases and the intake fresh air amount increases (excess air). Rate λ increases), and by increasing the intake air amount in this manner, the exhaust gas temperature (for example, the exhaust gas temperature at the turbine outlet) can be reduced. In FIG. 6, the two-dot chain line indicates the exhaust gas temperature of the turbocharger (fixed turbo) in which the supercharging pressure is fixed, and it can be lowered by about 20 ° C. from this.

Further, when the boost pressure and squeeze the opening of the nozzle vane 9c of the turbocharger 9 is controlled to be increased, since the amount of intake air increases, but so that the NO _X emissions increases, later by performing the EGR control so as to increase the EGR amount (EGR flow rate) as, for NO _X reduction effect can be obtained, it is possible to suppress the NO _X emissions substantially equal. As described above, since the control for increasing the supercharging pressure by reducing the opening degree of the nozzle vanes 9c of the turbocharger 9 and the EGR control for increasing the EGR amount are also performed, as shown by a solid line B in FIG. Is substantially constant. In FIG. 6,
The two-dot chain line indicates the exhaust gas temperature of the turbocharger (fixed turbo) in which the supercharging pressure is fixed, and can be made substantially constant with the excess air ratio λ larger than this.

Incidentally, even if the EGR amount is increased in order to make the NO _X emission amount the same, the amount of air introduced into the cylinder is increased. In addition, since the soot component (smoke rate) in INSOL is the same or slightly lower, there is no problem from this point. In FIG. 6, the two-dot chain line indicates the exhaust gas temperature of the turbocharger (fixed turbo) at which the supercharging pressure is fixed, and the smoke rate can be further reduced.

Further, as shown in FIG. 4, the purification rate characteristics of the SOF component, mainly HC, do not decrease so much in the temperature range where sulfate is generated. Therefore, even if the exhaust gas temperature is reduced by reducing the opening degree of the nozzle vanes 9c of the turbocharger 9 in order to suppress the generation of sulfate as described above, the HC purification rate does not decrease so much if the temperature decrease amount is small. Therefore, as shown by the solid line C in FIG. 6, the HC discharge amounts (total HC and THC) are substantially equal or do not increase so much. As described above, there is no problem in terms of HC emission. In FIG. 6, the two-dot chain line indicates the exhaust gas temperature of the turbocharger (fixed turbo) in which the supercharging pressure is fixed, which is substantially the same.

For this reason, in order to reliably reduce the amount of sulfate generated without deteriorating the purification rate of other exhaust gas components, the nozzle vane 9c of the turbocharger 9 is operated in a medium-speed, high-load operation region as described above. Is controlled to close the opening degree. By the way, in the idling operation region at the time of the warm state, the exhaust gas purification rate does not change so much even if the opening degree of the nozzle vane 9c of the turbocharger 9 is controlled. Therefore, the supercharging pressure control means 52 improves the starting acceleration of the vehicle. For this purpose, the opening degree of the nozzle vanes 9c of the turbocharger 9 is reduced, the turbine speed of the turbocharger 9 is kept high, and control is performed so as to increase the responsiveness of the turbocharger 9.

For this reason, as shown in FIG. 5, the supercharging pressure map at the time of the warm state is set such that the supercharging pressure becomes higher in the idling operation region. As described above, in the idle operation region during Yutakatai squeeze the opening of the nozzle vane 9c of the turbocharger 9 (closed) even if subjected to control, HC emissions, NO _X emissions impact on the fuel injection amount no problem.

That is, even if the supercharging pressure is increased by narrowing the opening degree of the nozzle vanes 9c of the turbocharger 9 in the idling operation region at the time of the warm state, as shown in FIG.
The generation level of C hardly changes and is almost equal. Further, even if the boost pressure is increased by narrowing the opening degree of the nozzle vanes 9c of the turbocharger 9 in the idle operation region at the time of the warm state, as shown in FIG. The injection amount does not change much. In particular, if the EGR amount is increased, the fuel injection amount can be made substantially the same.

When the pressure difference between the target supercharging pressure set by the supercharging map at the warm state and the actual supercharging pressure at the present time is equal to or more than a predetermined value, the supercharging pressure control means 52 sets the VG vane. The vacuum is quickly supplied to and discharged from the actuator 11 (that is, the vacuum is quickly raised or lowered), so that the opening control of the nozzle vanes 9c can be performed with good responsiveness.

By controlling the supercharging pressure by controlling the opening degree of the nozzle vanes 9c of the turbocharger 9 as described above, it is possible to prevent the HC discharge from increasing without providing a special device. Although as the production of reliably prevented, since the NO _X generation amount when intake fresh air amount by the supercharging pressure control is increased will increase further, as shown in FIG. 7 (B), EG
By increasing the R amount (referred to as high EGR), the NO _X generation amount can be significantly reduced. For this reason, in the present embodiment, such control is further performed by the EGR control means 53.

The EGR control means 53 controls the EGR valve 15b so as to adjust the amount of exhaust gas recirculated into the intake passage 3. The EGR control unit 53 determines whether the exhaust gas temperature is equal to or higher than the predetermined temperature T ₀ by the sulfate generation predicting unit 51 and, when it is predicted that a predetermined amount or more of sulfate is generated, the EGR valve 15 b
Is controlled so as to increase the opening degree. As a result, even if the amount of generated NO _X increases when the boost pressure is increased by reducing the opening degree of the nozzle vanes 9c of the turbocharger 9, the NO _X emission amount can be reduced by the EGR control.

Here, if the EGR amount is excessively increased, HC
Is increased rapidly (see curve C in FIG. 6).
The EGR control means 53 does not increase the EGR amount too much.
The opening degree control of the EGR valve 15b is performed using the in-cylinder excess ratio λ as a control parameter. Specifically, the EGR control unit 53 determines that the target exhaust air is to be generated when the sulfate generation prediction unit 51 determines that the exhaust gas temperature is equal to or higher than the predetermined temperature T ₀ and predicts that a predetermined amount or more of sulfate is generated. Excess rate setting means 5
The deviation Δλ ₁₀ (= λ ₁ −λ ₀ ) between the target excess air ratio λ ₀ set in step 4 and the actual excess air ratio λ ₁ estimated by the actual excess air ratio estimating means 55 is calculated. _Ten
EGR valve 15b so that is smaller than the minute amount ε.
The feedback control based on the excess air ratio λ of the opening degree is performed.

The minute amount ε is determined in advance by a bench test as a difference in excess air ratio such that the difference in the amount of generated HC is negligible. Here, the actual excess air ratio estimating means 55
The actual excess air ratio (actual excess air ratio) λ ₁ is estimated based on the intake amount G _cyl , the EGR amount G _egr , the fuel injection amount, and the like.

That is, the actual excess air ratio estimating means 55 calculates the intake manifold temperature [the temperature of the intake air in the intake manifold (also called the intake manifold), the intake air temperature] T _mani , the intake manifold pressure (the pressure of the intake air in the intake manifold, the intake pressure). ) P _mani ,
Atmospheric pressure P _a, based on the volumetric efficiency ηv to the engine rotational speed Ne and the engine rotational speed Ne, calculating the intake amount (intake weight flow rate) G _cyl and the EGR amount G _egr sucked into the combustion chamber 2 (in-cylinder) Then, the actual excess air ratio λ ₁ is calculated from the suction amount G _cyl and the EGR amount G _egr .

In order to calculate the suction amount G _cyl in this manner,
The intake manifold temperature _Tmani , the intake manifold pressure (gauge pressure) _Pmani ,
Atmospheric pressure P _a, by taking into account the volumetric efficiency .eta.v, are to be calculated more accurately the intake quantity G _cyl. Incidentally, the intake manifold temperature T _mani, intake manifold pressure (gauge pressure) P _mani, the atmospheric pressure P _a, the volumetric efficiency ηv are the data necessary for calculating the intake amount G _cyl, that the intake amount data.

For this reason, in the engine 1, an intake air temperature sensor (intake air temperature detecting means) 31, an intake air pressure sensor (intake air pressure detecting means) 32, an atmospheric pressure sensor (atmospheric pressure detecting means) 33 and the like are arranged at predetermined locations. Have been. These sensors are connected to the controller 50, and detection signals from the sensors are sent to the actual excess air ratio estimating means 54 of the controller 50.

The intake pressure sensor 32 is also called a boost pressure sensor (boost pressure detecting means). The intake pressure sensor 32 is attached to, for example, an intake manifold of the engine 1 and detects a pressure (boost pressure) of intake air pressurized by the turbocharger 9. Moreover, volumetric efficiency ηv is to vary by the intake manifold temperature T _mani, volumetric efficiency regardless of the temperature change η
v is treated as a constant and simply the engine speed Ne,
Instead of obtaining the volumetric efficiency ηv with respect to the engine load, the actual excess air
The effect of _mani is also taken into account, and temperature correction is performed when obtaining the volume efficiency ηv. As a result, the suction amount G _cyl can be accurately calculated using the volume efficiency ηv that is accurately obtained.

The actual excess air ratio estimating means 55 sets the reference intake manifold temperature to T0, sets the reference volumetric efficiency to the reference intake manifold temperature T0 to ηv0, and sets the volumetric efficiency index to m.
The volume efficiency ηv for an arbitrary intake manifold temperature T _mani is obtained by the following equation (1) for each engine speed Ne and engine load. ηv / ηv0 = (T _mani / T0) ^m (1) Specifically, first, for the target engine 1, the engine rotational speed Ne and the intake manifold temperature T for each engine load are set.
A characteristic between the _mani and the volumetric efficiency ηv is obtained by a bench test, and a map for calculating the volumetric efficiency ηv is created based on such a characteristic between the intake manifold temperature _Tmani and the volumetric efficiency ηv.

That is, the reference intake manifold temperature T0 (for example, about 25 ° C.) for each engine speed Ne and engine load.
The reference volume efficiency ηv0 for was measured by a bench test,
Based on this, a reference volumetric efficiency map is created in which the engine rotational speed Ne and the engine load at the reference intake manifold temperature T0 (for example, about 25 ° C.) are associated with the reference volumetric efficiency ηv0.

A characteristic indicating the relationship between the intake manifold temperature T _mani and the volumetric efficiency ηv is measured by a bench test for each engine speed Ne and engine load, and based on this, each engine speed Ne and engine load is measured. The volumetric efficiency index m is also determined for each of them, and is used as the reference intake manifold temperature T0 (for example, about
C), a volume efficiency index map is created in which the engine speed Ne, the engine load, and the volume efficiency index m are associated with each other.

Then, the volume efficiency ηv with respect to an arbitrary intake manifold temperature T _mani , engine speed Ne, and engine load
Is calculated based on the reference intake manifold temperature T0 (for example, about 25 ° C.), the reference volumetric efficiency ηv0 obtained from the reference volumetric efficiency map, and the volumetric efficiency index m obtained from the volumetric efficiency index map. Next, a method of calculating the intake amount G _cyl by the actual excess air ratio estimating means 55 will be described.

The actual excess air ratio estimating means 55 calculates the following equation (2).
Temperature T represented by_mani, Intake manifold pressure P_mani
Using the calculation formula of the volumetric efficiency ηv defined by
_cyl(Kg / s). ηv = 120G_cyl/ [Ne × Vh × γ_mani(P_mani, P_a, T_mani)] (2) where Ne is the engine speed and Vh is the engine speed.
Stroke volume, γ _mani(P_mani, P_a, T_mani) Is
Specific weight of air-fuel mixture (intake air and EGR) (k
g / m^Three).

When the above equation (2) is modified, it is expressed as the following equation (3). Therefore, the actual excess air ratio estimating means 55 calculates the intake amount G _cyl using this equation (3). It is to be calculated. G _cyl = _{[Ne × Vh × ηv × γ mani} (P mani, P a, T mani) ] / 120 (3) where specific weight _{γ mani (P mani, P a} , T mani) is intake manifold pressure (gauge pressure) to (kg / m ²⁾ and P _mani, atmospheric pressure (kg / m ²⁾ and P _a, the intake manifold temperature (K) as T _mani, represented by the formula (4). In addition, let the gas constant be R [kg · m / (kg · K)].

Γ _mani = (P _mani + P _a ) / (R × T _mani ) (4) Here, the engine stroke volume Vh and the gas constant R are constants, and the engine speed Ne and the intake manifold pressure P _mani , Atmospheric pressure P _a , and intake manifold temperature T _mani use the values detected by the sensors, and the volumetric efficiency ηv uses the values determined in advance by the bench test as described above using the suction amount G _cyl.
Is calculated.

Here, since the intake manifold pressure P _mani detected by the intake pressure sensor 32 is detected as a pressure difference from the atmospheric pressure, the intake pressure G _man is calculated by the atmospheric pressure sensor 33 to calculate the intake amount G _cyl. are also taken into consideration the atmospheric pressure P _a was.
However, if configured by the absolute pressure sensor so as to detect the intake manifold pressure P _mani, there is no need to consider the atmospheric pressure P _a.

[0059] Then, the real excess air rate estimating means 55 is adapted to calculate the actual excess air ratio lambda ₁ from this way inhalation volume G _{cy l} which is calculated. That is, the actual excess air ratio estimating means 55 sets the fuel injection amount (kg / s) for obtaining the desired output characteristic to Gf, and theoretically calculates the theoretical air amount (kg) necessary for completely burning 1 kg of fuel. / Kg) to L
The actual excess air ratio λ ₁ is calculated by the following equation (5), with 0 as the remaining air amount in the EGR as Ga _{, e} .

[0060] _{λ 1 = (G a + G} a, e) / (L0 × Gf) ··· (5) where the intake amount G _cyl is the intake air amount G _a, EGR amount passing through the EGR valve 15b (Weight flow rate of EGR gas) G _egr is expressed by the following equation (6). G _cyl = G _a + G _egr (6) Therefore, the intake air amount G _a is represented by the following equation (7).

G _a = G _cyl −G _egr (7) In consideration of such a relationship, the above equation (5) is expressed as the following equation (8). λ ₁ = (G _a + G _{a, e} ) / (L 0 × G f) = (G _a + G _egr ) / (L 0 × G _f ) −G _egr / G _a = G _cyl / (L 0 × Gf) −G _egr / ( G _cyl -G _egr ) (8) The fuel injection amount Gf is the engine speed detected by the engine speed sensor 34 and the accelerator depression amount (accelerator opening) detected as the engine load by the load sensor 35. ) Based on the engine rotation speed and the fuel injection amount map in the engine load region.

The EGR amount G _egr is calculated based on signals from the EGR gas pressure sensors 41, 42, the EGR valve temperature sensor 43, and the EGR valve lift sensor 44, as shown in FIG. That is, the EGR amount G _egr is
The specific weight of the EGR gas upstream of the EGR valve 15b is represented by γ
_Egr , the volume flow rate of the EGR gas is Q _egr, and EGR
EGR provided respectively on the upstream and downstream sides of the valve
The differential pressure calculated based on the signals from the gas pressure sensors 41 and 42 is ΔP, the temperature detected by the temperature sensor 43 disposed on the upstream side of the EGR valve is T _egr ,
EGR detected by EGR valve lift sensor 44
The effective opening area (including the flow coefficient) corresponding to the valve lift amount is defined as A _egr , and the gravitational acceleration is defined as g.
Is calculated by

G _egr = γ _egr × Q _egr = γ _egr × A _egr × [(2g × ΔP) / γ _egr ] ^1/2 = A _egr × (2g × γ _egr × ΔP) ^1/2 9) The target excess air ratio setting means 54 sets the target excess air ratio λ ₀ based on the operating state of the engine 1 (engine speed Ne, engine load). That is, the target excess air ratio setting means 54 is provided by the engine speed sensor 3.
The target excess air ratio λ ₀ is set based on the average effective pressure Pme calculated based on the engine rotation speed Ne detected by the control unit 4 and the load detected by the load sensor 35.

It should be noted that a target excess air ratio map in which the engine rotation speed, the engine load, and the target excess air ratio λ ₀ are associated is prepared in advance, and the engine rotation speed sensor 34,
And a load sensor 35 for detecting the load of the engine 1
The target excess air ratio λ ₀ according to the engine rotation speed and the engine load region set based on the detection information from the target air excess ratio may be obtained from the target excess air ratio map.

More specifically, the EGR control means 53 controls the EG
The opening control of the R valve 15b is performed as follows. That is, the deviation Δλ ₁₀ (= λ ₁ −λ ₀ )
Is negative, that is, the actual excess air ratio λ ₁ is
If ₀ is smaller than, since intake air amount G _a is the smaller to meet the target excess air ratio lambda _0, the boost pressure E in order to increase the (intake manifold pressure) the actual excess air ratio by increasing
Control for reducing the opening of the GR valve 15b (decreasing the opening) is performed.

[0066] On the other hand, when the deviation _{Δλ 10 (= λ 1 -λ 0} ) is positive, i.e. if the actual excess air ratio lambda ₁ is larger than the target excess air ratio lambda ₀ is inverse to the intake air amount G _a is the target Since it is too large to satisfy the excess air ratio λ ₀ , the opening degree of the nozzle vane 9c of the turbocharger 9 is increased to reduce the supercharging pressure (in-manifold pressure) and reduce the actual excess air ratio (opening degree (Extend) control is performed.

When the deviation Δλ ₁₀ between the actual excess air ratio λ ₁ and the target excess air ratio λ ₀ is large, the EGR amount control means 53 increases the response of the control (speeds up the response), and order to the generation amount of HC and NO _X to be sufficiently suppressed, nozzle vane 9 of the turbocharger 9 as follows
The opening degree control of c may be performed. That is, when the magnitude of the deviation [Delta] [lambda] ₁₀ is the predetermined value E (E> ε) above, changing the initial control amount of the opening degree of the nozzle vane 9c of the turbocharger 9 in accordance with the magnitude of the deviation [Delta] [lambda] ₁₀ You may do it. For example, when the magnitude of the deviation Δλ ₁₀ is equal to or larger than the predetermined value E (when the magnitude of the deviation Δλ ₁₀ is large)
It is to increase the initial control amount of the opening degree of the nozzle vane 9c of the turbocharger 9 in accordance with the deviation [Delta] [lambda] _10, squeezing increases the degree of opening of the nozzle vane 9c of the turbocharger 9 (to reduce the opening) so as to perform control You may do it. In this case, whether the deviation Δλ ₁₀ is a positive value or a negative value, that is, whether the actual excess air ratio λ ₁ is larger than the target excess air ratio λ ₀ ,
It is preferable to change the magnitude of the predetermined value E (for example, the predetermined values E ₁ and E ₂ ) depending on whether it is small or not.

The control device for an internal combustion engine as one embodiment of the present invention is configured as described above, and the supercharging pressure control and the EGR amount control by this device are performed as follows. First, the processing procedure for the supercharging pressure control and the EGR control by the present device will be described. First, as shown in the flowchart of FIG.
The exhaust gas temperature detected by the above is taken in, and step S2
The process proceeds to 0, and it is determined whether or not the exhaust gas temperature detected by the exhaust gas temperature sensor 36 is equal to or higher than a predetermined temperature T ₀ .

As a result of this determination, the exhaust gas temperature becomes equal to the predetermined temperature T
_When it is determined that the value is ₀ or more, it is predicted that a predetermined amount or more of sulfate is generated. Therefore, the processes of steps S30 and S40 are performed to lower the exhaust gas temperature. That is, in step S30, the engine rotation speed Ne and the engine load (for example, the average effective pressure Pme obtained from the accelerator opening) are fetched, and step S40 is performed.
Then, the supercharging pressure control means 52 controls the opening degree of the nozzle vanes 9c of the turbocharger 9 so that the target supercharging pressure is obtained based on the supercharging pressure map at the time of warming. That is,
Based on the engine rotation speed Ne detected by the engine rotation speed sensor 34 and the average effective pressure Pme calculated based on the load detected by the load sensor 35, a hot supercharging pressure map as shown in FIG. The target supercharging pressure is set by using the target supercharging pressure, and the opening degree of the nozzle vane 9c of the turbocharger 9 is controlled so that the actual supercharging pressure at the present time (actual supercharging pressure) matches the target supercharging pressure.

In this case, in the normal operation range, that is, in the medium-speed, high-load operation range, the exhaust gas temperature is lowered to the predetermined temperature T.
_The supercharging pressure is set to a higher value so that the generation of sulfate can be reliably suppressed while approaching ₀ to prevent the HC emission from increasing. Further, in the idling operation region, the supercharging pressure is set to be high in order to maintain the turbine speed of the turbocharger 9 at a high speed in order to improve the starting acceleration.

Next, at step S50, the actual excess air ratio λ
In order to estimate 1, the inhalation amount data is fetched, and step S
Proceeding to 60, the actual air excess
The remainder ratio λ1 is calculated. Specifically, the intake pressure sensor 32,
Detected by the atmospheric pressure sensor 33 and the intake air temperature sensor 31
Detection value P_mani,P_a,T_maniAnd load this
Intake temperature T _mani, A preset reference intake manifold temperature T
0 (for example, about 25 ° C.), engine speed Ne, engine
From the reference volumetric efficiency map according to the load
Volume efficiency ηv0, engine speed Ne, engine load
Volume efficiency index obtained from the volume efficiency index map according to
Using the number m, the volume efficiency ηv is calculated by the above equation (1).
Confuse.

Next, the read intake manifold pressure P _mani,
Using the atmospheric pressure P _{a, the} intake manifold temperature T _mani , and a preset gas constant R, the specific weight γ _mani (P
_mani, P _a, seek a T _mani). And the specific weight γ _{mani
(P mani, P a, T} mani), using volumetric efficiency .eta.v, the engine rotational speed Ne, the preset engine stroke volume Vh, calculates the intake amount G _cyl by the formula (3).

Next, the suction amount G thus calculated
_{Using cyl} , the EGR amount G _egr obtained from Expression (9), the fuel injection amount Gf set to obtain the desired output, and the theoretical air amount L0, the above Expression (5) [Expression (8)] To calculate the actual excess air ratio λ (actual excess air ratio λ1). Next, in step S70, the target excess air ratio setting means 54
Reads the target excess air ratio λ ₀ from the target excess air ratio map prepared for each engine rotation speed and engine load region based on the engine rotation speed Ne and the engine load Pme.

Then, in step S80, the deviation Δλ ₁₀ (= λ ₁ −λ) between the actual excess air ratio λ ₁ and the target excess air ratio λ ₀ is obtained.
₀₎ determines whether less or not than a very small amount epsilon, If it is determined that the deviation [Delta] [lambda] ₁₀ is determined to be a small amount epsilon or more, the process proceeds to step S90, further actual excess air ratio lambda ₁
Is larger or smaller than the target excess air ratio λ ₀ , that is, whether the deviation Δλ ₁₀ (= λ ₁ −λ ₀ ) is smaller than 0, and as a result of this determination, the deviation Δλ ₁₀ is larger than 0. If it is determined to be smaller, the process proceeds to step S100, in which the opening degree of the EGR valve 15b is controlled to reduce the EGR amount, and the process returns to step S50.
Step S100 is repeated.

[0075] On the other hand, in step S90, if the deviation lambda ₁₀ is determined to be 0 or more, the process proceeds to step S110,
In order to increase the EGR amount, the opening degree of the EGR valve 15b is controlled, and the process returns to step S50. Thereafter, the processes of steps S50 to S90 and step S110 are repeated. By the way, after such processing is repeated, in step S80, the deviation Δλ ₁₀ (= λ ₁ −λ ₀ ) between the actual excess air ratio λ ₁ and the target excess air ratio λ ₀ is reduced by a small amount ε.
If it is determined that the value is smaller than the above, the process returns.

Therefore, according to the control apparatus for an internal combustion engine according to the present embodiment, when the exhaust gas temperature is equal to or higher than the predetermined temperature T ₀ and it is predicted that a predetermined amount or more of sulfate is generated, the supercharging pressure is reduced. Since the exhaust gas temperature is lowered by raising the temperature and the exhaust gas temperature is brought close to the predetermined temperature T ₀ , there is an advantage that the production of sulfate can be surely suppressed while the HC discharge amount is not increased. In particular, medium and high speed,
Sulfate generation in a high load region can be reliably suppressed.

Further, since the excess air ratio λ is increased by increasing the supercharging pressure, the generation of soot can be suppressed, and the production of soot and sulfate constituting INSOL can be suppressed at the same time. In addition, since a temperature for reducing HC constituting SOF is secured, SO
There is also an advantage that purification of HC constituting F can be performed with high efficiency.

Further, since the exhaust gas temperature can be lowered only by controlling the opening degree of the nozzle vanes of the turbocharger, there is no need to provide a separate cooling fan or the like for lowering the exhaust gas temperature, and the cost can be reduced accordingly. In addition, there is an advantage that it is possible to prevent the consumption of the engine output for driving the cooling fan and the like, leading to the deterioration of the fuel efficiency.

Further, when the exhaust gas temperature reaches a predetermined temperature T₀Is over
Is expected to produce more than a certain amount of sulfate
The EGR amount is increased when
NO _XWhile ensuring that emissions do not increase,
Also has the advantage that the generation of
You. In particular, as long as EGR is within a range where HC does not increase rapidly,
The EGR valve 15 of the EGR device 15 is
The opening of the valve 15b is accurately controlled based on the excess air ratio λ.
Therefore, rapid introduction of EGR greatly suppressed combustion.
While preventing a sudden increase in HC emissions.
NO_XAlso has the advantage of greatly reducing
You.

In the above-described embodiment, the EGR amount control means 53 is configured to control the EGR amount based on the excess air ratio λ.
What is necessary is just to comprise so that the control which increases R amount may be performed.
Further, in the above-described embodiment, the intake air amount G _a are determined by the equation or a map, the intake air amount G _a, for example Karman vortex flow meter, hot wire (hot wire) airflow sensor of flowmeter (AFS ) May be used.

[0081] In this case, the intake air amount G _a is a detection value of the air flow sensor and Q (m ³ / s), is calculated by the following equation specific weight of the air of the air flow sensor unit as γ _{a, f} (10) You. G _a = Q × γ _{a, f} (10) where the specific weight γ _{a, f} is expressed by P _mani, T in the above equation (4).
The pressure P _a of the air flow sensor portion _{mani, f,} temperature T _a, is determined by substituting _f.

In the above-described embodiment, the supercharging pressure (in manifold pressure) is controlled by using the turbocharger with a variable nozzle vane. However, it is sufficient if the supercharging pressure (in manifold pressure) can be adjusted. . For example, the supercharging pressure may be adjusted using a turbocharger having a wastegate valve or a supercharger with a transmission.

In the above embodiment, the present invention is described as applied to a diesel engine.
If supercharging pressure control is performed while detecting knock by a knock sensor, the present invention can be applied to a gasoline engine (in particular, a direct injection type).

[0084]

As described above in detail, according to the control apparatus for an internal combustion engine according to the first aspect of the present invention, the HC emission amount is prevented from increasing without providing a special device.
There is an advantage that the production of sulfate can be reliably suppressed. According to the control apparatus for an internal combustion engine of the present invention of claim 2, wherein, while allowing the HC emissions does not increase, there is an advantage that it is possible to reduce the NO _X emissions.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of a control device for an internal combustion engine according to one embodiment of the present invention.

FIG. 3 is a schematic view showing a turbocharger with a variable nozzle vane provided in the internal combustion engine according to one embodiment of the present invention, wherein (A) shows a case where the nozzle vane opening is fully opened;
(B) shows the case where the nozzle vane opening is fully closed.

FIG. 4 is a diagram showing HC purification rate characteristics and sulfate generation rate characteristics of an oxidation catalyst provided in an internal combustion engine according to one embodiment of the present invention.

FIG. 5 is a diagram showing a supercharging pressure map at the time of a normal state used in a normal state (at the time of a hot state) in the control device for the internal combustion engine according to the embodiment of the present invention.

FIG. 6 shows the nozzle vane opening of the turbocharger, the turbine outlet temperature, and the air when the EGR control is performed in the internal combustion engine according to the embodiment of the present invention so that the same NO _X emission amount is obtained in a medium-speed, high-load operation range. It is a figure which shows the relationship between excess ratio (lambda), HC discharge amount, and smoke ratio.

FIG. 7 is a diagram for explaining a case where the nozzle vane opening control of the turbocharger is performed in an idling operation region in the internal combustion engine according to one embodiment of the present invention, wherein (A) shows the nozzle vane opening and the HC discharge amount; FIG. 5 is a diagram showing a relationship between the EGR amount and the NO _X emission amount;
(B) shows the relationship between the nozzle vane opening and the fuel injection amount and E
It is a diagram showing the relationship between the GR amount and NO _X emissions.

FIG. 8 is a flowchart showing a processing procedure for supercharging pressure control and EGR control by the control device for the internal combustion engine according to one embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 9 turbocharger (supercharger) 9c nozzle vane 15 EGR device (exhaust gas recirculation device, exhaust gas recirculation means) 15b EGR valve 19 exhaust gas purification catalyst 31 intake temperature sensor (intake temperature detection device) 32 intake pressure sensor (intake pressure detection device) , Boost pressure sensor) 33 Atmospheric pressure sensor (atmospheric pressure detecting means) 34 Engine rotational speed sensor (engine rotational speed detecting means) 35 Load sensor (accelerator opening degree sensor) 36 Exhaust gas temperature sensor 41 EGR valve upstream pressure sensor 42 EGR valve downstream Pressure sensor 43 EGR valve upstream temperature sensor 44 EGR valve lift sensor 50 Controller (ECU) 51 Sulfate generation prediction means 52 Supercharging pressure control means 53 Exhaust gas recirculation amount control means (EGR amount control means) 54 Target excess air ratio setting means 55 Actual Excess air ratio Constant means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 25/07 570 F02M 25/07 570J F-term (Reference) 3G005 DA02 EA04 EA15 EA16 FA35 FA46 FA52 FA54 GB12 GB81 GB92 GC04 GD14 GD23 HA04 HA05 HA12 HA13 HA18 HA19 JA02 JA06 JA13 JA16 JA22 JA23 JA26 JA32 JA39 JB02 JB05 JB08 3G062 AA01 AA03 AA06 BA04 BA05 BA06 DA01 DA04 DA05 EA10 EB04 EB06 EB07 EB10 ED03 GA09 FA04 GA13 GA14 GA18 GA21 GA23 3G091 AA02 AA10 AA11 AA17 AA18 AA24 AB02 AB13 BA04 BA11 BA20 BA31 BA33 CB02 CB07 CB08 DB06 DB07 DB08 DB09 DB10 DB13 DC01 EA01 EA03 EA06 EA07 EA12 EA15 HA14 FA12 FA12 FA09 FA12

Claims (2)

[Claims] 1. A control device for an internal combustion engine including an exhaust gas purifying catalyst and a supercharger for supercharging intake air in an exhaust passage, wherein the exhaust gas temperature is equal to or higher than a predetermined temperature based on a parameter correlated with the exhaust gas temperature. Sulphate generation predicting means for determining whether or not a predetermined amount or more of sulfate is generated by determining whether or not the sulphate has an exhaust gas temperature equal to or higher than a predetermined temperature and equal to or higher than a predetermined amount. And a supercharging pressure control means for performing control to increase the supercharging pressure when it is predicted that the pressure is generated. 2. An exhaust gas recirculation amount control means for controlling an exhaust gas recirculation amount by an exhaust gas recirculation means for recirculating a part of the exhaust gas into an intake passage, wherein the exhaust gas recirculation amount control means is provided with an exhaust gas temperature estimating means by the sulfate production prediction means. 2. The control of the internal combustion engine according to claim 1, wherein when it is predicted that the temperature is equal to or higher than a predetermined temperature at which a predetermined amount or more of sulfate is generated, the exhaust gas recirculation means increases the exhaust gas recirculation amount. apparatus.