DE102005005324B4 - Control device for a direct injection internal combustion engine - Google Patents

Abstract

A control device for a direct injection internal combustion engine (11) in which fuel is injected into a cylinder in an intake stroke or a compression stroke to be subjected to homogeneous combustion or stratified combustion, comprising: at least one of exhaust recirculation control means (34) for controlling an external exhaust gas recirculation amount; wherein exhaust gas is recirculated from an exhaust system to an intake system, or valve control means (39, 40) which varies an opening and closing operation of at least one of an intake valve (37) and an exhaust valve (38); fuel behavior decision means (30) for deciding a behavior of the fuel; and control means (30) for, when it has been decided by the fuel behavior decision means that the fuel is a heavy fuel, controlling at least one of the exhaust gas recirculation control means (34) and the valve control means (39, 40) in one direction so that at least one of the external exhaust gas recirculation amount or a valve overlap amount becomes smaller than in the case of using a light fuel.

Description

The present invention relates to a control device for a cylinder injection internal combustion engine, which improves a control characteristic in the case of using a heavy fuel.

In recent years, there has been a sudden demand for cylinder injection (direct injection) internal combustion engines, which have all the advantages of low fuel consumption, lower exhaust emission and high performance. The cylinder injection type internal combustion engine has two combustion modes of stratified charge combustion and a homogeneous combustion mode. In a low load region, the stratified charge combustion mode is formed in which a small amount of fuel is injected directly into a cylinder in a compression stroke to form a stratified air-fuel mixture in the vicinity of a spark plug and to perform stratified combustion. On the other hand, in the middle and high load ranges, the homogeneous combustion mode is formed in which the amount of fuel to be injected is increased and the fuel is injected directly into the cylinder in a one-stroke cycle to form a homogeneous air-fuel mixture and to carry out homogeneous combustion.

The cylinder injection internal combustion engine is equipped with an exhaust gas recirculator (EGR) that recirculates a portion of the exhaust gas into an intake system and a flow control valve that controls the intensity of a flow (swirl flow or falling flow) to be caused in the cylinder. Further, in the past, the cylinder injection type combustion engines each having a valve timing control means for varying the opening and closing timings of an intake valve and an exhaust valve have been increased. Various techniques for controlling such devices have been proposed.

For example, in JP H06 58067 B2 a swirl control valve is controlled to change a swirl ratio according to a load during a stratified charge combustion operation, thereby precluding the influence of the load.

In JP H11 50853 A For example, a swirl control valve is controlled to change a swirl intensity according to an engine speed during a stratified charge combustion operation, thereby preventing a combustion state from suddenly changing during acceleration or deceleration.

In JP H07 119513 A For example, the opening degree of an EGR valve is controlled in accordance with a combustion pressure fluctuation (torque fluctuation), whereby a NOx emission amount is reduced, whereby the torque fluctuation is lowered.

In JP H05 52145 A For example, a dual injection mode in which fuel is injected into a cylinder and burned in an intake stroke and a compression stroke, respectively, proceeds in the middle region between the stratified charge combustion mode and the homogeneous combustion mode.

In JP H05 71383 A That is, a ratio of an injection amount in the compression stroke in the dual injection mode to a total injection amount in the intake stroke and the compression stroke is changed according to a target air-fuel ratio.

In addition, in each of the combustion modes, the pressure of the injected fuel (hereinafter referred to as "fuel pressure") is an important control parameter that greatly influences the atomization state of the injected fuel and its moisture amount (the amount of fuel attached to a piston and the inner wall surface of the cylinder). Therefore, various methods have been proposed for a method of setting a target fuel pressure.

For example, in JP H09 21369 A the fuel pressure is lowered during a low load or a small injection amount, thereby ensuring the stability and the atomizability of an injection.

In addition, in JP 3 417 158 B2 the fuel pressure is lowered while the engine is cold, thereby decreasing the amount of moisture.

DE 102 17 095 A1 shows a control unit for an internal combustion engine in which a shift map is provided to determine a target speed. The displacement map determines a correction amount of an acceleration position corresponding to the target rotational speed. In a map of a demanded torque set for a driving state after warm-up, the operation amount of the accelerator and the correction amount of the operation amount of the accelerator, which is determined by the shift map corresponding to the target rotational speed, are added. A requested axle torque is set using a map of the corrected operation amount of the accelerator and the rotational speed.

DE 600 12 422 T2 12 shows a start control apparatus for an internal combustion engine having a start control operation means for selecting a start operation from first and second start operations according to the characteristic of fuel supplied to the internal combustion engine and starting the internal combustion engine, wherein operation detection means for detecting a running state of the internal combustion engine, and Switching means for switching the start operation to the second start operation, when the running state of the internal combustion engine is not detected within a predetermined time after starting the starting of the internal combustion engine using the first start operation, are provided.

In general, the control parameters of an exhaust gas recirculator, a flow control valve and a valve timing control device are adjusted by using a fuel having a standard fuel performance (standard fuel). Accordingly, in the techniques of the above patent documents, the control parameters and a fuel pressure control characteristic are adjusted assuming the use of the standard fuel, and the fuel performance is not considered at all.

Also, a combustion mode switching condition for switching a combustion mode (map of an engine speed and a load) is adjusted by using the fuel having the standard fuel behavior (standard fuel). Accordingly, in the techniques of the above-mentioned patent documents, the combustion mode switching condition is adjusted assuming the use of the standard fuel, and the fuel performance is not considered at all.

However, fuels actually used in the market have different fuel behaviors and, in turn, the vaporization characteristic and, in turn, an atomization characteristic of the fuel injected from a fuel injection valve differ depending on the fuel behaviors. Therefore, if a heavier fuel of a lower atomization characteristic is used, the injected fuel can not be sufficiently atomized with the control parameters adjusted for the standard fuel. This results in the problem that a combustion state deteriorates, so that the smoke emission amount of the internal combustion engine increases or driveability deteriorates.

In addition, when the heavy fuel of the low-grade atomization characteristic is used, the injected fuel may not be sufficiently atomized in the stratified charge combustion mode or the dual injection mode in which a stable combustion range is originally narrower than in the homogeneous combustion under the combustion mode switching condition appropriate for the Standard fuel is adjusted. Therefore, the combustion state sometimes deteriorates, so that the smoke emission amount increases or the drivability deteriorates.

In addition, when the heavy fuel having the inferior atomization characteristic is used, the fuel pressure control characteristic adapted to the standard fuel results in insufficient atomization of the injected fuel or the amount of moisture increases, so that the problem arises that the fuel pressure control characteristic increases Smoke emission quantity increased.

The present invention has been made in view of such circumstances. It is accordingly an object of the invention to provide a control device for a cylinder injection type internal combustion engine which can ensure a stable combustion state even when a heavy fuel is used, and which can realize the reduction of smoke and driveability when the heavy fuel is used.

This object is achieved with the respective control devices of claims 1, 3, 4, 5, 7 and 12.

Advantageous developments of the invention are the subject of the dependent claims.

To achieve the above object, the invention resides in a control device for a cylinder injection type internal combustion engine in which fuel is injected into a cylinder in an intake stroke or a compression stroke so as to be subjected to homogeneous combustion or stratified combustion with at least one exhaust gas recirculation control device 34 for controlling an external exhaust gas recirculation amount (external EGR amount) in which exhaust gas is recirculated from the exhaust system to an intake system, and a valve controller 39 . 40 , the opening and closing operations (or an opening or closing operation) of an intake valve and / or an exhaust valve varies, wherein a behavior of the fuel is decided by a fuel behavior decision means, so that when it is decided that the Fuel is a heavy fuel, the exhaust gas recirculation controller 34 and / or the valve control device 39 . 40 can be controlled by a controller in one direction so that the external EGR amount and / or a valve overlap amount is made smaller than in the case of using a light fuel.

Here, there is a relationship that, as the valve overlap amount increases, the internal EGR amount (amount of the combustion gases remaining in the cylinder) increases. As the external EGR amount or the internal EGR amount increases, the intake amount of the fresh air in the cylinder decreases and a combustion temperature lowers. Therefore, in the case of using the heavy fuel having less atomizability and combustibility than the light fuel, it is likely that a combustion state becomes unstable and smoke easily occurs due to the lowering of the combustion temperature in an operating range where the external EGR temperature is high. Amount or the internal EGR amount is large.

In consideration of this property, according to the invention, when it is decided that the used fuel is the heavy fuel, the exhaust gas recirculation control means 34 and / or the valve controller is controlled in the direction to make the external EGR amount and / or the valve overlap amount (internal EGR amount) smaller than in the case of using the light fuel. When the external EGR amount or the internal EGR amount is decreased, the intake amount of the fresh air in the cylinder increases and the combustion temperature increases. Therefore, when both or one of the external EGR amount and the valve overlap amount (internal EGR amount) is controlled in the decreasing direction in the case of using the heavy fuel, even the heavy fuel can stably control the effects of increasing the fresh air intake amount and the increase be burned the combustion temperature, so that the reduction of the smoke and the improvement of the drivability in the case of using the heavy fuel can be realized.

Meanwhile, the external EGR or the internal EGR has the effect of raising the in-cylinder temperature (intake air temperature) and thus promoting the atomization of the fuel. Therefore, if the external EGR amount or the internal EGR amount has become excessively small, the in-cylinder temperature becomes lower than a temperature range for atomizing the heavy fuel, and the atomization of the fuel becomes insufficient in the case of using the heavy fuel. Accordingly, the piston fuel moisture (fuel attached to a piston) increases and smoke is likely to occur.

The control according to the fuel behavior as described above may preferably be performed well only during the stratified charge combustion operation without being performed during the homogeneous combustion operation.

A period of time from fuel injection to ignition is longer in the homogeneous combustion operation in which the fuel is injected into the intake stroke than in the stratified charge combustion operation in which the fuel is injected in the compression stroke, and may include a sputtering period for the fuel in the former operation be set up. Therefore, during the homogeneous combustion operation, a period of time necessary for atomizing the heavy fuel can be ensured without performing any special control according to the fuel performance. Moreover, the mixture of the fuel and the air can be driven by the flow of intake air, so that combustion stability can be ensured even with the heavy fuel.

In addition, when it has been decided that the fuel used is the heavy fuel during the stratified charge combustion operation, according to the present invention, a flow control valve is well controlled in the direction of intensifying a flow more than in the case of using the light fuel. In this way, in the case where the stratified charge combustion operation is performed with the heavy fuel, the current (swirl flow or falling current) caused in the cylinder is intensified. Thus, the mixture of the fuel is advanced, so that the atomization of the fuel can be driven, and the combustion stability can be ensured even with the heavy fuel.

In addition, in the control device for a cylinder injection type internal combustion engine according to the invention, in which a stratified charge combustion mode and a homogeneous combustion mode are switched according to an engine speed and / or load, a fuel characteristic of a fuel used is decided by a fuel behavior decision device, and a combustion mode switching condition, which is the engine speed and / or the load in the case of switching the stratified charge combustion mode and the homogeneous combustion mode, subject to the decision of heavy fuel, decides to one side of a lower one Speed and a side of a lower load than in the case of using a light fuel modified.

During operation of the stratified charge combustion mode, the fuel is injected in the compression stroke, so that the sputtering period of the fuel from fuel injection to ignition is originally short. In addition, the sputtering period of the fuel becomes shorter as the engine speed becomes higher. Further, the amount of fuel to be injected is increased more as the load becomes larger, and a time duration for the fuel injection becomes longer, so that there is a relationship that as the load becomes larger, the sputtering period of the fuel Fuel from the end of the fuel injection to the ignition is shorter. On the other hand, a period of time necessary for atomizing the heavy fuel in a state capable of stable combustion is not longer than in the case of atomizing the light fuel. Therefore, if the heavy fuel is used, the sputtering time of the heavy fuel becomes insufficient and stable stratified combustion in the range of the operating range of the stratified charge combustion mode is difficult, which is on the side of the homogeneous combustion mode.

Taking such circumstances into consideration, the invention is that, when the heavy fuel is used, the combustion mode switching condition is changed to the lower-speed side and / or the lower-load side than in the case of using the light fuel the operating range of the stratified charge combustion mode, which is on the side of the homogeneous combustion mode, in the case of using the light fuel is changed to the operating range of the homogeneous combustion mode. Thus, in the operating region where the heavy fuel can not be exposed to stable stratified combustion, this heavy fuel is burned in the homogeneous combustion mode, whereby the heavy fuel can stably be burned, and the reduction of smoke and driveability in the Case of heavy fuel use can be realized.

The invention is not limited to a system in which the two combustion modes of a stratified charge combustion mode and a homogeneous combustion mode are switched, but is also applicable to a system in which the operating range of a dual injection mode in which fuel is injected in a cylinder and in an intake stroke or a compression stroke is set between the operating range of the stratified charge combustion mode and that of the homogeneous combustion mode. In this system, in a case where it has been decided that the fuel is a heavy fuel, combustion mode switching conditions for deciding engine speeds and / or loads when the stratified charge combustion mode and the dual injection mode are to be switched and when the dual injection mode and the homogeneous combustion mode are to be switched on the side of a lower speed and / or the side of the lower load are modified than in the case of using the light fuel. In this case, in this operating range in which the heavy fuel can not be exposed to stable stratified combustion, this heavy fuel is burned in the dual injection mode and further in the operation where the heavy fuel is not stably burned even in the dual injection mode can (the operating range in which the atomization of the heavy fuel that is injected in the compression stroke becomes insufficient) burned the heavy fuel in the homogeneous combustion mode. In this way, even in the case of switching the three combustion modes of the stratified charge combustion mode, the dual injection mode and the homogeneous combustion mode, the combustion mode in which the heavy fuel can be stably burned can be formed according to the operating range in the case of using the heavy fuel and can Reduction of smoke and the improvement of driveability in the case of using the heavy fuel can be realized.

Meanwhile, as the degree of heaviness of the fuel becomes higher, a period of time necessary for atomizing the fuel in a condition suitable for stable combustion becomes longer. In consideration of this property, it is also permissible to preferably provide means for deciding the degree of severity of the fuel used and an amount by which the combustion mode switching condition is changed to the lower-speed side and / or the lower-load side, according to the degree Gravity of the fuel used is modified to modify. In this way, an extent that the operating range of the stratified charge combustion mode is the good fuel consumption combustion mode in which the case of using the heavy fuel is reduced can be set to a required minimum according to the degree of severity of the fuel used. Thus, the reduction of the smoke are realized, preventing the fuel consumption from excessively deteriorating in the case of using the heavy fuel.

Moreover, in the system of the present invention in which the three combustion modes of the stratified charge combustion mode, the dual injection mode, and the homogeneous injection mode are switched, in the case where it has been decided that the used fuel is the heavy fuel, it is also permissible to set the injection timing of the combustion stroke To reduce the dual injection mode more than in the case of using the light fuel and to more increase the injection amount of the intake stroke. When the injection amount of the compression stroke is reduced, a period of time necessary for atomizing the injected fuel of the compression stroke in a state suitable for stable combustion is shortened. Therefore, if the injection amount of the compression stroke in the dual injection mode is reduced in the case of using the heavy fuel, the combustibility of the dual injection mode can be improved and the smoke can be reduced.

In the case, preferably, when it has been decided that the fuel is the heavy fuel, the injection amount of the compression stroke in the dual injection mode may also be set to the minimum injection amount of the stable injection region of a fuel injection valve. In this way, in the case of combustion of the heavy fuel in the dual injection mode, the ratio of the compression stroke injection at which the sputtering time of the fuel is likely to become insufficient can be minimized to maximize the ratio of the intake stroke injection that simply ensures the sputtering period of the fuel. Accordingly, the combustibility of the heavy fuel can be improved to the utmost.

In addition, it is also permissible to preferably arrange means for detecting the degree of severity of fuel used and to vary the injection amount of the compression stroke in the dual injection mode according to the degree of severity of the fuel used. In this way, in the case of using the heavy fuel in the dual injection mode, it is inevitable that the injection amount of the compression stroke injection with the good fuel consumption excessively decreases and the deterioration of the fuel consumption due to the reduction of the injection amount of the compression stroke to the required Minimum can be limited.

In addition, preferably, the dual injection mode may also be switched to the homogeneous combustion mode when the proportion of the injection amount of the compression stroke to the total injection amount of the intake stroke and the compression stroke has become a predetermined value or less during execution of the dual injection mode. In this way, in an operation range in which the fuel consumption in the dual injection mode becomes worse than in the homogeneous combustion mode in the case of using the heavy fuel, the dual injection mode can be switched to the homogeneous combustion mode, and the fuel consumption can be prevented from being excessive due to the dual injection mode deteriorated.

In addition, preferably, the ratio in the injection amount of the compression stroke at which the dual injection mode is switched to the homogeneous combustion mode may also be modified according to the degree of severity of the fuel used. In this way, the dual injection mode at the optimum timing can be switched to the homogeneous combustion mode corresponding to the degree of severity of the fuel used.

In addition, in a control device for a cylinder injection type internal combustion engine according to the present invention, in which a commanded value of injected fuel pressure (hereinafter referred to as "target fuel pressure") is set by a target fuel pressure adjusting device according to an operating state of the cylinder injection type internal combustion engine and the injected fuel pressure (hereinafter referred to as "fuel pressure &Numsp;                               . a heavy fuel is. The heavy fuel has an inferior atomization characteristic than the light fuel, and therefore, when the heavy fuel is injected into the cylinder under a high fuel pressure, an amount that keeps the fuel as fuel moisture at the same position of a piston increases and multiplies smoke emission amount. In the case of using the heavy fuel, therefore, the target fuel pressure is lowered within a range in which the atomization fineness of the fuel does not deteriorate, thereby prolonging the injection period of the fuel. When the injection period of the fuel becomes long, extends an area in which the piston moves from the start of the fuel injection to the end thereof, so that the amount by which the fuel that is injected from the fuel injection valve remains as the wet fuel at the same position of the piston , decreases and reduces the amount of smoke emission.

In general, the more the amount of moisture of the fuel decreases as the temperature of an internal combustion engine (the temperature of a piston surface or cylinder inner wall surface) becomes higher. As the engine is further warmed up, the amount of moisture decreases to a level that is not very problematic even in the case of using a heavy fuel.

In consideration of this point, it is also permissible to preferably provide a water temperature detecting means for detecting the cooling water temperature of the internal combustion engine and to set the target fuel pressure by neglecting the decision result of the fuel holding means when the detected cooling water temperature is a predetermined temperature or above. In this way, the control for lowering the fuel pressure in the case of using the heavy fuel is performed only in a low water temperature range in which the increase in the amount of moisture attributable to the heavy fuel is problematic. In a high water temperature range in which the amount of moisture of the heavy fuel does not become very problematic, the target fuel pressure is not lowered even in the case of using the heavy fuel. It is therefore possible to set the optimum target fuel pressure in accordance with the operating state of the internal combustion engine.

In addition, as the rotational speed of the engine becomes higher, a current caused in the cylinder is further intensified to advance the mixture of the injected fuel and the in-cylinder flow and reduce the amount of moisture.

Therefore, it is also permissible to preferably arrange an engine detection means for detecting an engine speed and establish the target fuel pressure by neglecting the decision result of the fuel behavior decision means when the detected engine speed is a predetermined value or above. In that case, only in a low speed range, in which the increase in the amount of moisture due to the heavy fuel becomes apparent, the target fuel pressure is lowered to reduce the smoke emission amount.

In addition, when it has been decided by the fuel behavior device that the fuel is the heavy fuel, the target fuel pressure may be lower than in the case of using the light fuel in a range of a large required injection amount and higher than in the case of using the light fuel in one Be set up area of small required injection quantity. More specifically, in the range of the large required injection amount, the target fuel pressure is set lower in the case of using the heavy fuel than in the case of using the light fuel, and a fuel injection period is lengthened, whereby the amount by which the fuel is used as the moisture fuel at the remains the same position of the piston is made small to reduce the smoke emission amount in the case of using the heavy fuel. On the other hand, in the range of the small required injection amount, the target fuel pressure is set higher in the case of using the heavy fuel than in the case of using the light fuel, considering that the amount of fuel serving as the moisture fuel at the same position of the piston remains small even in the case of using the heavy fuel, whereby the injected fuel is finely dispersed in the case of using the heavy fuel to promote atomization and improve the combustibility.

1 FIG. 13 is a schematic structural view of the entire engine control system in Embodiment 1 of the present invention; FIG.

2 FIG. 10 is a flowchart showing the process flow of an external EGR amount calculating routine in Embodiment 1; FIG.

3 Fig. 10 is a flowchart showing the process flow of a valve timing calculation routine in the embodiment 1;

4 Fig. 12 is a graph for explaining the relationship between an external EGR amount (the opening degree of an EGR valve) and a smoke emission amount in the case of using a heavy fuel;

5 Fig. 12 is a graph for explaining the relationship between a valve overlap amount (an internal EGR amount) and the smoke emission amount in the case of using the heavy fuel;

6 Fig. 10 is a flowchart showing the process flow of an external EGR amount calculating routine in an embodiment 2;

7 Fig. 10 is a flowchart showing the process flow of a valve timing calculation routine in Embodiment 2;

8th Fig. 10 is a flowchart showing the process flow of a flow control valve opening degree calculation routine in an embodiment 3;

9 Fig. 12 is a graph for explaining the relationship between the opening degree of a flow control valve (a current intensity), a smoke emission amount, and a torque fluctuation during a stratified charge combustion operation;

10 FIG. 10 is a flowchart showing the process flow of an engine control main routine in Embodiment 4; FIG.

11 Fig. 10 is a flowchart showing the process flow of a required combustion mode determination routine in Embodiment 4;

12 FIG. 12 is a graph for explaining the relationship between a heavy fuel combustion mode switching map and a light fuel combustion mode switching map in Embodiment 4; FIG.

13A and 13B FIG. 16 is graphs for explaining the relationship between a heavy fuel combustion mode switching map and a light fuel combustion mode switching map in an embodiment 5; FIG.

14 Fig. 12 is a graph for explaining relationships between a smoke emission amount and a fuel behavior in a dual injection mode and a stratified charge combustion mode;

15 Fig. 10 is a flowchart showing the process flow of a dual injection mode injection amount calculation routine in an embodiment 6;

16 Fig. 10 is a flowchart showing the process flow of a dual injection mode injection amount calculation routine in an embodiment 7;

17 Fig. 12 is a graph for explaining the relationship between a fuel consumption efficiency and a compression stroke injection rate K in the dual injection mode;

18 Fig. 10 is a timing chart showing an example of switching from the dual injection mode and a homogeneous combustion mode in the embodiment 7;

19 Fig. 10 is a flowchart showing the process flow of a target fuel pressure calculation routine in an embodiment 8;

20A and 20B Fig. 10 is graphs for explaining relationships between a target fuel pressure setting map for a light fuel and a target fuel pressure setting map for a heavy fuel in the embodiment 8;

21 FIG. 12 is a graph for explaining the relationship between a required torque, a target fuel pressure, and a fuel behavior in Embodiment 8; FIG.

22 Fig. 10 is a flowchart showing the process flow of a target fuel pressure calculation routine in an embodiment 9;

23 FIG. 10 is a flowchart showing the process flow of a target fuel pressure calculation routine in an embodiment 10; FIG. and

24 FIG. 10 is a flowchart showing the process flow of a target fuel pressure calculation routine in an embodiment 11. FIG.

EMBODIMENT 1

An embodiment 1 of the present invention will be described with reference to FIGS 1 to 5 described. First, the schematic structure of the entire engine control system will be described with reference to FIG 1 described. An air purifier 13 is at the most upstream part of the inlet pipe 12 a cylinder injection combustion engine 11 arranged, which is an internal combustion engine of the cylinder injection type. An air flow meter 14 that detects the amount of intake air is located downstream of the air cleaner. A throttle valve 16 that by a motor 15 how to drive a DC motor, for example, is downstream from the air flow meter 14 arranged and the opening degree of the throttle valve 16 (Throttle opening degree) is determined by a throttle opening degree sensor 17 detected.

There is also a compensation tank 18 downstream of the throttle valve 16 arranged and is this with an inlet pipe pressure sensor 19 provided for detecting an intake pipe pressure. Of the balance tank 18 is also with an intake manifold 20 for introducing the air into each cylinder of the internal combustion engine 11 provided and the intake manifold 20 Each cylinder is equipped with a flow control valve 31 for controlling a current intensity in the cylinder (swirl current intensity or falling current intensity).

A fuel injector 21 , which injects fuel directly into the corresponding cylinder, is on each cylinder of the internal combustion engine 11 assembled. A spark plug 22 is on the cylinder head of the internal combustion engine 11 mounted for each cylinder and a mixture in the cylinder is caused by the spark discharge of the corresponding spark plug 22 ignited. In addition, the inlet valve 37 and an exhaust valve 38 of the internal combustion engine 11 each with valve timing controllers (valve controllers) 39 and 40 which vary the opening and closing timings of the respective valves.

A knock sensor 32 for detecting knocking and a cooling water temperature sensor 23 for detecting the temperature of cooling water are on the cylinder block of the internal combustion engine 11 assembled. In addition, a crank angle sensor 24 which outputs a crank angle signal every predetermined crank angle is mounted on the outer peripheral side of a crankshaft (not shown). The crank angle and the engine rotation speed are determined based on the output signal of the crank angle sensor (engine rotation speed detecting device) 24 detected.

On the other hand, the exhaust pipe 25 of the internal combustion engine 11 with an upstream catalyst 26 and a downstream catalyst 27 for purifying exhaust gas and is an exhaust gas sensor (such as an air-fuel ratio sensor or an oxygen sensor) 28 for detecting the air-fuel ratio, lean / rich state, or the like state of the exhaust gas upstream of the upstream side catalyst 26 arranged. In Embodiment 1, a ternary catalyst, which purifies CO, HC, NOx and so on contained in the exhaust gas, is cleaned in the vicinity of a theoretical air-fuel ratio than the upstream-side catalyst 26 while a NOx occluding and reducing type catalyst is used as the downstream side catalyst 27 is used. The NOx occlusion and reduction catalyst 27 has characteristics of occluding the NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is lean, and reducing and purifying the occluded NOx, and then emitting the resulting gas when the air-fuel ratio has become almost the theoretical air-fuel ratio or rich.

There is also an EGR pipe 33 for recirculating a part of the exhaust gas to the inlet side between the downstream side of the upstream side catalyst 26 on the exhaust pipe 25 and the equalization tank 18 connected downstream of the throttle valve 16 in the inlet pipe 12 is located, and is an EGR valve (exhaust gas recirculation control device) 34 for controlling an external exhaust gas recirculation amount (external EGR amount) midway of the EGR pipe 33 arranged. In addition, the pedaling amount (accelerator opening degree) of an accelerator pedal becomes 35 by an accelerator sensor 36 detected.

The outputs of the various sensors given above are given to an engine control unit (hereinafter abbreviated as "ECU"). 30 entered. The ECU 30 is mainly composed of a microcomputer and executes various control routines stored in a built-in ROM (storage medium). Thus, according to the operating state, the internal combustion engine controls 11 the ECU 30 the fuel injection amount and the fuel injection timing of each fuel injection valve 21 , the ignition timing of each spark plug 22 and so on, and controls the respective valve timing controllers 39 and 40 of the inlet valve 37 and the exhaust valve 38 to the actual valve timings of the intake valve 37 and the exhaust valve 38 in accordance with target valve timings.

The ECU 30 switches a stratified charge combustion mode and a homogeneous combustion mode according to the engine operating condition (such as required torque or engine speed). In the stratified charge combustion mode, a small amount of fuel is injected directly into the cylinder in a compression stroke around a stratified mixture in the vicinity of the spark plug 22 form and perform stratified combustion, thereby improving fuel economy. On the other hand, in the homogeneous combustion mode, the amount of fuel to be injected is increased, and the fuel is injected directly into the cylinder in the intake stroke to form a homogeneous mixture and perform homogeneous combustion, thereby increasing the engine output.

In general, there is a relationship that when a valve overlap increases, both the intake valve 37 as well as the exhaust valve 38 are open, an internal EGR amount (the amount of burned gases remaining in the cylinder) increases. As in 4 or 5 In the case of using heavy fuel, the smoke increases as the external EGR amount or the internal EGR amount increases in excess of an appropriate range during the stratified charge combustion operation. The reason for this is given below. As the external EGR amount or the internal EGR amount increases, the amount of intake of fresh air in the cylinder decreases and a combustion temperature decreases. Therefore, in the case of using the heavy fuel having lower atomizability and combustibility than light fuel, it is likely that a combustion state becomes unstable in a high EGR range in which the external EGR amount or the internal EGR amount is large, and the smoke easily occurs due to the lowering of the combustion temperature.

Therefore, the ECU performs 30 the routines of the 2 and 3 during the stratified charge combustion operation. Thus, in the high EGR areas where the external EGR amount and the valve overlap amount exceed predetermined values A and B, respectively, the ECU controls the ECU 30 the external EGR amount and the valve overlap amount (internal EGR amount) toward reduction in the case of using the heavy fuel to increase the amount of intake of the fresh air in the cylinder and to raise the combustion temperature, thereby reducing the smoke in the Case of heavy fuel use decrease. In this way, the ECU plays 30 the role of a control device, which is mentioned in the appended claims.

In addition, the ECU performs 30 a fuel behavior decision routine, not shown, thereby serving as a fuel behavior decision means and deciding the fuel behavior of the injected fuel based on a combustion stability (revolution fluctuation) after the start of the engine, the deviation of the air-fuel ratio during a transient operation, or the like. Alternatively, the fuel behavior of the injected fuel may be decided on the basis of the output (evaporative ability of the fuel) of a sensor such as a fuel behavior sensor disposed in a fuel tank.

The process contents of the respective routines in the 2 and 3 by the ECU 30 will be described below. (Calculation routine of external EGR quantity)

The calculation routine of the external EGR quantity in 2 becomes in the control cycle of the EGR valve 34 during the stratified charge combustion operation. When this routine is activated, first, an engine speed Ne at one step 101 and a required torque established based on an accelerator opening degree or the like is loaded at the next step 102 loaded. Then the routine goes one step 103 Further, in which an external EGR basic amount EGRB is calculated by a map or a formula according to an engine operating state (for example, an engine rotation speed Ne and the required torque).

Subsequently, the routine proceeds to a step 104 Next, which decides whether a used fuel is a heavy fuel or not. Depending on the resulting decision that the fuel is not the heavy fuel (namely, that it is a light fuel), the problems of increasing the smoke and deteriorating the driveability attributable to the heavy fuel do not occur. Therefore, the routine goes to a step 107 which sets a correction amount EGRC of the external EGR amount to the minimum value (0).

On the other hand, in a case where in the step 104 It has been decided that the fuel used is the heavy fuel, the problems of the increase of the smoke and the deterioration of the drivability when the external EGR amount becomes excessively large. Therefore, the routine goes to a step 105 Next, it decides if the external EGR baseline EGRB, at the step 103 is calculated larger than a predetermined value A or not. As in 4 is shown, the predetermined value A is set to an external EGR amount at which the occurrence of the smoke starts to be manifested in the high EGR range. This predetermined value A may be set to a preset fixed value for simplifying a calculation process, but may also be a map or a formula according to the engine operating condition (eg, the engine speed Ne and the required torque) and / or the severity of the fuel used be calculated.

If at the step 105 It has been decided that the external EGR basic amount EGRB is not larger than the predetermined value A, it is judged that the problem of the increase of the smoke or the deterioration of the drivability does not occur. Then the routine proceeds to the step 107 Next, which sets the EGR amount correction amount EGRC to the minimum value (0).

On the other hand, in a case where in the step 105 It was decided that the external EGR base quantity EGRB is greater than the predetermined value A, the routine becomes one step 106 Further, the external EGR amount correction amount EGRC is calculated by the map, the formula or the like according to the engine operating state (for example, the engine speed Ne and the required torque) to avoid the problems of smoke increase and driveability deterioration which are due to the heavy fuel.

After the correction amount EGRC of the external EGR amount in the step 106 or 107 has been determined in the above-mentioned manner, the routine goes to a step 108 Next, in which a final external EGR amount EGR is found by subtracting the EGR amount correction amount EGRC from the external EGR basic amount EGRB. Thus, when the heavy fuel is used, the external EGR amount is decrementally corrected by the external EGR amount correction amount EGRC set according to the engine operating condition in the high EGR range in which the external EGR basic amount EGRB is greater than the predetermined value is A

(Valve timing calculation routine)

The valve timing calculation routine in FIG 3 becomes in the control cycle of the valve timing control means 39 and 40 during the stratified charge combustion operation. When this routine is activated, first, the engine rotation speed Ne becomes one step 201 and the required torque established based on the accelerator opening degree or the like is loaded at the next step 202 loaded. Then the routine goes one step 203 in which the base valve timing VCTB of the intake valve 37 is calculated by a map or a formula according to the engine operating state (for example, the engine speed Ne and the required torque).

Subsequently, the routine proceeds to a step 204 which decides whether the fuel used is the heavy fuel or not. Depending on the result of the decision that the used fuel is not the heavy fuel (namely, it is the light fuel), the problems of the increase of the smoke and the deterioration of the driveability attributable to the heavy fuel do not occur , Therefore, the routine goes to a step 208 which sets a valve timing correction amount VCTC to the minimum value (0).

On the other hand, in a case where the fuel used is the heavy fuel in the step 204 The problems of increase of smoke and deterioration of driveability have been decided when the valve overlap amount (internal EGR amount) becomes excessively large. Therefore, the routine goes to a step 205 Further, in which the valve overlap amount OL is calculated on the basis of the base valve timing VCTB which is the step 203 is calculated. Then the routine goes one step 206 Further, which judges whether the valve overlap amount OL is greater than a predetermined value B or not. As in 5 4, the predetermined value B is set to a valve overlap amount at which the occurrence of the smoke in the region where the valve overlap amount (internal EGR amount) is large begins to become noticeable. This predetermined value B may be set at a preset fixed value for simplifying the calculation process, but may also be calculated by a map or a formula according to the engine operating state (eg, the engine speed Ne and the required torque) and / or the degree of gravity.

If at the step 206 It has been decided that the valve overlap amount DL is not larger than the predetermined value B, it is judged that the problem of the increase of the smoke or the deterioration of the driveability is not attributable to the heavy fuel. Then the routine proceeds to the step 208 Further, the valve timing correction amount VCTC is set to the minimum value (0).

On the other hand, in a case where in the step 206 it has been decided that the valve overlap amount DL is larger than the predetermined value B, the routine goes to a step 207 Further, in which the valve timing correction larger VCTC is calculated by the map, the formula or the like according to the engine operating state (for example, the engine speed Ne or the required torque) to avoid the problems of the increase of the smoke and the deterioration of the driveability, which are on the heavy fuel are attributed.

After the valve timing correction amount VCTC at the step 207 or 208 has been determined in the above-mentioned manner, the routine goes to a step 209 Next, the final valve timing VCT is calculated by subtracting the valve timing correction quantity VCTC from the base valve timing VCTB. So if the heavy fuel is used, the valve overlap amount (internal EGR amount) is decrementally corrected by the valve timing correction amount VCTC established according to the engine operating state in the operating range in which the valve overlap amount OL (internal EGR amount) is larger than the predetermined value B. ,

In Embodiment 1 thus far described, in the high EGR regions in which the external EGR amount and the valve overlap amount become larger than the predetermined values A and B, respectively, during the stratified charge combustion operation, the external EGR amount and the valve overlap amount become in the direction for decreasing controlled in the case of using the heavy fuel. Therefore, in the high EGR ranges, with respect to which the problems of increase of smoke and deterioration of drivability in the case of using the heavy fuel are grasped, the amount of intake of the fresh air into the cylinder can be increased to raise a combustion temperature. Accordingly, the heavy fuel can also be exposed to stable stratified combustion, and the reduction of the smoke and the improvement of the driveability can be realized in the case of using the heavy fuel.

Incidentally, in Embodiment 1, the corrections of the external EGR amount and the valve overlap amount in the case of using the heavy fuel corresponding to the respective routines in FIGS 2 and 3 are not made during the homogeneous combustion operation and are made only during the stratified charge combustion operation. The reasons are given below. A period from the fuel injection to the ignition is longer in the homogeneous combustion mode in which the fuel is injected in the intake stroke than in the stratified charge combustion mode in which the fuel is injected in the compression stroke, and a sputtering period for the fuel may be in the former operation be set up long. Therefore, during the homogeneous combustion mode, a period of time necessary for atomizing the heavy fuel can be ensured without making the corrections in the case of using the heavy fuel. Moreover, the mixture of the fuel and the air can be driven by the flow of intake air, so that combustion stability can be ensured even with the heavy fuel.

Of course, however, the external EGR amount and / or the valve overlap amount may be corrected even in the case of using the heavy fuel even during the homogeneous combustion operation.

In addition, in the embodiment 1, the external EGR amount correction amount EGRC and the valve timing correction amount VCTC are calculated according to the engine operating state (for example, the engine speed Ne and the required torque). However, the external EGR amount correction amount EGRC and / or the valve timing correction amount VCTC may be set to a preset fixed value (preset fixed values) for simplifying the calculation process, or may be set according to the degree of gravity or the degree of gravity and the Engine operating condition can be calculated.

In addition, in the embodiment 1, both the external EGR amount and the valve overlap amount are corrected in the case of using the heavy fuel, but also one of them can be corrected.

EMBODIMENT 2

Meanwhile, the external EGR or the internal EGR has the effect of raising an in-cylinder temperature (intake air temperature) and thus promoting the atomization of the fuel. Therefore, when an external EGR amount or an internal EGR amount has become excessively small, the in-cylinder temperature becomes lower than a temperature range necessary for atomizing the heavy fuel, and the heavy fuel used can not be sufficiently atomized. Accordingly, piston fuel moisture (fuel adhering to a piston) increases and smoke is likely to occur (see 4 and 5 ).

In the embodiment 2 of the present invention, therefore, the respective routines in the 6 and 7 during the stratified charge combustion operation. Thus, in the low EGR ranges where the external EGR amount and the valve overlap amount (internal EGR amount) become smaller than predetermined values C and D, respectively, the external EGR amount and the valve overlap amount become in the direction to increase in the case controlling the use of the heavy fuel to raise the in-cylinder temperature and promote the atomization of the fuel to thereby reduce the smoke in the case of using the heavy fuel. The process contents of the respective routines in the 6 and 7 are described below.

(Calculation routine of external EGR quantity)

The calculation routine of the external EGR quantity in 6 is such that the process contents of the steps 105 and 108 the calculation routine of the external EGR quantity in 2 each to the process contents of the steps 105a and 108a have been modified. The process contents of the other steps in 6 are each identical to those of the corresponding steps in 2 ,

If at the step 104 the routine in 6 it has been decided that the used fuel is the heavy fuel, this routine proceeds to the step 105a Next, who decides whether the external EGR baseline EGRB, at the step 103 is calculated smaller than the predetermined value C or not. As in 4 2, the predetermined value C is set to an external EGR amount necessary for reducing the smoke in the low EGR range. The predetermined value C may be set to a preset fixed value for simplifying the calculation process, but may also be calculated by a map or a formula according to the engine operating state (eg, the engine speed Ne and the required torque) and / or the degree of gravity.

If at the step 105a It has been decided that the external EGR basic amount EGRB is not smaller than the predetermined value C, it is judged that the problem of the increase of the smoke or deterioration of the drivability attributable to the seriousness of the fuel does not occur. Then the routine proceeds to the step 107 Next, which sets the EGR amount correction amount EGRC to the minimum value (0).

On the other hand, in a case where in the step 105a it has been decided that the external EGR basic amount EGRB is smaller than the predetermined value C, the routine goes to the step 106 Further, the EGR amount correction amount EGRC is calculated by a map, formula or the like according to the engine operating state (for example, the engine speed Ne and the required torque) to avoid the problems of smoke increase and driveability deterioration which are due to the heavy fuel.

After the correction amount EGRC of the external EGR amount in the step 106 and 107 was determined in the above-mentioned manner, the routine proceeds to the step 108a Next, in which the final external EGR amount EGR is found by adding the external EGR amount correction amount EGRC to the basic EGR basic amount EGRB. Thus, when the heavy fuel is used, the external EGR amount is incrementally corrected by the external EGR amount correction amount EGRC set according to the engine operating condition in the low EGR range in which the external EGR basic amount ERGB is smaller than the predetermined value is C Consequently, the in-cylinder temperature is raised to promote the atomization of the fuel and to reduce the smoke in the case of using the heavy fuel.

(Valve timing calculation routine)

The valve timing calculation routine in FIG 7 is such that the process contents of the steps 206 and 209 the valve timing calculation routine in FIG 3 each to the process contents of the steps 206a and 209a have been modified. The process contents of the other steps in 7 are each identical to those of the corresponding steps in 3 ,

If at the step 204 the routine in 7 It has been decided that the used fuel is the heavy fuel, this routine goes to a step 205 Next, the valve overlap amount OL is calculated. Then the routine goes to the step 206a Further, which decides whether the valve overlap amount OL is smaller than the predetermined value D or not. As in 5 11, the predetermined value D is set to a valve overlap amount necessary for reducing the smoke in the area where the valve overlap amount (internal EGR amount) is small. This predetermined value may be set to a preset fixed value for simplifying the calculation process, but may also be calculated by a map or a formula according to the engine operating state (eg, the engine speed Ne and the required torque) and / or the degree of gravity.

If at the step 206a It has been decided that the valve overlap amount CL is not smaller than the predetermined value D, it is judged that the problem of the increase of the smoke or the drivability does not occur due to the heavy fuel. Then the routine proceeds to the step 208 which sets the valve timing correction amount VCTC to the minimum value (0).

On the other hand, in a case where in the step 206a It has been decided that the valve overlap amount CL is smaller than that predetermined value D is the routine to the step 207 Further, in which the valve timing correction amount VCTC is calculated by the map, the formula or the like according to the engine operating state (for example, the engine speed Ne and the required torque) to avoid the problems of the increase of smoke and drivability due to the heavy Fuel are due.

After the valve timing correction amount VCTC at the step 207 or 208 was determined in the above-mentioned manner, the routine proceeds to the step 209a Next, in which the final valve timing VCT is found by adding the valve timing correction amount VCTC to the base valve timing VCTB. Thus, when the heavy fuel is used, the valve overlap amount (internal EGR amount) is incrementally corrected by the valve timing correction amount VCTC established according to the engine operating condition in the operation range in which the valve overlap amount OL (internal EGR amount) is smaller than the predetermined one Value is D. Consequently, the in-cylinder temperature is raised to promote the atomization of the fuel and to reduce the smoke in the case of using the heavy fuel.

Incidentally, also in the embodiment 2, corrections of the external EGR amount and the valve overlap amount are not increased in the case of using the heavy fuel during the homogeneous combustion operation, and are made only during the stratified charge combustion operation. Of course, the external EGR amount and / or the valve overlap amount may also be corrected in the case of using the heavy fuel even during the homogeneous combustion operation.

In addition, in the embodiment 2, the external EGR amount correction amount EGRC and the valve timing correction amount VCTC are calculated according to the engine operating state (for example, the engine speed Ne and the required torque). However, the external EGR amount correction amount EGRC and / or the valve timing correction amount VCTC may be a preset preset value (default fixed values) to simplify the calculation process, or may also be according to the severity or severity level and the engine operating condition be calculated.

In addition, in Embodiment 2, both the external EGR amount and the valve overlap amount are calculated in the case of using the heavy fuel, but only one of them may be corrected.

EMBODIMENT 3

Meanwhile, there is a current (swirl flow or falling stream) in each cylinder through the flow control valve 31 is caused, the action for promoting the mixture of the injected fuel and the air and thus to promote the atomization of the fuel. Therefore, when the intensity of the current caused in the cylinder is small during the stratified charge combustion operation in which the atomizability of the fuel is originally worse than in the homogeneous combustion operation, the fuel is insufficiently atomized to deteriorate the combustion state of stratified charge combustion. As in 9 is shown, this causes the problems that the smoke increases and the torque fluctuation increases to deteriorate the drivability of the internal combustion engine.

Therefore, in Embodiment 3 of the present invention, a flow control valve opening degree calculation routine is described in FIG 8th running to the flow control valve 31 in the direction to intensify the flow more than in the case of using a light fuel, when it has been decided that a used fuel is a heavy fuel during the stratified charge combustion operation. Thus, the mixture of the injected fuel and the air is promoted, and the atomization of the fuel is promoted to thereby stabilize the combustion state of the stratified charge combustion.

The flow control valve opening degree calculation routine in FIG 8th becomes in the control cycle of the air control valve 31 during operation of the internal combustion engine 11 executed. When this routine is activated, first, an engine speed Ne at one step 301 and a required torque established based on an accelerator opening degree or the like is loaded at the next step 302 loaded. Then the routine goes one step 303 Further, in which a base current control value opening degree SCVB is calculated by a map, a formula or the like according to an engine operating state (for example, the engine rotation speed Ne and the required torque).

Subsequently, the routine proceeds to a step 304 which decides whether the fuel used is the heavy fuel or not. Depending on the resulting decision that the fuel used is not the heavy fuel (namely, it is the light fuel), the problems of the increase of the smoke and the deterioration of the driveability due to the heavy fuel do not occur. Therefore, the routine goes to a step 307 which sets a current control valve opening degree correction amount SCVC to the minimum value (0).

On the other hand, in a case where in the step 304 It has been decided that the fuel used, the heavy fuel, the problems of increasing the smoke and the deterioration of driveability, when the current intensity is excessively low. Therefore, the routine goes to a step 305 Next, which decides whether the internal combustion engine is in the stratified charge combustion operation or not. When it has been decided that the internal combustion engine is not in the stratified charge combustion operation (namely, the homogeneous combustion operation), it is judged that the problems of increase of smoke and deterioration of driveability due to the heavy fuel do not occur. Then the routine proceeds to the step 307 Next, the current control valve opening degree correction amount SCVC is set to the minimum value (0).

On the other hand, in a case where in the step 305 It has been decided that the internal combustion engine is in the stratified charge combustion operation, the routine to a step 306 Further, in which the flow control valve opening degree correction amount SCVC is calculated by the map, the formula or the like according to the engine operating condition (eg, the engine speed Ne and the required torque), to avoid the problems of the increase of smoke and drivability due to the heavy Fuel are due.

After the flow control valve opening degree correction amount SCVC at the step 306 or 307 determined in the above-mentioned manner, the routine goes to a step 308 Further, a final current control valve opening degree SCV is found by subtracting the current control valve opening degree correction amount SCVC from the base flow control valve opening degree SCVB. Thus, in the case where the heavy fuel is used during the stratified charge combustion operation, the opening degree of the flow control valve becomes 31 corrected in a decremental manner by the flow control valve opening degree correction amount SCVC set in accordance with the engine operating condition to thereby increase the current intensity.

According to Embodiment 3 described so far, in the case of using the heavy fuel during the stratified charge combustion operation, the opening degree of the flow control valve becomes 31 is decrementally corrected by the flow control valve opening degree correction amount SCVC according to the engine operating state to intensify the flow (swirl flow or falling flow) caused in the cylinder. Therefore, the mixture of the fuel and the air can be advanced to promote the atomization of the fuel. Accordingly, combustion stability can be ensured even with the heavy fuel, and the reduction of smoke and driveability can be realized.

Incidentally, in the embodiment 3, the current control valve opening degree correction amount SCVC is calculated according to the engine operating condition (for example, the engine speed Ne and the required torque). However, the flow control valve opening degree correction amount SCVC may be made a preset fixed value for simplifying the calculation process, or may also be calculated according to the degree of gravity or the degree of gravity and the engine operating state.

In addition, the embodiment 3 can also be performed in combination with the embodiment 1 or the embodiment 2.

Also, in the example of the system architecture that is in 1 is shown, the valve timing control means 39 arranged only on the inlet side, while the valve timing control means 40 can also be arranged on the outlet side. In this respect, however, the invention can also be applied to and performed for a cylinder injection type internal combustion engine equipped with any of various valve timing devices that vary valve lift amounts and operation angles other than valve timings.

EMBODIMENT 4

The ECU 30 in 1 switches a stratified charge combustion mode and a homogeneous combustion mode according to an engine speed and a load (a required torque). As in 12 11, the operation range of the stratified charge combustion mode is set to the lower speed / lower load sides as compared with those of the homogeneous combustion mode. In the A stratified charge combustion mode, a small amount of fuel is injected directly into each cylinder in each compression stroke to form a stratified mixture in the vicinity of the spark plug 22 form and perform the stratified combustion to thereby improve the fuel consumption. On the other hand, in the homogeneous combustion mode, the amount of fuel to be injected is increased, and the fuel is injected directly into the cylinder in an intake stroke to form a homogeneous mixture to perform homogeneous combustion to thereby increase the engine output.

During operation of the stratified charge combustion mode, the fuel is injected in the compression stroke, so that the sputtering period of the fuel from the fuel injection to the ignition is originally short. However, the atomization period of the fuel becomes shorter as the engine speed becomes higher. Further, as the load becomes larger, the amount of fuel to be injected increases more, and a fuel injection period becomes longer, so that there is a relationship that as the load becomes larger, the sputtering period of the fuel from the end of the fuel injection to the ignition becomes shorter. On the other hand, a time period necessary for atomizing a heavy fuel into a condition suitable for stable combustion is longer than in the case of atomizing a light fuel. Therefore, when the heavy fuel is used, a sputtering period of the heavy fuel becomes insufficient and stable stratified combustion becomes difficult in the range of the operating range of the stratified charge combustion mode, which is on the side of the homogeneous combustion mode.

Taking this disadvantage into account, the ECU performs 30 the respective routines described below during engine operation. Thus, when determining the combustion mode based on the engine speed and the load (required torque) depending on the decision of using the heavy fuel, a combustion mode switching condition (engine speed and load at the time of switching the combustion modes) is decided ) is modified to the side of a lower speed and to the side of a lower load than in the case of using the light fuel, whereby the range of the operating range of the stratified charge combustion mode, which is on the homogeneous combustion mode side, in the case of using the light fuel in the operating range the homogeneous combustion mode is modified (see 12 ). Consequently, in the operating region where the heavy fuel can not be stably exposed to the stratified combustion, this heavy fuel is burned in the homogeneous combustion mode to stably burn. The process contents of the respective routines that the ECU 30 will be described below.

(Internal combustion engine control main routine)

The engine control main routine in FIG 10 is executed in the predetermined cycle during the operation of the internal combustion engine. When this main routine is activated, first, the fuel behavior decision routine, which is not shown, at a step 401 performed to decide the fuel behavior of a fuel used on the basis of a combustion stability (rotation fluctuation) after the start of the internal combustion engine, the deviation of an air-fuel ratio during a transitional operation or the like. Alternatively, the fuel performance of the injected fuel may also be decided based on the output (evaporative ability of the fuel) of a sensor such as a fuel-performance sensor disposed in a fuel tank. The process of the step 401 plays the role of a fuel behavior decision device, which is mentioned in the appended claims.

Then the routine goes one step 402 Further, in which a required torque is calculated on the basis of an accelerator opening degree and an engine speed or the like, and the routine proceeds to a step 403 Further, in which a required combustion mode by performing the determination routine of the required combustion mode in 11 is determined, to which reference is made below. Hereinafter, an air-system control routine, a fuel-system control routine, and an ignition-system control routine, which are not shown, are respectively at the steps 404 - 406 executed, whereby the control parameters of an air system, a fuel system and an ignition system are respectively set to the set values of the required combustion mode, in the step 403 is determined, and the injected fuel is burned in the required combustion mode.

(Determination Routine of Required Combustion Mode)

When the determination routine of the required combustion mode in 11 at the step 401 the engine control main routine in 10 is activated, first, the engine speed Ne in one step 411 and the required torque established based on the accelerator opening degree is loaded at the next step 412 loaded. Then the routine goes one step 413 which decides whether the fuel used is a heavy fuel or not. Depending on the resulting decision that the fuel used is not the heavy fuel (namely, this is the light fuel), the routine goes to one step 414 Further, in which a combustion mode switching map (see 12 ) is selected for the light fuel, and wherein one of the stratified charge combustion mode and the homogeneous combustion mode is selected as the required combustion mode according to the engine speed Ne and the required torque at the present time.

On the other hand, in a case where in the step 413 It was decided that the fuel used is the heavy fuel, the routine to a step 415 Further, in which a combustion mode switching map (see 12 ) is selected for the heavy fuel, and one of the stratified charge combustion mode and the homogeneous combustion mode is selected as a required combustion mode according to the engine speed Ne and the required torque at the present time. The data of the heavy-fuel combustion mode switching map is shifted to the lower-speed side and lower-load side than in the light-fuel combustion mode switching map and this range of the operation region of the stratified-charge combustion mode operating on the homogeneous combustion mode side in the case of using the light-weight Fuel is changed into the operating range of the homogeneous combustion mode. Thus, in the operating range in which the heavy fuel can not be stably exposed to the stratified combustion, this heavy fuel can be burned in the homogeneous combustion mode to stably burn, and the reduction of smoke and the drivability in the case of the Use of heavy fuel can be realized.

Incidentally, the process of switching the heavy fuel combustion mode switching map and the light fuel combustion mode switching map depending on whether or not the used fuel is the heavy fuel plays in the steps 413 - 415 the role of a combustion mode switching condition modifying device mentioned in the appended claims.

EMBODIMENT 5

In Embodiment 4, the two combustion modes of the stratified charge combustion mode are switched to the homogeneous combustion mode, whereas in an embodiment 5, as in each of FIGS 13A and 13B 10, the operation range of a dual injection mode in which fuel is injected in each cylinder and burned in an intake stroke and a compression stroke, respectively, is set between the operation range of the stratified charge combustion mode and that of the homogeneous combustion mode. Embodiment 5 sets a light-fuel combustion mode switching map as shown in FIG 13A and a heavy fuel combustion mode switching map as shown in FIG 13B is shown. The heavy fuel combustion mode switching map data as shown in FIG 13B are shifted to the lower speed side and the lower load side than the light fuel combustion mode switching map as shown in FIG 13A shown.

Also, in Embodiment 5, substantially the same determination routine of the required combustion mode is executed as in FIG 11 is shown. More specifically, it is decided whether or not a used fuel is the heavy fuel. Depending on the resulting decision that the fuel used is not the heavy fuel (namely, it is the light fuel), the light fuel combustion mode switching map becomes 13A is selected, and one of the three combustion modes of the stratified charge combustion mode, the dual injection mode and the homogeneous combustion mode is selected as a required combustion mode according to an engine speed Ne and according to a required torque at the present time.

On the other hand, in a case where it has been decided that the used fuel is the heavy fuel, the heavy fuel combustion mode switching map as in FIG 13B is selected and selected one of the three combustion modes as the required combustion mode selected according to the engine speed Ne and the required torque at the present time. The heavy fuel combustion mode switching map data is shifted to the lower-speed side and the lower-load side than the light-fuel combustion mode switching map. Thus, in the case of using the light fuel, the range of the operating range of the stratified charge combustion mode, which is on the side of the dual injection mode, is changed to the operating range of the dual injection mode. Also, the width of the operating range of the dual injection mode is reduced and the operating range of the homogeneous combustion mode to the dual injection mode side is increased.

According to Embodiment 5 thus far described, in the operating region where the heavy fuel can not be stably exposed to the stratified combustion, this heavy fuel is combusted in the dual injection mode and proceeding in the operating range where the heavy fuel is not stable combustion Dual injection mode (operating range in which the heavy fuel injected in the compression stroke is insufficiently atomized) this heavy fuel burned in the homogeneous combustion mode. Then, also in the case of switching the three combustion modes of the stratified charge combustion mode, the dual injection mode and the homogeneous combustion mode, the combustion mode in which the heavy fuel can be stably combusted according to the operating range can be formed in the case of using the heavy fuel and the reduction of the Smoke and the improvement of drivability in the case of the use of heavy fuel can be realized (see 14 ).

Incidentally, in each of Embodiments 4 and 5, the two types of the heavy fuel and the light fuel combustion mode switching maps are set. However, it is also permissible to divide the degree of the severity of the fuel used in three or more stages and to set up three or more types of combustion mode switching maps corresponding to the respective stages, whereby a map corresponding to the degree of the severity of the fuel is selected from the established maps; to decide a required combustion mode. Alternatively, it is also permissible to set only a combustion mode switching map for a standard fuel (for example, the light fuel) and the data of the combustion mode switching map for the standard fuel (engine speed Ne and required torque at the time of switching the combustion modes) by correction coefficients corresponding to the degree of severity of the used Fuel during engine operation, whereby a combustion mode switching map corresponding to the degree of severity of the fuel used is automatically formed to decide a required combustion mode.

In this way, when the combustion mode switching map is selected and corrected according to the severity of the fuel used, an amount by which the data of the combustion mode switching map is changed to the lower-speed side and the lower-load side can be changed according to the degree Gravity of the fuel used to be modified. Therefore, an extent to which the operating range of the stratified charge combustion mode or the dual injection mode, which is the good fuel consumption combustion mode, is reduced in the case of using the heavy fuel to the required minimum according to the degree of severity of the fuel used. Accordingly, the reduction of the smoke can be realized while preventing the fuel consumption from excessively deteriorating excessively in the case of using the heavy fuel.

In addition, it is also permissible to set only the combustion mode switching map for the standard fuel (for example, the light fuel) and to correct the engine speed Ne and the required torque at the present time, namely by the correction coefficients corresponding to the degree of severity of the fuel used and the required one Combustion mode by comparing the engine speed Ne and the required torque after the corrections with the data of the combustion mode switching map for the standard fuel to decide. Also, in this case, the same advantages as mentioned above can be obtained.

Incidentally, in each of Embodiments 4 and 5, when the heavy fuel is used, the combustion mode switching condition is changed to both the lower-speed side and the lower-load side. However, the combustion mode switching condition may be modified to one of the lower speed side and the lower load side.

EMBODIMENT 6

In an embodiment 6 of the present invention, in a system in which one of the three combustion modes of a stratified charge combustion mode, a dual injection mode, and a homogeneous combustion mode as a required combustion mode according to an engine speed Ne and a required torque at the present time, for example, by substituting the in 13A is selected when, during operation of the dual injection mode, it has been decided that a used fuel is the heavy fuel, the injection amount of a compression stroke in the dual injection mode is decreased, and the injection amount of an intake stroke is increased. When the injection amount of the compression stroke is reduced, a period of time necessary for atomizing the injected fuel of the compression stroke into a state ensuring stable combustion is shortened. Therefore, if the injection amount of the compression stroke in the dual injection mode is reduced in the case of using the heavy fuel, the combustibility of the dual injection mode can be improved and the smoke can be reduced.

The control of the dual injection mode is performed by a dual injection mode injection quantity calculation routine in FIG 15 executed. This routine is executed by ECU every predetermined cycle during the operation of the internal combustion engine 30 in 1 and plays the role of a dual injection mode control device mentioned in the appended claims. When this routine is activated, first, the engine rotation speed Ne becomes one step 501 and the required torque established based on an accelerator opening degree or the like is loaded at the next step 502 loaded. Then the routine goes one step 503 Further, it decides whether or not a combustion mode at the present time is the dual-injection mode. If the combustion mode is not the dual injection mode, the routine is terminated without performing a subsequent process.

On the other hand, in a case where in the step 503 it has been decided that the combustion mode at the present time is the dual-injection mode, the routine goes to a step 504 which decides whether the fuel used is the heavy fuel or not. Depending on the resulting decision that the fuel used is not the heavy fuel (namely, that it is the light fuel), the routine goes to one step 505 wherein the ratio K of the compression amount of the compression stroke (compression stroke injection ratio) to the total injection amount Qall of the intake stroke and the compression stroke is calculated by a map, a formula or the like according to the engine rotational speed Ne and the required torque at the present time. Then the routine goes one step 506 Further, in which the total injection amount Qall is multiplied by the compression stroke injection ratio K to find the injection amount QC of the compression stroke.

If, on the other hand, at the step 504 it has been decided that the used fuel is the heavy fuel, the routine goes to a step 507 Further, in the dual injection mode, the minimum injection amount QCmin of the compression stroke in the dual injection mode is calculated by a map, a formula or the like according to the engine rotation speed Ne and the required torque at the present time. The minimum injection amount QCmin corresponds to the minimum injection amount of a region (stable injection region) in which the injection state of the fuel injection valve 21 in 1 is stabilized. Then the routine goes one step 508 Further, in which a correction coefficient KQC for correcting the minimum injection amount QCmin of the compression stroke corresponding to the degree of severity of the fuel used is calculated by a map, a formula or the like whose parameter is the degree of severity of the fuel. Thus, the correction coefficient KQC is set to a smaller value within the range 0 <KQC ≦ 1 as the fuel used becomes heavier. Subsequently, the routine proceeds to a step 509 Further, in which the minimum injection amount QCmin of the compression stroke, as in the step 507 is calculated, is multiplied by the correction coefficient KQC to find the injection amount QC of the compression stroke.

After the injection amount QC of the compression stroke at the step 506 or 506 was calculated in the above-mentioned manner, the routine goes to a step 510 Further, in which the injection amount QC of the compression stroke is subtracted from the total injection amount Qall to find the injection amount QI of the intake stroke.

According to Embodiment 6 described so far, when it has been decided that the used fuel is the heavy fuel, the injection amount of the compression stroke in the dual injection mode is set to the minimum injection amount of the stable injection range of FIG Fuel injector 21 set up. In the case of using the heavy fuel in the dual injection mode, therefore, the ratio of the compression stroke injection at which the sputtering time of the fuel is likely to become insufficient can be minimized to maximize the intake stroke injection that easily ensures the sputtering period of the fuel. Accordingly, the combustibility of the heavy fuel can be improved to the utmost and the smoke can be reliably reduced.

Moreover, in the embodiment 6, the minimum injection amount of the compression stroke in the dual injection mode is corrected with the correction coefficient KQC corresponding to the degree of gravity. In the case of the heavy fuel combustion in the dual injection mode, therefore, it is inevitable that the injection amount of the compression stroke injection of the good fuel consumption excessively decreases, and the deterioration of the fuel consumption due to the reduction of the injection amount of the compression stroke is limited to the minimum required become.

In the invention, however, the minimum injection amount of the compression stroke, as in the step 507 is also used directly as the final injection amount of the compression stroke without being corrected according to the degree of severity. Also in this case, the invention can reduce the smoke in comparison with the prior art system, wherein the injection amount of the compression stroke is determined without regard to the fuel behavior.

In addition, in the case of using the heavy fuel, the injection amount of the compression stroke in the dual injection mode does not constantly need to be the minimum injection amount of the stable injection range of the fuel injection valve 21 to be reduced. For example, the injection amount of the compression stroke of the dual injection mode may also be made smaller only than in the case of using the light fuel according to the engine operating condition (the engine speed Ne, the required torque, or the like) and / or the degree of severity of the fuel. When the injection amount of the compression stroke in the dual injection mode is made smaller in the case of using the heavy fuel than in the case of the light fuel, the combustibility of the dual injection mode can be improved more than in the prior art.

EMBODIMENT 7

Meanwhile, a dual injection mode is a combustion mode in which a required amount of fuel divided into an intake stroke and a compression stroke is injected to save the fuel consumption by the compression stroke injection. As in 17 Therefore, in the dual injection mode, fuel consumption efficiency in the dual injection mode has the relationship of deterioration with the reduction of a compression stroke injection ratio of K. In the dual injection mode, when the compression stroke injection ratio K becomes excessively small, the negative impact (depression of power) of the compression stroke injection becomes larger than that positive effect (improvement of fuel consumption) and the fuel consumption efficiency in the dual injection mode becomes worse than a fuel consumption efficiency in a homogeneous combustion mode.

Therefore, in Embodiment 7 of the present invention, the compression stroke injection ratio K of a point (D) at which the fuel consumption efficiency in the dual injection mode becomes substantially identical to the fuel consumption efficiency in the homogeneous combustion mode is obtained from test data, design data, and the like in advance, and this is considered as a shift decision value D set up. Furthermore, as in 18 4, at the time when the compression stroke injection ratio K has become lower than the switching decision value D during operation of the dual injection mode, the dual injection mode is switched to the homogeneous combustion mode.

A control for the switching is performed by a dual injection mode injection amount calculation routine in FIG 16 executed. The routine is such that the process contents of the steps 511 - 513 between the steps 509 and 510 the dual injection mode injection amount calculation routine in FIG 15 to be added. The process contents of the other steps in 16 are each identical to those of the corresponding steps in 15 , When in the routine of 16 the heavy fuel is used, the injection amount QC of the compression stroke by the process of step 507 - 509 calculated. Then the routine goes to the step 511 Further, in which the injection amount QC of the compression stroke is divided by the total injection amount Qall, and find the compression stroke injection ratio K. Subsequently, the routine proceeds to the step 512 which judges whether or not the compression stroke injection ratio K is less than the shift decision value D. When the compression stroke injection ratio K is not lower is the switching decision value D, it is judged that the dual injection mode has better fuel consumption than the homogeneous combustion mode, and the operation of the dual injection mode is continued.

In contrast, in a case where in the step 512 It has been decided that the compression stroke injection ratio K is less than the shift decision value D, judges that the homogeneous combustion mode has the better fuel consumption than the dual injection mode. Then the routine proceeds to the step 513 Next, in which the required combustion mode is switched from the dual injection mode to the homogeneous combustion mode.

In the embodiment 7 thus far described, at the time when the compression stroke injection ratio K has become lower than the shift decision value D during operation of the dual injection mode, this dual injection mode is switched to the homogeneous combustion mode. Therefore, in the operation range in which the fuel consumption becomes worse in the dual injection mode than in the homogeneous combustion mode, in the case of using the heavy fuel, the dual injection mode can be switched to the homogeneous combustion mode and the excessive deterioration of the fuel consumption due to the dual injection mode can be prevented is.

Incidentally, in the embodiment 7, the switching decision value is set to a fixed value obtained in advance from the test data, the design data or the like. However, the switching decision value D may be varied according to the degree of the severity of the fuel used so that this switching decision value D is further increased as the fuel used becomes heavier. In this way, the dual injection mode can be switched to the homogeneous combustion mode at the optimum timing corresponding to the degree of severity of the fuel used.

Of course, the invention can also be performed by combining the embodiment 5 with the embodiment 6 (or the embodiment 7).

EMBODIMENT 8

As in the 20A and 20B and 21 shows the ECU 30 in 1 It sets a target fuel pressure according to an engine operating condition (a required torque, an engine speed Ne, or the like), and controls the fuel suppression amount of a high-pressure pump through a solenoid valve for controlling a fuel pressure and performs feedback control to control the pressure (fuel pressure) of the fuel flowing to the fuel injection valve 21 in 1 to be conveyed in accordance with the target fuel pressure. On this occasion, when the engine speed Ne or the required torque becomes higher, the target fuel pressure is set to a higher fuel pressure. Further, in the embodiment 8, for changing the target fuel pressure according to the fuel behavior of the fuel used, a target fuel pressure adjusting map for a light fuel as in FIG 20A and a target fuel pressure adjustment map for a heavy fuel as shown in FIG 20B is shown, whereby the target fuel pressure adjustment map to be used is switched between a case of using the light fuel and a case of using the heavy fuel. The target fuel pressure setting map for the heavy fuel is formed to set the target fuel pressure to a value lower than the target fuel pressure adjustment map for the light fuel, namely, within a range in which the atomization fineness of the fuel does not deteriorate (see 21 ).

The process contents of the target fuel pressure calculation routine in FIG 19 by the ECU 30 is executed, will be described below. The routine will be in the predetermined cycle during the engine 11 and plays the role of the target fuel pressure adjusting device mentioned in the appended claims. When the routine is activated, first, the engine rotation speed Ne becomes one step 601 is loaded and goes to the next step 602 loaded the required torque, which is established on the basis of the accelerator opening degree or the like. Then the routine goes one step 603 which decides whether the fuel used is the heavy fuel or not. Depending on the resulting decision that the fuel used is not the heavy fuel (namely, it is the light fuel), the routine goes to one step 604 in which the target fuel pressure setting map for the light fuel, as in 20A is selected, and the target fuel pressure is set according to the engine speed Ne and the required torque at the present time.

On the other hand, in a case where in the step 603 It was decided that the fuel used is the heavy fuel that Routine to a step 605 in which the target fuel pressure setting map for the heavy fuel as in 20B is selected, and the target fuel pressure is set in accordance with the engine speed Ne and the required torque at the present time. The target fuel pressure setting map for the heavy fuel is formed to set the target fuel pressure to a value lower than the target fuel pressure adjustment map for the light fuel, namely, within the range in which the atomization fineness of the fuel does not deteriorate. In the case of using the heavy fuel, therefore, the target fuel pressure is set lower than in the case of using the light fuel, namely, within the range in which the atomization fineness of the fuel does not deteriorate. Thus, the injection period of the fuel becomes longer in the case of using the heavy fuel than in the case of using the light fuel, and a range in which a piston moves from the start of the fuel injection to the end thereof increases. Therefore, an amount decreases with which the fuel flowing from the fuel injection valve 21 is injected as fuel moisture remains at the same position of the piston and reduces a smoke emission amount.

Incidentally, in the embodiment 8, the two types of the target fuel pressure adjustment maps for the heavy fuel and the light fuel are set. However, it is also permissible to divide the degree of the severity of the fuel used into three or more stages and to set three or more kinds of the target fuel pressure setting maps corresponding to the respective stages, whereby a map corresponding to the severity of the used fuel is selected from the established maps to set the target fuel pressure. Alternatively, it is also permissible to set only a target fuel pressure setting map for a standard fuel (for example, the light fuel) and to correct the data of the target fuel pressure setting map for the standard fuel (engine speed Ne and required torque) by correction coefficients corresponding to the degree of severity of the fuel used during engine operation; whereby a target fuel pressure adjusting map corresponding to the degree of severity of the fuel used is automatically formed to establish the target fuel pressure.

In this way, when the target fuel pressure adjusting map is selected or corrected according to the degree of the fuel used, an amount by which the data of the target fuel pressure adjusting map is modified may be modified according to the degree of the severity of the fuel used. Therefore, an amount by which the target fuel pressure is lowered in the case of using the heavy fuel can be set to the required minimum according to the degree of the severity of the fuel used. Accordingly, the reduction of the smoke can be realized while preventing the target fuel pressure from excessively decreasing in the case of using the heavy fuel.

EMBODIMENT 9

In general, a quantity of moisture decreases further when the temperature of the internal combustion engine 11 in 1 (the temperature of a piston surface or a cylinder inner wall surface) becomes higher. When the internal combustion engine 11 is further warmed up, the amount of moisture decreases to a level that is not very problematic even in the case of using a heavy fuel.

Considering this point, in the embodiment 9 of the present invention, when the temperature of cooling water flowing through the cooling water temperature sensor becomes high 23 in 1 is, a predetermined temperature Ta or above, set a target fuel pressure by selecting a target fuel pressure adjustment map for a light fuel despite the fact that a used fuel is the heavy fuel. Only in a case where the cooling water temperature is lower than the predetermined temperature Ta, a target fuel pressure adjustment map for the heavy fuel is selected in the case of using the heavy fuel, and the target fuel pressure is set lower than in the case of using the light fuel.

The target fuel pressure setting process is performed by a target fuel pressure calculating routine in FIG 22 executed. The routine is such that the process of a step 603a between the steps 603 and 605 the target fuel pressure calculation routine in FIG 19 is added. The process contents of the other steps in 22 are each identical to those of the corresponding steps in 19 , If at the step 603 it has been decided that the used fuel is the heavy fuel, the routine goes to a step 603a Next, it decides if the cooling water temperature caused by the cooling water temperature sensor 23 is detected lower than the predetermined temperature Ta or not. This predetermined temperature Ta is set to the lower limit temperature of a temperature range in which the amount of moisture of the heavy fuel is reduced to a level that is not very problematic.

Accordingly, in the case where step 603a It has been decided that the cooling water temperature is lower than the predetermined temperature Ta judges that the increase in the amount of moisture due to the heavy fuel is problematic. Then the routine proceeds to the step 605 Further, in which the target fuel pressure setting map for the heavy fuel is selected, and the target fuel pressure is set lower than in the case of using the light fuel according to an engine speed Ne and a required torque at the present time.

On the other hand, in the case where in the step 603a It has been decided that the cooling water temperature is the predetermined temperature Ta or above, judges that the amount of moisture of the heavy fuel does not become very problematic. Then the routine proceeds to the step 604 Next, in which the target fuel pressure adjustment map for the light fuel is selected, and the target fuel pressure in accordance with the engine rotation speed Ne and the required torque at the current time is established.

In the embodiment 9 thus far described, the control for lowering the target fuel pressure in the case of using the heavy fuel is performed only in the low water temperature region in which the increase in the amount of moisture attributable to the heavy fuel is problematic. In the range of the high water temperature, in which the amount of moisture of the heavy fuel does not become very problematic, the target fuel pressure is not lowered even in the case of using the heavy fuel. It is therefore possible to set the optimum target fuel pressure in accordance with the engine operating condition.

EMBODIMENT 10

In general, as an engine speed Ne becomes higher, a flow caused in each cylinder becomes more intense to advance the mixture of the injected fuel and the in-cylinder flow and to reduce the moisture amount of the fuel.

Therefore, in Embodiment 10 of the present invention, when the engine rotation speed Ne is a predetermined value Kne or above, a target fuel pressure is established by selecting a target fuel pressure adjustment map for a light fuel despite the fact that a used fuel is a heavy fuel.

The target fuel pressure setting process is performed by a target fuel pressure calculating routine in FIG 23 executed. The routine is such that the process of a step 603b between the steps 603a and 605 the target fuel pressure calculation routine in FIG 22 is added. The process contents of the other steps in 23 are each identical to those of the corresponding steps in 22 , In a case where at the step 603 it was decided that the fuel used is the heavy fuel, and if at the step 603a It was decided that the cooling water temperature Tw, by the cooling water temperature sensor 23 is detected lower than the predetermined temperature Ta, the routine proceeds to the step 603b Further, which judges whether the engine rotation speed Ne is lower than the predetermined value Kne or not. This predetermined value Kne is set to the lower limit of a speed range in which the amount of moisture from even the heavy fuel decreases to a level that is not very troublesome.

Accordingly, in the case where in the step 603b It has been decided that the engine rotation speed Ne is lower than the predetermined value Kne, judges that it is problematic to increase the amount of moisture attributable to the heavy fuel. Then the routine proceeds to the step 605 Further, in which the target fuel pressure adjustment map for the heavy fuel is selected, and the target fuel pressure is set lower than in the case of using the light fuel according to the engine speed Ne and a required torque at the present time.

On the other hand, in the case where in the step 603b It has been decided that the engine rotation speed Ne is the predetermined value Kne or above, judging that the amount of moisture from even the heavy fuel does not become very problematic. Then the routine proceeds to the step 604 Next, in which the target fuel pressure adjustment map for the light fuel is selected, and the target fuel pressure in accordance with the engine speed Ne and the required torque at the current time is established.

In the embodiment 10 described so far, the target fuel pressure is lowered to reduce a smoke emission amount, namely only in the low speed range in which the Increase in the amount of moisture that is due to the heavy fuel is evident. In the other area, it is possible to set the optimum target fuel pressure in accordance with the engine operating condition.

In addition, the step 603a (the switching of the target fuel pressure setting maps based on the cooling water temperature) also in the target fuel pressure calculating routine in FIG 23 be omitted.

EMBODIMENT 11

In the embodiment 11 of the present invention, depending on the decision that a used fuel is a heavy fuel, in a region where a required injection amount is large, a target fuel pressure becomes lower than in the case of using a light fuel by a fuel injection period as in the embodiments 8-10 to extend. Thus we have a lot with which the fuel coming from the fuel injector 21 in 1 is injected, as fuel moisture remains at the same position of a piston, made small to reduce the smoke emission amount in the case of using the heavy fuel. On the other hand, in a region where the required injection amount is small, the target fuel pressure is set higher in the case of using the heavy fuel than in the case of using the light fuel in consideration of the amount that the fuel is used as the fuel moisture remains at the same position of the piston, even in the case of using the heavy fuel is small. Thus, in the case of using the heavy fuel, the injected fuel is finely dispersed to promote the atomization and improve the combustibility.

In order to establish such a target fuel pressure, in Embodiment 11, two types of higher pressure and lower pressure maps are set as target fuel pressure adjustment maps for the heavy fuel in addition to the target fuel pressure adjustment map for the light fuel. The target higher pressure fuel pressure setting map for the heavy fuel is formed to set the target fuel pressure higher than the target fuel pressure setting map for the light fuel while the target fuel pressure setting map for the heavy fuel low pressure is made lower than the target fuel pressure setting map for the target fuel pressure set up light fuel. The target fuel pressure adjustment map for the lower pressure of the heavy fuel may be the same as the target fuel pressure adjustment map for the heavy fuel used in the embodiments 8-10, or may also have characteristics that are slightly changed.

The target fuel pressure setting process in Embodiment 11 is determined by a target fuel pressure calculating routine in FIG 24 executed. The routine will be in a predetermined cycle during operation of the internal combustion engine 11 executed. When the routine is activated, first, an engine speed Ne at one step 701 and a required torque established based on an accelerator opening degree or the like is loaded at the next step 702 loaded. Then the routine goes one step 703 Further, in which the required injection amount by a map or the like in accordance with the engine speed Ne and the required torque at the present time is. Subsequently, the routine proceeds to a step 704 which decides whether the fuel used is the heavy fuel or not. Depending on the resulting decision that the fuel used is not the heavy fuel (namely, it is the light fuel), the routine goes to one step 705 Next, in which the target fuel pressure adjustment map for the light fuel is selected, and we set the target fuel pressure in accordance with the engine speed Ne and the required torque at the present time.

On the other hand, in a case where in the step 704 It was decided that the fuel used is the heavy fuel, the routine to a step 706 Next, which decides whether the required injection amount is smaller than a predetermined value Kc or not. If the required injection amount is smaller than the predetermined value Kc, the routine goes to a step 707 Further, in which the target fuel pressure adjustment map for the higher pressure of the heavy fuel is selected, and the target fuel pressure is set higher than in the case of using the light fuel according to the engine speed Ne and the required torque at the present time. On the other hand, in a case where in the step 706 It has been decided that the required injection amount is the required value Kc or above, the routine becomes one step 708 Further, in which the target fuel adjusting map for the lower pressure of the heavy fuel is selected, and the target fuel pressure is set lower than in the case of using the light fuel according to the engine speed Ne and the required torque at the present time.

In the embodiment 11 thus far described, in the region where the required injection amount is large, the target fuel pressure is set lower in the case of using the heavy fuel than in the case of using the light fuel as in the embodiments 8-10, whereby the Smoke emission amount is reduced in the case of using the heavy fuel. On the other hand, in the area where the required injection amount is small, the target fuel pressure is set higher in the case of using the heavy fuel than in the case of using the light fuel, considering that the amount by which the fuel moisture is at the same position of the piston remains, even in the case of the use of heavy fuel is small. In this range, therefore, the injected fuel can be dispersed in the case of using the heavy fuel to promote the atomization and improve the combustibility, whereby the smoke emission amount in the case of using the heavy fuel can be reduced.

Incidentally, in the target fuel pressure calculating routine shown in FIG 24 shown is the step 603a (Switching the Sollkraftstoffdruckeinstellkennfelder based on the cooling water temperature) and / or the step 603b (the switching of the target fuel pressure adjustment maps based on the engine speed Ne) as in FIG 23 is shown, even between the steps 704 and 706 may be added to judge that the amount of moisture also of the heavy fuel will not be very problematic in the case that the cooling water temperature is not lower than the predetermined temperature Ta and / or if the engine speed Ne is not lower than the predetermined value Kne. Then the routine proceeds to the step 705 further, wherein the target fuel pressure is established by selecting the target fuel pressure adjustment map for the light fuel.

Thus, in the control of the direct injection engine decides 11 a computer 30 whether a used fuel is a heavy fuel or not. In the case of heavy fuel become an EGR valve 34 and a valve timing controller 39 . 40 set so that the sum of an external EGR amount and an internal EGR amount within a predetermined range during the stratified charge combustion operation of the internal combustion engine 11 can lie. In addition, in the case of the heavy fuel, one of a stratified charge combustion mode and a homogeneous combustion mode based on a heavy fuel combustion mode shift map is selected. The data for the heavy fuel combustion mode switching map is shifted to the lower speed side and the lower load side in comparison with the data of a combustion mode switching map for a light fuel. Further, in the case of the heavy fuel, the target fuel pressure is set based on a target fuel pressure adjusting map for the heavy fuel. The target fuel pressure is set to be lower than in the case of using the light fuel.

Claims (15)

Control device for a direct injection internal combustion engine ( 11 ) in which fuel is injected into a cylinder in an intake stroke or a compression stroke to be subjected to homogeneous combustion or stratified combustion, comprising: at least one of exhaust recirculation control means (14); 34 ) for controlling an external exhaust gas recirculation amount at which exhaust gas is recirculated from an exhaust system to an intake system or a valve control device ( 39 . 40 ), which controls an opening and closing operation of at least one inlet valve ( 37 ) or an outlet valve ( 38 ) varies; a fuel behavior decision device ( 30 for deciding a behavior of the fuel; and a control device ( 30 ), when it has been decided by the fuel behavior decision means that the fuel is a heavy fuel, at least either the exhaust gas recirculation control means (15) 34 ) or the valve control device ( 39 . 40 ) in one direction so that at least one of the external exhaust gas recirculation amount and a valve overlap amount becomes smaller than in the case of using a light fuel. Control device for a direct injection internal combustion engine ( 11 ) according to claim 1, wherein the control device ( 30 ) the controller according to the fuel behavior during a homogeneous combustion operation of the internal combustion engine ( 11 ) does not execute. Control device for a direct injection internal combustion engine ( 11 ) in which fuel is injected into a cylinder in a compression stroke to be subjected to stratified combustion, comprising: a flow control valve (10); 31 ) that controls an intensity of a current caused in the cylinder; a fuel behavior decision device ( 30 for deciding a behavior of the fuel; and a control device ( 30 ) for controlling the flow control valve ( 31 ) in a direction to intensify the flow stronger than in the case of using a light fuel when it is decided by the fuel behavior decision means that the fuel is a heavy fuel during a stratified charge combustion operation of the internal combustion engine ( 11 ). Control device for a direct injection internal combustion engine ( 11 ) in which a stratified charge combustion mode in which a fuel is injected into a cylinder in a compression stroke to be exposed to stratified combustion and a homogeneous combustion mode in which the fuel is injected into the cylinder in an intake stroke are subjected to homogeneous combustion be switched in accordance with an engine speed and / or a load, comprising: a fuel behavior decision device ( 30 ) for deciding a fuel behavior of the fuel used; and a combustion mode switching condition modifying means (FIG. 30 ) in a case where the fuel behavior decision means ( 30 ) has been decided that the fuel used is a heavy fuel to modify a combustion mode switching condition for switching the stratified charge combustion mode and the homogeneous combustion mode to at least one lower speed side and one lower load side than in a case of using a light fuel , Control device for a direct injection internal combustion engine ( 11 ) in which an operating range of a dual injection mode in which fuel is injected into a cylinder and burned in an intake stroke and a compression stroke, respectively, between an operating region of a stratified charge combustion mode in which the fuel is injected into the cylinder in the compression stroke is a stratified combustion and that of a homogeneous combustion mode in which the fuel is injected into the cylinder in the intake stroke to be exposed to homogeneous combustion, and wherein the three combustion modes are switched in accordance with an engine speed and / or a load, comprising: a fuel behavior decision device ( 30 ) for deciding a fuel behavior of the fuel used; and a combustion mode switching condition modifying means (FIG. 30 ) in a case where the fuel behavior decision means ( 30 that the fuel is a heavy fuel, combustion mode switching conditions for switching the stratified charge combustion mode and the dual injection mode, and switching the dual injection mode and the homogeneous combustion mode to at least one lower speed side and one lower load side than in a case of FIG Use of a light fuel to modify. Control device for a direct injection internal combustion engine ( 11 ) according to one of claims 4 and 5, wherein: the fuel behavior decision device ( 30 ) has means for deciding a degree of severity of the fuel used; and wherein the combustion mode switching condition modifying means ( 30 ) A degree by which the combustion mode switching condition is changed to at least one side from the lower-speed side and the lower-load side, according to the degree of severity of the fuel used. Control device for a direct injection internal combustion engine ( 11 ) in which an operating range of a dual injection mode in which fuel is injected into a cylinder and burned in an intake stroke and a compression stroke, respectively, between an operating region of a stratified charge combustion mode in which the fuel is injected into the cylinder in the compression stroke is a stratified combustion and that of a homogeneous combustion mode in which the fuel is injected into the cylinder in the intake stroke to be exposed to homogeneous combustion, and the three combustion modes are switched according to an engine speed and / or load, comprising: a fuel behavior decision means ( 30 ) for deciding a fuel behavior of the fuel used; and a dual injection mode control device ( 30 ) in a case where the fuel behavior decision means ( 30 ), it has been decided that the fuel is a heavy fuel to reduce an injection amount of the compression stroke more in the dual injection mode than in the case of using a light fuel and to increase an injection amount in the intake stroke. Control device for a direct injection internal combustion engine ( 11 ) according to claim 7, wherein when the fuel behavior decision means ( 30 ) has been decided that the fuel is the heavy fuel that Dual injection mode control device ( 30 ) sets the injection amount of the compression stroke in the dual injection mode to a minimum injection amount of a stable injection region of a fuel injection valve. Control device for a direct injection internal combustion engine ( 11 ) according to one of claims 7 and 8, wherein: the fuel behavior decision device ( 30 ) has means for deciding a degree of severity of the fuel used; and wherein the dual injection mode control means (15) 30 ) modifies the injection amount of the compression stroke in the dual-injection mode according to the degree of severity of the fuel used. Control device for a direct injection internal combustion engine ( 11 ) according to any one of claims 7 to 9, wherein said dual injection mode control means (16) 30 ), the dual injection mode switches to the homogeneous combustion mode when a ratio of the injection amount of the compression stroke to a total injection amount of the intake stroke and compression stroke has become substantially a predetermined value during execution of the dual injection mode. Control device for a direct injection internal combustion engine ( 11 ) according to claim 10, wherein: the fuel behavior decision device ( 30 ) has means for deciding a degree of severity of the fuel used; and wherein the dual injection mode control means (15) 30 ) the ratio of the injection amount of the compression stroke at which the dual injection mode is switched to the homogeneous combustion mode is changed according to the degree of severity of the fuel used. Control device for a direct injection internal combustion engine ( 11 ) in which a desired fuel pressure setting device ( 30 ) a control target value of a pressure of an injected fuel (hereinafter referred to as "target fuel pressure") according to an operating state of the cylinder injection internal combustion engine ( 11 ), in which fuel is injected directly into a cylinder and is burned, and wherein the fuel pressure control device ( 30 ) controls the pressure of the injected fuel (hereinafter referred to as "fuel pressure") to the target fuel pressure, comprising: a fuel behavior decision device (10) 30 ) for deciding a fuel behavior of the fuel used; a desired fuel pressure setting device ( 30 ) that sets the target fuel pressure at a value lower than that in the case of using a light fuel when judged by the fuel behavior decision means (FIG. 30 ) it was decided that the fuel used is a heavy fuel. Control device for a direct injection internal combustion engine ( 11 ) according to claim 12, comprising: a water temperature detection device ( 23 ) for detecting a cooling water temperature of the internal combustion engine ( 11 ); when the cooling water temperature detected by the water temperature sensing device ( 23 ), at least a predetermined temperature is, the target fuel pressure setting means (16) 30 ) the target fuel pressure by neglecting a decision result of the fuel behavior decision device (FIG. 30 ). Control device for a direct injection internal combustion engine ( 11 ) according to one of claims 12 and 13, comprising: an engine speed detection device ( 24 ) for detecting a rotational speed of the internal combustion engine ( 11 ); wherein, when the engine speed is determined by the engine speed sensing means (14) 24 ), at least a predetermined value is, the target fuel pressure setting device ( 30 ) the target fuel pressure by neglecting a decision result of the fuel behavior decision device (FIG. 30 ). Control device for a direct injection internal combustion engine ( 11 ) according to any one of claims 12 to 14, wherein when said fuel behavior decision means ( 30 ) has been decided that the fuel used is the heavy fuel, the target fuel pressure setting device ( 30 ) sets the target fuel pressure at a value lower than in the case of using the light fuel in a range where a required injection amount is large, and sets the target fuel pressure at a value higher than in the case of using the light fuel is established in a range in which the required injection quantity is small.

Images