DE102005005324A1 - Control apparatus for cylinder injection type internal combustion engine has target fuel setting device which decreases target fuel pressure when light fuel is used in engine - Google Patents

Abstract

The characteristics of fuel is identified by fuel characteristic determination device. A target fuel setting device decreases a target fuel pressure when light fuel is used in the engine.

Description

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

In In recent years, there has been a sudden demand for cylinder injection internal combustion engines (Direct injection internal combustion engines), all the advantages of a low Fuel consumption, a low exhaust emission and a high Own power. The cylinder injection engine has two Combustion modes of a stratified charge combustion and a Homogeneous combustion mode. In a low load range is the stratified charge combustion mode is formed in which a lower Quantity of fuel directly into a cylinder in a compression stroke is injected to a stratified air fuel mixture in the Environment of a spark plug form and perform stratified combustion. on the other hand becomes the homogeneous combustion mode in the medium and high load ranges 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 is to form a homogeneous air-fuel mixture and a to carry out homogeneous combustion.

Of the Cylinder internal combustion engine is equipped with an exhaust gas recirculator (EGR), which recirculates part of the exhaust gas into an intake system, and equipped with a flow control valve that reduces the intensity of a Strom (swirl flow or falling stream) controls that in the cylinder to cause. Furthermore, in the past, the Cylinder internal combustion engines multiplied, each with a Valve timing control means for varying the opening and closing times an intake valve and an exhaust valve are equipped. Various techniques for controlling such devices were proposed.

For example For example, in JP-B-6-58067, a swirl control valve is controlled to turn on swirl ratio according to a Load during of a stratified charge combustion operation to thereby reduce the influence to exclude the load.

In JP-A-11-50853, a swirl control valve is controlled to a swirl intensity in accordance with an engine speed while of a stratified charge combustion operation to thereby prevent that a combustion state during acceleration or a delay suddenly changes.

In JP-A-7-119513 becomes the opening degree an EGR valve according to a Controlled combustion pressure fluctuation (torque fluctuation), thereby a NOx emission amount is reduced, wherein the torque fluctuation is lowered.

In JP-A-5-52145 proceeds to a dual injection mode in which fuel is injected into a cylinder and in an intake stroke respectively a compression stroke is burned in the middle area between the stratified charge combustion mode and the homogeneous combustion mode Ahead.

In JP-A-5-71383 is a ratio 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 according to one Target air fuel ratio changed.

Besides that is at each of the combustion modes, the pressure of the injected one Fuel (hereinafter referred to as "fuel pressure") an important Control parameters, which have a great influence on the atomization state of the injected fuel and its amount of moisture (the Amount of fuel flowing on a piston and the inner wall surface of the piston Cylinder adheres) exercises. Therefore have been various methods regarding a method proposed for establishing a desired fuel pressure.

For example In JP-A-9-21369, the fuel pressure during a low load or lowered a small injection quantity, thereby the stability and the atomizability to ensure an injection.

In addition, will in Japanese Patent No. 3,417,158, the fuel pressure is lowered, while the internal combustion engine is cold, thereby reducing the amount of moisture lower.

in the In general, the control parameters of an exhaust gas recirculator, a flow control valve and a valve timing control means adjusted using a fuel that has a standard fuel behavior has (standard fuel). In the techniques of the above Patent documents accordingly become the control parameters and a fuel pressure control characteristic assuming the Use of the standard fuel adjusts and will fuel behavior at all not considered.

Also, a combustion mode switching condition for switching a combustion becomes adjusted operating mode (map of an engine speed and a load) 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 have fuels that actually used in the market, various fuel behaviors and differs the evaporation characteristics and thus again a sputtering characteristic of fuel injected from a fuel injector will, depending from the fuel behaviors. If therefore a heavy fuel a lower atomization characteristic used, the injected fuel may not be sufficient be atomized where the control parameters for the standard fuel are adjusted. That gives the problem that a combustion state deteriorates, so that the smoke emission amount of the internal combustion engine increases or deteriorates its driveability.

If Furthermore the heavy fuel of the inferior atomization characteristic is used In some cases, the injected fuel may be in the stratified charge combustion mode or the dual injection mode, in the case of a stable combustion region originally narrower than in the homogeneous Combustion is under the combustion mode switching condition not sufficiently atomized be that for the standard fuel is adjusted. Therefore, it deteriorates the combustion state sometimes, so that the smoke emission amount enlarged or driveability deteriorates.

If Furthermore the heavy fuel with the inferior atomization characteristic is used leads the fuel pressure control characteristic corresponding to the standard fuel is adapted to insufficient atomization of the injected Fuel or to increase the amount of moisture, so that the problem arises that the amount of smoke emission increases.

The The present invention has been made in view of such circumstances. It is accordingly a task of the invention, a control device for a cylinder injection internal combustion engine to ensure a stable state of combustion even then can, if a heavy fuel is used, and the reduction of Smoke and the improvement of driveability can realize, though the heavy fuel is used.

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 that varies opening and closing operations (or an opening or closing operation) of an intake valve and / or an exhaust valve, wherein a behavior of the fuel is decided by a fuel behavior decision device so that when it is decided that the fuel is a heavy fuel, the exhaust gas recirculation control device 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 when the valve overlap amount increases, the internal EGR amount (amount of combustion gases contained in the cylinder remain). As the external EGR amount or the internal EGR amount increases, the intake amount of fresh air decreases in the cylinder and lowers a combustion temperature. Therefore it is in the case of using the heavy fuel, the a lower atomisability and combustibility as the light fuel has, probably, that a combustion state becomes unstable and smoke due to the lowering of the combustion temperature in an operating range simply occurs where the external EGR 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, if both or one of the external EGR amount and the valve overlap size (Internal EGR amount) is controlled in the decreasing direction in the case of using the heavy fuel, also the heavy fuel can stably burn the effects of increasing the fresh air intake amount and the rise of the combustion temperature, so that the reduction of the smoke and the Improvement of drivability in the case of using the heavy fuel can be realized.

however the external EGR or the internal EGR has the effect of lifting the cylinder internal temperature (intake air temperature) and thus the Driving the atomization of the fuel. Therefore, if the external EGR amount or the internal EGR amount is excessively small has become the in-cylinder temperature lower than one Temperature range for sputtering is the heavy fuel, and will the atomization of the fuel in the Case of using the heavy fuel insufficient. Accordingly, rising piston fuel moisture (fuel attached to a piston adheres) and it is likely that smoke will occur.

As a countermeasure, in a case where the external exhaust gas recirculation amount and / or the overlap amount (internal EGR amount) are not larger than predetermined values (or a predetermined value), the exhaust gas recirculation control means may be dependent on the decision of the heavy fuel 34 and / or the valve control means are controlled in the direction of increasing the external EGR amount and / or the valve overlap amount (internal EGR amount).

On This path becomes an operating range in which the cylinder internal temperature lower than the temperature range that is necessary for the atomization of heavy fuel necessary if the external EGR amount or the internal EGR amount is reduced, both or one of the external EGR amount and the Valve overlap size (internal EGR amount) in the Case of using the heavy fuel increases and the in-cylinder temperature can be raised become. Thus, the atomization of the fuel for reducing the piston humidifying fuel and to reduce the smoke in the case of using the heavy one Fuel are driven forward.

The Control according to the fuel behavior, as described above is, can only during of the stratified charge combustion operation can be performed well without them during the Homogeneous combustion operation is performed.

A Time duration from a fuel injection to an ignition is in the homogeneous combustion operation in which the fuel in the Intake stroke is injected, longer as in the stratified charge combustion mode in which the fuel is injected in the compression stroke, and may have a sputtering time for the Fuel can be set up in the former operation. During the Homogeneous combustion operation may therefore be a period of time for atomizing the heavy fuel is necessary without performing any special control be ensured according to the fuel behavior. Furthermore can the mixture of the fuel and the air through the stream of Intake air are driven forward, so that combustion stability also with the heavy fuel can be ensured.

If Furthermore it was decided that the fuel used was the heavy fuel while of the stratified charge combustion operation, may be a flow control valve good in the direction of the stronger Intensifying a current than in the case of using the light Fuel can be controlled. In this way, in the case, in the stratified charge combustion operation with the heavy fuel carried out is the current (swirl flow or falling stream) that is in the cylinder caused to be intensified. Thus, the mixture of the fuel pushed forward, so that the atomization of the fuel pushed ahead can be, and can combustion stability with heavy fuel be ensured.

In addition, will in a control device for a cylinder injection internal combustion engine, in a stratified charge combustion mode and a homogeneous combustion mode according to a Engine speed and / or a load are switched, a fuel behavior of a fuel used by a Fuel Behavior decision device decided and will a combustion mode switching condition indicating 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 a heavy fuel decides on one side of a lower one Speed and one side of a lower load than in the case of Use of 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 increases as the load becomes larger a period for the fuel injection is 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 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.

Under consideration such circumstances exists the invention in that when the heavy fuel is used becomes, the combustion mode switching condition on the page the lower speed and / or the lower load side as modified 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 side of the homogeneous combustion mode in which Case of using the light fuel to the operating range the homogeneous combustion mode is modified. Thus, will in the operating area where the heavy fuel is not one stable stratified combustion can be exposed to this heavy fuel burned in the homogeneous combustion mode, whereby the heavy fuel can be burned stably, and reducing the smoke and improving driveability in the case of using the heavy fuel can be.

The The invention is not limited to a system in which the two combustion modes a stratified charge combustion mode and a homogeneous combustion mode but it is equally applicable to a system wherein the operating range of a dual injection mode the fuel is injected in a cylinder and in one Intake stroke or a compression stroke is burned between the operating range of the stratified charge combustion mode and that the homogeneous combustion mode is set up. In this system can in a case where it was decided that the fuel was on heavy fuel is combustion mode switchover conditions for deciding engine speeds and / or loads, when switching the stratified charge combustion mode and the dual injection mode and when to switch the dual injection mode and the homogeneous combustion mode are on the side of a lower speed and / or side the lower load than in the case of using the light weight Be modified fuel. In this case, in this operating area, in which the heavy fuel is not a stable layered Combustion can be exposed to this heavy fuel the dual injection mode is burned and is further in the operation where the heavy fuel is also in the dual injection mode can not be stably burned (the operating area in which the atomization heavy fuel injected in the compression stroke becomes insufficient), the heavy fuel in the homogeneous combustion mode burned. This way can 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 is stable can be burned, according to the operating range in the case The use of heavy fuel can and can be made reducing smoke and improving driveability in the case of using the heavy fuel become.

however becomes as the degree of heaviness of the fuel becomes higher, a period of time for atomization of the fuel is necessary in a state that is for a stable Combustion is suitable for longer. Considering It is also permissible for this property to be a means of decision to provide the degree of severity of the fuel used, and a degree with the combustion mode switching condition on the page the lower speed and / or the lower load side modified is modified according to the degree of severity of the fuel used is going to modify. In this way, an extent with which the operating range of the stratified charge combustion mode is the combustion mode with the good fuel consumption, in which the case of using the heavy fuel decreases will, to a required minimum according to the degree of severity the fuel used. Thus, the Reduction of the smoke to be realized, thereby preventing in the case of using the heavy fuel, the Fuel consumption deteriorates excessively.

In addition, in the system 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, also the injection quantity of the combustion stroke in the dual injection mode is permissible more than in the case of using the light force substance and to increase the injection rate of the intake stroke more. 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 In the case, if it has been decided that the fuel is heavy Fuel is the injection rate of the compression stroke at the Dual injection mode also on the minimum injection quantity the stable injection range of a fuel injection valve be set up. In this way, in the case of combustion heavy fuel in dual injection mode the ratio of Compression stroke injection, where the atomization time of the fuel will probably be minimized to minimize the ratio of To maximize intake stroke injection, the atomization time duration simply ensuring the fuel. Accordingly, the combustibility heavy fuel to the utmost.

Besides that is it also permissible means for detecting the degree of severity of a used one To arrange fuel and the injection quantity of the compression stroke in the dual injection mode according to the degree of gravity to modify the fuel used. This way it is in in the case of using the heavy fuel in the dual-injection mode, unavoidable that the injection quantity of the compression stroke injection with the good fuel consumption is excessively reduced and the deterioration of fuel economy, which is due to the reduction the injection rate of the compression stroke is due to the required Minimum limited can be.

In addition, can the dual injection mode also to the homogeneous combustion mode be switched when the proportion of the injection amount of the compression stroke to the total injection amount of the intake stroke and the compression stroke while the execution the dual injection mode is a predetermined value or less has become. This way can work in an operating area where the fuel consumption in the dual injection mode in the Case of heavy fuel use worse than at the homogeneous combustion mode becomes the dual injection mode can be switched to the homogeneous combustion mode and can prevents fuel consumption due to the Dual injection mode deteriorated excessively.

In addition, can The relationship in the injection amount of the compression stroke at which the dual injection mode is switched to the Homogenverbrennungsbetriebsart, also according to the Degree of severity of the fuel used to be modified. In this way, the dual injection mode can be at the optimum Timing switched to the homogeneous combustion mode which corresponds to the degree of severity of the fuel used.

In addition, will in a control device for a cylinder injection internal combustion engine, at a control target value of a pressure of an injected fuel (hereinafter referred to as "target fuel pressure") by a target fuel pressure adjusting device according to an operating state of Cylinder injection internal combustion engine is set up and the pressure of the injected fuel (hereinafter referred to as "fuel pressure") the desired fuel pressure by the fuel pressure control device is controlled, a fuel behavior of the fuel used decided by a fuel behavior device and the target fuel pressure set to a value lower than in the case of use of a light fuel, if it was decided that used Fuel is a heavy fuel. The heavy fuel has an inferior atomization characteristic as the light fuel, and therefore the heavy fuel is injected into the cylinder under a high fuel pressure, elevated itself a lot, with which the fuel as fuel moisture remains at the same position of a piston and multiplies a 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, reducing the injection period of the fuel becomes. When the injection period of the fuel becomes long, it becomes longer an area where the piston moves from the start of fuel injection moved to the end of it, so that the amount with whom the fuel, which is injected from the fuel injection valve than the Moist fuel stays in the same position of the piston itself decreases and the amount of smoke emission decreases.

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 continues to warm up, the moisture decreases to a level which is not very problematic even in the case of heavy fuel use.

Under consideration this point, it is equally permissible a water temperature detecting means for detecting the cooling water temperature of Provide internal combustion engine and the desired fuel pressure by To neglect set up the decision result of the fuel-holding device, when the detected cooling water temperature is a predetermined temperature or above. This way will the control for lowering the fuel pressure in the case of Use of heavy fuel only in a low water temperature range carried out, in which the increase in the amount of moisture becomes problematic, which is due to the heavy fuel. In a high water temperature range, in that the amount of moisture also heavy fuel not is very problematic, the target fuel pressure is also in the Case of heavy fuel use not lowered. It is therefore possible, the optimum target fuel pressure in accordance with the operating condition set up the internal combustion engine.

In addition, When the speed of the engine becomes higher, a current flowing in the Cylinder is further intensified to the mixture of injected fuel and the cylinder internal flow to advance and reduce the amount of moisture.

Therefore is it equally permissible an engine detection device for detecting an engine speed to arrange and the target fuel pressure by neglecting the decision result the fuel behavior decision device to set up when the detected engine speed is a predetermined value or about that is. In the case, only in a low speed range, in the increase in the amount of moisture that becomes evident on the heavy fuel is due the desired fuel pressure is lowered to increase the amount of smoke emission reduce.

If Furthermore was decided by the fuel behavior device that the fuel that is heavy fuel may be the target fuel pressure lower than in the case of using the light fuel in a range of a big one required injection amount and higher than in the case of use light fuel in a range of small required Injection quantity to be set up. More specifically, in the field the big required injection amount of the target fuel pressure in the case the use of heavy fuel lower than in the case set up the use of light fuel and becomes one Fuel injection time lengthens, whereby the amount, with the fuel as the moisture fuel at the same Position of the piston remains, made small, to the amount of smoke emission in the case of using the heavy fuel. On the other hand, in the range of the small injection quantity required Target fuel pressure in the case of using the heavy fuel higher than in the case of using the light fuel under consideration set up the fact that the amount of fuel that as Moisturizing fuel stays at the same position of the piston, even in the case of using the heavy fuel is small whereby the injected fuel in the case of use of heavy fuel is dispersed to promote atomization and the burning ability to improve.

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. The equalization 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 used while a catalyst of a NOx occlusion and reduction type 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 has been decided that the external EGR basic amount EGRB is larger than the predetermined value A, the routine goes to a 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 quantity EGRC of the ex the amount of EGR 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 11, 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 OL 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 OL is greater than the predetermined value Bist, 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. Thus, when 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 condition in the operation range in which the valve overlap amount OL (internal EGR amount) is larger than the predetermined one Value is B.

In Embodiment 1 thus far described, in the high EGR ranges, where the external EGR amount and the valve exceed cutting amount larger than the predetermined values A and B during the stratified charge combustion operation, the external EGR amount and the valve overlap amount are controlled in the direction for decreasing 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 size too in the case of using the heavy fuel even during the Homogeneous combustion operation can be corrected.

In addition, will in the embodiment 1, the correction quantity EGRC the external EGR amount and the valve timing correction amount VCTC according to the engine operating condition calculated (for example, the engine speed Ne and the required torque). However, the correction quantity EGRC the external EGR amount and / or the valve timing correction quantity VCTC to a preset fixed value (default fixed value) Values) are made to simplify the calculation process, or can she also according to the degree the severity or the degree the severity and the engine operating condition are calculated.

In addition, will in the embodiment FIG. 1 shows both the external EGR amount and the valve overlap size in FIG Case of heavy fuel use corrected, but also one from 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 OL is not smaller than the predetermined value D, it is judged that the problem of the increase of the smoke or 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 OL is smaller than the predetermined value D, the routine goes 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, will be also in the embodiment 2 Corrections of external EGR amount and valve overlap size in the Case of using the heavy fuel during the homogeneous combustion operation they are not increased and only become active during the stratified charge combustion operation performed. Naturally can the external EGR amount and / or the valve overlap size too in the case of using the heavy fuel even during the Homogeneous combustion operation can be corrected.

In addition, will in the embodiment 2, the correction quantity EGRC the external EGR amount and the valve timing correction amount VCTC according to the engine operating condition calculated (for example, the engine speed Ne and the required torque). However, the correction quantity EGRC the external EGR amount and / or the valve timing correction quantity VCTC a preset fixed value (preset fixed Values) to simplify the calculation process, or they can also according to the degree the severity or degree of severity and the engine operating condition be calculated.

In addition, will in the embodiment 2 both the external EGR amount and the valve overlap size in the Case of using heavy fuel is calculated, but can too only one of these will 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 augmenting the smoke and deteriorating 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).

In contrast, occur in a case in which 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, will in the embodiment 3 the flow control valve opening degree correction amount SCVC 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 to a preset fixed value to simplify the calculation process or can also be made according to the degree of severity or according to the degree the severity and the engine operating condition are calculated.

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

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 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 directly introduced into the cylinder in an intake stroke injects to form a homogeneous mixture to perform a homogeneous combustion, thereby increasing the engine output.

During the Operation of the stratified charge combustion mode becomes the fuel injected in the compression stroke, so that the sputtering time The fuel from the fuel injection to the ignition originally short is. However, the sputtering time becomes shorter of fuel, when the engine speed becomes higher. Furthermore, if the load gets bigger, the amount of fuel to be injected more increased and will be a period of time for the fuel injection longer, so that there is a relationship that when the load gets bigger, the sputtering time of the fuel from the end of the fuel injection to the ignition becomes shorter. On the other hand, a period of time for atomizing a heavy fuel in a condition necessary for stable combustion is suitable for longer than in the case of atomization a light fuel. Therefore, if the heavy fuel used becomes, becomes a sputtering time of heavy fuel is insufficient and becomes a stable layered Combustion in the range of the operating range of the stratified charge combustion mode difficult, 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 step 401 plays the role of a fuel behavior decision device referred to 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, it is the light fuel), the routine goes to a 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 one of the three combustion modes is selected as the required combustion mode 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. Likewise, the width of the operating range of the dual injection mode is reduced and the Be Increased operating range of the homogeneous combustion mode to the dual injection mode page.

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, will be in each of the embodiments 4 and 5 show the two types of the combustion mode switching maps for the serious Fuel and for set the light fuel. However, it is also permissible for the Degree of severity of fuel used in three or more Divide stages and three or more types of Verbrennungsmodusartumschaltkennfelder accordingly set up the respective stages, creating a map accordingly the degree of severity of the fuel from the established maps selected is to decide a required combustion mode. Alternatively, it is also permissible only one combustion mode switching map for one Standard fuel (for example, the light fuel) set up and the data of the combustion mode switching map for the standard fuel (Engine speed Ne and required torque to the Timing of switching the combustion modes) by correction coefficients according to the degree of severity of the fuel used during the Correcting engine operation, thereby providing a combustion mode switching map according to the degree of severity of the fuel used automatically is formed to a required combustion mode decide.

If in this way, the combustion mode switching map selected according to the degree of severity of the fuel used and corrected, an extent, with the data of the combustion mode switching map the lower speed side and the lower side Last modified, according to the degree of severity of the used Be modified fuel. Therefore, an extent with which the operating range of the stratified charge combustion mode or the dual injection mode, the combustion mode of a good fuel consumption, is reduced, in the case of Use the heavy fuel to the required minimum be set to the degree of severity of the fuel used. Accordingly, the Reduction of the smoke to be realized, thereby preventing That fuel consumption becomes excessive in the case of use of heavy fuel deteriorates excessively.

Besides that is it also permissible only the combustion mode switching map for the standard fuel (For example, the light fuel) and set the engine speed Ne and the required torque at the present time to correct, namely by the correction coefficients according to the degree of severity of the used fuel, and the required combustion mode by comparing the engine speed Ne and the required one Torque after correction with the data of the combustion mode switching map for the Standard fuel to decide. Likewise, in this case, the same benefits as stated above.

Incidentally, will in each of the embodiments 4 and 5, when the heavy fuel is used, the combustion mode switching condition on both the lower speed side and the lower one Modified load side. The combustion mode switching condition However, it can also be on one of the lower speed side and the be modified 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 In the dual injection mode, clocks are decreased and the injection quantity 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 is decided that the used fuel is the heavy fuel, the injection amount of the compression stroke in the dual injection mode becomes the minimum injection amount of the stable injection region of the fuel injection valve 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 Embodiment 6, the minimum injection amount of the compression stroke in the dual injection mode becomes the correction coefficient KQC corresponding to the degree the severity is corrected. 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. If the compression stroke injection ratio K is not less than the shift 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 described so far 7 becomes at the time when the compression stroke injection ratio K less than the switching decision value D during the operation of the dual injection mode has become, this dual injection mode to the homogeneous combustion mode switched. Therefore, in the operating range where the fuel consumption deteriorates in the dual injection mode than in the homogeneous combustion mode in the case of using the heavy fuel, the dual injection mode becomes can be switched to the homogeneous combustion mode and can the excessive deterioration of the fuel consumption that is due to the dual injection mode is due.

Incidentally, will in the embodiment 7 the switching decision value is set to a fixed value, obtained from the test data, the design data or the like in advance. However, the switching decision value D may be according to the degree the severity of the fuel used are modified so that this shift decision value D is further increased when the one used Fuel gets heavier. In this way, the dual injection mode to the homogeneous combustion mode at the optimum timing be switched according to the degree of severity of the fuel used equivalent.

Of course you can the invention also by combining the embodiment 5 with the embodiment 6 (or the embodiment 7) become.

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, the 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 adjustment 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 atomizer The fineness of the fuel does not worsen. 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, will be in the embodiment 8 shows the two types of the target fuel pressure setting maps for the heavy one Fuel and for set the light fuel. However, it is also permissible for the Degree of severity of fuel used in three or more Divide stages and three or more types of Sollkraftstoffdruckeinstellkennfelder set up according to the respective levels, creating a map according to the degree of severity of the fuel used the selected maps is selected to the desired fuel pressure to set up. Alternatively, it is also allowed to have only one target fuel pressure setting map for one Standard fuel (for example, the light fuel) set up and the data of the target fuel pressure setting map for the standard fuel (Engine speed Ne and required torque) by Correction coefficients according to the degree of severity of the used Fuel during of the engine operation, whereby a target fuel pressure adjustment map according to the degree of severity of the fuel used automatically is formed to establish the desired fuel pressure.

If in this way, the target fuel pressure setting map selected according to the degree of severity of the fuel used or corrected, an extent, with which the data of the target fuel pressure adjustment map is modified according to the severity of the fuel used be modified. Therefore, an extent with which the target fuel pressure is lowered in the case of using the heavy fuel, to the required minimum according to the degree of severity the fuel used. Accordingly, the Reduction of smoke can be realized, which prevents the target fuel pressure in the case of using the heavy Fuel drops excessively.

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 moisture amount of even the heavy fuel decreases to a level that is not very troublesome.

Accordingly, in the case where it is decided at step 603a that the cooling water temperature is lower than the predetermined temperature Ta, it is judged 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 described so far 9, the control for lowering the target fuel pressure in the Case of heavy fuel use only in the area the low water temperature in which the increase in the Moisture level becomes problematic on the heavy fuel is due. In the range of high water temperature, where the amount of moisture also heavy fuel is not very problematic, the Target fuel pressure even in the case of using the heavy Fuel not lowered. It is therefore possible to set the optimum target fuel pressure in accordance with the engine operating condition.

EMBODIMENT 10

in the Generally, when an engine speed Ne becomes higher, a current that is caused in each cylinder, more intense, around the Mixture of injected fuel and cylinder internal flow to advance and to increase the amount of moisture of the fuel reduce.

In the embodiment 10 of the present invention is therefore when the engine speed Ne is a predetermined value Kne or above, a target fuel pressure by selecting a target fuel pressure adjustment map for a light fuel despite the fact that a used fuel is a heavy one Fuel is set up.

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.

at the embodiment described so far 10, the target fuel pressure is lowered to a smoke emission amount to reduce, namely only in the low speed range where the increase in the amount of moisture, which is due to the heavy fuel, becomes clear. By doing other area it is possible the optimum target fuel pressure in accordance with the engine operating condition to set up.

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 becomes heavier Fuel is, in a range where a required injection amount is large, a target fuel pressure lower than in the case of using a light fuel to extend a fuel injection period as in the embodiments 8-10. 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.

To the Establishment of such a target fuel pressure are in the embodiment 11 two types of maps for the higher one Pressure and for the lower pressure than target fuel pressure setting maps for the heavy fuel in addition to the target fuel pressure setting map for the light fuel. The desired fuel pressure setting map for the higher pressure for the heavy Fuel is made to exceed the desired fuel pressure in the target fuel pressure setting map for the light fuel while the Sollkraftstoffdruckeinstellkennfeld for the low pressure of the heavy Fuel is formed to lower the target fuel pressure as in the target fuel pressure setting map for the light fuel. The target fuel pressure setting map for the lower pressure of heavy fuel may be the same as the desired fuel pressure setting map for the heavy fuel used in Embodiments 8-10 or it 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 use the 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 also added between steps 704 and 706 to judge that the amount of moisture from 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 when 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 (16)

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 (FIG. 34 ) or the valve control device ( 39 . 40 ) in one direction so that at least one of the external exhaust gas recirculation amount and the valve overlap amount becomes smaller than in the case of using a light fuel. 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 is 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 ), which operates when it has been decided by the fuel behavior device that the fuel is a heavy fuel to at least either the exhaust gas recirculation control device ( 34 ) or the valve control device ( 39 . 40 ) in a direction to increase at least one of the external exhaust gas recirculation amount and the valve overlap amount in a case where at least one of the external exhaust gas recirculation amount and the valve overlap amount is not larger than a predetermined value. Control device for a direct injection internal combustion engine ( 11 ) according to one of claims 1 and 2, wherein the control device ( 30 ) the control 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 subjected to stratified combustion, and a homogeneous combustion mode in which the fuel is injected into the cylinder in an intake stroke to be subjected to homogeneous combustion be switched in accordance with an engine speed and / or a load, comprising: a fuel behavior decision means ( 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 a range of operation of a stratified charge combustion mode in which the fuel is injected into the cylinder in the compression stroke to 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 5 and 6, 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 8, wherein when said fuel behavior decision means ( 30 ) is decided that the fuel is the heavy fuel, the dual injection mode control means ( 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 8 and 9, 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 8 to 10, wherein the 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 11, 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 13, 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 13 and 14, comprising: an engine speed detecting means (14) 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 13 to 15, wherein when the 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 set the target fuel pressure at a value higher than in the case of using the light fuel in a range where the required injection amount is small.