JP2003214235A - Control device of spark ignition direct injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of smoke while sufficiently providing the effect of temperature rise of exhaust when the temperature of the exhaust is increased by the combustion of weak stratified mixture by injecting fuel two times at forward and afterward stages in a period ranging from the intake stroke of a cylinder 2 to an ignition timing at least in a low load area when catalysts 40 and 42 are not heated in a direct injection engine 1. <P>SOLUTION: The ECU 50 of a control device A comprises an ignition timing control means 50a for delaying the ignition timings of the engine 1 for each cylinder 2 after a TDC when at least one of the catalysts 40 and 42 is not heated and a fuel injection control means 50b reducing the ratio of the amount of injection on the afterward stage to the overall amount of injection while increasing the amount of injection of fuel on the forward stage more than that on the backward stage and as the overall amount of injection of fuel per cycle injected on both forward and backward stages is larger, and delaying the timing of start of injection on the backward stage according to a reduction in the ratio of the amount of injection. A swirl valve control means 50c for reinforcing a swirl flow by closing a swirl control valve 35 may be installed in this case. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a spark ignition engine, in which fuel is directly injected into a combustion chamber in a cylinder by a fuel injection valve for combustion, and more particularly,
This belongs to the field of control technology that raises the temperature of exhaust gas when the catalyst for purifying exhaust gas is not warmed up and promotes temperature rise of the catalyst.

[0002]

2. Description of the Related Art Conventionally, as a control device for a direct injection engine of this type, as disclosed in, for example, Japanese Unexamined Patent Publication No. 2000-45844, when the catalyst is not warmed up, the intake stroke to the compression stroke of the cylinder are changed. Over a period of two times, the fuel is injected in two steps to form a weak stratified mixture with a relatively small concentration distribution bias of the mixture in the combustion chamber (weak degree of stratification).
There is one in which the temperature of the exhaust gas is raised by the combustion of this air-fuel mixture to promote the temperature rise of the catalyst.

In this fuel injection system, for example, fuel injection (early injection) in the former stage is performed in the intake stroke of a cylinder to form a uniform and lean air-fuel mixture in the combustion chamber, and fuel injection in the latter stage (late stage injection) is performed in the subsequent compression stroke. ) Is performed to increase the concentration of the air-fuel mixture in the vicinity of the spark plug to form a weakly stratified air-fuel mixture as a whole. In this weakly stratified air-fuel mixture, the air-fuel ratio near the spark plug becomes richer than the stoichiometric air-fuel ratio, which improves ignition stability and increases the initial combustion speed, while a lean air-fuel mixture is used from the latter half of the combustion period. The relatively slow combustion (so-called afterburning) continues and the temperature of the exhaust gas rises.

Further, in the above-mentioned publication, the higher the ratio of the fuel injection amount in the latter stage in the combustion of the above-mentioned weakly stratified mixture, or the later the start timing of the latter stage injection is, the higher the exhaust gas temperature becomes. In addition, it is disclosed that the concentration of HC and NOx in the exhaust gas decreases, and further, the ignition timing of the cylinder is retarded to near the compression top dead center to intentionally reduce the cycle efficiency of the engine. Also, it is disclosed that the temperature of exhaust gas can be increased.

[0005]

However, in the combustion of the weakly stratified air-fuel mixture as described above, the air-fuel mixture formed around the spark plug by the fuel injection in the latter stage becomes richer than the stoichiometric air-fuel ratio. A new problem was found that smoke was generated with combustion. This is because the combustion speed locally increases in the rich mixture formed around the spark plug by the fuel injection in the latter stage, and the vaporization and atomization of the fuel in this rich mixture (with air) It is believed that this is due to insufficient mixing and evaporation).

[0006] Further, the total amount of fuel injected per cycle, which is the combination of the injections of the preceding stage and the latter stage, influences the generation of the smoke, and the smoke tends to increase as the total injection amount increases. I found out. That is, for example, when the oil viscosity is high, such as when the engine is cold started, when the load due to mechanical friction is large, or when the drive load of the auxiliary machinery is applied, the fuel load must be adjusted to correspond to that load. The total injection amount increases, the amount of fuel injection in the latter stage naturally increases, and it becomes more difficult to vaporize and atomize it, and the penetrating force of the fuel spray increases and the adhesion of fuel to the piston crown surface increases, It is considered that the situation is such that smoke is likely to be generated synergistically.

On the other hand, when the ratio of the fuel injection amount of the latter stage is simply reduced or the injection start timing of the latter stage is advanced to extend the time of vaporization and atomization of the fuel until ignition, that Although the generation of smoke can be suppressed by this, the original effect of the weak stratified combustion of increasing the temperature of the exhaust gas cannot be sufficiently obtained. Further, if the injection start timing of the latter stage is set too advanced, the fuel spray may diffuse quickly due to the air flow in the cylinder, which may impair the ignition stability.

The present invention has been made in view of the above points, and an object of the present invention is to control fuel and ignition when a catalyst for exhaust purification in a spark ignition type direct injection engine is not warmed up. The idea is to suppress the generation of smoke at that time while sufficiently obtaining the effect of increasing the temperature of the exhaust gas due to the combustion of the weakly stratified air-fuel mixture.

[0009]

In order to achieve the above object, in the present invention, when the catalyst is not warmed up, the ignition timing of the cylinder is retarded to or after the compression top dead center, and the intake air of the cylinder is In the period from the stroke to the ignition timing, two fuel injections of the front stage and the rear stage are performed, and further, in association with the change in the total injection amount of the front stage and the rear stage injection,
The injection amount ratio and the injection start timing of the second-stage injection are optimized.

Specifically, the invention of claim 1 is provided with a fuel injection valve for directly injecting fuel into a combustion chamber in a cylinder of an engine, and a catalyst for purifying exhaust gas from the combustion chamber. When the catalyst is in an unwarmed state lower than the activation temperature, at least in the low load region of the engine within the period from the intake stroke to the ignition timing of the cylinder, the fuel injection valve causes the latter-stage injection after the middle stage of the compression stroke and It is premised on a control device for a spark ignition type direct injection engine which is designed to perform two fuel injections including the previous front injection.

Ignition timing control means for delaying the ignition timing after the compression top dead center of the cylinder when the catalyst is not warmed up, and fuel by the pre-injection when the catalyst is not warmed up. While the injection amount of is larger than that of the post-injection and the total injection amount of fuel per cycle including the pre-stage injection and the post-stage injection is larger, the ratio of the post-stage injection amount to the total injection amount is reduced, Fuel injection control means for delaying the start timing of the latter-stage injection according to the decrease in the injection amount ratio is provided. It should be noted that the start timing of the latter-stage injection may be controlled so that the smaller the latter-stage injection amount ratio is, the more retarded the side is, even if the engine speed is the same.

With the above construction, when the catalyst is in an unwarmed state in which the temperature is lower than the activation temperature, the fuel injection control means controls the fuel injection valve to ignite from the intake stroke of the cylinder at least when the engine is in the low load region. Two fuel injections, the first stage and the second stage, are performed within the period until the timing, and the fuel spray by the first stage injection relatively spreads to the combustion chamber in the cylinder to form a mixture leaner than the stoichiometric air-fuel ratio. At the same time, the fuel spray produced by the latter-stage injection forms a relatively rich air-fuel mixture around the spark plug, resulting in a weakly stratified air-fuel mixture as a whole. Then, in the combustion of the weakly stratified air-fuel mixture, a conventional example (JP 2000-45844 A)
Similar to the above, the effect of increasing the temperature of exhaust gas and the effect of reducing HC due to afterburning in the latter half of combustion can be obtained.

At this time, the fuel injection amount ratio of the latter stage is 1
The larger the total injection amount of fuel per cycle is, the smaller the amount is, and the start timing of the second-stage injection is retarded in accordance with the decrease in the second-stage injection amount ratio. That is, when the total injection amount of fuel is relatively large, the injection amount ratio in the latter stage becomes relatively small, so the injection amount itself does not become so large, and therefore this fuel is well atomized and atomized by the time of ignition. Let me
It is possible to sufficiently suppress the generation of smoke accompanying combustion. Moreover, when the total injection amount of fuel is relatively large, the amount of heat generated due to combustion naturally increases, and the amount of heat of exhaust gas also relatively increases.

Further, by delaying the start timing of the latter-stage injection, the fuel spray is not relatively diffused to the retard side, but a fuel-air mixture is formed around the spark plug. The ignition timing can be sufficiently retarded while maintaining the ignition stability. Then, the ignition timing control means delays the ignition timing to the maximum in response to the retard control of the subsequent injection timing, whereby the cycle efficiency of the engine can be significantly reduced and the exhaust temperature can be increased. . This makes it possible to sufficiently raise the temperature of the exhaust gas and accelerate the temperature rise of the catalyst together with the effect of the combustion of the weakly stratified mixture.

That is, when the exhaust temperature is raised by the combustion of the weakly stratified air-fuel mixture to accelerate the early temperature rise of the catalyst, when the total injection amount of fuel per cycle is relatively large, the exhaust gas is relatively exhausted. While the amount of heat of the smoke increases, smoke is likely to be generated, and by delaying the start timing while reducing the ratio of the latter-stage injection amount, the smoke temperature is sufficiently raised while giving priority to the suppression of smoke. be able to.

On the contrary, when the total fuel injection amount is relatively small, the heat quantity of the exhaust gas naturally decreases, but it is difficult to generate smoke. At this time, the fuel injection amount in the latter stage is relatively increased. Therefore, the temperature of exhaust gas should be increased.

According to the second aspect of the present invention, the ignition timing control means controls the ignition timing to the retard side of 5 ° CA after the compression top dead center of the cylinder, and the fuel injection control means uses the catalyst. In the unwarmed state, the total fuel injection amount is controlled so that the average air-fuel ratio in the cylinder becomes approximately the stoichiometric air-fuel ratio at least in the low-speed low-load range of the engine, and the latter-stage injection amount relative to the total injection amount is controlled. Is about 1/3 or less and the start timing of the latter-stage injection is 20 ° CA before the compression top dead center of the cylinder.
It shall be as before. Note that “° CA” represents the unit of crank angle.

That is, by controlling the ignition timing of the cylinder to the retard side of 5 ° CA after the compression top dead center, the cycle efficiency of the engine is significantly lowered and the combustion of the air-fuel mixture becomes slow as a whole. Therefore, the exhaust temperature can be significantly increased. Further, the total injection amount of fuel per cycle is controlled so that the average air-fuel ratio in the cylinder becomes approximately the theoretical air-fuel ratio, and the ratio of the latter-stage injection amount to the total injection amount is approximately one third or less. By doing so, it is possible to relatively reduce the generation of smoke while securing the effect of increasing the temperature of the exhaust gas due to the combustion of the weakly stratified air-fuel mixture. In addition to this, the start timing of the latter-stage injection is set to the compression timing of the cylinder. 20 ° C before top dead center
By setting A before, it is possible to secure the vaporization and atomization time of the fuel by the latter-stage injection, and to sufficiently suppress the generation of smoke.

According to the third aspect of the invention, at least the catalyst is provided with a swirl flow enhancing means for enhancing the swirl flow in the combustion chamber in the cylinder when the catalyst is not warmed up. With this,
When the catalyst is not warmed up, the swirl flow strengthening means strengthens the swirl flow in the cylinder, and this swirl flow collapses in the latter part of the compression stroke of the cylinder, which is suitable for the post injection and retard control of the ignition timing. During this period, strong turbulence occurs in the combustion chamber, improving the ignition stability of the air-fuel mixture.

In the invention of claim 4, the fuel injection valve is arranged so as to directly inject the fuel into the combustion chamber in the cylinder from the peripheral portion thereof, and the ignition plug is arranged substantially in the center of the ceiling portion of the combustion chamber. On the other hand, a recess is provided on the crown surface of the piston that is the bottom of the combustion chamber, and the spread angle of the fuel spray from the fuel injection valve is set to approximately 40 ° or more and approximately 70 ° or less, and the fuel pressure is approximately 4 MPa or more. In addition, the structure is set to approximately 6 MPa or less.

In this structure, the fuel spray injected into the combustion chamber by the fuel injection valve in the compression stroke of the cylinder is trapped in the recess formed in the crown surface of the piston and along the wall surface thereof, the spark plug side. As a result, the air-fuel mixture can be reliably stratified around the spark plug, and high ignition stability can be obtained. On the other hand, since a part of the fuel spray collides with the bottom wall surface of the recess, etc., the concentration of HC in the exhaust increases due to the adhesion of the fuel to the recess, and further causes the generation of smoke. There is also a risk of becoming.

On the other hand, in the present invention (claim 1),
As described above, as the total injection amount of fuel per cycle is larger, the injection amount ratio of the latter stage is reduced, so that the penetrating force of the fuel spray by the latter stage injection can be made relatively small.
In addition, the fuel pressure at that time is about 4 MPa or more and about 6 MPa.
By setting the angle to a or less and further setting the spread angle of the fuel spray to approximately 40 ° or more and approximately 70 ° or less, the penetration force of the fuel spray can be optimized and adhesion to the piston crown surface can be suppressed.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall construction of a control device A for a spark ignition type direct injection engine according to the present invention. Reference numeral 1 denotes a gasoline engine mounted on a vehicle. The engine 1 is, for example, a multi-cylinder engine having a plurality of cylinders 2, 2, ... (Only one is shown) arranged in series, and an upper portion of a cylinder block 3 in which the respective cylinders 2 are formed. A cylinder head 4 is arranged, and a piston 5 is inserted in each cylinder 2 so as to be capable of reciprocating in the vertical direction, and the inside of the cylinder 2 between the crown surface of the piston 5 and the lower surface of the cylinder head 4 is arranged. A combustion chamber 6 is formed in the partition. Further, the side wall of the cylinder block 3 surrounding the cylinders 2, 2, ...
Although not shown, a water jacket is formed, and in the lower part of the cylinder block 3, the cylinders 2,
A crank chamber 7 is formed so as to communicate with the crankshafts 2, and a crankshaft 8 is housed therein. An electromagnetic crank angle sensor 9 for detecting the rotation angle of the crank shaft 8 is provided on one end side thereof.

As shown in an enlarged view in FIG. 2, the detailed structure of each of the cylinders 2 is such that the ceiling of the combustion chamber 6 is formed with two inclined surfaces having a roof-like shape that is fitted to each other. Two intake ports 10 and two exhaust ports 11 are opened on each of the two inclined surfaces, and intake and exhaust valves 12, 12, 13, 13 are arranged at the respective open ends. The two intake ports 10, 10 respectively extend obliquely upward from the combustion chamber 6 and open on one side surface of the cylinder head 4 independently of each other.
The two exhaust ports 11, 11 merge into one on the way, extend substantially horizontally, and open to the other side surface of the cylinder head 4.

The intake valves 12, 12, ... And the exhaust valve 1
The two cam shafts 14, 13 disposed on the cylinder head 4 are rotationally driven by the crank shaft 8 via a timing belt, so that the cylinders 3, 13, ... It is designed to be opened and closed at the timing. As shown only in FIG. 1, the intake side camshaft 14 has a known variable valve mechanism 15 (Va) for continuously changing the rotation phase with respect to the crankshaft 8 within a predetermined angle range.
A liable valve timing (hereinafter abbreviated as VVT) is additionally provided, and the operation timing of the intake valve 12 can be changed by the operation of the VVT 15.

An ignition plug 16 is provided at a central position in the ceiling portion of the combustion chamber 6 of each cylinder 2 so as to be surrounded by the four intake / exhaust valves 12 and 13. An ignition circuit 17 (only shown in FIG. 1) is connected to the base end portion, and the ignition plug 16 is energized at a predetermined ignition timing for each cylinder 2. Further, an injector (fuel injection valve) 18 is disposed below the two intake ports 10, 10 at the peripheral portion of the ceiling of the combustion chamber 6 on the intake side, so as to be sandwiched between them.
The injector 18 injects fuel from an injection hole on the tip side thereof toward the cylinder center line Z and obliquely below the cylinder 2. The injector 18 may be, for example, a known swirl injector that ejects fuel as a swirling flow from an injection hole to inject in a hollow cone shape, and the spread angle of the fuel spray is approximately 40 ° or more and approximately 70 ° or less. Is preferred.

On the other hand, on the crown surface of the piston 5 corresponding to the bottom of the combustion chamber 6, a cavity 5a (recess) is formed eccentrically to the intake side (front side in FIG. 2) with respect to the cylinder center line Z. When fuel is injected after the middle stage of the compression stroke of the cylinder 2 by the operation of the injector 18, this fuel spray is trapped by the cavity 5a and moved to the spark plug 16 side along the wall surface of the cavity 5a. Then, an air-fuel mixture is formed around the electrodes of the ignition plug 16. That is, the engine 1 is a so-called wall guide type direct injection engine in which the fuel spray is guided by the wall surface of the cavity 5a of the piston 5 to be stratified in the stratified combustion state.

When the fuel is injected in the intake stroke of the cylinder 2 by the operation of the injector 18, the fuel spray diffuses in accordance with the expansion of the volume of the combustion chamber 6 as the piston 5 descends, so that the intake air is sufficiently absorbed. When mixed and evaporated, a substantially uniform air-fuel mixture is formed throughout the combustion chamber 6.

The injectors 18, 18 arranged in each cylinder 2 as described above are connected to the fuel distribution pipe 19 common to all the cylinders 2, 2, ... And supplied from the fuel supply system 20. The high-pressure fuel thus generated is distributed to the cylinders 2 by the fuel distribution pipe 19. Specifically, the fuel supply system 20 is configured as shown in FIG. 3, and the low-pressure fuel pump 23 extends from the upstream side to the downstream side of the fuel passage 22 that connects the fuel distribution pipe 19 and the fuel tank 21. , A low-pressure regulator 24, a fuel filter 25, a high-pressure fuel pump 26, and a high-pressure regulator 27 are arranged in order, and the fuel sucked from the fuel tank 21 by the low-pressure fuel pump 23 is regulated by the low-pressure regulator 24, and the fuel filter It is filtered by 25 and sent under pressure to the high-pressure fuel pump 26.

Then, a part of the fuel whose pressure is further increased by the high pressure fuel pump 26 is adjusted in flow rate by the high pressure regulator 27 and supplied to the fuel distribution pipe 19, and the remaining fuel is adjusted in pressure by the low pressure regulator 28 while returning. It is returned to the fuel tank 21 by the passage 29. The adjustment of the fuel pressure by the high pressure regulator 27 is performed by the ECU 50 described later based on the output of the fuel pressure sensor 30 arranged in the fuel distribution pipe 19, whereby the pressure of the fuel supplied to the fuel distribution pipe 19, that is, Fuel pressure is about 4 ~
It is controlled mainly in the range of 10 MPa according to the engine rotation speed. The configuration of the fuel supply system 20 is not limited to that described above, and may be, for example, a returnless system.

An intake passage 32 communicating with the intake ports 10, 10 of each cylinder 2 is connected to one side surface of the cylinder head 4 located on the right side of the engine 1 in FIG. The intake passage 32 is for supplying the air filtered by an air cleaner (not shown) to the combustion chamber 6 of each cylinder 2 of the engine 1. An electric throttle valve 33 composed of a valve and a surge tank 34 are sequentially arranged. The electric throttle valve 33 is not mechanically connected to an accelerator pedal (not shown), and is driven by an electric motor (not shown) so as to be appropriately opened corresponding to the operation amount (accelerator opening) of the accelerator pedal. It will be opened and closed at regular intervals.

Further, the intake passage 32 on the downstream side of the surge tank 34 is an independent passage branched for each cylinder 2, and the downstream end portion of each independent passage is further branched into two and individually. To the intake ports 8 and 8, and a swirl control valve 35 is provided in one of the branch passages. The swirl control valve 35 is a butterfly valve as shown in FIG. 2, and is opened and closed by an actuator (not shown). When the swirl control valve 35 is closed, most of the intake air is swirl control valve 35.
It comes to be sucked into the inside of the cylinder 2 only from the other branch passage without the above, and thereby a strong swirl flow is generated in the inside of the cylinder 2.

An exhaust passage 36 for discharging combustion gas (exhaust gas) from the combustion chamber 6 of each cylinder 2 is connected to the other side surface of the cylinder head 4 located on the left side of the engine 1 in FIG. The upstream end of the exhaust passage 36 branches for each cylinder 2 and communicates with the exhaust port 11 through the exhaust manifold 3.
7, a linear O2 sensor 38 for detecting the oxygen concentration in the exhaust gas is arranged at the collecting portion of the exhaust manifold 37. The linear O2 sensor 38 is used to detect the air-fuel ratio based on the oxygen concentration in the exhaust gas, and is a sensor that can obtain a linear output with respect to the oxygen concentration in a predetermined air-fuel ratio range including the theoretical air-fuel ratio. is there.

The exhaust passage 36 on the downstream side of the collecting portion of the exhaust manifold 37 is constituted by an exhaust pipe 39. The exhaust pipe 39 is arranged in the order from the upstream side to the downstream side of the exhaust pipe 39 in the vicinity of the theoretical air-fuel ratio. HC, CO, NOx in exhaust gas of
A three-way catalyst 40 that purifies the three-way catalyst, a lambda O2 sensor 41 for determining the deterioration state of the three-way catalyst 40, and a so-called lean NOx catalyst 42 that can purify NOx in the exhaust that is leaner than the stoichiometric air-fuel ratio. It is arranged. Further, the downstream end of the exhaust manifold 37 is connected to an upstream end of an exhaust gas recirculation passage 43 (hereinafter referred to as an EGR passage) that branches off a portion of the exhaust gas flowing in the exhaust passage 36 to the intake system. Has been done. The downstream end of the EGR passage 43 is connected to the intake passage 32 between the throttle valve 33 and the surge tank 34, and an EGR valve 44, which is an electric flow control valve with adjustable opening, is arranged in the vicinity of the intake passage 32. The EGR valve 44 controls the recirculation amount of the exhaust gas flowing through the EGR passage 43.

The VVT 15, the ignition circuit 17, the injector 18, the fuel supply system 20, the electric throttle valve 33,
The swirl control valve 35, the EGR valve 44, etc. are all engine control units 50 (hereinafter referred to as ECUs).
Operation is controlled by. On the other hand, the ECU 50 has
At least the crank angle sensor 9 and the fuel pressure sensor 3
Output signals from the 0, O2 sensors 38, 41, etc., and an output signal from an air flow sensor 46 which is arranged near the air cleaner case and measures the flow rate of the air sucked into the intake passage 32. Cylinder block 3
The output signal from the water temperature sensor 47 that detects the cooling water temperature (engine water temperature) is input to the water jacket, and the output signal from the accelerator opening sensor 48 that detects the accelerator opening and the engine rotation speed. The output signal from the rotation speed sensor 49 for detecting (the rotation speed of the crankshaft 8) is input.

Specifically, the ECU 50 detects the operating state (load and rotational speed) of the engine based on the signals respectively input from the air flow sensor 46, the accelerator opening sensor 48 and the rotational speed sensor 49. Ignition circuit 17, injector 18, mainly depending on the detection result,
The engine 1 is controlled by controlling the throttle valve 33 and the like.
Operating in different combustion states. That is, although not shown, when the engine 1 is in a warm low-speed low-load operating state, basically, the fuel is collectively injected by the injector 18 after the middle stage of the compression stroke of the cylinder 2, and the spark plug 1
Combustible air-fuel mixture is burned in a state of being unevenly distributed around the electrode of No. 6 (stratified combustion). At this time, the throttle valve 33
The pump loss of the engine 1 is reduced by relatively increasing the opening degree of.

On the other hand, when the engine 1 is in a cold or warm operating state on the high speed or high load side, basically, the fuel is injected by the injector 18 mainly in the intake stroke of the cylinder 2, and the combustion chamber 6 as a whole. A substantially uniform air-fuel mixture is formed and then burned (uniform combustion). At this time, the total injection amount of the fuel per cycle is controlled based on the signal from the air flow sensor 46 so that the air-fuel ratio of the air-fuel mixture becomes substantially stoichiometric air-fuel ratio or richer than that, and the throttle valve The opening degree of 33 is controlled based on the signal from the accelerator opening sensor 48 so that an output corresponding to the operation amount of the accelerator pedal can be obtained.

Incidentally, the control of the injector 18, the throttle valve 33, etc. for switching the combustion state of the engine 1 to either the stratified combustion state or the uniform combustion state as described above,
It is realized by executing a predetermined control program in the ECU 50.

(Control when the catalyst is not warmed up) In this embodiment, the three-way catalyst 40 disposed in the exhaust passage 36 of the engine 1 is used.
And at least one of the lean NOx catalysts 42 (which may be only the three-way catalyst 40) is in a non-warming state lower than its activation temperature, the temperature state of the exhaust gas from the engine 1 is raised to raise the temperature of the catalysts 40, 42. Trying to promote. That is, as in the case of the conventional example (Japanese Patent Laid-Open No. 2000-45844), when at least one of the catalysts 40 and 42 is not warmed up and the engine 1 is in the low load region, as schematically shown in FIG. In addition, the ignition timing of each cylinder 2 is controlled to be relatively retarded, and fuel is injected by the injector 18 in each of the intake and compression strokes of the cylinder 2 to reduce the concentration distribution in the combustion chamber 6 in each cylinder 2. A weakly stratified mixture with a relatively small bias is formed and burned (weakly stratified combustion).

In the combustion of such a weakly stratified air-fuel mixture, the spark plug 16 is used as described in the prior art publication.
Since the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio in the vicinity of the electrode, it is easy to secure ignition stability. Further, while the initial combustion speed of the air-fuel mixture becomes high, from the latter half of the combustion period, relatively slow combustion of the air-fuel mixture leaner than the stoichiometric air-fuel ratio, that is, afterburning will continue until relatively late, As a result, the temperature of the exhaust gas becomes relatively high and HC is reduced.

However, in the combustion of the weakly stratified air-fuel mixture, there is a problem that smoke is generated in the rich air-fuel mixture portion formed around the spark plug 16. That is, as shown by the solid line or broken line graph in FIG. 5, particularly in the combustion of a weakly stratified mixture, the ignition timing is set at the compression top dead center (TD).
Smoke generation is more remarkable on the advance side than C), and when the latter injection amount ratio shown by the solid line in the figure is large (50%), it is smaller (shown by the broken line: 25). %)
The smoke concentration in the exhaust becomes higher than that. In addition, the start timing of the latter-stage injection (Start of Injection: hereinafter, simply referred to as SOI)
10 ° to 30 ° before compression top dead center (BTDC)
In the range of CA, the smoke concentration tends to decrease as the angle of advance increases. It should be noted that, in the combustion of the homogeneous mixture (shown by the phantom line graph in the figure), smoke is not generated regardless of the change in the ignition timing.

With respect to this point, the inventor of the present application uses two types of engines having different specifications to perform the fuel injection in the front stage at a predetermined timing in the intake stroke of the cylinder, while the injection amount in the fuel injection in the rear stage thereafter. Was changed and the injection start timing was changed, and the change in the smoke concentration in the exhaust gas at that time was examined. The results are shown in the graphs of FIGS. 6 (a) and 6 (b), and the smoke concentration in the exhaust gas increases as the ratio of the injection amount in the latter stage increases and the injection start timing in the latter stage becomes late for any engine. Was found to be high.

More specifically, for example, according to the graph of FIG. 6A, if the injection amount ratio of the latter stage is set to approximately 25% or less, the latter stage injection start timing SOI = BTDC 20 to 50 ° CA The concentration falls within an allowable range where it does not matter practically. Also, SOI = BTDC 30 to 50 ° CA
If the range is set, the smoke concentration can be kept within the allowable range even if the injection amount ratio in the subsequent stage is further increased. In these experiments, the ignition timing was not changed even if the injection start timing in the latter stage was retarded.

Considering on the basis of such experimental results, when increasing the injection amount ratio of the latter stage in the combustion of the weakly stratified air-fuel mixture, the local air-fuel ratio of the air-fuel mixture around the spark plug 16 is thereby increased. Since the fuel is rich, it is considered that the combustion is locally generated with a higher heat release rate and smoke is easily generated. Further, if the injection start timing of the latter stage is retarded, the time until ignition is shortened by that, and it is considered that the vaporization and atomization of the fuel becomes insufficient and smoke is easily generated.

Therefore, if it is desired to simply suppress the generation of smoke, it is preferable to reduce the injection amount ratio in the latter stage or set the injection start timing to the advance side. Only by doing so, the original effect of the weak stratified charge combustion, which raises the temperature of the exhaust gas, cannot be sufficiently obtained, and the HC concentration in the exhaust gas increases. In particular, when the injection start timing of the latter stage is set to the advance side, it becomes easy to secure the time for the vaporization and atomization of the fuel by the ignition time, but the fuel spray is diffused by the air flow in the cylinder 2. May easily occur, and ignition stability may be impaired.

Here, considering the change in the total injection amount of fuel per cycle, the relationship between the exhaust temperature and the amount of smoke produced in the combustion of the weakly stratified mixture is reconsidered. When the total fuel injection amount is large, the amount of heat of the exhaust gas is increased by that amount.
It can be said that it is easy to promote the temperature rise of 2. Further, when the fuel injection amount is large, the intake air amount is large accordingly. Therefore, if the injection amount ratio of the front stage and the rear stage is made constant, it can be considered that the local air-fuel ratio around the spark plug 16 becomes substantially constant. Since the fuel injection amount itself is large even if the air-fuel ratio is the same, it becomes more difficult to vaporize and atomize the fuel by the time of ignition, and smoke is likely to be generated.

That is, when the total injection amount of fuel is relatively large, the heat amount of the exhaust gas increases, so that the catalysts 40, 4
Although it is easy to promote the temperature rise of 2, the problem of smoke tends to increase. Therefore, at this time, it can be said that it is preferable to increase the exhaust gas temperature as much as possible while giving priority to suppression of smoke. On the contrary, when the total injection amount of fuel is relatively small, the amount of heat of exhaust gas is small, but it becomes difficult to generate smoke. Therefore, at this time, the temperature rise of exhaust gas may be prioritized.

Based on such a technical idea, the engine control device A of this embodiment is characterized by the present invention in the intake and compression strokes of each cylinder 2 in order to promote the temperature rise of the unheated catalysts 40 and 42. When each fuel is injected and burned in a weakly stratified state, the injection amount ratio and the injection start timing in the latter stage are changed as follows in association with the change in the total injection amount.

That is, first, based on the output signals from the air flow sensor 46 and the rotation speed sensor 49, the ECU
By controlling the valve opening time of the front-stage injection and the rear-stage injection of the injector 18 by 50, per cycle including the front-stage injection and the rear-stage injection so that the average air-fuel ratio in each cylinder 2 becomes approximately the theoretical air-fuel ratio. Control the total injection amount of fuel. Then, as shown in FIG. 4, when the total fuel injection amount is relatively large (when the load is relatively high), the injection amount ratio of the latter stage is relatively decreased so that the latter stage fuel injection amount itself. Try to be less. By doing so, it is possible to sufficiently vaporize and atomize the fuel by the latter-stage injection by the time of ignition to suppress the generation of smoke, and suppress the penetration force of the latter-stage injection performed in the latter stage of the compression stroke of the cylinder 2 to suppress the fuel. Of the smoke on the crown surface of the piston 5 is reduced, and this also suppresses the generation of smoke.

The ratio of the post injection amount to the total injection amount of fuel is preferably controlled in the range of approximately 20% to approximately 40%, and more preferably approximately one third or less of the total injection amount. Further, in order to prevent the fuel from adhering to the crown surface of the piston 5, it is preferable to control the fuel pressure within a range of approximately 4 to approximately 6 MPa to suppress the penetration force of the fuel spray to an appropriate level.

Further, as shown in FIG. 4, on the relatively high load side, the injection start timing is controlled to be on the retard side in accordance with the decrease in the fuel injection amount in the latter stage. By doing so, the fuel spray injected into the combustion chamber 6 in the latter half of the compression stroke of each cylinder 2 becomes difficult to be diffused by the swirl flow in the cylinder 2,
Even with a relatively small amount of fuel spray, the air-fuel mixture can be retained near the electrode of the spark plug 16 until TDC and thereafter. As a result, the ignition timing of each cylinder 2 can be significantly retarded after TDC while maintaining the ignition stability. However, since a certain amount of time is required from the fuel injection in the latter stage to the ignition point for good vaporization and atomization of the fuel spray, after all, as shown in FIG. 4, the start timing of the latter stage injection is BTDC 20-40 ° CA. The range is preferably

The ECU 50 controls the ignition circuit 17 for each cylinder 2 in response to the retard control of the latter-stage injection timing.
Is controlled to significantly retard the ignition timing of each cylinder 2 to, for example, 15 ° CA after TDC (ATDC). As a result, the cycle efficiency of the engine 1 can be significantly reduced and the slow combustion of the air-fuel mixture can be continued relatively to the retard side, so that the exhaust temperature is sufficiently increased. It is preferable to control the ignition timing so that it is retarded from ATDC 5 ° CA, and in consideration of the balance with combustion stability, it is set in the range of ATDC 5 to 15 ° CA as shown in FIG. Preferably.

In addition to the above fuel injection control and ignition timing control, the opening degree of the throttle valve 33 is determined by the ECU 50 depending on the engine water temperature, the time from the start of the engine 1, the operating state of the auxiliary machinery, etc. Control. The swirl control valve 35 is fully closed to generate a strong swirl flow in each cylinder 2. This swirl flow is maintained until the latter stage of the compression stroke of the cylinder 2 and then collapses, causing strong turbulence in the entire combustion chamber 6 until after TDC so as to correspond to the retard control of the ignition timing. This improves the ignition stability of the air-fuel mixture.

Ignition circuit 17 and injector 1 described above
The control of the throttle valve 33, the swirl control valve 35, etc. is realized by executing a predetermined control program in the ECU 50. That is, in the memory of the ECU 50, as illustrated in FIGS. 7 (a) and 7 (b), as a control map of the injector 18 when the catalyst is not warmed up, the optimum post-injection amount ratio corresponding to the load state of the engine 1 and A map in which the injection start timing is experimentally set is stored. According to these maps, for example, when the engine 1 is in a net no-load operating state, that is, in the operating state where the load is the smallest while the vehicle is stopped including mechanical loss and the like, the post-stage injection amount ratio becomes maximum (see the example in FIG. Is about 35%), and the injection start timing is most advanced (BTDC is about 35 ° C in the illustrated example).
A) On the other hand, the latter-stage injection amount ratio gradually decreases from there, and the start timing of the latter-stage injection is gradually retarded accordingly.

Then, for example, based on the engine water temperature detected by the water temperature sensor 47, the time elapsed from engine start (measured by a timer), and the like, at least one of the catalysts 40 and 42 in the ECU 50 is in an unwarmed state in which it is lower than the activation temperature. Is determined, and it is determined that the net load state of the engine 1 is a low load operation state below a predetermined value, the ignition circuit 17, the injector 18, the throttle valve 33, and the swirl control are performed as described above. By controlling the valve 35 and the like, the average air-fuel ratio of each cylinder 2 of the engine 1 is set to a substantially stoichiometric air-fuel ratio, and fuel is injected in the intake stroke and compression stroke of each cylinder 2 to cause a weak stratified combustion state. And the ignition timing of each cylinder 2 becomes, for example, ATDC5-1.
The temperature of the exhaust gas temperature rises by being retarded to about 5 ° CA, which accelerates the early temperature rise of the catalysts 40, 42.

In other words, the ECU 50 controls the ignition timing to retard the ignition timing of each cylinder 2 of the engine 1 to ATDC 5 ° CA or later when at least one of the exhaust purification catalysts 40 and 42 is not warmed up. Fuel is injected in the intake stroke and the compression stroke by the portion 50a and the injector 18 of each cylinder 2 at that time so that the average air-fuel ratio in each cylinder 2 becomes approximately the theoretical air-fuel ratio. A fuel injection control unit 50b that controls the total injection amount of fuel and a swirl valve control unit 50c that closes the swirl control valve 35 at that time to strengthen the swirl flow in the combustion chamber 6 are provided.

Then, the fuel injection control unit 50b makes the ratio of the post injection amount in the intake stroke to the total injection amount while making the pre injection fuel injection amount larger than the post injection fuel injection amount in the compression stroke. It is configured such that the larger the total injection amount is, the smaller the total injection amount is, and that the start timing of the second-stage injection is retarded according to the decrease in the injection amount ratio.

Therefore, according to the control device A of the spark ignition type direct injection engine according to this embodiment, for example, during the idle operation after the cold start of the engine 1, as shown in the time chart of FIG. Control is performed to promote early temperature rise of the catalysts 40 and 42.

First, when the start-up of the engine 1 by the starter motor is completed (t = t1), the ignition timing control unit 50a of the ECU 50 sets the ignition timing of each cylinder 2 to ATDC.
The fuel injection control unit 5 is retarded to 15 ° CA.
By controlling the operation of the injector 18 by 0b, the fuel injection is performed twice in each of the first and second stages. Further, by controlling the opening degree of the throttle valve 33 and the fuel injection amount (total injection amount) by the injector 18, the engine rotation speed is maintained at the idle rotation speed set according to the engine water temperature and the like. That is, immediately after the engine 1 is started, the idle speed is higher than normal (for example, 1200 rpm), and then gradually returned to the normal idle rotation speed (for example, 650 rpm).

Immediately after starting, the engine oil has a high viscosity, a large mechanical friction, and a fast idle as described above, and the engine speed is high. The total injection amount of fuel is increased to correspond to this load, the injection amount ratio of the latter stage is relatively reduced (for example, 20%), and the injection start timing of the latter stage is relatively retarded. It is set (for example, BTDC 25 ° CA).

At this time, in the first half of the intake stroke of each cylinder 2 (for example, BTDC 300 ° CA), the fuel spray ejected from the injection hole of the injector 18 into the combustion chamber 6 by the fuel injection in the first stage is accompanied by the downward movement of the piston 5 and the combustion chamber 5 Diffuse all over to form a homogeneous mixture leaner than the stoichiometric air-fuel ratio. Further, the fuel spray produced by the fuel injection in the latter stage is trapped in the cavity 5a on the crown surface of the piston 5 which is rising, and the combustion chamber 6
An air-fuel mixture is formed at a substantially central portion, that is, near the electrode of the spark plug 16. As a result, the spark plug 1 is provided in the entire combustion chamber 6.
A weakly stratified air-fuel mixture having a high concentration distribution around the air-fuel mixture 6 is formed.

At this time, although the total injection amount of fuel is relatively large, the injection amount ratio of the latter stage is small and the injection amount itself is rather small. Therefore, the penetration force of the fuel spray by the latter stage injection is It does not become so large, and its adhesion to the crown surface of the piston 5 is small. Further, a relatively small amount of the injected fuel in the latter stage is sufficiently atomized and atomized by the time of ignition, and becomes a good combustible mixture. Moreover, since the latter-stage fuel injection is performed relatively on the retard side, the fuel spray becomes difficult to be diffused by the swirl flow in the cylinder 2, etc., and the rich air-fuel mixture ignites after TDC. Up to the center of the combustion chamber 6, the ignition plug 16 ensures ignition.

At the beginning of combustion, the rich air-fuel mixture rapidly becomes a good combustion state with a small amount of smoke, and thereafter, the flame surface propagates to the air-fuel mixture leaner than the stoichiometric air-fuel ratio and is relatively slow. Combustion (afterburning) continues for a long time until the latter half of the expansion stroke of the cylinder 2. In other words, while ensuring good ignition stability even when the engine 1 is cold,
It is possible to suppress the generation of smoke, raise the temperature of exhaust gas, and reduce HC. Moreover, at this time, since the total amount of fuel injected per cycle is relatively large, the heat amount of the exhaust gas itself also increases, and the temperature rise of the catalysts 40, 42 is effectively promoted by the relatively high temperature and large amount of exhaust gas. can do.

Then, as the engine 1 warms up, the viscosity of the engine oil decreases and the engine speed gradually decreases (t = t1 to t2). As a result, the operating load of the engine 1 gradually decreases, so that the total injection amount of fuel gradually decreases corresponding to the decrease in the load, which gradually reduces the heat amount of exhaust gas and weak stratification. Even if it burns, it becomes difficult to generate smoke. At this time, the ratio of the injection amount in the latter stage gradually increases corresponding to the gradual decrease of the total injection amount of fuel, the effect of increasing the exhaust temperature due to the combustion of the weakly stratified air-fuel mixture becomes high, and the HC also decreases. To be done. Further, the injection start timing is gradually changed to the advance side with the increase of the fuel injection amount in the latter stage, and the vaporization atomization time of the fuel spray is secured.

That is, in this embodiment, 1 of each cylinder 2
Even if the total injection amount of fuel per cycle changes, the fuel injection ratio and the injection start timing of the latter stage are optimized correspondingly, so that the combustion of the weakly stratified mixture and the retard control of the ignition timing are performed. The effect of increasing the temperature of the exhaust gas can be sufficiently obtained, and HC in the exhaust gas at that time can be reduced and the increase of smoke can be prevented.

As shown in the time chart of FIG. 8, when promoting the early temperature rise of the catalysts 40 and 42,
The average air-fuel ratio in the combustion chamber 6 of each cylinder 2 is controlled to be substantially the stoichiometric air-fuel ratio, and this also minimizes the production of HC, CO, and NOx accompanying combustion. Also,
By fully closing the swirl control valve 35 and strengthening the swirl flow in the combustion chamber 6, the ignition stability to the weakly stratified mixture is further improved.

When both the catalysts 40 and 42 are activated (t = t3), the ignition timing of each cylinder 2 is returned to the advance side, and the fuel injection is performed only in the intake stroke of the cylinder 2. After that, the engine 1 is operated in a uniform combustion state until the engine water temperature reaches a predetermined temperature (for example, 40 ° C.), and if the engine water temperature is equal to or higher than the predetermined temperature, the engine 1 is stratified on the low load side. It operates in the combustion state, and in the high load side, in the uniform combustion state.

FIG. 9 shows that the exhaust temperature rises due to the weak stratified combustion of the direct injection engine 1 according to this embodiment, and the HC
Is an experimental result showing that the engine load is about 100 kPa and the rotation speed is about 1200 rpm. The horizontal axis of the graph shown in the figure shows the exhaust heat flow rate (heat flux: product of exhaust temperature and flow rate, divided by engine exhaust volume), and the vertical axis shows unit time per unit time. The amount of HC in the exhaust gas is shown. Then, as shown by the solid line graph, the injection amount ratio in the latter stage is set to approximately 25%, and the injection start timing SOI is SOI = BTDC20 to 3
It can be seen that when the temperature is 0 ° CA, HC in the exhaust gas is significantly reduced and the heat flow rate of the exhaust gas is significantly increased as compared with the case of the uniform combustion state.

As shown in the figure, the injection amount ratio in the latter stage is set to about 2
Even if it is 5%, the injection start timing is BTDC 10 ° C.
When it is too late to A, the vaporization and atomization of the fuel spray becomes insufficient, the combustion state deteriorates, and HC in the exhaust gas increases. Further, as shown by the dotted line graph in the figure, when the injection amount ratio in the latter stage becomes about 50% (comparative example), the local air-fuel ratio around the spark plug becomes too rich because the injection ratio is too large, and combustion also occurs. As the condition deteriorates, the amount of HC in the exhaust increases.

(Other Embodiments) The structure of the present invention is not limited to the above-described embodiment, but includes various other structures. That is, in the direct injection engine 1 of the above-described embodiment, when accelerating the temperature rise of the catalysts 40 and 42, the average air-fuel ratio of each cylinder 2 is set to the approximate theoretical air-fuel ratio (A /
However, the air-fuel ratio is, for example, A / F = approximately 13 to 16
You may make it set to the range of.

Further, in the above embodiment, the catalysts 40, 4
When accelerating the temperature rise of 2, the injector 18 of each cylinder 2 injects the fuel in the front stage in the intake stroke and the fuel in the rear stage in the compression stroke to form a weak stratified mixture in the combustion chamber 6. However, the present invention is not limited to this, and for example, the fuel injection in the previous stage may be performed in the first half of the compression stroke of the cylinder 2.

In the above embodiment, the catalysts 40, 4
Although the swirl control valve 35 is closed when the temperature increase of 2 is promoted, the invention is not limited to this.

Further, in the above embodiment, the catalysts 40 and 4
The determination that 2 is in the unwarmed state is made based on the engine water temperature, the time elapsed from the engine start, etc., but is not limited to this. For example, a temperature sensor is provided in the exhaust passage 36, and The determination may be reduced based on the output.

Further, although the present invention is applied to the so-called wall guide type direct injection engine 1 in the above embodiment, the present invention is not limited to this. That is, for example, the behavior of the fuel spray injected into the cylinder 2 by the injector 18 is controlled by the air flow in the cylinder 2 so as to stratify around the electrode of the spark plug 16 so-called air guide type direct injection. The control of the present invention can be applied to accelerate the temperature rise of the unwarmed catalyst even in the engine or in the direct injection engine which is always operated in the uniform combustion state.

Furthermore, the structure of the engine 1 described in the above embodiment is only one example, and does not limit the structure of the direct injection engine to which the present invention is applied. That is, for example, only one catalyst may be provided in the exhaust passage 36, or the injector 18 for each cylinder 2 may not be a swirl injector. Also, a total of 4 per cylinder 2
Equipped with two intake and exhaust valves 12, 13 and EGR passage 43
Needless to say, the present invention is not limited to those equipped with.

[0077]

As described above, according to the control apparatus for a spark ignition type direct injection engine according to the invention of claim 1, the ignition timing of the cylinder is compressed when the catalyst for purifying the exhaust gas is not warmed up. The engine is retarded until after top dead center, and the fuel injection is performed twice in the front stage and the rear stage within the period from the intake stroke to the ignition timing of the cylinder. As the total injection amount per hit is larger, the injection amount ratio of the latter-stage injection is reduced and the injection start timing is retarded, whereby the temperature of the exhaust gas is reduced while promoting the temperature rise of the catalyst by the high temperature exhaust gas. It is possible to prevent smoke from increasing.

According to the invention of claim 2, by optimizing the combination of the ignition timing of each cylinder of the engine, the air-fuel ratio, the fuel injection amount ratio of the latter stage and the injection start timing, the effect of the invention of claim 1 is sufficiently obtained. Can be obtained.

According to the third aspect of the present invention, by strengthening the swirl flow in the combustion chamber in the cylinder by the swirl flow strengthening means, a strong turbulence is generated in the combustion chamber at the optimum timing corresponding to the post-injection and the ignition timing retard control. And the ignition stability of the air-fuel mixture can be improved.

According to the fourth aspect of the present invention, in the so-called wall guide type direct injection engine, the penetration force of the fuel spray due to the latter stage injection can be optimized and the adhesion to the piston crown surface can be suppressed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine control device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic structure of a combustion chamber in a cylinder of an engine.

FIG. 3 is an explanatory diagram schematically showing the configuration of a fuel supply system.

FIG. 4 is an explanatory diagram showing a fuel injection timing by an injector.

FIG. 5 is a graph showing a change characteristic of smoke concentration with respect to a change in ignition timing while changing a fuel injection amount ratio and an injection start timing in a latter stage.

FIG. 6 is a graph showing a change characteristic of a smoke concentration with respect to a change of a fuel injection amount ratio of a latter stage while changing a fuel injection start timing of the latter stage.

FIG. 7 is an explanatory diagram showing an example of a control map in which the injection amount ratio or the injection start timing in the latter stage when the catalyst is not warmed up is set in association with the load state of the engine.

FIG. 8 is a time chart showing an example of control at the time of engine cold start.

FIG. 9 is a graph of experimental results showing that HC in exhaust gas is reduced and heat flux is increased by combustion of a weakly stratified mixture.

[Explanation of symbols]

A engine control device 1 engine Two cylinder 5 pistons 5a Cavity (recess) 6 Combustion chamber 16 spark plugs 18 Injector (fuel injection valve) 35 Swirl control valve (Swirl flow enhancement means) 40 three way catalyst 42 lean NOx catalyst 50 Control Unit (ECU) 50a Ignition timing control unit (ignition timing control means) 50b Fuel injection control unit (fuel injection control means) 50c Swirl valve control unit (Swirl flow strengthening means)

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/02 F02D 41/02 330G 41/04 335 41/04 335Z 41/06 330 41/06 330Z 43/00 301 43 / 00 301B 301H 301J 301U 45/00 312 312 45/00 312B 364 364N F02P 5/15 F02P 5/15 E (72) Inventor Toshinari Takashi Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture F-term in Mazda Co., Ltd. (Reference) 3G022 AA07 AA08 CA02 DA02 EA01 GA01 GA02 GA05 GA06 GA08 GA09 GA10 GA17 3G084 AA04 BA05 BA09 BA13 BA15 BA17 CA02 CA03 CA09 DA10 EA07 EA11 EC01 EC03 FA07 FA10 FA20 FA27 FA30 FA33 A33 A38 AG17 GA30 GA33 BA15 BA19 BA32 CA13 CB02 CB03 CB05 CB07 CB08 DA01 DA02 DB10 EA00 EA01 EA05 EA07 EA16 EA17 EA26 EA30 EA31 EA34 FA02 FA04 FA12 FA13 FB02 FB11 FC07 HA08 HA10 HA05 HA08 HA10 HA05 HA13 HA16 HA05 HA13 HA16 HA17 HA04 HA16 HA16 HA17 HA04 HA16 HA16 HA17 HA04 HA16 HA17 HA04 HA05 HA16 HA17 HA04 HA16 HA16 HA17 HA04 HA05 HA16 HA17 HA04 HA16 HA17 HA04 HA16 HA17 HA04 HA05 HA16 HA17 HA04 HA10 LB04 MA01 MA11 MA19 MA27 NA08 NE06 NE08 NE11 NE12 NE13 NE14 NE23 PA01Z PB08Z PD03Z PD04Z PD09Z PD12Z PE01Z PE03Z PE04Z PE08Z PF03Z PF11Z

Claims (4)

[Claims] 1. A fuel injection valve for directly injecting fuel into a combustion chamber in a cylinder of an engine, and a catalyst for purifying exhaust gas from the combustion chamber, the catalyst being unheated below an activation temperature. During the engine state, at least in the low load region of the engine, during the period from the intake stroke of the cylinder to the ignition timing, the fuel injection valve causes two injections of the latter stage injection after the middle stage of the compression stroke and the former stage injection before this. In a control device for a spark ignition direct injection engine configured to perform fuel injection, ignition timing control means for delaying ignition timing after compression top dead center of a cylinder when the catalyst is not warmed up, and When the catalyst is in a non-warm state, while the amount of fuel injected by the preceding-stage injection is larger than that of the latter-stage injection, and the total amount of fuel injected per cycle including the preceding-stage injection and the latter-stage injection is larger, To the total injection amount And a fuel injection control means for delaying the start timing of the second-stage injection according to the decrease in the ratio of the second-stage injection amount. . 2. The ignition timing control means according to claim 1, wherein the ignition timing is set to 5 after the compression top dead center of the cylinder.
The fuel injection control means controls the average air-fuel ratio in the cylinder to be approximately the theoretical air-fuel ratio at least in the low-speed low-load range of the engine when the catalyst is not warmed up. The total injection amount of the fuel is controlled so that the ratio of the post-injection amount to the total injection amount is approximately one third or less, and the start timing of the post-injection is 20 ° CA before the compression top dead center of the cylinder. A control device for a spark ignition type direct injection engine, which is characterized by what it was before. 3. The spark ignition type direct ignition system according to claim 1, further comprising swirl flow enhancing means for enhancing the swirl flow of the combustion chamber in the cylinder at least when the catalyst is in an unwarmed state. Control device for injection engine. 4. The fuel injection valve according to claim 1, wherein the fuel injection valve is arranged so as to directly inject fuel into a combustion chamber in a cylinder from a peripheral portion thereof, and An ignition plug is arranged substantially in the center, while a recess is provided in the crown surface of the piston, which is the bottom of the combustion chamber, and the spread angle of the fuel spray from the fuel injection valve is about 40 ° or more and about 70 °. A control device for a spark ignition type direct injection engine, which has a fuel pressure of approximately 4 MPa or more and approximately 6 MPa or less.