JP2002332849A - Controller for spark ignition type direct-injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a fuel economy improving effect by stratified charge combustion further by properly retaining an air-fuel mixture stratified state, from the low load side to the high load side within a stratified charge combustion zone. SOLUTION: In the engine is provided with a tumble generating means, comprising an intake port or the like formed so as to generate tumble flow in a combustion chamber, a fuel injection valve 18 for injecting fuel inside the combustion chamber, so that the fuel retrogrades against the tumble flow, and an injection control means 52 for controlling fuel injection timing so as to produce a combustible mixture near an ignition plug at ignition time, a tumble-regulating valve 27 and a tumble control means 45 for controlling the tumble regulator valve 27 are provided also, and the tumble-regulating valve 27 is operated at a non-fully opened state in the stratified combustion zone and an opening of the tumble regulating valve 27 in the low-load side of the stratified combustion zone is provided larger, in comparison with the high-load side of the zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a fuel injection valve for directly injecting fuel into a combustion chamber, and stratifies a combustible air-fuel mixture around an ignition plug using a tumble flow during stratified combustion operation. The present invention relates to a control device for controlling tumble in a spark ignition type direct injection engine.

[0002]

2. Description of the Related Art Conventionally, in a spark ignition type engine, a fuel injection valve for directly injecting fuel into a combustion chamber is provided, and in an operation region on a low rotation speed and low load side, an air-fuel ratio is made lean and a compression stroke from the fuel injection valve is performed. Various types of spark-ignition direct-injection engines have been known in which a fuel-air mixture is unevenly distributed around an ignition plug to perform stratified combustion, thereby improving fuel efficiency.

[0003] For example, in an engine disclosed in Japanese Patent Application Laid-Open No. 2000-204954, an air flow control valve (TCV: tumble control valve) that generates a tumble in a combustion chamber and adjusts the strength of the tumble. The fuel spray from the fuel injector collides with the tumble flow and ignites by arranging the fuel injection valve in the intake passage and arranging the fuel injection valve that injects fuel into the combustion chamber so as to reverse the tumble flow with respect to the combustion chamber. It is designed to be transported near the plug.

Further, in the engine control device disclosed in this publication, when the strength of the tumble flow changes with the change in the engine speed, the balance between the energy of the fuel spray and the energy of the tumble flow is lost, and In order to solve the problem that the spray is not conveyed well near the spark plug, control is performed so that the opening of the air flow control valve and the fuel pressure of the fuel injected from the fuel injection valve are changed according to the engine speed. ing.

[0005]

In the conventional apparatus disclosed in the above-mentioned publication, air is adjusted to adjust the stratification of the air-fuel mixture in response to the tendency of the strength of the tumble flow to change with the change in the engine speed. Although the opening degree and the fuel pressure of the flow control valve are controlled, the following problems have been left in terms of adjustment for fluctuations in engine load in the stratified combustion region.

[0006] In an operation region (stratified combustion region) on the low rotation speed and low load side, fuel is injected from the fuel injection valve within a predetermined period of the compression stroke in order to stratify the air-fuel mixture. When the amount is small, the fuel injection timing is delayed within the above-mentioned predetermined period and brought closer to the ignition timing to suppress the dispersion of the fuel, and as the fuel injection amount increases, the above-described operation is performed to avoid excessive concentration of the injected fuel. The fuel injection timing is advanced within a predetermined period. That is, the fuel injection timing is late on the low load side where the fuel injection amount is small, and the fuel injection timing is advanced within the above-mentioned predetermined period as the load increases in the stratified combustion region.

[0007] In the compression stroke, the cylinder pressure increases as the timing becomes late (approaching the top dead center), and the penetration force of the fuel spray decreases as the cylinder pressure at the fuel injection timing increases, so that stratified combustion occurs. As the fuel injection timing is changed according to the load in the region as described above, the penetration force of the fuel spray is lower on the low load side in the stratified combustion region than on the high load side in the same region even at the same fuel pressure. .

For this reason, for example, on the high load side in the stratified combustion region, the fuel spray and the tumble flow collide with the same force to obtain a state in which the mixture is stratified around the ignition plug. Even when the strength of the fuel spray is adjusted, the balance between the fuel spray and the strength of the tumble flow is lost due to a decrease in the penetration force of the fuel spray on the low load side in the stratified combustion region, and the fuel spray becomes a tumble flow around the combustion chamber. There is a problem that a good stratification state cannot be obtained by being swept away to the side, and the fuel efficiency improvement effect is impaired.

In view of the foregoing, the present invention further enhances the fuel efficiency improvement effect by stratified combustion by maintaining a good mixture stratification state from the low load side to the high load side in the stratified combustion region. It is an object of the present invention to provide a control device for a spark ignition type direct injection engine which can be used.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a tumble generating means for generating a tumble flow in a combustion chamber, and a fuel injection valve for injecting fuel into the combustion chamber in a direction opposite to the tumble flow. And control the fuel injection timing from the fuel injection valve in association with the ignition timing so that a combustible mixture is generated near the ignition plug at the ignition timing in the stratified combustion region, which is a predetermined operation region on the low speed and low load side of the engine. A spark-ignition direct injection engine provided with a tumble control valve for adjusting the intensity of the tumble flow, and a tumble control means for controlling the tumble control valve,
The tumble control valve is provided in an intake passage that guides intake air to the combustion chamber via the tumble generating means, and is configured to increase the tumble as its opening degree decreases, and the tumble control means operates in the stratified combustion region. The tumble control valve is operated in a non-full open state, and the opening of the tumble control valve is controlled to be larger on the low load side of the stratified combustion region than on the high load side of the stratified combustion region.

According to this configuration, in the stratified combustion region, the fuel is injected in such a manner as to reverse the tumble flow while the fuel injection timing from the fuel injection valve is controlled in accordance with the ignition timing. A combustible mixture is generated near the ignition plug, and stratified combustion is performed.

In particular, the tumble flow is adjusted by the tumble control means so that a stratified state can be favorably obtained.
That is, on the low load side of the stratified combustion region, the injection timing is delayed so as to suppress the dispersion of the fuel spray, and accordingly,
The in-cylinder pressure at the time of fuel injection increases and the penetration force of fuel spray decreases, but the tumble flow is weakened by increasing the opening of the tumble control valve to correspond to this. Even if the load changes in the combustion area, the balance between the fuel spray penetration force and the strength of the tumble flow is appropriately adjusted, so that the air-fuel mixture stratification state is favorably maintained.

In the present invention, it is preferable that the tumble control means performs control so as to increase the opening of the tumble control valve on a low load side in a region of the stratified combustion region where the engine speed is higher than an idle speed.

In this case, in the idle speed range where the tumble flow tends to be weakened due to the low intake flow velocity, the tumble flow is too weakened by increasing the opening of the tumble control valve, and the combustion stability is impaired. On the other hand, in the region higher than the idle speed,
As described above, by adjusting the opening of the tumble control valve to be large on the low load side, the balance between the penetration force of the fuel spray and the strength of the tumble flow is appropriately adjusted.

Further, the tumble control means detects a combustion fluctuation rate of the engine and controls the opening of the tumble control valve to be maximum within a range where the combustion fluctuation rate is equal to or less than a predetermined allowable limit value. Is preferred. Further, the tumble control means sets the basic control value of the opening of the tumble control valve to a value corresponding to the operating state within a range in which the combustion fluctuation ratio is maintained at or below the allowable limit value. It is preferable to correct the opening of the tumble control valve in the increasing direction until the temperature reaches the limit point, and to determine a learning value to be reflected in the control of the subsequent tumble adjustment based on this correction.

With this arrangement, in addition to the control according to the load and the like in the stratified combustion region, the correction control of the opening of the tumble control valve is performed so as to weaken the tumble flow within a range where the combustion fluctuation rate does not exceed the allowable limit value. (Furthermore, learning is performed), thereby improving the fuel efficiency improving effect as described later.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of a spark ignition type direct injection engine according to an embodiment of the present invention. In this figure, an engine body 1 has a cylinder block 3 in which a plurality of cylinders 2 are arranged, and a cylinder head 4 arranged on the cylinder block 3. The combustion chamber 6 is formed between the piston 5 and the cylinder head 4. The piston 5 is connected via a connecting rod 8 to a crankshaft 7 rotatably supported below the cylinder block 3. Crankshaft 7
Is the crank angle (the rotation angle of the crankshaft 7)
Is provided with an electromagnetic crank angle sensor 9 for detecting the angle.

The combustion chamber 6 of each cylinder 2 is of a so-called pent roof type whose ceiling is formed by two inclined surfaces extending from the central portion to the lower end of the cylinder head. Two intake ports 10 and two exhaust ports 11 are respectively opened (only one is shown in the drawing) on two inclined surfaces constituting the ceiling portion of the combustion chamber 6. An intake valve 12 and an exhaust valve 13 are provided. The intake valve 12 and the exhaust valve 13 are opened and closed at a predetermined timing for each cylinder by a valve mechanism including two camshafts 14 and the like supported on the upper part of the cylinder head 4. ing.

Above the center of the combustion chamber 6, the above-mentioned 4
An ignition plug 16 is disposed so as to be surrounded by the two intake / exhaust valves, and a tip of the ignition plug 16 projects into the combustion chamber 6 from the ceiling. An ignition circuit 17 is connected to the ignition plug 16, and the ignition plug 16 is energized at a predetermined timing for each cylinder 2.

A fuel injection valve 18 is arranged at the periphery of the combustion chamber 6 so as to be sandwiched between the two intake ports 10, and fuel is directly injected from the fuel injection valve 18 into the combustion chamber 6. It has become. A fuel distribution pipe 19 common to all the cylinders 2 is connected to a base end of the fuel injection valve 18 so that high-pressure fuel supplied from a fuel supply system 20 is distributed to each cylinder. . The fuel supply system 20
Although a detailed illustration and description are omitted, a low-pressure fuel pump, a low-pressure regulator, a fuel filter, a high-pressure fuel pump, a high-pressure regulator, and the like are disposed in a fuel passage between the fuel distribution pipe 19 and the fuel tank. ing.

The structure of the engine body 1 will be described in more detail with reference to an enlarged sectional view of FIG. 2. The intake port 10 extends straight from the combustion chamber 6 obliquely upward. 2, and two intake ports (one not shown) are formed independently of each other. These intake ports 1
0 constitutes a tumble generating means, and the intake port 10
The tumble flow T is generated in the combustion chamber 6 by the intake air flowing into the combustion chamber 6 through the combustion chamber 6. As shown in FIG. 2, a tumble flow T is generated in a counterclockwise direction (a direction indicated by an arrow in FIG. 2) in a cross section where the intake port 10 is located on the right side of the combustion chamber 6 and the exhaust port 11 is located on the left side.

The direction of fuel injection from the fuel injection valve 18 is set so as to reverse the tumble flow T in the combustion chamber 6. That is, the fuel is injected obliquely downward and leftward from the fuel injection valve 18 located on the right side of the combustion chamber 6 in the cross section shown in FIG. And go in the opposite direction.

The crown 5 of the piston 5 has a recess 5a.
Are formed. The recess 5a extends substantially equally to both the left and right sides of the cylinder axis, and the bottom surface is smoothly curved in the cross section shown in FIG. 2, and as shown in FIG. The fuel injection direction (the direction in which the center line of the fuel spray extends: the left-right direction in FIG. 3) is a substantially elliptical shape having a major axis and a minor axis in a direction perpendicular to the major axis. The tumble flow T and the fuel spray are introduced into the recess 5a from directions opposite to each other, so that the tumble flow T and the fuel spray collide head-on in the recess 5a.

The outer peripheral portion 5b of the crown surface of the piston 5 excluding the concave portion 5a is shaped so as to extend substantially parallel to the inclined surface of the ceiling of the opposed combustion chamber 6, and has a compression top dead center of the cylinder 2. A gap sandwiched between the outer peripheral side portion 5b of the crown surface of the piston 5 and the ceiling of the combustion chamber 6 is configured to be a squish area in a previous predetermined period, for example, a period of BTDC 40 ° CA to TDC. TDC is top dead center, B
TDC means before top dead center, CA means crank angle.

As shown in FIG. 1, an intake passage 21 communicating with the intake port 10 of each cylinder is connected to one side of the engine body 1, while an exhaust passage 22 communicating with the exhaust port 11 of each cylinder is formed. It is connected to the other side of the engine body 1.

The intake passage 21 supplies intake air filtered by an air cleaner (not shown) to the combustion chamber 6 of each cylinder 2 of the engine body 1. A hot wire for detecting an intake air amount is arranged in order from the upstream side. Airflow sensor 23
, An electric throttle valve 24 that is opened and closed by being driven by an electric motor 25, and a surge tank 26. In addition, the intake passage 2 downstream of the surge tank 26
Reference numeral 1 denotes an independent intake passage that branches off for each cylinder 2. The downstream end of each independent intake passage is further branched into two and communicates with two intake ports 10, respectively.

A tumble control valve 27 for adjusting the flow rate of tumble in the combustion chamber 6 is disposed upstream of each of the two intake ports 10. The tumble control valve 27 is opened and closed by an actuator 28 composed of, for example, a stepping motor. Activated. This tumble control valve 27 cuts out a part of a circular butterfly valve,
For example, it is formed by notching a portion below the valve shaft. When the tumble control valve 27 is closed, the intake air flows downstream from the notch portion, and a strong tumble flow is generated in the combustion chamber 6, As the tumble control valve 27 is opened, the intensity of the tumble flow is gradually reduced.

The intake port 10 and the tumble control valve 2
The shape of 7 is not limited to the above, and for example, the intake port 10 may be a so-called common port that merges into one at the upstream side. In this case, the tumble control valve 27 is based on a shape corresponding to the cross-sectional shape of the common port,
A part of the shape may be cut away.

On the other hand, the exhaust passage 22 is for discharging burned gas from the combustion chamber 6, and has an exhaust manifold 2 communicating with the exhaust port 11 of each cylinder 2 at an upstream end thereof.
2a. A linear O ₂ sensor 30 for detecting the concentration of oxygen in the exhaust gas is provided at the gathering portion of the exhaust manifold 22a. The linear O ₂ sensor 30 is used for detecting the air-fuel ratio based on the oxygen concentration in the exhaust gas. The linear O ₂ sensor 30 is designed to obtain a linear output with respect to the oxygen concentration in a predetermined air-fuel ratio range including the stoichiometric air-fuel ratio. Has become.

The upstream end of an exhaust pipe 22b is connected to the gathering portion of the exhaust manifold 22a, and a catalyst 31 for purifying exhaust gas is provided downstream of the exhaust pipe 22b. An upstream end of an EGR passage 33 that recirculates part of the exhaust gas flowing through the exhaust passage 22 to the intake passage 21 is connected to an upstream side of the exhaust pipe 22b. This EGR passage 33
Is connected to the intake passage 21 between the throttle valve 24 and the surge tank 26, and an EGR valve 34 whose opening can be adjusted is disposed in the middle of the EGR passage 33. The amount of exhaust gas recirculated by the exhaust gas 33 can be adjusted.

The motor 25 for driving the ignition circuit 17, the fuel injection valve 18, the fuel supply system 20, and the throttle valve 24,
Actuator 28 for tumble control valve 27, electric EG
The R valve 34 and the like are controlled by an engine control unit 40 (hereinafter, referred to as ECU). On the other hand, this ECU 40, the crank angle sensor 9, the air flow sensor 23, a signal from the linear O ₂ sensor 30 etc. are inputted, further, an accelerator opening sensor 36 for detecting an accelerator opening (the operation amount of the accelerator pedal) , A detection signal from a rotation speed sensor 37 for detecting the rotation speed of the engine, and the like.

FIG. 4 shows the structure of the means functionally included in the ECU 40. In this figure, the ECU 40
Has a target load setting means 41. The target load setting means 41 obtains a virtual filling efficiency corresponding to the required engine torque from a map or the like according to the accelerator opening accel and the engine speed ne. A target indicated average effective pressure corresponding to this is obtained, and this is set as a target load.

In this case, the first target indicated mean effective pressure Piobj is obtained from the virtual filling efficiency by a predetermined calculation, while the virtual filling efficiency is subjected to an averaging process, and the virtual filling efficiency after the averaging process is used to obtain the second target indicated average effective pressure Piobj. Of the target indicated mean effective pressure Piobjd.

The ECU 40 further includes an operation mode setting means 4
The operation mode setting means 42 sets a basic operation mode mods according to the target load (target indicated average effective pressure Piobj) and the engine speed ne. That is, as shown in FIG. 5, in a region where the target load (target indicated average effective pressure Piobj) is lower than the set value P2 and the engine speed ne is lower than the set speed (stratified combustion region), the stratified combustion mode is set. In a region on the higher load side and a higher rotation side (uniform combustion region) than this region, a uniform combustion mode in which the air-fuel ratio is equal to or less than the stoichiometric air-fuel ratio (excess air ratio λ is λ ≦ 1) is set.

Preferably, in the uniform combustion region,
The target load (target indicated average effective pressure Piobj) is the set value P3
In most lower regions, the air-fuel ratio is set to the stoichiometric air-fuel ratio, and in this region and the stratified combustion region, the EGR valve 34 is controlled to return a required amount of exhaust gas to the combustion chamber 6. If necessary, the air-fuel ratio is richer than the stoichiometric air-fuel ratio (λ <1), for example, when the accelerator is fully opened (the target load is equal to or greater than the set value P3).
The EGR valve 34 may be closed in the rich setting region.

The ECU 40 further controls the intake air amount adjusted by the throttle valve 24, the tumble intensity adjusted by the tumble control valve 27, the fuel injection amount and fuel injection timing from the fuel injection valve 18, the ignition timing of the ignition plug 16, and the like. The values of various control parameters are determined according to the target load, the engine speed ne, and the like. In this case, the timing of control of a control parameter having a low response speed (a low-speed response system) such as the intake air amount and the control of a control parameter having a high response speed (a high-speed response system) such as a fuel injection amount, an injection timing, and an ignition timing are determined. In order to adjust, the first target indicated mean effective pressure Piobj is used as a target load for determining a control value of the low-speed response system among the control parameters.
Is used, and the second target indicated mean effective pressure Piobjd is used as the target load for determining the control value of the high-speed response system.

More specifically, the means for controlling the amount of intake air includes a target air-fuel ratio setting means 43 and a throttle opening degree calculating means 44. The target air-fuel ratio setting means 43 sets the target air-fuel ratio afwb for controlling the intake air amount for each operation mode mods set by the operation mode setting means 42. In the stratified combustion mode, the first target indicated average According to the effective pressure Piobj and the engine speed ne, a target air-fuel ratio afwb is obtained from a map created in advance, and
In the uniform combustion region, the target air-fuel ratio afwb is set to a stoichiometric air-fuel ratio or the like.

The throttle opening calculating means 44 calculates a virtual charging efficiency (a value corresponding to a target load assuming a state of operation at a stoichiometric air-fuel ratio) corresponding to a target load and a target air-fuel ratio af.
A target charging efficiency is calculated from wb, a target throttle opening is calculated based on the target charging efficiency and the engine speed ne, and a control signal corresponding to the target throttle opening is output to the throttle valve driving motor 25.

As means for controlling the tumble strength, there are a control valve opening calculating means 45a and a control valve control amount output means 45b.
And a tumble control means 45 comprising: As described later in detail, the control valve opening degree calculating means 45a operates the operation mode mods and the target load (the target indicated average effective pressure Piobj).
And the opening of the tumble control valve is set based on the engine speed ne. Further, the control valve control amount output means 45b outputs a control amount corresponding to the opening of the tumble control valve obtained by the control valve opening calculating means 45a to the actuator 28 of the tumble control valve 27.

The means for controlling the fuel injection from the fuel injection valve 18 includes a target air-fuel ratio creating means 46, an operation mode setting means 47, an injection amount calculating means 48, and an injection timing setting means 4.
9 and an injection control means 50.

The target air-fuel ratio creating means 46 obtains a target air-fuel ratio for controlling the fuel injection amount and the like. The target air-fuel ratio afw0 in a transient state and the target air-fuel ratio afwbd in a steady state are obtained. Select one of the target air-fuel ratios afw0 and afwbd to set the final target air-fuel ratio af
Determine w.

The target air-fuel ratio afw0 during the transition is determined based on the actual charging efficiency ce and the second target indicated mean effective pressure Piobjd so that a torque corresponding to the target load can be obtained under the actual charging efficiency. . The actual filling efficiency ce is obtained from the output of the air flow sensor 23. On the other hand, the steady-state target air-fuel ratio
afwbd is obtained from a map prepared in advance according to the second target indicated average effective pressure Piobjd and the engine speed ne in the stratified combustion mode, and is set to a stoichiometric air-fuel ratio or the like in the uniform combustion mode.

At the time of transition when the deviation between the target air-fuel ratio afwb for controlling the intake air amount and the target air-fuel ratio afw0 becomes large,
The target air-fuel ratio afw0 is set as the final target air-fuel ratio afw, and the target air-fuel ratio afwbd is set as the final target air-fuel ratio afw in a steady state where the deviation is small.

The operation mode setting means 47 sets the operation mode modf used to determine the control parameters of the high-speed system,
The target air-fuel ratio afw for controlling the fuel injection amount is set in accordance with the target air-fuel ratio afw. When the target air-fuel ratio afw is equal to or higher than a predetermined value, the stratified combustion mode is set.

The injection amount calculating means 48 calculates the basic injection amount based on the actual charging efficiency ce obtained from the output of the air flow sensor 23 and the target air-fuel ratio afw obtained by the target air-fuel ratio creating means 46. Further, the final injection amount is calculated in consideration of various correction values (for example, a feedback correction value based on a comparison between the detection value of the linear O ₂ sensor 30 and the target air-fuel ratio), and an injection pulse width proportional to the final injection amount is calculated. Ask.

The injection timing setting means 49 sets the fuel injection timing for each operation mode. In the stratified charge combustion mode, a map prepared in advance in accordance with the second target indicated mean effective pressure Piobjd and the engine speed ne. , The injection timing for the compression stroke injection is determined, and in the uniform combustion mode, the injection timing for the intake stroke injection is determined according to the engine speed ne and the like.
In particular, in the stratified combustion mode, when the fuel injection amount is small, the fuel injection timing is made closer to the ignition timing to suppress the dispersion of the fuel, and when the fuel injection amount is large, the injection is somewhat performed to avoid excessive concentration of the injected fuel. Since it is required to advance the timing, the fuel injection timing is changed according to the load within a predetermined period of the compression stroke, and is delayed on the low load side in the stratified combustion region and is advanced on the high load side in the same region. It is set as follows.

The injection control means 50 operates the fuel injection valve 18 for a time corresponding to the injection pulse width calculated by the injection quantity calculation means 48 at the injection timing set by the injection timing setting means 49. , An ejection pulse is output.

The means for controlling the ignition timing includes a setting means 51 for setting a basic ignition timing and a correction amount, and an ignition timing calculating means 52.

The setting means 51 sets the basic ignition timing and the like for each operation mode modf set by the operation mode setting means 47. In the stratified combustion mode, the second target indicated mean effective pressure Piobjd and the engine speed ne are set. The basic ignition timing is determined from the map according to
The basic ignition timing is determined from a map according to ce and the engine speed ne, and various correction amounts according to the water temperature and the like are also determined. The ignition timing calculation means 52 obtains a final ignition timing from the basic ignition timing and various positive amounts, and outputs a signal for controlling the ignition timing to the ignition circuit 17 in accordance with the final ignition timing.

FIG. 6 is a flowchart showing a process mainly performing the functions of the target load setting means 41, the operation mode setting means 42, the target air-fuel ratio setting means 43, the throttle opening calculating means 44, and the tumble control means 45. .

When the process of this flowchart is started, first, in step S1, the target load (Piobj) is calculated from the engine speed (ne) and the accelerator opening (accel) by the function of the target load setting means 41. In step S2, the operation mode (mods) is determined from the target load and the engine speed by the function as the operation mode setting means 42. Next, in step S3, the target air-fuel ratio (afw) is calculated from the target load, the engine speed, and the operation mode by the function of the target air-fuel ratio setting means 43.
b) is calculated. Further, in step S4, the target throttle opening is calculated based on the target load, the target air-fuel ratio, the engine speed and the like by the function as the throttle opening calculating means 44.

Next, in steps S5 to S10, processing for performing the function of the tumble control means 45 is performed. Specifically, it is determined in step S5 whether the target load and the engine speed are in the stratified combustion region. If the target load and the engine speed are in the stratified combustion region in FIG. The target opening TCV of the tumble control valve 27 is calculated.

In this case, in the stratified combustion region, the tumble control valve 27 is not fully opened for stratification using the tumble. However, in this stratified combustion region, the rotation speed is higher than the idling speed, and , The target load is a predetermined value P1 (P1
<P2) The low-load region that is lower than the low-load region is defined as a weak tumble region (see FIG. 5). In this weak tumble region, the opening of the tumble control valve 27 is larger than that in the high-load region in the stratified combustion region. Is done.

That is, at a constant engine speed (N1) higher than the idle speed, the tumble control valve 2
The relationship between the target opening TCV of FIG. 7 and the target load is shown by a solid line in FIG. 7, and the height of the stratified combustion region in which the target load is in the range from the predetermined value P1 to the value P2 corresponding to the upper limit of the stratified combustion region. On the load side, the target opening TCV is set to a small opening close to the fully closed position. On the low load side where the target load is smaller than the predetermined value P1, the target opening TCV is made larger than on the high load side in the stratified combustion region, and , Target opening TCV within the range that does not result in full opening
Is set to increase as the load decreases.

In the idle speed range, the target opening TCV is kept at a small value even on the low load side as shown by the broken line in FIG.

The characteristics of the target opening TCV according to the target load and the engine speed in the stratified combustion region are stored in the ECU 40 in advance as a map, and are stored in the ECU 40 in step S in FIG.
In step 6, the target opening TCV is obtained from this map according to the target load and the engine speed at that time. Then, in step S7, a control amount corresponding to the target opening TCV is output to the actuator 28, and the tumble control valve 27 is driven to the target opening TCV.

If it is determined in step S5 that the engine is not in the stratified combustion area, that is, if it is in the uniform combustion area, then in step S8, the exhaust gas recirculation area (the target load as shown in FIG. It is determined whether or not it is the above region), and if it is the region where the exhaust gas is not recirculated, step S9
, The tumble control valve 27 is fully opened. When it is determined in step S8 that the exhaust gas recirculates (the target load is lower than the set value P3), the target opening is determined from the map of the uniform combustion region in step S10 according to the target load and the engine speed. TVC is required. Then, control goes to a step S7.

According to the apparatus of the present embodiment as described above,
In the stratified combustion region, fuel is injected from the fuel injection valve 18 in the compression stroke, a tumble flow T is generated in the combustion chamber 6, and the fuel is injected so as to go backward to the tumble flow T. In the combustion chamber 6, the tumble flow T and the fuel spray collide with each other, and while atomization of fuel is promoted, a combustible mixture is generated near the ignition plug 16 at the ignition timing, and stratified combustion is performed.

In this case, the tumble flow is weakened by increasing the opening of the tumble control valve 27 on the low load side in the rotational speed range higher than the idle speed in the stratified combustion region (see FIG. 7). Thereby, the balance between the penetration force of the fuel spray and the strength of the tumble flow is appropriately adjusted, and the stratified state of the air-fuel mixture is favorably maintained.

That is, by controlling the fuel injection timing by the injection timing setting means 49 as described above, the fuel injection timing is delayed on the low load side of the stratified combustion region,
Since the in-cylinder pressure during fuel injection increases and the penetration force of the fuel spray decreases as the in-cylinder pressure increases, the relationship between the load in the stratified region and the penetration force of the fuel spray is as shown in FIG. As shown in the upper part, the penetration force of the fuel spray decreases on the low load side.

In order to stratify the combustible mixture around the spark plug by the collision of the tumble flow and the fuel spray, it is necessary to maintain a balance between the penetration force of the fuel spray and the strength of the tumble flow. is there. Accordingly, in response to the change in the penetration force of the fuel spray according to the load as described above, the required tumble ratio becomes smaller on the low load side (middle in FIG. 8), and in order to satisfy this required tumble ratio, Tumble control valve 27
May be increased on the low load side (lower part in FIG. 8).

As described above, on the low-load side in the stratified combustion region, the opening of the tumble control valve 27 is increased to weaken the tumble flow (decrease the tumble ratio) to balance the fuel spray penetration force. In addition, when the fuel injection amount is small, weakening the tumble flow is advantageous for stratification in that diffusion of fuel can be suppressed. By these actions, stratification is favorably performed, and the effect of improving fuel economy by stratified combustion is enhanced.

Since the intake flow rate is originally small and the tumble flow is weak in the idle speed range, the tumble control valve 2 is located on the low load side of the speed range (that is, the idling operation range).
If the opening degree of No. 7 is increased, almost no tumble is generated, and the combustion stability deteriorates. For this reason, in the idling operation region, the opening of the tumble control valve 27 is reduced so that tumble is generated to the extent that combustion stability is ensured.

FIGS. 9 and 10 show another embodiment of the tumble control means 45. The tumble control means 45 of this embodiment detects a combustion fluctuation of the engine, and the combustion fluctuation is set to a predetermined allowable limit value. The control is performed so that the opening of the tumble adjustment valve 27 is maximized in the following range.
Although FIG. 9 shows only the configuration of the tumble control means 45, the configuration of the entire engine and the configuration other than the tumble control means 45 in the ECU are the same as those of the embodiment shown in FIGS.

In FIG. 9, the tumble control means 45
Basic target opening setting means 45 for calculating a basic target opening in accordance with the target indicated average effective pressure Piobj and the engine speed ne.
c, a roughness index calculating means 45d for detecting a combustion fluctuation by examining engine rotation fluctuation and calculating a roughness index representing the fluctuation ratio, and a correction amount calculating means 45e for calculating a correction amount according to the roughness index. A control valve opening calculating means 45f for calculating a final target opening from the basic target opening and the correction amount; and outputting a tumble control valve control amount corresponding to the target opening to the actuator 28 of the tumble control valve 27. And control valve output means 45g.

In the flow chart of FIG. 10, the processing of steps S1 to S5, the processing of step S7, and the processing of steps S8 to S10 are the same as the processing of each step of the same reference numerals in the flow chart of FIG.

If it is determined in step S5 that the vehicle is in the stratified combustion region, in step S60, the basic target opening TC of the tumble control valve is calculated from the target load and the engine speed.
V1 is calculated. The basic target opening TCV1 may be the same as the target opening TCV obtained in step S6 in the flowchart of FIG. 6 described above, and, for example, at a constant engine speed (N1) on the higher rotation side than the idle rotation speed. 7, the relationship between the basic target opening and the target load is as shown by a solid line in FIG. 7, and in the idling speed range, the basic target opening may be as shown by the broken line in FIG. The basic target opening TCV1 is stored in advance as a map, and is calculated from the map in step S60.

Next, in step S61, it is determined whether the correction amount ΔTCV of the opening of the tumble control valve 27 is between a predetermined lower limit and an upper limit. The lower limit value and the upper limit value are limiters for preventing the correction amount ΔTCV from excessively fluctuating due to erroneous detection of roughness, and when the correction amount ΔTCV is equal to or more than the upper limit value or equal to or less than the lower limit value, After being fixed to the upper limit or the lower limit in step S62, the process proceeds to step S68 described later.

If the determination in step S61 is YES,
In step S63, a roughness index R1 indicating the combustion variation ratio is calculated from the engine rotation variation, and in step S64, a roughness index threshold R1T corresponding to an allowable limit of roughness is obtained from the engine speed and the accelerator opening. Then, in step S65, the roughness index R1 is compared with the roughness index threshold R1T, and the roughness index R1
Is smaller than the threshold value R1T, the correction amount ΔTCV is increased (step S66), and if the roughness index R1 is equal to or larger than the threshold value R1T, the correction amount ΔTCV is reduced (step S6).
7).

Next, at step S68, the final target opening TCV is calculated by adding the correction amount ΔTCV to the basic target opening TCV1. Then, the tumble control valve 27 is driven to reach the target opening TCV (step S7).

The operation of this embodiment will be described with reference to FIG.

FIG. 11 shows the relationship between the opening degree of the tumble control valve 27 (the strength of the tumble flow), the fuel consumption rate, and the combustion fluctuation when the engine shown in FIG. 1 is in the low load region of the stratified combustion region. Shows the relationship. As shown in this figure, in the low-load region where the fuel injection amount is small, if the tumble control valve opening is reduced and the tumble flow is strengthened, the fuel spray is pushed to the periphery of the cylinder by the tumble flow and the fuel is easily diffused. Therefore, the fuel efficiency and the combustion fluctuation are relatively high.

When the opening of the tumble control valve is increased (the tumble flow is weakened), the stratification is improved and the fuel efficiency is gradually lowered, and the fuel efficiency reaches the minimum value at an opening close to the full opening. On the other hand, the combustion fluctuation decreases as the opening of the tumble control valve increases up to the vicinity of the intermediate opening of the tumble control valve 27, but when the opening of the tumble control valve increases, the vaporization rate of the spray decreases and the tumble flow increases. The combustion fluctuation tends to increase due to a decrease in the combustion promoting action, and the combustion fluctuation reaches an allowable limit value before the fuel efficiency reaches the minimum value.

Therefore, in this embodiment, steps S63 to S63 are performed.
By the process of S68, the tumble control valve opening TCV is controlled so that the roughness index becomes the roughness threshold (corresponding to the permissible limit value of the combustion fluctuation). As a result, the opening degree of the tumble control valve is maximized, and the fuel efficiency is brought as close as possible to the minimum value.

The control device of the present invention can be variously modified in addition to the above embodiments. For example, in FIG.
In the embodiment shown in FIG. 10, the feedback correction amount of the tumble control valve opening is obtained based on the comparison between the roughness index and the threshold value, and the feedback control is performed. However, learning may be performed based on the feedback control. Good. In this case, for example, the basic control value of the opening degree of the tumble control valve is set to a value corresponding to the operating state within a range in which the combustion fluctuation ratio is kept below the allowable limit value, and the combustion fluctuation ratio is set to the above value. Until the allowable limit value is reached, the opening of the tumble control valve is feedback corrected in the increasing direction, and a learning value is obtained based on the feedback correction amount. And
After learning in this way, the learned value is reflected in the control of the tumble control valve, that is, after adding the learned value to the basic control amount, feedback correction according to the combustion fluctuation ratio is further performed. I just need.

[0077]

As described above, the present invention relates to an engine provided with a tumble generating means, a fuel injection valve for injecting fuel into a combustion chamber so as to reverse a tumble flow, and an injection control means. A control valve, and a tumble control means for controlling the control valve, wherein the tumble control valve is operated in a non-full open state in the stratified combustion region, and the tumble control is performed on a low load side of the stratified combustion region as compared with a high load side of the same region. On the low load side of the stratified combustion region, the fuel injection timing is delayed and the in-cylinder pressure at the fuel injection timing increases, so that the fuel spray penetrates. The tumble flow is correspondingly weakened while the force is reduced, thus balancing the penetration of the fuel spray and the strength of the tumble flow even when the load changes in the stratified combustion region. It can be properly adjusted. Therefore, the stratified state of the air-fuel mixture can be favorably maintained, and the effect of improving fuel efficiency by stratified combustion can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the overall structure of a spark ignition type direct injection engine to which a control device of the present invention is applied.

FIG. 2 is a sectional view of an engine body.

FIG. 3 is a plan view of a piston.

FIG. 4 is a block diagram illustrating an example of a configuration of an engine control unit according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an example of a control map in which operation regions such as a stratified combustion region and a uniform combustion region are set.

FIG. 6 is a flowchart showing control of the tumble control valve according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a target load and a target opening of the tumble control valve according to the first embodiment of the present invention.

FIG. 8 is a diagram showing changes in spray penetration force, required tumble ratio, and tumble control valve opening in accordance with a change in load in a stratified combustion region.

FIG. 9 is a block diagram showing a configuration of a tumble control unit according to a second embodiment of the present invention.

FIG. 10 is a flowchart illustrating control of a tumble control valve according to a second embodiment of the present invention.

FIG. 11 is a diagram showing a relationship between a tumble control valve opening degree, a fuel consumption rate, and combustion fluctuation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 6 Combustion chamber 10 Intake port (tumble generating means) 16 Spark plug 18 Fuel injection valve 27 Tumble control valve 45 Tumble control means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuri Seto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda F-term (reference) 3G023 AA01 AA02 AA07 AA18 AB01 AC04 AC05 AD02 AD06 AD09 AG01 3G301 HA01 HA04 HA09 HA16 HA17 JA02 JA26 KA08 LA05 LB02 LB04 LC01 LC03 LC04 LC10 MA11 MA18 MA29 NA04 NA05 NA08 NB20 ND02 ND05 NE01 NE15 PA01Z PA04Z PD02Z PD04Z PE01Z PE03Z PF03Z

Claims (4)

[Claims] 1. A tumble generating means for generating a tumble flow in a combustion chamber, a fuel injection valve for injecting fuel into the combustion chamber so as to run counter to the tumble flow, and a predetermined operating region on a low speed and low load side of the engine. Injection control means for controlling the fuel injection timing from the fuel injection valve in association with the ignition timing so as to generate a combustible mixture near the spark plug at the ignition timing in the stratified combustion region. A tumble control valve for adjusting the intensity of the tumble flow, and tumble control means for controlling the tumble control valve; and the tumble control valve is provided in an intake passage for guiding intake air to a combustion chamber via a tumble generation means. The tumble control means is configured to intensify the tumble as the opening degree decreases, and the tumble control means sets the tumble control valve in the non-fully opened state in the stratified combustion region. And a control device for controlling the opening of the tumble control valve to be larger on the low load side of the stratified combustion region than on the high load side of the stratified combustion region. . 2. The tumble control means controls the tumble control valve to increase the opening of the tumble control valve on a low load side in a region where the engine speed is higher than an idle speed in the stratified combustion region. Item 2. A control device for a spark ignition type direct injection engine according to Item 1. 3. The tumble control means detects an engine combustion fluctuation ratio and controls the tumble control valve so that the opening degree of the tumble control valve is maximized in a range where the combustion fluctuation ratio is equal to or less than a predetermined allowable limit value. The control device for a spark ignition type direct injection engine according to claim 1 or 2, wherein: 4. The tumble control means sets a basic control value of an opening degree of the tumble control valve to a value according to an operation state within a range in which a combustion variation ratio is kept below the allowable limit value. And correcting the opening of the tumble control valve in the increasing direction until the combustion fluctuation rate reaches the limit point, and obtaining a learning value to be reflected in subsequent control of the tumble control based on the correction. Item 3. A control device for a spark ignition type direct injection engine according to Item 3.