JP2002038993A - Control device for in-cylinder injection engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To correct the fuel injection timing based on the difference between the calculation of the fuel injection timing and the engine speed at the time of actual fuel injection, perform stratified combustion at the time of engine startup, and perform exhaust gas emission control. The present invention provides a control device for a direct injection engine that can reduce exhaust gas, improve engine output, and improve exhaust emission and startability at the time of starting. A control device for a direct injection engine including a fuel injection device for directly injecting fuel into a combustion chamber of each cylinder, wherein the control device performs a stratified combustion when starting the engine. Means for correcting the fuel injection timing, and means for estimating the engine speed at the time of fuel injection relative to the engine speed at the time of calculating the fuel injection timing. The means for correcting the fuel injection timing comprises: The fuel injection timing is corrected based on the output signal of the means for estimating the fuel injection timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a direct injection engine, and more particularly to a control device for a direct injection engine which corrects fuel injection timing and achieves stratified combustion when the engine is started.

[0002]

2. Description of the Related Art Current automobiles require reduction of exhaust gas substances such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) contained in automobile exhaust gas from the viewpoint of environmental protection. In order to reduce these,
A direct injection engine (in-cylinder injection engine) is being developed.

[0003] In the cylinder injection engine, fuel is injected by a fuel injection device directly in a combustion chamber of a cylinder to reduce exhaust gas substances and improve engine output. Injecting fuel into the combustion chamber and diffusing the fuel into the combustion chamber to form a homogeneous air-fuel mixture, the injected fuel adheres to the piston and the gap between the piston and the combustion chamber and is not vaporized. The fuel increases. Further, when the engine is started at a low temperature, it is difficult for the fuel to vaporize, and it is difficult for an air-fuel mixture necessary for combustion to be formed around the spark plug.

In these cases, if a large amount of fuel is injected into the fuel injection device in anticipation of the unvaporized fuel, there is a problem that exhaust emission at the time of starting is deteriorated. In order to perform combustion, the combustion method is switched according to the engine operating state, that is, a homogeneous combustion method in which fuel is injected during an intake stroke to diffuse fuel into a combustion chamber to form a homogeneous mixture, and a fuel during a compression stroke. In-cylinder injection engine that controls the fuel injection timing by switching to a stratified combustion system that injects and forms a stratified mixture intensively around the spark plug, thereby promoting the combustion of the injected fuel and improving fuel efficiency. Various control techniques have been proposed (see, for example, JP-A-59-37236, JP-A-10-103117, etc.).

[0005] In the stratified combustion system, the air-fuel mixture required for starting is concentrated around the spark plug.
If the fuel injection timing is fixed, the combustion range with respect to the change in the ignition timing is narrow, and there is a problem such as misfire if the fuel injection timing is out of the combustion range. Therefore, when switching to the stratified combustion method, the ignition timing is corrected. There has been proposed a technique for controlling the ignition timing of an in-cylinder injection engine (see, for example, JP-A-11-30177).

Further, in order to improve the startability of the direct injection engine and to reduce the amount of HC emission at the time of starting the engine, various techniques of a fuel injection control device for correcting the fuel injection timing based on the engine water temperature and the like have been proposed. (For example, JP-A-11-343914, JP-A-10-3
18021, JP-A-8-193536, JP-A-11-200922, JP-A-2000-548
No. 84, etc.).

[0007]

The fuel injection timing and the ignition timing are both controlled based on information on a predetermined crank angle with respect to a reference signal of a crankshaft of the engine. FIG. 20 is a timing chart showing the relationship among the engine speed, the crank angle, the fuel injection timing, and the ignition timing at the time of starting the engine, and shows the cylinder at a predetermined crank angle with respect to a reference signal (0 °) of the crankshaft. Is set. Then, the fuel injection timing is calculated at the reference position of the cylinder, the fuel is actually injected at a predetermined crank angle from the reference position of the cylinder, and the fuel is ignited at the reference signal position of the crankshaft.

Here, when the engine is started, the engine speed rapidly rises and the fluctuation of the engine speed becomes large. With this fluctuation, the fuel is actually injected from the time of calculating the fuel injection timing. The time from when the fuel injection timing is calculated to when the fuel is ignited becomes shorter as time elapses from the start.

For example, when starting the engine, the first cylinder #
In a four-stroke four-cylinder engine state (1) in which fuel injection by the above-described stratified combustion method is performed in the order of the first cylinder # 3, the fourth cylinder # 4, the second cylinder # 2, the cylinder # 1
The fuel injection timing of the cylinder # 1 is calculated at the reference position, and the fuel injection is actually performed in the compression stroke of the cylinder # 1 at a predetermined crank angle position from the reference position of the cylinder # 1, Next, when ignition of the cylinder # 1 is performed at the reference signal position of the crankshaft in the cylinder # 1,
The engine speed increases during the expansion stroke of cylinder # 1.

Here, the third cylinder # 3, which is in the compression stroke during the expansion stroke of the first cylinder # 1, has a reference position of the cylinder # 3 based on the engine speed immediately before the reference position of the cylinder # 3. Then, the fuel injection timing of the cylinder # 3 is calculated. The engine speed immediately before the reference position of the cylinder # 3 corresponds to the engine speed increased during the expansion stroke of the first cylinder # 1, but fuel injection is actually performed during the compression stroke of the cylinder # 3. As shown in the figure, the engine speed when
It can be seen that the engine speed is lower than the engine speed when the calculation of the fuel injection timing of the cylinder # 3 is performed.

Therefore, when the fluctuation range of the engine speed is large, such as when starting the engine, there is a difference between the engine speed at the time of calculating the fuel injection timing and the engine speed at the time of actual injection. This causes a problem that the calculated target fuel injection timing does not correspond.
Further, in combination with this problem and the change in the ignition timing,
Since ignition occurs before a stratified air-fuel mixture is formed around the spark plug or after the air-fuel mixture is formed, misfire is likely to occur, causing not only deterioration of exhaust emission but also failure to start. There is a risk.

Therefore, the control of the fuel injection timing needs to correct the deviation of the fuel injection timing caused by the difference between the engine speed at the time of calculating the fuel injection timing and the engine speed at the time of actually performing the fuel injection. There is. Further, in a four-stroke four-cylinder engine state (2) in which the engine friction changes with time and machine differences, etc., in addition to the effects of the rapid increase in the engine speed, the engine friction changes with time and machine differences are also considered. Also need to be considered.

For example, the fourth cylinder # 4, which is in the compression stroke during the expansion stroke of the third cylinder # 3, has an engine speed immediately before the reference position of the cylinder # 4, that is, the expansion stroke of the third cylinder # 3. The fuel injection timing of the cylinder # 4 is calculated at the reference position of the cylinder # 4 based on the increased engine speed. On the other hand, the engine speed when the fuel injection is actually started in the compression stroke of the cylinder # 4 is lower than the engine speed when the calculation of the fuel injection timing of the cylinder # 4 is performed. You can see that.

Further, as shown in the figure, when the calculation of the fuel injection timing of the cylinder # 4 in the engine state (2) is performed, the engine speed is changed to the third cylinder # 3 in the engine state (1). May be the same as the engine speed at the time of calculation of the fuel injection timing in the above, but the engine when the fuel injection is actually started in the compression stroke of the cylinder # 4 in the engine state (2) As shown, there is a difference between the engine speed and the engine speed at the time when fuel injection is actually started in the compression stroke of the cylinder # 3 in the engine state (1). Has occurred.

Therefore, in the engine state (2), a fuel injection timing and an ignition timing for forming an optimum air-fuel mixture around the ignition plug are set based on the value of the engine speed in the engine state (1). Then, even if the target fuel injection timing is the same, since the engine speed is higher, ignition may occur before a stratified mixture is formed around the ignition plug. On the other hand, in the engine state (1), when a fuel injection timing and an ignition timing for forming an optimal air-fuel mixture around the ignition plug are set based on the value of the engine speed in the engine state (2), There is a risk of ignition after the mixture is formed. Therefore, in this case as well, misfire is likely to occur, which not only leads to deterioration of exhaust emission,
Since there is a possibility that the engine cannot be started, the control of the fuel injection timing needs to consider the difference between the engine speed at the time of calculating the fuel injection timing and the engine speed at the time of starting the fuel injection.

The time from when the fuel is injected to when the air-fuel mixture is formed around the ignition plug is affected by the fuel pressure during the fuel injection. That is, even when the fuel injection timing and the ignition timing are fixed, when the fuel pressure is high,
The fuel transfer speed increases, and the air-fuel mixture around the spark plug concentrates quickly. On the other hand, when the fuel pressure is low,
The fuel transfer speed becomes slower, and the air-fuel mixture around the spark plug concentrates later. Therefore, in this case as well, misfire is likely to occur, which not only leads to deterioration of exhaust emission,
Since there is a possibility that the engine cannot be started, the control of the fuel injection timing can be performed more reliably by considering the influence of the fuel pressure during the fuel injection.

As described above, the present inventor considers the difference between the engine speed at the time of calculating the fuel injection timing and the engine speed at the time of starting the fuel injection, and the effect of the fuel pressure at the time of fuel injection. However, in the above-mentioned conventional technologies, no special consideration has been given to this point. In particular,
The prior art of the fuel injection control device at the time of starting the engine described in Japanese Patent Application Laid-Open No. H11-343914 is intended to improve the startability and the like by suppressing an increase in the engine speed at the time of starting. No special consideration has been given to the point that the fuel injection timing is performed in consideration of the difference between the engine rotation speed when calculating the injection timing and the engine rotation speed when the fuel injection is started.

The present invention has been made in view of such a problem, and an object thereof is based on a difference between an engine speed at the time of calculating fuel injection timing and an actual engine speed at the time of fuel injection. In-cylinder injection that corrects the fuel injection timing and performs stratified combustion at the time of engine start to reduce exhaust gas substances and improve engine output, as well as to improve exhaust emissions and startability at startup. It is to provide an engine control device.

[0019]

In order to achieve the above object,
The control device for a direct injection engine according to the present invention is basically a control device for a direct injection engine including a fuel injection device for directly injecting fuel into a combustion chamber of each cylinder. In order to perform stratified combustion, there is provided means for correcting the fuel injection timing at the time of starting the engine, and means for estimating the engine speed at the time of fuel injection with respect to the engine speed at the time of calculating the fuel injection timing, The means for correcting the fuel injection timing corrects the fuel injection timing based on an output signal of the means for estimating the engine speed.

The control apparatus for a direct injection engine according to the present invention, configured as described above, corrects the fuel injection timing based on the estimated value of the engine speed at the time of fuel injection with respect to the engine speed at the time of calculating the fuel injection timing. However, since stratified combustion is performed at the time of starting the engine, even at the time of engine start where there is a sharp rise in the engine speed, the engine speed at the time of calculation of the fuel injection timing and the engine speed at the start of fuel injection are different. By correcting the difference in the fuel injection timing caused by the difference between the two, the stratified combustion at the time of starting the engine can be reliably performed, and the startability and the exhaust emission at the time of starting can be improved.

In a specific aspect of the control device for a direct injection engine according to the present invention, the means for estimating the engine speed calculates a rise value of the engine speed until the fuel injection timing is calculated. Means for calculating, based on the calculated rise value, a decrease value of the engine speed at the time of the fuel injection with respect to the engine speed at the time of calculation of the fuel injection timing, the calculated decrease value The engine speed at the time of the fuel injection is estimated based on

Further, in another specific embodiment of the control apparatus for a direct injection engine according to the present invention, the means for estimating the engine speed includes an increase value of the engine speed until the fuel injection timing is calculated. Means for calculating, and a correction amount of the fuel injection timing corresponding to a decrease value of the engine speed at the time of the fuel injection with respect to the engine speed at the time of calculating the fuel injection timing is calculated based on the calculated increase value. Means, or the means for calculating the increase value of the engine speed is a function of increasing the engine speed between the time of calculating the fuel injection timing of one cylinder and the time of calculating the fuel injection timing of another cylinder. It is characterized in that a value is calculated.

Further, the control device for a direct injection engine according to the present invention is a control device for a direct injection engine having a fuel injection device for directly injecting fuel into a combustion chamber of each cylinder. In order to perform stratified combustion, the device corrects the fuel injection timing at the time of starting the engine, and calculates the fuel pressure corresponding to the fuel pressure at the time of calculating the fuel injection timing from the fuel pressure of the fuel injection device at the time of calculating the fuel injection timing. Means for calculating a correction amount of the fuel pressure during injection, wherein the means for correcting the fuel injection timing corrects the fuel injection timing based on an output signal of the means for calculating the correction amount for the fuel pressure. And

The control device for a direct injection engine according to the present invention having the above-described structure is configured so that the fuel injection device of the direct injection engine injects fuel to form a mixture around the ignition plug. In consideration of the influence of the fuel pressure, the deviation of the fuel injection timing at the start of the engine caused by the difference between the fuel pressure at the time of calculating the fuel injection timing and the fuel pressure at the start of the fuel injection is corrected. High fuel injection timing control can be performed to achieve stratified combustion more reliably.

Further, the means for calculating the correction amount of the fuel pressure includes means for calculating a rise value of the engine speed up to the time of calculating the fuel injection timing, and based on the calculated rise value, The means for calculating the correction amount of the fuel pressure at the time of the fuel injection with respect to the fuel pressure at the time of calculating the injection timing, correcting the fuel injection timing, and calculating the increase value of the engine speed are the fuel injection timing of one cylinder. Calculating the increase value of the engine speed between the time of calculating the fuel injection timing of the other cylinders, or the control device determines that the fuel pressure of the fuel injection device at the time of calculating the fuel injection timing When high, the time from the fuel injection to the ignition timing is set short, and when the fuel pressure of the fuel injection device is low, the time from the fuel injection to the ignition timing is set long. There.

Further, the control device is characterized by comprising means for switching between a homogeneous combustion system in which fuel is injected during an intake stroke and a stratified combustion system in which fuel is injected during a compression stroke, according to operating conditions of the engine. .

[0027]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control system for a direct injection engine according to the present invention. FIG. 1 shows an overall configuration of a control system of a direct injection engine 1 including a control device 15 of the first embodiment. The in-cylinder injection engine 1 is composed of four cylinders. Air introduced into each combustion chamber 2 is taken in from an air cleaner 3, passes through an air flow meter (air flow sensor) 5, and accommodates a throttle valve 6 for controlling an intake flow rate. And enters the collector 8 through the throttle body 7. The air taken into the collector 8 is distributed to each intake pipe 19 and then guided to each combustion chamber 2 in each cylinder 31. The throttle valve 6 is connected to a motor 10, and operates the throttle valve 6 by driving the motor 10 to control the amount of intake air.

The airflow sensor 5 outputs a signal indicating the intake flow rate to a control unit (control unit) 15 for the direct injection engine. Further, a throttle sensor 18 for detecting the opening of the throttle valve 6 is attached to the throttle body 7, and a signal thereof is also output to the control unit 15.

On the other hand, fuel such as gasoline
The fuel is sucked and pressurized by a fuel pump 12 and supplied to a fuel system provided with a fuel injection valve (injector) 13 and a fuel pressure regulator 14 each having a fuel injection opening in each combustion chamber 2. A fuel pressure sensor 2 is provided in the piping of the fuel system.
7 is provided at an appropriate position, an electric signal corresponding to the fuel pressure is output to the control unit 15, and the fuel pressure sensor 2
7, the fuel pressure regulator 14 is controlled so as to reach a target fuel pressure. The fuel system is regulated to a predetermined pressure by the fuel pressure regulator 14, and fuel is directly injected from the injector 13 into each combustion chamber 2. The injector 13 injects fuel from the control unit 15 into the combustion chamber 2 in an intake stroke or a compression stroke in synchronization with the engine speed, and the fuel injected into the combustion chamber 2 The ignition is performed by the ignition plug 22 according to the converted ignition signal.

The crank angle sensor 16 attached to the crankshaft 28 of the engine 1 outputs a signal indicating the rotational position to the control unit 15 every time the crankshaft 28 rotates by a predetermined angle (for example, 10 degrees). Axis 2
A cam angle sensor 4 attached to the cylinder 9 is a reference angle signal indicating a predetermined rotational position of the camshaft 29, for example, a predetermined angle before the compression top dead center of each cylinder (for example, 110 degrees before the compression top dead center).
) Is output to the control unit 15 (that is, a crank angle of 180 in a four-stroke four-cylinder engine).
And outputs an electric signal different for each cylinder 31 to the control unit 15. Then, the time between the input of signals from the crank angle sensor 16 and the cam sensor 4 is measured to calculate the engine speed, and based on the signal of each cylinder 31 of the cam sensor 4, Recognizing 110 degrees before the compression top dead center, the reference positions of the fuel injection timing and the ignition timing are calculated. Further, an A / F sensor 20 provided upstream of a catalyst (not shown) in the exhaust pipe 21 detects the exhaust gas and outputs a detection signal to the control unit 15.

The accelerator sensor 9 connected to the accelerator pedal 12 outputs the amount of operation of the accelerator pedal 12 by the driver to the control unit 15, and the power supply (battery) 23 and the control unit 15
Between them, a control unit relay 24 and an ignition switch 25 are provided.

The main parts of the control unit 15 are as follows:
The crank angle sensor 1 includes an MPU, an EP-ROM, an I / OLSI including a RAM, and an A / D converter.
6, taking in signals from various sensors including the cam angle sensor 4 and the cooling water temperature sensor 26 as inputs, executing predetermined arithmetic processing, outputting various control signals calculated as the arithmetic results, and A predetermined control signal is supplied to the injector 13, the ignition coil 17, the motor 10, and the like to execute fuel injection control, ignition timing control, and the like.

The control unit 15 has a processing means 30. The processing means 30
Means for switching the combustion mode between homogeneous combustion in which fuel is injected during the intake stroke and stratified combustion in which fuel is injected during the compression stroke, and means for determining when the engine 1 is started,
A means for calculating the fuel injection amount based on the intake air amount of the airflow sensor 5; a means for calculating the fuel ignition timing based on the engine speed by the crank angle sensor 16 and the like and the intake air amount of the airflow sensor 5; Means for calculating the fuel injection timing for combustion and for stratified combustion,
The means for calculating the fuel injection timing includes means for setting a fuel injection timing for homogeneous combustion or stratified combustion, and means for correcting the fuel injection timing.

As will be described later, the means for correcting the fuel injection timing calculates the engine speed at the time of fuel injection with respect to the engine speed at the time of calculation of the fuel injection timing in order to perform stratified combustion at the time of starting the engine 1. The fuel injection timing is corrected based on the estimating means.

The means for estimating the engine speed includes means for calculating an increase in the engine speed until the fuel injection timing is calculated, and the fuel injection timing based on the calculated increase value. And a means for calculating a decrease in the engine speed at the time of the fuel injection with respect to the engine speed at the time of calculation. As will be described later, the engine speed N
e, the fuel injection amount is corrected based on the fuel pressure and the like. The fuel injection control (drive of the injector 13) and the ignition control (drive of the ignition coil 17 and the spark plug 22) of the control unit 15 having the processing means 30 will be described with reference to flowcharts of FIGS.

FIG. 2 shows a main routine of the fuel injection control and the ignition control.
10 ms). In step 1, the starting-time determining means determines whether or not the engine speed is equal to or higher than a predetermined engine speed after the ignition switch is turned on (complete explosion determination). , Or whether the engine is in a normal engine rotation state, and proceeds to step 2.

In step 2, the means for switching the combustion mode determines whether the combustion is homogeneous combustion or stratified combustion in accordance with the operating state of the engine 1, and performs switching. Specifically, a plurality of maps defining the combustion method (and the target equivalent ratio TFBYA) using the engine speed Ne and the basic fuel injection amount Tp representing the load as parameters are provided for each condition such as the water temperature TW and the starting time. A combustion method (and a target equivalent ratio TFBYA) is set to either homogeneous stoichiometric combustion, homogeneous lean combustion, or stratified lean combustion according to the parameters of the actual engine operating state from a map selected from the respective conditions. I do. In the present embodiment, the stratified-lean combustion method is set at least before the complete explosion is determined.

The target equivalent ratio TFBYA is 1
It is a value corresponding to 4.6 / target air-fuel ratio. The target air-fuel ratio in the case of homogeneous lean combustion is set to 20 to 30, and the target air-fuel ratio in the case of stratified lean combustion is set to about 40. Then, in Step 3, the fuel injection amount Ti is calculated by the means for calculating the fuel injection amount, and in Step 4, the ignition timing ADV is calculated by the means for calculating the fuel ignition timing, and in Step 5, The fuel injection timing IT is calculated by the means for calculating the fuel injection timing, and the routine proceeds to step 6, where the injector 13 executes the combustion injection to end a series of operations.

FIG. 3 is a flowchart of the calculation of the fuel injection amount Ti in the means for calculating the fuel injection amount in step 3. In step 21, the air flow meter 5
Step 2 reads the intake air amount Qa detected in
Proceed to 2. In step 22, based on the intake air amount Qa and the engine speed Ne, as shown in the equation (1), a raw basic fuel injection amount (pulse width) RTp corresponding to the intake air amount per combustion. Is calculated.

[0040]

RTp = K × Qa / Ne (1) where K is a constant. In step 23, the raw basic fuel injection amount RTp is subjected to a delay process corresponding to the manifold filling delay, and the basic fuel injection amount (pulse width) corresponding to the cylinder intake air amount is calculated by the weighted average expression shown in Expression (2).
Calculate Tp.

[0041]

Tp = RTp × Load + Tp ₋₁ × (1-Flood) (2) where Fload is a weighted average ratio constant, and Tp− ₁ is a basic fuel injection amount corresponding to the previous cylinder intake air amount of Tp. is there. In step 24, various corrections are made to the basic fuel injection amount Tp corresponding to the cylinder intake air amount,
As shown in Expression (3), the final fuel injection amount (pulse width) Ti is calculated.

[0042]

T = Tp × KTR × TFBYA × α × αm + Ts (3) Here, KTR is a transient correction coefficient, and TFBYA is the target equivalence ratio (= 14.6 / target air-fuel ratio) corresponding to a combustion method or the like. α is the air-fuel ratio feedback correction coefficient, αm is the learning correction coefficient, and Ts is the invalid injection amount (invalid pulse width).

FIG. 4 is a flowchart of the calculation of the ignition timing ADV in the means for calculating the fuel ignition timing in the step 4. In step 31, the means for determining the combustion method determines whether the combustion is homogeneous combustion (homogeneous stoichiometric combustion or homogeneous lean combustion) or stratified combustion (stratified lean combustion). , Step 3
In step 2, the basic ignition timing ADVH for homogeneous combustion with respect to the reference signal of the crankshaft 28 is searched from the basic ignition timing map for homogeneous combustion (see FIG. 5) in accordance with the engine speed Ne and the basic fuel injection amount Tp. Step 36
Proceed to.

On the other hand, if stratified combustion is determined in step 31, the routine proceeds to step 33, where the means for determining the start time determines whether or not the idle switch is ON (idle state). State, ie N
In the case of O, the routine proceeds to step 34, where the engine speed Ne is determined from the basic ignition timing map for stratified combustion (see FIG. 6).
And the basic ignition timing AD for stratified combustion with respect to the reference signal of the crankshaft 28 according to the basic fuel injection amount Tp.
VS is searched and the process proceeds to step 36. Step 3
When the engine is in the idle state in step 3, the routine proceeds to step 35, where the basic ignition timing GOV for idling with respect to the reference signal of the crankshaft 28 is retrieved from the table (see FIG. 7) based on the engine speed Ne, and the routine proceeds to step 36. .

In step 36, the ignition timing correction amount is added to the basic ignition timing based on the search results of the basic ignition timing ADVH for homogeneous combustion, the basic ignition timing ADVS for stratified combustion, and the basic ignition timing GOV for idling. ADV
HOS is added, the final ignition timing ADV is calculated, and a series of operations is ended. The ignition timing correction amount ADVHO
S is at least a correction amount for idling stabilization.

FIG. 8 is a flowchart of the calculation of the fuel injection timing IT in the means for calculating the fuel injection timing in step 5. In step 40, the engine speed Ne calculated from the electric signals of the crank angle sensor 16 and the cam sensor 4 is read, and the routine proceeds to step 41.

In step 41, the means for judging the combustion mode judges whether the combustion is homogeneous combustion (homogeneous stoichiometric combustion or homogeneous lean combustion) or stratified combustion (stratified lean combustion). In this case, the routine proceeds to step 42, where the means for setting the fuel injection timing for the homogeneous combustion uses the engine speed Ne and the basic fuel injection amount Tp from the injection timing map for the homogeneous combustion (see FIG. 9).
The fuel injection timing ITH corresponding to the reference signal of the crankshaft 28 in the intake stroke for homogeneous combustion is searched, and the routine proceeds to step 50.

If it is determined in step 41 that the engine is stratified combustion, the routine proceeds to step 43, where it is determined whether or not the engine has been started by the means for determining the start of the engine. If, step 4
Then, the program proceeds to Step 4 and the means for setting the fuel injection timing for stratified combustion uses the compression timing for stratified combustion according to the engine speed Ne and the basic fuel injection amount Tp from the injection timing map for stratified combustion (see FIG. 10). The crankshaft 2 in the stroke
The fuel injection timing ITS for the reference signal of No. 8 is searched, and the routine proceeds to step 50.

On the other hand, if it is determined in step 43 that the engine has been started, the process proceeds to step 45 in which the means for estimating the engine speed at the time of fuel injection with respect to the engine speed at the time of calculating the fuel injection timing is used. The engine speed increase value 分 Ne up to the time of calculating the fuel injection timing is calculated by the means for calculating the increase, for example, when calculating the fuel injection timing of one cylinder and when calculating the fuel injection timing of another cylinder. , That is, between the reference positions of the cylinders 31, the engine speed increase value △ Ne is calculated.
By means for setting the fuel injection timing for stratified combustion, the fuel injection timing map for stratified combustion (see FIG. 10) is used in accordance with the engine speed Ne and the basic fuel injection amount Tp.
Then, the basic fuel injection timing BASEITS in the compression stroke for stratified combustion at startup is searched for, and the routine proceeds to step 47.

In step 47, the means for estimating the engine speed is used to calculate the decrease in the engine speed. The increase value of the engine speed is calculated from the engine speed decrease value map (see FIG. 11). According to ΔNe and the basic fuel injection timing BASEITS, a reduction value ΔMNe of the engine speed at the time of the fuel injection with respect to the calculation of the fuel injection timing is searched. Then, the engine speed Ne corrected by subtracting the engine speed Ne read in step 40 from the engine speed decrease value △ MNe is subtracted.
OSNE is calculated, and the routine proceeds to step 49.

In step 49, the engine speed HOSNE and the basic fuel injection after correction from the injection timing map for stratified combustion (see FIG. 10) are again set by the means for setting the fuel injection timing for stratified combustion. According to the amount Tp, the corrected fuel injection timing HOSITS in the compression stroke for stratified combustion at startup is searched, and the routine proceeds to step 50.

In step 50, the fuel injection timing ITH in the intake stroke for the homogeneous combustion, the fuel injection timing ITS in the compression stroke for the stratified combustion, and the stratification at the start are calculated by the means for calculating the fuel injection timing. Each search result of the corrected fuel injection timing HOSITS in the compression stroke for combustion is used as the final fuel injection timing IT, and a series of operations is ended. When the final fuel injection timing IT is calculated, an injection pulse signal having a pulse width of the final fuel injection amount Ti is output to the injector 13 at the fuel injection timing IT, and fuel injection is performed.

FIG. 12 shows the means for calculating the rise of the engine speed, which is used to calculate the increase in the engine speed between the reference positions (4
FIG. 9 is a timing chart of an initialization process for calculating an increase value △ Ne of the engine speed at a crank angle of 180 degrees for a four-stroke cylinder). Step 70 is a flowchart for calculating an increase value △ Ne of the engine speed. Nemi
n and Nemax are set as the engine speed Ne at the reference position, and are set as threshold values for the previous engine speed.

FIG. 13 is a flowchart of the calculation of the increase value of the engine speed △ Ne by the means for calculating the increase amount of the engine speed in step 45. If it is determined by the means for determining the start time that the engine has been started, the process proceeds to step 60, where it is determined whether the engine speed Ne is smaller than a minimum value Nemin of the engine speed between the reference positions of the cylinders 31. If the engine speed Ne is smaller than the minimum value Nemin, that is, if YES, the process proceeds to step 61, where the engine speed Ne is updated to the minimum value Nemin of the engine speed, and the process proceeds to step 64. On the other hand, when the engine speed Ne is larger than the minimum value Nemin, the routine proceeds to step 62, where it is determined whether or not the engine speed Ne is larger than the maximum value Nemax of the engine speed between the reference positions of the cylinders 31.

If the engine speed Ne is larger than the maximum value Nemax at step 62, that is, if YES, the routine proceeds to step 63, where the engine speed Ne is updated to the maximum engine speed Nemax, and the routine proceeds to step 64. move on. On the other hand, at step 62, the engine speed N
When e is smaller than the maximum value Nemax, the process proceeds to step 64. In step 64, the updated maximum value Nemax and the minimum value Nemin are subtracted to calculate an increase value △ Ne of the engine speed.

FIGS. 14 and 15 show a flowchart of the fuel injection control and the ignition control of the control unit 15 according to the second embodiment. The fuel injection control and the ignition control in the control unit 15 of the second embodiment are shown in FIGS. The control and ignition control are different from the control unit 15 of the first embodiment only in the calculation of the fuel injection timing IT by the means for calculating the fuel injection timing. .

FIG. 14 shows a main routine of the fuel injection control and the ignition control of the control unit 15 having the processing means 30. The main routine is executed at predetermined time intervals (for example, 10 ms). A complete explosion is determined. In step 2, it is determined whether the combustion is the homogeneous combustion or stratified combustion. In step 3, the fuel injection amount Ti is calculated. In step 4, the ignition timing ADV is calculated. move on. In step 5 ', as described later, the fuel injection timing IT is calculated by the fuel injection timing calculating means. In step 6, combustion injection is executed by the injector 13, and a series of operations is completed.

FIG. 15 is a flow chart of the calculation of the fuel injection timing IT in the means for calculating the fuel injection timing in step 5 '. In step 40, the engine speed Ne is read, and in step 41, it is determined whether the combustion is the homogeneous combustion or the stratified combustion. The fuel injection timing ITH in the intake stroke for homogeneous combustion is searched from the injection timing map (see FIG. 9), and step 50 is executed.
Proceed to.

If it is stratified combustion in step 41,
Proceeding to step 43, it is determined whether or not the engine has been started. If it has not been started, that is, if NO, the process proceeds to step 44, where the stratified charge combustion timing map (see FIG. 10) is used. The fuel injection timing ITS in the compression stroke is searched, and the routine proceeds to step 50.

On the other hand, if it is determined in step 43 that the engine is being started, the process proceeds to step 45 in which the engine speed increase calculating means of the engine speed estimating means calculates the fuel injection timing. In step 46, the engine speed NＮ is calculated from the stratified combustion injection timing map (see FIG. 10) by means for setting the stratified combustion fuel injection timing.
e and the basic fuel injection amount Tp, the basic fuel injection timing BASEIT in the compression stroke for stratified combustion at startup.
After searching for S, the process proceeds to step 47 '.

In step 47 ', the means for estimating the engine speed calculates the fuel injection timing correction amount corresponding to the decrease in the engine speed. 16), the injection according to the decrease in the engine speed at the time of the fuel injection with respect to the engine speed at the time of calculating the fuel injection timing, according to the increase value △ Ne of the engine speed and the basic fuel injection timing BASEITS. The timing correction value DIT is searched, and the routine proceeds to step 48 '.

In step 48 ', means for correcting the fuel injection timing adds the basic fuel injection timing BASEITS read in step 46 and the injection timing correction value DIT for the decrease in the engine speed. The subsequent fuel injection timing HOSITS is calculated, and the routine proceeds to step 50. In step 50, the means for calculating the fuel injection timing includes a fuel injection timing ITH in the intake stroke for the homogeneous combustion, a fuel injection timing ITS in the compression stroke for the stratified combustion, and a fuel injection timing ITS for the starting stratified combustion. A series of operations is ended with each search result of the corrected fuel injection timing HOSITS in the compression stroke as the final fuel injection timing IT. When the final fuel injection timing IT is calculated, an injection pulse signal having a pulse width of the final fuel injection amount Ti is generated at the fuel injection timing IT.
3 and fuel injection is performed.

FIGS. 17 to 19 show flowcharts of the fuel injection control and the ignition control of the control unit 15 according to the third embodiment, and the fuel injection control and the ignition control in the control unit 15 of the third embodiment. The control and the ignition control differ from the control unit 15 of the first and second embodiments only in the calculation of the fuel injection timing IT by the means for calculating the fuel injection timing. Will be described.

FIG. 17 shows a main routine of the fuel injection control and the ignition control of the control unit 15 having the processing means 30. In step 1, the complete explosion is determined, and in step 2, the homogeneous combustion or stratification is performed. It is determined whether or not combustion has occurred. In step 3, the fuel injection amount Ti is calculated, in step 4, the ignition timing ADV is calculated, and the process proceeds to step 5 ". In step 5", as described later, the fuel injection timing is determined. The fuel injection timing IT is calculated by the calculating means, and in step 6, the fuel injection is executed by the injector 13 and a series of operations is completed.

FIG. 18 is a flow chart of the calculation of the fuel injection timing IT in step 5 ″.
At 0, the engine speed Ne is read, and at step 41, it is determined whether the combustion is the homogeneous combustion or the stratified combustion. If the combustion is the homogeneous combustion, the routine proceeds to step 42, where the injection timing map for the homogeneous combustion is determined. From FIG. 9 (see FIG. 9), the fuel injection timing ITH in the intake stroke for homogeneous combustion is retrieved, and the routine proceeds to step 50.

If it is stratified combustion in step 41,
Proceeding to step 43, it is determined whether or not the engine is being started. If it is not, the process proceeds to step 44, where the injection timing map for stratified combustion (see FIG. 10) is used in the compression stroke for stratified combustion. The fuel injection timing ITS is searched, and the routine proceeds to step 50.

On the other hand, if it is determined in step 43 that the engine has been started, the process proceeds to step 45 in which the means for calculating the correction amount of the fuel pressure during fuel injection with respect to the fuel pressure at the time of calculating the fuel injection timing calculates the increase in the engine speed. Means for calculating an increase in engine speed △ Ne between the time of calculating the fuel injection timing of one cylinder and the time of calculating the fuel injection timing of another cylinder, which is an example until the time of calculating the fuel injection timing. Then, in step 46, the injection timing map for stratified combustion (see FIG. 10)
, The basic fuel injection timing BASEITS in the compression stroke for stratified combustion at start-up is retrieved according to the engine speed Ne and the basic fuel injection amount Tp, and the routine proceeds to step 47 ". In step 47", the fuel pressure is measured by the fuel pressure sensor 27. The fuel pressure PFUEL calculated based on the obtained electric signal is read, and the routine proceeds to step 48 ".

In step 48 ", a means for calculating the correction amount of the fuel pressure is used to calculate a correction value table of the fuel pressure during the fuel injection with respect to the fuel pressure at the time of calculating the fuel injection timing (FIG. 19).
), A fuel pressure correction value PFHOSIT corresponding to the fuel pressure PFUEL of the fuel pressure sensor 27 is searched, and the routine proceeds to step 49 ".
It is represented by a straight line having a different slope as L increases.

In step 49 ", the means for correcting the fuel injection timing is used to correct the basic fuel injection timing BASEIT.
S and the fuel pressure correction value PFHOSIT are subtracted to calculate a corrected fuel injection timing HOSITS, and the routine proceeds to step 50. In step 50, the means for calculating the fuel injection timing includes a fuel injection timing ITH in the intake stroke for the homogeneous combustion, a fuel injection timing ITS in the compression stroke for the stratified combustion, and a fuel injection timing ITS for the starting stratified combustion. A series of operations is ended with each search result of the corrected fuel injection timing HOSITS in the compression stroke as the final fuel injection timing IT. When the final fuel injection timing IT is calculated, an injection pulse signal having a pulse width of the final fuel injection amount Ti is output to the injector 13 at the fuel injection timing IT, and fuel injection is performed. Further, when the fuel pressure of the injector 13 at the time of calculating the fuel injection timing is high, the means for calculating the fuel ignition timing sets a shorter time from the time of the fuel injection to the ignition timing, and the fuel pressure of the injector 13 is reduced. If it is low, the time from the fuel injection to the ignition timing is set to be long.

As described above, the above embodiment of the present invention
The following functions are provided by the above configuration. That is, the control device 15 for the direct injection engine of the first embodiment is a means for calculating an increase in the engine speed by means for estimating the engine speed when the engine is being started. Is calculated from the injection speed map for stratified combustion based on the engine speed Ne and the basic fuel injection amount Tp by means of calculating the engine speed increase value △ Ne between the reference positions of and 設定, and setting the fuel injection timing for stratified combustion. Basic fuel injection timing BAS in compression stroke for stratified charge combustion
EITS is searched, and the means for estimating the engine speed is means for calculating a decrease in the engine speed. The means for increasing the engine speed △ Ne and the basic fuel injection timing B
Based on the ASEITS, a decrease value of the engine speed at the time of fuel injection △ MNe relative to the engine speed at the time of calculating the fuel injection timing is set from the engine speed decrease value map, that is, how much the rotational speed falls. And estimating the engine speed corresponding to the fuel injection, and calculating the corrected engine speed HOSNE by subtracting the engine speed Ne and the decrease value of the engine speed △ MNe by means for estimating the engine speed. Then, based on the corrected engine speed HOSNE and the basic fuel injection amount Tp by means for correcting the fuel injection timing, the fuel after the correction in the compression stroke for the stratified combustion at start-up is obtained from the injection timing map for the stratified combustion. The fuel injection timing HOSITS is searched, and the final fuel injection timing I is determined by means for setting the fuel injection timing for stratified combustion.
Since T is used, even at the start of the engine where the engine speed sharply increases, the difference in the fuel injection timing caused by the difference in the engine speed between the time of calculating the fuel injection timing and the start of fuel injection can be corrected. In addition to the case where the target fuel injection timing does not correspond to the target fuel injection timing and the change in the ignition timing, the ignition is performed before a stratified air-fuel mixture is formed around the ignition plug, or It is possible to prevent ignition after the air has been formed, reliably perform stratified combustion at the time of engine start, and improve startability and exhaust emission at start. Further, the control device 15 of the present embodiment corrects the difference in the fuel injection timing caused by the difference between the calculation of the fuel injection timing and the engine speed at the start of the fuel injection. Even when there is a change, a machine difference, or the like, it is possible to realize the startability and the reduction of the emission at the start.

The in-cylinder injection engine control device 15 of the second embodiment calculates a fuel injection timing correction amount corresponding to a decrease in the engine speed by the engine speed estimating means. From the injection timing correction value map corresponding to the decrease in the engine speed at the time of the fuel injection with respect to the engine speed at the time of calculating the fuel injection timing, based on the increase value of the number ΔNe and the basic fuel injection timing BASEITS. Since the correction value DIT is searched, only one map is required, and the fuel injection timing control can be simplified.

Further, the control device 15 for the direct injection engine according to the third embodiment is a means for calculating a correction amount of the fuel pressure, and a fuel pressure correction value table based on the fuel pressure by the fuel pressure sensor 27 (see FIG. 19). From the fuel pressure correction value PFH at the time of fuel injection with respect to the fuel pressure PFUEL at the time of calculation of the fuel injection timing
Since the OSIT is searched, the time from fuel injection to the formation of an air-fuel mixture around the ignition plug 22 is more reliably set in consideration of the influence of the pump 12 and the like driven by the rotation of the engine 1. Therefore, more accurate fuel injection timing control can be performed.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments.
Various changes in design may be made without departing from the spirit of the invention as set forth in the appended claims. For example, in each of the above embodiments, the means for calculating the increase value of the engine speed calculates the increase value of the engine speed between the reference positions of the cylinders 31. However, the present invention is not limited to this. The increase value of the engine speed between various reference positions of the injection may be calculated.

[0074]

As will be understood from the above description, the control apparatus for a direct injection engine according to the present invention is capable of calculating the difference between the engine speed at the time of calculating the fuel injection timing and the engine speed at the start of the fuel injection. The deviation of the fuel injection timing caused by the difference can be corrected, and the stratified combustion at the time of starting the engine can be reliably achieved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine including a control device for a direct injection engine according to a first embodiment.

FIG. 2 is a flowchart of fuel injection control and ignition timing control in the control device of FIG. 1;

FIG. 3 is a flowchart of a fuel injection amount calculation in the control device of FIG. 1;

FIG. 4 is a flowchart of calculation of an ignition timing in the control device of FIG. 1;

FIG. 5 is a characteristic diagram of a homogeneous combustion ignition timing map in the control device of FIG. 1;

FIG. 6 is a characteristic diagram of a stratified combustion ignition timing map in the control device of FIG. 1;

FIG. 7 is a characteristic diagram of an idle ignition timing map in the control device of FIG. 1;

FIG. 8 is a flowchart of a fuel injection timing calculation in the control device of FIG. 1;

FIG. 9 is a characteristic diagram of a homogeneous combustion fuel injection timing map in the control device of FIG. 1;

FIG. 10 is a characteristic diagram of a stratified combustion fuel injection timing map in the control device of FIG. 1;

FIG. 11 is a characteristic diagram of an engine speed reduction value map in the control device of FIG. 1;

FIG. 12 is a flowchart of an initialization process for calculating an engine speed increase value in the control device of FIG. 1;

FIG. 13 is a flowchart for calculating an engine speed increase value in the control device of FIG. 1;

FIG. 14 is a flowchart of fuel injection control and ignition timing control in the control device for a direct injection engine according to the second embodiment.

FIG. 15 is a flowchart of a fuel injection timing calculation in the control device of FIG. 14;

FIG. 16 is a characteristic diagram of an injection timing correction value map for a decrease in engine speed in the control device of FIG. 14;

FIG. 17 is a flowchart of fuel injection control and ignition timing control in the control device for a direct injection engine according to the third embodiment.

FIG. 18 is a flowchart of a fuel injection timing calculation in the control device of FIG. 17;

FIG. 19 is a characteristic diagram of a fuel pressure correction value table in the control device of FIG. 17;

FIG. 20 is a timing chart showing a reference position of a cylinder, an engine speed, a fuel injection timing, and an ignition timing in a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 engine 2 combustion chamber 4 cam sensor 5 air flow sensor 13 fuel injection device (injector) 15 control device (control unit) 16 crank angle sensor 17 ignition coil 27 fuel pressure sensor 30 processing means 31 cylinder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/34 F02D 41/34 F 43/00 301 43/00 301B 301J 45/00 362 45/00 362K 362J F02P 5/15 F02P 5/15 E (72) Inventor Yoshiyuki Yoshida 2520 Oji Takaba, Hitachinaka City, Ibaraki Prefecture Within the Hitachi, Ltd. Automotive Equipment Group (72) Inventor Kentaro Shiga 2477 Oji Takaba Hitachinaka City, Ibaraki Prefecture Hitachi Car Engineering Co., Ltd. (72) Inventor Yoshikuni Kurashima 2520 Oaza Takaba, Hitachinaka-shi, Ibaraki F-term in the Automotive Equipment Group of Hitachi, Ltd. 3G022 AA07 BA01 CA01 DA01 DA02 GA00 GA05 3G084 AA00 AA03 AA04 BA05 BA13 BA15 BA17 BA22 CA01 CA02 DA09 DA10 DA11 DA12 DA22 DA23 EB09 EB1 2 EB15 EB16 FA07 FA10 FA20 FA29 FA33 FA36 3G301 HA01 HA04 HA06 HA15 HA16 JA00 JA05 JA15 JA23 JA26 KA01 LA03 LB04 LB06 LC01 MA03 MA12 MA18 MA22 MA28 NA06 NA07 NC04 ND03 ND12 ND15 NE03 NE11 NE13 PA01Z PA11ZBZZ08P11ZB08Z PF03Z

Claims (9)

[Claims] 1. A control device for a direct injection engine having a fuel injection device for injecting fuel directly into a combustion chamber of each cylinder, wherein the control device performs a stratified charge combustion when starting the engine. Means for correcting the fuel injection timing, and means for estimating the engine speed at the time of fuel injection with respect to the engine speed at the time of calculation of the fuel injection timing, wherein the means for correcting the fuel injection timing comprises: A control device for a direct injection engine, wherein the fuel injection timing is corrected based on an output signal of an estimating means. 2. The means for estimating the engine speed,
Means for calculating an increase value of the engine rotation speed until the time of calculation of the fuel injection timing, and based on the calculated increase value,
Means for calculating a decrease value of the engine speed at the time of the fuel injection with respect to the engine speed at the time of calculating the fuel injection timing, and estimating the engine speed at the time of the fuel injection based on the calculated decrease value. The control device for a direct injection engine according to claim 1, wherein 3. The means for estimating the engine speed,
Means for calculating an increase value of the engine rotation speed until the time of calculation of the fuel injection timing, and based on the calculated increase value,
2. The cylinder according to claim 1, further comprising: means for calculating a correction amount of the fuel injection timing according to a decrease value of the engine rotation speed at the time of the fuel injection with respect to the engine rotation speed at the time of calculating the fuel injection timing. Control device for internal injection engine. 4. The means for calculating the increase value of the engine rotation speed calculates the increase value of the engine rotation speed between the time of calculating the fuel injection timing of one cylinder and the time of calculating the fuel injection timing of another cylinder. 4. The control device for a direct injection engine according to claim 2, wherein the control is performed. 5. A control device for a direct injection engine having a fuel injection device for directly injecting fuel into a combustion chamber of each cylinder, wherein the control device performs a stratified charge combustion when starting the engine. Means for correcting fuel injection timing, and means for calculating a correction amount of fuel pressure at the time of fuel injection with respect to fuel pressure at the time of calculating the fuel injection timing from the fuel pressure of the fuel injection device at the time of calculating the fuel injection timing, A control device for a direct injection engine, wherein the means for correcting the fuel injection timing corrects the fuel injection timing based on an output signal of the means for calculating the correction amount of the fuel pressure. 6. The means for calculating the correction amount of the fuel pressure includes means for calculating a rise value of the engine speed until the fuel injection timing is calculated, and the fuel injection based on the calculated rise value. 6. The control device for a direct injection engine according to claim 5, wherein a correction amount of the fuel pressure at the time of the fuel injection with respect to the fuel pressure at the time of calculating the timing is calculated. 7. The means for calculating the increase value of the engine rotation speed includes calculating the increase value of the engine rotation speed between the time of calculating the fuel injection timing of one cylinder and the time of calculating the fuel injection timing of another cylinder. The control apparatus for a direct injection engine according to claim 6, wherein the control is performed. 8. The control device, when the fuel pressure of the fuel injection device at the time of calculating the fuel injection timing is high,
Set a short time from the time of the fuel injection to the ignition timing,
The control of the direct injection engine according to any one of claims 5 to 7, wherein when the fuel pressure of the fuel injection device is low, the time from the time of the fuel injection to the ignition timing is set long. apparatus. 9. A homogeneous combustion system for injecting fuel during an intake stroke according to an operating condition of the engine,
The control apparatus for a direct injection engine according to any one of claims 1 to 8, further comprising means for switching between a stratified combustion method in which fuel is injected during a compression stroke.