JP2671606B2 - Fuel injection controller for direct injection type internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for a direct injection type internal combustion engine, and particularly to a lean N system for an exhaust system.
In a cylinder direct injection internal combustion engine equipped with an Ox catalyst (a catalyst made of zeolite supporting a transition metal or a noble metal and reducing NOx in the presence of HC in an oxidizing atmosphere), the NOx purification rate of the lean NOx catalyst is wide. The present invention relates to a fuel injection control device that raises the engine operating range.

[0002]

2. Description of the Related Art It is known that a lean NOx catalyst is provided in an exhaust system of an internal combustion engine for automobiles to reduce NOx (for example, Japanese Patent Laid-Open Nos. 1-130735 and 1-135735).
-135541). Lean NOx catalyst is NOx
HC (hydrocarbon) is required to reduce the amount of hydrocarbons, but depending on the operating condition of the engine, the amount of HC in the exhaust gas will be insufficient, so in order to inject HC into the exhaust system, an HC source such as an HC cylinder must be installed. Measures such as injecting HC into the exhaust system have been considered (Japanese Patent Laid-Open No. 63-283727).

[0003]

However, in the conventional measures, there is a problem that a special HC source and a supply device are required to supply HC, and the device becomes complicated. Moreover, since the type of HC that is effective for NOx purification changes depending on the exhaust temperature, there is a problem that even if HC is uniformly supplied, a high NOx purification rate cannot be obtained in a wide engine operating range.

[0004] The present invention has been made in order to solve the above problems.
An object of the present invention is to improve the NOx purification rate of a lean NOx catalyst in a wide engine operating range without providing an HC supply device.

[0005]

To achieve the above object, a fuel injection control device for a direct injection type internal combustion engine according to the present invention comprises the following means. A direct injection type internal combustion engine and a lean NOx catalyst provided in its exhaust system,
An engine state, a means for detecting the catalyst bed temperature of the lean NOx catalyst, a first injection timing setting means for setting the timing of the main injection from the fuel injection valve based on the catalyst bed temperature within the period from the intake stroke to the compression stroke, Based on the catalyst bed temperature, the timing of the sub-injection from the fuel injection valve is set within the period from the intake stroke to the beginning of the compression stroke when the catalyst bed temperature is low, and within the period from the latter half of the combustion period to the beginning of the exhaust stroke when the catalyst bed temperature is high. Second injection timing setting means to be set, and fuel injection executing means for driving the fuel injection valve to execute fuel injection when the engine state is the timing set by the first and second injection timing setting means.

[0006]

In the above-mentioned device of the present invention, the main injection is an injection for generating torque, and the sub-injection is an injection mainly for producing HC which is a reducing agent of the lean NOx catalyst. When the catalyst bed temperature is low, secondary injection is performed within the period from the intake stroke to the beginning of the compression stroke, so the fuel in the secondary injection spreads lean into the combustion chamber and remains partially burned, passing through the compression, combustion, and exhaust strokes. It is pyrolyzed and partially oxidized over a sufficient time to produce a large amount of low boiling point component HC, and enhances the NOx purification rate of the lean NOx catalyst regardless of the low catalyst bed temperature. When the catalyst bed temperature is high, the secondary injection fuel is injected within the period from the latter half of the combustion stroke to the beginning of the exhaust stroke, and since it does not go through the combustion stroke, it is almost not directly oxidized and is close to the high boiling point component HC. Is supplied to the lean NOx catalyst in the form of, and increases the NOx purification rate of the lean NOx catalyst regardless of the high catalyst bed temperature. In this way, lean NO
The NOx purification rate of the x catalyst increases over a wide catalyst bed temperature range.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overall view of a 4-cylinder gasoline engine adopting an embodiment of the present invention. In the figure, 1 is an engine body, 2 is a surge tank, 3 is an air cleaner, 4 is an intake pipe connecting the surge tank 2 and the air cleaner 3, 5 is an electrostrictive fuel injection valve for injecting fuel into each cylinder, 6 is an ignition snare, 7 is a high-pressure reservoir tank, 8 is a high-pressure fuel pump whose discharge pressure is controllable, 9 is a high-pressure conduit for guiding high-pressure fuel from the high-pressure fuel pump 8 to the reservoir tank 10, 10 is a fuel tank, 11 Denote low-pressure fuel pumps for supplying fuel from the fuel tank 10 to the high-pressure fuel pump 8 via conduits 12, respectively. The discharge side of the low-pressure fuel pump 11 is connected to each fuel injection valve 5
It is connected to a piezoelectric element cooling introducing pipe 13 for cooling the piezoelectric element. The piezoelectric element cooling return pipe 14 is connected to the fuel tank 10, and the fuel flowing to the piezoelectric element cooling introduction pipe 13 via this return pipe 14 is collected in the fuel tank 10. Each branch pipe 15 connects each high-pressure fuel injection valve 5 to the high-pressure reservoir tank 7.

The electronic control unit 20 comprises a digital computer and comprises a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 24, an input port 25 and an output port 26 which are interconnected by a bidirectional path 21. . The pressure sensor 27 attached to the high pressure reservoir tank 7 is
The internal pressure is detected, and the detected signal is the A / D converter 2
It is input to the input port 25 via 8. Engine speed N
Crank angle sensor 2 that generates an output pulse proportional to E
The output pulse of 9 is input to the input port 25. An output voltage of an accelerator opening sensor 30 that generates an output voltage according to an opening θA of an accelerator pedal (not shown) is input to an input port 25 via an A / D converter 31. Further, the output pulse of the cylinder discrimination sensor 32 that generates an output pulse at the compression top dead center of the first cylinder and the fourth cylinder is also input to the input port 25. On the other hand, each fuel injection valve 5 is connected to the output port 26 via each drive circuit 34 and each counter 35. Further, each ignition snail 6 is connected to each drive circuit 36.
And is connected to the output port 26 via each counter 37. The spark plug 6 is connected to the output port 26 via each drive circuit 36 and each counter 37. Further, the high-pressure fuel pump 8 is connected to the output port 26 via the drive circuit 38.

FIG. 2 shows a side sectional view of the fuel injection valve 5.
Referring to FIG. 2, 40 is a needle inserted in the nozzle 50, 41 is a pressure rod, 42 is a movable plunger, 4
3 is a compression spring arranged in the spring accommodating chamber 44 and pressing the needle 40 downward, 45 is a pressure piston, 4
Reference numeral 6 is a piezoelectric element, 47 is a pressure chamber formed between the top of the movable plunger 42 and the piston 45 and filled with fuel, and 48 is a needle pressure chamber. The needle pressurizing chamber 48 is connected to the high-pressure reserve tank 7 (FIG. 1) via the fuel passage 49 and the branch pipe 15, so that the high-pressure fuel in the high-pressure reservoir tank 7 can flow into the branch pipe 15 and the fuel passage 49.
And is supplied into the needle pressurizing chamber 48 via. When the piezoelectric element 46 is charged with electric charge, the piezoelectric element 46 expands, whereby the fuel pressure in the pressurizing chamber 47 is increased. As a result, the movable plunger 42 is pressed downward, and the nozzle opening 53 is kept closed by the needle 40. On the other hand, when the charge charged in the piezoelectric element 46 is discharged, the piezoelectric element 46 is discharged.
Contract and the fuel pressure in the pressurizing chamber 47 decreases. As a result, the movable plunger 42 rises and the needle 40
Rises and fuel is injected from the nozzle 53.

FIG. 3 shows a longitudinal sectional view of the engine shown in FIG.
Referring to FIG. 3, 60 is a cylinder block, 62 is a piston, 63 is a substantially cylindrical recess formed in the top surface of the piston 62, 64 is the top surface of the piston 62 and the cylinder head 61.
Each of the cylinder chambers formed between the inner wall surfaces is shown. Ignition snoop 6
Is attached to a substantially central portion of the cylinder head 61 so as to face the cylinder chamber 64. Although not shown in the drawing, an intake port and an exhaust port are formed in the cylinder head 61, and the cylinder chamber 6 of these intake port and exhaust port is formed.
An intake valve and an exhaust valve are arranged at the openings to the inside of the valve 4, respectively. The fuel injection valve 5 is a swirl-type fuel injection valve, and injects spray-like fuel having a large divergence angle and a low penetration force.
The fuel injection valve 5 is directed diagonally downward and is directed toward the cylinder chamber 64.
Is arranged at the top of the fuel cell and is arranged so as to inject fuel toward the vicinity of the ignition sled 6. The fuel injection direction and the fuel injection timing of the fuel injection valve 5 are determined so that the injected fuel is directed to the concave portion 63 formed at the top of the piston 62.

As shown in FIG. 1, an exhaust system 70 of an internal combustion engine.
Is provided with a catalytic converter having a lean NOx catalyst 71. The lean NOx catalyst 71 is made of zeolite supporting a transition metal or a noble metal, and is defined as a catalyst that reduces NOx in the presence of HC in an oxidizing atmosphere. The lean NOx catalyst 71 has a certain temperature range in which it can exhibit a high NOx purification rate, for example, 400 ° C to 550 ° C. When the temperature is higher than this temperature range, HC is directly oxidized and the amount of active species generated by partial oxidation of HC is decreased, so the NOx purification rate is lowered, and when it is lower than the temperature range, the activity of the catalyst itself is lowered. Therefore, the NOx purification rate also decreases. The NOx purification rate of the lean NOx catalyst 71 also depends on the type of HC supplied. When the catalyst bed temperature is low, relatively small HC is effective for NOx purification, and when the catalyst bed temperature is high, relatively large HC is effective for NOx purification.

In the present invention, the NO of the lean NOx catalyst 71 is
The HC necessary for the x reduction is generated by utilizing the fuel injection from the fuel injection valve 5 without providing a special HC supply device. As shown in FIG. 4, in addition to the main injection for torque generation, the fuel injection is provided with a small amount of sub-injection compared to the main injection by making the injection timing different from that of the main injection, and the injection is performed in this sub-injection. Lean NOx catalyst 71 using fuel
Generate and supply HC for use. Since the required HC type changes according to the catalyst bed temperature, the injection timing of the sub-injection is changed according to the catalyst bed temperature or the exhaust gas temperature that changes correspondingly. That is, as shown in FIG. 4, in the region where the exhaust gas temperature is low (for example, 400 ° C.) or less, the auxiliary injection timing is set within the period from the intake stroke to the initial stage of the compression stroke. In addition, the injection amount at that time is set to a large value of about 5% of the main injection because it is partially burned off in the combustion process. The fuel given here undergoes a process of compression, combustion, and exhaust, and is thermally decomposed or partially oxidized to a low boiling point HC, regardless of the region where the exhaust temperature is low,
The lean NOx catalyst 71 can sufficiently remove NOx. When the exhaust temperature exceeds 400 ° C, the sub injection timing is set in the latter half of the combustion period, and the exhaust temperature is 500 ° C.
As it rises above, it is further retarded until the beginning of the exhaust stroke. The injection amount at this time is 2-1% of the main injection because there is almost no rate of burning out by combustion. The fuel given here has a high boiling point HC, and the lean NOx catalyst 71 effectively purifies NOx in a region where the exhaust temperature is high.

FIG. 5 shows the injection in the low temperature region. The sub-injection is executed in the intake stroke (FIG. 5A) or in the early stage of the compression stroke, and the fuel injection valve 5 to the recessed portion 6 of the piston 62.
Fuel is injected in the direction of 3. This injected fuel is a spray-like fuel having a large divergence angle and a weak penetration force. Most of the injected fuel floats in the cylinder 64, and the rest collides with the recess 63. These injected fuels are diffused in the cylinder chamber 64 by the turbulence T in the cylinder chamber 64 caused by the intake airflow flowing into the cylinder chamber 64 from the intake port, so that the air-fuel mixture P having a sufficiently lean air-fuel ratio is formed. (FIG. 5 (b)). The air-fuel ratio of this lean air-fuel mixture P is too thin for the ignition flame to propagate, and therefore, even in the combustion stroke, part of it remains in the unburned state and is thermally decomposed or partially oxidized. Subsequently, main injection is executed in the latter half of the compression stroke (FIG. 5C), and fuel is injected from the fuel injection valve 5 toward the vicinity of the ignition loop and the recess 63 on the top surface of the piston 62. Since the injected fuel is originally directed to the ignition sled 6, the penetration force is weak, and the pressure in the cylinder chamber 64 is large, the injected fuel is unevenly distributed in the region K near the ignition sled 6. Since the fuel distribution in this region K is also non-uniform and changes from the rich air-fuel mixture layer to the air layer, in this region K there is a combustible air-fuel mixture layer near the stoichiometric air-fuel ratio where combustion is most likely to occur. Therefore, when the combustible air-fuel mixture layer near the ignition loop 6 is ignited, the combustion proceeds around the heterogeneous air-fuel mixture region K. In this combustion process, the flame propagates to the air-fuel mixture P sequentially from the periphery of the combustion gas B whose volume is expanded, and the combustion proceeds (FIG. 5 (d)). Then, in the exhaust stroke, the exhaust valve opens and exhaust gas is discharged from the cylinder chamber 64 (FIG. 5 (e)).

FIG. 6 shows an extremely high temperature region (exhaust temperature is 500
The injection is shown in the case of (° C or more). During the intake stroke (Fig. 6 (a))-the initial stage of the compression stroke (Fig. 6 (b)), neither main injection nor auxiliary injection is performed. The main injection is executed in the latter half of the compression stroke (Fig. 6 (c)), and the auxiliary injection is executed in the early stage of the exhaust stroke (Fig. 6 (e)) after the combustion and expansion strokes (Fig. 6 (d)). The secondary injection fuel, which is injected after the main injection fuel is burned, is vaporized and atomized due to the high exhaust temperature, but is discharged with almost no thermal decomposition and partial oxidation, and the high boiling HC component is It is supplied to the lean NOx catalyst 71. This high boiling HC component is suppressed from being directly oxidized regardless of the exhaust gas temperature being high, is partially oxidized in the lean NOx catalyst 71 to become HC of an appropriate size, and improves the NOx purification rate of the lean NOx catalyst 71. .

As described above, the injection timing of the main injection and the auxiliary injection must be controlled. FIG. 7 shows the timing of this fuel injection control. In FIG.
At each time point indicated by a black circle in the engine control value calculation, a plurality of engine control values, for example, a sub injection control value (sub injection time, etc.),
And the ignition control value (ignition timing etc.) is calculated based on the engine operating state and the accelerator opening. The black circle in the figure is 5 ms
Therefore, a plurality of engine control values are continuously calculated every 5 ms.

FIG. 8 shows a routine for executing fuel injection and ignition according to the embodiment of the present invention. This routine is executed by interruption every fixed crank angle, for example, every 30 degrees of crank angle. Referring to FIG. 8, first step 1
At 00, the count of the angle determination counter CNE is executed. CNE is 0 to 5 and 1 for every 30 degrees of crank angle
After the CNE reaches 5, the CNE is set to 0 and again increased by 1 every 30 degrees of the crank angle (see FIG. 7). Next, at step 102, the cylinder discrimination counter CCYL is counted. CCYL is 0 to 3
Is increased by 1 every 180 degrees of crank angle until CCYL
CCYL is set to 0 after C becomes 3 and the crank angle becomes 18 again.
It is incremented by 1 every 0 degrees (see FIG. 7). As shown in FIG. 7, the time point at which CCYL changes indicates the compression top dead center of each cylinder, and for example, the time point at which CCYL is increased to 3 indicates the compression top dead center of the fourth cylinder. Indicates the compression top dead center of the second cylinder at the time when is cleared from 3 to 0, and the time at which CCYL is increased to 1 is the first
The compression top dead center of the cylinder is shown. CNE is 5 to 0
The time point when CCYL is changed coincides with the time point when CCYL changes, and indicates the compression top dead center of each cylinder.

Referring to FIG. 8, in step 104,
The cylinder ns for which the secondary injection is to be executed is calculated based on CNE and CCYL. The cylinder ns is a cylinder from the intake stroke to the early stage of the compression stroke, and taking the case of the intake stroke as an example, the cylinder between the time when the piston is located at the intake top dead center and the time when the piston reaches the intake bottom dead center. Is. Next, at step 106, it is judged if the CNE has reached a value CNEs at which an injection start time ts and a sub-injection period τs described later should be set in the counter 35 (see FIG. 1). CNE
= CNEs, go to Step 108 and CNE
The injection start time ts and the sub injection period τs from s to the sub injection start timing are set in the counter 35 (see FIG. 1). When the injection start time ts is set in the counter 35, the counter 35 starts counting, and when the injection start time elapses, the sub injection is executed. At this time, counting of the fuel injection period τs is started, and when the sub injection period τs elapses, the sub injection is stopped. For example, referring to FIG. 7, regarding the first cylinder, when CNEs calculated from the engine speed and the engine load (accelerator opening) is 0, the injection start time ts and the sub injection period τs at time T _1. Is set in the counter 35. The sub-injection is started at time T ₂ when the injection start period τs has elapsed from the time T _1, and is stopped at time T ₃ when the sub-injection period τs has elapsed from the time T ₂ . When τs = 0, the sub injection is not executed. When a negative determination is made in step 106, step 108 is skipped and the secondary injection is not executed.

Then, in step 110, the cylinder nm for which main injection and ignition are to be performed is calculated based on CNE and CCYL. The cylinder nm is a cylinder in the compression stroke, and the piston is a cylinder between the intake bottom dead center and the compression top dead center. Then in step 112, the CNE
The injection start time tm and the main injection period τm are counted by the counter 35.
It is determined whether or not the value CNEm to be set (see FIG. 1) has been reached. When CNE = CNEm, the routine proceeds to step 114, where the injection start period tm and the main injection period τm are set in the counter 35. When tm is set in the counter 35, the counter 35 starts counting, and when tm elapses, execution of main injection is started. At this time, counting of τm is started, and when τm elapses, the main injection is stopped.
For example, referring to FIG. 7, regarding the first cylinder, when the calculated CNEm is 3, tm and τ at time T _4.
m is set in the counter 35. Main injection is started at time T ₅ when tm has elapsed from time T _4, and τ is started from time T _5.
The main injection is stopped at time T ₆ when m has elapsed. In addition,
When τm = 0, the main injection is not executed. When a negative determination is made in step 112 of FIG. 8, step 114 is skipped and the main injection is not executed.

Next, at step 116, it is judged if the CNE has reached the value CNEi at which the ignition control value should be set in the counter 37 (see FIG. 1). CNE = CNEi
Then, the routine proceeds to step 118, where the energization start time tbi and the energization period ti from CNEi until the energization of the igniter primary coil is started are set in the counter 37 (see FIG. 1). When tbi is set in the counter 37, the counter 37 starts counting, and when tbi elapses, energization of the igniter primary side coil is started. At this time, counting of the counter ti is started, and when ti has elapsed, ignition is executed. For example, referring to FIG. 7, regarding the first cylinder, when the calculated CNEi is 3, tbi and ti are set in the counter 37 at the time point T ₄ . T ₄ time tbi started energized igniter primary coil at T ₇ after a lapse from, t from T ₇ time
Ignition is performed at time T ₈ when i has elapsed. Return after ignition. On the other hand, if a negative determination is made in step 116, step 118 is skipped and ignition is not executed.

FIG. 9 shows a main routine of fuel injection and ignition control of the embodiment of the present invention. First, step 13
At 0, the main injection amount Qm is calculated based on the engine speed NE (calculated from the output of the crank angle sensor 29) and the accelerator opening θA (output of the accelerator opening sensor 30). Then, in step 132, NE, Qm
Based on, the main injection start time tm, the main injection period τm, and the count value CNEm of the angle determination counter for setting tm, τm in the counter 35 (FIG. 1) are calculated. Up to this point, it is the same as the conventional calculation. Then, Step 1
At 34, the exhaust temperature THE is calculated from the NE-Qm map of FIG. Next, the main injection amount Qm and the exhaust temperature T
Based on HE, the sub injection amount Qs is calculated from the THE-sub injection amount / main injection amount map of FIG. Here, FIG.
As shown in, when the exhaust temperature exceeds 400 ° C, the sub injection amount Qs is set to 5% of the main injection amount Qm, and below 400 ° C, the sub injection amount Qs is set to 2% of the main injection amount Qm. The ratio is gradually decreased as becomes higher and becomes about 1% of the main injection amount Qm near 700 ° C. Next, at step 138, based on NE, Qs, and THE, using the THE-sub injection injection timing map of FIG. 12, the sub injection start crank angle CN
Es, sub injection start time ts, and sub injection period τs are calculated. Next, in step 140, the energization start time tbi, the energization time ti, and tbi, ti from NE and Qm.
Is calculated in the counter 37 (see FIG. 1). The calculations of these main routines are sequentially calculated, for example, every 5 ms, based on the engine operating state at the same time point, as indicated by black circles in the engine control timing of FIG.

In the fuel injection control device constructed as described above, a crank angle sensor 29, an accelerator opening sensor 30, and a crank angle sensor 29 are provided as means for detecting the engine operating state and the catalyst bed temperature.
A cylinder discrimination sensor 32 is included. The catalyst bed temperature is indirectly obtained from the exhaust temperature, and the exhaust temperature is calculated using the map 10 from the injection amount obtained from the accelerator opening degree and the rotation speed, and the rotation speed. Further, the first injection timing setting means for setting the timing of the main injection includes steps 130 and 132 of the main routine of FIG. 9 which is stored in the ROM 22 and read by the CPU 24 to execute the calculation.
Further, the second injection timing setting means for setting the timing of the sub-injection includes step 1 of the main routine of FIG.
34, 136, 138 and C stored in ROM 22
FIG. 10 (used to determine the exhaust temperature), which is read by the PU 24 and used for calculation, FIG. 11 (used to determine the injection amount of the secondary injection), and FIG. 12 (used to determine the injection timing of the secondary injection). Includes a map of. Further, in the fuel injection executing means for executing the main injection, step 1 in FIG.
10, 112, 114 are included, and the fuel injection executing means for executing the secondary injection includes steps 104, 106, 1 in FIG.
08 are included.

In the above description, the case where the main injection is fully injected at one time in the latter half of the compression stroke is taken as an example. However, the main injection itself is also in the latter half of the compression stroke and the period from the intake stroke to the initial compression stroke. Alternatively, divided injection may be performed.

Next, the operation will be described. When the exhaust gas temperature (correlated with the catalyst bed temperature) is 400 ° C. or lower, FIG. 4 and FIG.
As shown in, the sub-injection is executed within the period from the intake stroke to the early stage of the compression stroke, so that the fuel of the sub-injection injected in the cylinder is sufficiently diffused and becomes lean. Therefore, in the subsequent main injection, ignition of the main injected fuel, combustion, and expansion stroke,
The flame does not propagate to completely oxidize the sub-injection fuel, and a part of the fuel of the sub-injection is thermally decomposed or partially oxidized to be discharged as a small HC component.
It reaches the Ox catalyst 71. Since the lean NOx catalyst 71 is not at a high temperature, HC, which is a small component, is not promoted to complete oxidation and reacts with NOx in the state of active species to generate N.
Reduces and purifies Ox. In this case, if the large HC
Is less effective in producing less active species. When the exhaust gas temperature exceeds 400 ° C., as shown in FIGS. 4 and 6, the sub-injection is executed within the period from the latter half of the combustion period to the exhaust stroke, so that the fuel injected by the sub-injection passes through the combustion stroke. It is discharged as it is without passing through. Therefore,
Most of the fuel is in a state of large HC and lean NOx
It is supplied to the catalyst 71. However, lean NOx catalyst 71
Since the temperature is high, HC is lean NOx catalyst 71
While passing through the inside, large HC is pyrolyzed and partially oxidized to become an appropriately sized HC, which results in lean NOx catalyst 71.
It produces a large amount of active species inside and improves the NOx purification rate. In this case, if a small amount of HC is supplied, almost all of it is directly oxidized, which is not effective. In this way,
The auxiliary injection is executed separately from the main injection, and by controlling the injection timing of the auxiliary injection, the quality and quantity of HC supplied to the lean NOx catalyst 71 are controlled, and the lean NOx catalyst that is optimum over a wide temperature range is obtained. NOx purification rate control is performed.

[0024]

According to the present invention, the auxiliary injection is provided in addition to the main injection, and the injection timing of the auxiliary injection is set within the period from the intake stroke to the early stage of the compression stroke in the low temperature range, and the combustion period in the high temperature range. Since it was set within the period from the latter half of the period to the beginning of the exhaust stroke, HC of optimum quality can be supplied to the lean NOx catalyst over a wide temperature range without providing a special HC supply device, and the NOx purification rate of the lean NOx catalyst can be increased. Can be increased.

[Brief description of the drawings]

FIG. 1 is a system diagram of a fuel injection control device for a direct injection internal combustion engine, according to an embodiment of the present invention.

2 is a cross-sectional view of a fuel injection valve used in the apparatus of FIG.

3 is a cross-sectional view of an internal combustion engine used in the apparatus of FIG.

FIG. 4 is a change diagram of an injection timing of a fuel injection valve according to an exhaust temperature.

FIG. 5 is a schematic cross-sectional view of a continuous stroke when the sub-injection is executed within a period from an intake stroke to an initial compression stroke.

FIG. 6 is a schematic cross-sectional view of a continuous stroke when the sub-injection is executed within the period from the latter half of the combustion period to the exhaust stroke.

FIG. 7 is a time chart showing the relationship between the operation of each cylinder and injection.

FIG. 8 is a flowchart of a fuel injection / ignition execution routine of control according to the present invention.

FIG. 9 is a flowchart of a control main routine of the present invention.

FIG. 10 is an engine speed NE-fuel injection amount map.

FIG. 11 is an exhaust temperature THE-sub injection amount / main injection amount map.

FIG. 12 is an exhaust temperature THE-sub injection injection timing map.

[Explanation of symbols]

 1 Internal Combustion Engine 5 Fuel Injection Valve 6 Ignition Slave 20 Electronic Control Unit 29 Crank Angle Sensor 30 Accelerator Opening Sensor 32 Cylinder Discrimination Sensor 62 Piston 71 Lean NOx Catalyst

Claims (1)

(57) [Claims] 1. A fuel injection control device for a direct injection internal combustion engine, comprising a lean NOx catalyst in an exhaust system and a fuel injection valve in each cylinder.
x means for detecting the catalyst bed temperature of the catalyst, first injection timing setting means for setting the timing of main injection from the fuel injection valve within the period from the intake stroke to the compression stroke, and fuel injection based on the catalyst bed temperature Second injection timing that sets the timing of sub-injection from the valve within the period from the intake stroke to the beginning of the compression stroke when the catalyst bed temperature is low, and within the period from the latter half of the combustion stroke to the beginning of the exhaust stroke when the catalyst bed temperature is high Setting means and fuel injection executing means for driving the fuel injection valve to execute fuel injection when the engine state is the timing set by the first and second injection timing setting means. Fuel injection control device for direct injection type internal combustion engine.