JP2005048748A - Automatic combustion control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform the optimum permission/continuation/inhibition of combustion by realizing combustion without deterioration of smoke even if the air fuel ratio is made rich when an exhaust emission temperature rise request or an under-stoichio rich operation request is given on the basis of the state of an exhaust emission control device (NOx trap catalyst and DPF (diesel particulate filter)). <P>SOLUTION: Main combustion for generating main torque and preliminary combustion prior to the main combustion are performed (step 101), fuel injection is controlled to cause at least one preliminary combustion near the upper dead center, the fuel injection is controlled to start the main combustion after the end of the preliminary combustion, and on the other hand, the DPF temperature of an engine is detected. According to the above temperature state, the combustion performed by the preliminary combustion and the main combustion is inhibited (step 108). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a combustion control device for an internal combustion engine.

Conventionally, as disclosed in Patent Document 1, in a fuel injection device for a diesel engine, when the temperature of the catalyst is urged, the fuel of the basic fuel injection amount corresponding to the required torque of the engine is supplied by the fuel injection valve. It is known that the fuel is divided into three injections in the vicinity of the compression top dead center of each cylinder. In addition to this, it is also known that the fuel injection amount may be increased.
JP 2000-320386 A

  However, in the apparatus described in Patent Document 1, since the fuel is injected so that the combustion by the split injected fuel continues, the fuel is injected into the flame of the initially injected fuel. The fuel injected after the second time becomes the combustion mainly of diffusion combustion. When the air-fuel ratio is reduced in such a combustion state, there has been a problem that a significant deterioration of smoke is inevitable.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize combustion that does not cause smoke deterioration even when the air-fuel ratio is enriched, for example, when the exhaust gas temperature is raised. Another object is to optimally permit, continue, and prohibit this combustion.

  Therefore, in the present invention, the main combustion for generating the main torque and the preliminary combustion performed prior to the main combustion are performed, and the fuel injection is controlled so that at least one of the preliminary combustion occurs in the vicinity of the top dead center. Controls the fuel injection to start after the pre-combustion is completed, while detecting each state of the engine, and prohibits the combustion by the pre-combustion and the main combustion by at least one of the states.

  According to the present invention, the in-cylinder temperature is increased by pre-combustion, and main combustion starts after the pre-combustion is completed, so that the main combustion is mainly premixed combustion, and the exhaust temperature can be increased and a rich air-fuel ratio can be realized. . Further, since the prohibition of combustion by the preliminary combustion and the main combustion is optimally performed according to each state of the engine, it is possible to prevent overheating of the exhaust purification device and deterioration of smoke.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a control device of an internal combustion engine (here, a diesel engine using light oil as a fuel, hereinafter referred to as an “engine”) 1.
In the intake system of the engine 1, an intake compressor 3a of a turbocharger (supercharger) 3 is disposed upstream of the intake passage 2, and the intake air is supercharged by the intake compressor 3a and cooled by the intercooler 4, After passing through the intake throttle valve 6, it flows into the combustion chamber of each cylinder through the collector.

The fuel (light oil) is increased in pressure by the common rail fuel injection device, that is, the fuel injection pump 8, sent to the common rail 9, and directly injected from the fuel injection valve 10 of each cylinder into the combustion chamber. The air flowing into the combustion chamber and the injected fuel are combusted by compression ignition here, and the exhaust gas flows out to the exhaust passage 12.
A part of the exhaust gas flowing into the exhaust passage 12 is recirculated to the intake side through the EGR valve 19 through the EGR passage 11 as EGR gas. The remainder of the exhaust passes through the exhaust turbine 3b of the variable nozzle type turbocharger 3 and drives it.

Here, downstream of the exhaust turbine 3 b in the exhaust passage 12, a NOx trap catalyst 13 as an exhaust purification device (catalyst) and a diesel particulate filter (hereinafter referred to as “DPF”) 14 are arranged. Yes.
The NOx trap catalyst 13 traps NOx in the exhaust gas that flows when the exhaust air-fuel ratio is lean (oxygen excess state), and desorbs and purifies the trapped NOx when the exhaust air-fuel ratio is rich (fuel excess state). The NOx trap catalyst 13 carries an oxidation catalyst (noble metal such as Pt) such as a noble metal and has a function of oxidizing the exhaust components (HC, CO) that flow in.

The DPF 14 has a PM trap function that collects exhaust particulate matter (PM) in the exhaust. The DPF 14 also carries an oxidation catalyst (noble metal) and has a function of oxidizing the exhaust components (HC, CO) flowing in.
The NOx trap catalyst 13 and the DPF 14 may be reversed, or the NOx trap catalyst 13 may be supported integrally on the DPF 14, or the catalyst that supports the oxidation catalyst may be combined with the NOx trap catalyst 13. You may arrange | position independently separately from DPF14.

In order to control the engine 1, an engine control unit (hereinafter referred to as “ECU”) includes a crank angle sensor (rotational speed sensor) 20 for detecting the engine rotational speed Ne and an accelerator opening sensor 21 for detecting the accelerator opening APO. From, the signal is input.
Further, a catalyst temperature sensor 22 for detecting the temperature of the NOx trap catalyst 13 (catalyst temperature), an exhaust pressure sensor 17 for detecting exhaust pressure on the inlet side of the DPF 14 in the exhaust passage 12, and a temperature of the DPF 14 (DPF temperature) are detected. A DPF temperature sensor 23, an air-fuel ratio sensor 16 for detecting the exhaust air-fuel ratio λ on the outlet side of the DPF 14 in the exhaust passage 12, and a smoke concentration sensor 18 for detecting smoke concentration are provided, and these signals are also input to the ECU 25. Yes. However, the temperature of the NOx trap catalyst 13 and the temperature of the DPF 14 may be detected indirectly from the exhaust temperature by providing an exhaust temperature sensor downstream of these.

Based on these input signals, the ECU 25 performs fuel injection to the fuel injection valve 10 for controlling the fuel injection amount and injection timing of main injection by the fuel injection valve 10 and at least one preliminary injection performed prior thereto. A command signal, an opening command signal to the intake throttle valve 6, an opening command signal to the EGR valve 19, and the like are output.
Here, the ECU 25 purifies the PM collected and accumulated in the DPF 14 (DPF regeneration), purifies the NOx trapped and accumulated in the NOx trap catalyst 13 (NOx regeneration), and performs SOx poisoning on the NOx trap catalyst 13. Exhaust gas purification control for purifying SOx deposited on the gas (SOx regeneration) is performed, and the exhaust gas purification control will be described below.

  As control for recovering the purification ability of the NOx trap catalyst 13 or DPF 14, the ECU 25 changes the operating condition of the engine 1. For example, when there is a rich operation request less than stoichiometric (theoretical air-fuel ratio: λ = 1), the amount of air supplied to the engine 1 is reduced by controlling the opening of the intake throttle valve 6 to be small, Alternatively, the fuel injection pump 8 is controlled to increase the amount of fuel injected from the fuel injection valve 10.

When the DPF 14 is regenerated, the target air-fuel ratio λ is controlled between 1 and 1.4 (1 ≦ λ ≦ 1.4), and the temperature of the DPF 14 is 600 ° C. or more (DPF temperature ≧ 600 ° C.). It is necessary to drive.
Here, in the normal operation region under the lean condition, pilot injection is normally performed to alleviate initial rapid combustion, and this pilot injection timing is 40 to 10 ° BTDC (crank angle timing before bottom dead center). The pilot injection amount is 1 to ³ mm ³ / st, the main injection timing is about 10 to −5 ° BTDC, and the interval between the pilot injection and the main injection is set to about 10 to 30 ° CA (crank angle). .

  In order to realize a low air-fuel ratio and high exhaust temperature such as regeneration of the DPF 14 and cancellation of sulfur poisoning from normal operation, it is necessary to reduce the intake air amount. However, if the intake air amount is reduced, the compression end temperature in the cylinder (in-cylinder atmosphere temperature in the vicinity of the compression stroke top dead center) decreases, so that the combustion becomes unstable and is similar to the normal lean operation. In the pilot injection setting, it is necessary to advance the injection timing of the main injection (see FIG. 13, which is referred to as “first example”).

In such setting of fuel injection amount and injection timing, even if you want to retard (retard) the injection timing to raise the exhaust temperature, the combustion becomes unstable, so there is a limit to the retard, For example, in order to cancel sulfur poisoning, it is difficult to achieve the target values where the target λ is 1 or less (λ ≦ 1) and the exhaust temperature is 600 ° C. or higher (exhaust temperature ≧ 600 ° C.).
Therefore, as described in Patent Document 1, it has become possible to increase the retard limit of the injection timing by dividing the main injection, and to realize a high exhaust temperature and a low air-fuel ratio (see FIG. 14). 2nd example ").

  However, the combustion of the fuel injected for the main combustion is continuous, and the next fuel is injected while the combustion of the previously injected fuel is active. For this reason, the combustion is continuous as shown in FIG. The fuel divided for the main combustion is injected into the flame of the previously injected combustion, and as soon as it is injected, combustion starts, the diffusion combustion ratio increases, and the partial equivalence ratio is very high. It becomes rich and the smoke is greatly deteriorated.

Therefore, switching from the normal lean operation to the operation by the combustion control by the preliminary combustion and the main combustion is performed to recover the exhaust purification function of the exhaust purification device (NOx trap catalyst 13, DPF 14).
The combustion control by the preliminary combustion and the main combustion includes the preliminary combustion in which the fuel is injected and burned before the compression top dead center so that the injected fuel burns in the vicinity of the compression top dead center, and after the preliminary combustion is completed. This is performed by controlling main combustion that generates main torque.

  In the pre-combustion, as shown in FIG. 15 (this is referred to as “third example”), fuel is first injected in the compression stroke (a in the figure), and the in-cylinder temperature near the compression top dead center (TDC) is increased. At this time, the amount of fuel that generates heat for preliminary combustion differs depending on the operating conditions, but at least fuel that can be confirmed to generate heat for preliminary combustion is injected. Thereby, the retard limit of the main combustion is expanded by raising the in-cylinder temperature by the combustion of the preliminary combustion.

Further, the preliminary combustion may be performed a plurality of times in one cycle. In this case, fuel injection is performed so that at least one of the plurality of preliminary combustions occurs in the vicinity of the compression top dead center.
In the preliminary combustion, the in-cylinder compression end temperature may be estimated from the operating state of the engine 1, and at least one of the fuel injection amount or the fuel injection timing may be changed according to this temperature. Also in this case, the fuel injection amount is an amount that can confirm the heat generation of the preliminary combustion, and at least one of the multiple preliminary combustions in one cycle occurs near the compression top dead center.

Further, the fuel injection amount at the time of preliminary combustion is set to a fuel injection amount necessary for the in-cylinder temperature at the time of fuel injection in the main combustion to exceed the temperature at which self-ignition is possible.
Then, as shown in FIG. 15, control is performed so that fuel for main combustion is injected after top dead center so that combustion for main combustion starts after completion of preliminary combustion (illustration b).
The control of the fuel injection timing for the main combustion is such that the combustion start timing of the main combustion is separated from the combustion start timing of the preliminary combustion by 20 degrees or more from the combustion start timing according to the operating state of the engine 1 (especially the engine speed Ne). At the right time. As a result, the in-cylinder temperature is increased by pre-combustion combustion, thereby extending the retard limit of main combustion. On the other hand, the main combustion fuel is injected after the pre-combustion is completed, so that an ignition delay period for main combustion is ensured. As a result, the premixed combustion ratio of the main combustion can be increased, and smoke emission can be suppressed.

Then, the combustion end timing of the main combustion is set to a timing away from the compression top dead center by 50 degrees or more in crank angle. By controlling the fuel injection timing of the main combustion, the exhaust temperature is controlled according to the operating state of the engine 1.
In the main combustion control, the fuel injection amount, the fuel injection timing, and the fuel injection period of the main combustion are controlled so that the generated torque of the engine 1 is constant.

By controlling the preliminary combustion and the main combustion, the retard limit is increased by the preliminary combustion, thereby improving the controllability to the target temperature. After the preliminary combustion is completed, the main combustion is started and the main combustion is predicted. Smoke can be suppressed by increasing the mixed combustion ratio.
Here, FIG. 17 is a diagram comparing the exhaust temperature, smoke concentration, and HC (hydrocarbon) concentration when the combustion in FIGS. 13 to 15 (first to third examples) described above is realized. In the figure, the combustion result of the first example is indicated by (1), the combustion result of the second example is indicated by (2), and the combustion result of the third example is indicated by (3).

As shown in the drawing, if the combustion by the pre-combustion and the main combustion (third example) is realized, the combustion at the high exhaust temperature and the low smoke state can be realized when the rich condition is realized. Further, the HC concentration is much lower than that in the case where enrichment is performed by conventional combustion (first example) or the conventional device (second example).
In addition, because the in-cylinder temperature rises due to the preliminary combustion and the retard limit of the main combustion is widened, even if the injection timing of the main injection is retarded, the combustion under the low air-fuel ratio condition is stable and a high exhaust temperature can be realized. Become.

FIG. 18 is a diagram showing the state of the exhaust gas with respect to the main combustion timing. (A) is the exhaust gas temperature, (b) is the smoke concentration, (c) is the CO (carbon monoxide) concentration, and (d) is HC concentration is shown. The exhaust air-fuel ratio is constant (λ = const).
As shown in the figure, if the timing of the main combustion is retarded, the premixing ratio of the main combustion is increased. Therefore, even if the exhaust air-fuel ratio is small, the smoke is suppressed only by the retarding.

FIG. 19 is a diagram showing the target fuel injection timing for main combustion when performing combustion by preliminary combustion and main combustion. The horizontal axis shows the engine rotational speed Ne, and the vertical axis shows the engine load Q.
As shown in the figure, when the load Q is low, the combustion timing of the main combustion for achieving the target exhaust temperature is largely retarded, so that the in-cylinder temperature at the injection timing of the main combustion cannot be maintained high only once by the preliminary combustion. There is also. In this case, as shown in FIG. 16, by performing preliminary combustion a plurality of times so that the heat generation does not overlap, it is possible to achieve both low smoke and high exhaust temperature even under low load conditions. it can.

From the above, when there is a request for a rise in exhaust temperature or a rich operation less than stoichiometric, based on the state of the exhaust purification device, the operation of the combustion control by the preliminary combustion and the main combustion from the normal operation (lean operation) (preliminary operation) In the state of high exhaust temperature and low air-fuel ratio, regeneration of the NOx trap catalyst 13 or DPF 14 is performed.
However, depending on the operating state of the engine 1, there is a problem that when the combustion is switched, the exhaust temperature rises and the NOx trap catalyst 13 and the DPF 14 are overheated. In addition, there is a problem that the ratio of diffusion combustion is increased and smoke is deteriorated. Further, when the fuel property supplied to the engine 1 is changed, the ignitability of the fuel is changed, so that there is a problem that the operation region in which these problems occur is changed.

  Therefore, whether or not the combustion control can be continued by the preliminary combustion and the main combustion is determined based on the temperature of the NOx trap catalyst 13 detected by the catalyst temperature sensor 22 and the temperature of the DPF 14 detected by the DPF temperature sensor 23. Thereby, according to the temperature of the exhaust purification device (NOx trap catalyst 13, DPF 14), the combustion by the preliminary combustion and the main combustion is prohibited and appropriately switched to the combustion in the normal lean state, the smoke deterioration and the exhaust purification device This is to prevent overheating.

In addition, according to the smoke concentration detected by the smoke concentration sensor 18, it is determined whether to continue the combustion control by the preliminary combustion and the main combustion, and the combustion by the preliminary combustion and the main combustion is switched to the operation in the normal lean state combustion. , Mainly to prevent the deterioration of smoke.
Next, processing performed by the control device for an internal combustion engine of the present invention will be described with reference to the flowcharts of FIGS.

FIG. 2 is a main flowchart of combustion control.
In step 1 (referred to as “S1” in the figure, the same applies hereinafter), various sensor signals are read, and the operating state of the engine 1 calculated based on these signals, that is, the engine speed Ne, the accelerator opening APO, the catalyst temperature, The exhaust pressure, DPF temperature, etc. at the inlet side or outlet side of the DPF 14 are read.

In step 2, it is determined whether or not the NOx trap catalyst 13 disposed in the exhaust passage 12 is in a warm-up state (active state). This determination is based on whether or not the exhaust gas temperature T calculated based on the output signal of the exhaust gas temperature sensor 15 at the outlet of the NOx trap catalyst 13 is higher than a predetermined exhaust gas temperature T5 at the start of activation of the NOx trap catalyst 13 (T> T5). Depending on
If the exhaust temperature T is higher than the predetermined exhaust temperature T5 (T> T5), it is determined that the NOx trap catalyst 13 is warming up, and the routine proceeds to step 3.

On the other hand, when the exhaust temperature T is equal to or lower than the predetermined exhaust temperature T5 (T ≦ T5), it is determined that the NOx trap catalyst 13 is cold, and the process proceeds to step 1001 in FIG. Thus, when the NOx trap catalyst 13 is cooled, the combustion is switched so as to rapidly warm up the NOx trap catalyst 13 from normal operating conditions.
In step 3, the amount of NOx trapped and deposited on the NOx trap catalyst 13 is calculated. This calculation method may be a method of estimating from the integrated value of the engine rotational speed Ne, for example, as in the calculation of the NOx absorption amount described in Japanese Patent No. 2600492, page 6, or every time the vehicle travels a predetermined distance. Alternatively, the NOx absorption amount may be added to the above. When the integrated value is used, the integrated value is reset at the time when NOx regeneration is completed (including the time when NOx regeneration is simultaneously performed by performing SOx regeneration).

In step 4, the amount of sulfur (SOx) deposited on the NOx trap catalyst 13 is calculated. Here, the method for calculating the sulfur accumulation amount may be estimated from the integrated value of the engine speed Ne and the travel distance, for example, similarly to the above-described NOx accumulation amount. When using the integrated value, the integrated value is reset when the reproduction is completed.
In step 5, the amount of PM collected and deposited in the DPF 14 is detected. The PM accumulation amount is calculated by detecting the exhaust pressure on the inlet side of the DPF 14 by the exhaust pressure sensor 17 and comparing it with the reference exhaust pressure in the current operation state (engine rotational speed Ne, fuel injection amount Q). This is because the exhaust gas pressure on the inlet side of the DPF 14 naturally increases as the PM accumulation amount of the DPF 14 increases. The PM accumulation amount may be estimated by combining the travel distance from the previous DPF regeneration, the integrated value of the engine rotational speed Ne, and the exhaust pressure.

In step 6, it is determined whether or not a reg flag indicating that the DPF 14 is in the regeneration mode is set. If the DPF 14 is not in the regeneration mode (reg flag = 0), the process proceeds to step 7. On the other hand, if the regeneration mode is selected (reg flag = 1), processing in the DPF regeneration mode after step 101 in FIG.
In step 7, it is determined whether or not a desul flag indicating that the NOx trap catalyst 13 is in the sulfur poisoning release mode (SOx regeneration mode) is set. If the sulfur poisoning release mode is not in progress (desul flag = 0), the process proceeds to step 8. On the other hand, when the sulfur poisoning release mode is in progress (desul flag = 1), processing in the rich combustion mode after step 201 in FIG. 4 described later is performed.

  In step 8, it is determined whether or not the sp flag indicating that the rich spike mode during regeneration of the NOx trap catalyst 13 is being set is set. If it is not the rich spike mode (sp flag = 0), the process proceeds to step 9. On the other hand, in the rich spike mode (sp flag = 1), processing in the rich spike mode (NOx regeneration mode) after step 301 in FIG. 5 described later is performed.

  In step 9, the determination is made based on whether or not the rec flag indicating that the DPF 14 is in the regeneration mode and is in the melting prevention mode when the sulfur poisoning is released is set. If the rec flag is not set (rec flag = 0), the process proceeds to step 10. On the other hand, when the rec flag is set (rec flag = 1), processing in the melting prevention mode after step 401 in FIG.

  In step 10, it is determined whether or not the rq_DPF flag indicating that a regeneration request is issued to the DPF 14 is set. If no DPF regeneration request has been issued (rq_DPF flag = 0), the process proceeds to step 11. On the other hand, when a DPF regeneration request is issued (rq_DPF flag = 1), processing for determining the priority of regeneration when a DPF regeneration request is issued is performed in step 501 and subsequent steps in FIG. 7 described later.

  In step 11, it is determined whether or not an rq_desul flag indicating that a sulfur poisoning release request (SOx regeneration request) has been issued to the NOx trap catalyst 13 is set. If the poisoning release request has not been issued (rq_desul flag = 0), the process proceeds to step 12. On the other hand, when a poisoning cancellation request has been issued (rq_desul flag = 1), processing for determining the priority of regeneration when a sulfur poisoning cancellation request has been issued in step 601 and later in FIG. .

  In step 12, it is determined whether the PM accumulation amount of the DPF 14 calculated in step 5 has reached a predetermined amount PM1 that requires regeneration of the DPF 14 (PM accumulation amount <PM1), that is, whether the DPF regeneration timing has come. Note that the DPF inlet side exhaust pressure when the PM accumulation amount of the DPF 14 reaches the predetermined amount PM1 is obtained for each operating state (engine rotational speed Ne, fuel injection amount Q), and is mapped as shown in FIG. When the DPF inlet side exhaust pressure detected by the pressure sensor 17 reaches an exhaust pressure threshold value corresponding to the current operating state (engine rotational speed Ne, fuel injection amount Q) in the map of FIG. The regeneration time (PM accumulation amount> PM1) may be determined.

If it is determined that it is not the DPF regeneration time (PM deposition amount ≦ PM1), the process proceeds to Step 13.
On the other hand, if it is determined that it is the DPF regeneration time (PM deposition amount> PM1), the process proceeds to step 701 in FIG. 9, and the rq_DPF flag of the regeneration request is set to 1, and a DPF regeneration request is issued. Thus, when a predetermined amount of PM1 is deposited on the DPF 14, the combustion is controlled so as to raise the exhaust temperature from the normal operating condition (lean operation) to a temperature at which the PM deposited on the DPF 14 self-oxidizes.

In step 13, whether or not the sulfur accumulation amount (SOx amount) of the NOx trap catalyst 13 calculated in step 4 has reached a predetermined amount S1 and the regeneration time has come (sulfur accumulation amount <S1), that is, sulfur poisoning release. The necessity of (SOx regeneration request) is determined.
If the sulfur deposition amount is less than the predetermined amount S1 (sulfur deposition amount <S1), it is determined that the sulfur poisoning cancellation is unnecessary, and the routine proceeds to step 14.

  On the other hand, when the sulfur accumulation amount S is equal to or greater than the predetermined amount S1 (sulfur accumulation amount ≧ S1), it is determined that sulfur poisoning is necessary, and the process proceeds to step 801 in FIG. 10, and the rq_desul flag (sulfur poisoning release request flag) ) Is set to 1, and a sulfur poisoning cancellation request is issued. Note that the regeneration time may be determined when the travel distance from the previous regeneration exceeds a predetermined distance and the exhaust pressure based on the exhaust pressure sensor 17 exceeds a predetermined threshold. As a result, the sulfur content trapped in the NOx trap catalyst 13 is set to a temperature at which the sulfur content trapped in the rich atmosphere and the NOx trap catalyst 13 can be purified from the normal operating conditions for each travel distance.

In step 14, it is determined whether the NOx accumulation amount of the NOx trap catalyst 13 calculated in step 3 has reached a predetermined amount NOx1 and the regeneration time has come (NOx accumulation amount <NOx1), that is, whether or not NOx regeneration is necessary.
If the NOx accumulation amount is less than the predetermined amount NOx1 (NOx accumulation amount <NOx1), it is determined that NOx regeneration is unnecessary, and the process is terminated.

  On the other hand, if the NOx accumulation amount is equal to or greater than the predetermined amount NOx1 (NOx accumulation amount ≧ NOx1), it is determined that NOx regeneration is necessary, and the rq_sp flag (NOx regeneration request flag) is set to 1 in step 901 of FIG. And NOx regeneration request. Note that the regeneration time may be determined when the travel distance from the previous regeneration exceeds a predetermined distance and the exhaust pressure based on the exhaust pressure sensor 17 exceeds a predetermined threshold. As a result, the combustion can be switched so as to purify the NOx trapped in the NOx trap catalyst 13 from the normal operating conditions for each travel distance.

Next, the processing when the DPF regeneration mode flag is present in step 6 (reg flag = 1), that is, DPF regeneration (melting prevention) when the NOx trap catalyst 13 is warmed up will be described with reference to the flowchart of FIG. To do.
In step 101, assuming that the predetermined condition is satisfied, the combustion is switched from the normal lean combustion to the operation in the combustion control by the preliminary combustion and the main combustion described above. That is, based on the state of the exhaust purification device (NOx trap catalyst 13, DPF 14), main torque is generated from normal lean operation when there is at least one of an exhaust temperature increase request or a rich operation request less than stoichiometric. The operation is switched to the main combustion to be performed and at least one preliminary combustion to be performed prior to the main combustion.

In step 102, the exhaust air-fuel ratio is controlled to a target value. Here, the target air-fuel ratio in the regeneration of the DPF 14 varies depending on the PM accumulation amount. Therefore, the PM accumulation amount is predicted from the exhaust pressure threshold value of the DPF 14 shown in FIG. 20, and the exhaust gas is controlled to the target air-fuel ratio with respect to the predicted PM accumulation amount shown in FIG.
Here, after switching to pre-combustion and combustion by main combustion in step 101, the target exhaust air-fuel ratio is controlled by the intake throttle valve 6 or the EGR valve 19. In order to obtain the target intake air amount, the intake air throttle valve 6 controls the target air amount (target intake air amount for the operation of λ = 1) obtained by multiplying the target air-fuel ratio by the value of the map shown in FIG. When the air amount is different from the target value after controlling to the air amount shown in FIG. 22, the target air / fuel ratio is adjusted by the intake throttle valve 6 or the EGR valve 19.

However, when switching to the combustion by the preliminary combustion and the main combustion, the fuel injection timing is significantly retarded. Therefore, in addition to the control of the intake air amount, in order to suppress the torque fluctuation at the time of switching, the target fuel injection timing shown in FIG. The target intake air amount and the fuel injection amount shown in FIG.
In step 103, it is determined whether or not the temperature of the DPF 14 is equal to or higher than a target lower limit value (predetermined temperature) T22 during regeneration (DPF temperature ≧ T22). When the DPF temperature is equal to or higher than the target lower limit value T22 (DPF temperature ≧ T22), the routine proceeds to step 104. On the other hand, when it is less than the target lower limit value T22 (DPF temperature <T22), the process proceeds to Step 113 and Step 114 described later.

  In step 104, it is determined whether or not the temperature of the DPF 14 is equal to or lower than the first target upper limit value (predetermined temperature) T21 being regenerated (DPF temperature ≦ T21). When the DPF temperature is equal to or lower than the first target upper limit value T21 (DPF temperature ≦ T21), the process proceeds to step 105. On the other hand, if the first target upper limit value T21 is exceeded (DPF temperature> T21), the routine proceeds to step 108 described later.

  In step 105, it is determined whether or not the time t during which the exhaust air-fuel ratio is controlled to the target value has passed the reference time tDPFreg1 (t> tDPFreg1). If it is determined that the reference time tDPFreg1 has elapsed (t> tDPFreg1), the process proceeds to step 106. This reliably burns and removes the PM deposited on the DPF 14. On the other hand, if it is determined that the reference time tDPFreg1 has not elapsed (t ≦ tDPFreg1), the process ends.

In step 106, the reg flag in the DPF regeneration mode is set to zero. Thus, after the regeneration of the DPF 14 is completed, the operation of the combustion control including the preliminary combustion and the main combustion is switched to the operation by the normal combustion, and the heating of the DPF 14 is stopped.
In step 107, the rec flag in the melting prevention mode is set. As a result, when the DPF regeneration mode is finished, but PM remains in the DPF 14, the exhaust air-fuel ratio is suddenly increased to prevent the DPF 14 from burning at once and the DPF 14 from being melted.

If the routine proceeds from step 103 to step 113, the fuel injection timing for main combustion is retarded (retarded) at step 113. Thus, when the DPF temperature falls below the lower limit value T22 during DPF regeneration (DPF temperature <T22), the exhaust gas temperature is raised by retarding the fuel injection timing of the predetermined main combustion.
In step 114, a torque drop is caused by the retarded amount of the fuel injection timing. Therefore, the target torque correction coefficient is calculated from the torque correction coefficient calculation map corresponding to the fuel injection timing of the main combustion shown in FIG. Then, the torque is corrected (increased), and the process ends.

  When the routine proceeds from step 104 to step 108, the temperature of the DPF 14 is not more than the second target upper limit value (predetermined temperature) T23 being regenerated at step 108 (DPF temperature ≦ T23: T21 <DPF temperature ≦ T23). It is determined whether or not there is. This is for determining whether or not the combustion by the preliminary combustion and the main combustion can be continued according to the DPF temperature. When the DPF temperature is equal to or lower than the second target upper limit value T23 (DPF temperature ≦ T23), the process proceeds to step 109. On the other hand, if the second target upper limit value T23 is exceeded (DPF temperature> T23), the routine proceeds to step 112 described later.

When the routine proceeds from step 108 to step 109, the fuel injection timing for main combustion is advanced at step 109. As a result, the fuel injection timing of the predetermined amount of main combustion is advanced, the exhaust temperature is lowered, and the temperature of the DPF 14 is lowered.
In step 110, the target torque correction coefficient is calculated from the torque correction coefficient calculation map corresponding to the fuel injection timing of the main combustion shown in FIG. 23 according to the advance amount, thereby correcting the torque, and the process proceeds to step 111.

  In step 111, it is determined whether or not the smoke concentration in the exhaust gas detected by the smoke concentration sensor 18 is equal to or lower than the upper limit value (predetermined value) SMOKE (SMOK ≧ smoke concentration). This is for determining whether or not to continue the combustion by the preliminary combustion and the main combustion according to the exhaust component (smoke concentration). When the smoke concentration in the exhaust gas exceeds the upper limit value SMOKE (SMOK <smoke concentration), the routine proceeds to step 112 described later. On the other hand, if it is equal to or less than the upper limit (SMOK ≧ smoke density), the process is terminated.

  When the routine proceeds from step 108 or 111 to step 112, it is determined that the continuation of the combustion control by the preliminary combustion and the main combustion is inappropriate, and the rec flag in the melting prevention mode is set at step 112, and the routine proceeds to step 401 of FIG. move on. Thereby, the continuation of the combustion control by the preliminary combustion and the main combustion is stopped, and the abnormal rise of the DPF temperature and the deterioration of the smoke are prevented. Then, when the exhaust air-fuel ratio is suddenly increased, the DPF 14 is burnt at once, so that the DPF 14 is prevented from being melted.

Next, the flowchart of the sulfur poisoning release mode in FIG. 4 will be described.
In step 201, as in step 101 of FIG. 3 described above, since the sulfur poisoning release request is made in a high exhaust temperature and rich atmosphere, the combustion control is switched to preliminary combustion and main combustion.
In step 202, the amount of sulfur deposited on the NOx trap catalyst 13 reaches a predetermined amount, so the exhaust air-fuel ratio is controlled to stoichiometric. Then, the intake air is throttled (the opening degree of the intake throttle valve 6 is reduced) so as to reach the target air-fuel ratio so that the target intake air amount (the air amount that satisfies λ = 1) shown in FIG. When the actual air-fuel ratio deviates from the target air-fuel ratio, the exhaust air-fuel ratio is adjusted by the intake throttle valve 6 and the EGR valve 19. Thus, similarly to step 102, the intake air amount and the fuel injection amount are corrected according to the fuel injection timing of the main combustion.

In step 203, it is determined whether or not the temperature of the NOx trap catalyst 13 is higher than the target lower limit temperature T41 (predetermined value) during the release of sulfur (catalyst temperature> T41). For example, when a Ba-based NOx trap catalyst is used as the NOx trap catalyst 13, it is necessary to make the temperature higher than 600 ° C. in a rich to stoichiometric atmosphere, and therefore the predetermined temperature T41 is set to 600 ° C.
When the catalyst temperature is higher than the target lower limit temperature T41 during the release of sulfur (catalyst temperature> T41), the routine proceeds to step 204. On the other hand, if the catalyst temperature is equal to or lower than the target lower limit temperature T41 during release of sulfur (catalyst temperature ≦ T41), the process proceeds to step 216 described later.

  In step 204, it is determined whether or not the temperature of the NOx trap catalyst 13 is higher than the first target upper limit temperature T42 (predetermined value) during the release of sulfur (catalyst temperature> T42). When the catalyst temperature is higher than the first target upper limit temperature T42 during the release of sulfur (catalyst temperature> T42), the process proceeds to step 211 described later. On the other hand, if the catalyst temperature is equal to or lower than the first target upper limit temperature T42 during release of sulfur (catalyst temperature ≦ T42), the routine proceeds to step 205.

In step 205, it is determined whether or not the sulfur poisoning release processing has been performed at a target air-fuel ratio and bed temperature for a predetermined time tdesul (t> tdesul). If the sulfur poisoning release process has been performed (t> tdesul), the process proceeds to step 206. On the other hand, when the sulfur poisoning release process is not performed (t ≦ tdesul), the process ends.
In step 206, since the sulfur poisoning release is completed, the stoichiometric operation is released.

In step 207, the rec flag in the melting prevention mode is set (rec flag = 1). As a result, although the sulfur poisoning release mode is completed, when PM is accumulated in the DPF 14 under such a high temperature condition, if the exhaust air-fuel ratio is suddenly increased, the PM burns at once in the DPF 14. Prevent melting damage.
In step 208, the desul flag is set to 0 because the sulfur poisoning release mode is completed.

In step 209, since the sulfur poisoning release mode is completed, the amount of sulfur deposition on the NOx trap catalyst 13 is reset (the amount of sulfur deposition on the catalyst 13 = 0).
In step 210, the NOx regeneration request flag rq_sp flag is set to 0 (rq_sp flag = 0). This is because the NOx regeneration is performed when the NOx trap catalyst 13 is exposed to the stoichiometric air-fuel ratio for a long time by releasing the sulfur poisoning. And when the request | requirement of NOx reproduction | regeneration has come out, NOx reproduction | regeneration is also performed simultaneously by performing sulfur poisoning cancellation | release.

Further, when the process proceeds from step 203 to step 216, the same processing as the above-described step 113 and step 114 in FIG. 3 is performed. That is, in step 216, since the temperature of the NOx trap catalyst 13 is equal to or lower than the target lower limit temperature T41 during release of the sulfur (catalyst temperature ≦ T41), the fuel injection timing of the predetermined amount of main combustion is retarded (retarded) and the exhaust temperature is increased. To raise.
In step 217, the target torque correction coefficient is calculated from the torque correction coefficient calculation map corresponding to the fuel injection timing of the main combustion shown in FIG. 23 according to the retard amount, and torque correction (increase correction) is performed thereby, processing. Exit.

  When the routine proceeds from step 204 to step 211, whether the temperature of the NOx trap catalyst 14 is equal to or lower than the second target upper limit value (predetermined temperature) T43 during the release of sulfur in step 211 (catalyst temperature ≦ T43: T41 <T43 ) Determine whether or not. This is for determining whether or not to continue the combustion by the preliminary combustion and the main combustion according to the temperature of the NOx trap catalyst 13. When the catalyst temperature is equal to or lower than the second target upper limit value T43 (catalyst temperature ≦ T43), the process proceeds to step 212. On the other hand, if the second target upper limit value T43 is exceeded (catalyst temperature> T43), the routine proceeds to step 215 described later.

  When the process proceeds to step 212, the same processing as step 109, step 110, and step 111 in FIG. 3 is performed. That is, in step 212, the fuel injection timing of the main combustion is advanced. As a result, the fuel injection timing of the predetermined amount of main combustion is advanced, the exhaust temperature is lowered, and the temperature of the NOx trap catalyst 13 is lowered. In step 213, the target torque correction coefficient is calculated from the torque correction coefficient calculation map corresponding to the fuel injection timing of the main combustion shown in FIG. 23 according to the advance amount, and torque correction (decrease correction) is performed thereby, step 214 Proceed to

  In step 214, it is determined whether or not the smoke concentration in the exhaust gas detected by the smoke concentration sensor 18 is equal to or lower than the upper limit value (predetermined value) SMOKE (SMOK ≧ smoke concentration). This is for determining whether or not to continue the combustion by the preliminary combustion and the main combustion according to the exhaust component (smoke concentration). When the smoke concentration in the exhaust gas exceeds the upper limit value SMOKE (SMOK <smoke concentration), the process proceeds to step 215 described later. On the other hand, if it is equal to or less than the upper limit (SMOK ≧ smoke density), the process is terminated.

When the process proceeds from step 211 or step 214 to step 215, the same process as step 112 in FIG. 3 is performed. That is, in step 215, it is determined that the continuation of the combustion control by the preliminary combustion and the main combustion is inappropriate, and in step 215, the reclamation prevention mode rec flag is set and the process proceeds to step 401 in FIG.
Next, processing when performing combustion switching to perform NOx desorption purification by rich spike will be described using the flowchart of FIG.

In step 301, combustion control is switched.
In step 302, the air-fuel ratio is controlled to a predetermined target air-fuel ratio for performing rich spike. The target air-fuel ratio is realized by adjusting the intake air amount to the intake air amount shown in FIG. As a result, when rich spike control is executed, the reducing agent is supplied to the exhaust gas upstream from the NOx trap catalyst 13 at an appropriate timing in a short cycle to temporarily reduce the air-fuel ratio of the exhaust gas flowing into the NOx trap catalyst 13. In step 303, the time during which the rich spike control is performed (rich condition) has passed for a predetermined time tspike (t> tspike) or not. Determine whether. If the predetermined time tspike has elapsed (t> tspike), the process proceeds to step 304. On the other hand, if the predetermined time tspike has not elapsed (t ≦ tspike), the process is terminated.

In step 304, the spike flag is set to 0 (sp flag = 0). Thus, after the spike is executed from the predetermined time tspike, the rich operation is cancelled.
Next, the melting prevention mode will be described with reference to FIG.
In step 401, the exhaust air / fuel ratio is controlled to a predetermined value or less in order to prevent the DPF 14 from being burnt at a stretch by suddenly increasing the exhaust air / fuel ratio and causing the DPF 14 to melt. At this time, since it is desirable that the exhaust gas temperature is low, the exhaust air-fuel ratio is controlled to a predetermined value by normal lean combustion (combustion shown in FIG. 13) instead of combustion by preliminary combustion and main combustion. Then, when the target intake air amount shown in FIG. 25 is set and the sensor output deviates from the target air-fuel ratio, the target air-fuel ratio is realized by adjusting the intake throttle valve 6 or the EGR valve 19.
In step 402, the temperature of the DPF 14 is detected. If it is difficult to directly detect the temperature of the DPF 14, the temperature of the DPF 14 is estimated from a parameter (for example, exhaust gas temperature) instead.

In step 403, it is determined whether or not the temperature of the DPF 14 is lower than a predetermined temperature T3 (DPF temperature <T3). Thereby, it is determined whether or not the DPF temperature is lower than a temperature T3 at which the rapid oxidation of PM does not start (DPF temperature <T3).
When the temperature of the DPF 14 is lower than the predetermined temperature T3 (DPF temperature <T3), the process proceeds to step 404. As a result, even if the oxygen concentration is the same as the atmosphere, the melting loss of the DPF 14 can be avoided.

On the other hand, when the temperature of the DPF 14 is equal to or higher than the predetermined temperature T3 (DPF temperature ≧ T3), the process is terminated while the exhaust air-fuel ratio is controlled to be equal to or lower than the predetermined value.
In step 404, the air-fuel ratio control is stopped because there is no risk of melting of the DPF 14.
In step 405, the rec flag in the melting prevention mode is set to zero. Thereby, the melting prevention mode is terminated.

Next, the priority order when one or both of the DPF regeneration request, NOx regeneration, and sulfur poisoning release requests occur simultaneously will be described with reference to FIG.
In step 501, it is determined whether or not the sulfur accumulation amount of the NOx trap catalyst 13 is less than a predetermined amount S1 that requires sulfur poisoning release (sulfur accumulation amount <S1). If it is less than the predetermined amount S1 (sulfur deposition amount <S1), the routine proceeds to step 502. On the other hand, if the amount is equal to or greater than the predetermined amount S1 (sulfur deposition amount ≧ S1), the process proceeds to the process of FIG.

In step 502, the presence / absence of a NOx regeneration request (spike request) rq_sp is determined. If there is no NOx regeneration request (rq_sp = 0), the process proceeds to step 503. On the other hand, if there is a NOx regeneration request (rq_sp = 1), the process proceeds to step 506.
In step 503, it is determined whether or not the NOx accumulation amount is less than a predetermined amount NOx1 required for NOx regeneration after the DPF regeneration request is made (NOx accumulation amount <NOx1). If it is less than the predetermined amount NOx1 (NOx accumulation amount <NOx1), the routine proceeds to step 504. On the other hand, if the amount is equal to or greater than the predetermined amount NOx1 (NOx accumulation amount ≧ NOx1), the process proceeds to the process of FIG.

  In step 504, it is determined whether or not it is a DPF regeneration, SOx regeneration (sulfur poisoning release) possible region. These reproducible areas are determined based on the current rotational speed Ne and load of the engine 1 using the DPF regeneration and SOx reproducible area map shown in FIG. If it is a reproducible area, the process proceeds to step 505. On the other hand, if it is not in the reproducible area, the process is terminated.

In step 505, the reg flag in the playback mode is set to 1. As a result, in the state where there is a DPF regeneration request, there is no NOx regeneration or SOx regeneration request, and the region is in the DPF regeneration possible region, so that the process shifts to DPF regeneration.
If the process proceeds from step 502 to step 506, it is determined in step 506 whether the low NOx condition is satisfied. This is because both the DPF regeneration request and the NOx regeneration request are issued, so that it is determined whether the engine operating condition is a condition with a small NOx emission amount, for example, a steady condition.

  If it is a low NOx condition, the process proceeds to step 507. If this is a condition where the amount of NOx emission is small, even if the regeneration of the NOx trap catalyst 13 is somewhat delayed, the exhaust of the tailpipe is hardly deteriorated. Therefore, the regeneration of the DPF 14 that greatly affects the operability is prioritized. This is for giving priority to NOx regeneration in order to prevent deterioration of the exhaust of the tail pipe under conditions where the amount of NOx emission is large, such as acceleration conditions.

On the other hand, if the low NOx condition is not satisfied, the process proceeds to step 508, where the sp flag is set to 1 (sp flag = 1), and the process ends.
In Step 507, it is determined whether or not the bed temperature Tbed of the DPF 14 is higher than a predetermined temperature T3 (Tbed> T3). Thereby, it is determined whether or not to give priority to the regeneration of NOx.

  When the DPF bed temperature Tbed is higher than the predetermined temperature T3 (Tbed> T3), the process proceeds to step 504. On the other hand, if the temperature is equal to or lower than the predetermined temperature T3 (Tbed ≦ T3), the process proceeds to step 508. This is the temperature T3 or less at which the NOx trap catalyst 13 supported on the DPF 14 is activated when starting to raise the temperature of the DPF 14 (Tbed ≦ T3). Since it takes time to do so, there is a concern about deterioration of NOx in the tailpipe during the temperature rise, so that NOx regeneration is given priority.

In step 508, since NOx regeneration is prioritized, a spike flag is set (sp flag = 1), and the process proceeds to NOx regeneration.
Next, SOx regeneration and NOx regeneration priority processing when an SOx regeneration request and NOx regeneration request occur simultaneously will be described with reference to the flowchart of FIG.
In step 601, it is determined whether the amount of PM deposited on the DPF 14 is less than a predetermined amount PM1 (PM deposition amount <PM1). If it is less than the predetermined amount PM1 (PM deposition amount <PM1), the process proceeds to step 602. On the other hand, when the amount is equal to or greater than the predetermined amount PM1 (PM accumulation amount ≧ PM1), as shown in step 701 of FIG. 9, the rq_DPF flag is set to 1 and the DPF 14 is regenerated. As a result, even if an SOx regeneration request is issued, DPF regeneration has priority.

In step 602, it is determined whether or not the bed temperature Tbed of the NOx trap catalyst 13 is higher than a predetermined temperature T1 (Tbed> T1). The predetermined temperature T1 is a temperature at which the supported NOx trap catalyst 13 is suitable for SOx regeneration.
When the bed temperature Tbed of the NOx trap catalyst 13 is higher than the predetermined temperature T1 (Tbed> T1), the process proceeds to step 603. On the other hand, if the temperature is equal to or lower than the predetermined temperature T1 (Tbed ≦ T1), the process proceeds to step 605. This is for giving priority to NOx regeneration since it takes time to reach the reproducible temperature even when the temperature rise is started, and there is a concern about deterioration of the tail pipe NOx during the temperature rise.

  In step 603, it is determined whether or not it is a DPF / SOx regeneration (sulfur poisoning release) possible region. These reproducible areas are determined based on the current engine speed Ne and the load by using the DPF regeneration and SOx reproducible area map shown in FIG. If it is a reproducible area, the process proceeds to step 604. On the other hand, when it is not in the reproducible area (when it is in the non-reproducible area), the process is terminated.

In step 604, a desul flag is set (desul flag = 1), and the process ends. This is because there is neither a spike request nor a DPF regeneration request, and all conditions that the bed temperature is equal to or higher than a predetermined value and a recyclable operation region are satisfied, so that the operation shifts to SOx regeneration.
If the process proceeds from step 602 to step 605, the presence / absence of a spike request is determined in step 605. If there is no spike request (rq_sp = 0), the process proceeds to step 606. As a result, even if an SOx regeneration request is issued, if the temperature of the NOx trap catalyst 13 is equal to or lower than the predetermined temperature T1 (NOx trap catalyst temperature ≦ T1), NOx regeneration of the tail pipe is deteriorated by giving priority to NOx regeneration. Suppress.

On the other hand, if there is a spike request in step 605 (rq_sp = 1), the process proceeds to step 607, a NOx regeneration flag is set (sp flag = 1), and the process proceeds to NOx regeneration. Thereby, although the SOx regeneration request is issued, it is determined that NOx regeneration is prioritized.
In step 606, after the SOx regeneration request is issued, it is determined whether or not the NOx accumulation amount is less than a predetermined amount NOx1 that requires NOx regeneration (NOx accumulation amount <NOx1). If the NOx accumulation amount is less than the predetermined amount NOx1 (NOx accumulation amount <NOx1), the process is terminated. On the other hand, if the predetermined amount is NOx1 or more (NOx accumulation amount ≧ NOx1), the rq_sp flag is set (rq_sp flag = 1) in step 901 shown in FIG. 11, and a NOx regeneration request is issued.

Next, a process for warming up the NOx trap catalyst 13 using the combustion control by the preliminary combustion and the main combustion in Step 2 of FIG. 2 will be described with reference to FIG.
In step 1001, it is determined in step 2 whether or not the NOx trap catalyst 13 can be warmed up. This is because the temperature of the NOx trap catalyst 13 is determined to be equal to or lower than the activation temperature T5 (catalyst temperature ≦ T5), and it is necessary to raise the temperature of the NOx trap catalyst 13 by the warm-up promotion operation. As shown in FIG. 26, this determination is made based on whether or not the DPF and SOx reproducible region is based on the engine speed Ne and the load.

If the warm-up promotion operation is possible, the process proceeds to step 1002. On the other hand, if the warm-up promotion operation is not possible, the process is terminated.
In step 1002, the combustion is switched to the preliminary combustion and the main combustion. Thus, by performing preliminary combustion, the in-cylinder temperature near the compression top dead center is raised, and the ignition limit (retard limit) of main combustion is delayed. And exhaust temperature becomes high temperature and warming-up of the NOx trap catalyst 13 is accelerated | stimulated.

  In step 1003, it is determined whether or not the temperature of the NOx trap catalyst 13 has become higher than the activation temperature (predetermined temperature) T5 (catalyst temperature> T5). This is to determine whether or not the combustion by the preliminary combustion and the main combustion can be continued. If the temperature is higher than the predetermined temperature T5 (catalyst temperature> T5), the process proceeds to step 1004. On the other hand, when the temperature is equal to or lower than the predetermined temperature T5 (catalyst temperature ≦ T5), the process is terminated and the combustion control by the preliminary combustion and the main combustion is continued.

In step 1004, the warm-up promotion operation is canceled. Since it was determined that the NOx trap catalyst 13 was sufficiently warmed up, that is, the NOx trap catalyst 13 was activated, the operation by the combustion by the preliminary combustion and the main combustion was switched to the operation by the normal combustion, This is to end the warm-up of the NOx trap catalyst 13.
According to the present embodiment, in the internal combustion engine (engine) 1 provided with the exhaust purification device (NOx trap catalyst 13, DPF 14) in the exhaust passage 12, the exhaust temperature increase request or the When at least one of the rich operation requests below stoichiometric is present, main combustion for generating main torque and at least one preliminary combustion performed prior to main combustion are performed (steps 101, 201, 1002), Pre-combustion controls fuel injection so that at least one occurs near top dead center, and main combustion controls fuel injection so that it starts after pre-combustion ends, while Detecting and prohibiting the combustion by the preliminary combustion and the main combustion by at least one of the states. For this reason, by increasing the in-cylinder temperature by the pre-combustion and starting the main combustion after the pre-combustion is completed, the main combustion is mainly premixed combustion, and it is possible to realize an increase in exhaust temperature and a rich air-fuel ratio. Furthermore, since prohibition of combustion by preliminary combustion and main combustion is optimally performed according to each state of the engine 1, overheating of the NOx trap catalyst 13 and the DPF 14 and deterioration of smoke can be prevented.

  Further, according to the present embodiment, as the states of the engine 1, the temperature of the exhaust purification device (NOx trap catalyst 13, DPF 14) is detected, and preliminary combustion and main combustion are performed according to the detected temperatures of the exhaust purification devices 13, 14. It is determined whether combustion can be continued due to combustion (steps 108, 211, 1003). For this reason, the continuation of combustion by the preliminary combustion and the main combustion can be determined according to the temperatures of the NOx trap catalyst 13 and the DPF 14, and the NOx trap catalyst 13 and the DPF 14 can be prevented from being overheated.

Further, according to the present embodiment, the exhaust component is detected as each state of the engine 1, and in accordance with the detected exhaust component, it is determined whether or not the combustion by the preliminary combustion and the main combustion can be continued (steps 111 and 214). 1003), which can mainly prevent deterioration of exhaust components.
Further, according to the present embodiment, since the exhaust component to be detected is smoke (steps 111 and 214), the deterioration of smoke can be mainly prevented.

  Further, according to the present embodiment, the fuel injection amount for the preliminary combustion is the fuel injection amount necessary for the in-cylinder temperature at the time of fuel injection for the main combustion to exceed the temperature at which self-ignition is possible (steps 101, 201, 1002). ). For this reason, the in-cylinder temperature is raised by fuel injection at the time of preliminary combustion, the in-cylinder temperature when fuel injection for main combustion is performed can be maintained high, and combustion for each cycle can be stabilized. .

Further, according to the present embodiment, the combustion start timing of the main combustion is a timing that is separated from the combustion start timing of the preliminary combustion by 20 degrees or more in crank angle (steps 101, 201, 1002). For this reason, the interval from the start of the pre-combustion to the start of the main combustion can be made longer than a predetermined period, and the deterioration of the combustion of the main combustion can be suppressed and the deterioration of the smoke can be prevented.
Further, according to the present embodiment, the end time of the main combustion is a time away from the compression top dead center by 50 degrees or more in crank angle (steps 101, 201, 1002). For this reason, by making the end timing of the main combustion as late as possible, the combustion of the main combustion becomes slow and the deterioration of the combustion noise can be suppressed.

  Further, according to the present embodiment, at least one of the fuel injection amount or the fuel injection timing for the preliminary combustion is changed according to the compression end temperature (steps 101, 201, 1002). For this reason, the fuel injection for the preliminary combustion can be changed to the minimum necessary amount according to the compression end temperature in each operating condition, and the preliminary combustion can be stabilized and the preliminary combustion is started before the main combustion starts. Can be terminated reliably.

According to the present embodiment, the main combustion controls the exhaust gas temperature by changing the fuel injection timing (steps 101, 201, 1002). For this reason, the exhaust temperature can be changed freely by changing the combustion end timing of the main combustion.
Further, according to the present embodiment, the main combustion is controlled so that the torque generated by the engine 1 is constant (steps 101, 201, 1002). For this reason, by correcting the fuel injection amount according to the fuel injection timing of the main combustion, the target exhaust temperature or the exhaust atmosphere can be obtained, and torque fluctuation at the time of switching the combustion and controlling the exhaust temperature can be suppressed. .

  In addition, according to the present embodiment, the exhaust purification device includes the filter (DPF) 14 that collects exhaust particulates, and when there is a request for raising the exhaust gas temperature or a rich operation less than stoichiometric, the filter 14 has a predetermined amount PM1. This is the time when exhaust particulates (PM) are deposited (step 12) and the exhaust particulates are brought to a temperature at which they are self-oxidized. For this reason, the timing for performing the combustion control can be changed according to the operating conditions (engine speed Ne, fuel injection amount Q, etc.) of the engine 1. And when the regeneration time of DPF14 comes, it can switch to the combustion control by preliminary combustion and main combustion, can implement | achieve high exhaust temperature with low smoke, and can implement | achieve regeneration of DPF14 stably.

  Further, according to the present embodiment, the exhaust purification device includes the NOx trap catalyst 13 that traps NOx during the lean operation. When there is a request for a rise in exhaust temperature or a rich operation request that is less than the stoichiometric condition, the NOx trap catalyst 13 traps the NOx trap catalyst 13. It is time to desorb and purify NOx. For this reason, rich spike can be performed using combustion control by preliminary combustion and main combustion, and the purification performance of the NOx trap catalyst 13 can be maintained high.

  Further, according to the present embodiment, the exhaust purification device includes the NOx trap catalyst 13 that traps NOx during the lean operation. When there is a request for a rise in exhaust temperature or a rich operation request that is less than the stoichiometric condition, the NOx trap catalyst 13 traps the NOx trap catalyst 13. It is time to purify the sulfur content (SOx). For this reason, sulfur poisoning release (SOx regeneration) can be performed using combustion control by preliminary combustion and main combustion, and it is possible to achieve both low smoke and high exhaust temperature and rich conditions, and the performance of the NOx trap catalyst 13. To make the best use of.

  Further, according to the present embodiment, the exhaust purification device includes the NOx trap catalyst 13 that traps NOx during the lean operation. When there is a request for a rise in exhaust temperature or a rich operation request that is less than the stoichiometric condition, the NOx trap catalyst 13 is cold. (Step 2), when the NOx trap catalyst 13 is rapidly warmed up. For this reason, combustion control by preliminary combustion and main combustion can be used when the NOx trap catalyst 13 is cold, and the NOx trap catalyst 13 can be brought to the activation temperature in a short time.

Next, a second embodiment of the present invention will be described.
FIG. 27 is a configuration diagram of a control device for the internal combustion engine (diesel engine) 1 according to the present embodiment.
The configuration of the control device for the engine 1 in this embodiment is basically the same as the control device for the engine 1 shown in FIG. 1, but a fuel property determination device is installed to estimate the ignition delay period of fuel. Has been.

  That is, an air flow meter 7 serving as intake air amount detection means is provided at an upstream position of the intake compressor 3a (on the outlet side of an air cleaner not shown). A water temperature sensor 31 that detects the cooling water temperature is attached to an appropriate position of the engine 1 as a representative of the temperature of the engine 1. Further, a cylinder discrimination crank angle sensor 33, a pressure sensor 34 for detecting the fuel pressure in the common rail 14, and a temperature sensor 35 for detecting the fuel temperature are provided.

  Signals from these sensors are input to the ECU 25, and each process is performed. This process will be described. Since the basic processing of the second embodiment is the same as that of the first embodiment, the difference from the first embodiment (combustion control main flowchart, step 2 fuel property detection control routine) Only the DPF regeneration mode flowchart and sulfur poisoning release mode flowchart) will be described.

FIG. 28 is a main flowchart of combustion control, in which step 20 is newly added between step 1 and step 2.
In step 1, various sensor signals are read, and the operating state of the engine 1 calculated based on these signals, that is, the engine speed Ne, the accelerator opening APO, the catalyst temperature, the exhaust pressure on the inlet side or the outlet side of the DPF 14, DPF Read temperature, etc. Further, the load Q calculated from a map using the engine speed Ne and the accelerator opening APO as parameters is read. The load Q may be replaced with a fuel injection amount, an intake air amount, or the like.

In step 20, for example, as in Japanese Patent Application No. 2003-031832, a fuel property (cetane number) is searched, and a fuel ignition delay period is detected from this. This is because in this embodiment, the fuel property is detected and the ignition delay period is estimated. Specifically, this is performed by a subroutine shown in FIG.
Here, the fuel property is affected by the cetane number contained in the fuel (light oil) used in the diesel engine 1 and is ignited if the cetane number is high (that is, if it is light and the actual specific gravity Gfuel of the fuel described later is small). Although the delay period is shortened, if the cetane number is low (heavy and the actual specific gravity Gfuel is large), the ignition delay period is long.

FIG. 29 is an ignition delay period estimation routine.
In step 2001, based on the signal Qa of the air flow meter 7 for detecting the intake air amount, table data of a predetermined intake air amount Qair stored in advance in the ROM of the ECU 25 is searched using the value of the signal Qa as a parameter. Then, the process proceeds to Step 2002.
In step 2002, a fuel injection amount (fuel supply amount) Qmain set using the engine speed Ne and the accelerator opening APO as parameters is obtained by searching a predetermined map stored in the ROM of the ECU 25 in advance. Then, the process proceeds to Step 2003.

  Even if the fuel injection amount (fuel supply amount) Qmain is not the above-described method, the fuel injection period Mperiod of the fuel injection device set using the engine speed Ne and the load Q as parameters is stored in the ROM of the ECU 25 in advance. The fuel injection amount (fuel supply amount) Qmain, which is obtained by searching a predetermined map stored and set with the fuel injection period Mperiod and the common rail pressure PCR as parameters, is stored in advance in the ROM of the ECU 25. You may be made to search for the map of.

In step 2003, based on the signal O2 of the air-fuel ratio sensor 16, the table data of the actual air-fuel ratio AFreal stored in advance in the ROM of the ECU 25 is retrieved using the value of the signal O2 as a parameter. Then, the process proceeds to Step 2004.
In step 2004, it is determined whether or not the conditions are suitable for detecting the fuel property.
For example, in general, an automobile engine is generally provided with an exhaust gas recirculation device including an EGR valve 19 or the like for NOx reduction. Since the fuel ratio shifts to the rich side, it is necessary to correct the exhaust gas recirculation in order to accurately obtain the actual air fuel ratio. Accordingly, since there is a concern that the detection accuracy of the actual air-fuel ratio deteriorates due to the correction, it is desirable to issue the actual air-fuel ratio detection command only in a region where exhaust gas recirculation is stopped.

If the detection condition is not suitable in step 2004, the process proceeds to step 3 without detecting the fuel property.
If the detection condition is suitable in step 2004, the process proceeds to step 2005, and the actual fuel supply weight Gmain is obtained based on the intake air flow rate Qair obtained in step 2001 and the actual air-fuel ratio AFreal obtained in step 2003. Specifically, the intake air flow rate Qair is divided by the actual air-fuel ratio AFreal to obtain the actual fuel supply weight Gmain (Gmain = Qair ÷ AFreal). Then, the actual specific gravity G fuel is determined based on the determined actual fuel supply weight Gmain and the fuel injection amount (fuel supply amount) Qmain determined in step 2002. Specifically, the actual fuel supply weight Gmain is divided by the fuel injection amount (fuel supply amount) Qmain to obtain an actual specific gravity Gfuel (Gfuel = Gmain ÷ Qmain). Then, the process proceeds to Step 2006.

  In step 2006, standard specific gravity (reference temperature, for example, specific gravity at a standard temperature of 20 ° C.) Gstd is obtained from the actual specific gravity Gfuel and the fuel temperature TF. Specifically, a map of the standard specific gravity Gstd stored in advance in the ROM of the ECU 25 is searched using the actual specific gravity Gfuel and the fuel temperature TF as parameters, and a corresponding value is obtained. Then, the process proceeds to Step 2007.

In step 2007, using the standard specific gravity Gstd as a parameter, the fuel property of light oil, for example, table data of the cetane number Cnumber, stored in advance in the ROM of the ECU 25 is searched. The fuel properties tend to be higher in density (heavy) and lower in cetane number as the standard specific gravity Gstd is higher.
In step 2008, the ignition delay period is estimated from the retrieved fuel property (cetane number Cnumber). This ignition delay period tends to be longer as the fuel property is heavier, that is, as the cetane number is lower.

In this flowchart, the fuel property is detected and the fuel ignition delay period is estimated. However, a fuel injection valve lift sensor is provided to detect the start of lift of the fuel injection valve, and an in-cylinder pressure sensor of the engine 1 is provided. Fuel ignition may be detected, and the fuel ignition delay period may be obtained from the detected time difference.
Referring to FIG. 28 again, the same processing as in FIG. 2 is performed.

That is, in step 2, it is determined whether or not the NOx trap catalyst 13 is in a warm-up state (active state).
In step 3, the amount of NOx trapped and deposited on the NOx trap catalyst 13 is calculated. In step 4, the amount of sulfur (SOx) deposited on the NOx trap catalyst 13 is calculated. The amount of PM collected and deposited is detected.

In steps 6 to 11, it is determined whether or not the reg flag, desul flag, sp flag, rec flag, rq_DPF flag, and rq_desul flag are set.
In step 12, it is determined whether the PM accumulation amount of the DPF 14 calculated in step 5 has reached a predetermined amount PM1 that requires regeneration of the DPF 14 (PM accumulation amount <PM1), that is, whether the DPF regeneration timing has come.

In step 13, whether or not the sulfur accumulation amount (SOx amount) of the NOx trap catalyst 13 calculated in step 4 has reached a predetermined amount S1 and the regeneration time has come (sulfur accumulation amount <S1), that is, sulfur poisoning release. The necessity of (SOx regeneration request) is determined.
In step 14, it is determined whether the NOx accumulation amount of the NOx trap catalyst 13 calculated in step 3 has reached a predetermined amount NOx1 and the regeneration time has come (NOx accumulation amount <NOx1), that is, whether or not NOx regeneration is necessary.

Next, the processing when the DPF regeneration mode flag is present in step 6 (reg flag = 1), that is, DPF regeneration (melting prevention) when the NOx trap catalyst 13 is warmed up will be described with reference to the flowchart of FIG. To do. In this embodiment, steps 120 and 121 are newly added to the flowchart of FIG.
In step 120, an upper limit value RPMbase (predetermined value) and a load (fuel injection amount) of the engine speed for determining permission to switch from the operation by the normal lean combustion to the operation by the combustion control by the preliminary combustion and the main combustion described above. The upper limit value Q1base (predetermined value) is corrected using the coefficients a and b shown in FIGS. 32 and 33 in accordance with the ignition delay period detected from the fuel properties in the flowchart of FIG. For this, the correction upper limit value RPM of the engine speed and the correction upper limit value Q1 of the load Q are obtained by the following equations, respectively.

RPM = RPMbase × a
Q1 = Q1base × b
Here, FIG. 32 is a table for calculating the engine rotation speed upper limit correction coefficient a. When the fuel ignition delay period is long, the correction coefficient a is small, and when the ignition delay period is short, the correction coefficient a is large. Show. FIG. 33 is a table for calculating the fuel injection amount upper limit correction coefficient b, which shows that the correction coefficient b is small when the fuel ignition delay is long, and the correction coefficient b is large when the ignition delay period is short.

  32 and 33 are for correcting a region in which switching from normal lean combustion to operation by preliminary combustion and main combustion combustion is permitted in accordance with the fuel ignition delay period. That is, the combustion switching permission region shown in FIG. 34 is corrected according to the ignition delay period estimated by the fuel property (cetane number). When the ignition delay period is long, that is, when the cetane number is low, the preliminary combustion and the main combustion This is because the permitted region of combustion due to combustion is shifted to the low rotation speed and low load region.

  In step 121, permission to switch to operation in combustion control by preliminary combustion and main combustion is determined. In this determination, as shown in FIG. 34, the engine rotational speed Ne is equal to or less than the correction upper limit RPM (Ne ≦ RPM) of the engine rotational speed that permits switching to the operation in the combustion control by the preliminary combustion and the main combustion. The load Q is determined based on whether or not the load is not more than the correction upper limit Q1 (Q ≦ Q1) that permits switching to the operation in the combustion control by the preliminary combustion and the main combustion.

This is because when the engine speed becomes higher than the upper limit value RPM, the crank angle from the preliminary combustion to the main combustion is the same, but since this time is shortened, the preliminary combustion and the main combustion overlap, and the main combustion On the other hand, if the load Q becomes higher than the upper limit value Q1, the smoke is deteriorated even in the combustion by the preliminary combustion and the main combustion.
When the operation state is within a predetermined region (Ne ≦ RPM and Q ≦ Q1), the process proceeds to Step 101.

On the other hand, when either one of the engine speed Ne or the load Q does not satisfy the condition, the process is terminated without switching to the operation in the combustion control by the preliminary combustion and the main combustion. In this case, the process waits until the predetermined area in Step 121 is reached (Ne ≦ RPM and Q ≦ Q1).
Note that the determination of permission to switch to the operation in the combustion control by the preliminary combustion and the main combustion may be performed by replacing the load Q with the accelerator opening APO or the fuel injection amount.

In step 101, since the sulfur poisoning release request is made in a high exhaust temperature and rich atmosphere, the combustion is switched from the normal lean combustion to the operation by the combustion by the preliminary combustion and the main combustion.
In step 102, the exhaust air-fuel ratio is controlled to a target value.
In step 103, it is determined whether or not the temperature of the DPF 14 is equal to or higher than a target lower limit value (predetermined temperature) T22 during regeneration (DPF temperature ≧ T22). DPF temperature is the target lower limit value T22 or more (
If DPF temperature ≧ T22), the routine proceeds to step 104. On the other hand, when the DPF temperature is less than the target lower limit value T22 (DPF temperature <T22), the fuel injection timing of the main combustion is retarded in step 113, and torque correction is performed in step 114.

  In step 104, it is determined whether or not the temperature of the DPF 14 is equal to or lower than the first target upper limit value (predetermined temperature) T21 being regenerated (DPF temperature ≦ T21). When the DPF temperature is equal to or lower than the first target upper limit value T21 (DPF temperature ≦ T21), the process proceeds to step 105. On the other hand, if the target temperature first upper limit value T21 is exceeded (DPF temperature> T21), the fuel injection timing of the main combustion is advanced in step 109, and torque correction is performed in step 111.

In step 105, it is determined whether or not the time t during which the exhaust air-fuel ratio is controlled to the target value has passed the reference time tDPFreg1 (t> tDPFreg1).
In step 106, the reg flag in the DPF regeneration mode is set to 0, and in step 107, the rec flag in the melting prevention mode is set (rec flag = 1).
Next, the flowchart of the sulfur poisoning release mode in FIG. 31 will be described. In this flowchart, steps 120 and 121 described with reference to FIG. 30 are newly added to the flowchart of FIG.

In step 120, the upper limit value RPMbase (predetermined value) of the engine speed and the upper limit value Q1base (predetermined value) of the fuel injection amount are determined according to the ignition delay period detected from the fuel property in the flowchart of FIG. 32 and the coefficients a and b shown in FIG. 33 are used to determine a correction upper limit value RPM of the engine rotational speed Ne and a correction upper limit value Q1 of the load Q, respectively.
In step 121, permission to switch to operation in combustion control by preliminary combustion and main combustion (Ne ≦ RPM and Q ≦ Q1) is determined.

In step 201, as in step 101 of FIG. 30, the sulfur poisoning release request is made in a high exhaust temperature and rich atmosphere, so the combustion is changed from normal lean combustion to operation by combustion by preliminary combustion and main combustion. Switch.
In step 202, the amount of sulfur deposited on the NOx trap catalyst 13 reaches a predetermined amount, so the exhaust air-fuel ratio is controlled to stoichiometric.

  In step 203, it is determined whether or not the temperature of the NOx trap catalyst 13 is higher than the target lower limit temperature T41 (predetermined value) during the release of sulfur (catalyst temperature> T41). When the catalyst temperature is higher than the target lower limit temperature T41 during the release of sulfur (catalyst temperature> T41), the routine proceeds to step 204. On the other hand, when the catalyst temperature is equal to or lower than the target lower limit temperature T41 during release of sulfur (catalyst temperature ≦ T41), the injection timing of main combustion is retarded (retarded) in step 216, and torque correction is performed in step 217. .

  In step 204, it is determined whether or not the temperature of the NOx trap catalyst 13 is lower than the first target upper limit temperature T42 (predetermined value) during the release of sulfur (catalyst temperature <T42). When the catalyst temperature is lower than the first target upper limit temperature T42 during the release of sulfur (catalyst temperature <T42), the routine proceeds to step 205. On the other hand, when the temperature is equal to or higher than the first target upper limit temperature T42 (catalyst temperature ≧ T42), the fuel injection timing of the main combustion is advanced in step 212, and torque correction is performed in step 213.

In step 205, it is determined whether or not the sulfur poisoning release processing has been performed at a target air-fuel ratio and bed temperature for a predetermined time tdesul (t> tdesul).
Then, the stoichiometric operation is canceled in step 206, the rec flag in the melt prevention mode is set in step 207 (rec flag = 1), and the desul flag is set to 0 because the sulfur poisoning release mode is completed in step 208. Since the sulfur poisoning release mode is completed in step 209, the sulfur accumulation amount on the NOx trap catalyst 13 is reset (sulfur deposition amount on the catalyst 13 = 0), and in step 210, the NOx regeneration request flag rq_sp flag. Is set to 0 (rq_sp = 0).

According to the present embodiment, an operating state is detected as each state of the engine 1, and permission to switch to combustion by preliminary combustion and main combustion is determined according to the detected operating state (step 121). For this reason, combustion switching can be performed according to the operating state, and overheating of the NOx trap catalyst 13 and the DPF 14 and deterioration of smoke can be prevented in advance.
Further, according to the present embodiment, as the operating state, the rotational speed Ne and the load Q of the engine 1 are detected, and permission to switch to combustion by preliminary combustion and main combustion is determined when within the permission region determined by these. (Step 121). Therefore, combustion switching permission can be determined according to the rotational speed Ne and the load Q, and overheating of the NOx trap catalyst 13 and the DPF 14 and deterioration of smoke due to an abnormal increase in exhaust temperature can be prevented.

Further, according to the present embodiment, the permission area is on the low rotation and low load side of the engine 1 (steps 120 and 121, FIG. 34). For this reason, overheating of the NOx trap catalyst 13 and the DPF 14 can be prevented.
In addition, according to the present embodiment, a means for estimating the ignition delay period (step 2008) is provided, and the permission area is corrected according to the ignition delay period (step 120). For this reason, combustion switching permission determination can always be performed appropriately.

Further, according to the present embodiment, when the ignition delay period is long (the cetane number is low), the permission region is narrowed to the low rotation and low load side (Ne ≦ RPM, Q ≦ Q1) (step 120). For this reason, in particular, overheating of the NOx trap catalyst 13 and the DPF 14 can be prevented.
Further, according to the present embodiment, the fuel property detecting means (step 2007) is provided, and the ignition delay period is estimated from the fuel property (step 2008). For this reason, the ignition delay period can be appropriately determined according to the fuel properties.

  Further, according to the present embodiment, the fuel property is determined by detecting the specific gravity Gfuel of the fuel and calculating the cetane number based on the specific gravity Gfuel (steps 2005 to 2007). For this reason, it is possible to appropriately switch the combustion in consideration of the cetane number.

The block diagram of the combustion control apparatus of the internal combustion engine in 1st Embodiment Main flow chart of combustion control Flow chart of DPF regeneration when NOx trap catalyst is warmed up Flow chart of sulfur poisoning release mode Flow chart when switching combustion by rich spike Flowchart mode flowchart Flow chart for determining the priority order of DPF regeneration, NOx regeneration, and sulfur poisoning release Flow chart for determining the priority order of SOx regeneration and NOx regeneration DPF regeneration flowchart Flow chart for removing sulfur poisoning NOx regeneration flowchart Flow chart for warming up NOx trap catalyst The figure which shows the conventional (1st example) fuel injection A diagram showing conventional (second example) fuel injection The figure which shows the combustion (the 3rd example) by preliminary combustion and main combustion Diagram showing another combustion control by pre-combustion and main combustion Comparison of exhaust gas status between conventional (first and second examples) and pre-combustion and main combustion (third example) The figure which showed the state of exhaust gas with respect to the main combustion time by preliminary combustion and main combustion Diagram showing target fuel injection timing for main combustion The figure which shows the exhaust pressure threshold value of DPF The figure which shows the target air fuel ratio with respect to PM accumulation amount Diagram showing target intake air volume A figure to calculate the torque correction coefficient according to the target fuel injection timing Diagram showing target intake air amount for rich spike operation Target intake air volume to prevent DPF melting Diagram showing DPF / SOx regeneration impossible area The block diagram of the combustion control apparatus of the internal combustion engine in 2nd Embodiment Main flow chart of combustion control Ignition delay period estimation routine Flow chart of DPF regeneration when NOx trap catalyst is warmed up Flow chart of sulfur poisoning release mode Calculation table of engine speed upper limit correction coefficient a Calculation table of fuel injection amount upper limit correction coefficient b Diagram showing combustion switching permission area

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 6 Intake throttle valve 7 Air flow meter 8 Fuel injection pump 9 Common rail 10 Fuel injection valve 11 EGR passage 12 Exhaust passage 13 NOx trap catalyst 14 DPF
16 Air-fuel ratio sensor 17 Exhaust pressure sensor 18 Smoke concentration sensor 19 EGR valve 20 Crank angle sensor 21 Accelerator opening sensor 22 Catalyst temperature sensor 23 DPF temperature sensor 25 ECU
31 Water temperature sensor 33 Crank angle sensor for cylinder discrimination 34 Fuel pressure sensor 35 Fuel temperature sensor

Claims (22)

In an internal combustion engine provided with an exhaust purification device in an exhaust passage,
Based on the state of the exhaust purification device, when there is at least one of an exhaust temperature increase request or a rich operation request less than stoichiometric, main combustion that generates main torque and at least one time that is performed prior to main combustion Pre-combustion,
The pre-combustion controls fuel injection such that at least one occurs near top dead center;
While the main combustion controls the fuel injection to start after the pre-combustion is finished,
A combustion control device for an internal combustion engine, wherein each state of the engine is detected, and combustion by the preliminary combustion and the main combustion is prohibited by at least one of the states. A combustion control device for an internal combustion engine,
An exhaust purification device disposed in the exhaust passage of the engine;
A fuel injection valve that injects fuel directly into the combustion chamber of the engine;
A control unit for controlling the operation of the fuel injection valve;
Comprising
The control unit is
Based on the state of the exhaust purification device, when there is at least one of an exhaust temperature increase request or a rich operation request less than stoichiometric, main combustion that generates main torque and at least one time that is performed prior to main combustion Pre-combustion,
The pre-combustion controls fuel injection such that at least one occurs near top dead center;
While the main combustion controls the fuel injection to start after the pre-combustion is finished,
A combustion control device for an internal combustion engine, wherein each state of the engine is detected, and combustion by the preliminary combustion and the main combustion is prohibited by at least one of the states.   The temperature of the exhaust gas purification device is detected as each state of the engine, and whether to continue the combustion by the preliminary combustion and the main combustion is determined according to the detected temperature of the exhaust gas purification device. The combustion control device for an internal combustion engine according to claim 1 or 2.   The exhaust gas component is detected as each state of the engine, and whether to continue the combustion by the preliminary combustion and the main combustion is determined according to the detected exhaust gas component. A combustion control device for an internal combustion engine as described.   The combustion control apparatus for an internal combustion engine according to claim 4, wherein the detected exhaust component is smoke.   The operation state is detected as each state of the engine, and permission to switch to combustion by the preliminary combustion and the main combustion is determined according to the detected operation state. A combustion control device for an internal combustion engine as described.   The engine speed and load are detected as the operating state, and switching to combustion by the preliminary combustion and the main combustion is permitted when the engine speed is within a permission region determined by these. A combustion control device for an internal combustion engine as described.   The combustion control device for an internal combustion engine according to claim 7, wherein the permission region is on a low rotation and low load side of the engine. Means for estimating the ignition delay period,
9. The combustion control apparatus for an internal combustion engine according to claim 7, wherein the permission area is corrected according to the ignition delay period.   10. The combustion control device for an internal combustion engine according to claim 9, wherein when the ignition delay period is long, the permission region is narrowed to a low rotation and low load side. A means for detecting fuel properties;
The combustion control apparatus for an internal combustion engine according to claim 9 or 10, wherein the ignition delay period is estimated from fuel properties.   The combustion control device for an internal combustion engine according to claim 11, wherein the fuel property is determined by detecting a specific gravity of the fuel and calculating a cetane number based on the specific gravity.   13. The fuel injection amount for pre-combustion is a fuel injection amount required for the in-cylinder temperature during fuel injection for main combustion to exceed a temperature at which self-ignition is possible. A combustion control apparatus for an internal combustion engine according to one of the above.   14. The combustion of the internal combustion engine according to claim 1, wherein the combustion start timing of the main combustion is a timing that is separated from the combustion start timing of the preliminary combustion by 20 degrees or more in crank angle. Control device.   The combustion control device for an internal combustion engine according to any one of claims 1 to 14, wherein the end time of the main combustion is a time separated from the compression top dead center by a crank angle of 50 degrees or more.   The combustion of the internal combustion engine according to any one of claims 1 to 15, wherein at least one of a fuel injection amount or a fuel injection timing for preliminary combustion is changed according to a compression end temperature. Control device.   The combustion control apparatus for an internal combustion engine according to any one of claims 1 to 16, wherein in the main combustion, the exhaust gas temperature is controlled by changing a fuel injection timing.   The combustion control apparatus for an internal combustion engine according to any one of claims 1 to 17, wherein the main combustion is controlled so that the generated torque of the engine is constant. Equipped with a filter that collects exhaust particulates as an exhaust purification device,
The claim 1 is characterized in that when there is a request for raising the exhaust gas temperature or a rich operation request less than the stoichiometric condition, a predetermined amount of exhaust particulates is deposited on the filter and the exhaust particulates are brought to a temperature at which they are self-oxidized. Item 19. The combustion control device for an internal combustion engine according to any one of Items 18 above. As an exhaust purification device, equipped with a NOx trap catalyst that traps NOx during lean operation,
The time when there is a request for a rise in exhaust temperature or a rich operation less than stoichiometric is a time when NOx trapped in the NOx trap catalyst is desorbed and purified, according to any one of claims 1 to 18. A combustion control device for an internal combustion engine as described. As an exhaust purification device, equipped with a NOx trap catalyst that traps NOx during lean operation,
19. The exhaust gas temperature increase request or the rich operation request equal to or less than the stoichiometric time is a time for purifying the sulfur content trapped in the NOx trap catalyst. Combustion control device for internal combustion engine. As an exhaust purification device, equipped with a NOx trap catalyst that traps NOx during lean operation,
19. The exhaust gas temperature increase request or the rich operation request less than the stoichiometric condition is when the NOx trap catalyst is cold and when the NOx trap catalyst is rapidly warmed up. A combustion control device for an internal combustion engine according to claim 1.

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