JP2007211648A - Internal combustion engine controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine controller realizing quick and smooth sulfa purge while restricting an increase in combustion sounds and exhaust PM. <P>SOLUTION: If an LNC temperature T<SB>LNC</SB>is lowered below a first temperature determination level T1 during the control of combustion sound restriction, the determination of Step S5 becomes No notwithstanding that combustion sounds exceed a first combustion sound determination value NL1, and so the stage moves to Step S6 to control temperature rise. This inhibits the increase of PM contents of exhaust gas in the state of low exhaust temperatures (i.e., the state where no PM burns in DPF42), and prevents the clogging, etc. of DPF42. If the LNC temperature T<SB>LNC</SB>exceeded the first temperature determination value T1 after the control of combustion sound restriction interrupted, the determination of Step S5 also becomes Yes, the control of combustion sound restriction is executed again if combustion sounds increase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a control device for an internal combustion engine equipped with a lean NO _X catalyst, and more particularly to a technique for performing a quick and smooth sulfur purge while suppressing an increase in combustion noise and PM emission.

The exhaust system of an automobile equipped with the diesel engine, the nitrogen oxides in the exhaust gas (hereinafter, referred to as NO _X) NO _X storage reduction type lean NO _X catalyst for reducing and purifying the (lean NOx Catalyst: In the following, the LNC (Abbreviated) may be provided. LNC is intended that the catalytic material such as _the NO _X storage material and palladium barium was supported on a carrier such as alumina, the air-fuel ratio of the exhaust gas (hereinafter, abbreviated as the exhaust A / F) when the lean ( That is, when the oxygen concentration is high), NO _X is oxidized by the catalyst substance and stored in the NO _X storage material in the form of nitrate. When the exhaust A / F is rich (that is, when the oxygen concentration is low), NO _X is stored. It has the function of releasing NO ₂ from the occlusion material and simultaneously reducing and detoxifying it with a catalyst substance.

In diesel engines, the exhaust A / F is lean in most of the operating range, so if you continue constant speed operation etc., the amount of NO _X stored in the NO _X storage material will gradually increase, and the NO _X storage capacity of the LNC Will fall. Therefore, increasing the concentration of regeneration operation for operating a very short time in the rich state (rich spike operation) a reducing agent in the exhaust gas by performing (CO and HC), the release and reduction of the NO _X from _the NO _X storage material by accelerated so that to restore _the NO _X storage capability of the LNC.

  In the case of a common rail type diesel engine, the rich spike operation is various operations such as fuel injection timing, common rail internal pressure, intake throttle amount using DBW (Drive By Wire System), opening degree of EGR (Exhaust gas recirculation) valve, etc. This is done by controlling the parameters. In general, when the rich spike operation is performed, the combustion state in the combustion chamber changes from that in the normal operation, which may increase the combustion noise and cause problems such as the driver feeling uncomfortable. Therefore, in order to suppress changes in combustion noise when transitioning from normal operation to rich spike operation, a technology has been proposed that controls operation parameters so that the change in in-cylinder pressure approximates that during normal operation during rich spike operation. (See Patent Document 1).

On the other hand, since diesel fuel and engine oil contain sulfur, a small amount of sulfur oxide (hereinafter referred to as SO _X ) exists in the exhaust gas, and NO _X storage material contains NO _X. This SO _X is also absorbed by the same mechanism. When SO _X is absorbed by the NO _X storage material, the NO _X purification performance is naturally reduced. Therefore, SO _X removal operation (hereinafter referred to as sulfur purge operation) is performed at an appropriate time to remove SO _X from the LNC. Must. Since SO _X forms a stable sulfate in the lean NO _X catalyst, it is not released from the LNC simply by making the exhaust A / F rich like NO _X , and the temperature of the LNC is raised to a predetermined temperature ( It is necessary to raise the temperature (see Patent Document 2).
JP 2004-346844 A JP 2005-23822 A

  When the sulfur purge operation is performed, as in the rich spike operation, the combustion state in the combustion chamber changes from the normal operation and the combustion noise often increases. At this time, the method of Patent Document 2 is adopted, that is, by performing operation parameter control (hereinafter referred to as combustion noise suppression control) that approximates the change in in-cylinder pressure during normal operation, the sulfur purge from normal operation is performed. Although it is possible to suppress changes in combustion noise when shifting to operation, in this case, another type of problem described below occurs.

  Since the sulfur purge operation is performed in a rich state continuously for a relatively long time, the amount of particulate matter (hereinafter referred to as PM) in the exhaust gas increases. PM is captured by a DPF (Diesel Particulate Filter) installed upstream of the LNC, and combusts in the DPF when the exhaust gas temperature rises. However, when combustion noise suppression control is performed during the sulfur purge operation, the exhaust temperature does not reach the temperature at which PM is combusted in the DPF, and the back pressure increases (decreases in output) due to clogging of the DPF and the DPF regeneration operation interval. There is a risk of shortening the time.

  The present invention has been made in view of the above situation, and it is an object of the present invention to provide a control device for an internal combustion engine that realizes a quick and smooth sulfur purge while suppressing an increase in combustion noise and PM emission.

An internal combustion engine control apparatus according to a first aspect of the present invention is provided in an internal combustion engine in which a lean NO _X catalyst is installed in an exhaust passage, and has predetermined conditions for removing sulfur contained in the lean NO _X catalyst. A control device for an internal combustion engine that causes the internal combustion engine to perform a sulfur purge operation, comprising combustion sound detection means for detecting a combustion sound of the internal combustion engine, and detected by the combustion sound detection means during the sulfur purge operation When the burned combustion noise exceeds a predetermined value, the combustion noise suppression control is performed to suppress the combustion noise.

  According to a second aspect of the present invention, there is provided the control apparatus for an internal combustion engine according to the first aspect of the invention, wherein the combustion noise suppression control reduces a supply amount of fuel supplied to the internal combustion engine. And at least one of delaying the supply timing of the fuel.

The control apparatus for an internal combustion engine according to the invention of claim 3 is the control apparatus for an internal combustion engine according to the invention of claim 1 or claim 2, the temperature of the exhaust gas temperature or the lean NO _X catalyst of the internal combustion engine A temperature detecting means for detecting is further provided, and when the detected temperature of the temperature detecting means becomes a predetermined value or less during the combustion noise suppression control, the combustion noise suppression control is stopped.

  According to the present invention, it is possible to perform a quick and smooth sulfur purge while suppressing an increase in combustion noise and PM emission.

Hereinafter, an embodiment of an engine system to which the present invention is applied will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an engine system according to the embodiment, and FIG. 2 is a block diagram showing a connection state between components of the engine system and an engine ECU.

<< Configuration of Embodiment >>
As shown in FIG. 1, the engine system 1 includes a diesel engine (internal combustion engine) E as a core, an intake system including an air cleaner 2, an intake pipe 3, an intake manifold 4, and the like, an exhaust manifold 5, an exhaust pipe 6, and the like. An exhaust system and a fuel supply system including a common rail 7 and an electronically controlled fuel injection valve 8 are provided. In the present embodiment, an engine ECU (Electronic Control Unit: hereinafter simply referred to as an ECU) 9 for overall control of the engine system 1 is installed in the passenger compartment, while an accelerator pedal 10 operated by the driver is provided in the driver's seat. is set up. The engine E is provided with a crank angle sensor 11 for detecting the crank angle and an in-cylinder pressure sensor 12 for detecting the pressure in the cylinder. The accelerator pedal 10 is additionally provided with an accelerator pedal sensor 13 for detecting the amount of depression.

  A variable capacity turbocharger (hereinafter referred to as VG turbo) 21 is installed between the intake pipe 3 and the exhaust pipe 6 so that air pressurized by the energy of the exhaust gas is always supplied to the engine E. Is done. In addition, an electronically controlled throttle valve 22 is installed in the pipe line of the intake pipe 3, and the intake amount of the engine E is reduced in a predetermined operation region. In addition, a swirl control valve 23 is provided between the intake pipe 3 and the intake manifold 4 in order to reduce the flow passage cross-sectional area and increase the intake flow velocity in a low rotation and low load operation region or the like. The intake pipe 3 is provided with an intake flow rate sensor 24 that detects the intake flow rate upstream of the VG turbo 21, and a boost pressure sensor 25 that detects the boost pressure downstream of the VG turbo 21. ing. Further, the throttle valve 22 is provided with a throttle valve opening sensor 26 for detecting the opening thereof.

  The swirl control valve 23 and the exhaust manifold 5 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 31 so as to guide high-temperature exhaust gas to the combustion chamber. The EGR passage 31 includes a cooler passage 31a and a bypass passage 31b that are branched via a switching valve 32, and an EGR valve 33 that adjusts the amount of exhaust gas (EGR gas) that flows into the combustion chamber. Is provided. The EGR valve 33 is provided with an EGR valve opening sensor 34 for detecting the opening.

  The exhaust pipe 6 is connected to a diesel oxidation catalyst (Diesel Oxidation Catalyst: hereinafter referred to as DOC) 41, a DPF 42, and an LNC 43 in this order along the exhaust flow. Is installed. An exhaust temperature sensor 45 that detects the exhaust temperature is installed between the DOC 41 and the DPF 42. The LNC 43 is provided with an LNC temperature sensor 46, an upstream LAF (Linear Air Fuel Ratio) sensor 47U, and an upstream NOx sensor 48U on the upstream side, and a downstream LAF sensor 47L and a downstream NOx sensor 48L on the downstream side. Is installed.

  The fuel in the fuel tank 52 is pumped to the common rail 7 with a predetermined pressure by an engine-driven supply pump 51. The common rail 7 is provided with a rail pressure sensor 53 that detects its internal pressure (hereinafter referred to as rail pressure).

  The ECU 9 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like. As shown in FIG. 2, detection signals from the sensors (crank angle sensor 11, in-cylinder pressure sensor 12, etc.) are input to the ECU 9, while engine control devices (fuel injection valve 8, VG turbo 21, etc.) are input from the ECU 9. A driving signal is output.

<< Operation of Embodiment >>
When the engine system 1 is activated, the ECU 9 repeatedly executes sulfur purge control whose procedure is shown in the flowchart of FIG. 3 at a predetermined processing interval (for example, 10 ms).

  When starting the sulfur purge control, the ECU 9 first determines whether or not the sulfur purge start flag Fsp having an initial value 0 is 1 in step S1 of FIG. Since this determination is naturally No immediately after the start of the sulfur purge control, the ECU 9 estimates the SOx poisoning amount of the LNC 43 and calculates the amount of reducing agent (required reducing agent amount) necessary for sulfur purge in step S2. I do.

SO _X poisoning amount is in relation of the NO _X purification rate and inversely as shown in FIG. 4, the NO _X purification rate is high SO _X poisoning amount is small, NO _X purifying the SO _X poisoning progresses Since the rate decreases, the SO _X poisoning amount can be estimated from the degree of decrease in the NO _X purification rate. Here, the NO _X purification rate can be calculated by determining the ratio between the output of the upstream NO _X sensor 48U installed upstream of the LNC 43 and the output of the downstream NO _X sensor 48L installed downstream. . Further, since the required amount of reducing agent is directly proportional to the SO _X poisoning amount as shown in FIG. 5, it can be calculated from the SO _X poisoning amount. The SO _X poisoning amount can also be estimated from the travel distance, the operation time, the fuel consumption amount, and the like.

ECU9 then, SO _X poisoning amount is determined whether exceeds a judgment value set in advance in step S3, if the determination is No, the process is repeated in steps S1~S3 back to the start.

The long-term operating SO _X poisoning amount of LNC43 increases, if the determination in step S3 becomes Yes, ECU 9, after the 1 sulfur purge start flag Fsp in step S4, LNC temperature sensor in step S5 LNC temperature _{T LNC} input from 46 the first temperature determination value T1 (for example, 600 ° C.) determines whether exceeded. The first temperature judgment value T1 is a temperature at which PM in the exhaust gas can be estimated to be combustible in the DPF 42. If the LNC temperature _TLNC exceeds the first temperature judgment value T1, the exhaust A / F is made rich. However, it is difficult for the DPF 42 to be clogged by PM. Note that the determination in step S5 may be performed based on the exhaust temperature Tex input from the exhaust temperature sensor 45.

<Temperature control>
When the LNC temperature T _LNC is lower than the first temperature determination value T1 and the determination in step S5 is No, the ECU 9 proceeds to step S6 and executes the temperature increase control whose procedure is shown in the flowchart of FIG. .

  When the temperature raising control is started, the ECU 9 first determines whether or not the map selection flag Fmap having an initial value of 0 is 1 in step S21 of FIG. Since this determination is naturally No immediately after the start of the temperature increase control, the ECU 9 selects the map for temperature increase in step S22, and then sets the map selection flag Fmap to 1 in step S23.

  The temperature increase map includes the fuel injection amount and fuel injection timing by the fuel injection valve 8, the supercharging pressure by the VG turbo 21, the swirl strength in the combustion chamber by the swirl control valve 23, the rail pressure by the supply pump 51, the throttle valve 22 The new intake air amount and the like are mapped so as to raise the exhaust temperature. When the map for temperature increase is selected, the main injection timing is retarded, the post injection is increased, the intake air amount is decreased, etc., and the exhaust A / F becomes rich and at the same time the exhaust temperature rises to reduce the load Sulfur purge is possible even in an area or the like.

  After setting the map selection flag Fmap to 1 in step S23, the ECU 9 in step S24, the crankshaft rotational speed input from the crank angle sensor 11 and the operation amount of the accelerator pedal 10 input from the accelerator pedal sensor 13, that is, the engine E Based on the operation load, it is determined whether or not the current operation state is in the post-injection region from a region determination map (not shown).

  When the engine E is in the low rotation / low load operation region and the determination in step S24 is Yes, the ECU 9 determines in step S25 that the first L / R timer (for example, lean 5 seconds (L1) / rich 30 seconds (R1)). ) And controlling the opening degree of the throttle valve 22 and the like to change the intake flow rate, the exhaust A / F is higher than a predetermined value (the intake amount is relatively large), and the A / F Is repeatedly lower than a predetermined value (the intake amount is relatively small), and a rich state is alternately repeated at a constant period.

Next, the ECU 9 determines whether or not the LNC temperature _TLNC exceeds the first temperature determination value T1 in step S26. If this determination immediately after temperature increase control start was No, ECU 9 is to increase the post-injection amount in step S27, increasing the LNC temperature _{T LNC} by increasing the unburned HC concentration.

When the process of step S27 is is repeated by LNC temperature _{T LNC} exceeds a first temperature determination value T1, ECU 9 is, LNC temperature _{T LNC} in step S28 exceeds the second temperature determination value T2 (e.g., 650 ° C.) In step S29, the post-injection amount is reduced, and the unburned HC concentration is lowered to lower the LNC temperature _TLNC . The second temperature determination value T2 is a temperature within a range in which the durability of the exhaust purification device 40 (DOC41, DPF42, and LNC43) is not impaired, and the LNC temperature _TLNC must not exceed this even during sulfur purge control. Is desirable.

As a result, in the low rotation / low load operation region where post injection is performed, the post injection amount is increased or decreased by feeding back the LNC temperature _TLNC as shown in the operation image of FIG. The lean state (the upper side of the alternate long and short dash line) and the rich state (the lower side of the alternate long and short dash line) are alternately repeated at a constant period (L ₁ : R ₁ ). As a result, the LNC temperature _TLNC is maintained between the first temperature determination value T1 and the second temperature determination value T2, and the sulfur purge of the LNC 43 can be advanced while burning PM in the DPF 42. it can. Note that the EGR valve 33 is closed so that the post injection does not flow into the EGR passage 31 during the temperature rise control in the post injection region.

On the other hand, in the high rotation speed and high load range where the LNC temperature T _LNC that can be sulfur purged without performing the post injection is maintained because the high exhaust temperature is obtained, it depends on the reaction heat in the unburned HC by the post injection. not, as described below, to maintain the LNC temperature by changing the lean / rich cycle in accordance with the LNC temperature _{T LNC.}

If the determination in step S24 is No, the ECU 9 determines in step S30 whether the LNC temperature _TLNC exceeds the first temperature determination value T1. If the determination in step S30 is No, the ECU 9 activates the _second L / R timer (lean 3 seconds (L ₂ ) / rich 30 seconds (R ₂ )) in step S31, and the main fuel injection amount is determined. The LNC temperature T _LNC is raised by increasing the intake flow rate to make the rich time relatively long and reacting HC with O ₂ (reaction formula: HC + O ₂ → H ₂ O + CO ₂ ).

If the LNC temperature T _LNC exceeds the first temperature determination value T1 and the determination in step S30 is Yes, the ECU 9 determines whether or not the LNC temperature T _LNC exceeds the second temperature determination value T2 in step S32. judge. If this determination is No, the ECU 9 starts the third L / R timer (lean 3 seconds (L ₃ ) / rich 50 seconds (R ₃ )) in step S33, and the intake air flow rate with respect to the main fuel injection amount the by reduced lowering the LNC temperature T _LNC with relatively short rich time.

Thus, in the high speed and high load operating region, as the working image shown in FIG. 8, the lean / repetition period of the rich is dimensional worlds in accordance with the temperature of the LNC temperature T _LNC, LNC temperature T _LNC first This is maintained between the temperature determination value T1 and the second temperature determination value T2. The reason for this is that when switching from rich to lean, the concentration of O ₂ supplied is low at the time of rich, so HC cannot react, and an oxidation reaction is performed with a high concentration of O ₂ supplied at the time of lean. This is because the temperature rises temporarily (see FIG. 9). That is, by changing the lean period, the frequency of the oxidation reaction changes, and the temperature level changes.

Further, as shown in FIG. 10, by changing the lean / rich repetition period, a difference occurs in the stable temperature of the LNC 43. That is, by changing in accordance with the lean / rich ratio LNC temperature _{T LNC,} it is possible to stabilize the LNC temperature _{T LNC} at a predetermined value.

Note that generation mechanism of _{H 2} S is, SO ₄ contained in the exhaust is adsorbed by the LNC43 as sulfide salt such as BaSO _4, the sulfide salt LNC43 there is _{H 2} S becomes SO ₂ when the rich atmosphere It is generated.
Reaction formula:
BaSO ₄ + CO → BaCO ₃ + SO ₂
SO ₂ + H ₂ → H ₂ S + O ₂
At this time, as shown in FIG. 11, there is a predetermined time lag from the start of the release of SO _X and SO ₂ until the generation of H ₂ S. Therefore, by returning to lean within this time, the generation of H ₂ S is suppressed. This can alleviate odors.

<Combustion noise suppression control>
If the LNC temperature T _LNC is higher than the first temperature determination value T1 and the determination in step S5 of FIG. 3 is Yes, the ECU 9 determines whether the combustion sound of the engine E is greater than the first combustion sound determination value NL1 in step S7. It is further determined whether or not, and if this determination is Yes, combustion noise suppression control whose procedure is shown in the flowchart of FIG. 12 is executed in step S8. Even higher than LNC temperature _{T LNC} first temperature determination value T1, if Shooto is equal to or lower than the first combustion sound determination value NL1, since the determination in step S7 is No, the ECU 9, step S6 The temperature rise control is performed. In this embodiment, the combustion noise is obtained by calculating the in-cylinder pressure change amount dp / dθ from the detection result of the in-cylinder pressure sensor 12 and the detection result of the crank angle sensor 11, but a noise sensor is attached to the cylinder head. Then, it may be obtained directly.

  When the combustion noise suppression control is started, the ECU 9 first determines whether or not the map selection flag Fmap having an initial value 0 is 1 in step S41 of FIG. Since this determination is naturally No immediately after the start of the combustion noise suppression control, the ECU 9 selects a combustion noise suppression map in step S42, and then sets the map selection flag Fmap to 1 in step S43.

  The combustion noise suppression map includes the fuel injection amount and fuel injection timing by the fuel injection valve 8, the supercharging pressure by the VG turbo 21, the swirl strength in the combustion chamber by the swirl control valve 23, the rail pressure by the supply pump 51, and the throttle valve. The new intake air amount by 22 is mapped so as to suppress combustion noise. When the combustion noise suppression map is selected, the rail pressure is reduced and the main and pilot injection timings are retarded during the temperature rise control, and sulfur purge can be performed in a range that does not increase the combustion noise. Become. In addition, when switching from normal operation control to temperature rise control and combustion noise suppression, and when switching between temperature increase control and combustion noise suppression, drivability due to sudden fluctuations in operating parameters Lamp control is performed to suppress the deterioration of the lamp.

  After setting the map selection flag Fmap to 1 in step S43, the ECU 9 determines in step S44 whether or not the combustion sound is greater than the first combustion sound determination value NL1, and if this determination is Yes, the rail in step S45. Reduce pressure. Thereby, the fuel injection amount by the fuel injection valve 8 decreases, and the combustion noise decreases due to the decrease in the in-cylinder pressure.

  On the other hand, when the process of step S45 is repeated and the combustion noise decreases and the determination in step S44 becomes No, the ECU 9 determines in step S46 whether or not the combustion sound is smaller than the second combustion sound determination value NL2. If this determination is Yes, the rail pressure is increased in step S47. The second combustion sound determination value NL2 is set to a value that is significantly smaller than the first combustion sound determination value NL1 in order to prevent control hunting.

In the combustion noise suppression control, the A / F rich state and the LNC temperature T _LNC are maintained within a range where the combustion noise does not increase, and the sulfur purge proceeds as in the temperature increase control.

<Interruption of combustion noise suppression control>
During the execution of the combustion noise suppression control, the LNC temperature _TLNC may become equal to or lower than the first temperature determination value T1 due to a change in traveling state or the like. In this case, even if the combustion sound exceeds the first combustion sound determination value NL1, the determination in step S5 of FIG. 3 is No, so the ECU 9 proceeds to step S6 and performs temperature rise control. As a result, an increase in PM in the exhaust gas in a state where the exhaust temperature is low (that is, a state where PM is not combusted in the DPF 42) is suppressed, and clogging of the DPF 42 is less likely to occur. Even after the combustion noise suppression control is interrupted, if the LNC temperature _TLNC exceeds the first temperature determination value T1, the determination in step S5 in FIG. 3 becomes Yes, so the combustion noise suppression control is performed when the combustion noise increases. It will be executed again.

<Sulfur purge completion judgment>
In parallel with the temperature increase control in step S6 and the combustion noise suppression control in step S8 in FIG. 3, the ECU 9 executes a sulfur purge completion determination whose procedure is shown in the flowchart of FIG. 13 or FIG.

  In the sulfur purge completion determination, the ECU 9 estimates the reducing agent consumption by integrating the difference between the detection result of the upstream LAF sensor 47U and the detection result of the downstream LAF sensor 47L, and the estimated value is the step in FIG. It is determined that the sulfur purge is completed when the amount of the necessary reducing agent calculated in S2 is exceeded. Alternatively, the reducing agent supply amount is estimated by integrating the difference between a predetermined reference value (for example, the theoretical air-fuel ratio: 14.7) and the detection result of the upstream LAF sensor 47U, and the estimated value is obtained in step S2 of FIG. It is determined that the sulfur purge has been completed when the amount of the necessary reducing agent calculated in (1) has been exceeded.

(Completion judgment by reducing agent consumption)
When performing the sulfur purge completion determination based on the amount of reducing agent consumed, the ECU 9 first calculates the difference between the detection result LAF1 of the upstream LAF sensor 47U and the detection result LAF2 of the downstream LAF sensor 47L in step S51 of FIG. Accumulate with Here, the symbol k in the following expression is a temperature correction coefficient. Note that the difference between LAF1 and LAF2 multiplied by the exhaust gas flow rate SV may be integrated. In this case, the calculation accuracy of the reducing agent consumption can be further improved.
Consumption = Σ (LAF1-LAF2) · k
Next, the ECU 9 determines whether or not the reducing agent consumption amount exceeds the necessary reducing agent amount in step S52, and sets the sulfur purge completion flag Ffin having an initial value 0 to 1 when this determination becomes Yes.

Figure 15 is a graph showing the output difference between the upstream side LAF sensor 47U and downstream LAF sensors 47L when the sulfur purge execution transition between SO _X concentration. As can be seen from the figure, the sulfur purge start early on both LAF sensor 47U, large output difference between 47L, the output difference As the the SO _X concentration is decreased sulfur purge progresses Yuku reduced. From this, it is understood that the SO _X release amount can be estimated based on the output difference between both the LAF sensors 47U and 47L.

As shown in FIG. 16, the sulfur purge tends to be completed earlier when the LNC temperature _TLNC is higher. However, since the sensitivity of the LAF sensor has a correlation with the temperature, when the environmental temperature during sulfur purge changes by multiplying the integrated value of the reducing agent consumption by the temperature correction coefficient k corresponding to the LNC temperature _TLNC. In addition, the amount of reducing agent consumption can be accurately grasped, and the accuracy of sulfur purge completion determination can be improved.

(Completion judgment by reducing agent supply amount)
When performing the sulfur purge completion determination based on the reducing agent supply amount, the ECU 9 first integrates the difference between the theoretical air-fuel ratio (14.7) and the detection result LAF1 of the upstream LAF sensor 47U in step S61 of FIG.
Consumption = Σ (LAF1-LAF2) · k
Next, the ECU 9 determines whether or not the reducing agent supply amount exceeds the necessary reducing agent amount in step S62, and sets the sulfur purge completion flag Ffin to 1 when this determination becomes Yes.

  Note that either one of the completion determination based on the reducing agent consumption amount and the completion determination based on the reducing agent supply amount may be performed, but the determination accuracy is further improved by comparing both completion determinations after being executed in parallel. be able to.

<Sulfur purge end processing>
The ECU 9 determines whether or not the sulfur purge completion flag Ffin is 1 in step S10 after the sulfur purge completion determination in step S9 of FIG. Since this determination is No during the sulfur purge control, the process returns to the start and the processing from step S1 to step S10 is repeated, but when the sulfur purge is completed (the sulfur purge completion flag Ffin is 1 in the sulfur purge completion determination). Then, the sulfur purge end process is executed in step S11. That is, the temperature rise control and the combustion noise suppression control are stopped, and the sulfur purge start flag Fsp and the sulfur purge completion flag Ffin are reset to 0 and the sulfur purge control is terminated.

Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, in the above embodiment, the present invention is applied to sulfur purge in a diesel engine, but the present invention may be applied to other types of internal combustion engines including a lean NO _X catalyst. In addition, the specific configuration of the internal combustion engine, the specific procedure of control, and the like can be changed as appropriate without departing from the gist of the present invention.

1 is a schematic configuration diagram of an engine system according to an embodiment. It is a block diagram which shows the connection state of the component of an engine system, and engine ECU. It is a flowchart which shows the procedure of sulfur purge control. It is a graph showing the relationship between the SO _X poisoning amount and NO _X purification rate. It is a graph showing the relationship between the SO _X poisoning amount and the reducing agent required amount. It is a flowchart which shows the procedure of temperature rising control. It is an operation image which shows the change of each parameter in temperature rising control. It is an operation image which shows the change of each parameter in temperature rising control. It is a graph which shows the relationship between oxygen concentration and LNC temperature. It is a graph which shows the relationship between the repetition period of lean / rich, and LNC temperature. SO _X, is a graph showing the change in concentration of _{SO 2, H} 2 S. It is a flowchart which shows the procedure of combustion noise suppression control. It is a flowchart which shows the procedure of sulfur purge completion determination. It is a flowchart which shows the procedure of sulfur purge completion determination. Is a graph showing changes in the output difference and SO _X concentration of the LAF sensor. It is a graph which shows the relationship between a sulfur purge speed | rate and LNC temperature.

Explanation of symbols

1 Engine system 6 Exhaust pipe (exhaust passage)
8 Fuel injection valve 9 Engine ECU
11 Crank angle sensor (combustion sound detection means)
12 In-cylinder pressure sensor (combustion sound detection means)
42 DPF
43 LNC (lean NO _X catalyst)
45 Exhaust temperature sensor (temperature detection means)
46 LNC temperature sensor (temperature detection means)
E engine (internal combustion engine)

Claims (3)

An internal combustion engine provided in an internal combustion engine in which a lean NO _X catalyst is installed in an exhaust passage, and causing the internal combustion engine to perform a sulfur purge operation under a predetermined condition in order to remove sulfur stored in the lean NO _X catalyst A control device of
Combustion sound detection means for detecting combustion sound of the internal combustion engine,
A control apparatus for an internal combustion engine, which performs combustion noise suppression control for suppressing combustion noise when the combustion noise detected by the combustion noise detection means exceeds a predetermined value during the sulfur purge operation.   2. The combustion noise suppression control according to claim 1, wherein the combustion noise suppression control is executed by at least one of reducing a supply amount of fuel supplied to the internal combustion engine and delaying a supply timing of the fuel. Control device for internal combustion engine. Further comprising a temperature detecting means for detecting the temperature of the exhaust gas temperature or the lean NO _X catalyst of the internal combustion engine,
3. The control of the internal combustion engine according to claim 1, wherein the combustion noise suppression control is stopped when a temperature detected by the temperature detection unit becomes a predetermined value or less during the combustion noise suppression control. 4. apparatus.

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