JP2010112198A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely separate the sulfur content from an NOx catalyst, without affecting a person, even when a person stays near a vehicle, in an exhaust emission control device of an internal combustion engine. <P>SOLUTION: This exhaust emission control device of the internal combustion engine has the NOx catalyst arranged in an exhaust passage, a sulfur regeneration control means for performing sulfur regeneration control when necessary for separating the sulfur content adsorbed to the NOx catalyst, and a determining means for determining whether or not to be high in the possibility that a person stays near the vehicle. The sulfur regeneration control means performs the sulfur regeneration control in an ordinary mode when not determined as being high in the possibility that a person stays near the vehicle when requiring the sulfur regeneration control, and performs the sulfur regeneration control in a toxic component restraining mode of being less in a discharge quantity of a toxic component from the NOx catalyst than the ordinary mode when determined as being high in the possibility that a person stays near the vehicle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  Conventionally, a three-way catalyst for purifying exhaust gas of an internal combustion engine has been widely used. The three-way catalyst cannot obtain a high purification rate unless the air-fuel ratio of the inflowing exhaust gas is close to the stoichiometric air-fuel ratio. For this reason, in the case of an internal combustion engine capable of lean combustion that is burned at an air / fuel ratio that is leaner than the stoichiometric air / fuel ratio, the exhaust gas is provided with a NOx catalyst that can store NOx (nitrogen oxide) under the lean air / fuel ratio. A purification device is used.

In a system equipped with a NOx catalyst, it is necessary to periodically execute a rich spike that temporarily makes the air-fuel ratio of the exhaust gas flowing into the NOx catalyst richer than the stoichiometric air-fuel ratio. By executing the rich spike, NOx occluded in the NOx catalyst can be desorbed and reduced to N ₂ for purification.

  The exhaust gas of the internal combustion engine also contains sulfur oxide (SOx) generated by burning the sulfur content in the fuel. The NOx catalyst also has a property of occluding (adsorbing) this SOx. In the occlusion material included in the NOx catalyst, NOx is retained as nitrate and SOx is retained as sulfate. Sulfate is more stable than nitrate. For this reason, even if rich spike is executed, SOx does not desorb from the storage material. Therefore, SOx gradually accumulates in the occlusion material, and the occlusion material loses its ability to occlude NOx by that amount. Such a phenomenon is called sulfur poisoning.

  S regeneration control is known as a method for recovering the NOx storage capacity of a sulfur-poisoned NOx catalyst. In the S regeneration control, exhaust gas having a rich air-fuel ratio or stoichiometric air-fuel ratio is caused to flow into the NOx catalyst while the NOx catalyst is at a high temperature. By executing this S regeneration control, the sulfur content can be desorbed from the NOx catalyst, and the NOx storage capacity of the NOx catalyst can be recovered.

When the S regeneration control is executed, hydrogen sulfide (H ₂ S) or the like may be generated due to the sulfur component desorbed from the NOx catalyst reacting with hydrogen in the exhaust gas. Hydrogen sulfide has a unique odor. For this reason, if hydrogen sulfide or the like is generated when a person is near the vehicle, the person may sense a smell and feel uncomfortable.

  Japanese Patent Application Publication No. 2003-511601 gazette discloses an exhaust gas from an internal combustion engine that detects data related to the current location or travel route of a host vehicle using a navigation device and performs a purification procedure (S regeneration control) of the storage catalyst according to the current location or travel route. A purification device is disclosed. Specifically, this apparatus prohibits or cancels the execution of S regeneration control in an urban area, a recreation area, or the like, and executes S regeneration control during free running on an expressway or main road. As a result, the exhaust gas is quickly diffused by the traveling wind blown to the vehicle traveling at a high speed, thereby preventing the human being from detecting the odor.

Special Table 2003-511601 JP 2005-113691 A JP 2003-155925 A JP 2004-116320 A

  However, in the technique disclosed in the above-described conventional publication, there is a case in which the S regeneration control is not performed even though the S regeneration control is necessary. In such a case, sulfur poisoning of the NOx catalyst cannot be eliminated, and the vehicle travels with the NOx storage capability of the NOx catalyst remaining reduced. As a result, emission deterioration such as an increase in the amount of NOx emissions into the atmosphere is caused.

  The present invention has been made to solve the above-described problems. Even when a person is near the vehicle, the sulfur content can be reliably removed from the NOx catalyst without affecting the person. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can be desorbed.

In order to achieve the above object, a first invention is an exhaust purification device for an internal combustion engine,
A NOx catalyst installed in the exhaust passage of the internal combustion engine;
S regeneration control means for executing S regeneration control for desorbing the sulfur component adsorbed on the NOx catalyst when necessary;
Determining means for determining whether or not there is a high possibility that a person is near a vehicle equipped with the internal combustion engine;
With
The S regeneration control means executes the S regeneration control in a normal mode when it is not determined that there is a high possibility that a person is near the vehicle when the S regeneration control is necessary. When it is determined that there is a high possibility that a person is near the vehicle, the S regeneration control is executed in a harmful component suppression mode in which the amount of harmful components discharged from the NOx catalyst is small compared to the normal mode. It is characterized by that.

The second invention is the first invention, wherein
The S regeneration control means controls so that the air-fuel ratio of the exhaust gas flowing into the NOx catalyst periodically becomes leaner than the stoichiometric air-fuel ratio in the harmful component suppression mode.

The third invention is the first invention, wherein
The S regeneration control unit controls the lower limit value of the air-fuel ratio of the exhaust gas flowing into the NOx catalyst so as to be leaner than the normal mode in the harmful component suppression mode.

According to a fourth invention, in any one of the first to third inventions,
The determination means determines whether or not there is a high possibility that a person is near the vehicle based on at least one of the operating state of the internal combustion engine, navigation information, and a video of an in-vehicle camera that captures the outside of the vehicle. It includes a means for determining.

  According to the first aspect, when the S regeneration control of the NOx catalyst is necessary, if it is not determined that there is a high possibility that a person is near the vehicle, the S regeneration control is executed in the normal mode. The On the other hand, if it is determined that there is a high possibility that a person is near the vehicle, the S regeneration control is executed in the harmful component suppression mode in which the amount of harmful components emitted from the NOx catalyst is small compared to the normal mode. The For this reason, it is possible to reliably prevent the influence (odor, discomfort, etc.) of the S regeneration control from being exerted on a person near the vehicle. In addition, according to the first invention, even when a person is near the vehicle, the S regeneration control can be executed, so that the NOx occlusion capability of the sulfur-poisoned NOx catalyst can be reliably recovered. Can do. Therefore, it is possible to reliably prevent a situation in which the internal combustion engine is operated for a long time with the NOx catalyst being poisoned with sulfur. For this reason, it can avoid reliably that the NOx discharge | emission amount to air | atmosphere increases.

  According to the second invention, in the S regeneration control in the harmful component suppression mode, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst can be controlled to be periodically leaner than the stoichiometric air-fuel ratio. Thereby, oxygen can be periodically replenished to the oxygen storage material in the NOx catalyst. For this reason, even during execution of the S regeneration control, it is possible to maintain a state where oxygen is stored in the oxygen storage material in the NOx catalyst. As a result, it is possible to reliably prevent the sulfur component desorbed from the NOx catalyst from being reduced, and to reliably suppress the generation of harmful components.

  According to the third invention, in the S regeneration control means in the harmful component suppression mode, the lower limit value of the air-fuel ratio of the exhaust gas flowing into the NOx catalyst can be controlled to be leaner than in the normal mode. This reliably prevents the air-fuel ratio of the exhaust gas flowing into the NOx catalyst from becoming an extremely rich value in which harmful components are easily generated. Therefore, generation | occurrence | production of a harmful | toxic component can be suppressed reliably.

  According to the fourth invention, whether or not there is a high possibility that a person is near the vehicle based on at least one of the operating state of the internal combustion engine, navigation information, and the image of the in-vehicle camera that captures the outside of the vehicle. Can be determined. Thereby, it can be determined with high accuracy whether or not a person is near the vehicle.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system according to the first embodiment of the present invention includes an internal combustion engine 10. It is assumed that the internal combustion engine 10 is mounted on a vehicle as a power source. The internal combustion engine 10 has a plurality of cylinders, and FIG. 1 shows a cross section of one of the cylinders.

  Each cylinder of the internal combustion engine 10 is provided with a piston 11, an intake valve 12, an exhaust valve 13, a spark plug 14, and a fuel injector 15. The fuel in the fuel tank 16 is supplied to the fuel injector 15 through the fuel pipe 17. In the present embodiment, the fuel injector 15 is installed so as to inject fuel directly into the cylinder, but the present invention is also applicable to an internal combustion engine having a fuel injector that injects fuel into the intake port. is there.

  In addition to the stoichiometric air-fuel ratio combustion, the internal combustion engine 10 can perform lean combustion in which fuel is burned at an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. As the lean combustion, either homogeneous combustion or stratified combustion may be used.

  An intake system 20 and an exhaust system 30 are connected to the internal combustion engine 10. The intake system 20 has an intake passage 22 communicating with the intake valve 12 of each cylinder, and a throttle valve 24 provided in the middle of the intake passage 22. The intake air amount of the internal combustion engine 10 is adjusted by the opening degree of the throttle valve 24.

  The exhaust system 30 has an exhaust passage 32 communicating with the exhaust valve 13 of each cylinder. In the middle of the exhaust passage 32, a start catalyst 34 and a NOx catalyst 36 are installed.

  The start catalyst 34 is a three-way catalyst that can simultaneously purify HC, CO, and NOx when the air-fuel ratio of the inflowing exhaust gas is near the stoichiometric air-fuel ratio. The start catalyst 34 is close to the internal combustion engine 10 and has a relatively small capacity. Therefore, the start catalyst 34 can be activated early after the internal combustion engine 10 is started to purify the exhaust gas.

The NOx catalyst 36 is disposed on the downstream side of the start catalyst 34. This NOx catalyst 36 can occlude NOx when the air-fuel ratio of the inflowing exhaust gas is leaner than the stoichiometric air-fuel ratio, and occludes when the air-fuel ratio of the inflowing exhaust gas is less than or equal to the stoichiometric air-fuel ratio. This is a storage reduction type NOx catalyst (NSR: NOx Storage Reduction) that can remove and purify the NOx that has been removed. As the catalyst layer of the NOx catalyst 36, for example, on the surface of alumina (Al ₂ O ₃ ), a noble metal such as platinum Pt having catalytic action, and occlusion of barium Ba or the like that can absorb NOx and hold it as nitrate. What disperse | distributed material can be used. In this specification, the term “occlusion” includes all concepts similar to “holding”, “adsorption”, “absorption”, and the like.

  The NOx catalyst 36 can function as a three-way catalyst that simultaneously purifies HC, CO, and NOx when the air-fuel ratio of the inflowing exhaust gas is near the stoichiometric air-fuel ratio. The NOx catalyst 36 further includes an oxygen storage material capable of absorbing and releasing oxygen. When the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 36 is in the vicinity of the stoichiometric air-fuel ratio, the three components can be purified with high efficiency by the oxygen storage material absorbing and releasing oxygen.

  An air-fuel ratio sensor 37 is installed on the upstream side of the NOx catalyst 36, and an oxygen sensor 38 is installed on the downstream side of the NOx catalyst 36. The air-fuel ratio sensor 37 can continuously detect an air-fuel ratio over a relatively wide range and generates an output corresponding to the air-fuel ratio. The oxygen sensor 38 generates an output that suddenly changes with the theoretical air-fuel ratio as a boundary.

  The system of the present embodiment also includes an engine speed sensor 41 that detects the engine speed of the internal combustion engine 10, an air flow meter 42 that detects the intake air amount of the internal combustion engine 10, and the vehicle speed of the vehicle on which the internal combustion engine 10 is mounted. A vehicle speed sensor 43 that detects the coolant temperature, a water temperature sensor 44 that detects the coolant temperature of the internal combustion engine 10, and an accelerator position sensor 45 that detects the position of the accelerator pedal in the driver's seat of the vehicle (hereinafter referred to as "accelerator opening"). And.

  Furthermore, the system of this embodiment includes a navigation system 46 and an ECU (Electronic Control Unit) 50. The ECU 50 is electrically connected to the various actuators and sensors described above and the navigation system 46.

  The navigation system 46 is a device that can perform route guidance to a destination for a driver. The navigation system 46 includes a storage medium such as a hard disk in which map information and the like are stored, a control unit having an input / output port, a communication port, and the like, a GPS antenna that receives information on the current position of the vehicle, traffic jam information, and regulation information. , A VICS antenna for receiving information such as a parking lot full condition and a display. The navigation system 46 searches the travel route to the destination based on the current position of the vehicle, the destination, and the map information, and displays the searched travel route on the display to guide the route to the driver. be able to.

  The map information includes road information. The road information includes distance information, width information, type information (city roads, suburban roads, mountain roads, highways), gradient information, legal speed, number of traffic lights, presence / absence of signals, and the like. Based on the map information and the current position of the vehicle, the control unit of the navigation system 46 constantly detects information such as road information, traffic jam information, and regulation information about the currently traveling road, and the information Can also be output to the ECU 50.

  In principle, the ECU 50 can switch between a lean combustion mode in which combustion is performed at an air-fuel ratio leaner than the stoichiometric air-fuel ratio and a stoichiometric air-fuel ratio combustion mode in which combustion is performed in the vicinity of the stoichiometric air-fuel ratio. The lean combustion mode and the stoichiometric air-fuel ratio combustion mode are selected according to the operating state of the internal combustion engine 10. For example, the stoichiometric air-fuel ratio combustion mode is selected during warm-up immediately after the start of the internal combustion engine 10 or during a high-load operation that requires high output, and the lean combustion mode is selected during low-medium load operation after the warm-up is completed. Is done. The ECU 50 can control the combustion air-fuel ratio by controlling the intake air amount by the throttle valve 24 and controlling the fuel injection amount from the fuel injector 15.

During lean combustion, NOx in the exhaust gas is stored in the NOx catalyst 36. As the amount of NOx accumulated in the NOx catalyst 36 increases, the NOx absorption rate decreases. Therefore, in the lean combustion mode, rich spike control is performed periodically in which the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 36 is temporarily set to the theoretical air-fuel ratio or less. By executing the rich spike control, the oxygen concentration in the exhaust gas decreases, and the fuel as the reducing agent can flow into the NOx catalyst 36. Thereby, NOx occluded in the NOx catalyst 36 can be desorbed and reduced to N ₂ for purification.

  In the present embodiment, the ECU 50 can control the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 36 by controlling the combustion air-fuel ratio of the internal combustion engine 10.

  In the storage material of the NOx catalyst 36, SOx in the exhaust gas gradually accumulates. As SOx accumulates in the NOx catalyst 36, the NOx storage capacity of the NOx catalyst 36 decreases. In order to recover the NOx occlusion capacity of the sulfur-poisoned NOx catalyst 36 in this way, the ECU 50 periodically executes S regeneration control (for example, every 2000 km). Normally, in the S regeneration control, the exhaust gas having an air-fuel ratio richer than the stoichiometric air-fuel ratio is allowed to flow into the NOx catalyst 36 for about 5 to 10 minutes with the NOx catalyst 36 at a high temperature (for example, 600 to 650 ° C.). . Thereby, SOx can be desorbed from the NOx catalyst 36, and the NOx storage capacity can be recovered.

  When the S regeneration control is executed, hydrogen sulfide or the like (hereinafter referred to as “hydrogen sulfide”) may be generated due to a reaction between the sulfur component desorbed from the NOx catalyst and the unburned fuel component. . Hydrogen sulfide has a specific odor and is harmful. For this reason, if hydrogen sulfide is generated when a person is near the vehicle, the person may sense the odor and feel uncomfortable.

  However, when control is performed so that the execution of the S regeneration control is prohibited or stopped when a person is near the vehicle, the internal combustion engine remains in a state where the NOx purification ability of the NOx catalyst 36 cannot be sufficiently recovered. The situation where 10 is driven comes out. For this reason, there is a problem that the amount of NOx emission to the atmosphere increases.

  Therefore, in the present embodiment, when it is determined that there is a person near the vehicle when the execution of the S regeneration control is requested, a method in which the generation of hydrogen sulfide is suppressed as compared with the normal method. The S regeneration control is executed. Hereinafter, a case where the S regeneration control is executed by a normal method is referred to as a “normal mode”, and a case where the S regeneration control is executed by a method for suppressing the generation of hydrogen sulfide is referred to as a “hazardous component suppression mode”.

  In the present embodiment, in the S regeneration control in the harmful component suppression mode, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 36 (hereinafter referred to as “inflow gas”) periodically becomes leaner than the stoichiometric air-fuel ratio. It was decided to control. That is, every time the state in which the air-fuel ratio of the inflow gas is richer than the stoichiometric air-fuel ratio continues for a predetermined time, the air-fuel ratio of the inflow gas is made lean and oxygen is caused to flow into the NOx catalyst 36.

  In the S regeneration control in the normal mode, a state where the air-fuel ratio of the inflowing gas is richer than the stoichiometric air-fuel ratio is continued for a long time. For this reason, the oxygen storage material in the NOx catalyst 36 is in a state in which all oxygen is released. According to the knowledge of the present inventor, when the oxygen in the oxygen storage material of the NOx catalyst 36 is depleted, the SOx desorbed from the NOx catalyst 36 is reduced and hydrogen sulfide is easily generated.

  On the other hand, according to the S regeneration control in the harmful component suppression mode, oxygen can periodically flow into the NOx catalyst 36. Thereby, oxygen can be periodically replenished to the oxygen storage material in the NOx catalyst 36. For this reason, even during execution of the S regeneration control, it is possible to maintain a state where oxygen is stored in the oxygen storage material in the NOx catalyst 36. According to the knowledge of the present inventors, by maintaining the state where oxygen is stored in the oxygen storage material in the NOx catalyst 36, it is possible to reliably prevent the SOx desorbed from the NOx catalyst 36 from being reduced. Can do. That is, generation of hydrogen sulfide can be reliably prevented. For this reason, even when a person is near the vehicle, the S regeneration control can be executed and the NOx occlusion capacity of the NOx catalyst 36 can be recovered without affecting the person (odor or discomfort). it can.

  On the other hand, when there is no person near the vehicle and hydrogen sulfide is allowed to be generated, it is preferable to execute the S regeneration control in the normal mode. This is because SOx can be more reliably desorbed in a shorter time than in the harmful component suppression mode.

[Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time. According to the routine shown in FIG. 2, first, the sulfur poisoning amount of the NOx catalyst 36 is read (step 100). The ECU 50 sequentially calculates the current sulfur poisoning amount based on the travel distance from the previous execution of the S regeneration control, the integrated fuel injection amount, and the like. In this step 100, the value of the sulfur poisoning amount is read.

  Next, based on the value of the sulfur poisoning amount read in step 100, it is determined whether or not execution of S regeneration control is necessary (step 102). That is, when the sulfur poisoning amount exceeds a predetermined determination value, it is determined that the S regeneration control needs to be executed, and when the sulfur poisoning amount is equal to or less than the determination value, the S regeneration control is performed. Is determined not yet to be executed.

  If it is determined in step 102 that it is not necessary to execute the S regeneration control, it is not necessary to execute the following processing, and thus the processing of this routine is terminated here. On the other hand, if it is determined in step 102 that it is necessary to execute the S regeneration control, then the current operating state of the internal combustion engine 10 and the vehicle (engine speed, intake air amount, throttle valve opening, The accelerator opening, vehicle speed, etc.) are read (step 104). Note that these parameters representing the operating state are detected by the various sensors described above.

  Subsequently, based on the driving state read in step 104, it is determined whether or not the vehicle is traveling at high speed (step 106). If it is determined in step 106 that the vehicle is traveling at high speed, it can be estimated that there is no human being near the vehicle. In this case, the control target air-fuel ratio is set to a predetermined rich air-fuel ratio (a value richer than the theoretical air-fuel ratio) (step 108), and then S regeneration control is executed (step 118). That is, in this case, the control target air-fuel ratio is maintained at the rich air-fuel ratio during the execution of the S regeneration control. That is, the S regeneration control is executed in the normal mode.

  On the other hand, if it is determined in step 106 that the vehicle is not traveling at a high speed, next, information about the current location of the vehicle and the surrounding situation is acquired from the navigation system 46 (step 110).

  Next, based on the information acquired in step 110, it is determined whether there is a high or low possibility that a person is near the vehicle (step 112). For example, if the current location of the vehicle is an urban area, it can be estimated that there is a high possibility that a pedestrian is nearby. If the current location of the vehicle is a toll road toll gate, there is a possibility that a toll collector is nearby. It can be estimated to be high. On the other hand, when the current location of the vehicle is in the suburbs or mountains, it can be estimated that there is a low possibility that a person is near the vehicle. In step 112, it is determined by such a predetermined method whether or not there is a high possibility that a person is near the vehicle.

  If it is determined in step 112 that it is unlikely that a person is near the vehicle, the control target air-fuel ratio is set to a predetermined rich air-fuel ratio (step 108), and then S regeneration control is executed. (Step 118). That is, in this case, the S regeneration control is executed in the normal mode, as in the case of high speed traveling described above.

  On the other hand, if it is determined in step 112 that there is a high possibility that a person is near the vehicle, the elapsed time after the control target air-fuel ratio is set to the rich air-fuel ratio is set to a predetermined time. Is determined (step 114). If it is determined in step 114 that the elapsed time has not reached the predetermined time, the control target air-fuel ratio is set to a rich air-fuel ratio (step 108). On the other hand, when it is determined in step 114 that the elapsed time has reached the predetermined time, the control target air-fuel ratio is set to a predetermined lean air-fuel ratio (a value leaner than the theoretical air-fuel ratio) (step). 116). In this way, after the control target air-fuel ratio is set to the rich air-fuel ratio or the lean air-fuel ratio, the S regeneration control is executed (step 118). Accordingly, in the S regeneration control in this case, the control target air-fuel ratio is temporarily set to the lean air-fuel ratio every time a predetermined time elapses when the control target air-fuel ratio is set to the rich air-fuel ratio. Note that the predetermined time (that is, the cycle for switching the control target air-fuel ratio from the rich air-fuel ratio to the lean air-fuel ratio) is such that the air-fuel ratio of the inflowing gas is reduced before the oxygen storage amount of the oxygen storage material in the NOx catalyst 36 becomes zero. It is preferable that the length is such that the lean air-fuel ratio can be switched.

  As described above, according to the routine processing shown in FIG. 2, when it is determined that there is a high possibility that a person is near the vehicle, the air-fuel ratio of the inflowing gas is periodically changed from the stoichiometric air-fuel ratio. The S regeneration control is executed in the lean harmful component suppression mode. For this reason, since generation | occurrence | production of hydrogen sulfide can be suppressed reliably, it can prevent reliably having a bad influence on the person near the vehicle. Further, even when it is determined that there is a high possibility that a person is near the vehicle, the S regeneration control can be executed, so that the NOx occlusion capability of the sulfur poisoned NOx catalyst 36 is reliably recovered. Can be made. Therefore, it is possible to reliably prevent the situation in which the internal combustion engine 10 is operated for a long time with the NOx catalyst 36 being sulfur-poisoned, and the amount of NOx emission to the atmosphere increases. Can be reliably avoided.

  In the first embodiment described above, the ECU 50 executes the processing of the routine shown in FIG. 2 so that the “S regeneration control means” in the first and second inventions becomes the steps 106, 110 and 112 described above. The “determination means” in the first and fourth aspects of the present invention is realized by executing the above process.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 3 and FIG. 4. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

  FIG. 3 is a diagram for explaining a system configuration according to the second embodiment of the present invention. In FIG. 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  As shown in FIG. 3, the system of the second embodiment includes an in-vehicle camera 47 and an image recognition device 48 instead of the navigation system 46. The in-vehicle camera 47 captures an image around the vehicle. The image recognition device 48 is configured to recognize a person in the video by performing image recognition processing on the video. In the system of the present embodiment, it is possible to detect whether or not there is a person around the vehicle by processing an image captured by the in-vehicle camera 47 with the image recognition device 48. And when execution of S regeneration control is requested | required, when it was detected that a person exists around the vehicle, it decided to perform S regeneration control in harmful | toxic component suppression mode.

  In the present embodiment, the method of S regeneration control in the harmful component suppression mode is different from that in the first embodiment. In the present embodiment, in the harmful component suppression mode, control is performed such that the lower limit value of the air-fuel ratio of the inflowing gas is leaner (richer than the theoretical air-fuel ratio) than in the normal mode.

  In the S regeneration control, it becomes easier to desorb SOx as the air-fuel ratio of the inflowing gas becomes richer. However, when the air-fuel ratio of the inflowing gas becomes a very rich value (for example, less than 12 when the fuel is gasoline), the amount of hydrogen sulfide generated increases. Therefore, in the present embodiment, when the S regeneration control in the harmful component suppression mode is executed, the control target air-fuel ratio is set to a value on the lean side than in the normal mode. Thereby, it is possible to reliably prevent the air-fuel ratio of the inflowing gas from becoming an extremely rich value as described above, and to suppress the generation of hydrogen sulfide.

[Specific Processing in Second Embodiment]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 4, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 4, first, the sulfur poisoning amount of the NOx catalyst 36 is read (step 100), and whether or not the S regeneration control needs to be executed based on the value of the sulfur poisoning amount. Is determined (step 102). If it is determined in step 102 that the S regeneration control needs to be executed, then the current operating state of the internal combustion engine 10 and the vehicle is read (step 104), and the read operating state is obtained. Based on this, it is determined whether or not the vehicle is traveling at high speed (step 106).

  If it is determined in step 106 that the vehicle is traveling at high speed, it can be estimated that there is no human being near the vehicle. In this case, the control target air-fuel ratio is set to a predetermined air-fuel ratio with a high degree of richness (hereinafter referred to as “strong rich”) (step 120), and then S regeneration control is executed (step 128). ). The S regeneration control in this case corresponds to the normal mode. In the S regeneration control in the normal mode, the air-fuel ratio of the inflowing gas is controlled to be rich, so that SOx can be desorbed quickly and reliably, but hydrogen sulfide may be generated.

  On the other hand, if it is determined in step 106 that the vehicle is not traveling at a high speed, the situation around the vehicle is detected based on the video of the in-vehicle camera 47 (step 122). In this step 122, the video of the in-vehicle camera 47 is captured, and the image recognition device 48 executes a process for recognizing whether or not a person is captured in the video.

  Subsequently, based on the situation around the vehicle (image recognition result) detected in step 122, it is determined whether or not there is a person near the vehicle (step 124). As a result, when it is determined that there is no person near the vehicle, the control target air-fuel ratio is set to be rich (step 120), and then S regeneration control is executed (step 128). That is, in this case, the S regeneration control is executed in the normal mode, as in the case of high speed traveling described above.

  On the other hand, if it is determined in step 124 that there is a person near the vehicle, the control target air-fuel ratio is a predetermined air-fuel ratio (hereinafter referred to as “weak”) that is less rich than the strong rich. (Referred to as “rich”) (step 126), and then S regeneration control is executed (step 128). The S regeneration control in this case corresponds to a harmful component suppression mode. In this case, the air-fuel ratio of the inflowing gas is controlled to be slightly rich with a relatively small rich degree. For this reason, it is reliably prevented that the air-fuel ratio of the inflowing gas becomes an extremely rich value (less than about 12 in the case of gasoline) where hydrogen sulfide is easily generated. Therefore, the generation of hydrogen sulfide can be reliably suppressed, and the S regeneration control can be executed without adversely affecting a person near the vehicle.

  According to the second embodiment described above, the same effect as in the first embodiment described above can be obtained. In the present invention, the S regeneration control method in the harmful component suppression mode is not limited to the method described in the first or second embodiment, and the generation of hydrogen sulfide is suppressed as compared with the normal mode. Any method can be used as long as it is possible. For example, in the harmful component suppression mode, the temperature of the NOx catalyst 36 during execution of the S regeneration control may be controlled to be lower than that in the normal mode. Hydrogen sulfide tends to be generated as the temperature of the NOx catalyst 36 increases. For this reason, the generation of hydrogen sulfide can also be suppressed by a method in which the temperature of the NOx catalyst 36 during the execution of the S regeneration control is made lower than that in the normal mode.

  In the second embodiment described above, the ECU 50 executes the process of the routine shown in FIG. 4 so that the “S regeneration control means” in the first and third inventions is the process of steps 106, 122, and 124 described above. By executing this, the “determination means” in the first and fourth inventions are realized.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the system configuration | structure of Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake valve 13 Exhaust valve 14 Spark plug 15 Fuel injector 16 Fuel tank 17 Fuel piping 20 Intake system 22 Intake passage 24 Throttle valve 30 Exhaust system 32 Exhaust passage 34 Start catalyst 36 NOx catalyst 37 Air-fuel ratio sensor 38 Oxygen sensor 50 ECU

Claims (4)

A NOx catalyst installed in the exhaust passage of the internal combustion engine;
S regeneration control means for executing S regeneration control for desorbing the sulfur component adsorbed on the NOx catalyst when necessary;
Determining means for determining whether or not there is a high possibility that a person is near a vehicle equipped with the internal combustion engine;
With
The S regeneration control means executes the S regeneration control in a normal mode when it is not determined that there is a high possibility that a person is near the vehicle when the S regeneration control is necessary. When it is determined that there is a high possibility that a person is near the vehicle, the S regeneration control is executed in a harmful component suppression mode in which the amount of harmful components discharged from the NOx catalyst is small compared to the normal mode. An exhaust emission control device for an internal combustion engine.   The S regeneration control means controls the air-fuel ratio of the exhaust gas flowing into the NOx catalyst to be periodically leaner than the stoichiometric air-fuel ratio in the harmful component suppression mode. The exhaust gas purification apparatus for an internal combustion engine according to claim 1.   The S regeneration control unit controls the lower limit value of the air-fuel ratio of the exhaust gas flowing into the NOx catalyst so as to be leaner than the normal mode in the harmful component suppression mode. Item 2. An exhaust emission control device for an internal combustion engine according to Item 1.   The determination means determines whether or not there is a high possibility that a person is near the vehicle based on at least one of the operating state of the internal combustion engine, navigation information, and a video of an in-vehicle camera that captures the outside of the vehicle. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3, further comprising means for determining.

Images