JP2014173558A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of suitably executing S purge processing of an oxidation catalyst.SOLUTION: A normal S purge request is read when an execution request of diesel particulate filter regeneration processing is made (S10, S12). Diesel particulate filter regeneration processing is started after execution of normal S purge control when the normal S purge request is made (S14-S18). The normal S purge processing request is stored when an oxidation catalyst inside temperature is equal to or lower than a first prescribed value and an oxidation catalyst outlet temperature is higher than a second prescribed value (S20-S24). When the oxidation catalyst inside temperature is equal to or lower than the first prescribed value and the oxidation catalyst outlet temperature is equal to or lower than the second prescribed value, diesel particulate filter regeneration processing is temporarily interrupted, and diesel particulate filter regeneration processing is restarted after execution of forcible S purge control, and the processing is continued until prescribed conditions are satisfied (S22, S26-S30).

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to a purge process for a catalyst.

Conventionally, in a diesel engine, a catalyst that collects or oxidizes hydrocarbons (HC) and carbon monoxide (CO) contained in exhaust gas from the engine in an exhaust passage, and a diesel particulate that collects particulate matter (PM). An exhaust gas purification device such as a curate filter is provided.
In such an exhaust gas purification device, if PM accumulates on the diesel particulate filter during engine operation, the diesel particulate filter will eventually become clogged, and the exhaust pressure will increase, causing an adverse effect. When the amount of PM accumulated in the diesel particulate filter exceeds a certain amount, fuel is supplied to the oxidation catalyst, and an oxidation reaction is caused in the oxidation catalyst to increase the temperature of exhaust gas flowing into the diesel particulate filter. A regeneration process for burning and removing PM accumulated in the curate filter is performed.

  However, the oxidation catalyst is configured to contain palladium (Pd), and the palladium is deteriorated by sulfur content (S) contained in the fuel, so-called sulfur poisoning, and the oxidation catalyst is sulfur. If poisoning occurs, even if fuel is supplied to the oxidation catalyst during the regeneration process of the diesel particulate filter, the oxidation catalyst will not sufficiently oxidize and the exhaust gas temperature cannot be raised to the optimum temperature for the regeneration process. , Diesel particulate filter may become poorly regenerated.

  Therefore, in Patent Document 1, an appropriate oxidation catalyst temperature increase value, which is an appropriate temperature increase value of the oxidation catalyst, is calculated based on the fuel injection amount and the exhaust gas amount during the regeneration process of the diesel particulate filter. In addition, the measured oxidation catalyst temperature rise value, which is the actual temperature rise value of the oxidation catalyst, is calculated from the exhaust gas temperature discharged from the oxidation catalyst. Then, the exhaust gas temperature flowing into the oxidation catalyst is raised from the appropriate oxidation catalyst temperature rise value and the measured oxidation catalyst temperature rise value, and the sulfur content adsorbed in the oxidation catalyst is removed.

JP 2010-10200 A

  In the exhaust gas aftertreatment device of Patent Document 1 above, during the regeneration processing of the diesel particulate filter, the actual oxidation catalyst temperature rise value obtained from the appropriate oxidation catalyst temperature rise value calculated from the fuel injection amount and the exhaust gas amount and the exhaust gas temperature. If the measured oxidation catalyst temperature rise value is determined to be lower than the appropriate oxidation catalyst temperature rise value, the regeneration process of the diesel particulate filter is completed, the exhaust gas temperature flowing into the oxidation catalyst is raised, Sulfur poisoning recovery processing, so-called S purge processing is performed.

  However, if it is determined that the measured oxidation catalyst temperature rise value is lower than the appropriate oxidation catalyst temperature rise value, diesel particulates may be used even if there is little sulfur poisoning and there is no need to recover from sulfur poisoning early. Since the S purge process of the oxidation catalyst is performed after the filter regeneration process is completed, the frequency of performing the S purge process increases. In addition, after the regeneration process of the diesel particulate filter, hydrocarbon (HC) components may be accumulated without being burned by the oxidation catalyst. This is not preferable because exhaust gas is introduced into the oxidation catalyst, hydrocarbons are discharged as unburned gas, and white smoke is generated.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can appropriately perform an S purge process of an oxidation catalyst. .

  In order to achieve the above object, in the exhaust gas purification apparatus for an internal combustion engine according to claim 1, the oxidation catalyst disposed in the exhaust passage of the internal combustion engine and the exhaust passage downstream of the oxidation catalyst are disposed. Exhaust purification means, temperature detection means capable of detecting temperatures of a plurality of parts in the oxidation catalyst in the exhaust gas flow direction in the exhaust passage, and a plurality of purge processing methods for desorbing exhaust gas components adsorbed on the oxidation catalyst And purge processing control means for switching the purge processing method in accordance with the temperature of each of the plurality of parts during regeneration processing of the exhaust gas purification means.

  Further, in the exhaust emission control device for an internal combustion engine according to claim 2, in claim 1, the temperature raising means for raising the temperature of the exhaust gas flowing into the oxidation catalyst, and the fuel for supplying fuel upstream of the oxidation catalyst of the internal combustion engine A plurality of purging methods, wherein the exhaust gas flowing into the oxidation catalyst is heated, and the exhaust gas flowing into the oxidation catalyst is heated, and then the exhaust gas is exhausted. The second purging process for supplying a small amount of the fuel with respect to the fuel supply amount during the regeneration process of the purification means.

Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 3, in claim 1, the plurality of purge processing methods include a first purge process for performing a purge process before the start of the regeneration process of the next exhaust purification unit. And a second purge process in which the regeneration process of the exhaust gas purification means is interrupted and a purge process is performed.
Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 4, the purge process control means in claim 3 restarts the regeneration process of the exhaust gas purification means after performing the second purge process. And

  Further, in the exhaust emission control device for an internal combustion engine according to claim 5, in any one of claims 2 to 4, the temperature detecting means includes a first temperature sensor for detecting an internal temperature of the oxidation catalyst, and the oxidation catalyst. A second temperature sensor for detecting the outlet temperature of the oxidation catalyst, and the purge process control means performs the first purge process when the internal temperature of the oxidation catalyst is equal to or lower than a first predetermined value, When the outlet temperature of the oxidation catalyst is equal to or lower than a second predetermined value, the second purge process is performed.

  Further, in the exhaust emission control device for an internal combustion engine according to claim 6, in claim 5, the temperature raising means for raising the temperature of the exhaust gas flowing into the oxidation catalyst, and the fuel for supplying fuel upstream of the oxidation catalyst of the internal combustion engine A supply means, and the purge process control means terminates the temperature rise of the exhaust gas flowing into the oxidation catalyst when the internal temperature of the oxidation catalyst becomes higher than a third predetermined value during the first purge process. In the second purge process, when the internal temperature of the oxidation catalyst becomes higher than a third predetermined value, the temperature of the exhaust gas flowing into the oxidation catalyst is terminated, and then the exhaust purification unit is in the regeneration process. Supply of a small amount of the fuel relative to the supply amount of fuel is started, and when the outlet temperature of the oxidation catalyst becomes higher than a fourth predetermined value, the temperature of the exhaust gas flowing into the oxidation catalyst and the supply of the fuel are increased. Characterized in that it terminate the.

  Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 7, in claim 2 or 6, the temperature raising means is provided in an intake passage of the internal combustion engine, and reduces the amount of intake air flowing into the combustion chamber of the internal combustion engine. Intake air amount adjusting means for adjusting, wherein the purge process control means is configured to control the combustion chamber of the internal combustion engine in the first purge process or the second purge process with respect to the regeneration process of the exhaust gas purification unit. The exhaust gas flowing into the oxidation catalyst is heated by controlling the opening of the intake air amount adjusting means so that the amount of intake air flowing into the exhaust gas decreases.

  Further, in the exhaust gas purification apparatus for an internal combustion engine according to claim 8, the oxidation catalyst disposed in the exhaust passage of the internal combustion engine, the exhaust purification means disposed in the exhaust passage downstream of the oxidation catalyst, and the oxidation A temperature detecting means for detecting the exhaust gas temperature downstream of the catalyst; and a plurality of purge processing methods for desorbing exhaust gas components adsorbed on the oxidation catalyst. Purge processing control means for switching the purge processing method in accordance with the exhaust gas temperature.

  The oxidation catalyst is deteriorated by adsorption of sulfur (S) contained in the fuel, so-called sulfur poisoning. The adsorbed sulfur content is, for example, that the sulfur content adsorbed in the oxidation catalyst supplies fuel to the oxidation catalyst, raises the temperature of the exhaust gas by the oxidation reaction in the oxidation catalyst, and converts the high temperature exhaust gas to the oxidation catalyst. When regeneration processing is performed by supplying PM to the downstream exhaust purification means and burning or reducing and removing PM, sulfur, NOx, etc. deposited on the exhaust purification means, an oxidation reaction takes place in the oxidation catalyst, and the outlet of the oxidation catalyst The oxidation catalyst is desorbed as it goes to the high temperature, and is desorbed, and it decreases as it goes to the outlet of the oxidation catalyst. And the temperature of an oxidation catalyst falls because the oxidation reaction in an oxidation catalyst reduces as the adsorbed sulfur content increases.

  Therefore, according to the first aspect of the present invention, for example, during the regeneration process of the exhaust purification means, the sulfur content adsorbed at each part is desorbed according to the respective temperatures of the plurality of parts such as the inside and the outlet of the oxidation catalyst. By switching to a purge method that is optimal for separation, if there is a large amount of sulfur adsorbed only inside the oxidation catalyst, there is no need to perform the purge process at an early stage. This can reduce the frequency of the purge process. Further, for example, by temporarily suspending the regeneration process of the exhaust purification unit and performing the purge process before or immediately after the regeneration process of the exhaust purification unit, the oxidation catalyst of the hydrocarbon (HC) component by the regeneration process of the exhaust purification catalyst Therefore, the generation of white smoke can be suppressed even if high-temperature exhaust gas is introduced into the oxidation catalyst during the purge process.

  Therefore, the oxidation catalyst purge process can be appropriately performed while suppressing an excessive purge process of the oxidation catalyst.

1 is a schematic configuration diagram of an engine to which an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied. It is a flowchart of S purge control which the engine control unit of the exhaust gas purification apparatus of the internal combustion engine which concerns on this invention performs. 3 is a flowchart of normal S purge processing of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. It is a flowchart of the forced S purge process of the exhaust gas purification apparatus for an internal combustion engine according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an engine 1 to which an exhaust gas purification apparatus for an internal combustion engine is applied.
As shown in FIG. 1, an exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a fuel injection nozzle (fuel supply means) 2 provided in an engine (internal combustion engine) 1 mounted on a vehicle (not shown) as a power source, and an electronic device. A control throttle valve (intake air amount adjusting means) 9, a temperature sensor (first temperature sensor) 16, a temperature sensor (second temperature sensor) 17, and an engine control unit (purge processing control means) 30 are configured. .

  The engine 1 is a multi-cylinder direct injection internal combustion engine (for example, a common rail diesel engine). Specifically, the high-pressure fuel accumulated in the common rail is supplied to the fuel injection nozzle 2 of each cylinder, and can be injected from the fuel injection nozzle 2 into the combustion chamber 3 of each cylinder at an arbitrary injection timing and injection amount. doing. Further, an intake port 4 for introducing fresh air into the combustion chamber 3 is formed upstream of the combustion chamber 3 of each cylinder of the engine 1 so as to communicate with the combustion chamber 3. An exhaust port 5 for discharging exhaust gas in the combustion chamber 3 is formed downstream of the combustion chamber 3 of each cylinder of the engine 1 so as to communicate with the combustion chamber 3.

  Upstream of the intake port 5, an air cleaner 6 that removes dust in the intake air sucked from the uppermost stream, a compressor housing (not shown) of a turbocharger 7 that compresses the intake air using the energy of the exhaust gas, and a compressed high temperature An intercooler 8 that cools the intake air, an electronically controlled throttle valve 9 that adjusts the flow rate of the intake air, and an intake manifold 10 that distributes the intake air to each cylinder are provided in communication with each other. The electronically controlled throttle valve 9 is provided with a throttle position sensor 11 for detecting the degree of opening of the throttle valve.

An exhaust manifold 12 that collects exhaust gas discharged from each cylinder, a turbine housing (not shown) that introduces exhaust gas into the turbocharger 7, and an exhaust pipe (exhaust passage) 13 are provided downstream of the exhaust port 5. It has been.
In the exhaust pipe 13, an oxidation catalyst 14 and a diesel particulate filter (exhaust gas purification means) 15 are provided so as to communicate with each other in order from upstream.

  The oxidation catalyst 14 includes palladium (Pd) and oxidizes components to be oxidized such as hydrocarbon (THC) or carbon monoxide (CO) in the exhaust gas. When the sulfur content in the fuel is adsorbed on palladium (Pd), the oxidation catalyst 14 reduces the oxidation reaction at the oxidation catalyst 14, and the temperature of the oxidation catalyst 14 and the temperature of the exhaust gas discharged from the oxidation catalyst 14 are reduced. It has the characteristic of not rising.

  The diesel particulate filter 15 collects and burns particulate matter (PM) (corresponding to the exhaust gas component of the present invention) whose main component is graphite in the exhaust gas. The PM deposited on the diesel particulate filter 15 is injected with fuel from the fuel injection nozzle 2 by combustion post injection or HC addition post injection, and the exhaust gas having a rich air-fuel ratio is oxidized by the oxidation catalyst 14 to generate high-temperature exhaust gas. Thus, the high-temperature exhaust gas flows into the diesel particulate filter 15 and is removed by combustion.

The oxidation catalyst 14 is provided with a temperature sensor 16 for detecting the internal temperature of the oxidation catalyst 14 so as to protrude into the oxidation catalyst 14.
Further, a temperature sensor 17 for detecting the outlet temperature of the oxidation catalyst 14 is provided downstream of the oxidation catalyst 14 in the exhaust pipe 13 so as to protrude into the exhaust pipe 13.
The intake manifold 10 and the exhaust manifold 12 are provided with an exhaust gas recirculation path 18 for returning a part of the exhaust gas to the intake air so as to communicate with each other. The exhaust gas recirculation path 18 is provided with an exhaust gas recirculation amount control valve 19 for adjusting the amount of exhaust gas returning to the intake air, that is, the exhaust gas recirculation amount, and a recirculation gas cooler 20 for cooling the exhaust gas returning to the intake air. .

  Various devices and various sensors such as the fuel injection nozzle 2, the electronically controlled throttle valve 9, the throttle position sensor 11, and the temperature sensors 16 and 17 are control devices for comprehensive control of the engine 1. It is electrically connected to an engine control unit 30 including an output device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a timer, a central processing unit, and the like. The engine control unit 30 controls the operation of various devices (not shown) provided in the engine 1 based on information from various sensors.

Sensors such as a throttle position sensor 11, temperature sensors 16 and 17, and an engine 1 and a sensor (not shown) provided in the vehicle are electrically connected to the input side of the engine control unit 30. Detection information is input.
On the other hand, the fuel injection nozzle 2 and the electronic control throttle valve 9 are electrically connected to the output side of the engine control unit 30.

  As a result, the engine control unit 30 supplies a drive signal to the fuel injection nozzle 2 during normal operation of the engine 1 based on the detection values of the sensors, and the pre-injection, main injection, and after-injection from the fuel injection nozzle 2. The fuel injection amount and injection timing of the main injection group contributing to the output torque of the engine 1 are optimally controlled. Further, the engine control unit 30 determines the driving state of the vehicle based on the detection value of each sensor, determines the amount of PM deposited on the diesel particulate filter 15, and determines that the amount of PM deposited is large. In order to perform fuel addition for making the exhaust gas flowing into the catalyst 14 a rich air-fuel ratio, combustion post injection for injecting fuel from the fuel injection nozzle 2 after the main injection group and HC addition post injection are performed. Is supplied to the oxidation catalyst 14 and is oxidized by the oxidation catalyst 14 to burn the PM accumulated on the diesel particulate filter 15 as high-temperature exhaust gas (regeneration of the exhaust purification means of the present invention). Equivalent to processing). The combustion post injection does not contribute to the output torque of the engine 1 but injects the fuel into the combustion chamber 3 in the first stage of the expansion stroke so that the combustion of the fuel is completed in the cylinder (cylinder) of the engine 1. . Further, the HC addition post-injection does not contribute to the output torque of the engine 1 but injects the fuel into the combustion chamber 3 at the later stage of the expansion stroke so that the fuel is combusted by the oxidation catalyst 14. The engine control unit 30 performs S purge control for desorbing the sulfur content of the fuel adsorbed on the oxidation catalyst 14. The S purge control is performed during the diesel particulate filter regeneration process. In the S purge control, based on the internal temperature of the oxidation catalyst 14 detected by the temperature sensor 16 or the outlet temperature of the oxidation catalyst 14 detected by the temperature sensor 17, the normal S purge process (the first step of the present invention) is performed. A plurality of S purge processing methods (corresponding to a plurality of purge processing methods of the present invention) of forced S purge processing (corresponding to the second purge processing of the present invention) are switched and adsorbed on the oxidation catalyst 14 Desorb sulfur.

Next, the S purge control of the oxidation catalyst 14 in the engine control unit 30 according to the present invention will be described.
FIG. 2 is a flowchart of the S purge control executed by the engine control unit 30 of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. FIG. 3 is a flowchart of a normal S purge process of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. FIG. 4 is a flowchart of the forced S purge process of the exhaust gas purification apparatus for an internal combustion engine according to the present invention.

  As shown in FIG. 2, in step S10, it is determined whether or not there is a diesel particulate filter regeneration request. More specifically, it is determined that PM has accumulated on the diesel particulate filter 15 based on the detection result of the sensor provided in the vehicle or the engine 1, and it is determined whether or not there is a request to perform the diesel particulate filter regeneration process. . If the determination result is true (Yes) and there is a diesel particulate filter regeneration request, the process proceeds to step S12. If the determination result is NO (No) and there is no request for regeneration of the diesel particulate filter, this routine is returned.

In step S12, a normal S purge request is read. Specifically, the normal S purge request stored at the previous S purge control is read. Then, the process proceeds to step S14.
In step S14, it is determined whether or not there is a normal S purge request. If the determination result is true (Yes) and there is a normal S purge request, the process proceeds to step S16. If the determination result is NO (No) and there is no normal S purge request, the process proceeds to step S18.

In step S16, a normal S purge process is performed. Specifically, the normal S purge process is performed based on the flowchart of the normal S purge process shown in FIG. Then, the process proceeds to step S18.
In step S18, the diesel particulate filter regeneration process is started. Specifically, combustion post injection and HC addition post injection are performed after the main injection group, fuel is supplied to the oxidation catalyst 14, the fuel is burned by the oxidation catalyst 14, and the diesel particulate filter 15 is heated to a high temperature. The diesel particulate filter regeneration process that introduces the exhaust gas is started. Then, the process proceeds to step S20.

  In step S20, it is determined whether or not the oxidation catalyst internal temperature is higher than a first predetermined value. Specifically, it is determined whether or not the internal temperature of the oxidation catalyst 14 detected by the temperature sensor 16 is higher than a first predetermined value. If the determination result is true (Yes) and the internal temperature of the oxidation catalyst is higher than the first predetermined value, the process proceeds to step S28. If the determination result is negative (No) and the internal temperature of the oxidation catalyst is not higher than the first predetermined value, the process proceeds to step S22. The first predetermined value is a threshold value for determining that the amount of sulfur adsorbed inside the oxidation catalyst 14 has increased to a predetermined amount or more. Therefore, the first predetermined value is set in advance by experiment, analysis, or the like to a value that can determine that the amount of sulfur content adsorbed inside the oxidation catalyst 14 has increased. Further, the first predetermined value is stored as a map for each operating state of the engine 1.

  In step S22, it is determined whether or not the oxidation catalyst outlet temperature is higher than a second predetermined value. Specifically, it is determined whether or not the outlet temperature of the oxidation catalyst 14 detected by the temperature sensor 17 is higher than a second predetermined value. If the determination result is true (Yes) and the oxidation catalyst outlet temperature is higher than the second predetermined value, the process proceeds to step S24. If the determination result is no (No) and the oxidation catalyst outlet temperature is not higher than the second predetermined value, the process proceeds to step S26. Note that the second predetermined value is a threshold value for determining that the amount of sulfur adsorbed on the outlet side of the oxidation catalyst 14 has increased to a predetermined amount or more. Therefore, the second predetermined value is set in advance by experiment, analysis, or the like so that it can be determined that the amount of adsorption of the sulfur component at the outlet of the oxidation catalyst 14 has increased. Further, the second predetermined value is set to a value higher than the first predetermined value because the temperature increases as the temperature of the oxidation catalyst 14 moves from the inside of the oxidation catalyst 14 toward the outlet. And the 2nd predetermined value is mapped and memorized for every operation situation of engine 1 like the 1st predetermined value.

In step S24, a normal S purge process request is output. Specifically, the normal S purge process request is stored so that the normal S purge process shown in FIG. 3 is performed during the next diesel particulate filter regeneration process. Then, the process proceeds to step S28.
On the other hand, in step S26, a forced S purge process is performed. Specifically, the diesel particulate filter regeneration process is temporarily interrupted, and the forced S purge process is performed based on the flowchart of the forced S purge process shown in FIG. Then, the process proceeds to step S28.

In step S28, the diesel particulate filter regeneration process is continued. Specifically, if the diesel particulate filter regeneration process is being performed, the process is continued, and if the diesel particulate filter regeneration process is not being performed, the diesel particulate filter regeneration process is resumed. Then, the process proceeds to step S30.
In step S30, the diesel particulate filter regeneration process is terminated. Specifically, after the diesel particulate filter regeneration process is performed, the diesel particulate filter regeneration process is terminated when a predetermined condition is satisfied. Then, this routine is returned.

Next, the normal S purge process will be described.
As shown in FIG. 3, in step S110, exhaust temperature increase control is executed. Specifically, the opening degree of the electronically controlled throttle valve 9 is decreased so that the air-fuel ratio in the combustion chamber 3 of the engine 1 becomes deep, and the amount of intake air introduced into the combustion chamber 3 of the engine 1 is decreased. Exhaust temperature rise control for raising the temperature of the exhaust gas discharged from the combustion chamber 3 is executed. Then, the process proceeds to step S112.

  In step S112, it is determined whether or not the oxidation catalyst internal temperature is higher than a third predetermined value. Specifically, it is determined whether or not the internal temperature of the oxidation catalyst 14 detected by the temperature sensor 16 is higher than a third predetermined value. If the determination result is true (Yes) and the internal temperature of the oxidation catalyst is higher than the third predetermined value, the process proceeds to step S114. If the determination result is no (No) and the internal temperature of the oxidation catalyst is not higher than the third predetermined value, the process returns to step S110. The third predetermined value is set to a value equal to or higher than the first predetermined value in advance by experiment, analysis, or the like because the temperature of the oxidation catalyst 14 increases as the amount of sulfur adsorbed inside the oxidation catalyst 14 decreases. Is done. Further, the third predetermined value is mapped and stored for each operating state of the engine 1 in the same manner as the first predetermined value.

In step S114, the exhaust temperature raising control is terminated. Then, this routine is returned.
Next, the forced S purge process will be described.
As shown in FIG. 4, in step S210, exhaust temperature increase control is executed in the same manner as in step S110 of the normal S purge process. Then, the process proceeds to step S212.

In step S212, as in step S112 of the normal S purge, it is determined whether or not the internal temperature of the oxidation catalyst is higher than a third predetermined value. If the determination result is true (Yes) and the internal temperature of the oxidation catalyst is higher than the third predetermined value, the process proceeds to step S214. If the determination result is no (No) and the internal temperature of the oxidation catalyst is not higher than the third predetermined value, the process returns to step S210.
In step S214, post injection control is additionally performed. Specifically, in addition to exhaust temperature increase control for increasing the temperature of the exhaust gas discharged from the combustion chamber 3 of the engine 1 by reducing the opening of the electronically controlled throttle valve 9, the combustion post injection is performed after the main injection group. Post injection control for performing HC addition post injection is performed. Then, the process proceeds to step S216. The injection amounts of the combustion post injection and the HC addition post injection here decrease the opening degree of the electronically controlled throttle valve, so that the combustion post injection and the HC addition post injection during the diesel particulate filter regeneration processing are performed. It is set small with respect to the injection amount.

  In step S216, it is determined whether or not the oxidation catalyst outlet temperature is higher than a fourth predetermined value. Specifically, it is determined whether or not the outlet temperature of the oxidation catalyst 14 detected by the temperature sensor 17 is higher than a fourth predetermined value. If the determination result is true (Yes) and the oxidation catalyst outlet temperature is higher than the fourth predetermined value, the process proceeds to step S218. If the determination result is no (No) and the oxidation catalyst outlet temperature is not higher than the fourth predetermined value, the process returns to step S214. The fourth predetermined value is set to a value equal to or greater than the second predetermined value in advance by experiment, analysis, or the like because the temperature of the oxidation catalyst 14 increases as the amount of sulfur content adsorbed inside the oxidation catalyst 14 decreases. Is done. Further, the fourth predetermined value is mapped and stored for each operating state of the engine 1 in the same manner as the first predetermined value.

In step S218, the exhaust temperature raising control and the post injection control are terminated. Then, this routine is returned.
As described above, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, it is determined that PM has accumulated on the diesel particulate filter 15 based on the detection result of the sensor provided in the vehicle or the engine 1, and the diesel particulate filter regeneration process is performed. When there is an execution request, the normal S purge request stored during the previous S purge control is read. When there is a normal S purge request, the electrons are controlled so that the air-fuel ratio in the combustion chamber 3 of the engine 1 is concentrated until the internal temperature of the oxidation catalyst 14 detected by the temperature sensor 16 becomes higher than the third predetermined value. Exhaust temperature increase in which the opening degree of the control throttle valve 9 is decreased, the amount of intake air introduced into the combustion chamber 3 of the engine 1 is decreased, and the temperature of the exhaust gas discharged from the combustion chamber 3 of the engine 1 is increased. The normal S purge control for performing the control is performed. Thereafter, combustion post injection and HC addition post injection are performed after the main injection group, fuel is supplied to the oxidation catalyst 14, the fuel is burned by the oxidation catalyst 14, and high temperature exhaust gas is supplied to the diesel particulate filter 15. Diesel particulate filter regeneration process is started. If the internal temperature of the oxidation catalyst 14 detected by the temperature sensor 16 is higher than the first predetermined value, the diesel particulate filter regeneration process is performed until a predetermined condition is satisfied after the diesel particulate filter regeneration process is performed. Continue. On the other hand, if the internal temperature of the oxidation catalyst is not higher than the first predetermined value, it is determined whether or not the outlet temperature of the oxidation catalyst 14 detected by the temperature sensor 17 is higher than the second predetermined value. If the oxidation catalyst outlet temperature is higher than the second predetermined value, the normal S purge process request is stored so that the normal S purge process is performed at the next diesel particulate filter regeneration process. The diesel particulate filter regeneration process is continued until it is satisfied. On the other hand, if the oxidation catalyst outlet temperature is not higher than the second predetermined value, the diesel particulate filter regeneration process is temporarily stopped, and the exhaust temperature rise is increased in the same manner as in the normal S purge until the oxidation catalyst internal temperature becomes higher than the third predetermined value. Temperature control is performed, and then the combustion post injection and HC addition are performed after the main injection group in addition to the exhaust temperature increase control until the outlet temperature of the oxidation catalyst 14 detected by the temperature sensor 17 becomes higher than the fourth predetermined value. Forced S purge control for performing post injection control for performing post injection is performed. Thereafter, the diesel particulate filter regeneration process is resumed, and the diesel particulate filter regeneration process is continued until a predetermined condition is satisfied.

  Therefore, if the internal temperature of the oxidation catalyst 14 during the diesel particulate filter regeneration process is equal to or lower than the first predetermined value, the internal temperature of the oxidation catalyst 14 is not increased and the sulfur content adsorbed inside the oxidation catalyst 14 is increased. However, since the sulfur content is adsorbed only inside the oxidation catalyst 14 and there is no need to perform the normal S purge process at an early stage, before the next diesel particulate filter regeneration process is started, the oxidation catalyst 14 Until the internal temperature becomes higher than the third predetermined value, the opening degree of the electronically controlled throttle valve 9 is decreased, the amount of intake air introduced into the combustion chamber 3 of the engine 1 is decreased, and the exhaust air is discharged from the combustion chamber 3 of the engine 1. The sulfur content adsorbed inside the oxidation catalyst 14 can be desorbed by performing a normal S purge process that performs exhaust temperature rise control for raising the temperature of the exhaust gas to be produced. Runode, can reduce the frequency of S purge process.

  In addition, the diesel particulate filter is subjected to the normal S purge process before the diesel particulate filter regeneration process, or the suspension process is interrupted immediately after the diesel particulate filter regeneration process and the forced S purge process is performed. Since retention of hydrocarbon (HC) components in the oxidation catalyst 14 due to filter regeneration processing can be suppressed, white smoke is not generated even when high-temperature exhaust gas is introduced into the oxidation catalyst 14 during normal S purge processing and forced S purge processing. Occurrence can be suppressed.

  In the forced S purge process, the opening degree of the electronically controlled throttle valve 9 is decreased, the amount of intake air introduced into the combustion chamber 3 of the engine 1 is decreased, and the exhaust gas flowing into the oxidation catalyst 14 is heated. Later, by setting the combustion post-injection and HC addition post-injection of a small injection amount to the injection amount of combustion post-injection and HC addition post-injection in the diesel particulate filter regeneration process, the sulfur content in the oxidation catalyst 14 is increased. Can be prevented from adsorbing again.

  When the internal temperature of the oxidation catalyst 14 is higher than the third predetermined value, the normal S purge process is terminated. When the outlet temperature of the oxidation catalyst 14 is higher than the fourth predetermined value, the forced S purge process is terminated. The sulfur content adsorbed in each part of the oxidation catalyst 14 is changed by changing the temperature of each part of the oxidation catalyst 14 that terminates the normal S purge process or the forced S purge process according to the adsorption state of the sulfur part in each part 14. Can be removed with certainty.

  Further, in the normal S purge process or the forced S purge process, the opening degree of the electronically controlled throttle valve 25 is reduced so that the amount of intake air flowing into the combustion chamber 3 of the engine 1 is reduced compared to the diesel particulate filter regeneration process. Thus, the temperature of the exhaust gas flowing into the oxidation catalyst 14 is raised, and the temperature of the exhaust gas flowing into the oxidation catalyst 14 is increased by, for example, adding or increasing fuel injection into the exhaust pipe 13 or HC addition post injection. Therefore, by reducing the amount of fuel supplied to the oxidation catalyst 14, it is possible to suppress the sulfur component from being adsorbed again inside the oxidation catalyst 14.

This is the end of the description of the embodiment of the invention, but the invention is not limited to this embodiment.
For example, in this embodiment, the internal temperature and the outlet temperature of the oxidation catalyst 14 are detected by the temperature sensor 16 and the temperature sensor 17, respectively, and the amount of sulfur accumulated in each part of the oxidation catalyst 14 is estimated. However, the present invention is not limited to this. For example, the relationship between the adsorption amount of the sulfur for each part of the oxidation catalyst 14 and the exhaust gas temperature downstream of the oxidation catalyst 14 is obtained in advance through analysis, experiment, etc. Based on the relationship between the exhaust gas temperature detected by the temperature sensor 17 provided downstream of the oxidation catalyst 14, the amount of sulfur adsorbed for each site of the oxidation catalyst 14, and the exhaust gas temperature downstream of the oxidation catalyst 14, You may make it determine a site | part with much adsorption amount of a sulfur content.

  In this embodiment, a diesel particulate filter 15 is provided downstream of the oxidation catalyst 14 in the exhaust gas flow direction, and S purge control is performed to desorb sulfur adsorbed on the oxidation catalyst 14 during the diesel particulate filter regeneration process. However, the present invention is not limited to this. For example, a NOx trap catalyst for reducing and detoxifying nitrogen oxides in the exhaust gas is provided downstream of the oxidation catalyst 14 in the exhaust gas flow direction, and the fuel is used as an oxidation catalyst. The sulfur component adsorbed on the oxidation catalyst 14 is desorbed during the NOx purge process for desorbing the NOx adsorbed on the NOx trap catalyst supplied to the NOx 14 and the S purge process for desorbing the sulfur component adsorbed on the NOx trap catalyst. S purge control may be performed.

  In step S214 of the present embodiment, combustion post injection and HC addition post injection are performed after the main injection group to supply fuel to the oxidation catalyst 14, but the present invention is not limited to this. For example, Alternatively, an exhaust pipe fuel injection device that directly injects fuel into the exhaust pipe 13 may be provided in the exhaust pipe 13 upstream of the oxidation catalyst 14 so as to supply the fuel to the oxidation catalyst 14.

1 engine (internal combustion engine)
2 Fuel injection nozzle (fuel supply means)
3 Combustion chamber 9 Electronically controlled throttle valve (intake air volume adjusting means)
13 Exhaust pipe (exhaust passage)
14 Oxidation catalyst 15 Diesel particulate filter (exhaust gas purification means)
16 Temperature sensor (first temperature sensor)
17 Temperature sensor (second temperature sensor)
30 Engine control unit (purge processing control means)

Claims (8)

An oxidation catalyst disposed in an exhaust passage of the internal combustion engine;
Exhaust purification means disposed in the exhaust passage downstream of the oxidation catalyst;
Temperature detecting means capable of detecting temperatures of a plurality of portions in the oxidation catalyst in the exhaust gas flow direction in the exhaust passage;
A purge process having a plurality of purge processing methods for desorbing exhaust gas components adsorbed on the oxidation catalyst, and switching the purge processing method in accordance with the respective temperatures of the plurality of parts during the regeneration process of the exhaust gas purification means And an exhaust gas purifying device for an internal combustion engine. A temperature raising means for raising the temperature of the exhaust gas flowing into the oxidation catalyst;
Fuel supply means for supplying fuel upstream of the oxidation catalyst of the internal combustion engine,
The plurality of purge processing methods include a first purge process for raising the temperature of the exhaust gas flowing into the oxidation catalyst, and a temperature during the regeneration process of the exhaust purification means after raising the temperature of the exhaust gas flowing into the oxidation catalyst. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising a second purge process for supplying a small amount of the fuel with respect to the fuel supply amount.   The plurality of purge processing methods include a first purge process that performs a purge process before the start of the regeneration process of the exhaust purification unit next time, and a purge process that interrupts the regeneration process of the exhaust purification unit. The exhaust emission control device for an internal combustion engine according to claim 1, comprising a second purge process.   4. The exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein the purge process control means restarts the regeneration process of the exhaust gas purification means after performing the second purge process. The temperature detection means includes a first temperature sensor that detects an internal temperature of the oxidation catalyst, and a second temperature sensor that detects an outlet temperature of the oxidation catalyst,
The purge process control means performs the first purge process when the internal temperature of the oxidation catalyst is equal to or lower than a first predetermined value, and the outlet temperature of the oxidation catalyst is equal to or lower than a second predetermined value. The exhaust emission control device for an internal combustion engine according to any one of claims 2 to 4, wherein the second purge process is performed. A temperature raising means for raising the temperature of the exhaust gas flowing into the oxidation catalyst;
Fuel supply means for supplying fuel upstream of the oxidation catalyst of the internal combustion engine,
In the first purge process, the purge process control means ends the temperature rise of the exhaust gas flowing into the oxidation catalyst when the internal temperature of the oxidation catalyst becomes higher than a third predetermined value, and in the second purge process When the internal temperature of the oxidation catalyst becomes higher than a third predetermined value, the temperature of the exhaust gas flowing into the oxidation catalyst is terminated, and then the amount of fuel supplied during the regeneration process of the exhaust purification means Supply of a small amount of the fuel is started, and when the outlet temperature of the oxidation catalyst becomes higher than a fourth predetermined value, the temperature rise of the exhaust gas flowing into the oxidation catalyst and the supply of the fuel are terminated. An exhaust purification device for an internal combustion engine according to claim 5. The temperature raising means is an intake air amount adjusting means that is provided in an intake passage of the internal combustion engine and adjusts an intake air amount flowing into a combustion chamber of the internal combustion engine,
In the first purge process or the second purge process, the purge process control unit is configured so that the amount of intake air flowing into the combustion chamber of the internal combustion engine is smaller than that during the regeneration process of the exhaust gas purification unit. The exhaust purification device for an internal combustion engine according to claim 2 or 6, wherein the exhaust gas flowing into the oxidation catalyst is heated by controlling the opening degree of the intake air amount adjusting means. An oxidation catalyst disposed in an exhaust passage of the internal combustion engine;
Exhaust purification means disposed in the exhaust passage downstream of the oxidation catalyst;
Temperature detecting means for detecting the exhaust gas temperature downstream of the oxidation catalyst;
Purging having a plurality of purge processing methods for desorbing exhaust gas components adsorbed on the oxidation catalyst, and switching the purge processing method according to the exhaust gas temperature downstream of the oxidation catalyst during regeneration processing of the exhaust gas purification means And an exhaust emission control device for an internal combustion engine.

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