DE112016003417T5 - Control device for an internal combustion engine - Google Patents

Abstract

A control apparatus for an internal combustion engine, comprising: an exhaust gas component elimination control means that performs an exhaust gas component elimination process to eliminate a certain exhaust gas component from a catalyst; a filter regeneration control means that performs a filter regeneration process to regenerate a filter by the burning of particles accumulated in the filter; a determination means which, when the introduction of the EGR gas is requested, determines whether the filter regeneration process is performed after the exhaust gas component removal process has been performed; an air warm-up control means that warms up fresh air using an air-heating device when the determining means determines that the filter regeneration process is not yet performed; and an EGR gas introduction control means which performs the introduction of the EGR gas using an EGR device after the fresh air has been warmed up by the air warming device, when the determining means determines that the filter regeneration process is not yet performed.

Description

Technical area

The present invention relates to a control apparatus for an internal combustion engine equipped with an EGR apparatus.

background

In an internal combustion engine that performs lean combustion, such as in a diesel engine, it is necessary to suppress the emission of nitrogen oxide (hereinafter referred to as NOx) to the atmosphere. An exhaust gas recirculation (EGR: exhaust gas recirculation) device, which returns a portion of exhaust gas to an intake passage or intake passage, is a means for reducing NOx production of the internal combustion engine. Patent Document 1 discloses an internal combustion engine equipped with an LPL (low pressure loop) EGR device which communicates through an EGR passage between an exhaust passage downstream of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) and a suction passage upstream of a turbine of a turbocharger and returns a portion of the exhaust gas as EGR gas to the intake passage.

Furthermore, the EGR gas contains a lot of moisture. Therefore, when the EGR gas is mixed with fresh air, there is a possibility that the EGR gas is cooled by the fresh air at a relatively low temperature, the moisture condenses in the EGR gas, and therefore condensed water is generated in the intake passage. Furthermore, the exhaust gas contains sulfur components and a hydrocarbon component. These are exhaust components that not only reduce the purification performance of a diesel oxidation catalyst and a NO x storage reduction catalyst, but also exert an acid activity when dissolved in water. Therefore, when the EGR gas contains a certain exhaust gas component, such as the sulfur component and the hydrocarbon component, there is a possibility that the particular exhaust gas component will be dissolved in the condensed water and so acidify the condensed water, causing the engine to corrode or otherwise degrade ,

The disclosed in Patent Document 1 internal combustion engine is equipped with an intake air heater for heating the fresh air. By warming up the fresh air introduced into the intake passage by the intake air heater to increase its temperature, it is possible to raise a temperature of a gas mixture of the EGR gas and the fresh air so as to increase the condensation from that in the To suppress the moisture contained in the EGR gas. As a result, the generation of the condensed water in the intake passage can be suppressed and therefore corrosion and deterioration of the engine can be prevented.

quote list

patents

• Patent document 1: JP 2009-174444 A
• Patent document 2: JP 2013-231363 A

Summary of the invention

Technical problem

However, the process disclosed in Patent Literature 1 constantly operates the intake air heater and is not designed to control the activation and deactivation of the intake air heater depending on an operating condition. Therefore, the intake air heater is unnecessarily activated even under conditions which do not result in the acid condensed water, resulting in excessive electric power consumption. Excessive electrical energy consumption reduces fuel efficiency.

The present invention has been made to solve the problem described above. An object of the present invention is to provide a control apparatus for an internal combustion engine which prevents corrosion and deterioration of an internal combustion engine due to acid condensed water without reducing the fuel efficiency.

the solution of the problem

According to one aspect of the present invention, a control device for an internal combustion engine is provided. The internal combustion engine includes: an air-heating device provided in a suction passage; a catalyst provided in an exhaust passage; a filter provided in the exhaust passage downstream of the catalyst and configured to collect particulate matter contained in the exhaust gas; and an EGR device that provides communication between the exhaust passage downstream of the filter and the intake passage and configured to return a part of the exhaust gas as an EGR gas to the intake passage. The control apparatus includes: an exhaust-gas component elimination control means, a filter regeneration control means, a determination means, an air-warming control means, and a EGR gas introduction control means. The exhaust component elimination control means performs an exhaust gas component elimination process to eliminate a certain exhaust gas component from the catalyst, wherein the particular exhaust gas component has an acid activity when dissolved in water and reduces the purification performance of the catalyst when accumulated or accumulated in the catalyst. The filter regeneration control means performs a filter regeneration process to regenerate the filter by burning the particulate matter accumulated in the filter. The determination means determines, when the introduction of EGR gas is requested, whether the filter regeneration process is performed by the filter regeneration control means after the exhaust gas component removal process has been performed by the exhaust gas component elimination control means. The air warm-up control means warms up fresh air using the air-heating device when the determining means determines that the filter regeneration process is not yet performed. The EGR gas introduction control means performs the introduction of the EGR gas using the EGR device after the fresh air has been warmed up by the air warming device, when the determining means determines that the filter regeneration process is not yet performed.

For example, the catalyst is a NOx storage reduction catalyst and the particular exhaust gas component is a sulfur component. In this case, the exhaust gas component elimination process increases a temperature of the catalyst and generates a reducing atmosphere around the catalyst.

As another example, the catalyst is a NOx storage reduction catalyst or an oxidation catalyst, and the particular exhaust gas component is a hydrocarbon component. In this case, the exhaust gas component removal process increases a temperature of the catalyst.

When the determining means determines that the filter regeneration process has already been performed, the air warm-up control means may turn off the air warm-up device. In this case, the EGR gas introduction control means may perform the introduction of the EGR gas by using the EGR device while the air warm-up device is turned off.

The control device may further comprise a dew condensation determination means. When the determining means determines that the filter regeneration process is not yet performed, the dew condensation determination means determines whether a dew condensation occurs when the EGR gas is mixed with the fresh air. When the dew condensation determination means determines that dew condensation occurs, the air warm-up control means heats the fresh air by using the air-heating device. When the dew condensation determination means determines that no dew condensation is occurring, the EGR gas introduction control means performs the introduction of the EGR gas using the EGR device.

Advantageous Effects of the Invention

When the exhaust gas component elimination process for eliminating the specific exhaust gas component (ie, an exhaust gas component such as a sulfur component and a hydrocarbon component having acidic activity when dissolved in water and purifying performance of the catalyst when stored or accumulated in the catalyst) is exhausted carried out on the catalyst, the particular exhaust gas component which has been eliminated from the catalyst can adhere to the downstream filter. Through the filter regeneration process, the particular exhaust gas component adhering to the filter is removed from the filter along with the particulate matter accumulated in the filter. When the filter regeneration process is performed and the particular exhaust gas component is already removed from the filter, inflow of the particular exhaust gas component into the intake passage during the introduction of the EGR gas is suppressed. Therefore, even if the EGR gas is cooled by the fresh air and condensed water is generated, there is little risk of the condensed water becoming acidic. However, if the filter regeneration process has not yet been performed after the exhaust gas component eliminating process has been performed, the specific exhaust gas component adhering to the filter flows away from the filter, and therefore the EGR gas containing the specific exhaust gas component flows into the intake passage, when the introduction of the EGR gas is performed by the use of the EGR device.

According to the present invention, when the filter regeneration process is not yet performed after the exhaust gas component eliminating process has been performed, the introduction of the EGR gas is performed by the use of the EGR device after fresh air has been warmed up using the air heating device. As a result, the dew condensation of moisture contained in the EGR gas is suppressed, and therefore the generation of acid condensed water suppressed, which is generated by the specific exhaust gas component dissolved in water. As described above, when the introduction of the EGR gas is requested, the warm-up of the fresh air is performed by the use of the air-heating device under the condition that the filter-cleaning process is not yet performed after the exhaust-gas component removal process has been performed. It is therefore possible to prevent corrosion and deterioration of the internal combustion engine due to the acid condensed water without reducing the fuel efficiency.

list of figures

• 1 FIG. 12 is a schematic configuration diagram for explaining a configuration of a system according to a first embodiment. FIG.
• 2 Fig. 12 is a diagram for explaining an effect of a sulfur component eliminating process.
• 3 FIG. 10 is a flowchart showing processes associated with the introduction of LPL-AGR, which are performed in the first embodiment.
• 4 FIG. 10 is a flowchart showing processes associated with the introduction of LPL-AGR, which are performed in a second embodiment.

Description of the embodiments

First embodiment

Configuration of the system

1 FIG. 12 is a schematic configuration diagram for explaining a configuration of a system according to a first embodiment. FIG. This in 1 shown system has a motor (internal combustion engine) 10 on. The motor 10 is a diesel engine with a supercharger.

In the first embodiment, a turbocharger, which uses exhaust gas to compress intake air, is used as the supercharger. The turbocharger has a structure in which a compressor 16 which is in a suction passage 18 is provided, and a turbine 26, which in an exhaust passage 30 is provided, are connected to each other via a shaft.

The intake passage 18 is connected to a motor main unit 24. The intake passage 18 has an air purifier 12 at her entrance. An intake air heater 54 , which is an air-heating device for heating fresh air, which enters the intake passage 18 is located downstream of the air cleaner 12 is arranged. A bypass passage 52 which houses the intake air heater 54 bypasses, is with the intake passage 18 connected. A bypass valve 15 is provided in the bypass passage 52.

A first throttle valve 14 is downstream of the intake air heater 54 intended. The compressor 16 is provided downstream of the first throttle valve 14. A charge air cooler 38 The water-cooled type is provided downstream of the compressor 16. A radiator 40 for cooling coolant is with the intercooler 38 connected. The radiator 40 is equipped with an electric water pump 42 for conducting the coolant. A second throttle valve 20 is downstream of the charge air cooler 38 intended.

The exhaust passage 30 is connected to the engine main unit 24. The turbine 26 is in the exhaust passage 30 intended. The turbine 26 is rotated by the exhaust gas from the engine main unit 24. By the rotation of the turbine 26, the compressor 16 is rotated about the shaft, whereby a charging is performed.

An NOx storage reduction (NSR) catalyst 44 is in the exhaust passage 30 provided downstream of the turbine 26. A fuel addition valve 28 for providing fuel as a reduction component to the NSR 44 is upstream of the NSR 44 fixed.

A particulate filter (hereinafter simply referred to as a filter) 46 is downstream of the NSR 44 provided. For example, the filter 46 made of a porous ceramic structure and is configured to collect particulate matter (PM) contained in the exhaust gas when the exhaust gas flows through a porous wall.

An H2S cleaner 48 having an oxygen storage ability and adsorbing a sulfur component in the exhaust gas is downstream of the filter 46 provided. The H2S cleaner 48 has a transition metal such as. Cerium (CeO ₂ ), which has an oxygen storage ability. However, the H2S cleaner 48 is not indispensable and can from the in the 1 omitted configuration shown.

The motor 10 is equipped with an HPL (High Pressure Grinding) EGR device, which uses high pressure exhaust gas as an EGR gas to the intake passage 18 recirculated and equipped with an LPL (Low Pressure Grinding) EGR device which supplies low pressure exhaust gas as EGR gas to the intake passage 18 recycled. In 1 form an HPL-EGR passage 21 and a HPL EGR valve 22, the HPL EGR device. The HPL EGR passage 21 connects the exhaust passage 30 between the engine main unit 24 and the turbine 26 with the intake passage 28 downstream of the second throttle valve 20. In 1 For example, the LPL-EGR device has an LPL-EGR passage 36 , an EGR cooler 34 and an LPL EGR valve 35 on. The LPL-AGR passage 36 establishes a connection between the exhaust gas passage 30 downstream of the filter 36 and the intake passage 18 downstream of the intake air heater 54 and upstream of the compressor 16.

An operation of the engine 10 is controlled by an ECU (electronic control unit) 100, which is a control device. The ECU 100 has at least one suction / output interface, a ROM, a RAM and a CPU. The intake / output interface receives sensor signals from a plurality of sensors mounted in the engine 10 and a vehicle are installed, and outputs operating signals to a plurality of actuators and devices, such. Example, the first throttle valve 14, the second throttle valve 20, the HPL-EGR valve 22, the LPL-EGR valve 35 , the electric water pump 42, the bypass valve 50, and the intake air heater 54 , A variety of data including a variety of programs and maps and used to power the engine 10 are stored in the ROM. Various functions of the ECU 100 This is achieved by the CPU reading the programs from the ROM and executing the programs.

Filter regeneration process

One of the functions of the ECU 100 is a function as a "filter regeneration control means" which performs a filter regeneration process to a PM collection performance of the filter 46 restore. In the filter regeneration process, fuel from the fuel addition valve 28 injected. The injected fuel is in the NSR 44 oxidized and a temperature of the exhaust gas increases due to the heat of the oxidation reaction. When the exhaust gas, whose temperature is elevated, enters the filter 46 flows, becomes an increase of a temperature of the filter 46 simplified to achieve a PM firing temperature, and thereby the PM, which in the filter 46 accumulated, burned off and from the filter 46 away. The in the filter 46 Accumulated PM decrease through the above process. When a predetermined time (an estimated time for the PM accumulation amount to be reduced to a certain amount) has elapsed, the fuel injection from the fuel addition valve becomes 28 finished and the filter regeneration process ends.

Sulfur component eliminating process

In addition, the ECU has 100 a function of restoring the NOx storage performance of the NSR 44 which is decreased due to a sulfur component (NOx) contained in the exhaust gas. The sulfur component contained in the exhaust gas can bind barium (Ba), which is present in the NSR 44 so as to be accumulated in the form of an ionic crystalline component such as barium sulfate (BaSO ₄ ) and barium sulfite (BaSO ₃ ), or may be adsorbed on a catalyst support in the form of SO ₃ , SO ₄ or the like. The accumulation (or adsorption) of the sulfur component reduces the NOx storage performance of the NSR 44 , Therefore, the ECU performs 100 at a predetermined time, a sulfur component removal process to remove the sulfur component from the NSR 44 to eliminate.

In the sulfur component eliminating process, first, fuel is supplied from the fuel adding valve 28 to the exhaust passage 30 performed, in a state of a lean air-fuel ratio, so that an oxidation reaction heat, a catalyst bed temperature of the NSR 44 increased above a predetermined temperature. Thereafter, a fuel injection amount from the fuel addition valve 28 is increased or an amount of air is reduced to a reduction atmosphere around the NSR 44 whereby the sulfur component is eliminated from the NOx reducing material, ie, a reduction purification is achieved. The performance of the sulfur component eliminating process is a function of "exhaust gas component eliminating control means" of the ECU 100 ,

2 Fig. 4 is a diagram showing how the sulfur component (S) used in the NSR 44 is accumulated by performing the sulfur component elimination process in the NSR 44 is moved in and eliminated from this. (A) in 2 shows a distribution of the sulfur component along a longitudinal direction of the NSR 44 before the sulfur component eliminating process is performed. Since it is more likely that the upstream side of the NSR 44 comes in contact with the sulfur component contained in the exhaust gas, a distribution density of the sulfur component in the NSR 44 up to the upstream side and toward the downstream side of the NSR 44 lower. However, when the sulfur component eliminating process is performed, the sulfur component moves in the NSR 44 from the upstream side to the downstream side and a maximum value position (indicated by X in the diagram) of the accumulation amount of Sulfur component also gradually moves toward the downstream side as in (B) in FIG 2 shown. The way to the furthest downstream side of the NSR 44 Moving sulfur component is from the NSR 44 eliminated to the outside.

Characteristic control in the first embodiment

In the system configuration of the first embodiment, when the above-described sulfur component eliminating process is performed, a part of the NSR adheres 44 eliminated sulfur component on the filter 46 at which downstream of the NSR 44 is arranged. As the exhaust gas temperature increases due to high load operation, the sulfur component that is on the filter desorbs 46 adheres to the filter 46 , During such high load operation while desorbing the adhered sulfur component, introduction of LPL-EGR gas is performed. Therefore, it flows from the filter 46 Desorbed sulfur component together with the LPL-EGR gas in the intake passage 18 through the LPL-AGR passage 36 ,

At a connection point between the intake passage 18 and the LPL-AGR passage 36 For example, the LPL-EGR gas is mixed with the fresh air at a relatively low temperature. Because the LPL-EGR gas contains much moisture, condensation may form due to dew condensation when the LPL-EGR gas is mixed with the fresh air and its temperature decreases. The sulfur component contained in the exhaust gas is an exhaust gas component (a certain exhaust gas component) which exerts an acidic activity when dissolved in water. Therefore, when the sulfur component of the filter 46 is desorbed and contained in the LPL-EGR gas, the sulfur component dissolved in the condensation water generated by the dew condensation and thus produces acid condensed water. The acidic condensation causes corrosion of parts of the engine 10 , It should be noted that the generation of condensation due to dew condensation also occurs in the EGR cooler 34 and the intercooler 38 can occur. Concerning the condensate, which is in the EGR cooler 34 and the intercooler 38 produced, various countermeasures have been proposed so far. Therefore, in the present description, a countermeasure for the acid condensed water which is generated when the LPL-EGR gas is mixed with the fresh air is proposed.

The following two methods can be used for preventing the generation of acidic condensation in the intake passage 18 be considered. A first method is to prevent dew condensation when the LPL-EGR gas is mixed with the fresh air. By warming up the fresh air through the use of the intake air heater 54 For example, it is possible to make a temperature of a gas mixture of fresh air and LPL-EGR gas higher than a dew point temperature. The second method is to introduce the LPL-EGR gas in a state in which the sulfur component is not attached to the filter 46 adheres. For example, when the filter regeneration process is performed after the sulfur component eliminating process has been performed, the filter 46 hot and therefore the sulfur component is already desorbed from it; it can be said that such a state is preferable for the introduction of the LPL-EGR gas even if it is later than the execution of the sulfur component eliminating process. However, the first method is disadvantageous in that the consumption of electric power reduces the fuel efficiency, and the second method is disadvantageous because the introduction of the LPL-EGR gas is limited.

In view of the above, according to the first embodiment, when the sulfur component eliminating process is performed and then the filter regeneration process is further performed, the introduction of the LPL-EGR gas is performed without responding to a request for the introduction of the LPL-EGR gas Fresh air using the intake air heater 54 is warmed up. On the other hand, if the filter regeneration process is not yet performed after the sulfur component eliminating process has been performed, the introduction of LPL-EGR gas is not performed immediately, but performed after the fresh air using the intake air heater 54 has been warmed up. In this way, the process of introducing the LPL-EGR gas is switched depending on the execution status of the sulfur component eliminating process and the filter regeneration process. It is therefore possible to cause corrosion and deterioration of the engine 10 due to acidic condensation, without reducing fuel efficiency.

Concrete processes

Hereinafter, concrete processes associated with the introduction of the LPL-AGR and performed in the first embodiment will be described with reference to an embodiment of the present invention 3 shown flowchart described. A program for the conversion logic shown in this flowchart is in the ROM of the ECU 100 saved. The program is read out from the ROM and executed by the CPU, therefore functions are referred to as "determining means", as a " Air warm-up control means ", as an" EGR gas introduction control means "and as a" dew condensation determination means ", which are defined in the claims, the ECU 100 assigned.

First, the ECU determines 100 based on an operating condition of the engine 10 whether there is an LPL-EGR introduction request (step S100). For example, the ECU calculates 100 a load of the engine 10 from an accelerator opening degree or a throttle valve opening degree. If the calculated load is within a predetermined high load range, the ECU determines 100 in that it is necessary to introduce the LPL-EGR gas, ie that there is an LPL-EGR introduction request.

If there is an LPL EGR introduction request, the ECU determines 100 Whether an accumulation amount of the sulfur component in the NSR 44 is saturated (step S102). The accumulation amount of the sulfur component may be estimated based on an integrated amount of the exhaust gas exhausted from the engine main unit 24. The ECU 100 calculates the accumulation amount of the sulfur component based on the integrated amount of the exhaust gas and resets the accumulation amount when the above-described sulfur component eliminating process has been performed.

When the accumulation amount of the sulfur component in the NSR 44 is saturated, it is estimated that the sulfur component from the NSR 44 flows downstream. When the introduction of the LPL-EGR gas is performed in this situation, the LPL-EGR gas having the sulfur component flows into the intake passage 18 , In view of the above, when it is determined in step S102 that the accumulation amount of the sulfur component in the NSR 44 saturated, the ECU 100 the following process to suppress the generation of acid condensed water due to the LPL-EGR gas having the sulfur component.

First, the ECU calculates 100 a predicted value of the dew point temperature in the intake passage 18 and a predicted value of the temperature of the mixed gas of the fresh air and the LPL-EGR gas when the introduction of the LPL-EGR gas is performed based on a fresh air temperature (an intake air temperature), an atmospheric pressure, an air humidity, an exhaust gas temperature , an exhaust pressure, an air-fuel ratio of combustion, and an EGR amount (step S104). Then the ECU leads 100 a comparison between the dew point temperature and the temperature of the mixed gas, which has been calculated in step S104, to determine whether the temperature of the mixed gas is lower than the dew point temperature (step S106).

The determination in step S106 is equivalent to determining whether condensed water is generated when the LPL-EGR gas is mixed with the fresh air. When the temperature of the mixed gas is equal to or higher than the dew point temperature, no condensed water is generated even when the introduction of the LPL-EGR gas is performed, and therefore, there is no risk of corrosion and deterioration due to the acid condensed water. Therefore, when it is determined in step S106 that the temperature of the mixed gas is equal to or higher than the dew point temperature, the ECU 100 the introduction of the LPL-EGR gas without air heating through the use of the intake air heater 54 (Step S110).

On the other hand, when the temperature of the mixed gas is lower than the dew point temperature, condensed water is generated when the introduction of the LPL-EGR gas is performed. Therefore, when it is determined in step 106 that the temperature of the mixed gas is lower than the dew point temperature, the ECU heats 100 the fresh air using the intake air heater 54 on (step S 108). When the intake air heater 54 is of an electric type, the power supply is switched from OFF to ON. When the intake air heater 54 is of the hot water type, the supply of hot water becomes the intake air heater 54 switched from OFF to ON. In addition, the ECU 100 at the same time the electric water pump 42 to a temperature of the intercooler 38 increase the generation of condensation in the intercooler 38 to suppress.

The ECU 100 repeatedly performs the calculation of the dew point temperature and the temperature of the mixed gas in step S104 and the determination in step S106, while still the fresh air through the use of the intake air heater 54 in step S108, until the determination in step S106 returns no. Then, when it is determined in step S106 that the temperature of the mixed gas becomes equal to or higher than the dew point temperature, the ECU performs 100 the introduction of the LPL-EGR gas (step S110).

When the accumulation amount of the sulfur component in the NSR 44 is not saturated, it is unlikely that the sulfur component from the NSR 44 flows. However, when the sulfur component elimination process for eliminating the sulfur component from the NSR 44 has been carried out by the NSR 44 eliminated sulfur component on the filter 46 , which downstream of the NSR 44 is arranged, adhere. If the introduction of the LPL-EGR gas is performed in such a situation where the sulfur component on the filter 46 clings, there is a possibility that the filter 46 desorbed sulfur component flows together with the LPL-EGR gas in the intake passage. However, if the process of regeneration of the filter 46 has been performed after the sulfur component eliminating process has been performed, the sulfur component of the filter 46 removed at that time, and there is little risk that the sulfur component together with the LPL-EGR gas in the intake passage 18 flows.

When it is determined in step S102 that the accumulation amount of the sulfur component in the NSR 44 is not saturated, the ECU determines 100 Whether the filter regeneration process (DPF regeneration) has been performed before after the sulfur component eliminating process (S regeneration / S elimination) has been performed (step S112). For example, if a condition in which a bed temperature of the filter 46 is equal to or higher than a predetermined temperature (for example, 650 ° C) for more than a predetermined time (for example, 10 seconds), it may be determined that the filter regeneration process has already been performed. Alternatively, it may be determined whether the filter regeneration process has already been performed based on the PM accumulation amount calculated by another logic different from the logic shown in the present flowchart.

If the determination in step S112 is yes, there is little risk of the sulfur component downstream of the filter 46 flows. In this case, the ECU is running 100 so that continues, the intake air heater 54 to turn off (step S114), and performs the introduction of the LPL-EGR gas (step S116). At this time, the ECU 100 Open the bypass valve 50 to allow fresh air to flow through the bypass passage 52.

If the filter regeneration process is not yet performed after the sulfur component eliminating process has been performed, it is determined that during the high load operation in which the exhaust gas temperature is high, the sulfur component attached to the filter 46 adheres to the filter 46 Flows downstream direction. When the introduction of the LPL-EGR gas is performed in this situation, the LPL-EGR gas containing the sulfur component flows into the intake passage 18 , In view of the above, when it is determined in step S112 that the filter regeneration process is not yet performed after the sulfur component eliminating process has been performed, the ECU 100 the following process to suppress the generation of acid condensed water due to the sulfur component-containing LPL-EGR gas.

First, the ECU calculates 100 a predicted value of the dew point temperature in the intake passage 18 and a predicted value of the temperature of the mixed gas of the fresh air and the LPL-EGR gas when the introduction of the LPL-EGR gas is performed based on a fresh air temperature (an intake air temperature), an atmospheric pressure, a humidity, an exhaust gas temperature , an exhaust pressure, an air-fuel ratio of combustion, and an EGR amount (step S118). Then the ECU leads 100 a comparison between the dew point temperature and the temperature of the mixed gas, which has been calculated in step S 118, to determine whether the temperature of the mixed gas is lower than the dew point temperature (step S120).

The determination in step S 120 is equivalent to determining whether condensation is generated when the LPL-EGR gas is mixed with the fresh air. When the temperature of the mixed gas is equal to or higher than the dew point temperature, no condensed water is generated even when the introduction of the LPL-EGR gas is performed, and therefore, there is no risk of corrosion and deterioration due to the acid condensed water. Therefore, when it is determined in step S120 that the temperature of the mixed gas is equal to or higher than the dew point temperature, the ECU 100 the introduction of LPL-EGR gas without warming the air by using the intake air heater 54 by (step S124).

On the other hand, when the temperature of the mixed gas is lower than the dew point temperature, condensed water is generated when the introduction of the LPL-EGR gas is performed. Therefore, if it is determined in step S 120 that the temperature of the mixed gas is lower than the dew point temperature, the ECU heats 100 the fresh air using the intake air heater 54 on (step S 122). In addition, the ECU 100 at the same time the electric water pump 42 to the temperature of the intercooler 38 increase the generation of condensation in the intercooler 38 to suppress.

The ECU 100 repeatedly performs the calculation of the dew point temperature and the temperature of the mixed gas in step S118 and the determination in step S120 as long as it continues, in step S122, the fresh air using the intake air heater 54 warm up until the Determination in step S 120 results in a no. Then, when it is determined in step S120 that the temperature of the mixed gas becomes equal to or higher than the dew point temperature, the ECU performs 100 the introduction of the LPL-EGR gas (step S124).

According to the first embodiment, as described above, when the filter regeneration process is not yet performed after the sulfur component eliminating process has been performed, the introduction of the LPL-EGR gas is performed using the LPL-EGR device after the fresh air using the intake air heater 54 has been warmed up. As a result, dew condensation of moisture contained in the LPL-EGR gas is suppressed, and therefore, generation of acid condensed water generated by dissolving the sulfur component in water is suppressed. As described above, when the introduction of the LPL-EGR gas is requested, warming up the fresh air using the intake air heater 54 performed under the condition that the filter regeneration process is not yet performed after the sulfur component eliminating process has been performed. It is therefore possible to cause corrosion and deterioration of parts of the engine 10 due to acidic condensation, without reducing fuel efficiency.

It should be noted that the determination in step S112 in the concrete process described above corresponds to a function as the "determining means" defined in the claims. The processes in step S114 and step S120 correspond to a function as the "air warm-up control means" defined in the claims. The processes in step S116 and step S124 correspond to a function as "EGR gas introduction control means" defined in the claims. The processes in steps S118 and step S120 correspond to a function as the "dew condensation determination means" defined in the claims. In a modification example of the above-described concrete processes, the process at step S118 and the determination at step S120 may be omitted. In this case, if the determination in step S112 is No, the introduction of the LPL-EGR gas is performed after the fresh air is exhausted using the intake air heater 54 has been warmed up for a predetermined time.

Second embodiment

Hydrocarbon component eliminating process

In a second embodiment, focus is on a hydrocarbon (HC) component contained in the exhaust gas. When the hydrocarbon component contained in the exhaust gas is on an end face of the NFR 44 when adsorbed, particulate matters adsorb to the hydrocarbon component having an adherence property, causing clogging of the end surface of the NFR 44 causes. The clogging of the end surface of the NFR 44 reduces the NOx storage capacity of the NFR 44 , Therefore, the ECU performs 100 at a predetermined timing, carry out a hydrocarbon component elimination process to remove the hydrocarbon component from the NFR 44 to eliminate.

In the hydrocarbon component eliminating process, fuel supply from the fuel adding valve becomes 28 in the exhaust passage 30 in a lean air-fuel ratio state to cause the oxidation reaction heat to have a catalyst bed temperature of the NFR 44 increased above a predetermined temperature. As a result, the accumulated hydrocarbon component is burned off along with the particulate matter. By burning off and removing the hydrocarbon component along with the particulate matter, clogging of the NFR 44 Fixed. The performance of the hydrocarbon component elimination process is a function of the "exhaust component elimination control means" of the ECU 100 ,

Characteristic control in the second embodiment

At the in 1 shown system configuration adheres when performing the above-described hydrocarbon component elimination process by the NFR 44 flowing hydrocarbon component during the burn back at the downstream of the NFR 44 arranged filters 46 at. As the exhaust gas temperature increases due to high load operation, it desorbs on the filter 46 adherent hydrocarbon component from the filter 46 , Since the introduction of the LPL-EGR gas is performed during such a high load operation, the hydrocarbon component flowing from the filter flows 46 is desorbed, along with the LPL-EGR gas through the LPL-AGR passage 36 in the intake passage 18 , The hydrocarbon component is an exhaust gas component (a certain exhaust gas component) which exhibits acidic activity when dissolved in water. When the hydrocarbon component contained in the LPL-EGR gas in the condensation in the intake passage 18 is dissolved, acid condensed water (such as HCOOH and CH ₃ COOH) is produced, causing corrosion and deterioration of parts of the engine 10 causes.

When the filter regeneration process is performed, it becomes the one on the filter 46 adhering hydrocarbon component burned off and along with the particulate matter contained in the filter 46 accumulated, removed. Therefore, when the filter regeneration process is performed after the hydrocarbon component eliminating process has been performed, the hydrocarbon component attached to the filter 46 adheres, already burned off and removed and therefore it can be said that this condition is preferred for the introduction of the LPL-EGR gas.

In view of the above, according to the second embodiment, when the hydrocarbon component eliminating process has been performed and thereafter the filter regeneration process is further performed, the introduction of the LPL-EGR gas is performed in response to a request for the introduction of the LPL-EGR gas. On the other hand, if the filter regeneration process is not yet performed after the hydrocarbon component eliminating process has been performed, the introduction of the LPL-EGR gas is not performed immediately, but performed after the fresh air using the intake air heater 54 has been warmed up. The reason is to suppress the generation of the condensed water when the LPL-EGR gas is mixed with the fresh air. In this way, according to the second embodiment, the process associated with the introduction of the LPL-EGR gas is switched depending on the execution states of the hydrocarbon component eliminating process and the filter regeneration process.

Concrete processes

Hereinafter, concrete processes concerning the introduction of the LPL-EGR gas, which are performed in the second embodiment, will be described with reference to an embodiment of the present invention 4 shown flowchart described. A program for implementing the logic shown in this flowchart is in the ROM of the ECU 100 saved. The program is read from the ROM and executed by the CPU, the functions of the "determining means", the "air warm-up control means", the "EGR gas introduction control means" and the "dew condensation determination means" defined in the claims of the ECU 100 be assigned. It should be noted that in 4 the same step number is given to the step which performs the same process as in the first embodiment.

In the second embodiment, in step S202, a determination is made as a substitute for the determination in step S102, and the determination in step S212 is made as a replacement for the determination S112. If there is an LPL EGR introduction request, the ECU determines 100 whether it is immediately after the execution of the hydrocarbon component eliminating process (step S202). Whether it is immediately after execution can be determined based on whether an elapsed time since the execution of the hydrocarbon component eliminating process exceeds a predetermined time.

If it is immediately after performing the hydrocarbon component elimination process, it is estimated that a large amount of hydrocarbon components on the filter 46 adheres. When the introduction of the LPL-EGR gas is performed in this situation, the LPL-EGR gas having the hydrocarbon component flows into the intake passage 18 , In view of the above, when it is determined in step S202 that it is immediately after the execution of the hydrocarbon component eliminating process, the ECU 100 the processes in steps S104 to S110 to suppress the generation of the acid condensed water due to the LPL-EGR gas containing the hydrocarbon component.

That is, if the determination in step S202 is yes, the ECU calculates 100 the dew point temperature of the intake passage 18 and the temperature of the mixed gas when the introduction of the LPL-EGR gas is performed (step S104), and determines whether the temperature of the mixed gas is lower than the dew point temperature (step S106). If the temperature of the mixed gas is equal to or higher than the dew point temperature, the ECU will perform 100 the introduction of the LPL-EGR gas without warming up the air using the intake air heater 54 by (step S110). On the other hand, when the temperature of the mixed gas is lower than the dew point temperature, the ECU heats up 100 the fresh air using the intake air heater 54 on (step S108). The ECU 100 waiting for the temperature of the mixed gas to reach or exceed the dew point temperature, and then perform the introduction of the LPL-EGR gas (step S110).

If it is not immediately after performing the hydrocarbon component elimination process, it is expected that the amount of hydrocarbon component attached to the filter 46 is smaller than that immediately after the performance of the hydrocarbon component elimination process. Nevertheless, during high load operation, there is a risk of being in the filter 46 remaining hydrocarbon component from the filter 46 flows out into the intake passage together with the LPL-EGR gas 18 to stream. However, if the process of regeneration of the filter 46 is performed after the hydrocarbon component eliminating process has been performed, the hydrocarbon component of the filter 46 removed along with the particulate matter at that time, and therefore, there is little risk of the hydrocarbon component entering the intake passage together with the LPL-EGR gas 18 flows.

If it has been determined in step S202 that it is not immediately after the execution of the hydrocarbon component eliminating process, the ECU determines 100 whether the filter regeneration process (DPF regeneration) has been performed before after the hydrocarbon component eliminating process has been performed (step S212). If the filter regeneration process is already in progress, the ECU will run 100 so that continues, the intake air heater 54 to turn off (step S114) and performs the introduction of the LPL-EGR gas (step S116).

If the filter regeneration process is not yet performed after the hydrocarbon component eliminating process has been performed, it is likely that, during the high load operation in which the temperature of the exhaust gas is high, that on the filter 46 adherent hydrocarbon component from the filter 46 flows out in the direction downstream. When the introduction of the LPL-EGR gas is performed in this situation, the LPL-EGR gas containing the hydrocarbon component flows into the intake passage 18 , In view of the above, when it is determined in step S212 that the filter regeneration process is not yet performed after the hydrocarbon component eliminating process has been performed, the ECU 100 the processes in steps S118 to S124 to suppress the generation of the acid condensed water due to the LPL-EGR gas containing the hydrocarbon component.

That is, if the determination in step S212 is no, the ECU calculates 100 the dew point temperature in the intake passage 18 and the temperature of the mixed gas when the introduction of the LPL-EGR gas is performed (step S118), and determines whether the temperature of the mixed gas is lower than the dew point temperature (step S120). When the temperature of the mixed gas is equal to or higher than the dew point temperature, the ECU performs 100 the introduction of the LPL-EGR gas without air heating using the intake air heater 54 (Step S124). On the other hand, when the temperature of the mixed gas is lower than the dew point temperature, the ECU heats 100 the fresh air using the intake air heater 54 (Step S122). The ECU 100 waits for the temperature of the mixed gas to reach or exceed the dew point temperature, and then performs the introduction of the LPL-EGR gas (step S124).

According to the above-described second embodiment, when the filter regeneration process has not yet been performed after the hydrocarbon component eliminating process has been performed, the introduction of the LPL-EGR gas is performed by the use of the LPL-EGR device after the fresh air using the intake air heater 54 has been warmed up. As a result, the dew condensation of the moisture contained in the LPL-EGR gas is suppressed, and therefore, the generation of the acid condensed water generated by the hydrocarbon component dissolved in water is suppressed. As described above, when the introduction of the LPL-EGR gas is requested, warming up the fresh air using the intake air heater 54 performed under the condition that the filter regeneration process is not yet performed after the hydrocarbon component eliminating process has been performed. It is therefore possible to cause corrosion and deterioration of parts of the engine 10 due to the acid condensed water without reducing the fuel efficiency.

It should be noted that the above-described processes according to the second embodiment can also be applied to a system having a diesel oxidation catalyst (DOC) downstream of the particulate filter. Since the hydrocarbon component is also accumulated in the DOC, it is preferable to perform the hydrocarbon component eliminating process also with respect to the DOC. However, the hydrocarbon component which does not burn and pass the DOC adheres to the filter located downstream of the DOC and then flows out of the filter during high load operation downstream. In order to prevent generation of acid condensed water when the hydrocarbon component flows into the intake passage together with the LPL-EGR gas, the introduction of the LPL-EGR gas is performed after the fresh air has been warmed up using the intake air heater.

LIST OF REFERENCE NUMBERS

10

engine

18

intake passage

28

Fuel addition valve

30

exhaust passage

34

EGR cooler

35

LPL-EGR valve

36

LPL-EGR passage

38

Intercooler

44

NFR

46

filter

54

Ansaugluftheizer

100

ECU

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2009174444 A [0004]
• JP 2013231363 A [0004]

Claims (5)

Control device for an internal combustion engine, the internal combustion engine comprising: an air-heating device provided in a suction passage; a catalyst provided in an exhaust passage; a filter provided in the exhaust passage downstream of the catalyst and configured to collect particulates contained in the exhaust gas; and an EGR device providing communication between the exhaust passage downstream of the filter and the intake passage and configured to recirculate a part of the exhaust gas as an EGR gas to the intake passage; wherein the control device comprises: an exhaust gas component elimination control means that performs an exhaust gas component elimination process to eliminate a certain exhaust gas component from the catalyst, the particular exhaust gas component exerting an acid activity when dissolved in water and reducing the purification performance of the catalyst when stored or accumulated in the catalyst; a filter regeneration control means that performs a filter regeneration process to regenerate the filter by burning off the particulates accumulated in the filter; a determining means which, when an introduction of the EGR gas is requested, determines whether the filter regeneration process is performed by the filter regeneration control means after the exhaust gas component removal process has been performed by the exhaust gas component removal control means; an air warm-up control means that warms up fresh air using the air-heating device when the determining means determines that the filter regeneration process is not yet performed; and an EGR gas introduction control means which performs the introduction of the EGR gas using the EGR device after the fresh air has been warmed up by the air warming device, when the determining means determines that the filter regeneration process is not yet performed. Control device for the internal combustion engine according to Claim 1 wherein the catalyst is a NOx storage reduction catalyst; the particular exhaust gas component is a sulfur component; and the exhaust gas component removal process increases a temperature of the catalyst and creates a reduction atmosphere around the catalyst. Control device for the internal combustion engine according to Claim 1 wherein the catalyst is a NOx storage reduction catalyst or an oxidation catalyst; the particular exhaust gas component is a hydrocarbon component; and the exhaust gas component removal process increases the temperature of the catalyst. Control device for the internal combustion engine according to one of Claims 1 to 3 wherein, when the determining means determines that the filter regeneration process is already performed, the air warmup control means turns off the air warmup device and the EGR gas introduction control means performs the introduction of the EGR gas using the EGR device while the air warmup device is turned off. Control device for the internal combustion engine according to one of Claims 1 to 4 , further comprising a dew condensation determination means, wherein, when the determination means determines that the filter regeneration process is not yet performed, the dew condensation determination means determines whether dew condensation occurs when the EGR gas is mixed with the fresh air, when the dew condensation determination means determines that the dew condensation occurs wherein the air warm-up control means warms up the fresh air using the air-heating device, and when the condensation-condensation determining means determines that the condensation is not occurring, the EGR-gas introduction control means performs the introduction of the EGR gas using the EGR device.

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