JP2010106753A - Exhaust emission control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly regenerate a filter 8b while inhibiting or preventing oil dilution by not doing post fuel injection unnecessarily during execution of filter regeneration in an exhaust emission control device regenerating the filter 8b of an exhaust passage of an internal combustion engine 1 as the occasion demands. <P>SOLUTION: The control device 10 for an exhaust emission control device includes a decision means accompanying execution demand of filter regeneration and deciding whether the temperature of an oxidation catalyst 8a is not less than an activation temperature or not, a first coping means executing filter regeneration in a style adding and supplying fuel component to an upstream side of the oxidation catalyst 8a in the exhaust gas passage in affirmative decision by the decision means, and a second coping means executing filter regeneration in a style of making post injection control and fuel addition control operate together in negation decision by the decision means. The second coping means sets a post injection quantity not greater than a dilution limit value of oil dilution by post injection so as to compensate component short to a temperature rise control target value to a filter regeneration temperature by fuel addition control. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust purification device used for an internal combustion engine (also referred to as an engine) mounted on a vehicle such as an automobile, and more particularly to an exhaust purification device that can automatically regenerate a filter installed in an exhaust passage. .

  In a diesel engine or the like mounted on a vehicle or the like, exhausted exhaust gas contains particulate matter (PM) containing carbon as a main component, and it is not preferable to discharge it to the atmosphere. Therefore, conventionally, a catalyst device is provided in the exhaust passage of the diesel engine.

  The catalyst device is included in an oxidation catalyst for oxidizing and purifying hydrocarbon (HC) and carbon monoxide (CO) contained in exhaust gas passing through the exhaust passage, and in exhaust gas passing through the exhaust passage. It includes a filter that collects PM and reduces the amount of emissions released into the atmosphere.

  The filter is generally called a DPF (Diesel Particulate Filter) or a DPR (Diesel Particulate active Reduction system). The DPF has a configuration in which a porous member is provided, and the DPR has a configuration in which an oxidation catalyst is supported on the porous member.

  In such a filter, clogging occurs when the amount of collected PM increases, and in such a case, the PM trapping function decreases and the pressure loss of the exhaust gas passing through the filter increases. The accompanying increase in engine exhaust back pressure leads to a decrease in engine output and fuel consumption.

  In order to eliminate such problems, conventionally, when the PM collection amount (deposition amount) of the filter reaches a predetermined limit amount, so-called regeneration is performed to recover the PM collection function by cleaning the filter. It is considered to do. In this filter regeneration, it is effective to raise the temperature of the exhaust gas entering the filter and to burn and remove the PM collected by the filter.

  Various forms of filter regeneration have been conventionally considered, and will be specifically described below.

  First, at the time of filter regeneration, it is conceivable that the exhaust throttle valve provided downstream of the filter in the exhaust passage of the internal combustion engine is throttled to raise the exhaust temperature and burn and remove PM collected in the filter. (For example, refer to Patent Document 1).

  In the conventional example according to Patent Document 1, it is effective to raise the inlet temperature of the filter by restricting the exhaust throttle valve. However, when the exhaust throttle valve is throttled, the exhaust resistance increases and the output of the internal combustion engine increases. As a result, the drivability deteriorates, and there is a problem that a loud exhaust sound is generated when the exhaust throttle valve is once throttled and then opened.

  As a method not using such an exhaust throttle valve, generally, at the time of filter regeneration, fuel is added and supplied upstream of the oxidation catalyst in the exhaust passage of the internal combustion engine, and this fuel is oxidized by the oxidation catalyst (combustion). It is known to raise the temperature of the filter by causing the temperature to rise.

  In this conventional example, for example, when the internal combustion engine is cold-started or when the exhaust gas temperature entering the filter is low because the oxidation catalyst is not activated due to continuous long-term operation of the vehicle, the fuel is discharged into the exhaust passage. Even if is supplied, the oxidation reaction of the fuel by the oxidation catalyst cannot be expected. As a result, the exhaust temperature entering the filter is unlikely to rise, and the filter regeneration is unlikely to proceed, for example, the exhaust temperature does not reach the temperature at which PM is combusted (filter regeneration temperature). Such filter regeneration by fuel addition control is insufficient because there is a period when it cannot be regenerated.

In addition, it is considered that a small amount of fuel is secondarily injected (so-called post-injection) when the filter is regenerated, for example, after the main fuel is injected into the combustion chamber of the internal combustion engine and before the exhaust valve is closed (for example, patents). (Refer to Literature 2.)
When this post-injection is performed, unburned gas is discharged into the exhaust passage, and this unburned gas is oxidized by the oxidation catalyst. Therefore, the temperature of the exhaust gas passing through the oxidation catalyst rises, and the temperature of the filter rises. Is done. However, when such post injection is performed, it is known that the post-injected fuel is less likely to be vaporized and easily adheres to the cylinder wall, so that oil dilution in which the fuel is mixed into the engine oil is likely to occur. It has been.

As described above, various forms of filter regeneration have been proposed. However, since they have advantages and disadvantages, it is considered to use them together. For example, Patent Document 3 discloses that filter regeneration is performed by a combination of exhaust throttle control and post injection control.
JP 2005-282534 A JP 2008-133738 A JP 2008-144726 A

  In the conventional example according to Patent Document 3, there is a concern that the drivability is reduced as described above, because of the exhaust throttle control.

  By the way, for example, in Japanese Patent Application Laid-Open No. 2003-172185, post-injection control and fuel addition control are selectively performed, or both of the above are performed together, in order to control the exhaust and Nox catalyst temperatures to optimum values. It is described to do. However, this prior art does not select the above two controls or use them together when performing filter regeneration. That is, this prior art has a technical idea different from that of the present invention, and is merely presented as a reference document.

  In view of such circumstances, the present invention is an exhaust purification device that automatically regenerates a filter that collects PM in the exhaust gas of an internal combustion engine so that post injection control is not performed unnecessarily when filter regeneration is performed. An object of the present invention is to enable quick filter regeneration while suppressing or preventing oil dilution.

  The present invention includes an oxidation catalyst provided in an exhaust passage of an internal combustion engine, a filter provided downstream of the oxidation catalyst in the exhaust passage to collect particulate matter in exhaust, and the filter as necessary. And a control device that executes filter regeneration by raising the temperature to a filter regeneration temperature that burns and removes particulate matter that has accumulated on the filter, the control device responding to a request for executing the filter regeneration. A determination unit for determining whether or not the oxidation catalyst is at an activation temperature or higher, and a filter configured to add and supply a fuel component to the upstream side of the oxidation catalyst in the exhaust passage when an affirmative determination is made by the determination unit The first coping means for performing the regeneration and the filter regeneration in the form of cooperating the post injection control and the fuel addition control when the determination means makes a negative determination. The second coping means sets the post injection amount below the dilution limit value of oil dilution by post injection, and is insufficient for the temperature increase control target value to the filter regeneration temperature. Is set to be supplemented by the fuel addition control.

  The filter regeneration is to restore the function of the filter by burning and removing particulate matter accumulated on the filter.

  In addition, in order to add and supply fuel to the exhaust passage, fuel addition means installed upstream of the oxidation catalyst in the exhaust passage is used.

  Further, the post-injection is a secondary injection of a small amount of fuel after the main fuel injection to the combustion chamber of the internal combustion engine and before the exhaust valve is closed, and the fuel is directly injected and supplied to the combustion chamber of the internal combustion engine. The fuel injection means is used.

  When this post-injection is performed, unburned gas is easily discharged from the combustion chamber to the exhaust passage, so the unburned gas discharged to the exhaust passage is oxidized (combusted) by the oxidation catalyst, and downstream of the oxidation catalyst. As the exhaust temperature rises, the temperature of the filter rises accordingly.

  However, if post injection is performed, oil dilution is likely to occur. As is well known, this oil dilution occurs when the post-injected fuel does not vaporize and adheres to the cylinder wall of the internal combustion engine, and this fuel mixes with the oil of the internal combustion engine. Therefore, a large amount of post-injection is not preferable because oil dilution tends to occur.

  In this configuration, first, when performing filter regeneration only by fuel addition control to the exhaust system without performing post-injection control, it is assumed that the oxidation catalyst has already been activated, so that it is added to the exhaust passage. The fuel component is immediately oxidized by the already activated oxidation catalyst.

  As a result, the filter quickly rises to the filter regeneration temperature (the temperature at which the particulate matter deposited on the filter can burn). In addition, since post injection is not performed, it is possible to avoid oil dilution due to post injection.

  Therefore, when the filter regeneration is executed only by controlling the addition of fuel to the exhaust system as described above, it is possible to quickly terminate the filter regeneration while avoiding the occurrence of oil dilution due to post injection.

  On the other hand, when filter regeneration is performed by cooperating post injection control and fuel addition control, oil dilution is likely to occur due to post injection, but this post injection amount is diluted with oil dilution. Since it is set as small as possible based on the limit value (less than the target temperature increase control amount when filter regeneration is performed by post injection alone), it is possible to suppress the occurrence of oil dilution. In addition, if the post-injection amount is reduced, it is considered that the temperature raising capability of the filter is insufficient, but the shortage is compensated by control of fuel addition to the exhaust system.

  That is, the unburned gas discharged from the combustion chamber to the exhaust passage along with the post-injection is caused to undergo an oxidation reaction with the oxidation catalyst, so that the exhaust temperature downstream of the oxidation catalyst can be quickly raised. As a result, the temperature of the filter also increases. This makes it possible to burn off particulate matter that has accumulated on the filter relatively early.

  Accordingly, even when the filter regeneration is performed by cooperating the post injection control and the fuel addition control as described above, the filter regeneration can be completed quickly while suppressing or preventing the occurrence of oil dilution. become.

  Preferably, after the control operation by the first coping means or the second coping means is performed, the control device determines whether the temperature rise is insufficient or excessive, and the temperature rise determination means First correction means for correcting an increase by the fuel addition control when it is determined to be insufficient, and second correction means for correcting a decrease in the next post injection amount when it is determined that the temperature increase is excessive by the temperature increase determination means It can be set as the structure containing.

  In this configuration, after execution of the control operation by the first coping means or the second coping means, the deviation state with respect to the filter regeneration temperature with respect to the temperature rise control target value is examined, and the form of correction is devised according to the deviation situation. I have to.

  As a result, the temperature increase correction can be performed with the existing configuration without adding the configuration of the exhaust emission control device, so that an increase in equipment cost can be avoided.

  Preferably, the execution request for the filter regeneration may be issued when the estimated value of the amount of particulate matter deposited on the filter becomes equal to or greater than a predetermined upper limit (limit deposition amount). .

  In this case, considering that the PM accumulation amount of the filter increases as the operating time of the internal combustion engine elapses, it depends on the operating conditions of the internal combustion engine (for example, exhaust temperature, fuel injection amount, engine speed, etc.). It is conceivable that the amount of deposited PM is examined in advance through experiments or the like and mapped, and the amount of deposited PM obtained from this map is integrated to obtain the amount of deposited PM. Thereby, if the operation elapsed time is detected, the corresponding PM accumulation amount can be obtained based on the map.

  Preferably, the control device can divide the post-injection according to the operating condition of the internal combustion engine when the negative response is determined by the third countermeasure unit that performs filter regeneration in the form of dividing the post-injection and the determination unit. And further includes a selection unit that shifts to the third coping unit when an affirmative determination is made, and the third coping unit is performed once. It is possible to set the total post injection amount to the temperature increase control target value after setting the hit post injection amount to be equal to or less than the dilution limit value.

  Here, the form of post injection control is specified, and the form of filter regeneration is diversified. Conventionally, it is known that when post injection is divided, the amount of post injection per time is reduced, so that the fuel is easily vaporized and the degree of oil dilution can be reduced. Based on this, the post-injection is divided and the post-injection amount per time is set below the dilution limit value for oil dilution, which is further advantageous in reducing the degree of oil dilution by post-injection. .

  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, when performing filter regeneration, whether or not to perform post-injection control in which the temperature rise efficiency of the filter is good, but oil dilution is likely to occur in consideration of the operating condition of the internal combustion engine To choose. As a result, when performing filter regeneration, it is possible to minimize post-injection control, and even when it is necessary to perform post-injection control, the post-injection amount is less likely to cause oil dilution. I do it under conditions.

  Therefore, regardless of the operating state of the internal combustion engine when performing filter regeneration, it is possible to quickly perform filter regeneration while suppressing or preventing the occurrence of oil dilution due to post injection.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  1 to 3 show an embodiment of the present invention. First, with reference to FIG. 1, a schematic configuration of an internal combustion engine that is an object of use of the exhaust purification apparatus according to the present invention will be described.

  An internal combustion engine 1 shown in FIG. 1 is, for example, an in-cylinder direct injection type in-line four-cylinder diesel engine. Basically, air supplied from an intake system and fuel supplied from a fuel supply system are appropriately used. After the air-fuel mixture mixed at the air-fuel ratio is injected into the combustion chamber 2 and burned, the exhaust gas in the combustion chamber 2 is released into the atmosphere through the exhaust system.

  The intake system has a configuration in which an air cleaner 23 and a throttle valve 24 are sequentially arranged from the upstream side in the air flow direction in an intake passage formed by connecting an intake pipe 22 to an intake manifold 21 connected to an intake port 3 of a cylinder head. is there.

  The fuel supply system has a structure in which a fuel tank 32, a supply pump 33, a common rail 34, a plurality of fuel injection valves 35,... The supply pump 33 is driven by a crankshaft (not shown) of the internal combustion engine 1 and pumps fuel from the fuel tank 32 and supplies the pumped fuel to the common rail 34 via the fuel supply path 31. The common rail 34 has a function as a pressure accumulation chamber that holds (accumulates) the high-pressure fuel supplied from the supply pump 33 at a predetermined pressure, and distributes the accumulated fuel to each fuel injection valve 35. The fuel injection valve 35 is an electromagnetically driven on-off valve that opens when a predetermined voltage is applied and supplies fuel into the combustion chamber 2.

  The exhaust system includes an exhaust passage configured by connecting a muffler 42 to an exhaust manifold 41 connected to the exhaust port 4 of the cylinder head.

  The internal combustion engine 1 exemplified in this embodiment is equipped with a turbocharger (supercharger) 5, an intercooler 6, an EGR device 7 as an exhaust gas recirculation device, a catalyst device 8, and a fuel addition valve 9. This will be described below.

  As is generally known, the turbocharger 5 boosts and supercharges intake air using exhaust gas, and mainly includes a compressor impeller 5a and a turbine wheel 5b. The compressor impeller 5 a is disposed in the intake pipe 22, and the turbine wheel 5 b is disposed between the collecting portion of the exhaust manifold 41 and the muffler 42.

  The intercooler 6 forcibly cools the intake air boosted and supercharged by the turbocharger 5, and is disposed between the compressor impeller 5 a of the turbocharger 5 and the throttle valve 24. The throttle valve 24 is an electronically controlled on-off valve whose opening degree can be adjusted steplessly, and the flow area of the intake air is reduced under a predetermined condition, and the supply amount of the intake air is adjusted (reduced). ) Function.

  The EGR device 7 lowers the combustion temperature by returning a part of the exhaust gas (EGR gas) to the intake system and supplying it again to the combustion chamber 2, thereby reducing the amount of NOx generated. The EGR cooler 7b and the EGR valve 7c are arranged from the upstream.

  The EGR passage 7a includes a bypass passage that bypasses the combustion chamber 2 and is connected from the exhaust system to the intake system. The EGR cooler 7b includes a heat exchanger that lowers the temperature of the exhaust gas by exchanging heat between the exhaust gas passing through the EGR passage 7a and the coolant of the internal combustion engine 1, for example. The EGR valve 7c controls the recirculation amount of the exhaust gas recirculated from the exhaust system side to the intake system side in the EGR passage 7a.

  The catalyst device 8 is interposed between an exhaust manifold 41 and a muffler 42 that constitute an exhaust passage, and includes an oxidation catalyst 8a and a particulate filter 8b. The oxidation catalyst 8a is provided upstream of the particulate filter 8b in the exhaust passage.

  The particulate filter 8b is generally called a known DPF (Diesel Particulate Filter) or DPR (Diesel Particulate active Reduction system), for example.

  In addition, DPF is set as the structure which provided the porous member. The DPR has a structure in which, for example, a honeycomb structure made of a porous ceramic is supported with an oxidation catalyst (for example, a precious metal such as platinum as a main component), and in principle, harmful substances in exhaust gas are removed. It is oxidized with an oxidation catalyst, converted into carbon dioxide and water vapor, and further PM is collected in the fine pores of the porous ceramic substrate of the honeycomb structure.

  The fuel addition valve 9 is installed in the exhaust manifold 41, and injects fuel toward a portion where the exhaust manifold 41 is gathered.

  Fuel is supplied to the fuel addition valve 9 from the supply pump 33 via the additive supply path 52. The fuel addition valve 9 is used, for example, when performing filter regeneration for regenerating the particulate filter 8 b, and its operation is controlled by the controller 10.

  Various operations of the internal combustion engine 1 are controlled by the controller 10. The controller 10 is generally a known ECU (Electronic Control Unit), and includes, for example, a CPU 101, a ROM 102, a RAM 103, a backup RAM 104, and the like as shown in FIG. The controller 10 corresponds to the control device described in the claims.

  The ROM 102 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 101 executes various arithmetic processes based on various control programs and maps stored in the ROM 102. The RAM 103 is a memory that temporarily stores calculation results of the CPU 101, data input from each sensor, and the like. The backup RAM 104 is a nonvolatile memory that stores data to be saved when the internal combustion engine 1 is stopped, for example. Sex memory. The ROM 102, CPU 101, RAM 103, and backup RAM 104 are connected to each other via a bidirectional bus 107 and are connected to an input interface 105 and an output interface 106.

As shown in FIG. 2, the input interface 105 includes a water temperature sensor 71, an air flow meter 72, an intake air temperature sensor 73, an intake air pressure sensor 74, an A / F (air / fuel ratio) sensor 75, an O ₂ (oxygen) sensor 76, a temperature. A sensor 77, a rail pressure sensor 78, a throttle opening sensor 79, an accelerator opening sensor 80, a crank position sensor 81, and the like are connected.

  The water temperature sensor 71 outputs a detection signal corresponding to the cooling water temperature of the internal combustion engine 1. The air flow meter 72 outputs a detection signal corresponding to the flow rate (intake air amount) of intake air upstream from the throttle valve 24 of the intake system. The intake air temperature sensor 73 is disposed in the intake manifold 21 and outputs a detection signal corresponding to the intake air temperature. The intake pressure sensor 74 is disposed in the intake manifold 21 and outputs a detection signal corresponding to the intake air pressure. The A / F sensor 75 outputs a detection signal that continuously changes according to the oxygen concentration in the exhaust gas downstream of the catalyst device 8 of the exhaust system 7.

  The temperature sensor 77 is provided between the oxidation catalyst 8a and the particulate filter 8b in the catalyst device 8, and similarly to the outlet temperature (exhaust temperature) of the oxidation catalyst 8a or the inlet temperature (exhaust temperature) of the particulate filter 8b. A corresponding detection signal is output. The rail pressure sensor 78 outputs a detection signal corresponding to the fuel pressure stored in the common rail 34. The throttle opening sensor 79 detects the opening of the throttle valve 24. The accelerator opening sensor 80 outputs a detection signal corresponding to the depression amount of the accelerator pedal. The crank position sensor 81 outputs a detection signal (pulse) every time a crankshaft (not shown) of the internal combustion engine 1 rotates by a certain angle.

  On the other hand, the throttle valve 24, the fuel injection valve 35, the EGR valve 7c, the fuel addition valve 9, and the like are connected to the output interface 106.

  The controller 10 controls various operations of the internal combustion engine 1 based on signals from various sensors (operation parameters: signals according to the running state of the vehicle and the operating state of the internal combustion engine). Only control related to the characteristics of the present invention (for example, filter regeneration) will be described, and description of control unrelated to the characteristics of the present invention will be omitted.

  In this embodiment, the controller 10 devises an execution form of filter regeneration for recovering the PM collection function of the particulate filter 8b of the catalyst device 8.

  In this filter regeneration, basically, the PM trapped in the particulate filter 8b is burned and removed by raising the exhaust temperature entering the particulate filter 8b, and this is a specific example for raising the exhaust temperature. The specific form will be described below.

  In the first place, when the internal combustion engine 1 is cold-started or when operating conditions such as the vehicle's non-noro operation (low speed and low load operation) continue for a long period of time, the temperature of the oxidation catalyst 8a and the exhaust temperature entering the particulate filter 8b. Is low. On the other hand, after the warm-up, the exhaust temperature of the internal combustion engine 1 is high, so the oxidation catalyst 8a has reached the activation temperature, and the exhaust temperature entering the particulate filter 8b is high.

  Therefore, in this embodiment, in short, when performing the filter regeneration, if the oxidation catalyst 8a has reached the activation temperature, the filter regeneration is performed so that only the fuel addition control is performed, while the oxidation catalyst 8a When the operating temperature of the internal combustion engine 1 is such that the activation temperature is not reached and the exhaust temperature entering the particulate filter 8b is unlikely to rise, the post-injection control and the fuel addition control are coordinated. Filter regeneration in the form to be executed is performed.

  The fuel addition control is control in which fuel is directly injected into the exhaust passage by the fuel addition valve 9. When this fuel addition control is performed, the fuel is oxidized (combusted) by the oxidation catalyst 8a installed on the upstream side of the catalyst device 8, and therefore enters the particulate filter 8b on the downstream side of the oxidation catalyst 8a. The exhaust gas temperature rises and the particulate filter 8b itself rises in temperature.

  In this fuel addition control, for example, the controller 10 calculates the required addition amount and the addition interval with reference to a map created in advance by experiments or the like based on the engine speed Ne read from the output of the crank position sensor 81, The fuel addition to the exhaust manifold 41 is performed by controlling the opening of the fuel addition valve 9 according to the calculation result.

  In addition, the post-injection control is, for example, that a small amount of fuel is burned by the fuel injection valve 35 before the exhaust valve (not shown) is closed after the main fuel is injected into the combustion chamber 2 of the internal combustion engine 1 by the fuel injection valve 35. This is a control for secondary injection into the chamber 2.

  In this post-injection control, there are generally a case where a non-divided configuration in which post injection is performed once and a configuration in which, for example, post injection is divided into a plurality of times for injection. Incidentally, the form in which the post injection is injected in two is called double post injection.

  In general, when post-injection control is performed, unburned gas is easily discharged from the combustion chamber 2 of the internal combustion engine 1 into the exhaust passage. Therefore, the unburned gas discharged into the exhaust passage is oxidized by the oxidation catalyst 8a ( The temperature of the exhaust gas flowing into the particulate filter 8b from the oxidation catalyst 8a rises, and the temperature of the particulate filter 8b itself rises.

  However, when post-injection is generally performed, the fuel is difficult to vaporize and easily adheres to the cylinder wall. Therefore, the attached fuel is likely to be mixed into the oil of the internal combustion engine 1 and oil dilution is likely to occur. Become. Considering this point, the filter regeneration mode is selected in accordance with the engine operating condition.

  In this embodiment, the exhaust purification device is mainly configured by including the fuel injection valve 35, the catalyst device 8, the fuel addition valve 9, and the controller 10.

  Specifically, the form of filter regeneration by the controller 10 will be described in detail with reference to the flowchart shown in FIG.

  The flowchart shown in FIG. 3 is entered when filter regeneration is requested. That is, the controller 10 estimates the PM accumulation amount of the particulate filter 8b.

  As a method for estimating the PM accumulation amount, for example, the PM adhesion amount according to the operating conditions (for example, exhaust temperature, fuel injection amount, engine speed, etc.) of the internal combustion engine 1 is examined in advance through experiments and mapped. In addition, the PM deposition amount obtained from this map is integrated to obtain the PM deposition amount, the PM deposition amount is estimated according to the vehicle travel distance or travel time, or the inlet (upstream) of the particulate filter 8b. Side pressure) and outlet (downstream side) pressure differential sensor is provided, and the PM accumulation amount collected by the particulate filter 8b is estimated based on the sensor output.

  When the estimated value of the PM accumulation amount exceeds a predetermined upper limit value (limit accumulation amount), the controller 10 determines that the function recovery of the particulate filter 8b, that is, regeneration is necessary, and turns on the filter regeneration flag. .

  That is, the controller 10 monitors whether or not the filter regeneration flag is turned on at regular intervals during the operation of the internal combustion engine 1, and when determining that the filter regeneration flag is turned on, the flow chart shown in FIG. Entry.

  First, in step S1, it is determined whether or not the temperature of the oxidation catalyst 8a is equal to or higher than a predetermined specified value. Here, based on the detection output of the temperature sensor 77 installed between the oxidation catalyst 8a and the particulate filter 8b, the exhaust temperature discharged from the oxidation catalyst 8a is examined, and whether the exhaust temperature is equal to or higher than a specified value. It is determined whether or not.

  This specified value is set to, for example, the activation temperature (for example, 200 ° C.) of the oxidation catalyst 8a. In short, if the detected exhaust gas temperature is equal to or higher than the activation temperature of the oxidation catalyst 8a, the fuel addition control is executed later so that the fuel component is introduced into the exhaust passages (41, 42). This is because it is possible to quickly raise the PM accumulated on the particulate filter 8b to the filter regeneration temperature (for example, 600 ° C.) that can be combusted when the additive is supplied. This specified value is preferably set to a value that allows an appropriate margin for the optimum value.

  Here, when an affirmative determination is made in step S1, that is, when the temperature of the oxidation catalyst 8a is equal to or higher than a specified value, the process proceeds to steps S2 and S3 described below. On the other hand, if a negative determination is made in step S1, that is, if the temperature of the oxidation catalyst 8a is less than the specified value, the process proceeds to the following steps S4 to S10.

  In step S2, filter regeneration is executed only by fuel addition control. At this time, since the oxidation catalyst 8a is equal to or higher than the activation temperature, when fuel is added to the upstream side of the oxidation catalyst 8a, the fuel is immediately oxidized by the oxidation catalyst 8a and passes through the oxidation catalyst 8a. The exhaust temperature, that is, the exhaust temperature entering the particulate filter 8b quickly rises. As a result, the temperature of the particulate filter 8b rises quickly, and the combustion of PM deposited on the particulate filter 8b progresses.

  Thereafter, in subsequent step S3, it is determined whether or not the filter regeneration is completed. In short, in this step S3, it is examined whether or not the estimated value of the PM accumulation amount has become equal to or less than a predetermined lower limit value.

  Here, if a negative determination is made in step S3, that is, if the estimated value of the PM accumulation amount is not less than or equal to a predetermined lower limit value, it means that the filter regeneration has not been completed. Return.

  On the other hand, if an affirmative determination is made in step S3, that is, if the estimated value of the PM accumulation amount is less than or equal to a predetermined lower limit value, it means that filter regeneration has been completed, so the filter regeneration flag is turned off. Then, the filter regeneration is finished.

  Next, the flow of steps S4 to S10 will be described. First, in step S4, it is determined whether or not post injection can be divided based on the current operating state of the internal combustion engine 1. Here, for example, it is examined whether or not the limit of the control capability by the driver (EDU) for driving the fuel injection valve 35, that is, whether or not a response sufficient to divide the post injection within the post injection time is possible. . Examples of the operating conditions that limit the control capability include a high-speed rotation region of the internal combustion engine 1 and a region where the common rail 34 has a high rail pressure.

  Here, first, when a negative determination is made in step S4, that is, when it is impossible to divide the post injection, in step S5, the non-split post injection control and the fuel addition control are cooperated. Perform filter regeneration with.

  At this time, the post-injection amount is set to be equal to or less than the dilution limit value of oil dilution by post-injection, with emphasis on suppressing the occurrence of oil dilution. Since such a post injection amount is insufficient with respect to the temperature increase control target value to the filter regeneration temperature, the shortage is set to be compensated by the fuel addition control.

  The post injection amount is set by checking the dilution limit value of oil dilution from a map prepared in advance and using this dilution limit value as a reference. The map is created based on values obtained by experiments and calculations, etc., using as parameters the engine speed, post injection amount, injection timing, degree of fuel dilution with respect to engine oil, and the like. The dilution limit value is a value indicating the ease of oil dilution and is set empirically.

  On the other hand, if a negative determination is made in step S4, that is, if it is possible to divide the post-injection, filter regeneration by only the divided post-injection is executed in step S6. The post injection amount per injection, the injection interval, the injection timing, and the like in this divided post injection are appropriately set based on the current operating condition of the internal combustion engine 1 and the dilution limit value of the oil dilution. For example, it is preferable to set the post injection amount per one time in the divided post injection to be equal to or less than the dilution limit value, and then set the total post injection amount in the divided post injection to the temperature increase control target value.

  When the filter regeneration in step S5 or step S6 is executed, the unburned gas and the added fuel supplied to the exhaust passage are oxidized by the oxidation catalyst 8a, so that the oxidation catalyst 8 itself quickly rises in temperature. To do. As the exhaust gas temperature entering the particulate filter 8b rises with time and the particulate filter 8b rises to the filter regeneration temperature, the PM deposited on the particulate filter 8b is burned and removed. .

  Thereafter, in step S7, it is determined whether or not the temperature of the particulate filter 8b is insufficient. Here, for example, the exhaust temperature entering the particulate filter 8b is checked based on the detection output of the temperature sensor 77 installed on the upstream side of the particulate filter 8b, and it is determined whether or not the exhaust temperature is below the target value. .

  The target value is appropriately set based on, for example, the filter regeneration temperature (for example, 600 ° C.), but is preferably set to a value that allows an appropriate margin for the optimum value.

  If an affirmative determination is made in step S7, that is, if the particulate filter 8b is equal to or lower than the filter regeneration temperature, in step S8, the shortage of fuel is corrected by the fuel addition valve 9, and then the process proceeds to step S3. To do.

  On the other hand, if a negative determination is made in step S7, that is, if the temperature of the particulate filter 8b is near or exceeds the filter regeneration temperature, the process proceeds to step S9.

  In this step S9, it is determined whether or not the particulate filter 8b is excessively heated. Here, for example, the exhaust temperature entering the particulate filter 8b is checked based on the detection output of the temperature sensor 77 installed on the upstream side of the particulate filter 8b, and it is determined whether or not the exhaust temperature exceeds an appropriate specified value. judge. This specified value can be arbitrarily set on the side higher than the filter regeneration temperature.

  If a negative determination is made in step S9, that is, if the particulate filter 8b has not excessively heated, the process proceeds to step S3.

  On the other hand, if an affirmative determination is made in step S9, that is, if the particulate filter 8b is excessively heated, a reduction correction is performed in step S10 so as to reduce the next post-injection amount in steps S5 and S6. Then, the process proceeds to step S3. As for the subsequent post-injection amount reduction correction, in the non-divided post-injection control in step S5, one post-injection amount is corrected to decrease, but in the divided post-injection control in step S6, the total amount is reduced. The post injection amount is corrected to decrease, and the post injection amount per one time is calculated based on the correction.

  As is clear from the above description, the above steps executed by the controller 10 as the control device are function realizing means. Step S1 corresponds to the determination means described in the claims, Step S2 corresponds to the first countermeasure means described in the claims, and Step S5 corresponds to the second countermeasure means described in the claims. Step S4 corresponds to the selection means described in the claims, and step S6 corresponds to the third coping means described in the claims. Further, steps S7 and S9 correspond to the temperature rise determination means described in the claims, step S8 corresponds to the first correction means described in the claims, and step S10 corresponds to the second correction means described in the claims. is doing.

  As described above, according to the embodiment to which the feature of the present invention is applied, when performing the filter regeneration, if the oxidation catalyst 8a is activated, the filter regeneration is performed only by the fuel addition control, If the oxidation catalyst 8a is not activated, filter regeneration in a form that combines post-injection control and fuel addition control is performed.

  If the fuel addition control is performed in a situation where the oxidation catalyst 8a is at or above the activation temperature as in the former filter regeneration, the particulate filter 8b can be quickly raised to the filter regeneration temperature. Filter regeneration can be completed quickly. In this case, since post-injection control is not performed, the occurrence of oil dilution due to post-injection can be prevented.

  On the other hand, when the post-injection control and the fuel addition control are performed in cooperation in the situation where the oxidation catalyst 8a is below the activation temperature as in the latter filter regeneration, the particulate filter 8b is brought to the filter regeneration temperature. The temperature can be raised relatively quickly, and the filter can be regenerated relatively quickly. In the post-injection control here, it is possible to reduce the post-injection amount as much as possible by using the fuel addition control together, so that oil dilution by post-injection can be suppressed or prevented. It becomes possible.

  For this reason, according to the embodiment to which the features of the present invention are applied, the particulate filter 8b can be automatically regenerated regardless of the operating state of the internal combustion engine, and the oil length of the internal combustion engine 1 can be increased. This makes it possible to extend the service life, thereby contributing to improvement in performance and durability of the internal combustion engine 1.

  In addition, this invention is not limited only to embodiment mentioned above, All the deformation | transformation and application included in the range equivalent to the claim and the said range are possible. Examples are given below.

  (1) In the internal combustion engine 1 exemplified in the above embodiment, an example in which the fuel addition valve 9 is installed in the exhaust manifold 41 is given. However, the present invention is not limited thereto, and for example, as shown in FIG. In addition, it can be installed in a region between the turbocharger 5 and the catalyst device 8 in the exhaust passage.

  In this case, since the fuel supplied from the fuel addition valve 9 can be prevented or suppressed from adhering to the turbocharger 5, it is possible to prevent or suppress the emission of white smoke from the muffler 42.

  (2) Although the internal combustion engine 1 exemplified in the above embodiment is exemplified by the one equipped with the turbocharger 5 and the EGR device 7, even if one or both of them are eliminated, the present invention. Can be applied. Further, the present invention may be configured such that, for example, an exhaust throttle valve for adjusting the exhaust flow rate is provided on the downstream side of the catalyst device 8 in the exhaust passage.

  (3) In the above embodiment, an example is given in which the particulate filter 8b of the catalyst device 8 is a DPF or a DPR. However, the filter 8b can be a DPNR (Diesel Particulate-NOx Reduction system). .

  The DPNR is capable of removing nitrogen oxides (NOx) in addition to the function of the DPR. For example, an oxidation catalyst (for example, a main component of a noble metal such as platinum) is formed on a porous ceramic structure. A NOx occlusion reduction catalyst is supported. This DPNR is collected when PM in the exhaust gas passes through the porous wall, and when the air-fuel ratio of the exhaust gas is lean, NOx in the exhaust gas is occluded in the NOx occlusion reduction type catalyst, When the air-fuel ratio becomes rich, the stored NOx is reduced and released.

  In the case of such DPNR, in addition to performing the same process as the filter regeneration described above, it is necessary to perform a NOx reduction process for recovering from S poisoning of the NOx storage reduction catalyst. Also in this case, the control described in the above embodiment can be performed during the filter regeneration.

  (4) In the above embodiment, the catalyst device 8 is configured to include the oxidation catalyst 8a and the particulate filter 8b. However, in addition to these, an NSR catalyst may be added. is there.

In short, this NSR catalyst is a kind of what is called a NOx occlusion reduction type catalyst. For example, alumina (Al ₂ O ₃ ) is used as a carrier, and, for example, potassium (K), sodium (Na), lithium ( Li), alkali metals such as cesium (Cs), alkaline earths such as barium (Ba) and calcium (Ca), rare earths such as lanthanum (La) and yttrium (Y), and platinum (Pt) It is configured to carry a noble metal.

This NSR catalyst occludes NOx in a state where a large amount of oxygen is present in the exhaust gas, the exhaust gas has a low oxygen concentration, and a large amount of reducing components (for example, unburned components (HC) of the fuel) are present. In this state, NOx is reduced to NO ₂ or NO and released. NO NOx released as NO ₂ or NO, the N ₂ is further reduced due to quickly reacting with HC or CO in the exhaust gas. Further, HC and CO are oxidized to H ₂ O and CO ₂ by reducing NO ₂ and NO.

  (5) In the flowchart of FIG. 3 described in the above embodiment, it is possible to eliminate steps S4 and S6 and shift to step S5 when a negative determination is made in step S1. Are also included in the present invention.

1 is a schematic configuration diagram showing an embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention. It is a schematic block diagram of the controller of FIG. FIG. 3 is a flowchart used for explaining an operation of filter regeneration by the controller of FIGS. 1 and 2. FIG. FIG. 3 is a view corresponding to FIG. 1 in another embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Combustion chamber 8 Catalyst apparatus 8a Oxidation catalyst 8b Particulate filter 9 Fuel addition valve 10 Controller (equivalent to control apparatus)
35 Fuel injection valve 41 Exhaust manifold (corresponding to a part of the exhaust passage)
42 Muffler (part of exhaust passage)
75 A / F sensor 76 O ₂ sensor 77 Temperature sensor

Claims (4)

An oxidation catalyst provided in the exhaust passage of the internal combustion engine, a filter provided downstream of the oxidation catalyst in the exhaust passage to collect particulate matter in the exhaust, and the filter deposited on the filter as necessary An exhaust purification device having a control device for performing filter regeneration by raising the temperature to a filter regeneration temperature for burning and removing particulate matter,
The control device determines whether or not the oxidation catalyst is at an activation temperature or higher in accordance with the execution request for the filter regeneration;
First coping means for performing filter regeneration in a form in which a fuel component is added and supplied to the upstream side of the oxidation catalyst in the exhaust passage when an affirmative judgment is made by the judging means;
And a second coping means for performing filter regeneration in a form in which post-injection control and the fuel addition control cooperate when the determination is negative.
The second coping means sets the post injection amount to be equal to or less than a dilution limit value of oil dilution by post injection, and then adds a shortage to the target temperature increase control value to the filter regeneration temperature by the fuel addition control. An exhaust emission control device for an internal combustion engine, characterized in that it is set so as to compensate. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The control device includes a temperature rise determination means for determining whether the temperature rise is insufficient or the temperature rise is excessive after execution of the control operation by the first coping means or the second coping means,
First correction means for correcting an increase by the fuel addition control when the temperature increase determination means determines that the temperature increase is insufficient;
An exhaust gas purification apparatus for an internal combustion engine, further comprising: a second correction unit that corrects a decrease in the next post-injection amount when the temperature increase determination unit determines that the temperature increase is excessive. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2,
The exhaust request of the internal combustion engine is characterized in that the execution request for the filter regeneration is issued when the estimated value of the accumulation amount of the particulate matter on the filter becomes a predetermined upper limit value (limit accumulation amount) or more. Purification equipment. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3,
The control device includes third coping means for performing filter regeneration in a form in which post injection is divided,
When the negative determination is made by the determination means, it is further determined whether or not the post-injection can be divided according to the operating state of the internal combustion engine, and when the negative determination is made, the second coping means is determined positively And further selecting means for shifting to the third coping means,
The third coping means sets the post-injection amount per time to be equal to or less than the dilution limit value, and sets the total post-injection amount to the temperature increase control target value. Exhaust purification equipment.

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