JP2008215110A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

An object of the present invention is to provide an exhaust emission control device for an internal combustion engine capable of suitably maintaining the temperature of a filter while suppressing oil dilution due to the post-injection when performing post-injection during execution of fuel cut during deceleration.
An exhaust passage 26 of an engine 1 is provided with a filter 32 that collects particulate matter in the exhaust. The control device 25 performs a regeneration process in which the temperature of the filter 32 is raised by burning the particulate matter by controlling the injection timing of the fuel injection valve 4 and performing post injection. The control device 25 sets the target temperature of the filter 32 at the time of executing the regeneration process, and sets the injection amount so that the post-injection injection amount decreases as the target temperature is lower. Further, when the fuel cut at the time of deceleration is executed, the target temperature of the filter 32 is set to a lower temperature than when the fuel cut is not performed.
[Selection] Figure 1

Description

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

As an exhaust emission control device provided in an exhaust passage of an internal combustion engine, an apparatus including a filter that collects PM (Particulate Matter) in exhaust gas is known.
In such an exhaust purification device, as the amount of PM collected by the filter increases, pressure loss in the filter increases, and as a result, engine output and the like are adversely affected. Therefore, a regeneration process is performed in which the collected PM is burned by raising the temperature of the filter.

In this regeneration process, fuel injection that is performed again at a time delayed from the main fuel injection timing, so-called post-injection, is performed to supply the fuel to the exhaust passage, and the temperature of the exhaust gas is raised using the oxidation heat of this fuel. As a result, the temperature of the filter is increased.
JP 2004-197576 A (paragraph “0085” etc.)

By the way, it is desirable to perform post-injection in order to maintain the temperature of the filter even if the fuel cut at the time of deceleration is performed during the regeneration process.
However, since the fuel is not burned in the cylinder during the fuel cut, the temperature in the cylinder is lowered. Therefore, the fuel injected by the post-injection is not easily vaporized in the cylinder, and tends to adhere to the cylinder wall or the like. Thus, the fuel adhering to the cylinder wall or the like is mixed into the engine lubricating oil and causes oil dilution.

  Here, as described in Patent Document 1, if the amount of post-injection is reduced during such deceleration, the amount of fuel adhering to the cylinder wall can be reduced, so that the occurrence of oil dilution is suppressed. be able to. However, if the post injection amount is reduced, the temperature of the filter may be excessively lowered in some cases, and it may be difficult to maintain the temperature at a temperature suitable for the regeneration process. Therefore, there is room for further improvement in reducing the post injection amount.

  The present invention has been made in view of such circumstances, and its object is to appropriately reduce the temperature of the filter while suppressing oil dilution due to post injection when performing post injection during execution of fuel cut during deceleration. An object of the present invention is to provide an exhaust purification device for an internal combustion engine that can be maintained.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 includes a filter that is provided in an exhaust passage of the internal combustion engine and collects particulate matter in the exhaust gas, and performs post injection by controlling the injection timing of the fuel injection valve of the engine. In an exhaust gas purification apparatus for an internal combustion engine that performs a regeneration process for increasing the temperature of the filter and burning the particulate matter, target temperature setting means for setting a target temperature of the filter at the time of executing the regeneration process, and the target An injection amount setting means for setting the injection amount so that the post-injection amount becomes smaller as the temperature is lower, and the target temperature setting means is not so when the fuel cut at the time of deceleration is being executed. The gist of the invention is to set the target temperature to a low temperature.

  According to this configuration, when the fuel cut at the time of deceleration is being executed, the target temperature of the filter is set to a lower temperature than when it is not. Therefore, when post-injection is performed during execution of fuel cut during deceleration, the post-injection amount is reduced compared to when fuel cut is not performed. Therefore, even when the fuel cut is being performed and the post-injection is performed under a condition where the temperature in the cylinder is low, the occurrence of oil dilution due to the post-injection can be suppressed.

  Here, in the same configuration, the post-injection amount is reduced by lowering the target temperature of the filter. Therefore, when the post injection amount is reduced, the filter is easily maintained at the target temperature, and an excessive temperature drop of the filter is suppressed. Therefore, according to this configuration, when post injection is performed during fuel cut during deceleration, the temperature of the filter can be suitably maintained while suppressing oil dilution due to the post injection.

  As for the setting of the target temperature, as in the invention described in claim 2, the target temperature is set to a lower temperature as the temperature in the cylinder of the engine is lower, so that the fuel cut during deceleration is being executed. When the temperature in the cylinder decreases, the target temperature can be reliably decreased.

  Further, since the temperature in the cylinder tends to decrease as the engine load is lower, the target temperature of the filter is set to a lower temperature as the engine load is lower, as in the third aspect of the invention. By adopting the configuration, the target temperature can be surely lowered when the fuel cut is being executed during deceleration and the temperature in the cylinder falls without measuring the temperature in the cylinder. Incidentally, the engine load is fuel injection that is performed prior to post-injection, and can be estimated based on the injection amount of main injection that is performed in order to obtain engine output.

  According to a fourth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to third aspects, the injection amount setting means further includes an engine rotational speed and an engine load in addition to the target temperature. The gist is to set the injection amount based on the above.

  When the temperature of the filter is raised to the target temperature, a larger amount of post-injection is required as the exhaust gas temperature is lower. Further, as the flow rate of the exhaust gas increases, the time for the exhaust gas to pass through the filter is shortened and the heat receiving time of the filter is also shortened, so that the temperature of the filter is less likely to rise. For this reason, when the temperature of the filter is raised to the target temperature, a larger amount of post-injection is required as the flow rate of exhaust gas increases. Therefore, when raising the temperature of the filter to the target temperature through post injection, it is desirable to consider the exhaust temperature and the exhaust flow rate.

  Here, as the engine load increases, the injection amount of the main injection increases, so the exhaust temperature increases. Further, the higher the engine speed, the shorter the interval at which hot exhaust flows into the exhaust passage, and the exhaust temperature in the exhaust passage becomes higher.

  Also, the higher the engine load, the larger the intake air amount, and the exhaust flow rate also increases. Further, as the engine speed increases, the interval at which the exhaust flows into the exhaust passage becomes shorter as described above, and the exhaust flow rate per unit time increases. As described above, the exhaust temperature and the exhaust flow rate vary depending on the engine load and the engine speed.

  Therefore, in this configuration, in addition to the target temperature, the injection amount of the post injection is set based on the engine speed and the engine load that are further related to the exhaust temperature and the exhaust flow rate. Therefore, the post injection amount necessary for setting the filter to the target temperature can be set appropriately.

  According to a fifth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to fourth aspects, the injection amount is corrected according to a deviation between the temperature of the filter and the target temperature. The gist of the invention is to further include correction means and restriction means for restricting the maximum injection amount of post-injection during execution of fuel cut during deceleration.

In this configuration, the post-injection amount is corrected according to the deviation between the filter temperature and the target temperature, whereby the filter temperature is appropriately controlled toward the target temperature.
By the way, an error may occur between the command value of the injection amount and the actual injection amount due to variations in the injection characteristics of the fuel injection valve, etc., and the actual injection amount is smaller than the command value. The exhaust temperature rise amount is insufficient. Therefore, the correction value of the post injection amount according to the deviation is increased, and the post injection amount after correction is increased. Here, as described above, the temperature in the cylinder is low during the fuel cut at the time of deceleration, and the fuel is likely to adhere to the cylinder wall. Therefore, if the post-injection amount is corrected to increase excessively during execution of such fuel cut, the amount of fuel adhering to the cylinder wall or the like due to post-injection may increase and oil dilution may proceed.

  Therefore, in this configuration, the maximum post-injection amount during fuel cut during deceleration is limited, so that even if the correction value increases, the post-injection amount after correction is limited to a predetermined amount or less. Thus, an excessive increase in the post injection amount can be suppressed. Accordingly, it is possible to suppress the occurrence of oil dilution due to variations in the injection characteristics of the fuel injection valve during the fuel cut that is likely to cause fuel adhesion to the cylinder wall or the like. In this configuration, during the fuel cut at the time of deceleration, the post injection amount that can suitably suppress oil dilution is set as a guard value while setting the filter temperature to the target temperature, and the post value is set based on the guard value. It is desirable to limit the maximum amount of injection.

(First embodiment)
A first embodiment of an internal combustion engine exhaust purification apparatus according to the present invention will be described below with reference to FIGS.

FIG. 1 shows a schematic configuration diagram illustrating a control device for a diesel engine including an exhaust purification device according to the present embodiment, an engine 1 to which the control device is applied, and peripheral configurations thereof.
The engine 1 is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4 corresponding to the respective cylinders # 1 to # 4 are attached to the cylinder head 2. In addition, the cylinder head 2 is provided with intake ports for introducing outside air into the cylinders and exhaust ports 6a to 6d for discharging combustion gas to the outside of the cylinders corresponding to the respective cylinders # 1 to # 4. ing.

  Each fuel injection valve 4 is connected to a common rail 9 for accumulating fuel. A high pressure pump 10 is connected to the common rail 9, and high pressure fuel is supplied to the common rail 9 by the high pressure pump 10. The high pressure fuel supplied to the common rail 9 is injected and supplied to the combustion chamber of each cylinder when the fuel injection valve 4 is opened.

  An intake manifold 7 is connected to the intake port. The intake manifold 7 is connected to the intake passage 3. A throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3. The throttle valve 16 is driven to open and close by a motor 17.

An exhaust manifold 8 is connected to the exhaust ports 6a to 6d. The exhaust manifold 8 is connected to the exhaust passage 26.
In the middle of the exhaust passage 26, there is provided a turbocharger 11 that supercharges intake air introduced into the cylinder using exhaust pressure. An intercooler 18 is provided in the intake passage 3 between the intake side compressor of the turbocharger 11 and the throttle valve 16. The intercooler 18 cools the intake air whose temperature has risen due to supercharging of the turbocharger 11.

  A first oxidation catalyst 30 for purifying exhaust components is provided in the middle of the exhaust passage 26 and downstream of the exhaust-side turbine of the turbocharger 11. A converter 34 for purification is provided. Inside the converter 34, a second oxidation catalyst 31 and a filter 32 are arranged in series with respect to the flow direction of the exhaust gas.

  The first oxidation catalyst 30 and the second oxidation catalyst 31 carry a catalyst for oxidizing HC in the exhaust. The filter 32 is a member that collects PM (particulate matter) in the exhaust gas and is composed of a porous ceramic structure. When the PM in the exhaust gas passes through the porous wall, It is collected.

  An exhaust throttle valve 35 that restricts the flow rate of exhaust gas is provided in the middle of the exhaust passage 26 and downstream of the converter 34. When the exhaust throttle valve 35 is not operated, the valve element is fully open. On the other hand, during operation, the valve body is closed to some extent to reduce the flow rate of the exhaust.

  In addition, the engine 1 is provided with an EGR device. This EGR device is a device that reduces the combustion temperature in the cylinder by introducing a part of the exhaust gas into the intake air, thereby reducing the amount of NOx generated. This apparatus includes an EGR passage 13 that communicates the intake manifold 7 and the exhaust manifold 8, an EGR valve 15 provided in the EGR passage 13, an EGR cooler 14, and the like. Then, by adjusting the valve opening degree of the EGR valve 15, the amount of exhaust gas introduced from the exhaust manifold 8 to the intake manifold 7, that is, the EGR amount is adjusted. Further, the temperature of the exhaust gas flowing through the EGR passage 13 is lowered by the EGR cooler 14. When a part of the exhaust gas is returned to the combustion chamber of the engine 1 by this EGR device, the combustion temperature of the air-fuel mixture decreases and the amount of NOx generated decreases.

  Various sensors for detecting the engine operation state are attached to the engine 1. For example, the intake air amount GA is detected by the air flow meter 40 provided on the upstream side of the intake passage 3. Further, the opening degree of the throttle valve 16 (throttle opening degree TA) is detected by a throttle opening degree sensor 41 provided in the motor 17 that opens and closes the throttle valve 16. A first exhaust temperature Ta, which is the temperature of the exhaust gas flowing into the second oxidation catalyst 31, is detected by a first exhaust temperature sensor 42 provided on the exhaust upstream side of the second oxidation catalyst 31. The second exhaust temperature sensor 43 provided between the filter 32 and the filter 32 detects a second exhaust temperature Tb that is the temperature of the exhaust immediately after passing through the second oxidation catalyst 31. Further, the pressure sensor 44 provided between the second oxidation catalyst 31 and the filter 32 detects the pressure on the upstream side of the filter 32. Also, the crank angle sensor 45 provided in the vicinity of the crankshaft of the engine 1 detects the rotation speed of the crankshaft, that is, the engine rotation speed NE, and the accelerator sensor 46 provided on the accelerator pedal depresses the accelerator pedal, that is, the accelerator pedal. A manipulated variable ACCP is detected.

  The outputs of these various sensors are input to the control device 25. The control device 25 includes a central processing control device (CPU), a read only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, a timer counter, an input The microcomputer is mainly configured with an interface, an output interface, and the like.

  The control device 25 controls the fuel injection amount control and fuel injection timing control of the fuel injection valve 4, the discharge pressure control of the high pressure pump 10, the opening control of the throttle valve 16, the opening control of the EGR valve 15, etc. 1 is performed. Various exhaust purification controls such as a regeneration process for a filter that burns the PM collected by the filter 32 are also performed by the controller 25.

The regeneration process of the filter 32 is performed as follows.
First, as the accumulation amount of PM collected by the filter 32 increases, the pressure P detected by the pressure sensor 44 tends to increase. Therefore, the PM accumulation amount PMsm in the filter 32 is estimated based on the pressure P.

When the PM accumulation amount PMsm reaches the regeneration start reference value PMstart, the regeneration process of the filter 32 is started.
When the regeneration process is started, the control device 25 performs post injection by controlling the injection timing of the fuel injection valve 4. This post-injection is a fuel injection that is performed again at a timing delayed from the injection timing of the main fuel injection for obtaining the engine output, and the fuel injected by the post-injection is supplied to the exhaust passage 26. When the fuel supplied to the exhaust passage 26 reaches the first oxidation catalyst 30, a part of the fuel is oxidized and the exhaust temperature rises due to the oxidation heat. The temperature of the second oxidation catalyst 31 is increased by the action of the exhaust temperature increase by the first oxidation catalyst 30, whereby the activation of the second oxidation catalyst 31 is promoted. When the fuel that has passed without being oxidized by the first oxidation catalyst 30 reaches the second oxidation catalyst 31, it is oxidized by the second oxidation catalyst 31 and the exhaust temperature rises. The heated exhaust gas flows into the filter 32 and the temperature of the filter 32 rises, so that the collected PM is combusted.

The amount of PM that decreases by performing the regeneration process, in other words, the PM accumulation amount PMsm during the regeneration process is estimated based on the following equation (1).

PMsm during the regeneration process = PMsm + PMe−PMc at the start of the regeneration process (1)
PMsm: PM deposition amount
PMe: PM emissions
PMc: PM oxidation amount

The PM emission amount PMe is the amount of PM discharged from all combustion chambers of the engine 1, and is a map set through previous experiments, for example, a PM emission amount calculation map using the engine speed NE and the engine load as parameters. Sought with reference to The parameter indicating the engine load is fuel injection performed prior to post-injection, and is estimated based on an injection amount of main injection performed to obtain engine output (hereinafter referred to as main injection amount). .

  The PM oxidation amount PMc is an amount by which PM collected by the filter 32 is burned. This PM oxidation amount PMc is a map set through a prior experiment or the like, that is, the filter temperature FT which is the temperature of the filter 32 (here, the second exhaust temperature Tb indicating the exhaust temperature flowing into the filter 32 is used) and the air flow. It is calculated on the basis of a PM oxidation rate map using the intake air amount GA detected by the meter 40 as a parameter.

When the estimated PM accumulation amount PMsm during the regeneration process is sufficiently reduced and falls below a predetermined regeneration completion reference value PMend, the regeneration process of the filter 32 is terminated.
Further, when the regeneration process is performed in an operation region where the exhaust temperature is low, such as when the engine is under a low load, the exhaust throttle valve 35 is operated in conjunction with the execution of post injection. When the exhaust flow rate is limited by the operation of the exhaust throttle valve 35, the back pressure on the upstream side of the exhaust throttle valve 35 increases and the exhaust temperature rises. Further, the increase in the back pressure also increases the engine load, and the exhaust gas temperature also rises when the amount of fuel injected from the fuel injection valve 4 is increased. As described above, since the exhaust temperature rises by operating the exhaust throttle valve 35, the regeneration process of the filter 32 can be performed even in an operation region where the exhaust temperature is low, such as during low-load operation. become.

  By the way, a so-called fuel cut is performed in which fuel injection is stopped when the vehicle decelerates. In this embodiment, the temperature of the filter 32 is maintained even when the fuel cut is performed during the regeneration process. Therefore, post injection is performed.

  Here, since the fuel is not burned in each of the cylinders # 1 to # 4 during the fuel cut, the temperature in each cylinder becomes low. Therefore, the fuel injected by the post injection is not easily vaporized in each cylinder, and easily adheres to the cylinder wall or the like. Thus, the fuel adhering to the cylinder wall or the like is mixed into the engine lubricating oil and causes oil dilution.

  Therefore, in the present embodiment, the post injection amount setting process for setting the fuel injection amount at the time of post injection (hereinafter referred to as the post injection amount) is performed in the following manner, so that the post cut during the fuel cut at the time of deceleration is performed. When performing injection, the temperature of the filter is appropriately maintained while suppressing oil dilution due to the post injection.

  FIG. 2 shows the procedure of the post injection amount setting process. This process is repeatedly executed by the control device 25 during the execution of the reproduction process. Further, this process constitutes the changing means.

  When this processing is started, first, the main injection amount Q, the PM accumulation amount PMsm during regeneration processing calculated by the above equation (1), the engine speed NE, and the filter temperature FT are read (S100).

  Next, based on the main injection amount Q and the PM accumulation amount PMsm, the target temperature FTp of the filter 32 to be heated by the regeneration process is set with reference to the target temperature setting map FTmap stored in the ROM of the control device 25. (S110). In addition, the process of step S110 comprises the said target temperature setting means.

  This target temperature FTp is set with the following tendency. That is, the lower the temperature in each cylinder # 1 to # 4, the lower the target temperature FTp. Here, the temperature in each of the cylinders # 1 to # 4 tends to decrease as the engine load is low, and the main injection amount Q decreases as the engine load is low. Therefore, as shown in FIG. 3, the smaller the main injection amount Q, in other words, the lower the engine load, and the lower the temperature in each cylinder # 1 to # 4, the lower the target temperature FTp. The

  Further, the target temperature FTp is set to be lower as the PM accumulation amount PMsm is larger. This is because, as the PM accumulation amount PMsm is larger, the temperature rise of the filter 32 is promoted by the combustion of PM itself. Therefore, even if the temperature rise effect of the filter 32 by post injection is reduced, the temperature of the filter 32 is This is because the temperature becomes necessary for burning PM.

  Next, a post injection amount setting map corresponding to the set target temperature FTp is selected from a plurality of post injection amount setting maps PQmap that are stored in the ROM of the control device 25 and are prepared according to the target temperature FTp. PQmap is selected (S120).

  Then, with reference to the selected post injection amount setting map PQmap, the basic post injection amount PQb, which is the basic value of the post injection amount, is set based on the main injection amount Q and the engine speed NE (S130).

  The basic post injection amount PQb is basically set in the following tendency. First, as shown in FIG. 4, the basic post injection amount PQb is decreased as the target temperature FTp is lower. This is because the post injection amount necessary to raise the temperature of the filter 32 to the target temperature FTp decreases as the target temperature FTp decreases.

  Further, as shown in FIG. 4, the basic post injection amount PQb is decreased as the exhaust gas temperature is higher. Conversely, the basic post injection amount PQb is increased as the exhaust temperature is lower. This is because when the temperature of the filter 32 is raised to the target temperature FTp, a larger post injection amount is required as the exhaust gas temperature is lower.

  As shown in FIG. 4, the basic post-injection amount PQb is reduced as the exhaust gas flow rate decreases. Conversely, the basic post injection amount PQb is increased as the exhaust gas flow rate is increased. This is because, as the exhaust gas flow rate increases, the time for the exhaust gas to pass through the filter 32 is shortened, and the heat receiving time of the filter 32 is also shortened. For this reason, when the temperature of the filter 32 is raised to the target temperature FTp, the larger the exhaust flow rate, the more post injection amount is required.

  Here, as the engine load increases, the main injection amount Q increases, so the exhaust temperature increases. Further, the higher the engine speed NE, the shorter the interval at which hot exhaust flows into the exhaust passage 26, and the higher the exhaust temperature in the exhaust passage 26.

  Also, the higher the engine load, the larger the intake air amount, and the exhaust flow rate also increases. Further, as the engine rotational speed NE becomes higher, as described above, the interval at which the exhaust flows into the exhaust passage 26 becomes shorter, so that the exhaust flow rate per unit time increases. As described above, the exhaust temperature and the exhaust flow rate vary depending on the amount of the main injection amount Q indicating the engine load and the engine rotational speed NE.

  Therefore, in the present embodiment, when setting the basic post-injection amount PQb according to the target temperature FTp, as described above, the exhaust temperature and the exhaust flow rate that affect the temperature rise of the filter 32 are taken into consideration. The basic post injection amount PQb is set based on the engine speed NE and the main injection amount Q that are related to the temperature and the exhaust flow rate, and the target temperature FTp. Thereby, the basic post injection amount PQb necessary for setting the filter 32 to the target temperature FTp is appropriately set. In addition, the process of step S120 and step S130 comprises the said injection amount setting means.

  Next, a deviation ΔT between the filter temperature FT and the target temperature FTp is calculated (S140), and a correction amount H for the basic post injection amount PQb is calculated based on the deviation ΔT (S150). This correction amount H is set to a larger value as the deviation ΔT increases.

  Next, a post injection amount PQ obtained by correcting the basic post injection amount PQb by the correction amount H is calculated (S160). Thus, the basic post-injection amount PQb is corrected according to the deviation ΔT, so that the temperature of the filter 32 is appropriately feedback-controlled toward the target temperature FTp. In addition, the process of step S140-step S160 comprises the said correction | amendment means.

Then, at an appropriately set injection timing, a command value corresponding to the post-injection amount PQ is output from the control device 25 to the fuel injection valve 4, and valve opening control of the fuel injection valve 4 is performed.
Thus, in the post-injection amount setting process, the target temperature FTp is lowered as the main injection amount Q is smaller, in other words, the engine load is lower and the temperature in each cylinder # 1 to # 4 is lower. Is set. Therefore, when the engine load is very low, such as during fuel cut during deceleration, compared to when fuel cut is not being performed and fuel injection from the fuel injection valve 4 is being performed, The target temperature FTp is set to a lower temperature. Since the basic post-injection amount PQb is set to a smaller amount as the target temperature FTp is lower, when post-injection is performed during execution of fuel cut during deceleration, the fuel cut is not being executed as described above. In comparison, the basic post injection amount PQb is reduced. Therefore, even when the fuel cut is being performed and the post injection is performed under the condition where the temperature in each of the cylinders # 1 to # 4 is low, the occurrence of oil dilution due to the post injection can be suppressed.

  In particular, in the post injection amount setting process, the basic post injection amount PQb is decreased through a decrease in the target temperature FTp of the filter 32. Therefore, even if the basic post injection amount PQb is reduced, the filter 32 is easily maintained at the target temperature FTp, and an excessive temperature drop of the filter 32 is suppressed. Therefore, when post injection is performed during fuel cut during deceleration, the temperature of the filter 32 can be appropriately maintained while suppressing oil dilution due to the post injection.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The target temperature FTp of the filter 32 at the time of executing the regeneration process is set, and the injection amount is set so that the basic post injection amount PQb decreases as the target temperature FTp decreases. When the fuel cut at the time of deceleration is executed, the target temperature FTp is set to a lower temperature than when the fuel cut is not performed. Accordingly, the basic post-injection amount PQb is reduced through a decrease in the target temperature FTp of the filter 32. Therefore, when the basic post injection amount PQb is reduced, the filter 32 is easily maintained at the target temperature FTp, and an excessive temperature drop of the filter 32 is suppressed. Therefore, when post injection is performed during fuel cut during deceleration, the temperature of the filter 32 can be suitably maintained while suppressing oil dilution due to the post injection.

  (2) The lower the temperature in each of the cylinders # 1 to # 4, the lower the target temperature FTp is set. Thus, the fuel cut is being executed during deceleration and each cylinder # 1 is being executed. When the temperature in .about. # 4 falls, the target temperature FTp can be reliably lowered.

  (3) The temperature in each cylinder # 1 to # 4 tends to decrease as the engine load is lower. Therefore, the lower the engine load, the lower the target temperature FTp of the filter 32 is set. Therefore, without directly measuring the temperature in each cylinder # 1 to # 4, when the fuel cut is being executed at the time of deceleration and the temperature in each cylinder # 1 to # 4 decreases, the target temperature FTp is surely set. Can be reduced.

(4) The basic post injection amount PQb is set not only based on the target temperature FTp but also based on the main injection amount Q indicating the engine speed NE and the engine load. Accordingly, the basic post injection amount PQb necessary for setting the filter 32 to the target temperature FTp can be set appropriately.
(Second Embodiment)
Next, a second embodiment in which the exhaust gas purification apparatus for an internal combustion engine according to the present invention is embodied will be described with reference to FIGS.

  In the first embodiment, the basic post-injection amount PQb is corrected according to the deviation ΔT between the filter temperature FT and the target temperature FTp, whereby the temperature of the filter 32 is appropriately controlled toward the target temperature FTp. Is done.

  Incidentally, an error may occur between the command value of the post injection amount PQ corrected with the correction amount H and the actual injection amount due to variations in the injection characteristics of the fuel injection valve 4 and the like. When the injection amount is smaller than the command value, the exhaust temperature rise amount becomes insufficient. Therefore, the correction amount H set based on the deviation ΔT is increased, and as a result, the post injection amount PQ after correction is increased. Here, as described above, the temperature in each of the cylinders # 1 to # 4 is low during the fuel cut at the time of deceleration, and the fuel is likely to adhere to the cylinder wall. Therefore, if the post-injection amount PQ is corrected to increase excessively during execution of such fuel cut, the amount of fuel adhering to the cylinder wall or the like resulting from post-injection may increase, and oil dilution may proceed. .

  Therefore, in the present embodiment, the maximum post-injection amount during the fuel cut at the time of deceleration is limited. More specifically, in the post-injection amount setting process shown in FIG. 2, the processes of steps S200 to S220 shown in FIG. 5 are further performed after the process of step S160.

That is, when the post injection amount PQ corrected with the correction amount H is calculated in step S160, the process of step S200 is performed.
In this step S200, a guard value G for limiting the maximum injection amount of the post injection amount PQ based on the main injection amount Q and the engine speed NE with reference to a guard value setting map Gmap stored in the ROM of the control device 25. Is set.

  This guard value G is set with the following tendency. First, as shown in FIG. 6, the guard value G is set to a smaller value as the engine load is lower, in other words, as the main injection amount Q is smaller. In particular, as a guard value G that is set during the fuel cut at the time of deceleration when the engine load is very small and the temperature in each of the cylinders # 1 to # 4 is low, the temperature of the filter 32 is set to the target temperature FTp, and the oil A post injection amount that can suppress the dilution within an allowable range is set. Incidentally, when post injection is being executed, there is a risk that excessive increase correction of the post injection amount PQ as described above may occur, and such excessive increase correction is performed at the time of high load operation where the exhaust temperature becomes high. Although temporarily, the exhaust temperature may rise excessively. Therefore, in the present embodiment, the guard value G is variably set according to the engine load so as to suppress the temporary increase in the exhaust temperature as described above.

  Further, as shown in FIG. 6, the guard value G is set to a smaller value as the engine speed NE is lower. This is because as the engine speed NE is lower, the number of combustions in the cylinder per unit time tends to decrease and the temperature in each cylinder # 1 to # 4 tends to be lower. Therefore, the lower the engine speed NE, the more easily the fuel injected by post injection adheres to the cylinder wall and the like, and it is necessary to limit the maximum injection amount of the post injection amount to a smaller value.

  When the guard value G is thus set, it is next determined whether or not the post injection amount PQ calculated in step S160 is greater than or equal to the guard value G (S210), and the post injection amount PQ is greater than or equal to the guard value G. In some cases (S210: YES), the guard value G is set as the final post-injection amount PQ (S220), and this process is temporarily terminated.

On the other hand, when the post injection amount PQ is less than the guard value G (S210: NO), this process is temporarily ended. Thus, when a negative determination is made in step S210, the post injection amount PQ calculated in step S160 is set as the final post injection amount PQ as it is. In addition, the process of step S200-step S220 comprises the said restriction | limiting means.

  As described above, in the post injection amount setting process in the present embodiment, the maximum injection amount is limited when the post injection is executed. In particular, the maximum post-injection amount during fuel cut during deceleration is also limited. Even if the correction amount H increases, the post-injection amount PQ after correction is limited to a guard value G or less, and An excessive increase in the injection amount PQ can be suppressed. Accordingly, it is possible to suppress the occurrence of oil dilution due to variations in the injection characteristics of the fuel injection valve 4 during the execution of the fuel cut that tends to cause fuel adhesion to the cylinder wall or the like.

As described above, according to the present embodiment, the following effects can be obtained in addition to the effects of the first embodiment.
(5) When correcting the basic post-injection amount PQb in accordance with the deviation ΔT between the filter temperature and the target temperature FTp, the maximum post-injection amount during the fuel cut at the time of deceleration is limited. ing. Accordingly, it is possible to suppress the occurrence of oil dilution due to variations in the injection characteristics of the fuel injection valve 4 during the execution of the fuel cut that tends to cause fuel adhesion to the cylinder wall or the like.

In addition, each said embodiment can also be changed and implemented as follows.
In the first embodiment, the temperature in each cylinder # 1 to # 4 is estimated or directly detected, and the target temperature FTp is set to a lower temperature as the estimated or detected temperature in the cylinder is lower. You may make it do. Also in this case, when the fuel cut at the time of deceleration is being executed and the temperature in the cylinder decreases, the target temperature FTp can be reliably decreased, and as a result, the post injection amount through the decrease in the target temperature FTp. You will be able to lose weight.

  In the first embodiment, a plurality of post injection amount setting maps PQmap corresponding to the target temperature FTp are provided. However, the basic post injection amount PQb is set and set based on the engine load and the engine rotational speed NE. The basic post injection amount PQb may be corrected according to the target temperature FTp.

  In the first embodiment, the parameters for setting the target temperature FTp are the engine load and the PM accumulation amount, but the PM accumulation amount may be omitted. The parameters for setting the basic post injection amount PQb are the target temperature FTp, the engine load, and the engine rotational speed NE. However, the engine load may be omitted or the engine rotational speed NE may be omitted. Good.

In the second embodiment, the parameters for setting the guard value G are the engine load and the engine speed NE, but either one may be omitted.
In the second embodiment, the guard value G is variably set based on the engine load and the engine speed NE, so that the maximum post injection is performed not only during fuel cut during deceleration but also in other engine operating states. Although the amount is limited, a guard value that limits the maximum post-injection amount may be set only during execution of fuel cut during deceleration.

In each of the above embodiments, the main injection amount Q is used as a parameter indicating the engine load. However, an accelerator pedal operation amount, an intake air amount, or the like may be used.
-The exhaust gas purification apparatus demonstrated in 1st Embodiment oxidizes a fuel with the 1st oxidation catalyst 30 or the 2nd oxidation catalyst 31, and raises exhaust gas temperature. In addition, for example, the present invention can be similarly applied to an exhaust purification apparatus that includes only the filter 32 and raises the temperature of the filter 32 by oxidizing fuel on the filter 32.

  Although the engine 1 is an in-line four-cylinder internal combustion engine, the present invention can be similarly applied to an exhaust gas purification apparatus for an internal combustion engine having other numbers of cylinders or cylinder arrangements.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the internal combustion engine to which this is applied, and its periphery structure about 1st Embodiment of the exhaust gas purification device of the internal combustion engine concerning this invention. The flowchart which shows the procedure about the post injection amount setting process performed in the embodiment. In the same embodiment, the graph which shows the relationship between engine load and PM accumulation amount, and the target temperature of a filter. In the same embodiment, the graph which shows the relationship between target temperature, exhaust temperature, exhaust flow volume, and basic post injection quantity. The flowchart which shows a part of the procedure about the post injection amount setting process performed in 2nd Embodiment. In the same embodiment, the graph which shows the relationship between an engine load, an engine speed, and a guard value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4 ... Fuel injection valve, 6a-6d ... Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, 10 ... High pressure pump, 11 ... Turbocharger , 13 ... EGR passage, 14 ... EGR cooler, 15 ... EGR valve, 16 ... throttle valve, 17 ... motor, 18 ... intercooler, 25 ... control device, 26 ... exhaust passage, 30 ... first oxidation catalyst, 31 ... first 2. Oxidation catalyst 32 ... Filter 34 ... Converter 35 ... Exhaust throttle valve 40 ... Air flow meter 41 ... Throttle opening sensor 42 ... First exhaust temperature sensor 43 ... Second exhaust temperature sensor 44 ... Pressure sensor 45 ... Crank angle sensor, 46 ... Accelerator sensor, # 1 to # 4 ... Cylinder.

Claims (5)

Provided with a filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust, and controlling the injection timing of the fuel injection valve of the engine to perform post injection to increase the temperature of the filter In an exhaust gas purification apparatus for an internal combustion engine that performs a regeneration process for burning particulate matter,
Target temperature setting means for setting a target temperature of the filter at the time of executing the regeneration process;
An injection amount setting means for setting the injection amount so that the injection amount of post injection decreases as the target temperature is lower,
The target temperature setting means sets the target temperature to a lower temperature when the fuel cut at the time of deceleration is being executed than when the fuel cut is not performed. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the target temperature setting means sets the target temperature to a lower temperature as the temperature in the cylinder of the engine is lower. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the target temperature setting means sets the target temperature to a lower temperature as the engine load is lower. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3, wherein the injection amount setting means sets the injection amount based on an engine rotation speed and an engine load in addition to the target temperature. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4,
Correction means for correcting the injection amount in accordance with a deviation between the temperature of the filter and the target temperature;
An exhaust emission control device for an internal combustion engine, further comprising: a limiting unit that limits the maximum post-injection amount during execution of fuel cut during deceleration.

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