JP4799456B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device including an exhaust purification catalyst, an exhaust gas recirculation passage, and a supercharger.

  Patent Document 1 discloses an internal combustion engine that includes an exhaust purification catalyst, a first EGR passage that connects a catalyst upstream side of an exhaust passage and an intake passage, and a second EGR passage that connects a catalyst downstream side and an intake passage. A controller is shown. According to this control device, when it is detected that the catalyst is in a low temperature state, the exhaust gas is recirculated through the second EGR passage, and when it is detected that the catalyst is not in a low temperature state, the first EGR passage is The exhaust gas is recirculated. Thereby, when the catalyst is in a low temperature state, the temperature rise of the catalyst is accelerated, and when it is not in a low temperature state, a decrease in the catalyst temperature is suppressed when the exhaust gas temperature is lower than the catalyst temperature.

Japanese Patent Application Laid-Open No. 11-229973

  Although the activation of the catalyst can be accelerated at the time of cold start by the method disclosed in Patent Document 1, it is desirable to further accelerate the activation of the catalyst from the viewpoint of exhaust purification.

  The present invention has been made paying attention to this point, and an object of the present invention is to provide a control device for an internal combustion engine that can further accelerate the activation of a catalyst for purifying exhaust gas.

In order to achieve the above object, the invention according to claim 1 is directed to an exhaust purification catalyst (31) provided in the exhaust passage (8), a downstream side of the catalyst (31) in the exhaust passage (8), and In a control device for an internal combustion engine comprising a first exhaust gas recirculation passage (41) connecting the intake passage (7) and a supercharger (9) for compressing intake air, the temperature increase of the catalyst (31) is promoted. An activation determination means for determining whether or not to perform catalyst temperature increase control, and when performing the catalyst temperature increase control, exhaust recirculation is performed through the first exhaust recirculation passage (41), and the catalyst temperature increase control is performed. And a catalyst temperature increase control means for controlling the supercharger (9) so as to increase the intake pressure (PB) when not performing temperature control, and the catalyst (31) is a turbine (9a) of the supercharger. The first exhaust gas recirculation passage (41) is disposed further downstream, and the first exhaust gas recirculation passage (41) Characterized that you have provided between the upstream side of the downstream side of the supercharger compressor (31) (9b).

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the engine includes an upstream side of the catalyst (31) in the exhaust passage (8) and the intake passage (7). In the case where the second exhaust gas recirculation passage (25) to be connected is provided and the catalyst temperature increase control means is not operating, when the engine load (TRQ) is equal to or less than a determination threshold value (TRQTHR, TRQTHP, TRQTHL), While exhaust gas recirculation is performed via the second exhaust gas recirculation passage (25), when the load (TRQ) of the engine is larger than the determination threshold value (TRQTHR, TRQTHP, TRQTHL), the first exhaust gas recirculation passage (41) It further has an exhaust gas recirculation control means for performing exhaust gas recirculation via the.

  According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the second aspect of the present invention, the control device for the internal combustion engine further includes a enrichment control unit that performs a enrichment control in which the exhaust gas is a reducing atmosphere. The determination threshold value (TRQTHR, TRQTHP, TRQTHL) is changed according to whether or not the control unit is activated.

  Here, the “riching control” is executed by enriching the air-fuel ratio of the air-fuel mixture before combustion in the combustion chamber and / or post injection. The post-injection is a fuel injection that is executed in the expansion stroke or the exhaust stroke after the normal fuel injection is executed.

According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to third aspects, the catalyst temperature increase control means performs a fuel injection timing when performing the catalyst temperature increase control. retarding the reduction of the fuel injection pressure, increasing the exhaust gas recirculation amount, increased fuel injection number is characterized by further performing at least one of elevation posts injection.

According to the first aspect of the present invention, when performing the catalyst temperature increase control, the exhaust gas recirculation is performed via the first exhaust gas recirculation passage connecting the catalyst downstream side and the compressor upstream side, and the catalyst temperature increase control is performed. The supercharger is controlled so as to increase the intake pressure more than when the engine is not operated. By performing the exhaust gas recirculation through the first exhaust gas recirculation passage, the entire exhaust gas passes through the catalyst, and a part of the exhaust gas that has passed through the catalyst is recirculated to the intake air passage. Obtainable. Further, by increasing the intake pressure, the flow rate of exhaust gas passing through the catalyst increases, and the temperature rise of the catalyst can be further promoted.

  According to the second aspect of the present invention, when the catalyst temperature increase control is not performed and the engine load is equal to or less than the determination threshold, the exhaust gas is recirculated through the second exhaust gas recirculation passage, and the engine load is reduced. When it is larger than the determination threshold, the exhaust gas is recirculated through the first exhaust gas recirculation passage. When the engine load is small, the second exhaust recirculation passage is used to recirculate relatively high-temperature exhaust to maintain stable combustion, and when the engine load is large, the first exhaust recirculation passage is used to return the exhaust. By increasing the flow rate, the amount of NOx in the exhaust gas (feed gas) discharged from the combustion chamber and flowing into the catalyst can be sufficiently reduced.

  According to the third aspect of the present invention, the determination threshold is changed depending on whether or not the enrichment control using the exhaust gas as the reducing atmosphere is performed. During enrichment control, the amount of NOx in the feed gas decreases compared to that during normal lean operation. Therefore, the judgment threshold is set with emphasis on the stability of combustion, and the amount of NOx in the feed gas is reduced during lean operation. By setting the determination threshold value with an emphasis on doing, exhaust gas recirculation suitable for each operation state can be performed.

According to the invention of claim 4, when performing the catalyst Atsushi Nobori control, the retard of the fuel injection timing, reducing the fuel injection pressure, increasing the exhaust gas recirculation amount, increased fuel injection number, at least morphism post injection Since one is further performed, the temperature rise of the catalyst can be further promoted.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 6 is provided in each cylinder. The fuel injection valve 6 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 4, and the valve opening timing and the valve opening time (fuel injection timing and fuel injection time) of the fuel injection valve 6 are determined by the ECU 4. Controlled by

  The engine 1 includes an intake pipe (intake passage) 7, an exhaust pipe (exhaust passage) 8, and a turbocharger 9. The turbocharger 9 includes a turbine 9a that is rotationally driven by the kinetic energy of the exhaust, and a compressor 9b that is connected to the turbine 9a via a shaft. The turbocharger 9 pressurizes (compresses) air sucked into the engine 1.

  The turbine 9a includes a turbine wheel 9c, a plurality of variable vanes 9d (only two are shown) that are driven to change the flow rate of exhaust gas blown to the turbine wheel 9c, and an actuator that drives the variable vanes 9d to open and close (see FIG. By changing the opening VO (hereinafter referred to as “vane opening”) VO of the variable vane 9d, thereby changing the flow rate of the exhaust gas blown to the turbine wheel 9c and rotating the turbine wheel 9c. It is configured to change the speed. The actuator that drives the variable vane 9d is connected to the ECU 4, and the vane opening degree VO is controlled by the ECU 4. More specifically, the ECU 4 supplies a control signal with a variable duty ratio to the actuator, thereby controlling the vane opening VO. The configuration of a turbocharger having a variable vane is widely known, and is disclosed in, for example, Japanese Patent Laid-Open No. 1-208501.

  An intake shutter 22 is provided on the upstream side of the compressor 9 b of the intake pipe 7. The intake shutter 22 is configured such that its opening degree can be controlled by the ECU 4 via an actuator (not shown). On the downstream side of the compressor 9b of the intake pipe 7, there are an intercooler 21, a bypass passage 23 that bypasses the intercooler 21, and a first switching valve 24 that switches the air intake path between the bypass passage 23 side and the intercooler 21 side. Is provided. The first switching valve 24 is connected to the ECU 4 and its operation is controlled by the ECU 4.

  Between the upstream side of the turbine 9 a of the exhaust pipe 8 and the downstream side of the intercooler 21 of the intake pipe 7, a high-pressure exhaust gas recirculation passage 25 that recirculates part of the exhaust gas to the intake pipe 7 is provided. The high-pressure exhaust gas recirculation passage 25 is provided with a first exhaust gas recirculation control valve (hereinafter referred to as “first EGR valve”) 26 for controlling the exhaust gas recirculation amount. The first EGR valve 26 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 4.

  The intake pipe 7 is provided with a supercharging pressure sensor 51 that detects an intake pressure (supercharging pressure) PB on the downstream side of the compressor 9b, and an intake air temperature sensor 52 that detects an intake air temperature TI. These sensors 51 and 52 are connected to the ECU 4, and the detection signals of the sensors 51 and 52 are supplied to the ECU 4.

  On the downstream side of the turbine 9 a of the exhaust pipe 8, a three-way catalyst 31 that performs oxidation of hydrocarbons (unburned fuel component) and carbon monoxide contained in the exhaust, and reduction of NOx, and particulates in the exhaust A DPF (diesel particulate filter) 32 that collects a substance (mainly composed of soot) and a NOx purification catalyst 33 that collects and reduces NOx in the exhaust gas are provided.

  A low-pressure exhaust gas recirculation passage 41 that connects the portion of the exhaust pipe 8 between the DPF 32 and the NOx purification catalyst 33 and the upstream side of the compressor 9b of the intake pipe 7 is provided. A second exhaust gas recirculation control valve (hereinafter referred to as “second EGR valve”), which is an electromagnetic valve similar to the first EGR valve, is provided. The low pressure exhaust gas recirculation passage 41 includes a recirculation exhaust cooler 43 that cools the recirculated exhaust gas, a bypass passage 44 that bypasses the recirculation exhaust cooler 43, and a recirculation exhaust passage that is connected to the recirculation exhaust cooler 43 side. A second switching valve 45 that switches to the bypass passage 44 side is provided. The second switching valve 45 is connected to the ECU 4 and its operation is controlled by the ECU 4.

  The ECU 4 includes an accelerator sensor 53 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 54 that detects a cooling water temperature TW of the engine 1, and an engine speed sensor that detects an engine speed NE. 55 and a catalyst temperature sensor 56 for detecting the temperature TCAT of the three-way catalyst 31 are connected, and detection signals from these sensors are supplied to the ECU 4.

  The ECU 4 is connected to a fuel injection valve 6 provided in the combustion chamber of each cylinder of the engine 1, and a drive signal is supplied from the ECU 4 to the fuel injection valve 6.

  The ECU 4 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, etc., and a central processing unit (hereinafter referred to as “CPU”). The control signal is supplied to a storage circuit for storing various calculation programs executed by the CPU and calculation results, the fuel injection valve 6, the EGR valves 26 and 42, the actuator of the variable vane 9d, the switching valves 24 and 45, and the like. It consists of an output circuit.

  Since the temperature of the exhaust gas recirculated through the low pressure exhaust gas recirculation passage 41 is lower than the temperature of the exhaust gas recirculated through the high pressure exhaust gas recirculation passage 25, the exhaust gas recirculation amount can be increased. Therefore, basically, the low pressure exhaust gas recirculation passage 41 is used in a high load operation state where the engine load is relatively high. In the present embodiment, since the exhaust gas is recirculated from the downstream side of the DPF 32, since the particulate matter in the exhaust gas is small, the supercharging pressure PB can be maintained high regardless of the amount of exhaust gas recirculation.

  On the other hand, since the temperature of the exhaust gas recirculated through the high-pressure exhaust gas recirculation passage 25 is higher than the temperature of the exhaust gas recirculated through the low-pressure exhaust gas recirculation passage 41, the exhaust gas recirculation amount cannot be increased. The ignitability when performed is higher than when the low pressure exhaust gas recirculation passage 41 is used. Therefore, the high-pressure exhaust gas recirculation passage 25 is mainly used in a low-load operation state in which the engine load is relatively low in order to ensure combustion stability.

  The first switching valve 24 is basically controlled to the intercooler 21 side. However, when the intake air temperature TI is low, the first switching valve 24 is controlled to the bypass passage 23 side to ensure combustion stability.

  The second switching valve 45 is basically switched to the recirculation exhaust cooler 43 side, but it is desired to obtain an exhaust purification effect by exhaust recirculation when it is necessary to maintain a high supercharging pressure or without lowering the recirculation exhaust temperature. Sometimes it is switched to the bypass passage 44 side.

FIG. 2 is a flowchart of a switching control process between the low pressure exhaust gas recirculation passage 41 and the high pressure exhaust gas recirculation passage 25. This process is executed every predetermined time by the CPU of the ECU 4.
In step S11, it is determined whether or not the catalyst temperature increase control flag FTCAT is "1". The catalyst temperature increase control flag FTCAT is set to “1” when the detected catalyst temperature TCAT is equal to or lower than a predetermined temperature TCATTH (for example, 200 ° C.). When FTCAT = 1 and the catalyst temperature increase control is executed, intake pressure increase control is performed (step S12) and exhaust gas recirculation is performed via the low pressure exhaust gas recirculation passage 41 (step S18). That is, the first EGR valve 26 is closed and the duty control of the second EGR valve 42 is performed.

Specifically, in the intake pressure increase control, when the turbocharger 9 is not operating, the operation is started, and when the turbocharger 9 is already operating, the supercharging pressure PB is set higher than that during normal control. Increase the vane opening VO. The vane opening VO is controlled by changing the duty ratio DUTY of the drive signal supplied to the actuator of the variable vane 9d, and the duty ratio DUTY is calculated by the following equation (1). By increasing the duty ratio DUTY, the vane opening degree VO increases.
DUTY = DUTYM + DUTCAT (1)

  Here, DUTYM is a basic duty ratio calculated by searching a DUTYM map (not shown) set in accordance with the required torque TRQ and the engine speed NE. The required torque TRQ is calculated according to the accelerator pedal operation amount AP, and is calculated so as to increase as the accelerator pedal operation amount AP increases. DUTCAT is a catalyst temperature increase correction term, and is set to a predetermined value (> 0) when the intake pressure increase control is executed in step S12, and is set to “0” when the intake pressure increase control is not performed.

  If FTCAT = 0 in step S11 and the catalyst temperature increase control is not executed, it is determined whether or not the air-fuel ratio enrichment flag FRICH is “1”. The air-fuel ratio enrichment flag FRICH is set to “1” when performing air-fuel ratio enrichment control in which the air-fuel ratio of the air-fuel mixture in the combustion chamber is set near the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio. The air-fuel ratio enrichment control is performed, for example, when a regeneration process for burning soot accumulated in the DPF 32 is performed, or when a regeneration process for removing sulfur oxide (SOx) accumulated in the NOx purification catalyst 33 is performed. The air-fuel ratio enrichment control is performed by increasing the fuel injection amount and / or decreasing the intake air flow rate.

  If the answer to step S13 is affirmative (YES) and air-fuel ratio enrichment control is being executed, a TRQTHR table indicated by a broken line in FIG. 3 is searched according to the engine speed NE, and an air-fuel ratio enrichment control threshold value is retrieved. TRQTHR is calculated (step S14). The TRQTHR table is set so that the air-fuel ratio enrichment control threshold value TRQTHR decreases as the engine speed NE increases.

  In step S15, it is determined whether or not the required torque TRQ of the engine is equal to or less than the air-fuel ratio enrichment control threshold value TRQTHR calculated in step S14. When this answer is affirmative (YES), that is, when the engine 1 is in a low load operation state, exhaust gas recirculation is performed via the high pressure exhaust gas recirculation passage 25 (step S19). That is, the second EGR valve 42 is closed and the duty control of the first EGR valve 26 is performed. On the other hand, if TRQ> TRQTHR in step S15, the process proceeds to step S18.

  In step S13, when FRICH = 0 and the air-fuel ratio enrichment control is not executed, the TRQTHL table indicated by the solid line in FIG. 3 is searched according to the engine speed NE, and the normal operation threshold (lean operation threshold) is obtained. TRQTHL is calculated (step S16). The TRQTHL table is set so that the normal operation threshold value TRQTHL decreases as the engine speed NE increases as in the air-fuel ratio enrichment control threshold value TRQTHR. If the engine speed NE is the same, TRQTHR> TRQTHL is established.

  In step S17, it is determined whether or not the required torque TRQ of the engine is equal to or less than the normal operation threshold value TRQTHL calculated in step S16. When the answer is affirmative (YES), the process proceeds to step S19, and exhaust gas recirculation is performed via the high-pressure exhaust gas recirculation passage 25. On the other hand, when TRQ> TRQTHL, the process proceeds from step S17 to step S18. Exhaust gas recirculation is performed through the passage 41.

  According to the process of FIG. 2, when performing the catalyst temperature rise control, the exhaust gas recirculation is performed via the low pressure exhaust gas recirculation passage 41, and the supercharging pressure (intake pressure) PB is set higher than when the catalyst temperature rise control is not performed. The vane opening VO is controlled to increase. By performing exhaust gas recirculation through the low pressure exhaust gas recirculation passage 41, the entire exhaust gas passes through the three-way catalyst 31, and a part of the exhaust gas that has passed through the three-way catalyst 31 is recirculated to the intake air passage. Can be obtained. Further, by increasing the supercharging pressure PB, the flow rate of exhaust gas passing through the three-way catalyst 31 increases, and the temperature rise can be further promoted.

  Further, when the catalyst temperature increase control is not performed and the required torque TRQ is equal to or less than the air-fuel ratio enrichment control threshold value TRQTHR or the normal operation threshold value TRQTHL, the exhaust gas is recirculated through the high-pressure exhaust gas recirculation passage 25. In the low load operation state where the required torque TRQ is small, by using the high pressure exhaust gas recirculation passage 25, it is possible to recirculate relatively high temperature exhaust gas and maintain stable combustion. On the other hand, when the required torque TRQ is larger than the air-fuel ratio enrichment control threshold value TRQTHR or the normal operation threshold value TRQTHL, the exhaust gas is recirculated through the low-pressure exhaust gas recirculation passage 41. Therefore, by increasing the exhaust gas recirculation amount, The amount of NOx in the exhaust gas (feed gas) discharged can be sufficiently reduced.

  Further, the air-fuel ratio enrichment control threshold value TRQTHR or the normal operation threshold value TRQTHL is selected depending on whether or not the air-fuel ratio enrichment control that uses the exhaust gas as the reducing atmosphere is performed. During air-fuel ratio enrichment control, the amount of NOx in the feed gas decreases compared to during normal lean operation. Therefore, the air-fuel ratio enrichment control threshold value TRQTHR, which emphasizes the stability of combustion, is used to perform normal operation (lean operation). ), It is possible to perform exhaust gas recirculation suitable for each operation state by using the normal operation threshold value TRQTHL which places importance on reducing the amount of NOx in the feed gas.

  In this embodiment, the low pressure exhaust gas recirculation passage 41 corresponds to the first exhaust gas recirculation passage, the high pressure exhaust gas recirculation passage 25 corresponds to the second exhaust gas recirculation passage, and the first EGR valve 26 and the second EGR valve 42 are the exhaust gas recirculation control means. Part of it. The ECU 4 constitutes an activation determination means, a catalyst temperature increase control means, a part of the exhaust gas recirculation control means, and a enrichment control means. Specifically, step S11 in FIG. 2 corresponds to the activation determination means, steps S12 and S18 correspond to the catalyst temperature increase control means, and steps S13 to S19 correspond to the exhaust gas recirculation control means. The enrichment control means is realized by a fuel injection control process (not shown) executed by the CPU of the ECU 4.

[Second Embodiment]
In the present embodiment, post-injection control is executed as enrichment control in addition to the air-fuel ratio enrichment control described above, and the exhaust gas recirculation used is replaced by the process of FIG. 4 instead of the process of FIG. Switch the passage. For example, when the regeneration process of the NOx purification catalyst 33 is performed, when the temperature TNLOX of the NOx purification catalyst 33 is lower than a predetermined temperature threshold value TCTH, post injection control is executed, and when the temperature TNLOX is equal to or higher than the predetermined temperature threshold value TCTH, Air-fuel ratio enrichment control is executed. Except for these points and the points described below, the second embodiment is the same as the first embodiment.

  FIG. 4 is obtained by adding steps S21 to S23 to the process of FIG. If the answer to step S13 is negative (NO), that is, if the air-fuel ratio enrichment control is not being performed, the process proceeds to step S21 to determine whether or not the post-injection flag FPINJ is “1”. The post injection flag FPINJ is set to “1” when the post injection is executed. The post-injection flag FPINJ is set to “1”, for example, when performing a regeneration process for burning soot accumulated in the DPF 32, or when performing a regeneration process for removing sulfur oxide (SOx) accumulated in the NOx purification catalyst 33. Is set.

  If the answer to step S21 is affirmative (YES) and post injection is being performed, the TRQTHP table indicated by the one-dot chain line in FIG. 5 is searched according to the engine speed NE to calculate the post injection control threshold TRQTHP. (Step S22). The TRQTHP table is set so that the post-injection control threshold TRQTHP decreases as the engine speed NE increases as in the air-fuel ratio enrichment control threshold TRQTHR. If the engine speed NE is the same, TRQTHR> TRQTHP> TRQTHL is established.

  In step S23, it is determined whether or not the required torque TRQ of the engine is equal to or less than the post injection control threshold value TRQTHP calculated in step S22. When the answer is affirmative (YES), the process proceeds to step S19, and exhaust gas recirculation is performed through the high pressure exhaust gas recirculation passage 25. On the other hand, when TRQ> TRQTHP, the process proceeds from step S23 to step S18, and low pressure exhaust gas recirculation is performed. Exhaust gas recirculation is performed through the passage 41.

  The three threshold tables shown in FIG. 5 are set so that TRQTHR> TRQTHP> TRQTHL if the engine speed NE is the same. The reason will be described below.

  In order to make the exhaust atmosphere into a reducing atmosphere, it is necessary to reduce the intake air flow rate, and the ignitability tends to be worse than in the normal operation state (lean operation state). Therefore, when performing enrichment control (air-fuel ratio enrichment control or post-injection control), the air-fuel ratio enrichment control is performed so that the region in which the high-pressure exhaust gas recirculation passage 25 is used is relatively wider than during normal operation. The threshold value TRQTHR and the post injection control threshold value TRQTHP are set on the higher load side than the normal operation threshold value TRQTHL. Further, when comparing the air-fuel ratio enrichment control and the post-injection control, the air-fuel ratio enrichment control needs to increase the exhaust gas recirculation amount in order to reduce NOx in the feed gas, and the intake air flow rate Since it is necessary to further increase the aperture (the aperture by the intake shutter 22), the air-fuel ratio enrichment control threshold value TRQTHR is set on the higher load side than the post injection control threshold value TRQTHP from the viewpoint of stabilization of combustion. Therefore, each threshold table is set as shown in FIG. By setting in this way, it is possible to perform exhaust gas recirculation suitable for each operating state, and to obtain good exhaust characteristics while ensuring combustion stability (avoiding misfire).

  The relative relationship among the air-fuel ratio enrichment control threshold TRQTHR, the post injection control threshold TRQTHP, and the normal operation threshold TRQTHL is not limited to that shown in FIG. For example, from the viewpoint of optimizing both the combustion stability and the exhaust characteristics, when setting the threshold value table, the required exhaust gas recirculation amount changes depending on the purification performance of the NOx purification catalyst 33, for example. The relative relationship may need to be changed.

  In the present embodiment, steps S13 to S19 and S21 to S23 in FIG. 4 correspond to the exhaust gas recirculation control means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, the process shown in FIG. 6 may be used instead of the process shown in FIG. The process of FIG. 6 is obtained by adding step S31 to the process of FIG.

In step S31, at least one of the following controls 1) to 5 ) is executed to perform exhaust gas temperature raising control for increasing the exhaust gas temperature.
1) Delay in fuel injection timing 2) Reduction in fuel injection pressure 3) Increase in exhaust gas recirculation amount 4) Increase in fuel injection frequency 5) Post injection
By executing the step S31, immediately after a cold start, it is possible to further accelerate the Atsushi Nobori of the three-way catalyst 31 (activated).

  Further, the low pressure exhaust gas recirculation passage 41 is replaced with a low pressure exhaust gas recirculation passage 41a that recirculates exhaust gas from the portion of the exhaust pipe 8 between the three-way catalyst 31 and the DPF 32 to the intake pipe 7, as shown in FIG. Also good. Alternatively, as shown in FIG. 7B, a low pressure exhaust gas recirculation passage 41 b that circulates exhaust gas from the downstream side of the NOx purification catalyst 33 to the intake pipe 7 may be used. The three-way catalyst 31 may be replaced with a diesel oxidation catalyst.

  In the embodiment described above, the catalyst temperature increase control is executed when the catalyst temperature TCAT is equal to or lower than the predetermined temperature TCATTH. For example, within a predetermined period set according to the cooling water temperature TW0 immediately after the engine is started. The catalyst temperature increase control may be executed. In this case, the “predetermined period” is defined as a period until an elapsed time measured by a normal timer reaches a predetermined time, or a period until an integrated value of the engine speed NE reaches a predetermined value.

  The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. 5 is a flowchart (first embodiment) of processing for selecting one of a high pressure exhaust gas recirculation passage and a low pressure exhaust gas recirculation passage. It is a figure which shows the table referred by the process of FIG. It is a flowchart (2nd Embodiment) of the process which selects one of a high pressure exhaust gas recirculation passage and a low pressure exhaust gas recirculation passage. It is a figure which shows the table referred by the process of FIG. It is a flowchart which shows the modification of the process shown in FIG. It is a figure which shows the modification of a low pressure exhaust gas recirculation passage.

Explanation of symbols

1 Internal combustion engine 4 Electronic control unit (activation determination means, catalyst temperature rise control means, exhaust gas recirculation control means, enrichment control means)
6 Fuel injection valve 7 Intake pipe (intake passage)
8 Exhaust pipe (exhaust passage)
9 Turbocharger (supercharger)
9a Turbine 9b Compressor 9d Variable vane 25 High pressure exhaust gas recirculation passage (second exhaust gas recirculation passage)
26 First exhaust gas recirculation control valve (exhaust gas recirculation control means)
31 Three-way catalyst 41 Low pressure exhaust gas recirculation passage (first exhaust gas recirculation passage)
42 Second exhaust gas recirculation control valve (exhaust gas recirculation control means)

Claims (4)

An internal combustion engine comprising an exhaust purification catalyst provided in an exhaust passage, a first exhaust gas recirculation passage connecting a downstream side of the exhaust passage and the intake passage, and a supercharger that compresses intake air. In the control device,
Activation determination means for determining whether or not to perform catalyst temperature increase control for promoting temperature increase of the catalyst;
When performing the catalyst temperature rise control, exhaust gas recirculation is performed through the first exhaust gas recirculation passage, and the catalyst riser for controlling the supercharger so as to increase the intake pressure is higher than when the catalyst temperature rise control is not performed. Temperature control means ,
The catalyst is disposed downstream of the turbine of the turbocharger, the first exhaust gas recirculation passage, Rukoto provided between the upstream side of the compressor on the downstream side of the supercharger of the catalyst A control device for an internal combustion engine. The engine includes a second exhaust gas recirculation passage that connects the upstream side of the catalyst in the exhaust passage and the intake passage,
When the catalyst temperature increase control means is not operating and the engine load is equal to or less than the determination threshold value, exhaust gas recirculation is performed through the second exhaust gas recirculation passage, while the engine load is the determination threshold value. 2. The control apparatus for an internal combustion engine according to claim 1, further comprising exhaust gas recirculation control means for performing exhaust gas recirculation through the first exhaust gas recirculation passage when larger. Further comprising a enrichment control means for performing enrichment control in which the exhaust gas is a reducing atmosphere;
The control apparatus for an internal combustion engine according to claim 2, wherein the exhaust gas recirculation control means changes the determination threshold according to whether or not the enrichment control means is operating. The catalyst Atsushi Nobori control means, when performing the catalyst Atsushi Nobori control, the retard of the fuel injection timing, reducing the fuel injection pressure, increasing the exhaust gas recirculation amount, increased fuel injection number, at least one of the morphism post injection The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising:

Images