JP6636863B2 - diesel engine - Google Patents

Description

  The present invention relates to a diesel engine, and more particularly, to a diesel engine that can promote regeneration of a DPF during low-load operation.

DESCRIPTION OF RELATED ART Conventionally, as the invention of a diesel engine, there exists the following (for example, refer patent document 1).
An engine ECU, a DOC, a DPF disposed downstream of the DOC exhaust gas, and a fuel supply device disposed upstream of the DOC exhaust gas, and the PM accumulated amount estimation value of the DPF becomes a predetermined DPF regeneration start determination value. However, when the estimated temperature of the DOC has not reached the activation temperature range, the DOC activation process is performed in accordance with a command from the engine ECU that has detected the information, and in the DOC activation process, the exhaust gas temperature is increased and the DOC is increased. When the estimated temperature reaches the activation temperature range, a DPF regeneration process is performed according to a command from the engine EUC that has detected the information. In the DPF regeneration process, fuel is supplied from the fuel supply device to the exhaust gas, and the DOC of the fuel is used. A diesel engine configured to raise the temperature of exhaust gas by the catalytic combustion described above and to incinerate PM deposited on the DPF by the heat of the exhaust gas.

  This type of invention has an advantage that the DPF can be regenerated by the DOC activation process even when the exhaust gas temperature is low.

  In the invention of Patent Document 1, the DOC activation process is performed by reducing the opening of the intake throttle valve.

JP-A-2010-151058 (see FIGS. 1 to 4)

<< Problems >> DPF regeneration during low load operation is stagnant.
In the invention of Patent Document 1, since the DOC activation process is performed by reducing the opening of the intake throttle valve, the DOC activation is low during low load operation with low DOC temperature increase efficiency and low exhaust gas temperature. It takes a long time, and the DPF regeneration at low load stagnates.

  It is an object of the present invention to provide a diesel engine capable of promoting DPF regeneration during low-load operation.

The matters specifying the invention of claim 1 are as follows.
As illustrated in FIG. 1, the engine ECU (5), the DOC (2), the DPF (7) disposed downstream of the DOC (2) exhaust gas, and the DPF (7) disposed upstream of the DOC (2) exhaust gas. Fuel supply device (8),
As illustrated in FIG. 2, although the estimated PM accumulation amount (F) of the DPF (7) has reached a predetermined DPF regeneration start determination value (FS), the estimated temperature (T) of the DOC (2) is activated. When the temperature has not reached the temperature range (T5), DOC activation processing is performed in accordance with a command from the engine ECU (5) that has detected the information. In the DOC activation processing, the exhaust gas (9) is heated and the DOC (2) When the estimated temperature (T) reaches the activation temperature region (T5), a DPF regeneration process (S10) is performed by a command from the engine ECU (5) that has detected the information, and in the DPF regeneration process (S10) Fuel is supplied to the exhaust gas (9) from the fuel supply device (8) illustrated in FIG. 1, and the temperature of the exhaust gas (9) is raised by catalytic combustion of the fuel in the DOC (2). In a diesel engine, wherein heat is configured to incinerate PM deposited on the DPF (7),
As illustrated in FIG. 1, an exhaust throttle valve (9a) is provided between the DOC (2) and the DPF (7), and in the DOC activation process, the opening of the exhaust throttle valve (9a) decreases (S5). Is configured to be
As illustrated in FIGS. 2 and 3, an electric heater (3) is provided on the exhaust upstream side of the DOC (2),
In the DOC activation process, when the estimated temperature (T) of the DOC (2) is in the low temperature region (T1) which does not reach the activation temperature region (T5), the command of the engine ECU (5) based on the detection of the information is given. The electric heater (3) is configured to generate heat (S4).
As illustrated in FIGS. 2 and 3, in the DOC activation process, the estimated temperature (T) of the DOC (2) is lower than the activation temperature region (T5) and higher than the low temperature region (T1). (T3) A diesel engine characterized in that heat generation (S4) of the electric heater (3) is prohibited by a command of the engine ECU (5) based on the detection of the information.

(Invention according to claim 1)
The invention according to claim 1 has the following effects.
<< Effect >> The regeneration of the DPF during the low load operation can be promoted.
In the present invention, as illustrated in FIG. 1, an exhaust throttle valve (9a) is provided between the DOC (2) and the DPF (7), and as illustrated in FIG. Since the opening degree of the valve (9a) is configured to be reduced (S5), the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) illustrated in FIG. ) The temperature of the surrounding exhaust gas (9) rises smoothly, the efficiency of raising the temperature of the DOC (2) increases, and even during low-load operation where the temperature of the exhaust gas (9) is low, it takes time to activate the DOC (2). Therefore, regeneration of the DPF (7) during low load operation can be promoted.
<< Effect >> The regeneration of the DPF during the low load operation can be promoted.
In the present invention, as illustrated in FIGS. 2 and 3, in the DOC activation process, the estimated temperature (T) of the DOC (2) is in the low temperature region (T1) that does not reach the activation temperature region (T5). In this case, since the heat generation (S4) of the electric heater (3) is performed by a command of the engine ECU (5) based on the detection of the information, the temperature rise of the DOC (2) is further promoted, The regeneration of the DPF (7) during low-load operation can be promoted.
<< Effect >> Power consumption due to inefficient heat generation of the electric heater can be suppressed.
In the present invention, as illustrated in FIGS. 2 and 3, in the DOC activation process, the estimated temperature (T) of the DOC (2) is lower than the activation temperature region (T5) and higher than the low temperature region (T1). When the temperature is in the medium temperature range (T3), the heat generation (S4) of the electric heater (3) is prohibited by a command of the engine ECU (5) based on the detection of the information, so that the temperature is relatively high. Power consumption due to inefficient heat generation (S4) of the electric heater (3) in the middle temperature region (T3) where the heating efficiency is high and the heating efficiency is low.

(Invention according to claim 2)
The invention according to claim 2 has the following effect in addition to the effects of the invention according to claim 1.
<< Effect >> It is possible to prevent a decrease in output due to an increase in back pressure.
In the present invention, as illustrated in FIG. 2, when the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) reaches a predetermined excess pressure region (P3) in the DOC activation process, the information is obtained. Since the opening degree of the exhaust throttle valve (9a) is increased (S15) in response to the command from the engine ECU (5) that detects the above, it is possible to prevent a decrease in output due to an increase in back pressure.

(Invention according to claim 3)
The invention according to claim 3 has the following effect in addition to the effects of the invention according to claim 1 or 2.
<< Effect >> It is possible to prevent a decrease in output due to an increase in back pressure.
In the present invention, as shown in FIG. 2, when the estimated temperature (T) of the DOC (2) reaches the activation temperature region (T5) in the DOC activation process, the engine ECU detects the information. Since the exhaust throttle valve (9a) is configured to be fully opened (S9) according to the command (5), it is possible to prevent a decrease in output due to an increase in back pressure.

(Invention according to claim 4 )
The invention according to claim 4 has the following effect in addition to the effects of the invention according to any one of claims 1 to 3 .
<< Effect >> The regeneration of the DPF during the low load operation can be promoted.
In the present invention, as illustrated in FIG. 1, since the electric heater (3) is arranged along the DOC inlet (2a), the conduction loss of heat from the electric heater (3) to the DOC (2) is reduced. Small, DOC (2) temperature rise efficiency is high, and even during low load operation with low exhaust gas temperature, activation of DOC (2) does not take much time and promotes regeneration of DPF (7) during low load operation can do.

(Invention according to claim 5 )
The invention according to claim 5 has the following effect in addition to the effects of the invention according to any one of claims 1 to 4 .
<< Effect >> The regeneration efficiency of the DPF can be improved.
In the present invention, as illustrated in FIG. 1, a honeycomb structure (10) is provided on the exhaust upstream side of the DOC (2), and as illustrated in FIG. 4 (A), the honeycomb structure (10) A plurality of cells (10a) (10b) penetrating in the exhaust passage direction of the exhaust passage (1) are provided, and only the central honeycomb portion (10d) of the honeycomb structure (10) serves as the electric heater (3). Therefore, the temperature of the exhaust gas (9) is increased by the electric heater (3) of the central honeycomb portion (10d) where the heat is hard to escape to the outside of the exhaust gas passage (1), and the temperature rising efficiency of the exhaust gas (9) is reduced. Even during a light load operation in which the temperature of the exhaust gas (9) is high and the temperature of the exhaust gas (9) is low, the DOC (2) is quickly activated and the regeneration efficiency of the DPF (7) can be increased.

(Invention according to claim 6 )
The invention according to claim 6 has the following effect in addition to the effect of the invention according to claim 5 .
<< Effect >> The regeneration efficiency of the DPF can be improved.
In the present invention, as exemplified in FIG. 4A, the central honeycomb part (10d) constituting the electric heater (3) has a higher cell density than the surrounding honeycomb part (10e) surrounding the periphery. Therefore, the radiator area of the electric heater (3) is large, the efficiency of raising the temperature of the exhaust gas (9) is increased, and the DOC (2) is quickly activated even in a light load operation in which the temperature of the exhaust gas (9) is low, and the DPF is activated. The regeneration efficiency of (7) can be improved.

1 is a schematic diagram of a diesel engine according to an embodiment of the present invention. 5 is a flowchart of a DOC activation process and a DPF regeneration process by the engine ECU used in the embodiment of the present invention. FIG. 4 is a diagram illustrating a combination of adjustment of an opening degree of an exhaust throttle valve by an engine ECU and heat generation of an electric heater used in an embodiment of the present invention. FIG. 4A is a diagram illustrating an electric heater and a DOC used in an embodiment of the present invention. FIG. 4A is a front view of a honeycomb structure provided with the electric heater viewed in a direction parallel to a central axis thereof, and FIG. Is a front view of the DOC as viewed in a direction parallel to the central axis thereof.

  1 to 4 are diagrams illustrating an engine according to an embodiment of the present invention. In this embodiment, a vertical in-line four-cylinder diesel engine will be described.

The configuration of the engine is as follows.
The direction in which the crankshaft (11) is installed is the front-rear direction, the side on which the flywheel (12) is disposed is the rear side, the opposite side is the front side, and the engine width direction orthogonal to the front-rear direction is the lateral direction.
As shown in FIG. 1, the engine includes an intake manifold (14) mounted on one side of a cylinder head (13) and an exhaust manifold (15) mounted on the other side of the cylinder head (13). It has.
As shown in FIG. 1, the engine includes an engine ECU (5).
The engine ECU is an abbreviation of an electronic control unit, and the engine ECU (5) is a microcomputer.

As shown in FIG. 1, the engine includes an exhaust device.
The exhaust device includes an exhaust manifold (15), an exhaust turbine (16a) of a supercharger (16) provided in the exhaust manifold (15), and exhaust gas discharged from an exhaust outlet (16b) of the exhaust turbine (16a). An outlet passage (16c) is provided.

As shown in FIG. 1, the engine includes an intake device.
The intake device includes a compressor (16d) of the supercharger (16), an air flow sensor (17) provided upstream of the intake port (16e) of the compressor (16d), and a supercharger of the compressor (16d). An intercooler (18) disposed between the outlet (16f) and the intake manifold (14); an intake throttle valve (19) disposed between the intercooler (18) and the intake manifold (14); and an exhaust manifold. An EGR cooler (20) arranged between the (15) and the intake manifold (14), and an EGR valve (21) arranged between the EGR cooler (20) and the intake manifold (14). EGR is an abbreviation for exhaust gas recirculation.
Each of the intake throttle valve (19) and the EGR valve (21) is an electric open / close valve, and these are electrically connected to a power supply (4) via an engine ECU (5). The air flow sensor (17) includes an intake air temperature sensor and is electrically connected to the engine ECU (5). The power supply (4) is a battery.

As shown in FIG. 1, the engine includes a fuel injection device.
The fuel injection device includes a fuel injection valve (24) provided in each combustion chamber (23), a common rail (25) for accumulating fuel injected from the fuel injection valve (24), and a fuel tank (25) in the common rail (25). 26), a fuel supply pump (27) for pumping fuel from the fuel supply pump.
The fuel injection valve (24) includes an electromagnetic on-off valve, the fuel supply pump (27) includes an electric pressure regulating valve, and these are electrically connected to a power supply (4) via an engine ECU (5). I have.

As shown in FIG. 1, the engine includes a speed control device.
The speed governor includes an accelerator sensor (29) for detecting a set position of an accelerator lever (28) for setting a target engine speed, and an actual speed sensor (30) for detecting the actual engine speed. The sensors (29) and (30) are electrically connected to the engine ECU (5).

As shown in FIG. 1, the engine includes a starting device.
The starter includes a starter motor (31) and a key switch (22). The starter motor (31) and the key switch (22) are electrically connected to a power supply (4) via an engine ECU (5). ing. The key switch (22) has an OFF position, an ON position, and a start position.

The engine ECU (5) is configured to perform the following operation control.
The fuel injection amount and the injection timing from the fuel injection valve (24) are set so as to reduce the rotation speed deviation between the target rotation speed and the actual rotation speed of the engine, and the fluctuation of the rotation speed of the engine due to load fluctuation is reduced.
The opening degree of the intake throttle valve (19) and the EGR valve (21) is adjusted according to the engine speed, load, intake air amount, and intake air temperature to adjust the intake air amount and EGR rate.
When the key switch (22) is turned on to the start position, the starter motor (31) is driven to start the engine. When the key switch (22) is turned on , the engine operating state is maintained by energizing the power supply (4) to each part of the engine, and when the key switch (22) is turned on to the off position, the fuel injection valve is turned on. The fuel injection from (24) is stopped, and the engine is stopped.

As shown in FIG. 1, the exhaust treatment device includes an engine ECU (5), a DOC (2), a DPF (7) disposed downstream of the DOC (2), and an exhaust gas of the DOC (2). A fuel supply device (8) is provided on the upstream side.
As shown in FIG. 2, in this exhaust treatment device, the PM accumulation amount estimated value (F) of the DPF (7) has reached a predetermined DPF regeneration start determination value (FS), but the estimated temperature (DOC) of the DOC (2) If (T) does not reach the activation temperature region (T5), the DOC activation process is performed according to a command from the engine ECU (5) that has detected the information, and in the DOC activation process, the exhaust gas (9) is heated. When the estimated temperature (T) of the DOC (2) reaches the activation temperature region (T5), a DPF regeneration process (S10) is performed according to a command from the engine ECU (5) that has detected the information, and a DPF regeneration process is performed. In (S10), fuel is supplied to the exhaust gas (9) from the fuel supply device (8) shown in FIG. 1, and the temperature of the exhaust gas (9) is raised by catalytic combustion of the fuel in the DOC (2). The heat accumulated in (9) is configured to incinerate the PM deposited on the DPF (7).
Therefore, in this exhaust treatment device, even when the temperature of the exhaust gas (9) is low, the DPF (7) can be regenerated by the DOC activation process.

As shown in FIG. 1, in this exhaust treatment device, an exhaust throttle valve (9a) is provided between the DOC (2) and the DPF (7). As shown in FIG. The opening degree of the valve (9a) is reduced (S5).
For this reason, in this exhaust treatment device, the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) shown in FIG. 1 rises, and the temperature of the exhaust gas (9) around the DOC (2) rises smoothly, Even during low load operation with high DOC (2) temperature rise efficiency and low exhaust (9) temperature, activation of DOC (2) does not take much time and regeneration of DPF (7) during low load operation Can be promoted. As shown in FIG. 1, the exhaust throttle valve (9a) is an electric open / close valve, which is electrically connected to a power supply (4) via an engine ECU (5).

DOC is an abbreviation for diesel oxidation catalyst.
As shown in FIG. 1, the DOC (2) includes a carrier for supporting an oxidation catalyst component. The carrier is a flow-through type metal honeycomb in which a number of cells along the axial direction are arranged in a penetrating manner inside, and an oxidation catalyst component such as platinum, palladium, and rhodium is carried in the cells.

DPF is an abbreviation for diesel particulate filter, and DPF (7) captures PM contained in exhaust gas (9). PM is an abbreviation for particulate matter.
The DPF (7) is a wall-flow type ceramic honeycomb in which a number of cells are arranged side by side in the axial direction and the inlets and outlets of adjacent cells are alternately plugged.

As shown in FIG. 1, the DOC (2) and the DPF (7) are arranged in the exhaust path (1).
The exhaust path (1) is disposed downstream of an exhaust outlet passage (16c) derived from an exhaust outlet (16b) of the exhaust turbine (16a), and is disposed on the way to the DOC storage case (1a) and the exhaust downstream thereof. The DOC housing case (1a) houses the electric heater (3) and the DOC (2), and the DPF housing case (1b) houses the DPF (7).

The PM accumulation amount of the DPF (7) is estimated as follows.
As shown in FIG. 1, the exhaust treatment device includes a differential pressure sensor (32) for detecting a differential pressure between the entrance and exit of the DPF (7), and the differential pressure sensor (32) is electrically connected to the engine ECU (5). Then, based on the pressure difference between the entrance and exit of the DPF (7), the engine ECU (5) calculates an estimated value of the amount of PM accumulated in the DPF (7).

The temperature of the DOC (2) is estimated as follows.
As shown in FIG. 1, the exhaust treatment device includes a DOC inlet-side exhaust temperature sensor (34) and a DOC outlet-side exhaust temperature sensor (35) of the DOC (2), and these sensors (34) and (35) are engine ECUs. It is electrically connected to (5). The engine ECU (5) calculates the estimated temperature of the DOC (2) based on the exhaust temperature information from the sensors (34) and (35).

A common rail type fuel injection device is used for the fuel supply device (8). In the DPF regeneration process, post injection is performed from the fuel injection valve (24), fuel is mixed into the exhaust gas (9), and the DOC of the fuel is used. The exhaust gas (9) is heated by the catalytic combustion in (2), and the PM accumulated in the DPF (7) is incinerated by the heat of the exhaust gas (9).
The post-injection is a fuel injection performed in the combustion chamber (23) in the expansion stroke or the exhaust stroke after the main injection from the fuel injection valve (24) during the combustion cycle.
In the DPF regeneration process, the post injection amount is adjusted so that the exhaust gas temperature at the inlet of the DPF (7) maintains a predetermined regenerable temperature.
In the DPF regeneration process, exhaust pipe injection for injecting fuel to exhaust gas from a fuel injection valve provided in an exhaust pipe may be performed instead of post injection.

When the estimated value of the accumulated amount of PM accumulated in the DPF (7) is lower than the regeneration end determination value (FF) of the DPF (7), the DPF regeneration process is terminated by a command from the engine ECU (5) based on the detection.
The DPF regeneration process is terminated when the time during which the exhaust gas temperature at the inlet of the DPF (7) maintains the predetermined regenerable temperature reaches a predetermined regeneration end determination value after the DPF (7) regeneration process is started. You may. The exhaust gas temperature at the inlet of the DPF (7) can be detected by the exhaust gas temperature sensor (38) at the inlet of the DPF.
The exhaust treatment device includes an exhaust gas temperature sensor (33) on the outlet side of the DPF (7), and when the exhaust gas outlet temperature of the DPF (7) exceeds a predetermined abnormal combustion reference value, the engine ECU based on the detection. The DPF regeneration process is terminated urgently by the command of (5).

As shown in FIG. 2, in this exhaust treatment device, when the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) reaches a predetermined excess pressure region (P3) in the DOC activation process, Since the opening degree of the exhaust throttle valve (9a) is increased (S15) by a command from the engine ECU (5) that has detected the information, it is possible to prevent a decrease in output due to an increase in back pressure. .
The engine ECU (5) calculates an estimated value of the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) based on a map for calculating the exhaust pressure from the intake air amount and the DOC outlet exhaust temperature.

  As shown in FIG. 2, in the exhaust treatment device, when the estimated temperature (T) of the DOC (2) reaches the activation temperature region (T5) in the DOC activation process, the engine that detects the information is used. Since the exhaust throttle valve (9a) is configured to be fully opened (S9) in response to a command from the ECU (5), it is possible to prevent a decrease in output due to an increase in back pressure. .

As shown in FIG. 1, in this exhaust treatment device, an electric heater (3) is provided on the exhaust upstream side of the DOC (2), and as shown in FIGS. ) Is in the low temperature region (T1) which does not reach the activation temperature region (T5), the electric heater (3) generates heat by a command of the engine ECU (5) based on the detection of the information. (S4).
For this reason, in this exhaust treatment device, the temperature rise of the DOC (2) is further promoted, and the regeneration of the DPF (7) during the low-load operation can be promoted.

As shown in FIGS. 2 and 3, in this exhaust treatment device, in the DOC activation process, the estimated temperature (T) of the DOC (2) is lower than the activation temperature region (T5) and is lower than the low temperature region (T1). Is also in the high medium temperature range (T3), the heat generation (S4) of the electric heater (3) is prohibited by a command of the engine ECU (5) based on the detection of the information.
For this reason, in this exhaust treatment device, it is possible to suppress power consumption due to inefficient heat generation (S4) of the electric heater (3) in the medium temperature region (T3) where the temperature is relatively high and the heating efficiency is low.

  As shown in FIG. 1, in this exhaust treatment device, the electric heater (3) is arranged along the DOC inlet (2a), so that the heat conduction loss from the electric heater (3) to the DOC (2) is reduced. , The DOC (2) can be activated quickly, and the regeneration of the DPF (7) can be promoted without activating the DOC (2) even during low load operation with low exhaust gas temperature. .

As shown in FIG. 1, in this exhaust treatment device, a honeycomb structure (10) is provided on the exhaust gas upstream side of the DOC (2), and as shown in FIG. A plurality of cells (10a) (10b) penetrating in the exhaust passage direction of the exhaust passage (1) are provided, and only the central honeycomb portion (10d) of the honeycomb structure (10) serves as the electric heater (3). I have.
For this reason, in this exhaust treatment device, the temperature of the exhaust gas (9) is increased by the electric heater (3) of the central honeycomb portion (10d) where heat is hardly released to the outside of the exhaust gas passage (1), and the exhaust gas (9) is increased. ), The DOC (2) is quickly activated even during a light load operation in which the temperature of the exhaust gas (9) is low and the regeneration efficiency of the DPF (7) can be increased.
A peripheral honeycomb portion (10e) surrounding the electric heater (3) from the periphery is electrically insulated from the electric heater (3) via an insulator (10f).

As shown in FIG. 4A, in this exhaust treatment device, the central honeycomb portion (10d) constituting the electric heater (3) has a higher cell density than the surrounding honeycomb portion (10e) surrounding the periphery thereof. ing.
For this reason, in this exhaust treatment device, the DOC (2) can be quickly operated even in a light load operation in which the heat radiating area of the electric heater (3) is large, the temperature of the exhaust (9) is high, and the temperature of the exhaust (9) is low. Is activated, and the regeneration efficiency of the DPF (7) can be increased.
The cell density is indicated by the number of cells per unit area of a surface orthogonal to the central axis of the honeycomb, and the higher the numerical value, the higher the cell density.

The relationship between the honeycomb structure (10) and the DOC (2) shown in FIGS. 4A and 4B is as follows.
The honeycomb structure (10) shown in FIG. 4 (A) has a central honeycomb portion (10d) serving as an electric heater (3) and a peripheral honeycomb portion (10e) surrounding the electric heater (3) from the periphery. This is a flow-through type metal honeycomb in which a number of cells along the axial direction are arranged in a penetrating manner. Both the honeycomb structure (10) and the DOC (2) have a cylindrical diameter and the same outer diameter, and the central axis (10c) of the honeycomb structure (10) and the central axis (2b) of the DOC (2) are Located in the same straight line, the electric heater (3) of the honeycomb structure (10) faces the central portion (36) of the DOC (2), and the peripheral honeycomb portion (10e) of the honeycomb structure (10) is , DOC (2) and a peripheral portion (37) surrounding a central portion (36). The cell density of the peripheral honeycomb portion (10e) of the honeycomb structure (10) and the DOC (2) is set to be the same.

The flow of the DOC activation process and the DPF regeneration process by the engine ECU (5) shown in FIG. 2 is as follows.
In step (S1), the PM accumulation amount of the DPF (7) is estimated, and the process proceeds to step (S2).
In step (S2), it is determined whether or not the estimated PM accumulation value (F) of the DPF (7) is equal to or greater than the DPF regeneration start determination value (FS). Until the determination is affirmed, the process proceeds to step (S1). Step (S2) is repeated, and if the determination in step (S2) is affirmative, the process proceeds to step (S3).
In step (S3), it is determined whether or not the estimated temperature (T) of the DOC (2) is equal to or more than the medium temperature determination value (T2) less than the activation determination value (T4). If the estimated temperature (T) of the DOC (2) is in the low temperature region (T1), the process proceeds to step (S4), and a DOC activation process is performed.

In step (S4), the electric heater (3) generates heat, and proceeds to step (S5). In step (S5), the opening degree of the exhaust throttle valve (9a) is reduced, and the process proceeds to step (S6).
In step (S6), the opening degree of the intake throttle valve (19) is increased, the intake air amount is increased, and the exhaust pressure is increased by increasing the exhaust air amount, thereby promoting the temperature rise of the exhaust gas (9). Then, the process proceeds to step (S7).
In step (S7), it is determined whether or not the exhaust pressure (P) on the exhaust upstream side of the DOC (2) is equal to or greater than an excess determination value (P2). If the determination is negative, that is, the exhaust pressure (P) is If it is in the allowable pressure range (P1), the process proceeds to step (S8).
In step (S8), it is determined whether the estimated temperature (T) of the DOC (2) is equal to or higher than the activation determination value (T4). If the determination is affirmative, that is, the estimated temperature (T) of the DOC (2) is If the temperature has reached the activation temperature region (T5), the DOC activation process ends, and the process proceeds to step (S9).

In step (S9), the exhaust throttle valve (9a) is fully opened, and the process proceeds to step (S10).
In step (S10), DPF regeneration processing is performed, and the process proceeds to step (S11).
In step (S11), the PM accumulation amount of the DPF (7) is estimated, and the process proceeds to step (S12).
In step (S12), it is determined whether the PM accumulation amount estimated value (F) of the DPF (7) is equal to or less than the DPF regeneration end determination value (FF), and when the determination is affirmed, that is, the DPF regeneration end. When the determination is made, the process proceeds to step (S13). In step (S13), the DPF regeneration process ends, and the process returns to step (S1).

If the determination is negative in step (S3), that is, if the estimated temperature (T) of the DOC (2) has reached the medium temperature region (T3) or the activation temperature region (T5), the process proceeds to step (S14). move on.
In step (S14), it is determined whether or not the estimated temperature (T) of the DOC (2) is equal to or higher than the activation determination value (T4). If the determination is negative, that is, the estimated temperature (T) of the DOC (2) is determined. ) Is in the middle temperature region (T3), the process proceeds to step (S5), and the DOC activation process is performed in a state where the heat generation (S4) of the electric heater (3) is prohibited. If the determination is affirmative in step (S14), that is, if the estimated temperature (T) of the DOC (2) has reached the activation temperature region (T5), the process proceeds to step (S9), and the DOC activation process is performed. Instead, a DPF regeneration process (S10) is performed.
If the determination in step (S7) is affirmative, that is, if the exhaust pressure (P) has reached the excessive pressure region (P3), the process proceeds to step (S15). In step (S15), the opening of the exhaust throttle valve (9a) is increased, and the process proceeds to step (S8).
If the determination is negative in step (S8), that is, if the estimated temperature (T) of the DOC (2) is in the low temperature region (T1) or the medium temperature region (T3), the process returns to step (S3).
When the determination is negative in step (S12), that is, when the DPF regeneration end determination is not made, the process returns to step (S10), and the DPF regeneration process (S10) is continued.

  (1) ... exhaust passage, (1a) ... DOC housing case, (1b) ... DPF housing case, (2) ... DOC, (2a) ... DOC inlet, (3) ... electric heater, (5) ... engine ECU, (7) ... DPF, (8) ... fuel supply device, (9) ... exhaust, (9a) ... exhaust throttle valve, (10) ... honeycomb structure, (10a) ... cell, (10b) ... cell, (10d) ): Central honeycomb portion, (10e): peripheral honeycomb portion, (F): estimated value of PM accumulation amount, (FS): DPF regeneration start determination value, (T): estimated temperature of DOC, (T1): low temperature region (T3): Medium temperature range, (T5): Activation temperature range, (S4): Electric heater generates heat, (S6): Exhaust throttle valve opening decreases, (S9): Exhaust throttle valve fully open, (S10): DPF regeneration processing, (S15): The opening degree of the exhaust throttle valve increases, (P): exhaust pressure, (P3): excessive pressure region.

Claims (6)

The engine ECU (5), the DOC (2), the DPF (7) arranged on the exhaust downstream side of the DOC (2), and the fuel supply device (8) arranged on the exhaust upstream side of the DOC (2) Prepared,
The PM accumulation amount estimation value (F) of the DPF (7) has reached the predetermined DPF regeneration start determination value (FS), but the estimated temperature (T) of the DOC (2) has not reached the activation temperature region (T5). In this case, a DOC activation process is performed in response to a command from the engine ECU (5) that has detected the information, and in the DOC activation process, the temperature of the exhaust gas (9) is increased, and the estimated temperature (T) of the DOC (2) is activated. When the temperature reaches the activation temperature region (T5), the DPF regeneration process (S10) is performed by a command of the engine ECU (5) that has detected the information, and in the DPF regeneration process (S10), the exhaust gas is discharged from the fuel supply device (8). The fuel is supplied to (9), and the exhaust gas (9) is heated by catalytic combustion of the fuel in the DOC (2), and the PM accumulated in the DPF (7) is incinerated by the heat of the exhaust gas (9). In a diesel engine configured to be
An exhaust throttle valve (9a) is provided between the DOC (2) and the DPF (7), and in the DOC activation process, the opening degree of the exhaust throttle valve (9a) is reduced (S5) .
An electric heater (3) is provided on the exhaust upstream side of the DOC (2),
In the DOC activation process, when the estimated temperature (T) of the DOC (2) is in the low temperature region (T1) which does not reach the activation temperature region (T5), the command of the engine ECU (5) based on the detection of the information is given. The electric heater (3) is configured to generate heat (S4) .
In the DOC activation process, when the estimated temperature (T) of the DOC (2) is lower than the activation temperature region (T5) and is in the middle temperature region (T3) higher than the low temperature region (T1), the information is detected. A diesel engine characterized in that heat generation (S4) of the electric heater (3) is prohibited by a command of the engine ECU (5) based on the following. The diesel engine according to claim 1,
In the DOC activation process, when the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) reaches a predetermined excessive pressure region (P3), a command from the engine ECU (5) that has detected the information indicates: A diesel engine, wherein the degree of opening of the exhaust throttle valve (9a) is increased (S15). The diesel engine according to claim 1 or claim 2,
In the DOC activation process, when the estimated temperature (T) of the DOC (2) reaches the activation temperature region (T5), the exhaust throttle valve (9a) is instructed by the engine ECU (5) that has detected the information. ) Is fully opened (S9). The diesel engine according to any one of claims 1 to 3 ,
A diesel engine, wherein the electric heater (3) is arranged along the DOC inlet (2a). The diesel engine according to any one of claims 1 to 4 ,
A honeycomb structure (10) is provided on the exhaust upstream side of the DOC (2), and the honeycomb structure (10) includes a large number of cells (10a) (10b) penetrating in the exhaust passage direction of the exhaust path (1). A diesel engine, wherein only the central honeycomb portion (10d) of the honeycomb structure (10) is the electric heater (3). The diesel engine according to claim 5 ,
A diesel engine characterized in that the central honeycomb part (10d) constituting the electric heater (3) has a higher cell density than the surrounding honeycomb part (10e) surrounding the central honeycomb part (10d).

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