JP2017223182A - diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diesel engine capable of promoting regeneration of a DPF during a low load operation.SOLUTION: In a diesel engine, a DOC 2 comprises an exhaust gas upstream side DOC 2b and an exhaust gas downstream side DOC 2c disposed on the exhaust gas downstream side of the exhaust gas upstream side DOC, and an exhaust throttle valve 9a is provided between the exhaust gas upstream side DOC and the exhaust gas downstream side DOC. In DOC activation processing, an opening of the exhaust throttle valve is reduced, an estimated temperature of the exhaust gas upstream side DOC is raised to an activation temperature region and then, DPF regeneration processing is performed.SELECTED DRAWING: Figure 1

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.

Conventionally, there are the following diesel engine inventions (see, for example, Patent Document 1).
An engine ECU, a DOC, a DPF disposed on the exhaust downstream side of the DOC, and a fuel supply device disposed on the exhaust upstream side of the DOC, and the estimated PM accumulation amount 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 according to the command of the engine ECU that has detected the information. In the DOC activation process, the exhaust gas is heated, and the DOC When the estimated temperature reaches the activation temperature region, DPF regeneration processing is performed according to the command of the engine EUC that has detected the information. In the DPF regeneration processing, fuel is supplied from the fuel supply device to the exhaust gas. The diesel engine is configured such that the temperature of the exhaust gas is raised by the catalytic combustion, and the PM accumulated in the DPF is incinerated by the heat of the exhaust gas.

  In this kind of invention, even when the exhaust temperature is low, there is an advantage that the DPF can be regenerated by the DOC activation process.

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

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

<< Problem >> 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 process is performed during low load operation with low DOC temperature rise efficiency and low exhaust temperature. Takes time, and DPF regeneration at low load stagnate.

  The subject of this invention is providing the diesel engine which can accelerate | stimulate regeneration of DPF at the time of low load driving | operation.

Invention specific matters of the invention according to claim 1 are as follows.
As illustrated in FIG. 1, the engine ECU (5), the DOC (2), the DPF (7) disposed on the exhaust downstream side of the DOC (2), and the exhaust upstream side of the DOC (2). A fuel supply device (8),
As illustrated in FIG. 2, the estimated PM accumulation amount (F) of the DPF (7) reaches a predetermined DPF regeneration start determination value (FS), but the estimated temperature (T) of the DOC (2) is activated. When the temperature range (T5) has not been reached, the DOC activation process is performed in accordance with a command from the engine ECU (5) that has detected the information. In the DOC activation process, the exhaust (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 according to a command from the engine ECU (5) that has detected the information. In the DPF regeneration process (S10), Fuel is supplied from the fuel supply device (8) illustrated in FIG. 1 to the exhaust (9), and the temperature of the exhaust (9) is raised by catalytic combustion of the fuel (9) in the DOC (2). In the diesel engine configured to incinerate PM accumulated in the DPF (7) with the heat of 9),
As illustrated in FIG. 1, the DOC (2) includes an exhaust upstream DOC (2b) and an exhaust downstream DOC (2c) disposed on the exhaust downstream side of the exhaust upstream DOC (2b). An exhaust throttle valve (9a) is provided between the exhaust upstream DOC (2b) and the exhaust downstream DOC (2c). As illustrated in FIG. 2, in the DOC activation process, the exhaust throttle valve (9a) is opened. The degree is decreased (S5), the estimated temperature (T) of the exhaust upstream DOC (2b) is raised to the activation temperature region (T5), and then the DPF regeneration process (S10) is performed. A diesel engine characterized by that.

(Invention of Claim 1)
The invention according to claim 1 has the following effects.
<Effect> It is possible to promote regeneration of the DPF during low-load operation.
In the present invention, the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) illustrated in FIG. 1 is increased by the DOC activation process, and the exhaust DOC (2) The exhaust upstream DOC (2b) that constitutes a part of the exhaust is heated smoothly, and the exhaust gas (9) is obtained by catalytic combustion at the exhaust upstream DOC (2b) of the fuel supplied in the subsequent DPF regeneration process (S10). The temperature of the exhaust (9) is increased, and the exhaust downstream DOC (2c) is also activated in parallel with the DOC regeneration process (S10), and the temperature increase efficiency of the DOC (2) is increased. Even during the low load operation at a low temperature of 9), the activation of the DOC (2) does not take time, and the regeneration of the DPF (7) during the low load operation can be promoted.

(Invention of Claim 2)
The invention according to claim 2 has the following effect in addition to the effect of the invention according to claim 1.
<Effect> It is possible to promote regeneration of the DPF during low-load operation.
Since the exhaust upstream DOC (2b) is configured to have a smaller heat capacity than the exhaust downstream DOC (2c), the time required for activation of the exhaust upstream DOC (2b) is shortened, and the low load operation is performed. The regeneration of the DPF at the time can be promoted.

(Invention of Claim 3)
The invention according to claim 3 has the following effect in addition to the effect of the invention according to claim 1 or claim 2.
<Effect> It is possible to prevent a decrease in output due to a back pressure increase in the DOC activation process.
In the present invention, as illustrated in FIG. 2, 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), the information Since the opening degree of the exhaust throttle valve (9a) is increased (S15) in response to a command from the engine ECU (5) that detects this, output reduction due to increased back pressure in the DOC activation process is prevented. can do.

(Invention of Claim 4)
The invention according to claim 4 has the following effects in addition to the effects of the invention according to any one of claims 1 to 3.
<Effect> It is possible to prevent a decrease in output due to a back pressure increase after the DOC activation process.
In the present invention, as illustrated in FIG. 2, when the estimated temperature (T) of the exhaust upstream DOC (2b) reaches the activation temperature region (T5) in the DOC activation process, the information is detected. Since the exhaust throttle valve (9a) is fully opened (S9) in response to the command from the engine ECU (5), it is possible to prevent a decrease in output due to a back pressure increase after the DOC activation process.

(Invention according to claim 5)
The invention according to claim 5 has the following effects in addition to the effects of the invention according to any one of claims 1 to 4.
<Effect> It is possible to promote regeneration of the DPF during low-load operation.
In the present invention, as illustrated in FIGS. 2 and 3, in the DOC activation process, the estimated temperature (T) of the exhaust upstream DOC (2b) does not reach the activation temperature range (T5) (T1). ), The electric heater (3) generates heat (S4) in response to a command from the engine ECU (5) based on the detection of the information. Therefore, the exhaust upstream side DOC (2b) rises. The temperature is further promoted, and regeneration of the DPF (7) during low load operation can be promoted.

(Invention of 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> It is possible to suppress power consumption due to heat generated by the inefficient electric heater.
In the present invention, as illustrated in FIGS. 2 and 3, in the DOC activation process, the estimated temperature (T) of the exhaust upstream DOC (2b) is lower than the activation temperature region (T5), and the low temperature region (T1). When the temperature is higher than the middle temperature region (T3), the heat generation (S4) of the electric heater (3) is prohibited by the command of the engine ECU (5) based on the detection of the information. It is possible to suppress power consumption due to heat generation (S4) of the inefficient electric heater (3) in the intermediate temperature region (T3) where the temperature is relatively high and the heating efficiency is low.

(Invention of Claim 7)
The invention according to claim 7 has the following effect in addition to the effect of the invention according to claim 5 or claim 6.
<Effect> It is possible to promote regeneration of the DPF during low-load operation.
In the present invention, as illustrated in FIG. 1, since the electric heater (3) is disposed along the DOC inlet (2a) of the exhaust upstream DOC (2b), the electric heater (3) is connected to the exhaust upstream side. The heat conduction loss to the DOC (2b) is small, the temperature rise efficiency of the exhaust upstream DOC (2b) is increased, and it takes time to activate the exhaust upstream DOC (2b) even during low load operation where the exhaust temperature is low. However, regeneration of the DPF (7) during low load operation can be promoted.

(Invention of Claim 8)
The invention according to claim 8 has the following effects in addition to the effects of the invention according to any one of claims 5 to 7.
<Effect> The regeneration efficiency of the DPF can be increased.
In the present invention, as illustrated in FIG. 1, the honeycomb structure (10) is provided on the exhaust upstream side of the exhaust upstream side DOC (2b), and as illustrated in FIG. 4 (A), the honeycomb structure (10 ) Includes a large number of cells (10a) (10b) penetrating in the exhaust passage direction of the exhaust passage (1), and only the central honeycomb portion (10d) of the honeycomb structure (10) is the electric heater (3). Therefore, the temperature of the exhaust (9) is increased by the electric heater (3) of the central honeycomb portion (10d) where heat escape to the outside of the exhaust path (1) is difficult to occur, and the exhaust (9) is increased. Even during a light load operation where the temperature efficiency is high and the temperature of the exhaust (9) is low, the exhaust upstream DOC (2b) is quickly activated, and the regeneration efficiency of the DPF (7) can be increased.

(Invention according to claim 9)
The invention according to claim 9 has the following effect in addition to the effect of the invention according to claim 8.
<Effect> The regeneration efficiency of the DPF can be increased.
In the present invention, as illustrated in FIG. 4A, the central honeycomb portion (10d) constituting the electric heater (3) has a higher cell density than the surrounding honeycomb portion (10e) surrounding the periphery. Therefore, the heat release area of the electric heater (3) is large, the temperature raising efficiency of the exhaust (9) is increased, and the exhaust upstream DOC (2b) is activated quickly even during light load operation where the temperature of the exhaust (9) is low. Thus, the regeneration efficiency of the DPF (7) can be increased.

It is a mimetic diagram of a diesel engine concerning an embodiment of the present invention. It is a flowchart of the DOC activation process and DPF regeneration process by the engine ECU used in the embodiment of the present invention. It is a figure explaining the combination of the opening degree adjustment of the exhaust throttle valve by engine ECU used by embodiment of this invention, and heat_generation | fever of an electric heater. FIG. 4A is a view for explaining an electric heater and an exhaust upstream DOC used in the embodiment of the present invention, and FIG. 4A is a front view of the honeycomb structure including the electric heater as viewed in a direction parallel to the central axis. (B) is the front view which looked at the exhaust upstream DOC in the direction parallel to the central axis.

  1 to 4 are diagrams for explaining 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 installation direction of the crankshaft (11) 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) assembled on one side of the cylinder head (13) and an exhaust manifold (15) assembled 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 for 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 system includes an exhaust manifold (15), an exhaust turbine (16a) of a supercharger (16) provided in the exhaust manifold (15), and an exhaust derived from an exhaust outlet (16b) of the exhaust turbine (16a). A lead-out passage (16c) is provided.

As shown in FIG. 1, this engine includes an intake device.
The intake device includes a compressor (16d) of the supercharger (16), an air flow sensor (17) provided on the intake upstream side of the intake inlet (16e) of the compressor (16d), and a supercharged air 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 EGR cooler (20) disposed between (15) and intake manifold (14), and EGR valve (21) disposed between EGR cooler (20) and intake manifold (14). EGR is an abbreviation for exhaust gas recirculation.
The intake throttle valve (19) and the EGR valve (21) are both electrically operated on / off valves, and these are electrically connected to the power source (4) via the 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 source (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 ( 26) a fuel supply pump (27) that pumps fuel from 26).
The fuel injection valve (24) includes an electromagnetic on-off valve, and the fuel supply pump (27) includes an electric pressure regulating valve, which are electrically connected to a power source (4) via an engine ECU (5). Yes.

As shown in FIG. 1, the engine includes a speed governor.
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 engine 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 starting device includes a starter motor (31) and a key switch (22), and the starter motor (31) and the key switch (22) are electrically connected to a power source (4) via the 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 rotational speed deviation between the target engine speed and the actual engine speed, and the engine speed fluctuation due to load fluctuation is reduced.
In accordance with the engine speed, load, intake air amount, and intake air temperature, the opening degree of the intake throttle valve (19) and the EGR valve (21) is adjusted to adjust the intake air amount and the EGR rate.
When the key switch (22) is turned 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 each part of the engine from the power supply (8). When the key switch (22) is turned on, the fuel injection valve 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 on the exhaust downstream side of the DOC (2), and an exhaust of the DOC (2). A fuel supply device (8) is provided on the upstream side.
As shown in FIG. 2, in this exhaust treatment apparatus, the PM accumulation amount estimated value (F) of the DPF (7) reaches a predetermined DPF regeneration start determination value (FS), but the estimated temperature of the DOC (2) ( When T) does not reach the activation temperature region (T5), the DOC activation process is performed according to the command of the engine ECU (5) that has detected the information. In the DOC activation process, the exhaust (9) is heated. When the estimated temperature (T) of the DOC (2) reaches the activation temperature region (T5), the DPF regeneration process (S10) is performed by the command of the engine ECU (5) that has detected the information, and the DPF regeneration process In (S10), fuel is supplied from the fuel supply device (8) shown in FIG. 1 to the exhaust (9), and the temperature of the exhaust (9) is raised by catalytic combustion of the fuel (9) at the DOC (2). The PM accumulated in the DPF (7) is incinerated by the heat of the exhaust (9).
For this reason, in this exhaust treatment apparatus, even when the temperature of the exhaust (9) is low, the DPF (7) can be regenerated by the DOC activation treatment.

In this exhaust treatment apparatus, as shown in FIG. 1, the DOC (2) includes an exhaust upstream DOC (2b) and an exhaust downstream DOC (2c) disposed on the exhaust downstream side of the exhaust upstream DOC (2b). ), And an exhaust throttle valve (9a) is provided between the exhaust upstream DOC (2b) and the exhaust downstream DOC (2c). As illustrated in FIG. 2, in the DOC activation process, the exhaust throttle valve The opening degree of (9a) is decreased (S5), the estimated temperature (T) of the exhaust upstream DOC (2b) is raised to the activation temperature region (T5), and then the DPF regeneration process (S10) is performed. It is configured as follows.
Therefore, in this exhaust treatment apparatus, the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) illustrated in FIG. The exhaust upstream DOC (2b) that constitutes a part of the DOC (2) is heated smoothly, and catalytic combustion at the exhaust upstream DOC (2b) of the fuel supplied in the subsequent DPF regeneration process (S10) The temperature of the exhaust (9) is increased, and the heat of the exhaust (9) activates the exhaust downstream DOC (2c) in parallel with the DOC regeneration process (S10). Thus, even during low load operation where the temperature of the exhaust (9) is low, it takes less time to activate the DOC (2), and regeneration of the DPF (7) during low load operation can be promoted.
As shown in FIG. 1, the exhaust throttle valve (9a) is an electrically operated on / off valve, which is electrically connected to a power source (4) via an engine ECU (5).

  In this exhaust treatment device, the exhaust upstream side DOC (2b) is configured to have a smaller heat capacity than the exhaust downstream side DOC (2c), and therefore the time required for activation of the exhaust upstream side DOC (2b). Thus, the regeneration of the DPF during low-load operation can be promoted.

DOC is an abbreviation for diesel oxidation catalyst.
As shown in FIG. 1, both the exhaust upstream DOC (2b) and the exhaust downstream DOC (2c) constituting the DOC (2) include a carrier carrying an oxidation catalyst component.
The support is a flow-through type metal honeycomb in which a large number of cells along the axial length direction are arranged in a penetrating manner inside, and an oxidation catalyst component such as platinum, palladium, and rhodium is supported in the cell.
As shown in FIG. 1, the exhaust upstream DOC (2b) has the same material, the same external shape, and the same cell density as the exhaust downstream DOC (2c), but the axial length is larger than that of the exhaust downstream DOC (2c). Is small, has a small volume, and has a small heat capacity. The exhaust upstream DOC (2b) is electrically insulated from the electric heater (4).

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

As shown in FIG. 1, the DOC (2) and the DPF (7) are disposed in the exhaust path (1).
The exhaust path (1) is arranged downstream of the exhaust outlet passage (16c) led out from the exhaust outlet (16b) of the exhaust turbine (16a), and the upstream DOC housing case (1a) and its exhaust downstream side in the middle The downstream DOC storage case (1b) is provided, the electric heater (3) and the exhaust upstream DOC (2b) are stored in the upstream DOC storage case (1a), and the downstream DOC storage case (1b). The exhaust downstream DOC (2c) and the DPF (7) are accommodated, and the DPF (7) is accommodated on the exhaust downstream side of the exhaust downstream DOC (2c).

The estimation of the PM deposition amount of the DPF (7) is performed as follows.
As shown in FIG. 1, the exhaust treatment device includes a differential pressure sensor (32) that detects a differential pressure at the inlet / outlet of the DPF (7), and the differential pressure sensor (32) is electrically connected to the engine ECU (5). Then, based on the differential pressure at the inlet / outlet of the DPF (7), the engine ECU (5) calculates an estimated value of the amount of PM deposited on the DPF (7).

The temperature estimation of DOC (2) is performed as follows.
As shown in FIG. 1, the exhaust treatment apparatus includes a DOC inlet side exhaust temperature sensor (34) and a DOC outlet side exhaust temperature sensor (35) of the exhaust upstream DOC (2b), and these sensors (34) (35). Is electrically connected to the engine ECU (5). The engine ECU (5) calculates the estimated temperature of the exhaust upstream DOC (2b) based on the exhaust temperature information from the sensors (34) and (35).

As the fuel supply device (8), a common rail type fuel injection device is used. In the DPF regeneration process, post injection is performed from the fuel injection valve (24), and fuel is mixed into the exhaust (9). Due to catalytic combustion in the upstream DOC (2b) and the exhaust downstream DOC (2c), the temperature of the exhaust (9) is increased, and the PM accumulated in the DPF (7) is incinerated by the heat of the exhaust (9). .
Post-injection is fuel injection performed in the combustion chamber (23) in the expansion stroke or 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 inlet exhaust temperature of the DPF (7) maintains a predetermined reproducible temperature.
In the DPF regeneration process, exhaust pipe injection for injecting fuel into the exhaust from a fuel injection valve provided in the exhaust pipe may be performed instead of post injection.

When the estimated PM accumulation amount accumulated in the DPF (7) falls below the regeneration end determination value (FF) of the DPF (7), the DPF regeneration process is terminated by an instruction of the engine ECU (5) based on the detection.
The DPF regeneration process is terminated when the time during which the inlet exhaust temperature of the DPF (7) maintains a predetermined regeneration possible temperature reaches a predetermined regeneration end determination value after the regeneration process of the DPF (7) is started. May be. The inlet exhaust temperature of the DPF (7) can be detected by the DPF inlet side exhaust temperature sensor (38).
The exhaust treatment device includes an outlet side exhaust temperature sensor (33) of the DPF (7). When the exhaust side 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 (5).

As shown in FIG. 2, in this exhaust treatment apparatus, when the exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) reaches a predetermined excessive pressure region (P3) in the DOC activation process, Since the opening of the exhaust throttle valve (9a) is increased (S15) in response to a command from the engine ECU (5) that has detected the information, the output is reduced due to the back pressure increase in the DOC activation process. Can be prevented.
The exhaust pressure (P) on the exhaust upstream side of the exhaust throttle valve (9a) is calculated by the engine ECU (5) based on a map for calculating the exhaust pressure from the intake air amount and the DOC outlet side exhaust temperature.

  As shown in FIG. 2, in this exhaust treatment apparatus, when the estimated temperature (T) of the exhaust upstream DOC (2b) reaches the activation temperature region (T5) in the DOC activation process, the information is displayed. Since the exhaust throttle valve (9a) is configured to be fully opened (S9) according to the detected command from the engine ECU (5), it is possible to prevent a decrease in output due to an increase in back pressure after the DOC activation process. . .

As shown in FIG. 1, in this exhaust treatment apparatus, an electric heater (3) is provided on the exhaust upstream side of the exhaust upstream side DOC (2b), and as shown in FIGS. When the estimated temperature (T) of the exhaust upstream DOC (2b) is in a low temperature region (T1) that does not reach the activation temperature region (T5), an electric ECU command (5) based on the detection of the information The heater (3) is configured to generate heat (S4).
For this reason, in this exhaust treatment apparatus, the temperature increase of the exhaust upstream DOC (2b) is further promoted, and the regeneration of the DPF (7) during the low load operation can be promoted.

As shown in FIG. 2 and FIG. 3, in this exhaust treatment apparatus, in the DOC activation process, the estimated temperature (T) of the exhaust upstream DOC (2b) is less than the activation temperature region (T5) and the low temperature region ( When the temperature is in the intermediate temperature range (T3) higher than T1), the heat generation (S4) of the electric heater (3) is prohibited by the command of the engine ECU (5) based on the detection of the information. .
For this reason, in this exhaust treatment apparatus, it is possible to suppress power consumption due to heat generation (S4) of the inefficient electric heater (3) in the intermediate temperature region (T3) where the temperature is relatively high and the heating efficiency is low.

  As shown in FIG. 1, in this exhaust treatment apparatus, since the electric heater (3) is disposed along the DOC inlet (2a) of the exhaust upstream DOC (2b), the electric heater (3) is connected to the exhaust upstream. The heat loss to the side DOC (2b) is small, the temperature rise efficiency of the exhaust upstream DOC (2b) is increased, and it takes time to activate the exhaust upstream DOC (2b) even during low load operation where the exhaust temperature is low Therefore, the regeneration of DPF (7) can be promoted.

As shown in FIG. 1, in this exhaust treatment apparatus, a honeycomb structure (10) is provided on the exhaust upstream side of the exhaust upstream side DOC (2b), and as shown in FIG. 4 (A), the honeycomb structure (10 ) Includes a large number of cells (10a) (10b) penetrating in the exhaust passage direction of the exhaust passage (1), and only the central honeycomb portion (10d) of the honeycomb structure (10) is the electric heater (3). It is said that.
For this reason, in this exhaust treatment device, the temperature of the exhaust (9) is increased by the electric heater (3) of the central honeycomb portion (10d) where heat escape to the outside of the exhaust path (1) hardly occurs, and the exhaust (9 ), The exhaust upstream side DOC (2b) is quickly activated, and the regeneration efficiency of the DPF (7) can be increased. The surrounding honeycomb portion (10e) surrounding the electric heater (3) from the periphery is electrically insulated from the electric heater (3) through an insulator (10f).

As shown in FIG. 4A, in this exhaust treatment apparatus, the central honeycomb portion (10d) constituting the electric heater (3) is configured with a higher cell density than the surrounding honeycomb portion (10e) surrounding the periphery. ing.
For this reason, in this exhaust treatment device, the heat dissipation area of the electric heater (3) is wide, the temperature raising efficiency of the exhaust (9) is high, and the exhaust (9) temperature is low. The side DOC (2b) 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 the plane orthogonal to the central axis of the honeycomb. The larger the numerical value, the higher the cell density.

The relationship between the honeycomb structure (10) shown in FIGS. 4A and 4B and the exhaust upstream DOC (2b) is as follows.
The honeycomb structure (10) shown in FIG. 4 (A) includes both a central honeycomb portion (10d) serving as an electric heater (3) and a peripheral honeycomb portion (10e) surrounding the electric heater (3) from the inside. This is a flow-through type metal honeycomb in which a large number of cells along the axial direction are arranged side by side. The honeycomb structure (10) and the exhaust upstream DOC (2b) are both cylindrical and have the same outer diameter, and the central axis (10c) of the honeycomb structure (10) and the exhaust upstream DOC (2b) The central axis (2d) of the honeycomb structure (10) is positioned in the same straight line, and the electric heater (3) of the honeycomb structure (10) faces the center (36) of the exhaust upstream DOC (2b), and the honeycomb structure ( The peripheral honeycomb portion (10e) of 10) faces the peripheral portion (37) surrounding the central portion (36) of the exhaust upstream DOC (2b). The cell densities of the surrounding honeycomb portion (10e) of the honeycomb structure (10) and the exhaust upstream DOC (2b) are set to be the same.

The flow of DOC activation processing and DPF regeneration processing 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 PM accumulation amount estimated value (F) of the DPF (7) is greater than or equal to the determination value (FS) for starting DPF regeneration, and step (S1) is continued until the determination is affirmed. Step (S2) is repeated, and if the determination in step (S2) is affirmed, the process proceeds to step (S3).
In step (S3), it is determined whether or not the estimated temperature (T) of the exhaust upstream DOC (2b) is equal to or higher than the intermediate temperature determination value (T2) less than the activation determination value (T4), and the determination is denied. In the case, that is, when the estimated temperature (T) of the exhaust upstream DOC (2b) is in the low temperature region (T1), the process proceeds to step (S4), and the DOC activation process is performed.

In step (S4), the electric heater (3) generates heat, and the process proceeds to step (S5). In step (S5), the opening degree of the exhaust throttle valve (9a) is decreased, and the process proceeds to step (S6).
In step (S6), the opening degree of the intake throttle valve (19) is increased, the intake amount is increased, the exhaust amount is increased, the exhaust pressure (P) is increased, and the temperature rise of the exhaust (9) is promoted. 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 exhaust upstream DOC (2b) is equal to or higher than the excess determination value (P2). If the determination is negative, that is, the exhaust pressure ( If P) is in the allowable pressure region (P1), the process proceeds to step (S8).
In step (S8), it is determined whether or not the estimated temperature (T) of the exhaust upstream DOC (2b) is equal to or higher than the activation determination value (T4). If the determination is affirmative, that is, the exhaust upstream DOC (2b). If the estimated temperature (T) has reached the activation temperature region (T5), the DOC activation process is terminated 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 or not the PM accumulation amount estimated value (F) of the DPF (7) is equal to or less than the DPF regeneration end determination value (FF). If the determination is affirmative, that is, the DPF regeneration end When the determination is made, the process proceeds to step (S13). In step (S13), the DPF regeneration process is terminated, and the process returns to step (S1).

If the determination is negative in step (S3), that is, if the estimated temperature (T) of the exhaust upstream DOC (2b) has reached the intermediate temperature region (T3) or the activation temperature region (T5), the step ( Go to S14).
In step (S14), it is determined whether or not the estimated temperature (T) of the exhaust upstream DOC (2b) is equal to or higher than the activation determination value (T4). If the determination is negative, that is, the estimation of DOC (2). When the temperature (T) is in the intermediate 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 in step (S14) is affirmative, that is, if the estimated temperature (T) of the exhaust upstream DOC (2b) has reached the activation temperature region (T5), the process proceeds to step (S9) to activate the DOC. The DPF regeneration process (S10) is performed without performing the process.
If the determination is affirmative in step (S7), that is, if the exhaust pressure (P) reaches the excessive pressure region (P3), the process proceeds to step (S15). In step (S15), the opening degree 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 exhaust upstream DOC (2b) is in the low temperature region (T1) or the intermediate temperature region (T3), step (S3) Return to.
If the determination is negative in step (S12), that is, if the DPF regeneration end determination is not made, the process returns to step (S10) and the DPF regeneration process (S10) is continued.

(1) ... Exhaust path, (1a) ... DOC storage case, (1b) ... DPF storage case, (2) ... DOC, (2a) ... DOC inlet, (2b) ... Exhaust upstream DOC, (2c) ... Exhaust Downstream DOC, (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 part, (10e) ... surrounding honeycomb part, (F) ... estimated PM deposition amount, (FS) ... DPF regeneration start determination Value, (T) ... Estimated temperature of DOC, (T1) ... Low temperature region, (T3) ... Medium temperature region, (T5) ... Activation temperature region, (S4) ... Electric heater generates heat, (S6) ... Exhaust (S9) ... Exhaust throttle valve fully opened, (S10) ... DPF regeneration processing, (S15) ... Exhaust throttle valve opening increased, (P) ... Exhaust pressure, (P3) ... Overpressure Pass.

Claims (9)

Engine ECU (5), DOC (2), DPF (7) disposed on the exhaust downstream side of DOC (2), and fuel supply device (8) disposed on the exhaust upstream side of DOC (2) Prepared,
The PM deposition amount estimated value (F) of the DPF (7) reaches the predetermined DPF regeneration start determination value (FS), but the estimated temperature (T) of the DOC (2) does not reach the activation temperature region (T5). In this case, the DOC activation process is performed by the command of the engine ECU (5) that has detected the information. In the DOC activation process, the exhaust (9) is heated and the estimated temperature (T) of the DOC (2) is activated. When the temperature reaches the control temperature range (T5), a DPF regeneration process (S10) is performed in response to a command from the engine ECU (5) that has detected the information. In the DPF regeneration process (S10), the fuel supply device (8) exhausts the exhaust gas. Fuel is supplied to (9), and the temperature of the exhaust (9) is raised by catalytic combustion of the fuel (9) at the DOC (2), and the heat of the exhaust (9) accumulates on the DPF (7). In a diesel engine configured to incinerate PM,
The DOC (2) includes an exhaust upstream DOC (2b) and an exhaust downstream DOC (2c) disposed on the exhaust downstream side of the exhaust upstream DOC (2b). The exhaust upstream DOC (2b) An exhaust throttle valve (9a) is provided between the exhaust downstream DOC (2c), and in the DOC activation process, the opening of the exhaust throttle valve (9a) is decreased (S5), and the exhaust upstream DOC (2b) A diesel engine characterized in that the estimated temperature (T) is raised to an activation temperature region (T5) and then a DPF regeneration process (S10) is performed. The diesel engine according to claim 1,
The diesel engine characterized in that the exhaust upstream DOC (2b) is configured to have a smaller heat capacity than the exhaust downstream DOC (2c). In the diesel engine according to claim 1 or 2,
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), the command of the engine ECU (5) that detects the information A diesel engine characterized in that the opening of the exhaust throttle valve (9a) is increased (S15). In the diesel engine according to any one of claims 1 to 3,
When the estimated temperature (T) of the exhaust upstream DOC (2b) reaches the activation temperature region (T5) in the DOC activation process, the exhaust throttle is controlled by the command of the engine ECU (5) that detects the information. A diesel engine characterized in that the valve (9a) is configured to be fully opened (S9). In the diesel engine according to any one of claims 1 to 4,
An electric heater (3) is provided on the exhaust upstream side of the exhaust upstream side DOC (2b),
In the DOC activation process, when the estimated temperature (T) of the exhaust upstream DOC (2b) is in the low temperature region (T1) that does not reach the activation temperature region (T5), the engine ECU (5 ), The electric heater (3) is configured to generate heat (S4). The diesel engine according to claim 5, wherein
In the DOC activation process, when the estimated temperature (T) of the exhaust upstream DOC (2b) is lower than the activation temperature range (T5) and in the middle temperature range (T3) higher than the low temperature range (T1), 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 detection of information. In the diesel engine according to claim 5 or 6,
The diesel engine, wherein the electric heater (3) is disposed along the DOC inlet (2a) of the exhaust upstream DOC (2b). In the diesel engine according to any one of claims 5 to 7,
A honeycomb structure (10) is provided on the exhaust upstream side of the exhaust upstream DOC (2b), and the honeycomb structure (10) has a large number of cells (10a) (10b) penetrating in the exhaust passage direction of the exhaust path (1). ), And only the central honeycomb portion (10d) of the honeycomb structure (10) is the electric heater (3). A diesel engine according to claim 8,
A diesel engine characterized in that the central honeycomb portion (10d) constituting the electric heater (3) has a higher cell density than the surrounding honeycomb portion (10e) surrounding the periphery.

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