JP2022090198A - diesel engine - Google Patents

Abstract

To provide a diesel engine capable of regenerating a DPF even during no-load and/or low-load operation.SOLUTION: In DPF regeneration processing, after starting conditions S1 for the regeneration processing of the DPF where PMs are accumulated are established, the opening reduction control S2 of an exhaust throttle valve is performed. When the temperature of exhaust gas is equal to or higher than a predetermined after-injection permission temperature TA, after-injection control is started S5 thereafter, and after the temperature of the exhaust gas is equal to or higher than a predetermined post-injection permission temperature TP with the combustion of after-injection fuel, post-injection control is started S7. The exhaust gas whose temperature is raised by the catalyst combustion of the post injection fuel on a downstream side DOC incinerates the PMs accumulated on the DPF. The exhaust throttle valve is arranged on the exhaust downstream side of the DPF.SELECTED DRAWING: Figure 2

Description

The present invention relates to a diesel engine, and more particularly to a diesel engine capable of regenerating a DPF even during no-load and / or light-load operation.

Conventionally, as a diesel engine, when the DPF regeneration start condition is satisfied by the accumulation of PM, the post-injection control is started after the activation of the DOC, and the exhaust gas is regenerated by the catalytic combustion of the post-injection fuel in the DOC. In some cases, the temperature is raised to a temperature and the PM deposited on the DPF is incinerated (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-151058 (see FIGS. 1 and 2)

<< Problem >> The DPF may not be regenerated during no-load and light-load operation.
In the above-mentioned conventional engine, the opening of the intake throttle valve is narrowed at the start of DPF regeneration, but the efficiency of raising the exhaust gas is low by this alone, and the DOC is not activated during no-load and light-load operation where the exhaust temperature is low. , Post injection cannot be performed, and there is a possibility that the DPF cannot be regenerated.

An object of the present invention is to provide a diesel engine capable of regenerating a DPF even during no-load and / or light-load operation.

The configuration of the present invention is as follows.
As illustrated in FIG. 1, the fuel injection device (3) that injects the fuel (2) into the combustion chamber (1), the DOC (12) arranged in the exhaust path (4), and the exhaust of the DOC (12). The DPF (7) arranged on the downstream side, the exhaust throttle valve (5) arranged on the exhaust downstream side of the DPF (7), the opening degree of the exhaust throttle valve (5), and the fuel of the fuel injection device (3). Equipped with an electronic control device (8) that controls injection
As illustrated in FIG. 2, the DPF (7) is configured to be regenerated.
In the regeneration process of the DPF (7), after the start condition (S1) of the regeneration process of the DPF (7) in which PM is deposited is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed, and the exhaust (9) is exhausted. ) Is at a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), the after-injection control is started (S5), and the exhaust gas (9) is equal to or higher than the predetermined post-injection permitted temperature (TP) due to the combustion of the after-injection fuel. The post-injection control is started (S7) after the temperature is reached, and the exhaust gas (9) heated by the catalytic combustion of the post-injection fuel at the downstream DOC (6) exemplified in FIG. 1 is deposited on the DPF (7). PM is configured to be incinerated

The invention of the present application has the following effects.
<< Effect 1 >> The DPF (7) can be regenerated even during no-load and / or light-load operation.
In this engine, as illustrated in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the back pressure increases due to the decrease in the opening degree of the exhaust throttle valve (5), and after-sales. Since the combustion of the injected fuel occurs, the temperature rise efficiency of the exhaust (9) is higher and the exhaust temperature is lower than in the case of the intake throttle, even during no-load and / or light-load operation, the downstream DOC (exemplified in FIG. 1). 6) is activated and the DPF (7) can be regenerated by post-injection.

<< Effect 2 >> The engine output can be increased.
In this engine, since the exhaust (9) rises due to the combustion of the after-injection fuel, the degree of decrease in the opening degree of the exhaust throttle valve (5) illustrated in FIG. 1 is small, and the output loss due to back pressure is small. The engine output can be increased.

<< Effect 3 >> The reduced catalytic function of DOC (12) can be restored during DPF (7) regeneration.
In this engine, even if unburned deposits consisting of unburned fuel and PM are deposited on the DOC (12) due to the continuation of no-load and / or light-load operation with a low exhaust temperature, the catalytic function thereof is deteriorated. As illustrated in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the exhaust (9) rises due to the decrease in the opening degree of the exhaust throttle valve (5) and the after injection. Upon warming, the unburned deposits are vaporized or burned and the reduced catalytic function of DOC (12) illustrated in FIG. 1 can be restored during regeneration of DPF (7). In addition, since there is no unburned deposit that causes white smoke, the generation of white smoke can be suppressed.

<< Effect 4 >> The regeneration efficiency of the DPF (7) is high.
In this engine, during the regeneration process of the DPF (7), the temperature on the exhaust upstream side of the exhaust throttle valve (5) rises due to the exhaust throttle of the exhaust throttle valve (5), and the temperature of the DPF (7) also rises. The regeneration efficiency of the DPF (7) is high.

It is a schematic diagram of the diesel engine which concerns on embodiment of this invention. It is a flowchart of the regeneration process of the DPF of the engine of FIG. It is a flowchart of the catalytic function recovery process of the downstream side DOC of the engine of FIG. It is a flowchart of the catalytic function recovery process of the upstream side DOC of the engine of FIG.

1 to 4 are views for explaining a diesel engine according to an embodiment of the present invention, and in this embodiment, a common rail type vertical in-line multi-cylinder diesel engine will be described.

The configuration of this engine is as follows.
As shown in FIG. 1, the erection direction of the crank shaft (21) is the front-rear direction, the side where the flywheel (22) is arranged 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. And.
As shown in FIG. 1, this engine has an intake manifold (24) assembled on one lateral side of the cylinder head (23) and an exhaust manifold (25) assembled on the other lateral side of the cylinder head (23). It is equipped with.
As shown in FIG. 1, this engine includes an electronic control device (8).
The electronic control device (8) is an engine ECU. The engine ECU is an abbreviation for an electronic control unit and is a microcomputer.

As shown in FIG. 1, this engine is equipped with an exhaust system.
The exhaust device includes an exhaust manifold (25), an exhaust turbine (26a) of a supercharger (26) connected to the exhaust manifold (25), and an exhaust derived from an exhaust outlet (26b) of the exhaust turbine (26a). It is provided with a lead-out passage (26c).

As shown in FIG. 1, this engine is equipped with an intake system.
The intake device includes a compressor (26d) of a supercharger (26), an intake flow sensor (16) provided on the intake upstream side of the intake inlet (26e) of the compressor (26d), and a supercharge of the compressor (26d). An intercooler (28) arranged between the air outlet (26f) and the intake manifold (24), an intake throttle valve (11) arranged between the intercooler (28) and the intake manifold (24), and an exhaust gas recirculation. It comprises an EGR cooler (30) disposed between the manifold (25) and the intake manifold (24) and an EGR valve (31) disposed between the EGR cooler (30) and the intake manifold (24). EGR is an abbreviation for exhaust gas recirculation.
The intake throttle valve (11) and the EGR valve (31) are both electric on-off valves, and these are electrically connected to the power supply (29) via the electronic control device (8). The intake flow rate sensor (16) includes an intake temperature sensor and is electrically connected to the electronic control device (8). The power source (29) is a battery.

As shown in FIG. 1, this engine is equipped with a common rail type fuel injection device (3).
The fuel injection device (3) includes a fuel injection valve (34) provided in each combustion chamber (1), a common rail (35) for accumulating fuel injected from the fuel injection valve (34), and a common rail (35). Is equipped with a fuel supply pump (37) that pumps fuel from the fuel tank (36).
The fuel injection valve (34) comprises an electromagnetic on-off valve and the fuel supply pump (37) comprises an electric pressure regulating valve, which are electrically connected to a power source (29) via an electronic control device (8). ing.

As shown in FIG. 1, this engine is equipped with a speed governor.
The speed control device includes an accelerator sensor (39) for detecting the set position of the accelerator lever (38) for setting the target rotation speed of the engine, and an actual rotation speed sensor (40) for detecting the actual rotation speed of the engine. The sensors (39) and (40) are electrically connected to the electronic control device (8).

As shown in FIG. 1, this engine is equipped with a starter.
The starting device comprises a starter motor (41) and a key switch (42), and the starter motor (41) and the key switch (42) are electrically connected to a power source (29) via an electronic control device (8). Has been done. The key switch (42) has an OFF position, an ON position, and a start position.

The electronic control device (8) is configured to perform the following operation control.
The fuel injection amount and injection timing from the fuel injection valve (34) 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 rotation speed fluctuation of the engine due to the load fluctuation is reduced.
The opening degrees of the intake throttle valve (11) and the EGR valve (31) are adjusted according to the engine rotation speed, the load, the intake amount, and the intake temperature, and the intake amount and the EGR rate are adjusted.
When the key switch (42) is turned on to the start position, the starter motor (41) is driven to start the engine. When the key switch (42) is turned on to the ON position, the engine operating state is maintained by energizing each part of the engine from the power supply (29), and when the key switch (42) is turned on to the OFF position, the fuel injection valve The fuel injection from (34) is stopped and the engine is stopped.

This engine is equipped with an exhaust treatment device.
As shown in FIG. 1, the exhaust treatment device includes a fuel injection device (3) that injects fuel (2) into a combustion chamber (1), a DOC (12) arranged in an exhaust path (4), and a DOC (. The opening degree of the DPF (7) arranged on the exhaust downstream side of the 12), the exhaust throttle valve (5) arranged on the exhaust downstream side of the DPF (7), the opening degree of the exhaust throttle valve (5), and the fuel injection device ( It is equipped with an electronic control device (8) that controls the fuel injection of 3).

In this engine, during the regeneration process of the DPF (7), the temperature on the exhaust upstream side of the exhaust throttle valve (5) rises due to the exhaust throttle of the exhaust throttle valve (5), and the temperature of the DPF (7) also rises. The regeneration efficiency of the DPF (7) is high.

Each of the above elements will be described.
The combustion chamber (1) shown in FIG. 1 is formed in a cylinder. The fuel (2) is light oil. The exhaust throttle valve (5) is an electric on-off valve, which is electrically connected to the power supply (29) via the electronic control device (8). DOC is an abbreviation for diesel oxidation catalyst, which is a through-flow type in which an oxidation catalyst component such as platinum or palladium is supported on a ceramic honeycomb carrier, and CO (carbon monoxide) and NO (nitric oxide) in the exhaust (9). ) Is oxidized. DPF is an abbreviation for diesel particulate filter, which is a wall flow type that alternately blocks the entrance and exit of adjacent cells of ceramic honeycomb, and captures PM in the exhaust gas (9). PM is an abbreviation for particulate matter.
The DPF (12) includes an upstream DOC (17) and a downstream DOC (6) on the exhaust downstream side of the upstream DOC (17).
The upstream DOC (17) is housed in the upstream DOC case (4b) arranged in the middle of the exhaust path (4), and the downstream DOC (6) and DPF (7) are in the middle of the exhaust path (4). It is housed in the exhaust upstream side and the downstream side of the exhaust treatment case (4a) arranged in the exhaust gas treatment case (4a), respectively.

This DPF system captures the PM in the exhaust (9) with the DPF (7) and oxidizes NO (nitrogen monoxide) in the exhaust (9) with the downstream DOC (6) to obtain NO ₂ (dioxide dioxide). The PM deposited on the DPF (7) is continuously oxidatively combusted at a relatively low temperature with nitrogen), and the unburned fuel supplied to the exhaust (9) by the post injection of the common rail type fuel injection device (3) is used. The PM deposited on the DPF (7) is burned at a relatively high temperature by catalytic combustion in the downstream DOC (6) to regenerate the DPF (7).

This exhaust gas treatment device has the following configuration for the regeneration processing of the DPF (7).
As shown in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) in which PM is deposited is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is subsequently performed. When the exhaust (9) reaches a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), the after-injection control is started (S5) after that, and the exhaust (9) is sent to the predetermined post by combustion of the after-injection fuel. When the temperature becomes higher than the injection permitted temperature (TP), the post injection control is started (S7) after that, and the temperature is raised by the catalytic combustion of the post injection fuel at the downstream DOC (6) shown in FIG. The exhaust gas (9) is configured to incinerate the PM deposited on the DPF (7).

This engine has the following advantages:
As shown in FIG. 2, after the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the back pressure increases due to the decrease in the opening degree of the exhaust throttle valve (5) and the after-injection fuel burns. Compared with the case of throttle, the temperature rise efficiency of the exhaust (9) is high, and the downstream DOC (6) shown in FIG. 1 is activated even during no-load and / or light-load operation where the exhaust temperature is low, and the post injection is performed. , DPF (7) can be reproduced.

Further, in this engine, since the exhaust (9) is heated by the combustion of the after-injection fuel, the degree of decrease in the opening degree of the exhaust throttle valve (5) shown in FIG. 1 is small, and the output loss due to the back pressure is small. , The engine output can be increased.

In this engine, unburned deposits consisting of unburned fuel and PM are deposited on the downstream DOC (6) due to the continuation of no-load and / or light-load operation with low exhaust temperature, and its catalytic function is deteriorated. Even in this case, as shown in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the exhaust (9) is exhausted by the decrease in the opening degree of the exhaust throttle valve (5) or the after injection. The temperature is raised, the unburned deposits are vaporized or burned, and the reduced catalytic function of the downstream DOC (6) shown in FIG. 1 can be restored during the regeneration of DPF (7).

Each element in the case of regeneration of DPF (7) will be described.
As shown in FIG. 2, the start condition (S1) of the regeneration process of the DPF (7) is such that the estimated PM deposition amount (APM) deposited on the DPF (7) is the start determination value (7) of the regeneration process of the DPF (7). RSJ) It is established when it becomes more than. As the PM accumulation amount estimation value (APM), for example, a method of estimation by the PM accumulation amount estimation value calculation device (32) based on the differential pressure (ΔP) between the entrance and exit of the DPF (7) shown in FIG. 1 may be used. be. The PM deposit amount estimation value calculation device (32) is composed of a calculation unit of the electronic control device (8).

The types of injection performed from the fuel injection device (3) during one combustion cycle include blur injection (pilot injection), main injection, after injection, and post injection.
In a four-stroke engine, one combustion cycle consists of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.
The blur injection (pilot injection) is an injection for suppressing the ignition delay of the main injection fuel, and is started during the intake stroke or the compression stroke.
The main injection is the main injection for obtaining output and is started before the compression top dead center.
The after injection is an injection for raising the temperature of the exhaust gas (9), and is started during the expansion stroke after the main injection.
The post injection is an injection for raising the temperature of the exhaust gas (9), and is started during the expansion stroke after the after injection. The post injection may be initiated during the exhaust stroke.

In the case of the regeneration process of the DPF (7) shown in FIG. 2, the after injection is set as follows.
The after-injection allowable temperature (TA) is set to 150 ° C or higher and 700 ° C or lower.
In the after injection control, the inlet side exhaust temperature (T1) of the downstream DOC (6) shown in FIG. 1 is maintained at 400 ° C or higher and 700 ° C or lower (preferably 450 ° C or higher and 500 ° C or lower). Is set to.

The after-injection permit temperature (TA) is a determination temperature for the outlet side exhaust temperature (T0) of the upstream side DOC (17) detected by the upstream side DOC outlet side exhaust temperature sensor (19), and is the upstream side DOC (17). The outlet side exhaust temperature (T0) of) is detected by the upstream side DOC outlet side exhaust temperature sensor (19) and is controlled by adjusting the injection timing and the fuel injection amount by the electronic control device (8).
The inlet side exhaust temperature (T1) of the downstream DOC (6) is detected by the inlet side exhaust temperature sensor (43) of the downstream DOC (6), and the injection timing and fuel injection amount are adjusted by the electronic control device (8). Controlled by.
The inlet side exhaust temperature (T1) of the downstream side DOC (6) may be estimated from the valve upstream side exhaust temperature (T0) detected by the valve upstream side exhaust temperature sensor (19).

The after-injection allowable temperature (TA) is preferably 150 ° C or higher and lower than 250 ° C, and more preferably 150 ° C or higher and lower than 200 ° C.
The reason why the after-injection allowable temperature (TA) may be as low as about 150 ° C. is as follows.
That is, when the exhaust pressure on the upstream side is set to 80 kPa or more and 120 kPa or less (absolute pressure 181.32 kPa or more and 221.23 kPa or less) by the exhaust throttle of the exhaust throttle valve (5), the exhaust pressure is increased. This is because the atmospheric pressure is about twice that of 101.32 kPa, the upstream DOC (17) is activated even at a low temperature of about 150 ° C, and the after-injection fuel oxidation reaction (catalytic combustion) occurs at the upstream DOC (17). be.

In the after-injection, the after-injection fuel whose injection is started in the combustion chamber (1) in the expansion stroke burns with the heat of the exhaust (9), and even when the temperature of the exhaust (9) is low in the no-load and low-load operation. , The exhaust gas (9) is heated to a temperature at which the unburned deposits deposited on the downstream DOC (6) are vaporized or incinerated, and the catalytic function of the downstream DOC (6) lowered by the unburned deposits is restored. At the same time, the downstream DOC (6) is activated.

In the case of the regeneration process of the DPF (7) shown in FIG. 2, the post injection is set as follows.
The post injection permitted temperature (TP) is set to 200 ° C. or higher and 700 ° C. or lower.
The post-injection permit temperature (TP) is set to a temperature higher than the after-injection permit temperature (TA).
In the post injection control, the inlet side exhaust temperature (T1) of the downstream DOC (6) is maintained at 400 ° C or higher and 700 ° C or lower, and the inlet side exhaust temperature (T2) of the DPF (7) is 550 °. It is set to be maintained above C and below 700 ° C. In particular, the inlet side exhaust temperature (T2) of the DPF (7) is preferably set to 700 ° C. or lower in order to prevent abnormal combustion of the accumulated PM.
The post injection permitted temperature (TP) is a determination temperature for the outlet side exhaust temperature (T0) of the upstream side DOC (17) detected by the upstream side DOC outlet side exhaust temperature sensor (19), and is the upstream side DOC (17). The outlet side exhaust temperature (T0) of) is detected by the upstream side DOC outlet side exhaust temperature sensor (19) and is controlled by adjusting the injection timing and the fuel injection amount by the electronic control device (8).
The inlet side exhaust temperature (T2) of the DPF (7) is detected by the DPF inlet side exhaust temperature sensor (27) and is controlled by adjusting the injection timing and the fuel injection amount by the electronic control device (8).
When the outlet side exhaust temperature (T3) of the DPF (7) detected by the DPF outlet side exhaust temperature sensor (33) becomes a temperature equal to or higher than a predetermined upper limit temperature, the control of the electronic control device (8) is performed. As a result, after-injection and post-injection are urgently stopped.
In the post-injection, the post-injection fuel that was started to be injected into the combustion chamber in the expansion stroke or the exhaust stroke is catalytically burned in the downstream DOC (6), the exhaust (9) is heated, and the PM accumulated in the DPF (7). Is incinerated and removed.

As shown in FIG. 1, this engine includes an intake throttle valve (11) arranged in an intake path (10), and the opening degree thereof is controlled by an electronic control device (8). FIG. In the regeneration treatment of the DPF (7) shown in FIG. 3 or the catalytic function recovery treatment of the downstream DOC (6) shown in FIG. 3, after the start condition (S1) of the regeneration treatment of the DPF (7) is satisfied, or in the downstream DOC ( After the start condition (13) of the catalyst function recovery process of 6) is satisfied, the opening degree reduction control (S2) (S15) of the exhaust throttle valve (5) is performed, and the opening degree of the intake throttle valve (11) is performed. The reduction control (S2) (S15) is configured to be performed.
Therefore, in this engine, the intake throttle is performed together with the exhaust throttle, so that the efficiency of raising the temperature of the exhaust (9) is increased by reducing the intake amount.

In this engine, as shown in FIG. 2 or 3, after the opening degree reduction control (S2) (S15) of the exhaust throttle valve (5) is performed, the valve upstream side exhaust pressure (P3) becomes a predetermined pressure upper limit value. When (Pmax) is exceeded, the opening degree increase control (S4-2) (S17-2) of the exhaust throttle valve (5) is subsequently performed.
Therefore, in this engine, excessive boosting of the exhaust pressure on the upstream side of the valve (P3) is suppressed, so that the pressurization does not easily cause the exhaust throttle valve (5) and the parts on the upstream side to break down.
The pressure upper limit value (Pmax) is determined from the specifications of the exhaust throttle valve (5), the EGR valve (31), the supercharger (26), etc. shown in FIG. 1, or the airtightness of the piping of the exhaust path (4).
The exhaust throttle valve (5) is arranged in the middle of the exhaust path (4).
The upper limit of the pressure (Pmax) is preferably 80 kPa or more and 120 kPa or less in gauge pressure, and more preferably 100 kPa.
The valve upstream side exhaust pressure (P3) is detected by the valve upstream side exhaust pressure sensor (44) arranged between the DPF (7) and the exhaust throttle valve (5). The exhaust downstream side of the exhaust throttle valve (5) has an atmospheric pressure. Atmospheric pressure is detected by the atmospheric pressure sensor (14).
The valve upstream exhaust pressure (P3) may be calculated by calculation.

In this engine, as shown in FIG. 1, the DOC (12) includes an upstream DOC (17) and a downstream DOC (6) arranged on the exhaust downstream side of the upstream DOC (17).
In this engine, with no load and / or continued operation, unburned deposits consisting of unburned fuel and PM are deposited on the downstream DOC (6), and the catalytic function of the downstream DOC (6) is deteriorated. Even in this case, as shown in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the after-injection fuel and the post-injection fuel are DOC on the upstream side by the subsequent after-injection and post-injection. Since the catalyst is burned in (17) and the exhaust (9) rises significantly, the unburned deposits are rapidly vaporized or burned, and the downstream DOC (6) shown in FIG. 1 decreases during DPF (7) regeneration. The catalyst function can be restored.
The upstream DOC (17) is housed in an upstream DOC case (4b) arranged in the middle of the exhaust path (4). The upstream DOC outlet side exhaust temperature sensor (19) is arranged at the exhaust outlet of the upstream DOC (17).

In this engine, as shown in FIG. 1, the upstream DOC (17) and the downstream DOC (6) are of a flow-through type in which a catalyst component is supported on a honeycomb carrier through which the exhaust gas (9) passes through the cell. Oxidation catalysts are used.
Therefore, in this engine, as shown in FIG. 1, since a flow-through type oxidation catalyst is used for the upstream DOC (17) and the downstream DOC (6), the output loss due to back pressure is small, and the engine The output can be increased.

In this engine, as shown in FIG. 1, the diameter of the upstream DOC (17) is formed to be smaller than the diameter of the downstream DOC (6).
Therefore, in the engine, the passing speed of the exhaust (9) passing through the cell of the upstream DOC (17) is faster than the passing speed of the exhaust (9) passing through the cell of the downstream DOC (6). Unburned deposits consisting of unburned fuel and PM are unlikely to accumulate on the upstream DOC (17).

In this engine, as shown in FIG. 1, the (overall) cell density of the upstream DOC (17) is formed higher than the cell density of the downstream DOC (6).
Therefore, in this engine, as shown in FIG. 1, the passing speed of the exhaust gas (9) passing through the cell of the upstream DOC (17) is the passing speed of the exhaust gas (9) passing through the cell of the downstream DOC (6). Since the speed is higher than the passing speed, it is difficult for unburned deposits composed of unburned fuel and PM to deposit on the upstream DOC (17).

As shown in FIG. 3, this exhaust gas treatment device is configured to perform the catalytic function recovery treatment of the downstream DOC (6), and in the catalytic function recovery treatment of the downstream DOC (6), unburned fuel or PM. After the start condition (S13) of the catalytic function recovery process of the downstream DOC (6) whose function has deteriorated based on the accumulation of unburned deposits is satisfied, the opening degree reduction control (S15) of the exhaust throttle valve (5) is performed. After the exhaust gas (9) reaches a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), the after-injection control is started (S18), and the exhaust gas (9) whose temperature has been raised by the combustion of the after-injection fuel is on the downstream side. The unburned deposits deposited on the DOC (6) are configured to be vaporized or incinerated.

In this engine, as shown in FIG. 3, the exhaust throttle valve (5) is opened after the start condition (S13) for recovering the catalytic function of the downstream DOC (6) is satisfied, even when the DPF (7) is not regenerated. Due to the decrease in degree and after injection, the exhaust gas (9) rises, the unburned deposits are vaporized or burned, and the reduced catalytic function of the downstream DOC (6) shown in FIG. 1 is restored before the regeneration of the DPF (7). Therefore, it is difficult for the catalytic function to deteriorate. In addition, since there is no unburned deposit that causes white smoke, the generation of white smoke is suppressed.

As shown in FIG. 3, as the start condition (S13) of the catalytic function recovery process of the downstream DOC (6), the integrated value (tL) of the operation time of no load and light load is a predetermined start determination of the catalytic function recovery process. It is established when the value (ISJ) or more is reached. The integrated value (tL) of the operation time of no load and light load is based on the fact that the exhaust temperature (T0) on the outlet side of the upstream DOC (17) is equal to or less than the determination temperature (LJ) of no load and light load operation. , Calculated by the operating time integrating device (18) shown in FIG. The operation time integrating device (18) is composed of a calculation unit of the electronic control device (8).

In the case of the catalytic function recovery treatment of the downstream DOC (6) shown in FIG. 3, the after injection is set as follows.
The after-injection allowable temperature (TA) is set to 150 ° C. or higher and 700 ° C. or lower.
In the after injection control, the inlet side exhaust temperature (T1) of the downstream DOC (6) shown in FIG. 1 is maintained at 180 ° C or higher and 700 ° C or lower (preferably 250 ° C or higher and 300 ° C or lower). Is set to. ((
In the after-injection, the after-injection fuel injected into the combustion chamber in the expansion stroke is burned by the heat of the exhaust (9), and the exhaust (9) is exhausted (9) even when the temperature of the exhaust (9) is low in the no-load and low-load operation. The temperature of the unburned deposits deposited on the downstream DOC (6) is raised to the temperature at which it is vaporized or incinerated, and the catalytic function of the downstream DOC (6) that was lowered by the unburned deposits is restored, resulting in a decrease in the catalytic function. It's hard to progress.

The after-injection allowable temperature (TA) is preferably 150 ° C or higher and lower than 250 ° C, and more preferably 150 ° C or higher and lower than 200 ° C.
The reason why the after-injection allowable temperature (TA) may be as low as about 150 ° C. is as follows.
That is, when the exhaust pressure on the upstream side is set to 80 kPa or more and 120 kPa or less (absolute pressure 181.32 kPa or more and 221.23 kPa or less) by the exhaust throttle of the exhaust throttle valve (5), the exhaust pressure is increased. This is because the atmospheric pressure is about twice that of 101.32 kPa, the upstream DOC (17) is activated even at a low temperature of about 150 ° C, and the after-injection fuel oxidation reaction (catalytic combustion) occurs at the upstream DOC (17). be.

As shown in FIG. 1, this engine is provided with an operation time integrating device (18) for integrating the operating time of no-load and / or light-load operation, and as shown in FIG. 3, no-load and / or light-load. When the integrated value (tL) of the operation time reaches the predetermined start determination value (ISJ) of the catalytic function recovery process, the start condition (S13) of the catalytic function recovery process of the downstream DOC (6) is satisfied. It is configured in.
Therefore, in this engine, improvement of the catalytic function can be started at a time when the probability of deterioration of the catalytic function of the downstream DOC (6) is high, so that unnecessary exhaust throttle and after injection can be eliminated.

As shown in FIG. 4, it is configured so that the catalytic function recovery treatment of the upstream DOC (17) is performed, and in the catalytic function recovery treatment of the upstream DOC (17), unburned deposits composed of unburned fuel and PM. After the condition (S13) for starting the catalytic function recovery process of the upstream DOC (17) whose function has deteriorated based on the accumulation of fuel is satisfied, the opening degree reduction control (S15) of the exhaust throttle valve (5) is performed, and the exhaust (9) is performed. After the temperature reaches the predetermined after-injection permitted temperature (TA) or higher, the after-injection control is started (S18), and the exhaust (9) is at the predetermined post-injection permitted temperature (TP) or higher due to the combustion of the after-injection fuel. Post-injection control is started (S18-3), the post-injection fuel is burned by the combustion heat of the after-injection fuel, and the heat of the heated exhaust (9) shown in FIG. 1 causes the upstream DOC (17). ) Is configured to be vaporized or incinerated.

In this engine, unburned deposits consisting of unburned fuel and PM are deposited on the upstream DOC (17) shown in FIG. 1 by continuing no-load and / or light-load operation with a low exhaust temperature, and its catalytic function is Even if it is lowered, as shown in FIG. 4, when the start condition (S13) for recovering the catalytic function of the upstream DOC (17) is satisfied, the opening degree of the exhaust throttle valve (5) shown in FIG. 1 is satisfied. Due to the decrease, after-injection and post-injection combustion, the temperature of the exhaust (9) rises, and the heat of the exhaust (9) vaporizes or burns the unburned deposits. ) Decreased catalytic function is restored, and it is difficult for the catalytic function to decline. Therefore, the DPF (7) can be regenerated even when no load and / or light load operation is continued. In addition, since there is no unburned deposit that causes white smoke, the generation of white smoke can be suppressed.

In this engine, since the exhaust (9) shown in FIG. 1 rises due to the combustion of the after-injection fuel, the degree of decrease in the opening degree of the exhaust throttle valve (5) is small, the output loss due to back pressure is small, and the engine The output can be increased.

As shown in FIG. 1, this engine is provided with an operation time integrating device (18) that integrates the operating time of no-load and / or light-load operation, and as shown in FIG. 4, no-load and / or light-load. When the integrated value (tL) of the operation time reaches the predetermined start determination value (ISJ) of the catalytic function recovery process, the start condition (S13) of the catalytic function recovery process of the upstream DOC (17) is satisfied. It is configured in.
Therefore, in this engine, the catalytic function recovery process can be started under the condition that the accuracy of the catalytic function deterioration of the upstream DOC (17) shown in FIG. 1 is high, so that unnecessary exhaust throttle, after injection and post injection are eliminated. be able to.

In the start condition (S13) of the catalytic function recovery process of the upstream DOC (17) shown in FIG. 4, the integrated value (tL) of the operation time of no load and / or light load is a predetermined start determination value of the catalytic function recovery process. Not only when (ISJ) is reached, the valve upstream exhaust pressure (P3) shown in FIG. 1 and the number of regeneration processes of the DPF (7) shown in FIG. 1 are set to the start determination values of the predetermined catalytic function recovery process. It may be established when it is reached.
In this engine, in any case, the catalytic function recovery process can be started under the condition that the catalytic function of the upstream DOC (17) is highly likely to deteriorate due to the unburned deposits, so that unnecessary exhaust throttle and after injection can be performed. Post injection can be eliminated.
When the regeneration process of the DPF (7) is set as the start condition (S13), the number of regeneration processes is counted by the electronic control device (8), and the count number of the regeneration processes reaches a predetermined value (for example, 5 times). In that case, the start condition (S13) is satisfied, and when the catalytic function recovery process or the end is completed, the count number of the regeneration process is reset to 0.

In the case of the regeneration process of the DPF (7) shown in FIG. 2, the exhaust temperature (T2) on the inlet side of the DPF (7) is higher than in the case of the catalytic function recovery process of the upstream DOC (17) shown in FIG. It is set to be.
In this engine, in the case of the regeneration process of the DPF (7), the exhaust temperature (T2) on the inlet side of the DPF (7) becomes high, so that the regeneration of the DPF (7) can be reliably performed.

In the case of the regeneration process of the DPF (7) shown in FIG. 2, the injection amount of the after-injection fuel is set to be smaller than in the case of the catalytic function recovery process of the upstream DOC (17) shown in FIG. There is.
In this engine, in the case of DPF (7) regeneration processing, since the injection amount of the after-injection fuel is small, the combustion heat and the post-injection fuel burned by the combustion heat are also small, and many post-injection fuels are upstream. It passes through the side DOC (17) and conducts catalytic combustion in the downstream side DOC (6), so that the inlet side exhaust temperature (T2) of the DPF (7) becomes high. Therefore, the DPF (7) can be reliably regenerated.
Further, in the case of the catalytic function recovery treatment of the upstream DOC (17), since there is a large amount of after-injection fuel, a large amount of post-injection fuel is burned on the upstream side of the upstream DOC (17) due to the combustion heat, and the combustion heat thereof is generated. The unburned deposits deposited on the upstream DOC (17) are vaporized or incinerated by the heat of combustion. Therefore, the catalytic function of the upstream DOC (17) can be reliably restored.

In the case of the regeneration process of the DPF (7) shown in FIG. 2, the injection amount of the post-injection fuel is set to be larger than in the case of the catalytic function recovery process of the upstream DOC (17) shown in FIG. There is.
In this engine, in the case of the DPF (7) regeneration process, the injection amount of the post-injection fuel is large, so that many post-injection fuels pass through the upstream side DOC (17) shown in FIG. 1 and the downstream side DOC (6). ), The exhaust temperature (T2) on the inlet side of the DPF (7) becomes high. Therefore, the DPF (7) can be reliably regenerated.

In this engine, the flow of the regeneration process of the DPF (7) by the electronic control device (8) shown in FIG. 1 is as follows.
As shown in FIG. 2, in step (S1), it is determined whether or not the start condition of the regeneration process of the DPF (7) is satisfied. Specifically, it is determined whether or not the estimated PM accumulation amount (APM) of the DPF (7) becomes a value equal to or higher than the start determination value (RSJ) of the regeneration process of the DPF (7). The PM accumulation amount estimation value (APM) of the DPF (7) is calculated by the PM accumulation amount estimation value calculation device (32) based on the differential pressure (ΔP) between the entrance and exit of the DPF (7) shown in FIG. The PM deposit amount estimation value calculation device (32) is composed of a calculation unit of the electronic control device (8). The PM accumulation amount estimated value (APM) of the DPF (7) may be calculated by a method other than the calculation by the differential pressure (ΔP).
As shown in FIG. 2, the determination in step (S1) is repeated until the determination is affirmed, and if the determination is affirmed, the process proceeds to step (S2).

As shown in FIG. 2, in step (S2), the opening degree reduction control of the intake throttle valve (11) and the opening degree reduction control of the exhaust throttle valve (5) are performed, and the process proceeds to step (S3).
The opening reduction control of the intake throttle valve (11) and the exhaust throttle valve (5) in the step (S2) is performed by the actuator (11a) for driving the intake throttle valve (11) and the actuator for driving the exhaust throttle valve (5). (5a) is controlled by the electronic control device (8).

As shown in FIG. 2, in step (S3), it is determined whether or not the valve upstream exhaust pressure (P3) is equal to or less than the pressure upper limit value (Pmax), and if the determination is affirmative, step (S4-1). ).
In step (S4-1), it is determined whether or not the outlet side exhaust temperature (T0) of the upstream DOC (17) is equal to or higher than the after injection permitted temperature (TA), and if the determination is affirmed, step (S5). ).
In step (S5), after injection control is started, and the process proceeds to step (S6).
If the determination in step (S3) is denied, the process proceeds to step (S4-2), the opening degree increase control of the exhaust throttle valve (5) is performed, and the process proceeds to step (S4-1).
The opening degree increase control of the exhaust throttle valve (5) in the step (S4-2) is performed by controlling the actuator (5a) for driving the exhaust throttle valve (5) by the electronic control device (8).
If the determination in step (S4-1) is denied, the process returns to step (S3).

In step (S6), it is determined whether or not the outlet side exhaust temperature (T0) of the upstream side DOC (17) is equal to or higher than the post injection permitted temperature (TP). The determination in step (S6) is repeated until the determination is affirmed, and when the determination is affirmed, the process proceeds to step (S7).
In step (S7), post injection control is started, and the process proceeds to step (S8).

In step (S8), it is determined whether or not the end condition of the regeneration process of the DPF (7) is satisfied. Specifically, the end condition is that the estimated PM accumulation amount (APM) of the DPF (7) is equal to or less than the end determination value (REJ) of the regeneration process of the DPF (7), and in step (S8). , It is determined whether or not this termination condition is affirmed.
The determination in step (S8) is repeated until the determination is affirmed, and if the determination is affirmed, the process proceeds to step (S9).
In step (S9), the post injection control is terminated, the after injection control is also terminated, and the process proceeds to step (S10).
In step (S10), the intake throttle valve (11) is reset to fully open, and the exhaust throttle valve (5) is also reset to fully open, returning to step (S1).

The PM accumulated amount estimated value (APM) of the DPF (7) in step (S8) is calculated by the PM accumulated amount estimated value calculation device (32) based on the differential pressure (ΔP) between the entrance and exit of the DPF (7). Will be done.
The end condition of the regeneration process of the DPF (7) in the step (S8) is that the inlet side exhaust temperature (T2) of the DPF (7) shown in FIG. 1 maintains a value equal to or higher than the predetermined DPF (7) regeneration process temperature for a predetermined time. It may be done.

In this engine, the flow of the catalytic function recovery processing of the downstream DOC (6) by the electronic control device (8) shown in FIG. 1 is as follows.
As shown in FIG. 3, in step (S11), it is determined whether or not the outlet side exhaust temperature (T0) of the upstream DOC (17) is equal to or lower than the determination temperature (LJ) for no-load and light-load operation. Will be done. The determination in step (S11) is repeated until the determination is affirmed, and when the determination is affirmed, the process proceeds to step (S12).
In step (S11), it may be determined whether or not the inlet side exhaust temperature (T1) of the downstream side DOC (6) becomes a value equal to or lower than the determination temperature (LJ) for no-load or light-load operation.
In step (S12), the no-load and light-load operation times are integrated, and the process proceeds to step (S13).
In step (S13), it is determined whether or not the start condition of the catalytic function recovery process is satisfied. Specifically, when it is determined whether or not the integrated value (tL) of the operation time of no load and light load is equal to or higher than the start determination value (ISJ) of the catalytic function recovery process, and the determination is affirmed. Proceeds to step (S14). If the determination is denied in step (S13), the process returns to step (S11).

In step (S14), the integrated value (tL) of the operation time of no load and light load integrated in step (S12) is reset to 0, the integration of the catalytic function recovery processing time performed after the fact is started, and the integration of the catalytic function recovery processing time performed after the fact is started. Proceed to S15).
In step (S15), the opening degree reduction control of the intake throttle valve (11) and the opening degree reduction control of the exhaust throttle valve (5) are performed, and the process proceeds to step (S16).
The opening degree reduction control of the intake throttle valve (11) and the exhaust throttle valve (5) in the step (S15) is performed in the same manner as in the case of the step (S2).

In step (S16), it is determined whether or not the valve upstream exhaust pressure (P3) is equal to or less than the pressure upper limit value (Pmax), and if the determination is affirmative, the process proceeds to step (S17-1).
In step (S17-1), it is determined whether or not the outlet side exhaust temperature (T0) of the upstream DOC (17) is equal to or higher than the after injection permitted temperature (TA), and if the determination is affirmed, step (S18). ).
In step (S18), after injection control is started, and the process proceeds to step (S19).
If the determination in step (S16) is denied, the process proceeds to step (S17-2), the opening degree increase control of the exhaust throttle valve (5) is performed, and the process proceeds to step (S17-1).
The opening degree reduction control of the exhaust throttle valve (5) in the step (S17-1) is performed in the same manner as in the case of the step (S4-2).
If the determination in step (S17-1) is denied, the process returns to step (S16).

In step (S19), it is determined whether or not the termination condition of the catalytic function recovery process is satisfied. Specifically, it is a termination condition that the integrated value (tI) of the catalytic function recovery processing time becomes a value equal to or higher than the end determination value (IEJ) of the catalytic function recovery processing, and in step (S19), this termination condition is set. Whether or not it is satisfied is determined.
The determination in step (S19) is repeated until the determination is affirmed, and if the determination is affirmed, the process proceeds to step (S20).
In step (S20), after injection control is terminated, and the process proceeds to step (S21).
In the step (S21), the intake throttle valve (11) is reset to the fully open position, and the exhaust throttle valve (5) is also reset to the fully open position. ) Is reset to 0, and the process returns to step (S11). It should be noted that the integrated value (tL) of the operation time of no load and light load in the upper stage of step (S14) may be reset to 0 in step (S21) instead of step (S14).

In this engine, the flow of the catalytic function recovery process of the upstream DOC (17) by the electronic control device (8) shown in FIG. 4 is almost the same as the flow of the catalytic function recovery process of the downstream DOC (6) shown in FIG. I am doing it.
The difference from the flow of FIG. 3 is that the step (S18-2) and the step (S18-3) are set after the step (S18), and the step (S20) is set after the step (S19) instead of the step (S20). The point is that a similar step (S20') is set.
That is, when the after injection control is started in step (S18), the process proceeds to step (S18-2).
In step (S18-2), it is determined whether or not the outlet side exhaust temperature (T0) of the upstream side DOC (17) is equal to or higher than the post injection permitted temperature (TP). The determination in step (S18-2) is repeated until the determination is affirmed, and when the determination is affirmed, the process proceeds to step (S18-3).
In step (S18-3), post injection control is started, and the process proceeds to step (S19).
If it is determined in step (S19) that the end condition of the catalytic function recovery process is satisfied, the process proceeds to step (S20').
In step (S20'), post injection control and after injection control are terminated, and the process proceeds to step (S21).

Each of the processes shown in FIGS. 2 to 4 is executed independently, and none of them are executed at the same time. If any of the processes is started, the other processes are not started until the process is completed. Further, the catalytic function recovery treatment of the downstream DOC (6) in FIG. 3 and the catalytic function recovery treatment of the upstream DOC (17) in FIG. 4 may be alternately performed once, once, and the former and the latter. A plurality of times (for example, 2 times or 3 times) may be alternately performed, or a plurality of times (for example, 2 times or 3 times) of the former and 1 time of the latter may be alternately performed.

The upstream exhaust pressure of the exhaust throttle valve (5) of the above embodiment is actually measured by the exhaust pressure sensor and calculated by calculation, and based on the difference, the exhaust throttle valve (5) fails and the exhaust path (4). ), Failure diagnosis such as gas leakage from), omitting the downstream side DOC (6), or performing post injection with the injection pipe injector arranged at the exhaust inlet of the exhaust downstream side DOC (6). Deformation of the form is also conceivable. When the downstream side DOC (6) is omitted, the DPF (7) with the DOC function is used, and the injection pipe injector is arranged on the exhaust inlet side of the DPF (7) with the DOC function. When the downstream side DOC (6) is omitted, the inlet side exhaust temperature (T2) of the DPF (7) with the DOC function is used instead of the inlet side exhaust temperature (T1) of the downstream side DOC (6).

(1) ... combustion chamber, (2) ... fuel, (3) ... fuel injection device, (4) ... exhaust path, (5) ... exhaust throttle valve, (6) ... downstream DOC, (7) ... DPF, (8) ... Electronic control device, (9) ... Exhaust, (10) ... Intake path, (11) ... Intake throttle valve, (12) ... DOC, (17) ... Upstream DOC, (18) ... Operation time integration Device, (S1) ... DPF regeneration processing start condition, (S2) ... Exhaust gas throttle valve opening reduction control, (S4-2) ... Exhaust gas throttle valve opening increase control, (S5) ... After injection control Start, (S7) ... Post injection control starts, (S20) ... Post injection control starts, (T0) ... Upstream DOC outlet side exhaust temperature, (TA) ... After injection permitted temperature, (TP) ... Post injection Allowed temperature, (P3) ... Exhaust pressure on the upstream side of the valve, (Pmax) ... Pressure upper limit.

Claims (11)

A fuel injection device (3) that injects fuel (2) into the combustion chamber (1), a DOC (12) arranged in the exhaust path (4), and a DPF (12) arranged on the exhaust downstream side of the DOC (12). 7), an exhaust throttle valve (5) arranged on the exhaust downstream side of the DPF (7), and an electronic control device (5) that controls the opening degree of the exhaust throttle valve (5) and the fuel injection of the fuel injection device (3). Equipped with 8)
It is configured so that the DPF (7) regeneration process is performed.
In the regeneration process of the DPF (7), the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed after the start condition (S1) of the regeneration process of the DPF (7) in which PM is deposited is satisfied, and the exhaust gas (9) is exhausted. ) Is above the predetermined after-injection permitted temperature (TA), the after-injection control is started (S5), and the exhaust (9) is equal to or higher than the predetermined post-injection permitted temperature (TP) due to the combustion of the after-injection fuel. The post-injection control is started (S7) after the temperature is reached, and the PM deposited on the DPF (7) is incinerated by the exhaust gas (9) whose temperature has been raised by the catalytic combustion of the post-injection fuel at the downstream DOC (6). A diesel engine characterized by being configured to. In the diesel engine according to claim 1,
The intake throttle valve (11) arranged in the intake path (10) is provided, and the opening degree thereof is configured to be controlled by the electronic control device (8).
In the regeneration process of the DPF (7), after the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the opening reduction control (S2) of the exhaust throttle valve (5) is performed, and the intake throttle valve (11) is performed. ) Is configured to be controlled to reduce the opening degree (S2). In the diesel engine according to claim 1 or 2.
In the regeneration process of the DPF (7), the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed, and when the valve upstream exhaust pressure (P3) exceeds a predetermined pressure upper limit value (Pmax), A diesel engine characterized in that the opening degree increase control (S4-2) of the exhaust throttle valve (5) is subsequently performed. In the diesel engine according to any one of claims 1 to 3.
The DOC (12) is a diesel engine including an upstream DOC (17) and a downstream DOC (6) arranged on the exhaust downstream side of the upstream DOC (17). In the diesel engine according to claim 4,
The upstream DOC (17) and the downstream DOC (6) are characterized in that a flow-through type oxidation catalyst in which a catalyst component is supported on a honeycomb carrier through which the exhaust (9) passes through the cell is used. Diesel engine. In the diesel engine according to claim 4 or 5.
It is configured so that the catalytic function recovery treatment of the downstream DOC (6) is performed.
In the catalytic function recovery treatment of the downstream DOC (6), the start condition (S13) of the catalytic function recovery treatment of the downstream DOC (6) whose function has deteriorated due to the accumulation of unburned deposits consisting of unburned fuel and PM is set. After the establishment, the opening reduction control (S15) of the exhaust throttle valve (5) is performed, and the after injection control is started (S18) after the exhaust (9) reaches a temperature equal to or higher than the predetermined after injection permitted temperature (TA). A diesel engine characterized in that the unburned deposits deposited on the downstream DOC (6) are vaporized or incinerated by the exhaust gas (9) heated by the combustion of the after-injection fuel. In the diesel engine according to claim 6,
Equipped with an operation time integration device (18) that integrates the operation time of no-load and / or light-load operation.
When the integrated value (tL) of the operation time of no load and / or light load reaches the predetermined start determination value (ISJ) of the catalytic function recovery process, the catalytic function recovery process of the downstream DOC (6) is started. A diesel engine characterized in that it is configured so that the condition (S13) is satisfied. In the diesel engine according to any one of claims 4 to 7.
It is configured so that the catalytic function recovery treatment of the upstream DOC (17) is performed.
In the catalytic function recovery treatment of the upstream DOC (17), the start condition (S13) of the catalytic function recovery treatment of the upstream DOC (17) whose function has deteriorated due to the accumulation of unburned deposits consisting of unburned fuel and PM is set. After the establishment, the opening reduction control (S15) of the exhaust throttle valve (5) is performed, and the after injection control is started (S18) after the exhaust (9) reaches a temperature equal to or higher than the predetermined after injection permitted temperature (TA). Post-injection control is started (S18-3) after the exhaust (9) reaches a temperature equal to or higher than the predetermined post-injection permitted temperature (TP) due to the combustion of the after-injection fuel, and the post-injection fuel is generated by the combustion heat of the after-injection fuel. A diesel engine characterized in that the unburned deposits deposited on the upstream DOC (17) are vaporized or incinerated by the heat of the exhaust (9) that has been burned and heated. In the diesel engine according to claim 8,
Equipped with an operation time integration device (18) that integrates the operation time of no-load and / or light-load operation.
When the integrated value (tL) of the operation time of no load and / or light load reaches the predetermined start determination value (ISJ) of the catalytic function recovery process, the catalytic function recovery process of the upstream DOC (17) is started. A diesel engine characterized in that it is configured so that the condition (S13) is satisfied. In the diesel engine according to claim 8 or 9.
When the valve upstream side exhaust pressure (P3) reaches a predetermined catalytic function recovery processing start determination value, the catalyst function recovery processing start condition (S13) of the upstream DOC (17) is configured to be satisfied. A diesel engine characterized by being. In the diesel engine according to any one of claims 8 to 10.
When the number of regeneration processes of the DPF (6) reaches the predetermined start determination value (ISJ) of the catalytic function recovery process, the start condition (S13) of the catalytic function recovery process of the upstream DOC (17) is satisfied. The diesel engine is characterized by being configured in.

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