JP2022090200A - 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. After the temperature of exhaust gas is equal to or higher than a predetermined after-injection permission temperature TA, after-injection control of a fuel injection device is started S5, and after the temperature of the exhaust gas is equal to or higher than a predetermined exhaust pipe injection permission temperature TP with the combustion of after-injection fuel injected from an exhaust pipe injector into an exhaust pipe, exhaust pipe injection control is started S7. The exhaust gas whose temperature is raised by the catalyst combustion of the exhaust pipe injection fuel injected from the exhaust pipe injector into the exhaust pipe on a valve downstream side DOC incinerates the PMs accumulated on 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) and the fuel (2) in the exhaust pipe (4) on the exhaust downstream side of the combustion chamber (1). The exhaust pipe injector (3a) for injecting fuel, the exhaust throttle valve (5) arranged in the exhaust pipe (4), the valve downstream side DOC (6) arranged on the exhaust downstream side thereof, and the exhaust downstream side thereof. The DPF (7) arranged in the above, the opening degree of the exhaust throttle valve (5), the fuel injection device (3), and the electronic control device (8) for controlling the fuel injection of the exhaust pipe injector (3a) are provided.
As illustrated in FIG. 2, the DPF (7) is configured to be regenerated.
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 (9). ) Is at a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), the after-injection control of the fuel injection device (3) is started (S5), and the exhaust (9) is exhausted by the combustion of the after-injection fuel. Exhaust pipe injection control is started (S7) after the temperature reaches the injection permitted temperature (TP) or higher, and the exhaust pipe injection fuel injected from the exhaust pipe injector (3a) illustrated in FIG. 1 into the exhaust pipe (4). The PM deposited in the DPF (7) is incinerated by the exhaust gas (9) whose temperature has been raised by the catalytic combustion in the DOC (6) on the downstream side of the valve.

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 valve downstream side DOC exemplified in FIG. (6) is activated, and the DPF (7) can be regenerated by the exhaust pipe 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 the valve downstream DOC (6) can be restored during DPF (7) regeneration.
In this engine, unburned deposits consisting of unburned fuel and PM are deposited on the DOC (6) on the downstream side of the valve due to the continuation of no-load and / or light-load operation with a low exhaust temperature, and its catalytic function deteriorates. Even if the exhaust gas is present, as illustrated in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the opening of the exhaust throttle valve (5) is reduced or the after injection is performed to exhaust the exhaust gas (9). ) Raises the temperature, the unburned deposit is vaporized or burned, and the reduced catalytic function of the valve downstream DOC (6) exemplified in FIG. 1 can be restored during the regeneration of the 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 heating efficiency of the exhaust gas (9) is high.
Compared to the case where the structure different from this engine, that is, the exhaust throttle valve (5) is arranged on the exhaust downstream side of the DPF (7), in this engine, as illustrated in FIG. 1, the exhaust throttle valve (5) Is located on the upstream side of the exhaust gas from the DPF (7), so that the volume of the exhaust pipe (4) on the upstream side of the exhaust gas of the exhaust throttle valve (5) becomes small, and the opening degree of the exhaust throttle valve (5) decreases. The exhaust pressure (P0) on the upstream side of the valve is rapidly increased, and the temperature rise efficiency of the exhaust (9) is high.

<< Effect 5 >> It is difficult for the valve noise of the exhaust throttle valve (5) to be emitted to the outside of the exhaust pipe (4).
In this engine, as illustrated in FIG. 1, since the valve downstream side DOC (6) and the DPF (7) are arranged on the exhaust downstream side of the exhaust throttle valve (5), the valve noise of the exhaust throttle valve (5) Sound is hard to be emitted to the outside of the exhaust pipe (4).

<< Effect 6 >> Oil dilution is suppressed.
In post-injection, which injects fuel into the cylinder, the fuel adhering to the cylinder mixes with the engine oil and oil dilution occurs. The engine is suppressed.

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 processing of the valve downstream side DOC (or valve upstream side DOC) of the engine of FIG. The relational expression used for calculating the valve upstream side exhaust pressure (P0) of the engine of FIG. , Equation 2 is a relational expression such as the mass flow rate (G) of the exhaust (9) and the volume flow rate (V) of the exhaust, and Equation 3 is the volume flow rate (V) of the exhaust (9) and the mass flow rate (G) of the exhaust (9). ) And the fuel injection amount (Q), etc., and equation 4 is a relational expression between the valve downstream exhaust pressure (P1) and the differential pressure (ΔP) between the atmospheric pressure (P3) and the entrance / exit of the DPF (7).

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 is provided in a fuel injection device (3) for injecting fuel (2) into a combustion chamber (1) and in an exhaust pipe (4) on the exhaust downstream side of the combustion chamber (1). An exhaust pipe injector (3a) for injecting fuel (2), an exhaust throttle valve (5) arranged in the exhaust pipe (4), and a valve downstream side DOC (6) arranged on the exhaust downstream side thereof. The DPF (7) arranged on the downstream side of the exhaust, the opening degree of the exhaust throttle valve (5), the fuel injection device (3), and the electronic control device (8) for controlling the fuel injection of the exhaust pipe injector (3a) are provided. I have.
The exhaust pipe injector (3a) is connected to the common rail (35) and is controlled to open and close by the electronic control device (8).
The exhaust pipe injector (3a) may be connected to a fuel injection mechanism (for example, a fuel injection pump) different from the common rail (35). The fuel injection valve (34) may also be connected to a fuel injection mechanism (for example, a fuel injection pump) that is not a common rail type.

Compared to the case where the exhaust throttle valve (5) is arranged on the exhaust downstream side of the DPF (7), which is different from this engine, in this engine, the exhaust throttle valve (5) is provided as shown in FIG. Since it is located on the exhaust upstream side of the DPF (7), the volume of the exhaust pipe (4) on the exhaust upstream side of the exhaust throttle valve (5) becomes smaller, and the valve is reduced by reducing the opening degree of the exhaust throttle valve (5). The upstream exhaust pressure (P0) is rapidly increased, and the temperature rise efficiency of the exhaust (9) is high.
Further, in this engine, as shown in FIG. 1, since the valve downstream side DOC (6) and the DPF (7) are arranged on the exhaust downstream side of the exhaust throttle valve (5), the valve of the exhaust throttle valve (5). It is difficult for the noise to be emitted to the outside of the exhaust pipe (4).
Further, in the post injection in which the fuel is injected into the cylinder, the fuel adhering to the cylinder is mixed with the engine oil and oil dilution occurs. However, in this engine, the exhaust pipe injection is performed instead of the post injection, so the oil Dilution is suppressed.

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 valve downstream side DOC (6) and DPF (7) are housed in the exhaust upstream side and the exhaust downstream side of the exhaust treatment case (4a) arranged in the middle of the exhaust pipe (4), 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 DOC (6) on the downstream side of the valve to obtain NO ₂ ( The PM deposited on the DPF (7) is continuously oxidatively combusted at a relatively low temperature with nitrogen dioxide), and is not supplied to the exhaust (9) by the exhaust pipe injection fuel injected from the exhaust pipe injector (3a). The fuel fuel is catalytically burned at the DOC (6) on the downstream side of the valve, and the PM deposited on the DPF (7) is burned at a relatively high temperature 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, 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. ) Is performed, and after the exhaust (9) reaches a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), the after-injection control of the fuel injection device (3) is started (S5), and the exhaust (S5) is exhausted by the combustion of the after-injection fuel. Exhaust pipe injection control is started (S7) after 9) reaches a temperature equal to or higher than a predetermined exhaust pipe injection permitted temperature (TP), and the exhaust pipe injector (3a) illustrated in FIG. 1 is inserted into the exhaust pipe (4). The PM deposited in the DPF (7) is incinerated by the exhaust gas (9) whose temperature has been raised by the catalytic combustion at the DOC (6) on the downstream side of the valve of the injected exhaust pipe injection fuel.

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 even during no-load and / or light-load operation where the exhaust temperature is low, the valve downstream side DOC (6) shown in FIG. 1 is activated and the exhaust pipe. DPF (7) can be regenerated by injection.

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 DOC (6) on the downstream side of the valve due to the continuation of no-load and / or light-load operation with a low exhaust temperature, and its catalytic function deteriorates. Even if it is, as shown in FIG. 2, when the start condition (S1) of the regeneration process of the DPF (7) is satisfied, the opening of the exhaust throttle valve (5) is reduced or the after injection is performed to exhaust (9). The temperature rises, the unburned deposits are vaporized or burned, and the reduced catalytic function of the valve downstream DOC (6) shown in FIG. 1 can be restored during DPF (7) regeneration.

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, and after 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 exhaust pipe injection is an injection for raising the temperature of the exhaust (9), and is injected from the exhaust pipe injector (3a).

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 valve downstream side DOC (6) shown in FIG. 1 is maintained at 400 ° C or higher and 700 ° C or lower (preferably 450 ° or higher and 500 ° or lower). Is set to.

The after-injection permit temperature (TA) is a determination temperature for the valve upstream side exhaust temperature (T0) detected by the valve upstream side exhaust temperature sensor (19), and the valve upstream side exhaust temperature (T0) is the valve upstream side exhaust gas temperature (T0). It is detected by the exhaust temperature sensor (19) and controlled by the adjustment of the injection timing and the fuel injection amount by the electronic control device (8).
The inlet side exhaust temperature (T1) of the valve downstream side DOC (6) is detected by the DOC inlet side exhaust temperature sensor (43) 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 valve downstream side DOC 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. It becomes about twice the atmospheric pressure 101.32 kPa, the valve upstream side 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 valve upstream side DOC (17). Because.

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 the temperature at which the unburned deposits deposited on the valve downstream DOC (6) are vaporized or incinerated, and the catalytic function of the valve downstream DOC (6) lowered by the unburned deposits As it recovers, the valve downstream DOC (6) is activated.

In the case of the regeneration process of the DPF (7) shown in FIG. 2, the exhaust pipe injection is set as follows.
The exhaust pipe injection permitted temperature (TP) is set to 200 ° C. or higher and 700 ° C. or lower.
The exhaust pipe injection permitted temperature (TP) is set to a temperature higher than the after injection permitted temperature (TA).
In the exhaust pipe injection control, the inlet side exhaust temperature (T1) of the valve downstream side 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 maintained. It is set to be maintained at 550 ° C or higher and 700 ° C or lower. 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 exhaust pipe injection permitted temperature (TP) is a determination temperature for the valve upstream side exhaust temperature (T0) detected by the valve upstream side exhaust temperature sensor (19), and the valve upstream side exhaust temperature (T0) is the valve upstream side exhaust temperature (T0). It is detected by the side exhaust temperature sensor (19) and controlled by the electronic control device (8).
The inlet side exhaust temperature (T1) of the valve downstream side DOC is determined by the injection timing by the electronic control device (8) according to the valve upstream side exhaust temperature (T0) detected by the valve upstream side exhaust temperature sensor (19). It is controlled by adjusting the fuel injection amount.
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 DPF outlet side exhaust temperature (T3) detected by the DPF outlet side exhaust temperature sensor (33) reaches a temperature equal to or higher than a predetermined upper limit temperature, after injection or after injection is performed under the control of the electronic control device (8). Exhaust pipe injection is stopped urgently.
In the exhaust pipe injection, the exhaust pipe injection fuel that has been started to be injected into the exhaust pipe (4) is catalytically burned at the DOC (6) on the downstream side of the valve, the exhaust (9) is heated, and is accumulated in the DPF (7). PM 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 valve downstream side DOC (6) shown in FIG. 3, after the start condition (S1) of the regeneration treatment of the DPF (7) is satisfied, or on the valve downstream side. After the start condition (13) of the catalytic function recovery process of the DOC (6) is satisfied, the opening degree reduction control (S2) (S15) of the exhaust throttle valve (5) is performed, and the intake throttle valve (11) is operated. It is configured so that the opening degree reduction control (S2) (S15) is 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 (P0) 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 (P0) 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 exhaust pipe (4).
The exhaust throttle valve (5) is arranged in the middle of the exhaust pipe (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.

As shown in FIG. 1, this engine includes a calculation device (12) for the valve upstream side exhaust pressure (P0), and as shown in FIG. 4, the valve upstream side exhaust pressure (P0) is the exhaust (9). It is configured to be calculated from the mass flow rate (G), the valve upstream side exhaust temperature (T0), and the valve downstream side exhaust pressure (P1). The arithmetic unit (12) of the valve upstream exhaust pressure (P0) is composed of the arithmetic unit of the electronic control device (8).

In this engine, as shown in FIG. 4, since the exhaust pressure (P0) on the upstream side of the valve can be accurately calculated from the mass flow rate (G) of the exhaust (9) and the like, the exhaust throttle valve (5) shown in FIG. Control accuracy can be increased.

In this engine, the exhaust pressure on the upstream side of the valve (P0) may be detected by an exhaust pressure sensor arranged on the upstream side of the exhaust of the exhaust throttle valve (5). In this case, since the exhaust pressure (P0) on the upstream side of the valve can be quickly detected, the control accuracy of the exhaust throttle valve (5) shown in FIG. 1 can be improved.

When calculating the valve upstream exhaust pressure (P0) by calculation, the following relational expression can be used.
The valve upstream exhaust pressure (P0) is calculated from the mass flow rate (G) of the exhaust (9), the valve upstream exhaust temperature (T0), and the valve downstream exhaust pressure (P1) according to Equation 1 in FIG. Can be calculated.
The mass flow rate (G) of the exhaust gas (9) can be calculated by calculation from the density (ρ0) of the exhaust gas (9) and the volume flow rate (V) of the exhaust gas (9) by the equation 2 of FIG.
The volumetric flow rate (V) of the exhaust (9) can be calculated by calculation from the mass flow rate (G) of the exhaust (9), the fuel injection amount (Q), and the like according to the formula 3 of FIG.
The fuel injection amount (Q) is the fuel injection amount obtained by adding the blur injection (pilot injection), the main injection, the after injection, and the exhaust pipe injection per second.

Since the intake flow rate can be used as a substitute value for the exhaust flow rate, it was measured by the intake flow rate sensor (16) instead of the precise calculation of the volume flow rate (V) of the exhaust (9) in FIG. The calculation of Equation 2 may be performed by regarding the intake flow rate as the volumetric flow rate (V) of the exhaust (9).

In this engine, as shown in FIG. 1, a differential pressure sensor (13) for detecting the differential pressure (ΔP) between the entrance and exit of the DPF (7) and an atmospheric pressure sensor (14) for detecting the atmospheric pressure (P3) are used. As shown in Equation 4 of FIG. 4, the valve downstream exhaust pressure (P1) is configured to be calculated from the differential pressure (ΔP) between the inlet and outlet of the DPF (7) and the atmospheric pressure (P3). Has been done.

In this engine, as shown in FIG. 4, the exhaust pressure on the downstream side of the valve (P1) can be accurately calculated from the differential pressure (ΔP) between the entrance and exit of the DPF (7) and the atmospheric pressure (P3). The control accuracy of the exhaust throttle valve (5) shown in the above can be improved.

In this engine, the exhaust pressure on the downstream side of the valve (P1) may be detected by the exhaust pressure sensor arranged on the downstream side of the exhaust of the exhaust throttle valve (5). In this case, since the exhaust pressure (P1) on the downstream side of the valve can be quickly detected, the control accuracy of the exhaust throttle valve (5) shown in FIG. 1 can be improved.

As shown in FIG. 1, this engine is provided with a valve upstream side exhaust temperature sensor (19), and as shown in FIG. 4, the valve upstream side exhaust temperature (T0) detected by the sensor is the valve upstream side exhaust pressure. In addition to being used in the calculation of (P0), as shown in FIG. 2, it is also used in the temperature comparison determination between the after injection permitted temperature (TA) and the exhaust pipe injection permitted temperature (TP).

In this engine, the number of sensors can be reduced because the above calculation and the comparison determination are performed using the valve upstream side exhaust temperature (T0) detected by the single valve upstream side exhaust temperature sensor (19).

In this engine, the exhaust pressure on the upstream side of the valve (P0) is detected by the exhaust pressure sensor exhausted to the upstream side of the exhaust of the exhaust throttle valve (5), and the exhaust temperature sensor on the upstream side of the valve is used for comparison determination of the after-injection allowable temperature (TA). The detected temperature of (19) may be used, and the detected temperature of the exhaust gas temperature sensor on the downstream side of the valve may be used for the comparison determination of the exhaust pipe injection permitted temperature (TP). In this case, the detection of the valve upstream exhaust pressure (P0), the comparison determination of the after injection allowable temperature (TA), and the comparison determination of the exhaust pipe injection allowable temperature (TP) can be performed quickly.

As shown in FIG. 1, this engine includes a valve upstream side DOC (17) arranged on the exhaust upstream side of the exhaust throttle valve (5).
In this engine, with no load and / or continued operation, unburned deposits consisting of unburned fuel and PM are deposited on the valve downstream side DOC (6), and the catalytic function of the valve downstream side DOC (6) deteriorates. Even if this is the case, as shown in FIG. 2, if the start condition (S1) for the regeneration process of the DPF (7) is satisfied, the after-injection fuel is DOC (17) on the upstream side of the valve due to the subsequent after-injection. Since the exhaust (9) is significantly heated by the catalyst combustion, the unburned deposits are rapidly vaporized or burned, and the reduced catalytic function of the valve downstream DOC (6) shown in FIG. 1 during DPF (7) regeneration. Can be recovered.
The valve upstream side DOC (17) is housed in a valve upstream side DOC case (4b) arranged in the middle of the exhaust pipe (4). The valve upstream side exhaust temperature sensor (19) is arranged between the valve upstream side DOC (17) and the exhaust throttle valve (5).

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

In this engine, as shown in FIG. 1, the diameter of the valve upstream side DOC (17) is formed to be smaller than the diameter of the valve downstream side DOC (6).
Therefore, in the engine, the passing speed of the exhaust gas (9) passing through the cell of the valve upstream DOC (17) is faster than the passing speed of the exhaust gas (9) passing through the cell of the valve downstream DOC (6). Therefore, it is difficult for unburned deposits composed of unburned fuel and PM to accumulate on the DOC (17) on the upstream side of the valve.

In this engine, as shown in FIG. 1, the (overall) cell density of the valve upstream DOC (17) is formed higher than the cell density of the valve 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 valve upstream side DOC (17) is the exhaust gas (9) passing through the valve downstream side DOC (6) cell. ) Is faster than the passing speed, so that unburned deposits consisting of unburned fuel and PM are unlikely to deposit on the DOC (17) on the upstream side of the valve.

As shown in FIG. 3, this exhaust gas treatment device is configured so that the catalytic function recovery treatment of the valve downstream side DOC (6) is performed, and in the catalytic function recovery treatment of the valve downstream side DOC (6), the unburned fuel is used. Control to reduce the opening of the exhaust throttle valve (5) after the conditions (S13) for starting the catalytic function recovery process of the valve downstream DOC (6) whose function has deteriorated due to the accumulation of unburned deposits consisting of fuel and PM are satisfied. After S15) is performed and the exhaust (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 (9) is heated by the combustion of the after-injection fuel. , The unburned deposits deposited on the valve downstream DOC (6) are configured to be vaporized or incinerated.

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

As shown in FIG. 3, the start condition (S13) of the catalytic function recovery process of the valve downstream side DOC (6) is the start of the catalytic function recovery process in which the integrated value (tL) of the operation time of no load and light load is predetermined. It is established when the judgment value (ISJ) or more is reached. The integrated value (tL) of the operation time of no load and light load is the operation shown in FIG. 1 based on the fact that the exhaust gas temperature (T0) on the upstream side of the valve is equal to or less than the determination temperature (LJ) of no load and light load operation. Calculated by the time integration device (18). 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 valve downstream side 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 valve downstream side 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 side DOC (6) of the valve is raised to the temperature at which it is vaporized or incinerated, and the catalytic function of the downstream side DOC (6) of the valve, which has decreased due to the unburned deposits, is restored and the catalytic function is increased. It is difficult for the decline 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. It becomes about twice the atmospheric pressure 101.32 kPa, the valve upstream side 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 valve upstream side DOC (17). Because.

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 a predetermined start determination value (ISJ) of the catalytic function recovery process, the start condition (S13) of the catalytic function recovery process of the valve downstream side DOC (6) is satisfied. It is configured as follows.
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 DOC (6) on the downstream side of the valve is high, so that unnecessary exhaust throttle and warm air injection can be eliminated.

As shown in FIG. 1, a valve upstream side DOC (17) arranged on the exhaust upstream side of the exhaust throttle valve (5) is provided, and as shown in FIG. 3, a catalytic function recovery process of the valve downstream side DOC (6) is provided. In the same procedure as above, the catalytic function recovery treatment of the valve upstream side DOC (17) is configured to be performed, and in the catalytic function recovery treatment of the valve upstream side DOC (17), unburned deposition consisting of unburned fuel and PM is performed. After the start condition (S13) of the catalytic function recovery process of the valve upstream side DOC (17) whose function has deteriorated due to the accumulation of an object is satisfied, the opening degree reduction control (S15) of the exhaust throttle valve (5) is performed and the exhaust (S15) is performed. After injection control is started (S18) after 9) reaches a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), and the heat of the exhaust (9) raised by the combustion of the after-injection fuel causes the valve upstream side DOC. The unburned deposits deposited in (17) are configured to be vaporized or incinerated.

In this engine, unburned deposits consisting of unburned fuel and PM are deposited on the DOC (17) on the upstream side of the valve shown in FIG. 1 by continuing no-load and / or light-load operation with a low exhaust temperature, and its catalytic function. As shown in FIG. 3, when the start condition (S13) for recovering the catalytic function of the valve upstream side DOC (17) is satisfied, the exhaust throttle valve (5) shown in FIG. The temperature of the exhaust (9) rises due to the decrease in opening and the combustion of the after-injection, 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. 3, the no-load and / or light-load operation. When the integrated value (tL) of the operation time reaches a predetermined start determination value (ISJ) of the catalytic function recovery process, the start condition (S13) of the catalytic function recovery process of the valve upstream DOC (17) is satisfied. It is configured as follows.
Therefore, in this engine, the catalytic function recovery process can be started under the condition that the catalytic function of the valve upstream DOC (17) is highly likely to deteriorate as shown in FIG. It can be eliminated.

As for the start condition (S13) of the catalytic function recovery process of the valve upstream side DOC (17) shown in FIG. 3, the integrated value (tL) of the operation time of no load and / or light load is a predetermined start determination of the catalytic function recovery process. Not only when the value (ISJ) is reached, the valve upstream exhaust pressure (P0) shown in FIG. 1 and the number of regeneration processes of the DPF (7) shown in FIG. 1 are the start determination values of the predetermined catalytic function recovery process. It may be established when it reaches.
In this engine, in any case, the catalytic function recovery process can be started under the condition that the catalytic function of the valve upstream DOC (17) is highly likely to deteriorate due to unburned deposits, so that wasteful exhaust throttle and after-injection can be started. And 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.

Differences between DPF (7) regeneration and catalytic function recovery In the case of the DPF (7) regeneration treatment shown in FIG. 2, the catalytic function recovery treatment of the valve upstream DOC (17) shown in FIG. 3 is higher than in the case of the catalytic function recovery treatment. The inlet side exhaust temperature (T2) of the DPF (7) is set to be high.
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 valve upstream DOC (17) shown in FIG. ing.
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 exhaust pipe injection fuel burned by the combustion heat are also small, and many exhaust pipe injection fuels. Passes through the valve downstream DOC (6) and burns at the DPF (7). Therefore, the DPF (7) can be reliably regenerated.
Further, in the case of the catalytic function recovery treatment of the valve upstream side DOC (17), since there is a large amount of after-injection fuel, the unburned deposits deposited on the valve upstream side DOC (17) are vaporized or incinerated by the combustion heat. .. Therefore, the catalytic function of the DOC (17) on the upstream side of the valve can be reliably restored.

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 (P0) 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 valve upstream side exhaust temperature (T0) is equal to or higher than the after-injection permitted temperature (TA), and if the determination is affirmed, the process proceeds to 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 valve upstream side exhaust temperature (T0) is equal to or higher than the exhaust pipe 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), exhaust pipe 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 exhaust pipe injection control is terminated, the warm air pipe 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 valve downstream side DOC (6) or the valve upstream side DOC (17) 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 valve upstream side exhaust temperature (T0) has become a value equal to or lower than the determination temperature (LJ) for no-load and light-load operation. 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 valve 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 (P0) 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 valve upstream side exhaust temperature (T0) is equal to or higher than the after injection permitted temperature (TA), and if the determination is affirmed, the process proceeds to 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).

Each of the processes shown in FIGS. 2 and 3 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 valve downstream side DOC (6) and the catalytic function recovery treatment of the valve upstream side DOC (17) in FIG. 3 may be alternately performed once, once, and a plurality of the latter. The times (for example, 2 times or 3 times) may be alternately performed, or the former multiple times (for example, 2 times or 3 times) and the latter 1 time 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). ), Or the exhaust throttle valve (5) is placed on the exhaust downstream side of the DPF (7), or the valve downstream side DOC (6) is omitted, and the injection pipe injector is It is also possible to modify the embodiment, such as arranging it on the exhaust inlet side of the DPF (7) having a DOC function. When the valve 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 valve downstream side DOC (6). ..

(1) ... Combustion chamber, (2) ... Fuel, (3) ... Fuel injection device, (3a) ... Exhaust pipe injector, (4) ... Exhaust pipe, (5) ... Exhaust throttle valve, (6) ... Valve downstream Side DOC, (7) ... DPF, (8) ... Electronic control device, (9) ... Exhaust, (10) ... Intake path, (11) ... Intake throttle valve, (12) ... Valve upstream side exhaust pressure calculation device , (13) ... differential pressure sensor, (14) ... atmospheric pressure sensor, (15) ... exhaust flow rate calculator, (16) ... intake flow rate sensor, (17) ... valve upstream side DOC, (18) ... operation time Integrator, (19) ... Valve upstream exhaust temperature sensor, (20) ... Intake, (S1) ... DPF regeneration processing start condition, (S2) ... Exhaust throttle valve opening reduction control, (S4-2) ... Exhaust throttle valve opening increase control, (S5) ... After injection control started, (S7) ... Exhaust injection control started, (S20) ... Exhaust pipe injection control started, (T0) ... Valve upstream side exhaust temperature , (TA) ... After injection permitted temperature, (TP) ... Exhaust pipe injection permitted temperature, (P0) ... Valve upstream side exhaust pressure, (Pmax) ... Pressure upper limit value, (G) ... Exhaust mass flow rate, (P1) ... Exhaust pressure on the downstream side of the valve, (ΔP) ... Differential pressure, (P3) ... Atmospheric pressure.

Claims (14)

A fuel injection device (3) that injects fuel (2) into the combustion chamber (1) and an exhaust pipe injector (3a) that injects fuel (2) into the exhaust pipe (4) on the exhaust downstream side of the combustion chamber (1). ), The exhaust throttle valve (5) arranged in the exhaust pipe (4), the valve downstream side DOC (6) arranged on the exhaust downstream side thereof, and the DPF (7) arranged on the exhaust downstream side thereof. And an electronic control device (8) that controls the opening degree of the exhaust throttle valve (5) and the fuel injection of the fuel injection device (3) and the exhaust pipe injector (3a).
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 (9). ) Is at a temperature equal to or higher than the predetermined after-injection permitted temperature (TA), the after-injection control of the fuel injection device (3) is started (S5), and the exhaust (9) is exhausted by the combustion of the after-injection fuel. Exhaust pipe injection control is started (S7) after the temperature reaches the injection permitted temperature (TP) or higher, and the DOC (DOC) on the downstream side of the valve of the exhaust pipe injection fuel injected from the exhaust pipe injector (3a) into the exhaust pipe (4). A diesel engine characterized in that the PM deposited in the DPF (7) is incinerated by the exhaust gas (9) whose temperature has been raised by the catalytic combustion in 6). 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 (P0) 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 claim 3,
A calculation device (12) for the valve upstream side exhaust pressure (P0) is provided, and the valve upstream side exhaust pressure (P0) includes the mass flow rate (G) of the exhaust (9), the valve upstream side exhaust temperature (T0), and the valve. A diesel engine characterized in that it is configured to be calculated from the downstream exhaust pressure (P1). In the diesel engine according to claim 4,
A differential pressure sensor (13) for detecting the differential pressure (ΔP) between the entrance and exit of the DPF (7) and an atmospheric pressure sensor (14) for detecting the atmospheric pressure (P3) are provided.
A diesel engine characterized in that the valve downstream exhaust pressure (P1) is configured to be calculated from the differential pressure (ΔP) between the entrance and exit of the DPF (7) and the atmospheric pressure (P3). In the diesel engine according to claim 4 or 5.
A valve upstream side exhaust temperature sensor (19) is provided, and the valve upstream side exhaust temperature (T0) detected by the valve upstream side exhaust temperature sensor (19) is used in the calculation of the valve upstream side exhaust pressure (P0), and the after injection allowable temperature (TA) is used. ) And the diesel engine used for the temperature comparison determination with the exhaust pipe injection permitted temperature (TP). In the diesel engine according to any one of claims 1 to 6.
A diesel engine characterized by having a valve upstream side DOC (17) arranged on the exhaust upstream side of the exhaust throttle valve (5). In the diesel engine according to claim 7.
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 for the valve upstream side DOC (17) and the valve downstream side DOC (6). Diesel engine featuring. In the diesel engine according to any one of claims 1 to 8.
It is configured so that the catalytic function recovery treatment of the valve downstream DOC (6) is performed.
In the catalytic function recovery treatment of the valve downstream side DOC (6), the start condition (S13) of the catalytic function recovery treatment of the valve downstream side DOC (6) whose function has deteriorated due to the accumulation of unburned deposits consisting of unburned fuel and PM. ) Is satisfied, the opening reduction control (S15) of the exhaust throttle valve (5) is performed, and the after injection control is started after the exhaust (9) reaches a temperature equal to or higher than the predetermined after injection permitted temperature (TA) (S18). ), And the exhaust gas (9) heated by the combustion of the after-injection fuel is configured to vaporize or incinerate the unburned deposits deposited on the DOC (6) on the downstream side of the valve. diesel engine. In the diesel engine according to claim 9,
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 valve downstream side DOC (6) is performed. A diesel engine characterized in that it is configured so that the start condition (S13) is satisfied. In the diesel engine according to any one of claims 1 to 8.
It is equipped with a valve upstream side DOC (17) arranged on the exhaust upstream side of the exhaust throttle valve (5).
It is configured so that the catalytic function recovery treatment of the valve upstream DOC (17) is performed.
In the catalytic function recovery treatment of the valve upstream side DOC (17), the start condition (S13) of the catalytic function recovery treatment of the valve upstream side DOC (17) whose function has deteriorated due to the accumulation of unburned deposits consisting of unburned fuel and PM. ) Is satisfied, the opening reduction control (S15) of the exhaust throttle valve (5) is performed, and the after injection control is started after the exhaust (9) reaches a temperature equal to or higher than the predetermined after injection permitted temperature (TA) (S18). ), And the heat of the exhaust (9) raised by the combustion of the after-injection fuel is configured to vaporize or incinerate the unburned deposits deposited on the DOC (17) on the upstream side of the valve. Diesel engine. In the diesel engine according to claim 11,
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 valve upstream DOC (17) is performed. A diesel engine characterized in that it is configured so that the start condition (S13) is satisfied. In the diesel engine according to claim 11 or 12.
When the valve upstream side exhaust pressure (P0) reaches a predetermined catalytic function recovery processing start determination value, the valve upstream side DOC (17) is configured to satisfy the catalytic function recovery processing start condition (S13). A diesel engine that is characterized by being. In the diesel engine according to any one of claims 11 to 13.
When the number of regeneration processes of the DPF (6) reaches a predetermined start determination value (ISJ) of the catalytic function recovery process, the start condition (S13) of the catalytic function recovery process of the valve upstream DOC (17) is satisfied. A diesel engine characterized by being configured in such a way.

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