JP7366876B2 - diesel engine - Google Patents

Description

The present invention relates to a diesel engine, and more particularly, to a diesel engine that can regenerate a DPF even during no-load and/or light-load operation.

Conventionally, in a diesel engine, when the conditions for starting DPF regeneration are met due to PM accumulation, post-injection control is started after activation of DOC, and the exhaust gas is regenerated by DPF through catalytic combustion of post-injected fuel in DOC. There is one in which the temperature is raised to a high temperature and the PM deposited on the DPF is incinerated (for example, see Patent Document 1).

Japanese Patent Application Publication No. 2010-151058 (see Figures 1 and 2)

<<Problem>> There is a possibility that the DPF cannot be regenerated during no-load or light-load operation.
In the conventional engine mentioned above, the opening of the intake throttle valve is reduced when DPF regeneration begins, but this alone has a low efficiency in raising the temperature of the exhaust gas, and the DOC is not activated during no-load or light-load operation when the exhaust temperature is low. , there is a possibility that post-injection cannot be performed and the DPF cannot be regenerated.

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

(Matters specifying the invention common to the inventions of claims 1, 10, and 14)
As illustrated in FIG. 1, a fuel injection device (3) that injects fuel (2) into a combustion chamber (1), an exhaust throttle valve (5) arranged in an exhaust path (4), and an exhaust downstream side thereof A DOC (6) located downstream of the valve, a DPF (7) located downstream of the exhaust gas, and an electronic device that controls the opening of the exhaust throttle valve (5) and the fuel injection of the fuel injection device (3). comprising a control device (8);
As illustrated in FIG. 2, it is configured to perform regeneration processing of the DPF (7),
In the regeneration process of the DPF (7), after the start condition (S1) for the regeneration process of the DPF (7) on which PM has accumulated is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed, and the exhaust throttle valve (5) is ) becomes a predetermined after-injection permission temperature (TA) or higher, after-injection control is started (S5), and the combustion of the after-injected fuel causes the exhaust gas (9) to rise to a predetermined post-injection permission temperature (TP) or higher. Post-injection control is started (S7) after the temperature reaches the temperature, and the exhaust gas (9) heated by the catalytic combustion of the post-injected fuel in the DOC (6) on the downstream side of the valve, as shown in FIG. The structure is such that the accumulated PM is incinerated.
In addition, as illustrated 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, and the exhaust pressure (P0) on the upstream side of the valve is set to a predetermined pressure upper limit value. (Pmax), the exhaust throttle valve (5) is then controlled to increase the opening degree (S4-2).
Further, as illustrated in FIG. 1, a valve upstream exhaust pressure sensor (12a) disposed on the exhaust upstream side of the exhaust throttle valve (5) is provided, and the valve upstream exhaust pressure sensor (12a) The exhaust pressure (P0) is detected, and based on the detected value of the exhaust pressure (P0) on the upstream side of the valve by the exhaust pressure sensor (12a) on the upstream side of the valve, the exhaust throttle valve (5) is activated as illustrated in FIG. The opening degree increasing control (S4-2) is performed.
(Matters specifying the invention specific to claim 1)
As illustrated in FIG. 1, a valve upstream side exhaust temperature sensor (19) is provided, and the valve upstream side exhaust temperature (T0) detected by this is the after injection permission temperature (TA) and the post injection permission temperature (TP). It is used for temperature comparison judgment with
When the differential pressure value between the detected value of the valve upstream exhaust pressure (P0) and the predicted value of the valve upstream exhaust pressure (P0) reaches a predetermined abnormality judgment value, the electronic control unit (8) performs a failure diagnosis. A diesel engine characterized in that it is configured to perform.
(Matters specifying the invention specific to claim 10)
As illustrated in FIG. 3, the structure is such that the catalytic function recovery process of the DOC (6) on the downstream side of the valve is performed,
In the catalytic function recovery process of the valve downstream DOC (6), the start conditions (S13 ) is established, the opening degree reduction control of the exhaust throttle valve (5) is performed (S15), and after the temperature of the exhaust gas (9) reaches a predetermined after-injection permission temperature (TA) or higher, the after-injection control is started (S18). ), and the unburned deposits accumulated on the DOC (6) on the downstream side of the valve are vaporized or incinerated by the exhaust gas (9) heated by combustion of the after-injected fuel,
As illustrated in FIG. 1, it includes an operation time integration device (18) that integrates the operation time of no-load and/or light-load operation,
As illustrated in FIG. 3, when the integrated value (tL) of no-load and/or light-load operation time reaches a predetermined catalyst function recovery processing start judgment value (ISJ), the valve downstream side DOC ( 6) A diesel engine characterized in that it is configured such that the start condition (S13) of the catalyst function recovery process is satisfied.
(Matters specifying the invention specific to claim 14)
As illustrated in FIG. 1, it includes a valve upstream DOC (17) disposed on the exhaust upstream side of the exhaust throttle valve (5),
As illustrated in FIG. 3, the catalyst function recovery process of the DOC (17) on the upstream side of the valve is performed,
In the catalytic function recovery process of the valve upstream DOC (17), the start conditions (S13 ) is established, the opening degree reduction control of the exhaust throttle valve (5) is performed (S15), and after the temperature of the exhaust gas (9) reaches a predetermined after-injection permission temperature (TA) or higher, the after-injection control is started (S18). ), and after the exhaust gas (9) reaches a temperature equal to or higher than the predetermined post-injection permission temperature (TP) due to the combustion of the after-injected fuel, post-injection control is started (S18-3), and the post-injection control is started using the combustion heat of the after-injected fuel. The injected fuel is combusted, and the unburned deposits deposited on the upstream side DOC (17) of the valve are vaporized or incinerated by the heat of the heated exhaust gas (9),
Equipped with an operation time accumulation device (18) for accumulating operation time of no-load and/or light-load operation,
When the integrated value (tL) of no-load and/or light-load operation time reaches a predetermined catalyst function recovery process start judgment value (ISJ), the catalyst function recovery process of the valve upstream DOC (17) is started. A diesel engine characterized in that it is configured such that a starting condition (S13) is satisfied.

(Effects common to the inventions of claims 1, 10, and 14)
<<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) for the regeneration process of the DPF (7) is satisfied, the back pressure increases due to the decrease in the opening of the exhaust throttle valve (5), and the after-sales Since combustion of the injected fuel occurs, the temperature increase efficiency of the exhaust (9) is higher than in the case of intake throttling, and even during no-load and/or light-load operation where the exhaust temperature is low, the valve downstream DOC illustrated in FIG. (6) is activated and DPF (7) can be regenerated in post-injection.

[Effect 2] Engine output can be increased.
In this engine, the temperature of the exhaust gas (9) rises due to the combustion of the after-injected fuel, so the degree of reduction in the opening of the exhaust throttle valve (5) illustrated in FIG. 1 is small, and output loss due to back pressure is small. Can increase engine output.

<<Effect 3>> During regeneration of the DPF (7), the reduced catalytic function of the DOC (6) on the downstream side of the valve can be restored.
In this engine, due to continuous no-load and/or light-load operation with low exhaust temperature, unburned deposits consisting of unburned fuel and PM accumulate in the DOC (6) on the downstream side of the valve, and its catalytic function deteriorates. Even if the exhaust throttle valve (5) is opened less or after injection is performed, the exhaust gas (9 ), the unburned deposits are vaporized or burned, and the degraded catalytic function of the DOC (6) on the downstream side of the valve illustrated in FIG. 1 can be recovered during regeneration of the DPF (7). Furthermore, since there is no unburned deposits that cause white smoke, the generation of white smoke is also suppressed.

<<Effect 4>> The temperature raising efficiency of the exhaust gas (9) is high.
Compared to this engine with a different structure, that is, the exhaust throttle valve (5) is located downstream of the DPF (7), in this engine, the exhaust throttle valve (5) is located downstream of the DPF (7). is located on the exhaust upstream side of the DPF (7), the volume of the exhaust path (4) on the exhaust upstream side of the exhaust throttle valve (5) becomes smaller, and the opening degree of the exhaust throttle valve (5) decreases. The exhaust pressure (P0) on the upstream side of the valve increases quickly, and the temperature increase efficiency of the exhaust gas (9) is high.

<<Effect 5>> The sound of the exhaust throttle valve (5) is unlikely to be emitted outside the exhaust path.
In this engine, as illustrated in Fig. 1, the valve downstream side DOC (6) and DPF (7) are arranged on the exhaust downstream side of the exhaust throttle valve (5), so the exhaust throttle valve (5) makes a noise. Sound is difficult to be emitted outside the exhaust path (4).

<<Effect 6>> Parts are less likely to break down.
In this engine, an excessive increase in the exhaust pressure (P0) on the upstream side of the valve is suppressed, so that the exhaust throttle valve (5) and its upstream parts are less likely to malfunction due to the increased pressure.

<<Effect 7>> The exhaust throttle valve (5) can be controlled with high precision.
Based on the detected value of the exhaust pressure (P0) on the upstream side of the valve by the exhaust pressure sensor (12a) on the upstream side of the valve, as illustrated in FIG. 1, the opening degree increase control of the exhaust throttle valve (5) is performed as illustrated in FIG. (S4-2), it is possible to control the exhaust throttle valve (5) with high precision based on the accurately measured value of the upstream exhaust pressure (P0) of the valve. can.
(Effect specific to the invention according to claim 1)
<<Effect 8>> Not limited to the failure of the exhaust throttle valve (5), but also gas leakage from the exhaust path (4), failure of the exhaust pressure sensor (12a) on the upstream side of the valve, failure of the exhaust temperature sensor (19) on the upstream side of the valve, etc. If there is, a fault diagnosis will be made in either case.
(Effect specific to the invention according to claim 10)
<<Effect 9>> Before the DPF (7) is regenerated, the degraded catalytic function of the DOC (6) on the downstream side of the valve illustrated in FIG. 1 is recovered, and the deterioration of the catalytic function is difficult to progress.
<<Effect 10>> Since improvement of the catalyst function can be started at a time when there is a high probability that the catalyst function of the DOC (6) on the downstream side of the valve has deteriorated, wasteful exhaust throttling and after-injection can be eliminated.
(Effect specific to the invention according to claim 14)
<<Effect 11>> Before the DPF (7) is regenerated, the degraded catalytic function of the DOC (17) on the upstream side of the valve is restored, making it difficult for the catalytic function to deteriorate further.
<<Effect 12>> Catalytic function recovery processing can be started in a situation where there is a high probability that the catalyst function of the DOC (17) on the upstream side of the valve has deteriorated, so unnecessary exhaust throttling, after-injection, and post-injection can be eliminated.

1 is a schematic diagram of a diesel engine according to an embodiment of the present invention. 2 is a flowchart of a DPF regeneration process of the engine in FIG. 1. FIG. 2 is a flowchart of catalyst function recovery processing of the DOC on the downstream side of the valve of the engine in FIG. 1. FIG. 2 is a flowchart of catalyst function recovery processing for the valve upstream DOC of the engine in FIG. 1. FIG. This is a relational expression used to calculate the exhaust pressure (P0) on the upstream side of the valve of the engine shown in Figure 1. Equation 1 is the relational expression between the mass flow rate (G) of the exhaust (9) and the exhaust pressure (P0) on the upstream side of the valve. , Equation 2 is the relational expression between the mass flow rate (G) of the exhaust (9) and the volumetric flow rate (V) of the exhaust, and Equation 3 is the relational expression between the volumetric flow rate (V) of the exhaust (9) and the mass flow rate (G) of the exhaust (9). ) and the fuel injection amount (Q), Equation 4 is a relational expression between the exhaust pressure (P1) on the downstream side of the valve, the atmospheric pressure (P3), and the differential pressure (ΔP) between the inlet and outlet of the DPF (7).

1 to 5 are diagrams illustrating a diesel engine according to an embodiment of the present invention. In this embodiment, a common rail type vertical in-line multi-cylinder diesel engine will be explained.

The configuration of this engine is as follows.
As shown in Figure 1, the installation direction of the crankshaft (21) is the front-rear direction, the side where the flywheel (22) is placed is the rear side, the opposite side is the front side, and the engine width direction perpendicular to the front-rear direction is the lateral direction. shall be.
As shown in FIG. 1, this engine has an intake manifold (24) assembled on one side of the cylinder head (23), and an exhaust manifold (25) assembled on the other side of the cylinder head (23). It is equipped with
As shown in FIG. 1, this engine is equipped with an electronic control device (8).
The electronic control unit (8) is an engine ECU. Engine ECU is an abbreviation for electronic control unit, and is a microcomputer.

As shown in FIG. 1, this engine is equipped with an exhaust system.
The exhaust system includes an exhaust manifold (25), an exhaust turbine (26a) of a supercharger (26) connected to the exhaust manifold (25), and exhaust gas led out 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 device.
The intake device includes a compressor (26d) of the supercharger (26), an intake flow rate sensor (16) provided upstream of the intake inlet (26e) of the compressor (26d), and a supercharger (26d) of the compressor (26d). An intercooler (28) disposed between the air outlet (26f) and the intake manifold (24), an intake throttle valve (11) disposed between the intercooler (28) and the intake manifold (24), and an exhaust It includes 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 electrically operated on-off valves, and are electrically connected to a power source (29) via an electronic control device (8). The intake air flow rate sensor (16) includes an intake air temperature sensor and is electrically connected to the electronic control unit (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).
This fuel injection device (3) includes a fuel injection valve (34) provided in each combustion chamber (1), a common rail (35) that accumulates pressure of fuel injected from the fuel injection valve (34), and a common rail (35). The engine is equipped with a fuel supply pump (37) that pumps fuel from the fuel tank (36).
The fuel injection valve (34) is equipped with an electromagnetic on-off valve, and the fuel supply pump (37) is equipped with 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 governor includes an accelerator sensor (39) that detects the setting position of an accelerator lever (38) that sets a target engine speed, and an actual engine speed sensor (40) that detects the actual engine speed. The sensors (39) (40) are electrically connected to the electronic control unit (8).

As shown in FIG. 1, this engine is equipped with a starter.
The starting device includes a starter motor (41) and a key switch (42), and the starter motor (41) and 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 operational 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 engine speed and the actual engine speed, thereby reducing engine speed fluctuations due to load fluctuations.
The openings of the intake throttle valve (11) and EGR valve (31) are adjusted according to the engine speed, load, intake air amount, and intake air temperature to adjust the intake air amount and EGR rate.
When the key switch (42) is turned to the start position, the starter motor (41) is driven to start the engine. When the key switch (42) is turned 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 to the OFF position, the fuel injection valve 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), an exhaust throttle valve (5) disposed in an exhaust path (4), The valve downstream side DOC (6) placed on the downstream side of the exhaust gas, the DPF (7) placed on the downstream side of the exhaust gas, the opening degree of the exhaust throttle valve (5), and the fuel injection of the fuel injection device (3). It is equipped with an electronic control device (8) that controls the

Compared to this engine with a different configuration, that is, where the exhaust throttle valve (5) is located downstream of the DPF (7), in this engine, the exhaust throttle valve (5) is located downstream of the DPF (7). Since it is arranged on the exhaust upstream side of the DPF (7), the volume of the exhaust path (4) on the exhaust upstream side of the exhaust throttle valve (5) becomes smaller, and the opening degree of the exhaust throttle valve (5) decreases. The upstream exhaust pressure (P0) increases quickly, and the temperature increase efficiency of the exhaust gas (9) is high.
In addition, in this engine, as shown in Fig. 1, the valve downstream side DOC (6) and DPF (7) are arranged on the exhaust downstream side of the exhaust throttle valve (5). It is difficult for the noise to be emitted outside the exhaust path (4).

Each of the above elements will be explained.
The combustion chamber (1) shown in FIG. 1 is formed within a cylinder. Fuel (2) is light oil. The exhaust throttle valve (5) is an electric on-off valve, and is electrically connected to a power source (29) via an electronic control device (8). DOC is an abbreviation for diesel oxidation catalyst, which is a through-flow type in which oxidation catalyst components such as platinum and palladium are supported on a ceramic honeycomb carrier. ) to oxidize. DPF is an abbreviation for diesel particulate filter, and is a wall flow type in which the entrances and exits of adjacent cells of a ceramic honeycomb are alternately blocked, and traps PM in the exhaust gas (9). PM is an abbreviation for particulate matter.
The valve downstream side DOC (6) and DPF (7) are respectively housed on the exhaust upstream side and downstream side of the exhaust treatment case (4a) disposed in the middle of the exhaust path (4).

This DPF system traps PM in the exhaust (9) with the DPF (7), and oxidizes NO (nitric oxide) in the exhaust (9) with the DOC ( ₆ ) on the downstream side of the valve. PM accumulated in the DPF (7) is continuously oxidized and burned at a relatively low temperature with nitrogen dioxide), and unburned fuel is supplied to the exhaust gas (9) by post injection from the common rail fuel injection device (3). is catalytically combusted in the DOC (6) on the downstream side of the valve, and the PM accumulated in the DPF (7) is combusted at a relatively high temperature to regenerate the DPF (7).

This exhaust treatment device has the following configuration for regenerating the DPF (7).
As shown in FIG. 2, when the start condition (S1) for the regeneration process of the DPF (7) on which PM has accumulated is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is then performed, When the temperature of the exhaust gas (9) reaches or exceeds the predetermined after-injection permission temperature (TA), after-injection control is then started (S5), and the exhaust gas (9) is directed to the predetermined post by combustion of the after-injected fuel. If the temperature reaches or exceeds the injection permission temperature (TP), post-injection control is then started (S7), and the temperature is raised by catalytic combustion of the post-injected fuel in the valve downstream DOC (6) shown in Figure 1. The exhaust gas (9) is configured to incinerate PM accumulated on the DPF (7).

This engine has the following advantages:
As shown in Fig. 2, after the start condition (S1) for the regeneration process of the DPF (7) is satisfied, the back pressure increases due to the decrease in the opening of the exhaust throttle valve (5) and the combustion of the after-injected fuel occurs. Compared to the case of throttling, the temperature raising efficiency of the exhaust gas (9) is higher, and even during no-load and/or light-load operation when the exhaust gas temperature is low, the DOC (6) on the downstream side of the valve shown in Figure 1 is activated and post injection is performed. Then, DPF(7) can be regenerated.

In addition, in this engine, the temperature of the exhaust gas (9) rises due to the combustion of after-injected fuel, so the degree of reduction in the opening of the exhaust throttle valve (5) shown in Figure 1 is small, and output loss due to back pressure is small. , the engine output can be increased.

In this engine, due to continuous no-load and/or light-load operation with low exhaust temperature, unburned deposits consisting of unburned fuel and PM accumulate in the DOC (6) on the downstream side of the valve, and its catalytic function deteriorates. As shown in Fig. 2, even if the condition (S1) for starting the regeneration process of the DPF (7) is satisfied, the exhaust gas (9) is temperature rises, unburned deposits are vaporized or burned, and the degraded catalytic function of the DOC (6) on the downstream side of the valve shown in FIG. 1 can be restored when the DPF (7) is regenerated.

Each element in the case of regeneration of the DPF (7) will be explained.
As shown in FIG. 2, the start condition (S1) for the regeneration process of the DPF (7) is such that the estimated amount of PM accumulated in the DPF (7) (APM) is the start determination value for the regeneration process of the DPF (7) ( RSJ) or higher. The PM accumulation amount estimate (APM) may be estimated by the PM accumulation amount estimate calculation device (32) based on the differential pressure (ΔP) between the entrance and exit of the DPF (7) shown in FIG. 1, for example. be. The PM accumulation amount estimated value calculation device (32) is constituted by a calculation section of the electronic control device (8).

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 injected fuel, and is started during the intake stroke or the compression stroke.
Main injection is the main injection for obtaining output, and is started before 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 to raise the temperature of the exhaust gas (9), and is started during the expansion stroke after the after injection. Post injection may be initiated during the exhaust stroke.

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

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

The after-injection permission temperature (TA) is preferably 150°C or more and less than 250°C, more preferably 150°C or more and less than 200°C.
The reason why the after-injection permission temperature (TA) may be as low as about 150°C is as follows.
In other words, when the exhaust pressure on the upstream side of the exhaust throttle valve (5) is set to 80 kPa or more and 120 kPa or less in gauge pressure (181.32 kPa or more and 221.23 kPa or less in absolute pressure), the exhaust pressure The atmospheric pressure is approximately twice that of 101.32 kPa, and the valve upstream DOC (17) is activated even at temperatures as low as 150°C, and an oxidation reaction (catalytic combustion) of the after-injected fuel occurs in the valve upstream DOC (17). It's for a reason.

In after-injection, the after-injected fuel that is injected into the combustion chamber (1) during the expansion stroke is combusted by the heat of the exhaust gas (9), and even when the temperature of the exhaust gas (9) is low during no-load or low-load operation, , the exhaust gas (9) is heated to a 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), which has been degraded by the unburned deposits, is reduced. Upon recovery, the DOC (6) on the downstream side of the valve is activated.

In the case of the DPF (7) regeneration process shown in FIG. 2, the post injection is set as follows.
The post-injection permission temperature (TP) is set at 200°C or higher and 700°C or lower.
The post-injection permission temperature (TP) is set to a higher temperature than the after-injection permission temperature (TA).
In post injection control, the exhaust temperature (T1) on the inlet side of the DOC (6) on the downstream side of the valve is maintained at 400°C or more and below 700°C, and the exhaust temperature (T2) on the inlet side of the DPF (7) is maintained at 550°C or higher. The temperature is set to be maintained at a temperature above 700°C and below 700°C. In particular, it is desirable to set the exhaust temperature (T2) on the inlet side of the DPF (7) to 700° C. or lower in order to prevent abnormal combustion of accumulated PM.
The post injection permission temperature (TP) is the determination temperature for the valve upstream exhaust temperature (T0) detected by the valve upstream exhaust temperature sensor (19), and the valve upstream exhaust temperature (T0) is the valve upstream exhaust temperature (T0). It is detected by an exhaust gas temperature sensor (19) and controlled by an electronic control unit (8).
The exhaust temperature (T1) on the inlet side of the DOC (6) on the downstream side of the valve is determined by the injection timing and timing by the electronic control device (8) depending on the exhaust temperature (T0) on the upstream side of the valve detected by the exhaust temperature sensor (19) on the upstream side of the valve. Controlled by adjusting the fuel injection amount.
The exhaust temperature (T2) on the inlet side of the DPF (7) is detected by the DPF inlet side exhaust temperature sensor (27), and is controlled by adjusting the injection timing and fuel injection amount by the electronic control device (8).
If the DPF outlet side exhaust temperature (T3) detected by the DPF outlet side exhaust temperature sensor (33) exceeds the predetermined upper limit temperature, after-injection or Post injection is stopped immediately.
In post-injection, post-injected fuel, which is injected into the combustion chamber during the expansion stroke or exhaust stroke, undergoes catalytic combustion in the DOC (6) on the downstream side of the valve, raising the temperature of the exhaust gas (9) and accumulating it in the DPF (7). PM is removed by incineration.

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

In this engine, as shown in FIG. 2 or 3, after the opening reduction control (S2) (S15) of the exhaust throttle valve (5) is performed, the exhaust pressure (P0) on the upstream side of the valve reaches a predetermined pressure upper limit value. (Pmax), the opening degree increasing control (S4-2) (S17-2) of the exhaust throttle valve (5) is performed thereafter.
Therefore, in this engine, an excessive increase in the exhaust pressure (P0) on the upstream side of the valve is suppressed, so that the exhaust throttle valve (5) and its upstream parts are less likely to malfunction due to the increased pressure.
The pressure upper limit value (Pmax) is determined based on the specifications of the exhaust throttle valve (5), EGR valve (31), 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 pressure value (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 valve upstream exhaust pressure sensor (12a) disposed on the exhaust upstream side of the exhaust throttle valve (5), and this valve upstream exhaust pressure sensor (12a) The side exhaust pressure (P0) is detected, and based on the detected value of the valve upstream side exhaust pressure (P0) by the valve upstream side exhaust pressure sensor (12a), as shown in FIG. The opening degree increasing control (S4-2) is performed.
In this engine, the exhaust throttle valve (5) is opened as shown in FIG. 2 based on the detected value of the valve upstream exhaust pressure (P0) by the valve upstream exhaust pressure sensor (12a) shown in FIG. The exhaust throttle valve (5) is controlled with high precision based on the accurately measured value of the upstream exhaust pressure (P0). It can be carried out.

As shown in FIG. 1, this engine is equipped with a valve upstream exhaust temperature sensor (19), and as shown in FIG. 5, the valve upstream exhaust temperature (T0) detected by this sensor is as shown in FIG. In addition, it is used for temperature comparison judgment with the after-injection permission temperature (TA) and the post-injection permission temperature (TP), and is also used to calculate the predicted value of the valve upstream exhaust pressure (P0).
When the differential pressure value between the detected value of the valve upstream exhaust pressure (P0) and the predicted value of the valve upstream exhaust pressure (P0) reaches a predetermined abnormality judgment value, the electronic control unit (8) performs a failure diagnosis. It is configured so that

In this engine, the problem is not limited to the failure of the exhaust throttle valve (5), but also gas leakage from the exhaust path (4), failure of the exhaust pressure sensor (12a) on the upstream side of the valve, failure of the exhaust temperature sensor (19) on the upstream side of the valve, etc. If there is, a fault diagnosis will be made in either case.

As shown in FIG. 1, a failure display device (8a) is provided, and when a failure diagnosis is performed by the electronic control device (8), a failure indication is displayed on the failure display device (8a) by the electronic control device (8). It is configured to
Therefore, at the time of fault diagnosis, the driver is notified of the fault.

When the electronic control unit (8) performs a fault diagnosis, the fault display device (8a) displays the occurrence of a fault, the diagnostic storage device (8b) stores a fault diagnosis code, and the fault diagnosis tool performs the following: The failure history is confirmed after the fact by reading the failure diagnosis code from the diagnostic storage device (8b).
The fault display device (8a) is placed on the dashboard of the engine-equipped machine. A liquid crystal display, an organic EL display, etc. can be used as the failure display device (8a). EL is an abbreviation for electroluminescence.
A nonvolatile memory built into the electronic control unit (8) can be used as the diagnostic storage device (8b), and for example, a flash memory, P-ROM, EP-ROM, or E2P-ROM can be used.

A fault diagnosis code is indicated by a multi-digit number or symbol.
As the failure diagnosis tool, a notebook computer, a portable terminal, or the like on which a failure diagnosis program is installed can be used.
A port is installed on the dashboard of an engine-equipped machine, and when checking the failure history, a failure diagnosis tool plug is inserted into this port, and the failure diagnosis code is displayed on the failure diagnosis tool's display. A USB port or the like can be used as the port. USB is an abbreviation for Universal Serial Bus.

As shown in FIG. 1, this engine is equipped with a calculation device (12) for calculating the exhaust pressure (P0) on the upstream side of the valve, and as shown in FIG. 9), the valve upstream exhaust temperature (T0), and the valve downstream exhaust pressure (P1). The calculation device (12) for the valve upstream exhaust pressure (P0) is constituted by the calculation section of the electronic control device (8).

In this engine, as shown in Fig. 5, the predicted value of the valve upstream exhaust pressure (P0) can be calculated with high accuracy from the mass flow rate (G) of the exhaust gas (9), etc., so the accuracy of failure diagnosis can be improved. Can be done.

When calculating the valve upstream exhaust pressure (P0) by calculation, the following relational expression can be used.
The valve upstream exhaust pressure (P0) can be calculated from the mass flow rate (G) of the exhaust (9), the valve upstream exhaust temperature (T0), and the valve downstream exhaust pressure (P1) using equation 1 in Figure 5. It can be calculated.
The mass flow rate (G) of the exhaust gas (9) can be calculated from the density (ρ0) of the exhaust gas (9) and the volumetric flow rate (V) of the exhaust gas (9) using Equation 2 in FIG.
The volumetric flow rate (V) of the exhaust gas (9) can be calculated from the mass flow rate (G) of the exhaust gas (9), the fuel injection amount (Q), etc. using Equation 3 in FIG.
The fuel injection amount (Q) is the fuel injection amount that is the sum of blur injection (pilot injection), main injection, after injection, and post injection per second.

In addition, since the intake flow rate can be used as a substitute value for the exhaust flow rate, instead of calculating the precise volume flow rate (V) of the exhaust air (9) in Equation 3 of Fig. 5, the intake flow rate measured by the intake flow rate sensor (16) can be used. Equation 2 may be calculated by regarding the intake flow rate as the volumetric flow rate (V) of the exhaust gas (9).

As shown in Fig. 1, this engine has a differential pressure sensor (13) that detects the differential pressure (ΔP) between the entrance and exit of the DPF (7), and an atmospheric pressure sensor (14) that detects the atmospheric pressure (P3). As shown in Equation 4 in Fig. 5, the exhaust pressure (P1) on the downstream side of the valve is 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. 5, the exhaust pressure (P1) on the downstream side of the valve can be calculated with high accuracy from the differential pressure (ΔP) between the inlet and outlet of the DPF (7) and the atmospheric pressure (P3). The control accuracy of the exhaust throttle valve (5) shown in FIG.

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

In this engine, the exhaust pressure (P0) on the upstream side of the valve is detected by the exhaust pressure sensor disposed on the exhaust upstream side of the exhaust throttle valve (5), and the exhaust temperature sensor on the upstream side of the valve is used to compare and determine the after-injection permission temperature (TA). Using the detected temperature in (19), the detected temperature of the exhaust gas temperature sensor on the downstream side of the valve may be used for comparison and determination of the post injection permission temperature (TP). In this case, the detection of the valve upstream exhaust pressure (P0), the comparative determination of the after-injection permitted temperature (TA), and the comparative determination of the post-injection permitted temperature (TP) can be quickly performed.

As shown in FIG. 1, this engine includes a valve upstream DOC (17) disposed on the exhaust upstream side of the exhaust throttle valve (5).
In this engine, due to no load and/or continued operation, unburned deposits consisting of unburned fuel and PM accumulate on the DOC (6) downstream of the valve, and the catalytic function of the DOC (6) downstream of the valve deteriorates. As shown in Fig. 2, even if the start condition (S1) for the regeneration process of the DPF (7) is satisfied, the after-injection fuel or post-injection fuel will be released from the valve by the subsequent after-injection or post-injection. Catalytic combustion occurs in the upstream DOC (17), and the temperature of the exhaust gas (9) rises significantly, so unburned deposits quickly vaporize or burn, and when the DPF (7) is regenerated, the valve downstream DOC ( 6) The reduced catalytic function can be restored.
The valve upstream DOC (17) is housed in a valve upstream DOC case (4b) disposed in the middle of the exhaust path (4). The valve upstream exhaust gas temperature sensor (19) is arranged between the valve upstream DOC (17) and the exhaust throttle valve (5).

In this engine, as shown in Fig. 1, the valve upstream side DOC (17) and the valve downstream side DOC (6) have flow through cells in which catalyst components are supported on a honeycomb carrier through which exhaust gas (9) passes through the cells. type oxidation catalyst is used.
For this reason, in this engine, as shown in Figure 1, flow-through type oxidation catalysts are used in the valve upstream side DOC (17) and the valve downstream side DOC (6), so 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 DOC (17) is smaller than the diameter of the valve downstream DOC (6).
Therefore, in the engine, the passage speed of the exhaust gas (9) passing through the cells of the DOC (17) on the upstream side of the valve is faster than the passage speed of the exhaust gas (9) passing through the cells of the DOC (6) on the downstream side of the valve. Therefore, unburned deposits consisting of unburned fuel and PM are difficult to accumulate in the DOC (17) on the upstream side of the valve.

In this engine, as shown in FIG. 1, the cell density (over the entire area) of the valve upstream DOC (17) is larger than the cell density of the valve downstream DOC (6).
Therefore, in this engine, as shown in FIG. ), it is difficult for unburned fuel and unburned deposits such as PM to accumulate on the valve upstream side DOC (17).

As shown in FIG. 3, this exhaust treatment device is configured to perform catalyst function recovery processing of the valve downstream DOC (6), and in the catalyst function recovery processing of the valve downstream DOC (6), unburned fuel is After the start condition (S13) for the catalyst function recovery process of the DOC (6) on the downstream side of the valve whose function has deteriorated due to the accumulation of unburned deposits consisting of S15) is performed, and after the exhaust gas (9) reaches a temperature equal to or higher than the predetermined after-injection permission temperature (TA), after-injection control is started (S18), and the exhaust gas (9) whose temperature has increased due to the combustion of the after-injected fuel is , the unburned deposits accumulated on the DOC (6) on the downstream side of the valve are vaporized or incinerated.

In this engine, even if the DPF (7) is not being regenerated, the exhaust throttle valve (5) is activated after the start condition (S13) for catalyst function recovery of the DOC (6) on the downstream side of the valve is satisfied, as shown in Fig. 3. Due to the reduced opening and after injection, the temperature of the exhaust gas (9) rises, unburned deposits are vaporized or burned, and the catalytic function of the DOC (6) on the downstream side of the valve shown in Figure 1 decreases before the DPF (7) is regenerated. is recovered, and the deterioration of catalytic function is difficult to progress. Furthermore, since there is no unburned deposits that cause white smoke, the generation of white smoke is also suppressed.

As shown in FIG. 3, the start condition (S13) for the catalyst function recovery process of the DOC (6) on the downstream side of the valve is such that the cumulative value (tL) of the no-load and light-load operation time is the start of the predetermined catalyst function recovery process. This is established when the value is equal to or greater than the judgment value (ISJ). The integrated value (tL) of the operation time for no-load and light-load operation is calculated based on the fact that the exhaust gas temperature (T0) on the upstream side of the valve is below the determination temperature (LJ) for no-load and light-load operation. A time integration device (18) calculates. The operating time integration device (18) is composed of a calculation section of an electronic control device (8).

In the case of the catalytic function recovery process of the DOC (6) on the downstream side of the valve shown in FIG. 3, the after injection is set as follows.
The after-injection permission temperature (TA) is set at 150°C or higher and 700°C or lower.
In the after injection control, the exhaust temperature (T1) on the inlet side of the valve downstream DOC (6) shown in Fig. 1 is maintained at 180°C or more and 700°C or less (preferably 250°C or more and 300°C or less). is set to
In after-injection, the after-injected fuel injected into the combustion chamber during the expansion stroke is combusted by the heat of the exhaust gas (9), and even when the temperature of the exhaust gas (9) is low during no-load or low-load operation, the exhaust gas (9) The temperature is raised to a temperature at which the unburned deposits deposited on the DOC (6) on the downstream side of the valve are vaporized or incinerated, and the catalytic function of the DOC (6) on the downstream side of the valve, which has decreased due to the unburned deposits, is restored, and the catalytic function is improved. The decline is difficult to progress.

The after-injection permission temperature (TA) is preferably 150°C or more and less than 250°C, more preferably 150°C or more and less than 200°C.
The reason why the after-injection permission temperature (TA) may be as low as about 150°C is as follows.
In other words, when the exhaust pressure on the upstream side of the exhaust throttle valve (5) is set to 80 kPa or more and 120 kPa or less in gauge pressure (181.32 kPa or more and 221.23 kPa or less in absolute pressure), the exhaust pressure The atmospheric pressure is approximately twice that of 101.32 kPa, and the valve upstream DOC (17) is activated even at temperatures as low as 150°C, and an oxidation reaction (catalytic combustion) of the after-injected fuel occurs in the valve upstream DOC (17). It's for a reason.

As shown in FIG. 1, this engine is equipped with an operating time accumulating device (18) for accumulating operating time during no-load and/or light-load operation, and as shown in FIG. When the cumulative value (tL) of the operating time reaches a predetermined catalyst function recovery process start determination value (ISJ), the start condition (S13) for the catalyst function recovery process for the valve downstream DOC (6) is satisfied. It is configured as follows.
Therefore, in this engine, it is possible to start improving the catalyst function at a time when there is a high probability that the catalyst function of the DOC (6) on the downstream side of the valve has deteriorated, so that wasteful exhaust throttling and after-injection can be eliminated.

As shown in FIG. 1, a valve upstream DOC (17) is provided on the exhaust upstream side of the exhaust throttle valve (5), and as shown in FIG. 4, catalyst function recovery processing of the valve upstream DOC (17) is performed. In the catalyst function recovery process of the valve upstream DOC (17), the catalyst function of the valve upstream DOC (17) whose function has deteriorated due to the accumulation of unburned deposits consisting of unburned fuel and PM is recovered. After the start condition (S13) of the function recovery process is satisfied, the opening degree reduction control (S15) of the exhaust throttle valve (5) is performed, and the temperature of the exhaust gas (9) becomes higher than the predetermined after-injection permission temperature (TA). Later, after-injection control is started (S18), and after the exhaust gas (9) reaches a temperature equal to or higher than a predetermined post-injection permission temperature (TP) due to combustion of after-injected fuel, post-injection control is started (S18-3). The post-injected fuel is combusted by the combustion heat of the after-injected fuel, and the unburned deposits accumulated on the DOC (17) on the upstream side of the valve are vaporized or incinerated by the heat of the heated exhaust gas (9) shown in Figure 1. It is composed of

In this engine, due to continuous no-load and/or light-load operation with low exhaust temperature, unburned deposits consisting of unburned fuel and PM accumulate on the upstream side DOC (17) of the valve shown in Fig. 1, causing the catalyst to function. Even in the case where the exhaust throttle valve (5) shown in FIG. The temperature of the exhaust gas (9) rises due to the reduction in opening and the combustion of after-injection and post-injection, and the unburned deposits are vaporized or burned by the heat of this exhaust gas (9), and the upstream side of the valve is heated before the DPF (7) is regenerated. The decreased catalytic function of DOC (17) is restored, and the deterioration of the catalytic function is difficult to progress. Therefore, the DPF (7) can be regenerated even when no-load and/or light-load operation continues. Furthermore, since there is no unburned deposits that cause white smoke, the generation of white smoke is also suppressed.

In this engine, the temperature of the exhaust gas (9) shown in Fig. 1 rises due to the combustion of after-injected fuel, so the degree of reduction in the opening of the exhaust throttle valve (5) is small, and output loss due to back pressure is small. Can increase output.

As shown in FIG. 1, this engine is equipped with an operating time accumulating device (18) for accumulating operating time during no-load and/or light-load operation, and as shown in FIG. When the cumulative value (tL) of operating time reaches a predetermined catalyst function recovery process start determination value (ISJ), the start condition (S13) for the catalyst function recovery process for the valve upstream DOC (17) is satisfied. It is configured as follows.
Therefore, in this engine, the catalyst function recovery process can be started in a situation where there is a high probability that the catalyst function of the DOC (17) on the upstream side of the valve has deteriorated as shown in Figure 1, thereby eliminating wasteful exhaust throttling, after-injection, and post-injection. It can be eliminated.

The start condition (S13) for the catalyst function recovery process of the valve upstream side DOC (17) shown in FIG. (ISJ), the valve upstream exhaust pressure (P0) shown in Fig. 1 and the number of regeneration processes of the DPF (7) shown in Fig. It may be made to hold true when .
In any case, with this engine, the catalyst function recovery process can be started under conditions where there is a high probability that the catalyst function of the DOC (17) on the upstream side of the valve has deteriorated due to unburned deposits, resulting in unnecessary exhaust throttling and after-injection. and post injection can be eliminated.
When the regeneration process of the DPF (7) is set as the start condition (S13), the electronic control unit (8) counts the number of regeneration processes, and when the count of regeneration processes reaches a predetermined value (for example, 5 times). In this case, the start condition (S13) is satisfied, and when the catalyst function recovery process is completed, the count number of the regeneration process is reset to 0.

In the case of the DPF (7) regeneration process shown in Fig. 2, the exhaust temperature (T2) on the inlet side of the DPF (7) is lower than in the case of the catalyst function recovery process of the DOC (17) on the upstream side of the valve shown in Fig. 4. It is set to be high.
In this engine, when the DPF (7) is regenerated, the exhaust temperature (T2) on the inlet side of the DPF (7) increases, so that the DPF (7) can be regenerated reliably.

In the case of the DPF (7) regeneration process shown in FIG. 2, the injection amount of after-injection fuel is set to be smaller than in the case of the catalyst function recovery process of the DOC (17) on the upstream side of the valve shown in FIG. ing.
In this engine, in the case of DPF (7) regeneration processing, the amount of after-injected fuel injected is small, so the combustion heat and the post-injected fuel combusted by the combustion heat are also small, and a lot of the post-injected fuel is burned at the valve. It passes through the upstream DOC (17) and undergoes catalytic combustion in the valve downstream DOC (6), increasing the exhaust temperature (T2) on the inlet side of the DPF (7). Therefore, the DPF (7) can be regenerated reliably.
In addition, in the case of catalyst function recovery processing of the valve upstream side DOC (17), since there is a lot of after-injected fuel, the combustion heat causes a lot of post-injected fuel to be combusted upstream of the valve upstream side DOC (17). The heat of combustion vaporizes or incinerates the unburned deposits deposited on the DOC (17) on the upstream side of the valve. Therefore, the catalytic function of the DOC (17) on the upstream side of the valve can be reliably restored.

In the case of the DPF (7) regeneration process shown in FIG. 2, the injection amount of post-injected fuel is set to be larger than in the case of the catalyst function recovery process of the DOC (17) on the upstream side of the valve shown in FIG. ing.
In this engine, in the case of DPF (7) regeneration processing, since the amount of post-injected fuel is large, much of the post-injected fuel passes through the valve upstream side DOC (17) shown in Fig. 1 and passes through the valve downstream side DOC. Catalytic combustion occurs in (6), and the exhaust gas temperature (T2) on the inlet side of the DPF (7) increases. Therefore, the DPF (7) can be regenerated reliably.

In this engine, the flow of regeneration processing of the DPF (7) by the electronic control unit (8) shown in FIG. 1 is as follows.
As shown in FIG. 2, in step (S1), it is determined whether the start condition for the regeneration process of the DPF (7) is satisfied. Specifically, it is determined whether the estimated PM accumulation amount (APM) of the DPF (7) has reached a value equal to or greater than the regeneration process start determination value (RSJ) of the DPF (7). The PM accumulation amount estimated value (APM) of the DPF (7) is calculated by the PM accumulation amount estimated value calculation device (32) based on the differential pressure (ΔP) between the entrance and exit of the DPF (7) shown in FIG. The PM accumulation amount estimated value calculation device (32) is constituted by a calculation section of the electronic control device (8). The estimated PM accumulation amount (APM) of the DPF (7) may be calculated by a method other than calculation using the differential pressure (ΔP).
As shown in FIG. 2, the determination in step (S1) is repeated until the determination is positive, and if the determination is positive, 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 step (S2) is performed by an actuator (11a) that drives the intake throttle valve (11) and an actuator that drives 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 the valve upstream exhaust pressure (P0) is equal to or lower than the pressure upper limit value (Pmax), and if the determination is affirmative, step (S4-1 ).
In step (S4-1), it is determined whether the exhaust gas temperature (T0) on the upstream side of the valve is equal to or higher than the after-injection permission temperature (TA), and if the determination is affirmative, 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 negative, the process proceeds to step (S4-2), where 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 step (S4-2) is performed by the electronic control device (8) controlling the actuator (5a) that drives the exhaust throttle valve (5).
If the determination in step (S4-1) is negative, the process returns to step (S3).

In step (S6), it is determined whether the valve upstream exhaust temperature (T0) is equal to or higher than the post injection permission temperature (TP). The determination in step (S6) is repeated until it 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 the conditions for ending the regeneration process of the DPF (7) are satisfied. Specifically, the termination condition is that the estimated PM accumulation amount (APM) of the DPF (7) becomes a value 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 this termination condition is affirmed.
The determination in step (S8) is repeated until the determination is affirmative, and if the determination is affirmative, the process proceeds to step (S9).
In step (S9), the post injection control is ended, and the after injection control is also ended, 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, and the process returns to step (S1).

The PM accumulation amount estimate (APM) of the DPF (7) in step (S8) is calculated by the PM accumulation amount estimate calculation device (32) based on the differential pressure (ΔP) between the entrance and exit of the DPF (7). be done.
The conditions for terminating the regeneration process of the DPF (7) in step (S8) are such that the exhaust temperature (T2) on the inlet side of the DPF (7) shown in FIG. It may be something you did.

In this engine, the flow of the catalyst function recovery process of the valve 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 the valve upstream 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 the inlet side exhaust temperature (T1) of the valve downstream side DOC (6) has become 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 operating times are integrated, and the process proceeds to step (S13).
In step (S13), it is determined whether or not conditions for starting the catalyst function recovery process are satisfied. Specifically, it is determined whether the cumulative value (tL) of the no-load and light-load operation times has become a value equal to or greater than the catalyst function recovery processing start determination value (ISJ), and if the determination is affirmative, The process proceeds to step (S14). If the determination in step (S13) is negative, the process returns to step (S11).

In step (S14), the integrated value (tL) of the no-load and light-load operation times integrated in step (S12) is reset to 0, the integration of the catalyst function recovery processing time to be performed after the fact is started, and step ( 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 reduction control of the intake throttle valve (11) and the exhaust throttle valve (5) in step (S15) is performed in the same manner as in step (S2).

In step (S16), it is determined whether the valve upstream exhaust pressure (P0) is equal to or lower 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 the exhaust gas temperature (T0) on the upstream side of the valve is equal to or higher than the after-injection permission temperature (TA), and if the determination is affirmative, 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 negative, the process proceeds to step (S17-2), where 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 step (S17-1) is performed in the same manner as in step (S4-2).
If the determination at step (S17-1) is negative, the process returns to step (S16).

In step (S19), it is determined whether the conditions for ending the catalyst function recovery process are satisfied. Specifically, the termination condition is that the integrated value (tI) of the catalyst function recovery processing time becomes a value equal to or greater than the termination determination value (IEJ) of the catalyst function recovery process, and in step (S19), this termination condition is determined. It is determined whether the conditions are satisfied or not.
The determination in step (S19) is repeated until the determination is affirmative, and if the determination is affirmative, the process proceeds to step (S20).
In step (S20), after-injection control is ended, and the process proceeds to step (S21).
In step (S21), the intake throttle valve (11) is reset to full open, and the exhaust throttle valve (5) is also reset to full open. ) is reset to 0, and the process returns to step (S11). Note that the reset of the integrated value (tL) of the no-load and light-load operation times in the upper stage of step (S14) to 0 may also be performed in step (S21) instead of step (S14).

In this engine, the flow of the catalytic function recovery process for the valve upstream DOC (17) by the electronic control unit (8) shown in FIG. 4 is the same as the flow of the catalytic function recovery process for the valve downstream DOC (6) shown in FIG. They almost match.
The difference from the flow in FIG. 3 is that step (S18-2) and step (S18-3) are set after step (S18), and step (S20) is set after step (S19) instead of step (S20). The point is that a similar step (S20') is set.
That is, when after-injection control is started in step (S18), the process proceeds to step (S18-2).
In step (S18-2), it is determined whether the valve upstream exhaust temperature (T0) is equal to or higher than the post injection permission temperature (TP). The determination in step (S18-2) is repeated until it is affirmed, and if 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 conditions for ending the catalyst function recovery process are satisfied, the process proceeds to step (S20').
In step (S20'), the post injection control and after injection control are ended, and the process proceeds to step (S21).

Each of the processes shown in FIGS. 2 to 4 is executed independently and not simultaneously. If any process is started, no other process will be started until that process is finished. Further, the catalytic function recovery process for the valve downstream DOC (6) in FIG. 3 and the catalytic function recovery process for the valve upstream DOC (17) in FIG. 4 may be performed alternately, or once the former and the latter multiple times (for example, two or three times) may be performed alternately, or the former multiple times (for example, two or three times) and the latter once may be performed alternately.

In addition, the exhaust throttle valve (5) of the above embodiment is arranged on the exhaust downstream side of the DPF (7), or the valve downstream side DOC (6) is omitted, or the exhaust inlet of the exhaust downstream side DOC (6) is arranged. Variations of the embodiment can also be made, such as post-injection with an injection tube injector located at the injection tube. When the DOC (6) on the downstream side of the valve is omitted, a DPF (7) with a DOC function is used, and the injection pipe injector is placed on the exhaust inlet side of the DPF (7) with a DOC function. When the valve downstream DOC (6) is omitted, the inlet exhaust temperature (T2) of the DPF (7) with DOC function is used in place of the inlet exhaust temperature (T1) of the valve downstream DOC (6). .

(1) Combustion chamber, (2) Fuel, (3) Fuel injection device, (4) Exhaust path, (5) Exhaust throttle valve, (6) Valve downstream DOC, (7) DPF , (8)...Electronic control device, (8a)...Failure display device, (9)...Exhaust, (10)...Intake path, (11)...Intake throttle valve, (12)...Valve upstream exhaust pressure calculation device , (12a)...valve upstream exhaust pressure sensor, (13)...differential pressure sensor, (14)...atmospheric pressure sensor, (15)...exhaust flow rate calculation device, (16)...intake flow rate sensor, (17)... Valve upstream DOC, (18)...Operating time integration device, (19)...Valve upstream exhaust temperature sensor, (20)...Intake, (S1)...Start condition for DPF regeneration process, (S2)...Exhaust throttle valve (S4-2)... Control to increase the opening of the exhaust throttle valve, (S5)... After injection control starts, (S7)... Post injection control starts, (S20)... Post injection control starts. , (T0)...Valve upstream exhaust temperature, (TA)...After injection permission temperature, (TP)...Post injection permission temperature, (P0)...Valve upstream exhaust pressure, (Pmax)...Pressure upper limit value, (G) ...Exhaust mass flow rate, (P1)...Valve downstream exhaust pressure, (ΔP)...Differential pressure, (P3)...Atmospheric pressure.

Claims (17)

A fuel injection device (3) that injects fuel (2) into the combustion chamber (1), an exhaust throttle valve (5) arranged in the exhaust path (4), and a valve downstream side DOC arranged on the exhaust downstream side. (6), a DPF (7) located downstream of the exhaust gas, and an electronic control device (8) that controls the opening of the exhaust throttle valve (5) and the fuel injection of the fuel injection device (3),
It is configured to perform regeneration processing of the DPF (7),
In the regeneration process of the DPF (7), after the start condition (S1) for the regeneration process of the DPF (7) on which PM has accumulated is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed, and the exhaust throttle valve (5) is ) becomes a predetermined after-injection permission temperature (TA) or higher, after-injection control is started (S5), and the combustion of the after-injected fuel causes the exhaust gas (9) to rise to a predetermined post-injection permission temperature (TP) or higher. Post-injection control is started (S7) after the temperature has reached the temperature, and the PM accumulated in the DPF (7) is incinerated by the exhaust gas (9) heated by catalytic combustion of the post-injected fuel in the DOC (6) on the downstream side of the valve. configured to be
In the DPF (7) regeneration process, 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), After that, the opening degree increasing control (S4-2) of the exhaust throttle valve (5) is performed,
A valve upstream exhaust pressure sensor (12a) is provided on the exhaust upstream side of the exhaust throttle valve (5), and the valve upstream exhaust pressure (P0) is detected by this valve upstream exhaust pressure sensor (12a). The exhaust throttle valve (5) is configured to increase the opening degree (S4-2) based on the detected value of the exhaust pressure (P0) on the upstream side of the valve by the exhaust pressure sensor (12a) on the upstream side of the valve,
A valve upstream side exhaust temperature sensor (19) is provided, and the valve upstream side exhaust temperature (T0) detected by this is used for temperature comparison judgment with the after injection permission temperature (TA) and the post injection permission temperature (TP). It is also used to calculate the predicted value of the valve upstream exhaust pressure (P0).
When the differential pressure value between the detected value of the valve upstream exhaust pressure (P0) and the predicted value of the valve upstream exhaust pressure (P0) reaches a predetermined abnormality judgment value, the electronic control unit (8) performs a failure diagnosis. A diesel engine characterized in that it is configured to perform. The diesel engine according to claim 1 ,
It is equipped with a fault display device (8a), and is configured such that when a fault diagnosis is made by the electronic control device (8), a fault display is displayed on the fault display device (8a) by the electronic control device (8). , a diesel engine characterized by: In the diesel engine according to claim 1 or claim 2 ,
A calculation device (12) for the exhaust pressure (P0) on the upstream side of the valve is provided, and the predicted value of the exhaust pressure (P0) on the upstream side of the valve is calculated based on the mass flow rate (G) of the exhaust (9) and the exhaust temperature (T0) on the upstream side of the valve. A diesel engine characterized in that it is configured to be calculated from a valve downstream exhaust pressure (P1). The diesel engine according to claim 3 ,
Equipped with a differential pressure sensor (13) that detects the differential pressure (ΔP) between the entrance and exit of the DPF (7) and an atmospheric pressure sensor (14) that detects the atmospheric pressure (P3),
A diesel engine characterized in that the valve downstream exhaust pressure (P1) is calculated from the differential pressure (ΔP) between the inlet and outlet of the DPF (7) and the atmospheric pressure (P3). The diesel engine according to any one of claims 1 to 4 ,
The intake throttle valve (11) is arranged in the intake path (10), and the opening degree thereof is controlled by an electronic control device (8).
In the DPF (7) regeneration process, after the DPF (7) regeneration process start condition (S1) is satisfied, the exhaust throttle valve (5) is controlled to reduce the opening degree (S2), and the intake throttle valve (11) is ) A diesel engine characterized in that it is configured to perform opening reduction control (S2). The diesel engine according to any one of claims 1 to 5 ,
A diesel engine characterized by comprising a valve upstream DOC (17) disposed on the exhaust upstream side of an exhaust throttle valve (5). The diesel engine according to claim 6 ,
The DOC (17) on the upstream side of the valve and the DOC (6) on the downstream side of the valve use a flow-through type oxidation catalyst in which catalyst components are supported on a honeycomb carrier through which the exhaust gas (9) passes through the cells. A diesel engine featuring The diesel engine according to any one of claims 1 to 7 ,
It is configured to perform catalyst function recovery processing of the DOC (6) on the downstream side of the valve,
In the catalytic function recovery process of the valve downstream DOC (6), the start conditions (S13 ) is established, the opening degree reduction control of the exhaust throttle valve (5) is performed (S15), and after the temperature of the exhaust gas (9) reaches a predetermined after-injection permission temperature (TA) or higher, the after-injection control is started (S18). ), and the exhaust gas (9) heated by combustion of the after-injected fuel vaporizes or incinerates unburned deposits deposited on the DOC (6) on the downstream side of the valve. diesel engine. The diesel engine according to claim 8 ,
Equipped with an operation time accumulation device (18) for accumulating operation time of no-load and/or light-load operation,
When the cumulative value (tL) of no-load and/or light-load operation time reaches a predetermined catalyst function recovery process start judgment value (ISJ), the catalyst function recovery process of the valve downstream DOC (6) is started. A diesel engine characterized in that it is configured such that a starting condition (S13) is satisfied. A fuel injection device (3) that injects fuel (2) into the combustion chamber (1), an exhaust throttle valve (5) arranged in the exhaust path (4), and a valve downstream side DOC arranged on the exhaust downstream side. (6), a DPF (7) located downstream of the exhaust gas, and an electronic control device (8) that controls the opening of the exhaust throttle valve (5) and the fuel injection of the fuel injection device (3),
It is configured to perform regeneration processing of the DPF (7),
In the regeneration process of the DPF (7), after the start condition (S1) for the regeneration process of the DPF (7) on which PM has accumulated is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed, and the exhaust throttle valve (5) is ) becomes a predetermined after-injection permission temperature (TA) or higher, after-injection control is started (S5), and the combustion of the after-injected fuel causes the exhaust gas (9) to rise to a predetermined post-injection permission temperature (TP) or higher. Post-injection control is started (S7) after the temperature has reached the temperature, and the PM accumulated in the DPF (7) is incinerated by the exhaust gas (9) heated by catalytic combustion of the post-injected fuel in the DOC (6) on the downstream side of the valve. configured to be
In the DPF (7) regeneration process, 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), After that, the opening degree increasing control (S4-2) of the exhaust throttle valve (5) is performed,
A valve upstream exhaust pressure sensor (12a) is provided on the exhaust upstream side of the exhaust throttle valve (5), and the valve upstream exhaust pressure (P0) is detected by this valve upstream exhaust pressure sensor (12a). The exhaust throttle valve (5) is configured to increase the opening degree (S4-2) based on the detected value of the exhaust pressure (P0) on the upstream side of the valve by the exhaust pressure sensor (12a) on the upstream side of the valve,
It is configured to perform catalyst function recovery processing of the DOC (6) on the downstream side of the valve,
In the catalytic function recovery process of the valve downstream DOC (6), the start conditions (S13 ) is established, the opening degree reduction control of the exhaust throttle valve (5) is performed (S15), and after the temperature of the exhaust gas (9) reaches a predetermined after-injection permission temperature (TA) or higher, the after-injection control is started (S18). ), and the unburned deposits accumulated on the DOC (6) on the downstream side of the valve are vaporized or incinerated by the exhaust gas (9) heated by combustion of the after-injected fuel,
Equipped with an operation time accumulation device (18) for accumulating operation time of no-load and/or light-load operation,
When the cumulative value (tL) of no-load and/or light-load operation time reaches a predetermined catalyst function recovery process start judgment value (ISJ), the catalyst function recovery process of the valve downstream DOC (6) is started. A diesel engine characterized in that it is configured such that a starting condition (S13) is satisfied. The diesel engine according to claim 10 ,
The intake throttle valve (11) is arranged in the intake path (10), and the opening degree thereof is controlled by an electronic control device (8).
In the DPF (7) regeneration process, after the DPF (7) regeneration process start condition (S1) is satisfied, the exhaust throttle valve (5) is controlled to reduce the opening degree (S2), and the intake throttle valve (11) is ) A diesel engine characterized in that it is configured to perform opening reduction control (S2). The diesel engine according to any one of claims 1 to 11 ,
A valve upstream DOC (17) is provided on the exhaust upstream side of the exhaust throttle valve (5),
It is configured so that the catalytic function recovery process of the DOC (17) on the upstream side of the valve is performed,
In the catalytic function recovery process of the valve upstream DOC (17), the start conditions (S13 ) is established, the opening degree reduction control of the exhaust throttle valve (5) is performed (S15), and after the temperature of the exhaust gas (9) reaches a predetermined after-injection permission temperature (TA) or higher, the after-injection control is started (S18). ), and after the exhaust gas (9) reaches a temperature equal to or higher than the predetermined post-injection permission temperature (TP) due to the combustion of the after-injected fuel, post-injection control is started (S18-3), and the post-injection control is started using the combustion heat of the after-injected fuel. A diesel engine characterized in that the injected fuel is combusted and the unburned deposits deposited on the upstream DOC (17) of the valve are vaporized or incinerated by the heat of the heated exhaust gas (9). engine. The diesel engine according to claim 12 ,
Equipped with an operation time accumulation device (18) for accumulating operation time of no-load and/or light-load operation,
When the integrated value (tL) of no-load and/or light-load operation time reaches a predetermined catalyst function recovery process start judgment value (ISJ), the catalyst function recovery process of the valve upstream DOC (17) is started. A diesel engine characterized in that it is configured such that a starting condition (S13) is satisfied. A fuel injection device (3) that injects fuel (2) into the combustion chamber (1), an exhaust throttle valve (5) arranged in the exhaust path (4), and a valve downstream side DOC arranged on the exhaust downstream side. (6), a DPF (7) located downstream of the exhaust gas, and an electronic control device (8) that controls the opening of the exhaust throttle valve (5) and the fuel injection of the fuel injection device (3),
It is configured to perform regeneration processing of the DPF (7),
In the regeneration process of the DPF (7), after the start condition (S1) for the regeneration process of the DPF (7) on which PM has accumulated is satisfied, the opening degree reduction control (S2) of the exhaust throttle valve (5) is performed, and the exhaust throttle valve (5) is ) becomes a predetermined after-injection permission temperature (TA) or higher, after-injection control is started (S5), and the combustion of the after-injected fuel causes the exhaust gas (9) to rise to a predetermined post-injection permission temperature (TP) or higher. Post-injection control is started (S7) after the temperature has reached the temperature, and the PM accumulated in the DPF (7) is incinerated by the exhaust gas (9) heated by catalytic combustion of the post-injected fuel in the DOC (6) on the downstream side of the valve. configured to be
In the DPF (7) regeneration process, 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), After that, the opening degree increasing control (S4-2) of the exhaust throttle valve (5) is performed,
A valve upstream exhaust pressure sensor (12a) is provided on the exhaust upstream side of the exhaust throttle valve (5), and the valve upstream exhaust pressure (P0) is detected by this valve upstream exhaust pressure sensor (12a). The exhaust throttle valve (5) is configured to increase the opening degree (S4-2) based on the detected value of the exhaust pressure (P0) on the upstream side of the valve by the exhaust pressure sensor (12a) on the upstream side of the valve,
A valve upstream DOC (17) is provided on the exhaust upstream side of the exhaust throttle valve (5),
It is configured so that the catalytic function recovery process of the DOC (17) on the upstream side of the valve is performed,
In the catalytic function recovery process of the valve upstream DOC (17), the start conditions (S13 ) is established, the opening degree reduction control of the exhaust throttle valve (5) is performed (S15), and after the temperature of the exhaust gas (9) reaches a predetermined after-injection permission temperature (TA) or higher, the after-injection control is started (S18). ), and after the exhaust gas (9) reaches a temperature equal to or higher than the predetermined post-injection permission temperature (TP) due to the combustion of the after-injected fuel, post-injection control is started (S18-3), and the post-injection control is started using the combustion heat of the after-injected fuel. The injected fuel is combusted, and the unburned deposits deposited on the upstream side DOC (17) of the valve are vaporized or incinerated by the heat of the heated exhaust gas (9),
Equipped with an operation time accumulation device (18) for accumulating operation time of no-load and/or light-load operation,
When the integrated value (tL) of no-load and/or light-load operation time reaches a predetermined catalyst function recovery process start judgment value (ISJ), the catalyst function recovery process of the valve upstream DOC (17) is started. A diesel engine characterized in that it is configured such that a starting condition (S13) is satisfied. The diesel engine according to claim 14 ,
The intake throttle valve (11) is arranged in the intake path (10), and the opening degree thereof is controlled by an electronic control device (8).
In the DPF (7) regeneration process, after the DPF (7) regeneration process start condition (S1) is satisfied, the exhaust throttle valve (5) is controlled to reduce the opening degree (S2), and the intake throttle valve (11) is ) A diesel engine characterized in that it is configured to perform opening reduction control (S2). The diesel engine according to any one of claims 12 to 15 ,
When the valve upstream exhaust pressure (P0) reaches a predetermined catalytic function recovery process start determination value, the valve upstream side DOC (17) is configured so that the catalytic function recovery process start condition (S13) is satisfied. A diesel engine characterized by: The diesel engine according to any one of claims 12 to 16 ,
When the number of regeneration processes for the DPF (6) reaches a predetermined catalytic function recovery process start determination value (ISJ), the start condition (S13) for the catalytic function recovery process for the valve upstream DOC (17) is satisfied. A diesel engine characterized by being configured as follows.

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