JP2013068185A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diesel engine that can prevent failure in which unburnt fuel slips through a DOC due to degradation of the DOC.SOLUTION: After PM deposition amount estimate of a DPF reaches a predetermined regeneration required value, based on an exhaust air flow rate and a temperature of the DOC intake exhaust gas, a control means calculates post injection quantity S3, after making regeneration processing of the DPF done by the post injection S4, the control means compares the detection value of the temperature of the DOC outlet exhaust gas with a theoretical value of a temperature of the DOC outlet exhaust gas in case there is no degradation of the DOC, when the detection value of the temperature of the DOC outlet exhaust gas is lower than the theoretical value of the temperature of the DOC outlet exhaust gas, the control means executes volume reduction correction for the post injection quantity S7.

Description

  The present invention relates to a diesel engine, and more particularly to a diesel engine that can prevent a problem that unburned fuel slips through the DOC due to deterioration of the DOC. In this specification and claims, DOC refers to a diesel oxidation catalyst, DPF refers to a diesel particulate filter, and PM refers to a particulate material.

Conventionally, as a diesel engine, DOC and DPF are arranged in the exhaust path, and after the estimated PM accumulation value of the DPF reaches a predetermined regeneration required value, the control means performs DPF regeneration processing by post injection on the DPF regeneration means When the unburned fuel is mixed in the exhaust gas, the exhaust temperature is raised by catalytic combustion of the unburned fuel in the DOC, the PM accumulated in the DPF is incinerated, and a predetermined DPF regeneration completion condition is satisfied In some cases, the control means completes the regeneration process of the DPF by post injection (see, for example, Patent Document 1).
According to this type of diesel engine, there is an advantage that the DPF can be regenerated and reused.
However, this conventional technique has a problem because the post injection amount is increased as the DOC outlet exhaust temperature increases.

Japanese Patent Laying-Open No. 2005-307744 (see FIG. 1)

<< Problem >> It is not possible to prevent the unburned fuel from slipping through the DOC due to the deterioration of the DOC.
Since the post-injection amount is increased as the DOC outlet exhaust temperature increases, even when the DOC is deteriorated, the DOC outlet temperature increases due to an increase in the main fuel injection amount at high loads. The amount of post-injection exceeding the oxidation capacity of the DOC is performed, and the failure of the unburned fuel to slip through the DOC due to the deterioration of the DOC cannot be prevented. When the unburned fuel slips through the DOC, the unburned fuel may burn in the downstream DPF, and the DPF may be thermally damaged by the combustion heat.

  The subject of this invention is providing the diesel engine which can prevent the malfunction which unburned fuel slips DOC by deterioration of DOC.

Invention specific matters of the invention according to claim 1 are as follows.
As shown in FIGS. 1 and 2, the DOC (1) and the DPF (2) are arranged in the exhaust path, and after the PM accumulation estimated value of the DPF (2) reaches a predetermined regeneration request value, the control means (3) causes the DPF regeneration means (4) to perform the regeneration process of the DPF (2) by post injection (S4), and mixes unburned fuel into the exhaust (5), so that the unreacted fuel in the DOC (1) When the exhaust temperature is raised by catalytic combustion of the fuel, PM deposited on the DPF (2) is incinerated, and when a predetermined DPF regeneration completion condition is satisfied, the control means (3) performs post injection DPF (2) In the diesel engine that completes the regeneration process (S11),
As illustrated in FIGS. 1 and 2, after the estimated PM accumulation value of the DPF (2) reaches a predetermined regeneration required value, the control means (3) performs post-injection based on the exhaust flow rate and the DOC inlet exhaust temperature. After calculating the amount (S3) and carrying out the regeneration process of DPF (2) by post injection (S4), the control means (3) has no deterioration of the detected value of the DOC outlet exhaust temperature and DOC (1) In the case where the detected value of the DOC outlet exhaust temperature is lower than the theoretical value of the DOC outlet exhaust temperature, the control means (3) sets the exhaust flow rate and the DOC inlet exhaust temperature. A diesel engine characterized in that a post-injection amount calculated based on a reduction correction (S7).

(Invention of Claim 1)
The invention according to claim 1 has the following effects.
<Effect> It is possible to prevent the unburned fuel from slipping through the DOC due to the deterioration of the DOC.
As illustrated in FIG. 1 and FIG. 2, when the detected value of the DOC outlet exhaust temperature is lower than the theoretical value of the DOC outlet exhaust temperature, the control means (3) corrects the post-injection amount by decreasing (S7). When the DOC (1) is deteriorated, the detected value of the DOC outlet exhaust temperature becomes lower than the theoretical value of the DOC outlet exhaust temperature, so that the post injection amount is corrected to decrease, and the oxidation of the DOC (1) is performed. The amount of post-injection exceeding the capacity is prevented, and a problem that unburned fuel slips through the DOC (1) due to deterioration of the DOC (1) can be prevented.

It is a mimetic diagram of a diesel engine concerning an embodiment of the present invention. It is a flowchart of the process by the control means of the engine of FIG.

  1 and 2 are diagrams for explaining a diesel engine according to an embodiment of the present invention. In this embodiment, a common rail type water-cooled vertical in-line multi-cylinder diesel engine will be described.

This diesel engine is configured as follows.
The cylinder head (7) is assembled to the top of the cylinder block (6), the engine cooling fan (8) is arranged at the front of the cylinder block (6), and the flywheel (9) is arranged at the rear of the cylinder block (6). doing. An exhaust manifold (10) is assembled to one side of the cylinder head (7), a supercharger (11) is assembled to the exhaust manifold (10), and an exhaust treatment device ( 12) is arranged.

A common rail (15) is connected to the fuel tank (13) via a fuel supply pump (14), and a fuel injector (16) for each cylinder is connected to the common rail (15).
The pulsar rotor (17) is attached to the flywheel (9), the camshaft rotor (19) is attached to the valve camshaft (18), the pickup coil (20) is opposed to the pulsar rotor (17), and the camshaft rotor (19) The cylinder discrimination sensor (21) is opposed to the engine, the actual engine speed and the crank angle are detected by the pickup coil (20), and the top dead center of a predetermined cylinder is the compression top dead center by the cylinder discrimination sensor (21). The combustion stroke of each cylinder is detected, such as whether it is exhaust top dead center. The target rotational speed detection sensor (23) detects the speed control position of the speed control lever (22), that is, the engine target speed.
A pickup coil (20), a cylinder discrimination sensor (21), and a target rotational speed detection sensor (23) are linked to the electromagnetic valve (30) of the fuel injector (16) via the control means (3).
The control means (3) calculates a fuel injection amount (main injection amount) based on the target engine speed and the actual engine speed, and based on the crank angle, the solenoid valve (16) of the fuel injector (16) at a predetermined timing. 30) is opened and closed, and a predetermined amount of main injection is performed at a predetermined timing from the fuel injector (16). The control means (3) is a microcomputer.

The configuration of the exhaust treatment device (12) is as follows.
The DOC (1) and the DPF (2) are accommodated in the casing (24). The DOC (1) is arranged upstream, and the DPF (2) is arranged downstream.
The DOC (1) is a ceramic honeycomb carrier that supports the oxidation catalyst and is a flow-through type in which both ends of the cell (1a) are opened. The exhaust (5) passes through the inside of the cell (1a). Yes.
The DPF (2) is a ceramic honeycomb carrier and is a wall flow type in which the ends of adjacent cells (2a) are alternately plugged. The exhaust gas passes through the inside of the cell (2a) and the wall (1b) of the cell (2a), and captures PM by the wall (2b) of the cell (2a).

A DOC inlet exhaust temperature sensor (25) is disposed on the inlet side of the DOC (1), and a DOC outlet exhaust temperature sensor (31) is disposed on the outlet side of the DOC (1). A DFF inlet exhaust temperature sensor (26) is disposed between the DOC (1) and the DPF (2). In addition, a DPF inlet exhaust pressure sensor (27) is arranged between the DOC (1) and the DPF (2), and the exhaust pressure on the inlet side and the outlet side is between the inlet side and the outlet side of the DPF (2). A differential pressure sensor (28) for detecting the differential pressure is arranged.
The DOC inlet exhaust temperature sensor (25), the DOC outlet exhaust temperature sensor (31), the DFF inlet exhaust temperature sensor (26), the DPF inlet exhaust pressure sensor (27), and the differential pressure sensor (28) are control means (3). It is made to cooperate with the solenoid valve (30) of a fuel injector (16) through this.

  The control means (3) calculates the first PM accumulation estimated value of the DPF (2) based on the fuel injection amount and the DPF inlet exhaust temperature, and also calculates the DPF inlet exhaust pressure, the inlet side and the outlet of the DPF (2). Based on the differential pressure on the side, a second PM deposition estimated value of DPF (2) is calculated. After either the first PM deposition estimated value or the second PM deposition estimated value reaches a predetermined regeneration request value, the control means (3) causes the DPF regeneration means (4) to regenerate the DPF (2). Let it be implemented. The DPF regeneration means (4) comprises a combination of the common rail system (29) and the DOC (1), and the regeneration process of the DPF (2) performs the post-injection after the main injection from the fuel injector (16), and the unburned fuel. This is performed by catalytic combustion of the fuel with DOC (1).

  As shown in FIGS. 1 and 2, the DOC (1) and DPF (2) are arranged in the exhaust path, and after the estimated PM accumulation amount of the DPF (2) reaches a predetermined regeneration request value, the control means ( 3) causes the DPF regeneration means (4) to perform post-injection (S4), and mixes unburned fuel into the exhaust (5), so that the exhaust temperature is increased by catalytic combustion of unburned fuel in the DOC (1). The PM accumulated in the DPF (2) is incinerated, and when a predetermined DPF regeneration completion condition is satisfied, the control means (3) completes the regeneration process of the DPF (2) by post injection (S11). I have to.

  As shown in FIGS. 1 and 2, after the estimated PM accumulation value of the DPF (2) reaches a predetermined regeneration required value, the control means (3) performs post injection amount based on the exhaust flow rate and the DOC inlet exhaust temperature. Is calculated (S3) and post injection is performed (S4), then the control means (3) detects the DOC outlet exhaust temperature and the theoretical value of the DOC outlet exhaust temperature when DOC (1) is not deteriorated. If the detected value of the DOC outlet exhaust temperature is lower than the theoretical value of the DOC outlet exhaust temperature, the post-injection amount calculated by the control means (3) based on the exhaust flow rate and the DOC inlet exhaust temperature is reduced. Correction (S7) is performed.

The flow of processing by the control means (3) is as follows.
In step (S1), it is determined whether the PM deposition estimated value of DPF (2) has reached the DPF regeneration request value. If the determination is negative, step (S1) is repeated until the determination is positive. If the determination in step (S1) is affirmed, it is determined in step (S2) whether or not the estimated temperature of DOC (1) has reached the activation temperature. If the determination is negative, the determination is affirmed. Repeat step (S2). If the determination in step (S2) is affirmative, the post-injection amount is calculated based on the exhaust flow rate and the DOC inlet exhaust temperature in step (S3), and the DPF (2) regeneration process by post-injection is performed in step (S3). To implement.

  Next, post injection is performed in step (S4), the DOC outlet exhaust temperature is detected in step (S5), and whether or not the detected value of the DOC outlet exhaust temperature is lower than the theoretical value of the DOC outlet temperature in step (S6). Is determined. If the determination in step (S6) is affirmative, in step (S7), the post-injection amount is corrected to decrease based on the temperature deviation between the detected value of the DOC outlet exhaust temperature and the theoretical value of the DOC outlet exhaust temperature. Next, in step (S8), it is determined whether or not the estimated temperature of DOC (1) has reached the activation temperature. If the determination is negative, step (S8) is repeated until the determination is affirmed. If affirmative is determined, post injection is performed in step (S9).

Next, in step (S10), it is determined whether or not the DPF regeneration end condition is satisfied. If the determination is affirmative, the regeneration process of DPF (2) by post injection is completed in step (S11).
If the determination in step (S6) is negative, it is determined in step (S12) whether or not the DPF regeneration end condition is satisfied. If the determination is affirmative, post injection is performed in step (S11). When the DPF regeneration process is completed and the determination is negative, the process returns to step (S2). If the determination in step (S10) is negative, the process returns to step (S5).

The estimated temperature of the DOC (1) is calculated by the control means (3) based on the DOC inlet exhaust temperature, the specific heat of the DOC (1), the heat radiation from the DOC (1), and the like.
The activation temperature of DOC (1) is 250 ° C.
The post-injection amount is calculated by the control means (3) based on the DPF inlet exhaust temperature, the DOC inlet exhaust temperature, and the exhaust flow rate, with the target temperature of the DPF inlet exhaust temperature being 600 ° C. The exhaust gas flow rate is calculated by the control means (3) from the intake air amount, the main injection amount, and the DOC inlet exhaust temperature.
Post injection is performed during the exhaust stroke after the main injection near the compression top dead center from the injector (16) of the common rail system (29).
The theoretical value of the DOC outlet exhaust temperature is calculated by the control means (3) based on the estimated temperature of the DOC (1), the oxidation ability when the DOC (1) is not deteriorated, and the post injection amount.
The completion condition of the regeneration process of the DPF (2) is when the regeneration progress integration time when the DPF inlet exhaust temperature reaches 600 ° C. or more has passed 15 minutes.

(1) DOC
(2) DPF
(3) Control means
(4) DPF regeneration means
(5) Exhaust
(S3) Calculate post injection amount
(S4) Post injection
(S7) Reduce post-injection amount
(S11) Complete playback process

Claims (1)

After the DOC (1) and the DPF (2) are arranged in the exhaust path, and the estimated PM accumulation value of the DPF (2) reaches a predetermined regeneration request value, the control means (3) is connected to the DPF regeneration means (4). The regeneration process of DPF (2) by post injection is performed (S4), and unburnt fuel is mixed into the exhaust (5), so that the exhaust temperature is raised by catalytic combustion of unburned fuel in DOC (1). Then, the PM deposited on the DPF (2) is incinerated, and when a predetermined DPF regeneration completion condition is satisfied, the control means (3) completes the regeneration process of the DPF (2) (S11). In
After the PM accumulation estimated value of the DPF (2) reaches a predetermined regeneration required value, the control means (3) calculates the post injection amount (S3) based on the exhaust flow rate and the DOC inlet exhaust temperature, and the post injection After the DPF (2) regeneration process is performed (S4), the control means (3) calculates the detected value of the DOC outlet exhaust temperature and the theoretical value of the DOC outlet exhaust temperature when the DOC (1) is not deteriorated. In comparison, if the detected value of the DOC outlet exhaust temperature is lower than the theoretical value of the DOC outlet exhaust temperature, the control means (3) reduces the post-injection amount (S7).

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