JP2013068186A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diesel engine capable of suppressing unnecessary post injection after the completion of substantial DPF regeneration.SOLUTION: In the diesel engine, a control means performs the operation S7 of a PM deposit estimated value on the basis of a temperature estimated value of a DPF and a fuel injection amount, and when the PM deposit estimated value of the DPF reaches a prescribed regeneration completion determination value, the control means performs the completion S9 of the regeneration processing of the DPF performed by post injection. The control means performs an operation S6 of the temperature estimated value of the DPF on the basis of a DPF inlet exhaust temperature and a slip estimated value of post-injection fuel which sneaks through a DOC.

Description

  The present invention relates to a diesel engine, and more particularly to a diesel engine that can suppress useless post injection after completion of substantial DPF regeneration. 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 By mixing the unburned fuel into 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 the control means calculates the estimated DPF temperature. Then, based on the estimated DPF temperature and the fuel injection amount, the control means calculates the PM accumulation value. When the estimated PM accumulation value of the DPF reaches a predetermined regeneration completion determination value, the control means performs post injection. There is one that completes the regeneration process of the DPF (for example, see 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 calculation of the estimated DPF temperature does not reflect the combustion of the post-injected fuel passing through the DOC in the DPF.

Japanese Patent Laying-Open No. 2005-155575 (see FIG. 1)

<< Problem >> Even after substantial DPF regeneration is completed, there is a possibility that wasteful post-injection may be carried out for a long time.
Since the post-injection fuel passing through the DOC does not reflect the combustion in the DPF in the calculation of the DPF temperature estimate, the DPF temperature estimate is estimated to be substantially lower, and the PM deposition estimate is substantially higher. Therefore, even when the regeneration of the DPF is substantially completed, the time until the estimated PM accumulation value of the DPF reaches the regeneration completion determination value is greatly delayed, and a wasteful post after the substantial completion of the DPF regeneration is achieved. There is a possibility that the injection is carried out for a long time.

  The subject of this invention is providing the diesel engine which can suppress the useless post injection after completion of substantial DPF regeneration.

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) The exhaust temperature is raised by catalytic combustion of the fuel, the PM deposited on the DPF (2) is incinerated, the control means (3) calculates the estimated temperature value of the DPF (2), and the temperature of the DPF (2) Based on the estimated value and the fuel injection amount, the control means (3) calculates the PM accumulation estimated value (S7), and when the PM accumulation estimated value of the DPF (2) reaches a predetermined regeneration completion determination value, the control means In the diesel engine in which (3) completes the regeneration process of DPF (2) by post injection (S9),
As illustrated in FIG. 1 and FIG. 2, the control means for calculating the temperature estimation value (S6) of the DPF (2) based on the DPF inlet exhaust temperature and the post injection slip estimation value passing through the DOC (1). A diesel engine characterized in that (3) calculates.

(Invention of Claim 1)
The invention according to claim 1 has the following effects.
<< Effect >> Wasteful post-injection after substantial DPF regeneration is completed can be suppressed.
As illustrated in FIGS. 1 and 2, the calculation (S6) of the estimated temperature value of the DPF (2) is controlled based on the DPF inlet exhaust temperature and the estimated slip value of the post-injected fuel passing through the DOC (1). Since the means (3) calculates, the estimated temperature value of the DPF (2) becomes accurate reflecting the combustion of the post-injected fuel passing through the DOC (1) in the DPF (2). The estimation of the PM deposition estimated value based on the temperature estimated value is also accurate, and the time when the PM deposition estimated value of the DPF (2) reaches the regeneration completion determination value is not significantly delayed from the substantial DPF regeneration completion timing. In addition, useless post injection after completion of substantial DPF regeneration can be suppressed.

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 side temperature sensor (25) is arranged on the inlet side of the DOC (1), and a DFF inlet side temperature sensor (26) is arranged between the DOC (1) and the DPF (2). Further, a DPF inlet side exhaust pressure sensor (27) is disposed between the DOC (1) and the DPF (2), and the inlet side and outlet side exhaust pressures are arranged 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 side temperature sensor (25), the DFF inlet side temperature sensor (26), the DPF inlet side exhaust pressure sensor (27), and the differential pressure sensor (28) are connected to the fuel injector (16) via the control means (3). The electromagnetic valve (30) is linked.

  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 temperature, and also the DPF inlet side exhaust pressure, the DPF (2) inlet side and the outlet Based on the pressure difference on the side, the second estimated PM deposition value of the 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). And the regeneration of the DPF (2) is completed. 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) is performed after the main injection from the fuel injector (16) and post-injection. This is performed by catalytic combustion of the fuel with DOC (1).

  As shown in FIGS. 1 and 2, the DOC (1) and the DPF (2) are arranged in the exhaust path, and after the estimated PM deposition value of the DPF (2) reaches a predetermined regeneration request value, the control means ( 3) The DPF regeneration means (4) performs the regeneration process of the DPF (2) by post injection (S4), and the unburned fuel is mixed into the exhaust (5), thereby unburned in the DOC (1). The exhaust temperature is raised by catalytic combustion of the fuel, the PM deposited on the DPF (2) is incinerated, the control means (3) calculates the estimated temperature of the DPF (2), and the temperature of the DPF (2) is estimated. Based on the value and the fuel injection amount, the control means (3) calculates the PM accumulation estimated value (S7), and when the PM accumulation estimated value of the DPF (2) reaches a predetermined regeneration completion determination value, the control means ( 3) completes the regeneration process of the DPF (2) by post injection (S9).

  As shown in FIG. 1 and FIG. 2, the control means for calculating the estimated temperature value (S6) of the DPF (2) is based on the DPF inlet exhaust temperature and the estimated slip value of the post-injected fuel passing through the DOC (1). (3) calculates.

The flow of processing by the control means (3) is as follows.
As shown in FIG. 2, in step (S1), it is determined whether the PM accumulation estimated value of DPF (2) has reached the DPF regeneration request value. If the determination is negative, the determination is affirmed. Step (S1) is repeated.
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 affirmative. Step (S2) is repeated until
If the determination in step (S2) is affirmed, the post injection amount is calculated in step (S3), and the DPF regeneration process by post injection is performed in step (S4).

  Next, in step (S5), an estimated slip value of post-injected fuel that passes through DOC (1) is calculated. Based on the estimated temperature value of the DPF (2) based on the temperature estimated value of the DPF (2) and the fuel injection amount in step (S7), the estimated PM deposition value of the DPF (2) is calculated. In S8), it is determined whether or not the PM accumulation estimated value of the DPF (2) has reached the regeneration completion value of the DPF (2). If the determination is affirmative, in Step (S9), the DPF (2) by post injection is determined. Complete the playback process. If the determination in step (S8) is negative, the process returns to step (S2).

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 (2) 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 flow rate is calculated by the control means (3) based on the intake flow rate, 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 slip estimated value of the post-injection fuel that passes through the DOC (1) is the temperature estimation of the DPF (2) calculated by the control means (3) based on the DOC inlet exhaust temperature, the post-injection amount, and the unburned fuel purification rate of the DOC. The value is calculated by the control means (3) based on the DPF inlet exhaust temperature, the exhaust flow rate, the estimated post-injection slip value of DOC (1), and the amount of heat of PM combustion.
The PM accumulation estimated value of the DPF (2) is calculated by the control means (3) based on the PM generation disappearance map experimentally obtained based on the main injection amount, the post injection amount, the engine speed, and the temperature estimated value of the DPF (2). ) Calculates the amount of production and disappearance of PM per unit time, and integrates them.

(1) DOC
(2) DPF
(3) Control means
(4) DPF regeneration means
(5) Exhaust
(S4) Perform playback processing
(S6) Calculation of estimated DPF temperature
(S7) Calculate PM deposition estimate
(S9) 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 the control means (3) calculates the estimated temperature value of the DPF (2), and controls based on the estimated temperature value of the DPF (2) and the fuel injection amount. The means (3) calculates the PM accumulation estimated value (S7), and when the PM accumulation estimated value of the DPF (2) reaches a predetermined regeneration completion determination value, the control means (3) causes the post-injection DPF (2). In the diesel engine that completes the regeneration process (S9),
The control means (3) calculates the temperature estimation value (S6) of the DPF (2) based on the DPF inlet exhaust temperature and the estimated slip value of the post-injected fuel passing through the DOC (1). Diesel engine.

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