JP2011220260A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device in which combustion of particulate corrected in a particulate filter can be performed surely.SOLUTION: The engine control device 100 controlling an engine 10 having a particulate filter 80 has such constitution that the device includes: an exhaust gas temperature detector 82; an oxygen quantity detector detecting oxygen quantity in the exhaust gas; and a reproduction necessary/unnecessary discriminator for discriminating necessary/unnecessary of the reproduction of the particulate filter; wherein when it is discriminated that reproduction of the particulate filter is necessary, a normal reproduction mode, in which temperature of exhaust gas is made to be high temperature relative to temperature during normal operation, and a combustion promotion mode, in which temperature of exhaust gas is made to be low relative to the normal reproduction mode and also oxygen quantity included in exhaust gas is increased, are switched based on output of the exhaust gas temperature detector and the oxygen quantity detector.

Description

  The present invention relates to an engine control device that controls an engine having a particulate filter that collects particulate matter (PM) in exhaust gas, and in particular, can reliably burn PM collected in the particulate filter. About things.

    A diesel engine for automobiles is provided with a diesel particulate filter (DPF) that collects particulate matter (PM) such as soot generated during combustion. In such a DPF, in particular, in the case of a closed type using a so-called plug-type filter element, the performance is remarkably lowered when the amount of accumulated PM increases. On the other hand, it is known to perform regeneration control in which PM deposited on the surface of the DPF is burned (oxidized) at a high temperature by performing post-injection immediately before or when the exhaust valve is opened in fuel injection control of the engine. ing.

  As a prior art related to such DPF regeneration control, for example, in Patent Document 1, until the temperature of the DPF reaches a temperature necessary for PM combustion, a rich operation is performed to reduce the oxygen concentration in the exhaust gas, It is described that the temperature of exhaust gas is increased by post-injection, the DPF is set to a high temperature, and then the lean operation is switched to burn PM at a stroke.

JP 2002-213229 A

However, the amount of oxygen contained in the exhaust gas of the engine decreases with respect to the normal operating state during high loads such as when the vehicle is fully open (when the fuel is rich) or during high altitude travel where the atmospheric pressure is low.
In such a case, even if a lean operation is intended to burn PM as engine control, oxygen in the exhaust gas flowing into the DPF is actually insufficient, and the amount of oxygen necessary for PM combustion There is a concern that unburned PM may remain in the DPF.
The subject of this invention is providing the engine control apparatus which can perform reliably combustion of the particulate matter trapped by the particulate filter.

The present invention solves the above-described problems by the following means.
The invention of claim 1 is an engine control device for controlling an engine having a particulate filter that collects particulate matter in exhaust gas, and detects the temperature of the exhaust gas flowing into the particulate filter. Means for detecting the amount of oxygen in the exhaust gas flowing into the particulate filter, and a regeneration necessity judging means for judging whether or not the particulate filter needs to be regenerated. When it is determined that regeneration is necessary, a normal regeneration mode in which the temperature of the exhaust gas is higher than that during normal operation, and a combustion promotion mode in which the amount of oxygen contained in the exhaust gas is increased with respect to the normal regeneration mode Are switched based on the outputs of the exhaust gas temperature detecting means and the oxygen amount detecting means. It is an engine control unit.
According to this, when oxygen necessary for the combustion of the particulate matter is insufficient, the particulate matter is surely burned by performing the combustion promotion mode in which the amount of oxygen is increased, and the particulate filter is improved. Can be played. In addition, when the exhaust gas is at a low temperature, by executing the normal regeneration mode, the inlet temperature of the particulate filter can be reliably improved, and the particulate matter can be reliably ignited.

The invention of claim 2 includes a throttle valve that adjusts an intake air amount of the engine, and a turbocharger that is driven by exhaust gas of the engine and is provided with a variable nozzle at a turbine inlet, and in the normal regeneration mode, 2. The engine control device according to claim 1, wherein a plurality of post fuel injections for improving the temperature of the exhaust gas are executed, the throttle valve is closed and the variable nozzle of the turbocharger is opened during normal operation. It is.
According to this, the temperature of the exhaust gas entering the particulate filter is improved by a plurality of post fuel injections, and further, the throttle valve is closed and the variable nozzle of the turbocharger is opened to reduce the flow rate of the exhaust gas. The temperature of the filter can be reliably improved and the particulate matter can be ignited satisfactorily.

According to a third aspect of the present invention, in the combustion promotion mode, the number of post fuel injections or the fuel injection amount is reduced, and the throttle valve is opened and the variable nozzle of the turbocharger is closed with respect to the normal regeneration mode. The engine control device according to claim 2.
According to this, by reducing the number of post fuel injections or reducing the injection amount, the amount of oxygen consumed for fuel combustion is reduced, and furthermore, the throttle valve is opened and the variable nozzle of the turbocharger is closed to increase the exhaust gas flow rate. Therefore, it is possible to increase the amount of oxygen supplied to the particulate filter, and to prevent defective combustion of particulate matter due to lack of oxygen.

According to a fourth aspect of the present invention, when it is determined that regeneration of the particulate filter is necessary, the normal regeneration mode is executed when the amount of oxygen in the exhaust gas is equal to or greater than a predetermined value. The engine control device according to any one of claims 1 to 3.
According to this, in the normal regeneration mode, oxygen necessary for the combustion of the particulate matter is not deficient, and the particulate filter can be regenerated reliably and satisfactorily.

According to a fifth aspect of the present invention, when it is determined that regeneration of the particulate filter is necessary, the normal regeneration mode is executed when the temperature of the exhaust gas is less than a predetermined value. The engine control device according to any one of claims 1 to 4.
According to this, when the temperature of the exhaust gas is low, the exhaust gas temperature is increased by the normal regeneration mode, so that it is possible to prevent the combustion acceleration mode from being executed in a state where the temperature of the exhaust gas is low and the combustion state of the particulate matter being deteriorated. .

According to a sixth aspect of the present invention, when it is determined that regeneration of the particulate filter is necessary, the combustion is performed when the amount of oxygen in the exhaust gas is less than a predetermined value and the temperature of the exhaust gas is not less than a predetermined value. The engine control device according to any one of claims 1 to 3, wherein an acceleration mode is executed.
According to this, by executing the combustion promotion mode, oxygen shortage for particulate matter combustion can be solved, and the particulate filter can be regenerated well.

  ADVANTAGE OF THE INVENTION According to this invention, the engine control apparatus which can perform combustion of the particulate matter collected by the particulate filter reliably can be provided.

1 is a schematic diagram showing a system configuration of an engine provided with an embodiment of an engine control device to which the present invention is applied. 3 is a flowchart showing selection of a DPF regeneration mode in the engine control device of FIG. 1. It is a schematic diagram which shows oxygen amount transition in the exhaust gas in DPF reproduction | regeneration in a common diesel engine. It is a schematic diagram which shows an example of transition of DPF inlet_port | entrance temperature at the time of DPF reproduction | regeneration in the engine of an Example.

  An object of the present invention is to provide an engine control device capable of reliably burning particulate matter collected by a particulate filter when the oxygen concentration in the exhaust gas is low and the exhaust gas temperature is high during DPF regeneration. Has been solved by executing the PM combustion promotion mode for increasing the oxygen supply amount to the DPF.

Embodiments of an engine control apparatus to which the present invention is applied will be described below.
FIG. 1 is a schematic diagram showing a system configuration of an engine.
The engine 10 includes a turbocharger 20, an intake system 30, an exhaust system 40, a fuel supply device 50, an EGR device 60, an oxidation catalyst (DOC) 70, a diesel particulate filter (DPF) 80, an engine control unit (ECU 100), and the like. Configured.

The engine 10 is, for example, a four-stroke diesel engine used as a driving power source for automobiles such as passenger cars.
The engine 10 includes a crankshaft 11, a piston 12, a cylinder block 13, a head 14, a combustion chamber 15, a glow plug 16, a glow controller 17, and the like.
The crankshaft 11 is an output shaft of the engine 10.
The piston 12 is a member that reciprocates in the cylinder and transmits the combustion pressure to the crankshaft 11 via the connecting rod.
The cylinder block 13 is formed integrally with a cylinder portion in which the piston 12 is accommodated and a crankcase portion in which the crankshaft 11 is rotatably supported.
The head 14 is provided at the crown-side end of the piston 12 of the cylinder block 13 and includes an intake port, an exhaust port, a valve drive mechanism that opens and closes the intake valve and the exhaust valve, and the like.
The combustion chamber 15 is formed between the crown surface of the piston 12 and the portion of the head 14 facing this.
The glow plug 16 is a preheating device provided in the head 14 with the tip portion exposed in the combustion chamber 15.
The glow controller 17 controls the energization amount to the glow plug 16 according to the control of the ECU 100.

The turbocharger 20 compresses combustion air (fresh air) taken in by the engine 10 using energy of exhaust gas (burned gas) of the engine 10.
The turbocharger 20 includes a compressor 21, a turbine 22, an actuator 23, a negative pressure control valve 24, and the like.
The compressor 21 is a centrifugal compressor that compresses combustion air.
The turbine 22 is provided coaxially with the compressor 21 and is driven by the exhaust gas of the engine 10 and drives the compressor 21. The turbine 22 is of a variable geometry type in which the nozzle can be opened and closed by a movable vane provided in the nozzle around the turbine wheel, and the geometry can be continuously changed.
The actuator 23 is a negative pressure type actuator that drives a movable vane of the turbine 22.
The negative pressure control valve 24 is an electromagnetic valve that introduces a negative pressure from a negative pressure source (not shown) into the actuator 23 according to the control of the ECU 100.

The intake system 30 introduces combustion air into the engine 10.
The intake system 30 includes an intake duct 31, an air cleaner 32, an air flow meter 33, an intercooler 34, a throttle valve 35, an actuator 36, an intake chamber 37, an intake pressure sensor 38, an intake manifold 39, and the like.

The intake duct 31 is an air flow path that introduces combustion air from the atmosphere and supplies it to the engine 10 via the compressor 21 of the turbocharger 20.
The air cleaner 32 includes a filter element that filters air to remove dust and the like. The air that has passed through the air cleaner 32 is introduced into the compressor 21 of the turbocharger 20 and compressed.
The air flow meter 33 is provided at the outlet of the air cleaner 32 and includes a sensor that detects the air flow rate. The air flow meter 33 includes an intake air temperature sensor for detecting the intake air temperature.

The intercooler 34 is a heat exchanger that cools the air that has exited the compressor 21 of the turbocharger 20 by heat exchange with the traveling wind.
The throttle valve 35 is provided on the downstream side of the intercooler 34 and adjusts the intake air amount of the engine 10.
The actuator 36 opens and closes the throttle valve 35 in response to a control signal from the ECU 100.
The intake chamber 37 is an air chamber into which air that has passed through the throttle valve 35 is introduced, and is connected to an intake port of the engine 10 via an intake manifold 39.
The intake pressure sensor 38 is provided in the intake chamber 37 and detects a pressure in the intake chamber 37 substantially equal to the intake pressure of the engine 10.
The intake manifold 39 is a branch pipe that introduces air from the intake chamber 37 to the intake port of each cylinder of the engine 10.

The exhaust system 40 includes an exhaust manifold 41, an exhaust pipe 42, and the like.
The exhaust manifold 41 is a pipe line that collects exhaust gas discharged from the exhaust port of each cylinder of the engine 10 and introduces the exhaust gas into the turbine 22 of the turbocharger 20.
The exhaust pipe 42 is a pipe line that discharges the exhaust discharged from the turbine 22 to the outside of the vehicle. The exhaust pipe 42 is provided with an exhaust gas aftertreatment device such as a DOC 70 and a DPF 80.

  The fuel supply device 50 supplies fuel into the combustion chamber 15 of the engine 10. The fuel supply device 50 is a common rail type high pressure fuel injection device including a supply pump 51, a suction metering solenoid valve 52, a fuel temperature sensor 53, a common rail 54, a fuel pressure sensor 55, an injector 56, and the like.

The supply pump 51 includes, for example, an inner cam type pressure feeding system, and pressurizes light oil as fuel and supplies it to the common rail 54.
The intake metering solenoid valve 52 adjusts the fuel intake amount of the supply pump 51 and is driven according to a control signal from the ECU 100.
The fuel temperature sensor 53 detects the temperature of the fuel in the supply pump 51.

The common rail 54 is a pressure accumulator that stores high-pressure fuel discharged from the supply pump 51.
The fuel pressure sensor 55 detects the fuel pressure (fuel pressure) in the common rail 54. The above-mentioned intake metering solenoid valve 52 is adjusted in its opening degree by feedback control using the output of the fuel pressure sensor 55 so that the fuel pressure becomes a predetermined target value set according to, for example, the engine speed and load. The
The injector 56 injects fuel supplied from the common rail 54 into the combustion chamber 15 of each cylinder. The injector 56 has a valve body that is opened and closed by an actuator such as a piezo element or a solenoid, and is opened in response to an injection pulse signal from the ECU 100. The injection timing and injection amount of the injector 56 are controlled by the ECU 100.

The EGR device 60 is intended to recirculate a part of the exhaust gas of the engine 10 extracted from the exhaust manifold 41 into the intake duct 31 for the purpose of reducing the NOx emission amount by suppressing the combustion temperature.
The EGR device 60 includes an EGR passage 61, an EGR control valve 62, an EGR cooler 63, and the like.
The EGR passage 61 is a conduit for introducing exhaust gas from the exhaust manifold 41 to the intake duct 31.
The EGR control valve 62 adjusts the exhaust gas flow rate (EGR amount) of the EGR passage 61 according to the control of the ECU 100.
The EGR cooler 63 cools the exhaust gas flowing through the EGR passage 61 by heat exchange with the traveling wind.

The DOC 70 is provided in the exhaust pipe 42 and mainly oxidizes hydrocarbons (HC) in the exhaust gas. The DOC 70 is formed by supporting a noble metal such as platinum or palladium or a metal oxide such as alumina on the surface of a ceramic carrier such as a cordierite honeycomb structure.
The DOC 70 is provided with a temperature sensor 71 for detecting the exhaust gas temperature at the inlet portion.

The DPF 80 is provided on the downstream side of the DOC 70 of the exhaust pipe 42 and includes a filter that collects particulate matter (PM) by filtering the exhaust gas. Here, PM includes soot (soot), organic solvent soluble components (SOF), sulfate (SO ₄ ), and the like.
For example, the filter is formed by forming heat resistant ceramics such as cordierite in a honeycomb structure, and sealing a large number of cells serving as gas flow paths at the end face so that the inlet side and the outlet side are staggered. It is a closed type (wall flow type).
The DPF 80 includes a differential pressure sensor 81 that detects a differential pressure between the inlet pressure and the outlet pressure, and temperature sensors 82 and 83 that detect exhaust gas temperatures at the inlet and the outlet, respectively.
Since the differential pressure sensor 81 detects a larger differential pressure as the soot accumulation amount increases in the DPF 80, it functions as a soot accumulation amount estimation unit in cooperation with the engine control unit 100.

The ECU 100 controls the above-described engine 10 and its auxiliary devices in an integrated manner, and includes an information processing device such as a CPU, a storage device such as a ROM and a RAM, an input / output interface, an A / D converter, Peripheral circuits such as timers, counters and various logic circuits are provided.
In addition to the various sensors described above, the outputs of the accelerator pedal sensor 101 and the atmospheric pressure sensor 102 are input to the ECU 100.
The accelerator pedal sensor 101 is request torque detection means for detecting driver request torque by detecting the position of the accelerator pedal operated by the driver.
The atmospheric pressure sensor 102 detects atmospheric pressure in the ambient atmosphere of the vehicle.

The ECU 100 controls the opening degree of the throttle valve 35, the fuel injection amount and timing of the fuel supply device 50, the fuel pressure, and the like according to the required torque set according to the output of the accelerator pedal sensor 101.
The ECU 100 also has a function of performing DPF regeneration control, which will be described later.

Next, DPF regeneration control in the embodiment will be described.
In this embodiment, the temperature of exhaust gas flowing into the DPF 80 by post-injection is increased, and the normal DPF regeneration mode in which PM deposited on the DPF 80 is subjected to combustion treatment, and the oxygen supply amount to the DPF 80 is increased with respect to the normal DPF regeneration mode. PM combustion acceleration mode.

FIG. 2 is a flowchart showing mode selection during regeneration of the DPF 80.
Hereinafter, the steps will be described step by step.
<Step S01: DPF regeneration>
The ECU 100 determines to execute the DPF regeneration control when the estimated accumulation amount of PM calculated based on the output of the differential pressure sensor 81 of the DPF 80 becomes a predetermined value or more.
Thereafter, the process proceeds to step S02.

<Step S02: Determination of oxygen concentration>
When the oxygen concentration in the exhaust gas discharged from the engine 10 is equal to or higher than a preset threshold value x%, the ECU 100 converts oxygen sufficient for PM combustion into the DPF even if the normal DPF regeneration mode is executed. The process proceeds to step S04 assuming that supply is possible. On the other hand, if the oxygen concentration is less than x%, the process proceeds to step S03.
Here, the oxygen concentration is, for example, an estimated value of the oxygen concentration from the operating state of the engine 10 (various parameters such as the rotational speed, fuel injection amount, supercharging pressure, atmospheric pressure, throttle opening, fuel injection amount, and injection timing). Can be estimated on the basis of a readable driving region map. Further, the exhaust system 40 may be directly detected by providing an O ₂ sensor (A / F sensor) for detecting the oxygen concentration in the exhaust gas.

<Step S03: DPF inlet temperature determination>
If the DPF inlet temperature detected by the temperature sensor 82 at the inlet of the DPF 80 is equal to or lower than the predetermined threshold y ° C., the ECU 100 proceeds to step S04 because it is necessary to increase the DPF inlet temperature. On the other hand, if the DPF inlet temperature is higher than y ° C., it is determined that PM can be burned well even if the PM combustion acceleration mode is executed, and the process proceeds to step S05.

<Step S04: Normal DPF regeneration>
The ECU 100 sets the PM combustion promotion mode flag to 0, executes DPF regeneration in the normal DPF regeneration mode, and ends (returns) a series of processes.
<Step S05: PM combustion promotion>
The ECU 100 sets the PM combustion acceleration mode flag to 1, executes DPF regeneration in the PM combustion acceleration mode, and ends a series of processes.
Each of these modes will be described in detail below.

Ａ：温度に無関係な定数（頻度因子）
Ｅ：活性化エネルギ（アレニウスパラメータとも称される）
Ｒ：気体定数
Ｔ：絶対温度[Ｋ]

ここで、活性化エネルギＥ及び気体定数Ｒは定数であるとみなせるため、ＰＭ燃焼に影響を及ぼすパラメータは、酸素量、絶対温度（雰囲気温度）と言い換えることができる。 By the way, the combustion of PM is supposed to be governed by the Arrhenius type reaction rate equation.
The rate constant k of this reaction is represented by Equation 1 below.

A: Constant independent of temperature (frequency factor)
E: Activation energy (also called Arrhenius parameter)
R: Gas constant T: Absolute temperature [K]

Here, since the activation energy E and the gas constant R can be regarded as constants, the parameters affecting the PM combustion can be paraphrased as oxygen amount and absolute temperature (atmosphere temperature).

In general, a diesel engine is operated in an oxygen-rich (fuel lean) state. During regeneration of the DPF, in order to raise the exhaust gas temperature, the throttle valve 35 is closed and the pump loss is increased by the intake air throttle. The amount of oxygen in the exhaust gas is reduced compared to normal driving due to timing delay, post-burn injection (after injection), etc. Also, during DPF regeneration, exhaust stroke injection (post injection) is also performed The fuel is burned on the oxidation catalyst to raise the downstream temperature of the catalyst. Since oxygen is also consumed in fuel combustion on the catalyst, the oxygen concentration at the DPF inlet further decreases.

FIG. 3 is a schematic diagram showing a change in the amount of oxygen during regeneration. FIG. 3 (a) shows a general operating state, and FIG. 3 (b) shows a low oxygen operating state.
As shown in FIG. 3A, when regeneration control is executed, the amount of oxygen at the outlet of the engine 10 decreases with respect to normal travel. Further, although the amount of oxygen is reduced by the fuel combustion on the oxidation catalyst, the consumption by the PM combustion on the DPF still remains normally and does not hinder the PM combustion.

  On the other hand, for example, in fully open running where the oxygen consumption due to fuel combustion in the cylinder increases, during high load running, or during high altitude running where the intake oxygen amount of the engine decreases, the amount of oxygen in the exhaust gas decreases. As shown in FIG. 3B, the amount of oxygen necessary for PM combustion may not be ensured. In this case, unburned soot remains in the DPF 80 even if normal regeneration control is continued.

In such a situation, it is effective in improving the regeneration performance of the DPF to secure the oxygen amount for PM combustion by increasing the oxygen amount in the exhaust gas.
On the other hand, the PM burning rate also depends on the exposure temperature. For example, it is generally known that the burning rate rapidly decreases below 550 to 600 ° C. Therefore, even if the amount of oxygen is secured, if the temperature at the DPF inlet is lowered, the regeneration performance cannot be expected.
Therefore, in order to improve the regeneration performance, control using the oxygen concentration in the exhaust gas and the DPF inlet temperature is effective as in this embodiment.

Table 1 shows differences in main parameters between the normal DPF regeneration mode and the PM combustion acceleration mode in this embodiment.

As shown in Table 1, in the normal DPF regeneration mode, post injection 1 and post injection 2 are executed, the throttle valve 35 is closed with respect to the normal operation, and the variable nozzle of the turbocharger 20 is opened with respect to the normal operation. Take control.
The post-injection 1 is performed after the main injection in the vicinity of the top dead center and after-injection (post-combustion injection) during the expansion stroke, and is performed at the latter stage of the expansion stroke or during the exhaust stroke, and increases the exhaust gas temperature.
The post-injection 2 is performed subsequent to the post-injection 1 and increases the inlet temperature of the DPF 80.
In the normal DPF regeneration mode, the injection timing of the main injection is retarded (delayed) in order to raise the exhaust gas temperature, and the common rail internal combustion pressure is further reduced.

On the other hand, in the PM combustion acceleration mode, post injection 1 is stopped in order to reduce oxygen consumption due to fuel combustion in the DOC 70.
Further, in the PM combustion promotion mode, in order to increase the flow rate of exhaust gas and increase the amount of oxygen supplied to the DPF 80, control is performed to open the throttle valve 35 and close the variable nozzle of the turbocharger 20 with respect to the normal DPF regeneration mode. Do.
In addition, since the exhaust gas temperature tends to decrease with respect to the normal DPF regeneration mode by the control described above, the inlet temperature of the DPF 80 does not decrease so that PM ignition failure, combustion rate decrease, misfire, etc. do not occur. In this embodiment, the PM combustion promotion mode is prohibited when the exhaust gas temperature at the DPF 80 inlet is below the threshold value.

FIG. 4 is a schematic diagram showing an example of the transition of the DPF inlet temperature during DPF regeneration in the present embodiment. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the DPF inlet temperature. In FIG. 4, the flag value of the PM combustion promotion mode flag is also shown.
As shown in FIG. 4, first, the normal DPF regeneration mode is executed until the inlet temperature of the DPF 80 becomes sufficiently high and reaches the temperature at which PM ignites. Thereafter, when the DPF inlet temperature exceeds y ° C. and the oxygen concentration in the exhaust gas becomes less than x%, the PM combustion acceleration mode is executed in order to prevent PM combustion failure due to oxygen shortage. However, during the execution of the PM combustion acceleration mode, the temperature of the exhaust gas at the inlet of the DPF 80 decreases due to the decrease in the exhaust gas temperature and the increase in the flow rate. When the exhaust gas temperature becomes y ° C. or lower, the exhaust gas temperature is raised again, so that the normal DPF regeneration mode is executed.
For example, when DPF regeneration control is performed during high load traveling or high altitude traveling, the normal DPF regeneration mode and the PM combustion promotion mode are sequentially repeated as described above.
Such DPF regeneration control is executed, for example, until it is determined that the combustion process of the PM accumulation amount estimated based on the output of the differential pressure sensor 81 is completed, and then returns to normal operation.

According to the embodiment described above, the following effects can be obtained.
(1) When oxygen necessary for combustion of PM such as soot is insufficient, the PM combustion promotion mode in which the amount of oxygen is increased is executed, so that PM can be reliably burned and the DPF 80 can be regenerated well. it can. Further, when the exhaust gas at the inlet of the DPF 80 is at a low temperature, the normal DPF regeneration mode is executed, so that the inlet temperature of the DPF 80 can be reliably improved and PM can be reliably ignited and maintained.
(2) In the normal DPF regeneration mode, the throttle valve 35 is closed and the variable nozzle of the turbocharger 20 is opened to increase the pump loss, and the exhaust gas temperature is improved by the post-combustion injection of the post injection 1. Further, by burning the fuel from the post injection 2 in the DOC, the temperature of the DPF 80 can be reliably improved, and PM can be reliably ignited and burnt.
(3) In the PM combustion acceleration mode, the amount of oxygen consumed for fuel combustion is reduced by stopping the post injection 1, and the throttle valve 35 is opened and the variable nozzle of the turbocharger 20 is closed to increase the flow rate of exhaust gas. As a result, the amount of oxygen supplied to the DPF 80 can be increased and PM combustion failure due to oxygen shortage can be prevented.
(4) When the oxygen concentration in the exhaust gas is low and the temperature of the exhaust gas is high, the regeneration failure of the DPF 80 due to lack of oxygen can be prevented by executing the PM combustion promotion mode. Further, even when the oxygen concentration in the exhaust gas is low, if the exhaust gas temperature is low, the PM combustion failure can be prevented by executing the normal DPF regeneration mode.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configurations of the engine and its accessories are not limited to those of the above-described embodiments, and can be changed as appropriate. For example, in the embodiment, the throttle valve is used to throttle the intake air amount of the engine, but a valve throttle that varies the valve opening / closing timing and the lift amount may be used instead. Further, in the multistage fuel injection, other injections than those described in the embodiments may be added.
(2) In the embodiment, the second post fuel injection is stopped in the PM combustion promotion mode. However, the present invention is not limited to this, and the injection amount may be decreased with respect to the normal regeneration mode.
(3) In the embodiment, the temperature of the exhaust gas is determined after determining the oxygen concentration in the exhaust gas. However, the present invention is not limited to this, and the temperature of the exhaust gas may be determined first or simultaneously.

DESCRIPTION OF SYMBOLS 10 Engine 11 Crankshaft 12 Piston 13 Cylinder block 14 Head 15 Combustion chamber 16 Glow plug 17 Glow controller 20 Turbocharger 21 Compressor 22 Turbine 23 Actuator 24 Negative pressure control valve 30 Intake system 31 Intake duct 32 Air cleaner 33 Air flow meter 34 Intercooler 35 Throttle valve 36 Actuator 37 Intake chamber 38 Intake pressure sensor 39 Intake manifold 40 Exhaust system 41 Exhaust manifold 42 Exhaust pipe 50 Fuel supply device 51 Supply pump 52 Suction metering solenoid valve 53 Fuel temperature sensor 54 Common rail 55 Fuel pressure sensor 56 Injector 60 EGR device 61 EGR passage 6 2 EGR control valve 63 EGR cooler 70 Oxidation catalyst (DOC) 71 Temperature sensor 80 Diesel particulate filter (DPF)
81 Differential pressure sensor 82, 83 Temperature sensor 100 Engine control unit (ECU)
101 accelerator pedal sensor 102 atmospheric pressure sensor

Claims (6)

An engine control device that controls an engine having a particulate filter that collects particulate matter in exhaust gas,
Exhaust gas temperature detecting means for detecting the temperature of the exhaust gas flowing into the particulate filter;
Oxygen amount detection means for detecting the amount of oxygen in the exhaust gas flowing into the particulate filter;
A regeneration necessity judging means for judging whether or not the particulate filter needs to be reproduced,
When it is determined that regeneration of the particulate filter is necessary, the normal regeneration mode in which the temperature of the exhaust gas is set higher than that during normal operation, and the amount of oxygen contained in the exhaust gas is increased with respect to the normal regeneration mode. The engine control device is configured to switch between the combustion promotion mode that has been set based on the outputs of the exhaust gas temperature detection means and the oxygen amount detection means. A throttle valve for adjusting the intake air amount of the engine;
A turbocharger driven by exhaust gas from the engine and provided with a variable nozzle at the turbine inlet;
2. In the normal regeneration mode, a plurality of post fuel injections for improving the temperature of the exhaust gas are executed, the throttle valve is closed and the variable nozzle of the turbocharger is opened during normal operation. The engine control apparatus according to 1. The number of post fuel injections or the amount of fuel injection is decreased in the combustion promotion mode, and the throttle valve is opened and the variable nozzle of the turbocharger is closed in the normal regeneration mode. The engine control device described in 1. The normal regeneration mode is executed when it is determined that regeneration of the particulate filter is necessary, and the amount of oxygen in the exhaust gas is equal to or greater than a predetermined value. The engine control device according to any one of the above. 5. The normal regeneration mode is executed when it is determined that regeneration of the particulate filter is necessary, and the temperature of the exhaust gas is lower than a predetermined value. 5. The engine control apparatus according to claim 1. When it is determined that regeneration of the particulate filter is necessary, the combustion promotion mode is executed when the amount of oxygen in the exhaust gas is less than a predetermined value and the temperature of the exhaust gas is not less than a predetermined value. The engine control device according to any one of claims 1 to 3, wherein the engine control device is characterized in that:

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