JPH06159042A - Exhaust emission control device of diesel engine - Google Patents

Abstract

PURPOSE:To suppress the generation of smoke without reducing the NOx purifying performance, in a diesel engine in which a fuel component for promoting the NOx purification is to be fed in the exhaust stroke of each cylinder by using the injector for fuel feeding provided to each cylinder, while an NOx purifying catalyst is set to the exhaust system. CONSTITUTION:While a catalyst converter 7 having an NOx purifying catalyst is provided on the way of an exhaust pipe 6 provided to the exhaust system of an engine 1, a high pressure fuel discharged from a fuel injection pump 8 driven by the engine 1 is to be fed to injectors 10...10 provided to the cylinders through fuel feeding pipings 9...9 respectively. And when the exhaust stroke injection is carried out by the operation of an ECU 40, the main injection amount is reduced smaller than a normal operation, and at the same time, a set value and the actual value of the exhaust stroke injection amount are compared, and the main injection amount is corrected to reduce as the actual value is made the larger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device for a diesel engine, in particular, a NOx purification catalyst installed in the exhaust system, and a fuel component added to the exhaust gas upstream of the NOx purification catalyst. The present invention relates to an exhaust emission control device for an engine.

[0002]

2. Description of the Related Art In engines for automobiles and the like, a catalyst for purifying exhaust gas after combustion may be provided in an exhaust system. Among the harmful components contained, carbon monoxide (CO) and hydrocarbon (H
A three-way catalyst that exhibits excellent purification characteristics for the three components of C) and nitrogen oxide (NOx) is widely known.

However, in a diesel engine in which combustion is carried out in an oxygen excess state relative to the stoichiometric air-fuel ratio, the composition of the exhaust gas after combustion also reflects the air-fuel ratio at combustion and becomes an oxygen excess state. In the atmosphere (lean atmosphere), there is a problem that NOx cannot be removed effectively with the conventional three-way catalyst whose NOx purification performance is extremely reduced. Therefore, when installing an exhaust gas purification catalyst in the exhaust system of a diesel engine, For example, a catalyst that exhibits excellent NOx purification characteristics even in a lean atmosphere such as metal-supported zeolite (hereinafter referred to as NOx purification catalyst) will be installed.

By the way, according to recent research, if an HC component (fuel component) is added to this type of NOx purification catalyst, N
It has been clarified that the Ox purification rate is improved, and by utilizing this phenomenon, in a diesel engine having an NOx purification catalyst installed in the exhaust system, NOx purification performance is further improved by adding and supplying fuel to the exhaust gas. Is being attempted.

In this case, it may be first considered that an injector for adding fuel is installed in the exhaust system to directly supply the fuel component to the NOx purification catalyst. In this case, the fuel supply for each cylinder is provided. In addition to the injector, a dedicated injector is required, resulting in an increase in the number of parts and a cost increase.

[0006] In contrast, for example, the actual Kaihei 3-685
As disclosed in Japanese Patent Laid-Open No. 16, there is an idea of injecting and supplying fuel for promoting NOx purification to a cylinder in an exhaust stroke by using an injector for fuel supply provided for each cylinder. According to this, it is not necessary to install a dedicated injector for adding the fuel component in the exhaust system, so that the above inconvenience is avoided.

[0007]

However, when the fuel is injected during the exhaust stroke using the injector provided for each cylinder as in the prior art described in the above publication, the following problems occur. there's a possibility that.

That is, most of the fuel injected during the exhaust stroke flows out through the exhaust port while the exhaust valve is open, but some fuel remains in the cylinder even during the intake stroke. It will be. In that case, the remaining fuel is apt to ignite due to adiabatic compression in the compression stroke, and the ignition delay of the main injection injected near the compression top dead center is shortened to increase exhaust smoke called smoke. Of.

According to the present invention, a NOx purification catalyst is installed in the exhaust system, and an injector for fuel supply provided for each cylinder is used to supply a fuel component for promoting NOx purification during the exhaust stroke of the cylinder. The present invention addresses the above problems in a diesel engine and aims to effectively suppress the generation of smoke without deteriorating the NOx purification performance.

[0010]

That is, in the exhaust gas purification apparatus for a diesel engine according to the invention of claim 1 of the present application (hereinafter referred to as the first invention), the fuel injection means for injecting fuel in the vicinity of the compression top dead center is provided. In a diesel engine provided for each cylinder and provided with an NOx purification catalyst for purifying nitrogen oxides in exhaust gas in an exhaust system, an exhaust stroke in which fuel is injected from a fuel injection means of the cylinder during an exhaust stroke of the cylinder An injection control unit is provided, and when the fuel injection amount of the fuel injection unit during the exhaust stroke changes, the fuel injection amount from the fuel injection unit near the compression top dead center is corrected according to the change. It is characterized in that a fuel injection amount correction means is provided.

In the exhaust gas purifying apparatus for a diesel engine according to the second aspect of the present invention (hereinafter referred to as the second invention), fuel injection means for injecting fuel near the compression top dead center is provided for each cylinder. Further, in a diesel engine in which an NOx purification catalyst for purifying nitrogen oxides in exhaust gas is installed in the exhaust system, an exhaust stroke injection in which fuel is injected from a fuel injection means of the cylinder during an exhaust stroke of each cylinder under predetermined conditions A fuel injection amount that reduces the fuel injection amount near the compression top dead center from the fuel injection means when the fuel injection is performed during the exhaust stroke by the exhaust stroke injection control means, in addition to the control means. It is characterized in that a correction means is provided.

Further, the invention of claim 3 of the present application (hereinafter, referred to as the third
The exhaust purification device for a diesel engine according to the invention)
In a diesel engine in which fuel injection means for injecting fuel near the compression top dead center is provided for each cylinder and a NOx purification catalyst for purifying nitrogen oxides in the exhaust gas is installed in the exhaust system, the exhaust stroke of each cylinder At the same time, an exhaust stroke injection control means for injecting fuel from the fuel injection means of the cylinder is provided, and a fuel injection quantity detection means for detecting the fuel injection quantity injected by the fuel injection means during the exhaust stroke, and a detection means for detecting the fuel injection quantity The detected value of the fuel injection amount during the exhaust stroke is compared with the set value of the fuel injection amount by the exhaust stroke injection means, and when the detected value is larger than the set value, the compression from the fuel injection means is performed. A fuel injection amount correction means for reducing the fuel injection amount near the dead point is provided.

Further, in the exhaust emission control system for a diesel engine according to the invention of claim 4 of the present application (hereinafter referred to as the fourth invention), fuel injection means for injecting fuel near the compression top dead center is provided for each cylinder, Further, in a diesel engine in which an NOx purification catalyst for purifying nitrogen oxides in exhaust gas is installed in the exhaust system, an exhaust stroke injection control means for injecting fuel from a fuel injection means of each cylinder is provided in an exhaust stroke of each cylinder. When the injection amount of the fuel injected from the fuel injection unit during the exhaust stroke changes, the fuel that advances the fuel injection timing from the fuel injection unit near the compression top dead center as the injection amount increases It is characterized in that an injection timing correction means is provided.

[0014]

According to the above construction, the following operation can be obtained.

In any of the first to fourth aspects of the invention, since fuel is injected from the fuel injection means of each cylinder during the exhaust stroke of each cylinder, in order to add the fuel component for promoting NOx purification. It is not necessary to install such an injector in the exhaust system, which makes it possible to improve the NOx purification performance with a simple configuration.

In particular, according to the first aspect of the invention, when the fuel injection amount of the fuel injection means of each cylinder changes during the exhaust stroke, the fuel injection amount for combustion is injected in the vicinity of the compression top dead center according to the change. Since the fuel injection amount will be corrected, NO
x It is possible to effectively suppress the generation of smoke without deteriorating the purification performance.

According to the second aspect of the invention, when the fuel injection is performed during the exhaust stroke, the fuel injection amount for combustion injected near the compression top dead center of the cylinder is reduced as compared with the normal time. Therefore, the amount of fuel involved in the combustion is reduced, and the generation of smoke is reduced.

According to the third aspect of the invention, when the fuel injection amount during the exhaust stroke increases for some reason, the fuel injection amount for combustion near the compression top dead center is decreased. The generation of smoke will be reduced without lowering the NOx purification performance.

Further, according to the fourth aspect of the invention, when the fuel injection amount by the fuel injection means of each cylinder changes during the exhaust stroke, the fuel injection timing near the compression top dead center is increased as the injection amount increases. Therefore, even in this case, the generation of smoke is reduced without lowering the NOx purification performance.

[0020]

EXAMPLES Examples in which the present invention is applied to an in-line four-cylinder diesel engine will be described below.

First, referring to FIG. 1, an engine 1 according to an embodiment.
Explaining the overall configuration of the engine, the engine body 2 has 4
The cylinders are arranged in a row, and fresh air is introduced into these cylinders through four independent intake pipes 4 ... 4 branched from the surge tank 3, respectively.

On the other hand, the exhaust system of the engine 1 is provided with an exhaust manifold 5 for collecting exhaust gas discharged from each cylinder, and an exhaust pipe 6 connected to the exhaust manifold 5. In the middle of the exhaust pipe 6, a catalytic converter 7 including a NOx purification catalyst composed of, for example, metal-supported zeolite is installed.

A fuel injection pump 8 driven by the engine 1 is provided, and high-pressure fuel discharged from the fuel injection pump 8 is supplied to the fuel supply pipes 9 ... 9 respectively.
Injector 10 provided for each cylinder via
It is supplied to 0.

Here, the specific construction of the engine 1 according to the embodiment will be described. As shown in FIGS. 2 and 3, the piston 23 is provided in the cylinder bore 22 formed in the cylinder block 21 constituting the engine body 2. Combustion is performed by the lower surface of the cylinder head 24 mounted on the upper portion of the cylinder block 21, the inner peripheral surface of the cylinder bore 21 in the cylinder block 21, and the upper surface of the piston 23. The chamber 25 is configured.

The cylinder head 24 has two intake ports 26, 26 which communicate with the combustion chamber 25 from one side surface, and the combustion chamber 25 from the other side surface.
Is provided with two exhaust ports 27, 27 leading to the combustion chamber 25, and the openings 26a, 26a, 27a, 27a of the ports 26, 26, 27, 27 to the combustion chamber 25 are arranged in a rectangular shape on the lower surface of the cylinder head. Two intake valves 28, 28 that are provided and that open and close the openings 26a, 26a of the intake ports 26, 26, respectively, and two exhaust valves that open and close the openings 27a, 27a of the exhaust ports 27, 27, respectively. Valve 2
9 and 29 are provided. Then, the valve shaft portions 28a, 28a of the intake and exhaust valves 28, 28, 29, 29,
29a and 29a penetrate the cylinder head 24 and project upward, and the respective valve shaft portions 28a and 28a
a, 29a, a disc-shaped umbrella portion 28b continuously provided on 29a,
28b, 29b, 29b have respective ports 26, 26, 2
The valve seats 30 ... 30 fitted in the openings 26a, 26a, 26b, 26b of the holes 7, 27 are brought into close contact with and separated from each other.

The cylinder head 24 has a combustion chamber 25.
Stepped injector insertion hole 31 opening at the central position of
Is provided in the vertical direction, and the injector 1 according to the embodiment
0 is inserted into the injector insertion hole 31 in a state in which the fuel injection portion 10a at the tip is exposed inside the combustion chamber 25, and the two mounting bolts 32, 32 are provided on the flange portion 10b of the intermediate portion of the injector 10. The injector 10 and the cylinder head 24 are integrated by being screwed into the cylinder head 24 through the fixing plate 33 supported by the upper surface of the cylinder head 24.

Next, a specific structure of the injector 10 will be described.

As shown in FIG. 4, the injector body 10
1, a nozzle 102 having a fuel injection portion 10a bulging downward is provided integrally therewith, and the nozzle 1
An oil chamber 104 for temporarily storing fuel is provided around the needle valve 103 slidably inserted into the valve 02. In the embodiment, as shown in the enlarged view of FIG. 5, the fuel injection portion 10a provided in the nozzle 102 is provided with four injection holes 106 ... It is arranged in a letter shape.

A fuel inlet 107 for introducing the fuel supplied through the fuel supply pipe 9 is provided in the flange portion 10b provided at the intermediate portion of the injector body 101, and the fuel inlet 107 is introduced. The fuel thus supplied is supplied to the oil chamber 104 through the fuel supply passage 108. A plunger 109 whose lower end is organically coupled to the needle valve 103 is slidably inserted in an intermediate portion of the injector body 101, and a pressure control chamber formed facing the upper end of the plunger 109 is formed. 110 is configured to selectively communicate with a fuel outlet 112 provided on the flange portion 10b and the fuel inlet 107 via an electromagnetic three-way valve 111 provided on the upper portion of the injector body 101.

That is, the electromagnetic three-way valve 111 has a valve body 113 that can advance and retreat in the axial direction and a solenoid coil 114 that attracts the valve body 113 by an electromagnetic force, and in the non-energized state of the solenoid coil, The valve body 113 receives the biasing force of the spring 115, and the supply port 116 branched from the fuel supply passage 108 immediately downstream of the fuel inlet 107 is connected to the control port 11 as shown in FIG.
7 through the orifice 118 and the pressure control chamber 110.
The exhaust port 119 leading to the fuel outlet 112 is shut off in the state of communicating with the fuel outlet 112. Therefore, the fuel inlet 107
The high-pressure fuel introduced from the fuel injection unit 10 is introduced into the pressure control chamber 110 through the supply port 116, and the upward movement of the needle valve 103 is regulated by the pressure.
Fuel injection from a is hindered.

On the other hand, when the solenoid coil 114 is energized, as shown in FIG. 6, the valve body 113 of the electromagnetic three-way valve 111 is attracted by the solenoid coil 114, and thus moves upward against the biasing force of the spring 115. . Therefore, when the pressure control chamber 110 communicates with the discharge port 119, the pressure acting on the plunger 109 is released, and the regulation state of the upward movement of the needle valve 103 is released. As a result, the fuel supplied to the oil chamber 104 via the fuel supply passage 108 pushes the needle valve 103 upward as shown in the figure, and the fuel injection unit 10a.
10 into the sack 105 provided in the
It will be injected into the combustion chamber 25 through 6. In that case, the fuel spray X injected from the injection holes 106 ...
... X will be scattered and scattered as shown in the figure.

In this embodiment, the injection holes 106 ... 1 provided in the fuel injection portion 10a of the injector 10 are arranged.
As shown in FIG. 3, the axis line L ... L of 06 sucks in a plan view,
Exhaust valves 28, 28, 29, 29 valve stems 28a, 28
a, 29a, the injector 10 so as to point to 29a
Are attached to the cylinder head 24.

Further, the engine 1 includes a control unit (hereinafter referred to as ECU) 4 as shown in FIG.
0 is provided. The ECU 40 includes a signal from a crank angle sensor 41 that detects a crank angle of the engine 1, a signal from an engine load sensor 42 that detects an engine load, a signal from a water temperature sensor 43 that detects an engine water temperature, and an exhaust manifold. 5 installed in the combustion chamber 25
A signal from a first exhaust temperature sensor 44 that detects the exhaust temperature immediately after being discharged from the exhaust gas, and a signal from a second exhaust temperature sensor 45 that detects the exhaust temperature immediately upstream of the catalytic converter 7,
A signal from a third exhaust temperature sensor 46 that detects the exhaust temperature immediately downstream of the catalytic converter 7, a signal from a first O ₂ sensor 47 that detects the residual oxygen concentration immediately upstream of the catalytic converter 7, and a signal from the catalytic converter 7 A signal from the _second O ₂ sensor 48 for detecting the residual oxygen concentration immediately downstream and the flow rate of the fuel supplied from the fuel injection pump 8 to the injectors 10 ... 10 of each cylinder via the fuel supply pipes 9 ... 9 are detected. The signals from the fuel flow rate sensor 49 are input, the fuel injection pressure control for the fuel injection pump 8 is performed based on these signals, and for the injectors 10 ... 10 of each cylinder, mainly in the vicinity of the compression top dead center. Main injection control for injecting fuel for combustion and exhaust stroke injection control for injecting additive fuel for promoting NOx purification in the exhaust stroke are performed.

Explaining the outline of the exhaust stroke injection control in the embodiment, the ECU 40 indicates, for example, the catalyst inlet side exhaust temperature Ti indicated by the signal from the second exhaust temperature sensor 46.
n is compared with a predetermined exhaust stroke injection prohibiting temperature Tk, and when it is determined that the inlet side exhaust temperature Tin is higher than the prohibiting temperature Tk, a predetermined exhaust stroke injection amount is set, and then,
The signal from the crank angle sensor 41 is read. Then, when the crank angle indicated by the signal is a predetermined crank angle belonging to the valve overlap period set at the end of the exhaust stroke as shown in FIG. 6, the set exhaust stroke injection amount is set to the injector 10 of the cylinder. The exhaust stroke injection signal is output so that the fuel corresponding to is injected.

As a result, the following effects can be obtained.

That is, as shown in FIG. 7, the additive fuel for promoting NOx purification is injected from the injector 10 of the cylinder concerned within the valve overlap period set at the end of the exhaust stroke. Therefore, the amount of heat that the added fuel receives from the combustion chamber wall surface or the exhaust gas is small, so that even if the injection amount is small, most of the fuel reaches the catalytic converter 7 in an activated state, and the NOx purification performance is improved. Will be secured.

Moreover, as shown in FIG. 2, the intake valves 28,
Since the fuel is injected from the injector 10 of the cylinder between the time when the valve 28 is opened and the time when the exhaust valves 29, 29 are closed, the injected fuel passes from the intake valves 28, 28 through the combustion chamber 25. Since the air that flows through the exhaust valves 29, 29 flows out to the exhaust manifold 45, the added fuel reaches the catalytic converter 7 more efficiently, so that the amount of added fuel is good and the amount of NOx is good. Purification performance will be obtained.

The exhaust stroke injection prohibition temperature is set for the following reason.

That is, when the catalyst inlet side exhaust temperature detected by the second exhaust temperature sensor 45 is used as a parameter, as the catalyst inlet side exhaust temperature Tin decreases as shown in FIG.
The Ox purification rate tends to decrease. In that case, if the exhaust stroke injection is always performed irrespective of the catalyst temperature, the fuel injected from the injector 10 is exhausted with little contribution to the catalytic reaction in the catalytic converter 7 at low temperatures where the NOx purification rate is low. The fuel efficiency is deteriorated. Therefore, in this embodiment, the exhaust stroke injection inhibition temperature Tk is set corresponding to the allowable lower limit value α of the NOx purification rate as shown in the figure.

Next, the main injection control which is a characteristic part of the present invention will be described. Specifically, the main injection control is performed as follows according to the flowchart of FIG.

That is, the ECU 40 sets the basic injection amount Tp based on the operating state of the engine 1 and calculates various correction amounts according to the engine water temperature and the like (steps S1 and S2). Next, in step S3, it is determined whether or not the exhaust stroke injection is being performed. When the exhaust stroke injection is being performed, the routine proceeds to step S4, where a predetermined base correction amount Tb (<0) is set. That is, the main injection amount is reduced as compared with the normal time.

The ECU 40 then executes step S5 to read the fuel flow rate indicated by the signal from the fuel flow rate sensor 49, and in step S4 calculates the actual exhaust stroke injection amount Qr based on the fuel flow rate. The ECU 40 subsequently executes step S7 to read the set exhaust stroke injection amount Qs, calculates the deviation amount ΔQ of the actual exhaust stroke injection amount Qr from the set exhaust stroke injection amount Qs in step S8, and then calculates step S9. Then, it is determined whether or not the absolute value of the deviation amount ΔQ is larger than a predetermined allowable value Qo. When it is determined that the absolute value of the deviation amount ΔQ is larger than the allowable value Qo, the process proceeds to step S10 and the deviation amount ΔQ is increased.
Is compared with the map of the exhaust injection correction amount shown in FIG. 10, and the exhaust injection correction amount Th corresponding to the deviation amount ΔQ is set. This map of the exhaust injection correction amount is the deviation amount ΔQ
When the deviation amount ΔQ is 0, the exhaust injection correction amount Th decreases in the negative direction as the deviation amount ΔQ increases, and the exhaust injection correction amount Th decreases in the negative direction as the deviation amount ΔQ increases. The amount Th is set to increase in the positive direction. Therefore, when the deviation amount ΔQ indicates a positive value in which more fuel is injected from the injector 10 than the set exhaust stroke injection amount Qs, the fuel injection amount is reduced as the value of the exhaust injection correction amount Th. Will be set to a negative value.

Next, the ECU 40 executes step S11 to set the final injection amount, and then outputs the main injection signal to the injector 10 so that the final injection amount is obtained in step S12.

Next, the operation of the embodiment will be described.

That is, the main injection is performed near the exhaust top dead center of each cylinder. When the exhaust stroke injection is performed as shown in FIG. 11, the main injection amount Qm is as shown by the solid line in the figure. The injection amount will be smaller than the normal injection amount shown by the chain line. As a result, even if some of the fuel injected in the exhaust stroke of each cylinder remains in the expansion stroke through the intake and compression strokes, the amount of fuel that is involved in combustion is small, so the occurrence of smoke is reduced. Become.

Further, as shown in FIG. 12, the deviation amount Δ of the actual exhaust stroke injection amount Qr is larger than the set exhaust stroke injection amount Qs.
When it increases by Q, the main injection amount Qm becomes the deviation amount ΔQ.
The amount is corrected by reducing the exhaust injection correction amount Qh corresponding to. Due to this, even if for some reason an excess amount of fuel above the set value is injected in the exhaust stroke and the residual amount of fuel in the expansion stroke increases, the amount of main injection is small, so the amount of fuel involved in combustion is small. As a result, the generation of smoke will be reduced even in this case.

On the other hand, when the actual exhaust stroke injection amount Qr is smaller than the set exhaust stroke injection amount Qs, the main injection amount Qm is increased corresponding to the decrease amount.

In this embodiment, the main injection amount is decreased with the increase of the exhaust stroke injection amount, but the main injection timing is advanced and corrected in accordance with the increase of the exhaust stroke injection amount. You can Even in this case, the generation of smoke is effectively suppressed.

[0049]

As described above, according to the present invention, the fuel is injected from the fuel injection means of each cylinder during the exhaust stroke of each cylinder, so that the fuel component for promoting NOx purification is added. It is not necessary to install an injector for this in the exhaust system, which makes it possible to improve the NOx purification performance with a simple configuration.

Particularly, according to the first aspect of the invention, when the fuel injection amount of the fuel injection means of each cylinder changes during the exhaust stroke, the fuel injection for combustion is performed in the vicinity of the compression top dead center according to the change. Since the fuel injection amount will be corrected, NO
x It is possible to effectively suppress the generation of smoke without deteriorating the purification performance.

Further, according to the second aspect of the invention, when the fuel injection is performed during the exhaust stroke, the fuel injection amount for combustion injected near the compression top dead center of the cylinder is reduced as compared with the normal time. Therefore, the amount of fuel involved in the combustion is reduced, and the generation of smoke is reduced.

According to the third aspect of the invention, if the fuel injection amount during the exhaust stroke increases for some reason, the fuel injection amount for combustion near the compression top dead center is decreased. The generation of smoke will be reduced without lowering the NOx purification performance.

Further, according to the fourth aspect of the invention, when the fuel injection amount by the fuel injection means of each cylinder changes during the exhaust stroke, the fuel injection timing near the compression top dead center is increased as the injection amount increases. Therefore, even in this case, the generation of smoke is reduced without lowering the NOx purification performance.

[Brief description of drawings]

FIG. 1 is a control system diagram of an engine.

FIG. 2 is an enlarged cross-sectional view of a main part of an engine showing a configuration around a combustion chamber.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a vertical sectional view of the injector.

5 is an enlarged cross-sectional view taken along the line BB of FIG.

FIG. 6 is a vertical sectional view showing an operating state of the injector.

FIG. 7 is a characteristic diagram showing a relationship between a valve lift amount and a working state of an injector with respect to a crank angle.

FIG. 8 is a characteristic diagram showing a relationship between a catalyst inlet side exhaust temperature and a NOx purification rate.

FIG. 9 is a flowchart showing main injection control according to the embodiment.

FIG. 10 is an explanatory diagram of a map of an exhaust injection correction amount using a deviation amount of an actual exhaust stroke injection amount with respect to a set exhaust stroke injection amount as a parameter.

FIG. 11 is a time chart diagram showing the operation of the embodiment.

FIG. 12 is a time chart diagram showing the operation of the same embodiment.

[Explanation of symbols]

 1 Engine 6 Exhaust Pipe 7 Catalytic Converter 10 Injector 40 ECU 45 Second Exhaust Temperature Sensor 49 Fuel Flow Sensor

Front page continuation (72) Inventor Masaaki Kashimoto 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (4)

[Claims] 1. Exhaust gas of a diesel engine in which fuel injection means for injecting fuel near compression top dead center is provided for each cylinder, and an NOx purification catalyst for purifying nitrogen oxides in exhaust gas is installed in an exhaust system. A purification device, which is provided with exhaust stroke injection control means for injecting fuel from the fuel injection means of the cylinder during the exhaust stroke of each cylinder, and changes the amount of fuel injected during the exhaust stroke by the fuel injection means. An exhaust emission control device for a diesel engine, which is provided with a fuel injection amount correction unit that corrects the fuel injection amount in the vicinity of the compression top dead center from the fuel injection unit according to the change. 2. The exhaust gas of a diesel engine in which fuel injection means for injecting fuel near the compression top dead center is provided for each cylinder, and a NOx purification catalyst for purifying nitrogen oxides in exhaust gas is installed in the exhaust system. A purification device, which is provided with an exhaust stroke injection control means for injecting fuel from a fuel injection means of the cylinder during an exhaust stroke of each cylinder under predetermined conditions, and at the time of an exhaust stroke by the exhaust stroke injection control means. Exhaust of a diesel engine, characterized in that, when fuel injection is performed, fuel injection amount correction means is provided for reducing the fuel injection amount from the fuel injection means in the vicinity of the compression top dead center compared to the normal time. Purification device. 3. Exhaust gas of a diesel engine in which fuel injection means for injecting fuel near the compression top dead center is provided for each cylinder, and an NOx purification catalyst for purifying nitrogen oxides in exhaust gas is installed in the exhaust system. In the purification device, an exhaust stroke injection control means for injecting fuel from the fuel injection means of the cylinder during the exhaust stroke of each cylinder is provided, and the fuel injection amount injected by the fuel injection means during the exhaust stroke is set. The fuel injection amount detection means for detecting is compared with the detected value of the fuel injection quantity at the exhaust stroke detected by the detection means and the set value of the fuel injection quantity by the exhaust stroke injection means, and the detected value is set as above. Exhaust of a diesel engine, which is provided with fuel injection amount correction means for reducing the fuel injection amount near the compression top dead center from the fuel injection means when the value is larger than the value. Purification device. 4. An exhaust gas of a diesel engine in which fuel injection means for injecting fuel in the vicinity of the compression top dead center is provided for each cylinder, and an NOx purification catalyst for purifying nitrogen oxides in exhaust gas is installed in the exhaust system. A purification device, which is provided with an exhaust stroke injection control means for injecting fuel from a fuel injection means of each cylinder during an exhaust stroke of the cylinder, and an injection amount of fuel injected from the fuel injection means during the exhaust stroke. Fuel injection timing correction means for advancing the fuel injection timing in the vicinity of the compression top dead center from the fuel injection means as the injection amount increases. Exhaust purification device.