JP3153660B2 - Engine exhaust purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine
Exhaust purification apparatus etc., particularly with installing the NOx purifying catalyst in an exhaust system, an exhaust purifying apparatus for an engine which is adapted to add a fuel component to the exhaust gas upstream of the NOx purifying catalyst.

[0002]

2. Description of the Related Art In an engine for an automobile or the like, a catalyst for purifying exhaust gas after combustion is sometimes provided in an exhaust system. Among the harmful components contained, carbon monoxide (CO) and hydrocarbon (H
There are widely known three-way catalysts that exhibit excellent purification characteristics for the three components C) and nitrogen oxides (NOx).

However, in the engine <br/> which combustion takes place in an oxygen excess state than physical <br/> Ronsora ratio such as a diesel engine, reflect the air-fuel ratio at the time of combustion the composition of the exhaust gas after combustion since the oxygen-excess state by, there is a problem that oxygen-rich atmosphere NOx purification performance in (lean atmosphere) can not effectively remove NOx in the conventional three-way catalyst significantly lowered, therefore the exhaust gas in the exhaust system When a purification catalyst is installed, a catalyst such as a metal-supported zeolite that exhibits excellent NOx purification characteristics even in a lean atmosphere (hereinafter referred to as a NOx purification catalyst) is installed.

According to recent studies, this type of N
NO if HC component (fuel component) is added to Ox purification catalyst
It has been clarified that the x-purification rate is improved, and even in an engine in which a NOx purification catalyst is installed in the exhaust system, the NOx purification performance is further improved by adding and supplying a fuel component to the exhaust gas using the above phenomenon. Attempts have been made to improve it.

As one example, there is a concept of directly supplying a fuel component to a NOx purification catalyst by installing an injector for fuel addition in an exhaust system.

Further, as disclosed in Japanese Utility Model Laid-Open No. 3-68516, fuel for promoting NOx purification is supplied to a cylinder in an exhaust stroke by using a fuel supply injector provided for each cylinder. There is also an idea to supply by injection. In this case, there is no need to install an injector for fuel addition in the exhaust system of the engine, and thus there is an advantage that the system configuration is simplified.

[0007]

However, when fuel is added to the exhaust gas on the upstream side of the NOx purification catalyst installed in the exhaust system, the NOx purification rate is increased and the exhaust performance is improved. There is another aspect that fuel consumption increases because the used fuel does not contribute to combustion, and it is required to achieve both high levels of exhaust performance and fuel efficiency.

By the way, in this kind of engine ,
Depending on the injection conditions of the main injection and the operating conditions of the engine, HC
May increase.

That is, for example, in an engine in which the injection pressure of the fuel is variably controlled in accordance with the operating state, the actual value of the fuel injection pressure becomes larger than the set value due to, for example, the abnormality of the engine or the relationship with other controls. In this case, the atomization of the fuel is promoted, and at the same time, the formation of the fuel-lean region proceeds, so that HC is easily generated.

In this type of engine , pilot injection for injecting a small amount of fuel may be performed prior to main injection in order to reduce combustion noise and NOx. Without generating complete combustion, the amount of generated HC increases.

The present invention has been made in view of the above-mentioned problem in an engine in which a fuel component is added to exhaust gas on the upstream side of a NOx purification catalyst installed in an exhaust system. By focusing attention, it is an object to improve fuel economy performance without impairing NOx purification performance.

[0012]

That is, a diesel engine according to the invention of claim 1 of the present application (hereinafter referred to as the first invention).
Exhaust gas purifying apparatus for engine, the fuel injection means is provided for injecting fuel for combustion in each cylinder, and the diesel engine NOx purifying catalyst is installed to purify the nitrogen oxides in the exhaust gas in the exhaust system, the NO in exhaust system
a fuel addition means for adding fuel to the exhaust gas on the upstream side of the x purification catalyst, and when fuel for combustion is injected from the fuel injection means at a pressure exceeding a set value, the fuel added by the fuel addition means Characterized in that control means for reducing the amount of addition of is provided.

The invention of claim 2 of the present application (hereinafter referred to as the second invention)
The exhaust gas purifying apparatus for a diesel engine according to the present invention is provided with fuel injection means for separately injecting fuel for combustion into a main injection and a pilot injection thereof for each cylinder. In a diesel engine provided with a NOx purification catalyst for purifying substances, a fuel addition means for adding fuel to exhaust gas on the upstream side of the NOx purification catalyst in the exhaust system is provided, and the fuel injection means precedes main injection. Control means for reducing the amount of fuel added by the fuel adding means in an operating state in which pilot injection is performed.

The invention of claim 3 of the present application (hereinafter referred to as “third invention”)
The exhaust purification device for an engine according to the invention
Fuel injection means for injecting fuel for combustion is provided,
In addition, nitrogen oxides in the exhaust gas are supplied to the exhaust system in an oxygen-excess atmosphere.
Engine equipped with NOx purification catalyst
Therefore, on the upstream side of the NOx purification catalyst in the exhaust system,
HC component adding means for adding HC components to exhaust gas;
Detecting means for detecting the oxygen concentration on the outlet side of the NOx purification catalyst
And the outlet-side oxygen concentration detected by the detection means is high
Control means for reducing the amount of addition of the HC component.
It is characterized by

The invention of claim 4 of the present application (hereinafter referred to as “fourth invention”)
This is referred to as the invention).
In the gasification device, the detection means is provided on the inlet side of the NOx purification catalyst.
The difference between the oxygen concentration and the outlet oxygen concentration is detected, and the control means
The smaller the absolute value of the difference, the smaller the amount of HC component added
It is characterized by being made to be.

Furthermore, the invention of claim 5 of the present application (hereinafter referred to as the
The fifth aspect of the invention relates to the exhaust gas of the engine according to the fourth aspect.
In the purification device, the detection means is an inlet of the NOx purification catalyst.
O2 sensor for detecting the oxygen concentration on the inlet side and oxygen sensor on the outlet side
An outlet O2 sensor for detecting the concentration is provided.
Based on the sensor values.
It is characterized in that a difference in degrees is detected.

The invention of claim 6 of the present application (hereinafter referred to as the
The sixth invention) relates to the first to third inventions.
For diesel engine or engine exhaust purification system
Here, the NOx purification catalyst is a metal-supported zeolite.
It is characterized by the following.

[0018]

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

First, the diesel engine of the first and second inventions
According to the exhaust gas purifying device, when the operating condition is liable to generate HC , specifically, the set value exceeds the set value from the fuel injection means.
When the fuel for combustion is injected at
The pilot injection that precedes the main injection is performed from the injection means.
In such an operating state, the amount of fuel added to the exhaust gas is reduced, so that unnecessary fuel consumption is suppressed and the fuel efficiency is improved, and the HC originally contained in the exhaust gas reduces the fuel consumption. Since the catalytic reaction is promoted, good NOx purification performance can be obtained.

An engine exhaust purification device according to a third aspect of the present invention.
According to the report, nitrogen oxides in exhaust gas were
In an engine equipped with a NOx purification catalyst for purification
Te, the higher the outlet oxygen concentration above Symbol NOx purifying catalyst,
Further, according to the fourth invention, similarly, the input of the NOx purification catalyst is performed.
The smaller the absolute value of the difference between the mouth oxygen concentration and the outlet oxygen concentration,
To the exhaust gas upstream of the NOx purification catalyst
Since the HC component was reduced, it was exhausted in an oxygen-rich atmosphere.
HC in the gas is oxidized and NOx is sufficiently
When not reduced, HC components added to exhaust gas
The amount is increased to purify NOx, and conversely, NOx is exhausted.
Unnecessary when it is sufficiently reduced by HC in the
Addition of HC to the fuel, fuel efficiency and exhaust purification
Performance can be achieved.

Further, according to the fifth invention, the fourth invention
Oxygen Concentration and Outlet Oxygen of NOx Purification Catalyst at High Temperature
The difference in concentration detects the oxygen concentration on the inlet side of the NOx purification catalyst.
This difference is detected by the inlet O2 sensor.
Fuel efficiency and exhaust purification performance
Will be effectively achieved.

According to the sixth aspect of the present invention,
The function is applied to NOx purification catalyst using metal-supported zeolite.
Will be achieved for

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to an in-line four-cylinder diesel engine.
For embodiment applied to down it will be described.

First, FIG. 1 shows an engine 1 according to an embodiment.
The overall configuration of the engine will be described.
The cylinders are arranged in a row, and fresh air is introduced into these cylinders via four independent intake pipes 4... 4 branched from the surge tank 3.

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 provided with a NOx purification catalyst made of, for example, metal-supported zeolite is provided.

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 fuel supply pipes 9.
Injectors 10... 1 provided for each cylinder via
0 is supplied.

Here, the specific structure of the engine 1 according to the embodiment will be described. As shown in FIGS. 2 and 3, a piston 23 is provided in a cylinder bore 22 formed in a cylinder block 21 constituting the engine body 2. Are slidably inserted vertically, and the lower surface of a cylinder head 24 attached to 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 A chamber 25 is configured.

The cylinder head 24 has two intake ports 26, 26 communicating with the combustion chamber 25 from one side, respectively, and the combustion chambers 25, 26 respectively from the other side.
And two exhaust ports 27, 27 communicating with the combustion chamber 25. Openings 26a, 26a, 27a, 27a of these ports 26, 26, 27, 27 to the combustion chamber 25 are arranged in a rectangular shape on the lower surface of the cylinder head. And two exhaust valves 28, 28 for opening and closing the openings 26a, 26a of the intake ports 26, 26, respectively, and two exhaust valves for opening and closing the openings 27a, 27a of the exhaust ports 27, 27, respectively. Valve 2
9, 29 are provided. And, the valve stems 28a, 28a, of these intake and exhaust valves 28, 28, 29, 29,
29a, 29a penetrate the cylinder head 24 and protrude upward, and the respective valve shaft portions 28a, 28
a, 29a, 29a, a disk-shaped umbrella portion 28b,
28b, 29b, and 29b are ports 26, 26, and 2 respectively.
30 come into close contact with and separate from the valve seats 30 fitted in the openings 26a, 26a, 26b, 26b of the respective 7, 27.

The cylinder head 24 has a combustion chamber 25
Stepped injector insertion hole 31 opening at the center of
Are provided in the vertical direction, and the injector 1 according to the embodiment is
0 is inserted into the injector insertion hole 31 in a state where the fuel injection portion 10a at the tip is exposed in the combustion chamber 25, and two mounting bolts 32, 32 are connected to the flange portion 10b at 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 a fixing plate 33 supported on the upper surface of the injector 10.

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

As shown in FIG. 4, the injector body 10
1 is provided integrally with a nozzle 102 having a fuel injection section 10a swelling downward.
An oil chamber 104 for temporarily storing fuel is provided around the needle valve 103 which is slidably inserted in 02. In the embodiment, the fuel injection section 10a provided in the nozzle 102 has four injection holes 106... It is arranged in the shape of a letter.

A fuel inlet 107 for introducing fuel supplied through the fuel supply pipe 9 is provided in the flange portion 10b provided at an intermediate portion of the injector main body 101. The supplied fuel is supplied to the oil chamber 104 via the fuel supply passage 108. A plunger 109 whose lower end is organically coupled to the needle valve 103 is slidably inserted into an intermediate portion of the injector body 101, and a pressure control chamber formed facing the upper end of the plunger 109. Reference numeral 110 selectively communicates 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 an upper portion of the injector body 101.

That is, the electromagnetic three-way valve 111 has a valve body 113 which can move forward and backward in the axial direction, and a solenoid coil 114 for attracting the valve body 113 by electromagnetic force, and when the solenoid coil is not energized, The valve body 113 receives the urging force of the spring 115, and connects the supply port 116 branched from the fuel supply passage 108 immediately downstream of the fuel inlet 107 to the control port 11 as shown in the figure.
7 and the pressure control chamber 110 via the orifice 118.
The discharge port 119 communicating with the fuel outlet 112 is shut off in a state of communication with the fuel outlet 112. Therefore, the fuel inlet 107
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.
The fuel injection from a is hindered.

On the other hand, when the solenoid coil 114 is energized, the valve body 113 of the electromagnetic three-way valve 111 is attracted by the solenoid coil 114 to move upward against the urging force of the spring 115 as shown in FIG. . Accordingly, the pressure acting on the plunger 109 is released by the communication of the pressure control chamber 110 with the discharge port 119, and the restricted state of the upward movement of the needle valve 103 is released. As a result, the fuel supplied to the oil chamber 104 through the fuel supply passage 108 pushes the needle valve 103 upward as shown in FIG.
Flows into the sack 105 provided at the
6 and injected into the combustion chamber 25. In this case, the fuel spray X injected from the injection holes 106.
.. X are diffused 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 provided.
As shown in FIG. 3, the axes L...
Valve shaft portions 28a, 28 of the exhaust valves 28, 28, 29, 29
a, 29a, 29a.
Are attached to the cylinder head 24.

The engine 1 further includes a control unit (hereinafter referred to as an ECU) 4 as shown in FIG.
0 is provided. The ECU 40 includes a signal from a crank angle sensor 41 for detecting a crank angle of the engine 1, a signal from an engine load sensor 42 for detecting an engine load, a signal from a water temperature sensor 43 for detecting an engine water temperature, and an exhaust manifold. 5 and the combustion chamber 25
A signal from a first exhaust gas temperature sensor 44 for detecting an exhaust gas temperature immediately after being exhausted from the catalyst, a signal from a second exhaust gas temperature sensor 45 for detecting an exhaust gas temperature immediately upstream of the catalytic converter 7,
A signal from a third exhaust gas temperature sensor 46 for detecting the exhaust gas temperature immediately downstream of the catalytic converter 7, a signal from a first O2 sensor 47 for detecting the residual oxygen concentration immediately upstream of the catalytic converter 7, A signal from the second O2 sensor 48 for detecting the concentration of residual oxygen downstream and a pressure sensor 4 for detecting the pressure of the fuel discharged from the fuel injection pump 8
9 to control the fuel injection pressure of the fuel injection pump 8 based on these signals. The injectors 10... 10 of each cylinder are mainly used for combustion near the compression top dead center. Combustion fuel injection control for injecting fuel and additional fuel injection control for injecting additional fuel for promoting NOx purification in the exhaust stroke are performed.

Here, the fuel injection pressure control and the fuel injection control for combustion will be described. First, the former fuel injection pressure control is performed roughly as follows.

That is, the ECU 40 calculates the engine speed based on the signal from the crank angle sensor 41, and then calculates the engine speed and the engine load indicated by the signal from the engine load sensor 42 at a predetermined fuel injection pressure. The fuel injection pressure corresponding to the actual engine speed and the engine load is set by referring to the map, and a pressure control signal is output to the fuel injection pump 8 so as to obtain the set fuel injection pressure. Here, as shown in FIG. 7, the map of the fuel injection pressure uses the engine speed and the engine load as parameters, and has a predetermined low pressure value in a low rotation low load region and a predetermined low pressure value in a high rotation high load region. The predetermined high pressure value is set to be selected, and the medium pressure value is set to be selected in the low rotation high load region and the high rotation low load region. Therefore, when the operating state of the engine 1 (engine speed and engine load) is in a low rotation and low load state, a pressure control signal is output to the fuel injection pump 8 so that the fuel injection pressure becomes low.

On the other hand, the latter control of fuel injection for combustion is generally performed as follows.

That is, as shown in FIG. 8, the ECU 40 compares the actual operating condition indicated by the actual engine speed and the engine load with a map of the operating region in which the engine speed and the engine load are set as parameters. It is determined whether or not the operating state belongs to the pilot injection region set on the low rotation and low load side, and when the operating state belongs to the pilot injection region, the pilot injection precedes the main injection near the compression top dead center. The fuel injection signal for combustion is output to the injector 10 so that the injection is performed, and when the operating state does not belong to the pilot injection region, the fuel is injected to the injector 10 so that the normal injection without the pilot injection is similarly performed near the compression top dead center. And outputs a fuel injection signal for use.

Next, the additional fuel injection control, which is a feature of the present invention, will be described. Specifically, the additional fuel injection control is performed as follows in accordance with the flowchart shown in FIG.

That is, the ECU 40 first executes step S
1 is executed, and as shown in FIG. 10, the basic fuel injection pressure set value for the main injection is set as a parameter, and the basic fuel injection pressure map is compared with the actual fuel injection pressure set value Po to correspond to the basic fuel injection pressure map. Set the injection amount. The map is set so that the basic injection amount decreases as the fuel injection pressure set value Po increases.

Next, the ECU 40 subtracts the fuel injection pressure set value Po from the actual fuel injection pressure value P indicated by the signal from the pressure sensor 49, thereby obtaining a pressure deviation ΔP of the actual value P from the set value Po. After calculating the pressure deviation △
It is determined whether P is greater than 0 (step S2).
That is, it is determined whether the injection pressure of the main injection is larger than the set value. If it is determined that the pressure deviation ΔP is larger than 0, a pressure correction coefficient corresponding to the pressure deviation ΔP is set from a preset map (step S3). Here, as shown in FIG. 11, the map uses the pressure deviation ΔP as a parameter,
The pressure correction coefficient is set to a characteristic in which the pressure correction coefficient linearly decreases in a negative range as P increases. Therefore, when the pressure deviation ΔP is larger than 0, the pressure correction coefficient becomes a negative value, and the absolute value of the pressure correction coefficient set with the increase of the pressure deviation ΔP increases.

Next, the ECU 40 executes step S4 to determine whether or not pilot injection is being performed.
When YES is determined, the process proceeds to step S5 to set a pilot correction coefficient. The pilot correction coefficient is set to a negative value.

Next, the ECU 40 executes step S6, and stores the actual engine water temperature Tw indicated by the signal from the water temperature sensor 43 in a map of the water temperature correction coefficient preset with the engine water temperature as a parameter as shown in FIG. And a water temperature correction coefficient corresponding to the engine water temperature Tw is set. Here, the map is set so that the water temperature correction coefficient decreases as the engine water temperature Tw decreases.

Further, the ECU 40 determines in steps S7 and S8
To set the exhaust gas temperature correction coefficient and the oxygen concentration correction coefficient.

Here, the exhaust gas temperature correction coefficient is set as follows. That is, the ECU 40 subtracts the catalyst inlet-side exhaust temperature Ti indicated by the signal from the second exhaust temperature sensor 45 from the catalyst outlet-side exhaust temperature To indicated by the signal from the third exhaust temperature sensor 46 to obtain the exhaust gas temperature difference ΔT. After the calculation, as shown in FIG. 13, the actual exhaust gas temperature difference △ is stored in a map of the exhaust gas temperature correction coefficient set using the exhaust gas temperature difference as a parameter.
T is applied, and an exhaust gas temperature correction coefficient corresponding to the exhaust gas temperature difference ΔT is set. In this case, the exhaust gas temperature correction coefficient has a characteristic that it decreases linearly with an increase in the exhaust gas temperature difference ΔT. Therefore, an extra HC component is supplied to the catalytic converter 7 and the catalyst outlet side exhaust gas temperature To due to oxidation reaction. When the exhaust gas temperature rises, the exhaust gas temperature correction coefficient is set to a small value, the amount of added fuel is reduced, and deterioration of fuel economy performance is avoided. Then, the exhaust gas temperature correction coefficient is set to a large value, the amount of fuel added is increased, and the NOx purification rate is favorably maintained.

The oxygen concentration correction coefficient is set as follows. That is, the ECU 40 calculates the oxygen concentration difference ΔD by subtracting the catalyst inlet oxygen concentration Di indicated by the signal from the first O2 sensor 47 from the catalyst outlet oxygen concentration Do indicated by the signal from the second O2 sensor 48. Then, as shown in FIG. 14, the actual oxygen concentration difference ΔD is applied to the map of the oxygen concentration correction coefficient set using the oxygen concentration difference as a parameter, and the oxygen concentration correction coefficient corresponding to the oxygen concentration difference ΔD is set. I do. In this case, the oxygen concentration correction coefficient has a characteristic of linearly decreasing with an increase in the oxygen concentration difference ΔD. Therefore, when the oxygen concentration Do on the catalyst outlet side increases due to the reduction of NOx in the catalytic converter 7, the oxygen concentration correction coefficient When the concentration correction coefficient is set to a small value, the addition amount of fuel is reduced to avoid deterioration of fuel efficiency, and when the reduction amount of the NOx component is small and the catalyst outlet side oxygen concentration Do decreases, Since the oxygen concentration correction coefficient is set to a large value, the amount of added fuel is increased, and the NOx purification rate is maintained satisfactorily.

Then, the ECU 40 executes step S9 in the flowchart of FIG. 9 to set the final injection amount based on the basic injection amount and the respective correction coefficients, and then executes step S10 to execute the exhaust temperature difference. It is determined whether ΔT is higher than a predetermined maximum allowable temperature Tmx. If the determination is NO, the process proceeds to step S11, where an additional fuel injection signal is output to the injector 10 near the exhaust top dead center, and When it is determined that the exhaust gas temperature difference ΔT is higher than the maximum allowable temperature Tmx, the process proceeds to step S12, and the output of the injection signal to the injector 10 is stopped. Therefore, thermal destruction of the catalytic converter 7 is prevented.

Next, the operation of the embodiment will be described.

If the actual value of the fuel injection pressure of the main injection becomes larger than the set value as shown in FIG. 15 due to an abnormality of the engine 1 or the like, the pressure correction coefficient is set so that the pressure difference ΔP is eliminated. Is set. In this case, since the pressure correction coefficient is set to a negative value, the amount of fuel to be added is changed to be smaller than the set value, so that the fuel consumption is reduced and the catalytic converter 7 Is NO due to the HC component which increases due to the increase of the fuel injection pressure.
Since the reduction reaction of x is promoted, the NOx purification rate is also maintained satisfactorily.

When the pilot injection is performed prior to the main injection as shown in FIG. 16, the pilot injection correction coefficient is reduced as compared to before the pilot injection is performed. As a result, as shown in the figure, the lift amount of the needle valve 102 of the injector 10 near the top dead center of the exhaust gas becomes small, so that the amount of added fuel is reduced, the fuel consumption is reduced, and the pilot injection is performed. Since the reduction of NOx is promoted by the HC component that is increased by performing the process, the NOx purification rate is also favorably maintained in this case.

In this embodiment, the additional fuel injection amount is reduced as the engine coolant temperature Tw decreases, so that it is possible to purify NOx efficiently while suppressing unnecessary fuel consumption. Become.

In the above-described embodiment, the fuel injection injector 10 is used to inject the additional fuel for NOx purification during the exhaust stroke. However, a special injector for injecting the NOx purification fuel is used. It is also possible to apply the present invention to one that is installed in an exhaust system.

[0055]

As described above, according to the present invention, an engine, such as a diesel engine , in which a fuel component is added to exhaust gas on the upstream side of a NOx purification catalyst installed in an exhaust system.
In operating conditions where HC is likely to occur ,
Is that HC in exhaust gas is sufficiently involved in NOx reduction
Occasionally, the fuel or fuel component HC in the exhaust gas
Is reduced, unnecessary fuel consumption is suppressed, fuel efficiency is improved, and a catalytic reaction is promoted by HC originally contained in exhaust gas. NOx purification performance can also be obtained.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is an enlarged sectional view taken along line BB of FIG. 4;

FIG. 6 is a longitudinal sectional view showing an operation state of the injector.

FIG. 7 is an operating region diagram showing a map of a fuel injection pressure using an engine speed and an engine load as parameters.

FIG. 8 is an operating region diagram showing a pilot injection region in which the engine speed and the engine load are used as parameters.

FIG. 9 is a flowchart illustrating additional fuel injection control according to the embodiment.

FIG. 10 is a characteristic diagram showing a relationship between a fuel injection pressure set value used for the control and a basic injection amount.

FIG. 11 is a characteristic diagram showing a relationship between a deviation of an actual value from a set value of a fuel injection pressure used for the control and a pressure correction coefficient.

FIG. 12 is a characteristic diagram showing a relationship between an engine water temperature and a water temperature correction coefficient used for the control.

FIG. 13 is a characteristic diagram showing a relationship between an exhaust gas temperature difference before and after a catalytic converter used for the control and an exhaust gas temperature correction coefficient.

FIG. 14 is a characteristic diagram showing a relationship between an oxygen concentration difference before and after a catalytic converter used for the control and an oxygen concentration correction coefficient.

FIG. 15 is a time chart showing a change in a fuel addition amount when a fuel injection pressure changes.

FIG. 16 is a time chart showing a change in fuel addition amount when pilot injection is performed.

[Explanation of symbols]

 Reference Signs List 1 engine 6 exhaust pipe 7 catalytic converter 10 injector 40 ECU 41 crank angle sensor 42 engine load sensor 43 water temperature sensor 45 second exhaust temperature sensor 46 third exhaust temperature sensor 49 pressure sensor

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Saki ▼ Masashi Moto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-48-93814 (JP, A) JP-A-3-253713 (JP, A) JP-A-6-117225 (JP, A) JP-A-6-108828 (JP, A) JP-A-4-232359 (JP, A) JP-A-61-197740 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3/08-3/38 F01N 9/00-11/00

Claims (6)

(57) [Claims] 1. Diesel provided with fuel injection means for injecting fuel for combustion for each cylinder, and provided with an NOx purification catalyst for purifying nitrogen oxides in exhaust gas in an exhaust system.
An exhaust gas purifying apparatus for an engine , comprising: a fuel adding means for adding fuel to exhaust gas upstream of a NOx purifying catalyst in the exhaust system, and burning at a pressure exceeding a set value from the fuel injection means. An exhaust gas purifying apparatus for a diesel engine , further comprising control means for reducing the amount of fuel added by the fuel adding means when fuel for fuel is injected. 2. A fuel injection means for separately injecting fuel for combustion into a main injection and a pilot injection thereof for each cylinder is provided, and a NOx purification catalyst for purifying nitrogen oxides in exhaust gas is provided in an exhaust system. An exhaust purification device for a diesel engine installed, comprising: fuel addition means for adding fuel to exhaust gas on the upstream side of the NOx purification catalyst in the exhaust system, and from the fuel injection means to main injection. Diesel characterized by being provided with control means for reducing the amount of fuel added by the fuel adding means in an operating state in which the preceding pilot injection is performed.
Engine exhaust purification device. 3. Fuel for injecting fuel for combustion for each cylinder
Injection means is provided, and nitrogen acid in the exhaust gas is provided to the exhaust system.
NOx purification catalyst installed to purify oxides in an oxygen-rich atmosphere
Exhaust purification device for an engine, wherein the exhaust system
HC in the exhaust gas upstream of the NOx purification catalyst
Component adding means for adding nitrogen and the NOx purification catalyst
Detecting means for detecting the oxygen concentration at the outlet side of the
The higher the outlet oxygen concentration detected, the higher the
Control means for reducing the amount of added
An exhaust gas purification device for an engine, characterized in that: 4. The detecting means comprises an acid on the inlet side of the NOx purification catalyst.
The difference between the oxygen concentration and the oxygen concentration at the outlet is detected, and the control means
The smaller the absolute value of the difference, the smaller the amount of HC component added
The exhaust gas purification of an engine according to claim 3, wherein
Device. 5. The detecting means comprises an acid on the inlet side of the NOx purification catalyst.
O2 sensor on the inlet side to detect elemental concentration and oxygen concentration on the outlet side
And an outlet-side O2 sensor for detecting
Of the oxygen concentration on the inlet side and the oxygen concentration on the outlet side based on the detected value of
The engine according to claim 4, wherein the difference is detected.
Exhaust purification device. 6. The NOx purification catalyst is a metal-supported zeolite.
4. The method according to claim 1, wherein
An exhaust gas purifying apparatus for an engine according to any one of the claims.