JP2003056391A - Diesel engine having operation mode for activating exhaust catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for properly activating a catalyst in compliance with a load and the number of revolutions. SOLUTION: This diesel engine 100 is provided with the catalyst 50 in an exhaust passage. The diesel engine is also provided with an oxygen enriching system 110 capable of separating gas containing oxygen into an oxygen enriched gas OEG with a comparatively high oxygen concentration and an oxygen depleted gas ODG with a comparatively low oxygen concentration and feeding the oxygen enriched gas OEG to the catalyst 50. According to the load and the number of revolutions of the diesel engine, the oxygen enriching system 110 controls an amount of the oxygen enriched gas OEG and a post-injection fuel amount for maintaining activity of the catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for maintaining an activated state of an exhaust gas catalyst of a diesel engine.

[0002]

2. Description of the Related Art Conventionally, various filters and catalysts for collecting and burning suspended particulate matter (particulates, PM) in exhaust gas of an internal combustion engine have been used. A catalyst that reduces NOx in exhaust gas is also used. Post injection is a technique for maintaining such an activated state of the catalyst.

[0003]

However, it may be more preferable to use a catalyst activation technique other than post injection depending on the load and the engine speed of the engine.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a technique for appropriately activating the catalyst according to the load and the rotation speed.

[0005]

Means for Solving the Problem and Its Action / Effect To achieve the above object, the present invention performs a predetermined process on a diesel engine having a catalyst in the exhaust path. This diesel engine produces gas containing oxygen,
An oxygen enrichment system that can separate the oxygen-enriched gas with a relatively high oxygen concentration and the oxygen-depleted gas with a relatively low oxygen concentration to send the oxygen-enriched gas to the catalyst, and the fuel in the combustion chamber The fuel injection part which injects, and the control part which controls an oxygen enrichment system and a fuel injection part are provided.

In such a diesel engine,
Controls the amount of oxygen-enriched gas that the oxygen-enrichment system sends to the catalyst and the amount of post-injection fuel that the fuel injection unit injects fuel after compression top dead center, depending on the load and speed of the diesel engine Then, an operation mode for maintaining activation of the catalyst is provided. According to this mode, it is possible to appropriately activate the catalyst according to the load and the rotation speed by utilizing the characteristics of the oxygen-enriched gas supply and the post injection.

In the operating mode for maintaining the activation of the catalyst, the amount of oxygen-enriched gas is set to a relatively small value in the first range related to the combination of the load and the rotational speed of the diesel engine, and The amount of injected fuel is set to a relatively large value, and the amount of the oxygen-enriched gas is relatively large in the second range where at least one of the load and the rotational speed of the diesel engine is lower than the first range. It is preferable to set the value to a value and to make the amount of post-injection fuel relatively small. With such a mode, it is possible to reduce torque fluctuation and noise change while activating the catalyst when the load is low and the rotation speed is low.

Further, in the operation mode in which the activation of the catalyst is maintained, the amount of the oxygen-enriched gas is increased in the third range where at least one of the load and the rotational speed of the diesel engine is higher than the first range. It is preferable to set it to a relatively large value and to make the amount of fuel for post injection relatively small. According to this mode, it is possible to reduce the rise in exhaust temperature while activating the catalyst under high load or high rotation.

When the temperature of the catalyst is relatively low, the operation of the operation mode for maintaining the activation of the catalyst is performed, and when the temperature of the catalyst is relatively high, the operation of the operation mode for maintaining the activation of the catalyst. It is also possible to adopt a mode in which the step is not performed. According to this mode, when the temperature of the catalyst is relatively low and it is difficult to activate the catalyst, it is possible to perform the operation for maintaining the activation of the catalyst.

Further, when the temperature of the cooling water of the diesel engine is 70 ° C. or lower, and when the load is 0 for 3 minutes or more, at least one of the conditions is satisfied, the catalyst is activated. It is also possible to adopt a mode in which the operation in the operation mode for maintaining is performed. According to such a mode, it is possible to perform the operation for maintaining the activation of the catalyst by determining whether or not the catalyst is in a state where it is difficult to activate by a simple method.

The present invention can be implemented in various modes. For example, an exhaust emission control device for an internal combustion engine or a method thereof, a vehicle or a moving body using the device, a function of the device or a method thereof. The present invention can be implemented in the form of a computer program for implementation, a recording medium recording the computer program, a data signal embodied in a carrier wave including the computer program, and the like.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in the following order based on examples. A. First Example: B. Second Embodiment: C.I. Modification

A. First Embodiment: (1) Configuration of Diesel Engine: FIG. 1 is an explanatory diagram showing a schematic configuration of a diesel engine 100 in the first embodiment. The diesel engine 100 is a four-cylinder engine having four combustion chambers # 1 to # 4. Air is supplied to each of the combustion chambers # 1 to # 4 via the manifold 12 of the intake pipe 10. Also, this engine 100
Uses a common rail fuel injection system,
High-pressure fuel is supplied from the high-pressure fuel pump 74 to the fuel injection valves 72 of the combustion chambers # 1 to # 4. Fuel injection valve 72
When fuel is injected from the air, the air and the fuel burn in the combustion chambers # 1 to # 4, and the exhaust gas is discharged from the exhaust pipe 20.

In the present specification, the engine body is referred to as a "diesel engine" in a narrow sense, but in a broader sense, a configuration including an exhaust pipe 20 and an oxygen enrichment system 110, which will be described later, in addition to the engine body. The "diesel engine"
And "Diesel engine" in the claims
Is a diesel engine in a broad sense.

The intake pipe 10 is provided with a supercharger 30. The supercharger 30 includes a turbine 32 provided in the exhaust pipe 20 and a compressor 34 provided in the intake pipe 10.
And a shaft connecting them. The supercharger 30 is a so-called variable nozzle type supercharger, and is provided with an actuator 36 for adjusting the opening area of the inlet nozzle 35 of the turbine 32. The actuator 36 can reduce the opening area of the inlet nozzle of the turbine 32 during low power operation of the engine 100, thereby improving the efficiency of the supercharger 30. An intercooler 40 for cooling the compressed air is provided downstream of the compressor 34, and an electromagnetic throttle valve 42 is provided further downstream thereof.
An air flow meter 44 is provided on the upstream side of the compressor 34.

The exhaust pipe upstream of the turbine 32 has an EG
The R passage 60 is connected. This EGR passage 60 is
It is connected to the intake manifold 12. EGR passage 6
At 0, an EGR cooler 62 and an EGR valve 64 are provided. As is well known, EGR is a technique for recirculating a part of exhaust gas into a combustion chamber to lower the combustion temperature and thereby improving the quality of exhaust gas. Exhaust gas amount (EGR amount) recirculated to the intake pipe
Can be controlled by adjusting the opening of the EGR valve 64. Further, the throttle valve 42 is connected to the intake pipe 1
It has a function of lowering the pressure in 0 to facilitate the return of exhaust gas to the intake pipe 10. That is, the EGR amount is the EGR amount.
It is controlled by adjusting the opening of the valve 64 and the opening of the throttle valve 42.

The crankshaft of the engine 100 is provided with a rotation angle sensor 76 and a rotation speed sensor 78.
An accelerator pedal sensor (not shown) is provided with an accelerator opening sensor 48. The control unit 200 determines the high-pressure fuel pump 74, the fuel injection valve 72, the EGR valve 64, the throttle valve 42, and the supercharger 30 according to the operating condition parameters detected by various sensors including these sensors.
The actuator 36 and the like are controlled.

The exhaust pipe 20 has an oxygen enrichment system 110.
Is provided. The oxygen enrichment system 110 includes first and second bypass exhaust pipes 24 and 26, an oxygen enrichment device 80, and a switching valve 90.

The first bypass exhaust pipe 24 is the main exhaust pipe 2
It branches from 2, and a switching valve 90 is provided at the branch point. The main exhaust pipe 22 is provided with a catalytic converter 50 for purifying exhaust gas. In this embodiment, a DPNR (diesel particulate NOx reduction system) having a particulate filter and a NOx occlusion reduction type three-way catalyst is used as the catalytic converter 50. The catalyst of the catalytic converter 50 is not limited to the NOx occlusion reduction type three-way catalyst, and a catalyst having a NOx reducing function can be used. An air-fuel ratio sensor 52 is provided at the inlet of the catalytic converter 50.

The oxygen enrichment device 80 separates the exhaust gas EG passing through the first bypass exhaust pipe 24 into an oxygen enriched gas OEG having a higher oxygen concentration and an oxygen depleted gas ODG having a lower oxygen concentration. It is a device for. The oxygen-enriched gas OEG is returned to the portion of the main exhaust pipe 22 on the upstream side of the catalytic converter 50 via the first bypass exhaust pipe 24. The oxygen-depleted gas ODG is used in the oxygen enrichment device 80.
Is returned to the portion of the main exhaust pipe 22 on the downstream side of the catalytic converter 50 via the second bypass exhaust pipe 26 connected to.

FIG. 2 is a conceptual diagram showing the structure of the oxygen enrichment device 80. An oxygen enriched film 84 is provided in the storage case 82 so as to face the exhaust passage 81. Further, inside the oxygen-enriched film 84, the porous support film 86 and the continuous foam 88 are provided.
And are arranged in this order. The continuous foam 88 is the second
Is connected to the bypass exhaust pipe 26.

A part of the exhaust gas EG passing through the exhaust passage 81 passes through the oxygen-enriched film 84, the porous support film 86 and the continuous foam body 88, and becomes the first bypass exhaust pipe as the oxygen-enriched gas OEG. It is discharged to 24. The remaining exhaust gas is used as the oxygen depletion gas ODG in the second bypass exhaust pipe 2
It is discharged to 6.

When the oxygen-enriched gas OEG is supplied to the catalytic converter 50 via the first bypass exhaust pipe 24,
Inside, the oxidation of HC is promoted. Particularly, in the state where the catalyst is not activated, HC exists in the catalytic converter 50. Therefore, the oxygen-enriched gas OEG is supplied to the catalyst, so that the oxidation of HC is promoted and the heat of reaction thereof causes the catalytic converter 50 to react. The temperature inside rises and the catalyst is activated. Further, when the engine is at low speed and when the load is low, a large amount of HC exists in the exhaust gas. Therefore, when the engine speed is low and the load is low, the oxygen-enriched gas OEG is supplied into the catalytic converter 50 to accelerate the oxidation of the HC, thereby further activating the catalyst.

(2) Post injection: FIG. 3 is an explanatory view showing the post injection performed in this embodiment. The horizontal axis of the figure is the crank angle CA, and the vertical axis is the pressure in the cylinder.
The graph shown by the solid line is the pressure in the cylinder when combustion is not performed. In the present embodiment, in addition to the normal fuel injection that is performed at the timing ta from before the compression top dead center TDC to near the top dead center TDC, the fuel is injected again at the timing tb after the compression top dead center. Such fuel injection is called post injection. When the compression top dead center TDC is 0, the timing ta is normally −30 ° to + 5 °, and the timing t
a is around + 60 °.

By executing the post-injection, unburned fuel is supplied to the main exhaust pipe 22 after the exhaust pipe 20 connected to the internal combustion engine, the catalytic converter 50 and the like. Then, the unburned fuel undergoes an oxidation reaction to raise the temperature of the catalyst of the catalytic converter 50 and activate the catalyst. Thereby, combustion of HC in the catalytic converter 50 is promoted.

When the amount of post-injection performed at timing tb is larger than the amount of normal fuel injection performed at timing ta, engine torque fluctuation and noise change may occur. Specifically, such torque fluctuation and noise change are likely to occur at low load when the amount of normal fuel injection performed at the timing ta decreases, and at low rotation.

Further, when the engine speed is low and the load is high, the amount of HC in the exhaust gas is large, and therefore the amount of HC in the exhaust gas is further increased by performing the post injection. Therefore, a large amount of HC may adhere to the EGR cooler 62 and the EGR valve 64 provided in the EGR passage 60.

On the other hand, in an internal combustion engine in which EGR (exhaust gas circulation) is performed, exhaust gas that has become hot due to post injection is circulated again from the intake manifold 12 into the combustion chamber through the EGR passage 60, so that the exhaust gas becomes hot. It is easy to become. For this reason, at the time of high load and high rotation, the thermal influence on each component attached to the exhaust pipe such as the turbine 32 becomes large.

(3) Oxygen enrichment control and post injection control: FIG. 4 is a flow chart showing the procedure of the oxygen enrichment control and post injection control in this embodiment. This procedure is executed under the control of the control unit 200 while the engine 100 is operating. First, in step S2, it is determined whether the temperature of the cooling water is low or whether the engine 100 has been in an idling state for a certain time or longer. Specifically, in step S2, it is determined whether the temperature of the cooling water is 70 ° C. or lower, and whether the idling time is 3 minutes or longer. This is because in such a case, the temperature of the catalyst is low and the catalyst is hard to be activated. In step S2, it is more preferable to determine whether or not the temperature of the cooling water is 80 ° C or lower. Then, it is more preferable to judge whether or not the idling time is 5 minutes or more.

The determination in step S2 is always made during the operation of the engine 100, and the processing in step S4 and subsequent steps is executed only when either of the conditions of the cooling water temperature and the idling time is satisfied. Then, if none of the conditions is satisfied, the processes of step S4 and thereafter are not executed. The processing from step S4 onward is the "operation mode for maintaining activation of the catalyst" in the claims.

If the result of the determination in step S2 is Yes, subsequently, in step S4, the number of revolutions Ne of the engine 100 and the load Me are determined. Information on the rotation speed Ne of the engine 100 is provided to the control unit 200 from the rotation speed sensor 78. Also, the load Me
Is determined based on data provided from the accelerator opening sensor 48 to the control unit 200.

FIG. 5 is a map showing how to perform oxygen enrichment control and post injection control in this embodiment. The horizontal axis of the figure is the engine speed Ne, and the vertical axis is the load Me. When the combination of the rotation speed Ne and the load Me is within a certain range (hereinafter, this state is referred to as a first range), the post injection amount is set to a relatively large value, and the combustion of the oxygen enrichment system 310 is performed. The valve 90 in the intake passage leading to the chamber is closed. In the first range, even if post injection is performed, the rise in exhaust temperature is tolerable, and torque fluctuation and noise change are tolerable. This first range is indicated by I in FIG.

In the second range in which at least one of the rotation speed Ne and the load Me is lower than the first range, the post injection amount is set to a relatively small value and the valve 90 of the oxygen enrichment system 310 is opened. . Also, the rotation speed Ne and the load M
At least one of e sets the post injection amount to a relatively small value and opens the valve 90 of the oxygen enrichment system 310 even in the third range which is higher than the first range. Figure 5
In, the second range is indicated by II and the region of the third range is indicated by III. As can be seen from FIG. 5, there is a region I between the regions II and III.

In this embodiment, the injection amount of post injection is reduced when the load on the engine 100 is low or when the rotation speed of the engine 100 is low. For this reason,
Normal timing t before compression top dead center in the combustion chamber
Combustion by the fuel injected in a becomes dominant, and torque fluctuations and noise changes of the engine are reduced. Further, since the injection amount of post injection is reduced at low rotation speed and low load, E
The amount of HC attached to the GR cooler 62 and the EGR valve 64 can be reduced.

Further, in this embodiment, the engine 10
When the load of 0 is high or the rotation speed of the engine 100 is high, the injection amount of post injection is reduced. For this reason, it is possible to prevent the exhaust temperature from rising, which greatly exceeds the temperature required to activate the catalyst. And as a result,
It is possible to reduce the thermal influence on each component attached to the exhaust pipe such as the turbine 32 due to the high temperature.

Further, the oxygen-enriched gas OEG is supplied instead of the post injection at the time of low rotation and low load and at the time of high rotation and high load. Therefore, the fuel consumption amount can be reduced in the operation mode in which the activation of the catalyst is maintained. Then, in all regions, the size of the device can be made smaller than that of the internal combustion engine in which the catalyst is activated by controlling the supply amount of the oxygen-enriched gas OEG. In this embodiment, the valve 9 of the oxygen enrichment system 310 is used.
0 is opened or closed to adjust the supply amount of the oxygen-enriched gas OEG, but finer control is performed by finely controlling the amount of opening the valve 90, for example, to more finely control the activation of the catalyst. can do.

Further, in this embodiment, the operation in the operation mode for maintaining the activation of the catalyst is carried out only when the temperature of the catalyst is considered to be low, that is, when the result of the determination in step S2 is Yes. . Therefore, in other cases, it is possible to reduce the fuel consumption throughout the operation of the engine by not performing the post injection.

B. Second Embodiment: FIG. 6 is an explanatory diagram showing a schematic configuration of a diesel engine 100a in the second embodiment. This diesel engine 100a differs from the first embodiment in the configuration of the oxygen enrichment system 110a. The other construction is the diesel engine 100 of the first embodiment.
Is the same as.

The oxygen enrichment system 110a has an oxygen enrichment device 80. The configuration of the oxygen enriching device 80 is the same as that of the oxygen enriching device 80 of the first embodiment. The intake pipe 16 is connected to the oxygen enrichment device 80, and the pump 94 is connected to the intake pipe 16.

In addition, the oxygen enrichment device 80 includes an exhaust pipe 2
7, 28 are connected. The other end of the exhaust pipe 28 is open to the atmosphere. On the other hand, the exhaust pipe 27 is connected to the oxygen-enriched gas tank 96 via a check valve. The exhaust pipe 29 is connected to the oxygen-enriched gas tank 96, and the exhaust pipe 29 is connected to the catalytic converter 50 of the main exhaust pipe 22.
Is connected to the upstream part of the. A gas injection valve 98 is provided in the exhaust pipe 29.

The pump 94 supplies air Ar to the oxygen enriching device 80 through the intake pipe 14. Then, the oxygen enrichment device 80 separates the oxygen-enriched gas OEG into the oxygen-depleted gas ODG having a lower oxygen concentration, and supplies the oxygen-enriched gas OEG to the oxygen-enriched gas tank 96. Oxygen-depleted gas OD
G is released into the atmosphere through the exhaust pipe 29. The oxygen-enriched gas tank 96 stores the oxygen-enriched gas OEG supplied from the oxygen-enrichment device 80. Control unit 200
Controls the gas injection valve 98 to supply the required amount of oxygen-enriched gas OEG to the main exhaust pipe 22 upstream of the catalytic converter 50.

Even in such a mode, FIG. 4 and FIG.
Oxygen enrichment control and post injection control as shown in can be performed. Further, in such a mode, the oxygen-enriched gas OEG is controlled by controlling the opening degree of the gas injection valve 98.
It is possible to finely control the supply amount of. And
If the pressure in the oxygen-enriched gas tank 96 is set high, the supply amount of the oxygen-enriched gas OEG can be rapidly increased.

C. Modifications: The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are also possible. is there.

C1. Modification 1: The present invention is applicable to various vehicles such as automobiles and other vehicles using diesel engines, airplanes, and ships.

C2. Modified Example 2: Each of the above-described embodiments is based on EGR.
Although the engine having the system and the supercharger 30 has been described, the present invention is also applicable to an engine having no EGR system or the supercharger 30.

[0046]

[Brief description of drawings]

FIG. 1 is a diesel engine 100 according to a first embodiment.
Explanatory diagram showing a schematic configuration of.

FIG. 2 is a conceptual diagram showing the configuration of an oxygen enrichment device 80.

FIG. 3 is an explanatory diagram showing post injection performed in this embodiment.

FIG. 4 is a flowchart showing a procedure of oxygen enrichment control and post injection control in the first embodiment.

FIG. 5 is a map showing how to perform oxygen enrichment control and post injection control in the first embodiment.

FIG. 6 is a diesel engine 100 according to the second embodiment.
Explanatory diagram showing a schematic configuration of.

[Explanation of symbols]

10 ... Intake pipe 12 ... Manifold 12 ... Intake manifold 14 ... Intake pipe 16 ... Intake pipe 20 ... Exhaust pipe 22 ... Main exhaust pipe 24 ... First bypass exhaust pipe 26 ... Second bypass exhaust pipe 27, 28, 29 ... Exhaust pipe 30 ... Supercharger 32 ... Turbine 34 ... Compressor 35 ... Inlet nozzle 36 ... Actuator 40 ... Intercooler 42 ... Electromagnetic throttle valve 44 ... Air flow meter 48 ... Accelerator opening sensor 50 ... Catalytic converter 52 ... Air-fuel ratio sensor 60 ... EGR passage 62 ... EGR cooler 64 ... EGR valve 72 ... Fuel injection valve 74 ... High-pressure fuel pump 76 ... Rotation angle sensor 78 ... Rotation speed sensor 80 ... Oxygen enrichment device 81 ... Exhaust passage 82 ... Storage case 84 ... Oxygen enrichment film 86 ... Porous support membrane 88 ... Continuous foam 90 ... Valve (switching valve) 94 ... Pump 96 ... Oxygen-enriched gas tank 98 ... Gas injection valve 100, 100a ... Diesel engine 110, 110a ... Oxygen enrichment system 200 ... Control unit 310 ... Oxygen enrichment system Ar ... Air CA ... Crank angle EG ... Exhaust gas I ... Number of combinations of rotation speed Ne and load Me Region II in the range of 1 ... Region III in the second range relating to the combination of the rotational speed Ne and load Me ... Region Me in the third range regarding the combination of the rotational speed Ne and load Me ... Load NOx ... Diesel particulate Ne ... Rotation Number ODG ... Oxygen-depleted gas OEG ... Oxygen-enriched gas TDC ... Compression top dead center ta ... Fuel injection timing tb ... Post injection timing

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 43/00 F02D 43/00 301M 45/00 360 45/00 360B 360C 364 364G F02M 33/00 F02M 33 / 00 CF Term (reference) 3G084 AA01 BA04 BA13 BA15 CA01 DA10 EA11 FA00 FA18 FA20 FA33 3G091 AA02 AA10 AA11 AA18 AB05 BA03 CB02 CB03 DA02 EA01 EA03 EA18 3G301 HA02 HA11 HA13 JA21 KA01 MA11 MA19 PA08Z PE01

Claims (5)

[Claims] 1. A diesel engine having a catalyst in an exhaust path, wherein an oxygen-containing gas is separated into an oxygen-enriched gas having a relatively high oxygen concentration and an oxygen-depleted gas having a relatively low oxygen concentration. ,
An oxygen enrichment system capable of sending the oxygen enriched gas to the catalyst; a fuel injector for injecting fuel into a combustion chamber; and a controller for controlling the oxygen enrichment system and the fuel injector. According to the load and the rotation speed of the diesel engine, the control unit, the amount of the oxygen-enriched gas sent to the catalyst by the oxygen-enrichment system, and the fuel injection unit supplies fuel after compression top dead center. By controlling the amount of post-injection fuel to be injected,
A diesel engine having an operation mode for maintaining activation of the catalyst. 2. The diesel engine according to claim 1, wherein the control unit, in an operation mode for maintaining activation of the catalyst, in a first range regarding a combination of a load and a rotational speed of the diesel engine, The amount of the oxygen-enriched gas is set to a relatively small value, the amount of the post-injection fuel is set to a relatively large value, and at least one of the load and the rotational speed of the diesel engine is set to the first value. A diesel engine in which, in a second range lower than the range, the oxygen-enriched gas amount is set to a relatively large value and the post-injection fuel amount is set to a relatively small value. 3. The diesel engine according to claim 2, wherein, in the operation mode in which the control unit maintains the activation of the catalyst, at least one of a load and a rotation speed of the diesel engine is the first engine. A diesel engine in which, in a third range higher than the range, the oxygen-enriched gas amount is set to a relatively large value and the post-injection fuel amount is set to a relatively small value. 4. The diesel engine according to claim 1, wherein the control unit operates in an operation mode for maintaining activation of the catalyst when the temperature of the catalyst is relatively low, A diesel engine that does not operate in an operation mode for maintaining activation of the catalyst when the temperature is relatively high. 5. The diesel engine according to claim 1, wherein the control unit is 3 minutes or more when the temperature of the cooling water of the diesel engine is 70 ° C. or lower and when the load is 0. Then, when at least one of the following conditions is satisfied, the diesel engine is operated in an operation mode for maintaining activation of the catalyst.