JP2002357116A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a filter from clogging, by burning PM early, in the exhaust emission control device for an internal combustion engine. SOLUTION: The exhaust emission control comprises: a filter 20 disposed to an exhaust passage 19 of the internal combustion engine 1 and trapping particulate maters contained in exhaust; and an ultrasonic generating means 37 for giving vibrations to the exhaust inside the exhaust passage 19 upstream of the filter 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a particulate matter represented by soot, which is a suspended particulate matter contained in exhaust gas of a diesel engine. The present invention relates to an exhaust gas purification device having means for collecting PM as far as possible.

[0002]

2. Description of the Related Art While diesel engines are excellent in economical efficiency, removal of PM contained in exhaust gas is an important issue. For this reason, a technique of providing a particulate filter (hereinafter, simply referred to as “filter”) for trapping PM in an exhaust system of a diesel engine so that PM is not released into the atmosphere is well known.

[0003] This filter can prevent PM in exhaust gas from being once collected and released into the atmosphere. However, PM trapped in the filter may accumulate on the filter and cause clogging of the filter. When this clogging occurs, the pressure of the exhaust gas upstream of the filter increases, which may cause a decrease in the output of the internal combustion engine or damage to the filter. In such a case, the PM deposited on the filter can be removed by igniting and burning. Removing PM accumulated on the filter in this way is called filter regeneration.

However, in order to ignite and burn PM trapped in the filter, the temperature of the filter is set to, for example, 50.
Although it is necessary to keep the temperature at 0 ° C. or higher, it is difficult to burn off PM because the temperature of the exhaust gas of the diesel engine is lower than this temperature except in a high rotation and high load region.

Therefore, it is conceivable to heat and raise the temperature of the filter to a temperature at which the collected PM is ignited and burned by using an electric heater, a burner, or the like. There is. For this issue,
For example, according to JP-A-6-159037, NOx
Using a filter carrying a catalyst and a device for supplying hydrocarbons to the exhaust gas, the hydrocarbons supplied to the exhaust gas are
Easily use PM generated by burning with catalyst
Enables combustion.

On the other hand, as a method of reducing the amount of nitrogen oxides (NOx) discharged from the internal combustion engine, an exhaust gas recirculating a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage of the internal combustion engine is used. Recirculation (EGR: Exhaust Gas Recircul)
ation) Methods using devices are known.

[0007] The EGR device uses water vapor (H ₂ O), carbon monoxide (CO), carbon dioxide (CO ₂ ) contained in exhaust gas.
Utilizing the incombustibility and endothermic properties of the inert gas components such as the above, the combustion speed and combustion temperature of the air-fuel mixture in the combustion chamber of the internal combustion engine are reduced, and the amount of nitrogen oxides (NOx) generated during combustion Is to be reduced.

[0008]

The PM deposited on the filter as described above can be burned by adding hydrocarbon (HC) to the exhaust gas.
In (C), the fuel of the internal combustion engine is used, so that burning and removing PM deteriorates fuel efficiency.

On the other hand, the PM deposited on the filter as described above is burned and removed when the internal combustion engine is operated in a high speed and high load region because the temperature of the exhaust gas is high.
In such a case, the smaller the particle size of PM, the sooner it can be burned. That is, if the particle size of the PM is small, the amount of the PM burned when the internal combustion engine is operated at a high rotation speed and a high load increases, so that clogging can be prevented.

[0010] In addition, E
In the GR device, PM contained in the EGR gas may flow into the EGR cooler. If such a phenomenon is repeated, PM may adhere to the EGR cooler and the EGR gas cooling efficiency in the EGR cooler may be reduced.

In addition, when clogging of the EGR cooler occurs, it becomes difficult to recirculate a desired amount of EGR gas to the intake passage. As a result, the amount of generated nitrogen oxides (NOx) in the internal combustion engine is sufficiently reduced. May not be able to be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems.
It is an object of the present invention to provide a technique for preventing PM from being clogged by burning PM at an early stage.

[0013]

Means for Solving the Problems In order to achieve the above object, an exhaust gas purifying apparatus for an internal combustion engine according to the present invention employs the following means. That is, a filter is provided in the exhaust passage of the internal combustion engine and collects particulate matter contained in the exhaust gas, and an ultrasonic wave generating means for applying vibration to the exhaust gas inside the exhaust passage upstream of the filter.

The most significant feature of the present invention is an exhaust gas purifying apparatus for an internal combustion engine, which is provided with an ultrasonic wave generating means in an exhaust passage,
An object of the present invention is to achieve an effect of applying a vibration to PM contained in exhaust gas by the ultrasonic waves generated from the ultrasonic wave generating means to atomize the PM and promoting the combustion of the PM.

In the exhaust gas purifying apparatus for an internal combustion engine thus configured, PM contained in the exhaust gas is collected by the filter. This filter may carry a catalyst.

The PM collected by the filter combusts when the temperature of the exhaust gas is high, for example, when the internal combustion engine is operated in a high speed and high load region. However, even if the temperature of the exhaust gas becomes high, if the particle size of the trapped PM is large, it takes time to burn out the PM. If the temperature of the exhaust gas drops during this time, the PM will remain unburned. The PM left unburned in this way accumulates on the filter and causes clogging.

Therefore, if the PM is vibrated by the ultrasonic waves generated by the ultrasonic wave generating means before the PM is trapped by the filter and the PM is atomized, the combustion in the filter is promoted and the clogging is prevented. Can solve the problem.

In the present invention, an EGR device for recirculating a part of exhaust gas to an intake system of an internal combustion engine, an EGR cooler for cooling EGR gas recirculating the EGR device,
The exhaust gas purification apparatus for an internal combustion engine, comprising:
Ultrasonic wave generating means for applying vibration to the R cooler may be provided.

In the present invention, the EGR cooler comprises:
The EGR gas is cooled by heat exchange between the cooling water and the EGR gas, and the ultrasonic wave generating means can apply vibration to the cooling water flowing inside the EGR cooler.

Since the exhaust gas flowing into the EGR cooler also contains PM, the PM may adhere to the EGR cooler. If PM adheres to the EGR cooler, the heat exchange rate decreases, and the effect of the EGR cooler decreases.

In such a case, when the EGR cooler is vibrated through a heat medium such as cooling water which exchanges heat with the EGR gas, PM adhering to the wall surface is separated from the wall surface. The separated PM is sucked into the combustion chamber together with the EGR gas and can be burned together with the fuel.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of a heat storage device for an internal combustion engine according to the present invention will be described below with reference to the drawings. Here, the case where the heat storage device for an internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purifying apparatus according to the present invention is applied and an intake / exhaust system thereof.

The engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.

The engine 1 has a fuel injection valve 3 for directly injecting fuel into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 for accumulating fuel up to a predetermined pressure. The common rail 4 is provided with a common rail pressure sensor 4a that outputs an electric signal corresponding to the pressure of the fuel in the common rail 4.

The common rail 4 communicates with a fuel pump 6 via a fuel supply pipe 5. This fuel pump 6
Is a pump that operates using the rotational torque of the output shaft (crankshaft) of the engine 1 as a driving source. A pump pulley 6a attached to the input shaft of the fuel pump 6 is attached to the output shaft (crankshaft) of the engine 1. And is connected via a belt 7 to the crank pulley 1a.

In the fuel injection system thus configured, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 is transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure corresponding to the rotating torque.

The fuel discharged from the fuel pump 6 is
The fuel is supplied to the common rail 4 via the fuel supply pipe 5, accumulated in the common rail 4 to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.

Next, an intake branch pipe 8 is connected to the engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).

The intake branch pipe 8 is connected to an intake pipe 9,
This intake pipe 9 is connected to an air cleaner box 10. An air flow meter 11 that outputs an electric signal corresponding to a mass of the intake air flowing through the intake pipe 9 is provided in an intake pipe 9 downstream of the air cleaner box 10 and a temperature corresponding to the temperature of the intake air flowing through the intake pipe 9. And an intake air temperature sensor 12 that outputs a detected electric signal.

An intake throttle valve 13 for adjusting the flow rate of intake air flowing through the intake pipe 9 is provided at a position immediately upstream of the intake branch pipe 8 in the intake pipe 9. The intake throttle valve 13 is provided with an intake throttle actuator 14 which is constituted by a step motor or the like and drives the intake throttle valve 13 to open and close.

The intake pipe 9 located between the air flow meter 11 and the intake throttle valve 13 is provided with a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 which operates using heat energy of exhaust gas as a driving source. And
An intercooler 16 for cooling intake air, which has been compressed in the compressor housing 15a and has become high temperature, is provided in the intake pipe 9 downstream of the compressor housing 15a.
Is provided.

In the intake system configured as described above, the intake air flowing into the air cleaner box 10 passes through the intake pipe 9 after dust or the like in the intake is removed by an air cleaner (not shown) in the air cleaner box 10. And flows into the compressor housing 15a.

The intake air flowing into the compressor housing 15a is compressed by rotation of a compressor wheel provided inside the compressor housing 15a. The intake air that has been compressed in the compressor housing 15a and has become high temperature is cooled by the intercooler 16, and then flows into the intake branch pipe 8 with the flow rate adjusted by the intake throttle valve 13 as necessary. The intake air flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 via each branch pipe, and is burned using the fuel injected from the fuel injection valve 3 of each cylinder 2 as an ignition source.

On the other hand, an exhaust branch pipe 18 is connected to the engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown).

The exhaust branch pipe 18 is connected to the centrifugal turbocharger 15.
Of the turbine housing 15b. The turbine housing 15b is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected downstream to a muffler (not shown).

In the middle of the exhaust pipe 19, there is provided an ultrasonic generator 37 for generating ultrasonic waves in the exhaust gas to atomize the PM, and further downstream thereof is a particulate supporting a storage-reduction type NOx catalyst. A filter 20 is provided. An exhaust pipe 19 downstream of the filter 20 has an air-fuel ratio sensor 23 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing through the exhaust pipe 19 and a temperature corresponding to the temperature of the exhaust flowing through the exhaust pipe 19. And an exhaust gas temperature sensor 24 for outputting a detected electric signal.

The exhaust pipe 19 downstream of the air-fuel ratio sensor 23 and the exhaust temperature sensor 24 is provided with an exhaust throttle valve 21 for adjusting the flow rate of exhaust flowing through the exhaust pipe 19. The exhaust throttle valve 21 is provided with an exhaust throttle actuator 22 configured by a step motor or the like and driving the exhaust throttle valve 21 to open and close.

In the exhaust system configured as described above, the air-fuel mixture (burned gas) burned in each cylinder 2 of the engine 1 is discharged to the exhaust branch pipe 18 through the exhaust port, and then from the exhaust branch pipe 18. Turbine housing 15b of centrifugal turbocharger 15
Flows into The exhaust gas flowing into the turbine housing 15b rotates a turbine wheel rotatably supported in the turbine housing 15b by using thermal energy of the exhaust gas. At this time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.

The exhaust gas discharged from the turbine housing 15b flows into a filter 20 via an exhaust pipe 19, where PM in the exhaust gas is collected and harmful gas components are removed or purified. The exhaust gas from which PM has been collected by the filter 20 and harmful gas components have been removed or purified is discharged to the atmosphere via a muffler after the flow rate is adjusted by an exhaust throttle valve 21 as necessary.

The exhaust branch pipe 18 and the intake branch pipe 8 are connected via an exhaust gas recirculation passage (EGR passage) 25 for recirculating a part of the exhaust gas flowing through the exhaust branch pipe 18 to the intake branch pipe 8. Are in communication. In the middle of the EGR passage 25, a solenoid valve or the like is provided.
A flow control valve (EGR valve) 26 for changing the flow rate of exhaust gas (hereinafter, referred to as EGR gas) flowing through the passage 25 is provided.

In the middle of the EGR passage 25, the EGR valve 26
Further upstream, an EGR cooler 27 that cools the EGR gas flowing through the EGR passage 25 is provided. A cooling water passage (not shown) is provided in the EGR cooler 27, and a part of cooling water for cooling the engine 1 circulates.

In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 26 is opened, the EGR passage 25 is brought into a conductive state, and a part of the exhaust gas flowing through the exhaust branch pipe 18 is partially discharged. And is guided to the intake branch pipe 8 through the EGR cooler 27.

At this time, in the EGR cooler 27, heat exchange is performed between the EGR gas flowing through the EGR passage 25 and the cooling water of the engine 1, and the EGR gas is cooled.

The EGR gas recirculated from the exhaust branch pipe 18 to the intake branch pipe 8 through the EGR passage 25 is guided to the combustion chamber of each cylinder 2 while mixing with fresh air flowing from the upstream of the intake branch pipe 8. Then, the fuel injected from the fuel injection valve 3 is burned using the ignition source.

Here, the EGR gas contains an inert gas component such as water (H ₂ O) or carbon dioxide (CO ₂ ) which does not burn itself and has endothermic properties, such as water (H ₂ O) and carbon dioxide (CO ₂ ). Therefore, if EGR gas is contained in the air-fuel mixture,
The combustion temperature of the air-fuel mixture is lowered, so that nitrogen oxides (NO
x) is suppressed.

Further, when the EGR gas is cooled in the EGR cooler 27, the temperature of the EGR gas itself decreases and the volume of the EGR gas decreases, so that when the EGR gas is supplied into the combustion chamber, The ambient temperature of the air does not unnecessarily rise, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber does not unnecessarily decrease.

Next, the filter 20 will be described.

FIG. 4 shows the structure of the filter 20. In addition,
4A shows a cross section of the filter 20 in the horizontal direction, and FIG. 4B shows a cross section of the filter 20 in the vertical direction. As shown in FIGS. 4A and 4B, the filter 20 is a so-called wall flow type including a plurality of exhaust passages 50 and 51 extending parallel to each other. These exhaust passages are constituted by an exhaust inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust outflow passage 51 whose upstream end is closed by a plug 53. FIG.
In FIG. 5A, the hatched portion indicates the plug 53. Accordingly, the exhaust inflow passages 50 and the exhaust outflow passages 51 are alternately arranged with the thin partition walls 54 interposed therebetween. In other words, the exhaust inflow passage 50 and the exhaust outflow passage 51 are arranged such that each exhaust inflow passage 50 is surrounded by the four exhaust outflow passages 51 and each exhaust outflow passage 51 is surrounded by the four exhaust inflow passages 50.

The filter 20 is formed of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust inflow passage 50 flows through the surrounding partition wall 54 as shown by an arrow in FIG. Then, it flows out into the adjacent exhaust outflow passage 51.

In the embodiment according to the present invention, each exhaust inflow passage 5
0 and the peripheral wall surface of each exhaust outflow passage 51, that is, each partition wall 54
A layer of a carrier made of, for example, alumina is formed on both side surfaces and on the inner wall surface of the pores in the partition wall 54, and the storage reduction type NOx catalyst is carried on this carrier.

Next, the operation of the storage reduction type NOx catalyst carried by the filter 20 according to the present embodiment will be described.

The filter 20 uses, for example, alumina as a carrier, and places potassium (K) and sodium (N) on the carrier.
a) Alkali metals such as lithium (Li) or cesium (Cs), alkaline earths such as barium (Ba) or calcium (Ca), and rare earths such as lanthanum (La) or yttrium (Y). And a noble metal such as platinum (Pt). In the present embodiment, a description will be given of an example of an occlusion reduction type NOx catalyst constituted by supporting barium (Ba) and platinum (Pt) on a carrier made of alumina.

[0054] The NOx catalyst thus configured is
When the oxygen concentration of the exhaust gas flowing into the Ox catalyst is high, nitrogen oxides (NOx) in the exhaust gas are absorbed.

On the other hand, the NOx catalyst releases the absorbed nitrogen oxides (NOx) when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. At this time, if reducing components such as hydrocarbons (HC) and carbon monoxide (CO) are present in the exhaust gas, the NOx catalyst converts the nitrogen oxides (NOx) released from the NOx catalyst into nitrogen (N ₂ ) can be reduced.

When the engine 1 is operating in the lean burn mode, the air-fuel ratio of the exhaust gas discharged from the engine 1 becomes a lean atmosphere and the oxygen concentration of the exhaust gas becomes high.
The nitrogen oxides (NOx) contained in the exhaust gas are absorbed by the NOx catalyst. However, if the lean burn operation of the engine 1 is continued for a long time, the NOx absorption capacity of the NOx catalyst is saturated, and Nitrogen oxides (NOx) are released to the atmosphere without being removed by the NOx catalyst.

In particular, in a diesel engine such as the engine 1, a mixture having a lean air-fuel ratio is burned in most of the operating region, and the air-fuel ratio of exhaust gas becomes a lean air-fuel ratio in most of the operating region. , N of the NOx catalyst
Ox absorption capacity is easily saturated.

Therefore, when the engine 1 is operating in the lean burn operation, the concentration of oxygen in the exhaust gas flowing into the NOx catalyst is reduced and the concentration of the reducing agent is increased before the NOx absorption capacity of the NOx catalyst is saturated. It is necessary to release and reduce nitrogen oxides (NOx) absorbed by the catalyst.

The exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment is provided with a reducing agent supply mechanism for adding fuel (light oil) as a reducing agent to the exhaust gas flowing through the exhaust pipe 19 upstream of the filter 20. By adding fuel from the agent supply mechanism to the exhaust gas, the oxygen concentration of the exhaust gas flowing into the filter 20 is reduced and the concentration of the reducing agent is increased.

As shown in FIG. 1, the reducing agent supply mechanism is mounted on the cylinder head of the engine 1 so that its injection hole faces the inside of the exhaust branch pipe 18, and the valve is opened by a signal from the ECU 35 to inject fuel. A reducing agent injection valve 28, a reducing agent supply passage 29 for guiding the fuel discharged from the fuel pump 6 to the reducing agent injection valve 28, and a reducing agent supply passage 29.
And a shutoff valve 31 for shutting off the flow of the fuel in the reducing agent supply passage 29.

In the reducing agent injection valve 28, the injection hole of the reducing agent injection valve 28 is located downstream of the connection portion of the exhaust branch pipe 18 with the EGR passage 25, and the four branch pipes of the exhaust branch pipe 18 It is preferable that the projection is protruded to the exhaust port of the cylinder 2 closest to the collecting portion and is attached to the cylinder head so as to face the collecting portion of the exhaust branch pipe 18.

This prevents the reducing agent (unburned fuel component) injected from the reducing agent injection valve 28 from flowing into the EGR passage 25, and also prevents the reducing agent from being centrifuged in the exhaust branch pipe 18 without centrifugation. This is to reach the turbine housing 15b of the supercharger.

In the example shown in FIG. 1, the first (# 1) cylinder 2 of the four cylinders 2 of the engine 1 is located closest to the gathering portion of the exhaust branch pipe 18, so that the first (# 1) Although the reducing agent injection valve 28 is attached to the exhaust port of the cylinder 2, when the cylinder 2 other than the first (# 1) cylinder 2 is located closest to the gathering portion of the exhaust branch pipe 18, that cylinder is The reducing agent injection valve 28 is attached to the second exhaust port.

Further, the reducing agent injection valve 28 is designed to penetrate a water jacket (not shown) formed in the cylinder head or to be mounted close to the water jacket, and to use cooling water flowing through the water jacket. The reducing agent injection valve 28 may be cooled.

In such a reducing agent supply mechanism, the high-pressure fuel discharged from the fuel pump 6 is applied to the reducing agent injection valve 28 through the reducing agent supply passage 29. And ECU3
In response to the signal from 5, the reducing agent injection valve 28 is opened, and fuel as a reducing agent is injected into the exhaust branch pipe 18.

The reducing agent injected from the reducing agent injection valve 28 into the exhaust branch pipe 18 flows into the turbine housing 15b together with the exhaust gas flowing from the upstream of the exhaust branch pipe 18.
The exhaust gas and the reducing agent that have flowed into the turbine housing 15b are stirred and uniformly mixed by the rotation of the turbine wheel to form exhaust gas having a low oxygen concentration.

The exhaust gas having a low oxygen concentration formed as described above flows into the filter 20 from the turbine housing 15b via the exhaust pipe 19, and emits nitrogen oxides (NOx) absorbed by the filter 20. It will be reduced to nitrogen (N ₂ ).

Thereafter, the reducing agent injection valve 28 is closed by a signal from the ECU 35, and the addition of the reducing agent into the exhaust branch pipe 18 is stopped.

The engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the engine 1. The ECU 35 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and a driver's request.

The ECU 35 includes a common rail pressure sensor 4
a, air flow meter 11, intake air temperature sensor 12, intake pipe pressure sensor 17, air-fuel ratio sensor 23, exhaust gas temperature sensor 24, crank position sensor 33, water temperature sensor 3
4. Various sensors such as the accelerator opening sensor 36 are connected via electric wiring, and the output signals of the various sensors are E
The data is input to the CU 35.

On the other hand, the ECU 35 includes the fuel injection valve 3, the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the shut-off valve 31, and the ultrasonic generator 3.
7 and the like are connected via electric wiring,
U35 can be controlled.

Here, as shown in FIG. 3, the ECU 35 is connected to a C
A PU 351, a ROM 352, a RAM 353, a backup RAM 354, an input port 356, and an output port 357.
And an A / D converter (A / D) 355 connected to.

The input port 356 inputs the output signals of a sensor which outputs a digital signal, such as the crank position sensor 33, and outputs those signals to the C port.
The data is transmitted to the PU 351 and the RAM 353.

The input port 356 is connected to the common rail pressure sensor 4a, the air flow meter 11, the intake air temperature sensor 1
2, intake pipe pressure sensor 17, air-fuel ratio sensor 23, exhaust temperature sensor 24, water temperature sensor 34, accelerator opening sensor 3
6, and the like, input through an A / D 355 of a sensor that outputs a signal in an analog signal format, and transmit those output signals to the CPU 351 and the RAM 353.

The output port 357 is connected to the fuel injection valve 3,
The control signal output from the CPU 351 is connected to the intake throttle actuator 14, the exhaust throttle actuator 22, the EGR valve 26, the shut-off valve 31, the ultrasonic generator 37, and the like via electric wiring, and transmits the control signal output from the CPU 351 to the fuel injection valve 3. , Intake throttle actuator 14, exhaust throttle actuator 2
2. Transmit to the EGR valve 26, the shut-off valve 31, or the ultrasonic generator 37.

The ROM 352 includes a fuel injection control routine for controlling the fuel injection valve 3, an intake throttle control routine for controlling the intake throttle valve 13, an exhaust throttle control routine for controlling the exhaust throttle valve 21, and EGR. Application programs such as an EGR control routine for controlling the valve 26 and a PM combustion control routine for burning and removing PM trapped in the filter 20 are stored.

The ROM 352 stores various control maps in addition to the application programs described above. The control map includes, for example, a fuel injection amount control map indicating a relationship between an operating state of the engine 1 and a basic fuel injection amount (basic fuel injection time), and a fuel indicating a relationship between an operating state of the engine 1 and a basic fuel injection timing. Injection timing control map,
An intake throttle valve opening control map showing the relationship between the operating state of the engine 1 and the target opening of the intake throttle valve 13, and the exhaust throttle valve opening showing the relationship between the operating state of the engine 1 and the target opening of the exhaust throttle valve 21. Degree control map, operating state of engine 1 and EGR
An EGR valve opening control map showing a relationship with a target opening of the valve 26, a reducing agent addition amount control map showing a relationship between an operating state of the engine 1 and a target adding amount of a reducing agent (or a target air-fuel ratio of exhaust), It is a reducing agent injection valve control map or the like showing the relationship between the target addition amount of the reducing agent and the opening time of the reducing agent injection valve 28.

The RAM 353 stores an output signal from each sensor, a calculation result of the CPU 351 and the like. The calculation result is, for example, an engine speed calculated based on a time interval at which the crank position sensor 33 outputs a pulse signal. These data are rewritten to the latest data each time the crank position sensor 33 outputs a pulse signal.

The backup RAM 354 is a nonvolatile memory capable of storing data even after the operation of the engine 1 is stopped.

The CPU 351 operates in accordance with an application program stored in the ROM 352 to control fuel injection valve control, intake throttle control, exhaust throttle control, E
Execute GR control, PM combustion control, and the like.

By the way, in the conventional exhaust gas purifying apparatus, the PM accumulated on the filter is burned and removed by the high-temperature exhaust gas discharged when the engine is operated in a high-speed high-load region. However, since it takes time to burn PM, if the operating region of the engine deviates from the high-speed high-load region before the PM is completely burned and removed, the PM remains unburned. It is difficult to maintain the operating state of the engine suitable for such PM combustion for a long period of time. Therefore, the unburned PM gradually accumulates on the filter, which causes the filter to be clogged.

One of the methods for effectively removing the PM remaining after burning is to add fuel to the exhaust gas.

Next, PM combustion control by adding fuel to exhaust gas will be described.

In the PM combustion control, the CPU 351 executes fuel addition control for adding fuel to the exhaust gas flowing into the filter 20.

In the fuel addition control, the CPU 351 determines whether or not the fuel addition control execution condition is satisfied at predetermined intervals. Examples of the fuel addition control execution conditions include, for example, whether the filter 20 is in an active state, and whether the output signal value (exhaust temperature) of the exhaust temperature sensor 24 is equal to or lower than a predetermined upper limit. can do.

When it is determined that the above-described fuel addition control execution condition is satisfied, the CPU 351 controls the reducing agent injection valve 28 to inject fuel as a reducing agent from the reducing agent injection valve 28. Thereby, the air-fuel ratio of the exhaust gas flowing into the filter 20 is temporarily set to a predetermined target air-fuel ratio.

More specifically, the CPU 351
Engine speed, accelerator opening sensor 3 stored in
6 output signal (accelerator opening), air flow meter 11
The output signal value (intake air amount), fuel injection amount, and the like are read out. Further, the CPU 351 accesses the reducing agent addition amount control map of the ROM 352 using the engine speed, the accelerator opening, the intake air amount, and the fuel injection amount as parameters, and sets the exhaust air-fuel ratio to a preset target air-fuel ratio. Then, the addition amount (target addition amount) of the reducing agent necessary for the calculation is calculated.

Subsequently, the CPU 351 accesses the flow rate control valve control map of the ROM 352 using the target addition amount as a parameter, and injects the reducing agent injection necessary for injecting the target addition amount of the reducing agent from the reducing agent injection valve 28. The valve opening time of the valve 28 (target valve opening time) is calculated.

When the target valve opening time of the reducing agent injection valve 28 is calculated, the CPU 351 opens the reducing agent injection valve 28.

The CPU 351 closes the reducing agent injection valve 28 when the target valve opening time has elapsed since the opening of the reducing agent injection valve 28.

When the reducing agent injection valve 28 is opened for the normal target valve opening time, the fuel of the normal target addition amount is injected from the reducing agent injection valve 28 into the exhaust branch pipe 18. Then, the reducing agent injected from the reducing agent injection valve 28 mixes with the exhaust gas flowing from the upstream of the exhaust branch pipe 18 to form an air-fuel mixture having a target air-fuel ratio and flows into the filter 20.

As a result, the oxygen concentration of the exhaust gas flowing into the filter 20 changes in a relatively short cycle. Then, the active oxygen is released by the fuel flowing into the filter 20, whereby the PM is transformed into a substance easily oxidized, and the oxidizable amount per unit time is improved. In addition, the addition of fuel removes oxygen poisoning of the catalyst and increases the activity of the catalyst, so that active oxygen is easily released. Then, the PM is oxidized and combusted and removed by the active oxygen.

In the engine 1 having the conventional filter,
In this way, it has been possible to remove PM by oxidizing and burning it, but there is a problem that fuel consumption is deteriorated because fuel is consumed as described above.

Therefore, in the present embodiment, the PM is atomized by ultrasonic waves to increase the amount of P during operation in a high rotation and high load region.
M can be burned. By doing so, the number of times of fuel addition can be reduced, and fuel efficiency can be improved.

Next, the PM atomization method according to the present embodiment will be described.

The time until PM burns and disappears is P
The smaller the size of M, that is, the smaller the particle size, and the larger the surface area of PM, the shorter it becomes.

Therefore, if the particle size of PM trapped in the filter is reduced in advance, the burning time of PM can be shortened, so that the operation in the operating region suitable for burning PM can be performed for only a short period of time. Even if it is not performed, it becomes possible to burn and remove PM.

In the present embodiment, an ultrasonic generator 37 is provided in the exhaust pipe 19 to generate ultrasonic waves during exhaust to make PM fine. The ultrasonic generator 37 includes a piezoelectric type,
Magnetostrictive type, electrostrictive type and the like can be used. When the ultrasonic wave generated from the ultrasonic wave generator 37 reaches the PM which is transmitted through the exhaust and flows with the exhaust, the PM is vibrated to be crushed and atomized. The atomized PM is collected by the filter, and can be burned in a short period of time in an operation region where the temperature of the exhaust gas is high.

The CPU 351 sends a signal to the ultrasonic generator 37 simultaneously with the start of the engine 1 to generate ultrasonic waves during exhaust. In the present embodiment, the ultrasonic waves may be constantly generated, but the ultrasonic waves may be generated in an operation region in which the amount of generated PM is large based on the operation state of the engine.

By the way, in the past, fuel was sometimes added to exhaust gas to burn PM trapped in the filter. The more PM to be removed, the more fuel to be added, the more fuel efficiency will be reduced.

In this regard, in the exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment, PM can be atomized.
Even if PM cannot be burned and removed when the engine is under high rotation and high load, fuel consumption can be improved because only a small amount of fuel needs to be added to exhaust gas.

Next, the EGR cooler 2 according to the present embodiment
The method for preventing clogging of No. 7 will be described.

Here, in the conventional EGR device, PM in the exhaust gas adheres to the wall surface of the EGR cooler, causing clogging of the EGR cooler and reduction of the heat exchange rate. In the EGR cooler, cooling water flows inside to exchange heat between the cooling water and the high-temperature EGR gas, and the temperature of the wall surface of the EGR cooler is lowered by the cooling water. When the EGR gas comes into contact with the wall surface of the cooled EGR cooler, EG
Water vapor in the R gas condenses to form water droplets and adheres to the EGR cooler wall surface. The PM contained in the exhaust gas easily adheres to the EGR cooler wall surface due to the water droplets thus attached. E
Unlike the filter, the GR cooler does not raise the temperature to a temperature at which PM can be burned, so it is difficult to remove the PM attached to the EGR cooler wall surface.

In this respect, in the present embodiment, an ultrasonic generator 27e for generating ultrasonic waves in the cooling water circulating in the EGR cooler is provided, and the PM adhering to the EGR cooler wall surface via the cooling water is vibrated. The PM can be separated from the wall surface. The PM separated from the EGR cooler wall surface is sucked into the combustion chamber of the engine together with the EGR gas, and is burned together with the fuel.

FIG. 3 is a diagram showing the internal structure of EGR cooler 27 according to the present embodiment. EGR cooler 27
A cooling water inlet 27a through which cooling water flows, a cooling water outlet 27b through which cooling water flows, a plurality of EGR flow pipes 27c through which EGR gas flows, a cooling water and an EGR gas. Two partition walls 2 separating
7d, an ultrasonic generator 27e for generating ultrasonic waves in the cooling water in response to a signal from the ECU 35. Here, two partition walls 27d are provided with a cooling water inlet 27a.
And it is fitted in the EGR cooler 27 main body so as to surround the cooling water outlet 27b. E is provided between the two partition walls 27d.
A plurality of GR flow pipes 27c are provided, and the EGR flow pipe 27
Both ends of c are fixed through the partition wall 27d. The ultrasonic generator 27e is provided in a passage through which the cooling water flows between the two partition walls 27d.

In the EGR cooler 27 configured as described above, the EGR gas flowing through the EGR passage 25 flows inside the EGR flow pipe 27c. On the other hand, the cooling water inlet 27
The cooling water introduced from a flows through the outside of the EGR flow pipe 27c and is discharged from the cooling water outlet 27b. The heat of the high-temperature EGR gas is transmitted to the cooling water via the EGR flow pipe 27c, and the temperature of the EGR gas decreases.

The ultrasonic generator 27e operates according to a signal from the ECU 35 to generate an ultrasonic wave. The ultrasonic waves reach the EGR flow pipe 27c via the cooling water, and vibrate the EGR flow pipe 27c. This vibration causes the EGR flow pipe 2
PM adhering to the wall surface of 7c is peeled off from the wall surface.

In this way, it is possible to prevent the heat exchange rate of the EGR cooler 27 from decreasing and clogging.

In this embodiment, when an ultrasonic generator is provided in an oil pan (not shown), ultrasonic waves are generated in engine lubricating oil stored in the oil pan,
PM in the lubricating oil can be crushed.

The CPU 351 sends a signal to the ultrasonic generator during operation of the engine 1 to generate ultrasonic waves in the lubricating oil. In the present embodiment, the ultrasonic waves may be generated at all times, but may be generated after a predetermined period of time has elapsed or after a predetermined travel distance.

Here, in a diesel engine, PM generated in the combustion chamber passes through a gap between a piston ring (not shown) and a cylinder liner (not shown), and sinks without being dissolved in lubricating oil. The lubricating oil circulates through the engine and reduces friction and wear of the sliding portion. However, if PM is mixed in the lubricating oil, the PM may wear the sliding portion.
However, it is difficult to prevent PM from being mixed into the lubricating oil at all.

In this regard, in the engine 1 according to the present embodiment, the oil pan is provided with an ultrasonic generator so that the P
M can be crushed and wear of the sliding surface can be suppressed. This makes it possible to extend the lubricating oil replacement cycle.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment, the ultrasonic generator 37 is provided in the exhaust pipe 19 to crush PM and prevent clogging of the filter. On the other hand, the amount of added fuel can be reduced, and fuel efficiency can be improved.

Further, the ultrasonic generator 27e is provided in the EGR cooler 27 to prevent PM from adhering, thereby preventing a decrease in heat exchange rate and clogging of the EGR cooler, thereby preventing deterioration of exhaust emission. Can be.

Further, by providing an ultrasonic generator in the oil pan, PM in the lubricating oil can be crushed, and wear on the sliding surface can be suppressed. Further, the replacement cycle of the lubricating oil can be extended.

[0116]

According to the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the particulate matter contained in the exhaust gas is atomized to promote the combustion of the particulate matter, thereby preventing the exhaust gas purifying apparatus from being clogged. it can.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing both an engine to which an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention is applied and an intake / exhaust system thereof.

FIG. 2 is a block diagram showing an internal configuration of an ECU.

FIG. 3 is a diagram showing an internal structure of an EGR cooler provided with the ultrasonic generator according to the embodiment of the present invention.

FIG. 4A is a diagram showing a horizontal cross section of a particulate filter. (B) is a figure which shows the longitudinal direction cross section of a particulate filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 1a ... Crank pulley 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 4a ... Common rail pressure sensor 5 ... Fuel supply pipe 6 ... ..Fuel pump 6a ... Pump pulley 8 ... Intake branch pipe 9 ... Intake pipe 18 ... Exhaust branch pipe 19 ... Exhaust pipe 20 ... Particulate filter 21 ... Exhaust throttle Valve 23 Air-fuel ratio sensor 24 Exhaust temperature sensor 25 EGR passage 26 EGR valve 27 EGR cooler 27a Cooling water inlet 27b Cooling water outlet 27c Flow pipe 27d ··· partition wall 27e ··· ultrasonic generator 28 ··· reducing agent injection valve 29 ··· reducing agent supply path 31 ··· shutoff valve 33 ··· crank position sensor 34 ··· water temperature sensor 35 ··· ECU 351, CPU 352, ROM 353, RAM 354, backup RAM 36, accelerator opening sensor 37, ultrasonic generator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (reference) // B01D 46/42 B01D 46/42 B Z 51/00 51/00 A F term (reference) 3G062 AA01 AA03 AA05 EA10 ED00 ED08 3G090 AA02 BA01 EA01 EA06 4D058 JA32 JB02 KC01 MA41 MA60 SA08 TA06 UA25

Claims (3)

[Claims] 1. A filter provided in an exhaust passage of an internal combustion engine for trapping particulate matter contained in exhaust gas, and an ultrasonic wave generating means for applying vibration to exhaust gas inside the exhaust passage upstream of the filter. An exhaust gas purifying apparatus for an internal combustion engine, comprising: 2. An EGR device for recirculating a part of exhaust gas to an intake system of an internal combustion engine, and an EGR device for cooling EGR gas recirculated through the EGR device.
The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, further comprising: an ultrasonic wave generating unit that applies vibration to the EGR cooler. 3. The EGR cooler cools the EGR gas by heat exchange between the cooling water and the EGR gas, and the ultrasonic wave generating means applies vibration to the cooling water flowing inside the EGR cooler. An exhaust purification device for an internal combustion engine according to claim 2.