JP2003193824A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of surely avoiding falling into an excessively scavenging state of a catalyst carrying type particulate filter. <P>SOLUTION: This device is provided with the catalyst carrying type particulate filter 13 equipped in mid-way of an exhaust pipe 11 in which exhaust gas 9 circulates, a flow through type oxidation catalyst 14 provided just before the position of the particulate filter 13, a fuel addition means (a control device 20 and a fuel injection device 21) for adding fuel in exhaust gas 9 on an upstream side of the oxidation catalyst 14, and temperature rising means (an intake throttle valve 24 and an EGR valve 17: intake throttle means, an exhaust throttle valve 25: an exhaust throttle means, the control device 20 and the fuel injection device 21: combustion injection control means) for raising an exhaust temperature up to a temperature enabling an oxidation reaction on the oxidation catalyst 14 of the fuel added by the fuel addition means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device.

[0002]

2. Description of the Related Art Particulate Matter (Particulate Matter) emitted from a diesel engine is
Soot composed of carbonaceous matter and SO composed of high boiling hydrocarbon components
It has a composition containing F component (Soluble Organic Fraction) as a main component and further contains a trace amount of sulfate (mist-like sulfuric acid component). As a measure for reducing such particulates, exhaust gas is used. It has been conventionally practiced to equip a particulate filter in the middle of an exhaust pipe through which gas flows.

This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow passages partitioned in a grid pattern are alternately plugged, and the inlets are plugged. The outlets of the non-flow passages are configured to be plugged so that only the exhaust gas that has permeated the porous thin wall defining each flow passage is discharged to the downstream side.

Since the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate the particulate filter, but in normal diesel engine operating conditions, there is little opportunity to obtain a high exhaust temperature that allows particulates to self-combust.Therefore, for example, alumina loaded with platinum is recommended. Practical application of a catalyst-supporting particulate filter that integrally supports an oxidation catalyst formed by adding an appropriate amount of a rare earth element such as cerium has been advanced.

That is, if such a catalyst-supporting particulate filter is adopted, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates are burned and removed even at a lower exhaust temperature than before. It becomes possible to do it.

However, even when such a catalyst-supporting particulate filter is used, the oxidation catalyst carried by the particulate filter has an active temperature range, which is lower than the lower limit of the activity. If the operating condition at the exhaust temperature continues (generally, the region where the exhaust temperature is low spreads to the operating region of light load), the oxidation catalyst will not be activated and the particulates will not be burned and removed well. Therefore, it is considered that fuel is added to the exhaust gas on the upstream side of the particulate filter to perform forced regeneration of the particulate filter when the amount of accumulated particulates increases.

That is, if the fuel is added upstream of the particulate filter, the added fuel is thermally decomposed in the exhaust gas to generate a high concentration of hydrocarbon, and the hydrocarbon is oxidized by the particulate filter. An oxidation reaction is carried out on the catalyst, the catalyst bed temperature is raised by the reaction heat, and the particulates are burned out, so that the particulate filter is regenerated.

[0008]

However, even if a fuel addition means for carrying out this kind of forced regeneration is provided, a high concentration of hydrocarbon cannot be oxidized on the oxidation catalyst of the particulate filter. When operating in an operating region where the exhaust gas temperature is extremely low (for example, when traveling only on congested roads such as route buses in Tokyo), it is expected that the catalyst bed temperature rise due to such fuel addition. However, there is a risk that the particulate filter may fall into an excessively trapped state and the exhaust pressure may rise, adversely affecting the engine performance, or that a large amount of particulates may burn rapidly and cause the particulate filter to melt. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas purification device which can reliably prevent a catalyst-supporting particulate filter from falling into an excessively trapped state.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a catalyst-supporting particulate filter provided in the middle of an exhaust pipe through which exhaust gas flows, and a flow-through type particulate filter installed immediately in front of the particulate filter. Oxidation catalyst, fuel addition means for adding fuel to the exhaust gas on the upstream side of the oxidation catalyst, and exhaust temperature up to a temperature that enables the oxidation reaction of the fuel added by the fuel addition means on the oxidation catalyst The present invention relates to an exhaust gas purification device, comprising: a temperature raising means for raising the temperature.

Thus, in this way, when the amount of accumulated particulate matter increases and the forced regeneration of the particulate filter is required, a high concentration of hydrocarbons is present on the oxidation catalyst of the particulate filter. Even if the operation is performed in an operating region where the exhaust temperature is extremely low so that the oxidation reaction cannot be performed, if the fuel is added by the fuel adding means after appropriately raising the exhaust temperature by the temperature raising means, The high-concentration hydrocarbon produced by combustion addition undergoes an oxidation reaction in the oxidation catalyst to generate reaction heat, and the heat of reaction causes the exhaust gas passing through the oxidation catalyst to rise in temperature significantly, resulting in a rise in temperature through the oxidation catalyst. The exhaust gas is introduced into the particulate filter to uniformly raise the temperature of the entire area of the particulate filter, whereby the particulates are burned and removed well. So that regeneration of the particulate filter can be achieved.

Further, in implementing the exhaust gas purifying apparatus of the present invention more specifically, a temperature sensor for detecting the exhaust gas temperature is arranged between the oxidation catalyst and the catalyst-supporting particulate filter, and the temperature sensor Only when the detected value exceeds the predetermined threshold, the fuel is appropriately added by the fuel addition means, and when the detected value of the temperature sensor is equal to or lower than the predetermined threshold, the temperature rise of the exhaust gas is interrupted. Therefore, it is preferable that the fuel addition means appropriately performs the fuel addition.

Further, in the present invention, the temperature raising means for raising the exhaust gas temperature may be an intake throttle means for appropriately narrowing the intake air flow rate, or may be an exhaust throttle means for appropriately narrowing the exhaust gas flow rate. The fuel injection control means may perform the injection with a delay from the normal injection timing within the combustible range of the fuel injection device.

That is, when the temperature raising means for raising the exhaust gas temperature is an intake throttle means for appropriately narrowing the intake air flow rate, if the intake air flow rate is narrowed down by the intake throttle means in an operating state where the exhaust gas temperature is low, the internal combustion engine The pumping loss increases due to the decrease in the operating air amount of the engine, which increases the fuel injection amount and raises the exhaust temperature so that the required output is generated, while the amount of exhaust gas generated by combustion in the internal combustion engine increases. Even if the heat capacity decreases and the heat capacity decreases, the exhaust gas temperature can be further increased.

Further, when the temperature raising means for raising the exhaust gas temperature is an exhaust gas throttle means for appropriately narrowing the exhaust gas flow rate, if the exhaust gas flow rate is narrowed down by the exhaust gas throttle means in an operating state where the exhaust gas temperature is low, the internal combustion engine As the exhaust resistance from each cylinder increases, the pumping loss increases, which increases the fuel injection amount and raises the exhaust temperature so that the required output is generated. The intake of low intake air becomes difficult, and the residual amount of exhaust gas with a relatively high temperature increases, and the air in the cylinder containing a large amount of exhaust gas with a relatively high temperature is compressed in the compression stroke to reach the explosion stroke. However, the exhaust temperature can be further raised.

Further, when the temperature raising means for raising the exhaust temperature is a fuel injection control means for performing the injection with a delay from the normal injection timing within the combustible range for the fuel injection device, the fuel of the delayed injection is injected. Is burned at a timing at which it is difficult to be converted to an output, the thermal efficiency of the internal combustion engine is reduced, the amount of heat not used for power of the fuel increases, and the exhaust temperature rises.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an example of a mode for carrying out the present invention. In FIG. 1, 1 is a turbocharger 2.
The intake air 4 guided from the air cleaner 3 is sent to the compressor 2a of the turbocharger 2 through the intake pipe 5, and the intake air 4 pressurized by the compressor 2a is intercooler 6 shown in FIG. Is sent to and cooled by the intercooler 6, and the intake air 4 is further guided to the intake manifold 7 and distributed to each cylinder 8 of the diesel engine 1 (the case of inline 6 cylinders is illustrated in FIG. 1). It has become so.

Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is exhausted by an exhaust manifold 10.
To the turbine 2b of the turbocharger 2 via
The exhaust gas 9 that has driven the turbine 2b is exhausted to the outside of the vehicle through an exhaust pipe 11 (exhaust flow passage).

A filter case 12 is interposed in the middle of the exhaust pipe 11, and the filter case 1
A catalyst-supporting particulate filter 13 that integrally supports an oxidation catalyst is housed in the latter part of the inside of the catalyst 2, and as shown in an enlarged view of FIG. Each of the channels 1 has a porous honeycomb structure and is divided into a lattice shape.
The inlets of 3a are alternately plugged, and the passages 13a whose inlets are not plugged are designed so that their outlets are plugged, and the porous thin wall 1 for partitioning each passage 13a is formed.
Only the exhaust gas 9 that has passed through 3b is discharged to the downstream side.

A flow-through type oxidation catalyst 14 having a honeycomb structure as shown in an enlarged view in FIG. 3 is housed in the filter case 12 just before the particulate filter 13.

Further, in the example shown in FIG. 1, one end portion of the exhaust manifold 10 in the direction in which the cylinders 8 are arranged,
An EGR pipe 15 is connected to one end of the intake pipe 5 connected to the intake manifold 7, and a part of the exhaust gas 9 extracted from the exhaust manifold 10 is water-cooled EGR.
It recirculates to the intake pipe 5 via the cooler 16 and the EGR valve 17, and the exhaust gas 9 recirculated from the exhaust side to the intake side suppresses the combustion of fuel in each cylinder 8 and burns it. By lowering the temperature, the generation of NOx can be reduced.

A temperature sensor 18 for measuring the temperature of the exhaust gas 9 is provided between the oxidation catalyst 14 and the particulate filter 13 in the filter case 12.
And a pressure sensor 19 for measuring the pressure of the exhaust gas 9.
And the temperature sensor 18 and the pressure sensor 1
The detection signals 18a and 19a of 9 are input to a control device 20 that constitutes an engine control computer (ECU: Electronic Control Unit). On the other hand, in this control device 20, each cylinder 8 of the diesel engine 1 is Fuel injection signal 21a for instructing fuel injection timing and injection amount toward a fuel injection device 21 for injecting fuel into
Is output.

Here, the fuel injection device 21 is composed of a plurality of injectors (not shown) provided for each cylinder 8, and the solenoid valves of these injectors are controlled to be opened appropriately by the fuel injection signal 21a. Thus, the injection timing (injection start timing and injection end timing) and the injection amount (valve opening time) of the fuel are appropriately controlled.

Furthermore, the driver's seat accelerator (not shown)
An accelerator sensor 22 (load sensor) that detects the accelerator opening as a load of the diesel engine 1 is provided, and a rotation sensor 23 that detects the number of revolutions is provided at an appropriate position of the diesel engine 1, The accelerator opening signal 22a and the rotation speed signal 23a from the accelerator sensor 22 and the rotation sensor 23 are also input to the control device 20.

Further, in the control device 20, an intake throttle valve 24 provided in the middle of the intake pipe 5, an EGR valve 17 of the EGR pipe 15, and an exhaust throttle valve 25 provided in the middle of the exhaust pipe 11. On the other hand, the opening command signals 24a, 17a, 25a for instructing the respective opening are output.

Here, the intake throttle valve 24 may functionally function as an intake shutter used together with an idling stop device, a noise suppressor used together with an auxiliary brake, and the exhaust throttle valve 25 is It suffices that the exhaust brake also serves as a function, and in this embodiment, the intake throttle valve 24, the EGR valve 17, and the exhaust throttle valve 25 are instructed to perform another operation independent of the original operation. As a result, it is utilized as an intake throttle means and an exhaust throttle means which form a temperature raising means for raising the exhaust temperature as described later.

In the controller 20, the normal mode fuel injection signal 21a is determined based on the accelerator opening signal 22a and the rotation speed signal 23a, while the particulate filter 13 is forcibly regenerated. When the need arises, the normal mode is switched to either the temperature raising mode or the forced regeneration mode based on the detection signal 18a of the temperature sensor 18, and when the temperature raising mode is switched, the compression top dead center (crank angle 0 Fuel injection signal 21a for performing after injection (the main injection itself may be a delayed injection, or a delayed injection that continues from the main injection) at a combustible timing immediately after the main injection of fuel that is performed in the vicinity of Is determined, and when the mode is switched to the forced regeneration mode, the fuel amount measured near the compression top dead center (crank angle 0 °) is measured. Following down injection fuel injection signal 21a that performs post injection at a timing slower non-ignition compression top dead center is adapted to be determined.

In other words, if after-injection is performed at a combustible timing immediately after the main injection of fuel, the thermal efficiency of the diesel engine 1 is reduced due to combustion of the after-injected fuel at a timing at which it is difficult to convert it into output, and heat generation of the fuel. The amount of heat that is not used for powering increases the exhaust temperature.

On the other hand, if post-injection is performed at a non-ignition timing later than the compression top dead center following the main injection, unburned fuel is added to the exhaust gas 9 by this post-injection. The unburned fuel becomes a high-concentration hydrocarbon due to thermal decomposition and undergoes an oxidation reaction in the oxidation catalyst 14, and the temperature of the exhaust gas 9 passing through the oxidation catalyst 14 is significantly raised by the reaction heat, and this greatly rises. The heated exhaust gas 9 is introduced into the particulate filter 13 and the entire area of the particulate filter 13 is uniformly heated.

Here, supplementary description of the above-mentioned switching of the control device 20 from the normal mode to the temperature raising mode or the forced regeneration mode will be made. In the present embodiment, the particulates are detected by the detection signal 19a from the pressure sensor 19. While monitoring the measured pressure value on the inlet side of the filter 13, the predicted value of the exhaust pressure in the current operating state is estimated based on the accelerator opening signal 22a and the rotation speed signal 23a, and the predicted value and the measured pressure value are The control device 20 determines whether or not the deviation is within the normal range, and when there is a large amount of residual particulate matter (non-burned residue) collected by the particulate filter 13, Since the actually measured pressure value on the inlet side of the particulate filter 13 rises beyond the normal range, a state in which forced regeneration of the particulate filter 13 is necessary Determines that have fallen, and is from the normal mode to switch to the heating mode or the forced regeneration mode is executed.

Regarding whether to select the temperature rising mode or the forced regeneration mode when switching the mode,
A threshold temperature is set as a threshold temperature at which a high concentration of hydrocarbons cannot oxidize on the oxidation catalyst 14, and the forced regeneration mode is selected only under conditions where the detection value of the temperature sensor 18 exceeds this threshold value. When the detected value of the temperature sensor 18 is less than or equal to the threshold value, the temperature raising mode is sandwiched as a pre-process for shifting to the forced regeneration mode.

That is, when the temperature raising mode is executed by the control device 20, the intake throttle valve 24 of the intake pipe 5 and the EGR valve 17 of the EGR pipe 15 cause the intake throttle means (temperature raising means) to raise the exhaust gas temperature. ), More specifically, these intake throttle valve 24 and EGR
When the valve 17 is in the temperature raising mode, the opening degree instruction signals 24a, 17
It is designed to be narrowed down by a.

That is, in this way, the intake throttle valves 24 and E
When the GR valve 17 is narrowed down in the temperature raising mode, the pumping loss is increased due to a decrease in the working air amount including the intake air 4 and the recirculation gas (exhaust gas 9), and the fuel injection amount is thereby increased so that a required output is generated. While the exhaust gas temperature is increased and the exhaust gas temperature is increased, the exhaust gas temperature is further increased by reducing the amount of exhaust gas 9 generated by combustion in the diesel engine 1 and decreasing the heat capacity.

Further, when the temperature raising mode is executed by the control device 20, the exhaust throttle valve 25 of the exhaust pipe 11 is used as an exhaust throttle means (temperature raising means) for raising the exhaust temperature. And, more specifically, this exhaust throttle valve 25
Is narrowed down by the opening degree instruction signal 25a in the temperature rising mode.

That is, when the exhaust throttle valve 25 is narrowed down in the temperature increasing mode in this manner, the exhaust resistance from each cylinder of the diesel engine 1 increases and the pumping loss increases, so that the required output is generated. While the injection amount is increased and the exhaust gas temperature is increased, it becomes difficult for intake air having a relatively low temperature to flow into the cylinder of the diesel engine 1 and the residual amount of the exhaust gas 9 having a relatively high temperature is increased. Even when the air in the cylinder containing a large amount of exhaust gas 9 having a high target temperature is compressed in the compression stroke and reaches the explosion stroke, the exhaust temperature is further increased.

When the turbocharger 2 is a variable nozzle turbo having a variable capacity, the controller 20 issues an opening command signal 26a for instructing the actuator 26 of the turbocharger 2 to open the nozzle vane of the turbine 2b. By outputting and performing the capacity control, the turbocharger 2 can be utilized as an intake throttle means and an exhaust throttle means that form a temperature raising means for raising the exhaust temperature.

That is, the variable nozzle turbo has a structure in which the nozzle vanes on the turbine 2b side can be tilted by the actuator 26 to adjust the opening degree of each nozzle vane, as is well known in the art. When the rotational speed of the exhaust gas 9 in the turbine 2b is reduced by expanding the opening of the nozzle vane, the rotation speed of the turbine 2b is reduced and the intake flow rate on the compressor 2a side is appropriately narrowed down. By increasing the exhaust resistance by reducing the opening of the nozzle vane of
The exhaust gas flow rate is appropriately reduced on the turbine 2b side.

However, if the opening of the nozzle vane on the turbine 2b side is reduced, the rotational speed of the exhaust gas 9 in the turbine 2b increases, the rotational speed of the turbine 2b increases, and the boost pressure on the compressor 2a side increases. Therefore, it is necessary to use the control together with the control for reducing the opening degree of the intake throttle valve 24. It is needless to say that proper tuning is necessary regardless of whether it is used as the intake throttle means or the exhaust throttle means.

Thus, the detection signal 1 from the pressure sensor 19
9a, the controller 20 determines that the particulate filter 13 is in a state in which forced regeneration is required, and the forced regeneration is performed under the condition that the detected value of the temperature sensor 18 exceeds a predetermined threshold value. A mode is selected, the fuel injection pattern is switched from the normal mode to the forced regeneration mode by the control device 20, and an injection pattern is adopted in which post injection is performed at a non-ignition timing later than the compression top dead center following the main injection. As a result, the fuel added unburned in the exhaust gas 9 by the post-injection becomes a high-concentration hydrocarbon due to thermal decomposition and undergoes an oxidation reaction in the oxidation catalyst 14 to generate reaction heat, which is oxidized by the reaction heat. The temperature of the exhaust gas 9 passing through the catalyst 14 is greatly increased, and the oxidation catalyst 1
By introducing the exhaust gas 9 whose temperature has risen via 4 into the particulate filter 13, the entire area of the particulate filter 13 is uniformly heated, whereby the particulates are burned and removed well, and the particulate filter 13 is removed. Will be reproduced.

Here, as a supplementary explanation, if the oxidation catalyst 14 is not arranged immediately in front of the particulate filter 13, the high-concentration hydrocarbon produced by the fuel addition will be generated. Oxidation reaction occurs on the catalyst surface of the particulate filter 13, but the substantial oxidation reaction in such a form tends to be biased to the rear part of the particulate filter 13, and only the rear part of the particulate filter 13 is present. As the temperature rises, unburned particulates tend to remain in the front part.

On the other hand, the particulate filter 1
By disposing the oxidation catalyst 14 in the position immediately before 3, even if the oxidation reaction in the oxidation catalyst 14 is biased toward the rear part, if the temperature of the exhaust gas 9 passing therethrough can be increased, the exhaust gas 9 By introducing the above, it becomes possible to raise the temperature of the particulate filter 13 uniformly over the entire region from the front portion to the rear portion.

On the other hand, when the engine is operating in an operating region where the exhaust gas temperature is so low that a high concentration of hydrocarbons cannot oxidize in the oxidation catalyst 14, the detection signal 18a of the temperature sensor 18 is used. Then, the temperature rising mode is executed by the control device 20 before shifting to the forced regeneration mode, so that the fuel injection pattern is switched from the normal mode to the temperature rising mode, and at a timing at which combustion is possible immediately after the main injection of fuel. After-injection is performed, and the intake throttle valve 2
4 and the EGR valve 17 are narrowed down, and further, the exhaust throttle valve 25 is narrowed down (when the turbocharger is a variable nozzle turbo with a variable capacity, the capacity control of the turbocharger can also be used), and as a result, the oxidation catalyst 14 is reached. The temperature of the exhaust gas 9 is increased.

At the stage when the detected value of the temperature sensor 18 exceeds a predetermined threshold value and shifts to the forced regeneration mode, since the hydrocarbon is surely in the oxidation reaction state in the oxidation catalyst 14, the reaction heat The exhaust gas 9 whose temperature has been significantly raised by 1 causes the entire temperature of the particulate filter 13 to uniformly rise in temperature, whereby the particulates are satisfactorily burned and removed, and the particulate filter 13 is regenerated.

Therefore, according to the above embodiment, the fuel is added to the exhaust gas 9 to generate a high concentration of hydrocarbons even in an operating region where the exhaust temperature is low, in which it is difficult to remove particulates by burning, The exhaust gas 9 passing through the oxidation catalyst 14 is significantly heated by the reaction heat generated by the oxidation reaction of this hydrocarbon with the oxidation catalyst 14, and the exhaust gas 9 is introduced into the particulate filter 13 so that the particulate Even in the operating region where the exhaust gas temperature is extremely low such that the entire area of the curate filter 13 can be uniformly heated and the high-concentration hydrocarbon cannot oxidize in the oxidation catalyst 14, Since the temperature of the exhaust gas can be raised by the temperature raising means to make the oxidation reaction of the hydrocarbon in the oxidation catalyst 14 possible and the fuel can be added, The particulates trapped in the particulate filter 13 can be burned and removed satisfactorily and irrespective of the operating state of the engine 1, thereby reliably avoiding the possibility that the particulate filter 13 falls into an overtrapped state. As a result, it is possible to prevent adverse effects on engine performance due to an increase in exhaust pressure, melting damage of the particulate filter, and the like.

In the above description, the fuel injection device 2 is used as the fuel addition means for adding the fuel to the exhaust gas 9.
Although the means for switching the injection pattern of No. 1 is shown as an example, this kind of fuel adding means is, for example, as shown in FIG.
As indicated by a chain double-dashed line, a fuel injection pipe 27 is penetratingly attached to an appropriate position of the exhaust pipe 11 (the exhaust manifold 10 may be used), and a fuel addition valve 28 of the fuel injection pipe 27 is opened and closed as appropriate. It is also possible to appropriately add to the exhaust gas 9.

Further, the exhaust gas purifying apparatus of the present invention is not limited to the above-mentioned embodiment, and it is not always necessary to use all of the temperature raising means described in the drawing together, and each of them can be used independently. Needless to say, it is also possible to use some of them in combination, and in addition, various changes can be made without departing from the scope of the present invention.

[0048]

According to the exhaust gas purification apparatus of the present invention described above, various excellent effects as described below can be obtained.

(I) According to the first aspect of the present invention, the fuel is added to the exhaust gas by the fuel addition means even in an operating region where the exhaust temperature is low, in which it is difficult to remove particulates by burning. To generate a high concentration of hydrocarbons, and the reaction heat generated by the oxidation reaction of this hydrocarbon with an oxidation catalyst causes the exhaust gas passing through the oxidation catalyst to rise in temperature significantly, and this exhaust gas is passed through a particulate filter. By introducing it, it is possible to uniformly raise the temperature of the entire area of the particulate filter, and in addition, it is an operating region where the exhaust gas temperature is extremely low such that a high concentration hydrocarbon cannot undergo an oxidation reaction by an oxidation catalyst. Also, since it is possible to add fuel after raising the exhaust temperature by the temperature raising means to make it possible to oxidize hydrocarbons in the oxidation catalyst, the operation of the internal combustion engine Regardless of the state, it is possible to satisfactorily burn and remove the particulates trapped in the particulate filter without fail, whereby it is possible to reliably avoid the possibility that the particulate filter falls into an over-trapping state, It is possible to prevent adverse effects on engine performance due to an increase in exhaust pressure and melting damage of the particulate filter.

(II) According to the second aspect of the present invention, the fuel adding means and the temperature raising means are appropriately operated based on the detected value of the temperature sensor to efficiently regenerate the particulate filter. It can be carried out.

(III) According to the third aspect of the present invention, the amount of working air in the internal combustion engine is reduced to increase pumping loss and the amount of exhaust gas generated by combustion in the internal combustion engine is reduced. By lowering the heat capacity,
The temperature of the exhaust gas reaching the oxidation catalyst can be reliably increased.

(IV) According to the invention described in claim 4 of the present invention, the exhaust resistance from each cylinder of the internal combustion engine is increased to increase the pumping loss, and the exhaust gas of relatively high temperature in each cylinder is exhausted. By increasing the residual amount and compressing the air in the cylinder containing a large amount of the exhaust gas in the compression stroke to reach the explosion stroke, the temperature of the exhaust gas reaching the oxidation catalyst can be reliably increased.

(V) According to the invention described in claim 5 of the present invention, the fuel of the delayed injection is burned at a timing at which it is difficult to convert it into an output, thereby lowering the thermal efficiency of the internal combustion engine and reducing the heat generation amount of the fuel. Increase the amount of heat not used to power
As a result, the temperature of the exhaust gas reaching the oxidation catalyst can be reliably increased.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment for carrying out the present invention.

FIG. 2 is a cross-sectional view showing details of the particulate filter of FIG.

3 is a partially cutaway perspective view showing details of the oxidation catalyst of FIG. 1. FIG.

[Explanation of symbols]

1 Diesel engine (internal combustion engine) 2 Turbocharger (intake throttle means: exhaust throttle means:
Temperature raising means) 4 Intake 8 Cylinder 9 Exhaust gas 11 Exhaust pipe 13 Particulate filter 14 Oxidation catalyst 17 EGR valve (intake throttle means: temperature raising means) 20 Control device (fuel injection control means: temperature raising means: fuel addition means) 21 fuel injection device (fuel injection control means: temperature raising means: fuel addition means) 24 intake throttle valve (intake throttle means: temperature raising means) 25 exhaust throttle valve (exhaust throttle means: temperature raising means) 27 fuel injection pipe (fuel Addition means) 28 Fuel addition valve (fuel addition means)

Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) F01N 3/18 F01N 3/24 C 4D058 3/24 EN R 3/28 301P 3/28 301 3/36 A 3 / 36 B C F02D 41/04 360A F02D 41/04 360 385A 385 385M 43/00 301J 43/00 301 301K 301T 45/00 301A 45/00 301 310T 310 B01D 46/42 B // B01D 46/42 53/36 103C F-term (reference) 3G084 AA01 AA04 BA02 BA05 BA08 BA09 BA13 BA15 BA19 BA20 BA24 DA10 DA27 EA11 EB01 EB22 FA10 FA18 FA27 FA33 3G090 AA03 BA01 CA01 CA04 DA03 DA12 DA18 DA20 EA02 EA05 EA06 EA07 3G091 AA02 AA11 AA18 AA28 AB02 AB13 BA00 BA03 BA04 BA08 BA15 BA19 BA38 CA18 CB02 CB03 CB07 CB08 DA01 DA02 DB10 EA01 EA03 EA07 EA17 EA32 FA02 FA04 FA12 FB02 FC02 FC05 FC07 GA16 GA18 GA20 GA24 GB01X GB10X GB17X HA36 HA37 HA09 HA15 HA11 HA03 HA06 HA11 HA02 HA04 HA06 HA11 HA02 HA04 HA06 HA11 HA02 HA04 HA03 HA11 HA02 HA04 HA06 HA11 HA02 HA04 HA13 HA24 B11 MA01 MA11 MA18 NA06 NA07 NA08 NE01 NE06 NE11 NE12 PA17B PA17Z PD11B PD11Z PE01B PE01Z PF03B PF03Z 4D048 AA14 AB01 AC02 BB02 CC43 CC52 CC53 CD05 4D058 JA32 MA44 MA51 MA54 SA08 TA06

Claims (5)

[Claims] 1. A catalyst-supporting particulate filter provided in the middle of an exhaust pipe through which exhaust gas flows, a flow-through type oxidation catalyst provided immediately in front of the particulate filter, and the oxidation catalyst A fuel adding means for adding fuel to the exhaust gas on the upstream side; and a temperature raising means for raising the exhaust temperature to a temperature at which the fuel added by the fuel adding means can oxidize on the oxidation catalyst. An exhaust gas purification device characterized in that 2. A temperature sensor for detecting the exhaust gas temperature is arranged between the oxidation catalyst and the catalyst-supporting particulate filter, and fuel is added only under the condition that the detected value of the temperature sensor exceeds a predetermined threshold value. A fuel addition is appropriately performed by the means, and when the detected value of the temperature sensor is equal to or less than a predetermined threshold value, the fuel addition is appropriately performed by the fuel addition means with the exhaust gas temperature increase by the temperature increase means interposed. The exhaust emission control device according to claim 1, wherein 3. The exhaust gas purification device according to claim 1, wherein the temperature raising means for raising the exhaust gas temperature is an intake throttle means for appropriately narrowing the intake air flow rate. 4. The exhaust gas purifying apparatus according to claim 1, wherein the temperature raising means for raising the exhaust gas temperature is an exhaust throttle means for appropriately narrowing the exhaust gas flow rate. 5. The fuel injection control means for increasing the exhaust gas temperature is a fuel injection control means for injecting fuel into the fuel injection device with a delay from the normal injection timing within a combustible range. Or the exhaust emission control device according to 2.