JPH11182231A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a particulate trap regenerative even in the case of engine required fuel not lasting in a large quantity area. SOLUTION: An exhaust emission control device for an internal combustion engine is provided with a particulate trap 2 disposed in an engine exhaust system 1, and an inflow preventing means 3a preventing exhaust gas from flowing into at least a part of the particulate trap 2 at the time of operation. In the case of dividing an area of engine required fuel into a large quantity area, a medium quantity area and a small quantity area, in the case of an engine operating state where engine required fuel does not last in the large quantity area so as not to be able to continue combustion of particulates collected in the particulate trap 2 by exhaust gas flow, the inflow preventing means 3a is operated, and the operation of the inflow preventing means 3a is stopped after the lapse of a specified period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art Exhaust gas from an internal combustion engine, particularly a diesel engine, contains harmful particulates containing carbon as a main component, and such particulates are discharged before the exhaust gas is released to the atmosphere. It is desired to remove it. Therefore, it has been proposed to arrange a particulate trap as a filter for trapping particulates in an exhaust system of a diesel engine. Since such a particulate trap has a large exhaust resistance as the amount of trapped particulates increases, it is necessary to burn the collected particulates and regenerate the particulate trap itself.

[0003] The exhaust gas temperature increases as the fuel injection amount increases. As a result, if the required fuel for the engine is in a large range, such as in the high-load, high-speed operation region of the engine, the exhaust gas flow becomes high in temperature, and first, the particulates upstream of the particulate trap start burning. Then, since the high-temperature exhaust gas flow removes only a small amount of this particulate combustion heat, the combustion continues and propagates to the particulates downstream of the particulate trap, and regeneration of the particulate trap is realized. . When the engine required fuel is in the middle amount range, the exhaust gas flow does not become so high, but the exhaust gas temperature at this time can slightly burn the particulates upstream of the particulate trap. However, since the exhaust gas flow at this time removes a large amount of the particulate combustion heat, the combustion cannot be sustained, and the particulate trap cannot be regenerated.

[0004] Further, even if the fuel required for the engine becomes large only momentarily, the combustion of the particulates cannot be sustained. Thus, in order to realize the regeneration of the particulate trap, the engine needs to be regenerated. It is necessary for the fuel to last for a while in a large area. There is no guarantee that such an engine operation will be performed periodically, and there is a possibility that the particulate trap will be trapped in the particulate trap enough to greatly increase exhaust resistance before the next regeneration. Therefore, it is necessary to make the particulate trap reproducible even when the engine required fuel does not continue for a while in a large area.

Japanese Patent Application Laid-Open No. 56-18016 discloses that an oxidation catalyst is supported on a particulate trap and fuel is supplied to an upstream side of the particulate trap. Thereby, it is intended that the fuel supplied to the particulate trap is burned by the oxidation catalyst, and the burning heat is used to burn the particulate.

[0006]

In the above-mentioned prior art, the combustion heat of the fuel supplied to the particulate trap is greatly increased by the exhaust gas flow from the particulate trap unless the exhaust gas flow is at a high temperature. It is robbed downstream and cannot burn particulates as intended.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine that can regenerate a particulate trap even when engine required fuel does not continue in a large amount range.

[0008]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, comprising: a particulate trap disposed in an engine exhaust system; and at least a portion of the particulate trap during operation. Inflow prevention means for preventing the inflow of exhaust gas, and when the region of engine required fuel is divided into at least a large region, a medium amount region, and a small region, the engine required fuel does not continue in the large amount region. In the case of an engine operating state in which it is not possible to sustain the combustion of the particulates trapped in the particulate trap by the exhaust gas flow, the inflow prevention means is operated, and after a predetermined period of time, the inflow prevention means is operated. The operation of the means is stopped.

According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the present invention, wherein the combustion of the particulates cannot be maintained. Is characterized by an engine operating state in which the engine required fuel is maintained in the medium amount range.

According to a third aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the present invention, wherein the operating state of the engine is such that the particulate combustion cannot be sustained. "Is characterized by an engine operating state in which the required engine fuel tends to decrease from the large amount region to the medium amount region or from the medium amount region to the small amount region.

According to a fourth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to third aspects, further comprising supplying fuel to the particulate trap. When the inflow prevention means is operated, at least a part of an exhaust upstream end face of the particulate trap, in which exhaust gas inflow is prevented by the inflow prevention means, is provided by the supply means. The fuel is supplied.

According to a fifth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects, wherein the operation and the stop of the inflow prevention means are continuously performed. It is repeated a predetermined number of times.

According to a sixth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourth aspects, wherein the inflow prevention means comprises:
Even before the lapse of the predetermined period, the operation is stopped when the engine required fuel reaches the large amount range.

According to a seventh aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fifth aspects, the temperature of the particulate trap is further grasped. Equipped with grasping means,
The predetermined period is set according to the temperature grasped by the grasping means.

According to an eighth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the fourth aspect, further comprising a grasping means for grasping the temperature of the particulate trap. The amount of the fuel supplied by the supply means is set according to the temperature grasped by the grasping means.

According to a ninth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the fifth aspect, further comprising a temperature grasping means for grasping the temperature of the particulate trap. The predetermined number of repetitions is set according to the temperature grasped by the grasping means.

According to a tenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to any one of the seventh to ninth aspects, wherein the grasping means comprises: It is characterized in that the temperature is directly detected.

According to an eleventh aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fifth aspects, the exhaust gas purifying apparatus according to any one of the first to fifth aspects, wherein It is characterized in that a predetermined period is set.

According to a twelfth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the fourth aspect of the present invention, wherein the exhaust gas purifying apparatus is supplied by the supply means in accordance with the amount of fuel required for the engine. The amount of the fuel is set.

According to a thirteenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the fifth aspect, wherein the predetermined number of times is repeated according to the amount of fuel required for the engine. It is characterized by setting.

According to a fourteenth aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to thirteenth aspects, the exhaust gas purifying apparatus is further trapped in the particulate trap. The apparatus is provided with a particulate quantity grasping means for grasping the particulate quantity, and permits the operation of the inflow prevention means only when the particulate quantity grasped by the particulate quantity grasping means is equal to or larger than a predetermined particulate quantity. It is characterized by the following.

According to a fifteenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourteenth aspects, further comprising a normally closed state which bypasses the particulate trap. The inflow prevention means prevents exhaust gas from flowing into the entire particulate trap during operation, and the bypass passage is opened when the inflow prevention means operates. Features.

According to a sixteenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the fifteenth aspect, wherein the bypass passage has a particulate trap different from the particulate trap. Are arranged.

According to a seventeenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to any one of the first to fourteenth aspects, wherein the inflow prevention means is configured such that the inflow preventing means operates during the operation. A second particulate trap arranged in parallel with the particulate trap, and prevents an exhaust gas from flowing into the entire second particulate trap during operation. And a second inflow prevention means for preventing the particulate matter trapped in the second particulate trap from burning by the exhaust gas flow. The inflow prevention means is operated, and after a predetermined period of time, the operation of the second inflow prevention means is stopped, and the inflow prevention means and Serial wherein the is not activated at the same time as the second inlet preventing means.

According to an eighteenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the seventeenth aspect, wherein the inflow prevention means and the second inflow prevention means are integrated. The operation of the second inflow prevention means is stopped when the inflow prevention means is operated, and the operation of the inflow prevention means is stopped when the second inflow prevention means is operated.

According to a nineteenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to any one of the fifteenth to eighteenth aspects, further comprising: An exhaust passage communicating with a space between the particulate trap and an ash amount grasping means for grasping an ash amount accumulated in the particulate trap, wherein the discharge passage continuously burns the particulate. In the engine operating state where it is impossible to perform the operation, the at least the ash amount grasped by the ash amount grasping means is closed between the time when the inflow prevention means is operated and the time when the operation of the inflow prevention means is stopped. When the amount is equal to or more than the predetermined ash amount, the discharge passage is at least open and the inflow prevention means is operated. It is characterized in.

[0027]

FIG. 1 is a sectional view showing a first embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention. In FIG. 1, reference numeral 1 denotes an engine exhaust passage, and reference numeral 2 denotes a particulate trap disposed in the expanded portion 1 a of the engine exhaust passage 1. The particulate trap 2 is, for example, a porous material particulate trap made of a porous material such as ceramic. This particulate trap has a plurality of axial spaces subdivided by a plurality of longitudinally extending partitions, and in two adjacent axial spaces, one is an exhaust upstream side and the other is an exhaust downstream side. Is closed by a closing material such as ceramic. Thus, the two adjacent axial spaces serve as a trap passage through which the exhaust gas flowing in from the exhaust upstream side flows out to the exhaust downstream side via the partition wall, and the partition wall made of the porous material serves as a trap wall to allow the exhaust gas to pass therethrough. At the time, it collects particulates.

The particulate trap 2 may be, for example, a metal fiber particulate trap composed of a heat-resistant metal fiber nonwoven fabric and a heat-resistant metal corrugated sheet. In this particulate trap, two nonwoven fabrics and two corrugated sheets are stacked in a thickness direction differently from each other and spirally wound, and a plurality of axial spaces are formed by the nonwoven fabrics and the corrugated sheets. Things. As the heat-resistant metal fiber forming the nonwoven fabric and the heat-resistant metal forming the corrugated sheet, for example, an Fe-Cr-Al alloy or a Ni-Cr-Al alloy can be used. The two nonwoven fabrics are continuously welded in a spiral shape with one surface in close contact with each other at the exhaust upstream end, and spirally with the other surfaces in close contact with each other at the exhaust downstream end. Welded continuously. In this way, the two axially adjacent spaces in the radial direction serve as a trap passage through which the exhaust gas flowing from the upstream of the exhaust flows to the downstream of the exhaust via any of the nonwoven fabrics. At the time of the collection of particulates.

The upstream side of the expanded portion 1a of the engine exhaust passage 1 is divided into an upstream upper space 1c and an upstream lower space 1d by a dividing wall 1b.
The particulate trap 2 has a trap upper portion 2a and a trap lower portion 2 on the extension surface of the partition wall 1b by a shielding wall that does not allow the passage of exhaust gas.
b. Reference numeral 3a denotes a first valve body for preventing exhaust gas from flowing into the exhaust upstream end surface of the trap upper portion 2a during the operation shown in FIG. 1B, and 3b denotes a first valve body during the operation shown in FIG. This is a second valve body for preventing exhaust gas from flowing into the exhaust upstream end surface of the trap lower portion 2b. In the present embodiment, the first valve body 3a and the second valve body 3b have an integral structure connected to a common drive shaft 3c. When the first valve body 3a is operated, the operation of the second valve body 3b is not performed. The operation is stopped, and the operation of the first valve element 3a is stopped when the second valve element 3b operates.

A first discharge passage 4a is connected to the upstream upper space 1c, and a second discharge passage 4b is connected to the upstream lower space 1d. The first discharge passage 4a and the second discharge passage 4b join together and are connected to an exhaust gas recirculation passage 4c, and a switching valve 5 is disposed at the junction. The exhaust recirculation passage 4c is connected to the engine intake system. Thus, by recirculating a part of exhaust gas into the cylinders, the main component to lower the exhaust gas combustion temperature is an inert gas, the amount of the NO _x is reduced.

In a normal state, the first valve body 3a and the second valve body 3b are rotated to the positions shown in FIG. 1A, that is, the operation of the first valve body 3a is stopped, and
Exhaust gas can flow into the exhaust upstream end face a of FIG. 2A, the second valve element 3b is operated, and exhaust gas can be prevented from flowing into the exhaust upstream end face of the trap lower portion 2b. The switching valve 5 is switched to the first discharge passage 4a side. Thereby,
The exhaust gas at this time is as shown by an arrow in FIG.
In the engine exhaust passage 1, an upper space 1c on the upstream side of the expanded portion 1a,
Upper part 2a of the trap and the downstream space 1e of the expanded part 1a
Flows through. Further, a part of the exhaust gas at this time is recirculated to the engine exhaust system via the first exhaust passage 4a and the exhaust recirculation passage 4c.

When the exhaust gas passes through the upper portion 2a of the trap, the particulates in the exhaust gas are collected by the upper portion 2a, and the exhaust resistance of the upper portion 2a gradually increases. If the amount of particulates trapped in the upper portion 2a of the trap is equal to or more than a predetermined amount, exhaust resistance increases and the engine output is greatly reduced. It is necessary to regenerate the upper part 2a. In order to determine whether or not the amount of particulates is equal to or greater than a predetermined amount, it is possible to detect a differential pressure between the upstream side and the downstream side of the trap upper portion 2a and to use the fact that the differential pressure has become equal to or greater than the predetermined differential pressure. is there. It is also possible to use that the traveling distance is equal to or longer than a predetermined distance.

FIG. 2 shows an engine operating range determined by the engine speed and the engine load. All engine operating areas are
It is divided into three regions according to the exhaust gas temperature. The engine high-load high-speed operation region A is a region where a large amount of fuel is injected and a large amount of engine required fuel is injected, and the exhaust gas temperature becomes high. If the engine required fuel lasts for a while in this large area, the high-temperature exhaust gas flow first burns the particulates upstream of the trap upper portion 2a, and the heat of combustion is generated by the high-temperature exhaust gas flow. Since only a small amount is removed, the combustion continues to propagate downstream of the upper trap portion 2a, and regeneration of the upper trap portion 2a is realized.

The engine high-load medium-speed / medium-load medium-speed / medium-load high-speed operation region B is a medium amount region of the engine required fuel in which a medium amount of fuel is injected, and the exhaust gas temperature does not become so high. Even at this exhaust gas temperature, the particulates on the upstream side of the trap upper portion 2a can slightly start combustion. However, since the exhaust gas flow at this time removes a large amount of the heat of combustion of the particulates, combustion cannot be sustained, and the trap upper portion 2a cannot be regenerated.

The engine high-load low-speed / medium-load low-speed / low-load low-speed / low-load medium-speed / low-load high-speed operation region C is a small amount of required engine fuel where a small amount of fuel is injected, and the exhaust gas temperature is low. It is. As a result, particulates upstream of the trap upper portion 2a cannot even start combustion.

As described above, as long as the engine required fuel does not continue for a while in the large amount region, even if the engine required fuel changes from the large amount region to the medium amount region due to the deceleration from the time of high engine load and high speed, the engine required fuel becomes medium. Due to the removal of the heat of combustion by the exhaust gas flow at the time of the volume range, the burning of the particulates cannot be sustained, and the regeneration of the upper portion 2a of the trap becomes impossible.

The operation in the region where the engine required fuel is large is not so frequently performed, but the operation in the region where the engine required fuel is medium is performed frequently. At this time, it is possible to regenerate the particulate trap. For this purpose, the exhaust emission control device of the present embodiment is controlled according to the flowchart shown in FIG. First, in step 101, as described above, it is determined whether or not the upper portion 2a of the particulate trap 2 is at the regeneration time based on the pressure difference between the upstream side and the downstream side of the upper portion 2a of the trap. You. If this determination is denied, the process is terminated as it is, but if it is determined that it is the regeneration time, the routine proceeds to step 102, where it is determined whether or not the engine required fuel in the current engine operating state is in the small amount range. If this determination is affirmative, the process ends.

The above-mentioned regeneration timing has some allowance before the exhaust resistance is significantly reduced. When the regeneration timing is reached, it is preferable to carry out regeneration as early as possible. It does not mean that the reproduction has to be carried out at the moment when it becomes. Since engine operation in the medium fuel range where engine fuel is required is performed relatively frequently, step 1
The determination in 02 is made affirmatively early after the reproduction time, and proceeds to step 103.

In step 103, as shown in FIG. 1B, the first valve body 3a is actuated to prevent exhaust gas from flowing into the exhaust upstream end face of the trap upper portion 2a.
The switching valve 5 is switched to the second discharge passage side 4b, and the first discharge passage 4a is closed, so to speak. As a result, the exhaust gas at this time flows through the engine exhaust passage 1 in the upper space 1c on the upstream side of the expanded portion 1a, the lower portion 2b of the trap, and the expanded portion 1a, as indicated by arrows in FIG. It flows through the downstream space 1e. Further, a part of the exhaust gas at this time is recirculated to the engine exhaust system through the exhaust recirculation passage 4c via the second exhaust passage 4b.

Next, at step 104, it is determined whether or not the fuel required for the engine is in the large amount range. If this determination is denied, at step 105, the first valve element 3
It is determined whether or not a predetermined period has elapsed since the operation of a. When this determination is denied, the process returns to step 104, but when affirmed, the process proceeds to step 106, in which the operation of the first valve body 3a is stopped to cause the exhaust gas to flow into the exhaust upstream end face of the trap upper portion 2a, and The switching valve 5 is switched to the first discharge passage side 4a. In addition, even before the predetermined period elapses, if the engine required fuel is in the large amount region, the routine proceeds to step 106, where the above-described processing is performed.

FIG. 4 is a time chart showing the operation and stoppage of the operation of the first valve element 3a when the engine required fuel changes. La is equal to L when the engine required fuel is maintained in the middle range.
b indicates that the engine required fuel is decreasing from a large amount to a medium amount region, Lc indicates that the engine required fuel is decreasing from a medium amount region to a small amount region, and Ld indicates that the engine necessary fuel is increasing from a medium amount region to a large amount region. , Respectively. According to the above-described flowchart, at the time of the regeneration, the first valve body 3a is operated at the time D because the required engine fuel is in the medium amount range or more in any case. Thereafter, in the case of La, Lb, and Lc, a predetermined period Te
At time S after the lapse, the operation of the first valve body 3a is stopped.

In this way, when the engine required fuel is at least in the middle amount range, the combustion of particulates on the upstream side in the trap upper portion 2a can be slightly started by the exhaust gas temperature at this time. In the present embodiment, the first valve body 3a is operated at the time D, and the trap upper portion 2
As shown in FIG. 5, this heat of combustion is not taken away by the not so high-temperature exhaust gas flow at this time, and the combustion continues, and the combustion continues, as shown in FIG. 5. Temperature rises. However, in this state, the fuel is terminated before burning all the particulates due to lack of oxygen.

In order to prevent this, at the time S after the elapse of the predetermined period Te, the operation of the first valve body 3a is stopped, and the exhaust gas is caused to flow into the upper portion 2a of the trap. At this time, the entire upper portion 2a of the trap is at a high temperature due to the continuation of the combustion for a predetermined period, and even if non-high-temperature exhaust gas is introduced and combustion heat is taken away, the combustion is not forcibly terminated. Since the oxygen in the exhaust gas is provided, the combustion of the particulates is promoted, and as shown in FIG. 5, the temperature of the upper portion 2a of the trap rises rapidly, and all the particulates in the upper portion 2a of the trap are burned. Can be done. Thus, it is possible to regenerate the upper portion 2a of the trap even if the engine required fuel does not continue for a while in a large amount region.

If the determination in step 104 is affirmative, the required fuel for the engine continues in a large amount range during the regeneration period, or the required fuel for the engine tends to increase from a medium amount region to a large amount region due to engine acceleration or the like. (Ld), and the high-temperature exhaust gas flow in which the engine required fuel is in a large area contributes to the particulate combustion without depriving a large amount of combustion heat. Time S shown in 4
At d, the exhaust gas flows into the upper portion 2a of the trap, and regeneration of the upper portion 2a of the trap is performed.

As described above, the exhaust gas temperature is proportional to the fuel injection amount, while the oxygen concentration in the exhaust gas is inversely proportional to the fuel injection amount. That is, the lower the exhaust gas temperature, the higher the oxygen concentration in the exhaust gas. According to the above-described flowchart, the operation of the first valve body 3a is stopped after a predetermined period elapses when the engine required fuel is decreasing. In this case, the temperature of the exhaust gas flowing into the upper portion 2a of the trap becomes low because the required fuel of the engine decreases.

Of course, it is preferable that the temperature of the exhaust gas flowing into the upper portion 2a of the trap is higher. However, since the upper portion 2a of the trap has a high temperature due to the burning of the particulates during the operation of the first valve body 3a, the exhaust gas is exhausted. Even at very low gas temperatures, combustion is not forced to end. Conversely, the exhaust gas flow at this time has a high oxygen concentration due to the reduced fuel injection amount, and the exhaust gas having such a high oxygen concentration is supplied to the trap upper portion 2a.
The burning of the particulates in the upper portion 2a of the trap is rapidly promoted. In this way, the operation of the first valve body 3a is stopped particularly when the engine required fuel is decreasing, such as when the engine is decelerated, so that the trap upper portion 2a can be surely regenerated.

Further, when the fuel required for the engine is in the small amount region even in the medium amount region, the combustion of the particulates is further reduced, and if the first valve body 3a is operated to prevent the inflow of the exhaust gas, Although the combustion can be continued, the temperature of the upper portion 2a of the trap cannot be increased significantly during the combustion for a predetermined period. In this case, the first valve body 3a
If the operation of is continuously stopped, the oxygen deficiency is eliminated, but the combustion may be forcibly terminated by removing heat by the exhaust gas flow.

In order to prevent this, as shown in the time chart of FIG. 6, if the engine required fuel is in the small amount region in the medium amount region when the regeneration time is reached, the timing D1 is increased in the same manner as described above.
In addition to activating the first valve element 3a and stopping the operation of the first valve element 3a at a time S1 after a predetermined period, the first valve element 3a is again activated at a time D2 when a short period has elapsed and oxygen deficiency has been reduced to some extent. The valve element 3a is operated, and thereafter, similarly, the operation of the first valve element 3a is stopped at time S2, the first valve element 3a is operated at time D3, and the operation of the first valve element 3a is stopped at time S3. Thus, the first valve body 3a
The operation and the stop of the operation may be repeated.

Thus, in one operation and suspension of the first valve body 3a, even if the high temperature of the trap upper portion 2a cannot be increased so much, the operation and suspension of the operation are repeated a predetermined number of times. The upper portion 2a of the trap can be heated to a high temperature. At this time, even if the operation of the first valve body 3a is stopped for a relatively long time, the combustion is not forcibly terminated, and the combustion is performed because oxygen is sufficiently supplied. Is rapidly promoted, and all the particulates collected in the upper portion 2a of the trap are burned off, so that reliable regeneration of the upper portion 2a of the trap can be realized.

As described above, the more fuel required for the engine, the higher the temperature of the exhaust gas and the lower the oxygen concentration in the exhaust gas. In the case where it is equal to or higher than the range, it is preferable that the predetermined period during which the first valve body 3a is operated is set longer as the engine required fuel is smaller. Furthermore, when the engine required fuel is on the small fuel range side in the medium fuel range,
As described above, it is preferable that the operation and the stop of the operation of the first valve element 3a are repeated, and the number of repetitions is increased as the engine required fuel decreases. Even when the operation and the stop of the operation of the first valve body 3a are repeated, it is preferable that the predetermined period during which the first valve body 3a is operated becomes longer as the engine required fuel is smaller. FIG. 7 is a table summarizing such controls. In this table, the engine required fuel is at the time of operation of the first valve body 3a, and Te ′ is a reference predetermined period.

By doing so, the particulate combustion during the operation of the first valve element 3a can be reliably maintained without oxygen shortage, and finally, the temperature of the trap upper portion 2a can be reduced. In addition, the temperature can be assuredly raised so that combustion is not forcibly terminated even by a relatively low temperature exhaust gas flow. Of course, such control of the predetermined period and the number of repetitions is performed by directly detecting the temperature of the upper portion 2a of the trap, for example, the temperature of the exhaust upstream portion of the upper portion 2a of the trap by a temperature sensor or the like, so that the engine It may be used in place of the required fuel amount. Also, the exhaust gas temperature, for example, the upper part 2 of the trap
It is also possible to directly detect the temperature of the exhaust gas flowing into a, and to use this temperature in place of the required engine fuel amount.

In the combustion of the internal combustion engine, not only fuel but also engine oil that has entered the cylinder is burned, so that oxides and sulfides such as calcium and phosphorus, which are components thereof, are generated. Usually, particulates have these as components. Oxides or sulfides of calcium or phosphorus are very difficult to burn, and during the regeneration of the trap upper portion 2a, they remain as ash in the trap upper portion 2a and accumulate to increase exhaust resistance. Therefore, it is necessary to discharge such ash from the upper portion 2a of the trap.

In this embodiment, for example, when the regeneration of the upper trap portion 2a is completed, the differential pressure between the upstream side and the downstream side of the upper trap portion 2a is detected, and this differential pressure is equal to or higher than a predetermined differential pressure. That is, the ash accumulation is grasped from the fact that the traveling distance has become equal to or more than the predetermined distance, and at this time, the first valve body 3a is operated and the switching valve 5 is connected to the first discharge passage regardless of the engine operating state. 4a side is left. As a result, the exhaust gas flows through the engine exhaust passage 1 through the lower space 1d on the upstream side of the expanded portion 1a, the lower portion 2b of the trap, and the space 1e downstream of the expanded portion 1a, as shown in FIG. And a part of the exhaust gas flows into the downstream space 1e.
From the trap upper portion 2a, and is discharged from the first discharge passage 4a via the upstream space 1c.

Although the ash deposited in the upper portion 2a of the trap cannot pass through the eyes of the upper portion 2a due to its size, the exhaust gas is caused to flow backward in the upper portion 2a of the trap. It is easily discharged to the upstream space 1c through a relatively large opening on the upstream side of the trap passage in 2a. Thereafter, the expanded portion 1a is used together with the exhaust gas flow using the first exhaust passage 4a.
It is discharged outside. Since this exhaust gas is used as recirculated exhaust gas, it is preferable to remove ash at least before being supplied into the cylinder.

The regeneration and ash removal in the trap upper portion 2a of the particulate trap 2 have been described above, but the trap lower portion 2b is also used in the second valve body 3b.
The same regeneration is possible by controlling the exhaust gas in exactly the same way, and as shown in FIG. 8A, the ash can be removed by causing the exhaust gas to flow backward. The first discharge passage 4a and the second discharge passage 4b do not need to be particularly connected to the exhaust gas recirculation passage 4c as long as they are for discharging ash. In this case, the first discharge passage 4a may be closed at least during operation of the first valve body 3a and opened during removal of ash from the trap upper portion 2a. Similarly, the second discharge passage 4b is provided at least with the second valve body 3b
Is closed during the operation of, and opened during removal of the ash from the trap lower portion 2b.

In this embodiment, the particulate trap 2 is divided into a trap upper portion 2a and a trap lower portion 2b by a shielding wall. As described above, the particulate trap 2 is adjacent in the radial direction. Using a trap passage consisting of two axial spaces,
Since the exhaust gas is mainly passed in the axial direction, it is not necessary that the exhaust gas is divided by a shielding wall if only the regeneration of the particulate trap is intended.

FIG. 9 shows a second embodiment of the exhaust gas purifying apparatus according to the present invention. In this embodiment, the single valve element 3
This makes it possible to prevent the exhaust gas from flowing into the upper part of the particulate trap 2. The particulate 2 is not particularly divided by the shielding wall. In such a configuration, the upper part of the particulate trap can be regenerated by the same method as described above. If this regeneration is carried out relatively frequently, the exhaust gas mainly passes through the upper part of the particulate trap, which has a low exhaust resistance. As a result, the exhaust gas passes through the lower part of the particulate trap only during the regeneration of the upper part, and the regeneration is not required for a long period of time. If the entire particulate trap is naturally regenerated, the particulate trap 2 will not have a problem such as an increase in exhaust resistance. In the present embodiment, if the particulate trap 2 is divided into an upper portion and a lower portion using a shielding wall, and a discharge passage is connected upstream of the upper portion of the particulate trap 2, the
The ash can be removed in the upper part of the.

FIG. 10 shows a third embodiment of the exhaust gas purifying apparatus according to the present invention. This embodiment differs from the first embodiment in that the first valve body 3a 'and the second valve body 3b' can be operated separately. Accordingly, in normal times, the operation of the first valve body 3a 'and the second valve body 3b' is stopped, so that the exhaust gas passes through both the upper portion 2a and the lower portion 2b of the trap, and the exhaust gas passes through the respective portions. Curate collection is performed. When it is time to regenerate the particulate trap, the first valve body 3a 'and the second valve body 3b' are not operated at the same time.
And one of the trap lower part 2b is regenerated, and then the other is regenerated. This embodiment has the same first discharge passage 4a and second discharge passage 4b as described above,
Ash removal in the upper portion 2a and the lower portion 2b of the trap is also possible based on the same concept as described above. In the present embodiment, one particulate trap is divided into two, but at least two particulate traps are arranged in parallel in the engine exhaust system, and for each particulate trap, the exhaust gas is exhausted to the entire exhaust upstream end face. This is equivalent to an arrangement in which inflow prevention means for preventing inflow is provided.

FIG. 11 shows a fourth embodiment of the exhaust gas purifying apparatus according to the present invention. In this embodiment, a particulate trap 2 is disposed in an engine exhaust passage 1, and a bypass passage 6 that bypasses the particulate trap 2 is provided.
Is provided. The valve element 3 'prevents the exhaust gas from flowing into the entire particulate trap 2 during operation. The valve element 3' closes the bypass passage 6 when the operation is stopped, and the bypass passage 6 during the operation. Is to be released. Even with such a configuration, the above-mentioned regeneration of the particulate trap 2 is possible. At the time of the regeneration, the exhaust gas passes through the bypass passage and the particulates are not collected. However, since the regeneration is performed in a short time, it does not cause a serious problem. In this embodiment, the discharge passage 4 is provided between the particulate trap 2 and the valve body 3 ′.
Is connected, and ash can be removed from the particulate trap 2 based on the same concept as described above.

In this embodiment, a fuel supply device 7 for supplying fuel to the particulate trap 2 is provided on the downstream side of the valve element 3 ', and the particulate trap 2 carries an oxidation catalyst. Thus, fuel is supplied to the particulate trap 2 immediately before the valve body 3 'is operated, and the fuel is burned by the oxidation catalyst, whereby the temperature of the particulate trap 2 can be increased. In this way, even when the fuel required for the engine is in a small amount range and the exhaust gas temperature is low, it is possible to start the slight combustion of the particulates.
Can be reproduced.

The lower the required engine fuel, the lower the exhaust gas temperature, and accordingly the lower the temperature of the particulate trap 2. Therefore, in order to reliably start particulate combustion immediately before the operation of the valve element 3 ', it is preferable to increase the amount of fuel supplied to the particulate trap 2 as the engine required fuel decreases. Of course, the amount of fuel supplied to the particulate trap may be controlled by directly detecting the temperature of the particulate trap 2 or the temperature of the exhaust gas and based on the detected temperature.

The fuel supply device 7 is not limited to the downstream side of the valve body 3 ′, and can supply fuel to the particulate trap 2 using exhaust gas if it is on the upstream side of the particulate trap 2. Alternatively, it can be placed at any position. Further, if the fuel injection valve of the internal combustion engine injects fuel directly into the cylinder, the fuel supply device 7 may be provided with the fuel even in the exhaust stroke, for example, without providing the fuel supply device 7 in the engine exhaust passage. The unburned fuel may be supplied to the particulate trap 2 by injecting. The concept of supplying fuel to the particulate trap as described above is applicable to all the above-described embodiments.

[0063]

As described above, according to the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the combustion of the particulates trapped in the particulate trap by the exhaust gas flow is performed without maintaining the required engine fuel in a large amount range. In the case of an engine operating state where it is impossible to maintain the state, it is possible to prevent the inflow of exhaust gas into at least a part of the particulate trap by operating the inflow prevention means, and to remove combustion heat by the exhaust gas flow. Since the burning of the particulates in this portion of the particulate trap is continued, the temperature of at least this portion can be increased. Next, after the elapse of a predetermined period, the operation of the inflow prevention means is stopped, and the exhaust gas flows into at least a part of the particulate trap. At this time, even if the temperature of the exhaust gas is low, this part of the particulate trap is at a high temperature, so that the combustion of the particulate is not forcibly terminated. Conversely, since the oxygen in the exhaust gas is supplied, the particulate trap is not performed. Combustion is rapidly promoted mainly to the downstream side of the exhaust gas, and the particulates in at least a part of the particulate traps can be surely burned off. Can be reproduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention, in which (A) shows when the operation of a first valve body is stopped, and (B) shows when the first valve body is working. Is shown.

FIG. 2 is a diagram showing an engine operation region divided by a difference in a combustion state of particulates.

FIG. 3 is a flowchart for reproducing a particulate trap.

FIG. 4 is a time chart for explaining the flowchart of FIG. 3 when the engine required fuel changes.

FIG. 5 is a time chart showing a temperature change of the particulate trap when the flowchart of FIG. 3 is implemented.

FIG. 6 is a time chart showing a temperature change of the particulate trap when the operation and stop of the first valve body are repeated in the flowchart of FIG. 3;

FIG. 7 is a table showing a case where the predetermined period during the operation of the first valve body is changed and a case where the number of repetitions of the operation and the stop of the operation of the first valve body is changed in the flowchart of FIG.

8A and 8B are diagrams for explaining ash removal in the first embodiment of FIG. 1, wherein FIG. 8A shows ash removal from a lower portion of a trap and FIG. 8B shows ash removal from an upper portion of the trap.

FIG. 9 is a sectional view showing a second embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention.

FIG. 10 is a sectional view showing a third embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention.

FIG. 11 is a sectional view showing a fourth embodiment of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine exhaust passage 2 ... Particulate trap 2a ... Trap upper part 2b ... Trap lower part 3, 3 '... Valve element 3a, 3a' ... First valve element 3b, 3b '... Second valve element 4 ... Discharge path 4a ... First discharge passage 4b ... Second discharge passage

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI F01N 3/02 301 F01N 3/02 301B

Claims (19)

[Claims] 1. An engine exhaust system comprising: a particulate trap disposed in an engine exhaust system; and an inflow prevention means for preventing an exhaust gas from flowing into at least a part of the particulate trap during operation. At least when divided into a large area, a medium amount area, and a small area, the engine required fuel does not continue in the large area, and the combustion of the particulates trapped in the particulate trap by the exhaust gas flow is continued. An exhaust gas purifying apparatus for an internal combustion engine, wherein, when the engine is in an operating state in which it is impossible to perform the operation, the inflow prevention means is operated, and the operation of the inflow prevention means is stopped after a predetermined period has elapsed. 2. The engine operating state in which the particulate combustion cannot be sustained is an engine operating state in which the engine required fuel is maintained in the medium amount range. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 3. The engine operating state in which the particulate combustion cannot be sustained means that the engine required fuel tends to decrease from the large amount region to the medium amount region or from the medium amount region to the small amount region. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas purifying apparatus is in an operating state. 4. The particulate trap according to claim 1, further comprising a supply unit for supplying fuel to said particulate trap, wherein said inflow prevention unit prevents exhaust gas from flowing when said inflow prevention unit is operated. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the fuel is supplied to at least a part of the exhaust upstream end surface by the supply means. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the operation and the stop of the inflow prevention means are continuously repeated a predetermined number of times. 6. The method according to claim 1, wherein the inflow prevention means is stopped when the required fuel for the engine reaches the large amount range even before the predetermined period has elapsed. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 7. The apparatus according to claim 1, further comprising: grasping means for grasping the temperature of said particulate trap, wherein said predetermined period is set in accordance with said temperature grasped by said grasping means. 6. The exhaust gas purification device for an internal combustion engine according to any one of 5. 8. An apparatus according to claim 1, further comprising a grasping unit for grasping a temperature of said particulate trap, wherein an amount of said fuel supplied by said supplying unit is set according to said temperature grasped by said grasping unit. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein: 9. The apparatus according to claim 1, further comprising a temperature grasping means for grasping the temperature of said particulate trap, wherein said predetermined number of repetitions is set according to said temperature grasped by said grasping means. Item 6. An exhaust gas purification device for an internal combustion engine according to item 5. 10. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, wherein said grasping means directly detects a temperature of said particulate trap. 11. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the predetermined period is set according to an amount of fuel required for the engine. 12. An exhaust gas purifying apparatus for an internal combustion engine according to claim 4, wherein an amount of said fuel supplied by said supply means is set according to an amount of said engine required fuel. 13. The exhaust gas purifying apparatus for an internal combustion engine according to claim 5, wherein the predetermined number of times to be repeated is set according to the amount of fuel required for the engine. 14. The apparatus according to claim 11, further comprising: a particulate amount grasping means for grasping the amount of the particulate matter trapped in said particulate trap, wherein said particulate matter amount grasped by said particulate amount grasping means is a predetermined particulate matter. 2. The operation of the inflow prevention means is permitted only when the amount is equal to or greater than the curated amount.
14. The exhaust gas purification device for an internal combustion engine according to any one of claims to 13. 15. A normally closed bypass passage for bypassing the particulate trap, wherein the inflow prevention means prevents exhaust gas from flowing into the entire particulate trap during operation.
15. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the bypass passage is opened when the inflow prevention unit operates. 16. The exhaust gas purifying apparatus for an internal combustion engine according to claim 15, wherein a particulate trap different from the particulate trap is disposed in the bypass passage. 17. The inflow prevention means prevents exhaust gas from flowing into the entirety of the particulate trap during operation, and comprises a second particulate trap arranged in parallel with the particulate trap, and And a second inflow prevention means for preventing inflow of exhaust gas into the entire second particulate trap, wherein the combustion of the particulates trapped in the second particulate trap by the exhaust gas flow is continued. In the case of the engine operating state where it is impossible to perform the operation, the second inflow prevention means is operated, and after a predetermined period of time, the second
The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 14, wherein the operation of the inflow prevention unit is stopped, and the inflow prevention unit and the second inflow prevention unit are not operated at the same time. 18. The inflow prevention means and the second inflow prevention means are integral with each other. When the inflow prevention means is activated, the operation of the second inflow prevention means is stopped, and when the second inflow prevention means is activated, 18. The exhaust gas purifying apparatus for an internal combustion engine according to claim 17, wherein the operation of the inflow prevention means is stopped. 19. An exhaust passage communicating with a space between the inflow prevention means and the particulate trap during operation, and an ash amount grasping means for grasping an ash amount accumulated in the particulate trap. The exhaust passage has a small amount of time between the time when the inflow prevention means is operated and the time when the operation of the inflow prevention means is stopped in an engine operating state in which the combustion of the particulates cannot be sustained. When the ash amount grasped by the ash amount grasping means is equal to or more than a predetermined ash amount, the discharge passage is at least opened and the inflow prevention means is operated. An exhaust gas purification device for an internal combustion engine according to any one of claims 15 to 18.