JP2000080912A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate an increase in the exhaust resistance of a particulate trap by a pile of ashes, in an exhaust emission control device for an internal combustion engine to be equipped with a communicating path to make each exhaust port communicating with at least one of the other exhaust ports. SOLUTION: This device is equipped with an inflow restraining means 10 which makes an inflow of exhaust gas into at least one of particulate traps 4 temporarily restrainable. In this constitution, it temporarily restrains the inflow of the exhaust gas into the particulate traps 4 by the inflow restraining means at need, while it closes each on-off valve 6a set up in communicating passage 6 for communicating the exhaust port 3 wherein the particulate trap 4 is set up, to the other exhaust ports.

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] If the exhaust gas is heated to a high temperature as in high-speed high-speed operation of the engine, the particulates spontaneously ignite and burn, so that the particulate trap can be regenerated. Japanese Utility Model Laid-Open No. 5-69311 proposes disposing a particulate trap for each exhaust port. With this configuration, the particulate trap can be made to approach the engine body, and the heat of the exhaust gas can be effectively used for the regeneration of the particulate trap.

[0004] While the size of the particulate is very small, the pores of the particulate trap are very large compared to the particulate so that the particulate trap itself does not have a large exhaust resistance. Have been. In such a particulate trap, the particulates adhere and accumulate around the pores and are collected. If the deposited particulates grow relatively large and the substantial pore size of the particulate trap is reduced to some extent, the particulate trapping rate in the particulate trap is greatly improved.

However, when the particulate trap is arranged close to the engine body as described above, relatively high-speed exhaust gas immediately after being discharged from each cylinder always passes through each particulate trap. The deposited particulates around the pores of the particulate trap are likely to collapse before growing relatively large. As a result, the particulate collection rate in each particulate trap is kept low without improvement.

In order to solve this problem, it is conceivable that the exhaust ports communicate with each other on the upstream side of the particulate trap. Accordingly, in the exhaust stroke of each cylinder, the exhaust gas is dispersed into each particulate trap and flows at a reduced speed, so that the growth of the adhered and deposited particulates is not hindered, and the particulate trap in the particulate trap is not hindered. Collection efficiency can be improved.

[0007]

However, when the particulate trapping efficiency in the particulate trap is improved in this way, on the other hand, the combustion products of engine oil called ash contained in the exhaust gas are also improved. Is trapped in a particulate trap. The ash is very difficult to burn, and remains in the particulate trap even after burning out of the particulates, and increases the exhaust resistance of the particulate traps.

In order to break down the ash accumulation and discharge the ash to the downstream side of the particulate trap, a closing valve capable of closing each communication passage is provided to invalidate each communication passage, thereby discharging the ash from each cylinder. It is conceivable that the relatively high-speed exhaust gas immediately after the exhaust gas passes only through the corresponding particulate trap.

However, the deposition of ash is more robust than that of particulates, and even in this case, the deposition ash in the particulate trap cannot be easily broken.

Accordingly, an object of the present invention is to provide a particulate trap disposed at each of the exhaust ports communicating the exhaust collecting section and each cylinder in the engine exhaust system, and an exhaust upstream side of each of the particulate traps. An object of the present invention is to prevent an increase in exhaust resistance of a particulate trap due to ash accumulation in an exhaust gas purification device for an internal combustion engine having an exhaust port and a communication passage for communicating with at least one other exhaust port.

[0011]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the present invention. A curable trap, a communication path for communicating each exhaust port with at least one other exhaust port on an exhaust upstream side of each of the particulate traps, and a normally open on-off valve disposed in each of the communication paths. And an inflow suppressing means for temporarily suppressing the inflow of exhaust gas into at least one of the particulate traps. If necessary, the inflow suppressing means exhausts the gas into the at least one particulate trap. While temporarily suppressing the inflow of gas,
The on-off valve arranged in the communication passage for communicating the exhaust port in which the at least one particulate trap is arranged with another exhaust port is closed.

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 inflow suppression means is provided in an exhaust system of the engine. It is characterized by being.

According to a third 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 inflow suppressing means includes a turbocharger disposed in an engine exhaust system. It is a variable nozzle throttle mechanism for a turbine.

According to a fourth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the first aspect, wherein the at least one inflow suppressing means comprises the at least one particulate of an engine exhaust system. It is a control valve of an exhaust gas recirculation passage connected downstream of the trap.

According to a fifth 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 inflow suppressing means delays the opening timing of the exhaust valve. It is a retarding means.

According to a sixth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the present invention, wherein a particulate trap disposed at each of the exhaust ports communicating the exhaust collecting section and each of the cylinders in the engine exhaust system; An engine on the exhaust upstream side of the particulate trap, comprising: a communication path for communicating each of the exhaust ports with at least one of the other exhaust ports; and a normally open on-off valve disposed in each of the communication paths. When a high load is applied, the on-off valve arranged in the communication path for communicating at least one of the exhaust ports with another of the exhaust ports is temporarily closed as needed.

According to a seventh aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the present invention, wherein a particulate trap disposed at each of the exhaust ports communicating the exhaust collecting section and each cylinder in the engine exhaust system; On the exhaust upstream side of the particulate trap, a communication path for communicating each of the exhaust ports with at least one of the other exhaust ports, and a deactivating means for temporarily deactivating at least one cylinder are provided. The at least one cylinder is temporarily stopped by the stopping means as necessary.

According to an eighth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the seventh aspect of the present invention, wherein a normally open on-off valve is arranged in each of the communication paths.
When the at least one cylinder is temporarily deactivated by the deactivation means, the at least one cylinder is disposed in the communication passage for communicating the exhaust port communicating with the exhaust collecting portion with another exhaust port. Further, the on-off valve is closed.

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 seventh or eighth aspect, wherein the at least one cylinder is deactivated by the deactivating means. Means for increasing the pressure difference between the in-cylinder pressure in the exhaust stroke and the pressure on the downstream side of the particulate trap disposed in the exhaust port communicating the at least one cylinder and the exhaust collecting portion. It is characterized by having.

According to a tenth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the ninth aspect, wherein the differential pressure increasing means is provided when the pausing means is stopped by the pausing means. It is characterized in that it is an outflow suppressing means for suppressing an outflow of exhaust gas from the exhaust collecting section prior to an exhaust stroke of the at least one cylinder.

According to an eleventh aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the ninth aspect, wherein the differential pressure increasing means is provided when the pausing means is stopped by the pausing means. An intake throttle mechanism for reducing the amount of intake air to the at least one cylinder is provided.

According to a twelfth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the eleventh aspect, wherein the intake throttle mechanism comprises an at least one cylinder, an intake branch portion, Is disposed at an intake port that communicates with

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 ninth aspect, wherein the differential pressure increasing means is provided when the pausing means is stopped by the pausing means. An intake valve closing timing changing unit that changes a closing timing of the intake valve so as to reduce the amount of intake air to the at least one cylinder.

According to a fourteenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the ninth aspect, wherein the differential pressure increasing means is provided when the intake means is stopped. An exhaust valve opening timing changing means for changing the opening timing of the exhaust valve of the at least one cylinder to near the bottom dead center.

[0025]

FIG. 1 is a schematic diagram of an engine exhaust system provided with an exhaust gas purifying apparatus according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes a mounting flange on the exhaust side of a cylinder head, 2 denotes an exhaust collecting portion of each cylinder, and 3 denotes an exhaust port for communicating the exhaust collecting portion 2 with each cylinder. The downstream side of the exhaust collecting portion 2 communicates with the atmosphere via a turbine 8 of a turbocharger, and the exhaust passage downstream of the turbine 8 extends in the axial direction of the turbine 8. Each exhaust port 3 is provided with a particulate trap 4.

Further, an exhaust recirculation passage 5 for recirculating a part of the exhaust gas into the cylinder through the engine intake system is connected to the exhaust collecting section 2. A control valve 5a for controlling the amount of recirculated exhaust gas is disposed in the exhaust gas recirculation passage 5. For the main component of the exhaust gas is large inert gas heat capacity, by recirculating the exhaust gas into the cylinder, it is possible to reduce the amount of NO _x generated to lower the combustion temperature. However, since exhaust gas recirculation involves some deterioration of combustion, it is generally performed except when the engine is under a low load where combustion is relatively unstable and when the engine is at a high load where high output is required. Therefore, the control valve 5a is closed when the engine is under a low load and when the engine is under a high load, and is opened according to the recirculated exhaust gas amount when the engine is under a medium load.

Each of the particulate traps 4 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.

Each of the particulate traps 4
For example, a metal fiber particulate trap composed of a heat-resistant metal fiber nonwoven fabric and a heat-resistant metal corrugated sheet may be used. 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.
Thus, two radially adjacent axial spaces are:
A trap passage through which the exhaust gas flowing in from the exhaust upstream side flows out to the exhaust downstream side through any of the nonwoven fabrics, and the nonwoven fabric serves as a trap wall to collect particulates when the exhaust gas passes. .

The exhaust gas purifying apparatus of this embodiment further includes:
On the exhaust upstream side of each particulate trap 4,
A communication path 6 for communicating each exhaust port 3 with an adjacent exhaust port 3 is provided. Each communication passage 6 is provided with a normally open on-off valve 6a. Further, a first pressure sensor 7a is disposed at a portion immediately upstream of the particulate trap of the engine exhaust system, that is, at a portion upstream of the particulate trap of the exhaust port 3 that is communicated with each other by the communication passages 6. A second pressure sensor 7 is provided on the downstream side of the particulate trap,
b is arranged.

An exhaust passage immediately upstream of the turbine 8 of the turbocharger is configured to surround the turbine 8, and is provided with a variable nozzle 9 for adjusting the flow rate and flow rate of the exhaust gas flowing into the turbine 8. ing. With this variable nozzle, the rotation speed of the turbine can be controlled to a desired rotation speed without being uniquely determined by the flow rate of exhaust gas discharged from the cylinder. Further, an exhaust control valve 10 that is normally open is disposed immediately downstream of the exhaust collecting section 2. The exhaust control valve 10 is provided to reduce the exhaust gas flow rate. If the exhaust gas flow rate can be reduced by the variable nozzle 9 described above,
It can be omitted.

In the exhaust gas purification apparatus thus configured, relatively high-speed exhaust gas discharged from each cylinder is distributed to all the exhaust ports 3 by each communication path 6. Thereby, the change in the flow velocity of the exhaust gas flowing into the specific particulate trap 4 changes relatively slowly as shown in FIG. Although the size of the pores of the particulate trap 4 is much larger than that of the particulate trap, the particulates in the exhaust gas are small because the flowing exhaust gas is slow. The adhered and deposited particulates are collected and collected around the holes, and the deposited particulates can easily grow relatively large without being destroyed. Thus, the size of the substantial pores of the particulate trap 4 is reduced to some extent, and the particulate collection rate in the particulate trap 4 is increased.

Since each of the particulate traps 4 is arranged near the engine body, the particulates collected by each of the particulate traps 4 can be used if the exhaust gas becomes hot at the time of high-load high-speed operation of the engine or the like. Each of the particulate traps 4 is burned out by effectively utilizing the heat of the exhaust gas.
Playback is completed.

The exhaust gas contains oxides and sulfides such as calcium and phosphorus, which are combustion products of the engine oil that has entered the cylinder. These are called ash and have the same size as particulates,
Although the amount of generation is smaller than that of the particulates, they are collected well in each of the particulate traps 4 similarly to the particulates. Since ash is very difficult to burn, even if the particulates are burned off from each of the particulate traps 4, the ash remains in the particulate traps and accumulates to increase exhaust resistance.

The dashed line in FIG. 3 shows the change in the flow velocity of the exhaust gas flowing into a specific particulate trap 4 when each communication path 6 is closed by each on-off valve 6a. And two peak velocities occur. The first peak flow velocity is caused by the ejection of high-pressure burned gas in the cylinder simultaneously with the opening of the exhaust valve. Further, the second peak flow velocity is obtained by discharging a large amount of burned gas in the cylinder as the piston rises.

Thus, the burned gas in the cylinder flows into the particulate trap 4 at two peak flow rates. Although each peak flow velocity is relatively high, the ash deposition is stronger than the particulate deposition, and therefore the deposited ash cannot be broken. in this way,
Ash that accumulates in the particulate trap 4 cannot be removed from the particulate trap 4 simply by closing the communication passages 6 by the on-off valves 6a.

In this embodiment, when the exhaust resistance of the particulate trap 4 increases due to the accumulation of ash, the first control is to close each communication passage 6 by each on-off valve 6a at high engine load. Has become.
At the time of high engine load, the combustion pressure is increased by a large amount of injected fuel, so that the two peak flow velocities generated in the exhaust stroke of each cylinder are higher than those in normal times.
Thereby, the deposited ash can be broken down and made finer by the exhaust gas flowing into the particulate trap 4 at two peak flow speeds higher than usual, and can be discharged downstream of the particulate trap 4.

In the present embodiment, when the exhaust resistance of the particulate trap 4 increases due to the accumulation of ash, as the second control, each of the communication passages 6 is closed by each of the on-off valves 6a, and the exhaust of each cylinder is exhausted. Only at the beginning of the stroke, the exhaust control valve 10 is operated in the valve closing direction. The solid line in FIG. 3 shows a change in the flow velocity of the exhaust gas flowing into the specific particulate trap 4 as a result of the second control.

At the beginning of the exhaust stroke, the exhaust control valve 10
Is operated in the valve closing direction to increase the exhaust resistance in the exhaust system, so that the amount of burned gas ejected from the cylinder decreases simultaneously with the opening of the exhaust valve. Lower. Thereafter, as the piston rises, the burned gas in the cylinder is forcibly discharged by increasing the amount of burned gas ejected from the cylinder at the same time as the opening of the exhaust valve. Since the exhaust control valve 10 is sometimes fully opened, the second peak flow velocity is much higher than usual. As a result, the deposition ash is separated from the particulate trap 4 at a second peak flow rate higher than normal.
By the exhaust gas flowing into the trap, it is broken down and made fine, and can be discharged downstream of the particulate trap 4.

In the present embodiment, when the exhaust resistance of the particulate trap 4 increases due to the accumulation of ash, as the third control, each of the communication passages 6 is closed by each of the on-off valves 6a, and the exhaust of each cylinder is exhausted. Only at the beginning of the stroke, the variable nozzle 9 of the turbocharger is operated to the throttle side. In this third control,
Since the exhaust resistance in the exhaust system is increased at the beginning of the exhaust stroke of each cylinder, the second peak flow velocity can be increased,
The same effect as in the second control can be obtained.

In the second and third controls, each communication passage 6 is closed by each on-off valve 6a, and the exhaust passage is controlled by the exhaust control valve 10 or the variable nozzle 9 or the like only at the beginning of the exhaust stroke of each cylinder. This restricts the flow of the exhaust gas into the particulate trap 4 at this time, so that when the restrictor is subsequently opened, the flow rate of the exhaust gas flowing into the particulate trap 4 is increased. , Making it possible to break up the deposited ash.

In such control, the mechanism for suppressing the flow of exhaust gas into the particulate trap 4 is not limited to the exhaust control valve 10 or the variable nozzle 9 in the configuration of the present embodiment. The position of the control valve 10 corresponds to the position of the particulate trap 4 of each exhaust port 3.
Upstream or downstream. Also, the timing for suppressing the flow of exhaust gas into each particulate trap 4 is as follows.
The present invention is not limited to the initial exhaust stroke of each cylinder. For example, the entire exhaust stroke of each cylinder may be used. In this case, the exhaust gas to the particulate trap 4 is discharged to the next exhaust stroke of each cylinder. When releasing the inflow suppression, the flow velocity of the exhaust gas flowing into each of the particulate traps 4 can be increased as compared with the normal time. That is, if the inflow of the exhaust gas into the particulate trap 4 is temporarily suppressed together with the closing of the communication paths 6, the above-described effect can be obtained.

In this embodiment, when the exhaust resistance of the particulate trap 4 increases due to the accumulation of ash, the fourth control is to close each communication passage 6 by each on-off valve 6a and to exhaust each cylinder. Only at the beginning of the stroke, the control valve 5a of the exhaust gas recirculation passage 5 is operated in the valve closing direction. Thus, at this time, the flow rate of the exhaust gas passing through the exhaust recirculation passage 5 is reduced, and the exhaust gas is accordingly reduced by the particulate traps 4.
Hard to pass through. In this way, the amount of burned gas injected from the cylinder in the early stage of the exhaust stroke can be reduced,
The same effect as in the second and third controls can be obtained.

Of course, in the fourth control as well, the timing at which the control valve 5a of the exhaust gas recirculation passage 5 is operated in the valve closing direction is not limited to the initial stage of the exhaust stroke of each cylinder. Particulate trap 4 as a whole
The effect similar to the above can be obtained by temporarily suppressing the flow of the exhaust gas into the exhaust gas.

In the present embodiment, a camshaft for an exhaust valve of an internal combustion engine is provided with a generally known variable valve timing mechanism. This is to relatively rotate between a camshaft and a pulley for rotating the camshaft.For example, the camshaft and the pulley are connected via an intermediate gear having helical teeth as external teeth. The relative rotation described above is realized by moving the intermediate gear in the axial direction using hydraulic pressure or electromagnetic force or the like, whereby the opening timing of the exhaust valve 4 can be changed steplessly. Becomes

By utilizing such a variable valve timing mechanism, in this embodiment, when the exhaust resistance of the particulate trap 4 increases due to the deposition of ash,
As a fifth control, each communication path 6 is closed by each on-off valve 6a, and the opening timing of the exhaust valve is retarded. As a result, as shown by the dotted line in FIG. 3, the burning of the burned gas from the cylinder in the early stage of the exhaust stroke is prevented, and thereafter, a large amount of the burned gas in the cylinder is discharged at once with the rise of the piston. As a result, the inflow of exhaust gas to the particulate trap 4 is temporarily suppressed,
The same effect as described above can be obtained. As a means for freely changing the opening timing of the exhaust valve, an electromagnetically driven (solenoid or piezoelectric element) type intake / exhaust valve capable of independently controlling only the exhaust valve or both the intake valve and the exhaust valve is used. The same control can be realized.

FIG. 4 is a schematic view of an internal combustion engine equipped with an exhaust gas purifying apparatus according to a second embodiment of the present invention. In the present embodiment, unlike the first embodiment, an on-off valve is not provided in each communication path 6. In the present embodiment, when the exhaust resistance of the particulate trap 4 increases due to the accumulation of ash, the fuel supply to the specific cylinder is stopped and the specific cylinder is stopped. Since combustion does not occur in the cylinder when the exhaust valve of the specific cylinder is opened,
The downstream side of the surge tank during the intake stroke has a negative pressure.
On the other hand, the pressure in the exhaust collecting section 2 at this time has become higher than the atmospheric pressure due to the end of the exhaust stroke of the other cylinders. Accordingly, when the exhaust valve of the specific cylinder is opened, as shown in FIG. 5, which is a change in the flow rate of the exhaust gas flowing into the particulate trap 4 corresponding to the specific cylinder to be stopped, the pressure in the cylinder of the specific cylinder decreases. The flow rate of the exhaust gas flowing into the particulate trap 4 becomes a negative value due to the pressure difference between the pressure downstream of the particulate trap 4 corresponding to the specific cylinder and the exhaust gas.
Flows back through the particulate trap 4 into the specific cylinder.

The ash is deposited on the particulate trap 4 so as to minimize the passage resistance against the positive exhaust gas flowing toward the exhaust collecting section 2. As a result, the passage resistance to the backflow exhaust gas is relatively large, and is easily broken down and fined by the backflow exhaust gas generated by the above-mentioned differential pressure. Unlike the ash immediately after being generated in the cylinder, the ash refined in this way is less likely to adhere to the particulate trap 4 because the sticky SOF has disappeared, and the subsequent exhaust stroke of the specific cylinder Is easily discharged to the downstream side of the particulate trap 4 by the positive flow generated at

In the present embodiment, since no on-off valve is provided in the communication passage 6, during the exhaust stroke of the stopped specific cylinder, all the particulate traps 4 are returned through the respective communication passages 6 to the backflow exhaust gas. Will be passed.
However, in the particulate traps 4 other than the particulate trap 4 corresponding to the specific cylinder, the amount of the backflow exhaust gas is inevitably small because the extra flow has to pass through the communication passage 6. Results in a slow flow velocity. As described above, the ash is liable to be broken by the backflow exhaust gas at the slow flow rate because the ash is deposited on the particulate trap 4 so that the passage resistance against the backflow is relatively large. However, in order to more reliably remove the ash in all the particulate traps 4, it is preferable to sequentially change the specific cylinders to be stopped.

Further, each communication passage 6 may be provided with an on-off valve similar to that of the first embodiment, and each on-off valve may close each communication passage 6 in the exhaust stroke of a specific cylinder to be stopped. As a result, it is necessary to sequentially change the specific cylinder to be stopped. However, the backflow exhaust gas passes only through the particulate trap 4 corresponding to the specific cylinder, and the backflow exhaust gas passing through the other particulate traps 4 is generated. As a result, the amount and flow velocity of the backflow exhaust gas passing through the particulate trap 4 corresponding to the specific cylinder are increased, and good ash removal can be achieved.

In the cylinder deactivation control of this embodiment, if the opening of a throttle valve (not shown) arranged upstream of the intake branching section 22 is reduced only during the intake stroke of a specific cylinder, the cylinder enters the specific cylinder. Since the supplied intake air amount is reduced, the degree of the negative pressure in the cylinder when the exhaust valve is opened can be increased. As a result, the differential pressure between the in-cylinder pressure of the specific cylinder and the pressure downstream of the particulate trap 4 corresponding to the specific cylinder increases, and the flow velocity of the backflow exhaust gas flowing into the particulate trap 4 increases, and Ash can be broken more easily.

Even if the throttle valve opening is reduced during the intake stroke of a specific cylinder and the throttle valve opening is increased immediately thereafter, the throttle valve is supplied to the cylinder that will enter the next intake stroke due to a delay in the increase in intake. The amount of intake air also decreases, and the engine output may decrease more than intended. In order to solve this problem, in the present embodiment, an intake throttle valve 21 is provided at each of the intake ports 20 that communicates the intake branch portion 22 with each of the cylinders. Thus, the intake throttle valve 21 provided at the intake port 20 of the specific cylinder to be stopped
By reducing the amount of intake air supplied to a specific cylinder by
Ash can be more reliably removed from the particulate trap 4 corresponding to a specific cylinder without affecting the amount of intake air supplied to another cylinder.

Further, when the exhaust valve of the specific cylinder to be stopped is opened, if the exhaust control valve 10 has been operated in the valve closing direction before that, the outflow of exhaust gas from the exhaust collecting section 2 to the downstream side is suppressed. As a result, the pressure in the exhaust collecting section 2 is increased.
Thereby, the differential pressure between the in-cylinder pressure of the specific cylinder and the pressure on the downstream side of the particulate trap 4 corresponding to the specific cylinder increases, and the flow velocity of the backflow exhaust gas generated by this differential pressure can be further increased. Thus, the accumulated ash can be more reliably broken down and removed.

Instead of operating the exhaust control valve 10 in the valve closing direction, the variable nozzle 9 of the turbocharger is operated to the throttle side, or the control valve 5a of the exhaust gas recirculation passage 5 is operated in the valve closing direction. However, similarly, when the exhaust valve of the specific cylinder to be stopped is opened, the outflow of the exhaust gas from the exhaust collecting section 2 is suppressed, and the pressure in the exhaust collecting section 2 can be increased. Can be obtained.

As described above, in the first embodiment, the exhaust control valve 10, the variable nozzle 9 of the turbocharger, and the control valve 5a of the exhaust gas recirculation device 5 temporarily prevent the exhaust gas from flowing into the particulate trap. In this embodiment, it functions as an outflow suppressing means for suppressing the outflow of the exhaust gas from the exhaust gas collecting section 2.

In this embodiment, the camshaft for the intake valve and the camshaft for the exhaust valve of the internal combustion engine are
A variable valve timing mechanism similar to that of the first embodiment is provided. Thereby, in particular, it is possible to continuously change the closing timing of the intake valve and the opening timing of the exhaust valve.

In the case where such a variable valve timing mechanism is provided, the closing timing of the intake valve is generally set at, for example, from the bottom dead center of the intake to prevent the intake air from returning at low speed. , 20 crank angles, and at a high speed, for example, 60 crank angles from the intake bottom dead center in consideration of an increase in the intake air amount due to the inertia of the intake air. Therefore, the closing timing of the intake valve in each engine operating state is controlled by the variable valve timing mechanism.
By changing from such an optimal timing for increasing the intake air amount, the intake air amount supplied to the specific cylinder to be stopped can be reduced, and the degree of the negative pressure in the specific cylinder when the exhaust valve is opened Can be increased. As a result, the differential pressure between the in-cylinder pressure of the specific cylinder and the pressure downstream of the particulate trap 4 corresponding to the specific cylinder increases, and the flow velocity of the backflow exhaust gas flowing into the particulate trap 4 increases, and Ash can be broken more easily.

If the closing timing of the intake valve is set near the intake top dead center, the negative pressure in the specific cylinder at the time of opening the exhaust valve can be maximized. It is possible to further increase the pressure difference from the pressure on the downstream side of the particulate trap 4 corresponding to the specific cylinder. Such closing of the intake valve can be easily performed by, for example, a variable valve timing mechanism that enables the intake valve to be kept closed by disabling the cam.

In general, the opening timing of the exhaust valve is set at, for example, 30 crank angles before the explosion bottom dead center at low speed, and from the explosion bottom dead center at high speed.
For example, it is set 80 crank angles before. Therefore, by changing the valve opening timing of the exhaust valve to near the bottom dead center of the explosion by the variable valve timing mechanism, the amount of intake air supplied to the specific cylinder to be deactivated is reduced by the variable cylinder timing when the exhaust valve is opened. The degree of negative pressure can be maximized. As a result, the differential pressure between the in-cylinder pressure of the specific cylinder and the pressure downstream of the particulate trap 4 corresponding to the specific cylinder increases, and the flow velocity of the backflow exhaust gas flowing into the particulate trap 4 increases, and Ash can be broken more easily.

As described above, by reducing the in-cylinder pressure of the specific cylinder to be deactivated or increasing the pressure on the downstream side of the particulate trap corresponding to the specific cylinder to be deactivated by various means, the differential pressure between the two is reduced. As a result, the flow rate of the backflow exhaust gas flowing into the particulate trap is increased, and the accumulated ash can be easily broken. However, an on-off valve similar to the first embodiment is provided in each communication passage 6. If provided, in the exhaust stroke of the specific cylinder to be deactivated, by closing each communication passage 6 by each open / close valve, the backflow exhaust gas passes only through the particulate trap 4 corresponding to the specific cylinder. As a result, since the amount and the flow velocity of the backflow exhaust gas are increased, it is possible to remove ash more favorably.

By the way, there is no guarantee that the high-load high-speed operation of the engine for regenerating each particulate trap 4 by burning out the collected particulates will be performed frequently. A relatively large amount of particulates may be trapped in the particulate trap 4.

If a relatively large amount of particulates is trapped, a large amount of heat may be generated at the time of burning, and the particulate trap 4 may be damaged. To prevent this problem, each particulate trap 4
When a relatively large amount of particulates is deposited, the deposited particulates must be broken down and discharged from each of the particulate traps 4 quickly and reliably.

Although the deposited particulates are more likely to collapse than ash, the relatively high-speed positive flow exhaust gas generated by closing each communication passage 6 by each on-off valve 6a quickly and reliably deposits the particulates. May not be able to be broken. Also in this case, if each control of the first embodiment and the second embodiment is used, a relatively large amount of deposited particulates can be quickly and reliably discharged from each particulate trap 4.

Each control of the first embodiment and the second embodiment for discharging ash or particulates from the particulate trap is performed by the first pressure sensor 7a and the second pressure sensor 7b immediately upstream of the particulate trap 4. The differential pressure between the side portion and the immediately downstream portion may be detected, and the detection may be performed when the exhaust resistance becomes equal to or more than a predetermined value based on the differential pressure. You may make it implement.

Further, in the first embodiment, in order to discharge ash or particulates from the particulate trap, in the second embodiment, in order to discharge ash or particulates from the particulate trap more reliably, Although the on-off valves arranged in each communication passage are closed, it is not necessary to close all on-off valves at the same time, and an exhaust port in which a specific particulate trap for discharging ash or particulates is arranged. What is necessary is just to close at least the on-off valve arranged in the communication path for communicating with another exhaust port.

[0065]

According to the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, a particulate trap disposed at each of the exhaust ports communicating the exhaust collecting section and each of the cylinders in the engine exhaust system; A communication path for communicating each exhaust port with at least one other exhaust port, a normally open / closed valve disposed in each communication path, and exhaust gas to at least one particulate trap. Inflow suppression means for temporarily suppressing the inflow of exhaust gas, and, if necessary, temporarily suppressing the inflow of exhaust gas into at least one particulate trap by the inflow suppression means. The exhaust port where the particulate trap is located is placed in a communication passage for communicating with the other exhaust port. To adapted to close the open-close valve, this inhibition when it is released all at once to a large amount of exhaust gas passes through the particulate trap at a very high speed. This very high-speed exhaust gas can easily break the ash that accumulates in the particulate trap into small pieces and discharge it to the downstream side of the particulate trap.

Further, according to another exhaust gas purifying apparatus for an internal combustion engine according to the present invention, a particulate trap disposed at each of the exhaust ports communicating the exhaust collecting section and each of the cylinders in the engine exhaust system; On the exhaust upstream side of the particulate trap, a communication path for communicating each exhaust port with at least one other exhaust port, and a normally open on-off valve arranged in each communication path,
At the time of high engine load, the on-off valve arranged in the communication passage for communicating at least one exhaust port with another exhaust port as necessary is temporarily closed. The combustion pressure is increased as compared with the normal case, and very high-speed exhaust gas passes through the corresponding particulate trap in the exhaust stroke of the cylinder corresponding to at least one exhaust port. Thereby, the same effect as described above can be obtained.

According to still another exhaust gas purifying apparatus for an internal combustion engine according to the present invention, there is provided a particulate trap disposed at each of the exhaust ports communicating the exhaust collecting section and each cylinder in the engine exhaust system, A communication path for communicating each exhaust port with at least one other exhaust port on the exhaust upstream side of each particulate trap, and a deactivating means for temporarily deactivating at least one cylinder are required. At least one of the cylinders is temporarily stopped by the stop means in accordance with the following.When the exhaust valve is opened in the exhaust stroke of the stopped cylinder, the negative pressure in the stopped cylinder and the stopped cylinder Exhaust gas flows back into the deactivated cylinder through this particulate trap due to the pressure difference with the pressure downstream of the corresponding particulate trap. To. Since the shape of the ash deposited on the particulate trap is relatively easily collapsed with respect to the backflow exhaust gas, the ash deposited on the particulate trap is easily broken by the backflow exhaust gas, and the same effect as described above is obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view of an engine exhaust system to which an exhaust gas purifying apparatus according to a first embodiment of the present invention is attached.

FIG. 2 is a graph showing a flow rate of exhaust gas flowing into a specific particulate trap when the on-off valve is opened in the exhaust gas purification apparatus of the first embodiment.

FIG. 3 is a graph showing a flow rate of exhaust gas flowing into a specific particulate trap when the on-off valve is closed in the exhaust gas purification apparatus of the first embodiment.

FIG. 4 is a schematic view of an internal combustion engine to which an exhaust gas purifying apparatus according to a second embodiment of the present invention is attached.

FIG. 5 is a graph showing a flow rate of exhaust gas flowing into a specific particulate trap when a specific cylinder is stopped in a second embodiment.

[Explanation of symbols]

 Reference Signs List 2 Exhaust collecting part 3 Exhaust port 4 Particulate trap 5 Exhaust recirculation passage 6 Communication path 6a On-off valve 9 Variable nozzle 10 Exhaust control valve 20 Intake port 21 Intake throttle valve 22 Intake branch Department

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02B 37/12 302 F02D 9/04 E F02D 9/04 G 13/02 J 13/02 17/02 M 17/02 Q F02M 25/07 550R F02M 25/07 550 F02B 37/12 301N (72) Inventor Jun Tahara 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hiromichi Yanagihara 1 Toyota Town, Toyota City, Aichi Prefecture No. Toyota Motor Co., Ltd. (72) Inventor Yasushi Yasushi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd.

Claims (14)

[Claims] 1. A particulate trap disposed at each exhaust port that communicates between an exhaust collecting portion and each cylinder in an engine exhaust system, and at least one of the exhaust ports is disposed at an exhaust upstream side of each of the particulate traps. A communication path for communicating with one of the other exhaust ports, a normally open / closed valve disposed in each of the communication paths, and a flow of exhaust gas to at least one of the particulate traps can be temporarily suppressed; Wherein the at least one particulate trap is disposed while temporarily suppressing the inflow of exhaust gas into the at least one particulate trap by the inflow suppression means as required. The opening disposed in the communication passage for communicating the exhaust port with another exhaust port. An exhaust gas purifying apparatus for an internal combustion engine, comprising closing a valve. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said inflow suppressing means is an exhaust throttle mechanism arranged in an engine exhaust system. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said inflow suppressing means is a variable nozzle throttle mechanism for a turbocharger / turbine disposed in an engine exhaust system. 4. The internal combustion engine according to claim 1, wherein the inflow suppressing means is a control valve of an exhaust gas recirculation passage connected to a downstream side of each of the particulate traps in the engine exhaust system. Exhaust gas purification device. 5. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said inflow suppressing means is a retarding means for retarding an opening timing of an exhaust valve. 6. A particulate trap disposed in each of exhaust ports communicating an exhaust collecting section and each cylinder in an engine exhaust system, and at least one of the exhaust ports is provided at an exhaust upstream side of each of the particulate traps. A communication path for communicating with one of the other exhaust ports, and a normally open on-off valve arranged in each of the communication paths, and at least one of the exhaust ports as necessary at a high engine load. An exhaust gas purification apparatus for an internal combustion engine, wherein the on-off valve arranged in the communication passage for communicating with another exhaust port is temporarily closed. 7. A particulate trap disposed at each exhaust port that communicates between an exhaust collecting part and each cylinder in an engine exhaust system, and at least one of the exhaust ports is provided at an exhaust upstream side of each of the particulate traps. A communication path for communicating with one of the other exhaust ports, and a deactivating means for temporarily deactivating at least one cylinder, and the deactivating means temporarily stops the at least one cylinder if necessary. An exhaust gas purifying apparatus for an internal combustion engine, wherein the exhaust gas purifying apparatus is temporarily stopped. 8. A normally open on-off valve is arranged in each of said communication passages, and when said at least one cylinder is temporarily stopped by said stopping means, said at least one cylinder communicates with said exhaust collecting part. 8. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, wherein the on-off valve arranged in the communication passage for communicating the exhaust port with another exhaust port is closed. 9. The cylinder according to claim 1, wherein said at least one cylinder is in an exhaust stroke when the cylinder is deactivated by said deactivation means, and said exhaust port is disposed in said exhaust port communicating said at least one cylinder and said exhaust collecting part. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7 or 8, further comprising a differential pressure increasing unit configured to increase a differential pressure between the pressure on the downstream side of the particulate trap and the pressure on the downstream side of the particulate trap. 10. The outflow suppressing means for suppressing outflow of exhaust gas from the exhaust collecting part prior to an exhaust stroke of the at least one cylinder when the engine is stopped by the stopping means. The exhaust gas purifying apparatus for an internal combustion engine according to claim 9, wherein: 11. The internal combustion engine according to claim 9, wherein said differential pressure increasing means is an intake throttle mechanism for reducing an amount of intake air to said at least one cylinder when stopped by said stopping means. Engine exhaust purification device. 12. The exhaust gas purifying apparatus for an internal combustion engine according to claim 11, wherein the intake throttle mechanism is disposed in an intake port communicating the at least one cylinder and an intake branch. 13. An intake valve closing timing for changing a closing timing of an intake valve so as to reduce an intake amount to the at least one cylinder when the differential pressure increasing means is stopped by the stopping means. The exhaust gas purifying apparatus for an internal combustion engine according to claim 9, which is a changing means. 14. An exhaust valve opening time changing means for changing an opening time of an exhaust valve of at least one of the cylinders near the bottom dead center when the intake means is stopped by the intake pressure means. The exhaust gas purifying apparatus for an internal combustion engine according to claim 9, wherein: