JPH05195752A - Exhaust gas purification device with alternate filter regeneration - Google Patents

Abstract

PURPOSE:To lessen the intra-filter temp. difference of an exhaust gas purification device equipped with a dual filter of alternate regeneration system by reducing heat radiation at the peripheral part when filter is to be regenerated. CONSTITUTION:An exhaust gas purification device changes over, at the time of filter regeneration, two filters 5, 6 from the particulate collecting mode to regenerating mode one after the other for regenerating the filters alternately. When the two filters 5, 6 are installed within inner casings 3, 4 in a muffler 1 for regeneration of one of the filters 5/6, the exhaust gas passing through the filter 6/5 on the particulates collection side is left flowing to the peripheral space b/a of the filter 5/6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device provided in an internal combustion engine, and more particularly to a so-called dual filter type exhaust gas purification device having two filters for collecting diesel particulates discharged from a diesel engine.

[0002]

2. Description of the Related Art For example, exhaust gas of a diesel engine contains a large amount of exhaust particulates, that is, particulates. Therefore, the exhaust system of the engine has a particulate filter (hereinafter referred to as a filter) for collecting the particulates. Called) is installed.

When the amount of particulates accumulated inside the filter increases as it is used, the air permeability is gradually impaired, and the engine performance deteriorates. Therefore, the filter is regularly used depending on the amount of particulates collected. Must be regenerated.

This filter regeneration treatment is accomplished, for example, by heating an electric heater provided in the vicinity of the end face of the filter to ignite the particulates in the filter. At this time, because of particulate combustion in the filter,
For example, regeneration gas represented by air (also called secondary air) is introduced.

By the way, in this field, in order to improve the performance of collecting particulates, a so-called dual filter type exhaust purification device is known in which one exhaust pipe is branched and a filter is arranged in parallel inside each. In addition, in Japanese Utility Model Laid-Open No. 63-14819, in connection with this exhaust gas purification device, when the filter is regenerated, the downstream passage of the regeneration side filter is shut off and the exhaust gas is allowed to flow only to the particulate collection side filter. There is disclosed a regeneration device in which a heater of a regeneration filter is energized, secondary regeneration air is supplied from the downstream side, and the regeneration process is alternately performed by the two filters.

[0006]

However, in this regenerator, when one of the filters is regenerated, the exhaust gas from the engine body is entirely guided to the particulate trapping side filter, so that the outer periphery of the regenerating side filter is There is a possibility that it will be cooled by heat radiation and there will be a large amount of unburned particulate residue, and there is a risk that stable filter regeneration processing cannot always be executed.

The present invention has been made in view of the problems of the alternate filter regeneration exhaust gas purification device, and an object of the present invention is to provide an exhaust gas purification device that enables stable filter regeneration at all times.

[0008]

To achieve the above object, according to the present invention, an exhaust passage of a diesel engine is branched into two parts, and a filter for collecting particulates is arranged in each of the branched exhaust passages. Therefore, in the exhaust gas purification device in which these two filters are alternately regenerated, the exhaust gas before or after passing through the particulate collection side filter is recirculated to the outer space of the regeneration side filter during the filter regeneration. There is provided a filter alternate regeneration exhaust gas purification device characterized in that it is made to flow to the exhaust gas.

[0009]

When the filter is regenerated, the outer peripheral portion of the filter on the regeneration side is heated by the exhaust gas before or after passing through the filter on the particulate collection side, so that the temperature drop of the regeneration side filter is prevented. Therefore, it is possible to suppress the occurrence of unburned particulates.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1 showing a schematic structure in which an exhaust emission control device according to the present invention is incorporated in a muffler of a diesel engine, reference numeral 1 is a muffler into which exhaust gas from an engine body (not shown) to be located on the left side in the figure flows. is there.

The muffler 1 is composed of a cylindrical outer casing 2 extending along the exhaust gas flow direction, and the inside of the muffler 1 is divided into two by a partition wall 2a located approximately in the longitudinal direction. ing.

According to this embodiment, in each space in the casing divided by the partition wall 2a, a first tubular member is further provided.
An inner casing 3 and a second inner casing 4 are arranged, and a first filter 5 and a second filter 6 for collecting particulates are housed inside each of them via a holding material 7.

With respect to the muffler 1 constructed as described above, the exhaust gas from the main body of the diesel engine is divided into a first branch pipe 8 and a second branch pipe which are branched on the upstream side of the exhaust gas.
The first branch pipe 8 passes through the end wall 2b of the outer casing 2 as it is, and flows through the branch pipe 9 of
To the inner space a of the inner casing 3, while the second branch pipe 9 is connected to the end wall 2b and to the space b defined between the outer casing 2 and the first inner casing 3. ..

The partition wall 2a located substantially in the center of the outer casing 2 extends to the first inner casing 3 on one side and a pipe 2c opening to the space a, and the second on the other side.
A pipe 2d extending into the inner casing 4 and opening into its inner space c, so that the pipe 2c defines a space d and a space a defined between the outer casing 2 and the second inner casing 4. And the pipe 2d allows the space b and the space d to communicate with each other.

Regarding the exhaust gas discharge from the muffler 1 constructed as described above, the third branch pipe 10 and the fourth branch pipe 11 are connected to the other end wall 2e similarly to the inflow. , The third branch pipe 10 penetrates the end wall 2e
The inner wall of the inner casing 4 opens to the inner space c (downstream side of the second filter 6), the fourth branch pipe 11 is directly connected to the end wall 2e, and opens to the space d.

According to the present embodiment, in the exhaust gas purifying device built in the muffler 1, the exhaust gas flow direction at the time of particulate collection is the flow direction of the regeneration gas (secondary air etc.) at the time of filter regeneration. Since it is a so-called reverse flow regeneration type exhaust emission control device, the electric heater 12 for heating the filter at the time of regeneration of the filter is provided at the ends of the filters 5, 6 on the exhaust downstream side. 4th branch pipe 1
Regeneration gas introduction pipes 13 and 14 for guiding the secondary air for regeneration from the electric air pump P from the downstream side to the corresponding filters are connected to 0 and 11 respectively when the filters are regenerated.

In addition, inside the branch pipes 10 and 11, in the vicinity of the connection with the gas introduction pipe, there is provided a first regeneration gas control valve 15 for achieving a reverse flow of regeneration gas at the time of regeneration of the filter. A second regeneration gas control valve 16 is provided, and on-off valves 17 and 18 for controlling the introduction of regeneration gas are also provided inside the regeneration gas introduction pipes 13 and 14 described above.
In this embodiment, an air filter 19 is also provided on the air intake side of the electric air pump P.

These regeneration gas control valves 15 described above,
16 and the on-off valves 17 and 18 are controlled to be opened and closed by a control circuit (ECU) 20 for inputting operating conditions of the engine and the like.
Outputs a drive signal to the actuators 21-24 which control the operation of each valve.

Further, the control circuit 20 also controls energization to the electric heaters 12 provided in the filters 5 and 6, and when the filters are regenerated, the corresponding electric heaters 12 are regenerated.
The drive signal is output to the heater relay 25 that controls the energization of the power source.

In order to discharge the particulate combustion gas generated at the time of filter regeneration, the first branch pipe 8 and the second branch pipe 9 each have an opening / closing valve inside of which the opening / closing is controlled by a control circuit 20. Gas discharge pipes 28 and 29 with 26 and 27 are connected. In addition, inside the branch pipe near the connection between the branch pipes 8 and 9 and the gas discharge pipes 28 and 29, a first exhaust control valve 30 and a first exhaust control valve 30 that prevent the exhaust gas from being introduced into the muffler 1 during filter regeneration are provided. 2 exhaust control valve 31
Is provided. Incidentally, these valves are opened and closed by the actuators 32 to 35 which are operated by the drive signal from the control circuit 20, like the regeneration gas control valves 15 and 16 described above.

The operation of the exhaust gas purifying apparatus of the present embodiment constructed as above will be described below with reference to FIGS. 2 and 3. 2 (a), (b), and (c) show the particulate collection mode, the first filter regeneration mode, and the particulate collection mode of the exhaust purification system, respectively.
The second filter mode is shown, in which the flow of exhaust gas is shown by solid arrows and the flow of regeneration gas is shown by dotted arrows, and FIG. 3 shows a transition from particulate collection mode to filter regeneration mode. 6 is a time chart showing the operations of the control valves, on-off valves, electric heaters, and electric air pumps described above.

First, when collecting particulates, the first and second regeneration gas control valves 15 and 16 and the first and second exhaust control valves 30 and 31 are both branched pipes 8 to 1 as shown in FIG.
1 is opened so that the exhaust gas from the engine body is guided to the muffler 1. At this time, the on-off valves 17, 18 described above are
Reference numerals 26 and 27 close the gas introduction pipes 13 and 14 and the gas discharge pipes 28 and 29, respectively, and prevent the exhaust gas from flowing into the pipes.

As a result, the exhaust gas flowing into the muffler internal space a through the first branch pipe 8 passes through the first filter 5 as shown in FIG. 2 (a), and at this time, the particulates in the exhaust gas are Is collected, further flows into the space d through the pipe 2c of the partition wall 2a, passes through the outer periphery of the second filter 6, and is then discharged to the outside of the vehicle through the fourth branch pipe 11.

Similarly, the exhaust gas flowing into the outer space b of the first filter 5 through the second branch pipe 9 flows into the space c through the pipe 2d of the partition wall 2a, where the second filter is provided. After the particulates are collected by 6, the particulates are discharged to the outside of the vehicle through the third branch pipe 10.

If the particulates are collected as described above and the control circuit 20 determines that the filter is being regenerated based on the information such as the pressure difference before and after the filter, the traveling distance, and the fuel consumption amount, the exhaust gas purifying apparatus determines that In the filter regeneration mode, the regeneration processes of the first filter 5 and the second filter 6 are sequentially executed.

In operation, however, as shown in FIG. 3, first, a drive signal is output to the corresponding actuator 34 to close the first exhaust control valve 30, and at the same time, the opening / closing valve 26 of the gas exhaust pipe 28 is opened. A drive signal is also output to the actuator 32 to cause the valve to operate. Also, in response to this, the first filter 5
Second regeneration gas control valve 1 for supplying regeneration gas to the
6 is also closed, and a drive signal is output to each of the actuators 22 and 24 so as to open the open / close valve 18 of the gas introduction pipe 14.

Then, in synchronism with the operation of the valve, the electric heater 12 of the first filter 5 is energized to heat the filter, and the electric air pump P is further started to drive the secondary secondary for regeneration necessary for particulate combustion. Supply air. Regarding the supply of the regeneration gas, in this embodiment, as shown in FIG. 3, the regeneration gas is initially supplied to the filter at a low flow rate to prevent the particulate flame from being blown out.

When the first filter 5 is regenerated, the exhaust gas from the engine body is discharged from the second branch pipe as shown in FIG. 2 (b) by operating each valve, the electric heater and the electric air pump as described above. It flows into the space b on the outer peripheral side of the first filter via 9 and heats the outer peripheral portion of the filter at this time, and then is discharged to the outside of the muffler through the pipe 2d, the space c and the second filter 6. Become.

Further, the regeneration gas from the electric air pump P flows into the space d from the fourth branch pipe 11, enters the space a in which the first filter 5 is accommodated via the pipe 2c, and is collected in the first filter 5. After the particulates are burned, they are discharged to the outside from the first branch pipe 8 through the gas discharge pipe 28.

When the regeneration of the first filter 5 is completed in this way, the control circuit 20 stops the output of the drive signals to the actuators of the above-mentioned control valves and on-off valves, and the exhaust gas purification device operates as described above. It comes to take the particulate collection mode. It should be noted that the apparatus will move to the regeneration processing of the second filter 6 next, but in the present embodiment, the regeneration processing of FIG.
As shown in (2), the two filters are not continuously regenerated, and after the particulate collection is executed to some extent in the meantime, the regeneration processing of the second filter 6 is started.

Therefore, in regenerating the second filter 6, the valve operation opposite to the regenerating operation of the first filter 5 described above is executed, and the second exhaust control valve 31 is closed and the gas exhaust pipe 29 is closed. The actuators 35, 33, 21 and 2 are arranged so that the opening / closing valve 27 is opened, the first regeneration gas control valve 15 is closed, and the opening / closing valve 17 of the gas introduction pipe 13 is opened.
The drive signal is output to 3. Also, almost in synchronism with this valve operation, the electric heater 12 of the second filter 6 is energized to start driving the electric air pump P to supply the secondary air for regeneration necessary for particulate combustion.

As a result, as shown in FIG. 2 (c), the exhaust gas from the engine body passes through the first branch pipe 8 and the first filter 5
Will flow into the space a in which the particulate matter is stored, and after the particulates are collected here, the particulates flow into the space d on the outer peripheral side of the second filter 6 on the regeneration side via the pipe 2c, where the regeneration side filter is Is heated from the outer peripheral side and finally discharged from the fourth branch pipe 11 to the outside.

Regarding the regeneration gas flow from the electric air pump P at this time, it flows into the space c from the third branch pipe 10 and, after filter regeneration here, enters into the space b through the pipe 2d and the second The exhaust gas is exhausted from the branch pipe 9 to the outside via the gas exhaust pipe 29, and when the regeneration of the second filter 6 is completed, the exhaust gas purification device is returned to the particulate collection mode again. ..

As described above, according to the present embodiment, since the exhaust gas always passes through the outer periphery of the regeneration side filter at the time of regeneration of the filter, the regeneration side filter is heated (or kept warm) by the exhaust gas heat. ) Will be done,
It is possible to prevent defective reproduction (occurrence of particulate unburned residue) due to heat radiation from the outer peripheral portion at the time of reproduction and generation of cracks due to the difference in inner and outer peripheral temperatures.

In addition, according to the present embodiment, since it has both the function as the exhaust gas purification device and the function as the muffler, the mountability is significantly improved as compared with the case where these devices are separately configured. ..

By the way, when a vehicle equipped with the above-described exhaust gas purification device operates at high speed and under high load, the temperature of the exhaust gas naturally rises and the temperature of the filter rises. There is a risk that the air will flow into the filter, and the particulate matter trapped in the filter will burn at once and melt, even though it is not at the regeneration time.

FIG. 4 shows an exhaust purification system as a second embodiment of the present invention in which the exhaust gas temperature at the filter inlet is set to, for example, 500 ° C. or lower in order to cope with such a problem. In the present embodiment, the configuration will be described by taking an example of a forward flow regeneration type exhaust emission control device, but it is naturally applicable to a reverse flow regeneration type device as in the first embodiment. Further, regarding the present drawing, the same components as those in the first embodiment are designated by the same reference numerals, and the description of their operation will be omitted.

In order to achieve the above object, according to this embodiment, between the first and second exhaust control valves 30 and 31 and the muffler 1, bellows pipes (bellows pipes) 36 and 37 having an appropriate length are provided. Is provided. This is the bellows pipe 36,3
Due to the unique shape of 7 itself, the surface area is increased as compared with a normal pipe, the heat radiation amount of the branch pipe is increased, and the bellows pipes 36, 37 are interposed so that the muffler 1 itself is positioned on the exhaust gas downstream side as much as possible. The temperature of the gas flowing into the filter is intended to be lowered with the extension of the exhaust gas flow path. In the present embodiment, the first and second regeneration gas control valves 15 and 16 are provided in the vicinity of the exhaust retarder valve 38 acting as an exhaust brake, and because of their positions (high temperature locations), the control valve body It prevents sticking to the inner wall of the branch pipe.

The exhaust gas purifying apparatus according to the present invention has been described above with reference to the two examples of the muffler united type. However, as described above, the present invention is applicable to any regeneration method (forward flow, reverse flow).
However, it is applicable and may be configured separately from the muffler.

[0040]

As described above, according to the present invention, when the filter is regenerated, the outer peripheral portion of the regeneration side filter is heated by the exhaust gas on the particulate collection side, so that the temperature reduction of the regeneration side filter is prevented. Therefore, it is possible to suppress the unburned particulates in this portion and the generation of cracks due to the temperature difference.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an exhaust emission control device as a first embodiment according to the present invention.

2 shows the operation of the exhaust emission control device of FIG. 1, (a) during particulate collection, (b) during regeneration of the first filter, (c).
[Fig. 3] is a diagram showing the time of reproduction of the second filter, respectively.

FIG. 3 is an operation time chart of each component corresponding to each operation in FIG.

FIG. 4 is a diagram showing a configuration of an exhaust emission control device as a second embodiment according to the present invention.

[Explanation of symbols]

 1 ... Muffler 5, 6 ... Filter 8, 9, 10, 11 ... Branch pipe 12 ... Electric heater 20 ... Control circuit P ... Electric air pump b, d ... Peripheral space

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Iwa ▲ Saki ▼ Eiji 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hiromichi Yanagihara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation Stock In the company

Claims (1)

[Claims] 1. An exhaust gas obtained by bifurcating an exhaust passage of a diesel engine, and arranging a filter for collecting particulates in each of the branched exhaust passages, thereby alternately regenerating the two filters. In the purifying device, when the filter is regenerated, exhaust gas before or after passing through the particulate trapping side filter is made to flow into the outer space of the regenerating side filter. Alternate regeneration regeneration exhaust gas purifying device. ..