JPH05272326A - Exhaust particulate trap device - Google Patents

Abstract

PURPOSE:To provide an exhaust particulate trap device by which CO gas is not generated when an exhaust particulate trap is regenerated. CONSTITUTION:An exhaust particulate trap device 1, which is connected to the downstream part of an air exhaust passage 3 of a diesel engine 2, is provided with an oxidized catalyst 5 arranged upstream of the air exhaust passage and an exhaust particulate trap 7 arranged downstream of the oxidized catalyst 5. The exhaust particulate trap device 1 is also provided with the first passage 10 to communicate the oxidized catalyst with the trap 7, a secondary air introducing passage 11 to introduce secondary air to the trap 7, a discharge passage 12 to discharge exhaust air or regenerated gas from the downstream part of the trap 7, the second passage 13 which communicates the discharge passage 12 with the first passage 10 so as to discharge the regenerated gas from the oxidized catalyst 5 to the atmosphere and the third passage (circulating passage) 14 which communicates the discharge passage 12 with the air exhaust passage 3 so as to circulate the regenerated gas from the trap 7 to the upstream part of the oxidized catalyst 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust particulate trap device for collecting particulate matter (particulates) discharged from a diesel engine, and more specifically, an exhaust particulate trap device capable of regenerating the trap. Regarding

[0002]

2. Description of the Related Art Conventionally, a diesel engine burns in a region where the excess air ratio is large, so that CO and HC
Small amount of discharge is that in addition to the emission of NO _X, the property that emissions of soot and organic matter (carbide) particulate material consisting of (particulates) is large. Of these, the reduction of particulates has been an issue because it has a large visual field deterioration and a large effect on health.

Therefore, for the purpose of reducing particulates, an apparatus has been developed in which an exhaust particulate trap composed of a filter is provided in the exhaust passage of the engine and the particulates are collected by the exhaust particulate trap. For example, as shown in FIG. 12, a device has been proposed in which an oxidation catalyst and an exhaust particulate trap are arranged in an exhaust passage of an engine. In this device, during normal operation, the unburned gas in the exhaust is first burned by the oxidation catalyst, and then the particulates are collected by the exhaust particulate trap.

In such an apparatus, the exhaust particulate trap is purified and regenerated by periodically burning and removing the particulates trapped in the exhaust particulate trap. When performing this regeneration, a method is adopted in which secondary air is introduced into the exhaust particulate trap and the particulate is burned and removed by heating with a heater by closing the valve.

[0005]

However, when the exhaust particulate trap is regenerated in this manner, when secondary air is introduced into the exhaust particulate trap and heated, the carbides trapped in the trap are removed. Although it burns, there is a problem that CO gas that cannot be completely oxidized is generated during the burning.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an exhaust particulate trap in which CO gas is not generated during regeneration in the exhaust particulate trap.

[0007]

In order to achieve this object, the present invention is directed to an exhaust passage of a diesel engine in which an oxidation catalyst and an exhaust particulate trap are arranged from the upstream side of the exhaust, and the exhaust particulate trap is provided. In an exhaust particulate trap device that regenerates the exhaust particulate trap by heating with a heater and introducing secondary air from a secondary air introduction path, the exhaust particulate trap is regenerated from the exhaust particulate trap when the exhaust particulate trap is regenerated. The exhaust gas particulate trap device is characterized in that the regenerated gas flowing out is returned to the oxidation catalyst.

Here, the oxidation catalyst may be CO or H.
Platinum or the like that oxidizes C or the like into CO ₂ or H ₂ O can be used. Further, it is preferable to dispose a heater on the upstream side or inside of the oxidation catalyst because the oxidation of CO in the regeneration gas in the oxidation catalyst is promoted. The exhaust particulate trap is not particularly limited as long as it is a regenerable trap, but, for example, a trap having a wall flow type filter structure is preferable because it has excellent trapping ability and durability.

As the heater, for example, a meandering or spiral ribbon heater made of an Fe--Cr alloy arranged upstream or inside the exhaust particulate trap can be adopted. The secondary air introduction passage may be provided on either the upstream side or the downstream side of the exhaust gas of the exhaust particulate trap as long as the secondary air is sent to the exhaust particulate trap during regeneration.

[0010]

According to the present invention having the above-mentioned structure, when the exhaust particulate trap is regenerated by introducing and heating the secondary air, the regeneration gas flowing out from the exhaust particulate trap is returned to the oxidation catalyst. As a result, CO contained in the regeneration gas is oxidized to CO ₂ by the oxidation catalyst.

That is, in the present invention, the CO contained in the regenerated gas can be reduced by causing the regenerated gas in the exhaust particulate trap to flow back to the oxidation catalyst used for the purification of ordinary exhaust gas. Is.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the exhaust particulate trap device of the present invention will be described below. FIG. 1 shows an exhaust particulate trap device 1 as a first embodiment.
The system configuration of is shown.

As shown in FIG. 1, the exhaust particulate trap device 1 is connected to a downstream side of an exhaust passage 3 of a diesel engine 2. The exhaust particulate trap device 1 is mainly composed of an oxidation catalyst 5 arranged on the upstream side of an exhaust gas passage and an exhaust particulate trap 7 (hereinafter referred to as a trap) arranged on the downstream side of the oxidation catalyst 5. It is configured.

Around the oxidation catalyst 5 and the trap 7, there is provided a first passage 10 for communicating the oxidation catalyst 5 and the trap 7.
And a secondary air introduction path 1 for introducing secondary air into the trap 7.
1, a discharge passage 12 for discharging exhaust gas or regeneration gas from the downstream side of the trap 7, and a second passage 13 for connecting the discharge passage 12 and the first passage 10 to discharge the regeneration gas from the oxidation catalyst 5 to the outside. And a third passage (reflux passage) 14 that connects the exhaust passage 12 and the exhaust passage 3 to recirculate the regenerated gas from the trap 7 to the upstream side of the oxidation catalyst 5.

The first passage 10 is provided with a first valve 21 between the second passage upstream opening 13a and the secondary air introduction passage 11 for restricting the passage of gas by an opening / closing operation. A similar second valve 22 is provided in the. In addition, the discharge passage 12 has a third passage downstream opening 14b.
A similar third valve 23 is provided between the second passage downstream opening portion 14b and the second passage downstream opening 14b, and a similar fourth valve 2 is provided in the third passage 14.
4 are provided.

The oxidation catalyst 5 is an ordinary oxidation catalyst made of, for example, platinum, and the HC in the inflowing exhaust gas or regeneration gas is
And CO are oxidized and discharged as H ₂ O and CO ₂ . On the other hand, the trap 7 collects particulate matter (particulates) of carbide such as soot and organic matter contained in the exhaust gas to purify the exhaust gas. For example, FIG. 2 schematically shows its front surface and cross section. As shown in (1), a wall flow type filter structure having a porous thin wall 7a is formed.

When the trap 7 is used for a long period of time, a large amount of particulates adhere and its performance deteriorates. Therefore, the trap 7 is normally regenerated every predetermined period. Regeneration of the trap 7 is a process of introducing and heating outside air (secondary air) into the trap 7 to burn and remove particulates adhering to the trap 7. A heater 26 as shown is attached.

The heater 26 is a meandering ribbon heater arranged on the upstream side and the downstream side of the trap 7.
In addition to the above, the spiral heater 27 shown in FIG. 4 and a portion of the trap 28 shown in FIG.
A structure in which 9 is embedded may be adopted. Further, the heaters 26, 27, 29 may be arranged not only outside the traps 7, 8 but also inside the traps 7, 8.

Further, the first to fourth valves 21 to 24
For example, as shown in FIG. 6, a shutter is driven by air pressure, and by driving the magnet valve 31, the shutter is driven to open and close the passage. Other than that, there is no particular limitation as long as the passage of air is restricted by an opening / closing operation, such as an EGR valve.

Next, the operation of the exhaust particulate trap device 1 having the above structure will be described. First, a normal exhaust gas purification operation will be described with reference to FIG. When the normal diesel engine 2 is operated, the first valve 21 and the third valve 23 are opened and the second valve 22 and the fourth valve 24 are closed.

When the diesel engine 2 is driven in this state, the exhaust gas flows in the order of the exhaust passage 3, the oxidation catalyst 5, the first passage 10, the trap 7, and the exhaust passage 12, as shown by the arrow. As a result, CO and HC are oxidized in the oxidation catalyst 5 and converted into CO ₂ and H ₂ O, and then trap 7 collects particulates such as soot and organic matter in the exhaust gas. The purified exhaust gas is discharged to the outside through the discharge passage 12.

Next, the operation of the trap 7 during regeneration will be described with reference to FIG. When the trap 7 is regenerated, the first valve 21 and the third valve 23 are closed and the second valve 2 is closed, contrary to the case of purifying the exhaust gas.
The second and fourth valves 24 are opened and the second passage 13 is opened.
And the third passage 14 is enabled.

When the diesel engine 2 is driven in this state, the driving force is used to introduce the secondary air into the trap 7 through the secondary air introduction path 11 and the heating by the heater 26. This makes trap 7
Regeneration, that is, combustion of particulates in trap 7.
After the removal, the regeneration gas flowing out of the trap 7 is returned to the oxidation catalyst 5 via the third passage 14, as indicated by the solid arrow. Then, in the recycled regeneration gas, CO in the regeneration gas is oxidized by the oxidation catalyst 5 to generate CO.
It changes to ₂ , and is discharged to the outside through the second passage 13 and the discharge passage 12.

During the regeneration, the exhaust gas from the diesel engine 2 is mixed with the regenerated gas and passes through the oxidation catalyst 5 as shown by a dotted arrow, unless a separate exhaust passage is provided. Then, it is discharged to the outside through the second passage 13 and the discharge passage 12. As described above, in the exhaust particulate trap device 1 of the present embodiment, when the trap 7 is regenerated, the regenerated gas flowing out from the trap 7 is returned to the oxidation catalyst 5 and then discharged. Therefore, the remarkable effect that CO in the regeneration gas can be reduced with a simple configuration is achieved.

Next, the second embodiment will be described with reference to FIG. As shown in FIG. 9, the exhaust particulate trap device 31 of this embodiment has substantially the same configuration as that of the first embodiment, but the heater 3 is provided upstream of the oxidation catalyst 32.
The difference is that 3, 34 are provided. In addition, this heater 3
The ribbon heater and the like described above can be used as 3, 34.

In this embodiment, the same effect as the above embodiment is obtained, and the regeneration gas is heated by the heaters 33 and 34 when the trap 35 is regenerated.
Is advantageous in that the temperature of the oxidation catalyst 32 is low.

Next, a third embodiment will be described with reference to FIG. As shown in FIG. 10, in the exhaust particulate trap device 41 of the present embodiment, the position of the secondary air introduction passage 42 is greatly different from that of the first embodiment.
That is, the secondary air introduction passage 42 is arranged on the downstream side (at the time of exhaust) of the trap 43, and thus the third passage 44, which is the return passage, communicates with the upstream side of the trap 43 (at the time of exhaust).

Therefore, when the trap 43 is regenerated, as indicated by the solid arrow, the secondary air is introduced into the trap 43 as opposed to the exhaust, and the regenerated gas flowing out of the trap 43 recirculates through the third passage 44. Is introduced into the oxidation catalyst 45 and discharged. In this embodiment, the same effect as that of the above embodiment is obtained, and the secondary air flows in the opposite direction to the exhaust flow,
There is an advantage that the particulates can be burned and removed more easily.

Next, a fourth embodiment will be described with reference to FIG. As shown in FIG. 11, the exhaust particulate trap device 51 of this embodiment is provided with two traps 52 and 53, unlike the above-mentioned embodiments. That is, the oxidation catalyst 55 is provided on the downstream side of the exhaust passage 54, and two branched first A and first B passages 56a and 56b are provided on the downstream side of the oxidation catalyst 55, and the respective first A and first B passages 56 are provided.
a, 56b, secondary air introduction paths 57, 58 and trap 5
2, 53 are provided. And each trap 52, 5
3A and 3B, upstream of the oxidation catalyst 55, there are provided third A and third B passages 60, 61.
In the present embodiment, the second passage 13 for discharging the gas as in the first embodiment is not provided, but the flow paths of the traps 52, 53 play the role.

In the present embodiment, when the diesel engine 63 is driven to regenerate the trap 52, for example, the first A valve 65, the third A valve 66, and the fourth B valve 67.
Is closed and the first B valve 70 and the third B valve 7 are closed.
The first and fourth A valves 72 are opened.

Therefore, as indicated by the solid line arrow, the secondary air is introduced into the trap 52 from the secondary air introduction passage 57, and the regeneration gas flowing out of the trap 52 recirculates through the third A passage 60 to generate an oxidation catalyst. Introduced in 55. Then, the regeneration gas oxidized by the oxidation catalyst 55 passes through the first B passage 56.
It is introduced into the trap 53 through b, passes through the trap 53, and is discharged to the outside. At this time, the exhaust gas from the diesel engine 63 is discharged from the oxidation catalyst 5 as indicated by a dotted arrow.
5, passing through the first B passage 56b and the trap 53, and discharged to the outside.

Incidentally, when the other trap 53 is regenerated, the regenerating gas is caused to flow through a route which is symmetrical to the flow passage in which the trap 52 is regenerated, and therefore its explanation is omitted. Therefore, in this embodiment, the same effect as that of the first embodiment is obtained, and the exhaust gas from the diesel engine 63 is also recovered from the oxidation catalyst 55 and the trap 5 when the traps 52 and 53 are regenerated.
2,53 has the advantage of being sufficiently purified.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that the present invention can be carried out in various modes within the scope of the gist of the present invention.

[0034]

As described above in detail, according to the present invention, when the secondary air is introduced to regenerate the exhaust particulate trap, the regeneration gas flowing out from the exhaust particulate trap is returned to the oxidation catalyst. By letting
The CO contained in the regeneration gas is sufficiently converted into CO ₂ by the oxidation catalyst.
It is possible to purify the regenerated gas by changing to. .

That is, according to the present invention, the exhaust particulate trap can be easily regenerated with a simple structure,
Moreover, a remarkable effect that CO gas is reduced at the time of regeneration is exhibited.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an entire exhaust particulate trap device of a first embodiment.

FIG. 2 is an explanatory view showing a front surface and a cross section of a filter structure of an exhaust particulate trap.

FIG. 3 is an explanatory view showing a front surface and a side surface of an exhaust particulate trap in a cutaway manner.

FIG. 4 is a sectional view showing a heater of another embodiment.

FIG. 5 is a perspective view showing a heater of another embodiment.

FIG. 6 is an explanatory diagram showing a configuration of a valve.

FIG. 7 is an explanatory diagram showing an operation of the exhaust particulate trap device of the first embodiment during purification of exhaust gas.

FIG. 8 is an explanatory diagram showing an operation of the exhaust particulate trap device of the first embodiment during purification of regenerated gas.

FIG. 9 is a system configuration diagram showing an entire exhaust particulate trap device of a second embodiment.

FIG. 10 is a system configuration diagram showing an entire exhaust particulate trap device of a third embodiment.

FIG. 11 is a system configuration diagram showing an entire exhaust particulate trap device of a fourth embodiment.

FIG. 12 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

1, 31, 41, 51 ... Exhaust particulate trap device 2, 63 ... Diesel engine 3, 54 ... Exhaust passage 5, 52, 45, 55 ... Oxidation catalyst 7, 35, 43, 52, 53 ... Exhaust particulate trap ( Trap) 10, 56a, 56b ... First passage 11, 42, 57, 58 ... Secondary air introduction passage 12 ... Discharge passage 13 ... Second passage 14, 44, 60, 63 ... Third passage (reflux passage) 21, 22, 23, 24, 65, 66, 67, 70, 7
1, 72 ... Valve 26, 33, 34 ... Heater

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area F01N 3/24 N

Claims (1)

[Claims] 1. An oxidation catalyst and an exhaust particulate trap are arranged in the exhaust passage of a diesel engine from the upstream side of the exhaust, the exhaust particulate trap is heated by a heater, and secondary air is introduced from a secondary air introduction passage. In an exhaust particulate trap device for introducing and regenerating the exhaust particulate trap, the regeneration gas flowing out of the exhaust particulate trap is refluxed to the oxidation catalyst when the exhaust particulate trap is regenerated. Exhaust particulate trap device.