JPH03134214A - Diesel exhaust purifying device - Google Patents

Abstract

PURPOSE:To increase a regeneration interval without melt-damaging a filter by providing a particulate capture means in the downstream side from the filter in a flow of exhaust gas, reversed to flow, when the filter is regenerated. CONSTITUTION:The second honeycomb filter 36, in which a honeycomb filter 16 is made small, is provided as a particulate capture means halfway the second bypass passage 34 provided to connect an exhaust passage 12 between the first open-close valve 22 and the honeycomb filter 16 to communicate with a part closed by the second open-close valve 26. Here for filter regeneration, prior to electrification to a heater 18 of the filter 16, the open-close valves 22, 26 are actuated to the second operational position for a predetermined time to allow exhaust gas, introduced to the exhaust passage 12 through the first bypass passage 14, to reversely flow to the filter 16. In this way, a particulate, accumulated in the filter 16, is reduced while collecting the splashed particulate by the second filter 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diesel exhaust purification device that collects and removes particulates in the exhaust gas of a diesel engine.

[Conventional technology]

In order to prevent exhaust particulates such as carbon particles contained in the exhaust gas of diesel engines from being released into the atmosphere, it is known that a honeycomb-shaped filter made of ceramic is placed in the exhaust pipe to collect the exhaust particulates. be.

Honeycomb filters become clogged during long use and must be regenerated. For this purpose, a heater for regenerating the filter is provided downstream of the exhaust gas from the honeycomb filter, and a first bypass passage connected to the exhaust pipe is provided at a position upstream of the filter and a position downstream of the heater. Further, a first on-off valve is disposed in the exhaust passage between the upstream connection position (branching part) and the filter, and the first bypass passage is closed and the exhaust is exhausted at the downstream connection position (merging part). a second on-off valve that occupies a first operating position in which the passage is opened and a second operating position in which the first bypass passage is communicated with an exhaust passage upstream from the merging part and an exhaust passage downstream from the merging part; and further includes an exhaust passage between the first on-off valve and the filter, and a first bypass passage in a portion communicating with the exhaust passage downstream of the confluence in the second operating position of the second on-off valve. The present applicant has previously filed an application for a diesel exhaust purification device using a so-called reverse flow regeneration method, which is provided with a second bypass passage that communicates with the . (Patent application 1986-063655
issue).

[Problem to be solved by the invention]

By the way, in the above exhaust gas purification device, if the filter regeneration interval is lengthened and the amount of particulates accumulated in the honeycomb filter increases, the thermal energy associated with particulate combustion during filter regeneration will increase, and the filter will become hotter. There is a risk that the filter itself may be damaged by melting.

Therefore, currently, the filter regeneration standard is to energize the heater with a small amount of accumulated particulates to prevent the filter from melting during regeneration, and as a result, the regeneration interval is set relatively short. It turns out. Therefore, in such a case, power consumption increases and the running cost of the filter also increases. An object of the present invention is to provide a diesel exhaust purification device that can lengthen the regeneration interval without damaging the filter during regeneration.

[Means to solve the problem]

For the above purpose, according to the present invention, an inlet passage which is defined by a partition wall having air permeability and is open on the exhaust upstream side and an outlet passage which is open on the exhaust downstream side are arranged adjacent to each other, and the exhaust passage downstream end thereof is A filter equipped with a heater is interposed in the exhaust passage of a diesel engine, so that the exhaust gas discharged from the engine is caused to flow from the inlet passage to the outlet passage, and particulates in the exhaust gas are collected in the filter, In the exhaust gas purification device of the backflow regeneration method, which regenerates the filter by igniting and burning the collected particulates by energizing the heater and causing exhaust gas to flow back from the outlet passage to the inlet passage, during filter regeneration, prior to energizing the heater. An exhaust gas purification device is provided, which causes exhaust gas to flow back from the outlet passage to the inlet passage, and further comprises a particulate trapping means provided downstream of the filter in the flow of the exhaust gas that has flowed back.

[For production]

In an exhaust gas purification device using a backflow W generation method, where the flow direction of exhaust gas in the filter during particulate collection is different from the flow direction of exhaust gas in the filter during filter regeneration, the movement of exhaust gas toward the filter during filter regeneration is The pressure blows away some of the particulates that have accumulated in the filter.

The present invention makes use of the above-mentioned features of the backflow regeneration type exhaust gas purification device, and prior to filter regeneration, exhaust gas flows back into the filter to increase the amount of particulates blown away, and when the heater is energized, the amount of particulates present in the filter. By reducing particulate combustion energy by reducing particulate combustion energy, the filter is prevented from being eroded, and by providing particulate capture means on the downstream side of the filter in the reverse flow of exhaust gas, blown particulates are removed from the outside. Prevent spills.

〔Example〕

Preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a so-called backflow regeneration type exhaust purification device in which the flow direction of exhaust gas in the filter during particulate collection is opposite to the flow direction of exhaust gas during filter regeneration. , for example, so as to allow exhaust gas from a diesel engine (not shown) to flow in the direction indicated by the arrow.

Further, the exhaust pipe 10 includes an exhaust passage 12 and a first bypass passage 1.
4, and houses a honeycomb filter 16 made of, for example, a ceramic material for collecting particulates in the exhaust passage 12, and an electric heater wire 18 made of, for example, Kunkle wire (Fe-Cr-A1 alloy). Container 20 is assembled. The honeycomb filter 16 is
An inlet passage 16b defined by a partition wall 16a made of a porous material (for example, cordierite material) is opened on the upstream side of the exhaust gas on the right side in the figure, and an outlet passage 16c is opened on the downstream side of the exhaust gas on the left side in the figure. It is configured. The first bypass passage 14 branches on the upstream side of the exhaust gas from the trap container 20 and is reconnected to the exhaust passage 12 on the downstream side of the exhaust gas from the trap container 20 .

A first on-off valve 22 made of a butterfly valve is arranged in the exhaust passage 12 between the branch position 24 of the first bypass passage 14 and the filter 16. Further, a second on-off valve 26 is arranged at a bypass passage connection position 28 downstream of the exhaust gas from the trap container 20.

The first on-off valve 22 and the second on-off valve 26 are rotatable around valve shafts 30 and 32 that are perpendicular to the plane of the paper in the figure,
It is possible to occupy a first operating position, which is substantially horizontal, as shown in dotted lines in the figure, and a second operating position, as shown in solid lines. In the first operating position, the first on-off valve 22
- side opens the exhaust passage 12, - side, the second on-off valve 26 opens the first
The bypass passage 14 is closed and the exhaust passage 12 is opened. This state shows that particulates in the exhaust gas are collected by the filter 16, the filter, and the inlet passage 16a, and the exhaust gas is flowing in the direction indicated by the dotted arrow in the figure.

In the second operating position, the lower half of the second on-off valve 26 can close the lower half of the first bypass passage 14, but the other part of the first bypass passage 14 is connected to the exhaust passage 12. It goes through. Therefore, the first bypass passage 14 communicates with a portion of the exhaust passage 12 upstream of the connection position 28 on the downstream side and a portion of the exhaust passage 12 downstream of the connection position 28. At this time, the second on-off valve 26 protrudes into the exhaust passage 12, and the second on-off valve 26 protrudes into the exhaust passage 1 toward the exhaust downstream side from the second on-off valve 26.
2 is partially throttled to apply back pressure to the flow of exhaust gas toward the trap container 20, and about 1710 of the exhaust gas guided by the first bypass passage 14 passes through the filter 16 at a desired speed. It can be so.

Further, a second bypass passage 34 is provided to communicate the exhaust passage 12 between the first on-off valve 22 and the honeycomb filter 16 and the other portion closed by the second on-off valve 26 . That is, in the second operating position of the first on-off valve 22 shown by the solid line, the exhaust passage 12 is closed, the exhaust gas from the engine is allowed to flow into the first bypass passage 14, and the exhaust gas is branched by the second on-off valve 26 and passed through the filter. 16 is caused to flow into the second bypass passage 34 via the filter 16. This state includes a filter regeneration pretreatment state (described later) in which particulates in the filter 16 are reduced without heating the heater 18, and a filter regeneration processing state in which the heater 18 is heated to incinerate particulates in the filter 16. The flow of exhaust gas in both directions is shown, and the exhaust gas flows in the direction of the solid line arrow in the figure. Note that the downstream opening 34a of the second bypass passage 34 is controlled to open and close by the second on-off valve 26, and in the second operating position,
The exhaust gas that has passed through the second bypass passage 34 flows directly to the downstream side.

According to the present invention, a second honeycomb filter 36, which is smaller than the honeycomb filter 16 described above, is provided in the middle of the second bypass passage 34 as particulate trapping means. In addition, the first on-off valve 22 and the second on-off valve 26
Actuators 38 and 40 are provided for respectively driving the .

The actuators 38, 40 are actuated according to the output from the engine control computer (B['U) 42, and can rotate the first on-off valve 22 and the second on-off valve 32 to the second operating position. can. Additionally, the electric heater wire 18 can also be energized via a relay 44 controlled by the combinator 42 .

46 is a battery.

FIG. 2 shows an enlarged cross section of the second honeycomb filter 36, in which 36a is a porous partition wall made of a conductive material capable of self-heating (for example, 5iC-silicon carbide);
Reference numeral 36b indicates an inlet passage that is defined by the partition wall 36a and is open on the upstream side of the exhaust gas (in the exhaust gas flow during filter regeneration), which is on the left side in the figure, and 36c is an inlet passage that is open on the downstream side of the exhaust gas, which is on the right side in the figure. It shows the exit passage.

Further, on the end face of the second honeycomb filter 36 on the exhaust upstream side, a + (plus) side collective electrode 36d connected to the partition wall 36a of each passage 36b, 36C is arranged, and on the other hand, on the end face on the exhaust downstream side, a collective electrode 36d is arranged. − (minus) side collective electrode 36e
will be provided.

Like the previous honeycomb filter 16, this second honeycomb filter 36 is energized via a relay 48 controlled by a computer 42 (FIG. 1), and each passage 36b, 36
C itself generates heat, making it possible to ignite and burn the collected particulates.

The operation of the exhaust gas purification device according to the present invention configured as above will be explained.

According to this embodiment, when regenerating the filter of the exhaust gas purification device described above, prior to energizing the heater 18 of the filter 16, the first on-off valve 22 and the second on-off valve 22 and the second
The on-off valve 26 is operated to the second operating position as shown by the solid line in FIG. toward the passage 16G, and the filter 16 due to its dynamic pressure.
The particulates accumulated in the inlet passage 16b are blown away. As a result, the total amount of particulates accumulated in the filter 16 is reduced, and the blown particulates are transferred to the second bypass passage 34, which is downstream of the filter 16 in the exhaust gas flow direction. It will be collected by the interposed second honeycomb filter 36.

In this way, after reducing the amount of particulates accumulated in the filter 16, the heater 18 of the filter 16 is energized. As a result, the amount of heat generated by igniting and burning the particulates by the heater 18 is reduced compared to when the particulates in the filter 16 are burned before exhaust gas is introduced, and problems such as filter melting are prevented. be able to.

FIG. 3 is a conceptual diagram comparing the change over time in the amount of particulates accumulated in the filter of the exhaust gas purification device according to the present invention with that of a conventional device.

As is clear from this figure, the device according to the present invention allows the exhaust gas to flow backwards for a predetermined period of time during filter regeneration, thereby reducing the amount of particulates that had been accumulated up to that point to an amount that has a low possibility of melting. can,
Therefore, the particulate trapping ability of the filter 16 can be maximized without considering melting loss, and the regeneration interval can be set longer than that of conventional devices. Note that the regeneration interval and exhaust gas introduction time as pre-regeneration treatment in this device can be set to optimal values through various experiments, and the second honeycomb filter 36 for collecting blown particulates can be set to the optimum value through various experiments. The regeneration interval can also be determined experimentally by taking into account the capacity of the filter. Note that, as described above, this second honeycomb filter 36 does not always collect particulates, so its capacity can be reduced in size to match the second bypass passage 32 inserted therein, and The regeneration interval can also be set longer than that of the honeycomb filter 16 (reducing the energy required for regeneration). Furthermore, a second honeycomb filter 36
Since it is provided in the second bypass passage 32 through which exhaust gas does not flow during collection, the second honeycomb filter 36 does not become a pressure loss resistance during normal running (during collection). Furthermore, in the embodiment described above, the second on-off valve 26
is formed so that about 1710 of the exhaust gas that is bypassed throughout the filter regeneration process flows back toward the filter, but in another embodiment, the second on-off valve 26
The valve body is made larger, and the intake passage 12 is completely closed only when exhaust gas is introduced before the heater is energized, and all exhaust gas is directed to the filter, and by increasing the dynamic pressure, many particulates are blown away in a short time. Alternatively, the second on-off valve 26 may be controlled in two stages so that it opens slightly so that about 1 to 10 of the exhaust gas is introduced into the filter when the heater is energized.

[Effects of the Invention] As explained above, according to the present invention, during filter regeneration,
By back-flowing the exhaust gas before energizing the heater, it is possible to reduce the particulates accumulated in the filter, and even if there is a large amount of particulates in the filter, it can be regenerated without melting. be. Further, as a result, the particulate collection ability of the filter itself can be increased, and the regeneration interval can therefore be set longer, so power consumption can also be reduced and running costs can be kept low.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the exhaust purification device according to the present invention; Fig. 2 is an enlarged sectional view of the second honeycomb filter; Fig. 3 shows the change over time in the amount of particulates collected by the device of the present invention compared to the conventional device. A conceptual diagram comparing it. 16... Honeycomb filter, 16a... Partition wall, 16b... Inlet passage, 1
6c...Exit passage, 18...Heater, 34...
- Second bypass passage, 36... second honeycomb filter.

Claims (1)

[Claims] 1. An inlet passage which is defined by a partition wall having air permeability and is open on the upstream side of the exhaust gas, and an outlet passage where the downstream side of the exhaust gas is open are arranged adjacent to each other, and a heater is provided at the end on the downstream side of the exhaust gas. The provided filter is interposed in the exhaust passage of the diesel engine, so that the exhaust gas discharged from the engine flows from the inlet passage to the outlet passage, and particulates in the exhaust gas are collected in the filter, and the heater In a diesel exhaust purification device using a backflow regeneration method, which regenerates the filter by igniting and burning the collected particulates by energizing the filter and causing the exhaust gas to flow back from the outlet passage to the inlet passage. An exhaust purification device characterized by causing gas to flow backward from the outlet passage to the inlet passage, and further comprising particulate trapping means provided downstream of the filter in the flow of the reversed exhaust gas.