JPH04166603A - Backwash type regenerator for diesel particulate filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a backwash regeneration device for a diesel particulate filter that removes particulate matter (diesel particulates) contained in the exhaust gas of a diesel engine. be.

(Prior Art) Diesel engines normally perform combustion in an excess air condition, so the concentrations of HC and CO in their exhaust gas are generally low. However, when a diesel engine lacks air, even when there is sufficient air, carbon particles are generated in the exhaust, which is the main cause of the black exhaust characteristic of diesel engines.

In recent years, installation of an after-treatment device to reduce particulate matter, so-called particulates, emitted from diesel engines, including carbon particles, has been considered. As a post-processing device, there is a particle collector, generally called a particulate trapper, which is equipped with a heat-resistant particle collector filter in the middle of the exhaust passage.

Particulate filters for collecting particles include a ceramic wall type having a porous ceramic wall, a wire mesh type having an aluminum-coated wire mesh, and a ceramic foam type having a foam-shaped ceramic.

However, in the case of any particulate filter,
As the amount of trapped particles increases, the air permeability decreases and the flow of exhaust gas is obstructed, so it is necessary to periodically remove the trapped particles from the filter and regenerate the filter.

Various types of regenerators have been proposed to regenerate diesel particulate filters, but among them, so-called backwash air is flowed through the filter part of the exhaust pipe in the opposite direction to that during exhaust, to collect the particulates in the filter. A backwash type regeneration device is known that blows out particulates into a predetermined storage area.

(Problem to be Solved by the Invention) However, in the conventional backwash type regenerator, one or two backwash nozzles are provided on the exhaust gas downstream side of the filter toward the exhaust gas downstream end of the filter. It is. The backwashing air is controlled by opening and closing the solenoid valve by passing compressed air of 3 to 8 kg/cm2 stored in an air tank through a pipe connected to the nozzle via a solenoid valve. . Since the backwash air released in this manner is released by the nozzle at a speed close to the speed of sound, it is difficult to process the shape of the nozzle so that the velocity distribution is approximately uniform over the entire rear end surface of the filter. Therefore, effective backwashing is limited to only those areas that are hit by this air flow. Therefore, a valve is also provided downstream of the backwash air nozzle for the exhaust gas (i.e., on the opposite side of the main filter), and by closing this valve, a secondary backwash flow is generated over the entire surface of the filter due to the pressure increase in the conical part inside the housing 12. We are doing a full backwash. By the way, the particulates removed from the filter surface by this strong primary backwash flow continue to float along with this strong flow, and when exhaust gas filtration starts again, they return to the filter surface of the raw filter, so the backwash is carried out. There was a problem that reduced the effectiveness of

The purpose of the present invention is to increase the force of backwash air during regeneration in a backwash type regeneration device to completely blow out particulates, and to efficiently and reliably collect particulates blown out from a filter. , to prevent it from remaining on the upstream side of the filter.

(Means for Achieving the Object) In order to achieve the above object, the diesel particulate filter of the present invention adopts the following configuration. That is, in a backwash type regenerator, a Venturi tube-shaped diffuser is disposed in a cavity at the downstream end of a housing that houses a filter, a backwash air nozzle is disposed in the downstream end of the diffuser, and the The throat of the diffuser and the upstream side of the filter are communicated through a return passage, and a storage filter for collecting blown particulates is disposed in the return passage.

(Function) In a backwash type regenerator with such a configuration, during backwashing, the air ejected from the air nozzle imparts kinetic energy to the surrounding air in the process of passing through the diffuser, accelerating it and distributing it evenly across the passage. As a result, a large amount of backwash air, which is larger than the amount of air injected from the air nozzle, is injected almost uniformly over the entire surface of the filter at a moderate speed, and the air is compensated for by the filter. Most of the collected particulates are blown out to the upstream side. On the other hand, since negative pressure is generated at the throat of the diffuser, the air on the upstream side of the filter is sucked into the return passage together with the blown particulates, of which the particulates are stored in the storage area, and the remaining air is re-inhaled into the throat.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the backwash regeneration device 10 according to the present invention includes a substantially cylindrical housing 12 in the middle of an exhaust pipe 11 from an engine (not shown), similar to the conventional device. A filter 13 for collecting diesel battiquinate is housed inside. Housing 12
Inside, there is further a storage filter 14 below the filter 13.
are stored adjacent to each other, and particulates blown out into the upstream cavity 15 of the filter 13 during backwashing are stored in the storage filter 14. (The term "upstream" (or "downstream") is an expression based on the normal flow of exhaust gas, and is used hereinafter with the same meaning unless otherwise specified.) Filter 13 and storage filter 14 are essentially the same type, and in this embodiment, they are formed into a honeycomb structure of porous ceramic material. Elongated rectangular hollow cell 1 inside the filter
3a, 14a, one end of which is closed with a plug 9 at every other end on the upstream side end face and the downstream end face, and a particulate collecting area is provided in the cell having an opening communicating with the upstream end face. A hollow region is formed within the cell having an opening communicating with the downstream end face.

Of the exhaust pipes 11, the upstream exhaust pipe 11a is connected to approximately the center of the end surface 12a of the housing 12. A valve 17 that is opened and closed by an actuator 16 is disposed inside the exhaust pipe 11a, and although this valve 17 is normally open, it is closed during backwashing.

On the other hand, the exhaust pipe 11b on the downstream side is coaxially connected to a substantially conical portion 12b at the rear of the housing 12. A venturi tube-shaped diffuser 16 is coaxially disposed within the exhaust pipe 11b and spaced slightly from the inner wall of the pipe. The diffuser 16 is connected to the inner wall of the exhaust pipe 11b by a suitable support member (not shown), such as a plurality of thin plates extending radially outward from the outer peripheral surface of the diffuser 16.

The downstream end of the diffuser 16 has a slightly widened opening 16.
b, and the tip of the backwash air nozzle 8 has an opening 1 inside it.
It is coaxially inserted with a slight gap between it and 6b. This air nozzle 8 is connected to the near reservoir 1 by a pipe 18.
Air at a predetermined pressure (backwash air) is injected from the air nozzle 8 by opening a valve 20 connected to the air nozzle 9 and disposed in the middle of the pipe 18.

A narrow throat 16 formed in the center of the diffuser 16
A suction hole 21 is formed in the side wall of a, and the suction hole 21 and the downstream end of the storage filter 14 are connected by a return passage 22. This return passage 22 is arranged adjacent to the conical part 12b of the housing 12, and its downstream end passes through the wall of the exhaust pipe 11b and is connected to the suction hole 21. The upstream end of the return passage 22 is connected to a storage filter 14.
However, since the storage filter 14 itself also functions as a passage, the return passage 22 essentially extends to the upstream side of the filter 13.

More specifically, as shown in FIG.
The apex angle θ2 of the diffuser 16 is made to be greater than or equal to the apex angle θ2 of the conical portion 12b, and the apex of the aperture angle of the diffuser 16 and the apex of the conical portion 12b are made to coincide at a point P. With this configuration, the flow of backwash air becomes smooth.

The opening and closing of the actuator 16 and the valve 20 are controlled by a computer 23 that comprehensively controls various devices of the engine.

The action will be explained below.

While the diesel engine is operating, the valve 17 is open, and exhaust gas from the engine flows into the housing 12 from the exhaust pipe 11a, is filtered by the filter 13, and then flows into the exhaust pipe 11b.
is discharged to the outside. Note that a portion of the exhaust gas passes through the storage filter 14 and the return passage 22, and flows from the suction hole 21 to the exhaust pipe 11b.

As the engine 2 continues to operate, particulates in the exhaust gas accumulate in the filter 13. On the other hand, the engine speed and engine load representing the operating state of the engine 2 are sequentially input to the computer 23 and integrated. It is considered that the total amount of particulates collected in the filter 13 increases as the engine speed and the integrated value of the engine load increase. The computer 23 utilizes this relationship, and when the integrated value reaches a predetermined value, the filter 1
It is determined that the time for backwash regeneration in step 3 has come.

If the computer 23 determines that the filter 13 should be regenerated, the computer 23 sends a control signal to the actuator 16 to close the valve 17 when the engine is stopped. Next, the computer 23 controls the valve 20 to open, and the compressed air in the near reservoir 19 is injected from the air nozzle 8 into the opening 16b of the diffuser 16. This injected air passes through the throat portion 16a of the diffuser 16 and the upstream opening 16c, and flows into the conical portion 12b of the housing 12 with force. At this time, the air around the opening 16b of the diffuser 16 is sucked into the diffuser 16 by the air jetted from the air nozzle 8. Further, air around the opening 16c is introduced into the conical portion 12b by an air flow exiting from the opening 16C. Therefore, the total flow rate of the backwash air introduced into the conical part 12b becomes larger than the flow rate of the air injected from the air nozzle 8, and due to the action of the diffuser 16, the conical part
The flow velocity distribution of backwash air in the radial direction of 2b is made uniform. As a result, sufficient and uniform backwash air is injected toward the entire downstream end of the filter 13, and the particulates collected by the filter are evenly and almost completely blown out into the upstream space 15.

On the other hand, since the flow velocity is high in the throat part 16a of the diffuser 16, negative pressure is generated in this part according to Bernoulli's principle, and this negative pressure is passed through the return passage 22 to the cavity 15.
The air containing particulates is sucked out. Therefore, the particulates blown into the cavity 15 do not stay near the upstream end of the filter 13 (they are collected in the storage filter 14).

The particulates collected in the storage filter 14 can be disposed of by, for example, attaching an electric heater to the upstream end of the filter 13, and heating the filter 14 with the electric heater while injecting air from the air nozzle 8 with the valve 17 closed. to burn and burn away the particulates.

After completing the backwash regeneration of the filter 13 and the heating regeneration of the storage filter 14, the computer 23 closes the valve 20 and opens the valve 17, making the engine ready to start.

Although one embodiment of the present invention has been described above, the present invention can be configured in a manner other than the above-described embodiment if necessary. For example, the filters 13 and 14 may be made of heat-resistant materials such as foam metal or the like in addition to ceramics. Various filters with different characteristics are also available. Further, the storage filter 14 and the return passage 22 can also be separately provided apart from the housing 12.

(Effects of the Invention) As described above, the present invention provides a backwash type diesel particulate filter in which a diffuser is disposed on the downstream side of the filter, and a backwash air nozzle is disposed within the downstream end of the diffuser. Therefore, the flow of a large amount of backwash air can be uniformized to an appropriate flow rate over the entire surface by effectively utilizing the air pressure applied to the downstream end face of the filter. As a result, not only the particulates collected in the central part of the filter, but also the particulates collected in the middle and peripheral parts, where unblown air is likely to occur in the past, can be evenly and reliably blown out.

In addition, since the throat of the diffuser and the upstream side of the filter are connected by a return passage, and the storage filter is disposed within the passage, the negative pressure generated in the throat by backwash air can cause the upstream side of the filter to The particulates blown out to the side do not remain in the vicinity of the upstream end of the filter, but are sucked into the return passage together with the backwash air and collected in the storage filter.

Therefore, part of the particulates blown out by the backwash air can be prevented from being collected in the same filter again after the engine is started. Furthermore, since the diffuser creates a backwash flow that acts uniformly over the entire surface of the filter, it is also possible to eliminate the valve on the nozzle side, resulting in the effect of reducing the number of parts.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a backwash type regeneration device for diesel particulate filters according to the present invention, and FIG. 2 is an enlarged sectional view of a diffuser portion of the device. 8... Air nozzle 10... Backwash type regenerator 11... Exhaust pipe 12... Housing 12
b...Conical part 13...Filter 14...
Storage filter 16... Diffuser 17.20.
...Valve 19...Near reservoir 22...Return passage 23...Computer patent applicant Hino Motors Co., Ltd.

Claims (2)

[Claims] (1) A filter is disposed in the middle of the exhaust passage of a diesel engine, a valve is disposed in the exhaust passage on the upstream side of the filter, and an air nozzle that opens toward the upstream side is disposed on the downstream side. , when a predetermined amount of diesel particulates are collected in the filter, the valve is closed and the diesel particulates are blown out to a predetermined storage area by air injected from the air nozzle. In a particulate filter backwash type regeneration device, a ventilary tube-shaped diffuser having a throat in the center is disposed in a cavity on the downstream side of the housing that houses the filter, and a diffuser in the shape of a bench lily tube is disposed in the downstream end of the diffuser. 1. A backwash type regeneration device for a diesel particulate filter, characterized in that the air nozzle is positioned at (2) In addition to the main filter of the backwash type particulate filter, a storage filter is provided in the dust collecting section, and the outlet section of this storage filter and the throat section 16a of the diffuser 16 are connected by a return passage 22, and filtration is carried out by the storage filter. 2. A backwash type regeneration device for a diesel particulate filter according to claim 1, wherein the recovered gas is returned to a diffuser.