WO2018012382A1

WO2018012382A1 - Exhaust gas purification device

Info

Publication number: WO2018012382A1
Application number: PCT/JP2017/024720
Authority: WO
Inventors: 浩典猪股; 浩司夏目
Original assignee: いすゞ自動車株式会社
Priority date: 2016-07-14
Filing date: 2017-07-05
Publication date: 2018-01-18
Also published as: JP2018009507A

Abstract

According to the present invention, a filter 12 that traps particulate matter contained in exhaust gas is disposed at an intermediate position in an exhaust pipe 1. The present invention comprises: a decreasing diameter pipe 27 having a diameter that decreases in the direction of the flow of exhaust gas toward the downstream side; and a filter accommodation pipe 23 that accommodates the filter 12. The decreasing diameter pipe 27 has an outlet 29 connected to an inlet of the filter accommodation pipe 23. The area of an inlet opening plane S7 in the decreasing diameter pipe 27 is larger than the area of a filter projection plane S2 in the flow direction x.

Description

Exhaust gas purification device

The present disclosure relates to an exhaust gas purification device, and more particularly, to an exhaust gas purification device that reduces the frequency of forced regeneration of a filter.

There has been proposed an exhaust gas purification device in which an oxidation catalyst device is disposed in the front stage of the filter case and a filter is disposed in the rear stage (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-013808

By the way, the exhaust gas discharged from the engine tends to have a lower speed and flow rate at the outer peripheral portion than at the central portion in the radial direction of the exhaust pipe before reaching the exhaust gas purification device. That is, the speed and flow rate of the exhaust gas flowing into the oxidation catalyst device is reduced at the outer peripheral portion with respect to the radial central portion of the oxidation catalyst device.

Thereby, in the filter for collecting PM (particulate matter) arranged on the downstream side of the oxidation catalyst device, the amount of PM deposited on the outer peripheral portion is smaller than that in the central portion. Accordingly, when the filter is forcibly regenerated, the central portion with a large amount of accumulation is heated to a high temperature because of the large amount of heat generated by burning PM deposited on the outer peripheral portion with a small amount of accumulation, resulting in a difference in thermal expansion. Therefore, in order to avoid damage to the filter due to the difference in thermal expansion, the amount of PM deposited in the center must be limited.

That is, in addition to the fact that the amount of accumulation at the outer peripheral portion is small, it is necessary to limit the amount of accumulation at the central portion, so that the entire area of the filter cannot be used effectively. Therefore, there is a problem that the frequency with which the filter is forcibly regenerated increases and the fuel consumption deteriorates.

The present disclosure has been made in view of the above, and an object of the present disclosure is to provide an exhaust gas purification device capable of effectively using the entire area of the filter and reducing the frequency of forced regeneration of the filter. It is in.

In the exhaust gas purification device of the present disclosure that achieves the above object, a filter that collects particulate matter contained in the exhaust gas is disposed in the middle of the exhaust pipe through which the exhaust gas discharged from the engine passes. The exhaust gas purification apparatus includes a reduced diameter pipe that is reduced in diameter toward the downstream side in the exhaust gas flow direction and a filter storage pipe that stores the filter, and an outlet of the reduced diameter pipe and an inlet of the filter storage pipe And the area of the inlet opening surface of the reduced diameter pipe is larger than the area of the filter projection surface of the filter in the flow direction.

According to the exhaust gas purifying apparatus according to the present disclosure, the reduced diameter pipe and the filter storage pipe are connected, and the area of the inlet opening surface of the reduced diameter pipe is formed larger than the area of the filter projection surface. Before flowing in, exhaust gas outside in the radial direction can be contracted by the reduced diameter tube and gathered inward. This is advantageous for increasing the speed and flow rate of the outer exhaust gas that has been reduced before flowing into the filter, and makes it possible to make the speed and flow rate of the exhaust gas flowing into the filter uniform.

Therefore, by adjusting the speed and flow rate of the exhaust gas flowing into the filter according to the difference in the passage resistance between the central part and the outer peripheral part of the oxidation catalyst device, the amount of accumulation on the outer peripheral part in the radial direction of the filter is increased. it can. As a result, the difference in the amount of accumulation between the central portion and the outer peripheral portion of the filter is reduced, and the difference in thermal expansion during PM combustion is reduced, so that the amount of PM deposited until forced regeneration of the filter can be increased. That is, according to the present disclosure, the frequency of forced regeneration of the filter can be reduced by effectively utilizing the entire filter area.

FIG. 1 is a perspective view illustrating a first embodiment of an exhaust gas purification device of the present disclosure. FIG. 2 is a longitudinal sectional view in the flow direction illustrating the exhaust gas purification apparatus of FIG. FIG. 3 is a radial cross-sectional view illustrating the size and arrangement position of each device of the exhaust gas purification device of FIG. FIG. 4 is a longitudinal sectional view in the flow direction illustrating the flow of exhaust gas in the vicinity of the reduced diameter tube of FIG. FIG. 5 is a longitudinal sectional view in the flow direction illustrating the second embodiment of the exhaust gas purifying apparatus of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the figure, x is the exhaust gas flow direction (the tube axis direction of the exhaust pipe 1), and y is the radial direction of the exhaust pipe 1 (the direction perpendicular to the flow direction x).

As illustrated in FIG. 1, the exhaust gas purifying device 10 of the first embodiment is disposed in the middle of the exhaust pipe 1 through which exhaust gas discharged from an engine (not shown) passes. In the exhaust gas purification device 10, an oxidation catalyst device 11 and a filter 12 are arranged in order from the upstream side toward the downstream side in the exhaust gas flow direction x. The exhaust gas purification device 10 includes a tubular case 20 that houses the oxidation catalyst device 11 and the filter 12.

As illustrated in FIG. 2, the oxidation catalyst device 11 is composed of a full-through honeycomb substrate formed in a columnar shape in which a cross section in the radial direction y is a circle having a diameter R1. The filter 12 is formed of a wall flow type honeycomb substrate formed in a columnar shape in which a cross section in the radial direction y is a circle having a diameter R2.

The oxidation catalyst device 11 has a porous partition wall 13 made of ceramics using cordierite or the like as a raw material. The partition wall 13 extends in the flow direction x. The oxidation catalyst device 11 is partitioned by the partition wall 13 and has a plurality of vent holes (cells) 14 that pass from the inlet through which the exhaust gas flows in to the outlet through which the exhaust gas flows and serve as exhaust gas flow paths.

The partition wall 13 carries an oxidation catalyst. This oxidation catalyst is a catalyst that oxidizes the purification target component contained in the exhaust gas. Examples of the oxidation catalyst include noble metals such as platinum (Pt), rhodium (Rh) and palladium (Pd). Examples of components to be purified include hydrocarbons, carbon monoxide, and nitric oxide.

The filter 12 has a porous partition wall 15 and a sealing member 16 made of ceramics made of silicon carbide, cordierite or the like. In the filter 12, a plurality of ventilation holes (cells) 17 are formed by the partition wall 15 so as to penetrate from the inlet where the exhaust gas flows in to the outlet where the exhaust gas flows out and serve as the exhaust gas flow path. Either the inlet or the outlet of the vent hole 17 is blocked by the sealing member 16, and the adjacent vent holes 17 are alternately blocked on the inflow side end face and the outflow side end face of the filter 12. .

The case 20 has a connecting diameter-expanding pipe 21, a catalyst accommodating pipe 22, a diameter-reducing pipe 27, a filter accommodating pipe 23, and a connecting diameter-reducing pipe 24. The connecting diameter-expanding pipe 21, the catalyst accommodating pipe 22, the diameter-reducing pipe 27, the filter accommodating pipe 23, and the connecting diameter-reducing pipe 24 are arranged in order from the upstream side to the downstream side in the exhaust gas flow direction x. Are connected to each other. The tube diameters L1 of the connecting diameter-expanding tube 21, the catalyst housing tube 22, the diameter-reducing tube 27, the filter housing tube 23, and the connecting diameter-reducing tube 24 are arranged in a straight line in the flow direction x.

The connecting diameter-expanding pipe 21 connects the exhaust pipe 1 and the catalyst housing pipe 22, and the diameter of the pipe increases toward the downstream side in the flow direction x. The catalyst housing pipe 22 houses the oxidation catalyst device 11 through the holding material 25 inside, and is a circular pipe having a constant tube diameter R7. The filter storage tube 23 stores the filter 12 through the holding member 26 therein, and is a circular tube having a constant tube diameter R8. The connecting diameter-reducing pipe 24 connects the filter housing pipe 23 and the exhaust pipe 1, and the pipe diameter is reduced toward the downstream side in the flow direction x.

The

holding members

25 and 26 are cylindrical inorganic fiber molding mats, and the column surfaces of the filter 12 and the filter storage tube 23 are disposed between the column surface of the oxidation catalyst device 11 and the inner cylinder surface of the catalyst storage tube 22. Each is interposed between the cylindrical surfaces. Examples of the

holding materials

25 and 26 include a material in which a heat expansion material such as vermiculite or a heat resistant material such as ceramic fiber is formed in a mat shape with a binder.

The reduced diameter pipe 27 connects the catalyst storage pipe 22 and the filter storage pipe 23, and the diameter of the pipe is reduced toward the downstream side in the flow direction x. The inlet 28 of the reduced diameter tube 27 is connected to the outlet of the catalyst storage pipe 22, and the outlet 29 of the reduced diameter pipe 27 is connected to the inlet of the filter storage pipe 23.

The inlet 28 of the reduced diameter tube 27 has a tube diameter R7, and the outlet 29 has a tube diameter R8. Between the catalyst storage tube 22 and the filter storage tube 23, a reduced diameter tube 27 having a diameter R7 of the inlet 28 larger than a tube diameter R8 of the outlet 29 is interposed, so that the diameter R7 of the catalyst storage tube 22 is It is larger than the tube diameter R8 of the filter storage tube 23.

Next, the size relationship of each device will be described with reference to FIG. The tube diameter R7 is longer than the diameter R1 of the cross section in the radial direction y of the oxidation catalyst device 11 by the holding material 25. The tube diameter R8 is longer than the diameter R2 in the radial direction y of the cross section of the filter 12 by the holding material 26. That is, the tube diameter R7, the diameter R1, the tube diameter R8, and the diameter R2 are shortened in this order.

The area of the inlet opening surface S7 of the reduced diameter tube 27 (hereinafter referred to as inlet opening area) is larger than the area of the filter projection surface S2 of the filter 12 in the flow direction x (hereinafter referred to as filter projection area). Further, the area of the catalyst projection surface S1 of the oxidation catalyst device 11 in the flow direction x (hereinafter referred to as catalyst projection area) is larger than the filter projection area. That is, the inlet opening area, the catalyst projection area, the area of the outlet opening surface S8 (hereinafter referred to as the outlet opening area), and the filter projection area become narrower in this order.

The filter projection plane S2 referred to here is a plane when the filter 12 is projected in the flow direction x with respect to a plane perpendicular to the exhaust gas flow direction x (a cross section in the radial direction y of the exhaust pipe 1). It is.

Since each of the oxidation catalyst device 11 and the filter 12 of this embodiment has a cylindrical shape, the cross-sectional area obtained from the diameters R1 and R2 of the cross section becomes the catalyst projected area and the filter projected area. In the case where the oxidation catalyst device 11 and the filter 12 have a shape that bulges outward in the middle of the flow direction x or a shape that decreases in diameter toward the flow direction x, the maximum exhaust gas passage area is the catalyst projection area or filter. It becomes the projected area.

When viewed in the flow direction x, the outlet opening surface S8 and the filter projection surface S2 are within the range of the inlet opening surface S7. Further, the outlet opening surface S8 and the filter projection surface S2 are within the range of the catalyst projection surface S1. In this embodiment, each of the catalyst projection surface S1, the filter projection surface S2, the inlet opening surface S7, and the outlet opening surface S8 is arranged concentrically around the tube axis L1.

The region surrounded by the inlet opening surface S7 and the filter projection surface S2, or the region surrounded by the catalyst projection surface S1 and the filter projection surface S2, is the speed and flow rate of the exhaust gas after passing through the oxidation catalyst device 11. It is preferable to be equal to the region where the decrease occurs. In this embodiment, the tube diameter R7 and the diameter R1 are set to a length of 110% or more with respect to the diameter R2.

In the exhaust gas purification device 10, the exhaust gas passes through the oxidation catalyst device 11 and the filter 12 in this order. The oxidation catalyst device 11 oxidizes hydrocarbons contained in the exhaust gas that has flowed into water vapor and carbon dioxide, carbon monoxide to carbon dioxide, and nitrogen monoxide to nitrogen dioxide by the supported oxidation catalyst. In the filter 12, when the inflowing exhaust gas passes through the porous partition wall 15, PM (particulate matter) contained in the exhaust gas is filtered and collected by the sealing member 16.

Exhaust gas discharged from an engine (not shown) flows through the exhaust pipe 1 and reaches the exhaust gas purification device 10. Before reaching the exhaust gas purification device 10, the speed and flow rate of the exhaust gas are reduced at the outer peripheral portion from the central portion in the radial direction y of the exhaust pipe 1 due to friction with the inner cylindrical surface of the exhaust pipe 1. To do.

Here, the speed and flow rate of the exhaust gas flowing into the filter 12 of the exhaust gas purification device 10 will be described with reference to FIG. In FIG. 4, the length of each arrow represents the speed and flow rate of the exhaust gas.

In the exhaust gas purification apparatus 10, the reduced diameter tube 27 and the filter housing tube 23 are connected, and the inlet opening area of the reduced diameter tube 27 is formed larger than the filter projection area. That is, before flowing into the filter 12, the exhaust gas outside in the radial direction y is contracted by the reduced diameter tube 27 and gathered toward the inside. As a result, the speed and flow rate of the exhaust gas that has decreased before flowing into the filter 12 increases, so the speed and flow rate of the exhaust gas flowing into the filter 12 are made uniform.

As described above, the exhaust gas purification device 10 can make the speed and flow rate of the exhaust gas flowing into the filter 12 uniform, so that it is possible to increase the deposition amount of the outer peripheral portion in the radial direction y of the filter 12 as compared with the conventional case. Further, the difference in the amount of accumulated PM between the central portion and the outer peripheral portion of the filter 12 is reduced, and the difference in thermal expansion during PM combustion can be reduced. Therefore, the amount of accumulated PM until the filter 12 is forcedly regenerated can be increased. . That is, according to the exhaust gas purifying apparatus 10 described above, since the entire area of the filter 12 is effectively used and PM that can be collected before the filter 12 forcibly regenerates the filter 12 as compared with the prior art increases. The frequency of 12 forced regenerations can be reduced.

In this embodiment, since the outlet opening surface S8 and the filter projection surface S2 are within the range of the inlet opening surface S7 of the reduced diameter tube 27 when viewed in the flow direction x, the exhaust gas before flowing into the filter 12 is reduced. Since the speed and flow rate can be increased over the entire outer periphery, the speed and flow rate of the exhaust gas flowing into the filter 12 is advantageous for equalization.

In this embodiment, since the exhaust gas purification device 10 desirably has the oxidation catalyst device 11 disposed upstream of the filter 12, the example in which the oxidation catalyst device 11 is disposed upstream of the filter 12 has been described. However, the oxidation catalyst device 11 is not necessarily provided.

When the exhaust gas passes through the oxidation catalyst device 11 and the filter 12 in this order as in this embodiment, the flow of the exhaust gas can be rectified by the oxidation catalyst device 11. That is, in the exhaust gas after passing through the oxidation catalyst device 11, the speed and flow rate on the outside in the radial direction y are lower than those on the center side in the same manner as before reaching the oxidation catalyst device 11. This is advantageous for increasing the speed and flow rate of the exhaust gas outside the diameter tube 27.

Further, when the area of the catalyst projection surface S1 is larger than the area of the filter projection surface S2, the total length of the oxidation catalyst device 11 in the flow direction x can be shortened. The capacity (volume) of the oxidation catalyst device 11 is determined by experiments and tests based on the oxidation rates of hydrocarbons, carbon monoxide, and nitric oxide in the oxidation catalyst device 11. Therefore, when the area of the catalyst projection surface S1 of the oxidation catalyst device 11 is increased, the total length of the oxidation catalyst device 11 in the flow direction x can be shortened, and the capacity of the oxidation catalyst device 11 can be secured in a limited space. This is advantageous for shortening the overall length of the exhaust gas purification device 10 in the flow direction x, and the layout of the exhaust gas purification device 10 can be improved.

In this embodiment, the oxidation catalyst device 11 is made of ceramics, but it may be a full-through type honeycomb substrate made of metal partition walls. Further, although the filter 12 is constituted by a wall flow type honeycomb substrate, a metal mesh type filter may be used. Further, a selective reduction catalyst device for reducing and removing nitrogen oxides contained in the exhaust gas may be provided on the downstream side of the filter 12.

The separation distance between the oxidation catalyst device 11 and the filter 12, that is, the length in the flow direction x of the reduced diameter tube 27 may be shortened within an allowable range.

As illustrated in FIG. 5, the exhaust gas purification device 10 of the second embodiment is different from the first embodiment in that a heat retaining member 30 is provided outside the filter storage tube 23 in the radial direction y.

The heat retaining member 30 is formed in an annular shape and is adjacent to the outside in the radial direction y of the filter storage tube 23 and covers the filter storage tube 23. The heat retaining member 30 fills the step between the outer periphery of the catalyst storage tube 22 and the outer periphery of the filter storage tube 23 generated by the reduced diameter tube 27. Examples of the heat retaining member 30 include a heat retaining mat buried in a step and a tube filling the step. When the heat retaining member 30 is constituted by a tube, an air layer is formed between the filter housing tube 23 and the tube, and functions as a double tube.

Thus, by providing the heat retaining member 30 outside the filter housing tube 23 so as to fill the step formed by the reduced diameter tube 27, it is advantageous for the heat retention of the filter 12. Further, since the heat retaining member 30 can fill a step formed by inserting the reduced diameter tube 27 between the catalyst storage tube 22 and the filter storage tube 23, it is advantageous for the installation of the exhaust gas purification device 10. Become.

This application is based on a Japanese patent application (Japanese Patent Application No. 2016-139104) filed on July 14, 2016, the contents of which are incorporated herein by reference.

The exhaust gas purification apparatus according to the present disclosure is useful in that the fuel efficiency of the internal combustion engine can be improved by reducing the frequency of forced regeneration of the filter.

DESCRIPTION OF SYMBOLS 1 Exhaust pipe 10 Exhaust gas purification apparatus 11 Oxidation catalyst apparatus 12 Filter 22 Catalyst storage pipe 23 Filter storage pipe 27 Reduced diameter pipe S1 Catalyst projection surface S2 Filter projection surface S7 Inlet opening surface

Claims

In the exhaust gas purification apparatus in which a filter that collects particulate matter contained in the exhaust gas is disposed in the middle of the exhaust pipe through which the exhaust gas discharged from the engine passes,
A diameter-reducing pipe reduced in diameter toward the downstream side in the exhaust gas flow direction and a filter storage pipe for storing the filter;
The outlet of the reduced diameter pipe and the inlet of the filter storage pipe are connected,
An exhaust gas purifying apparatus, wherein an area of an inlet opening surface of the reduced diameter pipe is larger than an area of a filter projection surface of the filter in the flow direction.
The exhaust gas purification device according to claim 1, wherein the filter projection surface is within the range of the inlet opening surface as viewed in the flow direction.
An oxidation catalyst device that oxidizes the purification target component contained in the exhaust gas, and a catalyst storage pipe that stores the oxidation catalyst device;
The outlet of the catalyst housing pipe and the inlet of the reduced diameter pipe are connected,
The exhaust gas purification device according to claim 1 or 2, wherein an area of a catalyst projection surface of the oxidation catalyst device in the flow direction is larger than an area of the filter projection surface.
The exhaust gas purification device according to claim 3, wherein the filter projection surface is within the range of the catalyst projection surface when viewed in the flow direction.