阅读说明：本技术 颗粒过滤器及其制造方法 (Particulate filter and method for manufacturing same ) 是由 川岛幸博 于 2019-09-05 设计创作，主要内容包括：颗粒过滤器(23)通过将多个具有多个腔室(32)的蜂窝形状的部分(29)、(30)、(31)并列设置而构成。配置于外周部的部分(30)、(31)的腔室的密度被设定为比配置于中央部的部分(29)的腔室的密度低。另外,配置于外周部的部分(30)、(31)被设定为端面的面积越小则腔室(32)的密度越低。(The particulate filter (23) is configured by arranging a plurality of honeycomb-shaped portions (29), (30), and (31) having a plurality of chambers (32) in parallel. The density of the chambers in the portions (30, 31) disposed in the outer peripheral portion is set to be lower than the density of the chambers in the portion (29) disposed in the central portion. The density of the cavity (32) is set to be lower as the area of the end faces of the portions (30, 31) disposed on the outer peripheral portion is smaller.)

1. A particulate filter comprising a plurality of honeycomb-shaped portions having a plurality of chambers arranged in parallel,

the density of the chambers of the portion arranged at the outer peripheral portion is set to be lower than the density of the chambers of the portion arranged at the central portion,

the density of the chamber is set to be lower as the area of the end surface of the portion disposed in the outer peripheral portion is smaller.

2. The particulate filter as claimed in claim 1,

the portion disposed in the outer peripheral portion is set so that the density of the chamber is lower as the portion is farther from the center of the particulate filter.

3. The particulate filter of claim 1 or 2,

the portion is composed of silicon carbide.

4. A method for manufacturing a particulate filter, which is configured by arranging a plurality of honeycomb-shaped portions having a plurality of chambers in parallel,

the combustion remaining amount of the particulate matter disposed in the portion of the outer peripheral portion is measured in advance for each position thereof,

the density of the chambers of the portion arranged at the outer peripheral portion is set to be lower than the density of the chambers of the portion arranged at the central portion,

the density of the chamber is set to be lower as the area of the end surface of the portion arranged on the outer peripheral portion is smaller,

the density of the chamber disposed in the portion of the outer peripheral portion is set to be lower at a position where the residual combustion amount of the particulate matter is larger.

Technical Field

The present disclosure relates to particulate filters and methods of making the same.

Background

The Particulate filter traps Particulate Matter (PM) contained in the exhaust gas.

Therefore, the particulate filter on which the particulate matter is deposited needs to be regenerated by burning the particulate matter or the like.

Patent document

Patent document 1: japanese laid-open patent publication No. 2003-275521

Patent document 2: japanese laid-open patent publication No. 2016-029272

Disclosure of Invention

Technical problem to be solved by the invention

However, in the particulate filter, there is a possibility that combustion residue of particulate matter is generated at the time of filter regeneration. Therefore, the particulate filter may be gradually clogged by repeating the filter regeneration, and the regeneration interval may be shortened. In particular, the combustion residue of the particulate matter tends to be generated in the outer peripheral portion of the particulate filter.

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a particulate filter capable of suppressing combustion residue of particulate matter during filter regeneration, and a method for manufacturing the same.

Means for solving the problems

According to an embodiment of the present disclosure, there is provided a particulate filter configured by arranging a plurality of honeycomb-shaped portions having a plurality of chambers in parallel,

the density of the chambers of the portion arranged at the outer peripheral portion is set to be lower than the density of the chambers of the portion arranged at the central portion,

the density of the chamber is set to be lower as the area of the end surface of the portion disposed in the outer peripheral portion is smaller.

Preferably, the portion disposed in the outer peripheral portion is set so that the density of the chamber is lower as the portion is farther from the center of the particulate filter.

Preferably, the portion is composed of silicon carbide.

In addition, a method for manufacturing a particulate filter, which comprises arranging a plurality of honeycomb-shaped portions having a plurality of chambers in parallel to form a particulate filter,

the combustion remaining amount of the particulate matter disposed in the portion of the outer peripheral portion is measured in advance for each position thereof,

the density of the chambers of the portion arranged at the outer peripheral portion is set to be lower than the density of the chambers of the portion arranged at the central portion,

the density of the chamber is set to be lower as the area of the end surface of the portion arranged on the outer peripheral portion is smaller,

the density of the chamber disposed in the portion of the outer peripheral portion is set to be lower at a position where the residual combustion amount of the particulate matter is larger.

Effects of the invention

According to the above aspect, the combustion residue of the particulate matter during filter regeneration can be suppressed.

Drawings

Fig. 1 is a schematic explanatory view of an internal combustion engine according to an embodiment of the present disclosure.

Fig. 2 is an enlarged view of a main portion of fig. 1.

Fig. 3 is a perspective view of the particulate filter.

Fig. 4 is an enlarged view of a portion a of fig. 3.

Fig. 5 is a diagram showing a state where the regeneration interval is shortened.

Fig. 6 is a front explanatory view of a particulate filter showing a combustion residual amount of particulate matter.

Fig. 7 is a front view showing a particulate filter according to another embodiment.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the embodiments described later, for convenience of explanation, the upstream side is also referred to as the front side, and the downstream side is also referred to as the rear side.

[ embodiment 1 ]

Fig. 1 is a schematic explanatory view of an internal combustion engine (engine) according to the present embodiment. The engine 1 is a multi-cylinder compression ignition type internal combustion engine mounted on a vehicle, i.e., a diesel engine. The illustrated example shows an inline four-cylinder engine, but the engine may have any cylinder arrangement form, number of cylinders, and the like.

The engine 1 includes an engine main body 2, an intake passage 3 and an exhaust passage 4 connected to the engine main body 2, and a fuel injection device 5. The engine body 2 includes structural components such as a cylinder head, a cylinder block, and a crankcase, and movable components such as a piston, a crankshaft, and a valve, which are accommodated therein.

The fuel injection device 5 is a common rail type fuel injection device, and includes an injector 7, which is a fuel injection valve provided in each cylinder, and a common rail 8 connected to the injector 7. The injector 7 directly injects fuel into the cylinder 9. The common rail 8 stores the fuel injected from the injectors 7 in a high-pressure state.

The intake passage 3 is mainly defined by an intake manifold 10 and an intake pipe 11, the intake manifold 10 being connected to the engine main body 2 (particularly, the cylinder head), the intake pipe 11 being connected to an upstream end of the intake manifold 10. The intake manifold 10 distributes and supplies intake air sent from an intake pipe 11 to intake ports of the respective cylinders. An air cleaner 12, a compressor 14C of a turbocharger 14, an intercooler 15, and an electronically controlled intake throttle valve 16 are provided in this order from the upstream side in the intake pipe 11.

The exhaust passage 4 is mainly defined by an exhaust manifold 20 and an exhaust pipe 21, the exhaust manifold 20 being connected to the engine body 2 (particularly, the cylinder head), and the exhaust pipe 21 being disposed downstream of the exhaust manifold 20. The exhaust manifold 20 collects exhaust gas sent from the exhaust ports of the respective cylinders. A turbine 14T of the turbocharger 14 is provided between the exhaust pipe 21 or the exhaust manifold 20 and the exhaust pipe 21. An oxidation catalyst 22 and a particulate filter (hereinafter referred to as "DPF") 23 are provided in the exhaust pipe 21 on the downstream side of the turbine 14T in this order from the upstream side.

As shown in fig. 2, the oxidation catalyst 22 and the DPF23 are formed in a cylindrical shape having substantially the same diameter. The oxidation catalyst 22 and the DPF23 are disposed coaxially and with a slight gap therebetween in the canister housing 24. The outer peripheral surfaces of the oxidation catalyst 22 and the DPF23 are held in the canister housing 24 via a mat 25. A differential pressure sensor 26 for detecting a differential pressure between an inlet and an outlet of the DPF23 is connected to the canister case 24. The differential pressure sensor 26 is connected to a control device 27. The differential pressure sensor 26 transmits differential pressure information as an electric signal to the control device 27. Further, an exhaust pipe injection nozzle 28 is provided in the exhaust pipe 21 on the upstream side of the tank housing 24. The exhaust pipe injection nozzle 28 injects fuel containing Hydrocarbon (HC) into the exhaust pipe 21 in accordance with a command from the control device 27.

The oxidation catalyst 22 oxidizes and purifies unburned components (hydrocarbons HC and carbon monoxide CO) in the exhaust gas, heats the exhaust gas by the reaction heat at that time, and oxidizes NO in the exhaust gas to NO₂。

The DPF23 traps and removes Particulate Matter (PM) contained in exhaust gas. The DPF23 is of the so-called wall flow type. DPF23 is composed of silicon carbide.

The DPF23 is composed of the continuous regeneration type catalyzed DPF having a noble metal such as Pt supported on the inner wall thereof. The precious metals oxidize and burn HC in the exhaust gas supplied to the DPF23 by the catalytic action thereof. With this combustion, PM accumulated in the DPF23 is burned and removed.

The DPF23 performs filter regeneration (removal of PM by combustion) by filter regeneration control. As an example of the filter regeneration control, there is a forced regeneration control in which when the amount of PM deposited in the DPF23 exceeds a predetermined amount, the deposited PM is forcibly burned and removed to recover the PM trapping ability. Whether the PM deposition amount exceeds a predetermined amount is determined based on the differential pressure information transmitted from the differential pressure sensor 26 to the control device 27. The combustion removal of the accumulated PM is performed by injecting fuel into the exhaust pipe 21 from the exhaust pipe injection nozzle 28. By this injection, the exhaust gas air-fuel ratio is enriched. Thus, HC in the exhaust gas reacts with the catalyst in the DPF23, and the accumulated PM is oxidized and burned by the reaction heat at that time. That is, when the differential pressure transmitted from the differential pressure sensor 26 exceeds a predetermined value, the control device 27 injects fuel from the exhaust pipe injection nozzle 28 to perform filter regeneration (forced regeneration) on the DPF 23. In addition, in the filter regeneration control, there are also cases where: even when the PM accumulation amount does not exceed a predetermined value, the accumulated PM is burned and removed when the travel distance of the vehicle from the end of the previous filter regeneration control exceeds the predetermined value. Further, the filter regeneration control is not limited thereto. For example, the filter regeneration control may perform a far post injection from the injector 7 (in-cylinder injection performed in an expansion stroke after the main injection) instead of the fuel injection from the exhaust pipe injection nozzle 28. In addition to the above-described filter regeneration control (automatic regeneration), there is also a manual regeneration performed by a manual operation of a driver or the like regardless of the differential pressure between the inlet and outlet of the DPF23 and the travel distance of the vehicle.

Fig. 3 is a perspective view of the DPF23 viewed from the upstream side of the exhaust gas flow. Fig. 4 is an enlarged view of a portion a of fig. 3. The mesh lines in fig. 4 represent the seals of the chamber 32. For convenience of explanation, the upstream side of the DPF23 is referred to as the front side, and the downstream side is referred to as the rear side.

As shown in fig. 3, the DPF23 is formed by arranging a plurality of sections 29, 30, and 31 adjacent to each other in parallel. The portions 29, 30, 31 are formed in a honeycomb shape having a plurality of chambers 32, and are formed by alternately closing both end openings of the chambers 32 in a checkered pattern. The DPF23 is manufactured by manufacturing a plurality of portions 29, 30, 31 having a rectangular cross section, bonding a plurality of these portions 29, 30, 31 in parallel, and cutting the outer surface thereof to match the shape of the canned housing 24. The canister housing 24 and the DPF23 are formed to have a circular cross section. The adhesive material is made of, for example, silicon carbide. The surfaces where the portions 29, 30, and 31 are bonded to each other hardly pass through the exhaust gas, and do not have a function of trapping PM in the exhaust gas.

The DPF23 is configured by combining a plurality of types of portions 29, 30, and 31 having different densities of the cells 32 (hereinafter referred to as "cell densities"). The portion 29 having the highest density among the plurality of types of portions 29, 30, and 31 is disposed in the center of the DPF 23. The portions 30 and 31 having a lower cell density than the center portion are disposed on the outer peripheral portion of the DPF 23.

Further, the portions 30 and 31 disposed on the outer peripheral portion of the DPF23 are set to have a lower chamber density at positions where the area of the end face is smaller. This makes it possible to increase the amount of gas flowing to the portions 30 and 31 at a position where PM is more likely to be burned and left during filter regeneration. Further, a decrease in temperature of the outer peripheral portions 30 and 31 due to heat transfer to the can housing 24 can be suppressed.

In the present embodiment, the DPF23 is configured by combining 3 (plural) kinds of parts 29, 30, 31. As shown in fig. 3 and 4, DPF23 includes high density portion 29, medium density portion 30 having a lower cell density than high density portion 29, and low density portion 31 having a lower cell density than medium density portion 30. The high density portion 29 is set to a cell density of the same level as that of the DPF of the conventional same type. The cell densities of the medium density portion 30 and the low density portion 31 are determined by experiments, simulations, and the like to be optimal for regeneration performance (performance capable of regeneration without combustion residue) at the time of filter regeneration, PM trapping performance, resistance to temperature change, and the like.

The center portion of the DPF23 is made up of groups of 2 high density sections 29 each in length and width. The middle density portion 30 is formed at a position where the area of the end face is large in the outer peripheral portion of the DPF23, that is, at an outer peripheral portion adjacent to each of the upper, lower, left, and right surfaces of the group of high density portions 29. The outer periphery of the position where the area of the end face is small, that is, the position adjacent to the group of high-density portions 29 in the diagonal direction is formed of a low-density portion 31.

Next, the operation of the present embodiment will be described.

The exhaust gas from the engine main body 2 flows to the exhaust pipe 21 if the engine 1 is operated. Thereafter, the exhaust gas flows through the oxidation catalyst 22 to the DPF 23. The exhaust gas flowing into the DPF23 flows into the chambers 32 having open tips, and flows into the adjacent chambers 32 through fine pores (not shown) formed in the partition walls 33 between the chambers 32. At this time, PM does not pass through the pores. Therefore, the PM is trapped by the partition walls 33 between the chambers 32. In this case, the partition walls 34 formed by bonding the partition walls 33 of the portions 29, 30, and 31 to each other are not air-permeable.

The control device 27 acquires differential pressure information from the differential pressure sensor 26 at predetermined intervals, and determines whether or not the differential pressure exceeds a predetermined value. When the differential pressure exceeds a predetermined value, the control device 27 injects fuel from the exhaust pipe injection nozzle 28 to regenerate the filter (forced regeneration) of the DPF 23.

However, in a conventional DPF (not shown), a large amount of exhaust gas flows to the central portion and a small amount of exhaust gas flows to the outer peripheral portion. Further, the outer peripheral portion of the DPF is close to the canister housing 24. Therefore, the outer peripheral portion of the DPF is easily cooled by heat transfer to the canned case 24. Therefore, in the conventional DPF, the temperature of the outer peripheral portion is more likely to decrease than that of the central portion during filter regeneration, and combustion residue of PM is more likely to occur in the outer peripheral portion.

Fig. 5 is a graph showing a relationship between a PM accumulation weight and a differential pressure in a conventional DPF and a travel distance. The solid line indicates the PM accumulation weight, and the dashed dotted line indicates the differential pressure detected by the differential pressure sensor 26. The vertical axis represents the PM accumulation weight and the differential pressure, and the horizontal axis represents the travel distance. As shown in the figure, the differential pressure and the PM accumulation weight rapidly decrease each time the differential pressure exceeds a predetermined value. This is caused by the filter regeneration control. That is, the fuel injection is performed every time the differential pressure exceeds a predetermined value, and the DPF filter regeneration (forced regeneration) is performed. Further, the initial value of the PM accumulation weight immediately after regeneration tends to increase due to repetition of filter regeneration. That is, PM remaining after combustion accumulates during filter regeneration.

Therefore, in the DPF23 of the present embodiment, the cavity density of the portions 30 and 31 disposed in the outer peripheral portion is set lower than that of the portion 29 disposed in the central portion. Therefore, the flow rate of the exhaust gas can be made larger in the outer peripheral portion of the DPF23 than in the conventional DPF. Further, a decrease in temperature of the portions 30 and 31 disposed on the outer peripheral portion of the DPF23 can be suppressed. Therefore, the combustion residue of PM in the outer peripheral portion, which is generated when the conventional DPF is subjected to filter regeneration, can be eliminated or suppressed.

In addition, in the conventional DPF, there are a position of the outer peripheral portion where combustion of PM is extremely likely to be left and a position of the outer peripheral portion other than this.

Fig. 6 is an explanatory diagram showing an example of the combustion residual amount at the time of filter regeneration of the DPF50 in which the cell density is uniformly formed. The DPF50 was prepared for experiments and was formed in a manner similar to the DPF23 of the present embodiment. In the figure, a, b and c represent residual combustion amounts (g/L). a. The relationship between b and c is a < b < c. As shown in the figure, the smaller the area of the end face of the portion 51, the more PM tends to be left by combustion.

In the present embodiment, the portions 30 and 31 disposed on the outer peripheral portion are set so that the smaller the area of the end face, the lower the chamber density. That is, the outer peripheral portion of the end face where the cross-sectional area is small and where many PMs are easily burned and left is constituted by the low density portion 31. This prevents or suppresses the combustion residue of PM. On the other hand, the outer peripheral portion of the end surface where the cross-sectional area is large and the combustion residue of PM is small is constituted by the medium density portion 30. Thereby, the cell density is prevented or suppressed from becoming excessively low, and the reduction in the PM trapping performance is prevented or suppressed. Further, the balance between the PM trapping performance and the regeneration performance can be optimized.

Further, the following is also considered: depending on conditions such as the position where the pot housing 24 is disposed, the PM combustion residual amount varies although the area of the end face is the same. In such a case, the type of the portions 30, 31 may be appropriately changed according to the combustion residual amount of PM. As a specific method, first, the combustion-remaining amount of PM in a portion located in the outer peripheral portion is measured in advance with respect to the position thereof. Next, the chamber density of the portions 30 and 31 located at the outer peripheral portion is set lower than the chamber density of the portion 29 located at the central portion. The portions 30 and 31 disposed on the outer peripheral portion are set such that the smaller the area of the end face, the lower the chamber density. Further, the portions 30 and 31 disposed in the outer peripheral portion may be set such that the chamber density is lower as the combustion residual amount of PM is larger.

In addition, when the conventional DPF and the oxidation catalyst 22 are accommodated in the same canister housing 24, the flow rate in the outer peripheral portion of the oxidation catalyst 22 becomes smaller than that in the center side, and the PM is likely to be clogged in the outer peripheral portion of the oxidation catalyst 22. However, the flow rate in the outer peripheral portion of the DPF23 of the present embodiment is larger than that of the conventional DPF. Therefore, the DPF23 of the present embodiment can favorably circulate the exhaust gas around the outer periphery of the oxidation catalyst 22 even in a state where the DPF is accommodated in the same canister housing 24 as the oxidation catalyst 22. Also, clogging of PM in the outer peripheral portion of the oxidation catalyst 22 can be improved.

[ 2 nd embodiment ]

The DPF23 is formed to be circular in cross section, but is not limited thereto. As shown in fig. 7, for example, the DPF40 may also be formed in an elliptical shape in cross section. Further, on the outer peripheral portion of the DPF40, the portions 30, 31, and 41 may be arranged so that the density of the cavity decreases as the distance from the center O of the DPF40 increases.

Specifically, in the present embodiment, the DPF40 is configured by combining 4 types of parts 29, 30, 31, and 41. The DPF40 is formed by combining the high density portion 29, the medium density portion 30, the low density portion 31, and the ultra-low density portion 41. The ultra-low density portion 41 is set to have a lower chamber density than the low density portion 31.

The high density portion 29 is disposed in the center of the DPF 40. Here, the central portion refers to a position where the entire outer peripheral surface is surrounded by the other portions 30, 31, and 41. Specifically, the high-density portion 29 is provided with a total of 6 positions at a position facing the center O of the DPF40 and positions adjacent to the position in the longitudinal direction (left-right direction). Here, the major radius direction refers to a direction based on an ellipse which is an end surface shape of the DPF.

The medium density portion 30 is disposed at a position closest to the center O of the DPF40 among the positions of the outer peripheral portion. Specifically, the middle density portion 30 is disposed at a position adjacent to the upper and lower surfaces of the high density portions 29 located above and below the center in the left-right direction among the 6 high density portions 29 constituting the center portion.

The low density portion 31 is disposed at a position of the center of the distance from the center O of the DPF40, among the positions of the outer peripheral portion. The position at the center distance from the center O is the position at which the distance from the center O of the DPF40 is neither the maximum nor the minimum. Specifically, the low-density portion 31 is disposed adjacent to each of the left and right surfaces of the medium-density portion 30. Further, the low-density portions 31 are also disposed adjacent to the left and right surfaces of the group of high-density portions 29.

The ultra-low density portion 41 is disposed at the farthest position from the center O of the DPF40, among the positions of the outer peripheral portion. Specifically, the ultra-low density portions 41 are arranged at positions adjacent to the group of high density portions 29 in the diagonal direction.

Next, the operation of the present embodiment will be described.

In the present embodiment, the portions 30, 31, and 41 are arranged such that the farther from the center O of the DPF40, the lower the density of the cavity. For example, the outermost peripheral portion, which is farthest from the center O of the DPF40 and in which much PM easily remains by burning, is constituted by the ultra-low density portion 41. This prevents or suppresses the combustion residue of PM. Conversely, the outer peripheral portion closer to the center O of the DPF40 than the ultralow density portion 41 and having less PM combustion residue than the ultralow density portion 41 is constituted by the intermediate density portion 30 and the low density portion 31. Thereby, the cell density is prevented or suppressed from becoming excessively low, and the reduction in the PM trapping performance is prevented or suppressed. Further, the balance between the PM trapping performance and the regeneration performance can be optimized.

Further, the structures of the above embodiments may be combined partially or entirely as long as there is no apparent contradiction. The embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the idea of the present disclosure defined by the scope of protection are included in the present disclosure. Therefore, the present disclosure should not be construed restrictively, and can be applied to any other techniques within the scope of the idea of the present disclosure.

The present application is based on the japanese patent application (japanese application 2018-167881) filed on 09/07/2018, the contents of which are incorporated herein by reference.

Industrial applicability

The present disclosure is useful in providing a particulate filter capable of suppressing combustion residue of particulate matter during filter regeneration, and a method for manufacturing the same.

Description of the reference numerals

1 Engine

2 Engine main body

3 air intake passage

4 exhaust passage

5 Fuel injection device

7 ejector

8 common rail

9 air cylinder

10 air intake manifold

11 air inlet pipe

12 air filter

14 turbo charger

14C compressor

14T turbine

15 intercooler

16 air inlet throttle valve

20 exhaust manifold

21 exhaust pipe

22 oxidation catalyst

23 DPF (particulate Filter)

24-tank shell

25 pad

26 differential pressure sensor

27 control device

28 exhaust pipe injection nozzle

29 high density part (portion)

30 medium density part (part)

31 Low Density portion (part)

32 Chamber (cell)

33 bulkhead

34 bulkhead

40 DPF

41 ultra low density part (portion)

O center