JP3391160B2 - Exhaust particulate processing equipment for internal combustion engines - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for collecting exhaust particulates contained in exhaust gas of an internal combustion engine and treating the collected exhaust particulates, and more particularly, to improving durability of an exhaust particulate collecting member. Technology.

[0002]

2. Description of the Related Art Conventionally, from the viewpoint of environmental protection, in order to prevent exhaust particulate matter (particulate (hereinafter referred to as PM)) contained in exhaust gas of an internal combustion engine from being discharged into the atmosphere,
Various exhaust particulate processing apparatuses have been proposed in which PM is collected and removed by a filter element (hereinafter referred to as a filter) made of ceramic or the like provided in an exhaust system.

However, when the collected PM accumulates on the filter, the filter becomes clogged, and the filter becomes a large passage resistance to increase exhaust pressure, resulting in deterioration of engine performance and deterioration of fuel consumption. . Therefore, conventionally, heating means such as a heater or a burner is provided, and PM collected by the heating means is burned to regenerate the filter.

In such a conventional exhaust particulate treatment apparatus, the regeneration air is insufficient at the time of regeneration, resulting in a reduction in regeneration efficiency. Therefore, the present applicant has previously proposed a technique of supplying secondary air for regeneration through an air pump during regeneration to eliminate the shortage of the air for regeneration (Japanese Patent Application No. 6-639).
94).

However, in such a device, the playback device 2
It is necessary to provide an expensive air pump for supplying the secondary air, which complicates the system and changes the discharge rate of the air pump depending on the progress of regeneration, so when the secondary air for regeneration passes through the filter. The amount of heat that is taken away from the product fluctuates and the reproduction is not stable. Therefore, the applicant of the present invention provides a plurality of outside air communicating portions in a filter case that incorporates a filter to generate natural convection in the filter case at the time of regeneration so that the regeneration air can be satisfactorily treated with PM even without an air pump or the like. Next, a technology that enables combustion was proposed (see Japanese Patent Application No. 6-251785).

[0006]

However, in such an exhaust particulate treatment apparatus, when the filters having the same trapping amount and pressure loss characteristics are combined, the exhaust inlets are arranged unevenly. As shown in FIG. 5, a large amount of PM is deposited on the filter near the exhaust inlet. For this reason, as shown in FIG. 11, the temperature of the filter near the exhaust inlet rises too much when the filter is regenerated. In order to solve this, the reproduction interval must be shortened.

In view of the above-mentioned conventional circumstances, the present invention specifies the collection amount and pressure loss characteristics of the filter element near the exhaust inlet and other filter elements in a unique relationship, and The purpose of this is to make the amount of exhaust particulates deposited uniform.

[0008]

Therefore, in the invention according to claim 1, a filter case having a plurality of filter elements for collecting exhaust particulates in exhaust gas is installed in the exhaust passage of the internal combustion engine. The exhaust gas is introduced into the filter case from the exhaust passage while connecting the exhaust passage to the filter case while providing a regenerating means for regenerating the filter element by heating and removing the collected exhaust particulate by burning. In an exhaust particulate treatment device for an internal combustion engine, the opening of which is biased near any of the plurality of filter elements, a filter element near the exhaust introduction port of the plurality of filter elements is provided with the exhaust particulate collection. The capacity is smaller than that of other filter elements, and the pressure loss when collecting the same exhaust particulates is different from other filter elements. It was set to be larger than.

In the invention according to the first aspect, by setting the filter element having a low trapping ability but a large pressure loss as the filter element near the exhaust inlet, even if there is a difference in the amount of exhaust particulates flowing in. The exhaust particulate deposition amounts of the respective filter elements become equal, and the filter temperature during regeneration can be suppressed to the target temperature or less for both filter elements without shortening the regeneration interval by the heater or the like.

The filter element generally has a larger exhaust particulate collection capacity as the wall thickness in the exhaust flow direction is larger, and as the filter element material density is larger,
When the filter element is made of foam, the smaller the pore diameter, the larger the pressure loss of the filter element. The invention according to claim 2 is
Among the plurality of filter elements, the filter element in the vicinity of the exhaust introduction port has a wall thickness in the exhaust flow direction smaller than that of the other filter element, and the density of the filter material is larger than that of the other filter elements. Set.

According to a third aspect of the present invention, the plurality of filter elements are formed of foam, and the filter element near the exhaust introduction port among the plurality of filter elements has a different wall thickness in the exhaust flow direction. It was thinner than that and the pore size of the foam was set smaller than that of the other filter elements.

[0012] In the invention according to claim 2 or 3, by utilizing the above characteristics, the filter element near the exhaust introduction port among the plurality of filter elements has a different wall thickness in the exhaust flow direction. By setting the density of the filter element material to be larger than that of other filter elements, or by setting the pore size of the foam to be smaller than that of other filter elements. The effects of the invention according to claim 1 can be more effectively exhibited.

In the invention according to claim 4, the plurality of filter elements are formed in a hollow cylindrical shape. In the invention according to claim 4, when the filter element is formed in a hollow cylindrical shape, the wall thickness of the cylinder is appropriately set. In the invention according to claim 5, the plurality of filter elements are formed into a hollow cylindrical shape by winding a fiber around a core material,
Of the plurality of filter elements, the filter element in the vicinity of the exhaust introduction port is set to have a smaller number of radial fiber windings, a thinner wall thickness than other filter elements, and a smaller axial fiber winding pitch. did.

In the invention according to the fifth aspect, when the filter element is wound into a hollow cylindrical shape by winding a fiber around the core material, the smaller the winding pitch of the filter element material, the greater the ventilation resistance and the pressure of the filter element. By utilizing the characteristic that the loss is large, specifically, the filter element in the vicinity of the exhaust introduction port among the plurality of filter elements has a smaller number of windings of the radial fiber and has a wall thickness larger than that of other filter elements. By setting a thin and small axial winding pitch,
The effect of the invention according to claim 1 can be more effectively exhibited.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In FIG. 1, a filter case 1 is provided in an exhaust passage connected to an exhaust manifold of an internal combustion engine (not shown). This filter case 1
An inlet 2 for the exhaust gas from the exhaust passage is formed on the lower side of one end, and a main exhaust port 3 is formed on the upper side of the other end. Further, the communication ports 4 and 5 are provided below the end of the filter case 1 on the exhaust introduction port 2 side and on the upper side of the end on the main exhaust port 3 side, respectively.
Has been established.

In the filter case 1, two hollow cylindrical porous filters 6 and 7 on the upper side and the lower side are arranged in parallel. Heaters 8 and 9 as filter regenerating means are mounted on the inner peripheral surfaces of the filters 6 and 7, respectively. The heaters 8 and 9 are for burning PM and are formed by using an electric heating element of SUS system, Fe-Cr-Al system, or Ni-Cr-Fe system, and have a large number of exhaust ventilation holes. Have

Further, the exhaust gas introduction port 2 of both the filters 6 and 7
The end on the side of the main exhaust port 3 is open, and the end on the side of the main exhaust port 3 is closed. The filters 6 and 7 are housed in hollow cylindrical heat shield sheaths 10 and 11, respectively.
There are two communication ports 10A, 10B and 11A, 11 on the peripheral wall of the
B is opened.

Then, in the filters 6 and 7, the exhaust gas from the internal combustion engine is introduced from its open end to the inside, and the introduced exhaust gas is passed to the outer peripheral side, from the inside to the outside. PM is trapped while the exhaust gas passes through. In the above structure, the exhaust gas inlet 2 from the exhaust passage to the filter case 1 at the connecting portion between the exhaust passage and the filter case 1 is provided unevenly on the lower filter 7.

That is, the lower filter 7 is provided on the exhaust introduction port 2 side. On the other hand, electrodes 12 and 1 for energizing the heaters 8 and 9 are provided at closed ends of the filters 6 and 7, respectively.
3 is provided, and the electrodes 12 and 13 are electrically insulated from the filter case 1 and led out to the outside. The open ends of the filters 6 and 7 are the filter case 1
Grounded by.

The electrodes 12 and 13 are the reproduction switch 1
4, a timer / relay 15 for regeneration, a regeneration warning lamp 16 and the like, which is connected to a battery 18 via a heater drive circuit 17, and under a predetermined condition as described later, a predetermined amount is determined via the battery 18 when the internal combustion engine is stopped. It is adapted to be electrically heated for a time, for example, 10 minutes. An exhaust pressure sensor 19 for detecting the regeneration timing of the filters 6, 7 is provided in the passage on the upstream side of the filters 6, 7 in the filter case 1. The exhaust pressure sensor 19 or the like detects the filter regeneration timing. Means are configured.

The operation of the exhaust particulate treatment apparatus having the above-mentioned structure will be described. When the PM is collected by the filters 6 and 7,
The exhaust gas is passed through the filters 6 and 7. In addition, the filter 6,
When 7 is the regeneration time, the engine is stopped and the heater drive circuit 1
7 is driven after the engine is stopped, the heaters 8 and 9 are energized, and the regeneration of the filters 6 and 7 is started. Heaters 8 and 9
By energizing, the filters 6 and 7 are heated, and the PM collected and accumulated on the filters 6 and 7 is burned and removed.

Here, in the embodiment of the invention according to claim 1, as described above, the exhaust introduction port 2 from the exhaust passage to the filter case 1 is provided so as to be biased to the lower filter 7. Assuming the configuration, the filter 7 in the vicinity of the exhaust introduction port 2 of the two filters 6 and 7 is
The M trapping capacity is set to be smaller than that of the other filters 6, and the pressure loss (hereinafter referred to as pressure loss) at the same PM trapping time is set to be larger than that of the other filters 6.

Generally, the filter has the characteristics that the thicker the wall thickness in the exhaust flow direction is, the larger the PM trapping capacity is, and the higher the density of the filter material is, the larger the pressure loss of the filter is (FIG. 4 (A), ( See B)). Therefore, in the embodiment of the invention according to claim 2, as shown in FIG. 2, the thickness t of the lower filter 7 is t ₁ and the density γ is γ.
_As shown in FIG. 3, when the thickness t of the upper filter 6 is t ₂ and the density γ is γ ₂ , t ₁ <t
₂ and γ ₁ <γ ₂ are set.

FIGS. 5 (A) and 5 (B) are diagrams showing the relationship between the amount of PM flowing into the filter case, the amount of PM accumulation and the filter pressure loss in the conventional example. Since the regeneration time is detected by the average pressure loss of the two filters, if the exhaust inlets are arranged in a biased manner with respect to each filter, there will be a difference in the amount of PM flowing into each filter, and the same trapping amount The combination of filters having pressure drop characteristics causes an imbalance in the PM deposition amount, and one of the filters significantly exceeds the target PM deposition amount.

On the other hand, FIGS. 6A and 6B show the amount of PM flowing into the filter case in the above embodiment,
It is a figure which shows the relationship with PM accumulation amount and filter pressure loss,
As is clear from this figure, the trapping ability is low by utilizing the characteristics that the thicker the wall in the exhaust flow direction is, the larger the PM trapping capacity is, and the higher the density of the filter material is, the larger the pressure loss of the filter is. By using a filter with a large pressure loss as the lower filter 7 near the exhaust inlet, even if there is a difference in the inflowing PM amount (the lower filter 7 has a larger PM inflow amount than the upper filter 6), The PM accumulation amounts of the upper filter 6 and the lower filter 7 can be equalized, and the filter temperature during regeneration can be suppressed to the target temperature or less for both filters 6 and 7 without shortening the regeneration interval by the heater. it can.

Next, in the embodiment of the invention according to claim 3, the two filters 6 and 7 are each formed of foam, and the lower side of the two filters 6 and 7 in the vicinity of the exhaust introduction port 2 is formed. The thickness of the filter 7 in the exhaust flow direction is set to be smaller than that of the other filters, and the pore diameter of the foam is set to be smaller than that of the upper filter 6. That is, as the foamed material, a material having pores in which the size and density of the pores can be freely changed is applied, and for example, ceramic, sintered metal, foamed metal, Sic, or the like is used.

In the case of a metal material, the filters 6 and 7 are held by welding, and the non-metal has a structure in which both ends are held in the case via gaskets or the like. Therefore, as shown in FIG. 7, the thickness t of the lower filter 7 is set to t ₁ , the pore diameter d is set to d _1, and the thickness t of the upper filter 6 is set to t ₂ as shown in FIG. Together with the pore diameter d
The when the d _2, is set to the relationship of _{t 1 <t 2, d 1} <d 2.

In the structure of this embodiment, the trapping capacity is utilized by utilizing the characteristics that the thicker the wall in the exhaust flow direction, the larger the PM trapping capacity, and the smaller the pore diameter of the filter material, the larger the pressure loss of the filter. However, the filter temperature at the time of regeneration of both filters 6 and 7 can be suppressed to the target temperature or less by using the lower filter 7 near the exhaust inlet as the filter having a large pressure loss.

Next, in the embodiment of the invention according to claim 5, the two filters 6 and 7 are hollow by winding a fiber excellent in heat resistance and oxidation resistance, for example, ceramic or glass fiber around a core material. Of the two filters 6 and 7, the lower filter 7 in the vicinity of the exhaust introduction port 2 is formed into a cylindrical shape, and the wall thickness of the lower filter 7 is reduced by reducing the number of windings of radial fibers.
It is thinner than that and the winding pitch of the fiber in the axial direction is set smaller.

That is, as shown in FIG. 9, the lower filter 7
The thickness t with the t ₁ of, p ₁ the winding pitch p
Then, as shown in FIG. 9, the thickness t of the upper filter 6 is t
₂ and the winding pitch p is p ₂ ,
The relations of t ₁ <t ₂ and p ₁ <p ₂ are set. Also in the configuration of this embodiment, as described above, the larger the wall thickness in the exhaust flow direction, the larger the PM collection capacity, and the smaller the winding pitch of the filter material, the larger the ventilation resistance and the larger the pressure loss of the filter. By using a filter having a low trapping ability but a large pressure loss as the lower filter 7 in the vicinity of the exhaust gas introduction port 2, the filter temperature at the time of regeneration can be suppressed to the target temperature or less for both filters. .

[0031]

As described above, according to the invention of claim 1, even if there is a difference in the amount of exhaust particulate matter that flows in, the exhaust particulate matter deposition amounts of the respective filter elements become equal, and the regeneration interval is set. Without shortening, the filter element temperature during regeneration can be suppressed below the target temperature for both element filters.

According to the second or third aspect of the invention, specifically, among the plurality of filter elements, the filter element in the vicinity of the exhaust introduction port has a smaller wall thickness in the exhaust flow direction than the other filter elements, and The density of the filter material is set to be larger than that of the other filter element, or the pore diameter of the foam is set to be smaller than that of the other filter element. The effect can be exhibited more effectively.

According to the invention of claim 4, when the filter element is formed in a hollow cylindrical shape, the exhaust particulate collection capacity can be changed by appropriately setting the wall thickness of the cylinder. According to the invention of claim 5, when the filter element is formed by winding a fiber around a core material to form a hollow cylindrical shape, the smaller the winding pitch of the filter element material, the greater the ventilation resistance and the greater the pressure loss of the filter element. Specifically, the filter element in the vicinity of the exhaust introduction port among the plurality of filter elements has a wall thickness smaller than that of other filter elements by reducing the number of radial fibers wound, and The method according to claim 1, wherein the winding pitch of the fibers in the axial direction is set small.
The effects of the invention according to can be more effectively exhibited.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the invention according to claim 1.

2A and 2B are diagrams showing a configuration of a lower filter in one embodiment of the invention according to claim 2, wherein FIG. 2A is a plan view and FIG.
Is a side sectional view

FIG. 3 is a side sectional view showing a configuration of an upper filter in one embodiment of the invention according to claim 2;

FIG. 4 is a characteristic diagram showing the relationship between the amount of PM flowing into the filter, the amount of PM accumulation, and the pressure loss of the filter.

FIG. 5: Inflow PM into the filter case in the conventional example
Diagram showing the relationship between the amount of PM, the amount of PM accumulated and the pressure loss of the filter

FIG. 6 is a characteristic diagram showing the relationship between the amount of PM flowing into the filter case, the amount of PM accumulation, and the filter pressure loss in the embodiment of the invention according to claim 2;

7A and 7B are diagrams showing a configuration of a lower filter in one embodiment of the invention according to claim 3, wherein FIG. 7A is a plan view and FIG.
Is a side sectional view

FIG. 8 is a side sectional view showing a configuration of an upper filter in an embodiment of the invention according to claim 3;

9A and 9B are diagrams showing a configuration of a lower filter in one embodiment of the invention according to claim 5, wherein FIG. 9A is a plan view and FIG.
Is a side sectional view

FIG. 10 is a diagram showing a configuration of an upper filter in one embodiment of the invention according to claim 5, (A) is a plan view, and (B) is a diagram.
Is a side sectional view

FIG. 11 is a characteristic diagram illustrating conventional problems.

[Explanation of symbols]

1 filter case 2 Exhaust inlet 6 Upper filter 7 Lower filter 8,9 heater

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-58-28505 (JP, A) JP-A-1-143618 (JP, A) JP-A-4-231614 (JP, A) JP-A-6- 264711 (JP, A) JP-A-6-264721 (JP, A) JP-A-7-34855 (JP, A) JP-A-7-54636 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 3/02

Claims (5)

(57) [Claims] 1. An exhaust gas passage of an internal combustion engine is provided with a filter case containing a plurality of filter elements for collecting exhaust particulates in exhaust gas, and the collected exhaust particulates are heated and burned and removed. While providing a regenerating means for regenerating the filter element, an exhaust gas introduction port from the exhaust passage to the filter case, which is a connecting portion between the exhaust passage and the filter case, is biased near any one of the plurality of filter elements. In an exhaust particulate treatment device for an internal combustion engine, the filter element near the exhaust introduction port of the plurality of filter elements has an exhaust particulate collection capacity smaller than that of other filter elements, and has the same exhaust gas. It is characterized in that the pressure loss during particulate collection is set to be larger than that of other filter elements. Exhaust particulate treatment device for internal combustion engine. 2. The filter element in the vicinity of the exhaust introduction port of the plurality of filter elements has a wall thickness in the exhaust flow direction smaller than that of the other filter elements and a filter material density higher than that of the other filter elements. The exhaust particulate treatment device for an internal combustion engine according to claim 1, wherein the exhaust particulate treatment device is set to be large. 3. The plurality of filter elements are formed of foam, and the filter element near the exhaust introduction port of the plurality of filter elements has a wall thickness in the exhaust flow direction smaller than that of the other filter elements. The exhaust particle treating apparatus for an internal combustion engine according to claim 1, wherein the pore diameter of the foam is set smaller than that of the other filter elements. 4. The exhaust particulate treatment system for an internal combustion engine according to claim 1, wherein the plurality of filter elements are formed in a hollow cylindrical shape. 5. The plurality of filter elements are formed in a hollow cylindrical shape by winding a fiber around a core material, and the filter element near the exhaust introduction port among the plurality of filter elements has a small number of windings in the radial direction. 2. The exhaust particulate treatment system for an internal combustion engine according to claim 1, wherein the wall thickness is set smaller than that of the other filter elements and the winding pitch of the fibers in the axial direction is set smaller.