JPH0527215U - Diesel Patty Quilt Filter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an exhaust gas purifying device having excellent durability by preventing thermal stress from concentrating on a specific portion of a filter during regeneration. [Structure] By providing a specific slit 13 in the filter 12 formed of porous silicon carbide, it is possible to prevent thermal stress from concentrating substantially on a specific portion of the filter 12.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a filter for removing particulates contained in exhaust gas discharged from an internal combustion engine such as a diesel engine.

[0002]

[Prior Art]

 In recent years, it has been proposed to manufacture a diesel particulate filter of this type by using porous silicon carbide. In the diesel particulate filter, a plurality of gas passage holes extending in parallel along the exhaust gas passage are formed, and one of both end openings of each gas passage hole is alternately sealed, A plurality of cells are formed that are open on either the inflow side or the outflow side of the exhaust gas. When a certain amount of particulates is captured by such a filter, the exhaust gas inflow side end surface of the filter is heated to around 700 ° C by a burner or the like, and then secondary air for combustion promotion is supplied. , The particulates are burnt and removed, and the filter is restored to its original state.

When the filter is locally heated in the regeneration process, a temperature difference is generated between the respective parts in the filter, and stress (tensile stress or compressive stress) is easily generated in the filter. It is known that when this stress exceeds the material strength of the filter, cracks occur and the filter is destroyed. Therefore, in the conventional filter disclosed in, for example, Japanese Patent Laid-Open No. 3-121213, the temperature between the parts is divided by dividing the cylindrical filter into four equal parts along two surfaces that pass through the central axis and are orthogonal to each other. The difference is prevented from expanding and cracks are prevented from occurring.

[0004]

[Problems to be solved by the device]

 However, in the conventional filter, in order to connect the divided pieces to each other, it is necessary to fill the sealing material between the divided pieces. Therefore, there are drawbacks that the structure of the filter is complicated and the manufacturing is troublesome. There is also a problem that the heat resistance of the entire filter depends on the heat resistance of the sealing material, and the heat resistance of the filter itself cannot be validated.

Further, in order to prevent the temperature difference from expanding regardless of the division of the filter, a cross-shaped slit is formed in approximately 1 / th of the filter along two planes that pass through the central axis of the filter and are orthogonal to each other. It is conceivable to form over a length of 2. However, this method cannot form the slit over the entire length of the filter, and thus it is difficult to sufficiently prevent the temperature difference from increasing in the filter. Further, stress is likely to concentrate on the inner end of the slit on the outer peripheral surface of the filter, and cracks may occur from that portion.

In order to prevent the occurrence of cracks due to stress, if the shape of the slit is specified, the response will not be concentrated at a specific part of the filter, and the temperature difference between the parts in the filter can be surely increased. We found that it can be prevented. Then, the present invention was completed based on this knowledge.

[0007]

[Means and Actions for Solving the Problems]

 In order to solve the above problems, in the present invention, in a diesel particulate filter for purifying exhaust gas of a diesel engine, which is arranged in a casing having a passage communicating with the exhaust side of the diesel engine, an axis line of the filter is provided. A center hole extending along the entire length of the filter and a slit communicating with the center hole and opening on the outer peripheral surface of the filter and extending over the entire length of the filter are provided.

With this, it is possible to surely avoid concentration of the response to a specific portion of the filter, despite the simple structure. Therefore, even if the filter regeneration process is repeated, the filter will not be damaged, and the filter can be used for a longer period than before.

The width of the slit is preferably 1 mm to 5 mm. If this width is within the above range, the concentration of stress on a specific portion can be avoided without lowering the mechanical strength and filtering ability of the filter.

The inner diameter of the central hole is preferably set to 3 mm to 5 mm. This is because if the inner diameter is within the above range, it is possible to surely avoid the concentration of stress on a specific portion without impairing the mechanical strength and filtering ability of the filter.

It is desirable that a heat insulating material be disposed in at least the slit. The reason is to prevent the exhaust gas introduced into the filter from leaking through the slit and the central hole. Also, by disposing a heat insulating material, it is possible to reduce the loss of thermal energy during regeneration.

Further, it is preferable that the slit has a spiral cross section. The reason is that by forming the slit into the above shape, a wider opposing surface can be secured between the outer peripheral surface of the filter and the central hole. As a result, the temperature difference between the respective parts in the filter becomes smaller, and the stress concentration on the specific part of the filter can be more surely avoided.

[0013]

【Example】

 An embodiment in which the present invention is embodied in an exhaust gas purifying device for a diesel engine will be described in detail with reference to the drawings.

As shown in FIG. 1, the exhaust gas purification device 1 includes a casing 2 made of a metal pipe, and a passage 2a of the casing 2 is connected to an exhaust pipe Ea of a diesel engine E. A diesel particulate filter 3 for purifying exhaust gas emitted from the diesel engine E is arranged in the casing 2. Further, a burner 4 for regeneration treatment is provided on the exhaust gas inflow side of the filter 3 in the passage 2a.

As shown in FIGS. 2 and 3, the filter 3 of the present embodiment is formed of a porous silicon carbide sintered body in a honeycomb shape and has a cylindrical shape with a length of 140 mm and a diameter of 150 mm. .. A large number of gas passage holes 5 are formed in the filter 3 along the axial direction, and one end opening of each gas passage hole 5 on the exhaust gas inflow side or the outflow side is a seal made of a porous sintered body. The stoppers 6 are alternately sealed. As a result, cells 7a, 7b are formed which are open on either the inflow side or the outflow side of the exhaust gas.

On the surface of the inner wall 8 of each of the cells 7a and 7b, an oxidation catalyst composed of a platinum group element, another metal element, an oxide thereof or the like is carried. Therefore, as shown by an arrow A in FIG. 3, the exhaust gas introduced from the cell 7a opening to the inflow side is opened to the adjacent outflow side via the inner wall 8 located between the cells 7a and 7b. Flow into the cell 7b side. Then, when the exhaust gas passes through the inner wall 8, only the particulates are collected on the inner wall 8 surface, and only the purified exhaust gas is discharged from the filter 3.

When a predetermined amount of particulates is trapped in the filter 3, the ignition of the burner 4 starts the heating of the filter 3. When the filter 3 is heated to a predetermined temperature (about 700 ° C.), the particulates in the filter 3 are burned and the filter 3 is regenerated to the original state in which the particulates are not captured.

Next, the structure for relieving the stress acting on the filter 3 during the regeneration process will be described in detail. As shown in FIGS. 2 and 3, a central hole 9 having a circular cross section and an inner diameter of 4 mm is formed on the central axis of the filter 3. The central hole 9 extends over the entire length of the filter 3 and is open at the exhaust gas inflow side and outflow side end surfaces of the filter 3. A slit 10 having a width of 1.5 mm and extending in the radial direction from the central hole 9 is formed in the filter 3 over the entire length of the filter 3. As shown in FIGS. 2 and 3, the slit 10 communicates with the central hole 9 and opens on the outer peripheral surface of the filter 3. Further, the central hole 9 and the slit 10 can be formed at the same time when a honeycomb green molded body made of porous silicon carbide is manufactured by extrusion molding or the like. It is also possible to cut and form the both 9 and 10 by using an arbitrary means after manufacturing the molded body.

A heat insulating material 11 made of ceramic fiber is disposed in the center hole 9 and the slit 10, and the heat insulating material 11 prevents the exhaust gas from leaking from the filter 3.

Further, another diesel particulate filter 12 is shown in FIG. The filter 12 is made of the same material as the filter 3 of the first embodiment and has the same size. However, a slit 13 having a width of 1.5 mm is formed over the entire length of the filter 12 so as to have a spiral shape in a vertical cross section. The slit 13 communicates with the central hole 14 and is opened on the outer peripheral surface of the filter 12. Inside the both 13, 14, a heat insulating material 15 made of ceramics fiber is arranged as in the first embodiment. ing. Then, an exhaust gas purifying apparatus was manufactured using this filter 12, and this was designated as Example 2.

Now, in order to examine the characteristics of the exhaust gas purifying apparatuses of the first and second embodiments formed as described above, the air compressor is used for the filters 3 and 12 heated to 700 ° C. by the burner 4. (Not shown), secondary air for combustion promotion was circulated at a rate of 1 cubic meter per minute for 5 minutes, and the regeneration treatment of the filters 3 and 12 was repeated 500 times. As shown in FIG. 1, at the position Pa near the center and the position Pb near the outer periphery on the end faces of the exhaust gas inflow side of the filters 3 and 12, and the position Pc near the center on the end face of the exhaust gas outflow side. Then, the temperatures Ta, Tb, and Tc (° C) were measured with time. Further, based on these measured values, the maximum temperature difference ΔTab (° C) between Pa and Pb and the maximum temperature difference ΔTac (° C) between Pa and Pc during the regeneration treatment were obtained. Furthermore, by observing the filters 3 and 12 with the naked eye, the occurrence of cracks due to the treatment was investigated. The results are shown in Table 1.

Further, a filter made of the same material and of the same size as those of the above-mentioned respective examples but having neither the central holes 9 and 14 nor the slits 10 and 13 as described above was manufactured. Then, this filter was attached to the exhaust gas purification device. This was designated as Comparative Example 1 with respect to Examples 1 and 2 above.

Further, using the filter of Comparative Example 1 as a starting material, a filter is divided into four by forming cross slits along two planes that pass through the central axis and are orthogonal to each other, and each divided portion is divided. An insulating material was placed between them and assembled to the exhaust gas purification device. This was designated as Comparative Example 2. The same measurements and investigations were performed for Comparative Examples 1 and 2. The results are shown in Table 1.

[0024]

[Table 1]

As is clear from Table 1, in the filter 3 of Example 1, the maximum temperature difference ΔTab between Pa and Pb and the maximum temperature difference ΔTac between Pa and Pc in the regeneration process are 100 ° C. and 300 ° C., respectively. However, none of them exceeded the temperature difference (400 to 500 ° C.) at which cracks occurred. The maximum temperature differences ΔTab and ΔTac in the filter 12 of Example 2 were 100 ° C. and 300 ° C., respectively, which were smaller than those of the filter 3. Therefore, it was suggested that in these filters 3 and 12, the stress acting in the radial direction and the circumferential direction was somewhat relaxed, and that the stress was not concentrated on a specific part of the filter.

Further, when the observation was carried out after the regeneration treatment was repeated 500 times or more, no crack was found in any of the filters 3 and 12 of the practical examples, and the durability was remarkably superior to that of the conventional filter. I found out.

On the other hand, in the filters of Comparative Examples 1 and 2, the maximum temperature differences ΔTab and ΔTac were both larger than the values of Examples 1 and 2 described above. Further, in particular, ΔTac has a value larger than the temperature difference (400 to 500 ° C.) at which cracks occur, suggesting that a larger stress is acting on the filter than in Examples 1 and 2 above. As a result, in Comparative Example 1, the regeneration process was repeated 4 times, and in Comparative Example 2, the regeneration process was repeated 8 times, and a crack was generated, resulting in damage to the filter.

[0028]

[Effect of the device]

 As described in detail above, according to the diesel particulate filter of the present invention, it is possible to surely avoid the concentration of stress on a specific portion of the filter, despite the simple structure. Therefore, even if the filter regeneration process is repeated, the filter will not be damaged and can be used for a longer period than in the past.

[Brief description of drawings]

FIG. 1 is a partial front sectional view of an embodiment in which the present invention is embodied in an exhaust gas purification device.

FIG. 2 is an enlarged perspective view showing a diesel particulate filter of the exhaust gas purification apparatus of FIG.

FIG. 3 is a partially enlarged sectional view of the diesel particulate filter of FIG.

FIG. 4 is an enlarged perspective view showing a diesel particulate filter according to a second embodiment.

[Explanation of symbols]

2 casing, 2a passage, 3,12 (diesel particulate) filter, 9,14 center hole, 1
0,13 slits, 11,15 insulation, E diesel engine.

Claims (5)

[Scope of utility model registration request] 1. A diesel particulate filter (3) disposed in a casing (2) provided with a passage (2a) communicating with the exhaust side of a diesel engine (E) and purifying exhaust gas of the diesel engine (E). At 12), a central hole (9, 14) extending along the axis of the filter (3, 12) and extending over the entire length of the filter (3, 12).
With the central hole (9, 14) and open at the outer peripheral surface of the filter (3, 12).
12) A diesel particulate filter having slits (10, 13) extending over the entire length. 2. The width of the slits (10, 13) is 1 mm to
It is 5 mm, The diesel particulate filter of Claim 1 characterized by the above-mentioned. 3. The inner diameter of the central hole (9, 14) is 3 mm to 5
The diesel particulate filter according to claim 1 or 2, wherein the diesel particulate filter is set to mm. 4. The diesel particulate filter according to any one of claims 1 to 3, wherein a heat insulating material (11, 15) is arranged at least in the slit (10, 13). . 5. The diesel particulate filter according to claim 1, wherein the slit (13) has a spiral cross section.