JP3427481B2 - Cylindrical honeycomb filter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a honeycomb filter used for collecting particulate matter in exhaust gas discharged from a diesel engine, for example, and removing it by combustion, and more particularly to the arrangement of its heater wire.

[0002]

2. Description of the Related Art As a means for regenerating the honeycomb filter by burning and removing the particulates collected by the honeycomb filter, there is an exhaust gas purifying means for embedding a heater wire in the end face of the filter and electrically heating the heater wire. This exhaust gas purification means is, for example, as shown in FIG. 7, in which a honeycomb filter 9 made of ceramic is arranged in a housing 95.

The honeycomb filter 9 has a large number of gas passages 90 defined by porous air-permeable partition walls 900. The gas passage 90 includes an outlet passage 903 having a closed portion 93 on the upstream side and an inlet passage 9 having a closed portion 91 on the downstream side.
01 and. A large number of heater wires 92 are embedded in the closed portion 91 on the downstream side. As the honeycomb filter 9, a cylindrical honeycomb filter having a circular cross section perpendicular to the gas passage is often used.

A heating power source 96 is connected to the heater wire 92. In the above honeycomb filter 9,
Exhaust gas 97 is introduced from the upstream side of the housing 95, the exhaust gas enters the inlet passage 901, and the breathable partition wall 90 is introduced.
After passing through 0, it enters the outlet passage 903 and is then discharged from the housing 95. Then, the particulates in the exhaust gas are collected by the breathable partition wall 900.

After the particulates are collected in a predetermined amount, air 9 is trapped in the housing 95 in the direction opposite to the exhaust gas.
8 is introduced and the heater wire 92 is energized.
As a result, the collected particulates are burned and removed,
The honeycomb filter 9 is regenerated.

By the way, conventionally, a large number of heater wires 92 are arranged in parallel along the diameter direction of the honeycomb filter. Regarding the length of the heater wire, when the honeycomb filter has a cylindrical shape, each heater wire is long at the central portion (near the diameter) of the filter and short near the outer peripheral portion of the filter. Therefore, the heater resistance is different for each heater wire, and uniform heat generation cannot be achieved as a whole. Further, since the heat is radiated to the filter case in the outer peripheral portion with respect to the central portion of the filter, it is difficult to keep the filter at a uniform temperature.

Therefore, in order to solve the above problem, the conventional example 1
In (Japanese Patent Laid-Open No. 3-217617), (1) the length of each heater wire depends on the arrangement of the heater wire electrodes and the heater wire embedding pattern (in this case, the heater wire is bent when viewed from the filter end face side). In other words, the heater resistance is made uniform to obtain uniform heat generation.

(2) As another embodiment, when the heater wire embedding pattern is embedded linearly without bending and embedding when viewed from the filter end face side, the heater length increases toward the outer peripheral portion of the filter. Since the length is shorter and the resistance is smaller, we are also proposing a method to adjust the resistance by making the heater wire diameter thinner.

Conventional example 2 (actual Kaihei 4-47125)
Proposed to increase the heater wire embedding depth in the area of the filter where heat radiation is large, in an attempt to make the temperature uniform. Therefore, assuming that the heater wire has an embedded depth of about 10 mm in the central portion of the filter, the peripheral portion has at least 20 mm or more to accommodate the heater resistance because the number of embedded peaks is small.

[0010]

[Problems to be Solved] However, the above-mentioned conventional example 1
Has the following problems. (1) As a means for adjusting the resistance values of many heater wires, the length of each heater wire (the number of embedded peaks) is limited. However, since the end face of the filter is circular, the heater wire in the center of the filter can be arranged in a straight line when viewed from the end face side of the filter, but the outer peripheral part of the filter has a small number of through-holes, so it must be bent. Need to be embedded. FIG. 8 shows a case where the heater wires 921 to 927 are bent and arranged in this manner.

Therefore, in this case, the heater wire must be bent in the vertical direction and also in the lateral direction according to the embedding pattern, which is difficult to manufacture. In addition, positioning is complicated when the bent heater wire is inserted into the filter.

(2) When the embedded pattern of the heater wire is arranged linearly without bending when viewed from the filter end face side,
I am trying to match the heater resistance by changing the heater wire diameter. However, when the filter is circular, the number of through holes in the outer peripheral portion is about 1/3 of the number of through holes in the center (the number of embedded heaters), and the heater wire length is three times different.

When the resistance is adjusted by the heater wire diameter, for example, when the central heater wire diameter is 0.6 mm, the outer peripheral heater wire diameter needs to be 0.3 mm or less. When the heater wire diameter is 0.3 mm or less, the heater wire itself has no strength, and it is difficult to obtain dimensional accuracy in bending. In addition, it is difficult to maintain its shape after processing.

Further, when the heater wire diameter becomes small as described above, it is difficult to maintain the shape when the heater wire is embedded in the filter, and the heater is embedded as desired or is not reliable.
In addition, there is a danger that the wire is easily broken when the heater is energized.
On the other hand, it is conceivable that the diameter of the heater wire in the central portion is set to 0.7 mm or more. However, if the heater wire is thickened in this way, the insertion side and the insertion side of the one side gas passage of the honeycomb filter are closed. It becomes impossible to arrange the two heater wires back and forth.

Next, the conventional example 2 has the following problems. (1) The heater wire embedding depth of the outer peripheral portion is increased to cover the heat radiation of the outer peripheral portion of the filter. However, basically, a large number of heater wires arranged in parallel between the positive electrode and the negative electrode cannot generate uniform heat unless the resistances are aligned. In this example, since the heater wire diameter is constant, the difference between the number of embedded heater wires in the center of the circular filter end surface and the number of embedded heater wires in the outer peripheral portion of the filter (about 3 times) Is adjusted by the heater wire embedding depth to match the heater wire length (heater resistance).

For example, if the heater wire embedding depth in the central portion is 10 mm, the heater wire embedding depth in the filter outer peripheral portion must be at least 20 mm or more. Therefore, although the temperature seen on the filter end face is uniform,
The temperature in the depth (in the axial direction of the filter) becomes uneven, and thermal stress is generated in this direction, causing vertical cracking of the filter.

(2) In this case, if it is attempted to reduce the difference in the embedded depth of the heater wire in order to reduce the temperature difference in the axial direction, the heater will be affected by the difference in the number of embedded peaks between the central portion of the filter and the outer peripheral portion. The line embedding pattern cannot be embedded linearly when viewed from the filter end face. Therefore, it is necessary to bend and embed (see FIG. 8) to adjust the resistance of the heater, which complicates processing of the heater wire and positioning when inserting the heater wire into the filter.

In view of the above conventional problems, the present invention is excellent in soaking of the end face of the filter, soaking in the axial direction of the filter, workability of the heater wire, ease of assembling to the filter, and durability. It is intended to provide a cylindrical honeycomb filter.

[0019]

According to the present invention, a large number of gas passages defined by breathable partition walls, a closed portion provided in a part of the gas passages, and a meandering shape embedded in the closed portion and arranged linearly in parallel. A cylindrical honeycomb having a large number of heater wires, each end of each heater wire being connected to a common electrode on the positive electrode side and a common electrode on the negative electrode side, and having a circular cross section in the direction orthogonal to the gas passages. In the filter, each heater wire has an embedded depth near the outer periphery of the filter.
The length of each heater wire is larger than that of the other portions and is within twice the length, and each heater wire has a minimum number of embedded ridges so that the electric resistance values are almost the same in its entire length. , The number of peaks of the maximum heater wire with the maximum number of embedded threads is more than 1 and less than or equal to 2 and the diameter of each heater wire is within the range of 0.4 to 0.6 mm. A cylindrical honeycomb filter is characterized in that the heater wire having a smaller number of ridges has a smaller diameter than the heater wire having a large number of embedded ridges.

What is most noticeable in the present invention is the embedding depth of the heater wire near the outer peripheral portion of the filter, the ratio of the number of peaks of the minimum heater wire to the maximum heater wire, the heater wire having a small number of embedding peaks and the heater wire having a large number of embedding peaks. The wire diameter ratio of and is defined as above. In the present invention, each of the heater wires is linearly arranged in parallel along the diametrical direction of the honeycomb filter, and is embedded in the closed portion in a U-shape in that direction. Therefore, the heater wire has a zigzag meandering shape when viewed from the side (see FIG. 1).

Both ends of each heater wire are connected to a common electrode on the positive electrode side and a common electrode on the negative electrode side (see FIG. 2). Also, as shown in FIG. 1C, the heater wire has an embedding depth d near the outer peripheral portion (a portion parallel to the diameter direction and away from the center) of the filter, and an embedding depth e in the other portion. And its size is less than double.

The embedding depth is the length between the peak (uppermost end) and the valley (lowermost end) of the meandering heater wire. As described above, by adjusting the embedding depth d of the outer peripheral portion and the embedding depth e of the other portions, it is possible to prevent the temperature from decreasing in the outer peripheral portion and to ensure the uniform heating in the axial direction of the filter. If the depth ratio exceeds twice, the temperature of the outer peripheral portion becomes too high, and it becomes difficult to achieve soaking.

The outermost heater wire located at the outermost side of the heater wires preferably has the same embedding depth in the outer peripheral portion and other parts (see FIG. 1A). In addition, each heater wire has the smallest number of embedded ridges (Fig. 1) so that the electric resistance values are substantially the same in each length.
It is necessary that the peak number ratio of the maximum heater wire (FIG. 1 (C)) having the maximum number of embedded peaks with respect to (A)) is larger than 1 and within twice.

When the ratio of the number of peaks is not within the above range, it is necessary to make the wire diameter of the smallest heater wire less than 0.4 mm, for example, in order to make the electric resistance values of the respective heater wires substantially the same. The strength of the heater wire is reduced, processing is difficult, and assembly to the honeycomb filter is difficult. Also,
In the case of arranging the heater wires in a straight line (the present invention),
Prevents hot spots.

The diameter of the heater wire is 0.4 to 0.6.
It is necessary that the heater wire having the number of embedded ridges within the range of mm has a smaller diameter than the heater wire having a large number of embedded ridges. That is, the wire diameter becomes smaller as it goes away from the diameter portion (center portion) of the honeycomb filter.

When the wire diameter is larger than 0.6 mm, it becomes difficult to embed the heater wire in the closed portion of the one air-permeable partition wall. That is, when embedding in the closed portion, the meandering U-shaped portion of the heater wire is embedded in one closed portion. Therefore, two heater wires come in and go out from one closed portion. Therefore, when the heater wire exceeds 0.6 mm, the heater wires are too close to each other, and it is difficult to process and embed them in the closed portion. On the other hand, if the wire diameter is less than 0.4 mm, the strength of the heater wire decreases, the accuracy of the bending process decreases, it is difficult to maintain the shape of the heater, and further, the heater may break, resulting in a decrease in durability.

Further, the heater wire is within the above wire diameter range, and the heater wire with less embedding has a smaller diameter than the heater wire with many embedding. As a result, the temperature of the end face of the filter can be equalized and the axial direction of the filter can be equalized.
Next, in the heater wire, it is preferable that the number of crests in the portion having a large embedding depth near the outer peripheral portion is 2 to 4 crests. If it is less than 2 peaks, it becomes difficult to maintain the temperature of the outer peripheral portion, while if it exceeds 4 peaks, the temperature of the outer peripheral portion rises too much, and it becomes difficult to equalize the temperature.

Of the heater wires, the outermost heater wire located at the outermost part is preferably wired in a substantially U-shape when viewed from the filter end face (reference numeral 21 in FIG. 2).
That is, since the outermost heater wire is close to the outer periphery of the filter,
It is difficult to secure the electric resistance value close to the heater wire of other parts with only one straight line, and the wire diameter becomes less than 0.4 mm if it is forcibly made straight, and the problems of strength and durability occur as described above. To do. Therefore, only the outermost heater wire is U-shaped 2
It is preferably arranged in rows.

Further, the honeycomb filter is composed of a heater support portion in which the heater wire is embedded and arranged, and a filter portion in which the gas passage is provided, and it is preferable that the both are separable. As a result, for example, when the heater support portion is damaged due to disconnection or the filter portion is deteriorated or damaged, the heater support portion can be easily replaced with a substitute and maintenance is easy.

Further, it is preferable that the honeycomb filter is made of a sintered body of ceramic powder, and the outer periphery thereof is housed in a metal cylinder. This makes it possible to obtain a honeycomb filter that is particularly easy to collect particulates in the exhaust gas of the diesel engine and has excellent durability. When the mat is housed in a metal tube, a mat containing ceramic fibers as a main component is placed around the filter. Further, the heater wire is provided in either one or both of the closed portion on the inlet side of the exhaust gas and the closed portion on the outlet side of the exhaust gas in the honeycomb filter.

[0031]

In the present invention, first, the heater wire embedding depth in the outer peripheral portion of the filter is set larger than the other portions within the above range. As a result, it is possible to prevent a temperature drop in the outer peripheral portion. In addition, since the ratio of the depth is set to be less than twice, it is possible to secure uniform heat distribution in the axial direction of the filter.

Further, since the peak number ratio of the maximum heater wire to the minimum heater wire is set to 1 to 2, the electric resistance value of the heater wire can be made almost the same, and the heater wire diameter can be prevented from becoming extremely thin. it can. Also, by arranging the heater wires in a straight line, it is possible to prevent hot spots, and prevent the strength and durability of the heater wires from being reduced due to the thinning of the heater wires.

The heater wire diameter is 0.4 to 0.6 mm.
In addition, the heater wire having a small number of embedded crests has a smaller diameter than the heater wire having a large number of embedded crests. Therefore, while ensuring the strength of the heater wire, it is possible to obtain the reliability of bending the meandering heater and the ease of assembling the heater in the filter. In addition, heater breakage can be prevented and durability is improved. Further, it is possible to achieve uniform heat distribution in the entire area of the end surface of the filter and in the axial direction.

Therefore, according to the present invention, the temperature uniformity in the entire area of the end face of the filter, the temperature uniformity in the axial direction of the filter, the workability of the heater wire, the ease of assembly to the filter, and the durability are excellent. A cylindrical honeycomb filter can be provided.

[0035]

【Example】

Example 1 A cylindrical honeycomb filter according to an example of the present invention will be described with reference to FIGS. As shown in FIGS. 1 to 3, the honeycomb filter 1 of this example has a large number of gas passages 10 divided by gas permeable partition walls 15, a closed portion 11 provided in a part of the gas passages 10, and the closed portion 11 It has a large number of meandering heater wires 2 (21 to 31) embedded and arranged in parallel in a straight line.

As shown in FIG. 2, each heater wire 2 has its both ends connected to a positive electrode side common electrode 41 and a negative electrode side common electrode 42 by lead wires 411 and 421, respectively.
The honeycomb filter 1 is a cylindrical honeycomb filter having a circular cross section in the direction orthogonal to the gas passage 10 (FIG. 2). Next, the heater wire 2 is
As shown in (B) and (C), the embedding depth d in the vicinity of the outer peripheral portion of the filter is larger than the embedding depth e in the other portions and is within twice the length. The outer peripheral portion means a portion close to the outer periphery in the direction parallel to the diametrical direction of the filter.

In addition, in each heater wire, the number of embedded ridges is smaller than that of the minimum heater wire 22 (FIG. 1 (A), FIG. 2) having the minimum number of embedded ridges so that the electric resistance values are substantially the same in the entire length. Is the maximum heater wire 31 (Fig. 1
The mountain number ratio in (C) and FIG. 2) is larger than 1 and within 2 times. The diameter of each heater wire 21 to 31 is 0.4 to
Within a range of 0.6 mm, a heater wire having a small number of embedded peaks (for example, heater wires 21 to 23) has a smaller diameter than a heater wire having a large number of embedded peaks (for example, heater wires 29 to 31). .

The heater wires 2 are arranged in a straight line in parallel with the diameter of the filter. And
From the heater wire for the outermost part of the filter, that is, the outermost heater wire 21, to the central heater wire, that is, the maximum heater wire 31, the heater wires are sequentially lengthened. As shown in FIG. 2, the heater wire 2 is arranged in parallel from the outermost heater wire 21 to the largest heater wire 31 and further to the outermost heater wire 21 in the upper and lower parts of the drawing.

Further, as shown in FIG. 3, one of the gas passages of the filter is provided with a checkered pattern of closed portions 11, and the heater wires 2 are linearly arranged along the adjacent closed portions 11. ing. The blocking portions are provided in a checkered pattern on the gas inlet side and the gas outlet side of the honeycomb filter, respectively. The gas passage of the portion where the closed portion is provided on the gas inlet side constitutes the gas outlet passage 111 (FIG. 1). On the other hand, the gas passage in the portion where the closed portion is provided on the gas outlet side constitutes the gas inlet passage 12 (FIG. 3).

The heater wire can be provided in either or both of the closed portion on the gas inlet side and the closed portion on the gas outlet side. In the honeycomb filter of this example, the heater wire embedding depth in the outer peripheral portion of the filter, the peak number ratio of the minimum heater wire and the maximum heater wire, the condition of the heater wire diameter, etc. are configured as described above. Therefore, as described above, it is excellent in soaking of the entire area of the end face portion of the filter, soaking in the axial direction of the filter, workability of the heater wire, easy assembling to the filter, and durability.

Example 2 As shown in FIGS. 1 to 5, in this example, a concrete example of the cylindrical honeycomb filter shown in Example 1 was used.
The measurement experiment result of the temperature distribution will be described. The honeycomb filter of this example is used for a device for purifying particulates in exhaust gas in a diesel engine. This honeycomb filter has a diameter of 140 and a length of 130.
A cordierite honeycomb filter having a size of mm (2 liters), a mesh of 150 pieces / in ² , and a gas permeable partition wall thickness of 0.45 mm was used.

The heater wire is made of Nichrome or Kanthal material containing Cr, Al and Fe as main components, and in this embodiment, Kanthal material having a diameter of 0.4 to 0.55 mm is used. In the above-mentioned honeycomb filter, every other opening of a large number of through holes (gas passages) is sealed by a closing part. The heater wires are inserted every other row in a direction in which the closed portions are continuously arranged without passing through the openings, and are fixed by the closed portions (FIG. 2).

Basically, one heater wire is provided in one row, but only the heater wire in the outermost peripheral portion is one heater in two U-shaped rows (FIG. 2). This prevents the heater wire diameter from becoming extremely thin due to the extremely small number of embedded ridges and the adjustment of the electric resistance value of the heater wire. Since the through hole for inserting the heater wire and the closed portion is selected as a through hole through which exhaust gas on the filter end face does not flow, it does not become exhaust resistance.

The number of embedded ridges of each heater wire, wire diameter, depth,
The shape is shown in Table 1. The feature is that each combination of heater wires is changed depending on the location. In Table 1, No. Reference numeral 21 corresponds to the outermost heater wire located at the outermost side of the heater wire,
Since there is no deep embedding in the outer periphery of this product,
And d are not shown.

In Table 1, No. Indicates the numbers of the heater wires shown in FIGS. The wire diameter is indicated by the diameter mm of the heater wire. As shown in FIG. 1, the number of peaks indicates the number of peaks a at the outer peripheral portion, the number of peaks inwardly from that, and the total number of peaks c.
The depth indicates the embedding depth d on the outer peripheral portion of the filter and the embedding depth e on the inner side thereof. “Watt / mountain” in Table 1 indicates the number of watts (output) per mountain of the heater wire.

In Table 1, FIG. 1 and FIG. 2, for example, the heater wire 31 arranged at the center of the filter has a wire diameter of 0.55 m.
m, the number of embedded ridges is 44, and two ridges (a) at both ends corresponding to the outer periphery of the filter are set to an embedded depth of 11 mm in consideration of heat dissipation, and the other 40 ridges (b) are set to an embedded depth of 7 mm. There is. In the case of the heater wire 21 arranged on the outer peripheral portion of the filter, the wire diameter is 0.55 mm, the number of embedded ridges is 35, and the embedded depth is 10 mm.

The number of embedded ridges of each heater wire, wire diameter, depth,
The shape is determined as follows. First, the heater wire embedding range on the filter end face is about 3 mm from the filter outer edge to avoid interference with the filter case and electrodes.
Provide a clearance. In this example, the diameter of about 134 mm is the embedded range of the heater wire. Count the through holes on the filter center line with the longest distance in this embedding range,
Maximum number of peaks of heater wire. In this example, 44 mountains is the maximum number of mountains.

The heater wire diameter is set within a range that can be inserted into the through hole, but in this example, the maximum wire diameter is 0.55 mm.
On the contrary, the minimum wire diameter was set to 0.4 mm from the viewpoint of the accuracy of the bending of the heater wire and the strength (maintaining the heater shape).
The embedded depth e of the heater wire is basically 7 to 10 mm,
The depth d of the range (two peaks from the outside in this example) corresponding to the outer peripheral portion of the filter that releases a large amount of heat was set to the range of 10 to 13 mm. In this example, the minimum embedding depth and the maximum embedding depth are set within 2 times to reduce the temperature difference in the axial direction of the filter.

After the heater wire specifications on the center line of the filter are determined, the number of outer embedding peaks is sequentially counted and determined every other row within the heater wire embedding range. After that, the heater wire diameter and embedding depth are determined for each heater wire.
Basically, the electric power (watt / watt) per mountain of each heater wire
(Mountain) should be within a certain range. In this example, 12V, 2
With KW specifications, it is set to be 2.36 to 2.65 W (watt) per heater peak to achieve soaking on the filter end face, but generally within ± 0.7 W If so, soaking is possible.

The temperature of each part of the honeycomb filter of this example was measured to compare the soaking tendency with that of the conventional product. The results are shown in FIGS. FIG. 4 is a conceptual diagram of the cylindrical honeycomb filter according to the present invention. on the other hand,
The conventional honeycomb filter differs from the honeycomb filter of this example in the following points. That is, the heater embedding depth is constant up to the vicinity of the outer periphery of the filter, and the heater is bent and embedded as seen from the filter end face side (FIG. 8).

As is known from FIG. 5, in the conventional product (curve S), the temperature of the outer peripheral portion of the filter is low, or the temperature of that portion is raised, so that the temperature of other portions rises too much or the heater is embedded. Depending on the pattern, there were hot spots where the temperature rose abnormally. Further, although not shown, in the case of a honeycomb filter of a type having an extremely deep embedding depth in the outer peripheral portion, the temperature in the axial direction of the filter naturally has a difference. Therefore, uniform heat distribution cannot be achieved in the axial direction.

The product of the present invention has a very uniform temperature distribution as shown by the curve P in FIG. Further, in the product of the present invention, in addition to the direction of embedding the heater wire, it is considered that the temperatures in the directions of 45 ° and 90 ° are also equalized. In other words, the temperature is soaked in all directions when viewed from the entire end face of the filter.

In the conventional product, even if one direction on the end face of the filter can be soaked, the 90 ° direction cannot be maintained at the same soaking level. Or, if it is attempted to equalize the temperature on the entire end face, the equalization in the axial direction will be sacrificed. Also,
As shown in FIG. 5, the temperature difference ΔT in the embedding area
The conventional product had a temperature of 250 ° C.
It can be seen that the temperature is within ℃ and excellent soaking can be achieved.

[0054]

[Table 1]

Example 3 As shown in FIG. 6, this example shows a cylindrical honeycomb filter composed of a heater supporting part 200 and a filter part 100, which are arranged so as to be separable from each other. The heater supporting portion 200 has the blocking portion 11 and the heater wire 2 arranged, as in the honeycomb filter shown in the first embodiment.

On the other hand, the filter 100, as shown in FIGS. 1 and 3, has the upstream side 16 facing the heater supporting portion 200.
1 and the downstream side 162 are provided with closed portions. The heater supporting part 200 and the filter part 100 are housed and fixed in a cylindrical case and used as a honeycomb filter for collecting particulates as in the first embodiment. Others are the same as in the first and second embodiments.

According to this embodiment, since the heater supporting portion 200 and the filter portion 100 are provided so as to be separable from each other, maintenance is easy when either of them is damaged. Moreover, the same effects as those of the first and second embodiments can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the honeycomb filter according to the first embodiment taken along the lines AA, BB, and CC of FIG.

FIG. 2 is a plan view of the honeycomb filter according to the first embodiment.

FIG. 3 is an explanatory view of the heater wire arrangement of the honeycomb filter in the first embodiment.

FIG. 4 is an explanatory view of a honeycomb filter of Example 2.

FIG. 5 is a temperature distribution measurement diagram of the honeycomb filter according to the second embodiment.

FIG. 6 is an explanatory diagram of a honeycomb filter according to a third embodiment.

FIG. 7 is an explanatory diagram of a conventional honeycomb filter.

FIG. 8 is an explanatory view of the heater wire arrangement of the honeycomb filter in the conventional example.

[Explanation of symbols]

1. ． ． Cylindrical honeycomb filter, 10. ． ． Gas passage, 100. ． ． Filter part, 11. ． ． Blockage, 15. ． ． Breathable bulkhead, 2, 21-31. ． ． Heater wire, 200. ． ． Heater support, 41. ． ． Positive side common electrode, 42. ． ． Common electrode on the negative side,

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-217617 (JP, A) JP-A-5-222914 (JP, A) JP-A-6-55021 (JP, A) Actual development Sho-60- 3221 (JP, U) Actual Kaihei 4-47125 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 3/02

Claims (5)

(57) [Claims] 1. A large number of gas passages defined by air-permeable partition walls, a closed portion provided in a part of the gas passages, and a plurality of meandering heater wires embedded in the closed portion and arranged in a straight line in parallel. In each of the heater wires, each end of each heater wire is connected to each of the common electrodes on the positive electrode side and the negative electrode side, and the cross section in the direction orthogonal to the gas passage is circular. The heater wire has a buried depth near the outer periphery of the filter which is larger than and equal to or less than twice that of the other parts, and the heater wires have substantially the same electric resistance value over their entire length. Therefore, for the minimum heater wire with the smallest embedded peak number, the maximum heater wire with the largest embedded peak number is
The heater wire having a number of ridges larger than 1 and less than or equal to 2 and having a wire diameter of 0.4 to 0.6 mm and a small number of embedded ridges has the above embedded ridges. A cylindrical honeycomb filter having a diameter smaller than that of many heater wires. 2. The cylindrical honeycomb filter according to claim 1, wherein the number of peaks in a portion having a large embedding depth near the outer peripheral portion is 2 to 4. 3. The cylindrical shape according to claim 1 or 2, wherein the outermost heater wire located at the outermost side among the heater wires is wired in a substantially U-shape when viewed from the end face of the filter. Honeycomb filter. 4. The honeycomb filter according to claim 1, wherein the honeycomb filter includes a heater support portion in which the heater wire is embedded and wiring, and a filter portion including the gas passage, both of which are separable from each other. A cylindrical honeycomb filter characterized by the above. 5. The cylindrical honeycomb filter according to any one of claims 1 to 3, wherein the honeycomb filter is made of a ceramic powder sintered body, and the outer periphery thereof is housed in a metal cylinder.