JPH06264711A - Heat resistant cylindrical filter - Google Patents

Abstract

PURPOSE:To enhance the particulate collection rate by using an excellent heat resistant and brittle ceramic fiber without performing textured process and embodying an equal result as using a textured processed ceramic fiber. CONSTITUTION:A cylindrical filter 1 is made of a three dimensional cylindrical textile fabric F which is composed of a circumferential yarn 2 wound in multilayers in the circumferential direction and numerous radius yarn 3 turned back in a manner orthogonal to the circumferential yarn 21 and arranged continuously and snakily in axial and radial directions. The circumferential yarn 2 and the radius yarn 3 are very excel in heat resistance and are made of a fiber bundle composed of numerous pieces of ceramic fiber filament of which the diameter of one piece of a single fiber is not more than 20mum. The circumferential yarn 2 is wound in the condition of stretched yarn and long looser yarn mutually adjoining each other. Orientation of the fiber composing fiber bundles of loosen yarn fall into disorder and presents a condition of forming find gaps between the fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant tubular filter, and more particularly, it is suitable for collecting particulates (mixture of carbon fine particles and engine oil, unburned fuel) contained in high temperature diesel engine exhaust gas. Heat resistant tubular filter.

[0002]

2. Description of the Related Art Conventionally, as a filter for removing particulates contained in exhaust gas of a diesel engine,
Various things have been proposed. The filter is required to have good air permeability and be capable of capturing even fine particles. Suitable materials for this purpose include woven fabrics represented by fiber aggregates, knits, nonwoven fabrics, textured fiber bundles, and the like.

When the filter collects a certain amount of particulates due to use, the particulates are accumulated, so that the filtering function is lowered and the back pressure of the exhaust pipe is increased to lower the output of the engine. To prevent this, it is necessary to remove the accumulated particulates and regenerate the filtration function. It is preferable that the filter can be regenerated while the engine is in operation. As such a filter, it has been proposed that a large number of filter units are arranged in parallel in one housing and an electric heater is incorporated in each filter unit. (For example, JP-A-2-256812).

[0004]

The particulates are mainly composed of carbon, and in order to burn them, it is necessary to raise the temperature to 600 ° C. or higher. Further, it has been reported that the temperature of the filter reaches 1000 ° C. or higher due to the combustion heat of carbon during the combustion of particulates, and a fiber material having extremely high heat resistance such as ceramic fiber is suitable for this application. However, since fiber materials with extremely high heat resistance such as ceramic fibers have high rigidity and low elongation and are brittle, they easily break due to deformation such as bending and twisting, not only fluffing but also rupture and woven fabrics. It is extremely difficult to process it into a knitted fabric.

Further, the non-woven fabric can be formed from long fibers (filaments) or short fibers, but in both cases, a binder for binding the fibers to each other is required. However, there is no binder capable of withstanding the high temperature at the time of burning particulates, and even if it is, the presence of the binder causes clogging.

The textured processing is to disturb the filament fiber bundle by a jet stream of air to reduce the parallelism and to widen the gap between the fibers. Textured fibers improve fluid permeability while at the same time
The chances of contact between the enormous surface of the dispersed fibers and particles in the fluid to be filtered are increased, and the suitability as a filter material is increased. However, the brittleness of ceramic fibers cannot withstand this process and breaks creating short fiber waste. A glass fiber filter that processes a fluid at a relatively high temperature uses a bulky fiber bundle that is formed by winding a bulky fiber bundle that is disturbed in the fiber array by subjecting glass fiber to a textured process by a jet stream. There is. However, the heat resistance of glass fiber is not sufficient for the high temperature during the burning of particulates. Also, among ceramic fibers, there are types in which flexibility is increased by increasing elongation by adjusting constituent components. Although they can withstand light textured processing, they have a small amount of alumina component and poor heat resistance, so they are problematic as a filter material for long-term use by burning away particulates.

The present invention has been made in view of the above problems, and its purpose is to use brittle ceramic fibers having high heat resistance as a fiber bundle material constituting a filter,
Without applying textured processing to the ceramic fiber,
Another object of the present invention is to provide a heat-resistant tubular filter having a high collection rate of particulates as in the case of using a textured ceramic fiber.

[0008]

In order to achieve the above object, in the present invention, a ceramic fiber bundle having a small elongation and heat resistance is wound at least in the circumferential direction to form a layer for trapping impurities. The fiber bundles wound in the circumferential direction have different lengths and are wound close to each other.

[0009]

The tubular filter of the present invention is made of fibers (ceramic fibers) having a high heat resistance and a small elongation, so that it can sufficiently withstand the high temperature when burning and removing the impurities trapped by the tubular filter. obtain. The fiber bundle that is wound in the circumferential direction to form the layer for capturing impurities is wound in a state in which those having different lengths are wound close to each other.
The orientation of the fiber bundle is disturbed. The minute gaps formed by the disordered orientation of the fiber bundle exert an effective function for capturing fine particles.

[0010]

【Example】

(Embodiment 1) A first embodiment embodying the present invention will be described below with reference to FIGS. In this embodiment, the tubular filter 1 is composed of a three-dimensional cylindrical fabric F. The three-dimensional cylindrical fabric F has a circumferential yarn 2 wound in multiple layers (6 layers in FIG. 2) in the circumferential direction, and is folded back so as to be orthogonal to the circumferential yarn 2 and meanders continuously in the axial direction and the radial direction. It is composed of a large number of radial threads 3 arranged in a state. The radial threads 3 are folded back in the middle of the layer of the circumferential threads 2, and the radial threads 3 having different folding positions are arranged at predetermined intervals in the circumferential direction. The fibers of the circumferential yarns 2 are bundled in various thicknesses by the radial yarns 3, and the fibers of each layer are overlapped so that some of them overlap at different positions in the circumferential direction.
Are bundled by. The radial threads 3 prevent delamination of the circumferential threads 2 contained between their turns.

When the radial thread 3 is continuously folded back at the innermost layer and the outermost layer of the circumferential thread layer, a void is likely to be formed around the yarn, and the void has a shape penetrating the inner and outer layers, so that the filtering function is achieved. There is a risk that the particles will decrease (fine particles will pass through the voids). Therefore, at least one of the continuous folding positions of the radial thread 3 is an intermediate layer of the circumferential thread 2. For example, when the circumferential yarn layers are three layers, as shown in FIG. 3, the radial yarns 3 are folded back inside the innermost layer of the circumferential yarn layers and outside the second layer, and outside the outer and inner layers. The ones folded back inside the two layers are alternately arranged.

The circumferential yarn 2 and the radial yarn 3 are composed of a fiber bundle composed of a large number (several hundred to 1,000 or more) of ceramic fiber filaments each having a diameter of 20 μm or less. Silicon carbide fiber as the ceramic fiber,
Alumina fiber, Tyranno fiber (amorphous fiber made of silicon, titanium, carbon and oxygen, which has excellent heat resistance, trade name of Ube Industries Ltd.), etc. Among them, ALTEX (product name of Sumitomo Chemical Co., Ltd.), which has little strength deterioration, is preferable.
As the circumferential thread 2, a thread in a tensioned state and a thread in a loosened state longer than that are wound in a state of being close to each other. Since the circumferential thread 2 is composed of a large number of filaments, it becomes flat when wound as the circumferential thread 2. Therefore, the circumferential yarn 2 wound closely
3, the circumferential threads 2 do not maintain a circular shape and are not completely independent, but partially overlap each other and are indistinguishable. Then, of the fibers forming the fiber bundle of the two circumferential yarns 2, the orientation of the fibers forming the loose yarn is disturbed, and a fine gap is formed between the fibers. When schematically shown, as shown in FIG. 4A, the meandering fiber fa and the straight fiber fb are mixed. If there is no loose circumferential thread 3,
As shown in FIG. 4B, only straight fibers fb are formed.

The above-mentioned three-dimensional cylindrical woven fabric F is a method for manufacturing a three-dimensional woven fabric previously proposed by the applicant of the present application (Japanese Patent Laid-Open No. 22214/1990).
40). When manufacturing the three-dimensional cylindrical woven fabric F, a cylindrical core metal is fixed between a pair of fixing plates. Then, the ends of the radial threads 3 fed from a large number of radial thread bobbins are fixed to one fixed plate, and the ends of the circumferential threads 2 drawn from the circumferential thread bobbins are also fixed to the same fixed plate. Woven in a fixed state.

As shown in FIG. 5, a large number of radial thread bobbins 4 are held by a bobbin holder (not shown).
The radial threads 3 are arranged so as to extend radially around the three-dimensional cylindrical fabric F. Then, the bobbin holder is moved to reciprocate in the axial direction of the three-dimensional cylindrical woven fabric F, and is arranged at the position shown by the solid line and the position shown by the broken line. Two bobbins 5a, 5b having different diameters are coaxially and integrally rotatably arranged in the circumferential thread bobbin 5, and revolve around the three-dimensional cylindrical fabric F. The bobbins 5a and 5b are integrally rotated by winding the tensioned circumferential yarn 2 around the outside of the core metal, and the two circumferential yarns 2 are wound.
Are being delivered at the same time. The circumferential thread 2 is wound on the bobbins 5a and 5b to have substantially the same thickness, and
The diameter of each of the bobbins 5a and 5b is the bobbin 5 having a large diameter.
The circumferential yarn 2 fed from a is set to a ratio such that the circumferential yarn 2 is over-supplied by about 1 to 2% of the circumferential yarn 2 fed from the bobbin 5b having a small diameter.

Between the core metal (not shown) and the bobbin 5 for circumferential thread, a set of guide rollers 6a, as shown in FIG.
6b is provided coaxially and integrally rotatable. The guide rollers 6a and 6b are formed to have a diameter ratio of 1: 2, and revolve around the three-dimensional cylindrical fabric F integrally with the circumferential yarn bobbin 5 and are fed from the bobbins 5a and 5b. The circumferential thread 2 is fed to the core metal side by friction between the surface of the guide roller and the thread.

Then, the operation of winding the circumferential thread 2 a predetermined number of times and the operation of moving the radial thread bobbin 4 by the movement of the bobbin holder are repeated, so that the three-dimensional cylindrical woven fabric F of a predetermined length is placed outside the cored bar. It is formed. Then, after the three-dimensional cylindrical woven fabric F having a predetermined length is formed, the three-dimensional cylindrical woven fabric F is removed from the cored bar. The number of layers of the circumferential thread 2 and the folding position of the radial thread 3 are appropriately set according to the usage conditions of the tubular filter 1.

Two circumferential yarns 2 are simultaneously fed from the circumferential yarn bobbin 5 and wound at substantially the same positions in a state of being close to each other. Since the circumferential thread 2 fed from the small-diameter bobbin 5b is wound around the outside of the core metal in a tensioned state, the circumferential thread 2 fed from the large-diameter bobbin 5a is wound.
Is in a state of oversupply. As a result, unlike the case where only the circumferential yarn 2 in the tension state is formed, the circumferential yarn 2 is wound in a state in which the fiber orientation is disturbed, and a fine gap effective for capturing fine particles is formed between the fibers. It

Out of the circumferential yarns 2 fed from the circumferential yarn bobbin 5, the circumferential yarns 2 fed in an excessive supply state.
In the case of slackening, a phenomenon of slackening is seen on the way, and slackening may become unstable at the winding point. However, when a pair of guide rollers 6a and 6b having different diameters are arranged in the middle of the yarn path of the circumferential yarn 2, the circumferential yarn 2 fed in the excessive supply state is excessively fed to the core metal side. Therefore, the slack was postponed and did not pose a practical problem. Since the peripheral velocities of the two guide rollers 6a and 6b are twice different, the circumferential yarn 2 delivered in the excessive supply state is delivered while slipping.

Three-dimensional cylindrical woven fabric F formed as described above
Is used as the cylindrical filter 1 with one end closed. Although only one tubular filter 1 is used, a large number of tubular filters 1 are usually used as a filter device assembled in parallel in one housing in order to increase the filtration area.

FIG. 6 shows an example of the filter device 7. A plurality of cylindrical filters 1 are arranged in parallel in the housing 8. The housing 8 is formed in a cylindrical shape, and an exhaust gas introducing pipe 9 is projectingly provided on a peripheral surface near the first end of the housing 8.
An exhaust pipe 10 is provided at the center of the end. A pair of circular partition plates 11 and 12 are fixedly arranged in the housing 8 in a state orthogonal to the longitudinal direction of the housing 8, and the inlet-side space 13 is close to the first end of the housing 8 and close to the second end. An outlet side space 14 is formed in each of the. The exhaust gas introduction pipe 9 communicates with the inlet side space 13, and the exhaust pipe 10 communicates with the outlet side space 14. The partition plate 11 has an inlet space 1
Through holes 11a for guiding the exhaust gas introduced into the inside of each cylindrical filter 1 to the inside of each cylindrical filter 1 are formed at a predetermined interval, and a cylindrical fixing member 15 is fitted and fixed in the through hole 11a. The partition plate 12 is formed with a through hole 12a for communicating the space partitioned by both partition plates 11 and 12 with the outlet side space 13. The partition plate 12 is formed with a fitting projection 12b that closes the second end of the tubular filter 4. The first end of the tubular filter 1 is fitted to the fixing fitting 15,
The second end is fitted in the fitting projection 12b, and is fixed between the partition plates 11 and 12 in parallel with each other at equal intervals.

A heater 16 is arranged inside the cylindrical filter 1. The heater 16 is made of a Kanthal wire (Fe, Cr, Al alloy, trade name of Kanthal Gadelius Co., Ltd.), which is excellent in high temperature durability. The heater 16 has a first end fixed to the fixing member 15 and a second end fixed to the fitting projection 12b via the insulator 17 with the screw 18 and the nut 19. The end of the heater 16 is connected to the electric wire 20. The electric wire 20 is fed from the outlet side of the housing 8 to the housing 8
And is energized via a heater relay (not shown).

Further, an actuator 21 is attached to a side wall 8a of the housing 8 corresponding to the inlet side space 13 at a position facing each cylindrical filter 1. The piston rod 21a of the actuator 21 is projected into the inlet side space 13, and a lid 22 for opening and closing the opening 15a of the fixing fitting 15 is fixed to the tip thereof. And the tubular filter 1
At the time of regeneration, the actuator 21 corresponding to the tubular filter 1 is operated and the lid 22 is arranged at the closed position.

The filter device 7 constructed as described above is used by being connected in the middle of the exhaust pipe of a diesel engine. The exhaust gas introduced from the exhaust gas introduction pipe 9 into the inlet side space 13 is guided to the inside of each cylindrical filter 1 through the opening 15a and passes through the cylindrical filter 1 from the inside to the outside. Then, while passing through the tubular filter 1, particulates and the like contained in the exhaust gas are filtered, and the cleaned exhaust gas is discharged from the exhaust pipe 10 through the outlet side space 14.

The particulates in the exhaust gas are collected by the cylindrical filter 1 by the inertial action and the diffusive action. The cylindrical filter 1 has a large number of voids surrounded by three-dimensionally interwoven fibers. Then, while the exhaust gas passes through the tubular filter 1, the particulates collide with the fibers and are trapped and accumulated in the voids due to the inertial action and the diffusing action, and the filtration performance is maintained for a long period of time.

The pressure (back pressure) in the exhaust gas introducing pipe 9 rises as the amount of particulates collected in the tubular filter 1 increases. Then, the tubular filter 1 is regenerated when the back pressure reaches a predetermined regeneration start pressure. When the pressure in the exhaust gas introduction pipe 9 reaches a predetermined pressure, one tubular filter 1 is selected and the tubular filter 1 is regenerated, that is, particulates are burned and removed.

At the time of regeneration, the actuator 21 corresponding to the tubular filter 1 is actuated to place the lid 22 in the closed position, and the introduction of exhaust gas into the tubular filter 1 is blocked. Next, the heater 16 of the tubular filter 1 is energized to generate heat. Then, the heat generated by the heater 16 heats the particulates up to the combustion temperature and burns them off.

The closed state of the opening 15a by the lid 22 is as follows.
Either the state in which the inflow of the exhaust gas from the opening 15a is completely blocked or the state in which the exhaust gas flows in as far as the amount is small may be used. Even when the inflow of exhaust gas from the opening 15a is completely blocked, the combustion is relatively smoothly performed. Combustion proceeds without supplying oxygen required for combustion.
Unburned oxygen contained in exhaust gas (usually 5
It is said to contain about 16% oxygen. )
It is estimated that However, in order to promote the movement of heat inside the tubular filter 1 and to assist the burning of the accumulated particulates, it is preferable that a small amount of exhaust gas be introduced.

After a lapse of a predetermined time (1 to 1.5 minutes) required for burning particulates, energization of the heater is stopped. After that, the actuator 21 is operated, the lid 22 is placed in the open position, and the tubular filter 1 after regeneration is brought into an operating state again. After that, when the back pressure rises again and the tubular filter 1 needs to be regenerated, the next tubular filter 1 is regenerated. This operation is repeated as long as the operation of the engine is continued.

Tertiary yarn 2 has a three-layer structure in which circumferential yarn 2 has a three-layer structure using 10 μmφ × 1000 filaments of Altex fiber (trade name of alumina fiber manufactured by Sumitomo Chemical Co., Ltd.) as circumferential yarn 2 and radial yarn 3. An original cylindrical woven fabric F was created. Two circumferential yarns 2 were simultaneously fed, and one circumferential yarn 2 was fed in a 1.5% overfeed state to produce a three-dimensional cylindrical woven fabric having a thickness of about 1.5 mm. Using the three-dimensional cylindrical fabric F, the filter device 7 having the above-described structure was assembled (the number of the tubular filters 1 was 6).

Then, the filter device 7 is provided with a displacement of 3 ×
It was connected to an exhaust pipe of a 10 ³ cc diesel engine, operated at an engine speed of 1600 rpm and 50% load, and continuously collected and regenerated particulates. The collection rate of particulates was as high as around 85%. In the regeneration, when the back pressure reaches a certain level, the introduction of the exhaust gas into one tubular filter 1 is shut off and the tubular filter 1 is regenerated. When the regeneration of the tubular filter 1 is finished, the lid 2
2 was opened, the exhaust gas treatment was performed on all the tubular filters 1, and when the back pressure reached a certain level, the operation of regenerating the next tubular filter 1 was repeated. As a result of a test corresponding to a traveling distance of about 20,000 km, the tubular filter 1 was not damaged. Further, although the collection rate was high, the rate of increase in back pressure was rather low, and the air permeability was slightly higher than in the case of using the three-dimensional cylindrical woven fabric produced without oversupply.

For comparison, two circumferential yarns 2 were fed at the same feeding speed, that is, without being over-fed, to produce a three-dimensional cylindrical fabric, and the same test was conducted. The collection rate of particulates was less than 80%. The particulate collection rate was determined by measuring the amount of particulates in the exhaust gas before passing through the filter device 7 and the amount of particulates in the exhaust gas after passing through the filter device 7.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. The cylindrical filter 1 of this embodiment is formed by winding a multiplicity of threads 24 around the outer circumference of a perforated tube 23. The perforated tube 23 is configured by rolling a heat-resistant metal plate on which a large number of holes (not shown) are formed by a punch press into a cylindrical shape so that a part of the holes overlap. Hole is thread 2
4 is formed in a portion to be wound. The thread 24 is wound so as to form a predetermined angle with respect to the axis of the porous tube 23. As the thread 24, a thread in a tensioned state and a thread in a loosened state longer than that are wound in a state of being close to each other. Since the yarn 24 is composed of a large number of ceramic fiber filaments, it becomes flat in the wound state, the orientation of the fibers forming the loosened yarn is disturbed, and a fine gap is formed between the fibers. It is in the state of being The overlapping portion of the metal plates forming the perforated tube 23 is not fixed and is movable.

During regeneration of the tubular filter 1, the tubular filter 1
Becomes hot. Since the coefficient of thermal expansion of the perforated tube 23 is several times larger than that of the ceramic fiber, if the perforated tube 23 is a perfect tube, the force due to the expansion is applied to all the threads 24 wound around the perforated tube 23. Become. However, since the overlapping portion of the metal plates forming the porous tube 23 is not fixed, the difference in thermal expansion between the porous tube 23 and the ceramic fiber is absorbed by the overlapping portion of the porous tube 23.

This cylindrical filter 1 has a yarn supplying device 25 in which bobbins 25a and 25b having a large diameter and a small diameter are integrally rotated.
From the two perforated tubes 24 at the same time
It is formed by winding the wire around it while rotating it horizontally. The yarn 24 is guided by guide rollers 6a and 6b arranged between the yarn supplying device 25 and the perforated tube 23.
And is supplied via a traverse device (not shown) that reciprocates along the perforated tube 23 in the vicinity of the perforated tube 23.

Altex fiber (trade name of alumina fiber manufactured by Sumitomo Chemical Co., Ltd.) 10 μmφ × as thread 24
Using 1000 filaments, the thread 24 was wound around the perforated tube 23 so that five thread layers were formed on the outer periphery of the porous tube 23 to prepare the tubular filter 1. Opening rate 50%, diameter 55
One yarn was supplied and wound around the outer periphery of the perforated tube 23 having a length of mm and a length of 320 mm in a state of 1% oversupply. Using this tubular filter 1, a filter device 7 similar to that of the above-mentioned embodiment was assembled (the number of tubular filters 1 was 6). Then, the filter device 7 is connected to an exhaust pipe of a diesel engine having a displacement of 3 × 10 ³ cc, and an engine speed of 160
It was operated at 0 rpm and 50% load, and the collection and regeneration of particulates were continuously repeated. Compared to the case of using a tubular filter manufactured in the state where there is no over-supplied yarn, the collection rate of particulates is high at 74 to 78%, but the increase rate of back pressure is low and the air permeability is slightly it was high. And, even if the combustion of the accumulated particulates was repeated, the cylindrical filter 1 was hardly damaged.

The present invention is not limited to the above-mentioned embodiments, and for example, when the circumferential yarn 2 or the yarn 24 is wound, the number of yarns wound at the same time is not limited to two and may be three or more. In this case, the rate of oversupply may be changed for each yarn.

The three-dimensional cylindrical fabric F may have a structure including not only the circumferential yarns 2 and the radial yarns 3 but also axial yarns arranged so as to extend only in the axial direction of the three-dimensional cylindrical fabric F. The filter 1 may have a structure in which a fiber bundle is wound around the outer periphery of the three-dimensional cylindrical fabric F.

Further, as a method of simultaneously supplying a plurality of yarns so that at least one yarn is oversupplied at a predetermined ratio, a bobbin having the same diameter is used and a space between the bobbin and the yarn winding portion is used. It is also possible to provide a pair of rollers corresponding to each yarn and positively rotate the yarn while gripping the yarn, and change the peripheral speeds of these rollers.

Further, the tubular filter 1 is used in such a structure that the fluid passes from the outside to the inside, and it is not limited to the diesel engine for automobiles, but the exhaust gas treatment of the diesel engine for power generation and the filtration of other high temperature fluids are performed. You may use it for the purpose.

[0040]

As described in detail above, according to the present invention, it is possible to collect a high amount of particulates without using a textured ceramic fiber, as in the case of using a textured ceramic fiber. The filter can be captured at a high rate, and even if the filter is repeatedly regenerated by burning and removing particulates, the filter is unlikely to be damaged, and the predetermined filtering function can be maintained for a long time.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a tubular filter according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a tubular filter.

FIG. 3 is a cross-sectional view of another tubular filter.

FIG. 4A is a schematic view showing an arrangement state of fibers constituting a circumferential yarn, and FIG. 4B is a schematic view of a comparative example.

FIG. 5 is a schematic view showing a weaved state of a three-dimensional cylindrical woven fabric.

FIG. 6 is a partial cross-sectional view of a filter device using a tubular filter.

FIG. 7 is a perspective view of a guide roller.

FIG. 8 is a schematic view showing a manufacturing state of the tubular filter according to the second embodiment.

[Explanation of symbols]

1 ... Cylindrical filter, 2 ... Circumferential thread, 3 ... Radial thread, 5
... bobbin for circumferential thread, 5a, 5b ... bobbin, 23 ... perforated tube, 24 ... thread, 25 ... thread supply device, 25a, 25
b ... bobbin, F ... three-dimensional cylindrical woven fabric, fa, fb ... fiber.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Matsuura 2-chome, Toyota-cho, Kariya-shi, Aichi Stock company Toyota Industries Corporation (72) Inventor Yoshiharu Yasui 2-chome, Toyota-cho, Kariya-shi, Aichi Stock Company Toyota Loom Works

Claims (1)

[Claims] 1. A ceramic fiber bundle having a small elongation and heat resistance is wound at least in a circumferential direction to form a layer for capturing impurities, and the fiber bundle wound in the circumferential direction has different lengths. Heat-resistant tubular filters wound in close proximity to each other.