JPH09303141A - Catalytic converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a retainer and an outer cylinder by a separate member, bring both of them into contact in a disconnection condition, so that the generation of thermal stress due to a thermal expansion difference between both of them can be prevented, in arranging the retainer between an end part of an intermediate member provided, between a carrier and the outer cylinder and the outer cylinder. SOLUTION: A catalytic converter 1 is constituted by a carrier 10, outer cylinder 11, intermediate member 12 and a retainer 2 arranged between an end part 120 of the intermediate member 12 and the outer cylinder 11. An internal diameter d of the retainer 2, in a use temperature condition of the catalytic converter 1, is formed smaller than an external diameter D of the carrier 10, the retainer 2 is formed into an L-shaped section so as to cover the end part 120 of the intermediate member 12. On the other hand, the outer cylinder 11 has a cone-shaped tapered part 110 contracted in a lengthwise direction thereof, the retainer 2 has an outer side surface 219 into slidable contact relating to an inner surface 119 of the tapered part 110. That is, the retainer 2 and the outer cylinder 11 are manufactured by a separate member, to be into contact in a disconnection condition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalytic converter installed in an exhaust path of an automobile engine.

[0002]

2. Description of the Related Art Conventionally, as a catalytic converter installed in the exhaust path of an automobile engine, for example, Japanese Patent Laid-Open No. 58-
As shown in Japanese Patent No. 165516, it is composed of a carrier, an outer cylinder for accommodating the carrier, and an elastic intermediate member provided between them. A ceramic honeycomb carrier is generally used as the carrier. The outer cylinder is made of a heat resistant metal material.

On the surface of the ceramic honeycomb carrier, Pt and Rh for converting harmful components such as CO, HC and NOx contained in exhaust gas discharged from an automobile engine into harmless gas or water, A noble metal catalyst such as Pd is supported. The material of the carrier is generally cordierite-based ceramic (2MgO.2Al ₂ O).
₃・ 5SiO ₂ ) is used, and this material has a smaller coefficient of thermal expansion than the metal outer cylinder.

Therefore, when the catalytic converter is heated by the exhaust gas flowing from the automobile engine, the difference in thermal expansion between the ceramic honeycomb carrier and the metal outer cylinder causes the above-mentioned converter. An increase in the distance between the carrier and the outer cylinder occurs in the radial direction.
The intermediate member has an elastic force capable of absorbing the increase in the space, and the honeycomb carrier made of ceramic is held inside the outer cylinder by the intermediate member.

By the way, the intermediate member has a high temperature (800
If it is directly exposed to exhaust gas (° C), it may be scattered. Therefore, conventionally, for example, Japanese Patent Laid-Open No. 56-476
As shown in No. 19, a retainer is joined to the outer cylinder, and this is used as an exhaust gas shielding plate for the intermediate member, and the retainer protects the intermediate member.

[0006]

[Problems to be Solved] In recent years, in order to make it possible to purify exhaust gas immediately after the engine is started, there is an increasing tendency to arrange a catalytic converter closer to the combustion chamber of the engine. This is because the carrier supporting the catalyst is rapidly heated from the cold state before the engine is started to the temperature of 300 ° C. to 350 ° C. which is the reaction temperature of the catalyst. However, for the above-mentioned purpose, when the catalytic converter is arranged closer to the combustion chamber of the engine, for example, directly below the exhaust manifold, the maximum temperature of the exhaust gas flowing into the engine at high engine load is 800 to 900.
It will be over ℃.

By the way, as described above, the retainer has a function of preventing scattering of the intermediate member by the exhaust gas. That is, the exhaust gas directly impinges on the retainer. Therefore, when the engine load is high as described above,
Exhaust gas having a high temperature of 800 ° C. or higher is directly blown onto the retainer. On the other hand, the outer cylinder to which the retainer is joined is cooled at the outside air temperature, so that a large temperature difference occurs between the retainer and the outer cylinder.

The retainer is mechanically joined to the outer cylinder or the flange provided on the outer cylinder. Alternatively, it was integrally formed with the outer cylinder or flange. Therefore, a temperature difference occurs between the retainer and the outer cylinder, and a difference in thermal expansion between the retainer and the outer cylinder occurs. Therefore, thermal stress is generated between the two, and the retainer may be deformed due to the thermal stress. When such deformation occurs, the retainer presses the brittle carrier, destroys the carrier, shifts the mounting position of the retainer, exposes the intermediate member to exhaust gas, and exhausts at this exposed portion. There is a risk that the intermediate member may be scattered by the gas.

In view of the above problems, the present invention provides a catalytic converter in which exhaust gas does not flow into the intermediate member, the intermediate member does not scatter, and the retainer is not deformed to damage the carrier. It is the one we are trying to provide.

[0010]

According to a first aspect of the present invention, there is provided a catalytic converter arranged in an exhaust path of an engine, the catalytic converter being provided between a carrier, an outer cylinder accommodating the carrier, and both. And a retainer arranged between the end of the intermediate member and the outer cylinder for preventing exhaust gas from flowing into the intermediate member. , The retainer and the outer cylinder are made of different members, and they are in contact with each other in a non-bonded state, and the retainer is pressed against the outer cylinder by the elastic force of the intermediate member. And in a catalytic converter.

The operation of the present invention will be described below. In the catalytic converter according to the present invention, the retainer and the outer cylinder are configured as separate members, and both are in non-bonded contact with each other. Therefore, thermal stress does not occur even if a difference in thermal expansion occurs between the two, and therefore the retainer does not deform.

Therefore, the retainer can always completely cover the end surface of the intermediate member, the intermediate member is not directly exposed to the exhaust gas, and the intermediate member is not scattered. In addition, thermal stress does not occur in the above retainer,
Therefore, there is no deformation of the retainer, and thus it is possible to prevent excessive force from acting on the carrier from the retainer, and the carrier is not damaged. Therefore, the catalytic converter of the present invention can be mounted on the upstream side of the exhaust path closer to the engine as compared with the conventional product. Therefore, the temperature rise of the carrier supporting the catalyst is enhanced, and the exhaust gas can be efficiently purified immediately after the engine is started.

As described above, according to the present invention, the exhaust gas does not flow into the intermediate member, the intermediate member does not scatter, and the retainer is not deformed to damage the carrier. Can be provided.

Next, as in the invention of claim 2, it is preferable that the retainer is provided at least on the upstream side of the engine exhaust path. As a result, it is possible to prevent the intermediate member from scattering due to the high-temperature exhaust gas blown from the upstream side. On the downstream side, the exhaust gas is rectified by passing through the carrier, and the radial swirl velocity component is reduced in the flow of the exhaust gas. Even if the intermediate member is exposed to the exhaust gas in such a state, scattering may not occur. In this case, the retainer on the downstream side may be omitted.

Next, it is preferable that the inner diameter of the retainer is always smaller than the outer diameter of the carrier under the operating temperature condition of the catalytic converter. As a result, under the operating temperature condition of the catalytic converter, it is possible to secure the overlapping portion of the retainer and the honeycomb carrier, and it is possible to reliably prevent the intermediate member from being exposed to the exhaust gas (see FIG. 1).

Next, as in the invention of claim 4, it is preferable that the retainer is formed in an L-shaped cross section so as to cover the end portion of the intermediate member. As a result, the L-shaped portion functions as a current plate, and the flow of the exhaust gas blown into the retainer can be guided to be blown into the carrier in the direction along the inner peripheral surface of the retainer. Therefore, it is possible to reliably prevent the exhaust gas from blowing into the intermediate member.

Next, according to the invention of claim 5, the outer cylinder has a conical taper portion which contracts in the longitudinal direction,
On the other hand, the retainer preferably has an outer surface that slidably contacts the inner surface of the tapered portion. The intermediate member is an elastic body, and the elastic force generated by the intermediate member serves as an axial force for holding the retainer.

Therefore, the elastic force is converted into a centripetal force with respect to the central axis of the substantially cylindrical catalytic converter by the conical taper portion, and this centripetal force suppresses radial eccentricity of the retainer. As a result, the retainer and the carrier can be reliably overlapped with each other, and the exhaust gas can be prevented from being blown into the intermediate member.

Next, according to the invention of claim 6, the intermediate member has an Al ₂ O ₃ .SiO ₂ composition and Al ₂ O.
It is preferable that the alumina fiber has a content of ₃ of 70% by weight or more. The above-mentioned alumina fiber has a heat resistant temperature of 1300 ° C. or higher, and the crystallization of the fiber hardly occurs up to this temperature, and the elastic force for holding the carrier can be maintained (see Embodiment 3). ). Therefore, even when the catalytic converter is installed in a higher temperature atmosphere, the carrier does not rattle and can be stably held.

The upper limit of the Al ₂ O ₃ content is 9
It is preferably 5%. If the content is higher than this value, the refining process for increasing the purity in the production of alumina fibers becomes complicated and the production cost may increase.

The conventional intermediate member is usually made of Al ₂ O ₃
Ceramic fibers containing approximately 50% by weight were often used. Such a ceramic fiber is 850
Crystallization may occur at a temperature of about ℃ and the elastic force of the ceramic fiber may decrease. In this case, the intermediate member cannot hold the carrier and the retainer, which may cause rattling inside the outer cylinder.

If the retainer rattles and its position is changed, the exhaust gas may blow into the intermediate member and the intermediate member may scatter. In addition, the carrier is often made of brittle ceramic or the like, and if the carrier is rattling inside the outer cylinder, damage such as cracking or chipping may occur. By using the above alumina fiber, it is possible to prevent such a problem from occurring.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A catalytic converter according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2,
The catalytic converter 1 includes a carrier 10, an outer cylinder 11 for accommodating the carrier 10, an elastic intermediate member 12 provided between the carrier 10, an end 120 of the intermediate member 12, and the outer cylinder 11. The exhaust gas is disposed between the intermediate member 12 and
And the retainer 2 for preventing the inflow.

The retainer 2 and the outer cylinder 11 are made of separate members, and they are in contact with each other in a non-bonded state. Further, the retainer 2 is attached to the outer cylinder 11 by the elastic force of the intermediate member 12. It has been pressed.

As shown in FIG. 1, the inner diameter d of the retainer 2 is always smaller than the outer diameter D of the carrier 10 under the operating temperature condition of the catalytic converter 1. Also, FIG.
As shown in FIG. 5, the retainer 2 is formed to have an L-shaped cross section so as to cover the end portion 120 of the intermediate member 12.
Further, the outer cylinder 11 has a conical taper portion 110 that contracts in the longitudinal direction thereof, while the retainer 2 has an outer surface 219 that slidably contacts the inner surface 119 of the taper portion 110.

The catalytic converter 1 will be described in detail below. As shown in FIG. 3, the catalytic converter 1 of this example is mounted on an exhaust manifold 36 which is an exhaust path of an automobile engine 3. The carrier 2 has a diameter of 7
1mm, length 60mm, wall thickness 0.08-0.13mm
Is a thin-walled ceramic monolith made of cordierite-based ceramic (2MgO · 2Al ₂ O ₃ ·
5SiO ₂ ). In addition, on the surface of the carrier 2,
A catalyst for purifying harmful components of the exhaust gas of the engine 3 is carried.

The intermediate member 12 contains 72 W of Al ₂ O ₃ .
made of alumina fiber (mullite fiber) with t% and SiO ₂ of 28 wt%, and the diameter of one fiber is 2 to 4 μm.
The thickness before assembly to the outer cylinder is 15 mm, and the bulk density is 0.0
It was 8 g / cm ³ . Further, the thickness after mounting this on the outer cylinder was 4.5 mm, and the bulk density was 0.27 g / cm ³ .

The outer cylinder 11 is a molded product obtained by press-molding a ferritic heat-resistant stainless steel plate having a plate thickness of 1.5 mm into a half-divided cylindrical shape. And the carrier 10
And a catalytic converter 1 serving as an outer wall covering the intermediate member 12
The diameter-enlarged portion forming the central portion of the has an inner diameter of 80 mm and an axial length of 75 mm. On the other hand, the openings 18 on the upstream side where the exhaust gas flows into the catalytic converter 1 and the downstream side where the exhaust gas flows out,
Reference numeral 19 has an inner diameter of 70 mm and an axial length of 10 mm.

The enlarged diameter portion 17 and the opening 18,
A taper portion 110 is provided between each of them and 19.
As shown in FIG. 2, the taper portion 110 has a conical shape, and the taper angle with respect to the exhaust gas flow direction is approximately 60 degrees.

The retainer 2 is provided in the openings 18 and 19 of the catalytic converter 1 and is made of ferritic heat resistant stainless steel. The inner diameter (d in FIG. 1) is 67 m
m, the outer diameter is 77 mm, and the plate thickness is 1.5 mm. Also,
The retainer 2 includes the enlarged diameter portion 17 of the outer cylinder 11 and the opening portion 1.
8 and 19, respectively. The taper portion 110 is held by the elastic force acting from the end surface 120 of the intermediate member 12, and is not particularly joined to the outer cylinder 11.

Next, the engine 3 of the catalytic converter 1
The state of arrangement in the exhaust path will be described. As shown in FIG. 3, the catalytic converter 1 of this example is arranged with respect to the exhaust manifold 36 provided in the engine 3. Then, as shown in FIG.
On the downstream side of the exhaust gas flow of the catalytic converter 1,
Start catalyst 21 having a capacity of 1300 cc
Is arranged. The start catalyst 21 is held and fixed in the outer cylinder 211 for the start catalyst via a wire net or a ceramic fiber mat.

Next, the assembly process of the catalytic converter 1 will be described with reference to FIG. First, the intermediate member 12 is compression-molded into the same shape as the outer peripheral shape of the carrier 10 using a binder (eg, epoxy resin), and then wound around the outer circumference of the carrier 10. Next, the retainer 2 is attached to the end surface 12 of the intermediate member 12.
Push it to 0. Next, the carrier 10, the intermediate member 12,
The retainer 2 is sandwiched between the semi-cylindrical steel plates 111 and 112 that can form the outer cylinder 11 after assembly.

At this time, since the retainer 2 is arranged so as to cover the end surface 120 of the intermediate member 12, the intermediate member 12 is
The semi-cylindrical steel plates 111 and 112 can be assembled without biting the end faces of the semi-cylindrical steel plates 111 and 112. Finally, the semi-cylindrical steel plates 111 and 112 are line-welded without a gap so that exhaust gas does not leak to form the outer cylinder 11. As described above, the catalytic converter 1 was obtained.

Next, the function and effect of this example will be described. The catalytic converter 1 according to this example is arranged in the exhaust manifold 36, and therefore, when the engine 3 is under a heavy load, a very high temperature exhaust gas flows in. Therefore, the retainer 2 is kept at a high temperature by the high temperature exhaust gas. On the other hand, since the outer cylinder 11 is cooled by the outside air temperature, it is kept at a temperature lower than that of the retainer 2. Therefore, a large temperature difference occurs between the retainer 2 and the outer cylinder 11, and thus a thermal expansion difference occurs.

However, in this example, the retainer 2 and the outer cylinder 11 are separate parts, and the two are not joined, so that stress is generated even if a difference in thermal expansion occurs between the two. There is no. Therefore, the deformation of the retainer 2 can be prevented, and therefore, the damage of the carrier 10 due to the deformation of the retainer 2 which has been conventionally seen and the scattering of the intermediate member 12 by the exhaust gas can be prevented. As a result, this example is the catalytic converter 1 that can be used even in an environment in which high-temperature exhaust gas of 900 ° C. or higher flows.

Further, as shown in FIG. 2, the retainer 2 is
Is formed to have an L-shaped cross section so as to cover the end portion 120 of the intermediate member 12. As a result, the L-shaped portion functions as a straightening plate, and the flow of the exhaust gas blown into the retainer 2 can be guided to be blown into the carrier 10 in the direction along the inner peripheral surface of the retainer 2. Therefore, it is possible to reliably prevent the exhaust gas from blowing into the intermediate member 12.

Further, as shown in FIG. 1, the inner diameter d of the retainer 2 is always smaller than the outer diameter D of the carrier under the operating temperature condition of the catalytic converter 1. As a result, an overlapping portion can be secured between the retainer 2 and the carrier 10, and the intermediate member 12 can be surely suppressed from being exposed to the exhaust gas.

Although the retainer 2 is provided at each of the upstream side and the downstream side in the present embodiment, the flow of the exhaust gas is weakened to the extent that the intermediate member 12 is not scattered by the rectifying action of the carrier 10. In this case, one retainer 2 may be provided on the upstream side.

Embodiment 2 As shown in FIGS. 6 and 7, this embodiment is a low-cost catalytic converter 4 having a retainer 29 according to the present invention.
As shown in FIG. 6, the catalytic converter 4 according to the present embodiment includes the carrier 1
0, an outer cylinder 41 accommodating the carrier 10, an elastic intermediate member 12 provided therebetween, and the intermediate member 1
The retainer 29 is disposed between the second end 120 and the outer cylinder 41 to prevent exhaust gas from flowing into the intermediate member 12.

The retainer 29 and the outer cylinder 41 are made of separate members, and both are in non-bonded contact with each other. The retainer 29 is pressed against the outer cylinder 41 by the elastic force of the intermediate member 12. The retainer 29 is provided only on the upstream side of the engine exhaust path.

The carrier 10 has the same shape, structure and material as in the first embodiment. The outer cylinder 41 has a plate thickness of 1.5.
It is a molded product obtained by press-molding a ferritic heat-resistant stainless steel sheet of mm into a substantially cylindrical shape. In the press forming process, first, a stainless steel plate is formed into a cylindrical shape with only one end squeezed, and the other end is squeezed into the same shape during the assembling process of the catalytic converter described later, and the inner diameter of the large diameter portion is 80 mm ，
Shaft length 70mm, 70mm at opening, Shaft length 10mm
And

The retainer 29 is a ring-shaped molded product of a heat resistant stainless steel having a plate thickness of 1.5 mm and having an inner diameter of 67 mm and an outer diameter of 77 mm.
Although the retainer 29 of this example has an annular shape, the retainer 29 may be formed by joining two half-divided annular shaped molded products together. The intermediate member 12 is made of the same material as in the first embodiment.

Next, the assembly process of the catalytic converter 4 will be described with reference to FIG. First, the intermediate member 12 is compression-molded into a shape similar to the outer peripheral shape of the carrier 10 using a binder (eg, epoxy resin), and then wound around the outer circumference of the carrier 10. Next, the retainer 2 is pressed against one end surface 120 of the intermediate member 12.

Next, as shown in FIG. 7, the carrier 10, the intermediate member 12, and the retainer 205 are pressed into the outer cylinder 41 from the end face 120 opposite to the end face against which the retainer is pressed. Then, the unmolded end of the outer cylinder 41 is drawn from the upper portion of the retainer 29 so as to have an inner diameter of 67 mm. As described above, the catalytic converter 4 was obtained.
Others are the same as the first embodiment.

According to the present invention, the annular retainer 29 is provided only on the upstream side of the engine exhaust path, and it is possible to obtain the low-cost catalytic converter 4 having four components. Others have the same operation and effects as those of the first embodiment.

Embodiment 3 As shown in FIGS. 8 and 9, this embodiment will explain the performance of the alumina fiber used as the intermediate member in Embodiment 1 and Embodiment 2. The composition of the alumina fiber is Al
₂ O ₃ is 72 wt% and SiO ₂ is 28 wt%. The alumina fiber was compressed to a predetermined bulk density under a temperature environment of 25 ° C and 1000 ° C. The thickness before compression is 15 mm and the bulk density is 0.08 g / cm ³ , which corresponds to the state before being assembled in the outer cylinder in the above-described embodiment example.

FIG. 8 shows the relationship between the elastic force acting per unit area of the alumina fiber, that is, the surface pressure and the thickness of the alumina fiber after compression. The surface pressure was measured by transmitting an elastic force, which changes with compression, to a load cell set outside the high temperature atmosphere furnace by a ceramic compression rod.

According to the figure, the surface pressure of the alumina fiber is 2
In the case of 5 ° C. and 1000 ° C., both are about the same. That is, it was found that the surface pressure of the alumina fiber was stable even if the temperature changed.

Next, FIG. 9 shows the X-ray diffraction result of the above alumina fiber. According to the figure, the diffraction results of the alumina fiber have the same shape at 25 ° C. and at 1000 ° C. As a result, the alumina fiber was
It shows that the crystal structure does not change at any temperature of 000 ° C.

From the above, it has been found that when the alumina fiber is used as the intermediate member, the carrier can be stably held under all temperature environments, particularly in a high temperature atmosphere of 900 ° C. or higher.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a catalytic converter according to a first embodiment.

FIG. 2 is an explanatory cross-sectional view of a main part of the catalytic converter in the first embodiment.

FIG. 3 is an explanatory view of mounting the catalytic converter on the engine in the first embodiment.

FIG. 4 is a partial cross-sectional view of a catalytic converter and a start catalyst according to the first embodiment.

FIG. 5 is a development view of the catalytic converter according to the first embodiment.

FIG. 6 is an explanatory cross-sectional view of a catalytic converter according to the second embodiment.

FIG. 7 is an assembly explanatory diagram of the catalytic converter according to the second embodiment.

FIG. 8 is an explanatory diagram showing the relationship between the surface pressure of the alumina fiber and the thickness of the alumina fiber after compression in the third embodiment.

FIG. 9 is an explanatory diagram of an X-ray diffraction intensity distribution of alumina fiber in the third embodiment.

[Explanation of symbols]

 1,4. . . Catalytic converter, 10. . . Carrier, 11, 41. . . Outer cylinder, 12. . . Intermediate member, 120. . . End, 2,29. . . Retainer, 110. . . Taper part,

Front page continuation (72) Inventor Yushi Fukuda 1-1, Showa-cho, Kariya city, Aichi Prefecture

Claims (6)

[Claims] 1. A catalytic converter arranged in an exhaust path of an engine, the catalytic converter comprising a carrier, an outer cylinder for accommodating the carrier, and an elastic intermediate member provided between the carrier and the outer cylinder. And a retainer arranged between the end portion of the intermediate member and the outer cylinder to prevent exhaust gas from flowing into the intermediate member. The retainer and the outer cylinder A catalytic converter characterized by being manufactured by separate members, contacting each other in a non-bonded state, and the retainer being pressed against the outer cylinder by the elastic force of the intermediate member. 2. The catalytic converter according to claim 1, wherein the retainer is provided at least on the upstream side of an engine exhaust path. 3. The inner diameter of the retainer according to claim 1 or 2, wherein:
A catalytic converter which is always smaller than the outer diameter of the carrier. 4. The method according to claim 1, wherein
The catalytic converter, wherein the retainer is formed in an L-shaped cross section so as to cover an end portion of the intermediate member. 5. In any one of claims 1 to 4,
The catalytic converter according to claim 1, wherein the outer cylinder has a conical taper portion that contracts in the longitudinal direction, and the retainer has an outer surface that slidably contacts the inner surface of the taper portion. 6. The method according to any one of claims 1 to 5,
A catalytic converter characterized in that the intermediate member is an alumina fiber having an Al ₂ O ₃ .SiO ₂ composition and an Al ₂ O ₃ content of 70% by weight or more.