JP3288558B2 - Metal carrier for exhaust gas purification catalyst with excellent warming performance and heat retention performance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst for the metal responsible body for purifying exhaust gas of an internal combustion engine such as an automobile or a private power generator
About the.

[0002]

2. Description of the Related Art With the trend of stricter exhaust gas regulations for automobiles, metal carriers having many advantages have been increasingly used instead of conventional ceramic honeycombs as the base of exhaust gas purifying catalysts. This is because the honeycomb of the metal carrier is made of a thin heat-resistant stainless steel foil of about 50 μm and its heat capacity is small, so that the temperature rise after engine start is fast, the start of catalytic reaction is quick, and the heat resistance is high. Because it can be mounted closer to the engine, higher temperature exhaust gas can be used, and there are advantages such as improvement of the overall exhaust gas purification rate. Normally, as shown in FIG. 3, a honeycomb body formed by overlapping and winding a corrugated foil 7 and a flat foil 8 is inserted into a heat-resistant stainless steel outer cylinder 1 and brazed or resisted to each other, as shown in FIG. It is configured by welding.

[0003] Further, by reducing the foil thickness of the honeycomb body constituting the metal carrier, the heat capacity is reduced, and
It is also known that the heat transfer in the radial direction is reduced and a heat spot is easily generated, so that the start of the catalytic reaction is accelerated. For example, Japanese Unexamined Patent Publication No. Hei 6-99076 discloses a technique in which a metal carrier is divided into two stages by utilizing this property, and the thickness of the honeycomb body on the gas inlet side is made thinner than that on the outlet side. ing.

[0004]

However, due to recent advances in computer control of automobile engines, the temperature of the exhaust gas temporarily drops because the fuel is cut off in the engine braking state. A metal carrier having a small heat capacity has a disadvantage that the temperature of the catalyst at this time drops to a temperature lower than the catalyst reaction temperature, and the start of the catalyst reaction is delayed when the next exhaust gas to be purified flows.

[0005] The present invention provides such problems to solve in the conventional metal carrier, the temperature is hardly lowered, metal <br/> responsible body capable of achieving a significant improvement in the warm-up performance and the insulation performance of the catalyst The purpose is to do.

[0006]

The gist of the present invention is as follows. (1) In a metal carrier for an exhaust gas purifying catalyst in which a honeycomb body formed by laminating and winding a corrugated foil and a flat foil is inserted into an outer cylinder and joined to each other, a radius of 55 to 55 mm from the center axis of the carrier is obtained.
The honeycomb of cylindrical section within 85% as well as consists of foil 20~40μm thickness, it more honeycomb outer cylindrical portion constituted by a foil of 50~200μm thickness, the honeycomb body thin
The foil part should be flat foil and corrugated foil at least on the gas entry side end face.
Metal carrier for exhaust gas purification catalyst with excellent warming performance and heat retention performance characterized by being joined . ( 2 ) The flat foil and the corrugated foil are joined to each other at least in the vicinity of the gas inlet side end face of the thin foil honeycomb and the thick foil honeycomb, and the above-mentioned joint is formed between the thin foil honeycomb part and the thick foil honeycomb part. The metal carrier according to (1), which is joined at a portion other than the above. ( 3 ) The thin foil portion of the honeycomb body joins the flat foil and the corrugated foil at the gas entry side end surface, the thick foil portion joins at or near the gas exit side end surface, and the outermost peripheral portion 2 of the thin foil portion. The metal carrier according to (1), wherein in the first to fifth layers, the metal foil carrier is joined from the gas inlet side end face to the joining portion of the thick foil portion, and the thin foil portion and the thick foil portion are joined at the joining portion of the thick foil portion.

[0007] Since the thin-walled honeycomb arranged near the central axis has a small heat capacity, the temperature rise after the engine is started is fast, and the catalytic reaction is started quickly. Once the catalytic reaction starts, since the calorific value of the reaction in this part is large, the honeycomb part of the thick foil having a large heat capacity arranged on the outer peripheral part is also heated and starts to participate in the reaction, and the heat generated by the reaction causes this to occur. The parts also get hotter. Thereafter, when the engine is brought into the brake state, the thin-walled honeycomb portion near the center axis is cooled by the exhaust gas, and the temperature drops quickly, but the thick-walled honeycomb portion on the outer peripheral portion has a large heat capacity, so that cooling is slow. Thereafter, when the engine is in an accelerated state, the temperature of the honeycomb portion on the outer peripheral portion is high, so that the catalytic reaction starts quickly and generates heat. Due to this heat generation, the thin foil honeycomb near the central axis is heated, and due to the originally small heat capacity, the temperature rises rapidly and the catalytic reaction starts relatively early. That is, in the carrier of the present invention, when the engine is started, the thin-walled honeycomb rapidly starts the catalytic reaction during the acceleration after engine braking and generates heat, thereby accelerating the temperature rise in other parts, thereby increasing the overall reaction efficiency. Enhance.

In the present invention, the reason why the radius of the thin foil honeycomb is set to 55 to 85% of the radius of the entire honeycomb is that if the radius is less than 55%, the catalytic reaction after the start of the engine is started slowly. This is because the rise of the catalytic reaction during acceleration is delayed. In addition, the thickness of the thin foil is 2
The reason for limiting the thickness to 0 to 40 μm is that if the thickness is less than 20 μm, the mechanical strength of the honeycomb cannot be sufficiently obtained and the honeycomb is easily broken.
If it exceeds m, the rise of the catalytic reaction after the start of the engine is slightly delayed. Further, the thickness of the thick foil is 50 to 200 μm
The reason for the limitation is that if the thickness is less than 50 μm, the heat retention is not sufficient, the cooling by the engine brake is slightly faster, the rise of the catalytic reaction at the next acceleration is slow, and if it exceeds 200 μm, the heat capacity is too large and the temperature rise is slow. In addition, the exhaust resistance of this portion increases, and the gas inflow rate deteriorates.

Regarding the joining structure, the thin foil portion of the honeycomb body is
The reason that the flat foil and the corrugated foil should be joined at least near the gas entry side end face is that the flat foil and the corrugated foil near the gas entry side end face are not joined in the case of a thickness of 20 to 40 μm. This is because the foil material vibrates due to the exhaust gas flowing in and the foil is torn off. On the other hand, when the foil thickness is 50 to 200 μm, since the foil has high rigidity, even if the flat foil and the corrugated foil near the gas entry side end face are not joined, the foil does not break off. In addition, the reason that the thin foil honeycomb and the thick foil honeycomb should be joined to each other at a portion other than the above-mentioned joint portion is that the mechanical strength of the thin foil honeycomb is lower than that of the thick foil honeycomb, so that the exhaust gas If both honeycombs are joined at the joints in both honeycombs near the entry side end face, if thermal stress ~ strain occurs due to the variation of the temperature distribution in the honeycomb, this stress ~ strain concentrates on the thin foil honeycomb This is because the thin foil honeycomb is destroyed early.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a metal carrier according to the present invention, in which a honeycomb body formed by superposing and winding a flat foil and a corrugated foil made of stainless steel in an outer cylinder 1 made of stainless steel is loaded. ing. This honeycomb body has a thick foil honeycomb 2 formed of a flat foil and a corrugated foil having a thickness of 50 to 200 μm near the outer peripheral portion thereof, and a thin foil honeycomb 3 formed of a flat foil and a corrugated foil having a thickness of 20 to 40 μm inside thereof. It is composed of The ratio between the thick foil honeycomb 2 and the thin foil honeycomb 3 is as follows:
The radius of the thin foil honeycomb 3 is 55 to 85% of the total honeycomb radius.
Range.

The gas inlet side end face portions 4 and 4 '(shaded portions in the figure) of the honeycomb body having the above-mentioned structure have flat foils and corrugated foils joined to each other. The thin foil honeycombs 3 are joined at a portion other than the joining portion between the flat foil and the corrugated foil, for example, at the gas outlet side end face portion 5, and
The joint 6 between the outer cylinder 1 and the thick foil honeycomb 2 extends over the gas inlet side end face portion 4 'where the flat foil and the corrugated foil are joined, and the portion where the flat foil and the corrugated foil are not joined. Provided. The joint between the outer cylinder 1 and the thick foil honeycomb 2 may be any other than shown.

Further, many variations of the embodiment of the present invention are possible. For example, in the joining structure shown in FIGS.
It is located near it. In the present invention, since an ultra-thin foil is used, thermal fatigue fracture at a high temperature is apt to occur. To prevent this, the joining structure shown in FIGS. The flat foil and the corrugated foil are joined at the end face part, the thick foil part 2 is joined at or near the gas discharge end face part, and the outermost peripheral part of the thin foil part is the thick foil from the gas entry side end face in 2 to 5 layers. It is effective to form a structure in which the thin foil portion and the thick foil portion are joined at the joining portion of the thick foil portion. In particular, when using a foil having a thickness of about 30 μm in the thin foil portion or using a foil having a thickness of about 50 μm in the thick foil portion,
It is desirable to adopt these joining structures.

Next, the manufacturing process of the metal carrier of the present invention will be described with reference to FIG. As shown in FIG. 2, a honeycomb body is manufactured by winding a flat foil and a corrugated foil spirally around a winding shaft (not shown) to manufacture a honeycomb body. This manufacturing process is particularly different from the conventional one. There is no place. In the present invention, it is necessary to partially change the thickness of the foil in the middle of the honeycomb body. Therefore, as shown in FIG. In other words, the ends of the thick flat foil 8b and the corrugated foil 8b may be overlapped and fixed by spot welding 9 or the like, and then continuously wound.
The connection between the flat foil and the corrugated foil is not particularly limited, and there is no problem even if the position is arbitrarily shifted. Of course, the corrugated foil needs to be corrugated to the same pitch size in advance.

In this way, the honeycomb of the cylindrical portion within 55 to 85% from the center of the target honeycomb body radius is set to 2
It is made of a foil having a thickness of 0 to 40 μm, and the remaining honeycomb of the cylindrical portion located outside the foil is made of a foil having a thickness of 50 to 200 μm to produce a desired honeycomb body. Also, the specification of the subsequent foil can be selected regardless of the preceding foil,
If necessary, not only the foil thickness but also the material can be changed, or the wave height and pitch of the corrugated foil can be arbitrarily changed.

[0015]

【Example】

(Example 1) 20Cr-5Al-0.3Nb-0.08
A flat foil made of a Y composition and made of stainless steel foil having a thickness of 30 μm and a corrugated foil were overlapped and wound to produce a honeycomb having a length of 70 mmφ × 100 mm. In addition, 20 outside the honeycomb
Cr-5Al-0.05Ti-0.08REM (REM
Is composed of Ce, La, and misch metal).
A flat foil and a corrugated foil with a thickness of μm are stacked and wound, and
A honeycomb body having a length of 100 mm and a length of 103 mmφ × 1.
It was charged into a stainless steel outer cylinder having a thickness of 5 × 102 mm. The flat foil and the corrugated foil are brazed to a length of 20 mm from the gas entry side end face of the thin foil / thick foil honeycomb body, and the thin foil honeycomb / thick honeycomb / outer cylinder is joined at the gas exit end. Was brazed over a length of 30 mm. As a comparative example, a 10 μm thick foil having the same composition as the thick foil was used.
A honeycomb having a length of 0 mmφ × 100 mm is prepared and inserted into a stainless steel outer cylinder, and a flat foil and a corrugated foil are bonded to each other for 20 mm from the entrance end face of the honeycomb, and a gas outlet side is formed between the honeycomb and the outer cylinder. Of 30 mm was brazed. These two metal supports were subjected to wash coating of γ-Al ₂ O ₃ and supported Pt, Ph and Pb noble metal catalysts.

These metal carriers are mounted directly below the exhaust manifold of an engine with a displacement of 2000 cc. After the engine is started, the exhaust gas is discharged from the inlet side of the metal carriers after 30 seconds while maintaining the rotation speed at 1500 rpm and the intake pressure of -58 KPa. The sample was collected from the side, and the purification rate of HC was measured. As a result, the catalyst device using the carrier of the present invention had already shown a purification rate of 63%, while that of the comparative example had reached a purification rate of only 41%.

(Example 2) The carrier of the present invention produced in Example 1 and the carrier of Comparative Example in which a catalyst was carried were passed through an exhaust gas pipe having a length of 1 m from an exhaust manifold of an engine having a displacement of 2000 cc. The catalyst device was mounted on the gas outlet side. 2000rpm after engine start
The engine was abruptly stopped after it was confirmed that the HC purification rate of the catalyst device was stabilized at around 90% after being left for 10 minutes or more at an operating condition of suction pressure of -41 KPa. At the same time, assuming the engine braking condition, an atmosphere at room temperature was allowed to flow for 5 seconds at a rate of 20 liters per minute from immediately below the exhaust manifold to cool the catalyst device, then the air was stopped and the engine was started. 2000rpm, suction pressure-
The exhaust gas was adjusted to 41 KPa and sampled after 15 seconds, and the HC purification rate was measured. As a result, in the catalyst device using the carrier of the present invention, the purification rate was 82% and returned to almost the previous purification rate, but the purification rate of the comparative example was still low at 48%.

Example 3 20Cr-5Al-0.3N
A flat foil and a corrugated foil made of a stainless steel foil having a composition of b-0.08Y and having a thickness of 20 μm are superposed and wound, and 54 mmφ ×
A 90 mm long honeycomb was made and 20Cr-5Al-0.05Ti-0.08REM was added to the end of the outer periphery of these foils.
The flat foil and the corrugated foil having a thickness of 52 μm each having the composition of
A honeycomb having a size of 8.5 mmφ × 90 mm was manufactured. On this occasion,
A PVA liquid serving as a binder of a brazing material was applied to the top of the corrugated foil corresponding to the hatched portions in FIGS. 8 and 9 in the honeycomb cross section. These honeycombs were press-fitted into an outer cylinder made of a stainless steel sheet having an inner diameter of 78 mmφ, and solder powder was sprinkled from both end surfaces to produce two types of metal carriers such that the hatched portions in both figures became the joining portions.

These two types of metal carriers were brazed in a vacuum heat treatment furnace, washed and coated in the same manner as in Example 1, and supported with a noble metal catalyst. In addition, the displacement is 25
8 was attached to the front side of a 00 cc V6 engine, and the one shown in FIG. 9 was attached to the rear side. The HC purification rate was measured 30 seconds after engine startup under the same conditions as in Example 1. As a result, the front and rear sides were 69% and 7% respectively.
It showed a purification rate of 2%.

As a comparative example, a metal carrier 2 having the same dimensions and a foil from the center to the outermost periphery (the latter component) all having a thickness of 40 μm
The individual pieces were mounted in the same manner, and the purification rate of HC was measured under the same conditions. As a result, the front and rear sides are 44
%, 47%.

(Embodiment 4) Two types of carriers of the present invention were mounted on a V6 engine in the same manner as in Embodiment 3, and after the catalyst was once warmed up to 90% in purification ability in the same manner as in Embodiment 2, The engine was stopped, air was allowed to flow from the exhaust manifold for 5 seconds to slightly cool the catalyst, the engine was started again, and the HC purification ability after 15 seconds was measured. As a result, in the case of the present invention, the front side and the rear side exhibited a purifying ability of 76% and 78%.

As a comparative example, a metal carrier 2 having the same dimensions and a foil from the center to the outermost periphery (the latter component) all having a thickness of 40 μm was used.
Each was mounted on a V6 engine. Similarly, the metal carrier was once warmed up, the engine was stopped, cooling air was flown, and then the engine was started again. After 15 seconds, the HC purification rate was measured. As a result, the front and rear sides were 39% and 4% respectively.
It showed a purification rate of 3%.

[0023]

As shown in the above embodiments, the present invention provides a metal carrier which enables a catalyst device having excellent catalyst warm-up performance after engine start and excellent catalyst heat retention performance during engine braking. It improves the purification efficiency of catalytic devices such as automobiles and contributes to environmental purification.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the structure of the carrier of the present invention.

FIG. 2 is an explanatory view showing a process of manufacturing a honeycomb body used for a metal carrier according to the present invention.

FIG. 3 is a perspective view showing an outline of a metal carrier.

FIG. 4 is a sectional view showing another example of the structure of the carrier of the present invention.

FIG. 5 is a sectional view showing still another example of the structure of the carrier of the present invention.

FIG. 6 is a sectional view showing still another example of the structure of the carrier of the present invention.

FIG. 7 is a sectional view showing still another example of the structure of the carrier of the present invention.

FIG. 8 is a sectional view showing still another example of the structure of the carrier of the present invention.

FIG. 9 is a sectional view showing still another example of the structure of the carrier of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer cylinder 2 Thick-honeycomb 3 Thin-foil honeycomb 4,4 'Joining part in a honeycomb 5 Joining part of a honeycomb 6 Joint part between a thick-foil honeycomb and an outer cylinder 7a Thin corrugated foil 7b Thick corrugated foil 8a Thin flat foil 8b thick flat foil 9 spot welds

Continuation of the front page (72) Inventor Tadayuki Otani 5-3 Tokaicho, Tokai City, Aichi Prefecture Nippon Steel Corporation Nagoya Works (72) Inventor Hitoshi Ota 5-3 Tokaicho, Tokai City, Aichi Prefecture Nippon Steel Corporation Nagoya Works, Ltd. (56) References JP-A-5-220405 (JP, A) JP-A-2-253826 (JP, A)

Claims (3)

(57) [Claims] In a metal carrier for an exhaust gas purifying catalyst, a honeycomb body formed by laminating and winding a corrugated foil and a flat foil is inserted into an outer cylinder and joined to each other, a radius of 55 mm from a center axis of the carrier is obtained. Up to 85% of cylindrical honeycombs within 20 to 40%
μm with constituted by foil thickness, it more honeycomb outer cylindrical portion constituted by a foil of 50~200μm thick, honeycomb
The thin foil part of the rubber body is a flat foil at least on the gas entry side end face.
Metal carrier for exhaust gas purifying catalyst with excellent warming performance and heat retention performance, characterized by joining with corrugated foil . 2. A flat foil and a corrugated foil are joined to each other at least in the vicinity of an end face portion on the gas entry side of the thin foil honeycomb and the thick foil honeycomb, and the gap between the thin foil honeycomb part and the thick foil honeycomb part is the same. 2. The metal carrier according to claim 1, wherein the metal carrier is joined at a portion other than the joining portion. 3. The thin foil portion of the honeycomb body is formed by joining a flat foil and a corrugated foil at an end face on a gas inlet side, and a thick foil portion is joined at or near an end face on a gas exit side, and the outermost periphery of the thin foil portion. 2. The metal according to claim 1, wherein the second to fifth layers are joined from the gas inlet side end surface to the joining portion of the thick foil portion, and the thin foil portion and the thick foil portion are joined at the joining portion of the thick foil portion. Carrier.