JPH08224443A - Electric heating catalyst device - Google Patents

Abstract

PURPOSE: To raise the temp. rise velocity of the whole catalyst device to speed up the activation of a catalyst on starting by setting the number of layers of flat plate- shaped belt members and corrugated plate-shaped belt members so that the closer the layers get to the central region, the smaller the number thereof, and enlarging the electric resistance value of an electric current fed to a carrier at the central region. CONSTITUTION: A carrier is constituted by winding plural layer plates 20 each alternately provided with flat plate-shaped belt members 21 and corrugated plate-shaped belt members 22 in a spiral. The number of layers of the flat plate-shaped belt members 21 and the corrugated plate-shaped belt members 22 in a layer plate 20 constituting a carrier is set so that the closer the layers get to the central region, the smaller the number thereof, to enlarge the electric resistance value per unit length of an electric current fed to the carrier at the central region 20a compared to that on the carrier peripheral edge side. In this way, the temp. rise of the carrier at the central region in which a flow rate is large is rapidly performed, and this becomes the starting point of catalyst activation to allow the catalyst activation to spread to the peripheral edge side. In the whole region from the central region to the peripheral edge side, a catalyst rapidly responds to the startup of an engine to improve the purifying efficiency of waste gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating catalyst device which is provided in an exhaust passage of an engine and heats a carrier by electric heat, and in particular, a flat strip member and a corrugated strip member are alternately provided. The present invention relates to an electrically heated catalyst device including a carrier in which one or a plurality of layer plates are spirally wound and which generates heat by an electric current supplied via an electrode.

[0002]

2. Description of the Related Art In an automobile engine, in order to reduce harmful substances such as unburned hydrocarbons discharged immediately after the engine is started, an electrically heated catalyst device is provided which rapidly heats the catalyst immediately after the engine is started. There is.

FIG. 4 shows an example of an automobile engine equipped with such an electrically heated catalyst device. In the figure, 01 is an engine, 02 is a combustion chamber of the engine, 03 is an exhaust passage,
Reference numeral 04 is a muffler, and 10 is an electrically heated catalyst device provided in the exhaust passage 03 between the combustion chamber 02 and the muffler 04.

In the electrically heated catalyst device 10, a voltage is applied from the battery power supply 13 to the carrier 17 which is a heating element on which a catalyst is carried by a switch 12 to rapidly heat the carrier, and the carrier 17 is carried on the carrier 17. Activates the catalyst, combustion chamber 0
CO (carbon monoxide), H in the exhaust gas discharged from 2
It removes harmful substances such as C (hydrocarbons).

FIG. 5 shows a conventional example of an electrically heated catalyst device used in an automobile engine. In the figure, 15
a and 15b are the inner side made of cordierite or heat-resistant alloy,
An outer base cylinder, 31 is a heat insulating material interposed between both base cylinders 15a and 15b, 16 is an electrode provided on the outer peripheral portion, and the electrode 16 is connected to the battery power source 13 via the switch 12. There is.

Reference numeral 17 denotes a carrier composed of a heating element housed in the base cylinders 15a and 15b. The carrier 17 is a multi-layer formed by laminating a flat plate-shaped band member and a corrugated plate-shaped band member described later. It is formed by spirally winding a plate, the electrode 16 is connected to the outer peripheral portion thereof, and a catalyst made of a noble metal such as palladium, platinum or platinum rhodium is carried on the surface of the layer plate. Reference numeral 18 denotes an exhaust gas passage formed between the carriers 17.

[0007]

In the automobile engine as shown in FIG. 4, the flow rate of the exhaust gas flowing in the exhaust pipe forming the exhaust passage 03 is at the center of the exhaust pipe due to the principle of fluid friction. A large amount is reduced in the outer peripheral portion, and therefore, when flowing in the carrier 10, the flow amount is large in the central portion and small in the peripheral side.

However, in the carrier which constitutes the conventional catalyst device shown in FIG. 5, one or a plurality of layers of plate-like band members and corrugated plate-like band members are spirally wound to form an inner circumference. A multilayer structure having a uniform layer thickness is formed over the entire area from the outer peripheral portion to the outer peripheral portion. Therefore, in such a device, since the thickness of the carrier 17 supporting the catalyst is uniform, the resistance becomes the same from the central portion to the peripheral side, and therefore the amount of heat generated by the energization from the electrode 16 is also in the central and peripheral sides. It is the same.

Therefore, since the exhaust gas flow rate in the central portion is larger than that in the peripheral side as described above, it is required that the heat generation amount of the catalyst carrier in the central portion is larger than that in the peripheral side. In that case, since the calorific value is substantially the same on the central side and the peripheral side, the temperature rise in the central part is not rapid and the peripheral side heating efficiency is low, as will be described later. Therefore, the temperature rising rate of the entire catalyst device is small, and the activation of the catalyst at the time of start-up (engine start) is unavoidably delayed.

An object of the present invention is to uniformly increase the temperature rising rate from the central portion of the catalytic device to the entire area on the peripheral side, thereby speeding up the activation of the temperature rising catalyst on the central side, and It is an object of the present invention to provide an electrically heated catalyst device capable of promptly purifying exhaust gas by a catalyst at the time of starting.

[0011]

SUMMARY OF THE INVENTION According to the present invention, one or a plurality of layer plates, which are provided in an exhaust passage of an engine and alternately include flat band members and corrugated band members, are spirally wound. The present invention is applied to an electric heating catalyst device composed of a carrier that generates heat by an electric current supplied through an electrode, and is characterized in that a flat plate-shaped band member and a corrugated plate-shaped band in a layer plate constituting the carrier are used. The number of layers with the member is set to be smaller toward the central part, and the electric resistance value per unit length of the electric current supplied to the carrier is larger in the central part than on the peripheral side of the carrier. There is something I did.

In the case of the present invention, the electric resistance distribution of the layer plate in the carrier from the peripheral side to the central part is set to be convex with respect to the flow rate distribution of the exhaust gas from the peripheral side to the central part, and It is better to set the amount of heat generation larger on the central part side.

[0013]

The operation of the present invention will be described with reference to FIG. In the carrier, the flow rate distribution of the exhaust gas from the peripheral side to the central portion is a convex quadratic curve that is convex upward. On the other hand, as shown in (A), in the prior art, since the electric resistance distribution of the layer plate in the carrier from the peripheral side to the central part is horizontal and straight, the calorific value per unit flow rate is closer to the central part. It becomes a concave quadratic curve that is convex downwards. Therefore, the temperature rise in the central part is delayed, and the heating efficiency on the peripheral side is also low, so the temperature rise rate of the entire catalyst device is low, and the activation of the catalyst at startup (engine start) is likely to be delayed. I have no choice.

On the other hand, in the present invention, as shown in (B), by making the electric resistance distribution of the layer plate in the carrier from the peripheral side to the central part a convex quadratic curve corresponding to the flow rate distribution of exhaust gas, In other words, by configuring the resistance value of the central portion to be larger than that of the peripheral portion, the heat generation amount of the central portion becomes larger than that of the peripheral portion in accordance with the flow rate distribution.

On the other hand, as a result, in the above (B), the calorific value per unit flow rate can be balanced from the central part to the peripheral side, and the temperature increase in the central part and the temperature increase in the peripheral side are balanced, and the carrier Due to the synergistic effect of electric heating and heating by exhaust gas, the catalyst can be rapidly activated, and the catalyst can be activated quickly when the engine is started.

Further, as shown in FIG. 3C, the electric resistance distribution of the layer plate in the carrier from the peripheral side to the central part is set to be convex with respect to the flow rate distribution of the exhaust gas from the peripheral side to the central part. By setting the heat generation amount per unit flow rate to be larger on the central part side, the temperature rise of the carrier at the central part where the exhaust gas flow rate is large becomes faster than on the peripheral side, resulting in catalyst activation from the central side. Start more quickly, and this center side serves as a base point to spread the activation of the catalyst on the peripheral side, and the catalyst reacts promptly to the start of the engine from the central portion to the peripheral side, and the exhaust gas Gas purification efficiency is improved.

As a technique similar to the present invention, in a honeycomb-type electric heating catalyst device using a spiral foil as a heating element, the thickness of the foil is thinner on the central side than on the peripheral side (Japanese Patent Application Laid-Open No. Hei 10 (1999)). No. 6-33746), the carrier in such a technique is formed by extrusion molding ceramic clay containing cordierite as a main component, so that the thin center portion is apt to have insufficient strength. The invention is manufactured by spirally winding a layer plate, and even if the number of layers of the flat plate-shaped band member and the corrugated plate-shaped band member is reduced to the central portion, there is no concern about the strength. However, in this respect, it has the significance of the above-mentioned conventional technology.

According to the present invention, the number of layers of the flat plate-shaped band member and the corrugated plate-shaped band member in the layer plate constituting the carrier is set to be smaller toward the central portion, and the diameter of the carrier can be reduced. Since it has not been modified in any way, it can be easily applied to existing devices.

[0019]

Embodiments of the present invention will be described in detail below with reference to FIGS. However, the dimensions, materials, shapes, relative positions, etc., of the components described in this embodiment are not intended to limit the scope of the present invention thereto, unless there is a specific description, and are merely illustrative examples. Nothing more than. FIG. 1 shows a cross-sectional view of an electric heating catalyst device according to an embodiment of the present invention in a direction perpendicular to an exhaust gas flow path, and FIGS. 2 and 3 show the shape of a carrier and an external view for explaining a manufacturing process. The figure is shown. 1 to 3, 15a and 15b are cylindrical inner and outer base cylinders made of cordierite or heat resistant alloy, 31 is a heat insulating material interposed between the inner and outer base cylinders 15a and 15b, 16 , 16 are electrodes provided on the outer peripheral portion. The electrodes 16 and 16 are connected to a battery power source 13 via a switch 12 as shown in FIG.

Reference numeral 25 denotes a carrier housed in the base cylinders 15a and 15b, which is formed by spirally winding a layer plate 20 shown below, which is alternately provided with flat plate-shaped band members and corrugated plate-shaped band members. ,
A catalyst 24 made of a noble metal such as platinum or platinum rhodium is carried on the surface of the layer plate 20. Reference numeral 18 is an exhaust gas passage formed between the layer plates. Such a configuration is similar to that of the conventional technique shown in FIG.

2 and 3, the layer plate 20 and the carrier 2 are shown.
5 shows details and manufacturing process. As shown in FIG. 2, the layer plate 20 constituting the carrier 25 has four conductive flat plate-shaped band members 21a disposed between the outer insulating flat plate-shaped band members 21b. Five corrugated strip members 2 between the members 21
It has a 5-layer structure with 2 interposed.

Of the corrugated plate-shaped band members 22, the band members 22a located at the center are formed with the same wave height (width) and the same wave pitch from the center to the outside, and then the central band member 22a.
Each of the two layers of band members 22b located on the upper and lower sides has no wave portion at the central portion 20a, and the wave height is gradually increased as it goes outward, in other words, at the outer peripheral portions 20b at both ends, a corrugated plate shape is formed. The height of the band member 22b is high, and the corrugated band member 22 on the outer side is crushed as it goes to the central portion 20a, and becomes linear at the central portion. As a result, the outer flat strip members, that is, the insulating layers 21b and 21b are formed in a substantially arcuate curved surface as shown in FIG.

When the layer plate 20 is housed in the base cylinder 15a, as shown in FIG. 3, the central portion 20a of the layer plate 25 is fitted to a bifurcated rotating jig 23, The jig 23 is rotated, for example, in the M direction in FIG.
A circular carrier 25 is formed such that a is located at the central portion 15c of the inner base cylinder 15a.

When the carrier 25 molded in this manner is housed in the inner base cylinder 15a, the central portion of the base cylinder 15a is
A central portion 20a having a small number of layers of one corrugated plate member 22a is arranged, and an outer peripheral portion 20b having a plurality of corrugated plate members 22a and 22b is arranged on the peripheral edge side 15d in the base cylinder 15a. It will be.

Therefore, the carrier 2 thus constructed
In the electrically heated catalyst device 10 provided with 5, the layer plate 20 in the central portion 15c of the base cylinder 15a has a large electric resistance value per unit length of the supplied current, and the peripheral side 15d in the base cylinder 15a is large.
Therefore, the layer plate 20 has electrical characteristics such that the resistance value becomes small.

Thus, when the automobile engine equipped with the electrically heated catalyst device 10 constructed as described above is in operation, the exhaust gas from the engine 01 is introduced into the electrically heated catalyst device 10 through the exhaust passage 03. .

On the other hand, when the switch 12 is turned on to connect the electric heating catalyst device 10 to the battery power source 13, the carrier 25 is heated via the electrodes 16 on the outer circumference. At this time, as described above, since the central portion 15c of the base cylinder 15a is provided with the layer plate 20a having a small number of layers and has a large electric resistance value, the calorific value is large, and the vicinity of the peripheral edge 15d of the base cylinder 15a is a layer. Since a large number of layer plates 20b are arranged and the electric resistance value is small, the amount of heat generated is small.

As described above, since the flow rate of exhaust gas is large in the central portion of the exhaust pipe and small in the portion near the outer periphery, the flow rate of exhaust gas is also near the central portion 15c of the base cylinder even in the electric heating catalyst device 10. There are many on the peripheral side 15d.

In the catalyst device 10, however, since the calorific value of the carrier 25 is large in the vicinity of the central portion 15c, the temperature of the carrier 25 rises extremely quickly and is sufficient for exhaust gas having a larger flow rate than the outer peripheral portion. A catalytic reaction is performed.

Further, by forming an electric resistance distribution as shown in FIG. 6 (C), since the exhaust gas temperature is high in the central portion 15c, the heating action of the carrier 20 by the exhaust gas is added. Then, the high-temperature carrier 20 near the central portion 15c serves as a base point for activating the catalyst in the base cylinder and affects the activation of the catalyst on the peripheral side, and particularly when the engine is started, the central portion 15c of the catalyst device 10 is activated. Thus, the catalyst reacts promptly over the entire area on the periphery side, and a high exhaust gas purification efficiency can be obtained.

[0031]

As described above, according to the present invention, the number of layers of the flat plate-shaped band member and the corrugated plate-shaped band member in the layer plate constituting the carrier is set to be smaller toward the central portion, In the electric heating type catalytic device for purifying exhaust gas, the electric resistance value per unit length of the supply current of the carrier carrying the catalyst is set to increase toward the central part, so that the heat generation in the central part of the catalytic device is increased. The amount becomes larger than that on the peripheral side. As a result, the temperature of the carrier is rapidly increased in the central portion where the flow rate of exhaust gas is high, and this serves as the base point for catalyst activation, which also affects the activation of the catalyst on the peripheral side.
The catalyst reacts promptly to the start of the engine in the entire region from the central portion to the peripheral side, and the exhaust gas purification efficiency is improved.

Further, according to the present invention, it is possible to provide a carrier having no problem in strength simply by reducing the number of layers of the flat plate-shaped band member and the corrugated plate-shaped band member constituting the layer plate toward the central portion. Becomes It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electric heating catalyst device for an automobile engine according to an embodiment of the present invention in a direction perpendicular to an exhaust gas flow path.

FIG. 2 is a front external view showing a shape of a carrier of the catalyst device before being incorporated.

FIG. 3 is an external perspective view showing a molding state of the carrier.

FIG. 4 is an exhaust system diagram of an automobile engine.

FIG. 5 is a corresponding diagram of FIG. 1 of a conventional electrically heated catalyst device.

FIG. 6 is a graph showing resistance distribution / flow rate distribution / heat generation distribution of a carrier according to the related art and the present invention.

[Explanation of symbols]

 Reference Signs List 01 engine 03 exhaust passage 10 electric heating catalyst device 15a, 15b base cylinder 15c center portion of base cylinder 15d peripheral edge of base cylinder 16 electrode 18 exhaust gas passage 20 layer plate 20a center portion of layer plate 20b outer peripheral portion of layer plate 21 flat plate Strip member 22 corrugated strip member 24 catalyst

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F01N 3/24 ZAB F01N 3/24 ZABL

Claims (2)

[Claims] 1. A spirally wound one or a plurality of layer plates provided in an exhaust passage of an engine and alternately provided with flat plate-shaped band members and corrugated plate-shaped band members, and supplied through electrodes. In an electrically heated catalyst device including a carrier that generates heat by an electric current, the number of layers of a flat plate-shaped band member and a corrugated plate-shaped band member in a layer plate that constitutes the carrier is set to be smaller toward a central portion,
The electric heating catalyst device, wherein the layer plate is configured such that the electric resistance value per unit length of the electric current supplied to the carrier is larger in the central portion than in the peripheral side of the carrier. 2. A calorific value per unit flow rate is set by setting the electric resistance distribution of the layer plate in the carrier from the peripheral side to the central part to be convex with respect to the exhaust gas flow distribution from the peripheral side to the central part of the carrier. 2. The electrically heated catalyst device according to claim 1, wherein the central portion side is set larger.