JPH07189667A - Induction heating type catalytic converter for automobiles - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the efficiency of exhaust gas purification by inductively heating the central portion of the catalyst carrier, which has a large flow rate of exhaust gas, like the surface. A monolith catalyst carrier 1 in which an inner peripheral carrier 1b 'is made of a material having a relatively higher magnetic permeability than that of an outer peripheral carrier 1a', and the outer periphery of the monolith catalyst carrier 1 is provided with an electric insulation and heat insulating material 2 interposed therebetween. And a coil not shown in the figure, and the monolith catalyst carrier 1 is induction-heated by energizing this coil.
Further, the monolith catalyst carrier 1 may be formed such that the inner peripheral carrier 1b 'is relatively thicker than the outer peripheral carrier 1a'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating type catalytic converter for an automobile, which is installed in an exhaust system of an engine, and more particularly, to deal with exhaust gas when the temperature at the time of engine starting is low. It is a thing.

[0002]

2. Description of the Related Art In order for a catalytic converter for an automobile engine to exert a substantial catalytic function, the temperature of the catalyst must be raised above its activation temperature. For this reason, various proposals have been made regarding means for directly or indirectly heating the catalyst by an electric heater or the like so that the catalyst function can be promptly exhibited even at the cold start of an engine having a low exhaust gas temperature. .

One of the proposals is an induction heating type catalytic converter in which the temperature of the catalyst is raised by inductively heating the carrier. This is equipped with an induction heating type monolith catalyst in which a coil for inductively heating the monolith catalyst carrier is provided on the outer periphery of the monolith catalyst carrier on which the catalyst is carried, with an electrical insulating material interposed therebetween.

In this monolith catalyst carrier, the carrier is formed of an electric resistor to generate an induced current in the carrier.
Therefore, it is not necessary to form an electrode portion on the catalyst carrier itself as in the conventional method of directly passing an electric current to the carrier itself from the outside, so-called direct heating method, and oxidation of the electrode portion, contact resistance due to thermal shock Problems such as changes are eliminated.
Further, in the adjustment of the heat generation amount, there is an advantage that the control can be performed using an optimum method from a number of methods such as adjustment of the oscillation frequency, pulse width, and pulse duty cycle.

FIG. 5 shows a schematic structure of a conventional induction heating type catalytic converter for automobiles. In FIG. 5, reference numeral 101 denotes a honeycomb-shaped monolith catalyst carrier on which a catalyst is supported, and a converter case 106 includes a seal 104 and a cushion 1.
Supported via 05. FIG. 6 is a view showing a cross section of the monolith catalyst carrier 101, and a catalyst 101b such as platinum is deposited on the carrier 101a. The seal 104 is for preventing exhaust gas from passing through the outside of the monolith catalyst carrier 101 and is provided at an upstream portion of the converter case 106 in the exhaust gas flow direction. The cushion 105 is a monolith catalyst carrier 101.
Is elastically supported on the converter case 106 to prevent damage due to its vibration, and is formed of an iron wire net, and is provided on the downstream side of the seal 104. The white arrow indicates the flow direction of the exhaust gas. The outer periphery of the monolith catalyst carrier 101 is shown in FIG.
As shown in, a coil 103 for passing an induced current through the monolith catalyst carrier 101 is provided via an electrical insulation and heat insulating material 102, and further, an electrical insulation and heat insulating material 102 is provided on the outer periphery of the coil 103 to form a cushion. It is electrically insulated from 105. Then, a high-frequency current is supplied to the coil 103 from a power supply device (not shown), so that the carrier 10
An induced current is generated in 1a, the carrier 101a is heated, and the catalyst 101b is heated to the activation temperature.

[0006]

The conventional induction heating type catalytic converter is constructed as described above, but as shown in FIG. 8, it is affected by the penetration depth of the induced current and the skin effect. Most of the induced current is generated in the vicinity of the outer peripheral portion of. That is, this induced current does not flow uniformly in each part of the cross section of the monolith catalyst carrier 1, but concentrates in the outer peripheral part as shown in the equation (1) and exponentially decreases as it approaches the central part. The phase is also delayed. This phenomenon is called the skin effect of electric current and is a characteristic of induction heating by high-frequency electric current.

I _x = I ₀ ε- ^{(x / p)} × ε ^{j (x / p)} (1) where I _x : current value (A) I _{0 at} the point x (m) from the surface toward the center : Current value (A) p on the surface of the monolith catalyst carrier p: Depth (m) at which the current value is reduced to 1 / ε times that on the surface j: Complex unit (j ² = -1) ε: Base of natural logarithm (2 .71828 ...) Here, p in the equation (1) is called the penetration depth of the high frequency current, and as shown in the equation (2), the relative permeability μ _r and the resistance of the electric resistor forming the monolith catalyst carrier are It is determined by the rate ρ (Ω · m) and the frequency f (Hz) of the high frequency current flowing in the coil.

P = √ (ρ × 10 ⁷ ) / [2π√ (μ _r f)] (2) In induction heating, the total heat generated by induction heating between the surface and the depth of p (penetration depth). It is well known that about 90% of the current is concentrated, and it is safe to assume that all of the induced current is concentrated in this portion.

Here, the monolith catalyst carrier is formed of only a single stainless steel material SUS403.
In the case of US403, μ _r = 100, ρ = 100 μΩmm
And the frequency of the high frequency current is f = 20k
When Hz, p = 0.113 mm is obtained from the equation (2). The radius of the monolith catalyst carrier 1 is r = 42.
It is 5 mm. That is, the radius r of the monolith catalyst carrier 1
= 42.5 mm, p = 0.113 mm from the surface
In between, about 90% of the total heat generated by induction heating is made.
Therefore, when the monolith catalyst carrier is made of an electrically conductive material, the central portion is hard to be heated.

Further, it is expected that the heat generated by the loss of the induced current will heat the central portion by heat conduction and radiant heat, but the honeycomb structure used for the catalyst carrier is apt to transfer heat in the axial direction. Since it has a characteristic that heat is hardly transferred in the radial direction, it is difficult to heat the central portion.

However, in actuality, when the exhaust gas of an automobile passes through the inside of the monolith catalyst carrier, the flow rate is large in the central portion (high flow velocity) and hardly flows in the outer peripheral portion (low flow velocity). Therefore, the catalyst function is not sufficiently exerted at the cold start of the engine having a low exhaust gas temperature.

The present invention was devised to solve the above-mentioned problems, and it is possible to activate the catalyst by effectively inductively heating even the central portion of the catalyst carrier to enhance the exhaust gas purification effect. An object of the present invention is to provide an induction heating type catalytic converter for automobiles.

[0013]

The first invention of the present application comprises a monolith catalyst carrier on which a catalyst is supported, and a coil provided on the outer periphery of the monolith catalyst carrier via an electric insulating material, and by energizing the coil. In the induction heating type catalytic converter for an automobile in which the monolith catalyst carrier is induction-heated, the magnetic permeability of the catalyst carrier is relatively increased from the outer periphery toward the center.

The second invention of the present application comprises a monolith catalyst carrier on which a catalyst is carried, and a coil provided on the outer periphery of the monolith catalyst carrier via an electric insulating material, and the monolith catalyst carrier is induced by energizing the coil. In the induction heating type catalytic converter to be heated, the material of the metal body of the catalyst carrier is relatively thicker from the outer periphery toward the central portion.

[0015]

Function: An electric current is generated in the monolith catalyst carrier by energizing the coil wound around the monolith catalyst carrier through the electric insulating material. At this time, in the induction heating catalytic converter of the first invention of the present application, since the magnetic permeability of the central portion material of the monolith catalyst carrier is large, a large amount of induced current flows in the central portion catalyst carrier, and the surface of the central portion catalyst carrier is also increased. It is heated in the same way as the catalyst carrier in the vicinity.

Further, in the induction heating type catalytic converter of the second invention of the present application, since the film thickness of the central portion material of the monolith catalyst carrier is large, a large amount of induced current flows in the central portion catalyst carrier, and in the central portion catalyst carrier. Is heated in the same manner as the catalyst support near the surface.

[0017]

FIG. 1 shows a schematic structure of a monolith catalyst carrier in an induction heating type catalytic converter for an automobile according to the first invention of the present application. The structure of the induction heating type catalytic converter for automobiles other than the monolith catalyst carrier is the same as the conventional one and will not be described. In FIG. 1, reference numeral 1 denotes a monolith catalyst carrier, which is composed of an outer peripheral carrier 1a and an inner peripheral carrier 1b.
2 is an electric insulation and heat insulating material. Further, FIG. 2 shows a flow of the induced current n in the cross section of the monolith catalyst carrier.

Next, the operation of the induction heating type catalytic converter for automobiles of FIG. 1 will be described with reference to FIG. An induced current is generated in the monolith catalyst carrier 1 by energizing a coil (not shown) wound around the monolith catalyst carrier 1 via the electric insulation and heat insulating material 2 as in the conventional case. At this time, for example, the inner peripheral carrier 1b of the monolith catalyst carrier 1 is a stainless steel material SUS403 (magnetic material) having a high magnetic permeability, and the outer peripheral carrier 1a outside thereof is a stainless steel material SUS having a low magnetic permeability.
It is formed of 304 (non-magnetic material). Since the magnetic flux has the property of gathering in a magnetic substance with a high magnetic permeability,
The magnetic flux density is higher in the medium having the higher magnetic permeability. Therefore, it is possible to prevent the central portion from being in a state where it is difficult to generate heat, and it is possible to collect the induced current also in the central portion as shown in FIG. 2, and it is possible to efficiently raise the temperature of the catalyst in this portion.
As a result, the central portion of the monolith catalyst carrier 1 having a large flow rate is also rapidly heated and the temperature of the catalyst is raised, so that the catalyst function is promptly exhibited at the cold start of the engine with a low exhaust gas temperature. Become.

In this embodiment, the carrier is composed of two kinds of materials at the outer circumference and the center, but it may be composed of three or more kinds of materials. In this case, a material having a relatively large magnetic permeability is arranged in the central portion.

Next, an embodiment of the second invention of the present application will be described with reference to FIG. In FIG. 3, the monolith catalyst carrier 1 is composed of an outer peripheral carrier 1a ′ and an inner peripheral carrier 1b ′. Specifically, as shown in FIG. 4, a ceramic flat plate 3a and corrugated plate 3b are provided with metal bodies, for example, Ferrite metal (N
i-Zn ferrite film, MaFe ₂ O ₄ film, Mn-Zn
Etc.) or silicide (MoSi _x , WSi _x, etc.) as C
The outer peripheral carrier 1a ′ and the inner peripheral carrier 1b ′ are created by vapor-depositing by means of VD or the like and winding the flat plate 3a and the corrugated plate 3b in an overlapping manner. At this time, the metal body is vapor-deposited on the flat plate 3a and the corrugated plate 3b so that the inner peripheral carrier 1'b is thicker and the outer peripheral carrier 1a 'is thinner. In this way, the inner peripheral carrier 1b 'is formed with a film thickness of a metal body that is thicker than the outer peripheral carrier 1a'. By thinning the outer peripheral portion, magnetic saturation is generated in the outer peripheral portion, and the magnetic flux corresponding to that is concentrated in the central portion. As a result, it is possible to prevent the central portion from being in a state where it is difficult to generate heat, and it is possible to collect the induced current also in the central portion as shown in FIG. 2, and it is possible to efficiently raise the temperature of the catalyst in this portion. As a result, the central portion of the monolith catalyst carrier 1 having a large flow rate is also rapidly heated and the temperature of the catalyst is raised, so that the catalyst function is promptly exhibited at the cold start of the engine with a low exhaust gas temperature. Become.

In this embodiment, two types of carriers having different thicknesses of the metal body from the outer periphery to the center are used. However, the metal body is provided on the ceramic carrier so that the thickness is relatively increased from the outer periphery to the center. The monolith catalyst carrier may be formed by vapor deposition.

[0022]

INDUSTRIAL APPLICABILITY In the induction heating type catalytic converter for automobiles of the present invention, since the magnetic permeability of the material of the monolith catalyst carrier is relatively large from the outer periphery to the central portion, the film thickness of the metal body of the monolith catalyst carrier is greater than the outer periphery. Since it is relatively thick toward the central portion, in the central portion of the monolith catalyst carrier with a large flow rate of exhaust gas, an induced current is generated similarly to the surface to facilitate induction heating, and the catalyst is quickly heated to the activation temperature, The catalytic function is fully exerted.

[Brief description of drawings]

FIG. 1 shows a schematic structure of a monolith catalyst carrier in an induction heating type catalytic converter for automobiles according to the first invention of the present application.

FIG. 2 shows how an induced current flows in the embodiment of FIG.

FIG. 3 shows a schematic structure of a monolith catalyst carrier in an induction heating type catalytic converter for automobiles according to the second invention of the present application.

FIG. 4 shows a procedure for producing the monolith catalyst carrier of the present invention.

FIG. 5 shows a schematic configuration of a vertical section of an induction heating type catalytic converter for an automobile.

FIG. 6 shows an example of a cross section of a monolith catalyst support.

FIG. 7 shows how to wind a coil in an induction heating type catalytic converter for an automobile.

FIG. 8 shows how an induced current flows in a conventional monolith catalyst carrier.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B01J 35/04 301 Z F01N 3/24 ZAB L 3/28 ZAB 301 P

Claims (2)

[Claims] 1. A monolith catalyst carrier on which a catalyst is supported,
A monolith catalyst carrier is provided with a coil provided on the outer periphery of the monolith catalyst carrier via an electrical insulating material, and the monolith catalyst carrier is induction-heated by heating the monolith catalyst carrier in an induction heating type catalytic converter for an automobile. An induction heating type catalytic converter for automobiles, which is relatively large from the outer periphery toward the center. 2. A monolith catalyst carrier carrying a catalyst,
A monolith catalyst carrier is provided with a coil provided on the outer periphery thereof via an electric insulating material, and the monolith catalyst carrier is induction-heated by energizing the coil. An induction heating type catalytic converter for automobiles, characterized in that the film thickness is relatively increased from the outer periphery toward the center.