JP2002364351A - Catalyst temperature raising device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat a part in the vicinity of an exhaust upstream end face of an exhaust purifying catalyst to prevent the occurrence of a difference in temperature. SOLUTION: The exhaust purifying catalyst 7 having electric conductivity is arranged in an engine exhaust passage 2. A conductive material 9 is arranged by facing the exhaust upstream end face 8 of the catalyst. A part in the vicinity of the upstream end face of the catalyst is induced and heated by supplying an alternating current to the conductive material. Furthermore, a central electrode 11 connected to the conductive material is connected to the center of the upstream end face of the catalyst substantially to connect an external electrode 13 with an outer peripheral face of a part 16 in the vicinity of the upstream end face of the catalyst. The alternating current flowing in the conductive material passes the part in the vicinity of the upstream end face of the catalyst through the central electrode and flows into the external electrode to heat the part in the vicinity of the upstream end face of the catalyst directly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst temperature raising device for an internal combustion engine, and more particularly to a catalyst temperature raising device for supplying an alternating current to an electric conductor for induction heating.

[0002]

2. Description of the Related Art In an internal combustion engine of an automobile, harmful gas components in exhaust gas emitted, for example, carbon monoxide (CO),
In order to purify components such as nitrogen oxides (NO _x ) and hydrocarbons (HC) before releasing them to the atmosphere, platinum (Pt)
An exhaust gas purification catalyst carrying a noble metal such as palladium (Pd) or a noble metal as a catalyst is provided in the exhaust system.

[0003] In order for the catalyst to perform a catalytic action in the exhaust purification catalyst, the temperature of the exhaust purification catalyst must be raised to the activation temperature or higher. However, especially when the engine is started, the temperature of the exhaust purification catalyst is low and the exhaust gas is also low temperature, so that it is difficult for the exhaust purification catalyst to rise to its activation temperature. Therefore, it is difficult for the exhaust purification catalyst to actively perform the catalytic action. Therefore, when the temperature of the exhaust purification catalyst is low, for example, when starting the engine, it is necessary to heat the exhaust purification catalyst to a temperature higher than its activation temperature by means other than the exhaust gas to activate the catalytic action.

One of the methods for raising the temperature of the exhaust purification catalyst is a method using induction heating. In the configuration of the conventional catalyst temperature raising device using such a method, a spiral induction heating coil is disposed so as to face the exhaust upstream end face of the exhaust purification catalyst, and an alternating current flows through the induction heating coil. Thus, the vicinity of the exhaust upstream end surface of the exhaust purification catalyst is induction-heated. By inductively heating the exhaust purification catalyst in this way, it is possible to heat only the portion near the exhaust upstream end surface of the exhaust purification catalyst (hereinafter, simply referred to as the upstream end portion). Therefore, the temperature in the vicinity of the exhaust upstream end surface can be quickly raised to a desired temperature with a small amount of electric power.

[0005]

However, in the structure of the above-described conventional catalyst heating device, the central region of the upstream end portion of the exhaust gas purification catalyst facing the central portion of the spiral of the induction heating coil (hereinafter, referred to as the central region). The amount of heating by induction heating of the central region portion) tends to be smaller than the amount of heating by induction heating of the portion around the central region portion (surrounding region portion) of the upstream end portion of the exhaust purification catalyst. It is in. For this reason, the temperature rise rate in the central region of the upstream end portion of the exhaust gas purification catalyst is lower than the temperature rise speed in the peripheral region portion of the upstream end portion. The temperature will be lower than the temperature of the area around the upstream end.

[0006] In view of such a problem, an object of the present invention is to heat a portion of an exhaust purification catalyst in the vicinity of an exhaust upstream end face so that a temperature difference does not occur.

[0007]

According to a first aspect of the present invention, a conductive exhaust purification catalyst is disposed in an engine exhaust passage, and the exhaust purification catalyst faces an exhaust upstream end face of the exhaust purification catalyst. In a catalyst temperature increasing device for an internal combustion engine in which a conductor is disposed and an electric current is supplied to the conductor to inductively heat a portion near an exhaust upstream end face of the exhaust purification catalyst, an exhaust upstream end face of the exhaust purification catalyst is provided. In addition to the induction heating of the vicinity, the current is supplied to the vicinity of the exhaust upstream end face of the exhaust purification catalyst to heat the vicinity of the exhaust upstream end face of the exhaust purification catalyst. In this catalyst heating device, the portion near the exhaust upstream end face of the exhaust purification catalyst has two parts: induction heating by flowing an alternating current through the conductor, and direct heating by flowing current to the portion near the exhaust upstream end face. Since the heating is performed by the two heating methods, a part of the portion of the exhaust purification catalyst that is difficult to be heated by the one heating method in the vicinity of the exhaust upstream end face can be heated by the other heating method. That is, the portion near the exhaust upstream end face of the exhaust purification catalyst can be complementarily heated by the two heating methods.

According to a second aspect of the present invention, in the first aspect, a central electrode connected to a conductor is connected substantially at the center of the exhaust upstream end face of the exhaust purification catalyst, and the central electrode is connected to the outer peripheral face near the exhaust upstream end face of the exhaust purification catalyst. The outer electrode was connected to allow the alternating current flowing through the conductor to flow to the outer electrode through the central electrode through a portion near the exhaust upstream end face of the exhaust purification catalyst.
In this catalyst warming device, the alternating current flowing through the conductor flows through the central electrode through the portion near the exhaust upstream end face of the exhaust gas purification catalyst to the outer electrode, so that only one current path is used for direct induction heating and direct heating. And two types of heating methods.

According to a third aspect, in the second aspect, the center electrode is formed of a rigid conductive material, and the center electrode is provided on the exhaust upstream end face of the exhaust purification catalyst so that the center electrode supports the conductor. It was connected.

[0010] In a fourth aspect based on the second aspect, the outer electrode is an encircling electrode that surrounds the outer peripheral surface near the exhaust upstream end surface of the exhaust purification catalyst.

According to a fifth aspect, in the fourth aspect, a conductive casing for accommodating the exhaust gas purifying catalyst is formed in the engine exhaust passage, and this casing is used as the surrounding electrode.

In a sixth aspect based on the third to fifth aspects, a conductive exhaust purification catalyst is additionally arranged upstream of the conductor separately from the exhaust purification catalyst, and the central electrode is provided with the additional exhaust purification catalyst. The additional exhaust purification catalyst was connected to the center electrode to support the purification catalyst. In this catalyst heating device,
Since the exhaust gas purifying catalyst having conductivity is arranged on the exhaust upstream side and the exhaust downstream side of the conductor, the magnetic field lines generated by flowing the alternating current through the conductor almost pass only through the heating target region.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The same reference numerals in the drawings indicate similar elements.

FIG. 1 is a schematic configuration diagram of an internal combustion engine including a catalyst temperature increasing device according to a first embodiment of the present invention. In FIG.
1 is a catalytic converter, 2 is an engine main body, and 3 is an engine exhaust passage. The engine exhaust passage 3 is connected to an exhaust port of the engine body 2. Catalytic converter 1 is arranged in engine exhaust passage 3. The catalytic converter 1 has an inlet 4 and an outlet 5. The exhaust gas discharged from the engine body 2 flows into the catalytic converter 1 from the inlet 4 through the engine exhaust passage 3 and is discharged from the catalytic converter 1 at the outlet 5. As described above, since the exhaust gas flows through the inside of the catalytic converter 1 from the inlet 4 to the outlet 5, the inlet 4 is referred to as the exhaust upstream side, and the outlet 5 is referred to as the exhaust downstream in the following description.

The catalytic converter 1 includes a substantially cylindrical casing 6 and a substantially cylindrical exhaust purification catalyst 7. The upstream side wall surface of the casing 6 has a substantially conical shape. The exhaust purification catalyst 7 is accommodated in the casing 6 so that its longitudinal axis is coaxial with the longitudinal axis of the casing 6. Further, the exhaust purification catalyst 7 is accommodated in the casing 6 such that the outer peripheral surface of the exhaust purification catalyst 7 contacts the inner peripheral surface of the casing 6, and the outer peripheral surface of the exhaust purification catalyst 7 and the inner peripheral surface of the casing 6 Is electrically connected over the entire outer peripheral surface of the exhaust purification catalyst 7. The exhaust upstream end face 8 of the exhaust purification catalyst 7 is a flat surface perpendicular to the axial direction of the exhaust purification catalyst 7 and located on the exhaust upstream side of the exhaust purification catalyst 7.

The exhaust gas purifying catalyst 7 is a catalyst which exhibits a good catalytic action at a certain temperature (active temperature) or higher. The carrier of the exhaust purification catalyst 7 is a metal carrier having a suitable conductivity and a magnetic permeability, or a carrier having a suitable conductivity and a magnetic permeability in which a material having a high magnetic permeability and a high conductivity is interspersed. . Further, the electric resistivity of the exhaust purification catalyst 7 is higher than the electric resistivity of the casing 6. A conductor 9 is arranged in the casing 6 so as to face the exhaust upstream end face 8 of the exhaust purification catalyst 7.

Next, the conductor 9 of this embodiment will be described in detail with reference to FIGS. FIG. 2 is an enlarged sectional view of the upstream side of the catalytic converter shown in FIG. 1, and FIG. 3 is a sectional view of the catalytic converter along line III-III in FIG. FIG. 2 shows magnetic lines of force described later only on the left side of the drawing with respect to the longitudinal axis of the catalytic converter, but in actuality the magnetic lines of force are present in all radial directions from the longitudinal axis to the outer periphery of the catalytic converter. .

As shown in FIG. 3, the conductor 9 of the present embodiment is a coil. The coil 9 is formed by spirally winding a single conductive material made of a material having a low electric resistivity, for example, a conductive wire. As shown in FIG. 2, the coil 9 extends along the exhaust upstream end face 8 of the exhaust purification catalyst 7 about the longitudinal axis 10 of the catalytic converter 1 (coaxial with the longitudinal axis of the casing 6 and the longitudinal axis of the exhaust purification catalyst 7). Catalytic converter 1
Spirally extend to the vicinity of the outer periphery of the. The coil 9 is disposed so as to face the exhaust upstream end face 8 of the exhaust purification catalyst 7 with a space. The shape of the cross section of the conductor constituting the coil 9 is elongated and rectangular. Stainless steel or copper can be used as the conductor constituting the coil 9. And
A central electrode 11 is mechanically and electrically connected to one end located inside the coil 9 in the radial direction. At this time, the coil 9 is connected such that the upstream surface of one end of the coil 9 is flush with the upstream end 14 of the center electrode 11. Alternatively, the center electrode 11 may be integrally formed as a part of the coil 9. The center electrode 11 is formed of a rigid cylindrical conductive material, and is disposed substantially at the center of the spiral of the coil 9. The downstream end 15 of the central electrode 11 is mechanically and electrically connected to substantially the center of the exhaust upstream end face 8 of the exhaust purification catalyst 7. With such a configuration, the center electrode 11 is arranged such that the coil 9 is disposed so as to face the exhaust upstream end face 8 of the exhaust purification catalyst 7, that is, the coil 9 is parallel to the exhaust upstream end face 8 of the exhaust purification catalyst 7. The coil 9 is supported on the exhaust upstream end face 8 of the exhaust purification catalyst 7 so as to be located on a proper surface.

Coil 9 located radially outside coil 9
A first outer electrode 12 is mechanically and electrically connected to the other end of. The first outer electrode 12 extends from the connection with the coil 9 inside the casing 6 to the outside of the casing 6 across the casing 6, and is insulated from the casing 6 and fixed to the casing 6. With this configuration, the first outer electrode 12 supports the coil 9 with respect to the exhaust upstream end face 8 of the exhaust purification catalyst 7, similarly to the above-described center electrode 11.

A second outer electrode 13 is connected to a portion of the casing 6 disposed on the outer peripheral surface of a portion (hereinafter simply referred to as an upstream end portion) 16 near the exhaust upstream end surface 8 of the exhaust purification catalyst 7. As described above, since the outer peripheral surface of the exhaust purification catalyst 7 and the inner peripheral surface of the casing 6 are electrically connected,
The second outer electrode 13 functions as a surrounding electrode connected to the exhaust purification catalyst 7 so as to surround the exhaust purification catalyst 7.
The first outer electrode 12 and the second outer electrode 13 are connected to an alternating current generating power supply 17 via a conductor. The alternating current generating power supply 17 is a power supply formed to generate an alternating current by combining a DC power supply with a resonance circuit. However, the alternating current generating power supply 17 may be an AC power supply.

Next, the induction heating will be described with reference to FIG. When an alternating current flows through the coil 9, an alternating magnetic field, that is, a magnetic force line 18 is formed around the coil 9 perpendicular to the direction in which the current flows in the coil 9. Further, the exhaust purification catalyst 7 has a higher magnetic permeability than the atmosphere around the coil 9 (for example, exhaust gas or air). Therefore, the magnetic force lines 18 pass through the exhaust purification catalyst 7 without passing through the atmosphere between the coil 9 and the exhaust purification catalyst 7. As described above, since the exhaust purification catalyst 7 has an appropriate magnetic permeability, the lines of magnetic force 18 passing through the exhaust purification catalyst 7 pass through the upstream end portion 16 of the exhaust purification catalyst 7 near the exhaust upstream end surface 8. Due to the magnetic force lines 18, an induced current (eddy current) around the magnetic force lines 18 is generated in the upstream end portion 16 of the exhaust purification catalyst 7 perpendicular to the magnetic force lines 18. Since the upstream end portion 16 of the exhaust purification catalyst 7 has electric resistance, the eddy current generated by the magnetic field lines 18 loses energy at the upstream end portion 16 of the exhaust purification catalyst 7, thereby causing the upstream end portion 16 of the exhaust purification catalyst 7 to lose its energy. Is induction heated.

Here, the advantage of heating the exhaust purification catalyst by induction heating will be described. When the exhaust purification catalyst 7 is induction-heated as described above, the entire exhaust purification catalyst 7 is not heated, but only the upstream end portion 16 of the exhaust purification catalyst 7 facing the coil 9 is heated. The heating is performed over a depth d (hereinafter, simply referred to as a heated depth) from the exhaust upstream end face 8 toward the exhaust downstream direction. The heated depth d of the upstream end portion 16 is a depth in the direction from the exhaust upstream end surface 8 of the exhaust purification catalyst 7 where the eddy current is generated by the magnetic force lines 18 toward the exhaust downstream direction (hereinafter, simply referred to as the current penetration depth). ) Δ. That is, as described above, the eddy current generated by the alternating magnetic field loses energy due to the electric resistance of the upstream end portion 16 of the exhaust purification catalyst 7, so that the induction heating is performed. The portion 16 is substantially the same as the region where the eddy current is generated by the alternating magnetic field, so that the heating depth d of the upstream end portion 16 is substantially the same as the current penetration depth δ. The current penetration depth δ is a function of the resistivity ρ of the exhaust purification catalyst 7, the relative magnetic permeability μ _r of the exhaust purification catalyst 7, and the frequency f of the alternating current flowing through the coil 9, and follows the following equation.

(Equation 1) Here, a is a constant. As can be seen from equation (1), the current penetration depth δ is inversely proportional to the square root of the frequency f and relative permeability mu _r of the exhaust gas purifying catalyst 7 of the alternating current, the exhaust gas purifying catalyst 7
Is proportional to the square root of the resistivity ρ. For this reason, the current penetration depth δ can be reduced and the heated depth d can be reduced by a simple operation of increasing the frequency f of the alternating current. Further the exhaust purification catalyst 7 resistivity ρ is small and relative magnetic permeability mu _r current penetration depth by forming in a large carrier δ
And the depth d to be heated can be reduced. Along with this, the heated depth d of the upstream end portion 16 of the exhaust purification catalyst 7 also decreases, and only the extremely thin upstream end portion 16 near the exhaust upstream end surface 8 of the exhaust purification catalyst 7 can be heated. Therefore, one of the advantages of heating the exhaust purification catalyst 7 by induction heating is that the exhaust upstream end face 8 of the exhaust purification catalyst 7
Only the very thin upstream end portion 16 in the vicinity can be heated.

As described above, by increasing the frequency of the alternating current flowing through the coil 9, the eddy current flows only in the extremely thin upstream end portion 16 near the exhaust upstream end surface 8 of the exhaust purification catalyst 7, so that the upstream end portion 16 In the eddy current flowing through, the current flowing per unit volume increases. Further, since the resistivity of the exhaust purification catalyst 7 is constant, the calorific value of the exhaust purification catalyst 7 increases as the current flowing per unit volume increases. Therefore, if induction heating is performed by passing a high-frequency alternating current through the coil 9, only the extremely thin upstream end portion 16 near the exhaust upstream end surface 8 of the exhaust purification catalyst 7 can be more strongly heated and rapidly heated. , Exhaust purification catalyst 7
The heating efficiency of the upstream end portion 16 can be increased. Therefore, another advantage of heating the exhaust purification catalyst 7 by induction heating is that the heating efficiency of the upstream end portion 16 of the exhaust purification catalyst 7 can be improved.

Further, the exhaust upstream end face 8 of the exhaust purification catalyst 7
Since only the extremely thin upstream end portion 16 in the vicinity can be heated more strongly to rapidly raise the temperature, the area of the upstream end portion 16 exposed to the exhaust gas passing through the upstream end portion 16 is also very small. Therefore, the amount of heat in the upstream end portion 16 that is taken away by the low-temperature exhaust gas at the time of starting the engine or the like is small, and therefore, the temperature of the upstream end portion 16 can be rapidly increased with small electric power. That is, another advantage of heating the exhaust purification catalyst 7 by induction heating is as follows.
The point is that the upstream end portion 16 of the exhaust purification catalyst 7 can be rapidly raised with a small amount of electric power.

When an alternating current is applied to the coil 9, as shown in FIG. 4, the lines of magnetic force 19 generated by the alternating current cause a portion of the central region of the upstream end portion 16 of the exhaust purification catalyst 7 facing the central portion 20 of the coil 9. (Hereinafter, it is simply referred to as a central region portion.) That is, most of the lines of magnetic force 19 do not pass through the central region 21 of the upstream end portion 16 of the exhaust purification catalyst 7 and the exhaust upstream end face 8 of the exhaust purification catalyst 7
Pass through the atmosphere located upstream of. Therefore, an eddy current is less likely to be generated in the central region 21 of the upstream end portion 16 of the exhaust purification catalyst 7, and the central region 21 is less likely to be induction-heated. Therefore, the amount of heating of the central region 21 facing the central portion of the coil 9 by induction heating is induced in the region around the central region of the upstream end portion 16 (hereinafter, simply referred to as a peripheral region) 22. It becomes smaller than the amount of heating by heating.

When an alternating current is applied to the coil 9 configured as described above, the alternating current tends not to flow uniformly in the coil 9 but to flow in a specific area. And, due to this, the upstream end portion 16 by induction heating
The heating amount of the central region 21 tends to be smaller than the heating amount of the peripheral region 22. Hereinafter, this will be described. As described above, when an alternating current flows in the coil 9, the magnetic force lines 19 are generated. The magnetic force lines 19 have a force for attracting electrons flowing in the coil 9, that is, an alternating current (hereinafter, referred to as an attractive force). The attraction force differs depending on the magnitude of the intensity of the magnetic force line 19 around the coil 9 and the distance between the coil 9 and the magnetic force line 19. As the intensity of the magnetic force line 19 increases, the attraction force increases. The shorter the distance, the stronger the suction power.

Referring now to FIG. 4, adjacent magnetic field lines 1
The distance between the coils 9 is reduced at a position downstream of the coil 9 when passing through the peripheral region 22 of the upstream end portion 16 of the exhaust purification catalyst 7. On the other hand, the distance between the adjacent magnetic force lines 19 is long on the exhaust upstream side of the coil 9.
Therefore, in the cross section of the coil 9, the attraction force from the exhaust downstream side is larger than the attraction force from the exhaust upstream side, so that the alternating current tends to concentrate on the exhaust downstream side of the cross section of the coil 9. Further, the distance between the adjacent magnetic lines of force 19 near the center of the coil 9 is longer than the distance between the adjacent magnetic lines of force 19 downstream of the coil 9 on the exhaust downstream side, but the distance between the magnetic lines 19 near the center of the coil 9 and the coil 9 is large. Is shorter than the distance between the magnetic field line 19 and the coil 9 on the exhaust downstream side of the coil 9. For this reason, in the innermost coil 9, the attraction force from the center side is relatively large, so that the alternating current is applied to the central portion of the cross section of the coil 9, that is, FIG.
As shown in (1), the coil 9 tends to flow intensively at a specific portion 23 of the cross section.

By the way, the shorter the distance between the alternating current flowing through the coil 9 and the exhaust upstream end face 8 of the exhaust purification catalyst 7, the shorter the distance.
An eddy current is likely to be generated in the upstream end portion 16 of the exhaust purification catalyst 7, so that the upstream end portion 16 is easily heated by induction. The alternating current flowing in the coils 9 other than the coil 9 near the center flows on the exhaust downstream side of the coil 9 as shown in FIG. On the other hand, the alternating current flowing in the coil 9 near the center flows through the center of the coil 9 as shown in FIG. When the alternating current flows on the center side of the coil 9, the upstream end portion 16 is less likely to be induction-heated because the distance between the coil 6 and the exhaust upstream end face 8 is longer than when the alternating current flows on the exhaust downstream side of the coil 9. . Therefore, the central region 21 of the upstream end portion 16 of the exhaust purification catalyst 7 facing the vicinity of the center of the coil 9 is less likely to be induction-heated. For this reason, the amount of heating of the central region 21 of the upstream end portion 16 by induction heating is smaller than the amount of heating of the peripheral region 22 by induction heating. For this reason, the temperature of the central region 21 of the upstream end portion 16 tends to be lower than the temperature of the peripheral region 22.

Here, in the embodiment of the present invention, the alternating current flowing between the first outer electrode 12 and the second outer electrode 13 flows from the coil 9 to the exhaust purification catalyst 7 via the center electrode 11. Has become. That is, the alternating current generating power supply 1
The current generated by the first outer electrode 1
2. Flow in the order of coil 9, central electrode 11, exhaust purification catalyst 7, and second outer electrode 13, or vice versa.
In this case, the upstream end portion 16 of the exhaust purification catalyst 7 is induction-heated by the alternating current flowing through the coil 9 as described above. Further, the alternating current flows through the upstream end portion 16 of the exhaust purification catalyst 7, causing an energy loss of the alternating current due to electric resistance in the upstream end portion 16 of the exhaust purification catalyst 7.
Is heated (hereinafter, such heating is referred to as direct heating). Upstream end portion 1 of exhaust purification catalyst 7
6, the upstream end portion 16 is heated according to the principle described later.
Is larger in the central region 21 than in the peripheral region 22. Therefore, in addition to inductively heating the upstream end portion 16 of the exhaust purification catalyst 7 by passing an alternating current through the coil 9, an alternating current is passed through the upstream end portion 16 of the exhaust purification catalyst 7 to directly connect the upstream end portion 16. By heating, it is possible to increase the amount of heating of the central region 21 of the upstream end portion 16 in which the amount of heating is smaller than that of the peripheral region 22 of the upstream end portion 16 in the induction heating.

Further, since the magnetic flux generated by the coil 9 also passes through the center electrode 11, an eddy current also flows through the center electrode 11, whereby the center electrode 11 is also induction-heated. When the central electrode 11 is induction-heated, the heat moves to the central region portion 21 of the upstream end portion 16 of the exhaust purification catalyst 7.
Therefore, by arranging the center electrode 11 near the center of the spiral of the coil 9, the upstream end portion 1 of the exhaust purification catalyst 7 can also be formed.
The central region 21 of 6 is heated. In this way, the central region 21 of the upstream end portion 16 is made uniform with the peripheral region portion 22 by the direct heating of the upstream end portion 16 and the induction heating of the central electrode 11 of the exhaust purification catalyst 7, or the peripheral region portion 22 is made larger than the above. Can be heated. Along with this,
The temperature of the central region portion 21 of the upstream end portion 16 can be equal to or higher than the temperature of the peripheral region portion 22.

Next, in the direct heating of the upstream end portion 16 of the exhaust purification catalyst 7, the central region 21
The principle by which the amount of heating is larger than the amount of heating of the peripheral region portion 22 will be described. As described above, the direct heating of the upstream end portion 16 of the exhaust purification catalyst 7 is performed by the alternating current flowing between the center electrode 11 and the second outer electrode 13. Further, the center electrode 11 is connected to substantially the center of the exhaust upstream end face 8 of the exhaust purification catalyst 7, and the second outer electrode 13 is connected to the casing 6, as described above.
Functions as an electrode connected to the exhaust purification catalyst 7 so as to surround the exhaust gas purification catalyst 7. Since the electric resistivity of the casing 6 is lower than the electric resistivity of the exhaust purification catalyst 7, the alternating current passes through the casing 6 more easily than the exhaust purification catalyst 7, and the casing 6 surrounding the central electrode 11 and the exhaust purification catalyst 7. It flows between all points around. That is, the alternating current flowing in the upstream end portion 16 of the exhaust purification catalyst 7 flows radially from the central electrode 11 to the second outer electrode 13 or vice versa.

As described above, when the alternating current flows radially,
Since the current flowing in the central region 21 and the peripheral region 22 of the upstream end portion 16 of the exhaust purification catalyst 7 is the same, the current flowing per unit volume of the central region 21 of the upstream end portion 16 is reduced to the peripheral region 22. Is larger than the current flowing per unit volume. Since the resistivity of the exhaust purification catalyst 7 is constant, the calorific value of the exhaust purification catalyst 7 increases as the current flowing per unit volume increases. Therefore, the heating amount of the central region portion 21 of the upstream end portion 16 by the direct heating is larger than the heating amount of the peripheral region portion 22.

Generally, when an alternating current is applied to a conductor,
The alternating current flows near the surface of the conductor due to the magnetic field generated by the alternating current (skin effect). The higher the frequency of the alternating current, the more the alternating current flows near the surface of the conductor. is there. For this reason,
In this embodiment, the alternating current having a high frequency flowing through the upstream end portion 16 of the exhaust purification catalyst 7 flows through the extremely thin upstream end portion 16 near the exhaust upstream end face 8 of the exhaust purification catalyst 7. Also,
The alternating current is an extremely thin upstream end portion 16 of the exhaust purification catalyst 7.
Therefore, the alternating current flowing through the upstream end portion 16 increases the current flowing per unit volume. As described above, in the exhaust purification catalyst 7, since the calorific value increases as the current flowing per unit volume increases, the exhaust purification catalyst is compared with a case where a DC current is flown in the vicinity of the exhaust upstream end face 8 of the exhaust purification catalyst 7, for example. Only the extremely thin upstream end portion 16 in the vicinity of the exhaust upstream end face 8 can be heated more strongly and rapidly heated. In this way, an alternating current flows through the upstream end portion 16 of the exhaust purification catalyst 7 to
When the is heated directly, the extremely thin upstream end portion 16 in the vicinity of the exhaust upstream end surface 8 of the exhaust purification catalyst 7 is mainly heated, and as described above, the heating amount of the central region portion 21 of the upstream end portion 16 due to the direct heating is It is larger than the heating amount of the region portion 22. For this reason, according to the present embodiment, the central region 21 of the upstream end portion 16 is primarily heated by direct heating.

By the way, if an alternating current is applied to the upstream end portion of the exhaust purification catalyst between the center electrode and the casing without arranging the coil facing the exhaust upstream end surface of the exhaust purification catalyst, for example, The current locally concentrates on a portion where the resistance of the end portion is slightly lower or the like. If the current concentrates on a certain portion of the upstream end portion of the exhaust purification catalyst, not only the entire central region of the upstream end portion of the exhaust purification catalyst cannot be heated, but also the portion where the current is concentrated burns out. Would. Here, in the embodiment of the present invention, the alternating current flowing through the exhaust purification catalyst 7 receives a force by the magnetic flux generated by the coil 9 and passing through the exhaust purification catalyst 7. In particular, the magnetic flux passing through the central region 21 of the exhaust purification catalyst 7 is substantially perpendicular to the exhaust upstream end face 8 of the exhaust purification catalyst 7. For this reason, the central region 21 of the upstream end portion 16 of the exhaust purification catalyst 7 is separated from the central electrode 11 by the upstream end portion 1 of the exhaust purification catalyst 7.
The alternating current flowing radially toward the outer periphery of the exhaust gas 6 or vice versa is subjected to a force in the circumferential direction of the exhaust gas purifying catalyst 7 according to Fleming's left-hand rule. Therefore, when the current concentrates in the central region 21 of the upstream end portion 16 of the exhaust purification catalyst 7, a large force is applied to the current for the reason described above, and the current is applied to the central region 21 of the upstream end portion 16 of the exhaust purification catalyst 7.
Distributed throughout. By arranging the coil 9 so as to face the exhaust upstream end face 8 of the exhaust purification catalyst 7 in this way, not only the induction heating of the upstream end portion 16 of the exhaust purification catalyst 7 can be performed but also the exhaust purification. It is possible to prevent current concentration in direct heating of the upstream end portion 16 of the catalyst 7.

In the above-described embodiment, the cross section of the conductor constituting the coil 9 is elongated and rectangular, but may be another cross section such as a circle or an ellipse. Further, in the above-described embodiment, the shape of the exhaust upstream end face 8 of the exhaust purification catalyst 7 is a flat surface, but may be another shape such as a conical shape which is convex in the exhaust upstream direction. In this case as well, the coil 9 extends along the exhaust upstream end face 8 of the exhaust purification catalyst 7 about the longitudinal axis 10 of the catalytic converter 1.
The coil 9 is convex along the exhaust upstream end face 8 along the exhaust upstream end face 8 if the exhaust upstream end face 8 of the exhaust purification catalyst 7 has a conical shape that is convex in the exhaust upstream direction, for example. It is conical and extends spirally, ie spirally. In the embodiment described above, the central electrode 1
Reference numeral 1 denotes a rigid columnar conductive material. The center electrode 11 is simply a conductor, and is connected between one end of the coil 9 and the center of the exhaust upstream end face 8 of the exhaust purification catalyst 11. You may make it connect. In this case, the support of the coil 9 performed by the center electrode 11 in the above-described embodiment is performed by disposing an insulator between the exhaust upstream end face 8 of the exhaust purification catalyst 7 and the coil 9. By forming the center electrode with a conducting wire in this manner, the catalytic converter 1 can be easily manufactured.

In a modification of the first embodiment of the present invention, FIG.
As shown in (2), the annular conductor 26 is disposed between the outer peripheral surface of the upstream end portion 16 of the exhaust purification catalyst 7 and the inner peripheral surface of the casing 6. The annular conductor 26 is a thin annular conductor having higher conductivity than the exhaust purification catalyst 7 and the casing 6.
The upstream end of the annular conductor 26 on the exhaust side is arranged so as to be flush with the upstream end face 8 of the exhaust purification catalyst 7, and the downstream end of the annular conductor 26 is located on the upstream side of the exhaust. Extends slightly downstream. The second electrode 13 is provided on the annular conductor 26.
Is connected. By configuring the catalytic converter 1 in this manner, there is no need to flow an electric current between the central electrode 11 and the second outer electrode 13 via the casing 6, so that the casing 6 is formed of a highly conductive material. Eliminates the need. That is, the material of the casing 6 is not limited, and the casing 6 may be formed of any material. When the second electrode 13 is connected to the casing 6, the alternating current supplied to the second electrode 13 passes from the exhaust downstream side of the casing 6 to the central electrode 11 through the exhaust downstream side of the exhaust purification catalyst 7. And the exhaust gas may be consumed to heat the downstream side of the exhaust purification catalyst 7. However, if the catalytic converter is configured as in this modified example, the alternating current hardly flows to the exhaust downstream side of the exhaust purification catalyst 7, and therefore, the exhaust downstream side of the exhaust purification catalyst 7 is almost always heated. Disappears.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment of the present invention, as shown in FIG. 6, an additional exhaust purification catalyst 31 is added to the catalytic converter 1 of the first embodiment. The additional exhaust purification catalyst 31 is provided on the exhaust upstream side of the exhaust purification catalyst 7 coaxially with the exhaust purification catalyst 7 and on the exhaust upstream end face 8 of the exhaust purification catalyst 7.
And the exhaust downstream end face 32 of the additional exhaust purification catalyst 31 are arranged so as to be parallel and face each other. The exhaust upstream end face 8 of the exhaust purification catalyst 7 is separated from the exhaust downstream end face 32 of the additional exhaust purification catalyst 31 by a predetermined distance, and a coil 9 is disposed between the exhaust upstream end face 8 and the exhaust downstream end face 32. You. The axial length of the exhaust purification catalyst 7 is longer than the axial length of the additional exhaust purification catalyst 31. As a result, the coil 9 is disposed further upstream of the exhaust gas, and the heat of the exhaust gas is transmitted to the downstream of the exhaust gas by the flow of the exhaust gas, so that the temperature of the exhaust purification catalyst can be effectively raised.

The coil 9 is provided on the longitudinal axis 1 of the catalytic converter 1.
It extends spirally around the outer periphery of the catalytic converter 1 along the exhaust upstream end face 8 of the exhaust purification catalyst 7 and the exhaust downstream end face 32 of the additional exhaust purification catalyst 31 around 0. The coil 9 is located at the center of the exhaust upstream end face 8 of the exhaust purification catalyst 7 and the exhaust downstream end face 32 of the additional exhaust purification catalyst 31, that is, the distance between the coil 9 and the exhaust upstream end face 8 of the exhaust purification catalyst 7 And the exhaust downstream end face 3 of the additional exhaust purification catalyst 31
2 are arranged so as to be equal to the distance between them. One end of the coil 9 located inside in the radial direction is mechanically and electrically connected to the center of the center electrode 11 in the longitudinal direction.
Thereby, the coil 9 is supported by the center electrode 11. One end 14 of the center electrode 11 is mechanically and electrically connected to the exhaust downstream end face 32 of the additional exhaust purification catalyst 31, and the other end 15 is mechanically and electrically connected to the exhaust upstream end face 8 of the exhaust purification catalyst 7. Electrically connected. With this configuration, the center electrode 11 maintains the exhaust gas purifying catalyst 7 and the additional exhaust gas purifying catalyst 31 at a predetermined distance. That is, the center electrode 11 supports the additional exhaust purification catalyst 31 with respect to the exhaust purification catalyst 7.

In the catalytic converter 1 of the second embodiment, a first outer electrode 33 is connected to one end of the coil 9,
The first outer electrode 33 is insulated and mounted directly on the casing 6 between the exhaust upstream end face 8 of the exhaust purification catalyst 7 and the exhaust downstream end face 32 of the additional exhaust purification catalyst 31. Further, as shown in FIG. 7, the second outer electrode 3 is provided on the casing 6 in the middle between the exhaust upstream end face 8 of the exhaust purification catalyst 7 and the exhaust downstream end face 32 of the additional exhaust purification catalyst 31.
6 are connected and arranged to be spaced apart from the first outer electrode 12 in the circumferential direction. As in the first embodiment, the inner peripheral surface of the casing 6 is in electrical contact with the outer peripheral surface of the exhaust purification catalyst 7, and the current supplied to the casing 6 flows through the exhaust purification catalyst 7. I have.

Next, the induction heating of the second embodiment will be described with reference to FIG. When an alternating current is applied to the coil 9, an alternating magnetic field, that is, a magnetic field line 35 is formed around the coil 9 perpendicular to the direction in which the current flows in the coil 9. Further, since the exhaust gas purifying catalyst 7 and the additional exhaust gas purifying catalyst 31 have higher magnetic permeability than the atmosphere around the coil 9 (for example, exhaust gas or air), the magnetic force lines 35 pass through the inside of the exhaust gas purifying catalyst 7 and the additional exhaust gas purifying catalyst 31. pass. Further, since the exhaust gas purification catalyst 7 and the additional exhaust gas purification catalyst 31 have appropriate magnetic permeability, the magnetic field lines 35 are formed on the upstream end portion 16 near the exhaust upstream end face 8 of the exhaust gas purification catalyst 7 and the additional exhaust gas purification catalyst 31. (Hereinafter, simply referred to as a downstream end portion) 34 in the vicinity of the exhaust downstream end surface 32. This magnetic force line 35
As a result, an induced current (eddy current) around the magnetic force line 35 is generated in the upstream end portion 16 of the exhaust purification catalyst 7 and the downstream end portion 34 of the additional exhaust purification catalyst 31 perpendicularly to the magnetic force line 35.
As described above, the eddy current heats the upstream end portion 16 of the exhaust purification catalyst 7 and the downstream end portion 34 of the additional exhaust purification catalyst 31. In this way, by passing the alternating current through the coil 9, the upstream end portion 16 of the exhaust purification catalyst 7 and the downstream end portion 34 of the additional exhaust purification catalyst 31 are induction-heated.

Next, the direct heating of the second embodiment will be described with reference to FIGS. In the second embodiment,
The alternating current flowing between the first outer electrode 33 and the second outer electrode 36 flows from the coil 9 via the center electrode 11 to the exhaust purification catalyst 7 and the additional exhaust purification catalyst 31. That is, the current generated by the alternating current generation power supply 17 is supplied to the first outer electrode 33, the coil 9, the center electrode 11
, From there to the exhaust purification catalyst 7 and the additional exhaust purification catalyst 31, and then integrated again in the casing 6 to the second outer electrode 36 or vice versa. In this case, the alternating current flows through the coil 9 as described above, so that the upstream end portion 16 of the exhaust purification catalyst 7 and the downstream end portion 34 of the additional exhaust purification catalyst 31 are induction-heated. Further, an alternating current flows through the upstream end portion 16 of the exhaust purification catalyst 7 and the downstream end portion 34 of the additional exhaust purification catalyst 31, and the electric resistance of these portions 16 and 34 causes the upstream end portion of the exhaust purification catalyst 7 to have an electric resistance. 16 and the downstream end portion 34 of the additional exhaust purification catalyst 31 are directly heated.

When the exhaust gas purifying catalyst is disposed on only one side of the coil as in the first embodiment, the magnetic flux generated by the coil is generated in a region to be heated (the exhaust gas purifying catalyst) and a region other than the region to be heated (for example, the coil). Ambient atmosphere: hereinafter, simply referred to as a non-target area). As described above, the magnetic flux passes through the heating target area to be induction-heated and consumes electric power, but the electric power is also consumed in the area outside the heating symmetry. Moreover, the electric power consumed in the non-heating target area is not effectively converted into heat energy. Therefore, when the non-target area increases, the power loss increases. However, in the second embodiment, the exhaust purification catalyst 7 and the additional exhaust purification catalyst 31 whose magnetic permeability is higher than the magnetic permeability of the atmosphere around the coil 9 are arranged upstream and downstream of the coil 9. Therefore, the magnetic flux generated by the coil 9 passes through the exhaust gas purifying catalysts 7 and 31 almost without passing through the space region between the coil 9 and the exhaust gas purifying catalysts 7 and 31. Thereby, the magnetic flux formed by the coil 9 almost passes only through the region to be heated. For this reason, most of the consumed power is converted into heat energy, the conversion efficiency from electrical energy to heat energy is increased, and the amount of heat generated can be increased with a small loss of power. Therefore, the efficiency of induction heating is improved.

[0043]

According to the first aspect of the present invention, the portion of the exhaust purification catalyst near the exhaust upstream end face is complementarily heated by two heating methods, so that the portion of the exhaust purification catalyst near the exhaust upstream end face has a temperature difference. It can be heated so that it cannot be done. According to the second aspect, since two heating methods of induction heating and direct heating can be performed with only one current path, the configuration is simplified. According to the sixth aspect, the magnetic lines of force generated by passing the alternating current through the conductor almost pass only through the region to be heated, so that most of the consumed electric power is converted into heat energy, and thus the induction heating is performed. Efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a catalyst temperature raising device of a first embodiment.

FIG. 2 is an enlarged sectional view on the upstream side of the catalytic converter shown in FIG.

FIG. 3 is a cross-sectional view of the catalytic converter taken along a line III-III in FIG. 2;

FIG. 4 is a diagram showing a portion where a current flows in a coil.

FIG. 5 shows a catalytic converter according to a modification of the first embodiment.
FIG.

FIG. 6 is an enlarged sectional view of the upstream side of a catalytic converter according to a second embodiment.

FIG. 7 is a sectional view of the catalytic converter taken along the line VII-VII in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Catalytic converter 2 ... Engine main body 3 ... Engine exhaust passage 4 ... Inlet 5 ... Outlet 6 ... Casing 7 ... Exhaust purification catalyst 8 ... Exhaust upstream end face 9 ... Coil (conductor) 10 ... Longitudinal axis 11 ... Central electrode 12 ... first electrode 13 ... second electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takaaki Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toshihiro Sakurai 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hiroki Ichinose 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G091 AA02 AB01 BA03 CA04 GA08 GA10 HA45 4D048 CC32 CC43 CC53 EA03 4G069 AA20 CA03 DA06 EE03

Claims (6)

[Claims] An exhaust purification catalyst is disposed in an engine exhaust passage, a conductor is disposed facing an exhaust upstream end face of the exhaust purification catalyst, and an alternating current is supplied to the conductor to produce an exhaust gas. In the internal combustion engine catalyst temperature increasing device in which a portion near the exhaust upstream end face of the purification catalyst is induction-heated, in addition to induction heating the portion near the exhaust upstream end face of the exhaust purification catalyst, the exhaust upstream of the exhaust purification catalyst is increased. A catalyst temperature raising device for an internal combustion engine configured to heat a portion near an exhaust upstream end surface of an exhaust purification catalyst by flowing a current to a portion near an end surface. 2. A method according to claim 1, wherein a central electrode connected to said conductor is connected to a substantially center of an exhaust upstream end face of said exhaust purification catalyst, and an outer electrode is connected to an outer peripheral face near an exhaust upstream end face of said exhaust purification catalyst. 2. The catalyst heating device for an internal combustion engine according to claim 1, wherein the alternating current flowing through the exhaust gas passes through a portion near the exhaust upstream end face of the exhaust purification catalyst to the outer electrode via the central electrode. 3. The central electrode is formed of a rigid conductive material, and the central electrode is connected to an exhaust upstream end face of an exhaust purification catalyst so that the central electrode supports the conductor. 3. The catalyst temperature raising device for an internal combustion engine according to claim 1. 4. The catalyst heating device for an internal combustion engine according to claim 2, wherein the outer electrode is a surrounding electrode surrounding an outer peripheral surface near an exhaust upstream end surface of the exhaust purification catalyst. 5. The catalyst temperature raising device for an internal combustion engine according to claim 4, wherein a conductive casing accommodating the exhaust gas purification catalyst is formed in the engine exhaust passage, and the casing is used as the surrounding electrode. 6. An additional exhaust gas purification catalyst which is disposed upstream of said conductor separately from said exhaust gas purification catalyst, said additional exhaust gas purification catalyst being supported by a central electrode to support said additional exhaust gas purification catalyst. The catalyst is connected to the center electrode.
6. The catalyst purifying apparatus for an internal combustion engine according to any one of 5.