JP2501257Y2 - Catalyst heating device for internal combustion engine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst heating device used in an exhaust gas purifying device for an internal combustion engine using a catalytic converter.

[0002]

2. Description of the Related Art For the purpose of purifying exhaust gas of an internal combustion engine, an exhaust gas purifying apparatus in which a three-way catalytic converter is mounted in an exhaust gas passage and an air-fuel ratio is controlled by an oxygen sensor is widely used. The catalyst used has a property that it does not reach a sufficiently active state unless the temperature exceeds about 350 ° C. Therefore, in order to improve the exhaust gas purification efficiency during cold starting, it is necessary to mount an electrothermal heating device in the vicinity of the catalytic converter and energize it when the internal combustion engine is started to heat the exhaust gas or the catalytic converter.

However, since the heater element used in the electrothermal heating device reaches a high temperature of about 1000 ° C. during heating, it causes an electrical short circuit due to expansion or deformation of the heater element during use, and a normal heating function. May be lost.

In order to prevent such an extension or deformation of the heater element and prevent an electrical short circuit, a ceramic insulator formed so that the bent portion of the heater element is housed is elastic in the exhaust gas passage. A structure has been proposed in which the heater element is mounted by using a material (see FIG. 2).

[0005]

Since the ceramic insulator used in the above-mentioned prior art is formed in a shape formed by a straight line, when the inner wall surface of the frame body has a curved cross-section (for example, , In the case of a circular shape), the ceramic insulator is largely protruded toward the center of the exhaust gas passage.
There is a problem that the ventilation resistance of the exhaust gas increases, resulting in a decrease in the output of the internal combustion engine.

An object of the present invention is to reduce the ventilation resistance of exhaust gas and prevent the output of the internal combustion engine from decreasing in a catalyst heating device used in an exhaust gas purifying device using a catalytic converter equipped with an electrothermal heating device.

[0007]

As a means for solving the above problems, the present invention provides an exhaust gas purifying apparatus for an internal combustion engine, which has an electrothermal heating device near a catalytic converter, and has a curved inner wall surface. A catalyst heating device in which a ceramic insulator having a shape along the inner wall cross-sectional shape of a frame body is mounted along the inner wall surface using an elastic material, and a bent portion of a heater element is held by the ceramic insulator is proposed. To do.

[0008]

In the catalyst heating device of the present invention, the ceramic insulator for holding the heater element has a shape along the inner wall surface of the frame body, and the ceramic insulator is mounted along the inner wall surface of the frame body. Extrusion of the exhaust gas toward the center of the passage is reduced, and the ventilation resistance of the exhaust gas can be reduced. As a result, the output of the internal combustion engine can be maintained high.

Further, since the heater element is arranged more generally than the catalyst heating device of the prior art with respect to the cross section of the passage of the exhaust gas, the heating unevenness of the exhaust gas or the catalytic converter at the start of the internal combustion engine is reduced, and the catalyst is reduced. It is also effective in improving exhaust gas purification efficiency in the converter.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A catalyst heating device of the present invention will be described with reference to the embodiment shown in FIG. The catalyst heating device 1 comprises a meandering ribbon-shaped heater element 2, an energizing terminal portion 3, a ceramic insulator 4 and a frame body 5 having a circular inner wall cross-sectional shape, and an end portion 6 of the heater element 2 is an energizing terminal. In the portion 3, while maintaining electrical insulation through the frame body 5 and the mica-based insulating material 7, the bolt 9 has the washer 10 and the nut 1
It is concluded with 1. Further, a ceramic insulator 4 having a bottomed hole 12 formed in conformity with the shape of each bent portion 2 ′ of the heater element and having a shape along the inner wall cross-sectional shape of the frame body 5 is a leaf spring as the elastic material 13. Is fixed by pressure along the inner wall of the frame body 5. Each bent portion 2'of the heater element is inserted into the bottomed hole 12 provided in the ceramic insulator 4 with a proper gap enough to accommodate the extension of the heater element to hold the heater element 2. It is configured to do. The catalyst heating device thus obtained is installed upstream or in the middle of the catalytic converter and used as an exhaust gas purifying device.

The catalyst heating device having such a structure prevents an electrical short circuit due to extension or deformation of the heater element, and since the ceramic insulator is less likely to protrude toward the center side of the exhaust gas passage, the ventilation resistance of the exhaust gas is small. Therefore, when mounted in the exhaust gas passage of the internal combustion engine, the output of the internal combustion engine does not decrease. Further, since the heater elements are evenly arranged in the cross section of the exhaust gas passage, temperature unevenness during heating hardly occurs, and the exhaust gas purification efficiency is improved.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine equipped with the catalyst heating device of the present invention, the ventilation resistance of the exhaust gas is reduced and the output of the internal combustion engine can be maintained high.

The present invention is not limited to the range shown in the embodiment, and for example, the frame body 5 may be divided into two or more passages by one or more partition walls.
Further, the frame body 5 can be applied as long as a part of the inner wall cross section has a curved surface, and may have a flat part. Further, as the elastic material 13, a coil spring may be used instead of the leaf spring.

The insulator may be one in which ceramic is incorporated in a metal frame. Further, the gap between each bent portion of the heater element and the bottomed hole of the ceramic insulator may be filled with a ceramic fiber or a secondary molded body obtained by processing a ceramic fiber or the like. However,
In the case of using a secondary molded body obtained by processing all or part of the ceramic insulator with ceramic fibers or the like to give elasticity, it is not necessary to provide a gap between the heater element and the secondary molded body.

Further, the heating device according to the present invention is mounted on the intake side of the internal combustion engine to be used for heating the combustion air, thereby preventing the intake resistance from increasing and increasing the combustion efficiency to improve the output of the internal combustion engine. It is also possible.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of a catalyst heating device of the present invention.

FIG. 2 is a schematic view showing a cross-sectional structure of a conventional catalyst heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 catalyst heating device 2 heater element 2'heater element bent portion 3 energizing terminal portion 4 ceramic insulator 5 frame body 6 heater element end portion 7 mica insulating material 9 bolt 10 washer 11 nut 12 bottomed hole 13 elastic material

Claims (1)

(57) [Scope of utility model registration request] 1. An exhaust gas purifying apparatus for an internal combustion engine, comprising an electrothermal heating device in the vicinity of a catalytic converter, wherein a ceramic insulator formed along an inner wall cross-sectional shape of a frame body having a curved inner wall surface is made of an elastic material. A catalyst heating device, which is mounted along the inner wall surface using the ceramic insulator and in which the bent portion of the heater element is held by the ceramic insulator.