JP3089444B2 - Electric heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heater, for example, a heater used as a main component of an electrically heated catalytic converter installed in an exhaust system of an internal combustion engine.

The above-mentioned catalytic converter has a function of purifying low-temperature exhaust gas by being energized and heated only when the engine is started to activate its catalyst.

[0003]

2. Description of the Related Art Conventionally, as an electric heater of this type of catalytic converter, one end of a plurality of conductive corrugated sheets is separately welded to a central conductor, and each corrugated sheet is spirally wound around the central conductor. It is well-known that the other end is separately welded to a conductive casing surrounding the central conductor, and a heating element is constituted by the spiral corrugated sheet, and the heating element carries a catalyst. (See JP-A-3-72953).

[0004]

However, in the conventional heating element, since each corrugated sheet is not joined, each corrugated sheet moves in its radial direction and axial direction due to vibration of the vehicle or the like. In addition, there is a problem in terms of durability, for example, a welded portion is easily broken, and a corrugated plate is struck against each other so that a catalyst carried on the plate falls off.

In view of the above, the present invention relates to the above-described electric heating type in which the abutting portions of the corrugated plate in the heating element are joined to each other to improve the durability and to eliminate the problems associated with the joining. It is an object to provide a heater.

[0006]

Electrically heated heater according to the present invention According to an aspect of the mutually overlapping obtained conductive strip and the conductive corrugated sheet along the traveling direction of the wave of the corrugated plate of that spirally Rolled shape
A heating element to be formed, a center electrode fitted in a center hole of the heating element and electrically connected to the heating element, and a center electrode fitted to an outer peripheral portion of the heating element and electrically connected to the heating element. And a cylindrical outer peripheral electrode connected thereto, wherein the respective contact portions of the band plate and the corrugated plate in the heating element are joined via a conductive brazing material layer extending in the direction of the heating element bus line, Between the center electrode and the outer electrode
So that the current flows through the heating element in its radial direction
An electric heating type heater, wherein the length of the brazing material layer in the direction of the heating element bus from the brazing material layer on the center electrode side to the brazing material on the outer peripheral electrode side is adjusted so that the current density in each brazing material layer is substantially equal. It is characterized in that the insulating layer is formed in a non-joining area between the respective contact portions, the length being shortened toward the layer.

[0007]

When the contact portions of the strip and the corrugated sheet of the heating element are joined to each other via the brazing material layer as described above, the movement of the strip and the corrugated sheet due to vibration of a vehicle or the like is suppressed as much as possible. Can be.

In the heating element having the above-described joint structure, current flows in the radial direction of the heating element through each brazing material layer during energization. Is regulated by the length of the brazing material layer in the direction of the heating element bus.

Under these circumstances, when the contact portions of the strip and the corrugated plate are joined to each other through the brazing material layer over the entire length in the bus direction of the heating element, the center electrode side of the heating element is closer to the outer electrode side. Also, since the diameter is small and the current passage area is small, current concentration occurs at the center electrode and its vicinity, in other words, the current density of the brazing material layer on the center electrode side increases,
The current density of the brazing material layer becomes lower toward the outer peripheral electrode side. As a result, the heating element cannot generate heat uniformly over the entire area, and the brazing material layer melts due to the high temperature on the center electrode side.

Therefore, if the length of the brazing material layer in the direction of the heating element bus is reduced from the brazing material layer on the center electrode side to the brazing material layer on the outer peripheral electrode side, the current density is low in the brazing material layer on the center electrode side. Therefore, the length of the brazing material layer in the direction of the heating element bus is longer, and the length of the brazing material layer in the direction of the heating element bus is increased so that the current density becomes higher in the brazing material layer on the outer peripheral electrode side. Is shorter than the center electrode side. This makes it possible to make the current densities of the brazing material layers substantially equal, so that the heating element can generate heat almost uniformly over the entire area thereof, and it is possible to avoid a high temperature on the center electrode side. .

Further, when an insulating layer is formed in a non-joining area between the respective contact portions, it is possible to prevent electric leakage in the non-joining area and to surely realize uniform heating of the heating element.

[0012]

FIG. 1 shows an exhaust system in a vehicle. The exhaust system includes an exhaust manifold 3 connected to an exhaust port 2 of an internal combustion engine 1, an exhaust pipe 4 connected to the exhaust manifold 3, and an exhaust pipe. 4 and a muffler 5 connected to the muffler 5.
The exhaust pipe 4 includes a main catalytic converter 6 on the upstream side thereof,
On the downstream side, an electric heating type catalytic converter 7 having an electric heating type heater according to the first embodiment of the present invention as a main component is provided. The main catalytic converter 6 has a function of activating the catalyst when high-temperature exhaust gas is introduced during operation of the engine and purifying the exhaust gas. The electrically-heated catalytic converter 7 is energized and heated only when the engine is started, and activates its catalyst to purify low-temperature exhaust gas. Demonstrate.

2 to 6, an electric heater 8
Reference numeral ₁ denotes a cylindrical heating element 9, a rod-shaped center electrode 11 fitted in a center hole 10 of the heating element 9 and connected to the heating element 9, and a heating element fitted to an outer peripheral portion of the heating element 9. 9 connected to a cylindrical outer peripheral electrode 12. The outer peripheral electrode 12 has a conductive connection rod 13 at one end in the generatrix direction on the outer peripheral surface. The center electrode 11 is connected to the battery 1 via the switch 14.
5, the connection rod 13 of the outer peripheral electrode 12
Are connected to the (+) terminals of the battery 15, respectively.

The heating element 9 is configured as follows. That is,
As shown in FIG. 5 and FIG. 6, a thin conductive strip 16 having the same width over the entire length and a conductive corrugated plate 17 having a longitudinal direction in which the wave travels in the same width are similarly superimposed. 1
6 and 17 are spirally wound around the center electrode 11 along the traveling direction of the wave of the corrugated plate 17 with the band plate 16 positioned inside. The strip 16 and the corrugated plate 17 are made of stainless steel having a relatively high electric resistance.

In the heating element 9, the contact portions “a” and “a” between the center electrode 11 and the heating element 9, and between the band plate 16 and the corrugated plate 17.
b, and between the outer peripheral electrode 12 and the heating element 9 are joined via a brazing material layer 18 extending in the direction of the heating element bus. As clearly shown in FIG. 3, the length c of the brazing material layer 18 in the direction of the heating element bus becomes shorter from the brazing material layer 18 on the center electrode 11 side to the brazing material layer 18 on the outer peripheral electrode 12 side. Such a change in the length of each brazing material layer 18 is achieved by, for example, reducing the length c of the brazing material layer 18 in the direction of the heating element bus line for each unit number of turns of the corrugated sheet 17.

An insulating layer 20 is formed in the non-joining area 19 between the contact portions a and b and between the outer peripheral electrode 12 and the heating element 9 over the entire length of the heating element in the bus direction. The insulating layer 20 is a wash coat layer in the embodiment, and the wash coat layer is made of an exhaust gas purifying catalyst made of a noble metal such as Pt and Pd and a binder. 9 (the insulating layer 20 on the surface of the corrugated plate 17 is omitted in FIG. 3). Therefore, the heating element 9 is used as a carrier of the catalyst.

As described above, when the contact portions a and b of the strip 16 and the corrugated plate 17 of the heating element 9 are joined to each other via the brazing material layer 18, the strip 16 and the corrugated sheet due to the vibration of the vehicle or the like are formed. The movement of the plate 17 can be suppressed as much as possible.

The length c of the brazing material layer 18 in the direction of the bus of the heating element.
Is shortened from the brazing material layer 18 on the side of the center electrode 11 to the brazing material layer 18 on the side of the outer peripheral electrode 12, and as shown by arrows in FIG. When a current flows, the brazing material layer 18 on the center electrode 11 side
In order to reduce the current density, the length c of the brazing material layer 18 in the direction of the heating element bus is increased, while the brazing material layer 18 on the outer peripheral electrode 12 side has a high current density.
The length c of the brazing material layer 18 in the direction of the heating element bus is the center electrode 1.
Since it is shorter than the one side, the current density of each brazing material layer 18 can be made substantially equal, whereby the heating element 9 can be made to generate heat almost uniformly over its entire area. High temperature on the electrode 11 side can be avoided.

Further, the non-joining area 1 between the contact portions a and b
When the insulating layer 20 is formed on the heating element 9, it is possible to prevent electric leakage in the non-joining area 19 and reliably realize uniform heating of the heating element 9.

[0020] Figure 7 shows a second embodiment of the electrically heated heater _82, at the radially intermediate region d of the heating elements 9, the contact portions a, brazing material layer in the non-adhesive zones 19 between b 18 The part which is separated from is brazed over the length e in the direction of the busbar of the heating element. The remaining portion of each non-joining area 19 except the brazing part 21 and each non-joining area 1 without the brazing part 21
An insulating layer 20 is formed on 9. With this configuration, it is possible to more reliably prevent the movement of the band plate 16 and the corrugated plate 17 due to the vibration of the vehicle and the like. In the second embodiment, since the brazing length is c + e, it is necessary to appropriately adjust the brazing length c + e and the separation length f in order to compensate for the decrease in the calorific value due to the decrease in the current density. Sometimes
You.

FIG. 8 shows another example of the joint portion between the strip 16 and the corrugated plate 17. In this example, the two plates 16 and 17 are joined via a fillet-like brazing material layer 18.

The corrugated sheet 17 according to the present invention includes a corrugated sheet 17 in which peaks and valleys are formed obliquely in the longitudinal direction.

[0023]

According to the first aspect of the invention, it is possible to improve the durability by minimizing the movement of the corrugated sheet due to the vibration of the vehicle or the like, and to make the heating element generate heat uniformly over the entire area. it is Ru can provide an electro-heating type heater.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an exhaust device.

FIG. 2 is a perspective view of a first embodiment of an electric heater.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a view taken in the direction of arrows 4-4 in FIG. 3;

FIG. 5 is a perspective view showing a state in which a corrugated plate and a band plate are overlaid.

FIG. 6 is an explanatory view showing a method of forming a heating element.

FIG. 7 is a sectional view showing a second embodiment of the electric heater.

FIG. 8 is a cross-sectional view of a main part showing another example of a joint portion between a band plate and a corrugated plate .

[Explanation of symbols]

8 ₁ , 8 ₂ Electric heater 9 Heating element 10 Center hole 11 Center electrode 12 Peripheral electrode 16 Strip plate 17 Corrugated sheet 18 Brazing material layer 19 Non-joined area 20 Insulating layers a, b Contact part c Heating element bus length D radial intermediate area

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H05B 3/40 B01D 53/36 ZABC (72) Inventor Toshiyuki Nishida 1-4-1 Chuo, Wako-shi, Saitama Pref. ) Inventor Akira Nagao 1-4-1 Chuo, Wako City, Saitama Prefecture Inside Honda R & D Co., Ltd. Machido Niwa 274 (58) Field surveyed (Int.Cl. ⁷ , DB name) B01J 21/00-38/74 B01D 53/86 B01D 53/94 F01N 3/20 F16L 53/00 H05B 3/40

Claims (5)

(57) [Claims] A conductive strip (1) superimposed on one another.
6) a conductive corrugated plate (17) of the corrugated plate of that (17) the heating element is formed by winding spirally along the traveling direction of the wave (9)
And a center electrode (11) fitted in the center hole (10) of the heating element (9) and electrically connected to the heating element (9).
And a cylindrical outer peripheral electrode (12) fitted to an outer peripheral portion of the heating element (9) and electrically connected to the heating element (9), wherein the band plate of the heating element (9) is provided. The contact portions (a) and (b) of the corrugated plate (16) and the corrugated plate (17) are joined to each other via a conductive brazing material layer (18) extending in the direction of the bus of the heating element, and the center electrode (11) is formed. And between the outer electrode (12)
Current flows in the radial direction through the heating element (9)
An electric heater of the type described above, wherein each brazing material layer (1
The length (c) of the brazing material layer (18) in the bus direction of the heating element is changed from the brazing material layer (18) on the side of the center electrode (11) to the outer peripheral electrode (12) so that the current density in 8) becomes substantially equal. The length is shortened toward the brazing material layer (18) on the side, and the insulating layer (2) is formed in the non-joining area (19) between the contact portions (a) and (b).
An electric heating type heater characterized in that 0) is formed. 2. The electric heater according to claim 1, wherein the insulating layer (20) is formed over the entire length of the non-bonded area (19) in the direction of the heating element bus. 3. The electric heater according to claim 2, wherein said insulating layer (20) is a washcoat layer. 4. The non-bonded area (19) in the radially intermediate area (d) of the heating element (9) is brazed to a part of the non-bonded area (19) that is separated from the brazing material layer (18). Electric heating heater. 5. An electric heating type catalytic converter (6) installed in an exhaust system of an internal combustion engine, wherein the heating element (9) is used as a carrier of an exhaust gas purifying catalyst. An electric heater according to 2, 3, or 4 .