JPH0656096B2 - Engine exhaust particulate collection and purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a so-called diesel in which fine particles contained in exhaust gas of a diesel engine or the like are collected by a filter and the collected fine particles are burned. The present invention relates to an exhaust particulate collection and purification device for an engine used for party cue processing.

[Conventional technology]

For example, the exhaust gas of an internal combustion engine such as a diesel engine contains fine particles mainly composed of carbon and hydrocarbons, and in order to purify this exhaust gas, a ceramic honeycomb structure or a ceramic foam structure is used in the exhaust gas system. A means for collecting the fine particles by installing a heat resistant filter made of a body is adopted. However, such a filter causes clogging due to the collected particulates, increases the resistance of the exhaust flow, and causes a reduction in engine output.

In order to prevent such clogging of the filter, a means for arranging a heating device equipped with an electric heater on the upstream side of the filter and burning fine particles by this electric heat is adopted.

The electric heater is called a heater for regeneration heating because it regenerates and purifies the filter, and as a heater for regeneration heating of this kind, heat resistance because it is exposed to extremely high temperature of exhaust gas,
A conductive ceramic element heater with excellent oxidation resistance is used.

The conductive ceramic element heater is formed, for example, in a substantially V shape, and electrodes are formed at both ends thereof, and a voltage is applied between the electrodes to energize the conductive ceramic element heater to generate heat. The fine particles collected by the filter are burned. In this case, normally, in order to save power consumption, a plurality of conductive ceramic element heaters are intermittently and sequentially energized to generate heat.

[Problems to be solved by the invention]

By the way, the electrodes for energizing each of the heaters are formed by means such as metallizing the conductive ceramic element heater and crimping the metal electrode thereto, or brazing the metal electrode. However, even if the electrode has any structure, it is exposed to exhaust gas having a temperature as high as 800 ° C. to 900 ° C. at the maximum, so that the electrode is oxidized at an early stage and has a short life.

The present invention is intended to provide an exhaust particulate collection and purification device for an engine that prevents oxidation of the electrode portion of the conductive ceramic element heater and has a long life.

[Means for solving problems]

The present invention is characterized in that a cooling air introducing passage communicating with an electrode portion of a conductive ceramic element heater is formed in a heater case, and an air supply means is connected to the cooling air introducing passage.

[Action]

With such a configuration, the electrode portion is forcibly cooled by the air supplied by the air supply means, so that oxidation is prevented and the life is extended.

Example of Invention

Hereinafter, the details of the present invention will be described based on the embodiments shown in the drawings.

1 to 6 show a first embodiment of the present invention, and FIG. 6 shows the entire structure of the particle collecting and purifying apparatus, which will be described first.

The particulate collection and purification device mainly comprises a filter case 1, a filter 2, a heating device 3 provided in contact with the exhaust gas upstream side of the filter 2, and an exhaust gas introduction pipe 4.

The filter case 1 is made of a cylindrical casting and has a flange 5 at one end and an exhaust gas discharge pipe 6 at the other end. A flange 7 is formed at the end of the exhaust gas discharge pipe 6.

The filter 2 is filled in the filter case 1 via a heat insulating cushion material 8 and heat insulating sealing materials 9 and 10.
The filter 2 is made of cordierite porous foam ceramics, for example.

The exhaust gas introducing pipe 4 has an exhaust gas inlet 11 at one end and flanges 12 and 13 at both ends.

The heating device 3 includes the flange 5 of the filter case 1 and
Between the flange 12 of the exhaust gas introducing pipe 4, sealing materials 14, 15
It is sandwiched through.

The flange 7 provided on the exhaust gas exhaust pipe 6 of the filter case 1 and the flange 13 of the exhaust gas introduction pipe 4 are connected to an exhaust pipe of an engine (not shown) so that exhaust gas flows in the direction of arrow A.

The structure of the heating device 3 is shown in FIGS.
This will be described below.

The heating device 3 includes a heater case 20, at least one, for example, four conductive ceramic element heaters 21 ... Between the heater case 20 and the conductive ceramic element heaters 21.
Holder ring 22 that holds…, and screw cap
23 and an insulating ring 24 inserted between the screw cap 23 and the heater case 20.

Each of the conductive ceramic element heaters 21 ... Is arranged in a portion where the upstream end surface of the filter 2 is evenly divided into a substantially fan shape, and each of the conductive ceramic element heaters 21 has a substantially V-shaped planar shape. There are electrodes 24 on both ends of this V-shape.
a and 24b are joined by brazing. In this case, in this embodiment, as shown in FIGS. 2 and 3, the electrodes 24a and 24b are projected upward in the drawing.

The conductive ceramic element heaters 21 ...
The V-shaped part connected to a and 24b is the heat generating part,
Exhaust gas can pass through a portion surrounded by the V-shaped portion.

The conductive ceramic element heaters 21 ... Can be manufactured as follows. That is, for example, TiN
30% by weight of powder and 470% by weight of Si3N were dispersed in an organic binder composed of polyvinyl butyral, dibutyl phthalate and ethanol to form a slurry, and the slurry was formed into a plate shape by a doctor blade method, which was punched out. After being processed into a predetermined shape, it is obtained by heating and firing at a temperature of about 1750 ° C. for about 2 hours in an atmosphere of an inert gas such as nitrogen gas.

The conductive ceramic element heater 21 having such a structure ...
Both ends are supported by the heater case 20 described above, and the heat generating parts thereof are arranged toward the center of the exhaust passage so as to be perpendicular to the flow of the exhaust gas. Therefore, the conductive ceramic element heaters 21 are arranged at intervals in the circumferential direction of the exhaust passage. In this case, gaps are formed between the adjacent heat generating portions, and these gaps and the portion surrounded by the V-shaped portion secure a passage through which exhaust gas can pass.

Now, a structure for mounting the conductive ceramic element heaters 21 ... To the heater case 20 will be described.

The heater case 20 has a ring shape made of, for example, cast iron, and has a terminal mounting portion 25 formed at one location around the heater case 20 and cooling air intake portions 26 similarly formed at two locations surrounding each other. ing.

Further, the heater case 20 is formed with a ring-shaped projecting portion 27 extending toward the center in the middle portion in the vertical direction shown in FIGS. A female screw portion 28 is provided over the entire circumference.

On the lower surface of the projecting portion 27 in the drawing, an insulating coating 29 formed by ceramic spraying of spinel, alumina or the like is formed, and the projecting portion 27 is circumferentially separated from each other.
Insertion holes 30a ..., 30b ... Through which the electrodes 24a, 24b are inserted
Is provided.

The one insertion hole 30a has a diameter sufficiently larger than the thickness of the electrode 24a so that the electrode 24a inserted therein does not contact the inner surface of the insertion hole 30a, and the other insertion hole 30b.
Has a size into which the electrode 24b inserted therein is inserted. The one electrode 24a is loosely inserted in the insertion hole 30a, and the lead wire 31 made of nickel is welded to the upper end of the insertion hole 30a to form a positive electrode, while the other electrode 24b is inserted in the insertion hole 30b. It is inserted and welded to the protruding portion 27 to form a ground electrode.

Therefore, one electrode 24a is electrically insulated from the projecting portion 27, and the other electrode 24b is fixed to the projecting portion 27.

The conductive ceramic element heaters 21 ... Extend the protruding portion 27 of the heater case 20, and a holder ring fixed to the heater case 20 at a lower portion of the extended portion 27.
It is sandwiched between 22 and.

The holder ring 22 is made of metal and is attached to the heater case 20 with a bolt (not shown). An insulating coating 32 is formed on the upper surface of the holder ring 22 by thermal spraying of a ceramic such as spinel or alumina, and is spaced apart in the circumferential direction so as to face the electrodes 24a and 24b and is recessed.
33 ... is provided.

A cushion member 34 and an insulating ceramic insulating cap 35 that covers the cushion member 34 are housed in each of the recesses 33.

The lower surface of the conductive ceramic element heaters 21 ... Abuts on the insulating cap 35. Therefore, the conductive ceramic element heaters 21 ... Are substantially sandwiched between the projecting portion 27 and the insulating cap 35. .

A ring-shaped metal screw cap 23 is screwed into the female screw portion 28 of the heater case 20.

The screw cap 23 has a male screw portion 36 on the outer peripheral surface, and a retaining wall 37 protruding downward in the figure on the inner surface. On the lower surface of this screw cap 23, spinel,
An insulating coating 38 is formed by thermal spraying of a ceramic such as alumina.

In such a screw cap 23, when the male screw portion 36 is screwed to the female screw portion 28 of the heater case 20, the insulating ring 24 is held between the screw cap 23 and the projecting portion 27.

The insulating ring 24 is made of an insulating ceramic such as silicon nitride or alumina, and is divided into two in the circumferential direction in the present embodiment, and the both ends in the circumferential direction are abutted against each other to form a ring over the entire circumference. It is shaped.

The insulating ring 24 has an insertion hole 30a into which the one electrode 24a formed on the overhanging portion 27 of the heater case 20 is loosely inserted.
The electrode insertion holes 39 ... Are formed so as to communicate with the.

Then, on the upper surface of the insulating ring 24, these electrode insertion holes 39 ...
Is formed with a lead wire routing guide groove 40. The other end of the lead wire routing guide groove 40 ... Is guided so as to face the terminal mounting portion 25 of the heater case 20 described above.

The lead wires 31 connected to one electrode 24a of the conductive ceramic element heater 21 ... Are inserted into the lead wire routing guide grooves 40. The lead wires 31 ... Are attached to the terminal mounting portion 25. Connected to terminal 41. Reference numeral 42 is a connector.

The cooling air intake portions 26, 26 formed in the heater case 20
As shown in FIG. 4, the cooling air introduction passage 4
5, 45 are formed. These cooling air introduction passages 45, 4
The cooling air blower 5 is formed on the peripheral wall of the heater case 20 along the circumference thereof and extends toward the electrodes 24a and 24b.
46 ... is branched.

A cooling air supply pipe 48 is connected to the cooling air introduction passage 45 via a pipe connector 47, and a reed valve 49 as a cooling air supply means is connected to the tip of the cooling air supply pipe 48. .

The reed valve 49, as shown in FIG.
A filter 51 and an elastically deformable plate valve 52 are housed inside a valve 50, and the valve case 50 is connected to the cooling air supply pipe 48 via a rubber tube 53.

As will be described later, the plate valve 52 is opened / closed by the pulsation of exhaust gas flowing in the heater case 20.

By installing the heating device 3 having the above structure on the upstream side of the filter 2, the particulate collection and purification device is completed.

The particulate matter collecting and purifying apparatus of this embodiment having such a configuration is connected to the exhaust gas system of the internal combustion engine, introduces the exhaust gas from the exhaust gas inlet 11 of the exhaust gas introducing pipe 4, and removes the particulates in the exhaust gas from the surface of the filter 2. To focus on. When the pores of the filter 2 are narrowed by the fine particles collected on the surface of the filter 2, that is, when the filter 2 is clogged, the connector 42
A current is passed through the lead wire 31 through.

In this case, a current is intermittently and sequentially applied to each lead wire 31. As a result, each conductive ceramic element heater 21 ...
Generate heat intermittently and sequentially. Due to the heat generated by the conductive ceramic element heaters 21 ..., The upstream end face of the filter 2 is heated, the fine particles trapped in this portion start to burn, and that portion becomes the ignition point and becomes the downstream side. The particles attached to the surface of the filter 2 are also burned and removed.

Therefore, the filter 2 is regenerated.

According to the configuration of the above embodiment, it is known that exhaust pulsation pressure is generated in the exhaust gas system during the operation of the engine. Since this pulsating pressure is also generated in the exhaust passage of the heater case 20, it is transmitted from the cooling air outlet 46 to the cooling air introduction passage 45 through the gap between the conductive ceramic element heater 21 ... And the holder ring 22 and the projecting portion 27. , Acts on the plate valve 52 of the reed valve 49.

When the cooling air introduction passage 45 becomes negative pressure due to pulsating pressure,
The plate valve 52 is opened to introduce outside air.
When the cooling air introducing passage 45 has a positive pressure due to the pulsating pressure, the plate valve 52 is closed to prevent the introduced air from flowing out. Therefore, the reed valve 49 performs a pumping action by the pulsating pressure of the exhaust gas and takes in outside air.

The air taken into the cooling air introduction passage 45 is jetted to the electrodes 24a and 24b through the cooling air outlets 46 ...

The exhaust gas temperature reaches a maximum of 800 ° C to 900 ° C, whereby the electrodes 24a, 24b are exposed to a high temperature atmosphere, and the electrodes 24a, 24b are heated by the self-heating of the conductive ceramic element heaters 21 ... Since the external air ejected to the electrodes 24a, 24b through the cooling air outlets 46 ... Has a relatively low temperature, the electrodes 24a, 24b are forcibly cooled and prevented from reaching a high temperature. .

Therefore, the electrodes 24a and 24b and the brazing material are prevented from being oxidized.

For example, if about 5 minutes of external air is injected into each electrode 24a, 24b, in the case of a turbo diesel engine with a displacement of 2.4 class, the temperature of the electrodes will be changed under the condition of full load of 2500 to 3000 rpm. It has been confirmed that the temperature can be reduced by about 100 ° C to 200 ° C.

7 and 8 show other embodiments of the present invention, and are sectional views of electrode portions. In each of FIGS. 7 and 8, sealing materials 70, ..., 80 are provided around the electrodes around ceramic fibers, a metal mesh or the like to reduce the inflow of exhaust gas into the electrodes.

In these structures, an air pump is used instead of the reed valve 49 when the pulsating pressure of the exhaust gas is not effectively transmitted to the cooling air introduction passage 45 because the cooling air outlets 46 ... Are also shielded. You may do it.

Since an air pump requires a special driving force, the cooling air is driven by driving the air pump only when the temperature of the exhaust gas rises above a predetermined value or when the conductive ceramic element heater 21 ... It may be supplied.

FIG. 9 is a plan view of a heating device showing another embodiment of the present invention. Although the cooling air intake portion 26 shown in FIG. 1 in the first embodiment is formed at two locations on the outer peripheral portion of the heater case 20, the cooling air introduction passage 45 is substantially formed on the peripheral wall of the heater case 20. It has to be formed over one-half round, the length of the cooling air introduction passage 45 becomes long,
Moreover, since the temperature of the heater case 20 also rises,
There is a concern that the temperature of the introduced air will rise while passing through the cooling air introduction passage 45 and the cooling efficiency will decrease.

On the other hand, in the embodiment of FIG. 9, the cooling air intake section 26
Is formed for each electrode portion, and the cooling air introduction passage 45 is made as short as possible.

Further, as shown in FIG. 9, the cooling air intake portions 26 ... And the terminal mounting portions 25 ... can be variously modified and designed in terms of the number, arrangement position, direction and the like in consideration of mountability on the vehicle. is there.

〔The invention's effect〕

As described above, according to the present invention, in the heater case,
A cooling air introduction passage communicating with the electrode portion of the conductive ceramic element heater is formed, and an air supply means is connected to the cooling air introduction passage so that the electrode portion is forcibly cooled by the air supplied by the air supply means. Therefore, the electrode portion is prevented from being oxidized by the temperature of the exhaust gas and the heat generated by the conductive ceramic element heater, and the life is extended.

[Brief description of drawings]

The drawings show an embodiment of the present invention, and FIGS. 1 to 6 relate to the first embodiment. FIG. 1 is a plan view of a heating device, and FIGS. 2 and 3 are respectively II in FIG. -II line and III-I
II sectional view, FIG. 4 is a sectional view of the cooling air intake portion, FIG. 5 is a sectional view of the reed valve, FIG. 6 is an overall sectional view of the particulate collection and purification device, FIG. 7 and FIG. Is a cross-sectional view around an electrode portion showing another embodiment of the present invention, and FIG. 9 is a plan view of a heating device showing still another embodiment of the present invention. 1 ... Filter case, 2 ... Filter, 3 ... Heating device, 20 ... Heater case, 21 ... Conductive ceramic element heater, 22 ... Holder ring, 23 ... Screw cap, 24 ... Insulation ring, 24a, 24b ... Electrode, 26 ...
Cooling air intake, 27 ... Overhang, 45 ... Cooling air introduction passage, 46 ... Cooling air outlet, 48 ... Cooling air supply pipe, 49 ... Reed valve.

Front page continued (72) Inventor Terutaka Kageyama, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor, Yoshihiko Imamura, 1-town Toyota town, Toyota city, Aichi prefecture Toyota Motor Corporation ( 72) Inventor Kiyoshi Kobata, Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Kenichiro Takama, Toyota Town, Toyota City, Aichi Prefecture, Toyota City, Ltd. (72) Inventor, Shinichi Takeshima 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (56) Bibliographic references Sho 55-80894 (JP, U) JP 62-49451 (JP, B2) JP 61-10646 (JP, B2)

Claims (2)

[Claims] 1. A filter for collecting fine particles contained in exhaust gas is installed in an exhaust system of an engine, and a heater case supporting at least one conductive ceramic element heater is installed on the upstream side of the filter. In an exhaust particulate collection and purification device that burns fine particles collected by the filter by the conductive ceramic element heater to reheat and heat the filter, in the heater case, cooling air that communicates with the electrode portion of the conductive ceramic element heater. An exhaust particulate collection and purification device for an engine, characterized in that an introduction passage is formed and an air supply means is connected to the cooling air introduction passage. 2. The exhaust particulate collection and purification system for an engine according to claim 1, wherein the air supply means is a reed valve which operates by pulsation of exhaust gas pressure.