JPS6275013A - Device for collecting and cleaning exhaust fine particles for engine - Google Patents

Abstract

PURPOSE:To prevent stress from concentrating and a crack from generating on a ceramic insulating ring by holding a conductive ceramic element heater and said ring between the projected part of a heater case and a screw cap. CONSTITUTION:A conductive ceramic element heater 21 is placed on the upper course side of the filter 2 of an exhaust fine particle collecting and cleaning device. A projected part 26 is provided on a heater case 20, the heater 21 is place on it, and a ceramic insulating ring 23 is overlapped on the heater 21 and clamped by a screw cap 22 from above. Thereby, the insulating ring 23 is pressed and held by nearly a uniform pressure over its whole surface, preventing stress concentration and the generation of a crack.

Description

[Detailed Description of the Invention] [Field of Application in Industry-1-] The present invention is characterized in that particulates contained in exhaust gas from a diesel engine, etc. are collected by a filter, and the collected particulates are combusted. The present invention relates to an engine exhaust particulate collection and purification device used for so-called diesel particulate treatment.

[Conventional technology]

For example, the exhaust gas from internal combustion engines such as diesel engines contains fine particles mainly composed of carbon and hydrocarbons, and in order to purify this exhaust gas, the exhaust gas system is equipped with a ceramic honeycomb structure or a ceramic foam structure. A method of collecting the above-mentioned fine particles by installing a heat-resistant filter made of body material has been adopted. However, such filters become clogged with trapped particulates, increasing exhaust flow resistance and reducing engine output.

In order to prevent such filter clogging, a heating device equipped with an electric heater is placed on the downstream side of the filter.
This electric heat is used to burn the particles.

The electric heater described above is called a regenerative heating heater because it regenerates and purifies the filter, and recently, a conductive ceramic element heater has been adopted as this type of regenerative heating heater.

The conductive ceramic element heater is attached to a heater case. That is, the heater case is in the shape of a metal ring with an exhaust passage communicating with the filter, and the conductive ceramic element heater is formed, for example, in a substantially square shape. A plurality of cord heaters are attached to the heater case along the circumferential direction, with both leg portions in the shape of a -1 character (■) being fixed.

Then, the conductive ceramic element heater is energized to generate heat, thereby burning the particulates collected by the filter.

[Problem that the invention seeks to solve]

When attaching such a conductive ceramic element heater to a heater case, the conductive ceramic element heater or a lead wire for energizing the ceramic element heater,
It is necessary to electrically insulate the heater case, and an insulator is used to provide such an insulating structure. This type of insulator is required to have heat resistance because it is exposed to the extremely high temperature of exhaust gas, and therefore the use of a ring-shaped insulator made of ceramic such as alumina or silicon nitride is being considered.

However, the ceramic insulating ring described above is highly brittle, so if it is fixed to the heater case by bolting, stress will be concentrated in the tightened part and cracks will easily occur when it is subjected to vibration or impact. If a structure is adopted in which the metal spring is used to elastically press and hold the metal spring, the metal spring will sag due to high temperatures, resulting in a problem that reliable holding over a long period of time cannot be expected.

The present invention aims to provide an engine exhaust particulate collection and purification device that can reliably attach an insulating ring and a conductive ceramic cord heater to a heater case without causing cracks in the ceramic insulating ring. It is.

[Means for solving problems]

The present invention provides an overhanging portion on the heater case, and a ring-shaped screw cap is screwed onto the heater case opposite to the overhanging portion, and these screw caps and the overhanging portion combine to form an insulating ring and a conductive ceramic. It holds an element heater in between.

[Effect]

According to such a configuration, the insulating ring and the conductive ceramic element heater are held by the wide surfaces of the screw cap and the overhanging portion, respectively, so that they are held with substantially uniform pressure applied to the entire surface.

[Embodiments of the invention]

The details of the present invention will be explained below based on embodiments shown in the drawings.

1 to 6 show a first embodiment of the present invention, and FIG. 6 shows the overall structure of the particle collection and purification device, so it will be explained first.

The main components of the particulate collection and purification device are 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 cylindrical casting, has a flange 5 at one end, and integrally has 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 a filter case l via a heat insulating cushion material 8 and a heat insulating seal material 9.10. This filter 2 is made of, for example, cordierite porous foam ceramic.

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

The heating device 3 includes a flange 5 of the filter case I, and
The exhaust gas introduction pipe 4 is sandwiched between the flanges 12 of the two exhaust gas introduction pipes 4 with a heat insulating seal material 14 and 15 interposed therebetween.

In addition, the flange 7 provided on the v1 gas discharge pipe 6 of the filter case 1 and the flange 13 of the exhaust gas introduction pipe 4 are as follows:
Each is connected to an exhaust pipe of an engine (not shown) so that exhaust gas flows in the direction of arrow A.

-J- The structure of the heating device 3 is shown in FIGS. 1 to 5, and will be described below.

The heating device 3 includes a heater case 20 and at least one
For example, six conductive ceramic cord heaters 21...
, a screw cap 22 that clamps these conductive ceramic element heaters 21... with the heater case 20, and an insulator inserted between the screw cap 22 and the conductive ceramic element heaters 2I... The ring 28 is configured as a ring 28.

Each of the conductive ceramic element heaters 21... is arranged in a portion where the end face of the first flow side of the filter 2 is equally divided into approximately fan shapes. has been achieved. Electrodes are joined to both ends of this V-shape by brazing. in this case,
As shown in FIG. 4, the electrode 24 connected to one end is
It is designed to protrude upward as shown in the figure, and the electrode joined to the other end is designed to protrude downward although it is not shown in the figure.

In the conductive ceramic cord heaters 21, the V-shaped portion connected to the electrode serves as a heat generating portion, and the portion surrounded by the ■-shaped portion allows exhaust gas to pass through.

Incidentally, the conductive ceramic cord heater 21 described in item 1 can be manufactured as follows. That is, for example, 30% by weight of TiN powder and 70% by weight of 5i3N4,
Polyvinyl butyral, dibutyl phthalate, and ethanol are dispersed in an organic binder to make a slurry. This slurry is formed into a plate shape using a doctor blade method. After processing this into a predetermined shape using a punching method, the slurry is It is obtained by heating and baking at a temperature of about 1750° C. for about 2 hours in an active gas atmosphere.

Both ends of the conductive ceramic element heaters 21 having such a structure are supported by the heater case 20 mentioned above, and the heat generating portion thereof is disposed toward the center of the exhaust passage. Therefore, each conductive ceramic element heater 2
1... are arranged at intervals in the circumferential direction of the exhaust passage. In this case, a gap is formed between adjacent heat generating parts,
These gaps and the portion surrounded by the "2"-shaped portion secure a passage through which the exhaust gas can pass.

The structure for attaching the conductive ceramic element heaters 21 to the heater case 20 will now be described.

The heater case 20 has a ring shape made of cast iron, for example, and has a terminal mounting portion 25 formed at one location on its periphery, and a ring-shaped projecting portion 26 extending toward the center at the lower end. And -1, a female threaded portion 27 is provided on a part of the inner peripheral surface over the entire circumference.

An insulating wave film 28 made of spinel, alumina, or other ceramic sprayed is formed on the -1- side of the overhanging portion 26 as shown in the figure, and on the upper surface of the overhanging portion 26, it is spaced apart in the circumferential direction. , the above-described upwardly mounted electrode 24 of the conductive ceramic element heater 21 . Electrode insertion holes 90 are formed opposite the attached electrodes.

As shown in FIG. 4, each of these recesses 29 has a cushioning material 30 made of wire mesh and an insulating cap 3 made of insulating ceramic covering this cushioning material 30.
1 is accommodated.

A ring-shaped metal screw cap 22 is screwed into the female threaded portion 27 of the heater case 20 .

The screw cap 22 has a male tapered portion 32 on its outer peripheral surface, and a retaining wall 33 that protrudes downward in the figure on its inner surface. The bottom surface of the screw cap 22 is coated with an insulating wave film 34 made of spinel, alumina, or other ceramic sprayed material.
It is formed.

Note that 35 is a hole into which a jig (not shown) is inserted when screwing the screw cap 22 into the heater case 20 or removing it.

Such a screw cap 22 has a male threaded portion 3.
2 is screwed onto the female threaded portion 27 of the heater case 20, this screw cap 22 and the overhang portion 26
Between the above-mentioned conductive ceramic element heaters 21...
- and clamps the insulating ring 23.

The insulating ring 23 is made of insulating ceramic such as silicon nitride or alumina, and in this embodiment, there are two rings in the circumferential direction.
It is divided into two parts, and its circumferential ends are brought into contact with each other to form a ring shape over the entire circumference.

The lower surface of the insulating ring 23 has heater insertion grooves 3 in the radial direction.
5 are formed at intervals. The ends of the conductive ceramic element heaters 21 are inserted into these heater insertion grooves 35, respectively. Also,
The insulating ring 23 includes each conductive ceramic element heater 2.
1. The electrode 2 is attached to one end of the electrode in a negative direction.
4, electrode insertion holes 36 are formed. On the surface of the insulating ring 23, there are guide grooves 37 for leading wires connected to the electrode insertion holes 36.
... is formed. Guide groove for lead wire routing 3
7... The other end is guided so as to face the terminal mounting portion 25 of the heater case 20 described above.

Note that the inner diameter of the projecting portion 26 is the same as that of the insulating ring 2.
It is formed to be equal to or larger than the inner diameter of the lower side of No. 3.

Then, both ends of the conductive ceramic element heaters 21 are inserted into the heater insertion grooves 35 of the insulating ring 23, and the electrodes 24 bonded to one end of the conductive ceramic element heaters 21 are inserted. It is inserted into the hole 36... Then, the lead wires 38 are connected to the electrodes 24 inserted into the electrode insertion holes 36 by welding, and the lead wires 38 are fitted into the lead wire routing guide grooves 37. Then, the wires are routed along the lead wire routing guide grooves 37.

After such assembly, the conductive ceramic element heater 2
1... and the insulating ring 23 are placed on the overhanging portion 2Bi of the heater case 20, and the screw cap 22 is screwed in.

In this way, the conductive ceramic element heater 21.
. . . and the insulating ring 23 are held between the projecting portion 26 of the heater case 20 and the screw cap 22.

In this state, the lead wires 38 are connected to the terminals 39 attached to the terminal attachment portions 25. In addition, 4
0 is a connector.

Note that the conductive ceramic element heater 21 is connected to the overhanging portion 26 of the heater case 20 and the screw cap 22.
... and the insulating ring 23, the lower surface of the conductive ceramic element heater 21... is supported by the cushion moon 30 and the insulating cap 31 shown in FIG. 4, and the insulating ring 23 and the insulating cap substantially He will be arrested at 31. and conductive ceramic element heater 21
The other electrode (not shown) protruding downward from the other end is inserted into the electrode insertion hole 80 of the overhanging part 26 of the heater case 20, and is welded to the overhanging part 26 to form a ground electrode. Become.

Moreover, even if the insulating ring 23 is formed into two parts, the insulating ring 23 will not move because it is supported by the downwardly protruding retaining wall 33 formed on the screw cap 22.

By installing the heating device 3 having the above-described structure on the first stream side of the filter 2, a particulate collection and purification device is completed.

The particulate collection and purification device of this embodiment with such a configuration is connected to the exhaust gas system of an internal combustion engine, introduces exhaust gas from the exhaust gas inlet 11 of the exhaust gas introduction pipe 4, and removes the particulates in the exhaust gas from the surface of the filter 2. to be collected. When the pores of the filter 2 become narrowed due to particles collected on the surface of the filter 2, that is, when the filter 2 becomes clogged, the connector 4
0 through the lead wires 38...

In this case, current is passed through each lead wire 38 intermittently and sequentially. As a result, each conductive ceramic cord heater 21 generates heat intermittently and sequentially.

The heat generated by the conductive ceramic element heaters 21 heats the upstream end face of the filter 2, and the particulates collected in this part start to burn, and that part becomes the ignition point, which causes the downstream end face to heat up. The particulates that are colored blue on the surface of the filter 2 on the side are also burned and removed.

Therefore, filter 2 will be regenerated.

According to the configuration of the embodiment described above, the insulating ring 23 is held between the projecting portion 26 of the heater case 20 and the screw cap 22, as can be understood from FIG. In this case, both ends of the conductive ceramic element heaters 21 are inserted into the heater insertion grooves 35 of the insulating ring 23, and are held between the insulating ring 23 and the insulating cap 31. - and the lower surface are held by the lower surface of the screw cap 22 and the two surfaces of the overhanging portion 26, respectively.

For this reason, the negative and lower surfaces of the insulating ring 23 are pressed against the wide surfaces of the screw cap 22 and the overhanging portion 26, so that the entire area is clamped with a wide and even clamping force, which reduces vibrations. Even if an impact is applied, cracks will not occur in the insulating ring 23.

Furthermore, the insulating ring 23 is supported by a downwardly protruding retaining wall 33 formed on the screw cap 22, so that it does not move. Further, even if the insulating ring 23 is divided into two in the circumferential direction, it will not move.

7 and 8 show a second embodiment of the invention.

In this second embodiment, the projecting portion 26 is connected to the heater case 2.
The insulating ring 23 and the lead wire 38 are sandwiched between the projecting portion 26 and the screw cap 22. The conductive ceramic element heaters 21 are held between the -fZ overhang 26 and a metal holder ring 50 installed below it. Holder ring 50 is fixed to heater case 20 with bolts (not shown).

Note that an insulating coating 51 is formed by ceramic spraying on the lower surface of the projecting portion 26 so that the lower surface of the projecting portion 2B does not come into electrical contact with the negative side of the conductive ceramic cord heater 21 .

In the case of the second embodiment of such a configuration, the insulating ring 23
Since there is no need to form the heater insertion groove 35 in the insulating ring 23, problems such as damage to the insulating ring 23 are reduced.

Further, the conductive ceramic cord heater 2I has an overhanging portion 2.
6 and the holder ring 50, the installation of the insulating ring 23 is independent of the work, and the work of assembling them is simple.

9 and 10 show a third embodiment of the invention.

FIG. 9 is a bottom view of the screw cap 22. On the bottom surface of the screw cap 22, as shown in FIG. 10, a groove 60 for guiding a lead wire is formed all around the circumference. An insulating coating 34 is also formed on the inner surface of this lead wire guide groove 60 by ceramic spraying.

In this way, the depth of the lead wire routing guide groove 37 formed on the surface of the insulating ring 23 can be made shallow, making it possible to make the insulating ring 23 difficult to break. Since 23 can be made thinner, the entire heating device can be made smaller and lighter.

FIG. 11 and FIG. 12 each show other examples of screw caps.

Screw cap 2 of each embodiment described above
2 is ring-shaped, but the screw cap 70 shown in FIG. 11 is disk-shaped and has a large number of through holes 71 for passage of exhaust gas formed therein.

The exhaust gas passage holes 71 may have a circular or polygonal shape. Further, as shown in FIG. 12, a plurality of fan-shaped exhaust gas passage holes 72 may be formed.

Furthermore, FIG. 13 shows a modified example of the heater case, in which the terminals protruding outward from the heater case 20 are attached to the part 2.
5 is formed with a notch 80 whose inner and upper surfaces are open. By forming such a notch 80, the work of connecting the lead wire 38 to the terminal 39 becomes easier.

In this case, the inner surface of the heater case 20 has the above-mentioned notch 8.
0, the female thread 27 may be cut in the middle, but since the remaining female thread 27 has a sufficient length, the screw cap 22 can be screwed securely.

In each of the above embodiments, the insulating ring 23 is arranged in two directions in the circumferential direction.
Although the insulating ring 23 is divided into three parts.
It may be formed in more than one piece, or it may be formed integrally.

Further, although only one insulating ring 23 is used in the axial direction, two insulating rings 23 may be used in the axial direction, and the conductive ceramic cord heater 21 may be sandwiched between these two insulating rings. In this case, the insulating film formed by ceramic spraying can be omitted.

〔Effect of the invention〕

As explained above, according to the present invention, the ceramic insulating ring and the conductive ceramic element heater are held between the protruding portion formed on the heater case and the screw cap, so that the ceramic insulating ring and the conductive ceramic element heater are held together with substantially uniform pressure over the entire surface. Even if vibrations or shocks are transmitted, concentrated stress is not generated in the insulating ring, which prevents cracks from occurring, and the clamping force does not weaken, so it can be used for a long time. It is well maintained and has a long life.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIGS. 1 to 6 relate to the first embodiment, FIG. 1 is a plan view of the heating device, and FIG. 2 is a plan view with the screw cap removed. , 3rd
The figure is a view taken along the line X-X in Figure 9, Figure 4 is a sectional view taken along the line X-X in Figure 9, Figure 5 is an exploded perspective view, and Figure 6 is a particulate collection and purification device. 7 and 8.
The figures show a second embodiment of the present invention, and include a sectional view and a sectional view corresponding to FIGS. 3 and 4, and FIGS. 9 and 1.
0 shows the third embodiment of the present invention, FIG. 9 is a bottom view of the screw cap, FIG. 10 is a sectional view of the assembled state taken along line X-X in FIG. 9, and FIGS. The figures are a plan view and a thirteenth figure showing other examples of screw caps, respectively.
The figure is a plan view of a heating device to show another example of a heater case. l...filter case, 2...filter, 3...
Heating device, 20... Heater case, 21... Conductive ceramic element heater, 22... Screw cap, 23... Ceramic insulation ring, 26... Overhanging portion, 28.34... Ceramic Sprayed insulation film. = 20- Figure 3 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12

Claims (2)

[Claims] (1) A heater case in which a filter is installed in the engine exhaust system to collect particulates contained in exhaust gas, and at least one conductive ceramic element heater is supported along the circumferential direction on the upstream side of the filter. In the exhaust particulate collection and purification device, the particulate matter collected by the filter is burned by the conductive ceramic element heater to regenerate and heat the filter, wherein the conductive ceramic element heater is held down by a ceramic insulating ring; An engine exhaust particulate collection and purification device characterized in that this insulating ring is held between an overhang formed on the heater case and a ring-shaped screw cap screwed onto the heater case. (2) When the overhanging portion or the screw cap comes into contact with the conductive ceramic element heater, an insulating film is formed by ceramic spraying on the surface of the overhanging portion or the screw cap that comes into contact with the conductive ceramic element heater. An engine exhaust particulate collection and purification device according to claim 1.