JPS6275012A - Device for collecting and cleaning exhaust fine particles for engine - Google Patents

Abstract

PURPOSE:To suppress the generation of stress and prevent breakage in a conductive ceramic element heater by conductively fixing one end of said heater to a case while supporting the other end slidably in a thermally expanding direction by means of an insulator and connecting a lead wire to it. CONSTITUTION:An earth electrode 24b is brazed to one end of a conductive ceramic element heater 21 and inserted into an electrode inserting hole 29b provided on a heater case 20 while being fixed to a heater case 20 by means of an insulating cap 35. And, a positive electrode 24a is brazed to the other end of the heater 21 and inserted into an electrode inserting hole 29a, and a lead wire 30 is connected to it while the heater 21 is slidably supported by means of the insulating cap 35. Thereby, the generation of stress can be suppressed and breakage can be prevented in the heater.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a so-called diesel engine, in which 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 particulate rate processing.

[Conventional technology]

For example, the exhaust gas from internal combustion engines such as diesel engines contains fine particles mainly composed of carbon and hydrocarbons. A method of collecting the above-mentioned particulates by installing a heat-resistant filter made of a structural body has been adopted. However, such filters become clogged with the collected particulates, increasing the resistance of the exhaust flow, and causing damage to the engine. This will lead to a decrease in output.

In order to prevent such filter clogging, a heating device equipped with an electric heater is disposed on the flow side of the filter, and this electric heat is used to burn particulates.

The above-mentioned electric heater is called a regenerative heating heater because it regenerates and purifies the filter.As this kind of regenerative heating heater is exposed to extremely high temperatures of exhaust gas, it has poor heat resistance and
A conductive ceramic element heater with excellent oxidation resistance is used.

The conductive ceramic element heater is attached to a heater case. In other words, the heater case is
The conductive ceramic element heater has a metal ring shape with an exhaust passage communicating with the filter, and the conductive ceramic element heater is formed, for example, in the shape of a letter. A plurality of legs are fixedly attached to the heater case along the circumferential direction.

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, since the conductive ceramic element heater is brittle or large, if both ends of the heater are rigidly fixed, stress will be generated due to thermal expansion during heat generation and it will easily break. I end up. Further, when such a conductive ceramic element heater is supported only at one end, there is a problem that the vibration resistance is insufficient.

The present invention provides a highly reliable engine exhaust particulate collection and purification device that can withstand the thermal expansion of a conductive ceramic element heater when it generates heat, maintains vibration resistance, and prevents damage to the conductive ceramic element heater. This is what we are trying to provide.

[Means for solving problems]

In the present invention, one end of the conductive ceramic element heater is fixed to the heater case so as to be electrically conductive, and this one end is used as a ground electrode.The other end is supported by an insulator so as to be slidable in the direction of thermal expansion. It is characterized by having a lead wire connected to it.

[Effect]

According to such a configuration, the other end of the conductive ceramic element heater is slidably supported, allowing thermal expansion, thereby preventing the generation of stress, and the other end being slidably supported. However, since it is mechanically supported, its vibration resistance is increased.

[Embodiments of the invention]

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

1 to 5 show a first embodiment of the present invention, and FIG. 5 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 include 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 l is made of cylindrical casting and has a flange 5 at one end and an integral exhaust gas discharge pipe 6 at the other end. A flange 7 is formed on a part of the end 5 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 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 l, and
A sealing material 14 is provided between the flange 12 of the exhaust gas introduction pipe 4.
．． 15.

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

The structure of the heating device 3 is shown in FIGS. 1 to 4,
This will be explained below.

The heating device 3 includes a heater case 20 and at least one
For example, six conductive ceramic element heaters 21...
and the heater case 20, a halter ring 31 that holds the conductive upper ramic element heater 21, a screw cap 22, and the screw cap 2.
Insulating ring 23 inserted between 2 and heater case 20
It is made up of.

Each of the conductive ceramic element heaters 21... is arranged in a portion where the upstream end face of the filter 2 is equally divided into approximately fan shapes, and each of these conductive ceramic element heaters 21 forms a planar V-shape. There is. Electrodes 24a and 24b are connected to both ends of this V-shape by brazing. In this case, in this embodiment, as shown in FIGS. 2 and 3, each electrode 24a, 24b is
It protrudes upward as shown.

The conductive ceramic element heater 21... has a V-shaped part connected to the electrodes 24a and 24b as a heat generating part, and a part surrounded by the ■-shaped part through which exhaust gas can pass. There is.

Note that the conductive ceramic element heater 21 can be manufactured as follows. That is, for example,
A slurry was prepared by dispersing 30% by weight of TiN powder and 470% by weight of 5i3N in an organic binder consisting of polyvinyl butyral, dibutyl phthalate, and ethanol.
This slurry is formed into a plate shape using a doctor blade method, processed into a predetermined shape using a punching method, and then heated and fired at a temperature of about 1750°C for about 2 hours in an inert gas atmosphere such as nitrogen gas. can get.

The conductive ceramic element heater 21 having such a structure
. . . is supported by two heater cases 20 at both ends thereof, and the heat generating portion thereof is disposed toward the center of the exhaust passage. Therefore, each conductive ceramic element heater 21.
... are arranged at intervals in the circumferential direction of the exhaust passage. In this case, gaps are formed between adjacent heat generating parts, and these gaps and the area surrounded by the above-mentioned V-shaped part,
A passage is secured that allows the passage of exhaust gas.

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, for example, cast iron, and has a terminal mounting portion 25 formed at one location on its periphery, and a terminal mounting portion 25 at the middle portion in the vertical direction shown in FIGS. 2 and 3. has a ring-shaped projecting portion 26 extending toward the center, and a female screw portion 27 is provided on the inner peripheral surface of the second portion over the entire circumference.

An insulating coating 28 made of spinel, alumina, or other ceramic material is formed on the lower surface of the overhanging portion 26 as shown in the figure, and the electrodes 24a and 24b are inserted through the overhanging portion 26 spaced apart from each other in the circumferential direction. Insertion holes 29a..., 29b... are provided.

One of the insertion holes 29a... has an electrode 2 inserted therein.
The electrode 2 is movable in the radial and circumferential directions.
The other through-hole 29b has a diameter sufficiently larger than the thickness of the through-hole 4a, and the other through-hole 29b has a size that allows the electrode 24b to be inserted therein to be fitted therein. -The one electrode 24a is loosely inserted into the insertion hole 29a, and the -I
A nickel lead wire 30 is welded to one end and serves as a positive electrode, while the other electrode 24
[) is inserted into the insertion hole 29b, and the overhanging □ part 26
It is welded to form a ground electrode.

Therefore, one electrode 24a is movable relative to the protrusion 26, while the other electrode 241) is movable relative to the protrusion 26.
Fixed to . In other words, one end of the conductive ceramic element heaters 21 is movable relative to the heater case 20, but the other end is firmly fixed to the heater case 20.

"-2 conductive ceramic element heater 21... is held between the overhang part 26 of the heater case 20 and a holder ring 31 located below the overhang part 26 and fixed to the heater case 2o. has been done.

The holder ring 31 is made of metal, and the heater case 20
It is attached to the body by bolts (not shown). An insulating coating 32 is formed on the upper surface of the holder ring 31 by spraying a ceramic material such as spinel or alumina, and recesses 33 are provided at a distance in the circumferential direction facing each of the electrodes 24a and 24b. It is being

A cushioning material 34 and an insulating cap 35 made of insulating ceramic that covers the cushioning material 34 are housed in each of these recesses 33 .

= 10- The lower surfaces of the conductive ceramic element heaters 21... are in contact with the insulating cap 35, and therefore these conductive ceramic element heaters 21... are substantially connected to the overhanging portion 26 and -fx The conductive ceramic element heater 2 is sandwiched between the insulating caps 35 and the insulating caps 35 are pressed by the cushioning material 34.
1... are slidably supported. However, since the ground electrode 24b is welded to the projecting portion 26, the other end of the conductive ceramic element heater 21 cannot be slid, and only one end can be slid.

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 threaded portion 36 on its outer peripheral surface, and a retaining wall 37 that projects downward in the figure on its inner surface. The lower surface of this screw cap 22 is coated with an insulating coating 38 made of spinel, alumina, or other ceramic sprayed material.
It is formed.

Note that 45 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.
6 is screwed onto the female threaded portion 27 of the heater case 20, this screw cap 22 and the overhang portion 26
The above-mentioned insulating ring 23 is sandwiched between them.

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 parts, and its circumferential ends are brought into contact with each other to form a link shape over the entire circumference.

Electrode insertion holes 39 are formed in the insulating ring 23 in communication with an insertion hole 29a formed in the overhanging portion 26 of the heater case 20 and into which one electrode 24a is loosely inserted. These electrode insertion holes 39 have a size such that the electrode 24a inserted therein can move in the radial direction and the circumferential direction.

The "-" side of the insulating ring 23 has guide grooves 40 for leading wires connected to the electrode insertion holes 39.
・Or is formed. Lead wire routing guide full 40
. . . The other end is led to face the terminal mounting portion 25 of the heater case 20 described above.

Lead wires 30 connected to one electrode 24a of the conductive ceramic element heater 21 are inserted into these lead wire routing guide grooves 40. The terminal attachment is connected to terminals 41 attached to the portion 25. Note that 42 is a connector.

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
A current is applied to the lead wires 30 through 2.

In this case, each lead wire 30... is connected intermittently and sequentially.
13. Apply current to the first one. As a result, each conductive ceramic element heater 21 generates 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, 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. Particulates attached to 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 as described above, the conductive ceramic element heaters 21 . . . are held between the projecting portion 26 of the heater case 20 and the holder ring 31. In this case, among the electrodes 24a and 24b joined to both ends of the conductive ceramic element heater 21..., one electrode 24a is movably inserted loosely into the insertion hole 29a, and the other electrode 24b is inserted into the insertion hole 29a. 29b is inserted and welded to the overhanging portion 26 to form a ground electrode, one end of the conductive ceramic element heater 21 is movable relative to the heater case 20, but the other end is movable relative to the heater case 20. It is firmly fixed to 20.

Moreover, the conductive ceramic cord heater 21... is attached to the overhanging portion 26 and the holder ring 31;
Since it is slidably supported between the insulating caps 35, the conductive ceramic element heater 21...
・One end is capable of sliding i+J, and the other end is firmly fixed.

As a result, when the conductive ceramic element heaters 21... thermally expand and contract due to self-heat generation and exhaust gas heat, one end slides in the radial direction or circumferential direction to allow the thermal expansion and contraction. Therefore, stress is not generated in the conductive ceramic element heaters 21, and damage is prevented.

Moreover, although one end of the conductive ceramic element heater 21 is slidable, it is supported slidably between the overhanging portion 26 and the insulating cap 35 attached to the holder ring 31. Since it is mechanically supported and is supported at both ends, it is stably supported even if vibrations or shocks are transmitted.

Note that if the lead wire 30 is a thick ILT wire or a twisted wire made by twisting together multiple small cable wires, the rigidity will be low, so the conductive ceramic element heater 21
...Sliding on one end becomes easier.

Further, the structure is such that the lower surface of the conductive ceramic element heater 21 is pressed by the insulating cap 35 and the cushion material 34 attached to the holder ring 31;
The height at which the earth electrode 24b protrudes from the insertion hole 29b can be regulated with high precision, allowing reliable welding of the earth electrode 24b and the heater case 20.

FIG. 6 shows a sectional view of a positive electrode portion showing a second embodiment of the present invention. In the first embodiment, the insulating cap 35 and the cushioning material 34 were used, but in this embodiment, a cap slightly larger than the thickness t of the conductive ceramic element heater 21 was used around the holder ring 31. By forming the spacer portion 50 with a height, excessive clamping pressure is prevented from being applied to the positive electrode 24a portion of the conductive ceramic element heater 21 .

In this way, even if the insulating cap 35 and the cushioning material 34 in the first embodiment are omitted, the positive electrode 24a side end of the conductive ceramic element heater 21 can be slidably supported. can.

Note that the spacer portion 50 may be formed on the heater case 2o side, or may be constructed from a separate component.

7 to 11 show a third embodiment of the present invention.

In this third embodiment, the projecting portion 26 is connected to the heater case 2.
A conductive ceramic element heater 21 is sandwiched between the protruding portion 26 and the insulating ring 23 at the lower end of the ceramic element 23 .

Further, the conductive ceramic element heater 21... is the eighth
As shown in the figure, both ends are formed wide, and an insulating cap 35 and a cushion are placed at positions that do not overlap with the positive electrode 24a and the ground electrode 24b attached to these ends, respectively, when viewed from the plane. A material 34 is provided.

The positive electrode 24a is connected to the flange 6 as shown in FIG.
0 and stator 61 to form a conductive ceramic element heater 21.
The ground electrode 24b is attached to the conductive ceramic element heater 21 by a flange-shaped spacer 62 and a stator 63, as shown in Fig. 1. The other end is sandwiched and brazed, and this ground electrode 2
4b is fixed to the projecting portion 26 using a nut 64.

In this way, the attachment of the electrodes 24a and 24b depends on the structure and
The sandwiching structure of the conductive ceramic element heater 21...
The structure of the first embodiment is not limited to that described above, and various modifications are possible.

Furthermore, the shape of the conductive ceramic element heater 21 is not limited to the planar cross-shaped shape, but may be a linear shape (bar-like, linear) with a honeycomb structure as shown in FIG.

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 divided or more, 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 element 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, one end of the conductive ceramic element heater is fixed to the heater case so as to be electrically conductive, and this one end is used as a ground electrode, and the other end is slidable in the direction of thermal expansion by the insulator. Since the conductive ceramic element heater is supported by the support and the lead wire is connected to the other end, the conductive ceramic element heater is able to thermally expand and contract, preventing the generation of stress, and even though the other end is slidable. Since it is mechanically supported, its vibration resistance is increased. Therefore, damage to the conductive ceramic element heater is prevented and reliability is improved.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIGS. 1 to 5 relate to the first embodiment, FIG. 1 is a plan view of the heating device, and FIGS. −■ line and ■−■
4 is a plan view of the heating device with the screw cap removed, FIG. 5 is a sectional view of the entire particulate collection and purification device, and FIG. 6 is a sectional view of the second embodiment of the present invention. 7 to 11 show a third embodiment of the present invention, FIG. 7 is a plan view of the heating device, and FIG. 8 is a sectional view of the conductive ceramic element heater. The plan views of the parts, FIGS. 9 to 11, are respectively IX- in FIG. 8.
FIG. 12 is a plan view of a heating device showing another example of the conductive ceramic element heater. 1... Filter case, 2... Filter, 3...
Heating device, 20... Heater case, 21... Conductive ceramic element heater, 22... Screw cap, 23... Ceramic insulation ring, 24a... Positive electrode, 24b... Earth electrode, 26... Overhanging portion, 2g, 32.38... Ceramic sprayed insulation film, 29a, 29b... Electrode insertion hole,... Cushioning material, 35... Insulating cap. Applicant's representative Patent attorney Takehiko Suzue Figure 4 Figure 5 Figure 6 Illustration Figure 9 Figure 10 Figure 12 Figure 11

Claims (2)

[Claims] (1) A filter for collecting particulates contained in exhaust gas is installed in the engine exhaust system, a heater case supporting at least one conductive ceramic element heater is installed upstream of this filter, and the filter In the exhaust particulate collection and purification device that regenerates and heats the filter by burning the particulates collected by the conductive ceramic element heater, the conductive ceramic element heater has one end fixed to the heater case so as to be electrically conductive. 1. An engine exhaust particulate collection and purification device, characterized in that one end of the lever is used as a ground electrode, the other end is slidably supported by an insulator in the direction of thermal expansion, and a lead wire is connected to the other end. (2) The engine exhaust particulate collection and purification device according to claim 1, characterized in that an insulator pressing at least one surface of the conductive ceramic element heater is pressed by a cushion body.