JPH0422018Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an exhaust gas purification device for a diesel engine, and more specifically, to a back pressure for detecting the regeneration period of a diesel exhaust solid particulate collection device that can regenerate a filter. This invention relates to the structure of a back pressure introduction cap of a measuring device.

[Conventional technology]

Exhaust gas purification devices for purifying diesel exhaust gas by collecting solid particulate emissions (particulate matter) such as exhaust black particulates contained in the exhaust gas of diesel engines are well known. Such a purification device usually includes a trapper using a heat-resistant porous filter made of ceramic or the like. An example of a conventional exhaust solid particulate collector will be described with reference to FIG. 4. Reference numeral 30 is a diesel engine, 32 is an exhaust manifold, 1 and 1' are exhaust pipes, and 38 is a collector. A filter 42 is housed within a housing 40 of the collector 38.

If the solid particles collected during use of the collector accumulate in the filter, the filter will become clogged, increasing ventilation resistance and reducing the collection efficiency, so the filter must be regenerated at an appropriate time or periodically. Must be. Since the solid particulates in diesel exhaust are mainly composed of carbon and are therefore flammable, the filter can be regenerated by igniting some of the solid particulates accumulated in the filter and causing the fire to spread over the entire area of the filter. Is possible. Various methods are known for regenerating filters, but in the conventional example shown in FIG.
A control circuit 64 closes the relay 48 at an appropriate time and energizes the heater 44 for a certain period of time to heat it, thereby igniting the solid particles in the filter.

In order to determine when to regenerate the filter, it is necessary to understand the state of clogging of the filter, and for this purpose, the back pressure of the exhaust gas is detected. For example, in the example shown in FIG. 4, a back pressure detection port 45 is bored in the exhaust pipe 1, the back pressure is guided to a back pressure sensor 49 through a back pressure transmission pipe 47, and a piezoelectric resistance element built into the sensor or The strain gauge converts the back pressure value into a current value, and the control circuit 46 compares this with a set value to detect the regeneration timing.
The detection port 45 is generally equipped with an introduction cap for introducing exhaust back pressure, and a back pressure transmission pipe is connected to this cap.

In this method of determining filter regeneration timing by detecting the back pressure of exhaust gas, the structure of the back pressure introduction cap attached to the back pressure detection port bored in the exhaust pipe is extremely important. That is, during long-term use, solid particles and corrosive condensed components in the exhaust gas may act on the resistance element of the back pressure sensor, deteriorating the performance of the element. In addition, solid particulates and condensed liquid also adhere to the inner walls of the detection ports and back pressure transmission pipes, and if the amount of adhesion increases, the ports and pipes will eventually become clogged, making it difficult for the back pressure sensor to detect accurate pressure. This is because the reliability of the back pressure sensor is significantly impaired. Therefore, the back pressure introduction mouthpiece must be able to transmit exhaust gas pressure smoothly on the one hand, and completely block out solid particles and condensable components in the exhaust gas on the other hand.

FIG. 5 shows an example of a conventional back pressure measuring device with a built-in heater. (Refer to Japanese Utility Model Application Publication No. 61-29009.) In FIG. 5, the heater 51 is constituted by a cylindrical ceramic heater, and the pressure of the exhaust pipe 1 is introduced from the center thereof. 53 indicates a heat generating part. 54 is a protective cover for the heater 51. The positive terminal 59 connected to the heater 51 is
It is once attached to the pressure extraction/heater electrode 60 and taken out again using the connectors 61 and 62. On the other hand, the negative terminal is connected to the protective cover 54 and the flange 54a via the heater housing part and the metal ring 63.
It is grounded from the exhaust pipe 1 to the exhaust pipe 1. 67, 68
is a heat-resistant rubber gasket made of silicone or the like for insulation and airtightness.

The above-mentioned back pressure detection port is prone to breakage of the positive terminal 59 and dislocation of the welded part due to vibrations from the engine, etc. Also, when the silicone rubber 67, 68, etc. deteriorate due to heat, the inner tube (which is the positive electrode) The inner pipe (inner pipe) 70 may come into contact with the outer cylinder (rear cover) 71, which is at ground level, due to vibration and may be shot.

In order to eliminate the above drawbacks, the following back pressure detection port has been proposed. (See Utility Application No. 1983-037467). FIG. 6 and FIG. 7 show an embodiment based on the proposal. FIG. 7 shows an overall external view of the back pressure port structure of the back pressure measuring device according to the proposal, and its appearance is similar to that of FIG. 5.

FIG. 6 is an enlarged view of the internal structure of section A in FIG. 7. The most significant feature of the present invention is that the lower part of the inner pipe 80 is held by a ceramic spacer 81. That is, the inner tube 80 is fixedly held within an outer tube (rear cover) 82 via a cylindrical ceramic spacer 81.

The concave groove 83 formed in the ceramic spacer 81 has a hole 84 corresponding to the terminal extraction protrusion 91 of the heater 90.
It extends. A notch 85 is provided in the inner tube 80 at a position that does not interfere with the ceramic spacer 81, and the positive terminal 92 of the heater 90 is temporarily taken out from the cutout 85 and welded to the inner tube 80.
At this time, the positive terminal 92 is left with some slack in the extending direction. An airtight silicone rubber 86 is attached to the top of the ceramic spacer 81.

On the other hand, the lead wire 93 is passed through the lead wire holding silicone rubber 87 and then crimped to the lead connector 94. This is attached to the inner tube 80 as a positive lead wire by welding, and the outer tube 82 is attached so as to cover the whole.

[Problem that the invention attempts to solve]

1. The inner tube 80 is made of metal and is directly connected to the battery voltage (12 to 24 V), which is dangerous because it may be shot if it comes into contact with other parts.

2. The lead wire 92 is easily exposed to exhaust gas and easily deteriorates, and the contacts are also likely to peel off.

3. There is a risk of airtight leakage due to thermal deterioration of the silicone rubber 86 that holds the inner tube 80.

There are other problems.

The present invention aims to solve the above-mentioned problems and provide a simple and lightweight back pressure port structure that prevents poor insulation, airtight leakage, etc., and has sufficient strength against vibrations and the like.

[Means for solving problems]

In order to solve the above problems, in the present invention, an exhaust passage is formed by penetrating the back pressure port in the back pressure detection port of the back pressure measuring device,
The exhaust passage includes a cylindrical ceramic heater arranged at a certain length from the mouthpiece on the inlet side, and a metal cylindrical inner part connected to the end of the heater. The back pressure port is filled with an insulating hard material such as glass or ceramic as a spacer, and the junction between the inner tube and the heater and the lead wire of the heater are covered with a glass seal to ensure airtightness and A backpressure port configured to maintain insulation is provided.

[Effect]

When the back pressure of exhaust gas is introduced from the exhaust pipe into the back pressure port with the above configuration, the exhaust passage inside the back pressure port will be airtight due to the joint between the heater and the inner pipe being in close contact with each other and the glass seal. It is possible to reliably hold and send the correct back pressure to the sensor. Also,
The heater lead wires are also surrounded by a similar spacer, so there is no risk of deterioration or electrical leakage due to exposure to exhaust gas, and the spacers are also different from silicone rubber.
The performance of the back pressure port will not deteriorate due to deterioration or deformation over a long period of time.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The illustrated back pressure port includes a mouthpiece 3 for introducing exhaust gas G flowing inside the exhaust pipe 1, and a sensor 49 (a fourth
an outer cylinder (metal protective cover) 4 that communicates with the
It consists of a housing 5 which holds the mouthpiece 3 and an outer cylinder 4 and is attached to an exhaust pipe, and a cylindrical heater 6 made of ceramic is provided in the exhaust introduction passage 2.

Ground electrode 10 from the outside of ceramic heater 6
and the positive electrode 11 are taken out. The earth electrode 10 is connected to a holding fitting 12 and is further grounded via a metal housing 5 and an exhaust pipe 1.
The positive electrode 11 is taken out above the earth electrode 10 and is insulated from the holding fitting 12. A metal lead wire 13 is taken out from the positive electrode,
A ceramic sheet 14 is placed on the holding fitting 12 so as not to come into contact with the holding fitting 12. The opening 6a of the non-heat generating part of the ceramic heater 6 on the sensor 49 side is metallized with a step, and a metal inner pipe 9 housed in the outer cylinder 4 is inserted into this part. The opening 9a on the exhaust pipe 1 side is joined. The state in which the above components are assembled is called a heater assembly.

The upper part 8a of the protective cover 8 of the base part 3 is inserted into the metal housing 5, and is held in the metal housing 5 together with the heater assembly by the holding fitting 12. Furthermore, the outer cylinder 4 is assembled via the talc 16. In this state, the metal housing 5 is swaged through the ring spacer 17 to fix the entire structure and to make the exhaust gas airtight.

An insulating ceramic holder 15 is inserted into the upper part of the ceramic sheet 14 to fix the lead wire 13 so that it does not come into contact with the outer tube 4, and a glass plate is placed around the upper part of the joint between the inner tube 9 and the heater 6. A seal 18 is applied to ensure the airtightness of the joint and to securely fix the lead wire 13, and the lead wire 13 is electrically connected to the external power source of the back pressure port via the connecting fittings 19 and 20 above. An insulating ceramic holder 22 is inserted around the lead wire 21 to prevent the lead wire 21 from coming off when pulled and to insulate the outer tube 4 and the inner tube 9. A fixing rubber packing 23 is inserted into the upper part of the ceramic holder 22, and the outer cylinder 4 around it is inserted.
It's hardened.

With the above configuration, the positions of the positive terminal of the heater and the lead wire are securely fixed, eliminating the risk of short circuits due to contact with other parts, and also preventing the lead wire from coming into direct contact with exhaust gas. Therefore, deterioration of the lead wire due to exhaust gas is prevented. Furthermore, since the inner tube 9 is directly connected to the cylindrical part 6 of the heater and is further covered with a glass seal, there is less leakage due to thermal deterioration of silicone rubber as in the past, and the airtightness is improved. Back pressure measurement can be performed accurately.

FIG. 3 shows another embodiment. In the structure of the above embodiment, if the joint between the inner tube 9 and the heater 2 has sufficient airtightness, the glass seal 1
8 can be omitted, and a structure as shown in FIG. 3 can be obtained. That is, the heater assembly is fixed by caulking with the housing 5, the inner tube 9 is fixed using the insulating ceramic holder 22' and the fixing rubber packing 23 to prevent the lead wire from coming off, and the outer tube 4 around it is caulked. It is being At this time, the lead wires 13 and 21 are connected with a crimp terminal 19' or the like.

[Effect of idea]

According to the present invention, there is a remarkable effect in improving the following problems of the prior art.

(1) Short circuit of positive terminal of heater.

(2) Lead wire deterioration due to exhaust gas.

(3) Airtight leakage due to thermal deterioration of silicone rubber, etc.

In addition to the above, conventionally silicone rubber was used to maintain airtightness, so the length of the airtightness maintaining part was required to be below 200℃, but according to the present invention,
Since glass or ceramic is used for the airtight part, it is heat resistant and therefore requires a shorter distance than the heating part of the heater. This provides the following effects.

(4) The total length of the back pressure port can be shortened.

(5) The overall length is shorter, making it more resistant to vibration and lighter in weight.

(6) Restrictions on size and temperature have been improved, greatly increasing the degree of freedom in mounting on actual vehicles.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, Fig. 2 is an external view of a back pressure port equipped with the same embodiment, and Fig. 3 is a longitudinal cross-section of the main parts of a back pressure port according to another embodiment. Figure 4 is a schematic diagram of a conventional exhaust solid particulate collector and back pressure detection device; Figures 5 and 6 are conventional sectional views of different types of back pressure ports;
The figure shows the external view of FIG. DESCRIPTION OF SYMBOLS 1... Exhaust pipe, 2... Exhaust introduction passage, 3... Base part, 4... Outer tube, 5... Housing, 6... Ceramic heater, 7... Heater heating part, 9... Inner tube, 10 ...Earth electrode, 11...Positive electrode,
13, 21... Lead wire, 18... Glass seal, 15, 22, 22'... Ceramic holder for insulation, 23... Rubber gasket for fixing, G... Exhaust gas.

Claims (1)

[Scope of utility model registration request] In the back pressure detection port of the back pressure measuring device for detecting the regeneration period in the filter regeneration type exhaust solid particulate collector of a diesel engine, the exhaust gas introduction mouthpiece 3 for taking in the exhaust back pressure and the introduced exhaust gas are connected. An outer cylinder 4 that leads to the outside, and a housing 5 that holds both the above-mentioned 3 and 4 and is attached to the exhaust pipe 1.
An exhaust passage 2 is formed passing through each of the above parts, and the exhaust passage 2 includes a cylindrical ceramic heater 6 disposed at a constant length from the mouthpiece 3 on the inlet side, and Next, a metal cylindrical inner tube 9 is connected to the end of the heater, and the outer tube 4 and exhaust passage cylindrical tubes 6 and 9 are connected.
A spacer made of an insulating hard material such as ceramic is inserted into the gap between the inner tube 9 and the heater 6.
A back pressure detection port for a diesel engine, characterized in that a glass seal is applied to cover the joint with the heater 6 and the lead wire 13 of the heater 6 to maintain airtightness and insulation.