JPS6329134Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention generally relates to an exhaust gas purification device for a diesel engine, and more specifically, to an exhaust back pressure measuring device for a diesel exhaust solid particulate collector capable of regenerating a filter. Regarding the structure of the cap for introducing back pressure.

[Background technology]

BACKGROUND OF THE INVENTION Exhaust gas purification devices for purifying diesel exhaust gas by collecting solid particulate emissions, such as exhaust black particulates, contained in the exhaust gas of a diesel engine are well known. Such a purification device usually consists of a trap 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. 1, in which 10 is a diesel engine, 12 is an exhaust manifold, 14 and 16
is an exhaust pipe, and 18 is a collector. A monolithic filter 22 is housed within the housing 20 of the collector 18, and is adapted to collect solid particulates in diesel exhaust gas mainly based on the principle of collision collection. In order to withstand the high heat of exhaust gas and effectively collect solid particles, the filter 22 is generally made of a monolith body made of cordierite ceramic molded into a three-dimensional network structure or porous foam. The size of the micropores is selected to be around 2 mm, and fine particles such as gamma alumina are further coated on the inner surface of the micropores to increase the pore surface area, making it possible to easily collect exhaust particles. It has been devised as follows.

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 that have accumulated in the filter and causing the fire to spread and blow over the entire area of the filter. Is possible. Various filter regeneration methods are known, including a method in which solid particulates are ignited by throttling the engine intake system to reduce the amount of intake air and raising the exhaust gas temperature; There is a method of igniting particulates by increasing the fuel injection amount and raising the exhaust gas temperature, but in the conventional example shown in FIG. The control circuit 26 closes the relay 28 at an appropriate time and energizes the heater 24 for a certain period of time to heat it, thereby igniting the solid particles in the filter.

There are two methods to determine when to regenerate the filter: one is to integrate the number of engine revolutions with an integrator and regenerate the filter when the total number of revolutions reaches a set value, and the other is to add up the distance traveled by the vehicle and regenerate the filter every predetermined distance traveled. A method of detecting the exhaust gas back pressure upstream of the collector and regenerating it when the back pressure reaches a set value. A method of detecting the exhaust gas back pressure upstream and downstream of the collector and detecting the difference. There are methods to regenerate when the pressure reaches the set value, etc.
Since the former two methods do not necessarily accurately reflect the clogging state of the filter, the latter two methods using back pressure are the most rational. For example, in the example in Figure 1,
A back pressure detection port 30 is bored in the exhaust pipe 14, the back pressure is guided to the back pressure sensor 34 through the back pressure transmission pipe 32, and the back pressure value is measured as a current value using a piezoelectric resistance element or strain gauge built into the sensor. The control circuit 26 compares this with a set value to detect the reproduction timing. Generally, an introduction cap for taking in exhaust back pressure is attached to the detection port, and a back pressure transmission pipe is connected to this cap.

In this method of determining the filter regeneration timing by detecting the back pressure of exhaust gas, the structure of the back pressure introduction cap that is 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 condensate also adhere to the inner walls of 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, on the one hand, the back pressure introduction cap must be able to transmit exhaust gas pressure smoothly, and on the other hand, it must be able to completely block out solid particles and condensable components in the exhaust gas. .

Therefore, recently, a back pressure introduction structure has been proposed in which a honeycomb filter is loaded into the detection port and an electric heater is wound around the outer periphery of the honeycomb filter (Utility Model Application No. 57-61024). According to this, exhaust particulates in the exhaust gas are filtered by the honeycomb filter, and only clean exhaust gas enters the detection port. Fine particles and the like that adhere to the honeycomb filter due to filtration are incinerated by heating the electric heater, and the honeycomb filter is thus properly regenerated.

However, in this introduction part structure, since the filter is honeycomb-shaped and has multilayered internal passages, it is difficult to heat the inside. Furthermore, since the electric heater is provided outside the filter, heat is dissipated to the outside, resulting in a low heat utilization rate of the heater. Therefore, a large amount of electric power is required to heat the honeycomb filter to a temperature necessary for its regeneration, and there is a risk that the regeneration may be insufficient.

To solve this problem, a hollow cylindrical filter with an open top end and a closed bottom end is airtightly attached to the bottom surface of the cylindrical mouthpiece body, which has a back pressure transmission passage inside. The electric heater may be provided directly on the filter or inside the filter. However, in this case, the power supply line to the electric heater must be taken out to the outside of the pressure transmission path, and a complicated sealing structure is required to ensure airtightness of the power supply line outlet.

[Purpose of invention]

The purpose of the present invention is to comprehensively improve this type of back pressure introduction mouthpiece structure, and to effectively block solid particulates and harmful components in the exhaust gas while reducing the pressure of the exhaust gas. It is an object of the present invention to provide a back pressure introducing base structure which is capable of accurately transmitting back pressure to a back pressure measuring device, has a simple structure, and is capable of reliably regenerating a filter with a small amount of power consumption.

It is an object of the present invention to provide a back pressure introduction cap structure that allows a heater power supply line to be easily taken out to the outside of the back pressure transmission path while ensuring the airtightness of the back pressure transmission path.

[Structure of the idea]

Therefore, the present invention is characterized in that the pressure extraction pipe connected to the base body is constructed of a conductive metal pipe, and the extraction pipe is used as a part of the heater power supply circuit.
As a result, the pressure outlet and the power supply circuit outlet can be combined into one, and the structure can be simplified while ensuring the airtightness of the pressure transmission path.

〔Example〕

Embodiments of the present invention will be described with reference to FIG. 2 and the following drawings. FIG. 2 shows a back pressure introduction mouthpiece 50 according to an embodiment of the present invention on an exhaust pipe 5 of a diesel engine.
It is shown attached to the detection port 54 of No. 2. The cap 50 has a substantially cylindrical cap body 56, to which a flange 58 is secured by interference fit or welding. The flange 58 is connected to the exhaust pipe 5 by the bolt 62 via the gasket 60.
2, the cap 50 is airtightly fixed to the exhaust pipe.

A circular groove is provided on the lower surface of the cap body 56,
A cushioning ring 64 like go's wire is placed in this groove.
After inserting the filter 66, the filter 66 is fitted and held by a filter cover 68. Filter cover 68
is adapted to be appropriately snap-fitted to the base body 56, and has the function of a retainer to prevent the filter 66 from falling off, and also protects the filter from the impact of the exhaust gas flow indicated by the arrow and the substances accompanying it. It is something to do. Filter cover 6
A plurality of openings (not shown) are provided in the side wall of filter 66 to allow exhaust gas to freely flow in and out toward the surface of filter 66.

The filter 66 is made of porous ceramic having air permeability, and its micropores have a size of 10 to 100 microns. Such ceramic filter materials are known, and a ceramic filter having a desired pore size can be obtained by mixing carbon particles of the above-mentioned size into a semi-mixed ceramic material and sintering the mixture.

According to one feature of the present invention, ceramic filter 6
6 is formed into a hollow cylindrical shape, the lower end of which is closed and the upper end is open. In the illustrated example, the filter has a cylindrical shape, but it may have a polygonal or other arbitrary cross-sectional shape as long as it is hollow and cylindrical.

The lower end of an elongated tubular housing 70 is inserted into the upper opening of the cap body 56, and after a sealing material 72 such as a heat-resistant resin is injected and solidified, the housing 7
The tubular housing 70 is hermetically connected to the base body 56 by caulking the upper edge of the tube 0 radially inward as shown. A heater holding cylinder 74 made of a heat-resistant insulating material such as ceramic is inserted in advance inside the housing 70, and an electric heater 76 is inserted into the housing 70.
is seated on this heater holding cylinder 74. One end of the heating resistor (see FIG. 3) of the electric heater 76 is connected to a positive lead wire 78, and the other end is grounded to the tubular housing 70 by a ground terminal 80. Heater 76 and heater holding cylinder 74
is fixed by caulking a portion 84 of the housing 70 via a buffer ring 82.

A pressure extraction pipe 88 is inserted into the upper part of the tubular housing 70 via a packing 86, and by caulking the upper part of the housing 70, the space between the housing 70 and the pipe 88 is airtightly sealed. A flexible hose 90 is connected to the pressure extraction pipe 88 and communicates with a back pressure sensor (not shown). A positive lead wire 78 is connected to the pressure extraction pipe 88, and a connector 91 is connected to a DC power source via a switch (not shown).
Another positive lead wire 92 with . Therefore, this pressure take-off pipe 88 not only forms part of the pressure transmission path, but also forms part of the electrical path to the heater. 93 is an insulating boot.

The electric heater 76 has a tubular shape as shown in FIG. 2, and the inside thereof forms part of a back pressure transmission path leading to a back pressure sensor (not shown). electric heater 7
6 can be formed, for example, by printing an electrical resistance wire 96 on the surface of a ceramic cylinder 94 by screen printing or the like and sintering it, as shown in FIG. In order to exclusively heat only the ceramic filter 66, it is preferable to arrange the resistance wire 96 so that most of it faces the filter 66.

The function of this back pressure introduction cap is as follows. Exhaust gas flowing through the exhaust pipe 52 comes into contact with the filter 66 through an opening in the filter cover 68 . Solid particles and condensed liquid droplets in the exhaust gas are filtered out, and only clean gas flows into the filter. The pressure of this gas is communicated to the back pressure sensor via a back pressure transmission path consisting of the inner passage of the tubular electric heater 76, the tubular housing 70, the pressure takeoff pipe 88, and the hose 90. In this way, only clean gas enters and exits the back pressure transmission path, so there is no risk of the path becoming clogged or the back pressure sensor element deteriorating even after long-term use.
Accurate back pressure can be measured at all times.

By periodically supplying electricity to the electric heater from a power source (not shown) via an interrupter, the filter 66
is heated from the inside. As a result, the solid particles adhering to the filter are incinerated, and the filter is regenerated. Note that if the electric heater 76 is formed of a PTC (Positive Temperature Coefficient) heater whose electrical resistance value increases as the temperature rises, a weak current is constantly supplied to the heater to constantly heat and regenerate the filter. You can also.

Note that in the embodiment described above, the electric heater 76 was configured as a separate member from the filter 66;
The electrical heating resistance wire may be provided directly on the filter 66 by a printed wiring method or may be embedded in the filter 66, and such embodiments also belong to the technical scope of the present invention. However, in that case, the heater holding cylinder 74 and the electric heater cylinder 76 become unnecessary,
Lead wire 78 and ground terminal 80 may be connected directly to the heating resistance wire.

[Effect of idea]

As is clear from the above, in the present invention, a hollow cylindrical filter whose lower end is closed is airtightly attached to the lower surface of a cylindrical mouthpiece body having a back pressure transmission path inside, and an electric heater for filter heating and regeneration is installed. Since it is provided inside the filter or directly on the filter, solid particles can be effectively blocked without impairing accurate back pressure transmission, and the filter can be reliably regenerated with a small amount of power consumption.

Next, since the pressure extraction pipe was made of conductive metal and used as part of the power supply circuit to the heater, a complicated sealing structure was required to ensure the airtightness of the back pressure transmission path. The power supply line can be taken out to the outside of the pressure transmission path without
This has the remarkable effect of making the cap structure simple and compact.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an exhaust solid particulate collection device, FIG. 2 is a cross-sectional view of a back pressure introducing base of the present invention, and FIG. 3 is an enlarged perspective view of an example of an electric heater. 50... back pressure introduction cap, 56... cap body,
66... Filter, 70... Tubular housing, 7
6... Electric heater, 78, 92... Plus lead wire, 86... Packing, 88... Pressure extraction pipe.

Claims (1)

[Scope of claim for utility model registration] Back pressure installed in the back pressure detection port of the diesel engine exhaust system in order to introduce exhaust gas back pressure into the exhaust gas back pressure measuring device of the filter regeneration type diesel exhaust solid particulate collector. The introduction cap includes a substantially cylindrical cap body that can be attached to a back pressure detection port and has a back pressure transmission passage inside, and is airtightly attached to the bottom surface of the cap body, with an upper end open and a lower end closed. a hollow cylindrical filter; an electric heater provided directly on or inside the filter for heating and regenerating the filter; and a power supply circuit connected to the electric heater to supply current to the electric heater. , a pressure take-off pipe airtightly connected to the base body, the pressure take-off pipe being made of a conductive material and forming a part of the power supply circuit. Mouthpiece for pressure introduction.