JPS6327057Y2 - - 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 amount of fuel injection to raise 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 when the back pressure reaches a set value, a method of detecting the exhaust gas back pressure upstream and downstream of the collector. There are methods such as regenerating when the differential pressure reaches the set value, but the first two methods do not necessarily reflect the filter clogging condition accurately, so the latter two methods using back pressure are the most rational. be. For example, in the example shown in FIG.
The back pressure value is converted into a current value using a piezoelectric resistance element or a strain gauge built into the sensor, and the control circuit 26 compares this with a set value to detect the regeneration time. 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 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 cap must, on the one hand, be able to transmit exhaust gas pressure smoothly, and on the other hand, be able to completely block out solid particles and condensable components in the exhaust gas. .

Therefore, a back pressure introduction structure has recently 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 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 through 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. In this introduction part structure, a honeycomb filter made of ceramic is elastically supported between the introduction part housing and the honeycomb filter via a cushioning material such as a wire net.

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 on the outer periphery of the filter, heat is dissipated to the outside, resulting in poor heat utilization efficiency 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 ceramic filter with an open top end and a closed bottom end is attached to the bottom of the cylindrical mouthpiece body, which has a back pressure transmission passage inside. The electric heater may be provided inside the filter or directly on the filter. However, in this case, the above-described method of elastically supporting the filter cannot be used.

[Purpose of invention]

The overall purpose of the present invention is to further improve this type of back pressure introduction cap structure, and to effectively block solid particulates and harmful components in the exhaust gas while reducing the pressure of the exhaust gas. Simple and compact structure that can accurately transmit back pressure to the back pressure measuring device.
To provide a back pressure introducing base structure capable of reliably regenerating a filter with a small amount of electric power.

In particular, the object of the present invention is to provide a back pressure introduction mouthpiece in which a ceramic filter is elastically supported and is not easily damaged by engine vibration or the like.

Another object of the present invention is to provide a back pressure introduction cap that does not cause damage to the ceramic filter due to the impact of the exhaust gas flow.

[Structure of the idea]

The back pressure introduction cap of the present invention has a substantially cylindrical cap body that can be attached to a back pressure detection port and has a back pressure transmission passage inside, and a hollow cylindrical shape with an open upper end and a closed lower end. a porous ceramic filter, an electric heater for heating and regenerating the filter, and a filter retainer for holding the ceramic filter. It is elastically supported between

The filter retainer preferably substantially surrounds the filter and also serves as a filter cover to protect the filter.

〔Example〕

Embodiments of the present invention will be described with reference to FIG. 2 and the following drawings. FIG. 2 shows a back pressure introducing mouthpiece 50 according to an embodiment of the present invention on an exhaust pipe 5 of a diesel engine.
2 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 57 is provided on the lower surface of the base body 56, and after inserting a cushioning ring 64 such as goose wire into this groove 57, a filter 66 is fitted.
Another buffer material 65 is interposed at the lower end of the filter 66 and then held by a filter retainer 68.
The filter retainer 68 is removably snap-fitted onto the base body 56, and has the function of a retainer to prevent the filter 66 from falling off, and also protects the exhaust gas flow shown by the arrow and the substances accompanying it. It has the function of protecting the filter from impact. Filter retainer 68
substantially surrounds the filter 66 and has a plurality of openings (not shown) in its side walls to allow free passage of exhaust gases towards the surface of the filter 66.

The filter 66 is made of an air permeable porous ceramic such as cordierite, 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.

The ceramic filter 66 is formed into a hollow cylindrical shape, and its lower end is closed and its 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 upper edge of the housing 70 is pushed radially inward as shown. By tightening, the tubular housing 70 is airtightly connected to the base body 56. A heater holding tube 74 made of a heat-resistant insulating material such as ceramic is inserted in advance inside the housing 70, and the electric heater 7
6 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 7
4 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 another positive lead wire 92 is connected to a DC power source via a switch (not shown). 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. The exhaust gas flowing inside the exhaust pipe 52 is filtered.
The filter 66 is contacted through the opening in the retainer 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 applied to the inner passage of the tubular electric heater 76, the tubular housing 70,
The back pressure is transmitted to the back pressure sensor via a back pressure transmission path consisting of a pressure takeoff pipe 88 and a 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 the filter. It can also be played.

[Effect of idea]

As is clear from the above, according to the present invention, a simple and compact nozzle structure can be obtained which effectively blocks solid particles and harmful components in the exhaust gas, while allowing the back pressure of the exhaust gas to be freely and accurately introduced into the back pressure measuring device without any hindrance.

According to an important feature of the present invention, the filter is elastically supported by the filter retainer via the cushioning material, so there is no risk of the filter being damaged by engine vibrations or the like. Therefore, it is possible to use a filter with low strength, and it is also possible to form the filter from a highly porous material such as cordierite, which allows smooth transmission of back pressure.

Further, when the filter retainer is provided to substantially surround the filter according to one feature of the present invention, the filter retainer also functions as a filter protection member, which simplifies the introduction cap structure and at the same time protects the filter. Durability can be improved.

Furthermore, since the filter is held by the filter retainer and the mouthpiece body, it is securely held and there is no risk of the filter falling off.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an exhaust solid particulate collection device, FIG. 2 is a sectional view of a back-inlet nozzle of the present invention, and FIG. 3 is an illustration of an example of an electric heater. 50... back pressure introduction cap, 56... cap body,
64, 65...buffer material, 66...filter, 68
...Filter retainer, 76...Electric heater.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A back pressure sensor installed in a back pressure detection port of a diesel engine exhaust system in order to introduce exhaust gas back pressure into an exhaust gas back pressure measuring device of a filter regeneration type diesel exhaust solid particulate collector. It is a pressure introduction mouthpiece that can be attached to a back pressure detection port and has a substantially cylindrical mouthpiece body with a back pressure transmission passage inside, and a hollow cylindrical porous breathable body with an open top end and a closed bottom end. The filter includes a ceramic filter, an electric heater for heating and regenerating the filter, and a filter retainer for holding the filter and bringing it into contact with the mouthpiece body, and the filter is made of at least one cushioning material. A back pressure introduction cap characterized by being elastically supported between a cap body and a filter retainer. 2. The back pressure introduction cap according to claim 1, wherein the filter retainer substantially surrounds the filter, thereby protecting the filter. . 3. The back pressure introducing cap according to claim 1 or 2, wherein the filter retainer is detachably fitted to the cap body. 4. The back pressure introduction cap according to claim 3, wherein the buffer material is provided at both upper and lower ends of the filter, respectively.