JPH0122448B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine particulate collector, and more particularly to a particulate collector having electrical heating means. In recent years, diesel engines have come into widespread use as vehicle engines due to their good fuel efficiency, but they have the disadvantage of emitting a large amount of carbon particles, or smoke, compared to gasoline engines. There is a strong desire to complete a particulate purification device to reduce the amount of particles. Conventionally, this type of device includes a particulate collector equipped with a heat-resistant filter member, such as a filter member made of porous ceramics or metal fiber, installed in the exhaust system of an engine. Devices have been devised to attach and collect fine particles. However, in these devices, as the accumulation of particles on the filter surface progresses, the filter ventilation resistance increases, resulting in a decrease in engine output, and particles starting to fall off the filter surface, causing the filter to fail. Since the function deteriorates, it is necessary to remove the collected particles from the filter at appropriate intervals and regenerate the filter. It is known that since most of the fine particles deposited on the filter are carbon particles containing some fuel components, they can be burned and removed by heating to about 580°C or higher. The exhaust gas temperature of a diesel engine is considerably lower than that of a gasoline engine, etc., and the exhaust gas temperature does not exceed 580℃ except when driving at high speeds. Therefore, as a means to increase the exhaust gas temperature and burn particulates, U.S. Pat. No. 4,211,075 uses a throttle valve to reduce the intake air amount of the engine;
A method has been devised in which the temperature of the exhaust gas is increased by increasing the ratio of fuel to the amount of air, thereby burning particulates on the filter. However, even if this method is used, it has the drawback that it is impossible to sufficiently raise the temperature of the exhaust gas under driving conditions such as those encountered when driving in a city.

Another method is to install an electric heater on the upstream end of the particulate collection filter, and by heating the electric heater, the particulates on the filter are ignited. A method has been devised to burn off particulates on a filter by self-sustaining combustion of the particulates. According to this method, when the exhaust gas flow rate is low, such as when the engine is idling or running at low speed, it is possible to ignite the particles with a relatively small amount of heater power. Under high flow operating conditions,
The electric heater is significantly cooled by the exhaust gas flow.
This has the disadvantage that it is difficult to ignite fine particles.

In view of the above points, the present invention provides a flow rate control means that partially makes the flow rate of exhaust gas flowing into the filter member non-uniform, and installs an electric heater at a location where the flow rate is low, thereby controlling the exhaust gas as a whole. The object of the present invention is to provide an excellent particulate collection device that is capable of igniting particulates by heating the electric heater and regenerating the filter even under operating conditions with a large gas flow rate.

The configuration of the present invention will be explained below.

FIG. 1 shows an example of the configuration of a particulate purification device using a particulate collection device according to the present invention. 1 is an internal combustion engine such as a diesel engine, and 2 is an exhaust manifold pipe thereof. Reference numeral 3 denotes a particulate collecting device according to the present invention, which is provided with an exhaust gas inlet 3-a and an exhaust gas outlet 3-b, and has a particulate collecting filter member 4 embedded therein, and a particulate collecting filter member 4 embedded therein. An electric heater 5 is installed. 6 is a differential pressure sensor for measuring filter pressure loss, and 11 is a rotation speed sensor for measuring engine speed. Particulates in the engine exhaust gas are collected and removed on the filter member 4 as the exhaust gas passes through the filter member 4.

As the collection progresses, the ventilation resistance of the filter member gradually increases, which is detected by the differential pressure sensor 6. Of course, this differential pressure varies greatly depending on the engine speed, but by detecting the engine speed with the speed sensor 11, it is possible to know the true filter ventilation resistance that eliminates the influence of the speed, in other words, the degree of particle accumulation. Can be done.

When it is detected by this method that a predetermined amount of particulates has been deposited, this detection is carried out by the control device shown at 7 using the two signals mentioned above. 5 is energized, the electric heater 5 becomes red hot, the particulates present around the electric heater are heated, and combustion of the particulates begins. When particulates near the electric heater combust, the heat generated is transported downstream by the exhaust gas flow. The particulates present on the downstream side are sequentially heated and combusted by the heat flowing in from upstream, and most of the particulates on the filter are removed by combustion. The details of the particle collection device will be explained below. FIG. 2 is an example of a particulate collector having a conventional electric heating means. 3 is a metal container that stores a filter member inside, and has an exhaust gas inlet 3-a and an exhaust gas outlet 3-b.
have. 4 is a porous ceramic filter made of cordierite or the like.

A partially enlarged view of the filter is shown in FIG. The filter has a diameter of 1 to 4 mm, usually about 2 mm.
It has a spongy shape with many ventilation holes. 4-a shows the skeleton of the filter member, and 4-b shows the ventilation hole. Reference numeral 5 denotes an electric heater made of nichrome wire or the like, which is installed on the upstream end face of the filter member 4 and serves to ignite the fine particles collected on the filter. Numeral 4' is a ceramic honeycomb member that serves to hold the electric heater 5, and has a large number of ventilation holes 4''. Numeral 21 is a ceramic honeycomb member that serves to hold the electric heater 5, and has a large number of ventilation holes 4''. Metal fabric cushion material, 2
2 is a sealing material that prevents exhaust gas from flowing into the cushion material portion. 5' is a terminal for supplying power to the electric heater 5, to which one end of the electric heater is connected. Reference numeral 5'' indicates a grounding point to the container at the other end of the electric heater. Reference numeral 8 indicates a battery, and power is supplied to the electric heater 5 via a relay 9.

The above-mentioned operation is performed in the collection device with the above configuration, but in the conventional device shown in Fig. 2, when the exhaust gas flow rate is large at high engine speed, the electric heater using the exhaust gas flow is activated. The disadvantage is that the cooling of the particles is significant, making it difficult to heat and ignite the particles on the filter.

In this case, the flow rate of the exhaust gas flowing into the filter is substantially uniform everywhere on the exhaust gas inflow side end face of the filter.

In view of the above points, the present invention provides a means for partially making the flow velocity of exhaust gas flowing into the filter non-uniform, and installs an electric heater in the non-uniform part, particularly in the low-flow velocity part, to reduce the flow rate of the exhaust gas into the filter. The purpose is to make it easier to ignite fine particles attached to the filter material even during rotation, and to expand the engine operating conditions under which ignition is possible.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 4 showing the first embodiment of the present invention, the same reference numerals as in FIG. 2 indicate the same components. Reference numeral 24 denotes a guide pipe which is a component of the present invention, and the exhaust gas outflow side end face 24' is installed sufficiently close to the exhaust gas inflow side end face 4 of the honeycomb member. As described above, by providing a flow velocity control means for locally concentrating the flow of exhaust gas on the exhaust gas inflow side of the container, the flow velocity of the exhaust gas flowing into the filter can be made partially non-uniform.

The measurement results of the exhaust gas inflow velocity at the upstream end face of the filter in the conventional configuration shown in FIG. 2 and the filter according to the embodiment of the present invention shown in FIG.
As shown in the figure. For those without guide pipe,
The exhaust gas inflow velocity is completely uniform, but in the case where the guide pipe 24 of the embodiment of the present invention is provided (FIG. 1A), the inflow velocity at the part opposite to the outlet of the guide pipe is high, and ( Figure b) In other parts, on the contrary, the inflow speed is decreasing. In the present invention, by creating such non-uniformity in the inflow velocity and installing an electric heater at a location where the inflow velocity is low, fine particles can be ignited effectively. A conventional particulate collection device shown in FIG. 2,
The particulate collection device according to the present invention shown in FIG.
The relationship between the exhaust gas flow velocity and the engine speed at the heater installation part and the area where the heater can ignite are determined first.
Shown in Figure 2.

In the figure, curves A and B represent the conventional particle collection device;
It also shows the relationship between the engine rotation speed and the exhaust gas flow rate at the heater attachment part of the particulate collector according to the present invention.As is clear from this, at the same engine rotation speed, in the device according to the present invention, ,
The exhaust gas flow rate is approximately half that of the conventional model. Furthermore, the engine speed at which ignition is possible has been expanded to about 2800 rpm in the conventional engine, whereas the engine speed in the present invention has been expanded to about 2800 rpm, and it can be seen that it has an excellent effect.

In this case, the engine displacement is 2200c.c., and the exhaust gas inflow cross-sectional area of the filter is
This is the case for a 145cm ² item.

FIG. 6 shows a second embodiment. In the first embodiment shown in FIG. 4, only one guide pipe outlet is shown, but in this second embodiment, it is shown that there may be a plurality of outlets. 25 is a guide pipe, 25-a
indicates the exhaust gas outlet of the same pipe.

Further, FIG. 7 shows a third embodiment. In the above-described embodiment, a guide pipe was provided as a means to make the flow rate of exhaust gas flowing into the filter non-uniform, but in the third embodiment shown in FIG. 7, a guide pipe was provided instead of the guide pipe. This shows that a perforated plate may also be used. In the figure, 26 is a perforated plate provided near the honeycomb member 4', and 26' indicates a plurality of exhaust gas outlet ports provided on the plate. In both this embodiment and the above-mentioned embodiments, the distance between the exhaust gas outlet and the end face of the honeycomb member is set to about 3 to 10 mm. Incidentally, FIG. 8 shows a perspective view of the perforated plate. A fourth embodiment is shown in FIG. In the previous embodiments, an example was shown in which a container with a substantially axially symmetrical shape was used, but in the fourth embodiment, by devising the shape of the container itself, the velocity of exhaust gas flowing into the filter can be reduced. This is an example of what makes it possible to create non-uniformity. In the same figure, the filter material 4 has a cylindrical or elliptical shape, and the exhaust gas inlet 3-a is not located at the center of the filter material, but at the edge of the filter member, and at the upstream end surface of the filter member. It is arranged so that 17 openings are opened in the vicinity. Also, exhaust gas outlet 3-
b is provided at the edge opposite to the exhaust gas inlet 3-a, and the exhaust gas flow within the filter as a whole forms a flow that crosses the filter obliquely. In addition, as shown in the figure, electric heaters are installed in locations that are not directly exposed to the jet from the exhaust gas inlet.
provided. In addition, in the first to third embodiments, the case where a ceramic honeycomb member is used as a storage method for the heater is shown, but the electric heater can also be directly bonded to the end surface of the filter member using an inorganic adhesive or the like. It is. The embodiment shown in FIG. 9 shows a case where a heater is provided by such a method, and the honeycomb member shown in the first to third embodiments is not used.

Also, in the first to third embodiments, it is not necessary to use a honeycomb member, and even in that case,
It goes without saying that the method of the present invention makes it possible to create non-uniformity in the exhaust gas inflow velocity.

So far, we have described a method of making the flow rate of exhaust gas flowing into the filter non-uniform by devising the shape of the exhaust gas inlet of the filter storage container. In addition, as a method of making the flow velocity non-uniform, the same effect may be obtained by devising the structure of the exhaust gas upstream end face of the filter. This will be explained with reference to FIG. In the same figure,
4 is a ceramic filter member as described above;
Reference numeral 5 designates an electric heater, and reference numeral 27 designates an airflow resistance member that is a component of the present invention, which is made of porous ceramic like the filter member 4, and is installed in front of the electric heater 5 so as to cover the entire surface of each heater. do. The thickness of the ventilation resistance member 27 is approximately 2 to 8 mm. By installing the ceramic member 27 of the same quality as the filter member 4 on the front surface of the electric heater, the exhaust gas flow rate at the bonded part of the electric heater is significantly reduced compared to other parts. , which is characterized by good ignition of fine particles. Incidentally, FIG. 11 shows an exploded perspective view of the embodiment shown in FIG. 10. Ceramic member 27
and 4 can be joined using an inorganic adhesive.

Next, to discuss the specific effects of the particulate collection device of the present invention, first of all, in the conventional device shown in Fig. 2, when installed in an engine exhaust system with a displacement of 2200 c.c., the engine speed is 1500 rpm or more. In this case, the heater was cooled significantly by the flow of exhaust gas, making it impossible to ignite the particles, whereas in the first embodiment shown in FIG. 4, which constitutes the present invention, the engine speed was approximately It is known that it is possible to ignite fine particles at 2800 rpm and has excellent effects.

As described above, the present invention improves the flow rate of exhaust gas into the filter member, which has been almost uniform in the past, by using a guide pipe or a perforated plate provided at the exhaust gas inlet of the container, which is a flow rate control means. By installing an electric heater in the area where the flow rate is low due to nonuniformity due to It has the excellent effect of allowing fine particles to be ignited even at high engine speeds.

[Brief explanation of drawings]

FIG. 1 is a layout diagram showing the entire exhaust system of an internal combustion engine using the particulate collector of the present invention. Figure 2 is a vertical cross-sectional view of a conventional particle collection device, Figure 3 is a partially enlarged view of a ceramic filter used in the same device, and Figure 4
The figure is a longitudinal sectional view of the first embodiment of the present invention, FIG. 5 is an explanatory diagram of a comparison of flow velocity distribution between the device of the present invention and a conventional device, and FIG. 6 is a longitudinal sectional view of the second embodiment of the present invention. ,
FIG. 7 is a longitudinal sectional view of the third embodiment, FIG. 8 is a perspective view of a perforated plate in the same embodiment, FIG. 9 is a longitudinal sectional view of the fourth embodiment of the present invention, and FIG. FIG. 11 is a longitudinal cross-sectional view of the fifth embodiment, FIG. 11 is an exploded perspective view of the same embodiment, and FIG. 12 is a graph comparing the engine rotational speed versus the exhaust gas flow rate at the heater installation part in the device of the present invention and the conventional device. . DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Exhaust collecting pipe, 3... Filter storage container, 4... Filter, 5... Electric heater, 6... Differential pressure sensor, 7... Control device, 8... Battery, 9 ...Relay, 11...
Rotation speed sensor, 24, 25...Guide pipe,
26...Perforated plate, 27...Airflow resistance member.

Claims (1)

[Scope of Claims] 1. In a particulate collection device comprising a filter member having air permeability and heat resistance disposed in the exhaust system of an internal combustion engine, exhaust gas flowing into the filter member is disposed upstream of the filter member. An electric heating means characterized in that a flow velocity control means is installed to make the flow velocity distribution uneven, and an electric heater is disposed at a portion of the upstream end face of the filter member where the flow velocity becomes low due to the flow velocity control means. A particulate collection device having a 2. The particulate collection device according to claim 1, wherein the flow rate control means includes a member installed at the exhaust gas inlet of the filter storage container to form an exhaust gas jet flowing toward one or more filters. 3. As the flow rate control means, a ventilation resistance member is installed on the upstream side of an electric heater installed in close contact with the end face of the exhaust gas inflow side during regeneration of the filter member, covering the electric heater. The particulate collection device described in .