JP3323840B2 - Exhaust particulate collection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas particulate collecting apparatus for collecting particulates contained in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Exhaust gas of a diesel engine contains a large amount of fine particles mainly composed of carbon. Therefore, the exhaust gas path of the diesel engine is provided with a purifying filter for collecting such fine particles. A particulate collection device is installed. In such an exhaust gas particulate collecting device, when the amount of particulates collected in the purification filter increases with long-term use, the permeability decreases and the back pressure increases. There is. In this regeneration processing, a method is generally used in which a heater provided near the purification filter is energized and the purification filter is heated by the heater to incinerate the collected fine particles.

However, when the purification filter is heated by a heater provided in the vicinity of the purification filter, the heat of the heater is transmitted to the purification filter via air, so that the heat conductivity is poor and the regeneration process is performed efficiently. There was a problem that it was not possible. Regarding this point, Japanese Patent Laid-Open No. 7-80226
The publication discloses that the heater described above is abolished by using a porous silicon carbide-based ceramic having conductivity as a purification filter, and the purification filter itself is functioned as a heater when performing a regeneration process, and collected. An apparatus for efficiently incinerating fine particles has been proposed.

[0004]

By the way, when exhaust gas passes through the purification filter, a ventilation resistance is generated. In order to avoid an increase in back pressure due to the ventilation resistance, the cross-sectional area of the purification filter is reduced by that of the other exhaust passages. It is common to design larger than the cross-sectional area. For this reason, at the time of the regeneration processing, a large current flows through the purification filter, and the power consumption becomes large. However, considering that a vehicle-mounted battery has a voltage of about several tens of volts, it may be difficult to quickly reach the temperature of the purification filter to a temperature at which the fine particles trapped by the purification filter are incinerated.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust gas particulate collecting device capable of performing a regeneration process of a purification filter even with a vehicle-mounted battery.

[0006]

Means for Solving the Problems and Effects of the Invention In order to solve the above problems, the present invention relates to an exhaust gas particulate collecting device provided in an exhaust gas passage of a diesel engine, comprising: a silicon carbide-based porous ceramic block; Formed in the direction of exhaust gas flow in the porous ceramic block,
A plurality of passages in which either the exhaust gas inflow side or the exhaust gas outflow side is open, a purification filter formed by bundling a plurality of the porous ceramic blocks in an insulated state, the exhaust gas inflow side and the exhaust gas outflow side Between
The purifying filter is arranged inside. Placed cylindrical body
A first inflow path and a second
And the first and second streams
A flow that opens one of the entrances and closes the other
An inflow switching valve and the inflow of the first and second inflow paths
A plurality of the above-mentioned units arranged on a side closed by a path switching valve.
Each porous ceramic block per porous ceramic block
Energize sequentially for each lock or use multiple porous
For each group of ceramic blocks
An energization switching control means for sequentially energizing and the energization switching control
Control means arranged on the first inflow path side;
When energizing the ceramic block,
1 Supply air to the inflow path, and
A plurality of the porous ceramics arranged on the second inflow path side
When energizing the block, empty the second inflow channel.
Air supply means for supplying air . Divide one purification filter into halves and place one in the first
By disposing the inflow channel side and the other on the second inflow channel side
Has a dual type, that is, an exhaust gas particulate collection device
Installation space compared to the type with two exhaust pipes
Is actually a dual tie
Performance equivalent to that of

In the present invention, the power supply switching control means sequentially supplies power to the porous ceramic blocks one by one when regenerating the purification filter, or sorts a plurality of porous ceramic blocks in advance. Power is supplied to each group in sequence. Since the porous ceramic block is made of silicon carbide, it has a relatively low specific resistance (for example, 10%).
^{−2 to} 10 Ω · cm), so that when it is energized, it functions as a heater and incinerates the fine particles collected by itself. As a result, the porous ceramic block is regenerated before clogging occurs.

According to the present invention, a large amount of current is generated because the porous ceramic blocks constituting the purification filter are not energized at once but are energized one by one or in groups. It does not flow through the purification filter and does not consume large amounts of power at once. Therefore, the regeneration process of the purification filter can be performed even with the vehicle-mounted battery.

Here, as the group of porous ceramics, for example, the exhaust gas inflow amount is empirically measured in advance, and the porous ceramic blocks having substantially the same exhaust gas inflow amount are classified into the same group. In this case, the amount of the collected fine particles is substantially the same for each group. Therefore, if the energization time is the same for each group, the collected fine particles can be surely burned.

In the exhaust gas particulate collecting apparatus of the present invention,
It is preferable that the energization switching control means controls the energization time to be longer for a porous ceramic block having a passage with a large amount of exhaust gas flow than for a porous ceramic block without a passage with a large amount of exhaust gas flow. That is, in the porous ceramic block having a passage with a large amount of exhaust gas inflow, the energization time is lengthened and the incineration of the fine particles is sufficiently performed in consideration of the large amount of the collected fine particles. On the other hand, for a porous ceramic block that does not have a passage with a large amount of exhaust gas inflow, the amount of collected fine particles is small, so that the fine particles can be incinerated sufficiently with a short energizing time. Just consume. Therefore, it is preferable to control the porous ceramic block having a passage with a large amount of exhaust gas inflow so as to make the energization time longer than that of a porous ceramic block without a passage with a large amount of exhaust gas inflow.

Here, the passage having a large amount of exhaust gas inflow means, for example, a passage arranged near the center of the purification filter or a passage which has been previously empirically confirmed to have a large amount of exhaust gas inflow. In general, exhaust gas is more likely to flow into the passage disposed near the center of the purification filter than the passage disposed outside the purification filter. However, which passage the exhaust gas is likely to flow in depends on, for example, the size of the passage cross-sectional area and the density of the passage due to a manufacturing error. Is preferred.

Further, the exhaust gas particulate collecting apparatus of the present invention comprises:
Furthermore, a pressure sensor for detecting the pressure on the upstream side of the exhaust gas,
The inflow path switching valve is turned off by the detection signal from the pressure sensor.
And a playback processing timing generator for switching
You may.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory view of the exhaust gas particulate collecting apparatus of the present embodiment, FIG. 2 is a perspective view of a purification filter, FIG. 3 is an explanatory view of a porous ceramic block, and FIG. FIG. 3
3B is a front view, and FIG. 3C is a cross-sectional view.

The exhaust gas particulate collecting device 10 is provided in an exhaust gas path of the diesel engine 2. The exhaust gas particulate collecting apparatus 10 mainly includes a purification filter 11
, Regeneration processing timing generator 25, inflow path switching valve 2
7, an air switching valve 28, and a controller 30.

The purification filter 11 is arranged inside the cylindrical body 6 which forms a part of the exhaust gas path of the diesel engine 2. The cylindrical body 6 is disposed between an upstream exhaust pipe 4 connected to the diesel engine 2 and a downstream exhaust pipe 8 connected to a muffler (not shown), and has a larger diameter than the exhaust pipes 4 and 8. It is formed to become. The reason why the cross-sectional area of the cylindrical body 6 is set to be large in diameter is that the inside of the cylindrical body 6 is divided into the first inflow path R1 and the second inflow path R2, so that the inflow paths R1 and R2 are cut off. In order to make the area equal to or more than the cross-sectional area of each exhaust pipe 4, 8,
This is to improve the air permeability when the exhaust gas passes through the purification filter 11.

The purifying filter 11, as shown in FIG.
The cylinder 12a is formed of an insulating holding tube 12 divided into a plurality of spaces by a partition wall 12b, and a porous ceramic block 13 inserted into each of the divided spaces of the holding tube 12. That is, the purification filter 11 is formed by bundling a plurality of porous ceramic blocks 13 in an insulated state.

The porous ceramic block 13 is a silicon carbide ceramic block having excellent heat resistance.
As shown in FIG. 1, metal electrodes 14 and 15 are formed on the outer periphery of both ends by CVD, metal paste baking, or the like.
Although the overall shape of the porous ceramic block 13 is columnar, a plurality of passages 16 are formed in the inside thereof in the longitudinal direction (that is, the direction in which the exhaust gas flows). In each passage 16, one of an opening on the exhaust gas inflow side and an opening on the exhaust gas outflow side is closed with a plug 17, and the other is open. Specifically, the passage 1 whose opening on the exhaust gas inflow side is open
6a and a passage 16 whose opening on the exhaust gas outflow side is open
b are arranged adjacent to each other. As a result, when the exhaust gas flows through the porous ceramic block 13, the exhaust gas flows in from the passage 16 a whose opening on the exhaust gas inflow side is open, passes through the partition wall 16 c from the passage 16 a, and passes through the adjacent passage 16 b ( That is, the gas flows into a passage having an opening on the exhaust gas outflow side), and flows out of the passage 16b through the opening on the exhaust gas outflow side. The fine particles in the exhaust gas discharged from the diesel engine 2 are collected on the partition wall 16c when passing through the partition wall 16c.

The plurality of porous ceramic blocks 13 arranged on the first inflow path R1 are respectively numbered in order from No. 1, and the plurality of porous ceramic blocks 13 arranged on the second inflow path R2 side. Each of the high quality ceramic blocks 13 is also numbered sequentially from the first. The porous ceramic block 13 of the present embodiment has a porosity of 50%, an average pore diameter of 10 to 12 μm, a specific resistance of 0.59 at a temperature of 25 ° C.
Ωcm, a specific resistance of 0.42 Ωcm at a temperature of 800 ° C. (that is, the higher the temperature, the lower the specific resistance).

Returning to FIG. 1, a plurality of wires 21 drawn from the upstream end of the purification filter 11
Is connected to one terminal of a vehicle-mounted battery 23, and the other terminal of the vehicle-mounted battery 23 is connected to a plurality of conductors 24 drawn from the downstream end of the purification filter 11. . Specifically, each conducting wire 21 drawn from the upstream end of the purification filter 11 is connected to a metal electrode 14 provided at one end of each porous ceramic block 13, and the downstream of the purification filter 11. Each conductive wire 24 drawn out from the side end is connected to a metal electrode 15 provided at the other end of each porous ceramic block 13.
It is connected to the. In FIG. 1, the conductor 21 and the conductor 2
4 are shown four by four for the sake of convenience, but actually there are as many as the total number of the porous ceramic blocks 13.

The regeneration processing timing generator 25 determines whether or not it is the regeneration processing timing based on the detection signal of the pressure detection sensor 26 provided in the upstream side exhaust pipe 4. Since there is a correlation between the amount of fine particles accumulated in the filter 11 and the pressure in the upstream exhaust pipe 4, the pressure in the purification filter 11 is detected by detecting the pressure in the upstream exhaust pipe 4. Detect the amount,
A reproduction processing timing signal is generated when the amount of the fine particles exceeds a predetermined amount. In other words, the reproduction processing timing generator 25 includes the first and second inflow channels R1 and R2.
When the inflow path on the open side of the two has a tendency to clog, a reproduction processing timing signal is output.

The regeneration processing timing generator 25 receives the detection signal from the pressure detection sensor 26 as a voltage level signal, and compares the input value with a predetermined voltage value (for example, the trapping ability of the purification filter 11 is reduced). And a voltage value when the engine characteristics are affected empirically due to reduced air permeability) is compared with a comparator. If the input value is equal to or less than a predetermined voltage value, a low signal is output. It is configured to output a high signal if the input value is equal to or higher than a predetermined voltage value. At this time, the rising edge from the low signal to the high signal corresponds to the reproduction processing timing signal.

The inflow passage switching valve 27 separates the exhaust gas inflow passage into the purification filter 11 into two, first and second inflow passages R1, R2, and one of the first and second inflow passages R1, R2. Are opened and one of them is closed.
The inflow path switching valve 27 is positioned by a control signal from the controller 30.

The air switching valve 28 is connected to the first and second inflow paths R
Controller 3 determines which of R1 and R2 is supplied with air
This is a valve that is switched by a control signal from 0. Also,
The air supply source 29 supplies air through the air switching valve 28 to the first
Alternatively, it is a device for supplying to the second inflow paths R1 and R2, and the supply / non-supply of air is controlled by a control signal from the controller 30.

The controller 30 has a well-known C (not shown).
It is composed of a PU, a ROM, a RAM, a clock, a counter, and the like, and is connected so as to be able to input a signal from the reproduction processing timing generation unit 25.
The air switching valve 28 and the air supply source 29 are connected to be able to output signals. When the regeneration processing timing signal is input from the regeneration processing timing generator 25, the controller 30 executes the regeneration processing of the purification filter 11 in response thereto.

Next, an example of use of the exhaust gas particulate collecting apparatus 10 of the present embodiment will be described. The exhaust gas containing fine particles discharged from the diesel engine 2 passes through the upstream exhaust pipe 4, passes through the inflow path (here, the first inflow path R <b> 1) opened by the inflow path switching valve 27, and
It flows into the purification filter 11. And the first inflow path R1
Plural porous ceramic blocks 1 arranged on the side
3 and is led to the downstream side exhaust pipe 8 and discharged to the outside air through a muffler (not shown). The fine particles in the exhaust gas are collected when passing through the plurality of porous ceramic blocks 13 arranged on the first inflow path R1 side, and thus the purified exhaust gas is led out to the downstream exhaust pipe 8. . In this way, the fine particles in the exhaust gas are removed from the first inflow path R1.
Numerous porous ceramic blocks 1 arranged on the side
3, the clogging gradually occurs, and the back pressure of the upstream side exhaust pipe 4 increases. In the present embodiment, when the back pressure rises, the controller 30 executes a regeneration process of the purification filter 11. Hereinafter, the reproduction process will be described.

When the detection signal from the pressure detection sensor 26 is equal to or higher than a predetermined voltage value, that is, when the detection signal from the pressure detection sensor The output signal switches from low to high when the porous ceramic block 13 is clogged to some extent and the trapping ability is reduced or the air permeability deteriorates and the engine characteristics are affected.

When the signal from the reproduction processing timing generator 25 switches from low to high, the controller 30 regards this switching edge as a reproduction processing timing signal, and reproduces the reproduction processing stored in a ROM (not shown) in the controller 30. Run the program for. Less than,
This will be described with reference to the flowchart of FIG. First, the controller 30 switches the position of the inflow path switching valve 27 (S10). That is, the inflow path switching valve 27 has previously opened the first inflow path R1 and closed the second inflow path R2, and now closes the first inflow path R1 and opens the second inflow path R2. As a result, the exhaust gas passes through the plurality of porous ceramic blocks 13 disposed on the second inflow path R2 side, and since these are new or have already been subjected to the regeneration treatment, they have good air permeability. In addition, fine particles are efficiently removed. Subsequently, the position of the air switching valve 28 is switched (S11). That is, the air switching valve 28 has not
Since it was positioned at a position where air can be supplied to the inflow channel R2, it is positioned at a position where air can be supplied to the first inflow channel R1. Then, air is supplied to the first inflow path R1 by the air supply source 29 (S12). Thus the first
The air is supplied to the inflow passage R1 by the porous ceramic blocks 1 arranged on the first inflow passage R1 side as described later.
By heating up 3, the fine particles trapped in each block 13 are incinerated and regenerated, but at the time of incineration, oxygen for combustion is required.

Thereafter, the count value N of a counter (not shown) in the controller 30 is set to 1 (S13), and the Nth porous ceramic block 13 of the plurality of porous ceramic blocks 13 arranged on the first inflow path R1 side. Block 1
With respect to 3, the energization is started (S14). That is, the power supply switching unit 22 is controlled to connect the vehicle-mounted battery 23 and the Nth porous ceramic block 13. Then, since the porous ceramic block 13 is made of silicon carbide, it has a relatively low specific resistance, and functions as a heater when energized.
Incinerate the particles collected by yourself.

After the start of the energization, it is determined whether or not a predetermined energization time has elapsed (S15). If the predetermined energization time has not elapsed (NO in S15), the collected fine particles have been sufficiently incinerated. Since there is no power supply, power supply is continued. On the other hand, if the predetermined energizing time has elapsed (YE in S15)
S), the porous ceramic block 13 is 800 to 100
Since it has been heated to about 0 ° C., it is determined that the collected fine particles have been sufficiently incinerated, and the energization switching unit 22 is controlled to
The connection between the vehicle-mounted battery 23 and the Nth porous ceramic block 13 is released (S16). Then, one count value N is added (S17), and the count value N after the addition exceeds the total number (6 in the present embodiment) of the porous ceramic blocks 13 arranged on the first inflow path R1 side. If the count value N does not exceed the total number (NO in S18), the flow returns to S14 again because there is a porous ceramic block 13 that has not been subjected to the regeneration process. On the other hand, if the count value N exceeds the total number (YES in S18), the operation of the air supply source 29 is stopped because all the porous ceramic blocks 13 arranged on the first inflow path R1 have performed the regeneration processing. (S1
9), end this processing.

When the above-described regeneration process is completed, the next time the controller 30 inputs the regeneration process timing from the regeneration process timing generator 25, the inflow channel switching valve 27 is switched to open the first inflow channel R1 and the second inflow channel. Although the passage R2 is closed, the exhaust gas passes through the regenerated porous ceramic block 13 disposed on the first inflow passage R1 side, so that the air permeability is good and the fine particles are also efficiently collected. Is done. Note that the controller 30 of the present embodiment corresponds to the energization switching control means of the present invention, and the air switching valve 28 and the air supply source 29 correspond to the air supply means.

As described above in detail, according to the exhaust gas particulate collecting apparatus 10 of the present embodiment, not all of the porous ceramic blocks 13 constituting the purification filter 11 are energized at one time, but one. To energize one by one,
A large amount of current does not flow through the purification filter 11, and a large amount of power is not consumed at one time. Therefore, the regeneration process of the purification filter 11 can be sufficiently performed even when the on-vehicle battery 23 is, for example, 24 V, 20 A, and 500 W or less.

Further, one purification filter 11 is divided into halves, one of which is on the first inflow passage R1 side, and the other is on the second inflow passage R1.
By arranging them on the two sides, the dual type, that is, the dual type, is substantially smaller than the dual type, in which the installation space is smaller than that of the type in which two exhaust pipes provided with the exhaust gas particulate collecting device are arranged side by side. Equivalent performance is obtained.

It should be noted that the embodiments of the present invention are not limited to the above embodiments at all, and it goes without saying that various forms can be adopted as long as they fall within the technical scope of the present invention. For example, the predetermined energization time may be set long for a porous ceramic block having a passage with a large amount of exhaust gas inflow, and the predetermined energization time may be set short for a porous ceramic block without a passage with a large amount of exhaust gas inflow. . Here, the passage having a large exhaust gas inflow amount refers to, for example, a passage arranged near the center of the purification filter or a passage that has been previously empirically confirmed to have a large exhaust gas inflow amount. In general, exhaust gas is more likely to flow into the passage disposed near the center of the purification filter than the passage disposed outside the purification filter. However, which passage the exhaust gas is likely to flow in depends on, for example, the size of the passage cross-sectional area and the density of the passage due to a manufacturing error. Is preferred.

In the above embodiment, the porous ceramic blocks are sequentially energized one by one. However, the porous ceramic blocks may be classified into several groups in advance, and energized sequentially for each group. . In an example shown in FIG. 5, the porous ceramic block near the center is the first ceramic block.
The porous ceramic blocks on the left and right sides are classified into a second group, the porous ceramic blocks on the upper center are classified into a third group, and the porous ceramic blocks on both sides are classified into a fourth group. You may. In this case, the same effect as in the above embodiment can be obtained. In addition, since the exhaust gas inflow amount is almost the same in each group, the amount of collected fine particles is also almost the same. Therefore, if the same energizing time is applied to each group for the same energizing time, the collected fine particles are surely incinerated. it can.

Further, in the above-described embodiment, the regeneration processing timing is generated based on the detection signal of the pressure detection sensor. However, the regeneration processing timing may be generated by any other method. Processing timing may be generated. Furthermore, a three-way catalyst (a catalyst having a function of simultaneously performing an oxidation reaction of CO and HC and a reduction reaction of NOx, for example, a Pt-Rh-based catalyst) in the purification filter.
Such an exhaust gas purifying catalyst may be supported. In recent years, exhaust gas from diesel engines has been
Detoxification of O, HC and NOx is being studied, but it is difficult to install a catalytic converter separately from the exhaust gas particulate collection device in view of the installation space, so the purification filter is also used as a carrier of the exhaust gas purification catalyst. Is preferred.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an exhaust gas particulate collecting device of the present embodiment.

FIG. 2 is a perspective view of a purification filter.

FIG. 3 is an explanatory view of a porous ceramic block,
FIG. 3A is a perspective view of a porous ceramic block, and FIG.
3B is a front view, and FIG. 3C is a cross-sectional view.

FIG. 4 is a flowchart of a reproduction process executed by a controller.

FIG. 5 is an explanatory diagram illustrating an example of a group classification of a porous ceramic block.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Exhaust gas particulate collection apparatus, 11 ... Purification filter, 12 ... Holding cylinder, 13 ... Porous ceramic block, 14, 15 ... Metal electrode, 16, 16a,
16b: passage, 16c: partition wall, 21, 24
·································································
..Pressure detection sensors, 27...
··· Air switching valve, 29 ··· Air supply source, 30 ··· Controller, R1 ··· First inflow path, R1 ····· 2nd inflow path.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01N 3/02 B01D 46/42

Claims (4)

(57) [Claims] 1. An exhaust gas particulate collecting device provided in an exhaust gas passage of a diesel engine, comprising: a silicon carbide-based porous ceramic block; and an exhaust gas inflow side formed in the porous ceramic block in a direction in which exhaust gas flows. Or a plurality of passages in which one of the exhaust gas outflow sides is opened, a purification filter formed by bundling the plurality of porous ceramic blocks in an insulated state, and between the exhaust gas inflow side and the exhaust gas outflow side. Placed inside
The purifying filter is provided. A first inflow path and a second inflow path between the placed cylindrical body and the exhaust gas inflow side of the cylindrical body.
And the first and second inflow paths
Inflow channel that opens one of the two and closes the other
A switching valve, and the inflow path switching valve of the first and second inflow paths.
A plurality of the porous ceramics arranged on the closed side
Block for each porous ceramic block.
Next energizing or a plurality of said porous ceramic blow
Power is sequentially supplied to each group in which
The power supply switching control means and the power supply switching control means are arranged on the first inflow path side.
Field for energizing a plurality of the porous ceramic blocks
In this case, air is supplied to the first inflow path,
The control means includes a plurality of the plurality of multi-stages arranged on the second inflow path side.
When energizing the porous ceramic block,
An exhaust gas particulate collecting device, comprising: air supply means for supplying air to a second inflow path . 2. The energization switching control means makes the energization time of a porous ceramic block having a passage with a large amount of exhaust gas inflow longer than the energization time of a porous ceramic block without a passage with a large amount of exhaust gas inflow. The exhaust gas particulate collecting apparatus according to claim 1, wherein the control is performed in such a manner. 3. The passage having a large exhaust gas inflow amount is a passage arranged near the center of the purification filter or a passage which has been confirmed in advance empirically to have a large exhaust gas inflow amount. The exhaust gas particulate collecting device according to claim 2. 4. A pressure for detecting the pressure on the upstream side of the exhaust gas.
A force sensor and the inflow passage switching valve are detected by a detection signal from the pressure sensor.
Switching playback timing generator.
The exhaust gas particulate collecting device according to claim 1, wherein: