JP4281186B2 - Discharge regenerative collection filter - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a discharge regeneration type collection filter installed in an exhaust system such as a diesel engine for collecting and removing soot contained in exhaust gas.
[0002]
[Prior art]
In order to collect and remove the soot containing carbon and the like contained in the exhaust gas of the diesel engine, a collection filter made of a ceramic honeycomb or the like is installed in the diesel engine exhaust system.
An exhaust gas passage is provided in the collection filter, and soot in the exhaust gas accumulates on the inner wall surface of the exhaust gas passage when passing through the exhaust gas passage. As a result, the exhaust gas that has passed through the collection filter hardly contains soot.
However, if soot accumulates, the air permeability of the collection filter gradually deteriorates, the exhaust gas becomes worse, and the pressure loss increases. Therefore, it is necessary to remove the soot deposited by appropriate means.
Conventionally, soot deposited on the collection filter has been removed by combustion by heating the collection filter using an electric heater or burner provided outside the collection filter.
[0003]
[Problems to be solved]
However, if the collection filter is heated to remove the soot from burning, the temperature of the collection filter may be uneven due to the combustion heat of the soot, and cracks may occur. In addition, the collection filter may be melted by combustion heat.
In addition, the provision of the electric heater and burner complicates the configuration of the collection filter and the entire engine exhaust system. In addition, the installation cost and running cost of the electric heater and burner are necessary, resulting in high costs.
[0004]
The present invention has been made in view of such conventional problems. The discharge regenerative collection system is less likely to cause damage to the collection filter, has a simple structure, is low in apparatus cost and running cost, and is difficult to reduce engine performance. It is intended to provide a filter.
[0005]
[Means for solving problems]
According to the first aspect of the present invention, the exhaust gas introduction surface is opened and the exhaust gas discharge surface is closed, and the first exhaust gas passage is adjacent to the first exhaust gas passage with a partition wall therebetween, and the exhaust gas introduction surface is closed. And at least one set of a second exhaust gas passage having an exhaust gas outlet surface open, and the exhaust gas introduced into the first exhaust gas passage enters the second exhaust gas passage via the partition wall, and exhausts the exhaust gas. Configured to be derived from the surface to the outside,
A discharge electrode is provided in at least a part of the first exhaust gas passage in parallel with the exhaust gas flow direction, and a charging electrode having a polarity capable of generating a discharge with the discharge electrode is provided on the exhaust gas introduction surface. Yes,
The discharge electrode is configured to be in point contact with the inner wall surface of the first exhaust gas passage, and the charging electrode is configured such that soot in the introduced exhaust gas accumulates on the inner wall surface of the first exhaust gas passage. The discharge regeneration type collection filter is configured to be in electrical contact with the deposited soot layer formed in (1).
[0006]
The most notable aspect of the present invention is that a discharge electrode is provided on at least a part of the first exhaust gas passage, a charging electrode having a different polarity is provided on the exhaust gas introduction surface, and the charging electrode further comprises a deposited soot layer on the inner wall surface of the exhaust gas passage. It is comprised so that electrical contact is possible.
Further, the polarity of the charging electrode and the discharging electrode may be configured so as to enable discharge between them. For example, the discharging electrode may be positive and the charging electrode may be negative, or vice versa. Further, either the discharge electrode or the charging electrode may be grounded.
[0007]
Next, the operation of the present invention will be described.
A charging electrode is provided on the exhaust gas introduction surface of the discharge regeneration type collecting filter according to the present invention.
By the way, the discharge regeneration type collecting filter according to the present invention includes a first exhaust gas passage in which an exhaust gas introduction surface is opened and an exhaust gas discharge surface is closed, and is adjacent to the first exhaust gas passage with a partition wall therebetween. And a second exhaust gas passage having an introduction surface closed and an exhaust gas outlet surface opened.
The exhaust gas introduced from the exhaust gas introduction surface enters the second exhaust gas passage through the partition wall from the first exhaust gas passage and is led out from the exhaust gas discharge surface.
[0008]
Therefore, the soot is introduced into the discharge regeneration type collecting filter together with the exhaust gas, and when the exhaust gas passes through the partition wall, it accumulates on the inner wall surface of the first exhaust gas passage to form a deposited soot layer extending from the exhaust gas introduction surface to the exhaust gas exhaust surface. The deposited soot layer and the charging electrode are configured to be in electrical contact with each other, and soot in the exhaust gas is conductive. Therefore, the deposited soot layer functions as an electrode having the same polarity as the charging electrode.
[0009]
The discharge electrode is installed so as to be in point contact with the inner wall surface of the first exhaust gas passage. For this reason, the point where the electric field strength is highest in the discharge electrode is the point contact with the inner wall surface.
Therefore, a discharge is generated between the point contact point and the deposited soot layer.
In general, soot is fine and porous with a particle size of around 1 μm, so it easily generates heat and burns due to the discharge.
As described above, the vicinity of the deposited electrode layer and the point contact point of the discharge electrode is burned and removed by the discharge.
[0010]
Further, for example, in a portion where the discharge electrode is not in point contact, such as a corner portion of the first exhaust gas passage as shown in an embodiment described later, the deposited soot layer remains as it is because discharge does not occur or hardly occurs.
Since the remaining deposited soot layer functions as an electrode formed in the first exhaust gas passage with the same polarity as the charged electrode, soot will accumulate again and a deposited soot layer will be formed up to the point contact point between the discharge electrode and the inner wall surface. In this case, since these deposited soot layers have the same polarity as the charging electrode, discharge occurs between the discharge electrodes and the soot in the deposited soot layer can be burned and removed.
[0011]
In this way, a charging electrode in which the deposited soot layer is provided on the introduction surface of the collection filter by utilizing the fact that soot is mainly conductive without previously forming an electrode paired with the discharge electrode in the first exhaust gas passage. It can function as an electrode of the same polarity.
[0012]
In addition, since the deposited soot layer burns gradually due to the discharge, the pressure loss of the discharge regenerative collection filter does not increase, it is prevented from partially becoming high temperature, and the collection filter is hardly damaged. Also, for the same reason, the collection filter is hardly damaged.
[0013]
Moreover, it is only necessary to install a discharge electrode in the first exhaust gas passage of the discharge regenerative collection filter, and the charging electrode paired with the discharge electrode is provided outside the collection filter as the exhaust gas introduction surface to exert its function. Can do.
For this reason, since the structure of the collection filter is simple and easy to manufacture, the cost can be reduced.
[0014]
In addition, the running cost is low because there is almost no power consumption until the actual discharge occurs.
Moreover, as soot accumulates, the discharge starts gradually and can be burned and removed continuously, so that the first exhaust gas passage is always clear and the exhaust gas flow is hardly obstructed. For this reason, it is difficult for the engine back pressure to rise, and it is possible to prevent the engine performance from being lowered.
[0015]
As described above, according to the present invention, it is possible to provide a discharge regeneration type collection filter which is difficult to cause damage to the collection filter, has a simple configuration, is low in apparatus cost and running cost, and hardly deteriorates engine performance.
[0016]
According to a second aspect of the present invention, the discharge electrode is preferably a spiral wire or a wire having a protrusion protruding on the side surface.
Thereby, the discharge start voltage can be lowered, and the wear damage of the discharge electrode due to the discharge can be reduced.
[0017]
In the spiral wire, the outer peripheral side of the spiral is a point contact with the inner wall surface of the first exhaust gas passage. In the case of a wire having the above-mentioned projection, the tip of each projection becomes a point contact with the inner wall surface of the first exhaust gas passage.
In the case of a discharge electrode made of a wire having the above-mentioned protrusions, it is preferable that the number of protrusions is larger. This is because the discharge occurs at a point where the inner wall surface of the first exhaust gas passage and the discharge electrode are in point contact, so that the more protrusions, the more places where discharge occurs.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment An electric discharge regeneration type collecting filter according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a first exhaust gas passage 10 formed by opening an exhaust gas introduction surface 181 and closing an exhaust gas discharge surface 182 of a discharge regeneration type collection filter 1 (hereinafter referred to as a collection filter 1) according to this example, The first exhaust gas passage 10 and the partition wall 13 are adjacent to each other, the exhaust gas introduction surface 181 is closed, and the exhaust gas discharge surface 182 is opened. The exhaust gas 3 introduced from the passage 10 enters the second exhaust gas passage 101 through the partition wall 13 and is led out from the exhaust gas outlet surface 182 to the outside.
[0019]
The first exhaust gas passage 10 is provided with a discharge electrode 12 parallel to the exhaust gas flow direction. The exhaust gas introduction surface 181 is provided with a charging electrode 11 which is a negative electrode.
Further, a part of the discharge electrode 12 is configured to make point contact with the inner wall surface 130 of the first exhaust gas passage 10. As shown in FIG. 3, the charging electrode 11 is configured to be in electrical contact with a deposited soot layer 80 formed by depositing soot in the introduced exhaust gas 3 on the inner wall surface 130 of the first exhaust gas passage 10. Has been. For this reason, the deposited soot layer 80 functions as a negative electrode.
[0020]
This will be described in detail below.
The collection filter 1 of this example is a cylindrical cordierite ceramic honeycomb body as shown in FIGS. 1 and 2, and a large number of first and second exhaust gas passages 10 and 101 having a square cross section are provided therein. The honeycomb body is made of a gas permeable porous material.
The collection filter 1 is installed in an exhaust system of a diesel engine so that the exhaust gas 3 is introduced from the exhaust gas introduction surface 181 on the left side of the drawing and the purified exhaust gas 30 is derived from the exhaust gas extraction surface 182 on the right side of the drawing ( (See FIG. 4).
[0021]
As shown in FIG. 1, in the collection filter 1, the second exhaust gas passage 101 provided with plugging 141 on the introduction surface 181 side and the first exhaust gas passage 10 provided with plugging 142 on the lead-out surface 182 side are provided. It is arranged to be adjacent.
The honeycomb body has a circular cross section, the diameter on the exhaust gas introduction surface 181 side is 140 mm, and the length in the exhaust gas flow direction is 140 mm.
[0022]
As shown in FIG. 1, the exhaust gas 3 is introduced into the collection filter 1 from the first exhaust gas passage 10, and as shown in FIGS. 1 and 3 (a), the partition wall 13 passes through the inner wall 130 in the middle of the first exhaust gas passage 10. Then, it enters the adjacent second exhaust gas passage 101 and is then led out of the collection filter 1.
When moving from the first exhaust gas passage 10 to the second exhaust gas passage 101, soot contained in the exhaust gas 3 is left on the surface of the inner wall surface 130.
Thus, as shown in FIG. 3B, the deposited soot layer 80 is formed on the inner wall surface 130.
[0023]
As shown in FIGS. 1 and 2, a discharge electrode 12 made of a metal spiral wire having a diameter of 0.1 to 1.0 mm is disposed in the first exhaust gas passage 10, and the end of the discharge electrode 12 is the first end. 1 is drawn out of the collection filter 1 through the plug 142 of the exhaust gas passage 10.
As is known from FIG. 1, the charging electrode 11 is provided on the exhaust gas introduction surface 141 of the collection filter 1. The charging electrode 11 is a thin film electrode provided on the side of the inner wall surface 130 and is produced by baking a Pt paste.
Each charging electrode 11 and the discharge electrode 12 are connected to a circuit 190 provided with a power source 19 so that a potential difference can be applied between the two electrodes.
[0024]
The collection and removal of the soot 3 in the exhaust gas by the collection filter 1 of this example will be described.
The discharge electrode 12 and the charging electrode 11 are energized, and the exhaust gas 3 is introduced into the collection filter 1.
As shown in FIGS. 1 and 3 (a), the introduced exhaust gas 3 flows from the first exhaust gas passage 10 to the second exhaust gas passage 101 through the inner wall surface 130.
Therefore, as shown in FIG. 3B, soot accumulates on the surface of the inner wall surface 130 with the passage of time, and a deposited soot layer 80 is formed. As the deposited soot layer 80 grows, the deposited soot layer 80 comes into contact with the charging electrode 11 at the exhaust gas introduction surface 181.
Therefore, the deposited soot layer 80 is negatively charged by the charging electrode 11 and functions as an electrode. For this reason, the deposited soot layer 80 is located between the discharge electrode 12 and the inner wall surface 130 between the deposited soot layer 80 at the point contact point (A portion shown in FIG. 3). Discharge occurs.
[0025]
The deposited soot layer 80 is heated by the discharge, and soot is burned and removed. Therefore, as shown in FIG. 4B, the deposited soot layer 80 is removed from the side inner wall surface 131 in the vicinity of the A portion where the discharge has occurred, and the exhaust gas 3 again flows from the inner wall surface 130 through the partition wall 13. Further, since the discharge electrode 12 does not have a point contact point at the corner portion 132, almost no discharge is generated, and the deposited soot layer 80 remains as it is.
[0026]
Thereafter, the deposited soot layer 80 is formed again on the side inner wall surface 131, but discharge is generated from the same process as described above, and the deposited soot layer 80 is removed again.
The deposited soot layer 80 remaining in the corner portion 132 is always in conduction with the charging electrode 11 and functions as an electrode in the first exhaust gas passage 10 having the same polarity as the charging electrode 11.
With the mechanism described above, the collected reed collection filter 1 can automatically remove the collected soot.
[0027]
Next, the performance of the discharge regeneration type collection filter 1 according to this example is measured, and the result will be described.
A simple test machine 49 equipped with the actual diesel engine 4 was prepared. The structure of this testing machine 49 is shown in FIG.
The collection filter 1 of this example is installed in the middle of the exhaust system 41 connected to the exhaust part of the actual engine 4. A differential pressure gauge 45 is installed on the inlet side and the outlet side of the collection filter 1 to measure the pressure difference between the inlet side and the outlet side of the collector filter 1.
The charging electrode 11 provided on the exhaust gas introduction surface 182 of the collection filter 1 and the numerous discharge electrodes 12 in the exhaust passage 10 are connected to the power source 43, respectively.
[0028]
A sine wave AC voltage having a frequency of 60 Hz and an effective value of 500 V was applied from the power source 43 to the discharge electrode 12, and then the actual engine 4 was driven at a rotational speed of 2000 rpm and a low load to generate exhaust gas.
As a result, as can be seen from FIG. 6, the pressure loss of the collection filter 1 obtained from the differential pressure gauge 45 increased uniformly for a while immediately after the engine was driven, but hardly changed after a certain time.
This is because soot is burned by the discharge and air permeability is improved.
[0029]
As a comparative example, a test similar to the above was performed without applying a voltage to the discharge electrode 12. As a result, as can be seen from FIG. 6, the pressure loss continued to increase.
This is because soot accumulates on the inner wall surface 130 over time, and it becomes difficult for the exhaust gas 3 to move from the first exhaust gas passage 10 to the second exhaust gas passage 101 via the partition wall 13.
[0030]
Next, the effect of this example is demonstrated.
In this example, the charging electrode 11 is provided on the exhaust gas introduction surface 181 of the collection filter 1.
The soot is introduced into the collection filter 1 together with the exhaust gas 3 and deposited on the inner wall surface 130 of the exhaust gas passage to form a deposited soot layer 80 extending from the exhaust gas introduction surface 181 to the exhaust gas outlet surface 182. Since the deposited soot layer 80 and the charging electrode 11 are configured to be in electrical contact with each other, they are conducted and the deposited soot layer 80 functions as a negative electrode in the same manner as the charged electrode 11. Therefore, a discharge can be generated between the deposited soot layer 80 and the discharge electrode 12.
[0031]
The portion deposited on the side inner wall surface 131 of the deposited soot layer 80 is burned and removed by the discharge. In the corner portion 132, the deposited soot layer 80 and the inner wall surface 130 do not make point contact, so that no discharge occurs and the deposited soot layer 80 remains as it is.
The remaining deposited soot layer 80 is electrically connected to the charging electrode 11 and thereafter functions as a negative electrode paired with the discharge electrode 12 in the first exhaust gas passage 10.
[0032]
In this way, in this example, the deposited soot layer 80 is gradually burned and removed by the discharge, so that there is no increase in the pressure loss of the filter and the collection filter 1 is prevented from partially becoming high temperature. Therefore, damage and melting due to heat are unlikely to occur.
[0033]
Further, only the discharge electrode 12 may be provided in the first exhaust gas passage 10, and the charging electrode 11 can be provided outside the collection filter 1, which is the exhaust gas introduction surface 181. For this reason, the configuration is simple, the manufacturing is easy, and the cost is low.
[0034]
In addition, the running cost is low because there is almost no power consumption until the actual discharge occurs.
Further, since soot accumulates and is gradually discharged, burned, and removed, the first exhaust gas introduction path 10 is always clear and the exhaust gas flow is hardly obstructed. For this reason, it is difficult for the engine back pressure to rise, and it is possible to prevent the engine performance from being lowered.
[0035]
As described above, according to this example, it is possible to provide a discharge regeneration type collection filter that is difficult to cause damage to the collection filter, has a simple configuration, is low in apparatus cost and running cost, and is difficult to reduce engine performance.
[0036]
In addition, as shown in FIGS. 7A and 7B, the discharge electrode 12 may be made of a wire having a protruding portion 125 protruding from the side surface.
The discharge electrode 12 is installed such that the tip of the projection 125 is in point contact with the inner wall surface 130 of the exhaust gas passage, and discharge is generated around the tip of the projection 125.
For the discharge electrode 12 having such a configuration, the same operation and effect as in the above-described example can be obtained.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a discharge regeneration type collection filter that is less likely to cause damage to the collection filter, has a simple configuration, is low in apparatus cost and running cost, and is difficult to reduce engine performance. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view of a discharge regeneration type collection filter in an embodiment.
FIG. 2 is an explanatory diagram of a discharge regeneration type collection filter in the embodiment.
3A is a cross-sectional explanatory view of a first exhaust gas passage, and FIG. 3B is a cross-sectional explanatory view of a first exhaust gas passage in which a deposited soot layer is formed on an inner wall surface.
4A is a cross-sectional explanatory view in the vicinity of a corner portion of a first exhaust gas passage, and FIG. 4B is a cross-sectional explanatory view in a state where a deposited soot layer remains only in the corner portion.
FIG. 5 is an explanatory diagram showing a configuration of a testing machine in the embodiment.
FIG. 6 is a diagram showing a relationship between time and pressure loss in the present embodiment and a comparative example in the embodiment.
7A is an explanatory view of an exhaust gas passage provided with another discharge electrode, and FIG. 7B is an explanatory view of the discharge electrode in the embodiment.
[Explanation of symbols]
1. . . Discharge regenerative collection filter,
10. . . First exhaust gas passage,
101. . . Second exhaust gas passage,
11. . . Charging electrode,
12 . . Discharge electrode,
13. . . Bulkhead,
130. . . Inner wall,
181. . . Exhaust gas introduction surface,
182. . . Exhaust gas derivation surface,
3. . . Exhaust gas,

Claims (2)

An exhaust gas introduction surface is opened and the exhaust gas discharge surface is closed, and the first exhaust gas passage is adjacent to the first exhaust gas passage with a partition wall therebetween. The exhaust gas introduction surface is closed and the exhaust gas discharge surface is opened. At least one set of second exhaust gas passages, and the exhaust gas introduced into the first exhaust gas passage enters the second exhaust gas passage via the partition wall and is led out from the exhaust gas outlet surface. Has been
A discharge electrode is provided in at least a part of the first exhaust gas passage in parallel with the exhaust gas flow direction, and a charging electrode having a polarity capable of generating a discharge with the discharge electrode is provided on the exhaust gas introduction surface. Yes,
The discharge electrode is configured to be in point contact with the inner wall surface of the first exhaust gas passage, and the charging electrode is configured such that soot in the introduced exhaust gas accumulates on the inner wall surface of the first exhaust gas passage. A discharge regeneration type collection filter, characterized in that it is configured to be in electrical contact with the deposited soot layer formed in (1). 2. The discharge regeneration type collection filter according to claim 1, wherein the discharge electrode is a spiral wire or a wire having a protrusion on a side surface.

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