JPH06173635A - Exhaust emission control device for vehicle diesel engine - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device for a diesel engine by which insulating degradation of an insulator caused by accumulation of diesel particulates can be prevented. CONSTITUTION:Since an insulator 3 supports an electrode 42 and a diesel particulate incinerating means (nichrome wire) 95 is arranged close to a surface of an insulator, insulating resistance on the surface of the insulator 3 is restored by burning diesel particulates accumulated on the surface of the insulator 3 by the heating action.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for a vehicle diesel engine.

[0002]

2. Description of the Related Art Conventionally, the problem that diesel particulates (dust particles) contained in the exhaust gas of a diesel engine for vehicles such as buses and trucks pollute the environment and damage human health. However, in order to solve this problem, it is considered to improve the combustion system of the diesel engine or adopt a ceramic filter or the like.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since a variety of operations are performed in a Zel engine during cold start, climbing, and overloading, it is difficult to significantly reduce diesel particulates by improving the combustion method. On the other hand, the method of adsorbing the diesel particulates with a ceramic filter or the like has a drawback that the exhaust pressure loss is large and the engine efficiency is reduced accordingly.

In particular, when the amount of the diesel particulate adsorbed on the filter increases, the exhaust pressure loss increases at an accelerated rate, which causes the output of the diesel engine to decrease and the combustion characteristics to deteriorate. It will generate Zerupaticulate. Further, in order to reduce the exhaust pressure loss, the ceramic filter had to be upsized, and it was difficult to put it into practical use in terms of cost and space.

In order to solve this problem, the present applicant has developed an exhaust gas purifying apparatus for separating the diesel particulates from the exhaust gas by applying the electrostatic dust collection technology to the diesel engine for vehicles. did. Experiments have shown that good diesel particulate separation is possible with a simple device and a small exhaust gas pressure drop. It was also found that the diesel particulates are charged during combustion, so that the forced charging of the diesel particulates by corona discharge is not always necessary. Further, according to this exhaust gas purifying apparatus, since the exhaust gas pressure loss hardly increases due to the accumulation of the diesel particulates, there is no decrease in the engine output or deterioration of the combustion as compared with the ceramic filter method, which is accompanied by it. It has an excellent advantage as an engine for a vehicle that does not increase the emission amount of diesel particulates.

It has been found that the electrostatic dust collecting type exhaust gas purifying apparatus for a vehicle diesel engine has the following problems in spite of the excellent advantages as described above. That is, the diesel particulates in the exhaust gas are carbonaceous and electrically conductive. Therefore, the insulator that insulates the high-voltage side electrode of the electrode pair to which the high voltage is applied from the low-voltage side electrode is contaminated in a short time, and the discharge or collection efficiency is reduced.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an exhaust gas purifying apparatus for a diesel engine capable of preventing the insulation deterioration of the insulator due to the accumulation of diesel particulates. It is a problem to be solved.

[0008]

An exhaust gas purifying apparatus for a vehicle diesel engine according to the present invention is an electrode provided in an exhaust path of a vehicle diesel engine for collecting diesel particulates by electrostatic force. A pair, an insulator that electrically insulates and separates the pair of electrodes from each other, and a diesel particulate that is disposed close to the surface of the insulator and ignites and burns off the diesel particulate on the surface of the insulator. And a burn-out means.

The discharge electrode pair can also serve as the collecting electrode pair. In a preferred embodiment, the diesel particulate
The heater can be constituted by a heater (that is, electric resistance heating means) built in the insulator. By doing so, space saving can be achieved and heating efficiency can be improved as compared with the case where the diesel particulate burning-out means is provided separately from the insulator.

In a preferred embodiment, an oxygen supply means for supplying at least one of exhaust gas and air to the exhaust passage at the time of ignition is provided. In this way, the oxygen for burning diesel particulates will not run short. In particular, if the diesel engine itself is adopted as the oxygen supply means, it is not necessary to provide a special oxygen supply means. In a preferred embodiment, insulator pollution degree detection means for detecting the degree of insulator pollution by the leakage current when a test voltage that does not generate corona discharge is applied between the pair of electrodes is provided, and the determination result of this insulator pollution degree detection means To drive the diesel particulate burn-out means. In this way, it is possible to burn off at appropriate intervals.

[0011]

First, the principle of the exhaust gas purifying apparatus for a vehicle diesel engine according to the present invention will be described. In the present invention, the principle of electrostatic precipitator is applied to separate the diesel particulate contained in the exhaust gas of the diesel engine from the exhaust gas.
That is, the high-voltage power supply unit applies a predetermined voltage to the electrode pair, and the electrode pair collects the diesel particulates in the exhaust gas discharged from the vehicle diesel engine by electrostatic force.

The means for burning off the diesel particulate is
It is provided close to the insulator surface and burns the diesel particulates deposited on the insulator surface to restore the insulation resistance of the insulator surface.

[0013]

As described above, according to the present invention, a diode provided near the surface of the insulator and deposited on the surface of the insulator.
Equipped with a diesel particulate burn-out means that burns the diesel particulates to restore the insulation resistance of the insulator surface, it is possible to prevent the insulator deterioration of the insulator due to the diesel particulate accumulation, and It is possible to prevent the deterioration of the charging efficiency and the collection efficiency of the diesel particulate due to the insulation deterioration.

[0014]

Embodiments of the present invention will now be described in order with reference to the drawings. It is to be noted that, except for Example 8, it is an example of each component of the apparatus of the present invention. (Embodiment 1) FIGS. 1 and 2 are cross-sectional views of an exhaust gas purification apparatus of Embodiment 1.

In this device, an outer can portion 2 that fits into the upstream exhaust pipe 1a and the downstream exhaust pipe 1b of a vehicle diesel engine to connect the exhaust pipes 1a and 1b, and the outer can portion 2 are provided. The high-voltage electrode part 5 made of stainless steel supported on the insulator 3
And a high-voltage power supply unit 6 connected to the high-voltage electrode unit 5. The outer can 2 has a closed box shape made of stainless steel, and the upstream exhaust pipe 1a and the downstream exhaust pipe 1b are individually fitted into the inflow hole 21 and the outflow hole 22 provided on both side walls thereof. Inside the outer can portion 2, there is formed a flow passage of the shape of numeral 2 which is divided by the partition walls 25 and 29 and reaches the inflow hole 21 and the outflow hole 22, and the first straight line portion of this flow passage is the present invention. Forming the discharge space Sd, and the flow path thereafter is the collecting space (that is, the space between the collecting electrode pair) Sc in the present invention.
To form. Therefore, the outer can portion 2 surrounding the discharge space Sd
The portion 23 and one surface of the partition wall 25 form one of the discharge electrode pairs referred to in the present invention, and the portion 53 of the high voltage electrode portion 5 in the discharge space Sd forms the other of the discharge electrode pairs. Further, the portion 24 of the outer can portion 2 surrounding the collection space Sc, the other surface of the partition wall 25 and the partition wall 29 form one of the collection electrode pairs in the present invention,
The portion 54 of the high voltage electrode portion 5 in the collection space Sc forms the other of the collection electrode pair. As shown in FIG. 2, a portion (hereinafter, referred to as a discharge electrode portion) 23 of the outer can portion 2 that is one of the discharge electrode pairs is formed in a small-diameter long tube, and a portion of the outer can portion 2 that is one of the collection electrode pairs. (Hereinafter referred to as the collecting electrode portion) 24
Is formed in a rectangular box shape.

The discharge electrode side portion 53 of the high voltage electrode portion 5 is formed in a narrow and long plate shape, and the collecting electrode side portion 54 of the high voltage electrode portion 5 is formed in a wide and long plate shape, and the high voltage electrode portion 5 is formed. The board width direction is vertical. A support rod 55 extending in the vertical direction is welded to a portion 54 of the high-voltage electrode portion 5 on the collecting electrode side, and the upper and lower ends of the support rod 55 are supported by the insulator 3 made of alumina porcelain on the outer can portion 2 so as to be electrically insulated. Has been done. More specifically, the insulator 3 is fixed by penetrating a small hole (not shown) of the outer can portion 2, and the support rod 55 is fixed by penetrating the insulator 3. The support rod 55 is connected to the high-voltage power supply section 6 as a power supply member. The high-voltage power supply unit 6 applies a high negative DC voltage to the high-voltage electrode unit 5 to generate corona discharge between the high-voltage electrode unit 5 and the outer can unit 2 which is grounded via the vehicle body (not shown). . The circuit configuration of the high-voltage power supply unit 6 is well known, and therefore its explanation is omitted.

The operation of this device will be described below. The exhaust gas emitted from the diesel engine of the vehicle is the upstream exhaust pipe 1a.
Is sent to the inside of the outer can portion 2 via the
And is discharged to the outside through a silencer (not shown). The high-voltage power supply unit 6 applies a negative DC high voltage to the high-voltage electrode unit 5 to generate corona discharge between the high-voltage electrode unit 5 and the outer can unit 2 in the discharge space Sd having the small gap d1. Due to this corona discharge, the diesel particulate contained in the exhaust gas in the discharge space Sd is negatively charged. Since the gap d2 is wide in the collection space Sc, no corona discharge occurs and only an electrostatic field is formed. Therefore, the charged diesel particulates that have flowed into the collection space Sc are attracted by this electrostatic field and are deposited on the inner surface of the outer can portion 2, and clean exhaust gas is discharged from the downstream side exhaust pipe 1b.

The diesel particulates deposited inside the outer can 2 are burned off by a heater (not shown) at appropriate time intervals. In this embodiment, since the insulator 3 is not arranged in the discharge space Sd where a high electric field is generated, there is an advantage that the leakage current can be reduced. (Embodiment 2) Another embodiment of the present invention is shown in FIGS. Here, FIG. 3 is a cross-sectional view, FIG. 4 is a cross-sectional view taken along line BB,
5 is a sectional view taken along the line AA, and FIG. 6 is a sectional view of the nozzle portion.

This apparatus is attached to an upstream exhaust pipe 1a of a diesel engine for a vehicle (not shown) and constitutes a discharge electrode pair according to the present invention, a nozzle portion 4, a nozzle portion 4 and a downstream exhaust pipe. 1b and the outer can portion 7 that constitutes the collecting electrode pair in the present invention, and the nozzle portion 4 and the outer can portion 7
And a high voltage power supply unit 6 for applying a DC high voltage to the. As shown in FIG. 6, the nozzle portion 4 includes a tapered cylindrical cone portion (one of the discharge electrodes in the present invention) 41 and a cone portion 4.
The electrode rod 42 (the other side of the discharge electrode in the present invention) 42 extending along the axis of 1 is supported by the insulator 3. To further explain, the insulator 3 has the cone portion 4
1 is passed through a hole provided in the large diameter portion and is fixed to the cone portion 41 by a screw 43. The insulator 3 is bent in an L shape toward the tip of the nozzle, and the electrode rod 4 is provided at the center of the insulator.
The base of 2 penetrates. The outer ends of the electrode rods are connected to the high voltage power supply unit 6.

Outer can portion (one of the collecting electrodes in the present invention) 7
4 is a closed shallow-bottom can that includes a lid portion 71 and a bottom portion 72 as shown in FIGS. 4 and 5, and an outer can portion 7 as shown in FIG.
The tip of the nozzle portion 4 is fitted in a hole 74 provided at one end portion of the left side wall 7a of the outer wall 7a, and a downstream exhaust pipe is provided in a hole 75 provided at the other end portion of the right side wall 7b of the outer can portion 7. 1b is inserted.

A plurality of vertical partition plates 73 are provided in parallel with each other in the internal space of the outer can portion 7 (collection space Sc in the present invention). As shown in FIG. A plurality of flow paths 8a parallel to each other are formed. Each flow path 8a connects the upstream flow path 8b and the downstream flow path 8c, and each flow path 8a extends in a direction perpendicular to the upstream flow path 8b and the downstream flow path 8c. Upstream channel 8
The inlet of b communicates with the nozzle part 4, and the downstream flow path 8c
Is connected to the downstream exhaust pipe 1b.

An electrode plate (the other of the collecting electrodes in the present invention) 76 is provided in the center of each flow path 8a in parallel with the vertical partition plate 73. As shown in FIG. 4, each electrode plate 76 is welded to a horizontal frame 77 made of a thin metal rod supported by the insulator 3 and held in the collection space Sc. The thin metal rod that penetrates the insulator 3 and projects to the outside is connected to the output end of the high-voltage power supply unit 6.

Next, the operation of this device will be described. The nozzle unit 4 throttles the inflowing exhaust gas to increase the speed. The small-diameter tip end portion 44 of the cone portion 41 and the electrode rod 42 inside thereof constitute a discharge electrode pair in the present invention, and when corona discharge occurs in the discharge space Sd between them, this high speed The diesel particulates in the exhaust gas stream are charged.

According to this embodiment, since the discharge electrode pair is formed into a nozzle, the discharge space Sd can be downsized,
Corona discharge can be concentrated on this part. Also,
Since the exhaust gas flow is at a high speed, the diesel particulates adhering to the inner surface of the cone portion 41 and the electrode rod 42 are blown off and the discharge is prevented from becoming an obstacle. Further, in the present embodiment, the interval d1 between the discharge spaces Sd is small and the discharge voltage can be lowered. Further, since the discharge space Sd is small, the generation of NOx can be reduced in combination with the fact that the exhaust gas flow is high speed even if a large current is passed therethrough. In addition, since the discharge current can flow at a high density in the entire discharge space Sd, it is possible to prevent charge leakage of the diesel particulate, and since the exhaust gas flow is high in speed, the diesel particulate with electrons and ions can be prevented. It has good contact properties with the diesel particulates and is quickly charged. The charged diesel particulate is a collection space S
It is deposited on the inner wall of the outer can portion 7 and the vertical partition wall 73 at c.

The distance d2 between the collection spaces Sc is wider than the distance d1 between the discharge spaces Sd so that corona discharge does not occur even if the same voltage is applied. Further, it is assumed that the flow velocity of the exhaust gas in the collection space Sc is low and the traveling time of the diesel particulate is sufficiently secured. (Embodiment 3) Another embodiment of the present invention is shown in FIGS. Here, FIG. 7 is a horizontal sectional view, FIG. 8 is a sectional view taken along the line AA, and FIG. 9 is a sectional view taken along the line BB.

In this apparatus, the nozzle portion 4 shown in FIG. 6 of the second embodiment is enlarged without increasing the gap d1 for discharging, and the both ends of the insulator 3 have the diameter of the cone portion 41. Five electrode rods 42, which are fixed to a large portion and are parallel to each other, extend from the insulator 3 to a small-diameter tip portion 44 of the nozzle portion 4. The tip portion 44 of the nozzle portion 4 is formed by connecting concentric circles surrounding each electrode rod 42, and is devised so that a uniform corona discharge is generated inside.

In this way, the exhaust gas flow rate can be increased without increasing the diameter of the tip portion 44 which requires an increase in the discharge voltage. (Embodiment 4) Another embodiment of the present invention is shown in the horizontal sectional view of FIG. 10 and the vertical sectional view of FIG. In this device, the insulator 3 of the nozzle portion 4 shown in FIGS.
And the space 8 between the insulator cover 83 and the insulator 3
The structure used to fill the 4 with clean air.

To explain further, an insulator cover 83 made of alumina porcelain is formed in a horizontal U shape at a predetermined interval on the remaining surface of the insulator 3 excluding the outer surface on the nozzle tip side. Both side ends are in close contact with the inner surfaces of both side walls of the cone portion 41. Further, an air introduction hole 85 is opened in communication with a space 84 between the insulator cover 83 and the insulator 3, and the air compressor 8 is opened through the air introduction hole 85 and the pipe 81.
Clean air is introduced into the space 84 from.

The clean air introduced into the space 84 is blown out from the gap between the insulator cover 83 and the insulator 3 toward the tip of the nozzle, and the surface of the insulator 3 is kept in good electrical insulation. (Embodiment 5) Another embodiment of the present invention is shown in the vertical sectional view of FIG. This apparatus is a modification of the insulator structure of the nozzle portion 4 shown in FIG. 6 of the second embodiment.

That is, an air feed straight hole 33 is formed in the central portion of the insulator 3 of this embodiment in the longitudinal direction, and the inlet of the air feed straight hole 33 is provided by a pipe 81 to the air compressor 8
Is connected to the discharge port of. An air outlet 34 is formed on the bottom side surface of the direct air supply hole 33 toward the tip of the nozzle portion 4, and the electrode rod 42 is attached to the tip of the nozzle portion 4 along the center line of the air outlet 34. Stretching towards.

Therefore, if clean air is blown out from the air blowing port 34, the insulation of the electrode rod 42 can be secured even if the outer surface of the insulator 3 is contaminated by the diesel particulates and the insulation is deteriorated. . In particular, in this embodiment, the insulator 3 itself is the direct air supply hole 33 and the air outlet 3.
Since it has 4, the extra parts do not have to be provided inside the nozzle portion 4, and the structure is simplified.

(Embodiment 6) Another embodiment of the present invention is shown in FIG.
16 and FIG. Here, FIG. 13 is an upper longitudinal sectional view, FIG. 14 is a lower longitudinal sectional view, FIG. 15 is a sectional view taken along the line BB, and FIG. 16 is a sectional view taken along the line AA. This device is a large-sized and vertical type exhaust gas purifying device for buses or trucks, and has a fixed cylindrical portion 91 with a lower opening at the upper portion and a central portion and a large diameter at the lower portion, and the fixed cylindrical portion 91. It has a rotating cylinder portion 92 with both ends opening that is rotatably fitted to the lower part of the above, and a collection box 93 that fits into the lower end opening of the rotating cylinder portion 92 while allowing the rotation of the rotating cylinder portion 92.

An insulator 3 with an air supply hole 35 is fixed to the top of the fixed cylindrical portion 91, and a discharge electrode pair and a collection electrode pair are provided from the center of the lower surface of the insulator 3 along the center line of the fixed cylindrical portion 91. The electrode rod 42 that constitutes one side is suspended. An elliptical opening 94 is provided on the side surface near the top of the fixed cylindrical portion 91, and the small-diameter tip cylindrical portion 1c of the upstream exhaust pipe 1a is fitted into the elliptic opening 94. A large-diameter exhaust port 95 is provided on the lower side surface of the fixed cylindrical portion 91, and the downstream exhaust pipe 1b is fitted into the exhaust port 95.

The fixed cylindrical portion 91 is a small diameter portion 91a having the smallest diameter immediately below the elliptical opening 94, and the internal space of the small diameter portion 91a constitutes the discharge space Sd according to the present invention. The portion 91a constitutes the other of the discharge electrode pairs referred to in the present invention. The fixed cylindrical portion 91 is the largest diameter portion below the smallest diameter portion 91a, and the internal space of the large diameter portion 91b constitutes the collection space Sc referred to in the present invention. Constitutes the other of the pair of collecting electrodes referred to in the present invention.

The lower portion of the rotating cylindrical portion 92 has a frustoconical shape with a small diameter, and is rotated at a low speed by a deceleration motor (not shown). A long bar 96 stands upright from the inner surface of the rotating cylindrical portion 92, and the outer edge of the bar 96 is in contact with the inner surface of the large diameter portion 91b of the fixed cylindrical portion 91. The operation of this device will be described below.

The exhaust gas flow, which is narrowed by the small-diameter tip cylinder portion 1c of the upstream exhaust pipe 1a and has a high speed, is blown into the discharge space Sd. The diesel particulate is the discharge space Sd.
After being charged by the corona discharge between the electrode rod 42 and the small diameter portion 91a of the fixed cylindrical portion 91, it reaches the collecting space Sc below the discharge space Sd. The charged diesel particulates are attracted to the electrostatic field in the collecting space Sc and are deposited on the inner surface of the large diameter portion 91b of the fixed cylindrical portion 91.

As the rotating cylindrical portion 92 rotates, the bar 96
Is in contact with the inner surface of the large diameter portion 91b of the fixed cylindrical portion 91 and rotates at a low speed to drop the diesel particulate layer deposited on the inner surface of the large diameter portion 91b. The dropped diesel particulates are collected in the collecting box 93. In this way, the collection box 9 can be removed and the diesel particulates therein can be removed.

According to this embodiment, it is possible to prevent the diesel particulate layer from being excessively deposited on the inner surface of the large diameter portion 91b, so that the large diameter portion 91b can be downsized and the collecting voltage can be reduced. You can Also, continuous use of the device is possible. (Embodiment 7) Another embodiment of the present invention is shown in the vertical sectional view of FIG.

This device is a modification of the insulator structure of the nozzle portion 4 shown in FIG. 6 of the second embodiment. That is, a nichrome wire (a diesel particulate burning means in the present invention) 95 is embedded in the insulator 3 of this embodiment at a position apart from the electrode rod 42, and one end of the nichrome wire 95 is a terminal. It is connected to the terminal 99 and the other end of the nichrome wire 95 is connected to the low resistance electrode rod 42.

When a voltage is applied between the terminal 99 and the electrode rod 42, the nichrome wire 95 is heated and the insulator 3 becomes high in temperature, and the diesel particulates deposited on the surface thereof.
The insulating layer of the insulator 3 is restored by burning off the insulating layer.
In the present embodiment, since the nichrome wire 95 is built in the insulator 3, the insulator heating efficiency is good and the nichrome wire 95 is also used.
There is little deterioration. (Embodiment 8) Another embodiment of the present invention will be described with reference to the block circuit diagram of FIG. 18 and the flow chart of FIG. Figure 1
Reference numeral 8 denotes a control device for controlling energization to the nichrome wire 95 shown in FIG. 17 (Embodiment 7) in order to burn off the diesel particulates deposited on the surface of the insulator 3.

This control device comprises a current sensor 101, a detection circuit 102, a smoothing capacitor 103, and a microcomputer device (insulator pollution degree detecting means in the present invention). The high voltage power supply unit 6 is supplied with power from an alternator (not shown) driven by a vehicle diesel engine, generates a DC high voltage and applies it to the electrode rod 42. The current sensor 101 uses the current value supplied to the high-voltage power supply unit 6 (the high-voltage power supply unit 6 uses the electrode rod 42).
The current value detected is detected by the detection circuit 102, smoothed by the smoothing capacitor 103, and supplied to the microcomputer device 104.

Nichrome wire 95 by the microcomputer device 104
The energization control operation to the will be described with reference to the flowchart of FIG. First, the high voltage power supply unit 6 is instructed and the electrode rod
A test voltage of a fraction of the voltage for corona discharge is applied to (300), and the current (referred to as leakage current) supplied to the high-voltage power supply unit 8 at that time is detected from the current sensor 101 (301). Next, the average leakage current Im within a predetermined time is calculated (302), and it is checked whether the average leakage current Im is larger than a predetermined threshold current value Ith (304). Most of the leakage current is a current that leaks on the surface of the insulator 3, and as the diesel particulate (mostly made of carbon) is deposited on the surface of the insulator 3, the insulation resistance of the insulator 3 decreases, Leakage current increases.

If Im> Ith is not satisfied, it is assumed that the diesel particulates are not much deposited on the insulator 3, and after waiting at 300 for a predetermined time (306), the insulator 3 is returned. If Im> Ith, the insulator is Assuming that a large amount of diesel particulates are deposited on the 3rd engine, it is checked whether or not the diesel engine is in operation (308), and if not in operation (310), after waiting until warming up ( 31
2) The Nichrome wire 95 inside the insulator 3 is energized to heat the insulator 3 and burn the diesel particulate on the surface thereof. During operation of the diesel engine, high-temperature exhaust gas flows into the periphery of the insulator 3, which is advantageous for combustion of the diesel particulates. By the way, the exhaust gas of the diesel engine does not interfere with combustion because it contains a sufficient oxygen component, but it is also possible to introduce fresh air by an air compressor or the like.

Thereafter, the insulator particle 3 on the surface of the insulator 3 is waited for a sufficient time to disappear (3
16) and ends. By doing so, the degree of fouling of the insulator 3 can be automatically detected, and when it is determined that the fouling is large, the insulator 3 is heated to burn the diesel particulates. No need to clean 3 and the management is simple. (Embodiment 9) Another embodiment of the present invention will be described with reference to the block circuit diagram of FIG. 18 and the flow chart of FIG. Figure 1
The control device of No. 8 is the heater shown in FIGS. 3 and 5 (Example 7).
A controller for controlling the energization of the controller 100 to burn off the diesel particulates deposited on the surface of the collecting electrode 73 is shown. The controller has the same configuration as that of the controller of the eighth embodiment.

The current sensor 101 detects the current value supplied to the high-voltage power supply section 6 (the high-voltage power supply section 6 energizes only the collecting electrode 73), and the detected current value is detected by the detection circuit 102. It is smoothed by the smoothing capacitor 103 and supplied to the microcomputer device 104. Microcomputer device 10
20 is a flowchart showing the energization control operation of the heater 100 according to FIG.
An explanation will be given with reference to the chart.

First, when the high-voltage power supply unit 6 applies a collecting voltage (rated non-corona discharge voltage) to the collecting electrode 73, the current supplied to the high-voltage power supply unit 6 is detected (401). Next, the average current Im within a predetermined time is calculated (402), and it is checked whether the average current Im is larger than the threshold current value Ith (404). In addition, this current is generated by depositing a diesel particulate on the collecting electrode 73 and collecting electrode pair 7
The distance between 3,76 is shortened and the electric field is strengthened and increased.

If Im> Ith, the collecting electrode 7
As shown in FIG. 3, the diesel particulate was not deposited so much, and after waiting for a predetermined time (406), it returned to 401, and if Im> Ith, it was collected on the collecting electrode 73.
As a lot of zeru particulates are deposited,
It is checked whether the diesel engine is in operation (408), if it is not in operation (410), and after waiting until it warms up (412), the heater 100 (see FIGS. 3 and 5) Power is supplied (414) to burn the diesel particulates in the collection space Sc. The heater 100 is a collection space Sc
Since it is provided in the upstream portion of the exhaust gas, the exhaust gas flow quickly burns and spreads throughout the collection space Sc.

After that, the process waits for a sufficient time for the diesel particulate layer deposited on the surface of the collecting electrode 73 to disappear (416), and ends. If you do this,
The degree of deposition of the diesel particulates deposited on the collecting electrodes can be automatically detected, and when it is determined that the amount of deposits is large, the diesel particulates on the surfaces of the collecting electrode pairs 73 and 76 are burned. Therefore, it is not necessary to clean the collecting electrodes 73 and 76, and the management is easy.

In this embodiment, the amount of the diesel particulate deposit is determined by the change in the current supplied to the collecting electrode 73. However, the exhaust gas pressure loss caused by the diesel particulate deposit is detected by a pressure sensor or a detector. -It is naturally possible to detect the change in the operating condition of the diesel engine. (Embodiment 10) Another embodiment of the present invention will be described with reference to the flowchart of FIG.

This flow chart is intended to optimize the operation of the exhaust gas purifying device by using the control devices of the eighth and ninth embodiments. First, the operating conditions of the engine, especially the operating conditions linked to its diesel particulate emission, are investigated (500). The operating conditions that are linked to the diesel particulate emission are cooling water temperature, fuel injection amount,
There are speeds (loads) and the like, and the diesel particulate discharge amount when these conditions are changed is stored in advance in the storage unit of the microcomputer device 104 as a map.

Next, based on the detected operating conditions,
Search for the expected amount of zer particulates (50
2) Further, a minimum discharge current value Io (optimal discharge current value) that can process the expected discharge amount at a predetermined purification rate is obtained based on a map built in the storage unit (504). In addition, the same voltage (hereinafter referred to as a discharge voltage) is applied to the discharge electrode pair and the collection electrode pair referred to in the present invention, and the discharge current here means the sum of currents supplied to both electrode pairs.

Next, a predetermined voltage is applied to the discharge electrode pair and the collection electrode pair to charge and collect the diesel particulates, and the discharge current value at that time is detected (50
6) Then, the average value is calculated (508). Next, the average discharge current value Im and the minimum discharge current value Io are compared (51
0), if Im> Io, it is determined that Im is excessive, and the predetermined voltage ΔV is reduced from the discharge voltage V (512), Im> I.
If not o, it is checked whether Im <Io (51
4) If Im <Io, Im is considered to be too small and the predetermined voltage ΔV is increased to the discharge voltage V (516). If Im <Io is not satisfied, the process is returned to step 500 to return to the routine.
Repeat Chin.

According to this embodiment, since the discharge current value is changed to the optimum range according to the fluctuation of the diesel particulate discharge amount, a large discharge current is supplied when the diesel particulate discharge is small. Then, without causing electrode wear, increase in power consumption, and increase in NOx,
In addition, when a large amount of diesel particulates is discharged, a small discharge current is passed, and the purification efficiency of the diesel particulates is not lowered.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an exhaust gas purification device according to a first embodiment,

2 is a cross-sectional view taken along the line AA of the apparatus of FIG.

FIG. 3 is a cross-sectional view of an exhaust gas purifying device according to a second embodiment.

4 is a cross-sectional view taken along the line BB of the apparatus of FIG.

5 is a cross-sectional view taken along the line AA of the device of FIG.

6 is a cross-sectional view of the nozzle portion of the device of FIG.

FIG. 7 is a cross-sectional view of the nozzle portion of the device of Example 3,

8 is a cross-sectional view taken along the line AA of the apparatus of FIG.

9 is a sectional view taken along line BB of the apparatus of FIG.

FIG. 10 is a cross-sectional view of the nozzle portion of the device of Example 4,

11 is a sectional view taken along line BB of the apparatus of FIG.

FIG. 12 is a cross-sectional view of the nozzle portion of the device of Example 5,

FIG. 13 is a vertical cross-sectional view of the upper part of the device of Example 6,

FIG. 14 is a vertical cross-sectional view of the lower portion of the device of Example 6,

FIG. 15 is a sectional view taken along line BB of the apparatus of Example 6;

FIG. 16 is a cross-sectional view taken along the line AA of the device of Example 6;

FIG. 17 is a vertical cross-sectional view of the nozzle portion of the device of Example 7,

FIG. 18 is a block circuit diagram showing a control device of Example 8;

FIG. 19 is a flowchart of the control device according to the eighth embodiment.

FIG. 20 is a flowchart of the control device according to the ninth embodiment,

FIG. 21 is a flowchart of the control device according to the ninth embodiment,

[Explanation of symbols]

3 is an insulator, 4 and 42 are collection electrode pairs, and 95 is a nichrome wire (diesel particulate burn-out means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hisashi Matsunaga Hisashi Matsunaga 1-6-22 Daiho, Atsuta-ku, Nagoya-shi Aichi Prefecture

Claims (4)

[Claims] 1. An electrode pair provided in an exhaust path of a vehicle diesel engine for collecting a diesel particulate by electrostatic force, an insulator for electrically isolating and separating the electrode pair from each other, and an insulator for the insulator. Exhaust gas of a vehicle diesel engine, characterized in that it comprises a diesel particulate burning means for igniting and burning away the diesel particulate on the surface of the insulator which is arranged close to the surface. Purification device. 2. The exhaust gas purifying apparatus for a vehicle diesel engine according to claim 1, wherein the diesel particulate burning-out means comprises a heater built in the insulator. 3. The exhaust gas purifying apparatus for a diesel engine for a vehicle according to claim 1, further comprising oxygen supply means for supplying at least one of exhaust gas and air to the exhaust path at the time of ignition. 4. The vehicle diesel engine according to claim 1, further comprising insulator pollution degree detecting means for detecting the degree of insulator pollution by a leakage current when a test voltage which does not generate corona discharge is applied between the pair of electrodes. Exhaust gas purification device.