JP2001295629A - Dpf device for causing reaction and disappearance of particulate matter by means of plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DPF(diesel particulate filter) device for causing particulate matters collected by a filter to react and disappear by utilizing plasma energy, so that the filter is regenerated. SOLUTION: In this DPF device, an upstream screen 4 located on the upstream side and downstream screen 6 located on the downstream side are insulated electrically from a filter body 5 forming the filter 3. Particulate matters collected by the filter 3 are caused to react and disappear, by plasma energy in order for the filter 3 to regenerate. A plasma generator 1 generates plasma, by increasing voltage of power from a generator with a transformer 23, rectifying the power with a rectifying coil 22, performing on/off operation of signals transmitted by a high-frequency oscillator 20 through a power transistor of an interrupter 21 to generate alternate power, and then intermittently applying high-frequency direct current on both screens 4, 6 at a high voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel particulate filter device, that is, a DPF device that collects particulates in exhaust gas discharged from a diesel engine and uses plasma to react and eliminate particulate matter.

[0002]

2. Description of the Related Art Conventionally, an exhaust gas treatment apparatus for treating exhaust gas of an engine has a large filter area provided in an exhaust pipe, a heating coil attached to the filter, and a carbon or the like contained in the exhaust gas. The particulate matter is deposited on the front surface of the filter and collected, and then the carbon deposited on the filter is heated by energizing a heating coil to burn and burn the carbon, thereby regenerating the filter.

For example, a diesel particulate filter device disclosed in Japanese Utility Model Laid-Open Publication No. 1-144427 passes exhaust gas through a filter body, and the filter body collects particulates such as carbon and smoke in the exhaust gas. When particulates accumulate in the filter body and clog the filter, shut off the flow of exhaust gas to the filter body and switch to the flow of exhaust gas to another filter body. From the downstream side of the clogged filter body It blows in air and heats the filter body to incinerate the clogged particulates.

[0004]

The exhaust gas discharged from a diesel engine contains carbon, smoke, H
Although particulate matter such as C and SO _X , that is, SPM is contained, SPM is a composite of carbon and hydrocarbon, and its size is from very large particles to small ones, specifically, 40 μm to 40 μm. The particle size is in the range of 0.1 μm, often about 20 μm, and these sizes are dispersed in the exhaust gas. In particular, among the SPM sizes, those having a small particle size of 2.5 μm or less are environmentally friendly.
It is a problem because it has an adverse effect on the human body such as asthma.

[0005] However, when the particulate particulate matter (SPM) is collected by the diesel particulate filter device, that is, the DPF device, the particulate matter may be discharged through the intersection space between the fibers of the fiber filter. It is extremely difficult to collect. Therefore, trapping these SPMs having a small particle size has become a major issue from the viewpoint of preventing air pollution.

The SPM collected by the DPF device is
When heated to about 600 ° C. or higher in the presence of oxygen, it can react with oxygen and easily burn and incinerate. Therefore, the SPM collected by the filter body is installed in the DPF device.
It is necessary to have a function to regenerate the filter body by heating and burning the filter. Then, in order to regenerate the filter body, the wire mesh was energized while flowing exhaust gas through the filter body, and SP
It is conceivable to raise the temperature to the combustion state of M. When the filter is made of ceramic fiber,
SPM is deposited between the fibers. Since the SPM deposited between the filter fibers in which the ceramic fibers are randomly laminated is deposited three-dimensionally, a gap is easily formed between the SPMs, and the exhaust gas easily passes between the SPMs. SPM is ignited and burned by the air contained in the SPM.

By the way, plasma is a discharge current,
This is a phenomenon caused by positive and negative charged particles moving freely between gases. Therefore, the DPF device is composed of a filter body laminated with non-conductive ceramic fibers and holding members made of wire mesh on both sides thereof, and is formed into a cylindrical structure which is folded in a fold shape as a whole. When the wire mesh on both sides is composed of electrodes and high voltage is applied to the wire mesh at high frequency,
Plasma can be generated between both electrodes.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and a filter body made of a material such as ceramic fiber constituting a filter is formed from a wire mesh, a porous metal plate or the like from both sides thereof. Between metal members
The metal members on both sides of the filter body are constituted by electrodes, and high frequency and high voltage are applied between the electrodes to generate plasma, and particulate matter such as fine particles collected by the filter using plasma energy, that is, SPM. Particulate filter device, DP
F device.

The present invention relates to a casing incorporated in an exhaust pipe through which exhaust gas from an engine is discharged, a ceramic filter arranged in the casing to collect particulate matter contained in the exhaust gas, and the filter. A high-frequency intermittent current is intermittently applied at a high voltage between the upstream electrode and the downstream electrode, which are electrically insulated from each other, and between the upstream electrode and the downstream electrode. The present invention relates to an exhaust gas purifying apparatus comprising a plasma generator for generating plasma between the upstream electrode and the downstream electrode, and reacting and extinguishing the particulate matter collected by the filter with the plasma. .

The filter body has a laminated structure in which non-conductive ceramic fiber materials are randomly laminated.

The metal member constituting the electrode is coated insulatively by ceramic coating or enamelling to prevent the particulate matter collected by the filter from being energized.

The metal member constituting the electrode is formed from a wire mesh or a metal perforated plate. When the electrode is formed of a wire mesh, the wire mesh is stacked such that a vertical line and a horizontal line intersect, and the vertical line and the horizontal line are stacked so that a voltage difference does not occur between the vertical line and the horizontal line. They are connected alternately at a part of the intersection with the horizontal line.

The filter body is formed into a circular filter as a whole by folding a laminated fiber filter into a fold, and the exhaust gas is sent from the outer peripheral side to the inner peripheral side of the circular filter.

The power generated by a generator provided in the engine is used as a power source for generating a high voltage at a high frequency applied to the upstream electrode and the downstream electrode by the plasma generator.

In the plasma generator, the voltage from the AC generator is boosted by a transformer, the boosted high voltage is rectified by a rectifier coil, and the rectified high voltage is turned on by an RF signal from a RF oscillator. And turning off to generate an alternating high-frequency high voltage, and applying the high-frequency high voltage between the upstream electrode and the downstream electrode to generate plasma.

The engine incorporating this DPF device is:
NO by delaying fuel injection timing _XThe occurrence of
And controls to increase the generation of HC.
In addition, the DPF device has a configuration in which the
NO in Zuma_XAnd HC react with NO_XReduce the occurrence of
Is to reduce.

The plasma generator is applied to the electrodes to generate plasma when the engine load is a partial load and when the cooling water temperature is low immediately after starting, and the plasma energy promotes the extinction of the particulate matter by the plasma energy. N
The reaction of O _X and HC is promoted, it is to reduce the generation of NO _X.

Since this DPF device is constructed as described above, a high-frequency intermittent high voltage is applied between the electrodes of the metal members on both sides of the filter body, and a plasma state is continuously generated between the electrodes. The particulate matter (SPM) of fine particles existing between the electrodes collected by the plasma is turned into a radical (free radical, free radical) state by the plasma energy, and the particulate matter is converted into electrons e ⁻ ,
e ⁺ is released, HC changes to H ₂ O and CO ₂ , and C becomes C
As it changes to O ₂ , some of the particulate matter is ignited, burned, and incinerated.

For example, when a wire mesh is formed as a heater, heat in the wire mesh propagates, ignites SPM and black carbon, and burns particulate matter. However, as in the present invention, the wire mesh is formed as an electrode. When the plasma is generated, the vibration caused by the mixture of the positive and negative ions gives energy to the SPM and reacts, so that the start of the reaction of the particulate matter surely occurs. Once the particulate matter is in a radical state, it reacts with O ₂ in the exhaust gas, so that C is oxidized and HC is also oxidized. In this state, C, H
C, and NO _X coexist, the following reaction occurs. 2NO + CH → N ₂ + H ₂ O + CO 2CO + O ₂ → 2CO ₂ As described above, in other words, NO is reduced. Since the above plasma state occurs between wire meshes,
The power density is more concentrated than the metal plate, and the plasma energy increases. Also, once ignited, the SPM layer is transferred to the adjacent SPM layer, and all the particulate matter is incinerated.

In order to increase the voltage of the plasma power, AC
If the winding ratio is set to about 75 to 150 for the current from the stator coil wound in series so as to increase the voltage of the generator, a voltage of 5 to 30 KVA can be applied between both wire nets. The high voltage power may be loaded as it is.
The alternating current is once rectified, and the power transistor is turned on / off by the on / off signal oscillated by the crystal oscillator, thereby producing a high-voltage intermittent current. Here, the frequency is about 1 MH _Z.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a DPF device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory view showing one embodiment of a DPF device according to the present invention, FIG. 2 is a schematic circuit diagram showing a plasma generator provided in the DPF device of FIG. 1, and FIG. , FIG. 4 is an enlarged explanatory view of a region denoted by reference numeral I of the filter in FIG. 3, FIG. 5 is a circuit diagram showing a high-frequency oscillator in the plasma generator of FIG. 2, and FIG. FIG. 3 is a circuit diagram showing an interrupter in the generator.

This diesel particulate filter device (hereinafter, referred to as DPF device) is incorporated in an exhaust pipe 51 for discharging exhaust gas from a combustion chamber constituting an engine, and a particulate matter (hereinafter, referred to as DPF) contained in the exhaust gas. SPM) is collected by the filter 3 and the filter 3
The SPM collected by the plasma is caused to react with O ₂ in the exhaust gas by plasma generated by the plasma generator 1 to be extinguished, and a part of the SPM is ignited and burned to be incinerated to purify the exhaust gas. The filter 3 is a casing 2
Is supported by the support bar 52 on the inlet 12 side, and the outlet 1
The three sides are supported by a shielding plate 17 provided with a through hole 53 in the central part closing the filter end.

The filter 3 is disposed so as to form an upstream exhaust gas passage 14 and a downstream exhaust gas passage 15 in the casing 2 incorporated in the exhaust pipe 51. As shown in FIG. 3, the filter 3 is formed as an annular filter as a whole by laminating a laminated fiber filter folded in a fold shape, the upstream end surface of the filter 3 is closed by a shielding plate 16, and the downstream side is formed in a central portion. The downstream end face of the filter is closed by the shielding plate 17 in a state where the passage 53 is aligned with the downstream exhaust gas passage 15 thus formed. Therefore, the exhaust pipe 5
The exhaust gas flowing through the filter 1 passes through the filter 3 through the passage between the inlet 12 and the support bar 52 and the upstream exhaust gas passage 14 on the outer periphery of the filter 3 to the downstream exhaust gas passage 15 on the inner periphery. It is discharged and then discharged from the outlet 13 to the exhaust pipe 51. When the exhaust gas discharged from the engine passes through the filter 3, the SPM such as carbon, smoke, HC, and SO _X contained in the exhaust gas in the filter 3 is generated.
Is collected.

When the exhaust gas flows through the filter 3, the controller 10 receives the SP from the pressure sensor 9 provided on the upstream side of the filter 3 and the pressure sensor 11 provided on the downstream side.
Control for adjusting the state of plasma generation by the plasma generator 1 in response to the trapping state of M and the operating state of the engine from the rotation sensor 18 and the load sensor 19, to extinguish the reaction of SPM and ignite and burn to incinerate. do.

As shown in FIG. 4, for example, the filter 3 includes a filter body 5 formed of a felt material in which non-conductive ceramic fibers excellent in heat resistance and corrosion resistance are laminated at random, and a filter body 5. And wire meshes 4 and 6 containing heat-resistant and corrosion-resistant Ni, Cr and the like, which are fixed by sandwiching both sides thereof. As shown in FIG. 3, the filter 3 is formed in a predetermined shape of a pleated cylindrical shape as a whole, and is formed in a shape having a large surface area. At this time, an insulating material 66 is interposed between the wire mesh 6 and the adjacent wire mesh 6 as shown in FIG. 4 so that the wire mesh 6 and the adjacent wire mesh 6 are not short-circuited. The filter 3 may be formed in a cylindrical shape such as a cylindrical shape, a flat plate shape, a wavy shape, or the like, in addition to the above-mentioned pleated cylindrical shape. The material constituting the filter 3 is, for example, Si ₃ N ₄ coated with SiC and / or SiC (Si—CO, Si—Ti—CO, Si—
C) is formed of a non-woven fabric in which ceramic fibers and / or fibers obtained by coating carbon or alumina with SiC are laminated at random, and the fiber diameter of the ceramic fibers is, for example, 5 to 5.
The length is about 15 μm and the length is about 30 to 150 mm. The ceramic fiber material laminated in a felt shape is formed, for example, to have a thickness of about 3 to 5 mm.

In this DPF device, the metal members constituting the electrodes are formed of wire meshes 4, 6 or metal porous plates (not shown). In this DPF device, an upstream wire netting 4 which forms an electrode in contact with the upstream side surface of the filter body 5 of the exhaust gas flow, and a downstream wire mesh 6 which forms an electrode in contact with the downstream side surface are arranged. The wire mesh 6 is electrically insulated and a high-frequency current is intermittently applied at a high voltage to generate plasma between the upstream electrode and the downstream electrode, and the plasma is collected in the filter 3 by the plasma. The SPM reacts and is ignited and burned to be extinguished.

The wire nettings 4 and 6 constituting the electrodes are coated insulatively by ceramic coating or enamelling treatment to prevent the particulate matter collected by the filter 3 from being energized. In addition, wire mesh 4,
Numerals 6 are stacked such that the vertical and horizontal lines intersect, and are alternately connected at a part of the intersection of the vertical and horizontal lines so that no voltage difference occurs between the vertical and horizontal lines. By configuring the electrodes in wire meshes 4, 6, the plasma generation area is increased,
Plasma generation can be promoted. Due to the generation of plasma, the particulate matter emits electrons e ⁻ and e ⁺ , the hydrocarbon HC in the exhaust gas changes to H ₂ O and CO ₂ , and the carbon C in the exhaust gas changes to CO _2. Some of the particulate matter is ignited, burned and incinerated.

The plasma generating apparatus 1 generates plasma by, for example, a plasma generating circuit shown in FIG. 2, and the upstream wire mesh 4 uses a high-frequency oscillator 20 having a power source, that is, a battery 28, and an interrupter 21 to generate an AC generator. 24
Is connected to the alternator 24 through the line 7 so that the high voltage generated from the
Are connected to ground 25 through line 8. The voltage generated by the AC generator 24 is boosted to a predetermined high voltage by the transformer 23 and rectified by the rectifier coil 22.
Next, the interrupter 21 is controlled by the output of the high-frequency oscillator 20, and a high-frequency, high-voltage controlled by the interrupter 21 is applied between the upstream wire mesh 4 and the downstream wire mesh 6. Plasma is generated in a region of the filter body 5 between the downstream wire mesh 6 and the filter. As the alternator 24,
For example, the plasma generator 1 is composed of two types of low-power-side generators and high-power-side generators in which the number of windings of the winding wound around the stator core is changed to be large or small. For example, see Japanese Patent Application No. 2000-113915, which is an application of the present applicant.

The high frequency oscillator 20 oscillates a high frequency by, for example, a high frequency oscillation circuit shown in FIG. 5. The voltage from the battery 28 is adjusted by a variable resistor 35, and the voltage is passed through an RC circuit 29. A base voltage is input to the base of the transistor 26 through the crystal oscillator 27. When a base voltage is input to the base of the transistor 26, the current from the battery 28 passes through the transistor 26, and a high frequency signal is transmitted from the capacitor 33 as an output 34 from the terminal. In the high frequency oscillation circuit shown in FIG. 5, reference numerals 30, 31, and 32 denote capacitors, reference numeral 37 denotes a capacitor with a diode, and reference numerals 38, 3
9 and 40 are resistors.

An interrupter 21 for interrupting and controlling the high frequency generated by the high frequency oscillator 20 is formed, for example, in a high frequency interrupting circuit shown in FIG. In the high-frequency interrupting circuit, a current from a power source, that is, a battery 36 is output from a terminal through a transistor 41. The signal of the output 34 transmitted from the high-frequency oscillation circuit of the high-frequency oscillator 20 is applied to the input 50 of the high-frequency intermittent circuit, and is input as the base voltage of the transistor 42. The battery 36 is the AC generator 2
4, a transformer 23 and a rectifying coil 22. When the base voltage is input to the transistor 42, the base voltage is input to the transistor 41 and the battery 36
A high voltage from the terminal passes through a transistor 41, and a high-frequency, high-voltage intermittent current is output from a terminal 44. Output 44
Are the upstream wire mesh 4 and the downstream wire mesh 6.
In the high-frequency intermittent circuit shown in FIG. 6, reference numeral 43 denotes a transistor, and reference numerals 45, 46, 47, and 49 denote resistors.
That is, the AC voltage output from the AC generator 24 is adjusted to a high DC voltage by the transformer 23 and the rectifying coil 22,
Next, the high voltage is controlled by the high-frequency output signal controlled by the interrupter 21 and is applied between the upstream wire mesh 4 and the downstream wire mesh 6 to generate plasma.

The upstream electrode 4 is controlled by the plasma generator 1.
As a power source, that is, a battery for generating a high voltage at a high frequency applied to the power supply and the downstream electrode 6, a power generated by a generator provided in the engine is used. The power of the generator is set to a high voltage by the transformer 33 in the plasma generator 1, and the high voltage is rectified by the rectifying coil 22.
An interrupter 21 having power transistors 41, 42, 43 which are turned on / off by a signal transmitted by a signal 0
, An alternating power is applied, and a high voltage at a high frequency is applied to the upstream electrode 4 and the downstream electrode 6 to generate plasma.

Further, the engine incorporating the DPF device, as well to suppress the generation of the NO _X delaying the fuel injection timing, has the property of increasing the generation of HC. This DPF device has electrodes, namely wire mesh 4 and wire mesh 6.
Reacting the NO _X and HC in the plasma generated between the, it is to reduce the generation of NO _X.

The controller 10 generates plasma between the upstream wire mesh 4 and the downstream wire mesh 6 in response to the collection of particulates of a predetermined amount or more in the filter 3, and generates the plasma between the upstream wire mesh 4 and the downstream wire mesh 6. Control is performed so that the particulate matter collected in the filter body 5 between the wire mesh 4 and the downstream wire mesh 6 reacts and disappears, and the filter body 5 is regenerated. The amount of particulates collected in the filter 3 is calculated by the controller 10 by calculating the pressure ratio of the pressure detected by the pressure sensors 9 and 11 for detecting the exhaust gas pressure, or by a sensor or the like for detecting the flow resistance of the filter. Can be detected. When the filter body 5 is regenerated, although not shown, the exhaust gas that has been purified from the downstream side of the filter 3 and that has been released to the atmosphere and has a constant pressure is recirculated to the upstream side by a pump to supply oxygen for regeneration. The particulate matter trapped in the filter 3 can be heated and incinerated by the plasma generated in the upstream wire meshes 4, 6. Further, although not shown, a pair of the DPF devices are arranged side by side to collect particulate matter.
It is also possible to configure so as to switch between a PF device and a DPF device for regeneration.

The controller 10 includes the rotation sensor 1
The amount of particulate matter generated in the exhaust gas generated by the engine changes according to the engine speed detected at 8 and the operating state of the engine load detected by the load sensor 19. The plasma generator 1 is controlled in accordance with the amount and the amount of the collected particulate matter in the filter 3 to control the state of plasma generation, and the particulate matter in the exhaust gas is always satisfactorily extinguished. To play. For example, when the engine load is a partial load or when the temperature of the cooling water immediately after the start is low, the plasma generator 1 applies plasma to the wire meshes 4 and 6 of the electrodes to generate plasma, thereby facilitating the disappearance of the particulate matter, Promotes the oxidation of

[0035]

Since the DPF device according to the present invention is configured as described above, the SPM contained in the exhaust gas discharged from the diesel engine is collected by the filter, and the collected SPM is plasma energy. The filter is used to react and oxidize and extinguish, and is ignited and burned for incineration to regenerate the filter. The plasma generator applies a high voltage at a high frequency between the upstream wire mesh and the downstream wire mesh sandwiching the filter body to generate plasma in a region of the filter body. Therefore, the SPM existing in the region of the filter body between the upstream wire mesh and the downstream wire mesh, particularly the SPM having a small particle size of 0.25 μm or less, is annihilated or ignited by plasma energy, and clean exhaust gas is generated. It can be purified into gas and does not cause environmental pollution, which is detrimental to health.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing one embodiment of a DPF device according to the present invention.

FIG. 2 is a schematic circuit diagram showing a plasma generator provided in the DPF device of FIG.

FIG. 3 is a schematic explanatory view showing a relationship between a filter of a DPF device and a plasma generator.

FIG. 4 is an enlarged explanatory view of a region denoted by reference numeral I of the filter in FIG. 3;

FIG. 5 is a circuit diagram showing a high-frequency oscillator in the plasma generator of FIG.

FIG. 6 is a circuit diagram showing an interrupter in the plasma generator of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generator 2 Casing 3 Filter 4 Upstream wire mesh 5 Filter body 6 Downstream wire mesh 9,11 Pressure sensor 10 Controller 14 Upstream exhaust gas passage 15 Downstream exhaust gas passage 18 Rotation sensor 19 Load sensor 20 High frequency oscillator 21 Intermittent switch Reference Signs List 22 rectifier coil 23 high voltage generating transformer 24 alternator 26, 41, 42, 43 transistor 27 crystal oscillator 28 power supply 34, 44 output 36 power supply 51 exhaust pipe

Claims (10)

[Claims] 1. A casing incorporated in an exhaust pipe through which exhaust gas from an engine is exhausted, a ceramic filter disposed in the casing to collect particulate matter contained in the exhaust gas, and both surfaces of the filter. A high-frequency intermittent current is intermittently applied at a high voltage between the upstream electrode and the downstream electrode, which are electrically insulated from each other, and between the upstream electrode and the downstream electrode. An exhaust gas purifying apparatus, comprising: a plasma generator for generating plasma between a side electrode and the downstream electrode, wherein the plasma removes the particulate matter collected by the filter by the plasma. 2. The DPF device according to claim 1, wherein the filter body is formed in a laminated structure in which non-conductive ceramic fiber materials are randomly laminated. 3. A metal member forming the electrode is insulatively coated by ceramic coating or enamelling treatment to prevent the particulate matter collected by the filter from being energized. The DPF device according to claim 1, wherein: 4. The DPF device according to claim 1, wherein the metal member forming the electrode is formed of a wire mesh or a metal perforated plate. 5. The wire mesh is stacked with a vertical line and a horizontal line intersecting each other, and is formed at an intersection of the vertical line and the horizontal line so that a voltage difference does not occur between the vertical line and the horizontal line. 5. D according to claim 4, characterized in that they are partly connected alternately.
PF device. 6. The filter body according to claim 1, wherein the filter body is formed by folding a laminated fiber filter into a fold shape to form an annular filter as a whole, and the exhaust gas is sent from an outer peripheral side to an inner peripheral side of the annular filter. The DPF device according to claim 1, wherein: 7. A power source for generating a high voltage at a high frequency to be applied to the upstream electrode and the downstream electrode by the plasma generator is power generated by a generator provided in the engine. 2. The method according to claim 1, wherein
2. The DPF device according to 1. 8. The plasma generator includes a transformer for boosting a voltage from an AC generator, rectifying the boosted high voltage with a rectifying coil, and switching the rectified high voltage by a high-frequency signal from a high-frequency oscillator. 2. An alternating high-frequency high voltage is generated by controlling on / off of the high-frequency high voltage, and the high-frequency high voltage is applied between the upstream electrode and the downstream electrode to generate plasma. 2. The DPF device according to 1. 9. together to suppress the generation of the NO _X by delaying the fuel injection timing of the engine, increasing the generation of HC, NO in the plasma generated between said electrodes
Reacting the _X and HC, DPF device according to claim 1, characterized in that to reduce the generation of NO _X. 10. The plasma generator according to claim 1, wherein when the engine load is a partial load and when the temperature of the cooling water immediately after starting is low,
Plasma is generated by applying to said electrode, to accelerate the reaction the disappearance of the particulate material by the plasma energy, DPF device according to claim 1, characterized in that to accelerate the reaction between NO _X and HC.