JP2819850B2 - Filter regeneration device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for regenerating a filter for an internal combustion engine for collecting particulates (particulate matter) contained in exhaust gas discharged from a diesel engine by using microwave energy. It is.

[0002]

2. Description of the Related Art The high economic growth of so-called developed countries such as Europe, the United States and Japan has greatly contributed to civilization on the earth.
However, waste of fossil fuel energy, especially in the economic growth of developed countries, has polluted the Earth's atmosphere.

[0003] With respect to global environmental protection, measures against global warming, that is, measures for reducing CO _{2, have} recently been highlighted, but measures against acid rain that causes deforestation cannot be ignored.

[0004] Acid rain is a natural phenomenon caused by air pollutants such as sulfur oxides and nitrogen oxides as a polluting source.
There is a trend to strengthen stationary sources such as generation and mobile sources such as automobiles. In particular, regulations relating to automobile exhaust gas have been shifted from conventional concentration regulations to total quantity regulations, and the regulation values themselves are about to be significantly reduced.

[0005] Among automobiles, diesel cars are subject to stricter regulations on particulate emissions as well as nitrogen oxides. It is said that it is impossible to achieve the exhaust gas regulation value only by the conventional measures for reducing pollutants in exhaust gas by improving combustion such as delaying fuel injection timing. At present, it is indispensable to provide an exhaust gas aftertreatment device. This post-processing device has a filter for collecting particulates.

However, if particulates continue to be collected, the filter will be clogged and the collection capacity will be significantly reduced, and the flow of exhaust gas will be poor, leading to a decrease in engine output or an engine stop.

[0007] Therefore, although technology development for regenerating the collecting capacity of filters is currently being promoted all over the world, it has not yet been put to practical use.

[0008] It is known that particulates burn at about 600 ° C. As means for generating energy for raising particulates to this high temperature range,
A burner method, an electric heater method, a microwave method, and the like have been considered.

The inventors of the present invention have developed a microwave type filter regenerating apparatus in consideration of good temperature rising efficiency, safety, ease of apparatus configuration, and good regenerative control.

Japanese Patent Application Laid-Open No. 61-11416 discloses a microwave filter regenerating apparatus. FIG. 2 shows an apparatus disclosed in the publication. In the figure, 1 is a diesel engine, 2 is an exhaust pipe of the engine 1, 3 is a filter provided at a part of the exhaust pipe for filtering and collecting particulates contained in exhaust gas, and 4 is a filter for fixedly supporting the filter 3. A heating chamber, 5 is a magnetron which is a microwave generating means, 6 is a radio wave shielding means for limiting a microwave supplied from the microwave generating means to the heating chamber,
7 is a waveguide for transmitting the microwave generated by the microwave generating means to the heating chamber, 8 is an antenna for detecting the voltage of the microwave incident wave to the heating chamber, and a converter for converting the voltage into a control signal. An antenna and a converter for detecting a microwave reflected wave voltage from the room, 10 is a control device, 11 is a muffler, and 12 is a drive power supply for the magnetron 5.

In the above configuration, the exhaust gas of the engine is discharged to the atmosphere through the exhaust pipe 2, the filter 3, and the muffler 11. The filter 3 collects particulates contained in the exhaust gas, but the filter 3 has a finite collection capability as described above. When the collection capacity reaches the limit, the filter needs to be regenerated. Energy for heating the particulates in filter regeneration is supplied from the microwave generation means 5. The filter regeneration is completed through a predetermined process.

When the filter 3 is regenerated, it is necessary to detect what level the filter is at with respect to the trapping limit. Conventional techniques for detecting the amount of particulates collected by this filter include a method for detecting pressure loss of the filter, a method based on positive pressure characteristics on the exhaust gas upstream side of the filter, and integration of the operating state of the engine. In any case, the operation state of the engine is included in the detection system, and the error in the detection level is large, which makes it difficult to put the engine into practical use.

On the other hand, FIG. 2 proposes a method for detecting a trapping level using microwaves. This detection method is considered to have a great feature that can be executed independently of the engine operating state.

[0014]

However, in the above-described conventional trapping level detecting structure, the level can be detected as large as a small amount (for example, about 20 g or more or about 5 g or less). 15g ± 5g
It is difficult to detect the level at which the amount of A was collected. If the trapped amount of particulates is small, the performance of heating and burning the particulates is poor, and the entire filter cannot be efficiently regenerated. On the other hand, when the trapping amount exceeds a certain level, a phenomenon occurs in which the filter is melted by the particulate combustion heat.

Therefore, in order to guarantee high reproduction performance and further ensure the durability of the filter itself, it is necessary to detect the level of the trapping amount with high accuracy. It was difficult to do.

The present invention has been made to solve the above-mentioned problems, and provides an improved particulate trapping amount detecting means utilizing microwaves to assure filter regeneration performance and ensure filter durability performance for a filter regeneration for an internal combustion engine. It is intended to provide a device.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a heating chamber provided in an exhaust pipe for discharging exhaust gas of an internal combustion engine, and a heating chamber contained in the heating chamber and contained in the exhaust gas. A filter for collecting particulates,
The apparatus includes a microwave generating means for generating a microwave for heating the particulates, and an electromagnetic field detecting means for detecting the electromagnetic field strength at at least two places in the heating chamber.

Further, the electromagnetic field detecting means is disposed on substantially the same plane in a direction perpendicular to the flow direction of the exhaust gas.

The microwave generated by the microwave generating means is
The power supply means for supplying the microwave into the heating chamber is the exhaust of the filter.
Provided upstream of the gas, the electromagnetic field detection means
Provided on the downstream side of the

[0020]

According to the present invention, a unique electromagnetic field distribution is generated in the heating chamber when microwaves are supplied to the heating chamber containing the filter. This electromagnetic field distribution changes depending on the amount of particulates collected by the filter. The microwaves present in the filter due to the increase in the trapping amount cause wavelength compression. Therefore, the electromagnetic field distribution in the exhaust gas flow direction changes. When a substantially same plane in the vertical direction is considered for the exhaust gas flow, the electromagnetic field strength varies variously in that plane depending on the amount of trapped particulates.
Even in this plane, there is a distribution of the electromagnetic field strength. In the configuration of the present invention, the electromagnetic field detecting means is arranged at at least two places on this plane, and the change of the electromagnetic field distribution in the exhaust gas flow direction is corrected by a method of comparing the detection signals of the respective electromagnetic field detecting means.

[0021] Further, by the configuration in which the microwave feeding position and the disposing position of the electromagnetic field detecting means are arranged with a filter interposed therebetween,
The microwave energy absorbed by the particulates increases with an increase in the trapping amount, so that the microwave energy amount to the heating chamber space in which the electromagnetic field detecting means is disposed decreases. For this reason, the detection amount detected by the electromagnetic field detection means decreases. That is, the detection amount of the electromagnetic field detecting means increases or decreases following the electromagnetic field change in the exhaust gas flow direction caused by the increase of the trapping amount, but the absolute amount gradually decreases, so that the detection amount is grasped in time series. be able to.

Furthermore, by providing the electromagnetic field detecting means at the places where the electric field generated in the heating chamber is strong and weak when there is no trapping amount, it is possible to take advantage of the fact that each detection signal exhibits a unique change, so that the trapping level can be improved. Accuracy can be further improved.
In the present invention, this is achieved by providing the detection means at an angle of 90 ° on substantially the same plane in the vertical direction to the exhaust gas flow.

With the configuration of the electromagnetic field detecting means of the present invention corresponding to the behavior of the microwave electromagnetic field distribution in the heating chamber as described above, the amount of the particulates collected by the filter can be detected with high accuracy. As a result, particulate combustion can be effectively performed, and high regeneration performance of the filter can be ensured, and durability of the filter can be ensured.

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 13 denotes an exhaust pipe for exhausting exhaust gas of an internal combustion engine, 14 denotes a heating chamber provided in the middle of the exhaust pipe, and 15 denotes a heating chamber which is accommodated in the heating chamber and passes through the exhaust gas while the exhaust gas passes therethrough. , A filter that collects the particulates contained in the heating chamber, 16 is a microwave generating unit that generates a microwave to supply power to the heating chamber, and 17 is an annular ring that is provided around the exhaust pipe to generate the microwave generated by the microwave generating unit. A transmission hole (feeding means) provided in the annular rectangular waveguide for radiating microwaves to the heating chamber 14; and 20, a gas other than exhaust gas is supplied to the heating chamber. Air ducts 21 and 22 which are gas passages to be supplied or sucked
Is a radio wave shielding means having a microwave shielding function for limiting the heating chamber 14, and 23 is a heat insulating material for supporting a filter provided on the outer periphery of the filter 15 in the heating chamber 14.

Reference numerals 24 and 25 denote electromagnetic field detecting means for detecting the microwave electromagnetic field in the heating chamber 14, which is provided on the wall of the heating chamber on the substantially same plane in the direction perpendicular to the exhaust gas flow, and has about 90 on the same plane. It is arranged at an angle of °. The electromagnetic field detecting means is provided at a position between the microwave power supply hole 19 and the filter. In FIG. 1, the microwave power supply hole is provided on the exhaust gas upstream side of the filter, while the electromagnetic field detecting means is provided in the heating chamber on the exhaust gas downstream side of the filter.

The feed hole 19 provided on the E surface (the surface facing the filter) of the annular rectangular waveguide 18 has a slit opening angle of about 180 degrees. In order to efficiently radiate microwaves from the feed hole 19, a post for impedance matching can be provided at an appropriate position in the waveguide.

The basic process for filter regeneration of the apparatus of the present invention is described below. The exhaust gas flow of the internal combustion engine is normally distributed to a filter 15. In this collection cycle, the microwave generating means 16 operates at appropriate time intervals, and in that state, the electromagnetic field detecting means detects the electromagnetic field strength of the heating chamber. Although the processing of the detection signal will be described later, the amount of particulates collected by the filter 15 is detected based on the detection signal. When the amount of trapped particulates reaches a predetermined amount, the exhaust gas flowing through the filter is stopped. In this case, by providing an exhaust pipe branched from the exhaust pipe 13, exhaust gas can be introduced into the branched exhaust pipe.

Thereafter, the filter regeneration process starts. This reproduction control command is issued from a control unit (not shown) to which an electric field detection signal, which is a component of the present apparatus, is input. Based on a command from the control unit, a power source for driving the microwave generation unit 16 is supplied. Thereby, the microwave is applied to the heating chamber 14 containing the filter 15.
And the particulates collected by the filter are heated. At the beginning of the microwave power supply, the gas flowing through the filter is almost completely shut off. As a result, the particulates in the entire area of the filter are efficiently heated toward the combustible temperature area by microwave heating without being cooled by the active gas flow flowing through the filter. However, there is a microwave heating promoting region of particulates due to the microwave heating distribution. In the embodiment of the present invention, the annular region at the radial position facing the power supply means 19 in the filter radial direction (the direction perpendicular to the exhaust gas flow) (the heating promoting region also exists in this region) and the substantially center of the filter The portion becomes this heating promotion region.

When microwave heating proceeds and a predetermined time passes, a gas other than the exhaust gas (normally, air) is supplied from the gas guide passage 20 into the heating chamber. The predetermined time at this time is set to an optimum time according to the amount of microwave energy supplied to the heating chamber, a predetermined trapping amount area, and the like. The gas that is distributed to the filter by this gas supply is supplied through the exhaust pipe 13 through which the exhaust gas flow has flowed, so that the gas is distributed to the filter with a flow distribution substantially similar to the distribution of the exhaust gas flow to the filter. Therefore, the distribution is in accordance with the collection distribution of the particulates. In the structure of the embodiment of the present invention, the trapping amount is the largest at the center of the filter. Therefore, the supplied gas is distributed in the outer peripheral direction of the filter.

The initial flow rate of the gas supplied to the filter is such that, for example, when the temperature of the heated particulates is within the temperature range in which the particulates can be burned, combustion is promoted, but the particulates in the gas flow direction are accelerated. The gas is blown at a gas flow rate that suppresses the expansion of the combustion area.

On the other hand, in the filter region in which the temperature of the particulates has not reached the combustible temperature range, there is a possibility that a region in which the temperature increase is prevented by the supplied gas may occur, but the flow rate of the blown air is extremely small as described above. Therefore, a temperature drop in that region can be almost avoided.

This supply gas promotes combustion if the temperature of the particulate heated by microwaves reaches a combustible temperature range. Therefore, the heat generated by the combustion is added to the heat generated by the microwave heating, so that the heat is transferred inside the filter and the combustible region can be expanded.

Thereafter, the flow rate of the supplied gas is increased, and the combustible region is moved in the longitudinal direction of the filter (the direction in which the gas flows).

Thereafter, at an appropriate time, the flow direction of the supply gas flow is reversed. (A gas supply means (not shown) is operated as a gas suction means.) By this gas flow control, the particulate combustion heat generated in the filter is transferred toward the filter end face on the exhaust gas inflow side of the filter. This heat of combustion supplies heat to the filter end face in excess of heat radiation generated at the filter end face. Due to this amount of heat, the filter end face reaches the temperature at which particulate combustion is possible, and particulate combustion of the filter end face is performed.

When the regeneration of the filter end face on the upstream side of the exhaust gas is completed, the flow direction of the supply gas is reversed again, and the direction of the gas flow flowing through the filter becomes the same as the direction of the exhaust gas flow. This state continues until the complete regeneration of the filter is completed.

In this state, the microwave power supply can be stopped after an appropriate time has elapsed. The stop time is controlled by a predetermined time, but can also be controlled based on a detection signal of the electromagnetic field detecting means.
Thereafter, the gas supply is stopped at an appropriate time. The operation stop of the microwave generation means is executed at the same time as the stop of the gas supply or at an earlier time. However, normally, the entire filter can be completely regenerated by controlling the gas supply for a predetermined period of time after the microwave power supply is stopped.

In the determination of the predetermined time, it is also possible to use means for detecting the degree of regeneration, for example, detection of the combustion exhaust heat temperature downstream of the filter, detection of the filter pressure loss, and the like.

The regeneration of the filter is completed by the above regeneration control process. Thereafter, at an appropriate time, the exhaust gas can flow into the regenerated filter.

In the regeneration cycle, the flow direction of the gas flowing through the filter can be controlled only in one direction by taking the following measures. One of the means is, for example, to provide an anti-radiation body close to or in contact with the end face on the exhaust gas inflow side of the filter. The radiation preventing member may be a member separate from the filter or a member integrally formed with the filter, but is constituted by a structure having almost no filtering effect.

Next, detection contents of the electromagnetic field detecting means of the present invention and signal processing thereof will be described. When microwaves are supplied to the heating chamber, a unique electromagnetic field distribution is generated in the heating chamber in accordance with the amount of particulates collected by the filter. One of them is that the wavelength of the microwave generated inside the filter is compressed as the trapping amount increases. Due to this wavelength compression, the electromagnetic field distribution in the exhaust gas flow direction of the heating chamber changes. When considering the substantially same plane in the vertical direction to the exhaust gas flow,
In that plane, the electromagnetic field intensity increases or decreases as the amount of particulates increases. The second characteristic of the electromagnetic field distribution generated in the heating chamber is that the microwave energy radiated from the microwave feed hole is absorbed by the particulates with the increase in the amount of particulates, so that the opposite side of the filter This means that the intensity of the electromagnetic field in the heating chamber space (the space in which the electromagnetic field detecting means is disposed in the embodiment) gradually decreases. In addition, the distribution of the electromagnetic field intensity is generated even on the substantially same plane perpendicular to the exhaust gas flow due to the heating chamber configuration, the microwave power supply configuration, the distribution of the particulates collected by the filter, and the like. In this plane, electromagnetic field detecting means are provided at places where the electric field strength is strong and where the electric field strength is weak. In one embodiment of the present invention, the feed hole 19 is provided on the E-plane of the annular waveguide as a slit structure, and the slit angle is set to approximately 180 °. In the case of such a power supply configuration, the electric field intensity is high in the region facing both ends of the slit, and the electric field intensity is low in the central portion of the slit. Therefore, in the case of the embodiment, the electromagnetic field detecting means is disposed on substantially the same plane in the direction perpendicular to the exhaust gas flow at an angle of about 90 ° corresponding to such an electric field intensity distribution.

As the amount of particulates increases, the electromagnetic field detecting means gradually decreases in time while the amount of detection increases and decreases. This change in the detected amount is larger in the electric field detecting means placed in the region where the electric field intensity is strong. The control unit to which the detection signal of each electromagnetic field detection unit is input calculates the difference between each electromagnetic field detection signal. When the amount of collected particulates becomes infinite, the difference between the detection signals becomes almost zero as can be understood from the above description. (In fact, the amount of microwave energy input to the heating chamber also decreases.) The amount of trapped particulates can be detected with high accuracy by such a difference between the detection signals. Further, a difference between the electromagnetic field detection signals predetermined as a condition for determining the start of the filter regeneration is stored in the control unit. Accurate regeneration detection of the filter can be efficiently performed by accurate detection of the trapping amount, and generation of cracks and erosion in the filter can be avoided.

The cycle of performing the electromagnetic field detection may be performed at predetermined intervals, but it is more preferable to shorten the detection cycle with an increase in the amount of trapped particulates. By varying the detection cycle, the regeneration performance in the filter regeneration process can be more sufficiently ensured.

In the embodiment, two electromagnetic field detecting means are shown. However, the number of detecting portions can be increased in accordance with the structure of the heating chamber or the structure of the microwave feeding section.

[0045]

As described above, according to the filter regeneration device for an internal combustion engine of the present invention, the following effects can be obtained. (1) The amount of trapped particulates can be detected with high accuracy by detecting the electromagnetic field intensity at at least two places in the heating chamber. (2) Since the electromagnetic field detecting means is provided on substantially the same plane perpendicular to the flow direction of the exhaust gas flow, the electromagnetic field change in the heating chamber, particularly in the exhaust gas flow direction, corresponding to the increase in the amount of particulates Can be corrected, and the trapping amount can be detected with high accuracy. (3) The configuration in which the microwave feeding position and the electromagnetic field detection position are arranged with a filter interposed therebetween allows the electromagnetic field detection amount to be time-sequentially utilizing the increase in the amount of microwave absorption of the particulate due to the increase in the particulate. Since the amount can be gradually reduced, the trapping amount can be detected based on the absolute value of the detection signal. (4) With the configuration in which the electromagnetic field detecting means is provided on the exhaust gas downstream side of the filter, it is possible to prevent particulates and soot contained in the exhaust gas of the internal combustion engine from adhering to the electromagnetic field detecting means,
The performance of the detection means can be maintained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a filter regeneration device for an internal combustion engine showing one embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional filter regeneration device for an internal combustion engine.

[Explanation of symbols]

 13 exhaust pipe 14 heating chamber 15 filter 16 microwave generating means 24 electromagnetic field detecting means 25 electromagnetic field detecting means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-301118 (JP, A) JP-A-61-141616 (JP, A) JP-A-1-290910 (JP, A) JP-A-61-1 19916 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F01N 3/02 321

Claims (3)

(57) [Claims] 1. A heating chamber provided in an exhaust pipe for exhausting exhaust gas of an internal combustion engine, a filter housed in the heating chamber for collecting particulates contained in the exhaust gas, and heating the particulates A filter regeneration device for an internal combustion engine, comprising: a microwave generating means for generating microwaves; and electromagnetic field detecting means for detecting at least two electromagnetic field strengths in the heating chamber. 2. The filter regeneration device for an internal combustion engine according to claim 1, wherein said electromagnetic field detection means is disposed on substantially the same plane perpendicular to the flow direction of the exhaust gas. 3. A microwave generated by a microwave generating means.
The power supply means for supplying power to the heating chamber is on the exhaust gas of the filter.
Provided on the flow side, the electromagnetic field detecting means is located downstream of the exhaust gas of the filter.
2. The filter regeneration device for an internal combustion engine according to claim 1, wherein the filter regeneration device is provided on the side .