JP2792397B2 - 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 which collects particulates (substances on particles) contained in exhaust gas discharged from a diesel engine.

[0002]

2. Description of the Related Art 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.

[0003] Acid rain is a natural phenomenon caused by air pollutants such as sulfur oxides and nitrogen oxides as a polluting source.
There is a movement to be strengthened for fixed 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.

[0004] Among automobiles, diesel vehicles are subject to stricter regulations on particulate emissions as well as nitrogen oxides. It is said that it is impossible to achieve exhaust gas regulation values only by conventional measures to reduce pollutants in exhaust gas by improving combustion such as delaying fuel injection timing, and at present it is essential to install an exhaust gas aftertreatment device . This post-processing device has a filter for collecting particulates.

However, if the collection of particulates is continued, the filter is clogged, the flow of exhaust gas is deteriorated, and the engine output is reduced or the engine is stopped.

[0006] Therefore, technology development for regenerating the collection capability of filters is currently being promoted worldwide.
Ensuring durability performance is a major practical issue.

[0007] 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 device in consideration of good temperature rising efficiency, easy configuration of a safety device or good regenerating control.

An example of a microwave filter regenerating apparatus is disclosed in Japanese Patent Laid-Open No. 59-122022. FIG. 4 shows an apparatus disclosed in the publication. In the figure, 1 is an engine, 2 is an exhaust manifold, 3 is an exhaust pipe, 4 is an exhaust branch pipe, 5 is a filter, 6 is a filter 5
, A microwave generating means, 8 a waveguide for guiding the microwave generated by the microwave generating means 7 to the heating chamber 6, 9 a microwave reflecting plate, 10 an air pump,
Reference numeral 11 denotes an air supply path, 12 denotes a drive power source for the microwave generating means 7, 13 denotes a muffler, 14 denotes an air switching valve, and 15 denotes an exhaust gas flow switching valve.

In the above-described configuration, the exhaust gas of the engine is guided to the filter 5 by the exhaust gas flow switching valve 15 or directly discharged to the atmosphere. In the particulate collection cycle, the exhaust gas is guided to the filter 5 and the particulates contained in the exhaust gas are collected by the filter 5, but the collection capability of the filter 5 is limited as described above. When the collecting capacity reaches the limit, the exhaust gas to the exhaust pipe 3 in which the exhaust gas flow switching valve 15 is controlled is shut off, and all of the exhaust gas is exhausted to the atmosphere via the exhaust branch pipe 4. During this time, the regeneration of the filter 5 is performed. In this filter regeneration cycle, the energy for heating the particulates is supplied from the microwave generation means 7 and the air required for combustion is supplied from the air pump 10 at the same time. When the filter regeneration is completed after a predetermined time, the exhaust gas flow switching valve 15 is activated. The exhaust gas is guided to the filter 5 under the control again. This cycle of collection and reproduction is repeated.

[0011]

However, the above-mentioned conventional apparatus has the following problems when heating and removing particulates collected in a filter.

This problem is caused by the particulate ignition region and the direction of combustion. The temperature of the particulate heated by the microwave generation means reaches a combustible temperature level, and the combustion state is increased by the presence of the auxiliary combustion gas. , The amount of heat generated per unit time generated by the burning of the particulates is considerably larger than the amount of heat supplied from the heating means. Therefore, by supplying the combustion heat of the particulate ignition region to the particulate collection region (region that has not yet reached the combustible temperature) adjacent to the ignition region, the region can be easily raised to the combustible temperature level. be able to. However, as a matter of course, the combustion heat can be supplied only to the area downstream of the auxiliary combustion gas. By utilizing the heat generated by the combustion of the particulates themselves, it is possible to reduce the amount of energy supplied from the outside in performing the combustion of the particulates deposited on the entire filter to a relatively small amount. I have. However, when the particulates are heated and burned using the combustion heat itself of such particulates, the temperature control of the combustion becomes almost impossible. In particular, if the amount of particulate matter collected on the filter is large, the filter will be in a combustion state in a temperature range that causes mechanical destruction, or in the worst case, combustion at a high temperature exceeding the heat resistance temperature of the filter substrate. State.

[0013] To summarize the conventional problems caused by these phenomena, the region where the particulate heated by the external energy supply reaches the combustible temperature level is a very limited region of the entire filter (the microwave supply side). However, once combustion starts, this combustion heat is transmitted to the adjacent particulate deposition space that is leeward of the auxiliary gas, and the combustion is expanded by the supply of the auxiliary gas. For this reason, there is a defect that the combustion temperature during the burning of particulates cannot be freely controlled, the transition to high-temperature combustion cannot be prevented, and the filter is mechanically damaged. Had.

At this time, a method of controlling the combustion temperature by suppressing the combustion by reducing the supply of the auxiliary combustion gas may be considered.
At present, a method for controlling the supply of the auxiliary combustion gas for controlling the combustion temperature has not been realized.

The above is the problem when the amount of particulate collection is large. Conversely, when the amount of particulate collection is small, the problem is that the collection is performed by the microwave generation means near the filter end face on the microwave supply side. The heated particulates are heated first, but when the amount of collected particulates is small, the heating part penetrates more inside the filter than when the amount of collected particulates is large. Therefore, a large amount of unburned residue is generated near the filter end surface on the side of the auxiliary combustion gas supply side.

The present invention has been made to solve the above-mentioned problems, and effectively performs heating and burning of particulates, suppresses a high temperature during burning, guarantees high regeneration performance of the filter, and improves durability of the filter. It is an object of the present invention to provide a filter regeneration device for an internal combustion engine and a control method therefor.

[0017]

According to the present invention, there is provided an exhaust pipe for discharging exhaust gas of an internal combustion engine.
A filter housed in the exhaust pipe for collecting particulates contained in the exhaust gas, microwave generating means for supplying microwaves for dielectrically heating the particulates from the intake side or the exhaust side of the filter, and a dielectrically heated particulate. The fuel supply system further includes a combustion assisting means for causing a combustion assisting gas for burning the curate to flow from both the intake side and the exhaust side of the filter, and a control means for controlling the operation of the microwave generation means and the combustion assisting means. Is a filter that allows the auxiliary gas to flow from the non-power supply side of the microwave through the filter to the power supply side of the microwave, and then from the power supply side of the microwave to the non-power supply side of the microwave through the filter. It is controlled so that it is performed once for each reproduction.

[0018]

[0019]

[0020]

[0021]

In the above configuration, as a control method in the case where the amount of collected particulates is large, after the particulates have been subjected to dielectric heating for a predetermined time, first, a supporting gas is passed from the non-power supply side of the microwave to the filter. As a result, the burning of the particulates is started from the vicinity of the filter on the microwave supply side, the particulates in that region are completely burned, and the combustion heat generated at that time is directly radiated to the outside of the filter. Next, the direction of the assisting gas is switched from the microwave power supply side to the filter direction. As a result, the heat inside the filter after the burning of the particulates is transmitted to the filter region where the burning of the particulates is not finished, and the particulates in that portion are ignited promptly. Then, when the burning area of the particulates is appropriately expanded, the direction of the auxiliary combustion gas is switched from the non-power supply side of the microwave to the filter direction. As a result, the heat of combustion of the particulates is radiated to the outside through the filter region where the particulates have been burned, thereby preventing the combustion temperature from increasing. As described above, by switching the direction of the auxiliary combustion gas flowing through the filter at an appropriate time, the particulate combustion collected in the filter can be prevented in a short regeneration time while preventing the particulate combustion temperature from increasing. It can be almost completely burned off.

[0022]

[0023]

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

In FIG. 1, reference numeral 16 denotes an exhaust pipe for exhausting an exhaust gas of an internal combustion engine (diesel engine) 17, reference numeral 18 denotes a heating space provided in the middle of the exhaust pipe 16, and reference numeral 19 denotes an exhaust gas housed in the heating space. A filter having a honeycomb structure for collecting the particulates contained in the exhaust gas while passing through the filter. Reference numeral 20 denotes microwave generating means 21 and 22 for generating microwaves to be supplied to a heating space for dielectrically heating the particulates. Is a linear and annular rectangular waveguide for transmitting the microwave generated by the microwave generating means 20 to the heating space, 23 is a power supply hole for feeding the microwave to the heating space, and 24 is the combustion of the dielectrically heated particulates. Means for supplying a combustion gas containing oxygen that is led to the heating space to promote airflow, and is composed of a blower or a compressor. To have. 25, 26, 27, 28 These are flow guide tubes for the auxiliary gas supplied to the heating space and the gas after the auxiliary combustion.

Reference numeral 29 denotes an exhaust gas switching valve that allows exhaust gas discharged from the internal combustion engine 17 to flow through the filter 19 or to flow through the exhaust branch pipe 30 when the filter 19 is regenerated. 31 is a muffler. 32, 33, 3
Reference numeral 4 denotes an auxiliary gas flow switching valve, which controls the direction of the auxiliary gas flowing through the filter 19 during filter regeneration.
Reference numerals 35 and 36 denote auxiliary combustion gas flow temperature detecting means for detecting the temperature of the auxiliary combustion gas flow which is passed through the filter 19 at the time of regeneration of the filter and which promotes the combustion of particulates, after the passage of the filter. This detection signal is input to the control means 37.

The heating space 18 is provided with microwave shielding means 38, 3 having a punching hole structure or a honeycomb structure.
9, the microwave is substantially confined in the heating space. 40 is the outer periphery of the filter 19 and the filter support tube 41
And is also a heat insulating agent, and also serves as a filter support.

Reference numeral 42 denotes a collection amount detecting means for detecting the amount of particulates collected by the filter 19, which detects the intensity of the microwave electromagnetic field in the heating space 18 and detects the collection amount based on the change amount. I have. This collection amount detecting means 42
Is input to the control means 37. Control means 37
Controls the valves, the microwave generating means 20 and the combustion assisting means 24 to desired operating states when the predetermined collection amount is reached or according to the detected collection amount, and executes the regeneration of the filter 19.

The annular component 22 of the rectangular waveguide comprises the filter 1
The exhaust gas from 9 has a power supply hole 23 (one not shown) provided at the end of the gas discharge pipe 43 at the end. Further, the annular rectangular waveguide has an E-plane T-branch structure, and is configured such that transmission line lengths from the branch portion to each power supply hole are substantially equal. A structure 44 made of a microwave low-loss material that blocks the flow of exhaust gas is provided near the connection between the annular rectangular waveguide and the linear rectangular waveguide.

The exhaust gas discharged from the internal combustion engine 17 flows through the exhaust pipe 16 and flows into the filter 19. The filter 19 is formed of a honeycomb structure of a wall-passing type, and has a function of sucking exhaust gas contaminated in an intake portion, collecting particulates contained in the exhaust gas, and discharging purified air from the exhaust portion. When the amount of particulates collected in the filter 19 increases, the pressure loss of the filter 19 increases, and the load on the engine, which is the internal combustion engine, increases. In the worst case, the engine stops.

Therefore, it is necessary to remove the particulates collected by the filter 19 at an appropriate time. As a means for determining the appropriate timing, other than the microwave electromagnetic field intensity detection method, a filter pressure loss level detection, an integrated value of the operating state of the engine, and the like can be used. The particulates collected in the filter 19 are removed by heating and burning. This process is called filter regeneration.

FIG. 2 shows the state of each valve at the time of particulate collection when exhaust gas flows through the filter 19.
The hatched portion in the filter indicates the accumulation state of the particulate matter collected by the filter 19. Although the electromagnetic field distribution of the microwave in the heating space changes according to the particulate collection amount in the filter, the change amount is detected by the collection amount detecting means 42 to detect the collection amount. When the collection amount reaches a predetermined amount, regeneration of the filter 19 is started.

Next, a first control method of the configuration according to the present invention will be described with reference to FIG. FIG. 3 shows changes in the state of particulate heating, combustion and removal during filter regeneration in the apparatus configuration shown in FIG. 1 and shows the control contents of the auxiliary means in each state.

When the regeneration of the filter 19 is started, each valve is controlled as shown in FIG. That is, the exhaust gas switching valve 29 is controlled so that the exhaust gas is
And the flow of the exhaust gas in the filter 19 is stopped. When the microwave generating means 20 is operated in this state, the particulates on the exhaust gas side in the filter are dielectrically heated by the microwaves supplied from the exhaust side of the filter 19. The time required for the heated particulates to reach the combustible temperature (about 600 ° C.) varies depending on the temperature of the filter, the amount of accumulated particulates, and the like, but the particulates that have reached the combustible temperature are the residual air in the exhaust pipe. To burn slowly. However, in the time required to promote the combustion by supplying the auxiliary combustion gas, the combustion is not sufficiently promoted due to lack of oxygen, and the combustion region does not expand. The area where the particulate reached the combustible temperature was 1/1 of the entire filter.
In the state of about 4, the auxiliary combustion gas flow valve 33 is opened, the auxiliary combustion means 24 is operated, and the auxiliary combustion gas flows from the non-power supply side of the microwave toward the filter 19. The particulate heated by the flow of the auxiliary combustion gas immediately transitions to the combustion state (the area of the painted portion indicates the combustion state in the particulate existence area in FIG. 3A). As a result, the particulates collected near the end face of the filter 19 on the microwave supply side are burned, and the particulate combustion heat is radiated to the outside of the filter 19.

The temperature of the assisting gas flow temperature detecting means 36 detects the temperature of the assisting gas flow which promotes the combustion. Based on the detection signal from the temperature detecting means 36, the control means 37 determines the timing for switching the direction of flow of the auxiliary combustion air in the filter 19. This prevents the particulate combustion heat from excessively dissipating, and promptly ignites the next portion of the particulate unburned region.

Next, in order to expand the combustion region of the particulates, the auxiliary gas flow switching valves 32, 33 and 34 are connected to each other as shown in FIG.
Control is performed as shown in (b), and the auxiliary combustion gas flows through the flow guide tube 25 in the direction from the microwave supply side to the filter 19, and the heat inside the filter 19 after the particulate combustion is completed. It transmits to the unfinished part, ignites the particulate in that part promptly, and enlarges the particulate combustion area. The auxiliary gas is discharged to the atmosphere through the flow guide pipes 17 and 28. Filter 19
The temperature of the auxiliary gas flow after the flow is determined by the auxiliary gas flow temperature detecting means 3.
The control means 37 determines the timing for switching the flow direction of the assisting air in the filter 19 based on the detection signal of the assisting gas flow temperature detecting means 35. This prevents the particulate combustion from increasing in temperature.

If the temperature of the particulate combustion becomes too high, the auxiliary gas flow switching valves 32, 33 and 34 are again activated.
And the direction of the auxiliary gas flow is switched to the end direction of the filter 19 on the microwave feeding side {FIG. 3 (c)}, and the particulate combustion heat is passed through the region of the filter 19 where the particulate combustion has been completed. When the particulate combustion heat has been appropriately dissipated, the combustion assist gas flow switching valves 32, 33, and 34 are switched, and the direction of the combustion assist gas flow is switched to the direction of the filter 19 from the microwave power supply side. {FIG. 3 (d)}.

Further, when the combustion heat of the particulates disappears based on the detection signal of the auxiliary combustion gas temperature means 35, the control means 37 stops the operation of the microwave generation means 20 and the auxiliary combustion means 24 and sets the auxiliary gas flow switching valve. The state is controlled as shown in FIG. 2, and the regeneration of the filter is completed. Thereafter, the exhaust gas immediately flows into the filter 19, and the collection of the particulates can be executed.

As described above, the direction in which the assisting gas flow flows through the filter 19 is switched to an appropriate time in accordance with the particulate combustion treatment based on the detection signals of the assisting gas flow temperature detecting means 35 and 36, so that the supplementary gas flow is compensated. It was possible to avoid raising the particulate combustion temperature over a wide range of the collection amount, to eliminate mechanical damage to the filter, and to assure the durability performance of the filter. Further, since the particulates remaining in the vicinity of the end face of the conventional filter 19 can be removed by burning, the amount of unburned fuel in the filter can be reduced as much as possible, and the exhaust gas flow area of the filter can be sufficiently secured. Performance can be maintained.
This control method is particularly effective when the particulate collection amount is large.

Next, a second control method of the present invention will be described with reference to FIG. This control method is different from the first control method in that the particulate matter deposited on the filter 19 is heated by the microwave generation means 20 and then the auxiliary combustion means 24 is heated.
, And initially, the auxiliary combustion gas flow switching valves 32, 33,
4A is controlled as shown in FIG. 4A, and the auxiliary combustion gas is caused to flow in the direction of the filter 19 from the microwave power supply side. Thereby, the filter 19 on the non-feeding side of the microwave
The particulate combustion is expanded in the direction of the end face of the filter 19, and the particulate combustion heat is accumulated inside the filter 19. The temperature of the auxiliary gas flow after passing through the filter 19 is detected by the auxiliary gas flow temperature detecting means 35, and based on the detection signal of the auxiliary gas flow temperature detecting means 35, the control means 37 controls the flow of the auxiliary gas in the filter 19. Determine when to switch directions,
Where the particulate combustion area is spreading appropriately,
Next, the auxiliary gas flow switching valves 32, 33 and 34 are
Control is performed as shown in (b), and the auxiliary combustion gas is caused to flow from the non-power supply side of the microwave toward the filter 19. The particulate matter collected near the end face of the filter 19 on the microwave feeding side is burned by utilizing the accumulated particulate combustion heat. The subsequent control method is exactly the same as the first control method.

Such a control method is particularly effective when the amount of collected particulates is small, and the particulates collected near the end face of the filter 19 on the power supply side of the microwaves are burned using the particulate combustion heat. This makes it possible to minimize the amount of unburned fuel in the filter 19 and to secure a sufficient exhaust gas flow area of the filter, thereby maintaining the collection performance of the filter.

Further, if the first and second control methods are selectively used according to the particulate collection amount, the range of the reproducible particulate collection amount is further expanded.

The structure of the means for transmitting the microwave to the heating space is not limited to the embodiment of the present invention.
For example, a coaxial transmission line can be used.

Although the above embodiment has been described with respect to the example in which the microwave power supply is provided on the exhaust side of the filter, the same operation and effect can be obtained by providing the microwave on the intake side instead of the exhaust side.

[0044]

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 auxiliary combustion gas flows from the non-power supply side of the microwave in the direction of the filter, thereby releasing the combustion heat of the particulates to the outside through the filter area where the particulates have been burned and burning the inside. Excessive accumulation of heat can be prevented, the combustion temperature can be prevented from increasing, and mechanical destruction of the filter can be prevented. In addition, since particulates collected near the end face of the filter on the power supply side of microwaves can be removed by burning, the amount of unburned fuel in the filter can be reduced as much as possible, and the exhaust gas flow area of the filter can be sufficiently secured. The collection performance can be maintained. Further, by switching the direction of the auxiliary combustion gas from the microwave power supply side to the filter direction immediately after flowing the auxiliary combustion gas from the non-power supply side to the filter direction, the heat in the filter area where the particulate combustion has been completed is transferred to the particulate matter. It can be moved to a region where combustion has not been completed, and the time required for ignition, that is, the filter regeneration time can be reduced.

[0046]

[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 state diagram of each valve during particulate collection in the apparatus of FIG. 1;

FIG. 3 is a diagram illustrating a first control method and a combustion state transition diagram at the time of filter regeneration in the apparatus of FIG. 1;

FIG. 4 is a second control method and a combustion state transition diagram at the time of filter regeneration in the apparatus of FIG. 1;

FIG. 5 is a configuration diagram of a conventional filter regeneration device for an internal combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 16 Exhaust pipe 17 Internal combustion engine 19 Filter 20 Microwave generation means 23 Power supply hole 24 Burning means 35, 36 Burning gas flow temperature detecting means 37 Control means 42 Collection amount detecting means

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yasuyuki Motozuka 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-4-203309 (JP, A) JP-A-4-301125 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 3/02 301 -341

Claims (1)

(57) [Claims] An exhaust pipe for exhausting exhaust gas of an internal combustion engine,
A filter that is contained in the exhaust pipe and collects particulates contained in the exhaust gas, a microwave generating unit that supplies a microwave for dielectrically heating the particulates from an intake side or an exhaust side of the filter, and The filter includes a combustion assisting means for causing a combustion assisting gas for burning the dielectrically heated particulates to flow in both directions from an intake side and an exhaust side of the filter, and a control means for controlling operations of the microwave generation means and the combustion assistance means. At the start of the supply of the auxiliary gas, the control means allows the auxiliary gas to flow from the non-power supply side of the microwave through the filter to the power supply side of the microwave, and then passes through the filter on the power supply side of the microwave to transmit the micro gas. An internal combustion engine filter regeneration device that controls an operation of flowing a wave to a non-feeding side at least once for each filter regeneration.