JP2785659B2 - 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 that collects particulates (particulate matter) contained in exhaust gas discharged from a diesel engine.

[0002]

2. Description of the Related Art The high economic growth of so-called industrialized nations such as Europe, North America and Japan has greatly contributed to civilization on the earth. However, the waste of fossil fuel energy, mainly 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 CO2, have been greatly highlighted today, but measures against acid rain that causes deforestation cannot be ignored. Acid rain is a natural phenomenon that occurs as a source of air pollutants such as sulfur oxides and nitrogen oxides.In recent years, regulations on the emission of such air pollutants have been imposed on fixed and mobile sources such as cogeneration in many countries around the world. There is a move to be strengthened. In particular, regulations on exhaust gas from automobiles have been shifted from conventional concentration limits to total volume regulations, and the regulatory values themselves are about to be significantly reduced.

[0004] Among automobiles, diesel vehicles are about to be regulated for emission of particulates at the same time as nitrogen oxides. It is considered impossible to achieve the exhaust gas regulation value only by conventional measures for reducing pollutants in exhaust gas by improving combustion such as delaying fuel injection timing. At present, it is indispensable to provide a post-treatment device for exhaust gas. This post-processing device has a filter for collecting particulates.

However, if particulates continue to be collected, the filter is clogged and the pressure loss increases, and the flow of exhaust gas deteriorates, leading to a decrease in engine output or an engine stop.

[0006] Accordingly, technology development for regenerating the collection capacity of filters is currently being promoted worldwide.
It is not yet practical.

[0007] It is known that particulates burn at about 600 ° C. A burner method, an electric heater method, a microwave method, and the like are considered as means for generating energy for raising the particulates to the high temperature range.

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

An example of a microwave filter regenerating apparatus is disclosed in Japanese Patent Laid-Open No. 59-122022. FIG. 3 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 heating chamber containing the filter 5, 7 is a microwave generating means, and 8 is a microwave generator. A waveguide for guiding the microwave generated by the means 7 to the heating chamber 6, 9 a microwave reflecting plate, 10 an air pump, 11 an air supply path, 12 a driving power source for the microwave generating means 7, 13 a muffler, 14 is an air switching valve, and 15 is an exhaust gas flow switching valve.

In the above configuration, the exhaust gas of the engine is filtered by the exhaust gas flow switching valve 15.
Or is directly discharged to the atmosphere. Exhaust gas is collected by the filter 5 in the particulate collection cycle, but the filter 5 has a finite collection capability as described above. When the trapping capacity reaches the limit, the exhaust gas flow switching valve 15 is controlled, the exhaust gas to the exhaust pipe 3 is shut off, and all of the exhaust gas is exhausted to the atmosphere via the exhaust pipe branch pipe 4. During this time, the regeneration of the filter 5 is performed. In this filter regeneration cycle, energy for heating the particulates is supplied from the microwave generation means 7 and air required for combustion is supplied from the air pump 10 at the same time. When the regeneration of the filter is completed after a predetermined time, the exhaust gas flow switching valve 15 is controlled again, and the exhaust gas is led to the filter 5. This cycle of collection and regeneration is repeated.

[0011]

However, the filter regeneration control by the above-mentioned conventional apparatus has the following problems because the regeneration control is constant even when the amount of trapped particulates is large.

First, since the supply start time of the gas for accelerating the burning of the particulates is constant regardless of the amount of trapping, the heating rate of the particulates by the microwave increases as the trapping quantity increases. As a result, the particulates become excessively heated, and the particulates are rapidly ignited. As a result, the temperature gradient becomes steep in the first half of the regeneration of the filter, and the filter may be damaged by thermal stress.

Next, since the gas supply amount is constant irrespective of the trapping amount, the burning of the particulates proceeds rapidly, the combustion temperature rises, and the temperature of the filter rises more than necessary.
For this reason, there is a risk that the filter will be damaged by damage due to thermal stress caused by erosion and a large temperature gradient.

Next, another problem is caused by the fact that the total amount of supplied microwaves is constant irrespective of the collected amount. Here, the heat of the particulate combustion during the regeneration of the filter and the heating energy of the microwave (the filter itself is also heated by the microwave when the temperature of the filter exceeds about 400 ° C.) raises the temperature of the filter. Therefore, as the trapping amount increases, the heat generation energy of the particulates increases, and the filter temperature during regeneration increases.

If the amount of gas supplied to promote particulate combustion is reduced, the temperature of the filter can be suppressed to some extent even when the amount of trapped gas is large. In the vicinity of the filter end face on the downstream side of regeneration, the end face of the filter is in an open state, so the radiation from the same face causes a large amount of radiation and the temperature drops, and the total heat generation of the particulates decreases. There is a problem that it becomes difficult to maintain the burning of particulates even when the amount of trapped gas is large.

When the gas supply amount is constant irrespective of the trapping amount, as the trapping amount increases, the burning transfer speed of the particulates to the downstream side of the regeneration decreases. This is because when the trapping amount increases, oxygen is consumed more on the upstream side of the regeneration, and oxygen on the downstream side of the regeneration tends to be depleted. For this reason, when the gas supply amount is constant irrespective of the trapping amount (increase in the gas supply amount is not preferable because the burning of the particulates rapidly proceeds and the temperature of the filter becomes high, which is not desirable). Becomes longer as the collection amount increases. Conventionally, the microwave stop time is constant irrespective of the trapping amount, so when the trapping amount is large, the supply of microwaves stops during particulate combustion, the burning particulates suddenly misfire, and a large amount of This produces unburned residue.

Furthermore, since the operation stop time of the gas supply means is constant irrespective of the trapping amount, when the trapping amount is large, it takes a long time to burn the particulates, and the filter is not sufficiently cooled by the gas. If the exhaust gas flows into the filter in this state, the filter is rapidly cooled, and there is a risk of thermal shock destruction.

The present invention has been made to solve the above-mentioned problems, and it is possible to prevent a high filter temperature and a steep temperature gradient during regeneration while maintaining high particulate regeneration efficiency over a wide range of trapping amounts. It is an object of the present invention to provide a filter regeneration device for an internal combustion engine including regeneration control means for suppressing mechanical damage.

[0019]

According to the present invention, there is provided a filter for collecting particulates contained in exhaust gas of an internal combustion engine, and a micro-cell for dielectrically heating the particulates collected by the filter. Microwave supply means for supplying a wave, gas supply means for promoting combustion of the dielectrically heated particulates, and a trapping amount detecting means for detecting the amount of the particulates collected by the filter,
A control unit that controls the operation of the microwave supply unit and the gas supply unit, wherein the control unit starts operation of the gas supply unit.
The time is controlled so that it becomes faster as the collection amount increases.
You.

Further, the control means controls the gas supply amount to be reduced during the regeneration period so that the time at which the gas supply amount is reduced becomes earlier as the trapping amount increases.

Further, the control means reduces the microwave supply amount during the reproduction period, and controls the reduced microwave supply amount so as to decrease as the trapping amount increases.

Further, the time at which the microwave supply amount is reduced is controlled so as to be earlier as the trapping amount increases.

The control means controls the gas supply amount to be increased during the regeneration period, and the time at which the gas supply amount is increased is delayed as the trapping amount increases.

Further, the operation stop time of the microwave supply means is controlled to be delayed as the trapping amount increases.

Further, the operation stop time of the gas supply means is controlled so as to be delayed as the trapping amount increases.

[0026]

According to the above construction, the particulates collected by the filter are heated and heated to an appropriate temperature by the microwave. When the appropriate heating temperature (about 600 ° C.) is reached, a gas (which may be natural air) that promotes the burning of particulates is supplied to the filter. The combustion of the particulates is promoted by the gas, and the combustion area of the particulates is expanded in the gas flow direction by the heat transfer of the filter and the transport of the particulate combustion heat by the gas. Here, by controlling the operation start time of the gas supply means so as to be earlier as the trapping amount increases, the rapid ignition of the particulates due to excessive heating of the particulates is suppressed, and the temperature gradient inside the filter is sharp. Can be suppressed.

By reducing the gas supply amount during the regeneration period, the burning reaction speed of the particulates can be suppressed, and the combustion temperature can be prevented from increasing. As described above, when the trapping amount is large, the heating rate of the particulates increases, and the temperature reaches the ignitable temperature in a short time. By controlling, it is possible to suppress an increase in the filter temperature in the first half of the regeneration.

As described above, the temperature of the filter rises due to the heat generated by the particulate combustion and the heating energy of the microwave. However, the amount of the supplied microwave is reduced during the regeneration, and the reduced amount of the supplied microwave is collected. By controlling so that as the number increases,
Although the heat generated by the burning of the particulates increases as the trapping amount increases, the heating energy by the microwave can be suppressed correspondingly, and the temperature of the filter can be prevented from becoming higher than necessary.

Further, by controlling the time at which the microwave supply amount is reduced so as to be earlier as the trapping amount increases, the heating energy of the particulates is suppressed to an appropriate amount.
Unnecessarily high temperature of the filter can be suppressed.

Further, the gas supply amount is kept low until the latter half of the regeneration to suppress a rise in the combustion temperature and the gas supply amount is increased after the latter half of the regeneration, so that heat is transferred from the upstream side of the regeneration and the filter end face on the downstream side of the regeneration. Combustion is continued while the temperature of the particulates accumulated in the vicinity is maintained at a temperature equal to or higher than the combustible temperature, and the unburned portion at that portion can be reduced.

As described above, when the gas supply amount is constant irrespective of the trapping amount, as the trapping amount increases, the burning transfer speed of the particulates to the downstream side of the regeneration decreases. When the time at which the gas supply amount is increased is also constant, the unburned portion of the particulates at that time has a wider range when the trapping amount is large. When the gas supply amount is increased in this state, a wide range of unburned portions burns in a short time, a large amount of combustion heat is carried by the gas to the downstream side of the regeneration, and the temperature of the downstream side becomes high. Therefore, by controlling the time at which the gas supply amount is increased so as to be delayed as the trapping amount increases, most (about ／) of the particulates are burned in a state where the gas supply amount is small, and then the air is cooled. Since the supply amount is increased, the unburned particulates accumulated near the filter end face on the downstream side of the regeneration can be reduced, and the temperature on the downstream side of the regeneration can be prevented from increasing.

As described above, when the gas supply amount is constant irrespective of the trapping amount, as the trapping amount increases, the burning transfer speed of the particulates to the downstream side of the regeneration decreases, and the time required for regeneration increases. . Therefore, by controlling the operation stop time of the microwave supply means to be delayed as the trapping amount increases, the supply of the microwave is stopped in a state where the burning of the particulates is completed, and the particulates in the downstream portion of the regeneration are stopped. The unburned portion can be reduced.

Further, by controlling the operation stop time of the gas supply means so as to be delayed as the trapping amount increases,
After the cooling of the filter is completed (preferably at 400 ° C. or less), the gas supply is stopped, and the filter can be prevented from being rapidly cooled by the exhaust gas, thereby preventing the filter from cracking.

[0034]

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

In FIG. 1, reference numeral 21 denotes an exhaust pipe A for discharging exhaust gas of the internal combustion engine, which is connected to an internal combustion engine (not shown). 22 is a filter storage pipe provided in the middle of the exhaust pipe,
Reference numeral 23 denotes a filter which is stored in the filter storage tube 22 and collects particulates contained in the exhaust gas when the exhaust gas passes therethrough. Reference numeral 24 denotes a filter which injects microwaves into a space including the filter 23 for dielectrically heating the particulates. Microwave supply means for supplying; 25, a waveguide for transmitting microwaves generated by the microwave generation means; 26, a filter 23;
Feed holes for feeding microwaves to the space containing
Is a microwave shielding means constituted by a punching plate or the like for shielding microwaves. Reference numeral 29 denotes gas supply means for supplying a gas (such as air) containing oxygen to burn the particulates, and reference numeral 30 denotes an exhaust pipe for discharging the exhaust gas from which the particulates are collected by the filter 23 to the atmosphere. B. Reference numeral 31 denotes a valve A which is controlled so as to be opened during collection of particulates and closed during regeneration. 32 is an exhaust pipe C for discharging combustion exhaust gas at the time of regeneration,
Reference numeral 33 denotes a valve B which is controlled so as to be closed at the time of collecting particulates and open at the time of regeneration. 34 is a microwave supply means 24, an air supply means 29, a valve A3
1. Control means for controlling the operation of the valve B33. 3
Reference numeral 5 denotes a trapping amount detecting means for detecting the amount of microwaves and detecting the trapping amount of particulates, and the detection information is sent to the control means 34.

In the above configuration, when collecting particulates, the valve A31 is open and the valve B33 is closed, and the exhaust gas of the internal combustion engine flows into the exhaust pipe A21 into the flow filter 23 in the direction of the arrow. The filter 23 is formed of a wall flow type honeycomb structure and has a function of collecting particulates contained in exhaust gas. The exhaust gas from which the particulates are collected by the filter 23 is discharged into the atmosphere via the exhaust pipe B30.

At the time of regeneration for burning and removing the particulates trapped in the filter 23, when the internal combustion engine is in operation, the exhaust gas is bypassed from the filter 23 by a bypass pipe (not shown). When the command is issued, the valve A31 is closed and the valve B33 is opened.

FIG. 2 shows a microwave supply means 24 during reproduction.
4 shows an example of an operation time chart of the gas supply means 29.
When the reproduction is started, the microwave supply means 24 starts operating, and the microwave is supplied to the space including the filter 23 through the waveguide 25 and the power supply hole 26. Here, a large amount of microwave is supplied to advance the ignition time of the particulate. The particulates are heated by the microwaves and reach a temperature at which combustion is possible, and at time T1, the operation of the gas supply means 29 is started to supply continuously (for example, 20 l / min).
Combustion starts from a portion near the gas inflow surface by the oxygen in the gas. A part of the heat of combustion is transferred to the heat of conduction or gas to heat the downstream side and sequentially raise the downstream side to a combustible temperature. Therefore, the particulate combustion region sequentially moves downstream while expanding. Here, as shown in FIG. 3, the operation start time T1 of the gas supply means 29 is controlled to be advanced as the trapping amount increases. As a result, rapid ignition of the particulates due to excessive heating of the particulates can be suppressed, and steepening of the temperature gradient in the first half of the filter regeneration can be suppressed.

Next, from time T2 (time at which the temperature rising speed of the upstream portion of the regeneration becomes high), the gas supply means 29 is operated intermittently, and the operation and the rest are repeated to reduce the (average) gas supply amount (for example, 5 l / l) Minutes). This suppresses the temperature rise due to rapid burning of the particulates, and the temperature gradient inside the filter is reduced by the heat conduction of the filter 23 (details are omitted). Here, as shown in FIG. 2, by increasing the time T2 at which the gas supply amount is reduced as the trapping amount increases, it is possible to suppress an increase in the filter temperature in the first half of the regeneration.

Then, after time T3 (the time at which the ignition of the particulate matter in the upstream portion of the regeneration is completed), the supply amount of microwaves is reduced, and as shown in FIG. By reducing the power consumption, it is possible to prevent the temperature of the filter from increasing while suppressing power consumption, and to increase the combustion downstream of the regeneration.

Next, at time T4 (the filter 23 on the downstream side of regeneration)
After the time when the combustion expands to the vicinity of the end face), the gas supply means 29 is continuously driven again to increase the (average) gas supply amount (for example, 20 l / min). Thereby, the particulates accumulated near the end face on the downstream side of the regeneration of the filter 23 can be burnt and removed. Here, as shown in FIG. 2, by controlling the time T4 at which the gas supply amount is increased to be delayed as the trapping amount increases, the air supply amount is increased while the unburned portion of the particulates is reduced to some extent. In addition, it is possible to prevent the temperature of the downstream side of the regeneration from increasing while reducing the unburned particulates accumulated near the filter end surface on the downstream side of the regeneration.

Next, at time T5 (the time when the burning of the particulates is completed), the microwave supply means 24 stops its operation. Here, as shown in FIG. 2, by delaying the microwave operation stop time T5 as the trapping amount increases,
The supply of the microwave is stopped in a state where the burning of the particulates is completed, and the unburned portion of the particulates in the downstream portion of the regeneration can be reduced.

Finally, at time T6 (time at which the particulate cooling is completed), the gas supply means 29 is stopped to end the regeneration. Also in this case, as shown in FIG. 2, the time T6 at which the operation of the gas supply means 29 is stopped is delayed as the trapping amount increases, whereby the filter 23 is sufficiently cooled (preferably 400 ° C. or lower).

Thus, the regeneration is completed, the valve A31 is opened, the valve B33 is closed, and the particulates in the exhaust gas can be collected by the filter 23 again.

With the regeneration control of the present invention, the filter can be prevented from mechanical breakage by suppressing the temperature of the filter during regeneration and suppressing the steepness of the temperature gradient, while maintaining high particulate regeneration efficiency over a wide collection amount. As a result, the filter 23 can be used for a long time.

In this embodiment, the gas supply means 29
The gas supply amount is increased / decreased by switching the gas supply means 29 between intermittent drive and continuous drive using a constant air flow supply type such as a pump. The gas supply amount may be increased or decreased by adjusting the time. Further, when an electric fan or the like is used as the gas supply means 29, the (average) gas supply amount may be increased or decreased by increasing or decreasing the drive voltage.

Although the microwave has been described as an example of the particulate heating, for example, an electric heater or a burner may be used as the heating means.

[0048]

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) By controlling the operation start time of the gas supply means so as to be earlier as the trapping amount increases, rapid ignition of the particulate due to excessive heating of the particulate is suppressed, and the inside of the filter is suppressed. Steepening of the temperature gradient can be suppressed.

(2) By reducing the gas supply amount during the regeneration period, the burning reaction speed of the particulates can be suppressed and the combustion temperature can be prevented from increasing. Further, by controlling the time at which the gas supply amount is reduced so as to be earlier as the trapping amount increases, it is possible to suppress an increase in the filter temperature in the first half of the regeneration.

(3) By suppressing the supply amount of microwaves during the regeneration period and controlling the supply amount of the reduced microwaves so as to decrease as the trapping amount increases, it is possible to suppress the temperature of the filter from becoming high. Can be.

(4) By controlling the time at which the microwave supply amount is reduced so as to be earlier as the trapping amount increases, it is possible to suppress the filter from becoming unnecessarily hot.

(5) The gas supply amount is kept low until the latter half of the regeneration to suppress the increase in the combustion temperature, the gas supply amount is increased after the latter half of the regeneration, and the time is delayed as the trapping amount increases. It is possible to prevent the temperature of the downstream side of the regeneration from increasing while reducing the unburned particulates accumulated near the filter end face on the downstream side of the regeneration of the filter.

(6) By controlling the operation stop time of the microwave supply means so as to be delayed as the trapping amount increases, the unburned portion of the particulates in the downstream portion of the regeneration can be reduced.

(7) By controlling the operation stop time of the gas supply means to be delayed as the trapping amount increases, the cooling of the filter is completed, the filter is prevented from being rapidly cooled by the exhaust gas, and the filter is cracked. Generation can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially cut-away cross-sectional configuration view of a filter regeneration device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a control time chart of a microwave supply unit and a gas supply unit of the filter regeneration device for an internal combustion engine showing one embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between various times and the amount collected in FIG. 2;

FIG. 4 is a configuration diagram of a conventional filter regeneration device for an internal combustion engine.

[Explanation of symbols]

 23 filter 24 microwave supply means 29 gas supply means 34 control means 35 trapped amount detection means

──────────────────────────────────────────────────の Continued on front page (72) Inventor Takahiro Matsumoto 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-4-301120 (JP, A) JP-A-4-259919 (JP, A) JP-A-3-210011 (JP, A) JP-A-4-301118 (JP, A) JP-A-4-301126 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 3/02 321 F01N 3/02 301

Claims (7)

(57) [Claims] A filter for collecting particulates contained in exhaust gas of an internal combustion engine; microwave supply means for supplying microwaves for dielectrically heating the particulates collected by the filter; Gas supply means for promoting the combustion of the collected particulates, trapping amount detection means for detecting the amount of the particulate matter collected by the filter, and controlling operations of the microwave supply means and the gas supply means. and control means, said control
As for the means, the operation start time of the gas supply means will be larger
A filter regeneration device for an internal combustion engine that controls to be faster according to the following . 2. Patiki contained in exhaust gas of an internal combustion engine
A filter for collecting the swelling,
Microwaves for dielectrically heating the particulates.
Microwave supply means for supplying, and the dielectric-heated putty
Gas supply means for promoting the combustion of
Detect the amount of particulates collected by the filter
Collection amount detection means, the microwave supply means, and the gas
Control means for controlling the operation of the supply means;
The means reduces the gas supply amount during the regeneration period, and controls the time at which the gas supply amount decreases so as to be earlier as the trapping amount increases. 3. Patiki contained in exhaust gas of an internal combustion engine
A filter for collecting the swelling,
Microwaves for dielectrically heating the particulates.
Microwave supply means for supplying, and the dielectric-heated putty
Gas supply means for promoting the combustion of
Detect the amount of particulates collected by the filter
Collection amount detection means, the microwave supply means, and the gas
Control means for controlling the operation of the supply means;
The filter regeneration device for an internal combustion engine controls the microwave supply amount during a regeneration period and controls the reduced microwave supply amount as the trapping amount increases. 4. The system according to claim 3, wherein the time at which the amount of microwave supply is reduced is controlled so as to be earlier as the amount of trapped gas increases.
For an internal combustion engine mounting filter regeneration device. 5. Patiki contained in exhaust gas of an internal combustion engine
A filter for collecting the swelling,
Microwaves for dielectrically heating the particulates.
Microwave supply means for supplying, and the dielectric-heated putty
Gas supply means for promoting the combustion of
Detect the amount of particulates collected by the filter
Collection amount detection means, the microwave supply means, and the gas
Control means for controlling the operation of the supply means;
The filter regeneration device for an internal combustion engine controls the gas supply amount to be increased during the regeneration period, and controls the time at which the gas supply amount is increased so as to be delayed as the trapping amount increases. 6. a claim 1 for controlling to be slower in accordance with the amount of collecting the operation stop time of the microwave supply means is increased
6. The filter regeneration device for an internal combustion engine according to claim 5 . 7. claims 1 controlled to be slow according trapped amount the operation stop time of the gas supply means is increased 6
The filter regeneration device for an internal combustion engine according to any one of the preceding claims.