JP2858184B2 - Method and apparatus for regenerating filter 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 a method and an apparatus for regenerating a filter for an internal combustion engine which collects particulate matter (hereinafter referred to as "particulate") contained in exhaust gas discharged from an internal combustion engine such as a diesel engine. It is about.

[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 been highlighted in recent days, but measures against acid rain that causes deforestation cannot be ignored.

[0003] Acid rain is a phenomenon that is caused by air pollutants such as sulfur oxides and nitrogen oxides as pollutants. In recent years, emission control of such air pollutants has been regulated in many countries around the world such as cogeneration. There is a move to strengthen mobile sources such as cars and vehicles. 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 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 essential to provide an exhaust gas aftertreatment device. This post-processing device has a filter for collecting particulates.

However, if the particulates continue to be collected, the filter is clogged, the collecting capacity is reduced, the flow of exhaust gas is reduced, and the engine output is reduced or the engine is stopped.

[0006] Therefore, although technology development for regenerating the collecting ability of the filter is currently being promoted all over the world, it has not yet been put to practical use.

[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.

[0008] Considering good temperature-raising efficiency, safety, ease of device configuration, and good control of regeneration, a filter regeneration method using a microwave method and its device have been developed.

As a filter reproducing apparatus using a microwave system, there is, for example, JP-A-59-122022. FIG. 5 shows an apparatus disclosed in the publication. In the figure, an engine 51 is connected to an exhaust manifold 52 and connected to an exhaust pipe 53 and an exhaust branch pipe 54. Reference numeral 55 denotes a filter which is housed in a heating chamber 56 into which a microwave generated by a microwave generating means 57 is guided by a waveguide 58. 59 is a microwave reflecting plate, 60 is an air pump for sending air into the heating chamber 56 through an air supply path 61, 62 is a driving power source for the microwave generating means 57, 63 is a muffler, 64
Is an air switching valve for sending air to the heating chamber 56, and 65 is an exhaust gas flow switching valve exhausted from the heating chamber 56.

In the above configuration, the exhaust gas of the engine is guided to the filter 55 by the exhaust gas flow switching valve 65 or directly discharged to the atmosphere. In the particulate collection cycle, the exhaust gas passes through the filter 55.
And the particulates contained in the exhaust gas are collected by the filter 55. However, as described above, the collecting ability of the filter 55 is limited. When the trapping capacity reaches the limit, the exhaust gas flow switching valve 65 is controlled, the exhaust gas to the exhaust pipe 53 is shut off, and all of the exhaust gas is exhausted to the atmosphere via the exhaust branch pipe 54. During this time, regeneration of the filter 55 is performed. In this filter regeneration cycle, the energy for heating the particulates is supplied from the heating means 7 for generating microwaves, and the air required for combustion is simultaneously supplied from the air pump 60. When the regeneration of the filter is completed after a predetermined time, the exhaust gas flow switching valve 65 is controlled again, and the exhaust gas is guided to the filter 55. This cycle of collection and regeneration is repeated.

[0011] In the above-mentioned conventional configuration, there is the following problem when heating particulates collected by the filter. This problem occurs particularly remarkably in an actual use environment in which the timing of executing the heating of the particulates is during the operation of the engine such as when the vehicle is running or when the engine is stopped. The significant difference between the two is the temperature of the filter. That is, assuming that the particulate heating time is controlled mainly based on the filter temperature during the operation of the engine, when the engine is stopped, the particulates are not heated to a temperature sufficient for combustion transition under the heating condition, and the filter regeneration is insufficient. Become. If the heating time is controlled mainly based on the filter temperature when the engine is stopped, heating of the particulates is excessively promoted during operation of the engine, so that the combustion temperature during particulate combustion becomes too high and the filter is cracked. Alternatively, the risk of erosion increases. As described above, in the conventional apparatus, the control content at the time of particulate heating is not clarified, so that the durability of the filter is not sufficiently guaranteed.

Further, a problem arises due to the accuracy of estimation of the amount of particulates collected in the filter. Microwaves can selectively heat the particulates collected in the filter. In this case, as the amount of trapped particulates increases, the temperature rise of the particulates caused by the microwave heating increases. If the accuracy of estimating the amount of trapped particulates is low, when the amount of trapped particulates is large, heating is performed too much, the particulate combustion temperature becomes high, and the risk of causing mechanical damage to the filter increases. On the other hand, when the trapping amount is small, incomplete combustion of the particulates occurs, and effective regeneration of the filter is not performed. It is difficult to guarantee the durability of the filter due to the mechanical damage and incomplete regeneration of the filter with the particulate combustion control based on the inaccurate estimation of the amount of collected particulate as described above. Met.

[0013]

As described above, in the conventional method and apparatus for regenerating a filter for an internal combustion engine, the initial temperature of the filter differs between when the internal combustion engine is driven and when it is stopped. Since the amount of the particulates to be changed fluctuates each time, the heating time of the particulates collected in the filter and the start of the supply of the gas containing oxygen necessary for the burning and removal of the particulates and the supply amount of the gas are simply determined by the time. The idea was to control.

Therefore, depending on the time control, there is a problem that the filter is melted during regeneration or the regeneration is insufficient.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an internal combustion engine that effectively performs heating and combustion of particulates, guarantees high regeneration performance of a filter, and guarantees durability of the filter. It is an object of the present invention to provide a filter regeneration method and a device therefor.

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a filter for collecting particulates contained in exhaust gas of an internal combustion engine .
Oxygen is insufficient for particulates to burn
Heating step, and then the heating step
Filter temperature reaches the particulate combustion temperature and acid
Gas containing sulfur to the filter to remove particulates
In a method of regenerating a filter for an internal combustion engine for removing combustion,
The initial heating temperature of the filter and the heating for a predetermined time have elapsed
The heating step based on the subsequent change temperature of the filter
The heating time at
Therefore, the gas supply amount was determined.

[0017]

With the above-described means , the filter temperature at the start time of the heating step is detected, and at the same time, the amount of change in the filter temperature due to the temperature rise of the particulates caused by the subsequent heating is detected. First, a filter temperature after a lapse of a predetermined time from the start of heating is detected. The accuracy of estimating the accuracy of the amount of trapped particulate collected by the filter is checked again based on the amount of temperature rise from the initial filter temperature of the filter temperature. Based on the value of the estimated trapping amount and the filter temperature at the beginning of the heating, the heating time to reach the temperature range where the particulates can effectively shift to combustion is calculated, and the heating is continued for that time. The time after the elapse of this time is the gas supply operation start time. Also, the gas supply amount is determined at the same time.

By controlling the heating and combustion of the particulates based on the filter temperature detection information as described above, it is possible to avoid incomplete combustion of the particulates and to avoid cracks and erosion inside the filter by avoiding high-temperature combustion. Thus, the regeneration performance and durability of the filter can be guaranteed.

[0019]

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

In FIG. 1, reference numeral 1 denotes an exhaust pipe for discharging exhaust gas from an internal combustion engine, in which a heating space 2 is provided, and the heating space 2 is contained in the exhaust gas while the exhaust gas passes therethrough. A filter 3 having a honeycomb structure for collecting particulates to be collected is housed. 4 is a heating means for generating microwaves supplied to the heating space 2 for dielectric heating of the particulates, and 5 is a linear and annular rectangle for transmitting the microwaves generated by the heating means 4 to the space 2 for heating. A waveguide, 6 is a power supply hole for supplying microwaves to the heating space 2, and 7 is a gas supply means for supplying a gas containing oxygen guided to the heating space 2 to promote combustion of the dielectrically heated particulates. And a blower 8. Reference numeral 9 denotes a flow guide tube for gas supplied to the heating space 2, and reference numeral 10 denotes a gas for shutting off exhaust gas to leak from the exhaust pipe 1 when "closed" and gas to be supplied to the heating space 2 when "open". A and 11 are controlled so as to be sucked. A discharge pipe of the gas supplied to the heating space 2 at the time of regeneration of the filter 3 after the filter is circulated, 12 is an opening / closing valve B of the discharge pipe 11, and 13 is a discharge pipe of the exhaust gas. An exhaust gas valve 14 for opening or shutting off the flow is a drive power source for driving the heating means 4, the gas supply means 7, the valve A10, the valve B12 and the exhaust gas valve 13 for generating microwaves, and 15 controls their operation. It is a control unit.

The heating space 2 has a microwave shielding means 1 having a punching hole structure or a honeycomb structure.
The space for substantially confining the microwave is limited by 6 and 17. Reference numeral 18 denotes a heat insulating material provided between the outer periphery of the filter 3 and the filter support tube 19, and also serves as a filter support.

Reference numeral 20 denotes a filter temperature detecting means provided on the tube wall of the filter supporting tube 19 for detecting the side surface temperature of the filter 3. The detection signal of the temperature detecting means 20 is transmitted to the controller 1
5, and based on this signal, the control unit 15 controls the heating unit 4 and / or the gas supply unit 7 that generate microwaves.
Is optimally controlled.

The annular component of the rectangular waveguide 5 is provided at the end with a feed hole 6 (one not shown) provided facing the wall of the filter support tube 19. Further, the annular rectangular waveguide has an E-plane T-branch structure, and the transmission line lengths from the branch portion to the power supply holes 6 are substantially equal. A structure having a certain thickness made of a microwave low-loss material that blocks the flow of exhaust gas is provided at a connection portion with the annular and linear rectangular waveguide 5 (not shown). .

Exhaust gas 21 discharged from the internal combustion engine flows through the exhaust pipe 1 and flows into the filter 3. Filter 3
Consists of a wall flow type honeycomb structure,
It has a function of collecting particulates contained in exhaust gas. When the amount of the particulates collected in the filter 3 increases, the pressure loss of the filter 3 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 3 at an appropriate time. The appropriate timing is determined by detecting the pressure drop level of the filter 3, detecting the amount of trapped particulates by electrical means, or integrating the operating state of the engine. The particulate matter trapped in the filter 3 is removed by heating and burning. This process is called filter regeneration.

Next, FIG. 2 will be described. This figure shows a temperature rise characteristic inside the filter when the filter is heated in the microwave heating mechanism shown in FIG. The measurement points are characteristic examples of five measurement points in the exhaust gas flow direction of the filter at a position 10 mm from the outer peripheral surface of the filter. In the experiment, the amount of collected particulates is 10 g / l, and the broken line is the characteristic of 5 g / l.

The microwave heating mode is constituted by TE _OIP . When the trapping amount is small, the permeability of the microwave into the filter is increased. The temperature rise distribution and the rate of change, which vary with the trapping amount, are applied to reconfirm the particulate trapping amount.

Referring now to FIG. FIG. 3 shows a temperature change at a substantially central portion of a filter side surface caused by particulate heating and combustion at substantially the same trapping amount.

The characteristic shown by the solid line in the figure is an example of the characteristic when the filter temperature is different at the beginning of particulate heating. Further, the solid line "Lo" characteristic is indicated by a broken line when the gas supply amount is varied.

The characteristic of the solid line "Lo" indicates the case where the filter temperature immediately before the regeneration corresponding to the regeneration in the engine stopped state is room temperature ( _TL ), and the characteristic of the solid line "Hi" corresponds to the regeneration in the engine operating state. Filter temperature is about 150 ° C
( _TH ).

The details of the control will be described below.
Detecting the filter temperature at the time t ₁ set in advance. Here it detected the filter temperature T _L1 (the case of "Hi" T _H1: the same applies hereinafter) is performed to reconfirm the trapped amount estimation accuracy with heating the initial temperature T _L (T _H) data. At this time,
Data to be collated in the estimation of the collection amount is stored in advance.

The filter temperature T ₁ is a preset reference temperature, and is a filter ambient temperature corresponding to a point when the heated particulates reach a temperature (about 650 ° C.) at which the particulates can easily shift to a combustion state. Control unit 15 calculates the time to reach the reference temperature T ₁ of based on the initial stage of heating of the filter temperature and the trapped amount estimation data (in the figure,
t ₂ ′, t ₂ ). The optimum gas supply for particulate combustion is also determined.

At the time when the heating proceeds and reaches time t ₂ (t ₂ ′), the actual filter temperature T is compared with the reference temperature T ₁ . At this time, if the difference between T and T ₁ is too large (for example, 50 ° C. or more), the control content can be corrected again.

The characteristics of the experiment "Lo" indicate a temperature change when a gas (usually air) which promotes combustion is supplied to the filter at a flow rate of about 50 l / min.
The case where the flow rate is set to 0 liter / min is shown. The temperature quickly rises with the generation of particulate combustion heat. In the case of the example shown in the figure, the temperature rise is about 200 ° C. Thereafter, the temperature gradually decreases. The looseness of the gradual characteristic is caused by residual combustion in the filter, heat insulation of the heat insulating material, and the like.

FIG. 3 shows that the effect of the filter temperature before the regeneration of the filter on the regeneration performance can be canceled by executing the optimal control of the heating means and the gas supply means based on the filter temperature. This indicates that the filter collection estimation based on the particulate collection amount can be performed by correcting the estimation of the particulate collection amount, and the like.

Next, FIG. 4 will be described. This figure shows an example of the transition of the particulate combustion state inside the filter. The gas flow direction is indicated by the arrow in FIG. The hatched area is a particulate combustion area.

Although the peak of the particulate combustion temperature occurs in a combustion state as shown in FIG. 3C, it is the effective control of the progress of the combustion region up to this state that the peak of the combustion temperature is suppressed. This is the basis of measures. The present invention performs the above-described control with one of the objects of controlling the combustion peak temperature as a basic measure for avoiding mechanical damage of the filter. As specific means, by using the filter temperature information immediately before the filter regeneration and during the particulate heating period, the particulate heating conditions and the gas supply timing and supply amount are optimally controlled to prevent mechanical destruction of the filter. This makes it possible to prevent the filter and guarantee the regeneration performance and durability of the filter.

Next, the basic process of the filter regeneration will be described in detail. When the amount of particulates collected by the filter reaches the collection amount region where filter regeneration is to be performed, the filter regeneration process is started.

The reproduction control command is issued from the control unit 15. The exhaust gas valve 13 is controlled based on a command from the control unit 15. When the internal combustion engine is operating, the exhaust gas flowing into the filter is shut off and the exhaust gas is led to a bypass pipe (not shown).

Next, heating means 4 for generating microwaves
Is supplied with drive power. The microwave generated by the heating means 4 is supplied to the filter housing heating space 2 via the waveguide means. The particles trapped in the filter 3 are dielectrically heated by the microwaves, and the heated region extends to the inside of the filter 3 (see FIG. 2). As time passes, the temperature gradually increases from the particulates near the filter end face on the microwave incident side to a temperature at which combustion is possible, but the microwave power supply is continued. When the temperature at which combustion is possible is reached, the particulates in that region glow red and partially burn, but the steam rises due to lack of oxygen and the temperature rise saturates. Due to the continuation of the microwave power supply, the region where the temperature at which the particulates can be burned is extended to about の of the filter.
At this time, the flow of the exhaust gas and other gases in the filter is almost completely shut off, so that the particulate heated by the microwave efficiently rises in temperature to a temperature range where combustion is possible.

After the elapse of the microwave heating time determined based on the filter temperature, the valves A10 and B12 are controlled to open, the gas supply means 7 starts operating, and the gas containing oxygen at an appropriate flow rate is supplied to the heating space. 2 is led. Due to this gas, the particulates in the filter 3 which have been heated to a high temperature shift to a combustion state. This combustion region expands toward the center of the filter while moving in the flow direction of the gas containing oxygen, and after an appropriate time, particulates in almost the entire region of the filter are burned and removed. The variation of the gas supply capacity of the gas supply means 7 can be executed by varying the voltage of the drive power supply of the gas supply means 7.

When the filter regeneration cycle ends, the heating means 4 and the gas supply means 7 for generating microwaves stop operating, and the valves 10, 12, and 13 are controlled to the original state. Then, at an appropriate time, the exhaust gas can flow into the filter 3 to collect particulates.

Note that it is more preferable that the filter end face on which microwaves are incident be executed from the filter end face on the downstream side with respect to the exhaust gas flow. Microwave shielding means 1
6 and 17 may be unnecessary depending on the size of the diameter of the exhaust pipe 1.

Further, the regeneration performance is enhanced by increasing the gas supply capacity with the gas supply time, and the progress of the particulate combustion is promoted, so that the regeneration time can be shortened. By controlling so as to supply a very small amount of gas, higher regeneration performance can be obtained. Since the supply of gas at a small flow rate does not sufficiently supply oxygen required for combustion, it is possible to suppress an increase in combustion temperature. Therefore, generation of a steep temperature gradient generated inside the filter can be suppressed, and the filter 3 can be prevented from being mechanically damaged.

When the particulate combustion region moves to the other end of the filter 3, a gas flow is trapped inside the filter 3 and the movement of the combustion region in the gas flow direction of the filter 3 is stagnated. Cheap. This is because the particulate matter collected near the end face of the filter 3 is affected by the ambient temperature outside the filter 3 and its temperature rises slowly, making it difficult to reach a temperature at which combustion is possible. Therefore, when the combustion area near the end face of the filter 3 moves, the combustion area is not moved until the temperature near the end face of the filter 3 reaches a temperature at which combustion is possible due to heat generated in the combustion area. This state is the above-mentioned drift phenomenon. In this pool state, the temperature of the combustion area increases.

As means for avoiding this high temperature,
When it becomes a pool state, the operation of the heating means 4 is stopped to stop the supply of heat energy from the heating means 4 and a control method for suppressing a rise in temperature. It is necessary to control so as to avoid high temperature by the cooling action. When the stop control of the heating means 4 and the control of increasing the gas flow rate are executed, for example, a means for detecting the flow rate of the supplied gas flow is added to change the gas flow rate (in the case of using a blower, the gas flow rate increases. (Time to start to perform). The heating means may be a burner device or an electric heating device other than the device for generating microwaves, and the detection point of the temperature detection means may be a portion for indirectly detecting the temperature of the filter such as a heating space instead of the filter itself.

The above-described control contents and the configuration of the present invention can be combined with each other to further improve the regeneration performance of the filter, prevent mechanical damage to the filter, and ensure the durability of the filter. be able to.

[0048]

As described above, according to the filter regeneration method and apparatus for an internal combustion engine of the present invention, the following effects can be obtained. (1) The heating time of the particulates and the operation start time of the gas supply means based on the filter temperature immediately before the regeneration of the filter
By controlling both , the optimum filter regeneration can be executed independently of the state of the internal combustion engine. (2) It is possible to perform a recheck of the estimation of the trapped amount of particulates based on the amount of change in the filter temperature immediately before the regeneration of the filter and during the particulate heating time, and to perform optimal regeneration control (start of gas supply) according to the actual trapped amount. Time and supply amount control). As a result, it is possible to avoid incomplete combustion of particulates and mechanical damage (cracks, erosion) of the filter, and it is possible to guarantee the filter regeneration performance and the durability.

When the side surface temperature of the filter is detected, it is possible to easily take measures against the leakage of the exhaust gas from the detecting portion.

[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 diagram showing a temperature rise rate characteristic inside a filter by the apparatus.

FIG. 3 is a characteristic diagram of a change in filter temperature during filter regeneration by the apparatus.

FIG. 4 is a transition diagram of a combustion state inside a filter in the same device.

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

[Explanation of symbols]

 Reference Signs List 1 exhaust pipe 3 filter 4 heating means 7 gas supply means 15 control unit 20 temperature detection means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-8311 (JP, A) JP-A-59-126022 (JP, A) JP-A-5-1556928 (JP, A) JP-A-4- 265413 (JP, A) Japanese Utility Model Hei 4-87316 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 3/02 301-341 F01N 9/00

Claims (5)

(57) [Claims] 1. A heating step of heating a filter for collecting particulate matter contained in exhaust gas of an internal combustion engine in a state where oxygen is insufficient for burning of the particulate matter in the collected filter. then Oite that temperature of the filter by heating step reaches the combustion temperature of particulate matter, for an internal combustion engine filter regeneration process for burning and removing the particulate matter is supplied to the filter a gas containing oxygen, heating of the filter Early
Temperature and change of the filter after heating for a predetermined time
Based on the temperature, the heating time in the heating step,
Determine the supply amount of gas containing oxygen to be supplied to the filter
A method for regenerating a filter for an internal combustion engine. 2. A total supply for supplying a gas containing oxygen to a filter.
The feed rate is changed per unit time by changing the temperature of the filter.
The feature is to supply the filter with different supply amount
The method for regenerating a filter for an internal combustion engine according to claim 1, wherein 3. A method for supplying a gas containing oxygen to a filter.
Means that the air volume per unit time is larger at the end than at the beginning.
3. The filter for an internal combustion engine according to claim 2, wherein
Raw method. 4. A filter that communicates with exhaust gas of an internal combustion engine and collects particulate matter contained in the exhaust gas, heating means for heating the particulate matter in the filter, heating in an unburned state. Gas supply means for supplying gas containing oxygen for burning the particulate matter, and temperature detection means for detecting a filter temperature, wherein the heating means heats the filter at an initial stage and after heating for a predetermined time. The gas supply amount determined based on the change temperature of the filter is supplied to the filter.
A filter regeneration device for an internal combustion engine, comprising a control unit for supplying the same through means . 5. The gas supply means controls the amount of air blown per unit time.
Claims characterized by means that can be changed
The filter regeneration device for an internal combustion engine according to claim 4.