JPH0932532A - Exhaust gas treatment device and combustion control method for fine particles - Google Patents

Abstract

(57) Abstract: Exhaust gas treatment capable of suppressing explosive combustion due to self-ignition of fine particles in a filter and keeping the temperature of the filter at or below its heat-resistant temperature, thus preventing melting damage of the filter. An apparatus and a method for controlling combustion of fine particles are provided. A filter (1) provided in the middle of an exhaust pipe (3) of an internal combustion engine (2) for collecting fine particles in exhaust gas, and an air supply means (4) for supplying air for particulate combustion to the filter (1).
In an exhaust gas treatment apparatus provided with a combustion means 5 for heating and burning fine particles collected by the filter 1 together with air to remove from the filter 1, a temperature detecting means 11 for detecting the temperature is provided in the filter 1 and It is characterized in that a control means 7 for operating the air supply means 4 is provided when the temperature detected by the detection means 11 is equal to or higher than a set value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treating apparatus for collecting fine particles in exhaust gas discharged from an internal combustion engine such as a diesel engine, and a combustion control method for the particles.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine such as a diesel engine, when a fuel burns, fine particles containing carbon as a main component, which are called diesel particulates, are generated. Is provided to collect the fine particles. This particulate filter is clogged as fine particles are collected, and the operating condition of the engine becomes high load.Therefore, the particulate filter is heated regularly to burn the collected fine particles together with air to remove the filter. Playing.

As an example of an exhaust gas treating apparatus provided with this filter, for example, an exhaust gas post-treatment apparatus as disclosed in Japanese Utility Model Laid-Open No. 1-134715 has been proposed. This device is provided with a bypass passage for branching in the exhaust gas passage on the upstream side of the filter, and a heat exchanger for heating the air for particulate combustion by the exhaust gas passing through this bypass passage. The electric heater heats the filter to a predetermined temperature, and the air heated by the heat exchanger is supplied to the filter to burn the fine particles collected and remove the fine particles from the filter.

[0004]

By the way, in the above exhaust gas aftertreatment device, if the engine operating condition is low and the temperature of the filter is less than 600 ° C., the collection of fine particles by the filter will be hindered. However, if the temperature of the filter becomes 600 ° C. or higher due to a high load of the engine operating condition, some particles are collected in the filter, and the collected particles are burned. In this case, when the operating state of the engine suddenly becomes a low load, exhaust gas with a high oxygen concentration flows into the filter,
There is a problem that the filter is melted and damaged because the fine particles are explosively burned by self-ignition.

The present invention has been made in view of the above circumstances, and suppresses explosive combustion due to self-ignition of fine particles in a filter, and keeps the temperature of the filter below its heat-resistant temperature. An object of the present invention is to provide an exhaust gas treatment device and a particulate combustion control method capable of preventing melting damage.

[0006]

In order to solve the above problems, the present invention employs the following exhaust gas treating apparatus and particulate combustion control method. That is, the exhaust gas treating apparatus according to claim 1 is a filter provided in the middle of an exhaust pipe of an internal combustion engine for collecting fine particles in exhaust gas, and an air supply means for supplying air for particulate combustion to the filter. An exhaust gas treatment apparatus comprising: a combustion unit that heats and combusts fine particles collected by the filter together with air to remove from the filter, and the temperature detection unit that detects the temperature of the filter is provided in the filter; The control means is provided for operating the air supply means when the temperature detected by the temperature detection means is equal to or higher than a set value.

According to a second aspect of the present invention, there is provided an exhaust gas treatment device, wherein an air reservoir communicating with the air supply means is provided on the outer peripheral portion of either the filter or the exhaust pipe.

According to another aspect of the present invention, there is provided an exhaust gas treatment apparatus, wherein the filter is provided with an air supply amount supplied from the air supply means on the basis of output signals of the load detection means for detecting the load of the internal combustion engine and the temperature detection means. Is controlled or stopped to suppress the temperature rise of the filter due to the combustion of the collected fine particles within a predetermined temperature range.

The exhaust gas treating apparatus according to claim 4 is a filter provided in the middle of an exhaust pipe of an internal combustion engine having a turbocharger and a compressor driven by the turbocharger, for collecting fine particles in the exhaust gas, and the filter. When the particulate matter collected by the above is heated and burned with the air supplied by the compressor to remove it from the filter, and the pressure of the exhaust gas flowing into the filter is detected and the pressure exceeds a predetermined pressure. And a control means for operating the compressor and the combustion means,
An air reservoir is provided on the outer peripheral portion of either the filter or the exhaust pipe, and air for particulate combustion is supplied to the filter by the compressor via the air reservoir.

A method of controlling combustion of fine particles according to claim 5 is
A method for controlling the combustion of fine particles in exhaust gas collected in a filter provided in the middle of an exhaust pipe of an internal combustion engine, detecting the temperature of the filter and the load of the internal combustion engine, respectively, the temperature of the filter and When both the load of the internal combustion engine exceeds a first set value, the fine particles are burned while controlling the flow rate of the air flowing into the filter, and the temperature of the filter and the load of the internal combustion engine are detected again, Both the temperature of the filter and the load of the internal combustion engine are the first
If the second preset value smaller than the preset value is exceeded, combustion of fine particles is continued, and if either the temperature of the filter or the load of the internal combustion engine falls below the second preset value, the filter This is a method of stopping the flow rate of air flowing into the.

In the exhaust gas treating apparatus according to the first aspect, the filter collects fine particles in the exhaust gas. In the filter, as the amount of collected fine particles increases, the exhaust gas does not pass easily and the temperature rises. The control means, when the temperature of the filter detected by the temperature detection means becomes equal to or higher than a set value, operates the air supply means to supply air for particulate combustion to the filter to collect the collected particulates. A part is burned (oxidized) and removed from the filter. As a result, the amount of fine particles collected by the filter is reduced, and even when the fine particles burn by self-ignition, they do not burn rapidly, and explosive combustion is suppressed. Therefore, the combustion temperature of the fine particles can be set to be equal to or lower than the heat resistant temperature of the filter, and there is no risk of the filter being melted.

In the exhaust gas treating apparatus according to the second aspect, an air reservoir communicating with the air supply means is provided on the outer peripheral portion of either the filter or the exhaust pipe, so that heated air is passed through the filter. The temperature of the filter does not drop temporarily and the regeneration time is shortened. Further, the air reservoir serves as a heat insulating layer of the filter or the exhaust pipe when the temperature rises.

In the exhaust gas treatment device according to claim 3, the air supply amount supplied from the air supply means to the filter based on the output signals of the load detection means for detecting the load of the internal combustion engine and the temperature detection means. By controlling or stopping the temperature rise of the filter by suppressing the temperature rise of the filter due to the combustion of the collected fine particles within a predetermined temperature range, the temperature rise of the filter is always a predetermined It becomes possible to suppress the temperature within the temperature range, and the possibility that the filter is melted is further eliminated.

In the exhaust gas treating apparatus of the fourth aspect, the air for particulate combustion supplied by the compressor is heated by the heat of the exhaust gas while passing through the air reservoir, and then supplied to the filter. The particulates collected by the filter are partially burned by the heated air and removed from the filter. As a result, the amount of fine particles collected by the filter is reduced, and even when the fine particles burn by self-ignition, they do not burn rapidly, and explosive combustion is suppressed. Therefore, the combustion temperature of the fine particles can be set to be equal to or lower than the heat resistant temperature of the filter, and there is no risk of the filter being melted.

Moreover, by providing the air reservoir on the outer peripheral portion of either the filter or the exhaust pipe, the air is heated to a higher temperature and more quickly, the temperature of the filter is maintained at a higher temperature, and the regeneration time is shortened. To be done. Further, the compressor also has the function of air supply means,
Since it is not necessary to separately provide an air supply means such as an air pump, it is possible to save space and reduce costs.

In the particulate combustion control method according to the present invention, the temperature of the filter and the load of the internal combustion engine are respectively detected, and when both the temperature of the filter and the load of the internal combustion engine exceed a first set value. First, the fine particles are burned while controlling the flow rate of the air flowing into the filter. The temperature of the filter and the load of the internal combustion engine are respectively detected again, and the combustion of fine particles is continued when both the temperature of the filter and the load of the internal combustion engine exceed a second set value smaller than the first set value. However, either the temperature of the filter or the load of the internal combustion engine is the second
The flow rate of the air flowing into the filter is stopped when the value is below the set value. As described above, the temperature of the filter is suppressed to a predetermined temperature or lower. Therefore, it becomes possible to maintain the combustion temperature of the fine particles below the heat resistant temperature of the filter.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an exhaust gas treating apparatus and a particulate combustion control method of the present invention will be described below. (First Embodiment) FIG. 1 is a cross-sectional view showing an exhaust gas treating apparatus of a first embodiment of the present invention, in which 1 is coaxial with an exhaust pipe 3 of a diesel engine (internal combustion engine) 2. A cylindrical filter 4 is provided which collects fine particles in the exhaust gas g and has a closed upstream end portion.
An air pump (air supply means) 5 for supplying air for burning particulates to the unit has a lead portion 5a connected to a power source and is installed on the outer peripheral surface of the filter 1 so that the particulates collected by the filter 1 together with the air. A heater (combustion means) for heating and burning and removing from the filter 1, a pressure sensor 6 for detecting the pressure of the exhaust gas g flowing into the filter 1, a control unit (control means) 7 for operating the heater 5 and the air pump 4, Reference numeral 8 is a cylindrical air reservoir provided coaxially with the filter 1 at a predetermined interval.

Reference numeral 11 is a thermocouple (temperature detecting means) for detecting the temperature of the filter 1, and 12 is a diesel engine 2.
Is a throttle opening detector (load detecting means) for detecting the throttle opening (load of the engine), and the control unit 7 includes a thermocouple 11 and a throttle opening detector 12.
A temperature suppression unit (temperature suppression means) is installed which controls the flow rate of the air of the air pump 4 or stops the operation based on each output signal and suppresses the temperature of the filter 1 to a predetermined temperature or lower. .

The air reservoir 8 is, as shown in FIGS. 2 and 3,
A hollow ring portion 21 having a rectangular cross section, a hollow cylindrical tube portion 22 coaxially fixed to the ring portion 21 and having the same outer diameter, and a ring portion 2.
1 and the cylindrical portion 22 and is provided with a control valve 23 that connects them. A plurality of circular holes 24 are formed in the inner peripheral surface 21a of the ring portion 21 at equal intervals in the circumferential direction. On the other hand, inside the tubular portion 22, the air flowing in the tubular portion 22 meanders so as to meander at equal intervals in the circumferential direction of the tubular portion 22, radially from the axial line of the tubular portion 22, and in close contact with the ring portion 21. A plurality of partition plates 25, 25, ... Are provided so that those connected to each other and those separated from each other are alternately arranged.

Next, a combustion control method of fine particles in the exhaust gas treating apparatus of this embodiment will be described with reference to FIG. First, the thermocouple 11 detects the temperature of the filter 1 and the throttle opening detector 12 detects the throttle opening of the diesel engine 2 (step 1). Next, the detected temperature of the filter 1 and the first set value of the temperature of the filter 1 (600 ° C.) are compared with the detected value of the throttle opening and the first set value of the throttle opening (70%), respectively ( Step 2). Here, if one of the detected temperature of the filter 1 and the detected value of the throttle opening does not exceed the first set value, step 1 is executed again, and both of these values exceed the first set value. Then, the control valve 23 is opened and the air for particulate combustion is supplied to the filter 1 through the air reservoir 8 (step 3).

Next, the filter 1 is again connected by the thermocouple 11.
And the throttle opening detector 12 detects the throttle opening of the diesel engine 2 (step 4). Next, the detected temperature of the filter 1 and the second set value (500 ° C.) of the temperature of the filter 1 are compared with the detected value of the throttle opening and the second set value of the throttle opening (70%), respectively ( Step 5). Here, if both the detected temperature of the filter 1 and the detected value of the throttle opening exceed the second set value, step 3 is executed again, and if any one of these values falls below the second set value. , Control valve 23
Is closed to stop the supply of air for particulate combustion to the filter 1 (step 6). From the above, it becomes possible to set the combustion temperature of the fine particles to be equal to or lower than the heat resistant temperature of the filter 1,
There is no risk of the filter 1 being melted.

Here, the amount of air supplied is such that the oxygen concentration in the exhaust gas g is 10 V /
Since it is set so as not to exceed V%, the fine particles burn while the combustion temperature is suppressed to about 700 ° C. Even when the load is suddenly changed to the low load condition from this state, the combustion temperature can be suppressed to the melting temperature of the filter 1 or lower because the amount of the collected fine particles is reduced.

FIG. 5 is a diagram showing the temperature characteristic of the filter of the exhaust gas treating apparatus of this embodiment, and FIG. 6 is a diagram showing the temperature characteristic of the filter of the conventional exhaust gas treating apparatus. In the present embodiment, when the particulates are burnt and the load is suddenly changed to a low load, the combustion temperature (point A in the figure) is suppressed to below the melting temperature of the filter (about 900 ° C.).
In the conventional example, it can be seen that the combustion temperature (point A in the figure) exceeds the melting temperature of the filter and is about 1200 ° C. or higher.

FIG. 7 is a diagram showing a regeneration characteristic of the filter of the exhaust gas treating apparatus of the present embodiment, and FIG. 8 shows a regeneration characteristic when air at room temperature is supplied to the filter for comparison with the present embodiment. It is a figure. In the present embodiment, even if air is supplied when the filter temperature reaches 600 ° C. (point B in the figure), the filter temperature does not decrease at all and the regeneration time is shortened. It can be seen that the temperature of the filter decreases at the moment when air is supplied to the filter, the combustion start time is delayed, and the time required for regeneration becomes long.

As described above, according to the exhaust gas treatment apparatus of this embodiment, the cylindrical air reservoirs 8 are coaxially provided at the outer periphery of the filter 1 with a predetermined space therebetween, so that the filter 1 collects them. When the fine particles are burned by self-ignition, there is no possibility of rapid burning, and explosive burning can be suppressed. Therefore, the combustion temperature of the fine particles can be set to be equal to or lower than the heat resistant temperature of the filter 1, and the melting loss of the filter can be prevented. Further, since the air reservoir 8 functions as a heat insulating layer when the temperature is raised, it is possible to prevent heat dissipation when the temperature is raised.

According to the particulate combustion control method of the present embodiment, the thermocouple 11 detects the temperature of the filter 1 and the throttle opening detector 12 detects the throttle opening. If it exceeds the set value of, the air for particulate combustion is passed through the air reservoir 8 to the filter 1
To detect the temperature of the filter 1 and the throttle opening again, and if either of these values falls below the second set value, the supply of air for particulate combustion to the filter 1 is stopped. The temperature of the filter 1 can be suppressed below a predetermined temperature, and therefore, the combustion temperature of fine particles can be maintained below the heat resistant temperature of the filter 1.

(Second Embodiment) FIG. 9 shows a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the exhaust gas treating apparatus of the embodiment, in which 31 is a cylindrical air reservoir coaxially provided on the outer periphery of the exhaust pipe 3 on the upstream side of the filter 1, and 32 is an air reservoir 31.
Of the air supply pipe provided in communication with the end of the filter 1 on the side of the filter 1, and the tip of the air supply pipe provided in the exhaust pipe 3 and in the vicinity of the end of the filter 1 on the upstream side. It is a valve.

In this apparatus, the air for particulate combustion supplied by the air pump 4 is heated by the heat of the exhaust gas g passing through the exhaust pipe 3 while passing through the air reservoir 31, and then supplied to the filter 1. Here, since the air reservoir 31 is provided on the outer circumference of the exhaust pipe 3 on the upstream side of the filter 1, it comes into contact with the exhaust gas g having a temperature higher than that of the air reservoir 8 of the first embodiment, and the air Is heated to a higher temperature and more quickly.

Also in the exhaust gas treating apparatus of this embodiment,
The same action and effect as those of the first embodiment can be obtained. Moreover, since the air reservoir 31 is provided on the outer circumference of the exhaust pipe 3 on the upstream side of the filter 1, the air can be heated to a higher temperature and more quickly, and thus the temperature of the filter 1 can be maintained at a higher temperature. , The playback time can be further shortened.

(Third Embodiment) FIG. 10 is a sectional view showing an exhaust gas treating apparatus of a third embodiment of the present invention. In the figure, 41 is driven by a turbocharger and 42 is driven by a turbocharger 41. It is a compressor. The air reservoir 31 is connected to the compressor 42. In this device, since the compressor 42 serves as an air source for the air reservoir 31, it is not necessary to separately provide an air supply means such as the air pump 4, so that space saving and cost reduction can be realized.

Also in the exhaust gas treating apparatus of this embodiment,
The same action and effect as those of the second embodiment can be obtained. Moreover, since the compressor 42 is used as an air source for the air reservoir 31, it is not necessary to separately provide an air supply means such as the air pump 4, so that space saving and cost reduction can be achieved.

[0032]

As described above, according to the exhaust gas treating apparatus of the first aspect of the present invention, the filter is provided with the temperature detecting means for detecting the temperature of the filter, and the temperature detecting means detects the temperature. Since the control means for operating the air supply means when the temperature is equal to or higher than the set value is provided, the amount of fine particles trapped in the filter can be reduced, and even when the fine particles burn due to self-ignition, the amount of fine particles is rapidly increased. It is possible to suppress the explosive combustion because there is no possibility of burning. Therefore, the combustion temperature of the fine particles can be set to be equal to or lower than the heat resistant temperature of the filter, and it is possible to prevent the filter from being melted.

According to the exhaust gas treating apparatus of claim 2,
On the outer periphery of either the filter or the exhaust pipe,
Since the air reservoir communicating with the air supply means is provided, the heated air can be supplied to the filter, the temperature of the filter can be prevented from temporarily lowering, and the regeneration time can be shortened. can do. Further, since the air reservoir serves as a heat insulating layer of the filter or the exhaust pipe when the temperature is raised, heat dissipation from the filter can be reduced, and the temperature of the filter can be raised to a predetermined temperature in a shorter time.

According to the exhaust gas treating apparatus of claim 3,
In the filter, the amount of air supplied from the air supply unit is controlled or stopped based on the output signals of the load detection unit and the temperature detection unit that detect the load of the internal combustion engine. Since the temperature suppressing means for suppressing the temperature increase of the filter due to the combustion of the fine particles within the predetermined temperature range is provided, the temperature increase of the filter can be always suppressed within the predetermined temperature range, and the filter is melted. Can be further prevented.

According to the exhaust gas treating apparatus of claim 4,
A filter provided in the middle of an exhaust pipe of an internal combustion engine having a turbocharger and a compressor driven by the turbocharger, and a filter for collecting fine particles in the exhaust gas, and the fine particles collected by the filter are supplied by the compressor. Combustion means for heating and burning with air to remove from the filter, and control means for detecting the pressure of the exhaust gas flowing into the filter and operating the compressor and the combustion means when the pressure exceeds a predetermined pressure. Since an air reservoir is provided on the outer peripheral portion of either the filter or the exhaust pipe, and air for particulate combustion is supplied to the filter by the compressor through the air reservoir, the particulates burn by self-ignition. Even if it does, there is no danger of burning rapidly, and it is possible to suppress explosive combustion. That. Therefore, the combustion temperature of the fine particles can be set to be equal to or lower than the heat resistant temperature of the filter, and it is possible to prevent the filter from being melted.

Moreover, since the air reservoir is provided on the outer peripheral portion of either the filter or the exhaust pipe, the air can be heated to a higher temperature and more quickly by the higher temperature exhaust gas, and the temperature of the filter can be raised to a higher temperature. It can be held and the reproduction time can be shortened. Further, since the compressor also has the function of the air supply means, it is not necessary to separately provide an air supply means such as an air pump, so that space saving and cost reduction can be achieved.

According to the particulate combustion control method of the fifth aspect, the temperature of the filter and the load of the internal combustion engine are respectively detected, and both the temperature of the filter and the load of the internal combustion engine exceed a first set value. In this case, the fine particles are burned while controlling the flow rate of air flowing into the filter, the temperature of the filter and the load of the internal combustion engine are detected again, and the temperature of the filter and the load of the internal combustion engine are both the If the second set value smaller than the set value of 1 is exceeded, combustion of particulates is continued, and if either the temperature of the filter or the load of the internal combustion engine falls below the second set value, Since the flow rate of air flowing into the filter is stopped, it is possible to keep the temperature of the filter below a predetermined temperature at all times, and the combustion temperature of fine particles is equal to or lower than the heat resistant temperature of the filter. Held, it is possible to continue blocking the melting of the filter.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an exhaust gas treating apparatus of a first embodiment of the present invention.

FIG. 2 is a sectional view showing an air reservoir according to the first embodiment of the present invention.

FIG. 3 is a side view showing the air reservoir according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a combustion control method for fine particles according to the first embodiment of the present invention.

FIG. 5 is a diagram showing temperature characteristics of a filter of the exhaust gas treating apparatus of the first embodiment of the present invention.

FIG. 6 is a diagram showing temperature characteristics of a filter of a conventional exhaust gas treatment device.

FIG. 7 is a diagram showing a regeneration characteristic of the filter of the exhaust gas treating apparatus of the first embodiment of the present invention.

FIG. 8 is a diagram showing a reproduction characteristic of a filter of a comparative example.

FIG. 9 is a cross-sectional view showing an exhaust gas treating apparatus of a second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing an exhaust gas treating apparatus of a third embodiment of the present invention.

[Explanation of symbols]

 1 Filter 2 Diesel Engine (Internal Combustion Engine) 3 Exhaust Pipe 4 Air Pump (Air Supply Means) 5 Heater (Combustion Means) 6 Pressure Sensor 7 Control Unit (Control Means) 8 Air Reservoir 11 Thermocouple (Temperature Detection Means) 12 Throttle Opening Detector (load detection means) 21 Annular portion 21a Inner peripheral surface 22 Cylindrical portion 23 Control valve 24 Hole 25 Partition plate 31 Air reservoir 32 Air supply pipe 33 Control valve 41 Turbocharger 42 Compressor

Claims (5)

[Claims] 1. A filter provided in the middle of an exhaust pipe of an internal combustion engine for collecting fine particles in exhaust gas, air supply means for supplying air for combustion of fine particles to the filter, and the filter collected by the filter. In an exhaust gas treatment device comprising a combustion means for heating and burning fine particles together with air to remove them from the filter, the filter is provided with a temperature detection means for detecting the temperature of the filter, and the temperature detected by the temperature detection means. The exhaust gas treating apparatus is provided with a control means for operating the air supply means when is greater than or equal to a set value. 2. The exhaust gas treatment apparatus according to claim 1, wherein an air reservoir communicating with the air supply means is provided on an outer peripheral portion of either the filter or the exhaust pipe. 3. The filter is configured to control or stop an air supply amount supplied from the air supply means on the basis of output signals of the load detection means for detecting the load of the internal combustion engine and the temperature detection means. 3. A temperature suppressing means for suppressing an increase in temperature of the filter due to combustion of the collected fine particles within a predetermined temperature range is provided.
The exhaust gas treatment device according to the item. 4. A filter provided in the middle of an exhaust pipe of an internal combustion engine having a turbocharger and a compressor driven by the turbocharger, for collecting fine particles in the exhaust gas, and the fine particles collected by the filter. Combustion means that heats and burns with air supplied by the compressor to remove it from the filter, and operates the compressor and combustion means when the pressure of exhaust gas flowing into the filter is detected and the pressure exceeds a predetermined pressure. And an air reservoir provided on the outer peripheral portion of either the filter or the exhaust pipe, and air for particulate combustion is supplied to the filter by the compressor via the air reservoir. Exhaust gas treatment equipment. 5. A method for controlling combustion of fine particles in exhaust gas collected by a filter provided in the middle of an exhaust pipe of an internal combustion engine, the method comprising detecting a temperature of the filter and a load of the internal combustion engine, respectively. When both the temperature of the filter and the load of the internal combustion engine exceed a first set value, the fine particles are burned while controlling the flow rate of the air flowing into the filter, and the temperature of the filter and the internal combustion engine are again generated. The load of
If both the temperature of the filter and the load of the internal combustion engine exceed a second set value that is smaller than the first set value, combustion of fine particles is continued, and either the temperature of the filter or the load of the internal combustion engine Is less than the second set value, the flow rate of the air flowing into the filter is stopped, and the combustion control method for fine particles is characterized.