JPH062531A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a filter from being melted to destruction due to exhaust gas of high temperature by detecting the temperature of the exhaust gas and oxygen concentration in the exhaust gas separately and restricting an inflow of the exhaust gas to the filter on at least one side, according to the results of the detections. CONSTITUTION:In this exhaust emission control device 20, filters 5A, 5B for collecting particulates are arranged in a plurality of branch passages 2A, 2B, which are formed in an exhaust passage 2 of an internal combustion engine 1. In addition, a control valve V1, which switches the connection among the exhaust passage 2, branch passage 2A, 2B, and a discharge port 18 for the gas for regeneration, is arranged in at least a branch part a. In this case, the temperature of the exhaust gas is detected by a detecting means ST. In addition, the oxygen concentration of the exhaust gas is detected by a detecting means SO2. When the temperature of the exhaust gas is higher than a preset value, no exhaust gas is introduced into at least one filter. On the other hand, when the oxygen concentration becomes higher than a prescribed value, the exhaust gas is introduced into at least one filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly, it collects and removes particulates contained in the exhaust gas of a diesel engine with a filter, and burns the particulates collected with this filter. The present invention relates to an exhaust emission control device for an internal combustion engine, which can prevent the filter from being melted in an exhaust emission control device for an internal combustion engine that repeatedly uses the filter by regenerating it.

[0002]

2. Description of the Related Art Exhaust gas of an internal combustion engine of an automobile or the like, especially a diesel engine, contains exhaust particulates (particulates) containing carbon as a main component, which is a cause of exhaust black smoke. From the viewpoint of environmental pollution, it is desirable to remove the particulates. In recent years, it has been proposed to dispose a diesel particulate by this filter by disposing a ceramic filter in the exhaust passage of the diesel engine.

As described above, in the exhaust gas purifying apparatus for an internal combustion engine in which the particulates in the exhaust gas are removed by the filter, the air permeability is gradually increased when the amount of the particulates trapped inside the filter increases as the filter is used. Lost,
Since the engine performance will be deteriorated, it is necessary to periodically burn and regenerate the particulates collected in the filter.

Generally, in the conventional exhaust gas purifying apparatus for an internal combustion engine, when the particulate filter loses air permeability and the pressure of the exhaust gas on the upstream side of the filter becomes larger than the pressure on the downstream side by a predetermined value or more ( When the differential pressure exceeds a predetermined value) is detected by the pressure sensor, and the particulate regeneration process is performed. In this regeneration process, an electric heater usually provided in the vicinity of the filter is energized, or the particulates ignited by igniting the burner are ignited, and a regeneration gas such as secondary air is evacuated from the air pump in the vicinity of the filter. Is performed to burn the particulates.

As described above, normally, the particulates collected by the electric heater or the burner are ignited for regeneration, but in order to prevent battery consumption due to energization, etc., when the temperature of the exhaust gas is high, the collection is performed. An exhaust gas purification device for a dual type internal combustion engine has been proposed in which exhaust gas is introduced into a large amount of filter and the filter is regenerated by exhaust heat (JP-A-60-184917).

[0006]

SUMMARY OF THE INVENTION However, Japanese Patent Laid-Open No. Sho 60
In the exhaust gas purification apparatus for an internal combustion engine disclosed in Japanese Patent Publication No. 184917,
Since hot exhaust gas is made to flow into the particulate filter with a large amount of traps to ignite the particulates, when the engine slows down afterwards, if the amount of air in the exhaust gas increases, the particulates will burn up at once. ,
There was a risk that the combustion temperature would rise excessively and the filter would melt. Even if the engine does not decelerate for a while, the amount of oxygen in the exhaust gas will be small by simply letting the hot exhaust gas flow into the filter in which the particulates are trapped. It could not be regenerated, and there was a risk that a large amount of particulates would remain unburned.

Therefore, an object of the present invention is to solve the problems of the conventional exhaust gas purifying apparatus for an internal combustion engine and to provide an exhaust gas purifying apparatus capable of preventing melting damage of a filter due to high temperature exhaust gas. .

[0008]

In the exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the present invention, which achieves the above object, a plurality of branch passages are provided in a part of the exhaust passage of the internal combustion engine, and the respective branch passages are provided. In the exhaust gas purification device for an internal combustion engine, which is provided with a plurality of filters for collecting particulates, each of which is provided with a flow path switching valve in the vicinity of a branch portion of each branch passage, and which collects particulates by the plurality of filters. An exhaust gas temperature detecting means for detecting the temperature of the exhaust gas, an oxygen concentration detecting means for detecting the oxygen concentration in the exhaust gas, and when the exhaust gas temperature is equal to or higher than a predetermined value, the exhaust gas is supplied to at least one of the filters. When the oxygen concentration in the exhaust gas becomes equal to or higher than a predetermined value after the operation of the first flow path switching unit that switches the flow path switching valve so that the flow does not flow, the at least one of the at least one flow path switching unit Only the exhaust gas is characterized by providing a second flow path switching means for switching the flow path switching valve so as to flow into the filter.

In the exhaust gas purifying apparatus for an internal combustion engine according to the second aspect of the present invention, a plurality of branch passages are provided in a part of the exhaust passage of the internal combustion engine, and a plurality of particulate collecting traps are provided in each branch passage. The filter is provided, a flow path switching valve is provided in the vicinity of the branch portion of each branch passage, the particulates are alternately collected by a plurality of filters, and in an exhaust gas purification device of an internal combustion engine that alternately regenerates the filter, Exhaust gas temperature detecting means for detecting the temperature of the exhaust gas, and the flow path switching valve to prevent the exhaust gas from flowing into the filter for trapping and collecting and the filter during regeneration when the exhaust gas temperature is equal to or higher than a predetermined value. It is characterized in that a flow path switching means for switching is provided. In addition, in the exhaust gas purification apparatus for an internal combustion engine of the second embodiment, further, when the collection amount detecting means for detecting the collection amount of the collection and concentration filter and the collection amount of the collection and concentration filter are less than a predetermined value. It is also possible to provide a flow path switching operation inhibiting means for preventing the flow path switching means from operating even if the exhaust gas temperature is equal to or higher than a predetermined value.

Furthermore, an exhaust gas purification apparatus for an internal combustion engine according to a third aspect of the present invention is an exhaust gas purification apparatus for an internal combustion engine, wherein at least one filter for collecting particulates is provided in an exhaust passage of the internal combustion engine, Exhaust gas temperature detection means for detecting the temperature of the exhaust gas, oxygen supply means for increasing the oxygen component in the exhaust gas to the filter, when the exhaust gas temperature is a predetermined value or more, by operating the oxygen supply means An oxygen concentration increasing means for increasing the oxygen concentration in the exhaust gas is provided.

[0011]

According to the exhaust gas purification apparatus for an internal combustion engine of the first aspect of the present invention, the temperature of the exhaust gas and the oxygen concentration in the exhaust gas are detected, and when the exhaust gas temperature is above a predetermined value, at least 1
In order to prevent the exhaust gas from flowing into the individual filters, the flow path switching valves at the branch portions of the plurality of branch passages that incorporate the filters are switched, and after the operation of the flow path switching means, the oxygen concentration in the exhaust gas is adjusted to a predetermined level. When the value exceeds the value, the flow path switching valve can be switched to the state before switching, so high concentration oxygen is not supplied to the filter whose temperature has risen,
The filter is prevented from being melted.

According to the second embodiment of the present invention, the exhaust gas purification apparatus for an internal combustion engine which alternately collects and regenerates the exhaust gas, detects the temperature of the exhaust gas, and when the exhaust gas temperature is equal to or higher than a predetermined value, traps and collects the exhaust gas. In order to prevent the exhaust gas from flowing into the filter that is or is being regenerated, the flow path switching valves at the branch portions of the plurality of branch passages that incorporate the filter are switched, and the exhaust gas flows into the other filters. As a result, there is no risk that hot exhaust gas will flow through the filter with a small amount of trapping and the filter on the trapping side will be melted and damaged. In the exhaust gas purification device for the internal combustion engine of the second embodiment, the trapping amount of the trapping concentration filter is detected, and when the trapping amount of the trapping concentration filter is less than the predetermined value, the exhaust gas temperature is the predetermined value. Even in the above case, the flow path switching may not be performed.

Further, according to the exhaust gas purifying apparatus for an internal combustion engine of the third aspect of the present invention, the temperature of the exhaust gas is detected, and when the temperature of the exhaust gas is equal to or higher than a predetermined value, the oxygen supply means actuates the exhaust gas. Since the oxygen concentration of is increased, the combustion of particulates trapped when the exhaust gas temperature is high can be advanced.

[0014]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of an embodiment of an exhaust purification device 20 of a reverse flow alternate regeneration dual filter type according to the present invention. In the exhaust emission control system of the diesel engine of this embodiment, the exhaust pipe 2 that guides the exhaust gas from the engine 1 is branched into the branch pipes 2A and 2B at the branch portion a and then merged at the merge portion b to the muffler 6. Connected. A first filter 5A and a second filter 5B are provided in the casings 3A and 3B provided in the middle of the branch pipes 2A and 2B, respectively, in order to collect particulates in the exhaust gas. A honeycomb filter having a large number of filter cells is used as the first filter 5A and the second filter 5B, and the exhaust upstream end and the downstream end of each filter cell are alternately plugged with plugs. Therefore, the first filter 5A and the second filter 5A
The particulates in the exhaust gas flowing into the filter 5B are collected by the filter cell when the exhaust gas passes through the wall surface of the filter cell.

Further, an O ₂ sensor SO2 and an exhaust gas temperature sensor S are provided upstream of the branch portion a of the branch pipes 2A and 2B.
T and the pressure sensor SPU are provided, and the pressure sensor SPD is provided on the downstream side of the merging portion b. And
The pressure difference (differential pressure) between the upstream and downstream sides of the first and second filters 5A and 5B is obtained by inputting the outputs of the pressure sensors SPU and SPD to the ECU (control circuit) 100. Control circuit 100
Determines the regeneration timing of the first and second filters 5A and 5B based on this pressure difference.

On the other hand, the plug members (not shown) near the downstream end faces of the first and second filters 5A and 5B or at the downstream end portions are heated during filter regeneration to ignite particulates. Electric heaters HA and HB are provided, one ends of these electric heaters HA and HB are grounded, and the other ends are switches SW controlled by the control circuit 100.
It is connected to the battery 11 via A and SWB. Further, although not shown in this figure, a vehicle speed sensor for detecting the speed of the vehicle and an accelerator opening sensor for detecting the accelerator opening are provided, and a vehicle speed signal V from the vehicle speed sensor and an accelerator opening sensor are provided. The accelerator opening signal θ is also input to the control circuit 100.

During regeneration of the first and second filters 5A and 5B, the electric heater HA or HB is energized, and the first filter 5A or the second filter 5A or 2B on the energized side is energized.
It is necessary to flow the regeneration gas from the downstream side of the filter 5B and discharge the combustion gas from the upstream side thereof. Therefore, in this embodiment, the regeneration gas supply port 17 is provided at the joining portion b of the branch pipes 2A and 2B, and the regeneration gas supply port 17 is provided.
As a regeneration gas from the electric air pump 9 through a regeneration gas supply passage 7 provided with an on-off valve V3 on the way.
Next air is supplied. Both the electric air pump 9 and the on-off valve V3 are drive-controlled by the control circuit 100. A regeneration gas discharge port 18 is provided at the branch portion a of the branch pipes 2A and 2B. One end of the regeneration gas discharge port 18 is open to the atmosphere, and the on-off valve V
The regeneration gas discharge passage 8 provided with 4 is connected. The on-off valve V4 is also drive-controlled by the control circuit 100.

At the branch portion a where the regeneration gas discharge port 18 opens, the exhaust pipe 2 and the branch pipe 2 upstream of the branch portion a.
A first control valve V1 for switching the connection of A, 2B and the regeneration gas discharge port 18 is provided, and the regeneration gas supply port 17 is provided.
A second control valve V2 that switches the connection of the exhaust pipe 2, the branch pipes 2A and 2B, and the regeneration gas supply port 17 on the downstream side of the merging portion b is provided in the merging portion b that opens.

The first and second control valves V1 and V2 are both driven by a control circuit (ECU) 100, and the first and second control valves V1 and V2 are controlled by a control signal from the control circuit 100. Are linked to be positioned at the solid line position C, the broken line position B, and the alternate long and short dash line position B. Valve V1
The drive of V4 is actually performed by a diaphragm type actuator, a negative pressure switching valve, or an electric type actuator, but its drive mechanism is not particularly limited, and therefore illustration and description thereof are omitted here. .

FIG. 10 and FIG. 11 show an example of actual configurations of the first control valve V1 and the second control valve V2. Butterfly valves are used as the first control valve V1 and the second control valve V2, and the regeneration gas discharge port 18 is used.
And the valve bodies 10b and 11b are rotated around the rotating shafts 10a and 11a provided near the opening of the regeneration gas supply port 17, whereby the regeneration gas discharge port 18 and the regeneration gas supply port 17 are opened. The branch pipes 2A and 2B can be opened on either side.

The solid line position C of the first control valve V1 and the second control valve V2 is the position of the collection state, and the exhaust gas from the engine 1 is the first and second particulate filters 5A, 5
It flows through B and is discharged into the atmosphere through the muffler 6. At this time, the open / close valves V3 and V4 are closed. The position indicated by the one-dot chain line is the position when the first filter 5A is regenerated, and the exhaust gas from the engine 1 flows only through the second filter 5B and is discharged into the atmosphere through the muffler 6. At this time, the opening / closing valves V3, 4 are opened and the heater HA is energized, so that the regeneration gas from the air pump 9 is supplied to the supply port 17.
To flow through the first filter 5A to assist the combustion of particulates, and the combustion gas is exhausted from the exhaust port 18 to the atmosphere. Further, the broken line position B is the position when the second filter 5B is regenerated, and the exhaust gas from the engine 1 flows only through the first filter 5A, passes through the muffler 6, and is discharged into the atmosphere. At this time, the opening / closing valves V3, 4 are opened and the heater HB is energized, and the regeneration gas from the air pump 9 flows from the supply port 17 through the second filter 5B to assist the combustion of particulates and burn. The gas is discharged from the discharge port 18 into the atmosphere.

In the exhaust emission control system 20 for a diesel engine constructed as described above, the control of the first embodiment when the exhaust gas temperature becomes high will be described with reference to FIG. 2 (b). As shown in FIG. 2 (a), the exhaust temperature T, the oxygen concentration O ₂ , the vehicle speed V, the accelerator opening θ, and the pressure difference ΔP between the upstream side and the downstream side of the filters 5A and 5B are set at predetermined intervals. It is assumed to be loaded.

In the first embodiment, as described above, the trapping is performed by the first and second particulate filters 5A and 5B. Therefore, in step 201, the first control valve V1 and the second control valve V2 are controlled to the solid line position C. In step 202, it is judged by the pressure difference ΔP whether or not the filter is the regeneration time, and if it is the regeneration time, step 20
Proceeding to 3, the filter regeneration processing is performed. This reproduction processing is not the subject of the present invention, so its explanation is omitted.

When it is not the regeneration time, the routine proceeds to step 204, where it is judged if the exhaust gas temperature T exceeds 600 ° C. When T ≦ 600 ° C., the process returns to step 202 and T
If> 600 ° C., the routine proceeds to step 205, where it is judged if this state has continued for 10 seconds. If it has not continued for 10 seconds, the routine returns to step 202. If it has continued for 10 seconds, the routine proceeds to step 206, where the first control valve V1 and the second control valve V2 are controlled to the position B indicated by the broken line. As a result, the high temperature exhaust gas flows only in the second particulate filter 5B.

At step 207, it is judged if the engine has decelerated. In this deceleration state, when the engine speed V is reduced by 50%, the return amount of the accelerator opening θ is 50%.
The above is determined, or when the O ₂ concentration is increased by 50% or more. When the engine is in the deceleration state, the routine proceeds to step 208, where the first control valve V1 and the second control valve V2 are controlled to the broken line position b. As a result, the decelerated exhaust gas containing a large amount of oxygen does not flow to the second particulate filter 5B ignited by the high-temperature exhaust gas, but the exhaust gas flows to the first particulate filter 5A. Therefore, the particulates in the second particulate filter 5B do not burn up at once.

When the engine is not in the decelerating state and after the processing of step 208, the routine proceeds to step 209, where it is judged if the exhaust gas temperature T is less than 500.degree. T ≧ 500 ℃
If T <500 ° C., the process proceeds to step 210, and it is determined whether this state has continued for 10 seconds. When 10 seconds have not elapsed, the routine returns to step 209, and after 10 seconds has elapsed, the routine proceeds to step 211, where the first control valve V1 and the second control valve V2 are controlled to the position c of the collecting state and this routine is executed. finish.

As described above, in the exhaust gas purifying apparatus for the internal combustion engine of the first embodiment, when the exhaust gas temperature becomes high, the exhaust gas does not flow into at least one particulate filter, and thereafter the exhaust gas When the oxygen concentration exceeds a predetermined value, exhaust gas containing a large amount of oxygen will flow to the filter to which high-temperature exhaust gas did not flow, so high-concentration oxygen is supplied to the filter whose temperature has risen. And the filter is prevented from melting.

In the embodiment described above, the solid line positions c of the first control valve V1 and the second control valve V2 in the exhaust gas purification apparatus 20 of the reverse flow alternate regeneration dual filter type of FIG. 1 are the positions of the collecting state. The two filters 5A and 5B were used to collect the particulates at the same time, but the two filters 5A and 5B were used to collect the particulates alternately, and the regeneration was also performed after the collection amount reached a predetermined amount. Things are also done. The second embodiment of the present invention described below is a control for high-temperature exhaust gas in an exhaust gas purification apparatus for an internal combustion engine which alternately collects and alternately regenerates the system of FIG.

In the second embodiment shown in FIG. 3, as described above, the trapping is alternately performed by the first and second particulate filters 5A and 5B. In this control, since control is not performed when either the first or second particulate filter 5A or 5B is in the process of reproduction, it is first determined in step 301 whether the filter 5A or 5B is in the process of reproduction. Then, during reproduction, this routine is ended.

On the other hand, when neither filter is being regenerated, the routine proceeds to step 302, where the exhaust gas temperature T is 600 ° C.
It is determined whether or not If T ≦ 600 ° C., this routine is terminated while maintaining the current state, and if T> 600 ° C., the routine proceeds to step 303, where it is judged if this state has continued for 10 seconds. If it has not continued for 10 seconds, return to step 302. If it has continued for 10 seconds, step 3
Go to 04.

In step 304, it is determined whether the filter 5A or the filter 5B is currently in the collecting state. When the filter 5A is trapped and concentrated, the process proceeds to step 305 and the first
The control valve V1 and the second control valve V2 of FIG. As a result, the high-temperature exhaust gas is collected by the second particulate filter 5B which has not been collected until now.
Comes to flow. On the contrary, when the filter 5B is trapped and concentrated, the routine proceeds to step 309, where the first control valve V1 and the second control valve V2 are controlled to the position B of the broken line. As a result, the high-temperature exhaust gas flows into the first particulate filter 5A, which has not been collected so far.
As a result, high-temperature exhaust gas does not flow into the filter for trapping and collecting, so that the particulates in the filter for trapping and collecting are prevented from being ignited, and the exhaust gas containing much oxygen is collected by the deceleration operation of the engine thereafter. The generated particulates do not burn up all at once, and there is no risk of filter damage.

Steps 306 and 3 after step 305
07 and steps 310 and 31 after step 309
1 is for determining whether or not the high temperature exhaust gas temperature has dropped. Therefore, in steps 306 and 310, it is determined whether the exhaust gas temperature T is lower than 500 ° C., and T ≧ 50.
This determination is continued when the temperature is 0 ° C., and when T <500 ° C., the process proceeds to steps 307 and 311 to determine whether or not this state has continued for 10 seconds. When 10 seconds have not elapsed, the process returns to steps 306 and 310, and after 10 seconds has elapsed, the process proceeds to steps 308 and 312, where the first control valve V1 and the second control valve V2 are in the original trapped position (step In step 308, the position is controlled and in step 312, the position is controlled to position a), and this routine ends.

As described above, in the exhaust emission control system for the internal combustion engine of the second embodiment, when the exhaust gas temperature becomes high, the exhaust gas does not flow into the particulate filter on the trapping side, and then the exhaust gas temperature rises. When the temperature falls, the trapped state returns to the original state, so that the high-temperature exhaust gas flows through the filter with a small trapping amount, and the filter on the trapping side is prevented from being melted.

FIG. 4 shows a third embodiment of the present invention, which is a modification of the second embodiment described with reference to FIG. 3. Similar to the second embodiment, the alternate collection in the system of FIG. 1 is performed. , Is control for high-temperature exhaust gas in an exhaust gas purification apparatus for an internal combustion engine that performs alternate regeneration. The third embodiment is different from the second embodiment in that the flow of high temperature exhaust gas is reduced when only a small amount of particulates is trapped in the trap side filter even when the temperature of exhaust gas becomes high. The only difference is that it is not changed. This is because, even if the particulates that are trapped and concentrated are ignited by the high-temperature exhaust gas, the amount of particulates trapped is small and there is no risk of erosion of the filter.

Therefore, the control of the third embodiment is performed by the step 4 between the steps 303 and 304 of the second embodiment.
Since only 01 is inserted, the same steps as those in the second embodiment are designated by the same step numbers, and the description thereof will be omitted. Only the inserted step 401 will be described.
Step 401 is performed after the state where the exhaust gas temperature exceeds 600 ° C. continues for 10 seconds or more. Here, it is determined whether the differential pressure ΔP across the filter for collecting and concentrating exceeds the reference value P1. It As shown in FIG. 5, this reference value P1 is obtained by taking the collection amount on the horizontal axis and the differential pressure on the vertical axis,
It is the differential pressure across the filter when there is a trapped amount that may cause preheating melting loss in the filter. Therefore, in step 401, if the differential pressure ΔP is less than or equal to this reference value P1, there is no risk of melting damage to the filter even if the particulates in the filter ignite and burn, so this routine ends with the current state maintained. However, only in the case of ΔP> P1 that may cause melting loss, the process proceeds to step 304 and thereafter, and the high temperature exhaust gas is made to flow through the filter which is not trapped and concentrated as in the second embodiment.

Next, a fourth embodiment of the present invention will be described. In this embodiment, the electric air pump 9 is provided on the upstream side of the branches 5a of the filters 5A and 5B of the exhaust emission control device 20 shown in FIG. 2 through the secondary air supply passages 7A, 7B
This is realized in the exhaust emission control device 20 'shown in FIG. 6 which is adapted to be supplied with secondary air. On-off valves V5 and V6, which are controlled to be opened and closed by the control circuit 100, are provided in the middle of the secondary air supply passages 7A and 7B, respectively. Since the other configurations of the exhaust emission control device 20 'are the same as the configurations of the exhaust emission control device 20 shown in FIG. 1, the same components are designated by the same reference numerals and the description thereof will be omitted.

A fourth embodiment described here (see FIG. 7)
Are the filters 5A and 5B in the second embodiment.
If any of the above is not being regenerated, and the amount of particulates trapped in the filter for trapping and concentrating is less than a predetermined value that may cause melting damage, the exhaust gas temperature should The particulates that are raised and collected are actively burned and removed. Therefore, the control when the trapped amount of the particulates in the filter for trapping and concentration is larger than a predetermined value that may cause melting loss is the same as steps 301 to 312 of the control of the second embodiment. The same control part is given the same step number and its description is omitted.

The fourth embodiment is different from the control of the second embodiment in that step 301 is provided after step 301 to determine the amount of filter trapped.
Only when the determination in step 701 is NO will be described. When it is determined in step 701 that the trapped amount of the particulates in the trapping concentration filter is smaller than a predetermined value (ΔP ≦ P1) that may cause melting loss, the routine proceeds to step 702, where the exhaust gas temperature T is 450. ℃
It is determined whether or not Then, when T ≦ 450 ° C., this routine is ended while maintaining the current state, and T> 450
When the temperature is ° C, it is determined in step 703 whether this state has continued for 20 seconds or more. 2 when T> 450 ° C
If it is less than 0 seconds, the process returns to step 702, and if 20 seconds or more has elapsed, the process proceeds to step 704.

In step 704, a timer (not shown) of the injection pump is retarded, and the exhaust gas temperature is forcibly raised to a temperature at which the particulates can be self-regenerated. Then, the electric air pump 9 is turned on to assist combustion, and the open / close valve V5 or V6 on the filter side for collecting and collecting is opened to enter the self-regenerating state. In the following step 705, it is determined whether or not the exhaust gas temperature has dropped below 600 ° C., and if not, this self-regeneration state is continued. When it is determined in step 705 that T <600 ° C., the process proceeds to step 706, and it is determined whether or not this state continues for 10 seconds.
When the condition of T <600 ° C. does not continue for 10 seconds, the process returns to step 705, and when it continues for 10 seconds, step 70
7, the electric air pump 9 is turned off, and the open / close valve V5 or V6 that was in the valve open state is closed to end this routine.

As described above, in this embodiment, when the exhaust gas temperature rises above the predetermined temperature when the trapped amount is small,
The exhaust gas temperature is further raised by the retard control of the engine, and the particulates in the trapped state are forcibly combusted by the supply of the secondary air, so that the regeneration interval is lengthened and the number of times of the ordinary regeneration means is reduced. To be done. Lastly, a fifth embodiment of the present invention will be described. This embodiment is realized by the exhaust emission control device 30 shown in FIG. In FIG. 8, 1 is a diesel engine, 2 is an exhaust gas passage, 3 is a casing for accommodating a particulate filter 5 provided in a part of the exhaust gas passage 2, and 4 is an exhaust bypass that bypasses the particulate filter 5. A passage, 7 is a secondary air supply passage, 8 is a combustion gas discharge passage, 9 is an electric air pump for supplying secondary air, 11 is a battery, 100 is a control circuit, SW is a heater switch for energizing the electric heater H, SPU is a pressure sensor provided in the passage 2 on the exhaust gas inflow side of the particulate filter 5, SPD is a pressure sensor provided in the passage 2 on the exhaust gas outflow side of the particulate filter 5, and ST is the particulate filter 5 A temperature sensor provided on the inlet side of the valve, V7 is a switching valve for switching between the exhaust passage 2 and the exhaust bypass passage 4, and V8 is Air bypass passage 4 of the outlet switching valve provided in the outlet, V9 is opened and closed valve in the combustion gas discharge passage 8, V10 is the closing valve of the secondary air supply passage 7.

The control circuit 100 includes, for example, an interface INa for inputting an analog signal, an interface INd for inputting a digital signal, a converter A / D for converting an analog signal into a digital signal, a central processing unit CPU for performing various arithmetic processes, a random processor. Although it is configured by a microcomputer including an access memory RAM, a read-only memory ROM, an output circuit OUT, and a bus line 111 connecting these, a detailed operation description of the configuration will be omitted. The interface INa for inputting an analog signal of the control circuit 100 has a pressure detection signal from pressure sensors SPU and SPD for detecting the pressure of exhaust gas on the upstream side and the downstream side of the exhaust gas path of the particulate filter 5, and a temperature sensor ST. Filter inlet temperature detection signal from the engine, engine speed signal N from a speed sensor (not shown)
An accelerator opening signal θ from the accelerator pedal (not shown) or the like is input, and a signal from a key switch (not shown) is input to the digital signal input interface INd.

When collecting particulates in normal exhaust gas, the valves V7 to V10 are controlled to the positions indicated by the solid lines, and the exhaust gas discharged from the diesel engine 1 is contained in the casing 3 as a particulate filter. The particulates are removed by 5 and released into the atmosphere through a muffler (not shown). On the other hand, when the differential pressure across the particulate filter 5 exceeds the regeneration timing determination value and becomes large, the control circuit 100 switches the valves V7 to V10 from the position of the solid line to the position of the broken line, and the regeneration operation of the filter 5 is performed. Done. During the regenerating operation, the heater switch SW is turned on by the control circuit 100 to energize the heater H, the secondary air is supplied from the electric air pump 9, and the particulates in the filter 5 are burned.

Exhaust gas purification device 30 constructed as described above
In the fifth embodiment (see FIG. 9), first, in step 901, the engine speed Ne and the accelerator opening θ are read, and the engine load L is calculated based on these values. Then, in step 902, the engine load L is 8
It is determined whether or not the pressure exceeds 0 kgf · m. L ≦ 80k
When gf · m, it is judged that the engine load is small, and this routine is terminated. When L> 80 kgf · m, step 903.
Then, it is determined whether or not this state has continued for 10 seconds. When it does not continue for 10 seconds, this routine is ended and 1
When it continues for 0 seconds, it is determined that the engine load is large and the exhaust gas temperature is also high, and the routine proceeds to step 904. Step 90
In 4, the air pump 9 is turned on, and in the following step 905, only the open / close valve V9 is opened to the broken line position.

In step 906, the engine load L is 70 k.
It is determined whether or not gf · m has fallen below. L ≧ 70 kg
When f · m, it is judged that the engine load is large and the judgment of step 906 is repeated. When L <70 kgf · m, the routine proceeds to step 907, where it is judged whether or not this state has continued for 10 seconds. . Step 9 if not continued for 10 seconds
Returning to 06, when it continued for 10 seconds, the engine load was small,
It is determined that the exhaust gas temperature has also dropped, and the routine proceeds to step 908. In step 908, the air pump 9 is turned off, and in the following step 909, the on-off valve V9 is closed to the solid line position.

As described above, in the fifth embodiment, when the temperature of the exhaust gas is equal to or higher than the predetermined temperature, the secondary air is supplied to the filter 5, so that the amount of oxygen supplied to the filter 5 increases, and the exhaust gas of high temperature is increased. As a result, combustion of the particulates collected in the filter 5 is promoted, and the amount of particulates in the filter 5 is reduced. After that, when the exhaust gas temperature becomes lower than the predetermined value, the supply of secondary air is stopped, so the particulates do not burn at once, and at this time, the amount of particulates in the filter 5 also decreases,
Even if the particulates continue to burn, the filter temperature does not rise to melting loss.

In this embodiment, the exhaust gas temperature is estimated by calculating the engine load L from the engine speed Ne and the accelerator opening θ, but as in the first to fourth embodiments described above. The exhaust gas temperature may be detected by the temperature sensor ST. The control of the fifth embodiment is, of course, not executed when the filter 5 is reproducing.

[0047]

As described above, in the exhaust gas purifying apparatus for the internal combustion engine according to the first embodiment of the present invention, the high temperature oxygen is not supplied to the filter whose temperature is rising, so that the filter is prevented from being damaged. In the exhaust gas purification device for an internal combustion engine that alternately collects and alternately regenerates the second embodiment, there is no possibility that high-temperature exhaust gas flows through the filter having a small collection amount and the filter on the collection side is melted and damaged. In the exhaust gas purifying apparatus for the internal combustion engine according to the third aspect of the present invention, the combustion of the particulates trapped when the exhaust gas temperature is high can be advanced. As a result, according to the present invention, there is an effect that it is possible to prevent melting loss of the filter due to high temperature exhaust gas.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration example of an exhaust gas purification apparatus of a reverse flow alternate regeneration dual filter type to which the present invention is applied.

FIG. 2 (a) is a flowchart showing a detection value that is periodically updated, and FIG. 2 (b) is a flowchart showing control at a high temperature of exhaust gas according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the control of the second embodiment of the present invention.

FIG. 4 is a flowchart showing control of a third embodiment of the present invention.

5 is a diagram illustrating a differential pressure reference value in the embodiment of FIG.

FIG. 6 is a diagram showing a schematic configuration example of an exhaust gas purification apparatus of a reverse flow alternate regeneration dual filter type to which a fourth embodiment of the present invention is applied.

FIG. 7 is a flowchart showing the control of the fourth embodiment of the present invention.

FIG. 8 is a diagram showing a schematic configuration example of an exhaust gas purification device of a forward flow regeneration single filter type to which a fifth embodiment of the present invention is applied.

FIG. 9 is a flowchart showing the control of the fifth embodiment of the present invention.

FIG. 10 is an enlarged view showing a specific configuration example of the first control valve of FIG. 1.

11 is an enlarged view showing a specific configuration example of the second control valve of FIG. 1.

[Explanation of symbols]

2 ... Exhaust pipe 2A, 2B ... Branch pipe 5, 5A, 5B ... Filter 7 ... Regeneration gas supply passage 8 ... Regeneration gas discharge passage 9 ... Air pump 17 ... Regeneration gas supply port 18 ... Regeneration gas discharge port 100 ... Control circuit a ... Branching part b ... Merging part H, HA, HB ... Electric heater SO2 ... O ₂ sensor SPU, SPD ... Pressure sensor ST ... Temperature sensor V1 ... First control valve V2 ... Second control valve V3 to V10 … Open / close valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Oki 1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd. (72) Inventor Osamu Hishinuma 1-1-chome, Showa town, Kariya city, Aichi prefecture Nidec Within the corporation

Claims (4)

[Claims] 1. A plurality of branch passages are provided in a part of an exhaust passage of an internal combustion engine, a plurality of filters for collecting particulates are provided in each branch passage, and a flow is provided near a branch portion of each branch passage. In an exhaust gas purification device for an internal combustion engine that is equipped with a path switching valve and collects particulates with multiple filters, an exhaust gas temperature detection unit that detects the temperature of the exhaust gas and an oxygen concentration that detects the oxygen concentration in the exhaust gas. Detection means, first flow path switching means for switching the flow path switching valve so that exhaust gas does not flow into at least one of the filters when the exhaust gas temperature is equal to or higher than a predetermined value, and first flow path switching A second flow path switching means for switching the flow path switching valve so that the exhaust gas flows into only the at least one filter when the oxygen concentration in the exhaust gas exceeds a predetermined value after the operation of the means. Exhaust purification system of an internal combustion engine, wherein a provided. 2. A plurality of branch passages are provided in a part of an exhaust passage of an internal combustion engine, a plurality of filters for collecting particulates are provided in each branch passage, and a branch portion and a merging portion of each branch passage are provided. Each is equipped with a flow path switching valve, and in an exhaust gas purification device for an internal combustion engine that alternately collects particulates with multiple filters and alternately regenerates the filters, detects the temperature of the exhaust gas. Means, and when the exhaust gas temperature is equal to or higher than a predetermined value, the flow path switching valve is switched so that the exhaust gas does not flow into the filter that is trapped and concentrated and the filter that is being regenerated, and the exhaust gas flows into other filters. An exhaust gas purification device for an internal combustion engine, comprising: a flow path switching means. 3. The apparatus according to claim 2, further comprising: a collection amount detecting means for detecting a collection amount of the collection and concentration filter; and a collection amount of the collection and concentration filter being less than a predetermined value, An exhaust gas purifying apparatus for an internal combustion engine, comprising: flow passage switching operation inhibiting means for preventing the flow passage switching means from operating even if the exhaust gas temperature is equal to or higher than a predetermined value. 4. An exhaust gas purification apparatus for an internal combustion engine, wherein at least one filter for collecting particulates is provided in an exhaust passage of the internal combustion engine, an exhaust gas temperature detecting means for detecting a temperature of exhaust gas, and the filter. An oxygen supply means for increasing the oxygen component in the exhaust gas to the exhaust gas, and an oxygen concentration increasing means for operating the oxygen supply means to increase the oxygen concentration in the exhaust gas when the exhaust gas temperature is equal to or higher than a predetermined value. An exhaust purification device for an internal combustion engine, which is provided.