JP2003148130A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of positively reclaiming a filter in an exhaust emission control device purifying exhaust gas of an internal combustion engine by using the filter. SOLUTION: The exhaust emission control device for the internal combustion engine is provided with an exhaust after treatment device 4 arranged in an exhaust passage 2, a plasma generator (a high voltage generator 58) changing into a plasma state the exhaust gas flowing through the exhaust after treatment device 4 and generating activated species, and an ECU 60 controlling operation of the plasma generator. The ECU 60 determines whether the filter can be continuously reclaimed on the basis of sensor signals from temperature sensors 62 and 64 and information such as an operating state of the internal combustion engine 1, and it operates the plasma generator as needed.

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, which purifies exhaust gas of the internal combustion engine using a filter and which can be used by continuously regenerating the filter.

[0002]

2. Description of the Related Art This type of exhaust gas purification apparatus includes a filter provided in an exhaust passage of an internal combustion engine. This filter collects fine particles (PM) contained in the exhaust gas in the process of flowing the exhaust gas. It has a function to do. When a certain amount of fine particles are deposited on the filter, the exhaust resistance increases extremely, so it is necessary to periodically or appropriately oxidize and remove the fine particles from the filter to regenerate the filter.

In a continuous regeneration type filter having an oxidation catalyst on the upstream side, for example, when the exhaust gas temperature of an internal combustion engine rises (for example, about 350 ° C.), NO produced by the reaction between NO in the exhaust gas and oxygen. _{By 2} , fine particles can be removed by continuous combustion. When the particulates are burned and removed, the exhaust resistance of the filter is reduced to a normal level, so that the filter can be continuously used without removing the filter and performing a regeneration operation.

[0004]

However, the exhaust temperature does not rise so much depending on the operating conditions of the internal combustion engine,
Since the reaction between NO and oxygen in the exhaust gas is not promoted, the fine particles cannot be sufficiently burned and removed. If such a state continues for a long period of time, only particulate accumulation proceeds without regeneration of the filter, and the performance of the internal combustion engine may deteriorate due to an extreme increase in exhaust resistance.
Also, if the particulates are left to be deposited without being regenerated for a long period of time, the exhaust gas will reach a high temperature next time, and when the particulates are spontaneously ignited and become combustible, the particulates will burn in the filter. There is also a possibility that the filter progresses at once and emits high heat to melt the filter.

Therefore, the present invention has an object to provide a technique capable of surely regenerating a filter in an exhaust purification system of an internal combustion engine.

[0006]

An exhaust gas purification apparatus for an internal combustion engine according to the present invention (claim 1) is an exhaust aftertreatment apparatus having a continuously regenerable filter, and the exhaust gas flowing through the filter is activated in a plasma state. A plasma generator that generates seeds, a reproducibility determination unit that determines whether continuous regeneration of the filter by combustion of fine particles is possible, and an operation of the plasma generator when the determination result is impossible. The above problem is solved by providing a control means for generating active species by making the exhaust gas flowing through the filter into a plasma state. Incidentally, the exhaust post-treatment device to produce a NO ₂ at a location on the upstream side or the filter of the filter NO ₂
It has a production means, and the produced NO ₂ can burn the particulates collected by the filter. Further, the reproducibility determination means determines whether or not continuous regeneration of the filter is possible based on information on the temperature of the exhaust gas discharged from the internal combustion engine, the temperature of the exhaust aftertreatment device, or the operating state of the internal combustion engine. Can be determined.

Since continuous regeneration of the filter by the exhaust aftertreatment device requires conditions (exhaust temperature, etc.) necessary for combustion of fine particles, continuous regeneration of the filter is impossible by the regeneration possibility determining means (for example, 350 ° C.). In the following case), the operation of the plasma generator is controlled by the control means, and the exhaust gas is brought into the plasma state to generate the active species. As a result, even in the situation where the conditions required for continuous regeneration of the filter are not satisfied, it is possible to effectively burn the particulates collected by the filter.

If the plasma generator is operated in an operating state where the exhaust gas temperature is high, spark discharge is likely to occur. However, when the above control is performed, the plasma generator is operated in the operating state where the exhaust gas temperature is high. Therefore, the adverse effect of high heat due to spark discharge does not occur. Even if it is determined that the continuous regeneration of the filter is impossible as described above, it is considered that it is not necessary to burn the fine particles when the deposition amount is not particularly large. Therefore, the exhaust emission control device of the present invention (claim 2) further comprises regeneration necessity determining means for estimating whether or not the filter needs to be regenerated by estimating the accumulation amount of the particulates collected by the filter. Therefore, when the regeneration possibility determining means determines that the filter cannot be continuously regenerated and the regeneration necessity determining means determines that the filter needs to be regenerated, the control means sets the exhaust gas to a plasma state and activates the active species. The operation of the plasma generator can be controlled to generate In this case, the power consumption can be further reduced by minimizing the operation of the plasma generator.

When a certain amount of fine particles are deposited on the filter, the exhaust resistance increases, the pressure on the upstream side of the filter fluctuates, and the differential pressure across the filter becomes excessive. Further, it is considered that when the internal combustion engine is operated for a long time, the amount of accumulated fine particles increases by that amount, and when the operation time during which continuous regeneration is impossible continues at this time, the amount of accumulated increases accordingly. Therefore, the above-mentioned regeneration necessity determination means is configured to determine the upstream pressure of the filter, the pressure difference between the upstream pressure and the downstream pressure of the filter, the operating time of the internal combustion engine (or the integrated value of the operating time when continuous regeneration is not possible). A preferred mode is one in which it is determined whether or not the filter needs to be regenerated by estimating the deposition amount of the particulates collected by the filter based on any one of the traveling distance of the vehicle equipped with the internal combustion engine and the like.

The operating state of the internal combustion engine has a close correlation with the conditions that enable continuous regeneration of the filter. For example, the exhaust temperature is low in the idle operation range, the no-load low rotation range, the operation range in which the exhaust gas flow rate decreases, etc., and it is difficult to continuously regenerate the filter in the exhaust aftertreatment device. Therefore, in addition to the above-mentioned exhaust aftertreatment device and plasma generating device, a separate and independent configuration of the present invention (claim 3) includes an operating state detecting means for detecting an operating state of the internal combustion engine, and a detecting state of the operating state detecting means. Based on the result, an operating state determination means for determining whether the internal combustion engine is in a specific operating state of an idle operating range, a no-load low rotation range, or an operating range in which the flow rate of exhaust gas decreases, and an operating state determination And a control means for controlling the operation of the plasma generator so as to generate the active species by setting the exhaust gas in the plasma state when it is determined by the means to be in the specific operation state.

Since the space velocity (SV ratio) of the exhaust gas in the filter is low in each of the above-mentioned operating states, if the active species are generated with the exhaust gas in the plasma state at this time, the reaction efficiency of the active species is high and the combustion of fine particles is performed. Efficiency is improved. on the other hand,
If the plasma generator is operated in an operating state where the exhaust temperature is high, spark discharge is likely to occur, but when the above control is performed, the plasma generator is not operated in the operating state where the exhaust temperature is high. Therefore, the adverse effect of high heat due to spark discharge does not occur.

It is preferable that the plasma generator uses the exhaust gas on the upstream side of the filter and the exhaust gas passing through the filter in a plasma state to generate active species (claim 4). In this case, the exhaust gas on the upstream side of the filter is brought into a plasma state to generate active species, and the exhaust gas is further brought into a plasma state in the filter to regenerate / maintain active species.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can take a preferred embodiment as, for example, an exhaust emission control device for an internal combustion engine mounted on a vehicle. FIG. 1 shows an internal combustion engine 1 mounted on a vehicle.
Is schematically shown. In the exhaust passage 2 of the internal combustion engine 1,
An exhaust aftertreatment device 4 is provided. Exhaust aftertreatment device 4
Is a diesel particulate filter (hereinafter "DP
It is abbreviated as "F". ) 6, the DPF 6 can collect the fine particles (PM) in the exhaust gas to purify the exhaust gas. A pre-stage catalyst 8 is provided on the upstream side of the DPF 6, and the pre-stage catalyst 8 has a function of producing NO ₂ from the exhaust gas by its catalytic action (NO ₂ producing means). Instead of using the pre-stage catalyst 8, a catalyst having a NO ₂ generating function may be supported on the DPF 6.

2 and 3 show the exhaust aftertreatment device 4 in more detail. The exhaust after-treatment device 4 has a cylindrical case body 12, and one end (upstream side in FIG. 2) of the case body 12 is closed by an end plate 14. The above DPF
6 and the pre-catalyst 8 are housed in the case body 12, and the DPF 6 is longitudinally extended from one end side to the other end side.
And the pre-stage catalyst 8 is sequentially arranged. These DPF
A filter internal passage 18 and a catalyst internal passage 19 penetrating in a tunnel shape are formed in the central portions of 6 and the pre-catalyst 8, respectively. The filter internal passage 18 and the catalyst internal passage 19 are formed at both ends of the DPF 6 and the pre-catalyst 8, respectively. It is open on the surface. Therefore, DPF 6 and pre-catalyst 8
Each has a thick tubular shape as a whole, and the outer peripheral portions of the respective internal passages 18 and 19 are configured as a filter material and a catalyst material. In the case body 12, the filter internal passage 8 and the catalyst internal passage 19 are connected to each other by a connecting pipe 21, and the inside of the connecting pipe 21 is an intermediate internal passage 23.

An inlet pipe 20 is inserted through the filter internal passage 18 in a state where the DPF 6 is housed in the case body 12. The inlet pipe 20 projects from one end surface of the DPF 6 and extends through the end plate 14 described above. The inlet pipe 20 is connected to the exhaust passage 2, and the exhaust gas is introduced into the case body 12 through the inlet pipe 20. The DPF 6 and the pre-catalyst 8 can allow the exhaust gas to flow through the filter internal passage 18 and the catalyst internal passage 19, respectively, but sufficient airtightness is ensured on their peripheral walls.
Therefore, the exhaust gas flowing through the filter internal passage 18 and the catalyst internal passage 19 does not flow into the DPF 6 and the pre-stage catalyst 8 through the peripheral wall.

A lid member 22 is attached to the other end of the case body 12, and the case body 12 and the lid member 22 are flange-joined to each other. In this state, the lid member 22
Covers the other end opening of the case body 12 and hermetically seals the inside of the case body 12. As shown, the lid member 22 is formed in a cup shape, and a space of a certain size is secured inside the lid member 22. Therefore, the other end of the case body 12 is not closed by the opening, and the other end is opened inside the lid member 22.

A partition chamber 24 is secured in the case body 12 between the DPF 6 and the end plate 14, and the partition chamber 24 surrounds the outer circumference of the inlet pipe 20. Further, an opening 26 is formed laterally at one end of the case body 12, and the opening 26 communicates with the partition chamber 24. An outlet pipe 28 is attached to the opening 26, and the outlet pipe 28 is connected to the downstream side of the exhaust passage 2.

A stud bolt-shaped inner electrode 30 is inserted into the filter inner passage 18 and the catalyst inner passage 19, and the inner electrode 30 extends from the other end of the case body 12 to one end thereof. It extends approximately through the center of the passage 19. The base end of the inner electrode 30 is supported by the lid member 22 described above, and therefore, the inner electrode 30 is attached to the case body 12 integrally with the lid member 22.

More specifically, the base end portion of the inner electrode 30 is covered with a holder 32 made of an insulator (eg, insulator), and the periphery of the holder 32 is further covered with an inner cap 34 made of an insulator. There is. The inner cap 34 has a neck portion 36 in the center, and the inner cap 34 supports the inner electrode 30 in a state where one end portion of the holder 32 is inserted into the neck portion 36. An opening 38 is formed in the center of the lid member 22, and the inner cap 34 has the neck portion 36 inserted through the opening 38 in a state of being in close contact with the inner surface of the lid member 22. An outer cap 40 is covered on the neck portion 36 on the outer side of the lid member 22, and the outer cap 40 is placed between the outer cap 40 and the inner cap 34.
It is attached so that 2 is sandwiched. The outer peripheral surface of the inner cap 34 and the inner surface of the lid member 22 are sealed with an insulating seal mat 41. In addition, between the inner cap 34 and the holder 32, and between the neck portion 36 and the outer cap 40. The space between them is also properly sealed.

The base end portion of the inner electrode 30 projects outward from the lid member 22, and the projecting portion penetrates the outer cap 40. Both ends of the inner electrode 30 are threaded, and a nut 42 with a flange is screwed into the inner electrode 30 outside the case body 12. A hollow hole 44 is formed in the center of the outer cap 40,
A coil spring 46 is housed in the recess hole 44. The coil spring 46 is compressed by screwing the nut 42 described above in a state of being fitted to the outside of the inner electrode 30.

A large number of discharge plates 48 are arranged in the longitudinal direction on the inner electrode 30. As shown in FIG. 3, each discharge plate 48 is fixed to the outer periphery of the inner electrode 30 and spreads around, and a discharge tip 50 radially extending from the inner electrode 30 is formed on the outer peripheral edge thereof. The discharge tip 50 is not in contact with the peripheral wall of the filter internal passage 18 or the catalyst internal passage 19 and has an infinitely small curvature at its tip.

On the other hand, the inner electrode 30 is provided inside the case body 12.
A cap-type nut 52 is screwed into the tip of the electric discharge plate 48 by tightening the nut 52.
It is fixed at 0. The inner electrode 30 contacts one end of the holder 32 via the spacer 54, whereby the holder 32
The axial movement of the inner electrode 30 with respect to is restricted. Further, as described above, the inner electrode 30 is tightened to the outer nut 42 via the coil spring 46, so that the spacer 54 is elastically pressed against the holder 32.

An outer electrode 56 is arranged along the inner peripheral surface of the case body 12, and the outer electrode 56 is the DPF 6.
Is spread over the entire area between the outer periphery of the case and the inner peripheral surface of the case body 12. Further, a high voltage generator 58 is connected to the above-mentioned inner electrode 30 and outer electrode 56, so that a high voltage is applied between these inner and outer electrodes 30, 56.

When exhaust gas is introduced into the case body 12 from the exhaust passage through the inlet pipe 20 during operation of the internal combustion engine, the exhaust gas flows into the filter internal passage 18 of the DPF 6. At this time, a discharge is generated between the inner and outer electrodes 30, 56 by the high voltage generator 58, and the exhaust gas becomes a plasma state in the filter inner passage 18. Further, the exhaust gas that has passed through the filter internal passage 18 and the catalyst internal passage 19 of the DPF 6 escapes into the space inside the lid member 22 described above,
The flow direction of the exhaust gas is reversed in this space, and the exhaust gas is introduced into the pre-catalyst 8 from the other end opening of the case body 12. When the exhaust gas passes through the front catalyst 8, the DPF 6
Will be introduced to. When the exhaust gas flows through the pre-stage catalyst 8, NO ₂ is generated here. Also, the exhaust gas is DPF
When flowing through 6, the fine particles therein are collected and the exhaust gas is purified. Further, in both of the pre-stage catalyst 8 and the DPF 6, the high voltage generator 58 is used to
Discharge occurs between 56 and the exhaust gas becomes a plasma state.

As described above, in the process of the exhaust gas flowing through the case body 12, the exhaust gas is mixed with the pre-catalyst 8 and the DPF.
6, the plasma state is established in the filter internal passage 18 and the catalyst internal passage 19, and further in the pre-stage catalyst 8 and the DPF 6. Therefore, in any case, active species (for example, O ^* , O ²⁻ , N
O ₂ etc.) is generated (plasma generator).

The exhaust emission control device is an electronic control unit (hereinafter,
It is abbreviated as "ECU". ) 60 equipped with this EC
U60 can control the operation of high voltage generator 58. Specifically, the ECU 60 starts or stops power supply by the high voltage generator 58 as necessary, and controls the exhaust gas to be in a plasma state to generate active species (control means).

The ECU 60 collects information from various sensors in order to execute control. Specifically, temperature sensors 62 and 64 are provided in the exhaust passage 2 and the exhaust aftertreatment device 4, and the ECU 60 determines the exhaust gas temperature and the exhaust aftertreatment device 4 based on the sensor signals from these temperature sensors 62 and 64. The internal temperature can be detected. Also internal combustion engine 1
A crank angle sensor 66 and a vehicle accelerator position sensor 68 are provided to detect the driving state of
Based on the sensor signals from these sensors 66 and 68, E
The CU 60 can detect the operating state of the internal combustion engine 1, such as the load and rotation speed.

In the exhaust passage 2, exhaust pressure sensors 70 and 72 are provided before and after the exhaust aftertreatment device 4 (upstream side and downstream side), respectively.
Is provided, and the ECU 60 can detect the exhaust pressure on the upstream side and the downstream side of the DPF 6, respectively, based on the sensor signals from the sensors 70 and 72. E
The CU 60 can estimate the amount of fine particles deposited on the DPF 6 by performing arithmetic processing based on the various information detected. Specifically, as described above, the deposition amount of fine particles is DP
Since there is a correlation with the exhaust resistance of F6, it is possible to estimate the deposition amount of fine particles based on the exhaust pressure on the upstream side of DPF6 and the differential pressure between the upstream pressure and the downstream pressure.

Further, in the exhaust aftertreatment device 4, the DPF 6
If the continuous regeneration is not continuously performed, the particulates are accumulated on the DPF 6 without being burnt and removed during that period. In particular, the DPF 6 does not reach the combustion temperature of the particulates in the low exhaust temperature operation state, and the exhaust aftertreatment device 4 does not continuously regenerate the DPF 6 in such an operation state. Therefore, the ECU 60 can estimate the deposition amount of fine particles by accumulating the operating time of the internal combustion engine 1 (or the operating time when continuous regeneration is impossible) and the traveling distance of the vehicle (or the traveling distance in the city). it can.

FIG. 4 shows a control routine executed by the ECU 60. Hereinafter, the operation of the exhaust emission control device associated with the execution of this control routine will be described. First, the ECU 60
Reads various information at the start of control (step S1). Here, information such as the detected exhaust gas temperature, the temperature of the exhaust aftertreatment device 4, the operating state of the internal combustion engine 1, and the estimated particulate deposition amount is read.

Next, the ECU 60 determines whether or not the continuous regeneration of the DPF 6 is possible in the exhaust aftertreatment device 4 based on the read various information (step S2). This determination can be performed based on, for example, the exhaust gas temperature, the temperature of the exhaust aftertreatment device 4, or the operating state of the internal combustion engine 1 (regeneration availability determination means). When it is determined that the continuous regeneration of the DPF 6 is possible (Yes), the ECU 60 returns the control routine without executing the subsequent steps S3 to S5. In this case, N in DPF6
Since it is expected that O ₂ will perform continuous regeneration that promotes combustion of fine particles, the ECU 60 controls the high voltage generator 58,
That is, the control for operating the plasma generator is not performed.

On the other hand, if it is determined that continuous regeneration is impossible (No), the ECU 60 next determines whether or not regeneration of the DPF 6 is necessary (step S3). This determination can be performed based on the estimated deposition amount of fine particles. For example, when it is recognized that the exhaust resistance increases due to the deposition of fine particles and the performance of the internal combustion engine 1 may be adversely affected, the ECU 60 regenerates the DPF 6. Is determined to be necessary. Alternatively, if it is recognized that if the amount of accumulated fine particles further increases after this, and the DPF 6 is continuously regenerated next time, there is a risk that the combustion will progress at once and cause the DPF 6 to be melted and damaged. It is determined that reproduction is necessary (reproduction necessity determination means).

If it is determined that the continuous regeneration of the DPF 6 is not necessary (No), the ECU 60 returns the control routine without executing the subsequent steps S4 and S5. In this case, it is expected that the deposition amount of fine particles will not increase as compared with the case where continuous regeneration is required.
U60 does not control the high voltage generator 58. In this case, the generation of plasma is suppressed to the minimum, so that the power consumption is saved.

On the other hand, when it is determined that continuous regeneration is necessary (Yes), the ECU 60 next determines the space velocity (SV).
It is determined whether or not the operating ratio is low (step S4). This determination can be made based on the operating state of the internal combustion engine 1 read in step S1. here,
The space velocity is a value obtained by dividing the exhaust gas flow rate S by the catalyst capacity (capacities of the pre-stage catalyst 8 and the DPF 6 in this embodiment) V (= S
/ V), and it is considered that the spatial velocity of exhaust gas is relatively low in, for example, an idle operation region, a no-load low rotation region, and an operation region where the exhaust gas flow rate decreases.
Therefore, when the ECU 60 recognizes that the internal combustion engine 1 is in the above operating range from the information such as the load and the rotation speed, it can determine that the internal flow rate is in an operating state (specific operating state) in which the spatial flow velocity is low (operating state). Determination means).

When it is determined that the operating condition is not low (No), the ECU 60 returns the control routine without executing the next step S5. In this case, since the space flow velocity is high, it is expected that the particulates are difficult to be efficiently burned and removed even when the activated species are generated in the exhaust gas in the plasma state, and therefore the ECU 60 does not control the high voltage generator 58.

On the other hand, if it is determined that the operating condition is low (Yes), the ECU 60 starts the power supply by the high voltage generator 58 and causes the discharge between the inner and outer electrodes 30, 56 (step S5). In this case, the exhaust gas is in a plasma state in the filter internal passage 18 in the case body 12 and the DPF 6 as described above, and the active species generated at this time generate fine particles even under a relatively low temperature condition (for example, 150 ° C. or higher). Since it can be combusted, the DPF 6 is continuously regenerated. As described above, by generating the active species in an operating state where the space velocity is low, the reaction efficiency of the active species is high and the fine particles are efficiently burned, so that the regeneration efficiency of the DPF 6 is greatly improved.

Further, since the exhaust gas which has been in the plasma state in the filter internal passage 18 is again in the plasma state in the DPF 6, the active species are well regenerated and maintained during this period. Therefore, the fine particles can be burned uniformly throughout the DPF 6, and the purification performance thereof can be kept uniform as a whole. Further, since the exhaust gas in the plasma state is rendered harmless by the action of the active species, the purification of the exhaust gas itself is promoted also in the filter internal passage 18 and the DPF 6.

The exhaust gas that has passed through the DPF 6 escapes to the one end side in the case body 12, and is guided to the opening 26 via the partition chamber 24. Then, the exhaust gas is discharged through the opening 26.
Is discharged from the case body 12 to the outlet pipe 2
8 through the exhaust passage 2 on the downstream side. Figure 5
An example of temporal changes in the exhaust gas temperature and the deposition amount of fine particles due to the execution of the control routine described above is shown.

For example, the accumulation amount of fine particles gradually increases with the passage of the operating time from the initial time point (time t ₀ ), and at a time point (time t ₁ ) after a certain period of time, the accumulation amount of the predetermined amount PM Has reached ₁ . Thereafter, when the deposition amount further increases, it is determined in step S3 described above that the DPF 6 needs to be regenerated, but the exhaust temperature rises and reaches a predetermined value Ta (for example, 350 ° C.). Then, since the DPF 6 can be continuously regenerated from this point (time t ₂ ), the exhaust post-treatment device 4 satisfactorily burns fine particles by the generated NO ₂ .

Therefore, since the ECU 60 determines that the continuous regeneration of the DPF 6 is possible during the period when the exhaust gas temperature is equal to or higher than the predetermined value Ta (time t _{2 to} t ₃ ) (step S2 = Yes), the high voltage No power is supplied by the generator 58. Further, during the above period (time t _{2 to} t ₃ ), the DPF 6 is continuously regenerated, the amount of accumulated fine particles is decreased, and the inlet (upstream side) pressure of the DPF 6 is decreased.

After that, for example, when the vehicle is traveling in the city for a long time, the exhaust temperature is always lower than the predetermined value Ta (step S2 = No), and the amount of accumulated fine particles gradually increases. To go. Then, when the accumulated amount of fine particles reaches the predetermined value PM ₂ , the ECU 60 determines that the regeneration of the DPF 6 is necessary (step S3 = Yes). At this time, if it is determined that the operating state in which the space flow velocity is further low (step S4 = Yes), the ECU 60 starts the power supply by the high voltage generator 58 (step S5) and sets the exhaust gas to the plasma state to generate the active species. To generate.

When the power supply by the high voltage generator 58 is started, the DP is activated by the action of active species from that point (time t ₄ ).
The continuous regeneration of F6 is performed, and the fine particles are burned to reduce both the deposit amount and the inlet pressure. At this time, the high voltage generator 58 may apply a pulse voltage.
After this, for example, when a predetermined time Tb elapses, the ECU 60
Stops the power supply by the high voltage generator 58, and once ends the execution of the control routine. It should be noted that the end of the control routine may be judged by the elapsed time, or may be judged by confirming the decrease in the amount of accumulated fine particles and the decrease in the inlet pressure of the DPF 6.

By executing such control, even if the DPF 6 cannot be continuously regenerated due to continuous urban driving, the fine particles can be effectively burned by the generation of the active species. Therefore, the fine particles are DPF6.
It is possible to prevent the deterioration of the performance of the internal combustion engine 1 due to the pressure loss of the exhaust gas by continuing the operation in a state where a large amount is collected. Further, when a large amount of fine particles are collected in the DPF 6, when the internal combustion engine 1 next shifts to an operating region where the exhaust gas temperature is high, the fine particles are spontaneously ignited and regenerated, so that the combustion of the fine particles proceeds at once. However, there is a possibility that high heat may be generated and the DPF 6 may be melted and damaged, but by executing this control, such a situation can be avoided.

Further, when power is supplied by the high voltage generator 58 under high temperature conditions, spark discharge is likely to occur due to the high density of the air layer. However, by performing this control, the DPF 6 in the exhaust aftertreatment device 4 is performed. When the condition for continuous regeneration of is satisfied (for example, 350 ° C. or higher), the ECU 60 does not supply power by the high voltage generator 58 (step S2 = No). Therefore, the high heat due to the spark discharge does not adversely affect the operation of the plasma generator.

In the determination of step S4, plasma is generated by determining an operating range in which the space flow velocity (SV ratio) decreases, such as an idle operating range, a no-load low rotation range, or an operating range in which the exhaust gas flow rate decreases. Thereby, the efficiency of the oxidation reaction between the active species and the fine particles can be improved. In particular, by generating plasma in an idle operation range, a no-load low rotation range, or an operation range in which the exhaust gas flow rate decreases, for example, even in a situation in which city running continues and continuous regeneration of the DPF 6 is not performed, It is possible to effectively burn the collected fine particles. Therefore, as described above, it is possible to prevent problems such as performance deterioration of the internal combustion engine 1 and melting loss of the DPF 6 due to the large amount of accumulated fine particles.

The control routine shown in FIG. 4 is a preferred example, but it is also possible to execute a control example in which the processes of steps S3 and S4 are omitted. First, when the ECU 60 determines in step S2 that continuous regeneration of the DPF 6 is impossible (step S2 = No), steps S3 and S4 are performed.
Then, step S5 is immediately executed. In this control example, the fine particles are burned even in an operating state where the exhaust gas temperature is relatively low, for example, when driving in an urban area, so that the DPF 6 is regenerated satisfactorily throughout the operation of the vehicle.

In another control example, when the ECU 60 determines in step S2 that the DPF 6 cannot be continuously regenerated (step S2 = No), the process proceeds to step S3 to determine whether regeneration is necessary. Then, when it is determined that the regeneration is necessary (step S3 = Yes), the ECU 60 bypasses step S4 and executes step S5. In the case of this control example, in an operating state where the exhaust gas temperature is relatively low, for example, when driving in an urban area, the high voltage generator 58 supplies power only when the DPF 6 needs to be regenerated, so that plasma is generated. It is possible to further reduce power consumption by minimizing the above.

In the control routine described above, the ECU 60 performs various determinations (steps S2 to S4) by performing arithmetic processing based on various types of read information. For these determinations, a determination map prepared in advance is used. Good. In this case, the ECU 60 searches the determination map from various information,
Whether continuous regeneration of the DPF 6 is possible (step S
2) Whether the DPF 6 can be regenerated (step S)
3) It is possible to determine whether the space flow velocity is low (step S4).

Further, the above-described one embodiment is suitable as an exhaust gas purification apparatus for an internal combustion engine mounted on a vehicle,
INDUSTRIAL APPLICABILITY The present invention is widely applicable not only for vehicles but also as a general exhaust gas purification apparatus for internal combustion engines. In addition, it goes without saying that the specific shape and specifications of the exhaust post-treatment device 4 can be appropriately modified according to the embodiment of the present invention, and is not particularly limited to the illustrated embodiment.

In each of the above-described embodiments, the introduction passage is formed inside the DPF and the catalyst, and the flow of the exhaust gas passing around the inner electrode in the introduction passage is reversed to flow into the DPF and the catalyst. , A hollow portion independent of the exhaust gas is provided in the central portion of the DPF and the catalyst to dispose the inner electrode, and an introduction passage is formed outside the DPF and the catalyst to allow the flow of the exhaust gas passing through the introduction passage. Invert and DPF
And may be flowed into the catalyst.

[0051]

According to the exhaust gas purifying apparatus for an internal combustion engine (Claim 1) of the present invention, the filter can be regenerated in all operating regions of the internal combustion engine. Therefore, the performance of the internal combustion engine and the durability / reliability of the filter are enhanced, and the exhaust gas purification performance is significantly improved. In particular, if the plasma generator is operated by estimating the amount of particulates deposited on the filter (claim 2), power consumption can be minimized. Further, it is preferable to estimate the deposition amount of fine particles based on the exhaust pressure, the operating time, etc., so that highly reliable control can be realized.

In the exhaust gas purification device for an internal combustion engine according to the present invention (claim 3), the regeneration efficiency of the filter is high because the plasma generator is operated by judging the spatial flow velocity in the filter.
It is possible to efficiently improve the performance of the internal combustion engine and the durability and reliability of the filter. Also, by improving the regeneration efficiency of the filter, the operating time of the plasma generator can be shortened and power consumption can be saved.

In the plasma generator of the present invention, the filter and the exhaust gas on the upstream side thereof are put into a plasma state to generate active species (Claim 4). Therefore, active species are regenerated and maintained without an exhaust aftertreatment device. By doing so, it is possible to efficiently burn the fine particles collected by the filter even at a low exhaust gas temperature.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an exhaust gas purification device for an internal combustion engine of an embodiment.

FIG. 2 is a detailed view of an exhaust aftertreatment device.

3 is a sectional view of the exhaust aftertreatment device taken along the line III-III in FIG.

FIG. 4 is a flowchart showing an example of a control routine executed by an ECU.

FIG. 5 is a time chart showing changes in various states associated with execution of a control routine.

[Explanation of symbols]

1 Internal Combustion Engine 2 Exhaust Passage 4 Exhaust Aftertreatment Device 6 DPF (Filter) 8 Pre-stage Catalyst (NO ₂ Generation Means) 30 Inner Electrode (Plasma Generator) 56 Outer Electrode (Plasma Generator) 58 High Voltage Generator (Plasma Generator) ) 60 ECU

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 19/08 B01D 46/42 B // B01D 46/42 Z 53/36 101Z 103B 103C F term (reference) 3G090 AA01 AA03 BA01 DA03 DA04 DA12 DA18 DA20 DB03 EA01 EA02 4D048 AA06 AA14 AA18 AB01 AB06 CC41 CD05 CD08 DA01 DA02 DA06 DA20 EA03 4D058 JA32 MA44 MA51 MA60 PA04 SA08 TA06 4G075 AA03 AA22 BAA37 CA61 DA21 CAA37 AA61 A21 CAA37 A61 A21 CAA37 AA21 AA37 CA61 AA21 CAA37 A61 A21 CAA37

Claims (4)

[Claims] 1. A filter provided in an exhaust passage of an internal combustion engine for collecting fine particles in exhaust gas, and NO ₂ generating means for generating NO ₂ at an upstream side of the filter or at any position on the filter. And a continuous regeneration type exhaust aftertreatment device capable of combusting the particulates collected in the filter by the generated NO _2, and passing through at least one of the exhaust passage on the upstream side of the filter and the filter. A plasma generator that generates active species by using exhaust gas as a plasma state, the temperature of the exhaust gas discharged from the internal combustion engine, based on the information of the temperature of the exhaust aftertreatment device or the operating state of the internal combustion engine, Regeneration possibility determination means for determining whether or not the filter can be continuously regenerated by the exhaust aftertreatment device; and the filter by the regeneration possibility determination means. When it is determined that the continuous regeneration of the exhaust gas is not possible, the exhaust gas of the internal combustion engine is equipped with a control unit that controls the operation of the plasma generator to generate the active species by setting the exhaust gas in the plasma state. Purification device. 2. The apparatus further comprises regeneration necessity determining means for estimating whether or not the filter needs to be regenerated by estimating a deposition amount of fine particles trapped in the filter, and the control means includes the regeneration means. When the availability determination means determines that continuous regeneration of the filter is impossible and the regeneration necessity determination means determines that the filter needs to be regenerated, the plasma is generated to generate active species by using exhaust gas as a plasma state. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the operation of the device is controlled. 3. A filter provided in an exhaust passage of an internal combustion engine for collecting fine particles in exhaust gas, and a NO ₂ generating means for generating NO ₂ at an upstream side of the filter or at any position on the filter. And a continuous regeneration type exhaust aftertreatment device capable of combusting the particulates collected in the filter by the generated NO _2, and passing through at least one of the exhaust passage on the upstream side of the filter and the filter. A plasma generator that generates active species by using exhaust gas as a plasma state, an operating state detecting unit that detects an operating state of the internal combustion engine, and based on a detection result of the operating state detecting unit, the internal combustion engine has an idle operating range, An operating condition determining means for determining whether the engine is in a specific operating condition of either a no-load low rotation speed region or an operating region where the flow rate of exhaust gas decreases; When it is determined by the determination means that the exhaust gas is in the specific operation state, the control means controls the operation of the plasma generator to generate the active species by setting the exhaust gas in the plasma state. Exhaust purification device. 4. The plasma generation device generates active species by using exhaust gas upstream of the filter and exhaust gas passing through the filter in a plasma state to generate active species. An exhaust gas purification device for an internal combustion engine as described.