JP2001098931A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect abnormality of a discharge state caused by deposition of soot or dew condensation on the surfaces of insulator flow passages. SOLUTION: A plurality of fluid passage structures 12 made of insulators having a plurality of insulator flow passages 13 are layered, and insulation resistance detecting terminals 21, 22 for detecting resistance values on upstream end surfaces of the insulating flow passages 13. As the deposit of soot and dew condensation is increased, the resistance values on the surfaces of the insulator flow passages 13 are lowered to deteriorate a discharge state. With focusing on the fact, the resistance values (resistance values on the upstream end surfaces of the insulating flow passages 13) between the insulation resistance detecting terminals 21, 22 are detected in a period capable of stopping the discharge before starting an engine and/or when the engine is in operation. The discharge state is determined based on the resistance values. When the engine is in operation and discharge abnormality caused by the deposit of soot is determined, an air-fuel ratio of exhaust gas is controlled to be temporarlly rich to burn off the soot deposited to the insulator flow passages 13.

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 uses a discharge to promote a purification reaction of exhaust gas.

[0002]

2. Description of the Related Art In recent years, a new exhaust gas purifying technique for purifying exhaust gas using discharge energy has been studied.
In this technique, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-59934, an exhaust gas of an internal combustion engine is caused to flow through a flow path formed between discharge electrodes, and a high voltage is applied between the discharge electrodes to discharge. By generating the gas, the exhaust gas is purified. Further, in this publication, the relationship between the normal discharge voltage and the discharge current is stored in a memory in advance, and the relationship between the current discharge voltage and the discharge current is compared with the normal relationship stored in the memory. There is disclosed a technique for determining a current discharge state by using the above-described method.

[0003]

By the way, in the above publication, the exhaust gas comes into contact with the surface of the discharge electrode. However, the exhaust gas is at a high temperature and has an oxidizing component (such as NOx) or a reducing component (such as NOx). CO, HC, etc.), there is a disadvantage that the surface of the discharge electrode is easily deteriorated and durability is poor.

Therefore, a flow path of exhaust gas is formed by an insulator layer, and a discharge electrode is buried in the insulator layer.
It has been proposed to prevent the exhaust gas from contacting the discharge electrode, and to generate a discharge in the flow path via the insulator layer to purify the exhaust gas.

However, in this configuration, if soot such as unburned components in exhaust gas adheres to the surface of the insulator layer or dew forms, the insulation (resistance) of the surface of the insulator layer decreases. May not be able to obtain a good discharge state,
Even in such a state, there is a tendency that the detected value of the discharge current hardly changes. This is because even if the discharge decreases, the leakage current flowing on the surface of the insulator layer increases and the change in the current detection value decreases accordingly (only the discharge current is detected separately from the leakage current). It is difficult). Therefore, in the method of determining the discharge state based on the relationship between the discharge voltage and the discharge current as described in the above publication, even if the discharge state becomes abnormal due to soot adhesion or dew condensation on the surface of the insulating layer, It is difficult to accurately detect a discharge abnormality.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, has as its object to purify exhaust gas by generating discharge through an insulator layer. It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine that can accurately detect an abnormality in a discharge state due to adhesion of soot or dew condensation water.

[0007]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, comprising: an insulating layer that forms an insulator flow path; In a device that purifies exhaust gas by generating a discharge within the device, the resistance value of the surface of the insulator flow path is detected by the insulation resistance detecting means at a portion where the exhaust gas contacts, and the discharge state is determined based on the detected resistance value. The discharging state is determined by the determining means. That is, as the amount of soot or dew adhering water adhering to the surface of the insulator flow path increases, the resistance value of the surface of the insulator flow path decreases at that portion, and the discharge state deteriorates. Therefore, if the resistance value is detected at a location on the surface of the insulator flow path where soot and dew condensation water easily adheres, the resistance value is a parameter for evaluating the adhesion amount and the discharge state of the soot and dew water, If the discharge state is determined based on the resistance value, it is possible to accurately detect an abnormality in the discharge state due to the adhesion of soot or dew water on the surface of the insulator flow path.

In this case, it is preferable that the resistance value is detected at the upstream end face of the insulator flow path. That is, since the upstream end face of the insulator flow path is the place where soot in the exhaust gas is most likely to adhere, if the resistance value is detected on the upstream end face of the insulator flow path, the surface of the insulator flow path will be exposed. Abnormality of the discharge state due to the adhesion of soot can be detected at an early stage.

In a configuration in which a plurality of insulator flow paths are stacked, the flow rate of the exhaust gas in the exhaust pipe causes the flow rate of the exhaust gas in the central insulator flow path to be reduced by the outer circumferential insulator flow path. Therefore, the amount of soot adhering to each of the insulator flow paths tends to be larger in the insulator flow path on the center side. In addition, since the water droplets that have condensed on each of the insulator flow paths hang downward with time, the amount of the condensed water attached to the lower insulator flow paths tends to be larger.

In consideration of this point, the resistance value of the surface of the laminated body of the insulator flow path may be detected in a wide range in the vertical direction. This makes it possible to easily and reliably detect both the change in the resistance value due to the adhesion of the soot and the change in the resistance value due to the adhesion of the dew water.

According to a fourth aspect of the present invention, the laminated body of the insulator flow path is divided into a plurality of discharge control areas so that the discharge is controlled independently for each discharge control area. The resistance value of the surface of the insulator flow path is separately detected by the insulation resistance detecting means for each control area, and when a discharge abnormality is detected by the discharge state determination means, the discharge of the discharge control area where the discharge abnormality is detected is detected. The discharge may be stopped and the discharge in the other discharge control areas may be continued. In this way, even if a discharge abnormality occurs due to dew condensation water or the like in some of the insulator flow paths, the discharge is continued in the insulator flow path in which a normal discharge state is obtained, and the purification of the exhaust gas is continued. be able to.

By the way, dew condensation on the surface of the insulator flow path is as follows.
This occurs when the temperature of the insulator flow path is low, and when the temperature of the insulator flow path increases due to exhaust heat, even if dew condensation has occurred on the surface of the insulator flow path before that, the condensed water evaporates. As a result, condensation on the surface of the insulator flow path is eliminated. In addition, the soot in the exhaust gas gradually adheres to the surface of the insulator flow path over a considerably long period of time as compared with dew condensation. It does not decrease.

In consideration of this point, when the discharge abnormality is determined based on the resistance value of the surface of the insulator flow path, the soot contained in the exhaust gas to the surface of the insulator flow path is determined. The discharge abnormality due to the adhesion of water and the discharge abnormality due to dew condensation water may be determined based on the temperature state of the insulator flow path, a change in the detected resistance value, or the like. For example, when the temperature of the insulator flow path increases, dew condensation on the surface of the insulator flow path disappears. Can be determined. Also,
When the detection resistance value sharply increases or decreases from the previous detection value, it can be determined that the discharge is abnormal due to condensation.

In this case, when it is determined that the discharge is abnormal due to the adhesion of soot, the insulator flow path may be removed from the vehicle for cleaning or replacement. When it is determined that the air-fuel ratio of the exhaust gas is temporarily rich when the temperature of the insulator flow path is high, the soot attached to the insulator flow path may be burned. With this configuration, the soot can be automatically removed each time the amount of soot attached to the insulator flow path increases,
It is not necessary to clean or replace the insulator flow path, and the exhaust gas purifying ability can be favorably maintained for a long period of time.

Further, if the resistance value of the surface of the insulator flow path is detected during the discharge, noise due to the discharge is superimposed on the detected value. It is good to detect the resistance value of the surface. This makes it possible to accurately detect the resistance value of the surface of the insulator flow path without being affected by the discharge.

[0016]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the exhaust gas purification device 11 is provided in the middle of an exhaust pipe (not shown) of an internal combustion engine, and has a plurality of flow path structures 12 stacked thereon. Each of the flow path structures 12 is formed of a dielectric heat-resistant insulator (for example, ceramic such as alumina, glass, or the like) that easily generates a discharge, and a plurality of insulator flow paths 13 through which exhaust gas passes are arranged in a line. Is formed. On one surface (for example, the upper surface) of each flow path structure 12, a discharge electrode 14 is provided by a printed conductor or a conductive plate. This discharge electrode 14 is connected to a connection portion 14 a connected to the external terminal 15.
Are exposed to the outside, and the other portions are embedded inside the flow path structure 12. The inner wall of each of the insulator channels 13 is coated with a catalyst (not shown) that promotes a purification reaction of exhaust gas.

The stacked flow channel structures 12 are housed in an insulating housing 20 with the discharge electrodes 14 located between the flow channel structures 12. Each channel structure 12
Are alternately stacked in the left and right opposite directions, and the connection portions 14a of the discharge electrodes 14 are alternately located on the left and right opposite sides. Since the number of the discharge electrodes 14 is required to be one more than the number of laminations of the flow path structure 12, for example, the lower surface of the lowermost flow path structure 12 (the surface without the discharge electrode 14) The discharge electrodes 19 held by the insulator 18 are overlaid.

Auxiliary electrodes 16 are accommodated in the insulator channels 13 of the respective channel structures 12. Each auxiliary electrode 16 is formed in a corrugated shape from a conductive heat-resistant metal such as a stainless steel plate, and is accommodated so that its concave and convex portions extend along the flow path 13 and is fixed in the flow path 13 by its own spring force. ing.

The external terminal 15 connected to the connection portion 14a of the discharge electrode 14 is formed of a stainless steel plate or the like having a spring property, and the contact state between the external terminal 15 and the connection portion 14a is changed by the spring force of the external terminal 15. It is held so that a stable contact state is maintained against vibration and temperature changes. The external terminal 15 is connected to the connection portion 14a of the discharge electrode 14.
Alternatively, it may be fixed by heat-resistant fixing means such as caulking, rivets, welding, or the like.

One side of the exhaust purification device 11 (left side in FIG. 1)
Is connected to the ground side, and the external terminal 15 located on the other side (the right side in FIG. 1) is connected to the output terminal of a high voltage generator 17 for generating, for example, a high frequency AC high voltage. I have. Thereby, the high voltage generator 1
In the operation of 7, a high-frequency AC high voltage is applied between the discharge electrodes 14 opposed to each other across the flow path structure 12, and a discharge occurs in each of the insulator flow paths 13.

The resistance value of the surface of the insulator flow path 13 is detected at the upstream end face of the surface of the insulator flow path 13 where soot such as unburned components in exhaust gas is most likely to adhere. Resistance detection terminals 21 and 22 (insulation resistance detection means) are provided. The plus side insulation resistance detection terminal 21
The printed conductor or the conductive plate is formed so as to extend linearly in the vertical direction along the surface of the vertical partition wall of the insulator flow path 13 near the center of each flow path structure 12. The upper end of the insulation resistance detection terminal 21 is connected to a wiring conductor 23 embedded in the uppermost flow path structure 12 as shown in FIG. The wiring conductor 23 is connected to a resistance value detection circuit (not shown) in the engine control circuit 27 via the signal line 10.

On the other hand, the ground-side insulation resistance detection terminal 22
Is formed integrally with each of the discharge electrodes 14 and 19 connected to the ground side, and the tip of the insulation resistance detection terminal 22 is connected to the positive insulation resistance detection terminal 21 of the upstream end surface of the insulator flow path 13. Is exposed at a predetermined distance from the camera. Thus, the resistance value of the upstream end surface of the laminated body of the flow path structure 12 can be detected in a wide range in the vertical direction by the insulation resistance detection terminals 21 and 22.

Next, the configuration of the high voltage generator 17 will be described with reference to FIG. The high voltage generator 17 converts a DC voltage supplied from a battery 24 mounted on a vehicle into a DC voltage.
The DC / DC converter 25 boosts the voltage, converts the voltage into a high-frequency AC high voltage by an inverter circuit 26, and applies an AC high voltage between the discharge electrodes 14 facing each other with the flow path structures 12 interposed therebetween. The inverter circuit 26 is controlled by an engine control circuit 27, and the inverter drive circuit 28
The bridge inverter 29 is driven to control the secondary output of the transformer 30.

When a high frequency AC high voltage is applied between the discharge electrodes 14 facing each other across the flow path structure 12 by the inverter circuit 26, the flow path structure 12 Discharge plasma is generated between the insulator layer and the auxiliary electrode 16. As a result, the inner wall of each insulator channel 13 and the catalyst coated thereon are activated, and NOx and the like in the exhaust gas flowing through each insulator channel 13 are adsorbed, reduced and purified.

By the way, if soot such as unburned components in the exhaust gas adheres to the surface of the insulator flow path 13 or dew condensation occurs, the insulation (resistance) of the surface of the insulator flow path 13 decreases. As a result, a normal discharge state may not be obtained.
When dew water adheres to the surface of the insulator flow path 13,
After the engine starts, if the temperature of the insulator flow path 13 increases,
Since the dew water on the surface of the insulator flow path 13 evaporates and disappears, a normal discharge state can be secured thereafter. However, when a large amount of soot adheres to the surface of the insulator flow path 13, even if the temperature of the insulator flow path 13 increases, the amount of soot adhered does not decrease. The discharge state cannot be obtained, and the exhaust gas purifying ability remains reduced.

Thus, the engine control circuit 27 executes the discharge abnormality determination program shown in FIG.
The resistance value between the two, that is, the resistance value of the surface of the insulator flow path 13 was detected, the discharge state was determined based on the resistance value, and further, during the operation of the engine, it was determined that the discharge was abnormal due to the adhesion of soot. In this case, the air-fuel ratio of the exhaust gas is temporarily controlled to be rich to burn off the soot attached to the insulator flow path 13.

The discharge abnormality determination program shown in FIG. 4 is executed at the same time when the ignition switch is turned on, and functions as a discharge state determination means. When the program is started, first, in step 101, a predetermined detection voltage is applied between the insulation resistance detection terminals 21 and 22 to detect a resistance value R on the surface of the insulator flow path 13 before the engine is started. Before the start of the engine, since the discharge is stopped, the resistance value R on the surface of the insulator flow path 13 can be detected with high accuracy without being affected by noise due to the discharge.

After detecting the resistance value R, the process proceeds to step 102, where it is determined whether or not the resistance value R on the surface of the insulator flow path 13 is smaller than the abnormality determination value W. Here, the abnormality determination value W
Is set to the upper limit value of the resistance value at which the discharge state may become abnormal or a resistance value slightly higher than the upper limit value. If the resistance value R of the surface of the insulator flow path 13 is equal to or greater than the abnormality determination value W (normal range), it can be determined that adhesion of soot to the surface of the insulator flow path 13 or dew condensation is not a problem. Proceeding to step 110, it is determined that a normal discharge state can be ensured, discharge is started, and the procedure proceeds to step 111.

On the other hand, if it is determined in step 102 that the resistance value R on the surface of the insulator flow path 13 is smaller than the abnormality determination value W before the engine is started (before starting discharge), a discharge abnormality may occur. (However, it is unclear whether the cause of the discharge abnormality is due to the adhesion of soot or condensation.) In this case, the routine proceeds to step 103, where the engine is started without starting discharge.

After starting the engine, it is determined in step 104 whether a predetermined time T has elapsed since the start of the engine. Here, the predetermined time T is equal to the length of the insulator flow path 1 due to the exhaust heat.
The time is set to a time sufficient for the temperature of 3 to rise and for the condensation water on the surface of the insulator flow path 13 to evaporate and disappear. If the predetermined time T has not elapsed, the process waits in step 104, and thereafter, when the predetermined time T has elapsed, the process proceeds to step 105, where the resistance value R of the surface of the insulator flow path 13 is detected.

Thereafter, at step 106, the insulator flow path 1
It is determined whether or not the resistance value R of the surface No. 3 is smaller than the abnormality determination value W (this abnormality determination value W may be the same value as or different from the abnormality determination value W in step 102). If the resistance value R on the surface of the insulator flow path 13 has recovered to the normal range (R ≧ W), the process proceeds to step 110, where it is determined that the state has been recovered to a state where normal discharge is possible, and discharge is performed. Start and proceed to step 111.

That is, before the engine is started, the insulator flow path 13
When the resistance value R on the surface of the surface is in an abnormal range (R <W),
It is unknown whether the cause is due to the adhesion of soot or the dew condensation. However, if the resistance value R on the surface of the insulator flow path 13 recovers to the normal range (R ≧ W) during the operation of the engine, an abnormal discharge is detected. The cause is dew condensation.
It can be determined that the condensed water adhering to the surface of the sample has been evaporated by the exhaust heat during the operation of the engine, and has been restored to a state where normal discharge is possible.

On the other hand, the soot adhering to the surface of the insulator channel 13 does not decrease even when the temperature of the insulator channel 13 increases, unlike the dew condensation water. When the resistance value R falls within the abnormal range (R <W) due to soot, the resistance value R on the surface of the insulator flow path 13 does not recover to the normal range (R ≧ W) even during engine operation. Therefore, if it is determined in step 106 that the resistance value R on the surface of the insulator flow path 13 is again in the abnormal range (R <W) during the operation of the engine, the process proceeds to step 107, where the insulator flow path 1
It is determined that there is a possibility that a discharge abnormality may occur due to soot adhering to the surface of No. 3, and the routine proceeds to step 108, where the air-fuel ratio of the exhaust gas is temporarily controlled to be rich. When performing this process, the insulator flow path 13 is heated by exhaust heat after the warm-up is completed.
Therefore, if the air-fuel ratio of the exhaust gas is made rich, soot attached to the insulator flow path 13 can be burned out, and a state where normal discharge can be performed can be recovered. After this,
Proceeding to step 109, discharge is performed, and step 11
Proceed to 1.

In step 111, it is determined whether or not it is the discharge stoppable period. Here, the period during which the discharge can be stopped is:
For example, the period is set to a period in which the exhaust emission is extremely small, such as during fuel cut during deceleration or during idle operation after warm-up is completed. If the period is not the discharge stoppable period, the process waits at step 111, and thereafter, when the discharge stoppable period is reached, the processing from step 105 onward is repeated. In this way, during the operation of the engine, the discharge is stopped for an extremely short time every time the discharge stoppable period is reached, the resistance value R on the surface of the insulator flow path 13 is detected, and the resistance value R falls within the abnormal range (R <
In the case of W), it is determined that there is a possibility that a discharge abnormality may occur due to the soot attached to the surface of the insulator channel 13, and the soot attached to the insulator channel 13 is burned.

According to the embodiment (1) described above, as the amount of soot and dew water adhering to the surface of the insulator flow path 13 increases, the insulation (resistance value) of the surface of the insulator flow path 13 increases. ) Decreases and the discharge state worsens, and the insulator flow path 1 is set before the engine is started or during the operation of the engine.
3, the resistance value R is detected on the surface, and the resistance value R is compared with the abnormality determination value W to determine the discharge state. Discharge abnormality can be accurately determined.

Further, in the present embodiment (1), the insulation resistance detection terminals 21 and 22 are arranged on the upstream end face of the surface of the insulator flow path 13 where soot in the exhaust gas is most likely to adhere. An abnormal discharge due to the adhesion of soot to the surface of the body channel 13 can be detected at an early stage.

Moreover, in the present embodiment (1), the amount of soot adhering in the laminated body of the flow path structure 12 tends to be larger in the insulator flow path 13 on the center side, and the adhesion of dew In consideration of the fact that the amount tends to be larger in the lower insulator flow path 13, the resistance value of the upstream end face of the laminated body of the flow path structure 12 can be detected in a wide range in the vertical direction. Since the insulation resistance detection terminals 21 and 22 are arranged as described above, it is possible to easily and reliably detect both the change in the resistance value due to the adhesion of soot and the change in the resistance value due to the adhesion of dew water. Combined with the early detection effect of the discharge abnormality, the reliability of the discharge abnormality detection can be improved.

In this embodiment (1), when it is determined that there is a possibility of a discharge abnormality due to soot during the operation of the engine, the air-fuel ratio of the exhaust gas is temporarily made rich to allow the insulator flow path 13 to pass through. Since the attached soot is burned off, soot can be automatically removed every time the amount of soot attached to the insulator flow path 13 increases, and cleaning or replacement of the insulator flow path 13 is unnecessary. And the exhaust gas purifying ability can be maintained satisfactorily for a long period of time.

Further, if the resistance value of the surface of the insulator flow path 13 is detected during the discharge, noise due to the discharge will be superimposed on the detected value. Since the resistance value of the surface of the path 13 is detected, the resistance value of the surface of the insulator flow path 13 can be accurately detected without being affected by noise due to the discharge, and the accuracy of the determination of the discharge abnormality can be improved. Can be improved.

In this embodiment (1), the insulator flow path 1 is provided before the engine is started and during the period in which the discharge can be stopped during the operation of the engine.
3, the resistance value R on the surface of the insulator flow path 13 is detected to determine whether the abnormality (discharge abnormality) on the surface of the insulator flow path 13 is due to adhesion of soot or condensation. Immediately after the previous engine stop and before the present engine start, the resistance value R of the surface of the insulator flow path 13 is detected, respectively. If the resistance value R is in the range (R <W), it is determined that the resistance value R is abnormal due to dew condensation. If <W), it may be determined that the resistance value R is abnormal due to the adhesion of soot.

Further, in the embodiment (1), the detection of the resistance value R (discharge state determination) is repeated every time the discharge stoppage period is reached during the operation of the engine, but only once during the operation of the engine. Re-detection of resistance value R (discharge state determination)
May be performed.

Further, during operation of the engine, the insulator flow path 13
Is high, so that dew condensation does not occur, and soot in the exhaust gas adheres little by little to the surface of the insulator flow path 13 over a long period of time, and during one engine operation, Since the amount of soot does not increase rapidly, soot and dew on the surface of the insulator flow path 13 do not cause a problem before the start of the engine, soot during the operation of the engine this time. It may be determined that no discharge abnormality occurs due to adhesion or condensation. From this viewpoint, if the resistance value R of the surface of the insulator flow path 13 is within the normal range (R ≧ W) before the current engine start,
During the current operation of the engine, it may be determined that a normal discharge state can be ensured, and the re-detection of the resistance value R during the operation of the engine (re-determination of the discharge state) may not be performed.

Also, the resistance value R on the surface of the insulator flow path 13 is detected only during the period during which the discharge can be stopped during the operation of the engine without detecting the resistance value R before starting the engine (determining the discharge state). It may be possible to detect only the discharge abnormality due to the adhesion of the ink.

[Embodiment (2)] Next, an embodiment (2) of the present invention will be described with reference to FIGS. The exhaust gas purifying device 31 of the present embodiment (2) includes a right external terminal 32.
U and 32L are connected to the output terminal of the high-voltage generator 17 via a switch circuit 33, and the switch circuit 33 individually separates the upper half external terminal 32U and the lower half external terminal 32L of the exhaust gas purification device 31. A voltage can be applied. As a result, the exhaust gas purification device 31 is divided into two upper and lower discharge control regions, and the upper half flow path structure 12 of the exhaust gas purification device 31 belonging to the upper discharge control region.
The discharge in the insulator flow path 13U of the U and the lower half flow path structure 12 of the exhaust purification device 31 belonging to the lower discharge control area
The discharge in the L insulator flow path 13L can be turned on / off independently.

In the upper discharge control region, the resistance RU of the upstream end face of the flow path structure 12U near the center of the discharge control region is determined.
A pair of insulation resistance detection terminals 21U and 22U (insulation resistance detection means) are provided at predetermined intervals. on the other hand,
In the lower discharge control region, the resistance value RL of the upstream end face of the insulator 18 held on the lower surface of the lowermost flow path structure 12L.
A pair of insulation resistance detection terminals 21L and 22L (insulation resistance detection means) are provided at predetermined intervals.

The insulation resistance detection terminals 21U and 21L on the positive side of the two discharge control regions are formed integrally with the wiring conductors 23U and 23L embedded in the insulator layer (the flow path structure 12U or the insulator 18). And the respective signal lines 10
It is connected to a resistance value detection circuit (not shown) in the engine control circuit 27 via U and 10L. Also, the insulation resistance detection terminals 22U, 2 on the ground side of the two discharge control areas.
2L is a discharge electrode 14 connected to the ground side.
U and 19 are integrally formed.

In this embodiment (2), the engine control circuit 27 executes the respective discharge abnormality determination programs shown in FIGS. The upper discharge abnormality determination program in FIG. 6 is started at the same time as the ignition switch is turned on and is executed, for example, every predetermined time, and determines whether or not there is a discharge abnormality in the upper discharge control region as follows. First, step 20
In step 1, it is determined whether or not the engine is in a startable or discharge stoppable period. Every time the engine is started or in a discharge stoppable period, the process proceeds to step 202, in which the discharge is stopped for an extremely short time. Next, the resistance value RU of the surface of the insulator flow path 13U in the upper discharge control region is detected.

Thereafter, the process proceeds to step 203, where it is determined whether or not the detected resistance value RU is smaller than the abnormality determination value W. If the detected resistance value RU is within the normal range (RU ≧ W), the process proceeds to step 207. Proceeding, the upper discharge control area is determined to be able to secure a normal discharge state, and discharge in the upper discharge control area is permitted (step 208), and this program ends.

On the other hand, if it is determined in step 203 that the resistance value RU is in the abnormal range (RU <W), the process proceeds to step 20.
Then, the process proceeds to step 205, where it is determined that a discharge abnormality occurs in the upper discharge control region due to soot or condensation water attached to the surface of the insulator flow path 13U in the upper discharge control region. Prohibit the discharge of Thereafter, the process proceeds to step 206, in which a warning lamp (not shown) is turned on to notify the driver of the occurrence of a discharge abnormality, and an appropriate failure process such as storing an abnormality code in a nonvolatile memory of the engine control circuit 27. To end the program.

In the case where the resistance value RU is abnormal due to dew condensation, if the temperature of the insulator flow path 13U rises due to exhaust heat, dew water adhering to the surface of the insulator flow path 13U evaporates during engine operation. I do. Therefore, once the resistance value RU
Is determined to be in the abnormal range (RU <W), when the dew condensation water adhering to the surface of the insulator flow path 13U evaporates thereafter, in step 203, the resistance RU of the surface of the insulator flow path 13U is determined. Is determined to have recovered to the normal range (RU ≧ W). At that point, it is determined that the upper discharge control area can maintain a normal discharge state (step 207), and discharge of the upper discharge control area is permitted. (Step 208), the warning lamp is turned off.

The lower discharge abnormality determination program in FIG. 7 is started at the same time as the ignition switch is turned on and is executed at predetermined time intervals, similarly to the upper discharge abnormality determination program in FIG. The presence or absence of a discharge abnormality is determined as follows. Before the start of the engine or every time it is determined that the discharge can be stopped, the discharge is stopped and the resistance value RL of the surface of the insulator flow path 13L in the lower discharge control region is detected. It is determined whether it is smaller than W (steps 301 to 303).

If the detected resistance value RL is within the normal range (R
If L ≧ W, it is determined that the lower discharge control area can maintain a normal discharge state, and discharge in the lower discharge control area is permitted (steps 307 to 308). On the other hand, if the detected resistance value RU is in the abnormal range (RU <W), it is determined that a discharge abnormality has occurred in the lower discharge control area, and the discharge in the lower discharge control area is prohibited. Processing is performed (steps 304 to 306).

In the embodiment (2) described above, the discharge in the upper half discharge control region and the discharge in the lower half discharge control region of the exhaust gas purification device 31 can be turned on / off independently. Insulator flow path 13U in the discharge control region of FIG.
And the resistance value RL of the surface of the insulator flow path 13L of the lower discharge control region are separately detected to separately determine the discharge abnormality of the upper discharge control region and the lower discharge control region. Therefore, even if a discharge abnormality occurs due to the adhesion of soot or condensed water in one of the upper discharge control area and the lower discharge control area, a normal discharge state can be obtained. Discharge can be continued in the body flow path to purify the exhaust gas, and the exhaust gas purifying ability can be improved.

Also, in the present embodiment (2), in consideration of the fact that the amount of condensed water adhered to the lower insulator flow path tends to be larger, the lowermost discharge control region has the lowermost discharge control region. Since the insulation resistance detection terminals 21L and 22L are disposed in the above, when dew condensation occurs, a change in the resistance value RL due to the dew water can be reliably detected. However, the positions of the insulation resistance detection terminals 21L and 22L in the lower discharge control region may be appropriately changed, and similarly, the positions of the insulation resistance detection terminals 21U and 22U in the upper discharge control region may be appropriately changed. good.

In this embodiment (2), the detection of the resistance values RU and UL in the two discharge control areas (judgment of the discharge state) is repeated every time the discharge stoppage period is reached during the operation of the engine. However, only when the resistance values RU, UL before the engine start are determined to be in the abnormal range, the resistance values RU, UL are re-detected (discharge state re-determination) during the period during which the discharge can be stopped during the operation of the engine. Is also good. Further, when it is determined that the discharge is abnormal plural times continuously, it is determined that the discharge is abnormal due to the adhesion of the soot, and the air-fuel ratio of the exhaust gas is temporarily made rich to adhere to the insulator flow paths 13U and 13L. The soot may be burned.

In this embodiment (2), the laminated body of the flow path structure 12 is divided into two discharge control areas. However, the laminated body is divided into three or more discharge control areas, and the insulation of each discharge control area is divided. The resistance value of the surface of the body flow path may be separately detected, and the discharge may be independently controlled for each discharge control area according to the determination result of the discharge state of each discharge control area.

In addition to the above, the present invention may be applied to various configurations, such as a configuration in which the shape of the flow path structure, the insulator flow path, the insulation resistance detection terminal, the discharge electrode, the auxiliary electrode, and the like are not changed, and a configuration in which the auxiliary electrode is not used. Can be changed and implemented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of an exhaust emission control device according to an embodiment (1) of the present invention.

FIG. 2 is a cross-sectional view of the exhaust gas purification device.

FIG. 3 is a circuit diagram showing an electrical configuration of the exhaust gas purification device.

FIG. 4 is a flowchart showing a processing flow of a discharge abnormality determination program.

FIG. 5 is a vertical cross-sectional front view of the exhaust emission control device according to the embodiment (2) of the present invention.

FIG. 6 is a flowchart showing the processing flow of an upper discharge abnormality determination program

FIG. 7 is a flowchart showing a processing flow of a lower discharge abnormality determination program;

[Explanation of symbols]

11: Exhaust gas purification device, 12, 12U, 12L: Flow path structure, 13, 13U, 13L: Insulator flow path, 14, 14
U, 14L: discharge electrode, 15: external terminal, 16: auxiliary electrode, 17: high voltage generator, 19: discharge electrode, 21 and 22
1U, 21L, 22, 22U, 22L ... insulation resistance detection terminal (insulation resistance detection means), 23, 23U, 23L ... wiring conductor, 24 ... battery, 26 ... inverter circuit, 27 ...
Engine control circuit (discharge state determination means), 31: exhaust purification device, 32U, 32L: external terminal, 33: switch circuit.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) B01J 19/08 ZAB F-term (Reference) 3G091 AA02 AB01 AB14 BA03 BA14 BA34 CB02 DB10 EA26 EA29 EA30 FA04 FA05 FA06 FA12 FB02 FB12 FC02 FC04 FC07 4D002 AA08 AA12 AA40 BA05 BA07 CA20 DA70 GA02 GA03 GB20 HA01 4D048 AA06 AB02 CC41 EA03 EA04 4G075 AA03 AA37 AA62 BA05 BD12 BD24 CA15 EC21 FC15

Claims (7)

[Claims] 1. An exhaust gas of an internal combustion engine is caused to flow in an insulator flow path defined by an insulator layer between at least one pair of discharge electrodes, and a discharge is generated between the discharge electrodes via the insulator layer. In the exhaust gas purifying apparatus for an internal combustion engine that purifies the exhaust gas, the resistance value of the surface of the insulator passage is detected at a portion where the exhaust gas contacts, and the insulation resistance detection device detects the resistance value. And a discharge state determining means for determining a discharge state based on a resistance value of a surface of the insulator flow path. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said insulation resistance detection means detects a resistance value at an upstream end face of said insulator flow path. 3. The exhaust of an internal combustion engine according to claim 1, wherein the insulation resistance detecting means detects a resistance value of a surface of the laminated body of the insulator flow path in a wide range in a vertical direction. Purification device. 4. A structure in which the laminate of insulator flow paths is divided into a plurality of discharge control areas so that discharge is independently controlled for each discharge control area, and the insulation is provided for each discharge control area. The resistance value of the surface of the insulator flow path is separately detected by the resistance detection means, and when the discharge abnormality is detected by the discharge state determination means, the discharge in the discharge control area where the discharge abnormality is detected is stopped. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the discharge in the discharge control region is continued. 5. The discharge state judging means, when judging a discharge abnormality based on a resistance value detected by the insulation resistance detecting means, discharge by soot in exhaust gas on a surface of the insulator flow path. The exhaust gas purification of an internal combustion engine according to any one of claims 1 to 4, wherein an abnormality and a discharge abnormality due to dew water are determined based on a temperature state of the insulator flow path or a change in a detected resistance value. apparatus. 6. When the discharge state determination means determines that the discharge is abnormal due to the adhesion of soot, the air-fuel ratio of the exhaust gas is temporarily controlled to be rich when the temperature of the insulator flow path is high. The exhaust gas purifying apparatus for an internal combustion engine according to claim 5, wherein the soot attached to the body flow path is burned off. 7. The exhaust gas purification of an internal combustion engine according to claim 1, wherein said insulation resistance detection means detects a resistance value of a surface of said insulator flow path during a stop of discharge. apparatus.