JP7234953B2 - Exhaust purification device - Google Patents

Description

The present invention relates to an exhaust purification device.

2. Description of the Related Art Conventionally, as an exhaust gas purification device having an abnormality determination function, an exhaust gas purification device including an electrically heated catalytic device is known (for example, Patent Document 1). The electrically heating type catalyst device described in Patent Document 1 has so-called NTC characteristics in which the current resistance value of the catalyst carrier changes as the temperature of the catalyst carrier changes.

JP 2009-191681 A

In the above conventional technology, as the temperature of the catalyst increases, the amount of change in the energization resistance of the catalyst carrier decreases. Therefore, there is still room for improvement in the accuracy of the abnormality determination of the electrically heated catalyst device when the catalyst temperature is high. Further, in the above-described prior art, it is not easy to distinguish whether the cause of an abnormality in the electrically heated catalyst device is the catalyst carrier itself or the controller that controls the presence or absence of energization.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust emission control system capable of determining the presence or absence of an abnormality at least in a temperature range including a temperature at which thermal deterioration of a catalyst is accelerated, and identifying the cause of the abnormality.

An exhaust purification device according to an aspect of the present invention includes a catalyst provided in an exhaust flow path of an internal combustion engine, an electric heating element provided upstream of the catalyst for heating exhaust gas flowing through the exhaust flow path, and a heater connected to the electric heating element. a power supply control unit for controlling whether or not to energize the electric heating element of the supplied power supply; a first temperature detection unit including a PTC thermistor provided so as to be able to detect heat generation of the electric heating element; Determining whether the electric heating element or the power supply is abnormal based on the power supply control unit, the resistance value of the PTC thermistor, and the presence or absence of the power supply instruction, and the abnormality determination for determining whether the power supply control unit is abnormal The first temperature detection section is configured such that the resistance value of the PTC thermistor is highly sensitive in a first temperature range including a temperature at which thermal deterioration of the catalyst is accelerated.

In an exhaust purification device according to an aspect of the present invention, the first temperature detection section is configured such that the resistance value of the PTC thermistor is highly sensitive in the first temperature range including the temperature at which thermal deterioration of the catalyst is accelerated. to determine anomalies. Therefore, the abnormality can be determined in a temperature range including the temperature at which thermal deterioration of the catalyst is accelerated. In addition, since the abnormality is determined further based on the presence or absence of the energization instruction, it is possible to distinguish between the abnormality of the electric heating element or the power supply and the abnormality of the power control unit as the abnormality to be determined. Therefore, according to this exhaust purification device, it is possible to determine the presence or absence of an abnormality at least in a temperature range including the temperature at which thermal deterioration of the catalyst is accelerated, and to specify the cause of the abnormality.

In one embodiment, if the resistance value of the PTC thermistor exceeds a predetermined first resistance value threshold value corresponding to the temperature included in the first temperature range and there is an energization instruction, the abnormality determination unit , it may be determined that the power supply is abnormal, and if the resistance value of the PTC thermistor exceeds the first resistance value threshold and there is no energization instruction, it may be determined that the power supply control unit is abnormal. . In this case, since the resistance value of the PTC thermistor exceeds the first resistance value threshold value, the catalyst temperature has reached a temperature at which thermal deterioration of the catalyst is accelerated. Here, when there is an energization instruction, it is the result of heating due to energization, so it is considered that the power supply is abnormal, for example, overvoltage. Alternatively, if there is no energization instruction, there is heating due to energization even though there is no energization instruction, so it is considered that the power supply control unit is abnormal. In this way, it is possible to determine the presence or absence of an abnormality in a temperature range including the temperature at which thermal deterioration of the catalyst is accelerated, and to identify the cause of the abnormality.

In one embodiment, a second temperature detection unit including a CTR thermistor provided to detect heat generation of the electric heating element is provided, and the second temperature detection unit includes a second temperature range including a temperature at which the activity of the catalyst is insufficient. The resistance value of the CTR thermistor is configured to be highly sensitive at , and the abnormality determination unit detects when the resistance value of the CTR thermistor exceeds a predetermined second resistance value threshold corresponding to the temperature included in the second temperature range. If there is an energization instruction, it is determined that the electric heating element is abnormal, and if the resistance value of the CTR thermistor exceeds the second resistance value threshold and there is no energization instruction, , it may be determined that the power control unit is abnormal. In this case, since the resistance value of the CTR thermistor exceeds the second resistance value threshold value, the catalyst temperature has not reached a temperature at which the activity of the catalyst becomes sufficient. Here, when there is an energization instruction, it is considered that the electric heating element is abnormal, such as disconnection or poor contact, because heating by energization is insufficient despite the energization instruction. . Alternatively, if there is no energization instruction, there is no heating due to energization even though the activity of the catalyst is insufficient, so it is considered that the power control unit is abnormal. In this way, it is possible to determine whether there is an abnormality in a temperature range including the temperature at which the activity of the catalyst becomes insufficient, and to identify the cause of the abnormality.

In one embodiment, a current sensor is provided to detect leakage current from the electric heating element, and the abnormality determination unit determines whether the electric heating element is abnormal based on the current value of the current sensor. good too. In this case, it becomes possible to specify the electric leakage as the abnormality of the electric heating element.

In one embodiment, a target sensor including at least one of a catalyst temperature sensor that acquires the catalyst temperature, which is the temperature of the catalyst, and an air flow sensor, which acquires the air flow rate that is the flow rate of the intake air of the internal combustion engine; The energization control unit does not instruct the power supply control unit to energize when the target sensor is faulty, and the abnormality determination unit corresponds to a temperature included in the first temperature range when the target sensor is faulty. If the resistance value of the PTC thermistor exceeds a predetermined first resistance value threshold, it may be determined that the power control unit is abnormal. In this case, it is conceivable that the temperature of the catalyst has reached a temperature at which thermal deterioration of the catalyst is accelerated as a result of heating due to energization, even though the target sensor is out of order and there is no energization instruction. In this way, it becomes possible to identify an abnormality in the power control unit.

According to the present invention, it is possible to determine the presence or absence of an abnormality at least in a temperature range including a temperature at which thermal deterioration of the catalyst is accelerated, and to specify the cause of the abnormality.

1 is a schematic configuration diagram of an exhaust purification device of an embodiment; FIG. FIG. 2 is a block diagram showing a configuration relating to an ECU of the exhaust purification system of FIG. 1; FIG. It is a figure which illustrates the characteristic of a 1st temperature detection part. It is a figure which illustrates the characteristic of a 2nd temperature detection part. FIG. 2 is a flowchart illustrating processing of the exhaust emission control device of FIG. 1; FIG. FIG. 2 is a flowchart illustrating processing of the exhaust emission control device of FIG. 1; FIG. FIG. 2 is a flowchart illustrating processing of the exhaust emission control device of FIG. 1; FIG. FIG. 2 is a flowchart illustrating processing of the exhaust emission control device of FIG. 1; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are used for the same or corresponding elements, and overlapping descriptions are omitted.

[Configuration of exhaust gas purification device]
FIG. 1 is a schematic configuration diagram of an exhaust purification device of an embodiment. In FIG. 1, an exhaust purification device 100 of the present embodiment is mounted on a vehicle, for example, and purifies exhaust gas discharged from a diesel engine 1 (hereinafter simply referred to as engine 1), which is an internal combustion engine. The exhaust purification device 100 includes an ECU [Electronic Control Unit] 10 that executes various controls. The engine 1 has an injector (not shown) that injects fuel into the combustion chamber 2 .

The exhaust purification device 100 includes a diesel particulate filter [DPF: Diesel Particulate Filter] 3 and a selective reduction catalyst [SCR: Selective Catalytic Reduction] 4 . The DPF 3 and the SCR 4 are arranged in an exhaust passage 5 connected to the engine 1 in order from the upstream side to the downstream side. Regarding the exhaust passage 5, the "upstream side" means the upstream side in the flow direction of the exhaust gas, and the "downstream side" means the downstream side in the flow direction of the exhaust gas.

The DPF 3 may be provided with a diesel oxidation catalyst [DOC: Diesel Oxidation Catalyst]. DOC oxidizes and purifies HC, CO, etc. contained in the exhaust gas. The DPF 3 removes PM from the exhaust gas by collecting particulate matter [PM: Particulate Matter] contained in the exhaust gas. The SCR 4 reduces and purifies NOx contained in the exhaust gas.

SCR4 has a suitable carrier temperature range for efficiently reducing NOx. The normal temperature range is determined according to, for example, the composition of the noble metal supported on the SCR4. The normal temperature range has an upper temperature limit above which thermal degradation of the SCR 4 is accelerated. The normal temperature range has a lower temperature limit below which SCR4 activity becomes insufficient.

The exhaust purification device 100 includes an addition valve (not shown) arranged upstream of the SCR 4 in the exhaust passage 5 . The addition valve is controlled by the ECU 10 to add urea water to the SCR4. For example, when urea water is added to the SCR 4 in the normal temperature range by the addition valve, the urea water becomes NH ₃ and is adsorbed by the SCR 4, and the NH ₃ reacts with NOx in the exhaust gas to reduce NOx. be.

An electric heating element 7 is arranged upstream of the SCR 4 in the exhaust passage 5, for example, between the addition valve and the SCR 4. As shown in FIG. The electric heating element 7 is a member that generates heat when energized and heats the exhaust gas flowing through the exhaust passage 5 . The electric heating element 7 can adopt a known shape that can heat the exhaust gas while allowing the exhaust gas to flow. The energization of the electric heating element 7 is controlled by an EH [Electric Heater] controller (power supply control unit) 20 . Hereinafter, the electric heating element 7 and the constant voltage power source 8 may be collectively referred to as a heater section.

The EH controller 20 controls whether or not the constant-voltage power supply 8 connected to the electric heating element 7 energizes the electric heating element 7 based on whether or not there is an energization instruction from the ECU 10 . As the constant voltage power source 8, for example, a power source such as a vehicle battery can be used.

When the EH controller 20 is normal and an energization instruction is received from the ECU 10 , the EH controller 20 energizes the electric heating element 7 with electric power from the constant voltage power supply 8 . When the EH controller 20 is normal and there is no power supply instruction from the ECU 10 , the EH controller 20 does not allow the power of the constant voltage power supply 8 to flow through the electric heating element 7 .

If the EH controller 20 is abnormal, the EH controller 20 may not apply power from the constant-voltage power supply 8 to the electric heating element 7 even if the ECU 10 issues an energization instruction. When the EH controller 20 is abnormal, the EH controller 20 may cause the electric heating element 7 to be energized by the constant-voltage power supply 8 even without an energization instruction from the ECU 10 .

FIG. 2 is a block diagram showing the configuration of an ECU of the exhaust purification system of FIG. 1. As shown in FIG. As shown in FIGS. 1 and 2, the exhaust purification device 100 includes an air flow rate sensor (target sensor) 21, a catalyst temperature sensor (target sensor) 22, a PTC thermistor 23, a CTR thermistor 24, and a current sensor 25. and have. The ECU 10 is connected to the sensors 21 to 25, the addition valve, and the EH controller 20. FIG. Note that the illustration of the constant voltage power supply 8 is omitted in FIG.

The air flow rate sensor 21 is a detector that acquires the air flow rate, which is the flow rate of the intake air of the engine 1 . The air flow sensor 21 is provided, for example, in the intake passage 6 connected to the engine 1 . The air flow sensor 21 transmits a detection signal of the detected amount of intake air to the ECU 10 .

The catalyst temperature sensor 22 is a detector that acquires the catalyst temperature, which is the temperature of the SCR4. The catalyst temperature sensor 22 is provided in the SCR4, for example. The catalyst temperature sensor 22 transmits a detection signal regarding the detected catalyst temperature to the ECU 10 .

The PTC thermistor 23 is provided, for example, on the surface of the pipe forming the exhaust flow path 5 so as to detect heat generation of the electric heating element 7 . The PTC thermistor 23 has a characteristic that the resistance value changes with a positive slope according to the temperature to which heat is applied. The PTC thermistor 23 transmits a resistance value signal corresponding to the input temperature to the ECU 10 .

The PTC thermistor 23 is included in the first temperature detection section 23A. The first temperature detection section 23A is configured such that the resistance value of the PTC thermistor 23 is highly sensitive in the first temperature range including the temperature at which the thermal deterioration of the SCR 4 is accelerated. “Highly sensitive resistance value” means that the gradient of change in resistance value with respect to temperature change is large.

The first temperature detection section 23A may be composed of the PTC thermistor 23 only. In this case, the individual characteristics of the PTC thermistor 23 may be such that the resistance value of the PTC thermistor 23 is highly sensitive in the first temperature range including the temperature at which thermal deterioration of the SCR 4 is accelerated. FIG. 3 is a diagram illustrating characteristics of the first temperature detection section 23A. As shown in FIG. 3, the first temperature detector 23A is configured such that the resistance value of the PTC thermistor 23 is highly sensitive in the first temperature range Tr1. In the example of FIG. 3, the first temperature range Tr1 is a temperature range between temperature T1 and temperature T2. The first temperature range Tr1 includes an upper limit temperature at which thermal deterioration of the SCR 4 is accelerated. For example, the upper limit temperature is temperature T1 in FIG. The material and configuration of the PTC thermistor 23 are selected to have such temperature characteristics.

Alternatively, in addition to the PTC thermistor 23, the first temperature detection unit 23A may be configured by interposing a heat transfer adjusting member (not shown) between the PTC thermistor 23 and the pipe surface of the exhaust flow path 5. . In this case, the single PTC thermistor 23 can have a characteristic that the resistance value becomes highly sensitive in a temperature range lower than the first temperature range Tr1. Even with such a PTC thermistor 23, the heat transfer to the PTC thermistor 23 is adjusted, so that the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR 4 is promoted on the pipe surface of the exhaust flow path 5 In this case, the first temperature detector 23A can be configured so that the resistance value of the PTC thermistor 23 is highly sensitive. As the heat transfer adjusting member, for example, a heat insulator such as an aluminized steel plate or glass wool can be used. The aluminized steel sheet may have high heat resistance. The heat transfer adjusting member may be provided around the SCR 4 as well as between the PTC thermistor 23 and the piping surface of the exhaust flow path 5 .

The CTR thermistor 24 is provided, for example, on the surface of the pipe forming the exhaust flow path 5 so as to detect heat generation of the electric heating element 7 . The CTR thermistor 24 has a characteristic that the resistance value changes with a negative slope according to the temperature to which heat is applied. The CTR thermistor 24 transmits to the ECU 10 a resistance value signal corresponding to the input temperature.

The CTR thermistor 24 is included in the second temperature detection section 24A. The second temperature detection section 24A is configured such that the resistance value of the CTR thermistor 24 is highly sensitive in the second temperature range including the temperature at which the SCR 4 becomes insufficiently active.

The second temperature detection section 24A may be composed of the CTR thermistor 24 only. In this case, the single characteristic of the CTR thermistor 24 may be such that the resistance value of the CTR thermistor 24 is highly sensitive in the second temperature range including the temperature at which the SCR 4 becomes insufficiently active. FIG. 4 is a diagram illustrating characteristics of the second temperature detection section 24A. As shown in FIG. 4, the second temperature detection section 24A is configured such that the resistance value of the CTR thermistor 24 is highly sensitive in the second temperature range Tr2. In the example of FIG. 4, the second temperature range Tr2 is a temperature range above temperature T3 and below temperature T4. The second temperature range Tr2 includes the lower limit temperature at which the activity of SCR4 becomes insufficient, and the lower limit temperature is temperature T4 in FIG. 4, for example. The material and configuration of CTR thermistor 24 are selected to have such temperature characteristics.

Alternatively, the second temperature detection unit 24A may be configured by interposing a heat transfer adjustment member (not shown) between the CTR thermistor 24 and the pipe surface of the exhaust flow path 5 in addition to the CTR thermistor 24. . In this case, the single unit characteristic of the CTR thermistor 24 can have such a characteristic that the resistance value becomes highly sensitive in a temperature range lower than the second temperature range Tr2. Even with such a CTR thermistor 24, the heat transfer to the CTR thermistor 24 is adjusted so that the second temperature range Tr2 including the lower limit temperature at which the activation of the SCR 4 becomes insufficient on the pipe surface of the exhaust flow path 5. In this case, the second temperature detection section 24A can be configured so that the resistance value of the CTR thermistor 24 is highly sensitive. As the heat transfer adjusting member, for example, a heat insulator such as an aluminized steel plate or glass wool can be used. The aluminized steel sheet may have high heat resistance. The heat transfer adjusting member may be provided around the SCR 4 as well as between the CTR thermistor 24 and the piping surface of the exhaust flow path 5 .

The current sensor 25 is provided, for example, on the surface of the pipe forming the exhaust flow path 5 so as to detect leakage current from the electric heating element 7 . The current sensor 25 transmits a detection signal of the detected leakage current to the ECU 10 .

The ECU 10 is an electronic control unit having a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a CAN [Controller Area Network] communication circuit, and the like. The ECU 10 implements various functions by loading programs stored in the ROM into the RAM and executing the programs loaded into the RAM by the CPU. The ECU 10 may be composed of a plurality of electronic control units.

The ECU 10 has a current value acquisition unit 11, a resistance value acquisition unit 12, an energization control unit 13, and an abnormality determination unit 14 as functional configurations.

The current value acquisition unit 11 acquires the current value of the leakage current based on the detection signal of the current sensor 25 . For example, when the current sensor 25 detects a current, the current value acquisition unit 11 acquires the current as a leakage current from the electric heating element 7 .

The resistance value acquiring unit 12 acquires the resistance value of the PTC thermistor 23 based on the resistance value signal of the PTC thermistor 23 . The resistance value acquisition unit 12 acquires the resistance value of the CTR thermistor 24 based on the resistance value signal of the CTR thermistor 24 .

The energization control unit 13 instructs the EH controller 20 to energize. The energization control unit 13 may instruct the EH controller 20 to energize, for example, based on the catalyst temperature acquired by the catalyst temperature sensor 22 so that the temperature of the SCR 4 falls within the normal temperature range. The energization control unit 13 may issue an energization instruction to the EH controller 20 in consideration of the air flow rate obtained by the air flow sensor 21 . When at least one of the air flow rate sensor 21 and the catalyst temperature sensor 22 is out of order (when the target sensor is out of order), the energization control unit 13 does not have to issue an energization instruction to the EH controller 20 .

Based on the resistance value of the PTC thermistor 23 and whether or not there is an instruction to energize the EH controller 20, the abnormality determination unit 14 determines whether the electric heating element 7 or the constant voltage power supply 8 is abnormal, and the EH controller 20 Determine whether or not there is an abnormality.

Specifically, when the resistance value of the PTC thermistor 23 exceeds a predetermined first resistance value threshold and there is an instruction to energize the EH controller 20, the abnormality determination unit 14 determines that the constant voltage power source 8 is determined to be abnormal. If the resistance value of the PTC thermistor exceeds the first resistance value threshold and there is no instruction to energize the EH controller 20, the abnormality determination unit 14 determines that the EH controller 20 is abnormal. The first resistance value threshold value is a threshold value of the resistance value of the PTC thermistor 23 for determining whether or not the SCR 4 is excessively heated. The first resistance value threshold may be a resistance value corresponding to a temperature included in the first temperature range Tr1, and may be the resistance value Rth1 in FIG. 3, for example.

When the resistance value of the CTR thermistor 24 exceeds a predetermined second resistance value threshold and there is an instruction to energize the EH controller 20, the abnormality determination unit 14 determines that the electric heating element 7 is abnormal. You can judge. When the resistance value of the CTR thermistor 24 exceeds the second resistance value threshold and there is no instruction to energize the EH controller 20, the abnormality determination unit 14 determines that the EH controller 20 is abnormal. good too. The second resistance value threshold value is a threshold value of the resistance value of the CTR thermistor 24 for determining whether or not the SCR 4 is not heated when it should be heated. The second resistance value threshold may be a resistance value corresponding to a temperature included in the second temperature range Tr2, and may be the resistance value Rth2 in FIG. 4, for example.

The abnormality determination unit 14 may determine whether or not the electric heating element 7 is abnormal based on the current value of the current sensor 25 . For example, when the current value acquisition unit 11 acquires the leakage current from the electric heating element 7, the abnormality determination unit 14 determines that the electric heating element 7 has an electric leakage abnormality. For example, when the resistance value of the CTR thermistor 24 exceeds the predetermined second resistance value threshold and there is an instruction to energize the EH controller 20, the abnormality determination unit 14 further acquires the current value. When the leakage current from the electric heating element 7 is acquired by the unit 11, the electric heating element 7 may determine that the electric heating element 7 has an electric leakage abnormality.

The abnormality determination unit 14 determines that at least one of the air flow rate sensor 21 and the catalyst temperature sensor 22 is faulty (the target sensor is faulty) and the resistance value of the PTC thermistor 23 exceeds the first resistance threshold value. If so, it may be determined that the EH controller 20 is abnormal.

[Processing by ECU]
Next, an example of processing by the ECU 10 will be described with reference to FIGS. 5 to 8. FIG. 5 to 8 are flowcharts illustrating the processing of the exhaust emission control system of FIG. 1. FIG. While the engine 1 is running, the ECU 10 of the exhaust purification device 100 repeatedly executes the processes shown in FIGS. 5 to 8 independently or in parallel.

As shown in FIG. 5, in S01, the ECU 10 determines whether or not the current value acquiring unit 11 has detected an electric leakage. For example, when a current is detected by the current sensor 25, the current value acquisition unit 11 acquires the current as a leakage current from the electric heating element 7, and determines that the leakage has been detected. For example, when the current sensor 25 does not detect the current, the current value acquisition unit 11 determines that no leakage is detected.

When the current value acquiring unit 11 determines that an electric leakage has been detected (S01: YES), the ECU 10 proceeds to the process of S02. On the other hand, when the current value acquiring unit 11 determines that no electric leakage is detected (S01: NO), the ECU 10 terminates the processing of FIG.

In S<b>02 , the abnormality determination unit 14 of the ECU 10 determines that there is an abnormality in the heater section (earth leakage). In S03, the ECU 10 causes the energization control section 13 to stop the energization control. The energization control unit 13 does not issue an energization instruction to the EH controller 20, for example, until the abnormality is resolved. After that, the ECU 10 terminates the processing of FIG.

As shown in FIG. 6, in S11, the ECU 10 determines whether or not the PTC thermistor 23 has detected a large resistance by the abnormality determination unit 14 . The abnormality determination unit 14 determines whether or not the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold using the resistance value acquired by the resistance value acquisition unit 12, for example. When the abnormality determination unit 14 determines that the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold (S11: YES), the ECU 10 proceeds to the process of S12. On the other hand, when the abnormality determination unit 14 determines that the resistance value of the PTC thermistor 23 does not exceed the first resistance value threshold (S11: NO), the ECU 10 ends the processing of FIG.

In S12, the ECU 10 determines whether or not an energization instruction has been given by the abnormality determination unit 14 . The abnormality determination unit 14 determines whether or not there is an instruction to energize the EH controller 20 by referring to flag data output by the EH controller 20, for example. When the abnormality determination unit 14 determines that there is an instruction to energize the EH controller 20 (S12: YES), the ECU 10 proceeds to the process of S13.

In S13, the abnormality determination section 14 of the ECU 10 determines that there is an abnormality in the heater section (overvoltage). In S14, the ECU 10 causes the energization control section 13 to stop the energization control. After that, the ECU 10 terminates the processing of FIG.

On the other hand, when the abnormality determination unit 14 determines that there is no instruction to energize the EH controller 20 (S12: NO), the ECU 10 proceeds to the process of S15. In S15, the abnormality determination unit 14 of the ECU 10 determines that the EH controller 20 is abnormal. In S14, the ECU 10 causes the energization control section 13 to stop the energization control. After that, the ECU 10 terminates the processing of FIG.

As shown in FIG. 7, in S21, the ECU 10 determines whether or not the CTR thermistor 24 has detected a large resistance by the abnormality determination unit 14 . The abnormality determination unit 14 determines whether the resistance value of the CTR thermistor 24 exceeds the second resistance value threshold, for example, using the resistance value acquired by the resistance value acquisition unit 12 . When the abnormality determination unit 14 determines that the resistance value of the CTR thermistor 24 exceeds the second resistance threshold value (S21: YES), the ECU 10 proceeds to the process of S22. On the other hand, when the abnormality determination unit 14 determines that the resistance value of the CTR thermistor 24 does not exceed the second resistance value threshold value (S21: NO), the ECU 10 ends the processing of FIG.

In S22, the ECU 10 determines whether or not an energization instruction has been given by the abnormality determination unit 14 . The abnormality determination unit 14 determines whether or not there is an instruction to energize the EH controller 20 by referring to flag data output by the EH controller 20, for example. When the abnormality determination unit 14 determines that there is an instruction to energize the EH controller 20 (S22: YES), the ECU 10 proceeds to the process of S23.

In S23, the abnormality determination section 14 of the ECU 10 determines that there is an abnormality in the heater section (disconnection or poor contact). In S24, the ECU 10 causes the energization control unit 13 to stop the energization control. After that, the ECU 10 terminates the processing of FIG.

On the other hand, when the abnormality determination unit 14 determines that there is no instruction to energize the EH controller 20 (S22: NO), the ECU 10 proceeds to the process of S25. In S25, the abnormality determination unit 14 of the ECU 10 determines that the EH controller 20 is abnormal. In S24, the ECU 10 causes the energization control unit 13 to stop the energization control. After that, the ECU 10 terminates the processing of FIG.

As shown in FIG. 8, in S31, the ECU 10 determines whether or not at least one of the air flow rate sensor 21 and the catalyst temperature sensor 22 is out of order (the target sensor is out of order) by the abnormality determination unit 14. . The abnormality determination unit 14 determines whether or not the target sensor is out of order, for example, by referring to flag data related to sensor failure used in the ECU 10 . When the abnormality determination unit 14 determines that the target sensor is out of order (S31: YES), the ECU 10 proceeds to the process of S32. On the other hand, when the abnormality determination unit 14 determines that the target sensor is not out of order (S31: NO), the ECU 10 terminates the processing of FIG.

In S32, the abnormality determination unit 14 of the ECU 10 determines whether or not the PTC thermistor 23 has detected a large resistance. The abnormality determination unit 14 determines whether or not the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold using the resistance value acquired by the resistance value acquisition unit 12, for example. When the abnormality determination unit 14 determines that the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold (S32: YES), the ECU 10 proceeds to the process of S33. In S33, the abnormality determination unit 14 of the ECU 10 determines that the EH controller 20 is abnormal. In S34, the ECU 10 causes the energization control unit 13 to stop the energization control. After that, the ECU 10 terminates the processing of FIG.

On the other hand, when the abnormality determination unit 14 determines that the resistance value of the PTC thermistor 23 does not exceed the first resistance value threshold value (S32: NO), the process proceeds to S34. In S34, the ECU 10 causes the energization control unit 13 to stop the energization control. After that, the ECU 10 terminates the processing of FIG.

[Action and effect]
As described above, in the exhaust purification device 100, the resistance value of the PTC thermistor 23 is configured to have a high sensitivity in the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR 4 is accelerated. Abnormality is determined using the unit 23A. Therefore, the abnormality can be determined in the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR4 is accelerated. Further, since the abnormality is determined based on whether or not there is an instruction to energize the EH controller 20, the abnormality to be determined can be distinguished between the abnormality of the electric heating element 7 or the constant voltage power supply 8 and the abnormality of the EH controller 20. It becomes possible. Therefore, according to the exhaust purification device 100, it is possible to determine the presence or absence of an abnormality at least in the first temperature range Tr1 including the upper limit temperature at which thermal deterioration of the SCR 4 is accelerated, and to specify the cause of the abnormality.

In the exhaust purification device 100, the abnormality determination unit 14 determines that the resistance value of the PTC thermistor 23 exceeds a predetermined first resistance value threshold value corresponding to the temperature included in the first temperature range Tr1, and that the EH controller 20 When there is an energization instruction, it is determined that the constant-voltage power supply 8 is abnormal, the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold, and there is no energization instruction to the EH controller 20. If so, it is determined that the EH controller 20 is abnormal. As a result, the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold value, so the catalyst temperature has reached the upper limit temperature at which thermal deterioration of the SCR 4 is accelerated. Here, when there is an instruction to energize the EH controller 20, since it is the result of heating due to energization, it is considered that there is an abnormality in the power supply, such as overvoltage. Alternatively, when there is no instruction to energize the EH controller 20, the EH controller 20 is considered to be abnormal because heating due to the energization occurred even though there was no instruction to energize. In this way, it is possible to determine whether there is an abnormality in the first temperature range Tr1 including the upper limit temperature at which thermal deterioration of the SCR 4 is accelerated, and to identify the cause of the abnormality.

The exhaust purification device 100 includes a second temperature detection section 24A including a CTR thermistor 24 that is capable of detecting the heat generation of the electric heating element 7. The resistance value of the CTR thermistor 24 is configured to be highly sensitive in the second temperature range Tr2 including When the resistance value of the CTR thermistor 24 exceeds the threshold and there is an instruction to energize the EH controller 20, it is determined that the electric heating element 7 is abnormal, and the resistance value of the CTR thermistor 24 is reduced to the second If the resistance value exceeds the threshold value and there is no instruction to energize the EH controller 20, it is determined that the EH controller 20 is abnormal. As a result, the resistance value of the CTR thermistor 24 exceeds the second resistance threshold value, so the catalyst temperature has not reached a temperature at which the SCR 4 is sufficiently activated. Here, when there is an instruction to energize the EH controller 20, the heating by energization is insufficient despite the instruction to energize. It is considered abnormal. Alternatively, if there is no instruction to energize the EH controller 20, it is considered that the EH controller 20 is abnormal because there is no heating due to energization despite the insufficient activation of the SCR 4. In this way, it is possible to determine the presence or absence of abnormality in the second temperature range Tr2 including the lower limit temperature at which the activity of SCR4 is insufficient, and to identify the cause of the abnormality.

The exhaust purification device 100 includes a current sensor 25 that is capable of detecting a leakage current from the electric heating element 7, and the abnormality determination unit 14 determines whether the electric heating element 7 is abnormal based on the current value of the current sensor 25. determine whether or not Thereby, it becomes possible to specify the electric leakage as the abnormality of the electric heating element 7 .

The exhaust purification device 100 includes target sensors including at least one of an air flow rate sensor 21 that acquires the air flow rate, which is the flow rate of the intake air of the engine 1, and a catalyst temperature sensor 22 that acquires the catalyst temperature, which is the temperature of the SCR 4. In preparation, the energization control unit 13 does not issue an energization instruction to the EH controller 20 when the target sensor is faulty, and the abnormality determination unit 14 determines that the target sensor is faulty and the resistance value of the PTC thermistor 23 is exceeds the first resistance value threshold, it is determined that the EH controller 20 is abnormal. As a result, even though the target sensor is out of order and there is no energization instruction, as a result of heating due to energization, the catalyst temperature may have reached the upper limit temperature at which thermal deterioration of the SCR 4 is accelerated. can be specified.

[Modification]
Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments.

In the above embodiment, the PTC thermistor 23 is provided on the surface of the pipe forming the exhaust flow path 5, but is not limited to this, and may be provided so as to detect the heat generation of the electric heating element 7. FIG. For example, it may be provided so as to be in direct contact with the electric heating element 7 . Also, the characteristics of the PTC thermistor 23 are not limited to the example shown in FIG.

In the above embodiment, the CTR thermistor 24 is provided on the surface of the pipe forming the exhaust flow path 5, but is not limited to this, and may be provided so as to detect the heat generation of the electric heating element 7. FIG. For example, it may be provided so as to be in direct contact with the electric heating element 7 . Also, the characteristics of the CTR thermistor 24 are not limited to the example shown in FIG.

In the above embodiment, the current sensor 25 is provided on the surface of the pipe forming the exhaust flow path 5, but is not limited to this and may be provided so as to detect the leakage current from the electric heating element 7. For example, it may be provided so as to be in direct contact with the electric heating element 7 .

In the above-described embodiment, the abnormality is determined using the first resistance value threshold for the resistance value of the PTC thermistor 23, but the first resistance value threshold does not necessarily have to be used. Also, although the second resistance value threshold was used to determine the abnormality of the resistance value of the CTR thermistor 24, the second resistance value threshold need not necessarily be used. Also, one of the abnormality determination using the PTC thermistor 23 and the abnormality determination using the CTR thermistor 24 may be omitted. Also, the determination of abnormality using the current sensor 25 may be omitted.

In the above embodiment, the air flow rate sensor 21 is a flow rate sensor provided in the intake passage 6, but may be a pressure sensor provided in an intake manifold of the engine 1 or the like. The catalyst temperature sensor 22 may not be provided directly on the SCR4. For example, the catalyst temperature sensor 22 may be provided upstream or downstream of the SCR 4 in the exhaust flow path 5 and acquire the temperature of the exhaust gas as the catalyst temperature.

In the above embodiment, the air flow rate sensor 21 and the catalyst temperature sensor 22 are provided as target sensors, but either one may be omitted. Alternatively, both may be omitted.

In the above embodiments, SCR4 was used as an example of the catalyst, but other catalysts may be used.

Although the diesel engine 1 is illustrated as an internal combustion engine in the above embodiment, other internal combustion engines such as a gasoline engine may be used.

4...SCR, selective reduction catalyst (catalyst), 5...exhaust flow path, 7...electric heating element, 13...energization control unit, 14...abnormality determination unit, 20...EH controller (power supply control unit), 21...air flow rate sensor ( object sensor), 22... catalyst temperature sensor (object sensor), 23... PTC thermistor, 24... CTR thermistor, 25... current sensor, 100... exhaust emission control device.

Claims (5)

a catalyst provided in an exhaust passage of an internal combustion engine;
an electric heating element provided upstream of the catalyst for heating the exhaust gas flowing through the exhaust passage;
a power control unit that controls whether or not a power source connected to the electric heating element energizes the electric heating element;
a first temperature detection unit including a PTC thermistor capable of detecting heat generation of the electric heating element;
an energization control unit that instructs the power supply control unit to energize;
Abnormality determination for determining whether the electric heating element or the power supply is abnormal based on the resistance value of the PTC thermistor and the presence or absence of the energization instruction, and determining whether the power supply control unit is abnormal. and
The exhaust emission control device, wherein the first temperature detection unit is configured such that the resistance value of the PTC thermistor is highly sensitive in a first temperature range including a temperature at which thermal deterioration of the catalyst is accelerated. The abnormality determination unit is
When the resistance value of the PTC thermistor exceeds a predetermined first resistance value threshold value corresponding to the temperature included in the first temperature range and the power supply instruction is given, the power supply is abnormal. determined to be
2. The exhaust purification system according to claim 1, wherein the power supply control unit determines that there is an abnormality when the resistance value of the PTC thermistor exceeds the first resistance value threshold and the power supply instruction is not given. Device. A second temperature detection unit including a CTR thermistor provided to detect heat generation of the electric heating element,
The second temperature detection unit is configured such that the resistance value of the CTR thermistor is highly sensitive in a second temperature range including a temperature at which the activity of the catalyst is insufficient,
The abnormality determination unit is
When the resistance value of the CTR thermistor exceeds a predetermined second resistance value threshold value corresponding to the temperature included in the second temperature range and the energization instruction is given, the electric heating element is abnormal. determine that there is
3. The power control unit according to claim 1, wherein when the resistance value of said CTR thermistor exceeds said second resistance value threshold and said power supply instruction is not given, said power control unit determines that there is an abnormality. Exhaust purification device. A current sensor capable of detecting leakage current from the electric heating element,
The exhaust emission control system according to any one of claims 1 to 3, wherein the abnormality determination section determines whether or not the electric heating element is abnormal based on the current value of the current sensor. A target sensor including at least one of a catalyst temperature sensor that acquires a catalyst temperature, which is the temperature of the catalyst, and an air flow sensor, which acquires an air flow rate that is the flow rate of the intake air of the internal combustion engine;
The energization control unit does not instruct the power supply control unit to energize when the target sensor is out of order,
The abnormality determination unit is
When the target sensor is faulty and the resistance value of the PTC thermistor exceeds a predetermined first resistance value threshold value corresponding to the temperature included in the first temperature range, the power control unit The exhaust purification system according to any one of claims 1 to 4, which is determined to be abnormal.

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