JP2021116698A - Exhaust emission control device - Google Patents

Abstract

To provide an exhaust emission control device for enabling the determination of at least the presence or absence of abnormality in a temperature region including a temperature where the thermal deterioration of a catalyst is promoted, and the cause of the abnormality to be specified.SOLUTION: The exhaust emission control device includes a SCR 4 provided in an exhaust flow path 5 of an engine 1, an electric heater 7 provided upstream of the SCR 4 for heating exhaust gas, an EH controller 20 for controlling a constant voltage power source 8 to energize the electric heater 7 or not, a first temperature detection part including a PTC thermistor 23 provided for detecting the heat generation of the electric heater 7, an energization control part 13 for performing energization instruction to the EH controller 20, and an abnormality determination part 14 for determining whether the electric heater 7 or the constant voltage power source 8 is abnormal or not and determining whether the EH controller 20 is abnormal or not, on the basis of a resistance value for the PTC thermistor 23 and the energization instruction, the first temperature detection part being constructed so that the resistance value for the PTC thermistor 23 is highly sensitive in a first temperature region including the temperature where the thermal deterioration of the SCR 4 is promoted.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust gas purification device.

Conventionally, as an exhaust gas purification device having an abnormality determination function, an exhaust gas purification device including an energization heating type catalyst device is known (for example, Patent Document 1). The energization heating type catalyst device described in Patent Document 1 has a so-called NTC characteristic in which the energization resistance value of the catalyst carrier changes with the temperature change of the catalyst carrier.

Japanese Unexamined Patent Publication No. 2009-191681

In the above-mentioned prior art, the amount of change in the current-carrying resistance value of the catalyst carrier decreases as the catalyst temperature increases. Therefore, there is room for improvement in the accuracy of abnormality determination of the energization heating type catalyst device when the catalyst temperature is high. Further, in the above-mentioned prior art, it is not easy to distinguish whether the cause of the abnormality of the energization heating type catalyst device is the catalyst carrier itself or the controller that controls the presence or absence of energization.

An object of the present invention is to provide an exhaust gas purification device capable of determining at least the presence or absence of an abnormality in a temperature range including a temperature at which thermal deterioration of the catalyst is promoted, and identifying the cause of the abnormality.

The exhaust purification device according to one aspect of the present invention is connected to a catalyst provided in the exhaust flow path of the internal combustion engine, an electric heating body provided upstream of the catalyst and heating the exhaust gas flowing through the exhaust flow path, and an electric heating body. A power supply control unit that controls the presence or absence of energization of the power supply to the electric heating body, a first temperature detection unit including a PTC thermistor provided so as to detect heat generation of the electric heating body, and an energization instruction to the power supply control unit are performed. Based on the energization control unit, the resistance value of the PTC thermistor, and the presence / absence of an energization instruction, it is determined whether or not the electric heater or the power supply is abnormal, and whether or not the power supply control unit is abnormal. The first temperature detection unit is configured to have high sensitivity in the resistance value of the PTC thermistor in the first temperature range including the temperature at which the thermal deterioration of the catalyst is promoted.

In the exhaust gas purification device according to one aspect of the present invention, the first temperature detector is configured so that the resistance value of the PTC thermistor becomes highly sensitive in the first temperature range including the temperature at which the thermal deterioration of the catalyst is promoted. Use to determine anomalies. Therefore, the abnormality can be determined in the temperature range including the temperature at which the thermal deterioration of the catalyst is promoted. Further, since the abnormality is further determined based on the presence or absence of the energization instruction, it is possible to distinguish between the abnormality of the electric heating body or the power supply and the abnormality of the power supply control unit as the abnormality to be determined. Therefore, according to this exhaust gas purification device, it is possible to determine at least the presence or absence of an abnormality in the temperature range including the temperature at which the thermal deterioration of the catalyst is promoted, and it is possible to identify the cause of the abnormality.

In one embodiment, when the resistance value of the PTC thermistor exceeds the predetermined first resistance value threshold value corresponding to the temperature included in the first temperature range and the abnormality determination unit is instructed to energize. If it is determined that the power supply is abnormal, the resistance value of the PTC thermistor exceeds the first resistance value threshold, and there is no energization instruction, the power supply control unit may be determined to be abnormal. .. In this case, since the resistance value of the PTC thermistor exceeds the first resistance value threshold value, the catalyst temperature reaches a temperature at which thermal deterioration of the catalyst is promoted. Here, when there is an energization instruction, it is considered that the power supply is abnormal, for example, due to overvoltage, because it is the result of heating by energization. Alternatively, when there is no energization instruction, it is considered that the power supply control unit is abnormal because there was heating due to energization even though there was no energization instruction. In this way, the presence or absence of an abnormality can be determined in the temperature range including the temperature at which the thermal deterioration of the catalyst is promoted, and the cause of the abnormality can be identified.

In one embodiment, a second temperature detection unit including a CTR thermistor provided so as to detect heat generation of an electric heating body is provided, and the second temperature detection unit is a second temperature range including a temperature at which the activity of the catalyst becomes insufficient. The resistance value of the CTR thermistor is configured to be highly sensitive, and the abnormality determination unit exceeds the predetermined second resistance value threshold value corresponding to the temperature included in the second temperature range by the resistance value of the CTR thermistor. If there is an energization instruction, it is determined that the 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 is determined. , The power supply control unit may be determined to be 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 is sufficient. Here, when there is an energization instruction, it is considered that the electric heating body is abnormal, for example, due to disconnection or poor contact, because the heating by energization is insufficient despite the energization instruction. .. Alternatively, when there is no energization instruction, it is considered that the power supply control unit is abnormal because there was no heating due to energization even though the activity of the catalyst was insufficient. In this way, the presence or absence of an abnormality can be determined in the temperature range including the temperature at which the activity of the catalyst becomes insufficient, and the cause of the abnormality can be identified.

In one embodiment, a current sensor is provided so as to be able to detect the leakage current from the electric heating body, and the abnormality determination unit determines whether or not the electric heating body is abnormal based on the current value of the current sensor. May be good. In this case, it is possible to identify the leakage as an abnormality of the electric heating body.

In one embodiment, 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 intake air of an internal combustion engine, is provided. When the target sensor is out of order, the energization control unit does not give an energization instruction to the power supply control unit, and the abnormality determination unit corresponds to the temperature included in the first temperature range when the target sensor is out of order. When the resistance value of the PTC thermistor exceeds the predetermined first resistance value threshold value, it may be determined that the power supply control unit is abnormal. In this case, it is considered that the catalyst temperature may have reached the temperature at which the thermal deterioration of the catalyst is promoted as a result of heating by energization even though the target sensor is out of order and there is no energization instruction. In this way, it is possible to identify an abnormality in the power supply control unit.

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

It is a schematic block diagram of the exhaust gas purification apparatus of embodiment. It is a block diagram which shows the structure about the ECU of the exhaust gas purification apparatus of FIG. It is a figure which illustrates the characteristic of the 1st temperature detection part. It is a figure which illustrates the characteristic of the 2nd temperature detection part. It is a flowchart which illustrates the process of the exhaust gas purification apparatus of FIG. It is a flowchart which illustrates the process of the exhaust gas purification apparatus of FIG. It is a flowchart which illustrates the process of the exhaust gas purification apparatus of FIG. It is a flowchart which illustrates the process of the exhaust gas purification apparatus of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals will be used for the same or equivalent elements, and duplicate description will be omitted.

[Configuration of exhaust purification device]
FIG. 1 is a schematic configuration diagram of the exhaust gas purification device of the embodiment. In FIG. 1, the exhaust gas purification device 100 of the present embodiment is mounted on a vehicle, for example, and purifies the exhaust gas discharged from a diesel engine 1 (hereinafter, simply referred to as an engine 1) which is an internal combustion engine. The exhaust gas 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 gas purification device 100 includes a diesel exhaust particulate filter [DPF: Diesel Particulate Filter] 3 and a selective reduction catalyst (catalyst) [SCR: Selective Catalytic Reduction] 4. The DPF3 and the SCR4 are arranged in order from the upstream side to the downstream side in the exhaust flow path 5 connected to the engine 1. Regarding the exhaust flow path 5, the "upstream side" means the upstream side in the exhaust gas flow direction, and the "downstream side" means the downstream side in the exhaust gas flow direction.

The DPF3 may be provided with a diesel oxidation catalyst [DOC: Diesel Oxidation Catalyst]. DOC oxidizes and purifies HC, CO, etc. contained in the exhaust gas. DPF3 removes PM from the exhaust gas by collecting particulate matter [PM: Particulate Matter] contained in the exhaust gas. SCR4 reduces and purifies NOx contained in the exhaust gas.

SCR4 has a working temperature range of a carrier suitable for efficiently reducing NOx. The normal temperature range is determined according to, for example, the composition of the noble metal supported on SCR4. The normal temperature range has an upper limit temperature at which thermal deterioration of SCR4 is promoted when the temperature is exceeded. The normal temperature range has a lower limit temperature at which the activity of SCR4 becomes insufficient below that temperature.

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

An electric heater 7 is arranged on the upstream side of the SCR4 in the exhaust flow path 5, for example, between the addition valve and the SCR4. The electric heating body 7 is a member that generates heat when energized and heats the exhaust gas flowing through the exhaust flow path 5. The electric heating body 7 can adopt a known shape capable of heating the exhaust gas while allowing the exhaust gas to flow. The energization of the electric heating body 7 is controlled by the EH [Electric Heater] controller (power supply control unit) 20. Hereinafter, the electric heating body 7 and the constant voltage power supply 8 may be collectively referred to as a heater unit.

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

When the EH controller 20 is normal and there is an energization instruction from the ECU 10, the EH controller 20 energizes the electric heating body 7 with the electric power of the constant voltage power supply 8. When the EH controller 20 is normal and there is no energization instruction from the ECU 10, the EH controller 20 does not energize the electric heating body 7 with the power of the constant voltage power supply 8.

When the EH controller 20 is abnormal, the EH controller 20 may not energize the electric heating body 7 even if there is an energization instruction from the ECU 10. When the EH controller 20 is abnormal, the EH controller 20 may energize the electric heating body 7 with the electric power of the constant voltage power supply 8 even if there is no energization instruction from the ECU 10.

FIG. 2 is a block diagram showing a configuration of the exhaust gas purification device of FIG. 1 with respect to the ECU. As shown in FIGS. 1 and 2, the exhaust purification device 100 includes an air flow 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 sensors 21 to 25, the addition valve, and the EH controller 20 are connected to the ECU 10. Note that the constant voltage power supply 8 is not shown in FIG.

The air flow rate sensor 21 is a detector that acquires an air flow rate, which is the flow rate of the intake air of the engine 1. The air flow rate sensor 21 is provided in, for example, the intake flow path 6 connected to the engine 1. The air flow rate sensor 21 transmits a detection signal of the detected intake air amount 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, for example, the SCR4. The catalyst temperature sensor 22 transmits a detection signal regarding the detected catalyst temperature to the ECU 10.

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

The PTC thermistor 23 is included in the first temperature detection unit 23A. The first temperature detection unit 23A is configured so that the resistance value of the PTC thermistor 23 becomes highly sensitive in the first temperature range including the temperature at which the thermal deterioration of the SCR4 is promoted. “High sensitivity of resistance value” means that the change gradient of resistance value with respect to temperature change is large.

The first temperature detection unit 23A may be composed of only the PTC thermistor 23. In this case, as a single characteristic of the PTC thermistor 23, it suffices to have a characteristic that the resistance value of the PTC thermistor 23 becomes highly sensitive in the first temperature range including the temperature at which the thermal deterioration of the SCR4 is promoted. FIG. 3 is a diagram illustrating the characteristics of the first temperature detection unit 23A. As shown in FIG. 3, the first temperature detection unit 23A is configured so that the resistance value of the PTC thermistor 23 becomes highly sensitive in the first temperature range Tr1. In the example of FIG. 3, the first temperature range Tr1 is a temperature range having a temperature T1 or higher and a temperature T2 or lower. The first temperature range Tr1 includes an upper limit temperature at which thermal deterioration of SCR4 is promoted. For example, the upper limit temperature is the temperature T1 in FIG. The material and composition of the PTC thermistor 23 are selected to have such temperature characteristics.

Alternatively, the first temperature detection unit 23A may be configured such that, in addition to the PTC thermistor 23, a heat transfer adjusting member (not shown) is interposed between the PTC thermistor 23 and the pipe surface of the exhaust flow path 5. .. In this case, as a single characteristic of the PTC thermistor 23, it is possible to have a characteristic that the resistance value becomes high sensitivity in a temperature range lower than the first temperature range Tr1. Even in such a PTC thermistor 23, the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR4 is promoted on the pipe surface of the exhaust flow path 5 by adjusting the heat transfer to the PTC thermistor 23. In this case, the first temperature detection unit 23A can be configured so that the resistance value of the PTC thermistor 23 becomes highly sensitive. As the heat transfer adjusting member, for example, a heat insulator such as an aluminum-plated steel plate or glass wool can be used. The aluminum-plated steel sheet may have high heat resistance. The heat transfer adjusting member may be provided not only between the PTC thermistor 23 and the piping surface of the exhaust flow path 5, but also around the SCR4.

The CTR thermistor 24 is provided on the surface of a pipe forming, for example, an exhaust flow path 5 so that the heat generated by the electric heating body 7 can be detected. The CTR thermistor 24 has a characteristic that the resistance value changes with a negative slope according to the heat input temperature. The CTR thermistor 24 transmits a resistance value signal corresponding to the heat input temperature to the ECU 10.

The CTR thermistor 24 is included in the second temperature detection unit 24A. The second temperature detection unit 24A is configured so that the resistance value of the CTR thermistor 24 becomes highly sensitive in the second temperature range including the temperature at which the activity of SCR4 becomes insufficient.

The second temperature detection unit 24A may be composed of only the CTR thermistor 24. In this case, as a single characteristic of the CTR thermistor 24, it suffices to have a characteristic that the resistance value of the CTR thermistor 24 becomes highly sensitive in the second temperature range including the temperature at which the activity of SCR4 becomes insufficient. FIG. 4 is a diagram illustrating the characteristics of the second temperature detection unit 24A. As shown in FIG. 4, the second temperature detection unit 24A is configured so that the resistance value of the CTR thermistor 24 becomes highly sensitive in the second temperature range Tr2. In the example of FIG. 4, the second temperature range Tr2 is a temperature range having a temperature T3 or higher and a temperature T4 or lower. The second temperature range Tr2 includes a lower limit temperature at which the activity of SCR4 becomes insufficient, and for example, the lower limit temperature is the temperature T4 in FIG. The material and composition of the CTR thermistor 24 is selected to have such temperature characteristics.

Alternatively, the second temperature detection unit 24A may be configured such that, in addition to the CTR thermistor 24, a heat transfer adjusting member (not shown) is interposed between the CTR thermistor 24 and the pipe surface of the exhaust flow path 5. .. In this case, as a single characteristic of the CTR thermistor 24, it is possible to have a characteristic that the resistance value becomes high sensitivity in a temperature range lower than the second temperature range Tr2. Even with such a CTR thermistor 24, the second temperature range Tr2 including the lower limit temperature at which the activity of SCR4 becomes insufficient on the piping surface of the exhaust flow path 5 by adjusting the heat transfer to the CTR thermistor 24. In this case, the second temperature detection unit 24A can be configured so that the resistance value of the CTR thermistor 24 becomes highly sensitive. As the heat transfer adjusting member, for example, a heat insulator such as an aluminum-plated steel plate or glass wool can be used. The aluminum-plated steel sheet may have high heat resistance. The heat transfer adjusting member may be provided not only between the CTR thermistor 24 and the piping surface of the exhaust flow path 5, but also around the SCR4.

The current sensor 25 is provided on the surface of the pipe forming the exhaust flow path 5, for example, so as to be able to detect the leakage current from the electric heating body 7. The current sensor 25 transmits the detected leakage current detection signal 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 realizes various functions by loading the program stored in the ROM into the RAM and executing the program loaded in the RAM in 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. When the current value acquisition unit 11 detects a current with the current sensor 25, for example, the current value acquisition unit 11 acquires the current as a leakage current from the electric heater 7.

The resistance value acquisition 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 gives an energization instruction to the EH controller 20. The energization control unit 13 may instruct the EH controller 20 to energize the EH controller 20 so that the temperature of the SCR 4 is in the normal temperature range, for example, based on the catalyst temperature acquired by the catalyst temperature sensor 22. The energization control unit 13 may give an energization instruction to the EH controller 20 in consideration of the air flow rate acquired by the air flow rate 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 give an energization instruction to the EH controller 20.

The abnormality determination unit 14 determines whether or not the electric heating body 7 or the constant voltage power supply 8 is abnormal based on the resistance value of the PTC thermistor 23 and the presence or absence of an energization instruction to the EH controller 20, and the EH controller 20 determines whether or not the heating element 7 or the constant voltage power supply 8 is abnormal. Determine if it is abnormal.

Specifically, when the resistance value of the PTC thermistor 23 exceeds a predetermined first resistance value threshold value and the EH controller 20 is instructed to energize, the abnormality determination unit 14 supplies a constant voltage. 8 is determined to be abnormal. The abnormality determination unit 14 determines that the EH controller 20 is abnormal when the resistance value of the PTC thermistor exceeds the first resistance value threshold value and there is no instruction to energize the EH controller 20. The first resistance value threshold value is the resistance value threshold value of the PTC thermistor 23 for determining whether or not the SCR4 is in an excessively heated state. The first resistance value threshold value may be any resistance value corresponding to the temperature included in the first temperature range Tr1, and may be, for example, the resistance value Rth1 in FIG.

When the resistance value of the CTR thermistor 24 exceeds the predetermined second resistance value threshold value and the EH controller 20 is instructed to energize, the abnormality determination unit 14 determines that the electric heating body 7 is abnormal. You may judge. The abnormality determination unit 14 determines that the EH controller 20 is abnormal when the resistance value of the CTR thermistor 24 exceeds the second resistance value threshold value and there is no instruction to energize the EH controller 20. May be good. The second resistance value threshold value is the threshold value of the resistance value of the CTR thermistor 24 for determining whether or not the SCR4 is in a state where it should be heated and is not heated. The second resistance value threshold value may be any resistance value corresponding to the temperature included in the second temperature range Tr2, and can be, for example, the resistance value Rth2 in FIG.

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

In the abnormality determination unit 14, at least one of the air flow sensor 21 and the catalyst temperature sensor 22 is out of order (the target sensor is out of order), and the resistance value of the PTC thermistor 23 exceeds the first resistance value 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. 5 to 8 are flowcharts illustrating the processing of the exhaust gas purification device of FIG. The ECU 10 of the exhaust gas purification device 100 repeatedly executes the processes shown in FIGS. 5 to 8 independently or in parallel while the engine 1 is in operation.

As shown in FIG. 5, the ECU 10 determines in S01 whether or not an electric leakage has been detected by the current value acquisition unit 11. 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 body 7 and determines that the leakage has been detected. The current value acquisition unit 11 determines, for example, that no electric leakage is detected when the current sensor 25 does not detect the current.

When it is determined by the current value acquisition unit 11 that the electric leakage is detected (S01: YES), the ECU 10 shifts to the process of S02. On the other hand, when it is determined by the current value acquisition unit 11 that no electric leakage is detected (S01: NO), the ECU 10 ends the process of FIG.

In S02, the ECU 10 determines that the heater unit is abnormal (leakage) by the abnormality determination unit 14. In S03, the ECU 10 stops the energization control by the energization control unit 13. The energization control unit 13 does not give an energization instruction to the EH controller 20 until, for example, the abnormality is resolved. After that, the ECU 10 ends the process shown in FIG.

As shown in FIG. 6, the ECU 10 determines in S11 whether or not the abnormality determination unit 14 has detected a large resistance in the PTC thermistor 23. The abnormality determination unit 14 determines whether or not the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold value, 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 PTC thermistor 23 exceeds the first resistance value threshold value (S11: YES), the ECU 10 shifts 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 value (S11: NO), the ECU 10 ends the process 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 energization instruction to the EH controller 20 by, for example, referring to the flag data output by the EH controller 20. When the abnormality determination unit 14 determines that the EH controller 20 has been instructed to energize (S12: YES), the ECU 10 shifts to the process of S13.

In S13, the ECU 10 determines that the heater unit is abnormal (overvoltage) by the abnormality determination unit 14. In S14, the ECU 10 stops the energization control by the energization control unit 13. After that, the ECU 10 ends the process shown in FIG.

On the other hand, when the abnormality determination unit 14 determines that the EH controller 20 has not been instructed to energize (S12: NO), the ECU 10 shifts to the process of S15. In S15, the ECU 10 determines that the EH controller 20 is abnormal by the abnormality determination unit 14. In S14, the ECU 10 stops the energization control by the energization control unit 13. After that, the ECU 10 ends the process shown in FIG.

As shown in FIG. 7, the ECU 10 determines in S21 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 or not the resistance value of the CTR thermistor 24 exceeds the second resistance value threshold value, 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 value threshold value (S21: YES), the ECU 10 shifts 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 process of FIG. 7.

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 energization instruction to the EH controller 20 by, for example, referring to the flag data output by the EH controller 20. When the abnormality determination unit 14 determines that the EH controller 20 has been instructed to energize (S22: YES), the ECU 10 shifts to the process of S23.

In S23, the ECU 10 determines that the heater unit is abnormal (disconnection or poor contact) by the abnormality determination unit 14. In S24, the ECU 10 stops the energization control by the energization control unit 13. After that, the ECU 10 ends the process shown in FIG. 7.

On the other hand, when the abnormality determination unit 14 determines that the EH controller 20 has not been instructed to energize (S22: NO), the ECU 10 shifts to the process of S25. In S25, the ECU 10 determines that the EH controller 20 is abnormal by the abnormality determination unit 14. In S24, the ECU 10 stops the energization control by the energization control unit 13. After that, the ECU 10 ends the process shown in FIG. 7.

As shown in FIG. 8, the ECU 10 determines in S31 whether or not at least one of the air flow rate sensor 21 and the catalyst temperature sensor 22 has failed (the target sensor has failed) by the abnormality determination unit 14. .. The abnormality determination unit 14 determines whether or not the target sensor has failed, for example, by referring to the flag data related to the 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 shifts to the process of S32. On the other hand, when the abnormality determination unit 14 determines that the target sensor has not failed (S31: NO), the ECU 10 ends the process of FIG.

In S32, 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 value, 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 PTC thermistor 23 exceeds the first resistance value threshold value (S32: YES), the ECU 10 shifts to the process of S33. In S33, the ECU 10 determines that the EH controller 20 is abnormal by the abnormality determination unit 14. In S34, the ECU 10 stops the energization control by the energization control unit 13. After that, the ECU 10 ends the process shown in 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 stops the energization control by the energization control unit 13. After that, the ECU 10 ends the process shown in FIG.

[Action and effect]
As described above, in the exhaust gas purification device 100, the first temperature detection is configured so that the resistance value of the PTC thermistor 23 becomes highly sensitive in the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR4 is promoted. The 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 promoted. Further, since the abnormality is further determined based on the presence or absence of the energization instruction to the EH controller 20, it is possible to distinguish between the abnormality of the electric heating body 7 or the constant voltage power supply 8 and the abnormality of the EH controller 20 as the abnormality to be determined. It will be possible. Therefore, according to the exhaust gas purification device 100, it is possible to determine at least the presence or absence of an abnormality in the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR4 is promoted, and it is possible to identify 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 the resistance value to the EH controller 20 is reached. 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, since the resistance value of the PTC thermistor 23 exceeds the first resistance value threshold value, the catalyst temperature reaches the upper limit temperature at which the thermal deterioration of the SCR4 is promoted. Here, when there is an instruction to energize the EH controller 20, it is considered that the power supply is abnormal, for example, due to overvoltage, because it is the result of heating by energization. Alternatively, when there is no energization instruction to the EH controller 20, it is considered that the EH controller 20 is abnormal because there was heating due to energization even though there was no energization instruction. In this way, the presence or absence of an abnormality can be determined in the first temperature range Tr1 including the upper limit temperature at which the thermal deterioration of the SCR4 is promoted, and the cause of the abnormality can be identified.

The exhaust purification device 100 includes a second temperature detection unit 24A including a CTR thermistor 24 provided so as to be able to detect the heat generation of the electric heating body 7, and the second temperature detection unit 24A has a lower limit temperature at which the activity of the SCR4 becomes insufficient. The resistance value of the CTR thermistor 24 is configured to have high sensitivity in the second temperature range Tr2 including the above, and the abnormality determination unit 14 has a predetermined second resistance value corresponding to the temperature included in the second temperature range Tr2. If the resistance value of the CTR thermistor 24 exceeds the threshold value and there is an instruction to energize the EH controller 20, it is determined that the heating element 7 is abnormal, and the resistance value of the CTR thermistor 24 is the second. If the resistance value threshold is exceeded 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 value threshold value, so that the catalyst temperature has not reached a temperature at which the activity of SCR4 becomes sufficient. Here, when the EH controller 20 is instructed to energize, the heating by energization is insufficient even though the energization instruction is given. It is considered to be abnormal. Alternatively, when there is no instruction to energize the EH controller 20, it is considered that the EH controller 20 is abnormal because there was no heating due to energization even though the activity of SCR4 was insufficient. In this way, the presence or absence of an abnormality can be determined in the second temperature range Tr2 including the lower limit temperature at which the activity of SCR4 is insufficient, and the cause of the abnormality can be identified.

The exhaust purification device 100 includes a current sensor 25 provided so as to be able to detect the leakage current from the electric heating body 7, and the abnormality determination unit 14 determines whether the electric heating body 7 is abnormal based on the current value of the current sensor 25. Judge whether or not. This makes it possible to identify an electric leakage as an abnormality of the electric heating body 7.

The exhaust purification device 100 includes a target sensor including at least one of an air flow sensor 21 that acquires an air flow rate that is the flow rate of intake air of the engine 1 and a catalyst temperature sensor 22 that acquires a catalyst temperature that is the temperature of the SCR 4. If the target sensor is out of order, the energization control unit 13 does not give an energization instruction to the EH controller 20, and the abnormality determination unit 14 is in that the target sensor is out of order and the resistance value of the PTC thermistor 23. If exceeds the first resistance value threshold value, 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, the catalyst temperature may have reached the upper limit temperature at which thermal deterioration of SCR4 is promoted as a result of heating by energization. It becomes possible to identify.

[Modification example]
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 the present invention is not limited to this, and the PTC thermistor 23 may be provided so as to be able to detect the heat generated by the electric heating body 7. For example, it may be provided so as to come into direct contact with the electric heating body 7. Further, the characteristics of the PTC thermistor 23 are not limited to the example of FIG.

In the above embodiment, the CTR thermistor 24 is provided on the surface of the pipe forming the exhaust flow path 5, but the present invention is not limited to this, and the CTR thermistor 24 may be provided so as to be able to detect the heat generated by the electric heating body 7. For example, it may be provided so as to come into direct contact with the electric heating body 7. Further, the characteristics of the CTR thermistor 24 are not limited to the example of FIG. 4 above.

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

In the above embodiment, the resistance value of the PTC thermistor 23 is determined to be abnormal by using the first resistance value threshold value, but the first resistance value threshold value does not necessarily have to be used. Further, although the resistance value of the CTR thermistor 24 is determined to be abnormal by using the second resistance value threshold value, it is not always necessary to use the second resistance value threshold value. Further, either the determination of the abnormality using the PTC thermistor 23 or the determination of the abnormality using the CTR thermistor 24 may be omitted. Further, the determination of the 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 flow path 6, but may be, for example, a pressure sensor provided in the intake manifold of the engine 1. The catalyst temperature sensor 22 does not have to be directly provided on the SCR4. For example, the catalyst temperature sensor 22 is provided on the upstream side or the downstream side of the SCR 4 in the exhaust flow path 5, and the temperature of the exhaust gas may be acquired as the catalyst temperature.

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

In the above embodiment, SCR4 is exemplified as the catalyst, but other catalysts may be used.

In the above embodiment, the diesel engine 1 is exemplified as the internal combustion engine, but other internal combustion engines such as a gasoline engine may be used.

4 ... SCR, selective reduction catalyst (catalyst), 5 ... exhaust flow path, 7 ... electric heater, 13 ... energization control unit, 14 ... abnormality determination unit, 20 ... EH controller (power supply control unit), 21 ... air flow sensor ( Target sensor), 22 ... Catalyst temperature sensor (target sensor), 23 ... PTC thermistor, 24 ... CTR thermistor, 25 ... current sensor, 100 ... exhaust gas purification device.

Claims (5)

The catalyst provided in the exhaust flow path of the internal combustion engine and
An electric heater provided upstream of the catalyst and heating the exhaust gas flowing through the exhaust flow path, and
A power supply control unit that controls the presence or absence of energization of the power source connected to the electric heating body to the electric heating body, and
A first temperature detection unit including a PTC thermistor provided so as to be able to detect heat generation of the electric heating body, and
An energization control unit that gives an energization instruction to the power supply control unit, and
Based on the resistance value of the PTC thermistor and the presence / absence of the energization instruction, it is determined whether or not the electric heating body or the power supply is abnormal, and whether or not the power supply control unit is abnormal. With a department,
The first temperature detection unit is an exhaust gas purification device configured so that the resistance value of the PTC thermistor becomes highly sensitive in the first temperature range including the temperature at which the thermal deterioration of the catalyst is promoted. The abnormality determination unit
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 energization instruction is given, the power supply is abnormal. Judging that
The exhaust gas purification according to claim 1, wherein when the resistance value of the PTC thermistor exceeds the first resistance value threshold value and the energization instruction is not given, the power supply control unit is determined to be abnormal. Device. A second temperature detection unit including a CTR thermistor provided so as to be able to detect heat generation of the electric heating body is provided.
The second temperature detection unit is configured so that the resistance value of the CTR thermistor becomes highly sensitive in the second temperature range including the temperature at which the activity of the catalyst becomes insufficient.
The abnormality determination unit
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 heater is abnormal. Judging that there is
The first or second aspect of the present invention, wherein when the resistance value of the CTR thermistor exceeds the second resistance value threshold value and the energization instruction is not given, the power supply control unit is determined to be abnormal. Exhaust purification device. A current sensor provided so as to be able to detect the leakage current from the electric heating body is provided.
The exhaust gas purification device according to any one of claims 1 to 3, wherein the abnormality determination unit determines whether or not the electric heater 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 that is the temperature of the catalyst and an air flow sensor that acquires an air flow rate that is the flow rate of intake air of the internal combustion engine.
When the target sensor is out of order, the energization control unit does not give an energization instruction to the power supply control unit.
The abnormality determination unit
When the target sensor is out of order 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 supply control unit causes the power supply control unit. The exhaust purification device according to any one of claims 1 to 4, which is determined to be abnormal.

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