Abnormality detection device for electrically heated catalytic converters

Abstract

To provide an abnormality detection device for an electric heating type catalyst device that can accurately determine heating abnormality of an electric heating type catalyst.SOLUTION: The present invention relates to an abnormality detection device for an electric heating type catalyst device that has a catalyst for purifying the exhaust emission of an internal combustion engine housed in an electric conductive housing while insulated from the housing and electrifies the catalyst to raise a temperature of the catalyst. The abnormality detection device for the electric heating type catalyst device is configured to: previously hold a reference resistance value when the catalyst is electrified so as to raise its temperature (step S2); find an actual resistance value when the catalyst is electrified to heat the catalyst in a use state in which the catalyst is housed in the housing (step S6); find an insulation resistance value based upon the actual resistance value and the reference resistance value (step S7); and determine abnormality of the electric heating type catalyst device based upon the insulation resistance value and a predetermined determination threshold (step S8).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an abnormality detection device for an electrically heated catalyst device that includes an electrically heated catalyst that is provided in an exhaust passage and electrically heats the catalyst to increase its temperature. [Background technology]

[0002] Patent document 1 describes a vehicle control device that is provided with an insulation resistance detection device to detect leakage current in an electrically heated catalyst (EHC), and if the insulation resistance value detected by the insulation resistance detection device is less than a predetermined value, it determines that there is a leakage current and turns off a relay switch to cut off the flow of current to the electrically heated catalyst.

[0003] According to the vehicle control device described in Patent Document 1, the insulation resistance value between the EHC carrier and a case (exhaust pipe) made of a metal material is monitored, and it is said that this insulation resistance value can be used to detect a decrease in insulation of the electrically insulating retaining mat (insulating coating) provided between the EHC carrier and the case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-072665 Summary of the Invention [Problem to be solved by the invention]

[0005] In an electrically heated catalyst, the catalyst and its case are supposed to be insulated from each other. However, as described in Patent Document 1, electrical continuity between the catalyst and its case can occur due to the accumulation of conductive materials such as carbon. When continuity occurs between the catalyst and the case in two or more places, the case forms a parallel circuit with the catalyst, allowing current to flow through the case, resulting in abnormal catalyst heating. The device described in Patent Document 1 detects continuity between the catalyst and the case by passing current through an insulation resistance detector to measure the electrical resistance between the two. When current is passed through an EHC to heat or increase its temperature, even if there is continuity between the catalyst and the case in only one place due to the accumulation of conductive materials such as carbon, a parallel circuit is not formed, preventing leakage of heating current and allowing the catalyst to heat normally. However, when there is continuity in one place, passing current through the insulation resistance detector results in current flowing through the insulation resistance detector because a circuit is formed between the case, catalyst, insulation resistance detector, and the conductive part. In this case, the detected insulation resistance value may drop even though no abnormal heating has occurred, resulting in an abnormality determination, which poses a problem that the accuracy of the determination is not necessarily high.

[0006] This invention was made with an eye on the above-mentioned technical problems, and aims to provide an abnormality detection device for an electrically heated catalyst device that can accurately determine heating abnormalities in an electrically heated catalyst. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides an abnormality detection device for an electrically heated catalytic device in which a catalyst for purifying exhaust gas from an internal combustion engine is housed in a conductive housing insulated from the housing, and current is passed through the catalyst to raise the temperature of the catalyst, the device pre-stores a reference resistance value of the catalyst when current is passed through to raise the temperature of the catalyst, calculates the actual resistance value when current is passed through to heat the catalyst in the operating state in which the catalyst is housed in the housing, calculates an insulation resistance value based on the actual resistance value and the reference resistance value, and judges an abnormality in the electrically heated catalytic device based on the insulation resistance value and a predetermined judgment threshold value.

[0008] In addition, in this invention, the reference resistance value may be estimated from a predetermined relationship depending on the detection value of any one of a flow rate sensor in the exhaust pipe, an air-fuel ratio sensor of the exhaust passing through the exhaust pipe, and a temperature sensor of the exhaust.

[0009] In the present invention, the reference resistance value may be determined based on a detection value of a sensor attached to the catalyst.

[0010] In addition, this invention may include a current sensor that detects the value of the current flowing through the circuit when current is applied to heat the catalyst, and a voltage sensor that detects the voltage value of the circuit, and the actual resistance value may be determined by the current value and the voltage value. [Effects of the Invention]

[0011] According to the abnormality detection device for an electrically heated catalyst device of this invention, a reference resistance value when current is passed through the catalyst to heat it is stored in advance, the actual resistance value when current is passed through the catalyst to heat it when it is in use and housed in a housing is calculated, and an insulation resistance value is calculated based on this actual resistance value and the previously stored reference resistance value.An abnormality in the electrically heated catalyst device is then determined based on this insulation resistance value and a predetermined judgment threshold value, thereby making it possible to accurately determine a heating abnormality in the electrically heated catalyst.

[0012] The electrical heating catalyst is then turned on and the catalytic converter is turned on, and the catalytic converter is turned on.

[0013] Furthermore, according to the abnormality detection device for an electrically heated catalytic device of this invention, the reference resistance value can be estimated from the detection values ​​of the flow sensor in the exhaust pipe, the air-fuel ratio sensor of the exhaust passing through the exhaust pipe, and the exhaust temperature sensor.Therefore, by estimating the deterioration of the catalyst's resistance over time and then calculating the insulation resistance value based on the resistance value of the deteriorated catalyst and the actual resistance value of the entire circuit of the electrically heated catalytic device, it is possible to determine the deterioration of insulation due to deterioration over time and therefore determine that an abnormality has occurred in the electrically heated catalytic device.

[0014] In addition, according to the abnormality detection device for the electrically heated catalytic device of this invention, the reference resistance value can be determined by detection by a sensor attached to the catalyst, so by calculating the insulation resistance value based on the actual measured value of the resistance of the catalyst and the actual resistance value of the entire circuit of the electrically heated catalytic device, it is possible to determine the deterioration of insulation due to deterioration over time, and therefore it is possible to determine that an abnormality has occurred in the electrically heated catalytic device.

[0015] In addition, according to the abnormality detection device for an electrically heated catalytic device of this invention, the actual resistance value is determined by the current value and voltage value detected by a current sensor that detects the current value flowing in the circuit when electricity is passed through to heat the catalyst, and a voltage sensor that detects the voltage value of the circuit.This means that the resistance value of the entire circuit of the electrically heated catalytic device can be obtained as an actual measured value, making it possible to more accurately determine abnormalities in the electrically heated catalytic device. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1A is a schematic diagram for explaining the configuration of an embodiment of the invention, and FIG. 1B is an equivalent circuit diagram. [Figure 2] 4 is a flowchart illustrating an example of control executed in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings, which illustrate embodiments of an abnormality detection device for an electrically heated catalytic converter. Note that the embodiments described below are merely examples of how the present invention can be implemented, and are not intended to limit the scope of the present invention.

[0018] The configuration of an embodiment of the present invention will be described with reference to the schematic diagram of Figure 1(A). An internal combustion engine (hereinafter referred to as engine) 1 is, for example, a gasoline engine having multiple cylinders 2, and outputs power by burning a mixture of gasoline and air.

[0019] In each cylinder 2 of the engine 1, an air-fuel mixture containing intake air introduced from an intake manifold 4 connected via an intake pipe 3 and fuel injected from an injector (not shown) is combusted by spark discharge from an ignition device (not shown). Exhaust gas generated in each cylinder 2 by the combustion of the air-fuel mixture is discharged into an exhaust pipe 6 connected via an exhaust manifold 5. The exhaust pipe 6 is provided with at least a catalyst 7.

[0020] The catalyst 7 is an exhaust purification catalyst conventionally used in vehicles, such as an oxidation catalyst that oxidizes environmental pollutants such as hydrocarbons and carbon monoxide, or an occlusion-reduction catalyst that captures nitrogen oxides as nitrate nitrogen and then reduces them to render them harmless, and is housed in a conductive housing 8 while covered with an insulating material (not shown) such as glass. The front and rear ends of the housing 8 are connected to the exhaust pipe 6, respectively.

[0021] Since it takes time for the catalyst 7 to become active after the engine 1 is started, an electrically heated catalyst device (hereinafter sometimes referred to as EHC) 9 is provided to quickly activate the catalyst 7, and the temperature of the catalyst 7 is raised by electrically heating it, thereby activating it.

[0022] Next, the electrically heated catalytic device 9 will be described with reference to Fig. 1. The electrically heated catalytic device 9 includes at least one electrode 10, the other electrode 11, a power converter 12, and a battery 13. The one electrode 10 functions as an electrode for applying a positive voltage, with an end fixed to the outer periphery of the catalyst 7, and the other electrode 11 functions as an electrode for applying a negative voltage, with an end fixed to the outer periphery of the catalyst 7. Furthermore, the one electrode 10 and the other electrode 11 are each covered with an insulator (not shown) made of an insulating material such as glass, and an insulating state is maintained between the respective electrodes 10, 11 and the housing 8.

[0023] Power converter 12 is a power supply circuit unit for converting the power of battery 13, and the power of battery 13 is converted to a predetermined voltage by an isolation transformer 14 inside power converter 12. Power converter 12 is also provided with a current sensor 15 and a voltage sensor 16 for detecting a current I and a voltage V applied to the catalyst. Therefore, by passing the power converted by power converter 12 between electrodes 10, 11, catalyst 7 is heated and its temperature is increased by Joule heat.

[0024] The resistance of the catalyst 7 itself is represented as EHC resistance REHC, and the resistance of the entire circuit calculated from the detection values ​​of the current sensor 15 and voltage sensor 16 is represented as real resistance R. If the vehicle is still in a new condition before initial operation, insulation between the electrically heated catalytic device 9 and the housing 8 should be ensured, so the insulation resistance Rleak between the two is an infinitely high value. In other words, real resistance R represents the EHC resistance REHC.

[0025] It is known that the insulation resistance Rleak gradually decreases as the engine 1 is repeatedly operated. Examples of possible causes include insulation degradation due to initial manufacturing defects or carbon deposition. In particular, if carbon contained in exhaust gas accumulates at multiple locations on the edge of the catalyst 7, a conduction path is formed between the carbon-deposited portion (resistances Rα and Rβ) between the catalyst 7 and the housing 8 and the housing 8 (exhaust pipe 6) (resistance Rγ) connecting the carbon-deposited portion. This reduces the insulation resistance Rleak (in the above-mentioned example, Rleak = Rα + Rβ + Rγ) of the electrically heated catalytic device 9. This may result in insufficient current flowing to the catalyst 7, resulting in an overheating abnormality. In this embodiment of the present invention, control for determining an abnormality in the electrically heated catalytic device 9 is performed by an electronic control unit (hereinafter referred to as ECU) 17.

[0026] The ECU 17 is a device that controls at least the engine 1, and is mainly composed of a microcomputer consisting of arithmetic elements, memory, etc., and is configured to perform calculations using input data and pre-stored data, and to output the results of the calculations as control command signals.

[0027] The ECU 17 shown in FIG. 1A has a functional configuration that includes at least the functions of controlling an initial start determination means 18, an initial EHC resistance value calculation unit 19, an initial EHC abnormality determination means 20, an EHC resistance detection unit 21, an insulation resistance calculation unit 22, and an insulation degradation determination means 23.

[0028] The first start determination means 18 has a function of determining whether the electrically heated catalytic device 9 including the catalyst 7 is in a new vehicle state before initial activation. One specific example of such a means is to connect an external tool to the ECU 17 when the new vehicle is assembled at a factory, and send a message indicating that the vehicle is being started for the first time from the external tool to the ECU 17. The first start determination means 18 determines whether the ECU has received such a message indicating that the vehicle is being started for the first time. Note that the "first start" in the first start determination means 18 does not necessarily have to be a new vehicle, and may also be applied to a case where the electrically heated catalytic device 9 including the catalyst 7 has been replaced with a new one for repairs or other reasons.

[0029] The initial EHC resistance value calculation unit 19 has a function of calculating the value of the initial EHC resistance REHC_ini at the time of manufacture when the initial start determination means 18 affirmatively determines that "this is an initial start." The initial EHC resistance REHC_ini at the time of manufacture can be calculated from Ohm's law using values ​​detected by the current sensor 15 and voltage sensor 16 inside the power conversion device 12, for example. REHC_ini=V / I…(1)

[0030] In addition, since the value of the initial EHC resistance REHC_ini at the time of manufacture has initial variations at the time of manufacture, the initial EHC resistance value calculation unit 19 has a function of storing the value of the initial EHC resistance REHC_ini at the time of manufacture in the ECU 17 in order to grasp the degree of insulation deterioration such as aging deterioration described below.

[0031] The initial EHC abnormality determination means 20 has a function of determining whether the value of the initial EHC resistance REHC_ini at the time of manufacture calculated by the initial EHC resistance value calculation unit 19 is within a predetermined range calculated assuming that no insulation failure occurs, or whether the deviation from the resistance value in a normal state without insulation failure or the like is within a predetermined range. If the value is within the predetermined range, the electrically heated catalytic device 9 is determined to be normal, and if the value is outside the predetermined range, the electrically heated catalytic device 9 is determined to be abnormal. Note that this predetermined range may be a value read from an initial EHC resistance value map stored in advance in the ECU 17, for example.

[0032] The EHC resistance detection unit 21 has a function of detecting and acquiring the EHC resistance REHC (corresponding to the reference resistance value in the embodiment of the present invention) at times other than the initial start. The means for detecting the value of the EHC resistance REHC may be, for example, a conventionally known resistance meter. Alternatively, the deterioration of the resistance of the catalyst 7 over time may be determined in advance by experiment or simulation and stored, for example, as a map, and the deterioration of the resistance of the catalyst 7 over time may be estimated from the map. Specifically, the EHC resistance REHC′ after deterioration over time may be estimated from an EHC resistance value map that uses as parameters the detection values ​​of the flow rate sensor in the exhaust pipe 6, the air-fuel ratio sensor for the exhaust passing through the exhaust pipe 6, and the exhaust temperature sensor, or that has a predetermined relationship using any of the detection values ​​as parameters. The EHC resistance REHC may then be determined by adding the estimated deterioration EHC resistance REHC′ to the value of the initial EHC resistance REHC_ini at the time of manufacture, which was calculated and stored by the initial EHC resistance calculation unit 19.

[0033] The insulation resistance calculation unit 22 has a function of calculating the insulation resistance Rleak of the circuit of the electrically heated catalytic converter 9 based on the data (EHC resistance REHC) obtained by the EHC resistance detection unit 21. The insulation resistance Rleak can be calculated using the EHC resistance REHC and the actual resistance R=V / I, which is the combined resistance of the entire circuit obtained from the detection values ​​of the current sensor 15 and the voltage sensor 16. Specifically, Rleak=REHC·(V / I) / {REHC-(V / I)}…(2) Note that the equivalent circuit of the electrically heated catalytic converter 9 can be considered to be a series circuit in which the catalyst 7 acts as a resistor when the vehicle is new, but if electrical conduction occurs between the catalyst 7 and the housing 8 for some reason, a parallel circuit will be formed in which the housing 8 and the carbon or other foreign matter that caused the conduction are connected in parallel to the catalyst 7. This is shown as an equivalent circuit in Figure 1(B). Therefore, as can be seen from equation (2) above, the insulation resistance Rleak can be calculated using the relationship between voltage, current (i.e., actual resistance) and the resistance value of the catalyst 7 itself.

[0034] The insulation degradation determination means 23 has a function of determining whether the value of insulation resistance Rleak calculated by the insulation resistance calculation unit 22 exceeds a predetermined threshold value. If the value exceeds the predetermined threshold value, the electrically heated catalytic device 9 is determined to be normal, and conversely, if the value is equal to or less than the predetermined threshold value, the electrically heated catalytic device 9 is determined to be abnormal. Note that this predetermined threshold value may be a value previously determined as an insulation degradation map pre-stored in the ECU 17, for example.

[0035] FIG. 2 is a flowchart illustrating an example of control in the above-described configuration, and is executed by the ECU 17. The control shown in the flowchart in FIG. 2 is repeatedly executed by the ECU 17 while the engine 1 is operating. In the control example shown in FIG. 2, first, it is determined whether or not the engine is being started for the first time (step S1). This determination is made by the first-time start determination means 18 to determine whether or not the electrically heated catalytic device 9 including the catalyst 7 is in a new vehicle state before initial operation. If the determination in step S1 is affirmative, that is, if the engine is being started for the first time, the value of the initial EHC resistor REHC_ini at the time of manufacture is calculated and stored (step S2). The initial EHC resistance value calculation unit 19 calculates the value of the initial EHC resistor REHC_ini at the time of manufacture using values ​​detected by the current sensor 15 and the voltage sensor 16 inside the power conversion device 12, and stores the calculated value in the ECU 17.

[0036] Next, it is determined whether the value of the initial EHC resistor REHC_ini at the time of manufacture is within a predetermined range (step S3). This is performed by the initial EHC abnormality determination means 20 to determine whether the value of the initial EHC resistor REHC_ini at the time of manufacture calculated in step 2 is within a predetermined range set in advance by design. If the determination in step S3 is affirmative, i.e., if the value of the initial EHC resistor REHC_ini at the time of manufacture is determined to be within the predetermined range in step S3, the electrically heated catalytic device 9 is determined to be normal (step S4). After the determination is completed, the routine shown in this flowchart is temporarily terminated. Conversely, if the determination in step S3 is negative, i.e., if the value of the initial EHC resistor REHC_ini at the time of manufacture is determined to be outside the predetermined range in step S3, the electrically heated catalytic device 9 is determined to be abnormal (step S5). After the determination is completed, the routine shown in this flowchart is temporarily terminated. Therefore, in this case, some kind of warning or abnormality signal is output, and the device is replaced or repaired.

[0037] On the other hand, if the determination in step S1 is negative, that is, if it is determined in step S1 that the engine is not being started for the first time, the EHC resistor REHC is detected (step S6). The EHC resistor REHC can be determined from an appropriate sensor or an estimated value based on deterioration over time from the value of the initial EHC resistor REHC_ini at the time of manufacture stored in step S2, and is detected by the EHC resistor detection unit 21.

[0038] Next, the insulation resistance Rleak is calculated (step S7). Because the current and voltage are constantly detected by the above-mentioned sensors 15, 16, the resistance value of the entire circuit, i.e., the actual resistance value R (= V / I), is known, and the insulation resistance Rleak of the circuit of the electrically heated catalytic device 9 can be calculated based on this value and the EHC resistance REHC detected in step S6. That is, the insulation resistance Rleak is calculated by the insulation resistance calculation unit 22 using the above-mentioned equation (2).

[0039] Next, it is determined whether the insulation resistance Rleak exceeds a predetermined threshold (step S8). Here, it is determined whether the value of the insulation resistance Rleak obtained in step S7 exceeds the predetermined threshold, and this determination is made by the insulation degradation determination means 23. If the determination in step S8 is affirmative, i.e., if the value of the insulation resistance Rleak is determined to be higher than the predetermined threshold, the electrically heated catalytic device 9 is determined to be normal (step S9), and after the determination is completed, the routine shown in this flowchart is temporarily terminated. Conversely, if the determination in step S8 is negative, i.e., if the value of the insulation resistance Rleak is determined to be equal to or lower than the predetermined threshold, the electrically heated catalytic device 9 is determined to be abnormal (step S10), and after the determination is completed, the routine shown in this flowchart is temporarily terminated. In this case, as described above, some kind of warning or abnormality signal is output, and the device is replaced or repaired.

[0040] In the abnormality detection device for the electrically heated catalytic device 9 according to the embodiment of the present invention, in step S1, it is determined whether the electrically heated catalytic device 9 including the catalyst 7 is in a new vehicle state before initial operation, and in step S2, the value of the EHC resistance in the new vehicle state, i.e., the value of the initial EHC resistance REHC_ini at the time of manufacture, is stored and held in the ECU in advance. In addition, in step S3, it is determined whether the value of the initial EHC resistance REHC_ini at the time of manufacture is within a predetermined range, thereby detecting an abnormality due to an initial defect in the electrically heated catalytic device 9.

[0041] Furthermore, in step S6, the EHC resistance REHC is detected at times other than the initial start. When detecting the EHC resistance REHC, the EHC resistance REHC may be obtained as an actual measurement value using an appropriate sensor, or the EHC resistance REHC' corresponding to deterioration over time may be estimated and then combined with the value of the initial EHC resistance REHC_ini at the time of manufacture to obtain a more actual degree of deterioration of the EHC resistance REHC. Typically, the value of the initial EHC resistance REHC_ini at the time of manufacture is likely to vary, so estimating the degree of deterioration of the EHC resistance REHC by considering only the change over time may result in poor estimation accuracy. In other words, estimating the degree of deterioration of the EHC resistance REHC while taking into account the initial variation at the time of manufacture can further improve the estimation accuracy of the deterioration of the EHC resistance REHC.

[0042] Then, in the next step S7, the value of insulation resistance Rleak is calculated based on the value of EHC resistance REHC detected in step S6. In this way, the value of insulation resistance Rleak can be calculated based on the value of resistance R of the entire circuit of the electrically heated catalytic device 9 and the value of EHC resistance REHC, without directly measuring the value of insulation resistance Rleak between the catalyst 7 and the housing 8. In the conventional case where the value of insulation resistance Rleak between the catalyst 7 and the housing 8 is measured directly, even if there is only one location of carbon deposits, a voltage is intentionally applied between the catalyst 7 and the housing 8 to cause a current to flow, which could lower the value of insulation resistance Rleak and result in an erroneous determination of an insulation failure. In contrast, in this invention, the value of insulation resistance Rleak is calculated based on the value of resistance R of the entire circuit of the electrically heated catalytic device 9 and the value of EHC resistance REHC, making it possible to more accurately determine an abnormality in the electrically heated catalytic device 9.

[0043] The present invention is not limited to the above-described embodiment, but can be modified and implemented as appropriate within the scope of the object of the present invention. [Explanation of symbols]

[0044] 1 engine 2-cylinder 3 Intake pipe 4 intake manifold 5 exhaust manifold 6 exhaust pipe 7. Catalyst 8. Housing 9 Electrically heated catalytic converter 10 One electrode 11 Other electrode 12 Power conversion device 13 Battery 14 Isolation transformer 15 Current Sensor 16 Voltage Sensor 17 ECU 18 First start determination means 19 Initial EHC resistance value calculation section 20 Initial EHC abnormality determination means 21 EHC resistance detection unit 22 Insulation resistance calculation section 23. Means for determining insulation degradation

Claims

1. An abnormality detection device for an electrically heated catalyst device in which a catalyst for purifying exhaust gas from an internal combustion engine is housed in a conductive housing in a state insulated from the housing, and in which current is passed through the catalyst to raise the temperature of the catalyst, a reference resistance value of the catalyst when current is applied to raise the temperature of the catalyst is stored in advance; determining an actual resistance value when current is applied to heat the catalyst in a state in which the catalyst is housed in the housing and in use; determining an insulation resistance value based on the actual resistance value and the reference resistance value; The electrical heating catalyst device is determined to have an abnormality based on the insulation resistance value and a predetermined threshold value.

1. An abnormality detection device for an electrically heated catalytic converter.

2. 2. The abnormality detection device for an electrically heated catalytic converter according to claim 1, The reference resistance value is estimated from a predetermined relationship according to the detected value of any one of a flow rate sensor in the exhaust pipe, an air-fuel ratio sensor for the exhaust passing through the exhaust pipe, and a temperature sensor for the exhaust.

1. An abnormality detection device for an electrically heated catalytic converter.

3. 2. The abnormality detection device for an electrically heated catalytic converter according to claim 1, The reference resistance value is determined based on a detection value of a sensor attached to the catalyst.

1. An abnormality detection device for an electrically heated catalytic converter.

4. 4. An abnormality detection device for an electrically heated catalytic converter according to claim 1, a current sensor for detecting a current value flowing through a circuit when current is applied to heat the catalyst, and a voltage sensor for detecting a voltage value of the circuit; The actual resistance value is determined by the current value and the voltage value.

1. An abnormality detection device for an electrically heated catalytic converter.

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