JP5168089B2 - Catalyst diagnostic device - Google Patents

Description

  The present invention relates to deterioration diagnosis of an exhaust gas purification catalyst for an internal combustion engine, and more particularly, to deterioration diagnosis of a catalyst having a function of oxidizing a combustible component contained in exhaust gas.

  A so-called oxidation catalyst having a function of oxidizing unburned hydrocarbons is known as a catalyst for purifying unburned hydrocarbons contained in exhaust gas of an internal combustion engine.

Regarding the deterioration diagnosis of an oxidation catalyst, Patent Document 1 discloses a method for estimating the heat of reaction of an oxidation catalyst and determining whether the heat is deteriorated based on the magnitude of the heat of reaction.
JP 2003-106140 A

  However, in Patent Document 1, the temperature difference between before and after the catalyst is detected by the temperature sensor to estimate the reaction heat, and the influence of the exhaust flow rate is not taken into account, so the diagnostic accuracy is low.

  Therefore, an object of the present invention is to provide a deterioration diagnosis device that can accurately perform deterioration diagnosis of an oxidation catalyst.

The catalyst diagnostic device of the present invention is a diagnostic device for a catalyst that is provided in an exhaust passage of an internal combustion engine and has an oxidation function for oxidizing unburned hydrocarbons in exhaust when the temperature is higher than a predetermined temperature. Exhaust heat quantity calculation means for calculating the exhaust heat quantity, which is the product of the exhaust temperature and the exhaust flow rate, for the exhaust passage on the inlet side and the outlet side of the catalyst, respectively, and oxidation in the catalyst based on the exhaust heat quantity on the inlet side and the outlet side An oxidation reaction heat quantity estimating means for estimating the reaction heat quantity, and a deterioration diagnosis means for judging the presence or absence of deterioration of the catalyst based on the oxidation reaction heat quantity . The deterioration diagnosis means is a time integration of the oxidation reaction heat quantity during a predetermined traveling period. The value and the threshold value for deterioration diagnosis are calculated, and it is determined that the catalyst is deteriorated when the time integral value is smaller than the threshold value for deterioration diagnosis.

  According to the present invention, since it is determined whether or not the exhaust gas is deteriorated by using the exhaust heat quantity including the exhaust gas flow rate as a parameter, it is possible to perform the deterioration diagnosis in consideration of the influence of the exhaust gas flow rate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram to which this embodiment is applied.

  1 is a diesel engine body, 2 is a fuel injection valve for each cylinder, 3 is a fuel injection device having a pressure accumulating chamber for storing high-pressure fuel (common rail fuel injection device), 4 is an intake collector, 5 is an intake passage, and 10 is exhaust A passage, 9 is a control unit for performing various controls such as setting of a target regeneration temperature and temperature rise control during regeneration processing, and 14 is a transmission that transmits the driving force of the diesel engine body 1 to the drive shaft. The transmission 14 may be a stepped transmission or a continuously variable transmission.

  High pressure fuel is supplied to the fuel injection valve 2 by a common rail fuel injection device 3. Each fuel injection valve 2 opens and closes in response to an injection signal from a control unit (ECU) 9 as control means, and injects high-pressure fuel into the cylinder.

  An intake passage 4 is connected to an intake collector 4 connected to each intake port of the diesel engine body 1, and a compressor 6 a of a variable nozzle turbocharger 6 for supercharging from the upstream side is added to the intake passage 5. An intercooler 7 for cooling air that has been pressurized and heated, and an intake throttle valve 8 for controlling the intake air amount are arranged. Further, from the upstream side of the exhaust passage 10, the turbine 6 b of the variable nozzle turbocharger 6, the oxidation catalyst 11 that oxidizes unburned components (HC) in the exhaust, and the particulates as a filter that collects PM. Filters (DPF) 13 are sequentially arranged.

  Further, an EGR passage 15 branched from the upstream of the turbine 6b in the exhaust passage 10 and connected to the intake collector 4 is provided, and an EGR valve 16 is installed in the EGR passage 15 so that the exhaust gas recirculates into the intake air according to the operating conditions. Control the amount.

  The ECU 9 includes a crank angle sensor 17 that detects the engine speed, an accelerator opening sensor 18 that detects the opening of the accelerator pedal, an exhaust temperature sensor 19 that detects an exhaust temperature upstream of the oxidation catalyst 11, and a downstream side. The detection signals from the exhaust temperature sensor 12 for detecting the exhaust temperature of the exhaust gas, the exhaust air / fuel ratio sensor 20 for detecting the exhaust air / fuel ratio downstream of the DPF 13, and the temperature sensor 21 for detecting the bed temperature of the DPF 13 are input.

  Based on these detection signals, a signal for controlling the opening degree of the variable nozzle vane of the variable nozzle type turbocharger 6, a signal for controlling the opening degree of the EGR valve 16, and the opening degree of the intake throttle valve 8 are controlled. A signal for controlling the amount of fuel injected by the fuel injection valve 2, a signal for operating the fuel injection valve 2 for supplying fuel necessary for increasing the exhaust temperature for DPF regeneration, and the DPF 13 The estimation of the amount of accumulated PM, judgment of the regeneration timing, deterioration diagnosis of the oxidation catalyst 11 and the like are performed.

  Here, the deterioration diagnosis of the oxidation catalyst 11 will be described. FIG. 2 is a block diagram showing a configuration of deterioration diagnosis control of the oxidation catalyst 11.

  In the outlet heat quantity calculation unit B11, the outlet side heat quantity hout is calculated by multiplying the outlet side temperature Texh-in detected by the exhaust temperature sensor 12 on the downstream side of the oxidation catalyst 11 and the exhaust flow rate Qexh. The exhaust flow rate Qexh is calculated based on the intake air amount and the fuel injection amount of the diesel engine body 1. The intake air amount is estimated based on the opening degree of the intake throttle valve 8, the engine speed, the valve timing, and the like. In addition, when an air flow meter is provided, the detected value may be used. Further, in consideration of the time delay caused by the path length from the intake air amount detection position to the exhaust temperature sensors 12 and 19, if the exhaust flow rate Qexh used for calculating the heat amount is set to the intake air amount detection value before the delay time, , Diagnostic accuracy is further increased.

  In the inlet heat quantity calculation unit B12, the inlet side heat quantity Hin is calculated by multiplying the inlet side temperature Texh-out detected by the exhaust temperature sensor 19 upstream of the oxidation catalyst 11 and the exhaust gas flow rate Qexh.

  Then, the difference between the outlet side heat quantity hout and the inlet side heat quantity hin is calculated in the inlet / outlet heat quantity difference calculation unit B13.

  The vehicle speed correction amount calculation unit B14 calculates a correction amount corresponding to the vehicle speed based on a preset map. In the map used here, as shown in FIG. 2, the correction amount increases as the vehicle speed increases. This is because the higher the vehicle speed, the stronger the traveling wind and the greater the heat radiation.

  The outside air temperature correction amount calculation unit B15 calculates a correction amount according to the outside air temperature based on a preset map. In the map used here, as shown in FIG. 2, the correction amount decreases as the outside air temperature increases. This is because the amount of heat released from the oxidation catalyst 11 decreases as the outside air temperature increases.

  Then, the environmental correction term calculation unit B16 calculates an environmental correction term hloss that is the amount of heat radiated from the oxidation catalyst 11 based on the vehicle speed correction amount and the outside air temperature correction amount.

  In the catalytic reaction heat calculation unit B17, the difference between the outlet side heat quantity hout and the inlet side heat quantity hin is corrected by the environmental correction term hloss to calculate the catalytic reaction heat quantity ha. Specifically, the inlet-side heat quantity hin is subtracted from the outlet-side heat quantity hout, and the environment correction term hloss is further subtracted.

  In the integrating unit B18, a time integrated value (heat integrated value) Σha of the catalytic reaction heat quantity ha is calculated.

  On the other hand, in the diagnostic threshold correction amount calculation units B19 to B21, diagnostic thresholds to be described later are calculated according to the average vehicle speed, the average output, and the fuel injection amount integrated value, respectively. The average output is calculated based on the engine speed and the accelerator opening, that is, the detected values of the crank angle sensor 17 and the accelerator opening sensor 18.

  The diagnosis threshold selection unit B22 selects any one of the diagnosis thresholds calculated by the diagnosis threshold calculation units B19 to B21, and the selected diagnosis threshold is set as the deterioration determination threshold by the deterioration determination threshold setting unit B23.

  The deterioration diagnosis unit B24 determines whether or not the heat amount integrated value Σha is larger than the deterioration determination threshold. The deterioration determination unit B25 is deteriorated if it is larger than the deterioration determination value threshold based on the result of the deterioration diagnosis unit B24. If it is small, it is determined that it has not deteriorated.

  Here, the relationship between the deterioration of the oxidation catalyst 11 and the heat integrated value Σha and the diagnostic threshold will be described.

  FIG. 3 is a diagram showing the relationship between the absolute value of the heat quantity integrated value Σha and the engine operating time. A solid line A shows a state where the oxidation catalyst 11 has not deteriorated, and a solid line B shows a state where the oxidation catalyst 11 has deteriorated. .

  When the oxidation catalyst 11 is activated at t0, regardless of the presence or absence of deterioration, the heat amount integrated value Σha increases with time, but in the deteriorated state, the absolute value of the heat amount integrated value Σha is smaller. It has become. This is because the heat of catalytic reaction is reduced due to deterioration.

  That is, when the oxidation catalyst 11 deteriorates, the heat amount integrated value Σha becomes smaller than before the deterioration.

  4 and 5 show the relationship between the amount of HC discharged into the atmosphere (tail pipe HC discharge amount TPHC) and the integrated heat quantity Σha, and the amount of HC stored in the oxidation catalyst 11 (storage HC). The relationship between the amount ηHC) and the heat integrated value Σha is shown.

  As shown in FIG. P. HC increases as the heat value integrated value Σha decreases. Further, as shown in FIG. 5, the occluded HC amount ηHC decreases as the heat amount integrated value Σha decreases.

  Therefore, the calorific value integrated value Σha is calculated, and the tail pipe HC discharge amount T.P. P. A calorific value integrated value Σha1 at which HC is less than or equal to an allowable amount or a calorific value integrated value Σha2 at which the occluded HC amount ηHC is equal to or greater than an allowable amount is calculated, and this is set as a diagnostic threshold value as in diagnostic threshold correction amount calculation units B19 to B21. Thus, the deterioration of the oxidation catalyst 11 can be diagnosed. The diagnosis threshold value is set in advance according to the specifications of the engine to be applied and the oxidation catalyst 11.

  The diagnostic threshold increases as the average vehicle speed increases, the average output increases, and the fuel injection amount integrated value increases. This is because the higher the average vehicle speed, the higher the average output, or the larger the fuel injection amount integrated value, the greater the amount of HC discharged from the diesel engine body 1 and the greater the catalytic reaction heat ha. This is because, even in this case, the amount of heat integrated value Σha increases accordingly.

  FIG. 6 is an example of a flowchart of the above-described deterioration diagnosis control. This control is executed, for example, once during one trip or every predetermined time. Here, the diagnosis threshold value is set based on the average output.

  In step S100, it is determined based on the coolant temperature whether or not it is in a warm-up state. If it is in a warm-up state, the process proceeds to step S101, and if it is before warm-up, the determination is repeated.

  In step S101, the outlet side heat quantity hout and the inlet side heat quantity hin of the oxidation catalyst 11 are calculated. This step corresponds to the outlet heat quantity calculation unit B11 and the inlet heat quantity calculation unit B12 described above.

  In step S102, a catalytic reaction heat quantity ha is calculated. This step corresponds to the aforementioned inlet / outlet heat quantity difference calculation unit B13 and catalytic reaction heat calculation unit B17.

  In step S103, the heat amount integrated value Σha is calculated. This step corresponds to the integration unit B18 described above. Further, the average output of the diesel engine main body 1 during the period in which the heat amount integrated value Σha is integrated is calculated.

  In step S104, it is determined whether or not the deterioration diagnosis is permitted. Deterioration diagnosis is permitted because the amount of time for which the amount of heat is accumulated has passed a predetermined time, the travel distance during the period for which the amount of heat is being accumulated exceeds a predetermined value, or the amount of heat is accumulated It is assumed that either of the accumulated output values during the period exceeds a predetermined value is established. If the permission condition is satisfied, the process proceeds to step S105. If the permission condition is not satisfied, the process returns to step S101. The predetermined value used for determination in this step is set in advance according to the specifications of the engine and the oxidation catalyst 11.

  In step S105, a diagnosis threshold value corresponding to the average output is set. This step corresponds to the diagnostic threshold correction amount calculation unit B20.

  In step S106, deterioration diagnosis is performed based on the heat amount integrated value Σha and the diagnosis threshold value. This step corresponds to the deterioration diagnosis unit B24. If the integrated heat value Σha is smaller, the process proceeds to step S107, and if larger, the process proceeds to step S108.

  In step S107, it is determined that the oxidation catalyst 11 has deteriorated, and a warning lamp is turned on. In step S108, it is determined that the oxidation catalyst 11 is normal, and the above-described variables are cleared. This step corresponds to the deterioration determination unit B25.

  As described above, since the diagnosis is performed using the catalytic reaction heat of the oxidation catalyst 11, it is possible to perform the deterioration diagnosis even when the oxygen storage function and the lean NOx catalyst are not provided. In addition, special control such as rich spike and post injection becomes unnecessary, and it is possible to prevent fuel consumption from deteriorating for diagnosis. Furthermore, since the diagnosis is performed using the time integrated value of the amount of heat, it is possible to avoid the difficulty of determination based on the instantaneous value due to the magnitude of the time constant of the temperature.

  In the above description, the deterioration determination is performed using the heat amount integrated value Σha obtained by time-integrating the catalyst reaction heat ha. However, in the case of a simpler configuration, the catalyst reaction heat ha and the threshold value are compared. It may be. In this case, the diagnostic threshold is not an average value or an integrated value, but an instantaneous value is used.

  As described above, according to the present embodiment, the following effects can be obtained.

(1) In a diagnostic apparatus for a catalyst provided in an exhaust passage of an internal combustion engine and having an oxidation function of oxidizing unburned hydrocarbons in exhaust when a predetermined temperature or higher is reached,
The exhaust heat quantity h, which is the product of the exhaust temperature Texh and the exhaust flow rate Qexh, is calculated for the exhaust passages on the inlet side and the outlet side of the oxidation catalyst 11, respectively, and oxidation in the oxidation catalyst 11 is performed based on the exhaust heat quantities on the inlet side and the outlet side. Since the reaction heat amount ha is estimated and the presence / absence of deterioration of the oxidation catalyst 11 is determined based on the oxidation reaction heat amount ha, accurate deterioration diagnosis can be performed regardless of the exhaust gas flow rate. Further, it is possible to diagnose a system that does not have an oxygen storage function or a system that does not include a NOx catalyst. Furthermore, since the diagnosis is performed using the catalytic reaction heat, the diagnosis can be performed without performing special control such as rich spike or post injection.

  (2) The oxidation reaction heat quantity estimation means calculates a difference between the exhaust heat quantity hout on the outlet side and the exhaust heat quantity hin on the inlet side as the oxidation reaction heat quantity ha, and further converts the oxidation reaction heat quantity ha into at least one of the vehicle speed and the outside air temperature. Accordingly, the oxidation reaction heat quantity ha can be calculated with high accuracy, and as a result, accurate deterioration diagnosis can be performed regardless of the driving conditions.

  (3) The time integral value Σha of the oxidation reaction heat quantity ha during a predetermined traveling period is calculated, and it is determined that the oxidation catalyst 11 has deteriorated when this is smaller than the deterioration diagnosis threshold value. Even if the exhaust temperature at which the influence of the exhaust gas is likely to remain is included as a parameter of the oxidation reaction heat quantity ha, the deterioration diagnosis can be performed with high accuracy.

  (4) Since the presence or absence of deterioration is determined after any of the elapsed time, travel distance, or integrated output during the oxidation reaction calorie integration reaches a predetermined value, the instantaneous value resulting from the time constant of the temperature is used. Compared to the determination, deterioration diagnosis can be performed with high accuracy.

  (5) Since the threshold value for deterioration diagnosis is calculated based on one of the average vehicle speed, average output, and fuel injection amount integrated value during the oxidation reaction heat integration, diagnosis using the threshold corresponding to the travel history is performed. be able to.

  (6) For calculating the exhaust heat amount ha, the intake air amount detected before the exhaust temperature detection for the time required for the air to move from the position for detecting the intake air amount to the position for detecting the exhaust temperature. Since it is used as the exhaust flow rate, a more accurate exhaust heat quantity ha can be calculated, and as a result, a highly accurate diagnosis is possible.

  (7) Since diagnosis is prohibited when the cooling water temperature is equal to or lower than a predetermined value, erroneous diagnosis can be prevented.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a system configuration diagram. It is a block diagram of deterioration diagnosis control. It is a figure which shows the relationship between calorie | heat amount integrated value and travel time. It is a figure which shows the relationship between the tail pipe HC and the calorie | heat amount integrated value. It is a figure which shows the relationship between HC occlusion amount and a calorie | heat amount integrated value. It is an example of the flowchart of deterioration diagnosis control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel engine body 2 Fuel injection valve 3 Fuel injection device (common rail type fuel injection device)
4 Intake Collector 5 Intake Passage 6 Variable Nozzle Turbocharger 7 Intercooler 8 Inlet Throttle Valve 9 Control Unit (ECU)
10 Exhaust passage 11 Oxidation catalyst 12 Exhaust temperature sensor 13 Particulate filter (DPF)
14 Transmission 15 EGR passage 16 EGR valve 19 Exhaust temperature sensor

Claims (15)

In a diagnostic apparatus for a catalyst that is provided in an exhaust passage of an internal combustion engine and has an oxidation function for oxidizing unburned hydrocarbons in exhaust when the temperature is equal to or higher than a predetermined temperature,
Exhaust heat amount calculating means for calculating an exhaust heat amount which is a product of an exhaust temperature and an exhaust flow rate for the exhaust passage on the inlet side and the outlet side of the catalyst;
An oxidation reaction heat quantity estimating means for estimating an oxidation reaction heat quantity at the catalyst based on the exhaust heat quantity on the inlet side and the outlet side;
Deterioration diagnosis means for determining the presence or absence of deterioration of the catalyst based on the amount of heat of oxidation reaction;
Equipped with a,
The deterioration diagnosis means calculates a time integral value of the oxidation reaction heat quantity during a predetermined travel period and a threshold value for deterioration diagnosis, and the catalyst deteriorates when the time integral value is smaller than the deterioration diagnosis threshold value. A diagnostic apparatus for a catalyst, characterized in that it is determined that the catalyst is present. 2. The catalyst diagnosis apparatus according to claim 1, wherein the oxidation reaction heat quantity estimating unit calculates a difference between the exhaust heat quantity on the outlet side and the exhaust heat quantity on the inlet side as an oxidation reaction heat quantity. 3. The catalyst diagnostic apparatus according to claim 2, further comprising a reaction calorie correcting unit that corrects the oxidation reaction calorie calculated by the oxidation reaction calorie estimating unit according to at least one of a vehicle speed and an outside air temperature. 4. The catalyst diagnosis apparatus according to claim 3, wherein the reaction heat amount correction means increases the correction amount as the vehicle speed increases. 4. The catalyst diagnostic apparatus according to claim 3, wherein the reaction heat amount correction means decreases the correction amount as the outside air temperature increases. The deterioration diagnosis means, the elapsed time in the oxidation reaction heat accumulation, claim 1, the travel distance or integrated either output, is characterized by determining the presence or absence of deterioration of the catalyst after reaching a predetermined value 6. The catalyst diagnostic apparatus according to any one of 5 above. The deterioration diagnosis means, claim 1, characterized in that the set according to the threshold for the deterioration diagnosis to any one of the average vehicle speed during the oxidation reaction heat accumulation, average power, or fuel injection amount accumulated value 6 The diagnostic apparatus for a catalyst according to any one of the above. The deterioration diagnosis means sets the deterioration diagnosis threshold value larger as the average vehicle speed during the oxidation reaction heat integration is higher, as the average output is higher, or as the fuel injection amount integration value is larger. Item 8. The catalyst diagnostic device according to Item 7 . The degradation diagnostic device, diagnostic apparatus of a catalyst for any crab of claims 1 to 8, characterized in that to determine that the catalyst when the reaction heat is less than the threshold value for deterioration diagnosis is deteriorated. The degradation diagnostic device, diagnostic apparatus of a catalyst for any crab of claims 1 to 9, characterized in that calculated on the basis of a threshold for the deterioration diagnosis of the engine operating condition. 11. The catalyst diagnostic apparatus according to claim 10 , wherein the engine operating state is any one or more of an engine speed, an accelerator opening, a fuel injection amount, and a vehicle speed. The exhaust temperature, diagnostic apparatus of a catalyst for any crab of claims 1 to 11, characterized by detecting the exhaust gas temperature detection means provided in the exhaust passage. The exhaust flow rate, diagnostic apparatus of a catalyst for any crab of claims 1 to 12, characterized in that calculated on the basis of the intake air amount and the fuel injection amount. The exhaust heat quantity calculating means calculates the exhaust heat quantity based on the intake air quantity detected before the exhaust temperature detection by a delay time required from the position where the intake air quantity is detected to the position where the exhaust temperature is detected. diagnostic apparatus of the catalyst for any crab of claims 1 to 13, which comprises using as the exhaust flow rate. If the coolant temperature is below a predetermined value, the preceding claims, characterized in that it comprises inhibiting means for inhibiting the diagnosis by the exhaust heat calculation unit and the calculation by the oxidation reaction heat estimating means or the deterioration diagnosis means, 14 The diagnostic apparatus for a catalyst according to any one of the above.