JP5225428B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus having a function of warning a driver of deterioration of a catalytic converter.

  Conventionally, as an apparatus for diagnosing deterioration of a catalytic converter of an internal combustion engine (hereinafter referred to as catalyst deterioration diagnosing apparatus), oxygen concentration sensors are arranged on the upstream side and the downstream side of the catalytic converter, and based on the correlation between these output signals. It is known to estimate the oxygen storage capacity of a catalytic converter and diagnose that the catalytic converter has deteriorated when the storage capacity is low (the correlation between the output signals of upstream and downstream oxygen concentration sensors is high) (for example, patents) Reference 1).

  Some of such catalyst deterioration diagnosis devices are provided with a control means for prohibiting diagnosis depending on the temperature state of the catalytic converter. This is because when the temperature of the catalytic converter to be diagnosed is low, the oxygen storage capacity is low even if the catalytic converter is normal, and the same diagnostic result as the deteriorated catalytic converter is obtained. Because it ends up.

  As a method of prohibiting the diagnosis by the catalyst deterioration diagnosis device, an exhaust temperature sensor is provided in the vicinity of the catalytic converter, and when the exhaust temperature detected by the exhaust temperature sensor falls below a predetermined value, the temperature of the catalytic converter Is determined to be low, that is, the catalytic converter has insufficient activity and the oxygen storage capacity is low, and diagnosis is prohibited (Patent Document 2). In this example, since the exhaust gas temperature is directly detected by the exhaust gas temperature sensor disposed in the vicinity of the catalytic converter, it is possible to accurately determine whether the catalytic converter is insufficiently active.

  Further, as another conventional device, a warm-up counter set value having a counter increase region and a counter decrease region related to the engine load of the internal combustion engine is determined, and the “warm-up” of the catalytic converter that counts the warm-up counter set value is determined. There is one that judges whether or not the catalytic converter is in a predetermined warm-up state (whether or not the temperature of the catalytic converter is sufficiently high) by the “machine counter” and prohibits diagnosis (Patent Document 3). In this example, the information of the intake air temperature sensor used for the fuel control of the internal combustion engine is diverted to the calculation of the warm-up counter, thereby recognizing a decrease in the rate of increase in the temperature of the catalytic converter in a low temperature environment. The active state can be determined.

  Specifically, the offset value is determined according to the intake air temperature and added to the warm-up counter, or the intake air temperature coefficient is determined according to the intake air temperature and the warm-up counter is multiplied by the intake air temperature coefficient. Is used. Here, the offset value or the intake air temperature coefficient is set smaller than the normal temperature state (eg, 20 ° C.) when the intake air temperature is low (eg, 0 ° C.). With these actions, even if the amount of air taken in by the internal combustion engine is the same, the accumulated amount of the warm-up counter value per unit time becomes smaller as the intake air temperature becomes lower, so that the rise of the warm-up counter can be delayed. I can do it.

Japanese Patent No. 4578544 JP-A-8-177468 Japanese Patent No. 3265794

  However, since the exhaust temperature sensor used in the catalyst deterioration diagnosis device presented in Patent Document 2 is exposed to an extremely high temperature gas, there is a problem that a very durable sensor is required and the cost is high. Thermocouples that apply the Seebeck effect, which is commonly used as a sensor, output a very small voltage (for example, several tens of mV). While protecting this minute voltage from external noise in the control device of the internal combustion engine, the catalyst deteriorates. A complex circuit that amplifies the output of the sensor in order to recognize the temperature with high accuracy by an A / D converter (for example, the resolution of A / D conversion is 5 V / 1024 bits) of a microcomputer that is responsible for various arithmetic processes of the diagnostic device is necessary. For this reason, there has been a problem that the cost is further increased due to an increase in the substrate area of the control device and an increase in the number of electronic components constituting the circuit.

  In addition, the catalyst deterioration diagnosis device presented in Patent Document 3 does not require complicated circuits in the exhaust temperature sensor and the control device for the internal combustion engine as compared with that in Patent Document 2, so that the cost can be kept low. Can do. However, since the intake temperature sensor is disposed for the purpose of correcting the amount of intake air to the internal combustion engine that contributes to combustion, it is often disposed near the intake port of the internal combustion engine. For this reason, when the internal combustion engine is operated in a high load state, the temperature of the member near the intake air temperature sensor rises due to heat received from the combustion chamber of the internal combustion engine, and the intake air temperature measured by the intake air temperature sensor is higher than the outside air temperature. Becomes hotter. In an internal combustion engine having a supercharger, when the pressure of the intake air can be increased by the supercharger, the intake air temperature measured by the intake air temperature sensor disposed downstream of the supercharger is It becomes higher than the temperature.

  When the intake air temperature is higher than the outside air temperature in a low temperature environment, in the warm-up counter described in Patent Document 3, the offset value or the intake air temperature coefficient corresponding to the intake air temperature should be originally selected in the low temperature environment. No value is set, and a decrease in the rate of temperature increase of the catalytic converter cannot be recognized. Therefore, there is a problem that the deterioration diagnosis of the catalytic converter is permitted even when the temperature of the catalytic converter is not sufficiently high, that is, when the activity of the catalytic converter is insufficient.

  In order to solve this problem, in consideration of the amount of heat received by the members in the vicinity of the intake temperature sensor from the combustion chamber, a method of setting a high intake temperature condition in which the offset value or the intake temperature coefficient is set to be small in advance (for example, An area where the offset value or the intake air temperature coefficient is set to a small value is expanded to an area where the intake air temperature is 30 ° C. or lower). However, when the outside air temperature is high and the wind received by the vehicle is very strong, even if the temperature measured by the intake air temperature sensor is high, the amount of heat taken away by the exhaust pipe between the combustion chamber of the internal combustion engine and the catalytic converter is small. Since it is very large, there arises a problem that the deterioration diagnosis of the catalytic converter is permitted when the temperature of the catalytic converter is not sufficiently high.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine that can reliably inhibit deterioration diagnosis of a catalytic converter when the activity of the catalytic converter is insufficient. The purpose is to realize at low cost.

An internal combustion engine control apparatus according to the present invention is provided on an upstream oxygen concentration sensor disposed on an upstream side of a catalytic converter for purifying exhaust gas discharged from a combustion chamber of the internal combustion engine, and on a downstream side of the catalytic converter. Based on the correlation of the output signal of the downstream oxygen concentration sensor, the catalyst deterioration diagnosis device for determining the deterioration state of the catalytic converter, and the basic value of the parameter related to the temperature of the catalytic converter based on the operating state of the internal combustion engine The basic temperature parameter calculating means for calculating, the first temperature of the intake air output from the first intake temperature sensor disposed in the intake passage of the internal combustion engine, and the combustion chamber more than the first intake temperature sensor of the intake passage. The second temperature of the intake air output by the second intake temperature sensor disposed on the side is acquired, and the basic temperature is used using the correction value determined based on the difference between the second temperature and the first temperature. parameter A basic temperature parameter correcting means for correcting a parameter related to the temperature of the catalytic converter by correcting a basic value of the parameter calculated by the data calculating means, and a parameter related to the temperature of the catalytic converter calculated by the basic temperature parameter correcting means. And a catalyst deterioration diagnosis prohibiting means for prohibiting the diagnosis by the catalyst deterioration diagnosis device based on various parameters indicating the operating state of the internal combustion engine.

  According to the present invention, the output (second temperature) of the second intake air temperature sensor and the first intake air temperature sensor are utilized by utilizing the correlation between the heat loss amounts of the exhaust passage and the intake passage of the internal combustion engine. The temperature drop amount of the exhaust gas is estimated from the temperature drop amount in the intake passage obtained from the difference in the output (first temperature) of the exhaust gas, and is calculated by the basic temperature parameter calculation means using the correction value corresponding to this drop amount Since the basic value of the parameter is corrected, even if the output of the second intake air temperature sensor is higher than the outside air temperature in a low temperature environment, or even if the vehicle receives a very strong wind in a high temperature environment, the catalyst It is possible to accurately detect a state where the converter activity is insufficient, and an inexpensive thermistor can be used as the first and second intake air temperature sensors. A control device for an internal combustion engine capable of reliably prohibiting the deterioration diagnosis of the converter can be realized at low cost.

It is a figure which shows the structure of the internal combustion engine which concerns on Embodiment 1 of this invention, and its control apparatus. It is a block diagram which shows the internal structure of the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure explaining the flow of the process of a basic deterioration detection in the catalyst deterioration diagnostic apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the rotational speed of the internal combustion engine which concerns on Embodiment 1 of this invention, 25 degreeC, the vehicle speed of 20 km / h, and the catalyst temperature with respect to charging efficiency. It is a figure which shows the flow of a process of the basic temperature parameter calculation means in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a figure which shows the example which made the relationship of the basic value of the parameter relevant to the rotational speed in the internal combustion engine which concerns on Embodiment 1 of this invention, charging efficiency, and the temperature of a catalytic converter into the three-dimensional map. It is a figure which shows the relationship of the catalyst temperature with respect to the rotational speed and charging efficiency in the external temperature of the internal combustion engine which concerns on Embodiment 1 of this invention in 0 degreeC, and the vehicle speed of 20 km / h. It is a figure which shows the relationship of the catalyst temperature with respect to the rotational speed and charging efficiency in the external temperature of the internal combustion engine which concerns on Embodiment 1 of this invention at 25 degreeC, and the vehicle speed of 80 km / h. It is a figure explaining the relationship between the temperature of the exhaust gas of the internal combustion engine which concerns on Embodiment 1 of this invention, and the temperature of a catalytic converter. It is a figure explaining the relationship between the temperature of the exhaust gas of the internal combustion engine which concerns on Embodiment 1 of this invention, and the temperature of a catalytic converter. It is a figure which shows the relationship between the temperature fall amount in the intake pipe of the internal combustion engine which concerns on Embodiment 1 of this invention, and the temperature fall amount in an exhaust pipe. It is a figure which shows the relationship between the difference of the output of the 2nd intake temperature sensor in the internal combustion engine which concerns on Embodiment 1 of this invention, and a 1st intake temperature sensor, and the temperature fall amount in an exhaust pipe. It is a figure which shows the flow of a process of the basic temperature parameter correction | amendment means in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. FIG. 5 is a diagram showing an example in which a relationship between a difference between outputs of a second intake air temperature sensor and a first intake air temperature sensor in the internal combustion engine according to Embodiment 1 of the present invention and a temperature drop amount in the exhaust pipe is made into a two-dimensional table. is there. It is a figure which shows the flow of a process of the catalyst deterioration diagnosis prohibition means in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a block diagram which shows the internal structure of the control apparatus of the internal combustion engine which concerns on Embodiment 2 of this invention. It is a figure which shows the relationship between the difference of the output of the 2nd intake temperature sensor and the 1st intake temperature sensor in the internal combustion engine which concerns on Embodiment 2 of this invention, and the temperature fall amount in an intake pipe. It is a figure which shows the relationship between the difference of the output of the 2nd intake temperature sensor and the 1st intake temperature sensor in the internal combustion engine which concerns on Embodiment 2 of this invention, and the temperature fall amount in an exhaust pipe. It is a figure which shows the flow of a process of the basic temperature parameter correction | amendment means in the control apparatus of the internal combustion engine which concerns on Embodiment 2 of this invention. The relationship between the difference between the outputs of the second intake air temperature sensor and the first intake air temperature sensor in the internal combustion engine according to Embodiment 2 of the present invention, the intake air amount, and the temperature drop amount in the exhaust pipe is three-dimensionally mapped. It is a figure which shows an example.

Embodiment 1 FIG.
Hereinafter, an internal combustion engine control apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the internal combustion engine according to the first embodiment and its control device, and FIG. 2 shows the internal configuration of the control device for the internal combustion engine according to the first embodiment. In the drawing, the same and corresponding parts are denoted by the same reference numerals.

As shown in FIG. 1, the internal combustion engine according to the first embodiment includes a combustion chamber 1, an air cleaner 2 for removing dust in the air sucked by the internal combustion engine, and intake air from the air cleaner 2 to the combustion chamber 1 of the internal combustion engine. An intake pipe 3 serving as an intake passage to be introduced and an exhaust pipe 5 serving as an exhaust passage for introducing exhaust gas from the combustion chamber 1 of the internal combustion engine to the catalytic converter 4 are provided. Exhaust gas discharged from the internal combustion engine is purified by the catalytic converter 4 and discharged to the atmosphere. The injector 6 supplies fuel to the combustion chamber 1, and the spark plug 7 ignites a spark inside the cylinder.

  Various measuring instruments are arranged at various locations on the intake pipe 3 and the exhaust pipe 5 of the internal combustion engine. The intake pipe 3 is provided with an air flow sensor 8 for measuring the amount of air taken in by the internal combustion engine. A first intake air temperature sensor 9 that outputs the first temperature of the intake air is disposed at the farthest possible position from the combustion chamber 1 of the intake pipe 3. Further, a second intake air temperature sensor 10 that outputs a second temperature of the intake air is disposed closer to the combustion chamber 1 than the first intake air temperature sensor 7 of the intake pipe 3.

  An air-fuel ratio sensor 11 that is an upstream oxygen concentration sensor that detects the air-fuel ratio of the exhaust gas discharged from the combustion chamber 1 of the internal combustion engine is disposed upstream of the catalytic converter 4 provided in the exhaust pipe 5. Has been. Further, an oxygen concentration sensor 12 that is a downstream oxygen concentration sensor that detects the oxygen concentration of the exhaust gas downstream of the catalytic converter 4 is disposed on the downstream side of the catalytic converter 4. Further, a crank angle sensor 13 for detecting an angular position of the crankshaft and a crank signal plate 14 for generating a signal corresponding to a specific angle of the crankshaft are provided in the vicinity of the crank mechanism of the internal combustion engine.

  As shown in FIG. 1, output signals from an air flow sensor 8, a first intake air temperature sensor 9 and a second intake air temperature sensor 10, an air-fuel ratio sensor 11 and an oxygen concentration sensor 12, a crank angle sensor 13 and a crank signal plate 14. Is input to an internal combustion engine control unit (ECU) 20. The internal combustion engine control device 20 detects the operating state of the internal combustion engine from the crank angle sensor 13, the air flow sensor 8, the first and second intake air temperature sensors 9, 10 and the like, and controls the amount of fuel supplied and ignition timing. The deterioration state of the catalytic converter 4 is detected.

The internal configuration of the control device 20 for the internal combustion engine will be described with reference to FIG. As shown in FIG. 2, the control device 20 for the internal combustion engine includes a catalyst deterioration diagnosis device 21 and basic temperature parameter calculation means 2.
2. Basic temperature parameter correction means 23 and catalyst deterioration diagnosis prohibition means 24 are included.

  The catalyst deterioration diagnosis device 21 is based on the correlation between the output signals of the air-fuel ratio sensor 11 disposed upstream of the catalytic converter 4 and the oxygen concentration sensor 12 disposed downstream of the catalytic converter 4. A deterioration determination parameter corresponding to the degree of deterioration of the converter 4 is calculated. Further, the deterioration state of the catalytic converter 4 is determined from the deterioration determination parameter, and a warning is issued to the driver.

  Further, the basic temperature parameter calculation means 22 calculates a basic value of a parameter related to the temperature of the catalytic converter 4 based on the operation state information of the internal combustion engine obtained from the air flow sensor 8 and the crank angle sensor 13. Since the output of the crank angle sensor 13 is a signal corresponding to the angular position of the crank of the internal combustion engine, the rotational speed of the internal combustion engine can be obtained by counting the number of output signals per unit time. . Therefore, in the following description, the output of the crank angle sensor 13 that is an input to the basic temperature parameter calculation means 22 is treated as the rotational speed of the internal combustion engine.

  The basic temperature parameter correction means 23 acquires the first temperature of the intake air output from the first intake air temperature sensor 9 and the second temperature of the intake air output from the second intake air temperature sensor 10 to obtain the second temperature. The basic value of the parameter related to the temperature of the catalytic converter 4 calculated by the basic temperature parameter calculating means 22 is corrected using the correction value determined based on the difference between the temperature of the catalytic converter 4 and the first temperature. Calculate parameters related to temperature.

  The catalyst deterioration diagnosis prohibiting unit 24 determines whether or not the catalytic converter 4 is in an active state based on parameters related to the temperature of the catalytic converter 4 calculated by the basic temperature parameter correcting unit 23 and various parameters indicating the operating state of the internal combustion engine. If it is determined that the catalytic converter 4 is not in an active state, diagnosis by the catalyst deterioration diagnosis device 21 (execution of the catalyst deterioration detection process) is prohibited.

Next, a flow of basic deterioration detection processing in the catalyst deterioration diagnosis device 21 will be described with reference to FIG. The control device 20 of the internal combustion engine detects an operating state based on outputs from various sensors and an operating state detecting unit 25 that adjusts the fuel injection amount of the injector 6 based on the output from the operating state detecting unit 25. An injection amount adjusting means 26 is provided. Relative O ₂ storage amount calculation means 212 of the catalyst deterioration diagnosis means 21 calculates the relative O ₂ storage amount based on the output from the operating condition detecting means 25 and the air-fuel ratio sensor 11, the air-fuel ratio control means by the calculation result 211 Controls the air-fuel ratio.

  Based on the output of the air-fuel ratio sensor 11 disposed upstream of the catalytic converter 4, the oxygen concentration sensor output estimating means 213 at the time of catalyst deterioration of the catalyst deterioration diagnosing means 21 is the oxygen concentration when the catalytic converter 4 is completely deteriorated. The output signal of the sensor 12 is estimated. The deterioration determination parameter calculation means 214 compares the estimated output calculated by the catalyst deterioration oxygen concentration sensor output estimation means 213 with the actual output signal (actual output) of the oxygen concentration sensor 12, and approximates the estimated output to the actual output. Is calculated as a deterioration determination parameter.

  The deterioration determination unit 215 compares the deterioration determination parameter value calculated by the deterioration determination parameter calculation unit 214 with a deterioration determination reference value set experimentally in advance, and the deterioration determination parameter exceeds the deterioration determination reference value. In the case, it is determined that the deterioration has occurred. This point will be described in detail below.

In general, the exhaust gas purification capacity of the catalytic converter 4 is highly correlated with the maximum oxygen storage amount of the catalytic converter 4, and the exhaust gas purification capacity decreases as the maximum oxygen storage amount decreases. On the other hand, when the maximum oxygen storage amount decreases, the output signal of the oxygen concentration sensor 12 obtained when the air-fuel ratio is alternately reversed between rich and lean with respect to the internal combustion engine is output on the high voltage side (for example, about 1 V). ) And the low voltage side (for example, about 0 V).

  The estimated output calculated by the catalyst deterioration oxygen concentration sensor output estimating means 213 calculates the behavior of the oxygen concentration sensor 12 in a state where the maximum oxygen storage amount of the catalyst has almost disappeared. When the reversal operation is alternately performed between rich and lean, the high voltage side and the low voltage side are changed extremely greatly alternately.

  Therefore, from the output of the actual oxygen concentration sensor 12 obtained when the air-fuel ratio is reversed in the rich / lean direction with respect to the internal combustion engine, and the output calculated by the catalyst deterioration oxygen concentration sensor output estimating means 213. It can be determined that the larger the value of the required deterioration determination parameter (the higher the degree of approximation of both outputs), the lower the purification capacity of the catalytic converter 4, that is, deterioration. When the deterioration determination unit 215 determines that the catalytic converter 4 is deteriorated, a failure lamp or the like is turned on to notify the driver of deterioration (failure) of the catalytic converter 4.

  Next, the basic temperature parameter calculation processing of the basic temperature parameter calculation means 22 will be described with reference to FIGS. FIG. 4 shows the relationship between the catalyst speed Tcat and the rotational speed Ne of the internal combustion engine and the charging efficiency Ec at an outside air temperature of 25 ° C. and a vehicle speed of 20 km / h. In FIG. 4, the vertical axis represents the charging efficiency (%), and the horizontal axis represents the rotational speed (r / min) of the internal combustion engine. The charging efficiency is a parameter indicating the amount of air per process which is calculated based on the amount of air measured by the air flow sensor 8 and is sucked into the combustion chamber of the internal combustion engine.

  As shown in FIG. 4, the catalyst temperature Tcat depends on the rotational speed Ne of the internal combustion engine and the charging efficiency Ec. In general, when the charging efficiency or the rotational speed increases, the amount of fuel consumed by the internal combustion engine per unit time increases, so the amount of heat discharged per unit time from the combustion chamber 1 of the internal combustion engine to the exhaust system also increases. Accordingly, the amount of heat input to the catalytic converter 4 increases and the temperature of the catalytic converter 4 also increases. In the basic temperature parameter calculation means 22, the basic values of the parameters related to the temperature of the catalytic converter 4 under predetermined conditions (in this example, the outside air temperature is 25 ° C. and the vehicle speed is 20 km / h) from the rotation speed and charging efficiency of the internal combustion engine. Is calculated.

  FIG. 5 is a flowchart showing a processing flow of the basic temperature parameter calculation means 22. In FIG. 5, the numbers starting with S indicate the processing order (steps). First, in Step 1 (S1), the rotational speed Ne and the charging efficiency Ec are read. Subsequently, in step 2 (S2), a three-dimensional map (for example, NE-EC-TEMP (shown in FIG. 6) showing the relationship between the rotational speed Ne, the charging efficiency Ec, and the basic values of parameters related to the temperature of the catalytic converter 4 is used. Ne, Ec)), and Tcatb, which is a basic value of a parameter related to the temperature of the catalytic converter 4 according to Ne and Ec read in S1, is calculated. Note that the three-dimensional map shown in FIG. 6 is created in advance based on the characteristics shown in FIG.

Next, basic temperature parameter correction processing in the basic temperature parameter correction means 23 will be described. First, the relationship between the rotational speed of the internal combustion engine and the catalyst temperature with respect to the charging efficiency and its principle will be described with reference to FIGS. FIG. 7 shows the relationship between the catalyst speed Tcat and the rotational speed Ne of the internal combustion engine and the charging efficiency Ec at an outside air temperature of 0 ° C. and a vehicle speed of 20 km / h. In FIG. 7, the vertical axis indicates the charging efficiency (%), the horizontal axis indicates the rotation speed (r / min) of the internal combustion engine, the solid line indicates Tcat at an outside air temperature of 0 ° C., and the dotted line indicates the outside air temperature 25 shown in FIG. Tcat at ° C is shown. As shown in FIG. 7, even at the same rotation speed and filling efficiency, the catalyst temperature Tcat varies depending on the outside air temperature, and the catalyst temperature Tcat decreases as the outside air temperature decreases.

  FIG. 8 shows the relationship between the catalyst temperature Tcat and the rotational speed Ne of the internal combustion engine and the charging efficiency Ec at an outside air temperature of 25 ° C. and a vehicle speed of 80 km / h. In FIG. 8, the vertical axis indicates the charging efficiency (%), the horizontal axis indicates the rotational speed (r / min) of the internal combustion engine, the solid line indicates Tcat at a vehicle speed of 80 km / h, and the dotted line indicates the vehicle speed shown in FIG. Tcat at 20 km / h. As shown in FIG. 8, even at the same rotation speed and filling efficiency, the catalyst temperature Tcat varies depending on the vehicle speed, and the catalyst temperature Tcat decreases as the vehicle speed increases.

  The principle of obtaining the characteristics shown in FIGS. 7 and 8, that is, the relationship between the rotation speed and the catalyst temperature with respect to the charging efficiency will be described with reference to FIG. FIG. 9 shows the relationship between the exhaust gas temperature of the internal combustion engine and the temperature of the catalytic converter. The temperature Tex (Ne, Ec) of the exhaust gas immediately after being discharged from the combustion chamber 1 of the internal combustion engine is uniquely determined by the rotational speed Ne and the charging efficiency Ec of the internal combustion engine. The exhaust gas flows into the catalytic converter 4 through the exhaust pipe 5. In this process, the exhaust pipe 5 takes heat away from the air (atmosphere) around the exhaust pipe 5. The amount of heat taken, that is, the amount of heat loss, varies depending on the temperature of the air around the catalytic converter 4 and increases as the temperature of the air around the catalytic converter 4 decreases.

  In addition, when the air flow around the catalytic converter 4 is fast, the temperature of the air around the catalytic converter 4 is kept low compared to the case where the surrounding air is stagnant, so that the amount of heat loss increases. . Therefore, the amount of heat loss in the exhaust pipe 5 is determined by the temperature and flow velocity of the air around the exhaust pipe 5.

  Further, it has been found that the flow velocity of air around the catalytic converter 4 increases when the traveling speed of the vehicle is high or when the wind speed of the wind that the vehicle receives from the natural world due to weather factors is high. The exhaust gas discharged from the internal combustion engine is deprived of heat by the air around the exhaust pipe 5 and then flows into the catalytic converter 4. In the catalytic converter 4, reaction heat is generated by the oxidation / reduction reaction of the components contained in the exhaust gas. Therefore, the temperature of the catalytic converter 4 is higher than the exhaust gas flowing into the catalytic converter 4 by the amount of this reaction heat.

  When these phenomena are shown in a temperature unit system, they are as shown in FIG. The temperature Tex (Ne, Ec) of the exhaust gas immediately after being discharged from the combustion chamber 1 of the internal combustion engine is a temperature decrease amount Texls determined in the exhaust pipe 5 by the temperature Tia1 of the air around the exhaust pipe 5 and the flow velocity Ws. (Tia1, Ws) is subtracted and flows into the catalytic converter 4. Further, in the catalytic converter 4, the temperature Tcact resulting from the oxidation-reduction reaction is added to obtain the final temperature Tcat of the catalytic converter 4.

  Next, a method for estimating the above-described temperature drop amount Texls (Tia1, Ws) will be described with reference to FIG. The air that has flowed from the atmosphere to the upstream side of the intake pipe 3 of the internal combustion engine receives heat released from the combustion chamber 1 of the internal combustion engine, or is pressurized by a supercharger, so that the temperature rises. Thereafter, the intake pipe 3 is deprived of heat by the air around the intake pipe 3. When the flow of air around the intake pipe 3 is fast, the temperature of the air around the intake pipe 3 is kept low as compared with the case where the surrounding air is stagnating, so that the amount of heat loss becomes large.

  Therefore, the amount of heat loss in the intake pipe 3 is determined by the temperature and flow velocity of the air around the intake pipe 3. This phenomenon is particularly noticeable in an internal combustion engine having an intake system configuration in which intake air is compressed by a supercharger upstream of the intake side and the temperature of the intake air is lowered downstream by an intercooler (heat exchanger).

When these phenomena are shown in a temperature unit system, they are as shown in FIG. Intake pipe 3 of internal combustion engine
The temperature Tia1 of the air flowing upstream is added to the temperature rise Tcmp of the intake air due to heat received from the combustion chamber 1 or compression of the intake air by the supercharger. Thereafter, in the intake pipe 3, the temperature decrease amount Tils (Tia1, Ws) determined by the temperature Tia1 of the air around the intake pipe 3 and the flow velocity Ws is subtracted and flows into the final combustion chamber 1 of the internal combustion engine. It becomes air temperature Tia2.

  Based on this principle, the amount of heat loss in the exhaust pipe 5 and the intake pipe 3 both depends on the temperature and flow velocity of the surrounding air. If the amount of heat loss in the exhaust pipe 5 is large, the heat loss in the intake pipe 3 It can be seen that the loss amount is large. That is, there is a correlation between the amount of heat loss between the exhaust pipe 5 and the intake pipe 3, and the amount of heat loss can be estimated from the amount of decrease in temperature before and after the loss. It is possible to estimate the amount of heat loss and thus the amount of decrease in exhaust gas temperature. In other words, the temperature drop amount Texls (Tia1, Ws) in the exhaust pipe 5 can be estimated from the temperature drop amount Tils (Tia1, Ws) in the intake pipe 3.

  From the above, in the basic temperature parameter correction means 23, the second intake air temperature (Tia 2) that is the output of the second intake air temperature sensor 10 and the intake air that is the output of the first intake air temperature sensor 9. A difference in the first temperature (Tia1) is obtained, and a correction value of a basic value of a parameter related to the temperature of the catalytic converter 4 is calculated according to the difference. Further, the correction value is subtracted from the basic value of the parameter related to the temperature of the catalytic converter 4 calculated by the basic temperature parameter calculating means 22.

From the temperature relationship shown in FIG. 10, the temperature drop amount Tils in the intake pipe 3 is obtained by the following equation 1. However, when the intake pipe 3 is disposed away from the combustion chamber 1 of the internal combustion engine or has an intake system configuration without a supercharger, Tcmp is substantially constant regardless of the operating state of the internal combustion engine. Value. Therefore, the temperature drop amount Tils in the intake pipe 3 is uniquely determined from the difference (Tia2−Tia1) between the output of the second intake temperature sensor 10 and the output of the first intake temperature sensor 9.
Tils = − (Tia2−Tia1) + Tcmp (Formula 1)

FIG. 11 shows the relationship between the temperature drop amount Tils in the intake pipe 3 and the temperature drop amount Texls in the exhaust pipe 5. As shown in FIG. 11, the temperature decrease amount Texls in the exhaust pipe 5 increases as the temperature decrease amount Tils in the intake pipe 3 increases. These relationships can be obtained experimentally. Further, the relationship between (Tia2−Tia1) and Texls as shown in FIG. 12 can be obtained by Expression 2 obtained by modifying Expression 1 above.
(Tia2−Tia1) = − Tils + Tcmp (Formula 2)

  As shown in FIG. 12, when (Tia2−Tia1) approaches 0, that is, the second temperature (Tia2) of the intake air in the vicinity of the combustion chamber 1 of the internal combustion engine has the intake air at a position farthest from the combustion chamber 1. When approaching the first temperature (Tia1), it can be estimated that the temperature drop amount Texls in the exhaust pipe 5 is large.

  By utilizing such a principle, the basic temperature parameter correction means 23 reduces the temperature in the exhaust pipe 5 based on the difference between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9. A correction value for correcting the basic value of the parameter related to the amount Texls, that is, the temperature of the catalytic converter 4 is obtained, and the parameter related to the temperature of the catalytic converter 4 is calculated. The parameter calculated here is applied when the catalyst deterioration diagnosis prohibiting unit 24 determines the active state of the catalytic converter 4.

The processing flow of the basic temperature parameter correction means 23 will be described with reference to the flowchart of FIG. First, in step 11 (S11), the output Tia1 of the first intake air temperature sensor 9 and the output Tia2 of the second intake air temperature sensor 10 are read. Subsequently, in step S12 (S12), a basic value Tcatb of a parameter related to the temperature of the catalytic converter 4 calculated by the basic temperature parameter calculating means 22 is read.

  Subsequently, in step 13 (S13), a two-dimensional table (for example, a diagram) showing the relationship between the difference between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9 and the amount of temperature decrease in the exhaust pipe 5. TCMPST (Tia2−Tia1)) shown in FIG. 14, the correction value corresponding to the difference (Tia2−Tia1) between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9 obtained in S11 is obtained. Ask. Further, the parameter Tcat related to the temperature of the catalytic converter 4 is calculated by subtracting the correction value obtained from the two-dimensional table from the basic value Tcatb obtained in S12. The two-dimensional table shown in FIG. 14 is created in advance based on the characteristics shown in FIG.

  Next, the flow of processing of the catalyst deterioration diagnosis prohibiting means 24 will be described using the flowchart of FIG. First, in step 21 (S21), the parameter Tcat related to the temperature of the catalytic converter 4 calculated by the basic temperature parameter correction means 23 is read. Next, in step 22 (S22), it is determined whether or not Tcat read in S21 is equal to or greater than a preset catalytic converter 4 activation determination value. If Tcat is equal to or greater than the activation determination value (YES), It is determined that the catalytic converter 4 is active, and the process proceeds to step 23 (S23), where the catalyst deterioration detection process by the catalyst deterioration diagnosis device 21 is permitted. When Tcat is less than the activation determination value (NO), it is determined that the temperature of the catalytic converter 4 is low and is not sufficiently activated, and the process proceeds to step 24 (S24) to prohibit the catalyst deterioration detection process by the catalyst deterioration diagnosis device 21. To do.

  As described above, according to the control device 20 for an internal combustion engine according to the first embodiment, there is a correlation between the heat loss amounts of the exhaust pipe 5 and the intake pipe 3 of the internal combustion engine, that is, the exhaust pipe 5 and the intake pipe. The amount of heat loss at 3 depends on the temperature and flow velocity of the surrounding air, and when the amount of heat loss at the intake pipe 3 is large, the amount of heat loss at the exhaust pipe 5 is also large. The temperature drop amount of the exhaust gas is estimated from the temperature drop amount in the intake pipe 3 obtained from the difference between the output (Tia2) of the temperature sensor 10 and the output (Tia1) of the first intake air temperature sensor 9, and according to this drop amount Since the correction value is obtained, the parameter related to the temperature of the catalytic converter 4 is accurately measured regardless of the amount of heat received by the second intake air temperature sensor 10 from the combustion chamber 1 and the amount of heat taken away by the exhaust pipe 5. Can be calculated well

  As a result, the activity of the catalytic converter 4 is insufficient even when the output of the second intake air temperature sensor 10 is higher than the outside air temperature under a low temperature environment or when the vehicle receives a very strong wind under a high temperature environment. Therefore, the deterioration diagnosis of the catalytic converter 4 can be surely prohibited, and the erroneous diagnosis that diagnoses the deterioration of the normal catalytic converter 4 can be avoided.

  The second intake air temperature sensor 10 disposed in the vicinity of the combustion chamber 1 of the internal combustion engine may be an inexpensive thermistor and has been conventionally used for measuring the amount of intake air to the internal combustion engine that contributes to combustion. Therefore, there is no need to add a new one. The first intake air temperature sensor 9 newly disposed at a position farthest from the combustion chamber 1 of the internal combustion engine may be an inexpensive thermistor, like the second intake air temperature sensor 10. Furthermore, since the circuit inside the control device 20 of the internal combustion engine can be simply configured with few electronic parts, it can be realized at a lower cost than the configuration using the exhaust temperature sensor in the previous example.

Embodiment 2. FIG.
FIG. 16 shows the internal configuration of the control device for an internal combustion engine according to the second embodiment of the present invention. As shown in FIG. 16, the control device 20a for the internal combustion engine according to the second embodiment is different from the first embodiment in that the output of the air flow sensor 8 is input to the basic temperature parameter correction means 23a. Is different. Other internal configurations are the same as those in the first embodiment (FIG. 2), and thus the description thereof is omitted.

  The basic temperature parameter correction means 23a in the internal combustion engine control apparatus 20a according to the second embodiment will be described. As described in the first embodiment, the temperature drop amount Tils in the intake pipe 3 is obtained from the above equation 1. The temperature rise Tcmp of the intake air in Formula 1 is the amount of air that the internal combustion engine takes when the intake pipe 3 is disposed near the combustion chamber 1 of the internal combustion engine or has a supercharger in the intake system configuration. Changes in relation to.

  Specifically, when the charging efficiency or the rotational speed increases and the amount of air taken in by the internal combustion engine increases, the amount of fuel consumed by the internal combustion engine increases per unit time. The amount of heat released per unit time increases, and the amount of heat received by the intake air also increases. Further, when the amount of air taken in by the internal combustion engine increases, the amount of exhaust gas discharged from the combustion chamber 1 of the internal combustion engine also increases, so that the turbocharger turbine disposed in the exhaust gas discharge path can rotate at a high speed. The boost pressure will also increase. From these results, Tcmp increases as the amount of air taken in by the internal combustion engine increases.

  FIG. 17 shows the case where the temperature rise degree of the intake air Tcmp = Tcmp (Qa1) and the case of Tcmp = Tcmp (Qa2) are expressed as the function F1 (solid line) and the function F2 (dashed line), respectively. Show. Here, Qa1 and Qa2 are both parameters indicating the intake air amount of the internal combustion engine, and Qa1 <Qa2. In FIG. 17, the horizontal axis represents the difference between the output of the second intake temperature sensor 10 and the output of the first intake temperature sensor 9 (Tia2−Tia1) (° C.), and the vertical axis represents the amount of temperature decrease in the intake pipe 3. Tils (° C.).

  As described above, since the intake air temperature increase degree Tcmp increases as the intake air amount increases, the intake air temperature increase degrees Tcmp (Qa1) and Tcmp (Qa2) are large and small when the intake air amount is Qa1 and Qa2. The relationship is Tcmp (Qa1) <Tcmp (Qa2). When the difference (Tia2−Tia1) between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9 is td, F1 (td) <F2 (td). Therefore, when the difference between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9 (Tia2−Tia1) is the same, the temperature in the intake pipe 3 increases as the intake air amount of the internal combustion engine increases. The amount of decrease Tils also increases.

  Next, the relationship between the difference between the output of the second intake temperature sensor 10 and the output of the first intake temperature sensor 9 (Tia2−Tia1) and the temperature drop amount Texls in the exhaust pipe 5 is the amount of intake air amount of the internal combustion engine. How it changes with increase is explained. As described above, the temperature drop amount Tils in the intake pipe 3 and the temperature drop amount Texls in the exhaust pipe 5 are determined by the temperature Tia1 and the flow velocity Ws of the air around the intake pipe 3 or the exhaust pipe 5, so that the intake of the internal combustion engine Not directly related to air volume. Therefore, the relationship between Tils and Texls maintains the relationship shown in FIG. 11 described in the first embodiment, regardless of the intake air amount.

  Therefore, by applying the relationship between (Tia2−Tia1) and Tils shown in FIG. 17 to the relationship between Tils and Texls shown in FIG. 11 and deleting the parameter Tils, (Tia2−Tia1) as shown in FIG. ) And Texls. In FIG. 18, the horizontal axis is (Tia2−Tia1) (° C.) as in FIG. 17, and the vertical axis is the temperature drop amount Texls (° C.) in the exhaust pipe 5. Qa1 and Qa2 are both parameters indicating the intake air amount of the internal combustion engine, and Qa1 <Qa2.

  As shown in FIG. 18, the function in the case of Tils = F1 (solid line) and the function in the case of Tils = F2 (one-dot chain line) show the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9. When the difference (Tia2−Tia1) is td, tls1 and tls2 are obtained, and the magnitude relationship is tls1 <tls2. That is, the relationship between the difference between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9 (Tia2−Tia1) and the temperature drop amount Texls in the exhaust pipe 5 changes depending on the intake air amount. , (Tia2-Tia1) are the same, Texls increases when the intake air amount is large.

  By utilizing such a principle, the basic temperature parameter correction means 23a according to the second embodiment, in addition to the output of the first intake air temperature sensor 9 and the output of the second intake air temperature sensor 10, in addition to the air flow sensor 8 , That is, a measured value of the amount of air taken in by the internal combustion engine, and using the relationship shown in FIG. 18, the difference between the output of the second intake temperature sensor 10 and the output of the first intake temperature sensor 9 (Tia2− A temperature drop amount Texls in the exhaust pipe 5 is obtained from Tia1) and the intake air amount (Qa), and a parameter related to the temperature of the catalytic converter 4 is calculated. The parameter calculated here is applied when the catalyst deterioration diagnosis prohibiting unit 24 determines the active state of the catalytic converter 4.

  The processing flow of the basic temperature parameter correction means 23a will be described with reference to the flowchart of FIG. First, in step 31 (S31), the output Tia1 of the first intake air temperature sensor 9, the output Tia2 of the second intake air temperature sensor 10, and the intake air amount Qa that is the output of the airflow sensor 8 are read. Subsequently, in step 32 (S32), the basic value Tcatb of the parameter related to the temperature of the catalytic converter 4 calculated by the basic temperature parameter calculating means 22 is read.

  Subsequently, in step 33 (S33), the relationship between the difference between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9, the intake air amount, and the temperature decrease amount in the exhaust pipe 5 is shown. Referring to a dimension map (for example, MCMPST {(Tia2-Tia1), Qa} shown in FIG. 20), the difference (Tia2) between the output of the second intake air temperature sensor 10 and the output of the first intake air temperature sensor 9 obtained in S31. -A correction value corresponding to Tia1) and the intake air amount Qa is obtained. Further, the parameter Tcat related to the temperature of the catalytic converter 4 is calculated by subtracting the correction value obtained from the three-dimensional map from the parameter basic value Tcatb obtained in S32. Note that the three-dimensional map shown in FIG. 20 is created in advance based on the characteristics shown in FIG.

  As described above, according to the second embodiment, the difference between the output of the second intake temperature sensor 10 and the output of the first intake temperature sensor 9 and the intake air amount Qa that is the output of the air flow sensor 8 are used. Since the correction value of the basic value of the parameter related to the temperature of the catalytic converter 4 is calculated, in addition to the same effect as in the first embodiment, the amount of temperature increase due to the heat received from the combustion chamber 1 of the internal combustion engine, Even when the amount of temperature rise caused by pressurization by the supercharger varies depending on the intake air amount of the internal combustion engine, the parameter related to the temperature of the catalytic converter 4 can be calculated with high accuracy.

  The present invention can be used as a control device for an internal combustion engine having a function of warning a driver of deterioration of a catalytic converter.

1 combustion chamber, 2 air cleaner, 3 intake pipe, 4 catalytic converter, 5 exhaust pipe,
6 injector, 7 spark plug, 8 air flow sensor,
9 first intake air temperature sensor, 10 second intake air temperature sensor, 11 air-fuel ratio sensor,
12 oxygen concentration sensor, 13 crank angle sensor, 14 crank signal plate,
20, 20a Control device for internal combustion engine, 21 Catalyst deterioration diagnosis device,
22 basic temperature parameter calculating means, 23, 23a basic temperature parameter correcting means,
24 catalyst deterioration diagnosis prohibiting means, 25 operating state detecting means, 26 fuel injection amount adjusting means,
211 air-fuel ratio control means, 212 relative O ₂ storage amount calculation means,
213 oxygen concentration sensor output estimating means at the time of catalyst deterioration,
214 deterioration determination parameter calculation means, 215 deterioration determination means.

Claims (4)

The upstream oxygen concentration sensor disposed upstream of the catalytic converter for purifying exhaust gas discharged from the combustion chamber of the internal combustion engine and the output signal of the downstream oxygen concentration sensor disposed downstream of the catalytic converter A catalyst deterioration diagnosis device for determining a deterioration state of the catalytic converter based on the correlation;
Basic temperature parameter calculating means for calculating a basic value of a parameter related to the temperature of the catalytic converter based on the operating state of the internal combustion engine;
A first temperature of intake air output from a first intake temperature sensor disposed in an intake passage of the internal combustion engine, and a position closer to the combustion chamber than the first intake temperature sensor of the intake passage. The basic temperature parameter calculating means obtains the second temperature of the intake air output from the second intake temperature sensor and uses the correction value determined based on the difference between the second temperature and the first temperature. A basic temperature parameter correcting means for correcting the calculated basic value of the parameter and calculating a parameter related to the temperature of the catalytic converter;
Catalyst deterioration diagnosis prohibiting means for prohibiting diagnosis by the catalyst deterioration diagnosis device based on parameters related to the temperature of the catalytic converter calculated by the basic temperature parameter correcting means and various parameters indicating the operating state of the internal combustion engine. A control apparatus for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the first intake air temperature sensor is disposed at a position as far as possible from the combustion chamber of the intake passage. Control device.   2. The control device for an internal combustion engine according to claim 1, wherein the basic temperature parameter correction unit is configured such that the amount of heat loss in the exhaust passage and the intake passage of the internal combustion engine both depends on the temperature and flow velocity of the surrounding air. When the amount of heat loss in the intake passage is large, the characteristic that the amount of heat loss in the exhaust passage is also large is used, and the intake passage obtained from the difference between the second temperature and the first temperature of the intake air is used. The temperature reduction amount of the exhaust gas is estimated from the temperature reduction amount, and the correction value corresponding to this reduction amount is subtracted from the basic value of the parameter calculated by the basic temperature parameter calculating means, thereby obtaining the temperature of the catalytic converter. A control device for an internal combustion engine, characterized in that a related parameter is calculated.   4. The control apparatus for an internal combustion engine according to claim 3, wherein the basic temperature parameter correction means further obtains a measured value of the amount of air taken in by the internal combustion engine, and the larger the intake air amount, the more in the exhaust passage. A correction value determined based on a difference between the second temperature and the first temperature of the intake air and a parameter related to the amount of air taken in by the internal combustion engine is used by utilizing the property that the temperature decrease amount becomes large. A control apparatus for an internal combustion engine, wherein the basic value of the parameter calculated by the basic temperature parameter calculating means is corrected.

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