WO2002070873A1

WO2002070873A1 - Device and method for diagnosing internal combustion engine and internal combustion engine control method using the device and method

Info

Publication number: WO2002070873A1
Application number: PCT/JP2001/001659
Authority: WO
Inventors: Yoichi Iihoshi; Minoru Ohsuga; Yutaka Takaku
Original assignee: Hitachi, Ltd.
Priority date: 2001-03-02
Filing date: 2001-03-02
Publication date: 2002-09-12
Also published as: JPWO2002070873A1

Abstract

An internal combustion engine diagnosing device, comprising a catalyst for purifying exhaust gases and a catalyst temperature detector for detecting the temperature of the catalyst installed in the exhaust gas flow path of an internal combustion engine, a catalyst temperature prediction model (deteriorated catalyst model) not containing the heat reaction of the catalyst, a comparator for comparing the predicted value by the deteriorated catalyst model with the actually measured value by the temperature detector, and a judgment device for judging on whether the catalyst or temperature detector is abnormal or not based on the compared results.

Description

Specification

TECHNICAL FIELD The present invention relates to a diagnosis apparatus and a diagnosis method for an internal combustion engine, and a control method for an internal combustion engine using the same.

The present invention relates to a diagnosis apparatus and a diagnosis method for an internal combustion engine, and a control method for an internal combustion engine using the same. More particularly, the present invention relates to an apparatus and a diagnosis method for diagnosing a decrease in catalyst light-off performance and an abnormality in a temperature detector. Background art

As automobile exhaust regulations are tightening, various technologies for monitoring the purification efficiency of catalysts that purify exhaust gas and diagnosing catalysts have been proposed. For example, as described in Japanese Patent Application Laid-Open No. 5-248828 / 27, an exhaust sensor (02 sensor) is provided upstream and downstream of a catalyst converter installed in an exhaust pipe, and an 02 sensor on the upstream side is provided. (For example, from the output reversal of the upstream 02 sensor when the air-fuel ratio is reversed from lean to rich or from rich to lean, to the output reversal of the downstream 02 sensor) There is a technology for diagnosing catalyst deterioration based on a time measurement value, an output ratio between the upstream 02 sensor and the downstream 02 sensor, a response ratio, a phase difference, and the like. These techniques quantify the oxygen storage capacity (0SC) of the catalyst and determine the deterioration of the catalyst.

Also, Japanese Patent Application Laid-Open No. 9-32553 discloses a catalyst converter provided in an exhaust system of an internal combustion engine, measuring means for measuring a catalyst temperature of the catalyst converter, and engine operation. Means for estimating the catalyst temperature of the catalyst converter based on the state, and calculating means for calculating a change amount of the catalyst temperature measured by the measuring means with respect to a change in temperature of the catalyst temperature estimated by the estimating means, Determination means for determining that the catalyst converter is in a state of abnormal catalyst deterioration when the amount of change calculated by the calculation means is smaller than a predetermined value. A determination device is disclosed. However, as described in Japanese Patent Application Laid-Open No. 5-24888227, the catalyst is rapidly heated (for example, by installing the catalyst near the internal combustion engine or by adding electrothermal energy to the catalyst). according exhaust reduction technique to quickly activate the catalyst spread, noble metal deterioration of the catalyst can not be detected in a diagnostic method that focuses on 0SC is carried on _c ie catalyst in question is aggregated catalyst exhibits purification capacity Decrease in light-off performance, in which the temperature (light-off temperature) shifts to a higher temperature side, cannot be determined by the 0SC amount of the catalyst. Also, catalysts installed in some engine systems that perform lean operation to reduce fuel consumption do not include 0SC from the beginning, so the 0SC diagnostic method cannot be applied.

Therefore, as a method for solving these problems, a method for detecting catalyst deterioration focusing on the reaction heat of the catalyst is disclosed. That is, the deterioration diagnosis method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 9-32553 discloses a method of estimating the rate of change of the catalyst temperature in a new or normal state and the rate of change in the value measured by the temperature sensor after the catalyst. Judgment is made based on the difference. Therefore, in estimating the catalyst temperature, it is necessary to calculate the exact heat of reaction using the content ratio of the inflowing exhaust components, the air flow rate, the air-fuel ratio, etc.

However, the exhaust components and air-fuel ratio immediately after starting the engine are generally unsteady and have low reproducibility. Therefore, it is difficult to grasp them accurately, and even if they can be grasped accurately, the model incorporating them becomes very complicated. In order to detect the heat of reaction of the catalyst, not only the model but also the accuracy of the temperature detector is an important factor, but the diagnostic method of the temperature detector has not been clarified. Disclosure of the invention

A first object of the present invention is to provide a diagnostic device for an internal combustion engine that can accurately diagnose the light-off performance of a catalyst.

A second object of the present invention is to enable catalyst diagnosis with high accuracy, and to be simple and inexpensive. And a diagnostic device for the internal combustion engine.

A third object of the present invention is to provide a diagnostic device for an internal combustion engine that can diagnose a catalyst with high accuracy without being affected by the type of the catalyst, operating conditions of the internal combustion engine, and the like.

A fourth object of the present invention is to provide a highly reliable diagnosis device for an internal combustion engine having a self-diagnosis function.

A fifth object of the present invention is to provide a method for controlling an internal combustion engine, which enables a highly accurate diagnosis of a catalyst using an inexpensive diagnosis device.

In order to achieve the above object, a first invention is directed to a diagnosis of an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine, and a catalyst temperature detecting device for detecting a temperature of the catalyst. In the apparatus, a catalyst temperature estimation model (deterioration catalyst model) that does not include a thermal reaction of the catalyst, a comparison device that compares an estimated value obtained by the degraded catalyst model with an actual measurement value obtained by the temperature detector, and based on the comparison result A determination device for determining abnormality of the catalyst.

Also, a second invention includes a catalyst for purifying exhaust gas in an exhaust flow passage of an internal combustion engine, and a diagnostic device for an internal combustion engine including a catalyst temperature detecting device for detecting a temperature of the catalyst, wherein a thermal reaction of the catalyst is included. A comparison device that compares the estimated catalyst temperature model (degraded catalyst model) with the estimated value based on the deteriorated catalyst model and the measured value measured by the temperature detector, and determines whether the temperature detector is abnormal based on the comparison result. And a device. .

Further, a third invention is a diagnostic device for an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine, and a catalyst temperature detecting device for detecting a temperature of the catalyst, wherein a thermal reaction of the catalyst is included. A catalyst temperature estimating model (deteriorated catalyst model), a comparing device for comparing the estimated value based on the deteriorated catalyst model with the measured value measured by the temperature detector, and an abnormality of the temperature detector when the measured value is smaller than a predetermined temperature. And a determination device that determines abnormality of the catalyst when the temperature is higher than a predetermined temperature. In a fourth aspect of the present invention, in the diagnostic device for an internal combustion engine, the deteriorated catalyst model is a heat transfer model of a catalyst, and an air flow rate flowing into the catalyst and an exhaust gas temperature of the internal combustion engine are set as parameters. It was characterized by things.

According to a fifth aspect of the present invention, in the diagnostic device for an internal combustion engine, an estimated value of the temperature in the deteriorated catalyst model is corrected using an actually measured value of the temperature detecting device.

In a sixth aspect of the present invention, in the diagnostic device for an internal combustion engine, the estimated value of the temperature in the deteriorated catalyst model is corrected using an actually measured value of the temperature detecting device, and a rate of change of the estimated value at the time of the correction is a predetermined value. It is characterized by judging abnormality of the temperature detector based on the temperature below.

According to a seventh aspect of the present invention, in the comparison device according to the second aspect, the absolute value or the time rate of change of the actually measured value and the estimated value is compared.

An eighth invention is characterized in that, in the deterioration determination device, the deterioration determination is performed when an actual measured value of the catalyst temperature by the catalyst temperature detector is within a predetermined temperature range.

In a ninth aspect of the present invention, in the diagnostic device for an internal combustion engine, the deterioration determination is prohibited when a time change rate of an air amount or a fuel amount of the internal combustion engine is equal to or more than a predetermined value.

Further, a tenth invention includes a diagnostic device for the internal combustion engine and an engine temperature detecting device for detecting a temperature of the internal combustion engine, wherein when the temperature of the internal combustion engine is higher than a predetermined value, deterioration judgment is prohibited. It was characterized.

Further, an eleventh invention provides a diagnostic device for an internal combustion engine, comprising: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a catalyst temperature detecting device for detecting a temperature of the catalyst. The feature is to prohibit catalyst deterioration judgment.

Further, a twelfth invention provides a diagnostic device for an internal combustion engine, comprising: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a catalyst temperature detecting device for detecting a temperature of the catalyst. In the above, an air-fuel ratio sensor and a fuel adjusting device for adjusting a fuel injection amount are provided in an exhaust passage of the internal combustion engine, and the air-fuel ratio is kept constant during catalyst diagnosis.

A thirteenth invention is a diagnostic device for an internal combustion engine, comprising: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a catalyst temperature detecting device for detecting a temperature of the catalyst. In addition, during the deterioration confirmation mode, the fuel amount or ignition timing of the internal combustion engine is controlled so as to lower the catalyst temperature.

ADVANTAGE OF THE INVENTION According to this invention, the diagnosis of a catalyst is possible by the simple catalyst deterioration model which does not have a thermal reaction of a catalyst, and the diagnostic device of the internal combustion engine which can diagnose the light-off function of a catalyst accurately can be provided.

Further, it is possible to provide a diagnostic device for an internal combustion engine capable of performing a catalyst diagnosis with high accuracy without being affected by the type of the catalyst or the operating conditions of the internal combustion engine.

In addition, since the temperature detector can be diagnosed, the software capacity and the number of adaptation steps can be significantly reduced. In addition, the accuracy of diagnosis is improved by correcting the estimated temperature using the value of the temperature detector. As a result, the catalyst can be diagnosed with high accuracy, and a simple and inexpensive diagnostic device for an internal combustion engine can be provided.

In addition, a deterioration confirmation mode is provided, and during the confirmation mode, the exhaust gas temperature is reduced to the light-off temperature or less at the time of deterioration, and the temperature rise is slowed, so that the catalyst can be diagnosed reliably.

In addition, the diagnosis accuracy can be improved by prohibiting the diagnosis based on the change rate of the water temperature, the air amount, and the fuel injection amount of the internal combustion engine. Further, by switching the control method of the internal combustion engine when it is determined that the catalyst has deteriorated, further deterioration of the catalyst or deterioration of the exhaust gas can be prevented.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a system diagram of an embodiment in which the present invention is applied to an in-cylinder injection type internal combustion engine.

FIG. 2 is a block diagram showing functions of the diagnostic apparatus according to the embodiment of FIG. is there.

FIG. 3 is a flowchart showing a process for estimating the temperature of the deteriorated catalyst model. FIG. 4 is an explanatory diagram of the deteriorated catalyst model of FIG.

FIG. 5 is a diagram showing the relationship between the measured value and the estimated value at the time of catalyst deterioration.

FIG. 6 is a map referred to in the processing step si02 of FIG.

FIG. 7 is a flowchart of a process for correcting the estimated value obtained in the process of FIG. 3 as another embodiment of the present invention.

FIG. 8 is a diagram illustrating a difference between a case where the estimated value of the model is corrected by the actually measured value and a case where the model is not corrected by the method of FIG.

FIG. 9 is a flowchart of another embodiment of the present invention, in which the comparison device generates the number of counts Ci corresponding to the deterioration index Ti.

FIG. 10 is a diagram showing the difference between the deterioration index Ti at the time of deterioration and the deterioration index Ti at the time of normality in relation to FIG.

FIG. 11 is a flowchart of a deterioration determination process as another embodiment of the present invention.

FIG. 12 is a map referred to when setting Cout in step s305 in FIG.

FIG. 13 is a diagram for explaining a deterioration index AdTl using a temperature change rate. FIG. 14 is a diagram illustrating a deterioration index Δ (1Τ4 using a temperature change rate. FIG. 15 is a diagram illustrating a deterioration index Δ (1Τ5 using a temperature change rate. 9 is a flowchart of a comparison process as another embodiment of the present invention.

FIG. 17 is a diagram showing the relationship between the actually measured value and the estimated value when the temperature detector is abnormal. FIG. 18 is a flowchart of a process of detecting and determining an abnormality of a temperature detector according to another embodiment of the present invention.

FIG. 19 is an explanatory diagram of the flowchart in FIG.

FIG. 20 shows a temperature detector and a catalyst according to another embodiment of the present invention. It is a flowchart of a conversion determination process.

Fig. 21 is a flowchart of a comparison device that generates a deterioration index based on the temperature change rate.

FIG. 22 is a flowchart of a determination device that makes a determination based on a temperature change rate.

FIG. 23 is a flowchart showing another embodiment of the present invention.

FIG. 24 is a diagram illustrating the upper and lower temperatures in step s501 of FIG.

FIG. 25 is a flowchart of another embodiment of the present invention, in which diagnosis is prohibited to prevent erroneous diagnosis.

FIG. 26 is a diagram showing a time change of the internal combustion engine and the catalyst temperature after the engine is stopped. FIG. 27 is a flowchart of a process of deciding permission of deterioration determination based on the temperature of an internal combustion engine as another embodiment of the present invention.

FIG. 28 is a flowchart of a process according to another embodiment of the present invention, in which the deterioration determination is permitted when the temperature sensor is normal.

FIG. 29 is a flowchart of a process according to another embodiment of the present invention for permitting the deterioration determination when the air change rate is smaller than a predetermined value.

FIG. 30 is a diagram showing the relationship between the air-fuel ratio, the light-off temperature, and the purification rate at the time of catalyst diagnosis.

FIG. 31 is a flowchart of a process corresponding to FIG.

FIG. 32 is a flowchart of a process of switching between a diagnostic mode and a normal control mode according to another embodiment of the present invention.

FIG. 33 is a flowchart of the deterioration check mode in FIG. FIG. 34 is a diagram for explaining the operation of the embodiment of FIGS. 32 and 33, showing the relationship between the diagnostic mode and the exhaust gas temperature during normal control. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to an in-cylinder injection type internal combustion engine.

The diagnostic device of the present invention is implemented in a program of an engine control unit (ECU) 1. An air flow sensor 5 is provided upstream of the throttle 4 provided in the intake passage of the engine. The engine cylinder is provided with an injector 10 for fuel injection. Further, a catalyst 9 for purifying exhaust gas is provided in the exhaust passage 12, a temperature sensor 2 is provided downstream thereof, and an oxygen sensor 3 is provided upstream (or downstream) of the catalyst. .

ECU 1 has a temperature signal from temperature sensor 2, an oxygen concentration signal from oxygen sensor 3, and an air flow signal from air flow sensor 5, and a crank angle sensor mounted on crankshaft 7 connected to piston 6. The rotation angle signal from 8 is input. Based on the information, a fuel injection signal to the injector 10 for injecting fuel from the ECU 1, an ignition signal to the spark plug 11 or a throttle control signal to the throttle 4 for adjusting the air amount are output. Is done.

Although FIG. 1 shows an in-cylinder injection engine as an example, the present invention can also be realized by a port injection engine. Although the temperature sensor is arranged downstream of the catalyst in FIG. 1, the temperature sensor may be directly mounted in the catalyst. Hereinafter, the configuration of the first embodiment of the present invention will be described with reference to FIGS. In this embodiment, a catalyst temperature estimation model (a deteriorated catalyst model) that does not include a thermal reaction of a catalyst, a comparison device that compares an estimated value obtained by the deteriorated catalyst model with an actually measured value obtained by the temperature detector, And a judgment device for judging the abnormality of the catalyst based on the judgment.

FIG. 2 shows an overall functional block of the diagnostic apparatus according to the present embodiment. A catalyst 9 for purifying exhaust gas is attached to an exhaust passage 12 of an internal combustion engine, and a temperature at which a gas temperature T downstream of the catalyst is detected. Detector 2 is installed. This touch The medium 9 may be of various forms. For example, the catalyst 9 may or may not have OSC. Also, a catalyst heated by an electric heater or the like may be used.

On the other hand, the ECU 1 uses the deteriorated catalyst model 101 to estimate the gas temperature 下流 downstream of the catalyst from the operating state of the internal combustion engine (rotational speed, air amount, fuel amount, etc.), the estimated value Τ ^Λ, and the actual measurement using the temperature detector 2. The _t ECU 1 including the comparing device 102 for comparing the value と and the judging device 103 for judging an abnormality based on the comparison result and other conditions has a predetermined program code, etc. It is realized by microcomputer. Reference numeral 100 denotes an engine control unit, which generates control signals such as an engine fuel injection amount, a fuel injection timing, and an ignition timing based on information such as an intake air amount, a fuel amount, and a rotation speed of the engine. Output. Further, as will be described later, based on the output of the determination device 103 of the catalyst 9, a necessary engine control signal is generated and output. The diagnostic device may be configured to be separated from the ECU 1 and transmit and receive necessary data to and from each other.

Next, the operation of the first exemplary embodiment of the present invention will be described with reference to the flowchart of FIG. In step sio1, the operation state of the engine is read, and in step sio2, the inflow temperature is estimated.

Figure 6 shows a typical relationship between engine operating conditions and exhaust temperature. In general, the exhaust gas temperature increases as the air flow rate and the fuel amount increase, and the air-fuel ratio tends to be maximum at a slightly leaner stoichiometric ratio. In addition, the exhaust temperature tends to be higher until the ignition timing reaches the retard limit. In step a102, the inflow temperature Tin is estimated with reference to these maps. (In Fig. 2, a temperature sensor may be installed upstream of the catalyst, and its output may be reflected in step si02.)

Next, in step s103, the amount of heat _η per unit flowing into the catalyst is calculated using the air flow rate Qa (n) and the temperature Tin. Here, the inflow heat _η per unit time is calculated from the temperature Tin, the air flow Qa (n) (n is the current value, n-1 is the past value one step before) and the specific heat C1 of the exhaust. You. Next, at step sl 04, the calorie Qcat (n) of the catalyst is calculated. Heat changes of the catalyst, the inflow amount of heat q _in the heat radiation quantity _χ and the exhaust heat q. _This model considers only the heat balance of _ut . Here, the heat release q _ex is the amount of heat radiated from the catalyst to the atmosphere, and the exhaust heat _{ut ut} is the heat released to the exhaust gas passing through the catalyst.

However, as shown in Fig. 4, the actual calorific value of the catalyst includes the inflow calorific value and the reaction calorific value. And when the catalyst is new and fully functional, the reaction heat associated with the catalyst reaction is large enough. On the other hand, when the catalyst deteriorates, the heat of reaction associated with the reaction of the catalyst decreases. Therefore, by obtaining an estimated value based on the deteriorated catalyst model based on the amount of heat flowing into the catalyst and comparing the estimated value with the measured amount of heat, it is possible to detect only the amount of reaction heat and diagnose the deterioration of the catalyst.

Based on this heat balance, in step sl05, the catalyst outlet temperature 演算 is calculated. This estimation model is a model of a completely degraded catalyst that considers only heat transfer. By comparing this estimated value and the measured value T, deterioration diagnosis of the catalyst or the temperature detector can be performed.

This model is much simpler than the conventional catalyst model that takes into account the heat of reaction, so the software and memory occupancy is small, and matching is easy.The deteriorated catalyst model 101 uses only heat transfer from the internal combustion engine. Is considered. Therefore, the relationship between the estimated value Τ ^Λ and the measured value における at the same time is as shown in Fig. 5. In FIG. 5, the straight line having a slope of 1 represents a completely degraded catalyst in which the catalyst does not react with any exhaust components, and the model of the present invention has the same temperature profile as this degraded catalyst. Therefore, if the catalyst deteriorates and the reaction heat of the catalyst decreases, the plot of the estimated temperature and the measured temperature approaches the straight line with a slope of 1. Moves to the high temperature side.

Therefore, in the first embodiment, at least the reaction calorie or the light-off temperature is monitored from the comparison between the estimated temperature and the measured temperature in the comparison device 102 of FIG. In the evening, if the amount of reaction heat becomes lower than the predetermined value (ΔTout) or the light-off temperature becomes higher than the predetermined temperature (Cout) in the judgment device 103, it is judged that the catalyst has deteriorated, and a warning is issued. A lamp (not shown) is turned on, abnormality information is stored in memory 104, or abnormality information is transmitted to the outside by radio to notify the user or an external organization of the deterioration of the catalyst. Here, the external organization is an automobile repair organization such as an automobile manufacturer or a repair shop, and the environmental management organization that manages air pollution.

By the way, in the embodiment of the present invention, the measured value detected by the sensor 1 is not strictly accurate, and is affected by the evaporation of the water stored in the catalyst. May stop the temperature rise. In the model of the first embodiment of the present invention, since the influence of the water evaporation is not taken into account, a discrepancy occurs between the estimated value and the actually measured value, which causes erroneous diagnosis.

Therefore, in the present invention, as a second embodiment, erroneous diagnosis is prevented by correcting the estimated value of the model with the actually measured value. FIG. 7 shows a flowchart of the second embodiment of the present invention. In step s201, it is determined whether or not the measured value T is equal to or lower than a predetermined temperature TL. If the temperature is equal to or lower than the predetermined temperature, the process proceeds to step s202, and if not, the process ends without performing correction. Here, the predetermined temperature TL is preferably set at about 100 to 200 ° C., which is slightly lower than the light-off temperature at which the catalyst starts a thermal reaction. In step s202, the temperature change rate of the measured value T is calculated, and the calculated value is compared with a predetermined value ΔΤ0 (a positive number that is almost 0).

If the temperature change is smaller than the predetermined value ΔΤ0, the process proceeds to step s203 and substitutes the measured value T (N) for the estimated value Γ (Ν). If the condition is not satisfied in step s202, step 203 is skipped and no correction is performed. Next, in step s204, it is determined whether or not the estimated value Γ (Ν) is greater than or equal to the measured value Τ (Ν) by a predetermined value ΔΤ1 (a positive number that is almost 0). If it is equal to or more than the predetermined value T1 in step s204, the process proceeds to step s205 to correct the estimated temperature in the negative direction (K is a correction coefficient and a positive number smaller than 1). If not, skip step s203 To end the process.

Fig. 8 schematically shows the difference in the estimated value depending on the presence or absence of correction based on the actual measurement value. Since the magnitude of the correction amount indicates the difference between the temperature sensor and the estimated value, which is not related to the evaporation of moisture, the integrated value of the correction amount ΔΤ 1 * Κ is stored and compared with a predetermined value to obtain the temperature. Detector errors can also be diagnosed.

The measured temperature 水の (Ν) at the time of water evaporation depends on the atmospheric pressure at start-up and the mounting position of the temperature detector, but it is generally reproduced as a constant value of 70-90 ° C. Therefore, for example, in FIG. 7, T (N) in step s203 is extremely lower than the normal temperature (30-50 ° C), or when step s203 is started when the engine is started. If the reproducibility of the correction value T (N) cannot be obtained, it can be determined that the temperature detector is abnormal.

As described above, according to the second embodiment of the present invention, by correcting the temperature estimation value based on the deteriorated catalyst model based on the actually measured value, the estimation accuracy of the model is improved and the diagnosis can be performed more accurately.

Next, a third embodiment of the present invention will be described with reference to FIGS. The present embodiment discloses a method of generating a deterioration index that accurately indicates the degree of deterioration of a catalyst from a difference between an actually measured value and an estimated value or a difference in a change rate.

First, the first deterioration index Ti will be described. Figure 9 shows the change over time between the measured and estimated values immediately after starting. When the catalyst deteriorates, the temperature difference between the measured value and the estimated value decreases. Therefore, the light-off performance of the catalyst can be monitored by setting the time when the difference between the measured value and the estimated value becomes larger than the predetermined value ΔΤ2 as the deterioration index Ti.

The operations of the comparison device and the determination device for realizing this diagnosis will be described with reference to the flowcharts of FIGS. 10 and 11. First, the operation of the comparison device shown in Fig. 10 will be described. As an initialization process before entering this process, the count number Ci is set to 0 when the engine is stopped, and the count permission flag: fCUP0K = l is set Before performing the comparison process, update the measured and estimated values 推定 (Ν) of the measured values T (N). deep. If the difference from the measured value T (N) to the estimated value Γ (Ν) is smaller than the predetermined value ΔΤ2 in step s301, proceed to step S302, otherwise, step S303 Proceed to. In step s302, the count permission flag is cleared to stop the counter (fCUPOK = 0). In step s303, the countup permission flag is checked. If the flag is in the permitted state, the power up of Ci is performed in step S304, and if not, the processing ends.

Next, the determination device performs the deterioration determination according to the flowchart shown in FIG. In step S305, the counter value Ci is compared with the diagnostic threshold value Cout (Fig. 12 (a)). The deterioration flag is set (fCATNG = l), and if not, the process proceeds to step s306 and the flag is cleared as the catalyst is in the normal state (fCATNG = 0).

Here, generally, as shown in FIG. 12 (b), the light-off time Cout tends to be shortened as the flow rate Q increases, so that the predetermined value Cout is reduced to the exhaust flow rate Q in step S305. The more the number, the smaller the setting, the more accurate the diagnosis.

Next, a deterioration index using the temperature change rate will be described. The rate of change in temperature indicates the generation (change) of the heat of reaction. Figures 13 to 15 schematically show the relationship between catalyst temperature and catalyst temperature change rate. For the sake of simplicity, the case where temperature correction is performed is shown here. The estimated temperature change rate peaks slightly after the engine starts due to exhaust heat transfer, and then gradually decreases as the catalyst temperature rises. Therefore, the difference between the actually measured value and the temperature change rate increases after the temperature T1 at which the catalytic reaction starts.

In Fig. 13, Δ (1Τ1 is the difference of the temperature change rate at a predetermined temperature or under a predetermined condition. The index is an index indicating that the closer the AdTl becomes to 0, the more the measured value becomes the maximum value. The difference AdT2 between the estimated value and the measured value at the temperature taken, or the maximum value AdT3 of the difference between the estimated value and the measured value, also decreases with deterioration. Become a mark.

Also, as shown in Fig. 14, the temperature difference between the measured value and the estimated value at which the rate of temperature change is the maximum (difference in peak temperature) Δ (1Τ4 also decreases with deterioration, so it is used for deterioration diagnosis. be able to.

Similarly, as shown in Fig. 15, the area AS surrounded by the temperature change rate between the actually measured value and the estimated value becomes smaller due to deterioration, so that this can also be used for deterioration diagnosis.

Next, the embodiments shown in FIGS. 16 to 18 detect and determine an abnormality of the temperature detector 2. The apparatus of this embodiment includes a catalyst temperature estimation model (deterioration catalyst model) that does not include a thermal reaction of a catalyst, a comparison device that compares an estimated value obtained by the degraded catalyst model with an actual measurement value obtained by the temperature detector, And a determination device for determining an abnormality of the temperature detector based on the comparison result.

In this embodiment, first, as shown in FIG. 16, a difference Τ (Ν) between the estimated value Γ (Ν) and the actually measured value Τ (Ν) is obtained.

Here, as shown in Fig. 17, the measured value による by the temperature detector 2 does not become higher than the estimated value ため because there is no reaction heat below the light-off temperature at which the reaction starts, or conversely, the light-off Above the temperature, the measured value does not become lower than the estimated value due to the heat of reaction.

Therefore, as shown in the flowchart of FIG. 18 and the explanatory diagram of FIG. 19, when the monitor value of the light-off temperature is equal to or less than the predetermined value Τ11, which is lower than the normal light-off temperature, and the measured value Τ a difference between the estimated value ^Τ Λ Δ Τ (Ν) is a predetermined value delta T 11 or more, that is, when the upper left region of Fig. 1 9 (SX02), or higher than the predetermined high temperature value Thl than Rye-off temperature during normal If the reaction heat monitor value T is a negative value equal to or less than the predetermined value ΔΤΙιΙ, that is, if it is in the lower right region of FIG. 19 (SX03), it is diagnosed that the temperature detector is abnormal (sX05). . If there is no output from the temperature detector, it is diagnosed as abnormal (sXOl). If there is no abnormality in the temperature detector, diagnose the catalyst (sX04). Considering the difference between the estimated value and the measured value in more detail here, it can be seen that the measured value and the estimated value match below the light-off temperature, but show reaction heat above the light-off temperature. That is, in the present embodiment, the diagnosis of the temperature detector is performed at the predetermined value T11 or lower lower than the light-off temperature, and the diagnosis of the catalyst is performed at the light-off temperature or higher. In other words, a difference below the light-off temperature indicates an error of the temperature detector. If the difference exceeds a predetermined value, it is diagnosed that the temperature detector is abnormal. On the other hand, since the difference above the light-off temperature indicates the amount of heat of reaction, if the difference ΔΤ is equal to or less than a predetermined value, it is diagnosed that the catalyst is abnormal. As described above, since the diagnosis of the catalyst is performed after the diagnosis of the temperature detector, the reliability of the diagnosis is improved.

Another embodiment of the present invention provides a catalyst temperature estimation model (a deteriorated catalyst model) that does not include a thermal reaction of a catalyst, a comparison device that compares an estimated value obtained by the deteriorated catalyst model with an actually measured value obtained by the temperature detector, When the measured value is lower than the predetermined temperature, the abnormality of the temperature detector is determined, and when it is higher than the predetermined temperature, the abnormality of the catalyst is determined.

That is, as shown in the flow chart of FIG. 20, first, when the actually measured value T by the temperature detector 2 is smaller than the predetermined value T11 lower than the light-off temperature, the deterioration determination process of the temperature detector 2 is performed ( s XO 2). Conversely, if the temperature is larger than the predetermined value T11, which is lower than the light-off temperature, it is checked whether the temperature detector 2 is normal based on the diagnosis result of the temperature detector (sXO3). Perform the deterioration judgment processing (s XO 4).

Next, FIG. 21 shows a flowchart of a comparison device using a temperature change rate as one of the other embodiments. In step s401, the temperature change rate is calculated. In this example, the temperature change rate is calculated using the difference between the previous temperature and the current temperature. It is also possible to perform a blanking process, and it is not necessary to use the previous temperature, and the temperature change rate may be appropriately calculated from a previous value. Step s In 402, the difference in temperature change rate (Δ (1 41, Δ (1Τ2, Δ (1Τ3)) or the difference in peak temperature (Δ (1Τ4 ) Or Calculate at least one of the area (AS).

Next, the determination device will be described with reference to the flowchart of FIG. If the determination condition is satisfied in step S403 of FIG. 22, the process proceeds to step s404. If the determination condition is not satisfied, the following steps are skipped and the process ends. The branch based on the determination condition of s403 is a step provided for preventing erroneous diagnosis. For example, the process branches with reference to a determination permission flag fDIAGEX described later.

In step s404, the F calculated in step 402 of FIG. 22 is compared with the predetermined value ΔT, and if the value is larger than the predetermined value ΔΤ, the process proceeds to step s405. Proceed to s406. Here, one deterioration index may be used as F, or a new deterioration index may be created by weighting each of the plurality of deterioration indices to further improve accuracy, and may be compared with a predetermined value. In step s405, the catalyst is in a normal state because the deterioration index is larger than the predetermined value, and the catalyst deterioration flag is cleared (fCATNG = 0) .In step s406, the catalyst is low because the deterioration catalyst is smaller than the predetermined value. Sets the catalyst deterioration flag (fCATNG = l) as the deterioration state.

Next, as another embodiment of the present invention, an embodiment of the invention relating to prevention of misdiagnosis of a catalyst will be described. The present invention prevents erroneous diagnosis by limiting the diagnosis region to a temperature region where the catalyst starts a reaction. For example, in the deterioration determination device, it is desirable to perform the deterioration determination when the measured value of the catalyst temperature by the catalyst temperature detector is within a predetermined temperature range. Further, in the deterioration determination device, it is desirable to prohibit the deterioration determination when the time change rate of the air flow rate or the fuel injection amount of the internal combustion engine is a predetermined value or more. Further, in the deterioration determination device, it is desirable to prohibit the deterioration determination when the temperature of the internal combustion engine is higher than a predetermined value. Furthermore, in the internal combustion engine diagnostic device, when the temperature detecting device is abnormal, the catalyst It is desirable to prohibit the deterioration judgment.

An embodiment is shown in the flowchart of FIG. In step s501, it is determined whether or not the measured value is within a predetermined range, and if it is within the predetermined range, the flow advances to step s503 to set a diagnosis permission flag (fDIAGEX = l). If so, proceed to step s503 to clear the diagnosis permission flag (fDIAGEX = 0) _o

Figure 24 shows a typical relationship between the catalyst temperature and the rate of change of the catalyst temperature. First, the temperature change rate rises sharply after the engine is started, but decreases at low temperatures (70-100 ° C) and rises again due to evaporation of water. For this reason, the optimal temperature range for catalyst diagnosis is between 100-200 ° C and 300-400 ° C, taking into account the catalyst light-off temperature and the location of the temperature detector. Diagnosis should be performed at.

FIG. 25 is a flowchart illustrating an embodiment in which the diagnosis is prohibited. Here, the diagnosis permission flag: fDIAGEX is referred to in step s504, and if the diagnosis permission flag is not set, the diagnosis is prohibited by skipping the deterioration determination processing in step s505.

Next, another embodiment will be described with reference to FIGS. In the diagnostic device of the present invention, when the catalyst is already warmed, such as when the engine is restarted, the estimated value and the measured value greatly differ, and there is a possibility of erroneous diagnosis. Therefore, if the catalyst has already warmed up, the deterioration judgment is prohibited to prevent erroneous diagnosis.

Figure 26 shows the relationship between the internal combustion engine water temperature and the catalyst temperature after the internal combustion engine is stopped. After the engine stops, both the catalyst temperature and the water temperature approach the outside air temperature, but the catalyst temperature drops faster due to the difference in specific heat. Therefore, focusing on the water temperature, the difference between the estimated value at engine start and the measured value can be made sufficiently small.

FIG. 27 is a flowchart showing one embodiment of the present invention. If the water temperature is higher than the predetermined temperature in step s601 of Fig. 2.7, the process proceeds to step s602 and the deterioration judgment is prohibited. Otherwise, the deterioration judgment is performed in step s603. Allow

Next, another embodiment of the present invention will be described. If the temperature detector is abnormal, the catalyst diagnosis based on the output of the temperature detector has a high possibility of erroneous diagnosis. FIG. 28 shows a flowchart for carrying out the present invention. If the temperature sensor is abnormal in step s701 in FIG. 28, the flow advances to step s702 to inhibit the deterioration determination, and otherwise, the deterioration determination is permitted in step s703.

Further, another embodiment of the present invention will be described with reference to FIG. In the above-described deterioration determination device of the present invention, it is desirable to prohibit the deterioration determination when the time change rate of the air flow rate or the fuel injection amount of the internal combustion engine is equal to or more than a predetermined value. That is, when the exhaust gas heat is extremely large compared to the reaction heat, the catalyst diagnosis method using the temperature detector makes it difficult to separate the reaction heat from the actually measured value for diagnosis. Further, the method of comparing the temperature change rates described in the above embodiments causes erroneous diagnosis if the air flow rate or the fuel amount changes near the light-off temperature at which reaction heat is generated. Therefore, in the present embodiment, the diagnosis is prohibited when the rate of change of the displacement or the rate of change of the fuel exceeds a predetermined value.

FIG. 29 shows a flowchart for carrying out this embodiment. In step s801 of FIG. 29, the rate of change of the air amount is compared with a predetermined value. If the airflow rate is larger than the predetermined value, the process proceeds to step s802, and the deterioration determination is prohibited. Step 3 permits deterioration judgment. By replacing step s801 with the fuel amount, erroneous diagnosis due to a change in the fuel amount can be similarly prevented.

Next, another embodiment of the present invention will be described with reference to FIGS. 30 and 31. FIG. FIG. 30 schematically shows the relationship between the air-fuel ratio and the light-off temperature or HC purification rate. This figure shows that the write-off temperature is the lowest at a slightly leaner air-fuel ratio. If the air-fuel ratio is rich, HC does not react sufficiently in the catalyst, so the heat of reaction decreases. Therefore, by keeping the air-fuel ratio constant during catalyst diagnosis, it is possible to suppress variations in light-off temperature and reaction amount. Thus, erroneous diagnosis can be prevented.

Therefore, an air-fuel ratio sensor and a fuel adjusting device for adjusting the fuel injection amount are provided in the exhaust passage of the internal combustion engine, and as shown in s 3101 to s 3103 in FIG. 31, the air-fuel ratio is suitable for diagnosis during catalyst diagnosis. Control to maintain a constant diagnostic air-fuel ratio.

Next, another embodiment of the present invention will be described with reference to FIGS. In this embodiment, as shown by sX01 to sX06 in FIG. 32, a catalyst deterioration confirmation mode is provided, and during the deterioration confirmation mode, the fuel amount or the ignition timing of the internal combustion engine is controlled so as to lower the catalyst temperature.

FIG. 33 is a flowchart showing details of the deterioration confirmation mode sXO 3 in FIG. As shown in sXOl to sX03 in Fig. 33, when a failure is notified by catalyst diagnosis, the failure is recorded in memory and the engine ignition timing and fuel Controls radiation. FIG. 34 shows the exhaust temperature in the diagnostic mode and the exhaust temperature in the normal state. Thus, during the diagnosis mode, the exhaust gas temperature is lowered to control the catalyst temperature lower than the light-off temperature of the criteria catalyst (the catalyst warm-up such as retard or double injection or the engine warm-up control is stopped). As a result, the rate of change in temperature during deterioration is smaller than in normal times, and catalyst diagnosis can be performed reliably.

Further, in the case of catalyst abnormality processing in sXO 6 in FIG. 32, it is preferable to perform control to lower the exhaust gas temperature as shown in FIG. 34, for example, in order to prevent further deterioration of the catalyst.

Claims

The scope of the claims

1. A diagnosis device for an internal combustion engine, comprising: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a temperature detection device for detecting a temperature of the catalyst.

Means for separating and obtaining exhaust heat and reaction heat of the catalyst based on the measured value of the temperature detector, and means for determining the degree of deterioration of the catalyst based on the magnitude of the reaction heat. Diagnostic device for an internal combustion engine.

2. A diagnostic device for an internal combustion engine comprising: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a catalyst temperature detecting device for detecting a temperature of the catalyst.

A catalyst temperature estimation model that does not include the thermal reaction of the catalyst (deteriorated catalyst model); a comparison device that compares the estimated value obtained by the aforementioned degraded catalyst model with the actual measurement value obtained by the temperature detector; A diagnosis device for an internal combustion engine, comprising: a determination device for determining an abnormality;

3. A diagnostic device for an internal combustion engine including: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a catalyst temperature detecting device for detecting a temperature of the catalyst.

A comparison device that compares a catalyst temperature estimation model that does not include the thermal reaction of the catalyst (degraded catalyst model), an estimated value based on the aforementioned deteriorated catalyst model, and an actual measurement value obtained by the temperature detector, and detects a temperature based on the comparison result. A diagnostic device for an internal combustion engine, comprising: a determining device that determines an abnormality of a fuel cell.

4. In a diagnostic device for an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine, and a catalyst temperature detecting device for detecting a temperature of the catalyst,

A catalyst temperature estimation model that does not include the thermal reaction of the catalyst (deteriorated catalyst model); a comparison device that compares the estimated value obtained by the degraded catalyst model with the actually measured value by the temperature detector; A diagnostic device for an internal combustion engine, comprising: a determination device that determines an abnormality of a temperature detector when the temperature is lower than a predetermined value, and determines an abnormality of the catalyst when the temperature is higher than a predetermined temperature.

5. The deteriorated catalyst model is a heat transfer model of a catalyst, wherein the flow rate of air flowing into the catalyst and the exhaust gas temperature of the internal combustion engine are set to parameters. The diagnostic device for an internal combustion engine according to any one of claims 2 to 4.

6. The diagnostic device for an internal combustion engine according to claim 2, wherein the estimated value of the temperature in the deteriorated catalyst model is corrected using an actually measured value of the temperature detecting device.

7. The estimated value of the temperature in the deteriorated catalyst model is corrected using the actually measured value of the temperature detecting device, and the abnormality of the temperature detector is determined based on the temperature at which the rate of change of the estimated value at the time of correction is equal to or less than a predetermined value. The diagnostic device for an internal combustion engine according to any one of claims 3 to 5, wherein the determination is performed.

8. The diagnosis of an internal combustion engine according to any one of claims 2 to 5, wherein the comparison device compares an absolute value or a time rate of change between the measured value and the estimated value.

9. The internal combustion engine according to claim 2, wherein the deterioration determination device performs the deterioration determination when the measured value of the catalyst temperature by the catalyst temperature detector is within a predetermined temperature range. Diagnostic device.

10. The deterioration judging device according to any one of claims 2 to 5, wherein the deterioration judgment is prohibited when a time change rate of the air flow rate or the fuel injection amount of the internal combustion engine is equal to or more than a predetermined value. Diagnostic device for internal combustion engines.

11. The deterioration determination device, further comprising: an engine temperature detection device for detecting a temperature of the internal combustion engine, wherein the deterioration determination is prohibited when the temperature of the internal combustion engine is higher than a predetermined value. -Diagnosis of internal combustion engine according to any of 5

12. A diagnostic device for an internal combustion engine, comprising: a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine; and a catalyst temperature detecting device for detecting a temperature of the catalyst. Means for determining the exhaust heat and reaction heat of the catalyst separately to determine the degree of deterioration of the catalyst based on the magnitude of the reaction heat; and prohibiting the determination of deterioration of the catalyst when the temperature detection device is abnormal. Diagnostic device for internal combustion engine.

13. A control device for an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine, and a diagnostic device including a catalyst temperature detection device for detecting a temperature of the catalyst.

Means for separating and obtaining the exhaust heat and the reaction heat of the catalyst based on the actual value measured by the temperature detector, and diagnosing the degree of deterioration of the catalyst based on the magnitude of the reaction heat; and provided in the exhaust passage of the internal combustion engine. An internal combustion engine comprising: an air-fuel ratio sensor; and a fuel adjustment device that adjusts a fuel injection amount, and controls the fuel adjustment device so that the air-fuel ratio of the internal combustion engine is kept constant during diagnosis of the catalyst. Control device.

14. An internal combustion engine control device including a catalyst for purifying exhaust gas in an exhaust passage of the internal combustion engine and a diagnostic device including a catalyst temperature detection device for detecting a temperature of the catalyst.

The controller has a catalyst deterioration confirmation mode. In the deterioration confirmation mode, the exhaust heat and the reaction heat of the catalyst are separated and obtained based on the measured value of the temperature detector, and the catalyst heat is determined based on the magnitude of the reaction heat. A control device for an internal combustion engine, comprising: means for diagnosing the degree of deterioration of the internal combustion engine; and means for controlling the fuel amount or the ignition timing of the internal combustion engine so as to lower the catalyst temperature during the deterioration confirmation mode.

15. A diagnostic method for an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of an internal combustion engine and a catalyst temperature detecting device for detecting a temperature of the catalyst, the method comprising: A method for diagnosing an internal combustion engine, characterized in that exhaust heat and reaction heat of the catalyst are obtained separately, and the degree of deterioration of the catalyst is determined based on the magnitude of the reaction heat.

16. A diagnostic method for an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of an internal combustion engine and a catalyst temperature detecting device for detecting a temperature of the catalyst, wherein a degradation catalyst model including a thermal reaction of the catalyst is provided. A method for diagnosing an internal combustion engine, comprising: comparing an estimated value obtained by the temperature detector with an actually measured value obtained by the temperature detector; and determining an abnormality of the catalyst based on the comparison result.

17. A catalyst for purifying exhaust gas in the exhaust passage of the internal combustion engine, and detecting the temperature of the catalyst A method for diagnosing an internal combustion engine provided with a catalyst temperature detecting device that outputs an estimated value based on a deteriorated catalyst model that does not include a thermal reaction of a catalyst and an actual measured value obtained by the temperature detector, and based on the comparison result, detects the temperature based on the comparison result. A method for diagnosing an internal combustion engine, characterized by determining an abnormality of a fuel cell.

18. A method for diagnosing an internal combustion engine including a catalyst for purifying exhaust gas in an exhaust passage of an internal combustion engine and a catalyst temperature detecting device for detecting a temperature of the catalyst, wherein a deterioration catalyst model that does not include a thermal reaction of the catalyst is used. The estimated value is compared with the actual value measured by the temperature detector, and when the actual value is lower than a predetermined temperature, the abnormality of the temperature detector is determined. When the actual value is higher than the predetermined temperature, the abnormality of the catalyst is determined. A method for diagnosing an internal combustion engine, comprising:

1 9. An air-fuel ratio sensor provided in the exhaust passage, a fuel adjustment device for adjusting the fuel injection amount, a catalyst for purifying exhaust gas in the exhaust passage of the engine, and a catalyst temperature for detecting the temperature of the catalyst A control method for an internal combustion engine including a diagnostic device including a detection device,

The exhaust heat and the reaction heat of the catalyst are separated and obtained based on the actual value measured by the temperature detector, and the degree of deterioration of the catalyst is diagnosed based on the magnitude of the reaction heat. A method for controlling an internal combustion engine, comprising controlling the fuel adjusting device so as to maintain a constant fuel ratio.

20. A diagnostic device including a catalyst for purifying exhaust gas in an exhaust passage of an internal combustion engine, a means for controlling a fuel amount or an ignition timing of the internal combustion engine, and a catalyst temperature detecting device for detecting a temperature of the catalyst. In a control method for an internal combustion engine comprising:

The internal combustion engine has, as operation modes, a normal operation mode and a catalyst deterioration confirmation mode by the diagnostic device,

In the catalyst deterioration confirmation mode, the exhaust heat and the reaction heat of the catalyst are separated and obtained based on the actually measured values by the temperature detector, and the degree of deterioration of the catalyst is diagnosed based on the magnitude of the reaction heat. Controlling the fuel amount or the ignition timing so as to lower the catalyst temperature during the mode.