JP4779814B2 - Catalyst representative temperature acquisition device for internal combustion engine - Google Patents

Description

  The present invention relates to a catalyst representative temperature acquisition device for obtaining a representative temperature of an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine.

  In order to purify the exhaust gas of the internal combustion engine, for example, a catalyst such as a three-way catalyst or a NOx catalyst is widely installed in the exhaust passage. In order to fully extract the purification performance of the catalyst, it is possible to control the operation state of the internal combustion engine by accurately managing the catalyst state, for example, the sulfur poisoning amount, the NOx storage amount, the oxygen storage capacity, the deterioration degree, etc. is important. The state of the catalyst is closely related to the temperature of the catalyst. Therefore, in order to manage the state of the catalyst, the values of various engine parameters of the internal combustion engine are controlled based on the temperature representative of the catalyst.

  In JP-A-2005-127285, the exhaust gas temperature at the catalyst inlet and the exhaust gas temperature at the catalyst outlet are respectively measured by sensors, and the weighted average of the two is calculated successively by increasing the weighting at the outlet. A catalyst representative temperature estimation method is disclosed in which a value obtained by weighted averaging the present calculated value and the previous calculated value is used as the representative temperature of the catalyst.

JP 2005-127285 A Special table 2003-503622 gazette JP-A-10-159543 Japanese Patent Laid-Open No. 10-196433

  By the way, the catalyst used for the internal combustion engine gradually deteriorates with aging (accumulation of operation time). According to the knowledge of the present inventors, the temperature inside the catalyst is not always uniform, and the state of the temperature distribution inside the catalyst changes as the catalyst deteriorates. In the above-described conventional technology, such a situation is not taken into consideration, and therefore, an inappropriate representative temperature, that is, a representative temperature that does not accurately reflect the state of the catalyst is estimated as the catalyst deteriorates. If the internal combustion engine is controlled on the basis of such an inappropriate representative temperature, the emission is deteriorated or the catalyst is further deteriorated.

  The present invention has been made to solve the above-described problems, and provides a catalyst representative temperature acquisition device for an internal combustion engine capable of obtaining an appropriate catalyst representative temperature according to the deterioration state of the catalyst. Objective.

In order to achieve the above object, a first invention is a catalyst representative temperature acquisition device for an internal combustion engine,
A catalyst disposed in the exhaust passage of the internal combustion engine;
Catalyst temperature acquisition means for dividing the catalyst into a plurality of parts and detecting or estimating the catalyst temperature for each part;
Representative temperature determining means for determining a representative temperature of the catalyst based on the catalyst temperature of at least one of the sites;
A catalyst deterioration state acquisition means for detecting or estimating the deterioration state of the catalyst;
With
The representative temperature determining means includes a determining method changing means for changing the representative temperature determining method according to the deterioration state.

The second invention is the first invention, wherein
The representative temperature determining means determines a catalyst temperature of one selected part selected from the plurality of parts as the representative temperature,
The determination method changing means changes the selected portion according to the deterioration state.

The third invention is the second invention, wherein
The determination method changing means sets the portion closer to the outlet of the catalyst as the selected portion as the deterioration of the catalyst progresses.

Moreover, 4th invention is set in 1st invention,
The representative temperature determining means calculates the representative temperature by performing a weighted average of the catalyst temperature of each part.
The determination method changing means changes the weight for each part according to the deterioration state.

The fifth invention is the fourth invention, wherein
The determination method changing means is characterized in that the portion where the weight is maximized is closer to the catalyst outlet as the deterioration of the catalyst progresses.

The sixth invention is the first invention, wherein
The determination method changing means discriminates each part into a deteriorated part and a non-degraded part according to the deterioration state,
The representative temperature determining means determines the representative temperature based on at least one catalyst temperature among the parts determined to be the non-deteriorated parts.

According to a seventh invention, in any one of the first to sixth inventions,
The catalyst deterioration state acquisition means includes means for detecting or estimating an air-fuel ratio downstream of the catalyst, HC concentration or exhaust gas temperature, or NOx storage capacity or oxygen storage capacity of the catalyst, and the detected or estimated value The deterioration state is determined based on the above.

Further, an eighth invention is any one of the first to seventh inventions,
The catalyst deterioration state acquisition means determines the deterioration state based on at least one of the catalyst temperatures for each part.

According to a ninth invention, in any one of the first to eighth inventions,
According to the deterioration state, the determination method changing means increases the contribution to the catalyst temperature at a site where a large amount of catalytic reaction occurs, and decreases the contribution to a catalyst temperature at a site where the catalytic reaction is low. The determination method is changed.

  According to the first aspect, the interior of the catalyst is divided into a plurality of parts, and the representative temperature of the catalyst can be determined based on at least one of the catalyst temperatures obtained for each part. At this time, the method for determining the representative temperature can be changed according to the deterioration state of the catalyst. As the catalyst deteriorates, the internal temperature distribution and the position of the portion where the catalytic reaction occurs most frequently change. For this reason, the method of taking a temperature suitable for representing a catalyst differs depending on the deterioration state of the catalyst. According to the first invention, such a situation can be reflected, so that an accurate and appropriate representative temperature can always be determined regardless of the degree of deterioration of the catalyst. As a result, it is possible to improve the estimation accuracy of the state of the catalyst, for example, the sulfur poisoning amount, the NOx occlusion amount, the oxygen occlusion amount, and the degree of deterioration. Therefore, it becomes possible to control the internal combustion engine so as to maximize the exhaust gas purification capacity of the catalyst, and exhaust emission can be reduced.

  According to the second invention, when the catalyst temperature of one selected part selected from a plurality of parts is determined as the representative temperature, the selected part can be changed according to the deterioration state. Thereby, according to the deterioration state of a catalyst, the temperature of the site | part suitable for representing a catalyst can be made into a representative temperature.

  According to the third aspect of the present invention, the closer to the catalyst outlet, the more the catalyst is more deteriorated. As the deterioration of the catalyst progresses, the site where the most catalytic reaction occurs shifts to a site closer to the outlet side. According to the third aspect of the invention, the catalyst temperature near the outlet can be determined as the representative temperature as the deterioration of the catalyst progresses corresponding to the phenomenon. Therefore, regardless of the degree of deterioration of the catalyst, the catalyst temperature at the site where the catalytic reaction occurs most frequently, that is, the site most suitable for representing the catalyst, can be determined as the representative temperature.

  According to the fourth aspect of the invention, when the representative temperature is calculated by weighted averaging the catalyst temperature of each part, the weight for each part can be changed according to the deterioration state. Thereby, since the weight according to the deterioration state of the catalyst can be applied to the catalyst temperature of each part, an appropriate representative temperature can be obtained.

  According to the fifth aspect of the present invention, the portion where the weight is maximized can be made closer to the catalyst outlet as the deterioration of the catalyst progresses. As the deterioration of the catalyst progresses, the site where the most catalytic reaction occurs shifts to a site closer to the outlet side. According to the fifth invention, the representative temperature can be calculated by increasing the weight of the portion closer to the outlet as the deterioration of the catalyst progresses corresponding to the phenomenon. Therefore, regardless of the degree of deterioration of the catalyst, it is possible to reflect the catalyst temperature of the site where the most catalytic reaction occurs, that is, the most suitable site to represent the catalyst, so that an appropriate representative temperature can be obtained. . In addition, the catalyst temperatures at other sites can also be included in the representative temperature with a weight depending on the degree of contribution to emissions and the like. For this reason, a more appropriate representative temperature can be obtained.

  According to the sixth invention, each part is discriminated as a deteriorated part and a non-deteriorated part according to the deterioration state, and the representative temperature is determined based on at least one catalyst temperature of the parts determined as non-deteriorated parts. can do. That is, the representative temperature can be calculated on the basis of only the catalyst temperature of the non-deteriorated portion, excluding the deteriorated portion. For this reason, an appropriate representative temperature can be obtained irrespective of the degree of deterioration of the catalyst.

  According to the seventh aspect of the invention, the air-fuel ratio downstream of the catalyst, the HC concentration or the exhaust gas temperature, or the NOx storage capacity or oxygen storage capacity of the catalyst is detected or estimated, and the deterioration state is based on the detected or estimated value. Can be judged. Thereby, the deterioration state of the catalyst can be accurately determined.

  According to the eighth aspect, the deterioration state can be determined based on at least one of the catalyst temperatures for each part. Thereby, the deterioration state of the catalyst can be accurately determined.

  According to the ninth aspect of the invention, the representative temperature is determined so that the degree of contribution is larger as the catalyst temperature is higher at the site where the catalytic reaction occurs and the degree of contribution is lower as the temperature is lower at the site where the catalytic reaction is less. can do. This makes it possible to maximize the contribution of the catalyst temperature at the site where the most catalytic reaction occurs, that is, the site most suitable for representing the catalyst, regardless of the degree of catalyst degradation. Therefore, an appropriate representative temperature can be obtained regardless of the degree of deterioration of the catalyst.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. The internal combustion engine 10 is assumed to be a power source of a vehicle, for example. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited.

  An intake passage 12 and an exhaust passage 14 communicate with the cylinder of the internal combustion engine 10. An air flow meter 16 that detects an intake air amount GA is disposed in the intake passage 12. A throttle valve 18 is disposed downstream of the air flow meter 16. The throttle valve 18 is an electronically controlled valve that is driven by a throttle motor 20 based on an accelerator opening or the like. In the vicinity of the throttle valve 18, a throttle position sensor 22 for detecting the throttle opening is disposed. The accelerator opening is detected by an accelerator position sensor 24 provided in the vicinity of the accelerator pedal.

  The cylinder of the internal combustion engine 10 is provided with a fuel injection valve 26 for injecting fuel into the intake port. The internal combustion engine 10 is not limited to the port injection type as shown in the figure, and may be provided with a fuel injection valve that directly injects fuel into the cylinder. The cylinder of the internal combustion engine 10 is further provided with an intake valve 28, a spark plug 30, and an exhaust valve 32.

  The internal combustion engine in the present invention is not limited to the spark ignition type as in the internal combustion engine 10, but may be a compression ignition type.

  A crank angle sensor 38 for detecting the rotation angle of the crankshaft 36 is attached in the vicinity of the crankshaft 36 of the internal combustion engine 10. According to the output of the crank angle sensor 38, the rotational position of the crankshaft 36, the engine speed NE (engine speed), and the like can be detected.

  A catalyst 40 for purifying exhaust gas is provided in the middle of the exhaust passage 14 of the internal combustion engine 10. The type of the catalyst 40 is not particularly limited, and may be any one such as a three-way catalyst, an occlusion reduction type NOx catalyst, a selective reduction type NOx catalyst, an oxidation catalyst, and the like. Further, another catalyst may be disposed on the upstream side or the downstream side of the catalyst 40.

  An oxygen sensor 42 is installed in the exhaust passage 14 on the outlet side (downstream side) of the catalyst 40. The oxygen sensor 42 generates an output that suddenly changes depending on whether the exhaust air-fuel ratio at the outlet of the catalyst 40 is richer or leaner than the stoichiometric air-fuel ratio. Alternatively, the oxygen sensor 42 may emit an output that changes linearly according to the exhaust air-fuel ratio at the outlet of the catalyst 40.

  The system of the present embodiment further includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 can control the operating state of the internal combustion engine 10 based on those sensor outputs.

[Features of Embodiment 1]
2 and 3 are diagrams for explaining a method for obtaining the representative temperature of the catalyst 40 in the present embodiment, respectively. FIG. 2 shows a case where the catalyst 40 is nearly new (when it has not deteriorated), and FIG. 3 shows a case where the deterioration of the catalyst 40 has progressed to some extent.

  As shown in FIGS. 2 and 3, in this embodiment, when obtaining the representative temperature, first, the interior of the catalyst 40 is divided into a plurality of parts (regions) from the upstream side (inlet side) to the downstream side (outlet side). Separately, the temperature (bed temperature) of each part was determined. In this embodiment, it was decided to divide into five parts of No. 1 to No. 5 in order from the upstream side. In the present invention, the number of parts to be divided is not limited to five and may be any number.

  As a method for obtaining the catalyst temperature for each part, it may be detected directly using a temperature sensor, or may be estimated based on other information. In this embodiment, a temperature sensor (not shown) is attached to each part, and the catalyst temperature for each part is obtained by these temperature sensors.

In this embodiment, as shown in FIGS. 2 and 3, the temperature near the rear end of each part is set as the temperature of that part. Hereinafter, the temperature of each portion of the No. 1 to 5 th and _T 1 through T _5, respectively.

(Catalyst 40 is nearly new)
First, the case where the catalyst 40 is nearly new will be described. When the catalyst 40 is nearly new, when exhaust gas flows into the catalyst 40, a catalytic reaction (purification reaction) occurs immediately at a site near the inlet. The harmful reaction in the exhaust gas is almost eliminated by the catalytic reaction, so that the catalytic reaction does not occur so much at the downstream site. For this reason, as shown in FIG. 2, the catalytic reaction mainly occurs at the first site.

At the first site where the catalytic reaction has occurred, the temperature (T ₁ ) rises due to the heat of reaction. And in the inside of the catalyst 40, the part from the upstream side to the part downstream from the upstream part by the action of heat conduction in which heat moves in the component (in the carrier) or the action of heat transfer in which heat is transferred by the flow of the exhaust gas. Heat transfer occurs toward That is, heat is transferred from the first part to the second part or less. For this reason, the temperature (T2-T5) of the _{2nd- 5th} site | part also rises (refer FIG. 2). In the example shown in FIG. 2, T _{1 to} T ₅ are almost the same temperature, but this is an example, and this is not always the case.

(When the deterioration of the catalyst 40 has progressed to some extent)
Since the site where the catalytic reaction occurs is likely to become high temperature, it gradually deteriorates. Here, the deterioration refers to a reduction in purification capacity such as an oxygen storage capacity (OSC) and a NOx storage capacity. As described above, the catalytic reaction is more likely to occur in the upstream portion. For this reason, the deterioration of the catalyst 40 proceeds in order from the upstream portion.

FIG. 3 shows a state in which the deterioration has progressed to the second part. In this state, the catalytic reaction hardly occurs at the first and second sites. For this reason, the temperature (T ₁ , T ₂ ) of the _first and second portions does not increase so much. The harmful components that have not been purified in the first and second sites reach the third site. As a result, a catalytic reaction occurs mainly at the third site. As a result, the temperature (T ₃ ) of the _third part increases. By the site of the third heat is transferred to the site of the fourth and fifth, fourth and fifth portions of the temperature (T _{4, T 5)} also increases (see FIG. 3). In the example shown in FIG. 3, T _{3 to} T ₅ are almost the same temperature, but this is an example, and this is not always the case.

  From the above circumstances, as the catalyst 40 deteriorates, the state of the temperature distribution inside thereof changes as compared to when it is new. For this reason, when the representative temperature of the catalyst 40 is determined based on the temperature of each part, the value of the representative temperature varies greatly depending on how it is determined.

  In the deteriorated portion of the catalyst 40, the catalytic reaction does not occur so much or NOx is difficult to occlude. For this reason, it can be said that the temperature of the deteriorated portion is inappropriate for the representative temperature because it has little influence on the emission. Conversely, the temperature at the site where the most catalytic reaction occurs has the greatest effect on emissions. Accordingly, it can be said that the most suitable temperature for the representative temperature is the temperature at the site where the most catalytic reaction occurs. On the other hand, the site where the most catalytic reaction occurs differs depending on the deterioration state of the catalyst 40 as described above. Therefore, in the present embodiment, the catalyst temperature of one part selected from the first to fifth parts is set as the representative temperature, and the selected part is changed according to the deterioration state of the catalyst 40. did.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 4, first, the oxygen storage capacity of the catalyst 40 is measured (step 100). As the deterioration of the catalyst 40 progresses, the oxygen storage capacity decreases. Therefore, in this embodiment, the deterioration state of the catalyst 40 is determined using the oxygen storage capacity as an index.

In step 100, the oxygen storage capacity can be measured by a known method. For example, it can be measured as follows.
(1) First, the exhaust air-fuel ratio is intentionally maintained rich.
(2) When the output of the oxygen sensor 42 located downstream of the catalyst 40 is inverted to a rich output, it is determined that all the oxygen in the catalyst 40 has been released at that time, and the exhaust air-fuel ratio is inverted to lean.
(3) Waiting for the output of the oxygen sensor 42 to reverse to the lean output while integrating the excess oxygen amount in the exhaust gas set to lean.
(4) The integrated value of the surplus oxygen amount calculated when the reversal to the lean output is detected is set as the oxygen storage capacity of the catalyst 40.

  When the oxygen storage capacity is measured in the above step 100, a site for determining the representative temperature is then selected according to the deterioration state determined from the oxygen storage capacity (step 102). For example, when the oxygen storage capacity has hardly decreased as compared with the value at the time of a new article, it can be determined that the catalyst 40 has hardly deteriorated. In this case, the first part is the selected part. On the other hand, when the oxygen storage capacity is lower than when it is new, deterioration of the catalyst 40 is recognized. Therefore, in this case, any one of No. 2 to No. 5 is selected. At this time, as the value of the oxygen storage capacity is smaller, a portion closer to the outlet among the second to fifth is selected.

When the selected part is determined in step 102, the catalyst temperature of the selected part is determined as the representative temperature (step 104). That is, _one of T _{1 to} T ₅ is set as the representative temperature according to the selected part. When the representative temperature is determined in this way, the operating state of the internal combustion engine 10 is controlled based on the representative temperature. That is, based on the representative temperature of the catalyst 40, each engine parameter (for example, air-fuel ratio A / F, ignition timing SA, fuel injection amount, valve timing, etc.) is changed.

  As described above, as the deterioration of the catalyst 40 progresses, the site where the most catalytic reaction occurs shifts to a site closer to the outlet side. According to the processing of the routine shown in FIG. 4 described above, the catalyst temperature near the outlet can be determined as the representative temperature as the deterioration of the catalyst 40 progresses corresponding to the phenomenon. That is, regardless of the degree of deterioration of the catalyst 40, the catalyst temperature at the site where the most catalytic reaction occurs can be determined as the representative temperature. For this reason, an accurate and appropriate representative temperature can always be determined regardless of the degree of deterioration of the catalyst 40. As a result, in the system shown in FIG. 1, in estimating the state of the catalyst 40, for example, the sulfur poisoning amount, the NOx occlusion amount, the oxygen occlusion amount, the deterioration degree, etc., the estimation accuracy can be improved. Therefore, the internal combustion engine 10 can be controlled to maximize the exhaust purification capacity of the catalyst 40, and exhaust emission can be reduced.

  In Embodiment 1 described above, the catalyst temperature at each part is described as being directly detected by the temperature sensor. However, in the present invention, the catalyst temperature at each part may be obtained by estimation. Hereinafter, an example of a catalyst temperature estimation model that can be used when estimating the catalyst temperature of each part will be briefly described. In the catalyst temperature estimation model described below, first, the amount of energy flowing into the catalyst 40 is calculated as a factor for increasing the catalyst temperature. The energy flowing into the catalyst 40 is the thermal energy of the exhaust gas itself, the amount of heat of the unburned components contained in the exhaust gas, or the like. The amount of energy flowing into the catalyst 40 can be calculated by a known method based on the operating state of the internal combustion engine 10 (engine speed NE, load, air-fuel ratio A / F, ignition timing SA, etc.). Next, in the catalyst temperature estimation model, the amount of heat released from the catalyst 40 due to the influence of traveling wind or the like is calculated as a factor for lowering the catalyst temperature. The amount of heat released from the catalyst 40 can be calculated by a known method based on the outside air temperature, the vehicle speed, or the like. In the catalyst temperature estimation model, the amount of heat transfer inside the catalyst is calculated. In the inside of the catalyst 40, as described above, heat is sequentially transferred from the upstream portion to the downstream portion by the action of heat conduction and heat transfer. Such a heat transfer amount can be calculated by a known heat transfer model. In the catalyst temperature estimation model, the estimated temperature for each part of the catalyst 40 can be calculated based on the above calculated values. Further, an exhaust temperature sensor for detecting the exhaust gas temperature at the outlet of the catalyst 40 (hereinafter referred to as “exit gas temperature”) is provided, and the estimated temperature of each part is determined as follows based on the detected value of the outlet gas temperature. You may make it correct | amend. According to the exhaust temperature sensor, the outlet gas temperature of the catalyst 40 can be directly detected. On the other hand, the estimated value of the outlet gas temperature of the catalyst 40 can be calculated based on the estimated temperature of the fifth part located on the most downstream side and the operating state of the internal combustion engine 10. The deviation between the estimated value of the outlet gas temperature and the actually measured value detected by the exhaust temperature sensor can be determined to correspond to an error superimposed on the catalyst temperature estimation model. Therefore, the final estimated temperature is calculated by adding a value obtained by multiplying the deviation between the measured value and estimated value of the outlet gas temperature by a predetermined correction coefficient to the estimated temperature of each part calculated by the catalyst temperature estimation model. To do. As a result, when the temperature of each part of the catalyst 40 is obtained by estimation, the error superimposed on the catalyst temperature estimation model can be accurately corrected, and high estimation accuracy can be obtained.

  In Embodiment 1 described above, the deterioration state is determined using the oxygen storage capacity measured based on the air-fuel ratio A / F downstream of the catalyst 40 as an index. Is not limited to this. That is, not only the air-fuel ratio A / F downstream of the catalyst 40 and the oxygen storage capacity of the catalyst 40, but also the HC concentration and exhaust gas temperature downstream of the catalyst 40, the NOx storage capacity of the catalyst 40, and the like are detected or estimated. Alternatively, the deterioration state may be determined based on the estimated value. Further, the deterioration state may be determined based on at least one of the temperatures of each part of the catalyst 40.

  Further, in the first embodiment described above, the ECU 50 detects the catalyst temperature of each part based on the signal of the temperature sensor attached to each part of the catalyst 40, thereby obtaining “catalyst temperature acquisition” in the first invention. The “means” executes the processing of the above steps 102 and 104, whereby the “representative temperature determining means” in the first and second inventions executes the processing of the above step 100, The “determination method obtaining means” in the first, second, and third inventions is realized by executing the processing of step 102 described above.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 5 to FIG. 7. The difference from the first embodiment will be mainly described, and the description of the same matters will be described. Simplify or omit. The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 7 to be described later instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG.

[Features of Embodiment 2]
FIG. 5 and FIG. 6 are diagrams for explaining a method of obtaining the representative temperature of the catalyst 40 in the present embodiment, respectively. FIG. 5 shows a case where the catalyst 40 is nearly new, similar to FIG. 2 described above. FIG. 6 shows a case where the deterioration of the catalyst 40 has progressed to some extent, as in FIG. 3 described above. In the present embodiment, the representative temperature is calculated by performing a weighted average of the catalyst temperatures of the first to fifth portions. The lower diagram in FIGS. 5 and 6 shows the values of the weights W _{1 to} W ₅ for each part. In the present embodiment, the representative temperature T _rep is obtained by dividing the value obtained by multiplying the temperatures T _{1 to} T ₅ of the respective parts by the respective weights W _{1 to} W ₅ and adding them together by the number of parts (5 in this embodiment). The weighted average value calculated by That is, the representative temperature T _rep of this embodiment is represented by the following formula.
T _rep = (ΣT _n W _n ) / 5 (1)

(Weight W when catalyst 40 is nearly new)
As shown in FIG. 5, when the catalyst 40 is nearly new, the weights W _{1 to} W ₅ of the _{first to fifth} portions are almost the same.

(Weight W when catalyst 40 has progressed to some extent)
As shown in FIG. 6, when the deterioration of the catalyst 40 has progressed to some extent, the weights W ₁ and W ₂ of the deteriorated portion, that is, the portion where the catalytic reaction hardly occurs (here, No. 1 and No. 2) are small. Has been. On the other hand, the weight W ₃ of the _third part where the catalytic reaction occurs most frequently is the largest. Further, the weights W ₄ and W ₅ of the _fourth and _fifth portions downstream of the third are gradually reduced from the third.

  In the present embodiment, by setting the weight W of each part as described above in accordance with the deterioration state of the catalyst 40, the temperature of the part where the most catalytic reaction occurs is reflected to the representative temperature to the greatest extent. Can do. For this reason, the effect similar to Embodiment 1 is acquired. In addition, the catalyst temperatures at other sites can also be included in the representative temperature with a weight according to the degree of contribution to emissions. For this reason, a more appropriate representative temperature can be obtained.

[Specific Processing in Second Embodiment]
FIG. 7 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 7, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

According to the routine shown in FIG. 7, first, as in the first embodiment, the oxygen storage capacity of the catalyst 40 is measured (step 100). Next, the weights W _{1 to} W _{5 of} each part are determined according to the deterioration state determined from the oxygen storage capacity (step 106). For example, when the oxygen storage capacity has hardly decreased as compared with the new value, that is, when the catalyst 40 has hardly deteriorated, as shown in FIG. 5, all of W _{1 to} W ₅ are substantially the same. Determined by size. Alternatively, the weight W1 of the _first part where the most catalytic reaction occurs may be maximized and the weight of the downstream part may be decreased. On the other hand, when the oxygen storage capacity is lower than when new, that is, when deterioration of the catalyst 40 is recognized, the weights W _{1 to} W ₅ of the respective parts are set as illustrated in FIG. The In this case, the weight of any part of No. 2 to No. 5 is set to be the largest. And the site | part which makes the weight the largest is taken as a site | part close | similar to an exit, so that the value of oxygen storage capacity is small, ie, deterioration is progressing.

When the weights W _{1 to} W ₅ of each part are determined in the above step 106, the representative temperatures are calculated by weighted averaging the catalyst temperatures T _{1 to} T ₅ of each part using the weights W _{1 to} W _5. (Step 108). That is, the representative temperature is calculated based on the above equation (1).

  According to the routine processing shown in FIG. 7 described above, the catalyst temperature at the portion where the catalytic reaction occurs most frequently can be reflected in the representative temperature regardless of the degree of deterioration of the catalyst 40. For this reason, an accurate and appropriate representative temperature can always be determined regardless of the degree of deterioration of the catalyst 40. In addition, the catalyst temperatures at other sites can also be included in the representative temperature with a weight according to the degree of contribution to emissions. For this reason, a more appropriate representative temperature can be obtained. As a result, in the system shown in FIG. 1, the estimation accuracy can be further improved in estimating the state of the catalyst 40, for example, the sulfur poisoning amount, the NOx occlusion amount, the oxygen occlusion amount, the deterioration degree, and the like.

  In the second embodiment described above, the ECU 50 executes the processing of steps 106 and 108, whereby the “representative temperature determining means” in the first and fourth inventions executes the processing of step 106. By doing so, the “determination method changing means” in the first, fourth and fifth inventions is realized.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 8 to FIG. 10. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit. The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 10 described later instead of the routine shown in FIG. 4 described above, using the hardware configuration shown in FIG.

[Features of Embodiment 3]
FIG. 8 and FIG. 9 are diagrams for explaining a method of obtaining the representative temperature of the catalyst 40 in the present embodiment, respectively. FIG. 8 shows a case where the catalyst 40 is nearly new, similar to FIG. 2 described above. FIG. 9 shows a case where the deterioration of the catalyst 40 has progressed to some extent, as in FIG. 3 described above. In this embodiment, according to the deterioration state of the catalyst 40, each of the first to fifth parts is determined as a deteriorated part and a non-deteriorated part (normal part), and the catalyst temperature of the part determined as a non-deteriorated part is determined. The representative temperature was calculated based on at least one.

As shown in FIG. 8, when the catalyst 40 is nearly new, each of the first to fifth parts is determined as a non-deteriorated part. Therefore, the representative temperature is determined based on at least one of the temperatures T _{1 to} T ₅ of the _{first to fifth} portions. On the other hand, as shown in FIG. 9, when it is determined that the deterioration has progressed to the second part, the third, fourth and fifth parts are determined as non-deteriorated parts. Therefore, the representative temperature is determined based on at least one of the temperatures T _{3 to} T ₅ of the _{third to fifth} portions.

[Specific Processing in Embodiment 3]
FIG. 10 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 10, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 10, first, as in the first embodiment, the oxygen storage capacity of the catalyst 40 is measured (step 100). Next, each part is discriminated as a deteriorated part and a non-deteriorated part according to the deterioration state determined from the oxygen storage capacity (step 110). For example, when the oxygen storage capacity has hardly decreased as compared with the value at the time of a new article, as shown in FIG. 8, it is determined that any part from No. 1 to No. 5 is a non-degraded part. On the other hand, when the oxygen storage capacity is lower than when it is new, it can be determined that the deterioration has progressed from the upstream portion as illustrated in FIG. Therefore, a part after any part is determined as a non-degraded part, and a part upstream from it is determined as a deteriorated part. In this case, the smaller the value of the oxygen storage capacity, the smaller the number of non-degraded parts.

If the deterioration part and the non-deterioration part are determined in the step 110, the representative temperature is calculated based on at least one of the catalyst temperatures of the non-deterioration part (step 112). For example, the representative temperature can be obtained by any one of the following methods.
(1) The average value (simple average or weighted average) of the catalyst temperatures of all non-deteriorated parts is used as the representative temperature.
(2) The catalyst temperature of a predetermined one of the non-deteriorated parts (for example, the most upstream part) is set as the representative temperature.
(3) The average value (which may be a simple average or a weighted average) of catalyst temperatures at some (but not all) sites selected from non-degraded sites is used as the representative temperature.

  According to the routine processing shown in FIG. 10 described above, the representative temperature can be obtained based on only the catalyst temperature of the non-deteriorated portion, excluding the catalyst temperature of the deteriorated portion of the catalyst 40. For this reason, an accurate and appropriate representative temperature can always be determined regardless of the degree of deterioration of the catalyst 40. For this reason, the effect similar to Embodiment 1 is acquired. That is, in estimating the state of the catalyst 40, for example, the sulfur poisoning amount, the NOx occlusion amount, the oxygen occlusion amount, the deterioration degree, etc., the estimation accuracy can be further improved.

  In the third embodiment described above, the ECU 50 executes the processing of steps 110 and 112, so that the “representative temperature determining means” in the first and sixth inventions executes the processing of step 110. By doing so, the “determination method changing means” in the first and sixth inventions are realized.

  Although Embodiments 1 to 3 of the present invention have been described above, the method for determining the catalyst representative temperature in the present invention is not limited to the methods of Embodiments 1 to 3. That is, in the method for determining the catalyst representative temperature in the present invention, the degree of contribution is larger as the catalyst temperature is higher in the portion where the catalytic reaction occurs, and the degree of contribution is lower as the portion is lower in the catalytic reaction. Thus, as long as the method for determining the representative temperature is changed, the method is not limited to the method of the first to third embodiments, and any method may be used.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. 4 is a diagram for explaining a method for obtaining a representative temperature of a catalyst in Embodiment 1. FIG. 4 is a diagram for explaining a method for obtaining a representative temperature of a catalyst in Embodiment 1. FIG. It is a flowchart of the routine performed in Embodiment 1 of the present invention. 6 is a diagram for explaining a method for obtaining a representative temperature of a catalyst in Embodiment 2. FIG. 6 is a diagram for explaining a method for obtaining a representative temperature of a catalyst in Embodiment 2. FIG. It is a flowchart of the routine performed in Embodiment 2 of this invention. 6 is a diagram for explaining a method of obtaining a representative temperature of a catalyst in Embodiment 3. FIG. 6 is a diagram for explaining a method of obtaining a representative temperature of a catalyst in Embodiment 3. FIG. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

10 Internal combustion engine 12 Intake passage 14 Exhaust passage 18 Throttle valve 26 Fuel injection valve 30 Spark plug 40 Catalyst 42 Oxygen sensor 50 ECU

Claims (9)

A catalyst disposed in the exhaust passage of the internal combustion engine;
Catalyst temperature acquisition means for dividing the catalyst into a plurality of parts and detecting or estimating the catalyst temperature for each part;
Representative temperature determining means for determining a representative temperature of the catalyst based on the catalyst temperature of at least one of the sites;
A catalyst deterioration state acquisition means for detecting or estimating the deterioration state of the catalyst;
With
The representative catalyst temperature acquisition device for an internal combustion engine, wherein the representative temperature determination unit includes a determination method change unit that changes a determination method of the representative temperature according to the deterioration state. The representative temperature determining means determines a catalyst temperature of one selected part selected from the plurality of parts as the representative temperature,
2. The catalyst representative temperature acquisition apparatus for an internal combustion engine according to claim 1, wherein the determination method changing means changes the selected portion according to the deterioration state.   3. The catalyst representative temperature acquisition device for an internal combustion engine according to claim 2, wherein the determination method changing means sets a portion closer to an outlet of the catalyst as the selected portion as the deterioration of the catalyst progresses. The representative temperature determining means calculates the representative temperature by performing a weighted average of the catalyst temperature of each part.
2. The catalyst representative temperature acquisition apparatus for an internal combustion engine according to claim 1, wherein the determination method changing means changes the weight for each part according to the deterioration state.   5. The catalyst representative temperature of the internal combustion engine according to claim 4, wherein the determination method changing means sets a portion where the weight is maximized as the catalyst is more deteriorated, closer to the outlet of the catalyst. Acquisition device. The determination method changing means discriminates each part into a deteriorated part and a non-degraded part according to the deterioration state,
The said representative temperature determination means determines the said representative temperature based on the catalyst temperature of at least one of the site | parts discriminate | determined from the said non-deterioration site | part, The catalyst representative temperature acquisition of the internal combustion engine of Claim 1 characterized by the above-mentioned. apparatus.   The catalyst deterioration state acquisition means includes means for detecting or estimating an air-fuel ratio downstream of the catalyst, HC concentration or exhaust gas temperature, or NOx storage capacity or oxygen storage capacity of the catalyst, and the detected or estimated value The catalyst representative temperature acquisition device for an internal combustion engine according to any one of claims 1 to 6, wherein the deterioration state is determined based on   The catalyst representative of the internal combustion engine according to any one of claims 1 to 7, wherein the catalyst deterioration state acquisition means determines the deterioration state based on at least one of the catalyst temperatures for each part. Temperature acquisition device.   According to the deterioration state, the determination method changing means increases the contribution to the catalyst temperature at a site where a large amount of catalytic reaction occurs, and decreases the contribution to a catalyst temperature at a site where the catalytic reaction is low. The catalyst representative temperature acquisition device for an internal combustion engine according to any one of claims 1 to 8, wherein the determination method is changed.

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