JP6069827B2 - Exhaust gas recirculation amount adjustment device - Google Patents

Description

  The present invention relates to an exhaust gas recirculation amount adjusting device for an exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine to an intake pipe as EGR gas.

  As one of the fuel efficiency improvement means of an internal combustion engine type engine, an exhaust gas recirculation device in which an exhaust pipe and an intake pipe are connected by an EGR gas flow path and a part of the exhaust gas flowing through the exhaust pipe is recirculated to the intake pipe as EGR gas (External EGR device) is known. And because of the demand for further improvement in fuel consumption from the market for reasons such as global warming countermeasures and economic efficiency, not only when the internal combustion engine type engine is under a low load but also when the internal combustion engine type engine is under a high load, EGR It is considered to improve the fuel consumption by refluxing the gas.

  Further, since the EGR gas can be recirculated to the intake pipe as the exhaust gas temperature is lower, it is necessary to sufficiently cool the EGR gas in order to increase the EGR gas amount at the time of high load. The exhaust gas temperature is lower on the downstream side (rear side) of the catalyst than on the upstream side (front side) of the catalyst provided in the exhaust pipe. Therefore, instead of recirculating part of the exhaust gas upstream of the catalyst as EGR gas as in the prior art, it is preferable to recirculate part of the exhaust gas downstream of the catalyst as EGR gas. It is said that it is effective to recirculate the EGR gas at the time of high load.

  Furthermore, when a part of the exhaust gas upstream of the catalyst is recirculated as EGR gas as in the prior art, deposits of incomplete combustion products generated by combustion of fuel in the internal combustion engine type engine in the exhaust gas ( The EGR gas is recirculated to the intake pipe in a state where the deposit is included. In this case, deposits may accumulate on the EGR cooler or EGR valve provided in the EGR gas flow path, leading to a malfunction. On the other hand, when a part of the exhaust gas downstream of the catalyst is recirculated as EGR gas, deposits in the exhaust gas are collected by the catalyst, so that the EGR gas with less deposits is recirculated to the intake pipe. Therefore, it is possible to reduce the possibility of causing a malfunction due to the deposit of the EGR cooler or the EGR valve.

JP-A-8-296482

  However, when the catalyst is deteriorated, not only the collection efficiency of the deposit by the catalyst is lowered, but also the catalyst washcoat may be peeled off from the catalyst substrate. For this reason, when part of the exhaust gas on the downstream side of the catalyst is recirculated to the intake pipe as EGR gas, the catalyst washcoat may bite into the EGR valve, causing the EGR valve to malfunction, and in the worst case It leads to destruction of the internal combustion engine type engine.

  The present invention has been made to solve the above-described problem, and in an exhaust gas recirculation device that recirculates a part of exhaust gas as EGR gas from the downstream side of the catalyst, there is a risk of causing malfunction of the EGR valve due to deterioration of the catalyst. It is an object of the present invention to provide an exhaust gas recirculation amount adjusting device capable of reducing the above.

In order to achieve this object , an embodiment of the present invention is an exhaust gas recirculation amount adjustment device for an exhaust gas recirculation device that returns a part of exhaust gas of an internal combustion engine to an intake pipe, the exhaust gas recirculation amount adjusting device being provided in the exhaust pipe. A catalyst for purifying gas, an EGR gas flow path connecting the downstream side of the exhaust pipe with respect to the catalyst and the intake pipe, and an EGR gas recirculation amount provided in the EGR gas flow path and recirculated to the intake pipe An EGR valve for adjusting the pressure, an upstream oxygen sensor provided upstream of the catalyst in the exhaust pipe to detect the amount of oxygen in the exhaust gas, and provided downstream of the catalyst in the exhaust pipe A downstream oxygen sensor for detecting the amount of oxygen in the exhaust gas; and an EGR gas recirculation amount limiting device for controlling the EGR valve, wherein the EGR gas recirculation amount limiting device includes the upstream oxygen sensor and the downstream oxygen sensor. A catalyst deterioration degree calculation / recording unit that calculates and records an actual measured value of the catalyst deterioration degree from the detection result of the sensor, and an EGR gas recirculation amount restriction instruction unit that instructs the EGR valve to restrict the EGR gas recirculation amount. The EGR gas recirculation amount restriction device records the actual catalyst deterioration degree for each driving cycle, and the actual catalyst deterioration degree for the previous driving cycle and the actual catalyst deterioration degree for the current driving cycle, When the catalyst deterioration degree average value is equal to or higher than a first predetermined value, EGR gas recirculation amount restriction is started, and the catalyst deterioration degree average value is a second predetermined value. When the value is less than the value, the restriction on the EGR gas recirculation amount is released.

  Moreover, the embodiment of the invention is characterized in that the EGR gas recirculation amount is limited by closing the EGR valve.

  Further, the embodiment of the present invention is characterized in that the EGR gas recirculation amount is limited by decreasing the recirculation ratio as the catalyst deterioration degree average value or the catalyst deterioration degree actual measurement value of the current driving cycle is higher.

  In the exhaust gas recirculation amount adjusting apparatus according to the present invention, it is possible to suppress the deposit that the catalyst could not be collected due to the deterioration of the catalyst and the catalyst member that has flowed out of the catalyst from flowing to the EGR valve. The possibility of causing a malfunction can be reduced.

FIG. 1 is a view showing an internal combustion engine type engine having an exhaust gas recirculation amount adjusting device according to an embodiment of the present invention. FIG. 2 is a block diagram showing details of the EGR gas recirculation amount limiting device 30 shown in FIG. FIG. 3 is a graph for explaining the actual catalyst degradation degree value Ddm. FIG. 4 is a flowchart for explaining the operation of the exhaust gas recirculation amount adjusting device having the EGR gas recirculation amount limiting device 30 shown in FIG. FIG. 5 is a block diagram showing an exhaust gas recirculation amount adjusting apparatus according to another embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the catalyst deterioration degree (actual catalyst deterioration degree measured value Ddm, catalyst deterioration degree average value Dda) and the reflux ratio. FIG. 7 is a flowchart for explaining the operation of the exhaust gas recirculation amount adjusting device shown in FIG. FIG. 8 is a block diagram showing an exhaust gas recirculation amount adjusting apparatus according to another embodiment of the present invention. FIG. 9 is a graph showing an example of the degree of catalyst deterioration (actual catalyst deterioration degree measured value Ddm, catalyst deterioration degree average value Dda) in each driving cycle. FIG. 10 is a flowchart for explaining the operation of the exhaust gas recirculation amount adjusting apparatus shown in FIG.

(First embodiment)
An exhaust gas recirculation amount adjusting device according to an embodiment of the present invention will be described with reference to FIG. An intake pipe 11 and an exhaust pipe 12 are connected to a cylinder 10 of the internal combustion engine. A catalyst 13 and a muffler 14 are provided in the exhaust pipe 12. The catalyst 13 purifies the exhaust gas. An EGR gas flow path 15 that connects the intake pipe 11 and the downstream side of the catalyst 13 of the exhaust pipe 12 is provided. The EGR gas flow path 15 recirculates the exhaust gas to the intake pipe 11. An EGR cooler 16 is provided in the EGR gas flow path 15. An EGR valve 17 is provided in the EGR gas flow path 15. The EGR valve 17 adjusts the EGR gas recirculation amount that is recirculated to the intake pipe 11. An air-fuel ratio sensor (A / F sensor) 21 is provided upstream of the catalyst 13 in the exhaust pipe 12. An oxygen sensor (O 2 sensor) 22 is provided downstream of the catalyst 13 in the exhaust pipe 12. An EGR gas recirculation amount limiting device 30 that controls the EGR valve 17 is provided. The EGR gas recirculation amount limiting device 30 is configured by a computer. The exhaust gas recirculation amount adjusting device includes an air-fuel ratio sensor 21, an oxygen sensor 22, and an EGR gas recirculation amount limiting device 30.

  The EGR gas recirculation amount limiting device 30 shown in FIG. 1 will be described with reference to FIG. The EGR gas recirculation amount restriction device 30 includes a catalyst deterioration degree calculation unit 31, a catalyst deterioration degree determination unit 32, and an EGR gas recirculation amount restriction instruction unit 33.

  The catalyst deterioration degree calculation unit 31 calculates a catalyst deterioration degree actual measurement value Ddm indicating the deterioration degree of the catalyst 13 based on the air-fuel ratio detected by the air-fuel ratio sensor 21 and the oxygen concentration detected by the oxygen sensor 22. That is, the catalyst deterioration degree calculation unit 31 sets T1 as the change period of the air-fuel ratio (oxygen concentration) detected by the air-fuel ratio sensor 21, and T2 as the change period of the oxygen concentration detected by the oxygen sensor 22. A catalyst degradation degree actual measurement value Ddm that is / T2 is calculated.

  With reference to FIG. 3, the actual catalyst degradation degree value Ddm will be described. 3A shows a temporal change in the output value of the air-fuel ratio sensor 21, and FIG. 3B shows a temporal change in the output value of the oxygen sensor 22. Curve (B) shows the temporal change in the output value of the oxygen sensor 22 when the catalyst 13 is normal, and curve B shows the temporal change in the output value of the oxygen sensor 22 when the catalyst 13 deteriorates. Show. Further, when the concentration of fuel in the exhaust gas is high (rich), the output values of the air-fuel ratio sensor 21 and the oxygen sensor 22 approach “1”, and conversely, when the fuel in the exhaust gas is thin (lean). In this case, the output values of the air-fuel ratio sensor 21 and the oxygen sensor 22 approach “0”. As can be seen from FIG. 3, as the catalyst 13 deteriorates, the change period of the output value of the oxygen sensor 22 becomes shorter and the amplitude becomes larger. This is because when the catalyst 13 deteriorates, the oxygen storage capacity of the catalyst 13 decreases, and the change in the oxygen concentration on the downstream side of the catalyst 13 approaches the change in the oxygen concentration on the upstream side of the catalyst 13. That is, when the deterioration of the catalyst 13 proceeds, the change period T2 of the output value of the oxygen sensor 22 shown in FIG. 3B approaches the change period T1 of the output value of the air-fuel ratio sensor 21 shown in FIG. The actually measured deterioration degree Ddm (T1 / T2) approaches 1. Therefore, the degree of deterioration of the catalyst 13 can be determined by obtaining the catalyst deterioration degree measured value Ddm.

  The catalyst deterioration degree determination unit 32 determines whether or not the catalyst deterioration degree actual measurement value Ddm is equal to or greater than 0.43 (first predetermined value) after the catalyst deterioration degree calculation unit 31 calculates the catalyst deterioration degree actual measurement value Ddm. to decide.

  The EGR gas recirculation amount restriction instruction unit 33 restricts the EGR gas recirculation amount by controlling the EGR valve 17 when the catalyst deterioration degree determination unit 32 determines that the actual catalyst deterioration degree Ddm is 0.43 or more. To do. In this case, the EGR gas recirculation amount restriction instruction unit 33 closes the EGR valve 17. The EGR gas recirculation amount restriction instructing unit 33 does not restrict the EGR gas recirculation amount when the catalyst deterioration degree determining unit 32 determines that the catalyst deterioration degree actual measurement value Ddm is less than 0.43. That is, the EGR gas recirculation amount restriction instruction unit 33 instructs the EGR valve 17 to restrict the EGR gas recirculation amount based on the determination by the catalyst deterioration degree determination unit 32.

The operation of the exhaust gas recirculation amount adjusting device having the EGR gas recirculation amount limiting device 30 shown in FIG. 2 will be described with reference to FIG.
First, the catalyst deterioration degree calculation unit 31 calculates the catalyst deterioration degree actual measurement value Ddm (step S11). Next, the catalyst deterioration degree determination unit 32 determines whether or not the catalyst deterioration degree actual measurement value Ddm is 0.43 or more (step S12). When the catalyst deterioration degree determination unit 32 determines that the catalyst deterioration degree actual measurement value Ddm is 0.43 or more, the EGR gas recirculation amount restriction instructing unit 33 restricts the EGR gas recirculation amount (step S13). On the other hand, when the catalyst deterioration degree determination unit 32 determines that the actual catalyst deterioration degree Ddm is less than 0.43, the EGR gas recirculation amount restriction instructing unit 33 does not restrict the EGR gas recirculation amount (step S14). This exhaust gas recirculation amount adjustment is performed every driving cycle (DC), that is, after the ignition switch is turned on and the internal combustion engine is started, and then the ignition switch is turned off and the internal combustion engine is stopped. Do it every time. In the driving cycle, when the EGR gas recirculation amount is restricted, the EGR valve 17 is kept closed, and when the EGR gas recirculation amount is not restricted, the EGR valve 17 is kept open.

  In this exhaust gas recirculation amount adjusting device, the EGR gas recirculation amount restriction instructing unit 33 controls the EGR valve 17 when the catalyst deterioration degree actual measurement value Ddm (catalyst deterioration degree) is 0.43 (first predetermined value) or more. Since the EGR gas recirculation amount is limited by controlling, it is possible to suppress the deposit that could not be collected due to deterioration of the catalyst 13 and the catalyst member that has flowed out of the catalyst 13 from flowing to the EGR valve 17. The risk of causing malfunction of the valve 17 can be reduced.

(Second Embodiment)
An EGR gas recirculation amount limiting device 30A of an exhaust gas recirculation amount adjusting device according to another embodiment will be described with reference to FIG. The EGR gas recirculation amount restriction device 30A includes a catalyst deterioration degree calculation unit 31, a catalyst deterioration degree determination unit 32A, and an EGR gas recirculation amount restriction instruction unit 33A. The catalyst deterioration degree calculation unit 31 of the EGR gas recirculation amount restriction device 30A is the same as the catalyst deterioration degree calculation unit 31 of the EGR gas recirculation amount restriction device 30.

  The catalyst deterioration degree determination unit 32A calculates whether or not the catalyst deterioration degree actual measurement value Ddm is equal to or greater than 0.15 (second predetermined value) after the catalyst deterioration degree calculation unit 31 calculates the catalyst deterioration degree actual measurement value Ddm. to decide.

  The EGR gas recirculation amount restriction instructing unit 33A restricts the EGR gas recirculation amount by controlling the EGR valve 17 when the catalyst deterioration degree determining unit 32A determines that the catalyst deterioration degree actual measurement value Ddm is 0.15 or more. To do. FIG. 6 shows the relationship between the actual catalyst degradation degree value Ddm (catalyst degradation degree) and the reflux ratio (the ratio of the limited EGR gas reflux amount to the EGR gas reflux amount when the catalyst 13 is normal) in this case. Further, the EGR gas recirculation amount restriction instructing unit 33A does not restrict the EGR gas recirculation amount when the catalyst deterioration degree determining unit 32A determines that the catalyst deterioration degree actual measurement value Ddm is less than 0.15.

The operation of the exhaust gas recirculation amount adjusting device having the EGR gas recirculation amount limiting device 30A shown in FIG. 5 will be described with reference to FIG.
First, the catalyst deterioration degree calculation unit 31 calculates the catalyst deterioration degree actual measurement value Ddm (step S21). Next, the catalyst deterioration degree determination unit 32A determines whether or not the catalyst deterioration degree actual measurement value Ddm is 0.15 or more (step S22). When the catalyst deterioration degree determination unit 32A determines that the catalyst deterioration degree actual measurement value Ddm is equal to or greater than 0.15, the EGR gas recirculation amount restriction instruction unit 33A restricts the EGR gas recirculation amount (step S23). On the other hand, when the catalyst deterioration degree determination unit 32A determines that the catalyst deterioration degree actual measurement value Ddm is less than 0.15, the EGR gas recirculation amount restriction instruction unit 33A does not restrict the EGR gas recirculation amount (step S24). In these cases, when the actual catalyst deterioration degree Ddm is 0.15 or less, the reflux ratio is set to 100%. When the actual catalyst deterioration degree Ddm exceeds 0.15, the higher the actual catalyst deterioration degree Ddm is, the higher the catalyst deterioration degree Ddm is. The reflux ratio is reduced, and when the actual catalyst deterioration degree Ddm is 0.43 or more, the reflux ratio is set to 0%. The exhaust gas recirculation amount adjustment is performed for each driving cycle. In the driving cycle, when the EGR gas recirculation amount is limited, the EGR valve 17 is kept at a predetermined opening degree, and when the EGR gas recirculation amount is not limited, the EGR valve 17 is left fully opened. And

  In the exhaust gas recirculation device that recirculates a part of the exhaust gas from the downstream side of the catalyst 13 as EGR gas, the higher the catalyst deterioration degree of the catalyst 13, the more the deposits and catalyst members that flow out of the catalyst 13 flow into the EGR valve 17. However, in this exhaust gas recirculation amount adjusting device, when the catalyst deterioration degree measured value Ddm (catalyst deterioration degree) exceeds 0.15 (second predetermined value), the catalyst deterioration degree measured value Ddm is high. Since the recirculation ratio is reduced as much as possible, it is possible to appropriately reduce the possibility of causing an EGR valve malfunction due to catalyst deterioration, and to improve fuel efficiency.

(Third embodiment)
An EGR gas recirculation amount limiting device 30B of an exhaust gas recirculation amount adjusting device according to another embodiment will be described with reference to FIG. The EGR gas recirculation amount limiting device 30B includes an ignition switch determination unit 34, a post-start time determination unit 35, a catalyst deterioration degree calculation / recording unit 36, a catalyst deterioration degree average value calculation unit 37, a restriction continuation state determination part 38, and a restriction release. It has a determination unit 39, a restriction start determination unit 40, an EGR gas recirculation amount restriction instruction unit 33B, and a restriction continuation state recording unit 41.

  The ignition switch determination unit 34 determines whether or not the ignition switch 23 is on.

  When the ignition switch determination unit 34 determines that the ignition switch 23 is on, the post-start time determination unit 35 determines whether or not a predetermined time has elapsed after the engine is started.

  When the post-start time determination unit 35 determines that a predetermined time has elapsed after the engine is started, the catalyst deterioration degree calculation / recording unit 36 calculates the catalyst deterioration degree actual measurement value Ddm and records the catalyst deterioration degree actual measurement value Ddm. Therefore, the actual catalyst degradation degree value Ddm is recorded for each driving cycle.

  After the catalyst deterioration degree calculation / recording unit 36 records the actual catalyst deterioration degree value Ddm, the catalyst deterioration degree average value calculation unit 37 records the catalyst deterioration degree actual value Ddm recorded so far and the currently recorded catalyst deterioration degree Ddm. An average value of actually measured values Ddm, that is, a catalyst deterioration degree average value Dda is calculated.

  The restriction continuation state determination unit 38 determines whether or not the restriction continuation state recording unit 41 records the “restriction continuation state” after the catalyst deterioration degree average value calculation unit 37 calculates the catalyst deterioration degree average value Dda. To do.

  When the restriction continuation state determination unit 38 determines that the restriction continuation state recording unit 41 records the “restriction continuation state”, the restriction release determination unit 39 determines whether or not to release the restriction on the EGR gas recirculation amount. It is determined whether or not the catalyst deterioration degree average value Dda is less than 0.15 (second predetermined value). FIG. 9 shows an example of the actual measured catalyst degradation degree value Ddm (line A) and the average catalyst degradation degree value Dda (line B) for each driving cycle.

  When the restriction continuation state determination unit 38 determines that the restriction continuation state recording unit 41 does not record the “restriction continuation state”, the restriction start determination unit 40 determines whether to start limiting the EGR gas recirculation amount, that is, It is determined whether or not the catalyst deterioration degree average value Dda is 0.43 (first predetermined value) or more.

  The EGR gas recirculation amount restriction instruction unit 33 </ b> B controls the EGR valve 17 based on the determinations of the restriction release determination unit 39 and the restriction start determination unit 40. That is, when the restriction release determining unit 39 determines that the catalyst deterioration degree average value Dda is equal to or greater than 0.15, that is, when it is determined that the restriction on the EGR gas recirculation amount is not released, and the restriction start determining unit 40 determines the degree of catalyst deterioration. When the average value Dda is determined to be equal to or greater than 0.43, that is, when it is determined to start limiting the EGR gas recirculation amount, the EGR gas recirculation amount restriction instructing unit 33B controls the EGR valve 17 to thereby return the EGR gas recirculation amount. Limit the flow. Further, when the restriction release determination unit 39 determines that the catalyst deterioration degree average value Dda is less than 0.15, that is, when the restriction release determination unit 39 determines to release the restriction on the EGR gas recirculation amount, and the restriction start determination unit When it is determined that the catalyst deterioration degree average value Dda is less than 0.43, that is, when it is determined not to start limiting the EGR gas recirculation amount, the EGR gas recirculation amount restriction instructing unit 33B restricts the EGR gas recirculation amount. do not do.

  The restriction continuation state recording unit 41 records whether or not it is in the restriction continuation state after the EGR gas recirculation amount restriction instruction unit 33B controls the EGR valve 17. That is, when the restriction release determination unit 39 determines not to release the restriction on the EGR gas recirculation amount, and when the restriction start determination unit 40 determines to start limiting the EGR gas recirculation amount, the restriction continuation state recording unit 41 indicates “ “Limit continuation state” is recorded, and when the restriction release determination unit 39 determines that the restriction on the EGR gas recirculation amount is released, and when the restriction start determination unit 40 determines that the restriction on the EGR gas recirculation amount is not started, the restriction continues. The state recording unit 41 does not record the “restricted continuation state”, but erases it if the “restricted continuation state” is recorded.

The operation of the exhaust gas recirculation amount adjusting device having the EGR gas recirculation amount limiting device 30B shown in FIG. 8 will be described with reference to FIG.
First, the ignition switch determination unit 34 determines whether or not the ignition switch 23 is on (step S31). When the ignition switch 23 is not on, the ignition switch determination unit 34 repeatedly determines whether or not the ignition switch 23 is on. When the ignition switch determination unit 34 determines that the ignition switch 23 is on, the post-start time determination unit 35 determines whether or not a predetermined time has elapsed after the engine is started (step S32). When the post-start time determination unit 35 determines that a predetermined time has elapsed after the engine is started, the catalyst deterioration degree calculation / recording unit 36 calculates the catalyst deterioration degree actual measurement value Ddm, and records the catalyst deterioration degree actual measurement value Ddm (step). S33). After the catalyst deterioration degree calculation / recording unit 36 records the catalyst deterioration degree actual measurement value Ddm, the catalyst deterioration degree average value calculation unit 37 calculates the catalyst deterioration degree average value Dda (step S34).

  After the catalyst deterioration degree average value calculation unit 37 calculates the catalyst deterioration degree average value Dda, the restriction continuation state determination unit 38 determines whether or not the restriction continuation state recording unit 41 records “restriction continuation state”. (Step S35). When the restriction continuation state determination unit 38 determines that the restriction continuation state recording unit 41 records the “restriction continuation state”, the restriction release determination unit 39 determines whether to release the restriction on the EGR gas recirculation amount. (Step S36). On the other hand, when the restriction continuation state determination unit 38 determines that the restriction continuation state recording unit 41 does not record “limit continuation state”, the restriction start determination unit 40 determines whether or not to start limiting the EGR gas recirculation amount. Judgment is made (step S37).

  Then, the EGR gas recirculation amount restriction instructing unit 33B determines that when the restriction cancellation determining unit 39 determines that the catalyst deterioration degree average value Dda is 0.15 or more, that is, when it is determined not to cancel the restriction on the EGR gas recirculation amount. When the restriction start determining unit 40 determines that the catalyst deterioration degree average value Dda is 0.43 or more, that is, when it is determined to start limiting the EGR gas recirculation amount, the ignition switch 23 is controlled by controlling the EGR valve 17. The EGR valve 17 is kept closed until is turned off, and the EGR gas recirculation amount is limited (step S38). Further, the EGR gas recirculation amount restriction instructing unit 33B determines that the restriction release determining unit 39 determines that the catalyst deterioration degree average value Dda is less than 0.15, that is, determines that the restriction on the EGR gas recirculation amount is to be released, and When the restriction start determination unit 40 determines that the catalyst deterioration degree average value Dda is less than 0.43, that is, when it is determined not to start limiting the EGR gas recirculation amount, the EGR valve 17 is turned on until the ignition switch 23 is turned off. The open state is maintained, and the EGR gas recirculation amount is not limited (step S39). After the EGR gas recirculation amount restriction instruction unit 33B controls the EGR valve 17, the restriction continuation state recording unit 41 records whether or not the restriction continuation state is in effect (step S40).

  When the EGR gas recirculation amount restriction instruction unit 33B restricts the EGR gas recirculation amount, if the catalyst deterioration degree average value Dda exceeds 0.15, the higher the catalyst deterioration degree average value Dda, the smaller the recirculation ratio. When the catalyst deterioration degree average value Dda is 0.43 or more, the reflux ratio may be set to 0%.

  In this exhaust gas recirculation amount adjusting device, when there is a possibility that the catalyst 13 is deteriorated, the EGR gas recirculation amount is limited to reduce the possibility of causing the malfunction of the EGR valve 17, and When it can be determined that the catalyst has not deteriorated, the restriction on the EGR gas recirculation amount can be released, so that the fuel consumption can be improved.

  When the post-start time determination unit 35 determines that a predetermined time has elapsed after the engine is started, the catalyst deterioration degree calculation / recording unit 36 calculates the catalyst deterioration degree actual measurement value Ddm, so that the temperature of the internal combustion engine increases. After that, since the actual catalyst degradation degree value Ddm can be calculated, the accurate actual catalyst degradation degree value Ddm can be calculated.

(Other embodiments)
In the above embodiment, the first predetermined value is 0.43 and the second predetermined value is 0.15. However, the first predetermined value and the second predetermined value may be other values.

  In the above embodiment, the air-fuel ratio sensor 21 and the oxygen sensor 22 are used as the upstream oxygen sensor and the downstream oxygen sensor. However, an oxygen sensor provided upstream of the catalyst 13 is used as the upstream oxygen sensor. An air-fuel ratio sensor provided downstream of the catalyst 13 may be used as the downstream oxygen sensor. In addition, as the upstream oxygen sensor and the downstream oxygen sensor, any sensor that can detect the amount of oxygen in the exhaust gas can be used.

  In the first embodiment, when the catalyst deterioration degree determination unit 32 determines that the catalyst deterioration degree actual measurement value Ddm is 0.43 (first predetermined value) or more, the EGR gas recirculation amount restriction instruction unit. 33 restricts the EGR gas recirculation amount, but the EGR gas recirculation amount may be restricted when the catalyst deterioration degree determination unit determines that the catalyst deterioration degree average value Dda is equal to or greater than the first predetermined value. That is, in the first embodiment, the catalyst deterioration degree actual measurement value Ddm is used as the catalyst deterioration degree, but the catalyst deterioration degree average value Dda may be used as the catalyst deterioration degree.

  In the second embodiment, when the catalyst deterioration degree determination unit 32A determines that the catalyst deterioration degree actual measurement value Ddm is 0.15 (second predetermined value) or more, the EGR gas recirculation amount restriction instruction unit. Although 33A limits the EGR gas recirculation amount, the EGR gas recirculation amount may be limited when the catalyst deterioration degree determination unit determines that the catalyst deterioration degree average value Dda is equal to or greater than the second predetermined value. In this case, the higher the catalyst deterioration degree average value Dda, the smaller the reflux ratio. That is, in the second embodiment, the actual catalyst deterioration degree value Ddm is used as the catalyst deterioration degree, but the catalyst deterioration degree average value Dda may be used as the catalyst deterioration degree.

  In the third embodiment, when the catalyst deterioration degree average value Dda exceeds 0.15, the higher the catalyst deterioration degree average value Dda, the smaller the recirculation ratio, and the catalyst deterioration degree average value Dda becomes smaller. When the ratio is 0.43 or more, the reflux ratio is set to 0%, but when the actual catalyst deterioration degree Ddm of the current driving cycle exceeds 0.15, the actual catalyst deterioration degree Ddm of the current driving cycle is high. The reflux ratio may be decreased as much as possible, and the reflux ratio may be set to 0% when the actual catalyst deterioration degree Ddm of the current driving cycle is 0.43 or more.

  The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but includes all embodiments that provide the same effects as those intended by the present invention. Further, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but may be defined by any desired combination of particular features among all the disclosed features. .

  DESCRIPTION OF SYMBOLS 11 ... Intake pipe, 12 ... Exhaust pipe, 13 ... Catalyst, 15 ... EGR gas flow path, 17 ... EGR valve, 21 ... Air-fuel ratio sensor, 22 ... Oxygen sensor, 23 ... Ignition switch, 30, 30A, 30B ... EGR gas Reflux amount limiting device, 31 ... Catalyst deterioration degree calculating section, 32, 32A ... Catalyst deterioration degree determining section, 33, 33A, 33B ... EGR gas recirculation amount limiting instruction section, 34 ... Ignition switch determining section, 35 ... Post-start time determination , 36 ... Catalyst deterioration degree calculation / recording part, 37 ... Catalyst deterioration degree average value calculation part, 38 ... Restriction continuation state determination part, 39 ... Restriction release determination part, 40 ... Restriction start determination part, 41 ... Restriction continuation state record Part

Claims (3)

An exhaust gas recirculation amount adjusting device of an exhaust gas recirculation device for returning a part of exhaust gas of an internal combustion engine to an intake pipe,
A catalyst for purifying the exhaust gas provided in the exhaust pipe, an EGR gas flow path connecting the intake pipe downstream of the catalyst and the intake pipe, and the intake pipe provided in the EGR gas flow path An EGR valve that adjusts the EGR gas recirculation amount to be recirculated, an upstream oxygen sensor that is provided upstream of the catalyst in the exhaust pipe and detects the amount of oxygen in the exhaust gas, and the catalyst in the exhaust pipe A downstream oxygen sensor that is provided on the downstream side to detect the amount of oxygen in the exhaust gas, and an EGR gas recirculation amount limiting device that controls the EGR valve,
The EGR gas recirculation amount limiting device calculates a catalyst deterioration degree actual measurement value from the detection results of the upstream oxygen sensor and the downstream oxygen sensor, records the catalyst deterioration degree calculation / recording unit, and records the catalyst deterioration degree in the EGR valve. An EGR gas recirculation amount restriction instruction unit for instructing restriction of the EGR gas recirculation amount;
The EGR gas recirculation amount limiting device records the actual value of the catalyst deterioration degree for each driving cycle, and the actual value of the catalyst deterioration degree for the previous driving cycle and the actual value of the catalyst deterioration degree for the current driving cycle are recorded. An average catalyst deterioration degree average value is calculated, and when the catalyst deterioration degree average value is equal to or greater than a first predetermined value, EGR gas recirculation amount restriction is started, and the catalyst deterioration degree average value is a second predetermined value. The exhaust gas recirculation amount adjusting device is configured to release the restriction on the EGR gas recirculation amount when the amount is less than the predetermined value. The exhaust gas recirculation amount adjusting device according to claim 1 , wherein the EGR gas recirculation amount is limited by closing the EGR valve. 2. The exhaust gas recirculation amount according to claim 1 , wherein the restriction on the EGR gas recirculation amount is such that the recirculation ratio decreases as the average value of the catalyst deterioration degree or the actual measurement value of the catalyst deterioration degree of the current driving cycle increases. Adjustment device.

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