JP4640235B2 - How to adjust the variable nozzle opening of a turbocharger - Google Patents

Description

  The present invention relates to an adaptation method for setting an optimum variable nozzle opening degree at least for a specific engine operation state in an internal combustion engine equipped with a variable nozzle type turbocharger.

  In an internal combustion engine equipped with a variable nozzle turbocharger and an exhaust gas recirculation device (EGR device), etc., a throttle valve opening and recirculation exhaust for realizing good exhaust emission for each engine operating state determined by the rotational speed and load A combination of engine control parameters such as a gas amount control valve (EGR valve) opening degree is set by a conformance test in accordance with a predetermined priority order of each engine control parameter.

  When the internal combustion engine is a diesel engine, the fuel injection timing should be advanced to improve the fuel consumption rate if there is a margin in the exhaust emission in the combination of engine control parameters determined for each engine operating condition. (For example, refer patent document 1).

JP2004-124935 JP 2000-297673 A JP2000-240488 JP 2000-170580 A

  In the above-mentioned background art, the variable nozzle opening of the variable nozzle type turbocharger is not described in detail, but the variable nozzle opening in each engine operating state is the throttle valve opening and EGR that realize good exhaust emission. It is considered that the value is determined in advance before the valve opening is determined. Thereby, there is room for changing the predetermined variable nozzle opening degree so as to improve the fuel consumption rate while maintaining good exhaust emission.

  Accordingly, an object of the present invention is to provide an internal combustion engine having a variable nozzle type turbocharger and an exhaust gas recirculation device, at least in a specific engine operating state in advance so as to improve the fuel consumption rate without deteriorating exhaust emissions. To provide an adaptation method for setting an optimum variable nozzle opening by changing a variable nozzle opening of a determined turbocharger.

According to a first aspect of the present invention, there is provided a method for adapting a variable nozzle opening of a turbocharger in an internal combustion engine including a variable nozzle turbocharger and an exhaust gas recirculation device, at least in the specific engine operating state. a compatible method for setting a variable nozzle opening degree of the turbocharger, the the variable nozzle opening degree of the variable nozzle type turbocharger predetermined in a particular engine operating condition, throttling valve opening and re A combination of engine control parameters including the circulating exhaust gas amount control valve opening is set, and the predetermined variable nozzle opening is changed to the closed side with respect to the set combination, and the intake oxygen concentration or the exhaust is changed. so as not to change the gas recirculation rate or the intake air amount, by increasing the throttle valve opening, contact each variable nozzle opening That by measuring the fuel consumption rate, and the first test for searching the variable nozzle opening degree of the fuel consumption rate to a minimum, along with changing the variable nozzle opening degree predetermined to open side, intake oxygen concentration, or The fuel consumption rate is minimized by increasing the recirculation exhaust gas amount control valve opening and measuring the fuel consumption rate at each variable nozzle opening so as not to change the exhaust gas recirculation rate or the intake air amount. by performing at least one of the second test for searching the variable nozzle opening degree, determines the variable nozzle opening degree of the fuel consumption rate to a minimum, in the combination, a variable nozzle opening degree that is determine the set as a variable nozzle opening degree of the specific engine operating state, the first test, the absolute value of the fuel consumption rate or fuel consumption rate change rate of the value corresponding to the change in the variable nozzle opening is greater than the first set value The variable nozzle opening at this time is searched for as the variable nozzle opening that minimizes the fuel consumption rate, and the second test is performed for the change rate of the fuel consumption rate or the fuel consumption rate equivalent value with respect to the change of the variable nozzle opening. The variable nozzle opening when the absolute value is smaller than the first set value is searched for as the variable nozzle opening that minimizes the fuel consumption rate .

  The method for adapting the variable nozzle opening of the turbocharger according to claim 2 according to the present invention is the method for adapting the variable nozzle opening of the turbocharger according to claim 1, wherein the first test and the second test are: It is characterized in that one is performed first and then the other is also performed.

Adaptation method for a variable nozzle opening degree of the turbocharger of claim 3 of the present invention, in adaptation method for a variable nozzle opening degree of the turbocharger of claim 2, before Symbol of the first test and the second test On the other hand, when a variable nozzle opening that minimizes the fuel consumption rate is searched and the deviation between the searched variable nozzle opening and the predetermined variable nozzle opening is equal to or larger than a set deviation, the search is performed. The determined variable nozzle opening is determined as a variable nozzle opening that minimizes the fuel consumption rate, and the other of the first test and the second test is not performed.

Adaptation method for a variable nozzle opening degree of the turbocharger according to claim 4 of the present invention, in adaptation method for a variable nozzle opening degree of the turbocharger according to claim 2, by performing the first test, the variable nozzle The first test is stopped when the absolute value of the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change in the opening is equal to or greater than the second set value.

According to a fifth aspect of the present invention, there is provided a method for adapting a variable nozzle opening of a turbocharger according to a fifth aspect of the present invention, in the method for adapting a variable nozzle opening of a turbocharger according to the second aspect. and degree, if the variable nozzle opening which is searched by the second test are different, when the deviation of the fuel consumption rate corresponding to each larger than the third set value, a variable nozzle opening degree of the open side, the deviation Is smaller than the third set value , the closed variable nozzle opening is determined as the variable nozzle opening that minimizes the fuel consumption rate.

The method for adapting the variable nozzle opening of the turbocharger according to claim 6 according to the present invention is the method for adapting the variable nozzle opening of the turbocharger according to claim 2 , wherein the predetermined variable nozzle opening is When the variable nozzle type turbocharger is on the open side from the maximum efficiency opening, the first test is performed first, and when the variable nozzle type turbocharger is on the close side from the maximum efficiency opening, the second test is performed first. And

According to adaptation method of a variable nozzle opening degree of the turbocharger of claim 1 according to the present invention, the variable nozzle opening degree of the variable nozzle turbocharger predetermined in a particular engine operating condition, throttling valve opening A first test for setting a combination of engine control parameters including a degree of recirculation exhaust gas control valve opening, and changing a predetermined variable nozzle opening to a closed side with respect to the set combination; At least one of the second test for changing the determined variable nozzle opening to the open side is performed. In both the first test and the second test, in response to the change in the variable nozzle opening, the throttle valve opening or the recirculated exhaust gas amount control valve opening is changed to change the intake oxygen concentration that affects the exhaust emission or The exhaust gas recirculation rate or the intake air amount is not changed, and the variable nozzle opening that minimizes the fuel consumption rate without deteriorating the exhaust emission is searched. It can be set as the variable nozzle opening of the state. Here, in the first test, the variable nozzle opening when the absolute value of the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change of the variable nozzle opening is larger than the first set value is determined as the fuel consumption rate. Search for variable nozzle opening to minimize, the second test is variable nozzle when the absolute value of change rate of fuel consumption rate or fuel consumption rate equivalent value with respect to change of variable nozzle opening is smaller than the first set value The opening is searched as a variable nozzle opening that minimizes the fuel consumption rate. In general, when the variable nozzle opening is on the closed side, the fuel consumption rate becomes large. Therefore, the searched variable nozzle opening is the most closed variable nozzle opening that minimizes the fuel consumption rate. If such a variable nozzle opening is set as the variable nozzle opening in the specific engine operating state, not only the fuel consumption rate in the specific engine operating state is minimized, but also at the time of acceleration from the specific engine operating state, The control time for closing the variable nozzle to the desired opening is shortened, and the responsiveness of the variable nozzle turbocharger can be improved.

According to the method for adapting the variable nozzle opening of the turbocharger according to claim 2 according to the present invention, in the method of adapting the variable nozzle opening of the turbocharger according to claim 1, the first test and the second test are: After one is performed first, the other is also performed, so that the predetermined variable nozzle opening can be closed even if it is more open than the variable nozzle opening that minimizes the fuel consumption rate. Even in such a case, it is possible to reliably search for the variable nozzle opening that minimizes the fuel consumption rate.

According to the method for adapting the variable nozzle opening of the turbocharger according to claim 3 of the present invention, in the method of adapting the variable nozzle opening of the turbocharger according to claim 2, one of the first test and the second test is performed. If the deviation between the searched variable nozzle opening and the predetermined variable nozzle opening is equal to or larger than the set deviation when the variable nozzle opening that minimizes the fuel consumption rate is searched in FIG. Therefore, it is considered that there is no desired variable nozzle opening to be searched for in the remaining variable nozzle opening ranges, and the searched variable nozzle opening range is Is determined as the variable nozzle opening that minimizes the fuel consumption rate, and the time for the conformance test is shortened without performing the other of the first test and the second test.

According to the method for adapting the variable nozzle opening of the turbocharger according to claim 4 of the present invention, in the method for adapting the variable nozzle opening of the turbocharger according to claim 2 , the first test is carried out to make the variable When the absolute value of the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change in the nozzle opening is equal to or greater than the second set value, the desired variable nozzle opening to be searched for is a predetermined variable nozzle opening. It is thought that it exists in the open side from the degree, and the first test is stopped.

According to the method for adapting the variable nozzle opening of the turbocharger according to claim 5 of the present invention, the variable nozzle searched by the first test in the method of adapting the variable nozzle opening of the turbocharger according to claim 2. and opening, when the variable nozzle opening which is searched by the second test are different, when the deviation of the fuel consumption rate corresponding to each larger than the third set value, a variable nozzle opening degree of the open side, deviation When it is smaller than the third set value , the variable nozzle opening on the closed side is determined as the variable nozzle opening that minimizes the fuel consumption rate. As a result, when different variable nozzle openings are searched for in the first test and the second test, the variable nozzle openings are set with priority on improving the fuel consumption rate, and there is no significant difference in the fuel consumption rate. For example, the responsiveness of the variable nozzle turbocharger is set to be improved.

According to the method for adapting the variable nozzle opening of the turbocharger according to claim 6 of the present invention, in the method for adapting the variable nozzle opening of the turbocharger according to claim 2 , the predetermined variable nozzle opening is When the variable nozzle type turbocharger is on the open side with respect to the maximum efficiency opening, the first test is performed first, and when it is on the close side with respect to the maximum efficiency opening, the second test is performed first. The variable nozzle opening of a variable nozzle type turbocharger has a maximum efficiency opening, which does not necessarily minimize the fuel consumption rate, but should be searched near the maximum efficiency opening. Is often present. Thus, when the predetermined variable nozzle opening is on the open side from the maximum efficiency opening, the first test is performed first, and when the predetermined variable nozzle opening is on the closing side from the maximum efficiency opening, the second test is performed first. In this way, it is possible to search for a variable nozzle opening that improves the fuel consumption rate relatively early in the first test and the second test.

  FIG. 1 is a schematic view showing a part of an intake system and an exhaust system of an internal combustion engine to which a method for adapting a variable nozzle opening of a turbocharger according to the present invention is applied. In the figure, reference numeral 1 denotes a variable nozzle turbocharger 1 having a compressor 1 a disposed in the intake system 2 and a turbine 1 b disposed in the exhaust system 4. A variable nozzle 1c is arranged around the turbine 1b, and the supercharging pressure by the compressor 1a can be controlled by changing the flow rate of the exhaust gas flowing into the turbine 1b by the variable nozzle 1c.

  A throttle valve 3 is disposed on the upstream side of the compressor 1a of the intake system 2, and the downstream side of the compressor 1a of the intake system 2 is connected to an intake manifold IM of the internal combustion engine. On the other hand, the upstream side of the turbine 1b of the exhaust system 4 is connected to an exhaust manifold EM of the internal combustion engine. The upstream side of the turbine 1b of the exhaust system 4 and the downstream side of the throttle valve 3 of the intake system 2 (downstream side of the compressor 1a in FIG. 1) are connected by an exhaust gas recirculation device (EGR device) 5. The EGR device 5 is provided with a recirculation exhaust gas amount control valve (EGR valve) 6.

  In the internal combustion engine configured as described above, the throttle valve opening, the EGR valve opening, the fuel injection amount, and the fuel injection that realize good exhaust emission and low noise for each engine operating state determined by the rotational speed and load. Each engine control parameter combination such as timing (for diesel engines) or ignition timing (for spark ignition engines) must be set in the compliance test.

  Here, the opening degree of the variable nozzle 1c of the variable nozzle type turbocharger is empirically determined in advance for each engine operating state, and thus, with respect to the predetermined variable nozzle opening degree, the throttle valve opening degree and Each engine control parameter that achieves good exhaust emission and low noise in each engine operating state is implemented by measuring the exhaust emission and noise by slightly changing each engine control parameter such as EGR valve opening. Is set.

  However, in the combination of the engine control parameters for each engine operating state set in this way, there remains room for improving the fuel consumption rate by changing the predetermined variable nozzle opening. In the present embodiment, a sweep test for changing the variable nozzle opening is performed according to the flowchart shown in FIG. 2, and the variable nozzle opening that makes the fuel consumption rate good is searched and set anew.

  First, in step 101, the fuel consumption rate FC 'is measured in the operation with each engine control parameter set for the specific engine operation state. Next, in step 102, the variable nozzle opening D 'in the specific engine operating state is set as the variable nozzle opening D changed in step 103. In step 103, the variable nozzle opening D is decreased by d (closed side). As a result, the supercharging pressure of the compressor 1a increases, but the exhaust pressure in the exhaust system 4 on the upstream side of the variable nozzle 1c increases and the amount of exhaust gas recirculated through the EGR device 5 also increases. As a result, the oxygen concentration in the gas flowing into the cylinder (mixed gas of fresh air and recirculated exhaust gas) may be lower than before the variable nozzle opening is reduced. When the oxygen concentration is lowered in this way, exhaust emission deteriorates. Therefore, in step 104, the throttle valve opening is increased as necessary so that the oxygen concentration in the gas flowing into the cylinder to be estimated or measured does not change. Thus, deterioration of exhaust emission is prevented. If the throttle valve opening is almost fully opened, the EGR valve opening may be decreased to reduce the amount of recirculated exhaust gas so that the oxygen concentration in the gas flowing into the cylinder does not change.

  Next, in step 105, the fuel consumption rate FC in the operation at the current variable nozzle opening D and the current throttle valve opening (and the EGR valve opening) (other engine control parameters are not changed) is measured. . In step 106, it is determined whether or not the current variable nozzle opening D is 0% (fully closed), and the processing of steps 103 to 105 is repeated until this determination is affirmed. The fuel consumption rate FC for D is stored.

  If the determination in step 106 is affirmative, the variable nozzle opening D is again set to the variable nozzle opening D ′ that is predetermined for the specific engine operating state. In step 108, the variable nozzle opening D is increased by d (open side). As a result, the supercharging pressure of the compressor 1a is reduced, the exhaust pressure in the exhaust system 4 on the upstream side of the variable nozzle 1c is also reduced, and the amount of exhaust gas recirculated through the EGR device 5 is also reduced. As a result, the oxygen concentration in the gas flowing into the cylinder (mixed gas of fresh air and recirculated exhaust gas) may increase compared to before the variable nozzle opening is reduced. Even if the oxygen concentration increases, exhaust emission deteriorates. Therefore, in step 109, the EGR valve opening is increased as necessary, and the oxygen concentration in the gas flowing into the cylinder to be estimated or measured changes. To prevent deterioration of exhaust emissions.

  Next, at step 110, the fuel consumption rate FC in the operation at the current variable nozzle opening D and the current EGR valve opening (other engine control parameters are not changed) is measured. In step 111, it is determined whether or not the current variable nozzle opening D is 100% (fully opened), and the processing of steps 108 to 110 is repeated until this determination is affirmed. Is stored.

  Thus, in the specific engine operating state, the variable nozzle opening D can be changed from fully closed (0%) to fully open (100%) without deteriorating the exhaust emission, The fuel consumption rate FC is stored. Accordingly, if the variable nozzle opening D corresponding to the stored minimum value of the fuel consumption rate is set as the variable nozzle opening of the specific engine operation state, the fuel consumption rate in the specific engine operation state is improved. Can do. In the flowchart of FIG. 2, the change of the predetermined variable nozzle opening is performed first from the closed side (steps 103 to 105), but of course, it is performed first from the open side (steps 108 to 110). You may do it.

  At this time, when the throttle valve opening or the EGR valve opening is changed with respect to the variable nozzle opening corresponding to the minimum value of the fuel consumption rate in order to maintain good exhaust emission. In the combination of engine control parameters set for the specific engine operating state, the throttle valve opening or the EGR valve opening is also replaced with the changed value, and thus exhaust emission deteriorates in the specific engine operating state. There is no. Here, in order to maintain good exhaust emission when the variable nozzle opening is changed, the throttle valve opening or the EGR valve opening is changed to maintain the oxygen concentration in the gas supplied into the cylinder. However, for example, the EGR rate that is the ratio of the amount of recirculated exhaust gas and the amount of gas supplied into the cylinder (the sum of the amount of recirculated exhaust gas and the amount of fresh air) or the amount of fresh air itself is maintained. Even exhaust emissions will not deteriorate. Accordingly, the throttle valve opening or the EGR valve opening is controlled so that the estimated or measured EGR rate or fresh air amount is maintained before and after the change of the variable nozzle opening instead of the oxygen concentration. May be.

  By the way, as shown in FIG. 3, the fuel consumption rate FC is generally substantially constant and small when the variable nozzle opening D is on the open side, and when the variable nozzle opening D exceeds a predetermined value and closes. It changes so as to become larger as the closing side. If it is known that the predetermined variable nozzle opening is on the open side, for example, as shown by D1 in FIG. There is a high possibility that the variable nozzle opening does not exist, and the test for further opening the variable nozzle opening in steps 108 to 110 in FIG. 1 may be omitted. Further, if it is known that the predetermined variable nozzle opening is on the closed side, for example, as indicated by D2 in FIG. 3, there is a possibility that the desired variable nozzle opening does not exist on the further closed side. The test for further closing the variable nozzle opening in steps 103 to 105 in FIG. 1 may be omitted.

  In addition, if the change rate ΔFC / d of the fuel consumption rate with respect to the change in the variable nozzle opening is calculated in steps 105 and 110 in the flowchart of FIG. 2, for example, FIG. When D2 is a predetermined variable nozzle opening, if the variable nozzle opening is decreased by d from D2, the amount of change ΔFC in the fuel consumption rate before and after that increases, that is, the calculated fuel consumption rate The rate of change ΔFC / d is relatively large.

  Actually, there is no variable nozzle opening that makes the fuel consumption rate better on the closed side than the variable nozzle opening D2, so that when the fuel consumption rate change rate ΔFC / d is larger than the set value, It is not necessary to repeat steps 103 to 105 in the flowchart of FIG. 1, and it is preferable to shorten the conformance test time by stopping the test on the side where the variable nozzle opening is reduced. When not the fuel consumption rate but the fuel consumption rate equivalent value is measured, depending on the fuel consumption rate equivalent value (for example, the travel distance per unit fuel amount) when the variable nozzle opening is reduced from D2 by d, the variable nozzle The change rate of the fuel consumption rate equivalent value with respect to the change in the opening may be a negative value. In this case, when the absolute value is larger than the set value, the test for reducing the variable nozzle opening is stopped. You can do it.

  By the way, during engine acceleration, the variable nozzle opening is closed to a desired opening in order to increase the supercharging pressure. In this case, if the newly set variable nozzle opening is too open, the control time for closing to the desired opening becomes long, and the responsiveness of the variable nozzle turbocharger deteriorates. Thereby, the set variable nozzle opening is preferably set to the most closed opening for improving the fuel consumption rate, and the responsiveness of the variable nozzle turbocharger is preferably increased. In other words, the set variable nozzle opening is the variable nozzle opening on the direct opening side when the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change of the variable nozzle opening rapidly deteriorates (DS in FIG. 3). ) Is preferable.

  Specifically, in the test for reducing the variable nozzle opening to the closed side, if the fuel consumption rates measured continuously are FC1, FC2, and FC3, the first rate of change in fuel consumption rate (FC2-FC1) / d and the second rate of change (FC3−FC2) / d are calculated, and when the first rate of change is smaller than the set value and almost 0, and the second rate of change is larger than the set value, the rate of change of the fuel consumption rate is abrupt. At this time, the variable nozzle opening at which the fuel consumption rate is FC2 is determined as the variable nozzle opening at which the fuel consumption rate is good.

  In the test in which the variable nozzle opening is increased to the open side, the first rate of change (FC2-FC1) / d and the second rate of change (FC3-FC2) / d may be negative values. When the absolute value of the rate of change is larger than the set value and the absolute value of the second rate of change is smaller than the set value and becomes almost zero, the rate of change of the fuel consumption rate suddenly deteriorates. At this time, the fuel consumption rate Is determined as the variable nozzle opening degree that makes the fuel consumption rate good.

  When the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change in the variable nozzle opening rate suddenly deteriorates in one of the test for changing the variable nozzle opening degree to the closed side or the test for changing the variable nozzle opening side. If the deviation between the predetermined variable nozzle opening and the searched variable nozzle opening is equal to or larger than the set deviation when the variable nozzle opening on the directly open side is searched, it is within a certain variable nozzle opening range. In the remaining variable nozzle opening range, assuming that there is no desired variable nozzle opening to be searched, one of the subsequent tests is stopped and the other You may also cancel the test.

  In addition, as a result of performing both the test for changing the variable nozzle opening to the closed side or the test for changing the variable nozzle to the open side, the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change of the variable nozzle opening There are cases where the variable nozzle opening degree on the direct opening side when the temperature deteriorates rapidly is respectively searched. In this case, it is determined whether or not the deviation of the fuel consumption rate corresponding to the two variable nozzle openings is larger than the set value, and if this is affirmed, that is, the two fuel consumption rates have a relatively large difference. When there is a fuel consumption rate, give priority to the fuel consumption rate, select the variable nozzle opening corresponding to the smaller fuel consumption rate, that is, the open side of the two variable nozzle openings, and this particular engine operating state Is set as the variable nozzle opening.

  On the other hand, when the deviation of the fuel consumption rate corresponding to the two variable nozzle openings is smaller than the set value, that is, there is not much difference between the two fuel consumption rates, select the closed side of the two variable nozzle openings The response of the variable nozzle turbocharger during engine acceleration is improved.

  By the way, as the variable nozzle opening of the variable nozzle turbocharger, an opening that gives the maximum efficiency in design, that is, the maximum efficiency opening is set. The variable nozzle opening on the direct opening side when the rate of change of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change of the variable nozzle opening rapidly deteriorates is often located in the vicinity of the maximum efficiency opening. That is, when the predetermined variable nozzle opening is on the open side with respect to the maximum efficiency opening, a test for changing the variable nozzle opening to the close side is performed first, and on the close side with respect to the maximum efficiency opening. In some cases, it is preferable to first perform a test for changing the variable nozzle opening to the open side. Therefore, when searching for a variable nozzle opening on the direct opening side when the rate of change of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change of the variable nozzle opening rapidly deteriorates, the desired variable nozzle opening early If the subsequent test and the other test are stopped, the man-hours for the conformance test can be significantly reduced.

  In the above-described embodiment, the specific engine operation state has been described. Of course, the same applies to the other engine operation states. Thus, in each of the engine operation states, the predetermined variable nozzle opening is set to the fuel variable. It is preferable to reset the newly searched variable nozzle opening to improve the consumption rate.

It is the schematic which shows a part of intake system and exhaust system of an internal combustion engine to which the adaptation method of the variable nozzle opening degree of the turbocharger by this invention is applied. It is a flowchart which shows the adaptation method of a variable nozzle opening degree. It is a graph which shows the relationship between a variable nozzle opening degree and a fuel consumption rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Variable nozzle type turbocharger 1a Turbine 1b Compressor 1c Variable nozzle 2 Intake system 3 Throttle valve 4 Exhaust system 5 EGR device 6 EGR valve

Claims (6)

In an internal combustion engine having a variable nozzle turbocharger and an exhaust gas recirculation device, an adaptive method for setting a variable nozzle opening degree of the variable nozzle turbocharger at least in a specific engine operation state, the specific engine with respect to the variable nozzle type turbocharger variable nozzle opening degree of a predetermined in the operating state, to set the combination of engine control parameters including throttling valve opening degree and the recirculation exhaust gas amount control valve opening is set relative to the combined, the causes to change the variable nozzle opening degree predetermined to closing side, so as not to change the intake oxygen concentration, or exhaust gas recirculation rate or the intake air amount, increasing the throttle valve opening Te, by measuring the fuel consumption rate in the variable nozzle opening, a variable nozzle opening degree of the fuel consumption rate to a minimum A first test for search, the causes to change the variable nozzle opening degree predetermined to open side, so as not to change the intake oxygen concentration, or exhaust gas recirculation rate or the intake air amount, the recirculated exhaust gas quantity control valve By increasing the opening and measuring the fuel consumption rate at each variable nozzle opening, by performing at least one of the second test to search for the variable nozzle opening that minimizes the fuel consumption rate, the fuel determining a variable nozzle opening degree of the consumption rate to a minimum, in the combination, it sets the variable nozzle opening which is determine as a variable nozzle opening degree of the specific engine operating state, the first test, a variable nozzle opening The variable nozzle opening when the absolute value of the change rate of the fuel consumption rate or the fuel consumption rate equivalent value with respect to the change in the degree is greater than the first set value is searched as the variable nozzle opening that minimizes the fuel consumption rate In the second test, the variable nozzle opening when the absolute value of the change rate of the fuel consumption rate or the value corresponding to the fuel consumption rate with respect to the change of the variable nozzle opening is smaller than the first set value is expressed as the fuel consumption rate. A method for adapting a variable nozzle opening of a turbocharger, characterized by searching for a variable nozzle opening to be minimized .   The method for adapting a variable nozzle opening of a turbocharger according to claim 1, wherein one of the first test and the second test is performed after the first test is performed first. When a variable nozzle opening that minimizes the fuel consumption rate is searched for in one of the first test and the second test, a deviation between the searched variable nozzle opening and the predetermined variable nozzle opening is When the deviation is equal to or larger than the set deviation, the searched variable nozzle opening is determined as a variable nozzle opening that minimizes the fuel consumption rate, and the other of the first test and the second test is not performed. The method for adapting the variable nozzle opening of the turbocharger according to claim 2 . When the first test is performed and the absolute value of the change rate of the fuel consumption rate or the fuel consumption rate equivalent value with respect to the change in the variable nozzle opening is equal to or greater than the second set value, the first test is stopped. The method for adapting the variable nozzle opening of the turbocharger according to claim 2 . When the variable nozzle opening searched by the first test is different from the variable nozzle opening searched by the second test, when the deviation of the corresponding fuel consumption rate is larger than the third set value, The open variable nozzle opening is determined as a variable nozzle opening that minimizes the fuel consumption rate when the deviation is smaller than the third set value. Item 3. The method for adapting the variable nozzle opening of the turbocharger according to Item 2. When the predetermined variable nozzle opening is on the open side with respect to the maximum efficiency opening of the variable nozzle turbocharger, the first test is performed first, and when the predetermined variable nozzle opening is on the close side with respect to the maximum efficiency opening, the The method for adapting the variable nozzle opening of the turbocharger according to claim 2 , wherein the second test is performed first .

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