JP2015074985A - Control device for internal combustion engine - Google Patents

Abstract

Temperature drift that occurs in the output of an in-cylinder pressure detecting means during fuel cut is suppressed. A control apparatus for an internal combustion engine according to the present invention is applied to an internal combustion engine having an in-cylinder pressure detecting means for detecting an in-cylinder pressure. In this control apparatus, the temperature drift amount of the output of the in-cylinder pressure detecting means that is generated when the fuel cut of the internal combustion engine is started is estimated. When the fuel cut of the internal combustion engine is performed and the estimated temperature drift amount is larger than the reference, control for suppressing the temperature rise of the in-cylinder pressure detecting means is executed. [Selection] Figure 4

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device for an internal combustion engine including in-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine.

  For example, in Patent Document 1, when fuel cut of an internal combustion engine is performed, control is performed so that the minimum value of the in-cylinder pressure of each cylinder becomes the target minimum in-cylinder pressure set according to the viscosity or temperature of the engine oil. A system is disclosed. In this system, each cylinder is provided with an in-cylinder pressure sensor as in-cylinder pressure detecting means. For the control during the fuel cut, the value of the in-cylinder pressure detected according to the output of the in-cylinder pressure sensor is used.

JP 2004-162532 A Japanese Unexamined Patent Publication No. Sho 63-113163 JP 2011-163283 A Japanese Patent Laid-Open No. 2007-016609 JP 2013-155653 A

  During a transient operation such as when the internal combustion engine is fuel cut, the temperature change of the in-cylinder pressure sensor tends to increase. When a sudden temperature change occurs in the in-cylinder pressure sensor, a temperature drift occurs in the output of the in-cylinder pressure sensor, and an error occurs between the in-cylinder pressure detected according to the output of the in-cylinder pressure sensor and the actual in-cylinder pressure. There is. As a result, the control during the fuel cut using the in-cylinder pressure detected by the in-cylinder pressure sensor as in the system of Patent Document 1 may not be executed correctly.

  In addition, various controls such as idling stop and reduced-cylinder operation are considered due to the recent needs for low fuel consumption. Among these controls, control using the indicated torque calculated based on the output of the in-cylinder pressure sensor is used. There are many. When an error occurs in the output of the in-cylinder pressure sensor, the illustrated torque used for these controls may not be calculated correctly.

  Here, as a countermeasure against the temperature drift of the in-cylinder pressure sensor, it is conceivable to improve the structure of the in-cylinder pressure sensor itself. However, in general, the improvement of the structure for suppressing the temperature drift has a trade-off relationship with the pressure resistance of the in-cylinder pressure sensor, and there is a limit to cope with the temperature drift only by the improvement of the structure of the in-cylinder pressure sensor.

  The present invention has been made in view of the above points, and has improved the control device for an internal combustion engine so that the temperature drift of the in-cylinder pressure detecting means during fuel cut is reduced without changing the structure of the in-cylinder pressure detecting means. The purpose is to provide.

In order to achieve the above object, the present invention provides a control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine;
Drift estimating means for estimating a temperature drift amount of the output of the in-cylinder pressure detecting means, which is generated when fuel cut of the internal combustion engine is started;
Temperature suppression for executing control for suppressing temperature increase of the in-cylinder pressure detecting means when the fuel cut of the internal combustion engine is performed and the temperature drift amount estimated by the drift estimating means is larger than a reference Means,
Is provided.

  According to the present invention, the temperature rise of the in-cylinder pressure detecting means at the start of fuel cut is suppressed. As a result, temperature drift occurring in the output of the in-cylinder pressure detecting means during fuel cut can be suppressed to a small level, and the in-cylinder pressure can be detected with high accuracy even during fuel cut.

It is a schematic block diagram for demonstrating the whole structure of the system of Embodiment 1 of this invention. It is a figure for demonstrating the temperature drift of the cylinder pressure sensor before and behind a fuel cut start. It is a figure for demonstrating the relationship between the ignition timing retard amount and the temperature drift amount in Embodiment 1 of this invention. It is a figure for demonstrating the control in Embodiment 1 of this invention. It is a flowchart for demonstrating the control routine which ECU performs in Embodiment 1 of this invention. It is a flowchart for demonstrating the control routine which ECU performs in Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram for explaining the overall configuration of the system according to the first embodiment of the present invention. As shown in FIG. 1, the system according to the first embodiment of the present invention includes an internal combustion engine 10. The internal combustion engine 10 can be preferably used as a power source of, for example, a vehicle. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited. Each cylinder of the internal combustion engine 10 is provided with an intake valve 12, an exhaust valve 14, a spark plug 16, and an injector 18. An intake passage 22 is connected to the main body of the internal combustion engine 10 via an intake manifold, and an exhaust passage 24 is connected via an exhaust manifold. A throttle valve 26 is installed in the intake passage 22.

  An in-cylinder pressure sensor 28 (in-cylinder pressure detection means) is installed in each cylinder of the internal combustion engine 10. The in-cylinder pressure sensor 28 is a sensor that generates an output corresponding to the pressure in the cylinder, and can thereby detect the in-cylinder pressure.

  The system of the present embodiment includes an ECU (Electronic Control Unit) 30 as a control device. Various sensors such as the in-cylinder pressure sensor 28 described above and various actuators such as a spark plug 16 and a throttle valve 26 are connected to the ECU 30. The ECU 30 can control the operating state of the internal combustion engine 10 by driving each actuator according to a predetermined control program based on the output of each sensor.

  By the way, due to a temperature change or the like of the in-cylinder pressure sensor 28, a deviation may occur between the in-cylinder pressure based on the output of the in-cylinder pressure sensor 28 and the actual in-cylinder pressure. Such a shift in output caused by a temperature change is also called a temperature drift. For example, when the internal combustion engine 10 is in a fuel cut (hereinafter also referred to as F / C), the temperature around the in-cylinder pressure sensor 28 changes abruptly, especially during transient operation of the internal combustion engine 10. Temperature drift also increases.

  FIG. 2 is a diagram for explaining the temperature drift of the in-cylinder pressure sensor 28 before and after the start of F / C. As shown in FIG. 2, the value of the minimum in-cylinder pressure increases by ΔP before and after the start of F / C. This is considered to be a result of the temperature drift caused by the rapid drop in the in-cylinder temperature due to the start of F / C in the output of the in-cylinder pressure sensor 28. In the present embodiment, the change amount of the in-cylinder pressure based on the output of the in-cylinder pressure sensor 28 generated after the start of F / C is estimated as the drift index ΔP, and this is used as an index indicating the magnitude of the temperature drift of the in-cylinder pressure sensor 28. Use.

  The drift index ΔP can be estimated based on current operating conditions and transient conditions when shifting to F / C. The relationship between specific operating conditions and transient conditions and the drift index ΔP is obtained in advance by experiments, simulations, or the like. The correlation between the obtained operating conditions and transient conditions and the drift index ΔP is determined in advance as a map or the like and stored in the ECU 30.

  In the present embodiment, when the estimated drift index ΔP exceeds the reference value, control is performed to reduce the temperature of the in-cylinder pressure sensor 28 before the start of F / C. As a result, the occurrence of temperature drift in the output of the in-cylinder pressure sensor 28 is suppressed. Specifically, in the present embodiment, the temperature of the in-cylinder pressure sensor 28 is decreased by decreasing the temperature in the cylinder by the ignition timing retardation before the start of the F / C operation. Thereafter, F / C is executed.

  By the way, if the ignition timing is retarded rapidly, the temperature change in the cylinder increases, and the temperature drift of the cylinder pressure sensor 28 may increase. Therefore, the ignition timing retard amount is determined within a range in which the temperature drift of the in-cylinder pressure sensor 28 caused by the ignition timing retard is allowed.

  FIG. 3 is a diagram for explaining the relationship between the ignition timing retardation amount and the temperature drift amount in the first embodiment of the present invention. As shown in FIG. 3, the ignition timing retard amount and the temperature drift amount of the in-cylinder pressure sensor 28 have a certain correlation, and as the ignition timing retard amount increases, the temperature drift amount also increases. doing. Based on such a correlation, the ignition timing retardation amount ΔSA_α is determined so that the temperature drift amount of the in-cylinder pressure sensor 28 due to the ignition timing retardation is equal to or less than an allowable amount.

  Note that the relationship between the ignition timing retardation amount ΔSA and the temperature drift amount is obtained by experiment, simulation, or the like for each operating condition. Further, the allowable amount of temperature drift is appropriately set in consideration of the detection accuracy of the in-cylinder pressure. The ignition timing retardation amount ΔSA_α is set to a value corresponding to the allowable amount based on the obtained correlation for each operating condition.

  FIG. 4 is a diagram for describing the control in the first embodiment of the present invention. As shown in FIG. 4, when the drift index ΔP at the time of F / C request is larger than the reference value Ref, the first ignition retardation is performed. Further, the drift index ΔP is calculated based on the retarded ignition timing and the current operating condition, and the ignition timing is retarded step by step by the ignition timing retardation amount ΔSA_α until the calculated drift index ΔP becomes equal to or less than the reference value Ref. Repeat the delay. When it is recognized that the drift index ΔP has become equal to or less than the reference value Ref, F / C is started. The reference value Ref is a criterion set in advance with respect to the temperature drift at the time of F / C, and is a value set as appropriate.

  FIG. 5 is a flowchart for illustrating a control routine executed by ECU 30 in the first embodiment of the present invention. The routine of FIG. 5 is a routine that is repeatedly executed during operation of the internal combustion engine 10.

  In the routine of FIG. 5, it is first determined whether or not an F / C request has been issued (S100). Since the current control is a control for suppressing temperature drift during F / C, if there is no F / C request, the current routine ends. On the other hand, if it is recognized that an F / C request has been made, a drift index ΔP is then calculated (S102). The drift index ΔP is calculated according to a map or the like stored in the ECU 30 according to the current operating conditions.

  Next, it is determined whether or not the calculated drift index ΔP is greater than the reference value Ref (S104). The reference value Ref is a value that is set in advance and stored in the ECU 30. Here, if the drift index ΔP is equal to or less than the reference value Ref, it is recognized that the operating condition is such that the temperature drift does not exceed the criteria even if F / C is executed.

  If it is determined in step S104 that the drift index ΔP is greater than the reference value Ref, then the ignition timing is retarded (S106). The value of the ignition timing retardation amount ΔSA_α here is set to a value according to the current operating conditions and the allowable amount of temperature drift.

  Next, the drift index ΔP is recalculated according to the retarded ignition timing and other current operating conditions (S108). Next, it is determined whether or not the calculated drift index ΔP is equal to or less than the reference value Ref (S110). When it is not recognized that the drift index ΔP is less than or equal to Ref, the process returns to step S106 again. In step S110, the ignition timing retardation and the recalculation of the drift index ΔP are repeatedly performed until it is recognized that the drift index ΔP is equal to or less than the reference value Ref.

  On the other hand, if it is not determined in step S104 that the drift index ΔP is greater than the reference value Ref, or if it is determined in step S110 that the drift index ΔP is less than or equal to the reference value Ref, then F / C is executed (S112), and the current process ends.

  As described above, according to the system of the present embodiment, the temperature of the in-cylinder pressure sensor 28 is suppressed by suppressing the change in the in-cylinder temperature at the start of the F / C in which the in-cylinder pressure sensor 28 is likely to cause a temperature drift. Drift can be suppressed within an allowable range. Therefore, even if the in-cylinder temperature changes suddenly as at the start of F / C, the in-cylinder pressure can be detected with a certain degree of accuracy.

  By the way, in the present embodiment, the case where the ignition timing is retarded in order to suppress a sudden change in the in-cylinder temperature after the start of F / C has been described. However, the control for suppressing the decrease in the in-cylinder temperature in the present invention is not limited to this. For example, a control for reducing the fuel injection amount instead of the ignition timing retardation can be mentioned. Even when the fuel injection amount is reduced, a reduction amount within a range in which the temperature drift does not exceed the allowable amount is set for each operating condition. When there is an F / C request, the fuel injection amount is gradually reduced by a set amount of reduction until the drift index ΔP calculated according to the operating condition at each time point becomes equal to or less than the reference value Ref. The fuel injection amount may be reduced step by step.

  Further, both the fuel injection amount and the ignition delay angle may be performed. Also in this case, from the relationship between the ignition timing and the fuel injection amount and the temperature drift, the retard amount and the reduction amount are set for each operating condition so that the temperature drift falls within the allowable range, and the ignition timing retard and fuel injection are set. The amount may be reduced stepwise until the drift index ΔP becomes equal to or less than the reference value Ref.

  In the case where the ignition timing retardation and / or the fuel injection amount reduction is executed, the case where the retardation amount and / or the reduction amount corresponding to the allowable amount is set for each operation condition has been described. However, the present invention is not limited to this, and the retardation amount and / or the reduction amount may be a fixed value set according to the allowable amount.

  In the present embodiment, the “drift estimation unit” of the present invention is realized by executing the process of step S102 or S108, and the “temperature suppression unit” is realized by executing the process of step S106. To do.

Embodiment 2. FIG.
The system of the second embodiment has the same configuration as the system of FIG. Similar to the system of the first embodiment, the system of the present embodiment executes control for suppressing changes in the in-cylinder temperature during F / C. In the system of the first embodiment, the ignition timing retardation (or fuel injection amount reduction) is executed until the temperature drift does not exceed the criteria. However, if the F / C is performed after the ignition timing retardation as described above, the operating conditions adapted from the viewpoint of fuel consumption, drivability, emission, and the like are changed. Further, in the control of the first embodiment, it is considered that the execution of F / C is delayed and the fuel consumption is deteriorated.

  On the other hand, in the system according to the second embodiment, when there is an F / C request, the F / C is immediately executed. And simultaneously with F / C execution, the following control for suppressing the change in the in-cylinder temperature is performed.

  First, the throttle valve 26 is fully closed. Thereby, the inside of the intake passage 22 becomes a negative pressure. Further, the valve timing of the intake valve 12 is set to the most advanced angle state, and the valve timing of the exhaust valve 14 is set to the most retarded angle state. Thereby, the valve overlap can be maximized.

  As a result of the above control, at the same time as the start of F / C, fresh air does not enter the cylinder, and exhaust gas flows back into the cylinder. As a result, the in-cylinder temperature at the time of F / C, that is, rapid cooling of the in-cylinder pressure sensor 28 can be suppressed. Therefore, the temperature drift of the in-cylinder pressure sensor 28 at the time of F / C can be suppressed small.

  FIG. 6 is a flowchart for illustrating a control routine executed by ECU 30 in the second embodiment of the present invention. The routine of FIG. 6 is a routine that is repeatedly executed during operation of the internal combustion engine 10 instead of the routine of FIG. The routine in FIG. 6 is the same as the routine in FIG. 5 except that after the process in step S104, the process in steps S202 to S212 is performed instead of the process in steps S106 to S112.

  In step S104 of the routine of FIG. 6, when it is not recognized that the drift index ΔP is larger than the reference value Ref, F / C is immediately executed (S202), and the fuel supply is stopped. Thereafter, the current routine is temporarily terminated.

  On the other hand, if it is determined in step S104 that the drift index ΔP is greater than the reference value Ref, F / C is then executed (S208). Next, the throttle valve 26 is fully closed (S210), and the valve timing of the intake valve 12 is set to the most advanced angle and the valve timing of the exhaust valve 14 is set to the most retarded angle (S212). Thereafter, the current routine is temporarily terminated.

  As described above, according to the control of the second embodiment, the F / C can be executed immediately in response to the F / C request, and a sudden change in the in-cylinder temperature due to the F / C execution is suppressed. , Temperature drift of the in-cylinder pressure sensor 28 at the time of F / C can be suppressed.

  By the way, when the throttle valve 26 is fully closed or the valve timing of the intake / exhaust valves 12 and 14 is changed, the internal EGR may increase, making it difficult to start the next ignition. Therefore, in the present embodiment, these controls are executed only when the temperature drift is expected to exceed the criteria. As a result, it is possible to minimize the deterioration of the startability due to the fully closed throttle valve 26 and the change in the valve timing of the intake / exhaust valves 12 and 14.

  In the present embodiment, the “temperature suppression means” of the present invention is realized by executing the processing of steps S210 and S212.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the number referred to However, the present invention is not limited. The structures, steps, and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake valve 14 Exhaust valve 16 Spark plug 18 Injector 22 Intake passage 24 Exhaust passage 26 Throttle valve 28 In-cylinder pressure sensor 30 ECU

Claims (1)

In-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine;
Drift estimating means for estimating a temperature drift amount of the output of the in-cylinder pressure detecting means, which is generated when fuel cut of the internal combustion engine is started;
Temperature suppression for executing control for suppressing temperature increase of the in-cylinder pressure detecting means when the fuel cut of the internal combustion engine is performed and the temperature drift amount estimated by the drift estimating means is larger than a reference Means,
A control device for an internal combustion engine, comprising:

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