JP5035285B2 - Control device for an internal combustion engine with a supercharger - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine with a supercharger.

  Supercharged internal combustion engines are widely used. Since an internal combustion engine with a supercharger can generate a high output with a small displacement, it tends to be mounted on a vehicle having a larger vehicle weight than a naturally aspirated internal combustion engine with the same displacement. For this reason, in an internal combustion engine with a supercharger, a region with a higher load than that of a naturally aspirated internal combustion engine is used during acceleration. Further, in a vehicle equipped with an internal combustion engine with a supercharger, the gear setting of the transmission tends to be a low rotation and high load type in order to improve fuel efficiency.

JP 2006-348757 A JP 2001-90597 A JP-A-11-324758

  In the internal combustion engine with a supercharger, the smoldering of the spark plug is more likely to occur than in the naturally aspirated internal combustion engine due to the above-described use situation. Spark smoldering means that carbon adheres to the electrode of the spark plug. When carbon is attached to the electrode of the spark plug, the high voltage generated in the ignition coil escapes through the carbon and easily causes misfire.

  Moreover, in an internal combustion engine with a supercharger, as a factor that deteriorates smoldering of an ignition plug, traveling in a supercharging region immediately after starting at a cryogenic temperature can be mentioned. Immediately after starting at extremely low temperatures, the fuel is difficult to vaporize, so a large amount of fuel is increased to compensate for the amount of fuel vaporized. For this reason, if the vehicle runs in the supercharging region immediately after the cryogenic start and the amount of air in the cylinder increases, the amount of fuel injected into the low temperature cylinder becomes extremely large. As a result, the amount of fuel adhering to the wall surface and the spark plug increases, and the smoldering of the spark plug is thought to deteriorate.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine with a supercharger that can reliably suppress smoldering of a spark plug.

In order to achieve the above object, a first invention is a control device for an internal combustion engine with a supercharger,
A turbocharger,
An electronically controlled wastegate valve provided in a bypass passage that bypasses the turbine of the supercharger;
A cryogenic temperature judging means for judging whether or not the cooling water temperature of the internal combustion engine is in a cryogenic state lower than a predetermined temperature;
Air amount control that suppresses the in-cylinder air amount by opening the waste gate valve or limiting the opening of the throttle valve installed in the intake passage when it is determined that the cryogenic state is present Air amount suppression means for performing
Shift line changing means for compensating engine output by changing the shift line of the transmission so that the engine speed is higher than that in normal control when the air amount control is executed;
With
The shift line changing means sets an increase amount of the engine speed in consideration of an increase in friction due to an increase in the engine speed.

  According to the first aspect of the present invention, when the internal combustion engine with a supercharger is immediately after starting at a cryogenic temperature, the wastegate valve is opened or the opening of the throttle valve is limited to suppress the in-cylinder air amount. Air amount control can be performed. As a result, it is possible to avoid an excessive fuel injection amount into the cylinder by restricting the in-cylinder air amount immediately after the cryogenic start with a large amount of fuel increase. For this reason, the amount of fuel adhering to the wall surface and the spark plug can be reduced, and smoldering of the spark plug can be reliably suppressed. Further, according to the first aspect, when the air amount control is executed, the transmission shift line can be changed so that the engine speed is higher than that in the normal control. For this reason, even if the cylinder air amount is suppressed, the engine output can be compensated and the required output can be supplied. Further, when changing the shift line, an increase in the engine speed is set in consideration of an increase in friction caused by an increase in the engine speed. As a result, an acceleration feeling equivalent to that during normal control can be obtained. Further, since the engine speed is further increased and the electrode temperature of the spark plug can be further increased, smoldering of the spark plug can be more reliably suppressed.

It is a functional block diagram of the system of Embodiment 1 of this invention. It is a graph which shows the raise of the engine water temperature after a cryogenic start. It is a figure which shows the relationship between an engine load and an engine speed, and the electrode temperature of a spark plug. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a functional block diagram of the system according to the first embodiment of the present invention. The system of this embodiment includes an ECU 10. A supercharged internal combustion engine (hereinafter simply referred to as “engine”) to be controlled in the present embodiment is a direct-injection spark ignition internal combustion engine equipped with a turbocharger. It is assumed that the engine of this embodiment is mounted on a vehicle.

  In a bypass passage that bypasses the turbine of the turbocharger, a waste gate valve 12 that can be controlled to open and close by electronic control is provided. In addition to the waste gate valve 12, the ECU 10 includes a throttle valve 14 for adjusting the intake air amount, an ignition device 16 having an ignition plug, a fuel injection device 18 for injecting fuel into the cylinder, and an engine water temperature. A water temperature sensor 20 that detects (cooling water temperature), an air flow meter 22 that detects the intake air amount, a crank angle sensor 24 that detects the rotation angle of the crankshaft of the engine, and an automatic transmission 26 are electrically connected. Yes.

  When starting the engine at an extremely low temperature, the fuel is less likely to vaporize because the temperature in the cylinder is low. Therefore, a large amount of fuel is increased to compensate for the amount of fuel vaporized. For this reason, if the vehicle runs in the supercharging region immediately after the cryogenic start and the amount of air in the cylinder increases, the amount of fuel injected into the low temperature cylinder becomes extremely large. As a result, the amount of fuel adhering to the wall surface and the spark plug increases, and the smoldering of the spark plug deteriorates.

  In the present embodiment, in order to solve the above problem, air amount control is performed to suppress the amount of air in the cylinder from increasing immediately after the cryogenic start. Thereby, it is possible to prevent the amount of fuel injected into the cylinder in one cycle from becoming excessive. As a result, the amount of fuel adhering to the wall surface and the spark plug can be reduced, and the smoldering of the spark plug can be reliably suppressed.

  Examples of a method for suppressing the air amount in the air amount control include a method of opening the waste gate valve 12 or a method of limiting the opening of the throttle valve 14. When the waste gate valve 12 is opened, the increase in supercharging pressure is suppressed, so that the amount of air in the cylinder can be suppressed to a predetermined value or less. Further, when the opening degree of the throttle valve 14 is limited, the in-cylinder air amount is calculated based on the intake air amount detected by the air flow meter 22 and the engine speed detected by the crank angle sensor 24; The opening degree of the throttle valve 14 may be feedback-controlled so that the in-cylinder air amount becomes a predetermined value or less.

  FIG. 2 is a graph showing an increase in the engine water temperature after the cryogenic start. As shown in FIG. 2, in the present embodiment, after the cryogenic start, the air amount control is executed until the engine water temperature rises to a predetermined set value X ° C., and thereafter the normal control is performed. A region where the engine water temperature is lower than the set value X ° C. corresponds to a region where the fuel increase is large. In the region where the engine water temperature exceeds the set value X ° C., the amount of fuel increase is small, so that the smoldering of the spark plug does not deteriorate even if the air amount is not suppressed.

  When the air amount control is executed, the amount of air in the cylinder is suppressed, so that the engine torque is suppressed. For this reason, the required engine output may not be supplied. Therefore, in the present embodiment, during the execution of the air amount control, the shift line change control for changing the shift line of the automatic transmission 26 is executed so that the engine speed is higher than that during the normal control. As a result, the required engine output can be reliably supplied even during execution of the air amount control.

  In the shift line change control, it is desirable to increase the engine speed so that the intake air amount is equal to or higher than that during normal control.

  As the engine speed increases, engine friction increases. In particular, when the engine is cold, the viscosity of the oil is high, so the increase in friction is large. Therefore, in the shift line change control, the amount of increase in the engine speed is set so that an acceleration feeling equivalent to that in the normal control can be obtained in consideration of the friction increase due to the increase in the engine speed. This point will be described with reference to FIG.

  FIG. 3 is a graph showing the relationship between the engine load and the engine speed and the electrode temperature of the spark plug. In FIG. 3, the curve to the lower right indicates the electrode temperature of the spark plug, and the thicker the line, the higher the temperature. While the air amount control is being performed, the cylinder air amount is suppressed to a predetermined value or less, so that the engine load is suppressed to the upper limit load or less in FIG. The operating point indicated by white stars in FIG. 3 exceeds this upper limit load. For this reason, the engine cannot be operated at the operating point indicated by a white star while the air amount control is being executed. The broken line in FIG. 3 is an iso-output line connecting points where the engine output is equal to the operating point indicated by white stars. While the air amount control is being executed, if the engine speed is increased to the intersection A between the iso-output line and the upper limit load line, an output equivalent to the operating point indicated by the white star can be obtained. However, as described above, when the engine temperature is low, the amount of increase in friction accompanying the increase in engine speed is large. Therefore, in the shift line change control, the shift line is set so that the engine speed increases to a level higher than the intersection point A in order to obtain an acceleration feeling equivalent to that in the normal time in consideration of the increase width of the friction. It was decided to change. That is, control is performed so that the operating point of the engine becomes a hatched star in FIG.

  As shown in FIG. 3, as the engine speed increases, the electrode temperature of the spark plug tends to increase. Accordingly, the electrode temperature of the spark plug is higher at the shaded star point than the intersection A. In other words, as described above, by setting the allowance for increasing the engine speed in consideration of the increase in friction, the electrode temperature of the spark plug can be made higher. The higher the spark plug electrode temperature, the less likely the smoldering of the spark plug occurs. For this reason, according to this embodiment, the smoldering of a spark plug can be suppressed more reliably.

  FIG. 4 is a flowchart of a routine executed by the ECU 10 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time.

  According to the routine shown in FIG. 4, it is first determined whether or not the engine water temperature Tw detected by the water temperature sensor 20 is equal to or lower than a set value X ° C. (step 100). When the engine water temperature Tw exceeds the set value X ° C., the smoldering of the spark plug does not deteriorate even if the air amount is not suppressed. In this case, it is not necessary to perform the following processing, so the processing of this routine is terminated.

  On the other hand, if it is determined in step 100 that the engine water temperature Tw is equal to or lower than the set value X ° C., it can be determined that the amount of air needs to be suppressed because the smoldering of the spark plug is deteriorated. Therefore, in this case, air amount control for suppressing the air amount is executed (step 102). In this air amount control, as described above, the in-cylinder air amount is suppressed by opening the waste gate valve 12 or limiting the opening of the throttle valve 14.

  Subsequent to the process of step 102, shift line change control for changing the shift line of the automatic transmission 26 is executed (step 104). In step 104, as described with reference to FIG. 3, the shift line is changed in the direction in which the engine speed increases so that an acceleration feeling equivalent to that during normal control without air amount control can be obtained. The At this time, an allowance for increasing the engine speed is set in consideration of the increase in friction. When the processing of step 104 is performed, the processing after step 100 is executed again.

  In the first embodiment described above, the ECU 10 executes the process of step 100, so that the “extremely low temperature determination means” in the first invention executes the process of step 102. By executing the processing of step 104 described above, the “transmission line changing means” according to the first aspect of the present invention is realized.

10 ECU
12 Wastegate valve 14 Throttle valve 16 Ignition device 26 Automatic transmission

Claims (1)

A turbocharger,
An electronically controlled wastegate valve provided in a bypass passage that bypasses the turbine of the supercharger;
A cryogenic temperature judging means for judging whether or not the cooling water temperature of the internal combustion engine is in a cryogenic state lower than a predetermined temperature;
Air amount control that suppresses the in-cylinder air amount by opening the waste gate valve or limiting the opening of the throttle valve installed in the intake passage when it is determined that the cryogenic state is present Air amount suppression means for performing
Shift line changing means for compensating engine output by changing the shift line of the transmission so that the engine speed is higher than that in normal control when the air amount control is executed;
With
The control device for an internal combustion engine with a supercharger, wherein the shift line changing means sets an increase amount of the engine speed in consideration of an increase in friction due to an increase in the engine speed.

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