JP2007009807A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a combustion condition fine by controlling air fuel ratio optimally at a time of change over of a combustion mode in an internal combustion engine capable of changing over the combustion mode. <P>SOLUTION: This device is provided with a fuel injection valve 30 supplying fuel to the internal combustion engine 10, a combustion mode change over means changing over the combustion mode in a cylinder, a fuel injection quantity control means controlling fuel injection quantity from the fuel injection valve 30 according to the combustion mode, and a dulling process means dulling fuel injection quantity changing according to change over of the combustion mode at a time of change over of the combustion mode. Since fuel injection quantity can be changed according to change of quantity of fuel adhering on an intake valve or the like, air fuel ratio in the cylinder can be optimally controlled at a time of change over of the combustion mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Conventionally, for example, Japanese Patent Application Laid-Open No. 2003-120367 discloses a technique for changing a calculated fuel adhesion amount in response to switching between lean combustion and stoichiometric combustion in an internal combustion engine capable of switching between lean combustion and stoichiometric fuel. Has been.

JP 2003-120367 A JP-A-8-177556 Japanese Patent Laying-Open No. 2005-9467

  However, if it is assumed that the fuel injection amount is switched in response to lean combustion and stoichiometric combustion, if the calculation of the fuel injection amount is switched simultaneously with the switching of the combustion state, the fuel injection amount changes simultaneously with the switching, and the air-fuel ratio The problem that controllability deteriorates occurs. For this reason, there is a risk of causing problems such as a reduction in fuel consumption, a reduction in emissions, and a deterioration in drivability.

  The present invention has been made to solve the above-described problems. In an internal combustion engine capable of switching the combustion mode, the combustion state is controlled by optimally controlling the air-fuel ratio when the combustion mode is switched. The purpose is to improve.

In order to achieve the above object, a first invention provides a fuel injection valve for supplying fuel to an internal combustion engine,
Combustion mode switching means for switching the in-cylinder combustion mode, fuel injection amount control means for controlling the fuel injection amount from the fuel injection valve in accordance with the combustion mode, and switching of the combustion mode when switching the combustion mode And an annealing process means for performing an annealing process on the fuel injection amount that changes in response to the fuel injection amount.

  In a second aspect based on the first aspect, the fuel injection amount control means controls the fuel injection amount based on a basic injection amount and a correction value of the basic injection amount, and the annealing processing means comprises: An annealing process is performed on the correction value.

  According to a third aspect, in the second aspect, the smoothing processing unit performs a smoothing process so that the correction value changes with a first-order lag.

  According to a fourth invention, in any one of the first to third inventions, the combustion mode switching means switches the combustion mode between a lean combustion mode and a stoichiometric combustion mode.

  According to the first aspect of the invention, the smoothing process is performed on the fuel injection amount that changes in accordance with the switching of the combustion mode, so that the amount of fuel adhering to the intake valve, the intake port, the cylinder inner wall surface or the like is changed. The fuel injection amount can be changed. Therefore, it is possible to optimally control the air-fuel ratio in the cylinder when switching the combustion mode.

  According to the second aspect of the invention, the fuel injection amount is controlled based on the basic injection amount and its correction value, and the correction process is subjected to the smoothing process. Therefore, the fuel injection amount can be reliably subjected to the smoothing process. .

  According to the third aspect of the present invention, the amount of fuel adhering to the intake valve, the intake port, or the cylinder inner wall surface changes with a first-order lag, so that the correction value is subjected to a smoothing process so that the correction value changes with the first-order lag. The correction value can be varied in accordance with the change in the fuel adhesion amount at the time of mode switching. Therefore, the fuel injection amount at the time of switching the combustion mode can be controlled to an optimum value according to the change in the fuel adhesion amount.

  According to the fourth invention, in the internal combustion engine that switches the combustion mode between the lean combustion mode and the stoichiometric combustion mode, it is possible to optimally control the fuel injection amount at the time of switching.

  Several 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.

  FIG. 1 is a diagram for explaining a control device for an internal combustion engine according to an embodiment of the present invention and a structure around the control device. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. The air filter 16 is assembled with an intake air temperature sensor 18 for detecting the intake air temperature THA (that is, the outside air temperature). An exhaust purification catalyst 32 is disposed in the exhaust passage 14.

  An air flow meter 20 is disposed downstream of the air filter 16. A throttle valve 22 is provided downstream of the air flow meter 20. A throttle sensor 24 that detects the throttle opening degree TA and an idle switch 26 that is turned on when the throttle valve 22 is fully closed are disposed in the vicinity of the throttle valve 22.

  A surge tank 28 is provided downstream of the throttle valve 22. Further, a fuel injection valve 30 for injecting fuel into the intake port of the internal combustion engine 10 is disposed further downstream of the surge tank 28.

  The internal combustion engine 10 includes an intake valve 36 and an exhaust valve 38. The intake valve 36 is connected to a variable valve timing (VVT) 44 for changing the lift amount and / or the operating angle of the intake valve 36. An ignition plug is provided in the cylinder of the internal combustion engine 10 to ignite the fuel sprayed into the combustion chamber. Further, a piston 34 that reciprocates inside the cylinder is provided in the cylinder. Further, a water temperature sensor 42 for detecting the cooling water temperature is attached to the internal combustion engine 10.

  A crankshaft 36 that is rotationally driven by the reciprocating motion is connected to the piston 34. The vehicle drive system and accessories (air conditioner compressor, alternator, torque converter, power steering pump, etc.) are driven by the rotational torque of the crankshaft 36. A crank angle sensor 38 for detecting the rotation angle of the crankshaft 36 is attached in the vicinity of the crankshaft 36.

  As shown in FIG. 1, the control device of the present embodiment includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, ECU 40 includes a KCS sensor that detects the occurrence of knocking, and various sensors (not shown) for detecting vehicle speed, engine speed, exhaust temperature, lubricating oil temperature, catalyst bed temperature, and the like. It is connected. Further, the ECU 40 is connected to each actuator such as the fuel injection valve 30 and the variable valve mechanism 44 described above.

  In the system of the present embodiment configured as described above, the in-cylinder combustion mode is varied in accordance with the operating state of the internal combustion engine 10. That is, when the output required for the internal combustion engine 10 is relatively small, the fuel injection amount from the fuel injection valve 30 is suppressed so that the air-fuel ratio in the cylinder becomes leaner than the stoichiometric, and lean combustion is performed in the cylinder. Done. When the internal combustion engine 10 requires a high output, the air-fuel ratio in the cylinder is controlled to stoichiometric, and stoichiometric combustion is performed in the cylinder. Switching between lean combustion and stoichiometric combustion is performed based on parameters representing the operating state such as the engine speed Ne, the load factor KL, and the cooling water temperature Tw. According to the control by such two combustion modes, since the fuel injection amount from the fuel injection valve 30 is suppressed by lean combustion except during the operation where high output is required, fuel consumption can be improved, It becomes possible to improve the emission of exhaust gas.

  In the system of the present embodiment, the fuel injection amount from the fuel injection valve 30 is varied according to the operating state of the internal combustion engine 10. More specifically, the fuel injection amount is determined from the basic injection amount and its correction value. The basic injection amount is determined according to the intake air amount Ga. In the case of stoichiometric combustion, the air-fuel ratio is set to be stoichiometric with respect to the intake air amount Ga. In the case of lean combustion, the basic injection amount is set with respect to the intake air amount Ga. This value is set so that the air-fuel ratio becomes lean. The correction value is a value that is multiplied by the basic injection amount, and is calculated from the map based on various parameters that indicate the operation state such as the engine speed Ne, the load factor KL, the valve timing VT, and the cooling water temperature Tw. Is the value to be

  During operation of the internal combustion engine 10, fuel is injected into the intake port of the intake passage 12 by the fuel injection valve 30. Part of the fuel injected into the intake port adheres to the intake valve 36. When the internal combustion engine 10 is sufficiently warmed up and the intake valve 36 is at a high temperature, the adhering fuel is vaporized in a short time. Therefore, the influence of the adhering fuel amount is sucked into the cylinder. It does not extend greatly. That is, when the intake valve 36 is hot, the fuel injection amount from the fuel injection valve 30 substantially matches the fuel supply amount into the cylinder.

  However, under a situation where the temperature of the intake valve 36 is not sufficiently increased, a situation occurs in which the fuel adhering to the intake valve 36 is not completely vaporized during the opening period of the intake valve 36. In this case, with respect to the fuel injection amount from the fuel injection valve 30, the fuel supply amount into the cylinder is reduced by the amount of adhesion. Therefore, in order to accurately grasp the amount of fuel flowing into the cylinder, it is necessary to accurately estimate the proportion of fuel vaporized from the fuel adhering to the intake valve 36. The correction value described above corrects the basic injection amount in consideration of the influence of such fuel adhesion. Therefore, according to the system of the present embodiment, the amount of fuel sent into the cylinder can be optimally controlled even under conditions where fuel adheres to the intake valve 36 or the wall surface of the intake port.

  By the way, when the internal combustion engine 10 is operated by switching between two combustion modes of lean combustion and stoichiometric combustion as in the present embodiment, a situation occurs in which the amount of fuel attached to the intake valve 36 or the like differs in each combustion mode. This is due to the difference in the temperature of the intake valve 36 in both modes due to the difference in combustion energy between lean combustion and stoichiometric combustion.

  In the case of stoichiometric combustion, the combustion energy is larger than that in lean combustion, so the temperature of the intake valve 36 is higher than in the case of lean combustion. For this reason, the fuel adhering to the intake valve 36 is easily vaporized during the stoichiometric combustion, and the amount of fuel adhering to the intake valve 36 is smaller than in the case of lean combustion. Accordingly, in the case of lean combustion, it is necessary to increase the above-described correction value in consideration of the influence of adhesion, compared to the case of stoichiometric combustion.

  For this reason, in the present embodiment, two maps are used as the maps for calculating the correction values described above: a map for calculating correction values during stoichiometric combustion and a map for calculating correction values during lean combustion. When the combustion mode is switched between stoichiometric combustion and lean combustion, the map for calculating the correction value is simultaneously switched. Thereby, the fuel injection amount can be controlled to an optimum value according to the combustion mode, and the air-fuel ratio in the cylinder can be controlled to a desired value.

  In the system of the present embodiment, when the map is switched between stoichiometric combustion and lean combustion, a predetermined annealing process is performed on the correction value in order to avoid abrupt switching of the correction value. ing. Thereby, when the combustion mode is switched, the fuel injection amount can be prevented from changing abruptly, and the controllability of the air-fuel ratio can be prevented from being lowered.

  FIG. 2 is a characteristic diagram for explaining the annealing process performed when the combustion mode is switched. In FIG. 2, the horizontal axis indicates time, and the vertical axis indicates the fuel injection amount correction value. In the example of FIG. 2, it is assumed that switching from stoichiometric combustion to lean combustion is performed at time t0. In the vertical axis of FIG. 2, Mb is a correction value before switching the combustion mode, and indicates a correction value in stoichiometric combustion. In addition, Ma is a correction value after switching the combustion mode, and indicates a correction value in lean combustion. The correction value Mb is obtained from a map for calculating a correction value during stoichiometric combustion, and the correction value Ma is obtained from a map for calculating a correction value during lean combustion.

  When the combustion mode is switched from stoichiometric combustion to lean combustion at time t0, control for switching the correction value from Mb to Ma is performed. At this time, if the switching from the correction value Mb to the correction value Ma is instantaneously performed at the time t0, the correction value is rapidly switched, so that the controllability of the air-fuel ratio may be deteriorated.

  When the combustion mode is switched, the temperature of the intake valve 36 changes in accordance with the amount of heat generated in each combustion mode, but this temperature change is not instantaneous, but in time series according to the heat capacity of the intake valve 36 and the like. Changes. Under such circumstances, if the correction value of the fuel injection amount is switched instantaneously at the time of switching the combustion mode, the tracking of the temperature of the intake valve 36 is delayed with respect to the switching of the correction value. It becomes difficult to control the correction value in accordance with the change, that is, the change in the amount of fuel adhering to the intake valve 36. For this reason, a situation occurs in which the amount of fuel supplied into the cylinder cannot be optimally controlled when the combustion mode is switched.

  For this reason, in this embodiment, as shown in FIG. 2, the correction value is subjected to a smoothing process, and control is performed so that the correction value is gradually switched between times t0 and t1. This annealing process is performed in accordance with the temperature change of the intake valve 36 when the combustion mode is switched. Thereby, at the time of switching of the combustion mode, it becomes possible to optimally control the fuel injection amount in accordance with the change of the fuel adhesion amount at the intake valve 36.

More specifically, the correction value M after the time T1 has elapsed from the time t0 is calculated from the following equation (1).
M = (Mb−Ma) · exp (−T1 / T) + Ma (1)

  Equation (1) performs a first-order lag smoothing process on the correction value in accordance with the temperature change of the intake valve 36 when the combustion mode is switched. The temperature change of the intake valve 36 can be expressed by a first order lag, and the change of the correction value obtained from the equation (1) is also expressed by the first order lag. In the equation (1), T is a time constant, and the time constant when the temperature of the intake valve 36 changes is used. The time constant T is determined from a characteristic value such as the heat capacity of the intake valve 36. Therefore, according to the equation (1), the change in the correction value can be matched with the temperature change in the intake valve 36. Since the temperature of the intake valve 36 is a parameter representing the amount of fuel adhering to the intake valve 36, the correction value is varied in accordance with the temperature change of the intake valve 36, so that the correction value corresponds to the change in the amount of fuel adhering. Can be varied. Thereby, the fuel injection amount can be determined in consideration of the change in the fuel adhesion amount at the time of switching the combustion mode, and the controllability of the air-fuel ratio at the time of switching the combustion mode can be greatly improved.

  FIG. 3 is a characteristic diagram for explaining the annealing process performed at the time of switching of the combustion mode as in FIG. 2, and shows a case where switching from lean combustion to stoichiometric combustion is performed at time t0. In FIG. 3, Mb is a correction value before switching the combustion mode, and indicates a correction value in lean combustion. Further, Ma is a correction value after switching the combustion mode, and indicates a correction value in stoichiometric combustion. Also in the case of FIG. 3, the correction value M after the time T1 has elapsed from the time t0 can be calculated from the above-described equation (1). Therefore, as shown in FIG. 3, the correction value can be changed gradually when the combustion mode is switched, and the fuel injection amount can be changed in accordance with the change in the fuel adhesion amount, thereby improving the controllability of the air-fuel ratio. can do.

  Next, a processing procedure in the system of this embodiment will be described with reference to FIG. The process of FIG. 4 shows a process of calculating the correction value M, which has been subjected to the annealing process, for each cycle when the combustion mode is switched.

  First, in step S1, it is determined whether or not the combustion mode has been switched. That is, here, it is determined whether or not switching from lean combustion to stoichiometric combustion has been performed, or whether switching from stoichiometric combustion to lean combustion has been performed. If the combustion mode has been switched, the process proceeds to step S2, and if the switching has not been performed, the process is terminated (RETURN).

  In the next step S2, the correction value Mb before switching the combustion mode is acquired from the map. In the next step S3, the correction value Ma after switching the combustion mode is acquired from the map.

  In the next step S4, an elapsed time T1 after the switching of the combustion mode is obtained. In the next step S5, the correction value M at the time of the elapsed time T1 is calculated after switching the combustion mode based on the equation (1).

  In the next step 6, the time T0 is added to the elapsed time T1, and the value of T1 is updated. Here, the time T0 is a required time from the current cycle to the next cycle. In the next step S7, it is determined whether or not the correction value M calculated in step S5 has reached the corrected correction value Ma. If the correction value M has reached the correction value Ma, the process ends. (RETURN). On the other hand, if the correction value M has not reached the correction value Ma, the process returns to step S4, and the calculation of the correction value M is continued based on the value of T1 updated in step S6.

  According to the process of FIG. 4, the correction value can be gradually changed by performing the smoothing process on the correction value of the fuel injection amount when switching the combustion mode. Therefore, it is possible to suppress a sudden change in the fuel injection amount when switching the combustion mode, and it is possible to optimally control the air-fuel ratio at the time of switching.

  As described above, according to the present embodiment, since the fuel injection amount correction value is smoothed when the combustion mode is switched, it is possible to suppress a sudden change in the fuel injection amount during the switching. Become. This makes it possible to accurately control the air-fuel ratio when switching the combustion mode. Therefore, fuel consumption and drivability can be improved at the time of switching the combustion mode, and a reduction in emission can be suppressed.

  In the above description, the mode of performing the smoothing process on the correction value of the fuel injection amount has been described as an example. However, the present invention is not limited to this, and is caused by the amount of fuel adhering to the intake valve 36 and the like. Thus, the present invention can be applied to processing for all control amounts that change as a result. That is, the process of the present invention can be widely applied to the control amount controlled in accordance with the fuel adhesion amount.

  In the above description, an example in which the present invention is applied to the internal combustion engine 10 that injects fuel into the intake passage 12 is shown. However, the present invention is directed to the internal combustion engine 10 that directly injects fuel into the cylinder, or the intake passage. It is also possible to apply to the internal combustion engine 10 that injects fuel into both the cylinder 12 and the cylinder. In the case of the internal combustion engine 10 that directly injects fuel into the cylinder, the amount of fuel adhering in the cylinder changes in accordance with the temperature change of the piston 34. Therefore, when the time constant in the equation (1) is determined from the heat capacity of the piston 34, etc. By changing to a constant, the correction value smoothing process can be optimally performed. Further, in the case of the internal combustion engine 10 that injects fuel into both the intake passage 12 and the cylinder, each of the fuel injection amount into the intake passage 12 and the fuel injection amount into the cylinder is defined by a map, and the intake valve 36 It is preferable to perform the smoothing process on the correction value in each map using the time constant of the temperature change and the time constant of the temperature change of the piston 34.

It is a figure for demonstrating the structure of the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention, and its periphery. It is a characteristic view for demonstrating the annealing process performed at the time of switching of a combustion mode. It is a characteristic view for demonstrating the annealing process performed at the time of switching of a combustion mode. It is a flowchart which shows the procedure of the specific process which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 30 Fuel injection valve 40 ECU

Claims (4)

A fuel injection valve for supplying fuel to the internal combustion engine;
Combustion mode switching means for switching the combustion mode in the cylinder;
Fuel injection amount control means for controlling the fuel injection amount from the fuel injection valve in accordance with the combustion mode;
An annealing process means for performing an annealing process on the fuel injection amount that changes in accordance with the switching of the combustion mode when the combustion mode is switched;
A control apparatus for an internal combustion engine, comprising: The fuel injection amount control means controls the fuel injection amount based on a basic injection amount and a correction value of the basic injection amount,
2. The control apparatus for an internal combustion engine according to claim 1, wherein the annealing processing means performs an annealing process on the correction value.   The control apparatus for an internal combustion engine according to claim 2, wherein the smoothing processing means performs a smoothing process so that the correction value changes with a first-order delay.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the combustion mode switching means switches the combustion mode between a lean combustion mode and a stoichiometric combustion mode.

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