JP2007064032A - Control device and control method for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce and avoid adhesion of deposit to a fuel injection valve or an ignition plug, by promoting scavenging in engine start. <P>SOLUTION: In this control device, when an engine stop requirement is detected (S10), a fuel injection amount is increased (S14). When an actual engine speed rNe reaches a target engine speed tNe (S15), the fuel injection is stopped (S16). Then, throttle opening TVO is increased (S17) to increase a fresh air amount introduced into a combustion chamber, and the tumble flow control valve 17 is closed to reinforce the tumble flow (S18). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine suitably used for an automobile, and more particularly to control when the engine is stopped.

In Patent Document 1, in order to enable starting of an internal combustion engine without a starter, when an engine stop request is received, the throttle opening is increased and the fresh air amount is increased until the crankshaft is stationary. Discloses a technique for controlling the rotational position when the crankshaft is stopped and enhancing scavenging of residual gas in the combustion chamber.
JP 2004-162707 A

  FIG. 4 shows the stop of fuel injection in response to an engine stop request, that is, the engine speed at the time of fuel cut (crankshaft speed) and the remaining gas corresponding to the amount of unburned gas remaining in the combustion chamber, that is, residual gas. It shows the relationship with the rate. As shown in the figure, when the engine speed at the time of fuel cut is relatively high (for example, 1000 rpm or more), the crankshaft rotates relatively much due to inertia, so that almost no residual gas remains. On the other hand, when the engine speed is relatively low (for example, less than 1000 rpm), the amount of residual gas, that is, the residual gas rate, tends to increase rapidly as the engine speed decreases when the fuel is cut. Usually, since the engine is in an idle operation state immediately before the engine is stopped, if the fuel cut is performed in response to the engine stop request in the idle rotation state controlled to an idle rotation speed of about 600 to 800 rpm, the crankshaft is stopped. In other words, it can rotate only about 3 revolutions by inertia, and the residual gas rate of the combustion gas remaining in the cylinder becomes high. For this reason, residual gas, unburned fuel, soot, etc. may adhere to the spark plug and the fuel injection valve, leading to clogging of the fuel injection valve and smoldering of the spark plug. Further, if there is a large amount of residual gas, the startability of the next engine will be reduced.

  Patent Document 1 described above discloses a technique for increasing scavenging by increasing the throttle opening when a request for stopping the engine is received. However, simply increasing the throttle opening causes engine rotation at the time of fuel cut. When the number is low, a sufficient amount of fresh air cannot be secured, and a sufficient scavenging promoting effect cannot be obtained.

  The present invention has been made in view of such problems, and by introducing a large amount of fresh air into the combustion chamber immediately before the engine is stopped, the scavenging function in the combustion chamber is enhanced, and a fuel injection valve or The main purpose is to reduce or eliminate deposit adhesion to the spark plug.

  In a control apparatus for an internal combustion engine, comprising: an electronic throttle that opens and closes an intake passage for introducing fresh air into a combustion chamber of the internal combustion engine; and a fuel injection device that injects fuel into the intake passage or the combustion chamber. Stop request detection means for detecting a request, fuel cut means for stopping fuel injection to stop the engine, and increase in engine speed between detection of the engine stop request and stop of fuel injection by the fuel cut means Therefore, scavenging promotion for increasing the throttle opening so as to increase the amount of fresh air introduced into the combustion chamber after stopping the fuel injection by the fuel cut means and the speed increasing means for increasing the fuel injection amount And means.

  As described above, according to the present invention, the fuel injection amount is increased before the fuel cut to increase the engine speed, and the throttle opening is increased after the fuel cut. A large amount of fresh air can be introduced. Therefore, a large amount of fresh air can be introduced into the combustion chamber immediately before the engine stops, and the scavenging function in the combustion chamber can be strengthened, and deposit adhesion to the fuel injection valve and the spark plug can be reduced or eliminated.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a system configuration of an internal combustion engine 1 according to the present invention.

  A piston 12 is fitted in the cylinder 11 so as to be movable up and down, and a combustion chamber 13 is defined above the piston 12. An intake passage 14 for introducing fresh air and an exhaust passage 15 for discharging the gas after combustion are connected to the combustion chamber 13. The intake passage 14 is opened and closed by the intake valve 3, and the exhaust passage 15 is opened and closed by the exhaust valve 4. An ignition plug 9 is disposed substantially at the upper center of the combustion chamber 13, and the air-fuel mixture in the combustion chamber 13 is sparked by the ignition plug 9.

  The intake system is provided with an electronically controlled throttle 2 that opens and closes an intake passage 14, and fuel that injects fuel into an intake port 14 </ b> A connected to the combustion chamber 13 of each cylinder 11 downstream of the throttle 2. A fuel injection valve 8 as an injection device is provided. Further, a tumble control valve (TCV) 17 as an intake flow control valve for controlling the tumble flow of the intake air flowing into each combustion chamber 13 is provided on the upstream side of the slit plate 16 that divides the intake port 14A into upper and lower parts. Yes.

  As various sensors for detecting the engine operating state, a rotational speed sensor 18 for detecting the engine rotational speed, an accelerator opening sensor 19 for detecting the opening degree of the accelerator pedal corresponding to the driver's acceleration request / acceleration intention, and the like are provided. ing. The engine control unit (control unit: C / U) 10 is mainly composed of a microcomputer and has a function of storing and executing various control processes, that is, detection signals and operations from the various sensors described above. A control signal is output to the fuel injection valve, the spark plug 9, the throttle 2, the tumble control valve 17 and the like based on a signal from the ignition key 20 operated by a person to control its operation.

  FIG. 2 is a flowchart showing a flow of engine stop control according to the present embodiment, and FIG. 3 is a time chart thereof. The routine in FIG. 2 is started by the engine control unit 10 when an engine stop request is received in step 10. A time T0 in FIG. 3 corresponds to an engine stop request. The engine stop request is output when, for example, the ignition key 20 is operated to the OFF position corresponding to the engine stop.

  In step 11, it is determined whether or not the operation state requires scavenging promotion control which will be described later. In other words, depending on the previous engine operating state, is it in a state where coking occurs, is a state where a lot of soot is accumulated, or is it necessary to reduce the residual gas and improve the next engine startability? Etc. are determined. If the scavenging promotion control is not necessary, the routine proceeds from step 11 to step 12, where the fuel injection is immediately stopped, that is, the fuel is cut, and this routine is terminated. After the fuel cut, the crankshaft will stop after several turns due to inertia.

  If the exhaust promotion control is necessary, the process proceeds from step 11 to step 13 to set the target rotational speed rNe at the time of fuel cut T1 (see FIG. 3). This target rotational speed tNe corresponds to the rotational speed at which the crankshaft can rotate due to inertia so that scavenging in the combustion chamber 13 is sufficiently performed after the fuel cut, and is higher than at least the idle rotational speed (about 600 to 800 rpm). The value is, for example, about 1200 rpm (see FIG. 4). This target rotational speed tNe may be a fixed value or may be sequentially set based on the engine temperature or the like.

  In the following step 14, the rotation speed increase control is executed. In general, since the engine stop request is received in a state where the engine speed is low as in the idling operation state, in this step 14, the engine speed is increased toward a predetermined target speed tNe. Specifically, based on the deviation between the actual rotational speed rNe and the target rotational speed tNe, the throttle speed is adjusted so that the actual rotational speed rNe of the internal combustion engine detected by the rotational speed sensor 18 increases toward the target rotational speed tNe. 2 is controlled to increase, and the fuel injection amount is controlled to increase according to the throttle opening TVO. Specifically, as shown in FIG. 3, the throttle opening TVO is increased from the opening TVOi corresponding to the idle rotation speed to the predetermined rotation speed increase opening TVOup, and the fuel injection amount is rotated from the idle injection amount TPi to the predetermined rotation. It increases to the number rising injection amount TPup.

  In step 15, it is determined whether the actual rotational speed rNe has reached the target rotational speed tNe. When the actual rotational speed rNe reaches the target rotational speed tNe, the process proceeds to step 16. In this step 16, the fuel injection from the fuel injection valve 8 is stopped, so-called fuel cut. T1 in FIG. 3 corresponds to the fuel cut time. In step 17, the opening degree TVO of the throttle 2 is increased, more specifically, fully opened. In step 18, in order to strengthen the tumble flow in the combustion chamber 13, the tumble control valve (TCV) 17 is closed.

  In step 19, it is determined whether the engine stop has been completed, specifically, whether the crankshaft that has been rotated due to inertia has stopped. This determination may be made simply by determining whether a predetermined time ΔT (see FIG. 3) has elapsed since the fuel cut. When the engine stop is completed, the routine proceeds to step 20, where the control for increasing the throttle opening TVO and the closing control for the tumble control valve 17 in steps 17 and 18 are finished, that is, the throttle opening TVO and the tumble control valve 17 are initialized. Return to this routine. T2 in FIG. 3 corresponds to the time when the engine stop is completed.

  As described above, according to the present embodiment, when the engine stop request is received, the fuel injection amount is increased before the fuel cut T1 to increase the engine rotational speed, and then the fuel is cut, and after the fuel cut T1. The throttle opening TVO is increased (fully opened) to promote scavenging. In this way, by increasing the engine speed at the time of the fuel cut T1 to about 1200 rpm, for example, the amount of crankshaft rotation after the fuel cut T1 can be increased, and the throttle opening TVO after the fuel cut T1. Therefore, scavenging can be performed reliably by introducing a large amount of fresh air into the combustion chamber 13. As a result, unburned fuel and unburned gas remaining in the combustion chamber 13 and the intake port 14A can be reduced / eliminated, and deposit adhesion to the fuel injection valve 8 and the spark plug 9 can be suppressed / avoided. . In addition, since a large amount of fresh air flows after the fuel cut, discharge of deposits adhering to the fuel injection valve 8 and the spark plug 9 is also promoted.

  In particular, after the fuel cut, the throttle opening TVO is fully opened and the tumble control valve 17 is closed, whereby the tumble flow in the combustion chamber 13 can be strengthened and the scavenging effect can be further improved.

  The characteristic technical idea of the present invention and its operational effects that can be grasped from the above description will be described with reference to the above-described embodiment. However, the present invention is not limited to the configuration of the embodiment given the reference numerals, and includes various modifications and changes without departing from the spirit thereof. For example, the intake flow control valve is not limited to the tumble control valve 17 that imparts the tumble flow as in the above-described embodiment, and for example, a swirl control valve that imparts the swirl flow may be used. In the above embodiment, the present invention is applied to a port injection type internal combustion engine that injects fuel into an intake port. However, the present invention is also applied to an in-cylinder direct injection internal combustion engine that injects fuel directly into a combustion chamber. Can be applied.

  (1) An electrically controlled throttle 2 that opens and closes an intake passage 14 that introduces fresh air into the combustion chamber 13 of the internal combustion engine 1, and a fuel injection device 8 that injects fuel into the intake passage 14 or the combustion chamber 13. In the control apparatus for an internal combustion engine, a stop request detecting means (ignition key 20, step 10) for detecting an engine stop request, a fuel cut means (step 16) for stopping fuel injection to stop the engine, and the engine stop Between the request detection (timing) T0 and the stop of fuel injection T1 by the fuel cut means, in order to increase the engine speed, a speed increase means (step 14) for increasing the fuel injection amount, and the fuel cut means Scavenging promoting means (step 17) for increasing the throttle opening TVO so as to increase the amount of fresh air introduced into the combustion chamber 13 after the fuel injection is stopped by To have.

  As described above, when the engine stop request T0 is received, the fuel injection amount is increased to increase the engine speed, the fuel is cut, and after the fuel cut, the throttle opening TVO is increased to promote scavenging. A large amount of fresh air can be introduced into the combustion chamber 13. As a result, unburned fuel and unburned gas remaining in the combustion chamber 13 and the intake port 14A can be surely scavenged, and deposit adhesion to the fuel injection valve 8 and the spark plug 9 can be suppressed / eliminated.

  (2) The throttle opening TVO is preferably fully opened by the scavenging promoting means so that the scavenging effect is maximized.

  (3) Preferably, the intake flow control valve 17 that imparts a flow component to the intake air by closing a part of the intake passage 14 and the flow enhancement that closes the intake flow control valve 17 after the stop of the fuel injection T1. Means (step 18). Thus, the intake flow control valve 17 is closed after the fuel cut to strengthen the intake flow component, thereby further improving the deposit and residual gas discharge effect, that is, the scavenging effect.

  (4) More preferably, it is provided with a rotation speed detection means (rotation speed sensor 18) for detecting the actual rotation speed rNe of the internal combustion engine. In the rotation speed increase means (step 14), the target rotation speed tNe and the actual rotation speed tNe. And the throttle opening TVO is increased and the fuel injection amount is increased. As a result, the actual rotational speed rNe can be accurately raised to the target rotational speed tNe in a short time after the detection of the engine stop request.

  (5) The internal combustion engine is a spark ignition type internal combustion engine provided with an ignition plug 9 for spark ignition of an air-fuel mixture in a combustion chamber 13 such as a gasoline engine.

  (6) An internal combustion engine including a throttle 2 for opening and closing an intake passage 14 for supplying fresh air into the combustion chamber 13 of the internal combustion engine 1 and a fuel injection device 8 for injecting fuel into the combustion chamber 13 or the intake passage 14. In the control method of the engine 1, step 10 for detecting the engine stop request, step 14 for increasing the fuel injection amount to increase the engine speed when the engine stop request is detected, and fuel injection for engine stop. Step 16 for stopping and Step 17 for increasing the throttle opening TVO so as to increase the amount of fresh air introduced into the combustion chamber 13 are included. According to this method, as in the above (1), unburned fuel and unburned gas remaining in the combustion chamber 13 and the intake port 14A are surely scavenged, and deposits adhere to the fuel injection valve 8 and the spark plug 9. Can be suppressed or eliminated.

1 is a system configuration diagram showing an internal combustion engine according to an embodiment of the present invention. The flowchart which shows the flow of control at the time of the engine stop of a present Example. Time chart when the engine is stopped. The characteristic view which shows the relationship between the engine speed at the time of fuel cut, and a residual gas rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Throttle 8 ... Fuel injection valve (fuel injection apparatus)
DESCRIPTION OF SYMBOLS 9 ... Spark plug 10 ... Engine control part 13 ... Combustion chamber 14 ... Intake passage 17 ... Tumble control valve (intake flow control valve)
18 ... Rotation speed sensor 20 ... Ignition key

Claims (6)

In a control apparatus for an internal combustion engine, comprising: an electrically controlled throttle that opens and closes an intake passage for introducing fresh air into a combustion chamber of the internal combustion engine; and a fuel injection device that injects fuel into the intake passage or the combustion chamber.
A stop request detecting means for detecting an engine stop request;
Fuel cut means for stopping fuel injection to stop the engine;
Between the detection of the engine stop request and the stop of fuel injection by the fuel cut means, a rotation speed increasing means for increasing the fuel injection amount in order to increase the engine rotation speed;
Scavenging promoting means for increasing the throttle opening so as to increase the amount of fresh air introduced into the combustion chamber after stopping fuel injection by the fuel cut means;
A control apparatus for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the scavenging promotion means opens the throttle opening fully. An intake flow control valve for imparting a flow component to the intake air by closing a part of the intake passage;
Flow enhancement means for closing the intake flow control valve after stopping the fuel injection;
The control apparatus for an internal combustion engine according to claim 1, wherein A rotation speed detecting means for detecting the actual rotation speed of the internal combustion engine;
4. The rotation speed increasing means increases the throttle opening and increases the fuel injection amount based on a deviation between the target rotation speed and the actual rotation speed when fuel injection is stopped. The control apparatus for an internal combustion engine according to any one of the above.   The control apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the internal combustion engine is a spark ignition type internal combustion engine having an ignition plug for spark ignition of an air-fuel mixture in a combustion chamber. In a control method for an internal combustion engine comprising: a throttle that opens and closes an intake passage that supplies fresh air into a combustion chamber of the internal combustion engine; and a fuel injection device that injects fuel into the combustion chamber or the intake passage.
Detecting an engine stop request; and
Detecting an engine stop request, increasing the fuel injection amount to increase the engine speed;
Stopping fuel injection to stop the engine;
Increasing the throttle opening so as to increase the amount of fresh air introduced into the combustion chamber;
An internal combustion engine control method comprising:

Images