JP4835622B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with variable valve operating means, and more particularly to a control device for an internal combustion engine configured to control valve timing at the time of starting.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-16710), a control device configured to control valve timings of an intake valve and an exhaust valve when starting an internal combustion engine is known. The control device for an internal combustion engine according to this type of prior art holds the exhaust valve in a closed state and opens and closes only the intake valve when the internal combustion engine is started (motoring or cranking).

  Thus, at the time of start-up, the air compressed in the cylinder while the intake valve is closed becomes high-temperature and high-pressure compressed air, and this compressed air blows back to the intake port side when the intake valve opens. Become. As described above, in the prior art, the intake port and the like are preheated by using the blowback of compressed air between the start of the internal combustion engine and the first firing (hereinafter referred to as the first explosion). The preheat control is performed.

JP 2007-16710 A

  In the prior art described above, preheat control is performed during startup of the internal combustion engine to preheat intake ports and the like. However, at the start of the intake stroke when shifting from preheat control to firing, that is, the intake stroke performed immediately before the first explosion, the compressed air that has been compressed last by the preheat control remains in the cylinder. This compressed air is blown back to the intake port side when the intake valve is opened.

  Therefore, in the intake stroke immediately before the first explosion, even if the fuel is injected into the intake port, the injected fuel may be pushed back by the blow back of the compressed air, and it is difficult to flow the fuel into the cylinder. For this reason, in the prior art, the air-fuel ratio at the time of the first explosion may be in a lean state and misfire may occur, which causes a problem that drivability at start-up and exhaust emission deteriorate.

  The present invention has been made to solve the above-described problems, and can stably perform the first firing after the end of the preheat control, thereby improving the drivability at the start-up and the exhaust emission. It is an object of the present invention to provide a control device for a possible internal combustion engine.

A first aspect of the invention is a variable valve mechanism capable of holding at least the exhaust valve in a closed state among an intake valve and an exhaust valve provided in an internal combustion engine,
An exhaust side preheat that holds the exhaust valve in a closed state by the variable valve operating means during a preheating period that is at least part of a period from the start of the internal combustion engine to the start of the first firing. Control means;
Intake side preheat control means for opening and closing the intake valve by the variable valve means during the preheat period, and setting the opening timing of the intake valve in the vicinity of intake top dead center;
An intake valve early opening control means for advancing the valve opening timing of the intake valve with respect to the valve opening timing during the preheating period in at least an initial explosion intake stroke performed immediately before the first firing;
It is characterized by providing.

According to the second invention, in the first invention,
The intake valve early opening control means is configured to open the intake valve earlier than the injection timing of the fuel flowing into the cylinder during the initial explosion intake stroke.

According to the third invention, in the first or second invention,
It is configured to include fuel injection control means for initial explosion that starts injection after the intake top dead center after injecting fuel into the cylinder in the initial explosion intake stroke.

A fourth invention is the first to third inventions,
In a normal intake stroke performed after the initial explosion intake stroke, a normal intake valve control means for setting the valve opening timing of the intake valve in the vicinity of the intake top dead center is provided.

  According to the first invention, the intake valve early opening control means can advance the opening timing of the intake valve relative to the opening timing during the preheat control when performing the initial explosion intake stroke. That is, the opening timing of the intake valve can be set to the advance side with respect to the intake top dead center. For this reason, for example, when the fuel injection corresponding to the intake stroke for the first explosion is performed after the intake top dead center, the intake valve can be opened earlier than the start timing of the fuel injection.

  As a result, the remaining air can be blown back by the preheat control before the start of the fuel injection, and the fuel injection can be performed after the blowback is weakened. The intake valve early opening control means can open the intake valve before the air in the cylinder is compressed to the vicinity of the intake top dead center and becomes high pressure. As a result, not only can the timing of blowback of the residual air be advanced, but the momentum of blowback can be weakened, and the influence of blowback on the injected fuel can be further reduced.

  Therefore, according to the intake valve early opening control means, it is possible to reliably prevent the injected fuel from being pushed back to the intake port side by blowing back the residual air. In the initial explosion intake stroke, the injected fuel can flow smoothly into the cylinder, and the initial firing can be performed in a stable state. Thereby, even immediately after the preheat control, misfire and the like at the time of the first explosion can be surely prevented, and the drivability at the start-up and the exhaust emission can be improved. In addition, it becomes possible to inject the fuel for the initial explosion over a long period before the intake valve is opened. For this reason, the fuel injection amount at the time of the first explosion can be sufficiently secured, and the startability can be improved.

  According to the second aspect of the invention, the intake valve early opening control means can open the intake valve earlier than the start of fuel injection corresponding to the initial explosion intake stroke. Thereby, fuel injection can be performed after the blow-back of residual air weakens.

  According to the third aspect of the invention, the first explosion fuel injection control means can start the fuel injection corresponding to the first explosion intake stroke with a delay after the intake top dead center. As a result, in the first-explosion intake stroke, after the remaining air blows back sufficiently, fuel injection can be started, and a synergistic effect can be exhibited in cooperation with the intake valve early opening control means. . For this reason, for example, even when it is difficult to greatly advance the valve opening timing of the intake valve due to valve operating system or control restrictions, the intake valve early opening control means and the initial opening control means are suppressed while suppressing the amount of advancement of the intake valve. The explosion fuel injection control means can be used in combination.

  According to the fourth invention, in the second and subsequent intake strokes, the opening timing of the intake valve can be set in the vicinity of the intake top dead center by the normal intake valve control means. Thus, after the first firing is completed, it is possible to quickly shift to the valve timing during normal operation, and the exhaust gas in the cylinder can be discharged smoothly. Therefore, the scavenging efficiency in the cylinder can be increased, and deterioration of the combustion state (starting failure) can be prevented.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. First, FIG. 1 shows an overall configuration diagram for explaining the system configuration of the first embodiment. The system of the present embodiment includes a four-cylinder internal combustion engine 10, for example. A piston 14 is provided in each cylinder 12 of the internal combustion engine 10. These pistons 14 form combustion chambers 16 in each cylinder 12. Each piston 14 is connected to a crankshaft 18 of the internal combustion engine.

  Each cylinder 12 includes an intake port 20 and an exhaust port 22 that communicate with the combustion chamber 16. An intake passage 24 through which intake air flows is connected to the intake port 20, and an exhaust passage 26 through which exhaust gas flows is connected to the exhaust port 22. An air flow meter 28 for detecting the intake air amount and a throttle valve 30 for adjusting the intake air amount are provided in the vicinity of the inlet of the intake passage 24. The throttle valve 30 is driven by a throttle motor 32 based on the accelerator opening.

  Further, a fuel injection valve 34 that injects fuel into the intake port 20 is disposed in the intake passage 24. On the other hand, each cylinder 12 has an ignition plug 36 that ignites the air-fuel mixture in the combustion chamber 16, an intake valve 38 that opens and closes the intake port 20 with respect to the combustion chamber 16, and an exhaust port 22 that opens with respect to the combustion chamber 16. And an exhaust valve 40 that opens and closes.

  The internal combustion engine 10 is equipped with, for example, electromagnetically driven valve operating mechanisms 42 and 44, which constitute variable valve operating means. Here, the valve mechanism 42 on the intake side opens and closes the intake valve 38 by generating an electromagnetic force with a solenoid or the like, as described in, for example, Japanese Patent Application Laid-Open No. 2007-16710. In this case, the valve mechanism 42 can variably set the opening / closing timing (valve opening timing and valve closing timing) of the intake valve 38.

  On the other hand, the exhaust-side valve mechanism 44 can similarly open and close the exhaust valve 40 by electromagnetic force, and its opening / closing timing can be set variably. Further, the valve mechanism 44 can temporarily hold the exhaust valve 40 in a closed state as necessary. In the present invention, the intake side and exhaust side variable valve operating means are not limited to the electromagnetically driven valve operating mechanisms 42 and 44.

  The internal combustion engine 10 includes a crank angle sensor 46 for detecting the rotation angle (crank angle) of the crankshaft 18 and a motor 48 for starting the internal combustion engine. The motor 48 is operated, for example, when an operator operates a starter switch, and performs an operation (motoring) for rotationally driving the crankshaft 18. In this case, for example, in a hybrid vehicle using both the output of the internal combustion engine and the output of the electric motor, the motor 48 is also driven by the ECU 50, and the internal combustion engine is started.

  The system according to the present embodiment also includes an ECU (Electronic Control Unit) 50 for controlling the operating state of the internal combustion engine. The ECU 50 is configured by a microcomputer including a storage circuit such as a ROM and a RAM. On the input side of the ECU 50, in addition to the air flow meter 28, the crank angle sensor 46, and the like, a water temperature sensor that detects the cooling water temperature of the internal combustion engine, an accelerator opening sensor that detects the accelerator opening, and an empty exhaust gas A sensor system including an air-fuel ratio sensor for detecting the fuel ratio is connected.

  Various actuators including a throttle motor 32, a fuel injection valve 34, a spark plug 36, valve operating mechanisms 42, 44, and the like are connected to the output side of the ECU 50. The ECU 50 controls the operation by driving the actuators while detecting the operation state of the internal combustion engine using the sensor system. This operation control includes preheat control, intake valve early opening control, normal intake valve control, and the like, which will be described later.

(Preheat control)
FIG. 2 is a timing chart showing fuel injection, ignition, and valve lift states from the start of the internal combustion engine to after the start. As shown in this figure, preheat control is performed during startup (during motoring) of the internal combustion engine. In this case, the preheat control is executed during a period (preheat period) from when the motor 48 starts motoring of the internal combustion engine until a predetermined end condition is satisfied.

  Here, as an example of the end condition of the preheat control, (1) whether the time required for preheating the intake port 20 and the like has elapsed since the motor 48 started operating, or (2) the motor 48 operated. Whether or not the crankshaft 18 has been rotated as many times as necessary for preheating since the start, (3) whether or not the temperature of the intake port 20 detected by the temperature sensor or the like has sufficiently increased.

  During the preheating period, as shown in FIG. 2, the fuel injection control and the ignition control are held in a stopped state. The exhaust valve 40 is held in a closed state by a valve mechanism 44 on the exhaust side. On the other hand, the intake valve 38 is opened and closed at a predetermined valve timing by a valve mechanism 42 on the intake side.

  FIG. 3 shows the opening / closing timing of the intake valve 38 from the start of the internal combustion engine to after the start. As shown in FIG. 3A, the opening period of the intake valve 38 during the preheat period is, for example, a period from the vicinity of the intake top dead center to the vicinity of the intake bottom dead center, preferably from the intake top dead center to the intake down stroke. It is set as the period until dead center. For this reason, in the exhaust stroke in a normal combustion cycle, the piston 14 performs a compression operation with both valves 38 and 40 closed, and the air in the combustion chamber 16 becomes high-temperature and high-pressure compressed air. .

  When the piston 14 reaches the intake top dead center and the intake valve 38 is opened, the compressed air is blown back into the intake port 20 from the combustion chamber 16 as a high-temperature and high-pressure blowback. Therefore, according to the preheat control, the intake port 20, the intake valve 38 and the like can be preheated with high-temperature compressed air, and warming up of the internal combustion engine can be promoted.

  Moreover, during the preheat control, the intake valve 38 can be opened over a long period from the vicinity of the intake top dead center to the vicinity of the intake bottom dead center, and the intake stroke can be continued during this period. For this reason, in the intake stroke, air can be sucked into the combustion chamber 16 not only in the vicinity of the intake top dead center where strong blowback occurs, but also during a period in which blowback weakens thereafter.

  Thereby, it is possible to avoid that the intake operation into the combustion chamber 16 is hindered by the blown air flow. Therefore, warm air once ejected to the intake port 20 side can be efficiently sucked into the combustion chamber. In addition, by setting the closing timing of the intake valve 38 in the vicinity of the intake bottom dead center, the charging efficiency of the intake air charged in the combustion chamber 16 can be maximized.

  For this reason, in the next exhaust stroke, a high pressure and temperature can be stably obtained by compressing a sufficient amount of air, and preheating with compressed air can be performed efficiently. Therefore, after the preheat period has elapsed, the fuel can be injected into the preheated warm air, and the vaporization of the fuel can be promoted. Further, liquid fuel adhering to the combustion chamber 16, the intake port 20, the intake valve 38, etc. can be quickly vaporized. Thereby, even when the internal combustion engine is cold started, a good air-fuel mixture can be formed to stabilize the combustion state, and startability and exhaust emission can be improved.

(Intake valve early opening control)
The fuel is injected from the fuel injection valve 34 into the intake port 20 during the transition period from the end of the preheat control until the first firing (first explosion) is performed. This injected fuel flows into the cylinder during the intake stroke (hereinafter referred to as the initial explosion intake stroke) performed immediately before the first explosion, and is burned at the first explosion.

  However, at the start of the initial explosion intake stroke, the compressed air that has been compressed last by the preheat control remains in the cylinder. This compressed air blows back toward the intake port 20 when the intake valve 38 is opened, preventing the injected fuel from flowing into the cylinder.

  Therefore, in the present embodiment, the intake valve early opening control is performed during the above-described transition period. In the intake valve early opening control, as shown in FIG. 3B, the valve opening timing of the intake valve 38 is advanced from the valve opening timing during the preheating period. That is, in the intake valve early opening control, the valve opening timing of the intake valve 38 is advanced from the intake top dead center.

  In the present embodiment, as shown in FIG. 2, the injection of the fuel that flows into the cylinder in the initial stroke intake stroke is started after the intake top dead center (intake top dead center or more retarded). It is configured. Therefore, according to the intake valve early opening control, the intake valve 38 can be opened earlier than the start timing of the fuel injection.

  As a result, the compressed air remaining in the cylinder by the preheat control is blown back toward the intake port 20 before the fuel injection corresponding to the initial explosion intake stroke is started. The blowback is weakened in a relatively short time because the compressed air in the combustion chamber 16 moves toward the intake port 20 at a high speed.

  Therefore, in the first-explosion intake stroke, fuel injection can be performed after the blow-back of residual air is weakened, and it is possible to reliably prevent the injected fuel from being pushed back to the intake port 20 side by the blow-back of residual air. . The injected fuel can be smoothly flowed into the cylinder, and the first firing can be performed stably. Thereby, even immediately after the preheat control, misfire and the like at the time of the first explosion can be reliably prevented, and the drivability and exhaust emission at the start can be improved.

  Further, by opening the opening timing of the intake valve 38 from the intake top dead center, the intake valve 38 is opened before the air in the cylinder is compressed to the vicinity of the intake top dead center and becomes high pressure. be able to. As a result, not only can the timing of blowback of the residual air be advanced, but the momentum of blowback can be weakened, and the influence of blowback on the injected fuel can be further reduced.

  Further, in the conventional control, even if the fuel for the initial explosion is injected before the intake valve 38 is opened, the fuel hardly reaches the cylinder due to the blowback effect that occurs when the valve is opened. On the other hand, if the fuel injection timing is too late, the fuel is not reflected in the intake stroke, so there is a limit to delaying the injection timing. As described above, the injection timing of the initial explosion fuel is limited within a certain period, whereas the fuel injection period (injection amount) at the initial explosion tends to increase due to a demand for ensuring startability. For this reason, in the conventional control, it is difficult to inject a sufficient amount of the initial explosion fuel at an appropriate timing.

  On the other hand, in the present embodiment, the valve opening timing of the intake valve 38 can be advanced in the intake stroke at the time of the first explosion. For this reason, for example, as shown by an arrow A in FIG. 2, the injection period of the initial explosion fuel can be extended to the advance side, and the injection period can be sufficiently secured. Thereby, the fuel injection of the quantity requested | required at the time of the first explosion can fully be performed with an appropriate timing with respect to an intake stroke, and startability can be improved. Further, by extending the injection period, the time until the injected fuel reaches the cylinder becomes longer, so that the vaporization of the fuel can be promoted and the discharge amount of HC and the like can be reduced.

  Further, in the present embodiment, the fuel injection corresponding to the initial explosion intake stroke is started after being delayed after the intake top dead center (fuel injection delay control at the initial explosion). As a result, in the first explosion intake stroke, the fuel injection can be started after the blow-back of the residual air is sufficiently weak, and a synergistic effect can be exhibited in cooperation with the intake valve early opening control.

  Even if it is difficult to greatly advance the valve opening timing of the intake valve 38 due to, for example, a valve system or control restrictions, the intake valve early opening control and the initial fuel injection delay control are combined. Can be implemented. Thereby, the above-mentioned effect can be sufficiently obtained even in a state where the advance amount of the intake valve is suppressed.

(Normal intake valve control)
As described above, the fuel that has flowed into the cylinder during the initial explosion intake stroke is burned together with the intake air by ignition at the initial explosion. As a result, the operating state of the internal combustion engine is switched from motoring to normal self-sustained operation. As a result, the exhaust valve 40 is opened and closed at normal valve timing from the exhaust stroke at the time of the first explosion.

  Further, the intake valve 38 is opened and closed, for example, at the normal valve timing shown in FIG. 3C in the second and subsequent intake strokes. In this case, the opening timing of the intake valve 38 is set at or near the intake top dead center. Thus, after the first firing is completed, it is possible to quickly shift to the valve timing during normal operation, and the exhaust gas in the cylinder can be discharged smoothly. Therefore, the scavenging efficiency in the cylinder can be increased, and deterioration of the combustion state (starting failure) can be prevented.

[Specific Processing for Realizing Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in order to realize the system operation of the present embodiment. The routine shown in FIG. 4 is started when the ECU 50 is turned on, and is repeatedly executed at regular intervals.

  First, the ECU 50 determines whether or not motoring has been started by a driver's starting operation, a vehicle-side starting request, or the like (step 100). When there is no history of performing motoring, the system stands by at step 100.

  When the above determination is not established, since the motoring is finished, the process proceeds to Step 108 described later. When the determination is established, the preheating control described above is performed because the motoring is in progress. That is, the intake valve 38 is opened from the intake top dead center to the intake bottom dead center (step 102), and the exhaust valve 40 is kept closed (step 104).

  Then, while executing the preheat control, it is determined whether or not the above-mentioned preheat control end condition is satisfied (step 106). When this determination is not established, it is not the timing at which the preheat control should be terminated, so the preheat control is continued until the determination is established. Further, when the end condition is satisfied, the preheat control is ended, and it is determined whether or not it is the initial explosion intake stroke (step 108).

  In the initial stroke intake stroke, since compressed air still remains in the cylinder, the phase of the intake valve 38 (valve closing timing) is advanced by the valve mechanism 42 on the intake side, and the intake valve described above is advanced. The quick opening control is executed (step 110). Then, the fuel injection delay control at the initial explosion is performed by delaying the start timing of fuel injection after the intake top dead center (step 112).

  On the other hand, if it is the second and subsequent intake strokes, the fuel injection start timing is set to an advance side from the intake top dead center, and normal fuel injection control is performed (step 114). Further, the phase of the intake valve 38 is retarded to a normal state, and normal intake valve control is executed (step 116).

  Thus, according to the present embodiment, the intake valve early opening control can be executed at the first explosion of each cylinder. Thereby, even if preheat control is performed, the combustion state at the time of the first explosion does not need to be adversely affected, so that the control can be switched smoothly.

  In the above embodiment, step 102 in FIG. 4 shows a specific example of the intake side preheat control means, and step 104 shows a specific example of the exhaust side preheat control means. Step 110 shows a specific example of the intake valve early opening control means, step 112 shows a specific example of the fuel injection control means at the initial explosion, and step 116 shows a specific example of the normal intake valve control means.

  Further, in the embodiment, the fuel injection start timing corresponding to the first explosion intake stroke is delayed after the intake top dead center. However, the present invention is not limited to this, and normal fuel injection control may be performed during the initial explosion intake stroke.

  In the embodiment, the electromagnetically driven valve mechanisms 42 and 44 are used. However, the present invention is not limited to this, for example, a mechanical valve mechanism connected to the crankshaft 18 by means such as a chain, and a hydraulic variable valve timing mechanism (VVT) attached to the valve mechanism. The variable valve operating means may be configured as described above.

  Moreover, in each embodiment, it was set as the structure which performs preheat control at the time of general starting. However, the present invention is not limited to this. For example, by detecting the temperature state of the internal combustion engine 10 with a temperature sensor or the like, the preheat control is executed only at the cold start, and the preheat control is performed at the restart after the warm-up. It is good also as a structure which does not perform.

1 is an overall configuration diagram showing a system configuration according to a first embodiment of the present invention. 3 is a timing chart showing fuel injection, ignition, and valve lift states from the start of the internal combustion engine to after the start. It is explanatory drawing which shows the opening-and-closing timing of the intake valve after starting from the time of starting of an internal combustion engine. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder 14 Piston 16 Combustion chamber 18 Crankshaft 20 Intake port 22 Exhaust port 24 Intake passage 26 Exhaust passage 28 Air flow meter 30 Throttle valve 32 Throttle motor 34 Fuel injection valve 36 Spark plug 38 Intake valve 40 Exhaust valve 42 Intake side Valve mechanism (variable valve mechanism)
44 Exhaust valve mechanism (variable valve mechanism)
46 Crank angle sensor 48 Motor 50 ECU

Claims (4)

Variable valve operating means capable of holding at least the exhaust valve among the intake valve and the exhaust valve provided in the internal combustion engine; and
An exhaust side preheat that holds the exhaust valve in a closed state by the variable valve operating means during a preheating period that is at least part of a period from the start of the internal combustion engine to the start of the first firing. Control means;
Intake side preheat control means for opening and closing the intake valve by the variable valve means during the preheat period, and setting the opening timing of the intake valve in the vicinity of intake top dead center;
An intake valve early opening control means for advancing the valve opening timing of the intake valve with respect to the valve opening timing during the preheating period in at least an initial explosion intake stroke performed immediately before the first firing;
A control device for an internal combustion engine, comprising:   2. The control device for an internal combustion engine according to claim 1, wherein the intake valve early opening control means is configured to open the intake valve earlier than an injection timing of fuel flowing into the cylinder in the first explosion intake stroke.   The control apparatus for an internal combustion engine according to claim 1 or 2, further comprising fuel injection control means for initial explosion that starts injection of fuel that flows into the cylinder in the initial explosion intake stroke after intake top dead center.   The normal intake valve control means for setting the opening timing of the intake valve in the vicinity of the intake top dead center in the normal intake stroke performed after the initial explosion intake stroke is provided. The control device for an internal combustion engine according to any one of the preceding claims.

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