JP2006009724A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To largely decrease HC emission right after cold state starting, in an engine control device applied to an engine in which fuel is injected into an intake port. <P>SOLUTION: When start of the engine is determined, a valve close timing change means 16 is controlled to advance close timing of an intake valve. Along with the advance of the close timing of the intake valve, fuel injection timing of a fuel injection valve 6 which is attached to an intake port is advanced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine control device applied to an engine that injects fuel into an intake port.

FIG. 4 is a schematic diagram showing a configuration of a general port injection engine, where 1 is a cylinder block, 2 is a piston, 3 is an intake valve, 4 is an exhaust valve, 5 is an intake port, and 6 is an injector. The injector 6 is attached to the intake port 5 with its tip directed toward the intake valve 3, and is configured such that fuel is injected from the injector 6 at a predetermined timing.
Further, in such a port injection type engine, fuel injection is generally performed at a timing (specifically, for example, an exhaust stroke) at which the intake valve 3 is still closed. By injecting fuel into the intake port 5 in advance as described above, vaporization of fuel spray is promoted in the intake port 5 and mixing of fuel and intake air (fresh air) is promoted.
Then, when the intake valve 3 is opened and the piston 2 is lowered, the air-fuel mixture in the intake port 5 is taken into the combustion chamber, and when the piston 2 starts to rise, the intake valve 3 is closed and the air-fuel mixture is compressed. Then, ignition is performed, the air-fuel mixture burns, and exhaust gas is discharged through the exhaust valve 4.

By the way, generally, when the engine is cold-started, HC contained in the exhaust gas increases. For this reason, various techniques for reducing the amount of HC emission at the time of cold start have been proposed (see, for example, Patent Document 1).
In the technology of this patent technology 1, immediately after the cold start, the operation of the variable valve timing mechanism (VVT mechanism) is controlled so that the valve overlap includes the intake stroke range after the top dead center, and then before the top dead center. The operation of the VVT mechanism is controlled to increase the exhaust stroke range overlap.

Therefore, at the time of a cold start in which fuel vaporization is not promoted, the fuel injected into the intake port is stored in a liquid state near the valve seat during the valve closing period, but this liquid fuel is discharged as it is to the exhaust port. Rather, during the overlap of the intake stroke range immediately after starting, it flows into the cylinder as the piston descends and is reliably burned. Further, when the overlap of the exhaust stroke range is increased thereafter, for example, the exhaust gas once discharged to the exhaust side flows backward into the intake port to prevent the liquid fuel from being discharged, or the exhaust valve As a result of the afterburning effect due to the early opening of the catalyst, the catalyst is heated.
JP 2002-155767 A

However, the technique of Patent Document 1 merely prevents unburned gas from flowing from the intake port to the exhaust port during the overlap period of the intake valve and the exhaust valve, and the mixture gas in the combustion chamber It has not become something that increases combustion efficiency and reduces HC in the combustion gas itself.
By the way, the reason why HC increases immediately after the cold start is mainly because the fuel injected from the injector is not sufficiently vaporized, and in order to reduce the HC emission amount, the fuel vaporization time is sufficiently long. It is preferable to do this.

  In order to increase the fuel vaporization time as described above, it is preferable to inject fuel as soon as possible. However, as shown in FIG. 5, in a general port injection engine, the timing at which fuel can be injected earliest is the closing timing of the intake valve. Immediately after the valve, that is, after intake bottom dead center, the injection timing cannot be advanced any further. For this reason, the fuel vaporization time at the cold start cannot be made sufficiently long, and the HC reduction effect immediately after the cold start cannot be obtained sufficiently.

  The present invention was devised in view of such problems, and an object of the present invention is to provide an engine control device capable of greatly reducing the HC emission amount immediately after the cold start.

  For this reason, the engine control device according to the first aspect of the present invention is provided with a fuel injection valve attached to an intake port of the engine and injecting fuel into the intake port, and at least a closing timing capable of changing a closing timing of the intake valve. A valve timing changing means; a start determining means for determining or detecting start of the engine; and when the start determination means determines or detects start of the engine, the valve closing timing of the intake valve is advanced. And control means for controlling the valve closing timing changing means and for advancing the fuel injection timing of the fuel injection valve in accordance with the advance of the valve closing timing of the intake valve.

Further, in the engine control apparatus of the present invention as claimed in claim 2, the control means determines the closing timing of the intake valve from the intake bottom dead center when the start determination means determines or detects the start of the engine. It is characterized by being advanced.
Further, in the engine control apparatus according to the third aspect of the present invention, the control means is configured so that the valve closing timing of the intake valve is advanced when the start determination means determines or detects the start of the engine. The valve closing timing changing means is controlled, and the fuel injection timing is advanced so that fuel is injected from the fuel injection valve substantially simultaneously with the closing of the intake valve.

  Further, in the engine control device of the present invention according to claim 4, the control means is arranged so that the closing timing of the intake valve is advanced when the start determination means determines or detects the start of the engine. The fuel injection timing is controlled so that fuel injected from the fuel injection valve reaches the intake valve substantially simultaneously with the intake valve closing timing. It is characterized by advancing ahead of time.

The engine control device of the present invention according to claim 5 has a cold state detection means for detecting whether or not the engine is in a cold state, and the control means determines whether or not the engine is started. When it is detected and the cold state detection means detects that the engine is in a cold state, the valve closing timing changing means and the fuel injection valve are advanced.
The engine control apparatus of the present invention according to claim 6 is characterized in that the advance control of the valve closing timing changing means and the fuel injection valve is terminated when a predetermined stroke elapses after the engine is started.

  It is desirable that the fuel injection timing is set at the exhaust stroke after completion of closing of the intake valve after the valve closing timing changing means and the advance control of the fuel injection valve are completed.

According to the engine control device of the present invention, after the engine is started, the closing timing of the intake valve is advanced and the fuel injection timing is advanced, so that the vaporization time can be sufficiently long and the HC emission immediately after the engine is started. The amount can be greatly reduced.
In this case, if the closing timing of the intake valve is advanced from the intake bottom dead center, the fuel vaporization time due to the advance of the injection timing can be ensured sufficiently and reliably. Further, by performing fuel injection simultaneously with closing of the intake valve, the fuel vaporization time can be sufficiently long while reliably avoiding a situation in which fuel is sucked in the previous intake stroke There is. Also, taking into account the time it takes for the injected fuel to reach the intake valve, the fuel vaporization time can be set longer by injecting the fuel earlier than the intake valve closing timing by the considered time. Further reduction in HC emissions can be achieved.

Further, by controlling the advance of the intake valve closing timing and the fuel injection timing only at the time of cold start of the engine having a relatively large amount of HC emission, appropriate control according to the state of the engine can be performed. .
In addition, when a predetermined stroke has elapsed after the engine is started, the valve closing timing changing means and the advance control of the fuel injection valve are finished. Thereafter, the fuel injection start timing and the intake valve opening / closing timing according to the engine operating state are set. Can be set.

Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of the main part, FIG. 2 is a time chart for explaining the operation, and FIG. Is a flowchart for explaining the operation.
Now, the engine to which the present invention is applied has the same configuration as that described with reference to FIG. Specifically, an injector (fuel injection valve) 6 is attached to the intake port 5 of the engine, and fuel is injected from the injector 6 into the intake port 5. In the following description, a part of the reference numerals used in FIG.

  As shown in FIG. 1, the engine is provided with a VVT mechanism (variable valve timing mechanism) 15 that can change the valve opening / closing timing of the intake and exhaust valves. Here, the VVT mechanism 15 includes an intake valve side VVT mechanism (valve closing timing changing means) 16 and an exhaust valve side VVT mechanism 17, and these VVT mechanisms 16 and 17 are independently and individually provided. It is configured to be controllable.

  By the way, various known techniques can be applied to the VVT mechanisms 16 and 17. In this embodiment, the intake and exhaust valves 3 and 4 are changed by changing the phase of the camshaft with respect to the crankshaft of the engine. The valve opening timing and the valve closing timing are changed. In the VVT mechanisms 16 and 17 having such a configuration, the valve opening period of the intake valve 3 and the exhaust valve 4 is changed by changing the valve opening timing (valve opening timing) and the valve closing timing (valve closing timing). Instead, the valve lift curve is configured to be advanced or retarded as a whole.

In the present invention, the intake valve side VVT mechanism 16 may be any mechanism that can change at least the closing timing of the intake valve 3, and may be applicable even if the opening timing cannot be changed. Further, the exhaust valve side VVT mechanism 17 can be omitted.
The VVT mechanisms 16 and 17 are provided with an actuator 18 for operating the intake side VVT mechanism 16 and an actuator 19 for operating the exhaust side VVT mechanism 17, respectively. These actuators (hereinafter referred to as VVT actuators) 18, 19 are for advancing or retarding the phase of the camshaft relative to the crankshaft, and are, for example, electromagnetic valves disposed in an electric motor or a hydraulic circuit. is there.

The operating state of the injector 6 and the VVT actuators 18 and 19 described above is controlled based on a control signal from an ECU (control means) 13 shown in FIG.
As shown in FIG. 1, a key switch 11 and a water temperature sensor (cool state detection means or water temperature detection means) 12 are connected to the ECU 13, and the ECU 13 receives information from the key switch 11 and the water temperature sensor 12. Based on this, control signals for the injector and the VVT actuators 18 and 19 are set.

  Next, a specific control content of the present apparatus will be described. In the ECU 13, start determination means 14 for determining start of the engine based on information from the key switch 11 is provided. For example, when the key switch position is switched from the ON position to the start position, the start determination means determines the start of the engine. The engine start determination means is not limited to the above-described one, and for example, an engine start may be detected or determined by detecting energization to a starter motor (not shown).

When the start determination means 14 determines that the engine is started, the ECU 13 determines whether or not it is a cold start based on the water temperature information obtained from the water temperature sensor 12. In this embodiment, when the detected water temperature is equal to or lower than a predetermined temperature (for example, 70 ° C.), it is determined that the cold start is in progress.
When the ECU 13 determines the cold start, the control signal is issued to the injector 6 and the VVT actuator 18 to control the intake valve side VVT mechanism 16 so that the closing timing of the intake valve 3 is advanced. At the same time, the fuel injection start timing of the injector 6 is advanced with the advance of the valve closing timing of the intake valve 3.

  Specifically, at the time of cold start, the intake valve side VVT mechanism 16 advances the valve closing timing of the intake valve 3 as much as possible before the intake bottom dead center, and the fuel injection start timing of the injector 6 is set to the intake air. The valve is advanced at a timing earlier than the valve closing timing of the valve 3. The fuel injection start timing takes into account the time t1 (see FIG. 2) until the injected fuel spray reaches the intake valve, and the fuel injection start timing is the above time t1 rather than the valve closing timing. It is designed to advance. In other words, the fuel injection timing is advanced earlier than the closing timing of the intake valve 3 so that the fuel injected from the injector 6 reaches the intake valve 3 simultaneously or substantially simultaneously with the closing timing of the intake valve 3. It is like that.

  Such control is performed in order to reduce the HC emission amount at the time of cold start. That is, since the engine is not sufficiently warmed immediately after the cold start, the fuel injected from the injector 6 is not sufficiently vaporized, resulting in an increase in the HC emission amount. Therefore, in order to reduce the HC emission amount at the time of cold start, it is necessary to set the fuel vaporization time sufficiently long. In order to increase the fuel vaporization time, the fuel may be injected as soon as possible before the intake stroke starts. However, in a port injection engine, the timing at which fuel can be injected earliest is immediately after the intake valve 3 is closed, and more Can not be sprayed early.

Therefore, in this embodiment, when the engine is cold started, the closing timing of the intake valve 3 is further advanced from the intake bottom dead center, and the fuel injection timing of the injector 6 is advanced accordingly. is there.
Further, when the ECU 13 counts a predetermined stroke (for example, two strokes) after the cold start, the ECU 13 finishes the advance control of the fuel injection timing of the injector 6 and the closing timing of the intake valve 3 as described above, and the engine operating state Accordingly, the control is gradually shifted to the normal fuel injection timing control and the VVT mechanism 15 control.

Since the engine control apparatus according to one embodiment of the present invention is configured as described above, its operation will be described below with reference to the time chart shown in FIG. 2 and the flowchart shown in FIG.
First, when the key switch 11 is turned on, the flowchart shown in FIG. 2 starts. Here, in the present embodiment, the intake valve side VVT mechanism 16 is structured so that the valve opening timing and the valve closing timing of the intake valve 3 are the most retarded when the engine is stopped. Naturally, the valve closing timing is the most retarded immediately after turning on (step S1).

  Next, it is determined whether or not it is a cold start based on the engine water temperature (step S2). Here, if it is not cold start, the process proceeds to step S9, and fuel injection is started at the normal injection timing (exhaust stroke) (see e in FIG. 2). If it is determined that the engine is cold-started, the ECU 13 sets the closing timing of the intake valve 3 to the most advanced angle and sets the closing timing of the intake valve before the intake bottom dead center (step S3). . Here, in this embodiment, a mechanism that changes the opening / closing timing of the intake valve 3 by changing the phase of the camshaft as the intake valve side VVT mechanism 16 is applied, as shown in FIG. By opening the valve closing timing, the valve opening period of the intake valve 3 is advanced as a whole.

  Further, after the advance timing of the closing timing of the intake valve 3 (or almost simultaneously), the fuel injection start timing of the injector 6 is advanced (step S4). In this case, the fuel injection start timing is advanced to a timing (see c in FIG. 2) that is earlier than the intake valve closing timing (see b in FIG. 2). Thus, fuel injection can be started at a timing much earlier than the timing of closing the intake valve when the intake valve 3 is not advanced (see FIG. 2a), and fuel vaporization is promoted. Note that the fuel injection start timing (c in FIG. 2) in this case takes into account the time t1 until the injected fuel spray actually reaches the intake valve 3, and thus the fuel injection is performed at such timing. Even if the operation is started, the fuel is not taken into the combustion chamber in the previous intake stroke. The time t1 until the fuel spray reaches the intake valve 3 may be a value obtained in advance through experiments or tests, or may be mapped and stored in the ECU 13 according to parameters such as engine water temperature. May be set.

Thereafter, when the intake valve 3 is opened in the intake stroke, fuel and fresh air (air) in the intake port 6 are taken into the combustion chamber by negative pressure. At this time, since the fuel is sufficiently vaporized, mixing of the fuel and fresh air is promoted in the combustion chamber. Then, ignition is performed at a predetermined timing (see d in FIG. 2), and the air-fuel mixture burns efficiently.
Next, it is determined whether or not advance control of such fuel injection timing and intake valve closing timing has been executed for a predetermined stroke, and if it is determined that the predetermined stroke has elapsed (step S5), then the intake valve 3 is closed. The valve timing is gradually changed to a timing according to the engine operating state (step S6), and the fuel injection start timing is also gradually changed according to the valve closing timing (step S7).

When the closing timing of the intake valve 3 coincides with the timing according to the operating state of the engine, the fuel injection start timing is gradually changed (or at once) to the injection timing (exhaust stroke injection) during normal operation. (Step S8). And if it transfers to exhaust stroke injection (step S9), this control will be complete | finished.
As described above, according to the engine control apparatus of the present embodiment, after the engine is started, the valve closing timing of the intake valve 3 is advanced and the fuel injection start timing is advanced, so that the fuel vaporization time is sufficiently long. There is an advantage that the HC emission amount immediately after the engine start can be greatly reduced. Further, in consideration of the time until the injected fuel reaches the intake valve 3, the fuel vaporization time is further increased by injecting the fuel earlier than the closing timing of the intake valve 3 by the considered time. It can be set and HC emission can be further reduced.

Further, since the advance control of the closing timing of the intake valve 3 and the fuel injection start timing is performed only at the time of cold start of the engine having a relatively large amount of HC emission, appropriate control according to the state of the engine can be performed. it can.
In addition, when the predetermined stroke has elapsed after the engine is started, the valve closing timing changing means and the advance control of the fuel injection valve are finished. Thereafter, the fuel injection timing and the opening / closing timing of the intake valve 3 according to the operating state of the engine are set. can do.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible in the range which does not deviate from the meaning of this invention. For example, in the above embodiment, the valve closing timing of the intake valve 3 and the fuel injection start timing of the injector 6 are advanced only at the time of cold start. You may comprise. In the above-described embodiment, the closing timing of the intake valve 3 is advanced before the intake bottom dead center, but may be advanced to the intake bottom dead center or just after the intake bottom dead center.

  In the above-described embodiment, the fuel injection start timing is set earlier than the intake valve 3 closing timing so that the fuel injected from the injector 6 reaches the intake valve 3 simultaneously with the closing timing of the intake valve 3. Although the angle is advanced, the closing timing of the intake valve 3 and the fuel injection start timing may be simultaneous. In this case, a situation in which fuel is sucked in the previous intake stroke is surely avoided.

  Further, in the above-described embodiment, the configuration is such that the advance angle control of the valve closing timing of the intake valve 3 and the fuel injection start timing of the injector 6 ends when a predetermined stroke has elapsed after the engine is started. Various end triggers can be set in addition to the above. For example, the present control may be terminated based on a determination result such as whether a predetermined time has elapsed after the engine is started or whether the water temperature after the engine is started is equal to or higher than a predetermined value.

It is a block diagram showing typically the principal part composition of the engine control device concerning one embodiment of the present invention. It is a time chart for demonstrating the effect | action of the engine control apparatus concerning one Embodiment of this invention. It is a flowchart for demonstrating an effect | action of the engine control apparatus concerning one Embodiment of this invention. It is a schematic diagram which shows the structure of a general port injection engine. It is a time chart explaining operation | movement of a general port injection engine.

Explanation of symbols

3 Intake valve 5 Intake port 6 Injector (fuel injection valve)
12 Water temperature sensor (water temperature detection means)
13 ECU (control means)
14 Start determination means 16 Intake valve side VVT mechanism (valve closing timing changing means)

Claims (6)

A fuel injection valve attached to an intake port of the engine and injecting fuel into the intake port;
A closing timing changing means capable of changing at least the closing timing of the intake valve;
Start determination means for determining or detecting the start of the engine;
When the start determination means determines or detects the start of the engine, the valve closing timing changing means is controlled so that the closing timing of the intake valve advances, and the advance timing of the closing timing of the intake valve And a control means for advancing the fuel injection timing of the fuel injection valve. The control means includes
2. The engine control apparatus according to claim 1, wherein when the start of the engine is determined or detected by the start determination means, the closing timing of the intake valve is advanced from the intake bottom dead center. The control means includes
When the start determination means determines or detects the start of the engine, the valve closing timing changing means is controlled so that the closing timing of the intake valve is advanced, and at the same time as the closing of the intake valve, 3. The engine control device according to claim 1, wherein the fuel injection timing is advanced so that fuel is injected from the fuel injection valve. The control means includes
When the start determination means determines or detects the start of the engine, the valve closing timing changing means is controlled so that the closing timing of the intake valve is advanced, and the fuel injected from the fuel injection valve is The fuel injection timing is advanced earlier than the closing timing of the intake valve so as to reach the intake valve substantially simultaneously with the closing timing of the intake valve. Engine control device. Cold state detecting means for detecting whether or not the engine is in a cold state;
When the start of the engine is determined or detected, and the cold state detection unit detects that the engine is in a cold state, the control unit detects the valve closing timing changing unit and the fuel injection valve. The engine control apparatus according to any one of claims 1 to 4, wherein the advance angle control is performed. The engine control apparatus according to any one of claims 1 to 5, wherein the advance control of the valve closing timing changing means and the fuel injection valve is terminated when a predetermined stroke has elapsed after the engine is started.

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