JP2000328988A - Starting control system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve startability by scavenging the excessive fuel rapidly when an engine fails to start. SOLUTION: In this control system, an optimum valve timing in a normal state is set according to a driving condition (step 3) when a starter switch is not on (step 1) and an engine does not fail to start (step 2). When the starter switch is on while an opening of a throttle valve is a prescribed one or more, it is judged to be failure in which an accelerating pedal was intentionally stepped when the engine failed to start (step 2). Then closing timing of an intake valve is advanced (step 5). A greater amount of fresh air is sucked into a combustion chamber during cranking while remaining fuel is actively scavenged. Moreover, compression pressure generated during the cranking increases and temperature inside the combustion chamber rises, and evaporation of fuel drop adhered to an ignition plug is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start control device for a four-cycle spark ignition type internal combustion engine represented by a gasoline engine.

[0002]

2. Description of the Related Art In an internal combustion engine for an automobile, for example, at the time of starting, a starter motor is driven by a starter switch provided in a driver's seat, and the internal combustion engine is cranked. Then, along with this cranking, fuel supply and ignition are performed, and the engine is started.

[0003] Here, if the start-up fails for some reason, that is, if the start-up fails, as is well known, the mixture in the combustion chamber becomes excessively rich, making it difficult to ignite and burn. The plug becomes wet with the fuel droplets, making subsequent starting more difficult.

[0004] In order to reduce such a problem at the time of a failure, conventionally, when cranking is performed in a state where the throttle valve opening is opened to a predetermined opening or more, it is determined that the engine is started at the time of a failure. To stop fuel increase, or
A technique for completely stopping the fuel supply is known, and a part of the technique is practically used (for example, see Japanese Patent Publication No. 57-27972).

[0005]

As described above, even when the fuel supply is suppressed at the time of the start at the time of the failure, the air-fuel ratio at which the rich mixture by the fuel supplied before that becomes ignitable becomes ignitable. Until then, it also takes a long time, and cranking must be continued until then.

SUMMARY OF THE INVENTION An object of the present invention is to quickly scavenge surplus fuel at the time of a start failure and to further improve startability.

[0007]

The invention according to claim 1 is
At least on the intake valve side of the internal combustion engine, in a start control device for an internal combustion engine comprising a variable valve mechanism capable of variably controlling at least the closing timing of the intake valve, the failure of starting by cranking is directly or indirectly determined. It is equipped with a fail detecting means for detecting, and when this starting failure is detected,
It is characterized in that the closing timing of the intake valve is controlled to the valve timing for failure.

More specifically, the valve timing for a failure described above has a characteristic in which the intake valve closing timing is advanced to near the bottom dead center.

Various types of variable valve mechanisms for variably controlling the opening / closing timing of intake valves of an internal combustion engine have been proposed in the past, and some of them have already been put to practical use. For example, by relatively shifting the phase relationship between a camshaft and a crankshaft that drives the camshaft, the opening / closing timing of the intake valve is changed in the same direction (for example, Japanese Patent Application Laid-Open No. 10-68306). In practice, a device is provided in which two rocker arms driven by two cams having different cam profiles are provided, and the valve lift characteristics are switched between two types by selectively switching the rocker arm in which the intake valve actually works. ing. Also,
Japanese Patent Application Laid-Open No. Hei 6-185321 discloses a variable motion control system in which a valve lift characteristic can be continuously variably controlled by rotating a cylindrical cam shaft at a non-constant speed by applying the principle of a non-constant speed shaft coupling. A valve mechanism is disclosed.

According to the present invention, at the time of a start failure, the intake valve closing timing is advanced to a valve timing for failure, for example, near the bottom dead center, and a larger amount of fresh air is sucked into the combustion chamber with cranking. Is done. As a result, the combustion chamber is actively scavenged, and the rich mixture is promptly ignited. In addition, a large amount of air is taken into the combustion chamber and compressed, which increases the compression pressure during cranking and at the same time raises the gas temperature, making it easier for fuel droplets attached to the spark plug to evaporate. Become. Therefore, starting can be started in a short time by cranking.

A start failure or a start failure can be detected by various means. For example, if a complete explosion does not occur after a certain period of cranking, or if multiple crankings are performed intermittently, the driver intentionally increases the throttle valve opening to a very large value. When ranking is performed, it can be determined that a start failure has occurred. Further, the concentration of the air-fuel mixture in the combustion chamber can be directly detected, or can be detected from the total fuel injection amount up to the complete explosion.

According to a third aspect of the present invention, there is provided a start control device for an internal combustion engine, which is provided at least on an intake valve side of the internal combustion engine and variably controls at least a closing timing of the intake valve. Throttle valve opening detecting means for detecting the opening of the valve, cranking detecting means for detecting cranking of the internal combustion engine, and when the throttle valve opening is cranked in a state larger than a predetermined opening,
Valve timing control means for advancing the intake valve closing timing to the lower dead center side from the normal time through the variable valve operating mechanism.

According to a fourth aspect of the present invention, the fuel supply is stopped at the same time as the cranking is performed with the throttle valve opening being larger than a predetermined opening. It has fuel control means.

According to the third and fourth aspects of the present invention,
When cranking with the throttle valve opening larger than the predetermined opening, the driver judges that the driver intentionally wants to scavenge, and the intake valve closing timing is advanced to the lower dead center side from normal. Is done. This promotes scavenging of the combustion chamber and vaporization of the fuel droplets as described above.

[0015]

According to the present invention, even if start-up fails for any reason, during the subsequent cranking, the combustion chamber is actively scavenged and the fuel liquid adhering to the spark plug is removed. The vaporization of the droplet is promoted, and a quick start is possible.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a structural explanatory view showing an embodiment of the present invention. A piston 3 defining a combustion chamber 4 is slidably fitted to each cylinder 2 of an internal combustion engine 1. And a spark plug 5 is arranged at the center. The combustion chamber 4
A catalyst device 8 is interposed in an exhaust passage 7 connected to an exhaust valve 6 via an exhaust valve 6.

In an intake passage 11 connected to the combustion chamber 4 via an intake valve 10, a fuel injection valve 12 is disposed toward the intake valve 10, and a throttle valve 14 is provided upstream of a collector 13. And an air flow meter 15 are sequentially provided. The opening of the throttle valve 14 is detected by a throttle valve opening sensor 16, and the rotation angle of the crankshaft, and thus the rotation speed of the internal combustion engine 1, are detected by a crank angle sensor 17. The detection signals of these sensors are transmitted to the engine control unit 1
8 has been entered. Engine control unit 1
Reference numeral 8 comprehensively controls the fuel injection amount and injection timing of the fuel injection valve 12, the ignition timing of the ignition plug 5, and the like based on these detection signals. Further, the engine control unit 18 operates the starter motor 20 based on the signal of the starter switch 19.

The exhaust valve 6 and the intake valve 10 are each driven to open and close by a valve operating mechanism mainly comprising a camshaft. The variable valve mechanism 21 capable of variably controlling the valve lift characteristic by the control signal is provided. In this embodiment, as the variable valve mechanism 21, for example, by shifting the phase between the crankshaft and the camshaft, the valve opening timing and the closing timing can be simultaneously advanced by a fixed amount without changing the valve operating angle. A known configuration is used. It should be noted that a type that can variably control the valve operating angle as disclosed in JP-A-6-185321 or the like can also be used.

FIG. 2 is a flowchart showing a main part of the valve timing control in the above-described configuration. In step 1, it is determined whether or not the condition for performing the starting control is satisfied. For example, while the starter switch 19 is ON, predetermined start-up control is performed, the starter motor 20 is driven, and the fuel injection amount and the ignition timing are controlled to characteristics suitable for starting. If it is determined in step 1 that the starting control is not being performed, the process proceeds to step 3, and the normal optimal valve timing is set according to the operating conditions. Then, in order to achieve the target valve timing set in this way,
In step 5, a control signal is output to the variable valve mechanism 21.

If it is determined in step 1 that the starting control is being performed, the process proceeds to step 2, and it is determined whether or not the previous starting has failed, that is, a failure has occurred. In the present embodiment, this is determined based on the throttle valve opening. That is, when the starter switch 19 is turned on in a state where the opening of the throttle valve 14 operated by the driver is larger than a predetermined opening (this is set, for example, near full opening), the driver starts the operation. It is determined that the accelerator pedal is intentionally depressed with respect to the failure, and it is assumed that a failure has occurred.

If the opening of the throttle valve 14 is smaller than the predetermined opening, it is determined that the engine is a normal start, and the process proceeds from step 2 to step 3 to set the optimal valve timing at normal time. At this time, since cranking is being performed, valve timing characteristics suitable for starting are given.
For example, the dashed line in FIG. 3 shows an example of the valve lift characteristic of the intake valve 10 during normal cranking, and the opening and closing of the intake valve 10 is reduced in order to reduce the valve overlap in order to stabilize combustion at idling. The characteristics have a relatively retarded timing.

On the other hand, if it is determined in step 2 that a failure has occurred, the process proceeds from step 2 to step 4, and
Set the optimal valve timing during a failure. Then, a control signal is output to the variable valve mechanism 21 in step 5 so that the target valve timing set as described above is achieved. Specifically, as shown by the solid line in FIG. 3, the opening and closing timing of the intake valve 10 is advanced such that the closing timing of the intake valve 10 is near the bottom dead center.

At the same time, the fuel injection from the fuel injection valve 12 is stopped.

Accordingly, a larger amount of fresh air is sucked into the combustion chamber 4 as a result of the cranking, and the inside of the combustion chamber 4 in which the fuel remains last time is actively scavenged. Further, a large amount of air is taken into the combustion chamber 4 and is compressed by the piston 3, so that the compression pressure during cranking increases and the gas temperature in the combustion chamber 4 increases. Therefore, vaporization of the fuel droplets adhering to the ignition plug 5 is promoted. FIG. 4 shows the relationship between the compression pressure during cranking and the intake valve closing timing. As shown, the compression pressure increases with the advance of the intake valve closing timing. FIG.
Shows the state of the decrease in the amount of residual fuel in the combustion chamber 4 due to cranking, the broken line shows the conventional characteristics at normal valve timing, and the solid line shows the above-described embodiment in which the valve timing is advanced. The characteristics of the examples are shown respectively, but as is clear from the comparison between the two, the advance of the valve timing reduces the residual fuel more quickly, and it is necessary to reduce the remaining fuel to the air-fuel ratio range where the engine can be started. Time is shortened. And since the ignition device continues to operate,
Ignition combustion starts spontaneously when the air-fuel ratio range where the engine can be started is reached, and the internal combustion engine 1 starts.

It is preferable that the catalyst device 8 be configured to process unburned fuel components discharged along with scavenging.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of control of valve timing in the embodiment.

FIG. 3 is a characteristic diagram showing valve lift characteristics of the intake and exhaust valves according to the embodiment.

FIG. 4 is a characteristic diagram showing a relationship between a compression pressure during cranking and an intake valve closing timing.

FIG. 5 is a characteristic diagram showing a relationship between a cranking time and a residual fuel amount.

[Explanation of symbols]

 Reference Signs List 10 intake valve 16 throttle valve opening sensor 19 starter switch 21 variable valve mechanism

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Claims (4)

[Claims] 1. A start control device for an internal combustion engine including a variable valve mechanism at least on an intake valve side of the internal combustion engine, the variable valve mechanism being capable of variably controlling at least a closing timing of the intake valve. A start control device for an internal combustion engine, comprising: a failure detecting means for directly or indirectly detecting a failure of the engine, and when the failure of the start is detected, the intake valve closing timing is controlled to a valve timing for a failure. 2. The start control apparatus for an internal combustion engine according to claim 1, wherein the valve timing at the time of the failure has a characteristic in which the intake valve closing timing is advanced to near a bottom dead center. 3. A variable valve mechanism provided at least on an intake valve side of the internal combustion engine and capable of variably controlling at least a closing timing of the intake valve, and a throttle valve opening detection detecting an opening of a throttle valve of the internal combustion engine. Means, cranking detecting means for detecting cranking of the internal combustion engine, and when the throttle valve opening is cranked in a state larger than a predetermined opening, intake valve closing timing via the variable valve mechanism. And a valve timing control means for advancing to a lower dead center side than usual. 4. A fuel control system according to claim 3, further comprising fuel control means for stopping fuel supply when the throttle valve is cranked in a state where the throttle valve opening is larger than a predetermined opening. Start control device for internal combustion engine.