JP2002213261A - Engine start control method with minimum intake air volume - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize cranking noise in restarting an engine after it is frequently tentatively stopped like a fuel saving type vehicle or a hybrid vehicle. SOLUTION: In engine cranking, the intake air quantity per piston stroke in plural cylinders is set to the minimum amount capable of causing ignition. The setting may be carried out by the setting of the closing phase or lift of an intake valve by a valve timing variable setting mechanism, and my be done immediately before the tentative stop of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine of a vehicle such as an automobile, and more particularly, to an improvement relating to control of a starting operation of the engine.

[0002]

2. Description of the Related Art In an engine for the above-mentioned applications, variably adjusting the opening / closing timing and lift of an intake valve for the purpose of controlling the output of the engine and improving the idling stability is known as a VVT (Variable Valve Timing). ) Technology,
It has already been implemented in various forms since ancient times. Further, in an engine equipped with such a VVT mechanism, when the engine is started, the closing phase of the intake valve is set to the most retarded position by the VVT mechanism, and the compression ratio of the intake air at the time of starting the engine is reduced.
The ease of cranking by the engine starting motor is also described in JP-A-10-227236.

As described in the above publication, setting the closing phase of the intake valve to the most retarded position by the VVT mechanism at the time of starting the engine certainly lowers the effective intake air amount into the cylinder,
That makes cranking when starting the engine with the motor easier. However, when the VVT mechanism delays the closing phase of the intake valve to its most retarded position, the amount of air charged into the cylinder is determined as the amount of intake air per piston stroke, and the engine ignition (or ignition) by cranking. ) Is not necessarily the minimum amount that can occur. Here, the term “ignition or ignition” means that the engine completely explodes (so-called self-explosion) and becomes capable of rotating by itself.

[0004]

In a reciprocating piston type engine, there must always be a minimum amount of intake air per piston stroke that allows engine ignition to occur due to cranking. Its value will, of course, vary with engine temperature, intake air temperature and air-fuel ratio, fuel quality, ignition timing, cranking speed, and other parameters. However, based on the above-mentioned parameters such as the temperature state of the engine, the temperature of the intake air and the air-fuel ratio, the quality of the fuel, the ignition timing, and the number of revolutions of the cranking, the piston stroke enabling the engine to be ignited by the cranking The minimum value of the per-intake air amount can be obtained instantaneously using a microcomputer. Then, if each cylinder of the engine is cranked with such a minimal air charge, the engine should be cranked up (cranked up) as quietly as possible. Engine cranking as quiet as possible is frequently performed in fuel-saving vehicles and hybrid vehicles, which are rapidly gaining attention due to the need to conserve fuel resources and protect the environment. It is particularly significant because it is

According to the present invention, there is a minimum value that allows ignition to occur as an intake air amount per piston stroke at the time of starting by engine cranking. It is possible to calculate and execute, which is of great significance in fuel-saving vehicles and hybrid vehicles,
It is an object to further improve the engine start control from such a viewpoint.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for controlling the starting operation of an engine, in which the amount of intake air per piston stroke in each of a plurality of cylinders is ignited. It proposes a method characterized by setting to the smallest possible amount.

In the above-described engine start operation control method, the setting of the intake air amount per piston stroke capable of causing ignition may be performed by setting an intake valve closing phase by a variable valve timing setting mechanism.

Alternatively, in the above-described engine start operation control method, the setting of the intake air amount per the minimum piston stroke in which ignition can occur may be performed by setting an intake valve lift by a variable valve lift setting mechanism.

Further, in the above-described engine start operation control method, the setting of the minimum intake air amount per piston stroke in which ignition can occur is performed by setting the intake air amount per piston stroke in each of the plurality of cylinders to each other. Equalizing may be included.

Further, in the above-described engine start operation control method, the setting of the intake air amount per piston stroke capable of causing ignition may be performed immediately before the engine is stopped.

[0011]

As described above, in a reciprocating piston type engine, there must always be a minimum amount of intake air per piston stroke that allows the engine to be ignited by cranking. Each time the engine is started, if the intake air amount per piston stroke in each of the plurality of cylinders is set to such a minimum amount that ignition can occur, the engine will operate at the limit at which ignition can occur for cranking. It is cranked up as quietly as possible with minimal non-uniform rolling resistance. Once the engine starts firing, the smoothness of the engine rotation after that is no longer the same as the smoothness of cranking by the motor, and various optimal measures may be taken as such. .

As described above, setting the amount of intake air per piston stroke in each cylinder at the time of engine cranking to the minimum amount at which ignition can occur can be achieved by using an existing valve timing variable setting mechanism as long as the set value is determined. Setting of the intake valve closing phase, or setting of the intake valve lift, or both of them can be easily performed. In this case, the determination of the set value is sufficient because the parameters affecting the above are about the temperature state of the engine, the temperature of the intake air and the air-fuel ratio, the quality of the fuel, the ignition timing, the number of revolutions of the cranking, etc. By creating an appropriate map using these parameters as variables based on experiments, it can be performed as a matter of design and can be achieved instantaneously using a microcomputer.

Although the present invention is meaningful for fuel-saving vehicles and hybrid vehicles as described above, in these vehicles, when the engine load is low or when the vehicle decelerates, a plurality of fuel-saving vehicles or hybrid vehicles are used to save fuel. Cylinder number control for stopping some of the cylinders may be performed. When the number of cylinders is controlled and the number of operating cylinders is reduced, the vehicle is temporarily stopped, and the engine is also temporarily stopped. If the engine is restarted as it is, the compression stroke sequentially generated by cranking is performed. Irregularities occur in the timing, which causes vibration. At this point, if the setting of the minimum intake air amount per piston stroke capable of generating ignition as described above includes equalizing the intake air amount per piston stroke in each of the plurality of cylinders, Based on this, even if the number of working cylinders is reduced just before the engine is stopped, all cylinders are operated equally when restarting the engine, and the quietest possible engine crank-up is achieved.

Furthermore, if the setting of the intake air amount per piston stroke at which ignition is possible is performed immediately before the engine is stopped as described above, restarting after the engine is temporarily stopped as in a fuel-saving vehicle or a hybrid vehicle is performed. When it should be done as soon as possible, it can respond quickly. In particular, when the control of the number of working cylinders includes a mechanical or hydraulic configuration in the actuator section, the operation may not be obtained unless the engine is operated, but such a problem is also avoided. .

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention;

An engine start control method according to the present invention comprises:
In a vehicle operation control device using a computer that has already been widely used in recent years, the present invention may be implemented in such a manner as to be incorporated in a part of an arbitrary engine control program by the computer. Since the general basic configuration of a computer-based vehicle operation control device is already well known in the art, this type of vehicle operation control device is used to confirm that the method of the present invention can be performed. Is omitted in order to avoid making the description of the specification redundant.

FIG. 1 is a flowchart showing one embodiment of an engine start control method according to the present invention in a control operation flowchart. As can be seen from this flowchart, the engine start control according to the present invention is performed not at the time of starting the engine by the driver at the beginning of the operation of the vehicle but by the computer in a fuel-saving vehicle or a hybrid vehicle. This is the time when the engine is restarted after the engine is temporarily stopped during the operation of the vehicle under the control.

When operation of a vehicle such as an automobile is started and arbitrary engine operation control is started, control according to the present invention is started at the same time, and data related to control of the present invention is read in step 10. Will be These data include information for judging the running state of the vehicle and the engine load, the operation command for the engine, and the above-mentioned engine temperature state, intake air temperature and air-fuel ratio, fuel quality, ignition timing, cranking rotation. Numbers are included. Next, the control proceeds to a step 20, wherein it is determined whether or not the flag F is 1. The flag F is set to 1 at step 90 when the engine is temporarily stopped, and is reset to 0 at the start of the control, as is usual in this type of control. Therefore, the answer to step 20 is no, and the control proceeds to step 30, unless the engine is in a paused state.

In step 30, the engine load L
It is determined whether or not e is equal to or greater than a predetermined low load threshold L1. When the answer is yes, the following control is not necessary, and the control returns to step 10 before
Prepare for changes in vehicle driving conditions while re-reading data. If the answer is no, the control proceeds to step 40, in order to achieve better fuel efficiency for low engine load operation with the threshold value L1 or less, to reduce the number of cylinders of the engine and the closing phase and lift of the intake valve by the VVT mechanism. Control is performed. Numerous such engine-reduced-cylinder and engine-low-load-response controls using the VVT mechanism have been proposed, and any of them may be used here. Control then proceeds to step 5
Go to 0.

In step 50, it is determined whether a condition for temporarily stopping the engine has been satisfied. This means that the vehicle has been in a deceleration state for more than a predetermined time,
It may be determined that the vehicle has been stopped for more than a predetermined time or other conditions. If the answer is no, control returns to step 10; if the answer is yes, control proceeds to step 60.

In step 60, the countermeasures against low load operation by control of the reduced cylinder and the closing phase of the intake valve or the lift set in step 40 are temporarily canceled. The engine is returned to the operating state, and the engine is cranked by cranking based on the engine temperature at that time, the intake air temperature and air-fuel ratio, the quality of fuel, the ignition timing, the cranking speed expected based on the state of charge of the power storage device, and the like. The minimum intake air amount per piston stroke that can cause ignition is calculated, and the cranking setting for such engine cranking is performed by adjusting the closing phase and lift of the intake valve. Then, the control proceeds to step 80, where the engine is temporarily stopped. Next, at step 90, the flag F is set to "1".

Thereafter, the control proceeds to step 100, where it is determined whether or not a request for starting the engine has been issued from the vehicle operation control device. Control returns to step 1 while the answer is no
Return to before 0. When an engine restart command is issued to restart the engine, control proceeds to step 110, where engine cranking is performed. In a fuel-saving vehicle or a hybrid vehicle, the engine is usually temporarily stopped for a short period of time, and it is assumed that the engine temperature state does not change much more than when the cranking setting is performed in step 70. However, if desired, the cranking settings may be modified as the engine pause time elapses. Other conditions such as the temperature of the intake air and the air-fuel ratio, the quality of the fuel, the ignition timing, the state of charge of the power storage device, and the like are not affected by the length of the engine temporary stop time.

When it is detected in step 120 that the engine has started to fire due to the cranking of the engine, the control proceeds to step 130, in which the control proceeds to step 130.
Is released, and the engine is returned under the control of the vehicle operation control device. Finally, at step 140, the flag F is reset to 0, and the engine start control of the present invention according to the process shown in the drawing is ended once to prepare for the next operation.

While the present invention has been described in detail with reference to one embodiment, it will be apparent to those skilled in the art that various modifications can be made to such embodiment within the scope of the invention.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of an engine start control method according to the present invention.

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Claims (5)

[Claims] 1. A method for controlling the starting operation of an engine, wherein the amount of intake air per piston stroke in each of a plurality of cylinders is set to a minimum amount at which ignition can occur. 2. The method according to claim 1, wherein the setting of the intake air amount per piston stroke capable of causing ignition is performed by setting an intake valve closing phase by a variable valve timing setting mechanism. 3. The method according to claim 1, wherein the setting of the intake air amount per piston stroke capable of causing ignition is performed by setting an intake valve lift by a variable valve lift setting mechanism. 4. The method according to claim 1, wherein the setting of the minimum intake air amount per piston stroke in which ignition can occur includes equalizing the intake air amount per piston stroke in each of the plurality of cylinders. The method according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the setting of the amount of intake air per piston stroke at which the ignition can occur is performed immediately before the engine is stopped.